JPH0638505A - Eddy current speed reduction device - Google Patents

Abstract

PURPOSE:To suppress the concentration of magnetic flux at the front end of a ferromagnetic plate and raise braking efficiency by changing the shape of the sectional form of the ferromagnetic plate. CONSTITUTION:A hollow guide tube 10 box-shaped in cross section is arranged inside a braking drum 7. A magnet supporting tube 14, where many permanent magnets 24 are arranged so that the polarities may be alternate in circumferential direction in opposition to the inside periphery of the braking drum 7, is supported rotatably inside the fixed tube 10. A ferromagnetic plate 15 opposite to each permanent magnet 24 of the magnet supporting tube 14 is buried in the peripheral wall 10a of the fixed tube 10. The ferromagnetic plate 15 projects its outer peripheral section at the rear end in the direction of the rotation of a braking drum 7 rearward in the direction of the rotation of the rotation of the braking drum 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an eddy current type speed reducer for assisting a friction brake of a large-sized vehicle, and more particularly to a large number of permanent magnets arranged at equal intervals in a circumferential direction on an inner peripheral surface of a braking drum and a magnet supporting cylinder ( (Hereinafter, simply referred to as a magnet) The present invention relates to an eddy current type speed reducer that switches between braking and non-braking by changing the rotational phase of a ferromagnetic plate interposed between the ferromagnetic plate and the magnet supporting cylinder in the axial direction. .

[0002]

2. Description of the Related Art In an eddy current type speed reducer disclosed in Japanese Patent Application Laid-Open No. 1-298948, a fixed cylinder having a box-shaped cross section made of a non-magnetic material is arranged inside a braking drum, and an outer peripheral wall of the fixed cylinder is provided. A large number of ferromagnetic plates (pole pieces) are connected at equal intervals in the circumferential direction, and magnets that face each ferromagnetic plate are connected to a magnet support cylinder that is rotatably supported in the inner space of a fixed cylinder, thus supporting the magnet. Braking and non-braking are switched by changing the rotation phase of the cylinder only by the half-arranged pitch of the ferromagnetic plate.

As shown in FIG. 5, in the above-mentioned eddy current type speed reducer, the magnets 24 of the magnet supporting cylinder 14 have the same arrangement pitch as the ferromagnetic plate 15, and the polarities with respect to the ferromagnetic plate 15 are alternately arranged in the circumferential direction. They are arranged side by side so that they are different. In order to protect the magnet 24 from the environment such as external heat, water and dust, the magnet 24 is sealed in the inner space of the fixed cylinder 10 having a rectangular cross section, which is made of a non-magnetic material. During braking, the magnet 24 is attached to the outer peripheral wall 1 of the fixed barrel 10.
A magnetic circuit (indicated by line 26) is formed between the rotating drum 7 and the rotating braking drum 7 via the ferromagnetic plate 0a.
Exert braking force on. When the braking drum 7 is rotating, when a large amount of magnetic flux generated from the magnet 24 reaches the braking drum 7 through the ferromagnetic plate 15, a repulsive magnetic field based on an eddy current generated inside the braking drum 7 causes a magnetic circuit. Is distorted to be dragged in the rotation direction of the braking drum 7 (direction of arrow x). The above-mentioned distortion of the magnetic circuit becomes stronger as the rotation speed of the braking drum 7 becomes higher. That is, the braking drum 7 is indicated by the arrow x
When rotating in the direction, the magnetic flux density from the magnet 24 becomes thin at the front end of the ferromagnetic plate 15 (the front end in the rotating direction of the braking drum 7), and a part of the magnetic flux is fixed to couple the ferromagnetic plate 15. It reaches the braking drum 7 via the outer peripheral wall 10 a of the cylinder 10.

[0004]

As described above, the concentration of magnetic flux on the front end of the ferromagnetic plate causes magnetic saturation and weakens the magnetic field reaching the braking drum, resulting in a reduction in braking force. In view of the above problems, an object of the present invention is to provide an eddy current type speed reducer that changes the cross-sectional shape of a ferromagnetic plate to suppress the concentration of magnetic flux at the front end portion of the ferromagnetic plate and enhances braking efficiency. is there.

[0005]

In order to achieve the above object, in the structure of the present invention, a fixed cylinder having an inner hollow portion having a rectangular cross section is arranged inside a braking drum and fixed to the inner hollow portion of the fixed barrel. A magnet supporting cylinder in which a large number of permanent magnets are arranged so that the polarities opposed to the outer peripheral wall of the cylinder are alternately different in the circumferential direction is rotatably supported, and the outer peripheral wall of the fixed cylinder opposes each permanent magnet of the magnet supporting cylinder. The ferromagnetic plate is embedded, and the ferromagnetic plate is formed by projecting the outer peripheral side portion of the rear end portion in the rotation direction of the braking drum to the rear side in the rotation direction of the braking drum.

[0006]

In the present invention, the outer peripheral portion of the rear end of the ferromagnetic plate is
It projects rearward in the direction of rotation of the braking drum. Therefore, the braking drum magnetized on the front end side of the ferromagnetic plate will apply a magnetic field to the rear end of the magnet adjacent to the front side as the brake drum rotates,
As a result, the magnetic circuit is biased to the rear end of the ferromagnetic plate, that is, rearward in the rotation direction of the braking drum, and the magnetic flux concentration on the front end of the ferromagnetic plate is suppressed. In other words, the saturation of the magnetism (magnetic flux density) at the front end of the ferromagnetic plate is suppressed, so that an efficient magnetic circuit without magnetic saturation is generated between the magnet support cylinder and the braking drum, and the braking efficiency is increased. .

[0007]

1 is a side sectional view of an eddy current type speed reducer according to the present invention, and FIG. 2 is a front sectional view of the same. The eddy current type speed reducer according to the present invention includes, for example, a braking drum 7 formed of a conductor coupled to the output rotary shaft 1 of a vehicle transmission, and a braking drum 7.
A fixed cylinder 10 made of a non-magnetic material is disposed inside the magnet, and a magnet support cylinder 14 rotatably supported in an inner space of the fixed cylinder 10 having a rectangular cross section. The braking drum 7 is such that the flange portion 5a of the boss 5 and the end wall portion of the braking drum 3 of the parking brake are superposed on the mounting flange 2 that is spline-fitted and fixed to the rotary shaft 1, and the plurality of bolts 4 and nuts are provided. It is concluded by. One end of a braking drum 7 having a cooling fin 8 is coupled to a large number of spokes 6 extending radially from the boss 5.

The fixed cylinder 10 having a box-shaped cross section is constructed by, for example, connecting a ring-shaped cover plate 11 to a C-shaped cylinder. The fixed barrel 10 is fixed to the gear box of the transmission by any suitable means. A large number of ferromagnetic plates 1 are provided on the outer peripheral wall 10a of the fixed cylinder 10.
5 are connected at equal intervals in the circumferential direction. Preferably, the ferromagnetic plate 15 is cast around when the fixed cylinder 10 is molded. Ferromagnetic plate 15
Is a rectangular plate, and the plate surface is curved in an arc shape. The peripheral wall of the ferromagnetic plate 15 is integrally formed with the ridge 25 to enhance the degree of coupling between the outer peripheral wall 10a of the fixed barrel 10 and the ferromagnetic plate 15 by casting. The magnet support cylinder 14 is rotatably supported by the bearing 12 on the inner space of the fixed cylinder 10, specifically, on the inner peripheral wall 10b.

Three fluid pressure actuators 20, preferably three fluid pressure actuators 20, are connected to the left end wall of the fixed barrel 10 at equal intervals in the circumferential direction. The fluid pressure actuator 20 has a piston 17 fitted in a cylinder 18, and a rod protruding from the piston 17 to the outside has an arm 16 protruding from the magnet supporting cylinder 14 via an arc-shaped slit 18a on the left end wall of the fixed cylinder 10. Connected to.

As shown in FIG. 2, one magnet 24 is coupled to each ferromagnetic plate 15 of the magnet support cylinder 14.
The magnet support cylinder 14 is made of a magnetic material, and the magnets 24 facing the ferromagnetic plates 15 are arranged so that their polarities are alternately different in the circumferential direction.

According to the present invention, the length L in the circumferential direction of the inner peripheral surface of the ferromagnetic plate 15 is made the same as the length L in the circumferential direction of the outer peripheral surface of the magnet 24, and the outer peripheral side portion of the rear end portion 15b is arranged on the braking drum 7. It is made to project backward in the rotation direction (the direction opposite to the arrow x). In the embodiment shown in FIG. 2, the rear end portion 15b is formed as a surface inclined with respect to the radial line of the ferromagnetic plate 15. As shown in FIG. 3, the front end portion 15a of the ferromagnetic plate 15 may have an outer peripheral portion cut substantially parallel to the rear end portion 15b for weight reduction.

Next, the operation of the eddy current type speed reducer according to the present invention will be described. During non-braking, as shown in FIG. 3, two magnets 24 having different polarities partially share a common ferromagnetic plate 1.
Face 5 Between each ferromagnetic plate 15 and the magnet support tube 14, a short-circuit magnetic circuit shown by a line 27 is generated, and the magnet 24 does not apply a magnetic field to the braking drum 7.

During braking, when the magnet support cylinder 14 is rotated by the half-aligned pitch of the ferromagnetic plates 15 by the fluid pressure actuator 20, as shown in FIG. The magnetic field is applied to the braking drum 7 via the ferromagnetic plate 15 so as to face each other. When the rotating braking drum 7 crosses the magnetic field, an eddy current flows in the braking drum 7, and the braking drum 7 receives a braking torque.

When the braking drum 7 is rotating during braking,
The magnetic field that extends from the magnet 24 through the ferromagnetic plate 15 to the braking drum 7 is distorted to the extent that it is dragged in the rotation direction of the braking drum 7. However, according to the present invention, since the outer peripheral side portion of the rear end portion 15b of the ferromagnetic plate 15 projects rearward, the magnetic circuit formed in the braking drum 7 and the magnet supporting cylinder 14 with the magnet 24 interposed therebetween ( (Indicated by a line 26a) is a rear end portion 15b of the ferromagnetic plate 15 which is located in front of the braking drum 7 in the rotation direction, and forms a smooth magnetic circuit between the magnet 24 and the front adjacent magnet 24. Misalignment or distortion in the rotation direction can be suppressed. That is, the distribution of the magnetic flux passing through the ferromagnetic plate 15 becomes closer to the rear side in the rotation direction than in the conventional case,
Concentration of the magnetic flux density at the front end portion 15a of the ferromagnetic plate 15 is avoided. Therefore, since magnetic saturation does not occur at the front end portion 15a of the ferromagnetic plate 15, an efficient magnetic circuit is formed between the magnet 24 and the braking drum 7 (the magnetic flux passing through each ferromagnetic plate 15). The number increases) and the braking ability increases.

The present invention is not limited to the speed reducer of the type described above, but can be applied to an eddy current speed reducer of the type shown in FIG. In the speed reducer shown in FIG. 4, the magnet 23a
The magnet support cylinder 13 that supports the magnet and the magnet support cylinder 14 that supports the magnet 24 a are housed in the inner space of the fixed cylinder 10. The magnet support cylinder 13 is rotatably supported by the bearing 12 on the inner peripheral wall 10b by an amount corresponding to the arrangement pitch of the magnets, while the magnet support cylinder 14 is fitted to the inner peripheral wall 10b and fixed to the right end wall 11 by a bolt 21. It A large number of magnets 23 a are coupled to the outer peripheral surface of the magnet support cylinder 13 at equal intervals in the circumferential direction. A large number of magnets 24a are coupled to the outer peripheral surface of the magnet support cylinder 14 at the same intervals. Each of the magnets 23a and 24a has an inner surface joined to the magnet support cylinders 13 and 14 and an outer surface facing the ferromagnetic plate 15 as magnetic poles, and the outer surfaces are arranged so that their polarities are alternately different in the circumferential direction. The ferromagnetic plate 15 is fitted and supported in the opening of the outer peripheral wall 10a made of a non-magnetic material, and is arranged so as to be aligned with the magnets 23a and 24a in the same arrangement pitch. Other configurations are the same as those in FIG.

In the above embodiment, the magnet 24a of the magnet supporting cylinder 14 and the magnet 23a of the magnet supporting cylinder 13 are:
As shown in FIG. 4, the ferromagnetic plate 1 is displaced by the pitch of the magnets.
The polarities facing 5 are opposite to each other. At this time,
As shown by the arrow in FIG. 4, since the short-circuit magnetic circuit 27a is formed, the magnetic field that acts vertically from the magnets 23a and 24a to the inner peripheral surface of the braking drum 7 becomes extremely weak, and Does not exert braking torque.

During braking, when the magnet support cylinder 13 is rotated by the fluid pressure actuator 20 by the pitch of the magnet arrangement,
The magnet 23a of the magnet support cylinder 13 and the magnet 2 of the magnet support cylinder 14
The polarities of 4a are the same as that of 4a, and like the case of FIG.
The magnets 23a and 24a are connected to the braking drum 7 and the magnet support cylinder 1 respectively.
A magnetic circuit is formed between 3 and 14.

Further, according to the present invention, the magnet supporting cylinder is moved in the axial direction inside the fixed cylinder which is long in the axial direction, and the magnet is opposed to the ferromagnetic plate at the braking position and the magnet is retracted from the braking drum in the axial direction. The present invention can be applied to a speed reducer of a type that can be switched when not braking the ferromagnetic plate.

[0019]

As described above, according to the present invention, the fixed cylinder having the inner hollow portion having the rectangular cross section is arranged inside the braking drum, and the polarity facing the outer peripheral wall of the fixed cylinder is provided in the inner hollow portion of the fixed cylinder. A magnet support cylinder in which a large number of permanent magnets are arranged so as to be alternately different in the circumferential direction is rotatably supported, and a ferromagnetic plate facing each permanent magnet of the magnet support cylinder is embedded in the outer peripheral wall of the fixed cylinder to make it ferromagnetic. Since the plate is formed by projecting the outer peripheral side portion of the rear end portion of the braking drum in the rotation direction, the braking drum magnetized at the rear end side of each ferromagnetic plate is accompanied by rotation, The front-adjacent ferromagnetic plate is opposed to the front-adjacent magnet via the rear end thereof, and the magnetic flux is biased toward the rear end of the ferromagnetic plate (rear side in the rotation direction of the braking drum) by that much, and the ferromagnetic plate Magnetic flux concentration on the front end of the is suppressed. In other words, since the saturation of the magnetism at the front end of the ferromagnetic plate is suppressed, the magnetic flux that reaches the braking drum increases, and an efficient magnetic circuit is generated between the magnet support cylinder and the braking drum, so that the braking efficiency or braking The ability is enhanced.

[Brief description of drawings]

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

2 is a front cross-sectional view of the reduction gear transmission taken along the line 2A-2A in FIG. 1 during braking.

FIG. 3 is a front sectional view of a speed reducer including a ferromagnetic plate according to a modified embodiment of the present invention during non-braking.

FIG. 4 is a side sectional view of another type of eddy current type speed reducer according to the present invention.

FIG. 5 is a front sectional view of a conventional eddy current type speed reducer.

[Explanation of symbols]

7: Braking drum 10: Fixed cylinder 13, 14: Magnet support cylinder 15: Ferromagnetic plate 15b: Rear end 24, 23a,
24a: magnet

Claims (2)

[Claims] 1. A fixed cylinder having an inner hollow portion having a rectangular cross section is disposed inside a braking drum, and a large number of polarities facing the outer peripheral wall of the fixed barrel are alternately arranged in the inner hollow portion of the fixed barrel in the circumferential direction. Rotatably supports the magnet support cylinder in which the permanent magnets are arranged, and a ferromagnetic plate facing each permanent magnet of the magnet support cylinder is embedded in the outer peripheral wall of the fixed cylinder. An eddy current type speed reducer characterized in that an outer peripheral portion of the end portion is projected rearward in a rotation direction of the braking drum. 2. A fixed cylinder having an inner hollow portion having a rectangular cross section is disposed inside the braking drum, and a large number of polarities facing the outer peripheral wall of the fixed cylinder are alternately arranged in the inner hollow portion of the fixed cylinder in the circumferential direction. The magnet support cylinder in which the permanent magnets are arranged is movably supported in the axial direction, and a ferromagnetic plate facing each permanent magnet of the magnet support cylinder is embedded in the outer peripheral wall of the fixed cylinder. An eddy current type speed reducer characterized in that an outer peripheral side portion of a rear end portion is projected rearward in a rotation direction of a braking drum.