JP3760723B2 - Eddy current reducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an eddy current reduction device that assists a friction brake of a vehicle or the like, and more particularly to an eddy current reduction device that switches between non-braking and braking by forward and reverse rotation of a magnet support cylinder.
[0002]
[Prior art]
In an eddy current reduction device in which a rotatable magnet support tube is accommodated in the inner space of the guide tube, a sintered resin such as copper and fluorine resin (PTFE) are placed on the inner peripheral surface (shaft hole) of the magnet support tube. A drive bush (bearing bush) impregnated with lead is press-fitted, and the drive bush is extrapolated to the anodized portion of the outer peripheral surface of the inner tube portion (shaft portion) of the aluminum guide tube. It is easy to rotate. The magnet support cylinder is connected to the rod of the fluid pressure actuator and is rotated forward and backward between a braking position and a non-braking position.
[0003]
Since drive bushes use a material mainly composed of fluororesin such as Teflon (registered trademark), the friction coefficient increases when the surface pressure of the friction surface is low or high, causing the magnet support cylinder to malfunction. It was possible to wake up. In other words, the fluorine resin-based drive bush has a large friction coefficient when the surface pressure of the friction surface is low, and the friction surface temperature rises when the friction coefficient is large within a minute range of the friction surface. Further, when the ambient temperature is further increased due to the influence of heat caused by the eddy current from the braking drum during braking, the friction coefficient of the friction surface increases, preventing smooth operation of the magnet support cylinder.
[0004]
According to the experimental results of the magnet support cylinder sticking, when the inner cylinder part made of aluminum or the like is thermally expanded at a high temperature during braking, the gap with the drive bush becomes narrow, and the drive bush becomes plastic at the local wear part. A flow (softening and melting) is generated, pushed in the circumferential direction, and pushed into a narrow gap. When the rotational speed of the brake drum decreases over time, the plastic flow begins to solidify, the friction coefficient becomes abnormally large, and if the plastic flow remains solidified, it is considered that the magnet support cylinder is fixed. What is important here is that the drive bush made by impregnating a sintered metal such as copper with fluorine resin (PTFE) and lead has an elastic friction in the friction region where the frictional surface pressure is low. In the friction region where the frictional surface pressure is high, it is considered that the plastic friction characteristics of the underlying sintered metal are transferred.
[0005]
[Problems to be solved by the invention]
In view of the above problems, the problem of the present invention is to increase the friction surface pressure of the drive bush press-fitted into the inner peripheral surface of the magnet support cylinder with respect to the outer peripheral surface of the inner cylinder portion of the guide cylinder in consideration of the friction characteristics of the drive bush. Another object is to provide an eddy current reduction device that reduces the thermal load near the friction surface.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the configuration of the present invention includes a braking drum coupled to a rotating shaft, a guide cylinder made of aluminum supported in a non-rotating portion such as a vehicle body inside the braking drum, and the guide cylinder. A magnet support tube rotatably supported in an inner space having a rectangular cross section; a number of magnets coupled to the outer peripheral surface of the magnet support tube at equal intervals in the circumferential direction; and the magnets of the outer tube portion of the guide tube; In the eddy current reduction device having a ferromagnetic material disposed in the opposed portions and generating a braking force on the braking drum by an eddy current based on a magnetic field from the magnet, a resin-based drive is provided on the magnet support cylinder The bush is fitted and supported, and the portion facing the drive bush on the outer peripheral surface of the inner tube portion of the guide tube is provided with a portion subjected to alumite treatment and a portion not subjected to alumite treatment.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the outer peripheral surface of the inner tube portion of the guide tube is partially anodized to harden the surface so that the drive bush is frictionally engaged only with the anodized layer, and the friction surface pressure is increased. Thus, the friction coefficient of the friction engagement portion is lowered to suppress heat generation. The drive bush is frictionally engaged with the anodized layer on the outer peripheral surface of the inner tube portion of the guide tube, and a gap corresponding to the anodized layer is formed between the drive bush and the non-anodized layer. In addition, since the alumite non-treated layer has a higher thermal conductivity than the alumite treated layer, frictional heat is smoothly released to the outside.
[0008]
In short, the present invention pays attention to the fact that the coefficient of friction decreases when the surface pressure of the friction surface of the drive bush is increased, and by providing an alumite treatment layer partially on the outer peripheral surface of the inner tube portion of the guide tube, The friction area is reduced, the surface pressure of the friction surface is increased to a predetermined level, the friction coefficient of the friction engagement portion is lowered, and heat generation is suppressed.
[0009]
【Example】
FIG. 1 is a front sectional view of an eddy current reduction device according to the present invention, and FIG. 2 is a side sectional view thereof. The eddy current reduction device according to the present invention includes, for example, a brake drum 7 made of a conductor coupled to an output rotation shaft 1 of a vehicle transmission, and a guide cylinder 10 made of a nonmagnetic material disposed inside the brake drum 7. , A movable magnet support tube 14 accommodated in an inner space having a rectangular cross section of the guide tube 10, and a stationary magnet support tube 14 A fixed by a locking pin 13. The brake drum 7 is overlapped with the flange 5a of the boss 5 together with the end wall of the brake drum 3 of the parking brake on the mounting flange 2 that is spline-fitted to the rotary shaft 1, and is fastened by a plurality of bolts 4 and nuts. Is done. The base end of the brake drum 7 having the cooling fins 8 is coupled to a large number of spokes 6 extending radially from the boss 5.
[0010]
The guide cylinder 10 having a rectangular cross section is configured by coupling an end wall 11 made of an annular plate to a cylinder having a C-shaped cross section, for example. The guide tube 10 is fixed to, for example, a gear box of a vehicle transmission by appropriate means. A rectangular ferromagnetic plate (pole piece) 15 having retaining protrusions 15c is coupled to a large number of openings 25 provided at equal intervals in the circumferential direction on the outer cylinder portion 10a of the guide cylinder 10. Preferably, the ferromagnetic plate 15 is cast when the guide tube 10 is formed.
[0011]
The magnet support cylinder 14 made of a magnetic material is supported by the inner cylinder portion 10b so that it can be rotated forward and backward by the drive bush 26 in the inner space 37 of the guide cylinder 10. Although not shown, the protruding wall portion protruding in the axial direction from the left end wall of the magnet support cylinder 14 is the inner space portion 37, and the actuator 20 integrated with the left end wall of the guide cylinder 10 is from the piston fitted to the cylinder 18. Connected to protruding rod. The magnet support cylinder 14 is coupled to the outer peripheral surface of the magnets 24 facing the ferromagnetic plates 15 so that the polarities with respect to the ferromagnetic plates 15 are alternately different in the circumferential direction.
[0012]
As shown in FIG. 2, the magnetic flux density from the magnet 24 toward the braking drum 7 (and vice versa) is maximized at the central portion of the ferromagnetic plate 15 (the central portion in the rotational direction of the braking drum 7 (arrow y)). Thus, the area of the outer surface of the ferromagnetic plate 15 facing the inner peripheral surface of the brake drum 7 is configured to be smaller than the area of the inner surface facing the magnet 24. For this reason, the front surface 15a of the ferromagnetic plate 15 is inclined backward in the rotational direction (arrow y) of the braking drum 7 from the middle toward the outer surface. Similarly, the rear surface 15b of the ferromagnetic plate 15 is inclined forward in the rotational direction of the brake drum 7 from the middle toward the outer surface.
[0013]
In the present invention, in order to increase the surface pressure of the friction surface of the drive bush 26 to a predetermined level, the resin-based drive bush 26 is press-fitted and supported on the magnet support tube 14, and the outer peripheral surface 27 of the inner tube portion 10 b of the guide tube 10. In other words, the portion facing the resin drive bush 26 is provided with a portion 28 subjected to an alumite treatment and a portion 29 not subjected to an alumite treatment.
[0014]
In the embodiment shown in FIG. 3, as shown by the lattice pattern, two annular rings extending in the circumferential direction are provided on the outer peripheral surface 27 of the inner cylinder portion 10 b of the guide cylinder 10 that supports the drive bush 26 of the movable magnet support cylinder 14. A portion 28 subjected to the alumite treatment is provided, and a portion 29 not subjected to the alumite treatment is provided between two portions 28 subjected to the alumite treatment. The outer peripheral surface 27 of the inner cylinder portion 10b of the guide cylinder 10 that supports the stationary magnet support cylinder 14A may not be subjected to anodizing, but may be subjected to anodizing.
[0015]
In the embodiment shown in FIG. 4, as shown by the lattice pattern, there is an interval in the circumferential direction on the outer peripheral surface 27 of the inner cylinder portion 10 b of the guide cylinder 10 that supports the drive bush 26 of the movable magnet support cylinder 14. Thus, the strip-shaped alumite-treated portions 28 extending in a plurality of axial directions (rotating shaft direction of the braking drum 7) and the portions 29 not subjected to the alumite treatment are alternately provided. The outer peripheral surface 27 of the inner cylinder portion 10b of the guide cylinder 10 that supports the stationary magnet support cylinder 14A may not be subjected to anodizing, but may be subjected to anodizing.
[0016]
As shown in FIG. 5, a plurality of strip-shaped anodized portions 28 arranged alternately on the outer peripheral surface 27 of the inner tube portion 10 b of the guide tube 10 at intervals in the circumferential direction, and the strip-shaped anodized treatment The portion 29 not to be applied may be inclined with respect to the rotating shaft of the brake drum 7.
[0017]
Further, as shown by the lattice pattern in FIGS. 6 and 7, the portion 28 subjected to the alumite treatment provided on the outer peripheral surface 27 of the inner cylinder portion 10 b of the guide cylinder 10 has a plurality of required shapes such as a plurality of circles and rectangles. Alternatively, the circumferential direction and the axial direction may be spaced apart.
[0018]
In order to form the anodized portion 28 having the shape as shown in FIGS. 3 to 7 on the outer peripheral surface 27 of the inner tube portion 10b of the guide tube 10, the portion 29 that has not been previously anodized is coated with a required material. A paper or a coated film is affixed, and an alumite treatment is applied to the guide tube 10, and then the coated paper or the coated film is peeled from the guide tube 10. Alternatively, after the alumite treatment is performed on the entire surface of the guide tube 10, the alumite treatment layer 28 may be removed by machining to form a portion 29 that is not subjected to the alumite treatment.
[0019]
When the above-described eddy current reduction device is not braked, as shown in FIG. 1, the two magnets 24 and 24A arranged in the axial direction of the magnet support cylinders 14 and 14A have polarities facing the common ferromagnetic plate 15 entirely. Are opposite to each other. At this time, the two magnets 24 and 24A form a short-circuit magnetic circuit w between each ferromagnetic plate 15 and the magnet support cylinders 14 and 14A, and do not exert a magnetic field on the braking drum 7. At the time of braking, as shown in FIG. 2, the magnets 24, 24 </ b> A arranged in the axial direction (magnet 24 </ b> A see FIG. 1) have the same polarity facing the ferromagnetic plate 15, and the braking drum 7 passes through the ferromagnetic plate 15. Exert a magnetic field on At this time, each magnet 24, 24A forms a magnetic circuit z between the brake drum 7 and the magnet support cylinders 14, 14A. When the rotating brake drum 7 crosses the magnetic field, an eddy current flows through the brake drum 7 and the brake drum 7 receives a braking torque.
[0020]
As shown in FIG. 13, in the drive bush 26 in which a sintered metal such as copper is impregnated with fluorine resin (PTFE) and lead, the fluorine resin acts as an elastic body in the friction region where the frictional surface pressure is low. In the friction region where the friction characteristic is high and the friction coefficient is high, but the friction surface pressure is high, the transition is made to the plastic friction characteristic of the underlying sintered metal, and the friction coefficient is small and shows a substantially constant value. In the present invention, the outer peripheral surface 27 facing the drive bush 26 of the inner tube portion 10b of the guide tube 10 is provided with the alumite-treated portion 28 and the alumite-treated portion 29, so that the alumite-treated portion 28 is provided. Only forms a friction surface that supports the drive bush 26, and the friction area becomes narrow. Therefore, the friction surface pressure of the drive bush 26 against the inner cylinder portion 10b increases, the friction coefficient decreases, heat generation is suppressed, and alumite is suppressed. The heat load in the vicinity of the friction surface is reduced by the portion 29 not subjected to the alumite treatment having a higher thermal conductivity than the portion 28 subjected to the treatment, and the smooth operation of the magnet support cylinder 14 is guaranteed.
[0021]
In the above-described embodiment, the eddy current reduction device has been described in which a movable magnet support tube and a stationary magnet support tube are provided, and switching between braking and non-braking is performed by rotational differential between them. There is no limitation, and a single magnet support tube is rotatably supported inside the guide tube, and two magnets arranged in the circumferential direction of the magnet support tube are partially opposed to the common ferromagnetic plate. The present invention is also applicable to an eddy current reduction device of a type that switches between a braking position and a braking position in which one magnet entirely faces the ferromagnetic plate.
[0022]
In the embodiment shown in FIG. 8, a large number of magnets 24 having magnetic poles at circumferential ends are arranged on the outer peripheral surface of a single magnet support cylinder 14 at equal intervals in the circumferential direction, and the magnetic poles of the magnets 24 face each other. And support to be the same polarity. Other configurations are the same as those of the embodiment shown in FIG. At the braking position shown in FIG. 8, a magnetic field exerts a magnetic field on the braking drum 7 through the magnet support cylinder 14 and the ferromagnetic plate 15 from the opposing magnetic poles of a pair of magnets 24 adjacent in the circumferential direction. A magnetic circuit w is generated between the magnet 24 and the magnet 24. When non-braking, when the magnets 24 are rotated by the half arrangement pitch, a short-circuit magnetic circuit w is generated between each magnet 24 and the ferromagnetic plate 15 and no magnetic field is applied to the braking drum 7.
[0023]
In the embodiment shown in FIGS. 9 and 10, a guide cylinder 10 made of a non-magnetic material and having an inner space with a rectangular cross section is disposed inside the brake drum 7 coupled to the rotating shaft, and the outer cylinder of the guide cylinder 10 is arranged. A large number of ferromagnetic plates 15 are arranged at equal intervals in the circumferential direction on the portion 10a, and each outer peripheral surface of a magnet support cylinder 14 made of a magnetic material supported on the inner cylinder portion 10b of the guide cylinder 10 so as to be able to rotate forward and backward is provided on each outer circumferential surface. The magnets 24 are coupled so that the polarities opposed to the ferromagnetic plates 15 are alternately different in the circumferential direction, and the non-braking positions where the two magnets 24 adjacent in the circumferential direction partially face each of the ferromagnetic plates 15 (FIG. 9). And the magnet support cylinder 14 is rotated forward and backward by the actuator 20 between the braking position (same as the state shown in FIG. 2) where the one magnet 24 is completely opposed to each ferromagnetic plate 15. It is to switch. Although not shown, a resin-based drive bush 26 is fitted and supported on the magnet support cylinder 14, and a portion of the outer cylinder 27 of the inner cylinder portion 10 b of the guide cylinder 10 made of aluminum is opposed to the drive bush 26. A portion 28 subjected to an alumite treatment as shown in 3 to 7 and a portion 29 not subjected to an alumite treatment are provided.
[0024]
In the embodiment shown in FIGS. 11 and 12, a guide cylinder 10 made of a non-magnetic material and having an inner space with a rectangular cross section is disposed inside the brake drum 7 coupled to the rotating shaft, and the outer cylinder of the guide cylinder 10 is provided. A large number of ferromagnetic plates 15 are arranged at equal intervals in the circumferential direction on the portion 10a, and each outer peripheral surface of a magnet support cylinder 14 made of a magnetic material supported on the inner cylinder portion 10b of the guide cylinder 10 so as to be able to rotate forward and backward is provided on each outer circumferential surface. Two magnets 24 are coupled to each of the ferromagnetic plates 15 so as to face the two ferromagnetic plates 15 so that the polarities with respect to the ferromagnetic plates 15 are different every two in the circumferential direction. The magnet support cylinder 14 is switched by a forward and reverse rotation by the actuator 20 between a non-braking position facing the magnet and a braking position where the two magnets 24 having the same polarity are opposed to the respective ferromagnetic plates 15 entirely. . Although not shown, a resin-based drive bush 26 is fitted and supported on the magnet support cylinder 14, and a portion of the outer cylinder 27 of the inner cylinder portion 10 b of the guide cylinder 10 made of aluminum is opposed to the drive bush 26. A portion 28 subjected to an alumite treatment as shown in 3 to 7 and a portion 29 not subjected to an alumite treatment are provided.
[0025]
【The invention's effect】
As described above, the present invention provides a braking drum coupled to a rotating shaft, a guide tube made of aluminum supported on a non-rotating portion such as a vehicle body inside the braking drum, and an inner space of the guide tube having a rectangular cross section. A magnet support tube rotatably supported by the portion, a number of magnets coupled to the outer peripheral surface of the magnet support tube at equal intervals in the circumferential direction, and a portion of the outer tube portion of the guide tube facing the magnets In an eddy current reduction device that has a ferromagnetic body and generates a braking force on the braking drum by an eddy current based on a magnetic field from the magnet, a resin-based drive bush is fitted and supported on the magnet support cylinder In addition, since the portion facing the drive bush on the outer peripheral surface of the inner tube portion of the guide tube is provided with a portion subjected to alumite treatment and a portion not subjected to alumite treatment, the friction surface pressure of the drive bush against the inner tube portion is increased. High vat friction The number is lowered, together with the heat generation is suppressed, the thermal load near the friction surface is reduced.
[Brief description of the drawings]
FIG. 1 is a front sectional view of an eddy current reduction device to which the present invention is applied during non-braking.
FIG. 2 is a side sectional view of the eddy current reduction device during braking.
FIG. 3 is a perspective view showing an inner cylinder portion of a guide cylinder of the eddy current reduction device.
FIG. 4 is a perspective view showing a modified embodiment of the inner cylinder portion of the guide cylinder of the eddy current reduction device.
FIG. 5 is a perspective view showing a modified embodiment of the inner cylinder portion of the guide cylinder of the eddy current reduction device.
FIG. 6 is a perspective view showing a modified embodiment of the inner cylinder portion of the guide cylinder of the eddy current reduction device.
FIG. 7 is a perspective view showing a modified embodiment of the inner cylinder portion of the guide cylinder of the eddy current reduction device.
FIG. 8 is a side sectional view of another eddy current reduction device to which the present invention is applied.
FIG. 9 is a front sectional view of another eddy current reduction device to which the present invention is applied.
FIG. 10 is a side cross-sectional view of the eddy current reduction device when not braked.
FIG. 11 is a side cross-sectional view of another eddy current reduction device to which the present invention is applied during non-braking.
FIG. 12 is a side sectional view of the eddy current reduction device during braking.
FIG. 13 is a diagram showing the friction characteristics of the rotation support portion of the magnet support cylinder of the eddy current reduction device.
[Explanation of symbols]
1: Rotating shaft 6: Spoke 7: Braking drum 10: Guide cylinder 10a: Outer cylinder part 10b: Inner cylinder part 14: Magnet support cylinder 14A: Magnet support cylinder 15: Ferromagnetic plate 20: Actuator 24: Magnet 24A: Magnet 26 : Drive bush 27: Outer peripheral surface 28: Alumite-treated part 29: Alumite-treated part

Claims (3)

A brake drum coupled to the rotating shaft, a guide tube made of aluminum supported on a non-rotating portion of the vehicle body and the like inside the brake drum, and rotatably supported in an inner space of a rectangular cross section of the guide tube A magnet support cylinder, a number of magnets coupled to the outer peripheral surface of the magnet support cylinder at equal intervals in the circumferential direction, and a ferromagnetic body disposed in a portion of the outer cylinder portion of the guide cylinder facing the magnets. An eddy current reduction device for generating a braking force on the braking drum by an eddy current based on a magnetic field from the magnet, wherein a resin-based drive bush is fitted and supported on the magnet support cylinder, and an inner cylinder of the guide cylinder An eddy current reduction device characterized in that a portion of the outer peripheral surface of the portion facing the drive bush is provided with a portion subjected to alumite treatment and a portion not subjected to alumite treatment. The eddy current reduction device according to claim 1, wherein the portion subjected to the alumite treatment is an annular portion extending in a circumferential direction. The eddy current reduction device according to claim 1, wherein the alumite-treated portion is divided at equal intervals in the circumferential direction.

Images