JPH0979017A - Decompression device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a decompressed state smoothly with high freedom of valve selection to obtain the decompressed state with simple structure while being excellent in durability. SOLUTION: During low rotation at the time of starting an engine, the rotation of a camshaft 5 having a cam sprocket 26 at one end is slow, centrifugal force is weak, and a flyweight 27 is in a closed state being regulated by a stopper 32. A decompression cam 29 of a decompressor supporting shaft 28 integral with the flyweight 27 and rotatably inserted through from the other end side of the camshaft 5 eccentrically from the axis of the camshaft 5 makes a ball 30 in the camshaft 5 protrude from a cam base 24b of an exhaust cam 24 so as to open an exhaust valve 7 during a compression stroke, thus reducing compression pressure. When the engine is rotated at the set speed or more, centrifugal force is large, the flyweight 27 is opened being regulated by the stopper 32, and the ball 30 is housed inside the cam base 24b. The decompressor supporting shaft 28 is regulated in thrust direction movement by a cover 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decompression device for an engine which opens an intake valve or an exhaust valve to reduce a compression pressure during a compression process at a low rotation speed when starting.

[0002]

2. Description of the Related Art Conventionally, there has been known a decompression device for opening an intake valve or an exhaust valve to some extent at the time of starting an engine to bring a combustion chamber into a half-compression state (decompression state) to reduce a load at the time of starting the engine.

Many of the decompression devices utilize the centrifugal force generated by the rotation of the camshaft of the engine. For example, in Japanese Utility Model Laid-Open No. 224016/1990, in a decompression device that inserts a decompression needle in the diametrical direction of a cam shaft that opens and closes an intake / exhaust valve, and projects the decompression needle into a decompression state,
Insert the decompression support shaft, which is eccentric from the axial center of the camshaft and has a decompression cam that protrudes the decompression needle, in the axial direction of the camshaft so that the decompression support shaft is rotatable, and It is shown that a flyweight that rotates about the axis of the shaft is integrally provided on the decompression support shaft at the camshaft shaft end.

According to this technique, the decompression cam can be formed on the decompression support shaft at the cam position of the intake or exhaust valve to be in the decompression state and the decompression needle can be projected even though the decompression state is simple. It is also possible to freely select the intake or exhaust valve to be used.

[0005]

However, in the above prior art, since the tappet or rocker arm is pushed up by the decompression cam via the decompression needle, a decompression needle having a length close to the diameter of the camshaft must be used. However, when the load of the valve spring is high, the decompression needle is disadvantageous in strength.

The decompression needle is driven by the rotation of the decompression cam. Not only the longitudinal force of the decompression needle protruding from the cam crest, but also the shearing force acts on the decompression needle, so that its operation (projection and retraction of the decompression needle) is smooth. There is a problem that it lacks in size.

On the other hand, when a lubricating oil passage is formed in the camshaft of the engine, the number of parts can be reduced if the plug of the lubricating oil passage is also used as the member provided in the camshaft. .

The present invention has been made in view of the above circumstances. With a simple structure, it is possible to freely select an intake valve or an exhaust valve to be in a decompression state, excellent durability, and a smooth decompression state is realized. Another object of the present invention is to provide an engine decompression device that can reduce the number of parts even when a lubricating oil passage is formed in the camshaft of the engine.

[0009]

In order to achieve the above object, the engine decompression device according to the present invention according to claim 1 is provided with either an intake valve or an exhaust valve during start-up during a compression process at low speed. In a decompression device for an engine that opens a valve to reduce the compression pressure, a flyweight that is opened by a rotational centrifugal force of a camshaft of an engine having a rotational force transmission member at one end, and a flyweight formed integrally with the flyweight, The decompression support shaft that is eccentrically inserted from the other end side of the camshaft and rotatably inserted into the camshaft from the camshaft axis, and the spherical member provided in the camshaft when the flyweight is closed are described above. A decompression cam formed on the decompression support shaft protruding from the cam base of the cam corresponding to the valve of the camshaft, and the decompression cam. A cover for regulating the thrust movement of the shaft, in which a stopper for restricting the rotation angle of the flyweight.

The decompression device for an engine according to a second aspect of the present invention is the decompression device for an engine according to the first aspect, wherein the stopper is formed in the camshaft and the other end of the camshaft of the lubricating oil passage is formed. It is provided on the side opening.

In the above structure, when the engine is started at a low speed, the camshaft of the engine having the torque transmitting member at one end rotates slowly, and the centrifugal force due to the rotation of the camshaft is weak. The flyweight is closed by being restricted by a stopper, and is integrally formed with the flyweight. The flyweight is eccentric from the camshaft axial center from the other end side of the camshaft and is rotatable in the camshaft. The decompression cam of the decompression support shaft that has been inserted allows the spherical member provided in the camshaft to protrude from the cam base of the cam corresponding to the valve of the camshaft, so that either the intake valve or the exhaust valve is pressed during the compression process. Open the valve to reduce the compression pressure. Then, when the engine speed becomes equal to or higher than the set rotation speed, the centrifugal force due to the rotation of the camshaft becomes large, and the flyweight is expanded with the rotation angle thereof restricted by the stopper. Due to the expansion of the flyweight, the decompression support shaft rotates, and the decompression cam rotates 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 rotation of the decompression support shaft is restricted by the cover in the thrust direction, and the position of the decompression cam does not shift.

Further, by providing the stopper at the opening of the lubricating oil passage formed in the camshaft on the other end side of the camshaft, the stopper restricts the turning angle of the flyweight and It serves as a plug for the lubricating oil passage in the camshaft.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show Embodiment 1 of the present invention, FIG. 1 is an operation explanatory diagram of an engine decompression device, and FIG. 2 is a sectional explanatory diagram of a camshaft portion of the engine.
3 is a cross-sectional explanatory view of the camshaft portion of the engine viewed from the right side of FIG. 2, and FIG. 4 is a cross-sectional explanatory view of the camshaft.

2 and 3, reference numeral 1 indicates an engine body, reference numeral 2 indicates a cylinder head of the engine body 1, and reference numeral 3 indicates a combustion chamber.

A side wall 4a is provided on the upper portion of the cylinder head 2.
A rocker room 4 surrounded by a lid 4b is provided. A camshaft 5 and a rocker shaft 6 supported by a bearing member 4c are arranged in parallel with each other in the rocker room 4, and the rocker shaft 6 has an exhaust rocker arm that acts on a pair of exhaust valves 7. 8 and a pair of intake rocker arms 10 that act on a pair of intake valves 9 are pivotally mounted.

Adjuster bolts 8a are respectively screwed onto one side of the exhaust rocker arm 8, and the adjuster bolts 8a are in contact with the stem ends 7a of the pair of exhaust valves 7.

The valve stems 7b of the pair of exhaust valves 7 are slidably supported by the cylinder head 2 via stem guides 11a, and are formed at the other ends of the valve stems 7b. A valve head 7c is located at each exhaust port 13 between the combustion chamber 3 and the exhaust passage 12. The valve faces 7d of the valve heads 7c are connected to the exhaust port 13
The seat ring 14 is fitted in the valve seat (not shown).

Further, a spring retainer 15a is fixed to the stem end 7a side of each valve stem 7b, while the other 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 5a and 15b, and each exhaust valve 7 has a valve spring 16
It is always urged in the direction of the rocker room 4 by the urging force of the.

The pair of intake valves 9 are also constructed in the same manner. Adjuster bolts 8b are respectively screwed to one side of the intake rocker arm 10 and these adjuster bolts 8b are connected to the pair of intake valves 9. It is in contact with the stem end 9a.

The valve stems 9b of the pair of intake valves 9 are slidably supported by the cylinder head 2 via stem guides 11b, and are formed at the other ends of the valve stems 9b. The valve heads 9c are located in the respective intake ports 18 between the combustion chamber 3 and the intake passage 17. Each valve face 9d of each valve head 9c is connected to the intake port 18
The seat ring 19 is fitted in the valve seat (not shown).

A spring retainer 20a is fixed to the stem end 9a side of each of the valve stems 9b, while another spring retainer 2 facing 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 0a and 20b, and each intake valve 9 has a valve spring 21.
It is always urged in the direction of the rocker room 4 by the urging force of the.

Further, slipper portions 22 and 23 are formed on one side of the rocker arms 8 and 10 opposite to the side on which the adjuster bolts 8a and 8b are screwed, 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 cam surfaces 24a, 25a, 25a of the pair of intake cams 25, respectively, and the rotation of the camshaft 5 causes the rocker arms 8, 10 to rotate. Is designed to be swung.

On the other hand, at one end of the cam shaft 5 (on the left side in FIG. 2), a cam sprocket 26 is provided as a torque transmitting member for transmitting the torque generated by the engine rotation to the cam shaft 5.

As shown in FIGS. 1 and 4, the camshaft 5 has a flyweight 27 which expands by the rotational centrifugal force of the camshaft 5 on the other end side (right side in FIG. 2) of the camshaft 5. The fly weight 27 is provided.
A decompression support shaft 28 integrally formed with the camshaft 5 is rotatably inserted into the camshaft 5 from the other end side of the camshaft 5 while being eccentric from the axial center of the camshaft 5.

Further, at a position where the slipper portion 22 of the exhaust rocker arm 8 of the exhaust cam 24 slides, the exhaust rocker arm 8 is pushed up when it protrudes during the compression process, and the exhaust valves 7 A ball 30 for opening the is provided so as to be capable of projecting and retracting from the inside of the camshaft 5.

At the position of the ball 30 of the decompression support shaft 28, the ball 30 is located inside the cam base 24b of the camshaft 5 when the flyweight 27 is expanded by the centrifugal force of the camshaft 5. On the other hand, when the flyweight 27 is closed, a decompression cam 29 that projects the ball 30 is formed.

A cover 31 is provided on the other end side of the camshaft 5 so as to surround the flyweight 27, and this cover 31 positions the other end side of the camshaft 5 in the thrust direction. , Decompression support shaft 2 above
It also serves as a retainer for 8. A predetermined clearance is provided between the flyweight 27 and the other end surface of the camshaft 5 and between the flyweight 27 and the cover 31.
The rotating operation of is performed smoothly.

Further, on the other end side of the cam shaft 5, there is provided one positioning pin 32 for restricting an expanding angle and a closing angle of the flyweight 27, and the positioning pin 32 serves as the cam. It also serves as a plug for the lubricating oil passage 34 formed in the shaft 5.

Further, the decompression support shaft 28 is provided with a return spring 33 for constantly urging the flyweight 27 in a direction of closing the flyweight 27 to prevent the flyweight 27 from operating due to gravity or the like. .

The flyweight 27 and the positioning pin 3
2. Each part of the return spring 33 has the cover 3
It is housed in the decompression weight chamber 35 formed at the other end side of the camshaft 5 by 1.

In FIG. 3, reference numeral 36 indicates a spark plug.

Next, the operation of the above configuration will be described.
First, from the time the engine is stopped to the set speed after startup,
Since the rotation speed of the camshaft 5 is slow and the centrifugal force generated by the rotation of the camshaft 5 is 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 and is in a closed state.

In the decompression support shaft 28 formed integrally with the flyweight 27, the decompression cam 29 of the decompression support shaft 28 moves the ball 30 into the cam base 24.
The exhaust rocker arm 8 is pushed out against the urging force of the valve spring 16 so that each exhaust valve 7 is opened during the compression process.

Therefore, the decompression state is realized during the compression process, the compression pressure is reduced, and the engine is easily started.

Next, after the engine is started, when the rotational speed exceeds the set rotational speed, the rotational speed of the camshaft 5 also increases, and the centrifugal force generated by the rotation of the camshaft 5 increases, so that FIG. 1 (b) and FIG. Further, as shown in FIG. 3, the flyweight 27 expands against the biasing force of the return spring 33 until the other end of the flyweight 27 comes into contact with the positioning pin 32.

The decompression support shaft 28 formed integrally with the flyweight 27 is at a position where the decompression cam 29 of the decompression support shaft 28 can store the ball 30 inside the cam base 24b, and during the compression process. Does not push up the exhaust rocker arm 8 to open each exhaust valve 7. That is, the decompression state does not occur. The centrifugal force generated by the rotation of the camshaft 5 also acts on the balls 30, and the balls 30 tend to project from the cam base 24b. However, the balls 30 resist the urging force of the valve springs 16 and the exhaust valves. 7
Can't be opened.

As described above, according to the first embodiment of the present invention, the flyweight is provided on the other end side of the camshaft (on the side opposite to the side on which the cam sprocket is attached). The range of selection of the rotational force transmission member (cam sprocket or cam gear) attached to the shaft is widened, the design is facilitated, and the engine can be downsized by selecting a small rotational force transmission member.

Further, since the decompression support shaft is eccentric from the axial center of the camshaft so as to be rotatably inserted into the camshaft, the decompression support shaft and the flyweight can be integrated with each other, and a simple structure is provided. Can be

Further, since the positioning pin not only controls the rotation angle of the flyweight but also serves as a plug of the lubricating oil passage formed in the camshaft, the number of parts is reduced.

Further, since the cover also serves as a cover for the decompression weight chamber, it 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 the number of parts is reduced.

Furthermore, since the camshaft can be attached to the engine after the parts relating to the decompression device have been incorporated in the camshaft, the workability of assembling the engine is improved.

Further, since the decompression cam acts on the rocker arm of the exhaust valve via the ball, it is excellent in durability and can smoothly realize the decompression state.

Next, FIG. 5 shows a sectional explanatory view of a camshaft according to a second embodiment of the present invention. In the second embodiment of the present invention, in the engine of FIGS. 2 and 3, the pair of intake valves 9 can realize the decompression state, and the engine configuration and the like are the same. Also in the structure of the camshaft, the same components as those in the first embodiment of the present invention are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 5, reference numeral 41 indicates a cam shaft, and a cam sprocket 26 for transmitting a rotational force due to engine rotation is provided at one end (right side in FIG. 5) of the cam shaft 41.

The camshaft 41 is provided with a flyweight 27 which expands by a centrifugal force on the other end side (left side in FIG. 5) of the camshaft 41 and is formed integrally with the flyweight 27. The decompression support shaft 42 is rotatably inserted in the cam shaft 41, being eccentric from the axial center of the cam shaft 41 from the other end side of the cam shaft 41.

Further, at the position where the slipper portions 23, 23 of the intake rocker arms 10, 10 of the intake cams 25, 25 are in sliding contact, the intake rocker arms 10, 10 are pushed up when they protrude during the compression process. , The above intake valves 9, 9
A pair of balls 30, 30 for opening the cam is provided so as to be capable of projecting and retracting from the inside of the cam shaft 41.

The balls 3 of the decompression support shaft 42
At the positions 0 and 30, when the flyweight 27 is expanded by the centrifugal force of the camshaft 41, the ball 3
0 and 30 are cam bases 25b of the camshaft 41,
Decompression cams 43, 43 are formed to project the balls 30, 30 when the flyweight 27 is closed while being stored inside 25b.

That is, since the pair of intake rocker arms 10 and 10 are operated by the pair of intake cams 25 and 25, the pair of balls 30 and 30 and the pair of decompression cams are located at the corresponding positions. 43, 43 are formed.

First, since the rotation speed of the camshaft 41 is slow and the centrifugal force generated by the rotation of the camshaft 41 is low from the time when the engine is stopped to the set rotation speed after the engine is started, the flyweight 27 causes the return spring 3 to rotate.
One end of the flyweight 27 is brought into contact with the positioning pin 32 by the urging force of 3, and the flyweight 27 is closed.

At this time, in the decompression support shaft 42 formed integrally with the flyweight 27, the decompression cams 43, 43 of the decompression support shaft 42 project the balls 30, 30 from the cam bases 25b, 25b during the compression process. The intake rocker arms 10 and 10 are attached to the valve spring 21.
The intake valves 9, 9 are opened by pushing up against the urging force of. Therefore, a decompression state is realized during the compression process,
The compression pressure is reduced and the engine is started easily.

Next, after the engine is started, when the number of rotations exceeds the set number of rotations, the number of rotations of the camshaft 41 also increases
Since the centrifugal force generated by the rotation of the camshaft 41 becomes large, the flyweight 27 resists the urging force of the return spring 33 and the flyweight 2
The other end of 7 is expanded until it abuts on the positioning pin 32.

In the decompression support shaft 42 formed integrally with the flyweight 27, the decompression cams 43, 43 of the decompression support shaft 42 have the balls 30,
30 becomes a position where the cam bases 25b and 25b can be housed inside, and the intake rocker arm 1 is held during the compression process.
The intake valves 9 and 9 are not opened by pushing up 0 and 10. That is, the decompression state does not occur.

As shown in the second embodiment of the present invention, in the present invention, since the decompression support shaft having the decompression cam is inserted into the camshaft, the intake or exhaust valve to be in the decompression state is selected. Is also free. still,
It goes without saying that the effects produced in the first embodiment of the invention described above can be similarly obtained in the second embodiment of the present invention.

Next, FIG. 6 shows a sectional explanatory view of a camshaft according to a third embodiment of the present invention. Incidentally, the third embodiment of the present invention is an application of the second embodiment of the present invention to a camshaft having no lubricating oil passage.
The function and effect are similar to those of the second embodiment of the invention.

That is, in FIG. 6, reference numeral 45 indicates a cam shaft, and no lubricating oil passage is formed in this cam shaft 45. Therefore, the positioning pin 46 regulates the rotation angle of the flyweight 27. It is provided to do.

As shown in the third embodiment of the present invention, the present invention can be applied even if there is no lubricating oil passage in the camshaft.

Next, FIG. 7 is a sectional explanatory view of a camshaft according to a fourth embodiment of the present invention. In the fourth embodiment of the present invention, a lubricating oil passage is not formed in the cam shaft of the first embodiment of the present invention, and the length of the cover is further shortened. Other configurations, functions and effects are similar to those of the first embodiment of the invention.

That is, in FIG. 7, reference numeral 50 indicates a cam shaft, and no lubricating oil passage is formed in this cam shaft 50. Therefore, the positioning pin 46 regulates the rotation angle of the flyweight 27. It is provided to do.

The cover 51 is positioned on the other end side (left side in FIG. 7) of the camshaft 50 and the decompression support shaft 28.
It is formed by shortening the length so that it can be prevented from coming off.

As shown in the fourth embodiment of the present invention, the workability can be improved by shortening the length of the cover.

In the embodiments of the above inventions,
Although the example in which the present invention is applied to the OHC engine has been described, the present invention can also be applied to an OHV engine or an SV engine.

[0062]

As described above, according to the present invention,
With a simple structure, you can freely select the intake or exhaust valve to be in the decompression state, it has excellent durability, the decompression state can be realized smoothly, and the lubricating oil passage is formed in the engine camshaft. Even if there is, it is possible to reduce the number of parts.

[Brief description of drawings]

FIG. 1 is an operation explanatory diagram of an engine decompression device according to a first embodiment of the present invention.

FIG. 2 is an explanatory sectional view of a camshaft portion of the engine according to the first embodiment of the present invention.

FIG. 3 is an explanatory cross-sectional view of the camshaft portion of the engine seen from the right side of FIG.

FIG. 4 is an explanatory cross-sectional view of the camshaft according to the first embodiment of the present invention.

FIG. 5 is a sectional explanatory view of a camshaft according to a second embodiment of the present invention.

FIG. 6 is a sectional explanatory view of a camshaft according to a third embodiment of the present invention.

FIG. 7 is a sectional explanatory view of a camshaft according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Engine Main Body 5 Cam Shaft 7 Exhaust Valve 9 Intake Valve 24 Exhaust Cam 24b Cam Base 25 Intake Cam 25b Cam Base 26 Cam Sprocket (Rotating Force Transmission Member) 27 Fly Weight 28 Decompression Support Shaft 29 Decompression Cam 30 Ball (Spherical Member) 31 Cover 32 Positioning pin 33 Return spring

Claims (2)

[Claims] 1. At the time of starting, during a compression process at low rotation,
In an engine decompression device that reduces the compression pressure by opening either the intake valve or the exhaust valve, a flyweight that expands by the rotational centrifugal force of a camshaft of an engine that has a rotational force transmission member at one end, A decompression support shaft that is integrally formed with a flyweight and is eccentrically inserted from the other end side of the camshaft into the camshaft so as to be eccentric from the camshaft axis, and the cam when the flyweight is closed. A decompression cam formed on the decompression support shaft protruding from a cam base of a cam corresponding to the valve of the camshaft, a cover for restricting movement of the decompression support shaft in a thrust direction, and the fly. An engine decompression device characterized by having a stopper for regulating the turning angle of the weight. Place. 2. The decompression device for an engine according to claim 1, wherein the stopper is provided at an opening of the lubricating oil passage formed in the camshaft on the other end side of the camshaft.