Patent Grant
7219636
The present invention relates to a variable valve timing control system employing a hydraulically-operated phase converter capable of varying a relative phase of a camshaft to a crankshaft of an internal combustion engine by supplying working fluid (hydraulic pressure) selectively to either one of a phase-advance hydraulic chamber and a phase-retard hydraulic chamber, for variably adjusting an open-and-closure timing of an engine valve depending on an engine operating condition.
In recent years, there have been proposed and developed various variable valve timing control systems each employing a phase converter, such as a hydraulically-operated vane-type timing variator, a hydraulically-operated helical-gear-type timing variator, and the like. A hydraulically-operated vane-type timing variator has been disclosed in Japanese Patent Provisional Publication No. 2001-271616 (hereinafter is referred to as “JP2001-271616”), corresponding to German patent application No. 101 01 938 and also corresponding to U.S. Pat. No. 6,345,595, issued on Feb. 12, 2002 and assigned to the assignee of the present invention. In the hydraulically-operated vane-type variable valve timing control system disclosed in JP2001-271616, a vane member is fixedly connected to a camshaft end and rotatably enclosed in a cylindrical housing of a timing pulley whose opening ends are enclosed with front and rear covers. A phase-advance hydraulic chamber and a phase-retard hydraulic chamber are defined between diametrically-opposing partition walls and two blades of the vane member. The hydraulically-operated phase converter operates to vary a relative angular phase between the camshaft and the timing pulley (engine crankshaft) by supplying hydraulic pressure discharged from a reversible pump selectively to either one of the phase-advance hydraulic chamber and the phase-retard hydraulic chamber by switching one of a normal-rotational direction and a reverse-rotational direction of the reversible pump to the other, for variably adjusting a valve open timing and/or a valve closure timing of the engine valve depending on an engine operating condition.
However, in the system disclosed in JP2001-271616, the phase-advance hydraulic chamber is connected directly to a first port of two ports of the reversible pump via a first fluid line. In a similar manner, the phase-retard hydraulic chamber is connected directly to the second port of the reversible pump via a second fluid line. As is generally known, a comparatively large magnitude of alternating torque is exerted on the camshaft owing to a spring force of a valve spring for each engine valve and a reaction force resulting from each valve lifting during operation of the engine. Due to the alternating torque, a pulse pressure is applied to the working fluid in each of the phase-advance and phase-retard hydraulic chambers. There is an increased tendency for the pulse pressure, arising from alternating torque exerted on the camshaft, to be transmitted from the phase-advance and phase-retard hydraulic chambers through the first and second fluid lines to the respective ports of the reversible pump. The pulsating pressure serves as an undesirable load (in other words, undesirable energy loss) carried on the motor shaft of the electric motor of the reversible pump. Such an undesirable load means the necessity of an increased torque capacity of the electric motor of the reversible pump, in other words, large-sizing of the system, or higher system costs. It would be desirable to provide a means by which the pulse pressure, arising from alternating torque exerted on the camshaft, may be avoided from acting as a load carried on the motor shaft of the electric motor of the reversible pump.
Accordingly, it is an object of the invention to provide a variable valve timing control system employing a hydraulically-operated phase converter, capable of preventing a pulse pressure, arising from alternating torque exerted on a camshaft, from being transmitted from either one of phase-advance and phase-retard hydraulic chambers to a first port of two ports of a reversible pump as a load carried on a motor shaft of the pump, and promoting the outflow of working fluid from the other hydraulic chamber to the second port by the pulse pressure so that the promoted outflow serves as an assistance force (an assistive drive source for the pump).
In order to accomplish the aforementioned and other objects of the present invention, a variable valve timing control system of an internal combustion engine comprises a rotary member adapted to be driven in synchronization with rotation of an engine crankshaft, and rotatably supported on a camshaft to permit relative rotation of the camshaft to the rotary member, a hydraulically-operated phase converter disposed between the rotary member and the camshaft, and having a phase-advance hydraulic chamber and a phase-retard hydraulic chamber for changing an angular phase of the camshaft relative to the rotary member, an electric pump that supplies working fluid to the phase-advance hydraulic chamber and the phase-retard hydraulic chamber through a phase-advance hydraulic line connected to the phase-advance hydraulic chamber and a phase-retard hydraulic line connected to the phase-retard hydraulic chamber, a directional control valve disposed between a first pair of fluid lines including a discharge line and an induction line of the pump and a second pair of fluid lines including the phase-advance hydraulic line and the phase-retard hydraulic line, for determining a path through which the working fluid is directed from the discharge line to a first one of the phase-advance hydraulic line and the phase-retard hydraulic line and simultaneously determining a path through which the working fluid is directed from the second hydraulic line to the induction line, a control unit configured to be electronically connected to at least the directional control valve, for controlling the directional control valve depending on an engine operating condition, and a check valve disposed in the discharge line for permitting flow in a direction that the working fluid flows from the pump to the directional control valve and preventing any flow in the opposite direction.
According to another aspect of the invention, a variable valve timing control system of an internal combustion engine comprises a rotary member adapted to be driven in synchronization with rotation of an engine crankshaft, and rotatably supported on a camshaft to permit relative rotation of the camshaft to the rotary member, a hydraulically-operated phase converter disposed between the rotary member and the camshaft, and having a phase-advance hydraulic chamber and a phase-retard hydraulic chamber for changing an angular phase of the camshaft relative to the rotary member, an electric pump that supplies working fluid to the phase-advance hydraulic chamber and the phase-retard hydraulic chamber through a phase-advance hydraulic line connected to the phase-advance hydraulic chamber and a phase-retard hydraulic line connected to the phase-retard hydraulic chamber, an electromagnetic solenoid-operated directional control valve disposed between a first pair of fluid lines including a discharge line and an induction line of the pump and a second pair of fluid lines including the phase-advance hydraulic line and the phase-retard hydraulic line, for determining a path through which the working fluid is directed from the discharge line to a first one of the phase-advance hydraulic line and the phase-retard hydraulic line and simultaneously determining a path through which the working fluid is directed from the second hydraulic line to the induction line, a control unit configured to be electronically connected to at least the solenoid-operated directional control valve, for controlling the solenoid-operated directional control valve depending on an engine operating condition, a bypass line intercommunicating the discharge line and the induction line, and a bypass check valve disposed in the bypass line for permitting flow in a direction that the working fluid flows from the induction line via the bypass line to the discharge line and preventing any flow in the opposite direction.
According to a further aspect of the invention, a variable valve timing control system of an internal combustion engine comprises a rotary member adapted to be driven in synchronization with rotation of an engine crankshaft, and rotatably supported on a camshaft to permit relative rotation of the camshaft to the rotary member, a hydraulically-operated phase converter disposed between the rotary member and the camshaft, and having a phase-advance hydraulic chamber and a phase-retard hydraulic chamber for changing an angular phase of the camshaft relative to the rotary member, an electric pump that supplies working fluid to the phase-advance hydraulic chamber and the phase-retard hydraulic chamber through a phase-advance hydraulic line connected to the phase-advance hydraulic chamber and a phase-retard hydraulic line connected to the phase-retard hydraulic chamber, an electromagnetic solenoid-operated directional control valve disposed between a first pair of fluid lines including a discharge line and an induction line of the pump and a second pair of fluid lines including the phase-advance hydraulic line and the phase-retard hydraulic line, for determining a path through which the working fluid is directed from the discharge line to a first one of the phase-advance hydraulic line and the phase-retard hydraulic line and simultaneously determining a path through which the working fluid is directed from the second hydraulic line to the induction line, a bypass line intercommunicating the discharge line and the induction line, a control unit configured to be electronically connected to at least the solenoid-operated directional control valve, for controlling the solenoid-operated directional control valve depending on an engine operating condition, the control unit comprising a pump-failure detection section that detects a failure in the pump, and the control unit executes a fail-safe operating mode when the failure in the pump is detected by the pump-failure detection section, for creating a phase-control assistance force needed to supply the working fluid through the bypass line selectively to either one of the phase-advance hydraulic chamber and the phase-retard hydraulic chamber by a pulse pressure arising from alternating torque exerted on the camshaft, by controlling the solenoid-operated directional control valve without using the pump.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
Referring now to the drawings, particularly to
As shown in
Sprocket 1 has an outer toothed portion 1a formed on its outer periphery and in meshed-engagement with the timing chain, and a central bore 1b. Sprocket 1 is rotatably supported on the camshaft end by loosely fitting central bore 1b of sprocket 1 onto the outer peripheral surface of camshaft 2 in such a manner as to permit relative rotation of camshaft 2 to sprocket 1. Phase converter 3 is located on the front end (the left sidewall of sprocket 1 in
Camshaft 2 is rotatably supported on a cylinder head (not shown) by means of cam bearings. Camshaft 2 has a series of cams formed integral with the camshaft, for opening and closing engine valves via valve lifters (not shown).
Phase converter 3 includes a substantially cylindrical phase-converter housing 5 fixedly connected to sprocket 1 and a vane member 7 fixedly connected to the camshaft end. In the shown embodiment, housing 5 is bolted to the front end of sprocket 1, whereas vane member 7 is bolted to the front end of camshaft 2 with a vane mounting bolt 6 by tightening the bolt, so that vane member 7 is rotatably housed in the cylindrical housing 5. In lieu thereof, in order to change a relative phase of camshaft 2 to sprocket 1, vane member 7 is fixedly connected to the front end of sprocket 1 (the rotary member), whereas housing 5 is fixedly connected to the front end of camshaft 2. As best seen in
As can be appreciated from the hydraulic circuit diagram of
In the system of the embodiment shown in
As best seen in
As best seen in
Spool 36 is formed with the first, second, and third lands 36a, 36b, and 36c axially spaced from each other, for properly opening and closing the ports 35a–35e. Spool 36 is also formed with a communicating bore 40 comprised of a comparatively long, axially-extending central bore portion and a comparatively short, radial bore portion. The radial bore portion of communicating bore 40 communicates the fourth port 35d connected to induction line 17, whereas the axial bore portion of communicating bore 40 communicates a spring chamber of valve spring 37. The spring chamber of valve spring 37 is opened to the atmosphere. By virtue of communicating bore 40 intercommunicating the fourth port 35d connected to induction line 17 and the spring chamber opened to the atmosphere, it is possible to prevent a resistance to sliding movement of spool 36 from being generated or developed during operation of directional control valve 22.
Electromagnetic solenoid 38 includes a solenoid housing 38a, an electrically energized coil 38b, and a plunger (or an armature) 38c. As clearly shown in
As can be seen from the cross section of
In the system of the embodiment shown in
Electronic control unit (ECU) 33 generally comprises a microcomputer. ECU 33 includes an input/output interface (I/O), memories (RAM, ROM), and a microprocessor or a central processing unit (CPU). The input/output interface (I/O) of ECU 33 receives input information from various engine/vehicle switches and sensors, namely a crank angle sensor (or a crankshaft position sensor), a cam angle sensor (or a camshaft position sensor), an airflow meter, an engine temperature sensor (or an engine coolant temperature sensor), a throttle valve opening sensor (or a throttle position sensor), and an ignition switch. The crank angle sensor is provided for detecting revolutions of the engine crankshaft. Assuming that the number of engine cylinders is “n”, the crank angle sensor generates a reference pulse signal REF at a predetermined crank angle for every crank angle 720°/n, and simultaneously generates a unit pulse signal (1° or 2°). The processor of ECU 33 arithmetically calculates engine speed Ne based on the period of the reference pulse signal REF from the crank angle sensor. The cam angle sensor generates a cam-angle sensor signal indicative of an angular position θ
In a low engine speed and low engine load range (or with the engine at an idle rpm) just after the engine has been started, a control current is applied to motor 31 so as to rotate motor 31 in such a manner as to achieve an engine valve timing suitable to low engine speed and low engine load operation, while coil 38b of directional control valve 22 is de-energized with the duty ratio of the PWM signal switched to “0%”. Under such a low speed and low load condition, as shown in
Thereafter, assuming that the engine operating condition has been changed from low speed and low load operation to high speed and high load operation, a control current is applied to motor 31 so as to change from the valve timing (IVO, IVC) suitable to low speed and low load operation to the valve timing (IVO, IVC) suitable to high speed and high load operation, while the PWM signal of a high duty ratio suitable to the high speed and high load operation is applied to coil 38b of directional control valve 22. Under such a high speed and high load condition, as shown in
Thereafter, assuming that the engine operating condition has been changed from the high speed and high load operation to middle speed and middle load operation, by way of both of motor current control for electric motor 31 and PWM control for electric current applied to coil 38b of the solenoid-actuated directional control valve 22, vane member 7 rotates clockwise from its maximum phase-retarded angular position toward its intermediate angular position shown in
Thereafter, suppose that the engine operating condition shifts from the middle speed and middle load operation (or the low speed and low load operation) to engine stop operation. During a time period of engine idling that the engine is shifting to the stopped state, as described later in reference to the flow chart of
As can be appreciated from the above, the hydraulically-operated phase converter equipped variable valve timing control system of the embodiment can provide the following operation and effects (1)–(12).
(1) As is generally known, for instance, in the low engine speed range, a comparatively large magnitude of alternating torque (see
(2) When pump 18 is in inoperative during the phase-hold operating mode, each of the first and second ports 35a and 35b of directional control valve 22 are closed and thus there is no fluid flow through directional control valve 22 kept at the shut-off position. During the phase-hold operating mode, it is possible to certainly prevent the pulse pressure arising from the alternating torque from being transmitted from either one of phase-retard hydraulic line 14 and phase-advance hydraulic line 15 via directional control valve 22 to either one of discharge line 16 and induction line 17. Thus, it is possible to avoid the electric load needed to drive the motor shaft of non-reversible electric motor 31 of pump 18 from being affected by the pulse pressure during the phase-hold operating mode. Thus, it is possible to reduce the amount of electric current supplied to motor 31 when re-driving the motor shaft of motor 31.
(3) When the motor shaft of motor 31 of electric motor-driven pump 18 begins to rotate and thus the pumping action is insufficient or when pump 18 cannot be satisfactorily rotated owing to a pump failure (or a motor failure), bypass check valve 25 can be opened with the aid of the pulse pressure arising from the alternating torque and transmitted to induction line 17. With bypass check valve 25 opened with the aid of the pulse pressure, the working-fluid flow from induction line 17 via bypass line 21 to discharge line 16 is permitted, thus enabling working-fluid supply from one of phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10 via bypass line 21 to the other during low pump speed operation of pump 18 or in presence of a failure in pump 18. Thus, it is possible to operate the hydraulically-operated phase converter 3 by suitably controlling electromagnetic directional control valve 22 depending on an engine operating condition, even during low pump speed operation of pump 18 or in presence of a failure in pump 18.
(4) Furthermore, phase-converter housing 5 is comprised of a porous housing, which is made of a porous sintered metal member such as sintered alloy materials. Even when air has been mixed in working fluid in each of phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10 owing to oil leakage from the interior of phase converter 3 or oil leakage from each of phase-retard hydraulic line 14 and phase-advance hydraulic line 15, and discharge line 16 and induction line 17, arranged between pump 18 and phase converter 3 in the engine stopped state, it is possible to exhaust the air through the porous housing 5 to the exterior space by operating pump 18 and by rising the hydraulic pressure in each of hydraulic chambers 9 and 10. As a result, it is possible to prevent the control accuracy of variable valve timing control accomplished by means of phase converter 3 from being deteriorated owing to the air mixed in working fluid in each of hydraulic chambers 9 and 10. From the property of the porous housing 5, made of a porous sintered metal material, housing 5 permits only the air mixed in working fluid in each of hydraulic chambers 9 and 10 to be exhausted to the exterior space, but prevents undesirable leakage of working fluid having a comparatively high viscosity, thus avoiding a pressure drop in working fluid delivered from discharge line 16 to either one of hydraulic chambers 9 and 10.
(5) Moreover, reservoir check valve 26 is disposed in supply line 20 (see
(6) As can be seen from the system block diagram of
(7) Additionally, oil-purifying filter 27 of reservoir 19 is installed at a higher level than the oil level Lo of working fluid stored in reservoir 19 in a direction of acceleration of gravity. The working fluid splashed during operation of the valve operating mechanism tends to be dripped onto the upper face of oil-purifying filter 27. Thus, it is possible to effectively filter out or remove dust, dirt, or other contaminants mixed in the working fluid through oil-purifying filter 27. The upper oil-purifying filter 27, which is laid out at a higher level than the oil level Lo of reservoir 19, never serves as a fluid-flow resistance, in other words, an undesirable load carried on the motor shaft of electric motor-driven pump 18 during working-fluid supply from reservoir 19 to pump 18. This prevents or avoids the responsiveness of operation of electric motor-driven pump 18 from being deteriorated.
(8) To provide the fluid-tight sealing action for each of phase-retard hydraulic chambers 9, 9, 9, and 9 and phase-advance hydraulic chambers 10, 10, 10, and 10 of phase converter 3 and to prevent leakage of working fluid from at least hydraulic chambers 9 and 10, oil seals 41a, 41b, 41b, and 41b are placed at the fitting portion between front cover 11 and fluid-line structural block 30 formed with phase-retard hydraulic line 14, phase-advance hydraulic line 15 and supply line 44. Oil seals 42a and 42a are placed at the fitting portions between phase-converter housing 5 and front cover 11 and between phase-converter housing 5 and sprocket 1. An oil seal 42b is also placed at the fitting portion between vane rotor 12 and sprocket 1. Thus, it is possible to effectively prevent leakage of oil from at least phase-retard hydraulic chambers 9, 9, 9, and 9 and phase-advance hydraulic chambers 10, 10, 10, and 10, in the engine stopped state, thereby preventing air from being mixed in working fluid in each of hydraulic chambers 9 and 10.
(9) For the purpose of working fluid supply (or hydraulic pressure supply), electric motor-driven oil pump 18 is provided as a main working fluid source (or a main hydraulic pressure source). Also provided is oil pump 43 that supplies moving engine parts with lubricating oil and serves as a supplementary working-fluid source (or a supplementary pump operable independently of electric motor-driven pump 18) for the hydraulically-operated phase converter 3. Phase converter 3 is formed with an air bleeder (air bleeding means) that acts to exhaust air undesirably mixed in working fluid in each of hydraulic chambers 9 and 10 to the exterior space. As discussed above, the porous phase-converter housing 5, which is made of a porous sintered metal material, serves as the air bleeder. By the aid of the working fluid pressurized by and oil pump 43 and discharged and routed from oil pump 43 (the supplementary working-fluid source) through supply line 44, working-fluid chamber 45, inclined oil passages 46 and 46 and side clearance space 47 into each of phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10, it is possible to effectively forcibly exhaust the air mixed in working fluid in each of hydraulic chambers 9 and 10 through the porous housing 5 (serving as the air bleeder) to the exterior space. At the same time, by the aid of the pressurized working fluid discharged from oil pump 43 (the supplementary working-fluid source) to each of hydraulic chambers 9 and 10, it is possible to suitably compensate for the insufficiency of oil (working fluid) corresponding to the quantity of air exhausted. As a result, it is possible to prevent the control accuracy of variable valve timing control (phase control) of phase converter 3 from being deteriorated owing to the air mixed in working fluid in each of hydraulic chambers 9 and 10. Additionally, even when electric motor-driven pump 18 of two pumps 18 and 43 has been failed, it is possible to charge or feed working fluid from oil pump 43 to each of hydraulic chambers 9 and 10 of phase converter 3.
(10) As previously described (see the effect (3)), with bypass check valve 25 opened due to the pulse pressure, the working-fluid flow from induction line 17 through bypass line 21 to discharge line 16 is permitted, thus enabling working-fluid supply from one of hydraulic chambers 9 and 10 via bypass line 21 to the other during low pump speed operation of pump 18 or in presence of a failure of pump 18. Moreover, in the system of the embodiment, even during low pump speed operation of pump 18 or in presence of a failure in pump 18, it is possible to deliver or feed working fluid from oil pump 43 (the supplementary working-fluid source) through supply line 44, working-fluid chamber 45, inclined oil passages 46 and 46 and side clearance space 47 into each of hydraulic chambers 9 and 10. Thus, it is possible to more certainly keep a sufficient working-fluid charged state wherein working fluid is satisfactorily charged and stored in each of hydraulic chambers 9 and 10, even during low pump speed operation of pump 18 or in presence of a failure in pump 18.
(11) Furthermore, the working fluid, discharged from oil pump 43 (the supplementary working-fluid source), and then routed through the working-fluid passage 44–46 into each of hydraulic chambers 9 and 10 can be greatly restricted or constricted by means of a fluid-flow constricting orifice (side clearance space 47) located downstream of the working-fluid passage 44–46 and intercommunicating both of phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10. By the provision of the fluid-flow constricting orifice (side clearance space 47), it is possible to prevent a pressure differential between phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10 from being created during operation of oil pump 43. That is to say, the fluid-flow constricting orifice (side clearance space 47) acts to avoid or prevent the hydraulically-operated phase converter 3 from being undesirably operated owing to the working-fluid supply from oil pump 43 to each of hydraulic chambers 9 and 10 of phase converter 3. Additionally, the fluid-flow constricting orifice is comprised of side clearance space 47, which is defined between the inner peripheral surface of phase-converter housing 5 and the end face of vane member 7 in sliding-contact with the inner peripheral surface of housing 5. More concretely, the fluid-flow constricting orifice is comprised of side clearance space 47, which is defined between the rear end face of each blade 13 of vane member 7 and the front end face (the left-hand sidewall) of sprocket 1. In this manner, the fluid-flow constricting orifice (side clearance space 47) is simply formed or defined between the existing phase-converter housing 5 and vane member 7. Thus, there is no necessity of an additional orifice. Side clearance space 47, easily simply defined between vane member 7 and sprocket 1, contributes to the simplified hydraulic circuit (or the simplified hydraulic system) for the hydraulically-operated phase converter 3.
(12) Also provided is oil-purifying filter 48 disposed in the upstream portion of supply line 44 of oil pump 43 (the supplementary working-fluid source). By the provision of oil-purifying filter 48 disposed in supply line 44, it is possible to effectively filter out or remove dust, dirt, or other contaminants contained in working fluid discharged from oil pump 43 through oil-purifying filter 48. Oil-purifying filter 48 disposed in supply line 44 serves as a fluid-flow resistance, thus producing a slight energy loss (i.e., a slight pressure drop). However, there is no problem, since oil pump 43 itself functions as the supplementary working-fluid source that supplies a slight amount of working fluid to the hydraulically-operated phase converter 3, if needed.
Referring now to
At step S1, a check is made to determine whether switching from the turned-ON state of the ignition switch to the turned-OFF state occurs during idling of the engine. When the answer to step S1 is in the affirmative (YES), that is, when the ignition switch becomes turned OFF, the routine proceeds from step S1 to step S2. When the answer to step S1 is in the negative (NO), that is, when the ignition switch remains turned ON, the routine returns to the main program to execute the usual variable valve timing control based on the current engine operating condition.
At step S2, the latest up-to-date information concerning engine speed Ne, determined based on the sensor signal from the crank angle sensor, is read.
At step S3, a check is made to determine whether the current engine speed Ne is less than or equal to a predetermined engine-speed lower limit NTHL, such as 50 rpm. When the answer to step S3 is negative (NO), that is, in case of Ne>NTHL, the routine proceeds from step S3 to step S4.
At step S4, under the condition defined by the inequality of Ne>NTHL, the hydraulically-operated vane-type phase converter 3 (exactly, each of blades 13 of vane member 7 of phase converter 3) is controlled from the initial position (or the reference phase-angle position) obtained at the beginning of the engine starting period to the previously-discussed engine-restart standby position, properly phase-advanced from the maximum phase-retarded angular position shown in
At step S5, a check is made to determine, based on the latest up-to-date information concerning cam angle θ
At step S6, in order to achieve the phase-hold operating mode and to retain the engine-restart standby position of phase converter 3 unchanged, electromagnetic directional control valve 22 is controlled to its shut-off position (i.e., the intermediate axial position of spool 36 shown in
Returning to step S3, conversely when the answer to step S3 is affirmative (YES), that is, in case of Ne≦NTHL, the routine proceeds from step S3 to step S7.
At step S7, an engine-stop timer is set to a predetermined delay period during which the shut-off position of electromagnetic directional control valve 22 is retained unchanged, for measuring an elapsed time from the point of time when switching to the ignition-switch turned-OFF state has occurred.
At step S8, the duty ratio of the PWM signal applied to coil 38b of electromagnetic directional control valve 22 is fixed to the predetermined middle duty ratio so as to hold electromagnetic directional control valve 22 at the shut-off position.
At step S9, a check is made to determine whether the predetermined delay period of the engine-stop timer initialized at step S7 has expired. When the answer to step S9 is negative (NO), that is, when the predetermined delay period of the engine-stop timer has not yet expired, the routine returns from step S9 to step S8 in order to succeedingly hold electromagnetic directional control valve 22 at the shut-off position. Conversely when the answer to step S9 is affirmative (YES), that is, when the delay period of the engine-stop timer has expired, the routine advances from step S9 to step S10.
At step S10, the engine-stop timer is reset. After step S10, steps S11 and S12 occur.
At step S11, the electric current applied to non-reversible electric motor 31 of motor-driven oil pump 18 is controlled to “0” to stop electric motor 31 of pump 18.
At step S12, the duty ratio of the PWM signal applied to coil 38b of electromagnetic directional control valve 22 is controlled to the predetermined low duty ratio such as “0%”, so as to de-energize electromagnetic directional control valve 22.
As set out above, in accordance with the engine-stop-period phase control shown in
Referring now to
At step S21, just after switching to the ignition-switch turned-ON state, a system-failure detection timer is set to a predetermined delay period representing the time allowed for pressure switch 24 to be switched ON if there is no system failure, more concretely, if electric motor-driven pump 18 and/or non-reversible electric motor 31 is unfailed and operating normally.
At step S22, the solenoid-actuated directional control valve 22 is shifted to its operative state. Actually, coil 38b of directional control valve 22 is energized and de-energized by a duty cycle pulsewidth modulated (PWM) signal at a controlled duty ratio, so that the axial position of spool 36 of the solenoid-actuated directional control valve 22 is controlled and axially slid for a phase change (a phase advance or a phase retard), which is determined based on the current engine operating condition. For instance, when the phase advance is required, the duty ratio of the PWM signal applied to coil 38b is set to the predetermined low duty ratio such as “0%”, such that spool 36 is controlled to the spring-offset position in which fluid communication between discharge line 16 and phase-advance hydraulic line 15 is established and simultaneously fluid communication between induction line 17 (or drain line 39) and phase-retard hydraulic line 14 is established, in order to attain the phase-advance operating mode. Conversely when the phase retard is required, the duty ratio is set to the predetermined high duty ratio such as “100%”, such that spool 36 is controlled to the maximum actuated position in which fluid communication between discharge line 16 and phase-retard hydraulic line 14 is established and simultaneously fluid communication between induction line 17 and phase-advance hydraulic line 15 is established, in order to attain the phase-retard operating mode.
At step S23, electric motor 31 is energized.
At step S24, a switch signal from pressure switch 24 is read.
At step S25, a check is made to determine whether the switch signal from pressure switch 24 is high, in other words, pressure switch 24 is switched ON. When the answer to step S25 is negative (NO), that is, when pressure switch 24 is switched OFF, the routine proceeds from step S25 to step S26. Conversely when the answer to step S25 is affirmative (YES), that is, pressure switch 24 is switched ON, the routine proceeds from step S25 to step S33. The processor of ECU 33 determines, based on the state of pressure switch 24 switched OFF, that the hydraulic pressure in discharge line 16 is not satisfactorily risen. On the contrary, the processor of ECU 33 determines, based on the state of pressure switch 24 switched ON, that the hydraulic pressure in discharge line 16 is satisfactorily risen.
At step S26, a check is made to determine whether the predetermined delay period of the system-failure detection timer initialized at step S21 has expired. When the answer to step S26 is negative (NO), that is, when the predetermined delay period of the system-failure detection timer has not yet expired, the routine returns from step S26 to step S24 in order to repeatedly execute steps S24–S25. Conversely when the answer to step S26 is affirmative (YES), that is, when the delay period of the system-failure detection timer has expired, the routine advances from step S26 to step S27. When the flow from step S25 via step S26 to step S27 occurs, the processor of ECU 33 determines that there is a less amount of working fluid discharged from pump 18 in spite of electric motor 31 already energized. This is because the hydraulic pressure in discharge line 17 does not yet reach the predetermined pressure point after the predetermined elapsed time has expired with motor 31 energized. That is, steps S25–S26 and the system-failure detection timer and pressure switch 24 serve as an abnormal-condition detection means or a system-failure detection means that detects an abnormal-condition of motor 31 of electric pump 18 (or a motor/pump failure). In particular, steps S25–S26 serves as a pump-failure detection section of the processor of ECU 33 that detects a pump failure or determines that pump 18 is failed when the hydraulic pressure detected by pressure switch 24 remains at a pressure level less than the predetermined pressure point after electric motor 31 of pump 18 has been energized and thereafter the predetermined delay period (a set time of the system-failure detection timer) has expired.
At step S27, the system-failure detection timer is reset. After step S27, a series of steps S28–S32 occur.
At step S28, the duty ratio of the PWM signal applied to coil 38b of electromagnetic directional control valve 22 is controlled to the predetermined low duty ratio such as “0%”, so as to de-energize electromagnetic directional control valve 22.
At step S29, the electric current applied to non-reversible electric motor 31 of motor-driven oil pump 18 is controlled to “0” to stop electric motor 31 of pump 18.
At step S30, an electric motor-driven pump failure indicative flag (simply, a pump failure flag) is set to “1”.
At step S31, an electromagnetic-directional-control-valve (OCV) control map change from a normal-condition OCV control map (suitable to the absence of the pump failure) to an abnormal-condition OCV control map (suitable to the presence of the pump failure) occurs. Therefore, after switching to the abnormal-condition OCV control map, it is possible to keep bypass line 21 opened, and thus to return working fluid, which is flown from either one of phase-retard hydraulic chamber 9 and phase-advance hydraulic chamber 10 into induction line 17, utilizing the pulse pressure arising from alternating torque exerted on camshaft 2 and applied to the working fluid in each of hydraulic chambers 9 and 10, via bypass line 21 to discharge line 16, by continuously controlling electromagnetic directional control valve 22 based on the current engine operating condition in accordance with the abnormal-condition OCV control map. By the use of abnormal-condition OCV control map, it is possible to supply working fluid (hydraulic pressure) from induction line 17 through bypass line 21 and discharge line 16 selectively to hydraulic chambers 9 and 10, either one of which requires a hydraulic pressure rise, utilizing the pulse pressure, thus creating a phase-control assistance force by the pulse pressure without using pump 18, even in presence of the pump failure.
At step S32, ECU 33 outputs an alarm signal to the warning system (warning means) having the warning buzzer and/or instrument-cluster warning lamp 33
Returning to step S25, when pressure switch 24 is switched ON, ECU 33 determines that electric motor-driven pump 18 is operating normally, and thus the routine flows from step S25 to step S33. After step S33, a series of steps S34–S38 occur.
At step S33, the system-failure detection timer is reset.
At step S34, electromagnetic directional control valve 22 is controlled based on the current engine operating condition (the latest up-to-date information about engine speed and/or engine load) in accordance with the normal-condition OCV control map.
At step S35, a deviation (or an error signal) of an actual angular phase of vane member 7 of phase converter 3 from a desired angular phase determined based on the current engine operating condition is calculated or computed.
At step S36, a check is made to determine whether the deviation (the error signal value) between the actual angular phase and the desired angular phase is within a predetermined dead zone. When the answer to step S36 is affirmative (YES), that is, the deviation is within the dead zone, the routine proceeds from step S36 to step S37. Conversely when the answer to step S36 is negative (NO), that is, the deviation is out of the dead zone, the routine returns from step S36 to step S35, so as to repeatedly execute steps S35–S36.
At step S37, a check is made to determine whether a drive signal of non-reversible electric motor 31 of electric motor-driven pump 18 is generated from the output interface of ECU 33, in other words, motor 31 is energized (ON). When the answer to step S37 is affirmative (YES), the routine proceeds from step S37 to step S38. Conversely when the answer to step S37 is negative (NO), the routine returns from step S37 to step S35, so as to repeatedly execute steps S35–S37.
At step S38, the system-failure detection timer is set again. After step S38, the routine returns to step S24, so as to repeatedly execute the fail-safe routine.
As discussed above in reference to the flow chart of
The processor of ECU 33 incorporated in the system of the embodiment is also programmed to execute engine-stall-period phase control similar to the engine-stop-period phase control routine shown in
As a modification modified from the variable valve timing control system of the embodiment, an air bleeder (or air bleeding means) may be provided in a hydraulic pressure system laid out between the hydraulically-operated phase converter 3 and electric motor-driven pump 18 (a main working-fluid (hydraulic pressure) source) in order to exhaust or extract air mixed in working fluid in the hydraulic system to the exterior space. By means of the air bleeder, it is possible to effectively exhaust or extract undesirable air, which has been mixed in working fluid in each of hydraulic chambers 9 and 10 of phase converter 3 or in the hydraulic pressure system laid out between phase converter 3 and pump 18 due to leakage of working fluid in the engine stopped state, through the air bleeder to the exterior space. As a result of this, it is possible to prevent the control accuracy of variable valve timing control of the hydraulically-operated phase converter 3 from being deteriorated owing to the air mixed. In the system of the shown embodiment, phase-converter housing 5, which is comprised of a porous housing formed of a porous sintered metal material, serves as the air bleeder (air bleeding means). In lieu thereof, the air bleeder may be provided in the hydraulic pressure system laid out between the hydraulically-operated phase converter 3 and electric motor-driven pump 18, except the phase-converter housing. In such a case, a certain portion of the hydraulic pressure system may be formed of a porous sintered structural part. By the use of the porous sintered structural part, it is possible to effectively exhaust or extract only the air mixed in working fluid in the hydraulic pressure system for phase converter 3, while preventing leakage of working fluid (oil) having a comparatively high viscosity, as much as possible. This avoids a pressure fall in working fluid delivered from pump 18 through discharge line 16 to either one of hydraulic chambers 9 and 10.
Referring now to
In the shown embodiment, the hydraulically-operated phase converter 3 is constructed by hydraulically-operated vane-type timing variator. The fundamental concept of the invention can be applied to a variable valve timing control system employing a hydraulically-operated helical-gear-type timing variator. Furthermore, in the shown embodiment, the variable valve timing control system is exemplified to control a phase (intake valve open timing IVO and/or intake valve closure timing IVC) of the intake valve. In lieu thereof, the variable valve timing control system of the invention may be applied to each exhaust valve of an exhaust system so as to control a phase (exhaust valve open timing EVO and/or exhaust valve closure timing EVC) of the exhaust valve.
The entire contents of Japanese Patent Application No. 2004-149890 (filed May 20, 2004) are incorporated herein by reference.
While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-149890 | May 2004 | JP | national |
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