JPS6023567Y2 - chientensiyona - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a chain tensioner used in a camshaft drive chain of a four-stroke engine.

The camshaft drive chain of the 4-stroke engine is supported by a tension rail, and the tension rail is pushed out from behind by a shaft pressed by a spring, urging the chain 7 to stay tensioned at all times.

When the chain 7 extends, the pressing shaft advances by that amount, and the pressing shaft is prevented from returning from the advanced position by a ratchet device or one-way device, and the chain 7 is always kept in a tensioned state.

Providing a ratchet or a one-way device in this way requires small parts and several parts, which makes manufacturing time-consuming and increases costs.

In view of these points, this invention has been improved so that it can be made at low cost, and an embodiment of the invention shown in the drawings will be described below.

The engine is driven by winding a chain 75 between the sprocket 2 of the crankshaft 1 and the sprocket 4 of the camshaft 3.

The check 75 has a tension rail 6 along one side and a guide rail 7 along the other side.

One end of the tension rail 6 is fixed to a shaft 8, and the other end is left free.

According to the present invention, a tension arm 15 is rotatably attached to a holder 11 which is fastened to a machine frame 9 with bolts 10 via link pieces 12 and shafts 13 and 14.

At the distal end of the holder 11 and the proximal end of the tension arm 15, there are cam surfaces 16 and 17 that gradually move away from a reference circle (dotted chain line in FIG. 4A) centered on the shafts 13 and 14 as they move upward. and the two cam surfaces 16
．． 17 are in contact with each other.

The tension arm 15 is connected to the tension rail 6.
The tip of a spring 18 wound around the shaft 13 is latched onto a portion of the tension arm 15 near the shaft 14 so as to press the back surface of the tension arm 15.

A return lever 19 is rotatably attached to the shaft 13, and the tip of the return lever 19 is key-shaped and abuts against the base of the tension arm 15.

The effect will be explained.

When the chain 75 is extended by use, the tension arm 15 moves forward due to the pressing force of the spring 18, and the tension arm 15
Since the tension rail 6 is pushed out at the tip, the check 75 can be tensioned.

By the way, as mentioned above, both the cam surface 16 and the cam surface 17 are shaped so that they gradually move away from the reference circle centered on the respective axes 13 and 14 as they move upward.
As shown in FIG. 4, both the tension arm 15 and the link piece 12 can rotate clockwise about the shaft 13, and the chain 75 can be tensioned by advancing the tip of the tension arm 15.

However, since the counterclockwise rotation of the tension arm 15 is prevented by the wedge action of both cam surfaces 16 and 17, the tension arm 15 can move forward but cannot move backward.

Therefore, the tension arm 15 always maintains the tensioned position of the chain 75.

On the other hand, when replacing the chain 75, push the base of the tension arm 15 upward with the return lever 19 and rotate the tension arm 15 around the shaft 14, creating a gap between the cam surface 16 and the cam surface 17. , the tension arm 15 can be returned against the spring 18.

That is, as shown in Fig. 4a, if the centers of the shafts 13.14 are A and B, and the contact points of both cam surfaces 16.17 are C, then AB is constant and AB (AC + BC). .

Therefore, when the tension arm 15 is rotated clockwise around the shaft 14, it comes to the point shorter than BC on the cam surface 17 or the original point C, so a gap is created between both cam surfaces, and the link piece 12 and tension arm 15 with spring 1
It can be rotated against 8.

As explained above, in this invention, the tension arm is rotatably attached to a holder fixed to the machine frame via a link piece, a cam surface is provided at the tip of the holder, and a cam surface is provided at the base end of the tension arm. A cam surface is provided on the cam surface, both cam surfaces are in contact with each other, and a spring is used to press the tip of the tension arm against the tension rail, so the tension arm moves forward by the amount that the check 7 is extended, and the check 7 is moved forward. It can be stretched.

Since the holding body and the cam surface of the tension arm form a wedge and the tension arm does not move backward, the chain 7 can be kept in a tensioned state.

Moreover, since the cam surface is shaped like the end surface of the holder and the tension arm, the number of parts is small and the product can be manufactured at low cost.

In addition, it is compact and does not take up much space when installed, and the Che 7 can be easily replaced.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is an overall front view, Fig. 2 is an enlarged front view of main parts, Fig. 3 is a side view of the same, and Fig. 4 a.
and b are operation explanatory diagrams. 6... Tension rail, 9... Machine frame, 11... Holding body, 12... Link piece, 15... Curved tension arm, 16... ...Cam surface, 17...Cam surface, 18...Spring.

Claims (1)

[Scope of utility model registration request] The tension arm is rotatably attached to a holder fixed to the machine frame via a link piece, and the rotation axis of the link piece relative to the holder and the rotation axis of the link piece relative to the link piece are attached to the tip of the holder and the base end of the tension arm, respectively. A cam surface is provided that gradually moves away from the reference circle centered on the axis of rotation of the tension arm as it moves away from the engine, so that both cam surfaces are brought into contact and the tip of the tension arm is pressed against the tension rail. A chain tensioner characterized by being biased by a spring.