JPH066889B2 - Engine decompression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is designed to open an intake valve or an exhaust valve somewhat at the time of engine start to put a combustion chamber in a half-compressed state to facilitate start, and to automatically start at the time of normal operation. The present invention relates to an engine decompression device that controls to achieve a fully compressed state.

[Prior Art] Conventionally, there has been known a decompression device that slightly opens an intake valve or an exhaust valve at the time of starting an engine to put a combustion chamber in a semi-compressed state to reduce a starting load. This decompression device has a structure in which the combustion chamber is brought into a semi-compressed state manually or automatically. In the case of the manual type, the rocker arm is set to the decompression position by manually operating the decompression shaft provided on the cylinder head or the rocker shaft, and then the engine is started by the activation handle or the recoil starter. . On the other hand, in the case of an automatic system, for example, a conventional technique relating to an automatic compression / extraction device for an internal combustion engine utilizing centrifugal force has been proposed in Japanese Utility Model Publication No. 49-63337.

[Problems to be Solved by the Invention] However, unlike a gasoline engine, a diesel engine is started by injecting fuel into compressed air and spontaneously igniting the engine. The compression ratio is high, and the engine is manually rotated. Therefore, a considerable auxiliary device (in addition to automatic decompression, auxiliary fuel injection hole, delayed injection timing, increased flywheel mass, etc.) was required. Nevertheless, there are problems that it requires more physical strength than the gasoline engine and requires some skill, or the preparation work is complicated. Further, the above-mentioned proposal (Japanese Utility Model Laid-Open No. 49-63337) does not have a structure in which a semi-compressed state can be released early in a diesel engine having a low rotation speed at the time of starting. Further, the gasoline engine also has the same problem when the displacement is large.

The present invention has been made by paying attention to such conventional problems and the like, does not require any troublesome preparation work before starting the engine, and keeps the combustion chamber in a half-compressed state up to a predetermined number of revolutions, thus starting load. It is an object of the present invention to provide a decompression device for an engine, which reduces the above-mentioned problem and releases the semi-compressed state early and automatically to facilitate starting.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention operates a tappet by a cam provided on a camshaft by the rotation of the camshaft which receives a rotational force from a crankshaft by a cam gear, and burns the tappet. In a device for opening and closing an intake valve and an exhaust valve with respect to a chamber, a pin hole is formed in the end surface of the cam gear, and a decompression pin having a U-shaped engaging portion on one side is rotatably fitted in the pin hole. At the same time, the decompression pin end on the side opposite to the engaging portion is extended to the cam side, and the notch formed in the portion of the decompression pin end facing the tappet end so as to project and retract from the cam surface by the rotation of the decompression pin. While the weight lever is provided, one end of the weight lever is pivotally attached from the pin hole on the end face of the cam gear to a position substantially perpendicular to the cam shaft. The other end of the decompression pin engages with the U-shaped engaging portion of the decompression pin, and the rotation of the weight lever causes the end of the decompression pin to project from the cam surface to bring the combustion chamber into a semi-compressed state. The fuel chamber is configured to be in a pre-compressed state when the end portion is recessed into the cam surface.

[Operation] With the above configuration, since the decompression pin and the weight lever are engaged so as to interlock with each other, when the weight lever rotates due to the centrifugal force due to the rotation of the engine, the decompression pin rotates accordingly. Since the end of the decompression pin is extended to the cam side and the notch is provided so as to project and retract from the cam surface due to the rotation of the decompression pin, the tappet can be operated depending on the engine speed.
That is, the projection of the decompression pin end from the cam surface brings the combustion chamber into a semi-compressed state, and the depression of the decompression pin end into the cam surface brings the combustion chamber into a fully compressed state.
Therefore, it is possible to reduce the starting load up to a predetermined number of revolutions and automatically release the half-compressed state thereafter.

Further, since one end is pivotally attached to the end surface of the cam gear and the other end is provided with a weight lever that engages with the engaging portion of the decompression pin, depending on the position or shape of the decompression pin and the weight lever, the weight lever may be slightly different. The decompression pin can be largely rotated by the rotation. Therefore, the half-compressed state can be released early even when the engine speed is low.

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

1 to 5 relate to an embodiment of the present invention, and FIG. 1 is a sectional view of a camshaft portion of a diesel engine, and FIG.
1 is a right side view of FIG. 1, FIG. 3 is a perspective view of a decompression pin, FIGS. 4 and 5 are sectional views taken along the line AA of FIG. 1, and FIG. FIG. 5 is a diagram for explaining the operation of the engine during normal rotation.

In these drawings, reference numeral 1 is a cam shaft, and cams 4 and 5 are formed on the cam shaft 1 so as to correspond to the ends of the intake valve tappet 2 and the exhaust valve tappet 3. Further, the camshaft 1 is provided with a cam gear 6 which is close to the cam 4 and receives the rotational force of a crankshaft (not shown). Anti-cam 4 of this cam gear 6
A groove portion 7 formed in a concave shape is provided on the side end surface.
A pin hole 8 parallel to the axis of the cam shaft 1 is formed on the end surface of the cam gear 6 corresponding to the groove portion 7. A decompression pin 9 is inserted into the pin hole 8 and is rotatable in a predetermined angle range. The decompression pin 9 is formed in a shaft shape, and has an engaging portion 11 formed in a substantially U shape on one side of the shaft portion 10.
Is located on the groove portion 7 side of the cam gear 6 and is rotatably provided. Further, the decompression pin 9 has an end portion on the side opposite to the engaging portion 11 extending toward the cam 4 side, and a semicircular notch 12 cut out at the end portion of the decompression pin 9 facing the end portion of the tappet 2. Is formed. The portion of the decompression pin 9 facing the end of the tappet 2 is projected and retracted from the outer peripheral surface of the cam 4 by the cam action of the notch 12 caused by the rotation of the decompression pin 9. On the other hand, a weight lever 13 is provided on the end surface side of the cam gear 6 in which the groove portion 7 is formed. One end of the weight lever 13 is rotatably attached to a pin 14 projecting from the end face of the cam gear 6 in a direction substantially perpendicular to the rotation center of the decompression pin 9 with respect to the axis of the cam shaft 1. The other end side is extended to the decompression pin 9 side so as to slightly go around the outer circumference of the camshaft 1. An engaging pin 15 is provided on the other end side of the weight lever 13 that extends, and the engaging pin 15 is engaged with the engaging portion 11 of the decompression pin 9. That is, the decompression pin 9 and the weight lever 13 are interlocked and rotated. A return coil spring 16 having one end fixed to the cam gear 6 and the other end fixed to the weight lever 13 is fitted to the pin 14 projecting from the end face of the cam gear 6. The side provided with the engagement pin 15 is urged toward the axial center side of the camshaft 1. A notch 17 is formed on the shaft side of the cam gear 6 in which the groove 7 is provided so that the decompression pin 9 can rotate.

Reference numerals 18 and 19 in the figure denote push rods.

In such a configuration, first, when the engine is started, the urging force of the return coil spring 16 is larger than the centrifugal force,
The weight lever 13 and the decompression pin 9 are maintained counterclockwise as shown in FIG. The end of the decompression pin 9 provided with the cutout 12 projects from the outer peripheral surface of the cam 4 and pushes up the tappet 2 slightly to bring a combustion chamber (not shown) into a semi-compressed state.

Next, when the engine is started and the rotation speed of the camshaft 1 increases, the centrifugal force also increases due to the urging force of the return coil spring 16, and the weight lever 13 rotates clockwise as shown in FIG. The decompression pin 9 starts to move and rotates with this. Then, the end of the decompression pin 9 is recessed from the outer peripheral surface of the cam 4 to release the push-up of the tappet 2, and as a result, the combustion chamber (not shown) is fully compressed.

With the above operation, the starting load can be reduced without requiring any troublesome preparation work before starting the engine. or,
In this embodiment, since the decompression pin 9 can be largely rotated by a slight rotation of the weight lever 13 due to the centrifugal force, the semi-compressed state can be released early in the diesel engine having a low rotation speed at the time of starting.

In the above-described embodiment, the engagement pin 11 provided on the weight lever 13 is engaged with the U-shaped engaging portion 11 of the decompression pin 9 to interlock with the decompression pin 9. It suffices if the can be rotated greatly. Also, the return coil spring 16
Instead of this, a biasing member such as a tension coil spring can be used. Furthermore, the weight lever 13 may have any shape as long as it can release the half-compressed state at a predetermined rotation speed.
It is not limited to the embodiment.

In the present invention, the valve train that is slightly pushed up and opened by the decompression pin 9 may be either an intake system or an exhaust system. Further, the return coil spring 16 may be omitted. Furthermore, although a diesel engine is used in the embodiment, it can be similarly applied to a gasoline engine having a large exhaust capacity.

As described above, according to the present invention, a notch is formed at the end of the decompression pin so that the decompression pin projects from the cam surface, and the decompression pin and the weight lever are interlocked by centrifugal force. Since the decompression pin can be rotated significantly, the starting load can be automatically reduced without any troublesome preparation work before starting the engine, and the semi-compressed state is released early even at low speed rotation. Therefore, there is an effect that the starting can be facilitated.

In addition, one end of the weight lever is pivotally mounted at a position opened substantially at a right angle around the cam shaft from a pin hole for supporting the decompression pin on the end face of the cam gear, and the other end of the weight lever is formed in the decompression pin in a U-shape. Since the weight lever is engaged with the engaging portion, the decompression pin can be largely rotated by a large moment, and the decompression operation or the releasing operation can be surely performed.

[Brief description of drawings]

1 to 5 relate to an embodiment of the present invention, and FIG. 1 is a sectional view of a camshaft portion of a diesel engine, and FIG.
FIG. 4 is a right side view of FIG. 1, FIG. 3 is a perspective view of the decompression pin, and FIGS. 4 and 5 are sectional views taken along line AA of FIG.
FIG. 5 is an operation explanatory diagram when the engine is started, and FIG. 5 is an operation explanatory diagram when the engine is normally rotating. DESCRIPTION OF SYMBOLS 1 ... Cam shaft, 2, 3 ... Tappet 4, 5 ... Cam, 6 ... Cam gear 8 ... Pin hole, 9 ... Decompression pin 11 ... Engagement part, 12 ... Notch part 13 ... Weight lever

Claims (1)

[Claims] Claim: What is claimed is: 1. A cam gear, which receives a rotational force from a crankshaft by a cam gear, causes a cam provided on the camshaft to operate a tappet to open and close an intake valve and an exhaust valve with respect to a combustion chamber. A pin hole is formed on the end face of the cam gear, and a decompression pin having a U-shaped engaging portion on one side is rotatably fitted in the pin hole, and the decompression pin end on the side opposite to the engaging portion is placed on the cam side. An extension is provided in the portion of the decompression pin end portion facing the tappet end portion with a notch formed so as to project and retract from the cam surface by the rotation of the decompression pin, while the cam is formed from the pin hole of the cam gear end surface. One end of the weight lever is pivotally attached at a position substantially perpendicular to the shaft, and the other end of the weight lever is connected to the U of the decompression pin.
The combustion chamber is brought into a semi-compressed state by being engaged with the character-shaped engaging portion, and the decompression pin end portion protruding from the cam surface by the rotation of the weight lever,
A decompression device for an engine, characterized in that the fuel chamber is precompressed by the end of the decompression pin entering the cam surface.