US20020017258A1 - Variable performance valve train having three-dimensional cam - Google Patents
Variable performance valve train having three-dimensional cam Download PDFInfo
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- US20020017258A1 US20020017258A1 US09/963,561 US96356101A US2002017258A1 US 20020017258 A1 US20020017258 A1 US 20020017258A1 US 96356101 A US96356101 A US 96356101A US 2002017258 A1 US2002017258 A1 US 2002017258A1
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- Prior art keywords
- valve
- engine
- intake
- camshaft
- actuator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0203—Variable control of intake and exhaust valves
- F02D13/0207—Variable control of intake and exhaust valves changing valve lift or valve lift and timing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
- F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
- F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
- F01L13/0042—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction with cams being profiled in axial and radial direction
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0203—Variable control of intake and exhaust valves
- F02D13/0207—Variable control of intake and exhaust valves changing valve lift or valve lift and timing
- F02D13/0211—Variable control of intake and exhaust valves changing valve lift or valve lift and timing the change of valve timing is caused by the change in valve lift, i.e. both valve lift and timing are functionally related
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0223—Variable control of the intake valves only
- F02D13/0226—Variable control of the intake valves only changing valve lift or valve lift and timing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0242—Variable control of the exhaust valves only
- F02D13/0246—Variable control of the exhaust valves only changing valve lift or valve lift and timing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0261—Controlling the valve overlap
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L2800/00—Methods of operation using a variable valve timing mechanism
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L2800/00—Methods of operation using a variable valve timing mechanism
- F01L2800/11—Fault detection, diagnosis
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0203—Variable control of intake and exhaust valves
- F02D13/0215—Variable control of intake and exhaust valves changing the valve timing only
- F02D13/0219—Variable control of intake and exhaust valves changing the valve timing only by shifting the phase, i.e. the opening periods of the valves are constant
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0261—Controlling the valve overlap
- F02D13/0265—Negative valve overlap for temporarily storing residual gas in the cylinder
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Definitions
- the present invention relates to a variable performance valve train used in internal combustion engines. More particularly, the present invention pertains to a variable performance valve train having three-dimensional cams, the profile of which continuously changes along the axis of a camshaft.
- Japanese Unexamined Patent Publication No. 5-125966 discloses a first prior art apparatus, which includes a variable valve lift mechanism.
- the variable valve lift mechanism includes intake and exhaust valves, which are driven by camshafts, and low speed and high speed cams for driving the intake valves or the exhaust valves.
- the mechanism varies the valve lift, or the valve open angle, of the intake valves or the exhaust valves.
- the valve open angle refers to an angle of rotation of a crankshaft during which an intake valve or an exhaust valve is open.
- the mechanism of Japanese Unexamined Patent Publication No. 5-125966 selects a set of cams that will decrease the engine power. Specifically, the mechanism uses either high speed cams or low speed cams such that the vehicle speed is reduced.
- a variable performance valve train according to a second prior art apparatus has three-dimensional cams, the profile of which continuously changes along the axis of a camshaft.
- a valve train having three-dimensional cams cannot employ the valve switching control and fail-safe control for decreasing the engine power.
- a valve train according to a third prior art apparatus disclosed in Japanese Unexamined Patent Publication 8-177434 includes the high speed and low speed cams of Publication No. 5-125966 and a variable valve timing mechanism.
- the variable valve timing mechanism adjusts the rotational phase of the camshaft.
- variable valve lift mechanism uses the low speed cams, and the variable valve timing mechanism retards the rotational phase of the camshaft. This prevents the intake valves from interfering with the pistons and the exhaust valves.
- a malfunction of the variable valve lift mechanism could be either a malfunction of the low speed cams or a malfunction of the high speed cams.
- different programs must be prepared for a malfunction of the low speed cams and for a malfunction of the high speed cams.
- the two fail-safe controls increase the time and effort required to make the programs and increase the required memory capacity for storing the programs.
- variable valve lift mechanism If the variable valve lift mechanism malfunctions when the high speed cams are being used, the mechanism may not be able to switch to the low speed cams. In this case, engine starting and engine speed stability will deteriorate.
- variable performance valve train that facilitates engine starting and stabilizes the engine speed when there is a malfunction thereby making it easier for the driver take steps to correct the malfunction.
- the present invention provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of at least one of an intake valve and an exhaust valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to decrease valve overlap.
- the present invention further provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of an intake valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to advance the closing timing of the intake valve.
- the present invention provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of an exhaust valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to retard the opening timing of the exhaust valve.
- the present invention further provides a method for changing the valve performance of at least one of an exhaust valve and an intake valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and decreasing valve overlap when the engine is judged to be running abnormally.
- the present invention provides a method for changing the valve performance of an intake valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and advancing the closing timing of the intake valve for performing a failsafe when the engine is judged to be running abnormally.
- the present invention further provides a method for changing the valve performance of an exhaust valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and advancing the closing timing of the exhaust valve when the engine is judged to be running abnormally.
- the present invention provides a valve train for an internal combustion engine, comprising: an axially movable camshaft rotatably supported on the engine; a three-dimensional cam located on the camshaft to selectively open and close a valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction; an actuator for axially moving the camshaft to change at least the valve lift of the valve lift and the valve timing of the valve; a fluid pressure source for generating fluid pressure to actuate the actuator; and a control valve for adjusting the position of the camshaft by controlling fluid pressure supplied to the actuator from the fluid pressure source; wherein a default position toward which the camshaft is moved when the control of fluid pressure by the control valve is stopped is the same as a default position toward which the camshaft is moved when the fluid pressure source is not supplying fluid pressure to the actuator.
- FIG. 1 is a partial perspective view and a block diagram illustrating a variable performance valve train according to a first embodiment of the present invention
- FIG. 2 is a partial perspective view illustrating a three-dimensional cam in the valve train of FIG. 1;
- FIG. 3 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve in the valve train of FIG. 1;
- FIG. 4 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 3;
- FIG. 5 is a diagrammatic cross-sectional view illustrating an operational state of the oil control valve of FIGS. 3 and 4;
- FIGS. 6 (A) and 6 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train of FIG. 1;
- FIG. 7 is a flowchart showing a routine executed by an ECU for controlling the oil control valve of the valve train of FIG. 1;
- FIGS. 8 (A) and 8 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a valve train according to a second embodiment of the present invention.
- FIG. 9 is a flowchart showing a routine executed by an ECU for controlling an oil control valve of the valve train of the second embodiment
- FIGS. 10 (A) and 10 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a variable performance valve train according to a fourth embodiment of the present invention.
- FIG. 11 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve in a variable performance valve train according to a sixth embodiment of the present invention.
- FIG. 12 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 11;
- FIGS. 13 (A) and 13 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the sixth embodiment
- FIG. 14 is a flowchart showing a routine executed by an ECU for controlling the oil control valve of the valve train according to the sixth embodiment
- FIGS. 15 (A) and 15 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve according to a seventh embodiment of the present invention.
- FIG. 16 is a flowchart showing a routine executed by an ECU for controlling an oil control valve of a variable performance valve train according to the seventh embodiment
- FIGS. 17 (A) and 17 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a valve train according to a ninth embodiment of the present invention.
- FIG. 18 is a partial perspective view illustrating a variable performance valve train according to an eleventh embodiment of the present invention.
- FIG. 19 is a diagrammatic cross-sectional view illustrating a valve actuator and a first oil control valve of the valve train of FIG. 18;
- FIG. 20 is a diagrammatic cross-sectional view illustrating a variable valve timing mechanism and a second oil control valve of the valve train shown in FIG. 18;
- FIG. 21 is a front view illustrating the variable valve timing mechanism of FIG. 20 with the cover removed;
- FIG. 22 is an enlarged cross-sectional view illustrating a lock pin of the mechanism of FIG. 20;
- FIG. 23 is also an enlarged cross-sectional view illustrating a lock pin FIG. 22 when the pin is engaged with a recess;
- FIG. 24 is a front view illustrating the vane rotor of the mechanism of FIG. 20 with the cover removed;
- FIGS. 25 (A) and 25 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in the mechanism of FIG. 18;
- FIG. 26 is a flowchart showing a routine executed by an ECU for controlling the first oil control valve of the valve train shown in FIG. 18;
- FIG. 27 is a flowchart showing a routine executed by an ECU for controlling the second oil control valve of the valve train shown in FIG. 18;
- FIGS. 28 (A) and 28 (B) are maps for determining a target advance angle and a target shaft position of the valve train shown in FIG. 18;
- FIG. 29 is a perspective view illustrating a variable performance valve train according to a twelfth embodiment of the present invention.
- FIGS. 30 (A) and 30 (B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train shown in FIG. 29;
- FIG. 31 is a graph showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train shown in FIG. 29 when there is a malfunction in the engine;
- FIG. 32 is a graph showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of a variable performance valve train according to another embodiment of the present invention when there is a malfunction in the engine;
- FIG. 33 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve according to a fifteenth embodiment of the present invention.
- FIG. 34 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 33;
- FIG. 35 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve according to a seventeenth embodiment of the present invention.
- FIG. 36 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 35;
- FIG. 37 is a perspective view illustrating a cam follower mechanism for an intake cam or an exhaust cam
- FIG. 38 is a perspective exploded view showing the cam follower of FIG. 37;
- FIG. 39(A) is a front view showing the cam follower of the mechanism shown in FIG. 37;
- FIG. 39(B) is a top plan view showing the cam follower of FIG. 39(A);
- FIG. 39(C) is a right side view showing the cam follower of FIG. 39(A);
- FIG. 39(D) is a bottom view showing the cam follower of FIG. 39(A);
- FIG. 40 is a diagrammatic view showing the characteristics of the cam follower shown in FIG. 39(A).
- FIG. 41 is a perspective view illustrating an intermediate product when manufacturing the cam follower of FIG. 39(A).
- variable performance valve train according to a first embodiment of the present invention will now be described with reference to FIGS. 1 to 7 .
- an in-line four cylinder type engine 11 has a cylinder block 13 , an oil pan 13 a , which is located under the cylinder block 13 , and a cylinder head 14 , which is located on top of the cylinder block 13 .
- Pistons 12 (only one is shown) are reciprocally accommodated in the cylinder block 13 .
- An output shaft, or crankshaft 15 is rotatably supported in the lower portion of the engine 11 .
- Each piston 12 is connected to the crankshaft 15 by a connecting rod 16 .
- the connecting rods 16 convert reciprocation of the pistons 12 into rotation of the crankshaft 15 .
- a combustion chamber 17 is defined above each piston 12 .
- An exhaust passage 18 and an intake passage 19 are connected to the combustion chamber 17 .
- a pair of exhaust valves 20 selectively connect and disconnect the combustion chamber 17 with the exhaust passage 18 .
- a pair of intake valves 21 selectively connect and disconnect the combustion chamber 17 with the intake passage 19 .
- An exhaust camshaft 22 and an intake camshaft 23 are rotatably supported in the cylinder head 14 .
- the exhaust camshaft 22 and the intake camshaft 23 extend parallel to each other and to the crankshaft 15 .
- the exhaust camshaft 22 is axially fixed.
- the intake camshaft 23 is axially movable.
- a timing pulley 24 a is fixed to a first end (left end as viewed in the drawing) of the exhaust camshaft 22 .
- a variable valve lift actuator 25 which includes a timing pulley 25 a , is fixed to a first end (left end as viewed in the drawing) of the intake camshaft 23 .
- the variable valve lift actuator 25 axially moves the intake camshaft 23 to change the cam profile of three-dimensional intake cams 28 . Accordingly, the valve open angle and the valve lift of the intake valves 21 are adjusted.
- the timing pulleys 24 a , 25 a are connected to a timing pulley 15 a fixed to the crankshaft 15 by a timing belt 26 .
- the timing belt 26 transmits rotation of the crankshaft 15 to the exhaust and intake camshafts 22 , 23 . Accordingly, the exhaust and intake camshafts 22 , 23 are rotated in synchronization with the crankshaft 15 .
- Pairs of exhaust cams 27 are located on the exhaust camshaft 22 . Each pair of the exhaust cams 27 contacts a corresponding pair of valve lifters 29 located at the top of a corresponding pair of exhaust valves 20 .
- the intake cams 28 are located on the intake camshaft 23 . Each pair of intake cams 28 contacts a corresponding pair of valve lifters 29 located on the top of a corresponding pair of intake valves 21 .
- Rotation of the exhaust camshaft 22 causes each exhaust valve 20 to selectively open and close in accordance with the profile of the associated exhaust cam 27 .
- rotation of the intake camshaft 23 causes each intake valve 21 to selectively open and close in accordance with the profile of the associated intake cam 28 .
- each exhaust cam 27 does not vary along the axis of the exhaust camshaft 22 .
- the intake cams 28 are three-dimensional as illustrated in FIG. 2. That is, the profile of each intake cam 28 continuously changes along the axis of the intake camshaft 23 .
- the intake cams 28 When the intake camshaft 23 is moved in a direction indicated by arrow A, the intake cams 28 continuously increase the valve lift of the intake valves 21 , which advances the opening timing of the intake valves 21 and retards the closing timing of the intake valves 21 . Accordingly, the valve open angle of the intake valves 21 is gradually extended. If the intake camshaft 23 is moved in the opposite direction of arrow A, the intake cams 28 continuously decrease the valve lift of the intake valves 21 , which retards the opening timing of the intake valves 21 and advances the closing timing of the intake valves 21 . Accordingly, the valve open angle is gradually shortened.
- Axial movement of the intake camshaft 23 continuously changes the valve open angle and the valve lift of the intake valves 21 .
- variable valve lift actuator 25 and an oil supply system will be described with reference to FIG. 3.
- the oil supply system hydraulically drives the actuator 25 .
- the variable valve lift actuator 25 includes the timing pulley 25 a .
- the timing pulley 25 a includes a cylindrical boss 151 , a disk 152 and outer teeth 153 .
- the boss 151 slidably supports the intake camshaft 23 .
- the disk 152 extends radially from the boss 151 .
- the teeth 153 are formed on the circumferential surface of the disk 152 .
- the boss 151 is rotatably supported by a support 14 b of the cylinder head 14 .
- the intake camshaft 23 can move axially in the boss 151 .
- a cover 154 is secured to the pulley 25 a by bolts 155 to cover the distal end of the intake camshaft 23 .
- Inner teeth 157 are formed on the inner face of the cover 154 .
- the inner teeth 157 extend along the axis of the intake camshaft 23 and form an internal gear.
- a ring gear 162 is fastened to the distal end of the intake camshaft 23 by a hollow bolt 158 and a pin 159 .
- Outer teeth 163 are formed on the ring gear 162 .
- the outer teeth 163 extend along the axis of the intake camshaft 23 and form a spur gear.
- the outer teeth 163 mesh with the inner teeth 157 .
- the ring gear 162 does not rotate relative to the timing pulley 25 a but moves axially together with the intake camshaft 23 along the axis of the intake camshaft 23 .
- the ring gear 162 has a radially extending flange 162 a , which forms a piston.
- the ring gear 162 slidably contacts the inner surface of the cover 154 and defines first and second oil pressure chambers 165 , 166 .
- First and second oil conduits 167 and 168 are formed in the intake camshaft 23 .
- the first and second oil conduits 167 , 168 are connected to the first and second oil chambers 165 , 166 , respectively.
- the first oil conduit 167 is connected to the first oil chamber 165 by the interior of the hollow bolt 158 and extends through the cylinder head 14 to an oil control valve (OCV) 170 .
- the second oil conduit 168 is connected to the second oil chamber 166 through the boss 151 of the timing pulley 25 a and an oil hole 172 , and extends through the cylinder head 14 to the OCV 170 .
- a supply passage 128 and a drain passage 130 are connected to the OCV 170 .
- the supply passage 128 is connected to an oil pan 13 a via an oil pump P.
- the drain passage 130 is directly connected to the oil pan 13 a.
- the OCV 170 has a casing 116 .
- the casing 116 has first and second oil ports 118 , 120 , first and second drain ports 122 , 124 and a supply port 126 .
- the first oil port 118 is connected to a passage P 1 and the second oil port 120 is connected to a passage P 2 .
- the supply port 126 is connected to a supply passage 128 .
- the first and second drain ports 122 , 124 are connected to a drain passage 130 .
- Oil supplied by the oil pump P is conducted to the actuator 25 via the supply passage 128 and the OCV 170 . Oil from the actuator 25 is drained to the oil pan 13 a via the OCV 170 and the drain passage 130 .
- the OCV 170 includes a spool 138 , a coil spring 134 and an electromagnetic solenoid 136 .
- the spool 138 has four valve bodies 132 .
- the coil spring 134 urges the spool 138 axially toward the solenoid 136 .
- the solenoid 136 moves the spool 138 axially leftward (as viewed in FIG. 3).
- each cam follower 21 a contacts the small profile portion (low valve lift portion) of the associated intake cam 28 . This decreases the valve lift and the valve open angle of the intake valves 21 .
- the valve performance of the exhaust and intake valves 20 , 21 which includes the valve lift of the valves 20 , 21 , corresponding to FIG. 3, is shown in FIG. 6(A). As shown in FIG. 6(A), there is no valve overlap of the valves 20 , 21 .
- the solenoid 136 When excited, the solenoid 136 displaces the spool 138 to the leftmost position in the casing 116 against the force of the coil spring 134 as shown in FIG. 4. This communicates the second port 120 with the second drain port 124 and the first port 118 with the supply port 126 .
- oil in the oil pan 13 a is supplied to the first oil pressure chamber 165 via the supply passage 128 , the OCV 170 , the passage P 1 and the first conduit 167 .
- Oil in the second pressure chamber 166 is drained to the oil pan 13 a via the oil hole 172 , the second conduit 168 , the passage P 2 , the OCV 170 and the drain passage 130 .
- FIG. 6(B) shows a maximum valve overlap of the valves 20 , 21 .
- the spool 138 can be positioned midway between the leftmost position and the rightmost position in the casing 116 by controlling current to the solenoid 136 .
- the first and second ports 118 , 120 are closed and oil flow through the ports 118 , 120 is stopped. Oil is therefore not supplied to or drained from the first and second pressure chambers 165 , 166 . Oil remaining in the chambers 165 , 166 fixes the position of the ring gear 162 , which fixes the axial position of each intake cam 28 relative to the associated cam follower 21 a . In other words, the current valve lift and the valve open angle of the intake valves 21 are maintained.
- the vehicle includes an electronic control unit (ECU) 180 to control the valve lift of the intake valves 21 .
- ECU 180 controls the electricity supplied to the OCV 170 .
- the ECU 180 is a microcomputer, which includes a CPU 182 , a ROM 183 , a RAM 184 and external input and output circuits 187 , 188 .
- the ROM 183 stores various control programs and data such as maps and tables used in the programs.
- the CPU 182 executes various computations in accordance with the programs stored in the ROM 183 .
- the RAM 184 temporarily stores the results of the computations by the CPU 182 and data from various sensors.
- the backup RAM 185 is a non-volatile storage that stores necessary data when the engine 11 is stopped.
- the CPU 182 , ROM 183 , the RAM 184 , the backup RAM 185 and the external input and output circuits 187 , 188 are connected to one another by a bus 186 .
- An electromagnetic pickup 190 for the crankshaft 15 and a shaft position sensor 194 for the intake camshaft 23 are connected to the external input circuit 187 . Further, various sensors for detecting the state of the engine 11 such as an intake pressure sensor and a throttle sensor (neither is shown) are connected to the external input circuit 187 .
- the pickup 190 detects the rotational phase or the rotation speed of the crankshaft 15 .
- the shaft position sensor 194 detects the axial position of the intake camshaft 23 .
- the external output circuit 188 is connected to the OCV 170 .
- An ECU 201 for controlling a throttle valve 202 is connected to the external input and output circuits 187 , 188 .
- the ECUs 180 and 201 exchange data necessary for controlling the engine 11 .
- the ECU 201 computes a required torque based on detection values of a gas pedal sensor and other sensors for detecting the condition of the engine 11 .
- the ECU 201 adjusts the opening of the throttle valve 202 to an required opening amount.
- the ECU 201 also judges whether the opening of the throttle valve 202 is changing in accordance with commands from the ECU 201 based on detection signals from a throttle sensor located in the vicinity of at the throttle valve 202 . If the ECU 201 judges that the throttle valve 202 is not responding to the commands, the ECU 201 sends a throttle abnormality signal, or signal indicating an abnormality of the throttle valve 202 , to the ECU 180 .
- the ECU 180 controls the performance of the intake valves 21 .
- the ECU 180 optimizes the running state of the engine 11 .
- the ECU 180 controls the OCV 170 for adjusting the valve lift and the valve open angle of the intake valves 21 based on detection signals from the sensors that detect the state of the engine 11 .
- the ECU 180 receives the engine speed detected by the pickup 190 and the engine load detected by the intake pressure sensor.
- the ECU 180 uses the engine speed and the engine load as parameters and computes a target axial position of the intake camshaft 23 , which corresponds to a target valve lift.
- the target valve lift is related to the parameters according to function data.
- the ECU 180 controls the actuator 25 to move the intake camshaft 23 to the target axial position.
- the ECU 180 When controlling the OCV 170 , the ECU 180 receives signals from the shaft position sensor 194 and computes the axial position of the intake camshaft 23 based on the received signals. The ECU 180 uses the OCV 170 to feedback control the actuator 25 such that the intake camshaft 23 is moved to an axial position at which the valve lift and the open angle match target values.
- the ECU 180 executes the routine of FIG. 7 at predetermined intervals or at predetermined crank angles to control the OCV 170 .
- the ECU 180 judges whether the engine 11 is running normally (S 310 ). If a throttle abnormality signal is not sent from the ECU 201 , the ECU 180 judges that the engine 11 is running normally. If a throttle abnormality signal is sent from the ECU 201 , the ECU 180 judges that there is malfunction in the engine 11 .
- the ECU 180 controls the valve open angle of the intake valves 21 by a normal procedure (S 320 ). Specifically, the ECU 180 uses engine speed, which is detected by the pickup 190 , and the engine load, which is computed based on signals from the intake pressure sensor, as parameters. The ECU 180 computes a target axial position of the intake camshaft 23 , which corresponds to a target valve open angle, based on the parameters according to function data. The ECU 180 controls the actuator 25 such that the intake camshaft 23 is moved to the target shaft position.
- the ECU 180 receives detection signals from the shaft position sensor 194 and computes the axial position of the intake camshaft 23 based on the signals from the sensor 194 .
- the ECU 180 feedback controls the actuator 25 by means of the OCV 170 such that the intake camshaft 23 is moved to the target shaft position.
- the ECU 180 controls the valve open angle of the intake valves 21 at step S 330 according to a fail-safe procedure. Specifically, the ECU 180 moves the intake camshaft 23 to minimize or decrease the valve overlap. In other words, the ECU 180 sets the closing timing of the intake valves 21 to the most advanced position. At this time, the intake camshaft 23 is located at the leftmost position as shown in FIG. 3.
- the second embodiment is the same as the first embodiment except that the outer teeth 163 of the ring gear 162 and the inner teeth 157 of the cover 154 are replaced with left-handed helical gears (not shown), and except that the control routine differs from the routine of FIG. 7.
- the ECU 180 executes the routine of FIG. 9 at predetermined intervals or at a predetermined crank angles. Steps S 410 , S 420 are the same as steps S 310 , S 320 of the flowchart of FIG. 7.
- the ECU 180 moves the intake camshaft 23 such that the closing timing of the intake valves 21 is most advanced, which is a fail-safe procedure to facilitate starting of the engine 11 .
- the closing timing of the intake valves 21 is most advanced as shown in FIG. 8(A). In this state, the valve open angle of the intake valves 21 is the smallest. Since the closing timing of the intake valves 21 is most advanced, the starting of the engine 11 is facilitated.
- the third embodiment is the same as the second embodiment except that the routine of FIG. 9 is replaced by the routine of FIG. 7. That is, when there is a malfunction in the engine 11 , the intake camshaft 23 is moved to a position at which the valve overlap is minimum.
- the intake camshaft 23 is moved to the rightmost position like in FIG. 4 so that the valve overlap is minimized, or zero, as illustrated in FIG. 8(B). At this time, the valve open angle of the intake valves 21 is the widest and the phase of the intake camshaft 23 is most retarded. Decreasing the valve overlap stabilizes the engine speed.
- a fourth embodiment will now be described.
- the mechanism of the fourth embodiment is the same as the mechanism of the second embodiment except that the left-handed helical teeth are replaced with right-handed helical teeth.
- the routine of FIG. 7 is used to control the actuator 25 .
- the performance of the intake valves 21 according to the fourth embodiment is shown in FIGS. 10 (A) and 10 (B).
- the ECU 180 moves the intake camshaft 23 to the leftmost position like in FIG. 3 to minimize the valve overlap (step S 330 ).
- the valve open angle of the intake valves 21 is the smallest and its phase is most retarded. Therefore, the fourth embodiment has the same advantages as the first embodiment.
- a fifth embodiment will now be described.
- the fifth embodiment is the same as the fourth embodiment except that the routine of FIG. 7 is replaced by the routine of FIG. 9.
- the ECU 180 shifts the closing timing of the intake valves 21 to the most advanced timing (step S 430 ) by moving the intake camshaft 23 . At this time, the valve open angle of the intake valves 21 is the largest and its phase is most advanced. Therefore, the fifth embodiment has the same advantages as the second embodiment.
- a sixth embodiment will now be described with reference to FIG. 11.
- the sixth embodiment is different from the first embodiment in that the actuator 25 is attached to the exhaust camshaft 22 and in that the exhaust cams 27 are three-dimensional.
- the intake camshaft 23 does not move axially.
- the ECU 180 executes the routine of FIG. 14 at predetermined intervals or at predetermined crank angles.
- the ECU 180 judges whether the engine 11 is running normally (step S 510 ).
- step S 520 the ECU 180 feedback controls the valve open angle of the exhaust valves 20 by the normal procedure.
- step S 530 the ECU 180 moves the exhaust camshaft 22 axially to minimize the valve overlap.
- the opening timing of the exhaust valve 20 is retarded so that there is no valve overlap. This stabilizes the engine speed.
- the retarded opening timing of the exhaust valves 20 further stabilizes the engine speed.
- the seventh embodiment is different from the sixth embodiment in that the outer spur teeth 163 , or splines, of the ring gear 162 and the inner spur teeth 157 , or splines, of the cover 154 are replaced by left-handed helical teeth (not shown).
- the ECU 180 executes the routine of FIG. 16 to control the actuator 25 .
- Steps S 610 , S 620 are the same as steps S 510 , S 520 of the sixth embodiment.
- step S 630 If there is a malfunction in the engine 11 , the ECU 180 axially shifts the exhaust camshaft 22 , which changes the opening timing of the exhaust valve 20 to the most retarded timing in a fail-safe procedure (step S 630 ), which stabilizes the engine speed.
- the eighth embodiment is the same as the seventh embodiment except that the routine of FIG. 16 is replaced with a routine of FIG. 14.
- step S 530 the ECU 180 moves the exhaust camshaft 22 to minimize the valve overlap (step S 530 ), which stabilizes the engine speed.
- the ninth embodiment is different from the seventh embodiment in that the left-handed helical teeth are replaced with right-handed helical teeth (not shown).
- the ECU 180 moves the exhaust camshaft 22 such that the opening timing of the exhaust valve 20 is most retarded as illustrated in FIG. 17(A)(step S 630 ).
- the valve overlap is maximized accordingly, and the engine speed is stabilized.
- a tenth embodiment will now be described.
- the tenth embodiment is different from the ninth embodiment in that the routine of FIG. 16 is replaced with the routine of FIG. 14.
- the ECU 180 minimizes the valve overlap as shown in FIG. 17(B)(step S 530 ). Therefore, the tenth embodiment has the same advantages as those of the eighth embodiment.
- an engine 1011 basically has the same structure as the engine 11 shown in FIG. 1.
- the engine 1011 further has a first actuator 1022 a for varying valve open angle and a second actuator for varying the valve timing.
- the second actuator 1024 and a timing pulley 1024 a are provided at the left end of an intake camshaft 1022 .
- the first actuator 1022 a is provided at the right end of the intake camshaft 1022 .
- the actuator 1022 a includes a cylinder tube 1031 and a piston 1032 accommodated in the cylinder tube 1031 .
- a pair of end covers 1033 close the openings of the tube 1031 .
- the cylinder tube 1031 is fixed to the cylinder head 1014 .
- the intake camshaft 1022 extends through one of the covers 1033 and is coupled to the piston 1032 .
- the piston 1032 defines a first pressure chamber 1031 a and a second pressure chamber 1031 b in the tube 1031 .
- a first passage 1034 and a second passage 1035 are formed in the covers 1033 , respectively.
- the first passage 1034 communicates with the first pressure chamber 1031 a and the second passage 1035 communicates with the second pressure chamber 1031 b.
- the first passage 1034 and the second passage 1035 are connected to a first oil control valve (OCV) 1036 by passages P 11 and P 12 , respectively.
- the first OCV 1036 has the same structure as the OCV 170 of the first embodiment. That is, the first OCV 1036 is actuated by controlling the electric current fed to a solenoid. 1047 .
- the second actuator 1024 includes the timing pulley 1024 a .
- the timing pulley 1024 a includes a cylindrical boss 1051 and a disk 1052 and outer teeth 1053 .
- the boss 1051 slidably supports the intake camshaft 1022 .
- the disk 1052 radially extends from the boss 1051 .
- the teeth 1053 are formed on the circumferential surface of the disk 1052 .
- the boss 1051 is rotatably supported by a support 1014 a of the cylinder head 1014 .
- An inner gear 1054 is fixed to the distal end of the intake camshaft 1022 by a bolt 1055 .
- the inner gear 1054 includes a large diameter portion 1054 a and a small diameter portion 1054 b .
- the small diameter portion 1054 b has helical teeth, and the large diameter portion 1054 a has straight spur teeth, or splines.
- a ring-shaped sub-gear 1056 is fitted about the small diameter portion 1054 b of the inner gear 1054 .
- the sub gear 1056 includes outer teeth 1056 a and inner teeth 1056 b .
- the outer teeth 1056 a are parallel to the axis of the camshaft 1022 and the inner teeth 1056 b are helical.
- the outer diameter of the sub-gear 1054 is the same as that of the inner gear 1054 .
- the inner teeth 1056 b of the sub-gear 1056 mesh with the teeth of the small diameter portion 1054 b .
- a spring washer 1057 is located between the inner gear 1054 and the sub-gear 1056 . The spring washer 1057 urges the sub-gear 1056 away from the inner gear 1054 .
- a housing 1059 and a cover 1060 are coupled to the disk portion 1052 of the timing pulley 1024 a by four bolts 1058 .
- the cover 1060 seals first and second pressure chambers 1070 , 1071 , which will be described later.
- An opening 1060 a is formed in the center of the cover 1060 to communicate a cylindrical hole 1061 c , which will be described later, to the outside.
- the opening 1060 a allows the intake camshaft 1022 to move easily in the axial direction.
- FIG. 21 shows the mechanism of FIG. 20 viewed from the left.
- the bolts 1058 , the cover 1060 and the bolt 1055 are not shown.
- FIG. 20 is a cross-sectional view taken along line 21 - 21 of FIG. 21.
- the housing 1059 has four projections 1062 , 1063 , 1064 , 1065 , which protrude from the inner surface 1059 a .
- a vane rotor 1061 is rotatably fitted in the housing 1059 .
- the vane rotor 1061 has outer walls 1061 a , which contact the projections 1062 , 1063 , 1064 , 1065 .
- the cylindrical hole 1061 c is defined in the center of the vane rotor 1061 (see FIG. 20).
- Splines 1061 b are formed on the inner wall of the hole 1061 c .
- the splines 1061 b extend along the axis of the intake camshaft 1022 .
- the large diameter portion 1054 a of the inner gear 1054 and the outer teeth 1056 a of the sub-gear 1056 mesh with the splines 1061 b.
- Vanes 1066 , 1067 , 1068 , 1069 protrude from the outer walls 1061 a of the vane rotor 1061 .
- the vanes 1066 , 1067 , 1068 , 1069 are located in the spaces defined by the projections 1062 , 1063 , 1064 , 1065 .
- the distal ends of the vanes 1066 , 1067 , 1068 , 1069 contact the inner surface 1059 a of the housing 1059 .
- Each of the vanes 1066 , 1067 , 1068 , 1069 and the corresponding pairs of the projections 1062 , 1063 , 1064 , 1065 define first and second pressure chambers 1070 , 1071 .
- the vane 1066 has a through hole 1072 extending along the axis of the intake camshaft 1022 .
- a lock pin 1073 is fitted in the through hole 1072 to move axially.
- a spring hole 1073 a is formed in the lock pin 1073 .
- a spring 1074 is accommodated in the spring hole 1073 a to urge the lock pin 1073 toward the disk 1052 .
- An oil groove 1072 a is formed in the front face of the vane rotor 1061 .
- the oil groove 1072 a connects an arcuate opening 1072 b formed in the cover 1060 (see FIG. 18) to the through hole 1072 .
- the opening 1072 b and the oil groove 1072 a drain air and oil located in a space that is axially front of the lock pin 1073 in the through hole 1072 .
- FIG. 21 also illustrates the vane rotor 1061 when the distal end of the lock pin 1073 is not engaged with the recess 1075 .
- the pressure of the first and second pressure chambers 1070 , 1071 are zero or relatively low.
- the vane rotor 1061 is at the position of FIG. 21.
- cranking of the engine 1011 generates a reverse torque in the intake camshaft 1022 , which advances the rotational phase of the vane rotor 1061 relative to the housing 1059 .
- the lock pin 1073 is moved from the position of FIG. 22 to the position of FIG. 23 and enters the recess 1075 . This prohibits further relative rotation between the vane rotor 1061 and the housing 1059 and causes the rotor 1061 to rotate integrally with the housing 1059 .
- oil is supplied to an annular chamber 1077 from the second pressure chamber 1071 via an oil passage 1076 , which disengages the lock pin 1073 from the recess 1075 .
- a pressure increase of oil supplied to the annular chamber 1077 disengages the lock pin 1073 from the recess 1075 against the force of the spring 1074 .
- Oil is supplied to the recess 1075 from the first pressure chamber 1070 via an oil passage 1078 , which retains the lock pin 1073 at the disengaged position. Disengagement of the lock pin 1073 permits the vane rotor 1061 to rotate relative to the housing 1059 .
- the rotational position of the vane rotor 1061 relative to the housing 1059 is determined in accordance with pressure of the first and second pressure chambers 1070 , 1071 .
- the vane rotor 1061 is retained at an advanced position relative to the housing 1059 as illustrated in FIG. 24.
- the rotational phase of the vane rotor 1061 relative to the housing 1059 is advanced by controlling the pressures in the first and second pressure chambers 1070 , 1071 when the engine 1011 is running, the rotational phase of the intake camshaft 1022 is advanced relative to that of the crankshaft 1015 . Accordingly, the opening and closing timings of the intake valves 1020 are advanced as shown by an arrow in FIG. 25(B) while the valve open angle of the intake valves 1020 is maintained.
- the rotational phase of the vane rotor 1061 relative to the housing 1059 is retarded, the rotational phase of the intake camshaft 1022 is retarded relative to that of the crankshaft 1015 . Accordingly, the opening and closing timings of the intake valves 1020 are retarded, or retarded in a direction opposite to the arrow in FIG. 25(B). Specifically, while the valve open angle of the intake valve 1020 does not change, the intake valve timing is retarded.
- the disk 1052 has first openings 1080 and second openings 1081 .
- Each first opening 1080 is connected to one of the first pressure chambers 1070 and each second opening 1081 is connected to one of the second pressure chambers 1071 .
- Recesses 1062 a to 1065 a are formed in the vicinity of each projection 1062 to 1065 at a part adjacent to the openings 1080 .
- Each recess 1062 a to 1065 a supplies oil pressure to the first pressure chambers 1070 to advance the rotational phase of the vane rotor 1061 when the first openings 1080 are closed by the vanes 1066 to 1069 .
- recesses 1062 b to 1065 b are formed in the vicinity of the projections 1062 to 1065 adjacent to the second openings 1081 .
- the recesses 1062 b to 1065 b supply oil to the second pressure chambers 1071 to retard the rotational phase of the vane rotor 1061 when the vanes 1066 , 1069 close the second openings 1081 .
- Each first opening 1080 is connected to a first circumferential groove 1051 a formed on the cylindrical boss 1051 via first oil conduits 1084 , 1086 , 1088 .
- Each second opening 1081 is connected to a second circumferential groove 1051 b via second oil conduits 1085 , 1087 , 1089 .
- a lubricant passage 1090 is formed in the cylindrical boss 1051 .
- the lubricant passage 1090 is connected to the second oil conduit 1087 .
- a relatively wide inner groove 1091 is formed in the inner surface 1051 c of the boss 1051 .
- the groove 1091 is connected to the lubricant passage 1090 .
- Oil in the second conduit 1087 is conducted between the inner surface 1051 c of the boss 1051 and the outer surface 1022 b of the camshaft 1022 and serves as lubricant.
- the first circumferential groove 1051 a is connected to a second OCV 1094 by a passage P 21 in the cylinder head 1014 .
- the second circumferential groove 1051 b is connected to the second OCV 1094 by a passage P 22 in the cylinder head 1014 .
- a supply passage 1095 and a drain passage 1096 are connected to the second OCV 1094 .
- the supply passage 1095 is connected to an oil pan 1013 a by the oil pump P, which is also connected to the first OCV 1036 .
- the drain passage 1096 is directly connected to the oil pan 1013 a .
- the oil pump P supplies oil from the oil pan 1013 a to the supply passages 1037 , 1095 .
- the second OCV 1094 has the same structure as that of the first OCV 1036 .
- the second OCV 1094 includes a casing 1102 , a first oil port 1104 , a second oil port 1106 , valve bodies 1107 , a first drain port 1108 , a second drain port 1110 , a supply port 1112 , a coil spring 1114 , an electromagnetic solenoid 1116 and a spool 1118 .
- the first oil port 1104 is connected to the oil passage P 21 and the second oil passage 1106 is connected to the oil passage P 22 .
- the supply port 1112 is connected to the supply passage 1095 and the first and second drain ports 1108 , 1110 are connected to the drain passage 1096 .
- the first oil port 1104 is connected to the first drain port 1108 and the second oil port 1106 is connected to the supply port 1112 .
- Oil in the oil pan 1013 a is supplied to the second pressure chambers 1071 of the second actuator 1024 via the supply passage 1095 , the second OCV 1094 , the passages P 22 , the circumferential groove 1051 b , the second conduits 1089 , 1087 , 1085 , the second openings 1081 , the recesses 1062 b , 1063 b , 1064 b and 1065 b .
- Oil in the first pressure chambers 1070 of the second actuator 1024 is returned to the oil pan 1013 a via the grooves 1062 a , 1063 a , 1064 a , 1065 a , the first openings 1080 , the first conduits 1084 , 1086 , 1088 , the circumferential groove 1051 a , the passage P 21 , the second OCV 1094 and the drain passage 1096 .
- the rotational phase of the vane rotor 1061 is retarded relative to the housing 1059 , which retards the opening and closing timing of the intake valves 1020 . In other words, while the valve open angle of the intake valves 1020 does not change, the timing of the intake valves 1020 is retarded.
- the second oil port 1106 is connected to the second drain port 1110 and the first oil port 1104 is connected to the supply port 1112 .
- oil in the oil pan 1013 a is supplied to the first pressure chambers 1070 in the second actuator 1024 by the supply passage 1095 , the second OCV 1094 , the passage P 21 , the circumferential groove 1051 a , the first conduits 1088 , 1086 , 1084 , the first openings 1080 and the recesses 1062 a , 1063 a , 1064 a , 1065 a .
- Oil in the second pressure chambers 1071 of the second actuator 1024 is returned to the oil pan 1013 a via the recesses 1062 b , 1063 b , 1064 b , 1065 b , the second openings 1081 , the second conduits 1085 , 1087 , 1089 , the groove 1051 b , the passage P 22 , the second OCV 1094 and the drain passage 1096 .
- the rotational phase of the vane rotor 1061 is advanced relative to that of the housing 1059 .
- the opening and closing timings of the intake valve 1020 are advanced. That is, the timing of the intake valves 1020 is advanced while open angle does not change.
- the first oil port 1104 and second oil port 1106 can be closed by controlling current to the solenoid 1116 . Accordingly, oil is not conducted through the oil ports 1104 , 1106 . In this state, oil is not supplied to or drained from the first and second pressure chambers 1070 , 1071 . Oil remaining in the chambers 1070 , 1071 fixes the rotational phase of the vane rotor 1061 relative to the housing 1059 , which maintains the opening and closing timings of the intake valves 1020 . In other words, the valve open angle of the intake valves 1020 is not advanced or retarded.
- An electromagnetic pickup 1123 detects the rotational phase of the crankshaft 1015 .
- An electromagnetic pickup 1126 detects the rotational phase and the axial position of the intake camshaft 1022 .
- the ECU 1130 executes routines of FIGS. 26 and 27 at predetermined intervals or at a predetermined crank angles to control the performance of the intake valves 1020 .
- step S 1310 a routine for controlling the first OCV 1036 will be described.
- the ECU 1130 determines if the engine 1011 is running normally as in step S 310 of FIG. 7 (step S 1310 ).
- the ECU 1130 controls the valve open angle of the intake valve 1020 by a normal procedure (step S 1320 ). Specifically, the ECU 1130 determines a target position Lt of the intake camshaft 1022 based on a map L of FIG. 28(B).
- the map L of FIG. 28(B) uses the engine speed and the engine load (for example, intake pressure, intake amount or injection amount is used as a value to represent the engine load).
- the ECU 1130 controls the first actuator 1022 a such that the actual position of the intake camshaft 1022 matches the target shaft position Lt.
- the map L is designed such that an optimum valve open angle of the intake valves 1020 is selected for a required performance of the engine 1011 .
- the ECU 1130 controls the first actuator 1022 a to move the intake camshaft 1022 such that the valve open angle of the intake valves 1020 is minimized (step S 1330 ).
- step S 1310 the ECU 1130 judges whether the engine 1011 is running normally (step S 1410 ).
- the ECU 1130 controls the phase of the valve open angle of the intake valves 1020 by the normal procedure (step S 1420 ). Specifically, the ECU 1130 determines a target advance degree ⁇ t of the valve open angle based on a map i of FIG. 28(A) and feedback controls the valve open angle of the intake valves 1020 .
- the map i FIG. 28(A) uses the engine speed and the engine load (for example, intake pressure, intake amount or injection amount is used as a value to represent the engine load).
- the ECU 1130 controls the second actuator 1024 such that the actual valve open angle of the intake valve 1020 matches the target angle ⁇ t.
- the map i is designed such that an optimum valve open angle of the intake valves 1020 is selected for a required performance of the engine 1011 .
- the ECU 1130 controls the second actuator 1024 to shift the rotational phase of the intake camshaft 1022 such that the valve open angle of the intake valves 1020 is most advanced (step S 1430 ). Accordingly, the valve performance shown in FIG. 8(A) is obtained.
- the eleventh embodiment has the same advantages as the second embodiment.
- the second OCV 1094 may be controlled by the normal procedure even if there is a malfunction in the engine 1011 . In this case, only the first OCV 1036 is controlled. Therefore, this embodiment still has the same advantages as the first embodiment.
- the OCVs 1036 , 1094 may be moved in opposite directions when there is a malfunction in the engine 1011 .
- the eleventh embodiment has the same advantages as the third embodiment. Further, the OCVs 1036 and 1094 may be controlled to operate the intake valves 1020 in the manner of the fourth and fifth embodiments.
- a twelfth embodiment of the present invention will now be described. As shown in FIG. 29, the twelfth embodiment is different from the eleventh embodiment in that a first actuator 1225 is attached to a timing pulley 1225 a of an exhaust camshaft 1222 . Further, the exhaust camshaft 1222 is rotatably supported by a cylinder head. The exhaust camshaft 1222 is permitted to move axially, or in a direction shown by arrow D. Exhaust cams 1227 are three-dimensional. An intake camshaft 1223 is not axially moved, and the intake cams 1228 are normal cams. The rotational phase of he intake cams 1228 can be changed by the actuator 1224 .
- a first OCV controls the axial position of the exhaust camshaft 1222 to vary the valve open angle of the exhaust valves 1220 as shown in FIG. 30(A).
- a second OCV controls the rotational phase of the intake camshaft 1223 relative to that of a crankshaft 1215 thereby adjusting the valve timing of the intake valves 1221 .
- the ECU 1130 executes a routine like the routine of FIG. 26 to control the exhaust valves 1220 . Specifically, when there is a malfunction in the engine, the ECU 1130 minimizes the valve open angle of the exhaust valves 1220 . Also, the ECU 1130 rotates the intake camshaft 1223 to the most advanced rotational phase as in the routine of FIG. 27.
- the opening timing of the exhaust valves 1220 is most retarded and there is no valve overlap, which stabilizes the engine speed. Also, the closing timing of the intake valves 1221 is most advanced, which facilitates the starting of the engine.
- the first and second actuators 1225 , 1224 may both be attached to the exhaust camshaft 1222 .
- the valve performance of the exhaust valves 1220 is variable as the valve performance of the intake valves 1221 of FIGS. 25 (A) and 25 (B), and the valve performance of the intake valves 1221 is invariable as the valve performance of the exhaust valves 1220 of FIGS. 25 (A) and 25 (B).
- the second actuator 1224 may be attached to the exhaust camshaft 1222 and the first actuator 1225 may be attached to the intake camshaft 1223 .
- valve performance shown will be as in FIG. 32 when there is a malfunction in the engine. This embodiment therefore has the same advantages as the twelfth embodiment.
- the thirteenth embodiment has the same structure as the first embodiment. However, the ECU 201 may be omitted. The thirteenth embodiment is designed to deal with a malfunction in the hydraulic system, which includes the pump P and the OCV 170 .
- each cam follower 21 a contacts the smallest profile section of the associated intake cam 28 .
- the smallest profile section of the intake cam 28 is the default position. Therefore, if no electricity is supplied to the solenoid 136 due to a malfunction, the performance of the intake valves 21 is as shown in FIG. 6(A). Specifically, the valve lift of the intake valves 21 is minimum and there is no valve overlap.
- the ring gear 162 receives no pressure either from the first oil chamber 165 or from the second oil chamber 166 . Therefore, the ring gear 162 cannot maintain the axial position of the intake camshaft 23 .
- the ring gear 162 is moved leftward with the intake camshaft 23 , which maintains intake camshaft 23 at the default position as illustrated in FIG. 3. Therefore, if oil is not supplied to the actuator 25 due to a malfunction, the performance of the intake valves 21 is maintained in a state shown in FIG. 6(A). That is, the valve lift of each intake valve 21 is minimum and there is no valve overlap.
- a fourteenth embodiment of the present invention will now be described with reference to FIGS. 1 to 5 .
- the fourteenth embodiment is the same as the thirteenth embodiment except that the outer teeth 163 of the ring gear 162 and the inner teeth 157 on the cover 154 are replaced with left-handed helical teeth.
- the intake camshaft 23 rotates counterclockwise relative to the cover 154 when viewed from the left side of FIG. 3.
- the ring gear 162 receives no oil pressure either from the first oil pressure chamber 165 or the second oil pressure chamber 166 .
- the intake camshaft 23 receives a leftward force (as viewed in FIG. 3) at the contacting surface between the nose of each intake cam 28 and the associated cam follower 21 a.
- the outer teeth 163 and the inner teeth 157 are replaced with left-handed helical teeth.
- the camshaft 23 receives friction force from a journal bearing (not shown) located on the cylinder head 14 and each intake cam 28 receives friction force from the associated cam follower 21 a . Due to the friction forces, the intake camshaft 23 receives a force in the direction of arrow A from the inner helical teeth of the cover 154 .
- the angle of the cam surface of the intake cams 28 and the helical angle of the inner and outer teeth are determined such that the total leftward forces are greater than the axial forces in the direction of arrow A.
- the ring gear 162 and the intake camshaft 23 are moved leftward by default.
- the intake camshaft 23 is maintained at the smallest profile section (default position) as illustrated in FIG. 3.
- the valve lift of the intake valves 21 is the smallest and the closing timing of the intake valves 21 is most retarded.
- variable performance valve train according to a fifteenth embodiment will now be described with reference to FIGS. 33 and 34.
- the fifteenth embodiment is different from the fourteenth embodiment in that the magnitudes of opposite forces that act on the ring gear 162 when the ring gear 162 receives no oil pressure are opposite from those in the fourteenth embodiment.
- the angle of the cam surface of each intake cam 28 and the helical angle of the inner and outer teeth are determined such that a force urging the intake camshaft in the direction of arrow A is stronger than an opposite force.
- the oil passage P 11 from the first oil port 118 is connected to the second oil chamber 166 and the oil passage P 12 from the port 120 is connected to the first oil chamber 165 .
- the outer teeth 163 of the ring gear 162 and the inner teeth 157 of the cover 154 are replaced by helical teeth (not shown).
- the intake camshaft 23 receives forces in opposite axial directions as in the fourteenth embodiment. Specifically, the intake camshaft 23 receives a leftward force from the cam follower 21 a and a rightward force from the helical inner teeth of the cover 154 .
- the rightward force is greater than the leftward force, which moves the ring gear 162 and the intake camshaft 23 rightward. Accordingly, the intake camshaft 23 is maintained at the default position of FIG. 33 .
- the valve lift of the intake valve 21 is maximum and the valve overlap is zero as shown in FIG. 8(B).
- valve train of the sixteenth embodiment is the same as the valve train of the fourteenth embodiment except that the outer teeth 163 and the inner teeth 157 are replaced with right handed helical teeth (not shown).
- the inner teeth of the cover 154 and the outer teeth of the ring gear 162 are right-handed helical teeth.
- the camshaft 23 receives a friction force from a journal bearing (not shown) located on the cylinder head 14 and each intake cam 28 receives a friction force from the associated cam follower 21 a . Due to the friction forces, the intake camshaft 23 receives a rightward force from the inner teeth 157 of the cover 154 . These two forces move the intake camshaft 23 leftward.
- a seventeenth embodiment of the present invention will now be described with reference to FIGS. 35 and 36.
- the seventeenth embodiment is different from the sixteenth embodiment in that a spring 200 is located in the first oil pressure chamber 165 .
- the spring 200 urges the intake camshaft 23 rightward.
- the force of the spring 200 is greater than the resultant force urging the intake camshaft 23 leftward.
- Another difference is that an oil passage P 21 from the first oil port 118 is connected to the second pressure chamber 166 , and the oil passage P 22 from the port 120 is connected to the first pressure chamber 165 .
- the intake camshaft 23 receives a leftward force from the cam follower 21 a and the inner teeth 157 of the cover 154 as in the sixteenth embodiment. Since the force of the spring 200 is greater than the resultant of the forces of the cam follower 21 a and the inner teeth 157 , the ring gear 162 and the intake camshaft 23 are moved rightward. As a result, the intake camshaft 23 is stabilized at the default position as illustrated in FIG. 35. As shown in FIG. 10(B), the valve lift of each intake valve 21 is maximized and the closing timing is most advanced.
- the exhaust cams 27 may be three-dimensional and the actuator 25 may be attached to the exhaust camshaft 22 . If these changes are applied to the thirteenth embodiment, the valve performance of the exhaust valves 20 is changed to that illustrated in FIGS. 13 (A) and 13 (B). In this manner, if electricity to the solenoid 136 is stopped or if oil pressure is not supplied to the actuator 25 due to a malfunction, the exhaust camshaft 22 is maintained at the default position. At this time, the exhaust valves 20 have the performance illustrated in FIG. 13(A). The opening timing of the exhaust valves 20 is most retarded and there is no valve overlap, which stabilizes the engine speed.
- the exhaust valves 20 have the performance shown in FIG. 17(A). In this case, the valve overlap of the exhaust valve 20 is set to zero, which stabilizes the speed of the engine 11 .
- the exhaust valves 20 have the performance shown in FIG. 17(B). In this case, the opening timing of the exhaust valves 20 is most retarded, which stabilizes the engine speed.
- the exhaust valves 20 have the performance shown in FIG. 17(A). In this case, the opening timing of the exhaust valves 20 is most retarded, which stabilizes the engine speed.
- the exhaust valves 20 have the performance shown in FIG. 17(B). In this case, the valve overlap is set to zero, which stabilizes the speed of the engine 11 .
- the default position of the intake camshaft 23 in case of a malfunction according to the fourteenth embodiment is opposite to that in to the fifteenth embodiment.
- One of these default positions is selected depending on the type of the engine 11 when designing the engine 11 .
- Selecting one of the sixteenth and seventeenth embodiments is determined in the same manner.
- the valve performance of the exhaust camshaft 22 is also determined depending on the type of the engine 11 .
- the spring 200 of the seventeenth embodiment may be employed.
- the intake camshaft 23 is quickly moved to the default position when there is oil pressure acting on the actuator. 25 .
- both exhaust and intake camshaft 22 , 23 may have three-dimensional cams and the actuator 25 .
- a cam follower mechanism shown in FIGS. 38 and 39 may be employed.
- the mechanism includes a cylindrical valve lifter 2019 .
- a guide projection 2019 b is formed in the circumferential surface 2019 a of the valve lifter 2019 .
- the lifter bore 2019 is supported by and is axially moved relative to a lifter bore (not shown) formed in a cylinder head.
- the guide projection 2019 b is fitted in a rectangular groove formed in the inner surface of the lifter bore along the axial direction of the lifter bore, which prevents the valve lifter 2019 from rotating.
- a cam follower holder 2024 is integrally formed on the upper surface 2019 d of the valve lifter 2019 .
- a cam follower 21 a is pivotally fitted in a guide groove 2024 a formed in the cam follower holder 2024 .
- the valve lifter 2019 is pressed against the cams 27 , 28 by a compressed spring located between the cylinder head and the valve lifter 2019 .
- a sliding surface 2025 a of the cam follower 21 a is pressed against a cam surface 2011 a of the cam 27 , 28 , which causes the cam follower 21 a to pivot in accordance with the cam surface 2011 a.
- the cam follower 21 a includes a semi-cylindrical column 2025 b and a semi-circular flange 2025 c , which is located at the axial center, or at the center in the direction of arrow F, of the column 2025 b .
- the circular surface of the column 2025 b forms a sliding surface 2025 d , which is slidably fitted in the guide groove 2024 a of the cam follower holder 2024 .
- the flange 2025 c is fitted in a flange groove 2024 b formed in the axial center of the guide groove 2024 a , which allows thrust surfaces 2025 e of the flange 2025 c to contact thrust surfaces 2024 c of the flange groove 2024 b .
- the contact of the thrust surfaces 2025 e and 2024 c prevents the cam follower 21 a from moving in the direction of arrow F.
- the cam follower 21 a is not a complete half cylinder.
- the sliding surface 2025 a is offset from the radial center J of a circle defined by the cam follower 21 a by a distance E. If the offset E is relatively small, there will be no problem with the functioning of the cam follower 21 a compared to a case where there is no offset E. For example, if the offset is 0.3 mm, the resulting error in the valve lift will be 10 ⁇ m, which is very small, when the cam follower 21 a is inclined by fifteen degrees in accordance with the cam surface 2011 a . The error will be in the range of tolerance and will cause no problem.
- an intermediate product 2050 as shown in FIG. 41 is formed first. Then, the intermediate product 2050 is cut in half along a plane including the axis J shown in FIGS. 41 and 42. Thereafter, the cut surfaces are ground. As a result, two cam followers 21 a are manufactured. In this manner, two cam followers 21 a are easily manufactured.
- This manufacturing method has a high productivity and thus reduces the manufacturing cost. Further, compared to a method for manufacturing two complete semi-cylindrical cam followers, the illustrated method saves material.
Abstract
A valve train for an internal combustion engine has a variable valve performance mechanism for changing the valve open angle of at least one set of intake valves and exhaust valves. The valve train further includes an electronic control unit (ECU) for controlling the variable valve performance mechanism and a sensor for detecting the running state of the engine. The ECU judges whether there is a malfunction in the engine based on detection signals from the sensor. if there is a malfunction in the engine, the ECU actuates the variable valve performance mechanism to decrease the valve overlap thereby performing a failsafe. The ECU also advances the closing timing of the intake valves. Alternatively, the ECU retards the opening timing of the exhaust valves.
Description
- The present invention relates to a variable performance valve train used in internal combustion engines. More particularly, the present invention pertains to a variable performance valve train having three-dimensional cams, the profile of which continuously changes along the axis of a camshaft.
- Japanese Unexamined Patent Publication No. 5-125966 discloses a first prior art apparatus, which includes a variable valve lift mechanism. The variable valve lift mechanism includes intake and exhaust valves, which are driven by camshafts, and low speed and high speed cams for driving the intake valves or the exhaust valves. The mechanism varies the valve lift, or the valve open angle, of the intake valves or the exhaust valves. In this specification, the valve open angle refers to an angle of rotation of a crankshaft during which an intake valve or an exhaust valve is open.
- When there is a malfunction in the control of a throttle valve, the mechanism of Japanese Unexamined Patent Publication No. 5-125966 selects a set of cams that will decrease the engine power. Specifically, the mechanism uses either high speed cams or low speed cams such that the vehicle speed is reduced.
- Instead of having two types of cams, a variable performance valve train according to a second prior art apparatus has three-dimensional cams, the profile of which continuously changes along the axis of a camshaft. However, unlike the prior art apparatus of Japanese Unexamined Patent Publication No. 5-125966, a valve train having three-dimensional cams cannot employ the valve switching control and fail-safe control for decreasing the engine power.
- For example, if the mechanism having the three-dimensional cams simply decreases engine power for performing fail-safe control, engine starting is hindered or engine speed stability deteriorates.
- A valve train according to a third prior art apparatus disclosed in Japanese Unexamined Patent Publication 8-177434 includes the high speed and low speed cams of Publication No. 5-125966 and a variable valve timing mechanism. The variable valve timing mechanism adjusts the rotational phase of the camshaft.
- When either the variable valve lift mechanism or the variable valve timing mechanism malfunctions, the variable valve lift mechanism uses the low speed cams, and the variable valve timing mechanism retards the rotational phase of the camshaft. This prevents the intake valves from interfering with the pistons and the exhaust valves.
- A malfunction of the variable valve lift mechanism could be either a malfunction of the low speed cams or a malfunction of the high speed cams. In order to perform fail-safe control, different programs must be prepared for a malfunction of the low speed cams and for a malfunction of the high speed cams. The two fail-safe controls increase the time and effort required to make the programs and increase the required memory capacity for storing the programs.
- If the variable valve lift mechanism malfunctions when the high speed cams are being used, the mechanism may not be able to switch to the low speed cams. In this case, engine starting and engine speed stability will deteriorate.
- Accordingly, it is an objective of the present invention to provide a variable performance valve train that facilitates engine starting and stabilizes the engine speed when there is a malfunction thereby making it easier for the driver take steps to correct the malfunction.
- To achieve the above objective, the present invention provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of at least one of an intake valve and an exhaust valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to decrease valve overlap.
- The present invention further provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of an intake valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to advance the closing timing of the intake valve.
- The present invention provides a valve train for an internal combustion engine, comprising: a variable valve performance mechanism for continuously changing the valve open angle of an exhaust valve; a controller for controlling the variable valve performance mechanism; a sensor for detecting the running state of the engine; and a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to retard the opening timing of the exhaust valve.
- The present invention further provides a method for changing the valve performance of at least one of an exhaust valve and an intake valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and decreasing valve overlap when the engine is judged to be running abnormally.
- The present invention provides a method for changing the valve performance of an intake valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and advancing the closing timing of the intake valve for performing a failsafe when the engine is judged to be running abnormally.
- The present invention further provides a method for changing the valve performance of an exhaust valve by using a three-dimensional cam, the method comprising: detecting the running state of an engine; judging whether the engine is running normally based on the detected running state; controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and advancing the closing timing of the exhaust valve when the engine is judged to be running abnormally.
- The present invention provides a valve train for an internal combustion engine, comprising: an axially movable camshaft rotatably supported on the engine; a three-dimensional cam located on the camshaft to selectively open and close a valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction; an actuator for axially moving the camshaft to change at least the valve lift of the valve lift and the valve timing of the valve; a fluid pressure source for generating fluid pressure to actuate the actuator; and a control valve for adjusting the position of the camshaft by controlling fluid pressure supplied to the actuator from the fluid pressure source; wherein a default position toward which the camshaft is moved when the control of fluid pressure by the control valve is stopped is the same as a default position toward which the camshaft is moved when the fluid pressure source is not supplying fluid pressure to the actuator.
- Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
- The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
- FIG. 1 is a partial perspective view and a block diagram illustrating a variable performance valve train according to a first embodiment of the present invention;
- FIG. 2 is a partial perspective view illustrating a three-dimensional cam in the valve train of FIG. 1;
- FIG. 3 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve in the valve train of FIG. 1;
- FIG. 4 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 3;
- FIG. 5 is a diagrammatic cross-sectional view illustrating an operational state of the oil control valve of FIGS. 3 and 4;
- FIGS.6(A) and 6(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train of FIG. 1;
- FIG. 7 is a flowchart showing a routine executed by an ECU for controlling the oil control valve of the valve train of FIG. 1;
- FIGS.8(A) and 8(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a valve train according to a second embodiment of the present invention;
- FIG. 9 is a flowchart showing a routine executed by an ECU for controlling an oil control valve of the valve train of the second embodiment;
- FIGS.10(A) and 10(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a variable performance valve train according to a fourth embodiment of the present invention;
- FIG. 11 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve in a variable performance valve train according to a sixth embodiment of the present invention;
- FIG. 12 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 11;
- FIGS.13(A) and 13(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the sixth embodiment;
- FIG. 14 is a flowchart showing a routine executed by an ECU for controlling the oil control valve of the valve train according to the sixth embodiment;
- FIGS.15(A) and 15(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve according to a seventh embodiment of the present invention;
- FIG. 16 is a flowchart showing a routine executed by an ECU for controlling an oil control valve of a variable performance valve train according to the seventh embodiment;
- FIGS.17(A) and 17(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in a valve train according to a ninth embodiment of the present invention;
- FIG. 18 is a partial perspective view illustrating a variable performance valve train according to an eleventh embodiment of the present invention;
- FIG. 19 is a diagrammatic cross-sectional view illustrating a valve actuator and a first oil control valve of the valve train of FIG. 18;
- FIG. 20 is a diagrammatic cross-sectional view illustrating a variable valve timing mechanism and a second oil control valve of the valve train shown in FIG. 18;
- FIG. 21 is a front view illustrating the variable valve timing mechanism of FIG. 20 with the cover removed;
- FIG. 22 is an enlarged cross-sectional view illustrating a lock pin of the mechanism of FIG. 20;
- FIG. 23 is also an enlarged cross-sectional view illustrating a lock pin FIG. 22 when the pin is engaged with a recess;
- FIG. 24 is a front view illustrating the vane rotor of the mechanism of FIG. 20 with the cover removed;
- FIGS.25(A) and 25(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve in the mechanism of FIG. 18;
- FIG. 26 is a flowchart showing a routine executed by an ECU for controlling the first oil control valve of the valve train shown in FIG. 18;
- FIG. 27 is a flowchart showing a routine executed by an ECU for controlling the second oil control valve of the valve train shown in FIG. 18;
- FIGS.28(A) and 28(B) are maps for determining a target advance angle and a target shaft position of the valve train shown in FIG. 18;
- FIG. 29 is a perspective view illustrating a variable performance valve train according to a twelfth embodiment of the present invention;
- FIGS.30(A) and 30(B) are graphs showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train shown in FIG. 29;
- FIG. 31 is a graph showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of the valve train shown in FIG. 29 when there is a malfunction in the engine;
- FIG. 32 is a graph showing a relationship between the crank angle and the valve lift for an intake valve and an exhaust valve of a variable performance valve train according to another embodiment of the present invention when there is a malfunction in the engine;
- FIG. 33 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve according to a fifteenth embodiment of the present invention;
- FIG. 34 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 33;
- FIG. 35 is a diagrammatic cross-sectional view illustrating a variable valve lift actuator and an oil control valve according to a seventeenth embodiment of the present invention;
- FIG. 36 is a diagrammatic cross-sectional view illustrating an operational state of the actuator and the control valve of FIG. 35;
- FIG. 37 is a perspective view illustrating a cam follower mechanism for an intake cam or an exhaust cam;
- FIG. 38 is a perspective exploded view showing the cam follower of FIG. 37;
- FIG. 39(A) is a front view showing the cam follower of the mechanism shown in FIG. 37;
- FIG. 39(B) is a top plan view showing the cam follower of FIG. 39(A);
- FIG. 39(C) is a right side view showing the cam follower of FIG. 39(A);
- FIG. 39(D) is a bottom view showing the cam follower of FIG. 39(A);
- FIG. 40 is a diagrammatic view showing the characteristics of the cam follower shown in FIG. 39(A); and
- FIG. 41 is a perspective view illustrating an intermediate product when manufacturing the cam follower of FIG. 39(A).
- A variable performance valve train according to a first embodiment of the present invention will now be described with reference to FIGS.1 to 7.
- Referring to FIG. 1, an in-line four
cylinder type engine 11 has acylinder block 13, anoil pan 13 a, which is located under thecylinder block 13, and acylinder head 14, which is located on top of thecylinder block 13. Pistons 12 (only one is shown) are reciprocally accommodated in thecylinder block 13. - An output shaft, or
crankshaft 15, is rotatably supported in the lower portion of theengine 11. Eachpiston 12 is connected to thecrankshaft 15 by a connectingrod 16. The connectingrods 16 convert reciprocation of thepistons 12 into rotation of thecrankshaft 15. Acombustion chamber 17 is defined above eachpiston 12. Anexhaust passage 18 and anintake passage 19 are connected to thecombustion chamber 17. A pair ofexhaust valves 20 selectively connect and disconnect thecombustion chamber 17 with theexhaust passage 18. A pair ofintake valves 21 selectively connect and disconnect thecombustion chamber 17 with theintake passage 19. - An
exhaust camshaft 22 and anintake camshaft 23 are rotatably supported in thecylinder head 14. Theexhaust camshaft 22 and theintake camshaft 23 extend parallel to each other and to thecrankshaft 15. Theexhaust camshaft 22 is axially fixed. Theintake camshaft 23 is axially movable. - A timing
pulley 24 a is fixed to a first end (left end as viewed in the drawing) of theexhaust camshaft 22. A variablevalve lift actuator 25, which includes a timingpulley 25 a, is fixed to a first end (left end as viewed in the drawing) of theintake camshaft 23. The variablevalve lift actuator 25 axially moves theintake camshaft 23 to change the cam profile of three-dimensional intake cams 28. Accordingly, the valve open angle and the valve lift of theintake valves 21 are adjusted. - The timing pulleys24 a, 25 a are connected to a timing
pulley 15 a fixed to thecrankshaft 15 by atiming belt 26. Thetiming belt 26 transmits rotation of thecrankshaft 15 to the exhaust andintake camshafts intake camshafts crankshaft 15. - Pairs of
exhaust cams 27 are located on theexhaust camshaft 22. Each pair of theexhaust cams 27 contacts a corresponding pair ofvalve lifters 29 located at the top of a corresponding pair ofexhaust valves 20. Theintake cams 28 are located on theintake camshaft 23. Each pair ofintake cams 28 contacts a corresponding pair ofvalve lifters 29 located on the top of a corresponding pair ofintake valves 21. Rotation of theexhaust camshaft 22 causes eachexhaust valve 20 to selectively open and close in accordance with the profile of the associatedexhaust cam 27. Likewise, rotation of theintake camshaft 23 causes eachintake valve 21 to selectively open and close in accordance with the profile of the associatedintake cam 28. - The profile of each
exhaust cam 27 does not vary along the axis of theexhaust camshaft 22. Theintake cams 28 are three-dimensional as illustrated in FIG. 2. That is, the profile of eachintake cam 28 continuously changes along the axis of theintake camshaft 23. - When the
intake camshaft 23 is moved in a direction indicated by arrow A, theintake cams 28 continuously increase the valve lift of theintake valves 21, which advances the opening timing of theintake valves 21 and retards the closing timing of theintake valves 21. Accordingly, the valve open angle of theintake valves 21 is gradually extended. If theintake camshaft 23 is moved in the opposite direction of arrow A, theintake cams 28 continuously decrease the valve lift of theintake valves 21, which retards the opening timing of theintake valves 21 and advances the closing timing of theintake valves 21. Accordingly, the valve open angle is gradually shortened. - Axial movement of the
intake camshaft 23 continuously changes the valve open angle and the valve lift of theintake valves 21. - Next, the variable
valve lift actuator 25 and an oil supply system will be described with reference to FIG. 3. The oil supply system hydraulically drives theactuator 25. - As shown in FIG. 3, the variable
valve lift actuator 25 includes the timingpulley 25 a. The timingpulley 25 a includes acylindrical boss 151, adisk 152 andouter teeth 153. Theboss 151 slidably supports theintake camshaft 23. Thedisk 152 extends radially from theboss 151. Theteeth 153 are formed on the circumferential surface of thedisk 152. Theboss 151 is rotatably supported by asupport 14 b of thecylinder head 14. Theintake camshaft 23 can move axially in theboss 151. - A
cover 154 is secured to thepulley 25 a bybolts 155 to cover the distal end of theintake camshaft 23.Inner teeth 157 are formed on the inner face of thecover 154. Theinner teeth 157 extend along the axis of theintake camshaft 23 and form an internal gear. - A
ring gear 162 is fastened to the distal end of theintake camshaft 23 by ahollow bolt 158 and apin 159.Outer teeth 163 are formed on thering gear 162. Theouter teeth 163 extend along the axis of theintake camshaft 23 and form a spur gear. Theouter teeth 163 mesh with theinner teeth 157. Thering gear 162 does not rotate relative to the timingpulley 25 a but moves axially together with theintake camshaft 23 along the axis of theintake camshaft 23. - When the
engine 11 is running, rotation of thecrankshaft 15 is transmitted to the timingpulley 25 a by thetiming belt 26. Thepulley 25 a integrally rotates theintake camshaft 23. When rotated, theintake camshaft 23 actuates theintake valves 21 by means of thevalve lifters 29 and thecam followers 21 a, which are pivotally supported by thevalve lifters 29. - When the
ring gear 162 is hydraulically moved rightward (the direction of arrow A) by the oil supply system, so is theintake camshaft 23 as shown in FIG. 4. Accordingly, thecam follower 21 a of eachintake valve 21 is moved to the left portion (as viewed in FIG. 3) of the correspondingintake cam 28, which has a larger profile. Thus, the valve lift and the valve open angle of theintake valve 21 are increased. That is, the opening timing of theintake valves 21 is advanced and the closing timing of thevalves 21 is retarded. - As shown in FIG. 3, when the
ring gear 162 is moved leftward (in the opposite direction of arrow A), so is thecamshaft 23. Accordingly, thecam follower 21 a of eachintake valve 21 is moved to the right portion of the correspondingintake cam 28, which has a smaller cam profile. Thus, the valve lift and the valve open angle of theintake valve 21 are decreased. That is, the opening timing of theintake valve 21 is retarded and the closing timing of theintake valve 21 is advanced. - The oil supply system, which hydraulically actuates the
ring gear 162, will now be described. - The
ring gear 162 has aradially extending flange 162 a, which forms a piston. Thering gear 162 slidably contacts the inner surface of thecover 154 and defines first and secondoil pressure chambers second oil conduits intake camshaft 23. The first andsecond oil conduits second oil chambers - The
first oil conduit 167 is connected to thefirst oil chamber 165 by the interior of thehollow bolt 158 and extends through thecylinder head 14 to an oil control valve (OCV) 170. Thesecond oil conduit 168 is connected to thesecond oil chamber 166 through theboss 151 of the timingpulley 25 a and anoil hole 172, and extends through thecylinder head 14 to theOCV 170. - A
supply passage 128 and adrain passage 130 are connected to theOCV 170. Thesupply passage 128 is connected to anoil pan 13 a via an oil pump P. Thedrain passage 130 is directly connected to theoil pan 13 a. - The
OCV 170 has acasing 116. Thecasing 116 has first andsecond oil ports second drain ports supply port 126. Thefirst oil port 118 is connected to a passage P1 and thesecond oil port 120 is connected to a passage P2. Thesupply port 126 is connected to asupply passage 128. The first andsecond drain ports drain passage 130. Oil supplied by the oil pump P is conducted to theactuator 25 via thesupply passage 128 and theOCV 170. Oil from theactuator 25 is drained to theoil pan 13 a via theOCV 170 and thedrain passage 130. TheOCV 170 includes aspool 138, acoil spring 134 and anelectromagnetic solenoid 136. Thespool 138 has fourvalve bodies 132. Thecoil spring 134 urges thespool 138 axially toward thesolenoid 136. Thesolenoid 136 moves thespool 138 axially leftward (as viewed in FIG. 3). - When the
solenoid 136 is de-excited, the force of thespring 134 displaces thespool 138 to the rightmost position in thecasing 116 as illustrated in FIG. 3. This communicates thefirst oil port 118 with thefirst drain port 122 and thesecond oil port 120 with thesupply port 126. In this state, oil in theoil pan 13 a is supplied to the secondoil pressure chamber 166 via thesupply passage 128, theOCV 170, the passage P2, thesecond oil conduit 168 and theoil hole 172. Also, oil in the firstoil pressure chamber 165 is drained to theoil pan 13 a via thefirst oil conduit 167, the oil passage P1, theOCV 170 and thedrain passage 130. As a result, thering gear 162 and theintake camshaft 23 are moved leftward and eachcam follower 21 a contacts the small profile portion (low valve lift portion) of the associatedintake cam 28. This decreases the valve lift and the valve open angle of theintake valves 21. The valve performance of the exhaust andintake valves valves valves - When excited, the
solenoid 136 displaces thespool 138 to the leftmost position in thecasing 116 against the force of thecoil spring 134 as shown in FIG. 4. This communicates thesecond port 120 with thesecond drain port 124 and thefirst port 118 with thesupply port 126. In this state, oil in theoil pan 13 a is supplied to the firstoil pressure chamber 165 via thesupply passage 128, theOCV 170, the passage P1 and thefirst conduit 167. Oil in thesecond pressure chamber 166 is drained to theoil pan 13 a via theoil hole 172, thesecond conduit 168, the passage P2, theOCV 170 and thedrain passage 130. As a result, thering gear 162 and theintake camshaft 23 are moved in a direction of arrow A, which causes eachcam follower 21 a to contact the large profile portion (high valve lift portion) of the associatedintake cam 28. Accordingly, the valve lift and the valve open angle of theintake valves 21 are increased. The valve performance of the exhaust andintake valves valves valves - As shown in FIG. 5, the
spool 138 can be positioned midway between the leftmost position and the rightmost position in thecasing 116 by controlling current to thesolenoid 136. In this state, the first andsecond ports ports second pressure chambers chambers ring gear 162, which fixes the axial position of eachintake cam 28 relative to the associatedcam follower 21 a. In other words, the current valve lift and the valve open angle of theintake valves 21 are maintained. - Referring back to FIG. 1, the vehicle includes an electronic control unit (ECU)180 to control the valve lift of the
intake valves 21. Specifically, theECU 180 controls the electricity supplied to theOCV 170. TheECU 180 is a microcomputer, which includes aCPU 182, aROM 183, a RAM 184 and external input andoutput circuits - The
ROM 183 stores various control programs and data such as maps and tables used in the programs. TheCPU 182 executes various computations in accordance with the programs stored in theROM 183. The RAM 184 temporarily stores the results of the computations by theCPU 182 and data from various sensors. Thebackup RAM 185 is a non-volatile storage that stores necessary data when theengine 11 is stopped. TheCPU 182,ROM 183, the RAM 184, thebackup RAM 185 and the external input andoutput circuits bus 186. - An
electromagnetic pickup 190 for thecrankshaft 15 and ashaft position sensor 194 for theintake camshaft 23 are connected to theexternal input circuit 187. Further, various sensors for detecting the state of theengine 11 such as an intake pressure sensor and a throttle sensor (neither is shown) are connected to theexternal input circuit 187. Thepickup 190 detects the rotational phase or the rotation speed of thecrankshaft 15. Theshaft position sensor 194 detects the axial position of theintake camshaft 23. Theexternal output circuit 188 is connected to theOCV 170. - An
ECU 201 for controlling athrottle valve 202 is connected to the external input andoutput circuits ECUs engine 11. TheECU 201 computes a required torque based on detection values of a gas pedal sensor and other sensors for detecting the condition of theengine 11. TheECU 201 adjusts the opening of thethrottle valve 202 to an required opening amount. TheECU 201 also judges whether the opening of thethrottle valve 202 is changing in accordance with commands from theECU 201 based on detection signals from a throttle sensor located in the vicinity of at thethrottle valve 202. If theECU 201 judges that thethrottle valve 202 is not responding to the commands, theECU 201 sends a throttle abnormality signal, or signal indicating an abnormality of thethrottle valve 202, to theECU 180. - The
ECU 180 controls the performance of theintake valves 21. TheECU 180 optimizes the running state of theengine 11. Specifically, theECU 180 controls theOCV 170 for adjusting the valve lift and the valve open angle of theintake valves 21 based on detection signals from the sensors that detect the state of theengine 11. For example, theECU 180 receives the engine speed detected by thepickup 190 and the engine load detected by the intake pressure sensor. Then, theECU 180 uses the engine speed and the engine load as parameters and computes a target axial position of theintake camshaft 23, which corresponds to a target valve lift. The target valve lift is related to the parameters according to function data. TheECU 180 controls theactuator 25 to move theintake camshaft 23 to the target axial position. - When controlling the
OCV 170, theECU 180 receives signals from theshaft position sensor 194 and computes the axial position of theintake camshaft 23 based on the received signals. TheECU 180 uses theOCV 170 to feedback control theactuator 25 such that theintake camshaft 23 is moved to an axial position at which the valve lift and the open angle match target values. - The
ECU 180 executes the routine of FIG. 7 at predetermined intervals or at predetermined crank angles to control theOCV 170. - When entering the routine, the
ECU 180 judges whether theengine 11 is running normally (S310). If a throttle abnormality signal is not sent from theECU 201, theECU 180 judges that theengine 11 is running normally. If a throttle abnormality signal is sent from theECU 201, theECU 180 judges that there is malfunction in theengine 11. - If the
engine 11 is running normally, theECU 180 controls the valve open angle of theintake valves 21 by a normal procedure (S320). Specifically, theECU 180 uses engine speed, which is detected by thepickup 190, and the engine load, which is computed based on signals from the intake pressure sensor, as parameters. TheECU 180 computes a target axial position of theintake camshaft 23, which corresponds to a target valve open angle, based on the parameters according to function data. TheECU 180 controls theactuator 25 such that theintake camshaft 23 is moved to the target shaft position. - The
ECU 180 receives detection signals from theshaft position sensor 194 and computes the axial position of theintake camshaft 23 based on the signals from thesensor 194. TheECU 180 feedback controls theactuator 25 by means of theOCV 170 such that theintake camshaft 23 is moved to the target shaft position. - If there is a malfunction in the
engine 11, theECU 180 controls the valve open angle of theintake valves 21 at step S330 according to a fail-safe procedure. Specifically, theECU 180 moves theintake camshaft 23 to minimize or decrease the valve overlap. In other words, theECU 180 sets the closing timing of theintake valves 21 to the most advanced position. At this time, theintake camshaft 23 is located at the leftmost position as shown in FIG. 3. - In this manner, when there is a malfunction in the
engine 11, the valve overlap is set to zero, which stabilizes the engine speed. Also, since the closing timing of theintake valves 21 is advanced, starting of theengine 11 is facilitated. Thus, after being stopped, theengine 11 can be quickly restarted, which makes it easier for the driver to take steps to correct the malfunction. - A second embodiment will now be described. The second embodiment is the same as the first embodiment except that the
outer teeth 163 of thering gear 162 and theinner teeth 157 of thecover 154 are replaced with left-handed helical gears (not shown), and except that the control routine differs from the routine of FIG. 7. - In FIG. 3, if left-handed helical teeth were used on the
ring gear 162 and thecover 154 instead of spur teeth, or splines, according to the second embodiment, the phase of theintake camshaft 23 would be advanced relative to thecover 154. As shown in FIG. 8(A), under these circumstances, the valve open angle is advanced, and the closing timing Ci of theintake valves 21 is more advanced than the closing timing corresponding to the state of FIG. 3 in the first embodiment, which is shown in FIG. 6(A). - In the second embodiment when the
intake camshaft 23 is moved to the rightmost position like in FIG. 4, the phase of theintake camshaft 23 is retarded relative to thecover 154 due to the helical gear teeth (not shown). Accordingly, the valve open angle is retarded as shown in FIG. 8(B). - In the second embodiment, the
ECU 180 executes the routine of FIG. 9 at predetermined intervals or at a predetermined crank angles. Steps S410, S420 are the same as steps S310, S320 of the flowchart of FIG. 7. - If there is a malfunction in the
engine 11, theECU 180 moves theintake camshaft 23 such that the closing timing of theintake valves 21 is most advanced, which is a fail-safe procedure to facilitate starting of theengine 11. When theintake camshaft 23 is at the leftmost position as shown in FIG. 3, the closing timing of theintake valves 21 is most advanced as shown in FIG. 8(A). In this state, the valve open angle of theintake valves 21 is the smallest. Since the closing timing of theintake valves 21 is most advanced, the starting of theengine 11 is facilitated. - A third embodiment will now be described. The third embodiment is the same as the second embodiment except that the routine of FIG. 9 is replaced by the routine of FIG. 7. That is, when there is a malfunction in the
engine 11, theintake camshaft 23 is moved to a position at which the valve overlap is minimum. - The
intake camshaft 23 is moved to the rightmost position like in FIG. 4 so that the valve overlap is minimized, or zero, as illustrated in FIG. 8(B). At this time, the valve open angle of theintake valves 21 is the widest and the phase of theintake camshaft 23 is most retarded. Decreasing the valve overlap stabilizes the engine speed. - A fourth embodiment will now be described. The mechanism of the fourth embodiment is the same as the mechanism of the second embodiment except that the left-handed helical teeth are replaced with right-handed helical teeth. The routine of FIG. 7 is used to control the
actuator 25. The performance of theintake valves 21 according to the fourth embodiment is shown in FIGS. 10(A) and 10(B). - If there is a malfunction in the
engine 11, theECU 180 moves theintake camshaft 23 to the leftmost position like in FIG. 3 to minimize the valve overlap (step S330). Thus, the valve open angle of theintake valves 21 is the smallest and its phase is most retarded. Therefore, the fourth embodiment has the same advantages as the first embodiment. - A fifth embodiment will now be described. The fifth embodiment is the same as the fourth embodiment except that the routine of FIG. 7 is replaced by the routine of FIG. 9.
- If there is a malfunction in the
engine 11, theECU 180 shifts the closing timing of theintake valves 21 to the most advanced timing (step S430) by moving theintake camshaft 23. At this time, the valve open angle of theintake valves 21 is the largest and its phase is most advanced. Therefore, the fifth embodiment has the same advantages as the second embodiment. - A sixth embodiment will now be described with reference to FIG. 11. The sixth embodiment is different from the first embodiment in that the
actuator 25 is attached to theexhaust camshaft 22 and in that theexhaust cams 27 are three-dimensional. Theintake camshaft 23 does not move axially. - When the
exhaust camshaft 22 is at the leftmost position as illustrated in FIG. 11, the valve open angle of theexhaust valves 20 is the smallest as shown in FIG. 13(A). - When the
exhaust camshaft 22 is at the rightmost position as illustrated in FIG. 12, the valve open angle of theexhaust valves 20 is the largest as shown in FIG. 13(B). - In the sixth embodiment, the
ECU 180 executes the routine of FIG. 14 at predetermined intervals or at predetermined crank angles. - First, the
ECU 180 judges whether theengine 11 is running normally (step S510). - If there is a malfunction in the
engine 11, theECU 180 feedback controls the valve open angle of theexhaust valves 20 by the normal procedure (step S520). - If there is a malfunction in the
engine 11, theECU 180 moves theexhaust camshaft 22 axially to minimize the valve overlap (step S530). At this time, as shown in FIG. 13(A), the opening timing of theexhaust valve 20 is retarded so that there is no valve overlap. This stabilizes the engine speed. The retarded opening timing of theexhaust valves 20 further stabilizes the engine speed. - A seventh embodiment will now be described. The seventh embodiment is different from the sixth embodiment in that the
outer spur teeth 163, or splines, of thering gear 162 and theinner spur teeth 157, or splines, of thecover 154 are replaced by left-handed helical teeth (not shown). - When the
exhaust camshaft 22 is at the leftmost position like in FIG. 11, the valve lift and the valve open angle of theexhaust valve 20 are smallest as illustrated in FIG. 15(A). - If the
exhaust camshaft 22 is at the rightmost position like in FIG. 12, the valve lift of theexhaust valve 20 is maximum and the valve open angle is largest as shown in FIG. 15(B). At this time, the valve open angle of theexhaust valve 20 is most retarded. - In the seventh embodiment, the
ECU 180 executes the routine of FIG. 16 to control theactuator 25. Steps S610, S620 are the same as steps S510, S520 of the sixth embodiment. - If there is a malfunction in the
engine 11, theECU 180 axially shifts theexhaust camshaft 22, which changes the opening timing of theexhaust valve 20 to the most retarded timing in a fail-safe procedure (step S630), which stabilizes the engine speed. - An eighth embodiment of the present invention will now be described. The eighth embodiment is the same as the seventh embodiment except that the routine of FIG. 16 is replaced with a routine of FIG. 14.
- When there is a malfunction in the
engine 11, theECU 180 moves theexhaust camshaft 22 to minimize the valve overlap (step S530), which stabilizes the engine speed. - A ninth embodiment will now be described. The ninth embodiment is different from the seventh embodiment in that the left-handed helical teeth are replaced with right-handed helical teeth (not shown).
- When there is a malfunction in the
engine 11, theECU 180 moves theexhaust camshaft 22 such that the opening timing of theexhaust valve 20 is most retarded as illustrated in FIG. 17(A)(step S630). The valve overlap is maximized accordingly, and the engine speed is stabilized. - A tenth embodiment will now be described. The tenth embodiment is different from the ninth embodiment in that the routine of FIG. 16 is replaced with the routine of FIG. 14.
- When there is a malfunction in the
engine 11, theECU 180 minimizes the valve overlap as shown in FIG. 17(B)(step S530). Therefore, the tenth embodiment has the same advantages as those of the eighth embodiment. - An eleventh embodiment will now be described with reference to FIGS.18 to 24.
- As shown in FIG. 18, an
engine 1011 basically has the same structure as theengine 11 shown in FIG. 1. Theengine 1011 further has afirst actuator 1022 a for varying valve open angle and a second actuator for varying the valve timing. Thesecond actuator 1024 and a timingpulley 1024 a are provided at the left end of anintake camshaft 1022. Thefirst actuator 1022 a is provided at the right end of theintake camshaft 1022. - The
first actuator 1022 a and an oil supply system, which supplies hydraulic oil to theactuator 1022 a, will now be described with reference to FIG. 19. - The
actuator 1022 a includes acylinder tube 1031 and apiston 1032 accommodated in thecylinder tube 1031. A pair of end covers 1033 close the openings of thetube 1031. Thecylinder tube 1031 is fixed to thecylinder head 1014. - The
intake camshaft 1022 extends through one of thecovers 1033 and is coupled to thepiston 1032. Thepiston 1032 defines afirst pressure chamber 1031 a and asecond pressure chamber 1031 b in thetube 1031. Afirst passage 1034 and asecond passage 1035 are formed in thecovers 1033, respectively. Thefirst passage 1034 communicates with thefirst pressure chamber 1031 a and thesecond passage 1035 communicates with thesecond pressure chamber 1031 b. - When oil is supplied to the
first pressure chamber 1031 a or thesecond pressure chamber 1031 b via thefirst passage 1034 or thesecond passage 1035, respectively, thepiston 1032 is moved axially. Accordingly, theintake camshaft 1022 is moved axially in a direction corresponding to thechamber - The
first passage 1034 and thesecond passage 1035 are connected to a first oil control valve (OCV) 1036 by passages P11 and P12, respectively. Thefirst OCV 1036 has the same structure as theOCV 170 of the first embodiment. That is, thefirst OCV 1036 is actuated by controlling the electric current fed to a solenoid. 1047. - The
second actuator 1024 will now be described with reference to FIG. 20. - The
second actuator 1024 includes the timingpulley 1024 a. The timingpulley 1024 a includes acylindrical boss 1051 and adisk 1052 andouter teeth 1053. Theboss 1051 slidably supports theintake camshaft 1022. Thedisk 1052 radially extends from theboss 1051. Theteeth 1053 are formed on the circumferential surface of thedisk 1052. Theboss 1051 is rotatably supported by asupport 1014 a of thecylinder head 1014. - An inner gear1054 is fixed to the distal end of the
intake camshaft 1022 by abolt 1055. The inner gear 1054 includes alarge diameter portion 1054 a and asmall diameter portion 1054 b. Thesmall diameter portion 1054 b has helical teeth, and thelarge diameter portion 1054 a has straight spur teeth, or splines. - A ring-shaped
sub-gear 1056 is fitted about thesmall diameter portion 1054 b of the inner gear 1054. Thesub gear 1056 includesouter teeth 1056 a andinner teeth 1056 b. Theouter teeth 1056 a are parallel to the axis of thecamshaft 1022 and theinner teeth 1056 b are helical. The outer diameter of the sub-gear 1054 is the same as that of the inner gear 1054. Theinner teeth 1056 b of the sub-gear 1056 mesh with the teeth of thesmall diameter portion 1054 b. Aspring washer 1057 is located between the inner gear 1054 and the sub-gear 1056. Thespring washer 1057 urges the sub-gear 1056 away from the inner gear 1054. - A
housing 1059 and acover 1060 are coupled to thedisk portion 1052 of the timingpulley 1024 a by fourbolts 1058. Thecover 1060 seals first andsecond pressure chambers opening 1060 a is formed in the center of thecover 1060 to communicate a cylindrical hole 1061 c, which will be described later, to the outside. Theopening 1060 a allows theintake camshaft 1022 to move easily in the axial direction. - FIG. 21 shows the mechanism of FIG. 20 viewed from the left. In FIG. 21, the
bolts 1058, thecover 1060 and thebolt 1055 are not shown. FIG. 20 is a cross-sectional view taken along line 21-21 of FIG. 21. - The
housing 1059 has fourprojections inner surface 1059 a. Avane rotor 1061 is rotatably fitted in thehousing 1059. Thevane rotor 1061 hasouter walls 1061 a, which contact theprojections - The cylindrical hole1061 c is defined in the center of the vane rotor 1061 (see FIG. 20).
Splines 1061 b are formed on the inner wall of the hole 1061 c. Thesplines 1061 b extend along the axis of theintake camshaft 1022. Thelarge diameter portion 1054 a of the inner gear 1054 and theouter teeth 1056 a of the sub-gear 1056 mesh with thesplines 1061 b. - Engagement of the
inner teeth 1056 b and thesmall diameter portion 1054 b and the force of thespring washer 1057 urge thelarge diameter portion 1054 a and theouter teeth 1056 a in opposite rotational directions. Therefore, errors due to backlash between thesplines 1061 b and thegears 1054, 1056 are eliminated, which allows the inner gear 1054 to be accurately located at a predetermined rotational phase position relative to thevane rotor 1061. In other words, thevane rotor 1061 and theintake camshaft 1022 are accurately positioned relative to each other. In FIG. 20, only two of thesplines 1061 b are shown. However, thesplines 1061 b are formed along the entire wall of the hole 1061 c as shown in FIG. 21. -
Vanes outer walls 1061 a of thevane rotor 1061. Thevanes projections vanes inner surface 1059 a of thehousing 1059. Each of thevanes projections second pressure chambers - The
vane 1066 has a throughhole 1072 extending along the axis of theintake camshaft 1022. Alock pin 1073 is fitted in the throughhole 1072 to move axially. Aspring hole 1073 a is formed in thelock pin 1073. Aspring 1074 is accommodated in thespring hole 1073 a to urge thelock pin 1073 toward thedisk 1052. - An
oil groove 1072 a is formed in the front face of thevane rotor 1061. Theoil groove 1072 a connects anarcuate opening 1072 b formed in the cover 1060 (see FIG. 18) to the throughhole 1072. Theopening 1072 b and theoil groove 1072 a drain air and oil located in a space that is axially front of thelock pin 1073 in the throughhole 1072. - Operation of the
lock pin 1073 will now be described with reference to FIGS. 22 and 23. - When the
lock pin 1073 faces alock recess 1075 formed on thedisk 1052 as illustrated in FIG. 23, thespring 1074 causes thelock pin 1073 to engage, or enter, therecess 1075. Accordingly, the rotational position of thevane rotor 1061 relative to thedisk 1052 is fixed. - When the
vane rotor 1061 is at the most retarded position, thelock pin 1073 does not face therecess 1075 and the distal end of thelock pin 1073 is not engaged with therecess 1075 as illustrated in FIG. 22. FIG. 21 also illustrates thevane rotor 1061 when the distal end of thelock pin 1073 is not engaged with therecess 1075. - For example, when the
engine 1011 is being cranked or before theECU 1130 starts activating the hydraulic system, the pressure of the first andsecond pressure chambers vane rotor 1061 is at the position of FIG. 21. In this case, cranking of theengine 1011 generates a reverse torque in theintake camshaft 1022, which advances the rotational phase of thevane rotor 1061 relative to thehousing 1059. Accordingly, thelock pin 1073 is moved from the position of FIG. 22 to the position of FIG. 23 and enters therecess 1075. This prohibits further relative rotation between thevane rotor 1061 and thehousing 1059 and causes therotor 1061 to rotate integrally with thehousing 1059. - After the
engine 1011 is started, oil is supplied to anannular chamber 1077 from thesecond pressure chamber 1071 via anoil passage 1076, which disengages thelock pin 1073 from therecess 1075. Specifically, a pressure increase of oil supplied to theannular chamber 1077 disengages thelock pin 1073 from therecess 1075 against the force of thespring 1074. Oil is supplied to therecess 1075 from thefirst pressure chamber 1070 via anoil passage 1078, which retains thelock pin 1073 at the disengaged position. Disengagement of thelock pin 1073 permits thevane rotor 1061 to rotate relative to thehousing 1059. The rotational position of thevane rotor 1061 relative to thehousing 1059 is determined in accordance with pressure of the first andsecond pressure chambers vane rotor 1061 is retained at an advanced position relative to thehousing 1059 as illustrated in FIG. 24. - Therefore, when the
crankshaft 1015 is rotated by theengine 1011, the rotation is transmitted to the timingpulley 1024 a by atiming belt 1026. The timingpulley 1024 a and theintake camshaft 1022 are integrally rotated at an adjusted phase. The rotation of theintake camshaft 1022 drives intake valves 1020 (see FIG. 18). - If the rotational phase of the
vane rotor 1061 relative to thehousing 1059 is advanced by controlling the pressures in the first andsecond pressure chambers engine 1011 is running, the rotational phase of theintake camshaft 1022 is advanced relative to that of thecrankshaft 1015. Accordingly, the opening and closing timings of theintake valves 1020 are advanced as shown by an arrow in FIG. 25(B) while the valve open angle of theintake valves 1020 is maintained. - If the rotational phase of the
vane rotor 1061 relative to thehousing 1059 is retarded, the rotational phase of theintake camshaft 1022 is retarded relative to that of thecrankshaft 1015. Accordingly, the opening and closing timings of theintake valves 1020 are retarded, or retarded in a direction opposite to the arrow in FIG. 25(B). Specifically, while the valve open angle of theintake valve 1020 does not change, the intake valve timing is retarded. - The oil supply system of the
second actuator 1024 will hereafter be described. - The
disk 1052 hasfirst openings 1080 andsecond openings 1081. Eachfirst opening 1080 is connected to one of thefirst pressure chambers 1070 and eachsecond opening 1081 is connected to one of thesecond pressure chambers 1071.Recesses 1062 a to 1065 a are formed in the vicinity of eachprojection 1062 to 1065 at a part adjacent to theopenings 1080. Eachrecess 1062 a to 1065 a supplies oil pressure to thefirst pressure chambers 1070 to advance the rotational phase of thevane rotor 1061 when thefirst openings 1080 are closed by thevanes 1066 to 1069. Likewise, recesses 1062 b to 1065 b are formed in the vicinity of theprojections 1062 to 1065 adjacent to thesecond openings 1081. Therecesses 1062 b to 1065 b supply oil to thesecond pressure chambers 1071 to retard the rotational phase of thevane rotor 1061 when thevanes second openings 1081. - Each
first opening 1080 is connected to a firstcircumferential groove 1051 a formed on thecylindrical boss 1051 viafirst oil conduits second opening 1081 is connected to a secondcircumferential groove 1051 b viasecond oil conduits - A
lubricant passage 1090 is formed in thecylindrical boss 1051. Thelubricant passage 1090 is connected to thesecond oil conduit 1087. A relatively wideinner groove 1091 is formed in theinner surface 1051 c of theboss 1051. Thegroove 1091 is connected to thelubricant passage 1090. Oil in thesecond conduit 1087 is conducted between theinner surface 1051 c of theboss 1051 and theouter surface 1022 b of thecamshaft 1022 and serves as lubricant. - The first
circumferential groove 1051 a is connected to asecond OCV 1094 by a passage P21 in thecylinder head 1014. The secondcircumferential groove 1051 b is connected to thesecond OCV 1094 by a passage P22 in thecylinder head 1014. - A
supply passage 1095 and adrain passage 1096 are connected to thesecond OCV 1094. Thesupply passage 1095 is connected to anoil pan 1013 a by the oil pump P, which is also connected to thefirst OCV 1036. Thedrain passage 1096 is directly connected to theoil pan 1013 a. The oil pump P supplies oil from theoil pan 1013 a to thesupply passages - The
second OCV 1094 has the same structure as that of thefirst OCV 1036. Thesecond OCV 1094 includes acasing 1102, afirst oil port 1104, asecond oil port 1106,valve bodies 1107, afirst drain port 1108, asecond drain port 1110, asupply port 1112, acoil spring 1114, anelectromagnetic solenoid 1116 and aspool 1118. Thefirst oil port 1104 is connected to the oil passage P21 and thesecond oil passage 1106 is connected to the oil passage P22. Thesupply port 1112 is connected to thesupply passage 1095 and the first andsecond drain ports drain passage 1096. - Therefore, when the
solenoid 1116 is de-excited, thefirst oil port 1104 is connected to thefirst drain port 1108 and thesecond oil port 1106 is connected to thesupply port 1112. Oil in theoil pan 1013 a is supplied to thesecond pressure chambers 1071 of thesecond actuator 1024 via thesupply passage 1095, thesecond OCV 1094, the passages P22, thecircumferential groove 1051 b, thesecond conduits second openings 1081, therecesses first pressure chambers 1070 of thesecond actuator 1024 is returned to theoil pan 1013 a via thegrooves first openings 1080, thefirst conduits circumferential groove 1051 a, the passage P21, thesecond OCV 1094 and thedrain passage 1096. As a result, the rotational phase of thevane rotor 1061 is retarded relative to thehousing 1059, which retards the opening and closing timing of theintake valves 1020. In other words, while the valve open angle of theintake valves 1020 does not change, the timing of theintake valves 1020 is retarded. - When the
solenoid 1116 is excited, thesecond oil port 1106 is connected to thesecond drain port 1110 and thefirst oil port 1104 is connected to thesupply port 1112. In this state, oil in theoil pan 1013 a is supplied to thefirst pressure chambers 1070 in thesecond actuator 1024 by thesupply passage 1095, thesecond OCV 1094, the passage P21, thecircumferential groove 1051 a, thefirst conduits first openings 1080 and therecesses second pressure chambers 1071 of thesecond actuator 1024 is returned to theoil pan 1013 a via therecesses second openings 1081, thesecond conduits groove 1051 b, the passage P22, thesecond OCV 1094 and thedrain passage 1096. As a result, the rotational phase of thevane rotor 1061 is advanced relative to that of thehousing 1059. Accordingly, the opening and closing timings of theintake valve 1020 are advanced. That is, the timing of theintake valves 1020 is advanced while open angle does not change. - The
first oil port 1104 andsecond oil port 1106 can be closed by controlling current to thesolenoid 1116. Accordingly, oil is not conducted through theoil ports second pressure chambers chambers vane rotor 1061 relative to thehousing 1059, which maintains the opening and closing timings of theintake valves 1020. In other words, the valve open angle of theintake valves 1020 is not advanced or retarded. - The
ECU 1130 controls the first andsecond OCVs second actuators intake valves 1020 is varied. TheECU 1130 has substantially the same structure as theECU 180 in the first embodiment except that theECU 1130 controls both first andsecond OCVs - An
electromagnetic pickup 1123 detects the rotational phase of thecrankshaft 1015. Anelectromagnetic pickup 1126 detects the rotational phase and the axial position of theintake camshaft 1022. - The
ECU 1130 executes routines of FIGS. 26 and 27 at predetermined intervals or at a predetermined crank angles to control the performance of theintake valves 1020. - Referring to FIG. 26, a routine for controlling the
first OCV 1036 will be described. When entering the routine of FIG. 26, theECU 1130 determines if theengine 1011 is running normally as in step S310 of FIG. 7 (step S1310). - If the
engine 1011 is running normally, theECU 1130 controls the valve open angle of theintake valve 1020 by a normal procedure (step S1320). Specifically, theECU 1130 determines a target position Lt of theintake camshaft 1022 based on a map L of FIG. 28(B). The map L of FIG. 28(B) uses the engine speed and the engine load (for example, intake pressure, intake amount or injection amount is used as a value to represent the engine load). TheECU 1130 controls thefirst actuator 1022 a such that the actual position of theintake camshaft 1022 matches the target shaft position Lt. The map L is designed such that an optimum valve open angle of theintake valves 1020 is selected for a required performance of theengine 1011. - If there is a malfunction in the
engine 1011, theECU 1130 controls thefirst actuator 1022 a to move theintake camshaft 1022 such that the valve open angle of theintake valves 1020 is minimized (step S1330). - Referring to FIG. 27, a control of the
second OCV 1094 will be described. As in step S1310 above, theECU 1130 judges whether theengine 1011 is running normally (step S1410). - If the
engine 1011 is running normally, theECU 1130 controls the phase of the valve open angle of theintake valves 1020 by the normal procedure (step S 1420). Specifically, theECU 1130 determines a target advance degree θt of the valve open angle based on a map i of FIG. 28(A) and feedback controls the valve open angle of theintake valves 1020. The map i FIG. 28(A) uses the engine speed and the engine load (for example, intake pressure, intake amount or injection amount is used as a value to represent the engine load). TheECU 1130 controls thesecond actuator 1024 such that the actual valve open angle of theintake valve 1020 matches the target angle θt. The map i is designed such that an optimum valve open angle of theintake valves 1020 is selected for a required performance of theengine 1011. - If there is a malfunction in the
engine 1011, theECU 1130 controls thesecond actuator 1024 to shift the rotational phase of theintake camshaft 1022 such that the valve open angle of theintake valves 1020 is most advanced (step S1430). Accordingly, the valve performance shown in FIG. 8(A) is obtained. Thus, the eleventh embodiment has the same advantages as the second embodiment. - The
second OCV 1094 may be controlled by the normal procedure even if there is a malfunction in theengine 1011. In this case, only thefirst OCV 1036 is controlled. Therefore, this embodiment still has the same advantages as the first embodiment. - The
OCVs engine 1011. In this case, the eleventh embodiment has the same advantages as the third embodiment. Further, theOCVs intake valves 1020 in the manner of the fourth and fifth embodiments. - A twelfth embodiment of the present invention will now be described. As shown in FIG. 29, the twelfth embodiment is different from the eleventh embodiment in that a
first actuator 1225 is attached to a timingpulley 1225 a of anexhaust camshaft 1222. Further, theexhaust camshaft 1222 is rotatably supported by a cylinder head. Theexhaust camshaft 1222 is permitted to move axially, or in a direction shown by arrowD. Exhaust cams 1227 are three-dimensional. Anintake camshaft 1223 is not axially moved, and theintake cams 1228 are normal cams. The rotational phase of heintake cams 1228 can be changed by theactuator 1224. - A first OCV controls the axial position of the
exhaust camshaft 1222 to vary the valve open angle of theexhaust valves 1220 as shown in FIG. 30(A). A second OCV controls the rotational phase of theintake camshaft 1223 relative to that of acrankshaft 1215 thereby adjusting the valve timing of theintake valves 1221. - The
ECU 1130 executes a routine like the routine of FIG. 26 to control theexhaust valves 1220. Specifically, when there is a malfunction in the engine, theECU 1130 minimizes the valve open angle of theexhaust valves 1220. Also, theECU 1130 rotates theintake camshaft 1223 to the most advanced rotational phase as in the routine of FIG. 27. - If there is a malfunction in the engine, the opening timing of the
exhaust valves 1220 is most retarded and there is no valve overlap, which stabilizes the engine speed. Also, the closing timing of theintake valves 1221 is most advanced, which facilitates the starting of the engine. - The first and
second actuators exhaust camshaft 1222. In this case, the valve performance of theexhaust valves 1220 is variable as the valve performance of theintake valves 1221 of FIGS. 25(A) and 25(B), and the valve performance of theintake valves 1221 is invariable as the valve performance of theexhaust valves 1220 of FIGS. 25(A) and 25(B). Alternatively, thesecond actuator 1224 may be attached to theexhaust camshaft 1222 and thefirst actuator 1225 may be attached to theintake camshaft 1223. In this case, valve performance shown will be as in FIG. 32 when there is a malfunction in the engine. This embodiment therefore has the same advantages as the twelfth embodiment. - A thirteenth embodiment will now be described. The thirteenth embodiment has the same structure as the first embodiment. However, the
ECU 201 may be omitted. The thirteenth embodiment is designed to deal with a malfunction in the hydraulic system, which includes the pump P and theOCV 170. - If there is a break in wires that connect the
ECU 180 to thesolenoid 136 of theOCV 170, electricity cannot be supplied to thesolenoid 136. In this case, theECU 180 is unable to control thesolenoid 136. As a result, thespool 138 remains at the default position shown in FIG. 3. - Thus, each
cam follower 21 a contacts the smallest profile section of the associatedintake cam 28. The smallest profile section of theintake cam 28 is the default position. Therefore, if no electricity is supplied to thesolenoid 136 due to a malfunction, the performance of theintake valves 21 is as shown in FIG. 6(A). Specifically, the valve lift of theintake valves 21 is minimum and there is no valve overlap. - If the oil pump P malfunctions or if a pipe connecting the oil pump P with the
OCV 170 is broken, no pressurized oil is supplied to theactuator 25. - In this state, the
ring gear 162 receives no pressure either from thefirst oil chamber 165 or from thesecond oil chamber 166. Therefore, thering gear 162 cannot maintain the axial position of theintake camshaft 23. - However, since the surface of the nose of each
intake cam 28 is inclined, thecamshaft 23 receives a leftward force (as viewed in FIG. 3) from thecam followers 21 a. - Accordingly, the
ring gear 162 is moved leftward with theintake camshaft 23, which maintainsintake camshaft 23 at the default position as illustrated in FIG. 3. Therefore, if oil is not supplied to theactuator 25 due to a malfunction, the performance of theintake valves 21 is maintained in a state shown in FIG. 6(A). That is, the valve lift of eachintake valve 21 is minimum and there is no valve overlap. - In this manner, if electricity to the
solenoid 136 is stopped or if oil pressure is not supplied to theactuator 25 due to malfunction, theintake camshaft 23 is maintained at the default position of FIG. 3. Therefore, in either case, the valve lift and the opening timing of theintake valves 21 are the same. In other words, the two types of malfunctions can be dealt with by one fail-safe procedure. As a result, the development procedure of programs stored in theROM 183 and the required capacity of theROM 183 are reduced. - In either type of malfunction, there is no valve overlap, which stabilizes the speed of the
engine 11. Further, the valve lift is maintained minimum and the closing timing of theintake valves 21 is the most advanced. Starting of the engine is therefore facilitated, which allows the driver to quickly take steps to have the vehicle serviced. - A fourteenth embodiment of the present invention will now be described with reference to FIGS.1 to 5. The fourteenth embodiment is the same as the thirteenth embodiment except that the
outer teeth 163 of thering gear 162 and theinner teeth 157 on thecover 154 are replaced with left-handed helical teeth. When moved rightward in FIG. 3, theintake camshaft 23 rotates counterclockwise relative to thecover 154 when viewed from the left side of FIG. 3. - When the
solenoid 136 is de-excited, thering gear 162 is moved leftward with theintake camshaft 23 as shown in FIG. 3. At this time, the valve lift and the valve open angle of theintake valves 21 are small. Cooperation of the helical outer and inner teeth (not shown) displaces the rotational phase of theintake camshaft 23 to the most advanced position relative to thecover 154. Therefore, as shown in FIG. 8(A), the valve overlap between theintake valves 21 and theexhaust valves 20 is maximized. - When the
solenoid 136 is excited, thering gear 162 is moved in the direction of arrow A with theintake camshaft 23 as illustrated in FIG. 4, which increases the valve lift and the valve open angle of theintake valves 21. Cooperation of the helical outer and inner teeth retards the rotational phase of theintake camshaft 23 relative to thecover 154. As a result, the valve overlap between theintake valves 21 and theexhaust valves 20 becomes zero as shown in FIG. 8(B). - If the supply of electricity to the
solenoid 136 is stopped due to a malfunction, thespool 138 is maintained at the leftmost position in the casing by the force of thecoil spring 134 as illustrated in FIG. 3. In this state, eachintake cam 28 contacts the associatedcam follower 21 a at the smallest profile section (default position). Therefore, the valve lift of theintake valves 21 is the smallest and the closing timing Ci of thevalves 21 is most retarded as shown in FIG. 8(A). - If oil pressure is not supplied to the
actuator 25 due to a malfunction, thering gear 162 receives no oil pressure either from the firstoil pressure chamber 165 or the secondoil pressure chamber 166. However, theintake camshaft 23 receives a leftward force (as viewed in FIG. 3) at the contacting surface between the nose of eachintake cam 28 and the associatedcam follower 21 a. - As described above, in this embodiment, the
outer teeth 163 and theinner teeth 157 are replaced with left-handed helical teeth. Thecamshaft 23 receives friction force from a journal bearing (not shown) located on thecylinder head 14 and eachintake cam 28 receives friction force from the associatedcam follower 21 a. Due to the friction forces, theintake camshaft 23 receives a force in the direction of arrow A from the inner helical teeth of thecover 154. - The angle of the cam surface of the
intake cams 28 and the helical angle of the inner and outer teeth are determined such that the total leftward forces are greater than the axial forces in the direction of arrow A. - Accordingly, the
ring gear 162 and theintake camshaft 23 are moved leftward by default. Theintake camshaft 23 is maintained at the smallest profile section (default position) as illustrated in FIG. 3. As shown in FIG. 8(A), the valve lift of theintake valves 21 is the smallest and the closing timing of theintake valves 21 is most retarded. - In this manner, even if electricity to the
solenoid 136 is stopped or even if oil pressure is not supplied to theactuator 25 due to a malfunction, theintake camshaft 23 is stabilized at the default position. Further, when there is a malfunction, the valve lift of theintake valves 21 is the smallest and the closing timing Ci is most advanced, which facilitates the starting of theengine 11. - A variable performance valve train according to a fifteenth embodiment will now be described with reference to FIGS. 33 and 34.
- The fifteenth embodiment is different from the fourteenth embodiment in that the magnitudes of opposite forces that act on the
ring gear 162 when thering gear 162 receives no oil pressure are opposite from those in the fourteenth embodiment. Specifically, the angle of the cam surface of eachintake cam 28 and the helical angle of the inner and outer teeth are determined such that a force urging the intake camshaft in the direction of arrow A is stronger than an opposite force. A further difference is that the oil passage P11 from thefirst oil port 118 is connected to thesecond oil chamber 166 and the oil passage P12 from theport 120 is connected to thefirst oil chamber 165. As in the fourteenth embodiment, theouter teeth 163 of thering gear 162 and theinner teeth 157 of thecover 154 are replaced by helical teeth (not shown). - When the
solenoid 136 is de-excited, oil is supplied from theport 120 to thefirst oil chamber 165 as shown in FIG. 33, which moves thering gear 162 and theintake camshaft 23 in the direction of arrow A. As a result, eachintake cam 28 contacts the associatedcam follower 21 a at the largest profile section, which increases the valve lift and the valve open angle of theintake valves 21. Cooperation of the helical outer and inner teeth shifts the rotational phase of theintake camshaft 23 to the most retarded position relative to thecover 154. Therefore, as shown in FIG. 8(B), the valve lift of theintake valves 21 is maximized and the valve overlap is set to zero. - When the
solenoid 136 is excited, thering gear 162 is moved leftward with theintake camshaft 23 as illustrated in FIG. 34. As a result, eachintake cam 28 contacts thecam follower 21 a at the smallest profile section, which decreases the valve lift and the valve open angle of theintake valves 21. The cooperation of the helical outer and inner teeth shifts theintake camshaft 23 to the most advanced phase position relative to thecover 154. As a result, the valve lift of the intake valves is minimized and the valve overlap between theintake valves 21 and theexhaust valves 20 is maximized. - If the supply of electricity to the
solenoid 136 is stopped due to a malfunction, thespool 138 remains at the rightmost position in the casing by the force of thecoil spring 134 as illustrated in FIG. 33. In this state, eachintake cam 28 contacts the associatedcam follower 21 a at the largest profile section (default position). Therefore, the valve lift of theintake valves 21 is the maximum and there is no valve overlap as shown in FIG. 8(B). - If oil pressure is not supplied to the
actuator 25 due to a malfunction, theintake camshaft 23 receives forces in opposite axial directions as in the fourteenth embodiment. Specifically, theintake camshaft 23 receives a leftward force from thecam follower 21 a and a rightward force from the helical inner teeth of thecover 154. - As described above, the rightward force is greater than the leftward force, which moves the
ring gear 162 and theintake camshaft 23 rightward. Accordingly, theintake camshaft 23 is maintained at the default position of FIG. 33. The valve lift of theintake valve 21 is maximum and the valve overlap is zero as shown in FIG. 8(B). - In this manner, if electricity to the
solenoid 136 is stopped or if oil pressure is not supplied to theactuator 25 due to malfunction, theintake camshaft 23 is stabilized at the default position and the valve overlap is set to zero as shown in FIG. 8(B). Accordingly, the engine speed is stabilized. - A sixteenth embodiment will now be described with reference to FIGS.3 to 5. The valve train of the sixteenth embodiment is the same as the valve train of the fourteenth embodiment except that the
outer teeth 163 and theinner teeth 157 are replaced with right handed helical teeth (not shown). - When the
solenoid 136 is de-excited, thering gear 162 and theintake camshaft 23 are moved leftward as illustrated in FIG. 3, which decreases the valve lift and the valve open angle theintake valves 21. Cooperation of the helical outer and inner teeth shifts the rotational phase of theintake camshaft 23 to the most retarded position relative to thecover 154. Therefore, as shown in FIG. 10(A), the valve lift of theintake valves 21 is the smallest and is most retarded relative to theexhaust valve 20. Accordingly, the valve overlap is set to zero. - When the
solenoid 136 is excited, thering gear 162 is moved rightward with theintake camshaft 23 as illustrated in FIG. 4, which increases the valve lift and the valve open angle of theintake valves 21. Cooperation of the helical outer and inner teeth shifts the rotational phase of theintake camshaft 23 to the most advanced position relative to thecover 154. As a result, the valve lift of theintake valves 21 is the greatest and is most advanced relative to theexhaust valve 20. The valve overlap is therefore maximized. - If the supply of electricity to the
solenoid 136 is stopped due to a malfunction, thespool 138 is maintained at the rightmost position in the casing by thecoil spring 134 as illustrated in FIG. 3. In this state, eachintake cam 28 contacts the associatedcam follower 21 a at the smallest profile section (default position). Therefore, the valve lift of theintake valves 21 is minimum and there is no valve overlap as shown in FIG. 10(A). - If oil pressure is not supplied to the
actuator 25 due to a malfunction, theintake camshaft 23 receives a leftward force as a result of contact between thecam 28 and thecam follower 21 a. - The inner teeth of the
cover 154 and the outer teeth of thering gear 162 are right-handed helical teeth. Thecamshaft 23 receives a friction force from a journal bearing (not shown) located on thecylinder head 14 and eachintake cam 28 receives a friction force from the associatedcam follower 21 a. Due to the friction forces, theintake camshaft 23 receives a rightward force from theinner teeth 157 of thecover 154. These two forces move theintake camshaft 23 leftward. - Accordingly, the
ring gear 162 and theintake camshaft 23 are moved leftward and theintake camshaft 23 is maintained at the default position shown in FIG. 3. As shown in FIG. 10(A), the valve lift of theintake valves 21 is minimized and the valve overlap is zero. - In this manner, if electricity to the
solenoid 136 is stopped or if oil pressure is not supplied to theactuator 25 due to a malfunction, the valve overlap is set to zero as shown in FIG. 10(A). Accordingly, the engine speed is stabilized. - A seventeenth embodiment of the present invention will now be described with reference to FIGS. 35 and 36. The seventeenth embodiment is different from the sixteenth embodiment in that a
spring 200 is located in the firstoil pressure chamber 165. Thespring 200 urges theintake camshaft 23 rightward. The force of thespring 200 is greater than the resultant force urging theintake camshaft 23 leftward. Another difference is that an oil passage P21 from thefirst oil port 118 is connected to thesecond pressure chamber 166, and the oil passage P22 from theport 120 is connected to thefirst pressure chamber 165. - When the
solenoid 136 is de-excited, thering gear 162 and theintake camshaft 23 are moved in a direction of arrow A as illustrated in FIG. 35. As a result, the valve lift and the valve open angle of theintake valves 21 are increased. The cooperation of the helical outer and inner teeth shifts the rotational phase of theintake camshaft 23 to the most advanced position relative to thecover 154. Therefore, as shown in FIG. 10(B), the valve lift of theintake valves 21 is maximized and the opening timing of the intake valves Ci is most advanced. - When the
solenoid 136 is excited, thering gear 162 and theintake camshaft 23 are moved leftward as shown in FIG. 36. As a result, the valve lift and the valve open angle of theintake valve 21 are decreased. The cooperation of the helical outer and inner teeth shifts the rotational phase of theintake camshaft 23 to the most retarded position relative to thecover 154. Therefore, as shown in FIG. 10(A), the valve lift of theintake valve 21 is the smallest and the valve overlap is set to zero. - If the supply of electricity to the
solenoid 136 is stopped due to a malfunction, thespool 138 is maintained at the rightmost position in the casing. In this state, eachintake cam 28 contacts the associatedcam follower 21 a at the maximum profile section (default position). Therefore, the valve lift of theintake valves 21 is the maximum and the closing timing Ci of theintake valves 21 most advanced as shown in FIG. 10(B). - If oil pressure is not supplied to the
actuator 25 due to a malfunction, theintake camshaft 23 receives a leftward force from thecam follower 21 a and theinner teeth 157 of thecover 154 as in the sixteenth embodiment. Since the force of thespring 200 is greater than the resultant of the forces of thecam follower 21 a and theinner teeth 157, thering gear 162 and theintake camshaft 23 are moved rightward. As a result, theintake camshaft 23 is stabilized at the default position as illustrated in FIG. 35. As shown in FIG. 10(B), the valve lift of eachintake valve 21 is maximized and the closing timing is most advanced. - In this manner, if electricity to the
solenoid 136 is stopped or if oil pressure is not supplied to theactuator 25 due to a malfunction, theintake camshaft 23 is maintained at the default position. As illustrated in FIG. 10(B), the closing timing of theintake valves 21 is most advanced, which facilitates the starting of the engine. Therefore, theengine 11 can be quickly restarted after being stopped due to a malfunction. - It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.
- In the thirteenth to seventeenth embodiments, the
exhaust cams 27 may be three-dimensional and theactuator 25 may be attached to theexhaust camshaft 22. If these changes are applied to the thirteenth embodiment, the valve performance of theexhaust valves 20 is changed to that illustrated in FIGS. 13(A) and 13(B). In this manner, if electricity to thesolenoid 136 is stopped or if oil pressure is not supplied to theactuator 25 due to a malfunction, theexhaust camshaft 22 is maintained at the default position. At this time, theexhaust valves 20 have the performance illustrated in FIG. 13(A). The opening timing of theexhaust valves 20 is most retarded and there is no valve overlap, which stabilizes the engine speed. - If the
actuator 25 of the fourteenth embodiment is used for theexhaust camshaft 22, theexhaust valves 20 have the performance shown in FIG. 17(A). In this case, the valve overlap of theexhaust valve 20 is set to zero, which stabilizes the speed of theengine 11. - If the
actuator 25 of the fifteenth embodiment is used for theexhaust camshaft 22, theexhaust valves 20 have the performance shown in FIG. 17(B). In this case, the opening timing of theexhaust valves 20 is most retarded, which stabilizes the engine speed. - If the
actuator 25 of the sixteenth embodiment is used for theexhaust camshaft 22, theexhaust valves 20 have the performance shown in FIG. 17(A). In this case, the opening timing of theexhaust valves 20 is most retarded, which stabilizes the engine speed. - If the
actuator 25 of seventeenth embodiment is used for theexhaust camshaft 22, theexhaust valves 20 have the performance shown in FIG. 17(B). In this case, the valve overlap is set to zero, which stabilizes the speed of theengine 11. - The default position of the
intake camshaft 23 in case of a malfunction according to the fourteenth embodiment is opposite to that in to the fifteenth embodiment. One of these default positions is selected depending on the type of theengine 11 when designing theengine 11. Selecting one of the sixteenth and seventeenth embodiments is determined in the same manner. The valve performance of theexhaust camshaft 22 is also determined depending on the type of theengine 11. - In the thirteenth to sixteenth embodiments, the
spring 200 of the seventeenth embodiment may be employed. In this case, theintake camshaft 23 is quickly moved to the default position when there is oil pressure acting on the actuator. 25. - In the thirteenth to seventeenth embodiments, both exhaust and
intake camshaft actuator 25. - In the illustrated embodiments, a cam follower mechanism shown in FIGS. 38 and 39 may be employed. The mechanism includes a
cylindrical valve lifter 2019. Aguide projection 2019 b is formed in thecircumferential surface 2019 a of thevalve lifter 2019. The lifter bore 2019 is supported by and is axially moved relative to a lifter bore (not shown) formed in a cylinder head. Theguide projection 2019 b is fitted in a rectangular groove formed in the inner surface of the lifter bore along the axial direction of the lifter bore, which prevents thevalve lifter 2019 from rotating. - A
cam follower holder 2024 is integrally formed on theupper surface 2019 d of thevalve lifter 2019. Acam follower 21 a is pivotally fitted in aguide groove 2024 a formed in thecam follower holder 2024. Thevalve lifter 2019 is pressed against thecams valve lifter 2019. Thus, a slidingsurface 2025 a of thecam follower 21 a is pressed against acam surface 2011 a of thecam cam follower 21 a to pivot in accordance with thecam surface 2011 a. - As shown in FIGS.39(A) and 39(B), the
cam follower 21 a includes asemi-cylindrical column 2025 b and asemi-circular flange 2025 c, which is located at the axial center, or at the center in the direction of arrow F, of thecolumn 2025 b. The circular surface of thecolumn 2025 b forms a slidingsurface 2025 d, which is slidably fitted in theguide groove 2024 a of thecam follower holder 2024. - The
flange 2025 c is fitted in aflange groove 2024 b formed in the axial center of theguide groove 2024 a, which allows thrustsurfaces 2025 e of theflange 2025 c to contact thrust surfaces 2024 c of theflange groove 2024 b. The contact of the thrust surfaces 2025 e and 2024 c prevents thecam follower 21 a from moving in the direction of arrow F. - As shown in FIG. 40 (an enlarged drawing of FIG. 39(C)), the
cam follower 21 a is not a complete half cylinder. The slidingsurface 2025 a is offset from the radial center J of a circle defined by thecam follower 21 a by a distance E. If the offset E is relatively small, there will be no problem with the functioning of thecam follower 21 a compared to a case where there is no offset E. For example, if the offset is 0.3 mm, the resulting error in the valve lift will be 10 μm, which is very small, when thecam follower 21 a is inclined by fifteen degrees in accordance with thecam surface 2011 a. The error will be in the range of tolerance and will cause no problem. - When manufacturing the
cam follower 21 a, anintermediate product 2050 as shown in FIG. 41 is formed first. Then, theintermediate product 2050 is cut in half along a plane including the axis J shown in FIGS. 41 and 42. Thereafter, the cut surfaces are ground. As a result, twocam followers 21 a are manufactured. In this manner, twocam followers 21 a are easily manufactured. This manufacturing method has a high productivity and thus reduces the manufacturing cost. Further, compared to a method for manufacturing two complete semi-cylindrical cam followers, the illustrated method saves material. - The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.
Claims (19)
1. A valve train for an internal combustion engine, comprising:
a variable valve performance mechanism for continuously changing the valve open angle of at least one of an intake valve and an exhaust valve;
a controller for controlling the variable valve performance mechanism;
a sensor for detecting the running state of the engine; and
a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to decrease valve overlap.
2. The valve train according to claim 1 , wherein, when there is a malfunction in the engine, the controller sets the valve overlap to zero.
3. The valve train according to claim 1 , wherein the variable valve performance mechanism includes:
axially movable first and second camshafts rotatably supported on the engine;
a three-dimensional cam located at least on the first camshaft to selectively open and close a valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction; and
a first actuator for axially moving the first camshaft to change the valve open angle of the valve.
4. The valve train according to claim 3 , further comprising a crankshaft, wherein the variable valve performance mechanism includes a second actuator for continuously changing the rotational phase of at least one of the first and second camshafts relative to that of the crankshaft.
5. A valve train for an internal combustion engine, comprising:
a variable valve performance mechanism for continuously changing the valve open angle of an intake valve;
a controller for controlling the variable valve performance mechanism;
a sensor for detecting the running state of the engine; and
a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein, when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to advance the closing timing of the intake valve.
6. The valve train according to claim 5 , wherein the variable valve performance mechanism includes:
axially movable first and second camshafts rotatably supported on the engine;
a three-dimensional cam located at least on the first camshaft to selectively open and close an intake valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction; and
a first actuator for axially moving the first camshaft to change the valve open angle of the intake valve.
7. The valve train according to claim 6 , further comprising a crankshaft, wherein the variable valve performance mechanism includes a second actuator for continuously changing the rotational phase of at least one of the first and second camshafts relative to that of the crankshaft.
8. A valve train for an internal combustion engine, comprising:
a variable valve performance mechanism for continuously changing the valve open angle of an exhaust valve;
a controller for controlling the variable valve performance mechanism;
a sensor for detecting the running state of the engine; and
a judging device for judging whether there is a malfunction in the engine based on a detection signal of the sensor, wherein when the judging device judges that there is a malfunction in the engine, the controller actuates the variable valve performance mechanism to retard the opening timing of the exhaust valve.
9. The valve train according to claim 8 , wherein the variable valve performance mechanism includes:
axially movable exhaust and intake camshafts rotatably supported on the engine;
a three-dimensional cam located on the intake camshaft to selectively open and close an intake valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction; and
a first actuator for axially moving the intake camshaft to change the valve open angle of the intake valve.
10. The valve train according to claim 9 , further comprising a crankshaft, wherein the variable valve performance mechanism includes a second actuator for continuously changing the rotational phase of at least one of the exhaust and intake camshafts relative to that of the crankshaft.
11. A method for changing the valve performance of at least one of an exhaust valve and an intake valve by using a three-dimensional cam, the method comprising:
detecting the running state of an engine;
judging whether the engine is running normally based on the detected running state;
controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and
decreasing valve overlap when the engine is judged to be running abnormally.
12. A method for changing the valve performance of an intake valve by using a three-dimensional cam, the method comprising:
detecting the running state of an engine;
judging whether the engine is running normally based on the detected running state;
controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and
advancing the closing timing of the intake valve for performing a failsafe when the engine is judged to be running abnormally.
13. A method for changing the valve performance of an exhaust valve by using a three-dimensional cam, the method comprising:
detecting the running state of an engine;
judging whether the engine is running normally based on the detected running state;
controlling a valve open angle based on the detected running state when the engine is judged to be running normally; and
advancing the closing timing of the exhaust valve when the engine is judged to be running abnormally.
14. A valve train for an internal combustion engine, comprising:
an axially movable camshaft rotatably supported on the engine;
a three-dimensional cam located on the camshaft to selectively open and close a valve, wherein the profile of the three-dimensional cam continuously changes in the axial direction;
an actuator for axially moving the camshaft to change at least the valve lift of the valve lift and the valve timing of the valve;
a fluid pressure source for generating fluid pressure to actuate the actuator; and
a control valve for adjusting the position of the camshaft by controlling fluid pressure supplied to the actuator from the fluid pressure source;
wherein a default position toward which the camshaft is moved when the control of fluid pressure by the control valve is stopped is the same as a default position toward which the camshaft is moved when the fluid pressure source is not supplying fluid pressure to the actuator.
15. The valve train according to claim 14 , wherein the default position of the camshaft is a position at which the valve lift is the smallest.
16. The valve train according to claim 14 , wherein the actuator changes the valve timing as well as the valve lift, and wherein the default position of the camshaft is a position at which the valve timing is most retarded.
17. The valve train according to claim 16 , wherein the default position of the camshaft is a position at which the valve lift is maximized.
18. The valve train according to claim 14 , wherein the actuator changes the valve timing as well as the valve lift, wherein the default position of the camshaft is a position at which the valve timing is most advanced.
19. The valve train according to claim 14 , further comprising an urging member for urging the camshaft toward the default position when the fluid pressure source is not supplying fluid pressure to the actuator.
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US09/963,561 US6435149B2 (en) | 1998-10-06 | 2001-09-27 | Variable performance valve train having three-dimensional cam |
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JP10-284022 | 1998-10-06 | ||
JP28402298A JP2000110528A (en) | 1998-10-06 | 1998-10-06 | Variable valve system |
JP10301382A JP2000130196A (en) | 1998-10-22 | 1998-10-22 | Variable valve system |
JP10-301382 | 1998-10-22 | ||
US09/394,529 US6318313B1 (en) | 1998-10-06 | 1999-09-10 | Variable performance valve train having three-dimensional cam |
US09/963,561 US6435149B2 (en) | 1998-10-06 | 2001-09-27 | Variable performance valve train having three-dimensional cam |
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US09/394,529 Division US6318313B1 (en) | 1998-10-06 | 1999-09-10 | Variable performance valve train having three-dimensional cam |
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US20020017258A1 true US20020017258A1 (en) | 2002-02-14 |
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US09/394,529 Expired - Fee Related US6318313B1 (en) | 1998-10-06 | 1999-09-10 | Variable performance valve train having three-dimensional cam |
US09/963,561 Expired - Fee Related US6435149B2 (en) | 1998-10-06 | 2001-09-27 | Variable performance valve train having three-dimensional cam |
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IT1156204B (en) | 1982-10-12 | 1987-01-28 | Fiat Auto Spa | TAPPING SYSTEM FOR VERTICAL PROFILE CAMSHAFTS ENGINES |
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JP2855889B2 (en) | 1991-06-26 | 1999-02-10 | 日産自動車株式会社 | Control device for internal combustion engine |
JP3584476B2 (en) | 1993-05-11 | 2004-11-04 | トヨタ自動車株式会社 | Valve timing control device for internal combustion engine |
JPH07127407A (en) * | 1993-11-05 | 1995-05-16 | Toyota Motor Corp | Valve timing control device for internal combustion engine |
JP3228038B2 (en) | 1994-12-21 | 2001-11-12 | 日産自動車株式会社 | Variable valve train for internal combustion engine |
JP3309658B2 (en) * | 1995-08-25 | 2002-07-29 | トヨタ自動車株式会社 | Abnormality detection device for valve timing control device of internal combustion engine |
JP3354785B2 (en) | 1996-04-02 | 2002-12-09 | 日産自動車株式会社 | Intake and exhaust valve drive control device for internal combustion engine |
JP3812764B2 (en) | 1996-12-27 | 2006-08-23 | スズキ株式会社 | Engine control device |
-
1999
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-
2001
- 2001-09-27 US US09/963,561 patent/US6435149B2/en not_active Expired - Fee Related
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US20070034184A1 (en) * | 2003-03-21 | 2007-02-15 | Stefan Dengler | Valve drive of an internal combustion engine comprising a cylinder head |
US7409938B2 (en) * | 2003-03-21 | 2008-08-12 | Audi Ag | Valve drive of an internal combustion engine comprising a cylinder head |
EP1703091A3 (en) * | 2005-03-15 | 2009-06-17 | Nissan Motor Co., Ltd. | Internal combustion engine |
CN108571984A (en) * | 2017-03-07 | 2018-09-25 | 通用汽车环球科技运作有限责任公司 | Sliding cam axis cylinder position senses |
Also Published As
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US6318313B1 (en) | 2001-11-20 |
US6435149B2 (en) | 2002-08-20 |
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