JPH04368457A - 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 skies 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 fixed 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 17 and mobile magnets 7 rotatable around the axis in diametrical direction are arranged one over the other between the ferromagnetic plates 6 on both sides. A bevel gear 12 is driven by a motor, 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 12. If the direction of the magnetic field of each mobile magnet 7 is made the same as the fixed magnet 17, 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

BACKGROUND OF THE INVENTION 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 therebetween. , 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 as magnetic plates (hereinafter simply referred to as magnets). 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 half a pitch of the magnet array, each magnet is aligned between the ferromagnetic plates on both sides, and the circumferentially adjacent magnet is placed between 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, when not braking, the entire sides of the magnet are not covered by the ferromagnetic plates on both sides. Since it reaches the brake disc through the gap between the magnetic 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, an object of the present invention is to always cover both sides of the magnet with ferromagnetic plates so that no drag torque is applied to the brake disk when not braking. An object of the present invention is to provide a permanent magnet type 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 installed, and a large number of ferromagnetic plates are embedded in both side walls of the fixed frame at equal intervals in the circumferential direction, and between each pair of ferromagnetic plates there is a fixed magnet that rotates around the radial axis. The fixed magnets are arranged so that the direction of the magnetic field exerted on the braking disk alternately differs in the circumferential direction, and the magnetic field of the movable magnet of each pair of ferromagnetic plates is The movable magnet is provided with a drive means for rotating the movable magnet to a braking position in which the direction is the same as that of the fixed magnet and to a non-braking position in the opposite direction.

[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 a movable magnet whose polarity can be reversed from that of the fixed magnet. and are arranged so as to overlap in the radial direction. The fixed magnets are arranged so that the direction of the magnetic field relative to 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 pair of ferromagnetic plates, and the entire surfaces of both sides of the fixed magnet and the movable magnet are Since it is covered with a ferromagnetic plate, the leakage magnetic field does not reach the brake disc. On the other hand, during braking, if the direction of the magnetic field of the fixed magnet and the movable magnet between each pair of ferromagnetic plates with respect to the braking disk is the same, the fixed magnet and the movable magnet adjacent to the pair of braking disks in the circumferential direction will be included. A magnetic circuit is created between the ferromagnetic plate and an eddy current flows through the brake disc, exerting a braking torque 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 coupled to a rotary shaft (such as an output shaft of a transmission) 2, which transmits engine rotation to wheels, with an axial distance therebetween. In particular, the pair of brake discs 3 are formed as a rim 1 with a U-shaped cross section separated by a groove 22 . The rim 1 has a boss portion 16 connected to the rotating shaft 2.
The spokes 15 are connected to spokes 15 that extend radially from the base.

A fixed frame 4 made of a non-magnetic material is disposed between the brake discs 3, that is, inside the grooves 22. The fixed frame 4 is an annular member having a hollow portion 18 having a box-shaped or trapezoidal cross section, and is fixed to, for example, a wall of a transmission. The empty space 18 is partitioned by partition walls 4d (FIG. 3) arranged at equal intervals in the circumferential direction. A side wall defining each cavity 18 is provided with an opening 4c, and a ferromagnetic plate (pole piece) 6 is coupled to the opening 4c.

As shown in FIG. 2, between each pair of ferromagnetic plates 6 having a box-shaped cross section of the fixed frame 4, a pair of truncated conical fixed magnets 17 and a movable magnet 7 are arranged with a gap in the radial direction. are superimposed on each other. The fixed magnet 17 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. As shown in FIG. 3, the fixed magnets 17 are arranged so that their polarities are alternately reversed in the circumferential direction. Preferably, the movable magnet 7 is disposed between arc-shaped depressions 6a provided in the inner wall surfaces of the ferromagnetic plates 6 on both sides. As shown in FIG. 1, a shaft 8 extending in the radial direction of the brake disc 3 is coupled to the movable magnet 7 and rotatably supported by the outer peripheral wall 4a of the fixed frame 4. A bevel gear 10 coupled to an end of the shaft 8 is meshed with a bevel gear 12 rotatably supported on the outer peripheral wall 4a of the fixed frame 4. The bevel gear 12 is rotationally driven by an electric motor (not shown) and constitutes a driving means for reversing the direction of the magnetic field of each movable magnet 7.

As shown in FIG. 1 in a simplified manner, the fixed frame 4
When casting an annular plate that is thin on the outer circumferential side and thick on the inner circumferential side from aluminum alloy or the like, a ferromagnetic plate 6 is cast, and a cylindrical outer circumferential wall 4a and an inner circumferential wall 4b are joined to a pair of annular plates as side walls. configured.

Next, the operation of the permanent magnet type eddy current reduction device according to the present invention will be explained. As shown in Figures 1 and 2,
During non-braking, if the direction of the magnetic field of the movable magnet 7 between each pair of ferromagnetic plates 6 is opposite to that of the fixed magnet 17, a magnetic field between each pair of ferromagnetic plates 6, fixed magnet 17, and movable magnet 7 is created. , a short-circuit magnetic circuit is created, which is shown in dashed lines in FIG. 1, and no magnetic field is exerted on the brake disk 3. Since the fixed magnet 17 and the movable magnet 7 are covered on both sides by a 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 drag torque.

As shown in FIGS. 3 and 4, when the bevel gear 12 is rotated by an electric motor (not shown) during braking, the bevel gear 10
At the same time, the movable magnet 7 rotates half a rotation. At this time, the directions of the magnetic fields of the fixed magnet 17 and the movable magnet 7 sandwiched between each pair of ferromagnetic plates 6 become the same, and the whole works as one magnet. The directions of the magnetic fields passing through circumferentially adjacent ferromagnetic plates 6 and reaching the brake disk 3 are opposite to each other, forming a magnetic circuit shown by chain lines in FIG. When the rotating brake disc 3 crosses the magnetic fields from the fixed magnet 17 and the movable magnet 7, eddy currents flow through the brake disc 3 and the brake disc 3 receives a braking torque.

[0014]

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 fixed magnet and a movable magnet that can rotate around a radial axis are stacked radially between each pair of ferromagnetic plates. The fixed magnets are arranged so that the direction of the magnetic field applied to the braking disk alternately differs in the circumferential direction, and the direction of the magnetic field of the movable magnet of each pair of ferromagnetic plates is the same as that of the fixed magnet and opposite to the braking position. It is equipped with a driving means for rotating the movable magnet at the non-braking position, and when the braking is not performed, by reversing the directions of the magnetic fields of each set of movable magnet and fixed magnet with respect to the braking disc, the strength on both sides can be reduced. A short magnetic circuit is created between the brake disc and the magnetic plate, and no magnetic field is applied to the brake disc. In particular, since each set of movable magnet and fixed magnet is covered on both sides by ferromagnetic plates on both sides, no leakage magnetic field is exerted on the braking disc, and therefore the braking disc is not subjected to drag torque. .

[Brief explanation of the drawing]

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

FIG. 2 is a side cross-sectional view showing the eddy current reduction device in a non-braking state.

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

FIG. 4 is a side sectional view showing a braking state of the eddy current reduction device.

[Explanation of symbols]

2: Rotating shaft 3: Braking disk 4: Fixed frame 6: Ferromagnetic plate 7: Movable magnet 7a: Fixed magnet

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 embedded at equal intervals in the circumferential direction, and between each pair of ferromagnetic plates, a fixed magnet and a movable magnet that can be rotated around a radial axis are stacked and supported in the radial direction. The movable magnets are arranged so that the directions of the magnetic fields exerted on the braking disks are alternately different in the circumferential direction, and the movable magnets of each pair of ferromagnetic plates are arranged in a braking position where the direction of the magnetic field of the movable magnets is the same as that of the fixed magnets and in a non-braking position opposite to that of the fixed magnets. A permanent magnet type eddy current reduction device, characterized in that it is equipped with a driving means for rotating.