U.S. patent application number 09/907751 was filed with the patent office on 2001-11-15 for valve timing adjusting device.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Hori, Akira, Sato, Osamu.
Application Number | 20010039933 09/907751 |
Document ID | / |
Family ID | 27329535 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010039933 |
Kind Code |
A1 |
Sato, Osamu ; et
al. |
November 15, 2001 |
Valve timing adjusting device
Abstract
A seal plate partitions a sectorial space which houses a vane
and a circumferential groove which houses a torsion spring, so that
the sectorial space is formed to prevent the communication between
an advance angle pressure chamber and a retard angle pressure
chamber regardless of the space of the circumferential groove. As a
result, by setting the inner diameter of the vane smaller than the
outer diameter of the torsion spring, the outer diameter of the
vane can be made relatively small without lowering the engine
performance. Therefore, it is possible to reduce the actuator in
size without lowering the engine performance, to reduce the weight
of a valve timing adjusting device and to obtain a mounting space
easily for mounting the valve timing adjusting device on the
engine.
Inventors: |
Sato, Osamu; (Takahama-city,
JP) ; Hori, Akira; (Handa-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Assignee: |
DENSO CORPORATION
|
Family ID: |
27329535 |
Appl. No.: |
09/907751 |
Filed: |
July 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09907751 |
Jul 19, 2001 |
|
|
|
09358872 |
Jul 22, 1999 |
|
|
|
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 2001/34483
20130101; F01L 1/344 20130101; F01L 2001/34469 20130101; F01L
2001/34479 20130101 |
Class at
Publication: |
123/90.17 ;
123/90.15 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 1998 |
JP |
10-213705 |
Nov 11, 1998 |
JP |
10-320446 |
Dec 18, 1998 |
JP |
10-360496 |
Claims
What is claimed is:
1. A valve timing adjusting device for an internal combustion
engine having a drive shaft, an intake valve, an exhaust valve and
a driven shaft which opens and closes at least one of the intake
valve and the exhaust valve, comprising: a housing which rotates
together with one of the drive shaft and the driven shaft; a
housing chamber formed in said housing; a vane housed in said
housing chamber to rotate together with the other one of the drive
shaft and the driven shaft relatively to said housing within a
predetermined rotational phase difference; an advance angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in an
advancing direction by a fluid pressure; a retard angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in a
retarding direction by said fluid pressure; a hydraulic pump for
supplying a working fluid to said advance angle fluid pressure
chamber and said retard angle fluid pressure chamber; first bias
means housed in a housing space formed in said housing, for biasing
said vane in an advancing direction of the driven shaft relatively
to the drive shaft; and a partition member for separating said
housing chamber from said housing space.
2. A valve timing adjusting device as in claim 1, wherein said vane
includes a fixing hole for fixing one end of said first bias
means.
3. A valve timing adjusting device as in claim 2, wherein; said
partition member includes a through hole for passing said one end
of said first bias means; and said through hole communicates with
one of said advance angle fluid pressure chamber and said retard
angle fluid pressure chamber.
4. A valve timing adjusting device as in claim 3, wherein said
through hole communicates with said advance angle fluid pressure
chamber.
5. A valve timing adjusting device as in claim 1, wherein said
partition member includes seal means for preventing a fluid from
leaking from said housing chamber or said housing space to an
outside thereof.
6. A valve timing adjusting device as in claim 5, wherein said seal
means includes a corrugation formed on said partition member.
7. A valve timing adjusting device as in claim 5, wherein said seal
means includes an elastic member disposed on at least one of side
faces of said partition member.
8. A valve timing adjusting device as in claim 1, wherein said
partition member includes guide means for guiding an end of said
first bias means.
9. A valve timing adjusting device as in claim 8, wherein; said
guide means includes a fixing hole provided at said vane for fixing
said end of said first bias means and includes a through hole
provided at said partition member for passing said end of said
first bias means; and said guide means is arranged such that a
width of said fixing hole in diametrical direction of said vane is
larger than a width of said through hole in diametrical direction
of said partition member.
10. A valve timing adjusting device as in claim 1, further
comprising: an abutting portion and an abutted portion individually
formed at said housing and said vane for restraining said vane from
rotating relatively to said housing by abutting against each other
when said vane is positioned at one circumferential end portion in
said housing chamber; second bias means for biasing said abutting
portion in an abutting direction to abut against said abutted
portion; and restraint means including said second bias means for
displacing said abutting portion in a direction opposite to said
abutting direction against a biasing force of said second bias
means; wherein said vane includes a fixing hole for fixing an end
of said first bias means.
11. A valve timing adjusting device as in claim 1, wherein; said
vane includes regulation means for regulating at least one of the
most advanced position and the most retarded position of said vane
when retained on an inner wall of said housing forming said housing
chamber; and said vane includes a fixing hole for fixing an end of
said first bias means.
12. A valve timing adjusting device as in claim 1, wherein said
working fluid is supplied to a sliding portion between said housing
and at least one of the drive shaft and the driven shaft from said
housing space.
13. A valve timing adjusting device for an internal combustion
engine having a drive shaft, an intake valve, an exhaust valve and
a driven shaft which opens and closes at least one of the intake
valve and the exhaust valve, comprising: a housing which rotates
together with one of the drive shaft and the driven shaft; a
housing chamber formed in said housing; a vane housed in said
housing chamber to rotate together with the other one of the drive
shaft and the driven shaft relatively to said housing within a
predetermined rotational phase difference; an advance angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in an
advancing direction by a fluid pressure; a retard angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in a
retarding direction by said fluid pressure; a hydraulic pump for
supplying a working fluid to said advance angle fluid pressure
chamber and said retard angle fluid pressure chamber; first bias
means housed in a housing space formed in said housing, for biasing
said vane in an advancing direction of the driven shaft relatively
to the drive shaft; an abutting portion and an abutted portion
individually formed at said housing and said vane for restraining
said vane from rotating relatively to said housing by abutting
against each other when said vane is positioned at one
circumferential end portion in said housing chamber; second bias
means for biasing said abutting portion in an abutting direction to
abut against said abutted portion; and restraint means including
said second bias means for displacing said abutting portion in a
direction opposite to said abutting direction against a biasing
force of said second bias means; wherein said vane includes a
fixing hole for fixing an end of said first bias means.
14. A valve timing adjusting device as in claim 13, wherein said
working fluid is supplied to a sliding portion between said housing
and at least one of the drive shaft and the driven shaft from said
housing space.
15. A valve timing adjusting device for an internal combustion
engine having a drive shaft, an intake valve, an exhaust valve and
a driven shaft which opens and closes at least one of the intake
valve and the exhaust valve, comprising: a housing which rotates
together with one of the drive shaft and the driven shaft; a
housing chamber formed in said housing; a vane housed in said
housing chamber to rotate together with the other one of the drive
shaft and the driven shaft relatively to said housing within a
predetermined rotational phase difference; an advance angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in an
advancing direction by a fluid pressure; a retard angle fluid
pressure chamber for rotating one of said housing and said vane
relatively to the other one of said housing and said vane in a
retarding direction by said fluid pressure; a hydraulic pump for
supplying a working fluid to said advance angle fluid pressure
chamber and said retard angle fluid pressure chamber; and first
bias means housed in a housing space formed in said housing, for
biasing said vane in an advancing direction of the driven shaft
relatively to the drive shaft, wherein; said vane includes
regulation means for regulating at least one of the most advanced
position and the most retarded position of said vane when retained
on an inner wall of said housing forming said housing chamber; and
said vane includes a fixing hole for fixing an end of said first
bias means.
16. A valve timing adjusting device as in claim 15, wherein said
working fluid is supplied to a sliding portion between said housing
and at least one of the drive shaft and the driven shaft from said
housing space.
17. A valve timing adjusting device for an internal combustion
engine having a drive shaft, an intake valve, an exhaust valve and
a driven shaft which opens and closes at least one of the intake
valve and the exhaust valve, comprising: a housing which rotates
together with one of the drive shaft and the driven shaft; a
housing chamber formed in said housing; a vane housed in said
housing chamber to rotate together with the other one of the drive
shaft and the driven shaft relatively to said housing within a
predetermined rotational phase difference, said vane dividing said
housing chamber into an advance angle pressure chamber and a retard
angle pressure chamber; and first bias means for biasing said vane
in an advancing direction of the driven shaft relatively to the
drive shaft.
18. A valve timing adjusting device as in claim 17, wherein; a
biasing force of said first bias means is between 10% of an average
torque in an idling rotation range of the driven shaft and an
average torque in an inertial rotation range of the driven
shaft.
19. A valve timing adjusting device as in claim 17, further
comprising: an abutting portion and an abutted portion individually
formed at said housing and said vane for restraining said vane from
rotating relatively to said housing by abutting against each other
when said vane is positioned at one circumferential end portion in
said housing chamber; second bias means for biasing said abutting
portion in an abutting direction to abut against said abutted
portion; restraint means including said second bias means for
displacing said abutting portion in a direction opposite to said
abutting direction against a biasing force of said second bias
means; and a first pressure receiving surface formed on said
abutting portion for receiving a first fluid pressure such that
said vane rotates in said advancing direction relatively to said
housing to release a restraint between said housing and said vane,
wherein; releasing pressure for releasing said restraint between
said housing and said vane by said first fluid pressure is less
than minimum working pressure necessary for rotating said vane in
said advancing direction relatively to said housing.
20. A valve timing adjusting device as in claim 17, wherein; a
biasing force of said first bias means is between an average torque
in an inertial rotation range of the driven shaft and a maximum
torque in said inertial rotation range of the driven shaft.
21. A valve timing adjusting device as in claim 17, further
comprising: an abutting portion and an abutted portion individually
formed at said housing and said vane for restraining said vane from
rotating relatively to said housing by abutting against each other
when said vane is positioned at one circumferential end portion in
said housing chamber; second bias means for biasing said abutting
portion in an abutting direction to abut against said abutted
portion; restraint means including said second bias means for
displacing said abutting portion in a direction opposite to said
abutting direction against a biasing force of said second bias
means; and a second pressure receiving surface formed on said
abutting portion for receiving a second fluid pressure such that
said vane rotates in a retarding direction relatively to said
housing to release a restraint between said housing and said
vane.
22. A valve timing adjusting device as in claim 17, wherein; a
biasing force of said first bias means is between 10% of an average
torque in an idling rotation range of the driven shaft and a
maximum torque in an inertial rotation range of the driven shaft.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a valve timing adjusting
device for changing the opening/closing timing (hereinafter
referred to as the "valve timing") to open/close an intake valve
and/or an exhaust valve of an internal combustion engine
(hereinafter referred to as the "engine") in accordance with a
drive condition.
[0003] 2. Related Art
[0004] There has been known in the art a vane type valve timing
adjusting device in which a cam shaft is driven by driving force
transmitting mechanism such as a chain sprocket rotating in
synchronism with the crankshaft of an engine so that the valve
timing of at least one of the intake valve and the exhaust valve is
controlled with a phase difference resulting from the relative
rotations between the driving force transmitting mechanism and the
cam shaft.
[0005] In this vane type valve timing adjusting device, a vane
rotating with the cam shaft is housed in a housing rotating with
the driving force transmitting mechanism. By adjusting the relative
rotation phase difference of the vane to the housing hydraulically,
moreover, the cam shaft and the driving force transmitting
mechanism are rotated relatively to each other to adjust the valve
timing of at least one of the intake valve and the exhaust valve in
accordance with the drive condition of the engine.
[0006] The phase control valve timing adjusting device for
controlling the valve timing of the engine valve aims at improving
the stability and fuel efficiency of the engine or reducing the
exhaust emission. At a light load condition of the engine of this
kind, the intake air amount is so small as to make it desirable to
reduce the residual exhaust gas, as might otherwise deteriorate the
combustion, in the cylinder of the engine.
[0007] For a time period (or an overlap period) for which the
intake valve and the exhaust valve are simultaneously open, a
negative pressure is established on the intake side by the
throttle, whereas a positive pressure prevails in the exhaust side.
This may invite the case in which the exhaust gas is blown back to
the intake side to deteriorate the combustion or to invite a
misfire. Therefore, it is demanded to close the exhaust valve early
and to open the intake valve late.
[0008] By retarding the timing for closing the intake valve, on the
other hand, the pumping loss can be reduced to improve the fuel
efficiency. At the idling time and the starting time, therefore,
the control has to be made in the fundamental phase where the
exhaust valve is closed early and where the intake valve is opened
late. Here, the condition of this fundamental phase on the intake
side defines the most retarded angle, and the condition on the
exhaust side defines the most advanced angle.
[0009] At an intermediate or heavier load of the engine, however,
the EGR ratio is controlled to reduce the pumping loss by the
internal EGR thereby to improve the fuel economy and reduce the
exhaust emission. This makes it necessary to advance the valve
opening timing on the intake side or to retard the valve opening
timing on the exhaust side. In short, the intake valve is
controlled in the advancing direction whereas the exhaust valve is
controlled in the retarding direction.
[0010] At the heaviest load of the engine, moreover, a large amount
of air has to be introduced into the cylinder of the engine. This
makes it necessary to close the intake valve early in the low speed
range thereby preventing the reverse flow into the manifold and to
make use of the inertia of the air in the high speed range thereby
closing the intake valve late.
[0011] On the exhaust side, on the other hand, the exhaust valve is
controlled to the phase capable of making the maximum use of
exhaust pulsations so that the advanced angle has to be controlled
to the maximum if the exhaust pulsations cannot be used. In short,
on the exhaust side, the exhaust valve has to be controlled from
the light load of the engine in the retarding direction from the
most advanced position and again in the advancing direction in
accordance with the load.
[0012] At this time the intake/exhaust valve can desirably be
controlled quickly to the demanded phase if the drive condition
changes. When it is impossible to control the intake/exhaust valve,
however, there may occur a problem such as the misfire or the
combustion instability of the engine.
[0013] Usually, the hydraulic pump of the engine is driven by the
crankshaft. As a result, however, the flow amount of the oil to be
discharged varies according to the rotation speed of the engine,
and it decreases at a low rotation speed of the engine. As a
result, the oil pressure may be decreased by the leakage and the
drop of the viscosity especially at a high oil temperature, and the
actuator may not operate. At this time, the intake side is retarded
by the driving torque of the cam shaft so that it can take the
fundamental phase. When an actuator having the same hydraulic
piston area as that of the intake side, however, the exhaust side
may not be controlled to the fundamental position, and the residual
gas in the cylinder of the engine may increase to cause the misfire
or stop the engine.
[0014] To solve the above problem, a valve timing adjusting device
disclosed in JP-A-9-264110 moves the intake side to the retarded
position or moves the discharge side to the advanced position by
the biasing force of a torsion spring.
[0015] However, the torsion spring is structurally required to
construct a spring around the whole circumference of the cam shaft.
This requirement makes it necessary to form a housing space for
housing the torsion spring, around the whole circumference of the
cam shaft in the axial direction.
[0016] The vane type phase variable actuator generates an operating
torque by controlling the oil pressure between the front and back
of the vane members. If the aforementioned housing space is formed
around the whole circumference of the cam shaft in the axial
direction, therefore, the hydraulic chambers at the front and back
of the vane members may be connected to fail to generate a pressure
necessary for the operation.
[0017] In order to prevent the connection between the hydraulic
chambers at the front and the back of the vane members, it is
necessary to set the internal diameter of the hydraulic chamber,
that is, the internal diameter of the vane members larger than an
external diameter of the torsion spring. In short, the area across
the vane members has to be retained to retain the oil pressure for
rocking the vane members.
[0018] If the internal diameter of the vane members is set larger
than the external diameter of the torsion spring, however, the
external diameter of the hydraulic chamber, that is, the external
diameter of the vane members has to be made relatively large.
Accordingly, the actuator becomes bigger. This enlarged structure
raises problems that the valve timing adjusting device is so raised
in its weight and manufacturing cost as to make it difficult to
mount it on the engine.
[0019] If the area across the vane members is enlarged by
increasing the number of vane members so as to make the external
diameter of the hydraulic chamber relatively small, on the other
hand, there arises a problem that the number of parts increases to
raise the manufacturing cost. Another problem is that the increase
in the number of vane members reduces the rocking angle of the vane
members so that the rocking angle of the vane members necessary for
improving the engine performance cannot be achieved to lower the
engine performance.
[0020] Further, a valve timing adjusting device disclosed in
JP-A-10-68306 moves the discharge side to the advanced position by
the biasing force of a torsion spring. Accordingly, when a vane
type phase variable actuator is used, the response in the advancing
direction is improved. However, the response in the retarding
direction is compromised comparing to the one without the torsion
spring.
[0021] Furthermore, when the vane is held at a predetermined
position, hydraulic fluid, having higher pressure than that of
hydraulic fluid to be supplied to the retard angle hydraulic
chamber, is supplied to the advance angle hydraulic chamber.
Accordingly, the pressure difference between the advance angle
hydraulic chamber and the retard angle hydraulic chamber increases,
and an oil leakage may occur therebetween.
[0022] Further, the area of the vane has to be increased in order
to perform the phase control with substantially low hydraulic
pressure. Accordingly, the actuator is increased in size, and the
valve timing adjusting device is increased in weight and
manufacturing cost. Thus, it may be difficult to mount it on the
engine.
SUMMARY OF THE INVENTION
[0023] The invention is made in light of the foregoing problems,
and it is an object of the present invention to provide a valve
timing adjusting device which reduces the actuator in size without
deteriorating the engine performance and obtains the mounting space
easily for mounting itself on the engine.
[0024] Another object of the present invention is to provide a
valve timing adjusting device which reduces the number of parts and
the manufacturing cost.
[0025] Further, another object of the present invention is to
provide a valve timing adjusting device which has a uniform
response of the phase conversion and improves the
controllability.
[0026] Further, another object of the present invention is to
provide a valve timing adjusting device which reduces the leakage
of the hydraulic fluid between the advance angle hydraulic chamber
and the retard angle hydraulic chamber.
[0027] According to a valve timing adjusting device of the present
invention, a partition member separates a housing chamber for
housing a vane from a housing space for housing a spring.
Accordingly, the housing chamber is formed to prevent the
communication between an advance angle pressure chamber and a
retard angle pressure chamber regardless of the housing space. As a
result, by setting an inner diameter of the vane smaller than an
outer diameter of the spring, an outer diameter of the vane is
reduced without lowering the engine performance. Therefore, the
actuator is reduced in size without lowering the engine
performance, and the weight of a valve timing adjusting device is
reduced, and a mounting space for mounting the valve timing
adjusting device on the engine is easily obtained.
[0028] According to another aspect of the present invention, it
includes a spring which applies biasing force to a vane in a
direction in which the driven shaft advances against the drive
shaft. Accordingly, the phase transition response is uniformed, and
the controllability is improved.
[0029] Furthermore, since the pressure of a working fluid to be
supplied to an advance angle pressure chamber is reduced, the
pressure difference between the advance angle pressure chamber and
a retard angle pressure chamber is reduced. Accordingly, the
working oil leakage between the advance angle pressure chamber and
the retard angle pressure chambers is reduced.
[0030] Furthermore, the area of the vane is reduced, and the
actuator is reduced in size without compromising the engine D
performance. Accordingly, the weight of the valve timing adjusting
device is reduced, and the mounting space for mounting it on the
engine is easily obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Additional objects and advantages of the present invention
will be more readily apparent from the following detailed
description of preferred embodiments when taken together with the
accompanying drawings, in which:
[0032] FIG. 1 is a longitudinal sectional view showing a valve
timing adjusting device according to a first embodiment of the
present invention;
[0033] FIG. 2 is a sectional view taken along line II-II of FIG.
1;
[0034] FIG. 3 is a sectional view taken along line III-III of FIG.
1;
[0035] FIG. 4 is a side view taken in the direction of IV of FIG.
1;
[0036] FIG. 5 is a sectional view taken along line V-V of FIG.
2;
[0037] FIG. 6 is a sectional view taken along line VI-VI of FIG.
1;
[0038] FIG. 7 is an enlarged view of a portion VII of FIG. 6;
[0039] FIG. 8 is a top plan view showing a seal plate of the first
embodiment of the present invention;
[0040] FIG. 9 is a sectional view taken along line IX-IX of FIG.
8;
[0041] FIG. 10 is an enlarged view of a portion X of FIG. 9;
[0042] FIG. 11 is a longitudinal sectional view showing a valve
timing adjusting device according to a second embodiment of the
present invention;
[0043] FIG. 12 is a longitudinal sectional view showing a valve
timing adjusting device according to a third embodiment of the
present invention;
[0044] FIG. 13 is a sectional view taken along line XIII-XIII of
FIG. 12.
[0045] FIG. 14 is a longitudinal sectional view showing a valve
timing adjusting device according to a fourth embodiment of the
present invention;
[0046] FIG. 15 is a sectional view taken along line XV-XV of FIG.
14;
[0047] FIG. 16 is a longitudinal sectional view showing a valve
timing adjusting device according to a fifth embodiment of the
present invention;
[0048] FIG. 17 is a sectional view taken along line XVII-XVII of
FIG. 16; and
[0049] FIG. 18 is a characteristic graph showing relations between
engine rotation speed and cam torque.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0050] Preferred embodiments of the present invention will now be
described with reference to the accompanying drawings.
[0051] [First Embodiment]
[0052] An engine valve timing adjusting device according to a first
embodiment of the present invention is shown in FIGS. 1 to 10. This
valve timing adjusting device 100 in the first embodiment is a
hydraulic control type for controlling the valve timing of an
exhaust valve.
[0053] Achain sprocket 8, as shown in FIG. 1, is coupled through
the not-shown timing chain to a crankshaft acting as the drive
shaft of the not-shown engine so that it is rotated in synchronism
with the crankshaft by a driving force transmitted thereto. A front
member 50 comprises a housing portion 51 and a bearing portion 52.
The housing portion 51, the chain sprocket 8 and a later-described
seal plate 7 are coupled by a bolt 53.
[0054] A cam shaft 1 acting as a driven shaft receives the driving
force from the chain sprocket 8 to open/close the not-shown intake
valve. The cam shaft 1 is supported by the not-shown cylinder head
so that it can rotate with a predetermined phase difference
relatively to the chain sprocket 8. This chain sprocket 8 and the
cam shaft 1 rotate clockwise, as viewed from the left-hand side of
FIG. 1. This rotating direction will be called the "advance
direction" hereinafter.
[0055] The chain sprocket 8 and the front member 50 construct a
housing member. A vane rotor 4 is covered at its two axial end
surfaces with the seal plate 7 and the housing portion 51 of the
front member 50. The chain sprocket 8, the seal plate 7 and the
front member 50 construct a drive side rotor and are coupled on a
common axis by the bolt 53.
[0056] A torsion spring 60 acting as first bias means is housed in
a circumferential groove 61 formed as a housing space in the chain
sprocket 8, and is fixed at its one end portion to the vane rotor 4
and at its other end to the chain sprocket 8. The torsion spring 60
biases the vane rotor 4 in the direction for the vane rotor 4 to
advance with respect to the chain sprocket 8, that is, for the cam
shaft 1 to advance with respect to the crankshaft.
[0057] An oil passage 62, as extended from the circumferential
groove 61 to the side opposite to the front member, is formed to
lubricate a sliding portion, that is, a bearing portion between the
cam shaft 1 and the chain sprocket 8 with the working oil leaking
into the circumferential groove 61.
[0058] As shown in FIG. 2, the housing member 51 of the front
member 50 has shoes 51a, 51b and 51c formed in a trapezoidal shape
at a substantially equal spacing in the circumferential direction.
In the three circumferential clearances of the shoes 51a, 51b and
51c, there are individually formed sectorial spaces 55 as housing
chambers for housing vanes 4a, 4b and 4c as vane members. Inner
circumferential surface of the shoes 51a, 51b and 51c are formed to
have an arcuate cross section.
[0059] The vane rotor 4 is provided substantially equidistantly in
the circumferential direction with the vanes 4a, 4b and 4c which
are rotatably housed in the sectorial spaces 55 formed in the
circumferential clearances of the shoes 51a, 51b and 51c.
[0060] The vane 4c is provided on the advance side with an advance
stopper 41 and on the retard side with a retard stopper 42. Arrows,
as appearing in FIG. 2, indicate the retard direction and the
advance direction of the vane rotor 4 with respect to the housing
portion 51.
[0061] In FIG. 2, each vane is positioned at one circumferential
end portion of each sectorial space 55 so that the vane rotor 4 is
positioned at the most advanced position with respect to the
housing portion 51. The most advanced position is regulated by
retaining the advance stopper 41 on the retard side face of the
shoe 51c. On the other hand, the most retarded position is
regulated by retaining the retard stopper 42 on the advance side
face of the shoe 51c.
[0062] The advance stopper 41 and the retard stopper 42 construct
regulation means. As shown in FIG. 1, the vane rotor 4 is coupled
integrally to the cam shaft 1 by a bolt 5, and a bush 6 is
press-fitted in and supported by the vane rotor 4 to construct a
driven side rotor.
[0063] As shown in FIG. 1, the vanes 4a, 4b and 4c are set to have
an internal diameter smaller than the external diameter of the
torsion spring 60. As shown in FIG. 5, on the other hand, the vane
4c is provided with a fixing hole 40 for fixing one end portion of
the torsion spring 60. By fixing the other end portion of the
torsion spring 60 to the chain sprocket 8, therefore, this torsion
spring 60 can be assembled without providing any special member for
receiving the biasing force of the torsion spring 60 having a
larger external diameter than the internal diameter of the vanes
4a, 4b and 4c. Moreover, the fixing hole 40 is easily formed
because the vane 4c having the advance stopper 41 and the retard
stopper 42 is made thicker than the vane 4b so as to retain the
strength.
[0064] The cam shaft 1 and the bush 6 are so individually fitted as
to rotate relatively to the bearing portion 52 of the front member
50. As a result, the cam shaft 1 and the vane rotor 4 can rotate
coaxially relatively to the chain sprocket 8 and the front member
50.
[0065] As shown in FIG. 2, the seal member 9 is fitted on the outer
circumferential wall of the vane rotor 4. A small clearance is
provided between the outer circumferential wall of the vane rotor 4
and the inner circumferential wall of the housing portion 51 of the
front member 50. Seal members 9 prevents the leakage of the working
oil through the clearance between the oil pressure chambers. As
shown in FIG. 1, the seal members 9 are individually biased onto
the inner circumferential wall of the housing portion 51 by the
spring forces of leaf springs 10.
[0066] In the inner wall of the vane 4a, as shown in FIG. 2, there
is press-fitted a guide ring 91, into which there is inserted a
stopper piston 97 as an abutting portion. As shown in FIG. 1, the
stopper piston 97 is formed into a bottomed cylindrical shape of a
substantially equal external diameter, which is composed of a
bottomed cylindrical portion 97a and a flange portion 97b formed at
the open end portion of the cylindrical portion 97a. The stopper
piston 97 is so fitted in the guide ring 91 as to slide in the
axial direction of the cam shaft 1. The stopper piston 97 is biased
to the side opposite to the chain sprocket by a spring 96 acting as
second bias means.
[0067] In the stopper hole formed in the housing portion 51 of the
front member 50, there is press-fitted a fitting ring 54 having a
tapered hole 54a acting as an abutted portion, so that the stopper
piston 97 can be fitted in the tapered hole 54a when in the most
advanced position shown in FIG. 2. When the stopper piston 97 is so
fitted in the tapered hole 54a that the former comes into abutment
against the latter in the rotational direction, the vane rotor 4 is
restrained from rotating relatively to the housing portion 51. In
short, the stopper piston 97 and the tapered hole 54a take the
restrained positions at the most advanced position. The stopper
piston 97, the tapered hole 54a and the spring 96 construct
restraint means.
[0068] The oil pressure chamber 18, as located on the left-hand
side of the flange portion 97b, has communication with a
later-described advance angle oil pressure chamber 85 via an oil
passage 19 shown in FIG. 2. On the other hand, an oil pressure
chamber 27, as formed on the tip of the cylindrical portion 97a,
has communication with a later-described retard angle oil pressure
chamber 80 via an oil passage 31 shown in FIG. 2.
[0069] The area of a first pressure receiving surface of the flange
portion 97b for receiving the oil pressure of an oil pressure
chamber 18 is set smaller than that of a second pressure receiving
surface of the cylindrical portion 97a for receiving the oil
pressure of the oil pressure chamber 27. The pressures to be
received by the first pressure receiving surface and the second
pressure receiving surface from the working oils in the oil
pressure chamber 18 and the oil pressure chamber 27 respectively
act to extract the stopper piston 97 from the tapered hole 54a.
[0070] The pressure receiving area of the first pressure receiving
surface is substantially equal to the annular area corresponding to
the diametrical difference between the flange portion 97b and the
cylindrical portion 97a, and the pressure receiving area of the
second pressure receiving surface is substantially equal to the
sectional area of the cylindrical portion 97a. When a working oil
under a predetermined or higher pressure is fed to the advance
angle oil pressure chamber 85 or the retard angle oil pressure
chamber 80, the stopper piston 97 comes out of the tapered hole 54a
against the biasing force of the spring 96.
[0071] The position of the stopper piston 97 and the position of
the tapered hole 54a are so relatively set that the stopper piston
97 can be fitted in the tapered hole 54a by the biasing force of
the spring 96 when the vane rotor 4 is at the most advanced
position relatively to the housing portion 51 of the front member
50, that is, when the cam shaft 1 is at the most advanced position
relatively to the crankshaft.
[0072] As shown in FIG. 2: the retard angle oil pressure chamber 80
is formed between the shoe 51a and vane 4a; a retard angle oil
pressure chamber 81 is formed between the shoe 51b and the vane 4b;
and a retard angle oil pressure chamber 82 is formed between the
shoe 51c and the vane 4c. On the other hand: an advance angle oil
pressure chamber 83 is formed between the shoe 51a and the vane 4b;
an advance angle oil pressure chamber 84 is formed between the shoe
51b and the vane 4c; and the advance angle oil pressure chamber 85
is formed between the shoe 51c and the vane 4a.
[0073] As shown in FIG. 1, the seal plate 7 as a partition member
separates the sectorial space 55 from the circumferential groove
61. In other words, the seal plate 7 separates a housing chamber
for housing the vanes 4a, 4b and 4c from a housing chamber for
housing the torsion spring 60. As a result, the sectorial space 55
is constructed such that the advance angle oil pressure chambers
83, 84 and 85 and the retard angle oil pressure chambers 80, 81 and
82 are not connected regardless of the space of the circumferential
groove 61.
[0074] Over the whole circumference of the seal plate 7, as shown
in FIGS. 8, 9 and 10, there is formed a corrugation 72. This seal
plate 7 is constructed of a metal plate 73 and elastic members 74.
These elastic members 74 are provided by adhering or coating them
on the two faces of the metal plate 73 and are made of an elastic
material such as acrylic rubber resisting to heat or the working
oil. As a result, a seal member such as an O-ring need not be
provided so that the number of parts can be reduced.
[0075] Moreover, a groove for the O-ring need not be formed in the
seal plate 7 so that the number of manufacture steps can be
reduced. This makes it possible to lower the manufacture cost and
to prevent the working oil reliably by the simple construction from
leaking from the sectorial space 55 or the circumferential groove
61 to the outside. Here, the corrugation 72 and the elastic members
74 construct seal means.
[0076] As shown in FIG. 3, a circumferentially elongated through
hole 70 is formed in the seal plate 7. This through hole 70
receives one end portion of the torsion spring 60. As shown in FIG.
2, the through hole 70 has communication with the advance angle oil
pressure chamber 84 but not with the retard angle oil pressure
chamber 82. As a result, the vanes 4a, 4b and 4c rotate in the
retarding direction from the most advanced angular reference phase
so that the vane 4c can shut the through hole 70 as the vanes 4a,
4b and 4c rotate.
[0077] If the fixing hole 40 has an internal diameter W.sub.40 and
if the through hole 70 has a diametrical width W.sub.70, as shown
in FIGS. 6 and 7, the following relation is established:
W.sub.40>W.sub.7
[0078] Specifically, the width of the fixing hole 40 in the radial
direction of the vane rotor 4 is greater than the width of the
through hole 70 in the radial direction of the seal plate 7. As a
result, the biasing force of the torsion spring 60 in the radial
direction of the vane rotor 4 is restricted by the inner wall of
the through hole 70 so that it is prevented from being transmitted
to the vane 4c.
[0079] Therefore, the vanes 4a, 4b and 4c can be prevented from
becoming eccentric and from being eccentrically worn, as might
otherwise be caused by the frictions between the vanes 4a, 4b and
4c and the inner wall of the housing portion 51 forming the
sectorial space 55. Moreover, the vanes 4a, 4b and 4c are easily
assembled with the housing portion 51 so that the number of
manufacturing steps can be reduced. Here, the through hole 70
constructs guide means.
[0080] In the seal plate 7, as shown in FIG. 3, there is formed a
communication passage 71 which communicates with a back pressure
chamber 30 of the stopper piston 97 shown in FIG. 1. The
communication passage 71 communicates with the atmosphere in the
oil lubricating space of the not-shown engine via an oil passage 29
formed in the chain sprocket 8 at the most advanced position, so
that the back pressure chamber 30 communicates with the atmosphere
at the most advanced position. As a result, the movement of the
stopper piston 97 is not prevented at the most advanced
position.
[0081] In the vane rotor 4, as shown in FIG. 1, an oil passage 13
is formed at the portion abutting against the cam shaft 1, and an
oil passage 12 is formed at the portion abutting against the bush
6. The oil passage 13 communicates with either an hydraulic pump
140 functioning as drive means or a drain 141 via the oil passage
14 formed between the cam shaft 1 and the bolt 5 via the oil
passage 12, and an oil passage 15 formed in a housing 101, and
through a change-over valve 142.
[0082] The hydraulic pump 140 also functions as a drive source for
the engine lubricating oil. As shown in FIG. 2, moreover, the oil
passage 13 communicates with the advance angle oil pressure
chambers 83, 84 and 85. On the other hand, the oil passage 13
communicates with the oil pressure chamber 18 via the oil passage
19.
[0083] In the housing portion 51 of the front member 50, as shown
in FIGS. 4 and 5, an oil passage 32 is formed at the portion
abutting against the vane rotor 4. The oil passage 32 communicates
with the hydraulic pump 40 or the drain 41 via an oil passage 33
formed in the bearing portion 52 of the front member 50, and oil
passages 16 and 17 formed in the housing 101 via a whole
circumference groove 11 formed in the housing 101, and the
change-over valve 142.
[0084] Moreover, the oil passage 32 communicates with the retard
angle oil pressure chambers 80, 81 and 82, and also communicates
with the oil pressure chamber 27 via the oil passage 31 shown in
FIG. 2. In response to an instruction from an electronic control
unit (ECU) 143, the change-over valve 142 changes the connection
states between the oil passages 15, 17 and the hydraulic pump 40
and the drain 141.
[0085] Here will be described the operations of the valve timing
adjusting device 100.
[0086] (1) When the engine stops normally, the change-over valve
142 is so controlled by the instruction of the ECU 143 that the
retard angle oil pressure chambers 80, 81 and 82 are released to
the drain side whereas the individual advance angle oil pressure
chambers 83, 84 and 85 are held in the working oil pressure applied
state. Then, the vane rotor 4 moves to the most advanced position
with respect to the housing portion 51 of the front member 50, and
the housing portion 51 and the vane rotor 4 are coupled by the
restraint means so that the cam shaft 1 is held in the most
advanced position with respect to the housing portion 51.
[0087] According to the first embodiment of the present invention,
it is designed to have no overlap for valve opening period between
the exhaust valve and the intake valve at the most advanced
position shown in FIG. 2. Accordingly, it can reduce the internal
EGR ratio and start the engine normally. Even after the engine is
started, the housing portion 51 and the vane rotor 4 are held in
the coupled state by the restraint means. As a result, the cam
shaft 1 is at the most advanced position with respect to the
housing portion 51 till the working oil pressure to be applied to
the individual oil passages and the individual oil pressure
chambers exceeds a predetermined level.
[0088] (2) When the engine turns into the normal driving condition
and a working oil whose pressure is higher than the predetermined
level is introduced into the respective oil passages and oil
pressure chambers, the pressure is applied to the second pressure
receiving surface by the negative peak torque of the fluctuating
torque of the cam shaft 1 during the idling at a high oil
temperature, thereby releasing the coupling between the housing
portion 51 and the vane rotor 4 with the restraint means.
[0089] At this time, no shearing force is applied to catch the
stopper piston 97 so that the housing portion 51 and the vane rotor
4 can be promptly released from their restraint. As a result, the
vane rotor 4 is rotated relatively to the housing portion 51
against the biasing force of the torsion spring 60 by the working
oil pressure applied to the retard angle oil pressure chambers 80,
81 and 82 and the advance angle oil pressure chambers 83, 84 and
85, so that the phase difference of the cam shaft 1 relatively to
the housing portion 51 is adjusted.
[0090] In the first embodiment of the present invention, the seal
plate 7 separates the sectorial space 55 for housing the vanes 4a,
4b and 4c from the circumferential groove 61 for housing the
torsion spring 60. Accordingly, the sectorial space 55 prevents the
communication between the advance angle oil pressure chambers 83,
84 and 85 and the retard angle oil pressure chambers 80, 81 and 82
regardless of the space of the circumferential groove 61.
[0091] As a result, the external diameter of the vanes 4a, 4b and
4c can be relatively reduced without lowering the engine
performance by setting the internal diameter of the advance angle
oil pressure chambers 83, 84 and 85 and the retard angle oil
pressure chambers 80, 81 and 82, that is, the internal diameter of
the vanes 4a, 4b and 4c smaller than the external diameter of the
torsion spring 60.
[0092] Therefore, it is possible to reduce the actuator in size
without lowering the engine performance, to reduce the weight of
the valve timing adjusting device 100 and to retain the mounting
space easily for mounting the valve timing adjusting device on the
engine. Moreover, since the actuator is reduced in size with the
simple structure, the manufacturing cost is also reduced.
[0093] Furthermore, according to the first embodiment, the vane 4c
has the fixing hole 40 for fixing one end portion of the torsion
spring 60. By fixing the other end portion of the torsion spring 60
on the chain sprocket 8, therefore, the torsion spring 60 can be
assembled without providing any special member for receiving the
biasing force of the torsion spring 60 having a larger external
diameter than the internal diameter of the vanes 4a, 4b and 4c.
[0094] Moreover, the vane 4c having the advance side stopper 41 and
the retard side stopper 42 is made thicker than the vane 4b in
order to obtain the strength, so that the fixing hole 40 can be
easily formed. As a result, the manufacturing cost can be further
reduced with the simple structure.
[0095] In the first embodiment, moreover, the through hole 70
formed in the seal plate 7 communicates with the advance angle oil
pressure chamber 84 but not with the retard angle oil pressure
chamber 82. Since the vanes 4a, 4b and 4c rotate from the most
advanced reference phase to the retarding direction, the vane 4c is
enabled to shut the through hole 70 by the rotations of the vanes
4a, 4b and 4c.
[0096] As a result, the seal length of the vane 4c is not reduced,
as might otherwise be caused by the rotations of the vanes 4a, 4b
and 4c in the retarding direction, so that the angle of the vanes
4a, 4b and 4c necessary for shutting the through hole 70 can be set
at a relatively small value. By setting the rocking angle of the
vanes 4a, 4b and 4c to a relatively large value, therefore, the
exhaust emission of the engine can be reduced.
[0097] At the equal rocking angle of the vanes 4a, 4b and 4c,
moreover, the leakage of the fluid from the through hole 70 can be
minimized by making the seal length of the vane 4c relatively long.
Therefore, it is possible to improve the response in varying the
phase of the valve timing adjusting device 100.
[0098] According to the first embodiment, still moreover, the seal
plate 7 has the corrugation 72 and the elastic member 74, so that
the manufacturing cost is reduced and the leakage of the working
oil from the sectorial space 55 or the circumferential groove 61 to
the outside is reliably prevented with the simple structure. Here,
it is possible to prevent the leakage of the working oil no matter
whether the elastic member 74 might be provided on only one side
face of the seal plate 7 or only one of the corrugation 72 or the
elastic member 74 is provided.
[0099] In the first embodiment, still moreover, the following
relation is established between the internal diameter W.sub.40 of
the fixing hole 40 and the diametrical width W.sub.70 of the
through hole 70:
W.sub.40>W.sub.70
[0100] As a result, the radial biasing force of the torsion spring
60 is regulated by the inner wall of the through hole 70, and it is
prevented from being transmitted to the vane 4c. Therefore, the
eccentric wears of the vanes 4a, 4b and 4c are prevented, as might
otherwise be caused by the frictions between the inner wall of the
housing portion 51 forming the sectorial space 55 and the vanes 4a,
4b and 4c when these vanes 4a, 4b and 4c become eccentric.
[0101] Moreover, the vanes 4a, 4b and 4c can be easily assembled
with the housing portion 51, so that the number of manufacturing
steps are reduced.
[0102] In the first embodiment, still moreover, the sliding portion
between the cam shaft 1 and the chain sprocket 8 is fed with the
working oil from the circumferential groove 61 so that an excellent
sliding surface is formed without forming any special oil passage
in the cam shaft 1. Therefore, the sliding portion can be reduced
in its wear to improve the durability with the simple
structure.
[0103] [Second Embodiment]
[0104] With reference to FIG. 11, a second embodiment of the
present invention in which the fixing hole 40 of the first
embodiment shown in FIG. 2 is formed in the vane 4a will now be
described. The remaining structures are similar to those of the
first embodiment. In this and the following embodiments, components
which are substantially the same as those in previous embodiments
are assigned the same reference numerals.
[0105] In the second embodiment, as shown in FIG. 11, there is
formed in the vane 4a a fixing hole 44 for fixing one end portion
of the torsion spring 60. As a result, this torsion spring 60 is
assembled by fixing its other end portion on the chain sprocket
without providing any special member for receiving the biasing
force of the torsion spring 60 having a larger external diameter
than the internal diameter of the vanes 4a, 4b and 4c.
[0106] Moreover, the fixing hole 44 is easily formed because the
vane 4a to be provided with the stopper piston 97 as the abutting
portion is made thicker than the vane 4b for obtaining the
strength. Therefore, the manufacturing cost is lowered with the
simple structure.
[0107] [Third Embodiment]
[0108] With reference to FIGS. 12 and 13, here will be described a
third embodiment in which the other end portion of the torsion
spring 60 of the first embodiment shown in FIGS. 1 and 3 is
extended in the radial direction and in which the circumferential
groove 61 is also extended in the radial direction. The remaining
structures are similar to those of the first embodiment.
[0109] In the third embodiment, as shown in FIGS. 12 and 13, a
torsion spring 160 functioning as first bias means is housed in a
circumferential groove 161 formed as a housing space in a chain
sprocket 108. The torsion spring 160 is fixed at its one end
portion on the vane rotor 4 and at its other end portion on the
chain sprocket 108. The other end portion of the torsion spring 160
is extended in the radial direction, and the circumferential groove
161 is so formed in the chain sprocket 108 that it is also extended
in the radial direction.
[0110] The torsion spring 160 biases the vane rotor 4 in the
direction of the vane rotor 4 to advance with respect to the chain
sprocket 108, that is, in the direction of the cam shaft 1 to
advance with respect to the crank shaft.
[0111] According to the third embodiment, the circumferential
groove 161 is made relatively shallow, so that the number of
manufacturing steps is reduced. Since the chain sprocket 108 is
reduced in the axial direction, moreover, the valve timing
adjusting device is reduced in size to obtain the mounting space
more easily for mounting the valve timing adjusting device on the
engine.
[0112] According to the first through the third embodiments of the
present invention, the housing portion 51 of the front member 50
and the vane rotor 4 are coupled at the most advanced position by
the restraint means such that the valve opening periods of the
exhaust valve and the intake valve may not overlap. However, the
valve opening periods of the exhaust valve and the intake valve may
overlap if this overlap period is within a range where the engine
can be normally started to a driving state, and the coupling
positions between the housing member and the vane member by the
restraint means may be shifted to the retarded side from the most
advanced position.
[0113] Although the first through the third embodiments have been
described on the vane rotor 4 having the three vanes, the number of
vanes may be one or more instead.
[0114] Furthermore, according to the first through the third
embodiments of the present invention, the stopper piston 97 is
moved in the axial direction of the vane rotor 4 so that it is
fitted in the tapered hole. However, it may be modified such that
the stopper piston is moved in the radial direction of the vane
rotor and fitted in the tapered hole, or such that the stopper
piston is housed in the chain sprocket.
[0115] On the other hand, the embodiments have adopted the
structure in which the rotational driving force of the crankshaft
is transmitted to the cam shaft via the chain sprocket, but can be
modified to use a timing pulley, a timing gear or the like.
[0116] Furthermore, the driving force of the crankshaft as the
drive shaft can be received by a vane rotor to rotate the cam shaft
as the driven shaft integrally with the housing portion.
[0117] According to the first through the third embodiments, the
present invention is applied to the valve timing adjusting device
for the exhaust valve. However, the application of the present
invention is not limited thereto but can be applied to a system in
which an OHC engine or an OHV engine is provided with the valve
timing adjusting device.
[0118] In this case, the valve opening timings for the
intake/exhaust valves shift in parallel to the retarding direction
by the valve timing adjusting device, so that the fuel economy can
is improved by the parallel shifts of the valve opening timings. In
this case, the reference position at the engine starting time is
also located at the most advanced position, so that advantages
similar to those in the first through the third embodiments can be
obtained.
[0119] Furthermore, the present invention can also be applied to a
valve timing adjusting device for the intake valve. This valve
timing adjusting device for the intake valve is always subjected to
a force in the retarding direction like the valve timing adjusting
device for the exhaust valve. By providing the torsion spring as
the first bias means, therefore, the operation speed (or the
response) of the valve timing can be improved.
[0120] In this case, the biasing force of the torsion spring is
preferably set weaker than the force in the retarding direction, as
received by the valve timing adjusting device at the engine
starting time. By setting the biasing force of the torsion spring,
the most retarded position, that is, the reference position can be
maintained at the starting time.
[0121] [Fourth Embodiment]
[0122] A fourth embodiment of the present invention is shown in
FIGS. 14 and 15. This valve timing adjusting device 300 in the
fourth embodiment is a hydraulic control type for controlling the
valve timing of an intake valve.
[0123] A chain sprocket 308, as shown in FIG. 14, is coupled
through the not-shown timing chain to a crankshaft acting as the
drive shaft of the not-shown engine so that it is rotated in
synchronism with the crankshaft by a driving force transmitted
thereto. A shoe housing 350 comprises a peripheral wall portion 351
and a front portion 352. The front portion 352, the chain sprocket
308 and a later-described seal plate 307 are coupled by a bolt
353.
[0124] A cam shaft 301 as a driven shaft receives the driving force
from the chain sprocket 308 to open/close the not-shown intake
valve. The cam shaft 301 is supported by a not-shown cylinder head
so that it can rotate with a predetermined phase difference
relatively to the chain sprocket 308. This chain sprocket 308 and
the cam shaft 301 rotate clockwise, as viewed from the left-hand
side of FIG. 14. This rotating direction will be called the
"advance direction" hereinafter.
[0125] The chain sprocket 308 and the shoe housing 350 construct a
housing member. A vane rotor 304 is covered at its two axial end
surfaces with the seal plate 307 and the front portion 152 of the
shoe housing 350. The chain sprocket 308, the seal plate 307 and
the shoe housing 350 construct a drive side rotor and are coupled
on a common axis by the bolt 353.
[0126] The vane rotor 304 is integrally connected to the cam shaft
301 by a bolt 305. A bush 306 is force fitted in the vane rotor 304
and is supported to form a driven side rotor.
[0127] The cam shaft 301 and the bush 306 are fitting in the front
portion 352 of the shoe housing 350 respectively such that they can
relatively rotate with the front portion 352. Accordingly, the cam
shaft 301, the vane rotor 304 and the bush 306 are relatively
rotatable with the chain sprocket 308 and the shoe housing 350
coaxially.
[0128] A torsion spring 360 acting as first bias means is housed in
a circumferential groove 361 formed as a housing space in the chain
sprocket 308, and is fixed at its one end portion to the vane rotor
304 and at its other end to the chain sprocket 308. The torsion
spring 360 biases the vane rotor 304 in the direction for the vane
rotor 304 to advance with respect to the chain sprocket 308, that
is, for the cam shaft 301 to advance with respect to the
crankshaft.
[0129] As shown by the area designated by an arrow A in FIG. 18,
the biasing force of the torsion spring 360 is set to 10% of the
average torque in the idling rotation range of the cam shaft 301 or
greater. The biasing force of the torsion spring 360 is also set to
be equal to or less than the average torque in the inertial
rotation range of the cam shaft 301.
[0130] In the fourth embodiment, the torsion spring 360 has a
biasing force (spring force) P corresponding to the maximum value
of the average torque in the inertial rotation range.
[0131] The "inertial rotation range" is an engine rotation range
after engine stopping operation. Further, "equal to or less than
the average torque in the inertial rotation range" means that it is
equal to or less than the average torque at the lowest rotation
speed in the inertial rotation range right before stopping.
[0132] As shown in FIG. 15, the peripheral wall portion 351 of the
shoe housing 350 has shoes 351a, 351b, 351c and 351d formed in a
trapezoidal shape at a substantially equal spacing in the
circumferential direction. In the four circumferential clearances
of the shoes 351a, 351b, 351c and 351d, there are individually
formed sectorial spaces 355 as housing chambers for respective
housing vanes 34a, 34b, 34c and 34d as vane members. Inner
circumferential surface of the shoes 351a, 351b, 351c and 351d are
formed to have an arcuate cross section.
[0133] The vane rotor 304 is provided substantially equidistantly
in the circumferential direction with the vanes 304a, 304b, 304c
and 304d which are rotatably housed in the sectorial spaces 355
formed in the circumferential clearances of the shoes 351a, 351b,
351c and 351d.
[0134] The vane 4c is provided on the advance side with an advance
stopper 41 and on the retard side with a retard stopper 42. Arrows,
as appearing inFIG. 15, indicate the retard direction and the
advance direction of the vane rotor 304 with respect to the
peripheral wall portion 351.
[0135] In FIG. 15, each vane is positioned at one circumferential
end portion of each sectorial space 355 such that the vane rotor
304 is positioned at the most retarded position with respect to the
peripheral wall portion 351. The most retarded position is
regulated by retaining the retard stopper 341 provided at the
retard side face of the vane 304a to the advanced side face of the
shoe 351d. On the other hand, the most advanced position is
regulated by retaining the advance stopper 342 provided at the
advance side face of the vane 304a to the retard side face of the
shoe 351a.
[0136] As shown in FIG. 14, the vanes 304a, 304b, 304c and 304d are
set to have an internal diameter smaller than the external diameter
of the torsion spring 360. As shown in FIG. 15, on the other hand,
the vane 304a is provided with a fixing hole 340 for fixing one end
portion of the torsion spring 360.
[0137] By fixing the other end portion of the torsion spring 360 to
the chain sprocket 308, therefore, this torsion spring 360 can be
assembled without providing any special member for receiving the
biasing force of the torsion spring 360 having a larger external
diameter than the internal diameter of the vanes 304a, 304b, 304c
and 304d. Moreover, the fixing hole 340 is easily formed because
the vane 304a having the retard stopper 341 and the advance stopper
342 is made thicker than the vanes 304b, 304c and 304d to increase
the strength.
[0138] As shown in FIG. 15, the seal member 309 is fitted on the
outer circumferential wall of the vanes 304a, 304b, 304c and 304d.
Furthermore, the seal member 390 is fitted in the inner
circumferential wall of the shoes 351a, 351b, 351c and 351d. A
small clearance is provided between the outer circumferential wall
of the vane rotor 304 and the inner circumferential wall of the
peripheral wall portion 351 of the shoe housing 350. Seal members
309 and 390 prevent the leakage of the working oil between the oil
pressure chambers through the clearance.
[0139] A guide ring 391 is press fitted in the inner wall of the
vane 304a, and a stopper piston 397 is inserted in the guide ring
391. As shown in FIG. 14, the stopper piston 397 is formed into a
bottomed cylindrical shape of a substantially equal external
diameter, which is composed of a bottomed cylindrical portion 397a
and a flange portion 397b formed at the open end portion of the
cylindrical portion 397a.
[0140] The stopper piston 397 is housed in the guide ring 391 such
that the stopper piston 397 is slidable in the axial direction of
the cam shaft 301. The stopper piston 397 is biased to the side
opposite to the chain sprocket 308 by a spring 396 functioning as
second bias means.
[0141] In the stopper hole formed in the front portion 352 of the
shoe housing 350, there is press-fitted a fitting ring 354 having a
tapered hole 354a, so that the stopper piston 397 can be fitted in
the tapered hole 354a at the most retarded position shown in FIG.
15.
[0142] When the stopper piston 397 is so fitted in the tapered hole
354a that the former comes into abutment against the latter in the
rotational direction, the vane rotor 304 is restrained from
rotating relatively to the peripheral wall portion 351. In short,
the stopper piston 397 and the tapered hole 354a take the
restrained positions at the most retarded position. The stopper
piston 397, the tapered hole 354a and the spring 396 construct
restraint means.
[0143] The oil pressure chamber 318, as located on the left-hand
side of the flange portion 397b, communicates with a
later-described retard angle oil pressure chamber 380 via an oil
passage not shown. Furthermore, an oil pressure chamber 327, as
formed on the tip of the cylindrical portion 397a, communicates
with a later-described advance angle oil pressure chamber 387 via
an oil passage not shown.
[0144] The area of a second pressure receiving surface of the
flange portion 397b for receiving the oil pressure of the oil
pressure chamber 318 is less than that of a first pressure
receiving surface of the cylindrical portion 397a for receiving the
oil pressure of the oil pressure chamber 327. The pressures to be
received by the first pressure receiving surface and the second
pressure receiving surface from the working oil in respective oil
pressure chambers 327 and 318 act to extract the stopper piston 397
from the tapered hole 354a.
[0145] The pressure receiving area of the first pressure receiving
surface is substantially equal to the sectional area of the
cylindrical portion 397a, and the pressure receiving area of the
second pressure receiving surface is substantially equal to the
annular area corresponding to the diametrical difference between
the flange portion 397b and the cylindrical portion 397a. When the
working oil having a predetermined or higher pressure is supplied
to the advance angle oil pressure chamber 387 or the retard angle
oil pressure chamber 380, the stopper piston 397 is extracted from
the tapered hole 354a against the biasing force of the spring
396.
[0146] The position of the stopper piston 397 and the position of
the tapered hole 354a are so relatively determined that the stopper
piston 397 can be fitted in the tapered hole 354a by the biasing
force of the spring 396 when the vane rotor 304 is at the most
retarded position relatively to the peripheral wall portion 351 of
the shoe housing 350, that is, when the cam shaft 301 is at the
most retarded position relatively to the crankshaft.
[0147] As shown in FIG. 15: the retard angle oil pressure chamber
380 is formed between the shoe 351a and the vane 304a; a retard
angle oil pressure chamber 381 is formed between the shoe 351b and
the vane 304b; a retard angle oil pressure chamber 382 is formed
between the shoe 351c and the vane 304c; and a retard angle oil
pressure chamber 383 is formed between the shoe 351d and the vane
304d.
[0148] On the other hand: an advance angle oil pressure chamber 384
is formed between the shoe 351a and the vane 304b; an advance angle
oil pressure chamber 385 is formed between the shoe 351b and the
vane 304c; the advance angle oil pressure chamber 386 is formed
between the shoe 351c and the vane 304d; and an advance angle oil
pressure chamber 387 is formed between the shoe 351d and the vane
304a.
[0149] As shown in FIG. 14, the seal plate 307 as a partition
member separates the sectorial space 355 from the circumferential
groove 361. In other words, the seal plate 307 separates a housing
chamber for housing the vanes 304a, 304b, 304c and 304d from a
housing space for housing the torsion spring 360. As a result, the
sectorial space 355 is constructed such that the advance angle oil
pressure chambers 84, 85, 86 and 87 and the retard angle oil
pressure chambers 80, 81, 82 and 83 are not connected regardless of
the space of the circumferential groove 61.
[0150] As shown in FIG. 15, a circumferentially elongated through
hole 370 is formed in the seal plate 307. One end portion of the
torsion spring 360 can be passed through the through hole 370. The
vane 304a closes the through hole 370 at the most advanced position
shown in FIG. 15.
[0151] As shown in FIG. 14, a communication passage 371 which
communicates with a back pressure chamber 330 of the stopper piston
397 is formed in the seal plate 307. The communication passage 371
communicates with the atmosphere in the oil lubricating space of
the not-shown engine via an oil passage 329 formed in the chain
sprocket 308 at the most retarded position, so that the back
pressure chamber 330 communicates with the atmosphere at the most
retarded position. As a result, the movement of the stopper piston
397 is not prevented at the most retarded position.
[0152] In the vane rotor 304, an oil passage 312 is formed at the
portion abutting against the cam shaft 301, and an oil passage 313
is formed at the portion abutting against the bush 306. The oil
passage 313 communicates with the advance angle oil pressure
chambers 384, 385, 386 and 387 via an oil passage not shown.
Furthermore, the oil passage 312 communicates with either an
hydraulic pump functioning as drive means or a drain via the oil
passage 314 formed in the cam shaft 301. The hydraulic pump also
functions as a drive source for the engine lubricating oil.
[0153] Furthermore, the oil passage 315 shown in FIG. 14
communicates with the hydraulic pump or the drain via a switching
valve, and communicates with the retard angle oil pressure chambers
380, 381, 382 and 383. The oil pressure of the working oil supplied
to the advance angle oil pressure chambers 384, 385, 386 and 387 is
a first fluid pressure. The oil pressure of the working oil
supplied to the retard angle oil pressure chambers 380, 381, 382
and 383 is a second fluid pressure.
[0154] A release oil pressure at the advanced position for the
restraint means is less than the minimum working pressure necessary
for rotating the vane rotor 304 to the advancing direction with
respect to the shoe housing 350 by the first fluid pressure.
[0155] Operations of the valve timing adjusting device 300 will now
be described.
[0156] (1) When the engine stops normally, the change-over valve is
controlled such that the retard angle oil pressure chambers 380,
381, 382 and 383 are released to the drain side while respective
advance angle oil pressure chambers 384, 385, 386 and 387 are held
in the working oil pressure applied state. Then, the vane rotor 304
moves to the most retarded position with respect to the peripheral
wall portion 351 of the shoe housing 350, and the front portion 352
and the vane rotor 304 are coupled by the restraint means, so that
the cam shaft 301 is held in the most retarded position with
respect to the peripheral wall portion 351.
[0157] According to the fourth embodiment of the present invention,
it is designed to have no overlap for valve opening period between
the exhaust valve and the intake valve at the most retarded
position shown in FIG. 15. Accordingly, it can reduce the internal
EGR ratio and start the engine normally. Even after the engine is
started, the front portion 352 and the vane rotor 304 are held in
the coupled state by the restraint means. As a result, the cam
shaft 301 is at the most retarded position with respect to the
peripheral wall portion 351 till the working oil pressure to be
applied to respective oil passages and the oil pressure chambers
exceeds a predetermined level.
[0158] (2) When the engine turns into the normal driving condition
and a working oil whose pressure is higher than the predetermined
level is introduced into the respective oil passages and oil
pressure chambers, the pressure is applied to the first pressure
receiving surface by the negative peak torque of the fluctuating
torque of the cam shaft 301 during the idling, thereby releasing
the coupling between the front portion 352 and the vane rotor 304
by the restraint means.
[0159] At this time, no shearing force is applied to catch the
stopper piston 397 so that the front portion 352 and the vane rotor
304 can be promptly released from each other. As a result, the vane
rotor 304 is rotated relatively to the peripheral wall portion 351
against the biasing force of the torsion spring 360 by the working
oil pressure applied to the retard angle oil pressure chambers 380,
381, 382 and 383 and the advance angle oil pressure chambers 384,
385, 386 and 387, so that the phase difference of the cam shaft 301
relatively to the peripheral wall portion 351 is adjusted.
[0160] According to the fourth embodiment of the present invention,
the torsion spring 360 applies the biasing force to the vane rotor
304 ina direction in which the cam shaft 301 advances against the
crank shaft. Accordingly, the phase transition response is
uniformed, and the controllability is improved.
[0161] Furthermore, since the first fluid pressure is reduced, the
pressure difference between the advance angle oil pressure chambers
384, 385, 386 and 387 and the retard angle oil pressure chambers
380, 381, 382 and 383 is reduced. Accordingly, the working oil
leakage between the advance angle oil pressure chambers and the
retard oil pressure chambers is reduced.
[0162] Furthermore, the area of the vanes 304a, 304b, 304c and 304d
is reduced, and the actuator is reduced in size without
compromising the engine performance. Accordingly, the weight of the
valve timing adjusting device 300 is reduced, and the mounting
space for mounting it on the engine is easily obtained.
[0163] Furthermore, since the minimum working pressure of the
hydraulic pump is reduced, the hydraulic pump is reduced in size,
and the manufacturing cost is reduced.
[0164] According to the fourth embodiment of the present invention,
further, the biasing force of the torsion spring 360 is set to 10%
of the average torque in the idling rotation range of the cam shaft
301 or greater, and is also set to be equal to or less than the
average torque in the inertial rotation range of the cam shaft 301.
Accordingly, the biasing force of the torsion spring 360 is less
than a force in the retarding direction to be applied to the valve
timing adjusting device 300 at the start of the engine. Therefore,
the driven shaft is reliably returned to the most retarded position
at the stop of the engine, and the intake side is held at the most
retarded position, that is, the reference position at the start of
the engine. Therefore, the overlapping period, in which the exhaust
valve and the intake valve open their valves with a certain
overlap, can be reduced to certain degree to at least enable the
start of the engine. Accordingly, the engine start performance is
improved.
[0165] Furthermore, the exhausted amount of the unburned fuel,
exhausted from the exhaust valve after the fuel is sucked from the
intake valve, is reduced. Further, the phase transition response is
uniformed, and the controllability is improved.
[0166] Further, according to the fourth embodiment of the present
invention, the release oil pressure at the advanced position for
the restraint means is less than the minimum working pressure
necessary for rotating the vane rotor 304 to the advancing
direction with respect to the shoe housing 350 by the first fluid
pressure.
[0167] Accordingly, the restrained condition between the front
portion 352 and the vane rotor 304 by the restraint means is
reliably released even under low pressure of the working oil
without increasing the hydraulic pump in size to increase the oil
pressure, and without increasing the stopper piston 397 to increase
the pressure receiving area. Thus, the relative rotation between
the front portion 352 and the vane rotor 304 becomes possible.
[0168] [Fifth Embodiment]
[0169] A fifth embodiment of the present invention will now be
described according to FIGS. 16 and 17. In the fifth embodiment of
the present invention, the torsion spring 360 in the fourth
embodiment is replaced by a coil spring 560. other structures are
substantially the same as those in the fourth embodiment of the
present invention.
[0170] As shown in FIGS. 16 and 17, the coil spring 560 as first
bias means is housed in a circumferential groove 561, that is, a
housing space formed in the chain sprocket 308. One end of the coil
spring 560 is fixed to the cam shaft 301, and the other end is
fixed to a fixing portion 562 which is formed on the chain sprocket
308 and which protrudes in the axial direction.
[0171] The coil spring 560 applies its biasing force to the vane
rotor 304 in the advancing direction of the vane rotor 304 against
the chain sprocket 308, that is, the advancing direction of the cam
shaft 301 against the crank shaft.
[0172] The biasing force of the coil spring 560 is greater than 10%
of the average torque in the idling rotation range of the cam shaft
301, and is less than the average torque in the inertial rotation
range of the cam shaft 301.
[0173] According to the fifth embodiment of the present invention,
since the coil spring 560 applies its biasing force to the vane
rotor 304 in the advancing direction of the cam shaft 301 against
the crank shaft, the phase transition response is uniformed, and
the controllability is improved.
[0174] Furthermore, since the first fluid pressure is substantially
reduced, the pressure difference between the advance angle oil
pressure chamber and the retard angle oil pressure chamber is
reduced, and the working oil leakage between the advance angle oil
pressure chamber and the retard angle oil pressure chamber is
reduced.
[0175] Further, the area of the vane is reduced, and the actuator
is reduced in size without compromising the engine performance.
Accordingly, the weight of the valve timing adjusting device is
reduced, and the mounting space for mounting it on the engine is
easily obtained.
[0176] Furthermore, since the minimum working pressure of the
hydraulic pump is reduced, the hydraulic pump is reduced in size,
and the manufacturing cost is reduced.
[0177] According to the fifth embodiment of the present invention,
further, the biasing force of the coil spring 560 is set to 10% of
the average torque in the idling rotation range of the cam shaft
301 or greater, and is also set to be equal to or less than the
average torque in the inertial rotation range of the cam shaft 301.
Accordingly, the biasing force of the coil spring 560 is less than
a force in the retarding direction to be applied to the valve
timing adjusting device at the start of the engine.
[0178] Therefore, the driven shaft is reliably returned to the most
retarded position at the stop of the engine, and the intake side is
held at the most retarded position, that is, the reference position
at the start of the engine. Therefore, the overlapping period, in
which the exhaust valve and the intake valve open their valves with
a certain overlap, can be reduced to certain degree to at least
enable the start of the engine. Accordingly, the engine start
performance is improved.
[0179] Furthermore, the exhausted amount of the unburned fuel,
exhausted from the exhaust valve after the fuel is sucked from the
intake valve, is reduced. Further, the phase transition response is
uniformed, and the controllability is improved.
[0180] In the fourth and the fifth embodiments of the present
invention, the biasing force of the first bias means is set to 10%
of the average torque in the idling rotation range of the cam shaft
301 or greater, and is also set to be equal to or less than the
average torque in the inertial rotation range of the cam shaft
301.
[0181] However, the biasing force of the first bias means may be
greater than the average torque in the inertial rotation range of
the cam shaft and less than the maximum torque in the inertial
rotation range of the cam shaft, that is, the range designated by
the arrow B in FIG. 18. In this case, the phase transition response
for the relative rotation of the vane rotor against the shoe
housing in the advancing direction is improved.
[0182] Accordingly, the driven shaft is reliably returned to the
most retarded position when the engine stops, and the pressure of
the working oil supplied to the advance angle oil pressure chamber
is further reduced. Thus, the pressure difference between the
advance angle oil pressure chamber and the retard angle oil
pressure chamber is further reduced, and the working oil leakage
between the advance angle oil pressure chamber and the retard angle
oil pressure chamber is further reduced.
[0183] Furthermore, according to the fourth and fifth embodiments
of the present invention, the fluid pressure is applied to the
second pressure receiving surface by controlling the change-over
valve to move the intake valve in the advancing direction.
Accordingly, the restrained condition between the front portion and
the vane rotor is immediately released without being caught by
shearing force on the stopper piston. By controlling the
change-over valve thereafter, the vane rotor is rotated relatively
to the front portion in the advancing direction, and the intake
valve is promptly moved in the advancing direction.
[0184] Further, according to the fourth and fifth embodiments of
the present invention, the front portion of the shoe housing and
the vane rotor 304 are coupled at the most retarded position to
prevent an overlap of the valve opening period between the exhaust
valve and the intake valve. However, the valve opening periods of
the exhaust valve and the intake valve may overlap within a certain
range such that the engine normally starts and shifts to the
driving condition. Further, the coupling position between the
housing member and the vane member by the restraint means may be
advanced side than the most retarded position.
[0185] Although the fourth and fifth embodiments have been
described on the vane rotor 304 having the four vanes, the number
of the vanes may be one or more instead.
[0186] Furthermore, according to the fourth and fifth embodiments
of the present invention, the stopper piston 397 is moved in the
axial direction of the vane rotor 304 so that it is fitted in the
tapered hole. However, it may be modified such that the stopper
piston is moved in the radial direction of the vane rotor and
fitted in the tapered hole, or such that the stopper piston is
housed in the chain sprocket.
[0187] On the other hand, the embodiments have adopted the
structure in which the rotational driving force of the crankshaft
is transmitted to the cam shaft via the chain sprocket, but can be
modified to use a timing pulley, a timing gear or the like.
[0188] Furthermore, the driving force of the crankshaft as the
drive shaft can be received by a vane rotor to rotate the cam shaft
as the driven shaft integrally with the housing portion.
[0189] Although the present invention has been described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications will be apparent to those skilled in the art.
Such changes and modifications are to be understood as being
included within the scope of the present invention as defined in
the appended claims.
* * * * *