JPH04161054A - 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 ferromagnetic plate 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 ferromagnetic plate 14, 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 4e 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 ferromagnetic plate 14 or permanent magnet 6. By providing the recess 21 at the outer 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.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an eddy current speed reduction device that is mainly mounted on large vehicles to assist friction braking, and which suppresses the temperature rise of the brake drum especially 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. 7 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 is fastened with a nut to prevent it from coming 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 appropriate 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 outer cylindrical portion of the fixed frame 9 facing the inner peripheral surface of the brake drum 4, that is, on the peripheral wall of the frame 15, and ferromagnetic plates (pole pieces) 14 are fitted into these openings. 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. A magnet support ring 8 is coupled to an end of a rod 13 extending from a piston 12 fitted into a cylinder 11 of the actuator 10 to an 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 peripheral surface of the magnet support ring 8 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. It overlaps with the plate 14.

A rotating brake drum 4 or a ferromagnetic plate 1 from a permanent magnet 6
4, an eddy current flows through the brake drum J54 and receives a braking 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 circumferential surface becomes very high, and there is a risk that the brake drum 4 may be thermally deformed or cracked. Here, the reason why the highest temperature part of the brake drum 4 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 portion 4a by the spokes 4b. This is because the heat on the right end side of the brake drum 4 is quickly transmitted to the flange portion 4a, thereby suppressing a temperature rise.

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 (usually about 1 mm) between the inner circumferential surface of the brake drum 4 and the outer surface of the ferromagnetic plate 14 is enlarged, the temperature of the brake drum 4 will decrease; The braking torque exerted on the motor 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 brake drum 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. Our goal is to provide an eddy current reduction device that maintains the

[Means for Solving the Problems] 'In order to achieve the above object, the present invention has a fixed frame made of a cylindrical non-magnetic material and having an inner cavity with a box-shaped cross section inside a braking 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 ferromagnetic plates are placed on the outer circumferential surface of the magnet support ring, which is supported in the inner cavity of the fixed frame so as to be slidable in the axial direction. The same number of permanent magnets are connected to the plate at equal intervals so that the polarity is alternately different, and a circumferential recess is provided on one of the outer and inner surfaces of the ferromagnetic plate.

[Function] According to the present invention, by providing a circumferential recess in the axial center of the inner and outer surfaces of the ferromagnetic plate or on the open end side (open end side of the brake drum), the permanent magnet can perform braking at the recessed portion. The magnetic field exerted on the drum is weakened, and the amount of heat generated by eddy currents is suppressed. In addition, the depression partially widens the gap between the ferromagnetic plate and the brake drum, or the gap between the ferromagnetic plate and the permanent magnet, improving cooling performance, thereby reducing the temperature rise in the axial center of the brake drum, which is a high temperature area. The temperature is suppressed and becomes close to the temperature at both ends of the brake drum.

Since the recesses according to the present invention are locally provided on the inner or outer surface of the ferromagnetic plate, braking torque decreases less than when the gap is widened over the entire surface of the ferromagnetic plate. The durability of the brake drum is ensured.

[Embodiments 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. 7) made of a normal material with a U-shaped cross section and a cylindrical frame 15 made of a non-magnetic material with an inverted-shaped cross section to each other using a large number of bolts. Constructed by combining. A magnet support ring 8 is supported in the inner cavity of the frame 15 so as to be slidable in the axial direction of the brake drum 4, and a permanent magnet 6 connected to the outer peripheral surface of the magnet support ring 8 is connected to the outer cylindrical portion of the frame 5. When the rotating brake drum 4 crosses the line of magnetic force that passes through the ferromagnetic plate 14 and goes toward the brake drum 4, 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 a notch 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 ferromagnetic plate 14,
Preferably, a recess 21 having a shallow arcuate cross section in the circumferential direction is formed in a portion that is closer to the open end (left end) side of the brake drum than the center in the width direction. The depth d of the recess 21 is equal to the gap C (seventh
(see figure), and the width W of the recess 21 is approximately 0.1 to 0.3 times the width of the ferromagnetic plate 14 or the permanent magnet 6.

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 that temperature rise can be suppressed. Therefore, deterioration in braking performance due to temperature rise is suppressed, and safety against deformation and damage of the brake drum 4 due to heat is improved.

In the embodiment shown in FIG. 2, a recess 22 in the circumferential direction is formed in the ferromagnetic plate 14, having a width W from a portion offset to the left side of the widthwise center of the ferromagnetic plate 14 to the left edge, and a shallow depth d. It is provided on the outer surface of the Since the recess 22 extends to the left edge of the ferromagnetic plate 14, heat dissipation is improved, and the width W of the portion overlapping the permanent magnet 6 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, regarding the outer surface of the ferromagnetic plate 14,
The left end side (open end side of the brake drum 4) is cut into a tapered shape. Although 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 shown in FIG. 2, the cooling performance of the open end side of the brake drum 4 is high. Temperature rise in the center of the direction is suppressed.

In the embodiment shown in FIGS. 1 to 3, the depressions 21 to 23 are formed on the outer surface of the ferromagnetic plate 14;
4 may be formed on the inner surface of the permanent magnet 6 to widen the gap between the permanent magnet 6 and the permanent magnet 6.

In the embodiment shown in FIG. 4, a depression 21a corresponding to the depression 21 in FIG. 1 is provided on the inner surface of the ferromagnetic plate 14, and in the embodiment shown in FIG. In the embodiment shown in FIG. 6, a tapered depression 23a corresponding to the depression 23 in FIG. 3 is provided on the inner surface of the ferromagnetic plate 14.

During braking, the energy of eddy currents generated in the brake drum 4 is converted into heat. Since the eddy current in the axial center of the brake drum 4 is suppressed by the depressions 2] and a to 23a, the amount of heat generated is reduced, and together with the cooling effect of the depressions 21a to 23a, the eddy current in the axial center of the brake drum 4 is suppressed. temperature rise in the area is suppressed.

[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 ferromagnetic plates are connected so that the polarities are alternately different, and a circumferential recess is provided on one of the outer and inner surfaces of the ferromagnetic plates, the decrease in braking torque is minimal when viewed as a whole, and the ferromagnetic plates The gap between the brake drum or the permanent magnet widens at the recessed part, improving cooling performance and reducing the amount of heat generated by eddy currents, which prevents local temperature increases on the brake drum and reduces the heat resistance of the brake drum. Durability 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: Recess 21a-23a: <Recess Patent applicant Isupa Jidosha Co., Ltd. Patent applicant Sumitomo Metal Industries 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 the ferromagnetic plate at equal intervals and with alternating polarities on the outer circumferential surface of a magnet support ring that is buried and supported in the inner cavity of the fixed frame so as to be able to slide in the axial direction. An eddy current reduction device characterized by having a circumferential recess on one of the outer and inner surfaces.