JP3462316B2 - Engine decompression device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decompression device for an engine that opens an intake or exhaust valve to reduce a compression pressure during a compression process at a low rotation speed at the time of startup. . 2. Description of the Related Art Conventionally, a decompression device has been known in which an intake valve or an exhaust valve is slightly opened at the time of starting an engine to make a combustion chamber half-compressed (decompressed) to reduce the load at the time of starting the engine. I have. Many of these decompression devices utilize centrifugal force generated by rotation of a camshaft of an engine. For example, in Japanese Unexamined Utility Model Publication No. 2-24016, in a decompression device in which a decompression needle is inserted in a diametrical direction of a cam shaft for opening and closing an intake / exhaust valve and the decompression needle is projected to make a decompression state,
In the axial direction of the camshaft, a decompression support shaft that is eccentric from the axis of the camshaft and that has a decompression cam for projecting the decompression needle is rotatably inserted, and the decompression support shaft according to the rotation speed of the camshaft. A fly weight that rotates around the axis of the shaft is provided integrally with the decompression support shaft at the end of the cam shaft. According to this technique, a decompression cam can be formed on a decompression support shaft at a cam position of an intake or exhaust valve to be in a decompression state and a decompression needle can be protruded in a decompression state. Can be freely selected. However, in the above prior art, the tappet or the rocker arm is pushed up by the decompression cam via the decompression needle, so that a decompression needle having a length close to the diameter of the camshaft is used. When the load of the valve spring is high, the decompression needle is disadvantageous in strength. In addition, since the decompression needle is driven by the rotation of the decompression cam, not only the vertical force of the decompression needle protruding from the cam peak but also the shearing force acts on the decompression needle, the operation (decompression needle retraction) is smooth. There is a problem that lacks. On the other hand, when a lubricating oil passage is formed in a camshaft of an engine, the number of parts can be reduced if a member provided on the camshaft also serves as a plug for the lubricating oil passage. . The present invention has been made in view of the above circumstances, has a simple structure, and can freely select an intake or exhaust valve to be in a decompressed state, has excellent durability, and realizes a smooth decompressed state. can, also, has an object to provide a decompression device for an engine that can reduce the number of parts. In order to achieve the above object, a decompression device for an engine according to the present invention according to the first aspect of the present invention provides a method for starting an intake valve or an exhaust valve during a compression process at a low rotation speed. In a decompression device for an engine, in which one of the valves is opened to reduce the compression pressure, a flyweight that expands by a rotational centrifugal force of a camshaft of the engine having a rotational force transmitting member at one end, and is formed integrally with the flyweight. A decompression shaft eccentrically inserted from the other end of the camshaft to the camshaft axis and rotatably inserted into the camshaft; and a spherical shaft provided in the camshaft when the flyweight is closed. A decompression cam having a member formed on the decompression support shaft projecting from a cam base of a cam corresponding to the valve of the camshaft; , The position of the other end of the camshaft in the thrust direction.
A cover for both positioning and preventing the decompression support shaft from coming off, and a stopper for restricting the rotation angle of the flyweight are provided. In the above configuration, at the time of low rotation at the time of starting the engine, the rotation of the camshaft of the engine having the torque transmitting member at one end is slow, and the centrifugal force due to the rotation of the camshaft is weak. The flyweight is closed with the movement angle regulated by the stopper, is formed integrally with the flyweight, and is eccentric from the camshaft shaft center from the other end of the camshaft and is turned into the camshaft. The decompression cam of the decompression support shaft, which is movably inserted, causes a spherical member provided in the camshaft to protrude from a cam base of a cam corresponding to the valve of the camshaft. Open either valve to reduce compression pressure. When the number of revolutions of the engine becomes equal to or higher than the set number of revolutions, the centrifugal force due to the rotation of the camshaft increases, and the flyweight is expanded with the rotation angle regulated by the stopper. The expansion of the flyweight rotates the decompression support shaft, and rotates the decompression cam so that the spherical member can be stored inside the cam base of the cam corresponding to the valve of the camshaft. For this reason,
The intake valve or the exhaust valve will not be opened during the compression process. Further, the movement of the camshaft and the decompression support shaft in the thrust direction is regulated by a cover.
Are not displaced in the thrust direction . Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention, FIG. 1 is an explanatory view of an operation of an engine decompression device, FIG. 2 is a sectional explanatory view of a camshaft portion of an engine,
FIG. 3 is an explanatory cross-sectional view of the camshaft portion of the engine viewed from the right side in FIG. 2, and FIG. 4 is an explanatory cross-sectional view of the camshaft. In FIGS. 2 and 3, reference numeral 1 denotes an engine main body, reference numeral 2 denotes a cylinder head of the engine main body 1, and reference numeral 3 denotes a combustion chamber. A side wall 4a is provided on the upper part of the cylinder head 2.
A rocker room 4 is provided, which is surrounded by a cover 4b. In this rocker room 4, a camshaft 5 and a rocker shaft 6 supported by a bearing member 4c are disposed in parallel with each other. The rocker shaft 6 has a rocker arm for exhaust that acts on a pair of exhaust valves 7. 8 and a pair of intake rocker arms 10 acting on a pair of intake valves 9 are pivotally mounted on a shaft. Adjuster bolts 8 a are screwed to one side of the exhaust rocker arm 8, and the adjuster bolts 8 a are in contact with the stem ends 7 a of the pair of exhaust valves 7. Each of the valve stems 7b of the pair of exhaust valves 7 is slidably supported by the cylinder head 2 via a stem guide 11a, and is formed at the other end of each of the valve stems 7b. Valve heads 7c are located at respective exhaust ports 13 between the combustion chamber 3 and the exhaust passage 12. Each valve face 7d of each valve head 7c is connected to the exhaust port 13
The seat ring 14 fits closely with a valve seat (not shown). A spring retainer 15a is fixed to the stem end 7a side of each of the valve stems 7b, and another spring retainer 1 facing the spring retainer 15a is provided on the lower surface of the rocker room 4.
5b are formed. These spring retainers 1
A valve spring 16 is interposed between the valve springs 5a and 15b.
Is always urged in the direction of the locker room 4. The above-mentioned pair of intake valves 9 is similarly constructed, and an adjuster bolt 8b is screwed to one side of the above-mentioned intake rocker arm 10, and these adjuster bolts 8b are connected to the pair of intake valves 9 respectively. It is in contact with the stem end 9a. Each of the valve stems 9b of the pair of intake valves 9 is slidably supported by the cylinder head 2 via a stem guide 11b, and is formed at the other end of each of the valve stems 9b. Valve heads 9 c are located at respective intake ports 18 between the combustion chamber 3 and the intake passage 17. The valve faces 9d of the valve heads 9c are connected to the intake ports 18 respectively.
The seat ring 19 fits closely with a valve seat (not shown). A spring retainer 20a is fixed to the stem end 9a side of each of the valve stems 9b, and another spring retainer 2 opposed to the spring retainer 20a is provided on the lower surface of the rocker room 4.
0b is formed. These spring retainers 2
A valve spring 21 is interposed between the intake valves 9a and 20b.
Is always urged in the direction of the locker room 4. Further, slipper portions 22 and 23 are formed on one side of the rocker arms 8 and 10 opposite to the side where the adjuster bolts 8a and 8b are screwed, respectively, and these slipper portions 22 and 23 are formed. Are in sliding contact with the exhaust cam 24 formed on the camshaft 5 and the respective cam surfaces 24a, 25a, 25a of the pair of intake cams 25. The rotation of the camshaft 5 causes the rocker arms 8, 10 to rotate. Is to be swung. On the other hand, at one end of the camshaft 5 (on the left side in FIG. 2), a cam sprocket 26 is provided as a rotational force transmitting member for transmitting a rotational force due to engine rotation to the camshaft 5. As shown in FIGS. 1 and 4, the flyweight 27, which expands due to the rotational centrifugal force of the camshaft 5, has the other end of the camshaft 5 (the right side in FIG. 2). The fly weight 27 is provided.
A decompression support shaft 28 formed integrally with the camshaft 5 is rotatably inserted into the camshaft 5 from the other end of the camshaft 5 eccentrically from the axis of the camshaft 5. At the position where the slipper section 22 of the exhaust rocker arm 8 of the exhaust cam 24 slides, during the compression step, when the exhaust rocker arm 8 is protruded during the compression process, the exhaust rocker arm 8 is pushed up to release the exhaust valve 7. Is provided so as to be able to protrude and retract from inside the camshaft 5. When the flyweight 27 is expanded by the centrifugal force of the camshaft 5, the ball 30 is positioned inside the cam base 24 b of the camshaft 5 at the position of the ball 30 on the decompression support shaft 28. On the other hand, when the flyweight 27 is closed, a decompression cam 29 for projecting the ball 30 is formed. A cover 31 is provided at the other end of the camshaft 5 so as to surround the fly weight 27. This cover 31 is used to position the other end of the camshaft 5 in the thrust direction. , The decompression spindle 2
8 is also used as a stopper. A predetermined clearance is provided between the fly weight 27 and the other end surface of the camshaft 5 and between the fly weight 27 and the cover 31.
Is smoothly performed. Further, at the other end of the camshaft 5, there is provided one positioning pin 32 for regulating the angle at which the flyweight 27 expands and closes. The plug of the lubricating oil passage 34 formed in the shaft 5 is also used. The decompression support shaft 28 is provided with a return spring 33 for urging the fly weight 27 in a direction to always close the fly weight 27 to prevent the fly weight 27 from operating due to gravity or the like. . The fly weight 27 and the positioning pin 3
2, each part of the return spring 33
1 is housed in a decompression weight chamber 35 formed on the other end side of the camshaft 5. In FIG. 3, reference numeral 36 denotes a spark plug. Next, the operation of the above configuration will be described.
First, from the time the engine is stopped until the set number of revolutions after startup,
Since the rotation speed of the camshaft 5 is low and the centrifugal force generated by the rotation of the camshaft 5 is also weak, the flyweight 27 is moved by the urging force of the return spring 33 as shown in FIGS. One end of 27 is brought into contact with the positioning pin 32 to be in a closed state. The decompression support shaft 28 formed integrally with the fly weight 27 has a decompression cam 29 of the decompression support shaft 28 that connects the ball 30 to the cam base 24.
b, and pushes up the exhaust rocker arm 8 against the urging force of the valve spring 16 during the compression process to open each exhaust valve 7. For this reason, a decompression state is realized during the compression process, the compression pressure is reduced, and the engine can be easily started. Next, when the number of revolutions becomes equal to or higher than the set number of revolutions after the engine is started, the number of revolutions of the camshaft 5 also increases, and the centrifugal force generated by the rotation of the camshaft 5 increases. As shown in FIG. 3, the fly weight 27 expands against the urging force of the return spring 33 until the other end of the fly weight 27 comes into contact with the positioning pin 32. The decompression support shaft 28 formed integrally with the fly weight 27 is located at a position where the decompression cam 29 of the decompression support shaft 28 can store the ball 30 inside the cam base 24b. Pushes up the exhaust rocker arm 8 and does not open each exhaust valve 7. That is, the state is not decompressed. The centrifugal force generated by the rotation of the camshaft 5 also acts on the ball 30, and the ball 30 tends to protrude from the cam base 24b. 7
Cannot be opened. As described above, according to the first embodiment of the present invention, the fly weight is provided on the other end of the camshaft (on the side opposite to the side on which the cam sprocket is mounted). The range of selection of a rotational force transmitting member (cam sprocket or cam gear) to be attached to the shaft is widened, design is facilitated, and the size of the engine can be reduced by selecting a small rotational force transmitting member. Further, since the decompression support shaft is eccentric from the axis of the camshaft and is rotatably inserted into the camshaft, the decompression support shaft and the flyweight can be integrated with each other, and a simple configuration can be achieved. It can be. Further, since the positioning pin regulates the rotation angle of the fly weight and also serves as a plug for a lubricating oil passage formed in the camshaft, the number of parts is reduced. The cover also serves as a cover for the decompression weight chamber, and also serves to position the other end of the camshaft in the thrust direction and to prevent the decompression support shaft from coming off, so that the number of parts is reduced. Further, since the camshaft can be attached to the engine after the parts relating to the decompression device are incorporated into the camshaft, the workability of assembling the engine is improved. Since the decompression cam acts on the rocker arm of the exhaust valve via the ball, the decompression cam is excellent in durability and can realize a smooth decompression state. Next, FIG. 5 is an explanatory sectional view of a camshaft according to a second embodiment of the present invention. The second embodiment of the present invention is such that the decompression state can be realized in the pair of intake valves 9 in the engine shown in FIGS. 2 and 3, and the configuration of the engine is the same. Also in the configuration of the camshaft, the same components as those in the first embodiment of the present invention are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 5, reference numeral 41 denotes a camshaft. At one end (right side in FIG. 5) of the camshaft 41, there is provided a cam sprocket 26 for transmitting a rotational force due to engine rotation. The camshaft 41 is provided with a flyweight 27 that expands by rotational centrifugal force at the other end (left side in FIG. 5) of the camshaft 41, and is formed integrally with the flyweight 27. A decompression support shaft 42 is rotatably inserted into the camshaft 41 from the other end of the camshaft 41 eccentrically from the axis of the camshaft 41. Further, at the position where the slipper portions 23, 23 of the intake rocker arms 10, 10 of the intake cams 25, 25 come into sliding contact with each other, when they are protruded during the compression process, the intake rocker arms 10, 10 are pushed up. , Each of the above intake valves 9, 9
A pair of balls 30, 30 are provided so as to be able to protrude and retract from the camshaft 41. Each ball 3 of the decompression support shaft 42
When the flyweight 27 is expanded by the centrifugal force of the camshaft 41, the ball 3
0, 30 are the cam bases 25b of the camshaft 41,
When the flyweight 27 is closed while the flyweight 27 is closed, decompression cams 43, 43 for projecting the balls 30, 30 are formed. That is, since the pair of intake rocker arms 10, 10 are operated by the pair of intake cams 25, 25, the pair of balls 30, 30, the pair of decompression cams are located at positions corresponding to the pair of intake cams 25, 25. 43, 43 are formed. First, since the rotation speed of the camshaft 41 is low from the stop of the engine to the set rotation speed after the start, the centrifugal force generated by the rotation of the camshaft 41 is also weak.
Due to the urging force of 3, the one end of the fly weight 27 comes into contact with the positioning pin 32, and the fly weight 27 is closed. At this time, the decompression support shaft 42 formed integrally with the fly weight 27 has the decompression cams 43, 43 of the decompression support shaft 42 which project the balls 30, 30 from the cam bases 25b, 25b during the compression process. The intake rocker arms 10 and 10 are connected to the valve spring 21.
Is pushed up against the urging force of the above, and the respective intake valves 9, 9 are opened. For this reason, a decompression state is realized during the compression process,
The compression pressure is reduced, and the engine is easily started. Next, when the engine speed becomes equal to or higher than the set speed after the engine is started, the speed of the camshaft 41 also increases.
Since the centrifugal force generated by the rotation of the camshaft 41 increases, the flyweight 27 is opposed to the flyweight 2 against the urging force of the return spring 33.
7 is expanded until the other end thereof contacts the positioning pin 32. The decompression support shaft 42 formed integrally with the fly weight 27 has the decompression cams 43, 43 of the decompression support shaft 42 connected to the balls 30,
30 can be stored inside the cam bases 25b, 25b. During the compression process, the intake rocker arm 1
It does not push up 0,10 and open each intake valve 9,9. That is, the state is not decompressed. As shown in the second embodiment of the present invention, in the present invention, the decompression support shaft on which the decompression cam is formed is inserted into the camshaft. Is also free. still,
It goes without saying that the effect produced in the first embodiment of the present invention can be similarly obtained in the second embodiment of the present invention. Next, FIG. 6 is an explanatory sectional view of a camshaft according to a third embodiment of the present invention. The third embodiment of the present invention is obtained by adapting the second embodiment of the present invention to a camshaft having no lubricating oil passage.
The function and effect are the same as those of the second embodiment of the present invention. That is, in FIG. 6, reference numeral 45 denotes a camshaft. No lubricating oil passage is formed in the camshaft 45. Therefore, the positioning pin 46 regulates the rotation angle of the flyweight 27. Provided to do. As shown in the third embodiment of the present invention, the present invention can be applied even when there is no lubricating oil passage in the camshaft. FIG. 7 is an explanatory sectional view of a camshaft according to a fourth embodiment of the present invention. In the fourth embodiment of the present invention, the lubricating oil passage is not formed in the camshaft according to the first embodiment of the present invention, and the length of the cover is further reduced. Other configurations, functions and effects are the same as those of the first embodiment of the present invention. That is, in FIG. 7, reference numeral 50 denotes a camshaft, and no lubricating oil passage is formed in the camshaft 50. Therefore, the positioning pin 46 regulates the rotation angle of the flyweight 27. Provided to do. The cover 51 is used to position the other end of the camshaft 50 (the left side in FIG. 7),
The length is reduced to a length that can prevent the falling off. As shown in the fourth embodiment of the present invention, it is possible to shorten the length of the cover to improve the workability. In each of the embodiments of the present invention,
Although the example in which the present invention is applied to the OHC engine has been described, the present invention can be applied to an OHV engine or an SV engine. As described above, according to the present invention,
A simple structure, the selection of the intake or exhaust valve and decompression state can also be performed freely, durable, smooth can be realized decompression state, also, it is possible to reduce the number of parts .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an operation of an engine decompression device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional explanatory diagram of a camshaft portion of an engine according to a first embodiment of the present invention. 3 is a cross-sectional explanatory view of the camshaft portion of the engine as viewed from the right side of FIG. 2; FIG. 4 is a cross-sectional explanatory view of the camshaft according to the first embodiment of the present invention; FIG. FIG. 6 is a cross-sectional explanatory view of a camshaft according to a third embodiment of the present invention. FIG. 7 is a cross-sectional explanatory view of a camshaft according to a fourth embodiment of the present invention. 7 Exhaust Valve 9 Intake Valve 24 Exhaust Cam 24b Cam Base 25 Intake Cam 25b Cam Base 26 Cam Sprocket (Rotation Force Transmission Member) 27 Fly Weight 28 Decompression Support Shaft 2 The decompression cam 30 balls (spherical member) 31 cover 32 positioning pins 33 return spring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 13/08

Claims (1)

(57) [Claims] [Claim 1] At the time of startup, during the compression process at low rotation,
An engine decompression device for opening one of an intake valve and an exhaust valve to reduce a compression pressure, comprising: a flyweight that expands by a rotational centrifugal force of an engine camshaft having a rotational force transmitting member at one end; A decompression shaft formed integrally with the flyweight, eccentrically inserted from the camshaft axis from the other end of the camshaft, and rotatably inserted into the camshaft; and the cam when the flyweight is closed. A decompression cam formed on the decompression support shaft that projects a spherical member provided in the shaft from a cam base of a cam corresponding to the valve of the camshaft; and a thrust direction on the other end side of the camshaft.
Direction positioning and prevention of the decompression spindle from coming off
A decompression device for an engine, comprising: a cover that controls the rotation angle of the flyweight;