JPH061044B2 - Variable valve opening / closing timing device for 4-cycle engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve opening / closing timing varying device for a 4-cycle engine.

[Technical background and problems of the invention]

A 4-cycle engine is a cam that interlocks with a crankshaft, and rocks a rocker arm to push down an umbrella-shaped valve for intake and exhaust to open it. Therefore,
The opening / closing timing of the intake / exhaust valve is determined by the shape of the intake / exhaust cam. In a 4-cycle engine, as the valve speed is increased, the valve opening timing is increased, the opening is increased, and intake / exhaust is delayed, so that high output cannot be generated. However, since the valve opening / closing timing is determined by the cam shape, the cam shape is defined by focusing on either high speed or low speed to match the engine usage conditions. In some cases. It is also proposed to change the timing by providing a valve lifter on the rocker arm, but the structure is complicated and the adjustment is difficult because of hydraulic pressure, which is not practical.

[Object of the Invention]

In view of this point, the present invention provides two cams, a low speed cam and a high speed cam, connects and disconnects the rocker arm and the cam arm with a pin, and moves the pin with a rotation speed-dependent push rod to achieve both high and low speeds. An object of the present invention is to obtain a valve opening / closing timing variable device for a 4-cycle engine that can appropriately open / close the valve and obtain a high output over the entire area.

[Structure of Invention]

 The present invention will be described below with reference to embodiments shown in the drawings.

The camshaft 1 is adapted to rotate in conjunction with a crankshaft with a timing belt or the like, and a low speed cam 2 and a high speed cam 3 are provided side by side. The rocker arm 4 is swingably attached to a rocker shaft 5, and at its tip, an umbrella-shaped valve 6 for intake or exhaust is pushed down to open. The other end is the low speed cam 2
Abutted against. The cam arm 7 is pivotally mounted on the rocker shaft 5 side by side with the rocker arm 4 so that the tip of the cam arm 7 abuts the high speed cam 3. On the cam arm 7,
The pin 8 is slidably inserted, and the tip of the pin 8 is adapted to be engaged with and disengaged from the hole 9 of the rocker arm 4, and is normally urged by a spring 10 in the direction of removal. The pin 8 can be pushed by a push rod 13 of an electromagnetic solenoid 12 via a thrust bearing 11, and the electromagnetic solenoid 12 is energized by a rotation detection switch 14 at high speed. The electromagnetic solenoid 12 may be replaced with a hydraulic cylinder, and the rotation detection switch 14 may be replaced with a throttle lever, an oil pump hydraulic switch, or the like that approximates rotation.

In the low-speed range, the pin 8 uses the elasticity of the spring 10 to cause the rocker arm 4 to move.
The rocker arm 4 is swung by the low speed cam 2 to open and close the valve 6. In the high speed range, the rotation detection switch 14 is closed, the electromagnetic solenoid 12 is energized, the push rod 13 is pushed out against the spring 10, the tip of the pin 8 meshes with the hole 9, and the cam arm 7 and the rocker arm 4, the valve 6 is opened and closed by the movement of the cam arm 7 in which the high speed cam 3 swings. High speed cam 3
In comparison with the low-speed cam 2, the opening timing is long and the lift is large, so the low-speed cam 2 does not interfere with the idle rotation. In this way, the valve can be opened / closed at high and low speeds with optimum timing, high output can be obtained over the entire range, and fuel consumption can be reduced.

〔The invention's effect〕

As described above, according to the present invention, a low-speed cam and a high-speed cam are arranged in parallel on a cam shaft that interlocks with a crankshaft, and a rocker shaft is swingably attached to the rocker shaft and the rocker is opened by pushing down the valve. The other end of the arm is brought into contact with the low speed cam, the cam arm swingably mounted on the rocker shaft is brought into contact with the high speed cam, and the pin slidably provided on the cam arm is a push rod depending on the rotation speed. Since the cam arm is connected to the rocker arm by inserting it into the hole of the rocker arm at high speed, the valve for low speed is opened and closed by the low speed cam that is optimal for low speed range, and the high speed range is optimized for high speed range. The cam can open and close the valve, improving the output over the entire area and reducing fuel consumption. Then, by simply inserting and removing the pin, the structure can be made simple and highly reliable.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a plan view in which a principal part is a fracture surface, and FIG. 1 ... Cam shaft, 2 ... Low speed cam, 3 ... High speed cam,
4 ... rocker arm, 5 ... rocker shaft, 6 ... valve, 7 ... cam arm, 8 ... pin, 9 ... hole, 13 ... push rod.

Claims (1)

[Claims] 1. A low-speed cam and a high-speed cam are arranged side by side on a camshaft that interlocks with a crankshaft, and the other end of a rocker arm that swingably attaches to a rocker shaft and is opened by pushing down the valve at its tip A cam arm that abuts against a low-speed cam and is swingably mounted on a rocker shaft is abutted against a high-speed cam, and a pin that is slidably mounted on the cam arm is a push rod that depends on the number of revolutions to locker at high speed. A variable valve opening / closing timing device for a four-cycle engine, characterized in that the cam arm is connected to a rocker arm by being inserted into a hole of the arm.