JPH0440568B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to an anti-overload centrifugal clutch.

Conventional Technology Generally, in a centrifugal clutch, when an overload is applied to the driven part, the rotational speeds of the driven part and the drive part differ, causing slippage between the outer ring and the shoe. There was a risk of overheating and abnormal wear due to friction. For example, when the chain saw of an automatic pruning machine is locked by a tree, etc., slipping occurs between the outer ring of the centrifugal clutch that transmits power to the chain saw, overheating, and the life of the centrifugal clutch becomes extremely short. This causes the inconvenience that the length becomes shorter.

As a countermeasure to this problem, for example, it is possible to reverse the rotation transmission method of the centrifugal clutch from the conventional one, as in Japanese Patent Publication No. 52-2052, but when starting up, etc., it is necessary to operate a separately installed fluid pressure device. necessary, and the structure becomes more complex.

Problems to be Solved by the Invention Therefore, an object of the present invention is to provide an overload prevention centrifugal clutch that prevents overheating due to slippage between the outer ring and the shoe during overload. It is characterized in that the method is reversed to that of the conventional centrifugal clutch, and that the starting operation can be performed automatically.

Means for Solving the Problems That is, the centrifugal clutch according to the present invention is provided with a drive shaft on the outer ring side of the centrifugal clutch device and a driven shaft on the shoe side, so that when an overload is applied to the driven shaft, the driven shaft When the rotation of the shaft falls below a predetermined rotational speed, the engagement of the centrifugal clutch device is released, and an automatic interlocking device that interlocks the driven shaft side with the driving side only at the time of startup is installed between the driven shaft side and the driving shaft side. A locking member displaceable in the radial direction is formed between the locking member and a removable engagement portion.

Operation Therefore, when the drive shaft rotates, the outer ring fixed to the drive shaft rotates, and if there is a light load on the driven shaft side, the driven shaft is rotated through the automatic interlocking device, and the ring attached to the driven shaft rotates. When the rotation speed reaches a point where sufficient centrifugal force is applied to the inner peripheral surface of the outer ring, the outer ring and the shoe are firmly connected, and the drive shaft is no longer connected, regardless of the operation of the automatic interlocking device. The rotational force is reliably transmitted to the driven shaft via the outer ring and shoe. However, when the driven shaft is overloaded and decelerates or stops, sufficient centrifugal force is not applied to the shoe provided on the driven shaft side to connect it with the outer ring, and the shoe is instantly pushed against the inner circumferential surface of the outer ring. Even if the outer ring continues to rotate without losing pressure, the shoe only lightly slides against the inner peripheral surface of the outer ring due to its own weight, so it will not be overheated.
When power transmission from the outer ring to the shoe is cut off, an automatic interlocking device operates, but since this interlocking device only allows the drive shaft and driven shaft to interlock under a light load, the drive shaft continues to rotate. Even when the driven shaft is stopped, frictional heat that causes problems in the interlocking device is not generated.

Embodiments The present invention will be described below based on embodiments shown in the drawings.

This embodiment is an example in which the overload prevention centrifugal clutch according to the present invention is applied to a chain saw installed in the sawing section of an automatic pruning machine. The outer ring 7 of the overload prevention centrifugal clutch device 2 according to the present invention is attached to the drive shaft 1 driven by power from the internal combustion engine. A driven shaft 11 connected to the sprocket 3 engages with a saw chain 17 to which a saw blade is attached.
The rotation of the drive shaft 1 is transmitted to the sprocket 3 via the overload prevention centrifugal clutch device 2, and the chain 17 is driven to cut tree branches etc. with the saw blade. There is.

The drive member 4 connected to the drive shaft 1 has a joint part connected to the drive shaft 1 at one end, and forms a pin receiving recess 6 that engages with the pin 5 of the drive shaft 1.
The outer ring 7 of the overload prevention centrifugal clutch device 2 is attached to the other end.
is formed. The shoes 8 that are frictionally engaged with the inner circumferential surface of the outer ring 7 are formed of three pieces, and as shown in FIG. It is guided by a boss member 9 extending to. That is, each shoe 8 forms a groove 10 extending in its radial direction, and the groove 10 is loosely fitted with the boss member 9 to radially move the shoe 8 which is subjected to centrifugal force when the driven shaft 11 rotates. Slidably guide.

Incidentally, since the shoe 8 is provided on the driven shaft 11 side, there is no need for a return spring to maintain the clutch in the disengaged state.

The boss member 9 is fixed to the driven shaft 11 together with the sprocket 3 via a key 18.
The drive member 4 is attached to the outside of the needle bearing 1.
9 and are fitted concentrically. As shown in FIG. 1, a recess 12 is formed in a part of the surface of the driven shaft 11, and the recess 12 of the driven shaft 11
A hole 13 is formed in a portion facing the driven shaft 11, into which a spring 14 and a ball 15 are fitted, so that the ball 15 can be engaged with the recess 12 of the driven shaft 11. Since this ball 15 is always urged in the direction of the recess 12 by the spring 14, when the drive member 4 is rotated by the drive shaft 1 at the start of work, if the load on the driven shaft 11 side is light, , the engagement between the ball 15 and the recess 12 works to rotate the driven shaft 11 in the same direction, and when the load applied to the driven shaft 11 side increases,
The relative positions of the ball 15 and the recess 12 are shifted, the ball 15 is pushed up onto the surface of the driven shaft 11, and the spring 1
4 and moves out of the recess 12 and rolls around the driven shaft 11. Therefore, the driving member 4 is connected to the driven shaft 11
It can be rotated even if it is fixed. This configuration allows the automatic intermittent type to act as an interlocking device, and even if it is installed in the shoe 8 on the driven side, the centrifugal clutch can be automatically started, and the driven shaft can be rotated if the saw chain 17 gets caught in a branch, etc. When an overload is applied to the drive shaft 11 and the rotational speed of the driven shaft 11 falls below a predetermined rotational speed, the centrifugal force of the predetermined magnitude will no longer act on the shoe 8, and power transmission by the clutch device 2 will be interrupted instantaneously, causing the drive Even if the shaft 1 continues to rotate, the shoe 8 only makes light contact with the outer ring 7 due to its own weight, which prevents slipping between the outer ring and the shoe when an overload condition occurs with the clutch still engaged in the conventional device. This prevents overheating accidents caused by abnormal frictional heat.

FIG. 3 shows an embodiment of the automatic interlocking device, in which a gentle chevron-shaped convex portion 1 is formed on the inner peripheral surface of the outer ring 7.
6, and the shoe 8 also has a portion facing the inner circumferential surface of the outer ring formed between the convex portions 16 so as to match the shape of the inner circumferential surface. In this embodiment, when the driven shaft 11 is stopped and the outer ring 7 on the driving side rotates, the shoe 8 located below the driven shaft 11 side moves toward the tip of the boss member 9 by its own weight, and the outer ring 7 rotates. Since the outer end surface of the shoe 8 comes into contact with the side surface of the convex portion 16 and receives a resistance force, the drive shaft 1 and the driven shaft 11 are connected to each other.
The side can be interlocked only when the load is light under normal working conditions, and the driven shaft 11 is rotated to apply centrifugal force to the shoe 8 to automatically operate the centrifugal clutch device 2, and the outer ring 7 and shoe 8 are rotated. Power is normally transmitted to the driven shaft 11 side through the shaft.

Effects of the Invention The present invention reverses the outer ring and shoe of the centrifugal clutch that connects the drive shaft and the driven shaft from the conventional usage of the conventional centrifugal clutch, and interlocks both shafts only when the driven shaft side is under light load. By providing an automatic interlocking device, when an overload is applied to the driven shaft and the rotational speed decreases or stops, the engagement between the outer ring of the centrifugal clutch and the shoe is instantly released, and the clutch remains engaged. It prevents overheating accidents caused by abnormal frictional heat caused by slippage between the outer ring and the shoe, and can automatically start and restart.The automatic interlocking device can also be provided with a simple structure, making it suitable for mass production. It has the advantage of being suitable, inexpensive, and reliable in operation.

[Brief explanation of drawings]

The drawings show embodiments according to the present invention.
2 is a sectional view of essential parts of an embodiment of the overload prevention centrifugal clutch according to the present invention, FIG. 2 is a side view showing the state of engagement between the outer ring and shoe of the overload prevention centrifugal clutch device of FIG. 1, and FIG. 3 is a side view showing the state of engagement between the outer ring and shoe of another embodiment. 1... Drive shaft, 2... Centrifugal clutch device, 7...
...outer ring, 8...shu, 11...driven shaft, 12...
... recess, 13 ... hole, 14 ... spring, 15 ... ball, 16 ... convex part.

Claims (1)

[Claims] 1. A drive shaft 1 is provided on the outer ring 7 side of the centrifugal clutch device, and a driven shaft 11 is provided on the shoe 8 side, so that when an overload is applied to the driven shaft, the rotation of the driven shaft is a predetermined rotation. When the number of centrifugal clutches decreases, the engagement of the centrifugal clutch device is released, and an automatic interlocking device that interlocks the driven shaft side with the drive shaft side only at the time of startup is connected between the driven shaft side and the drive shaft side in the radial direction. An overload-preventing centrifugal clutch comprising locking members 15, 14, 8 that are freely displaceable, and engaging portions 12, 16 that are removable. 2. The locking member is provided on the driving shaft side and includes a ball 15 and a spring 14, and the engaging portion is a recess 12 formed in the driven shaft 11. An anti-overload centrifugal clutch according to item 1. 3. The overload prevention centrifugal clutch according to claim 1, wherein the locking member is the shoe 8, and the engaging portion is a convex portion 16 formed on the inner surface of the outer ring 7. .