JPH01300007A - Valve timing adjustment device of four-cycle engine - Google Patents

Abstract

PURPOSE:To simplify the structure and reduce the cost by mounting a passive element which is made displaceable at a specified angle in the direction of rotation on a driving element in a valve operating device, and rotates the passive element by the expanding motion of a centrifugal weight which is attached to the driving element by a shaft. CONSTITUTION:In a device where a cam shaft 3 sequentially rotates with the rotation of a crank shaft through a timing chain engaged with a cam sprocket 4, and a valve is opened and closed by a cam 6, a pair of centrifugal weights 13 are shafted 14 in the opposite position on the side face of a driving element 12 which also serves as a cam sprocket 4. When the centrifugal force expanded the centrifugal weights 13 outward by the increased rotation of the driving element 12 overcoming a spring 18, claws 21 at the top of the centrifugal weights 13 disengage from the clamping concave parts 22 on a passing element 16 which is coupled with the cam shaft 3, thus, the passive element 16 is displaced up to the extent of a specified angle through the engagement of a peaking 19 on the passive element 16 and a gradient groove 20, causing a delay in the valve timing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable valve timing device for a four-stroke engine.

[Conventional technology and its problems]

A four-stroke engine uses a camshaft that is linked to the crankshaft to open and close the intake and exhaust valves. Therefore, the opening/closing timing of the intake and exhaust valves is determined by the shape of the cam.

Generally, the shape of the cam is set so that the valve timing is correct when the engine obtains maximum torque.
It is known that it is better to set the valve timing a little earlier in the low rotation range.

For this reason, various valve timing variable devices are provided. For example, see Japanese Patent Publication No. 52-35819, Japanese Utility Model Application Publication No. 61-69412, and Japanese Utility Model Application Publication No. 57-92808.

These devices use a centrifugal weight as the displacement source, and combine this with planetary gears, racks and binions, link devices, etc. to create a variable device.The structure is **, high manufacturing costs, and there are problems with the mounting location. big.

In addition, there are also those that are controlled by hydraulic pressure or those that are equipped with an electric control unit, but this increases the manufacturing cost of the layer.

[Purpose of the invention]

In this invention, a variable device can be created using only a centrifugal weight attached to a driving body and a passive body that meshes with the pawl of the centrifugal weight. Furthermore, it can be installed at any position in the valve train, and the installation location can be selected. The purpose of the present invention is to obtain a variable valve timing device for a four-stroke engine that is convenient in terms of layout and can be produced at low cost.

(Structure of the invention) Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings.

FIG. 1 shows an example of a valve train for a four-stroke engine.

A crank sprocket 2 attached to the end of a crankshaft 1 and a cam sprocket 4 attached to the end of a camshaft 3 are connected by a timing chain 5, and the camshaft 3 is rotated by following the crankshaft 1.

The camshaft 3 is provided with a cam 6.7, which swings the rocker arm 8.9 and pushes up the intake valve 10 and the exhaust valve 11 against a spring to open and open them.

Note that a timing belt may be used instead of the timing chain 5.

2 to 4 show an embodiment of the present invention.

The driving body 12 includes a pair of centrifugal weights 1 facing each other on the side.
3 is pivotally attached by a support shaft 14, and the base protrusion 15 of the centrifugal weight 13 is inserted into the U417 of the passive body 16 and biased inward by a spring 18. The passive body 16 has an outer peripheral protrusion 19
is inserted into the long groove 20 of the driving body 12 so that it can be displaced by an angle θ in the rotational direction.

Further, the centrifugal weight 13 is provided with a claw 21 at its tip, which is adapted to engage with a locking recess 22 of the passive body 16.

The passive body 16 is attached to the end of the camshaft 3 by a spline so as to rotate integrally therewith, and a cam sprocket 4 is provided on the outer periphery of the driving body 12, and a timing chain 5 is wound around the cam sprocket 4.

FIGS. 5 and 6 show other embodiments of the present invention.

In this case, the driving body 12 is fixed to the crankshaft 1 with a spline, and the passive body 16 is provided with a crank sprocket 2 and attached to the crankshaft 1. The other parts are the same as those shown in FIGS. 2 to 4, and are given the same reference numerals.

FIGS. 7 and 8 show still another embodiment of the present invention.

In this case, the camshaft 3 is made into a hollow shaft and one end is used as the passive body 16, the sprocket shaft 23 to which the cam sprocket 4 is attached is placed inside the camshaft 3, and the driving body 12 is connected to the sprocket shaft 23 by a spline. It is fixed. The other parts are the same as those shown in FIGS. 2 to 4, and are given the same reference numerals.

(Operation of the invention) When the rotation is low, the centrifugal force is small and the centrifugal weight 13
The spring 18 has a large tension and is pressed inward, and the claw 21 engages with the locking hole 22 of the passive body 16.

When the rotation becomes high speed, the centrifugal force applied to the centrifugal weight 13 overcomes the tension of the spring 18, the centrifugal way 1-13 expands outward, and the pawl 21 disengages from the locking recess 22. As a result, the passive body 16 is displaced by the angle θ in the rotational direction, causing a delay in valve timing.

In addition to being attached to the crankshaft 1, the driving body 13 and the passive body 16 can also be attached to the camshaft 3, which is convenient because the mounting position can be selected based on the layout of the engine.

(Effects of the Invention) As explained above, the present invention connects and interlocks the crank sprocket of the crankshaft and the cam sprocket of the camshaft through a timing chain, and operates the intake and exhaust valves by the rotation of the cam of the camshaft. In a valve device, a passive body is attached to a drive body in the valve drive device so as to be able to be displaced by a predetermined angle in the rotational direction, a centrifugal weight that expands outward against a spring is pivoted to the drive body, and the centrifugal weight A pawl that engages with the passive body is provided, and the pawl engages and disengages according to the rotation speed, and the passive body is displaced by a predetermined angle in the direction of rotation, so it is easy to use the drive body with the centrifugal weight attached to the shaft and the passive body. The structure allows variable valve timing and can be produced at low cost.

The combination of the driving body and the passive body can be mounted on the crankshaft or the camshaft portion, and can be mounted at a convenient position on the engine layout.

Furthermore, since the centrifugal weight directly operates the passive body, it can be displaced with a small operating force.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of a valve train for a four-cycle engine, Figs. 2 to 4 show an embodiment of the present invention, Fig. 2 is a longitudinal sectional view, and Fig. 3 is a cross-sectional view at low speed. 4 is a cross-sectional view at high speed; FIGS. 5 and 6 show other embodiments of the present invention; FIG. 5 is a vertical sectional view; FIG. 6 is a cross-sectional view; 8 and 8 show still another embodiment of the present invention, FIG. 7 is a longitudinal cross-sectional view, and FIG. 8 is a cross-sectional view. 1... Crankshaft, 2... Crank sprocket, 3... Camshaft, 4... Cam sprocket, 5... Timing chain, 6... Cam, 7... Cam, 10...・Intake valve,
DESCRIPTION OF SYMBOLS 11...Exhaust valve, 12...Driver body, 13...Centrifugal weight, 16...Passive body, 18...Spring, 21...Claw. Applicant's agent Hiroshi Fujimoto

Claims (1)

[Claims] In a valve train, the crank sprocket of the crankshaft and the cam sprocket of the camshaft are connected and interlocked by a timing chain, and the intake and exhaust valves are opened and closed by the rotation of the cam of the camshaft. The passive body is mounted so that it can be displaced by a predetermined angle in the direction of rotation, a centrifugal weight that expands outward against a spring is pivotally attached to the driving body, and a claw that engages with the passive body is provided on the centrifugal weight. 1. A variable valve timing device for a four-cycle engine, characterized in that the device is provided so that a pawl is engaged and disengaged to displace a passive body by a predetermined angle in the direction of rotation.