EP0777039A1 - Valve drive apparatus for an internal combustion engine having a convex shim between a cam and a valve - Google Patents
Valve drive apparatus for an internal combustion engine having a convex shim between a cam and a valve Download PDFInfo
- Publication number
- EP0777039A1 EP0777039A1 EP96119089A EP96119089A EP0777039A1 EP 0777039 A1 EP0777039 A1 EP 0777039A1 EP 96119089 A EP96119089 A EP 96119089A EP 96119089 A EP96119089 A EP 96119089A EP 0777039 A1 EP0777039 A1 EP 0777039A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- shim
- cam
- valve
- drive apparatus
- lifter
- 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.)
- Granted
Links
Images
Classifications
-
- 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
-
- 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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
- F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
- F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
- F01L13/0042—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction with cams being profiled in axial and radial direction
Definitions
- the present invention relates to a valve drive apparatus for an internal combustion engine and, more particularly, to a valve drive apparatus having a shim interposed between a three-dimensional cam and a lifter.
- variable valve timing mechanism which varies a valve operation timing and an amount of valve lift in response to an operational condition of an internal combustion engine such as an engine revolution speed or engine load.
- the variable valve timing mechanism allows improvement in engine output and specific fuel consumption and reduction in exhaust emission.
- a valve drive apparatus used in the variable valve timing mechanism comprises a three-dimensional (3-D) cam.
- the 3-D cam has a slanting surface which is inclined with respect to the rotational axis of the 3-D cam, and is movable along the rotational axis.
- Valve operation timing and an amount of valve lift are optimized by controlling an amount of shift of the 3-D cam along the rotational axis.
- FIG.1 shows the valve drive apparatus 1 disclosed in the above-mentioned Japanese Laid-Open Utility Model Application.
- the valve drive apparatus 1 generally comprises a 3-D cam 2, a valve 3, a lifter 4 and a shim 5.
- the 3-D cam 2 comprises a cam portion and a cam shaft 7.
- a slanting surface 8 is formed on the cam portion.
- the slanting surface 8 of the cam portion 6 is inclined with respect to the rotational axis of the cam shaft 7 by an angle ⁇ .
- the 3-D cam 2 is movable in directions indicated by arrows X1 and X2 by an actuator not shown in the figure.
- the valve 3 is provided to an intake port or exhaust port of a cylinder head 10 of an engine.
- the valve 3 opens or closes the intake port or the exhaust port by being reciprocated by rotation of the 3-D cam 2.
- a retainer 9 is provided above the valve 3.
- the retainer 9 is urged by a spring 14 in a direction toward the cam 2.
- the valve 3 is urged by the spring 14 in the direction toward the cam 2.
- the valve 3 reciprocates in directions indicated by arrows Z1 and Z2.
- the direction Z1 may be referred to as an upward direction
- the direction Z2 may be referred to as a downward direction.
- the lifter 4 is provided above the valve 3.
- a top surface of the lifter 4 is formed as a convex spherical surface 11 having a shape corresponding to a part of a sphere.
- the lifter 4 transmits a displacement of the 3-D cam 2 to the valve 3 by being guided by and reciprocated within a valve opening 10a of a cylinder head 10.
- the shim 5 is interposed between the 3-D cam 2 and the lifter 4.
- the shim 5 has a flat surface 12 on the top and a concave spherical surface 13 on the bottom.
- the flat surface 12 contacts the 3-D cam 2.
- the concave spherical surface 13 engages the convex spherical surface 11 of the lifter 4.
- the convex spherical surface 11 and the concave spherical surface 13 have substantially the same radius of curvature.
- the shim 5 is rotationally slidable along the convex spherical surface 11 of the lifter 4.
- valve operation timing and an amount of valve lift can be varied, when the cam shaft 11 is moved by an actuator (not shown in the figure) in either direction X1 or X2, due to the slanting surface 8 formed on the 3-D cam 2. If the 3-D cam 2 moves, the shim 5 rotationally slides on the lifter 4. Thus, abrasion resistance between the lifter 4 and the shim 5 is improved since a large contact area is maintained between the lifter 4 and the ship 5 even when the 3-D cam 2 is shifted.
- FIG.2 shows a state where the shim 5 rotationally slides on the lifter 4. It should be noted that, in FIG.2, the shim 5 is shown protruding inside the cylinder head 10, however, practically, the shim 5 is rotatable up to a position where an end of the shim 5 contacts the cylinder head 10.
- the center of rotation of the shim 5 is at a position indicated by O1 which is located below the shim 5 since the spherical surface 11 of the lifter 4 is convex and the spherical surface 13 of the shim 5 is concave.
- the shim 5 moves along an arc indicated by arrows A1 and A2 with respect to the center O1 of rotation.
- the movement of the shim 5 is a movement by which the shim 5 approaches the cylinder head 10.
- the shim 5 interferes with an inner surface of the valve opening 10a of the cylinder head 10 when the shim 5 rotationally slides on the lifter 4.
- the shim 5 In order to avoid such an interference, the shim 5 must be formed in a predetermined size smaller than the diameter of the valve opening 10a. However, if the shim 5 is made smaller, the contact area between the shim 5 and the lifter 4 becomes smaller. As a result, the surface contact pressure between the lifter 4 and the shim 5 is increased, and causes another problem in that the abrasion resistance is decreased.
- a more specific object of the present invention is to provide a valve drive apparatus in which a shim is prevented from interfering with a cylinder head without decreasing abrasion resistance between the shim and a lifter contacting the shim.
- valve drive apparatus for driving a valve of an internal combustion engine, the valve drive apparatus comprises:
- the shim when the three-dimensional cam is rotated and the slant cam surface engages with the shim, the shim is rotated or swung so that the first surface of the shim follows the slant cam surface. Since the second surface of the shim has a convex spherical shape, the center of the radius of curvature of the second surface of the shim is positioned above the shim. In this construction, when the shim is rotated or swung, the shim moves substantially away from a cylinder head in which the force transmitting member is movably provided. Thus, interference of the shim with the cylinder head is prevented.
- a contact area between the shim and the force transmitting member can be increased. This allows a surface contact pressure between the shim and the force transmitting member, resulting in increased abrasion resistance between the shim and the force transmitting member.
- the second surface of the force transmitting member has the concave spherical shape, a lubricant is collected and remains on the second surface of the force transmitting member. Thus, a friction loss between the shim and the force transmitting member is decreased, and abrasion resistance between the shim and the force transmitting member is further increased.
- a radius of curvature of the second surface of the shim is substantially equal to a radius of curvature of the second surface of the force transmitting member.
- the force transmitting member may have a rim radially and outwardly extending from an outer periphery of the second surface of the force transmitting member
- the shim may have a collar radially and outwardly extending from an outer periphery of the second surface of the shim.
- a width of the cam portion of the three-dimensional cam may be less than a width of the first surface of the shim.
- the first surface of the shim may have a substantially circular shape, and the width of the first surface of the shim may correspond to a diameter of the first surface of the shim.
- the shim is rotated with respect to the force transmitting member substantially in the horizontal plane perpendicular to the moving direction of the force transmitting member when the three-dimensional cam is moved away from the center of the shim along the rotational axis of the three-dimensional cam.
- the position of the shim relative to the force transmitting member substantially in the horizontal plane is always changed. This rotation of the shim prevents local abrasion of the shim and the force transmitting member.
- a height of the shim is less than a radius of curvature of the shim, the height of the shim being a distance from a top of the second surface of the shim to the first surface of the shim.
- the contact area between the shim and the force transmitting member can be increased without increasing the height of the shim.
- the mass of inertia of the shim can be decreased as compared to a shim having a large contact area achieved by merely increasing the height of the shim. This allows a good response of the shim in a high speed operation of the engine.
- the radius of curvature of the second surface of the shim is increased, the maximum surface contact pressure is decreased, resulting in prevention of a local abrasion between the shim and the force transmission member.
- the force transmitting member may comprise a rocker arm having a first end adapted to be rotatably supported by a rocker shaft and a second end contacting the valve, the second surface of the force transmitting member being formed on the rocker arm between the first end and the second end.
- FIG.3A is a side view of a valve drive apparatus 20 according to the first embodiment of the present invention
- FIG.3B is a front view of the valve drive apparatus 20 shown in FIG.3A.
- the valve drive apparatus 20 is used for an internal combustion engine, and is of a directly driven valve type.
- the valve drive apparatus 20 generally comprises a 3-D cam 21, a valve 22, a lifter 23 and a shim 24.
- the 3-D cam 21 comprises a cam portion 25 and a cam shaft 26.
- the cam portion 25 comprises a basic circular portion 25a and a cam nose 25b which protrudes from the basic circular portion 25a.
- a slanting surface 27 which is inclined with respect to the rotational axis (cam axis) of the 3-D cam 2 by an angle ⁇ .
- the cam shaft 26 is connected to a crank shaft of the engine via timing gears and timing belts which are not shown in figures so that the cam shaft 26 is rotated in synchronization with a rotation of the crank shaft. Additionally, an actuator (not shown in the figures) is connected to an end of the cam shaft 26 so that the 3-D cam 21 is movable in either direction X1 or X2 in FIG.3B by being driven by the actuator.
- the valve 22 is provided to an intake port or an exhaust port provided in a cylinder head 28 of the internal combustion engine.
- a valve head 22a of the valve 22 opens or closes the intake port or the exhaust port by being reciprocated by a camming action of the 3-D cam 21.
- a retainer 30 is provided above the valve 22. The retainer 30 is urged by a valve spring 29 in a direction toward the 3-D cam 21. Thus, the valve 22 is urged by the valve spring 29 in the direction toward the 3-D cam 21.
- the valve 22 reciprocates in directions indicated by arrows Z1 and Z2.
- the direction Z1 may be referred to as an upward direction
- the direction Z2 may be referred to as a downward direction.
- the lifter 23 is provided above the valve 22, and has a cylindrical shape with a bottom surface.
- a top surface of the lifter 23 is formed as a concave spherical surface 32 having a shape corresponding to a part of a sphere.
- the lifter 23 transmits a displacement of the 3-D cam 21 to the valve 22 by being guided by and reciprocated within a valve opening 28a of the cylinder head 28.
- the shim 24 is interposed between the 3-D cam 21 and the lifter 23.
- the shim 24 has a flat surface 33 on the top and a convex spherical surface 34 on the bottom.
- the flat surface 33 contacts the 3-D cam 21.
- the convex spherical surface 34 of the shim 24 engages the concave spherical surface 32 of the lifter 23.
- the concave spherical surface 32 and the convex spherical surface 34 have substantially the same radius of curvature.
- the centers of both the concave spherical surface 32 and the convex spherical surface 34 are located at a point O2 positioned on the center axis B of the valve 22.
- a shim height H is less than the radius of curvature R of the convex spherical surface 34 of the shim 24, where the shim height H is a distance from a top of the convex spherical surface 34 to the flat surface 32 of the shim 24.
- the shim 24 is rotationally slidable along the concave spherical surface 32 of the lifter 23 while the convex spherical surface 34 contacts the concave spherical surface 32.
- a lubricant is supplied to the contact area between the 3-D cam 21 and the shim 24 and the contact area between the shim 24 and the lifter 23.
- the lubricant supplied between the convex spherical surface 34 of the shim 24 and the concave spherical surface 32 of the lifter 23 is positively retained in the contact area since the lifter 23 is positioned below the shim 24 and has the concave spherical surface which functions as a recess retaining the lubricant.
- good lubrication between the shim 24 and the lifter 23 is achieved, resulting in reduction in friction loss. That is, the abrasion resistance between the shim 24 and the lifter 23 is increased.
- the contact area between the convex spherical surface 34 of the shim 24 and the concave spherical surface 32 of the lifter 23 is large since the contact is made between the spherical portions having substantially the same radius of curvature. This large area contact results in a decrease in the surface contact pressure between the shim 24 and the lifter 23. Thus, abrasion resistance is increased.
- the lifter 23 has a rim 35 radially extending from the concave peripheral surface 32.
- the shim 24 has a collar 36 radially extending from the convex spherical surface 34. The collar 36 prevents excessive movement (rotation) of the shim 24 by contacting the rim 35 of the lifter 23 so that the shim 24 does not come out from the area between the shim 24 and the lifter 23.
- the diameter L1 of the flat surface 33 of the shim 24 is greater than a width L2 of the cam portion 25 of the 3-D cam 21 (L1>L2).
- the diameter L1 may be referred to as a shim width L1
- the width L2 may be referred to as a cam width L2.
- FIGS.4A, 4B, 5A and 5B show a state where the shim 24 contacts the basic circular portion 25a of the cam portion 25.
- FIGS.5A and 5B show a state where the shim 24 contacts the cam nose 25 of the cam portion 25.
- the valve spring 29, the retainer 30 and the valve seat 31 are omitted for the sake of simplification of illustration.
- the 3-D cam 21 rotates in synchronization with the crank shaft of the engine.
- the cam portion 25 presses the shim 24 by being rotated from the state shown in FIGS.4A and 4B, a pressing force is transmitted to the lifter 23 via the shim 24.
- the valve 22 is pressed via the lifter 23 and moved in the Z2 direction.
- the cam portion 25 has the slant surface 27 formed on the cam nose 25b, and the shim 24 can be rotatably moved along the concave spherical portion 32 of the lifter 23.
- the cam shaft 26 can be moved in either the X1 direction or X2 direction by an actuator not shown in the figures. Additionally, the slant surface 27 is formed on the cam nose 25b. Accordingly, the amount of valve lift of the valve 22 can be controlled by the cam shaft 26 being moved in the X1 direction or the X2 direction.
- the amount of valve lift of the valve 22 is decreased when the cam shaft 26 is moved in the X1 direction, resulting in a short travel of the valve 22 which condition is suitable for low speed operation of the engine which requires a lower amount of flow through the valve.
- the amount of valve lift of the valve 22 is increased when the cam shaft 26 is moved in the X2 direction, resulting in a longer travel of the valve 22 which condition is suitable for a high speed operation which requires a larger amount of flow.
- the center of the radius of curvature of the concave spherical surface 32 of the lifter 23 is positioned at the same position O2 with the center of the radius of curvature of the convex spherical surface 34 of the shim 24.
- the center O2 of the radius of curvature is positioned on the center axis B of the valve 22. Accordingly, the shim 24 can rotatably slide on the concave spherical surface 32 of the lifter 23. This enables the rotation of the shim 5 to be parallel to the slant surface 27 as shown in FIG.5B.
- the rotational movement of the shim 24 is a movement by which the shim 24 moves away from the cylinder head 28.
- the shim 24 does not interfere with the cylinder head 28 as is in the conventional valve drive apparatus in which the rotational direction of the shim is a direction which approaches the cylinder head.
- the contact area between the shim 24 and the lifter 23 can be increased so as to decrease surface contact pressure between the shim 24 and the lifter 23.
- the cam portion 25 can be moved on the flat surface 33 of the shim 24 by setting the shim width L1 to be grater than the cam width L2. Specifically, the cam portion 25 can be moved a distance in a range of (L1-L2) in the direction L1 or L2.
- the center line D (hereinafter, referred to as a cam side contact center line B) of the contact area between the shim 24 and the lifter 23 is offset from the center axis of the lifter 23.
- the center axis of the lifter 23 corresponds to the center axis B of the valve 22 as shown in FIG.5B, and is hereinafter referred to as a lifter side contact center line.
- the cam side contact center line D is offset from the lifter side contact center line B by a distance dL.
- a rotational force is generated in the shim 24 by which rotational force the shim 24 is rotated about the lifter side contact center line B in a direction E indicated by arrows E in FIG.5B.
- the shim 24 can be rotated in any direction with respect to the lifter 23 as mentioned above, the shim 24 can be rotated about the lifter side contact center line B in either direction E by the rotational force generated by the cam side contact center line D being offset from the lifter side contact center line B.
- FIG.6A shows a distribution of the surface contact pressure between the shim 24 and the lifter 23 in a state where the radius of curvature r of the shim 24 is substantially the same with the shim height H.
- FIG.6B shows a distribution of the surface contact pressure between the shim 24 and the lifter 23 in a state where the radius of curvature R of the shim 24 is greater than the shim height H.
- the surface contact pressure between the concave spherical surface 32 and the convex spherical surface 34 can be obtained by using a method for calculating a bearing pressure in a bearing.
- the surface contact pressure P can be calculated by dividing a pressing force F applied to the shim 24 by the 3-D cam 21 by a projected area S of the convex spherical surface 34.
- the surface contact pressure P2 can be obtained as follows. It is assumed that the pressing force F and the shim height H are the same as that of the structure shown in FIG.6A so as to facilitate a comparison therebetween.
- the shim height H is less than the radius of curvature R of the convex spherical surface 34 (H ⁇ R).
- H ⁇ R the radius of curvature of the convex spherical surface 34
- the surface contact pressure P2 of the present embodiment is smaller than the surface contact pressure of the structure shown in FIG.6A by setting shim height H to be smaller than the radius of curvature R of the shim 224. This reduces abrasion between the shim 24 and the lifter 23.
- the variation in the distribution of the surface contact pressure of the structure of the present embodiment shown in FIG.6B is smaller than that of the structure shown in FIG.6A.
- the maximum surface contact pressure of the structure shown in FIG.6B is smaller than the maximum surface contact pressure of the structure shown in FIG.6A
- the variation in the distribution of the surface contact pressure of the structure shown in FIG.6B is smaller than that of the structure shown in FIG.6A. That is, the surface contact pressure of the present embodiment is distributed evenly as compared to the structure shown in FIG.6A.
- the maximum surface contact pressure between the shim 24 and the lifter 23 can be reduced by increasing the radius of curvature R of the convex spherical surface 34 with respect to the shim height H of the shim 24.
- concentration of the surface contact pressure to a local area is prevented, resulting in preventing local abrasion of the convex spherical surface 34 of the shim 24 and the concave spherical surface of the lifter 23.
- FIG.7A is a side view of a valve drive apparatus 20A according to the second embodiment of the present invention
- FIG.7B is a front view of the valve drive apparatus 20A shown in FIG.7A.
- a rocker arm 40 is provided as a force transmitting member which transmits a pressing force from the 3-D cam 21 to the valve 22.
- rocker arm 40 One end of the rocker arm 40 is rotatably supported by a rocker shaft 41.
- the other end of the rocker arm 40 is formed as an acting portion 43 which contacts an upper end of the valve 22.
- a concave spherical surface 42 which is similar to the concave spherical portion 32 of the first embodiment, is formed on the rocker arm 40 between the rocker shaft 41 and the acting portion 43.
- the shim 24 is provided on the concave spherical portion 42.
- the 3-D cam 21 is provided above the shim 24 so that the shim 24 is pressed when the 3-D cam 21 is rotated by a rotation of the cam shaft 26.
- the pressing force is transmitted to the valve 22 via the rocker arm 40 so that the displacement of the shim 24 is increasingly transmitted to the valve 22 due to a leverage action.
- the shim 24 is rotatably movable on the concave spherical surface 42 similar to the above-mentioned first embodiment.
- the present embodiment has the same effects and advantages with the first embodiment. Accordingly, local abrasion between the shim 24 and the concave spherical surface 42 of the rocker arm 40 can be prevented.
- the present invention is not limited to the valve drive apparatus of the direct drive type or the rocker arm drive type as described in the above-mentioned embodiments.
- the present invention may be applied to a valve drive apparatus of a swing arm drive type, or further, to a cam drive apparatus other than the valve drive apparatus for an internal combustion engine.
- a valve drive apparatus having a shim (24) which is prevented from interfering with a cylinder head (28) without decreasing abrasion resistance between the shim and a lifter (23) contacting the shim (24).
- a three-dimensional cam (21) includes a cam portion (25) having a slanting cam surface (27) inclined with respect to a rotational axis of the cam. The cam (21) is movable in either direction along the rotational axis.
- the lifter (23) transmits a force generated by a camming action of the cam to a valve (22).
- the lifter has a first surface contacting the valve and a second surface (32) substantially opposite to the first surface.
- a shim (24) is interposed between the cam (21) and the lifter (23).
- the shim (24) has a first surface (33) contacting the cam and a second surface (34) opposite to the first surface (33).
- the second surface (34) of the shim (24) has a convex spherical shape
- the second surface (32) of the lifter (23) has a concave spherical shape so as to receive the second surface (34) of the shim (24).
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Valve Device For Special Equipments (AREA)
Abstract
Description
- The present invention relates to a valve drive apparatus for an internal combustion engine and, more particularly, to a valve drive apparatus having a shim interposed between a three-dimensional cam and a lifter.
- A variable valve timing mechanism is known which varies a valve operation timing and an amount of valve lift in response to an operational condition of an internal combustion engine such as an engine revolution speed or engine load. The variable valve timing mechanism allows improvement in engine output and specific fuel consumption and reduction in exhaust emission.
- A valve drive apparatus used in the variable valve timing mechanism comprises a three-dimensional (3-D) cam. The 3-D cam has a slanting surface which is inclined with respect to the rotational axis of the 3-D cam, and is movable along the rotational axis. Valve operation timing and an amount of valve lift are optimized by controlling an amount of shift of the 3-D cam along the rotational axis.
- Japanese Laid-Open Utility Model Application No.3-42001 discloses a valve drive apparatus of the above-mentioned type. FIG.1 shows the valve drive apparatus 1 disclosed in the above-mentioned Japanese Laid-Open Utility Model Application. The valve drive apparatus 1 generally comprises a 3-
D cam 2, avalve 3, alifter 4 and ashim 5. - The 3-
D cam 2 comprises a cam portion and acam shaft 7. Aslanting surface 8 is formed on the cam portion. Theslanting surface 8 of the cam portion 6 is inclined with respect to the rotational axis of thecam shaft 7 by an angle α. The 3-D cam 2 is movable in directions indicated by arrows X1 and X2 by an actuator not shown in the figure. - The
valve 3 is provided to an intake port or exhaust port of acylinder head 10 of an engine. Thevalve 3 opens or closes the intake port or the exhaust port by being reciprocated by rotation of the 3-D cam 2. A retainer 9 is provided above thevalve 3. The retainer 9 is urged by aspring 14 in a direction toward thecam 2. Thus thevalve 3 is urged by thespring 14 in the direction toward thecam 2. In FIG.1, thevalve 3 reciprocates in directions indicated by arrows Z1 and Z2. Hereinafter, the direction Z1 may be referred to as an upward direction, and the direction Z2 may be referred to as a downward direction. - The
lifter 4 is provided above thevalve 3. A top surface of thelifter 4 is formed as a convex spherical surface 11 having a shape corresponding to a part of a sphere. Thelifter 4 transmits a displacement of the 3-D cam 2 to thevalve 3 by being guided by and reciprocated within a valve opening 10a of acylinder head 10. - The
shim 5 is interposed between the 3-D cam 2 and thelifter 4. Theshim 5 has aflat surface 12 on the top and a concavespherical surface 13 on the bottom. Theflat surface 12 contacts the 3-D cam 2. The concavespherical surface 13 engages the convex spherical surface 11 of thelifter 4. The convex spherical surface 11 and the concavespherical surface 13 have substantially the same radius of curvature. Thus, theshim 5 is rotationally slidable along the convex spherical surface 11 of thelifter 4. - In the above-mentioned structure, valve operation timing and an amount of valve lift can be varied, when the cam shaft 11 is moved by an actuator (not shown in the figure) in either direction X1 or X2, due to the
slanting surface 8 formed on the 3-D cam 2. If the 3-D cam 2 moves, theshim 5 rotationally slides on thelifter 4. Thus, abrasion resistance between thelifter 4 and theshim 5 is improved since a large contact area is maintained between thelifter 4 and theship 5 even when the 3-D cam 2 is shifted. - However, there is a problem in that the
shim 5 interferes with thecylinder head 10 when theshim 5 rotationally slides along the convex spherical surface of thelifter 4. A detailed description will now be given, with reference to FIG.2, of the reason for the interference of theshim 5 with thecylinder head 10. - FIG.2 shows a state where the
shim 5 rotationally slides on thelifter 4. It should be noted that, in FIG.2, theshim 5 is shown protruding inside thecylinder head 10, however, practically, theshim 5 is rotatable up to a position where an end of theshim 5 contacts thecylinder head 10. - In the conventional valve drive apparatus, the center of rotation of the
shim 5 is at a position indicated by O1 which is located below theshim 5 since the spherical surface 11 of thelifter 4 is convex and thespherical surface 13 of theshim 5 is concave. Thus, theshim 5 moves along an arc indicated by arrows A1 and A2 with respect to the center O1 of rotation. - Thus, the movement of the
shim 5 is a movement by which theshim 5 approaches thecylinder head 10. Thus, in the conventional valve drive apparatus 1, there is a possibility that theshim 5 interferes with an inner surface of the valve opening 10a of thecylinder head 10 when theshim 5 rotationally slides on thelifter 4. - In order to avoid such an interference, the
shim 5 must be formed in a predetermined size smaller than the diameter of the valve opening 10a. However, if theshim 5 is made smaller, the contact area between theshim 5 and thelifter 4 becomes smaller. As a result, the surface contact pressure between thelifter 4 and theshim 5 is increased, and causes another problem in that the abrasion resistance is decreased. - It is a general object of the present invention to provide a valve drive apparatus for an internal combustion engine in which the above-mentioned problems are eliminated.
- A more specific object of the present invention is to provide a valve drive apparatus in which a shim is prevented from interfering with a cylinder head without decreasing abrasion resistance between the shim and a lifter contacting the shim.
- In order to achieve the above-mentioned object, there is provided according to the present invention a valve drive apparatus for driving a valve of an internal combustion engine, the valve drive apparatus comprises:
- a three-dimensional cam rotatable in synchronization with an operation of the internal combustion engine, the three-dimensional cam including a cam portion having a slanting cam surface inclined with respect to a rotational axis of the three-dimensional cam, the three-dimensional cam being movable along the rotational axis;
- a force transmitting member transmitting a force generated by a camming action of the three-dimensional cam to the valve, the force transmitting member having a first surface pressing the valve and a second surface; and
- a shim interposed between the three-dimensional cam and the force transmitting member, the shim having a first surface contacting the three-dimensional cam and a second surface opposite to the first surface of the shim, the second surface of the shim pressing the second surface of the force transmitting member,
- According to the above-mentioned invention, when the three-dimensional cam is rotated and the slant cam surface engages with the shim, the shim is rotated or swung so that the first surface of the shim follows the slant cam surface. Since the second surface of the shim has a convex spherical shape, the center of the radius of curvature of the second surface of the shim is positioned above the shim. In this construction, when the shim is rotated or swung, the shim moves substantially away from a cylinder head in which the force transmitting member is movably provided. Thus, interference of the shim with the cylinder head is prevented. Accordingly, a contact area between the shim and the force transmitting member can be increased. This allows a surface contact pressure between the shim and the force transmitting member, resulting in increased abrasion resistance between the shim and the force transmitting member. Additionally, the second surface of the force transmitting member has the concave spherical shape, a lubricant is collected and remains on the second surface of the force transmitting member. Thus, a friction loss between the shim and the force transmitting member is decreased, and abrasion resistance between the shim and the force transmitting member is further increased.
- Preferably, a radius of curvature of the second surface of the shim is substantially equal to a radius of curvature of the second surface of the force transmitting member.
- In one embodiment of the present invention, the force transmitting member may have a rim radially and outwardly extending from an outer periphery of the second surface of the force transmitting member, and the shim may have a collar radially and outwardly extending from an outer periphery of the second surface of the shim. An excessive rotation or swing of the shim can be prevented by the collar of the shim contacting the rim of the force transmitting member.
- Additionally, in the present invention, a width of the cam portion of the three-dimensional cam may be less than a width of the first surface of the shim. The first surface of the shim may have a substantially circular shape, and the width of the first surface of the shim may correspond to a diameter of the first surface of the shim.
- In this invention, the shim is rotated with respect to the force transmitting member substantially in the horizontal plane perpendicular to the moving direction of the force transmitting member when the three-dimensional cam is moved away from the center of the shim along the rotational axis of the three-dimensional cam. Thus, the position of the shim relative to the force transmitting member substantially in the horizontal plane is always changed. This rotation of the shim prevents local abrasion of the shim and the force transmitting member.
- Additionally, in the valve drive apparatus according to the present invention, a height of the shim is less than a radius of curvature of the shim, the height of the shim being a distance from a top of the second surface of the shim to the first surface of the shim.
- According to this invention, the contact area between the shim and the force transmitting member can be increased without increasing the height of the shim. Thus, the mass of inertia of the shim can be decreased as compared to a shim having a large contact area achieved by merely increasing the height of the shim. This allows a good response of the shim in a high speed operation of the engine. Additionally, since the radius of curvature of the second surface of the shim is increased, the maximum surface contact pressure is decreased, resulting in prevention of a local abrasion between the shim and the force transmission member.
- In one embodiment of the present invention, the force transmitting member may comprise a rocker arm having a first end adapted to be rotatably supported by a rocker shaft and a second end contacting the valve, the second surface of the force transmitting member being formed on the rocker arm between the first end and the second end.
- Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
-
- FIG.1 is a side view of a conventional valve drive apparatus;
- FIG.2 is a side view of the conventional valve drive apparatus in a condition where a shim is displaced;
- FIG.3A is a side view of a valve drive apparatus according to a first embodiment of the present invention; FIG.3B is a front view of the valve drive apparatus shown in FIG.3A;
- FIG.4A is a side view of the valve drive apparatus shown in FIG.3A in a state where a shim contacts a basic circular portion of a cam portion; FIG.4B is a front view of the valve drive apparatus shown in FIG.4A;
- FIG.5A is a side view of the valve drive apparatus shown in FIG.3A in a state where the shim contacts a cam nose of the cam portion; FIG.5B is a front view of the valve drive apparatus shown in FIG.5A;
- FIG.6A is an illustration for a distribution of the surface contact pressure between the shim and a lifter in a state where the radius of curvature of the shim is substantially the same with a height of the shim; FIG.6B is an illustration of a distribution of the surface contact pressure between the shim and the lifter in a state where the radius of curvature of the shim is greater than the height of the shim; and
- FIG.7A is a side view of a valve drive apparatus according to a second embodiment of the present invention; FIG.7B is a front view of the valve drive apparatus shown in FIG.7A.
- A description will now be given, with reference to FIGS.3A and 3B, of a first embodiment of the present invention. FIG.3A is a side view of a
valve drive apparatus 20 according to the first embodiment of the present invention; and FIG.3B is a front view of thevalve drive apparatus 20 shown in FIG.3A. Thevalve drive apparatus 20 is used for an internal combustion engine, and is of a directly driven valve type. Thevalve drive apparatus 20 generally comprises a 3-D cam 21, avalve 22, alifter 23 and ashim 24. - The 3-
D cam 21 comprises acam portion 25 and acam shaft 26. Thecam portion 25 comprises a basiccircular portion 25a and acam nose 25b which protrudes from the basiccircular portion 25a. A slantingsurface 27 which is inclined with respect to the rotational axis (cam axis) of the 3-D cam 2 by an angle α. - The
cam shaft 26 is connected to a crank shaft of the engine via timing gears and timing belts which are not shown in figures so that thecam shaft 26 is rotated in synchronization with a rotation of the crank shaft. Additionally, an actuator (not shown in the figures) is connected to an end of thecam shaft 26 so that the 3-D cam 21 is movable in either direction X1 or X2 in FIG.3B by being driven by the actuator. - The
valve 22 is provided to an intake port or an exhaust port provided in acylinder head 28 of the internal combustion engine. Avalve head 22a of thevalve 22 opens or closes the intake port or the exhaust port by being reciprocated by a camming action of the 3-D cam 21. Aretainer 30 is provided above thevalve 22. Theretainer 30 is urged by avalve spring 29 in a direction toward the 3-D cam 21. Thus, thevalve 22 is urged by thevalve spring 29 in the direction toward the 3-D cam 21. In FIGS.3A and 3B, thevalve 22 reciprocates in directions indicated by arrows Z1 and Z2. Hereinafter, the direction Z1 may be referred to as an upward direction, and the direction Z2 may be referred to as a downward direction. - The
lifter 23 is provided above thevalve 22, and has a cylindrical shape with a bottom surface. A top surface of thelifter 23 is formed as a concavespherical surface 32 having a shape corresponding to a part of a sphere. Thelifter 23 transmits a displacement of the 3-D cam 21 to thevalve 22 by being guided by and reciprocated within avalve opening 28a of thecylinder head 28. - The
shim 24 is interposed between the 3-D cam 21 and thelifter 23. Theshim 24 has aflat surface 33 on the top and a convexspherical surface 34 on the bottom. Theflat surface 33 contacts the 3-D cam 21. - The convex
spherical surface 34 of theshim 24 engages the concavespherical surface 32 of thelifter 23. The concavespherical surface 32 and the convexspherical surface 34 have substantially the same radius of curvature. The centers of both the concavespherical surface 32 and the convexspherical surface 34 are located at a point O2 positioned on the center axis B of thevalve 22. In the present embodiment, a shim height H is less than the radius of curvature R of the convexspherical surface 34 of theshim 24, where the shim height H is a distance from a top of the convexspherical surface 34 to theflat surface 32 of theshim 24. - In the above-mentioned construction, the
shim 24 is rotationally slidable along the concavespherical surface 32 of thelifter 23 while the convexspherical surface 34 contacts the concavespherical surface 32. - In the
valve drive apparatus 20, a lubricant is supplied to the contact area between the 3-D cam 21 and theshim 24 and the contact area between theshim 24 and thelifter 23. In the present embodiment, the lubricant supplied between the convexspherical surface 34 of theshim 24 and the concavespherical surface 32 of thelifter 23 is positively retained in the contact area since thelifter 23 is positioned below theshim 24 and has the concave spherical surface which functions as a recess retaining the lubricant. Thus, good lubrication between theshim 24 and thelifter 23 is achieved, resulting in reduction in friction loss. That is, the abrasion resistance between theshim 24 and thelifter 23 is increased. - The contact area between the convex
spherical surface 34 of theshim 24 and the concavespherical surface 32 of thelifter 23 is large since the contact is made between the spherical portions having substantially the same radius of curvature. This large area contact results in a decrease in the surface contact pressure between theshim 24 and thelifter 23. Thus, abrasion resistance is increased. - The
lifter 23 has arim 35 radially extending from the concaveperipheral surface 32. Theshim 24 has acollar 36 radially extending from the convexspherical surface 34. Thecollar 36 prevents excessive movement (rotation) of theshim 24 by contacting therim 35 of thelifter 23 so that theshim 24 does not come out from the area between theshim 24 and thelifter 23. - Additionally, in the
valve drive apparatus 20 according to the present invention, the diameter L1 of theflat surface 33 of theshim 24 is greater than a width L2 of thecam portion 25 of the 3-D cam 21 (L1>L2). Hereinafter, the diameter L1 may be referred to as a shim width L1, and the width L2 may be referred to as a cam width L2. - A description will now be given, with reference to FIGS.4A, 4B, 5A and 5B, of an operation of the valve drive apparatus. FIGS.4A and 4B show a state where the
shim 24 contacts the basiccircular portion 25a of thecam portion 25. FIGS.5A and 5B show a state where theshim 24 contacts thecam nose 25 of thecam portion 25. In FIGS.4A, 4B, 5A and 5B, thevalve spring 29, theretainer 30 and thevalve seat 31 are omitted for the sake of simplification of illustration. - As mentioned above, the 3-
D cam 21 rotates in synchronization with the crank shaft of the engine. Thus, when thecam portion 25 presses theshim 24 by being rotated from the state shown in FIGS.4A and 4B, a pressing force is transmitted to thelifter 23 via theshim 24. Thus, thevalve 22 is pressed via thelifter 23 and moved in the Z2 direction. Additionally, as also mentioned above, thecam portion 25 has theslant surface 27 formed on thecam nose 25b, and theshim 24 can be rotatably moved along the concavespherical portion 32 of thelifter 23. Thus, when theslant surface 27 comes in contact with theflat surface 33 as the 3-D cam 21 rotates, theshim 24 rotates or is inclined with respect to thelifter 23, as shown in FIGS.5A and 5B, so that theentire slant surface 27 contacts theflat surface 33. - The
cam shaft 26 can be moved in either the X1 direction or X2 direction by an actuator not shown in the figures. Additionally, theslant surface 27 is formed on thecam nose 25b. Accordingly, the amount of valve lift of thevalve 22 can be controlled by thecam shaft 26 being moved in the X1 direction or the X2 direction. - More specifically, the amount of valve lift of the
valve 22 is decreased when thecam shaft 26 is moved in the X1 direction, resulting in a short travel of thevalve 22 which condition is suitable for low speed operation of the engine which requires a lower amount of flow through the valve. On the other hand, the amount of valve lift of thevalve 22 is increased when thecam shaft 26 is moved in the X2 direction, resulting in a longer travel of thevalve 22 which condition is suitable for a high speed operation which requires a larger amount of flow. - A description will now be given in more detail of a rotational movement of the
shim 24 along the concavespherical surface 32 of thelifter 23 due to engagement of theslant surface 27 of the 3-D cam 21 with theflat surface 33 of theshim 23. - As mentioned above, the center of the radius of curvature of the concave
spherical surface 32 of thelifter 23 is positioned at the same position O2 with the center of the radius of curvature of the convexspherical surface 34 of theshim 24. The center O2 of the radius of curvature is positioned on the center axis B of thevalve 22. Accordingly, theshim 24 can rotatably slide on the concavespherical surface 32 of thelifter 23. This enables the rotation of theshim 5 to be parallel to theslant surface 27 as shown in FIG.5B. - In the present embodiment, since both the convex
spherical surface 34 of theshim 24 and the concavespherical surface 32 of thelifter 23 are closed downwardly, the center O2 of thesurfaces shim 24. Thus, theshim 24 rotates about the center O2 in either direction indicated by arrows C1 or C2 shown in FIG.5B. - The rotational movement of the
shim 24 is a movement by which theshim 24 moves away from thecylinder head 28. Thus, theshim 24 does not interfere with thecylinder head 28 as is in the conventional valve drive apparatus in which the rotational direction of the shim is a direction which approaches the cylinder head. - Additionally, since the interference of the
shim 24 with thecylinder head 28 is prevented, the contact area between theshim 24 and thelifter 23 can be increased so as to decrease surface contact pressure between theshim 24 and thelifter 23. - A description will now be given of an effect obtained by the shim width L1 being greater than the cam width L2.
- As mentioned above, the
cam portion 25 can be moved on theflat surface 33 of theshim 24 by setting the shim width L1 to be grater than the cam width L2. Specifically, thecam portion 25 can be moved a distance in a range of (L1-L2) in the direction L1 or L2. - If the shim width L1 is less than the cam width L2, the entire cam surface of the
cam portion 25 contacts theflat surface 33. In this case, the rotational force generated in theshim 24 is only in the direction C1 or C2. On the other hand, if the shim width L1 is greater than the cam width L2 as is in the present embodiment, the center line D (hereinafter, referred to as a cam side contact center line B) of the contact area between theshim 24 and thelifter 23 is offset from the center axis of thelifter 23. The center axis of thelifter 23 corresponds to the center axis B of thevalve 22 as shown in FIG.5B, and is hereinafter referred to as a lifter side contact center line. In FIG.5B, the cam side contact center line D is offset from the lifter side contact center line B by a distance dL. - In the above-mentioned construction, a rotational force is generated in the
shim 24 by which rotational force theshim 24 is rotated about the lifter side contact center line B in a direction E indicated by arrows E in FIG.5B. - Since the
shim 24 can be rotated in any direction with respect to thelifter 23 as mentioned above, theshim 24 can be rotated about the lifter side contact center line B in either direction E by the rotational force generated by the cam side contact center line D being offset from the lifter side contact center line B. - When the
shim 24 is rotated in the direction E, the contact point of theshim 24 with respect to thecam portion 25 is shifted in the direction E. This prevents theshim 24 from contacting thecam portion 25 always in the same area of theflat surface 33. Thus, theflat surface 33 of theshim 24 is prevented from being worn only in a particular area of theflat surface 33. This increases reliability of thevalve drive apparatus 20. Additionally, since theshim 24 is rotated in the direction E with respect thelifter 23, the convexspherical surface 34 of theshim 24 and the concavespherical surface 32 of thelifter 23 are also worn evenly over the entire contact area. - There is a possibility that when the
shim 24 having the concavespherical surface 34 is moved excessively, theshim 24 may come out of thelifter 23. However, in the present embodiment, since therim 35 is formed on thelifter 23 and thecollar 36 is formed on theshim 24, an excessive movement of theshim 24 is prevented. That is, the excessive movement of theshim 24 is prevented by thecollar 36 of theshim 24 from contacting therim 35 of thelifter 23. This also increases reliability of thevalve drive apparatus 20. - A description will now be given, with reference to FIGS.6A and 6B, of the effect achieved by the shim height H being less than the radius of curvature R of the
shim 24. FIG.6A shows a distribution of the surface contact pressure between theshim 24 and thelifter 23 in a state where the radius of curvature r of theshim 24 is substantially the same with the shim height H. FIG.6B shows a distribution of the surface contact pressure between theshim 24 and thelifter 23 in a state where the radius of curvature R of theshim 24 is greater than the shim height H. - The surface contact pressure between the concave
spherical surface 32 and the convexspherical surface 34 can be obtained by using a method for calculating a bearing pressure in a bearing. A bearing pressure P in a bearing can be calculated by dividing a force F applied to the bearing by a projected area S of the bearing (shim 24 by the 3-D cam 21 by a projected area S of the convexspherical surface 34. -
- On the other hand, in the structure shown in FIG.6B, the surface contact pressure P2 can be obtained as follows. It is assumed that the pressing force F and the shim height H are the same as that of the structure shown in FIG.6A so as to facilitate a comparison therebetween. The projected area S2 of the convex
spherical surface 34 is obtained as - Now, a comparison is made between the surface contact pressure P1 obtained in the structure shown in FIG.6A and the surface contact pressure P2 obtained in the structure shown in FIG.6B which corresponds to the present embodiment. As mentioned above, in the present embodiment, the shim height H is less than the radius of curvature R of the convex spherical surface 34 (H<R). Thus, if it is assumed that the shim height H is equal between the structures shown in FIGS.6A and 6B, a relationship r<R0<R is established as apparent from FIGS.6A and 6B. Accordingly, if the projected areas S1 and S2 are compared with each other, a relationship S1<S2 is established. By applying the above relationships to the equations (1) and (2), a relationship P1>P2 is established.
- As mentioned above, the surface contact pressure P2 of the present embodiment is smaller than the surface contact pressure of the structure shown in FIG.6A by setting shim height H to be smaller than the radius of curvature R of the shim 224. This reduces abrasion between the
shim 24 and thelifter 23. - Additionally, since the contact area S2 between the
shim 24 and thelifter 23 can be increased without increasing the shim height H, inertial mass of the valve drive system can be reduced as compared to the structure in which the contact area is increased by increasing the shim height H. Thus, a quick response of thevalve drive apparatus 20 at high speed operation of the engine can be achieved. - Now, attention is directed to a distribution of the surface contact pressure. The variation in the distribution of the surface contact pressure of the structure of the present embodiment shown in FIG.6B is smaller than that of the structure shown in FIG.6A. specifically, the maximum surface contact pressure of the structure shown in FIG.6B is smaller than the maximum surface contact pressure of the structure shown in FIG.6A, and the variation in the distribution of the surface contact pressure of the structure shown in FIG.6B is smaller than that of the structure shown in FIG.6A. That is, the surface contact pressure of the present embodiment is distributed evenly as compared to the structure shown in FIG.6A.
- As mentioned above, the maximum surface contact pressure between the
shim 24 and thelifter 23 can be reduced by increasing the radius of curvature R of the convexspherical surface 34 with respect to the shim height H of theshim 24. Thus, concentration of the surface contact pressure to a local area is prevented, resulting in preventing local abrasion of the convexspherical surface 34 of theshim 24 and the concave spherical surface of thelifter 23. - A description will now be given, with reference to FIGS.7A and 7B, of a second embodiment of the present invention. FIG.7A is a side view of a
valve drive apparatus 20A according to the second embodiment of the present invention; FIG.7B is a front view of thevalve drive apparatus 20A shown in FIG.7A. In FIGS.7A and 7B, parts that are the same as the parts shown in FIGS.3A and 3B are given the same reference numerals, and description thereof will be omitted. In thevalve drive apparatus 20A according to the second embodiment, arocker arm 40 is provided as a force transmitting member which transmits a pressing force from the 3-D cam 21 to thevalve 22. - One end of the
rocker arm 40 is rotatably supported by arocker shaft 41. The other end of therocker arm 40 is formed as an actingportion 43 which contacts an upper end of thevalve 22. A concavespherical surface 42, which is similar to the concavespherical portion 32 of the first embodiment, is formed on therocker arm 40 between therocker shaft 41 and the actingportion 43. Theshim 24 is provided on the concavespherical portion 42. - The 3-
D cam 21 is provided above theshim 24 so that theshim 24 is pressed when the 3-D cam 21 is rotated by a rotation of thecam shaft 26. Thus, the pressing force is transmitted to thevalve 22 via therocker arm 40 so that the displacement of theshim 24 is increasingly transmitted to thevalve 22 due to a leverage action. In the present embodiment, theshim 24 is rotatably movable on the concavespherical surface 42 similar to the above-mentioned first embodiment. Thus, the present embodiment has the same effects and advantages with the first embodiment. Accordingly, local abrasion between theshim 24 and the concavespherical surface 42 of therocker arm 40 can be prevented. - The present invention is not limited to the valve drive apparatus of the direct drive type or the rocker arm drive type as described in the above-mentioned embodiments. For example, the present invention may be applied to a valve drive apparatus of a swing arm drive type, or further, to a cam drive apparatus other than the valve drive apparatus for an internal combustion engine.
- The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the present invention.
- A valve drive apparatus having a shim (24) which is prevented from interfering with a cylinder head (28) without decreasing abrasion resistance between the shim and a lifter (23) contacting the shim (24). A three-dimensional cam (21) includes a cam portion (25) having a slanting cam surface (27) inclined with respect to a rotational axis of the cam. The cam (21) is movable in either direction along the rotational axis. The lifter (23) transmits a force generated by a camming action of the cam to a valve (22). The lifter has a first surface contacting the valve and a second surface (32) substantially opposite to the first surface. A shim (24) is interposed between the cam (21) and the lifter (23). The shim (24) has a first surface (33) contacting the cam and a second surface (34) opposite to the first surface (33). The second surface (34) of the shim (24) has a convex spherical shape, and the second surface (32) of the lifter (23) has a concave spherical shape so as to receive the second surface (34) of the shim (24).
Claims (7)
- A valve drive apparatus (20, 20A) for driving a valve (22) of an internal combustion engine, said valve drive apparatus comprising:a three-dimensional cam (21) rotatable in synchronization with an operation of said internal combustion engine, said three-dimensional cam (21) including a cam portion (25) having a slanting cam surface (27) inclined with respect to a rotational axis of said three-dimensional cam (21), said three-dimensional (21) cam being movable along said rotational axis;a force transmitting member (23, 40) transmitting a force generated by a camming action of said three-dimensional cam (21) to said valve (22), said force transmitting member (23, 40) having a first surface pressing said valve (22) and a second surface (32); anda shim (24) interposed between said three-dimensional cam (21) and said force transmitting member (23), said shim (24) having a first surface (33) contacting said three-dimensional cam (21) and a second surface (34) opposite to said first surface (33) of said shim (24), said second surface (34) of said shim (24) pressing said second surface (32) of said force transmitting member (23, 40),characterized in that:
said second surface (34) of said shim (24) has a convex spherical shape, and said second surface (32) of said force transmitting member (23, 40) has a concave spherical shape so as to receive said second surface (34) of said shim (24). - The valve drive apparatus as claimed in claim 1, characterized in that a radius of curvature of said second surface (34) of said shim (24) is substantially equal to a radius of curvature of said second surface (32) of said force transmitting member (23).
- The valve drive apparatus as claimed in claim 1 or 2, characterized in that said force transmitting member (23, 40) has a rim (35) radially and outwardly extending from an outer periphery of said second surface (32) of said force transmitting member (23), and said shim (24) has a collar (36) radially and outwardly extending from an outer periphery of said second surface (34) of said shim (24).
- The valve drive apparatus as claimed in one of claims 1-3, characterized in that a width of said cam portion (25) of said three-dimensional cam (21) is less than a width of said first surface (33) of said shim (24).
- The valve drive apparatus as claimed in claim 4, characterized in that said first surface (33) of said shim (24) has substantially a circular shape, and said width of said first surface (33) of said shim (24) corresponds to a diameter of said first surface (33) of said shim (24).
- The valve drive apparatus as claimed in one of claims 1-5, characterized in that a height of said shim (24) is less than a radius of curvature of said shim (24), said height of said shim (24) being a distance from a top of said second surface (34) of said shim (24) to said first surface (33) of said shim (24).
- The valve drive apparatus as claimed in one of claims 1-6, characterized in that said force transmitting member comprises a rocker arm (40) having a first end adapted to be rotatably supported by a rocker shaft (41) and a second end (43) contacting said valve (22), said second surface (42) of said force transmitting member being formed on said rocker arm (40) between said first end and said second end (43).
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP311164/95 | 1995-11-29 | ||
JP31116495 | 1995-11-29 | ||
JP31116495 | 1995-11-29 | ||
JP296746/96 | 1996-11-08 | ||
JP29674696 | 1996-11-08 | ||
JP29674696A JPH09209727A (en) | 1995-11-29 | 1996-11-08 | Valve system of internal combustion engine |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0777039A1 true EP0777039A1 (en) | 1997-06-04 |
EP0777039B1 EP0777039B1 (en) | 1999-06-16 |
Family
ID=26560821
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19960119089 Expired - Lifetime EP0777039B1 (en) | 1995-11-29 | 1996-11-28 | Valve drive apparatus for an internal combustion engine having a convex shim between a cam and a valve |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0777039B1 (en) |
JP (1) | JPH09209727A (en) |
DE (1) | DE69602913T2 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102007003969A1 (en) * | 2007-01-26 | 2008-07-31 | Schaeffler Kg | Cam valve drive, particularly for internal-combustion engine, has tap rollers arranged in roller recess, which allows separate tilting of tap rollers in support body arranged in another rocker axis |
DE102007042457A1 (en) | 2007-09-07 | 2009-03-12 | Schaeffler Kg | Valve actuator for a fully variable valve train |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1192099A (en) * | 1968-09-16 | 1970-05-20 | Caterpillar Tractor Co | Misalignment compensating cam follower |
US3915129A (en) * | 1974-09-18 | 1975-10-28 | Robert H Rust | Internal combustion engine |
US4850311A (en) * | 1988-12-09 | 1989-07-25 | General Motors Corporation | Three dimensional cam cardanic follower valve lifter |
JPH0342001U (en) | 1989-08-30 | 1991-04-22 | ||
EP0512698A1 (en) * | 1991-05-03 | 1992-11-11 | Ford Motor Company Limited | Adjustable valve system for an internal combustion engine |
-
1996
- 1996-11-08 JP JP29674696A patent/JPH09209727A/en active Pending
- 1996-11-28 DE DE1996602913 patent/DE69602913T2/en not_active Expired - Fee Related
- 1996-11-28 EP EP19960119089 patent/EP0777039B1/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1192099A (en) * | 1968-09-16 | 1970-05-20 | Caterpillar Tractor Co | Misalignment compensating cam follower |
US3915129A (en) * | 1974-09-18 | 1975-10-28 | Robert H Rust | Internal combustion engine |
US4850311A (en) * | 1988-12-09 | 1989-07-25 | General Motors Corporation | Three dimensional cam cardanic follower valve lifter |
JPH0342001U (en) | 1989-08-30 | 1991-04-22 | ||
EP0512698A1 (en) * | 1991-05-03 | 1992-11-11 | Ford Motor Company Limited | Adjustable valve system for an internal combustion engine |
Also Published As
Publication number | Publication date |
---|---|
JPH09209727A (en) | 1997-08-12 |
DE69602913D1 (en) | 1999-07-22 |
DE69602913T2 (en) | 2000-03-23 |
EP0777039B1 (en) | 1999-06-16 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4850311A (en) | Three dimensional cam cardanic follower valve lifter | |
US6055949A (en) | Variable valve actuator apparatus | |
US4615313A (en) | Automatic decompression device for internal combustion engine | |
US6244229B1 (en) | Valve lifter for three-dimensional cam and variable valve operating apparatus using the same | |
JPH01294907A (en) | Valve actuating state switching device for internal combustion engine | |
US5687683A (en) | Automatic decompressor for valve-controlled internal combustion engines | |
US5020488A (en) | Valve mechanism for an internal combustion engine | |
EP0563574B1 (en) | Valve-moving apparatus for internal combustion engine | |
EP0777039B1 (en) | Valve drive apparatus for an internal combustion engine having a convex shim between a cam and a valve | |
US5367991A (en) | Valve operating system of engine | |
US5832889A (en) | Valve driving apparatus | |
US5803033A (en) | Valve drive apparatus for an internal combustion engine having a convex shim between a cam and a valve | |
US5870984A (en) | Variable engine valve driver | |
US5983848A (en) | Finger follower | |
EP0129961B1 (en) | Reciprocating internal combustion engine with valve train means | |
EP1059423B1 (en) | Valve driving apparatus for internal combustion engine | |
US4436062A (en) | Rocker arm mechanism in overhead cam type engine | |
JPWO2003074845A1 (en) | Variable valve operating device for internal combustion engine | |
JPH082404Y2 (en) | Internal combustion engine rocker arm | |
JPS6143981Y2 (en) | ||
JPS6311287Y2 (en) | ||
JP2522200Y2 (en) | Valve train for internal combustion engine | |
JPH11270322A (en) | Valve system for internal combustion engine | |
JP3389070B2 (en) | Valve train for internal combustion engine | |
JP4367317B2 (en) | Variable valve operating device for internal combustion engine |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19961128 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB |
|
17Q | First examination report despatched |
Effective date: 19971103 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
REF | Corresponds to: |
Ref document number: 69602913 Country of ref document: DE Date of ref document: 19990722 |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20031110 Year of fee payment: 8 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20031126 Year of fee payment: 8 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20031211 Year of fee payment: 8 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20041128 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050601 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20041128 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050729 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |