JPH0229207Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a rotary valve mainly used to open and close an intake port of a two-stroke engine.

(Prior Art) In the rotary valve intake structure of a two-stroke engine, the rotary valve is conventionally fixed to the crankshaft, and the intake port is opened and closed at the same intake timing from low rotation to high rotation. For this reason, if the timing is adjusted to either low rotation or high rotation, matching will be poor at the other, and the desired performance will not be achieved.

Therefore, a configuration is already known in which an unbalanced rotating body is used in the valve, and the opening/closing timing of the rotary valve is changed by the deviation of the center of gravity of the rotating body and a spring that opposes the deviation (Japanese Patent Publication No. 1973-
No. 41652). However, with this configuration, not only is it difficult to adjust the timing of opening and closing the valve, but it is also susceptible to engine rotational fluctuations, making it difficult to obtain stable operation.

(Problem that the invention aims to solve) In the conventional configuration, the intake port opens and closes at the same intake timing from low rotation to high rotation.
The problem is that the matching becomes poor at either low or high rotations, and the desired performance is no longer achieved.

In addition, the above-mentioned conventional configuration in which an unbalanced rotor is used to change the opening/closing timing has the problem that not only is it difficult to adjust the opening/closing timing, but it is also easily affected by engine rotational fluctuations, making it difficult to obtain stable operation. have.

The present invention attempts to solve the above problems.

(Means for solving the problem) The present invention fixes an annular inner holder to a central drive shaft, and rotatably fits an annular outer holder to the outer periphery of the inner holder. A rotary valve body that opens and closes a passage is fixed to the outer periphery of the outer holder, and the inner holder and the outer holder are elastically connected in the circumferential direction by a spring. By inserting a ball into a radial guide hole, providing a cam groove into which approximately half of the ball can fit on the inner periphery of the outer holder facing the guide hole, and providing a cam surface that slopes in the circumferential direction in the cam groove. , a rotary valve characterized in that when the ball is subjected to centrifugal force and fitted into the cam groove, the ball comes into contact with the cam surface, causing twisting between the inner holder and the outer holder. .

(Example) In Fig. 1, which shows a case where the rotary valve according to the present invention is adopted in the intake port of a two-stroke engine, an external spline is formed on the crankshaft 11 whose rotation center is the center O, and an annular inner A circumferential holder 12 is spline-fitted to the crankshaft 11. Three grooves 13 extending in the circumferential direction are formed at equal intervals on the outer circumference of the inner holder 12, and three guide holes 14 formed in the radial direction are formed between each groove 13 at equal intervals. There are several. Balls 15 are inserted into the guide holes 14 so as to be slidable in the radial direction.

An annular outer holder 16 is rotatably fitted on the outer periphery of the inner holder 12, and a ring holder 16 is fitted on the inner periphery of the outer holder 16 facing the groove 13 and extends in the circumferential direction. grooves 17 are respectively formed therein. In the valve free state (the state shown in FIG. 1), each pair of grooves 13 and 17 forms a rectangular space extending generally in the circumferential direction, and each spring 18 is inserted approximately within the space. It is contracted so as to extend in the circumferential direction. Spring 18
The inner circumference of the valve fits into the groove 13 and the outer circumference of the valve fits into the groove 17.
The inner holder 12 and the outer holder 16 are elastically connected in the valve circumferential direction. Also, guide hole 14
Cam grooves 19 that open toward the inner periphery are formed in the inner periphery of the outer holder 16 facing the holder 16 . Each cam groove 19 has a cam surface 20 that is inclined in the reverse R direction from the inner circumferential side to the outer circumferential side in a portion on the rotation direction (arrow R direction) side of the crankshaft 11. In the valve free state, most of the ball 15 is fitted into the guide hole 14,
Only a portion of the outer circumferential side protrudes from the guide hole 14 toward the outer circumferential side so as to be able to come into contact with the inner circumferential side portion of the cam surface 20 .

An external spline 21 is formed on the outer periphery of the outer holder 16, and the inner periphery of the rotary valve body 22 is spline-fitted to the external spline 21. The rotary valve body 22 is a generally disc-shaped member extending perpendicularly to the center O, and has a circumferentially long notch 23 at one location on the outer periphery.
have. The notch 23 is arranged on the same circumference as the intake port 25 of the engine, and when the rotary valve body 22 rotates, the notch 23 crosses the intake port 25 and the intake port 2
5 can be opened and closed.

As shown in Figure 2, the rotary valve body 2
There is a gasket 27 on the downstream side of 2 (in the direction of arrow F).
A valve cover 28 is arranged on the upstream side of the rotary valve body 22, and both the gasket 27 and the valve cover 28 are fixed to a crankcase 29. That is, the rotary valve main body 22 has a gasket 27 and a valve cover 28.
It is designed so that it can be rotated between. Furthermore, the second
In the figure, 31 is a hole for the intake port 25 formed in the crankcase 29, 32 is a bearing for supporting the crankshaft 11 with the crankcase 29, and 33 is a primary transmission gear that fits into the crankshaft 11.

Next, the operation will be explained. In FIG. 1, when the engine starts, the crankshaft 11 rotates in the direction of arrow R, and the torque is transmitted to the rotary valve body 22 via the inner holder 12, spring 18, and outer holder 16, 22 rotates. Rotary valve body 2
2 rotates, the notch 23 opens the intake port 2.
5 is opened and closed, and intake is performed at a predetermined timing.

While the engine is at low rotation speed, the centrifugal force generated on the ball 15 is small and cannot overcome the spring force of the spring 18. Therefore, the inner holder 12
The relative positions of the rotary valve body 22 and the outer holder 16 are the same as in FIG. 1, and the opening and closing timing of the intake port 25 due to the rotation of the rotary valve body 22 is fast and suitable for low rotation.

When the engine speeds up, the rotational speed of the crankshaft 11 also increases, and a strong centrifugal force is generated in the balls 15. As a result, the ball 15 rolls on the cam surface 20 and moves toward the outer circumference, and the cam groove 1
9 reaches the outer circumferential side end portion, and is in a position where approximately each half is fitted into the guide hole 14 and the cam groove 19. As a result, the outer holder 16 is twisted relative to the inner holder 12 in the reverse R direction, and the spring 18
is compressed within grooves 13 and 17. In this state, the position of the notch 23 is slightly (for example, about 10 to 20 degrees) at the crank angle of the crankshaft 11.
The angle becomes retarded, and the notch 2 of the intake port 25
3, the opening timing is delayed. That is, the intake port 25 due to the rotation of the rotary valve body 22
The opening/closing timing is slow and suitable for high rotation.

When the engine shifts to low rotation again from the state in which the notch 23 is advanced, the rotational speed of the crankshaft 11 also becomes low, and the centrifugal force of the spring 18 becomes weak. As a result, the spring force of the spring 18 causes the outer holder 16 to move against the inner holder 12.
The twist is restored, and the ball 15 is pushed back into the guide hole 14 by the cam surface 20. Inner holder 1
When the relative position between the intake port 2 and the outer holder 16 returns to that shown in FIG.

Note that in order to change the timing at which the inner holder 12 and the outer holder 16 twist, the force of the spring 18 or the weight of the ball 15 may be changed.

(Effect of the invention) Central drive shaft (e.g. crankshaft 11)
An annular inner holder 12 is fixed to the inner holder 12 , an annular outer holder 16 is rotatably fitted to the outer periphery of the inner holder 12 , and a passage (for example, an intake port 25 ) is fixed, and the inner holder 12 and the outer holder 16 are elastically connected in the circumferential direction by a spring 18.
The ball 15 is inserted into the radial guide hole 14 provided in the
, a cam groove 19 into which approximately half of the ball 15 can fit is provided in the inner circumference of the outer holder 16 facing the guide hole 14, and a cam surface 20 inclined in the circumferential direction is provided in the cam groove 19. When the ball 15 receives centrifugal force and fits into the cam groove 19, the cam surface 20
Since the ball 15 comes into contact with the inner holder 12 and the outer holder 16 to cause twisting, (a) the intake timing is automatically changed between low rotation and high rotation. As a result, it becomes possible to perform matching suitable for each, and it is possible to exhibit a predetermined performance in both low rotation and high rotation conditions.

(b) Not only is it easy to adjust the opening/closing timing, but it is also less susceptible to engine rotational fluctuations, resulting in stable operation.

(Another embodiment) (a) A hole with a reed valve is provided on both sides or one side in the circumferential direction of the hole for the intake port 25 of the gasket 27 (for example, Japanese Patent Publication No. 59-24248) to further optimize the intake timing. It may be possible to make it possible to achieve this.

(b) Depending on the installation location of the rotary valve according to the present invention, the cam surface 20 may be provided in the opposite direction so that the outer holder 1 is opposed to the inner holder 12 during high rotation.
6 can also be twisted in the reverse R direction.

(c) The exhaust timing can also be adjusted by attaching the rotary valve according to the present invention to the exhaust port of the engine.

[Brief explanation of drawings]

FIG. 1 is a partial longitudinal sectional view of a rotary valve according to the present invention, and FIG. 2 is a partial sectional view taken from FIG. 1. 11...Crankshaft, 12...Inner peripheral side holder, 14...Guide hole, 15...Ball, 16
...Outer holder, 18...Spring, 19...
...Cam groove, 20...Cam surface, 22...Rotary valve body, 25...Intake port.

Claims (1)

[Scope of utility model registration request] An annular inner holder is fixed to the central drive shaft,
An annular outer holder is rotatably fitted to the outer periphery of the inner holder, and a rotary valve body that opens and closes the passage is fixed to the outer periphery of the outer holder, and the inner holder and outer holder are connected to each other. are elastically connected in the circumferential direction by a spring, and a ball is inserted into a radial guide hole provided in the inner holder,
A cam groove into which approximately half of the ball can fit is provided on the inner periphery of the outer holder facing the guide hole, and by providing the cam groove with a cam surface that slopes in the circumferential direction, the ball receives centrifugal force and moves into the cam groove. A rotary valve characterized in that when the holder is fitted, the balls come into contact with the cam surface, causing twisting between the inner holder and the outer holder.