U.S. patent application number 09/947437 was filed with the patent office on 2002-09-05 for valve timing control device.
This patent application is currently assigned to MITSUBISHI DENKI KABUSHIKI KAISHA. Invention is credited to Hase, Hirofumi.
Application Number | 20020121253 09/947437 |
Document ID | / |
Family ID | 18920151 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020121253 |
Kind Code |
A1 |
Hase, Hirofumi |
September 5, 2002 |
VALVE TIMING CONTROL DEVICE
Abstract
A valve timing control device includes a lock member and a push
member. The lock member locks a rotor in relation to a case at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position. At
all times, the push member pushes the lock member in a direction-of
fitting the lock member in the fitting hole arranged at any one
hand of the rotor or the case. A release hydraulic pressure for
releasing the fitting state of the lock member in the fitting hole
against the push force of the push member is set to be higher than
a lock hydraulic pressure for allowing the fitting state of the
lock member in the fitting hole.
Inventors: |
Hase, Hirofumi; (Tokyo,
JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Assignee: |
MITSUBISHI DENKI KABUSHIKI
KAISHA
|
Family ID: |
18920151 |
Appl. No.: |
09/947437 |
Filed: |
September 7, 2001 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 2001/3444 20130101;
F01L 1/3442 20130101; F01L 2001/34426 20130101; F01L 2001/34453
20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2001 |
JP |
2001-60770 |
Claims
What is claimed is:
1. A valve timing control device for modifying an opening and
closing timing of an intake valve or an exhaust valve making
contact with cams fixed on an intake camshaft or an exhaust
camshaft of an internal-combustion engine, comprising: a housing
rotating in synchronization with a driving force transmitting means
transmitting a driving force from a crankshaft of the
internal-combustion engine to an intake camshaft and an exhaust
camshaft; a case fixed on the housing and having a plurality of
shoes which are projected inwardly to form a plurality of hydraulic
pressure chambers; a rotor fixed on an end of the intake camshaft
or the exhaust camshaft and having a plurality of vanes to divide
the hydraulic pressure chambers into advance side hydraulic
pressure chambers and retardation side hydraulic pressure chambers;
a fitting hole arranged on one of the rotor or the case; a lock
member arranged on the other of the rotor or the case and fit in
the fitting hole to lock the rotor in relation to the case at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position; and
a push member normally biasing the lock member in a direction
fitting the lock member in the fitting hole, wherein a release
hydraulic pressure for releasing the fitting state of the lock
member in the fitting hole against the push force of the push
member is set to be higher than a lock hydraulic pressure for
allowing the fitting state of the lock member in the fitting
hole.
2. A valve timing control device according to claim 1, wherein the
lock hydraulic pressure is set to be nearly equal to or lower than
a hydraulic pressure generating a torque generated in the device,
the torque being equal to a cam-torque during
internal-combustion.
3. A valve timing control device according to claim 1, further
comprising first and second communication passages, wherein the
first communication passage communicates a backward pressure
chamber, in which the push member is arranged, to the advance side
hydraulic pressure chamber or the retardation side hydraulic
pressure chamber as an operational hydraulic pressure chamber of
operating the device, and wherein the second communication passage
communicates the backward pressure chamber to outside the
device.
4. A valve timing control device according to claim 3, wherein the
first communication passage is formed at an end of the case in an
axial direction of the case.
5. A valve timing control device according to claim 3, wherein the
first communication passage is a branch of a hydraulic pressure
supply passage of communicating the operational hydraulic pressure
chamber to a release hydraulic pressure chamber.
6. A valve timing control device according to claim 3, wherein the
cross sectional area of the second communication passage is set to
be larger than that the cross sectional area allowing discharge of
foreign materials.
7. A valve timing control device according to claim 3, wherein the
driving force transmitting means is a chain, wherein the lock
member moves in a radial direction of the device, and wherein a
stopper is arranged at the outermost section_of the device, the
stopper of holding the push member in the backward pressure chamber
and integrated with the second communication passage.
8. A valve timing control device according to claim 3, wherein the
cross sectional area of the first communication passage is set to
be larger than that of the second communication passage.
9. A valve timing control device according to claim 8, wherein the
cross sectional area of the second communication passage is set to
be larger than that the cross sectional area allowing discharge of
foreign materials.
10. A valve timing control device according to claim 8, wherein the
driving force transmitting means is a chain, wherein the lock
member moves in a radial direction of the device, and wherein a
stopper is arranged at the outermost of the device, the stopper of
holding the push member in the backward pressure chamber and
integrated with the second communication passage.
11. A valve timing control device for modifying opening and closing
timing of an intake valve or an exhaust valve making contact with
cams fixed on an intake camshaft or an exhaust camshaft of an
internal-combustion engine, comprising: a housing rotating in
synchronization with a driving force transmitting means
transmitting a driving force from a crankshaft of the
internal-combustion engine to an intake camshaft and an exhaust
camshaft; a case fixed on the housing and having a plurality of
shoes which are projected inwardly to form a plurality of hydraulic
pressure chambers; a rotor fixed on an end of the intake camshaft
or the exhaust camshaft and having a plurality of vanes to divide
the hydraulic pressure chambers into advance side hydraulic
pressure chambers and retardation side hydraulic pressure chambers;
a fitting hole arranged on one of the rotor or the case; a lock
member arranged on the other of the rotor or the case and fit in
the fitting hole to lock the rotor in relation to the case at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position, the
lock member including a head section fitting the fitting hole and a
flange section having a diameter larger than the head section; a
push member pushing the lock member in a direction fitting the lock
member in the fitting hole at all times; and a seal member of
stopping the flow of operational oil between the advance side
hydraulic pressure chamber and the retardation side hydraulic
pressure chamber, wherein the seal member may be arranged so as to
apply a hydraulic pressure from the retardation side hydraulic
pressure chamber on the flange section of the lock member, and to
apply a hydraulic pressure from the advance side hydraulic pressure
chamber on the head section and the flange section of the lock
member.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a valve timing control
device for modifying the opening and closing timing of an intake
valve or an exhaust valve making contact with cams fixed on an
intake camshaft or an exhaust camshaft of an internal-combustion
engine (hereafter, referred as an engine).
[0003] 2. Description of the Prior Art
[0004] Various types of solutions have been proposed for
conventional valve timing control devices. The majority of the
proposition includes a housing of rotating in synchronization with
a driving force transmitting means transmitting a driving force
from a crankshaft of the engine to an intake camshaft and an
exhaust camshaft, a case fixed on the housing and having a
plurality of shoes which are projected inwardly to form a plurality
of hydraulic pressure chambers, and a rotor fixed on an end of the
intake camshaft or the exhaust camshaft and having a plurality of
vanes to divide the hydraulic pressure chambers into advance side
hydraulic pressure chambers and retardation side hydraulic pressure
chambers, for example. A hydraulic pressure is provided to and
discharged from the advance side hydraulic pressure chamber and the
retardation side hydraulic pressure chamber due to an oil control
valve (hereafter, referred as OCV) and the rotor rotates relatively
at a required angle with respect to the case. In this way, it is
possible to variably control the phase of the intake camshaft or
the exhaust camshaft and to modify the opening and closing timing
of the intake valve and the exhaust valve as appropriate according
to any operation conditions.
[0005] Most of the conventional valve timing control devices have a
lock mechanism for locking the rotor, which is fixed on an end of
the camshaft, in relation to the case rotating in synchronism with
the crankshaft at a reference position on starting the engine. The
lock mechanism includes a fitting hole arranged at any one hand of
the rotor or the case, a lock member arranged at the other hand and
fit in the fitting hole to lock the rotor in relation to the case
at any one of the maximum advanced side and the maximum retarded
side positions, and a push member of pushing the lock member in a
direction of fitting the lock member in the fitting hole at all
times. With the conventional construction, the initial operation
direction of the rotor was limited to only retardation direction or
only advance direction.
[0006] However, if it is possible to operate the rotor of the valve
timing control device from the reference position (hereafter,
referred also as a lock position) on starting the engine toward the
advance side and the retardation side without the limitation of
only one direction such as the retardation direction or the advance
direction, it is a foregone conclusion that such a device will have
improved versatility.
[0007] An intermediate position lock type of the valve timing
control device is therefore proposed. With the device, the lock
position is set to an approximately intermediate position apart
from both of the maximum advanced side position and the maximum
retarded side position. It is possible to operate the rotor from
the lock position to the advance side and the retardation side.
[0008] However, the intermediate position lock type of the valve
timing control device has typical problems derived from the typical
construction, which is different from the conventional valve timing
control devices such as the maximum advanced side position lock
type or the maximum retarded side position lock type.
[0009] First, with the maximum advanced side position lock type or
the maximum retarded side position lock type of the valve timing
control device, when the lock member is able to fit in the fitting
hole, a hydraulic pressure is applied on the rotor to press the
rotor toward the lock position. Here, contact of one of the vanes
of the rotor is ensured with one of shoes of the case at the
maximum advanced side position or the maximum retarded side
position. Therefore, since no force is applied on the lock member,
the lock member does not catch on with the other parts. Further,
with the conventional valve timing control device, even if a
hydraulic pressure in the device is reduced when operation oil is
consumed by operation of the device or when a hydraulic pressure
passage in the OCV side becomes narrow in a hydraulic pressure
supply mode of the OCV side (hereafter, referred as OCV
intermediate retained mode) for keeping the rotor with respect to
the case at the intermediate position on normal operation, the lock
member does not fit or catch on or engage between the maximum
advanced side position and the maximum retarded side position
because the fitting hole is arranged at the maximum advanced side
position or the maximum retarded side position. Since the lock
member does not catch on or engage with the fitting hole, the valve
timing control device is not disabled during normal operation or in
an intermediate retained state.
[0010] On the other hand, with the intermediate position lock type
of valve timing control device, the fitting hole is arranged at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position.
First, when the rotor is held with respect to the case at the about
intermediate position due to the hydraulic pressure supplied from
the OCV, the hydraulic pressure passage in the OCV side narrows
when in the OCV intermediate retained mode. A hydraulic pressure in
the advance side hydraulic pressure chamber or the retardation side
hydraulic pressure chamber and a release hydraulic pressure chamber
is therefore substantially reduced to one half of the hydraulic
pressure in the OCV and the release hydraulic pressure is not
sufficient. As a result, the lock member sometimes catches on in or
fitted in the fitting hole. In this case, there is a problem that
the lock member and the fitting hole undergo wear which reduces
their durability, and that the valve timing control device becomes
incapable of operation from the intermediate retained state.
[0011] Second, when the lock member is operated beyond the fitting
hole as the intermediate lock position and the release hydraulic
pressure is reduced associated with the reduction of the hydraulic
pressure in the advance side hydraulic pressure chamber or the
retardation side hydraulic pressure chamber which is generated by
consuming the operating oil used for the operation of the device,
the lock member pops up due to the pushing force of the pushing
member under operation condition and catches on in the fitting hole
to prevent operation.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the present invention to
provide a valve timing control device being a type of locking a
rotor at a intermediate position defined between the maximum
advanced side and the maximum retarded side with respect to a case,
which can reliably control the operation of a lock member to
resolve the problems described above.
[0013] In order to achieve the object of the present invention, a
valve timing control device for modifying the opening and closing
timing of an intake valve or an exhaust valve making contact with
cams fixed on an intake camshaft or an exhaust camshaft of an
internal-combustion engine, comprises a housing rotating in
synchronization with a driving force transmitting means
transmitting a driving force from a crankshaft of the
internal-combustion engine to an intake camshaft and an exhaust
camshaft; a case fixed on the housing and having a plurality of
shoes which are projected inwardly to form a plurality of hydraulic
pressure chambers; a rotor fixed on an end of the intake camshaft
or the exhaust camshaft and having a plurality of vanes to divide
the hydraulic pressure chambers into advance side hydraulic
pressure chambers and retardation side hydraulic pressure chambers;
a fitting hole arranged on one of the rotor or the case; a lock
member arranged on the other of the rotor or the case and fit in
the fitting hole to lock the rotor in relation to the case at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position; and
a push member normally biasing the lock member in a direction of
fitting the lock member in the fitting hole, wherein a release
hydraulic pressure for releasing the fitting state of the lock
member in the fitting hole against the push force of the push
member is set to be higher than a lock hydraulic pressure for
allowing the fitting state of the lock member in the fitting hole.
In this way, a load of the pushing member corresponding to the lock
hydraulic pressure can be previously set to a low level. It can
therefore reliably prevent an operational failure of the device
even if a hydraulic pressure in the device is reduced by the OCV
intermediate retained mode or even if the operation oil is consumed
by operation of the device. The operational failure of the device
generates when the lock member pops up from the fitting hole due to
the pushing force of the pushing member to catch on or engage in
the fitting hole.
[0014] The lock hydraulic pressure may be set to be nearly equal to
or lower than a hydraulic pressure of generating a torque generated
in the device, the torque being equal to a cam-torque during
internal-combustion. In this way, even under a minimum hydraulic
pressure condition such as high temperature oil or idle rotation
for example, even in the intermediate retained state, it can
obviate the inconvenience of fitting the lock member in the fitting
hole or getting trapped therein. As a result, the operation of the
lock member can be reliably controlled.
[0015] The present invention may further comprise first and second
communication passages, wherein the first communication passage
communicates a backward pressure chamber, in which the push member
is arranged, to the advance side hydraulic pressure chamber or the
retardation side hydraulic pressure chamber as an operational
hydraulic pressure chamber of operating the device, and wherein the
second communication passage communicates the backward pressure
chamber to outside the device. In this way, since a backward
pressure can be applied to the lock member in a releasing
operation, the release hydraulic pressure can be set to be higher
than the lock hydraulic pressure. Since the release operation can
be also delayed, discharge of air remaining in each passage and
each chamber in the VVT can be ensured through the first and second
communication passages to the outside on starting the engine. As a
result, release operations, which are not predetermined and result
from residual air, can be reliably prevented.
[0016] The first communication passage may be formed at an end of
the case in an axial direction of the case. In this way, it is
possible to easily process the first communication passage. It is
also possible to shorten the length in the minimum cross sectional
area of the first communication passage to reduce passage
resistance in the first communication passage. It is further
possible to perform the release operation of the lock member with
stability.
[0017] The first communication passage may be a branch of a
hydraulic pressure supply passage of communicating the operational
hydraulic pressure chamber to a release hydraulic pressure chamber.
In this way, it is possible to easily process the first
communication passage and to reduce passage resistance in the first
communication passage.
[0018] The cross sectional area of the first communication passage
may be set to be larger than that of the second communication
passage. In this way, since the backward pressure can be surely
applied to the backward pressure chamber, the release hydraulic
pressure can be set to be higher than the lock hydraulic
pressure.
[0019] The cross sectional area of the second communication passage
may be set to be larger than that the cross sectional area allowing
discharge of foreign materials. In this way, since foreign
materials in drain oil can be surely discharged from the backward
pressure chamber to the outside, it can prevent the second
communication passage from being blocked by the foreign materials
and can ensure reliable operation of the lock member.
[0020] The driving force transmitting means may be a chain, the
lock member may move in a radial direction of the device, and a
stopper may be arranged at the outermost section of the device, the
stopper of holding the push member in the backward pressure chamber
and integrated with the second communication passage. In this way,
the backward pressure in the backward pressure chamber is drained
directly to the outside without the passage resistance due to the
passage length or diameter. A stable difference between the release
hydraulic pressure and the lock hydraulic pressure can be
predetermined even if air is mixed in oil in the hydraulic pressure
chamber such as an advance side hydraulic pressure chamber.
[0021] A valve timing control device for modifying opening and
closing timing of an intake valve or an exhaust valve making
contact with cams fixed on an intake camshaft or an exhaust
camshaft of an internal-combustion engine, may comprise a housing
rotating in synchronization with a driving force transmitting means
transmitting a driving force from a crankshaft of the
internal-combustion engine to an intake camshaft and an exhaust
camshaft; a case fixed on the housing and having a plurality of
shoes which are projected inwardly to form a plurality of hydraulic
pressure chambers; a rotor fixed on an end of the intake camshaft
or the exhaust camshaft and having a plurality of vanes to divide
the hydraulic pressure chambers into advance side hydraulic
pressure chambers and retardation side hydraulic pressure chambers;
a fitting hole arranged on one of the rotor or the case; a lock
member arranged on the other of the rotor or the case and fit in
the fitting hole to lock the rotor in relation to the case at an
approximately intermediate position apart from both of the maximum
advanced side position and the maximum retarded side position, the
lock member including a head section fitting the fitting hole and a
flange section having a diameter larger than the head section; a
push member pushing the lock member in a direction fitting the lock
member in the fitting hole at all times; and a seal member of
stopping the flow of operational oil between the advance side
hydraulic pressure chamber and the retardation side hydraulic
pressure chamber, wherein the seal member may be arranged so as to
apply a hydraulic pressure from the retardation side hydraulic
pressure chamber on the flange section of the lock member, and to
apply a hydraulic pressure from the advance side hydraulic pressure
chamber on the head section and the flange section of the lock
member. In this way, even if an active release hydraulic pressure
is reduced on selecting the OCV intermediate retained mode, it can
apply the release hydraulic pressure on larger area of the lock
member to ensure release of the lock member and to ensure stable
operation of the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a perspective view of a valve system of the engine
equipped with a valve timing control device according to the
present invention.
[0023] FIG. 2 is a partial cross sectional view of an internal
construction of an oil control valve for supplying a hydraulic
pressure to the valve timing control device shown in FIG. 1.
[0024] FIG. 3 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 1
according to the present invention.
[0025] FIG. 4 is a cross sectional view taken along lines A-A of
FIG.3.
[0026] FIG. 5 is an enlarged cross sectional view of a main point B
of FIG. 4.
[0027] FIG. 6 is a graph showing a relation of a release hydraulic
pressure and an operation of the lock member in the valve timing
control device shown in FIG. 3, FIG. 4 and FIG. 5.
[0028] FIG. 7 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 2
according to the present invention.
[0029] FIG. 8 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 3
according to the present invention.
[0030] FIG. 9 is a cross sectional view taken along lines C-C of
FIG.8.
[0031] FIG. 10A is a cross sectional view of a locked state in the
valve timing control device shown in FIG. 8 and FIG. 9.
[0032] FIG. 10B is a cross sectional view of a released state in
the valve timing control device shown in FIG. 8 and FIG. 9.
[0033] FIG. 11 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 4
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
[0034] Hereafter, a first embodiment of the present invention will
be explained.
[0035] Embodiment 1
[0036] FIG. 1 is a perspective view of a valve system of the engine
equipped with a valve timing control device according to the
present invention. FIG. 2 is a partial cross sectional view of an
internal construction of an oil control valve for supplying a
hydraulic pressure to the valve timing control device shown in FIG.
1. FIG. 3 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 1
according to the present invention. FIG. 4 is a cross sectional
view taken along lines A-A of FIG.3. FIG. 5 is an enlarged cross
sectional view of a main point B of FIG. 4. FIG. 6 is a graph
showing a relation of a release hydraulic pressure and an operation
of the lock member in the valve timing control device shown in FIG.
3, FIG. 4 and FIG. 5.
[0037] In FIG. 1, reference numeral 1 denotes a crankshaft of an
engine (not shown) and numeral 2 denotes a chain sprocket fixed on
an end of the crankshaft 1. Numeral 3 denotes an intake camshaft,
and numeral 4 denotes an exhaust camshaft. Numeral 5 denotes a
variable valve timing control device (hereafter, referred as an
intake VVT) arranged at an end of the intake camshaft 3. Numeral 6
denotes a variable valve timing control device (hereafter, referred
as an exhaust VVT) arranged at an end of the exhaust camshaft 4.
Numeral 7 denotes a timing chain (a driving force transmitting
means) transmitting a rotational driving force from the crankshaft
1 to the intake camshaft 3 and the exhaust camshaft 4 via the chain
sprocket 2, the intake VVT 5 and the exhaust VVT 6. A cam 8 has a
cam face making contact with an intake valve (not shown) of the
engine (not shown) and is integrally arranged on the intake
camshaft 3. A cam 9 has a cam face making contact with an exhaust
valve (not shown) and is integrally arranged on the exhaust
camshaft 4.
[0038] A hydraulic pressure is provided to and discharged from the
intake VVT 5 and the exhaust VVT 6 due to an OCV 10 as shown in
FIG. 2, for example. The OCV 10 is arranged in an engine block 11.
The OCV 10 includes a cylindrical-shaped valve housing 12; a spool
13 slidably arranged in the valve housing 12 in the axial direction
of the valve housing 12; and a magnetic drive section 14 of
slidably driving the spool 13 in the axial direction. A first pipe
15, a second pipe 16, a supply pipe 18, a first drain pipe 19 and a
second pipe 20 are connected with the perimeter of the valve
housing 12, respectively. The first pipe 15 applies a hydraulic
pressure to and discharges it from an advance side hydraulic
pressure chamber as described later, of the intake VVT 5 or the
exhaust VVT 6. The second pipe 16 applies a hydraulic pressure to
and discharges it from a retardation side hydraulic pressure
chamber as described later, of the intake VVT 5 or the exhaust VVT
6. The supply pipe 18 provides oil accumulated in an oil pan 17 to
the valve housing 12. The first and second drain pipes 19 and 20
return the oil in the valve housing 12 to the oil pan 17. An oil
pump 21 pumping up the oil from the oil pan 17 and an oil-filter 22
removing foreign materials from the oil pumped up by the oil pump
21 are arranged at the supply pipe 18.
[0039] A plurality of projections 13a and grooves 13b,
corresponding to the first and second pipes 15 and 16, the supply
pipe 18, the first and second drain pipes 19 and 20 are formed at
the perimeter of the spool 13. The sliding of the spool 13 in the
axial direction of the valve housing 12 allows communications
between a pipe and the corresponding pipes. One end of the spool
13, which is illustrated as a left end in FIG. 2, coaxially butts
against one end, which is illustrated as a right end in FIG. 2, of
a rod 23 arranged as a movable axial member in the magnetic drive
section 14. A magnetic attracting force due to a linear-solenoid 24
of the magnetic drive section 14 allows the rod 23 to push the
spool 13 toward the side of the valve housing 12 against a pushing
force due to a spring 25 arranged in the valve housing 12. A
cylindrical-shaped boss 26 is arranged at one end of the axial
direction of the magnetic drive section 14. A first sleeve 27 is
press-fitted and fixed in the boss 26 and functions as a sleeve
bearing which can accommodate and support one end of the rod 23. A
core 28 is opposed to the boss 26 in the axial direction and is
arranged at the other end of the axial direction of the magnetic
drive section 14 acting as a component of the magnetic drive
section 14. A second sleeve 29 is press-fitted and fixed in the
core 28 and functions as a sleeve bearing which can slide on and
support the other end of the rod 23. A plunger 30 as a moving core
is arranged between the first and second sleeves 27 and 29 and is
fixed on the rod 23.
[0040] The linear-solenoid 24 is connected with an engine control
unit (hereafter, referred as an ECU) 32 via a terminal 31. The ECU
32 is connected with various sensors including a crank-angular
sensor (not shown) acting as an angular sensor of the crankshaft 1,
and a cam-angular sensor (not shown) acting as an angular sensor of
the intake or exhaust cam 8 or 9, as shown in FIG. 1.
[0041] Next, an operation of the OCV 10 will be explained.
[0042] First, the ECU 32 drives the OCV 10 on the basis of signals
from the cam-angular sensor (not shown), for example. In other
words, signals from the ECU 32 bring the linear-solenoid 24 into
generation of the magnetic attracting force moving the plunger 30
in the axial direction of the valve housing 12. The rod 23 fixed on
the plunger 30 and the spool 13 butting the end of the rod 23 are
slid against the pushing force of the spring 25 by a required
stroke in synchronization with the movement of the plunger 30.
According to the sliding stroke, the spool 13 links communications
between the supply pipe 18 and the first pipe 15 or the second pipe
16, between the first drain pipe 19 or the second drain pipe 20 and
the first pipe 15 or the second pipe 16. In this way, it is
possible to provide the appropriate hydraulic pressure to and
discharge the same from the advance side hydraulic pressure chamber
and the retardation side hydraulic pressure chamber of the intake
VVT 5 or the exhaust VVT 6, if necessary.
[0043] Next, an internal construction of the intake VVT 5 or the
exhaust VVT 6 will be explained.
[0044] In FIG. 3 to FIG. 5, reference numeral 40 denotes a housing
integrated with a chain-sprocket section 40a receiving the
rotational driving force from the crankshaft 1 via the timing chain
7 as shown in FIG. 1. Numeral 41 denotes a case positioned and
fixed on the housing 40. The case 41 has a plurality of shoes 41a,
41b, 41c and 41d, which are projected inwardly to form a plurality
of hydraulic pressure chambers. Numeral 42 denotes a rotor having a
boss section 42a and a plurality of vanes 42b, 42c, 42d and 42e.
The boss section 42a is fixed on one end of the intake camshaft 3
or that of the exhaust camshaft 4 due to bolts (not shown). The
vanes 42b, 42c, 42d and 42e divide the hydraulic pressure chambers
into an advance side hydraulic pressure chambers 43 and a
retardation side hydraulic pressure chambers 44. Seal members 45
are arranged at ends of the shoes 41a, 41b, 41c and 41d of the case
41 and those of the vanes 42b, 42c, 42d and 42e of the rotor 42.
Each seal member 45 prevents operating oils from flowing between
the advance side hydraulic pressure chamber 43 and the retardation
side hydraulic pressure chamber 44 to keep the hydraulic pressure
in the each hydraulic pressure chamber. The seal member 45 includes
a seal 45a made of flexible resins and a plate spring 45b pushing
the seal 45a to a face as opposed to the seal 45a. The opposing
face is defined as the perimeter of the rotor 42 when the seal
member 45 is arranged at the case 41, and is defined as the inner
radius of the case 41 when the seal member 45 is arranged at the
rotor 42.
[0045] Assist springs 47 are arranged between the shoes 41a, 41b,
41c and 41d of the case 41 and the vanes 42b, 42c, 42d and 42e of
the rotor 42, respectively, in the advance side hydraulic pressure
chambers 43. The respective assist springs 47 are held by holders
46 to push the rotor 42 with respect to the case in an advance
direction (an X1 direction expressed by an arrow in FIG. 3).
[0046] In the drawings, numeral 48 denotes a lock-pin (lock member)
restricting free rotation defined between the case 41 and the rotor
42 on starting the engine and allowing the free rotation on normal
operation. The lock-pin 48 includes a cylindrical-shaped head
section 48a, a flange section 48b having an outer diameter larger
than that of the head section 48a and a recess section 48c formed
at a central bottom of the flange section 48b. With the embodiment,
the lock-pin 48 is arranged in an accommodation hole 49 formed at
the front end of the shoe 41a of the case 41 in a radial direction
of the device (hereafter, referred as a radial direction). The
accommodation hole 49 includes a minor radius section 49a and a
major radius section 49b. The minor radius section 49a has an inner
diameter corresponding to the outer diameter of the head section
48a of the lock-pin 48 and opens toward the boss 42a of the rotor
42. The major radius section 49b has an inner diameter
corresponding to the outer diameter of the flange section 48b of
the lock-pin 48 and opens toward the outermost perimeter of the
device. A stopper 50 is arranged in the major diameter section 49b
of the accommodation hole 49. The stopper 50 retains a coil-spring
as described later in the accommodation hole 49, and defines a
moving range of the lock-pin 48. A pin 51 prevents the stopper 50
from coming out of the accommodation hole 49. A coil-spring 52 is
arranged between the stopper 50 and the recess section 48c of the
lock-pin 48 to push the lock-pin 48 toward the boss 42a of the
rotor 42 at all times.
[0047] On the other hand, a fitting hole 53 is arranged at an
intermediate position, which is opposed to the shoe 41a of the case
41, of the perimeter of the boss 42a of the rotor 42 the position
being apart from both of the maximum advanced and retardation side
positions. With the maximum advanced side position, the shoe 41a
makes contact with the vane 42e of the rotor 42. With the maximum
retarded side position, the shoe 41a makes contact with the vane
42b. The fitting hole 53 is formed in the radial direction in a
manner similar to the accommodation hole 49 described above.
[0048] A hydraulic pressure switch valve 54 is arranged at the
confluence of an oil passage (not shown) communicating to the
advance side hydraulic pressure chamber 43 and an oil passage (not
shown) communicating to the retardation side hydraulic pressure
chamber 44. The confluence is formed on an end face of the housing
40 close to the case 41. The hydraulic pressure switch valve 54
selects and applies a higher hydraulic pressure from within the
hydraulic pressures of the advance side hydraulic pressure chamber
43 and the retardation side hydraulic pressure chamber 44 to a
release hydraulic pressure chamber 56 via a release hydraulic
pressure supply passage 55. The release hydraulic pressure chamber
56 is formed between the flange section 48b of the lock-pin 48 and
a tier section 49c, which is defined between the minor radius
section 49a and the major radius section 49b, of the accommodation
hole 49. When the release hydraulic pressure is provided to the
release hydraulic pressure chamber, the lock-pin 48 moves backward
against the pushing force of the coil-spring 52 and is released
from the fitting hole 53.
[0049] A cover 57 is fixed on the end face of the case 41 in the
axial direction due to a threaded member 58 such as bolts as shown
in FIG. 4 and FIG. 5. A first communication passage 59 is arranged
in the shoe 41a of the case 41. The first communication passage 59
includes a communication groove 59a formed at one end face of the
shoe 41a in the axial direction to communicate with the advance
side hydraulic pressure chamber 43; and a communication hole 59b
communicating the communication groove 59a to a rear space
(hereafter, referred as a backward pressure chamber) 60 of the
lock-pin 48 in the major radius section 49b of the accommodation
hole 49. A second communication passage 61 is arranged at a central
portion of the stopper 50 to communicate the backward pressure
chamber 60 to the outside of the device. The cross sectional area
of the second communication passage 61 is set to be smaller than
the minimum cross sectional area of the first communication passage
59, and is set to be larger than that the cross sectional area
allowing discharge of foreign materials. In this way, it is
possible to prevent instability of the release operation as a
result of blocking the passages with the foreign materials and of
increasing passage resistance in the passages. This also reduces
the frequency of maintenance which allows reductions in costs.
[0050] Next, an operation of the intake VVT 5 or the exhaust VVT 6
will be explained.
[0051] First, when the crankshaft 1 is rotated on starting the
engine, the rotational driving force is transmitted to the intake
camshaft 3 and the exhaust camshaft 4 via the timing chain 7, the
intake VVT 5 and the exhaust VVT 6. Here, on starting the engine,
the number of revolutions is naturally low and the oil pump is not
activated sufficiently. A hydraulic pressure is not provided for
keeping the VVT. However, even if the lock-pin 48 is not fit in the
fitting hole 53 on stopping the engine and the hydraulic pressure
is not provided sufficiently on starting the engine, flutters of
the rotor 42 do not cause abnormal noises due to the following
reasons. In other words, during cranking on starting the engine,
the rotor 42 rotates in the advance direction shown by the arrow X1
of FIG. 3 due to cam loads and the assist spring 47 as the camshaft
rotates. In this way, the rotor 42 rotationally moves to a lock
position and the head section 48a of the lock-pin 48 is fit in the
fitting hole 53 formed in the boss 42a of the rotor 42 due to the
pushing force of the coil-spring 52. The rotor 42 changes from the
release-state to the lock-state that the free rotation between the
rotor 42 and the case 41 is restricted. Since the rotor 42 is thus
locked at the reference position during the cranking on starting
the engine, abnormal noises caused by the flutters of the rotor 42
and engine knocking do not arise. The engine can be therefore
started with stability.
[0052] Moreover, in order to improve fitting of the lock-pin 48,
the oil passages are controlled so as to communicate with the
advance side hydraulic pressure chambers in both of the intake VVT
5 and the exhaust VVT 6 on starting the engine. In other words, in
the embodiment 1, a VVT fail-safe position of the intake VVT 5 is
set to the maximum retarded_side position and that of the exhaust
VVT 6 is set to the maximum advanced side position, for example. In
the intake VVT 5, the plunger 30 is slid in the axial direction of
the valve housing 12 due to the magnetic attracting force generated
by the linear-solenoid 24 on the basis of the control signal from
the ECU 32. The rod 23 fixed on the plunger 30 causes the spool
13-to slide in the valve housing 12 by a required stroke. In this
way, in the intake VVT 5, the oil passages can be communicated to
the advance side. On the other hand, in the exhaust VVT 6, the
control signal from the ECU 32 is set to 100 mA. The spool 13 is
held at a zero-moving position due to the pushing force of the
spring 25. In the exhaust VVT 6 in a manner similar to the intake
VVT 5, the oil passages can be communicated with the advance
side.
[0053] Next, after the engine undergoes complete combustion and a
certain hydraulic pressure is provided to the intake VVT 5 or the
exhaust VVT 6, the hydraulic pressure is provided to first the
advance side hydraulic pressure chamber 43 in any of the cases. The
pressure in the chamber 43 is further provided to the hydraulic
pressure switch valve 54, the release hydraulic pressure supply
passage 55 and the release hydraulic pressure chamber 56. Since the
flange section 48b of the lock-pin 48 is subjected to the hydraulic
pressure provided to the release hydraulic pressure chamber 56, the
lock-pin 48 moves backward when the hydraulic pressure overcomes
the pushing force of the coil-spring 52. Simultaneously, the
hydraulic pressure provided to the advance side hydraulic pressure
chamber 43 is discharged to the outside via the first and second
communication passages 59 and 61 until the time when the lock-pin
48 is entirely released and the flange section 48b closes the first
communication passage 59.
[0054] Here, when oil remains in the oil passages of the intake VVT
5 or the exhaust VVT 6 and in the hydraulic pressure chambers and
the engine is restarted for example soon after stopping the engine,
the oil pump activates after starting the engine to provide oil
pressure. Due to adequate hydraulic pressure, the lock-pin 48 can
be smoothly released and at the same time the rotor 42 can be held
against the cam loads. In this way, it can prevent the occurrence
of the abnormal noises due to the flutters of the rotor 42.
However, for example, when the engine is restarted after while
stopping the engine, oil is discharged from the oil passages of the
intake VVT 5 or the exhaust VVT 6 and the respective hydraulic
pressure chambers and air enters the above components. Here, air in
the oil passages is compressed as the oil is filled with starting
the engine to generate slightly pressure in the release hydraulic
pressure chamber 56 depending on the air pressure. As the lock-pin
48 is released under the air pressure, it is impossible to hold the
rotor 42 under an unstable hydraulic pressure resulting from air
filling the oil passages with a small quantity of oil and thus
causing abnormal noises by the flutters of the rotor 42. In order
to resolve this problem, it is assumed that a load of the
coil-spring 52 is set to a large amount. As the load of the
coil-spring 52 is however set to the large amount, the minimum
level of the hydraulic pressure allowing control of the intake VVT
5 or the exhaust VVT 6 increases and narrows a controllable
hydraulic pressure area.
[0055] With the embodiment 1, discharge of air in the intake VVT 5
or the exhaust VVT 6 at a required period after starting the engine
can be ensured due to the first and second communication passages
59 and 61 as described above. It can prevent the accidental release
of the lock-pin 48 due to the air pressure. The cross sectional
area of the second communication passage 61 is set to be smaller
than the minimum cross sectional area of the first communication
passage 59. The hydraulic pressure in the advance side hydraulic
pressure chamber 43 which acts as a backward pressure of the
lock-pin 48 is purged to the backward pressure chamber 60 via the
first communication passage 59. It is therefore possible to delay
the release operation on application of the hydraulic pressure to
the advance side hydraulic pressure chamber. In this case, the
lock-pin 48 is released under a condition that the hydraulic
pressure provided to the release hydraulic pressure chamber 56 is
larger than the sum of the load of the coil-spring 52 and the
backward pressure of the backward pressure chamber 60. In other
words, the hydraulic pressure keeps rising after starting the
engine and reaches a high hydraulic pressure (release-starting
hydraulic pressure) P2 as shown in FIG. 6. Here, the release
hydraulic pressure (hydraulic pressure in the release hydraulic
pressure chamber 56) is larger than the sum of the load of the
coil-spring 52 and the backward pressure of the backward pressure
chamber 60, the lock-pin 48 starts moving backward. Subsequently,
under a hydraulic pressure P3 being higher than the hydraulic
pressure P2, the head section 48a of the lock-pin 48 is completely
released out of the fitting hole 53 to finish the release
operation. If the first communication passage 59 is not disposed,
there is no difference between the release-starting hydraulic
pressure P2 and a hydraulic pressure P0 shown in FIG. 6, and there
is no difference between the hydraulic pressure (release-finishing
hydraulic pressure) P3 and a hydraulic pressure P1 shown in FIG. 6.
According to the embodiment 1, the first communication passage 59
is disposed, and the cross-sectional area of the passage 59 is
larger than that of the second communication passage 61 acting as a
drain passage for the hydraulic pressure and air pressure. It is
therefore possible to set a difference between the release-starting
hydraulic pressure P2 and the release-finishing hydraulic pressure
P3 as follows. In other words,the hydraulic pressure of the advance
side hydraulic pressure chamber 43 is provided to the release
hydraulic pressure chamber 56 via the hydraulic switch valve 54 and
the release hydraulic pressure supply passage 55, and to the
backward pressure chamber 60 via the first communication passage
59. The release hydraulic pressure chamber 56 is sealed due to a
clearance defined between the minor or major radius sections 49a or
49b of the accommodation hole 49 formed in the shoe 41a of the case
41 and the head or flange sections 48a or 48b of the lock-pin 48.
In this way, the hydraulic pressure in the release hydraulic
pressure chamber 56 can be kept. On the other hand, the hydraulic
pressure provided to the backward pressure chamber 60 is discharged
to the outside via the second communication passage 61 at the
constant quantity of flow, and does not rise to a pressure higher
than a certain hydraulic pressure. Because of the difference
between the hydraulic pressures in the chambers, the release
hydraulic pressure 56 reaches the hydraulic pressure P2 which is
larger than the sum of the load of the coil-spring 52 and the
backward pressure of the backward pressure chamber 60 and starts
the release operation. As the release operation is started, the
pushing force of the coil-spring 52 is increased by compressing the
coil-spring 52, and reaches the hydraulic pressure P3 on finishing
the release operation.
[0056] Moreover, as the lock-pin 48 moves backward to release the
lock-pin 48, the first communication passage 59 is closed with the
flange section 48b of the lock-pin 48. Thus, since the hydraulic
pressure is not discharged to the outside via the first and second
communication passages 59 and 61, a state of readiness is
maintained in order to perform normal operation later.
[0057] Inversely, on locking, the lock-pin 48 starts fitting in the
fitting hole 53 under a lower hydraulic pressure (lock-starting
hydraulic pressure) P1, and completely fits in the fitting hole 53
under the hydraulic pressure P0 to change to the lock-state. Here,
the value of the hydraulic pressures P1 and P0 change in response
to the set load of the coil-spring 52, respectively. The
lock-starting hydraulic pressure P1 is set to be nearly equal to or
lower than a hydraulic pressure of generating a torque generated in
the device, the torque being equal to a cam-torque of the engine.
In this way, even under the minimum hydraulic pressure condition
such as high temperature oil or idle rotation for example, it can
obviate the inconvenience of fitting the lock-pin 48 in the fitting
hole 53 or getting trapped therein. As a result, the device can
reliably control the operation of the lock-pin 48 and the VVT.
[0058] Next, when idling after the engine undergoes complete
combustion, the OCV 10 is set to a intermediate retained mode to
hold the rotor 42 at an approximately intermediate position (lock
position) as the reference position on starting, outside
controlling the intake VVT 5 or the exhaust VVT 6. In the
intermediate retained mode of the OCV 10, the first pipe 15 acting
as the advance side port is slightly opened, and the second pipe 16
acting as the retardation side port is opened as a drain. In this
way, the hydraulic pressure corresponding to the cam load can be
applied to the advance side hydraulic pressure chamber 43.
[0059] With the general intermediate retained mode of the OCV 10,
the first pipe 15 is small in cross-section opening area, and acts
as a throttle. The hydraulic pressure allowing application to the
advance side hydraulic pressure chamber 43 and the release
hydraulic pressure 56 is nearly equal to one-half of the minimum
hydraulic pressure of upstream the OCV 10. Thus, the lock-pin 48 is
not completely released. On keeping the intermediate position of
the rotor 42, as a lower hydraulic pressure provided from the oil
pump, there is a possibility that the lock-pin 48 fits in the
fitting hole 53 or getting trapped therein. Therefore, it is
impossible to operate the lock-pin 48 from the intermediate
retained position to the advance or retardation side. Since the
lock-pin 48 makes contact with the fitting hole 53 at all times,
both components undergo wear which decreases durability.
[0060] On the other hand, with the embodiment 1, since the
occurrence of abnormal noises due to the flutters of the rotor 42
can be prevented on starting the engine, the load of the
coil-spring 52 can be set to be small. Concretely, when the rotor
42 is kept at the intermediate position, an active hydraulic
pressure of the advance side hydraulic pressure chamber 43 is
reduced by half. In this case, the load of the coil-spring 52 can
be determined so as to surely release the lock-pin 48 under a
hydraulic pressure smaller than or equal to the hydraulic pressure
(one half of the minimum hydraulic pressure of upstream the OCV
10). Shortly, the load of the coil-spring 52 can be set to a level
smaller than the active release hydraulic pressure on keeping the
rotor 42 at the intermediate position. As seen from FIG. 6, the
lock-starting hydraulic pressure P1 corresponding to the load of
the coil-spring 52 can be set to be lower than the hydraulic
pressure of the release hydraulic pressure chamber 56 on the OCV
intermediate retained mode. Further, the release-starting hydraulic
pressure P2 can be set to be higher than an unstable hydraulic
pressure of mixing air on starting the engine. Thus, the device can
effectively change the release hydraulic pressure and the lock
hydraulic pressure of the lock-pin 48 in some cases.
[0061] As described above, with the embodiment 1, the release
hydraulic pressure P2 is set to be higher than the lock hydraulic
pressure P1. In this way, since the load of the coil-spring 52
corresponding to the lock hydraulic pressure P1 is set to a low
level. It can therefore reliably prevent an operational failure of
the device even if a hydraulic pressure in the device is reduced by
the OCV intermediate retained mode or even if the operation oil is
consumed by operation of the device. The operational failure of the
device is prevented, which generates when the lock-pin 48 pops up
due to the pushing force of the coil-spring 52 to catch on or
engage in the fitting hole 53.
[0062] With the embodiment 1, the lock hydraulic pressure P1 may be
set to be nearly equal to or lower than a hydraulic pressure of
generating a torque generated in the device, the torque being equal
to a cam-torque of the internal-combustion. In this way, even under
the minimum hydraulic pressure condition such as high temperature
oil or idle rotation for example, it can obviate the inconvenience
of fitting the lock-pin 48 in the fitting hole 53 or getting
trapped therein. As a result, the operation of the lock-pin 48 can
be reliably controlled.
[0063] With the embodiment 1, the first and second communication
passages 59 and 61 are disposed in the WT. In this way, since the
backward pressure can be applied to the lock-pin 48 on releasing
operation, the release hydraulic pressure P2 can be set to be
higher than the lock hydraulic pressure P1. Since the release
operation can be also delayed, air remaining in each passage and
each chamber in the VVT can be rapidly and surely discharged
through the first and second communication passages 59 and 61 to
the outside on starting the engine. As a result, release
operations, which are not predetermined and result from residual
air, can be prevented.
[0064] With the embodiment 1, the first communication passage 59 is
formed at the end of the case in the axial direction of the case
41. In this way, it is possible to easily process the first
communication passage 59. It is also possible to shorten the length
in the minimum cross sectional area of the first communication
passage 59 to reduce passage resistance in the first communication
passage 59. It is further possible to perform the release operation
of the lock-pin 48 with stability. Moreover, with the embodiment 1,
the communication groove 59a of the first communication passage 59
is formed at one end face of the shoe 41a in the axial direction of
the case 41. Alternatively, the communication groove 59a may be
formed at one end face of the cover 57 which makes contact with the
one end face of the shoe 41a. In this case, it is also possible to
easily process the communication passage and to reduce the passage
resistance in the communication passage.
[0065] With the embodiment 1, the cross sectional area of the first
communication passage 59 is set to be larger than that of the
second communication passage 61. In this way, since the backward
pressure can be surely applied to the backward pressure chamber 60,
the release hydraulic pressure can be set to be higher than the
lock hydraulic pressure.
[0066] With the embodiment 1, the cross sectional area of the
second communication passage 61 is set to be larger than that the
cross sectional area of allowing discharge of foreign materials. In
this way, since the foreign materials in drain oil can be surely
discharged from the backward pressure chamber 60 to the outside, it
can prevent the second communication passage 61 from being blocked
with the foreign materials and can reliably operate the lock-pin
48.
[0067] Moreover, with the embodiment 1, the stopper 50 is disposed
at the outermost of the device, length of the second communication
passage 61 formed at the center of the stopper 50 is made short to
shorten a distance between the backward pressure chamber 60 and the
outside. In other words, it is designed to leak oil for the release
hydraulic pressure to the outside via the second communication
passage 61. In this way, the backward pressure in the backward
pressure chamber 60 can be drained to the outside without passage
resistance resulting from the passage length or diameter. Even if
the air is mixed in the oil in the hydraulic pressure chamber such
as the advance side hydraulic pressure chamber 43 and so on, it is
possible to set a stable difference between the release hydraulic
pressure and the lock hydraulic pressure. This construction can be
applicable to a case of using the timing chain 7 as the driving
force transmitting means because the timing chain 7 has a driving
force transmitting function that there is no harm in making contact
with oil. If a timing belt is used as the driving force
transmitting means, there is a possibility that the timing belt is
cut due to making contact with the oil. It is therefore preferable
that the second communication passage 61 communicates with the oil
pan 17 of the device within the intake camshaft 3 or the exhaust
camshaft 4.
[0068] Embodiment 2
[0069] FIG. 7 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 2
according to the present invention. Components of the embodiment 2
of the present invention which are the same as those of the
embodiment 1 are denoted by the same reference numerals and further
description will be omitted.
[0070] In FIG. 7, a hydraulic pressure switch valve 54 includes a
valve groove 54a, an approximately cylindrical-shaped valve body
54b, an advance side communication groove 54c and a retardation
side communication groove 54d. The valve groove 54a is formed at an
end face of the housing 40 close to the case 41 and has an about
ellipse-shaped inner space. The valve body 54b is accommodated in
the valve groove 54a. The advance side communication groove 54c is
formed at the end face of the housing 40 close to the case 41 to
communicate between the valve groove 54a and the advance side
hydraulic pressure chamber 43. The retardation side communication
groove 54d is formed at the end face of the housing 40 close to the
case 41 to communicate between the valve groove 54a and the
retardation side communication groove 54d. The embodiment 2 is
characterized in that the communication groove 59a of the first
communication passage 59 formed as a branch from the advance side
communication groove 54c to communicate to the backward pressure
chamber 60 via the communication hole 59b.
[0071] Although the first communication passage 59 of the
embodiment 1 directly communicates the advance side hydraulic
pressure chamber 43 to the backward pressure chamber 60, the first
communication passage 59 of the embodiment 2 is formed as an
additional passage branched from the already-existing communication
groove. In this way, with embodiment 2, it is possible to easily
process the first communication passage and to prevent passage
resistance and to reduce manufacturing costs.
[0072] Moreover, with the embodiment 2, although the communication
groove 59a of the first communication passage 59 is disposed as a
branch from the advance side communication groove 54c, the
communication groove 54a may be branched from the retardation side
communication groove 54d, as required.
[0073] Embodiment 3
[0074] FIG. 8 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 3
according to the present invention. FIG. 9 is a cross sectional
view taken along lines C-C of FIG.8. FIG. 10A is a cross sectional
view of a locked state in the valve timing control device shown in
FIG. 8 and FIG. 9. FIG. 10B is a cross sectional view of a released
state in the valve timing control device shown in FIG. 8 and FIG.
9. Components of the embodiment 3 of the present invention which
are the same as those of the embodiment 1 are denoted by the same
reference numerals and further description will be omitted.
[0075] With the embodiment 3, the lock-pin 48 is slid in an axial
direction of the device. This point is different from the
embodiments 1 and 2 whose lock-pin 48 is slid in the radial
direction of the device. A belt type is used as the driving force
transmitting means in the embodiment 3. This point is different
from the embodiments 1 and 2 using the chain type as the driving
force transmitting means. Hereafter, the characterized construction
will be explained. The lock-pin 48 does not have the head section
48a having a minor diameter, and includes the flange section 48b
and the recess section 48c. The accommodation hole 49 is formed in
the vane 42b of the rotor 42 close to the housing 40 in the axial
direction. The fitting hole 53 is formed at a position of the
housing 40 facing the accommodation hole 49. The first
communication passage 59 communicating with the retardation side
hydraulic pressure chamber 44 is arranged in the backward pressure
chamber 60 acting as a backward section of the lock-pin 48 within
the accommodation hole 49. The second communication passage 61
communicating with the outside is arranged in the backward pressure
chamber 60. The second communication passage 61 is a path shown by
arrow Y of FIG. 9. The passage 61 includes communication grooves 62
and 63, an oil space 64 and a communication hole 65a. The groove 62
is formed at the boss 42a of the rotor 42, and the groove 63 is
formed at the inner radius of the cover 57. The oil space 64 is
defined between the cover 57 and the rotor 42, and the
communication hole 65a is formed in a center bolt 65 for fixing the
VVT device on the camshaft. The oil passed through the passage 61
is passed though oil passages within the intake camshaft 3 or the
exhaust camshaft 4, and is returned to the oil pan 17. In this way,
it can prevent the oil from discharging to the outside of the
device, and can also avoid the inconvenience due to the adhesion of
oil to the belt as the driving force transmitting means.
[0076] Next, an operation of the lock-pin 48 will be explained.
[0077] First, on releasing the lock-state, the hydraulic pressure
switch valve 54 is switched due to the hydraulic pressure of the
retardation side hydraulic pressure chamber 44. The release
hydraulic pressure is then provided to the fitting hole 53 via the
release hydraulic supply passage 55 and the release hydraulic
pressure chamber 56, and acts on the front end of the lock-pin 48.
The hydraulic pressure of the retardation side hydraulic pressure
chamber 44 is also provided to the backward pressure chamber 60 via
the first communication passage 59 as shown in FIG. 10A, and is
discharged via the second communication passage 61 to outside the
device. The hydraulic pressure is constantly applied to the
backward pressure chamber 60 until the time when the lock-pin 48
moves backward to close the first communication passage 59. The
supply of the hydraulic pressure to the backward pressure chamber
60 is stopped at the same time when the first communication passage
59 is closed as shown in FIG. 10B. In this way, the hydraulic
pressure supplied to the backward pressure chamber 60 acts as the
backward pressure of the lock-pin 48, and acts against the release
hydraulic pressure, in cooperation with the pushing force of the
coil-spring 52. It is therefore possible to delay the release
operation of releasing the lock-pin 48, and eventually enhance the
release hydraulic pressure.
[0078] As described above, with a type of sliding the lock-pin 48
in the axial direction of the embodiment 3, the release hydraulic
pressure can be set to be higher than the lock hydraulic pressure
corresponding to the load of the coil-spring 52. It is possible to
set the load of the coil-spring 52 to a low level. It can therefore
reliably prevent an operational failure of the device even if a
hydraulic pressure in the device is reduced by the OCV intermediate
retained mode or even if the operation oil is consumed by operation
of the device. The operational failure of the device is prevented,
which generates when the lock-pin 48 pops up due to the pushing
force of the coil-spring 52 to catch on or engage in the fitting
hole 53.
[0079] With the embodiment 3, the first and second communication
passages 59 and 61 are disposed to delay the release operation. Air
remaining in each passage and each chamber in the VVT can be
rapidly and surely discharged through the first and second
communication passages 59 and 61 to the outside on starting the
engine. As a result, release operations, which are not
predetermined and result from residual air, can be prevented.
[0080] Embodiment 4
[0081] FIG. 11 is a lateral cross sectional view of an internal
construction of a valve timing control device as embodiment 4
according to the present invention. Components of the embodiment 4
of the present invention which are the same as those of the
embodiment 1 are denoted by the same reference numerals and further
description will be omitted.
[0082] The embodiment 4 is characterized in that the seal member 45
is disposed at a position close to the retardation side hydraulic
pressure chamber 44 in comparison with a lock mechanism 66
including the lock-pin 48 and the fitting hole 53. In other words,
the hydraulic pressure of the advance side hydraulic pressure
chamber 43 is used as the release hydraulic pressure. In this case,
the advance side hydraulic pressure is applied to the flange
section 48b of the lock-pin 48 via the hydraulic pressure switch
valve 54, the release hydraulic pressure supply passage 55 and the
release hydraulic pressure chamber 56. Simultaneously, the pressure
is applied to the head section 48a of the lock-pin 48 fitted in the
fitting hole 53 via a slight gap defined between a front end of the
shoe 41a of the case 41 and the perimeter of the boss 42a of the
rotor 42. The hydraulic pressure of the retardation side hydraulic
pressure 44 is used as the release hydraulic pressure. In this
case, the pressure is applied to only the flange section 48b of the
lock-pin 48 via the hydraulic pressure switch valve 54, the release
hydraulic pressure supply passage 55 and the release hydraulic
pressure chamber 56.
[0083] As described above, with the embodiment 4, the seal member
45 is disposed in order that the release hydraulic pressure derived
from the retardation side hydraulic pressure chamber 44 acts on the
flange section 48b of the lock-pin 48, and that the release
hydraulic pressure derived from the advance side hydraulic pressure
chamber 43 acts on the head section 48a and the flange section 48b
of the lock-pin 48. In this way, even if an active release
hydraulic pressure is reduced on selecting the OCV intermediate
retained mode, it can apply the release hydraulic pressure on
larger area of the lock member to surely release the lock member
and to operate the device with stability.
[0084] The present invention may be embodied in other specific
forms without departing from the spirit or essential
characteristics thereof. The present embodiment is therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims
rather than by the foregoing description and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
* * * * *