Information
-
Patent Grant
-
6247439
-
Patent Number
6,247,439
-
Date Filed
Friday, October 15, 199925 years ago
-
Date Issued
Tuesday, June 19, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Birch, Stewart, Kolasch & Birch, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 1855
- 123 1856
- 123 1858
- 074 6
- 074 7 C
- 074 7 E
- 074 411
- 074 412 TA
- 074 414
- 029 8931
- 029 8932
-
International Classifications
-
Abstract
To provide a starter for an internal combustion engine which is capable of reducing a press-fit amount of a press-fit portion of a torque absorbing mechanism of a rotation transmitting means for transmitting the rotation of a kick shaft to a crank shaft, thereby enhancing the durability of the starter and making the starter compact. A kick-type starter for an internal combustion engine includes a rotation transmitting mechanism (a kick drive gear, a boss having a ratchet portion, a pinion gear, and an idler gear) for transmitting the rotation of a kick shaft to a crank shaft. The rotation transmitting mechanism is provided with a torque absorbing mechanism for absorbing an excessive torque due to an excessive input from the kick shaft. The torque absorbing mechanism is provided on the kick shaft, and includes a gear set composed of the boss having the ratchet and the pinion gear which are press-fitted to each other. At least one of the press-fit surface of the boss having the ratchet and the press-fit plane of the pinion gear is subjected to a low temperature sulphurizing treatment.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a starter for an internal combustion engine, and more particularly to a starter for an internal combustion engine, in which a rotation transmitting mechanism for transmitting the rotation of an input portion to a crank shaft is provided with a torque absorbing mechanism.
2. Description of Background Art
A kick type starter of an internal combustion engine mounted on a motorcycle is configured such that an actuated force of a kick pedal is converted into a kick shaft rotating force by a kick pedal shaft and the rotation of the kick shaft is transmitted to a crank shaft via a rotation transmitting mechanism. The rotation transmitting mechanism is composed of a kick drive gear, ratchet portion formed on a pinion gear, a pinion gear, gear train connected to a counter shaft and a main shaft of a transmission, and a primary reduction drive gear connected to the crank shaft.
Since the crank shaft is in a stopped state when the kick pedal is actuated, a large torque is applied to the gears of the rotation transmitting mechanism. Because of not only the excessively increased torque due to actuation of the kick pedal but also the occurrence of a compressive reaction upon upward movement of a piston during the kick operation or abnormality of an ignition timing, an excessive torque may be applied to the gears of the rotation transmitting mechanism during the starting operation. In the prior art rotation transmitting mechanism, the size and strength of each gear have been set in consideration of the above-described excessive torque applied to the gear.
A starter for starting an engine of a motorcycle, including a damper device for absorbing an excessive torque caused upon starting the engine, has been disclosed in Japanese Utility Model Publication No. Sho 63-16863. The starter is of a type using a starter motor, in which the rotation of the starter motor is transmitted to a crank shaft from a reduction gear through a starter, driven gear, characterized in that damper springs are contracted between a clutch outer and a clutch inner of an over-running clutch for absorbing an excessive torque caused upon starting the engine, on the other hand, a technique concerned with a drive shaft of a motorcycle and a gear press-fitted around the drive shaft has been disclosed, in Japanese Patent Publication No., Hei 4-16649. In this technique, one of contact surfaces (press-fit surfaces) of the drive shaft and the gear is subjected to a low temperature sulphurizing treatment for suitably setting a slip generating torque between both the members, thereby damping a reaction force from a tread or the like caused upon power transmission.
The starter described in Japanese Utility Model Publication No. Sho 63-16863, however, has a problem that since a plurality of the springs must be disposed between a plurality of projecting pieces of the clutch outer and a plurality of projecting pieces of the clutch inner in an annular shape as a whole, the structure of the damper is complicated and the size thereof is enlarged.
The technique described in Japanese Patent Publication No. Hei 4-16649 also has a problem. Since the driver shaft has a relatively small diameter for the portion subjected to the low temperature sulphurizing treatment being one of the press-fit surfaces of the driver shaft and the gear, a press-fit amount must be enlarged for obtaining a desired slip generating torque from the press-fitted portions of the drive shaft and the gear, with a result that the press-fitted portions tend to be made longer.
An object of the present invention is to provide a starter for an internal combustion engine, which is excellent in durability and has a compact structure, characterized in that a desired slip generating torque can be set with a small press-fit amount.
According to the present invention, there is provided a starter for an internal combustion engine including a rotation transmitting mechanism for transmitting the rotation of an input portion to a crank shaft, wherein the rotation transmitting mechanism is provided with a torque absorbing mechanism for absorbing an excessive torque caused by an excessive input from the input portion or a reversed input from the crank shaft, the starter being characterized in that the torque absorbing mechanism is provided on a supporting shaft and includes a gear set composed of an input gear and an output gear which are press-fitted to each other; and at least one of a press-fit surface of the input gear and a press-fit surface of the output gear is subjected to a low temperature sulphurizing treatment.
In accordance with the present invention, since at least one of the press-fit surfaces of the gear set is subjected to the low temperature sulphurizing treatment, the press-fit surfaces have a low friction coefficient and a good wear resistance. As a result, it is possible to obtain the starter including the rotation transmitting mechanism having the torque absorbing mechanism capable of stably keeping a slip generating torque for a long-period of time. Also, since the torque absorbing mechanism is configured by the gear set composed of the gears press-fitted to each other, the starter is made compact. This is advantageous in terms of layout of the starter. Further, since at least one of the press-fit surfaces of the input and output gears each of which has a diameter larger than that of the supporting shaft is subjected to the temperature sulphurizing treatment, a fastening force for setting a desired slip generating torque can be set at a value smaller than a fastening force obtained by press-fitting in the case where the torque absorbing mechanism is composed of the supporting shaft and a gear which is press-fitted around the supporting shaft. In other words, the press-fit amount in the case where the input and output gears, each of which has a diameter larger than that of the supporting shaft, are press-fitted to each other, maybe smaller than the press-fit amount in the case where the gear is press-fitted around the supporting shaft.
According to the present invention, because of the fact that the fastening force is small in addition to the fact that the press-fit surface is subjected to the low temperature sulphurizing treatment, the wear of the press-fit surface can be further reduced. This makes it possible to obtain the starter including the rotation transmitting mechanism having the torque absorbing mechanism which is further enhanced in durability.
According to the present invention, the above supporting shaft is a kick shaft. With this configuration, it is possible to obtain the kick-type starter capable of absorbing an excessive torque caused upon kick operation with a compact structure.
According to the present invention, the above supporting shaft is an idler shaft. With this configuration, since a rotatable gear set can be provided on an arbitrary shaft constituting part of the rotation transmitting mechanism, it is possible to increase the degree of freedom in design.
According to the present invention, one of the input gear and the output gear is press-fitted to a boss of the other of the input gear and the output gear, the other gear being different from the supporting shaft.
With this configuration, it is possible to broaden the ranges of selection of material characteristics such as the kinds of materials of the supporting shaft, the input gear, and the output gear.
According to the present invention, the above press-fitting is based on elastic deformation within an elastic limit. With this configuration, it is easy to set the fastening force at the press-fitted portion, and thereby the slip generating torque caused by press-fitting of the input gear and the output gear to each other.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
FIG. 1
is a vertical sectional view of a kick-type starter for an internal combustion engine according to a first embodiment of the present invention; and
FIG. 2
is a vertical sectional view of a kick-type starter for an internal combustion engine according to a second embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, a first embodiment of the present invention will be described with reference to
FIG. 1. A
single-cylinder/four-stroke-cycle internal combustion engine (not shown), which is started by a kick-type starter
10
according to the first embodiment, is mounted on a motorcycle (not shown) with its crank shaft extending in the width direction of a vehicle. A crank case of the internal combustion engine is divided into right and left parts with respect to the longitudinal center plane of the vehicle (only the right crank case
1
is shown), and a multi-stage gear transmission and a multi-disk friction clutch are integrally assembled in the crank case.
According to this embodiment, a kick shaft
11
of the kick-type starter
10
is equivalent to an input portion. The kick shaft
11
is rotatably supported by the right crank case
1
and a right crank case cover
4
positioning on the left side of the right crank case
1
. A kick pedal shaft including a kick pedal (both not shown) is removably mounted on a right end portion
11
a
of the kick shaft
11
projecting rightwardly from the right crank case cover
4
. A sleeve
12
is fitted around the outer periphery of a portion of the kick shaft
11
near the right crank case cover
4
in such a manner as to be in contact with the right end surface of a flange
11
b
formed on the kick shaft
11
. A return coil spring
13
is disposed outside the sleeve
12
with a gap kept therebetween. The sleeve
12
prevents falling-down of the return coil spring
13
.
One end
13
a
of the return coil spring
13
is inserted in an engagement hole
14
formed in the right crank case
1
, and the other end
13
b
of the return coil spring
13
passes through the sleeve
12
and is locked in a locking hole
15
formed in the kick shaft
11
.
A boss
17
is rotatably inserted around a portion, located leftwardly from the sleeve
12
, of the kick shaft
11
. The right side of the boss
17
is locked by the left end surface of the flange
11
b
, and the left side portion of the boss
17
is locked by a circlip
16
. The circlip
16
is engaged in a peripheral groove
11
c
formed in the kick shaft
11
. The boss
17
thus locked by the flange
11
b
and the circlip
16
is immovable in the axial direction. An oil passage lid is formed in the kick shaft
11
. The contact portions of the boss
17
and the kick shaft
11
are lubricated by oil supplied from the left opening end of the oil passage lid.
A pinion gear
18
having a toothed portion
18
a
is press-fitted around the outer periphery of the boss
17
. To be more specific, the center hole of the pinion gear
18
has a diameter being nearly equal to or slightly larger than the outside diameter of the boss
17
; at least one of the outer peripheral surface of the boss
17
and the inner peripheral surface of the pinion gear
18
, which constitute the press-fitted portions of the boss
17
and the pinion gear
18
, is subjected to a low temperature sulphurizing treatment, to be formed with a low temperature sulphurizing treatment film; and the boss
17
is press-fitted in the center hole of the pinion gear
18
. It should be noted that the pinion gear
18
is immovable in the axial direction by a flange
17
b
integrally formed on the boss
17
and a circlip
19
.
The low temperature sulphurizing treatment is well known as a surface treatment capable of giving a good wear resistance to the surface of a ferrous material (an iron-based material). With respect to the surface of the material having been subjected to this treatment, not only the friction coefficient is reduced, but also the fatigue strength is increased and thereby the wear resistance is improved.
One example of the low temperature sulphurizing treatment will be described below. The low temperature sulphurizing treatment is performed by a manner of masking a portion of a workpiece (for example, made from a ferrous material) not required to be formed with a low temperature sulphurizing treatment film; dipping the workpiece in a solution of an alkali metal salt containing sulfur kept at a temperature ranging from 185° C. to
195
° C., connecting a plus electrode to the workpiece and a minus electrode to a bath, and subjecting the solution to anodic electrolysis for a specific time, to form a diffusion layer (thickness: for example, about 7 μm) of a sulfide (for example, iron sulfide) on the surface of the workpiece. The sulfide (for example, iron sulfide) not only has a good lubricating property, but also a good durability because of diffusion thereof in the base material to thereby improve the wear resistance of the surface of the workpiece.
On the other hand, the press-fitted portions are set to cause a slip therebetween when an excessive torque is applied to the boss
17
or the pinion gear
18
, and therefore, they constitute a torque absorbing mechanism for absorbing such an excessive torque. The value of the torque allowed to generate a slip (slip generating torque) can be set by suitably selecting the press-fit amount between the boss
17
and the pinion gear
18
in consideration of the strength of the gear set. Incidentally, according to this embodiment, the pinion gear
18
is press-fitted around the outer peripheral surface of the boss
17
having a diameter larger than the outside diameter of the kick shaft
11
as the supporting shaft for supporting the boss
17
and the pinion gear
18
, and accordingly, to give a fastening force for setting a desired slip generating torque, the press-fit amount required in this embodiment may be smaller than that required for a torque absorbing mechanism configured by press-fitting the pinion gear
18
around the kick shaft
11
. To be more specific, the press-fitting of the pinion gear
18
around the boss
17
can be performed on the basis of elastic deformation of each of the boss
17
and the pinion gear
18
within the elastic limit thereof.
The left end surface of the boss
17
is provided with a ratchet portion
17
a
which is adapted to transmit only the rotation in the normal rotational direction of the kick shaft caused by actuation of the kick pedal, but not to transmit the rotation in the reversed direction to the above normal rotational direction of the kick shaft
11
.
Here, the boss
17
having the ratchet
17
a
and the pinion gear
18
constitute a set of gears press-fitted to each other on the kick shaft
11
, and simultaneously, as will be described later, they function as an input gear and an output gear with respect to transmission of the rotation of the kick shaft
11
.
A kick drive gear
20
, positioned leftwardly from the boss
17
, having a toothed portion
20
a
facing to the ratchet portion
17
a
is spline-connected via an inclined groove or spiral groove formed in the outer periphery of the kick shaft
11
. When the kick shaft
11
is rotated, the kick drive gear
20
is moved in the axial direction of the kick shaft
11
, so that the toothed portion
20
a
is meshed with the ratchet portion
17
a
. A damping coil spring
22
is provided between the kick drive gear
20
and a spring seat
21
which is fitted around the kick shaft
11
and is supported by the right crank case
1
. When the kick drive gear
20
is released from meshing with the ratchet portion
17
a
and is returned to the original position, the return speed of the kick drive gear
20
in the axial direction is decelerated by the damping coil spring
22
.
An idler shaft
23
is mounted to the crank case, and an idler gear
24
having a toothed portion
24
a
meshed with the toothed portion
18
a
of the pinion gear
18
is rotatably mounted on the idler shaft
23
via a bearing
25
.
The rotation of the idler gear
24
is transmitted to the crank shaft via a gear train (not shown).
Accordingly, in the first embodiment, the gear trains from the kick drive gear
20
provided on the kick shaft
11
equivalent to the input portion to a gear provided on the crank shaft constitute a rotation transmission mechanism of the kick-type starter
10
.
The operation of the kick-type starter having the above configuration will be described below.
When a rotational force is applied to the kick shaft
11
by actuation of the kick pedal, the kick shaft
11
is rotated against the return force of the return coil spring
13
, and thereby the kick drive gear
20
spline-connected to the kick shaft
11
is moved in the axial direction of the kick shaft
11
, with a result that the toothed portion
20
a
of the kick drive gear
20
is meshed with the ratchet portion
17
a
of the boss
17
. With such meshing, the rotation of the kick shaft
11
is transmitted to the boss
17
which is rotatably fitted around the kick shaft
11
. At this time, since a torque that is generated and caused by the rotation is generally smaller than the slip generating torque set for the press-fitted portions, the bass
17
and the pinion gear
18
press-fitted around the boss
17
are integrally rotated. The rotation of the pinion gear
18
is transmitted to the idler gear
24
rotatably held by the idler shaft
23
via the toothed portion
24
a
meshed with the toothed portion
18
a
of the pinion gear
18
. Accordingly, with respect to transmission of the rotation of the kick shaft
11
, the boss
17
having the ratchet portion
17
a
and the pinion gear
18
, which constitute the gear set, are taken as an input gear and an output gear, respectively.
In this way, the rotation of the kick shaft
11
is transmitted to the idler gear
24
, and the rotation of the idler gear
24
is finally transmitted to the crank shaft via the gear train (not shown), and thereby the crank shaft is rotated.
If the kick pedal is forcibly actuated, for example, and thereby an excessive torque over the slip generating torque set for the press-fitted portions of the boss
17
and the pinion gear
18
is applied to the gear trains which constitute the rotation transmitting mechanism extending from the kick shaft
11
to the crank shaft, a slip occurs at the press-fitted portions, so that the excessive torque is absorbed by the press-fitted portions.
The effects of the first embodiment will be described below. When an excessive torque is applied to the gear trains of the rotation transmitting mechanism upon starting of the internal combustion engine, a slip occurs at the press-fitted portions at least one of which is subjected to the low temperature sulphurizing treatment, so that the excessive torque can be absorbed by the press-fitted portions. As a result, it is not required to excessively enhance the strength of each gear of the rotation transmitting mechanism. Further, since at least one of the press-fitted portions is subjected to the low temperature sulphurizing treatment, the press-fitted surface has a small friction coefficient and a good wear resistance as described above, so that the slip force at the press-fitted portions can be stably kept for a long-period of time. This makes it possible to keep the slip generating torque set on the basis of the a suitable press-fit amount for a long-period of time, and hence to easily control the torque.
Since the torque absorbing mechanism is configured by the gear set composed of gears press-fitted to each other, it is possible to make the starter compact. This is advantageous in terms of layout of the starter. The torque absorbing mechanism provided on the kick shaft
11
also makes it possible to reduce the influence of an excessive torque caused by the reversed rotation of the crank shaft exerted on the driver. Since the boss
17
around which the pinion gear
18
is press-fitted is a different member from that of the kick shaft
11
, it is possible to broaden the range of selection of material characteristics such as the kinds of materials of the kick shaft
11
, the boss
17
, and the pinion gear
18
.
Unlike the prior art method, according to this embodiment, the low temperature sulphurizing treatment is not applied to the outer peripheral surface of the kick shaft having a relatively small diameter, but is applied to the outer peripheral surface of the boss
17
having a diameter larger than that of the kick shaft or the inner peripheral surface of the pinion gear
18
to be press-fitted around the outer peripheral surface of the boss
17
, and then the inner peripheral surface of the pinion gear
18
is press-fitted around the outer peripheral surface of the boss
17
. As a result, a fastening force for setting a desired slip generating torque can be set at a value smaller than a fastening force obtained, for example, in the case where the pinion gear is press-fitted around the kick shaft. In other words, the press-fit amount required in the case where the pinion gear is press-fitted around the boss may be smaller than the press-fit amount required in the case where the torque absorbing mechanism is configured by press-fitting the pinion gear around the kick shaft. In this way, because of the fact that the fastening force is small in addition to the fact that the press-fit surface is subjected to the low temperature sulphurizing treatment, the wear of the press-fit surface can be further reduced. This makes it possible to obtain the kick-type starter including the rotation transmitting mechanism having the torque absorbing mechanism which is further enhanced in durability. Further, as described above, since the press-fitting of the boss
17
and the pinion gear
18
to each other can be performed on the basis of elastic deformation of each of the boss
17
and the pinion gear
18
within the elastic limit thereof, it is easy to set the fastening force and thereby the slip generating torque at the press-fitted portions.
Next, a second embodiment of the present invention will be described with reference to FIG.
2
. An internal combustion engine, which is started by a kick-type starter according to the second embodiment, is mounted on a motorcycle (not shown) with its crank shaft extending in the width direction of the vehicle. A crank case of the internal combustion engine is divided into right and left parts with respect to the longitudinal center plane of the vehicle (only the right crank case
101
is shown), and a multi-stage gear transmission
102
and a multi-disk friction clutch
103
are integrally assembled in the crank case.
According to the second embodiment, a kick shaft
111
of a kick-type starter
110
is equivalent to an input shaft. The kick shaft
111
is rotatably supported at two positions by the right crank case
101
. A kick pedal shaft including a kick pedal (both not shown) is removably mounted to a right end portion
111
a
of the kick shaft
111
projecting rightwardly from the right crank case
101
. In
FIG. 2
, a bearing
112
is illustrated. A return coil spring
113
is disposed on the left side of a right crank case
101
, for supporting the right side of the kick shaft
111
, in such a manner as to surround the outer periphery of the kick shaft
111
with a gap kept therebetween. One end
113
a
of the return coil spring
113
is engaged with the right crank case
101
, and the other end
113
b
of the return coil spring
113
is locked in a locking hole
115
which is formed in the kick shaft
111
in such a manner as to extend up to an oil passage
111
c
formed in the kick shaft
111
. A boss
117
is rotatably inserted around a portion, located leftwardly from the return coil spring
113
, of the kick shaft
111
. The right side portion of the boss
117
is locked by the left end surface of a flange
111
b
and the left side portion of the boss
117
is locked by a circlip
116
engaged in a peripheral groove formed in the kick shaft
111
. The boss
117
thus locked by the flange
111
b
and the circlip
116
is immovable in the axial direction. The oil passage
111
c
is formed in the kick shaft
111
, so that the contact portions of the boss
117
and the kick shaft
111
are lubricated by oil supplied from the left opening portion of the oil passage
111
c.
A pinion gear
118
having a toothed portion
118
a
is press-fitted around the outer periphery of the boss
117
. To be more specific, the center hole of the pinion gear
118
has a diameter being nearly equal to or slightly larger than the outside diameter of the boss
117
; at least one of the outer peripheral surface of the boss
117
and the inner peripheral surface of the pinion gear
118
, which constitute the press-fitted portions of the boss
117
and the pinion gear
118
, is subjected to a low temperature sulphurizing treatment, to be formed with a low temperature sulphurizing treatment film; and the boss
117
is press-fitted in the center hole of the pinion gear
118
. It should be noted that the pinion gear
118
is immovable in the axial direction by a flange
117
b
integrally formed on the boss
117
and a circlip
119
.
The low temperature sulphurizing treatment is performed in the same manner as that described in the first embodiment. Like the first embodiment, the first press-fitted portions are set to cause a slip therebetween when an excessive torque is applied to the boss
117
or the pinion gear
118
, and therefore, they constitute a torque absorbing mechanism capable of absorbing such an excessive torque. The value of the slip generating torque can be set by suitably selecting the press-fit amount between the boss
117
and the pinion gear
118
in consideration of the strength of the gear set. Incidentally, according to this embodiment, the pinion gear
118
is press-fitted around the outer peripheral surface of the boss
117
having a diameter larger than the outside diameter of the kick shaft
111
as the supporting shaft for supporting the boss
117
and the pinion gear
118
, and accordingly, to give a fastening force for setting a desired slip generating torque, the press-fit amount required in this embodiment may be smaller than that required for a torque absorbing mechanism configured by press-fitting the pinion gear
118
around a small-diameter shaft, for example, the kick shaft
111
. To be more specific, the press-fitting of the pinion gear
118
around the boss
117
can be performed on the basis of elastic deformation of each of the boss
117
and the pinion gear
118
within the elastic limit thereof
The left end surface of the boss
117
is provided with a ratchet portion
117
a
which is adapted to transmit only the rotation in the normal rotational direction of the kick shaft caused by actuation of the kick pedal, but not to transmit the rotation in the reversed direction to the above normal rotational direction of the kick shaft
111
. Here, the boss
117
having the ratchet
117
a
and the pinion gear
118
constitute a set of gears press-fitted to each other on the kick shaft
111
, and simultaneously, as will be described later, they function as an input gear and an output gear with respect to transmission of the rotation of the kick shaft
111
.
A kick drive gear
120
positioned leftwardly from the boss
117
, having a toothed portion
120
a
facing to the ratchet portion
117
a
is spline-connected around the outer periphery of the kick shaft
111
via an inclined groove or spiral groove formed in the outer periphery of the kick shaft
111
. When the kick shaft ill is rotated, the kick drive gear
120
is moved in the axial direction of the kick shaft
111
, so that the toothed portion
120
a
is meshed with the ratchet portion
117
a
. A damping coil spring
122
is provided between the kick drive gear
120
and a spring seat
121
which is fitted around the kick shaft
111
and is supported by the right crank case
101
. When the kick drive gear
120
is released from meshing with the ratchet portion
117
a
and is returned to the original position, the return speed of the kick drive gear
120
in the axial direction is decelerated by the damping coil spring
122
.
An idler gear
124
for transmitting the rotation of the pinion gear
118
to a main shaft
126
of the multi-stage transmission
102
is rotatably mounted on a counter shaft
123
of the transmission
102
. Accordingly, in this kick-type starter
110
, the counter shaft
123
constitutes the idler shaft.
The idler gear
124
is composed of a first idler gear
127
and a second idler gear
128
. The first idler gear
127
is rotatably mounted on the counter shaft
123
via a bearing
125
. A toothed portion
127
a
meshed with the toothed portion
118
a
of the pinion gear
118
provided on the kick shaft
111
is formed on the left portion of the first idler gear
127
, and a boss
127
b
is formed on the right portion of the first idler gear
127
. The second idler gear
128
is press-fitted around the boss
127
b
. A toothed portion
128
a
of the second idler gear
128
is meshed with a toothed portion
131
a
of an auxiliary gear
131
integrally formed on a primary reduction driven gear
130
connected to a clutch housing of the multi-disk friction clutch
103
.
The center hole of the second idler gear
128
has a diameter being nearly equal to or slightly larger than the outside diameter of the boss
127
b
; at least one of the outer peripheral surface of the boss
127
b
and the inner peripheral surface of the second idler gear
128
, which constitute the second press-fitted portions of the boss
127
b
and the second idler gear
128
, is subjected to the same low temperature sulphurizing treatment as that described in the first embodiment; and the boss
127
b
is press-fitted in the center hole of second idler gear
128
.
The second press-fitted portions are set to cause a slip therebetween when an excessive torque is applied to the first idler gear
127
or the second idler gear
128
, and therefore, they constitute a torque absorbing mechanism for absorbing such an excessive torque. Like the press-fitted portions described in the first embodiment, the value of the slip generating torque can be set by suitably selecting the press-fit amount between the boss
127
b
and the second idler gear
128
in consideration of the strength of the boss
127
b
and the second idler gear
128
. Incidentally, according to this embodiment, the second idler gear
128
is press-fitted around the outer, peripheral surface of the boss
127
b
having a diameter larger than the outside diameter of the counter shaft
123
as the supporting shaft for supporting the first idler gear
127
and the second idler gear
128
, and accordingly, to give a fastening force for setting a desired slip generating torque, the press-fit amount required in this embodiment may be smaller than that required for a torque absorbing mechanism configured by press-fitting the gear around a small-diameter shaft, for example, the counter shaft
123
. To be more specific, the press-fitting of the second idler gear
128
around the boss
127
b
can be performed on the basis of elastic deformation of each of the boss
127
b
and the second idler gear
128
within the elastic limit thereof In the kick-type starter according to the second embodiment, the first idler gear
127
and the second idler gear
128
constitute a set of gears press-fitted to each other on the counter shaft
123
, and simultaneously, as will be described later, they function as an input gear and an output gear with respect to transmission of the rotation of the kick shaft
111
.
The rotation of the idler gear
124
is transmitted to the primary reduction driven gear
130
via the auxiliary gear
131
. The rotation of the, primary reduction driven gear
130
is finally transmitted to the crank shaft via a primary reduction drive gear (not shown).
Accordingly, in the second embodiment, the gear trains from the kick drive gear
120
provided on the kick shaft
111
equivalent to the input portion to a gear provided on the crank shaft constitute a rotation transmission mechanism of the kick-type starter
110
.
The operation of the kick-type starter having the above configuration will be described below.
When a rotational force is applied to the kick shaft
111
by actuation of the kick pedal, the kick shaft
111
is rotated against the return force of the return coil spring
113
, and thereby the kick drive gear
120
spline-connected to the kick shaft
111
is moved in the axial direction of the kick shaft
111
, with a result that the toothed portion
120
a
of the kick drive gear
120
is meshed with the ratchet portion
117
a
of the boss
117
.
With such meshing, the rotation of the kick shaft
111
is transmitted to the boss
117
which is rotatably fitted around the kick shaft
111
. At this time, since a torque generated caused by the rotation is generally smaller than the slip generating torque set for the first press-fitted portions, the boss
117
and the pinion gear
118
press-fitted around the boss
117
are integrally rotated. The rotation of the pinion gear
118
is transmitted to the first idler gear
127
rotatably held by the counter shaft
123
via the toothed portion
127
a
meshed with the toothed portion
118
a
of the pinion gear
118
. At this time, since a torque generated caused by the rotation is generally smaller than the slip generating torque set for the second press-fitted portions, the boss
127
b
and the second idler gear
128
press-fitted around the boss
127
b
are integrally rotated. The rotation of the second idler gear
128
is transmitted to the auxiliary gear
131
rotatably held by the main shaft
126
via the toothed portion
131
a
meshed with the toothed portion
128
a
. With respect to the transmission of the rotation of the kick shaft
111
, the boss
117
and the pinion gear
118
, which constitute the gear set on the gear shaft
111
, are taken as an input gear and an output gear, respectively, and the first idler gear
127
and the second idler gear
128
, which constitute the gear set on the counter shaft
123
as the idler shaft, are taken as an input gear and an output gear, respectively.
Like the first embodiment, if an excessive torque over the slip generating torque set for the first press-fitted portions of the boss
117
and the pinion gear
118
or the second press-fitted portions of the first idler gear
127
and the second idler gear
128
is applied to the gears of the rotation transmitting mechanism extending from the kick shaft
111
to the crank shaft, a slip occurs at the first or second press-fitted portions, so that the excessive torque is absorbed by the first or second press-fitted portions.
The effects of the second embodiment will be described below.
Like the first embodiment, when an excessive torque is applied to the gear trains of the rotation transmitting mechanism upon the starting of the internal combustion engine, a slip occurs at the first or second press-fitted portions at least one of which is subjected to the low temperature sulphurizing treatment, so that the excessive torque can be absorbed by the first or second press-fitted portions. As a result, it is not required to excessively enhance the strength of each gear of the rotation transmitting mechanism. Further, since at least one of the press-fitted portions is subjected to the low temperature sulphurizing treatment, the slip force at the press-fitted portions can be stably kept for a long-period of time. This makes it possible to keep the slip generating torque set on the basis of the a suitable press-fit amount for a long-period of time, and hence to easily control the torque. Since the torque absorbing mechanism is configured by the gear set composed of gears press-fitted to each other, it is possible to make the starter compact. This is advantageous in terms of layout of the starter. The torque absorbing mechanism provided on the kick shaft
111
also makes it possible to reduce the influence of an excessive torque caused by the reversed rotation of the crank shaft exerted on the driver. Since the boss
117
around which the pinion gear.
118
is press-fitted is a different member from that of the kick shaft
111
, it is possible to broaden the ranges of selection of material characteristics such as the kinds of materials of the kick shaft
111
, the boss
117
, and the pinion gear
118
. Since the gear set can be simply provided on an arbitrary shaft constituting part of the rotation transmitting mechanism, for example, the idler gear, it is possible to increase the degree of freedom in design.
Unlike the prior art method, according to this embodiment, the low temperature sulphurizing treatment is not applied to the outer peripheral surface of the kick shaft or counter shaft having a relatively small diameter, but is applied to the outer peripheral surface of the boss having a diameter larger than that of the kick shaft or counter shaft or to the inner peripheral surface of the gear to be press-fitted around the outer peripheral surface of the boss, and further the first or second press-fitted portions are provided at the outer periphery of the boss having a larger diameter. As a result, a fastening force for setting a desired slip generating torque can be set at a value smaller than that obtained, for example, in the case where the torque absorbing mechanism is configured by press-fitting the gear around the kick shaft or counter shaft. In other words, the press-fit amount required in the case where the gear is press-fitted around the boss may be smaller than the press-fit amount required in the case where the gear is press-fitted around the kick shaft or counter shaft. In this way, because of the fact that the fastening force is small in addition to the fact that the press-fit surface is subjected to the low temperature sulphurizing treatment, it is possible to further reduce the wear of the press-fit surface. This makes it possible to obtain the kick-type starter including the rotation transmitting mechanism having the torque absorbing mechanism which is further enhanced in durability. Further, like the first embodiment, since the press-fitting of the boss and the gear to each other can be performed on the basis of elastic deformation of each of the boss and the gear within the elastic limit thereof, it is easy to set the fastening force and thereby the slip generating torque at the press-fitted portions.
Further, it is possible to individually set the slip generating torques for the first and second press-fitted portions in accordance with the strength of the gears, and hence to increase the degree of freedom in design.
A kick-type starter according to a third embodiment has the same configuration as that of the kick-type starter according to the second embodiment except that the idler gear provided on the counter shaft is configured as a gear set composed of a second idler gear having a boss integrally formed on the left portion of the second idler gear and a first idler gear press-fitted around the boss, in place of the gear set composed of the first idler gear
127
having the boss
127
b
integrally formed on the right portion of the first idler gear
127
and the second idler gear
128
press-fitted around the boss
127
b
; and further, like the kick-type starter in the second embodiment, a toothed portion meshed with the toothed portion
118
a
of the pinion gear
118
is formed on the first idler gear and a toothed portion meshed with the toothed portion
131
a
of the auxiliary gear
131
is formed on the second idler gear. The function and the effect of the kick-type starter in the third embodiment are the same as those obtained by the kick-type starter in the second embodiment.
A kick-type starter according to a fourth embodiment of the present invention has the same configuration as that of the kick-type starter according to the third embodiment, except that a gear composed of a boss and a pinion gear which is not separated from but integrated with the boss is provided on the kick shaft
111
in place of the gear set composed of the boss
117
and the pinion gear
118
. The function and effect of the kick type starter in the fourth embodiment are the same as those obtained by the kick-type starter in the third embodiment, except for the function and effect obtained by the configuration in which the gear set is composed of the boss and the pinion gear which are not press-fitted to each other.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
- 1. A starter for an internal combustion engine includes a rotation transmitting mechanism for transmitting the rotation of an input portion to a crank shaft, wherein said rotation transmitting mechanism is provided with a torque absorbing mechanism for absorbing an excessive torque caused by an excessive input from said input portion or a reversed input from said crank shaft, said a torque absorbing mechanism comprising:a supporting shaft; a gear set composed of an input gear and an output gear, said input gear and said output gear being press-fitted to each other and being mounted on said supporting shaft; and at least one of a press-fit surface of said input gear and a press-fit surface of said output gear is subjected to a low temperature sulphurizing treatment.
- 2. The starter for an internal combustion engine according to claim 1, wherein said supporting shaft is a kick shaft.
- 3. The starter for an internal combustion engine according to claim 1, wherein said supporting shaft is an idler shaft.
- 4. The starter for an internal combustion engine according to claim 1, wherein one of said input gear and said output gear is press-fitted to a boss of the other of said input gear and said output gear, the other gear being a different member from that of said supporting shaft.
- 5. The starter for an internal combustion engine according to claim 1, wherein said press-fitting is based on elastic deformation within an elastic limit.
- 6. The starter for an internal combustion engine according to claim 1, and further including a biasing means operatively disposed relative to said supporting shaft for returning said shaft to an initial position after actuation.
- 7. The starter for an internal combustion engine according to claim 1, and further including a boss mounted on said supporting shaft, said boss including a ratchet portion and a pinion gear, an outer peripheral surface of said boss being subjected to a low temperature sulphurizing treatment.
- 8. The starter for an internal combustion engine according to claim 1, and further including a boss mounted on said supporting shaft, said boss including a ratchet portion and a pinion gear, an inner peripheral surface of said pinion gear being subjected to a low temperature sulphurizing treatment.
- 9. The starter for an internal combustion engine according to claim 7, wherein said low temperature sulphurizing treatment is conducted in an alkali metal salt bath containing sulfur maintained at a temperature in the range of 185° C. to 195° C.
- 10. The starter for an internal combustion engine according to claim 8, wherein said low temperature sulphurizing treatment is conducted in an alkali metal salt bath containing sulfur maintained at a temperature in the range of 185° C. to 195° C.
- 11. The starter for an internal combustion engine according to claim 1, wherein said press-fit surface of said input gear is a cylindrical press-fit surface.
- 12. The starter for an internal combustion engine according to claim 1, wherein said press-fit surface of said output gear is a cylindrical press-fit surface.
- 13. A method of treating a torque absorbing mechanism for absorbing an excessive torque caused by an excessive input from an input portion or a reversed input from a crank shaft comprising the following steps:forming a supporting shaft; masking a portion of a gear set not required to be treated, said gear set including an input gear and an output gear; dipping said gear set into a bath of alkali metal salt containing sulfur; connecting a plus electrode to said gear set; subjecting the solution to anodic electrolysis for a predetermined period of time for providing a low temperature sulphurizing treatment; and positioning said gear set composed of the input gear and the output gear on said supporting shaft, said input gear and said output gear being press-fitted to each other.
- 14. The method according to claim 13, wherein a diffusion layer of sulfide is formed on the unmasked surface of said gear set.
- 15. The method according to claim 14, wherein the diffusion layer has a thickness of approximately 7 μm.
- 16. The method according to claim 13, wherein the said bath of alkali metal salt is maintained in a temperature range of 185° C. to 195° C.
- 17. The method according to claim 14, wherein the said bath of alkali metal salt is maintained in a temperature range of 185° C. To 195° C.
- 18. The method according to claim 15, wherein the said bath of alkali metal salt is maintained in a temperature range of 185° C. to 195° C.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-295860 |
Oct 1998 |
JP |
|
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
2841989 |
Kreidler et al. |
Jul 1958 |
|
Foreign Referenced Citations (2)
Number |
Date |
Country |
63-16863 |
May 1988 |
JP |
4-16649 |
Mar 1992 |
JP |