JPH0638504A - Eddy current speed reduction device - Google Patents

Abstract

(57) [Abstract] [Purpose] When not braking, effectively suppresses the magnetic field leaking from the magnet to the braking drum through the gap between the ferromagnetic plates to reduce the drag torque. [Structure] Inside the braking drum 7 connected to the rotary shaft 1,
A guide tube 10 made of a non-magnetic material and having a box-shaped cross section is arranged. A large number of ferromagnetic plates 15 are coupled to the outer peripheral wall 10a of the guide cylinder 10 at equal intervals in the circumferential direction. Each ferromagnetic plate 15 is attached to a magnet support cylinder 14 rotatably supported in an inner space of the guide cylinder 10 having a rectangular cross section.
The permanent magnets 24 are coupled so that the polarities of the ferromagnetic plates 15 are alternately different in the circumferential direction. The ferromagnetic plate 15 has a rear end portion 15b in the rotation direction of the braking drum 7,
The outer peripheral side portion projects rearward in the rotation direction 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) By changing the rotation phase of the ferromagnetic plate (ball piece) that is interposed between
The present invention relates to an eddy current type speed reducer that switches between braking and non-braking.

[0002]

2. Description of the Related Art In an eddy current type speed reducer disclosed in Japanese Patent Laid-Open No. 1-298948, a guide 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 guide cylinder is provided. A large number of ferromagnetic plates are connected at equal intervals in the circumferential direction, and magnets facing each ferromagnetic plate are connected to a magnet support cylinder that is rotatably supported in the inner space of the guide cylinder. By changing only the half array pitch of the ferromagnetic plate, switching between braking and non-braking is performed.

As shown in FIG. 6, in the above-mentioned eddy current type speed reducer, the magnets 24 of the magnet support cylinder 14 have the same arrangement pitch p as the ferromagnetic plate 15, and the polarities with respect to the ferromagnetic plate 15 alternate in the circumferential direction. Are installed side by side in different ways. 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 non-magnetic guide cylinder 10 having a rectangular cross section.

During braking, each magnet 24 entirely overlaps the ferromagnetic plate on the outer peripheral wall 10a of the guide cylinder 10 and forms a magnetic circuit between the magnet 24 and the braking drum 7 which rotates via the ferromagnetic plate 15 to form a braking drum. Apply braking force to 7. During non-braking, as shown in FIG. 6, the magnet 24 is displaced from the ferromagnetic plate 15 by a half-arranged pitch, and the ferromagnetic plate 15 straddles the magnets 24 having different polarities.
A short circuit magnetic circuit 27 is formed. However, the magnet 24 exerts a leakage magnetic field on the braking drum 7 through the mutual clearance t between the adjacent ferromagnetic plates 15 to form a magnetic circuit 27a. When the rotating braking drum 7 crosses the leakage magnetic field, it receives drag torque, resulting in loss of power.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to prevent a magnetic field leaking from a magnet during non-braking to a braking drum through a gap between the ferromagnetic plates without impairing braking ability during braking. An object of the present invention is to provide an eddy current type speed reducer that effectively suppresses drag torque and reduces drag torque.

[0006]

In order to achieve the above object, the structure of the present invention is such that a guide cylinder having a box-shaped cross section and made of a non-magnetic material is disposed inside a braking drum connected to a rotary shaft. A large number of ferromagnetic plates are connected to the outer peripheral wall of the guide at equal intervals in the circumferential direction, and one ferromagnetic plate is provided for each magnet supporting cylinder that is rotatably supported in the inner space of the guide cylinder. The permanent magnets are connected to each other so that the polarities thereof are alternately different in the circumferential direction, and the ferromagnetic plate has an outer peripheral portion projecting rearward in the rotational direction of the braking drum at the rear end portion in the rotational direction of the braking drum.

[0007]

According to the present invention, since the outer peripheral side portion of the rear end of the ferromagnetic plate projects rearward, when no braking is applied, the ferromagnetic plates are passed through the mutual gap between the ferromagnetic plates arranged in the circumferential direction to the braking drum. The leaking magnetic field is blocked at the rear end of the ferromagnetic plate. As a result, the original leakage magnetic field interrupted at the rear end of the ferromagnetic plate forms a short-circuit magnetic circuit between the ferromagnetic plate and the magnet supporting cylinder, and the drag torque exerted on the braking drum by the leakage magnetic field is reduced. Will be reduced.

During non-braking, the center of the magnet in the circumferential direction is shifted rearward of the center of the ferromagnetic plate in the direction of rotation of the braking drum, so that the overlapping area of the front end of the ferromagnetic plate and the magnet (the circumferential overlap). The area) is increased, so that the magnetic resistance between the front end of the ferromagnetic plate and the magnet is reduced with respect to the increase in the magnetic flux passing through the ferromagnetic plate.

[0009]

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.
An immovable guide tube 10 made of a non-magnetic material disposed inside
And a magnet support cylinder 14 rotatably supported in an inner space of the guide cylinder 10 having a rectangular cross section. The braking drum 7 has the flange portion 5a of the boss 5 and the braking drum 3 of the parking brake.
Together with the end wall portion of the above, it is superposed on the mounting flange 2 which is spline-fitted and fixed to the rotary shaft 1, and is fastened by a plurality of bolts 4 and nuts. 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 guide cylinder 10 having a box-shaped cross section is constituted by, for example, connecting a ring-shaped cover plate 11 to a cylindrical body having a C-shaped cross section.
The guide tube 10 is fixed to the gear box of the transmission by any suitable means. A large number of ferromagnetic plates 15 are coupled to the outer peripheral wall 10a of the guide cylinder 10 at equal intervals in the circumferential direction (see the array pitch p shown in FIG. 6). Preferably, the ferromagnetic plate 15 is cast when forming the guide cylinder 10. The ferromagnetic plate 15 has a rectangular plate shape, 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 (FIG. 1) to enhance the degree of coupling between the outer peripheral wall 10a of the guide cylinder 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 guide cylinder 10, specifically, on the inner peripheral wall 10b.

Three fluid pressure actuators 20, preferably, are connected to the left end wall of the guide cylinder 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 guide 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 in the circumferential direction of the outer peripheral surface of the magnet 24, and the rear end portion (in the arrow x direction of the braking drum 7). The outer peripheral side portion of the rear end portion) 15b in the rotational direction is projected in the direction opposite to the arrow x. In the embodiment shown in FIGS. 2 and 3, the rear end portion 15b is configured as a surface inclined with respect to the center (plane) y of the ferromagnetic plate 15 in the axial direction. The front end portion 15a of the ferromagnetic plate 15 is
It is preferable to cut the outer peripheral side portion substantially parallel to the rear end portion 15b.

The outer peripheral wall 10a of the guide cylinder 10 and the ferromagnetic plate 15
The ridges 25 that enhance the degree of coupling with are biased to the inner peripheral side at the front end portion 15a and to the outer peripheral side at the rear end portion 15b for the convenience of molding the ferromagnetic plate 15. That is, the protrusions 25 are formed on the overlapping surfaces of the upper mold and the lower mold for molding the ferromagnetic plate 15.

Next, the operation of the eddy current type speed reducer according to the present invention will be described. At the time of braking, as shown in FIG. 5, each magnet 24 entirely faces each ferromagnetic plate 15, and forms a magnetic circuit 26 between the magnet support cylinder 14 and the braking drum 7.
When the rotating braking drum 7 crosses the magnetic field, the braking drum 7
An eddy current flows through the brake drum 7, and the braking drum 7 receives a braking torque.
At the time of braking, since the outer circumferential surface of the magnet 24 and the inner circumferential surface of the ferromagnetic plate 15 have the same circumferential length, the magnet 24 forms a magnetic circuit 26 extending to the braking drum 7. A short-circuit magnetic circuit that does not extend to the braking drum 7 is not formed between the end portion 15b and the front end portion 15a, and therefore the braking ability is not reduced.

When the magnet support cylinder 14 is rotated by the half-arranged pitch of the ferromagnetic plate 15 by the fluid pressure actuator 20 during non-braking, as shown in FIG. It faces the ferromagnetic plate 15. A short circuit magnetic circuit 27 is provided between each ferromagnetic plate 15 and the magnet support cylinder 14.
Occurs, the magnet 24 does not exert a magnetic field on the braking drum 7.

According to the invention, the rear end 1 of the ferromagnetic plate 15
Since the outer peripheral side portion of 5b projects rearward by the dimension t0, the mutual clearance t between the ferromagnetic plates 15 arranged in the circumferential direction is narrowed by the dimension t0 as compared with the conventional example shown in FIG. The magnetic field is reduced and, as a result, the drag torque exerted on the braking drum 7 by the leakage magnetic field is reduced.

Further, when the brake is not applied, the circumferential center z of the gap between the magnets 24 is rotated backward from the circumferential center y of the ferromagnetic plate 15 in the rotational direction of the braking drum 7 (opposite to the arrow x). By shifting by e, the front end portion 15 of the ferromagnetic plate 15
Since the overlapping area of a and the magnet 24 increases, the magnetic resistance between the front end portion 15a of the ferromagnetic plate 15 and the magnet 24 against the increase in the magnetic flux passing through the ferromagnetic plate 15 is reduced.

In the embodiment shown in FIG. 4, instead of using the front end portion 15a and the rear end portion 15b of the ferromagnetic plate 15 as inclined surfaces, the outer peripheral side half portion of the rear end portion 15b is made to project in a stepwise manner, and the front end portion is formed. 15a
In order to avoid the strength decrease at the corners, the outer half of the outer peripheral side of the is removed in a stepwise manner. Like the embodiments of FIGS. 2 and 3, the drag torque exerted on the braking drum by the leakage magnetic flux during non-braking Can be reduced.

Contrary to the above embodiment, the ferromagnetic plate 1
In the front end portion 15b of the braking drum 7 in the rotation direction, the outer peripheral side portion is projected forward in the rotation direction of the braking drum 7, and when the brake is not applied, the circumferential center z of the mutual gap of the magnets 24 is set to the ferromagnetic plate 15. The same effect can be obtained by slightly shifting the braking drum 7 from the circumferential center y in the rotational direction.

Further, the present invention is not limited to the eddy current type speed reducer of the type described above, but an eddy current type speed reducer of the type disclosed in Japanese Patent Application No. 2-112026 or Japanese Patent Laid-Open No. 3-86060. It can also be applied to devices.

[0022]

As described above, according to the present invention, a guide cylinder having a box-shaped cross section made of a non-magnetic material is provided inside the braking drum connected to the rotary shaft, and the guide cylinder is provided on the outer peripheral wall at equal intervals in the circumferential direction. A plurality of ferromagnetic plates are coupled to each other, and the magnet support cylinder rotatably supported in the inner space of the guide cylinder corresponds to the ferromagnetic plates one by one, and the polarities of the ferromagnetic plates are alternately different in the circumferential direction. The permanent magnets are coupled together as described above, and the ferromagnetic plate is such that the outer peripheral portion is projected rearward in the rotational direction of the braking drum at the rear end in the rotational direction of the braking drum. The magnetic field leaking to the braking drum through the gap is blocked by the rear end of the ferromagnetic plate. As a result, the original leakage magnetic field interrupted at the rear end of the ferromagnetic plate forms a short-circuit magnetic circuit between the ferromagnetic plate and the magnet supporting cylinder, and the drag torque exerted on the braking drum by the leakage magnetic field is reduced. Will be reduced.

[Brief description of drawings]

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

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

FIG. 3 is a front view of a ferromagnetic plate in the speed reducer.

FIG. 4 is a front view showing a modified embodiment of a ferromagnetic plate in the speed reducer.

FIG. 5 is a front sectional view showing the same speed reducer during braking.

FIG. 6 is a front sectional view of a conventional eddy current type speed reducer during non-braking.

[Explanation of symbols]

1: rotating shaft 7: braking drum 10: guide cylinder 10a:
Outer peripheral wall 14: Magnet support cylinder 15: Ferromagnetic plate 15b:
Rear end 24: Magnet

Claims (2)

[Claims] 1. A guide cylinder having a box-shaped cross section made of a non-magnetic material is provided inside a braking drum connected to a rotary shaft, and a large number of ferromagnetic plates are connected to an outer peripheral wall of the guide cylinder at equal intervals in the circumferential direction. A permanent magnet is coupled to a magnet support cylinder rotatably supported in the inner space of the guide cylinder so as to correspond to the ferromagnetic plates one by one such that the polarities of the ferromagnetic plates are alternately different in the circumferential direction, The eddy current type speed reducer characterized in that the ferromagnetic plate has an outer peripheral side portion projecting rearward in the rotational direction of the braking drum at the rear end in the rotational direction of the braking drum. 2. A guide cylinder having a box-shaped cross section made of a non-magnetic material is provided inside a braking drum connected to a rotary shaft, and a large number of ferromagnetic plates are connected to the outer peripheral wall of the guide cylinder at equal intervals in the circumferential direction. A permanent magnet is coupled to a magnet support cylinder rotatably supported in the inner space of the guide cylinder so as to correspond to the ferromagnetic plates one by one such that the polarities of the ferromagnetic plates are alternately different in the circumferential direction, The eddy current type speed reducer characterized in that the ferromagnetic plate has an outer peripheral portion projecting forward in the rotation direction of the braking drum at the front end in the rotation direction of the braking drum.