JPH0823374B2 - Clutch device - Google Patents

Description

The present invention relates to a clutch device, and more particularly to a clutch device for an electric power steering device.

[Conventional technology and its problems]

A general configuration of the electric power steering device is shown in FIG. In this device, when the handle 20 is rotated to the right or left, torque is generated on the handle shaft 22 due to resistance from the wheels 21. This torque is detected by the sensor 23 provided on the handle shaft 22, and the motor 25 is driven through the control device 24. The drive shaft of the motor 25 is the handle shaft via the speed reducer 26.
A rack 28 that is connected to and meshes with 22 pinions 27
The wheels 21 are steered via the. As a result, the wheels can be steered with a slight steering wheel operating force.

However, in such an electric power steering device, when an abnormality occurs in the drive system including the control device 24, the motor 25 and the speed reducer 26, and these do not operate, the speed reducer 26 and the motor 25 are attached to the handle shaft 22. However, there is a problem in that the steering wheel manual operation force becomes excessive and steering becomes substantially impossible.

Therefore, a method is known in which a clutch device 29 is interposed between the speed reducer 26 and the pinion gear 27. An electromagnetic clutch can be used as the clutch device 29 in this case, but it has a drawback that it is large in size to obtain a required transmission torque. Further, when the meshing clutch is used, there is a problem that a large force is required for aligning the meshing and releasing the meshing under load.

[Means to solve the problem and its action]

In order to solve the above-mentioned problems, the present invention makes the respective ends of a drive shaft and a driven shaft arranged on the same axis line face each other,
An inner ring member is provided at one end, and a cup-shaped outer ring end that fits on the outer circumference of the inner ring member is provided at the other end, and the opposing surface of any one of the above members is equally divided in the circumferential direction. Is
And a wedge surface having a wedge angle β in the circumferential direction with a small interval in both the forward and reverse rotations, and an axis with a small interval in the depth direction of the outer ring member between each of the wedge surfaces and the facing surface. Direction wedge angle α is formed, and a sphere is interposed between each of the above-mentioned wedge surfaces and the opposing surface thereof, and the above-mentioned wedge angle α is set to be larger than the friction angle of both members of the sphere, and the outer circumference of the outer ring member is set. The outer ring member with a pressing member that covers the outer surface and the end surface on the closing side and a pressing plate that covers the other end surface on the opening side, and a spring is interposed between the case portion and the closing end surface of the outer ring member. The elastic member presses the pressing plate against the spherical body, and an electromagnet that overcomes the elastic force of the spring and attracts the pressing member in the direction of returning the pressing member is provided in the device fixing portion in front of the pressing plate.

[Action]

In the clutch device configured as described above, when the electromagnet is not excited, the spherical body is pushed by the elastic force of the spring acting on the pressing member, and the spherical body is formed in the gap having the axial wedge angle α and the circumferential wedge angle β. The clutch engages to form a wedge action and the clutch is engaged, and torque is transmitted in both forward and reverse directions.

When the electromagnet is excited and the pressing member is pulled back, the pressing plate separates from the sphere. Since the axial wedge angle α is set to be larger than the friction angle of the spherical body, the spherical body is disengaged from between the two members and the clutch is disengaged.

〔Example〕

In the clutch device of the embodiment shown in FIGS. 1 to 3, the drive shaft 1 and the driven shaft 2 are arranged on the same axis, and the drive shaft 1
The inner ring member 3 is provided at the end of the inner ring member 3, the cup-shaped outer ring member 4 is provided at the end of the driven shaft 2, and the outer ring member 4 is fitted to the outer periphery of the inner ring member 3. The annular gap a formed between the members 3 and 4 is opened on the drive shaft 1 side.

On the outer peripheral surface of the inner ring member 3, as shown in FIG. 2, a wedge surface 7 that is equally divided in the circumferential direction is formed. In the illustrated case, the wedge surface 7 has a concave arc shape in cross section,
It is formed so as to have a constant circumferential wedge angle β in both the forward and reverse directions with the circumferential surface of the outer ring member 4.

Further, the wedge surface 7 is formed in a taper shape in the axial direction so as to approach the inner peripheral surface 6 of the outer ring member 4 toward the tip of the inner ring member 3, as shown in FIG. 1, and the inner peripheral surface 6 thereof. Is formed so as to come closer to the wedge surface 7 as far as it goes to the depth, and has a constant axial wedge angle α that reduces the distance in the depth direction of the fitting of both members 3 and 4 by both facing surfaces. Has been formed.

A pressing member 8 is attached to the outer ring member 4. The pressing member 8 includes a case portion 8a that covers the outer peripheral surface of the outer ring member 4 and the end surface on the closing side (driven shaft 2 side) thereof.
It is composed of an annular holding plate 8b made of a magnetic material that covers the open side of the gap a, and a wave spring 8c interposed between the open side end faces of the case portion 8a and the outer ring member 4. Presser plate
8b is fitted around the drive shaft 1 with some clearance, and contacts the sphere 5 at the open end of the gap a. In a normal state, the spherical body 5 is pushed in the axial direction by the elastic force of the wave spring 8c.

An annular electromagnet 10 is provided around the drive shaft 1 on the device fixing portion 9 so as to face the pressing plate 8b. The electromagnet 10 is energized only when the clutch is disengaged, that is, when torque is not transmitted.

By the way, the relationship between the wedge angle α, the elasticity of the wave spring 8c and the magnitude of the attraction force of the electromagnet 10 is set as follows. That is, as shown in FIG. 3, the force F of the spherical body 5 inserted between the inner ring member 3 and the outer ring member 4 in the withdrawal direction is
Component force 2P of load P acting on sphere 5 in proportion to the transmission torque
It is the difference between sin α / 2 and the component force 2Pμcosα / 2 of the friction reaction force (μ is the friction coefficient) and is expressed by the following equation.

F = 2P (sinα / 2-μcosα / 2) Here, the sphere 5 is ejected when F> 0, and is retained when F <0. The limit is F = 0, that is sin α / 2 / co
This is the case of sα / 2 = tanα / 2 = μ, and the wedge angle α at this time is referred to as a friction angle. The wedge angle α is set to be slightly larger than the friction angle, and the elastic force of the wave spring 8c is set to be slightly larger than the force F in the pulling direction when the maximum transmission torque acts. Further, the attractive force of the electromagnet 10 is set to be slightly larger than the elastic force of the wave spring 8c.

Therefore, when the electromagnet 10 is excited, when the holding plate 8b and the case portion 8a integral with the holding plate 8b are pulled back by the attraction force, the spherical body 5 is pulled out of the wedge surface by the pulling force F and the clutch is disengaged. When the electromagnet 10 is non-excited, the spherical body 5 causes the force F of the corrugated spring 8c acting on the holding plate 8b to be removed.
It is pushed in by greater elasticity.

The embodiment of the present invention is as described above, and is used by connecting the drive shaft 1 to the speed reducer 26 side and the driven shaft 2 to the pinion 27 side like the clutch device 29 in FIG. The lead wire of the electromagnet 10 is connected to the abnormality detection signal generator of the control device 24.

Since the electromagnet 10 is not excited in the normal state, the sphere 5
Is pressed by the presser plate 8b and has a wedge action by the axial wedge angle α, and has a wedge action by the circumferential wedge β in both the forward and reverse directions in the circumferential direction, and the clutch is in the engaged state (engaged state). ), Motor 25
Torque is transmitted between the steering wheel shaft 22 and the handle shaft 22.

When a failure of the drive system such as the motor 25 or other abnormality occurs, the electromagnet 10 is excited. As a result, the pressing plate 8b is sucked, so that the pressing member 8 moves against the elastic force of the wave spring 8c. When the holding plate 8b separates from the sphere 5, the sphere 5 overcomes the frictional resistance and is pushed out by the above-mentioned pulling force F, and the clutch is disengaged. This separates the drive system such as the motor 25 from the handle shaft 22.

In the above embodiment, the wedge surface 7 is formed on the outer periphery of the inner ring member 3, and the wedge surface 7 restrains the relative movement of the spherical body 5 and the inner ring member 3 in the rotational direction. No. 5 is in an unrestrained state. However, contrary to the above, the wedge surface 7 is formed on the inner circumference of the outer ring member 4,
The outer ring member 4 and the spherical body 5 may be constrained, and the spherical body 5 and the inner ring member 3 may be configured to be in a non-constrained state. Further, the pressing plate 8b may be attached to the inner ring member 3 or the drive shaft 1 side by giving a predetermined elasticity.

〔The invention's effect〕

Since the present invention is as described above, it has the following effects.

When the drive system is normal, the spherical force is pushed by the elastic force of the pressing member so that the clutch is engaged and the torque is surely transmitted in both forward and reverse directions.

By appropriately selecting the wedge angle between the inner ring member and the outer ring member, the elastic force of the pressing member and the attractive force of the electromagnet can be set to a small value, and when an abnormality occurs, the clutch is disengaged by the operation of the small and small capacity electromagnet. You can

Normally, the elastic force of the pressing member assists torque transmission, and it suffices to energize the small-capacity electromagnet only when an abnormality occurs, so that power consumption can be reduced.

Since the wear of the sphere is hardly a problem, the structure for the wear compensation is not necessary and the structure is simplified. Therefore, compared with a general friction clutch, the number of parts is small and the size can be reduced, and a large force is not required for aligning the engagement and releasing the engagement unlike the engagement clutch, and the clutch can be smoothly engaged and disengaged.

[Brief description of drawings]

1 is a longitudinal side view of an embodiment, FIG. 2 is a sectional view taken along line II-II of the same as FIG. 2, FIG. 3 is an explanatory view of a force relation of the same, and FIG. . 1 ... driving shaft, 2 ... driven shaft, 3 ... inner ring member, 4 ... outer ring member, 5 ... sphere, 6 ... inner peripheral surface, 7 ... wedge surface, 8 ... pressing member, 8a ...... Case, 8b ...... Presser plate, 8c ...... Wave spring, 9 ...... Fixed part, 10 ...... Electromagnet.

Claims (1)

[Claims] 1. A driving shaft and a driven shaft, which are arranged on the same axis, are made to face each other at their respective ends, and one of the ends is provided with an inner ring member,
The other end is provided with a cup-shaped outer ring end fitted to the outer periphery of the inner ring member, and on the facing surface of one of the above members,
A wedge surface is formed which is equally divided in the circumferential direction and has a circumferential wedge angle β with a small interval in both the forward and reverse rotations, and the depth of the outer ring member is provided between each wedge surface and the facing surface. Form an axial wedge angle α that reduces the distance in the direction, and insert a sphere between each wedge surface and its opposing surface, and set the wedge angle α to be larger than the friction angle of the sphere to both members. Then, the outer ring member is covered with a holding member consisting of a case portion covering the outer peripheral surface and the closing side end surface of the outer ring member and a pressing plate covering the other open side end surface, and the case portion and the closing side end surface of the outer ring member. A spring is interposed between the pressing plate and the pressing plate against the spherical body by its elasticity, and an electromagnet for overcoming the elasticity of the spring to attract the pressing member in the direction to pull back the pressing plate is provided in the device fixing part in front of the pressing plate. Become a clutch device.