JP4777955B2 - Engine decompression device - Google Patents

Description

  The present invention relates to an improvement in an engine decompression device that reduces cranking torque at the time of engine start.

When the engine stops, the decompression cam attached to the camshaft is rotated by the pressure in the combustion chamber and the intake or exhaust valve is pushed to lower the pressure in the combustion chamber, reducing the cranking torque at the next start. An apparatus is known (for example, refer to Patent Document 1).
JP 2002-295218 A (FIG. 8)

  In FIG. 8 of Patent Document 1, the decompression device of the engine is a decompression cam 35 attached to a camshaft 19 (the reference numeral is diverted from the same publication; the same applies hereinafter) via a one-way clutch 34, and an outer periphery of the decompression cam 35. And a stopper piece 41 which is attached to the cylinder head so as to be extendable and retractable and locks the locking protrusion 39.

  A stopper piece 41 (hereinafter referred to as “stopper pin 41”) is slidably provided in a through hole 40 formed in the cylinder head, and is pressed by a coil spring 42. The coil spring 42 is externally applied. It is supported by bolts 43.

  When the engine is rotating, the locking projection 39 of the decompression cam 35 hits the stopper pin 41 and prevents the decompression cam 35 from rotating in the same direction as the rotational direction of the engine. When the engine is stopped, the decompression cam 35 rotates in the direction opposite to the rotation direction of the engine due to the pressure in the combustion chamber, and the cam crest portion 38 of the decompression cam 35 presses the exhaust valve to lower the pressure in the combustion chamber. Reduce cranking torque at start-up.

  By the way, in the technique of patent document 1, since the stopper pin 41, the coil spring 42, and the volt | bolt 43 are arrange | positioned on the coaxial line, the head of the volt | bolt 43 is arrange | positioned away from the center of the camshaft 19. FIG. As a result, the length from the center of the camshaft 19 to the head of the bolt 43 is increased. If the length from the center of the camshaft 19 to the head of the bolt 43 can be shortened, the engine can be reduced in size, which is preferable.

  An object of the present invention is to provide an engine decompression device that can reduce the size of the engine.

According to a first aspect of the present invention, a camshaft provided in a cylinder head for opening and closing an intake valve and an exhaust valve, and rotation of the camshaft when the camshaft provided on the camshaft rotates in a direction opposite to the engine rotation direction. A one-way clutch that transmits force to the outside, a decompression cam that is fitted in the one-way clutch and pushes the intake valve or exhaust valve to lower the pressure in the combustion chamber of the engine, and a stopper pin that is provided on the cylinder head side and protrudes from the decompression cam And a locking portion that prevents the decompression cam from rotating in the same direction as the rotation direction of the engine.When the engine stops, the camshaft is moved in the direction opposite to the rotation direction of the engine by the pressure of the combustion chamber. The cam crest provided on the decompression cam by rotating the decompression cam in the direction opposite to the engine rotation direction. In the engine decompression device that reduces the cranking torque at the next start by pushing the intake valve or exhaust valve to reduce the cranking torque at the next start, the cylinder head side has a holding part that holds the stopper pin. The stopper pin and the spring member are accommodated in this order in the through hole opened in the part, and a pressing plate for pressing the spring member is arranged above the through hole, and the pressing plate is located at a position shifted from the axis of the spring member. The bridge is spanned between the front and rear of the engine, and bolt holes for fastening the cylinder head to the cylinder block are arranged at the front and rear of the bridge, and the holding plate is used as a holding part. The screw holes to be fastened are arranged so as to be arranged in the bridge portion together with the through holes .

  The invention according to claim 2 is characterized in that the holding portion is a camshaft holder that rotatably holds the camshaft on the cylinder head.

  In the invention which concerns on Claim 3, the through-hole is arrange | positioned at the upper part of the camshaft holder, It is characterized by the above-mentioned.

  The invention according to claim 4 is characterized in that the axis of the through hole coincides with the axis of the bolt hole for fastening the cylinder head to the cylinder block.

  In the invention according to claim 1, since the pressing plate that presses the stopper pin via the spring member is provided above the through hole opened in the holding portion, the spring member is pressed by the pressing plate. Further, the pressing plate is fastened at a position shifted from the axis of the spring member.

If the pressing plate is not used, the spring member is held on the axis of the spring member, so that the length of the stopper pin and the holding portion thereof is long.
In this respect, in the present invention, a pressing plate is provided, and the pressing plate is fastened at a position shifted from the axis of the spring member, so that the axial length of the stopper pin and the stopper pin holding portion can be shortened.
Since the lengths of the stopper pin and the holding portion thereof are shortened, it is difficult to increase the size of the engine due to the mounting of the decompression device.
In addition, the screw holes for fastening the pressing plate to the holding portion are arranged so as to be aligned with the bridge portion arranged in the longitudinal direction of the vehicle together with the through hole. In addition, bolt holes for fastening the cylinder head to the cylinder block are arranged at the front part and the rear part of the bridge part.
That is, since the screw hole, the through hole, and the bolt hole are arranged so as to be arranged in the bridge portion, the pressing plate can be arranged without spreading in the width direction of the vehicle. For this reason, a holding part can be efficiently arranged in a limited space above the engine. As a result, the engine can be further reduced in size.

  In the invention according to claim 2, since the holding portion is also used as a camshaft holder that rotatably holds the camshaft on the cylinder head, an increase in the number of parts can be suppressed. In addition, the space required around the stopper pin can be made compact.

  Further, if the camshaft holder is provided separately from the cylinder head, after the stopper pins are sub-assembled to the camshaft holder, they can be assembled to the cylinder head, thereby simplifying the assembly process. Furthermore, it is possible to assemble the stopper pin while observing the positional relationship with the decompression cam with the cylinder head removed. Therefore, workability can be improved when the stopper pin is assembled.

  In the invention which concerns on Claim 3, since the through hole is arrange | positioned at the upper part of a camshaft holder, a hand can be easily approached to a through hole from upper direction. Since the hand can be easily brought close to the through hole, the workability related to the assembly of the stopper pin, the spring member and the screw member can be improved.

  In the invention according to claim 4, since the axis of the through hole and the axis of the bolt hole for fastening the cylinder head are provided in parallel to each other, the cutting tool is compared with the case where these holes are arranged in different directions. There is no need to change the orientation of the hole, and the efficiency of drilling can be increased.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a left side view of a motorcycle equipped with an engine decompression device according to the present invention.
The motorcycle 100 has a body frame 101 and a power unit 102 including the engine 10 suspended from the body frame 101.
The body frame 101 is inclined obliquely downward and rearward from the head pipe 103 and left and right front forks 105L and 105R (only the left reference numeral 105L is shown) extending diagonally forward and downward from the head pipe 103 and supporting the front wheel 104. A main frame 106 extending in this manner, seat rails 107L and 107R (only the left reference numeral 107L is shown) extending rearward from the rear portion of the main frame 106, and a lower portion of the rear portion of the main frame 106. Pivot brackets 108L and 108R (only reference numeral 108L on the left is shown) that are mounted toward the rear and the rear swing that extends rearward from the pivot brackets 108L and 108R via the pivot shaft 111 and supports the rear wheel 112 Arms 113L, 113R (left side reference 113L Left and right rear cushion units 114L and 114R (only the left reference numeral 114L is shown) attached between the rear ends of these rear swing arms 113L and 113R and the intermediate portions of the seat rails 107L and 107R. ) And rear support frames 115L and 115R that extend obliquely rearward and upward from the pivot brackets 108L and 108R and support the seat rails 107L and 107R. Stays 117L and 117R to which passenger steps 116L and 116R (only the reference numeral 116L on the left are shown) are attached obliquely rearward and downward are provided at intermediate portions of the rear support frames 115L and 115R.

  The power unit 102 is suspended from the above-described pivot brackets 108L and 108R, is suspended from upper stays 118L and 118R provided on the main frame, and extends horizontally from the lower ends of the pivot brackets 108L and 108R. It is also supported by 121L and 121R (only the reference numeral 121L on the left is shown). Reference numeral 122 denotes a steering handle that is rotatably provided on the head pipe 15 and that steers the front wheels 104.

A luggage box 123 as a container and a fuel tank 124 are attached to seat rails 107L and 107R provided on the body frame 101. The fuel tank 124 is disposed behind the luggage box 123.
An occupant seat 125 on which an occupant is seated is disposed above the luggage box 123 and the fuel tank 124 arranged side by side.

  In the figure, 126 includes a straddle portion 127 disposed in front of the occupant seat, and front cowls 128L and 128R (only 128L on the front side) covering the front of the vehicle are upper cowls 129L and 129R that cover the steering wheel. Is a side cowl that covers the side of the vehicle, 131 is a front fender, and 132 is a rear fender.

The power unit 102 includes the engine 10. Hereinafter, the intake / exhaust system of the engine 10 will be described.
In the engine 10, a cylinder block 12 including a cylinder 12c is disposed so as to protrude forward in a substantially horizontal manner, and an intake port (reference numeral 72 in FIG. 4) as an inlet of an air-fuel mixture is formed on an upper surface of a cylinder head 13 covering the cylinder 12c. The fuel supply device 135 including the intake pipe 134 is attached to the intake port 72, and the air cleaner 136 is attached to the upper portion of the fuel supply device 135. The air cleaner 136 is attached to the front of the main frame 106 and below the main frame 106.
The main frame 106 is disposed so as to be inclined rearward and downward, and the intake pipe 134 is disposed above the cylinder 12 c and below the main frame 106.

  An exhaust port (reference numeral 71 in FIG. 4) as an exhaust gas outlet is provided on the lower surface of the cylinder head 13. An exhaust pipe 138 is connected to the exhaust port 71, and a rear end portion of the exhaust pipe 138 is connected to the exhaust port 138. The muffler 139 is connected. Details of the engine 10 will be described later.

  FIG. 2 is a cross-sectional view of an engine according to the present invention. The engine 10 is a four-cycle air-cooled single cylinder engine mounted on a motorcycle. In the figure, “left”, “right”, “up”, “down”, “front”, and “rear” are engine directions viewed from the driver when the engine is mounted on a motorcycle.

  The main body of the engine 10 includes a crankcase 11, a cylinder block 12 attached to the upper portion of the crankcase 11, and a cylinder head 13 attached to the upper portion of the cylinder block 12. A cylinder head cover 14 that covers the cylinder head 13 is attached to the top of the cylinder head 13.

  The crankcase 11 is provided with a pair of left and right crank bearings 15L, 15R. A crankshaft 16 is rotatably supported by the crank bearings 15L, 15R. A generator 17 is connected to the left end of the crankshaft 16. A centrifugal clutch 18 is connected to the right end of the crankshaft 16, and the centrifugal clutch 18 can intermittently rotate the crankshaft 16 with respect to the speed reducer.

  The cylinder block 12 is provided with a bore hole 22, and a piston 23 is provided in the bore hole 22 so as to be slidable up and down. The piston 23 is connected to the crankshaft 16 via a piston pin 24, a connecting rod 25, and a crankpin 26. A combustion chamber 27 is provided between the piston 23 and the cylinder head 13, and this combustion is performed. A spark plug 28 is disposed in the chamber 27. With such a structure, the combustion gas burns in the combustion chamber 27, and a downward force in the vertical direction is applied to the piston 23, which becomes the rotational force of the crankshaft 16. Reference numeral 29 denotes a cooling fin.

The cylinder head 13 is provided with a cam shaft 32 rotatably via a pair of left and right cam bearings 31L, 31R. A cam chain 33 for driving the cam shaft 32 is hung between the cam shaft 32 and the crankshaft 16. Has been passed. The camshaft 32 is provided with an intake cam 35 and an exhaust cam 36. The intake cam 35 and the exhaust cam 36 open and close an intake valve and an exhaust valve, which will be described later, to enter the combustion chamber 27. The intake of the air-fuel mixture and the combustion gas are exhausted from the combustion chamber 27 to the outside.
The details of the so-called valve operating mechanism 38 for driving the intake valve and the exhaust valve will be described in the following figures. In the figure, 41 is a camshaft drive sprocket, 42 is a cam sprocket, and 43 is an auxiliary sprocket.

  The centrifugal clutch 18 has a crankshaft 16 connected to the input side and a sleeve 44 connected to the output side. The main shaft 21 is connected to the sleeve 44 via a speed change clutch 45. A counter shaft 47 is disposed below the main shaft 21, and a plurality of speed change gears are provided on the main shaft 21 and the counter shaft 47. Gears 48... (... indicates a plurality, the same applies hereinafter), and rotational force is transmitted from the main shaft 21 to the counter shaft 47. An output drive sprocket 46 is attached to the left end of the counter shaft 47.

  Below the countershaft 47, a starter kick pedal 51 on which an occupant puts his or her foot at the start and a starter shaft 52 which is rotationally driven by the starter kick pedal 51 are provided. A pair of gears 53a and 53b are provided between them. A kick spring 54 returns the starter shaft 52 to its original position.

  When the engine is started, the rotational force applied to the starter shaft 52 by the occupant's pedaling force is transmitted to the crankshaft 16 through the pair of gears 53a, 53b, the countershaft 47 and the main shaft 21, and rotates the crankshaft 16 to burn it. The air-fuel mixture is sucked into the chamber 27, the spark plug 28 is ignited, and the engine 10 is started.

  After the engine is started, the force that pushes the piston 23 downward by combustion in the combustion chamber 27 is transmitted to the crankshaft 16 via the piston pin 24, the connecting rod 25, and the crankpin 26, and is connected to the crankshaft 16 automatically. The force applied to the sleeve 44 is transmitted to the sleeve 44 via the centrifugal clutch 18, and the force applied to the sleeve 44 is transmitted to the speed change clutch 45. The speed change clutch 45 and the plurality of speed change gears 48 cooperate with each other. A rotational force is applied to the counter shaft 47 as an output shaft at a predetermined rotational speed.

  3 is a view taken in the direction of arrow 3 in FIG. 2, FIG. 4 is a view for explaining a valve train of the engine according to the present invention, FIG. 5 is a sectional view taken along line 5-5 in FIG. It is line sectional drawing. Hereinafter, description will be made with reference to FIGS. In FIG. 3, the cylinder head cover 14 is removed.

On the upper part of the cylinder head 13, left and right bridge portions 56L and 56R are arranged in the front-rear direction of the engine as viewed from the driver . Four bolt holes 58... For fastening the cylinder head 13 to the cylinder block 12 are arranged at the front and rear portions of the left and right bridge portions 56 </ b> L and 56 </ b> R. Bolts 61 are inserted, and head nuts 62 are mounted on the head bolts 61.

Rocker arm shafts 64F and 64R are spanned between the left and right bridge portions 56L and 56R extending in the front-rear direction of the engine as viewed from the driver, in the width direction of the front and rear portions, and the front rocker arm An exhaust rocker arm 66 that drives the exhaust valve 65 is swingably attached to the shaft 64F, and an intake rocker arm 68 that drives the intake valve 67 is swingably attached to the rear rocker arm shaft 64R. Yes.
An exhaust port 71 is formed at the front of the cylinder head 13, and an intake port 72 is formed at the rear of the cylinder head 13.

  The exhaust valve 65 is a member that opens and closes the mouth of the exhaust port 71, and includes a valve main body 65 a and a shaft portion 65 b, and is slidably attached to a sleeve member 75 provided in the cylinder head 13. A spring retainer 73 is attached to the upper end of the shaft portion 65b. A valve spring 74 is provided between the spring retainer 73 and the cylinder head 13. When no force is applied to the exhaust valve 65, the valve spring 74 The spring retainer 73 is pressed and the mouth of the exhaust port 71 is closed.

  Similarly, the intake valve 67 is a member that opens and closes the mouth of the intake port 72, and includes a valve main body 67 a and a shaft portion 67 b, and is slidably attached to a sleeve member 75 provided in the cylinder head 13. A spring retainer 73 is attached to the upper end portion of the shaft portion 67b, and a valve spring 74 is provided between the spring retainer 73 and the cylinder head 13. When no force is applied to the intake valve 67, the spring is retained by the valve spring 74. The retainer 73 is pressed and the mouth of the intake port 72 is closed.

When the camshaft 32 rotates, the exhaust cam 36 provided on the camshaft 32 pushes the exhaust rocker arm 66 at a predetermined timing, and the exhaust rocker arm 66 pushes the exhaust valve 65 to open the mouth of the exhaust port 71, so Exhaust the combustion gas.
Similarly, the intake cam 35 provided on the camshaft 32 pushes the intake rocker arm 68 at a predetermined timing, the intake rocker arm 68 pushes the intake valve 67, opens the inlet port 72, and mixes the air into the combustion chamber 27. Supply.
In the figure, 77 is a cover bolt for fixing the cylinder head cover 14 to the cylinder head 13, and 78 is a seal member.

Hereinafter, the detailed structure of the decompression cam according to the present invention will be described.
The decompression cam 81 is an abbreviation for a decompression cam, and is a cam attached to the camshaft 32 separately from the intake cam 35 and the exhaust cam 36. The decompression cam 81 is fitted to the camshaft 32 via a one-way clutch 79.

  The one-way clutch 79 transmits the rotational force of the camshaft 32 to the decompression cam 81 provided outside when the camshaft 32 rotates in the direction opposite to the rotational direction of the engine 10, and the camshaft 32 rotates the engine 10. When rotating in the same direction as the direction, almost all of the rotational force of the cam shaft 32 is not transmitted to the decompression cam 81.

  On the outer periphery of the decompression cam 81, a latching portion 83 is provided so as to prevent the decompression cam 81 from rotating in the same direction as the rotational direction of the engine by contacting a stopper pin 82 provided on the cylinder head 13. A cam inclined portion 84 formed so as to gradually rise in the rotational direction of the engine toward the portion 83 is provided.

  Further, the decompression cam 81 is provided with a cam peak portion 85, the pickup portion 87 provided on the exhaust rocker arm 66 is pushed by the cam peak portion 85, the exhaust rocker arm 66 swings, and the exhaust valve 65 is pushed to burn. The pressure in the chamber 27 is lowered to reduce the cranking torque at the next start.

  The cylinder head 13 is provided with a holding portion 91 for holding the stopper pin 82, and the stopper pin 82 and the spring member 93 are accommodated in this order in a through hole 92 opened in the holding portion 91, and above the through hole 92. The holding plate 94 for holding the spring member 93 is disposed, and the holding plate 94 is fastened by a screw member 95 at a position shifted from the axis of the spring member 93.

  In this embodiment, since the cylinder head 13 is made to serve as the holding portion 91 by the camshaft holder 97 that holds the camshaft 32 rotatably, an increase in the number of parts can be suppressed.

  Further, if the camshaft holder 97 is provided separately from the cylinder head 13, after the stopper pin 82 is sub-assembled to the camshaft holder 97, they may be assembled to the cylinder head 13, and the assembling process is performed. It becomes simple. Furthermore, the stopper pin 82 can be assembled while visually observing the positional relationship with the decompression cam 81 with the cylinder head 13 removed. Therefore, workability can be improved when the stopper pin is assembled.

  Since the through hole 92 is arranged vertically above and below the camshaft holder 97, it is possible to easily approach the through hole 92 from above. Since the hand can be easily brought close to the through hole 92, the assembling workability of the stopper pin 82, the spring member 93 and the screw member 95 can be improved.

  Since the axis of the through hole 92 is parallel to the axis of the bolt hole 58... That fastens the cylinder head 13 to the cylinder block 12, there is no need to change the direction of the cutting tool as compared with the case where they are arranged in different directions. The efficiency of drilling can be greatly increased. Further, with this arrangement, the pressing plate 94 can be directly fastened by the head nut 62.

  The right bridge portion 56R of the left and right bridge portions 56L, 56R also serves as a holding portion 91 that holds the holding plate 94, and the holding plate 91 is fastened by a screw member 95 provided in the holding portion 91. The screw holes 98 are arranged so as to be aligned with the bridge portion 56 </ b> R together with the through holes 92 for accommodating the stopper pins 82.

  Since the screw hole 98 and the through hole 92 are arranged so as to be aligned with the bridge portion 56R, the pressing plate 94 can be arranged without expanding in the width direction of the vehicle. For this reason, the holding part 91 of the stopper pin 82 can be efficiently arranged in a limited space above the engine.

The operation of the engine decompression device described above will be described next.
FIG. 7 is an explanatory view of the operation of the decompression cam according to the present invention and will be described with reference to FIG.
In (a), when the engine is rotating, the camshaft 32 rotates in the direction of arrow a, the one-way clutch 79 slips, the locking portion 83 projecting from the decompression cam 81 hits the stopper pin 82, and the decompression cam 81 rotates. Therefore, the cam crest portion 85 of the decompression cam 81 does not push the pickup portion 87 of the rocker arm 66, and the decompression function does not act.

  In (b), when the crankshaft 16 stops before the compression stroke when the engine is stopped, the reaction force of the compression pressure generated in the combustion chamber 27 (or cylinder) is transmitted via the piston 23 and the connecting rod 25. Is transmitted to the crankshaft 16 and transmitted from the crankshaft 16 to the camshaft 32 via the cam chain 33. The camshaft 32 rotates in the direction of the arrow b1, and a one-way clutch 79 fitted to the outer periphery of the camshaft 32 is provided. The decompression cam 81 is reversely rotated in the direction of arrow b2 along with the reverse rotation of the camshaft 32, the cam crest 85 provided on the decompression cam 81 swings the exhaust rocker arm 66 in the direction of arrow b3, and the exhaust rocker arm 66 becomes the exhaust valve. By pressing 65 against the valve spring (reference numeral 74 in FIG. 3), the pressure in the combustion chamber 27 is increased. Pull out.

  Accordingly, when the engine 10 is started with the exhaust valve 65 opened and the combustion chamber 27 and the exhaust port 71 are in communication, the air in the combustion chamber 27 is released in the direction of the arrow b4. The kick pedal force applied to 51 can be reduced, and the burden on the passenger can be reduced. After the first compression pressure is released, the decompression cam 81 rotates in the same direction as the camshaft 32, the locking portion 83 hits the stopper pin 82, and the decompression function is released.

  That is, according to the decompression device 80 according to the present invention, when the engine 10 is stopped, the camshaft 32 is rotated in the direction opposite to the rotational direction of the engine 10 by the pressure of the combustion chamber 27, and the decompression cam 81 is By rotating in the direction opposite to the rotation direction, the cam peak portion 85 provided on the decompression cam 81 pushes the intake valve 67 or the exhaust valve 65 to lower the pressure in the combustion chamber 27, thereby reducing the cranking torque at the next start. .

FIG. 8 shows an example of a stopper pin holding portion constituting a decompression cam according to the present invention and a comparative example thereof.
An example is shown in (a), and a presser plate 94 that presses the stopper pin 82 via a spring member 93 is provided above a through hole 92 opened in the holding portion 91, and the spring member 93 is a presser plate 94. Is pressed by. The holding plate 94 is fastened by a screw member 95 at a position displaced from the axis 93 Ja of the spring member 93. The presser plate 94 can be fastened by the head nut 62 according to the arrangement described in claim 4.

  (B) shows a comparative example. When the pressing plate 94 is not provided, the spring member 93B is held by the screw member 95B on the axis 93Jb of the spring member 93B. There was a problem that the length of the holding portion of the pin 82B was increased.

  In this regard, in the embodiment according to the present invention, the holding plate 94 is provided, and the holding plate 94 is fastened by the screw member 95 at a position shifted from the axis of the spring member. Is suppressed.

  In (a), the length between the center of the decompression cam 81 and the head 95h of the screw member 95 is La, and in (b), the length between the center of the decompression cam 81B and the head 95Bh of the screw member 95B is Lb. Then, there is a relationship of La <Lb.

  Therefore, according to the present invention, since the length of the stopper pin 82 and its holding portion is shortened, the decompression device 80 can be downsized. Further, if the length of the holding portion is suppressed, the peripheral portion of the camshaft 32 can be made compact. The engine 10 can be downsized by downsizing the periphery of the camshaft 32.

Referring also to FIG. 1, the power unit 102 can be brought close to the front wheel 104 by downsizing the cylinder head cover 14 including the decompression device 80.
As a result, the front wheel share load can be increased. Further, the rear swing arms 113L and 113R can be made longer, which contributes to improving the riding comfort. When the rear swing arms 113L and 113R are not lengthened, the wheel base can be shortened and the vehicle body can be made compact.

  Further, the main frame 106 is disposed so as to be inclined rearward and the intake pipe 134 is disposed above the cylinder 12c and below the main frame 106. Therefore, by bringing the power unit 102 toward the front wheel 104, the intake pipe 134 is disposed. As a result, the intake pipe 134 can be disposed in a portion where the space 141 under the main frame 106 is widened. By arranging the intake pipe 134 in the space 141, it is possible to arrange the intake pipe 134 to supply air straight from the air cleaner 136 through the intake port 72 of the cylinder 12c, so that the output of the engine 10 is improved. Alternatively, the periphery of the intake pipe 134 of the main frame 106 can be further lowered downward, and the height of the straddling portion 127 can be lowered downward, making it easy to straddle when ascending and descending.

The engine decompression device according to the present invention is applied to an engine for a motorcycle in the embodiment, but can also be applied to an industrial engine including an agricultural machine or a generator.
According to a first aspect of the present invention, the holding portion may be provided upright on the cylinder head separately from the camshaft holder. The through hole may be provided on the side of the camshaft holder other than above the camshaft holder depending on the structure of the engine. Alternatively, the axis of the through hole and the axis of the bolt hole for fastening the cylinder head need not be parallel.

  The engine decompression device according to the present invention is suitable for a single-cylinder four-cycle engine for a motorcycle.

1 is a left side view of a motorcycle equipped with an engine decompression device according to the present invention. It is sectional drawing of the engine which concerns on this invention. FIG. 3 is a view taken in the direction of arrow 3 in FIG. It is a figure explaining the valve operating system of the engine which concerns on this invention. FIG. 5 is a sectional view taken along line 5-5 of FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG. It is action | operation explanatory drawing of the decompression cam concerning this invention. It is the Example figure of the holding | maintenance part of the stopper pin which comprises the decompression cam based on this invention, and its comparative example figure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 13 ... Cylinder head, 27 ... Engine combustion chamber, 32 ... Cam shaft, 56L, 56R ... Bridge part, 58 ... Bolt hole, 58J ... Axis of bolt hole, 65 ... Exhaust valve, 67 ... Intake valve, 79 ... One-way clutch, 80 ... Engine decompression device, 81 ... Decompression cam, 82 ... Stopper pin, 83 ... Locking portion, 85 ... Cam crest, 91 ... Holding portion, 92 ... Through hole, 92J ... Axis of through hole 93 ... Spring member, 94 ... Holding plate, 97 ... Camshaft holder, 98 ... Screw hole.

Claims (4)

The camshaft (32) provided on the cylinder head (13) for opening and closing the intake valve (67) and the exhaust valve (65) , and the camshaft (32) provided on the camshaft (32) is rotated by the engine (10) . A one-way clutch (79) that transmits the rotational force of the camshaft (32) to the outside when rotating in the opposite direction, and an intake valve (67) or an exhaust valve (65 ) fitted to the one-way clutch (79). ) and decompression cam (81) to lower the pressure of the press a combustion chamber of the engine (10) (27), the exposure to the decompression cam (projecting from the 81) the cylinder head (13) a stopper pin provided on the side (82) when a locking portion (83) to prevent that the decompression cam (81) rotates in the same direction as the rotation direction of the engine (10), the engine (10) is stopped in, Serial is rotated said cam shaft (32) in a direction opposite to the rotation direction of the engine (10) by the pressure of the combustion chamber (27) to rotate the decompression cam (81) in a direction opposite to the rotation direction of the engine (10) Then, the cam peak (85) provided on the decompression cam (81) pushes the intake valve (67) or the exhaust valve (65) to lower the pressure in the combustion chamber (27) , and cranking torque at the next start In the engine decompression device that reduces
Wherein the cylinder head (13) side, the holding portion for holding the stopper pin (82) (91) is provided with the stopper pin into the through hole (92) opened in the holding portion (91) (82) The spring member (93) is accommodated in this order, and a pressing plate (94) for pressing the spring member (93 ) is disposed above the through hole (92) . The pressing plate (94) Fastened at a position shifted from the axis of the member (81) ,
Bridge portions (56L, 56R) are stretched over the cylinder head (13) before and after the engine (10). The front and rear portions of the bridge portions (56L, 56R) are respectively connected to the cylinder head ( 13) A bolt hole (58) for fastening the cylinder block (12) is arranged, and a screw hole (98) for fastening the pressing plate (94) to the holding portion (91) is combined with the through hole (92). An engine decompression device, wherein the decompression device is arranged so as to line up with the bridge portions (56L, 56R) . The decompression device for an engine according to claim 1, wherein the holding portion (91) is a camshaft holder (97) that rotatably holds the camshaft (32) on the cylinder head (13) . The decompression device for an engine according to claim 1 or 2, wherein the through hole (92) is arranged at an upper portion of the camshaft holder (97) . The axis of the through hole (92), according to claim 1, the decompression device according to claim 2 or claim 3, wherein the engine, which is a parallel to the axis of the bolt hole (58).

Images