US20090178635A1

US20090178635A1 - Valve timing adjuster

Info

Publication number: US20090178635A1
Application number: US12/349,637
Authority: US
Inventors: Akihiko Takenaka
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2008-01-10
Filing date: 2009-01-07
Publication date: 2009-07-16
Also published as: JP2009167811A; DE102008055175A1; JP4518149B2

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.

Description

CROSS REFERENCE TO RELATED APPLICATION

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

1. Field of the Invention
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.
2. Description of Related Art
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.
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.
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.
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.
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

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.
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

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:

FIG. 1 is a schematic diagram of a valve timing adjuster according to a first embodiment of the present invention;

FIG. 2 is a chart showing the variable torque acting on the drive unit of the valve timing adjuster according to the first embodiment;

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;

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;

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;

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;

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;

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;

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;

FIG. 10 is a schematic diagram of a valve timing adjuster according to a second embodiment of the present invention;

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;

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;

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;

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;

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;

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

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

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

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.
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.
The drive unit 10 includes a housing 12 serving as a first rotor (driving rotor), which has a cylindrical sprocket 12 a and shoes 12 b to 12 e as partitions.
The sprocket 12 a 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 12 a, so that the housing 12 rotates with the crankshaft clockwise in FIG. 1.
The shoes 12 b to 12 e are formed on the inner periphery of the sprocket 12 a and spaced circumferentially at substantially regular intervals. The shoes 12 b to 12 e project radially inwardly from the sprocket 12 a and each of the shoes 12 b to 12 e 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 14 a. The radially inner surface of each of the shoes 12 b to 12 e is in slidable contact with an outer peripheral surface of the boss 14 a. A vane chamber 50 is formed between adjacent shoes 12 b to 12 c. Another vane chamber 50 is formed between adjacent shoes 12 c to 12 d. Another vane chamber 50 is formed between adjacent shoes 12 d to 12 e. Another vane chamber 50 is formed between adjacent shoes 12 e to 12 b.
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 14 b to 14 e.
The boss 14 a 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.
The vanes 14 b to 14 e are formed on the outer periphery of the boss 14 a and spaced circumferentially at substantially regular intervals. Each of the vanes 14 b to 14 e is positioned in one of the vane chambers 50. The vanes 14 b to 14 e radially outwardly project from the boss 14 a, and each of the vanes 14 b to 14 e 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 14 b to 14 e is in slidable contact with an inner peripheral surface of the sprocket 12 a.
The vane 14 b and the shoe 12 b define an advance chamber 52 therebetween in the corresponding vane chamber 50 associated with this vane. The vane 14 c and the shoe 12 c define an advance chamber 53 therebetween in the corresponding vane chamber 50. The vane 14 d and the shoe 12 d define an advance chamber 54 therebetween in the corresponding vane chamber 50. The vane 14 e and the shoe 12 e define an advance chamber 55 therebetween in the corresponding vane chamber 50. The vane 14 b and the shoe 12 c define a retard chamber 56 therebetween in the corresponding vane chamber 50. The vane 14 c and the shoe 12 d define a retard chamber 57 therebetween in the corresponding vane chamber 50. The vane 14 d and the shoe 12 e define a retard chamber 58 therebetween in the corresponding vane chamber 50. The vane 14 e and the shoe 12 b define a retard chamber 59 therebetween in the corresponding vane chamber 50.
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 14 b, 14 c, 14 d, 14 e in the advance direction against the shoes 12 c, 12 d, 12 e, 12 b, respectively, and thereby the engine phase is held fully advanced at a full advance phase (full phase on the advance side).
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 14 b to 14 e in the retard direction against the shoes 12 b to 12 e, respectively, and thereby the engine phase is held fully retarded at a full retard phase (full phase on the retard side).
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.
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.
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.
The control unit 30 further includes a control circuit 200, the main component of which is a microcomputer having a memory 200 a. 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.
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.
Characteristics of the valve timing adjuster 1 will be described below in detail.
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.
As shown in FIG. 3, the spool valve 100 further has a sleeve 110, a driving shaft 139, and a return spring 140.
The sleeve 110 is metallic and has a hollow cylindrical shape. The solenoid 120 is fixed to one end 110 a 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 110 a toward the other sleeve end 110 b.
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 130 a 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 130 b toward the spool end 130 a.
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 110 b 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.
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 110 a. 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 110 a, 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.
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.
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 110 b 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.
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.
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.
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.
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.
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 110 b. 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 215 a and a bottom. The peripheral wall part 215 a 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.
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.
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.
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.
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.
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.
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 235 a and a bottom. The peripheral wall part 235 a 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.
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.
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.
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.
Specifically, as shown in FIG. 5, the junction passage 260 has an open end 261 formed at the spool end 130 b 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 130 b and the adjacent sleeve end 110 b.
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.
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.
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

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.
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.
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.
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.
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.
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

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.
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.
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.
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.
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.
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

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.
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.
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.
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 14 b to 14 e is capable of being pressed reliably against the shoes 12 b to 12 e respectively. Thus, the fully retarded engine phase is capable of being held reliably and stably.
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.
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.
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 200 a 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 200 a, 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

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.
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.
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.
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.
Thus, the first embodiment enables quick and accurate valve timing adjustment suitable for the engine.

Second Embodiment

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.
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 110 a.
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.
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.
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.
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.
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.
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 14 b to 14 e are pressed in the advance direction reliably against the shoes 12 b to 12 e. Thus, it is possible to stably hold the engine phase fully advanced.
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.
The second embodiment, too, can make quick and accurate valve timing adjustment for the engine.

Other Embodiments

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.
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.
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.
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.
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.
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.
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.

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.