U.S. patent application number 11/389153 was filed with the patent office on 2006-11-30 for valve timing control apparatus and internal combustion engine.
This patent application is currently assigned to HITACHI, LTD.. Invention is credited to Seiji Suga, Tomoya Tsukada, Hidekazu Yoshida.
Application Number | 20060266318 11/389153 |
Document ID | / |
Family ID | 37461868 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060266318 |
Kind Code |
A1 |
Suga; Seiji ; et
al. |
November 30, 2006 |
Valve timing control apparatus and internal combustion engine
Abstract
Valve timing control apparatus includes a driving rotary member
driven by an engine; a driven rotary member arranged to rotate
relative to the driving rotary member and adapted to rotate a
camshaft of the engine; and a hydraulic control section to rotate
the driven rotary member relative to the driving rotary member
hydraulically. A lock mechanism is arranged to be brought, in
accordance with a hydraulic pressure supplied from the hydraulic
control section, from a lock state to prevent relative rotation of
the driven rotary member relative to the driving rotary member, to
an unlock state to allow the relative rotation, through an standby
state to prepare for the unlock state without allowing the relative
rotation of the driven rotary member relative to the driving rotary
member.
Inventors: |
Suga; Seiji; (Kanagawa,
JP) ; Yoshida; Hidekazu; (Kanagawa, JP) ;
Tsukada; Tomoya; (Kanagawa, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
HITACHI, LTD.
|
Family ID: |
37461868 |
Appl. No.: |
11/389153 |
Filed: |
March 27, 2006 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 1/3442 20130101;
F01L 2001/34456 20130101; F01L 2001/34473 20130101 |
Class at
Publication: |
123/090.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2005 |
JP |
2005-150320 |
Claims
1. A valve timing control apparatus for an internal combustion
engine, comprising: a driving rotary member adapted to be driven by
the engine; a driven rotary member arranged to rotate relative to
the driving rotary member and adapted to rotate a camshaft of the
engine; a hydraulic control section to rotate the driven rotary
member relative to the driving rotary member hydraulically; and a
lock mechanism arranged to be brought, in accordance with a
hydraulic pressure supplied from the hydraulic control section,
from a lock state to prevent relative rotation of the driven rotary
member relative to the driving rotary member, to an unlock state to
allow the relative rotation of the driven rotary member relative to
the driving rotary member, through an standby state to prepare for
the unlock state without allowing the relative rotation of the
driven rotary member relative to the driving rotary member.
2. The valve timing control apparatus as claimed in claim 1,
wherein the driven rotary member is arranged to rotate relative to
the driving rotary member in an advance direction when a fluid
pressure is supplied to an advance pressure chamber, and in a
retard direction when a fluid pressure is supplied to a retard
pressure chamber; wherein the hydraulic control section is
configured to first supply the fluid pressure to a first chamber
which is one of the advance and retard pressure chambers in an
engine starting operation, and then to supply the fluid pressure to
a second chamber which is the other of the advance and retard
chambers; and wherein the lock mechanism is arranged to shift from
the lock state to the unlock state when the fluid pressure in the
second chamber increases.
3. The valve timing control apparatus as claimed in claim 2,
wherein the lock mechanism is held in the lock state in the engine
starting operation, and shifted to the standby state before the
lock mechanism is shifted to the unlock state with an increase of
the fluid pressure in the second chamber.
4. The valve timing control apparatus as claimed in claim 2,
wherein the lock mechanism is held in the lock state in the engine
starting operation, and shifted to the standby state when an engine
speed increases.
5. The valve timing control apparatus as claimed in claim 2,
wherein the lock mechanism is allowed to shift from the lock state
to the standby state by an increase in an air pressure in one of
the advance and retard chambers, but prevented from being shifted
to the unlock state by the air pressure.
6. The valve timing control apparatus as claimed in claim 2,
wherein the lock mechanism is shifted from the lock state to the
standby state in accordance with the fluid pressure in the first
chamber.
7. The valve timing control apparatus as claimed in claim 2,
wherein the lock mechanism includes a movable lock member arranged
to move forwards when the fluid pressure in the second chamber is
low, and to move backwards when the fluid pressure in the second
chamber is increased; and an abutting portion arranged to abut
against the movable lock member when the movable lock member is
moved forwards and thereby to prevent the relative rotation of the
driven rotary member relative to the driving rotary member; and an
abutment area in which the movable lock member abuts on the
abutting portion to prevent the relative rotation between the
driving and driven rotary members is reduced when the lock
mechanism is brought from the lock state to the standby state, but
the abutting area remains greater than zero in the standby
state.
8. The valve timing control apparatus as claimed in claim 7,
wherein the lock mechanism further includes a bias member to bias
the movable lock member forwards toward the abutting portion.
9. The valve timing control apparatus as claimed in claim 7,
wherein a length of the abutment of the movable lock member against
the abutting portion, as measured along an imaginary line along
which the movable lock member moves forwards and backwards is
reduced when the lock mechanism is brought from the lock state to
the standby state.
10. The valve timing control apparatus as claimed in claim 9,
wherein the movable lock member abuts against the abutting portion
so that the abutting portion limits movement of the movable lock
member in a direction substantially perpendicular to the imaginary
line along which the movable lock member moves forwards and
backwards.
11. The valve timing control apparatus as claimed in claim 9,
wherein the length of the abutment of the movable lock member
against the abutting portion is equal to or smaller than 1 mm when
the lock mechanism is in the standby state.
12. The valve timing control apparatus as claimed in claim 9,
wherein the length of the abutment of the movable lock member
against the abutting portion is equal to or smaller than 0.2 mm
when the lock mechanism is in the standby state.
13. The valve timing control apparatus as claimed in claim 7,
wherein the abutting portion is stationary relative to a first
rotary member which is one of the driving and driven rotary
members, and the movable lock member is mounted in a second rotary
member which is the other of the driving and driven rotary
members.
14. The valve timing control apparatus as claimed in claim 7,
wherein the abutting portion is a portion of a movable abutting
member mounted movably in a first rotary member which is one of the
driving and driven rotary members, and the movable lock member is
mounted movably in a second rotary member which is the other of the
driving and driven rotary members.
15. The valve timing control apparatus as claimed in claim 14,
wherein the movable abutting member is arranged to move forwards
toward the movable lock member and backwards away from the movable
lock member; the lock mechanism is in the lock state when the
movable lock member is projected forwards and the movable abutting
member is projected forwards; the lock mechanism is in the unlock
state when the movable lock member is retracted backwards and the
movable abutting member is retracted backwards; and the lock
mechanism is in the standby state when the movable lock member is
projected forwards and the movable abutting member is retracted
backwards.
16. The valve timing control apparatus as claimed in claim 15,
wherein the lock mechanism further includes a second bias member to
bias the movable abutting member forwards toward the movable lock
member.
17. The valve timing control apparatus as claimed in claim 15,
wherein the movable lock member is held in the standby state even
if the movable abutting member is moved backwards to a backward
limit position to which a backward movement of the movable abutting
member is limited.
18. The valve timing control apparatus as claimed in claim 15,
wherein the movable abutting member is moved backwards away from
the movable lock member in accordance with the fluid pressure in
the first chamber to which the fluid pressure is first supplied in
the engine starting operation.
19. The valve timing control apparatus as claimed in claim 18,
wherein the movable abutting member includes a step shoulder
surface arranged to receive the fluid pressure in the first chamber
and thereby to be retracted backwards away from the movable lock
member in accordance with the fluid pressure in the first
chamber.
20. The valve timing control apparatus as claimed in claim 7,
wherein the abutting portion includes a lock recess arranged to
receive a forward end portion of the movable lock member.
21. The valve timing control apparatus as claimed in claim 2,
wherein the driven rotary member includes a vane projecting
radially outwards and separating the advance fluid pressure chamber
and the retard fluid pressure chamber; and the driving rotary
member enclosing the driven rotary member and defining the advance
and retard fluid pressure chambers between the driving rotary
member and the driven rotary member.
22. The valve timing control apparatus as claimed in claim 7,
wherein the movable lock member is arranged to move radially around
an axis of the driven rotary member.
23. The valve timing control apparatus as claimed in claim 7,
wherein the movable lock member is arranged to move axially along
an axis of the driven rotary member.
24. The valve timing control apparatus as claimed in claim 7,
wherein the lock mechanism includes a retracting section to guide
the movable lock member and the abutting portion into the lock
state by retracting at least one of the movable lock member and the
abutting portion.
25. The valve timing control apparatus as claimed in claim 24,
wherein the retracting section includes a tapered surface formed in
one of the movable lock member and the abutting portion.
26. The valve timing control apparatus as claimed in claim 2,
wherein the hydraulic control section includes a control valve to
control the fluid pressures in the advance and retard pressure
chambers; and a controller to control the control valve to first
supply the fluid pressure to the first chamber which is one of the
advance and retard pressure chambers at the time of a start of the
engine, and then to supply the fluid pressure to the second chamber
which is the other of the advance and retard chambers.
27. An internal combustion engine comprising: a crankshaft; a
camshaft; a valve timing control rotary mechanism including, a
driving rotary member driven by the crankshaft of the engine, and a
driven rotary member) which is arranged to be driven by the driving
rotary member and to drive the camshaft, and which is arranged to
rotate relative to the driving rotary member to alter a rotational
position of the driven rotary member relative to the driving rotary
member; a hydraulic section to rotate the driven rotary member
relative to the driving rotary member in an advance direction by an
advance fluid pressure in an advance pressure chamber and in a
retard direction by a retard fluid pressure in a retard pressure
chamber; a control section to control the hydraulic section to
supply a fluid pressure selectively to the advance pressure chamber
or the retard pressure chamber in accordance with an engine
operating condition, and to perform an engine starting operation by
first supplying the fluid pressure to a first chamber which is one
of the advance and retard pressure chambers, and then supplying the
fluid pressure a second chamber which is the other of the advance
and retard pressure chambers; and a lock mechanism arranged to
prevent relative rotation of the driven rotary member relative to
the driving rotary member when the lock mechanism is in a lock
state, and to allow the relative rotation of the driven rotary
member when in an unlock state, the lock mechanism being set in the
lock state at a time of an engine start and then brought to the
unlock state in accordance with the fluid pressure in the second
chamber after the engine start, the lock mechanism being further
arranged to be set, before the unlock state is reached, to a
standby state preparing for the unlock state while preventing the
relative rotation of the driven rotary member relative to the
driving rotary member.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an internal combustion
engine equipped with a valve timing control apparatus and/or a
valve timing control apparatus for controlling a valve timing of an
internal combustion engine such as opening and closing timings of
intake or exhaust valve.
[0002] A published Japanese Patent Specification Publication No.
2000-002104 shows a valve timing control apparatus (VTC) of a vane
type including a rotary unit of a timing sprocket member and a vane
member, and a lock mechanism including a lock pin to limit relative
rotation between the timing sprocket member and vane member.
SUMMARY OF THE INVENTION
[0003] When the engine remains in a stop state for a long time,
most of the oil is drained from the advance and retard pressure
chambers in the valve timing control apparatus of this document.
Therefore, when the hydraulic fluid is supplied to the advance or
retard pressure chamber at the time of a next engine start, air is
compressed in the pressure chamber. As a result, the air pressure
in the pressure chamber becomes higher and acts on the lock pin, so
that the lock mechanism may be unlocked improperly, and hence the
vane member may fluctuate in the forward and reverse directions and
cause undesired noises. Therefore, it is an object of the present
invention to provide valve timing control apparatus to solve
problems in earlier technology.
[0004] According to one aspect of the present invention, a valve
timing control apparatus for an internal combustion engine,
comprises: a driving rotary member adapted to be driven by the
engine; a driven rotary member arranged to rotate relative to the
driving rotary member and adapted to rotate a camshaft of the
engine; a hydraulic control section to rotate the driven rotary
member relative to the driving rotary member hydraulically; and a
lock mechanism arranged to be brought, in accordance with a
hydraulic pressure supplied from the hydraulic section, from a lock
state to prevent relative rotation of the driven rotary member
relative to the driving rotary member, to an unlock state to allow
the relative rotation of the driven rotary member relative to the
driving rotary member, through an standby state to prepare for the
unlock state without allowing the relative rotation of the driven
rotary member relative to the driving rotary member.
[0005] According to another aspect of the invention, an internal
combustion engine comprises: a crankshaft; a camshaft; a valve
timing control rotary mechanism including a driving rotary member
driven by the crankshaft of the engine, and a driven rotary member)
which is arranged to be driven by the driving rotary member and to
drive the camshaft, and which is arranged to rotate relative to the
driving rotary member to alter a rotational position of the driven
rotary member relative to the driving rotary member; a hydraulic
section to rotate the driven rotary member relative to the driving
rotary member in an advance direction by an advance fluid pressure
in an advance pressure chamber and in a retard direction by a
retard fluid pressure in a retard pressure chamber; a control
section to control the hydraulic section to supply a fluid pressure
selectively to the advance pressure chamber or the retard pressure
chamber in accordance with an engine operating condition, and to
perform an engine starting operation by first supplying the fluid
pressure to a first chamber which is one of the advance and retard
pressure chambers, and then supplying the fluid pressure a second
chamber which is the other of the advance and retard pressure
chambers; and a lock mechanism arranged to prevent relative
rotation of the driven rotary member relative to the driving rotary
member when the lock mechanism is in a lock state, and to allow the
relative rotation of the driven rotary member when in an unlock
state, the lock mechanism being set in the lock state at a time of
an engine start and then brought to the unlock state in accordance
with the fluid pressure in the second chamber after the engine
start. The lock mechanism is further arranged to be set, before the
unlock state is reached, to a standby state preparing for the
unlock state while preventing the relative rotation of the driven
rotary member relative to the driving rotary member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a sectional view taken across a line F1-F1 in FIG.
2, for showing an internal combustion engine provided with a valve
timing control system according to a first embodiment of the
present invention.
[0007] FIG. 2 is a sectional view taken across a line F2-F2 in FIG.
1, for showing the valve timing control system of FIG. 1.
[0008] FIG. 3A is a sectional view taken across the line F2-F2 in
FIG. 1, for showing the valve timing control system of FIG. 1 at
the time of a start of the engine. FIG. 3B is an enlarged view of a
part of FIG. 3A.
[0009] FIG. 4A is a sectional view taken across the line F2-F2 in
FIG. 1, for showing the valve timing control system of FIG. 1 at
the time of an idling operation of the engine. FIG. 4B is an
enlarged view of a part of FIG. 4A.
[0010] FIG. 5A is a sectional view taken across the line F2-F2 in
FIG. 1, for showing the valve timing control system of FIG. 1 at
the time of an operation in a low speed, low load region of the
engine. FIG. 5B is an enlarged view of a part of FIG. 5A.
[0011] FIG. 6A is a sectional view taken across the line F2-F2 in
FIG. 1, for showing the valve timing control system of FIG. 1 at
the time of an operation in a medium speed, medium load region of
the engine. FIG. 6B is an enlarged view of a part of FIG. 6A.
[0012] FIG. 7 is a partial cutaway view showing a valve timing
control apparatus according to a second embodiment of the present
invention.
[0013] FIG. 8 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 7 with a vane member
at a most retarded position.
[0014] FIG. 9 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 7 with the vane
member at an intermediate rotational position.
[0015] FIG. 10 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 7 with the vane
member at a most advanced position.
[0016] FIG. 11 is a partial cutaway view showing a valve timing
control apparatus according to a third embodiment of the present
invention.
[0017] FIG. 12 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 11 with a vane member
at the most retarded position.
[0018] FIG. 13 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 11 with the vane
member at the intermediate rotational position.
[0019] FIG. 14 is a partial cutaway view for illustrating operation
of the valve timing control apparatus of FIG. 11 with the vane
member at the most advanced position.
[0020] FIG. 15 is a sectional view taken across a line F15-F15
shown in FIG. 16, showing a valve timing control apparatus
according to a fourth embodiment of the present invention.
[0021] FIG. 16 is a sectional view taken across a line F16-F16
shown in FIG. 15.
[0022] FIG. 17 is a sectional view taken across a line F17-F17
shown in FIG. 18, showing a valve timing control apparatus
according to a fifth embodiment of the present invention.
[0023] FIG. 18 is a sectional view taken across a line F18-F18
shown in FIG. 17.
[0024] FIG. 19 is an enlarged view of a main portion of FIG.
17.
DETAILED DESCRIPTION OF THE INVENTION
[0025] FIG. 1 shows an internal combustion engine equipped with a
valve timing control apparatus or system according to a first
embodiment of the present invention. FIG. 2 shows the valve timing
control apparatus in section taken across a line F2-F2 in FIG. 1
whereas FIG. 1 is a sectional view taken across a line F1-F1 shown
in FIG. 2. In this embodiment, the present invention is applied to
an intake valve's side. However, it is possible to apply the
invention to an exhaust valve's side.
[0026] A timing sprocket member 1 is driven through a timing chain
61 by a crankshaft62 of the internal combustion engine. Timing
sprocket member 1 serves as a driving rotary member adapted to be
driven by the engine. A camshaft 2 is rotatable relative to
sprocket member 1. A vane member 3 serves as a driven rotary
member. Vane member 3 is fixed at an end of camshaft 2 so that they
rotate as a unit, and which is encased rotatably in sprocket member
1. A hydraulic circuit or hydraulic section 4 is a component of a
hydraulic control section to rotate vane member 3 in a forward
rotational direction and a reverse rotational direction in sprocket
member 1 by the action of oil pressure.
[0027] Timing sprocket member 1 includes a sprocket housing 5, a
front cover 6 and a rear cover 7 which are joined together by
fastening devices which, in this example, are three small-diameter
bolts 8. Housing 5 is a hollow cylindrical member extending axially
from a front open end to a rear open end. Housing 5 includes a
toothed portion 5a formed integrally on the periphery of housing 5,
and arranged to engage in links of timing chain 61. Vane member 3
is enclosed rotatably in housing 5. Front cover 6 is in the form of
a circular disk, and arranged to close the front open end of
housing 5. Rear cover 7 is in the form of an approximately circular
disk and arranged to close the rear open end of housing 5. Front
cover 6, housing 5 and rear cover 7 are joined together to form a
housing encasing the vane member 3, by the before-mentioned bolts 8
extending in the axial direction of camshaft 2.
[0028] Housing 5 is approximately in the form of a hollow cylinder
open at both ends. Housing 5 includes a plurality of partitions 10
projecting radially inwards from an inside circumferential wall
surface of cylindrical housing 5. Projecting partitions 10 serve as
shoes. In this example, the number of partitions 10 is three, and
these three partitions 10 are arranged at angular intervals of
approximately 120.degree., circumferentially in the inside
circumference of housing 5. Each partition 10 extends axially from
the front open end to the rear open end of housing 5, and has an
approximately trapezoidal cross section as viewed in FIG. 2. In
this example, housing 5 includes a front end surface which is
substantially flat and which is joined with front cover 6, and a
rear end surface which is substantially flat and which is joined
with rear cover 7. Each partition 10 of this example includes a
front end surface which is flat, and flush and continuous with the
flat front end surface of housing 5, and a rear end surface which
is flat, and flush and continuous with the flat rear end surface of
housing 5. A bolt hole 11 is formed approximately at the center of
each partition 10. Each bolt hole 11 passes axially through one of
partitions 10, and receives one of the axially extending bolts 8.
Each partition 10 includes an inner end surface which is sloping in
conformity with the outer shape of a later-mentioned vane rotor
(14) of vane member 3. A retaining groove 11 extends axially in the
form of cutout in the inner end surface of each partition at a
higher position. A U-shaped seal member 12 is fit in each retaining
groove 11, and urged radially inwards by a leaf spring (not shown)
fit in the retaining groove 11.
[0029] Front cover 6 includes a center bolt hole 6a having a
relatively large inside diameter; and three bolt holes 6b each
receiving one of the axially extending bolts 8. These three bolt
holes 6b are arranged around the center bolt hole 6a.
[0030] Rear cover 7 includes a center bearing hole 7a supporting
rotatably a front end portion 2a of camshaft 2; and three threaded
holes 7b into which three bolts 8 are screwed, respectively.
[0031] Camshaft 2 is rotatably supported through a cam bearing 13
on an upper portion of a cylinder head S of the engine. Camshaft 2
includes one or more cams formed integrally on the outer
circumference of camshaft 2 at predetermined positions. Each cam is
arranged to open an intake valve of the engine through a valve
lifter.
[0032] Vane member 3 of this example is a jointless single member
made of sintered alloy. Vane member 3 includes a central vane rotor
14 and a plurality of vanes 15 projecting radially outwards. In
this example, the number of vanes 15 is three, and these three
vanes 15 are arranged at angular intervals of approximately 1200
circumferentially around vane rotor 14. Vane rotor 14 is annular
and includes a center bolt hole 14a at the center. Vane member 3 is
fixed to a front end 2a of camshaft 2 by a cam bolt 16 extending
axially through the center bolt hole 14a.
[0033] The three vanes 15 are approximately rectangular, and these
vanes 15 are unequal in circumferential width L measured in the
circumferential direction around a common center axis of a rotary
mechanism composed of vane member 3 and timing sprocket 1. A first
one of the three vanes 15 is a smaller vane having a smallest
circumferential width L1, a second one is a medium vane having an
intermediate circumferential width L2 greater than L1, and a third
one is a larger vane having a largest circumferential width L3
greater than L2. These vanes are formed so that a weight balance is
attained as a whole of the vane member 3. The three vanes 15 of
vane member 3 and the three partitions 10 of timing sprocket member
1 are arranged alternately in the circumferential direction around
the center axis, as shown in FIG. 2. Namely, each vane 15 is
located circumferentially between adjacent two of the partitions
10. Each vane 15 includes a retaining groove receiving a U-shaped
seal member 16 in sliding contact with the inside cylindrical
surface of housing 5, and a leaf spring (not shown) for urging the
seal member 16 radially outward and thereby pressing the seal
member 16 to the inside cylindrical surface of housing 5.
[0034] Each vane 15 includes a first side surface facing in the
rotational direction of vane member 3 and a second side surface
facing in a rotational direction opposite to the rotational
direction. In the case of the smaller vane having the smallest
width L1, the retaining groove is formed at a middle of an outer
end of the vane. In the medium vane 15 having the intermediate
width L2, the retaining groove is formed in the outer end of the
vane at a position closer to the first side surface of the vane. In
the greater vane 15 having the greater width L3, the retaining
groove is formed in the outer end of the vane at a position closer
to the second side surface of the vane.
[0035] An advance fluid pressure chamber 17 and a retard fluid
pressure chamber 18 are formed on both sides of each vane 15.
Advance pressure chamber 17 is defined between the second side
surface of each vane 15 and the adjacent partition 10 to which the
second side surface of the vane faces. Retard pressure chamber 18
is defined between the first side surface of each vane 15 and the
adjacent partition 10 to which the first side surface of the vane
faces.
[0036] Hydraulic circuit 4 includes a first fluid pressure passage
or advance fluid pressure passage 19 leading to the advance
chambers 17 to supply and drain an advance fluid pressure of an
operating oil to and from advance chambers 17; a second fluid
pressure passage or retard fluid pressure passage 20 leading to the
retard chambers 18 to supply and drain a retard fluid pressure of
the operating oil to and from retard chambers 18, and a directional
control valve or selector valve 23 connecting the advance pressure
passage 17 and retard pressure passage 18 selectively with a supply
passage 21 and a drain passage 22. In this example, control valve
23 is a solenoid valve. A fluid pump 25 is connected with supply
passage 21, and arranged to draw the hydraulic operating fluid or
oil from an oil pan 24 of the engine, and to force the fluid into
supply passage 21. Directional control valve 23 of this example is
a one-way type pump. Drain passage 22 is connected to oil pan 24,
and arranged to drain the fluid to oil pan 24. At least one of
directional control valve 23 and pump 25 can serve as an actuating
device for forcing one of first and second movable (lock) members
backwards, as mentioned later.
[0037] Advance fluid pressure passage 19 includes a first passage
section 19a, a second passage section 19b serving as a pressure
chamber, and three branch passages (not shown) connecting second
passage section 19b, respectively, with the three advance chambers
17. Passage section 19a extends in cylinder head S, and further
extends axially in camshaft 2, to second passage section 19b.
Second passage section 19b is formed by vane member 3, at a
position between vane rotor 14 and the front end of camshaft 2. The
three branch passages are formed in vane member 3 and extend
radially in vane member 3.
[0038] Retard fluid pressure passage 20 includes a first passage
section 20a extending in cylinder head S and axially in camshaft 2,
and a second passage section 20b formed in vane rotor 14. Second
passage section 20b is approximately L-shaped, and connected with
each retard pressure chamber 18.
[0039] Directional control valve 45 of this example is a solenoid
valve having four ports and two positions. A valve element inside
the control valve 45 is arranged to alter the connection between
the passages 19 and 20 and the supply and drain passages 21 and
22.
[0040] A controller 26 produces a control signal, and controls the
solenoid control valve 45 by sending the control signal to the
valve 45. A sensor section 63 collects input information on
operating conditions of the engine and a vehicle in which this
timing control apparatus is installed. Input information is
supplied to controller 26. The sensor section 63 of this example
includes a crank angle sensor 64 for sensing a speed of the engine,
an air flowmeter 65 for sensing an intake air quantity of the
engine, a cam angle sensor 66 and an input device 67, such as an
ignition switch or a vehicle main switch, to sense a start of the
engine. Controller 26 determines a current operating state from the
signals from crank angle sensor 64 and air flowmeter 65, and
further determines a relative rotational position between sprocket
member 1 and camshaft 2. Controller 26 serves as a main component
of a control section in the hydraulic control section which
includes the hydraulic section 4 and the control section.
[0041] Vane member 3, advance and retard chambers 17 and 18 and
hydraulic circuit 4 form a varying mechanism varying the relative
rotational position between the driving rotary member such as
sprocket member 1 and the driven rotary member such as vane member
3. Sprocket member 1 and vane member 3 form a valve timing control
rotary mechanism. A control section for controlling the relative
displacement between the driving rotary member such as sprocket
member 1 and the driven rotary member such as vane member 3 may
include at least one of the hydraulic circuit 4 and controller 26.
The control section may further include the sensor section 63.
Control valve 23 or hydraulic circuit 4 including control valve 23
serves as a hydraulic control section.
[0042] A lock mechanism or restraint mechanism is a mechanism to
prevent and allow the relative rotation between the driving rotary
member that is sprocket member 1 in this example and the driven
rotary member that is vane member 3 in this example. The lock
mechanism is provided between the sprocket member 1 and vane member
3. In this example, the lock mechanism is formed between housing 5
and a portion of vane rotor 14 adjacent to the smaller vane 15
having the circumferential width L1. The lock mechanism includes a
first lock or restraint unit or mechanism 27 provided in vane rotor
14 of vane member 3 and a second lock or restraint unit or
mechanism 28 provided in housing 5 of sprocket member 3.
[0043] First lock or restraint unit or mechanism 27 (which is a
driven-side lock unit in this example), as shown in FIGS.
1.about.3, includes a first (or driven-side) movable lock member
30. First lock member 30 is slidably received in a first slide hole
29 formed in vane member 3. In this example, first slide hole 29 is
formed in a boss portion 14b formed in vane rotor 14. Boss portion
14b is located on an advance chamber's side of the smaller vane 15
having the smallest width L1. As shown in FIG. 2, boss portion 14b
is located circumferentially between the smaller vane 15 and the
adjacent partition 10 defining and bounding the advance chamber 17
for the smaller vane 15. First slide hole 29 extends radially in
vane member 3, and first lock member 30 is movable radially in the
radially extending first slide hole 29. First lock member 30 is a
cup-shaped member in the form of a hollow cylinder having one end
closed. First lock member 30 includes a circumferential wall
extending in a radial outward direction of vane member 3 from an
open inner end to an outer end, and a forward end portion 30a
closing the outer end of the circumferential wall.
[0044] First lock unit 27 on the driven side further includes a
first (or driven-side) spring 31. First spring 31 is disposed
between vane member 3 and first lock member 30 and arranged to bias
or urge first lock member 30 forwards toward the sprocket member 1
in a radial outward direction which may not be an exact direction
of a radius emanating from the center axis of vane member 3. In
this example, first spring 31 is a coil spring disposed between the
inside surface of the forward end portion 30a of first lock member
30 and the bottom of first slide hole 29 formed in boss portion 14b
of vane member 3. An outer portion of first spring 31 is inserted
into the inside of first lock member 30 and enclosed by the
circumferential wall of first lock member 30.
[0045] First slide hole 29 of this example extends radially from
the bottom to an outer end opening into the advance fluid pressure
chamber 17 for the vane 15 of the smallest width L1. The depth of
first slide hole 29 is longer than the length of first lock member
30.
[0046] The forward end portion 30a of first lock member 30 is
exposed to the advance fluid pressure in the advance chamber 17, so
that the advance fluid pressure is applied to the forward end
portion 30a so as to force the first lock member 30 backwards
toward the bottom of first slide hole 29, in a radial inward
direction away from the sprocket member 1. The forward end portion
30a of first lock member 30 of this example has an outside convex
surface which is spherical or shaped like a circular arc in
section. First lock member 30 further includes an outward flange
30b formed at the inner or backward end of the circumferential wall
of first lock member 30. A hollow cylindrical stopper 35 is fixed
in the first slide hole by press fitting, and arranged to limit a
radial outward movement of first lock member 30 by abutting against
the outward flange 30b of first lock member 30, as shown in FIG.
3A. Therefore, stopper 35 and outward flange 30b determines a
forward limit position beyond which first movable member 30 can not
be moved and projected by first spring 31.
[0047] First (or driven-side) spring 31 is set at such a spring
force that first spring 31 can push the first lock member 30
forwards when the hydraulic pressure in the advance fluid pressure
chamber 17 is low without the supply of the advance fluid pressure,
and that first spring 31 is compressed by the advance fluid
pressure in the advance fluid pressure chamber 17, to allow the
first lock member 30 to be moved backwards deeper in the first
slide hole 29 toward the bottom of first slide hole 29 when the
hydraulic pressure in the advance fluid pressure chamber 17 becomes
high by receiving the supply of the advance fluid pressure.
[0048] Second lock or restraint unit or mechanism 28 (which is a
driving-side lock unit in this example), as shown in FIGS.
1.about.3, includes a second (or driving-side) movable lock member
33 (which can serve as a movable abutting member). Second lock
member 33 is slidably received in a second slide hole 32 formed in
sprocket member 1. In this example, second slide hole 32 is formed
in a boss portion 5b formed integrally at the side of the partition
15 defining the advance chamber 17 of the vane 15 having the
smallest width L1. Boss portion 5b is located circumferentially
between the smaller vane 15 and the adjacent partition 10 defining
and bounding the advance chamber 17 for the smaller vane 15. Second
slide hole 32 extends radially in sprocket member 1, and second
lock member 33 is movable radially in the radially extending slide
hole 32. Second lock member 33 is shaped approximately like a cup,
and includes a circumferential wall extending in a radial inward
direction of sprocket member 1, from an outer end to an inner end,
and a forward end portion formed so as to close the inner end of
the circumferential wall.
[0049] Second lock unit 37 on the driving side further includes a
second (or driving-side) spring 34. Second spring 34 is disposed
between sprocket member 1 and second lock member 33, and arranged
to bias or urge second lock member 33 forwards toward the vane
member 3 in a radial inward direction which may not be an exact
direction of a radius converging to the center axis of vane member
3. In this example, second spring 34 is a coil spring disposed
between the inside surface of the forward end portion of second
lock member 33 and the bottom of second slide hole 32 formed in
boss portion 5b of sprocket member 1. An inner portion of second
spring 34 is inserted into the inside of second lock member 33 and
enclosed by the circumferential wall of second lock member 33.
[0050] Second slide hole 32 of this example extends radially inward
from an outer open hole end to an inner open hole end. A spring
retainer 40 is fit and fixed in second slide hole 32. Second spring
34 is disposed between this spring retainer 40 and the forward end
portion of second lock member 33. In this example, spring retainer
40 is composed of two discs each formed with a hole at the center.
Second slide hole 32 includes an outer large-diameter section
extending from the outer hole end, toward the inner hole end of
second slide hole 32; an inner small-diameter section extending
from the inner hole end toward the outer hole end of second slide
hole 32; and an annular step shoulder surface 32a formed between
the large-diameter section and the small-diameter section. Annular
step shoulder surface 32a faces approximately in the radial outward
direction toward the outer hole end. In this example, the spring
retainer 40 is fixed in the large-diameter section of second slid
hole 32 at an intermediate position between the outer hole end and
the step shoulder surface 32a.
[0051] Second lock member 33 includes an outer large-diameter
section slidably fit in the outer large-diameter portion of second
slide hole 32; an inner small-diameter section slidably fit in the
inner small-diameter section of second slide hole 32; and an
annular step shoulder surface 33a formed between the large-diameter
section and the small-diameter section of second lock member 33.
The inner small-diameter section of second lock member 33 is
greater in diameter than the forward end portion 30a of first lock
member 30. Inner small-diameter section includes a forward end
portion as mentioned more in detail later. Annular shoulder surface
33a faces approximately in the radial inward direction. Annular
step shoulder surface 33a serves as a pressure receiving surface of
an outward flange.
[0052] An annular pressure chamber 33b is formed around the second
lock member 33 between the annular shoulder surface 33a of second
lock member 33 and annular shoulder surface 32a of second slide
hole 32. The annular shoulder surface 33a of second lock member 33
is arranged to receive the pressure in the annular pressure chamber
33b. Sprocket member 1 is formed with a communication passage 36
for introducing one of the advance fluid pressure and the retard
fluid pressure to the annular pressure chamber 33b to apply the
hydraulic pressure to second lock member 33 to move the second lock
member 33 backwards. In this example, communication passage 36
extends from a first passage end opening in the retard fluid
pressure chamber 18, through the vane 15, to a second passage end
36a opening into the annular pressure chamber 33, as shown in FIG.
2. Therefore, second lock member 33 is arranged to move backwards
toward the spring retainer 40 serving as the bottom of second slide
hole 32, in the radial outward direction by the application of the
retard fluid pressure introduced from the retard fluid pressure
chamber 18 into the annular pressure chamber 33b. The annular step
shoulder surface 32a faces approximately in the radial outward
direction, and functions to limit radial inward movement of second
lock member 33 by abutting on the annular step shoulder surface 33a
of second lock member 33, and thereby to determine a forward limit
position (or a most projected position) of second lock member 33.
Spring retainer 40 confronts the back end of second lock member 33,
and functions to limit radial outward movement of second lock
member 33 by abutting on the back end of second lock member 33, and
thereby to determine a backward limit position (or a most retracted
position) of second lock member 33.
[0053] Second (or driving-side) spring 34 is set at such a spring
force that second spring 34 can push the second lock member 33
forwards when the hydraulic pressure in the retard fluid pressure
chamber 18 is low without supply of the retard fluid pressure, and
that second spring 34 is compressed by the retard fluid pressure
supplied to the annular pressure chamber 33b from the retard fluid
pressure chamber 18, to allow the second lock member 33 to be moved
backwards deeper in the second slide hole 32 toward the bottom of
second slide hole 32 when the hydraulic pressure in the annular
pressure chamber 33b becomes high by receiving the supply of the
retard fluid pressure. The spring force of second spring 34 is set
greater than the spring force of first spring 31.
[0054] The forward end portion of second lock member 33 includes a
disk-shaped wall 37 shaped like a circular disk, and a (lock)
recess 38 depressed backwards to the bottom formed by the
disk-shaped wall 37. On the other hand, the forward end portion of
first lock member 30 is in the form of a (lock) projection which
can engage in the recess 38 of second lock member 33. Forward end
portion of second lock member 33 includes the above-mentioned
disk-shaped wall 37 forming the bottom of recess 38, and separating
the inside cavity of the circumferential wall of second lock member
33 and the inside of recess 38. The inside diameter of recess 38
(which is a circular recess in this example) is set greater than
the outside diameter of the forward end portion (projection) 30a of
first lock member 30. Therefore, the forward end portion 30a of
first lock member 30 is loosely fit in recess 38 of second lock
member 33 in a lock state in which the forward end portion 30a of
first lock member 30 is received in recess 38 of second lock member
33 as shown in FIG. 2 and FIGS. 3A and 3B.
[0055] Forward end portion 30a of first lock member 30 includes an
outside circumferential side surface which abuts against an inside
circumferential side surface of recess 38 of forward end portion of
second lock member 33, and thereby prevents rotation of vane member
3 relative to sprocket member 1 when the first and second lock
members 30 and 33 are in the lock state. The outside
circumferential side surface of forward portion 30a of first lock
member 30 extends along the axis of first lock member 30, and the
inside circumferential side surface of recess 39 of second lock
member 33 extends along the axis of second lock member 33. In this
example, the outside circumferential side surface of forward
portion 30a of first lock member 30 is a cylindrical surface, and
the inside circumferential side surface of recess 38 of second lock
member 33 is also a cylindrical surface.
[0056] The forward end portion of second lock member 33 is further
formed with a guide surface 39 serving as guide means or retracting
means for guiding first and second lock members 30 and 33 into the
lock state in which the projection (30a) of first lock member 30 is
fit loosely in the recess 38 of second lock member 33. In this
example, the guide surface 39 is in the form of an annular tapered
surface or conical surface.
[0057] In the state in which no hydraulic pressures are supplied to
the advance and retard fluid pressure chambers 17 and 18 for
example at the time of engine stoppage, the vane member 3 is set at
a predetermined (lockable) rotational position (which is the most
retarded position in this example) as shown in FIGS. 1, 2, 3A and
3B. In this state, the vane 15 having the greatest circumferential
width L3 abuts against the adjacent partition 10 of sprocket member
1 in the retard rotational direction. In this state, the vane 15 of
the medium width L2 is spaced by a minute clearance C from the
adjacent partition 10 in the retard rotational direction. The vane
15 having the medium width L2 does not abut on the adjacent
partition 10. Similarly, the vane 15 of the smallest width L1 is
spaced by a minute clearance C from the adjacent partition 10
without abutting on the partition 10. When vane member 3 is located
at this predetermined (lockable or most retarded) position relative
to sprocket member 1, the forward end portion 30a of first lock
member 30 can enter the recess 38 of second lock member 33, and the
first and second lock members 30 and 33 can shift into the lock
state.
[0058] The relative positions of first and second lock members 30
and 33 relative to each other are set in the following manner. When
second lock member 33 is located at the backward limit (most
retracted) position and first lock member 30 is located at the
forward limit (most projected) position, a part of the forward end
portion 30a of first lock member 30 is engaged in the lock recess
38 of second lock member 33, and first and second lock member are
said to be in a standby or unlock ready state.
[0059] The minute clearance C of each of these vanes 15 (of the
medium and smallest widths) is determined in accordance with the
average torque, sliding friction and the size of the vane 15. These
minute clearances C are effective for preventing adhesion of the
vanes to partitions 10 and thereby improving the response speed of
vane rotation. It is possible set a clearance for each of all the
three vanes 15 so that, in the predetermined lockable rotational
position, each of all the vanes is set apart from the corresponding
partition 10.
[0060] The thus-constructed valve timing control apparatus is
operated as follows: At the time of start of the engine, controller
26 produces the control signal, and solenoid directional control
valve 23 is set to the position to connect the supply passage 21
with second (retard) fluid passage 20 and connect the drain passage
22 with first (advance) fluid passage 19. Therefore, the fluid
pressure produced by pump 25 is supplied through second passage 20
to retard chambers 18 whereas the advance chambers 17 are held in
the low pressure state with no supply of hydraulic pressure as in
the engine stop state.
[0061] Therefore, first lock member 30 projects forwards in the
radial outward direction by the force of first spring 31, as shown
in FIGS. 3A and 3B, until the forward limit position is reached by
abutment of flange 30b against the inner end of stopper 35. On the
other hand, second lock member 33 projects forwards in the radial
inward direction by the force of second spring 34 until the forward
limit position is reached by abutment of flange 33a against
shoulder surface 32a since the hydraulic pressure inside the retard
chambers 18 is not increased sufficiently. Therefore, the forward
end portion 30a of first lock member 30 is engaged in the recess 38
of second lock member 33. In this state, the outside
circumferential surface of forward end portion 30a of first lock
member 30 abuts against the inner side surface of lock recess 38 of
second lock member 33, and thereby prevents the relative rotation
between vane member 3 and sprocket member 1.
[0062] Therefore, as shown in FIG. 2 and FIG. 3A, the wide vane
having the greatest width L3 abuts against the adjacent partition
10 on the advance chamber's side, and the first and second lock
members 30 and 33 are put in the lock state to prevent the relative
rotation between vane member 3 and sprocket member 1.
[0063] In this state, the relative rotational angle of camshaft 2
relative to timing sprocket member 1 is held on the retard side,
and the opening and closing timings of the intake valve are
controlled to the retard side. By so doing, this valve timing
control system can improve the combustion efficiency by utilizing
inertial intake air, and improve the engine cranking performance.
Moreover, the lock mechanism of first and second lock members 30
and 33 in the lock state can prevent vibrations or flapping of vane
member 3 due to alternating torque of camshaft 2 between the
positive and negative sides in the engine starting operation.
[0064] In an idling operation after an engine start, for example,
the solenoid directional control valve 23 is held in the existing
state and the hydraulic pressure in retard fluid pressure chambers
18 becomes higher. When the hydraulic pressure in retard chambers
18 becomes higher than the level of the alternating torque, the
flange portion 33a of second lock member 33 is acted upon by the
fluid pressure introduced into the pressure chamber 33b through
communication passage 36; and the second lock member 33 compresses
second spring 34 and moves backwards against the spring force of
second spring 34.
[0065] However, in this state, the first lock member 30 is still
held at the forward limit position or most projected position by
the force of first spring 31. Therefore, the forward end portion
30a of first lock member 30 at the forward limit position is still
located in the lock recess 38 of second lock member 33 at the
backward limit position or most retracted position, as shown in
FIGS. 4A and 4B. In this state (called standby state or unlock
ready state) shown in FIGS. 4A and 4B, the first and second lock
members 30 and 33 still remain engaged with each other and prevent
the rotation of vane member 3 relative to sprocket member 1. In
this example, the length of the abutment of forward end portion 30a
of first lock member 30 against the lock recess 38 is approximately
equal to or lower than 0.2 mm. Thus, in this standby state, the
vane member 3 is not allowed to rotate freely but locked or
restrained. Vane member 3 is held stably at the position shown in
FIGS. 4A and 4B since the hydraulic pressure in the retard pressure
chambers 18 is increased.
[0066] When the vehicle starts moving, and the engine operating
point enters a predetermined low speed, low load region, the
controller 26 sends the control signal and switches the directional
control valve 23 to the state connecting the supply passage 21 with
first (advance) passage 19, and the drain passage 22 with second
(retard) passage 20. Therefore, the fluid is returned from retard
chambers 18 through second passage 20 and drain passage 22 to oil
pan 24, and the hydraulic pressure in retard chambers 18 becomes
low. On the other hand, the hydraulic pressure in advance chambers
17 becomes high by the supply of the fluid pressure.
[0067] Therefore, second lock member 33 tries to move forwards by
the force of second spring 34 to the forward limit position with a
decrease of the hydraulic pressure in the retard pressure chambers
18. However, the wall 37 of second lock member 33 receives the
hydraulic pressure of the advance chambers 17, and this hydraulic
pressure overcomes the spring force of second spring 34, so that
second lock member 33 is held at the backward limit position or
most retracted position, as shown in FIGS. 5A and 5B. On the other
hand, first lock member 30 moves backwards toward the bottom of
first slide hole 29 against the force of first spring 31 by
receiving the hydraulic pressure in advance chambers 17. In this
case, the forward end portion 30a of first lock member 30 in the
standby state of FIGS. 4A and 4B can disengage from lock recess 38
of second lock member 33 rapidly, and the lock mechanism is
unlocked or released immediately. Therefore, vane member 3 rotates
in the clockwise direction from the rotational position shown in
FIGS. 4A and 4B, to the rotational position shown in FIGS. 5A and
5B, intermediate between the most retarded position and the most
advanced position.
[0068] When the engine operating point shifts into a medium speed,
medium load region, and the supply pressure to advance chambers 17
becomes high, the vane member 3 is further rotated in the advance
direction (that is, the, clockwise direction as viewed in FIGS. 6A
and 6B) until the greater vane 15 abuts against the adjacent
partition 15 on the retard chamber's side as shown in FIG. 6A and
the most advanced position shown in FIGS. 6A and 6B is reached by
vane member 3. Therefore, camshaft 2 is rotated relative to timing
sprocket member 1 in the advance direction, and the opening and
closing timings of the intake valve are controlled to the advance
side. Therefore, the valve timing control system can decrease the
pumping loss of the engine and thereby improve the engine
output.
[0069] When the engine operating point further shifts into a high
speed region, the controller 26 switches the solenoid valve 23 to
the state connecting the supply passage 21 with second passage 20,
and the drain passage 22 with first passage 19 as in the idling
operation. By so doing, controller 26 decreases the hydraulic
pressure in advance chambers 17 and increases the hydraulic
pressure in retard chambers 18. Therefore, vane member 3 is
returned in the counterclockwise direction to the most retarded
position shown in FIG. 4A, and the camshaft 2 is rotated in the
retard direction relative to timing sprocket member 1, so that the
opening and closing timings of the intake valve are controlled to
the retard side. Thus, the valve timing control system can improve
the intake charging efficiency and improve the engine output.
[0070] In this case, first lock member 30 is projected forwards
toward the forward limit position by the force of first spring 31.
However, second lock member 33 is retracted backwards to the
backward limit position in second slide hole 32 by the force of the
retard fluid pressure in retard chambers 18 introduced into the
annular pressure chamber 33b through communication passage 36. When
vane member 3 is rotated to the retard side with the first lock
member in the forward limit position and the second lock member in
the backward limit position, the projecting end portion 30a of
first lock member 30 in the projected state abuts against the
tapered guide surface 39 and moves backward by being pushed by
guide surface 39. In this way, the forward end portion 30a of first
lock member 30 slides on the tapered guide surface 39 of second
lock member 33 and finally fits into the lock recess 38 of second
lock member 33.
[0071] In the stop state of the engine, the vane member 3 is
restored to the most retarded position shown in FIGS. 2 and 3A by
the idling operation before the stoppage of the engine. That is,
the vane member 3 returns to the most retarded position while
fluctuating by the effect of alternating torque. On the other hand,
with a decrease in the hydraulic pressure in retard chambers 18,
the second lock member 33 is projected forward to the forward limit
position, and the forward end portion 30a of first lock member 30
engages in the recess 38 of second lock member 33 by being guided
by guide surface 39.
[0072] If the engine is stopped by an engine stall without
experiencing the idling operation, the vane member 3 is rotated by
the effect of the alternating torque to the most retarded position,
and the first lock member 30 engages into the lock recess 38 of
second lock member 33 automatically under the guidance of guide
surface 39.
[0073] At the same time with the engine stall, the oil pump 25 is
stopped, and stops the supply of hydraulic pressure to the advance
and retard chambers. Therefore, the first and second lock members
30 and 33 are both projected forwards by first and second springs
31 and 34, respectively. When the vane member 3 is rotated from the
position shown in FIG. 6A toward the position shown in FIG. 4A by
the action of the alternating torque, the first lock member 10
remaining in the projected position collides against the second
lock member 33 in the projected position. In this case, the forward
end portion 30a of first lock member 30 abuts against the annular
tapered guide surface 39, and moves backwards gradually by being
pushed by the guide surface 39 against the force of first spring 31
until the forward end portion 30a of first lock member 30 enters
the lock recess 38 of second lock member 33.
[0074] Therefore, at the time of a restart of the engine, the vane
member 3 is locked against rotation relative to sprocket member 1,
and the engine can be started smoothly as in the normal engine
starting operation.
[0075] By controlling the supply and drainage of the hydraulic
pressure to and from the advance and retard chambers 17 and 18 in
accordance with the engine operating conditions, this valve timing
control system can hold the vane member 3 at a desired intermediate
rotational position as shown in FIG. 5A.
[0076] Thus, in addition to the valve timing control mechanism (1,
3 etc.) capable of controlling the valve timing by controlling the
hydraulic pressures in advance and retard chambers 17 and 18; the
valve timing control system according to this embodiment has the
lock mechanism including the first and second movable lock members
30 and 33 which are arranged to lock the vane member adequately
without being erroneously released. Even if an air pressure acts in
a starting operation of the engine after long term stoppage, and
pushes the second lock member backwards, the engagement between the
first and second lock members is not canceled as shown in FIGS. 4A
and 4B. Thus, the first and second lock members may be brought to
the standby state, but the vane member is not released by the air
pressure. The air pressure can only serve as a standby pressure or
an unlock preparing pressure. The air pressure cannot serve as a
control start pressure to unlock the lock mechanism.
[0077] Thereafter, the lock mechanism is unlocked when the solenoid
valve 23 is switched, and the hydraulic fluid pressure (control
start pressure) is supplied to advance chambers 17. In this case,
the first and second lock members are already in the standby state
in which the contact or abutting area between the first and second
lock members is reduced significantly as compared to the lock
state. Consequently, the engagement between the first and second
lock members can be canceled smoothly and quickly, by the supply of
the hydraulic pressure to advance chambers 17.
[0078] Therefore, this lock mechanism can ensure a reliable and
quick unlocking operation, and prevent flapping noises of the vane
member 3 by preventing the first and second lock members from being
unlocked erroneously by an air pressure. This lock mechanism can
prevent an undesired hanging state in which the forward end portion
of first lock member 30 is not disengaged from the lock recess 38
completely, but caught by lock recess 38 of second lock member
33.
[0079] FIGS. 7.about.10 show a valve timing control apparatus
according to a second embodiment of the present invention. In the
second embodiment, second lock member 33 is arranged to move
backwards against the spring force of second spring 34 by the
effect of a centrifugal force, instead of the hydraulic pressure in
retard chambers 18. The spring force of second spring 34 is set
smaller than a centrifugal force of a predetermined magnitude
produced in housing 5 during rotation. In this example, second
spring 34 is so set that second spring 34 starts compression by the
centrifugal force of housing 5 when the engine rotational speed
becomes equal to or higher than an idle speed of about 900 rpm.
[0080] An air release passage 41 is formed in the circumferential
wall of housing 5 of sprocket member 1. Air release passage 41
connects the annular pressure chamber 33b with the outside, and
thereby opens the inside of the annular pressure chamber 33a to the
atmosphere to allow free movement of second lock member 33 in
second slide hole 32. Therefore, second lock member 33 can compress
the second spring 34 and move smoothly backwards by receiving a
centrifugal force of a predetermined magnitude or more during
engine operation. In this embodiment, the communication passage 36
connecting the retard chamber 18 with the second slide hole 32 is
eliminated.
[0081] When the centrifugal force of housing 5 is still weak after
a start of the engine, the second lock member 33 is held projected
forwards by second spring 34, and engaged with first lock member
30.
[0082] Thereafter, when the engine speed enters an idling operation
of about 900 rpm, the centrifugal force of housing 5 increases, and
forces the second lock member 33 backwards into second slide hole
32 by compressing the second spring 34 gradually as shown in FIG.
8. On the other hand, first lock member 30 is held at the forward
limit position or most projected position by the force of first
spring 31. Therefore, the forward end portion 30a of first lock
member 30 is still in the lock recess of 38 of second lock member
33, and the side surface of forward end portion 30a of first lock
member 30 abuts against the inner side surface of lock recess 38 of
second lock member 33 with a reduced contact or abutting area. In
this state (that is, the standby state), the first and second lock
members 30 and 33 still engage with each other in the smaller
contact area, and thereby prevents the vane member 3 from rotating
relative to sprocket member 1. Moreover, the supply of hydraulic
pressure to retard pressure chambers 18 is still continued, and
hence the vane member 3 is held at the most retarded position shown
in FIG. 8.
[0083] When the engine speed increases from the low speed low load
region above 900 rpm to the medium speed medium load region, the
directional control valve 23 is switched by controller 26 to the
state to supply the hydraulic pressure to the advance chambers 17
instead of the retard chambers 18, so the hydraulic pressure in
retard chamber 18 decreases and the hydraulic pressure in advance
chambers 17 increases. Therefore, second lock member 33 is held at
the backward limit position by the hydraulic pressure acting on the
wall 37, and the first lock member 30 moves backwards into first
slide hole 29 by the hydraulic pressure of the advance chambers 17
acting on the forward end portion 30a.
[0084] Thus, first lock member 30 can disengage quickly from the
standby state shown in FIG. 8, and allow the relative rotation of
vane member 3. Therefore, vane member 3 rotates in the clockwise
direction as viewed in FIG. 8 or the advance direction, from the
most retarded position of FIG. 8, to an intermediate position shown
in FIG. 9 or to the most advanced position shown in FIG. 10. Thus,
camshaft 2 is rotated in the advance direction with respect to
timing sprocket member 1, and the same effects as in the first
embodiment can be obtained.
[0085] In this state, second lock member 33 receives the
centrifugal force, and the hydraulic pressure in advance pressure
chambers 17 at the forward end portion including wall 37.
Therefore, second lock member 33 is retracted to the backward limit
position as shown in FIGS. 9 and 10.
[0086] Thus, in the second embodiment, by utilizing the centrifugal
force to move second lock member 33 backwards, the lock mechanism
is simplified to the advantage of cost reduction.
[0087] FIGS. 11.about.14 show a valve timing control apparatus or
system according to a third embodiment of the present invention. In
the third embodiment, the first and second movable lock members 30
and 33 are in the form of a pin. In this embodiment, the first and
second lock members or lock pins 30 and 33 are identical in size
and shape. Each of first and second lock pins 30 and 33 includes a
flange or slide portion 30c or 33c formed integrally at the back
end of the pin.
[0088] Slide holes 29 and 32 are formed so that the axes of slide
holes 29 and 32 overlap each other in the circumferential direction
of vane member 3. Each slide hole 29 or 32 includes a front small
diameter section, a rear large diameter section, and a step
shoulder surface 29a or 32a formed between the small and large
diameter sections. The flange 30c or 33c of each lock pin 30 or 33
is slidably received in the rear large diameter section of the
corresponding slide hole 29 or 32. The step shoulder surface 29a or
32a of each slide hole 29 or 32 faces backwards toward the bottom
of the slide hole, and limits the forward movement of the
corresponding lock member 30 or 33 by abutting against the flange
30c or 33c of the lock pin, thereby to determine the most projected
position of the lock member.
[0089] First lock member 30 is moved backwards by the hydraulic
pressure in advance chambers 17. When first lock member 30 is at
the backward limit position or most retracted position, the forward
end of first lock member 30 (which is substantially flat in this
example) is flush with the outer surface in which first slide hole
29 is opened. This outer surface is substantially flat in this
example. On the other hand, second lock member 33 is retracted
backwards by the hydraulic pressure in the retard pressure chamber
18 introduced to the pressure chamber 33b, and the hydraulic
pressure in the advance chamber 17 acting on the forward end
portion of second lock member 33, to the backward limit position or
most retracted position determined by the abutment of second slide
portion 33c against spring retainer 40. In this backward limit
position or most retracted position, the forward end portion of
second lock member 33 projects slightly from the open end of second
slide hole 32 as shown in FIGS. 13 and 14.
[0090] At the most retarded position as shown in FIG. 12, the
forward portions of first and second lock pins 30 and 33 abut
against each other, and thereby the first and second lock pins 30
and 33 prevent rotation of vane member 3 in the clockwise (advance)
direction as viewed in FIG. 12. On the other hand, the vane 15
having the greatest circumferential width L3 abuts on the adjacent
partition 10. Therefore, the vane member 3 is held at the most
retarded position.
[0091] First and second springs 31 and 34 are set small relatively
in diameter. A back end portion of first spring 31 is received in a
spring retaining hole formed in the bottom of first slide hole 29.
A back end portion of second spring 34 is received in a spring
retaining hole formed in a spring retainer 40 defining the bottom
of second slide hole 32. In the other respects, the third
embodiment is substantially identical in construction to the first
embodiment.
[0092] In an engine starting operation, the first lock pin 30 abuts
against second lock pin 33 as shown in FIG. 11 and thereby prevents
rotation of vane member 3. In an idling operation, the hydraulic
pressure supplied from retard chambers 18 to the pressure chamber
33b pushes second lock pin 33 to the backward limit position.
However, the forward end portion of second lock pin 33 is still
projected slightly. Therefore, the forward end portion of second
lock pin 33 abuts against the first lock pin 30 with a smaller
contact (or abutting) area (the standby state).
[0093] When the engine speed is further increased, and the engine
operating point enters the low speed low load region, the solenoid
valve 23 is switched to the state supplying the hydraulic pressure
to advance chambers 17, and the pressure in advance chambers 17
become high. Therefore, as shown in FIG. 13, first lock pin 30 is
retracted backwards in first slide hole 29 by the hydraulic
pressure acting on the forward end of first lock pin 30, and
thereby disengaged from second lock pin 33 held slightly projected
at the backward limit position; and the vane member 3 is rotated in
the advance (clockwise) direction by the hydraulic pressure in
advance chambers 17. In a medium speed high load region, for
example, the hydraulic pressure in advance chambers 17 is further
increased, and the vane member 3 is held at the most advanced
position at which the vane 15 having the greatest circumferential
width L3 abuts on the adjacent partition 10 as shown in FIG.
14.
[0094] In the high speed high load region, the operating oil is
drained from advance chambers 17 and the vane member 3 is rotated
in the retard (counterclockwise) direction. However, immediately
after this switching operation, the hydraulic pressure is supplied
to retard chambers 18 and the hydraulic pressure in advance
chambers 17 is not abruptly decreased. Therefore, first lock pin 30
is not projected so much, and second lock pin 33 is slightly
retracted, so that the vane member 3 can rotate to the most
retarded position without interference between first and second
lock pins 30 and 33.
[0095] In the third embodiment, the first and second lock members
30 and 33 are identical to each other, so that the manufacturing
cost can be reduced. The valve timing control apparatus according
to the third embodiment can improve the fuel consumption and other
engine performance as in the preceding embodiments.
[0096] FIGS. 15 and 16 show a valve timing control apparatus or
system according to a fourth embodiment of the present invention.
In the fourth embodiment, first and second lock members 30 and 33
are arranged in the axial direction instead of the radial
direction.
[0097] An axial first slide hole 29 is formed in the vane 15 having
a larger circumferential width. First slide hole 29 extends in the
axial direction along the center axis of vane member 3. First slide
hole 29 is a stepped hole having a larger section and a smaller
section having a cross sectional size smaller than the cross
sectional size of the larger section. An axial second slide hole 32
is formed in a thick wall portion of rear plate 7 of timing
sprocket member 1 at a position confronting the first slide hole
when vane member 3 is at a predetermined (most retarded) rotational
position. Second slide hole 32 extends in the axial direction along
the common center axis of vane member 3 and timing sprocket member
1. A back end of second slide hole 32 is closed by a spring
retainer 40. Spring retainer 40 of this example is composed of two
thin circular disks. Spring retainer 40 is fixed to rear plate 7 so
as to form the bottom of second slide hole 32. An air release hole
is formed approximately at the center of each disk of spring
retainer 40 to ensure smooth movement of second lock member 33 in
second slide hole 32.
[0098] First lock member 30 is a cup-shaped member including a
cylindrical wall extending from a backward end to a forward end
toward rear cover 7, and a forward end portion 30a closing the
forward end of the cylindrical wall. Second lock member 33 is a
cup-shaped member including a cylindrical wall extending from a
backward end to a forward end toward front cover 6, and a forward
end portion closing the forward end of the cylindrical wall. First
lock member 30 is slidably received in first slide hole 29 so that
first lock member 30 can move forwards and backwards in the axial
direction. Second lock member 33 is slidably received in second
slide hole 32 so that second lock member 33 can move forwards and
backwards in the axial direction.
[0099] The forward end portion 30a of first lock member 30 is
formed with a (lock) projection which is a cylindrical projection
projected axially, in this example. First lock member 30 further
includes an outward flange formed integrally at the backward end
and arranged to abut on a step 29c formed in first slide hole 29 to
limit the forward movement of first lock member 30. In this
example, first lock member 30 is arranged to receive the advance
fluid pressure to move backwards.
[0100] The forward end portion of second lock member 33 is formed
with a (lock) recess 38 in which the projection formed in forward
end portion 30a of first lock member 30 can be fit loosely. Recess
38 of FIG. 15 is axially depressed. The outside surface of
cylindrical wall of second lock member 33 is stepped, and there is
formed an annular step shoulder surface 33b receiving the hydraulic
pressure in an annular pressure chamber 32a formed around second
lock member 33. The pressure receiving area of the annular step
shoulder surface 33b is set at an appropriate value.
[0101] A groove 42 is formed in the front side surface of vane
member 3 confronting front cover 6, as shown in FIG. 15. This
groove 42 connects the inside of first slide hole 29 with the
outside, and thereby ensures smooth movement of first lock member
30 in first slide hole 29 by releasing a back pressure of first
lock member 30.
[0102] A communication passage 36 extends from one of retard
chambers 18 to the annular pressure chamber 32a to supply the
hydraulic pressure from the retard chamber 18 to pressure chamber
32a. The hydraulic pressure in the advance chambers 17 is
introduced into the interspace between the forward end portion of
second lock member 33 and the forward end portion 30a of first lock
member 30. In the other respects, the fourth embodiment is
substantially identical to the first embodiment.
[0103] Therefore, the fourth embodiment can provide the same
effects as the first embodiment. In an engine starting operation,
the hydraulic pressure in annular pressure chamber 33b is not
increased yet, and the second lock member 33 is held engaged with
first lock member 30. In an idling operation, the hydraulic
pressure supplied in pressure chamber 33b is increased, and second
lock member 33 is retracted backwards to the backward limit
position. In this state (that is, the standby state), the first and
second lock members 30 and 33 engage with each other with a reduced
contact (or abutting) area to prevent the relative rotation of vane
member 3 relative to sprocket member 1.
[0104] When, for example, the engine speed is increased into the
low speed low load region, the solenoid valve 23 is switched to the
state supplying the hydraulic pressure to advance chambers 17, and
the first lock member 30 is retracted by the hydraulic pressure in
advance chambers 17 to the backward limit position against the
force of first spring 31. Therefore, first lock member 30
disengages from second lock member 33, and vane member 3 is rotated
in the advance (clockwise) direction by the hydraulic pressure in
advance chambers 17. When the engine operating point is further
shifted from the low speed low load region to the medium speed high
load region, the hydraulic pressure in advance chambers 17 is
further increased, and the vane member 3 is rotated to the most
advance position.
[0105] Thus, the timing control system of the fourth embodiment can
improve the engine performance sufficiently in accordance with the
engine operating conditions. Furthermore, even if, in the engine
starting operation, air is compressed and the air pressure in
pressure chamber 32a acts on second lock member 33 and moves second
lock member 33 to the backward limit position, the first and second
lock members 30 and 33 remain engaged with each other in the
standby state, and prevent undesired noises due to flapping
movement of vane member 3.
[0106] In the fourth embodiment, first and second lock members 30
and 33 are arranged axially along the axis of camshaft 2.
Therefore, the lock mechanism receives no influence of the
centrifugal force of housing 5, and the first and second lock
members 30 and 33 can be moved only by the hydraulic pressures and
the spring forces. Thus, the fifth embodiment can improve the
control response to control the relative rotation between timing
sprocket member 1 and camshaft 2.
[0107] FIGS. 17.about.19 show a valve timing control apparatus or
system according to a fifth embodiment of the present invention. In
the fifth embodiment, first and second lock members 30 and 33 are
arranged in the axial direction as in the fourth embodiment, and
the second lock mechanism is simplified or eliminated unlike the
fourth embodiment.
[0108] A fixed lock member or engaging member 44 is forcibly fit
and fixed in a mounting hole 43 formed in a rear cover 7 at a
position corresponding to the position of the second slide hole 32
of the fourth embodiment. Fixed lock member 44 is U-shaped in cross
section as shown in FIG. 17. A fixed lock recess 38 is formed in
fixed lock member 44. Fixed lock member 44 can serve as an abutting
portion to abut against a movable lock member.
[0109] A movable lock member 30 is approximately identical in
construction to the first lock member 30 of the fourth embodiment.
The forward end portion 30a of movable lock member 30 is tapered so
that the outer circumferential surface is conical, and the cross
sectional size become smaller toward the forward end. Movable lock
member 30 is biased forwards toward the fixed lock recess 38 by a
spring 31.
[0110] A pressure chamber 45 is formed between a step shoulder
surface of a flange 30b formed at the back end of movable lock
member 30 and a step shoulder surface 29c formed in a slide hole
29. The hydraulic pressure in one of the retard chambers 18 is
introduced into this pressure chamber 45 by a first fluid (oil)
passage 46 formed in the larger vane 15, as shown in FIG. 18.
[0111] The hydraulic pressure in one of the advance chambers 17 is
introduced by a second fluid (oil) passage 47 formed in the larger
vane 15, as shown in FIG. 18, into the interspace between the
forward end portion of movable lock member 30 and the fixed lock
recess 38.
[0112] The pressure chamber 45 is designed in the following manner.
The pressure receiving area of the portion receiving the hydraulic
pressure of the retard pressure chamber 18 is smaller than the
pressure receiving are of the forward end portion of lock member 30
receiving the hydraulic pressure of the advance chamber 17; and the
pressure force is slightly greater than the spring force of spring
31.
[0113] Therefore, in the thus-constructed system according to the
fifth embodiment, the hydraulic pressure introduced from the retard
chamber 18 into pressure chamber 45 is not increased so much in an
engine starting operation, and therefore the movable lock member 30
is held engaged in lock recess 38 by spring 31. In an idling
operation after the engine starting operation, the pressure in
pressure chamber 45 becomes higher, and the movable lock member 30
moves backward. However, since the pressure receiving area in the
pressure chamber 45 is set smaller as mentioned before, the movable
lock member 30 does not reach the backward limit position, but the
movable lock member 30 is retained at an intermediate position by
the relationship between the hydraulic pressure in pressure chamber
45 and the spring force of spring 31. In this state (that is, the
standby state) in which the movable lock member 30 is half or
partly retracted, a part of the forward end portion 30a of lock
member 30 is still engaged in lock recess 38, so that lock member
30 is engaged in the fixed lock recess 38.
[0114] When the engine speed is increased into the low speed low
load region, the solenoid valve 23 is switched to the state
supplying the hydraulic pressure to advance chambers 17, and the
movable lock member 30 is retracted, by the hydraulic pressure
supplied from one of the advance chambers 17 to the interspace
between forward end portion 30a and lock recess 38, up to the
backward limit position against the force of spring 31. Therefore,
movable lock member 30 quickly disengages from lock recess 38, and
vane member 3 is rotated in the advance (clockwise) direction by
the hydraulic pressure in advance chambers 17. When the engine
operating point is further shifted from the low speed low load
region to the medium speed high load region, the hydraulic pressure
in advance chambers 17 is further increased, and the vane member 3
is rotated to the most advanced position.
[0115] Thus, the timing control system of the fifth embodiment can
improve the engine performance sufficiently in accordance with the
engine operating conditions. Furthermore, even if, in the engine
starting operation, air is compressed in retard chambers 18 and the
air pressure acts in pressure chamber 45 and moves the lock member
30 backwards, the lock member 30 remains engaged with the lock
recess 38 in the standby state, and prevents undesired noises due
to flapping movement of vane member 3.
[0116] The present invention is not limited to the illustrated
embodiments. Various variations and modifications are possible. For
example, instead of the timing sprocket member 1, the driving
rotary member may be a timing pulley driven through a timing belt
of rubber. This arrangement is advantageous for reduction of
vibrations and noises.
[0117] Moreover, the driving rotary member may be a gear member
driven by a gear mechanism transmitting motion by a combination of
two or more gears. In this case, the driving force can be
transmitted securely. Furthermore, as the gear mechanism, it is
possible to employ scissors gear to reduce backlash noises.
[0118] The valve timing control actuator may be a helical type VTC
actuator, instead of the vane type VTC actuator. In the helical
type, the relative rotational phase is shifted with axial movement
of a tubular toothed member.
[0119] The valve timing control actuator may be electric or
electromagnetic, instead of the hydraulic actuator. In this case,
the relative rotational phase between the driving and driven
members is altered by an electric device such as an electric motor
or an electromagnetic brake.
[0120] It is sufficient to provide only one pair of the advance
fluid pressure chamber and retard fluid pressure chamber. The
number of pairs of the advance and retard chambers may be one, or
may be two, three or four or more. When the number of pairs is
increased especially in the case of the vane type VTC actuator, the
pressure receiving areas are increased, and the response
characteristic of the VTC actuator is improved.
[0121] It is not always necessary to dispose the first and second
lock members in one of the advance and retard fluid pressure
chambers. The first and second lock members may be placed at a
position separate from the advance and retard chambers.
[0122] The first and second lock members may be placed at various
portions of the driving and driven rotary members which are
arranged to rotate relative to each other. The first and second
lock members need not be placed between a member, such as a
sprocket, driven directly by a crankshaft, and a member, such as a
vane member, driving directly a camshaft. At least one of the first
and second lock members may be mounted in a member (such as the
above-mentioned tubular toothed member of the helical VTC actuator)
interposed between the member directly driven by the crankshaft and
the member directly driving the camshaft.
[0123] The first and second lock members may be shaped in various
forms. Either or both of the first and second movable members may
be in the form of a cylindrical pin, a polygonal pin polygonal in
cross section, a ring-shaped member, or a plate-shaped member, or
in the form of a lever.
[0124] Instead of the engagement between the (lock) recess 38 and
the (lock) projection like tenon and mortise, it is possible to
employ various forms for abutting portions of first and second lock
members. When the relative rotation of the rotary mechanism of
driving rotary member and driven rotary member is limited within a
predetermined range, it is possible to arrange the first and second
movable members to prevent the relative rotation between the
driving and driven members only in one direction by abutment
between the first and second movable members in the circumferential
direction, and to prevent the relative rotation in the opposite
direction by the rotary mechanism of the driving and driven
members.
[0125] Instead of a coil spring, it is possible to employ, as at
least one of the first and second bias members, a leaf spring or a
disk spring. The directions of forward and backward movement of the
first and second lock members are not limited to the radial
direction and the axial direction. It is possible to employ various
directions as the directions of the first and second movable
members.
[0126] Instead of the tapered or conical surface around the recess
38, it is possible to employ various forms of the retracting
portion for guiding the first and second lock member into
engagement or into the lock state. For example, a tapered surface
may be formed around the projection of one lock member to be
engaged in the recess of the other lock member. Moreover, it is
possible to form a tapered surface only in a part of the
circumference of the recess 38. In this case, the lock member
formed with the recess is arranged so that the rotation about its
own axis is limited or prevented. Furthermore, it is possible to
employ, as the retracting portion or retracting means, a mechanism
using one or more links, or a cam mechanism or other shaped portion
or device for moving at least one of the first and second lock
members backwards by using a relative rotation between the driving
and driven rotary members, or translating a relative rotation
between the driving and driven rotary members into a linear motion
of at least one of the first and second lock members.
[0127] This application is based on a prior Japanese Patent
Application No. 2005-150320 filed on May 24, 2005. The entire
contents of this Japanese Patent Application No. 2005-150320 are
hereby incorporated by reference.
[0128] 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.
* * * * *