JP2020063729A - Decompression device and valve mechanism - Google Patents

Abstract

To provide a rocker arm slide structure in a rocker arm type valve mechanism having a decompression device.SOLUTION: A decompression device 41 in a valve mechanism includes a decompression holder 45 rotatably holding a decompression shaft 42 within a recessed part 25. In an outer peripheral portion of the decompression holder 45, there is formed a receded part 51 partially receded in a direction toward the shaft center of a cam shaft 12. Viewing the decompression device 41 from one side in an axial direction of the cam shaft 12, the receded part 51 is positioned inside a base circle B of an exhaust side cam 14.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a decompression device that performs a decompression operation of an engine and a valve operating mechanism provided with the decompression device.

  For example, a valve operating mechanism that controls opening / closing of an intake valve and an exhaust valve is provided in a cylinder head of an engine mounted on a saddle type vehicle or the like. The valve train has a camshaft, and the camshaft has an intake side cam that controls the opening and closing of the intake valve, an exhaust side cam that controls the opening and closing of the exhaust valve, and a chain or belt that transmits the power of the crankshaft to the camshaft. A cam sprocket and the like are provided for hanging.

  In addition, the so-called rocker arm type valve operating mechanism further receives the power of the intake side cam to push the intake valve, opens the intake valve, and receives the power of the exhaust side cam to push the exhaust valve. An exhaust side rocker arm for opening the exhaust valve is provided. In the cylinder head, the intake side rocker arm is swingably supported by an intake side rocker shaft provided above the cam shaft, and one end side of the intake side rocker arm contacts the intake side cam via a roller or the like. The other end of the intake side rocker arm comes into contact with a shim or the like provided at the stem end of the intake valve. Similarly, the exhaust side rocker arm is swingably supported by the exhaust side rocker shaft provided above the cam shaft, and one end side of the exhaust side rocker arm contacts the exhaust side cam via a roller or the like. The other end of the exhaust side rocker arm comes into contact with a shim or the like provided at the stem end of the exhaust valve.

  Some rocker arm type valve operating mechanisms mainly include intake side and exhaust side in order to facilitate replacement of shims for adjusting valve clearance, which are provided at stem ends of intake valve and exhaust valve, respectively. There is a structure in which each rocker arm can be slid in the axial direction of each rocker shaft. Hereinafter, this structure is referred to as a "rocker arm slide structure".

  On the other hand, in some valve operating mechanisms, a decompression device is provided on the outer peripheral side of the camshaft. The decompression device is a device that performs a decompression operation to improve the engine startability by slightly opening the exhaust valve and reducing the pressure in the cylinder during the compression stroke when the engine is started. The decompression device is often arranged between the exhaust side cam and the cam sprocket at a position adjacent to the exhaust side cam. The following Patent Document 1 discloses a rocker arm type valve mechanism provided with a decompression device.

JP, 6-280531, A

  By the way, in the rocker arm type valve mechanism having the decompression device, there is a problem that the above rocker arm slide structure may not be provided.

  That is, when the rocker arm slide structure is applied to a single-cylinder engine, it is often the case that the rocker arm is slid into the space above the portion of the camshaft between the exhaust side cam and the cam sprocket. However, in most rocker arm type valve operating mechanisms having a decompression device, the decompression device is disposed between the exhaust side cam and the cam sprocket at a position adjacent to the exhaust side cam. Further, as described in Patent Document 1, the outer diameter of many decompression devices is larger than the diameter of the base circle of the exhaust side cam over the entire circumference thereof. Therefore, in the rocker arm type valve mechanism having the decompression device, the decompression device is an obstacle to move the rocker arm to the space above the portion of the camshaft between the exhaust side cam and the cam sprocket. May not be possible. As described above, the rocker arm type valve mechanism having the decompression device may not be provided with the rocker arm slide structure.

  The present invention has been made in view of the problems described above, and an object of the present invention is to provide a decompression device and a dynamic decompression device that enable a rocker arm slide structure to be provided in a rocker arm type valve mechanism having a decompression device. To provide a valve mechanism.

  In order to solve the above problems, the decompression device of the present invention is a decompression device provided on the outer peripheral side of a cam shaft provided with an exhaust side cam, and a radial direction of the cam shaft on the outer peripheral surface of the cam shaft. A decompression shaft having an axis extending in the axial direction of the camshaft, the decompression shaft being housed in a recess formed over the one side portion and the radial direction one side portion of the camshaft on the base surface of the exhaust side cam; A decompression cam formed on the decompression shaft and protruding and retracted with respect to the base surface of the exhaust side cam, and formed in an annular or arc shape, and provided on the outer peripheral side of the camshaft so as to cover the outer peripheral side of the decompression shaft; A decompression holder that rotatably holds the decompression shaft in the recess, and an arc-shaped extension that is provided on the outer peripheral side of the camshaft. A decompression arm that is displaced in a direction away from the axis of the camshaft by the centrifugal force of the camshaft; a biasing member that biases the decompression arm in a direction that approaches the axis of the camshaft; and the decompression shaft. And a coupling member that couples the decompression arm to the decompression arm and transmits the displacement of the decompression arm to the decompression shaft, wherein the camshaft has an axial center at an outer peripheral side portion of the decompression holder or an outer peripheral side portion of the decompression arm. When the decompression device is viewed from one axial side of the camshaft while the rotation of the camshaft is stopped, the retraction part is formed into the exhaust gas. It is characterized in that it is located inside the base circle of the side cam.

  Further, in order to solve the above-mentioned problems, a valve mechanism according to the present invention is provided with a cam shaft, an exhaust side cam provided on the cam shaft, and an upper side of the cam shaft in the same direction as the cam shaft. A rocker shaft that extends to the rocker shaft, a rocker arm that is swingably provided on the rocker shaft and that transmits the power of the exhaust side cam to an exhaust valve, and a decompression device that is provided on the outer peripheral side of the cam shaft. In the valve mechanism, the rocker arm is supported by the rocker shaft so as to be movable in the axial direction of the rocker shaft, and the decompression device is provided on the outer peripheral surface of the camshaft with a portion of the camshaft in the radial direction. The cam is housed in a recess formed in the base surface of the exhaust-side cam and over a portion of the camshaft in the radial direction. A decompression shaft having an axis extending in the axial direction of the shaft, a decompression cam formed on the decompression shaft and projecting and retracting with respect to the base surface of the exhaust side cam, and an annular or arc-shaped outer peripheral side of the decompression shaft. A decompression holder that is provided on the outer peripheral side of the cam shaft so as to cover the decompression shaft and rotatably holds the decompression shaft in the recess, and extends in an arc shape, and is provided on the outer peripheral side of the cam shaft. A decompression arm that is displaced in a direction away from the axis of the camshaft by a centrifugal force of the shaft, a biasing member that biases the decompression arm in a direction that approaches the axis of the camshaft, the decompression shaft, and the decompression arm. And a connecting member for transmitting the displacement of the decompression arm to the decompression shaft. At the outer peripheral side portion of the decompression holder or the outer peripheral side portion of the decompression arm, there is formed a retracted portion that is partially retracted in the direction toward the axis of the camshaft, and rotation of the camshaft is stopped. When the decompression device is viewed from one side in the axial direction of the camshaft, the retracted portion is located inside the base circle of the exhaust side cam.

  According to the present invention, a rocker arm slide structure can be provided in a rocker arm type valve mechanism having a decompression device.

1 is an external view showing an engine provided with a valve mechanism of an embodiment of the present invention. It is explanatory drawing which looked at the inside of the cylinder head of the engine in FIG. 1 from the upper part. It is explanatory drawing which shows the state which removed the intake side rocker shaft, the intake side rocker arm, the exhaust side rocker shaft, the exhaust side rocker arm, and the shaft support part from the inside of the cylinder head in FIG. FIG. 4 is a cross-sectional view showing a cylinder head and a cylinder head cover as seen from the direction of arrows IV-IV in FIG. 2. It is a perspective view showing a cam shaft, an intake side cam, and an exhaust side cam in the valve mechanism of the embodiment of the present invention. It is a perspective view showing a camshaft, an intake side cam, an exhaust side cam, and a decompression device in a valve mechanism of an example of the present invention. It is explanatory drawing which shows the cam shaft, the decompression apparatus, etc. which were seen from the arrow VII direction in FIG. FIG. 8 is an explanatory diagram showing a camshaft, a decompression device, and the like as seen from the direction of the arrow X in FIG. 7. It is a perspective view showing a decompression shaft, a decompression pin, and a decompression cam in a decompression device for a valve mechanism according to an embodiment of the present invention. It is explanatory drawing which shows the decompression holder in the decompression device of the valve mechanism of the Example of this invention. It is sectional drawing which shows the decompression holder seen from the arrow XI-XI direction in FIG. It is explanatory drawing which shows the positional relationship of the decompression holder in FIG. 10 and the base circle of an exhaust side cam. It is explanatory drawing which shows the positional relationship of the decompression apparatus in FIG. 7 and the base circle of an exhaust side cam. It is explanatory drawing which shows operation | movement of the decompression device in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the rocker arm slide structure in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the rocker arm slide structure in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the state which the recessed part of the decompression device was facing upwards in the valve mechanism of the Example of this invention. It is explanatory drawing which shows the decompression apparatus in the valve operating mechanism of the other Example of this invention. It is explanatory drawing which shows the modification of the decompression holder in the decompression device of the Example of this invention.

  A decompression device according to an embodiment of the present invention is provided on the outer peripheral side of a cam shaft provided with an exhaust side cam, and includes a decompression shaft, a decompression cam, a decompression holder, a decompression arm, a biasing member that biases the decompression arm, and a decompression arm. And a decompression pin.

  The decompression shaft is housed in a recessed portion formed on the outer peripheral surface of the cam shaft over the radial direction one side portion of the cam shaft and over the exhaust side cam base surface over the radial direction one side portion of the cam shaft. Further, the decompression shaft has an axis extending in the axial direction of the camshaft. The decompression cam is formed on the decompression shaft and projects in and out of the base surface of the exhaust side cam. The decompression holder has a function of rotatably holding the decompression shaft in the recess. The decompression holder is formed in an annular shape or an arc shape, and is provided on the outer peripheral side of the cam shaft so as to cover the outer peripheral side of the decompression shaft. The decompression arm extends in an arc shape, is provided on the outer peripheral side of the camshaft, and is displaced in a direction away from the axial center of the camshaft by the centrifugal force of the camshaft. The urging member urges the decompression arm in a direction to approach the axis of the camshaft. The connecting member connects the decompression shaft and the decompression arm, and transmits the displacement of the decompression arm to the decompression shaft.

  Further, a recessed portion that is partially retracted in the direction toward the axial center of the cam shaft is formed on the outer peripheral side portion of the decompression holder or the outer peripheral side portion of the decompression arm. The recessed portion is located inside the base circle of the exhaust side cam when the decompression device is viewed from one axial side of the cam shaft while the rotation of the cam shaft is stopped.

  In the decompression device according to the embodiment of the present invention, the rotation angle of the cam shaft is adjusted so that the retracted portion faces upward. As a result, the rocker arms on the intake side and the exhaust side can be slid into the space above the portion of the cam shaft between the exhaust side cam and the cam sprocket. That is, since the retracted portion is located inside the base circle of the exhaust side cam, the decompression device does not hinder the movement of the rocker arm. As described above, according to the decompression device of the embodiment of the present invention, it becomes possible to provide the rocker arm slide structure in the rocker arm type valve mechanism having the decompression device.

  The valve mechanism of the embodiment of the present invention includes a camshaft, an exhaust side cam provided on the camshaft, a rocker shaft provided above the camshaft and extending in the same direction as the camshaft, and a rocker. A rocker arm that is swingably provided on the shaft and that transmits the power of the exhaust side cam to the exhaust valve, and a decompression device that is provided on the outer peripheral side of the cam shaft are provided. The rocker arm is supported by the rocker shaft so as to be movable in the axial direction of the rocker shaft, and the decompression device has the same configuration as the decompression device of the above-described embodiment of the present invention. According to the valve mechanism having such a configuration, it is possible to realize a rocker arm type valve mechanism having a decompression device and a rocker arm slide structure.

  First, the engine and the valve operating mechanism in the embodiment of the present invention will be outlined. FIG. 1 shows an engine 1 provided with a valve mechanism according to an embodiment of the present invention. The engine 1 is, for example, a 4-cycle gasoline engine for a saddle type vehicle. As shown in FIG. 1, an engine 1 includes a crankcase 3 in which a crankshaft and the like are accommodated, a cylinder 4 in which a piston and the like are provided, and a cylinder head 5 in which an intake valve, an exhaust valve, a valve operating mechanism and the like are accommodated. And a cylinder head cover 6 that covers the upper part of the cylinder head 5.

  FIG. 2 shows a state in which the cylinder head 5 with the cylinder head cover 6 removed is viewed from above. FIG. 3 shows a state in which the intake side rocker arm 15, the exhaust side rocker arm 16, the intake side rocker shaft 20, the exhaust side rocker shaft 21, the shaft support portion 22 and the like are removed from the cylinder head 5 in FIG. . FIG. 4 shows a cross section of the cylinder head 5, the cylinder head cover 6, and the valve mechanism 11 as seen from the direction of the arrow IV-IV in FIG.

  As shown in FIGS. 3 and 4, in the cylinder head 5, two intake valves 7 and two exhaust valves 8 are provided. The engine 1 in this embodiment is a two-valve two-cylinder engine, and one intake valve 7 and one exhaust valve 8 are provided for each cylinder. Each intake valve 7 is urged by a valve spring 9 so as to close the intake port. Further, each exhaust valve 8 is biased by a valve spring 10 so as to close the exhaust port.

  Further, in the cylinder head 5, a valve mechanism 11 that controls opening / closing of each intake valve 7 and each exhaust valve 8 is provided. The valve mechanism 11 in this embodiment is of the SOHC type and has a single camshaft 12. Both axial end portions of the camshaft 12 are rotatably supported by shaft support portions 22 provided on both left and right sides within the cylinder head 5.

  Further, the camshaft 12 is provided with an intake-side cam 13 that controls opening / closing of each intake valve 7, and an exhaust-side cam 14 that controls opening / closing of each exhaust valve 8. The intake-side cam 13 is provided at a portion of the camshaft 12 which is located on the left side in the axial direction, and the exhaust-side cam 14 is provided at a substantially central portion in the axial direction of the camshaft 12. The intake side cam 13 and the exhaust side cam 14 are formed integrally with the cam shaft 12. A cam sprocket 24 is provided at the right end of the cam shaft 12, and a timing chain 23 (or a timing belt) is hung on the cam sprocket 24. The power of the crankshaft is transmitted to the camshaft 24 via the timing chain 23. Further, a decompression device 41 is provided on one side of the exhaust side cam 14 in the axial direction of the camshaft 12, that is, on the right side of the exhaust side cam 14. The decompression device 41 is adjacent to the exhaust side cam 14.

  Further, the valve mechanism 11 is a so-called rocker arm type valve mechanism, and as shown in FIG. 2, the intake side rocker arm 15 and the exhaust side cam 14 for transmitting the power of the intake side cam 13 to the intake valve 7. An exhaust side rocker arm 16 for transmitting the power of the above to the exhaust valve 8 is provided. A roller 17 is provided at one end of the intake side rocker arm 15, and the peripheral surface of the roller 17 is in contact with the peripheral surface of the intake side cam 13. The other end of the intake-side rocker arm 15 which is bifurcated is in contact with the adjusting member 19 provided on the stem end side of the intake valve 7. The adjusting member 19 is, for example, a shim for adjusting the valve clearance. Similarly, a roller 18 is provided at one end of the exhaust side rocker arm 16, and the peripheral surface of the roller 18 is in contact with the peripheral surface of the exhaust side cam 14. The other end of the exhaust side rocker arm 16 which is bifurcated is in contact with an adjusting member 19 provided on the stem end side of the exhaust valve 8.

  The intake side rocker arm 15 and the exhaust side rocker arm 16 are swingably supported by the intake side rocker shaft 20 and the exhaust side rocker shaft 21, respectively. The intake side rocker shaft 20 and the exhaust side rocker shaft 21 respectively extend in the same direction as the cam shaft 12. Further, the intake side rocker shaft 20 and the exhaust side rocker shaft 21 are arranged above the cam shaft 12, and the respective axial end portions of the intake side rocker shaft 20 and the exhaust side rocker shaft 21 are inside the cylinder head 5. It is fixed to shaft support portions 22 provided on both left and right sides.

  The operation of the exhaust side rocker arm 16 is as follows. That is, as the camshaft 12 rotates, the exhaust side cam 14 rotates, the roller 18 is pushed by the peripheral surface of the exhaust side cam 14, and one end of the exhaust side rocker arm 16 rises. The other end of the valve lowers and pushes the exhaust valve 8. As a result, the exhaust valve 8 is lowered against the biasing force of the valve spring 10 and the exhaust valve 8 is opened. The intake side rocker arm 15 also operates similarly to the exhaust side rocker arm 16.

  In addition, the valve mechanism 11 of the present embodiment mainly includes the intake side rocker arm 15 and the exhaust side in order to facilitate replacement of the adjusting members 19 provided at the stem ends of the intake valve 7 and the exhaust valve 8. It has a rocker arm slide structure capable of slidingly moving the side rocker arm 16 in the axial direction of the intake side rocker shaft 20 and the exhaust side rocker shaft 21, respectively. The rocker arm slide structure will be described later.

  Next, the cam shaft 12, the exhaust side cam 14, and the decompression device 41 in the embodiment of the present invention will be described. In the description of the camshaft 12, the exhaust-side cam 14, and the decompression device 41, the axial direction of the camshaft 12 is referred to as the “X direction” for convenience of description, and as indicated by arrows in FIGS. One side in the direction is referred to as "X1 side", and the other side in the X direction is referred to as "X2 side". Further, a direction orthogonal to the X direction is referred to as "Y direction", one side in the Y direction is referred to as "Y1 side", and the other side in the Y direction is referred to as "Y2 direction", as indicated by an arrow in FIGS. Side. Further, a direction orthogonal to both the X direction and the Y direction is referred to as a "Z direction", and one side in the Z direction is referred to as a "Z1 side" as indicated by an arrow in FIGS. The other side is called the "Z2 side".

  FIG. 5 shows the cam shaft 12, the exhaust side cam 14, and the like. As shown in FIG. 5, on the circumferential surface of the exhaust side cam 14, a base surface 14A is formed on the Y1 side and a projecting surface 14B is formed on the Y2 side. The base surface 14A is a surface forming a base circle (basic circle) of the exhaust side cam 14. The overhanging surface 14B is a surface of a portion overhanging outside the base circle of the exhaust side cam 14.

  Further, the camshaft 12 is formed with a decompression shaft accommodation recess 25 for accommodating the decompression shaft 42 of the decompression device 41. The decompression shaft accommodating recess 25 extends in the X direction so as to extend over the Y1 side portion of the outer peripheral surface of the camshaft 12 and the Y1 side portion of the base surface 14A of the exhaust side cam 14.

  On the outer peripheral surface of the camshaft 12, a clip mounting groove 30 for mounting the washer 28 and the circlip 29 is formed over the entire circumference of the camshaft 12 on the X1 side of the decompression shaft housing recess 25. .

  FIG. 6 shows the decompression device 41 provided on the camshaft 12. FIG. 7 shows the decompression device 41 as seen from the direction of arrow VII in FIG. FIG. 8 shows the decompression device 41 as seen from the direction of arrow VIII in FIG. As shown in FIGS. 6 to 8, the decompression device 41 includes a decompression shaft 42, a decompression pin 43, a decompression cam 44, a decompression holder 45, a decompression arm 58, and a coil spring 63.

  The decompression shaft 42 is arranged in the decompression shaft housing recess 25. The decompression pin 43 is provided on the X1 side of the decompression shaft 42, and the decompression cam 44 is formed on the X2 side of the decompression shaft 42. Here, FIG. 9 shows the decompression shaft 42, the decompression pin 43, and the decompression cam 44. As shown in FIG. 9, the decompression shaft 42 is formed of, for example, a metal material into a cylindrical outer shape having an axis extending in the X direction. The decompression pin 43 is a member (coupling member) that connects the decompression shaft 42 and the decompression arm 58 and transmits the displacement of the decompression arm 58 to the decompression shaft 42. The decompression pin 43 is, for example, a metal rod-shaped member, and is provided on the X1 side portion of the decompression shaft 42 so as to radially protrude from the peripheral surface of the decompression shaft 42. The decompression cam 44 is formed at the end of the decompression shaft 42 on the X2 side and has a flat surface portion 44A and a curved surface portion 44B. As shown in FIG. 8, the decompression cam 44 is arranged in a portion of the decompression shaft housing recess 25 located on the base surface 14A of the exhaust side cam 14. When the decompression shaft 42 rotates in the decompression shaft housing recess 25, the decompression cam 44 projects in and out of the base surface 14A of the exhaust side cam 14.

  As shown in FIG. 6, the decompression holder 45 is provided at a position facing a substantially central portion in the axial direction of the decompression shaft 42, and surrounds the outer peripheral side of the camshaft 12 and the decompression shaft 42. The decompression holder 45 is located on the right side of the exhaust side cam 14 and is adjacent to the exhaust side cam 14. The decompression holder 45 is a member mainly having a function of rotatably holding the decompression shaft 42 in the decompression shaft housing recess 25 and a function of supporting the decompression arm 58. Here, FIG. 10 shows the decompression holder 45, and FIG. 11 shows a cross section of the decompression holder 45 as seen from the direction of arrow XI-XI in FIG. 10. As shown in FIG. 10, the decompression holder 45 is formed in an annular shape by using, for example, a metal material. Further, on the inner peripheral surface of the decompression holder 45, a decompression shaft covering groove 46 is formed at a position facing the decompression shaft accommodating recess 25 so as to cover the portion of the decompression shaft accommodating recess 25 that extends from the decompression shaft accommodating recess 25. Has been done. An arm support portion 47 for rotatably supporting the shaft support portion 59 of the decompression arm 58 is provided on the Y2 side portion of the decompression holder 45. Further, at the center of the arm support portion 47, an insertion hole 49 for attaching the shaft support portion 59 of the decompression arm 58 to the decompression holder 45 and inserting the support member 48 (see FIG. 6) that serves as the rotation axis of the decompression arm 58 is provided. Has been formed.

  Further, in the outer peripheral side portion of the decompression holder 45, which is located on the Z2 side of the decompression holder 45, a recessed portion 51 that is partially retracted in the direction toward the axial center of the camshaft 12 is formed. Here, FIG. 12 shows the decompression holder 45 from which the spring hook 53 is removed, the outer shape of the exhaust side cam 14, and the base circle B of the exhaust side cam 14 in an overlapping manner. Further, FIG. 13 shows the decompression device 41, the outer shape of the exhaust side cam 14, and the base circle B of the exhaust side cam 14 in an overlapping manner. 12 and 13, the broken line shows the outer shape of the exhaust side cam 14, and the chain double-dashed line shows the base circle B of the exhaust side cam 14. As shown in FIG. 12, when the decompression device 41 is viewed from one side (X1 side) in the axial direction of the camshaft 12, the retracted portion 51 is located inside the base circle B of the exhaust side cam 14. The inside of the base circle B means a position within the base circle B and not in contact with the circumference of the base circle B. Further, as shown in FIG. 13, when the decompression device 41 is viewed from one side in the axial direction of the camshaft 12 while the rotation of the camshaft 12 is stopped, the retracted portion 51 has the axial center A1 of the camshaft 12. And a straight line L passing through the axial center A2 of the decompression shaft 42 is sandwiched between the decompression arm 42 and the decompression arm 42.

  Further, as shown in FIG. 10, a counterweight portion 52 is formed on the Z2 side portion of the decompression holder 45, that is, a portion where the retracted portion 51 is formed. The counter weight portion 52 is a weight for balancing the rotation of the camshaft 12. As shown in FIG. 11, the counterweight portion 52 is formed by a protruding portion protruding from the decompression holder 45 in the axial direction (X1 side) of the camshaft 12. In this embodiment, the counterweight portion 52 is integrally formed on the Z2 side portion of the decompression holder 45, and specifically, is formed by making the Z2 side portion of the decompression holder 45 thicker than other portions. Has been done.

  A spring hook 53 is attached to the Z2 side of the decompression holder 45. The spring hook 53 is a member to which the end of the coil spring 63 is attached. The spring hook 53 is formed of, for example, a metal plate. A spring hook portion 54 for hooking the end portion of the coil spring 63 is formed at the Y2 side end portion 53A of the spring hook 53. Further, the Y2 side end portion 53A of the spring hook 53 is rotatably supported by the decompression holder 45, and the Y1 side end portion 53B of the spring hook 53 is connected to the convex locking portion 55 formed on the decompression holder 45. It is locked. Further, as shown in FIG. 11, the spring hook 53 is arranged on the X1 side of the annular portion of the decompression holder 45. As a result, as shown in FIG. 8, the spring hook 53 is farther from the exhaust side cam 14 than the annularly formed portion of the decompression holder 45.

  Further, as shown in FIG. 10, a holder groove portion 56 having a shape recessed in the radial direction of the camshaft 12 is formed on the Y2 side portion of the inner peripheral surface of the decompression holder 45. On the other hand, as shown in FIG. 7, a holder fixing pin 31 is fixed to the Y2 side portion of the outer peripheral surface of the camshaft 12. The holder fixing pin 31 radially projects from the outer peripheral surface of the cam shaft 12, and the projecting end portion is inserted into the holder groove portion 56. The holder groove portion 56 and the protruding end portion of the holder fixing pin 31 are fitted to each other. Therefore, when the cam shaft 12 rotates during the operation of the engine 1, the decompression holder 45 rotates together with the cam shaft 12.

  Further, in FIG. 7, the decompression arm 58 is a member that is displaced in the direction away from the camshaft 12 by the centrifugal force when the camshaft 12 rotates, and thereby rotates the decompression shaft 42 via the decompression pin 43. The decompression arm 58 is made of, for example, a metal material, and extends in an arc shape from the Y2 side portion of the decompression device 41 to the Y1 side portion through the Z1 side portion. The Y2 side end of the decompression arm 58 is formed with a shaft support 59 for rotatably attaching the decompression arm 58 to the arm support 47 of the decompression holder 45 via the support member 48. By attaching to the decompression holder 45, the decompression arm 58 is arranged on the Z1 side on the outer peripheral side of the camshaft 12. Further, a stopper 60 that limits the amount of displacement of the decompression arm 58 in the direction away from the camshaft 12 is formed at the Y2 side end of the decompression arm 58. A spring hooking hole 61 for hooking the end of the coil spring 63 is formed at the Y2 side end of the decompression arm 58. Further, a connection groove 62 for connecting the decompression arm 58 and the decompression pin 43 is formed at the Y1 side end of the decompression arm 58. The decompression arm 58 and the decompression pin 43 are coupled by inserting the protruding side end of the decompression pin 43 into the coupling groove 62.

  The coil spring 63 is a biasing member that biases the decompression arm 58 in the direction of approaching the camshaft, and one end thereof is connected to the spring hook portion 54 of the spring hook 53 provided in the decompression holder 45. The other end is connected to the spring hooking hole 61 of the decompression arm 58.

  Further, as shown in FIG. 8, a washer 28 and a circlip 29 are attached to a clip attachment groove 30 formed on the camshaft 12. The circlip 29 and the washer 28 mainly have a function of preventing the decompression shaft 42 and the decompression holder 45 from moving to the X1 side.

  The operation of the decompression device 41 is as follows. That is, FIGS. 14A and 14B show cross sections of the exhaust side cam 14 and the decompression cam 44 as seen from the XIV-XIV direction indicated by the arrow in FIG. In FIG. 14 (A), while the rotation speed of the camshaft 12 is equal to or lower than a predetermined rotation speed, the inner peripheral surface of the decompression arm 58 contacts the outer peripheral surface of the camshaft 12 by the urging force of the coil spring 63, It is closest to the axis of the camshaft 12. In this state, the protruding end side of the decompression pin 43 connected to the decompression arm 58 is tilted toward the Z2 side, and the curved surface portion 44B of the decompression cam 44 faces the Y1 side. As a result, the decompression cam 44 projects from the base surface 14A of the exhaust side cam 14. As a result, the decompression operation is performed. On the other hand, in FIG. 14B, when the rotation speed of the camshaft 12 exceeds a predetermined rotation speed, the decompression arm 58 resists the biasing force of the coil spring 63 by the centrifugal force when the camshaft 12 rotates. The cam 60 is displaced in a direction away from the camshaft 12, and the stopper 60 of the decompression arm 58 contacts the outer peripheral surface of the camshaft 12. In this state, the projecting end side of the decompression pin 43 connected to the decompression arm 58 is tilted toward the Z1 side, and the flat surface portion 44A of the decompression cam 44 faces the Y1 side. As a result, the decompression cam 44 sinks into the base surface 14A of the exhaust side cam 14. As a result, the decompression operation is not performed.

  Next, the rocker arm slide structure will be described. 15 (A) and 15 (B) respectively show the valve mechanism 11 as viewed from above. 16A shows a cross section of the valve mechanism 11 as seen from the direction of arrow E-E in FIG. 15A, and FIG. 16B shows the arrow F- in FIG. 15B. The cross section of the valve mechanism 11 seen from the F direction is shown.

  15 (A) and 16 (A), both ends of the intake side rocker arm 15 are located above the intake side cam 13 and above the stem end of the intake valve 7, respectively, and the exhaust gas is exhausted. Both ends of the side rocker arm 16 are located above the exhaust side cam 14 and above the stem end of the exhaust valve 8, respectively. Hereinafter, the positions of the intake side rocker arm 15 and the exhaust side rocker arm 16 shown in FIGS. 15 (A) and 16 (A) are referred to as “normal operation positions”. With the intake side rocker arm 15 and the exhaust side rocker arm 16 in the normal operating position, the power of the intake side cam 13 is transmitted to the intake valve 7 via the intake side rocker arm 15 by the rotation of the cam shaft 12. The power of the exhaust side cam 14 is transmitted to the exhaust valve 8 via the exhaust side rocker arm 16. This is the state when the engine 1 is operating.

  On the other hand, in FIGS. 15B and 16B, both ends of the intake side rocker arm 15 are disengaged from the stem end of the intake side cam 13 and the intake valve 7 to the right side, and both ends of the exhaust side rocker arm 16 are removed. The state is shown in which the exhaust side cam 14 and the exhaust valve 8 are disengaged from the stem end to the right side. Hereinafter, the positions of the intake side rocker arm 15 and the exhaust side rocker arm 16 shown in FIGS. 15B and 16B are referred to as “release positions”. When performing maintenance work or the like, when the engine 1 is stopped, the operator removes the cylinder head cover 6 and adjusts the rotation angle of the camshaft 12 so that the retracted portion 51 formed on the decompression holder 45 of the decompression device 41 is moved upward. After that, the intake side rocker arm 15 and the exhaust side rocker arm 16 can be slid to the right from the normal operation position and moved to the release position. By moving the intake-side rocker arm 15 and the exhaust-side rocker arm 16 to the release position, the operator can easily replace the adjusting members 19 provided at the stem ends of the intake valve 7 and the exhaust valve 8, for example. be able to. When the intake side rocker arm 15 and the exhaust side rocker arm 16 move, the rollers 17 and 18 provided on the intake side rocker arm 15 and the exhaust side rocker arm 16, respectively, also move together with the intake side rocker arm 15 and the exhaust side rocker arm 16. Moving.

  The intake side rocker arm 15 is supported on the intake side rocker shaft 20 so as to be movable in the left-right direction between a normal operation position and a release position. Similarly, the exhaust side rocker arm 16 is supported by the exhaust side rocker shaft 21 so as to be movable in the left-right direction between the normal operation position and the release position. The intake side rocker arm 15 is biased to the left by an arm spring 26 provided between the intake side rocker arm 15 and the right shaft support portion 22 on the outer peripheral side of the intake side rocker shaft 20. . Similarly, the exhaust side rocker arm 16 is also urged to the left by an arm spring 26 provided on the outer peripheral side of the exhaust side rocker shaft 21. When the engine 1 is in operation, the arm spring 26 holds the intake side rocker arm 15 and the exhaust side rocker arm 16 in their normal operating positions. When performing maintenance work or the like, the operator applies a force larger than the biasing force of the arm spring 26 to move the intake side rocker arm 15 and the exhaust side rocker arm 16 from the normal operation position to the release position.

  Here, FIG. 17 shows a state in which the retraction part 51 formed in the decompression holder 45 of the decompression device 41 faces upward. In FIG. 17, the spring hook 53 is shown by a chain double-dashed line in order to make it easy to understand the positional relationship between the retracted portion 51 and the lowermost portion of the roller 18 when the retracted portion 51 faces upward. Hereinafter, with reference to FIG. 17 and the like, after the retraction portion 51 formed in the decompression holder 45 of the decompression device 41 is directed upward, the intake side rocker arm 15 and the exhaust side rocker arm 16 are slid from the normal operation position to the release position. A mechanism that can be moved will be described.

  The direction of the retracted portion 51 formed in the decompression holder 45 of the decompression device 41 changes depending on the rotation angle of the camshaft 12. When the retracted portion 51 faces other than upward, the upward-facing portion of the decompression device 41 is located higher than the lowermost portion of the roller 18, so that the decompression device 41 interferes with the intake-side rocker arm 15 as well. The exhaust side rocker arm 16 cannot move to the right from the normal operating position.

  However, when the retracted portion 51 faces upward, as shown in FIG. 17, the portion of the decompression device 41 facing upward, that is, the retracted portion 51 is located at a position lower than the lowermost portion of the roller 18. That is, a structure that slides in the rocker arm slide structure, specifically, the decompression device 41 when sliding to the right of the intake side rocker arm 15, the exhaust side rocker arm 16, the roller 17, and the roller 18. The part that can interfere is the roller 18. The roller 18 is in contact with the peripheral surface of the exhaust side cam 14. When the roller 18 is in contact with the base surface 14A of the exhaust side cam 14, the roller 18 descends most. Therefore, the downwardly facing portion of the circumferential surface of the roller 18 in contact with the base surface 14A of the exhaust side cam 14 is the lowest position of the portion of the sliding structure that interferes with the decompression device 41. Become. In the vertical direction, this position is equal to the position of the portion of the exhaust-side cam 14 that faces the base circle B upward. Here, as shown in FIG. 12 or FIG. 13, since the retraction part 51 is located inside the base circle B of the exhaust side cam 14, the position of the retraction part 51 when the retraction part 51 faces upward. Is a position lower than the portion of the exhaust side cam 14 facing upward of the base circle B. Therefore, when the retracted portion 51 faces upward, the position of the retracted portion 51 is lower than the lowermost portion of the roller 18. Therefore, by directing the retracted portion 51 upward, the intake side rocker arm 15 and the exhaust side rocker arm 16 can be slid from the normal operation position to the release position.

  When the retracted portion 51 faces upward, a part of the spring hook 53 is located above the retracted portion 51. However, as shown in FIG. 8, since the spring hook 53 is located on the X1 side in the decompression holder 45, as shown in FIG. 16B, the intake side rocker arm 15, the exhaust side rocker arm 16, and the roller. When the roller 17 and the roller 18 are moved to the release position, neither of them contacts the spring hook 53. That is, the spring hook 53 does not hinder the movement of the intake side rocker arm 15 and the exhaust side rocker arm 16 from the normal operation position to the release position.

  As described above, in the decompression device 41 of the embodiment of the present invention, since the decompression holder 45 is provided with the retracted portion 51, the decompression device 41 is provided on the right side of the exhaust side cam 14 adjacent to the exhaust side cam 14. Even when provided, the intake side rocker arm 15 and the exhaust side rocker arm 16 can be slid rightward toward the space above the portion of the camshaft 12 between the exhaust side cam 14 and the cam sprocket 24. it can. Therefore, according to the decompression device 41 of the embodiment of the present invention, it is possible to realize a rocker arm type valve mechanism having a decompression device and a rocker arm slide structure.

  Further, in the decompression device 41 according to the embodiment of the present invention, the recess 51 is formed in the decompression holder 45. If the recess 51 is formed on the decompression arm 58, the weight of the decompression arm 58 is reduced and the centrifugal force for displacing the decompression arm 58 is reduced. By forming the recessed portion 51 in the decompression holder 45 as in the present embodiment, it is possible to avoid a reduction in the centrifugal force that displaces the decompression arm 58.

  In addition, in the decompression device 41 of the embodiment of the present invention, the retraction portion 51 is such that when the decompression device 41 is viewed from one axial side of the camshaft 12 while the rotation of the camshaft 12 is stopped, The straight line L passing through the axis A1 of 12 and the axis A2 of the decompression shaft 42 is sandwiched between the decompression arm 58 and the decompression arm 58, and the decompression arm 58 is disposed at a position opposite to the position P at the substantially central portion in the extending direction (see FIG. 13). In this way, by providing the retraction part 51 on the opposite side of the portion of the decompression device 41 where the decompression arm 58 is provided, it is possible to prevent the design of the decompression arm 58 from being restricted by the formation of the retraction part 51. be able to.

  Further, in the decompression holder 45 of the decompression device 41 according to the embodiment of the present invention, a counterweight portion 52 for balancing the rotation of the camshaft 12 is provided at a portion where the retracted portion 51 is formed. As a result, the weight reduced by the formation of the recessed portion 51 can be compensated by the weight of the counterweight portion 52. Therefore, it is possible to easily balance the rotation of the camshaft 12 and reduce vibration when the camshaft 12 rotates.

  Further, in the decompression device 41 of the embodiment of the present invention, the counterweight portion 52 is provided with a cam when the decompression device 41 is viewed from one axial side of the camshaft 12 while the rotation of the camshaft 12 is stopped. The straight line L passing through the shaft center A1 of the shaft 12 and the shaft center A2 of the decompression shaft 42 is sandwiched between the decompression arm 58 and the decompression arm 58 in the extending direction. As a result, the position of the center of gravity of the decompression device 41 can be easily set by adjusting the weight balance between the counterweight portion 52 and the decompression arm 58 that are arranged on both sides of the camshaft 12 with the axis A1 therebetween. it can.

  Further, in the decompression device 41 according to the embodiment of the present invention, the counterweight portion 52 is formed by a protruding portion that protrudes from the decompression holder 45 in the axial direction of the camshaft 12. Thereby, the counterweight portion 52 can be integrally formed with the decompression holder 45, and the structure of the decompression holder 45 can be simplified. In addition, since the protruding portion as the counter weight portion 52 is configured to protrude from the decompression holder 45 in the axial direction of the cam shaft 12, the counter weight is utilized by utilizing the space between the exhaust side cam 14 and the cam sprocket 24. The volume of the portion 52 can be increased, and the weight of the counterweight portion 52 can be easily increased. In addition, by forming the counterweight portion 52 by a protruding portion that protrudes from the decompression holder 45 in the axial direction of the camshaft 12, the counterweight portion 52 is used for positioning the decompression holder 45 in the axial direction of the camshaft 12. It can be used as a member. In the present embodiment, as shown in FIG. 8, the decompression holder 45 is positioned in the axial direction of the camshaft 12 by extending the end surface of the counterweight portion 52 on the X1 side until it reaches the washer 28.

  In the decompression device 14 of the above-described embodiment, the retraction part 51 is formed on the outer peripheral side portion of the decompression holder 45, and the retraction part 51 is located at a position opposite to the position where the decompression arm 58 is disposed in the decompression device 41. I placed it. However, like the decompression device 71 shown in FIG. 18, the retraction part 74 may be formed on the outer peripheral side portion of the decompression arm 73. The retraction part 74 is located inside the base circle B of the exhaust side cam 14 when the decompression device is viewed from one axial side of the camshaft 12 while the rotation of the camshaft 12 is stopped. In the decompression device 71 shown in FIG. 18, a recess is also formed on the outer peripheral side portion of the decompression holder 72 on the Z1 side. The Z1 side portion of the decompression holder 72 overlaps with the Z1 side portion of the decompression arm 73, and the recessed portion formed on the decompression holder 72 overlaps the recessed portion 74 formed on the decompression arm 73.

  Further, the shape of the decompression holder of the decompression device of the present invention is not limited to the annular shape, and may be an arc shape like the decompression holder 81 shown in FIG.

  Further, the decompression device or the valve mechanism of the present invention is not limited to the engine for straddle type vehicle, but can be applied to various engines such as an engine for outboard motors.

  Further, the present invention can be appropriately modified without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a decompression device and a valve operating mechanism accompanied by such modifications are also included in the present invention. Included in the technical idea of.

11 Valve Mechanism 12 Camshaft 14 Exhaust Side Cam 14A Base Surface 16 Exhaust Side Rocker Arm (Rocker Arm)
17, 18 Roller 21 Exhaust side rocker shaft (rocker shaft)
25 Decompression shaft housing recess (recess)
41, 71 Decompression device 42 Decompression shaft 43 Decompression pin (connecting member)
44 Decompression cam 45, 72 Decompression holder 51 Retraction part 52 Counterweight part 58, 73 Decompression arm 63 Coil spring (biasing member)

Claims (5)

A decompression device provided on the outer peripheral side of a cam shaft provided with an exhaust side cam,
The camshaft is housed in a recess formed over the outer circumferential surface of the camshaft in the radial direction and the base surface of the exhaust side cam over the radial direction of the camshaft. A decompression shaft having an axis extending in the axial direction,
A decompression cam that is formed on the decompression shaft and that appears in and out of the base surface of the exhaust side cam;
A decompression holder that is formed in an annular shape or an arc shape, is provided on the outer peripheral side of the cam shaft so as to cover the outer peripheral side of the decompression shaft, and rotatably holds the decompression shaft in the recess.
A decompression arm that extends in an arc shape, is provided on the outer peripheral side of the cam shaft, and is displaced in a direction away from the axial center of the cam shaft by the centrifugal force of the cam shaft,
An urging member for urging the decompression arm in a direction of approaching the axis of the camshaft,
A connecting member for connecting the decompression shaft and the decompression arm, and transmitting a displacement of the decompression arm to the decompression shaft,
On the outer peripheral side portion of the decompression holder or the outer peripheral side portion of the decompression arm, a recessed portion that is partially retracted in the direction toward the axis of the camshaft is formed, and while the rotation of the camshaft is stopped. The decompression device, wherein the recessed portion is located inside a base circle of the exhaust side cam when the decompression device is viewed from one axial side of the camshaft.   The retraction part is formed on the decompression holder, and the retraction part is the camshaft when the decompression device is viewed from one axial side of the camshaft while the rotation of the camshaft is stopped. 2. The straight line that passes through the axis of the decompression shaft and the axis of the decompression shaft is sandwiched between the decompression arm and the decompression arm. Decompression device.   The decompression device according to claim 2, wherein a counterweight portion for balancing the rotation of the camshaft is provided in a portion of the decompression holder where the retracted portion is formed.   The decompression device according to claim 3, wherein the counterweight portion is formed by a protrusion that protrudes from the decompression holder in the axial direction of the camshaft. Camshaft,
An exhaust side cam provided on the cam shaft,
A rocker shaft provided above the cam shaft and extending in the same direction as the cam shaft;
A rocker arm that is swingably provided on the rocker shaft and that transmits the power of the exhaust side cam to an exhaust valve;
A valve mechanism including a decompression device provided on the outer peripheral side of the camshaft,
The rocker arm is supported on the rocker shaft so as to be movable in the axial direction of the rocker shaft,
The decompression device is
The camshaft is housed in a recess formed over the outer circumferential surface of the camshaft in the radial direction and the base surface of the exhaust side cam over the radial direction of the camshaft. A decompression shaft having an axis extending in the axial direction,
A decompression cam that is formed on the decompression shaft and that appears in and out of the base surface of the exhaust side cam;
A decompression holder that is formed in an annular shape or an arc shape, is provided on the outer peripheral side of the cam shaft so as to cover the outer peripheral side of the decompression shaft, and rotatably holds the decompression shaft in the recess.
A decompression arm that extends in an arc shape, is provided on the outer peripheral side of the cam shaft, and is displaced in a direction away from the axial center of the cam shaft by the centrifugal force of the cam shaft,
An urging member for urging the decompression arm in a direction of approaching the axis of the camshaft,
A connecting member for connecting the decompression shaft and the decompression arm, and transmitting a displacement of the decompression arm to the decompression shaft,
On the outer peripheral side portion of the decompression holder or the outer peripheral side portion of the decompression arm, a recessed portion that is partially retracted in the direction toward the axis of the camshaft is formed, and while the rotation of the camshaft is stopped. The valve mechanism, wherein the retracted portion is located inside a base circle of the exhaust side cam when the decompression device is viewed from one axial side of the camshaft.

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