The present invention relates to a valve train device for a vehicular engine or the like, and more particularly to a valve train device capable of switching cam portions for use in opening and closing valves.
As a valve train device for an engine, there is known a configuration, in which a plurality of cam portions whose shapes are different from each other are provided for each valve, and valve opening amounts or valve opening timings of intake valves and exhaust valves are switchable depending on an operating condition of an engine by selecting a cam portion for use in opening and closing a valve from among the cam portions.
For instance, Patent Literature 1 describes a valve train device provided with a camshaft including a shaft portion, and a tubular cam element portion which is mounted on the shaft portion to be displaceable relative to the shaft portion in the axial direction of the shaft portion, and to be integrally rotatable with the shaft portion; and an actuator which causes the cam element portion to move in the axial direction, wherein the positions of a plurality of cam portions provided in the cam element portion are changed by moving the cam element portion in the axial direction for switching the cam portions for use in opening and closing valves.
The valve train device is provided with the actuator including pin members at both sides of the cam element portion, wherein the pin members are operative to advance or retract (project/retract) in a direction orthogonal to the axial direction. The valve train device is configured to move the cam element portion in the axial direction, namely, to switch a cam portion by selectively operating (projecting) the pin members depending on the position of the cam element portion, and by causing the pin members to come into contact with end surface cams provided at both ends of the cam element portion in the axial direction.
In a valve train device, it is required to repeatedly switch a cam portion in a short period of time depending on an operating condition of an engine. When a response delay or an operation failure occurs in an actuator, however, pin members of the actuator located at both sides of a cam element portion may be simultaneously set to an operative state. In this case, the cam element portion may be made non-rotatable due to axial restriction the cam element portion by the pin members from both sides in association with rotation of the cam element portion. Therefore, it is required to avoid the aforementioned drawback in advance.
Patent Literature 1: Japanese Unexamined Patent Publication No. 2013-83202
In view of the above, an object of the present invention is to provide a technique for a valve train device, which enables to avoid that a cam element portion is made non-rotatable, with a simplified structure.
The present invention is directed to a valve train device for an engine. The valve train device includes a shaft portion which rotates by receiving a rotational force from a crankshaft; a cam element portion mounted on the shaft portion in such a manner as to be displaceable relative to the shaft portion in an axial direction of the shaft portion and to be integrally rotated with the shaft portion, the cam element portion including a plurality of cam portions aligned in the axial direction on an outer periphery of the cam element portion; and an operation member which causes the cam element portion to move in the axial direction, the valve train device being configured to switch the cam portions for use in opening or closing valves by causing the cam element portion to move in the axial direction by the operation member. The cam element portion includes a first end surface cam and a second end surface cam on both ends of the cam element portion in the axial direction, each of the first end surface cam and the second end surface cam including a reference surface which extends in a direction orthogonal to the axial direction, and a lift portion which projects outwardly from the reference surface in the axial direction in such a manner that an amount of projection of the lift portion increases toward a retard direction in terms of rotation, the reference surface and the lift portion being aligned in a rotational direction. The operation member includes a first operation member and a second operation member, each of which is operative to advance or retract in a range from an operative position where the operation member comes inside the outer periphery of the cam element portion, and a retracted position where the operation member comes outside the outer periphery, the first operation member being configured to move the cam element portion in a first direction along the axial direction by engagement with the lift portion of the first end surface cam in association with rotation of the cam element portion when the operation member is set to the operative position, and the second operation member being configured to move the cam element portion in a second direction opposite to the first direction by engagement with the lift portion of the second end surface cam in association with rotation of the cam element portion when the operation member is set to the operative position. The cam element portion includes, at least on the first end cam surface, a first slope portion which extends in the retard direction in terms of rotation from a maximum lift position where the amount of projection of the lift portion is maximized, and guides the first operation member radially outwardly of the cam element portion in association with rotation of the cam element portion, and a displacement allowing portion which is formed adjacent to the first slope portion in the axial direction, and allows relative displacement between the first operation member to be guided along the first slope portion and the cam element portion in the axial direction and in the rotational direction when both of the first operation member and the second operation member are projected to the operative position.
In the following, a preferred embodiment of the present invention is described in detail referring to the accompanying drawings.
(Overall Configuration of Valve Train Device)
The engine is provided with each two exhaust valves 1 for first to fourth cylinders C1 to C4, namely, eight exhaust valves 1 in total, and is provided with return springs 2 for urging the exhaust valves 1 in a valve closing direction. The engine is further provided with a camshaft 4 for opening the exhaust valves 1 against the urging force of the return springs 2 via locker arms 3. In the following description, the cylinder array direction is defined as the front-rear direction, and the first cylinder C1 side is referred to as the front side, and the fourth cylinder C4 side is referred to as the rear side, unless otherwise specifically mentioned.
The camshaft 4 is rotatably supported on vertical wall portions 5 of a cylinder head, each of which is formed above the center position of each of the cylinder C1 to C4 via a bearing portion 6. The camshaft 4 is connected to an unillustrated crankshaft via a chain, and is driven to rotate by the crankshaft.
The camshaft 4 includes a shaft portion 10, and first to fourth cam element portions CE1 to CE4 mounted on the shaft portion 10 at positions associated with the positions of the first to fourth cylinders C1 to C4. Each of the cam element portions CE1 to CE4 is spline-connected to the shaft portion 10 to be displaceable relative to the shaft portion 10 in the axial direction of the shaft portion 10 (hereinafter, simply referred to as the axial direction, or the front-rear direction), and to be integrally rotatable with the shaft portion 10.
Six operation devices M1 to M6 i.e. first to sixth operation devices M1 to M6 for moving the cam element portions CE1 to CE4 along the shaft portion 10 are provided above the camshaft 4. Specifically, the first operation device M1 is disposed at a front end of the cylinder array, the second operation device M2 is disposed between the first cylinder C1 and the second cylinder C2, the third operation device M3 is disposed on the front side between the second cylinder C2 and the third cylinder C3, the fourth operation device M4 is disposed on the rear side between the second cylinder C2 and the third cylinder C3, the fifth operation device M5 is disposed between the third cylinder C3 and the fourth cylinder C4, and the sixth operation device M6 is disposed at a rear end of the cylinder array.
As illustrated in
Each of the operation devices M1 to M6 is disposed on the opposite side of a cam follower 3a of the locker arm 3 with respect to the camshaft 4. Specifically, each of the operation devices M1 to M6 is disposed in such a manner that the pin portion 14 is directed toward the axis of the camshaft 4 (the shaft portion 10). In this example, each of the operation devices M1 to M6 are mounted on a cylinder head cover 7 which covers the camshaft 4 from above.
When the electromagnetic actuator is not energized, as illustrated by the broken line in
Each of the operation devices M1 to M6 is controlled by an unillustrated control device. The control device outputs a control signal in such a manner that the electromagnetic actuator of each of the operation devices M1 to M6 is energized at a predetermined timing corresponding to a rotational angle of the engine on the basis of a detection signal from a rotational angle sensor of the engine.
The camshaft 4 is provided with detent mechanisms 30 for positioning each of the cam element portions CE1 to CE4 at two positions different from each other in the axial direction.
As illustrated in
In the valve train device, the position of each of the cam element portions CE1 to CE4 is switched between a first layout as illustrated in
In this example, as illustrated in
On the other hand, as illustrated in
(Specific Configuration of Cam Element Portion)
Next, a configuration of each of the cam element portions CE1 to CE4 is described on the basis of
The first cam element portion CE1 has a tubular shape. The first cam element portion CE1 includes a journal portion 21 to be supported on the bearing portion 6 at an intermediate portion thereof in the axial direction. The first cam element portion CE1 further includes two operating portions 22 at front and rear sides thereof for operating the two exhaust valves 1 of the first cylinder C1. The configuration of the second cam element portion CE2 is the same as described above.
As illustrated in
The shape and the phase are the same between the first cam portions 23 (nose portions) of the operating portions 22 of the first cam element portion CE1. Likewise, the shape and the phase are the same between the second cam portions 24 (nose portions) of the operating portions 22 of the first cam element portion CE1. Further, the shape and the phase are the same between the first cam portions 23 of the operating portions 22 of the second cam element portion CE2. Likewise, the shape and the phase are the same between the second cam portions 24 of the operating portions 22 of the second cam element portion CE2.
The distance between the two operating portions 22 and 22 of each of the cam element portions CE1 and CE2 is set in such a manner that when each of the cam element portions CE1 and CE2 is in the first layout state, the first cam portions 23 of the operating portions 22 of each of the cam element portions CE1 and CE2 are associated with the cam followers 3a of the two locker arms 3 of the associated cylinder C1, C2 (see
Each of the third cam element portion CE3 and the fourth cam element portion CE4 includes a journal portion 21 and operating portions 22, as well as the second cam element portion CE2 and the first cam element portion CE1.
Further, each of the cam element portions CE3 and CE4 is configured in such a manner that when each of the cam element portions CE3 and CE4 is in the first layout state, the first cam portions 23 of the operating portions 22 of each of the cam element portions CE3 and CE4 are associated with the cam followers 3a of the two locker arms 3 of the associated cylinder C3, C4 (see
The engine in the embodiment is configured in such a manner that the order of explosion of the cylinders is the third cylinder C3, the fourth cylinder C4, the second cylinder C2, and the first cylinder C1. Therefore, the cam portions 23 and 24 of each of the cam element portions CE1 to CE4 are formed to have a phase difference between the cam element portions CE1 to CE4 in such a manner that the cam portions 23 and 24 come into sliding contact with the cam followers 3a in the aforementioned order, each time the camshaft 4 is rotated by 90°.
Each of the first cam element portion CE1 and the second cam element portion CE2 includes end surface cams 25A and 25B (referred to as a front end surface cam 25A and a rear end surface cam 25B) at front and rear ends thereof.
As illustrated in
The lift portion 26b is formed in such a manner that the amount of projection (referred to as a lift amount) gradually increases from the reference surface 26 toward a direction (referred to as a retard direction in terms of rotation) opposite to a rotational direction X of the camshaft 4 (the first cam element portion CE1) in a predetermined phase range α (e.g. about 120°) from a lift start position S to a lift end position F, and that the lift amount is maximized at the lift end position F. Further, the lift portion 26b of the front end surface cam 25A is formed in such a manner that the maximum lift amount is kept in the range from the lift end position F to a below-mentioned slope end position G1 located in a retard direction in terms of rotation than the lift end position F, and that the lift amount becomes zero at the slop end position G1 (the height of the lift portion 26b is returned to the reference surface 26a). On the other hand, the lift portion 26b of the rear end surface cam 25B is formed in such a manner that the lift amount becomes zero substantially at the lift end position F (corresponding to the maximum lift position of the present invention).
The lift portion 26b of the front end surface cam 25A and the lift portion 26b of the rear end surface cam 25B of the first cam element portion CE1 are offset from each other in the rotational direction in such a manner that the distance between the first operation device M1 and the second operation device M2 is narrowed as much as possible, while securing a required moving amount (stroke) of the first cam element portion CE1 in the axial direction.
As well as each of the end surface cams 25A and 25B of the first cam element portion CE1, as illustrated in
In other words, as illustrated in
Further, when the pin portion 14 of the second operation device M2 is set to an operative position by an operation of the second operation device M2 in a state that the second cam element portion CE2 is in the front position (see
According to the aforementioned configuration, the position of each of the first cam element portion CE1 and the second cam element portion CE2 is switchable between the front position and the rear position.
Each of the third cam element portion CE3 and the fourth cam element portion CE4 includes end surface cams 25A and 25B substantially in the same manner as the first cam element portion CE1 and the second cam element portion CE2 except that the front position and the rear position are reversed. Specifically, the third cam element portion CE3 includes end surface cams 25A and 25B, in which the front and rear positions are reversed with respect to the end surface cams 25A and 25B of the second cam element portion CE2. The fourth cam element portion CE4 includes end surface cams 25A and 25B, in which the front and rear positions are reversed with respect to the end surface cams 25A and 25B of the first cam element portion CE1. According to this configuration, the position of the third cam element portion CE3 is switched between the front position and the rear position by engagement of the pin portion 14 of the fourth operation device M4 with the lift portion 26b of the front end surface cam 25A of the third cam element portion CE3 by an operation of the fourth operation device M4, or by engagement of the pin portion 14 of the fifth operation device M5 with the lift portion 26b of the rear end surface cam 25B of the third cam element portion CE3 by an operation of the fifth operation device M5. Further, the position of the fourth cam element portion CE4 is switched between the front position and the rear position by engagement of the pin portion 14 of the fifth operation device M5 with the lift portion 26b of the front end surface cam 25A of the fourth cam element portion CE4 by an operation of the fifth operation device M5, or by engagement of the pin portion 14 of the sixth operation device M6 with the lift portion 26b of the rear end surface cam 25B of the fourth cam element portion CE4 by an operation of the sixth operation device M6.
The end surface cams 25A and 25B of each of the cam element portions CE1 to CE4 are formed to have a predetermined phase difference, in view of that the operating portions 22 (cam portions 23 and 24) of each of the cam element portions CE1 to CE4 are formed to have a predetermined phase difference depending on the order of explosion of the cylinders C1 to C4. In the embodiment, the first and second cam element portions CE1 and CE2 adjacent to each other, and the third and fourth cam element portions CE3 and CE4 adjacent to each other are formed in such a manner that the lift portions 26b of the opposing end surface cams 25A and 25B have different phases from each other. Further, as illustrated by the reference signs P1 and P2 in
According to the aforementioned configuration, when the second operation device M2 is operated in the first layout state (see
The lift portion 26b of the end surface cam 25B of the cam element portion CE1 and the lift portion 26b of the end surface cam 25A of the cam element portion CE2 opposing to each other are formed to have different phases from each other in such a manner that the cam element portions CE1 and CE2 are moved in the order of the second cam element portion CE2 and the first cam element portion CE1 when the second operation device M2 is operated. Likewise, the lift portion 26b of the end surface cam 25B of the cam element portion CE3 and the lift portion 26b of the end surface cam 25A of the cam element portion CE4 opposing to each other are formed to have different phases from each other in such a manner that the cam element portions CE3 and CE4 are moved in the order of the third cam element portion CE3 and the fourth cam element portion CE4 when the fifth operation device M5 is operated. Specifically, the lift portion 26b of the rear end surface cam 25B of the first cam element portion CE1 is offset from the lift portion 26b of the front end surface cam 25A of the second cam element portion CE2 in a retard direction in terms of rotation. Further, the lift portion 26b of the front end surface cam 25A of the fourth cam element portion CE4 is offset from the lift portion 26b of the rear end surface cam 25B of the third cam element portion CE3 in a retard direction in terms of rotation.
According to the aforementioned configuration, it is possible to change the layout of the first and second cam element portions CE1 and CE2 in the aforementioned order of explosion, while switching the layout of the first and second cam element portions CE1 and CE2 from the first layout to the second layout by the second operation device M2, which is provided common to the first and second cam element portions CE1 and CE2. Likewise, it is possible to change the layout of the third and fourth cam element portions CE3 and CE4 in the order of explosion, while switching the layout of the third and fourth cam element portions CE3 and CE4 from the first layout to the second layout by the fifth operation device M5, which is provided common to the third and fourth cam element portions CE3 and CE4.
In the embodiment, the first cam element portion CE1 (the fourth cam element portion CE4) corresponds to a first cam element portion of the present invention. The rear end surface cam 25B of the first cam element portion CE1 (the front end surface cam 25A of the fourth cam element portion CE4) corresponds to a first end surface cam of the present invention. The front end surface cam 25A of the first cam element portion CE1 (the rear end surface cam 25B of the fourth cam element portion CE4) corresponds to a second end surface cam of the present invention. Further, the second cam element portion CE2 (the third cam element portion CE3) corresponds to a second cam element portion of the present invention, and the front end surface cam 25A of the second cam element portion CE2 (the rear end surface cam 25B of the third cam element portion CE3) corresponds to a third end surface cam of the present invention. Furthermore, the second operation device M2 (the fifth operation device M5) corresponds to a first operation member of the present invention, and the first operation device M1 (the sixth operation device M6) corresponds to a second operation member of the present invention. Further, in the embodiment, the front side direction corresponds to a first direction of the present invention, and the rear side direction corresponds to a second direction of the present invention.
The operation of each of the operation devices M1 to M6 is performed by the control device at the following timing. Specifically, the first and fourth operation devices M1 and M4 are operated at a timing when the reference surface 26a of the front end surface cam 25A of each of the first and third cam element portions CE1 and CE3 faces the direction of the pin portion 14 in association with rotation of the camshaft 4. Further, the third and sixth operation devices M3 and M6 are operated at a timing when the reference surface 26a of the rear end surface cam 25B of each of the second and fourth cam element portions CE2 and CE4 faces the direction of the pin portion 14. Furthermore, the second operation device M2 is operated at a timing when both of the reference surface 26a of the end surface cam 25B of the first cam element portion CE1, and the reference surface 26a of the end surface cam 25A of the second cam element portion CE2 opposing to each other face the direction of the pin portion 14. The fifth operation device M5 is operated at a timing when both of the reference surface 26a of the end surface cam 25B of the third cam element portion CE3, and the reference surface 26a of the end surface cam 25A of the fourth cam element portion CE4 opposing to each other face the direction of the pin portion 14.
In this case, it is necessary to move each of the cam element portions CE1 to CE4 at a timing when the cam follower 3a of the locker arm 3 follows a base circle of the first cam portion 23 or the second cam portion 24 (a circumferential portion of the first cam portion 23 or the second cam portion 24 other than the nose portion), namely, when the target cylinder is in a cycle other than an exhaust cycle. In view of the above, in order to satisfy the conditions on these operation timings, as illustrated in
However, even if the lift portion 26b of each of the end surface cams 25A and 25B is formed to satisfy the aforementioned positional relationship, the pin portion 14 projecting to an operative position may not be reset to a retracted position due to an operation failure or a response delay, and for instance, both of the pin portions 14 of the first and second operation devices M1 and M2, which are located on both sides of the first cam element portion CE1, may be temporarily projected to an operative position. Then, the first cam element portion CE1 may be made non-rotatable due to axial restriction of the first cam element portion CE1 by the pin portions 14 from both sides.
In view of the above, in the embodiment, each of the end surface cams 25A and 25B of each of the cam element portions CE1 to CE4 includes a return slope portion 26c (corresponding to a first slope portion of the present invention) for forcibly retracting the pin portion 14 projecting to an operative position, to a retracted position after the layout of each of the cam element portions CE1 to CE4 is switched.
Regarding the end surface cam 25B of the first cam element portion CE1 and the end surface cam 25A of the second cam element portion CE2 opposing to each other, for which switching is performed by the operation device (the second operation device M2), which is provided common to the first and second cam element portions CE1 and CE2 in switching from the first layout to the second layout, the return slope portion 26c is formed only on the rear end surface cam 25B of the first cam element portion CE1, for which switching is performed later. Likewise, regarding the end surface cam 25B of the third cam element portion CE3 and the end surface cam 25A of the fourth cam element portion CE4 opposing to each other, for which switching is performed by the operation device (the fifth operation device M5), which is provided common to the third and fourth cam element portions CE3 and CE4 in switching from the first layout to the second layout, the return slope portion 26c is formed only on the front end surface cam 25A of the fourth cam element portion CE4, for which switching is performed later. This is because of the following reason. When it is assumed that the return slope portion 26c is formed on the front end surface cam 25A of the second cam element portion CE2, the pin portion 14 is forcibly reset to a retracted position after the layout of the second cam element portion CE2 is switched, and as a result, it may be impossible to switch the layout of the first cam element portion CE1. A return slope portion 26c is not formed on the rear end surface cam 25B of the third cam element portion CE2 for the same reason as described above.
As illustrated in
In other words, the return slope portion 26c pushes back the pin portion 14 from an operative position to a retracted position while guiding the pin portion 14 (the pin portion 14 that has reached the lift end position F) after moving the cam element portions CE1 to CE4 along the cam surface of the return slope portion 26c. Thereby, the return slope portion 26c forcibly resets the pin portion 14 from an operative position to a retracted position. As described above, the lift amount of the return slope portion 26c (cam surface) at the slope end position G1 is smaller than the height of the tip end of the pin portion 14 at a retracted position. However, the pin portion 14 is appropriately pushed back to the retracted position by an inertial force and a magnetic force of the electromagnetic actuator to be imparted to the pin portion 14 in the range from the slope start position F to the slope end position G1.
Further, in the embodiment, the rear end surface cam 25B of the first cam element portion CE1 includes a displacement allowing portion 27a, which allows relative movement between the pin portion 14 to be guided along the cam surface of the return slope portion 26c, and the first cam element portion CE1 in the axial direction and in the rotational direction. Specifically, as illustrated in
A difference is made clear when comparison is made with respect to the configuration of the rear end surface cam 25B of the second cam element portion CE2 illustrated in
As described above, the cam surface of the displacement allowing portion 27a is formed in such a manner that the cam surface of the return slope portion 26c extends toward the journal portion 21 side. According to this configuration, even when the first cam element portion CE1 is moved in the axial direction while the pin portion 14 of the second operation device M2 is pushed back along the cam surface of the return slope portion 26c, relative movement between the first cam element portion CE1 and the pin portion 14 is allowed to avoid that the first cam element portion CE1 is made non-rotatable. This point will be described later in detail. The displacement allowing portion 27a is also formed on the front end surface cam 25A of the fourth cam element portion CE4. According to this configuration, even when the fourth cam element portion CE4 is moved in the axial direction while the pin portion 14 of the fifth operation device M5 is pushed back along the cam surface of the return slope portion 26c of the front end surface cam 25A, relative movement between the fourth cam element portion CE4 and the pin portion 14 is allowed.
A reverse slope portion 26d (referred to as a first reverse slope portion 26d, corresponding to a second slope portion of the present invention) for forcibly retracting the pin portion 14 projecting to an operative position, to a retracted position when the camshaft 4 is rotated in a reverse direction, is formed on each of the end surface cams 25A and 25B of each of the cam element portions CE1 to CE4.
The first reverse slope portion 26d is formed with the return slope portion 26c on the same end surface cam as the end surface cam 25A or as the end surface cam 25B where the return slope portion 26c is formed, out of the end surface cams 25A and 25B of the cam element portions CE1 to CE4. In other words, in the embodiment, the first reverse slope portion 26d is formed on the end surface cams 25A and 25B of the cam element portions CE1 to CE4, except for the front end surface cam 25A of the second cam element portion CE2, and the rear end surface cam 25B of the third cam element portion CE3.
As illustrated in
As illustrated in
According to the aforementioned configuration, in rotating the camshaft 4 in a reverse direction, it is possible to forcibly retract the pin portion 14 from an operative position to a retracted position by guiding the tip end of the pin portion 14 along the cam surfaces 261 and 262 of the first reverse slope portion 26d, or along the cam surfaces 261 and 263 of the first reverse slope portion 26d. As described above, the lift amount of the first reverse slope portion 26d (cam surface) at the reverse-time slope end position G1 is smaller than the height of the tip end of the pin portion 14 at a retracted position. However, the pin portion 14 is appropriately pushed back to the retracted position by an inertial force to be imparted to the pin portion 14 in the range from the reverse-time slope start position H to the reverse-time slope end position G1.
Further, the rear end surface cam 25B of the first cam element portion CE1, and the front end surface cam 25A of the fourth cam element portion CE4, each of which includes the displacement allowing portion 27a, includes a reverse slope portion 27b (referred to as a second reverse slope portion 27b, corresponding to a third slope portion of the present invention) for forcibly retracting the pin portion 14 projecting to an operative position, to a retracted position when the camshaft 4 is rotated in a reverse direction in a state that the tip end of the pin portion 14 faces the displacement allowing portion 27a.
As illustrated in
According to the aforementioned configuration, when the camshaft 4 is rotated in a reverse direction in a state that the tip end of the pin portion 14 faces the displacement allowing portion 27a, it is possible to forcibly retract the pin portion 14 from an operative position to a retracted position by guiding the tip end of the pin portion 14 along the cam surface of the second reverse slope portion 27b.
Regarding the end surface cams 25A and 25B opposing to each other, out of the end surface cams 25A and 25B of the cam element portions CE1 to CE4, the end surface cams 25A and 25B are formed in such a manner that the return slope portion 26c and the first reverse slope portion 26d, and the lift portion 26b facing the return slope portion 26c and the first reverse slope portion 26d do not interfere with each other.
(Operations and Advantageous Effects of Valve Train Device)
Next, the operations and the advantageous effects of the valve train device of the embodiment are described.
As illustrated in
When the valves are switched in such a manner as to decrease the valve opening amount of the exhaust valves 1 from the aforementioned state accompanied by lowering of the engine speed, the pin portions 14 of the second operation device M2 and the fifth operation device M5 are caused to project from a retracted position to an operative position by operations of the second operation device M2 and the fifth operation device M5.
In this case, first of all, the pin portion 14 of the fifth operation device M5 is caused to project between the end cam surface 25B of the third cam element portion CE3, and the end surface cam 25A of the fourth cam element portion CE4 opposing to each other in a proximate state, and the pin portion 14 is engaged with the end surface cams 25A and 25B. Specifically, the pin portion 14 is caused to project between the end surface cams 25A and 25B at a position where the lift amounts of the opposing end surface cams 25A and 25B are zero, namely, at a position where the reference surfaces 26a of the opposing end surface cams 25A and 25B face to each other.
As described above, when the pin portion 14 comes between the end surface cams 25A and 25B, first of all, the pin portion 14 pushes the third cam element portion CE3 forward while coming into sliding contact (engaging) with the lift portion 26b of the rear end surface cam 25B of the third cam element portion CE3 in association with rotation of the camshaft 4. Thereby, the third cam element portion CE3 is moved from the rear position to the front position. Further, when the camshaft 4 is rotated by 90°, and the lift start position S of the front end surface cam 25A of the fourth cam element portion CE4 reaches the pin portion 14, the pin portion 14 pushes the fourth cam element portion CE4 rearward while coming into sliding contact with the lift portion 26b of the front end surface cam 25A of the fourth cam element portion CE4 in association with rotation of the camshaft 4. Thereby, the fourth cam element portion CE4 is moved from the front position to the rear position.
Then, when the lift end position F of the front end surface cam 25A of the fourth cam element portion CE4 reaches the pin portion 14, the fifth operation device M5 is stopped. Thereby, the pin portion 14 of the fifth operation device M5 is reset from an operative position to a retracted position by the urging force of the return spring 2.
Next, the pin portion 14 of the second operation device M2 comes between the end surface cam 25B of the first cam element portion CE1 and the end surface cam 25A of the second cam element portion CE2 opposing to each other in a proximate state, and the pin portion 14 is engaged with the end surface cams 25A and 25B. Also, in this case, the pin portion 14 comes between the end surface cams 25A and 25B at a position where the lift amounts of the opposing end surface cams 25A and 25B are zero, namely, at a position where the reference surfaces 26a of the opposing end surface cams 25A and 25B face to each other.
As described above, when the pin portion 14 comes between the end surface cams 25A and 25B, first of all, the pin portion 14 pushes the second cam element portion CE2 rearward while coming into sliding contact (engaging) with the lift portion 26b of the front end surface cam 25A of the second cam element portion CE2 in association with rotation of the camshaft 4. Thereby, the second cam element portion CE2 is moved from the front position to the rear position. Further, when the camshaft 4 is rotated by 90°, and the lift start position S of the rear end surface cam 25B of the first cam element portion CE1 reaches the pin portion 14, the pin portion 14 pushes the first cam element portion CE1 forward while coming into sliding contact with the lift portion 26b of the rear end surface cam 25B of the first cam element portion CE1 in association with rotation of the camshaft 4. Thereby, the first cam element portion CE1 is moved from the rear position to the front position.
Then, when the pin portion 14 of the second operation device M2 reaches the lift end position F of the rear end surface cam 25B of the first cam element portion CE1, the second operation device M2 is stopped. Thereby, the pin portion 14 of the second operation device M2 is reset from an operative position to a retracted position by the urging force of the return spring.
By performing the aforementioned operation, the layout of the first to fourth cam element portions CE1 to CE4 is switched from the first layout illustrated in
In the switching operation of each of the cam element portions CE1 to CE4 from the first layout to the second layout, the second operation device M2 (the fifth operation device M5) is reset to a retracted position by the urging force of the return spring immediately at a point of time when movement of the first cam element portion CE1 (the fourth cam element portion CE4) is completed, in other words, at a point of time when the lift end position F of the lift portion 26b reaches the pin portion 14. In this case, even when the pin portion 14 is not reset because the return spring does not sufficiently function due to e.g. an operation failure, the pin portion 14 is pushed upward along the cam surface of the return slope portion 26c in association with rotation of the camshaft 4, and is forcibly pushed back to a retracted position. Thus, the pin portion 14 of the second operation device M2 (the fifth operation device M5) is securely reset to a retracted position.
Further, as illustrated by the solid line in
On the other hand, as illustrated in
In this case, first of all, the pin portion 14 of the fourth operation device M4 is caused to project to a position where the lift amount of the front end surface cam 25A of the third cam element portion CE3 is zero, namely, at a position where the pin portion 14 faces the reference surface 26a. When the pin portion 14 is caused to project as described above, the pin portion 14 pushes the third cam element portion CE3 rearward while coming into sliding contact (engaging) with the lift portion 26b of the front end surface cam 25A of the third cam element portion CE3 in association with rotation of the camshaft 4. Thereby, the third cam element portion CE3 is moved from the front position to the rear position.
When the camshaft 4 is rotated by 90° as described above, next, the pin portion 14 of the sixth operation device M6 is caused to project to a position where the lift amount of the rear end surface cam 25B of the fourth cam element portion CE4 is zero (the position where the pin portion 14 faces the reference surface 26a). Thereby, the pin portion 14 pushes the fourth cam element portion CE4 forward while coming into sliding contact with the lift portion 26b of the rear end surface cam 25B of the fourth cam element portion CE4, and the fourth cam element portion CE4 is moved from the rear position to the front position.
Thereafter, the pin portion 14 of the third operation device M3 is caused to project to a position where the lift amount of the rear end surface cam 25B of the second cam element portion CE2 is zero (the position where the pin portion 14 faces the reference surface 26a). Thereby, the pin portion 14 pushes the second cam element portion CE2 forward while coming into sliding contact with the lift portion 26b of the rear end surface cam 25B of the second cam element portion CE2, and the second cam element portion CE2 is moved from the rear position to the front position.
Thereafter, the pin portion 14 of the first operation device M1 is caused to project to a position where the lift amount of the front end surface cam 25A of the first cam element portion CE1 is zero (the position where the pin portion 14 faces the reference surface 26a). Thereby, the pin portion 14 pushes the first cam element portion CE1 rearward while coming into sliding contact with the lift portion 26b of the front end surface cam 25A of the first cam element portion CE1, and the first cam element portion CE1 is moved from the front position to the rear position.
By performing the aforementioned operation, the layout of each of the first to fourth cam element portions CE1 to CE4 is switched from the second layout to the first layout. As illustrated in
In the switching operation of each of the cam element portions CE1 to CE4 from the second layout to the first layout, the first operation device M1 (the third operation device M3, the fourth operation device M4, and the sixth operation device M6) is reset to a retracted position by the urging force of the return spring immediately at a point of time when movement of the first cam element portion CE1 (the second cam element portion CE2, the third cam element portion CE3, and the fourth cam element portion CE4) is completed, in other words, at a point of time when the lift end position F of the lift portion 26b reaches the pin portion 14. In this case, even when the pin portion 14 is not reset because the return spring does not sufficiently function due to e.g. an operation failure, the pin portion 14 is pushed upward along the cam surface of the return slope portion 26c in association with rotation of the camshaft 4, and is forcibly pushed back to a retracted position. Thus, the pin portion 14 of the first operation device M1 (the third operation device M3, the fourth operation device M4, and the sixth operation device M6) is securely reset to a retracted position.
Further, the engine may be rotated in a reverse direction due to engine stall or the like in a state that the pin portion 14 of the first operation device M1 (the third operation device M3, the fourth operation device M4, and the sixth operation device M6) is caused to project to an operative position. In this case, the pin portion 14 is pushed upward along the first reverse slope portion 26d (cam surfaces 261 and 263) of the front end surface cam 25A of the first cam element portion CE1 (the rear end surface cam 25B of the second cam element portion CE2, the front end surface cam 25A of the third cam element portion CE3, and the rear end surface cam 25B of the fourth cam element portion CE4) in association with rotation of the camshaft 4 in a reverse direction. Thereby, the pin portion 14 is forcibly pushed back to a retracted position. This makes it possible to prevent interference of the pin portion 14 with the return slope portion 26c by rotation of the engine in a reverse direction.
According to the valve train device having the aforementioned configuration, each of the cam element portions CE1 to CE4 includes the return slope portion 26c, which is inclined outwardly toward the retard side in terms of rotation than the lift end position F of each of the end surface cams 25A and 25B to be engaged with the pin portion 14, and which is configured o forcibly retract the pin portion 14 from an operative position to a retracted position. According to this configuration, even when the pin portion 14 of each of the operation devices M1 to M6 is not reset to a retracted position due to e.g. an operation failure immediately after each of the operation devices CE1 to CE4 is moved, it is possible to securely retract the pin portion 14 to the retracted position in association with rotation of the camshaft 4.
This makes it possible to avoid simultaneous projection of the pin portions 14 at both sides of a specific cam element portion at an operative position due to an operation failure of operation devices located at both sides of the specific cam element portion, for instance, the first operation device M1 and the second operation device M2, which are located at both sides of the first cam element portion CE1. Thus, according to the valve train device, it is possible to avoid that a target cam element portion is made non-rotatable due to axial restriction of the cam element portion by the pin portions 14 on both sides.
In particular, each of the end surface cam 25B of the first cam element portion CE1 and the end surface cam 25A of the fourth cam element portion CE4 includes the displacement allowing portion 27a. This is advantageous in securely avoiding that a cam element portion is made non-rotatable as described above. In the following, this point is described in detail using
First of all, a mechanism as to how a cam element portion is made non-rotatable as described above is described by a comparative example as illustrated in
As illustrated in
In this case, it is assumed that the pin portion 14 of the first operation device M1 and the pin portion 14 of the second operation device M2 are projected to an operative position due to an operation failure. In this case, after the first cam element portion CE1′ is moved, the pin portion 14 of the second operation device M2 is forcibly pushed back to a retracted position while being guided along a return slope portion 26c. However, as described above, there is a wall of the lift portion 26b on a portion of the return slope portion 26c on the journal portion 21 side in the range from the lift end position F to the slope end position G1. Therefore, when the pin portion 14 of the second operation device M2 is not reset to a retracted position before the pin portion 14 of the first operation device M1 starts sliding contact with the lift portion 26b of the front end surface cam 25A, as illustrated in
On the other hand, as illustrated in
Thus, according to the valve train device, it is possible to securely avoid that each of the cam element portions CE1 to CE4 is made non-rotatable due to axial restriction of each of the cam element portions CE1 to CE4 by the pin portions 14 on both sides.
In particular, each of the first and fourth cam element portions CE1 and CE4 includes the second reverse slope portion 27b continuing to the displacement allowing portion 27a on the advance side in terms of rotation. When the camshaft 4 is rotated in a reverse direction as a result of rotation of the engine in a reverse direction, the pin portion 14 is forcibly reset to a retracted position while being guided along the second reverse slope portion 27b from the displacement allowing portion 27a. Thus, it is possible to avoid in advance a drawback that the pin portion 14 facing the displacement allowing portion 27a is damaged or broken by interference with the lift portion 26b when the engine is rotated in a reverse direction due to engine stall or the like.
Further, each of the end surface cams 25A and 25B of each of the cam element portions CE1 to CE4 includes the first reverse slope portion 26d continuing to the return slope portion 26c on the retard side in terms of rotation. When the camshaft 4 is rotated in a reverse direction as a result of rotation of the engine in a reverse direction, the pin portion 14 is forcibly reset to a retracted position along the first reverse slope portion 26d. This makes it possible to avoid in advance a drawback that the pin portion 14 facing the reference surface 26a in a state that the pin portion 14 is projected to an operative position is damaged or broken by interference with the return slope portion 26c when the engine is rotated in a reverse direction due to engine stall or the like.
Further, in the valve train device, the first and second cam element portions CE1 and CE2 adjacent to each other, and the third and fourth cam element CE3 and CE4 adjacent to each other are formed in such a manner that the lift portions 26b of the end cam surfaces 25A and 25B opposing to each other have phases different from each other. Thus, the valve train device is configured in such a manner that at least parts of the lift portions 26b of the end surface cams 25A and 25B opposing to each other overlap each other in the axial direction when the first and second cam element portions CE1 and CE2 are close to each other, and when the third and fourth cam element portions CE3 and CE4 are close to each other, in other words, when the layout of the cam element portions CE1 to CE4 is the first layout. Further, the valve train device is configured in such a manner that the layout of the first and second cam element portions CE1 and CE2 is switched from the first layout to the second layout by the second operation device M2, which is provided common to the first and second cam element portions CE1 and CE2, and the layout of the third and fourth cam element portions CE3 and CE4 is switched from the first layout to the second layout by the fifth operation device M5, which is provided common to the third and fourth cam element portions CE3 and CE4.
Therefore, according to the valve train device having the aforementioned configuration, it is possible to dispose the first and second cam element portions CE1 and CE2, and the third and fourth cam element portions CE3 and CE4 in a compact manner in the axial direction, and to move the first to fourth cam element portions CE1 to CE4 with a less number of operation devices i.e. with use of the operation devices M1 to M6. This makes it possible to miniaturize the valve train device in the axial direction, and consequently, to miniaturize the engine in the axial direction.
Furthermore, regarding the end surface cam 25B of the first cam element portion CE1, and the end surface cam 25A of the second cam element portion CE2 opposing to each other, the return slope portion 26c is formed only on the end surface cam 25B, which is switched later. Likewise, regarding the end surface cam 25B of the third cam element portion CE3, and the end surface cam 25A of the fourth cam element portion CE4 opposing to each other, the return slope portion 26c is formed only on the end surface cam 25A of the fourth cam element portion CE4, which is switched later. Therefore, in switching the layout from the first layout to the second layout, it is possible to securely reset the pin portion 14 to a retracted position, while moving the first and second cam element portions CE1 and CE2 by the first operation device M1, which is provided common to the first and second cam element portions CE1 and CE2 in the order of explosion. Likewise, it is possible to securely reset the pin portion 14 to a retracted position, while moving the third and fourth cam element portions CE3 and CE4 by the fifth operation device M5, which is provided common to the third and fourth cam element portions CE3 and CE4 in the order of explosion. This makes it possible to sequentially, appropriately, and speedily perform a switching operation of the first and second cam element portions CE1 and CE2 from the first layout to the second layout, and a switching operation of the third and fourth cam element portions CE3 and CE4 from the first layout to the second layout.
In the valve train device, as described above, forming the displacement allowing portion 27a on each of the first and fourth cam element portions CE1 and CE4 is advantageous in avoiding that the cam element portion is made non-rotatable, but the following advantages are further provided.
First of all, in switching each of the cam element portions CE1 to CE4 from the first layout to the second layout, it is possible to increase the degree of freedom of the operation timing of each of the pin portions 14 of the second and fifth operation devices M2 and M5. Specifically, as described above, the lift portion 26b of the front end surface cam 25A and the lift portion 26b of the rear end surface cam 25B of the first cam element portion CE1 are offset from each other in the rotational direction (formed to have a phase difference) in such a manner that the distance between the first and second operation devices M1 and M2 is narrowed as much as possible, while securing a required moving amount (stroke) of the first cam element portion CE1. In this case, it is preferable to set the offset amount (phase difference) as large as possible in order to avoid that a cam element portion is made non-rotatable as described above. However, it is preferable to set the offset amount small in order to increase the degree of freedom of the timing at which the pin portion 14 of each of the first and second operation devices M1 and M2 is caused to project to an operative position. In view of the above, as described above, the valve train device of the embodiment is configured in such a manner that the displacement allowing portion 27a is formed on the rear end surface cam 25B of the first cam element portion CE1 to allow relative displacement between the first cam element portion CE1 and the pin portion 14 of the second operation device M2 in the axial direction so as to avoid that the cam element portion is made non-rotatable. This makes it possible to set the offset amount of the lift portion 26b small on the front side and the rear side.
This also makes it possible to displace the lift portion 26b of the second cam element portion CE2 (the front end surface cam 25A) opposing to the lift portion 26b of the rear end surface cam 25B in the retard direction in terms of rotation by the aforementioned amount. Consequently, it is possible to increase the range by which the reference surfaces 26a face to each other in the rotational direction X by the amount indicated by the reference sign β in
Further, it is also possible to displace the lift end position F in the retard direction in terms of rotation while keeping the lift start position S of each of the lift portions 26b unchanged so as to decrease the inclination angle of each of the lift portions 26b. In this case, noise of collision of the pin portion 14 against the lift portion 26b can be reduced by the amount corresponding to a decrease in the slope of the lift portions 26b. This contributes to noise reduction of the engine.
In the foregoing description, the advantages by forming the displacement allowing portion 27a are described mainly regarding the first and second cam element portions CE1 and CE2. The same advantages as described above are also obtained regarding the third and fourth cam element portions CE3 and CE4.
Alternatively, a configuration as illustrated in
According to the configuration illustrated in
The valve train device of the embodiment described above is an example of a preferred embodiment of the valve train device for an engine according to the present invention. A specific configuration of the valve train device may be modified as far as the modification does not depart from the gist of the present invention.
For instance, in the embodiment, an example is described, in which the present invention is applied to the camshaft 4 on the exhaust side. The present invention is also applicable to a camshaft 4 on the intake side.
Further, in the embodiment, an example is described, in which the cam portions 23 and 24 of each of the cam element portions CE1 to CE4 are switched in the order of explosion, namely, in the order of the third cylinder C3, the fourth cylinder C4, the second cylinder C2, and the first cylinder C1. Alternatively, the cam portions may be switched in the order of explosion, namely, in the order of the second cylinder C2, the first cylinder C1, the third cylinder C3, and the fourth cylinder C4.
Further, in the embodiment, the second operation device M2 is disposed between the first cam element portion CE1 and the second cam element portion CE2, and the fifth operation device M5 is disposed between the third cam element portion CE3 and the fourth cam element portion CE4. Alternatively, operation devices may be respectively disposed in association with the rear end cam surface 25B of the first cam element portion CE1, and in association with the front end surface cam 25A of the second cam element portion CE2, and operation devices may be respectively disposed in association with the rear end cam surface 25B of the third cam element portion CE3, and in association with the front end surface cam 25A of the fourth cam element portion CE4 to allow the operation devices to individually operate the corresponding end surface cams 25A and 25B.
Further, the present invention is not limited to a 4-cylinder, 4-valve DOHC engine exemplified in the embodiment, but may be applied to various types of engines, whose number of cylinders and whose valve train mechanisms are different, such as an in-line 6-cylinder engine, a V-shaped multi-cylinder engine, a 4-cylinder 2-valve DOHC engine, a single-cylinder SOHC engine, and a multi-cylinder SOHC engine.
The following is a summary of the present invention described above.
In order to solve the aforementioned drawbacks, the present invention is directed to a valve train device for an engine including a shaft portion which rotates by receiving a rotational force from a crankshaft; a cam element portion mounted on the shaft portion in such a manner as to be displaceable relative to the shaft portion in an axial direction of the shaft portion and to be integrally rotated with the shaft portion, the cam element portion including a plurality of cam portions aligned in the axial direction on an outer periphery of the cam element portion; and an operation member which causes the cam element portion to move in the axial direction, the valve train device being configured to switch the cam portions for use in opening or closing valves by causing the cam element portion to move in the axial direction by the operation member. The cam element portion includes a first end surface cam and a second end surface cam on both ends of the cam element portion in the axial direction, each of the first end surface cam and the second end surface cam including a reference surface which extends in a direction orthogonal to the axial direction, and a lift portion which projects outwardly from the reference surface in the axial direction in such a manner that an amount of projection of the lift portion increases toward a retard direction in terms of rotation, the reference surface and the lift portion being aligned in a rotational direction. The operation member includes a first operation member and a second operation member, each of which is operative to advance or retract in a range from an operative position where the operation member comes inside the outer periphery of the cam element portion, and a retracted position where the operation member comes outside the outer periphery, the first operation member being configured to move the cam element portion in a first direction along the axial direction by engagement with the lift portion of the first end surface cam in association with rotation of the cam element portion when the operation member is set to the operative position, and the second operation member being configured to move the cam element portion in a second direction opposite to the first direction by engagement with the lift portion of the second end surface cam in association with rotation of the cam element portion when the operation member is set to the operative position. The cam element portion includes, at least on the first end cam surface, a first slope portion which extends in the retard direction in terms of rotation from a maximum lift position where the amount of projection of the lift portion is maximized, and guides the first operation member radially outwardly of the cam element portion in association with rotation of the cam element portion, and a displacement allowing portion which is formed adjacent to the first slope portion in the axial direction, and allows relative displacement between the first operation member to be guided along the first slope portion and the cam element portion in the axial direction and in the rotational direction when both of the first operation member and the second operation member are projected to the operative position.
According to the valve train device, when the first operation device is set to the operative position, and the first operation member is engaged with the lift portion of the first end surface cam in association with rotation of the cam element portion, the cam element portion is moved in the axial direction. After the cam element portion is moved in the axial direction as described above, allowing the first operation member to be guided along the first slope portion radially outwardly of the cam element portion makes it possible to forcibly push back the first operation member from the operative position to the retracted position. This makes it possible to avoid that the first operation member is kept at the operative position due to an operation failure or a response delay. Further, the cam element portion includes the displacement allowing portion which allows relative displacement between the operation member to be guided along the first slope portion and the cam element portion in the axial direction and in the rotational direction. This allows relative displacement between the operation member and the cam element portion due to an external force, even when the external force in the axial direction is acted on the cam element portion during guiding of the first operation member along the first slope portion. This makes it possible to avoid that the cam element portion is made non-rotatable. Specifically, when both of the first operation member and the second operation member are set to the operative position due to e.g. an operation failure after the cam element portion is moved in the first direction by engagement of the first operation member with the lift portion, and when it is assumed that the displacement allowing portion is not formed, the second operation member may be engaged with the lift portion of the second end surface cam in association with rotation of the cam element portion, and the cam element portion may be made non-rotatable due to axial restriction of the cam element portion from both sides by each of the operation members. However, in the valve train device according to the present invention, relative displacement between the first operation member and the cam element portion is allowed by the displacement allowing portion. Therefore, when the second operation member is engaged with the lift portion of the second end surface cam during guiding of the first operation member along the first slope portion, the cam element portion is pushed back in the axial direction. This makes it possible to prevent axial restriction of the cam element portion from both sides by each of the operation members, and to avoid that the cam element portion is made non-rotatable as described above.
In the valve train device, preferably, the first slope portion may include a slope portion side guide surface which guides the first operation member, and the displacement allowing portion may include an allowing portion side guide surface which continues to the slope portion side guide surface, and guides the first operation member radially outwardly of the cam element portion in association with rotation of the cam element portion.
According to the aforementioned configuration, it is possible to smoothly cause relative displacement between the first operation member and the cam element portion when the first operation member is pushed back to the retracted position along the slope portion (the slope portion side guide surface).
In the valve train device, preferably, the cam element portion may include a second slope portion which continues to a portion of the first slope portion on a retard direction side in terms of rotation and to a portion of the displacement allowing portion on the retard direction side in terms of rotation, and guides the first operation member at the operative position radially outwardly of the cam element portion when the cam element portion is rotated in a reverse direction.
According to the aforementioned configuration, when the shaft portion is rotated in a reverse direction as a result of rotation of the engine in a reverse direction, and when the cam element portion is rotated in a reverse direction accompanied by the reverse rotation of the shaft portion, the first operation member is guided from the operative position to the retracted position along the second slope portion. This makes it possible to avoid a drawback that the first operation member is damaged or broken by interference of the first operation member with the lift portion when the cam element portion is rotated in a reverse direction.
In the valve train device, preferably, the cam element portion may include a third slope portion which continues to a portion of the displacement allowing portion on an advance direction side in terms of rotation, and guides the first operation member at the operative position radially outwardly of the cam element portion.
According to the aforementioned configuration, when the cam element portion (the shaft portion) is rotated in a reverse direction in a state that the first operation member faces the displacement allowing portion, the first operation member is guided from the operative position to the retracted position along the third slope portion. This makes it possible to securely avoid a drawback that the first operation member is damaged or broken by interference of the first operation member with the lift portion due to reverse rotation of the cam element portion.
In the valve train device, when it is assumed that the lift portion of the first end surface cam is a first lift portion, preferably, the first end surface cam may include a second lift portion which continues to the first lift portion, extends from the maximum lift position in the retard direction in terms of rotation, and moves the cam element portion in the first direction by engagement with the first operation member facing the displacement allowing portion in association with rotation of the cam element portion in a reverse direction when the cam element portion is rotated in the reverse direction.
According to the aforementioned configuration, when the cam element portion (the shaft portion) is rotated in a reverse direction in a state that the first operation member faces the displacement allowing portion, the cam element portion is displaced in the axial direction by engagement of the first operation member with the second lift portion. In other words, it is possible to allow relative rotation between the cam element portion and the operation member while moving the cam element portion in the axial direction.
In the valve train device, when it is assumed that the cam element portion is a first cam element portion, the valve train device may preferably further include a second cam element portion which is formed adjacent to the first cam element portion, and is configured to be displaceable between a proximate position where the first cam element portion and the second cam element portion are close to each other, and a spaced position where the first cam element portion and the second cam element portion are spaced from each other. The second cam element portion may further include a third end surface cam which opposes to the first end surface cam of the first cam element portion. The third end surface cam may include a reference surface extending in a direction orthogonal to the axial direction, and a lift portion projecting outwardly from the reference surface in the axial direction in such a manner that an amount of projection of the lift portion increases toward the retard direction in terms of rotation, the reference surface and the lift portion being aligned in the rotational direction. The lift portion of the first end surface cam and the lift portion of the third end surface cam may be offset from each other in the rotational direction, and may be formed in such a manner that at least parts of the lift portions overlap each other in the axial direction when the first cam element portion and the third cam element portion are set to the proximate position. The first operation member may be engaged with the lift portion of the first end surface cam and with the lift portion of the third end surface cam when the first cam element portion and the third cam element portion are set to the proximate position, and the first operation member may be set to the operative position.
According to the aforementioned configuration, it is possible to dispose the first cam element portion and the second cam element portion in a compact manner in the axial direction. Further, it is possible to move both of the first cam element portion and the second cam element portion by an operation member (the first operation member), which is provided common to the first cam element portion and the second cam element portion. This makes it possible to miniaturize the valve train device in the axial direction, and consequently, to miniaturize the engine in the axial direction.
In the aforementioned configuration, preferably, the lift portion of the first end surface cam may be offset from the lift portion of the third end surface cam in the retard direction in terms of rotation, and the first slope portion may be formed only on the first end surface cam.
According to the aforementioned configuration, it is possible to appropriately push back the first operation member from the operative position to the retracted position after the second cam element portion and the first cam element portion are moved in the axial direction by the operation member (the first operation member), which is provided common to the second cam element portion and the first cam element portion.
Number | Date | Country | Kind |
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2014-112231 | May 2014 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2015/065216 | 5/27/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2015/182646 | 12/3/2015 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20100108006 | Elendt | May 2010 | A1 |
20150075468 | Takagi et al. | Mar 2015 | A1 |
Number | Date | Country |
---|---|---|
2013-083202 | May 2013 | JP |
2013083202 | May 2013 | JP |
2013-185462 | Sep 2013 | JP |
2015-059483 | Mar 2015 | JP |
Entry |
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International Search Report issued in PCT/JP2015/065216; dated Aug. 25, 2015. |
Number | Date | Country | |
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20170191387 A1 | Jul 2017 | US |