U.S. patent application number 09/887006 was filed with the patent office on 2001-12-27 for valve timing adjusting device.
Invention is credited to Okada, Motohiro, Sato, Osamu, Takenaka, Akihiko.
Application Number | 20010054406 09/887006 |
Document ID | / |
Family ID | 18688594 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054406 |
Kind Code |
A1 |
Okada, Motohiro ; et
al. |
December 27, 2001 |
Valve timing adjusting device
Abstract
A stopper piston is fitted into a fitting hole when a vane rotor
is located at an approximately intermediate position between a most
retard position and a most advance position with respect to a shoe
housing. When the stopper piston is fitted into the fitting hole, a
relative rotation of the vane rotor with respect to the shoe
housing is restrained. When the stopper piston rotates to an
advance side with respect to the shoe housing over the intermediate
position at which the stopper piston is fitted into the fitting
hole, a damper chamber communicates with an advance oil pressure
chamber through a through hole, an oil passage and a recess space.
When the vane rotor rotates to a retard side including the
intermediate position, the damper chamber is sealed hermetically,
and therefore the moving speed of the stopper piston toward the
fitting hole decreases.
Inventors: |
Okada, Motohiro; (Obu-city,
JP) ; Takenaka, Akihiko; (Anjo-city, JP) ;
Sato, Osamu; (Takahama-city, JP) |
Correspondence
Address: |
Larry S. Nixon, Esq.
NIXON & VANDERHYE P.C.
1100 North Glebe Rd., 8th Floor
Arlington
VA
22201-4714
US
|
Family ID: |
18688594 |
Appl. No.: |
09/887006 |
Filed: |
June 25, 2001 |
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 1/3442 20130101;
F01L 2001/34483 20130101 |
Class at
Publication: |
123/90.17 ;
123/90.15 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2000 |
JP |
2000-188879 |
Claims
What is claimed is:
1. A valve timing adjusting device provided in a driving force
transmission system which transmits a driving force from a driving
shaft of an internal combustion engine to a camshaft which drives
to open and close at least one of an intake valve and an exhaust
valve, for adjusting opening-closing timing of at least one of said
intake valve and said exhaust valve, comprising: a driving-side
rotor rotating together with said driving shaft of the internal
combustion engine, said driving-side rotor including a housing
chamber therein; a driven-side rotor provided in said housing
chamber and rotating together with said camshaft, said driven-side
rotor including vanes partitioning said housing chamber into retard
chambers and advance chambers, said driven-side rotor driven to
rotate with respect to said driving-side rotor within a
predetermined range of angle by a fluid pressure in said retard
chambers and said advance chambers; a restraining means including a
contacting portion provided within said driven-side rotor and a
contacted portion provided within said driving-side rotor, said
restraining means restrains a relative rotation of said driven-side
rotor with respect to said driving-side rotor when said contacting
portion contacts said contacted portion while said driven-side
rotor is at a predetermined angle position, said restraining means
further including an urging means for urging said contacting
portion toward said contacted portion; a fluid chamber applying a
fluid pressure to said contacting portion in a direction to cancel
the contact between said contacting portion and said contacted
portion; a damper chamber formed around said contacting portion for
decreasing a speed of movement of said contacting portion toward
said contacted portion, and a changeover means for opening said
damper chamber when said driven-side rotor is positioned at an
advance side over the predetermined angle position with respect to
the driving-side rotor, and for hermetically sealing said damper
chamber when said driven-side rotor is positioned at the
predetermined angle position or at a retard side over the
predetermined angle position.
2. A valve timing adjusting device according to claim 1, wherein
said contacting portion contacts said contacted portion when said
driven-side rotor is at an intermediate position between both
circumferential ends of the predetermined range of angle with
respect to said driving-side rotor.
3. A valve timing adjusting device according to claim 1, wherein
said vane partitions said housing chamber into retard chambers and
advance chambers, said retard chambers apply a fluid pressure to
said driven-side rotor to rotate toward the retard side with
respect to said driving-side rotor, said advance chambers apply a
fluid pressure to said driven-side rotor to rotate toward the
advance side with respect to said driving-side rotor, said
changeover means establishes and interrupts a communication between
said retard chamber or said advance chamber and said damper chamber
for switching between opening and sealing of said damper
chamber.
4. A valve timing adjusting device according to claim 3, further
including an advance control means for supplying an operation fluid
to said advance chamber when said internal combustion engine is
stopped.
5. A valve timing adjusting device according to claim 4, wherein
the fluid pressure in said damper chamber is applied to said
contacting portion to contact said contacted portion, and said
damper chamber is opened when said damper chamber communicates with
said advance chamber.
6. A valve timing adjusting device according to claim 3, wherein
said changeover means includes said driving-side rotor and said
driven-side rotor, a communication passage allowing said retard
chamber or said advance chamber to communicate with said damper
chamber is formed in said driving-side rotor or said driven-side
rotor, and when said driven-side rotor is positioned at the advance
side over the predetermined angle position with respect to said
driving-side rotor, said communication passage allows said retard
chamber or said advance chamber to communicate with said damper
chamber.
7. A valve timing adjusting device according to claim 1, further
including a support portion for supporting said contacting portion
reciprocatably, wherein said contacting portion has a first
small-diameter portion, a large-diameter portion and a second
small-diameter portion successively in this order from said
contacted portion, said support portion supports said first and
second small-diameter portions and said large-diameter portion, a
first fluid chamber is formed at a leading end of said first
small-diameter portion, said first fluid chamber applies one of a
fluid pressure which drives said driven-side rotor to the retard
side with respect to said driving-side rotor and a fluid pressure
which drives said driven-side rotor to the advance side with
respect to said driving rotor to said first small-diameter portion,
a second fluid chamber is formed at a contacted portion side of
said large diameter portion, said second fluid chamber applies the
other fluid pressure to said large-diameter portion, said damper
chamber is formed in said large-diameter portion at a side opposite
to said contacted portion, and fluid pressures in said first and
second fluid chambers are applied in a direction to cancel the
contact between said contact portion and said contacted
portion.
8. A valve timing adjusting device according to claim 1, wherein
fluid chambers, except said damper chamber, facing said contacting
portion are opened regardless a relative rotational position of
said driven-side rotor with respect to said driving-side rotor.
9. A valve timing adjusting device provided in a driving force
transmission system which transmits a driving force from a driving
shaft of an internal combustion engine to a camshaft which drives
to open and close at least one of an intake valve and an exhaust
valve, for adjusting opening-closing timing of at least one of said
intake valve and said exhaust valve, comprising: a driving-side
rotor rotating together with said driving shaft of the internal
combustion engine, said driving-side rotor including a housing
chamber therein; a driven-side rotor provided in said housing
chamber and rotating together with said camshaft, said driven-side
rotor including vanes partitioning said housing chamber into retard
chambers and advance chambers, said driven-side rotor driven to
rotate with respect to said driving-side rotor within a
predetermined range of angle by a fluid pressure in said retard
chambers and said advance chambers; a restraining means including a
contacting portion provided within said driven-side rotor and a
contacted portion provided within said driving-side rotor, said
restraining means restrains a relative rotation of said driven-side
rotor with respect to said driving-side rotor when said contacting
portion contacts said contacted portion while said driven-side
rotor is at a predetermined angle position, said restraining means
further including an urging means for urging said contacting
portion toward said contacted portion; fluid chambers applying
fluid pressure to said contacting portion in a direction to cancel
the contact between said contacting portion and said contacted
portion; and a damper chamber formed around said contacting portion
for decreasing a speed of movement of said contacting portion
toward said contacted portion, wherein fluid chambers, except said
damper chamber, facing said contacting portion are opened
regardless a relative rotational position of said driven-side rotor
with respect to said driving-side rotor.
10. A valve timing adjusting device according to claim 9, further
including a support portion for supporting said contacting portion
reciprocatably, wherein said contacting portion has a first
small-diameter portion, a large-diameter portion and a second
small-diameter portion successively in this order from said
contacted portion, said support portion supports said first and
second small-diameter portions and said large-diameter portion, a
first fluid chamber is formed at a leading end of said first
small-diameter portion, said first fluid chamber applies one of a
fluid pressure which drives said driven-side rotor to the retard
side with respect to said driving-side rotor and a fluid pressure
which drives said driven-side rotor to the advance side with
respect to said driving rotor to said first small-diameter portion,
a second fluid chamber is formed at a contacted portion side of
said large diameter portion, said second fluid chamber applies the
other fluid pressure to said large-diameter portion, said damper
chamber is formed in said large-diameter portion at a side opposite
to said contacted portion, fluid pressures in said first and second
fluid chambers are applied in a direction to cancel the contact
between said contact portion and said contacted portion, and a
communication means is provided for allowing said first fluid
chamber to communicate with said second fluid chamber when said
contact portion moves to contact said contacted portion.
11. A valve timing adjusting device according to claim 10, wherein
said communication means includes grooves formed in an outer wall
of said first small-diameter portion and an inner wall of said
support portion.
12. A valve timing adjusting device according to claim 11, wherein
said grooves extend in a reciprocating direction of said contacting
portion, and an annular groove is formed in the outer wall of said
first small-diameter portion or in the inner wall of said support
portion so as to connect with said grooves.
13. A valve timing adjusting device according to claim 10, wherein
when an area at which said first small-diameter portion receives
the fluid pressure from said first fluid chamber in the direction
to cancel the contact between said contacting portion and said
contacted portion is S1, an area at which said large-diameter
portion receives the fluid pressure from said second fluid chamber
in the direction to cancel the contact between said contacting
portion and said contacted portion is S2, and an area at which said
large-diameter portion receives the fluid pressure from said damper
chamber in the direction of allowing said contacting portion to
contact said contacted portion is S3, there exists a relationship
of S1.apprxeq.S2.apprxeq.S3.
14. A valve timing adjusting device according to claim 10, wherein
when a clearance between an outer wall of said large-diameter
portion and an inner wall of said support portion is C1, and a
clearance between an outer wall of said second small-diameter
portion and the inner wall of said support portion is C2, there
exists a relationship of C1<C2.
15. A valve timing adjusting device according to claim 10, wherein
when a seal length between an outer wall of said large-diameter
portion and an inner wall of said support portion is L1, and a seal
length between an outer wall of said second small-diameter portion
and the inner wall of said support portion is L2, there exists a
relationship of L1>L2.
16. A valve timing adjusting device according to claim 15, wherein,
before the contact between said contacting portion and said
contacted portion, the seal lengths L1 and L2 are constant
regardless a movement position of said contacting portion.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2000-188879 filed on Jun.
23, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a valve timing adjusting
device for changing valve opening-closing timing suitable for use
in intake and exhaust valves of an internal combustion engine.
[0004] 2. Description of the Prior Art
[0005] As a conventional valve timing adjusting device, there is a
well known vane-type device in which a camshaft is driven through a
timing pulley, a chain sprocket, etc. which turn synchronously with
an engine crankshaft. The valve timing of at least any one of an
intake valve and an exhaust valve is hydraulically controlled by a
phase difference of relative rotation of the timing pulley, the
chain sprocket, and the camshaft. Engine output and fuel
consumption ratio are improved by adjusting the phase difference
between the crankshaft and the camshaft to an optimum value in
accordance with engine operating state.
[0006] In such a vane-type valve timing adjusting device using
operation oil, when at least any one of the intake valve and the
exhaust valve is actuated, the camshaft receives a load torque
which varies between positive and negative loads. Therefore, when
the operation oil is not sufficiently supplied during cranking of
the engine, there might arise such a problem that a vane member
oscillates with respect to a housing member containing the vane
member, thereby hitting against the housing member to produce
knocks. Here, the positive load torque is applied in the retarding
direction of the camshaft with respect to the crankshaft, and the
negative load torque is added in the advancing direction of the
camshaft with respect to the crankshaft.
[0007] When operation fluid is not sufficiently supplied to the
valve timing adjusting apparatus, a stopper piston included in a
vane member is fitted into a fitting hole formed in a housing
member to prevent a swing motion of the vane member against the
housing member, thereby preventing the occurrence of the noise.
When the operation fluid is supplied sufficiently, the stopper
piston comes out of the housing member by the fluid pressure, so
that a relative rotation of the vane member is controlled with
respect to the housing member. The position at which the stopper
piston is fitted into the fitting hole may be either a most retard
or most advance position of the vane member with respect to the
housing member or an intermediate position between the most retard
and most advance positions.
[0008] However, when the stopper piston is fitted into the fitting
hole during the relative rotation control, the relative rotation
control is not executed. For avoiding such an inconvenience, a
damper chamber is provided on an outer periphery of the stopper
piston, thereby decreasing the speed of movement of the stopper
piston toward the fitting hole.
[0009] When the engine is stopped, the stopper piston is desired to
be fitted into the fitting hole promptly. However, when the damper
chamber is hermetically sealed, a damping action exerts even when
the stopper piston has reached a position where the stopper piston
is fitted into the fitting hole, so that the moving speed of the
stopper piston decreases and the stopper piston does not promptly
fit in the fitting hole. For example, in a configuration wherein
the stopper fin is fitted into the fitting hole at an advance side
with respect to the most retard position, the stopper pin might
pass over the fitting hole without being fitted therein due to the
action of a load torque acting on the retard side.
SUMMARY OF THE INVENTION
[0010] A first object of the present invention is to provide a
valve timing adjusting device which restrains a relative rotation
of a driven-side rotor with respect to a driving-side rotor when an
engine is stopped.
[0011] A second object of the present invention is to provide a
valve timing adjusting device which prevents the relative rotation
of the driven-side rotor with respect to the driving rotor from
being restrained when the engine operates normally.
[0012] According to a first aspect of the present invention, a
valve timing adjusting device includes a changeover means which
causes a damper chamber to be opened when a driven-side rotor is
positioned at an advance side over a predetermined angle position
of a contacting portion with respect to a driving-side rotor and
which causes the damper chamber to be sealed hermetically when the
driven-side rotor is positioned at the predetermined angle position
or at retard side over the predetermined angle position with
respect to the driving-side rotor.
[0013] When the contacting portion is positioned at the
predetermined angle position, the damper chamber is sealed
hermetically and the speed of movement of the contacting portion in
its contacting direction decreases. Thus, when the engine normally
operates, the contacting portion does not contact the contacted
portion even when a fluid pressure which the contacting portion
receives in a contact-canceling direction at the contacting
position changes, thereby preventing a relative rotation of the
driven-side rotor with respect to the driving-side rotor from being
restrained.
[0014] When the engine is stopped, if the driven-side rotor is
positioned at an advance side over the predetermined angle position
with respect to the driving-side rotor, the damper chamber is
opened. Then, upon turning OFF of the engine, the fluid pressure
applied to the contacting portion in the contact-canceling
direction drops. Therefore, when the driven-side rotor rotates to
the retard side toward the predetermined angle position due to a
load torque which is applied until the engine stop, the contacting
portion contacts the contacted portion. Thus, a relative rotation
of the driven-side rotor with respect to the driving-side rotor is
restrained when the engine starts.
[0015] According to a second aspect of the present invention, fluid
chambers facing a contacting portion are all opened except a damper
chamber. Thus, the other fluid chambers than the damper chamber do
not act as damper chambers. Therefore, when the engine is stopped,
the contacting portion contacts the contacted portion when the
driven-side rotor reaches the predetermined angle position, thereby
restraining a relative rotation of the driven-side rotor with
respect to the driving-side rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Additional objects and advantages of the present invention
will be more readily apparent from the following detailed
description of preferred embodiments thereof when taken together
with the accompanying drawings in which:
[0017] FIG. 1 is a schematic view showing a cross-sectional view
taken along line I-I in FIG. 2 showing a valve timing adjusting
device;
[0018] FIG. 2 is a cross-sectional view showing the valve timing
adjusting device;
[0019] FIG. 3 is a cross-sectional view taken along line III-III in
FIG. 2;
[0020] FIG. 4 is a cross-sectional view taken along line IV-IV in
FIG. 2;
[0021] FIG. 5 is a schematic cross-sectional view showing a stopper
piston and a guide ring;
[0022] FIG. 6A is a cross-sectional view showing a released state
of the stopper piston operation when an engine stops;
[0023] FIG. 6B is a cross-sectional view showing the stopper piston
operation in which the stopper piston is fitted with an enlarged
hole when the engine stops;
[0024] FIG. 6C is a cross-sectional view showing the stopper piston
operation in which the stopper piston is fitted with a fitting hole
when the engine stops;
[0025] FIG. 7A is a cross-sectional view showing the stopper piston
operation in which the stopper piston is fitted with the fitting
hole when the engine starts;
[0026] FIG. 7B is a cross-sectional view showing a released state
of the stopper piston operation when the engine starts, and FIG. 7C
is a cross-sectional view showing the stopper piston operation in
which the stopper piston rotates from an intermediate position to a
retard position when the engine starts.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0027] FIG. 3 shows an engine valve timing adjusting device 1 of
the present embodiment. The valve timing adjusting device 1 is of
an oil pressure control type and controls an intake valve
timing.
[0028] A chain sprocket 10 is connected to a crankshaft as a drive
shaft of the engine and receives a driving force through a chain.
The chain sprocket 10 rotates in synchronization with the
crankshaft. The driving force is transmitted to the camshaft 2 as a
driven shaft through the chain sprocket 10. The camshaft opens and
closes the intake valve. The camshaft 2 is rotatable with respect
to the chain sprocket 10 by a predetermined phase difference. The
chain sprocket 10 and the camshaft 2 rotate clockwise as viewed in
the direction of the arrow X in FIG. 3. Hereinafter, this rotating
direction defines an advance direction.
[0029] Between the chain sprocket 10 and a set of shoe housing 12
and vane rotors 15, a disk-shaped intermediate plate 17 is
provided. The intermediate plate 17 prevents oil leaks from between
the chain sprocket 10 and the set of shoe housing 12 and vane
rotors 15. The chain sprocket 10, the shoe housing 12, and the
intermediate plate 17 form a housing member and works as a
driving-side rotor, and coaxially secured by a bolt 20.
[0030] The shoe housing 12 integrally includes a side wall 13 and a
front plate 14. As shown in FIG. 2, the shoe housing 12 includes
shoes 12a, 12b and 12c formed in a trapezoidal shape and
circumferentially arranged at approximately equal spacing 20
intervals. In three spaces provided in the circumferential
direction of the shoes 12a, 12b and 12c, housing chambers 50 for
containing vanes 15a, 15b and 15c are formed. The inner peripheral
surfaces of the shoes 12a, 12b and 12c are formed in an arc in
cross section.
[0031] The vane rotor 15 includes vanes 15a, 15b and 15c arranged
at approximately equal spacing intervals in the circumferential
direction. The vanes 15a, 15b and 15c are rotatably accommodated
within each of housing chambers 50. Each vane divides the housing
chamber 50 into a retard hydraulic fluid chamber and an advance
hydraulic fluid chamber. Arrows in FIG. 2 indicating retard and
advance directions indicate the retard and advance directions of
the vane rotor 15 with respect to the shoe housing 12. The most
retarded position of the vane rotor 15 with respect to the shoe
housing 12 is determined by contact of the vane 15b with the shoe
12a. The most advanced position of the vane rotor 15 with respect
to the shoe housing 12 is determined by contact of the vane 15b
with the shoe 12b. As shown in FIG. 3, the vane rotor 15 and a
bushing 22 are integrally fixed by a bolt 21 on the camshaft 2, and
form a driven-side rotor. A pin 23 determines the positioning of
the vane rotor 15 in the rotational direction with respect to the
camshaft 2.
[0032] The camshaft 2 and the bushing 22 are correlatively
rotatably fitted in the inner wall 10a of the chain sprocket 10 and
in the inner wall 14a of the front plate 14. Therefore, the
camshaft 2 and the vane rotor 15 are coaxially correlatively
rotatable with respect to the chain sprocket 10 and the shoe
housing 12. The inner wall 10a of the chain sprocket 10 and the
inner wall 14a of the front plate 14 work as bearings for
supporting the driven-side rotor.
[0033] A spring 24 is installed in a cylindrical recess 11 formed
in the chain sprocket 10. The spring 24 is retained at one end by
the retaining portion 11a of the recess 11 and at the other end by
the vane rotor 15 as shown in FIG. 4 through a long hole 17a formed
in the intermediate plate 17 shown in FIGS. 2 and 4.
[0034] The load torque which the camshaft 2 receives while driving
the intake valve varies to both positive and negative sides. Here,
the positive direction of the load torque is the retard direction
of the vane rotor 15 with respect to the shoe housing 12, while the
negative direction of the load torque is the advance direction of
the vane rotor 15 with respect to the shoe housing 12. An average
load torque is applied in the positive direction, that is, in the
retard direction. The urging force of the spring 24 works as a
torque to rotate the vane rotor 15 to the advance side with respect
to the shoe housing 12. The torque of the spring 24 acting on the
vane rotor 15 in the advance direction is almost the same as the
average load torque acting on the camshaft 2.
[0035] A seal member 26 is fitted in the outer peripheral wall of
the vane rotor 15 as shown in FIG. 2. Between the outer peripheral
wall of the vane rotor 15 and the inner peripheral wall of the side
wall 13, a very small clearance is provided. The seal member 26
prevents the hydraulic fluid from leaking between the hydraulic
fluid chambers through the clearance. The seal member 26 is pressed
toward the side wall 13 by the force of the plate spring 27 shown
in FIG. 3.
[0036] A guide ring 30 is pressed and retained in the inner wall of
the vane 15a forming the housing hole 38. A guide ring 31 is
pressed and retained in the inner wall of the guide ring 30. A
cylindrical stopper piston 32 as a contacting portion is provided
in the guide rings 30 and 31, and is slidable in the axial
direction of the camshaft 2. A fitting member 40 as a contacted
portion formed in a circle in cross section is pressed and retained
in recess 14b formed in the front plate 14. As shown in FIG. 1, in
the fitting member 40, a fitting hole 41 in which the stopper
piston 32 can be fitted to contact the fitting member 40, and an
enlarged hole 43 extended on the advance side which is shallower
than the fitting hole 41, and has a retard-side end face on the
same plane as the retard-side end face of the fitting hole 41.
[0037] The stopper piston 32 is formed in a cylindrical shape
having a bottom and has a first small-diameter portion 33, a
large-diameter portion 34, and a second small-diameter portion 35
as viewed from the fitting member 40. The first small-diameter
portion 33 is tapered as it goes toward the fitting direction.
Since the fitting hole 41 is also tapered at approximately the same
angle of taper as the inclination of the first small-diameter
portion 33, the stopper piston 32 can smoothly fit in the fitting
hole 41. Furthermore, since the stopper piston 32 tightly fits in
the fitting hole 41, it is possible to prevent occurrence of knocks
likely to be produced by load torque variations. Furthermore, since
the first small-diameter portion 33 being in contact with the
fitting hole 41, has a large contact surface area, the first
small-diameter portion 33 receives small stress, thereby improving
a durability of the stopper piston 32.
[0038] A spring 37 in FIG. 1 urges the stopper piston 32 toward the
fitting member 40. A restraining means in the present invention
includes the stopper piston 32, the fitting member 40 and the
spring 37.
[0039] The first small-diameter portion 33 of the stopper piston 32
can fit in the fitting hole 41 when the vane rotor 15 is nearly in
the intermediate position between the most retarded position and
the most advanced position with respect to the shoe housing 12 as
shown in FIG. 2. When the stopper piston 32 is fitted in the
fitting hole 41, the relative rotation of the vane rotor 15 with
respect to the shoe housing 12 is restrained. In the intermediate
position, the relative rotation of the vane rotor 15 with respect
to the shoe housing 12 is restrained with the stopper piston 32
fitted in the fitting hole 41. In this intermediate position, the
phase difference of the camshaft 2 from the crankshaft, that is,
the intake valve timing is set in optimum such that the engine can
be reliably started up.
[0040] When the stopper piston 32 is withdrawn out of the fitting
hole 41, the vane rotor 15 is relatively rotatable with respect to
the shoe housing 12.
[0041] The front end face of the first small-diameter portion 33
receives the retard oil pressure from an oil pressure chamber 42.
Annular surface formed on the fitting hole 41 side of the
large-diameter portion 34 receives an advance oil pressure from an
oil pressure chamber 45 when an oil passage 47 formed by the oil
pressure chamber 45 and the vane 15a is not closed by the
large-diameter portion 34. The oil pressure that the stopper piston
32 receives from the oil pressure chambers 42 and 45 are applied in
the direction in which the stopper piston 32 moves out of the
fitting hole 41. The oil pressure chamber 42 communicates with a
retard oil pressure chamber 51 through an oil passage 44 formed
within the front plate 14. The oil pressure chamber 45 can
communicate with an advance oil pressure chamber 54 through a
through hole 30a formed in the guide ring 30 and an oil passage
47.
[0042] A damper chamber 46 communicates with an oil passage 48
through a through hole 30b formed in the guide ring 30. The oil
pressure chambers 42, 45, the damper chamber 46, and the housing
hole 38 face to the stopper piston 32. A recess space 49 is formed
on the sliding side of the intermediate plate 17 on which the vane
15a slides. The oil passage 48 and the recess space 49 form a
communication passage. The recess space 49 can communicate with the
advance oil pressure chamber 54 and the oil passage 48, that is,
with the damper chamber 46, in accordance with the relative
rotational position of the vane rotor 15 with respect to the shoe
housing 12. The connection of the advance oil pressure chamber 54
with the damper chamber 46 is interrupted by the sliding surface of
the vane rotor 15 and the intermediate plate 17. That is, the vane
rotor 15 and the intermediate plate 17 work as switching means for
switching the damper chamber 46 between opened and sealed. The
advance oil pressure chamber 54 communicates with the damper
chamber 46 through the recess space 49 when the vane rotor 15
rotates to the advance side with respect to the shoe housing 12
over the intermediate position where the stopper piston 32 fits in
the fitting hole 41.
[0043] When the damper chamber 46 is disconnected from the advance
oil pressure chamber 54, the damper chamber 46 is hermetically
sealed. When the damper chamber 46 is hermetically sealed, the
damper chamber 46 operates as a damper to decrease the speed of
movement of the stopper piston 32 toward the fitting hole 41. The
damper chamber 46 is opened when the damper chamber 46 communicates
with the advance oil pressure chamber 54. When the damper chamber
46 is opened and ceases to function as a damper, the stopper piston
32 can easily move toward the fitting hole 41. In this way, the
opening and hermetically sealing of the damper chamber 46 is
changed over by the relative rotational position of the vane rotor
15.
[0044] FIG. 5 schematically shows pressure receiving areas of the
stopper piston 32. FIG. 5 shows seal lengths and clearances between
the stopper piston 32 and the guide rings 30, 31. Here, it is
defined that the pressure receiving area at which the first
small-diameter portion 33 receives a retard oil pressure from the
oil pressure chamber 42 is S1, the pressure receiving area at which
the large-diameter portion 34 receives an advance oil pressure from
the oil pressure chamber 45 is S2, and the pressure receiving area
at which the large-diameter portion 34 receives an advance oil
pressure from the damper chamber 46 is S3. In the present
embodiment, S1.apprxeq.S2.apprxeq.S3.
[0045] The retard oil pressure in the oil pressure chamber 42 and
the advance oil pressure in the oil pressure chamber 45 are
pulsated and phases thereof are inverted each other.
[0046] Therefore, by setting S1.apprxeq.S2, the magnitudes of
pulsations which the stopper piston 32 receives from the oil
pressures in the oil pressure chambers 42 and 45 are averaged and
it is possible to prevent the vibration of the stopper piston
32.
[0047] When S2 and S3 are set to S2>S3, not S2.apprxeq.S3, even
when the operation oil in the oil chamber 45 leaks into the damper
chamber 46 through the clearance between the large-diameter portion
34 and the guide ring 30, the force which an abutting portion
receives from the damper chamber 46 becomes small because the area
at which the large-diameter portion 34 receives the oil pressure in
the damper chamber 46 is small. Thus, it is not necessary that the
size of the clearance between the large-diameter portion 34 and the
guide ring 30 be set highly accurately; in other words, forming of
the large-diameter portion 34 and the guide ring 30 becomes easier.
However, the damping effect is diminished because the volume of the
damper chamber 46 becomes small.
[0048] When S2 and S3 are set to S2<S3, the volume of the damper
chamber 46 becomes large and the damping effect becomes more
outstanding. However, since the area at which the large-diameter
portion 34 receives the oil pressure from the damper chamber 46
becomes large, it is necessary that the size of the clearance
between the large-diameter portion 34 and the guide ring 30 be set
highly accurately to decrease the amount of oil leaking from the
oil pressure chamber 45 to the damper chamber 46. Thus, it becomes
difficult to form the large-diameter portion 34 and the guide ring
30.
[0049] Therefore, by setting S2 and S3 to S2.apprxeq.S3, the
damping effect of the damper chamber 46 is ensured, and the
large-diameter portion 34 and the guide ring 30 are easily formed
without setting highly accurately the size of the clearance between
the large-diameter portion 34 and the guide ring 30.
[0050] Seal length between the large-diameter portion 34 and the
guide ring 30 and seal length between the second small-diameter
portion 35 and the guide ring 31 are defined to be L1 and L2,
respectively. Further, clearance between the large-diameter portion
34 and the guide ring 30 and clearance between the second
small-diameter portion 35 and the guide ring 31 are defined to be
C1 and C2, respectively. In the present embodiment, L1, L2, C1 and
C3 are set to L1>L2 and C1<C2. Therefore, the amount of
operation oil flowing out of the damper chamber 46 is larger than
that flowing into the damper chamber 46, and the oil pressure in
the damper chamber 46 does not rise.
[0051] As shown in FIG. 1, the housing hole 38 formed in the
stopper piston 32 on the opposite side to the fitting member 40 is
always open to the atmosphere in a relative rotational angle range
of the vane rotor 15 via a through hole 39 formed in the vane 15a,
a communication hole 17b formed in the intermediate plate 17 and
extending in the circumferential direction, and further via an oil
passage 10b (see FIG. 3) formed in the chain sprocket 10.
Therefore, the oil pressure of the operation oil leaking out from
the sliding clearance between the second small-diameter portion 35
and the guide ring 31 into the housing hole 38 is almost equal to
the atmospheric pressure. Thus, the operation oil leaking out into
the housing hole 38 does not act as a force for pushing the stopper
piston 32 toward the fitting member 40. Further, since the housing
hole 38 is always opened, no damping action occurs.
[0052] A groove 33a extending in the direction of movement of the
stopper piston 32 is formed in an outer peripheral wall of the
first small-diameter portion 33. An annular groove 33b is connected
to the groove 33a is formed on the fitting hole 41 side of the
groove 33a. Further, a groove 30c extending in the direction of
movement of the stopper piston 32 is formed in an inner peripheral
surface of the guide ring 30 which is in sliding contact with the
first small-diameter portion 33. An oil passage formed by the
groove 30c is always in communication with the oil pressure chamber
42. Oil passages formed by the grooves 33a, annular groove 33b and
groove 30c come into communication with one another, in accordance
with the position of movement of the stopper piston 32. The grooves
33a, annular groove 33b and groove 30c work as a communication
means.
[0053] As shown in FIG. 2, a retard oil pressure chamber 51 is
formed between the shoe 12a and the vane 15a, a retard oil pressure
chamber 52 is formed between the shoe 12b and the vane 15b, and a
retard oil pressure chamber 53 is formed between the shoe 12c and
the vane 15c. Similarly, an advance oil pressure chamber 54 is
formed between the shoe 12c and the vane 15a, an advance oil
pressure chamber 55 is formed between the shoe 12a and the vane
15b, and an advance oil pressure chamber 56 is formed between the
shoe 12b and the vane 15c.
[0054] The retard oil pressure chamber 51 communicates with an oil
passage 61. The retard oil pressure chambers 52, 53 communicate
through oil passages 62, 63 and with an oil passage 60 shown in
FIG. 2. The oil passage 60 is formed in a C shape and at a camshaft
2-side end face of a boss portion 15d. The retard oil pressure
chambers 51, 52 and 53 further communicate through the oil passages
60, 61 and with an oil passage 200 formed in the camshaft 2 (see
FIG. 3). As shown in FIG. 2, the advance oil pressure chamber 55
communicates with an oil passage 72. The advance oil pressure
chambers 54, 56 communicate through oil passages 71, 73 and with an
oil passage 70. The oil passage 70 is formed in a C shape and at a
bushing 22-side end face of the boss portion 15d. Further, the
advance oil pressure chambers 54, 55, 56 communicate with an oil
passage 201 formed within the camshaft 2 (see FIG. 3) through an
oil passage (not illustrated) axially formed in the boss portion
15d from the oil passages 70, 72.
[0055] The oil passage 200 communicates with a groove passage 202
formed in an outer peripheral wall of the camshaft 2. The oil
passage 201 communicates with a groove passage 203 also formed in
the outer peripheral wall of the camshaft 2. The groove passages
202, 203 are connected to a change-over valve 212 through oil
passages 204, 205, respectively. An oil feed passage 206 is
connected to an oil pump 210, and an oil discharge passage 207 is
open toward a drain 211. The oil pump 210 supplies the operation
oil pumped up from the drain 211 to each oil chamber through the
change-over valve 212. The change-over valve 212 is a four-port
guide valve.
[0056] A valve member 213 of the change-over valve 212 is urged in
one direction by means of a spring 214 and is reciprocated by
controlling the supply of electric power to a solenoid 215. An
engine control unit (ECU) 300 controls the supply of the electric
power. Detection signals from various sensors are input into the
ECU 300, and the ECU 300 outputs signals to various devices
associated with an engine. Communicative combinations of the oil
passages 204 and 205 with the oil feed passage 206 and the oil
discharge passage 207, as well as blocking of the communication,
are switched by reciprocating the valve member 213.
[0057] With the above-described oil passage configuration, the
operation oil is supplied from the oil pump 210 to the retard oil
pressure chambers 51, 52, 52, the advance oil pressure chambers
54,55, 56 and the oil pressure chambers 42, 45. Further, the
operation oil is discharged from those oil chambers to the drain
211.
[0058] Next, an operation of the valve timing adjusting apparatus 1
will be described.
[0059] When an ignition key is turned OFF and engine stop is
instructed, the stop of electric power to the ECU 300 is delayed by
a relay circuit. When the ECU 300 detects that the ignition key has
been turned OFF, it energizes the solenoid 215, so that a valve
member 213c is selected. As a result, the operation oil is fed to
the advance oil pressure chambers 54, 55, 56 and the oil pressure
chamber 45, and the retard oil pressure chambers 51, 52, 53 and the
oil pressure chamber 42 are open to the drain 211. Thus, the vane
rotor 15 rotates to the advance side with respect to the shoe
housing 12 and reaches the most advance position as shown in FIG.
6A. The ECU 300 and the change-over valve 212 work as an advance
control means.
[0060] Even when the stopper piston 32 reaches the intermediate
position to fit with the fitting hole 41 from the retard side, the
damper chamber 46 is sealed hermetically and exhibits a damping
action because the oil passage 48 does not communicate with the
recess space 49. Therefore, the stopper piston 32 does not move
toward the fitting hole 41. When the stopper piston 32 rotates to
the advance side over the intermediate position, the damper chamber
46 communicates with the advance oil pressure chamber 54 through
the recess space 49, so that the damper chamber 46 is opened and no
damper action occurs. Further, since the areas at which the
large-diameter portion 34 receives advance oil pressures from the
oil pressure chamber 45 and the damper chamber 46 are equal to each
other, the forces which the large-diameter portion 34 receives from
the advance oil pressures are canceled.
[0061] When the damper chamber 46 is opened, the stopper piston 32
moves toward the fitting hole 41 with the urging force of the
spring 37. Halfway in the movement of the stopper piston 32 toward
the fitting hole 41, the large-diameter portion 34 interrupts the
communication between the through hole 30a and the oil pressure
chamber 45. However, the oil passages formed by the groove 33a,
annular groove 33b and groove 30c come into communication with one
another and the oil pressure chambers 45, 42 are also put in
communication with each other, so that the oil pressure chamber 45
is not sealed hermetically. Thus, the oil pressure chamber 45 does
not act as a damper chamber. When the oil pressure chamber 45
communicates with the oil pressure chamber 42, no advance oil
pressure is applied to the oil pressure chamber 45, so that the
stopper piston 32 moves toward the fitting member 40 promptly with
the advance oil pressure in the damper chamber 46. As shown in FIG.
6B, the stopper piston 32 having moved toward the fitting member 40
is first fitted into the enlarged hole 43.
[0062] As shown in FIGS. 6A and 6B, before fitting of the stopper
piston 32 into the fitting hole 41, the seal lengths L1 and L2
shown in FIG. 5 are constant without change regardless a moving
position of the stopper piston 32. Since the amount of operation
oil flowing into the damper chamber 46 and the amount of operation
oil flowing out of the damper chamber 46 do not change, force that
the stopper piston 32 receives from the operation oil in the damper
chamber 46 is constant.
[0063] Due to the load torque applied to the vane rotor 15 until
the engine stop, the vane rotor 15 rotates to the retard side and
reaches the intermediate position as in FIG. 6C, whereupon the
stopper piston 32 is fitted into the fitting hole 41. As a result,
a relative rotation of the vane rotor 15 with respect to the shoe
housing 12 is restricted.
[0064] When the stopper piston 32 is fitted in the fitting hole 41
before start-up of the engine, the phase difference of the vane
rotor 15 with respect to the shoe housing 12, i.e., the phase
difference of the camshaft 2 with respect to the crank shaft, is
held at an optimum phase most suitable for starting the engine, so
that the engine starts in a short time with certainty.
[0065] During cranking for starting the engine, a valve portion
213a of the change-over valve 212 is selected, so that the
operation oil is supplied to the retard oil pressure chambers 51,
52, 53 and the oil pressure chamber 42, and the advance oil
pressure chambers 54, 55, 56 and the oil pressure chamber 45 are
opened to the drain 211. However, until the retard oil pressure
reaches a predetermined pressure, the stopper piston 32 does not
come out of the fitting hole 41 and is held at a state shown in
FIG. 7A.
[0066] After start-up of the engine, when the operation oil is
charged into the retard oil pressure chambers 51, 52, 53 and the
oil pressure in the oil pressure chamber 42 rises to a
predetermined pressure, the stopper piston 32 comes out of the
fitting hole 41, thereby allowing a relative rotation of the vane
rotor 15 with respect to the shoe housing 12, i.e., phase
control.
[0067] When the pressure of the operation oil rises to a sufficient
level after start-up of the engine, any of valve portions 213a,
213b and 213c of the valve member 213 is selected in accordance
with a command instructed by the ECU 300, whereby the supply of
operation oil to the oil pressure chambers and the discharge
thereof from the oil pressure chambers are controlled, and a
relative rotation of the vane rotor 15 with respect to the shoe
housing 12 is controlled.
[0068] While the engine is in normal operation, when the vane rotor
15 rotates to the retard side over the intermediate position, the
communication between the oil passage 48 and the recess space 49 is
interrupted by the sliding surfaces of the vane rotor 15 and the
intermediate plate 17, so that the damper chamber 46 is sealed
hermetically. Thus, even when the stopper piston 32 reaches the
position on the fitting hole 41 of which position is the
intermediate position, the stopper piston does not move toward the
fitting hole 41 due to the damping action of the damper chamber
46.
[0069] When the vane rotor 15 rotates to the advance side over the
intermediate position, the damper chamber 46 communicates with the
advance oil pressure chamber 54 through the recess space 49, so
that the damper chamber 46 does not exhibit its damping action any
longer. However, since the operation oil is supplied into one of
the oil pressure chambers 42, 45 and the stopper piston 32
undergoes a retard or advance oil pressure in a direction to come
out of the fitting hole 41, the stopper piston 32 does not move
toward the fitting hole 41. When the retard or advance oil pressure
which the stopper piston 32 undergoes in its disengaging direction
from the fitting hole 41 varies and drops, the stopper piston 32
might be fitted into the enlarged hole 43. However, when the vane
rotor 15 reaches the intermediate position, the damper chamber 46
is sealed hermetically and exhibits the damping action, so that the
stopper piston 32 does not fit into the fitting hole 41.
[0070] According to the above described embodiment, when the engine
operates normally, the damper chamber 46 is sealed hermetically at
the intermediate position as the abutting position, so that the
stopper piston 32 is prevented from being fitted into the fitting
hole 41. When the engine is stopped, the vane rotor 15 is
advance-controlled, so that the stopper piston 32 rotates to
advance side over the intermediate position. Thus, the damper
chamber 46 is opened. Therefore, due to a drop in oil pressure
caused by engine stop and by the action of a load torque, the
stopper piston 32 rotates to the intermediate position from the
advance side and is fit into the fitting hole 41 with
certainty.
[0071] Further, since the oil chambers 42, 45 and the housing hole
38 facing the stopper piston 32, except the damper chamber 46, are
not hermetically sealed and open constantly, the other fluid
chambers than the damper chamber 46 are prevented from working as a
damper chamber. Therefore, when the engine is stopped, by opening
the damper chamber 46, the stopper piston 32 is fit into the
fitting hole 41 with certainty.
[0072] In the above described embodiment, when the ignition key is
turned OFF and engine stop is indicated, the supply of electric
power to the ECU 300 is continued for a predetermined period of
time and ECU 300 energizes the solenoid 215 to select the valve
portion 213c, thereby allowing the operation oil to be supplied
into the advance oil pressure chambers 54, 55, 56 to execute the
advance control. Alternatively, the advance control may be executed
by adopting an oil passage configuration in which when the valve
portion 213a is selected, the operation oil is supplied into the
advance oil pressure chambers, and when the valve portion 213c is
selected, the operation oil is supplied into the retard oil
pressure chambers. In this case, when the supply of electric power
to the ECU 300 is cut off at the same time of turning OFF of the
ignition key, the valve portion 213a is selected due to the urging
force of the spring 214 and the operation oil is supplied into the
advance oil pressure chambers.
[0073] In the above described embodiment, since the sliding
surfaces of the vane rotor 15 and the intermediate plate 17
interrupts the communication between the damper chamber 46 and the
advance oil pressure chamber 54, the damper chamber 46 is certainly
switched between opening and closing at a predetermined relative
rotational position of the vane rotor 15 with respect to the shoe
housing 12. Further, there is no need to prepare any additional
switching means, thereby preventing the number of parts from
increasing.
[0074] In the above-described embodiment, the enlarged hole 43 is
formed in the fitting member 40 in addition to the fitting hole 41.
Alternatively, only fitting hole 41 may be formed without forming
the enlarged hole 43.
[0075] In the above-described embodiment, the valve timing
adjusting apparatus for actuating the intake valve is explained.
Alternatively, the valve timing adjusting apparatus of the
above-described embodiment may actuate only the exhaust valve or
both intake valve and exhaust valve.
[0076] In the above-described embodiment, the stopper piston moves
axially to be fit into the fitting hole, the stopper piston may
move radially to be fit into the fitting hole. Moreover, the
stopper piston may be accommodated at the housing member side, and
the fitting hole and enlarged hole may be formed at the vane rotor
side.
[0077] In the above-described embodiment, the rotational force of
the crank shaft is transmitted to the camshaft through the chain
sprocket. Alternatively, a timing pulley or a timing gear may be
used. Further, the vane member may receive the driving force of the
crank shaft as a driving shaft, and the camshaft as a driven shaft
and the housing member may rotate integrally.
* * * * *