JP2631418B2 - Eddy current type reduction gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to an eddy current type reduction device mounted on a large vehicle and assisting a friction brake, and in particular, suppresses a rise in the temperature of a braking drum against long-time braking. The present invention relates to an eddy current type reduction gear that exhibits stable braking performance.

[Prior Art] The present applicant has proposed an eddy current type speed reducer as shown in FIG. 7 according to Japanese Patent Application No. 1-218499. A mounting flange 2 is spline-fitted to an output rotary shaft 1 protruding from an end wall of a gear box of a vehicle transmission and fastened by a nut 1a so as not to come off. The end wall of the braking drum 3 of the parking brake and the flange portion 4a of the braking drum 4 of the eddy current reduction device are overlapped on the mounting flange 2 and fastened with a plurality of bolts 5 and nuts. A large number of cooling fins 7 are provided on the outer peripheral surface of the braking drum 4 at equal intervals in the circumferential direction.

Inside of the braking drum 4 from the conductor,
A fixed frame 9 made of a nonmagnetic material having 17 is provided. The fixed frame 9 is fixed to the wall of the gear box by an appropriate means, and may be formed by connecting annular end wall plates to both ends of the outer cylinder and the inner cylinder. Is a cylindrical frame part 16 with a U-shaped cross section in the left half made of a material such as ordinary iron
And a cylindrical frame portion 15 formed of a non-magnetic material such as aluminum and having an inverted L-shaped cross section.

A large number of openings are provided at equal intervals in the circumferential direction in the outer cylindrical portion of the fixed frame 9 facing the inner peripheral surface of the braking drum 4, that is, the peripheral wall of the frame portion 15, and a ferromagnetic material (pole piece) 14 is provided in these openings.
Are fitted and fixed. In practice, when the frame portion 15 is cast from aluminum, the ferromagnetic plate 14 is cast.
A plurality (preferably three) of actuators 10 are supported on the fixed frame 9 at equal intervals in the circumferential direction. The magnet support tube 8 is connected to an end of a rod 13 extending from the piston 12 fitted to the cylinder 11 of the actuator 10 to the inner space 17 of the fixed frame 9.

The magnet support tube 8 is an inner tube portion of the fixed frame 9, that is, a guide wall 16a.
Is supported so as to be movable in the axial direction. The same number of permanent magnets 6 opposing each ferromagnetic plate 14 are coupled to the outer peripheral surface of the magnet support cylinder 8 by alternately changing the polarity in the circumferential direction.

During braking, pressurized air supplied to the left end chamber of the actuator 10 causes the magnet support cylinder 8 to move through the rod 13 to the guide wall 16.
When pushed to the right along a, the permanent magnet 6
Overlap with the ferromagnetic plate 14. When the rotating braking drum 4 crosses the lines of magnetic force transmitted from the permanent magnet 6 through the ferromagnetic plate 14,
An eddy current flows through the braking drum 4 and receives a braking torque.

In the case of a large vehicle that frequently uses a highway or a mountain road, if braking is performed by an eddy current type reduction device on a long downhill, the temperature of the braking drum 4 may exceed 600 ° C.
Of course, the heat dissipation of the braking drum 4 is enhanced by the cooling fins 7. However, as shown by isotherms in FIG. 7 (hatching is omitted for the sake of understanding), the conventional braking drum 4 has an inner periphery. The temperature in the central portion in the axial direction of the surface becomes extremely high, and the braking drum 4 may be thermally deformed or cracked. Here, the reason why the highest temperature of the braking drum 4 is shifted to the left end (open end) side from the axial center is as follows.
The right end side of the braking drum 4 is a flange 4a by a spoke 4b.
This is because the heat on the right end side of the braking drum 4 is quickly transmitted to the flange portion 4a and the temperature rise is suppressed.

If the heat capacity of the braking drum 4 is increased in order to secure the strength of the braking drum 4 against heat, the braking drum 4 becomes large, increases in weight, and becomes difficult to mount on the vehicle. If the gap c (normally about 1 mm) between the inner peripheral surface of the braking drum 4 and the outer surface of the ferromagnetic plate 14 is enlarged, the temperature of the braking drum 4 drops, but the permanent magnet 6 The braking torque exerted on the motor is also reduced, and the original function is not achieved.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to partially widen a gap between a ferromagnetic plate and a braking drum or a magnet,
An object of the present invention is to provide an eddy current type speed reducer that lowers the temperature of a high-temperature portion of a brake drum and maintains heat resistance while avoiding a decrease in braking torque.

Means for Solving the Problems In order to achieve the above object, according to the configuration of the present invention, a base end of a braking drum made of a conductor is connected to a rotating shaft by a plurality of spokes, and a non-magnetic material is provided inside the braking drum. And a cylindrical fixed frame having an inner space with a rectangular cross section is arranged,
A ferromagnetic plate is coupled to a large number of openings provided at equal intervals in the circumferential direction in the outer cylindrical portion of the fixed frame, and a magnet supporting cylinder made of a magnetic material is supported in the inner space of the fixed frame so as to be movable in the axial direction, A magnet is coupled to the outer circumferential surface of the magnet support cylinder at equal intervals in the circumferential direction and so that the polarities facing the ferromagnetic plate are alternately different in the circumferential direction, and near the center of one of the outer surface and the inner surface in the width direction of the ferromagnetic plate. And a recess in the circumferential direction.

[Operation] According to the present invention, the permanent magnet is braked at the recess by providing a circumferential recess at the axial center or the open end (open end of the braking drum) of the inner and outer surfaces of the ferromagnetic plate. The magnetic field applied to the drum is weakened, and the amount of heat generated by the eddy current is suppressed. In addition, the gap partially widens the gap between the ferromagnetic plate and the braking drum, or the gap between the ferromagnetic plate and the permanent magnet, and enhances cooling performance. And the temperature at both ends of the braking drum approaches.

Since the circumferential depression according to the present invention is provided locally on the inner surface or the outer surface of the ferromagnetic plate, the reduction of the braking torque is smaller than the case where the gap is widened over the entire surface of the ferromagnetic plate, and the locality of the braking drum is reduced. Temperature rise is avoided, and the durability of the braking drum is ensured.

FIG. 1 is a side sectional view of a brake drum and a fixed frame of an eddy current type reduction gear according to the present invention. The base end of the braking drum 4 made of a conductor is connected to the rotating shaft by a plurality of spokes 4b,
A cylindrical fixed frame 9 made of a non-magnetic material and having an inner space with a rectangular cross section is disposed inside the braking drum 4. The fixing frame 9 is made up of a cylindrical frame portion having a U-shaped cross section made of ordinary material (see FIG. 7) and a cylindrical frame portion 15 having an L-shaped cross section made of a non-magnetic material. It is constituted by combining. A magnet support tube 8 is supported in the inner space of the fixed frame 9 so as to be slidable in the axial direction of the braking drum 4.
When the rotating brake drum 4 crosses when the rotating magnetic drum 4 traverses from the permanent magnet 6 connected to the outer peripheral surface of the permanent magnet 6 to the brake drum 4 through the ferromagnetic plate 14 bonded to the outer cylindrical portion of the fixed frame 9,
Generates an eddy current, and the braking drum 4 receives a braking torque.

In the illustrated embodiment, the base end of the braking drum 4 is supported by a number of spokes 4b extending radially from a flange portion connected to the rotating shaft in order to enhance heat dissipation. Spoke 4b
Is provided with a notch 4c provided at the edge of the base end of the braking drum 4.
And welded together.

The cooling fin 7 coupled to the outer peripheral surface of the braking drum 4
The cooling fin 7 is disposed obliquely with respect to the rotation direction of the braking drum 4, and the tip or left end of the cooling fin 7 protrudes leftward from the tip of the braking drum 4.

According to the present invention, the outer circumferential surface of the ferromagnetic plate 14 has a shallow cross-sectional circle in the circumferential direction at an axially or axially central portion, preferably at a portion offset toward the leading end or the open end side of the control drum from the widthwise center. An arc-shaped depression 21 is formed. The depth d of the recess 21 is about 1.2 to 1.4 times the gap c between the inner peripheral surface 4e of the braking drum 4 and the ferromagnetic plate 14 (see FIG. 7), and the width w of the recess 21 is between the ferromagnetic plate 14 and The width is about 0.1 to 0.3 times the width of the permanent magnet 6.

As described above, by providing the recess 21 on the outer surface of the ferromagnetic plate 14, the cooling effect near the recess 21 is enhanced, and the amount of heat generated by the eddy current is somewhat reduced, so that the temperature rise is suppressed. Accordingly, a decrease in the braking performance due to a temperature rise is suppressed, and the safety of the braking drum 4 against deformation and breakage due to heat is improved.

In the embodiment shown in FIG. 2, there is a width w from the portion deviated to the left (the tip side of the braking drum) from the center in the width direction of the ferromagnetic plate 14 to the left edge (the edge on the tip side of the braking drum). And
A circumferential recess 22 having a shallow depth d is provided on the outer surface of the ferromagnetic plate 14. Since the recess 22 extends to the left edge of the ferromagnetic plate 14, heat dissipation is improved and the permanent magnet 6
May have a small width w. The highest temperature portion of the braking drum 4 is closer to the center in the width direction than the recess 22. However, since the cooling performance is enhanced by the recess 22, the temperature rise in the axial center portion of the inner peripheral surface 4e of the braking drum 4 is reduced. Can be suppressed.

The embodiment shown in FIG.
The left end side (the end side of the braking drum 4) is cut in a tapered shape. Even if the width w of the portion where the tapered recess 23 overlaps the outer surface of the permanent magnet 6 is narrower than that of the embodiment of FIG. The temperature rise in the central part is suppressed.

In the embodiment of FIGS. 1-3, the recesses 21-23 are
However, these recesses may be formed on the inner surface of the ferromagnetic plate 14 so as to widen the gap between the permanent magnet 6.

In the embodiment of FIG. 4, the recess 21a corresponding to the recess 21 of FIG. 1 is provided on the inner surface of the ferromagnetic plate 14, and in the embodiment of FIG. 5, the recess of FIG. FIG. 6 shows an embodiment in which a recess 22a corresponding to 22 is provided.
Tapered recess corresponding to recess 23 in FIG. 3 on the inner surface of
23a. During braking, the energy of the eddy current generated in the braking drum 4 is converted into heat. Hollow 21a-2
Since the eddy current at the axial center of the brake drum 4 is suppressed by 3a, the amount of heat generation is reduced, and the temperature rise at the axial center of the brake drum 4 is suppressed in combination with the cooling effect of the recesses 21a to 23a. .

[Effect of the Invention] As described above, according to the present invention, a base end of a braking drum made of a conductor is connected to a rotating shaft by a plurality of spokes, and an inner space made of a non-magnetic material and having a rectangular cross section is formed inside the braking drum. Arrange a cylindrical fixed frame having a, ferromagnetic plate coupled to a number of openings provided at equal intervals in the circumferential direction in the outer cylindrical portion of the fixed frame,
A magnet support cylinder made of a magnetic material is supported in the inner space of the fixed frame so as to be movable in the axial direction. Since the magnet is coupled and a circumferential recess is provided near the center in the width direction on one of the outer surface and the inner surface of the ferromagnetic plate, the braking torque is slightly reduced as a whole when viewed from the whole. The gap between the brake drum and the permanent magnet expands in the recessed portion of the magnetic plate, increasing the cooling performance and reducing the amount of heat generated by the eddy current. The durability against heat is improved.

[Brief description of the drawings]

1 to 6 are side sectional views of a braking drum and a fixed frame of an eddy current type reduction gear according to first to sixth embodiments of the present invention, and FIG. 7 is a side sectional view of a conventional eddy current type reduction gear. . 4: braking drum, 6: permanent magnet, 8: magnet support cylinder, 9: fixed frame,
14: ferromagnetic plate, 17: inner space, 21-23: hollow, 21a-23a: hollow

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-208856 (JP, A) JP-A-4-12660 (JP, A) JP-A-60-103280 (JP, U) JP-A-2- 103532 (JP, U) Fully open Hei 3-74187 (JP, U)

Claims (2)

(57) [Claims] A base end of a brake drum made of a conductor is connected to a rotating shaft by a plurality of spokes, and a cylindrical fixed frame made of a non-magnetic material and having a hollow section having a rectangular cross section is provided inside the brake drum. Arranged, ferromagnetic plates are coupled to a number of openings provided at equal intervals in the circumferential direction on the outer cylindrical portion of the fixed frame, and a magnet supporting tube made of a magnetic material can be axially moved in the inner space of the fixed frame. And magnets are coupled to the outer peripheral surface of the magnet support cylinder at equal intervals in the circumferential direction and the polarities facing the ferromagnetic plate are alternately different in the circumferential direction, and one of the outer surface and the inner surface of the ferromagnetic plate is connected. An eddy current type reduction gear characterized in that a circumferential recess is provided near the center in the width direction. 2. A brake drum made of a conductor, the base end of which is connected to a rotating shaft by a plurality of spokes, and a cylindrical fixed frame made of a non-magnetic material and having an inner space having a rectangular cross section is provided inside the brake drum. Arranged, ferromagnetic plates are coupled to a number of openings provided at equal intervals in the circumferential direction on the outer cylindrical portion of the fixed frame, and a magnet supporting tube made of a magnetic material can be axially moved in the inner space of the fixed frame. And magnets are coupled to the outer peripheral surface of the magnet support cylinder at equal intervals in the circumferential direction and the polarities facing the ferromagnetic plate are alternately different in the circumferential direction, and one of the outer surface and the inner surface of the ferromagnetic plate is connected. An eddy current type reduction gear characterized in that a recess in the circumferential direction is provided in a portion from the vicinity of the center in the width direction to the end edge opposite to the spoke. Reduction gear.