JPH04161052A - Eddy current type reduction gear - Google Patents

Abstract

PURPOSE:To suppress the maximum temperature of the high temperature part of a braking drum, while avoiding the drop of braking torque, so as to keep the strength to heat by providing a circumferential recess at the center in axial direction of the surface of a permanent magnet or on the side of the opening end (the side of the opening end of the braking drum). CONSTITUTION:A shallow circumferential recess 21 circular in cross section is made at the center in width direction of the surface of a permanent magnet 6, preferably, at the section being biased toward the side of the opening end (left end) of a braking drum from the center in width direction. The depth d of the recess 21 is approximately 1.2 to 1.4 times the space c between the inside periphery of the braking drum 4 and a ferromagnetic plate 14, and the width w of the recess 21 is approximately 0.1 to 0.3 times the width of the permanent magnet 6. By providing the recess 21 at the surface of the ferromagnetic plate 14, cooling effect in the vicinity of the recess 21 becomes high, and also the calorific value by eddy currents decreases a little, so temperature rise is suppressed. Accordingly, the drop of the braking performance by the temperature rise is suppressed, and the safety on the deformation or the breakdown of the braking drum 4 by heat improves.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an eddy current speed reduction device that is mainly mounted on large vehicles to assist friction braking, and in particular, to suppress the temperature rise of the brake drum during long-term braking. This invention relates to an eddy current reduction gear that exhibits stable braking performance.

[Prior Art] The present applicant proposed an eddy current speed reduction device as shown in FIG. 6 in Japanese Patent Application No. 1-218499. A mounting flange 2 is spline-fitted to an output rotating shaft 1 protruding from an end wall of a gear box of a vehicle transmission and fastened with a nut 1a so as not to come off. The end wall of the brake drum 3 of the parking brake and the flange portion 4a of the brake drum 4 of the reduction gear are overlapped on the mounting flange 2 and fastened with a plurality of bolts 5.

A large number of cooling fins 7 are provided on the outer peripheral surface of the brake drum 4 at equal intervals in the circumferential direction.

A fixed frame 9 made of a non-magnetic material and having an inner cavity 17 having a box-shaped cross section is disposed inside the brake drum 4 made of a conductor.

The fixed frame 9 is fixed to the wall of the gear box by suitable means, and may be constructed by connecting annular end wall plates to both ends of the outer cylinder and the inner cylinder, but the fixed frame 9 shown in the figure The left half of the cylindrical frame 16 is made of a material such as ordinary iron and has a U-shaped cross section, and the cylindrical frame 15 is made of a non-magnetic material such as aluminum and has an inverted-shaped cross section. 18.

A large number of openings are provided at equal intervals in the circumferential direction on the peripheral wall of the fixed frame 9, which faces the inner peripheral surface of the brake drum 4, and a ferromagnetic plate (pole piece) 14 are fitted and fixed. In reality, when the frame 15 is cast from aluminum, the ferromagnetic plate 14 is cast inside. A plurality of (preferably three) actuators 10 are supported on the fixed frame 9 at equal intervals in the circumferential direction. The magnet support ring 8 is coupled to the end of a rod 13 extending from the piston 12 fitted into the cylinder 1 - 1 of the actuator 10 to the inner space 17 of the fixed frame 9 .

The magnet support ring 8 is supported by the guide wall 16a of the fixed frame 9 so as to be movable in the axial direction. The same number of permanent magnets 6 facing each ferromagnetic plate 14 are coupled to the outer circumferential surface of the magnet support ring 8, or with alternating polarities.

During braking, when the magnet support ring 8 is pushed to the right along the guide wall 16a via the rod 13 by the pressurized air supplied to the left end chamber of the actuator 10, the permanent magnet 6 becomes ferromagnetic as shown in the figure. Board] overlaps with -4.

A rotating brake drum 4 or a ferromagnetic plate 1 from a permanent magnet 6
When the magnetic field lines passing through the brake drum 4 are crossed, eddy currents flow through the brake drum 4 and the brake drum 4 receives a brake torque.

[Problems to be solved by the invention] In the case of large vehicles that often use expressways and mountain roads,
When braking is performed using an eddy current reduction device on a long downhill slope, the temperature of the brake drum 4 may exceed 600°C.

Of course, the heat dissipation of the brake drum 4 is improved by the cooling fins 7, but as shown in FIG. The temperature at the axial center of the surface becomes extremely high,
There is a risk that the brake drum 4 may be thermally deformed or cracked. Here, the part of the brake drum 4 that has the highest temperature is
The reason why it is biased toward the left end (open end) side with respect to the axial center is because the right end side of the brake drum 4 is connected to the flange part 4a by the spokes 4b, so the heat from the right end side of the brake drum 4 is transferred to the flange part 4a. This is because it is quickly transmitted and temperature rise can be suppressed.

In order to ensure the strength of the brake drum 4 against heat, increasing the heat capacity of the brake drum 4 results in a large size and weight increase, making it difficult to mount it on a vehicle. Furthermore, if the gap C between the inner circumferential surface of the brake drum 4 and the outer surface of the ferromagnetic plate 14 is enlarged (usually about 1 inch), the temperature of the brake drum 4 will decrease; The braking torque applied to 4 also decreases, and it no longer performs its original function.

In view of the above-mentioned problems, an object of the present invention is to partially widen the gap between the permanent magnet and the ferromagnetic plate, thereby suppressing the maximum temperature of the high-temperature part of the brake drum while avoiding a decrease in braking torque.
An object of the present invention is to provide an eddy current speed reduction device that maintains strength against heat.

Means for Solving Problem U] In order to achieve the above object, the structure of the present invention includes a fixed frame made of a cylindrical non-magnetic material having a box-shaped inner cavity in cross section inside a brake drum made of a conductor. A large number of ferromagnetic plates are embedded in the outer cylindrical part of the fixed frame at equal intervals in the circumferential direction, and the ferromagnetic plates are installed on the outer circumferential surface of the magnet support ring that is supported slidably in the axial direction in the inner cavity of the fixed frame. The same number of permanent magnets are connected at equal intervals with alternating polarities, and circumferential depressions are provided on the outer surface of the permanent magnets.

[Function] According to the present invention, by providing a circumferential recess in the axial center of the outer surface of the permanent magnet or on the open end side (open end side of the brake drum), the permanent magnet is attached to the brake drum at the recessed part. The applied magnetic field becomes weaker, and the amount of heat generated by eddy currents is suppressed. In addition, the gap between the permanent magnet and the ferromagnetic plate partially widens due to the depression, improving cooling performance, which suppresses the temperature rise in the axial center of the brake drum, which is a high temperature area.
The temperature will be close to that of both ends of the brake drum.

Since the recesses according to the present invention are locally provided on the outer surface of the permanent magnet, the reduction in braking torque is smaller than when the gap is widened over the entire surface of the permanent magnet, and local heating of the brake drum can be avoided. , the durability of the brake drum is ensured.

[Embodiment of the Invention] FIG. 1 is a side sectional view of a braking drum and a fixed frame of an eddy current reduction gear according to the present invention. The fixed frame 9 is made by connecting a cylindrical frame (see Fig. 6) made of an ordinary material with a U-shaped cross section and a cylindrical frame 15 made of a non-magnetic material and having an inverted-shaped cross section with a large number of bolts. It is composed of A magnet support ring 8 is supported in the inner space of the frame 15 so as to be slidable in the axial direction of the brake drum 4, and a permanent magnet 6 is coupled to the outer peripheral surface of the magnet support ring 8.
, the lines of magnetic force that pass through the ferromagnetic plate 14 coupled to the outer cylindrical portion of the frame 15 and go toward the brake drum 4 are directed to the rotating brake drum 4 .
When traverses, an eddy current is generated in the brake drum 4, and the brake drum 4 receives a braking torque.

In the illustrated embodiment, in order to improve heat dissipation, the brake drum 4 is supported by a number of spokes 4b extending radially from a flange portion connected to the rotating shaft. The outer ends of the spokes 4b are engaged with notches 4c provided on the right edge of the brake drum 4, and are coupled by welding.

The cooling fins 7 coupled to the outer circumferential surface of the brake drum 4 are arranged at an angle with respect to the rotational direction of the brake drum 4, and the left end of the cooling fins 7 protrudes leftward from the end of the brake drum 4. .

According to the present invention, the central part in the width direction of the outer surface of the permanent magnet 6, preferably the open end (left end) of the brake drum from the center in the width direction
A recess 21 having a shallow circular arc cross section in the circumferential direction is formed in the portion offset to the side. 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 brake drum 4 and the ferromagnetic plate 14 (see FIG. 6), and the width W of the recess 21 is Approximately 0.0 mm of the width of the permanent magnet 6. 1 to 0.3 times.

According to the present invention, by providing the recesses 21 on the outer surface of the ferromagnetic plate 14, the cooling effect in the vicinity of the recesses 21 is enhanced, and the amount of heat generated by eddy currents is somewhat reduced, so temperature rise is suppressed. Therefore, deterioration in braking performance due to temperature rise is suppressed, and safety against deformation and damage of the braking drum 4 due to heat is improved.

In the embodiment shown in FIG. 2, a circumferential recess 22 having a width W from a portion offset to the left side of the widthwise center of the permanent magnet 6 to the left edge and a shallow depth d is formed on the outer surface of the permanent magnet 6. It was established in Since the recess 22 extends to the left edge of the permanent magnet 6, heat dissipation is improved, and the width W of the recess 22 may be narrow.

The highest temperature part of the brake drum 4 is located closer to the center in the width direction than the depression 22, but since the cooling effect of the depression 22 is high, the temperature rise at the axial center of the inner circumferential surface 4e of the brake drum 4 is reduced. It can be suppressed.

In the embodiment shown in FIG. 3, the outer surface of the permanent magnet 6 is formed by cutting the left end side (the open end side of the brake drum 4) into a tapered shape.

In the embodiment shown in FIGS. 1 to 3, the recesses 21 to 23) are formed on the outer surface of the permanent magnet 6, sacrificing the thickness of the permanent magnet 6. However, as shown in FIG. If convex parts 22a and 23a are formed on the lower surface of the permanent magnet 6 in correspondence with the shape of the depressions 22 and 23 on the outer surface of the permanent magnet 6, and the cross-sectional shape of the permanent magnet 6 is made uniform in the width direction, the permanent magnet The strength of the magnetic field exerted by the recesses 22 and 23 on the inner circumferential surface 4e of the brake drum 4 is compensated for, and the temperature rise in the axial center of the brake drum 4 is suppressed by the cooling effect of the recesses 22 and 23.

[Effects of the Invention] As described above, the present invention provides a braking drum made of a conductor with a fixed frame made of a cylindrical non-magnetic material having a box-shaped inner cavity in cross section, and an outer cylinder of the fixed frame. A large number of ferromagnetic plates are embedded at equal intervals in the circumferential direction, and the same number of permanent magnets as the ferromagnetic plates are embedded at equal intervals on the outer circumferential surface of a magnet support ring that is supported slidably in the axial direction in the inner cavity of the fixed frame. Since the permanent magnets are connected so that the polarities are alternately different, and circumferential recesses are provided on the outer surface of the permanent magnets, the decrease in braking torque as a whole is slight, and the reduction in braking torque is only slight at the recessed parts of the permanent magnets. The gap between the brake drum and the magnetic plate is widened, the cooling performance is improved, and the amount of heat generated by eddy current is reduced, so a local temperature increase in the brake drum is avoided and the durability of the brake drum against heat is improved.

[Brief explanation of the drawing]

1 to 6 are side sectional views of the braking drum and fixed frame of the eddy current type reduction gear according to the 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 ring 9: Fixed frame 14: Ferromagnetic plate 17: Inner space 21-23: Hollow patent applicant Isu1 Jidosha Co., Ltd.

Claims (1)

[Claims] A fixed frame made of a cylindrical non-magnetic material with a box-shaped inner cavity in cross section is arranged inside a brake drum made of a conductor, and a large number of ferromagnetic plates are arranged at equal intervals in the circumferential direction on the outer cylinder of the fixed frame. The same number of permanent magnets are connected to a ferromagnetic plate at equal intervals on the outer circumferential surface of a magnet support ring that is buried and supported slidably in the axial direction in the inner cavity of the fixed frame, so that the polarity of the permanent magnets is alternately different. An eddy current reduction device characterized by having a circumferential recess on its outer surface.