U.S. patent application number 13/267082 was filed with the patent office on 2012-05-03 for valve timing control apparatus.
This patent application is currently assigned to Hitachi Automotive Systems, Ltd.. Invention is credited to Yoshinori Ichinosawa, Hiroyuki KATO.
Application Number | 20120103289 13/267082 |
Document ID | / |
Family ID | 45995274 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120103289 |
Kind Code |
A1 |
KATO; Hiroyuki ; et
al. |
May 3, 2012 |
Valve Timing Control Apparatus
Abstract
A valve timing control apparatus includes a driving rotary
member to receive a rotational force from a crankshaft of an
engine, and a vane rotor connected with a camshaft and arranged to
rotate relative to the driving rotary member, with at least one
vane defining a retard pressure chamber and an advance pressure
chamber in the inside of the driving rotary member. A lock member
is received slidably in the vane of the vane rotor and arranged to
engage with a lock hole when the vane is rotated to a predetermined
angular position. The lock member includes forward and rearward end
portions arranged to receive equal fluid pressures. The lock member
further includes a pressure receiving portion to which an operating
fluid pressure is selectively applied to force the lock member away
from the lock hole.
Inventors: |
KATO; Hiroyuki; (Koza-gun,
JP) ; Ichinosawa; Yoshinori; (Atsugi-shi,
JP) |
Assignee: |
Hitachi Automotive Systems,
Ltd.
Hitachinaka-shi
JP
|
Family ID: |
45995274 |
Appl. No.: |
13/267082 |
Filed: |
October 6, 2011 |
Current U.S.
Class: |
123/90.15 |
Current CPC
Class: |
F01L 2001/34469
20130101; F01L 1/3442 20130101; F01L 2001/34476 20130101; F01L
2001/34423 20130101 |
Class at
Publication: |
123/90.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2010 |
JP |
2010-243845 |
Claims
1. A valve timing control apparatus comprising: a driving rotary
member adapted to receive a rotational force from a crankshaft of
an internal combustion engine; a vane rotor which is adapted to be
fixed to a camshaft, which is arranged to rotate relative to the
driving rotary member within a predetermined angular range, and
which includes a vane defining a retard pressure chamber and an
advance pressure chamber in an inside of the driving rotary member;
a lock member received in the vane and arranged to slide forwards
and rearwards in an axial direction; a lock hole to receive a
forward end of the lock member when the vane is rotated relatively
to a predetermined intermediate position between a most retard
position and a most advance position; and a biasing member to urge
the lock member toward the lock hole; wherein the lock member
includes a forward end portion to receive a first fluid pressure
which is one of a fluid pressure in the retard pressure chamber and
a fluid pressure in the advance pressure chamber, in a pressure
receiving area, and a rearward end portion to receive the first
fluid pressure in a pressure receiving area, the forward and
rearward end portions being so shaped that the pressure receiving
area of the forward end portion receiving the first fluid pressure
is equal to the pressure receiving area of the rearward end portion
receiving the first pressure; and wherein the lock member further
includes a pressure receiving portion including a first surface to
which an operating fluid pressure is selectively applied, and a
second surface which is opened through an air passage formed in the
vane rotor, to atmosphere.
2. The valve timing control apparatus as claimed in claim 1,
wherein the lock hole is provided with a lock guide groove
elongated circumferentially from the lock hole and arranged to
allow the vane rotor to rotate relative to the driving rotary
member in a state in which the forward end of the lock member is
received in the lock guide groove.
3. The valve timing control apparatus as claimed in claim 1,
wherein the apparatus further comprises a canceling section to move
the lock member out of the lock hole selectively.
4. The valve timing control apparatus as claimed in claim 1,
wherein the lock member is a lock pin including an outward flange
serving as the pressure receiving portion.
5. The valve timing control apparatus as claimed in claim 1,
wherein the driving rotary member includes a cylindrical housing
including a shoe projecting radially inwards, and a cover member
closing an open end of the housing and including a through hole
formed on a radial inner side of an outside circumference of the
vane, the vane is formed with the air passage extending to the
though hole of the cover member and thereby opening the second
surface of the pressure receiving portion to the atmosphere.
6. The valve timing control apparatus as claimed in claim 1,
wherein the valve timing control apparatus further comprises a
first hydraulic circuit to regulate the fluid pressure in the
retard pressure chamber and the fluid pressure in the advance
pressure chamber, and a second hydraulic circuit to supply the
operating fluid pressure different from the fluid pressure in the
retard pressure chamber and the fluid pressure in the advance
pressure chamber.
7. The valve timing control apparatus as claimed in claim 6,
wherein the first hydraulic circuit includes a first control valve
to regulate the fluid pressure in the retard pressure chamber and
the fluid pressure in the advance pressure chamber, and the second
hydraulic circuit includes a second control valve to regulate the
operating fluid pressure applied to the first surface of the
pressure receiving portion of the lock member.
8. The valve timing control apparatus as claimed in claim 7,
wherein the first control valve is a proportional control valve,
and the second control valve has a first valve position to increase
the operating fluid pressure and a second valve position to
decrease the operating fluid pressure.
9. The valve timing control apparatus as claimed in claim 1,
wherein the first fluid pressure received by the forward end
portion and the rearward end portion of the lock member is the
fluid pressure in the advance pressure chamber.
10. The valve timing control apparatus as claimed in claim 2,
wherein the lock guide groove includes a stepped bottom descending
stepwise toward the lock hole.
11. The valve timing control apparatus as claimed in claim 1,
wherein the vane is a first vane, the lock member is a first lock
member received in the first vane, the lock hole is a first lock
hole, the biasing member is a first biasing member, the vane rotor
further includes a second vane defining a retard pressure chamber
and an advance pressure chamber in the inside of the driving rotary
member; the valve timing control apparatus further comprises a
second lock member received in the second vane and arranged to
slide forwards and rearwards in the axial direction, a second lock
hole to receive a forward end of the second lock member when the
second vane is at a predetermined intermediate position, and a
second biasing member to urge the second lock member toward the
second lock hole; wherein the second lock member includes a forward
end portion to receive a second fluid pressure which is one of the
fluid pressure in the retard pressure chamber and the fluid
pressure in the advance pressure chamber in a pressure receiving
area, and a rearward end portion to receive the second fluid
pressure in a pressure receiving area, the forward and rearward
portions being so shaped that the pressure receiving area of the
forward end portion of the second lock member is equal to the
pressure receiving area of the rearward end portion of the second
lock member; and wherein the second lock member further includes a
pressure receiving portion including a first surface to which an
operating fluid pressure is selectively applied, and a second
surface which is opened through an air passage formed in the vane
rotor, to the atmosphere.
12. The valve timing control apparatus as claimed in claim 11,
wherein the first lock hole is provided with a first lock guide
groove elongated in a circumferential direction around a rotation
axis of the vane rotor from the first lock hole and arranged to
allow the vane rotor to rotate relative to the driving rotary
member in a state in which the forward end of the first lock member
is received in the first lock guide groove, and the second lock
hole is provided with a second lock guide groove elongated in the
circumferential direction around the rotation axis of the vane
rotor from the second lock hole and arranged to allow the vane
rotor to rotate relative to the driving rotary member in a state in
which the forward end of the second lock member is received in the
second lock guide groove.
13. The valve timing control apparatus as claimed in claim 12,
wherein the first lock member and the first lock hole are arranged
to allow rotation of the vane rotor relative to the driving rotary
member within a predetermined angular range in a state in which the
first lock member is engaged with the first lock hole; and the
second lock member and the second lock hole are arranged to lock
the vane rotor to prevent rotation of the vane rotor relative to
the driving rotary member when the second lock member is engaged
with the second lock hole in the state in which the first lock
member is engaged with the first lock hole.
14. The valve timing control apparatus as claimed in claim 13,
wherein the second lock guide groove includes a stepped bottom
descending stepwise toward the second lock hole.
15. The valve timing control apparatus as claimed in claim 14,
wherein the first lock guide groove includes a stepped bottom
descending stepwise toward the first lock hole, and the first and
second lock holes are so arranged that the second lock member
descends the stepped bottom of the second lock guide groove and
engages in the second lock hole after the first lock member
descends the stepped bottom of the first lock guide groove and
engages in the first lock hole.
16. The valve timing control apparatus as claimed in claim 15,
wherein a number of steps of the stepped bottom of the first lock
guide groove is greater than a number of steps of the stepped
bottom of the second lock guide groove.
17. The valve timing control apparatus as claimed in claim 16,
wherein a height of a riser wall surface rising from a lowest
bottom surface of the second guide groove is greater than a height
of a riser wall surface rising from a lowest bottom surface of the
first lock guide groove.
18. The valve timing control apparatus as claimed in claim 13,
wherein at least one of the first lock hole, the first lock guide
groove, the second lock hole and the second lock guide groove is
elongated circumferentially.
19. A valve timing control apparatus comprising: a driving rotary
member adapted to receive a rotational force from a crankshaft; a
vane rotor which is adapted to be fixed to a camshaft, which is
arranged to rotate relative to the driving rotary member within a
predetermined angular range, and which includes a vane defining a
retard pressure chamber and an advance pressure chamber in an
inside of the driving rotary member; a lock member received in the
vane and arranged to slide axially; a lock receiving portion to
receive a forward end of the lock member when the vane is rotated
relatively to a predetermined intermediate position between a most
retard position and a most advance position; and a biasing member
to urge the lock member toward the lock receiving portion; wherein
the lock member includes a forward end portion to receive a first
fluid pressure which is one of a fluid pressure in the retard
pressure chamber and a fluid pressure in the advance pressure
chamber, and a rearward end portion to receive the first fluid
pressure, the forward and rearward end portions being so shaped
that a pressure receiving area of the forward end portion receiving
the first fluid pressure is equal to a pressure receiving area of
the rearward end portion receiving the first pressure; and wherein
the valve timing control apparatus further comprises a canceling
section to release the lock member from the lock receiving portion
selectively.
20. The valve timing control apparatus as claimed in claim 19,
wherein the cancelling section includes a cancelling hydraulic
circuit to supply a cancel fluid pressure to a cancel pressure
chamber to apply the cancel pressure to a pressure receiving
portion of the lock member to move the lock member against an
urging force of the biasing member.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to valve timing control
apparatus for controlling the opening timing and/or closing timing
of an engine valve such as an intake valve and an exhaust valve of
an internal combustion engine.
[0002] A vane type valve timing control system of a known type
includes a lock mechanism including a lock hole formed in a housing
of a sprocket on a driving side, and a lock pin which is slidably
received in a vane rotor joined to a camshaft and which is arranged
to engage with the lock hole to lock the vane rotor unrotational at
an intermediate phase position between a most advance position and
a most retard position.
[0003] The valve timing control system of this type maintains a
lock state of the vane rotor until the oil pressure supplied from
an oil pump to a retard pressure chamber or an advance pressure
chamber is increased at the time of engine start, and maintains an
unlock state by utilizing the oil pressure of the oil pump after
the oil pressure is increased.
[0004] Therefore, a valve timing control system as disclosed in
Patent Document (JP2003-222010 A) is arranged to achieve a desired
control timing by holding and canceling the lock state by using a
hydraulic pressure of a hydraulic circuit different from a
hydraulic circuit for the retard pressure and advance pressure.
SUMMARY OF THE INVENTION
[0005] However, the above-mentioned valve timing control system
uses a lock having an annular shoulder surface formed between a
large diameter portion and small diameter portion and selectively
applies the fluid pressure to the annular shoulder surface.
Accordingly, to ensure smooth axial movement of the lock pin, the
lock pin is so arranged that both axial ends of the lock pin are
always open to the atmosphere.
[0006] Therefore, to prevent leakage of the oil pressure in the
retard or advance chambers, the system requires a longer side seal
having a longer circumferential length for sealing the clearance
between one axial end of the lock pin and the inside surface of the
housing, and hence requires an increase of the circumferential
width of the vane, so that it becomes difficult to increase the
operating rotational angle of the vane.
[0007] Therefore, it is an object of the present invention to
provide a valve timing control apparatus for an internal combustion
engine, suitable for ensure a large operation angle of a vane rotor
despite a lock pin moved axially by using an operating fluid
pressure of a separate system.
[0008] According to one aspect of the present invention, a valve
timing control apparatus comprises: a driving rotary member; a vane
rotor; a lock member received in the vane and arranged to slide
forwards and rearwards in an axial direction; and a lock hole to
receive a forward end of the lock member; wherein the lock member
includes a forward end portion to receive a first fluid pressure
which is one of a fluid pressure in the retard pressure chamber and
a fluid pressure in the advance pressure chamber in a pressure
receiving area, and a rearward end portion to receive the first
fluid pressure in a pressure receiving area, the pressure receiving
area of the forward end portion receiving the first fluid pressure
being equal to the pressure receiving area of the rearward end
portion receiving the first pressure; and wherein the lock member
further includes a pressure receiving portion including a first
surface to which an operating fluid pressure is selectively
applied, and a second surface which is opened through an air
passage formed in the vane rotor, to atmosphere.
[0009] According to another aspect of the invention a valve timing
control apparatus comprises: a driving rotary member; a vane rotor;
a lock member received in the vane and arranged to slide axially; a
lock receiving portion to receive a forward end portion of the lock
member when the vane is at a predetermined intermediate position
between a most retard position and a most advance position; and a
biasing member to urge the lock member toward the lock hole;
wherein the lock member includes a forward portion to receive a
first fluid pressure which is one of a fluid pressure in the retard
pressure chamber and a fluid pressure in the advance pressure
chamber in a pressure receiving area, and a rearward portion to
receive the first fluid pressure, a pressure receiving area of the
forward portion receiving the first fluid pressure being equal to a
pressure receiving area of the rearward portion receiving the first
pressure; and wherein the valve timing control apparatus further
comprises a canceling section to release the lock member from the
lock receiving portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a view showing a valve timing control apparatus
according to an embodiment of the present invention.
[0011] FIG. 2 is a sectional view taken across a line II-II shown
in FIG. 1, showing a vane rotor or vane member at an intermediate
phase angular position.
[0012] FIG. 3 is a sectional view taken across the line II-II shown
in FIG. 1, showing the vane rotor at a most retard phase
position.
[0013] FIG. 4 is a sectional view taken across the line II-II shown
in FIG. 1, showing the vane rotor at a most advance phase
position.
[0014] FIG. 5 is a sectional view, taken across a line V(i)-V(i)
and a line V(ii)-V(ii) shown in FIG. 2, showing first and second
lock pins in a first operating state.
[0015] FIG. 6 is a sectional view, taken across the line V(i)-V(i)
and the line V(ii)-V(ii) shown in FIG. 2, showing the first and
second lock pins in a second operating state.
[0016] FIG. 7 is a sectional view, taken across the line V(i)-V(i)
and the line V(ii)-V(ii) shown in FIG. 2, showing the first and
second lock pins in a third operating state.
[0017] FIG. 8 is a sectional view, taken across the line V(i)-V(i)
and the line V(ii)-V(ii) shown in FIG. 2, showing the first and
second lock pins in a fourth operating state.
[0018] FIG. 9 is a sectional view, taken across the line V(i)-V(i)
and the line V(ii)-V(ii) shown in FIG. 2, showing the first and
second lock pins in a fifth operating state.
[0019] FIG. 10 is a sectional view, taken across the line V(i)-V(i)
and the line V(ii)-V(ii) shown in FIG. 2, showing the first and
second lock pins in a sixth operating state.
DETAILED DESCRIPTION OF THE INVENTION
[0020] FIGS. 1.about.10 show a valve timing control apparatus
according to an embodiment of the present invention. In this
embodiment, the valve timing control apparatus is applied to the
intake valve's side of an internal combustion engine for a vehicle
such as a hybrid vehicle or a vehicle provided with an idle stop
system.
[0021] As shown in FIGS. 1.about.4, the valve timing control
apparatus according to the embodiment includes a sprocket 1, a
camshaft 2 on the intake side, a phase varying mechanism 3 and a
first hydraulic circuit 4. The sprocket 1 is connected by a timing
chain with a crankshaft of the engine and adapted to be driven by
the engine. Sprocket 1 serves as a driving rotary member driven by
the engine. The camshaft 2 extends in the front and rear direction
of the engine. Camshaft 2 is rotatable relative to the sprocket 1.
The phase varying mechanism 3 is disposed between sprocket 1 and
camshaft 2, and arranged to vary the relative rotational phase of
the sprocket 1 and camshaft 2. The first hydraulic circuit 4 is
arranged to actuate the phase varying mechanism 3.
[0022] Sprocket 1 is a thick plate shaped like a circular disk.
Sprocket 1 includes a toothed portion 5 formed in an outer
circumferential portion and arranged to engage with the timing
chain. Sprocket 1 is arranged to close a rear opening of a housing
(7), and thereby to serve as a rear cover. Sprocket 1 includes a
support hole 6 opened through a central portion of sprocket 1, and
arranged to receive a vane rotor (9) rotatably. Vane rotor or vane
member (9) is fixed to camshaft 2.
[0023] Camshaft 2 is rotatably supported through cam bearings on a
cylinder head (not shown). Camshaft 2 includes a plurality of cams
which are integrally formed at positions arranged in the axial
direction, and which are designed to open a plurality of engine
valves (intake valves in this embodiment). Camshaft 2 extends from
a second end to a first end (left end as viewed in FIG. 1) which is
formed with a female threaded (or internally threaded) hole 2a
extending along the center line of camshaft 2.
[0024] As shown in FIGS. 1 and 2, the phase varying mechanism 3
includes a housing 7 joined axially to sprocket 1 so as to form a
single unit, and a vane rotor or vane member 9 serving as a driven
rotary member. The vane rotor or member 9 is fixed to the first
(left) end of camshaft 2 through a cam bolt 8 screwed into the
female threaded hole 2a of camshaft 2, and received rotatably in
housing 7. Housing 7 includes partition walls 10 projecting
radially inwards from a circumferential wall, and serving as shoes.
The partition walls 10 and vane member 9 define retard pressure
chambers 11 and advance pressure chamber 12. In this example, there
are three of the partition walls 10, three of the retard chambers
11 and three of the advance chambers 12.
[0025] Housing 7 of this example includes a main housing member 7a
of sintered metallic material having a hollow cylindrical shape, a
front cover 13 closing a front opening of the main housing member
7a, and the rear cover formed by the sprocket 1 and arranged to
close the rear opening of main housing member 7a. The main housing
member 7a, front cover 13 and sprocket 1 are joined together by
bolts 14 (three bolts) passing, respectively, through bolt holes
10a opened, respectively, in the partition walls 10. Front cover 13
includes a central through hole 13a.
[0026] Vane rotor or vane member 9 is a single integral member of a
metallic material including a central rotor 15 fixed to the first
(left) end of camshaft 2 by cam bolt 8, and a plurality (three) of
vanes 16a, 16b and 16c projecting radially outwards from the
outside circumferential surface of central rotor 15, respectively,
at positions arranged around the center axis at substantially
regular angular intervals (in this example, 120 degrees).
[0027] Central rotor 15 extends from a front (first) end 15b to a
rear (second) end 15c in the front and rear direction in the form
similar to a hollow cylinder. The front end 15b is formed
integrally with a tubular seal guide portion 15a which is located
approximately at the center of the front end 15b and which has a
thin wall tubular shape of a smaller diameter so as to form a step.
The rear end 15c includes an extension extending toward camshaft 2.
Central rotor 15 includes an inside cylindrical engagement hole or
bore 15d extending from the front end toward the rear end inside
the central rotor 15.
[0028] Vanes 16a.about.16c of vane rotor 9 and partition walls 10
of housing 7 are arranged alternately around the center axis so
that each vane is disposed circumferentially between adjacent two
of the partition walls 10. Vanes 16a.about.16c are unequal in
circumferential width in the circumferential direction. The vane
16a having a greatest width and the vane 16b having a medium width
are shaped like a fan or a circular sector. The vane 16c having a
smallest width is shaped like a projecting thick plate. The radial
outward end of each of vanes 16a.about.16c is provided with a seal
member 17a for sealing the boundary portion between the vane and
the inside circumferential surface of main housing member 7a. The
radial inward end of each of partition walls 10 of main housing
member 7a is provided with a seal member 17b for sealing the
boundary portion between the outside circumferential surface of
central rotor 15 and the radial inward end of the partition wall
10. As best shown in FIG. 2, the widest vane 16a includes a first
side surface 16d facing in the counterclockwise direction, and a
second side surface 16e facing in the clockwise direction.
[0029] When vane member 9 is rotated relatively to the retard side
(in the counterclockwise direction), as shown in FIG. 3, the
above-mentioned first (retard) side surface 16d (shown in FIG. 2)
of the widest vane 16a on the retard side abuts against a
projecting surface 10b formed in a confronting side surface of the
adjacent partition wall 10 on the retard side (or counterclockwise
side), and this abutment determines the rotational angular relative
position of vane member 9 of the greatest retard angle. When vane
member 9 is rotated relatively to the advance side (in the
clockwise direction), as shown in FIG. 4, the second (advance) side
surface 16e (shown in FIG. 2) of the widest vane 16a abuts against
a projecting surface 10c formed in a confront side surface of the
adjacent partition wall 10 on the advance side (or clockwise side),
and this abutment determines the rotational angular relative
position of vane member 9 of the greatest advance angle.
[0030] In these states shown in FIG. 3 and FIG. 4, the other vanes
16b and 16c are in a non-abutting free state without abutting
against either of the confronting side surfaces of the adjacent
partition walls 10 on the retard and advance side. This arrangement
is helpful for improving the abutment accuracy between the vane
member 9 and the partition walls 10, and improving the
responsiveness or response speed of vane member 9 in rotating in
the forward direction and reverse direction by increasing the
supply speed of the oil pressure to the pressure chamber 11 or 12
as mentioned later.
[0031] Each of the (three) retard fluid pressure chambers 11 is
defined between the second (advance) side surface of one of the
vanes 10 facing in the second (advance) rotational (clockwise)
direction and the first (retard) side surface of the adjacent
partition wall facing in the first (retard) rotational
(counterclockwise) direction on the advance (clockwise) side.
Similarly, each of the (three) advance fluid pressure chambers 12
is defined between the first (retard) side surface of one of the
vanes 10 facing in the first (retard) rotational (counterclockwise)
direction and the second (advance) side surface of the adjacent
partition wall facing in the second (advance) rotational
(clockwise) direction on the retard (counterclockwise) side. Each
of the retard pressure chambers 11 is connected through a radially
extending communicating hole 11a formed in the central rotor 15,
with the first hydraulic circuit 4. Similarly, each of the advance
pressure chambers 12 is connected through a radially extending
communicating hole 12a formed in the central rotor 15, with the
first hydraulic circuit 4.
[0032] First hydraulic circuit 4 is configured to control the
supply and drain of the operating oil (fluid pressure) for the
retard and advance chambers 11 and 12 selectively. As shown in FIG.
1, the first hydraulic circuit 4 includes a retard pressure passage
18, an advance pressure passage 19, an fluid pump or oil pump 20,
and a first electromagnetic selector valve 21. The retard pressure
passage 18 is a passage for supplying and draining the operating
fluid to and from each retard chamber 11 through one of the first
communication holes 11a. The advance pressure passage 19 is a
passage for supplying and draining the operating fluid to and from
each advance chamber 12 through one of the second communication
holes 12a. The fluid pump 20 is a fluid pressure source for
selectively supplying the fluid pressure to the retard or advance
pressure passages 18 or 19. Fluid pump 20 of this example is an oil
pump of a known type, such as a trochoid pump, driven by the
crankshaft of the engine.
[0033] Retard pressure passage 18 extends from a first port or
retard pressure port of first electromagnetic selector valve 21 to
an axial passage 18a extending axially in a passage forming end
member 37 having an approximately cylindrical shape inserted and
held in the central rotor 15 of vane rotor 9 and the seal guide
portion 15a. Retard fluid passage 18 is connected through the axial
passage 18a and the first communication passages 11a to the retard
pressure chambers 11. Similarly, the advance fluid passage 19
extends from a second port or advance pressure port of first
electromagnetic selector valve 21 to an axial passage 19a extending
axially in the passage forming end member 37. Advance fluid passage
19 is connected through the axial passage 19a and the second
communication passages 12a to the advance pressure chambers 12.
[0034] The passage forming end member 37 includes an external end
portion fixed to a chain cover (not shown) so that the external end
portion is non-rotational, and an internal axial portion formed
with the passage 18a and 19a and a passage 34a of a second
hydraulic circuit 28 for unlocking a lock mechanism as mentioned
later.
[0035] As shown in FIG. 1, first electromagnetic selector valve 21
of this example is a 4-port, 3-position proportional type valve
configured to move a spool (not shown) axially back and forth in a
bore of a valve body under the control of an electronic controller
(not shown) to select one of three valve positions. In a first
valve position, the selector valve 21 connects the retard pressure
passage 18 with a discharge or outlet passage 20a of oil pump 20,
and connects the advance pressure passage 19 with a drain passage
22 leading to an oil pan 23. In a second valve position, the
selector valve 21 connects the retard pressure passage 18 with the
drain passage 22, and connects the advance pressure passage 19 with
the discharge passage 20a of oil pump 20. At the time of stoppage
of the engine or in some other situation, the selector valve 21 is
held at a third (intermediate) position to seal off the operating
fluid in the pressure chambers 11 and 12, by shutting the retard
and advance passages 18 and 19 off from the discharge passage 20a
and drain passage 22.
[0036] A suction or inlet passage 20b of oil pump 20 and the drain
passage 22 are connected to the inside of oil pan 23. A main oil
gallery M/G for supplying a lubricating oil to sliding contact
portions in the internal combustion engine is connected to a
junction point on the downstream side of discharge passage 20a of
oil pump 20. A filter 50 is provided on the downstream side of
discharge passage 20a of oil pump 20. Oil pump 20 is provided with
a flow control valve 51 for controlling the discharge fluid
quantity to a desired level by returning an excess amount of the
discharged operating oil from the discharge passage 20a to oil pan
23.
[0037] The electronic controller includes a computer configured to
sense one or more current engine operating conditions by receiving
input information from various sensors such as a crank angle sensor
(for sensing an engine speed), an airflow meter, an engine coolant
temperature sensor, an engine temperature sensor, a throttle valve
opening sensor, and a cam angle sensor for sensing a current
rotational phase of camshaft 2, and to control the position of the
spool in each of the first electromagnetic selector valve 21 and a
later-mentioned second electromagnetic selector valve 36 by
delivering a control pulse current to the electromagnetic coil of
that selector valve in accordance with the sensed engine operating
conditions.
[0038] In this embodiment, there is provided a holding device (or
position holding means) to hold the vane member 9 relative to
housing 7 at an intermediate rotational phase position (shown in
FIG. 2) intermediate between the most retard rotational position
(shown in FIG. 3) and the most advance rotational position (shown
in FIG. 4).
[0039] As shown in FIGS. 5.about.10, the holding device serving as
a lock mechanism includes first and second lock hole forming
members 1a and 1b formed, respectively, with first and second lock
holes 24 and 25, first and second lock pins 26 and 27 for engaging
with the lock holes 24 and 25, respectively, and the
before-mentioned second hydraulic circuit 28 (shown in FIG. 1). The
lock hole forming members 1a and 1b are provided in the inner side
surface (1c) of sprocket 1 at predetermined circumferential
positions. Each of lock hole forming members 1a and 1b has a
T-shaped section. Each of the lock holes 24 and 25 serves as a lock
portion or lock receiving portion whereas each of the lock pins 26
and 27 serves as a lock member. The first and second lock pins 26
and 27 are provided, respectively, in the vane 16a and vane 16b and
arranged to engage with the first and second lock holes 24 and 25,
respectively. The second hydraulic circuit 28 is arranged to cancel
the engagement of first and second lock pins 26 and 27 with respect
to the first and second lock holes 24 and 25. Second hydraulic
circuit 28 serves as at least part of a canceling section or
means.
[0040] The first lock hole 24 is elongated in the circumferential
direction of sprocket 1 in the form of a circular arc (like a
cocoon), as shown in FIGS. 2.about.4. First lock hole 24 is formed
in the inner side surface 1c of sprocket 1, at an intermediate
position shifted from the most retard position of vane member 9
toward the advance side. Moreover, first lock hole 24 has a stepped
bottom depressed stepwise from the retard side to the advance side,
so as to form a plurality of steps (three steps in this example)
serving as a first lock guide groove.
[0041] As shown in FIGS. 5.about.10, the first lock guide groove
includes a first bottom surface 24a depressed from the inner side
surface 1c of sprocket 1 as an uppermost surface, a second bottom
surface 24b depressed from the first bottom surface 24a, and a
third bottom surface 24c depressed from the second bottom surface
22b. An inner side surface 24d on the retard pressure chamber's
side stands upright from the lowest bottom surface 24c. A forward
end portion 26a of the first lock pin 26 descends stepwise from the
inner side surface 1c of sprocket 1, through the first and second
bottom surfaces 24a and 24b to the lowest third bottom surface 24c
in the advance direction. On each of the bottom surfaces 24a, 24b
and 24c, the forward end portion 26a of first lock pin 26 is
prevented from moving in the retard direction by a riser wall
surface on the retard side. Thus, the staircase of the stepwise
bottom surfaces 24a, 24b and 24c functions as a one-way clutch
(ratchet).
[0042] The movement of first lock pin 26 in the advance direction
(toward the adjacent retard pressure chamber 11) is limited by the
abutment of the forward end portion 26a against the inner side
surface 24d (as shown in FIG. 10).
[0043] As shown in FIGS. 2.about.5, the second lock hole 25 is
elongated in the circumferential direction of sprocket 1 in the
form of a circular arc like the first lock hole 24. Second lock
hole 25 is formed in the inner side surface 1c of sprocket 1, at an
intermediate position shifted from the most retard position of vane
member 9 toward the advance side. Moreover, second lock hole 25 has
a stepped bottom depressed stepwise from the advance chamber's side
to the retard chamber's side, so as to form a plurality of steps
(two steps in this example) serving as a second lock guide
groove.
[0044] As shown in FIGS. 5.about.10, the second lock guide groove
includes a first bottom surface 25a depressed from the inner side
surface 1c of sprocket 1 as an uppermost surface, and a second
bottom surface 25b depressed from the first bottom surface 25a. An
inner side surface 25c on the retard pressure chamber's side stands
upright from the lowest bottom surface 25b. The depth of first
bottom surface 25a is made, through a riser wall surface rising
from the first bottom surface 25a, slightly greater than the depth
of the first bottom surface 24a of the first lock hole 24. The
depth of the second bottom surface 25b is set, through the riser
wall surface 25c, equal to a sum of the depth of the second bottom
surface 24b and the depth of the third bottom surface 24c.
Accordingly, the total depth of second lock hole 25 from the inner
side surface 1c of sprocket 1 to the deepest bottom 25b is
substantially equal to the total depth of first lock hole 24 from
the inner side surface 1c of sprocket 1 to the deepest bottom 24c,
and the deepest bottom surface 25b of second lock hole 25 is
substantially equal in depth to the deepest bottom surface 24c of
first lock hole 24. A forward end portion 27a of the second lock
pin 27 descends stepwise from the inner side surface 1c of sprocket
1, through the first bottom surface 25a to the lowest second bottom
surface 25b in the advance direction. On each of the bottom
surfaces 25a and 25b, the forward end portion 27a of second lock
pin 27 is prevented from moving in the retard direction by a riser
wall surface on the retard side. Thus, the staircase of the
stepwise bottom surfaces 25a and 25b functions as a one-way clutch
(ratchet).
[0045] The movement of second lock pin 27 in the retard direction
(toward the advance pressure chamber 12) is limited by the abutment
of the forward end portion 27a against the riser wall surface 25c
of the second bottom surface 25b (as shown in FIG. 10).
[0046] The positions of first and second lock holes 24 and 25
relative to each other are set as shown in FIGS. 5.about.10. In the
stages in which the first lock pin 26 abuts on the first, second or
third bottom surface 24a, 24b or 24c of first lock hole 24, the
second lock pin 27 is held still in the state in which the forward
end 27a of second lock pin 27 abuts on the inner side surface 1c of
sprocket 1, as shown in FIGS. 5.about.8.
[0047] Thereafter, as shown in FIGS. 9 and 10, the second lock pin
27 first enters the second lock hole 25 and the forward end portion
27a of second lock pin 27 abuts on the first bottom surface 25a of
second lock hole 25 when the forward end portion 26a of first lock
pin 26 moves on the lowest third bottom surface 24c slightly toward
the advance side in first lock hole 24. When the first lock pin 26
slides on third bottom surface 24c toward the advance side and
abuts against the inner side surface 24d, the forward end portion
27a of second lock pin 27 abuts against the lowest second bottom
surface 25b and abuts again the riser wall surface 25c. The first
and second lock holes 24 and 25 are positioned relative to each
other in this way.
[0048] Thus, as the vane rotor 9 rotates relatively from a
predetermined retard side position to an advance side position, the
first lock pin 26 first descends the stairway of bottom surfaces
24a, 24b and 24c of first lock hole 24, and subsequently the second
lock pin 27 descends the stairway of bottom surfaces 25a and 25b of
second lock hole 25. Therefore, the vane rotor 9 rotates relatively
in the advance direction with receiving limitation of a five-step
ratchet function of limiting rotation in the retard direction, and
finally reaches the intermediate phase position between the most
retard phase angle and the most advance phase angle. Then, vane
rotor 9 is held at the intermediate phase position.
[0049] First lock pin 26 is slidably received in a first pin hole
31a opened axially through the first vane 16a having the greatest
circumferential width, as shown in FIG. 1 and FIG. 5. First lock
pin 26 has a stepped outside circumference. The forward end portion
26a is a portion having the smallest outside diameter. In addition
to forward end portion 26a, the first lock pin 26 has an
intermediate portion 26b having a medium outside diameter,
extending from the forward end portion 26a toward the rear end of
first lock pin 26, and a first pressure receiving portion 26c
shaped like an outward flange forming a greatest diameter portion
on the rear side of intermediate portion 26b. In this example, the
forward end portion 26a, intermediate portion 26b and first
pressure receiving portion 26c are integral parts of the single
integral first lock pin 26.
[0050] The intermediate portion 26b of first lock pin 26 is fit
slidably and liquid-tightly in a sleeve 40 forcibly fit in a
forward portion of the first pin hole 31a. A rear end portion 26d
of first lock pin 26 on the rear side of first pressure receiving
portion 26c is slidable liquid-tightly in the first pin hole 31a.
The forward end portion 26a has a flat end surface which can abut
on each of the bottom surfaces 24a.about.24c snugly and
tightly.
[0051] A first spring 29 is arranged to urge the first lock pin 26
toward the first lock hole 24. First spring 29 is disposed in an
inside bore or recess formed in first lock pin 26, between the
bottom of the inside bore and the inside wall surface of front
cover 13 confronting the first lock hole 24 across first lock pin
26. The first spring 29 serves as an urging member or biasing
member.
[0052] First lock pin 26 is arranged to receive equal fluid
pressures on a front portion and a rear portion. In this example,
the forward end portion 26a and rear end portion 26d are arranged
to receive the same fluid pressure from the advance pressure
chambers 12, respectively, through front and rear fluid holes 45a
and 45b formed in the vane 16a. The fluid pressure from the front
fluid hole 45a is applied to a forward end surface 26f of the
forward end portion 26a and an forward facing annular surface 26g
of the front end of intermediate portion 26b. On the other hand,
the pressure from the rear fluid hole 45b is applied to a rear end
surface 26h of the rear end portion 26d, and the bottom surface 26i
of spring groove. The pressure receiving area on the front side
equaling the sum of the area of the forward end surface 26f of the
forward end portion 26a and the area of the forward facing annular
surface 26g is equal to the pressure receiving area on the rear
side equaling the sum of the area of the rear end surface 26h of
the rear end portion 26d, and the area of the bottom surface 26i of
spring groove. The equal pressure of the advance pressure chambers
12 is applied simultaneously to the equal pressure receiving areas
on the front side and the rear side in the opposite directions (the
forward direction toward the lock hole and the rearward direction
away from the lock hole).
[0053] Moreover, the first pressure receiving portion 26c includes
a forward facing first pressure receiving (annular shoulder)
surface 26e for receiving the fluid pressure of a first cancel
pressure chamber 32 as mentioned later. On the other hand, the
first pressure receiving portion 26c includes a rearward facing
atmospheric pressure receiving (annular shoulder) surface opening
to the atmosphere through a hole 43 (air passage) formed in vane
16a and front cover 13.
[0054] Second lock pin 27 is slidably received in a second pin hole
31b opened axially through the second vane 16b having the medium
circumferential width. Second lock pin 27 has a stepped outside
circumference like the first lock pin 26. The forward end portion
27a is a portion having the smallest outside diameter. In addition
to forward end portion 27a, the second lock pin 27 has an
intermediate portion 27b having a medium outside diameter,
extending from the forward end portion 27a toward the rear end of
second lock pin 27, and a second pressure receiving portion 27c
shaped like an outward flange forming a greatest diameter portion
on the rear side of intermediate portion 27b. In this example, the
forward end portion 27a, intermediate portion 27b and second
pressure receiving portion 27c are integral parts of the single
integral second lock pin 27.
[0055] The intermediate portion 27b of second lock pin 27 is fit
slidably and liquid-tightly in a sleeve 41 forcibly fit in a front
potion of the second pin hole 31b. A rear end portion 27d of second
lock pin 27 on the rear side of second pressure receiving portion
27c is slidable liquid-tightly in the second pin hole 31b. The
forward end portion 27a has a flat end surface which can abut on
each of the bottom surfaces 25a and 25b snugly and tightly.
[0056] A second spring 30 is arranged to urge the second lock pin
27 toward the second lock hole 25. Second spring 30 is disposed in
an inside bore or recess formed in second lock pin 27, between the
bottom of the inside bore and the inside wall surface of front
cover 13 confronting the second lock hole 25 across second lock pin
27. Second spring 30 serves as the urging member or biasing
member.
[0057] Second lock pin 27 is arranged to receive equal fluid
pressures on a front portion and a rear portion. In this example,
the forward end portion 27a and rear end portion 27d are arranged
to receive the same fluid pressure from the advance pressure
chambers 12, respectively, through front and rear fluid holes 46a
and 46b formed in the vane 16b. The fluid pressure from the front
fluid hole 46a is applied to a forward end surface 27f of the
forward end portion 27a and an forward facing annular surface 27g
of the front end of intermediate portion 27b. On the other hand,
the pressure from the rear fluid hole 46b is applied to a rear end
surface 27h of the rear end portion 27d, and the bottom surface 27i
of spring groove. The pressure receiving area on the front side
equaling the sum of the area of the forward end surface 27f of the
forward end portion 27a and the area of the forward facing annular
surface 27g is equal to the pressure receiving area on the rear
side equaling the sum of the area of the rear end surface 27h of
the rear end portion 27d, and the area of the bottom surface 27i of
spring groove. The equal pressure of the advance pressure chambers
12 is applied simultaneously to the equal pressure receiving areas
on the front side and the rear side.
[0058] Moreover, the second pressure receiving portion 27c includes
a forward facing second pressure receiving (annular) surface 27e
for receiving the fluid pressure of a second cancel pressure
chamber 33 as mentioned later. On the other hand, the second
pressure receiving portion 27c includes a rearward facing
atmospheric pressure receiving (annular) surface opening to the
atmosphere through a hole 44 (air passage) formed in vane 16b and
front cover 13.
[0059] As shown in FIGS. 1 and 5, the second hydraulic circuit 28
includes a supply/drain passage 34 for supplying the fluid pressure
to the first cancel pressure chamber 32 formed between the larger
diameter portion of first pin hole 31a and the first pressure
receiving portion 26c of first lock pin 26, and the second cancel
pressure chamber 33 formed between the larger diameter portion of
second pin hole 31b and the second pressure receiving portion 27b
of second lock pin 27, through a supply branch passage 35a
branching from the discharge passage 20a of the oil pump 20, and
for draining the operating fluid from the first cancel pressure
chamber 32 and the second cancel pressure chamber 33 through a
drain branch passage 35b branching from the drain passage 22.
Hydraulic circuit further includes the before-mentioned second
electromagnetic selector valve 36 for connecting the supply/drain
passage 34 selectively with the supply branch passage 35a and the
drain branch passage 35b in accordance with the engine operating
condition(s).
[0060] The first cancel pressure chamber 32 receives the fluid
pressure, applies the received pressure to the first pressure
receiving surface 26e, and thereby withdraws the first lock pin 26
from the first lock hole 24 against the spring force of the first
spring 29 to disengage the first lock pin 26 from first lock hole
24. Similarly, the second cancel pressure chamber 33 receives the
fluid pressure, applies the received pressure to the second
pressure receiving surface 27e, and thereby withdraws the second
lock pin 27 from the second lock hole 25 against the spring force
of the second spring 30 to disengage the second lock pin 27 from
second lock hole 25.
[0061] The supply/drain passage 34 extends from a first end
connected with a port of second electromagnetic valve 36, to a
second end connected with supply/drain branch passages 34a formed
in the passage forming member 37. Each of supply/drain branch
passages 34a first extends axially, and is bent to a radial
direction. The supply/drain branch passages 34a are connected,
respectively, through the first and second fluid passage holes 38a
and 38b, with the first and second cancel pressure chambers 32 and
33.
[0062] The passage forming member 37 includes annular grooves
formed in the outside circumference surface at axial positions and
arranged to receive (three) annular seal members 39, respectively,
to sealingly separate the open ends of the passages 18a and 19a and
the supply/drain passages 34a opened in the support hole 15d.
[0063] The second electromagnetic selector valve 36 of this example
is a 4-port, 3-position proportional type valve configured to move
a spool (not shown) axially back and forth against a valve spring
by an on-off control current delivered from the electronic
controller. Thus, second electromagnetic valve 36 connects the
supply/drain passage 34, selectively with the passage 35a or 35b,
and seals off the operating fluid in the cancel pressure chambers
32 and 33, by shutting the supply/drain passage 34 off from the
passages 35a and 35b.
[0064] [OPERATIONS] The thus-constructed valve timing control
apparatus or system is operated as follows:
[0065] [OPERATION CONTROL AFTER SHORT STOP] When the engine is
stopped by turn-off of the ignition switch after a normal vehicle
driving operation, the oil pump 20 is stopped too. Accordingly, the
supply of the operating oil to the pressure chambers 11 or 12 is
stopped, and the vane rotor 9 is allowed to rotate freely in the
forward and backward directions. When the cam torque timing in the
alternating torque at the time of the engine stoppage is a negative
torque, the vane rotor 9 rotates in the advance direction and the
system becomes unable to hold the vane rotor 9 at the most retard
phase, so that an engine stop control is required to achieve a
positive torque at the time of engine stoppage.
[0066] In this case, the electronic controller supplies electricity
to first electromagnetic selector valve 21, thereby holds the spool
at the intermediate neutral position, and shuts the passages 18 and
19 from the passages 20a and 22.
[0067] In the stop state in which the drive of oil pump 20 is
stopped, the operating fluid in discharge passage 20a may return
from oil pump 20 to oil pan 23 because of the lift (or head) of the
pump, and moreover the operating fluid in the pressure chambers 11
and 12 may flow downwards. If the operating oil is removed from
pressure chambers 11 and 12, the vane rotor 9 at the most retard
side may flap due to the alternating torque at the time of an
engine start, and cause flapping noises by collision with the
partition walls 10. Therefore, the control system according to this
embodiment seals the operating fluid in the pressure chambers 11
and 12 by shutting off the fluid passages 18 and 19, and thereby
prevent flapping of vane rotor 9.
[0068] If the engine is restarted in the state in which the warm up
state is maintained, after the elapse of a short time within 15
minutes, for example, the effective compression ratio is lowered
because, at this instant, the vane rotor 9 is held at the
rotational phase position on the most retard side shown in FIG. 3,
and the closing timing of the intake valve is on the retard side of
the piston bottom dead center. Accordingly, the system can reduce
the pumping loss, restrain undesired vibrations and improve the
engine starting performance.
[0069] The above-mention operation control after a short time
stoppage is performed, for example, in the case of idling stop of
stopping the operation of the engine during a driving operation of
the vehicle automatically irrespectively of turn on/off of the
ignition switch when the time from a stop to a restart is short.
The system can lower the effective compression ratio and improve
the engine starting performance in the same manner.
[0070] [OPERATION CONTROL AFTER LONG STOP] When the ignition key is
turned to start cranking after the elapse of a long time longer
than 15 minutes, for example, in the state in which the engine is
cooled, then the electronic controller shifts the spool in first
electromagnetic selector valve 21 axially to the valve position to
connect the discharge passage 20a with one of the retard pressure
passage 18 and advance pressure passage 19, and to connect the
drain passage 22 with the other of the retard and advance pressure
passages 18 and 19.
[0071] Simultaneously, the electronic controller energizes the
second electromagnetic selector valve 36 to connect the
supply/drain passage 34 with the drain branch passage 35b.
Therefore, the operating fluid is drained from the first and second
cancel pressure chambers 32 and 33, and the first and second lock
pins 26 and 27 are urged forwards (toward the respective lock holes
24 and 25) by the springs 29 and 30, respectively.
[0072] In this early stage of the cranking operation, the discharge
pressure of oil pump 20 is still low, the oil pressure supplied
through the one of the retard and advance pressure passage 18 and
19 is still low.
[0073] Therefore, the vane rotor or vane member 9 rotates slightly
to the advance side by the alternating torque acting on camshaft 2,
specifically by the negative torque, and hence the forward end
portion 26a of first lock pin 26 abuts on the first bottom surface
24a of first lock hole 24, as shown in FIGS. 5 and 6. In this
state, the positive toque acts on the lock pin 26 to try rotating
the lock pin 26 in the retard side. However, the forward end
portion 26a abuts against the riser wall surface rising from the
first bottom surface 24a, and this abutment prevents the rotation
toward the retard side.
[0074] Thereafter, the first lock pin 26 descends stepwise through
second bottom surface 24b to third bottom surface 24c and slides on
the third bottom surface 24c to the advance side as shown in FIGS.
7.about.9 in accordance with rotation of vane rotor 9 to the
advance side due to the negative torque, while the first lock pin
26 is receiving the ratchet function. Moreover, as shown in FIGS. 9
and 10, the forward end portion 27a of second lock pin 27 descends
stepwise through first bottom surface 25a to second bottom surface
25b of second lock hole 25 while receiving the ratchet function,
and finally the second lock pin 27 is held at the position on
second bottom surface 25b.
[0075] In this state, as shown in FIG. 10, the first lock pin 26 is
held at the position by the abutment of the forward end portion 26a
against the inner side wall surface 24d rising from third bottom
surface 24c on the advance side (on the retard chamber's side), and
the second lock pin 27 is held at the position by the abutment of
forward end portion 27a against the inner side wall surface 25c
rising from second bottom surface 25b on the advance chamber's
side. Therefore, the first and second lock pins 26 and 27 are held
at the respective positions stably.
[0076] With this operation of the lock pins 26 and 27, the vane
rotor 9 is held at the intermediate phase position as shown in FIG.
2, and the system controls the intake valve closing timing at a
position on the advance side before the piston bottom dead center.
Therefore, the system can improve the combustion by increasing the
engine compression ratio, and improve the startability in a cold
state.
[0077] When the normal engine operation is started after the
warm-up of the engine, and the engine speed enters a high speed
range, for example, then the first electromagnetic selector valve
21 connects the discharge passage 20a with advance pressure passage
19 and connects the drain passage 22 with retard pressure passage
18.
[0078] Therefore, the pressure in each retard pressure chamber 11
becomes lower and the pressure in each advance pressure chamber 12
becomes higher. As a result, the vane rotor 9 is rotated to the
most advance side. Thus, the system can advance the intake valve
opening timing, increase the overlap with the exhaust valve, and
increases the engine output by increasing the intake air
quantity.
[0079] In this state, as mentioned before, the second
electromagnetic selector valve 36 is held in the position to supply
the fluid pressure to each of the pressure chambers 32 and 33 by
connecting the supply/drain passage 34 with supply passage 35a and
to shut off the drain passage 35b. Therefore, the vane rotor 9 is
allowed to rotate freely.
[0080] In this way, the control system according to this embodiment
is arranged to vary the engine compression ratio at the time of a
restart, in accordance with the time length of the engine stop
period, that is, the temperature of the engine. Therefore, the
system can improve the engine startability by reducing the torque
load at the time of a start, reduce vibrations and improve the
exhaust emission performance.
[0081] Furthermore, the position holding device or means (26, 27,
24, 25, 28) can hold the vane rotor 9 reliably at the intermediate
phase position. The lock guide groove of each lock hole (24, 25) is
arranged to have the stepped bottom (24a.about.24c, 25a.about.25b)
to guide the lock pin only in the direction toward the lock hole
(24, 25), so that the lock pin is guided reliably and stably.
[0082] The operating fluid pressure for the cancel pressure
chambers 32 and 33 is prepared by a hydraulic circuit separately
from the pressure for the retard and advance chambers 11 and 12.
Therefore, the system can supply the operating fluid pressure
responsively to the cancel chambers 32 and 33, as compared to the
arrangement using the fluid pressure for the chambers 11 and 12 to
the chambers 32 and 33. As a result, the system can move each lock
pin 26 or 27 rearwards quickly, and eliminate the need for seal
mechanism between the chambers 11 and 12 and the chambers 32 and
33.
[0083] Instead of providing air passages to both axial ends of a
lock pin as in the earlier technology, each lock pin (26, 27)
according to the embodiment is balanced in the axial direction by
the application of the oil pressure on both ends of the lock pin to
ensure smooth movement of the lock pin. Therefore, the system can
move the lock pin quickly in the axial direction by the spring (29,
30) and the cancel pressure in the cancel pressure chamber (32,
33).
[0084] Thus, the system according to the embodiment can achieve the
same effect of air passages by applying the equal oil pressures to
the forward end portion and riverward end portion of the lock
member without the need for forming an air passage in the lock hole
forming member (1a, 1b). Therefore, it is possible to reduce side
clearances between both axial end surfaces of the widest vane 16a
and the confronting surfaces of front cover 13 and sprocket 1.
[0085] Therefore, it is possible to reduce the circumferential
width of the widest vane 16a as compared to the earlier technology.
Consequently, it is possible to increase the rotational angular
range of vane rotor 9 relative to housing 7 by increasing the
angular range of vane 16a between the circumferentially confronting
side surfaces 10b and 10c of the partition walls 10.
[0086] The air holes 43 and 44 for leading the upper side surfaces
of first and second pressure receiving portions 26c and 27c
opposite to the pressure receiving surfaces 26e and 27e, to the
outside or the atmosphere are formed in the vanes 16a and 16b and
the front cover 13. There are no connections with the advance
pressure chambers 12, so that the operating fluid does not leak in
this portion.
[0087] The arrangement of supplying the advance pressure of advance
chambers 12 to both of the forward and rearward end portions of the
lock pin (26, 27) is effective for stabilizing the behavior of the
lock pin. At the time of engine start, air may be involved in the
operating oil supplied to retard chambers 11. Therefore, if this
operating oil is supplied to both ends of each lock pin 26 or 27,
the air involved in the operating oil might make unstable the
behavior of the lock pin, resulting in generation of undesired
noises. On the other hand, the operating oil supplied to advance
chambers 12 during steady state operation after engine start is
almost free from air involvement. Therefore, the arrangement of
supplying the advance pressure of advance chambers 12 to both ends
of the lock pin can make stable the behavior of the lock pin (26,
27) and prevent generation of undesired noises.
[0088] The riser wall surface 25c between first and second bottom
surfaces 25a and 25b of the second lock guide groove is made high.
This riser wall structure can increase the strength, and improve
the durability of enduring repetitive collision of the second lock
pin 27 against the riser wall surface 25c. When, on the other hand,
first lock pin 26 is engaged with first lock hole 24, the forward
end portion 26a abuts against the inner side surface 24d rising
from the deepest bottom surface 24c and having a greater surface
area. This structure further improves the durability.
[0089] Each of the first and second lock guide grooves is
cocoon-shaped. Therefore, each of first and second lock pins 26 and
27 can move smoothly in the guide groove with rotation of vane
rotor 9.
[0090] The illustrated example of the embodiment employs, as a
parameter, the elapsed time from an engine stop to a restart. By
using the engine temperature sensed by the engine temperature
sensor directly as the parameter, instead of using the elapsed
time, it is possible to a practical control system arranged to
control the valve timing in accordance with the engine temperature,
for example by examining whether the engine temperature is lower
than or equal to a predetermined temperature or higher than the
predetermined temperature.
[0091] In the illustrated example, the position holding device is
constructed by the first lock section including first lock pin 26
and first, second and third bottom surfaces 24a.about.24c and the
second lock section including second lock pin 27 and first and
second bottom surfaces 25a and 25b. Therefore, it is possible to
reduce the wall thickness of the sprocket 1 in which the lock holes
24 and 25 are formed. The arrangement using a single lock pin and a
single staircase of steps 24a, 24b, 24c, 25a and 25b requires a
thick wall for the sprocket 1 to ensure the height of this
staircase. By contrast, the arrangement of the illustrated example
makes it possible to reduce the wall thickness of sprocket 1, to
reduce the axial dimension of the valve timing control apparatus
and to improve the flexibility of the layout.
[0092] The lock member (26, 27) is in the form of a cylindrical
lock pin and the pressure receiving portion (26c, 27c) is in the
form of an outward flange. Therefore, the lock member can be
fabricated easily and inexpensively.
[0093] The present invention is not limited to the illustrated
embodiment. The valve timing control apparatus according to the
present invention can be applied not only to the intake side, but
also to the exhaust side.
[0094] According to one of possible interpretations of the
illustrated embodiment, a valve timing control apparatus includes a
basic structure which comprises: a driving rotary member adapted to
receive a rotational force from a crankshaft; a vane rotor which is
adapted to be connected with a camshaft, which is arranged to
rotate relative to the driving rotary member, and which includes at
least one vane defining a retard pressure chamber and an advance
pressure chamber in the inside (cavity) of the driving rotary
member; a lock member received in the vane and arranged to slide
axially; a lock receiving portion such as a lock hole (formed in
the driving rotary member (lock hole forming member 1a, 1b)) to
receive a forward end of the lock member when the vane is rotated
relatively to a predetermined angular position; and a biasing
member to urge the lock member toward the lock receiving portion.
The lock member includes forward and rearward end portions arranged
to receive equal fluid pressures, respectively, in rearward and
forward directions (to balance the lock member in an axial
direction). In addition to the basic structure, the valve timing
control apparatus may further comprise any one or more of following
features (f1).about.(f19).
[0095] (f1)) The lock member (26, 27) may further include a
pressure receiving portion (26c, 27c) (in the form of an outward
flange, in the illustrated example) including a first surface (26e,
27e) (lower surface) to which an operating fluid pressure (cancel
pressure) is selectively applied, and a second surface (upper
surface) which is opened, through an air passage (43, 44) formed in
the vane rotor, to the atmosphere (to an outside to receive an
atmospheric pressure). (f2) The valve timing control apparatus
further comprises a canceling section to release the lock member
from the lock receiving portion (lock hole) selectively.
[0096] (f3) The lock hole is elongated circumferentially so as to
form a lock guide groove elongated in one of an advance direction
and a retard direction (or circumferentially around the center axis
of the vane rotor 9) and arranged to allow the vane rotor to rotate
relative to the driving rotary member in a state in which the
forward end of the lock member is received in the lock guide
groove. (f4) The lock member is a lock pin including a
(cylindrical) shank and an (circular) outward flange (26c, 27c)
serving as the pressure receiving portion (formed between the
forward end portion (26a, 27a) and the rearward end portion (26d,
27d)). In this case, the lock member can make easier the production
process and prevent an increase of the manufacturing cost.
[0097] (f5) The driving rotary member includes a cylindrical
housing including at least one shoe or partition wall projecting
radially inwards, and a cover member closing an open end of the
housing and including a through hole formed on a radial inner side
of an outside circumference of the vane rotor, the vane is formed
with the air passage extending to the though hole of the cover
member and thereby opening the second surface of the pressure
receiving portion to the atmosphere. (f6) The valve timing control
apparatus further comprises a first hydraulic circuit (4, 21) to
regulate the fluid pressure in the retard pressure chamber and the
fluid pressure in the advance pressure chamber, and a second
hydraulic circuit (28, 36) to supply the operating fluid pressure
different from the fluid pressure in the retard pressure chamber
and the fluid pressure in the advance pressure chamber. This
feature can improve the response speed for supplying the operating
fluid pressure to the cancel pressure chamber for the pressure
receiving portion, and eliminate the need for seals in various
portions.
[0098] (f7) The first hydraulic circuit includes a first control
valve to regulate the fluid pressure in the retard pressure chamber
and the fluid pressure in the advance pressure chamber, and the
second hydraulic circuit includes a second control valve to
regulate the operating fluid pressure applied to the first surface
of the pressure receiving portion of the lock member. (f8) The
second control valve is a selector valve having at least a first
valve position to increase the operating fluid pressure (by
connecting a cancel pressure chamber (32, 33) with a pump outlet
passage 20a) and a second valve position to decrease the operating
fluid pressure (by connecting the cancel pressure chamber (32, 33)
with a drain passage 22).
[0099] (f9) The first fluid pressure received by the forward end
portion (26a, 27a) and the rearward end portion (26b. 27b) of the
lock member (26, 27) is the fluid pressure in the advance pressure
chamber. In this case, the advance fluid pressure is applied
equally to both of the forward end portion and the rearward end
portion, so that the forward force and rearward force produced by
the fluid pressures are balanced and the lock member can move
quickly by the operating fluid pressure applied to the pressure
receiving portion (and a biasing member). (f10) The lock guide
groove includes a stepped bottom descending stepwise toward the
lock hole (or toward the deepest bottom).
[0100] (f11) In addition to the vane which is a first vane, the
lock member which is a first lock member received in the first
vane, the lock hole which is a first lock hole, the biasing member
which is a first biasing member, the vane rotor further includes a
second vane defining a retard pressure chamber and an advance
pressure chamber in the inside of the driving rotary member, and
the valve timing control apparatus further comprises a second lock
member received in the second vane and arranged to slide forwards
and rearwards in the axial direction (of the vane rotor 9), a
second lock hole (formed in the driving rotary member (lock hole
forming member 1a, 1b)) to receive a forward end of the second lock
member when the second vane is at a predetermined angular position,
and a second biasing member to urge the second lock member toward
the second lock hole. The second lock member includes forward and
rearward end portions arranged to receive equal fluid pressures,
respectively, in rearward and forward directions (to balance the
lock member in the axial direction). The second lock member (26,
27) may further include a pressure receiving portion (26c, 27c)
(outward flange) including a first surface (26e, 27e) (lower
surface) to which an operating fluid pressure (cancel pressure) is
selectively applied, and a second surface (upper surface) which is
opened, through an air passage (43, 44) formed in the vane rotor,
to the atmosphere (to an outside to receive an atmospheric
pressure).
[0101] (f12) Each of the first and second lock holes is elongated
circumferentially so as to form a (first or second) lock guide
groove elongated in one of an advance direction and a retard
direction (or circumferentially around the center axis of the vane
rotor 9) and arranged to allow the vane rotor to rotate relative to
the driving rotary member in a state in which the forward end of
the (first or second) lock member is received in the (first or
second) lock guide groove. (f13) The first lock hole is arranged to
allow the vane rotor to rotate relative to the driving rotary
member in a state in which the forward end of the first lock member
is received in the first lock guide groove, and the second lock
hole is arranged to allow the vane rotor to rotate relative to the
driving rotary member in a state in which the forward end of the
second lock member is received in the second lock guide groove.
[0102] (f14) The first lock member and the first lock hole are
arranged to allow rotation of the vane rotor relative to the
driving rotary member within a predetermined angular range in a
state in which the first lock member is engaged with the first lock
hole; and the second lock member and the second lock hole are
arranged to lock the vane rotor to prevent rotation of the vane
rotor relative to the driving rotary member when the second lock
member is engaged with the second lock hole (or the second lock
member abuts on a lowest bottom (25b) of the second lock hole) in
the state in which the first lock member is engaged with the first
lock hole. (f15) The second lock guide groove (or the second lock
hole) includes a stepped bottom descending stepwise toward a
deepest bottom. (f16) The first lock guide groove (or the first
lock hole) includes a stepped bottom descending stepwise to a
deepest bottom, and the first and second lock holes are so arranged
that the second lock member descends the stepped bottom of the
second lock guide groove and engages with the deepest bottom of the
second lock hole after the first lock member descends the stepped
bottom of the first lock guide groove and engages with the deepest
bottom of the first lock hole. (f17) The number of steps of the
stepped bottom of the first lock guide groove is greater than the
number of steps of the stepped bottom of the second lock guide
groove. (f18) The height of a riser wall surface rising from a
lowest bottom surface (25b) of the second guide groove is greater
than the height of a riser wall surface rising from a lowest bottom
surface (24c) of the first lock guide groove. (f19) At least one of
the first lock hole, the first lock guide groove, the second lock
hole and the second lock guide groove is elongated
circumferentially, or shaped like a cocoon.
[0103] This application is based on a prior Japanese Patent
Application No. 2010-243845 filed on Oct. 29, 2010. The entire
contents of this Japanese Patent Application are hereby
incorporated by reference.
[0104] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above. Modifications and
variations of the embodiments described above will occur to those
skilled in the art in light of the above teachings. The scope of
the invention is defined with reference to the following
claims.
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