U.S. patent application number 12/349637 was filed with the patent office on 2009-07-16 for valve timing adjuster.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Akihiko TAKENAKA.
Application Number | 20090178635 12/349637 |
Document ID | / |
Family ID | 40758610 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090178635 |
Kind Code |
A1 |
TAKENAKA; Akihiko |
July 16, 2009 |
VALVE TIMING ADJUSTER
Abstract
A valve timing adjuster includes a first rotor, a second rotor,
a spool valve, a connection passage, and a connection check valve.
A spool of the spool valve is displaceable to a first position such
that the first rotor is rotated relative to the second rotor. The
spool is displaceable to a second position to hold the phase of a
camshaft at a full phase. The connection passage connects a first
output port with a second output port of the spool valve when the
spool is positioned at the first position. The connection check
valve of the connection passage allows working fluid to flow from
the second output port toward the first output port.
Inventors: |
TAKENAKA; Akihiko;
(Anjo-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
40758610 |
Appl. No.: |
12/349637 |
Filed: |
January 7, 2009 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 2001/3443 20130101;
F01L 2001/34426 20130101; F01L 1/3442 20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/352 20060101
F01L001/352 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2008 |
JP |
2008-003604 |
Claims
1. A valve timing adjuster for an internal combustion engine having
a crankshaft, a valve, and a camshaft, wherein the adjuster adjusts
valve timing of the valve, which is opened and closed by the
camshaft through torque transmission from the crankshaft, the
adjuster comprising: a first rotor that is rotatable synchronously
with the crankshaft; a second rotor that is rotatable synchronously
with the camshaft, wherein: the first rotor and the second rotor
define therebetween an advance chamber and a retard chamber, which
are arranged circumferentially one after another; the second rotor
is adapted to drive the camshaft relative to the crankshaft in an
advance direction when working fluid is supplied to the advance
chamber; and the second rotor is adapted to drive the camshaft
relative to the crankshaft in a retard direction when working fluid
is supplied to the retard chamber; a spool valve that includes: an
input port, through which working fluid is supplied to the spool
valve from an external fluid supply source; a drain port, through
which working fluid is drained; a first output port, through which
working fluid is output to one of the advance chamber and the
retard chamber; a second output port, through which working fluid
is output to the other one of the advance chamber and the retard
chamber; and a spool that is adapted to be displaceable to a first
position, at which the first rotor is rotated relative to the
second rotor in order to shift a phase of the camshaft relative to
the crankshaft, wherein: the spool is adapted to be displaceable to
a second position, at which the second rotor is pressed against the
first rotor in order to hold the phase of the camshaft at a full
phase, at which the phase is fully shifted; when the spool is
positioned at the first position, the spool valve connects the
first output port with the input port and disconnects the second
output port from the drain port; and when the spool is positioned
at the second position, the spool valve connects the first output
port with the input port and connects the second output port with
the drain port; a connection passage that is provided in the spool,
wherein the connection passage connects the first output port with
the second output port when the spool is positioned at the first
position; and a connection check valve that is provided in the
connection passage, wherein: the connection check valve opens to
allow working fluid to flow from the second output port toward the
first output port when the spool is positioned at the first
position; and the connection check valve closes to limit working
fluid from flowing from the first output port toward the second
output port when the spool is positioned at the first position.
2. The valve timing adjuster according to claim 1, wherein: the
second position is a full retard phase position; the phase of the
camshaft is held fully retarded when the spool is positioned at the
full retard phase position; and when the spool is positioned at the
full retard phase position, the first output port acts as a retard
output port, through which working fluid is output to the retard
chamber, and the second output port acts as an advance output port,
through which working fluid is output to the advance chamber.
3. The valve timing adjuster according to claim 1, wherein: the
second position is a full advance phase position; the phase of the
camshaft is held fully advanced when the spool is positioned at the
full advance phase position; and when the spool is positioned at
the full advance phase position, the first output port acts as an
advance output port, through which working fluid is output to the
advance chamber, and the second output port acts as a retard output
port, through which working fluid is output to the retard
chamber.
4. The valve timing adjuster according to claim 1, wherein: the
drain port opens to atmosphere; the first position and the second
position are arranged adjacent to each other in a direction, in
which the spool is displaceable; the connection passage connects
the first output port with the second output port also when the
spool is positioned at the second position; the connection check
valve opens in a case, where pressure on one side of the connection
passage toward the second output port is higher than pressure on
the other side of the connection passage toward the first output
port when the spool is positioned at the one of the first position
and the second position; and the connection check valve closes in
another case, where pressure on the one side of the connection
passage is lower than pressure on the other side of the connection
passage when the spool is positioned at the one of the first
position and the second position.
5. The valve timing adjuster according to claim 1, further
comprising: an input line that is communicated with the fluid
supply source and the input port; and an input check valve that is
provided to the input line, wherein: the input check valve is
adapted to open to allow working fluid to flow from the fluid
supply source toward the input port; and the input check valve is
adapted to close to limit working fluid from flowing from the input
port toward the fluid supply source.
6. The valve timing adjuster according to claim 1, further
comprising: a controlling unit that controls displacement of the
spool based on a reference phase of the camshaft relative to the
crankshaft, wherein the controlling unit is adapted to learn an
actual phase of the camshaft relative to the crankshaft as the
reference phase under a condition, where the controlling unit
controls the spool to be positioned at the second position.
7. The valve timing adjuster according to claim 6, wherein the
controlling unit learns the actual phase as the reference phase by
controlling the spool to be positioned at the second position after
the engine has started.
8. The valve timing adjuster according to claim 6, wherein the
controlling unit learns the actual phase as the reference phase by
controlling the spool to be positioned at the second position in a
case, where a condition for adjusting the phase of the camshaft to
the full phase is satisfied while the engine rotates at a speed not
higher than a set value.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2008-3604 filed on Jan.
10, 2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a valve timing adjuster for
adjusting a valve of an internal combustion engine, which is opened
and closed by a camshaft of the engine through torque transmission
from a crankshaft of the engine.
[0004] 2. Description of Related Art
[0005] Hydraulic valve timing adjusters have been used widely, each
of which has a housing serving as a driving rotor (first rotor) and
a vane rotor serving as a driven rotor (second rotor). The housing
rotates synchronously with the crankshaft of an internal combustion
engine. The vane rotor rotates synchronously with the camshaft of
the engine. JP-A-2006-177344 corresponding to U.S. Pat. No.
7,124,722 discloses a hydraulic valve timing adjuster having a
housing and a vane rotor. An advance chamber is defined between one
of the shoes of the housing and the corresponding vane of the vane
rotor. A retard chamber is defined between the other shoe and the
vane. The advance and retard chambers are supplied with working
fluid to drive the camshaft relative to the crankshaft in a advance
direction and a retard direction, respectively, and thereby
adjusting valve timing of the valve of the engine.
[0006] Specifically, the valve timing adjuster disclosed in
JP-A-2006-177344 further has a spool valve, which supplies the
working fluid from a fluid supply source to the advance or retard
chamber by shifting a spool of the spool valve to change a phase
(engine phase) of the camshaft relative to the crankshaft. When
working fluid is supplied to one of the advance and retard
chambers, the working fluid discharged from the other one is
utilized again by being supplied to the one of the chambers. Even
if the variable torque transmitted from the camshaft to the vane
rotor increases the volume of the chamber supplied with working
fluid, the increase in volume is filled with the fluid utilized
again. This improves the responsibility of the valve timing
adjuster. It should be noted that the variable torque (torque
reversals) biases the camshaft alternately in the advance and
retard directions relative to the crankshaft.
[0007] The valve timing adjuster disclosed in JP-A-2006-177344
further has an advance output line and a retard output line, each
of which is fitted with a check valve. The spool valve has an input
port, an advance output port, a retard output port, an advance
return port, and a retard return port. The advance and retard
output ports can communicate with the advance and retard chambers,
respectively, through the advance and retard output lines
respectively. The advance and retard return ports communicate with
intermediate points of the advance and retard output lines
respectively.
[0008] For example, the valve timing adjuster retards the engine
phase by shifting the spool in the retard direction to connect the
advance return port and the retard output port in the spool valve.
As a result, the working fluid discharged from the advance chamber
to the advance return port is supplied from the retard output port
to the retard output line together with the working fluid, which is
supplied from the fluid supply source into the input port. The
pressure of the output fluid opens the check valve in the retard
output line, so that the fluid from the fluid supply source and the
advance chamber is supplied to the retard chamber. The fluid is
supplied to the retard chamber when positive variable torque, which
biases the camshaft in the retard direction relative to the
crankshaft, acts on the vane rotor. However, it is difficult to
supply the working fluid when negative variable torque, which
biases the camshaft in the advance direction relative to the
crankshaft, acts on the vane rotor, because the negative variable
torque increases the volume of the advance chamber, causing the
fluid, which has been supplied into the input port, to flow into
the advance chamber through the advance output port.
[0009] The back flow to the advance chamber lowers the
responsibility that the valve timing adjuster has when the engine
phase changes. The back flow also lowers the stability of the
engine phase when the valve timing adjuster holds the phase fully
retarded by pressing the vane against the appropriate shoe. The
responsibility and the phase stability lower as above when the
camshaft is driven or rotated relative to the crankshaft in the
advance direction. Therefore, it is demanded that the valve timing
adjuster be improved.
SUMMARY OF THE INVENTION
[0010] The present invention is made in view of the above
disadvantages. Thus, it is an objective of the present invention to
address at least one of the above disadvantages.
[0011] To achieve the objective of the present invention, there is
provided a valve timing adjuster for an internal combustion engine
having a crankshaft, a valve, and a camshaft, wherein the adjuster
adjusts valve timing of the valve, which is opened and closed by
the camshaft through torque transmission from the crankshaft, the
adjuster including a first rotor, a second rotor, a spool valve, a
connection passage, and a connection check valve. The first rotor
is rotatable synchronously with the crankshaft. The second rotor is
rotatable synchronously with the camshaft. The first rotor and the
second rotor define therebetween an advance chamber and a retard
chamber, which are arranged circumferentially one after another.
The second rotor is adapted to drive the camshaft relative to the
crankshaft in an advance direction when working fluid is supplied
to the advance chamber. The second rotor is adapted to drive the
camshaft relative to the crankshaft in a retard direction when
working fluid is supplied to the retard chamber. The spool valve
includes an input port, a drain port, a first output port, a second
output port, and a spool. Working fluid is supplied to the spool
valve from an external fluid supply source through the input port.
Working fluid is drained through the drain port. Working fluid is
output to one of the advance chamber and the retard chamber through
the first output port. Working fluid is output to the other one of
the advance chamber and the retard chamber through the second
output port. The spool is adapted to be displaceable to a first
position, at which the first rotor is rotated relative to the
second rotor in order to shift a phase of the camshaft relative to
the crankshaft. The spool is adapted to be displaceable to a second
position, at which the second rotor is pressed against the first
rotor in order to hold the phase of the camshaft at a full phase,
at which the phase is fully shifted. When the spool is positioned
at the first position, the spool valve connects the first output
port with the input port and disconnects the second output port
from the drain port. When the spool is positioned at the second
position, the spool valve connects the first output port with the
input port and connects the second output port with the drain port.
The connection passage is provided in the spool, wherein the
connection passage connects the first output port with the second
output port when the spool is positioned at the first position. The
connection check valve is provided in the connection passage. The
connection check valve opens to allow working fluid to flow from
the second output port toward the first output port when the spool
is positioned at the first position. The connection check valve
closes to limit working fluid from flowing from the first output
port toward the second output port when the spool is positioned at
the first position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention, together with additional objectives, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0013] FIG. 1 is a schematic diagram of a valve timing adjuster
according to a first embodiment of the present invention;
[0014] FIG. 2 is a chart showing the variable torque acting on the
drive unit of the valve timing adjuster according to the first
embodiment;
[0015] FIG. 3 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in an advance position;
[0016] FIG. 4 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in a retard position;
[0017] FIG. 5 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in a full retard position;
[0018] FIG. 6 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in a hold position;
[0019] FIG. 7 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in the advance position;
[0020] FIG. 8 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in the advance position;
[0021] FIG. 9 is an axial sectional view of the spool valve of the
valve timing adjuster according to the first embodiment, showing
the spool in the retard position;
[0022] FIG. 10 is a schematic diagram of a valve timing adjuster
according to a second embodiment of the present invention;
[0023] FIG. 11 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in a full advance position;
[0024] FIG. 12 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in an advance position;
[0025] FIG. 13 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in a retard position;
[0026] FIG. 14 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in a full retard position;
[0027] FIG. 15 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in a hold position;
[0028] FIG. 16 is an axial sectional view of the spool valve of the
valve timing adjuster according to the second embodiment, showing
the spool in the full advance position; and
[0029] FIG. 17 is an axial sectional view of the spool valve of a
valve timing adjuster according to another embodiment of the
present inventions this valve being a modified form of the spool
valve of the valve timing adjuster according to the second
embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] Embodiments of the present invention will be described below
with reference to the drawings. The counterparts in the embodiments
will be assigned the same reference numerals so that repeated
descriptions can be avoided.
First Embodiment
[0031] FIG. 1 is a schematic diagram of a valve timing adjuster 1
according to a first embodiment of the present invention. The
adjuster 1 is applied to an internal combustion engine of a
vehicle. The adjuster 1 is a hydraulic valve timing adjuster using
hydraulic oil serving as working fluid. The adjuster 1 adjusts
valve timing of an intake valve serving as a "valve" of the
engine.
[0032] The basic structure of the valve timing adjuster 1 will be
described below. The adjuster 1 includes a drive unit 10 and a
control unit 30. The drive unit 10 is fitted to a driving force
transmission system for transmitting the driving force of a
crankshaft (not shown) of the engine to a camshaft 2 of the engine
and is driven with hydraulic oil. The control unit 30 controls the
supply of hydraulic oil to the drive unit 10.
[0033] The drive unit 10 includes a housing 12 serving as a first
rotor (driving rotor), which has a cylindrical sprocket 12a and
shoes 12b to 12e as partitions.
[0034] The sprocket 12a is connected to the crankshaft by a timing
chain (not shown). While the engine is running, driving force is
transmitted from the crankshaft to the sprocket 12a, so that the
housing 12 rotates with the crankshaft clockwise in FIG. 1.
[0035] The shoes 12b to 12e are formed on the inner periphery of
the sprocket 12a and spaced circumferentially at substantially
regular intervals. The shoes 12b to 12e project radially inwardly
from the sprocket 12a and each of the shoes 12b to 12e has a
radially inner surface that has an arcuate recess shape in section
taken perpendicularly to a rotational axis of the housing 12. The
drive unit 10 further includes a vane rotor 14, which has a
cylindrical boss 14a. The radially inner surface of each of the
shoes 12b to 12e is in slidable contact with an outer peripheral
surface of the boss 14a. A vane chamber 50 is formed between
adjacent shoes 12b to 12c. Another vane chamber 50 is formed
between adjacent shoes 12c to 12d. Another vane chamber 50 is
formed between adjacent shoes 12d to 12e. Another vane chamber 50
is formed between adjacent shoes 12e to 12b.
[0036] The vane rotor 14 is a driven rotor (second rotor), which is
received in the housing 12 in axially slidable contact with it. The
vane rotor 14 further has vanes 14b to 14e.
[0037] The boss 14a is bolted to the camshaft 2 coaxially with it.
The vane rotor 14 rotates synchronously with the camshaft 2
clockwise in FIG. 1 and is rotatable relative to the housing
12.
[0038] The vanes 14b to 14e are formed on the outer periphery of
the boss 14a and spaced circumferentially at substantially regular
intervals. Each of the vanes 14b to 14e is positioned in one of the
vane chambers 50. The vanes 14b to 14e radially outwardly project
from the boss 14a, and each of the vanes 14b to 14e has a radially
outer surface that has an arcuate projecting shape in section taken
perpendicularly to the rotational axis of the vane rotor 14. The
top face of each of the vanes 14b to 14e is in slidable contact
with an inner peripheral surface of the sprocket 12a.
[0039] The vane 14b and the shoe 12b define an advance chamber 52
therebetween in the corresponding vane chamber 50 associated with
this vane. The vane 14c and the shoe 12c define an advance chamber
53 therebetween in the corresponding vane chamber 50. The vane 14d
and the shoe 12d define an advance chamber 54 therebetween in the
corresponding vane chamber 50. The vane 14e and the shoe 12e define
an advance chamber 55 therebetween in the corresponding vane
chamber 50. The vane 14b and the shoe 12c define a retard chamber
56 therebetween in the corresponding vane chamber 50. The vane 14c
and the shoe 12d define a retard chamber 57 therebetween in the
corresponding vane chamber 50. The vane 14d and the shoe 12e define
a retard chamber 58 therebetween in the corresponding vane chamber
50. The vane 14e and the shoe 12b define a retard chamber 59
therebetween in the corresponding vane chamber 50.
[0040] The supply of hydraulic oil to the advance chambers 52 to 55
turns or rotates the vane rotor 14 in the advance direction
relative to the housing 12, driving the camshaft 2 in the advance
direction relative to the crankshaft. As a result, the engine phase
that determines the valve timing is advanced. Continued supply of
hydraulic oil to the advance chambers 52 to 55 presses the vanes
14b, 14c, 14d, 14e in the advance direction against the shoes 12c,
12d, 12e, 12b, respectively, and thereby the engine phase is held
fully advanced at a full advance phase (full phase on the advance
side).
[0041] The supply of hydraulic oil to the retard chambers 56 to 59
turns the vane rotor 14 in the retard direction relative to the
housing 12, driving the camshaft 2 in the retard direction relative
to the crankshaft. This retards the engine phase. Continued supply
of hydraulic oil to the retard chambers 56 to 59 presses the vanes
14b to 14e in the retard direction against the shoes 12b to 12e,
respectively, and thereby the engine phase is held fully retarded
at a full retard phase (full phase on the retard side).
[0042] The control unit 30 has an advance output line 72 and a
retard output line 76, which lead through the camshaft 2 and the
bearing (not shown) for the camshaft. The advance output line 72
communicates with the advance chambers 52 to 55 in any operational
condition of the drive unit 10. The retard output line 76
communicates with the retard chambers 56 to 59 in any operational
condition of the drive unit 10.
[0043] The control unit 30 further has an input line 80, which
communicates with the discharge port of a pump 4 serving as a fluid
supply source. The pump 4 pumps up hydraulic oil from an oil pan 5
of the engine and discharges the oil to the input line 80 under a
pressure higher than the atmospheric pressure. The pump 4 is a
mechanical pump, which the crankshaft drives. While the engine is
running, the pump 4 keeps pumping hydraulic oil into the input line
80. The control unit 30 further has a drain line 82, which opens
into the atmosphere, and through which hydraulic oil is drained
into the oil pan 5.
[0044] The control unit 30 includes a spool valve 100, which is an
electromagnetic control valve having a solenoid 120 and a spool
130. The solenoid 120 creates electromagnetic driving force in
order to linearly reciprocate the spool 130. The valve 100 further
has an advance output port 112, a retard output port 114, an input
port 116, and a drain port 118. The valve 100 outputs hydraulic oil
through the advance output port 112 and the advance output line 72
to the advance chambers 52 to 55. The valve 100 outputs hydraulic
oil through the retard output port 114 and the retard output line
76 to the retard chambers 56 to 59. The oil from the pump 4 is
input through the input line 80 into the input port 116. The drain
port 118 opens into the atmosphere through the drain line 82. The
valve 100 drains hydraulic oil through the drain port 118 into the
drain line 82. According to the electric current supply to the
solenoid 120, the solenoid reciprocates the spool 130 such that
ports communicated with the input port 116 and the drain port 118,
respectively, are selected among the output ports 112, 114.
[0045] The control unit 30 further includes a control circuit 200,
the main component of which is a microcomputer having a memory
200a. The control circuit 200 is connected electrically to the
solenoid 120. The control circuit 200 controls the current supply
to the solenoid 120 and the operation of the engine. In the present
embodiment, the control circuit 200 is connected electrically to a
crank sensor 202 that senses the rotation of the crankshaft and a
cam sensor 204 that senses the rotation of the camshaft 2. The
sensors 202, 204 output signals for controlling the current supply
to the solenoid 120 and the operation of the engine.
[0046] According to the current supply from the control circuit 200
to the solenoid 120, the spool valve 100 controls the position of
the spool 130. When the spool 130 is in a certain position, where
the input port 116 communicates with the advance output port 112,
the oil supplied from the pump 4 to the input line 80 is output by
the valve 100 to the advance output line 72, and thereby the oil is
supplied to the advance chambers 52 to 55. When the spool 130 is in
another position, where the input port 116 communicates with the
retard output port 114, the oil supplied from the pump 4 to the
input line 80 is output by the valve 100 to the retard output line
76, and thereby the oil is supplied to the retard chambers 56 to
59. When the spool 130 is in the spool position where the drain
port 118 communicates with the advance output port 112, the valve
100 can drain the oil in the advance chambers 52 to 55 to the oil
pan 5 through the advance output line 72 and the drain line 82.
[0047] Characteristics of the valve timing adjuster 1 will be
described below in detail.
[0048] While the engine is running, variable torque (torque
reversals) caused by the spring reaction force of a valve spring of
the intake valve, which the camshaft 2 drives. The variable torque
is transmitted through the camshaft 2 and acts on the vane rotor
14. As shown in FIG. 2, the variable torque alternates periodically
between negative torque and positive torque, which bias the
camshaft 2 in the advance and retard directions respectively
relative to the crankshaft. The peak positive torque T+ and the
peak negative torque Tto may be substantially equal to each other
in absolute value, so that the average variable torque may be
substantially zero. Alternatively, the peak positive torque T+ may
be greater in absolute value than the peak negative torque Tto, so
that the average variable torque may deflect positively.
[0049] As shown in FIG. 3, the spool valve 100 further has a sleeve
110, a driving shaft 139, and a return spring 140.
[0050] The sleeve 110 is metallic and has a hollow cylindrical
shape. The solenoid 120 is fixed to one end 110a of the sleeve 110.
The retard output port 114, the input port 116, the advance output
port 112, and the drain port 118 are formed in the sleeve 110 in
this order in a direction away from the sleeve end 110a toward the
other sleeve end 110b.
[0051] The spool 130 is metallic, and has a column shape with lands
formed thereon, and positioned in the sleeve 110 coaxially with the
sleeve 110. One end 130a of the spool 130 is connected coaxially
with the driving shaft 139. The solenoid 120 drives the shaft 139
electromagnetically to move the spool 130 axially with the shaft.
The spool 130 has an advance support land 132, an advance switch
land 134, a retard switch land 136, and a retard support land 138,
which are formed in this order in a direction away from the other
spool end 130b toward the spool end 130a.
[0052] The advance support land 132 is supported slidably by the
portion of the sleeve 110 that lies between the advance output port
112 and the drain port 118. The advance switch land 134 is
supported slidably by at least one of the above portion of the
sleeve 110 and the other portion of the sleeve 110 that lies
between the advance output port 112 and the input port 116. When
the spool 130 is in the position shown in FIG. 3, where the advance
switch land 134 is supported only by the sleeve portion between the
advance output port 112 and the drain port 118, the advance output
port 112 communicates with the input port 116 through the space
between the switch lands 134, 136. When the spool 130 is in the
spool position shown in FIG. 4 or 5, where the advance switch land
134 is supported only by the sleeve portion between the advance
output port 112 and the input port 116, this output port 112
communicates with the space between the advance support land 132
and the advance switch land 134. When the spool 130 is in the spool
position shown in FIG. 6, where the advance switch land 134 is
supported by both the portion of the sleeve 110 that lies between
the advance output port 112 and the sleeve end 110b and the sleeve
portion between advance output port 112 and the input port 116, the
advance output port 112 is blocked from the other ports 114, 116,
118.
[0053] As shown in FIG. 3, the retard support land 138 is supported
slidably by a portion of the sleeve 110 that lies between the
retard output port 114 and the sleeve end 110a. The retard switch
land 136 is supported slidably by at least one of the above portion
of the sleeve 110 and the other portion of the sleeve 110 that lies
between the retard output port 114 and the input port 116. When the
spool 130 is in the position shown in FIG. 4 or 5, where the retard
switch land 136 is supported only by the sleeve portion between the
retard output port 114 and the sleeve end 110a, this output port
114 communicates with the input port 116 through the space between
the switch lands 134, 136. When the spool 130 is in the spool
position shown in FIG. 3, where the retard switch land 136 is
supported only by the sleeve portion between the retard output port
114 and the input port 116, the retard output port 114 communicates
with the space between the retard switch land 136 and the retard
support land 138. When the spool 130 is in the spool position shown
in FIG. 6, where the retard switch land 136 is supported by the
sleeve portions on both sides of the retard output port 114, the
retard output port 114 is blocked from the other ports 112, 116,
118.
[0054] As shown in FIGS. 3 to 6, the input port 116 communicates
with the space between the switch lands 134, 136 regardless of the
position of the spool 130.
[0055] The return spring 140 is a metallic compression coil spring,
which is positioned in the sleeve 110 coaxially with the sleeve
110. The spring 140 is positioned in the sleeve 110 between the
sleeve end 110b and the advance support land 132 of the spool 130.
The compressive deformation of the spring 140 creates a restoring
force that biases the spool 130 axially toward the solenoid 120.
The current supply to the solenoid 120 creates an electromagnetic
driving force that biases the spool 130 with the driving shaft 139
axially toward the spring 140. Accordingly, the spool 130 is driven
according to the balance between the restoring force created by the
spring 140 and the electromagnetic driving force created by the
solenoid 120.
[0056] As shown in FIGS. 1, 3, the present embodiment is
characterized by connection check valves 210, 230 fitted in the
connection passages 220, 240 respectively formed in the spool
130.
[0057] As shown in FIG. 3, one end 221 of the advance connection
passage 220 opens at a peripheral surface of the spool 130 between
the switch lands 134, 136 at multiple positions. Accordingly, as
shown in FIGS. 3 to 6, the passage end 221 communicates with the
space between the switch lands 134, 136, regardless of the position
of the spool 130. In particular when the spool 130 is in the spool
position shown in FIG. 3, the passage end 221 communicates with the
advance output port 112 and the input port 116 through the space
between the switch lands 134, 136.
[0058] The other end 222 of the advance connection passage 220
opens at the peripheral surface of the spool 130 between the retard
switch land 136 and the retard support land 138 at multiple
positions. Accordingly, as shown in FIGS. 3 to 6, this passage end
222 communicates with the space between these lands 136, 138,
regardless of the position of the spool 130. In particular, when
the spool 130 is in the spool position shown in FIG. 3, the advance
connection passage 220 communicates with the advance output port
112 as stated above, and the end 222 of the advance connection
passage 220 communicates with the retard output port 114 through
the space between the lands 136, 138. Thus, when the spool 130 is
in this position, the output ports 112, 114 communicate with each
other through the advance connection passage 220.
[0059] The advance connection check valve 210 closes to limit fluid
from flowing in a direction from the end 221 of the advance
connection passage 220 toward the other end 222. Also, the advance
connection check valve 210 opens to allow fluid to flow in the
opposite direction opposite from the above. The advance connection
check valve 210 includes an advance valve seat 212, an advance
valve member 214, an advance retainer 215, and an elastic member
216.
[0060] The advance valve seat 212 is a conical wall of the advance
connection passage 220, and the conical wall has a diameter that
becomes smaller toward the end 222 of the advance connection
passage 220. The advance retainer 215 is positioned between the
advance valve seat 212 and the other end 221 of the advance
connection passage 220. The advance valve member 214 is positioned
between the advance valve seat 212 and the advance retainer 215.
The retard connection check valve 230 is positioned between the
advance connection check valve 210 and the spool end 110b. The
elastic member 216 is interposed between the retard connection
check valve 230 and the advance retainer 215. The advance valve
member 214 is a metallic ball and is axially movable in the advance
connection passage 220 such that the advance valve member 214 is
brought into and out of contact with the advance valve seat 212.
The advance retainer 215 is metallic and has a peripheral wall part
215a and a bottom. The peripheral wall part 215a is supported by
the inner peripheral wall of the advance connection passage 220 and
receives the advance valve member 214 therein. The advance retainer
215 is axially slidable in the advance connection passage 220. The
elastic member 216 is a metallic compression spring. The
compressive deformation of the elastic member 216 creates a
restoring force, which biases the advance retainer 215 together
with the advance valve member 214 toward the advance valve seat
212.
[0061] When the end 222 of the advance connection passage 220 is
higher in pressure than the other end 221, the advance valve member
214 moves toward the end 221 out of contact with the advance valve
seat 212 as shown in FIG. 3. This opens the advance connection
check valve 210, allowing hydraulic oil to flow from the passage
end 222 to the other passage end 221.
[0062] When the end 222 of the advance connection passage 220 is
lower in pressure than the other end 221, the advance valve member
214 moves toward the end 222 into contact with the advance valve
seat 212 as shown in FIGS. 4 to 6. This closes the advance
connection check valve 210, restraining the flow of hydraulic oil
from the passage end 221 to the other passage end 222.
[0063] As shown in FIG. 3, the end 221 of the advance connection
passage 220, which communicates with the space between the switch
lands 134, 136, serves also as one end of the retard connection
passage 240. In other words, the passage end 221 is common to or
shared by the connection passages 220, 240. Accordingly, when the
spool 130 is in the spool position shown in FIG. 4 or 5, the common
passage end 221 communicates with the retard output port 114 and
the input port 116 through the space between the switch lands 134,
136.
[0064] The other end 242 of the retard connection passage 240 opens
at the peripheral surface of the spool 130 between the advance
support land 132 and the advance switch land 134 at multiple
positions. Accordingly, as shown in FIGS. 3 to 6, this passage end
242 communicates with the space between these lands 132, 134,
wherever the spool 130 is positioned. In particular, when the spool
130 is in the spool position shown in FIG. 4 or 5, the retard
connection passage 240 communicates with the retard output port 114
as stated above, and the end 242 of the retard connection passage
240 communicates with the advance output port 112 through the space
between the lands 132, 134. Thus, when the spool 130 is in this
position, the output ports 112, 114 communicate with each other
through the retard connection passage 240.
[0065] The retard connection check valve 230 closes to limit fluid
from flowing in a direction from the common end 221 of the retard
connection passage 240 toward the other end 242. Also, the retard
connection check valve 230 opens to allow fluid to flow in the
opposite direction opposite from the above. The retard connection
check valve 230 is similar in structure to the advance connection
check valve 210. Specifically, the retard connection check valve
230 includes a retard valve seat 232, a retard valve member 234, a
retard retainer 235, and the elastic member 216.
[0066] The retard valve seat 232 is a conical wall of the retard
connection passage 240, and the conical wall has a diameter that
becomes smaller toward the end 242 of this passage. The retard
retainer 235 is positioned between the retard valve seat 232 and
the common passage end 221. The retard valve member 234 is
positioned between the retard valve seat 232 and the retard
retainer 235. The elastic member 216 is interposed between the
retard retainer 235 and the advance retainer 215. The retard valve
member 234 is axially movable in the retard connection passage 240
such that the retard valve member 234 is brought into and out of
contact with the retard valve seat 232. The retard retainer 235 has
a peripheral wall part 235a and a bottom. The peripheral wall part
235a is supported by an inner peripheral wall of the retard
connection passage 240 and receives the retard valve member 234
therein. The restoring force created by the compressive deformation
of the elastic member 216 biases the retard retainer 235 together
with the retard valve member 234 toward the retard valve seat
232.
[0067] When the end 242 of the retard connection passage 240 is
higher in pressure than the common end 221, the retard valve member
234 moves toward the common end 221 such that the retard valve
member 234 becomes out of contact with or disengaged from the
retard valve seat 232 as shown in FIG. 4. As a result, the retard
connection check valve 230 opens and allows hydraulic oil to flow
in a direction from the passage end 242 to the common passage end
221.
[0068] When the end 242 of the retard connection passage 240 is
lower in pressure than the common end 221, the retard valve member
234 moves toward the end 242 such that the retard valve member 234
is brought into contact with or becomes engaged with the retard
valve seat 232 as shown in FIGS. 3, 5 to 9. As a result, the retard
connection check valve 230 closes and limits the hydraulic oil from
flowing in a direction from the common passage end 221 to the other
passage end 242.
[0069] The present embodiment is also characterized by a junction
passage 260 formed in the spool 130 so that the advance output port
112 can communicate with the drain port 118, as shown in FIGS. 1,
5.
[0070] Specifically, as shown in FIG. 5, the junction passage 260
has an open end 261 formed at the spool end 130b inside the advance
support land 132. At least when the spool 130 is in the spool
position shown in FIG. 5, the passage end 261 communicates with the
drain pod 118 through the space between the spool end 130b and the
adjacent sleeve end 110b.
[0071] The other end 262 of the junction passage 260 open to the
peripheral wall of the spool 130 at the advance support land 132 at
multiple positions. When the spool 130 is in the spool position
shown in FIG. 5, the passage end 262 communicates with the space
between the advance support land 132 and the advance switch land
134 through the space between the inner periphery of the sleeve 110
and the outer periphery of the support land 132. When the spool 130
is in the above position, the junction passage 260 communicates
with the drain port 118, and the space between the lands 132, 134
communicates with the advance output port 112, as stated above.
Accordingly, these ports 118, 112 communicate with each other
through the junction passage 260. When the spool 130 is in the
spool position shown in FIG. 3, 4, or 6, the passage end 262 is
blocked from the space between the lands 132, 134, so that the
advance output port 112 is blocked from the drain port 118.
[0072] As shown in FIGS. 1, 3, the input line 80, which
communicates with the pump 4 and the input port 116, is fitted with
an input check valve 280. When one end of the input line 80 that is
connected to the pump 4 is higher in pressure than the other end,
which is connected to the spool valve 100, the input check valve
280 opens, as shown in FIGS. 3 to 6. This allows hydraulic oil to
flow from the pump 4 to the input port 116. When the other end of
the input line 80 that is connected to the spool valve 100 is
higher in pressure than the one end, the input check valve 280
closes, as shown in FIGS. 7 to 9. This restrains the flow of
hydraulic oil from the input port 116 to the pump 4.
[0073] During the operation of the engine, where the pump 4 driven,
the control circuit 200 calculates the actual engine phase Pr and
target engine phase Pt of the camshaft 2 relative to the
crankshaft. Based on the calculated phases Pr and Pt, the control
circuit 200 controls the current supply to the solenoid 120 of the
spool valve 100. This controls the position of the spool 130 of the
spool valve 100. According to the controlled position, the spool
valve 100 supplies hydraulic oil to or discharge hydraulic oil from
the advance chambers 52 to 55 or the retard chambers 56 to 59. This
adjusts the engine phase, thereby adjusting the valve timing. The
valve timing adjustment through the valve timing adjuster 1 will be
described below in detail.
1. Advance Operation
[0074] In the advance operation, the valve timing adjuster 1
advances the valve timing by varying the engine phase of the
camshaft 2 relative to the crankshaft in the advance direction as
follows.
[0075] When an operating condition representing the off-state of
the accelerator of the engine or representing the low-speed or
medium-speed high-load operating state of the engine is satisfied,
the control circuit 200 controls the current to be supplied to the
solenoid 120 at a specified advance value Ia. As a result, the
spool 130 is shifted to the advance phase position (first position
on the advance side) shown in FIGS. 3, 7. When the spool 130 is in
the advance phase position, the advance connection passage 220
connects the retard output port 114 with the advance output port
112 communicating with the input port 116 and blocked from the
drain port 118.
[0076] While negative torque is acting on the vane rotor 14, in the
advance operation, as shown in FIG. 3, hydraulic oil is input from
the pump 4 through the input line 80 into the input port 116 and
supplied to the advance chambers 52 to 55 through the advance
output port 112 and the advance output line 72. Also, in the
advance connection passage 220, the oil input into the input port
116 flows into the common end 221 of the passage 220, and the oil
compressed by the action of the negative torque in the retard
chambers 56 to 59 flows into the other end 222 of the passage 220
through the retard output port 114. The oil flowing into the
passage end 222, which is currently adjacent to the retard output
port 114, is higher in pressure than the oil flowing into the
common passage end 221, which is currently adjacent to the advance
output port 112. As a result, the advance connection check valve
210 opens, allowing hydraulic oil to flow from the retard output
port 114 to the advance output port 112. In a case, where the
amount of hydraulic oil input from the pump 4 into the spool valve
100 decreases, the valve 100 is capable of being supplied with
hydraulic oil through the retard output port 114. This limits the
shortage of hydraulic oil in the advance chambers 52 to 55 that is
increased in volume by the action of the negative torque.
[0077] While negative torque is acting on the vane rotor 14 in the
advance operation, the oil from the pump 4 also flows into the
retard connection passage 240 communicating with the advance output
port 112 through the common passage end 221, but the closure of the
retard connection check valve 230 restrains the flow of hydraulic
oil toward the other end 242 of the passage 240. Also, the advance
output port 112 communicating with the advance connection passage
220 through the common passage end 221 is blocked or
discommunicated from the drain port 118. This restrains the drain
of hydraulic oil through the drain port 118.
[0078] While positive torque is acting on the vane rotor 14 in the
advance operation, the advance chambers 52 to 55 are compressed. As
a result, as shown in FIG. 7, hydraulic oil is forced to flow back
through the advance output port 112 to the connection passages 220,
240 and the input line 80. At this time, the closure of the
connection check valves 210, 230 restrains the flow of hydraulic
oil through the connection passages 220, 240 respectively toward
the retard output port 114 and the passage end 242 respectively.
Also, the closure of the input check valve 280 restrains the flow
of hydraulic oil through the input line 80 toward the pump 4. Thus,
hydraulic oil is restrained from flowing back through the advance
output port 112 to the connection passages 220, 240 and the input
line 80. This not only restrains hydraulic oil from flowing out of
the advance chambers 52 to 55 but also prevents erroneous supply of
hydraulic oil to the retard chambers 56 to 59.
[0079] The advance operation of advancing the valve timing enables
the connection check valves 210, 230 to function properly and
timely to discharge hydraulic oil from the retard chambers 56 to 59
and supply a sufficient amount of hydraulic oil to the advance
chambers 52 to 55. This enables high advance responsibility.
2. Retard Operation
[0080] IN a retard operation of retarding the valve timing, The
valve timing adjuster 1 retards the valve timing by varying the
engine phase or phase relation of the camshaft 2 relative to the
crankshaft in the retard direction as follows.
[0081] When an operating condition representing the light-load
normal operating state is satisfied, the control circuit 200
controls the current to be supplied to the solenoid 120 at a retard
value Ir that is smaller than the advance value Ia. As a result,
the spool 130 is shifted to the retard phase position (first
position on the retard side) shown in FIGS. 4, 8. When the spool
130 is in the above position, the retard connection passage 240
connects the retard output port 114 to the advance output port 112.
In the above, the retard output port 114 communicates with the
input port 116, and the advance output port 112 is blocked from the
drain port 118.
[0082] While positive torque is acting on the vane rotor 14 in the
retard operation, hydraulic oil is input from the pump 4 through
the input line 80 into the input port 116 and supplied through the
retard output port 114 and the retard output line 76 to the retard
chambers 56 to 59 as shown in FIG. 4. Also, the oil input into the
input port 116 flows into the common end 221 of the retard
connection passage 240, and the oil compressed by the positive
torque in the advance chambers 52 to 55 flows through the advance
output port 112 into the other end 242 of the passage 240. The oil
flowing into the passage end 242, which is currently adjacent to
the advance output port 112, is higher in pressure than the oil
flowing into the common passage end 221, which is currently
adjacent to the retard output port 114. As a result, the retard
connection check valve 230 opens and allows hydraulic oil to flow
in a direction from the advance output port 112 to the retard
output port 114. If the amount of hydraulic oil being input from
the pump 4 into the spool valve 100 decreases, the valve 100 is
capable of being supplied with hydraulic oil through the advance
output port 112. This limits the shortage of hydraulic oil in the
retard chambers 56 to 59, a volume of each of which has been
increased by the positive torque.
[0083] While positive torque is acting on the vane rotor 14 in the
retard operation, the oil from the pump 4 also flows into the
advance connection passage 220 communicating with the retard output
port 114 through the common passage end 221, but the closure of the
advance connection check valve 210 restrains the flow of hydraulic
oil toward the other end 222 of the passage 220. Also, the advance
output port 112 communicating with the retard connection passage
240 through the passage end 242 is blocked from the drain port 118.
This restrains the drain of hydraulic oil through the drain port
118.
[0084] While negative torque is acting on the vane rotor 14 in the
retard operation, the retard chambers 56 to 59 are compressed. As a
result, as shown in FIG. 8, hydraulic oil is forced to flow back
through the retard output port 114 to the connection passages 240,
220 and the input line 80. At this time, the closure of the
connection check valves 230, 210 restrains the flow of hydraulic
oil through the connection passages 240, 220, respectively, toward
the advance output port 112 and the passage end 222, respectively.
Also, the closure of the input check valve 280 restrains the flow
of hydraulic oil through the input line 80 toward the pump 4. Thus,
hydraulic oil is restrained from flowing back through the retard
output port 114 to the connection passages 240, 220 and the input
line 80. This not only restrains the flow of hydraulic oil out of
the retard chambers 56 to 59 but also prevents erroneous supply of
hydraulic oil to the advance chambers 52 to 55.
[0085] The retard operation of the valve timing enables the
connection check valves 230, 210 to function properly and timely to
discharge hydraulic oil from the advance chambers 52 to 55 and
supply a sufficient amount of hydraulic oil to the retard chambers
56 to 59. This enables high retard responsibility.
3. Full Retard Operation
[0086] In a full retard operation, the valve timing adjuster 1
retards the valve timing to the maximum or to the full by holding
the engine phase fully retarded as follows.
[0087] When an operating condition representing (a) an operational
condition immediately after the start of the engine or (b) an
operational condition (for example, the off-state of the throttle)
for adjusting the engine phase to the full retard phase while the
engine is rotating at a speed not higher than a set value R is
satisfied, the control circuit 200 controls the current to be
supplied to the solenoid 120 at a full retard value Ir0 smaller
than the retard value Ir. As a result, the spool 130 is driven to
the full retard phase position (second position on the retard side)
shown in FIGS. 5, 9, which is a position located in the retard
direction away from the retard phase position shown in FIGS. 4, 8.
Thus, the full retard phase position and the retard phase position
are arranged adjacent to each other in a direction, in which the
spool 130 is displaceable. When the spool 130 is in the full retard
phase position, the retard connection passage 240 connects the
retard output port 114 communicating with the input port 116 to the
advance output port 112 communicating with the drain port 118. The
set value R may be a low engine speed (for example, 500 to 1,400
rpm) at which the rotation of the drive unit 10 less influences the
engine phase.
[0088] In this case, the latest reference phase is learned when the
engine has started. This contributes to the improvement in the
accuracy in valve timing adjustment. In this case, because the
engine rotates at a relatively low speed when the start of the
engine has been completed, it is possible to learn the reference
phase while the housing 12 and the vane rotor 14 rotate with weak
or slight vibration. This, too, contributes to the improvement in
the adjustment accuracy.
[0089] While positive torque is acting on the vane rotor 14 in the
full retard operation, the oil from the pump 4 is supplied
continuously to the retard chambers 56 to 59, as is the case with
the retard operation. Also, as shown in FIG. 5, the oil input into
the input port 116 flows into the common end 221 of the retard
connection passage 240, and the oil compressed by the action of the
positive torque in the advance chambers 52 to 55 flows into the
advance output port 112. The oil flowing into the advance output
port 112 then flows into not only the other end 242 of the retard
connection passage 240 but also the drain port 118, which is open
to the atmosphere, so that the pressure of the oil becomes the
atmospheric pressure. As a result, the oil flowing into the passage
end 242, which is currently adjacent to the advance output port
112, is lower in pressure than the oil flowing into the common
passage end 221, which is currently adjacent to the retard output
port 114. This closes the retard connection check valve 230,
restraining not only the flow of hydraulic oil from the retard
output port 114 to the advance output port 112 but also the oil
flow in the opposite direction. Accordingly, a substantial part of
the oil flowing into the advance output port 112 is drained through
the drain port 118. This makes it possible to empty the advance
chambers 52 to 55 so that the vanes 14b to 14e is capable of being
pressed reliably against the shoes 12b to 12e respectively. Thus,
the fully retarded engine phase is capable of being held reliably
and stably.
[0090] When the spool 130 is in the full retard phase position
(second position on the retard side), the connection passage 240
connects the retard output port 114 and the advance output port 112
(first and second output ports) as is the case when the spool 130
is in the retard position (first position on the retard side). In
the above connection state, working fluid is discharged from the
advance chamber through the advance output port 112 to the
connection passage 240, and thereby the communication between the
advance output port 112 and the drain port 118 opening to
atmosphere causes pressure at the end 242 of the connection passage
240 that is adjacent to the advance output port 112 to be lower
than pressure at the other end 221, which is adjacent to the retard
output port 114 communicating with the input port 116. As a result,
the connection check valve 230 closes, and thereby limiting working
fluid from flowing through the connection passage 240 between the
advance and retard output ports 112, 114. This makes it possible to
simplify the valve timing adjuster 1 in structure by arranging the
first position and the second position adjacent to each other and
by making the connection passage 240 commonly provide connection
between the advance and retard output ports 112, 114 when the spool
130 is positioned at either of the above first and second
positions. This also makes it possible to stabilize the engine
phase by draining working fluid quickly from the advance chamber
through the output port 112 to the drain port 118.
[0091] As is the case with the retard operation, while positive
torque is acting on the vane rotor 14 in the full retard operation,
the oil from the pump 4 also flows into the advance connection
passage 220, but the closure of the advance connection check valve
210 restrains the flow of hydraulic oil toward the end 222 of the
passage 220. As is the case with the retard operation, while
negative torque is acting on the vane rotor 14 in the position full
retard operation, hydraulic oil is restrained from flowing back
from the retard output port 114 to the connection passages 240, 220
and the input line 80, as shown in FIG. 9.
[0092] During the full retard operation, the control circuit 200
monitors the actual engine phase Pr, which is calculated from the
signals from the crank sensor 202 and the cam sensor 204. The
control circuit 200 learns a stable value of the monitored phase Pr
(actual phase) as a reference phase Pr0, which is stored in a
memory 200a of the control circuit 200. The reference phase Pr0 is
updated every time the control circuit 200 learns a stable value of
the monitored phase Pr. For example, the above operation of
learning the reference phase Pr0 using the monitored phase Pr is
defined as learning of the reference phase Pr0 in the present
embodiment. Accordingly, based on the latest reference phase Pr0
stored in the memory 200a, the control circuit 200 calculates the
present actual engine phase Pr and the present target phase Pt,
which are necessary for controlling the current supply to the
solenoid 120. As stated above, the fully retarded engine phase is
capable of being held effectively stably when the control circuit
200 learns the reference phase Pr0. This makes it possible to
increase the accuracy of valve timing adjustment by realizing
current supply control based on accurate reference phase Pr0.
4. Normal Hold Operation
[0093] In a normal hold operation, the valve timing adjuster 1
keeps the valve timing by holding the engine phase within a
specified target phase range excluding the full retard phase, as
follows.
[0094] If an operating condition representing the stable operating
state of the engine, such as holding of the accelerator at a
certain position, is satisfied, the control circuit 200 controls
the current to be supplied to the solenoid 120 at a normal hold
value In smaller than the advance value la and larger than the
retard value Ir. As a result, the spool 130 is shifted to the
normal hold operation position shown in FIG. 6. When the spool 130
is in the above position, both of the output ports 112, 114 are
blocked from the input port 116 and the drain port 118.
[0095] Accordingly, the oil input from the pump through the input
line 80 to the input port 116 is not supplied to the advance and
retard chambers 52 to 59, and hydraulic oil is restrained from
flowing out of the advance and retard chambers 52 to 59. This makes
it possible to restrain engine phase changes within the target
phase range to hold the valve timing that corresponds to the target
phase range.
[0096] When the spool 130 is in the Normal Hold Operation position,
the oil from the pump 4 flows through the input port 116 into the
common end 221 of the connection passages 220, 240, but the closure
of the connection check valves 210, 230 restrains the flow of
hydraulic oil from the common end 221 toward the other ends 222,
242.
[0097] Thus, the first embodiment enables quick and accurate valve
timing adjustment suitable for the engine.
Second Embodiment
[0098] As shown in FIG. 10, a second embodiment of the present
invention is a modified form of the first embodiment. The control
unit 1030 of the second embodiment has a drain line 1082 in
addition to the drain line 82. The drain line 1082 opens into the
atmosphere, and hydraulic oil can be drained through this line to
the oil pan 5.
[0099] The spool valve 1100 of the control unit 1030 has a drain
port 1118 in addition to the drain port 118. The drain port 1118 is
open to the atmosphere through the drain line 1082, and hydraulic
oil is drained through the port 1118 to the line 1082. As shown in
FIG. 11, the drain port 1118 is positioned between the retard
output port 114 and the sleeve end 110a.
[0100] As shown in FIG. 10, the spool 1130 of the spool valve 1100
has a junction passage 1260 in addition to the junction passage
260. The junction passage 1260 enables the retard output port 114
to communicate with the drain port 1118. As shown in FIG. 11, the
junction passage 1260 extends through the retard support land 138.
The ends 1261, 1262 of the junction passage 1260 are open on an
outer peripheral surface of the spool 1130. The passage ends 1261,
1262 communicate with the drain port 1118 at least when the spool
1130 is in the spool position shown in FIG. 11. When the spool 1130
is in this position, the passage ends 1261, 1262 communicate with
the space between the retard switch land 136 and the retard support
land 138 through the space formed in the sleeve 1110 at the outer
peripheral side of the support land 138.
[0101] When the spool 1130 is in the spool position shown in FIG.
11, the retard switch land 136 is supported only on the side of the
retard output port 114 that is adjacent to the input port 116. This
makes the output port 114 communicate with the space between the
switch land 136 and the retard support land 138. Accordingly, when
the spool 1130 is in this position, the drain port 1118 and the
output port 114 communicate with each other through the junction
passage 1260. When the spool 1130 is in the spool position shown in
one of FIGS. 12 to 15, the ends 1261, 1262 of the junction passage
1260 are blocked from the space between the lands 136, 138, so that
the output port 114 is blocked from the drain port 1118.
[0102] When the spool 1130 is in the spool position shown in FIG.
11, the advance switch land 134 is supported only on the side of
the advance output port 112 that is adjacent to the drain port 118.
This makes the output port 112 communicate with the input port 116
through the space between the switch lands 134, 136.
[0103] Similarly to the first embodiment, the valve timing adjuster
1 according to the second embodiment advances the valve timing,
retards the valve timing, fully retards the valve timing, and holds
the valve timing by locating the spool 1130 at the positions shown
in FIGS. 12 to 15, respectively. In addition, this adjuster 1 fully
advances the valve timing by locating the spool 1130 in the
position shown in FIG. 11.
[0104] Specifically, the valve timing adjuster 1 according to the
second embodiment starts to fully advance the valve timing if a
certain operating condition for adjusting the engine phase to the
fully advanced phase is satisfied during the operation of the
engine at a speed not higher than a set value R. The above
operating condition may be that the throttle is fully open at an
engine speed of 4,000 or less rpm. In the full advance operation of
valve timing of the adjuster 1, the control circuit 200 controls
the current to be supplied to the solenoid 120 at a full advance
value Ia0 higher than the advance value Ia. As a result, the spool
1130 is driven to the full advance phase position shown (second
position on the advance side) in FIGS. 11, 16, which is a position
located in the advance direction away from the advance phase
position. Thus, the full advance phase position and the advance
phase position are arranged adjacent to each other in a direction,
in which the spool 130 is displaceable. When the spool 1130 is in
the full advance phase position, the advance connection passage 220
connects the advance output port 112 with the retard output port
114. In the above, the advance output port 112 communicates with
the input port 116, and the retard output port 114 communicates
with the drain port 1118. The set value R may be equal to the set
value R for the full retard operation in the first embodiment.
[0105] While negative torque is acting on the vane rotor 14, in the
full advance operation, the oil from the pump 4 is supplied
continuously to the advance chambers 52 to 55, as is the case with
the advance operation in the first embodiment. Also, as shown in
FIG. 11, the oil input into the input port 116 flows into the end
221 of the advance connection passage 220, and the oil in the
retard chambers 56 to 59 which is compressed by the action of the
negative torque flows into the retard output port 114. The oil
flowing into the retard output port 114 flows into not only the
other end 222 of the advance connection passage 220 but also the
drain port 1118, which opens into the atmosphere, so that the
pressure of the oil is atmospheric pressure. As a result, the oil
flowing into the passage end 222, which is adjacent to the retard
output port 114, is lower in pressure than the oil flowing into the
passage end 221, which is adjacent to the advance output port 112.
This closes the retard connection check valve 230, restraining not
only the flow of hydraulic oil from the advance output port 112 to
the retard output port 114 but also the oil flow in the opposite
direction. Consequently, substantially all part of the oil flowing
into the retard output port 114 is drained through the drain port
1118. This makes it possible to empty the retard chambers 56 to 59
so that the vanes 14b to 14e are pressed in the advance direction
reliably against the shoes 12b to 12e. Thus, it is possible to
stably hold the engine phase fully advanced.
[0106] While negative torque is acting on the vane rotor 14 in the
full advance operation, the oil from the pump 4 also flows into the
retard connection passage 240, as is the case with the advance
operation in the first embodiment, but the closure of the retard
connection check valve 230 restrains the flow of hydraulic oil
toward the end 242 of the passage 240. While positive torque is
acting on the vane rotor 14, with the spool 1130 in the full
advance operation, as shown in FIG. 16, the backflow from the
advance output port 112 to the connection passages 240, 220 and the
input line 80 is restrained, as is the case with the advance
operation in the first embodiment. The control circuit 200 may
alternatively learn the reference phase Pr0 during the full advance
operation, instead of learning the reference phase Pr0 during the
full retard operation. This makes it possible to increase the
accuracy of valve timing adjustment.
[0107] The second embodiment, too, can make quick and accurate
valve timing adjustment for the engine.
Other Embodiments
[0108] The present invention should not be interpreted as limited
to the above first and second embodiments but may be embodied into
various forms without departing from the spirit of the present
invention.
[0109] In each of the embodiments, the drive unit 10 might include
an assist spring or another elastic member for biasing the camshaft
2 in a direction opposite from a direction, in which the average
value of variable torque is biased or urged. The housing 12 of the
drive unit 10 might be rotated with the camshaft 2, and the vane
rotor 14 of the drive unit 10 might be rotated with the
crankshaft.
[0110] Each of the connection check valves 210, 230 of the spool
valves 100, 1100 might be fitted with an elastic member for biasing
the corresponding valve member 214 or 234. One end of this elastic
member would be in contact with the corresponding valve member 214
or 234, and the other end would be fixed to the wall of the
corresponding connection passage 220 or 240.
[0111] The solenoid 120 for actuating each of the spools 130, 1130
of the spool valves 100, 1100 may be alternatively replaced by a
piezoelectric or hydraulic actuator. The port 114 of each of the
sleeves 110, 1110 of the spool valves 100, 1100 may alternatively
communicate with the advance chambers 52 to 55 through the
corresponding advance output line 72. The port 112 of each of the
sleeves 110, 1110 may alternatively communicate with the retard
chambers 56 to 59 through the corresponding retard output line 76.
In the above alternative case, the relation between the advance
operation and the retard operation and the relation between the
full advance operation and the full retard operation are reverse to
those in the first and second embodiments.
[0112] The spool valve 1100 may, as shown in FIG. 17, not have the
drain port 118 and the junction passage 260. In this case, the
valve timing adjuster 1 may not fully retard the valve timing, and
the control circuit 200 may learn the reference phase Pr0 when the
adjuster 1 fully advances the valve timing.
[0113] The present invention can be applied to not only an
apparatus for adjusting the valve timing for a intake valve but
also an apparatus for adjusting the valve timing for an exhaust
valve as a valve and an apparatus for adjusting the valve timing
for both a intake valve and an exhaust valve.
[0114] Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader terms is
therefore not limited to the specific details, representative
apparatus, and illustrative examples shown and described.
* * * * *