JPH05284723A - Eddy current type reduction gear - Google Patents

Abstract

PURPOSE:To dissolve the dragging torque of a braking disc by leaked magnetic field by separating each magnet and a braking disc in braking thereby weakening the leaked magnetic magnetic flux. CONSTITUTION:A circular fixed frame 5, which has a hollow part oblong in cross section, is arranged between a pair of braking discs 3 coupled with a rotary shaft 2. Many ferromagnetic plates 6 are coupled, at equal intervals in circumferential direction, with both end walls of the fixed frame 5 opposed to the braking disc 3. A circular magnet supporting frame 15 consisting of a nonmagnetic substance is arranged rotatably inside the hollow part of the fixed frame 5. A permanent magnet 12, wherein the polarities facing to each ferromagnetic plate 6 are different alternately, is coupled to the magnet supporting frame 15. Grooves 12a extending in radial directions are provided at the center parts in circumferential directions of both the end faces opposed to the ferromagnetic plate 6 of the permanent magnet 12. Rotating means for rotating magnet supporting frames 15 are equipped in the position where the permanent magnet 12 is extensively opposed to each ferromagnetic plate 6 and in the position where it is astride a pair of ferromagnetic plates 6 adjacent in circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current type speed reducer for assisting a friction brake of a vehicle, and more particularly to an eddy current in which a non-braking permanent magnet (hereinafter simply referred to as a magnet) reduces a leakage magnetic field exerted on a braking disc. Type speed reducer.

[0002]

2. Description of the Related Art In an eddy current type speed reducer disclosed in Japanese Patent Application Laid-Open No. 1-298947, a fixed frame having a rectangular inner cross section is disposed between a pair of left and right braking discs. Ferromagnetic plates are connected to a large number of openings provided at equal intervals in the circumferential direction on both end walls of the, and a magnet support frame that supports magnets that entirely face each ferromagnetic plate is rotatable in the inner space of the fixed frame. Supported by. The magnets are arranged so that their polarities with respect to the ferromagnetic plate are alternately different in the circumferential direction.

When the magnet is entirely opposed to the ferromagnetic plate, 1
A magnetic circuit is generated from one magnet to a ferromagnetic material, a braking disc, an adjacent ferromagnetic plate, and an adjacent magnet, and when the rotating braking disc crosses the magnetic field, braking torque is generated by the eddy current in the braking disc. To do. When the magnet support frame is rotated by half of the magnet arrangement pitch, the ferromagnetic plates face each other across a pair of adjacent magnets. A short circuit magnetic circuit occurs between a pair of adjacent magnets and the ferromagnetic plate, and the braking disc does not receive braking torque. However, since the central portion in the circumferential direction of each magnet exerts a leakage magnetic field on the braking disc through the space between the adjacent ferromagnetic plates, there is a problem that the braking disc receives drag torque (see the leakage magnetic circuit W in FIG. 3). ).

[0004]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to weaken the leakage magnetic field by separating the magnets and the braking disc from each other during non-braking, and to reduce the braking disc due to the leakage magnetic field. An object of the present invention is to provide an eddy current type speed reducer that eliminates drag torque.

[0005]

In order to achieve the above object, the structure of the present invention is such that an annular fixing frame having an inner space having a rectangular cross section is arranged between a pair of braking disks connected to a rotating shaft. , A large number of ferromagnetic plates are connected at equal intervals in the circumferential direction to both end walls of the fixed frame facing the braking disc, and an annular magnet support frame made of a non-magnetic material is rotatably arranged in the inner space of the fixed frame. A permanent magnet, which is opposite to each ferromagnetic plate and has different polarities in the circumferential direction, is alternately connected to the magnet supporting frame, and a groove extending in the radial direction is formed in the circumferential center portion of both end faces of the permanent magnet facing the ferromagnetic plate. And a rotating means for rotating the magnet support frame at a position where the permanent magnets are entirely opposed to the ferromagnetic plates and a position where the permanent magnets straddle a pair of circumferentially adjacent ferromagnetic plates. ..

[0006]

According to the present invention, the gap between the magnet and the braking disc is widened by providing a deep groove extending in the radial direction in the circumferential center portion of both end faces of each magnet. At the time of non-braking, the central portions in the circumferential direction of both end faces of each magnet do not face the ferromagnetic plate, and a leakage magnetic field is exerted from between a pair of circumferentially adjacent ferromagnetic plates to the braking disc. Since the gap between the and is remoted by the groove, the leakage magnetic field becomes very weak, and the drag torque of the braking disc is eliminated.

[0007]

1 is a front sectional view of an eddy current type speed reducer according to the present invention, and FIG. 2 is a side sectional view of a magnet support frame of the speed reducer. The eddy current type speed reducer according to the present invention is disposed between a pair of braking discs 3 and a pair of braking discs 3 made of a conductor coupled to an output rotary shaft 2 of a vehicle transmission, for example. It is composed of a fixed frame 5 made of a non-magnetic material and a magnet support frame 15 housed in the inner space of the fixed frame 5. The braking disc 3 is provided with a cooling fin 3b on its outer surface, the boss portion 3a is connected to the rotary shaft 2 by a spline 2a, and the pair of stop rings 2b fitted to the rotary shaft 2 prevent axial movement. It

The fixed frame 5 has an outer cylinder 5a and an inner cylinder 5b, and annular end plates 5c are connected to both ends of the fixed cylinder 5 to form an inner hollow portion having a rectangular cross section. Both end plates 5c of the fixed frame 5 are provided with a large number of fan-shaped openings at equal intervals in the circumferential direction, and a ferromagnetic plate (pole piece) 6 is coupled to each opening. Actually, when the end plate 5c is cast from aluminum or the like, the ferromagnetic plate 6 is cast and integrally formed.

According to the present invention, the magnet support frame 15 made of a non-magnetic material is rotatably supported by the inner cylinder 5b of the fixed frame 5 by the bearing 18. As shown in FIG. 2, the magnet support frame 15
A magnet 12 facing each ferromagnetic plate 6 and having the same outer shape as the ferromagnetic plate 6 is coupled to the inner surface of the outer cylinder 15a. The magnet 12 is sandwiched between a large number of partition walls 15b which are integrated with the outer cylinder 15a and are arranged at equal intervals in the circumferential direction.

As shown in FIGS. 2 and 3, a relatively deep notch or groove 12a extending in the radial direction is formed in the central portion in the circumferential direction of both end faces of each magnet 12, that is, the end faces which can face the ferromagnetic plate 6. The groove 12a allows the inner surface of the braking disc 3 and the magnet 12
It is remoted from the central part of the. Although the cross-sectional shape of the groove 12a may be rectangular, it is semicircular in consideration of the strength of the magnet 12.

As shown in FIG. 1, a partial gear 15c is formed on the outer surface of the outer cylinder 15a in order to rotate the magnet support frame 15 forward and backward by half the arrangement pitch of the magnets 12.
The gear 19 meshing with c is supported by the opening of the outer cylinder 5a of the fixed frame 5, and the gear 19 is driven by the electric motor 20 with a brake.

Next, the operation of the eddy current type speed reducer according to the present invention will be described. As shown in FIG. 3, during non-braking, the magnets 12 face each other across a pair of circumferentially adjacent ferromagnetic plates 6, and a short-circuit magnetic circuit is provided between each magnet and the pair of ferromagnetic plates 6. Y occurs and the braking disc 3 receives no braking torque.

At this time, the central portion of the magnet 12 faces between the pair of ferromagnetic plates 6 and faces the braking disc 3. However, the magnet 12 has a groove 12a in the central portion of both end surfaces,
Since the distance between and the braking disc 3 is widened, the magnet 12
The strength of the leakage magnetic field exerted on the braking disc 3 via the end plate 5c of the fixed frame 5 is extremely weak, and drag torque is not exerted on the braking disc 3.

As shown in FIG. 4, when braking, the motor 20 rotates the magnet support frame 15 by half the pitch of the magnets 12, so that the magnets 12 are entirely opposed to the ferromagnetic plates 6. And lined up with alternating polarities in the circumferential direction 1
The pair of magnets 12 has a magnetic circuit X between the pair of braking disks 3 and the pair of magnets 12.
Exert. Therefore, when the rotating braking disc 3 crosses the magnetic field, an eddy current flows in the braking disc 3 and the braking disc 3 receives a braking torque.

[0015]

As described above, according to the present invention, since the deep groove in the radial direction is provided in the circumferential center portion of the end surface of each magnet supported by the magnet support frame, the magnet structure is very simple. The braking disc and the circumferential central portion of the end face of the magnet are remoted. Therefore, even when the central portion in the circumferential direction of the end surface of the magnet during non-braking is magnetically opposed to the braking disc 3 between the pair of adjacent ferromagnetic plates, the magnetic field exerted by the magnet on the braking disc is Becomes very weak and does not exert drag torque on the braking disc.

At the time of braking, both end portions of the magnet in the circumferential direction oppose and approach the braking disc or the ferromagnetic plate and exert a strong magnetic field on the braking disc. Therefore, even if a deep groove is provided in the circumferential central portion of each magnet, It has little effect on braking ability.

[Brief description of drawings]

FIG. 1 is a front sectional view of an eddy current type speed reducer according to the present invention.

FIG. 2 is a side sectional view of a magnet support frame of the eddy current type speed reducer.

FIG. 3 is a plan sectional view showing a braking state of the eddy current type reduction gear transmission in a circumferential direction.

FIG. 4 is a plan sectional view showing a non-braking state of the eddy current type speed reducer developed in the circumferential direction.

[Explanation of symbols]

2: rotating shaft 3: braking disc 5: fixed frame 6: ferromagnetic plate 12: permanent magnet 12a: groove 15: magnet support frame

Claims (1)

[Claims] 1. An annular fixed frame having an inner space with a rectangular cross section is disposed between a pair of braking discs connected to a rotating shaft, and both end walls of the fixing frame facing the braking disc are equally spaced in the circumferential direction. A large number of ferromagnetic plates are coupled to the fixed frame, and a ring-shaped magnet support frame made of a non-magnetic material is rotatably arranged in the inner space of the fixed frame. Different permanent magnets are coupled alternately in the direction, and a groove extending in the radial direction is provided in the circumferential center part of both end faces facing the ferromagnetic plate of the permanent magnet, and the permanent magnet is entirely opposed to each ferromagnetic plate. 1 adjacent to
An eddy current type speed reducer comprising a rotating means for rotating the magnet support frame at a position where it extends over a pair of ferromagnetic plates.