EP1783332B1 - Oscillating cam and dynamic valve mechanism of internal combustion engine - Google Patents
Oscillating cam and dynamic valve mechanism of internal combustion engine Download PDFInfo
- Publication number
- EP1783332B1 EP1783332B1 EP04772154A EP04772154A EP1783332B1 EP 1783332 B1 EP1783332 B1 EP 1783332B1 EP 04772154 A EP04772154 A EP 04772154A EP 04772154 A EP04772154 A EP 04772154A EP 1783332 B1 EP1783332 B1 EP 1783332B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- cam
- rocking
- roller
- shaft
- internal combustion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- 238000002485 combustion reaction Methods 0.000 title claims description 49
- 230000002093 peripheral effect Effects 0.000 description 23
- 230000009467 reduction Effects 0.000 description 13
- 238000010276 construction Methods 0.000 description 11
- 239000011435 rock Substances 0.000 description 7
- 230000003252 repetitive effect Effects 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 230000000994 depressogenic effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000011324 bead Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000009191 jumping Effects 0.000 description 1
Images
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
- F01L1/02—Valve drive
- F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
- F01L1/08—Shape of cams
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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
- F01L1/14—Tappets; Push rods
- F01L1/143—Tappets; Push rods for use with overhead camshafts
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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
- 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
- F01L2013/0068—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 "BMW-Valvetronic" 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
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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
- F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
- F01L3/08—Valves guides; Sealing of valve stem, e.g. sealing by lubricant
Definitions
- the present invention relates to a rocking cam, in particular for a valve mechanism, which includes a cam surface having a base circle portion and a lift portion, and which is disposed so as to make reciprocating motion, and relates to a valve mechanism for an internal combustion engine, which is provided with the rocking cam.
- this type of valve mechanism for an internal combustion engine has: a camshaft rotated by a crankshaft; a rotating cam provided to the camshaft; a rocking cam rocked by the rotating cam for reciprocating motion; and a rocker arm partly coming into contact with a cam surface of the rocking cam.
- the rocking cam When the rocking cam is rocked, the cam surface thereof allows the rocker arm to be rocked. This motion by the rocker arm presses an intake or exhaust valve to open/close the valve (See Patent Document 1).
- Patent Document 1 JP-A-H7-063023
- Another conventional rocking cam is disclosed in document JP-06272525 .
- the cam surface of the rocking cam has a base circle portion, a lift portion and a ramp portion for connecting therebetween
- the cam surface requires a certain width to secure strength enough to withstand a large force acting on the cam surface.
- other parts associated with the rocking cam also need to secure certain strength, causing increases in weight of the parts as well as in size of the entire system. This creates additional problem with an increase in wear and the like on a contact portion of the rocking cam.
- the present invention has been made in order to solve the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide a rocking cam and a valve mechanism for an internal combustion engine, which can achieve reductions in size and weight as well as in wear and the like on a contact portion of the rocking cam.
- the invention as described in Claim 1 provides a rocking cam including a cam surface having a base circle portion and a lift portion, and disposed so as to make reciprocating motion, in which a width of a contact surface of the base circle portion is formed smaller than a width of a contact surface of the lift portion
- the invention as described in Claim 2 provides a valve mechanism for an internal combustion engine, having: a camshaft rotated by a crankshaft of the internal combustion engine; a rotating cam provided to the camshaft; a rocking shaft provided in parallel to the camshaft; and a rocking cam supported with the rocking shaft and freely rockable by the rotating cam and capable of varying a lift amount of an intake valve or an exhaust valve of the internal combustion engine, in which the rocking cam includes a cam surface having a base circle portion and a lift portion, and is disposed so as to make reciprocating motion, and a width of a contact surface of the base circle portion is formed smaller than a width of a contact surface of the lift portion.
- the invention as described in Claim 3 provides the valve mechanism for an internal combustion engine according to Claim 2, in which the rocking cam is provided with a movable rotating cam abutment portion that comes into contact with the rotating cam to transmit a drive force from the rotating cam to the rocking cam, and provided with a guide portion for guiding the rotating cam abutment portion in a certain direction; the drive force from the rotating cam is inputted to the guide portion via the rotating cam abutment portion so that the rocking cam is rocked; a variable abutment portion mechanism is provided for making a relative distance between the rotating cam abutment portion and a center axis of the rocking shaft variable by making the rotating cam abutment portion movable along the guide portion; and a lift amount of each valve is made variable by thus making the relative distance variable.
- the rocking cam includes the cam surface having the base circle portion and the lift portion, and is disposed so as to make reciprocating motion, in which the width of the contact surface of the base circle portion is formed smaller than the width of the contact surface of the lift portion. Therefore, weight of the rocking cam can be reduced. This results in a reduction in inertia force of the rocking cam at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam.
- the valve mechanism for an internal combustion engine which is capable of changing the lift amount of the intake valve or the exhaust valve of the internal combustion engine, is provided with the rocking cam having the base circle portion and the lift portion, with the width of the contact surface of the base circle portion being formed smaller than the width of the contact surface of the lift portion. This allows this variable valve mechanism to provide the above-mentioned effects.
- FIGs. 1 through 5 illustrate Embodiment 1 of the present invention.
- reference numeral 1 denotes a variable valve mechanism for an intake valve 11 of an internal combustion gasoline engine.
- the variable valve mechanism 1 has a camshaft 2 rotated by a crankshaft (not shown) of the internal combustion engine, a rotating cam 3 provided to the camshaft 2, a rocking shaft 4 provided in parallel to the camshaft 2, a rocking cam 5 supported on the rocking shaft 4 and adapted to rock by the rotating cam 3, and a rocker arm 6 that is rocked in synchronization with the rocking cam 5 to open/close the intake valve 11.
- variable valve mechanism 1 is the same between the intake valve 11 and exhaust valve of the gasoline engine. Accordingly, Embodiment 1 focuses on the mechanism on the intake valve 11 side, and the description of the mechanism on the exhaust valve side is omitted.
- the camshaft 2 is arranged with its longitudinal direction extending toward the front and back (i.e. in the direction perpendicular to the plane) of FIG. 1 .
- the camshaft 2 is rotated about a center axis O1 at a half rotational speed of that of the crankshaft of the internal combustion engine.
- the rotating cam 3 is fixed onto the outer peripheral surface of the camshaft 2 and, as shown in FIG. 1 , the outer peripheral portion thereof is configured with a base surface 3a that is arc-shaped in plan view, and a nose surface 3b projecting from the base surface 3a.
- a center axis O2 of the rocking shaft 4 is arranged in parallel to the center axis O1 of the camshaft 2.
- the rocking cam 5 is in fitting engagement with the outer peripheral surface of the rocking shaft 4, and is supported so as to be rockable about the center axis O2 of the rocking shaft 4.
- a cam surface 5a for rocking the rocker arm 6 is formed in the lower end portion of the rocking cam 5.
- a width L1 of a contact surface of the base circle portion 5c is formed smaller than a width L2 of a contact surface of the lift portion 5d.
- a guide portion 5b as an elongate through-hole is formed at the longitudinally middle portion of the rocking cam 5.
- a roller 8 is provided to the roller shaft 7 as a "rotating cam abutting portion” that contacts and operates in synchronization with a base surface 3a or a nose surface 3b of the rotating cam 3, for transmitting the drive force from the rotating cam 3 to the rocking cam 5.
- the guide portion 5b is formed in the shape of an elongate hole so as to guide the roller shaft 7 along its longitudinal direction over a predetermined distance, and the guiding direction at this time is inclined with respect to the radial direction of the camshaft 2.
- the roller 8 is formed in a circular shape, and is arranged on the outer peripheral surface of the roller shaft 7 so that the center axis of the roller 8 becomes the same as the center axis O3 of the roller shaft 7.
- the outer peripheral surface of the roller 8 is capable of rolling on the base surface 3a and nose surface 3b of the rocking cam 3.
- the rotating cam abutment portion which abuts the rotating cam 3 is formed in the shape of a roller to rotate on the rotating cam 3 face. This reduces loss of the drive force transmitted from the rotating cam 3 to "the rotating cam abutment portion.”
- the rotating cam abutment portion is the roller 8 which rotates on the rotating cam 3 face, but is not limited to this.
- the rotating cam abutment portion may be the one which slides on the rotating cam 3 face, as long as the drive force from the rotating cam 3 is transmitted to the rocking cam 5.
- a spring 15 for urging the rocking cam 5 toward the rotating cam 3 side is in fitting engagement with the rocking shaft 4.
- the rocking cam 5 is urged toward the rotating cam 3 side by the urging force of the spring 15, so that the outer peripheral surface of the roller 8 is in constant contact with the base surface 3a or nose surface 3b of the rotating cam 3.
- variable valve mechanism 1 is provided with "a variable abutment portion mechanism" for making the relative distance between the roller 8 and the center axis O2 of the rocking shaft 4 variable.
- variable abutment portion mechanism has a drive shaft 9 fixedly provided onto the rocking shaft 4, and an arm 10 whose one end portion 10a is connected to the roller shaft 7 and whose other end portion 10b is connected to the drive shaft 9.
- the drive shaft 9 is provided to the rocking shaft 4 in such a manner that a center axis O4 thereof is located in parallel and eccentrically to the center axis O2 of the rocking shaft 4.
- an actuator (not shown) for rotating the rocking shaft 4 within a predetermined angle range about the center axis O2 is connected to one end portion of the rocking shaft 4.
- control means (not shown) for controlling the angle of the actuator according to the operational state of the internal combustion engine.
- the drive shaft 9 turns by a predetermined angle about the center axis O2 of the rocking shaft 4, whereby the position of the center axis O4 changes relative to the center axis O2 of the rocking shaft 4.
- the arm 10 is capable of keeping the distance between the center axis O3 of the roller shaft 7 and the center axis O4 of the drive shaft 9 constant.
- a through-hole 10c, with which the roller shaft 7 is fitted, is formed at the one end portion 10a of the arm 10, and an insertion portion 10d, into which the drive shaft 9 is inserted and which is partially open, is formed at the other end portion 10b thereof.
- the roller shaft 7 is rotatably fitted with the through-hole 10c at the one end portion 10a
- the drive shaft 9 is rotatably fitted with the insertion portion 10d at the other end portion 10b and mounted in place with a pin 16 so as to prevent dislodging thereof.
- the drive shaft 9 provided to the rocking shaft 4 is turned by a predetermined angle about the center axis O2 of the rocking shaft 4, and the roller shaft 7 is operated in synchronization with this turning movement through the arm 10.
- the roller shaft 7 can be thus moved within the guide portion 5b while keeping the distance between the center axis O3 of the roller shaft 7 and the center axis O4 of the drive shaft 9 constant with the arm 10, whereby the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 can be made variable.
- rocker arm 6 is disposed below the rocking cam 5 while being rockably supported on the rocker arm shaft 12.
- rocker arm 6 is rockably supported with the rocker arm shaft 12, the configuration is not limited to this.
- the rocker arm 6 may be rockably supported with a spherical pivot, hydraulic lash adjuster, or the like.
- valve pressing portion 6a is formed at the distal end portion of the rocker arm 6 for pressing on the upper surface of a shim 23 fitted on an intake valve 11 which will be described later.
- a roller 14 is rotatably provided to the roller shaft 13, and the outer peripheral surface of the roller 14 is capable of rolling on the cam surface 5a of the rocking cam 5.
- a spring 17 for urging the rocker arm 6 toward the rocking cam 5 side is in fitting engagement with the rocker arm shaft 12.
- the rocker arm 6 is urged toward the rocking cam 5 side by means of the spring 17, so that the outer peripheral surface of the roller 14 is in constant contact with the cam surface 5a of the rocking cam 5.
- the intake valve 11 pressed by the valve pressing portion 6a is arranged below the valve pressing portion 6a of the rocker arm 6 so as to be vertically movable.
- the intake valve 11 has a collet 20 and an upper retainer 21 that are provided in its upper portion.
- a valve spring 22 is arranged below the upper retainer 21.
- the intake valve 11 is urged toward the rocker arm 6 side by the urging force of the valve spring 22. Further, the shim 23 is fitted on the upper end portion of the intake valve 11.
- the intake valve 11 can be vertically moved by rocking the rocker arm 6 in synchronization with the rocking motion of the rocking cam 5.
- the relative distance between the center axis O2 of the rocking cam 4 and the roller 8 variable to adjust the rocking start position of the rocking cam 5 the lift amount and the maximum lift timing of the intake valve 11 can be adjusted and made variable through the rocker arm 6.
- variable valve mechanism 1 Operation of the variable valve mechanism 1 constructed as above will next be described.
- variable valve mechanism 1 for an internal combustion engine when the maximum lift amount is required, with reference to FIGs. 1 and 2 .
- FIG. 1 is a longitudinal sectional view of the main portion of variable valve mechanism 1 of the internal combustion engine according to Embodiment 1 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve 11 is closed.
- FIG. 2 is a longitudinal sectional view of the main portion of the variable valve mechanism 1 of the internal combustion engine according to Embodiment 2 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is open.
- the roller shaft 7 is moved to the rotating cam 3-side end portion of the guide portion 5b, thereby changing the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8. That is, the rocking shaft 4 is turned by a predetermined angle by the actuator, causing the drive shaft 9 to move in the circumferential direction of the rocking shaft 4.
- the roller shaft 7 is operated in synchronization with this movement via the arm 10 so as to be moved to the rotating cam 3-side end portion of the guide portion 5b, whereby the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 changes.
- the roller 14 is located at the position corresponding to the base circle portion 5c of the cam surface 5a of the rocking cam 5. Since no large abutment force acts between the roller 14 and the base circle portion 5c in the valve closure state, a sufficient durability can be secured even through the width L1 of the base circle portion 5c is small.
- the valve pressing portion 6a formed at the distal end portion of the rocker arm 6 that has thus undergone large rocking movement to the intake valve 11 side presses on the upper surface of the shim 23 to push down the intake valve 11 by a large distance.
- the roller shaft 7 to the end portion of the guide portion 5b in the rotating cam 3 side to make the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 variable, the relative distance between the center axis O2 of the rocking shaft 4 and the roller 14 in contact with the cam surface 5a of the rocking cam 5 can be largely changed, whereby the intake valve 11 can be pushed down by a large distance to bring the intake valve 11 into an open state at the maximum lift amount.
- the width L2 of the lift portion 5d is made large because a large reaction force acts on the cam surface 5a of the rocking cam 5, thereby making it possible to secure strength.
- variable valve mechanism 1 of the internal combustion engine when the minimum lift amount is required, with reference to FIG. 3 and 4 .
- FIG. 3 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is closed.
- FIG. 4 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is open.
- the rocking shaft 4 is turned within a predetermined angle range by the actuator, causing the drive shaft 9 to move in the circumferential direction of the rocking shaft 4.
- the roller shaft 7 is operated in synchronization with this movement via the arm 10 so that the roller shaft 7 is moved to the rocking shaft 4-side end portion of the guide portion 5b from the state where it is retained at the rotating cam 3-side end portion, whereby the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 decreases.
- the rocking cam 5 turns from the position as shown in FIG. 1 to the position as shown in FIG. 3 due to the urging force of the spring 15.
- the roller shaft 7 to the rocking shaft 4-side end portion of the guide portion 5b to make the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 variable the relative distance between the center axis O2 of the rocking shaft 4 and the roller 14 in contact with the cam surface 5a of the rocking cam 5 can be subjected to a small change to push down the intake valve 11 by a small distance, whereby, in Embodiment 1, the intake valve 11 can be brought into an open state at the minimum lift amount.
- the width L1 of the base circle portion 5c is small, since no large load acts on this portion, a requisite strength can be secured for the base circle portion 5c. Because a large load acts on the lift portion 5d, the width L2 thereof is made larger to secure a requisite strength.
- Weight of the rocking cam 5 can be reduced because of the small width L1 of the base circle portion 5c. This results in a reduction in inertia force of the rocking cam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). This allows the whole system to be smaller while reducing wear on a contact portion of the cam surface 5a.
- the base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force.
- the rocking cam 5 is provided with the roller 8 or the rotating cam abutment portion that comes into contact with the rotating cam 3 to transmit the drive force from the rotating cam to the rocking cam 5.
- the valve mechanism 1 is provided with the variable abutment portion mechanism for making the relative distance between the roller 8 and the center axis O2 of the rocking shaft 4 variable by making the roller 8 movable; the lift amount or the like of each valve is made variable by thus making the relative distance variable, whereby the structure can be simplified to achieve low-cost construction.
- the load from the rotating cam 3 is input to the roller 8, and the load is directly transmitted from the roller 8 to the guide portion 5a of the rocking cam 5. Then, the load is transmitted from the rocking cam 5 to the intake valve 11 via the rocker arm 6. Thus, no large load acts on the arm 10 that supports the roller 8, and since the arm 10 serves the sole function of moving the roller 8 along the guide portion 5a, not so large strength is required for the arm 10.
- FIGs. 6 through 8 illustrate Embodiment 2 of the present invention.
- FIG. 6 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine when the maximum lift amount is required, illustrating the state in which the intake valve is closed.
- FIG. 7 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine when the minimum lift amount is required, illustrating the state in which the intake valve is closed.
- the rocker arm 6 which opens and closes an intake valve 11 as in Embodiment 1 is not provided, but a rocking cam 5 directly moves the intake valve 11 upward and downward to open and close the intake valve 11.
- the rocking cam 5 is formed in the shape of a comma-shaped bead.
- the rocking cam 5 is fitted on the peripheral surface of a rocking shaft 4 and supported so as to be rockable about the center axis O2 of the rocking shaft 4.
- the rocking cam 5 includes a cam surface 5a having a base circle portion 5c, a lift portion 5d and a ramp portion 5e.
- a width L1 of a contact surface of the base circle portion 5c is formed smaller than a width L2 of a contact surface of the lift portion 5d.
- the bottom end of the rocking cam 5 is formed with a cam surface 5a.
- the cam surface 5a is curved toward the intake valve 11 to form a projection, and depresses a lifter 26 of the intake valve 11 to vertically move the intake valve 11.
- the upper portion of the cam surface 5a is formed with a guide portion 5b, along which a roller shaft 7 having a roller 8 slides.
- the roller shaft 7 is connected to one end portion 10a of an arm 10 connected to a drive shaft 9.
- a roller 8 rotatably supported with the roller shaft 7 comes into contact with a rotating cam 3.
- the rocking shaft 4 is provided with a spring (not shown) for urging the rocking cam 5 toward the rotating cam 3.
- the rocking cam 5 is thereby urged toward the rotating cam 3 by the urging force of the spring, so that the peripheral surface of the roller shaft 7 is normally in contact with the guide portion 5b, and the peripheral surface of the roller 8 is normally in contact with a base surface 3a or a nose surface 3b of the rotating cam 3.
- the drive shaft 9 provided to the rocking shaft 4 is turned by a predetermined angle about the center axis O2 of the rocking shaft 4, and the roller shaft 7 is operated in synchronization with this turning movement through the arm 10.
- the roller shaft 7 can be thus moved within the guide portion 5b while keeping the distance between the center axis O3 of the roller shaft 7 and the center axis O4 of the drive shaft 9 constant with the arm 10, whereby the relative distance between the center axis O2 of the rocking shaft 4 and the roller 8 can be made variable. Therefore, the lift amount and the maximum lift timing of the intake valve 11 can be adjusted and made variable.
- the width L1 of the base circle portion 5c is small, as in the Embodiment described above, since no large load acts on this portion, a requisite strength can be secured for the base circle portion 5c. Because a large load acts on the lift portion 5d, the width L2 thereof is made larger to secure a requisite strength.
- Weight of the rocking cam 5 can be reduced because of the small width L1 of the base circle portion 5c. This results in a reduction in inertia force of the rocking cam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). This allows the whole system to be smaller while reducing wear on a contact portion of the cam surface 5a.
- Embodiment 2 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated.
- FIGs. 9 through 11 are longitudinal sectional views of the main portion of valve mechanism for an internal combustion engine according to Embodiment 3 of the present invention, illustrating a state in which the intake valve is closed.
- a rocker arm 6 has a roller 14 that comes into contact with a cam surface 5a of a rocking cam 5, a roller arm 6c for supporting the roller 14, which is operated in synchronization with the rocking motion of the rocking cam 5, and a rocker arm main body 6d that rocks in synchronization with the roller arm 6c to vertically move an intake valve 11.
- a leaf spring 28 is used to urge the roller arm 6c to the rocking cam 5 side to bring the roller 14 and the cam surface 5a of the rocking cam 5 into contact with each other.
- the cam surface 5a has a base circle portion 5c, a lift portion 5d, and a ramp portion 5e, and a width L1 of the base circle portion 5c is formed smaller than a width L2 of the lift portion 5d.
- roller arm 6c is freely movable to a predetermined position. By changing the contact position between the roller 14 provided to the roller arm 6c and the cam surface 5a of the rocking cam 5, the life amount of each valve or the like can be adjusted.
- an eccentric shaft 29 is fixedly provided to the rocker arm shaft 12 in such a manner that a center axis O7 thereof is located in parallel and eccentrically to the center axis O5 of the rocker arm shaft 12.
- the roller arm 6c of the rocker arm 6 is rotatably locked onto the eccentric shaft 29 by means of the leaf spring 28.
- the roller arm 6c has an engaging portion 6e formed at its one end.
- the engaging portion 6e engages with the outer peripheral surface of the eccentric shaft 29, and is so shaped as to be capable of sliding on the outer peripheral surface of the eccentric shaft 29.
- a fitting engagement portion 6f Formed at a position adjacent to the engaging portion 6e is a fitting engagement portion 6f with which the leaf spring 28 for integrally locking the roller arm 6c and the eccentric shaft 29 in place is brought into fitting engagement so as to prevent dislodging thereof.
- a through-hole 6g with which the roller shaft 13 supporting the roller 14 that slides on the cam surface 5a of the rocking cam 5 is brought into fitting engagement, is formed at the other end of the roller arm 6c.
- a pressing portion 6h for pressing the rocker arm main body 6d to the intake valve 11 side when the roller arm 6c rocks to the intake valve 11 side in synchronization with the rocking motion of the rocking cam 5.
- the rocker arm main body 6d of the rocker arm 6 is rockably supported and arranged on the rocker arm shaft 12, and has the valve pressing portion 6a formed at is distal end portion.
- the valve pressing portion 6a presses on the upper surface of the shim 23 fitted on the intake valve 11. Further, a contact surface 6i with which a distal end portion 28b of the leaf spring 28, which will be described later, comes into contact is formed above the valve pressing portion 6a, and a guide portion 6j pressed on by the pressing portion 6h formed in the rocker arm 6c is formed above the contact surface 6i.
- the leaf spring 28 is formed into a predetermined configuration by bending a planar spring at several locations. More specifically, the leaf spring 28 is formed in a configuration allowing fitting engagement with the fitting engagement portion 6f of the roller arm 6c and with the eccentric shaft 29, and has formed therein a locking portion 28a for integrally locking the roller arm 6c and the eccentric shaft 29 onto each other. Further, the distal end portion 28b of the leaf spring 28 on the roller arm 6c side extends to the roller 14 side and comes into contact with the contact surface 6i formed in the rocker arm main body 6d.
- leaf spring 28 is formed in such a configuration as to urge the roller arm 6c and the rocker arm main body 6d so as to spread out from each other when the roller arm 6c and the eccentric shaft 29 are integrally locked onto each other by the locking portion 28a.
- a predetermined clearance A is provided between a pressing portion 6h of the roller arm 6c and a guide portion 6j of the rocker arm main body 6d.
- roller arm 6c is integrally locked onto the eccentric shaft 29 by the leaf spring 28 so that the roller arm 6c can slide on the outer peripheral surface of the eccentric shaft 29, when the rocking cam 5 is rocked, the roller arm 6c is caused via the roller 14 and the roller shaft 13 to rock to the intake valve 11 side against the urging force of the leaf spring 28. Further, as the rocker arm 6c is rocked to the intake valve 11 side, the pressing portion 6h of the roller arm 6c presses on the guide portion 6j of the rocker arm main body 6d, causing the rocker arm main body 6d to rock to the intake valve 11 side, thereby making it possible to open and close the intake valve 11.
- roller arm 6c is urged to the rocking cam 5 side by the leaf spring 28, so the outer peripheral surface of the roller 14 provided to the roller arm 6c is held in constant contact with the cam surface 5a of the rocking cam 5.
- an actuator for rotating the rocker arm shaft 12 within a predetermined angle range about the center axis O5 is connected to one end portion of the rocker arm shaft 12.
- control means for controlling the angle of the actuator according to the operational state of the internal combustion engine.
- the eccentric shaft 29 provided to the rocker arm shaft 12 is turned by a predetermined angle about the center axis O5 of the rocker arm shaft 12. Further, when the eccentric shaft 29 is turned by the predetermined angle, the roller arm 6c operating in synchronization therewith is moved, for example, from the position indicated by the solid line in FIG. 9 to a predetermined position indicated by the chain double-dashed line in FIG. 9 . Then, once the roller arm 6c has been moved to the predetermined position, the contact point where the cam surface 5a of the rocking cam 5 and the roller 14 provided to the roller arm 6c come into contact with each other changes. The rocking amount of the rocker arm main body 6d can be thus changed, which makes it possible to adjust the lift amount or the like of the intake valve 11 that is vertically moved by the rocker arm 6.
- the predetermined clearance (A) provided between the pressing portion 6h and the guide portion 6j allows the intake valve 11 to be reliably opened/closed even when, due to a rise in the temperature of the internal combustion engine, the intake valve 11 undergoes thermal expansion to cause upward jumping of the valve.
- valve mechanism 1 for an internal combustion engine constructed as described above in which the lift amount or the like of each valve can be adjusted by making the roller arm 6c be movable to the predetermined position and changing the contact position between the roller 14 provided to the roller arm 6c and the cam surface 5a of the rocking cam 5, the roller arm 6c is urged toward the rocking cam 5 side by the leaf spring 28. Accordingly, when the roller arm 6c has been moved to the predetermined position and the contact position between the roller 14 and the cam surface 5a changes, the roller 14 of the rocker arm 6 and the cam surface 5a of the rocking cam 5 constantly come into contact with each other, thereby making it possible to prevent adhesive wear.
- the width L1 of the base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for the base circle portion 5c. Because a large load acts on the lift portion 5d, the width L2 thereof is made larger to secure a requisite strength.
- Weight of the rocking cam 5 can be reduced because of the small width L1 of the base circle portion 5c. This results in a reduction in inertia force of the rocking cam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15).
- the base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force.
- Embodiment 3 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated.
- Embodiment 3 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated.
- FIGs. 12 and 13 are longitudinal sectional views of the main portion of a valve mechanism for an internal combustion engine according to Embodiment 4 of the present invention, illustrating a state in which the intake valve is closed.
- the valve mechanism 1 for an internal combustion engine according to Embodiment 4 is capable of adjusting the lift amount or the like of each valve by making the rocking shaft 4 movable to a predetermined position.
- a roller 33 is arranged on the outer peripheral surface of the rocking shaft 4.
- the roller 33 is in contact with a guide portion 19a formed in the cylinder head main body 19 for guiding the rocking shaft 4 to a predetermined position.
- the rocking shaft 4 is provided to the cylinder head main body 19 such that, when the rocking cam 5 is pressed by a control cam 34 that will be described next, the rocking shaft 4 can move in synchronization with the rocking cam 12 within a range from a position indicated by the solid line in FIG. 12 to that indicated by the chain double-dashed line in FIG. 12 .
- the control cam 34 is fixed onto the outer peripheral surface of a control shaft 35 provided in parallel to the camshaft 2. Further, the outer peripheral portion of the control cam 34 contacts the rocking cam 5 and is formed in a configuration allowing the rocking shaft 4 to be guided to a predetermined position by rotating the control cam 34 in a predetermined angle.
- the cam surface 5a of the rocking cam 5 has a base circle portion 5c, a lift portion 5d, and a ramp portion 5e, and a width L1 of the base circle portion 5c is formed smaller than a width L2 of the lift portion 5d.
- an actuator for rotating the control shaft 35 within a predetermined angle range about a center axis O8 of the control shaft 35 is connected to one end portion of the control shaft 35.
- control means for controlling the angle of the actuator according to the operational state of the internal combustion engine.
- the rocker arm 6 which makes reciprocating motion while rocking within a predetermined range in synchronization with the rocking cam 5, is of the same construction as that of Embodiment 1. That is, the rocker arm 6 has the valve pressing portion 6a formed therein, is provided with the roller shaft 13 and the roller 14, and is rockably supported on the rocker arm shaft 12.
- the rocker arm shaft 12 is provided with the torsion spring 17 as a spring member for bringing the roller 14 and the cam surface 5a into constant contact with each other.
- the control cam 34 is rotated by a predetermined angle about the center axis O8 of the control shaft 35.
- the roller 33 is caused via the rocking cam 5 to slide on the guide portion 19a of the cylinder head main body 19 so as to be moved, for example, from the position indicated by the solid line in FIG. 12 to a predetermined position indicated by the chain double-dashed line in FIG. 12 .
- the rocking shaft 4 is moved, the position of the cam surface 5a of the rocking cam 5 changes.
- the rocking amount of the rocker arm 6 can be thus changed, which makes it possible to adjust the lift amount or the like of the intake valve 11 that is vertically moved by the rocker arm 6.
- valve mechanism 1 which makes the lift amount or the like of each valve variable by moving the rocking shaft 4 to a predetermined position
- the rocker arm 6 is urged to the rocking cam 5 side by the torsion spring 17, so even when the rocking shaft 4 has been moved to the predetermined position, and the position of the cam surface 5a of the rocking cam 5 changes, the roller 14 of the rocker arm 6 and the cam surface 5a of the rocking cam 5 constantly come into contact with each other. Adhesive wear can be thus prevented.
- the width L1 of the base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for the base circle portion 5c. Because a large load acts on the lift portion 5d, the width L2 thereof is made larger to secure a requisite strength.
- Weight of the rocking cam 5 can be reduced because of the small width L1 of the base circle portion 5c. This results in a reduction in inertia force of the rocking cam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15).
- the base circle portion 5c formed in a position apart from the center axis O2, can more contribute to the reduced inertia force.
- Embodiment 4 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated.
- FIGs. 14 and 15 are longitudinal sectional views of the main portion of a valve mechanism for an internal combustion engine according to Embodiment 5 of the present invention, illustrating a state in which the intake valve is closed.
- Embodiment 5 provides the valve mechanism 1 for an internal combustion engine in which the rotating cam 3 has a tapered configuration, and the contact position between the outer peripheral portion of the rotating cam 3 and the rocking cam 5 is changed by moving the rotating cam 3 in the direction of the center axis O1 of the camshaft 2, thereby making it possible to adjust the lift amount or the like of each valve.
- the rotating cam 3 is fixed onto the outer peripheral surface of the camshaft 2.
- the outer peripheral portion of the rotating cam 3 is constructed with the base surface 3a that is arc-shaped in plan view, and the nose surface 3b projecting from the base surface 3a.
- the base surface 3a and the nose surface 3b are formed in the tapered configuration in the direction of the center axis O1 (in the direction perpendicular to the sheet plane) of FIG. 14 .
- an actuator for moving the camshaft 2 within a predetermined range in the direction of the center axis O1 is connected to one end portion of the camshaft 2.
- control means for controlling the angle of the actuator according to the operational state of the internal combustion engine.
- the outer peripheral surface of the roller 8 provided to the rocking cam 5 rocked by the rotating cam 3 is capable of sliding on the base surface 3a and base surface 3b of the rotating cam 3 formed in the tapered configuration.
- the cam surface 5a of the rocking cam 5 has a base circle portion 5c, a lift portion 5d, and a ramp portion 5e, and a width L1 of the base circle portion 5c is formed smaller than a width L2 of the lift portion 5d.
- the rocker arm 6 which makes reciprocating motion while rocking within a predetermined range in synchronization with the rocking cam 5, is of the same construction as that of Embodiment 4. That is, the rocker arm 6 has the valve pressing portion 6a formed therein, is provided with the roller shaft 13 and the roller 14, and is rockably supported on the rocker arm shaft 12.
- the rocker arm shaft 12 is provided with the torsion spring 17 for bringing the roller 14 and the cam surface 5a into constant contact with each other.
- the rotating cam 3 moves within a predetermine range in the direction of the center axis O1 of the camshaft 2. Since the rotating cam 3 is formed in the tapered configuration, when the rotating cam 3 is moved with the predetermined range, the rocking cam 5 is caused via the roller shaft 7 and the roller 8 to move, for example, from the position indicated by the solid line in FIG. 14 to a predetermined position indicated by the double-dashed chain line in FIG. 14 . Then, when the rocking cam 5 has been moved to the predetermined position, the position of the cam surface 5a of the rocking cam 5 changes. Therefore, the rocking amount of the rocker arm 6 can be changed, which makes it possible to adjust the lift amount or the like of the intake valve 11 that is vertically moved by the rocker arm 6.
- valve mechanism 1 constructed as described above, in which the rotating cam 3 is tapered, and the lift amount or the like of each valve variable is made variable by moving the rotating cam 3 in the direction of the center axis O1 of the camshaft 2 and changing the contact position between the outer peripheral portion of the rotating cam 3 and the rocking cam 5, the rocker arm 6 is urged to the rocking cam 5 side by the torsion spring 17, so even when the rocking shaft 4 has been moved to the predetermined position, and the position of the cam surface 5a of the rocking cam 5 changes, the roller 14 of the rocker arm 6 and the cam surface 5a of the rocking cam 5 constantly come into contact with each other. Adhesive wear can be thus prevented.
- the width L1 of the base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for the base circle portion 5c. Because a large load acts on the lift portion 5d, the width L2 thereof is made larger to secure a requisite strength.
- Weight of the rocking cam 5 can be reduced because of the small width L1 of the base circle portion 5c. This results in a reduction in inertia force of the rocking cam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15).
- the base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force.
- Embodiment 5 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated.
- the present invention is applied to the variable valve mechanism 1 provided with the rocking cam 5, the present invention is not limited to this construction.
- the present invention may also be applied to any valve mechanism incapable of changing the lift amount or the like.
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Abstract
Description
- The present invention relates to a rocking cam, in particular for a valve mechanism, which includes a cam surface having a base circle portion and a lift portion, and which is disposed so as to make reciprocating motion, and relates to a valve mechanism for an internal combustion engine, which is provided with the rocking cam.
- Conventionally, this type of valve mechanism for an internal combustion engine has: a camshaft rotated by a crankshaft; a rotating cam provided to the camshaft; a rocking cam rocked by the rotating cam for reciprocating motion; and a rocker arm partly coming into contact with a cam surface of the rocking cam. When the rocking cam is rocked, the cam surface thereof allows the rocker arm to be rocked. This motion by the rocker arm presses an intake or exhaust valve to open/close the valve (See Patent Document 1).
Patent Document 1:JP-A-H7-063023
Another conventional rocking cam is disclosed in documentJP-06272525 - However, in such a conventional valve mechanism that the cam surface of the rocking cam has a base circle portion, a lift portion and a ramp portion for connecting therebetween, the cam surface requires a certain width to secure strength enough to withstand a large force acting on the cam surface. This results in an increase in weight of the rocking cam on its distal end side, causing an increase in inertia force of the rocking cam which makes reciprocating motion. Accordingly, other parts associated with the rocking cam also need to secure certain strength, causing increases in weight of the parts as well as in size of the entire system. This creates additional problem with an increase in wear and the like on a contact portion of the rocking cam.
- In the view of the above, the present invention has been made in order to solve the above-mentioned problems of the prior art. Accordingly, it is an object of the present invention to provide a rocking cam and a valve mechanism for an internal combustion engine, which can achieve reductions in size and weight as well as in wear and the like on a contact portion of the rocking cam.
- In order to attain the above object, the invention as described in Claim 1 provides a rocking cam including a cam surface having a base circle portion and a lift portion, and disposed so as to make reciprocating motion, in which a width of a contact surface of the base circle portion is formed smaller than a width of a contact surface of the lift portion
- The invention as described in
Claim 2 provides a valve mechanism for an internal combustion engine, having: a camshaft rotated by a crankshaft of the internal combustion engine; a rotating cam provided to the camshaft; a rocking shaft provided in parallel to the camshaft; and a rocking cam supported with the rocking shaft and freely rockable by the rotating cam and capable of varying a lift amount of an intake valve or an exhaust valve of the internal combustion engine, in which the rocking cam includes a cam surface having a base circle portion and a lift portion, and is disposed so as to make reciprocating motion, and a width of a contact surface of the base circle portion is formed smaller than a width of a contact surface of the lift portion. - The invention as described in
Claim 3 provides the valve mechanism for an internal combustion engine according toClaim 2, in which the rocking cam is provided with a movable rotating cam abutment portion that comes into contact with the rotating cam to transmit a drive force from the rotating cam to the rocking cam, and provided with a guide portion for guiding the rotating cam abutment portion in a certain direction; the drive force from the rotating cam is inputted to the guide portion via the rotating cam abutment portion so that the rocking cam is rocked; a variable abutment portion mechanism is provided for making a relative distance between the rotating cam abutment portion and a center axis of the rocking shaft variable by making the rotating cam abutment portion movable along the guide portion; and a lift amount of each valve is made variable by thus making the relative distance variable. - According to the invention as described in Claim 1, the rocking cam includes the cam surface having the base circle portion and the lift portion, and is disposed so as to make reciprocating motion, in which the width of the contact surface of the base circle portion is formed smaller than the width of the contact surface of the lift portion. Therefore, weight of the rocking cam can be reduced. This results in a reduction in inertia force of the rocking cam at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam.
- According to the invention as described in
Claims -
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FIG. 1 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is closed. -
FIG. 2 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is open. -
FIG. 3 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is closed. -
FIG. 4 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is open. -
FIGs. 5(a) and 5(b) are views showing a rocking cam according to Embodiment 1 of the present invention, of whichFIG. 5 (a) is a front view, andFIG. 5(b) is a bottom view. -
FIG. 6 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according toEmbodiment 2 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is closed. -
FIG. 7 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according toEmbodiment 2 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is closed. -
FIGs. 8(a) and 8(b) are views showing a rocking cam according toEmbodiment 2 of the present invention, of whichFIG. 8 (a) is a front view, andFIG. 8(b) is a bottom view. -
FIG. 9 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according toEmbodiment 3 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is closed. -
FIGs. 10(a) and 10(b) are views showing a rocking cam according toEmbodiment 3 of the present invention, of whichFIG. 10 (a) is a front view, andFIG. 10(b) is a bottom view. -
FIG. 11 is a perspective view of a rocking cam according to Embodiment 3, viewed obliquely from below. -
FIG. 12 is a longitudinal sectional view of the main portion of variable valve mechanism for an internal combustion engine according toEmbodiment 4 of the present invention, illustrating a state in which the intake valve is closed. -
FIGs. 13(a) and 13(b) are views showing a rocking cam according toEmbodiment 4 of the present invention, of whichFIG. 13 (a) is a front view, andFIG. 13(b) is a bottom view. -
FIG. 14 is a longitudinal sectional view of the main portion of variable valve mechanism for an internal combustion engine according toEmbodiment 5 of the present invention, illustrating a state in which the intake valve is closed. -
FIGs. 15(a) and 15(b) are views showing a rocking cam according toEmbodiment 5 of the present invention, of whichFIG. 15 (a) is a front view, andFIG. 15(b) is a bottom view. - Hereinafter, embodiments of the present invention will be described with reference to the drawings.
-
FIGs. 1 through 5 illustrate Embodiment 1 of the present invention. - First, the construction will be described. In
FIG. 1 , reference numeral 1 denotes a variable valve mechanism for anintake valve 11 of an internal combustion gasoline engine. The variable valve mechanism 1 has acamshaft 2 rotated by a crankshaft (not shown) of the internal combustion engine, a rotatingcam 3 provided to thecamshaft 2, arocking shaft 4 provided in parallel to thecamshaft 2, a rockingcam 5 supported on therocking shaft 4 and adapted to rock by the rotatingcam 3, and arocker arm 6 that is rocked in synchronization with therocking cam 5 to open/close theintake valve 11. - It should be noted that the construction of the variable valve mechanism 1 is the same between the
intake valve 11 and exhaust valve of the gasoline engine. Accordingly, Embodiment 1 focuses on the mechanism on theintake valve 11 side, and the description of the mechanism on the exhaust valve side is omitted. - As shown in
FIG. 1 , thecamshaft 2 is arranged with its longitudinal direction extending toward the front and back (i.e. in the direction perpendicular to the plane) ofFIG. 1 . Thecamshaft 2 is rotated about a center axis O1 at a half rotational speed of that of the crankshaft of the internal combustion engine. - Further, the rotating
cam 3 is fixed onto the outer peripheral surface of thecamshaft 2 and, as shown inFIG. 1 , the outer peripheral portion thereof is configured with abase surface 3a that is arc-shaped in plan view, and anose surface 3b projecting from thebase surface 3a. - Further, a center axis O2 of the rocking
shaft 4 is arranged in parallel to the center axis O1 of thecamshaft 2. - The rocking
cam 5 is in fitting engagement with the outer peripheral surface of the rockingshaft 4, and is supported so as to be rockable about the center axis O2 of the rockingshaft 4. Acam surface 5a for rocking therocker arm 6 is formed in the lower end portion of therocking cam 5. - As shown in
FIGs. 1 through 5 , in thecam surface 5a, there are formed an arc-shapedbase circle portion 5c around the center axis O2, alift portion 5d for rocking therocker arm 6, and aramp portion 5e connecting between thelift portion 5d and thebase circle portion 5c. - Further, as shown in
FIG. 5 , a width L1 of a contact surface of thebase circle portion 5c is formed smaller than a width L2 of a contact surface of thelift portion 5d. - Further, a
guide portion 5b as an elongate through-hole is formed at the longitudinally middle portion of the rockingcam 5. Aroller shaft 7, which has a center axis O3 in parallel to the center axis O2 of a rockingshaft 4, is movably inserted through theguide portion 5b. Provided to theroller shaft 7 is aroller 8 as a "rotating cam abutting portion" that contacts and operates in synchronization with abase surface 3a or anose surface 3b of the rotatingcam 3, for transmitting the drive force from the rotatingcam 3 to the rockingcam 5. - Further, the
guide portion 5b is formed in the shape of an elongate hole so as to guide theroller shaft 7 along its longitudinal direction over a predetermined distance, and the guiding direction at this time is inclined with respect to the radial direction of thecamshaft 2. - Further, as shown in
FIG. 1 , theroller 8 is formed in a circular shape, and is arranged on the outer peripheral surface of theroller shaft 7 so that the center axis of theroller 8 becomes the same as the center axis O3 of theroller shaft 7. The outer peripheral surface of theroller 8 is capable of rolling on thebase surface 3a andnose surface 3b of therocking cam 3. - In such manner, "the rotating cam abutment portion" which abuts the rotating
cam 3 is formed in the shape of a roller to rotate on the rotatingcam 3 face. This reduces loss of the drive force transmitted from the rotatingcam 3 to "the rotating cam abutment portion." - Incidentally, "the rotating cam abutment portion" is the
roller 8 which rotates on the rotatingcam 3 face, but is not limited to this. The rotating cam abutment portion may be the one which slides on therotating cam 3 face, as long as the drive force from therotating cam 3 is transmitted to the rockingcam 5. - Further, a
spring 15 for urging the rockingcam 5 toward therotating cam 3 side is in fitting engagement with the rockingshaft 4. Thus, the rockingcam 5 is urged toward therotating cam 3 side by the urging force of thespring 15, so that the outer peripheral surface of theroller 8 is in constant contact with thebase surface 3a ornose surface 3b of therotating cam 3. - Furthermore, the variable valve mechanism 1 is provided with "a variable abutment portion mechanism" for making the relative distance between the
roller 8 and the center axis O2 of the rockingshaft 4 variable. - "The variable abutment portion mechanism" has a
drive shaft 9 fixedly provided onto the rockingshaft 4, and anarm 10 whose oneend portion 10a is connected to theroller shaft 7 and whoseother end portion 10b is connected to thedrive shaft 9. - The
drive shaft 9 is provided to the rockingshaft 4 in such a manner that a center axis O4 thereof is located in parallel and eccentrically to the center axis O2 of the rockingshaft 4. - Further, an actuator (not shown) for rotating the rocking
shaft 4 within a predetermined angle range about the center axis O2 is connected to one end portion of the rockingshaft 4. Connected to the actuator is control means (not shown) for controlling the angle of the actuator according to the operational state of the internal combustion engine. - Thus, when the rocking
shaft 4 turns by a predetermined angle, thedrive shaft 9 turns by a predetermined angle about the center axis O2 of the rockingshaft 4, whereby the position of the center axis O4 changes relative to the center axis O2 of the rockingshaft 4. - The
arm 10 is capable of keeping the distance between the center axis O3 of theroller shaft 7 and the center axis O4 of thedrive shaft 9 constant. A through-hole 10c, with which theroller shaft 7 is fitted, is formed at the oneend portion 10a of thearm 10, and aninsertion portion 10d, into which thedrive shaft 9 is inserted and which is partially open, is formed at theother end portion 10b thereof. Accordingly, theroller shaft 7 is rotatably fitted with the through-hole 10c at the oneend portion 10a, and thedrive shaft 9 is rotatably fitted with theinsertion portion 10d at theother end portion 10b and mounted in place with apin 16 so as to prevent dislodging thereof. - Thus, when the rocking
shaft 4 is rotated by a predetermined angle by the actuator, thedrive shaft 9 provided to the rockingshaft 4 is turned by a predetermined angle about the center axis O2 of the rockingshaft 4, and theroller shaft 7 is operated in synchronization with this turning movement through thearm 10. Theroller shaft 7 can be thus moved within theguide portion 5b while keeping the distance between the center axis O3 of theroller shaft 7 and the center axis O4 of thedrive shaft 9 constant with thearm 10, whereby the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 can be made variable. - Further, the
rocker arm 6 is disposed below the rockingcam 5 while being rockably supported on therocker arm shaft 12. - Although the
rocker arm 6 is rockably supported with therocker arm shaft 12, the configuration is not limited to this. Therocker arm 6 may be rockably supported with a spherical pivot, hydraulic lash adjuster, or the like. - Further, a
valve pressing portion 6a is formed at the distal end portion of therocker arm 6 for pressing on the upper surface of ashim 23 fitted on anintake valve 11 which will be described later. - A
roller 14 is rotatably provided to theroller shaft 13, and the outer peripheral surface of theroller 14 is capable of rolling on thecam surface 5a of the rockingcam 5. - Further, a
spring 17 for urging therocker arm 6 toward the rockingcam 5 side is in fitting engagement with therocker arm shaft 12. Thus, therocker arm 6 is urged toward the rockingcam 5 side by means of thespring 17, so that the outer peripheral surface of theroller 14 is in constant contact with thecam surface 5a of the rockingcam 5. - Further, the
intake valve 11 pressed by thevalve pressing portion 6a is arranged below thevalve pressing portion 6a of therocker arm 6 so as to be vertically movable. - The
intake valve 11 has acollet 20 and anupper retainer 21 that are provided in its upper portion. Avalve spring 22 is arranged below theupper retainer 21. Theintake valve 11 is urged toward therocker arm 6 side by the urging force of thevalve spring 22. Further, theshim 23 is fitted on the upper end portion of theintake valve 11. - Accordingly, the
intake valve 11 can be vertically moved by rocking therocker arm 6 in synchronization with the rocking motion of the rockingcam 5. Thus, by making the relative distance between the center axis O2 of the rockingcam 4 and theroller 8 variable to adjust the rocking start position of the rockingcam 5, the lift amount and the maximum lift timing of theintake valve 11 can be adjusted and made variable through therocker arm 6. - Operation of the variable valve mechanism 1 constructed as above will next be described.
- First, detailed description will be made on the operation of the variable valve mechanism 1 for an internal combustion engine when the maximum lift amount is required, with reference to
FIGs. 1 and2 . - Here,
FIG. 1 is a longitudinal sectional view of the main portion of variable valve mechanism 1 of the internal combustion engine according to Embodiment 1 of the present invention when the maximum lift amount is required, illustrating the state in which theintake valve 11 is closed.FIG. 2 is a longitudinal sectional view of the main portion of the variable valve mechanism 1 of the internal combustion engine according toEmbodiment 2 of the present invention when the maximum lift amount is required, illustrating the state in which the intake valve is open. - First, as shown in
FIG. 1 , theroller shaft 7 is moved to the rotating cam 3-side end portion of theguide portion 5b, thereby changing the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8. That is, the rockingshaft 4 is turned by a predetermined angle by the actuator, causing thedrive shaft 9 to move in the circumferential direction of the rockingshaft 4. Thus, theroller shaft 7 is operated in synchronization with this movement via thearm 10 so as to be moved to the rotating cam 3-side end portion of theguide portion 5b, whereby the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 changes. - Further, as shown in
FIG. 1 , while theroller 8 provided to the rockingcam 5 is in contact with thebase surface 3a of therotating cam 3, the rockingcam 5 is not rocked to theintake valve 11 side, therocker arm 6 is urged to the rockingcam 5 side by the urging force of thespring 17, and also theintake valve 11 is urged to therocker arm 6 side by the urging force of thevalve spring 22. Thus, the lift of theintake valve 11 does not occur and theintake valve 11 is brought into a closed state. - In this state, the
roller 14 is located at the position corresponding to thebase circle portion 5c of thecam surface 5a of the rockingcam 5. Since no large abutment force acts between theroller 14 and thebase circle portion 5c in the valve closure state, a sufficient durability can be secured even through the width L1 of thebase circle portion 5c is small. - Then, when the
rotating cam 3 is rotated via thecamshaft 2 due to the rotation of the crankshaft of the internal combustion engine, as shown inFIG. 2 , theroller 8 is pressed on by thenose surface 3b. As theroller 8 is further pressed, the rockingcam 5 is pressed via theroller shaft 7, causing the rockingcam 5 to rock counterclockwise inFIG. 1 against the urging force of thespring 15. - Through the rocking movement of the rocking
cam 5, the portion of thecam surface 5a of the rockingcam 5 which presses theroller 14 changes from thebase circle portion 5c to thelift portion 5d via theramp portion 5e, and therocker arm 6 is turned via theroller shaft 13 to theintake valve 11 side. In this way, a relative distance M between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 as shown inFIG. 1 is largely changed to a relative distance N between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 as shown inFIG. 2 . Therocker arm 6 thus undergoes large rocking movement to theintake valve 6 side. - Then, the
valve pressing portion 6a formed at the distal end portion of therocker arm 6 that has thus undergone large rocking movement to theintake valve 11 side presses on the upper surface of theshim 23 to push down theintake valve 11 by a large distance. As described above, by moving theroller shaft 7 to the end portion of theguide portion 5b in therotating cam 3 side to make the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 variable, the relative distance between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 can be largely changed, whereby theintake valve 11 can be pushed down by a large distance to bring theintake valve 11 into an open state at the maximum lift amount. - In the case where the
intake valve 11 is opened in this way, the width L2 of thelift portion 5d is made large because a large reaction force acts on thecam surface 5a of the rockingcam 5, thereby making it possible to secure strength. - Next, detailed description will be made on the operation of the variable valve mechanism 1 of the internal combustion engine when the minimum lift amount is required, with reference to
FIG. 3 and4 . - Here,
FIG. 3 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is closed.FIG. 4 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine according to Embodiment 1 of the present invention when the minimum lift amount is required, illustrating the state in which the intake valve is open. - First, as shown in
FIG. 3 , in the state as shown inFIG. 1 where theroller shaft 7 is retained at the rotating cam 3-side end portion, theroller shaft 7 is moved to the rocking shaft 4-side end portion of theguide portion 5b, thereby changing the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8. - That is, the rocking
shaft 4 is turned within a predetermined angle range by the actuator, causing thedrive shaft 9 to move in the circumferential direction of the rockingshaft 4. Accordingly, theroller shaft 7 is operated in synchronization with this movement via thearm 10 so that theroller shaft 7 is moved to the rocking shaft 4-side end portion of theguide portion 5b from the state where it is retained at the rotating cam 3-side end portion, whereby the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 decreases. Then, the rockingcam 5 turns from the position as shown inFIG. 1 to the position as shown inFIG. 3 due to the urging force of thespring 15. - Further, as shown in
FIG. 3 , while theroller 8 provided to the rockingcam 5 is in contact with thebase surface 3a of therotating cam 3, the rockingcam 5 is not rocked to theintake valve 11 side, therocker arm 6 is urged to the rockingcam 5 side by the urging force of thespring 17, and also theintake valve 11 is urged to therocker arm 6 side by the urging force of thevalve spring 22. Thus, the lift of theintake valve 11 does not occur and theintake valve 11 is brought into a closed state. - When the
rotating cam 3 is rotated via thecamshaft 2 due to the rotation of the crankshaft of the internal combustion engine, as shown inFIG. 4 , theroller 8 is pressed on by thenose surface 3b, and the rockingcam 5 is pressed via theroller shaft 7, causing the rockingcam 5 to rock counterclockwise inFIG. 3 against the urging force of thespring 15. - As the rocking
cam 5 is further rocked, theroller 14 in contact with the rocking shaft 4-side distal end portion of thecam surface 5a of the rockingcam 5 is pushed down to theintake valve 11 side by using the range of thecam surface 5a from the rocking shaft 4-side distal end portion to the center portion thereof, whereby therocker arm 6 is rocked to theintake valve 11 side via theroller shaft 13. In this way, a relative distance P between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 as shown inFIG. 3 undergoes a small change to become a relative distance Q between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 as shown inFIG. 4 . Therocker arm 6 thus undergoes small rocking movement to the intake valve side. - Then, the
valve pressing portion 6a formed at the distal end portion of therocker arm 6 that has thus undergone small rocking movement to theintake valve 11 side presses on the upper surface of theshim 23 to push down theintake valve 11 by a small distance. In this way, by moving theroller shaft 7 to the rocking shaft 4-side end portion of theguide portion 5b to make the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 variable, the relative distance between the center axis O2 of the rockingshaft 4 and theroller 14 in contact with thecam surface 5a of the rockingcam 5 can be subjected to a small change to push down theintake valve 11 by a small distance, whereby, in Embodiment 1, theintake valve 11 can be brought into an open state at the minimum lift amount. - Further, although the width L1 of the
base circle portion 5c is small, since no large load acts on this portion, a requisite strength can be secured for thebase circle portion 5c. Because a large load acts on thelift portion 5d, the width L2 thereof is made larger to secure a requisite strength. - Weight of the rocking
cam 5 can be reduced because of the small width L1 of thebase circle portion 5c. This results in a reduction in inertia force of the rockingcam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). This allows the whole system to be smaller while reducing wear on a contact portion of thecam surface 5a. - Particularly, the
base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force. - In the variable valve mechanism 1 of the internal combustion engine constructed as described above, the rocking
cam 5 is provided with theroller 8 or the rotating cam abutment portion that comes into contact with therotating cam 3 to transmit the drive force from the rotating cam to the rockingcam 5. The valve mechanism 1 is provided with the variable abutment portion mechanism for making the relative distance between theroller 8 and the center axis O2 of the rockingshaft 4 variable by making theroller 8 movable; the lift amount or the like of each valve is made variable by thus making the relative distance variable, whereby the structure can be simplified to achieve low-cost construction. - Further, the load from the
rotating cam 3 is input to theroller 8, and the load is directly transmitted from theroller 8 to theguide portion 5a of the rockingcam 5. Then, the load is transmitted from the rockingcam 5 to theintake valve 11 via therocker arm 6. Thus, no large load acts on thearm 10 that supports theroller 8, and since thearm 10 serves the sole function of moving theroller 8 along theguide portion 5a, not so large strength is required for thearm 10. -
FIGs. 6 through 8 illustrateEmbodiment 2 of the present invention.FIG. 6 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine when the maximum lift amount is required, illustrating the state in which the intake valve is closed.FIG. 7 is a longitudinal sectional view of the main portion of the variable valve mechanism for the internal combustion engine when the minimum lift amount is required, illustrating the state in which the intake valve is closed. - In
Embodiment 2, therocker arm 6 which opens and closes anintake valve 11 as in Embodiment 1 is not provided, but arocking cam 5 directly moves theintake valve 11 upward and downward to open and close theintake valve 11. - As shown in
FIGs. 6 through 8 , the rockingcam 5 is formed in the shape of a comma-shaped bead. The rockingcam 5 is fitted on the peripheral surface of a rockingshaft 4 and supported so as to be rockable about the center axis O2 of the rockingshaft 4. - More specifically, as shown in
FIG. 8 , the rockingcam 5 includes acam surface 5a having abase circle portion 5c, alift portion 5d and aramp portion 5e. A width L1 of a contact surface of thebase circle portion 5c is formed smaller than a width L2 of a contact surface of thelift portion 5d. Further, the bottom end of the rockingcam 5 is formed with acam surface 5a. Thecam surface 5a is curved toward theintake valve 11 to form a projection, and depresses alifter 26 of theintake valve 11 to vertically move theintake valve 11. The upper portion of thecam surface 5a is formed with aguide portion 5b, along which aroller shaft 7 having aroller 8 slides. - The
roller shaft 7 is connected to oneend portion 10a of anarm 10 connected to adrive shaft 9. Aroller 8 rotatably supported with theroller shaft 7 comes into contact with arotating cam 3. - The rocking
shaft 4 is provided with a spring (not shown) for urging the rockingcam 5 toward therotating cam 3. The rockingcam 5 is thereby urged toward therotating cam 3 by the urging force of the spring, so that the peripheral surface of theroller shaft 7 is normally in contact with theguide portion 5b, and the peripheral surface of theroller 8 is normally in contact with abase surface 3a or anose surface 3b of therotating cam 3. - There is provided, below the
cam surface 5a of the rockingcam 5, thelifter 26 attached on theintake valve 11. Thus, the swinging motion of the rockingcam 5 directly moves theintake valve 11 upward and downward. - Thus, when the rocking
shaft 4 is rotated by a predetermined angle by the actuator, thedrive shaft 9 provided to the rockingshaft 4 is turned by a predetermined angle about the center axis O2 of the rockingshaft 4, and theroller shaft 7 is operated in synchronization with this turning movement through thearm 10. Theroller shaft 7 can be thus moved within theguide portion 5b while keeping the distance between the center axis O3 of theroller shaft 7 and the center axis O4 of thedrive shaft 9 constant with thearm 10, whereby the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 can be made variable. Therefore, the lift amount and the maximum lift timing of theintake valve 11 can be adjusted and made variable. - As shown in
FIG. 6 , when theroller shaft 7 is displaced to the distal end portion of theguide portion 5b so that the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 is made variable, theintake valve 11 is depressed with thecam surface 5a of the rockingcam 5 by a larger amount. A maximum lift amount is thus obtained inEmbodiment 2. - As shown in
FIG. 7 , when theroller shaft 7 is displaced to the rockingshaft 4 side of theguide portion 5b so that the relative distance between the center axis O2 of the rockingshaft 4 and theroller 8 is made variable, theintake valve 11 is depressed with thecam surface 5a of the rockingcam 5 by a smaller amount. A minimum lift amount is thus obtained inEmbodiment 2. - Further, although the width L1 of the
base circle portion 5c is small, as in the Embodiment described above, since no large load acts on this portion, a requisite strength can be secured for thebase circle portion 5c. Because a large load acts on thelift portion 5d, the width L2 thereof is made larger to secure a requisite strength. - Weight of the rocking
cam 5 can be reduced because of the small width L1 of thebase circle portion 5c. This results in a reduction in inertia force of the rockingcam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). This allows the whole system to be smaller while reducing wear on a contact portion of thecam surface 5a. - Otherwise,
Embodiment 2 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated. -
FIGs. 9 through 11 are longitudinal sectional views of the main portion of valve mechanism for an internal combustion engine according toEmbodiment 3 of the present invention, illustrating a state in which the intake valve is closed. - In
Embodiment 3, arocker arm 6 has aroller 14 that comes into contact with acam surface 5a of a rockingcam 5, aroller arm 6c for supporting theroller 14, which is operated in synchronization with the rocking motion of the rockingcam 5, and a rocker armmain body 6d that rocks in synchronization with theroller arm 6c to vertically move anintake valve 11. - A
leaf spring 28 is used to urge theroller arm 6c to the rockingcam 5 side to bring theroller 14 and thecam surface 5a of the rockingcam 5 into contact with each other. - As shown in
FIG. 10 , as in the Embodiments described above, thecam surface 5a has abase circle portion 5c, alift portion 5d, and aramp portion 5e, and a width L1 of thebase circle portion 5c is formed smaller than a width L2 of thelift portion 5d. - Further, the
roller arm 6c is freely movable to a predetermined position. By changing the contact position between theroller 14 provided to theroller arm 6c and thecam surface 5a of the rockingcam 5, the life amount of each valve or the like can be adjusted. - Specifically, as shown in
FIG. 9 , aneccentric shaft 29 is fixedly provided to therocker arm shaft 12 in such a manner that a center axis O7 thereof is located in parallel and eccentrically to the center axis O5 of therocker arm shaft 12. Theroller arm 6c of therocker arm 6 is rotatably locked onto theeccentric shaft 29 by means of theleaf spring 28. - The
roller arm 6c has an engagingportion 6e formed at its one end. The engagingportion 6e engages with the outer peripheral surface of theeccentric shaft 29, and is so shaped as to be capable of sliding on the outer peripheral surface of theeccentric shaft 29. Formed at a position adjacent to the engagingportion 6e is afitting engagement portion 6f with which theleaf spring 28 for integrally locking theroller arm 6c and theeccentric shaft 29 in place is brought into fitting engagement so as to prevent dislodging thereof. Further, a through-hole 6g, with which theroller shaft 13 supporting theroller 14 that slides on thecam surface 5a of the rockingcam 5 is brought into fitting engagement, is formed at the other end of theroller arm 6c. Formed below the through-hole 6g is apressing portion 6h for pressing the rocker armmain body 6d to theintake valve 11 side when theroller arm 6c rocks to theintake valve 11 side in synchronization with the rocking motion of the rockingcam 5. - Further, the rocker arm
main body 6d of therocker arm 6 is rockably supported and arranged on therocker arm shaft 12, and has thevalve pressing portion 6a formed at is distal end portion. Thevalve pressing portion 6a presses on the upper surface of theshim 23 fitted on theintake valve 11. Further, acontact surface 6i with which adistal end portion 28b of theleaf spring 28, which will be described later, comes into contact is formed above thevalve pressing portion 6a, and a guide portion 6j pressed on by thepressing portion 6h formed in therocker arm 6c is formed above thecontact surface 6i. - Further, the
leaf spring 28 is formed into a predetermined configuration by bending a planar spring at several locations. More specifically, theleaf spring 28 is formed in a configuration allowing fitting engagement with thefitting engagement portion 6f of theroller arm 6c and with theeccentric shaft 29, and has formed therein a lockingportion 28a for integrally locking theroller arm 6c and theeccentric shaft 29 onto each other. Further, thedistal end portion 28b of theleaf spring 28 on theroller arm 6c side extends to theroller 14 side and comes into contact with thecontact surface 6i formed in the rocker armmain body 6d. - Further, the
leaf spring 28 is formed in such a configuration as to urge theroller arm 6c and the rocker armmain body 6d so as to spread out from each other when theroller arm 6c and theeccentric shaft 29 are integrally locked onto each other by the lockingportion 28a. - Further, a predetermined clearance A is provided between a
pressing portion 6h of theroller arm 6c and a guide portion 6j of the rocker armmain body 6d. - Thus, since the
roller arm 6c is integrally locked onto theeccentric shaft 29 by theleaf spring 28 so that theroller arm 6c can slide on the outer peripheral surface of theeccentric shaft 29, when the rockingcam 5 is rocked, theroller arm 6c is caused via theroller 14 and theroller shaft 13 to rock to theintake valve 11 side against the urging force of theleaf spring 28. Further, as therocker arm 6c is rocked to theintake valve 11 side, thepressing portion 6h of theroller arm 6c presses on the guide portion 6j of the rocker armmain body 6d, causing the rocker armmain body 6d to rock to theintake valve 11 side, thereby making it possible to open and close theintake valve 11. - Further, the
roller arm 6c is urged to the rockingcam 5 side by theleaf spring 28, so the outer peripheral surface of theroller 14 provided to theroller arm 6c is held in constant contact with thecam surface 5a of the rockingcam 5. - Further, an actuator (not shown) for rotating the
rocker arm shaft 12 within a predetermined angle range about the center axis O5 is connected to one end portion of therocker arm shaft 12. Connected to the actuator is control means (not shown) for controlling the angle of the actuator according to the operational state of the internal combustion engine. - Thus, when the
rocker arm shaft 12 is rotated by a predetermined angle by the actuator, theeccentric shaft 29 provided to therocker arm shaft 12 is turned by a predetermined angle about the center axis O5 of therocker arm shaft 12. Further, when theeccentric shaft 29 is turned by the predetermined angle, theroller arm 6c operating in synchronization therewith is moved, for example, from the position indicated by the solid line inFIG. 9 to a predetermined position indicated by the chain double-dashed line inFIG. 9 . Then, once theroller arm 6c has been moved to the predetermined position, the contact point where thecam surface 5a of the rockingcam 5 and theroller 14 provided to theroller arm 6c come into contact with each other changes. The rocking amount of the rocker armmain body 6d can be thus changed, which makes it possible to adjust the lift amount or the like of theintake valve 11 that is vertically moved by therocker arm 6. - Further, even in the case where a predetermined clearance is not provided between the
valve pressing portion 6a of the rocker armmain body 6d and theintake valve 11, the predetermined clearance (A) provided between thepressing portion 6h and the guide portion 6j allows theintake valve 11 to be reliably opened/closed even when, due to a rise in the temperature of the internal combustion engine, theintake valve 11 undergoes thermal expansion to cause upward jumping of the valve. - Also with the valve mechanism 1 for an internal combustion engine constructed as described above, in which the lift amount or the like of each valve can be adjusted by making the
roller arm 6c be movable to the predetermined position and changing the contact position between theroller 14 provided to theroller arm 6c and thecam surface 5a of the rockingcam 5, theroller arm 6c is urged toward the rockingcam 5 side by theleaf spring 28. Accordingly, when theroller arm 6c has been moved to the predetermined position and the contact position between theroller 14 and thecam surface 5a changes, theroller 14 of therocker arm 6 and thecam surface 5a of the rockingcam 5 constantly come into contact with each other, thereby making it possible to prevent adhesive wear. - Further, although the width L1 of the
base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for thebase circle portion 5c. Because a large load acts on thelift portion 5d, the width L2 thereof is made larger to secure a requisite strength. - Weight of the rocking
cam 5 can be reduced because of the small width L1 of thebase circle portion 5c. This results in a reduction in inertia force of the rockingcam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). - Particularly, the
base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force. - Otherwise,
Embodiment 3 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated. - Otherwise,
Embodiment 3 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated. -
FIGs. 12 and13 are longitudinal sectional views of the main portion of a valve mechanism for an internal combustion engine according toEmbodiment 4 of the present invention, illustrating a state in which the intake valve is closed. - The valve mechanism 1 for an internal combustion engine according to
Embodiment 4 is capable of adjusting the lift amount or the like of each valve by making the rockingshaft 4 movable to a predetermined position. - Specifically, as shown in
FIG. 12 , aroller 33 is arranged on the outer peripheral surface of the rockingshaft 4. Theroller 33 is in contact with aguide portion 19a formed in the cylinder headmain body 19 for guiding the rockingshaft 4 to a predetermined position. Further, the rockingshaft 4 is provided to the cylinder headmain body 19 such that, when the rockingcam 5 is pressed by acontrol cam 34 that will be described next, the rockingshaft 4 can move in synchronization with the rockingcam 12 within a range from a position indicated by the solid line inFIG. 12 to that indicated by the chain double-dashed line inFIG. 12 . - The
control cam 34 is fixed onto the outer peripheral surface of acontrol shaft 35 provided in parallel to thecamshaft 2. Further, the outer peripheral portion of thecontrol cam 34 contacts the rockingcam 5 and is formed in a configuration allowing the rockingshaft 4 to be guided to a predetermined position by rotating thecontrol cam 34 in a predetermined angle. - As shown in
FIG. 13 , thecam surface 5a of the rockingcam 5 has abase circle portion 5c, alift portion 5d, and aramp portion 5e, and a width L1 of thebase circle portion 5c is formed smaller than a width L2 of thelift portion 5d. - Further, an actuator (not shown) for rotating the
control shaft 35 within a predetermined angle range about a center axis O8 of thecontrol shaft 35 is connected to one end portion of thecontrol shaft 35. Connected to the actuator is control means (not shown) for controlling the angle of the actuator according to the operational state of the internal combustion engine. - Further, the
rocker arm 6, which makes reciprocating motion while rocking within a predetermined range in synchronization with the rockingcam 5, is of the same construction as that of Embodiment 1. That is, therocker arm 6 has thevalve pressing portion 6a formed therein, is provided with theroller shaft 13 and theroller 14, and is rockably supported on therocker arm shaft 12. - Further, as in Embodiment 1, the
rocker arm shaft 12 is provided with thetorsion spring 17 as a spring member for bringing theroller 14 and thecam surface 5a into constant contact with each other. - Thus, when the
control shaft 35 is turned by a predetermined angle by the actuator, thecontrol cam 34 is rotated by a predetermined angle about the center axis O8 of thecontrol shaft 35. When thecontrol cam 34 is rotated by the predetermined angle, by thecontrol cam 34, theroller 33 is caused via the rockingcam 5 to slide on theguide portion 19a of the cylinder headmain body 19 so as to be moved, for example, from the position indicated by the solid line inFIG. 12 to a predetermined position indicated by the chain double-dashed line inFIG. 12 . Then, as the rockingshaft 4 is moved, the position of thecam surface 5a of the rockingcam 5 changes. The rocking amount of therocker arm 6 can be thus changed, which makes it possible to adjust the lift amount or the like of theintake valve 11 that is vertically moved by therocker arm 6. - Also with the valve mechanism 1 constructed as described above, which makes the lift amount or the like of each valve variable by moving the rocking
shaft 4 to a predetermined position, therocker arm 6 is urged to the rockingcam 5 side by thetorsion spring 17, so even when the rockingshaft 4 has been moved to the predetermined position, and the position of thecam surface 5a of the rockingcam 5 changes, theroller 14 of therocker arm 6 and thecam surface 5a of the rockingcam 5 constantly come into contact with each other. Adhesive wear can be thus prevented. - Further, although the width L1 of the
base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for thebase circle portion 5c. Because a large load acts on thelift portion 5d, the width L2 thereof is made larger to secure a requisite strength. - Weight of the rocking
cam 5 can be reduced because of the small width L1 of thebase circle portion 5c. This results in a reduction in inertia force of the rockingcam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). - Particularly, the
base circle portion 5c, formed in a position apart from the center axis O2, can more contribute to the reduced inertia force. - Otherwise,
Embodiment 4 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated. -
FIGs. 14 and15 are longitudinal sectional views of the main portion of a valve mechanism for an internal combustion engine according toEmbodiment 5 of the present invention, illustrating a state in which the intake valve is closed. -
Embodiment 5 provides the valve mechanism 1 for an internal combustion engine in which therotating cam 3 has a tapered configuration, and the contact position between the outer peripheral portion of therotating cam 3 and the rockingcam 5 is changed by moving therotating cam 3 in the direction of the center axis O1 of thecamshaft 2, thereby making it possible to adjust the lift amount or the like of each valve. - Specifically, as shown in
FIG. 14 , the rotatingcam 3 is fixed onto the outer peripheral surface of thecamshaft 2. The outer peripheral portion of therotating cam 3 is constructed with thebase surface 3a that is arc-shaped in plan view, and thenose surface 3b projecting from thebase surface 3a. Thebase surface 3a and thenose surface 3b are formed in the tapered configuration in the direction of the center axis O1 (in the direction perpendicular to the sheet plane) ofFIG. 14 . - Further, an actuator (not shown) for moving the
camshaft 2 within a predetermined range in the direction of the center axis O1 is connected to one end portion of thecamshaft 2. Connected to the actuator is control means (not shown) for controlling the angle of the actuator according to the operational state of the internal combustion engine. - Further, the outer peripheral surface of the
roller 8 provided to the rockingcam 5 rocked by the rotatingcam 3 is capable of sliding on thebase surface 3a andbase surface 3b of therotating cam 3 formed in the tapered configuration. - Further, as shown in
FIG. 15 , thecam surface 5a of the rockingcam 5 has abase circle portion 5c, alift portion 5d, and aramp portion 5e, and a width L1 of thebase circle portion 5c is formed smaller than a width L2 of thelift portion 5d. - Further, the
rocker arm 6, which makes reciprocating motion while rocking within a predetermined range in synchronization with the rockingcam 5, is of the same construction as that ofEmbodiment 4. That is, therocker arm 6 has thevalve pressing portion 6a formed therein, is provided with theroller shaft 13 and theroller 14, and is rockably supported on therocker arm shaft 12. - Further, as in
Embodiment 4, therocker arm shaft 12 is provided with thetorsion spring 17 for bringing theroller 14 and thecam surface 5a into constant contact with each other. - Thus, when the
camshaft 2 moves within a predetermined range in the direction of the center axis O1 by the actuator, the rotatingcam 3 moves within a predetermine range in the direction of the center axis O1 of thecamshaft 2. Since therotating cam 3 is formed in the tapered configuration, when therotating cam 3 is moved with the predetermined range, the rockingcam 5 is caused via theroller shaft 7 and theroller 8 to move, for example, from the position indicated by the solid line inFIG. 14 to a predetermined position indicated by the double-dashed chain line inFIG. 14 . Then, when the rockingcam 5 has been moved to the predetermined position, the position of thecam surface 5a of the rockingcam 5 changes. Therefore, the rocking amount of therocker arm 6 can be changed, which makes it possible to adjust the lift amount or the like of theintake valve 11 that is vertically moved by therocker arm 6. - Also with the valve mechanism 1 constructed as described above, in which the
rotating cam 3 is tapered, and the lift amount or the like of each valve variable is made variable by moving therotating cam 3 in the direction of the center axis O1 of thecamshaft 2 and changing the contact position between the outer peripheral portion of therotating cam 3 and the rockingcam 5, therocker arm 6 is urged to the rockingcam 5 side by thetorsion spring 17, so even when the rockingshaft 4 has been moved to the predetermined position, and the position of thecam surface 5a of the rockingcam 5 changes, theroller 14 of therocker arm 6 and thecam surface 5a of the rockingcam 5 constantly come into contact with each other. Adhesive wear can be thus prevented. - Further, although the width L1 of the
base circle portion 5c is small, as in the Embodiments described above, since no large load acts on this portion, a requisite strength can be secured for thebase circle portion 5c. Because a large load acts on thelift portion 5d, the width L2 thereof is made larger to secure a requisite strength. - Weight of the rocking
cam 5 can be reduced because of the small width L1 of thebase circle portion 5c. This results in a reduction in inertia force of the rockingcam 5 at the time of rocking movement, as well as in a reduction in weight of parts associated with the rocking cam 5 (e.g. spring 15). - Particularly, the
base circle portion 5c is formed in a position apart from the center axis O2, and therefore can more contribute to the reduced inertia force. - Otherwise,
Embodiment 5 is of the same construction and operation as Embodiment 1 of the present invention, so repetitive description will not be repeated. - It should be noted that while, in the Embodiments described above, the present invention is applied to the variable valve mechanism 1 provided with the rocking
cam 5, the present invention is not limited to this construction. The present invention may also be applied to any valve mechanism incapable of changing the lift amount or the like. -
- 1:
- variable valve mechanism
- 2:
- camshaft
- 3:
- rotating cam
- 4:
- rocking shaft
- 5:
- rocking cam
- 5a:
- cam surface
- 5b:
- guide portion
- 5c:
- base circle portion
- 5d:
- lift portion
- 5e:
- ramp portion
- 6:
- rocker arm
- 7:
- roller shaft
- 8:
- roller (rotating cam abutting portion)
- 9:
- drive shaft
- 10:
- arm (variable abutment portion mechanism)
- L1:
- width of base circle portion
- L2:
- width of lift portion
Claims (3)
- Rocking cam (5), in particular for a valve mechanism for an internal combustion engine, comprising a cam surface (5a) having a base circle portion (5c) and a lift portion (5d), and being disposed so as to make reciprocating motion, characterized in that a width (L1) of a contact surface of the base circle portion (5c) is formed smaller than a width (L2) of a contact surface of the lift portion (5d).
- Valve mechanism (1) for an internal combustion engine, comprising: a camshaft (2) rotated by a crankshaft of the internal combustion engine; a rotating cam (3) provided to the camshaft (2); a rocking shaft (4) provided in parallel to the camshaft (2); and a rocking cam (5) according to claim 1, supported with the rocking shaft (4) and freely rockable by the rotating cam (3), and capable of varying a lift amount of an intake valve (11) or an exhaust valve of the internal combustion engine.
- Valve mechanism (1) for an internal combustion engine according to claim 2, wherein the rocking cam (5) is provided with a movable rotating cam abutting portion (8) that comes into contact with the rotating cam (3) to transmit a drive force from the rotating cam (3) to the rocking cam (5), and is provided with a guide portion (5b) for guiding the rotating cam abutment portion (8) in a certain direction,
wherein the drive force from the rotating cam (3) is inputted to the guide portion (5b) via the rotating cam abutment portion (8) so that the rocking cam (5) is rocked,
and wherein a variable abutment portion mechanism (9, 10) is provided for making a relative distance between the rotating cam abutment portion (8) and a center axis (02) of the rocking shaft (4) variable by making the rotating cam abutment portion (8) movable along the guide portion (5b); and a lift amount of each valve (11) is made variable by thus making the relative distance variable.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/JP2004/012193 WO2006021997A1 (en) | 2004-08-25 | 2004-08-25 | Oscillating cam and dynamic valve mechanism of internal combustion engine |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1783332A1 EP1783332A1 (en) | 2007-05-09 |
EP1783332A4 EP1783332A4 (en) | 2010-06-02 |
EP1783332B1 true EP1783332B1 (en) | 2011-04-27 |
Family
ID=35967220
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04772154A Expired - Lifetime EP1783332B1 (en) | 2004-08-25 | 2004-08-25 | Oscillating cam and dynamic valve mechanism of internal combustion engine |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1783332B1 (en) |
AT (1) | ATE507371T1 (en) |
CA (1) | CA2541726A1 (en) |
DE (1) | DE602004032479D1 (en) |
WO (1) | WO2006021997A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102006018510A1 (en) * | 2006-04-21 | 2007-10-25 | Schaeffler Kg | Swinging arm for stroke-variable valve gear of internal combustion engine, has stroke area, where maximum width of stroke area is formed larger or equal to maximum width of idle-stroke area and larger than minimum width of idle-stroke area |
DE102007033821B4 (en) * | 2007-07-18 | 2013-10-31 | Hydraulik-Ring Gmbh | Working curve of a variable valve train |
CN103089365B (en) * | 2013-02-28 | 2015-05-06 | 长城汽车股份有限公司 | Actuating mechanism of variable valve stroke drive device for engine |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3380582B2 (en) * | 1993-03-23 | 2003-02-24 | マツダ株式会社 | Engine valve timing control device |
JPH07133709A (en) * | 1993-09-17 | 1995-05-23 | Mazda Motor Corp | Engine valve timing variable equipment |
-
2004
- 2004-08-25 AT AT04772154T patent/ATE507371T1/en not_active IP Right Cessation
- 2004-08-25 EP EP04772154A patent/EP1783332B1/en not_active Expired - Lifetime
- 2004-08-25 CA CA002541726A patent/CA2541726A1/en not_active Abandoned
- 2004-08-25 WO PCT/JP2004/012193 patent/WO2006021997A1/en active Application Filing
- 2004-08-25 DE DE602004032479T patent/DE602004032479D1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
DE602004032479D1 (en) | 2011-06-09 |
CA2541726A1 (en) | 2006-03-02 |
ATE507371T1 (en) | 2011-05-15 |
WO2006021997A1 (en) | 2006-03-02 |
EP1783332A1 (en) | 2007-05-09 |
EP1783332A4 (en) | 2010-06-02 |
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