Information
-
Patent Grant
-
6615786
-
Patent Number
6,615,786
-
Date Filed
Wednesday, April 17, 200222 years ago
-
Date Issued
Tuesday, September 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Yuen; Henry C.
- Castro; Arnold
Agents
- Arent Fox Kintner Plotkin & Kahn, PLLC
-
CPC
-
US Classifications
Field of Search
US
- 123 17931
- 123 17925
- 060 625
- 060 626
- 060 627
- 074 7 C
- 074 7 E
-
International Classifications
-
Abstract
There is provided a starter system for an internal combustion engine, which is capable of preventing wear of a brush of an electric motor ascribable to the combined use of the electric motor with a hydraulic actuator and the resulting increase in the rotational resistance due to friction of the brush, as well as capable of using one of the hydraulic actuator and the electric motor without difficulty even when the other is disabled. The hydraulic motor is driven by hydraulic pressure. A rotational shaft of the hydraulic motor is driven for rotation by the hydraulic motor. A rotational shaft of an electric motor extends in parallel with the rotational shaft of the hydraulic motor, and is driven for rotation by the electric motor. A ring gear rotates in unison with the crankshaft. A pinion gear is brought into meshing engagement with the ring gear, for starting the engine. An output shaft is connected to the pinion gear. A first one-way clutch connects the rotational shaft of the hydraulic motor and the output shaft to each other in a disconnectable manner, for transmitting rotation of the hydraulic motor to the output shaft. A second one-way clutch connects the rotational shaft of the electric motor and the output shaft to each other in a disconnectable manner, for transmitting rotation of the rotational shaft of the electric motor to the output shaft.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a starter system for an internal combustion engine, for starting the engine by a hydraulic actuator driven by hydraulic pressure.
2. Description of the Prior Art
Conventionally, a starter system of this kind has been proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 2001-82202.
FIG. 12
schematically shows the arrangement of the starter system. This starter system
350
, which is a hydraulic motor-driven type, is comprised of an electric motor
351
, an oil pump
352
driven by the electric motor
351
, an accumulator
353
for storing hydraulic pressure boosted by the oil pump
352
, a hydraulic motor
355
connected to the accumulator
353
via an oil passage
354
, and a solenoid valve
356
arranged in the oil passage
354
. A drive shaft
355
a
of the hydraulic motor
355
is connected to a drive shaft
359
a
of a timing pulley
359
via a reduction gear
357
and a one-way clutch
358
. The timing pulley
359
is connected to a timing pulley
362
of an internal combustion engine (hereinafter referred to as “the engine”)
361
via a synchronous timing belt
360
. Further, the timing pulley
362
is mounted to one end of a crankshaft
363
.
According to the above construction, when the engine
361
is started, the solenoid valve
356
opens the oil passage
354
, whereby hydraulic pressure is supplied from the accumulator
353
to the hydraulic motor
355
to drive the same for rotation. Then, the rotation of the hydraulic motor
355
is transmitted to the crankshaft
363
via the reduction gear
357
, the one-way clutch
358
and the synchronous timing belt
360
to thereby start the engine
361
. During operation of the engine
361
after the start thereof, transmission of torque from the crankshaft
363
to the hydraulic motor
355
is inhibited by action of the one-way clutch
358
.
In general, if an engine stops halfway in a compression stroke when the operation of the engine is stopped or when the start of the same has failed, the crankshaft of the engine can be urged by pressure of the compressed air to rotate reversely to a stable position. In this case, since the direction of torque is reversed from the normal direction thereof, the one-way clutch
358
of the above starter system
350
transmits reverse torque to the hydraulic motor
355
. This causes the hydraulic motor
355
to rotate in the reverse direction to act as a hydraulic pump. On the other hand, the oil passage
354
is held in a closed state by the solenoid valve
356
except when the engine is started. As a result, the hydraulic fluid pressurized to a high pressure level when the operation of the engine is stopped flows into the closed portion of the oil passage
354
between the hydraulic motor
355
and the solenoid valve
356
, thereby developing high impact pressure within the oil passage
354
. The high impact pressure causes the drive shaft
355
a
of the hydraulic motor
355
to generate large impact torque which can adversely affect a torque-transmitting system including the hydraulic motor
355
and the one-way clutch
358
as well as a hydraulic circuit system including the solenoid valve
356
and the oil passage
354
. Similarly, when the start of the engine has failed, although the oil passage
54
is held open by the solenoid valve
356
, high impact pressure can be generated e.g. due to a pressure loss in the solenoid valve
356
.
Further, another starter system of the above-mentioned kind has been proposed e.g. by Japanese Laid-Open Utility Model Publication (Kokai) No. 59-73579. This starter system includes an electric motor, and a hydraulic motor, and is capable of starting an engine by selectively using the two motors. The electric motor has a pinion gear splined to a rotational shaft thereof. At the start of the engine, a plunging mechanism causes the pinion gear to axially slide toward the engine, for meshing engagement with a ring gear integrally formed with a crankshaft of the engine. On the other hand, the hydraulic motor is arranged on an opposite side to the pinion gear with respect to the electric motor, and serially connected to the electric motor via a one-way clutch arranged coaxially with the rotational shaft of the hydraulic motor. The hydraulic motor is driven by hydraulic pressure accumulated within the accumulator. The operation or stoppage of the hydraulic motor is controlled according to the hydraulic pressure accumulated in the accumulator, by opening and closing of a solenoid valve arranged between the accumulator and the hydraulic motor. The pressure accumulation is carried out by utilizing regenerative energy under conditions that the hydraulic pressure within the accumulator is equal to or lower than a predetermined value and that the vehicle is decelerating.
According to this starter system, when the engine is started, the pinion of the electric motor is brought into meshing engagement with the ring gear by the plunging mechanism, and when the hydraulic pressure within the accumulator is equal to or higher than the predetermined value, the hydraulic motor is driven. As a result, torque of the hydraulic motor is transmitted to the rotational shaft of the electric motor via the one-way clutch, and then further transmitted from the pinion gear to the ring rear, whereby the engine is started. On the other hand, when the hydraulic pressure within the accumulator is lower than the predetermined value, the hydraulic motor is stopped, and the electric motor is driven to start the engine. In this case, the electric motor and the hydraulic motor are disconnected from each other by the one-way clutch, which prevents the hydraulic motor from applying rotational load to the electric motor.
Normally, the hydraulic motor and the electric motor have respective different torque characteristics. More specifically, the hydraulic motor provides larger output torque than the electric motor, and the rise of rotational speed of the hydraulic motor is more rapid than that of the electric motor. Therefore, the hydraulic motor is characterized by being capable of starting the engine quickly. The quick starting of the engine is advantageous in reducing a time period during which the pinion gear and the ring gear are engaged with each other, thereby suppressing generation of noise due to the engagement between the two gears, as well as in ensuring smooth startability when the engine is frequently stopped and started by application of “idle stop” e.g. in traffic congestion. The “idle stop” is an engine operation control technique for stopping the operation of the engine when the engine speed is low under predetermined operating conditions of the engine including a fully warmed-up condition thereof. This technique has come to be increasingly valued as measures of environmental protection and fuel economy.
However, in the above conventional starter system, since the hydraulic motor is serially connected to the rotational shaft of the electric motor, when the engine is to be started by the electric motor, transmission of torque from the electric motor to the hydraulic motor is inhibited by free or idle rotation of the one-way clutch, whereas when the engine is to be started by the hydraulic motor, the torque of the hydraulic motor is transmitted to the electric motor via the one-way clutch, whereby the electric motor is caused to rotate at the same rotational speed as the hydraulic motor. This makes a brush in constant contact with the rotational shaft of the electric motor prone to wear or abrasion. This wear of the brush is particularly conspicuous when the high torque characteristic of the hydraulic motor is utilized for restarting the engine in an idle stop mode, so as to start the engine quickly, because the starting rotational speed of the engine is higher than when the electric motor is used. As the brush wears to a larger degree, the rotational resistance due to friction is increased, whereby transmission efficiency in transmitting torque from the hydraulic motor to the engine is lowered. This adversely affects the startability of the engine, and makes it necessary to design a hydraulic motor such that it has an larger output.
Further, as the hydraulic motor increases the starting rotational speed, the electric motor is required to be designed to have a robuster structure so as to endure high rotational speeds, though it is not originally necessary for engine starting operation, resulting in an extra increase in costs. Moreover, when the electric motor is disabled by fixture of movable components caused by entry of a foreign matter, it is also impossible to start the engine by using the hydraulic motor, so that the starting of the engine becomes totally impossible. In short, if quick starting by the hydraulic motor is to be executed so as to take advantage of the above characteristic of the hydraulic motor, it is required to employ an expensive electric motor capable of enduring high rotational speeds, which results in an increase in manufacturing costs. A possible solution to this problem is to provide overdrive/reduction mechanisms having respective different overdrive/reduction characteristics for the hydraulic motor and the electric motor, respectively. In this case, however, it is necessary to design another starter system anew, which also causes an increase in manufacturing costs. In addition, space for arranging the two overdrive/reduction mechanisms is needed, and hence the starter system is inevitably increased in size.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide a starter system for an internal combustion engine, which is capable of preventing wear of a brush of an electric motor ascribable to the combined use of the electric motor with a hydraulic actuator and the resulting increase in the rotational resistance due to friction of the brush, as well as capable of using one of the hydraulic actuator and the electric motor without difficulty even when the other is disabled.
It is a second object of the invention to provide a starter system for an internal combustion engine, which is capable of starting the engine by selectively making use of a driving force from a hydraulic actuator or a driving force from an electric motor at a properly increased or decreased rotational speed without any interference therebetween, and which can be constructed by a compact design and at a reduced cost.
It is a third object of the invention to provide a starter system for an internal combustion engine, which is capable of preventing a hydraulic actuator, a hydraulic pressure supply control valve and an oil passage from being adversely affected by reverse torque from the engine due to stoppage of operation of the engine or failure in starting the same.
To attain the above objects, the present invention provides a starter system for an internal combustion engine, for starting the engine by driving a crankshaft for rotation,
the starter system comprising:
a hydraulic actuator that is driven by hydraulic pressure;
a first rotational shaft that is driven for rotation by the hydraulic actuator;
an electric motor;
a second rotational shaft that extends in parallel with the first rotational shaft and is driven for rotation by the electric motor;
a driven gear that rotates in unison with the crankshaft;
a driving gear that is brought into meshing engagement with the driven gear when the engine is started;
a third rotational shaft that is connected to the driving gear;
a first driving force-transmitting mechanism that connects the first rotational shaft and the third rotational shaft to each other in a disconnectable manner, for transmitting rotation of the first rotational shaft to the third rotational shaft; and
a second driving force-transmitting mechanism that connects the second rotational shaft and the third rotational shaft to each other in a disconnectable manner, for transmitting rotation of the second rotational shaft to the third rotational shaft.
According to this starter system for an internal combustion engine, the first rotational shaft that is driven for rotation by the hydraulic actuator and the second rotational shaft that is driven for rotation by the electric motor extend in parallel with each other. Further, the first driving force-transmitting mechanism disconnectably connects the first rotational shaft to the third rotational shaft having the driving gear connected thereto, while the second driving force-transmitting mechanism disconnectably connects the second rotational shaft to the third rotational shaft. In this construction, when the engine is to be started by the hydraulic actuator, the driving gear is brought into meshing engagement with the driven gear which rotates in unison with the crankshaft, and the hydraulic actuator is driven with the first driving force-transmitting mechanism being held in a connection state in which this mechanism connects the first and third rotational shafts and the second driving force-transmitting mechanism being held in a disconnection state in which this mechanism disconnects the second and third rotational shafts from each other. As a result, the rotation or torque of the hydraulic actuator is transmitted to the third rotational shaft via the first rotational shaft and the first driving force-transmitting mechanism, and then further transmitted to the driven gear via the driving gear, whereby the engine is started. In this case, since the second rotational shaft is held disconnected from the third rotational shaft by the second driving force-transmitting mechanism, no driving force is transmitted from the engine or the hydraulic actuator to the electric motor, and hence the electric motor is neither caused to rotate nor offers a rotational resistance.
As described above, the starter system of the present invention makes it possible to selectively transmit one of the driving forces of the hydraulic actuator and the electric motor to the internal combustion engine in a state of transmission of a driving force between the hydraulic actuator and the electric motor being completely inhibited, thereby starting the engine. In other words, whichever of the hydraulic actuator and the electric motor may be used to start the engine, the hydraulic actuator or the electric motor can be operated independently of each other without causing rotation of the other. As a result, it is possible to prevent wear of a brush of the electric motor due to the use of the electric motor in combination with the hydraulic actuator, and an increase in rotational resistance due to friction resulting from the wear of the brush. Further, it is not necessary to provide an extra design so as to increase the robustness of the electric motor to adapt the same to the high rotational speed characteristic of the hydraulic actuator. Moreover, even when one of the hydraulic actuator and the electric motor is disabled, it is possible to use the other to start the engine without any difficulty.
Preferably, the first and second driving force-transmitting mechanisms are formed by respective first and second one-way clutches that allow transmission of respective rotations of the first and second rotational shafts to the third rotational shaft only when the first and second rotational shafts rotate in respective directions for driving the third rotational shaft.
According to this preferred embodiment, when the engine is to be started by the hydraulic actuator, the rotation of the first rotational shaft is transmitted to the third rotational shaft via the first one-way clutch, whereas the second one-way clutch performs idle or free rotation so that the second and third rotational shafts are in a state disconnected from each other. On the other hand, when the engine is to be started by the electric motor, inversely to the above case, the rotation of the second rotational shaft is transmitted to the third rotational shaft via the second one-way clutch, whereas the first one-way clutch performs idle or free rotation so that the first and third rotational shafts are in a state disconnected from each other. Thus, by implementing the first and second driving force-transmitting mechanisms by the respective one-way clutches, it is possible to make use of one of the hydraulic actuator and the electric motor and at the same time hold the other in a disconnected state, through the simple arrangement including the clutches, to thereby start the engine, with ease and without any need to execute control operation therefor.
Preferably, the starter system includes a planetary gear set having a sun gear, a carrier, and a ring gear, the second rotational shaft being connected to one of the sun gear, the carrier, and the ring gear, and
the first rotational shaft being connected to another of the sun gear, the carrier, and the ring gear of the planetary gear set, and
the third rotational shaft being connected to a remaining one of the sun gear, the carrier, and the ring gear of the planetary gear set.
According to this preferred embodiment, the second rotational shaft driven by the electric motor, the first rotational shaft driven by the hydraulic actuator, and the third rotational shaft provided with the driving gear are connected to one, another, and the remaining one of the sun gear, the carrier, and the ring gear of the planetary gear set. Accordingly, when the engine is to be started by the hydraulic actuator, the driving gear is brought into meshing engagement with the driven gear integrally formed with the crankshaft, and at the same time, the hydraulic actuator is driven for rotation by hydraulic pressure accumulated in the accumulator. As a result, the rotation of the first rotational shaft driven by the hydraulic actuator is transmitted from the another of the sun gear, the carrier, and the ring gear to the third rotational shaft via the remaining one of these, and then further transmitted to the driven gear via the driving gear, whereby the engine is started. On the other hand, when the engine is to be started by the electric motor, the driven gear is brought into meshing engagement with the driving gear, and the electric motor is driven for rotation. The rotation of the second rotational shaft driven by the electric motor is transmitted from the one of the sun gear, the carrier, and the ring gear to the third rotational shaft via the remaining one, and further via the driving gear to the driven gear, whereby the engine is started.
As described above, according to the above preferred embodiment, it is possible to transmit the driving force of the hydraulic actuator or the electric motor to the third rotational shaft via the planetary gear set without causing interference between the hydraulic actuator and the electric motor. Further, since the driving force-transmitting mechanism for the hydraulic actuator and the electric motor is formed by a single planetary gear set, it is possible to make the starter system compact in size and manufacture the same at a reduced cost.
More preferably, the starter system further comprises first fixing means for fixing the one of the sun gear, the carrier, and the ring gear, to which the second rotational shaft that is driven by the electric motor for rotation is connected, when the engine is to be started by the hydraulic actuator, and
second fixing means for fixing the another of the sun gear, the carrier, and the ring gear, to which the first rotational shaft that is driven by the hydraulic actuator for rotation is connected, when the engine is to be started by the electric motor.
According to this preferred embodiment, when the engine is to be started by the hydraulic actuator, the driving force of the hydraulic actuator is taken out by fixing or making immovable the one of the sun gear, the carrier and the ring gear, to which the second rotational shaft that is driven by the electric motor for rotation is connected, by using the first fixing means, and delivered to the third rotational shaft at an overdrive/reduction ratio dependent on the gear ratio of the planetary gear set. Similarly, when the engine is to be started by the electric actuator, the driving force of the electric motor is taken out by fixing or making immovable the one of the sun gear, the carrier and the ring gear, to which the first rotational shaft that is driven by the hydraulic actuator for rotation is connected, by using the second fixing means, and delivered to the third rotational shaft at an overdrive/reduction ratio different from that in the case of the hydraulic actuator being used. Thus, one of the driving forces of the hydraulic actuator and the electric motor can be selectively taken out without causing any interference between the hydraulic actuator and the electric motor, as well as to obtain overdrive/reduction ratios different from each other. In short, the planetary gear set functions not only as a driving force-transmitting mechanism, but also as an overdrive/reduction mechanism for the hydraulic actuator and the electric motor. This makes it possible to manufacture the starter system further compact in size at a reduced cost.
Alternatively, if the first and second fixing means are formed by respective locking means for mechanically locking the second rotational shaft that is driven by the electric motor and the first rotational shaft that is driven by the hydraulic actuator, fixing operations by the respective fixing means can be performed by mechanically locking the respective first and second rotational shafts, so that it is possible to easily and reliably carry out switching between the output of the driving force of the hydraulic actuator and that of the driving force of the electric motor.
Further preferably, the starter system further comprises an accumulator for storing hydraulic pressure, an oil passage connected to the accumulator, and third fixing means for fixing the remaining one of the sun gear, the carrier, and the ring gear, to which the third rotational shaft that is connected to the driven gear is connected, to thereby transmit a driving force of the electric motor to the hydraulic actuator and cause the hydraulic actuator to rotate the first rotational shaft in a direction opposite to a direction in which the first rotational shaft is driven for rotation, to thereby cause the hydraulic pressure to be accumulated in the accumulator via the oil passage.
According to this preferred embodiment, hydraulic pressure is accumulated in the accumulator by fixing the remaining one of the sun gear, the carrier, and the ring gear, to which the third rotational shaft is connected, to thereby transmit the driving force of the electric motor to the hydraulic actuator and cause reverse rotation of the first rotational shaft, whereby the hydraulic pressure is accumulated in the accumulator. Thus, it is possible to utilize the hydraulic actuator to accumulate the hydraulic pressure in the accumulator, and hence a dedicated oil pump or electric motor for the pressure accumulation can be dispensed with.
Alternatively, if the above third fixing means is formed by locking means for mechanically locking the third rotational shaft, the fixing operation by the third fixing means can be performed by mechanically locking the third rotational shaft, so that the hydraulic actuator can easily and reliably perform operation for the pressure accumulation.
Preferably, the third rotational shaft is connected to the ring gear, the second rotational shaft is connected to the sun gear, and the first rotational shaft is connected to the carrier.
As described in Description of the Prior Art, when the torque characteristic of the hydraulic actuator and that of the electric motor are compared with each other, the output torque of the hydraulic actuator is larger and hence suitable for quick starting by overdrive, whereas the output torque of the electric motor is smaller, and hence it is preferably output at a reduced rotational speed. According to the above preferred embodiment, since the output shaft (third rotational shaft), the electric motor, and the hydraulic actuator are each connected to the planetary gear set as described above, the rotation of the electric motor is output at a reduced rotational speed, while that of the hydraulic actuator is output at an increased rotational speed. Therefore, the starter system can be easily selectively placed in respective operative statuses in which the rotational speed of the output shaft is increased and decreased, in a manner adapted to the respective torque characteristics of the hydraulic actuator and the electric motor.
Preferably, the starter system of the invention further comprises a hydraulic pressure supply control valve arranged in the oil passage connected to the hydraulic actuator, for controlling the hydraulic pressure to be supplied to the hydraulic actuator via the oil passage, and
a torque limiter mechanism for suppressing an increase in the hydraulic pressure when a reverse torque equal to or larger than a predetermined value and acting in a direction opposite to a direction for starting the engine acts on the hydraulic actuator during stoppage of rotation of the engine.
According to this preferred embodiment, when the engine is started, the hydraulic pressure supply control valve opens the oil passage to permit supply of hydraulic pressure to the hydraulic actuator via the oil passage, whereby the hydraulic actuator is driven for rotation. The rotation of the hydraulic actuator is transmitted to the engine, whereby the engine is started. Further, even if a reaction force from the engine generated due to stoppage of the engine or failure in starting the same causes reverse rotation of the engine, causing the hydraulic actuator to act as an oil pump to increase the hydraulic pressure, the torque limiter mechanism prevents the hydraulic pressure from being further increased when a reverse torque equal to or larger than the predetermined value acts on the hydraulic actuator.
As described above, when the engine is being stopped if the reverse torque acting on the hydraulic actuator becomes equal to or larger than the predetermined value, the torque limiter mechanism is operated to limit the hydraulic pressure, so that an excessively large torque is not generated when the engine is stopped, and further large impact torque is prevented from being generated in the hydraulic actuator. Therefore it is possible to prevent the hydraulic actuator, the hydraulic pressure supply control valve, and the oil passage from being adversely affected by large impact torque.
Further preferably, the torque limiter mechanism is a relief valve arranged in the oil passage, for opening the oil passage when the hydraulic pressure in the oil passage becomes equal to or larger than a predetermined pressure corresponding to the reverse torque equal to or larger than the predetermined value.
According to this preferred embodiment, since the relief valve is arranged in the oil passage between the hydraulic actuator and the hydraulic pressure supply control valve, it is possible to open the oil passage by the relief valve to thereby relieve the hydraulic pressure. Therefore, generation of excessive hydraulic pressure within the oil passage can be prevented.
Alternatively, the torque limiter mechanism is a clutch arranged between the engine and the hydraulic actuator, for suppressing an increase in the reverse torque transmitted from the engine to the hydraulic actuator, when the reverse torque becomes equal to or larger than the predetermined value.
According to this preferred embodiment, the clutch is arranged between the engine and the hydraulic actuator, and when the reverse torque from the engine has become equal to or larger than the predetermined value, the clutch is operated to prevent the torque transmitted from the engine to the hydraulic actuator from being increased. This prevents excessive reverse torque from acting on the first rotational shaft of the hydraulic actuator, as well as resultant generation of excessive hydraulic pressure within the oil passage.
Preferably, the starter system further comprises a discharge oil passage for discharging the hydraulic pressure from the hydraulic actuator, and the hydraulic pressure supply control valve can open or close the oil passage and the discharge oil passage simultaneously.
According to this preferred embodiment, since it is possible to simultaneously open or close the oil passage, via which hydraulic pressure is supplied, and the discharge oil passage, it is possible to reduce time wasted before re-start of rotation of the hydraulic actuator when it is driven again.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a first embodiment of the invention;
FIG. 2
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a second embodiment of the invention;
FIG. 3
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a third embodiment of the invention;
FIG. 4
is a diagram schematically showing a variation of the third embodiment;
FIG. 5
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a fourth embodiment of the invention;
FIG. 6
is a diagram schematically showing a variation of the fourth embodiment;
FIG. 7
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a fifth embodiment of the invention;
FIG. 8
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a sixth embodiment of the invention;
FIG. 9
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a seventh embodiment of the invention;
FIG. 10
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to an eighth embodiment of the invention;
FIG. 11
is a diagram schematically showing the arrangement of a starter system for an internal combustion engine, according to a ninth embodiment of the invention; and
FIG. 12
is a diagram schematically showing the arrangement of a conventional starter system for an internal combustion engine.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention will now be described in detail with reference to the drawings showing preferred embodiments thereof. Referring first to
FIG. 1
, there is schematically shown the arrangement of a starter system for an internal combustion engine, according to a first embodiment of the invention. In the figure, reference numeral
1
designates the internal combustion engine (hereinafter simply referred to as “the engine”) (ENG). The starting system
10
drives a crankshaft
2
of the engine
1
for rotation, whereby the engine
1
is started.
The starter system
10
is comprised of an electric motor
7
, an oil pump
8
driven by the electric motor
7
, an accumulator
5
for storing hydraulic pressure boosted by the oil pump
8
, a hydraulic motor
4
(hydraulic actuator) connected to the accumulator
5
via an oil passage
9
, a solenoid valve
6
(hydraulic pressure supply control valve) arranged in the oil passage
9
, a relief valve
12
arranged in a branch oil passage
9
a
branching from the oil passage
9
to a reserve tank
11
, and an ECU (Electronic Control Unit), not shown, for controlling operations of the hydraulic motor
4
and other devices.
The hydraulic motor
4
is a swash-plate type, for instance, and driven for rotation by hydraulic pressure supplied from the accumulator
5
via the oil passage
9
opened by the solenoid valve
6
. A drive shaft
4
a
of the hydraulic motor
4
is connected to a crankshaft
2
via a one-way clutch
3
. That is, the starter system
10
is a constant-mesh type in which the drive shaft
4
a
of the hydraulic motor
4
is in constant mesh with the crankshaft
2
. The one-way clutch
3
allows transmission of rotation or torque from the drive shaft
4
a
to the crankshaft
2
only when the hydraulic motor
4
is driven by hydraulic pressure from the accumulator
5
, whereas after the engine
1
has been started, the one-way clutch
3
inhibits transmission of rotation or torque from the crankshaft
2
to the hydraulic motor
4
.
The oil pump
8
is directly connected to the drive shaft
7
a
of the electric motor
7
, with a suction port thereof connected to the reserve tank
11
via a pump oil passage
9
b
and a discharge port thereof connected to the accumulator
5
via the oil passage
9
. According to this construction, the oil pump
8
is driven by operation of the electric motor
7
, and hydraulic pressure boosted by the oil pump
8
is supplied to the accumulator
5
via the oil passage
9
and accumulated therein.
The solenoid valve
6
arranged between the accumulator
5
and the hydraulic motor
4
is a normally-closed valve. More specifically, in a non-excited state, the solenoid valve
6
closes the oil passage
9
, and when excited for starting the engine
1
, it opens the oil passage
9
to allow the hydraulic pressure accumulated in the accumulator
5
to be supplied to the hydraulic motor
4
. Hydraulic fluid or oil supplied to the hydraulic motor
4
is returned to the reserve tank
11
via a discharge oil passage
9
c
. On the other hand, the relief valve
12
opens the branch oil passage
9
a
when hydraulic pressure within the oil passage
9
becomes equal to or higher than a predetermined pressure level, to thereby return the hydraulic fluid to the reserve tank
11
so as to relieve hydraulic pressure in the oil passage
9
. The predetermined pressure level is set to be higher than a pressure level required for causing operation of the hydraulic motor
4
, whereby operation of the relief valve
12
is inhibited from operating during normal use. Further, the predetermined pressure level is set to a level corresponding to that of a hydraulic pressure generated in the oil passage
9
by action of a reverse torque from the engine
1
when the reverse torque is equal to or larger than a predetermined value.
Next, the operation of the starter system
10
constructed as above will be described. When the engine
1
is to be started, the solenoid valve
6
is excited to open the oil passage
9
. As a result, hydraulic pressure is supplied from the accumulator
5
to the hydraulic motor
4
, whereby the hydraulic motor
4
is driven for rotation. Then, the torque of the drive shaft
4
a
of the hydraulic motor
4
is transmitted to the crankshaft
2
via the one-way clutch
3
to start the engine
1
.
When the crankshaft
2
is rotated in the reverse direction by a reaction force generated from the engine
1
due to failure in starting the same, reverse torque acting in a direction opposite to the direction of torque for starting the engine
1
is transmitted to the drive shaft
4
a
of the hydraulic motor
4
, whereby the drive shaft
4
a
performs reverse rotation. This causes the hydraulic motor
4
to act as a hydraulic pump, which increases hydraulic pressure within the oil passage
9
. Then, when the hydraulic pressure becomes equal to or higher than the predetermined value, the branch oil passage
9
a
is opened by the relief valve
12
, which allows hydraulic pressure to be relived thereby preventing the hydraulic pressure within the oil passage
9
from getting even higher. Similarly, during stopping process of the engine
1
, when a hydraulic pressure equal to or higher than the predetermined pressure level is generated within the closed oil passage
9
between the hydraulic motor
4
and the solenoid valve
6
by reverse torque acting on the hydraulic motor
4
for the same reason as above, it is possible to open the branch oil passage
9
a
by the relief valve
12
, thereby relieve the hydraulic pressure in the oil passage
9
.
As described above, according to the present embodiment, when reverse torque equal to or higher than the predetermined value acts on the hydraulic motor
4
immediately before stoppage of the engine
1
or immediately after failure in starting the same to generate a hydraulic pressure equal to or higher than the predetermined pressure level within the oil passage
9
, the hydraulic pressure is relieved from the oil passage
9
by the relief valve
12
, so that it is possible to prevent generation of excessively high hydraulic pressure within the oil passage
9
and hence generation of impact torque in the hydraulic motor
4
. As a result, it is possible to prevent the hydraulic motor
4
, the solenoid valve
6
, the oil passage
9
, and so forth from being adversely affected by excessively high hydraulic pressure or large impact torque.
FIG. 2
schematically shows the arrangement of a starter system according to a second embodiment of the invention. It should be noted that in the following description, component parts and elements similar or equivalent to those of the first embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. This starter system
20
is distinguished from the starter system
10
of the first embodiment in that it has a torque limiter mechanism formed by a clutch
13
arranged between the engine
1
and the hydraulic motor
4
, in place of the relief valve
12
. The clutch
13
slips when reverse torque generated from the engine
1
and acting on the hydraulic motor
4
becomes equal to or larger than a predetermined value, so as to prevent transmission of a larger reverse torque than the predetermined value. The second embodiment is similar in construction to the first embodiment except for the above torque limiter mechanism.
As described above, according to the starter system
20
of the present embodiment, when the reverse torque generated from the engine
1
becomes equal to or larger than the predetermined value immediately after stoppage of the engine
1
or failure in starting the same, the clutch
13
slips to relieve the reverse torque. This makes it possible to prevent excessively large reverse torque from acting on the drive shaft
4
a
of the hydraulic motor
4
as well as to prevent generation of excessively high hydraulic pressure within the oil passage
9
. Thus, the second embodiment can provide the same advantageous effects as obtained from the above first embodiment.
FIG. 3
schematically shows the arrangement of a starter system according to a third embodiment of the invention. As shown in the figure, the starter system
30
of the present embodiment is distinguished from the starter system
10
of the first embodiment in which the solenoid valve
6
opens and closes only the oil passage
9
through which hydraulic pressure is supplied, in that there is provided a solenoid valve
14
which is capable of opening or closing the oil passage
9
and the discharge oil passage
9
c
simultaneously. The third embodiment is similar in construction to the first embodiment except for the above solenoid valve
14
. Therefore, the third embodiment can provide the same advantageous effects as obtained from the above first embodiment. Further, since the oil passage
9
and the discharge oil passage
9
c
can be held in respective closed states simultaneously, it is possible to reduce time wasted before re-start of rotation of the hydraulic motor
4
when it is driven again.
FIG. 4
schematically shows the arrangement of a variation of the third embodiment. In the following description as well, component parts and elements similar or equivalent to those of the first embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. As shown in the figure, the starter system
40
is distinguished from the
FIG. 3
starter system
30
of the constant-mesh type, in that it is a plunging-type which starts the engine
1
by causing a pinion gear
19
to plunge into a ring gear
22
integrally formed with the crankshaft
2
of the engine
1
. Further, the starter system
30
uses the hydraulic motor
4
and an electric motor
15
in combination. The driving forces from the motors
4
,
15
are selectively transmitted to the engine
1
via a planetary gear set
17
to thereby start the engine
1
.
The pinion gear
19
is fitted on an output shaft
25
such that it can move axially and rotate in unison with the output shaft
25
, and axially driven by a magnet switch
18
when the engine
1
is started. The drive shaft
4
a
of the hydraulic motor
4
extends in parallel with the output shaft
25
and is connected to the output shaft
25
via an output gear
4
b
integrally formed with the drive shaft
4
a
, a carrier
17
b
of the planetary gear set
17
, a ring gear
17
a
, and a one-way clutch
23
. Further, a drive shaft
15
a
of the electric motor
15
is arranged such that it extends coaxially with the output shaft
25
, and fixed to a sun gear
17
c
of the planetary gear set
17
and also connected to the output shaft
25
via the carrier
17
b
, the ring gear
17
a
, and the one-way clutch
23
. The starter system
40
has the same construction as the
FIG. 3
starter system except for the above points.
When the engine
1
is to be started by the hydraulic motor
4
, the magnet switch
18
is driven to bring the pinion gear
19
into meshing engagement with the ring gear
22
, and at the same time the hydraulic motor
4
is driven for rotation by hydraulic pressure supplied from a hydraulic motor-driving mechanism
24
. The rotation of the hydraulic motor
4
is transmitted to the ring gear
22
via the planetary gear set
17
, the pinion gear
19
, and so forth, whereby the engine
1
is started. At this time, the drive shaft
15
a
of the electric motor
15
is locked by a one-way clutch
16
, so that the sun gear
17
c
is fixed held immovable.
On the other hand, when the engine
1
is to be started by the electric motor
15
, the oil passage
9
, via which hydraulic pressure is supplied to the hydraulic motor
4
, and the discharge oil passage
9
c
are closed by the solenoid valve
14
simultaneously to completely cut off the flow of hydraulic fluid, whereby the drive shaft
4
a
of the hydraulic motor
4
is locked, so that the carrier
17
b
is fixed or made immovable. Thereafter, the same sequence of operations as carried out in the above case of using the hydraulic motor
4
is carried out, whereby the engine
1
is started by the electric motor
15
.
According to the above variation, when the crankshaft
2
is caused to perform reverse rotation by a reaction force generated from the engine
1
due to failure in starting the same, reverse torque generated by the reverse rotation of the crankshaft
2
is transmitted to the drive shaft
4
a
of the hydraulic motor
4
via the ring gear
22
, the pinion gear
19
, the one-way clutch
23
, and the carrier
17
b
of the planetary gear set
17
to cause reverse rotation of the drive shaft
4
a
. As a result, the hydraulic motor
4
acts as a hydraulic pump to increase hydraulic pressure within the oil passage
9
. Particularly when the start of the engine
1
by the electric motor
15
fails, since the oil passage
9
and the discharge oil passage
9
c
are each held in a closed state by the solenoid valve
14
, an excessively high hydraulic pressure is likely to be generated within the closed oil passage
9
. However, in the present variation, similarly to the above embodiment, when the hydraulic pressure within the oil passage
9
becomes equal to or higher than the predetermined pressure level, it is possible to open the branch oil passage
9
a
by the relief valve
12
to thereby relieve the hydraulic pressure, and hence generation of the excessively high hydraulic pressure can be prevented.
As described above, according to the starter system
40
, in which the electric motor
15
and the hydraulic motor
4
are selectively operated by using the plunging mechanism and the planetary gear set
17
, the operation of the relief valve
17
provides the same effects as obtained by the third embodiment.
Although in the second embodiment, when the reverse torque equal to or larger than the predetermined value acts on the hydraulic motor
4
, the clutch
13
is caused to slip to prevent the reverse torque from being further increased, this is not limitative, but in this case, the clutch may be disengaged.
Next, a fourth embodiment of the invention will be described.
FIG. 5
schematically shows the arrangement of a starter system of the present embodiment. The engine
101
has a crankshaft
102
on which a flywheel
103
is rigidly fitted. The flywheel
103
has a ring gear
104
a
integrally formed around a peripheral surface thereof.
The starter system
50
includes the ring gear
104
(driven gear), a pinion gear
112
(driving gear) fitted on an output shaft
113
, a magnet switch
114
for moving the pinion gear
112
toward the ring gear
104
when the engine is started so as to bring the pinion gear
112
into meshing engagement with the ring gear
104
, a hydraulic motor
115
(hydraulic actuator) for driving the pinion gear
112
for rotation when the engine
1
is started, a hydraulic motor-driving mechanism
116
for driving the hydraulic motor
115
, an electric motor
117
for auxiliary drive, a planetary gear set
118
for transmitting respective driving forces from the hydraulic motor
115
and the electric motor
117
to the output shaft
113
, and an ECU, not shown, for controlling operations of the hydraulic motor
115
and other devices.
The pinion gear
112
is formed by a helical gear meshable with the ring gear
104
. The pinion gear
112
is rigidly fitted on one end of a pinion shaft
112
a
which is coaxially splined to the output shaft
113
, whereby the pinion gear
112
can rotate in unison with the output shaft
113
and move in the axial direction.
The planetary gear set
118
is comprised of a sun gear
118
a
, a carrier
118
b
, and a ring gear
118
c
, and the three gears
118
a
,
118
b
,
118
c
are set to predetermined gear ratios. The output shaft
113
is connected to the ring gear
118
c
of the planetary gear set
118
via a one-way clutch
119
. The one-way clutch
119
allows transmission of torque only when the ring gear
118
c
drives the output shaft
113
in the direction for starting the engine
101
, whereas when the output shaft
113
is caused to rotate reversely, the clutch
119
cuts off the torque.
The magnet switch
114
is formed by a solenoid including a plunger, an exciting coil, and a return spring, none of which are shown. When the magnet switch
114
is in a non-excited state, the pinion gear
112
is held in a non-engagement position (i.e. a state shown in
FIG. 5
) where the pinion gear
112
is inhibited from meshing with the ring gear
104
. On the other hand, when the magnet switch
114
is excited, the plunger is caused to project to move the pinion shaft
112
a
toward the engine
101
, whereby the pinion gear
112
is displaced to an engagement position, not shown, for meshing engagement with the ring gear
104
.
A rotational shaft
115
a
of the hydraulic motor
115
extends in parallel with the output shaft
113
, and is connected to the carrier
118
b
of the planetary gear set
118
. Further, the rotational shaft
115
a
is provided with a hydraulic motor brake
120
(second fixing means). The hydraulic motor brake
120
has a disk shape, and mechanically locks the rotational shaft
115
a
by sandwiching a disk rotor
120
a
, which rotates in unison with the rotational shaft
115
a
, between pads, not shown, by hydraulic pressure, to thereby fix the carrier
118
b
of the planetary gear set
118
connected to the rotational shaft
115
a.
On the other hand, the electric motor
117
drives the pinion gear
112
for rotation in place of the hydraulic motor
115
to start the engine
101
auxiliarily, e.g. when the engine
101
is in a very low-temperature condition. A rotational shaft
117
a
of the electric motor
117
extends coaxially with the output shaft
113
, and is connected to the sun gear
118
a
of the planetary gear set
118
. The rotational shaft
117
a
also protrudes from the electric motor
117
in the direction away from the planetary gear set
118
, and has an electric motor brake
121
(first fixing means) provided at an end thereof. Similarly to the hydraulic motor brake
20
, the electric motor brake
121
has a disk shape, and mechanically locks the rotational shaft
117
a
by sandwiching a disk rotor
121
a
integrally formed with the rotational shaft
117
a
, between pads, not shown, to thereby fix the sun gear
118
a
of the planetary gear set
118
.
The hydraulic motor-driving mechanism
116
includes an oil pump
122
, an electric motor
123
for driving the oil pump
122
for pressure accumulation, and an accumulator
124
for accumulating hydraulic pressure boosted by the oil pump
122
. The oil pump
122
is directly connected to a rotational shaft
123
a
of the electric motor
123
, with a suction port thereof connected to a reserve tank
125
and a discharge port thereof connected to an inlet port
115
c
of the hydraulic motor
115
via an oil passage
126
provided with a check valve
127
. A branch passage
126
a
branches from a portion of the oil passage
126
at a location downstream of the check valve
127
. The accumulator
124
is arranged in the branch passage
126
a
. According to the construction described above, when the electric motor
123
is operated, the oil pump
122
is driven thereby to boost hydraulic pressure and supply the boosted hydraulic pressure to the accumulator
124
via the check valve
127
, whereby the hydraulic pressure is accumulated in the accumulator
124
.
Further, the oil passage
126
has a solenoid valve
128
arranged therein at a location between the accumulator
124
and the hydraulic motor
115
. The solenoid valve
128
is a normally-closed type. More specifically, in a non-excited state, the solenoid valve
128
closes the oil passage
126
, and whereas when excited, it opens the oil passage
126
to allow the hydraulic pressure accumulated in the accumulator
124
to be supplied to the hydraulic motor
115
. Oil supplied to the hydraulic motor
115
is returned to the reserve tank
125
via a discharge port
115
d
of the hydraulic motor
115
and a return oil passage
129
.
The respective operations of the magnet switch
114
, the electric motors
117
,
123
, the hydraulic motor brake
120
, the electric motor brake
121
, and the solenoid valve
128
are controlled by drive signals from the ECU in response to an operating status of an ignition key, not shown, and the like.
Next, the operation of the starter system
50
constructed as above will be described. First, when the engine
101
is in operation, the solenoid valve
128
is held in a non-excited state, and the electric motor
123
is driven under predetermined conditions to operate the oil pump
122
, whereby hydraulic pressure boosted by the oil pump
122
is accumulated in the accumulator
124
. After stoppage of the engine
101
, the hydraulic pressure stored in the accumulator
124
is preserved by the check valve
127
.
When the engine
101
is to be started by the hydraulic motor
115
, the magnet switch
114
is driven to shift the pinion gear
112
to the engagement position for meshing engagement with the ring gear
104
, and at the same time the solenoid valve
128
is excited to open the oil passage
126
. This allows the hydraulic pressure to be supplied from the accumulator
124
to the hydraulic motor
115
to drive the same for rotation. Further, simultaneously with the above control operation, the electric motor brake
121
is driven to lock the rotational shaft
117
a
of the electric motor
117
. This causes the sun gear
118
a
of the planetary gear set
118
connected to the rotational shaft
117
a
to be made immovable, and at the same time the rotation of the rotational shaft
115
a
of the hydraulic motor
115
is transmitted from the carrier
118
b
to the ring gear
118
c
at an increased rotational speed increased at an overdrive ratio corresponding to the gear ratio of the planetary gear set
118
.
The rotation or torque of the ring gear
118
c
is transmitted to the output shaft
113
via the one-way clutch
119
, and then transmitted to the ring gear
104
via the pinion gear
112
, whereby the engine
101
is started. After the engine
101
has been started and the rotational speed of the ring gear
104
has risen to exceed that of the pinion gear
112
, the one-way clutch
119
operates to cause the output shaft
113
to perform idle or free rotation, so that torque from the engine
101
is transmitted neither to the ring gear
118
c
nor to the hydraulic motor
115
.
On the other hand, when the electric motor
117
is used to start the engine
101
, the magnet switch
114
and the electric motor
117
are driven with the solenoid valve
128
held in the non-excited state, and at the same time the hydraulic motor brake
120
is driven to lock the rotational shaft
115
a
of the hydraulic motor
115
. As a result, the carrier
118
b
of the planetary gear set
118
connected to the rotational shaft
115
a
is made immovable, and at the same time, the rotation of the rotational shaft
117
a
of the electric motor
117
is transmitted from the sun gear
118
a
to the ring gear
118
c
at a reduced rotational speed reduced at a reduction ratio corresponding to the gear ratio of the planetary gear set
118
. Thereafter, similarly to the above case of the hydraulic motor
115
being used to start the engine
101
, the torque of the ring gear
118
c
is transmitted to the ring gear
104
via the one-way clutch
119
, the output shaft
113
and the pinion gear
112
, whereby the engine
101
is started. After the engine
101
has been started, torque from the engine
101
is cut off by the one-way clutch
119
, but transmitted neither to the ring gear
118
c
nor to the hydraulic motor
115
.
As described above, according to the present embodiment, respective driving forces of the hydraulic motor
115
and the electric motor
117
can be selectively output to the output shaft
113
via the planetary gear set
118
without interference between the motors, at the respective overdrive and reduction ratios. In short, the planetary gear set
118
functions not only as a driving force-transmitting mechanism, but also as an overdrive/reduction mechanism for the hydraulic motor
115
and the electric motor
117
, and hence it is possible to manufacture the starter system
50
compact in size at a reduced cost. Further, since the output shaft
113
is connected to the ring gear
118
c
of the planetary gear set
118
, the electric motor
117
to the sun gear
118
a
, and the hydraulic motor
115
to the carrier
118
b
, torque from the electric motor
117
can be transmitted to the output shaft
113
at a reduced rotational speed, while torque from the hydraulic motor
115
can be transmitted to the same at an increased rotational speed. Therefore, the starter system
50
can be easily selectively placed in respective operative statuses in which the rotational speed of the output shaft is increased and decreased, in a manner adapted to the respective torque characteristics of the hydraulic motor
115
and the electric motor
117
.
Further, the switching between outputs of the respective driving forces of the electric motor
117
and the hydraulic motor
115
can be carried out easily and reliably by mechanically locking the rotational shaft
115
a
of the hydraulic motor
115
by the hydraulic motor brake
120
or the rotational shaft
117
a
of the electric motor
117
by the electric motor brake
121
, and thereby making immovable the carrier
118
b
or the sun gear
118
a.
FIG. 6
shows a variation of the fourth embodiment. It should be noted that in the following description, component parts and elements similar or equivalent to those of the fourth embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. As shown in the figure, the starter system
60
is distinguished from the starter system
50
of the fourth embodiment in that it has a solenoid switch valve
142
(second fixing means) in place of the hydraulic motor brake
120
and the solenoid valve
128
, and that it has a one-way clutch
143
(first fixing means) mounted to the rotational shaft
117
a
of the electric motor
117
in place of the electric motor brake
121
. The present variation is similar in construction to the fourth embodiment except for the above points.
The solenoid switch valve
142
is a normally-closed type which is arranged in respective intermediate portions of the oil passage
126
and the return oil passage
129
such that the two oil passages
126
and
129
extend through the solenoid switch valve
142
. In a non-excited state, the solenoid switch valve
142
closes the oil passages
126
and
129
simultaneously, while in an excited state, it opens the oil passages
126
and
129
simultaneously. The one-way clutch
143
performs idle or free rotation when the electric motor
117
is driven in the direction for starting the engine
101
, whereas when the electric motor
117
is caused to perform reverse rotation, the one-way clutch
143
locks the rotational shaft
117
a.
The starter system
60
starts the engine
1
by the following starting operations: When the engine
101
is to be started by the hydraulic motor
115
, the magnet switch
114
is driven, and at the same time the solenoid switch valve
142
is excited to open the oil passage
126
and the return oil passage
129
. As a result, hydraulic pressure is supplied from the accumulator
124
via the oil passage
126
, whereby the hydraulic motor
115
is driven for rotation. At this time, the rotational shaft
117
a
of the electric motor
117
is locked by the one-way clutch
143
, whereby the sun gear
118
a
is fixed or made immovable. Thereafter, the starter system
60
operates similarly to the starter system
50
of the fourth embodiment, whereby the engine
101
is started by the hydraulic motor
115
.
On the other hand, when the engine
101
is to be started by the electric motor
117
, the electric motor
117
is driven, with the solenoid switch valve
142
held in the non-excited state. As a result, the oil passage
126
and the return oil passage
129
are both closed simultaneously, and the flows of oil in the two oil passages
126
,
129
are cut off completely. This causes the rotational shaft
115
a
of the hydraulic motor
115
to be locked, whereby the carrier
118
b
is fixed or made immovable. Thereafter, the starter system
60
operates similarly to the starter system
50
of the fourth embodiment, whereby the engine
101
is started by the electric motor
117
.
As described above, according to the starter system
60
, since the electric motor brake
121
in the fourth embodiment is replaced by the one-way clutch
143
, control of the electric motor brake
121
by the ECU can be dispensed with, which makes it possible to simplify the control system. Further, it is possible to substitute the solenoid switch valve
142
for the solenoid valve
128
in the fourth embodiment, and dispense with the hydraulic motor brake
120
at the same time, which contributes to further reduction of the size and manufacturing costs of the starter system.
Although not shown, the hydraulic motor brake
120
may also be replaced by a one-way clutch. Further, the electric motor
117
may be electrically locked, whereby the electric motor brake
121
and the one-way clutch
143
may be omitted.
FIG. 7
schematically shows the arrangement of a starter system according to a fifth embodiment of the invention. As shown in the figure, in the starter system
70
of the present embodiment, the check valve
127
and the solenoid valve
128
are arranged in parallel with each other in an intermediate portion of the oil passage
126
, and the oil pump
122
and the electric motor
123
in the fourth embodiment are omitted. The output shaft
113
is provided with an output shaft brake
152
(third fixing means). Similarly to the
FIG. 6
variation, the electric motor
117
is provided with the one-way clutch
143
in place of the electric motor brake
121
.
The output shaft
113
is connected to the pinion shaft
112
a
via a helical spline
153
, and a one-way clutch
154
for prevention of overrun, and the magnet switch
114
in the fourth embodiment is omitted. More specifically, in this plunging mechanism, when the output shaft
113
is driven for rotation at the start of the engine, the helical spline
153
displaces the pinion shaft
112
a
to bring the pinion gear
112
into meshing engagement with the ring gear
104
. Except during the start of the engine, the pinion gear
112
is always held in the non-engagement position (i.e. a state shown in
FIG. 7
) by a return spring, not shown. The one-way clutch
154
is provided for preventing overrun of the output shaft
113
after the start of the engine
101
. The fifth embodiment is similar in construction to the fourth embodiment except for the above points.
The operation of the starter system
70
is as follows. First, when the engine
101
is to be started by the hydraulic motor
115
, the solenoid valve
128
is excited. As a result, the hydraulic motor
115
is driven, and torque therefrom is transmitted to the output shaft
113
via the planetary gear set
118
with its sun gear
118
a
being fixed by the one-way clutch
154
, and at the same time the pinion gear
112
is brought into meshing engagement with the ring gear
104
as described above, whereby the engine
101
is started. On the other hand, when the engine
101
is to be started by the electric motor
117
, the electric motor
117
is driven with the solenoid valve
128
held in the non-excited state, and the hydraulic motor brake
120
is driven at the same time. As a result, the carrier
118
b
is fixed or made immovable, and torque from the electric motor
117
is transmitted to the output shaft
113
via the planetary gear set
118
, whereby the engine
101
is started.
Further, when hydraulic pressure is to be accumulated in the accumulator
124
, the electric motor
117
is driven with the solenoid valve
128
held in the non-excited state, and the output shaft brake
152
is driven at the same time. This causes the output shaft
113
to be locked, and the ring gear
118
c
of the planetary gear set
118
to be fixed or made immovable, whereby torque from the electric motor
117
is transmitted to the hydraulic motor
115
via the sun gear
118
a
and the carrier
118
b
to cause the rotational shaft
115
a
of the hydraulic motor
115
to rotate in a direction opposite to that of rotation thereof for starting the engine. As a result, hydraulic pressure boosted by the reverse rotation of the hydraulic motor
115
is supplied via the inlet port
115
c
, the oil passage
126
and the check valve
127
to the accumulator
124
, and accumulated therein.
As described above, according to the starter system
70
of the present embodiment, it is possible to accumulate hydraulic pressure in the accumulator
124
by driving the electric motor
117
in the state of the ring gear
118
c
of the planetary gear set
118
being fixed by the output shaft brake
152
, and thereby causing the hydraulic motor
115
to rotate in the direction opposite to that of rotation thereof for starting the engine. As a result, the oil pump
122
and the electric motor
123
used for pressure accumulation in the fourth embodiment can be omitted, which contributes to further reduction of the size and manufacturing costs of the starter system.
Although not shown, a one-way clutch may be employed as third fixing means for locking the output shaft
113
, in place of the output shaft brake
152
, or alternatively, the spring force of the return spring of the plunging mechanism may be utilized to cause engaging means, such as a dog clutch, to be engaged with the output shaft
113
to thereby lock the same. This makes it possible to lock the output shaft
113
without executing electrical control. Further, it is also possible to use the solenoid switch valve used in the
FIG. 6
variation for opening/closing the oil passage
126
and the return oil passage
129
simultaneously, in place of the hydraulic motor brake
120
, to lock the hydraulic motor
115
. Moreover, another type of fixing means may be employed in place of the one-way clutch
143
in the fifth embodiment so as to use the hydraulic motor
115
as an oil pump. In this case, the hydraulic motor
115
may be formed by a swash plate motor equipped with a rotation-reversing mechanism, and the electric motor
123
is caused to rotate in a direction opposite to that of rotation thereof for starting the engine, to thereby cause the hydraulic motor
115
to rotate in the same direction as it rotates at the start of the engine.
Next, a sixth embodiment of the invention will be described.
FIG. 8
schematically shows the arrangement of a starter system of the present embodiment. Reference numeral
201
designates an engine (ENG). The engine
201
has a crankshaft
202
thereof on which a flywheel
203
is rigidly fitted. The flywheel
203
has a ring gear
204
integrally formed around a peripheral surface thereof.
On the other hand, the starter system
80
includes the ring gear
204
(driven gear), a pinion gear
212
(driving gear), an output shaft
213
(third rotational shaft) having one end thereof connected to the pinion gear
212
, a magnet switch (MG.SW)
214
for moving the pinion gear
212
toward the ring gear
204
at the start of the engine so as to bring the pinion gear
212
into meshing engagement with the ring gear
204
, a hydraulic motor
215
(hydraulic actuator) for driving the pinion gear
212
for rotation at the start of the engine, a hydraulic motor-driving mechanism
216
for driving the hydraulic motor
215
, an electric motor
217
for auxiliary drive, and an ECU
205
for controlling operations of the hydraulic motor
215
and other devices.
The pinion gear
212
is formed by a helical gear meshable with the ring gear
204
. The pinion gear
212
is rigidly fitted on one end portion of a pinion shaft
212
a
which is coaxially splined to the output shaft
213
, whereby the pinion gear
212
is coupled to the output shaft
213
such that the pinion gear
212
can rotate in unison with the output shaft
213
and at the same time move in the axial direction.
The magnet switch
214
is formed by a solenoid comprised of a plunger
214
a
, and an exciting coil and a return spring incorporated therein, neither of which is shown. The plunger
214
a
extends coaxially with the output shaft
213
. According to this construction, when the magnet switch
214
is in a non-excited state, the plunger
214
a
is axially opposed to the pinion shaft
212
a
of the pinion gear
212
with a space therebetween, whereby the pinion gear
212
is held in a non-engagement position (i.e. a state shown in
FIG. 8
) where the pinion gear
212
is inhibited from meshing with the ring gear
204
. On the other hand, when the magnet switch
214
is excited, the plunger
214
a
is caused to project to urge the pinion shaft
212
a
toward the engine
201
, whereby the pinion gear
212
is driven to an engagement position, not shown, for meshing engagement with the ring gear
204
.
The hydraulic motor
215
is a swash-plate type, for instance, and driven by hydraulic pressure supplied from the hydraulic motor-driving mechanism
216
. The hydraulic motor
215
has a rotational shaft
215
a
(first rotational shaft) thereof extending in parallel with the output shaft
213
and connected to the same via an overdrive gear train
218
comprised of an output gear
215
b
integrally formed with the rotational shaft
215
a
and intermediate gears
218
a
,
218
b
, and a first one-way clutch
219
(first driving force-transmitting mechanism). The first one-way clutch
219
is configured such that it allows transmission of torque only when the hydraulic motor
215
is driven to drive the output shaft
213
, but cuts off torque when the rotational relationship is opposite to this.
On the other hand, the electric motor
217
drives the pinion gear
212
for rotation in place of the hydraulic motor
215
to perform the operation for starting the engine
201
auxiliarily when the starting of the engine
201
by the hydraulic motor
215
is disabled or unsuitable. For instance, when the engine
201
is in a very low-temperature condition, the startability of the engine
201
is low due to an increase in friction of the same, so that it takes time to complete starting of the engine
201
. The hydraulic motor
215
, however, can provide torque only for a relatively short time period due to its construction, and cannot ensure stable starting of the engine
201
. To overcome the problem, the electric motor
217
is used in starting the engine
201
. A rotational shaft
217
a
of the electric motor
217
extends in parallel with the output shaft
213
and the rotational shaft
215
a
of the hydraulic motor
215
, and connected to the output shaft
213
via a reduction gear train
220
comprised of an output gear
217
b
integrally formed with the rotational shaft
217
a
, and intermediate gears
220
a
,
220
b
, and a second one-way clutch
221
(second driving force-transmitting mechanism). Similarly to the first one-way clutch
219
, the second one-way clutch
221
is configured such that it allows transmission of torque only when the electric motor
217
is driven to drive the output shaft
213
.
The hydraulic motor-driving mechanism
216
includes an oil pump
222
, an electric motor
223
for driving the oil pump
222
for pressure accumulation, and an accumulator
224
for accumulating hydraulic pressure boosted by the oil pump
222
. The oil pump
222
is directly connected to a rotational shaft
223
a
of the electric motor
223
, with a suction port thereof connected to a reserve tank
225
and a discharge port thereof connected to an inlet port
215
c
of the hydraulic motor
215
via an oil passage
226
provided with a check valve
227
. A branch passage
226
a
branches from a portion of the oil passage
226
at a location downstream of the check valve
227
. The accumulator
224
is arranged in the branch passage
226
a
. According to the construction described above, when the electric motor
223
is operated, the oil pump
222
is driven to boost hydraulic pressure and supply the boosted hydraulic pressure to the accumulator
224
via the check valve
227
, whereby the hydraulic pressure is accumulated in the accumulator
224
.
Further, a solenoid valve
228
is arranged in the oil passage
226
at a location between the accumulator
224
and the hydraulic motor
215
. The solenoid valve
228
is a normally-closed type. More specifically, in a non-excited state, the solenoid valve
228
closes the oil passage
226
, and when excited by a drive signal from the ECU
205
, it opens the oil passage
226
to allow the hydraulic pressure accumulated in the accumulator
224
to be supplied to the hydraulic motor
215
. Oil supplied to the hydraulic motor
215
is returned to the reserve tank
225
via a discharge port
215
d
of the hydraulic motor
215
and a return oil passage
229
. Further, a hydraulic sensor
230
is inserted in the branch passage
226
a
, for detecting a hydraulic pressure POIL within the accumulator
224
and delivering a signal indicative of the sensed hydraulic pressure POIL to the ECU
205
.
The ECU
205
is formed by a microcomputer including an I/O interface, a CPU, a RAM, and a ROM, none of which are shown. The ECU
205
delivers drive signals to the magnet switch
214
, the electric motors
217
,
223
and the solenoid valve
228
in response to an operating status of an ignition key, not shown, and signals from the hydraulic sensor
230
and the like, to thereby control respective operations of these devices.
Next, the operation of the starter system
80
constructed as above will be described. First, during operation of the engine
201
, when the hydraulic pressure POIL within the accumulator
224
, which is detected by the hydraulic sensor
230
, has become equal to or lower than a predetermined level POILL, the electric motor
223
is driven to operate the oil pump
222
, whereby hydraulic pressure boosted by the oil pump
222
is accumulated in the accumulator
224
. It should be noted that the predetermined level POILL is set e.g. to a level high enough to drive the hydraulic motor
215
. On the other hand, when the hydraulic pressure POIL has reached a predetermined upper limit level POILH higher than the predetermined level POILL, the operations of the electric motor
223
and the oil pump
222
are stopped. Thus, when the engine
201
is in operation, the hydraulic pressure POIL within the accumulator
224
is increased to a level high enough to drive the hydraulic motor
215
, while after stoppage of the engine
201
, the hydraulic status is maintained by the check valve
227
.
When the engine
201
is to be started by the hydraulic motor
215
, the magnet switch
214
is driven to shift the pinion gear
212
to the engagement position for meshing engagement with the ring gear
204
, and at the same time the solenoid valve
228
is excited to open the oil passage
226
. As a result, hydraulic pressure is supplied from the accumulator
224
to the hydraulic motor
215
to drive the hydraulic motor
215
for rotation. The rotation of the hydraulic motor
215
is increased by the overdrive gear train
218
, and then transmitted to the output shaft
213
via the first one-way clutch
219
. As a result, the pinion gear
212
rotates in unison with the output shaft
213
to cause rotation of the ring gear
204
, whereby the engine
201
is started. In this case, since the second one-way clutch
221
is arranged between the output shaft
213
and the rotational shaft
217
a
of the electric motor
217
, transmission of the driving force from the output shaft
213
to the electric motor
217
is completely inhibited.
On the other hand, when the engine
201
is to be started by the electric motor
217
, the electric motor
217
is driven with the solenoid valve
228
held in the non-excited state. The rotation of the electric motor
217
is reduced by the reduction gear train
220
, and then transmitted to the output shaft
213
via the second one-way clutch
221
. As a result, the ring gear
204
is caused to rotate to start the engine
201
. In this case as well, since the first one-way clutch
219
is arranged between the output shaft
213
and the hydraulic motor
215
, transmission of the driving force from the output shaft
213
to the hydraulic motor
215
is completely inhibited. Further, after the engine
201
has been started and the rotational speed of the ring gear
204
has risen to exceed that of the pinion gear
212
, the first and second one-way clutches
219
,
221
cause only the output shaft
213
to perform idle or free rotation, so that the driving force of the engine
201
is transmitted neither to the hydraulic motor
215
nor to the electric motor
217
.
As described above, according to the present embodiment, the hydraulic motor
215
and the electric motor
217
are arranged such that the rotational shaft
215
a
of the hydraulic motor
215
and the rotational shaft
217
a
of the electric motor
217
extend in parallel with each other, and respective driving forces of the hydraulic motor
215
and the electric motor
217
are selectively transmitted to the output shaft
213
via the first and second one-way clutches
219
,
221
to start the engine
201
. Therefore, whichever of the two motors
215
and
217
may be used, the engine
201
can be started by operating one of them independently of the other without causing any rotation of the other motor, i.e. in a state of transmission of driving force between the two motors being completely inhibited. This makes it possible to prevent wear of a brush of the electric motor
217
due to the use of the electric motor
217
in combination with the hydraulic motor
215
, and an increase in rotational resistance due to friction resulting from the wear of the brush. Further, it is not necessary to provide an extra design so as to increase the robustness of the electric motor
217
to adapt the same to the high rotational speed characteristic of the hydraulic motor
215
. Moreover, even when one of the hydraulic motor
215
and the electric motor
217
is disabled, e.g. due to an immovable operative status of the electric motor
217
or a condition unsuitable for the starting by the hydraulic motor, such as a very low temperature, it is possible to use the other to start the engine without any difficulty.
Furthermore, according to the present embodiment, since the rotational shaft
215
a
of the hydraulic motor
215
and the rotational shaft
217
a
of the electric motor
217
are connected to the output shaft
213
via the respective first and second one-way clutches
219
,
221
, it is possible to start the engine
201
by using one of the hydraulic motor
215
and the electric motor
217
and at the same time hold the other in a disconnected state by the simple construction, easily without any need to execute control operation therefor.
FIG. 9
schematically shows the arrangement of a starter system according to a seventh embodiment of the invention. It should be noted that in the following description, component parts and elements similar or equivalent to those of the sixth embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. As shown in the figure, the starter system
90
is distinguished from the starter system
80
of the sixth embodiment in that the first and second one-way clutches
219
,
221
are arranged, respectively, coaxially with the rotational shaft
215
a
of the hydraulic motor
215
and the rotational shaft
217
a
of the electric motor
217
.
More specifically, the hydraulic motor
215
employed in the present embodiment is a higher-speed (smaller-sized) type than that in the sixth embodiment, and connected to the output shaft
213
via the first one-way clutch
219
provided on the rotational shaft
215
a
of the hydraulic motor
215
, and a constant-speed gear train
232
comprised of an output gear
232
a
integrally formed with the first one-way clutch
219
and an input gear
232
b
integrally formed with the output shaft
213
. On the other hand, the rotational shaft
217
a
of the electric motor
217
is connected to the output shaft
213
via the second one-way clutch
221
provided on the rotational shaft
217
a
, and a reduction gear train
233
comprised of an output gear
233
a
integrally formed with the second one-way clutch
221
, an intermediate gear
233
b
, and an input gear
233
c
integrally formed with the output shaft
213
. The seventh embodiment is similar in construction to the sixth embodiment except for the above points.
Therefore, according to the present embodiment, similarly to the sixth embodiment, the driving forces of the rotational shaft
215
a
of the hydraulic motor
215
and the rotational shaft
217
a
of the electric motor
217
extending in parallel with each other are selectively transmitted to the output shaft
213
via the respective first and second one-way clutches
219
,
221
in a state of transmission of the driving forces between the two motors being completely inhibited, to thereby start the engine
201
, and hence it is possible to provide the same advantageous effects as obtained by the above sixth embodiment.
It should be noted that the arrangement of the magnetic switch
214
, the hydraulic motor
215
and the electric motor
217
with respect to the output shaft
213
is not limited to those shown in
FIGS. 8 and 9
, but lots of variations are possible. Although not shown, for instance, as the hydraulic motor
215
, a high-rotational speed-type hydraulic motor may be employed and arranged coaxially with the output shaft
213
. This makes it possible to dispense with the overdrive gear train
218
, and thereby construct the starter system
80
compact in size. Further, as the electric motor
217
, a low-rotational speed/high output power type may be employed, whereby the electric motor
217
can be arranged coaxially with the output shaft
213
without interposing the planetary gear set between the same and the output shaft
213
. This makes it possible to omit the reduction gear train.
FIG. 10
schematically shows the arrangement of a starter system according to an eighth embodiment of the invention. In the following description as well, component parts and elements similar or equivalent to those of the sixth embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. As shown in the figure, the starter system
100
according to the present embodiment is distinguished from the starter system
80
of the sixth embodiment in the following points: The rotational shaft
217
a
of the electric motor
217
is connected to the oil pump
222
via a first solenoid clutch
242
. Further, the rotational shaft
217
a
of the electric motor
217
extends in parallel with the output shaft
213
and the rotational shaft
215
a
of the hydraulic motor
215
, and a second solenoid clutch
243
(second driving force-transmitting mechanism) is arranged between the reduction gear train
220
and the output shaft
213
, in place of the second one-way clutch
221
of the sixth embodiment. Accordingly, the electric motor
223
used in the sixth embodiment for pressure accumulation is omitted. The operations of the first and second solenoid clutch
242
,
243
are controlled by the ECU
205
. The eighth embodiment is similar in construction to the sixth embodiment except for the above points.
The starter system
100
is operated as follows. First, during operation of the engine
201
, the second solenoid clutch
243
is held in a disengaged state, and when the hydraulic pressure POIL has become equal to or lower than the predetermined level POILL, the electric motor
217
is driven, and at the same time the first solenoid clutch
242
is engaged. This allows torque or rotation of the electric motor
217
to be transmitted to the oil pump
222
via the first solenoid clutch
242
, whereby the oil pump
222
is driven to accumulate hydraulic pressure in the accumulator
224
. On the other hand, when the hydraulic pressure POIL has reached the predetermined upper limit level POILH, the electric motor
217
is stopped and the first solenoid clutch
242
is disengaged. Thus, similarly to the starter system
80
of the sixth embodiment, the hydraulic pressure POIL within the accumulator
224
is preserved at a level high enough to drive the hydraulic motor
215
.
When the engine
201
is to be started by the hydraulic motor
215
, similarly to the sixth embodiment, the magnet switch
214
is driven, the solenoid valve
228
is excited, and at the same time the second solenoid clutch
243
is disengaged. As a result, the engine
201
is started, but the driving force of the output shaft
213
is cut off by the second solenoid clutch
243
, i.e. not transmitted to the electric motor
217
at all. On the other hand, when the engine
201
is to be started by the electric motor
217
, the electric motor
217
is driven, and at the same time the second solenoid clutch
243
is engaged, and the first solenoid clutch
242
is disengaged. As a result, the engine
201
can be started without transmitting the torque of the electric motor
217
to the oil pump
222
or the hydraulic motor
215
. In this case as well, the driving force of the output shaft
213
is cut off by the first one-way clutch
219
, and not transmitted to the hydraulic motor
215
at all.
As described above, according to the starter system
100
, the second driving force-transmitting mechanism for transmitting the driving force from the electric motor
217
to the output shaft
213
is implemented by the second solenoid clutch
243
which is properly controlled by the ECU
205
. Therefore, it is possible to start the engine
201
by the first one-way clutch
219
and the second solenoid clutch
243
, in the state of transmission of the driving forces between the motors
215
,
217
being completely cut off or inhibited. Therefore, the present embodiment can provide the same advantageous effects as obtained by the sixth and seventh embodiments. Further, since the starting of the engine
201
and accumulation of hydraulic pressure in the accumulator
224
can be carried out by the single electric motor
217
, it is possible to make the starter system
100
more compact in size and manufacture the same at a lower cost than the starter system
80
of the sixth embodiment which necessitates two electric motors
217
,
223
.
Although not shown, the first one-way clutch
219
may be replaced by a solenoid clutch which is controlled by the ECU
205
. Alternatively, the first and second solenoid clutches
242
,
243
may be replaced by third and second one-way clutches, respectively, and a rotation-reversing circuit for driving the electric motor
217
in a direction opposite to that of rotation for starting the engine may be provided. In this case, the second one-way clutch allows transmission of torque of the electric motor
217
to the output shaft
213
only when the motor
217
performs normal rotation, while the third one-way clutch allows transmission of torque of the electric motor
217
to the oil pump
222
only when the motor
217
performs reverse rotation. According to this construction, by causing normal and reverse rotations of the electric motor
217
, it is possible to carry out starting of the engine
201
and accumulation of hydraulic pressure in the accumulator
224
, respectively. In short, so long as the driving force-transmitting mechanism is formed such that transmission and interruption of driving forces can be performed to meet requirements of the present embodiment, any device may be substituted for a one-way clutch or a solenoid clutch.
Although in the
FIG. 10
example, the first solenoid clutch
242
and the oil pump
222
are arranged on a side of the electric motor
217
remote from the output shaft
213
, the oil pump
222
may be connected to an idler shaft arranged in parallel between the rotational shaft
217
a
of the electric motor
217
and the output shaft
213
. In this case, the first solenoid clutch
242
is used for engaging or disengaging an idler gear in meshing engagement with the rotational shaft
217
a
and the output shaft
213
, with or from the idler shaft. This construction enables space to be saved and components to be used in a shared manner when an idler gear is required. Further, the first solenoid clutch
242
and the electric motor
217
may be arranged coaxially with each other.
Alternatively, the electric motor
217
may be constantly connected to the oil pump
222
, and at the same time, a passage-switching mechanism may be provided for switching an outlet passage for the flow of oil from the oil pump
222
between the accumulator side and the reserve tank side. According to this construction, it is possible to drive the electric motor
217
and at the same time switch the outlet passage from the oil pump
222
to the accumulator side, thereby accumulating hydraulic pressure in the accumulator
224
. Further, when the engine
201
is to be started by the electric motor
217
, it is possible to switch the outlet passage from the oil pump
222
to the reserve tank side to relieve pressure, thereby reducing load on the electric motor
217
. This construction is advantageous in terms of costs because the driving force-switching means including the expensive first and second solenoid clutches
242
,
243
and the reversing circuit used in the eighth embodiment for enabling the electric motor
217
to be commonly used for the starting of the engine and accumulation of hydraulic pressure can be dispensed with. Further, since the passage-switching mechanism can be arranged separately from the starter mechanism including the magnet switch
214
and the hydraulic motor
215
, the above construction also has an advantage in layout.
FIG. 11
schematically shows the arrangement of a starter system according to a ninth embodiment of the invention. In the following, component parts and elements similar or equivalent to those of the sixth embodiment are designated by identical reference numerals, and detailed description thereof is omitted when deemed proper. As shown in the figure, in the starter system
110
of the present embodiment, the check valve
227
and the solenoid valve
228
are arranged in parallel with each other in an intermediate portion of the oil passage
226
, and the oil pump
222
in the sixth embodiment is omitted. The rotational shaft
217
a
of the electric motor
217
is connected to the output shaft
213
via a planetary gear set
252
and a second one-way clutch
221
.
On the other hand, the rotational shaft
215
a
of the hydraulic motor
215
is connected to the output shaft
213
via a first one-way clutch
253
and a starting gear train
254
comprised of an output gear
253
a
integrally formed with the first one-way clutch
253
, an intermediate gear
254
a
, and a gear
254
b
integrally formed with the output shaft
213
. Further, the rotational shaft
215
a
of the hydraulic motor
215
has a gear
255
a
fitted on one end thereof, while the pinion shaft
212
a
has a gear
255
b
meshable with the gear
255
a
, fitted on one end thereof opposite to the other end thereof on which the pinion gear
212
is fitted. The gears
255
a
,
255
b
form a gear train
255
for use in pressure accumulation, and are in meshing engagement with each other (i.e. a state shown in
FIG. 11
) when the pinion gear
212
is held in the non-engagement position where the pinion gear
212
is inhibited from meshing engagement with the ring gear
204
, whereas when the pinion gear
212
is held in the engagement position, the gears
255
a
,
255
b
are disengaged from each other.
The operation of the starter system
110
is as follows. First, when the engine
201
is to be started by the hydraulic motor
215
, similarly to the sixth and eighth embodiments, the magnet switch
214
is driven, and at the same time the solenoid valve
228
is excited. This brings the pinion gear
212
into meshing engagement with the ring gear
204
, and torque from the hydraulic motor
215
is transmitted to the output shaft
213
via the first one-way clutch
253
and the starting gear train
254
, whereby the engine
201
is started. In this case, when the pinion gear
212
is shifted to the engagement position, the gear train
255
for pressure accumulation is brought into the disengaged state, so that the gear train
255
does not have any influence on the starting of the engine
201
. Further, the driving force from the hydraulic motor
215
is cut off by the second one-way clutch
221
, and not transmitted to the electric motor
221
at all.
On the other hand, when the engine
201
is to be started by the electric motor
217
, the magnet switch
214
is driven, and at the same time the electric motor
217
is driven with the solenoid valve
228
held in the non-excited state. As a result, torque from the electric motor
217
is transmitted to the output shaft
213
via the planetary gear set
252
and the second one-way clutch
221
, whereby the engine
201
is started. In this case, the disengaged state of the gear train
255
and the first one-way clutch
253
completely prevent the driving force of the electric motor
217
from being transmitted to the hydraulic motor
215
.
During operation of the engine
201
, with the magnet switch
214
held in an inoperative state, and the solenoid valve
228
in the non-excited state, the electric motor
217
is operated when the hydraulic pressure POIL becomes equal to or lower than the predetermined level POILL. As a result, torque of the electric motor
217
is transmitted to the output shaft
213
in the same way as when the engine is started, and then transmitted to the rotational shaft
215
a
of the hydraulic motor
215
via the gear train
255
in the engaged state. The first one-way clutch
253
prevents transmission of the torque from the electric motor
217
to the hydraulic motor
215
via the starting gear train
254
. Accordingly, the hydraulic motor
215
is driven for rotation by the electric motor
217
only via the gear train
255
for pressure accumulation. At this time, the rotational shaft
215
a
rotates in an opposite direction to that of rotation thereof for starting the engine because the number of gear stages of the gear train
254
is different from that of gear stages of the gear train
255
by one. As a result, the hydraulic pressure boosted by the reverse rotation of the hydraulic motor
215
is supplied to the accumulator
224
via the inlet port
215
c
of the hydraulic motor
215
, the oil passage
226
and the check valve
227
, and stored therein. Then, when the hydraulic pressure POIL reaches the upper limit level POILH, the electric motor
217
is stopped.
As described above, in the starter system
110
of the present embodiment as well, the engine
201
can be started in the state of transmission of the driving forces between the two motors
215
,
217
being completely cut off or inhibited by the respective first and second one-way clutches
253
,
221
, so that the present embodiment can provide the same advantageous effects as obtained by the sixth and seventh embodiments. Further, the hydraulic motor
215
can be switched by the starting gear train
254
or the gear train
255
for pressure accumulation, between a state driven for normal rotation by hydraulic pressure from the accumulator
224
, for starting the engine
201
, and a state driven for reverse rotation by the electric motor
217
, for storing hydraulic pressure in the accumulator
224
. As a result, it is possible to omit the oil pump
222
in the sixth embodiment, thereby further reducing the size and manufacturing costs of the starter system
110
. Further, according to the present embodiment, the driving force-switching means including the first and second solenoid clutches employed in the eighth embodiment, for enabling the electric motor
215
to be commonly used for the starting of the engine and the accumulation of hydraulic pressure can be dispensed with, which also makes the starter system
110
advantageous in terms of costs.
Although in the present embodiment, the hydraulic motor
215
is reversely rotated to use the same as the oil pump, this is not limitative, but a swash-plate type hydraulic motor with a rotation-reversing mechanism may be employed as the hydraulic motor, and it may be used for the oil pump without causing the same to be rotated reversely. In this case, the intermediate gear
254
a
for reverse rotation of the hydraulic motor
215
can be dispensed with, and the number of component parts of the starter system can be reduced thereby.
It is further understood by those skilled in the art that the foregoing is a preferred embodiment of the invention, and that various changes and modifications may be made without departing from the spirit and scope thereof.
Claims
- 1. A starter system for an internal combustion engine, for starting the engine by driving a crankshaft for rotation,the starter system comprising: a hydraulic actuator that is driven by hydraulic pressure; a first rotational shaft that is driven for rotation by said hydraulic actuator; an electric motor; a second rotational shaft that extends in parallel with said first rotational shaft and is driven for rotation by said electric motor; a driven gear that rotates in unison with the crankshaft; a driving gear that is brought into meshing engagement with said driven gear when the engine is started; a third rotational shaft that is connected to said driving gear; a first driving force-transmitting mechanism that connects said first rotational shaft and said third rotational shaft to each other in a disconnectable manner, for transmitting rotation of said first rotational shaft to said third rotational shaft; and a second driving force-transmitting mechanism that connects said second rotational shaft and said third rotational shaft to each other in a disconnectable manner, for transmitting rotation of said second rotational shaft to said third rotational shaft.
- 2. A starter system according to claim 1, wherein said first and second driving force-transmitting mechanisms are formed by respective first and second one-way clutches that allow transmission of respective rotations of said first and second rotational shafts to said third rotational shaft only when said first and second rotational shafts rotate in respective directions for driving said third rotational shaft.
- 3. A starter system according to claim 1, including a planetary gear set having a sun gear, a carrier, and a ring gear, said second rotational shaft being connected to one of said sun gear, said carrier, and said ring gear, andwherein said first rotational shaft being connected to another of said sun gear, said carrier, and said ring gear of said planetary gear set, and said third rotational shaft being connected to a remaining one of said sun gear, said carrier, and said ring gear of said planetary gear set.
- 4. A starter system according to claim 3, further comprising first fixing means for fixing said one of said sun gear, said carrier, and said ring gear, to which said second rotational shaft that is driven by said electric motor for rotation is connected, when the engine is to be started by said hydraulic actuator, andsecond fixing means for fixing said another of said sun gear, said carrier, and said ring gear, to which said first rotational shaft that is driven by said hydraulic actuator for rotation is connected, when the engine is to be started by said electric motor.
- 5. A starter system according to claim 4, further comprising an accumulator for storing hydraulic pressure, an oil passage connected to said accumulator, and third fixing means for fixing said remaining one of said sun gear, said carrier and said ring gear, to which said third rotational shaft that is connected to said driven gear is connected, to thereby transmit a driving force of said electric motor to said hydraulic actuator and cause said hydraulic actuator to rotate said first rotational shaft in a direction opposite to a direction in which said first rotational shaft is driven for rotation, to thereby cause the hydraulic pressure to be accumulated in said accumulator via said oil passage.
- 6. A starter system according to claim 3, wherein said third rotational shaft is connected to said ring gear, said second rotational shaft is connected to said sun gear, and said first rotational shaft is connected to said carrier.
- 7. A starter system according to claim 1, further comprising a hydraulic pressure supply control valve arranged in said oil passage connected to said hydraulic actuator, for controlling the hydraulic pressure to be supplied to said hydraulic actuator via said oil passage, anda torque limiter mechanism for suppressing an increase in the hydraulic pressure when a reverse torque equal to or larger than a predetermined value and acting in a direction opposite to a direction for starting the engine acts on said hydraulic actuator during stoppage of rotation of the engine.
- 8. A starter system according to claim 7, wherein said torque limiter mechanism is a relief valve arranged in said oil passage, for opening said oil passage when the hydraulic pressure in said oil passage becomes equal to or larger than a predetermined pressure corresponding to the reverse torque equal to or larger than the predetermined value.
- 9. A starter system according to claim 7, wherein said torque limiter mechanism is a clutch arranged between the engine and said hydraulic actuator, for suppressing an increase in the reverse torque transmitted from the engine to said hydraulic actuator, when the reverse torque becomes equal to or larger than the predetermined value.
- 10. A starter system according to claim 1, further comprising a discharge oil passage for discharging the hydraulic pressure from said hydraulic actuator, andwherein said hydraulic pressure supply control valve can open or close said oil passage and the discharge oil passage simultaneously.
Priority Claims (3)
Number |
Date |
Country |
Kind |
2001-141657 |
May 2001 |
JP |
|
2001-161367 |
May 2001 |
JP |
|
2001-213429 |
Jul 2001 |
JP |
|
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
2200781 |
Smith |
May 1940 |
A |
6460500 |
Ooyama et al. |
Oct 2002 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
01138369 |
May 1989 |
JP |