JPH04168970A - 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 deterioration of a braking torque and keep strength against heat by a method wherein at least one of a ferromagnetic sheet and a permanent magnet, which are arranged in the circumferential direction of the title gear, is provided with a notch at end rims neighboring to each other. CONSTITUTION:A multitude of ferromagnetic sheets 14, arranged in the circumferential direction of a braking drum 4, are provided with acuate notches 21 at both end rims 14a neighboring to each other. The widthwise position of the notches is determined so as to be corresponding to a part of the braking drum 4, whereat the temperature thereof becomes the maximum temperature. A permanent magnet 6 is also provided with notches 22 at both end rims opposing to the ferromagnetic sheet 14. The notches 21 are provided on both end rims 14a of the ferromagnetic sheet 14 whereby the strength of magnetic field of the permanent magnet 6, which is applied on the internal circumferential surface of the braking drum 4 in the axial direction of the braking drum 4 or the widthwise direction of the ferromagnetic sheet 14, becomes weak at parts corresponding to the notches 21 and the amount of heat generation due to the eddy current in the braking drum 4 is reduced in proportional thereto whereby a temperature rise of the central part of the axial direction if the braking drum 4, whereat the maximum temperature has been shown so far, can be suppressed.

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. 5 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 by a plurality of ports 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 having an inner cavity 17 with a box-shaped cross section is disposed inside the brake drum 4 made of a conductor. The fixing frame 9 is fixed to the wall of the gear box by suitable means. The fixed frame 9 may be constructed by joining annular end wall plates to both ends of the outer cylinder and the inner cylinder, but the illustrated fixed frame 9 is made of a material such as ordinary iron and has a U-shaped cross section on the left half. and a cylindrical frame 15 made of a non-magnetic material such as aluminum and having an inverted cross-section.
are connected by a large number of bolts 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. On the outer peripheral surface of the magnet support ring 8, the same number of permanent magnets 6 facing each ferromagnetic plate 14 are arranged in the circumferential direction 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 is connected to 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 inner peripheral surface becomes extremely 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 weaken the magnetic field exerted by the permanent magnet on the brake drum, thereby avoiding a decrease in braking torque, suppressing the maximum temperature of the high-temperature part of the brake drum, and increasing the strength against heat. Our objective 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 structure in which a fixed frame made of a cylindrical non-magnetic material having a box-shaped inner cavity in cross section is provided inside a braking drum made of a conductor. A large number of approximately rectangular ferromagnetic plates are embedded in the outer cylindrical part of the fixed frame at equal intervals in the circumferential direction, and are placed on the outer peripheral surface of the magnet support ring that is supported slidably in the axial direction in the inner cavity of the fixed frame. A ferromagnetic plate and the same number of permanent magnets of the same shape and equal spacing are combined with alternating polarities, and a notch is provided at the edge of at least one of the ferromagnetic plate and the permanent magnets adjacent to each other in the arrangement direction. It is.

[Function] According to the present invention, by providing a notch in the mutually adjacent end edge of at least one of the ferromagnetic plate and the permanent magnet arranged in the circumferential direction, the permanent magnet can be attached to the brake drum at the notch. The magnetic field exerted by the brake drum becomes weaker, the amount of heat generated by eddy currents is suppressed, and the temperature rise in the axial center of the brake drum, which conventionally has the highest temperature, is suppressed, and the temperature approaches the temperature at both ends of the brake drum.

Since the notch according to the present invention is provided at the edge of the ferromagnetic plate or the permanent magnet, the reduction in braking torque is smaller than increasing the distance between the ferromagnetic plate and the permanent magnet, and the cutout is provided at the edge of the ferromagnetic plate or the permanent magnet. This avoids excessive high temperatures and ensures the durability of the brake drum.

[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 15 made of a normal material and having a U-shaped cross section (see Fig. 5) and a cylindrical frame 15 made of a non-magnetic material and having an inverted-shaped cross section, using a large number of bolts. It is composed of A magnet support ring 8 is slidably supported in the inner cavity 17 of the frame 15 in the axial direction of the brake drum 4, and a large number of permanent magnets 6 coupled to the outer peripheral surface of the magnet support ring 8 are connected to the outer cylindrical portion of the frame 15. ferromagnetic plate 14 coupled to
When the rotating brake drum 4 crosses the lines of magnetic force passing through the magnetic field toward the brake drum 4, an eddy current is generated in the brake drum 4,
Braking drum 4 receives 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. .

As shown in FIG. 2, according to the present invention, a large number of ferromagnetic plates 14 arranged in the circumferential direction of the brake drum 4 are provided with arc-shaped notches 21 at both end edges 14a adjacent to each other. The position of the notch 21 in the width direction is determined in accordance with the portion of the brake drum 4 that has the highest temperature. Preferably, the permanent magnet 6 is also provided with notches 22 (FIG. 1) at both end edges corresponding to the ferromagnetic plate 14. Furthermore, instead of providing the notches 21 in the ferromagnetic plate 14, the notches 22 may be provided only at both end edges of the permanent magnet 6.

According to the present invention, by providing the notches 21 on both end edges 14a of the ferromagnetic plate 14, the permanent magnet 6 can be attached to the brake drum 4 in the axial direction of the brake drum 4, that is, in the width direction of the ferromagnetic plate 14. The strength of the magnetic field exerted on the inner circumferential surface becomes weaker in the part corresponding to the notch 21, and the braking drum 4
Since the amount of heat generated by eddy currents is reduced, the temperature rise at the axial center of the brake drum 4, which conventionally has the highest temperature, 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.

FIG. 3 is a developed view of the fixed frame 9. In this embodiment, a notch 23 is provided on one side in the width direction (open end side of the brake drum 4) of the end edge 14a of the rectangular ferromagnetic plate 14 relative to the frame 15, specifically at the corner. . In this example,
The amount of heat generated by the eddy current on the left side edge of the ferromagnetic plate 14, that is, on the open end side of the brake drum 4 is reduced, and at the same time, heat dissipation in the axial center of the brake drum 4 is promoted toward the open end side of the brake drum 4, and the temperature The rise can be suppressed.

FIG. 4 is a developed view of the magnet support ring. A notch 24 is provided on one side (open end side of the brake drum 4) of the end edge 6a of the permanent magnets 6 arranged in the circumferential direction of the magnet support ring 8 to reduce the amount of heat generated by the eddy current at the open end side of the brake drum 4. suppress.

[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 almost rectangular ferromagnetic plates are buried at equal intervals in the circumferential direction in the part, and the same shape as the ferromagnetic plates are embedded at equal intervals on the outer peripheral surface of a magnet support ring that is supported slidably in the axial direction in the inner cavity of the fixed frame. Since the same number of permanent magnets are connected with alternating polarities and a notch is provided at the edge of at least one of the ferromagnetic plates and the permanent magnets adjacent to each other in the arrangement direction, the overall reduction in braking torque is reduced. The notch reduces the strength of the magnetic field that the permanent magnet exerts on the inner peripheral surface of the brake disc, reducing the amount of heat generated by the eddy current, thereby avoiding local temperature rises in the brake drum. This improves the durability of the brake drum against heat.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of the braking drum and fixed frame of the eddy current reduction gear according to the first embodiment of the present invention, FIG. 2 is a perspective view of the same ferromagnetic plate, and FIG. 3 is the second embodiment of the present invention. A developed view showing the relationship between the ferromagnetic plate and the fixed frame according to the embodiment, FIG. 4 is the third embodiment of the present invention.
FIG. 5 is a developed view showing the relationship between the magnet support ring and the permanent magnet according to the embodiment, and FIG. 5 is a side sectional view of a conventional eddy current reduction gear. 4: Braking drum 6: Permanent magnet 6a: Edge portion 8: Magnet support ring 9: Fixed frame 141 Ferromagnetic plate 14a: Edge portion
17: Inner cavity 21-24: Notch Patent applicant Isupa Automobile Co., Ltd.

Claims (1)

[Claims] A fixed frame made of a cylindrical non-magnetic material and having a box-shaped inner cavity in cross section is arranged inside the braking drum made of a conductor, and a large number of almost rectangular reinforcements are arranged at equal intervals in the circumferential direction on the outer cylindrical part of the fixed frame. A magnetic plate is embedded and the same number of permanent magnets with the same shape and polarity are connected to the outer circumferential surface of a magnet support ring, which is axially slidably supported in the inner cavity of a fixed frame, and arranged at equal intervals with the ferromagnetic plate, so that the polarity is alternately different. An eddy current speed reduction device characterized in that a notch is provided in an edge portion of at least one of the ferromagnetic plate and the permanent magnet adjacent to each other in the arrangement direction.