JP3738557B2 - Permanent magnet type eddy current reducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet type eddy current reduction device that can easily achieve a switching operation between braking and non-braking.
[0002]
[Prior art]
In the permanent magnet type eddy current reduction device disclosed in Japanese Utility Model Publication No. 7-47989, etc., a large number of permanent magnets (hereinafter simply referred to as magnets) are provided on the outer peripheral surface of a magnet support cylinder that can project into the brake drum. By connecting the magnet support cylinders so that the polarities are alternately different in the circumferential direction, and reciprocating the magnet support cylinder into the braking position where it protrudes into the braking drum and the non-braking position where it retracts from the braking drum, Since the switching operation of braking is obtained and the annular projecting portion made of a ferromagnetic material is provided at the open end portion of the guide cylinder, the magnetic flux during non-braking is attracted to the annular projecting portion, and the magnetic flux does not leak to the braking drum. Therefore, the brake drum is not dragged.
[0003]
However, the eddy current reduction device described above has a problem that a very large driving force is required for reciprocating driving of the magnet support cylinder, and the amount of compressed air consumed by the pneumatic actuator increases. This is because when the magnet support cylinder is switched from the non-braking position to the braking position, the magnet support cylinder receives a magnetic field (repulsive magnetic field) of eddy current generated in the braking drum and is attracted to the guide cylinder.
[0004]
[Problems to be solved by the invention]
In view of the above problems, the problem of the present invention is that the magnetic drag that the magnet support cylinder receives when the magnet support cylinder is switched from the non-braking position to the braking position is weakened, and a light non-braking and braking switching operation can be obtained. It is to provide a magnet type eddy current reduction device.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the configuration of the present invention includes a braking drum coupled to a rotating shaft, a magnetic flux of a magnet that is fixed to the vehicle body side, has an inner end protruding into the braking drum, and is not braked at an outer end. A guide cylinder having an annular protrusion made of a ferromagnetic material that attracts the magnet, and an axially movable inner space of a rectangular cross section formed in the guide cylinder, and a large number of magnets on the outer circumferential surface of the brake drum. In a permanent magnet type eddy current reduction device comprising a magnet support cylinder coupled so that the polarities of the magnetic poles facing the circumferential surface are alternately different in the circumferential direction, the inner circumferential wall of the annular projection of the guide cylinder facing the magnet An annular groove is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
When the magnet support cylinder is moved from the non-braking position to the braking position, a large magnetic drag acts on the magnet support cylinder. That is, as the magnet support cylinder approaches the brake drum, a demagnetizing field acts from the brake drum to the magnet support cylinder, and the magnetic field from the magnet support cylinder is once attracted toward the annular protrusion due to the influence of the demagnetizing field. Therefore, in order to move the magnet support cylinder to the braking position, a driving force that overcomes the attractive force to the annular protrusion is required.
[0007]
In the present invention, by providing an annular groove on the inner peripheral wall of the annular protrusion, the attractive force between the magnet support tube and the annular protrusion is weakened.
[0008]
【Example】
FIG. 1 is a front sectional view of an eddy current reduction device to which the present invention is applied, and FIG. 2 is a side sectional view thereof. The eddy current reduction device has a braking drum 13 coupled to the rotating shaft 4. For this reason, a mounting flange 5 having a spline hole 5a is fitted to the output rotary shaft 4 supported by the bearing 3 on the end wall of the gear box 2 of the transmission and protruding from the end wall, and the nut 6 is prevented from coming out. It is concluded by. The end wall of the braking drum 7 of the parking brake and the boss 9 of the braking drum 13 of the eddy current speed reducing device 9 are integrated with the mounting flange 5 and are fastened by a plurality of bolts 10 and nuts 10a. .
[0009]
The brake drum 13 is made of a material having a high magnetic permeability such as iron, and the base end portion is coupled to a number of support arms (spokes) 12 extending in the radial direction from the boss portion 9. A number of cooling fins 13 a are integrally provided on the outer peripheral wall of the brake drum 13 at equal intervals in the circumferential direction.
[0010]
Inside the brake drum 13, a guide cylinder 18 having an inner space 23 having a box-shaped cross section is disposed coaxially. The guide tube 18 is fixed to the frame plate 31 that is externally fixed to the protruding wall 2 a of the gear box 2 by bolts 32 and 33. The guide tube 18 may be configured by connecting annular end wall plates to both ends of the outer tube portion and the inner tube portion. However, the illustrated guide tube 18 has a left half portion made of a magnetic material such as iron. A cylindrical portion 18b having a U-shaped cross section and a cylindrical portion 18a having an inverted L-shaped cross section in the right half made of a non-magnetic material such as aluminum are coupled by a large number of bolts 14.
[0011]
A large number of openings are provided at equal intervals in the circumferential direction in the cylindrical portion 18a of the guide cylinder 18 facing the inner peripheral surface 13c of the brake drum 13, and a ferromagnetic plate (pole piece) 21 is fitted and fixed to each opening. Actually, the ferromagnetic plate 21 is cast when the cylindrical portion 18a is cast from aluminum. The open end portion (left end portion in FIG. 1) of the brake drum 13 is provided with a conical surface 13b (FIG. 3) extending to the left end side, and heat near the inner peripheral surface 13c of the brake drum 13 tends to flow out to the outside. Configured as follows.
[0012]
A plurality of actuators (not shown) are supported on the frame plate 31 having the reinforcing ribs 31a at equal intervals in the circumferential direction. The actuator is fitted with a piston into a cylinder to define a pair of fluid pressure chambers, and a magnet support cylinder 19 made of a magnetic material is coupled to the end of a rod 17 projecting from the piston to the inner space of the guide cylinder 18. The The magnet support cylinder 19 is supported by the inner space 23 of the guide cylinder 18 so as to be movable in the axial direction. Magnets 20 facing the respective ferromagnetic plates 21 are coupled to the outer peripheral wall of the magnet support cylinder 19 so that the polarities are alternately different in the circumferential direction.
[0013]
During braking, the magnet support cylinder 19 is protruded into the brake drum 13 by an actuator rod 17 as shown in FIG. When the rotating brake drum 13 crosses the magnetic flux from the magnet 20 through the ferromagnetic plate 21 to the inner peripheral surface of the brake drum 13, an eddy current is generated in the brake drum 13, and the brake drum 13 generates a braking torque. The brake drum 13 generates heat due to an eddy current and is cooled by the outside air directly or via the cooling fin 13a. At this time, a magnetic circuit 40 is formed between the magnet support cylinder 19 and the brake drum 13 as shown in FIG. During non-braking, if the magnet support cylinder 19 is moved to the left in FIG. 1 by the actuator and retracted from the braking drum 13, the magnet 20 does not exert magnetic flux on the braking drum 13, and the braking drum 13 does not generate braking torque. .
[0014]
At the non-braking position in which the magnet support cylinder 19 is retracted to the left end of the guide cylinder 18, a thick annular protrusion 38 is provided at the left end of the guide cylinder 18 facing the magnet 20, and is not braked. At this time, a magnetic circuit is formed between the magnet support cylinder 19 and the annular projecting portion 38, and the magnetic flux is shielded from leaking to the outside of the guide cylinder 18, particularly the brake drum 13.
[0015]
As shown in FIG. 3, a conical portion 38 a is formed at a portion of the annular protrusion 38 that faces the open end of the braking drum 13. A conical portion 28 that is integral with the cylindrical portion 18a is fitted on the conical portion 38a, and is connected by a bolt (not shown). In the present invention, in order to weaken the magnetic drag applied to the magnet support cylinder 19 when the magnet support cylinder 19 is switched from the non-braking position to the braking position, an annular wall is formed on the inner peripheral wall of the annular protrusion 38 facing the magnet 20 during non-braking. A groove 35 is provided. Preferably, the annular groove 35 has a width (axial dimension) so as to face the right half of the magnet 20.
[0016]
According to the present invention, since the non-braking magnet 20 faces the annular protrusion 38, the leakage magnetic flux reaching the braking drum 13 from the magnet 20 via the annular groove 35 and the annular protrusion 38 is very small. Hardly receives drag torque from the magnet 20. The left half of the non-braking magnet 20 approaches and faces the annular protrusion 38, but the right half of the magnet 20 faces through the annular groove 35. Therefore, when the magnet support cylinder 19 is driven from the non-braking position to the braking position where the magnet 20 entirely overlaps the ferromagnetic plate 21, the magnet 20 of the magnet support cylinder 19 receives the magnetic drag from the annular protrusion 38. Since only the left half of the magnet 20, the driving force for driving the magnet support cylinder 19 to the braking position is almost halved compared to the conventional example shown by the broken line, as shown by the solid line in FIG. Easy switching operation between braking and non-braking is obtained.
[0017]
As is apparent from the above description, the present invention is not limited to an eddy current reduction device including a ferromagnetic plate (pole piece) as disclosed in, for example, Japanese Utility Model Publication No. 7-47989. The present invention can also be applied to an eddy current reduction device that is not provided with a ferromagnetic plate (pole piece) as disclosed in the Japanese Patent Publication.
[0018]
【The invention's effect】
As described above, the present invention includes a braking drum coupled to a rotating shaft, a ferromagnetic drum that is fixed to the vehicle body, has an inner end protruding into the braking drum, and attracts the magnetic flux of the magnet during non-braking to the outer end. A guide cylinder having an annular projecting portion made of a body and an inner space having a rectangular cross section formed in the guide cylinder are supported so as to be axially movable , and a large number of magnets are opposed to the inner peripheral surface of the brake drum on the outer peripheral surface In the permanent magnet type eddy current reduction device comprising a magnet support cylinder coupled so that the polarities of the magnetic poles are alternately different in the circumferential direction , an annular groove is provided on the inner peripheral wall of the annular projection portion of the guide cylinder facing the magnet. The driving force when the magnet support cylinder is moved from the non-braking position to the braking position is reduced, and the capacity of the actuator that drives the magnet support cylinder can be reduced.
[Brief description of the drawings]
FIG. 1 is a front sectional view of an eddy current reduction device according to the present invention.
FIG. 2 is a side sectional view of the eddy current reduction device.
FIG. 3 is an enlarged front sectional view showing a main part of the eddy current reduction device.
FIG. 4 is a diagram showing the relationship between the amount of movement for moving the magnet support cylinder to the braking position and the driving force.
[Explanation of symbols]
2: Gear box 4: Rotating shaft 12: Support arm 13: Braking drum 13c: Inner peripheral surface 18: Guide tube 18a: Tube portion 18b: Tube portion 19: Magnet support tube 20: Magnet 21: Ferromagnetic plate 23: Inside air Part 35: annular groove 38: annular protrusion

Claims (1)

A braking drum coupled to the rotating shaft, and an annular projecting portion made of a ferromagnetic material that is fixed to the vehicle body and has an inner end projecting into the braking drum and attracting the magnetic flux of the magnet during non-braking to the outer end. A guide cylinder and an inner space of a rectangular cross section formed in the guide cylinder are supported so as to be movable in the axial direction , and a large number of magnets are arranged on the outer peripheral surface. In a permanent magnet type eddy current reduction device comprising a magnet support cylinder coupled differently , a permanent magnet type characterized in that an annular groove is provided in an inner peripheral wall of the annular projection portion of the guide cylinder facing the magnet. Eddy current reducer.

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