Information
-
Patent Grant
-
6742483
-
Patent Number
6,742,483
-
Date Filed
Monday, October 21, 200222 years ago
-
Date Issued
Tuesday, June 1, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Chang; Ching
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 9015
- 123 9016
- 123 9017
- 123 9018
- 123 902
- 123 9021
- 123 9022
- 123 9039
- 123 904
- 123 9044
- 123 9045
- 123 9046
-
International Classifications
-
Abstract
An output from each of output rods is converted into an assisting force via a corresponding one of rollers, while an outer peripheral surface of each of the rollers moving together with a control shaft serves as a conversion plane. This output is applied to the control shaft. Hence, as the control shaft is moved in such a direction as to increase valve lift amounts of intake valves, the assisting force can be correspondingly increased. Thus, a suitable assisting force that can act against a thrust force can be applied to the control shaft. As a result, there is no apprehension that a minimum hydraulic fluid pressure will not be ensured on the side of a larger valve lift amount or that responding properties in movements of the control shaft will deteriorate.
Description
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-324757 filed on Oct. 23, 2001, including the specification, drawings, and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an assisting device and method for a variable valve mechanism. More particularly, the invention relates to an assisting device for applying an assisting force acting against a thrust force generated in a control shaft to a variable valve mechanism that allows valve lift amounts to continuously change in such a manner as to interlock with an axial position of the control shaft by axially moving the control shaft.
2. Description of Related Art
As a related art, there is known a variable valve mechanism in which a cam shaft having three-dimensional cams whose cam noses (surfaces) gradually increase in height along an axial direction is moved in the axial direction so as to continuously adjust valve lift amounts of intake valves of an internal combustion engine in accordance with an operational state thereof (Japanese Patent Application Laid-Open No. 2000-54814).
In a variable valve mechanism in which a cam shaft is thus axially moved to allow valve lift amounts to continuously change, a thrust force is generated in such a direction as to reduce the valve lift amounts due to an axial inclination of cam surfaces of three-dimensional cams. Moreover, as the valve lift amounts are increased, compression strokes of valve springs are increased, which leads to a gradual increase in restoring forces thereof. As a result, the aforementioned thrust force is increased as well.
In the case where such a variable valve mechanism is utilized to regulate the amount of intake air in an internal combustion engine by adjusting valve lift amounts of intake valves instead of adjusting a throttle valve, an actuator for axially moving a cam shaft is required to have high responding properties. Especially in the case where a hydraulic actuator is employed, in order to accomplish high responding properties, it is required that the flow rate of a hydraulic fluid be reduced by reducing the diameter of pistons. However, if the diameter of the pistons is reduced, the actuator output cannot be adapted for an increase in the aforementioned thrust force, which causes an apprehension that a minimum hydraulic fluid pressure will not be generated or that the responding properties will deteriorate.
In order to address these problems, one might consider providing an assisting spring for assisting the operation of the actuator by generating an assisting force that acts against the aforementioned thrust force. However, as described above, while the thrust force is increased in proportion to an increase in the valve lift amounts, the restoring force of the assisting spring is reduced as the cam shaft is shifted to the high-lift side. Hence, this restoring force is inadequate as an assisting force.
Such a problem is caused in other types of variable valve mechanisms in which valve lift amounts can continuously change due to axial movements of a control shaft, as well as in a variable valve mechanism employing three-dimensional cams.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an assisting device capable of applying a suitable assisting force to a variable valve mechanism that allows valve lift amounts to continuously change with changes in an axial position of a control shaft by axially moving the control shaft.
In order to achieve the aforementioned and/or other objects, an assisting device for applying an assisting force to counteract a thrust force generated in a variable valve mechanism according to one aspect of the invention comprises valves disposed in the variable valve mechanism, a control shaft for allowing valve lift amounts of the valves to continuously change with changes in an axial position of the control shaft, the control shaft receiving the thrust force from the valves, and an assisting force applying portion for generating and applying the assisting force on the basis of a restoring force of an elastic body or a pressure of a fluid and increasing the assisting force as the axial position of the control shaft is shifted to a high-lift side.
This structure allows a suitable assisting force capable of acting against a thrust force that is increased as the axial position of the control shaft is shifted to the high-lift side to be applied to the variable valve mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described with reference to exemplary embodiments illustrated in the drawings, in which:
FIG. 1
is a block diagram showing the overall structure of an engine equipped with an assisting device and a variable valve mechanism according to a first embodiment of the invention and a control system for the engine;
FIG. 2
is an explanatory view of the structure of a cylinder head portion of the engine;
FIG. 3
is a cross-sectional view of the internal structure of a slide actuator according to the first embodiment;
FIG. 4
is also a cross-sectional view according to the internal structure of the slide actuator;
FIG. 5
is a perspective view of a piston body of the first embodiment;
FIG. 6
is also a perspective view of the piston body;
FIGS. 7A-7C
are explanatory views of an assisting operation according to the first embodiment;
FIG. 8
is a graph showing how a thrust force Fs and an assisting force Fa are related to a moving distance of a control shaft;
FIG. 9
is a perspective view of the structure of an intermediary drive mechanism according to the first embodiment;
FIG. 10
is also a partially cutaway view of the internal structure of the intermediary drive mechanism;
FIGS. 11A-11C
are explanatory views of the shapes of a control shaft and a supporting pipe of the intermediary drive mechanism;
FIGS. 12A-12B
are explanatory views of a valve lift amount adjusting function of the intermediary drive mechanism according to the first embodiment;
FIGS. 13A-13B
are explanatory views of a valve lift amount adjusting function of the intermediary drive mechanism;
FIGS. 14A-14B
are explanatory views of a valve lift amount adjusting function of the intermediary drive mechanism;
FIG. 15
is a graph showing how the valve lift amount achieved by the intermediary drive mechanism according to the first embodiment changes;
FIG. 16
is an explanatory view of the structure of a variable valve mechanism and an assisting device according to a second embodiment of the invention;
FIG. 17
is an explanatory view of the functions of the variable valve mechanism and the assisting device according to the second embodiment;
FIG. 18
is an explanatory view of the structure of a modified example of the first embodiment; and
FIG. 19
is an explanatory view of the structure of a modified example of the second embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1
is a block diagram of the overall structure of a gasoline engine (hereinafter referred to as the “engine”)
2
as an internal combustion engine equipped with an assisting device and a variable valve mechanism to which the aforementioned invention is applied, and of a control system for the engine
2
.
The engine
2
is installed in an automobile as a drive source for causing the automobile to run. The engine
2
includes a cylinder block
4
, pistons (not shown), a cylinder head
8
mounted on the cylinder block
4
, and the like. A plurality of cylinders are formed in the cylinder block
4
. For example, in this case, four cylinders
2
a
are formed in the cylinder block
4
. Each of the cylinders
2
a
has a corresponding one of combustion chambers
10
, each of which is defined by the cylinder block
4
, a corresponding one of the pistons, and the cylinder head
8
. In each of the combustion chambers
10
, four valves, namely, a corresponding one of first intake valves
12
a
, a corresponding one of second intake valves
12
b
, a corresponding one of first exhaust valves
16
a
, and a corresponding one of second exhaust valves
16
b
are disposed. Each of the first intake valves
12
a
opens and closes a corresponding one of first intake ports
14
a
. Each of the second intake valves
12
b
opens and closes a corresponding one of second intake ports
14
b
. Each of the first exhaust valves
16
a
opens and closes a corresponding one of first exhaust ports
18
a
. Each of the second exhaust valves
16
b
opens and closes a corresponding one of second exhaust ports
18
b.
The first intake port
14
a
and the second intake port
14
b
of each of the cylinders
2
a
are connected to a surge tank
32
via a corresponding one of intake passages
30
a
formed in an intake manifold
30
. Disposed in each of the intake passages
30
a
is a corresponding one of fuel injectors
34
, which makes it possible to inject fuel into corresponding ones of the first intake ports
14
a
and the second intake ports
14
b.
The surge tank
32
is coupled to an air cleaner
42
via an intake duct
40
. It is to be noted herein that there is no throttle valve disposed in the intake duct
40
. An operation of an accelerator pedal
74
and an intake air amount control corresponding to an engine speed NE during an idle speed control are performed by adjusting valve lift amounts of the first intake valves
12
a
and of the second intake valves
12
b.
Lifting movements of intake cams
45
a
on an intake cam shaft
45
are transmitted via a corresponding one of later-described intermediary drive mechanisms
120
disposed in the cylinder head
8
as shown in
FIG. 2
, whereby it becomes possible to drive the intake valves
12
a
,
12
b
. In this transmission, a transmission state of lift by the intermediary drive mechanism
120
is adjusted through a function of a later-described slide actuator
100
, whereby the valve lift amounts are adjusted. The intake cam shaft
45
is interlocked with rotation of a crank shaft
49
of the engine
2
via a timing chain
47
and a timing sprocket (which may be replaced with a timing gear or a timing pulley) disposed at one end of the intake cam shaft
45
.
As shown in
FIG. 1
, each of the first exhaust valves
16
a
for opening and closing a corresponding one of the first exhaust ports
18
a
of a corresponding one of the cylinders
2
a
and each of the second exhaust valves
16
b
for opening and closing a corresponding one of the second exhaust ports
18
b
of a corresponding one of the cylinders
2
a
are opened and closed by a certain valve lift amount through rotation of exhaust cams
46
a
(
FIG. 2
) on an exhaust cam shaft
46
(
FIG. 2
) resulting from rotation of the engine
2
. The first exhaust port
18
a
and the second exhaust port
18
b
of each of the cylinders
2
a
are coupled to an exhaust manifold
48
. Thus, exhaust gas is discharged to the outside via a catalytic converter
50
.
An electronic control unit (hereinafter referred to as the ECU)
60
is constructed of a digital computer and includes components such as a CPU, a ROM, a RAM, various driver circuits, input ports, and output ports, which are interconnected via a bidirectional bus.
Various output voltages and various pulses are input to the input ports of the ECU
60
. The various output voltages include an output voltage proportional to a depression stroke of the accelerator pedal
74
as an output from an accelerator opening sensor
76
(hereinafter referred to as an “accelerator opening ACCP”), an output voltage corresponding to an amount GA of intake air flowing through the intake duct
40
as an output from an intake air amount sensor
84
, an output voltage corresponding to a coolant temperature THW of the engine
2
as an output from a coolant temperature sensor
86
disposed in the cylinder block
4
of the engine
2
, an output voltage corresponding to an air-fuel ratio as an output from an air-fuel ratio sensor
88
disposed in the exhaust manifold
48
, and an output voltage corresponding to an axial displacement as an output from a shaft position sensor
90
for detecting an axial moving distance of a later-described control shaft
132
that is moved by the slide actuator
100
.
The various pulses include a pulse that is output by a crank angle sensor
82
every time the crank shaft rotates by 30° and a pulse output from a cam angle sensor
92
for detecting cam angles of the intake cams
45
a
for driving the intake valves
12
a
,
12
b
via the intermediary drive mechanism
120
.
The ECU
60
calculates a current crank angle on the basis of an output pulse of the crank angle sensor
82
and a pulse of the cam angle sensor
92
and an engine speed NE on the basis of a frequency with which pulses are output from the crank angle sensor
82
.
Although various signals are input to the input ports of the ECU
60
in addition to the aforementioned output voltages and pulses, they are not shown in the drawings because they are not important in explaining the first embodiment.
Each of the output ports of the ECU
60
is connected to a corresponding one of the fuel injectors
34
via a corresponding one of drive circuits. The ECU
60
performs an opening control of the fuel injectors
34
in accordance with an operational state of the engine
2
and thus performs a fuel injection timing control and a fuel injection amount control. Furthermore, one of the output ports of the ECU
60
is connected to an oil control valve (hereinafter referred to as the “OCV”)
104
via a corresponding one of the drive circuits. The ECU
60
controls the slide actuator
100
through a hydraulic control by the OCV
104
in accordance with an operational state of the engine
2
such as a required intake air amount.
Each of
FIGS. 3 and 4
shows a cross-section of the internal structure of the slide actuator
100
.
FIG. 3
is a longitudinal cross-sectional view (taken along a line B—B in
FIG. 4
) when viewed from a location in front of the slide actuator
100
.
FIG. 4
is a longitudinal cross-sectional view (taken along a line A—A in
FIG. 3
) when viewed from a location on the right side of the slide actuator
100
.
The slide actuator
100
has a cylindrical space inside a housing
100
a
. The cylindrical space is formed so as to be coaxial with the control shaft
132
. This space is slightly reduced in diameter on the side of the control shaft
132
. A piston body
102
is axially movably disposed inside the space. As shown in perspective views of
FIGS. 5 and 6
, the piston body
102
includes a piston portion
102
a
and an assisting roller portion
102
b
. The piston portion
102
a
and the assisting roller portion
102
b
are integrally formed via a connecting portion
102
c.
The piston portion
102
a
is in the shape of a circular plate. A sealing groove
102
e
for accommodating a sealing ring
102
d
for oil seal is formed in an outer peripheral surface of the piston portion
102
a
. A leading end of the control shaft
132
is fitted into a fitting hole
102
f
formed in the center of the piston portion
102
a
. The control shaft
132
is fixed to the piston body
102
by a fixture bolt
102
h
penetrating from the right side in
FIG. 3
, through a bolt through-hole
102
g
axially penetrating the piston body
102
. As a result, the control shaft
132
is designed to be axially movable together with the piston body
102
.
The piston portion
102
a
is disposed on the smaller-diameter side (on the left side in the drawings) in the cylindrical space. Hence, the cylindrical space is divided into two pressure chambers
101
a
,
101
b
. The ECU
60
adjusts the supply and release of a hydraulic pressure for the two pressure chambers
101
a,
101
b
via the aforementioned OCV
104
, whereby the entire piston body
102
axially moves and adjusts an axial position of the control shaft
132
. The OCV
104
is a four-port three-position switching valve of an electromagnetic solenoid type. If the electromagnetic solenoid assumes a demagnetized state (hereinafter referred to as a “low-lift drive state”) as shown in
FIG. 3
, hydraulic fluid in the first pressure chamber
101
a
is returned to an oil pan
108
via a discharge passage
107
. A high-pressure hydraulic fluid is supplied from an oil pump P to the second pressure chamber
101
b
via a supply passage
106
. Hence, the control shaft
132
is moved in a direction indicated by L in
FIG. 3
, whereby it becomes possible to reduce valve operation angles and valve lift amounts of the intake valves
12
a
,
12
b
through the function of the intermediary drive mechanism
120
.
If the electromagnetic solenoid assumes an 100%-energized state (hereinafter referred to as a “high-lift drive state”), hydraulic fluid is supplied from the oil pump P to the first pressure chamber
101
a
via the supply passage
106
. Hydraulic fluid in the second pressure chamber
101
b
is returned to the oil pan
108
via the discharge passage
107
. Hence, the control shaft
132
is moved in a direction indicated by H in
FIG. 3
, whereby it becomes possible to increase valve lift amounts of the intake valves
12
a
,
12
b
through the function of the intermediary drive mechanism
120
.
Furthermore, if the supply of electricity to the electromagnetic solenoid is controlled so as to assume an intermediate state (hereinafter referred to as a “neutral state”), the pressure chambers
101
a
,
101
b
are sealed and connected to neither the supply passage
106
nor the discharge passage
107
. Hence, axial movements of the control shaft
132
are stopped, whereby it becomes possible to hold valve lift amounts of the intake valves
12
a
,
12
b.
The assisting roller portion
102
b
will now be described. A space
102
i
penetrating in a direction perpendicular to the axial direction is formed in a body of the assisting roller portion
102
b
. Two shaft portions
102
j
penetrating the space
102
i
are symmetrically disposed across the fixture bolt
102
h
. Axes “as” (
FIG. 5
) of the two shaft portions
102
j
are disposed parallel to a virtual plane (PS) that is perpendicular to an axis of the control shaft
132
. Each of rollers
102
k
is freely rotatably fitted to a corresponding one of the shaft portions
102
j.
Each of two push portions
103
is disposed in the housing
100
a
in such a manner as to face a corresponding one of the two rollers
102
k
. Each of the push portions
103
has an output rod
103
a
, a linear bearing
103
b
for axially movably supporting the output rod
103
a
, and a spring
103
c
for urging the output rod
103
a
toward the piston body
102
.
The direction in which the output rod
103
a
is urged is perpendicular to the axis of the control shaft
132
. Furthermore, although the direction in which the output rod
103
a
is urged is parallel to a virtual plane (QS) perpendicular to the axes “as” of the rollers
102
k
, the output rod
103
a
has an offset doff toward the control shaft
132
from the axes “as” (FIG.
3
). Accordingly, as shown in
FIG. 7A
, a pressure Fo
1
is diagonally applied to an outer peripheral surface of the roller
102
k
from a leading end portion
103
d
of the output rod
103
a
. Hence, a radial force Fr
1
is applied to the shaft portion
102
j
. As a result, an axial force Fa
1
is applied to the piston body
102
from the output rod
103
a
. That is, the pressure Fo
1
of the output rod
103
a
is converted into the axial force Fa
1
with the cylindrical outer peripheral surface of the roller
102
k
serving as a conversion plane. The force Fa
1
is applied in the direction H and acts as an assisting force that acts against a thrust force generated by the later-described intermediary drive mechanism
120
in the direction L.
FIG. 7A
shows a state where the piston body
102
is located at a critical position in the direction L and the offset doff is a minimum offset distance doff
1
.
If the piston body
102
is moved in the direction H as shown in FIG.
7
B through adjustment of hydraulic pressures in the pressure chambers
101
a
,
101
b
by the ECU
60
based on an OCV signal, the offset doff is an intermediate offset distance doff
2
. Hence, a pressure Fo
2
is applied to the cylindrical outer peripheral surface of the roller
102
k
from the leading edge portion
103
d
of the output rod
103
a
in a further inclined direction. Hence, a radial force Fr
2
is applied to the shaft portion
102
j
. As a result, an assisting force Fa
2
(>Fa
1
) is applied to the piston body
102
.
Furthermore, if the piston body
102
is moved to a critical position in the direction H as shown in
FIG. 7C
, the offset doff is a maximum offset distance doff
3
. Hence, a pressure Fo
3
is applied to the cylindrical outer peripheral surface of the roller
102
k
from the leading portion
103
d
of the output rod
103
a
in a most inclined direction. Hence, a radial force Fr
3
is applied to the shaft portion
102
j
. As a result, a maximum assisting force Fa
3
(>Fa
2
) is applied to the piston body
102
.
A solid line in
FIG. 8
indicates a relationship between an assisting force Fa and a moving distance of the control shaft
132
in the direction H which has been actually designed on the basis of the aforementioned relationship. That is, if the moving distance of the control shaft
132
in the direction H is “0(mm)” (at the critical position in the direction L), the assisting force Fa assumes a minimum value that is almost 0(kgf). The assisting force Fa increases as the control shaft
132
moves in the direction H. The assisting force Fa assumes a maximum value at the critical position in the direction H. An alternate long and short dash line in
FIG. 8
indicates a thrust force Fs (applied in the opposite direction) generated by the later-described intermediary drive mechanism
120
. The assisting force Fa is set so as to become substantially equal to the absolute value of the thrust force Fs. Such an ascending pattern of the assisting force Fa can be suitably set by the shape of the leading end portion
103
d
of the output rod
103
a
, the diameter of the roller
102
k
, and the initial offset doff
1
. Although the ascending pattern of the thrust force Fs generated by the intermediary drive mechanism
120
slightly changes depending on the speed of the engine
2
, it is appropriate that the ascending pattern of the assisting force Fa be adapted for, for example, a thrust force Fs at an average engine speed, a thrust force Fs at an engine speed during idling, or a thrust force Fs at a maximum engine speed.
The intermediary drive mechanism
120
will now be described.
FIG. 9
is a perspective view of the intermediary drive mechanism
120
. The intermediary drive mechanism
120
includes a shaft input portion
122
disposed at the center in the drawing, a first rocking cam
124
disposed on the left side in the drawing (corresponding to an “shaft output portion”), and a second rocking cam
126
disposed on the right side in the drawing (corresponding to an “shaft output portion”). A housing
122
a
of the shaft input portion
122
and housings
124
a
,
126
a
of the rocking cams
124
,
126
have a cylindrical shape and are equal in outer diameter.
FIG. 10
is a perspective view of the housings
122
a
,
124
a
,
126
a
that have been horizontally cut away. It is to be noted herein that an axially extending space is formed in the housing
122
a
of the shaft input portion
122
and that a helical spline
122
b
that axially spirals like a right-handed screw is formed in an inner peripheral surface of the space. Further, two arms
122
c
,
122
d
are formed so as to protrude from an outer peripheral surface in parallel with each other. A shaft
122
e
is hung between leading ends of the arms
122
c
,
122
d
. The shaft
122
e
is parallel to an axis of the housing
122
a
. A roller
122
f
is rotatably fitted to the shaft
122
e.
An axially extending space is formed in the housing
124
a
of the first rocking cam
124
, and a helical spline
124
b
that axially spirals like a left-handed screw is formed in an inner peripheral surface of the internal space. A ring-like bearing portion
124
c
having a center hole with a reduced diameter covers a left end of the internal space. A generally triangular nose
124
d
is formed so as to protrude from an outer peripheral surface. One side of the nose
124
d
constitutes a cam surface
124
e
that is concavely curved.
An axially extending space is formed in the housing
126
a
of the second rocking cam
126
, and a helical spline
126
b
that axially spirals like a left-handed screw is formed in an inner peripheral surface of the internal space. A ring-like bearing portion
126
c
having a center hole with a reduced diameter covers a right end of the internal space. A generally triangular nose
126
d
is formed so as to protrude from an outer peripheral surface. An upper side of the nose
126
d
constitutes a cam surface
126
e
that is concavely curved.
The first rocking cam
124
and the second rocking cam
126
are disposed such that their end surfaces are respectively in contact with opposed ends of the shaft input portion
122
in a coaxial manner with the bearing portions
124
c
,
126
c
facing outwards. As a whole, the first rocking cam
124
, the shaft input portion
122
, and the second rocking cam
126
assume a generally cylindrical shape having an internal space as shown in FIG.
9
.
A slider gear
128
is disposed in the internal space that is constituted by the shaft input portion
122
and the two rocking cams
124
,
126
. The slider gear
128
has a generally cylindrical shape, and an input helical spline
128
a
that spirals like a right-handed screw is formed at the center of an outer peripheral surface of the slider gear
128
. A first output helical spline
128
c
that spirals like a left-handed screw is formed at a left end portion of the input helical spline
128
a
, with a small-diameter portion
128
b
being interposed between the input helical spline
128
a
and the first output helical spline
128
c
. A second output helical spline
128
e
that spirals like a left-handed screw is formed at a right end portion of the input helical spline
128
a
, with a small-diameter portion
128
d
being interposed between the input helical spline
128
a
and the second output helical spline
128
e
. It is to be noted herein that the output helical splines
128
c
,
128
e
are smaller in outer diameter than the input helical spline
128
a.
A through-hole
128
f
is formed in the slider gear
128
in the direction of a center axis thereof. A long hole
128
g
for opening the inside of the through-hole
128
f
to the outer peripheral surface is formed in one of the small-diameter portions
128
d
. The long hole
128
g
has a circumferentially extended length.
A supporting pipe
130
as shown in
FIG. 11
is circumferentially slidably disposed in the through-hole
128
f
of the slider gear
128
. It is to be noted herein that
FIG. 11A
is a plan view, that
FIG. 11B
is a front view, and that
FIG. 11C
is a right side view. As shown in
FIG. 2
, the supporting pipe
130
is commonly provided for all the intermediary drive mechanisms
120
(the number of the intermediary drive mechanisms
120
is four in this case). For each of the intermediary drive mechanisms
120
, a corresponding one of axially extended long holes
130
a
is opened in the supporting pipe
130
.
Furthermore, a control shaft
132
axially slidably penetrates the supporting pipe
130
. As is the case with the supporting pipe
130
, the control shaft
132
is also commonly provided for all the intermediary drive mechanisms
120
. For each of the intermediary drive mechanisms
120
, a corresponding one of engaging pins
132
a
protrudes from the control shaft
132
. Each of the engaging pins
132
a
is formed so as to penetrate a corresponding one of the axially extended long holes
130
a
formed in the supporting pipe
130
. Furthermore, the leading end of each of the engaging pins
132
a
of the control shaft
132
is inserted through the circumferentially extended long hole
128
g
formed in the slider gear
128
of a corresponding one of the intermediary drive mechanisms
120
.
Because of the axially extended long holes
130
a
formed in the supporting pipe
130
, even if the supporting pipe
130
is fixed to the cylinder head
8
, each of the engaging pins
132
a
of the control shaft
132
can be axially moved and thus makes it possible to axially move the slider gear
128
. In addition, the slider gear
128
itself is engaged in the circumferentially extended long hole
128
g
with a corresponding one of the engaging pins
132
a
and is thereby axially positioned. On the other hand, however, the slider gear
128
can rock around the axis.
The input helical spline
128
a
of the slider gear
128
is engaged with the helical spline
122
b
inside the shaft input portion
122
. Further, the first output helical spline
128
c
is engaged with the helical spline
124
b
inside the first rocking cam
124
. The second output helical spline
128
e
is engaged with the helical spline
126
b
inside the second rocking cam
126
.
As shown in
FIG. 2
, each of the intermediary drive mechanisms
120
thus constructed can rock around the axis but is prevented from being axially moved while being interposed between rising wall portions
136
,
138
formed in the cylinder head
8
on the side of the bearing portions
124
c
,
126
c
of the rocking cams
124
,
126
. Holes are formed in the rising wall portions
136
,
138
at positions corresponding to the center holes of the bearing portions
124
c
,
126
c
, respectively. The supporting pipe
130
is passed through the holes and fixed thereby. Accordingly, the supporting pipe
130
is fixed to the cylinder head
8
and does not axially move or rotate.
The control shaft
132
in the supporting pipe
130
axially slidably penetrates the supporting pipe
130
and is connected at one end thereof to the piston body
102
of the slide actuator
100
shown in
FIGS. 3 and 7
. Thus, the axial position of the control shaft
132
can be adjusted by adjusting hydraulic pressures applied to the pressure chambers
101
a
,
101
b
. Hence, the difference in phase between the roller
122
f
of the shaft input portion
122
and the noses
124
d
,
126
d
of the rocking cams
124
,
126
can be adjusted by way of the control shaft
132
and the slider gear
128
. That is, as shown in
FIGS. 12
to
14
, valve lift amounts of the intake valves
12
a
,
12
b
can be made continuously variable by driving the slide actuator
100
.
It is to be noted herein that
FIGS. 12A and 12B
shows the intermediary drive mechanism
120
in a state where the control shaft
132
has been moved to the critical position in the direction H by the slide actuator
100
. That is,
FIGS. 12A and 12B
correspond to the state shown in FIG.
7
C. While
FIGS. 12
to
15
show a mechanism in which the second rocking cam
126
drives the first intake valve
12
a
, the same holds true for a mechanism in which the first rocking cam
124
drives the second intake valve
12
b
. Therefore, the following description will be accompanied by reference symbols of the first rocking cam
124
and the second intake valve
12
b
as well.
In
FIG. 12A
, a base circle portion (a portion other than the nose
45
c
) of the intake cam
45
a
is in contact with the roller
122
f
of the shaft input portion
122
in the intermediary drive mechanism
120
. Although not shown, the roller
122
is urged by a spring so as to be always in contact with the side of the intake cam
45
a
. In this state, the noses
124
d
,
126
d
of the rocking cams
124
,
126
are not in contact with a roller
13
a
of a rocker arm
13
. The base circle portion adjacent to the noses
124
d
,
126
d
is in contact with the roller
13
a
of the rocker arm
13
. Hence, the intake valves
12
a
,
12
b
are closed.
If the nose
45
c
of the intake cam
45
a
depresses the roller
122
f
of the shaft input portion
122
through rotation of the intake cam shaft
45
, rocking movements are transmitted from the shaft input portion
122
to the rocking cams
124
,
126
via the slider gear
128
in the intermediary drive mechanism
120
, and the rocking cams
124
,
126
rock in such a manner as to depress the noses
124
d
,
126
d
respectively. Hence, curved cam surfaces
124
e
,
126
e
formed on the noses
124
d
,
126
d
immediately come into contact with the roller
13
a
of the rocker arm
13
. As shown in
FIG. 12B
, the rocking cams
124
,
126
depress the roller
13
a
of the rocker arm
13
by means of the entire cam surfaces
124
e
,
126
e
, whereby the rocker arm
13
rocks around the side of a base end portion
13
c
supported by an adjuster
13
b
and a leading edge portion
13
d
of the rocker arm
13
greatly depresses a stem end
12
c
. Thus, the intake valves
12
a
,
12
b
open the intake ports
14
a
,
14
b
respectively with a maximum valve lift amount.
FIGS. 13A and 13B
show a state of the intermediary drive mechanism
120
in the case where the control shaft
132
has been returned by the slide actuator
100
from the state shown in
FIGS. 12A and 12B
in the direction L. That is,
FIGS. 13A and 13B
correspond to the state shown in FIG.
7
B.
In
FIG. 13A
, the base circle portion of the intake cam
45
a
is in contact with the roller
122
f
of the shaft input portion
122
in the intermediary drive mechanism
120
. In this state, the noses
124
d
,
126
d
of the rocking cams
124
,
126
are not in contact with the roller
13
a
of the rocker arm
13
. A base circle portion that is spaced slightly further apart from the noses
124
d
,
126
d
in comparison with the case of
FIGS. 12A and 12B
is in contact with the roller
13
a
of the rocker arm
13
. Hence, the intake valves
12
a
,
12
b
are closed. This is because the slider gear
128
has moved in the direction L in the intermediary drive mechanism
120
and thus the difference in phase between the roller
122
f
of the shaft input portion
122
and the noses
124
d
,
126
d
of the rocking cams
124
,
126
has become small.
If the nose
45
c
of the intake cam
45
a
depresses the roller
122
f
of the shaft input portion
122
through rotation of the intake cam shaft
45
, rocking movements are transmitted from the shaft input portion
122
to the rocking cams
124
,
126
via the slider gear
128
in the intermediary drive mechanism
120
, and the rocking cams
124
,
126
rock in such a manner as to depress the noses
124
d
,
126
d
respectively.
As described above, in the state shown in
FIG. 13A
, the base circle portion that is spaced apart from the noses
124
d
,
126
d
is in contact with the roller
13
a
of the rocker arm
13
. Hence, even if the rocking cams
124
,
126
have rocked, the roller
13
a
of the rocker arm
13
remains in contact with the base circle portion for a while without coming into contact with the curved cam surfaces
124
e
,
126
e
formed on the noses
124
d
,
126
d
. Thereafter, the curved cam surfaces
124
e
,
126
e
come into contact with the roller
13
a
and depress the roller
13
a
of the rocker arm
13
as shown in FIG.
13
B. Hence, the rocker arm
13
rocks around the base end portion
13
c
. However, since the roller
13
a
of the rocker arm
13
is spaced apart from the noses
124
d
,
126
d
at the beginning, the cam surfaces
124
e
,
126
e
have a correspondingly reduced area available. Thus, the rocking angle of the rocker arm
13
is reduced, and the amount by which the leading end portion
13
d
of the rocker arm
13
depresses the stem end
12
c
, namely, the valve lift amount is reduced. Hence, the intake valves
12
a
,
12
b
open the intake ports
14
a
,
14
b
respectively with a valve lift amount smaller than the maximum valve lift amount.
FIGS. 14A and 14B
show a state of the intermediary drive mechanism
120
in the case where the control shaft
132
has been returned by the slide actuator
100
to the maximum extent in the direction L. That is,
FIGS. 14A and 14B
correspond to the state shown in FIG.
7
A. In the state shown in
FIG. 14A
, the base circle portion that is spaced far apart from the noses
124
d
,
126
d
is in contact with the roller
13
a
of the rocker arm
13
. Hence, for an entire period of rocking movements, the roller
13
a
of the rocker arm
13
remains in contact with the base circle portion without coming into contact with the curved surfaces
124
e
,
126
e
formed on the noses
124
d
,
126
d
. That is, as shown in
FIG. 14B
, even if the nose
45
c
of the intake cam
45
a
has depressed the roller
122
f
of the shaft input portion
122
to the maximum extent, the curved cam surfaces
124
e
,
126
e
are not used to depress the roller
13
a
of the rocker arm
13
. Hence, the rocker arm
13
does not rock around the base end portion
13
c
, and the amount by which the leading end portion
13
d
of the rocker arm
13
depresses the stem end
12
c
, namely, the valve lift amount is “0”. Thus, even if the intake cam shaft
45
rotates, the intake valves
12
a
,
12
b
hold the intake ports
14
a
,
14
b
closed respectively.
By thus adjusting the axial position of the control shaft
132
by means of the slide actuator
100
, it becomes possible to continuously adjust valve lift amounts of the intake valves
12
a
,
12
b
as indicated by solid lines in a graph shown in FIG.
15
.
In the case where the intake valves
12
a
,
12
b
are opened, forces are applied from valve springs
12
d
of the intake valves
12
a
,
12
d
via the rocker arm in such a direction as to narrow an angle between the arm
122
c
and the noses
124
d
,
126
d
. Thus, a thrust force is generated in the slider gear
128
so as to cause a movement in the direction L. Hence, a thrust force Fs for moving the control shaft
132
in the direction L is applied via the engaging pins
132
a
. The more the valve lift amounts of the intake valves
12
a
,
12
b
are increased, the more firmly the valve springs
12
d
are compressed. Hence, the thrust force Fs generated in the control shaft
132
is increased as the slide actuator
100
moves the control shaft
132
in the direction H, as indicated by an alternate long and short dash line in FIG.
8
.
In the aforementioned structure of the first embodiment, a combination of the piston body
102
and the push portion
103
corresponds to an assisting force applying portion, the push portion
103
corresponds to an assisting force output portion, and the outer peripheral surface of the roller
102
k
corresponds to a conversion plane.
The following effects are obtained from the first embodiment that has been described above.
(a) A force output by the output rod
103
a
is converted into an assisting force via the roller
102
k
while the outer peripheral surface of the roller
102
k
moving together with the control shaft
132
serves as a conversion plane. The force thus converted is applied to the control shaft
132
. Hence, as shown in
FIG. 8
, as the control shaft
132
moves in such a direction as to increase valve lift amounts of the intake valves
12
a
,
12
b
, the assisting force can be correspondingly increased. Accordingly, a suitable assisting force that can act against a thrust force generated in the intermediary drive mechanism
120
can be applied to the control shaft
132
.
As a result, even if the pressure-receiving area of the piston portion
102
a
has been reduced for the sake of responding properties, there is no apprehension that a minimum hydraulic fluid pressure will not be ensured on the side with a large valve lift amount or that a delay will be caused in responding properties during movements of the control shaft
132
.
(b) A restoring force of the spring
103
c
is used in an output from the output rod
103
a
. Thus, the more easily the axial position of the control shaft
132
is shifted to the high-lift side with a relatively simple structure, the more the assisting force can be increased. Moreover, unlike the case of a magnetic force or the like, the restoring force is not weakened suddenly. That is, an assisting force that is sufficient even for axial movements of the control shaft
132
over an extensive range is generated.
(c) In particular, the slide actuator
100
is applied to the intake valves
12
a
,
12
b
and used to adjust their valve lift amounts. Even for such a use, a suitable assisting force can be applied to the control shaft
132
due to the aforementioned structure. Therefore, the intake air amount of the engine
2
can be regulated with a quick response.
In a second embodiment, valve lift amounts of intake valves
212
a
,
212
b
are adjusted by a slide actuator
300
through axial movements of an auxiliary shaft
250
that is connected to an intake cam shaft
245
via a roller bearing portion
250
a
as shown in FIG.
16
. The intake cam shaft
245
is interlocked with rotation of the crank shaft of the engine via a timing sprocket (which may be replaced with a timing gear or a timing pulley) disposed at one end of the intake cam shaft
245
. However, since the auxiliary shaft
250
is connected to the intake cam shaft
245
via the roller bearing portion
250
a
, it does not rotate in such a manner as to interlock with rotation of the intake cam shaft
245
. The auxiliary shaft
250
moves together with the intake cam shaft
245
only in the axial direction. It is to be noted herein that a timing sprocket
252
connected to the intake cam shaft
245
is supported so as to be rotatable with respect to the cylinder block of the engine but immovable in the axial direction. However, the timing sprocket
252
is connected at a central portion thereof to the intake cam shaft
245
via a straight spline mechanism
252
a
, thus allowing axial movements of the intake cam shaft
245
.
It is to be noted herein that intake cams
245
a
on the intake cam shaft
245
are designed as three-dimensional cams that continuously change in profile in the axial direction. More specifically, the intake cams
245
a
are formed such that their cam noses are reduced in height toward the right side in FIG.
16
and increased in height toward the left side in FIG.
16
. Such changes in profile make it possible to change valve lift amounts substantially in the same manner as shown in FIG.
15
.
The slide actuator
300
includes a piston portion
310
and an assisting portion
320
. The piston portion
310
is designed such that a piston
310
b
is accommodated in a cylinder
310
a
. The piston
310
b
is connected to the auxiliary shaft
250
. In accordance with a state of supply of a hydraulic pressure from the OCV
104
that is controlled by the ECU, the piston
310
b
moves as indicated by an arrow, whereby the intake cam shaft
245
can be axially moved via the auxiliary shaft
250
and the bearing portion
250
a.
The assisting portion
320
includes a slide cam
322
in a housing
320
a
. In this case, the slide cam
322
has a generally hemispherical shape and is connected in a rotational center axis portion on the spherical side to a coupling shaft
350
. The coupling shaft
350
is coaxially connected to the piston
310
b
on the other side of the auxiliary shaft
250
. Accordingly, the axial position of the slide cam
322
is interlocked with a position of displacement of the piston
310
b.
A roller
324
b
disposed at a leading end of an output rod
324
a
provided in a push portion
324
is in contact with a generally spherical cam surface
322
a
of the slide cam
322
. It is to be noted herein that the push portion
324
is different only in a roller portion
324
b
and basically identical in structure with the push portion
103
of the aforementioned first embodiment. That is, the output rod
324
a
presses the cam surface
322
a
of the slide cam
322
by means of a compressed spring
324
c
, and applies an assisting force acting in the direction H to the intake cam shaft
245
via the piston
310
b
, the auxiliary shaft
250
, and the bearing portion
250
a
. A stroke sensor core
360
a
is mounted in a central portion of the slide cam
322
on the other side of the coupling shaft
350
. A leading edge of the stroke sensor core
360
a
is inserted into a stroke sensor coil
360
b
that is attached to the housing
320
a
. Hence, a shaft position of the intake cam shaft
245
is detected, and a signal corresponding to the shaft position is output to the ECU from the stroke sensor coil
360
b.
As shown in the drawings, the intake cams
245
a
designed as three-dimensional cams are designed such that their valve lift amounts are increased toward the left side. Thus, restoring forces received from the valve springs
212
d
of the intake valves
212
a
,
212
b
generate a thrust force applied to the intake cam shaft
245
in the direction L by means of the cam surfaces of the intake cams
245
a
. Hence, the cam surface
322
a
of the slide cam
322
is inclined in a curved manner and reversely with respect to the cam surfaces of the intake cams
245
a
and thus generates an assisting force that acts against the aforementioned thrust force. If the piston
310
b
exists at a critical position in the direction L as shown in
FIG. 16
, the aforementioned thrust force is small. Therefore, the roller
324
b
is in contact with the cam surface
322
a
of the slide cam
322
at a position with a slight inclination with respect to the axis of the intake cam shaft
245
. If the piston
310
b
has been moved toward a critical position in the direction H, the restoring forces received from the valve springs
212
d
of the intake valves
212
a
,
212
b
are increased, and the thrust force is increased as well. Hence, the inclination of the cam surface
322
a
at a position for contacting the roller
324
b
is gradually increased, which causes an increase in the assisting force. If the piston
310
b
reaches the critical position in the direction H as shown in
FIG. 17
, the absolute values of the thrust force and the assisting force are maximized. The thrust force and the assisting force counterbalance each other as in the case of the aforementioned first embodiment shown in FIG.
8
.
In the structure of the aforementioned second embodiment, the intake cam shaft
245
corresponds to a control shaft and the cam surface
322
a
of the slide cam
322
corresponds to a conversion plane.
The following effects are obtained from the second embodiment that has been described above.
(a) A force output by the output rod
324
a
is converted into an assisting force while the cam surface
322
a
of the slide cam
322
axially interlocked with the intake cam shaft
245
serves as a conversion plane. The force thus converted is applied to the intake cam shaft
245
. Hence, as the intake cams
245
a
are moved by the intake cam shaft
245
in such a direction as to increase valve lift amounts, the assisting force can be correspondingly increased. Accordingly, a suitable assisting force that can act against a thrust force applied to the intake cam shaft
245
from the intake cams
245
a
can be applied to the intake cam shaft
245
.
As a result, even if the pressure-receiving area of the piston
310
b
has been reduced for the sake of responding properties, there is no apprehension that a minimum hydraulic fluid pressure will not be ensured on the side with a large valve lift amount or that responding properties will deteriorate.
(b) The effects (b) and (c) of the aforementioned first embodiment also are obtained.
In the aforementioned embodiments, the urging force of the springs
103
c
,
324
c
is utilized to apply a pressing force for the roller
102
k
or the slide cam
322
to the output rods
103
a
,
324
a
. However, it is also appropriate that a pressing force be applied to the output rods
103
a
,
324
a
through a fluid pressure such as an oil pressure or an air pressure. In this case, almost no drop in pressure is caused even by movements of the control shaft
132
and the intake cam shaft
245
. Therefore, a suitable assisting force that can be sufficient even for movements of the control shaft
132
and the intake cam shaft
245
over a more extensive range can be generated.
The slide actuator
300
of the second embodiment may be employed in the first embodiment instead of the slide actuator
100
. Further, the slide actuator
100
of the first embodiment may be employed in the second embodiment instead of the slide actuator
300
.
In the aforementioned embodiments, the number of the output rods
103
d
,
324
a
provided for the slide actuator
100
,
300
is two. However, it is also appropriate that this number be one, or three or more. Further, it is not absolutely required that the single slide actuator
100
or
300
be provided for the control shaft
132
or the intake cam shaft
245
. That is, two or more slide actuators may be axially coupled in series so as to strengthen an assisting force.
In the aforementioned embodiments, the output rods
103
a
,
324
a
protrude in the direction perpendicular to the axis of the control shaft
132
or the intake cam shaft
245
. However, as shown in
FIGS. 18
,
19
, even if the output rods
103
a
,
324
a
protrude in a direction that is not perpendicular to the axis but parallel to a virtual plane (PY, QY) perpendicular to the axis, an assisting force can be generated.
FIG. 18
shows a modified example of the first embodiment. In
FIG. 18
, each of two shaft portions
402
J disposed parallel to a piston body
402
is provided with a corresponding pair of rollers
402
k
. Axes “az” of the rollers
402
k
are parallel to a virtual plane (PY) that is perpendicular to an axis “ax” of a control shaft. Output rods
403
a
having axes “ay” protrude parallel to the virtual plane (PY) in such a manner as to be in contact with outer peripheral surfaces of the rollers
402
k
. Even in such a structure, the four rollers
402
k
receive pressing forces output by the four output rods
403
a
, whereby the pressing forces are converted into assisting forces acting in the direction of an axis “ax” of the control shaft on the outer peripheral surfaces of the rollers
402
k
. Thus, even if a large thrust force is generated in the intermediary drive mechanism, those assisting forces can act against the thrust force.
FIG. 19
shows a modified example of the second embodiment. Although the slide cam
322
of the second embodiment assumes a generally hemispherical shape, a slide cam
522
of this modified example assumes a generally semicolumnar shape. A coupling shaft
550
is fitted to the center of an outer peripheral surface of the slide cam
522
. Output rods
524
a
having axes “by” protrude parallel to a virtual plane (QY) perpendicular to an axis “bx” in such a manner as to be in contact with a cam surface
522
a
constructed of the outer peripheral surface. Rollers
524
b
are provided on the ends of the rods
524
a
. Even in such a structure, the cam surface
522
a
receives pressing forces output by the four output rods
524
a
(the lower two are not shown), whereby the pressing forces are converted into assisting forces acting in the direction of the axis “bx” of the coupling shaft
550
. Thus, even if a large thrust force is generated, those assisting forces can act against the thrust force.
In the aforementioned first embodiment (FIG.
3
), the rollers
102
k
are disposed on the side of the piston portion
102
a
. However, it is also appropriate that each of the rollers
102
k
be disposed at the leading end of a corresponding one of the output rods
103
a
and that a protrusion identical in shape to the leading end portions
103
d
of the output rods
103
(or a salient strip identical in cross-sectional shape to the leading end portions
103
d
of the output rods
103
) be formed on the side of the piston portion
102
a
. In this case, the same function as in the first embodiment can be substantially achieved. In the second embodiment (
FIG. 16
) as well, it is appropriate that the roller
324
b
be disposed on the side of the coupling shaft
350
and that a cam having a generally cylindrical surface identical in shape to the cam surface
322
a
of the slide cam
322
be disposed on the side of the output rod
324
a
. In this case, the same function as in the second embodiment can be substantially achieved. As for the examples described with reference to
FIGS. 18 and 19
as well, the structure in which the rollers are disposed at the leading ends of the output rods and the structure in which the rollers are disposed on the side of the control shaft or the coupling shaft may be interchanged. In this case as well, the same function as described above can be substantially achieved.
As described above, an embodiment according to one aspect of the invention is designed such that the assisting force applying portion increases the assisting force as the axial position of the control shaft is shifted to the high-lift side. Hence, a suitable assisting force capable of acting against a thrust force that is increased as the axial position of the control shaft is shifted to the high-lift side can be applied to the variable valve mechanism. Since the assisting force is generated on the basis of a restoring force of the elastic body or a pressure of the fluid, it is not weakened all of a sudden as in the case of a magnetic force. That is, an assisting force that is sufficient even for axial movements of the control shaft over an extensive range can be generated.
As a result, the apprehension that a minimum hydraulic fluid pressure will not be ensured on the side of a larger valve lift amount or that responding properties will deteriorate can be eliminated.
The assisting device of the aforementioned variable valve mechanism can be characterized as follows. The assisting force applying portion includes the assisting force output portion and the conversion plane. The assisting force output portion outputs a restoring force of an elastic body or a pressure of a fluid parallel to the virtual plane intersecting with the axis of the control shaft. The conversion plane receives a force output from the assisting force output portion, converts it into a force acting in the direction of the axis of the control shaft, and makes it available as an assisting force. The assisting force applying portion changes the inclination of the conversion plane at a position to which a force from the assisting force output portion is transmitted, in such a manner as to interlock with axial movements of the control shaft. Thus, as the axial position of the control shaft is shifted to the high-lift side, the assisting force can be correspondingly increased.
Since the aforementioned conversion plane is provided, the force output by the assisting force output portion is converted into a force acting in the direction of the axis of the control shaft. The inclination of the conversion plane to which the force is transmitted changes while interlocking with axial movements of the control shaft, whereby the assisting force is increased in proportion to a shift to the high-lift side. Therefore, a suitable assisting force that can act against the aforementioned thrust force can be applied to the variable valve mechanism.
In the embodiment according to one aspect of the invention, the output rod transmits a force by means of the conversion plane.
The output thus constructed makes it possible to easily transmit a force to the conversion plane and adjust the magnitude of an assisting force through an inclination of the conversion plane. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
Furthermore, in the embodiment according to one aspect of the invention, the conversion plane is designed as a cam surface and a cam having the cam surface is designed to be moved in the direction of the axis of the control shaft, whereby the assisting force can be easily increased by means of a restoring force of the elastic body or a pressure of the fluid as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
In addition, in the embodiment according to one aspect of the invention, the conversion plane is designed as an outer peripheral surface of a ring and the position of the output rod for contacting the outer peripheral surface is axially moved in such a manner as to interlock with the control shaft, whereby the assisting force can be easily increased by means of a restoring force of the elastic body or a pressure of the fluid as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
Instead of the structure of the aforementioned embodiments in which the output rods protrude in the direction substantially perpendicular to the axis of the control shaft, it is also appropriate that the output rods be in contact with the conversion plane by protruding parallel to the virtual plane that is substantially perpendicular to the axis of the control shaft as described above. This also makes it possible to easily increase the assisting force by means of a restoring force of the elastic body or a pressure of the fluid as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
The variable valve mechanism may also include the cam shaft, the cams, the intermediary drive mechanism, the control shaft, and the actuator. In such a structure as well, the structure of the aforementioned assisting force applying portion makes it possible to easily increase the assisting force by means of a restoring force of the elastic body or a pressure of the fluid as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
The variable valve mechanism may also include the three-dimensional cams and the control shaft. Even in such a structure, the structure of the aforementioned assisting force applying portion makes it possible to easily increase the assisting force by means of a restoring force of the elastic body or a pressure of the fluid as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
Further, it is also appropriate that the control shaft be used as the cam shaft having the three-dimensional cams as well. In this case as well, a suitable assisting force that can act against a thrust force can be applied to the variable valve mechanism.
As in the case of the aforementioned embodiments, the assisting device generates an assisting force by means of a restoring force of the spring. Thus, the spring can be used as the elastic body. Accordingly, since the assisting force can be easily increased by means of the restoring force of the spring as the axial position of the control shaft is shifted to the highlift side, a suitable assisting force that can act against the thrust force can be applied to the variable valve mechanism with a relatively simple structure.
Further, the assisting device can use oil as a fluid for generating an assisting force. Accordingly, the assisting force can be easily increased by means of a hydraulic pressure as the axial position of the control shaft is shifted to the high-lift side. Thus, a suitable assisting force that can act against the thrust force can be applied to the variable valve mechanism.
Furthermore, as in the case of the aforementioned embodiments, the variable valve mechanism makes it possible to continuously change valve lift amounts of the intake valves of the internal combustion engine.
By applying the aforementioned assisting device to the variable valve mechanism for adjusting valve lift amounts of the intake valves of the internal combustion engine, it becomes possible to apply a suitable assisting force to the variable valve mechanism and to adjust the amount of intake air in the internal combustion engine with a quick response.
While the invention has been described with reference to preferred exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments or constructions. On the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the disclosed invention are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more less or only a single element, are also within the spirit and scope of the invention.
Claims
- 1. An assisting device for applying an assisting force to counteract a thrust force generated in a variable valve mechanism, comprising:valves disposed in the variable valve mechanism; a control shaft that is movable to cause valve lift amounts of the valves to continuously change with changes in an axial position of the control shaft, the control shaft receiving the thrust force from the valves; a force applying member coupled to the control shaft and that receives an adjusting force from a first source of force to adjust the axial position of the control shaft; and an assisting force applying portion that generates and applies the assisting force to the control shaft on the basis of a restoring force of an elastic body or a pressure of a fluid, which is a second source of force that is in addition to the first source of force, the assisting force applying portion increasing the assisting force as the axial position of the control shaft is shifted to a high-lift side.
- 2. An assisting device for applying an assisting force to counteract a thrust force generated in a variable valve mechanism, comprising:valves disposed in the variable valve mechanism; a control shaft that is movable to cause valve lift amounts of the valves to continuously change with changes in an axial position of the control shaft, the control shaft receiving the thrust force from the valves; and an assisting force applying portion that generates and applies the assisting force to the control shaft on the basis of a restoring force of an elastic body or a pressure of a fluid, the assisting force applying portion increasing the assisting force as the axial position of the control shaft is shifted to a high-lift side, wherein the assisting force applying portion comprises: an assisting force output portion that outputs the restoring force of the elastic body or the pressure of the fluid parallel to a virtual plane perpendicular to an axis of the control shaft, and a conversion plane that converts a force output from the assisting force output portion into a force acting in a direction of the axis of the control shaft so as to use the force as the assisting force, and changes an inclination of the conversion plane at a position to which the force from the assisting force output portion is converted as the control shaft moves axially so as to increase the assisting force as the axial position of the control shaft is shifted to the high-lift side.
- 3. The assisting device according to claim 2, wherein:the assisting force output portion comprises an output rod protruding toward the conversion plane due to the restoring force of the elastic body or a pressure of the fluid; and the force from the output rod is transmitted to the conversion plane through contact of the output rod with the conversion plane.
- 4. The assisting device according to claim 3, wherein:the smaller an angle of the output rod with respect to an abutment surface between the output rod and the conversion plane becomes, the larger the force transmitted to the control shaft becomes; and the closer to a right angle the angle of the output rod with respect to the abutment surface between the output rod and the conversion plane becomes, the smaller the assisting force transmitted to the control shaft becomes.
- 5. The assisting device according to claim 4, wherein:the output rod protrudes in a direction substantially perpendicular to the axis of the control shaft; the conversion plane is formed as a cam surface on a cam moving in a direction of the axis of the control shaft while interlocking with the control shaft; and a position of the output rod that contacts the cam surface is axially moved as the control shaft axially moves, whereby the assisting force is increased as the axial position of the control shaft is shifted to the high-lift side.
- 6. The assisting device according to claim 4, wherein:the output rod protrudes in a direction substantially perpendicular to the axis of the control shaft; the conversion plane is formed as an outer peripheral surface of a ring that moves in the direction of the axis of the control shaft as the control shaft axially moves, with an axis parallel to the virtual plane substantially perpendicular to the axis of the control shaft serving as an axis of rotation; and a position of the output rod that contacts the outer peripheral surface is moved in the direction of the axis of the control shaft as the control shaft axially moves, whereby the assisting force is increased as the axial position of the control shaft is shifted toward the high-lift side.
- 7. The assisting device according to claim 4, wherein:the output rod protrudes parallel to the virtual plane substantially perpendicular to the axis of the control shaft; the conversion plane is formed as an outer peripheral surface of a ring that moves in the direction of the axis of the control shaft as the control shaft axially moves, with an axis parallel to the virtual plane substantially perpendicular to the axis of the control shaft serving as an axis of rotation; and a position of the output rod that contacts the outer peripheral surface is moved in the direction of the axis of the control shaft as the control shaft axially moves, whereby the assisting force is increased as the axial position of the control shaft is shifted toward the high-lift side.
- 8. The assisting device according to claim 1, wherein the variable valve mechanism comprises:a cam shaft that is rotationally driven by a crank shaft of an internal combustion engine; cams disposed on the cam shaft; intermediary drive mechanisms each of which is pivotally supported by a shaft other than the cam shaft and each of which has a shaft input portion and a shaft output portion so that a corresponding one of the valves is driven at the output portion in response to the driving of the input portion by a corresponding one of the cams; the control shaft whose axial moving distance is based on a difference in phase between the input portion and the output portion of each of the intermediary drive mechanisms; and an actuator for axially moving the control shaft and thus adjusting the difference in phase between the shaft input portion and the shaft output portion of each of the intermediary drive mechanisms, and thus allows valve lift amounts to continuously change with changes in the axial position of the control shaft.
- 9. The assisting device according to claim 1, wherein:the variable valve mechanism is a mechanism that allows valve lift amounts to continuously change by axially moving three-dimensional cams whose cam profile changes in the axial direction; and an axial moving distance of the control shaft changes with an axial moving distance of the three-dimensional cams.
- 10. The assisting device according to claim 9, wherein the control shaft also serves as a cam shaft for the three-dimensional cams.
- 11. The assisting device according to claim 1, wherein the assisting force applying portion generates the assisting force on the basis of a restoring force of a spring.
- 12. The assisting device according to claim 1, wherein the assisting force applying portion generates the assisting force on the basis of a hydraulic pressure.
- 13. The assisting device according to claim 1, wherein the variable valve mechanism allows valve lift amounts of intake valves of an internal combustion engine to continuously change.
- 14. An assisting method for applying an assisting force to counteract a thrust force generated in a variable valve mechanism, comprising the steps of:allowing valve lift amounts of valves disposed in the variable valve mechanism to continuously change with changes in an axial position of a control shaft; adjusting the axial position of the control shaft by applying an adjusting force to a force applying member that is coupled to the control shaft, the adjusting force is supplied from a first source of force; and increasing the assisting force that is applied to the control shaft on the basis of a restoring force of an elastic body or a pressure of a fluid as the axial position of the control shaft that receives the thrust force is shifted to a high-lift side, the elastic body that supplies the restoring force or the fluid that supplies the pressure being a second source of force that is in addition to the first source of force.
- 15. An assisting method for applying an assisting force to counteract a thrust force generated in a variable valve mechanism, comprising the steps of:allowing valve lift amounts of valves disposed in the variable valve mechanism to continuously change with changes in an axial position of a control shaft; and increasing the assisting force that is applied to the control shaft on the basis of a restoring force of an elastic body or a pressure of a fluid as the axial position of the control shaft that receives the thrust force is shifted to a high-lift side, wherein: the restoring force of the elastic body or the pressure of the fluid is output to a virtual plane that intersects with an axis of the control shaft; the force output to the virtual plane is converted by a conversion plane into a force acting in a direction of the axis of the control shaft as the assisting force; and an inclination of the conversion plane at a position to which the force is transmitted to the conversion plane is changed with changes in axial movement of the control shaft, whereby the assisting force is increased as the axial position of the control shaft is shifted to the high-lift side.
- 16. The assisting method according to claim 14, wherein the force applying member includes a piston, and the first source of force is a source of hydraulic force that applies pressure to the piston.
- 17. The assisting device according to claim 1, wherein the force applying member includes a piston, and the first source of force is a source of hydraulic force that applies pressure to the piston.
- 18. The assisting device according to claim 2, wherein the variable valve mechanism comprises:a cam shaft that is rotationally driven by a crank shaft of an internal combustion engine; cams disposed on the cam shaft; intermediary drive mechanisms each of which is pivotally supported by a shaft other than the cam shaft and each of which has a shaft input portion and a shaft output portion so that a corresponding one of the valves is driven at the output portion in response to the driving of the input portion by a corresponding one of the cams; the control shaft whose axial moving distance is based on a difference in phase between the input portion and the output portion of each of the intermediary drive mechanisms; and an actuator for axially moving the control shaft and thus adjusting the difference in phase between the shaft input portion and the shaft output portion of each of the intermediary drive mechanisms, and thus allows valve lift amounts to continuously change with changes in the axial position of the control shaft.
- 19. The assisting device according to claim 2, wherein:the variable valve mechanism is a mechanism that allows valve lift amounts to continuously change by axially moving three-dimensional cams whose cam profile changes in the axial direction; and an axial moving distance of the control shaft changes with an axial moving distance of the three-dimensional cams.
- 20. The assisting device according to claim 19, wherein the control shaft also serves as a cam shaft for the three-dimensional cams.
- 21. The assisting device according to claim 2, wherein the assisting force applying portion generates the assisting force on the basis of a restoring force of a spring.
- 22. The assisting device according to claim 2, wherein the assisting force applying portion generates the assisting force on the basis of a hydraulic pressure.
- 23. The assisting device according to claim 2, wherein the variable valve mechanism allows valve lift amounts of intake valves of an internal combustion engine to continuously change.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2001-324757 |
Oct 2001 |
JP |
|
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
A 2000-54814 |
Feb 2000 |
JP |