US20090235885A1 - Variable valve actuating apparatus - Google Patents
Variable valve actuating apparatus Download PDFInfo
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- US20090235885A1 US20090235885A1 US12/399,243 US39924309A US2009235885A1 US 20090235885 A1 US20090235885 A1 US 20090235885A1 US 39924309 A US39924309 A US 39924309A US 2009235885 A1 US2009235885 A1 US 2009235885A1
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- cam
- rocker arm
- variable valve
- control
- valve actuating
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Classifications
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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
- 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
- F01L13/0063—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 by modification of cam contact point by displacing an intermediate lever or wedge-shaped intermediate element, e.g. Tourtelot
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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
- F01L1/12—Transmitting gear between valve drive and valve
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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
- F01L1/12—Transmitting gear between valve drive and valve
- F01L1/18—Rocking arms or levers
- F01L1/185—Overhead end-pivot rocking arms
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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
- F01L1/20—Adjusting or compensating clearance
- F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
- F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
- F01L1/2405—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically by means of a hydraulic adjusting device located between the cylinder head and rocker arm
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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
- 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
- F01L13/0063—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 by modification of cam contact point by displacing an intermediate lever or wedge-shaped intermediate element, e.g. Tourtelot
- F01L2013/0073—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 by modification of cam contact point by displacing an intermediate lever or wedge-shaped intermediate element, e.g. Tourtelot with an oscillating cam acting on the valve of the "Delphi" type
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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
- F01L2305/00—Valve arrangements comprising rollers
-
- 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
- F01L2820/00—Details on specific features characterising valve gear arrangements
- F01L2820/03—Auxiliary actuators
- F01L2820/032—Electric motors
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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
- F02D13/0223—Variable control of the intake valves only
- F02D13/0226—Variable control of the intake valves only changing valve lift or valve lift and timing
- F02D13/023—Variable control of the intake valves only 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
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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
- F02D13/0261—Controlling the valve overlap
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/65—Constructional details of EGR valves
- F02M26/66—Lift valves, e.g. poppet valves
- F02M26/69—Lift valves, e.g. poppet valves having two or more valve-closing members
Definitions
- the present invention relates generally to internal combustion engines, and particularly to variable valve actuating apparatuses or systems for varying at least a lift of an engine valve, such as an intake valve or exhaust valve, of an internal combustion engine.
- Japanese Patent Application Publication No. 2002-38913 corresponding to U.S. Pat. No. 6,499,454 discloses a variable valve actuating system for varying at least a lift of an intake valve set of an internal combustion engine.
- This variable valve actuating system includes: a drive shaft rotated by a crankshaft; a drive cam fixedly mounted to an outer radial periphery of the drive shaft; a transmitting mechanism for converting rotary motion of the drive cam to swinging motion of a swing cam, the transmitting mechanism including a rocker arm, a link arm and a link rod; and the swing cam that slides on a top surface of a valve lifter for opening and closing an intake valve.
- the link arm links the drive cam with the rocker arm.
- the link rod links the rocker arm with the swing cam.
- the rocker arm is linked at one end portion with one end of the link arm and one end of the link rod, and has a relatively large hole at another end portion in which a control cam is rotatably supported.
- the control cam is fixed and eccentric with respect to a control shaft.
- the variable valve actuating system is configured to control the position of the control cam according to an engine operating state by rotating the control shaft by an actuator. Movement of the control cam causes a change in the range of motion of the swing cam, and thereby causes changes in the lift and operating angle of the intake valve.
- variable valve actuating system For assembling the variable valve actuating system described above and disclosed in Japanese Patent Application Publication No. 2002-38913, it is necessary to attach the control cam to the rocker arm by inserting the control cam into the hole formed in the rocker arm in the longitudinal direction of the control shaft. This imposes some requirements on the entire assembling process, for example, for avoiding interference between components.
- variable valve actuating apparatus or system which can be assembled more easily.
- a variable valve actuating apparatus for an internal combustion engine comprises: a drive cam adapted to be rotated by the internal combustion engine; a control shaft supported for rotation about a rotation axis; a control cam coupled to the control shaft, wherein the control cam is eccentric with respect to the rotation axis of the control shaft; a rocker arm linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam, the rocker arm including a recess slidably engaged with an outer radial periphery of the control cam; and a swing cam linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine.
- variable valve actuating apparatus may further comprise: a device for maintaining contact between the recess of the rocker arm and the outer radial periphery of the control cam; and a drive shaft adapted to be rotated by the internal combustion engine, wherein: the drive cam is fixedly mounted to an outer radial periphery of the drive shaft; change of a rotational position of the control shaft causes a movement of the control cam with respect to the drive shaft, and causes at least a change in a lift of the engine valve; and the rotational position of the control shaft is controlled according to an operating state of the internal combustion engine.
- variable valve actuating apparatus may further comprise: a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft; and an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein the recess of the rocker arm has an entrance directed opposite to a portion of the rocker arm which is linked with the swing cam.
- variable valve actuating apparatus may further comprise: a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft; and an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the engine valve is open, the recess of the rocker arm is pressed on the outer radial periphery of the control cam by an elastic force of a valve spring provided for the engine valve.
- FIG. 1 is a front view of a variable valve actuating system according to a first embodiment of the present invention in a position for a minimum lift set point.
- FIG. 2 is a front view of the variable valve actuating system of FIG. 1 in the position for the minimum lift set point at a moment when an associated intake valve is opened.
- FIG. 3 is a front view of the variable valve actuating system of FIG. 1 in a position for a maximum lift set point at a moment when the intake valve is closed.
- FIG. 4 is a front view of the variable valve actuating system of FIG. 1 in the position for the maximum lift set point at a moment when the intake valve is opened.
- FIG. 5 is a plan view of the variable valve actuating system of FIG. 1 .
- FIG. 6 is a side view of the variable valve actuating system of FIG. 1 .
- FIG. 7 is a graphic diagram showing lift curves of the intake valve which are achieved by the variable valve actuating system of FIG. 1 .
- FIG. 8 is a front view of a variable valve actuating system according to a second embodiment of the present invention.
- FIG. 9 is a plan view of the variable valve actuating system of FIG. 8 .
- FIG. 10 is a side view of the variable valve actuating system of FIG. 8 .
- FIG. 11 is a graphic diagram showing lift curves of intake valves which are achieved by the variable valve actuating system of FIG. 8 .
- FIG. 12 is an enlarged view of a structure in which a rocker arm engages with a control cam in a variable valve actuating system according to a third embodiment of the present invention.
- FIG. 13 is a plan view of the variable valve actuating system according to the third embodiment.
- FIG. 14 is a side view of the variable valve actuating system according to the third embodiment.
- FIG. 15 is a front view of a variable valve actuating system according to a fourth embodiment of the present invention.
- FIG. 16 is a front view of the variable valve actuating system of FIG. 15 in a position for a minimum lift set point at a moment when an associated intake valve is opened.
- FIG. 17 is a front view of the variable valve actuating system of FIG. 15 in a position for a maximum lift set point at a moment when the intake valve is closed.
- FIG. 18 is a front view of the variable valve actuating system of FIG. 15 in the position for the maximum lift set point at a moment when the intake valve is opened.
- FIG. 19 is a plan view of the variable valve actuating system of FIG. 15 .
- FIG. 20 is a side view of the variable valve actuating system of FIG. 15 .
- FIG. 21 is a front view of a variable valve actuating system according to a fifth embodiment of the present invention.
- FIG. 22 is a front view of the variable valve actuating system of FIG. 21 in a position for a minimum lift set point at a moment when an associated intake valve is opened.
- FIG. 23 is a front view of the variable valve actuating system of FIG. 21 in a position for a maximum lift set point at a moment when the intake valve is closed.
- FIG. 24 is a front view of the variable valve actuating system of FIG. 21 in the position for the maximum lift set point at a moment when the intake valve is opened.
- FIG. 25 is a plan view of the variable valve actuating system of FIG. 21 .
- FIG. 26 is a side view of the variable valve actuating system of FIG. 21 .
- FIG. 27 is a plan view of a variable valve actuating system according to a sixth embodiment of the present invention.
- FIG. 28 is a front view of the variable valve actuating system of FIG. 27 .
- FIG. 29 is a front view of a variable valve actuating system according to a seventh embodiment of the present invention.
- FIGS. 1 to 6 show a variable valve actuating apparatus or system according to a first embodiment of the present invention for an engine valve set of an internal combustion engine which is an intake valve set in this example.
- the variable valve actuating system according to the first embodiment generally includes an intake valve set which includes two intake valves 3 , 3 per cylinder, a drive shaft 4 , a drive cam 5 per cylinder, a swing arm set which includes two swing arms 6 , 6 per cylinder, a swing cam set which includes two swing cams 7 , 7 per cylinder, a transmitting mechanism 8 per cylinder, and a control mechanism 9 .
- Each intake valve 3 is slidably mounted in a valve guide not shown in a cylinder head 1 , for opening and closing an intake port formed in cylinder head 1 .
- Drive shaft 4 is hollow, having a longitudinal axis extending in a longitudinal direction of the engine.
- Drive cam 5 is fixedly mounted to drive shaft 4 .
- Each swing arm 6 is arranged close to an upper end of intake valve 3 .
- Each swing cam 7 opens and closes intake valve 3 by moving the swing arm 6 .
- Transmitting mechanism 8 which is of a multiple link type, links drive cam 5 with swing cams 7 , 7 , and converts rotary motion of drive cam 5 into swinging motion of swing cams 7 , 7 .
- control mechanism 9 varies the lift of intake valves 3 , 3 by moving a fulcrum of a rocker arm 15 of transmitting mechanism 8 .
- Each intake valve 3 is provided with a valve spring 10 , and biased by valve spring 10 in a direction to close the intake port, as shown in FIG. 6 .
- Each valve spring 10 is disposed between the bottom of a substantially cylindrical bore formed or provided in an upper end portion of cylinder head 1 , and a spring retainer provided in an upper end portion of a valve stem of intake valve 3 .
- Drive shaft 4 is rotatably mounted in cylinder head 1 .
- Drive shaft 4 includes longitudinal ends rotatably supported on bearings provided in an upper portion of cylinder head 1 .
- Drive shaft 4 is adapted to be rotated by a crankshaft of the engine.
- drive shaft 4 receives a torque from the crankshaft through a rotation transmitting mechanism which is, for example, a chain drive mechanism including a timing sprocket provided at one longitudinal end of drive shaft 4 , and a timing chain wounded around the timing sprocket.
- a rotation transmitting mechanism which is, for example, a chain drive mechanism including a timing sprocket provided at one longitudinal end of drive shaft 4 , and a timing chain wounded around the timing sprocket.
- Drive cam 5 is arranged between swing cams 7 , 7 in the longitudinal direction of drive shaft 4 , shaped like a circular disc, and formed with a hole extending in a longitudinal direction of drive cam 5 (in the longitudinal direction of drive shaft 4 ), as shown in FIGS. 1 and 6 .
- Drive cam 5 is coupled to or fixedly mounted on an outer radial periphery of drive shaft 4 for rotation therewith, where drive shaft 4 extends through the hole of drive cam 5 .
- Drive cam 5 is thus adapted to be rotated by the crankshaft of the engine.
- the hole is positioned in drive cam 5 so that drive cam 5 has an eccentric circular cam profile.
- the central axis Y of drive cam 5 is offset in a predetermined radial direction from the central axis X of drive shaft 4 by a predetermined distance.
- Each swing arm 6 extends in a lateral direction of drive shaft 4 , and has a first end portion 6 a which includes a slightly recessed lower surface in contact with the stem end of intake valve 3 , and a second end portion 6 b which includes a semispherically recessed lower surface in contact with and slidably supported by the tip of a hydraulic lash adjuster 11 retained in a retainer hole 2 formed in cylinder head 1 .
- Swing arm 6 is thus arranged to swing about the tip of hydraulic lash adjuster 11 .
- Swing arm 6 is provided with a needle roller 12 substantially at a center of swing arm 6 . Needle roller 12 is rotatably supported with respect to swing arm 6 , and is in rolling contact with swing cam 7 , serving to reduce the friction between swing cam 7 and swing arm 6 .
- Hydraulic lash adjuster 11 has a general structure, including a body 13 a, and a plunger 13 b.
- Body 13 a is cylindrically shaped with an open top and a closed bottom, and inserted and fixedly mounted in retainer hole 2 .
- Plunger 13 b is mounted in body 13 a for sliding through the top opening of body 13 a.
- Plunger 13 b has a semispherical upper end in sliding contact with the second end portion 6 b of swing arm 6 .
- Hydraulic fluid is supplied from a reservoir through a check valve to a high pressure chamber defined between the inner bottom of body 13 a and the outer bottom of plunger 13 b.
- Hydraulic lash adjuster 11 serves to constantly maintain the clearance between the tip of plunger 13 b and the second end portion 6 b of swing arm 6 (and the clearance between swing cam 7 and needle roller 12 ) substantially equal to zero by suitable supply of hydraulic fluid.
- Each swing cam 7 includes a fitting recess 7 a which is generally U-shaped, and fit on the outer radial periphery of drive shaft 4 , so that swing cam 7 is swingably supported with respect to drive shaft 4 , i.e. swing cam 7 is supported for swinging about the central axis X of drive shaft 4 with the fitting recess 7 a in sliding contact with the outer radial periphery of drive shaft 4 .
- Swing cam 7 has a cam surface 7 b at the lower side which is adapted to be in contact with needle roller 12 of swing arm 6 .
- the cam surface 7 b of swing cam 7 includes a base circle surface region closer to drive shaft 4 , a ramp surface region extending like a circular arc from the base circle surface region toward a cam nose 7 c, and a lift surface region extending from the ramp surface region toward an apex of the cam nose which defines a possible maximum lift set point of intake valve 3 .
- the cam surface 7 b abuts on the top surface of a corresponding portion of the outer radial periphery of needle roller 12 of swing arm 6 , and the contact point of the cam surface 7 b shifts among the base circle surface region, ramp surface region and lift surface region in dependence on the swing position of swing cam 7 .
- Swing cam 7 is arranged so that when swing cam 7 swings in the same direction as drive shaft 4 (clockwise direction as viewed in FIG. 1 ), the contact point of cam surface 7 b shifts toward the lift surface region for increasing the opening of intake valve 3 .
- the cam nose 7 c of swing cam 7 is formed with a pin hole 7 e extending in the longitudinal direction of drive shaft 4 .
- a connecting pin 20 is inserted through pin hole 7 e for connecting swing cam 7 and a link rod 17 .
- the structure that swing cam 7 is directly mounted to drive shaft 4 eliminates the necessity of an additional support shaft for supporting swing cam 7 . This is effective for cost reduction and downsizing of the variable valve actuating system.
- Swing cam 7 is linked with rocker arm 15 , and arranged to swing in response to swinging motion of rocker arm 15 for opening and closing the intake valve 3 .
- Transmitting mechanism 8 includes a rocker arm 15 , a link arm 16 , a link rod set which includes two link rods 17 , 17 per cylinder, as shown in FIG. 5 .
- Rocker arm 15 is arranged above drive shaft 4 , extending generally in the lateral direction of the engine.
- Rocker arm 15 is linked with drive cam 5 , and arranged to swing about control cam 26 in response to rotary motion of drive cam 5 , as detailed below.
- Link arm 16 links rocker arm 15 with drive cam 5 .
- Each link rod 17 links rocker arm 15 with the cam nose 7 c of the respective swing cam 7 .
- Rocker arm 15 includes a first longitudinal end portion defining a recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction of rocker arm 15 , wherein the second longitudinal end portion is linked with swing cam 7 for transmitting swinging motion of rocker arm 15 to swing cam 7 .
- rocker arm 15 is generally A-shaped in a lateral direction of drive shaft 4 as shown in FIG. 6 , and includes a first end portion 15 a, and a longitudinal end portion set which is Y-shaped as viewed in FIG. 5 and includes two second end portions 15 b, 15 b.
- the first end portion 15 a of rocker arm 15 includes a recess 21 which is slidably engaged with an outer radial periphery of a control cam 26 for allowing rotation of control cam 26 .
- the recess 21 of rocker arm 15 and the outer radial periphery of control cam 26 have shapes fit on each other.
- Each second 5 end portion 15 b of rocker arm 15 includes a pin hole 15 c extending in the longitudinal direction of drive shaft 4 .
- a connecting pin 22 extends through the pin holes 15 c, 15 c of the second end portions 15 b, 15 b which are coaxially positioned.
- the recess 21 of rocker arm 15 has an inner cylindrical surface 21 b which appears as a generally semicircular arc fit on the outer radial periphery of control cam 26 as viewed in the longitudinal direction of drive shaft 4 in FIG. 1 .
- Recess 21 has an inner diameter that is slightly larger than the outer diameter of control cam 26 .
- Recess 21 includes an entrance 21 a directed downward as viewed in FIG. 1 , i.e. directed toward intake valve 3 or toward hydraulic lash adjuster 11 .
- the first end portion 15 a of rocker arm 15 is thus slidably supported with respect to control cam 26 for rotating or swinging about control cam 26 so that the second end portions 15 b, 15 b can move upward and downward.
- the first end portion 15 a of rocker arm 15 is biased by a compression coil spring 24 toward control cam 26 or toward drive shaft 4 .
- Compression coil spring 24 includes a first end fixed to a rocker cover 14 , and a second end in pressing contact with the outer periphery of first end portion 15 a.
- Compression coil spring 24 serves as a device for mechanically pressing the recess 21 of rocker arm 15 on the outer radial periphery of control cam 26 , constantly maintaining contact between the inner cylindrical surface 21 b of the recess 21 and the outer radial periphery of control cam 26 , and preventing the recess 21 of rocker arm 15 from escaping from control cam 26 .
- Link arm 16 includes a circular portion 16 a, and a projecting portion 16 b.
- Circular portion 16 a has a relatively large outer diameter, and has a fitting hole 16 c at the center.
- the fitting hole 16 c is slidably fit on the outer radial periphery of drive cam 5 for allowing relative rotation of drive cam 5 .
- Projecting portion 16 b is projecting from circular portion 16 a in a radial direction of circular portion 16 a, and disposed between the second end portions 15 b, 15 b of rocker arm 15 as viewed the lateral direction of drive shaft 4 in FIG. 5 .
- Projecting portion 16 b includes a pin hole 16 d extending in the longitudinal direction of drive shaft 4 between both opposite surfaces, through which connecting pin 22 extends. Projecting portion 16 b is thus rotatably supported with respect to second end portions 15 b, 15 b through connecting pin 22 .
- Each link rod 17 is composed of a single piece made by press forming and folding.
- Link rod 17 has a U-shaped cross section as viewed in FIG. 5 , which is advantageous in compactness.
- Link rods 17 , 17 are arranged outside of the second end portions 15 b, 15 b of rocker arm 15 in the longitudinal direction of drive shaft 4 as viewed in FIG. 5 .
- Link rod 17 has a first end portion 17 a including a pin hole through which connecting pin 22 extends, and a second end portion 17 b including a pin hole through which connecting pin 20 extends.
- Link rod 17 is rotatably connected at the first end portion 17 a to the second end portion 15 b of rocker arm 15 through connecting pin 22 , and rotatably connected at the second end portion 17 b to the cam nose 7 c of swing cam 7 through connecting pin 20 .
- connecting pin 22 pivotally connects all of the projecting portion 16 b of link arm 16 , the first end portions 17 a of link rods 17 , and the second end portions 15 b, 15 b of rocker arm 15 .
- Connecting pin 22 is provided with snap rings 22 a, 22 a at both longitudinal ends for preventing the connected members from escaping from the connecting pin 22 .
- each connecting pin 20 is swaged at both longitudinal ends so as to prevent the link rod 17 and swing cam 7 from escaping from connecting pin 20 .
- Control mechanism 9 includes a control shaft 25 , control cam 26 , and an actuator 41 .
- Control shaft 25 is arranged above drive shaft 4 , extending in parallel to drive shaft 4 .
- Control shaft 25 is supported for rotation about a rotation axis which is a central axis P of control shaft 25 .
- Control cam 26 is coupled or fixedly mounted to control shaft 25 for serving as a fulcrum for rocking motion of rocker arm 15 .
- the rotational position of control shaft 25 is regulated or controlled by actuator 41 .
- Control shaft 25 includes a pair of shaft parts on both sides of the center of the cylinder in the longitudinal direction of control shaft 25 as shown in FIG. 5 .
- the ends of the shaft parts confronting each other are provided with flanges 25 a, 25 a between which the first end portion 15 a of rocker arm 15 is slidably supported.
- the flanges 25 a, 25 a of control shaft 25 serves to prevent the first end portion 15 a from inclining when rocker arm 15 is rocking.
- Control cam 26 is formed in a cylindrical shape having a smaller outer diameter than control shaft 25 .
- Control cam 26 is supported by and arranged between the flanges 25 a, 25 a of control shaft 25 as viewed in FIG. 5 .
- Control cam 26 is eccentric with respect to the central axis P of control shaft 25 .
- control cam 26 has a central axis Q which is offset from the central axis P of control shaft 25 by an eccentric distance a, where the eccentric distance a is substantially as large as the diameter of control shaft 25 , as shown in FIG. 1 .
- control cam 26 has an outer portion 26 a projecting beyond the outer radial periphery of control shaft 25 , where the outer portion 26 a is substantially half of control cam 26 , as viewed in FIG. 1 .
- Control shaft 25 and control cam 26 are thus formed as a unit shaped like a crank.
- Actuator 41 in control mechanism 9 includes an electric motor, and a speed reducer, such as a ball screw mechanism.
- the electric motor is fixed to a rear end wall of cylinder head 1 .
- the speed reducer is arranged to transmit an output torque of the electric motor to control shaft 25 .
- the electric motor is a linear DC motor which is driven according to a control signal outputted from an electric controller not shown.
- the controller measures or calculates an engine operating state with reference to feedback signals from sensors, and controls the electric motor according to the engine operating state.
- the sensors include a crank angle sensor for measuring engine speed, an airflow meter for measuring intake air quantity, an engine coolant temperature sensor for measuring engine coolant temperature, and a potentiometer for measuring the rotational position of control shaft 25 .
- control shaft 25 is controlled according to the engine operating state, and change of the rotational position of control shaft 25 causes a movement of control cam 26 with respect to drive shaft 4 , and causes at least a change in the lift of intake valve 3 , as detailed below.
- control shaft 25 rotates in a clockwise direction by a corresponding angle as viewed in FIG. 1 .
- the rotation of control shaft 25 causes the central axis Q of control cam 26 to revolve about the central axis P of control shaft 25 to a position below and slightly on the left of the central axis P so that the outer portion 26 a of control cam 26 moves away from drive shaft 4 .
- control shaft 25 rotates control cam 26 in the counterclockwise direction as viewed in FIG. 1 .
- the rotation of control shaft 25 causes the central axis Q of control cam 26 to revolve about the central axis P of control shaft 25 to a position below and on the right of the central axis P of control shaft 25 as shown in FIGS. 3 and 4 so that the outer portion 26 a of control cam 26 moves toward drive shaft 4 .
- the lift of the intake valve 3 is set to the minimum lift set point L.
- the central axis Q of control cam 26 as a pivot for swinging motion of the first end portion 15 a of rocker arm 15 moves to the position shown in FIG. 1 so as to move the link arm 16 in the counterclockwise direction about drive cam 5 with respect to the position for the maximum lift set point L 1 .
- This advances the lift peak phase so that the intake valve opening timing IVO advances little at about top dead center, and the intake valve closing timing IVC advances significantly, with respect to the condition of the maximum lift set point L 1 , as shown in FIG. 7 .
- the intake valve opening timing IVO closer to top dead center for the condition of the minimum lift set point L is effective for allowing a suitable control of valve overlap. This makes it possible to reduce an increase of residual burned gas, and suppress adverse effects on fuel efficiency, at the minimum lift set point L.
- variable valve actuating system can control the lift and operating angle of the engine valve set continuously between the minimum lift set point L and the maximum lift set point L 1 by actuating the control shaft 25 according to engine operating state.
- the crank structure of control shaft 25 and control cam 26 allows a large eccentric distance a between the central axis P of control shaft 25 and the central axis Q of control cam 26 . This allows a large range of movement of the central axis Q as a fulcrum of rotation of rocker arm 15 , and a large amount of change of the lift, operating angle, and peak lift phase, of intake valve 3 .
- the crank structure of control shaft 25 and control cam 26 is also effective for reducing the outer diameter of control shaft 25 . This leads to downsizing of parts such as bearings and thereby downsizing of the entire variable valve actuating system.
- the simple structure of the first end portion 15 a of rocker arm 15 also leads to downsizing of the entire variable valve actuating system.
- the structure that the first end portion 15 a of rocker arm 15 is sandwiched and slidably held between the flanges 25 a, 25 a of control shaft 25 , is effective for preventing the first end portion 15 a from inclining when rocker arm 15 is rocking, and thereby, is effective for preventing abnormal wear between control cam 26 and first end portion 15 a.
- the structure of transmitting mechanism 8 where the elastic force of valve spring 10 and the driving force of drive cam 5 are well balanced is effective for preventing stress concentration and occurrence of deformation.
- compression coil spring 24 is effective for keeping constant contact between the recess 21 of rocker arm 15 and the outer radial periphery of control cam 26 , and thereby efficiently transmitting the movement of control cam 26 to rocker arm 15 .
- control cam 26 is located at the first end portion 15 a of rocker arm 15 is effective for reducing the contact load between recess 21 and control cam 26 because the elastic force of valve spring 10 is absorbed by drive cam 5 .
- FIGS. 8 to 10 show a variable valve actuating system according to a second embodiment of the present invention.
- the structures of rocker arm 15 and swing cams 7 , 7 are modified, and two drive cams 5 , 5 and two link arms 16 , 16 are provided for swing cams 7 , 7 , with respect to the first embodiment.
- Rocker arm 15 is shaped so that the entrance 21 a of recess 21 is directed at an angle ⁇ 1 of about 30 degrees downward with reference to a line connecting the central axis Q of control cam 26 and the central axis O of connecting pin 22 , and the second end portion 15 b is single, not branched.
- the second end portion 15 b has a tip having a small width formed with a pin hole 15 c through which connecting pin 22 extends.
- the second end portion 15 b is rotatably connected substantially to the center of connecting pin 22 in the longitudinal direction of connecting pin 22 .
- Compression coil spring 24 for biasing the first end portion 15 a of rocker arm 15 is located at the position shown in FIG. 8 along the direction toward the central axis Q of control cam 26 so that the inner cylindrical surface 21 b of the recess 21 is constantly pressed to the outer radial periphery of control cam 26 .
- Each drive cam 5 is fixed to or integrated with drive shaft 4 , and is arranged at an interval from the other drive cam 5 , as shown in FIG. 10 .
- Each link arm 16 includes a circular portion 16 a, and a projecting portion 16 b, as in the first embodiment.
- the circular portion 16 a includes the fitting hole 16 c in which drive cam 5 is rotatably supported.
- the projecting portion 16 b is rotatably supported by connecting pin 22 extending through the pin hole 16 d.
- Projecting portions 16 b, 16 b are arranged on both sides of the second end portion 15 b of rocker arm 15 in the longitudinal direction of drive shaft 4 as shown in FIG. 9 .
- the cam surfaces 7 b, 7 b of swing cams 7 , 7 have different profiles as shown in FIG. 8 .
- the cam surface 7 b of one swing cam 7 is concaved or offset with respect to the cam surface 7 b of the other swing cam 7 .
- the drive shaft 4 and control shaft 25 are rotatably supported on bearings which are arranged between transmitting mechanisms 8 , 8 in the longitudinal direction.
- the structure of recess 21 that entrance 21 a is directed downward by the angle of about 30 degrees with respect to the reference line is effective for providing a tight contact between the rocker arm 15 and control cam 26 , and allowing the rocker arm 15 to follow the eccentric movement of control cam 26 well. Even when the difference between the profiles of the cam surfaces 7 b, 7 b of swing cams 7 , 7 causes the rocker arm 15 via connecting pin 22 to incline, the structure of recess 21 is also effective for resisting the moment of inclination of rocker arm 15 and connecting pin 22 . This enables the variable valve actuating system to precisely control the lift and operating angle of intake valve 3 .
- the structure that two drive cams 5 , 5 are arranged close to each other in the longitudinal direction of drive shaft 4 per cylinder, is effective for preventing the connecting pin 22 and rocker arm 15 from inclining, even when drive cams 5 , 5 are shaped to have different cam profiles so as to differentiate the lifts of intake valves 3 , 3 from each other.
- cam surfaces 7 b, 7 b of swing cams 7 , 7 have different profiles, is effective for slightly differentiating the lifts of intake valves 3 , 3 from each other under the condition of the minimum lift set point L as shown in FIG. 11 , promoting in cylinder intake swirl, improving the combustion process, stabilizing the engine rotation, and enhancing the fuel efficiency.
- FIGS. 12 to 14 show a variable valve actuating system according to a third embodiment of the present invention.
- This variable valve actuating system is presented by modifying the first embodiment so that two control cams 26 , 26 are provided per cylinder, and accordingly, rocker arm 15 has two branched first end portions 15 a, 15 a.
- Control shaft 25 and drive shaft 4 are rotatably supported by bearings not shown.
- Each first end portion 15 a of rocker arm 15 has a C-shaped recess 21 , where the entrance 21 a of recess 21 has a narrower entrance width Z than the outer diameter of control cam 26 , as shown in FIG. 12 .
- each control cam 26 has flat surfaces 26 b, 26 b at the outer radial periphery which are parallel to each other, as shown in FIG. 12 .
- the distance between flat surfaces 26 b, 26 b is smaller than the outer diameter of control cam 26 , and slightly smaller than the entrance width Z of recess 21 .
- the flat surfaces 26 b, 26 b of one control cam 26 is located in the same circumferential position as those of the other control cam 26 .
- control cam 26 partly has a thickness in a radial direction of control cam 26 which is narrower than the entrance 21 a of recess 21 of rocker arm 15 , and control cam 26 is engaged with rocker arm 15 in such a rotational position that control cam 26 is prevented from escaping through the entrance 21 a from the recess 21 of rocker arm 15 .
- Attaching the rocker arm 15 to control cams 26 , 26 is implemented by allowing the edges of entrance 21 a of each recess 21 to be in contact with the edges of the flat surfaces 26 b, 26 b of control cam 26 , then sliding the rocker arm 15 in the radial direction of control cams 26 , 26 so as to fit the inner cylindrical surface 21 b of each recess 21 to a portion of the outer radial periphery of control cam 26 between the flat surfaces 26 b, 26 b, finally rotating the rocker arm 15 about the control cams 26 , 26 to a predetermined rotational position.
- Each recess 21 is thus engaged with the circular outer radial periphery of control cam 26 , and prevented from escaping from control cam 26 .
- rocker arm 15 is rotatably supported by control cams 26 , 26 which are arranged at an interval, is effective for preventing the rocker arm 15 from inclining, even when the cam surfaces 7 b, 7 b of swing cams 7 , 7 have different profiles.
- FIGS. 15 to 20 show a variable valve actuating system according to a fourth embodiment of the present invention.
- two transmitting mechanisms 8 , 8 are provided for intake valves 3 , 3 independently of each other.
- two drive cams 5 , 5 are provided per intake valve 3 , and the total four drive cams 5 are attached to drive shaft 4 at predetermined intervals.
- link arm 16 is provided per drive cam 5 .
- Control shaft 25 are provided with two control cams 26 , 26 for two intake valves 3 , 3 .
- Control shaft 25 has flat surfaces 25 b, 25 b at the outer radial periphery each of which is located outside of control cam 26 in the longitudinal direction.
- Each control cam 26 is linked with the respective one of two rocker arms 15 , 15 .
- each first end portion 15 a has a C-shaped recess 21 , where the entrance 21 a of recess 21 has a narrower entrance width Z than the outer diameter of control cam 26 .
- each control cam 26 has flat surfaces 26 b, 26 b at the outer radial periphery which are parallel to each other.
- the distance between flat surfaces 26 b, 26 b is smaller than the outer diameter of control cam 26 , and slightly smaller than the entrance width Z of the recess 21 of rocker arm 15 .
- the entrance 21 a of each recess 21 is directed substantially in the longitudinal direction of rocker arm 15 , or in the longitudinal direction of the first end portion 15 a of rocker arm 15 toward the longitudinal end of rocker arm 15 , opposite to connecting pin 22 which is linked with swing cam 7 and is related to actuation of intake valve 3 .
- Control shaft 25 and drive shaft 4 are supported by a bearing 33 .
- Each rocker arm 15 has a pin hole 15 c at the second end portion 15 b through which connecting pin 22 passes. Rocker arm 15 is rotatably linked with the first end portion 17 a of link rod 17 through the connecting pin 22 . Each rocker arm 15 also has a pin hole 15 d substantially at the center of rocker arm 15 in the longitudinal direction through which a respective connecting pin 28 passes. Rocker arm 15 is rotatably linked with the projecting portions 16 b, 16 b of link arms 16 , 16 through the connecting pin 28 .
- One pair of link arms 16 , 16 are arranged on both sides of one combination of rocker arm 15 and link rod 17 , and the outer pair of link arms 16 , 16 are arranged on both sides of the other combination of rocker arm 15 and link rod 17 , in the longitudinal direction of drive shaft 4 , as shown in FIGS. 19 and 20 .
- variable valve actuating system operates as follows. For example, when the engine is at low speed and low load, control shaft 25 is controlled to rotate to the position shown in FIGS. 15 and 16 as in the first embodiment, so that the lift of intake valve 3 is set at the minimum lift set point L. When the engine shifts to a predetermined high speed region, control shaft 25 is controlled to rotate in the counterclockwise direction as shown in FIGS. 17 and 18 , so that the lift of intake valve 3 is set at the maximum lift set point L 1 .
- Attaching the rocker arm 15 to control cam 26 is implemented as in the third embodiment by allowing the edges of entrance 21 a of recess 21 to be in contact with the edges of the flat surfaces 26 b, 26 b of control cam 26 , then sliding the rocker arm 15 in the radial direction of control cam 26 so as to fit the inner cylindrical surface 21 b of recess 21 to a portion of the outer radial periphery of control cam 26 between the flat surfaces 26 b, 26 b, finally rotating the rocker arm 15 about the control cam 26 to a predetermined rotational position.
- Each recess 21 is thus engaged with the circular outer radial periphery of control cam 26 , and prevented from escaping from control cam 26 .
- the structure that the entrance 21 a of recess 21 is directed opposite to connecting pin 22 is effective for maintaining tight contact between rocker arm 15 and control cam 26 without compression coil spring 24 , because the force from valve spring 10 is transmitted to act the rocker arm 15 in the direction from the inner cylindrical surface 21 b of recess 21 toward the outer radial periphery of control cam 26 .
- each intake valve 3 is provided with the respective drive cam 5 and rocker arm 15 is effective for allowing to adjust the lift of intake valve 3 independently of the other intake valve 3 by adjusting the profiles of drive cam 5 and control cam 26 independently of the other drive cam 5 and control cam 26 .
- the structure that the projecting portion 16 b of link arm 16 is connected to substantially the center of rocker arm 15 is effecting for expanding the range of movement of link rod 17 and swing cam 7 . Simultaneously, the load acting on the recess 21 of rocker arm 15 increases. However, the increased load can be resisted because the recess 21 is rightly and stably engaged with control cam 26 .
- FIGS. 21 to 26 show a variable valve actuating system according to a fifth embodiment of the present invention.
- drive cam 5 is oval-shaped as viewed in the longitudinal direction of drive shaft 4 in FIG. 21 .
- Rocker arm 15 is arranged to extend generally in the horizontal direction above the drive cam 5 , and includes a roller support shaft 30 on which a roller 29 is rotatably supported. Roller 29 is in rolling contact with the outer radial periphery of drive cam 5 .
- drive cam 5 is prepared separately from or independently of drive shaft 4 , including a sleeve 5 c as shown in FIG. 25 .
- Drive cam 5 is fixed to the outer radial periphery of drive shaft 4 by a fixing pin 35 which passes through the sleeve 5 c and drive shaft 4 .
- Each cylinder is provided with one drive cam 5 .
- Drive cam 5 has such an asymmetrical cam profile that at least at the maximum lift set point L 1 , intake valve 3 accelerates more rapidly when ascending to a peak of lift than when descending from the peak.
- Drive cam 5 includes an ascending flank 5 a and a descending flank 5 b which have different profiles as shown in FIG. 21 .
- the ascending flank 5 a is substantially straight, while the descending flank 5 b is curved outwardly. Accordingly, the acceleration of intake valve 3 is larger when ascending (opening) than when descending (closing).
- Rocker arm 15 is integrally formed, and shaped like a crank as viewed in FIG. 25 .
- the first end portion 15 a of rocker arm 15 is formed with a recess 21 which is directed upward as viewed in FIG. 21 and slidably engaged with control cam 26 .
- the second end portion 15 b of rocker arm 15 is rotatably supported with respect to the first end portion 17 a of link rod 17 through the connecting pin 22 which passes through the pin hole 15 c.
- Recess 21 is U-shaped as in the first embodiment, and the entrance 21 a is directed upward in the direction of gravity or opposite to a direction in which a force of gravity acts.
- Roller 29 is rotatably supported on roller support shaft 30 in a space 31 which is defined in the center of rocker arm 15 as shown in FIG. 25 .
- Swing cams 7 , 7 are arranged at a predetermined interval, and connected to each other by a cylindrical member 32 , as shown in FIG. 25 .
- Each swing cam 7 is triangularly shaped, including a cam surface 7 b at the bottom edge.
- Cylindrical member 32 is rotatably supported on the outer radial periphery of drive shaft 4 .
- Cylindrical member 32 includes a journal 32 a at the center in the longitudinal direction as shown in FIG. 25 , and rotatably supported on bearing 33 which is provided at an upper end portion of cylinder head 1 .
- Drive shaft 4 is rotatably supported inside of and by cylindrical member 32 .
- Link rod 17 is liked with swing cam 7 by connecting pin 20 which passes through the hole of second the end portion 17 b of link rod 17 and a projecting portion 7 d of swing cam 7 , where the projecting portion 7 d is formed opposite to the cam nose 7 c.
- Compression coil spring 24 is arranged between the roller 29 and the tip of the second end portion 15 b of rocker arm 15 .
- Compression coil spring 24 has a relatively large spring constant, and pushes the second end portion 15 b of rocker arm 15 downward. Accordingly, roller 29 is pressed on the outer radial periphery of drive cam 5 in a radial direction of drive cam 5 . Simultaneously, the first end portion 15 a of rocker arm 15 is pushed upward, and the inner cylindrical surface 21 b of recess 21 is pressed on the bottom surface of control cam 26 , while roller 29 serves as a fulcrum.
- control shaft 25 is controlled to rotate so that the central axis Q of control cam 26 is substantially in a position just above the central axis P of control shaft 25 , as shown in FIGS. 21 and 22 .
- the second end portion 15 b of rocker arm 15 is moved to a relatively low position so that swing cam 7 is rotated in the counterclockwise direction via link rod 17 , and a portion of cam surface 7 b closer to the base circle is in contact with needle roller 12 of swing arm 6 .
- the range of movement of the contact point of swing cam 7 is close to the base circle as shown in FIGS. 21 and 22 , so that the lift of intake valve 3 is set at the minimum lift set point L.
- control shaft 25 is controlled to rotate in the clockwise direction so that the central axis Q of control cam 26 is moved to a position below and on the right of the central axis P of control shaft 25 , as shown in FIGS. 23 and 24 .
- the second end portion 15 b of rocker arm 15 is moved to a relatively high position so that swing cam 7 is rotated in the clockwise direction via link rod 17 , and a portion of cam surface 7 b closer to the lift region is in contact with needle roller 12 of swing arm 6 .
- the range of movement of the contact point of swing cam 7 is close to the cam nose 7 c as shown in FIGS. 23 and 24 , so that the lift of intake valve 3 is set at the maximum lift set point L 1 .
- the structure that the recess 21 of rocker arm 15 is directed upward in the direction of gravity, is effective for allowing the recess 21 to collect lubricating fluid which is scattered inside the housing of the variable valve actuating system, and thereby improving the condition of lubrication between rocker arm 15 and control cam 26 .
- the recess 21 of rocker arm 15 according to this embodiment is also effective in view of assembling and downsizing of the variable valve actuating system as in the first embodiment. When intake valve 3 is open, the recess 21 of rocker arm 15 is also pressed on the outer radial periphery of control cam 26 by the elastic force of 10.
- FIGS. 27 and 28 show a variable valve actuating system according to a sixth embodiment of the present invention.
- the structure of swing cam 7 is modified with respect to that in the fifth embodiment. Specifically, an upper portion of the structure of cylindrical member 32 and swing cams 7 , 7 is cut off so as to form a U-shaped recess 34 whose inner diameter is slightly larger than the outer diameter of drive shaft 4 so that the recess 34 engages with the outer radial periphery of drive shaft 4 .
- the U-shape of cylindrical member 32 is possible, because the projecting portion 7 d is located opposite (about 180 degrees) to the cam nose 7 c with respect to cylindrical member 32 , so that cylindrical member 32 is resistant to inclination with respect to drive shaft 4 , although projecting portion 7 d is provided offset to one swing cam 7 .
- Cylindrical member 32 is provided with ribs 34 b, 34 b which are projecting radially from cylindrical member 32 , in order to compensate for a fall in bending rigidity of cylindrical member 32 due to the U-shape.
- the construction described above is effective for allowing to attach the swing cams 7 , 7 to drive shaft 4 by engaging the drive shaft 4 with recess 34 through entrance 34 a in the radial direction of drive shaft 4 , not in the longitudinal direction of drive shaft 4 , and thus making it easy to attach the swing cams 7 , 7 to drive shaft 4 , although drive shaft 4 is provided with flanges at the longitudinal ends for positioning so that it may be difficult to attach the swing cams 7 , 7 to drive shaft 4 in the longitudinal direction.
- the integrated structure of drive cam 5 and drive shaft 4 is effective for reducing the sizes of the structure in the radial direction and longitudinal direction, and thereby reducing the size of the entire variable valve actuating system.
- the variable valve actuating system according to the sixth embodiment produces other advantageous effects as in the fifth embodiment.
- FIG. 29 shows a variable valve actuating system according to a seventh embodiment of the present invention.
- the shape of drive cam 5 is modified into a circular disc as in the first embodiment, as compared to the fifth and sixth embodiments.
- drive cam 5 in the form of a circular disc is attached to drive shaft 4 in a manner that the central axis Y of drive cam 5 is arranged eccentric by a predetermined distance from the central axis X of drive shaft 4 , and the outer radial periphery of drive cam 5 is slidably fit on the circular portion 16 a of link arm 16 .
- Link arm 16 is rotatably supported with respect to rocker arm 15 by connecting pin 28 which passes through the pin hole 15 c.
- Pin hole 15 c is formed in a substantially central portion of rocker arm 15 in the longitudinal direction of rocker arm 15 .
- rocker arm 15 is pressed by compression coil spring 24 upward and leftward to control cam 26 in the radial direction of control cam 26 , so that the inner cylindrical surface 21 b of recess 21 is constantly maintained in contact with the outer radial periphery of control cam 26 .
- Rocker arm 15 is linked at the second end portion 15 b with the projecting portion 7 d of swing cam 7 through connecting pins 20 and 22 and link rod 17 , as in the fifth embodiment.
- variable valve actuating system operates as in the fifth embodiment, but differs from the fifth embodiment in that the spring constant of compression coil spring 24 may be small, because movement of rocker arm 15 is supported by drive cam 5 via link arm 16 .
- the spring constant of compression coil spring 24 may be small, if the first end portion 15 a of rocker arm 15 as a fulcrum of movement of rocker arm 15 can be softly supported by compression coil spring 24 .
- compression coil spring 24 presses the first end portion 15 a of rocker arm 15 from below is effective for eliminating the necessity of arrangement of compression coil spring 24 above rocker arm 15 , and thereby reducing the height of the entire variable valve actuating system.
- variable valve actuating system may be applied to exhaust valves.
- the locations of control shaft 25 and control cam 26 may be adjusted according to specifications and sizes of the variable valve actuating system.
Abstract
A variable valve actuating apparatus for an internal combustion engine includes a drive cam, a control shaft, a control cam, a rocker arm, and a swing cam. The drive cam is rotated by the internal combustion engine. The control shaft is supported for rotation about a rotation axis. The control cam is coupled to the control shaft, and is eccentric with respect to the rotation axis of the control shaft. The rocker arm is linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam. The rocker arm includes a recess slidably engaged with an outer radial periphery of the control cam. The swing cam is linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine.
Description
- The present invention relates generally to internal combustion engines, and particularly to variable valve actuating apparatuses or systems for varying at least a lift of an engine valve, such as an intake valve or exhaust valve, of an internal combustion engine.
- Japanese Patent Application Publication No. 2002-38913 corresponding to U.S. Pat. No. 6,499,454 discloses a variable valve actuating system for varying at least a lift of an intake valve set of an internal combustion engine. This variable valve actuating system includes: a drive shaft rotated by a crankshaft; a drive cam fixedly mounted to an outer radial periphery of the drive shaft; a transmitting mechanism for converting rotary motion of the drive cam to swinging motion of a swing cam, the transmitting mechanism including a rocker arm, a link arm and a link rod; and the swing cam that slides on a top surface of a valve lifter for opening and closing an intake valve. The link arm links the drive cam with the rocker arm. The link rod links the rocker arm with the swing cam. The rocker arm is linked at one end portion with one end of the link arm and one end of the link rod, and has a relatively large hole at another end portion in which a control cam is rotatably supported. The control cam is fixed and eccentric with respect to a control shaft. The variable valve actuating system is configured to control the position of the control cam according to an engine operating state by rotating the control shaft by an actuator. Movement of the control cam causes a change in the range of motion of the swing cam, and thereby causes changes in the lift and operating angle of the intake valve.
- For assembling the variable valve actuating system described above and disclosed in Japanese Patent Application Publication No. 2002-38913, it is necessary to attach the control cam to the rocker arm by inserting the control cam into the hole formed in the rocker arm in the longitudinal direction of the control shaft. This imposes some requirements on the entire assembling process, for example, for avoiding interference between components.
- In view of the foregoing, it is desirable to provide a variable valve actuating apparatus or system which can be assembled more easily.
- According to one aspect of the present invention, a variable valve actuating apparatus for an internal combustion engine, comprises: a drive cam adapted to be rotated by the internal combustion engine; a control shaft supported for rotation about a rotation axis; a control cam coupled to the control shaft, wherein the control cam is eccentric with respect to the rotation axis of the control shaft; a rocker arm linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam, the rocker arm including a recess slidably engaged with an outer radial periphery of the control cam; and a swing cam linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine. The variable valve actuating apparatus may further comprise: a device for maintaining contact between the recess of the rocker arm and the outer radial periphery of the control cam; and a drive shaft adapted to be rotated by the internal combustion engine, wherein: the drive cam is fixedly mounted to an outer radial periphery of the drive shaft; change of a rotational position of the control shaft causes a movement of the control cam with respect to the drive shaft, and causes at least a change in a lift of the engine valve; and the rotational position of the control shaft is controlled according to an operating state of the internal combustion engine. The variable valve actuating apparatus may further comprise: a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft; and an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein the recess of the rocker arm has an entrance directed opposite to a portion of the rocker arm which is linked with the swing cam. The variable valve actuating apparatus may further comprise: a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft; and an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the engine valve is open, the recess of the rocker arm is pressed on the outer radial periphery of the control cam by an elastic force of a valve spring provided for the engine valve.
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FIG. 1 is a front view of a variable valve actuating system according to a first embodiment of the present invention in a position for a minimum lift set point. -
FIG. 2 is a front view of the variable valve actuating system ofFIG. 1 in the position for the minimum lift set point at a moment when an associated intake valve is opened. -
FIG. 3 is a front view of the variable valve actuating system ofFIG. 1 in a position for a maximum lift set point at a moment when the intake valve is closed. -
FIG. 4 is a front view of the variable valve actuating system ofFIG. 1 in the position for the maximum lift set point at a moment when the intake valve is opened. -
FIG. 5 is a plan view of the variable valve actuating system ofFIG. 1 . -
FIG. 6 is a side view of the variable valve actuating system ofFIG. 1 . -
FIG. 7 is a graphic diagram showing lift curves of the intake valve which are achieved by the variable valve actuating system ofFIG. 1 . -
FIG. 8 is a front view of a variable valve actuating system according to a second embodiment of the present invention. -
FIG. 9 is a plan view of the variable valve actuating system ofFIG. 8 . -
FIG. 10 is a side view of the variable valve actuating system ofFIG. 8 . -
FIG. 11 is a graphic diagram showing lift curves of intake valves which are achieved by the variable valve actuating system ofFIG. 8 . -
FIG. 12 is an enlarged view of a structure in which a rocker arm engages with a control cam in a variable valve actuating system according to a third embodiment of the present invention. -
FIG. 13 is a plan view of the variable valve actuating system according to the third embodiment. -
FIG. 14 is a side view of the variable valve actuating system according to the third embodiment. -
FIG. 15 is a front view of a variable valve actuating system according to a fourth embodiment of the present invention. -
FIG. 16 is a front view of the variable valve actuating system ofFIG. 15 in a position for a minimum lift set point at a moment when an associated intake valve is opened. -
FIG. 17 is a front view of the variable valve actuating system ofFIG. 15 in a position for a maximum lift set point at a moment when the intake valve is closed. -
FIG. 18 is a front view of the variable valve actuating system ofFIG. 15 in the position for the maximum lift set point at a moment when the intake valve is opened. -
FIG. 19 is a plan view of the variable valve actuating system ofFIG. 15 . -
FIG. 20 is a side view of the variable valve actuating system ofFIG. 15 . -
FIG. 21 is a front view of a variable valve actuating system according to a fifth embodiment of the present invention. -
FIG. 22 is a front view of the variable valve actuating system ofFIG. 21 in a position for a minimum lift set point at a moment when an associated intake valve is opened. -
FIG. 23 is a front view of the variable valve actuating system ofFIG. 21 in a position for a maximum lift set point at a moment when the intake valve is closed. -
FIG. 24 is a front view of the variable valve actuating system ofFIG. 21 in the position for the maximum lift set point at a moment when the intake valve is opened. -
FIG. 25 is a plan view of the variable valve actuating system ofFIG. 21 . -
FIG. 26 is a side view of the variable valve actuating system ofFIG. 21 . -
FIG. 27 is a plan view of a variable valve actuating system according to a sixth embodiment of the present invention. -
FIG. 28 is a front view of the variable valve actuating system ofFIG. 27 . -
FIG. 29 is a front view of a variable valve actuating system according to a seventh embodiment of the present invention. -
FIGS. 1 to 6 show a variable valve actuating apparatus or system according to a first embodiment of the present invention for an engine valve set of an internal combustion engine which is an intake valve set in this example. The variable valve actuating system according to the first embodiment generally includes an intake valve set which includes twointake valves drive shaft 4, adrive cam 5 per cylinder, a swing arm set which includes twoswing arms swing cams transmitting mechanism 8 per cylinder, and acontrol mechanism 9. Eachintake valve 3 is slidably mounted in a valve guide not shown in acylinder head 1, for opening and closing an intake port formed incylinder head 1.Drive shaft 4 is hollow, having a longitudinal axis extending in a longitudinal direction of the engine.Drive cam 5 is fixedly mounted to driveshaft 4. Eachswing arm 6 is arranged close to an upper end ofintake valve 3. Eachswing cam 7 opens and closesintake valve 3 by moving theswing arm 6.Transmitting mechanism 8, which is of a multiple link type,links drive cam 5 withswing cams drive cam 5 into swinging motion ofswing cams control mechanism 9 varies the lift ofintake valves rocker arm 15 oftransmitting mechanism 8. - Each
intake valve 3 is provided with avalve spring 10, and biased byvalve spring 10 in a direction to close the intake port, as shown inFIG. 6 . Eachvalve spring 10 is disposed between the bottom of a substantially cylindrical bore formed or provided in an upper end portion ofcylinder head 1, and a spring retainer provided in an upper end portion of a valve stem ofintake valve 3. -
Drive shaft 4 is rotatably mounted incylinder head 1.Drive shaft 4 includes longitudinal ends rotatably supported on bearings provided in an upper portion ofcylinder head 1.Drive shaft 4 is adapted to be rotated by a crankshaft of the engine. Specifically,drive shaft 4 receives a torque from the crankshaft through a rotation transmitting mechanism which is, for example, a chain drive mechanism including a timing sprocket provided at one longitudinal end ofdrive shaft 4, and a timing chain wounded around the timing sprocket. When driven by the crankshaft, thedrive shaft 4 rotates in a clockwise direction as shown by an arrow inFIG. 1 . - Drive
cam 5 is arranged betweenswing cams drive shaft 4, shaped like a circular disc, and formed with a hole extending in a longitudinal direction of drive cam 5 (in the longitudinal direction of drive shaft 4), as shown inFIGS. 1 and 6 . Drivecam 5 is coupled to or fixedly mounted on an outer radial periphery ofdrive shaft 4 for rotation therewith, wheredrive shaft 4 extends through the hole ofdrive cam 5. Drivecam 5 is thus adapted to be rotated by the crankshaft of the engine. The hole is positioned indrive cam 5 so thatdrive cam 5 has an eccentric circular cam profile. The central axis Y ofdrive cam 5 is offset in a predetermined radial direction from the central axis X ofdrive shaft 4 by a predetermined distance. - Each
swing arm 6 extends in a lateral direction ofdrive shaft 4, and has afirst end portion 6 a which includes a slightly recessed lower surface in contact with the stem end ofintake valve 3, and asecond end portion 6 b which includes a semispherically recessed lower surface in contact with and slidably supported by the tip of ahydraulic lash adjuster 11 retained in aretainer hole 2 formed incylinder head 1.Swing arm 6 is thus arranged to swing about the tip ofhydraulic lash adjuster 11.Swing arm 6 is provided with aneedle roller 12 substantially at a center ofswing arm 6.Needle roller 12 is rotatably supported with respect to swingarm 6, and is in rolling contact withswing cam 7, serving to reduce the friction betweenswing cam 7 andswing arm 6. - Hydraulic lash
adjuster 11 has a general structure, including abody 13 a, and aplunger 13 b.Body 13 a is cylindrically shaped with an open top and a closed bottom, and inserted and fixedly mounted inretainer hole 2.Plunger 13 b is mounted inbody 13 a for sliding through the top opening ofbody 13 a.Plunger 13 b has a semispherical upper end in sliding contact with thesecond end portion 6 b ofswing arm 6. Hydraulic fluid is supplied from a reservoir through a check valve to a high pressure chamber defined between the inner bottom ofbody 13 a and the outer bottom ofplunger 13 b. Hydraulic lashadjuster 11 serves to constantly maintain the clearance between the tip ofplunger 13 b and thesecond end portion 6 b of swing arm 6 (and the clearance betweenswing cam 7 and needle roller 12) substantially equal to zero by suitable supply of hydraulic fluid. - Each
swing cam 7 includes afitting recess 7 a which is generally U-shaped, and fit on the outer radial periphery ofdrive shaft 4, so thatswing cam 7 is swingably supported with respect to driveshaft 4, i.e.swing cam 7 is supported for swinging about the central axis X ofdrive shaft 4 with thefitting recess 7 a in sliding contact with the outer radial periphery ofdrive shaft 4.Swing cam 7 has acam surface 7 b at the lower side which is adapted to be in contact withneedle roller 12 ofswing arm 6. Thecam surface 7 b ofswing cam 7 includes a base circle surface region closer to driveshaft 4, a ramp surface region extending like a circular arc from the base circle surface region toward acam nose 7 c, and a lift surface region extending from the ramp surface region toward an apex of the cam nose which defines a possible maximum lift set point ofintake valve 3. Thecam surface 7 b abuts on the top surface of a corresponding portion of the outer radial periphery ofneedle roller 12 ofswing arm 6, and the contact point of thecam surface 7 b shifts among the base circle surface region, ramp surface region and lift surface region in dependence on the swing position ofswing cam 7.Swing cam 7 is arranged so that whenswing cam 7 swings in the same direction as drive shaft 4 (clockwise direction as viewed inFIG. 1 ), the contact point ofcam surface 7 b shifts toward the lift surface region for increasing the opening ofintake valve 3. Thecam nose 7 c ofswing cam 7 is formed with apin hole 7 e extending in the longitudinal direction ofdrive shaft 4. A connectingpin 20 is inserted throughpin hole 7 e for connectingswing cam 7 and alink rod 17. The structure that swingcam 7 is directly mounted to driveshaft 4 eliminates the necessity of an additional support shaft for supportingswing cam 7. This is effective for cost reduction and downsizing of the variable valve actuating system.Swing cam 7 is linked withrocker arm 15, and arranged to swing in response to swinging motion ofrocker arm 15 for opening and closing theintake valve 3. - Transmitting
mechanism 8 includes arocker arm 15, alink arm 16, a link rod set which includes twolink rods FIG. 5 .Rocker arm 15 is arranged abovedrive shaft 4, extending generally in the lateral direction of the engine.Rocker arm 15 is linked withdrive cam 5, and arranged to swing aboutcontrol cam 26 in response to rotary motion ofdrive cam 5, as detailed below.Link arm 16links rocker arm 15 withdrive cam 5. Eachlink rod 17links rocker arm 15 with thecam nose 7 c of therespective swing cam 7. -
Rocker arm 15 includes a first longitudinal end portion defining a recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction ofrocker arm 15, wherein the second longitudinal end portion is linked withswing cam 7 for transmitting swinging motion ofrocker arm 15 to swingcam 7. Specifically,rocker arm 15 is generally A-shaped in a lateral direction ofdrive shaft 4 as shown inFIG. 6 , and includes afirst end portion 15 a, and a longitudinal end portion set which is Y-shaped as viewed inFIG. 5 and includes twosecond end portions first end portion 15 a ofrocker arm 15 includes arecess 21 which is slidably engaged with an outer radial periphery of acontrol cam 26 for allowing rotation ofcontrol cam 26. Therecess 21 ofrocker arm 15 and the outer radial periphery ofcontrol cam 26 have shapes fit on each other. Each second 5end portion 15 b ofrocker arm 15 includes apin hole 15 c extending in the longitudinal direction ofdrive shaft 4. A connectingpin 22 extends through the pin holes 15 c, 15 c of thesecond end portions - The
recess 21 ofrocker arm 15 has an innercylindrical surface 21 b which appears as a generally semicircular arc fit on the outer radial periphery ofcontrol cam 26 as viewed in the longitudinal direction ofdrive shaft 4 inFIG. 1 .Recess 21 has an inner diameter that is slightly larger than the outer diameter ofcontrol cam 26.Recess 21 includes anentrance 21 a directed downward as viewed inFIG. 1 , i.e. directed towardintake valve 3 or towardhydraulic lash adjuster 11. Thefirst end portion 15 a ofrocker arm 15 is thus slidably supported with respect to controlcam 26 for rotating or swinging aboutcontrol cam 26 so that thesecond end portions - The
first end portion 15 a ofrocker arm 15 is biased by acompression coil spring 24 towardcontrol cam 26 or towarddrive shaft 4.Compression coil spring 24 includes a first end fixed to arocker cover 14, and a second end in pressing contact with the outer periphery offirst end portion 15 a.Compression coil spring 24 serves as a device for mechanically pressing therecess 21 ofrocker arm 15 on the outer radial periphery ofcontrol cam 26, constantly maintaining contact between the innercylindrical surface 21 b of therecess 21 and the outer radial periphery ofcontrol cam 26, and preventing therecess 21 ofrocker arm 15 from escaping fromcontrol cam 26. -
Link arm 16 includes acircular portion 16 a, and a projectingportion 16 b.Circular portion 16 a has a relatively large outer diameter, and has afitting hole 16 c at the center. Thefitting hole 16 c is slidably fit on the outer radial periphery ofdrive cam 5 for allowing relative rotation ofdrive cam 5. Projectingportion 16 b is projecting fromcircular portion 16 a in a radial direction ofcircular portion 16 a, and disposed between thesecond end portions rocker arm 15 as viewed the lateral direction ofdrive shaft 4 inFIG. 5 . Projectingportion 16 b includes apin hole 16 d extending in the longitudinal direction ofdrive shaft 4 between both opposite surfaces, through which connectingpin 22 extends. Projectingportion 16 b is thus rotatably supported with respect tosecond end portions pin 22. - Each
link rod 17 is composed of a single piece made by press forming and folding.Link rod 17 has a U-shaped cross section as viewed inFIG. 5 , which is advantageous in compactness.Link rods second end portions rocker arm 15 in the longitudinal direction ofdrive shaft 4 as viewed inFIG. 5 .Link rod 17 has afirst end portion 17 a including a pin hole through which connectingpin 22 extends, and asecond end portion 17 b including a pin hole through which connectingpin 20 extends.Link rod 17 is rotatably connected at thefirst end portion 17 a to thesecond end portion 15 b ofrocker arm 15 through connectingpin 22, and rotatably connected at thesecond end portion 17 b to thecam nose 7 c ofswing cam 7 through connectingpin 20. - As described above, connecting
pin 22 pivotally connects all of the projectingportion 16 b oflink arm 16, thefirst end portions 17 a oflink rods 17, and thesecond end portions rocker arm 15. Connectingpin 22 is provided with snap rings 22 a, 22 a at both longitudinal ends for preventing the connected members from escaping from the connectingpin 22. Also, each connectingpin 20 is swaged at both longitudinal ends so as to prevent thelink rod 17 andswing cam 7 from escaping from connectingpin 20. -
Control mechanism 9 includes acontrol shaft 25,control cam 26, and anactuator 41.Control shaft 25 is arranged abovedrive shaft 4, extending in parallel to driveshaft 4.Control shaft 25 is supported for rotation about a rotation axis which is a central axis P ofcontrol shaft 25.Control cam 26 is coupled or fixedly mounted to controlshaft 25 for serving as a fulcrum for rocking motion ofrocker arm 15. The rotational position ofcontrol shaft 25 is regulated or controlled byactuator 41. -
Control shaft 25 includes a pair of shaft parts on both sides of the center of the cylinder in the longitudinal direction ofcontrol shaft 25 as shown inFIG. 5 . The ends of the shaft parts confronting each other are provided withflanges first end portion 15 a ofrocker arm 15 is slidably supported. Theflanges control shaft 25 serves to prevent thefirst end portion 15 a from inclining whenrocker arm 15 is rocking. -
Control cam 26 is formed in a cylindrical shape having a smaller outer diameter thancontrol shaft 25.Control cam 26 is supported by and arranged between theflanges control shaft 25 as viewed inFIG. 5 .Control cam 26 is eccentric with respect to the central axis P ofcontrol shaft 25. Specifically,control cam 26 has a central axis Q which is offset from the central axis P ofcontrol shaft 25 by an eccentric distance a, where the eccentric distance a is substantially as large as the diameter ofcontrol shaft 25, as shown inFIG. 1 . Accordingly,control cam 26 has anouter portion 26 a projecting beyond the outer radial periphery ofcontrol shaft 25, where theouter portion 26 a is substantially half ofcontrol cam 26, as viewed inFIG. 1 .Control shaft 25 andcontrol cam 26 are thus formed as a unit shaped like a crank. -
Actuator 41 incontrol mechanism 9 includes an electric motor, and a speed reducer, such as a ball screw mechanism. The electric motor is fixed to a rear end wall ofcylinder head 1. The speed reducer is arranged to transmit an output torque of the electric motor to controlshaft 25. The electric motor is a linear DC motor which is driven according to a control signal outputted from an electric controller not shown. The controller measures or calculates an engine operating state with reference to feedback signals from sensors, and controls the electric motor according to the engine operating state. The sensors include a crank angle sensor for measuring engine speed, an airflow meter for measuring intake air quantity, an engine coolant temperature sensor for measuring engine coolant temperature, and a potentiometer for measuring the rotational position ofcontrol shaft 25. - The following describes operations of the variable valve actuating system according to the first embodiment. The rotational position of
control shaft 25 is controlled according to the engine operating state, and change of the rotational position ofcontrol shaft 25 causes a movement ofcontrol cam 26 with respect to driveshaft 4, and causes at least a change in the lift ofintake valve 3, as detailed below. - For example, when the engine is at idle or at low speed, the controller issues such a control signal to the electric motor of
control mechanism 9 that the electric motor rotates and outputs a torque which is transmitted to controlshaft 25 through the speed reducer, and accordingly,control shaft 25 rotates in a clockwise direction by a corresponding angle as viewed inFIG. 1 . The rotation ofcontrol shaft 25 causes the central axis Q ofcontrol cam 26 to revolve about the central axis P ofcontrol shaft 25 to a position below and slightly on the left of the central axis P so that theouter portion 26 a ofcontrol cam 26 moves away fromdrive shaft 4. This moves therocker arm 15 leftward so that an angle θ betweenrocker arm 15 and linkarm 16 increases, and moves the connectingpin 22 generally in the counterclockwise direction aboutdrive shaft 4 as viewed inFIG. 1 . Accordingly,swing cam 7 is rotated throughlink rod 17 in the counterclockwise direction as viewed inFIG. 1 so that thecam nose 7 c ofswing cam 7 is moved upward. Whendrive cam 5 rotates under the condition described above and shown inFIG. 1 , thesecond end portions rocker arm 15 are moved upward and downward throughlink arm 16. When thesecond end portions FIG. 1 ,swing cam 7 is moved downward throughlink rod 17. Under this condition, the amount of depression ofswing arm 6 caused by thecam surface 7 b ofswing cam 7 is relatively small. This setting achieves a minimum valve lift set point. - In this way, when the engine is at idle or at low speed, the lift of each
intake valve 3 is set by the variable valve actuating system at the minimum lift set point L as shown inFIG. 7 . This retards the opening timing of intake valve 3 (intake valve opening timing IVO), and produces no valve overlap in which both ofintake valve 3 and an exhaust valve are opened. This provides the engine with a small pumping loss, an improved combustion process, an improved fuel efficiency, and stable rotation performance. - For example, when the engine shifts to a predetermined high speed region from a predetermined low speed region, the controller issues such a control signal that the electric motor and speed reducer of
control mechanism 9 rotate in a reverse direction, and accordingly,control shaft 25 rotatescontrol cam 26 in the counterclockwise direction as viewed inFIG. 1 . The rotation ofcontrol shaft 25 causes the central axis Q ofcontrol cam 26 to revolve about the central axis P ofcontrol shaft 25 to a position below and on the right of the central axis P ofcontrol shaft 25 as shown inFIGS. 3 and 4 so that theouter portion 26 a ofcontrol cam 26 moves towarddrive shaft 4. This moves therocker arm 15 rightward so that the angle θ betweenrocker arm 15 and linkarm 16 decreases, and moves the connectingpin 22 generally in the clockwise direction aboutdrive shaft 4 as viewed inFIG. 3 . Accordingly,swing cam 7 is rotated throughlink rod 17 in the clockwise direction as viewed inFIG. 3 so thatcam nose 7 c ofswing cam 7 is moved downward. Accordingly, the contact point ofcam surface 7 b ofswing cam 7 with respect toneedle roller 12 ofswing arm 6 moves toward thecam nose 7 c (toward the lift region). Whendrive cam 5 rotates under the condition described above and shown inFIG. 3 , thesecond end portions rocker arm 15 are moved upward and downward throughlink arm 16. Whensecond end portions FIG. 4 ,swing cam 7 is moved downward throughlink rod 17. Under this condition, the amount of depression ofswing arm 6 caused by thecam surface 7 b ofswing cam 7 is relatively large. This setting achieves a maximum valve lift set point. - In this way, when the engine is at high speed, the lift of
intake valve 3 is set by the variable valve actuating system at the maximum lift set point L1 as shown inFIG. 7 . This advances the opening timing of intake valve 3 (intake valve opening timing IVO) so as to produce and increase a valve overlap in which both ofintake valve 3 and the exhaust valve are opened, and retards the closing timing of intake valve 3 (intake valve closing timing IVC). This provides the engine with an improved intake air charging efficiency, and thereby, a high engine output. - When the engine returns from the high speed region to the low speed region, the lift of the
intake valve 3 is set to the minimum lift set point L. The central axis Q ofcontrol cam 26 as a pivot for swinging motion of thefirst end portion 15 a ofrocker arm 15 moves to the position shown inFIG. 1 so as to move thelink arm 16 in the counterclockwise direction aboutdrive cam 5 with respect to the position for the maximum lift set point L1. This advances the lift peak phase so that the intake valve opening timing IVO advances little at about top dead center, and the intake valve closing timing IVC advances significantly, with respect to the condition of the maximum lift set point L1, as shown inFIG. 7 . The intake valve opening timing IVO closer to top dead center for the condition of the minimum lift set point L is effective for allowing a suitable control of valve overlap. This makes it possible to reduce an increase of residual burned gas, and suppress adverse effects on fuel efficiency, at the minimum lift set point L. - In this way, the variable valve actuating system can control the lift and operating angle of the engine valve set continuously between the minimum lift set point L and the maximum lift set point L1 by actuating the
control shaft 25 according to engine operating state. - The provision of the
recess 21 of thefirst end portion 15 a ofrocker arm 15 enables an operator to easily attach therocker arm 15 to controlcam 26 only by engaging therecess 21 ofrocker arm 15 withcontrol cam 26 in the radial direction ofcontrol cam 26. This leads to a low manufacturing cost in view of efficiency of assembling operation. - The arrangement that the projecting
portion 16 b oflink arm 16 and thefirst end portion 17 a oflink rod 17 are connected through the common connectingpin 22 at thesecond end portions rocker arm 15, is effective for allowing the reaction force of thevalve spring 10 applied to linkrod 17 and the driving torque applied fromdrive cam 5 to linkarm 16 to cancel each other whenintake valve 3 opens and closes under the condition of the maximum lift set point L1. Accordingly, the load acting on the central axis Q ofcontrol cam 26 fromrocker arm 15 is relatively small, and the required driving torque ofactuator 41 is relatively small accordingly. - The crank structure of
control shaft 25 andcontrol cam 26 allows a large eccentric distance a between the central axis P ofcontrol shaft 25 and the central axis Q ofcontrol cam 26. This allows a large range of movement of the central axis Q as a fulcrum of rotation ofrocker arm 15, and a large amount of change of the lift, operating angle, and peak lift phase, ofintake valve 3. The crank structure ofcontrol shaft 25 andcontrol cam 26 is also effective for reducing the outer diameter ofcontrol shaft 25. This leads to downsizing of parts such as bearings and thereby downsizing of the entire variable valve actuating system. The simple structure of thefirst end portion 15 a ofrocker arm 15 also leads to downsizing of the entire variable valve actuating system. - The structure that the
first end portion 15 a ofrocker arm 15 is sandwiched and slidably held between theflanges control shaft 25, is effective for preventing thefirst end portion 15 a from inclining whenrocker arm 15 is rocking, and thereby, is effective for preventing abnormal wear betweencontrol cam 26 andfirst end portion 15 a. - The structure of transmitting
mechanism 8 where the elastic force ofvalve spring 10 and the driving force ofdrive cam 5 are well balanced is effective for preventing stress concentration and occurrence of deformation. - The provision of
compression coil spring 24 is effective for keeping constant contact between therecess 21 ofrocker arm 15 and the outer radial periphery ofcontrol cam 26, and thereby efficiently transmitting the movement ofcontrol cam 26 torocker arm 15. - When the engine is stopping, an alternating torque occurs in the engine and acts on
control cam 26 in the direction toward the minimum lift set point L. However, whenactuator 41 applies no torque to controlshaft 25, the elastic force ofcompression coil spring 24 is effective for mechanically moving and holding thecontrol cam 26 to a position for an intermediate lift set point between the minimum lift set point L and maximum lift set point L1, specifically, to a position slightly displaced from the position for the minimum lift set point L toward the position for the maximum lift set point L1. This enables the engine to restart well. - The structure that control
cam 26 is located at thefirst end portion 15 a ofrocker arm 15 is effective for reducing the contact load betweenrecess 21 andcontrol cam 26 because the elastic force ofvalve spring 10 is absorbed bydrive cam 5. - The structure that the inner peripheral surface of
recess 21 has substantially the same shape as the outer radial periphery ofcontrol cam 26, is effective for providing a wide contact area betweenrocker arm 15 andcontrol cam 26, and thereby preventing stress concentration therebetween. -
FIGS. 8 to 10 show a variable valve actuating system according to a second embodiment of the present invention. In the second embodiment, the structures ofrocker arm 15 andswing cams drive cams arms swing cams -
Rocker arm 15 is shaped so that theentrance 21 a ofrecess 21 is directed at an angle θ1 of about 30 degrees downward with reference to a line connecting the central axis Q ofcontrol cam 26 and the central axis O of connectingpin 22, and thesecond end portion 15 b is single, not branched. Thesecond end portion 15 b has a tip having a small width formed with apin hole 15 c through which connectingpin 22 extends. Thesecond end portion 15 b is rotatably connected substantially to the center of connectingpin 22 in the longitudinal direction of connectingpin 22. -
Compression coil spring 24 for biasing thefirst end portion 15 a ofrocker arm 15 is located at the position shown inFIG. 8 along the direction toward the central axis Q ofcontrol cam 26 so that the innercylindrical surface 21 b of therecess 21 is constantly pressed to the outer radial periphery ofcontrol cam 26. - Each
drive cam 5 is fixed to or integrated withdrive shaft 4, and is arranged at an interval from theother drive cam 5, as shown inFIG. 10 . Eachlink arm 16 includes acircular portion 16 a, and a projectingportion 16 b, as in the first embodiment. Thecircular portion 16 a includes thefitting hole 16 c in which drivecam 5 is rotatably supported. The projectingportion 16 b is rotatably supported by connectingpin 22 extending through thepin hole 16 d. Projectingportions second end portion 15 b ofrocker arm 15 in the longitudinal direction ofdrive shaft 4 as shown inFIG. 9 . - The cam surfaces 7 b, 7 b of
swing cams FIG. 8 . Thecam surface 7 b of oneswing cam 7 is concaved or offset with respect to thecam surface 7 b of theother swing cam 7. - The
drive shaft 4 and controlshaft 25 are rotatably supported on bearings which are arranged between transmittingmechanisms - The structure of
recess 21 thatentrance 21 a is directed downward by the angle of about 30 degrees with respect to the reference line is effective for providing a tight contact between therocker arm 15 andcontrol cam 26, and allowing therocker arm 15 to follow the eccentric movement ofcontrol cam 26 well. Even when the difference between the profiles of the cam surfaces 7 b, 7 b ofswing cams rocker arm 15 via connectingpin 22 to incline, the structure ofrecess 21 is also effective for resisting the moment of inclination ofrocker arm 15 and connectingpin 22. This enables the variable valve actuating system to precisely control the lift and operating angle ofintake valve 3. - The structure that two
drive cams drive shaft 4 per cylinder, is effective for preventing the connectingpin 22 androcker arm 15 from inclining, even whendrive cams intake valves - The structure that the cam surfaces 7 b, 7 b of
swing cams intake valves FIG. 11 , promoting in cylinder intake swirl, improving the combustion process, stabilizing the engine rotation, and enhancing the fuel efficiency. -
FIGS. 12 to 14 show a variable valve actuating system according to a third embodiment of the present invention. This variable valve actuating system is presented by modifying the first embodiment so that twocontrol cams rocker arm 15 has two branchedfirst end portions Control shaft 25 and driveshaft 4 are rotatably supported by bearings not shown. - Each
first end portion 15 a ofrocker arm 15 has a C-shapedrecess 21, where theentrance 21 a ofrecess 21 has a narrower entrance width Z than the outer diameter ofcontrol cam 26, as shown inFIG. 12 . On the other hand, eachcontrol cam 26 hasflat surfaces FIG. 12 . The distance betweenflat surfaces control cam 26, and slightly smaller than the entrance width Z ofrecess 21. The flat surfaces 26 b, 26 b of onecontrol cam 26 is located in the same circumferential position as those of theother control cam 26. In this way, the outer radial periphery ofcontrol cam 26 partly has a thickness in a radial direction ofcontrol cam 26 which is narrower than theentrance 21 a ofrecess 21 ofrocker arm 15, andcontrol cam 26 is engaged withrocker arm 15 in such a rotational position that controlcam 26 is prevented from escaping through theentrance 21 a from therecess 21 ofrocker arm 15. - Attaching the
rocker arm 15 to controlcams entrance 21 a of eachrecess 21 to be in contact with the edges of theflat surfaces control cam 26, then sliding therocker arm 15 in the radial direction ofcontrol cams cylindrical surface 21 b of eachrecess 21 to a portion of the outer radial periphery ofcontrol cam 26 between theflat surfaces rocker arm 15 about thecontrol cams recess 21 is thus engaged with the circular outer radial periphery ofcontrol cam 26, and prevented from escaping fromcontrol cam 26. In this way, attaching therocker arm 15 to controlcam 26 is simply implemented so as to achieve stable and reliable engagement betweenrocker arm 15 andcontrol cam 26. According to the structure described above,compression coil spring 24 for maintaining therocker arm 15 in contact withcontrol cam 26 is omitted, in contrast to the first embodiment. This leads to reduction in the number of parts, and thereby leads to reduction in manufacturing cost, and improvement in assembling operation. - The structure that
rocker arm 15 is rotatably supported bycontrol cams rocker arm 15 from inclining, even when the cam surfaces 7 b, 7 b ofswing cams -
FIGS. 15 to 20 show a variable valve actuating system according to a fourth embodiment of the present invention. In this embodiment, two transmittingmechanisms intake valves FIGS. 19 and 20 , twodrive cams intake valve 3, and the total fourdrive cams 5 are attached to driveshaft 4 at predetermined intervals. Accordingly, linkarm 16 is provided perdrive cam 5. -
Control shaft 25 are provided with twocontrol cams intake valves Control shaft 25 hasflat surfaces control cam 26 in the longitudinal direction. Eachcontrol cam 26 is linked with the respective one of tworocker arms first end portion 15 a has a C-shapedrecess 21, where theentrance 21 a ofrecess 21 has a narrower entrance width Z than the outer diameter ofcontrol cam 26. On the other hand, eachcontrol cam 26 hasflat surfaces flat surfaces control cam 26, and slightly smaller than the entrance width Z of therecess 21 ofrocker arm 15. Theentrance 21 a of eachrecess 21 is directed substantially in the longitudinal direction ofrocker arm 15, or in the longitudinal direction of thefirst end portion 15 a ofrocker arm 15 toward the longitudinal end ofrocker arm 15, opposite to connectingpin 22 which is linked withswing cam 7 and is related to actuation ofintake valve 3.Control shaft 25 and driveshaft 4 are supported by abearing 33. - Each
rocker arm 15 has apin hole 15 c at thesecond end portion 15 b through which connectingpin 22 passes.Rocker arm 15 is rotatably linked with thefirst end portion 17 a oflink rod 17 through the connectingpin 22. Eachrocker arm 15 also has apin hole 15 d substantially at the center ofrocker arm 15 in the longitudinal direction through which a respective connectingpin 28 passes.Rocker arm 15 is rotatably linked with the projectingportions link arms pin 28. One pair oflink arms rocker arm 15 andlink rod 17, and the outer pair oflink arms rocker arm 15 andlink rod 17, in the longitudinal direction ofdrive shaft 4, as shown inFIGS. 19 and 20 . - The variable valve actuating system described above operates as follows. For example, when the engine is at low speed and low load,
control shaft 25 is controlled to rotate to the position shown inFIGS. 15 and 16 as in the first embodiment, so that the lift ofintake valve 3 is set at the minimum lift set point L. When the engine shifts to a predetermined high speed region,control shaft 25 is controlled to rotate in the counterclockwise direction as shown inFIGS. 17 and 18 , so that the lift ofintake valve 3 is set at the maximum lift set point L1. - Attaching the
rocker arm 15 to controlcam 26 is implemented as in the third embodiment by allowing the edges ofentrance 21 a ofrecess 21 to be in contact with the edges of theflat surfaces control cam 26, then sliding therocker arm 15 in the radial direction ofcontrol cam 26 so as to fit the innercylindrical surface 21 b ofrecess 21 to a portion of the outer radial periphery ofcontrol cam 26 between theflat surfaces rocker arm 15 about thecontrol cam 26 to a predetermined rotational position. Eachrecess 21 is thus engaged with the circular outer radial periphery ofcontrol cam 26, and prevented from escaping fromcontrol cam 26. In this way, attaching therocker arm 15 to controlcam 26 is simply implemented so as to achieve stable and reliable engagement betweenrocker arm 15 andcontrol cam 26. According to the structure described above,compression coil spring 24 for maintaining therocker arm 15 in contact withcontrol cam 26 is omitted, in contrast to the first embodiment. - The structure that the
entrance 21 a ofrecess 21 is directed opposite to connectingpin 22 is effective for maintaining tight contact betweenrocker arm 15 andcontrol cam 26 withoutcompression coil spring 24, because the force fromvalve spring 10 is transmitted to act therocker arm 15 in the direction from the innercylindrical surface 21 b ofrecess 21 toward the outer radial periphery ofcontrol cam 26. - The structure that each
intake valve 3 is provided with therespective drive cam 5 androcker arm 15 is effective for allowing to adjust the lift ofintake valve 3 independently of theother intake valve 3 by adjusting the profiles ofdrive cam 5 andcontrol cam 26 independently of theother drive cam 5 andcontrol cam 26. - The structure that the projecting
portion 16 b oflink arm 16 is connected to substantially the center ofrocker arm 15 is effecting for expanding the range of movement oflink rod 17 andswing cam 7. Simultaneously, the load acting on therecess 21 ofrocker arm 15 increases. However, the increased load can be resisted because therecess 21 is rightly and stably engaged withcontrol cam 26. -
FIGS. 21 to 26 show a variable valve actuating system according to a fifth embodiment of the present invention. In this embodiment, drivecam 5 is oval-shaped as viewed in the longitudinal direction ofdrive shaft 4 inFIG. 21 .Rocker arm 15 is arranged to extend generally in the horizontal direction above thedrive cam 5, and includes aroller support shaft 30 on which aroller 29 is rotatably supported.Roller 29 is in rolling contact with the outer radial periphery ofdrive cam 5. - Specifically, drive
cam 5 is prepared separately from or independently ofdrive shaft 4, including asleeve 5 c as shown inFIG. 25 . Drivecam 5 is fixed to the outer radial periphery ofdrive shaft 4 by a fixingpin 35 which passes through thesleeve 5 c and driveshaft 4. Each cylinder is provided with onedrive cam 5. Drivecam 5 has such an asymmetrical cam profile that at least at the maximum lift set point L1,intake valve 3 accelerates more rapidly when ascending to a peak of lift than when descending from the peak. Drivecam 5 includes an ascendingflank 5 a and a descendingflank 5 b which have different profiles as shown inFIG. 21 . The ascendingflank 5 a is substantially straight, while the descendingflank 5 b is curved outwardly. Accordingly, the acceleration ofintake valve 3 is larger when ascending (opening) than when descending (closing). -
Rocker arm 15 is integrally formed, and shaped like a crank as viewed inFIG. 25 . Thefirst end portion 15 a ofrocker arm 15 is formed with arecess 21 which is directed upward as viewed inFIG. 21 and slidably engaged withcontrol cam 26. Thesecond end portion 15 b ofrocker arm 15 is rotatably supported with respect to thefirst end portion 17 a oflink rod 17 through the connectingpin 22 which passes through thepin hole 15 c.Recess 21 is U-shaped as in the first embodiment, and theentrance 21 a is directed upward in the direction of gravity or opposite to a direction in which a force of gravity acts. -
Roller 29 is rotatably supported onroller support shaft 30 in aspace 31 which is defined in the center ofrocker arm 15 as shown inFIG. 25 . -
Swing cams cylindrical member 32, as shown inFIG. 25 . Eachswing cam 7 is triangularly shaped, including acam surface 7 b at the bottom edge.Cylindrical member 32 is rotatably supported on the outer radial periphery ofdrive shaft 4. -
Cylindrical member 32 includes ajournal 32 a at the center in the longitudinal direction as shown inFIG. 25 , and rotatably supported on bearing 33 which is provided at an upper end portion ofcylinder head 1. Driveshaft 4 is rotatably supported inside of and bycylindrical member 32. -
Link rod 17 is liked withswing cam 7 by connectingpin 20 which passes through the hole of second theend portion 17 b oflink rod 17 and a projectingportion 7 d ofswing cam 7, where the projectingportion 7 d is formed opposite to thecam nose 7 c. -
Compression coil spring 24 is arranged between theroller 29 and the tip of thesecond end portion 15 b ofrocker arm 15.Compression coil spring 24 has a relatively large spring constant, and pushes thesecond end portion 15 b ofrocker arm 15 downward. Accordingly,roller 29 is pressed on the outer radial periphery ofdrive cam 5 in a radial direction ofdrive cam 5. Simultaneously, thefirst end portion 15 a ofrocker arm 15 is pushed upward, and the innercylindrical surface 21 b ofrecess 21 is pressed on the bottom surface ofcontrol cam 26, whileroller 29 serves as a fulcrum. - For example, when the engine is operating at low speed and low load,
control shaft 25 is controlled to rotate so that the central axis Q ofcontrol cam 26 is substantially in a position just above the central axis P ofcontrol shaft 25, as shown inFIGS. 21 and 22 . Accordingly, thesecond end portion 15 b ofrocker arm 15 is moved to a relatively low position so thatswing cam 7 is rotated in the counterclockwise direction vialink rod 17, and a portion ofcam surface 7 b closer to the base circle is in contact withneedle roller 12 ofswing arm 6. Under the condition described above, the range of movement of the contact point ofswing cam 7 is close to the base circle as shown inFIGS. 21 and 22 , so that the lift ofintake valve 3 is set at the minimum lift set point L. - On the other hand, when the engine shifts to a predetermined high speed and high load region,
control shaft 25 is controlled to rotate in the clockwise direction so that the central axis Q ofcontrol cam 26 is moved to a position below and on the right of the central axis P ofcontrol shaft 25, as shown inFIGS. 23 and 24 . Accordingly, thesecond end portion 15 b ofrocker arm 15 is moved to a relatively high position so thatswing cam 7 is rotated in the clockwise direction vialink rod 17, and a portion ofcam surface 7 b closer to the lift region is in contact withneedle roller 12 ofswing arm 6. Under the condition described above, the range of movement of the contact point ofswing cam 7 is close to thecam nose 7 c as shown inFIGS. 23 and 24 , so that the lift ofintake valve 3 is set at the maximum lift set point L1. - When the central axis Q of
control cam 26 is just above the central axis P ofcontrol shaft 25 as shown inFIGS. 21 and 22 ,rocker arm 15 is moved to the left as compared to the position shown inFIGS. 23 and 24 . This movement is opposite to the direction of rotation ofdrive shaft 4. Accordingly, the peak lift phase ofintake valve 3 advances as shown inFIG. 7 , as compared to the position shown inFIGS. 23 and 24 . This changes the intake valve opening timing IVO little, and changes the intake valve closing timing IVC significantly. This is effective as in the first embodiment. The construction that the acceleration ofintake valve 3 is larger when ascending (opening) than when descending (closing), is effective for preventing thedrive cam 5 from bounding out of contact withroller 29, and thereby, preventing theintake valve 3 from disordered movement. - The structure that the
recess 21 ofrocker arm 15 is directed upward in the direction of gravity, is effective for allowing therecess 21 to collect lubricating fluid which is scattered inside the housing of the variable valve actuating system, and thereby improving the condition of lubrication betweenrocker arm 15 andcontrol cam 26. Therecess 21 ofrocker arm 15 according to this embodiment is also effective in view of assembling and downsizing of the variable valve actuating system as in the first embodiment. Whenintake valve 3 is open, therecess 21 ofrocker arm 15 is also pressed on the outer radial periphery ofcontrol cam 26 by the elastic force of 10. -
FIGS. 27 and 28 show a variable valve actuating system according to a sixth embodiment of the present invention. In this embodiment, the structure ofswing cam 7 is modified with respect to that in the fifth embodiment. Specifically, an upper portion of the structure ofcylindrical member 32 andswing cams U-shaped recess 34 whose inner diameter is slightly larger than the outer diameter ofdrive shaft 4 so that therecess 34 engages with the outer radial periphery ofdrive shaft 4. The U-shape ofcylindrical member 32 is possible, because the projectingportion 7 d is located opposite (about 180 degrees) to thecam nose 7 c with respect tocylindrical member 32, so thatcylindrical member 32 is resistant to inclination with respect to driveshaft 4, although projectingportion 7 d is provided offset to oneswing cam 7.Cylindrical member 32 is provided withribs cylindrical member 32, in order to compensate for a fall in bending rigidity ofcylindrical member 32 due to the U-shape. - The construction described above is effective for allowing to attach the
swing cams shaft 4 by engaging thedrive shaft 4 withrecess 34 throughentrance 34 a in the radial direction ofdrive shaft 4, not in the longitudinal direction ofdrive shaft 4, and thus making it easy to attach theswing cams shaft 4, althoughdrive shaft 4 is provided with flanges at the longitudinal ends for positioning so that it may be difficult to attach theswing cams shaft 4 in the longitudinal direction. The integrated structure ofdrive cam 5 and driveshaft 4 is effective for reducing the sizes of the structure in the radial direction and longitudinal direction, and thereby reducing the size of the entire variable valve actuating system. The variable valve actuating system according to the sixth embodiment produces other advantageous effects as in the fifth embodiment. -
FIG. 29 shows a variable valve actuating system according to a seventh embodiment of the present invention. In this embodiment, the shape ofdrive cam 5 is modified into a circular disc as in the first embodiment, as compared to the fifth and sixth embodiments. - Specifically, drive
cam 5 in the form of a circular disc is attached to driveshaft 4 in a manner that the central axis Y ofdrive cam 5 is arranged eccentric by a predetermined distance from the central axis X ofdrive shaft 4, and the outer radial periphery ofdrive cam 5 is slidably fit on thecircular portion 16 a oflink arm 16. -
Link arm 16 is rotatably supported with respect torocker arm 15 by connectingpin 28 which passes through thepin hole 15 c.Pin hole 15 c is formed in a substantially central portion ofrocker arm 15 in the longitudinal direction ofrocker arm 15. - The
first end portion 15 a ofrocker arm 15 is pressed bycompression coil spring 24 upward and leftward to controlcam 26 in the radial direction ofcontrol cam 26, so that the innercylindrical surface 21 b ofrecess 21 is constantly maintained in contact with the outer radial periphery ofcontrol cam 26.Rocker arm 15 is linked at thesecond end portion 15 b with the projectingportion 7 d ofswing cam 7 through connectingpins link rod 17, as in the fifth embodiment. - The variable valve actuating system according to the sixth embodiment operates as in the fifth embodiment, but differs from the fifth embodiment in that the spring constant of
compression coil spring 24 may be small, because movement ofrocker arm 15 is supported bydrive cam 5 vialink arm 16. The spring constant ofcompression coil spring 24 may be small, if thefirst end portion 15 a ofrocker arm 15 as a fulcrum of movement ofrocker arm 15 can be softly supported bycompression coil spring 24. - The structure that
compression coil spring 24 presses thefirst end portion 15 a ofrocker arm 15 from below, is effective for eliminating the necessity of arrangement ofcompression coil spring 24 aboverocker arm 15, and thereby reducing the height of the entire variable valve actuating system. - The variable valve actuating system according to the present embodiments may be applied to exhaust valves. The locations of
control shaft 25 andcontrol cam 26 may be adjusted according to specifications and sizes of the variable valve actuating system. - The entire contents of Japanese Patent Application 2008-074824 filed Mar. 24, 2008 are incorporated herein by reference.
- Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.
Claims (26)
1. A variable valve actuating apparatus for an internal combustion engine, comprising:
a drive cam adapted to be rotated by the internal combustion engine;
a control shaft supported for rotation about a rotation axis;
a control cam coupled to the control shaft, wherein the control cam is eccentric with respect to the rotation axis of the control shaft;
a rocker arm linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam, the rocker arm including a recess slidably engaged with an outer radial periphery of the control cam; and
a swing cam linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine.
2. The variable valve actuating apparatus as claimed in claim 1 , further comprising a device for maintaining contact between the recess of the rocker arm and the outer radial periphery of the control cam.
3. The variable valve actuating apparatus as claimed in claim 2 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein:
the drive cam is fixedly mounted to an outer radial periphery of the drive shaft;
change of a rotational position of the control shaft causes a movement of the control cam with respect to the drive shaft, and causes at least a change in a lift of the engine valve; and
the rotational position of the control shaft is controlled according to an operating state of the internal combustion engine.
4. The variable valve actuating apparatus as claimed in claim 2 , wherein the device is a device for mechanically pressing the recess of the rocker arm on the outer radial periphery of the control cam.
5. The variable valve actuating apparatus as claimed in claim 2 , wherein:
the recess of the rocker arm has an entrance that is narrower than a diameter of the recess;
the outer radial periphery of the control cam partly has a thickness in a radial direction of the control cam which is narrower than the entrance of the recess of the rocker arm; and
the control cam is engaged with the rocker arm in such a rotational position that the control cam is prevented from escaping through the entrance from the recess of the rocker arm.
6. The variable valve actuating apparatus as claimed in claim 2 , wherein the control shaft includes a flange supporting the control cam.
7. The variable valve actuating apparatus as claimed in claim 2 , wherein the recess of the rocker arm and the outer radial periphery of the control cam have shapes fit on each other.
8. The variable valve actuating apparatus as claimed in claim 2 , wherein the recess of the rocker arm has an entrance directed opposite to a direction in which a force of gravity acts.
9. The variable valve actuating apparatus as claimed in claim 2 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, and coupled to the drive cam, wherein the swing cam is swingably supported with respect to the drive shaft.
10. The variable valve actuating apparatus as claimed in claim 2 , wherein the rocker arm includes a first longitudinal end portion defining the recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction of the rocker arm, and wherein the second longitudinal end portion is linked with the swing cam for transmitting swinging motion of the rocker arm to the swing cam.
11. The variable valve actuating apparatus as claimed in claim 10 , further comprising a link rod linking the rocker arm with the swing cam.
12. The variable valve actuating apparatus as claimed in claim 2 , further comprising a roller rotatably supported with respect to the rocker arm, and arranged in rolling contact with the drive cam.
13. The variable valve actuating apparatus as claimed in claim 2 , wherein the drive cam has such an asymmetrical cam profile that at least at a maximum lift set point, the engine valve accelerates more rapidly when ascending to a peak of lift than when descending from the peak.
14. The variable valve actuating apparatus as claimed in claim 2 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the actuator applies no torque to the control shaft, the control cam is mechanically held at a position for an intermediate lift set point of the engine valve between a minimum lift set point and a maximum lift set point of the engine valve.
15. The variable valve actuating apparatus as claimed in claim 1 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein the recess of the rocker arm has an entrance directed opposite to a portion of the rocker arm which is linked with the swing cam.
16. The variable valve actuating apparatus as claimed in claim 15 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft.
17. The variable valve actuating apparatus as claimed in claim 15 , wherein the outer radial periphery of the control cam has an outer diameter which is larger than a width of an entrance of the recess of the rocker arm, and the outer radial periphery of the control cam partly has a thickness in a radial direction of the control cam which is smaller than the width of the entrance of the recess of the rocker arm.
18. The variable valve actuating apparatus as claimed in claim 15 , wherein the control shaft includes a flange supporting the control cam.
19. The variable valve actuating apparatus as claimed in claim 15 , wherein the recess of the rocker arm and the outer radial periphery of the control cam have shapes fit on each other.
20. The variable valve actuating apparatus as claimed in claim 15 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, and coupled to the drive cam, wherein the swing cam is swingably supported with respect to the drive shaft.
21. The variable valve actuating apparatus as claimed in claim 15 , wherein the rocker arm includes a first longitudinal end portion defining the recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction of the rocker arm, and wherein the second longitudinal end portion is linked with the swing cam for transmitting swinging motion of the rocker arm to the swing cam.
22. The variable valve actuating apparatus as claimed in claim 21 , further comprising a link rod linking the rocker arm with the swing cam.
23. The variable valve actuating apparatus as claimed in claim 15 , wherein the recess of the rocker arm has an entrance directed in a longitudinal direction of a longitudinal end portion of the rocker arm toward a longitudinal end of the rocker arm.
24. The variable valve actuating apparatus as claimed in claim 1 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the engine valve is open, the recess of the rocker arm is pressed on the outer radial periphery of the control cam by an elastic force of a valve spring provided for the engine valve.
25. The variable valve actuating apparatus as claimed in claim 24 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft.
26. The variable valve actuating apparatus as claimed in claim 24 , further comprising a device for preventing the recess of the rocker arm from escaping from the control cam.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2008074824A JP2009228556A (en) | 2008-03-24 | 2008-03-24 | Variable valve gear of internal combustion engine |
JP2008-074824 | 2008-03-24 |
Publications (1)
Publication Number | Publication Date |
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US20090235885A1 true US20090235885A1 (en) | 2009-09-24 |
Family
ID=41087651
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/399,243 Abandoned US20090235885A1 (en) | 2008-03-24 | 2009-03-06 | Variable valve actuating apparatus |
Country Status (2)
Country | Link |
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US (1) | US20090235885A1 (en) |
JP (1) | JP2009228556A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9057455B2 (en) | 2012-01-20 | 2015-06-16 | Hamilton Sundstrand Corporation | Crank |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5312301B2 (en) * | 2009-11-26 | 2013-10-09 | 日立オートモティブシステムズ株式会社 | Variable valve operating device for internal combustion engine |
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---|---|---|---|---|
US6029618A (en) * | 1997-11-07 | 2000-02-29 | Nissan Motor Co., Ltd. | Variable valve actuation apparatus |
US6499454B2 (en) * | 2000-07-21 | 2002-12-31 | Unisia Jecs Corporation | Variable-valve-actuation apparatus for internal combustion engine |
US20040003789A1 (en) * | 2002-07-04 | 2004-01-08 | Peter Kreuter | Methods and apparatus for providing variable valve lift for camshaft-actuated valves |
US7168403B2 (en) * | 2003-05-01 | 2007-01-30 | Yamaha Hatsudoki Kabushiki Kaisha | Valve train device for engine |
US20080257289A1 (en) * | 2007-04-23 | 2008-10-23 | Hitachi, Ltd. | Variable valve actuating apparatus for internal combustion engine |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1605142B1 (en) * | 2003-03-11 | 2014-01-01 | Yamaha Hatsudoki Kabushiki Kaisha | Variable valve mechanism for internal combustion engine |
-
2008
- 2008-03-24 JP JP2008074824A patent/JP2009228556A/en active Pending
-
2009
- 2009-03-06 US US12/399,243 patent/US20090235885A1/en not_active Abandoned
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6029618A (en) * | 1997-11-07 | 2000-02-29 | Nissan Motor Co., Ltd. | Variable valve actuation apparatus |
US6499454B2 (en) * | 2000-07-21 | 2002-12-31 | Unisia Jecs Corporation | Variable-valve-actuation apparatus for internal combustion engine |
US20040003789A1 (en) * | 2002-07-04 | 2004-01-08 | Peter Kreuter | Methods and apparatus for providing variable valve lift for camshaft-actuated valves |
US7168403B2 (en) * | 2003-05-01 | 2007-01-30 | Yamaha Hatsudoki Kabushiki Kaisha | Valve train device for engine |
US20080257289A1 (en) * | 2007-04-23 | 2008-10-23 | Hitachi, Ltd. | Variable valve actuating apparatus for internal combustion engine |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US9057455B2 (en) | 2012-01-20 | 2015-06-16 | Hamilton Sundstrand Corporation | Crank |
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JP2009228556A (en) | 2009-10-08 |
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