JPH0513925Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to an engine decompression device that puts a combustion chamber in a semi-compressed state when starting the engine to improve startability, and automatically returns the combustion chamber to a fully compressed state after the engine is started.

[Conventional technology]

Conventionally, as an engine decompression device, for example, Japanese Utility Model Application No. 60-97308 or No. 61-12913
The application shown in the publication was filed by the applicant,
It has been published. All of these use a release pin that has a notched decompression cam at one end and a flyweight at the other end. Here, in order to support the release pin rotatably around an axis parallel to the camshaft, a pin holding groove with a semicircular cross section is formed in the axial direction of the camshaft into which the cam gear is fitted and fixed. . In addition, the release pin that is held by being fitted into the pin holding groove has the decompression cam at one end facing near the cam of the camshaft, and the flyweight at the other end located closer to the end of the camshaft than the cam gear fitted to the camshaft. I am making it happen. A member such as a sleeve is attached to the camshaft in order to position the release pin in the axial direction and prevent it from coming off.

[Problem that the idea aims to solve]

By the way, in the conventional examples described in each of the above-mentioned publications, a separate member such as a sleeve is required to position the release pin in the axial direction or to prevent it from coming out, resulting in a problem that the structure becomes complicated. Furthermore, since the release pin has a structure in which one end faces near the cam of the camshaft and the other end faces the end of the camshaft from the cam gear fitted to the camshaft, the pin holding groove of the camshaft that accommodates the release pin is There was also the problem that the length of the camshaft decreased. Therefore, the present invention simplifies the structure by eliminating the need for any separate parts for positioning the release pin or preventing it from coming out.It also reduces the length of the pin holding groove to the minimum necessary and increases the strength of the camshaft compared to conventional models. It is an object of the present invention to provide an engine decompression device that can further improve performance.

[Means to solve the problem]

For this purpose, in the present invention, a release pin having a decompression cam and a flyweight is housed in a pin holding groove formed along the axial direction on the circumferential surface of the camshaft, is rotatably supported, and is mounted near the cam of the camshaft. When the engine starts, the facing decompression cam protrudes above the cam surface position to reduce the pressure in the combustion chamber to a semi-compressed state, and after the engine starts, the flyweight rotates the release pin and the decompression cam retracts below the cam surface position. In an engine decompression device that returns a combustion chamber to a fully compressed state by It has a structure in which one end has a flyweight and the other end faces the fitting part of the cam gear,
The camshaft is provided with an axially perpendicular notch groove into which the base end of the flyweight protruding from the intermediate portion of the release pin is inserted to position the release pin in the axial direction.

[Effect]

In an engine decompression device employing such means, the release pin is positioned in the axial direction by fitting the proximal end of the flyweight of the release pin into a notch groove provided in the camshaft in a direction perpendicular to the axis. In addition, since the release pin has a structure in which one end faces near the cam of the camshaft and the other end faces the cam gear fitting part of the camshaft, the pin holding groove of the camshaft that accommodates the release pin has a minimum length. It is possible to shorten the time to a minimum.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings. In FIG. 1 showing the overall configuration of one embodiment, reference numeral 1 indicates a camshaft of the engine, and reference numeral 2 indicates a cam gear that is press-fitted near the end of the camshaft 1 and is rotationally driven by meshing with a crank gear (not shown). Reference numeral 3 indicates a cam integrally formed with the camshaft 1, reference numeral 4 indicates a tappet that slides on the cam 3 and opens and closes intake and exhaust valves of the engine (not shown) as the camshaft 1 rotates, and reference numeral 5 indicates a decompression device according to the present invention. There is. The decompression device 5 includes a release pin 8 having a flyweight 6 and a decompression cam 7, and a pin holding groove 9 that is formed along the axial direction on the outer circumference of the camshaft 1 and accommodates the release pin 8 rotatably around the axis. It consists of The release pin 8 has one end facing near the cam 3 of the camshaft 1 and the other end facing the part where the cam gear 2 is press-fitted. A cut-shaped decompression cam 7 is formed. A flyweight 6 is integrally formed on the release pin 8 at an intermediate portion closer to one end than the cam gear 2. As shown in FIG. 2, the fly weight 6 has a predetermined thickness and protrudes from the release pin 8 in a curved manner in the radial direction of the camshaft 1, and its proximal end extends around the release pin 8. It protrudes in a semicircular shape. On the other hand, the pin holding groove 9 has a U-shaped cross section in which the release pin 8 can be rotatably accommodated around its axis (see Fig. 4), and is located in the large diameter portion of the camshaft 1 into which the cam gear 2 is fitted. It is formed in the shape of a keyway (see Figure 3). The large diameter portion of the camshaft 1 in which such a pin holding groove 9 is formed has a cutout groove 10 into which the base end of the flyweight 6 is rotatably inserted to position the release pin 8 in the axial direction. It is formed in the direction perpendicular to the axis. Therefore, the release pin 8 is accommodated in the pin holding groove 9 of the camshaft 1 with the decompression cam 7 at one end facing the vicinity of the cam 3, and the base end of the flyweight 6 is rotatably fitted into the notch groove 10. The other end is held between the camshaft 1 and the cam gear 2 and is rotatably supported, and in this state the decompression cam 7 faces the tappet 4. In FIG. 2, the reference numeral 11 is a stopper pin protruding from the side surface of the cam gear 2, which contacts the fly weight 6 raised by the centrifugal force generated by the rotation of the camshaft 1, and rotates the release pin 8. By regulating the decompression cam 7 at one end of the release pin 8, the decompression cam 7 is held in a recessed state below the cam surface position of the cam 3. In the decompression device 5 of the embodiment configured as described above, when the engine is started, the fly weight 6 of the release pin 8 is tilted toward the camshaft 1 side, and the decompression cam 7 protrudes above the cam surface position of the cam 3. Tappet 4 is pushed up slightly. For this reason,
The combustion chamber of the engine is depressurized to a semi-compressed state, making it easy to start the engine. After the engine is started, the flyweight 6 of the release pin 8 stands up in the radial direction of the camshaft 1 due to centrifugal force, comes into contact with the stopper pin 11, and is held in that state. Therefore, the decompression cam 7 of the release pin 8 is recessed below the cam surface position of the cam 3 and is out of contact with the tappet 4. Therefore, the combustion chamber of the engine returns to a fully compressed state and normal operation continues. Here, the release pin 8 is the fly weight 6
A notch groove 1 formed in the camshaft 1 at the base end of the
0, it is positioned in the axial direction, and a separate member for positioning as in the conventional case is not required and the structure is simple. Further, one end of the release pin 8 faces near the cam 3 of the camshaft 1, and the other end faces the cam 3 of the camshaft 1.
Since the structure faces the part into which the cam gear 2 is fitted, the length of the pin holding groove 9 of the camshaft 1 that accommodates the release pin 8 can be shorter than that of the conventional one, and the strength of the camshaft 1 is improved accordingly.

[Effect of the idea]

As explained above, according to the present invention, the release pin is positioned in the axial direction by fitting the base end of the flyweight of the release pin into the notch groove provided in the direction perpendicular to the axis of the camshaft. The structure can be simplified by eliminating the need for any separate members for positioning or retaining. In addition, since the release pin has a structure in which one end faces near the cam of the camshaft and the other end faces the cam gear fitting part of the camshaft, the length of the pin holding groove of the camshaft that accommodates the release pin should be kept to the minimum length necessary. The strength of the camshaft can be improved compared to the conventional one by shortening the length to a minimum.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing an embodiment of an engine decompression device according to the present invention, Fig. 2 is a sectional view taken along the line - - of Fig. 1, and Fig. 3 is a partial view showing a camshaft in one embodiment. The broken front view and FIG. 4 are sectional views taken along the line -- in FIG. 3. 1...Camshaft, 2...Cam gear, 3...
Cam, 4... Tappet, 5... Decompression device, 6
... Decomp weight, 7 ... Decomp cam, 8
...Release pin, 9...Pin holding groove, 10...
Notched groove.

Claims (1)

[Claims for Utility Model Registration] A release pin having a decompression cam and a flyweight is rotatably supported by being accommodated in a pin holding groove formed along the axial direction on the circumferential surface of the camshaft, and is mounted near the cam of the camshaft. The facing decompression cam protrudes above the cam surface when the engine starts, reducing the pressure in the combustion chamber to a semi-compressed state.
In an engine decompression device that returns the combustion chamber to a fully compressed state by retracting the decompression cam below the cam surface position by rotation of the release pin by the flyweight after the engine is started, the release pin is located near the cam of the camshaft. It has a decompression cam at one end facing the camshaft, a flyweight at the middle part closer to the one end than the cam gear fitted to the camshaft, and the other end faces the fitting part of the cam gear. The engine decompression device is characterized in that an axially perpendicular notch groove is provided into which a base end portion of a flyweight protruding from an intermediate portion of the release pin is inserted to position the release pin in the axial direction.