JPH0139843Y2 - - Google Patents

Description

[Detailed description of the invention] This invention makes it easier to start the engine by slightly opening the intake valve or exhaust valve to put the combustion chamber in a semi-compressed state when starting the engine, and automatically puts it into a fully compressed state during normal operation. This invention relates to a decompression device for an engine to be controlled.

2. Description of the Related Art Conventionally, there has been known a decompression device that opens an intake valve or an exhaust valve to a certain extent when starting an engine to bring the combustion chamber into a semi-compressed state to reduce the starting effort. This decompression device has a structure that manually or automatically brings the combustion chamber into a semi-compressed state, but in the case of a manual type, it is a hassle to manually open and close the pressure reducing valve, and in the case of an automatic type, there is a hassle of manually opening and closing the pressure reducing valve. In this case, as seen in Japanese Utility Model Publication No. 50-7381 and Publication No. 53-20593, the structure is complicated and the number of parts, processing man-hours, and assembly man-hours are large.

The present invention was developed in consideration of these circumstances, and has a relatively simple structure that reduces the effort required to start the engine, reduces the number of parts, machining time, and assembly time. It is an object of the present invention to provide an engine decompression device in which the degree of freedom in the weight, shape, etc. of the flyweight is increased by arranging it on the cam side, and the decompression rotation speed can be freely set.

In order to achieve the above object, the engine decompression device according to the present invention operates a tappet with a cam provided on the camshaft by the rotation of the camshaft which receives rotational force from the crankshaft through a cam gear, thereby opening intake valves and exhaust valves to the combustion chamber. In a device that opens and closes a camshaft, an axial groove with a semicircular cross section is formed on the outer periphery of the camshaft extending from the cam gear to the intake or exhaust cam, and a part of the outer side protrudes into this groove so as to be rotatable. The release pin is inserted, and the flyweight on one side of the release pin is positioned on the side opposite to the cam gear, and the notch formed at the end of the release pin on the side opposite to the flyweight is placed on the side of the intake or exhaust cam. When the release pin is inserted into the groove and rotated, the notch protrudes and retracts from the cam surface.The protrusion of the notch from the cam surface puts the combustion chamber in a semi-compressed state, and the notch retracts into the cam surface. The combustion chamber is configured to be in a fully compressed state.

Embodiments of the present invention will be described below with reference to the drawings.

Figures 1 to 5 relate to the first embodiment of the decompression device of the present invention, in which Figure 1 is a longitudinal sectional view, Figure 2 is a view taken along line A-A in Figure 1, and Figure 3 is a release pin. FIG. 4 is an explanatory diagram of the operation when the engine is started, and FIG. 5 is an explanatory diagram of the operation when the engine is normally rotating.

In these figures, numeral 1 is a camshaft supported by bearings 2, 2, and this camshaft 1
Intake valve tappet 3 and exhaust valve tappet 4 are installed.
Cams 5 and 6 are formed corresponding to the ends of. Further, the camshaft 1 is provided with a cam gear 7 adjacent to the cam 5 and receiving the rotational force of a crankshaft (not shown). The camshaft 1 has a groove 8 with a semicircular cross section formed in the direction of the outer circumferential axis extending from the cam gear 7 to the cam 5, and a release pin 9 is installed in the groove 8 so as to be vertically rotatable over a predetermined angular range.
is inserted and prevented from coming off with a stopper 10 such as a spacer or clip. The release pin 9 has a circular cross section, has a flyweight 11 on one side thereof, and has a semicircular notch 12 formed at the end opposite to the flyweight. This release pin 9 is fitted into the groove 8 with a part of its outer side protruding, and the fly weight 11 on one side is connected to the cam gear 7.
The notch 12 is located on the opposite side of the cam.
is located in the groove 8 on the cam 5 side and the release pin 9 is
Rotation causes this notch 12 to protrude and retract from the outer periphery of the cam 5. When the notch 12 of the release pin 9 protrudes from the outer periphery of the cam 5, the notch 12 pushes up the tappet 3 slightly and opens the intake valve (not shown) slightly to bring the combustion chamber into a semi-compressed state. When the tappet 3 retracts from the outer periphery of the cam 5, the push-up of the tappet 3 is released and the combustion chamber is brought into a fully compressed state.

Further, a tension coil spring 13 is installed between the flyweight 11 of the release pin 9 and the cam gear 7.
is tensioned, and when starting, spring 1
When the tension T of 3 is larger than the centrifugal force F, the release pin 9 rotates counterclockwise in FIG. The spring 13
When the tension T becomes larger than the fly weight 11
moves, the release pin 9 rotates clockwise in FIG. 2, and the notch 12 is recessed from the outer periphery of the cam 5. A stopper 14 is installed in the cam gear 7 to prevent excessive movement of the flyweight 11 due to centrifugal force.

In such a configuration, when the engine is started, the tension T of the coil spring 13 is greater than the centrifugal force F, and the release pin 9 and fly weight 11 are
As shown in the figure, when the cam 5 is rotated counterclockwise, the notch 12 protrudes from the outer periphery of the cam 5, pushing up the tappet 3 slightly and bringing the combustion chamber (not shown) into a semi-compressed state. Next, when the engine is started and the rotational speed increases, the centrifugal force F becomes larger than the tension T of the spring 13, and the release pin 9 and flyweight 11 rotate clockwise as shown in FIG. Notch 12 that pushed up 3 slightly
retracts from the outer periphery of the cam 5 to release the push-up of the tappet 3, and as a result, the combustion chamber (not shown) becomes fully compressed.

FIG. 6 is a front view of a decompression device according to a second embodiment of the present invention, FIG. 7 is an explanatory diagram of the operation when the engine is started, and FIG. 8 is an explanatory diagram of the operation when the engine is normally rotating. This embodiment uses a coil spring 1 that biases the flyweight 11 in the anti-centrifugal direction of the first embodiment.
3 is omitted. That is, when the gravity W of the flyweight 11 is larger than the centrifugal force F at the time of startup, the flyweight 11 and the release pin 9 are rotated counterclockwise and the notch 12 is rotated as shown in FIG.
protrudes from the outer periphery of the cam 5, and when the engine speed increases and the centrifugal force F becomes larger than the gravity W of the flyweight 11, the flyweight 11 and release pin 9 rotate clockwise as shown in FIG. is recessed from the outer circumference of the cam 5.

In this manner, in the embodiment described above, the flyweight directly drives the release pin to rotate, and its rotational fulcrum is a semicircular groove in cross section formed in the direction of the outer peripheral axis of the camshaft, and no metal fittings are required for the fulcrum. Also, since the flyweight is located on the opposite side of the cam and tappet, there is a large degree of freedom in the weight, shape, etc. of the flyweight. Furthermore, since the release pin has a circular cross section, there is a large degree of freedom in designing lift, timing, etc.

In addition, in this invention, the valve train system that is slightly pushed up and opened by the notch of the release pin is the intake system,
It may be any exhaust system.

As explained above, according to the present invention, the structure that reduces engine starting effort is relatively simple, and the number of parts, processing man-hours, and assembly man-hours can be reduced, and the fly weight of the release pin is moved to the opposite side of the cam gear. By arranging the flyweight, there is a large degree of freedom in the weight, shape, etc. of the flyweight, and there is an effect that the decompression rotation speed can be set freely.

[Brief explanation of the drawing]

Figures 1 to 5 relate to the first embodiment of the decompression device of the present invention, in which Figure 1 is a longitudinal sectional view, Figure 2 is a view taken along line A-A in Figure 1, and Figure 3 is a release pin. FIG. 4 is an explanatory diagram of the operation when the engine is started, FIG. 5 is an explanatory diagram of the operation when the engine is normally rotating,
FIG. 6 is a front view of a decompression device according to a second embodiment of the present invention, FIG. 7 is an explanatory diagram of the operation when the engine is started, and FIG. 8 is an explanatory diagram of the operation when the engine is normally rotating. 1... camshaft, 3, 4... tappet,
5, 6...Cam, 7...Cam gear, 8...Groove, 9
... Release pin, 11 ... Fly weight, 1
2...Notch.

Claims (1)

[Scope of utility model registration request] In a device that operates a tappet with a cam provided on the camshaft by the rotation of a camshaft that receives rotational force from a crankshaft through a cam gear to open and close an intake valve and an exhaust valve for a combustion chamber, the intake or exhaust cam is connected to the cam gear. An axial groove with a semicircular cross section is formed on the outer periphery of the camshaft, and a release pin with a circular cross section is rotatably inserted into this groove with a part of its outer side protruding, and a fly weight is provided on one side of the release pin. is located on the side opposite to the cam of the cam gear, and a notch formed at the end of the release pin on the side opposite to the flyweight is fitted into a groove on the intake or exhaust cam side, and as the release pin rotates, this notch is brought into contact with the cam surface. The notch protrudes from the cam surface to bring the combustion chamber into a semi-compressed state, and the notch retracts into the cam surface to bring the combustion chamber into a fully compressed state. Engine decompression device.