JP2020063728A - Decompression device and valve mechanism - Google Patents

Abstract

To allow employing a method of mounting a decompression holder to a cam shaft after inserting a decompression shaft provided with a decompression pin in a decompression shaft accommodating recessed part, as an assembly method of a decompression device.SOLUTION: In a decompression device in a valve mechanism, a decompression holder 45 is provided which is located in a position in an outer peripheral side of a cam shaft 12 and opposing to an approximately central part in an axial direction of a decompression shaft 42, and holds the decompression shaft 42 within a recessed part 25. In an inner peripheral surface of the decompression holder 45 and an outer peripheral surface of the cam shaft 12, there are formed pin-through parts 26, 47 which is a groove or recessed part for passing a decompression pin 43 when, in mounting the decompression holder 45 to the cam shaft 12, moving the decompression holder 45 from one end side of the cam shaft 12, across the decompression pin 43 provided in the decompression shaft 42 located within the recessed part 25, to an outer peripheral side of the approximately central part in the axial direction of the decompression shaft 42.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a valve operating mechanism including a decompression device that performs a decompression operation to release the pressure in a cylinder of an engine.

  In the valve train of a 4-cycle gasoline engine, the camshaft is provided with an exhaust side cam for opening the exhaust valve during the exhaust stroke. Further, a decompression device is provided on one side of the exhaust side cam of the cam shaft so as to be adjacent to the exhaust side cam. 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 structure of the conventional decompression device is generally as follows. That is, the decompression device includes the decompression shaft. A decompression pin that projects radially from the decompression shaft is provided on one end side of the decompression shaft, and a decompression cam for slightly opening the exhaust valve during the compression stroke is formed on the other end side of the decompression shaft. Further, in the cam shaft, a recess is formed in a part from a part of the outer peripheral surface of the cam shaft to a part of the base surface of the exhaust side cam. The decompression shaft is housed in this recess. Further, the decompression device includes a disc-shaped decompression holder having a hole formed in the center thereof. The decompression holder is mounted on the outer peripheral side of the camshaft by passing the camshaft through the central hole, and surrounds the decompression shaft and the outer peripheral side of the camshaft housed in the recess. As a result, the decompression shaft is rotatably held in the recess. The decompression device also includes a decompression arm and a spring that biases the decompression arm. The decompression arm is arranged on the outer peripheral side of the camshaft and is displaced in a direction away from the axial center of the camshaft by centrifugal force when the camshaft rotates. The spring urges the decompression arm in a direction to bring it closer to the axis of the camshaft. A part of the decompression arm is connected to the decompression pin. Accordingly, the displacement of the decompression arm is transmitted to the decompression shaft via the decompression pin, and the displacement of the decompression arm is converted into the rotation of the decompression shaft. The decompression arm is attached to the decompression holder, and the spring is attached between the decompression holder and the decompression arm.

  When the rotation speed of the camshaft is equal to or lower than a predetermined rotation speed, the decompression arm is biased by the spring and is located near the axis of the camshaft. In this state, the decompression cam projects from the base surface of the exhaust side cam. Therefore, in the compression stroke, the exhaust valve is slightly opened by the decompression cam, and the decompression operation is performed. On the other hand, when the rotation speed of the camshaft exceeds the predetermined rotation speed, centrifugal force generated by the rotation of the camshaft causes the decompression arm to displace to a position away from the axial center of the camshaft against the biasing force of the spring. To do. As a result, the decompression shaft rotates and the decompression cam sinks into the base surface of the exhaust side cam. Therefore, the exhaust valve is closed during the compression stroke, and the decompression operation is not performed.

  Patent Document 1 below describes an example of a conventional decompression device.

  The conventional decompression device is assembled in the following manner. First, a cam shaft, a decompression shaft, a decompression pin, a decompression holder, a decompression arm, a spring and the like are prepared. An exhaust side cam is provided in advance on the cam shaft, and a recess for accommodating the decompression shaft is formed. A decompression cam is formed in advance on the decompression shaft. Next, the decompression arm is attached to the decompression holder, and the spring is attached between the decompression holder and the decompression arm. Next, the decompression shaft is inserted into the recess formed in the camshaft. Next, the cam shaft is inserted into the central hole of the decompression holder to which the decompression arm and the spring are attached from one end side of the camshaft so that the outer circumferential side of the decompression shaft and the camshaft housed in the recess is surrounded. Attach the decompression holder to the camshaft. Next, the decompression pin is attached to the decompression shaft by press-fitting the decompression pin into a small-diameter mounting hole formed in the decompression shaft in advance. Next, the decompression arm and the decompression pin are connected to each other.

  Here, the decompression holder is arranged on one side of the exhaust side cam, and the diameter of the central hole of the decompression holder is smaller than the outer diameter of the exhaust side cam. Therefore, when assembling the decompression device, in order to mount the decompression holder on the camshaft, the camshaft must be inserted into the central hole of the decompression holder from one end side of the camshaft. That is, when the camshaft is inserted into the central hole of the decompression holder from the other end side of the camshaft, the decompression holder cannot be moved over the exhaust side cam to one side of the exhaust side cam.

JP, 6-280531, A

  In the conventional decompression device described above, when assembling the decompression device, the decompression shaft must be inserted into the recess of the camshaft, and the decompression holder must be attached to the camshaft, and then the decompression pin must be attached to the decompression shaft. That is, the decompression pin is attached so as to radially protrude from the peripheral surface on the one end side of the decompression shaft. The position where the decompression holder is attached to the cam shaft is a position that is substantially opposite to the axial center portion of the decompression shaft. Therefore, if the decompression shaft is inserted into the recess of the camshaft after the decompression pin is attached to the decompression shaft, and then the camshaft is inserted into the central hole of the decompression holder from its one end side, the decompression pin will hit the decompression holder. The decompression holder cannot be moved beyond the decompression pin to a position facing the axial center of the decompression shaft. Therefore, in the conventional decompression device, there is no choice but to adopt an assembly method in which the decompression shaft is inserted into the recess of the camshaft, the decompression holder is mounted on the camshaft, and then the decompression pin is attached to the decompression shaft.

  However, the assembling method of attaching the decompression pin to the decompression shaft after inserting the decompression shaft into the recess of the camshaft and mounting the decompression holder on the camshaft has the following problems.

  That is, in the state where the decompression shaft is inserted in the recess of the camshaft, pressure for press-fitting the decompression pin into the mounting hole of the decompression shaft is applied to the decompression pin, so that the pressure is also applied to the camshaft. Therefore, the hardness or strength of the camshaft must be increased to withstand the pressure. Further, when the decompression shaft is inserted in the recess of the camshaft, it is difficult to accurately determine the mounting position or the mounting angle of the decompression pin with respect to the decompression shaft when the decompression pin is mounted on the decompression shaft. Also, when pressing the decompression pin into the mounting hole of the decompression shaft inserted in the recess of the camshaft, it is necessary to hold the decompression pin.Therefore, the decompression pin must be provided with a portion for holding the decompression pin. It is necessary to increase the amount of protrusion of the decompression pin from the decompression shaft. As a result, the overall outer diameter of the decompression device becomes large, and the decompression device becomes large.

  The present invention has been made in view of the problems as described above, for example, and an object of the present invention is to assemble a decompression device by inserting a decompression shaft into a recess of a camshaft and mounting the decompression holder on the camshaft. After that, the method of attaching the decompression pin to the decompression shaft is abolished, and instead of this, a method of inserting the decompression shaft provided with the decompression pin into the recess of the camshaft and then attaching the decompression holder to the camshaft can be adopted. It is to provide a valve mechanism.

  In order to solve the above problems, the present invention provides a valve mechanism including a cam shaft provided with an exhaust side cam, and a decompression device arranged on one side of the exhaust side cam in the axial direction of the cam shaft. The camshaft and the exhaust-side cam include a decompression shaft extending in the axial direction of the camshaft over a part of a peripheral surface of the camshaft and a part of a base surface of the exhaust-side cam. An accommodating recess is formed, and the decompression device is formed in an outer cylindrical shape having an axis line extending in the axial direction of the camshaft, and the decompression shaft disposed in the decompression shaft accommodating recess and an axial direction of the decompression shaft. A decompression pin provided on one side portion so as to radially project from the peripheral surface of the decompression shaft, and a decompression pin on the other side portion in the axial direction of the decompression shaft. And a decompression cam protruding and retracting with respect to the base surface of the exhaust side cam, and formed in a ring shape or a C shape so as to surround the camshaft and the outer peripheral side of the decompression shaft, and the decompression shaft has a substantially center in the axial direction. A decompression holder that is provided at a position facing the decompression shaft and that rotatably holds the decompression shaft in the decompression shaft accommodating recess; and a decompression pin that is provided on the outer peripheral side of the camshaft and that is connected to the decompression pin. A decompression arm that rotates the decompression shaft through the decompression pin by being displaced in a direction away from the camshaft by a centrifugal force during rotation, and a biasing member that biases the decompression arm in a direction to approach the camshaft. And an inner peripheral surface of the decompression holder and the camshaft. When the decompression holder is mounted on the camshaft, the decompression holder is provided on one or both of the outer peripheral surfaces from one end side of the camshaft to the decompression shaft arranged in the decompression shaft accommodating recess. A pin passing portion that is a groove or a recess for passing the decompression pin when the decompression shaft is moved to the outer peripheral side of the substantially central portion in the axial direction of the decompression shaft is formed.

  According to the present invention, as a method of assembling the decompression device, a method of inserting the decompression shaft provided with the decompression pin into the recess of the camshaft and then mounting the decompression holder on the camshaft can be adopted.

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. FIG. 6 is a cross-sectional view showing a cam shaft and an exhaust side cam as seen from the direction of arrows VI-VI in FIG. 5. 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 VIII direction in FIG. It is explanatory drawing which shows the cam shaft, the decompression apparatus, etc. seen from the arrow IX direction in FIG. 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 XII-XII direction in FIG. 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 assembling method of the decompression apparatus in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the assembling method of the decompression apparatus in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the assembling method of the decompression apparatus in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows the assembling method of the decompression apparatus in the valve operating mechanism of the Example of this invention. It is explanatory drawing which shows two positions of the decompression shaft inserted in the decompression shaft accommodation recessed part in the assembly process of the decompression device in the valve mechanism of the Example of this invention. It is explanatory drawing which shows the decompression holder in the decompression device of the valve mechanism of other Example of this invention. It is explanatory drawing which shows the cam shaft of the valve operating mechanism of other Example of this invention. It is explanatory drawing which shows the decompression holder in the decompression device of the valve operating mechanism of another Example of this invention.

  A valve mechanism according to an embodiment of the present invention includes a cam shaft provided with an exhaust side cam, and a decompression device arranged on one side of the exhaust side cam in the axial direction of the cam shaft. The camshaft and the exhaust-side cam are formed with a decompression shaft accommodating recess extending in the axial direction of the camshaft over a part of the peripheral surface of the camshaft and a part of the base surface of the exhaust-side cam. The decompression device includes a decompression shaft, a decompression pin, a decompression cam, a decompression holder, a decompression arm, and a biasing member.

  The decompression shaft is formed in an outer cylindrical shape having an axis extending in the axial direction of the camshaft, and is arranged in the decompression shaft accommodating recess. The decompression pin is provided on one axial side portion of the decompression shaft so as to radially project from the peripheral surface of the decompression shaft. The decompression cam is formed on a portion of the decompression shaft on the other side in the axial direction, and the decompression cam projects into and out of the base surface of the exhaust side cam. The decompression holder is formed in a ring shape or a C shape so as to surround the camshaft and the outer peripheral side of the decompression shaft, and is provided at a position facing the substantially central portion in the axial direction of the decompression shaft. It is rotatably held inside. The decompression arm is provided on the outer peripheral side of the camshaft, is connected to the decompression pin, and is displaced in the direction away from the camshaft by the centrifugal force when the camshaft rotates, thereby rotating the decompression shaft via the decompression pin. The biasing member biases the decompression arm toward the camshaft.

  In addition, when mounting the decompression holder on the camshaft, the decompression holder may be placed on one or both of the inner peripheral surface of the decompression holder and the outer peripheral surface of the camshaft from one end side of the camshaft into the decompression shaft accommodating recess. A pin insertion portion, which is a groove or a recess for inserting the decompression pin when the decompression pin is moved to the outer peripheral side of the substantially central portion in the axial direction of the decompression shaft over the decompression pin provided on the arranged decompression shaft, is formed.

  In the valve operating mechanism of the embodiment of the present invention, as a method for assembling the decompression device, a conventional method, that is, after inserting the decompression shaft into the recess of the camshaft and mounting the decompression holder on the camshaft, The method of attaching the decompression pin can be omitted, and instead of this, for example, the following method can be adopted. First, attach the decompression pin to the decompression shaft. Alternatively, a decompression shaft integrally formed with the decompression pin is prepared. Further, the decompression arm and the biasing member are attached to the decompression holder. Next, the decompression shaft provided with the decompression pin is inserted into the decompression shaft accommodating recess. Next, the cam shaft is inserted into the inside of the ring-shaped or C-shaped decompression holder from one end side of the camshaft, and the decompression holder is moved to the outer peripheral side of the axial center of the decompression shaft. Attach it to the camshaft. Next, the decompression arm and the decompression pin are connected to each other.

  According to the valve mechanism of the embodiment of the present invention, since the pin insertion portion is formed on either or both of the inner peripheral surface of the decompression holder and the outer peripheral surface of the camshaft, the decompression holder is mounted on the camshaft. At this time, the decompression pin provided on the decompression shaft arranged in the decompression shaft accommodating recess can be passed through the pin insertion portion. Therefore, the decompression holder can be moved from one end side of the cam shaft to the outer peripheral side of the decompression shaft in the axially central portion thereof, over the decompression pin provided on the decompression shaft arranged in the decompression shaft accommodating recess.

  According to the valve mechanism of the embodiment of the present invention, the decompression pin can be attached to the decompression shaft before the decompression shaft is inserted into the decompression shaft accommodating recess, or the decompression shaft integrally formed with the decompression pin is used. be able to. This eliminates the step of press-fitting the decompression pin into the mounting hole of the decompression shaft with the decompression shaft inserted in the decompression shaft housing recess. It is not necessary to consider the pressure when press-fitting into the mounting hole of the decompression shaft. In addition, the mounting position or the mounting angle of the decompression pin with respect to the decompression shaft can be determined before the decompression shaft is inserted into the decompression shaft accommodating recess. Therefore, compared to the case where the mounting position or mounting angle of the decompression pin with respect to the decompression shaft is determined with the decompression shaft inserted in the decompression shaft housing recess, the accuracy of the mounting position or mounting angle of the decompression pin with respect to the decompression shaft is improved. You can Also, since the step of press-fitting the decompression pin into the mounting hole of the decompression shaft inserted into the decompression shaft accommodating recess can be omitted, the amount of protrusion of the decompression pin from the decompression shaft should be considered in consideration of gripping the decompression pin in this process. No need to increase. Therefore, the overall outer diameter of the decompression device can be reduced, and the decompression device can be downsized.

  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 housed, a cylinder 4 in which a piston and the like are provided, and a cylinder head 5 in which an exhaust valve, an intake valve, a valve mechanism, etc. are housed. 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. 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. 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.

  Further, as shown in FIG. 2, the valve mechanism 11 includes an intake side rocker arm 15 that pushes each intake valve 7 according to the rotation of the intake side cam 13, and an exhaust valve 8 according to the rotation of the exhaust side cam 14. An exhaust side rocker arm 16 for pushing 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 an adjusting member 19 such as a shim provided on the stem end side of the intake valve 7. 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 rotatably supported by the intake side rocker shaft 20 and the exhaust side rocker shaft 21, respectively.

  Further, the respective axial end portions of the cam shaft 12, the intake rocker shaft 20, and the exhaust rocker shaft 21 are supported by the cylinder head 5 by a pair of shaft support portions 22. Specifically, both axial end portions of the camshaft 12 are rotatably supported by the shaft support portions 22. Further, the intake side rocker shaft 20 and the exhaust side rocker shaft 21 are arranged above the cam shaft 12, and both axial end portions thereof are fixed by respective shaft support portions 22. In FIG. 2, a cam sprocket 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.

  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 the 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 arrows in FIGS. Side. Further, a direction orthogonal to both the X direction and the Y direction is referred to as “Z direction”, and one side in the Z direction is referred to as “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. FIG. 6 shows the camshaft 12 and the exhaust side cam 14 as seen from the direction of arrows VI-VI in FIG. 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 portion of the circumferential surface of the exhaust side cam 14 along a circle centered on the axial center of the cam shaft 12. The overhanging surface 14B is a portion of the circumferential surface of the exhaust-side cam 14 that overhangs outside a circle centered on the axial center of the camshaft 12.

  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.

  Further, a pin insertion recess 26 is formed on the outer peripheral surface of the camshaft 12. When the decompression holder 45 is attached to the camshaft 12, the pin insertion recess 26 is provided on the decompression pin 43 provided on the decompression shaft 42 disposed in the decompression shaft housing recess 25 from one end side of the camshaft 12. It is a concave portion (pin passing portion) through which the decompression pin 43 is inserted when the decompression shaft 42 is moved to the outer peripheral side of the substantially central portion in the axial direction of the decompression shaft 42. The pin insertion recess 26 is arranged on the X1 side of the decompression shaft accommodation recess 25 and at a position adjacent to the decompression shaft accommodation recess 25 on the substantially Z2 side of the decompression shaft accommodation recess 25 (one side in the circumferential direction of the camshaft 12). , Is integrated with the decompression shaft housing recess 25. As shown in FIG. 6, the bottom surface of the pin insertion recess 26 is continuous with the bottom surface of the decompression shaft accommodating recess 25, and these bottom surfaces are on the same plane.

  A fixing pin mounting hole 27 for mounting a holder fixing pin 31 that locks the decompression holder 45 in a non-rotatable manner with respect to the cam shaft 12 is formed on the Y2 side portion of the outer peripheral surface of the cam shaft 12. One end side of the holder fixing pin 31 is fitted into the fixing pin mounting hole 27. The other end side of the holder fixing pin 31 projects radially from the Y2 side portion of the outer peripheral surface of the camshaft 12. Further, as shown in FIG. 5, on the outer peripheral surface of the camshaft 12, a clip mounting groove 30 for mounting the washer 28 and the circlip 29 is provided on the outer peripheral surface of the camshaft 12 on the X1 side of the decompression shaft housing recess 25. It is formed over.

  FIG. 7 shows the decompression device 41 provided on the camshaft 12. FIG. 8 shows the decompression device 41 as seen from the direction of arrow VIII in FIG. FIG. 9 shows the decompression device 41 as seen from the direction of the arrow IX in FIG. As shown in FIGS. 7 to 9, 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. 10 shows the decompression shaft 42, the decompression pin 43, and the decompression cam 44. As shown in FIG. 10, the decompression shaft 42 is formed of, for example, a metal material into an outer cylindrical shape having an axis extending in the X direction. 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 pin 43 can be provided on the decompression shaft 42 by press-fitting the base end portion of the decompression pin 43 into a hole formed in the peripheral surface of the decompression shaft 42 on the X1 side. Alternatively, the decompression shaft 42 and the decompression pin 43 may be integrally formed by molding or the like. Further, the decompression pin 43 can be joined to the decompression shaft 42 by welding. On the other hand, 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. 9, the X1 side portion of the decompression shaft 42 provided with the decompression pin 43 is arranged in a portion of the decompression shaft housing recess 25 located on the outer peripheral surface of the camshaft 12. Further, 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. 7, the decompression holder 45 is provided at a position facing the substantially central portion of the decompression shaft 42 in the axial direction, and surrounds the outer peripheral side of the camshaft 12 and the decompression shaft 42. 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. 11 shows the decompression holder 45, and FIG. 12 shows a cross section of the decompression holder 45 as seen from the direction of arrow XII-XII in FIG. 11. As shown in FIG. 11, the decompression holder 45 is formed in, for example, a metal material in a ring shape. The inner diameter of the decompression holder 45 is slightly larger than the outer diameter of the camshaft 12. For example, the difference between the inner diameter of the decompression holder 45 and the outer diameter of the camshaft 12 is greater than 0 mm and 0.1 mm or less.

  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. The bottom surface of the decompression shaft covering groove 46 is formed in an arc shape along the outer peripheral surface of the decompression shaft 42.

  Further, a pin insertion groove 47 is formed on the inner peripheral surface of the decompression holder 45. When the decompression holder 45 is mounted on the camshaft 12, the pin insertion groove 47 is provided on the decompression pin 42 provided in the decompression shaft accommodating recess 25 from one end side of the decompression holder 45. It is a groove (pin insertion portion) for passing the decompression pin 43 when the decompression shaft 42 is moved to the outer peripheral side of the substantially central portion in the axial direction of the decompression shaft 42. The pin passing groove 47 is adjacent to the decompression shaft covering groove 46 on the Z2 side of the decompression shaft covering groove 46 (one side in the circumferential direction of the decompression holder 45) and is integrated with the decompression shaft covering groove 46. The bottom surface of the pin passing groove 47 and the bottom surface of the decompression shaft covering groove 46 are connected to each other, and the portion where the pin passing groove 47 and the decompression shaft covering groove 46 are formed is continuously formed on the inner peripheral surface of the decompression holder 45. It is dented.

  An arm support portion 49 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 49, an insertion hole 51 for attaching the shaft support portion 59 of the decompression arm 58 to the decompression holder 45 and inserting a support member 50 (see FIG. 7) which serves as a rotation axis of the decompression arm 58 is provided. Has been formed.

  A weight portion 52 is formed on the Z2 side of the decompression holder 45. The weight portion 52 is a portion for balancing the weight around the rotation axis of the cam shaft 12 with the decompression device 41 attached to the cam shaft 12. As shown in FIG. 12, the weight portion 52 is integrally formed on the Z2 side portion of the decompression holder 45, and specifically, by making the Z2 side portion of the decompression holder 45 thicker than other portions. Has been formed.

  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, 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. Into the holder groove portion 56, the protruding end portion of the holder fixing pin 31 mounted in the fixing pin mounting hole 27 of the cam shaft 12 is inserted. 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. 8, the decompression arm 58 is a member that rotates the decompression shaft 42 via the decompression pin 43 by being displaced in the direction away from the camshaft 12 by the centrifugal force when the camshaft 12 rotates. The decompression arm 58 is an arc-shaped member formed of, for example, a metal material. A shaft support portion 59 for rotatably attaching the decompression arm 58 to the arm support portion 49 of the decompression holder 45 via the support member 50 is formed at the Y2 side end of the decompression arm 58. 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. 9, 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. 13A and 13B show cross sections of the exhaust side cam 14 and the decompression cam 44 as seen from the direction of the arrow XIII-XIII in FIG. 9. In FIG. 13A, 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. 13B, 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 due to 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.

  14 to 17 show each step in the assembling method of the decompression device 41. 18 shows two positions of the decompression shaft 42 inserted into the decompression shaft housing recess 25 in the assembly process of the decompression device 41. The assembling method of the decompression device 41 is as follows.

  First, the camshaft 12, the decompression shaft 42, the decompression holder 45, the decompression arm 58, and the coil spring 63 are prepared as the components of the decompression device 41. The cam shaft 12 is pre-formed with the components shown in FIGS. 5 and 6, such as the intake cam 13, the exhaust cam 14, the decompression shaft housing recess 25, the pin insertion recess 26, and the fixed pin mounting hole 27. . Further, a holder fixing pin 31 is previously attached to the fixing pin attaching hole 27 of the camshaft 12. Further, as shown in FIG. 10, a decompression pin 43 is preliminarily provided on the decompression shaft 42 by means of press fitting, molding, welding or the like, and a decompression cam 44 is preliminarily formed. Further, as shown in FIG. 11, the decompression holder 45 is preliminarily formed with a decompression shaft covering groove 46, a pin insertion groove 47, and the like, and a spring hook 53 is previously attached thereto.

  Next, the decompression arm 58 and the coil spring 63 are attached to the decompression holder 45 (decompression arm attaching step).

  Next, as shown in FIG. 14, the decompression shaft 42 provided with the decompression pin 43 is inserted into the decompression shaft housing recess 25 of the camshaft 12 (decompression shaft insertion step). At this time, the decompression shaft 42 is arranged in the decompression shaft accommodating recess 25, and the decompression pin 43 is arranged in the pin passing recess 26, as shown by the chain double-dashed line in FIGS. That is, as shown in FIG. 18A, the decompression shaft accommodation recess 25 is formed such that its length in the X direction is longer than the length of the decompression shaft 42 in the X direction (axial direction). This allows the decompression shaft 42 to be moved in the X direction with the decompression shaft 42 arranged in the decompression shaft accommodating recess 25 so that the decompression pin 43 provided on the decompression shaft 42 can be inserted into and removed from the coupling groove 62 of the decompression arm 58. This is because When the decompression shaft 42 is inserted into the decompression shaft accommodating recess 25, the decompression shaft 42 is arranged so as to be close to the end side of the decompression shaft accommodating recess 25 on the X1 side, as indicated by the chain double-dashed line in FIG. 18 (A). To do. Further, as shown by the chain double-dashed line in FIG. 6, when the decompression shaft 42 is inserted into the decompression shaft accommodating recess 25, the protruding end side of the decompression pin 43 provided in the decompression shaft 42 falls into the pin insertion recess 26. , The decompression shaft 42 is arranged.

  Next, as shown in FIG. 15, the camshaft 12 is inserted from the X1 side of the camshaft 12 inside the decompression holder 45 to which the decompression arm 58 and the coil spring 63 are attached. Subsequently, the decompression holder 45 is passed through the position P corresponding to the X1 side end portion where the decompression pin 43 is provided in the decompression shaft 42 inserted into the decompression shaft accommodation recess 25, and is inserted into the decompression shaft accommodation recess 25. Further, the decompression shaft 42 is moved to the X2 side until it reaches the position Q facing the axially intermediate portion of the decompression shaft 42 (decompression holder insertion step).

  When the decompression holder 45 reaches the position P during the movement of the decompression holder 45 in this manner, the pin insertion groove 47 of the decompression holder 45 and the pin insertion recess 26 of the cam shaft 12 face each other in the Y direction. At this time, as shown in FIG. 11, a gap 48 through which the decompression pin 43 can be inserted (hereinafter, referred to as “pin insertion gap”) is formed between the pin insertion groove 47 and the pin insertion recess 26. . The decompression pin 43 can pass through the pin insertion gap 48 without contacting the decompression holder 45. That is, the decompression holder 45 can pass the Y1 side of the decompression pin 43 arranged in the pin insertion recess 26 without contacting the decompression pin 43. Therefore, the decompression holder 45 can move to the X2 side beyond the decompression pin 43 and reach the position Q.

  Further, when the decompression holder 45 is moved to the position Q, the protruding end portion of the holder fixing pin 31 is inserted into the holder groove portion 56, and both are fitted together.

  Then, as shown by the arrow in FIG. 16, the decompression pin 43 arranged in the pin insertion recess 26 is raised, and then the decompression shaft 42 is slid to the X2 side (see also FIG. 18B). As shown in FIG. 17, the decompression pin 43 is inserted into the connection groove 62 of the decompression arm 58. As a result, the decompression arm 58 and the decompression pin 43 are coupled (decompression pin coupling step).

  Then, as shown in FIG. 9, the washer 28 and the circlip 29 are attached to the clip attaching groove 30 formed in the camshaft 12 (clip attaching step). This completes the assembly of the decompression device 41.

  As described above, according to the valve mechanism 11 of the embodiment of the present invention, the pin insertion groove 47 is formed on the inner peripheral surface of the decompression holder 45, and the pin insertion recess 26 is formed on the outer peripheral surface of the camshaft 12. When the decompression holder 45 is attached to the camshaft 12, the pin insertion gap 48 through which the decompression pin 43 provided in the decompression shaft 42 disposed in the decompression shaft housing recess 25 can be inserted is defined by the inner circumference of the decompression holder 45. It can be formed between the surface and the outer peripheral surface of the camshaft 12. Therefore, as a method for assembling the decompression device 41, as shown in FIGS. 14 to 17, after inserting the decompression shaft 42 provided with the decompression pin 43 into the decompression shaft accommodating recess 25, the decompression holder 45 is attached to the camshaft 12. It is possible to adopt a method such as

  According to such an assembling method, the decompression pin 43 can be attached to the decompression shaft 42 before the decompression device 41 is assembled, or the decompression shaft 42 integrally formed with the decompression pin 43 can be used. Therefore, the accuracy of the position and the projection angle of the decompression pin 43 with respect to the decompression shaft 42 can be improved. Also, the conventional method of assembling the decompression shaft into the recess of the camshaft and the decompression holder into the camshaft and then pressing the decompression pin into the decompression shaft can be eliminated. It is not necessary to set the hardness or strength of the camshaft in consideration of the pressure applied to the camshaft. Further, in the above-described conventional assembling method, it was necessary to lengthen the decompression pin in order to hold the decompression pin when press-fitting the decompression pin into the decompression shaft during the assembling of the decompression device, but this is not necessary in the present embodiment. . Therefore, the decompression pin 43 can be shortened, and thus the overall outer diameter of the decompression device 41 can be reduced. Therefore, the decompression device can be downsized.

  Further, in the valve mechanism 11 of the embodiment of the present invention, the pin insertion groove 47 is formed on the inner peripheral surface of the decompression holder 45, and the pin insertion recess 26 is formed on the outer peripheral surface of the camshaft 12, and the pin insertion groove 47 is formed. Since the pin insertion gap 48 is formed by the pin insertion recess 26 and the pin insertion recess 26, as compared with the case where the pin insertion gap 48 is formed only by forming the pin insertion groove 47 on the inner peripheral surface of the decompression holder 45, The dimension of the pin insertion groove 47 in the depth direction, that is, the length dimension of the pin insertion groove 47 in the radial direction of the cam shaft 12 can be reduced. Therefore, when cutting the inner peripheral surface of the decompression holder 45 to form the pin insertion groove 47, the degree of cutting the inner peripheral surface of the decompression holder 45 can be reduced. Therefore, the outer diameter of the decompression holder 45 can be reduced while ensuring sufficient strength of the decompression holder 45, and the decompression device 41 can be downsized. In addition, since the outer diameter of the decompression holder 45 provided on the outer peripheral side of the camshaft 12 can be reduced, the moment of inertia during rotation of the camshaft 12 can be suppressed and the rotation of the camshaft 12 can be stabilized.

  Further, in the valve mechanism 11 of the embodiment of the present invention, the pin insertion groove 47 is adjacent to the decompression shaft covering groove 46 in the circumferential direction of the decompression holder 45 and is integrated with the decompression shaft covering groove 46. Further, the pin insertion recess 26 is arranged at one end side of the decompression shaft accommodation recess 25 in the axial direction of the camshaft 12 and at a position adjacent to the decompression shaft accommodation recess 25 in the circumferential direction of the camshaft 12. It is integrated with the recess 25. With these configurations, when the decompression holder 45 is mounted on the outer peripheral side of the camshaft 12, the decompression pin 43 can be passed through the pin insertion gap 48 in a state where the decompression pin 43 is tilted into the pin insertion recess 26 and stabilized. Therefore, when the decompression pin 43 is passed through the pin passing gap 48, the decompression pin 43 can be prevented from moving and hitting the decompression holder 45. Therefore, the decompression pin 43 can be smoothly passed through the pin insertion gap 48, and the workability of assembling the decompression device 41 can be improved.

  In addition, in the above-described embodiment, the case where the pin insertion groove 47 is formed on the inner peripheral surface of the decompression holder 45 and the pin insertion recess 26 is formed on the outer peripheral surface of the cam shaft 12 has been described, but the present invention is not limited to this. . Like the decompression holder 71 and the camshaft 72 shown in FIG. 19, the pin insertion groove 73 may be formed on the inner peripheral surface of the decompression holder 71, and the pin insertion recess may not be formed on the outer peripheral surface of the camshaft 72. . With this configuration as well, when the decompression holder 71 is mounted on the camshaft 72, the pin insertion gap 74 through which the decompression pin 43 provided on the decompression shaft 42 arranged in the decompression shaft housing recess 25 can be passed is set. It can be formed between the pin insertion groove 73 of 71 and the outer peripheral surface of the cam shaft 72.

  Further, like the cam shaft 81 and the decompression holder 82 shown in FIG. 20, the pin insertion recess 83 is formed on the outer peripheral surface of the cam shaft 81, and the pin insertion groove is not formed on the inner peripheral surface of the decompression holder 82. Good. With this configuration as well, when the decompression holder 82 is mounted on the camshaft 81, the pin insertion gap 84 through which the decompression pin 43 provided on the decompression shaft 42 disposed in the decompression shaft housing recess 25 can pass is provided. It can be formed between the pin insertion recess 83 of 72 and the inner peripheral surface of the decompression holder 71.

  Further, as shown in FIG. 21, the decompression holder 91 having the decompression shaft covering groove 46 and the pin insertion groove 47 may be formed in a C shape.

  Further, the valve mechanism of the present invention is not limited to the engine for a saddle-ride type vehicle, but can be applied to various engines such as an engine for an outboard motor.

  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 the valve operating mechanism accompanied by such modification is also the technical concept of the present invention. include.

11 Valve Operating Mechanism 12, 72, 81 Cam Shaft 14 Exhaust Cam 14 A Base Surface 25 Decompression Shaft Housing Recess 26, 83 Pin Passing Recess (Pin Passing Port)
41 decompression device 42 decompression shaft 43 decompression pin 44 decompression cam 45, 71, 82, 91 decompression holder 46 decompression shaft covering groove 47, 73 pin insertion groove (pin insertion part)
48 Pin through gap 58 Decompression arm 63 Coil spring

Claims (4)

A valve mechanism comprising a camshaft provided with an exhaust side cam, and a decompression device arranged on one side of the exhaust side cam in the axial direction of the camshaft,
In the camshaft and the exhaust side cam, a decompression shaft accommodating recess extending in the axial direction of the camshaft is formed over a part of a peripheral surface of the camshaft and a part of a base surface of the exhaust side cam. Is
The decompression device is
A decompression shaft that is formed in an outer cylindrical shape having an axis that extends in the axial direction of the camshaft and that is disposed in the decompression shaft accommodating recess;
A decompression pin provided on one axial side portion of the decompression shaft so as to radially project from the peripheral surface of the decompression shaft,
A decompression cam which is formed on a portion of the decompression shaft on the other side in the axial direction and protrudes and retracts with respect to the base surface of the exhaust side cam;
The camshaft and the decompression shaft are formed in a ring shape or a C shape so as to surround the outer peripheral sides thereof, and are provided at a position facing a substantially central portion in the axial direction of the decompression shaft. A decompression holder rotatably held in the recess,
A decompression provided on the outer peripheral side of the camshaft, coupled to the decompression pin, and displacing in a direction away from the camshaft by a centrifugal force during rotation of the camshaft to rotate the decompression shaft via the decompression pin. An arm,
A biasing member that biases the decompression arm in a direction of approaching the camshaft,
Either one or both of the inner peripheral surface of the decompression holder and the outer peripheral surface of the camshaft may be attached to the decompression holder from one end side of the camshaft when the decompression holder is attached to the camshaft. A pin insertion part that is a groove or a recess for passing the decompression pin when the decompression pin is provided in the decompression shaft arranged in the shaft accommodating recess and is moved to the outer peripheral side of the axially substantially central part of the decompression shaft. A valve operating mechanism characterized by being formed. A decompression shaft covering groove is formed on the inner peripheral surface of the decompression holder to cover a portion of the decompression shaft in the substantially central portion in the axial direction, the decompression shaft accommodating recess extending from the decompression shaft accommodating recess.
The pin passing portion is a groove formed on the inner peripheral surface of the decompression holder, and the groove is adjacent to the decompression shaft covering groove in the circumferential direction of the decompression holder and is integrated with the decompression shaft covering groove. The valve mechanism according to claim 1, wherein:   The pin insertion portion is a concave portion formed on the outer peripheral surface of the cam shaft, the concave portion being one end side of the decompression shaft housing concave portion in the axial direction of the cam shaft, and the decompression portion in the circumferential direction of the cam shaft. The valve mechanism according to claim 1, wherein the valve operating mechanism is arranged adjacent to the shaft accommodating recess and is integrated with the decompression shaft accommodating recess. A decompression shaft covering groove is formed on the inner peripheral surface of the decompression holder to cover a portion of the decompression shaft in the substantially central portion in the axial direction, the decompression shaft accommodating recess extending from the decompression shaft accommodating recess.
The pin passing portion includes a pin passing groove formed on an inner peripheral surface of the decompression holder, and a pin passing concave portion formed on an outer peripheral surface of the cam shaft,
The pin passing groove is adjacent to one side of the decompression shaft covering groove in the circumferential direction of the decompression holder, and is integrated with the decompression shaft covering groove,
The pin passing recess is disposed at one end side of the decompression shaft accommodating recess in the axial direction of the camshaft and adjacent to one side of the decompression shaft accommodating recess in the circumferential direction of the camshaft. The valve mechanism according to claim 1, wherein the valve mechanism is integrated with the accommodating recess.

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