JPH07118903B2 - Eddy current type speed reducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention mainly relates to an eddy current type speed reducer which is installed in a large vehicle and assists a friction brake, and particularly suppresses a temperature rise of a braking drum when braking for a long time. The present invention relates to an eddy current type speed reducer that exhibits stable braking performance.

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

Inside the braking drum 4 made of a conductor, a hollow box-shaped inner section is formed.
A fixed frame 9 having 17 is arranged. The fixed frame 9 is fixed to the wall of the gear box by a suitable means. The fixed frame 9 may be constructed by connecting 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 left-sided U-shaped cross section. A tubular frame 16 and a tubular frame 15 made of a non-magnetic material such as aluminum and having an inverted L-shaped cross section,
It is configured by being 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, that is, the peripheral wall of the frame 15 facing the inner peripheral surface of the braking drum 4, and the ferromagnetic plate (pole piece) 14 is fitted into these openings. Fixed together. In practice, when the frame 15 is cast from aluminum, the ferromagnetic plate 14 is formed by casting. 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 the rod 13 extending from the piston 12 fitted in the cylinder 11 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. On the outer peripheral surface of the magnet support ring 8, each ferromagnetic plate 14
The same number of permanent magnets 6 facing each other are arranged in the circumferential direction with their polarities being alternately different.

At the time of braking, the magnet support ring 8 is guided through the rod 13 by the pressurized air supplied to the left end chamber of the actuator 10 to the guide wall 16a.
When pushed to the right along with, the permanent magnet 6 overlaps the ferromagnetic plate 14 as shown. When the rotating braking drum 4 crosses the line 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.

For large vehicles that use many highways and mountain roads,
When braking by an eddy current type speed reducer on a long downhill, the temperature of the braking drum 4 may exceed 600 ° C.

Of course, the braking drum 4 has its heat dissipation enhanced by the cooling fins 7. However, as shown by the isotherms in FIG. 3 (hatching is omitted to facilitate understanding), the conventional braking drum 4 has an inner circumference. The temperature of the central portion of the surface in the direction of the rotation axis becomes very high, and the braking drum 4 may be thermally deformed or cracked. Here, the part where the maximum temperature of the braking drum 4 is offset to the left end (open end) side from the center of the rotation axis is that the right end side of the braking drum 4 is connected to the flange portion 4a by the spoke 4b. Therefore, the heat on the right end side of the braking drum 4 is quickly transferred 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 in size and increases in weight, making it difficult to mount it on a vehicle. Further, if the gap c (usually 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 decreases, but the permanent magnet 6 causes the braking drum 4 to rotate. The braking torque exerted on the vehicle also decreases, and the original function cannot be achieved.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to partially weaken a magnetic field exerted by a permanent magnet on a braking drum, thereby avoiding a decrease in braking torque and avoiding a high temperature portion of the braking drum. The object is to provide an eddy current type speed reducer that suppresses the maximum temperature of, and maintains the strength against heat.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the structure of the present invention includes a cylindrical fixed frame made of a non-magnetic material having a box-shaped inner cross-section inside a braking drum made of a conductor. A large number of substantially rectangular ferromagnetic plates are embedded in the outer cylinder of the fixed frame at equal intervals in the circumferential direction, and are mounted on the outer peripheral surface of the magnet support ring that is axially slidably supported in the inner space of the fixed frame. At least one of the ferromagnetic plate and the permanent magnets is provided with a notch at the circumferential edge, at least one permanent magnet having the same shape as the ferromagnetic plate and having the same shape and the same number of poles alternately coupled in the circumferential direction. The notch is the central portion of the permanent magnet or the ferromagnetic plate in the direction of the rotation axis, and is notched in the thickness direction.

[Operation] According to the present invention, at least one of the ferromagnetic plates and the permanent magnets arranged in the circumferential direction is provided with a notch at an edge portion in the circumferential direction, and the notch is in the rotation axis direction of the permanent magnet or the ferromagnetic plate. By notching in the thickness direction in the central part of the, the magnetic field that the permanent magnet exerts on the braking drum becomes weak at the notch, the amount of heat generated by the eddy current is suppressed, and the braking drum of the conventional maximum temperature The temperature rise in the central portion in the axial direction is suppressed, and the temperature becomes close to the temperatures at both ends of the braking drum. Here, the axial direction and the circumferential direction are based on the braking drum.

Since the notch according to the present invention is provided at the circumferential edge portion of the ferromagnetic plate or the permanent magnet, the braking torque is less decreased and the braking torque is reduced rather than the mutual spacing between the ferromagnetic plate and the permanent magnet is increased. Local temperature rise of the drum is avoided and durability of the braking drum is secured.

Embodiment of the Invention FIG. 1 is a side sectional view of a braking drum and a fixed frame of an eddy current type speed reducer according to the present invention. The fixed frame 9 is formed by connecting a cylindrical frame having a U-shaped cross section (see FIG. 3) made of an ordinary material and a cylindrical frame 15 having a reverse L-shaped cross section made of a non-magnetic material with a large number of bolts. Configured. The magnet support ring 8 is slidably supported in the inner space 17 of the frame 15 in the axial direction of the braking drum 4, and from the large number of permanent magnets 6 coupled to the outer peripheral surface of the magnet support ring 8, the outer cylindrical portion of the frame 15 is connected. When the rotating braking drum 4 traverses a magnetic field line that passes through the ferromagnetic plate 14 coupled to and goes toward the braking drum 4, an eddy current is generated in the braking drum 4 and the braking drum 4 receives a braking torque.

In the illustrated embodiment, the braking drum 4 is supported by a large number of spokes 4b extending in a radial direction from a flange portion coupled to the rotating shaft in order to enhance heat dissipation. The outer ends of the spokes 4b are engaged with the notches 4c provided on the right end edge of the braking drum 4,
And they are joined by welding.

The cooling fins 7 coupled to the outer peripheral surface of the braking drum 4 are arranged so as to be inclined with respect to the rotation direction of the braking drum 4, and the left end portion of the cooling fin 7 is projected to the left from the end portion of the braking drum 4 to the left. .

As shown in FIG. 2, according to the present invention, with respect to a large number of ferromagnetic plates 14 arranged in the circumferential direction of the braking drum 4, both end edge portions 14a are formed.
A notch 21 in the thickness direction (radial direction of the braking drum 4) is formed in the arc shape. The position of the notch 21 in the axial direction (the rotational axis direction of the braking drum 4) is determined in correspondence with the portion where the maximum temperature of the braking drum 4 is reached. Preferably permanent magnet 6
Also, the notches 22 on both edges corresponding to the ferromagnetic plate 14
(Fig. 1). Further, instead of providing the notch 21 on the ferromagnetic plate 14, the notch 22 may be provided only on both end edges of the permanent magnet 6.

According to the present invention, since the notches 21 are provided in the both end edges 14a of the ferromagnetic plate 14, the ferromagnetic plate 14 is axially moved (the braking drum 4
(In the axial direction of), the strength of the magnetic field that the permanent magnet 6 exerts on the inner peripheral surface of the braking drum 4 becomes weaker in the portion corresponding to the notch 21, and the amount of heat generated by the eddy current in the braking drum 4 decreases accordingly. The temperature rise of the central portion of the braking drum 4 in the rotation axis direction, which is the highest temperature in the past, can be suppressed. Therefore, the deterioration of the braking performance due to the temperature rise is suppressed, and the safety against the deformation and damage of the braking drum 4 due to the heat is improved.

[Advantages of the Invention] As described above, the present invention provides the thickness direction (radial direction) notch at the circumferential end portions of the ferromagnetic plate or the permanent magnet and in the central portion in the rotation axis direction. , The magnetic flux density in the central portion of the braking drum in the direction of the rotation axis becomes small, the amount of heat generated by the eddy current in the central portion of the braking drum in the direction of the rotation axis decreases, and the heat dissipation is poor and the rotation of the braking drum tends to become high. The temperature rise in the central part in the axial direction is suppressed (close to the temperature at both ends of the braking drum), the durability of the braking drum against heat is improved, and moreover, when viewed from the whole, the braking torque of the braking torque The decrease is slight.

[Brief description of drawings]

FIG. 1 is a side sectional view of a braking drum and a fixed frame of an eddy current type speed reducer according to the present invention, FIG. 2 is a perspective view of the same ferromagnetic plate, and FIG. 3 is a side sectional view of a conventional eddy current type speed reducer. It is a figure. 4: Braking drum, 6: Permanent magnet, 8: Magnet support ring, 9: Fixed frame,
14: Ferromagnetic plate, 14a: Edge, 17: Inner space, 21: Notch

Claims (1)

[Claims] 1. A braking frame made of a conductor is provided with a cylindrical fixed frame made of a non-magnetic material having a box-shaped inner cross section, and the outer frame of the fixed frame is circumferentially equidistant. A large number of rectangular ferromagnetic plates are embedded, and the same number of permanent magnets of the same shape as the ferromagnetic plates are arranged on the outer peripheral surface of the magnet support ring supported in the inner space of the fixed frame so as to be slidable in the axial direction. And a notch is provided in the circumferential edge of at least one of the ferromagnetic plate and the permanent magnet, and the notch is the central portion in the rotation axis direction of the permanent magnet or the ferromagnetic plate. And an eddy current type speed reducer characterized by being cut out in the thickness direction.