JP2003333824A - Eddy current speed reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy current speed reducer which can be miniaturized and lightened and can secure a stable braking force even in long-time brake, with superior magnetic efficiency. <P>SOLUTION: This reducer is an eddy current speed reducer of a magnet pole surface facing system or a pole pieceless system. A plurality of slits passing through a thickness into a brake disk are formed in the radial direction from the outer peripheral surface. The reducer has a plurality of brake disks divided in the circumferential direction. Moreover, an eddy current plate is provided in a part where magnetic flux from a permanent magnet acts in the brake disk. The eddy current plate is divided into a plurality of pieces in circumferential directions of the brake disks and fixed to the brake disks at the inner peripheral side or/and the outer peripheral side. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk type eddy current speed reducer for assisting a main brake used in a vehicle such as an automobile. More specifically, it has excellent magnetic efficiency during braking, has a simple structure and is small in size. The present invention relates to an eddy current speed reducer that can be reduced in weight and can suppress a deformation of a braking disc even when used for a long time, and can secure a stable braking force.

[0002]

2. Description of the Related Art In addition to a foot brake which is a main brake and an exhaust brake which is an auxiliary brake, a braking device for an automobile such as a truck or a bus is capable of performing stable deceleration on a descending slope of a long slope, and a foot brake. An eddy current speed reducer is used to prevent the vapor lock phenomenon and burnout.

Recently, demands for eddy current reduction gears have been diversified, and there has been a strong demand to improve the mountability on vehicles so as to reduce the manufacturing cost and enable the mounting on small vehicles. In order to improve the mountability, it is required that the size and weight be reduced, the structure be simple, and the economy be excellent.

In response to the above-mentioned demand, on the premise of a disk type eddy current speed reducer, a method in which a magnetic pole surface of a permanent magnet is opposed to a braking disk so as to approach the braking disk and a braking torque is generated in the disk itself (hereinafter, referred to as "magnet"). It is sometimes referred to as the "polar surface facing method") has been developed. With this method,
Since the magnetic lines of force of the permanent magnet can be added to the braking disk with a short magnetic path length, the magnetic resistance of the magnetic circuit is reduced, the magnetic efficiency is improved, and the braking torque can be increased.

FIG. 1 and FIG. 2 are cross-sectional views showing an example of the structure of a "magnet pole surface facing type" eddy current reduction device using permanent magnets. FIG. 1 shows the device configuration during braking, and FIG. 2 shows the device configuration during non-braking.

In this eddy current speed reducer, a braking disk 2 made of a ferromagnetic material is attached to the rotating shaft 1, and a guide cylinder 3 made of a non-magnetic material is provided on the side of the braking disk 2. . The guide cylinder 3 is supported by a non-rotating portion of a vehicle or the like, and inside thereof, a holding ring 4 made of a ferromagnetic material capable of moving forward and backward in a direction perpendicular to the braking surface of the braking disk 2 is accommodated. The guide cylinder 3 is provided with a cylinder 5 for moving the holding ring 4 forward and backward. On the other hand, a ferromagnetic material (pole piece) 8 is arranged on the end surface of the guide cylinder 3 facing the braking disk.

A plurality of permanent magnets 7 are circumferentially arranged on the side surface of the holding ring 4 facing the braking disc 2. The magnetic poles of the permanent magnets 7 face the braking surface of the braking disk 2, and the magnetic poles of the adjacent permanent magnets are arranged in opposite directions. A plurality of ferromagnetic materials 8 facing the magnetic pole surface of each permanent magnet 7 are arranged so as to make a pair with the permanent magnet 7 in the circumferential direction.

In the drive mechanism of the permanent magnet 7, the cylinder 5 is arranged on the outer end wall of the guide cylinder 3, and the piston rod 6 fitted into the cylinder 5 penetrates the outer end wall of the guide cylinder 3 to the holding ring 4. Are connected. With this configuration, the holding ring 4 can be moved forward and backward in the direction orthogonal to the braking disc 2 by the operation of the cylinder 5.

During braking, as shown by the arrow in FIG. 1, the piston rod 6 of the cylinder 5 moves to the right, the retaining ring advances in the direction of the rotation axis of the braking disc 2, and the permanent magnet 7 faces the braking disc. And approach.

At this time, when each rotating permanent magnet 7 passes through the ferromagnetic material 8 and passes through the magnetic force lines perpendicular to the braking surface of the braking disc 2, the rotating braking disc 2 crosses the rotating magnetic flux, and the braking disc 2 is changed due to the change in the magnetic flux in the braking disc 2. Eddy current flows and braking torque is generated.

When switching to non-braking, the cylinder 5
2 is switched to move the holding ring 4 directly connected to the piston rod 6 to the left as shown by the arrow in FIG. 2, so that the permanent magnet 7 is separated from the ferromagnetic material (pole piece) 8 and the permanent magnet 7 is moved. The magnetic force exerted by 7 on the braking disc 2 is weak.

A ferromagnetic material (pole piece) is provided in the "magnet pole surface facing type" eddy current reduction device using permanent magnets shown in FIGS. This is because the permanent magnet has a strong temperature dependency, and when the temperature exceeds a certain temperature, the magnetic force decreases and the braking torque decreases.Therefore, in order to suppress the temperature rise of the permanent magnet, between the permanent magnet and the braking disk that is the heat source This is because an appropriate distance is provided. That is, when these distances increase, the braking torque decreases, so that the ferromagnetic material (ball piece) is interposed between the two to minimize the gap on the magnetic circuit.

However, as compared with the drum type in which the guide tube is covered with a drum, the disk type has a structure in which the guide tube is exposed to the outside of the braking disk, which is the heat generating portion, and therefore the guide tube itself has excellent heat dissipation. Therefore, even if the amount of heat input to the guide tube is the same, the disk-type guide tube can be configured to be in direct contact with the outside air, and the area that can be allowed to cool down can be increased. Can be suppressed.

Further, by making the structure of the device disk type, it becomes easier to attach the cooling fins as compared with the drum type, and it is possible to increase the heat radiation capacity of the braking disk which is the heat source. Therefore, the temperature rise of the permanent magnet during braking can be suppressed, and in addition, the heat itself transmitted from the braking disk can be reduced, so that the distance between the permanent magnet and the braking disk can be extremely reduced.

As a result, the permanent magnet can be brought sufficiently close to the braking disk, and sufficient braking torque can be secured even if the magnetic circuit is constructed without using the ferromagnetic material (pole piece). Based on such knowledge, a "magnet pole surface facing type" eddy current reduction device that does not use a ferromagnetic material (pole piece) has been newly developed.

FIG. 3 is a diagram showing the structure of an eddy current reduction device of the "magnet pole surface facing type" which does not use a ferromagnetic material (pole piece). The eddy current speed reducer shown in FIG. 3 has the same basic structure and operation of each member as the eddy current speed reducer of the “magnet pole surface facing type” shown in FIG. 1 and FIG. , Is made of a non-magnetic material without disposing a ferromagnetic material (pole piece) on the end surface facing the braking disk.

Further, in the eddy current reduction device shown in FIG. 3, since the permanent magnet is covered with the guide tube including the end surface facing the permanent magnet, the magnetic pole surface of the permanent magnet is damaged by foreign matter or by moisture. There is no risk of rusting.
Further, without providing a ferromagnetic material (pole piece), the lines of magnetic force from the permanent magnet can be directly added to the braking disc with a short magnetic path length, so that the efficiency of generating braking torque can be improved.

In the following description, when specifying the "magnet pole surface facing type" eddy current reduction device that does not use a ferromagnetic material (pole piece) shown in FIG. 3, the "pole pieceless type" eddy current is used. It is called a current reduction gear.

[0019]

As described above, in the "magnet pole surface facing type" eddy current reduction device and the "pole pieceless type" eddy current reduction device in which the permanent magnets are arranged so as to face the braking disk. In addition to being excellent in magnetic efficiency at the time of braking, it is possible to reduce the size and weight with a simple structure, and it is also excellent in economic efficiency. However, as future demands are diversified, as a new issue to be addressed, there is a problem regarding improvement of stability and durability of braking force when used for a long time.

In the "magnet pole surface facing type" and "pole pieceless type" eddy current reduction gears, improvement of stability and durability of braking force when used for a long period of time should be taken up as a subject. It is based on such factors.

When the magnetic force exerted by the permanent magnet is applied to the surface of the braking disk during braking, an eddy current is generated in the braking disk and Joule heat is generated. The generated heat causes the braking disk to thermally expand, but since it is fixed to the rotating shaft, the thermal expansion in the radial direction is restricted.

Further, since the eddy current flows concentratedly near the surface due to the skin effect, the surface of the braking disk facing the permanent magnet becomes hot. As a result, the amount of thermal expansion of the surface of the braking disk facing the permanent magnet becomes larger than the amount of thermal expansion of the surface on the opposite side, and the braking disk warps in its thickness direction, that is, the rotation axis direction. Become.

The higher the temperature of the braking disc, the greater the amount of warpage, and the residual deformation of the braking disc occurs after cooling. By repeating braking and non-braking for a long period of time, the above deformation is accumulated in the braking disc.
When the braking disk is deformed, the distance between the braking disk and the permanent magnet changes, so that the magnetic flux acting on the surface of the braking disk is not constant and the braking force becomes unstable.

The present invention has been made in view of the new problems required for the "magnet pole surface facing type" and "pole pieceless type" eddy current reduction devices using the above-mentioned permanent magnets, The magnetic efficiency during braking is excellent, the size and weight can be reduced with a simple structure, and even when it is used for a long time, the deformation of the braking disk is suppressed and a stable braking force can be secured. It is an object of the present invention to provide an eddy current speed reducer that can be used.

[0025]

In order to solve the above-mentioned problems, the inventors of the present invention have made further detailed studies on the deformation state of the braking disc. As a result, the braking disc is repeatedly used for a long time during braking. In this case, it was possible to clarify the reason why the inelastic strain gradually accumulated and the braking force decreased.

As described above, at the time of braking, the part of the braking disk facing the permanent magnet becomes high temperature due to the generation of Joule heat, but the temperature is low at the outer peripheral side of the part. As an extreme example, even if the permanent magnet is opposed to the outermost circumferential side of the braking disc and the outermost circumferential side is heated to a high temperature, the braking disc has a structure that radiates heat from the outermost circumferential side, so the outermost circumferential side has the highest temperature. There is no.

Therefore, during braking, the braking disk has a high temperature portion facing the permanent magnet, a ring-shaped low temperature portion existing on the outer peripheral side thereof, and a low temperature on the opposite surface side, that is, the surface side not facing the permanent magnet. The department will exist.

The braking disk thermally expands as the temperature rises during braking, which becomes more prominent at the higher temperature portion. Therefore, since the part of the part that is significantly thermally expanded facing the permanent magnet is on the inner peripheral side, the thermal expansion of the part is restricted by the ring-shaped low temperature part on the outer peripheral side, that is, the part with small thermal expansion. It

As a result, when used at high temperature, inelastic strain (plastic strain + creep strain) is generated in the portion of the braking disc facing the permanent magnet and in the vicinity thereof, and residual deformation is caused. . By repeating braking and non-braking, the residual deformation is gradually accumulated, the deformation of the braking disc becomes large, the braking force becomes unstable, and the braking efficiency is reduced.

The present inventors have provided a slit in the braking disk to divide the ring-shaped low temperature portion on the outer peripheral side, which restricts the thermal expansion of the portion facing the permanent magnet and becomes high temperature, to thereby achieve the thermal expansion. We paid attention to the ability to reduce the binding force at the time. Furthermore, it has been noted that the same effect can be achieved by providing an eddy current plate in a portion of the braking disk where the magnetic flux from the permanent magnet acts.

If a plurality of circumferentially divided eddy current plates are provided in the portion of the braking disk where the magnetic flux from the permanent magnets acts, the eddy current plates generate heat during braking. At this time,
The outer peripheral portion and the inner peripheral portion of the eddy current plate are in contact with the braking disc, and the heat generated is conducted from the outer peripheral portion and the inner peripheral portion of the eddy current plate to the braking disc surface.

Therefore, the central portion of the eddy current plate has the highest temperature, and the outer peripheral portion and the inner peripheral portion have lower temperatures than the central portion. Also, since the eddy current plate is divided into multiple pieces in the circumferential direction,
The ring-shaped low temperature portion (that is, the outer peripheral portion and the inner peripheral portion) that restrains the thermal expansion of the high temperature portion is divided, and the restraining force during the thermal expansion can be reduced. This has the same effect as providing a slit in the braking disc, as described above.

As a result, inelastic strain generated in the eddy current plate is suppressed, and permanent deformation hardly occurs. As a result, even if the braking disc is used for a long time, the deformation of the braking disc is suppressed, and a stable braking force can be secured.

The present invention has been completed on the basis of the above findings, and has as its gist the following eddy current reduction gears (1) to (6). (1) An eddy current reduction device of "magnet pole surface facing type" using a permanent magnet, that is, a braking disc mounted on a rotating shaft and a non-rotating portion supported on the side of the braking disc. The guide tube and the inside of this guide tube,
A holding ring that is movable in the rotation axis direction of the braking disc, a plurality of permanent magnets facing the braking disc in the circumferential direction of the holding ring, and having adjacent magnetic poles arranged in opposite directions to each other, and the permanent magnet. Is a eddy current reduction device in which a ferromagnetic material is provided on the end surface of the guide cylinder so as to face the permanent magnet, and the permanent magnet is movable in the rotation axis direction. A plurality of slits are provided in the radial direction from the outer peripheral surface (hereinafter referred to as "first device"). (2) An eddy current speed reducer that uses a permanent magnet and is a “magnet pole surface facing type” eddy current speed reducer characterized in that the braking disk is divided into a plurality in the circumferential direction (hereinafter,
"Second device"). (3) An eddy current reduction device of the "magnet pole surface facing type" using permanent magnets, in which an eddy current plate is provided at the portion of the braking disc where the magnetic flux from the permanent magnet acts, and the eddy current plate is the braking disc. Is divided into a plurality of parts in the circumferential direction and is fixed to the braking disc on the inner peripheral side and / or the outer peripheral side thereof (hereinafter, referred to as “third part”).
Device)). (4) "Pole-pieceless" eddy current reducer, that is, a braking disc mounted on a rotating shaft, a guide cylinder supported by a non-rotating portion and arranged on the side of the braking disc, and this guide. A holding ring that is housed inside the cylinder and is movable in the rotation axis direction of the braking disc, and a plurality of holding magnetic poles that face the braking disc in the circumferential direction of the holding ring and that have adjacent magnetic poles arranged in opposite directions. A permanent magnet is provided, the guide cylinder is entirely made up of a non-magnetic material including an end surface facing the permanent magnet, and the permanent magnet is movable in a rotation axis direction. An eddy current speed reducer characterized in that a plurality of slits penetrating the wall are provided in the radial direction from the outer peripheral surface (hereinafter,
"Fourth device"). (5) An eddy current speed reducer of the "pole pieceless type", characterized in that the braking disk is divided into a plurality of parts in the circumferential direction (hereinafter referred to as "fifth device").
That). (6) In the "pole pieceless" eddy current speed reducer, an eddy current plate is provided at the portion of the braking disc where the magnetic flux from the permanent magnet acts. The eddy current speed reducer is characterized in that the eddy current speed reducer is divided into two parts and is fixed to the braking disc on the inner peripheral side and / or the outer peripheral side (hereinafter referred to as “sixth device”).

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION In the eddy current speed reducer of the present invention, the heat of a portion which becomes hot during braking is provided by providing slits or divisions on the braking disc or by providing an eddy current plate on the braking disc. It is characterized in that the restraint force due to the expansion is reduced, the deformation in the radial direction and the rotation axis direction is facilitated, the inelastic strain generated in the braking disk is reduced, and as a result, the permanent deformation is hard to occur. This makes it possible to stabilize the braking force of the eddy current speed reducer even when braking is repeated for a long time.

FIG. 4 is a diagram showing a planar shape of the first and fourth devices in which a braking disk surface is provided with a slit penetrating the wall thickness. In (a), a slit 9 is provided on the radiation extending from the center of the braking disc 2 from the outer peripheral surface to the inner peripheral side. Further, in the same (b), the slit 9 is provided from the outer peripheral side to the inner peripheral side by inclining in the rotation direction of the braking disk 2. With any of the slits, the restraining force due to the thermal expansion of the braking disc can be reduced, and the inelastic strain generated in the braking disc can be reduced.

Considering the weight balance of the braking disc 2 during rotation, the slits 9 need to be provided at equal intervals in the circumferential direction. Therefore, it is desirable that two or more slits 9 are provided symmetrically about the rotation axis.

FIG. 5 is a view showing a sectional shape in which the slit penetrates the thickness of the braking disk in the first device and the fourth device. In the same (a), the slit 9 is formed parallel to the rotation axis, in the same (b), the slit 9 inclined with respect to the rotation axis is formed, and in the same (c), the key-shaped slit is formed. 9 is formed.

When the sectional shape penetrating the thickness of the braking disc 2 shown in FIG. 5 is applied to any of the planar slits 9 shown in FIG. 4, the inelastic strain generated in the braking disc 2 is reduced. be able to.

FIG. 6 is a view showing a situation in which the braking disk is divided into a plurality of pieces in the circumferential direction in the second device and the fifth device. In the eddy current speed reducer of the present invention, the slit divides the ring-shaped low-temperature portion generated on the outer peripheral side of the braking disk, and therefore, as shown in FIG. 6, the slit extends from the outer peripheral side to the inner peripheral side extending from the rotating shaft. Even if the braking disk 2 is divided into a plurality of parts by providing 9, the same effect can be obtained.

FIG. 7 shows that in the third and sixth devices,
It is a figure showing the situation where an eddy current board is provided in a portion where a magnetic flux from a permanent magnet acts on a braking disc. This eddy current plate 10
Is a ferromagnetic material, and is divided into a plurality of parts in the circumferential direction of the surface of the braking disk 2 facing the permanent magnet.
Therefore, during braking, a magnetic force acts on the eddy current plate 10 to generate an eddy current, thereby generating a braking force. Since the eddy current plate 10 is fixed to the braking disc 2, the braking force reaches the braking disc.

In the fixing method shown in FIG. 7, the outer peripheral side of the eddy current plate 10 is fixed by the supporting end 2a of the braking disk having a U-shaped cross section, and the inner peripheral side is fixed by the slide supporting ring 11. There is. Furthermore, the slide support ring is fixed to the braking disc with bolts. Further, as shown in FIG. 7, the eddy current plate 10 is provided with slits 9 and divided in the circumferential direction. Along with this, the slide support ring 1
It is desirable that 1 is properly divided on the circumference. However, the eddy current reduction device of the present invention is not limited to the fixing method shown.

[0043]

EXAMPLES The specific effects of the eddy current speed reducer of the present invention will be described below based on examples.

A braking disk having various structures shown in FIGS. 4 to 7 was prepared and a durability test was conducted. The braking disk used in the durability test was made of CrMo-based low alloy steel and had an outer diameter of 450 mm and a thickness of 10 mm. The eddy current plate provided in the structure of FIG. 7 is a CrMo low alloy steel with a thickness of 4 mm.
The distance from the center of the braking disk to the outermost part of the eddy current plate was 218 mm, and the distance to the innermost part was 130 mm. The gap between the eddy current plate and the support plate was 3 mm.

In the durability test, the braking disc was rotated at 2,000 rpm, and after switching to braking, when the surface temperature of the braking disc facing the permanent magnet reached 650 ° C., switching to non-braking and cooling to 100 ° C. Then, the operation of switching to braking again was repeated.

The braking torque was measured every 1,000 cycles of the braking and non-braking, and the test was conducted up to 10,000 cycles. In addition, when the braking torque decreased by 10% or more from the initial (first cycle) by the time the test reached 10,000 cycles, the test was stopped at that point.

The shape of the slit provided on the braking disk is
The plane shape is divided into radial (corresponding to FIG. 4 (a)), inclination (corresponding to FIG. 4 (b)) and division (corresponding to FIG. 6), and inclination (FIG. 4).
(corresponding to (b)), the slit is rotated by 30 ° and 45
It was installed at an angle. Also, the length of the slit is from the outer peripheral side of the braking disc to the position where the diameter is 1/2 of the outer diameter,
The width of each slit was 0.5 mm.

Table 1 also shows the shape of the slits provided in the braking disk and the result of the durability test.

[0049]

[Table 1]

Since the test No. 10 of the comparative example does not have the slit, it is accompanied by repeated braking and non-braking.
The deformation of the braking disc increased and the braking force decreased. Specifically, at the time of 2,000 cycles, 1 compared to the initial torque
The test was stopped because the braking force decreased by 0% or more.

Test Nos. 1 to 3 and 5 which are examples of the present invention
In No. 9, the reduction in braking force was within 10% even after 10,000 cycles, and it was confirmed that the provision of the slit allows the braking force to be maintained even after long-term use.

In Test No. 4 of the examples of the present invention, the braking force decreased by 10% or more at the time of 7,000 cycles, so the test was stopped. However, the test N of the comparative example without slits
It was confirmed that the period during which the braking force can be maintained can be greatly extended compared to o.10.

[0053]

According to the eddy current speed reducer of the present invention, even a "magnet pole surface facing type" eddy current speed reducer using a permanent magnet can be used as a "pole pieceless type" eddy current speed reducer. Even if it is, the magnetic efficiency during braking is excellent, the size and weight can be reduced with a simple structure, and even when it is used for a long time, the deformation of the braking disc is suppressed and a stable braking force is provided. Can be secured.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration example during braking of an “magnet pole surface facing type” eddy current reduction device that uses a permanent magnet.

FIG. 2 is a diagram illustrating a configuration example of a “magnet pole surface facing type” eddy current reduction device using a permanent magnet when not braking.

FIG. 3 is a diagram showing a configuration of an eddy current reduction device of “magnet pole surface facing type” that does not use a ferromagnetic material (pole piece).

FIG. 4 is a diagram showing a planar shape of the first device and the fourth device in which a braking disk surface is provided with a slit penetrating the wall thickness.

FIG. 5 is a view showing a cross-sectional shape in which a slit penetrates the thickness of the braking disc in the first device and the fourth device.

FIG. 6 is a view showing a situation in which a braking disc is divided into a plurality of pieces in the circumferential direction in the second device and the fifth device.

FIG. 7 is a view showing a situation where an eddy current plate is provided in a portion of a braking disk where a magnetic flux from a permanent magnet acts in the third and sixth devices.

[Explanation of symbols]

1: rotating shaft 2: braking disc 2a: support end, 3: guide tube 4: Retaining ring, 5: Cylinder 6: Piston rod, 7: Permanent magnet 8: Ferromagnetic material, pole piece, 9: Slit 10: Eddy current plate, 11: Slide support ring

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinichiro Hiramatsu             4-53 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Sumitomo Metal Industries, Ltd. F term (reference) 5H649 AA01 BB03 GG09 GG18 HH05                       HH06 HH18 JK04 PP13

Claims (6)

[Claims] 1. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets, which are circumferentially opposed to the braking disc and have adjacent magnetic poles arranged in opposite directions, and a ferromagnetic material disposed on the end surface of the guide cylinder so as to face the permanent magnets. An eddy current decelerating device, wherein the permanent magnet is movable in a rotation axis direction, wherein a plurality of slits penetrating a thickness of the braking disk are provided in a radial direction from an outer peripheral surface. apparatus. 2. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets, which are circumferentially opposed to the braking disc and have adjacent magnetic poles arranged in opposite directions, and a ferromagnetic material disposed on the end surface of the guide cylinder so as to face the permanent magnets. An eddy current decelerating device, wherein the permanent magnet is movable in a rotation axis direction, wherein the braking disk is divided into a plurality of parts in a circumferential direction. 3. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets, which are circumferentially opposed to the braking disc and have adjacent magnetic poles arranged in opposite directions, and a ferromagnetic material disposed on the end surface of the guide cylinder so as to face the permanent magnets. An eddy current speed reducer in which the permanent magnet is movable in a rotation axis direction, wherein an eddy current plate is provided at a portion of the braking disc where a magnetic flux from the permanent magnet acts, and the eddy current plate is a brake disc. An eddy current decelerating device, which is divided into a plurality of parts in a circumferential direction and is fixed to a braking disc on an inner peripheral side and / or an outer peripheral side thereof. 4. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets are provided facing the braking disk in the circumferential direction, and adjacent magnetic poles are arranged in opposite directions to each other, and the guide cylinder is entirely made of a non-magnetic material including an end surface facing the permanent magnet, An eddy current speed reducer in which the permanent magnet is movable in a rotation axis direction, wherein a plurality of slits penetrating a thickness of the braking disk are provided in a radial direction from an outer peripheral surface. 5. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets are provided facing the braking disk in the circumferential direction, and adjacent magnetic poles are arranged in opposite directions to each other, and the guide cylinder is entirely made of a non-magnetic material including an end surface facing the permanent magnet, An eddy current speed reducer in which the permanent magnet is movable in a rotation axis direction, wherein the braking disk is divided into a plurality in a circumferential direction. 6. A braking disc mounted on a rotating shaft,
A guide tube which is supported by a non-rotating portion and is arranged laterally of the braking disc, a holding ring which is housed inside the guide tube and is movable in the rotation axis direction of the braking disc, and a circle of the holding ring. A plurality of permanent magnets are provided facing the braking disk in the circumferential direction, and adjacent magnetic poles are arranged in opposite directions to each other, and the guide cylinder is entirely made of a non-magnetic material including an end surface facing the permanent magnet, An eddy current reduction device in which the permanent magnet is movable in a rotation axis direction, wherein an eddy current plate is provided at a portion of the braking disc where a magnetic flux from the permanent magnet acts, and the eddy current plate is a circumference of the braking disc. The eddy current reduction device is characterized in that the eddy current reduction device is divided into a plurality of parts in the direction and is fixed to the braking disc on the inner peripheral side and / or the outer peripheral side.