JPH04368456A - Permanent magnet type eddy current speed reducer - Google Patents

Abstract

PURPOSE:To see that it does not exert dragging torque on a braking disc during nonbraking by covering both sides of a magnet with ferromagnetic plates at all times. CONSTITUTION:A pair of braking discs 3 are coupled, leaving an axial interval, with a rotary shaft 2. A bed frame 4, which consists of a nonmagnetic substance and has a cavity whose section is box-shaped, is arranged between a pair of braking discs 3. Many ferromagnetic plates 6 are coupled at regular intervals in circumferential direction on both sidewalls of the fixed frame 4. Fixed magnets 7a and mobile magnets 7 rotatable around the axis in diametrical direction are supported, leaving circumferential intervals, between the ferromagnetic plates 6 on both sides. A bevel gear 23 is driven by a motor 21, whereby the direction of the magnetic field of each mobile magnet 7 is inverted together with the bevel gear 10 engaging with the bevel gear 23. If the direction of the magnetic field of each mobile magnet 7 is made the same as the fixed magnet 7a, the braking disc 3 is subjected to braking force, and if it is reversed, the control disc 3 is not subjected to braking force.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an eddy current reduction device that assists the friction brakes of large vehicles, and more particularly to a permanent magnet type eddy current reduction device that prevents leakage magnetic fields from reaching the brake disc when not braking. It is something.

0002

2. Description of the Related Art A permanent magnet type eddy current reduction device disclosed in Japanese Patent Application Laid-Open No. 1-298947 has a pair of brake discs connected to a rotating shaft with an axial distance between them. , an annular fixed frame made of non-magnetic material and having a box-shaped cavity in cross section is arranged, a large number of ferromagnetic plates are supported at equal intervals in the circumferential direction on both side walls of the fixed frame, and a strong magnetic plate is placed inside the fixed frame. It is constructed by rotatably supporting an annular magnet support frame having the same number of permanent magnets (hereinafter simply referred to as magnets) as the number of magnetic plates. When not braking, the ferromagnetic plate straddles circumferentially adjacent magnets, a short magnetic circuit is created between the adjacent magnets and the ferromagnetic plates on both sides, and no magnetic field is applied to the braking disc. During braking, when the magnet support frame is rotated by a half-pitch of the magnet array, each magnet is aligned between the ferromagnetic plates on both sides, and a gap is created between the circumferentially adjacent magnets, the ferromagnetic plates on both sides, and the braking disk. A magnetic circuit is created. When the rotating brake disc crosses the magnetic field, eddy currents flow through the brake disc and the brake disc experiences a braking torque.

However, in the above-mentioned permanent magnet type eddy current reduction device, since the entire surface of the magnet is not covered by the ferromagnetic plates on both sides when not braking, the leakage magnetic field of the magnet is caused by ferromagnetic plates arranged in the circumferential direction. Since it reaches the brake disc through the gap between the plates (fixed frame portion made of non-magnetic material), there is a problem in that the brake disc receives drag torque.

0004

[Problems to be Solved by the Invention] In view of the above-mentioned problems, the object of the present invention is to permanently cover both sides of the magnet with ferromagnetic plates so that no drag torque is applied to the brake disc when not braking. An object of the present invention is to provide a magnetic eddy current reduction device.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention has a configuration in which a pair of brake discs are connected to the rotating shaft with an axial distance therebetween, and a non-magnetic material is placed between the brake discs. A fixed frame with a box-shaped cross section is provided, and a large number of ferromagnetic plates are embedded in both side walls of the fixed frame at equal intervals in the circumferential direction. The fixed magnets are arranged so that the direction of the magnetic field applied perpendicularly to the braking disk alternately differs in the circumferential direction, and the magnetic field of the movable magnet of each ferromagnetic plate is The movable magnet is provided with a drive means for rotating the movable magnet to a braking position where the direction is the same as that of the fixed magnet and to a non-braking position opposite to the direction of the fixed magnet.

[0006]

[Operation] According to the present invention, a large number of ferromagnetic plates are embedded in both side walls of a fixed frame made of a non-magnetic material at equal intervals in the circumferential direction, and between each pair of ferromagnetic plates there is provided a movable magnet whose polarity with respect to the fixed magnet can be reversed. and. The fixed magnets are arranged so that the direction of the magnetic field exerted on the brake disc alternates in the circumferential direction.

When not braking, if the directions of the magnetic fields of the fixed magnet and the movable magnet with respect to the braking disk are reversed, a short magnetic circuit is created between each ferromagnetic plate, and the entire surface of the fixed magnet and the movable magnet becomes ferromagnetic. Since it is covered by the plate, the leakage magnetic field does not reach the brake disc. On the other hand, during braking, if the directions of the magnetic fields of the fixed magnet and the movable magnet with respect to the braking disk are the same, the gap between the pair of braking disks and the ferromagnetic plate containing the circumferentially adjacent fixed magnet and the movable magnet is A magnetic circuit is generated in the brake disc, an eddy current flows through the brake disc, and a braking torque is exerted on the brake disc.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front sectional view of a permanent magnet type eddy current reduction device according to the present invention, FIG. 2 is a side sectional view of the eddy current reduction device, and FIG. 3 is a circumferentially expanded view of the eddy current reduction device. FIG. A pair of left and right brake discs 3 are spline-coupled to a rotary shaft (such as an output shaft of a transmission) 2 with an axial distance between them, which transmits the rotation of the engine to the wheels. 5 supports the boss portion 16 of the fixed frame 4 made of a non-magnetic material. The fixed frame 4 is an annular member having a box-shaped hollow section, and is fixed to, for example, a wall of a transmission. The inner circumferential wall 4b of the fixed frame 4 and the boss portion 16 are coupled by a large number of spokes 15 arranged radially. The fixed frame 4 has a large number of openings at equal intervals in the circumferential direction on both side walls, and a ferromagnetic plate (pole piece) 6 is coupled to each opening.

As shown in FIGS. 2 and 3, each pair of ferromagnetic plates 6
Fixed magnet 7a and movable magnet 7 with a circumferential interval between them.
is supported. The fixed magnet 7 a and the movable magnet 7 exert a magnetic field in the axial direction of the rotary shaft 2 , that is, a magnetic field perpendicular to the brake disc 3 . The fixed magnets 7a are arranged so that their polarities are alternately reversed in the circumferential direction.

The movable magnet 7 having a circular or oval cross section is preferably disposed between arcuate depressions 6a provided in the inner wall surfaces of the ferromagnetic plates 6 on both sides. A shaft 8 extending in the radial direction of the brake disc 3 is coupled to a movable magnet 7 and supported by a bearing 9 on an outer circumferential wall 4a and an inner circumferential wall 4b of the fixed frame 4. axis 8
The bevel gear 10 coupled to the end of the outer peripheral wall 4a of the fixed frame 4
The bevel gear 12 rotates along a guide member 13 (FIG. 1) coupled to the bevel gear 12. Although shown in a simplified manner in FIG. 1, the fixed frame 4 has a pair of annular plate side walls formed by casting a ferromagnetic plate 6 from aluminum alloy or the like, and a cylindrical outer periphery on the pair of side walls. It is constructed by combining a wall 4a and an inner circumferential wall 4b.

Next, the operation of the permanent magnet type eddy current reduction device according to the present invention will be explained. As shown in FIG. 3, when the magnetic field of the movable magnet 7 between each pair of ferromagnetic plates 6 is reversed to that of the fixed magnet 7a during non-braking, the ferromagnetic plate 6 of each pair and the fixed magnet 7a A short magnetic circuit shown by a chain line is created between the movable magnet 7 and the brake disc 3, and no magnetic field is exerted on the brake disc 3. Since the fixed magnet 7a and the movable magnet 7 are covered by the pair of ferromagnetic plates 6, there is no leakage magnetic field exerted on the brake disc 3, and the brake disc 3 is not subjected to any drag torque.

As shown in FIG. 4, when the electric motor 21 rotates the bevel gear 23 during braking, the movable magnet 7 rotates by half a rotation together with each bevel gear 10 meshing with the bevel gear 23. At this time,
The fixed magnet 7a and the movable magnet 7 sandwiched between each pair of ferromagnetic plates 6 have the same magnetic field direction, and the entire magnet acts as one magnet. The directions of the magnetic fields passing through the circumferentially adjacent ferromagnetic plates 6 are opposite to each other and extend to the brake disk 3, forming a magnetic circuit shown by a chain line. When the rotating brake disc 3 crosses the magnetic fields from the fixed magnet 7a and the movable magnet 7, an eddy current flows through the brake disc 3, and the brake disc 3 receives a braking torque.

[0013]

Effects of the Invention As described above, the present invention connects a pair of brake discs with an axial distance between them on a rotating shaft, and arranges a fixed frame having a box-shaped cross section made of a non-magnetic material between the brake discs. A large number of ferromagnetic plates are embedded in both walls of a fixed frame at equal intervals in the circumferential direction, and a movable structure that can rotate around a fixed magnet and a radial axis is provided with a circumferential interval between each ferromagnetic plate on both sides. The fixed magnets are arranged so that the direction of the magnetic field applied perpendicularly to the braking disk is alternately different in the circumferential direction, and the direction of the magnetic field of the movable magnet of each ferromagnetic plate is at the same braking position as that of the fixed magnet. It is equipped with a driving means for rotating the movable magnet in the opposite non-braking position, and since each set of movable magnet and fixed magnet is covered entirely by ferromagnetic plates on both sides, the movable magnet and the fixed magnet are separated when not braking. If the directions of the magnetic fields of the magnets are reversed, a short-circuit magnetic circuit will occur between the ferromagnetic plates on both sides, and the leakage magnetic field will not reach the braking disk.
The brake disc is not subjected to any drag torque.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of a permanent magnet type eddy current reduction device according to the present invention.

FIG. 2 is a side sectional view of the eddy current reduction device.

FIG. 3 is a plan cross-sectional view developed in the circumferential direction of the eddy current reduction device in a non-braking state.

FIG. 4 is a plan cross-sectional view showing the braking state of the eddy current reduction device expanded in the circumferential direction.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A pair of brake discs are coupled to a rotating shaft with an axial distance therebetween, a fixed frame having a box-shaped cross section made of a non-magnetic material is disposed between the brake discs, and both side walls of the fixed frame are provided. A large number of ferromagnetic plates are buried at equal intervals in the circumferential direction, and a fixed magnet and a movable magnet that can be rotated around a radial axis are supported with a circumferential interval between each ferromagnetic plate on both sides. are arranged so that the direction of the magnetic field applied perpendicularly to the braking disk is alternately different in the circumferential direction, and the direction of the magnetic field of the movable magnet of each ferromagnetic plate is movable between the same braking position as the fixed magnet and the opposite non-braking position. A permanent magnet type eddy current reduction device characterized by comprising a drive means for rotating a magnet.