VALVE GEAR FOR ENGINE
A valve gear includes a camshaft, a first cam and a second cam that drive an intake valve or an exhaust valve, and a synchronous cam that rotates in synchronism with the first and second cams. The valve gear includes a rocker shaft, a rocker arm, and a cam follower swingably supported by the rocker shaft and that comes into contact with the synchronous cam. The valve gear includes a thruster that converts the swinging motion of the cam follower into a thrust and moves the rocker arm to a first side or a second side in the axial direction. The valve gear makes the camshaft compact, and also increases the reliability of operation at high rotations and reduces an operation sound at low rotations.
The present invention relates to a valve gear for an engine, which switches between a plurality of cams with different cam profiles.
2. Description of the Related ArtSome recent engines mounted in vehicles are able to switch operation modes during operation. The operation modes to be switched include two operation modes having different fuel consumptions or output characteristics. Switching of the operation mode is often done using a valve gear that drives an intake valve and an exhaust valve.
A conventional valve gear capable of switching the operation mode is described in, for example, Japanese Patent Laid-Open No. 2010-249123. The valve gear disclosed in Japanese Patent Laid-Open No. 2010-249123 includes a camshaft, a rocker arm that transmits a driving force between the camshaft and an intake valve or an exhaust valve, and a driving device that switches the operation mode. The camshaft is provided with first and second cams that drive the intake valve or the exhaust valve, and an advancing and retreating cams that switch the operation mode.
The first cam and the second cam have shapes of different cam profiles. For example, the first cam has a shape with a cam nose projecting from a base circle, and the second cam has a shape of a perfect circle (for cylinder deactivation). The first and second cams or the rocker arm is movable in the axial direction of the camshaft. The first and second cams movable in the axial direction rotate integrally with the camshaft.
The valve gear described in Japanese Patent Laid-Open No. 2010-249123 presses the first and second cams or the rocker arm in the axial direction of the camshaft using the above-described advancing and retreating cams. That is, switching is performed between a first operation mode in which the rocker arm is pressed by the first cam and a second operation mode in which the rocker arm is pressed by the second cam.
The advancing cam and the retreating cam are constituted by spirally formed cam grooves and disposed side by side in the axial direction of the camshaft. The spiral of the advancing cam extends along the outer surface of the camshaft in one axial direction and the rotation direction. The spiral of the retreating cam extends along the outer surface of the camshaft in the other axial direction and the rotation direction. That is, the advancing cam and the retreating cam have shapes with spirals extending in opposite directions. This valve gear includes an advancing cam follower that selectively comes into contact with the advancing cam, and a retreating cam follower that selectively comes into contact with the retreating cam.
If the first and second cams are able to move in the axial direction, an arrangement to move the advancing cam and the retreating cam in the axial direction integrally with the first and second cams is used. In this case, the advancing cam follower, the retreating cam follower, and the rocker arm are supported by a cylinder head in a state in which they cannot move in the axial direction of the camshaft.
On the other hand, if the rocker arm is able to move in the axial direction, the advancing cam follower and the retreating cam follower are supported by a slide member that moves in the axial direction integrally with the rocker arm.
Another conventional valve gear of this type moves the rocker arm by the spring force of a helical compression spring without using the above-described advancing and retreating cams. In this valve gear, a timing of switching between the first operation mode and the second operation mode is defined by a switching timing control cam that rotates integrally with the first and second cams.
In the valve gear for an engine described in Japanese Patent Laid-Open No. 2010-249123, since the advancing cam and the retreating cam are needed on the camshaft, the total length of the camshaft increases. Recent camshafts have many functions to implement a 4-valve engine or expand capabilities. For example, the camshaft is provided with members such as gears and cams used to drive auxiliary machinery such as a high pressure fuel pump and a vacuum pump, and a rotation angle detection rotor. For this reason, to provide the advancing cam and the retreating cam on such a camshaft, the total length of the camshaft needs to be increased.
In the valve gear that moves the rocker arm in the axial direction by the spring force of a helical compression spring, a problem arises because the switching speed depends on only the spring load of the helical compression spring. In this valve gear, to correctly perform switching in a state in which the operation range of the engine is the high rotation range, a high spring load is necessary to increase the switching speed. However, if the spring load is high, a high impact load is applied to the switching portion at the time of switching, resulting in abnormal noise. The abnormal noise is not problematic in a high rotation mode with a loud engine sound. In a low rotation mode with a small engine sound, however, the abnormal noise may be unpleasant.
SUMMARY OF THE INVENTIONPreferred embodiments of the present invention provide a valve gear for an engine which provides a compact camshaft and also increases the reliability of a switching operation and reduces a switching operation sound.
According to a preferred embodiment of the present invention, a valve gear for an engine includes a camshaft rotatably supported by a cylinder head, a first cam provided on the camshaft and that drives one of an intake valve and an exhaust valve, a second cam provided on the camshaft spaced apart from the first cam in an axial direction, and that drives one of the intake valve and the exhaust valve, the second cam having a shape with a cam profile different from a cam profile of the first cam, a synchronous cam provided on the camshaft that rotates in synchronism with the first cam and the second cam, a rocker shaft parallel or substantially parallel to the camshaft, a rocker arm supported by the rocker shaft that swings and moves in the axial direction and converts a rotation of one of the first cam and the second cam into a reciprocal motion and transmits the reciprocal motion to one of the intake valve and the exhaust valve, a cam follower swingably supported by the rocker shaft and that comes into contact with the synchronous cam, and a thruster that converts the swing motion of the cam follower into a thrust in the axial direction and moves the rocker arm to one of a first side and a second side in the axial direction.
According to a preferred embodiment of the present invention, in the valve gear for the engine, the thruster preferably includes a slide portion that swings integrally with the cam follower and moves in the axial direction integrally with the rocker arm, and a switching portion supported by the cylinder head and including a first switch and a second switch, wherein the first switch and the second switch selectively come into contact with the slide portion, and the slide portion preferably includes a first inclined cam surface that receives a force in a first side thereof in the axial direction, wherein the force is generated by one of the first switch and the second switch in contact with the first inclined cam surface, and a second inclined cam surface that receives a force in a second side thereof in the axial direction, wherein the force is generated by the other of the first switch and the second switch in contact with the second inclined cam surface.
According to a preferred embodiment of the present invention, in the valve gear for the engine, a movement of the cam follower in the axial direction is preferably regulated or controlled, and the slide portion is separate from the cam follower and movable in the axial direction relative to the cam follower.
According to a preferred embodiment of the present invention, in the valve gear for the engine, each of the first switch and the second switch preferably include a pin that moves between an advancing position at which a first end comes into contact with the slide portion and a retreating position at which the first end separates from the slide portion, the second end of the pin preferably abuts against a pin cam of a moving member that moves in a direction perpendicular or substantially perpendicular to a direction in which the pin moves, and the pin cam has a shape such that when the moving member moves to a first side, the first switch moves to the advancing position and the second switch moves to the retreating position, and when the moving member moves to a second side, the first switch moves to the retreating position and the second switch moves to the advancing position.
In a preferred embodiment of the present invention, when the cam follower is pressed by the synchronous cam and swings, the thruster moves the rocker arm to a first side or a second side in the axial direction. When the rocker arm moves in the axial direction, switching is performed between a first operation mode in which the rocker arm is driven by the first cam and a second operation mode in which the rocker arm is driven by the second cam.
The synchronous cam is preferably short in the axial direction, as compared to conventional advancing and retreating cams including helical grooves.
In the valve gear, the switching speed when switching the operation mode depends on the profile (shape) and the cam rotational speed of the synchronous cam. For this reason, the switching speed changes in proportion to the cam rotational speed. As compared to a case in which the spring load of a spring member is increased when increasing the switching speed, reliability in switching at high rotations becomes high, and the operation sound at low rotations becomes small.
According to various preferred embodiments of the present invention, it is possible to provide a valve gear for an engine which provides a compact camshaft and also increases operation reliability and reduces the operation sound.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
A valve gear for an engine according to a first preferred embodiment of the present invention will now be described in detail with reference to
A valve gear 1 for an engine shown in
The rocker shaft 6 is supported by the cylinder head 2 to be parallel or substantially parallel to the camshaft 3. The position of the rocker arm 5 in the axial direction is controlled by a thruster 11 to be described below.
The present preferred embodiment is applicable to both the valve gear 1 for an intake valve shown in
Two intake valves 4 are provided for each cylinder. Each intake valve 4 includes a valve body 4a that opens/closes an intake port 13 in the cylinder head 2, and a valve stem 4b extending from the valve body 4a into a valve gear chamber 14 in the cylinder head 2. The valve stem 4b is movably supported on the cylinder head 2 via a valve stem guide 15. A valve spring 16 that biases the intake valve 4 in a closing direction is provided between the cylinder head 2 and the distal end of the valve stem 4b. A cap-shaped shim 17 is provided at the distal end of the valve stem 4b.
The intake port 13 preferably has a fork shape branching in the cylinder head 2. The upstream end of the intake port 13 opens to a side of the cylinder head 2, and the downstream end of the intake port 13 opens to a combustion chamber 18. A spark plug 19 is provided at the center of the combustion chamber 18. As shown in
The camshaft 3 rotates when the rotation of a crankshaft (not shown) is transmitted via a transmission mechanism. The camshaft 3 according to the present preferred embodiment includes a camshaft main body 21 preferably with a rod shape, and a plurality of cams provided on the camshaft main body 21, as shown in
The first cam 22 and the second cam 23 drive the intake valve 4. The second cam 23 has a cam profile different from that of the first cam 22, and has a shape the provides a different valve lift amount in the present preferred embodiment. In addition, the second cam 23 is provided on the camshaft 3 at a position spaced apart from the first cam 22 in the axial direction. As shown in
Each of the nose portions 22b and 23b has a shape projecting from a corresponding one of the base circle portions 22a and 23a outward in the radial direction by a predetermined projecting amount so as to have a mountain-shaped section. The projecting amount of the nose portion 22b of the first cam 22 is larger than the projecting amount of the nose portion 23b of the second cam 23.
The synchronous cam 24 drives the thruster 11 (to be described below), and includes a base circle portion 24a and a nose portion 24b. The synchronous cam 24 rotates in synchronism with valve driving cams including the first cams 22 and the second cams 23. The nose portion 24b of the synchronous cam 24 is located at a position different from the positions of the nose portions 22b and 23b of the first cam 22 and the second cam 23 in the rotation direction of the camshaft 3.
The rocker arm 5 is substantially U-shaped in a plan view including two arm main bodies 25 that each convert the rotation of the first cam 22 or the second cam 23 into a reciprocal motion and transmit it to the intake valve 4, and a connector 26 that connects the swing ends of the arm main bodies 25 to each other. The rocker shaft 6 extends through the proximal portions of the two arm main bodies 25.
A presser 27 that presses the intake valve 4 is provided at each swing end of the rocker arm 5, as shown in
As shown in
As shown in
The slide portion 32 includes the slider 31 through which the rocker shaft 6 extends, and a plurality of functional portions (to be described below in detail) provided on the slider 31. As shown in
A cam follower 34 that contacts the synchronous cam 24 is integral with the slider 31 in the present preferred embodiment. As shown in
As shown in
The synchronous cam 24 has a shape that presses the cam follower 34 when the rocker arm 5 contacts the base circle portion 22a of the first cam 22 or the base circle portion 23a of the second cam 23, as shown in
The plurality of functional portions provided on the slider 31 include a first inclined cam surface 35 (see
As shown in
The first inclined cam surface 35 and the second inclined cam surface 36 according to the present preferred embodiment are preferably flat surfaces that are inclined in directions opposite to each other in the axial direction of the rocker shaft 6, as shown in
The second inclined cam surface 36 is inclined to gradually lower from the center of the convex portion 39 to the second end. Note that the first inclined cam surface 35 and the second inclined cam surface 36 may have concave curved surfaces, although not illustrated.
As shown in
As shown in
As shown in
As shown in
On the other hand, as shown in
The first pin 41 and the second pin 42 move between an advancing position to advance toward the slider 31 and a retreating position to retreat in a direction opposite to the slider 31. When the slider 31 swings integrally with the cam follower 34, the first pin 41 and the second pin 42 that advance to the advancing position are brought into contact with the first inclined cam surface 35 or the second inclined cam surface 36. In a state in which the first pin 41 and the second pin 42 move to the retreating position, the movement of the first inclined cam surface 35 or the second inclined cam surface 36 is not impeded even if the slider 31 swings.
The moving member 43 preferably has a columnar shape and is movably fitted in an oil hole 45 of the cylinder head 2. The oil hole 45 is parallel or substantially parallel to the rocker shaft 6. For this reason, the moving member 43 moves in a direction perpendicular or substantially perpendicular to the direction in which the first pin 41 and the second pin 42 move.
The moving member 43 according to the present preferred embodiment includes a piston that moves in the oil hole 45. A helical compression spring 46 is inserted on a first end (the left side in
The second end of the oil hole 45 is connected to an oil pressure supply device (not shown). Hence, an oil pressure propagated from the oil pressure supply device is applied to the second end (the end on the right side in
A first pin cam 47 that moves the first pin 41 between the advancing position and the retreating position and a second pin cam 48 that moves the second pin 42 between the advancing position and the retreating position are provided in the moving member 43. The cams 47 and 48 preferably symmetrical to each other with respect to a plane of symmetry defined by a virtual plane perpendicular or substantially perpendicular to the axis of the moving member 43.
The first pin cam 47 and the second pin cam 48 include curved surfaces extending from concave portions 49 and 50 in which the ends of the first pin 41 and the second pin 42 are inserted to the outer surface of the moving member 43. The first pin 41 and the second pin 42 are inserted in the concave portions 49 and 50 and thus located at the retreating position.
The first pin cam 47 is provided at a first end of the moving member 43. When the moving member 43 moves to a first end (the left side in
The second pin cam 48 is provided at the second end of the moving member 43. The second pin cam 48 has a shape that moves the second pin 42 to the advancing position (see
That is, the first pin 41 and the second pin 42 selectively come into contact with the slide portion 32 (slider 31) when the moving member 43 moves to the first end or the second end.
The first pin cam 47 and the second pin cam 48 are arranged such that, when one of the first pin 41 and the second pin 42 is located at the advancing position, the other of the first pin 41 and the second pin 42 moves to the retreating position. That is, when the moving member 43 moves to a first end, the first pin 41 moves to the advancing position, and the second pin 42 returns to the retreating position, as shown in
As shown in
In addition, the third pin 44 is pressed against the first concave groove 37 or the second concave groove 38 by the spring force of a helical compression spring 51 provided between the third pin 44 and the cylinder head 2. For this reason, the slider 31 is biased by the spring force of the helical compression spring 51 in a direction in which the cam follower 34 separates from the camshaft 3 about the rocker shaft 6. When biased by the spring force of the helical compression spring 51, the slider 31 swings in the swinging direction A about the rocker shaft 6 until the first inclined cam surface 35 or the second inclined cam surface 36 comes into contact with the first pin 41 or the second pin 42. For this reason, the slider 31 and the cam follower 34 are maintained in a state in which the first inclined cam surface 35 or the second inclined cam surface 36 is in contact with the first pin 41 or the second pin 42 when the cam follower 34 is not pressed by the synchronous cam 24.
The first concave groove 37 and the second concave groove 38 each preferably include a V-shaped section, as shown in
Then, the third pin 44 moves across the top that defines the boundary between the first concave groove 37 and the second concave groove 38 and enters the second concave groove 38. The third pin 44 that has entered the second concave groove 38 presses the side wall of the second concave groove 38 by the spring force of the helical compression spring 51. Since this side wall is inclined as well, the movement of the slider 31 is assisted by the spring force of the helical compression spring 51. The slider 31 stops when the third pin 44 advances to the deepest point of the second concave groove 38. The operation of the third pin 44 is performed similarly even if the slider 31 moves in a direction opposite to the above-described direction.
In a state in which the third pin 44 is inserted in the first concave groove 37, as shown in
In a state in which the third pin 44 is inserted in the second concave groove 38, as shown in
The operation of the valve gear 1 will be described next with reference to
When the second operation mode is performed, the rocker arm 5 is located at a position where it is pressed by the second cams 23, as shown in
When switching from the second operation mode to the first operation mode, the moving member 43 is moved from the second end to the first end, as shown in
When the camshaft 3 rotates in this state, the cam follower 34 is pressed by the synchronous cam 24 in a state in which the rocker arm 5 is in contact with the base circle portions 23a of the second cams 23, and the slider 31 integrally swings in the swinging direction A with the cam follower 34, as shown in
As described above, when the projecting end of the first inclined cam surface 35 is pressed against the first pin 41, the first inclined cam surface 35 receives a thrust. The direction in which the thrust acts is the direction in which the low portion of the first inclined cam surface 35 approaches the first pin 41. As a result, the slider 31 integrally moves to the second end (the right side in
As shown in
When the top of the synchronous cam 24 passes through the cam follower 34, the third pin 44 is in a state in which it presses the side wall of the first concave groove 37. For this reason, although the first inclined cam surface 35 separates from the first pin 41, the side wall of the first concave groove 37 is pressed by the third pin 44 according to the spring force of the helical compression spring 51, and the slider 31 further moves to the second end. The slider 31 stops when the third pin 44 advances to the deepest point of the first concave groove 37. When the slider 31 stops in this way, the rocker arm 5 is located at the first position at which the rocker arm 5 contacts the first cams 22, as shown in
A shift from this operation mode to the second operation mode in which the intake valve 4 is driven by the second cams 23 is made by moving the moving member 43 to the second end (the right side in
The synchronous cam 24 used in the valve gear 1 for an engine is preferably short in the axial direction, as compared to conventional advancing and retreating cams including helical grooves. This means that the camshaft 3 is short. In addition, the synchronous cam 24 is able to be made by the same manufacturing method as the first cam 22 and the second cam 23. That is, the synchronous cam 24 is able to be made using a cam processing machine used to make the first cam 22 and the second cam 23.
In the valve gear 1 according to the present preferred embodiment, the switching speed when switching the operation mode is determined depending on the profile (shape) and the cam rotational speed of the synchronous cam 24. For this reason, the switching speed changes in proportion to the cam rotational speed. As compared to a case in which the spring load of a spring member is increased when increasing the switching speed, reliability in switching in a high rotation state becomes high, and the operation sound in a low rotation state becomes small.
In the valve gear 1 according to the present preferred embodiment, the main operation sound generated when switching the operation mode includes the sound of friction between the first inclined cam surface 35 or the second inclined cam surface 36 and the first pin 41 or the second pin 42, and the sound of friction between the third pin 44 and the slider 31. Such a sound is smaller than the sound of collision between metal members.
Hence, according to the present preferred embodiment, it is possible to provide a valve gear for an engine, in which the camshaft 3 is made compact and at low cost and also increases the reliability of the operation and reduces the operation sound.
The slide portion 32 of the thruster 11 according to the present preferred embodiment includes the first inclined cam surface 35 and the second inclined cam surface 36, and moves in the axial direction of the rocker shaft 6 when the cam follower 34 swings to press the cam surface 35 or 36 against the first pin 41 or the second pin 42.
For this reason, the thruster 11 according to the present preferred embodiment is small and has a simple structure, as compared to a case in which a link or gear is used to convert the swinging motion of the cam follower 34 into a thrust in the axial direction. Hence, according to the present preferred embodiment, it is possible to provide a valve gear for an engine that has a small size at a reduced cost.
As for the first pin 41 and the second pin 42 according to the present preferred embodiment, when one pin is located at the advancing position, the other pin moves to the retreating position. Hence, according to the present preferred embodiment, since the first pin 41 and the second pin 42 never simultaneously move to the advancing position, it is possible to provide a valve gear for an engine in which the thruster 11 has high operation reliability.
Second Preferred EmbodimentA valve gear for an engine according to a second preferred embodiment of the present invention will be described in detail with reference to
A valve gear 61 (see
As shown in
A swing end 34b of the cam follower 34 is swingably inserted into a concave groove 66 of a stopper 65 fixed to a cylinder head (not shown). Each side wall of the concave groove 66 contacts the cam follower 34 when the cam follower 34 moves in the axial direction of the rocker shaft 6. That is, movement of the cam follower 34 according to the present preferred embodiment is regulated or controlled by the side walls of the concave groove 66 and, therefore, cannot move in the axial direction of the rocker shaft 6.
To allow the slider 31 to move relative to the cam follower 34 in the axial direction of the rocker shaft 6, the concave portion 62 of the slider 31 is longer than the cam follower 34 by a predetermined length in the axial direction of the rocker shaft 6. The predetermined length is a length that allows the slider 31 to move relative to the cam follower 34 between a position at which a rocker arm 5 contacts first cams 22, as shown in
The proximal portion 34a of the cam follower 34 is provided with a first convex portion 67 and a second convex portion 68 to regulate or control its swinging motion relative to the slider 31. The first convex portion 67 and the second convex portion 68 are provided at positions spaced apart to one side and the other side in the radial direction of the rocker shaft 6. The first convex portion 67 comes into contact with a pressure receiving portion 69 of the slider 31, and the second convex portion 68 comes into contact with a transmitting portion 70 of the slider 31. That is, when the cam follower 34 is pressed by a synchronous cam 24 and swings, the pressing force is transmitted from the cam follower 34 to the slider 31 via the contact portion between the first convex portion 67 and the pressure receiving portion 69. When the slider 31 is pressed by a third pin 44 and swings, the pressing force is transmitted from the slider 31 to the cam follower 34 via the contact portion between the second convex portion 68 and the transmitting portion 70.
In the valve gear 61 according to the present preferred embodiment, even if the slider 31 moves in the axial direction of the rocker shaft 6, the position of the cam follower 34 does not change. For this reason, as compared to a case in which the cam follower 34 moves in the axial direction of the rocker shaft 6, the synchronous cam 24 that presses the cam follower 34 is short in the axial direction. Hence, according to the present preferred embodiment, since the location of the synchronous cam 24 on a camshaft 3 is narrow, the camshaft 3 is able to be shorter.
Third Preferred EmbodimentA valve gear according to a third preferred embodiment the present invention is shown in
A valve gear 71 for an engine according to the present preferred embodiment is different from the valve gear 1 described in the first preferred embodiment in the structures of a camshaft 3, a rocker arm 5, a cam follower 34, and a thruster 11. As for the cam follower 34 according to the present preferred embodiment, the movement in the axial direction is regulated or controlled, as in a case of the second preferred embodiment. The rest of the arrangement of the valve gear 71 is preferably the same as in the valve gear 1 described in the first preferred embodiment.
As shown in
As shown in
A slide portion 32 of the thruster 11 according to the present preferred embodiment includes a first slider 72 and a second slider 73, which are separated from the cam follower 34, and a plurality of functional portions provided on each of the sliders 72 and 73. The first slider 72 and the second slider 73 are preferably symmetrical to each other with respect to a plane of symmetry defined by a virtual plane perpendicular or substantially perpendicular to the axis of the rocker arm 5. Through holes 74 that receive the rocker shaft 6 (see
The functional portions provided on the first slider 72 and the second slider 73 include a first inclined cam surface 35 and a second inclined cam surface 36 (see
As shown in
The outer concave portion 75 has a shape that allows the rocker arm 5 to swing and regulates or controls the movement of the rocker arm 5 in the axial direction relative to the first slider 72 and the second slider 73.
The rocker arms 5 are swingably supported by the first slider 72 and the second slider 73 via the rocker shaft 6 by inserting the rocker shaft 6 into the through holes 74 of the sliders 72 and 73 and shaft holes 78 of the rocker arms 5 in a state in which the proximal portions are inserted in the outer concave portions 75. The rocker arm 5 supported by the first slider 72 moves in the axial direction of the rocker shaft 6 together with the first slider 72. The rocker arm 5 supported by the second slider 73 moves in the axial direction of the rocker shaft 6 together with the second slider 73.
As shown in
The hollow portion of the boss 76 has a shape that allows the rocker shaft 6 to be rotatably fitted therein. The length of the boss 76 in the axial direction is larger than the width (the width in the axial direction of the rocker shaft 6) of the lever 79. The lever 79 is located at the center of the boss 76 in the axial direction. For this reason, the two ends of the boss 76 project from the lever 79 in the axial direction. As shown in
The first connector 80 and the second connector 81 regulate or control the swinging motion of the cam follower 34 relative to the sliders 72 and 73, and are located at different positions in the swinging direction of the cam follower 34. As shown in
The second connector 81 is located on the upstream side of the first connector 80 in the swinging direction A. The second connector 81 comes into contact with transmitting portions 83 provided on the first slider 72 and the second slider 73 from the downstream side in the swinging direction A. That is, when the first slider 72 and the second slider 73 are pressed by third pins 44 (to be described below) and swing, the pressing force is transmitted from the first slider 72 and the second slider 73 to the cam follower 34 via the contact portions between the second connector 81 and the transmitting portions 83.
As shown in
As shown in
The first pin 41 faces the first inclined cam surface 35, and the second pin 42 faces the second inclined cam surface 36.
The first pin cam 47 and the second pin cam 48 of the moving member 43 are provided for each slider. The first pin cam 47 and the second pin cam 48 according to the present preferred embodiment include an arrangement to move the first slider 72 and the second slider 73 in directions opposite to each other. More specifically, when the moving member 43 moves from the position on the second end shown in
When the moving member 43 moves from the position on the first end shown in
In the valve gear 71 for an engine according to the present preferred embodiment, when the moving member 43 moves from the position on the first end shown in
When the first slider 72 and the second slider 73 move in this way, the rocker arms 5 contact the first cams 22, and the intake valves 4 are driven by the first cams 22, as shown in
On the other hand, when the moving member 43 moves from the position on the second end shown in
For this reason, according to the present preferred embodiment, it is possible to provide a valve gear for an engine that is able to switch between the first operation mode in which the intake valves 4 operate and the second operation mode in which the intake valves 4 are at rest.
Fourth Preferred EmbodimentA slider and a cam follower in a valve gear according to a fourth preferred embodiment of the present invention is shown in
A valve gear 91 for an engine according to the present preferred embodiment is different from the valve gear 61 described in the second preferred embodiment (
The tubular shaft 93 is inserted into shaft holes 94 of the two rocker arms 5 and through holes 64 of the slider 92 and extends through these members. A rocker shaft 6 is fitted in the hollow portion of the tubular shaft 93. The tubular shaft 93 is supported by the rocker shaft 6 to be rotatable and movable in the axial direction. The two rocker arms 5 and the slider 92 are mounted on the tubular shaft 93 in a state in which they are in contact with each other in the axial direction of the tubular shaft 93. Circlips 95 are attached to the two ends of the tubular shaft 93 in a state in which the circlips 95 are in contact with the rocker arms 5. That is, the two rocker arm 5, the slider 92, and the tubular shaft 93 integrally move relative to the rocker shaft 6 in the axial direction.
Each rocker arm 5 according to the present preferred embodiment includes a roller 96 that contacts a first cam 22 or a second cam 23.
The slider 92 according to the present preferred embodiment is different from the slider 31 described in the second preferred embodiment in the location of a convex portion 39 including a first inclined cam surface 35, a second inclined cam surface 36, a first concave groove 37, and a second concave groove 38. The convex portion 39 extends almost parallel or substantially parallel to a cylinder axis C (see
The slider 92 includes a pressure receiving portion 97 (see
In the valve gear 91 for an engine according to the present preferred embodiment, since the switching portion 33 of the thruster 11 is provided at the same position as the cam follower 34 in the axial direction of the cylinder, a wide space in which to locate other elements is provided between the rocker arm 5 and the combustion chamber 18.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Claims
1-4. (canceled)
5: A valve gear for an engine comprising:
- a camshaft rotatably supported by a cylinder head;
- a first cam on the camshaft that drives one of an intake valve and an exhaust valve;
- a second cam on the camshaft spaced apart from the first cam in an axial direction, and that drives the other of the intake valve and the exhaust valve, the second cam including a cam profile different from a cam profile of the first cam;
- a synchronous cam on the camshaft that rotates in synchronism with the first cam and the second cam;
- a rocker shaft parallel or substantially parallel to the camshaft;
- a rocker arm supported by the rocker shaft to swing and move in the axial direction and to convert a rotation of one of the first cam and the second cam into a reciprocal motion and transmit the reciprocal motion to one of the intake valve and the exhaust valve;
- a cam follower swingably supported by the rocker shaft and that comes into contact with the synchronous cam; and
- a thruster that converts a swinging motion of the cam follower into a thrust in the axial direction and moves the rocker arm to one of a first side and a second side in the axial direction.
6: The valve gear for the engine according to claim 5, wherein the thruster includes:
- a slide portion that swings integrally with the cam follower and moves in the axial direction integrally with the rocker arm; and
- a switching portion supported by the cylinder head and including a first switch and a second switch, wherein the first switch and the second switch selectively come into contact with the slide portion; and
- the slide portion includes:
- a first inclined cam surface that receives a force at a first side thereof in the axial direction, wherein the force is generated by one of the first switch and the second switch in contact with the first inclined cam surface; and
- a second inclined cam surface that receives a force at a second side thereof in the axial direction, wherein the force is generated by the other of the first switch and the second switch in contact with the second inclined cam surface.
7: The valve gear for the engine according to claim 6, wherein the cam follower cannot move in the axial direction; and
- the slide portion is separate from the cam follower and is movable in the axial direction relative to the cam follower.
8: The valve gear for the engine according to claim 6, wherein each of the first switch and the second switch includes a pin that moves between an advancing position such that a first end of the pin comes into contact with the slide portion and a retreating position at which the first end of the pin separates from the slide portion;
- a second end of the pin abuts against a pin cam of a moving member that moves in a direction perpendicular or substantially perpendicular to a direction in which the pin moves; and
- the pin cam has a shape such that when the moving member moves to a first side, the first switch moves to the advancing position and the second switch moves to the retreating position, and when the moving member moves to a second side, the first switch moves to the retreating position and the second switch moves to the advancing position.
Type: Application
Filed: Nov 13, 2015
Publication Date: Dec 7, 2017
Inventor: Takuro KAMICHIKA (Shizuoka)
Application Number: 15/536,737