JP6197727B2 - Eddy current reducer - Google Patents

Description

  The present invention relates to an eddy current type reduction gear mounted as an auxiliary brake on a vehicle such as a truck or a bus, and more particularly to an eddy current type reduction gear using a permanent magnet to generate a braking force.

  In general, an eddy current type speed reducer (hereinafter also simply referred to as “speed reducer”) using a permanent magnet (hereinafter also simply referred to as “magnet”) includes a braking member fixed to a rotating shaft such as a propeller shaft, and brakes. Sometimes, an eddy current is generated on the surface of the braking member facing the magnet by the action of the magnetic field from the magnet. As a result, a braking force in the direction opposite to the rotation direction is generated in the braking member that rotates integrally with the rotation shaft, and the rotation of the rotation shaft is decelerated. The speed reducer is roughly classified into a drum type and a disk type according to the shape of a braking member that generates an eddy current that generates a braking force, and a magnet holding member that holds the magnet and forms a pair with the braking member. There are various structures for switching between braking and braking.

  2. Description of the Related Art In recent years, in order to meet the demand for downsizing of a device, a reduction device has been proposed in which a magnet holding member that holds a magnet is rotatably supported on a rotating shaft and the magnet holding member is stopped by a friction brake during braking. (For example, refer to Patent Documents 1 to 5). There is also a reduction device that replaces the arrangement of the braking member and the magnet holding member, fixes the magnet holding member to the rotating shaft, supports the braking member rotatably on the rotating shaft, and stops the braking member by a friction brake during braking. It has been proposed (see, for example, Patent Document 5). These reduction gears are called synchronous rotation type reduction gears because the magnet holding member and the braking member rotate integrally in synchronism during non-braking.

  In the synchronous rotation type reduction gears described in Patent Documents 1 to 5, a friction brake (disc brake) is used to stop a member that is rotatably supported on a rotating shaft among the braking member and the magnet holding member during braking. ) Is essential and a separate and independent brake disc is required. For this reason, the reduction gear must be expanded in the axial direction, and the downsizing of the device is limited. Patent Document 6 proposes a synchronous rotation speed reduction device that improves this problem.

  1 and 2 are schematic views showing the overall configuration of a synchronous rotation type reduction device proposed in Patent Document 6. FIG. Among them, FIG. 1 shows a side view partially showing a cross section, and FIG. 2 shows a cross-sectional view taken along the line AA of FIG. The speed reduction device shown in FIGS. 1 and 2 corresponds to a disk type, and has a disk-shaped magnet holding disk 4 as a magnet holding member for holding the permanent magnet 5 and a braking member for enclosing the entire magnet holding disk 4. 101.

  The magnet holding disk 4 is configured to rotate integrally with the rotary shaft 11. A plurality of permanent magnets 5 are fixed to the magnet holding disk 4 in the circumferential direction so as to be exposed from both surfaces orthogonal to the rotating shaft 11. The permanent magnet 5 is arranged such that the direction of the magnetic poles (N pole, S pole) is the direction along the rotation axis 11 and the magnetic poles are alternately different between those adjacent in the circumferential direction (see FIG. 2). .

  The braking member 101 is configured to be rotatable with respect to the rotating shaft 11 while surrounding the magnet holding disk 4. Specifically, the braking member 101 is opposed to the both sides of the magnet holding disk 4 so as to face the outer peripheral surface of the magnet holding disk 4 and the donut-shaped disk portions 101a and 101b having a pair of front and rear. It is comprised from the cylindrical part 1c which connects the outer peripheral part of disk part 101a, 101b. Each disk part 101a, 101b is supported by a sleeve 13 integrated with the rotary shaft 11 via bearings 15a, 15b, whereby the brake member 101 has a pair of disk parts 101a, 101b and a cylindrical part 1c. Integrally, it can rotate freely with respect to the rotating shaft 11.

  The speed reducer shown in FIGS. 1 and 2 includes a friction brake that stops the braking member 101 during braking. The friction brake includes a brake caliper 7 having brake pads 8a and 8b as friction members sandwiching an outer peripheral portion of the braking member 101, that is, outer peripheral portions of the outer surfaces of the disc portions 101a and 101b, and the brake caliper 7 And an electrically driven linear actuator 9 to be driven.

  The brake caliper 7 includes a pair of brake pads 8a and 8b at the front and rear, a bolt mounted with a spring in a state where the braking member 101 is disposed between the brake pads 8a and 8b, and a predetermined gap is provided therebetween. Therefore, the bracket 17 is biased and supported. The bracket 17 is attached to a non-rotating part of the vehicle. The bracket 17 is rotatably supported by a sleeve 13 integrated with the rotary shaft 11 via a bearing 18.

  An actuator 9 is fixed to the brake caliper 7 with a bolt or the like. The actuator 9 is driven by the electric motor 10, converts the rotational motion of the electric motor 10 into a linear motion, and linearly moves the rear brake pad 8b toward the rear disc portion 101b. As a result, the rear brake pad 8b presses the rear disc portion 101b, and the front brake pad 8a moves toward the front disc portion 101a by the action of the reaction force associated therewith. The braking member 101 is strongly sandwiched between the front and rear brake pads 8a and 8b.

  In the speed reducer having such a configuration, the friction brake is not operated during non-braking. At this time, as the magnet holding disk 4 rotates integrally with the rotating shaft 11, the braking member 101 includes a pair of disk portions 101 a and 101 b constituting the same, and the permanent magnet 5 held by the magnet holding disk 4. The magnetic attraction action (when the braking member 101 is made of a magnetic material) or the action of a magnetic field (when the braking member 101 is made of a nonmagnetic material) is rotated integrally with the magnet holding disk 4. For this reason, since a relative rotational speed difference does not arise between the disc parts 101a and 101b (braking member 101) and the permanent magnet 5 in the magnet holding disk 4, no braking force is generated.

  On the other hand, during braking, the friction brake is operated, and the braking member 101 is sandwiched between the brake pads 8a and 8b, which are friction members, whereby the rotation of the braking member 101 stops and the braking member 101 stops. If only the braking member 101 is stationary while the magnet holding disk 4 is rotating, the relative rotational speed difference between the disk portions 101a and 101b (braking member 101) and the permanent magnet 5 in the magnet holding disk 4 is reduced. As a result, eddy currents are generated on the inner surfaces of the disk portions 101a and 101b. Then, according to Fleming's left-hand rule due to the interaction between the eddy currents generated on the inner surfaces of the disc portions 101a and 101b of the braking member 101 and the magnetic flux density from the permanent magnet 5, the rotating magnet holding disk 4 is rotated in the direction of rotation. A reverse braking force is generated, and the rotation of the rotary shaft 11 can be decelerated via the magnet holding disk 4.

  According to the speed reducer proposed in Patent Document 6, a separate and independent brake disk required in the speed reducers described in Patent Documents 1 to 5 is eliminated, and the friction member is pressed directly against the brake member 101 during braking. Since the friction brake that stops the member 101 is employed, the axial dimension of the apparatus can be reduced.

JP-A-4-331456 Japanese Utility Model Publication No. 5-80178 JP 2011-97696 A JP 2011-139574 A JP 2011-182574 A Japanese Patent Application No. 2012-179138

  By the way, in the speed reducer proposed in Patent Document 6, the kinetic energy of the rotating shaft is converted into thermal energy by the eddy current generated in the disc portion of the braking member during braking, and the disc of the braking member is converted by this thermal energy. The part generates heat. At this time, since the permanent magnet is close to the heat generation area (disk portion) of the braking member, the temperature is likely to rise.

  If the temperature of the magnet rises above the heat-resistant temperature, the magnet itself undergoes thermal demagnetization, which reduces the braking force, so that the performance required as a reduction gear cannot be ensured. In order to prevent this, the braking time may be controlled so that the magnet temperature does not exceed the heat resistance temperature. In this case, the time during which continuous braking is possible is shortened. Furthermore, in order to increase the heat-resistant temperature, the magnet generally contains rare earth such as Dy (dysprosium), etc. However, in response to the recent rapid increase in the price of rare earth, not only the product cost becomes unstable, Securing rare earths can be difficult.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a synchronous rotation type eddy current reduction device that can effectively suppress the temperature rise of a permanent magnet.

An eddy current type speed reducer according to an embodiment of the present invention is
A magnet holding disk that holds a plurality of permanent magnets arranged with magnetic poles alternately different over the circumferential direction, and is fixed to the rotating shaft of the vehicle;
A pair of braking disks disposed opposite to both surfaces of the magnet holding disk and supported so as to be rotatable about the rotation axis and movable in the axial direction;
A brake caliper having a pair of brake pads sandwiched between the pair of braking discs and fixed to a non-rotating portion of the vehicle;
An actuator that drives the brake caliper during the braking, moves the pair of brake pads toward the braking disk and presses them, and stops the braking disk.
In this speed reducer, the brake disks are connected to each other via an elastic member, and are biased in a direction away from each other along the axial direction.
The braking disk is subjected to a pressing force accompanying the movement of the brake pad during braking and approaches the elastic member against the elastic force of the elastic member, and the pressing force is unloaded during non-braking. The elastic members are separated from each other by the elastic force.

  In the above speed reducer, the elastic member is preferably a compression coil spring.

  The speed reducer preferably includes a first restricting member that restricts a spaced position of each of the braking disks during non-braking and a second restricting member that restricts the approached position of each of the braking disks during braking. .

  In the case of this speed reducer, the first restricting member is a first ring member that is disposed outside the brake discs and is fixed to the rotating shaft, and the first ring members are arranged at the time of non-braking. It can be set as the structure which hits the inner peripheral part of the outer surface of a brake disc. The second restricting member may be a second ring member that protrudes from the outer peripheral portion of the inner surface of each brake disk, and the second ring members may abut each other during braking.

  The speed reducer preferably includes an extendable cover that surrounds the space between the brake disks from the outer peripheral side.

  According to the speed reducer of one embodiment of the present invention, when the brake is not braked, the brake disks are separated from each other, and the gap between the magnet and each brake disk is enlarged. The heat transfer amount from the heat generation area (inner surface) to the magnet is reduced, and the temperature rise of the magnet can be effectively suppressed.

FIG. 1 is a schematic diagram showing an overall configuration of a synchronous rotation type reduction device proposed in Patent Document 6, and shows a side view partially showing a cross section. FIG. 2 is a schematic diagram showing the overall configuration of the synchronous rotation type reduction gear proposed in Patent Document 6, and shows a cross-sectional view taken along line AA of FIG. FIG. 3 is a schematic diagram showing the arrangement relationship between the braking member and the magnet in order to explain the phenomenon in which the temperature of the permanent magnet rises. FIG. 4 is a schematic view showing an overall configuration of a synchronous rotation type reduction gear device according to an embodiment of the present invention, and shows a side view partially showing a cross section. FIG. 5 is a schematic diagram showing an overall configuration of a synchronous rotation type reduction gear device according to an embodiment of the present invention, and shows a cross-sectional view taken along line BB in FIG. FIG. 6A is a schematic diagram for explaining the operation of the synchronous rotation speed reduction device according to the embodiment of the present invention, and shows a state during non-braking. FIG. 6B is a schematic diagram for explaining the operation of the synchronous rotation speed reduction device according to the embodiment of the present invention, and shows a state during braking. FIG. 7 is a schematic diagram for explaining conditions for realizing the operation of the speed reducer according to the embodiment of the present invention.

  The present inventors have eliminated the speed reduction device proposed in Patent Document 6 (see FIGS. 1 and 2), that is, a separate and independent brake disk, and pressed the friction member (brake pad) directly against the braking member during braking. Based on the assumption of a synchronous rotation type speed reducer that stops the braking member, the phenomenon that the temperature of the magnet rises as the braking member generates heat during braking was considered. On top of that, earnest studies were made on the configuration capable of achieving the above object, and the following knowledge was obtained.

  FIG. 3 is a schematic diagram showing the arrangement relationship between the braking member and the magnet in order to explain the phenomenon in which the temperature of the permanent magnet rises. In the same figure, the relevant part of the reduction gear shown in FIG. 1 is shown enlarged.

  As shown in FIG. 3, when braking, the disc portions 101 a and 101 b of the braking member are stationary, and on the other hand, when the magnet holding disk holding the magnet 5 is rotating integrally with the rotating shaft, the rotational speed of both of them is increased. Due to the difference, an intense flow of atmospheric gas (air) occurs in the gap between the inner surfaces of the disk portions 101a and 101b and the surface of the magnet 5 (see the dotted arrows in FIG. 3). For this reason, atmospheric gas heats up by flowing in the heat_generation | fever area | region (main surface) of the disc parts 101a and 101b. The magnet 5 is heated by convection heat transfer (heat exchange) with the ambient gas flowing at such a high temperature, and further, radiant heat transfer from the heat generation regions of the disk portions 101a and 101b (the wavy arrow in FIG. 3). (See). Thus, the temperature rise of the magnet at the time of braking is due to convective heat transfer and radiant heat transfer accompanying the heat generation of the brake member (disk portion).

  Here, since the speed reducer proposed in Patent Document 6 is a synchronous rotation method, the magnet 5 and the disk portions 101a and 101b rotate integrally during non-braking. Furthermore, the magnet 5 and the disk parts 101a and 101b are always close to each other regardless of whether braking or not. For this reason, even during non-braking, the magnet 5 continues to receive heat transfer from the heat generating areas of the disk portions 101a and 101b that generate heat during braking, and thus is difficult to be cooled.

  In this regard, during braking, the magnet 5 and the disk portions 101a and 101b are secured in proximity to each other, and an effective braking force is generated. On the other hand, during non-braking, the magnet 5 and the disk portions 101a and 101b are separated from each other. If the state is ensured, the gap between the two is enlarged, so that the amount of heat transfer from the heat generation area of the disk portions 101a and 101b to the magnet 5 is reduced. Thereby, at the time of non-braking, cooling of the magnet 5 is accelerated | stimulated and the temperature rise of the magnet 5 can be suppressed effectively.

  The present invention has been completed based on the above findings. Below, preferable embodiment of the eddy current type reduction gear of this invention is described.

  FIG. 4 and FIG. 5 are schematic views showing the overall configuration of a synchronous rotation type reduction gear device according to an embodiment of the present invention. Among them, FIG. 4 shows a side view partly in section, and FIG. 5 shows a BB cross-sectional view of FIG. The speed reduction device of this embodiment shown in FIGS. 4 and 5 is equivalent to a disk type like the speed reduction device proposed in Patent Document 6 (see FIGS. 1 and 2). The speed reduction device of the present embodiment includes a disk-shaped magnet holding disk 4 as a magnet holding member that holds the permanent magnet 5, and a pair of disk-shaped braking disks 1a and 1b that are paired with the magnet holding disk 4. Is provided.

  The magnet holding disk 4 is configured to rotate integrally with the rotary shaft 11. Specifically, the tubular connecting shaft 12 is fixed coaxially with the rotating shaft 11 by a bolt or the like, and the magnet holding disk 4 is fixed to the connecting shaft 12 via a sleeve 13 press-fitted into the connecting shaft 12. Yes. As a result, the magnet holding disk 4 rotates integrally with the rotating shaft 11.

  A plurality of permanent magnets 5 are fixed to the magnet holding disk 4 in the circumferential direction so as to be exposed from both surfaces orthogonal to the rotating shaft 11. In the permanent magnet 5, the direction of the magnetic poles (N pole, S pole) is the direction along the rotation axis 11, that is, the axial direction of the magnet holding disk 4, and the magnetic poles are alternately different between those adjacent in the circumferential direction. (See FIG. 5).

  4 and 5, the magnet holding disk 4 is provided with windows penetrating in the axial direction at equal angular intervals in the circumferential direction, and the magnet 5 is inserted into each of these windows, and adhesive or The aspect fixed using the metal fitting is shown. However, the magnets 5 may be individually fixed to both surfaces of the magnet holding disk 4.

  The magnet holding disk 4 may be made of a nonmagnetic material such as aluminum or austenitic stainless steel when the magnet 5 is inserted into a window penetrating in the axial direction. Although desirable, the portion connected to the rotating shaft may be a non-magnetic material or a ferromagnetic material such as carbon steel. On the other hand, in the case where the magnet holding disk 4 has no window and the magnets 5 are individually fixed on both surfaces, the portion to which the magnets 5 are fixed is efficient as a ferromagnetic material such as carbon steel, ferritic stainless steel or cast iron. Although it is desirable to construct a magnetic circuit well, the portion connected to the rotating shaft may be a ferromagnetic material or a nonmagnetic material such as aluminum.

  The brake disks 1a and 1b are a pair of front and rear, and are disposed so as to face both surfaces of the magnet holding disk 4. Each brake disk 1a, 1b is configured to be rotatable about an axis relative to the rotation shaft 11 and movable in the axial direction. Specifically, each of the brake disks 1a and 1b has bushes 20a and 20b fitted in inner peripheral portions thereof, and is supported by a sleeve 13 integrated with the rotary shaft 11 via bearings 15a and 15b. Thereby, each brake disk 1a, 1b can freely rotate with respect to the rotating shaft 11. Furthermore, each brake disk 1a, 1b can freely move along the axial direction with respect to the rotary shaft 11 by sliding between the bushes 20a, 20b and the outer rings of the bearings 15a, 15b.

  The material of the brake disks 1a and 1b is a conductive material, among which a ferromagnetic material such as carbon steel and cast iron, a weak magnetic material such as ferritic stainless steel, or a nonmagnetic material such as an aluminum alloy and a copper alloy. It is. However, in order to use such a material as a base material of the braking disks 1a and 1b and further improve the braking efficiency, the surface layer portion of the inner surface facing the magnet 5 is a highly conductive material such as copper or copper alloy. More preferred.

  Further, since the bushes 20a and 20b slide with the outer ring of the bearings 15a and 15b each time switching between braking and non-braking, even if the speed reducer is operated up to the number of operating lifetimes, wear resistance sufficient to be used. The material must have For this reason, the material of the bushes 20a and 20b is preferably, for example, a resin material in which a copper alloy sintered material and PTFE (tetrafluoroethylene resin) are mixed. Here, since the speed reducer is used in a maintenance-free manner after the vehicle is mounted on the vehicle until the vehicle becomes a scrapped vehicle, the number of operating lifetimes of the speed reducing device is necessarily the number of operating times assuming the vehicle lifetime.

  Between the brake disks 1a and 1b, a plurality of compression coil springs 21 are arranged in the circumferential direction on the outer peripheral portion of each inner surface. The brake disks 1a and 1b are connected to each other via their compression coil springs 21, and are urged in directions away from each other along the axial direction. The compression coil spring 21 can be changed to another elastic member (for example, a leaf spring) as long as it can bias the braking disks 1a and 1b in the direction of separating them.

  Further, in the present embodiment, each of the brake disks 1a and 1b is configured to be movable in the axial direction with respect to the rotary shaft 11, and can take a position separated from each other during non-braking and a position close to each other during braking. For this reason, the 1st limiting member which restrict | limits the separated position of each brake disc 1a, 1b at the time of non-braking is provided. Along with this, a second restricting member is provided for restricting the approaching position of each brake disk 1a, 1b during braking.

  As first limiting members, ring-shaped first ring members 22a and 22b are arranged outside the respective brake disks 1a and 1b. Each of the first ring members 22 a and 22 b is fitted into a sleeve 13 integrated with the rotating shaft 11. However, as long as each 1st ring member 22a, 22b exists in the state fixed with respect to the rotating shaft 11, it may be integrally formed with the sleeve 13, for example, and may be engage | inserted by the connection shaft 12. FIG. When the brake disks 1a and 1b are separated from each other during non-braking, the inner peripheral portions (including the bushes 20a and 20b) of the outer surfaces abut against the first ring members 22a and 22b. In 1b, the movement further away is restricted, and the position of the most separated state is determined.

  On the other hand, ring-shaped second ring members 23a and 23b projecting inward from the outer peripheral portions of the inner surfaces of the respective brake disks 1a and 1b are provided as second restricting members. The second ring members 23a and 23b may be formed integrally with the brake disks 1a and 1b, or may be separately formed and attached to the brake disks 1a and 1b with bolts or the like. During braking, as each brake disk 1a, 1b approaches, each second ring member 23a, 23b abuts against each other, so that the movement of each brake disk 1a, 1b further is limited, and the closest The position of the completed state is determined.

  As the second restricting member, the first ring members 22a and 22b can be employed. That is, a mode in which the second ring member fixed to the rotating shaft 11 is arranged inside each brake disk 1a, 1b may be employed. In the case of this aspect, when braking, each braking disk 1a, 1b approaches the second ring member because the inner peripheral portion (including bushes 20a, 20b) of each inner surface hits each braking disk. Positions 1a and 1b are closest to each other.

  In the present embodiment, an extendable cover 24 that surrounds the space between the brake disks 1a and 1b from the outer peripheral side is provided. Since the magnet holding disk 4 holding the magnet 5 is disposed between the braking disks 1a and 1b, foreign matter and moisture of a ferromagnetic material such as iron powder can inadvertently enter from outside. This is to prevent it.

  The speed reducer according to the present embodiment includes a friction brake for stopping the brake disks 1a and 1b during braking. This friction brake includes brake pads 8a and 8b as friction members sandwiching the outer peripheral portions of the outer surfaces of the respective brake disks 1a and 1b, a brake caliper 7 having these brake pads 8a and 8b, and the brake caliper 7 And an electric linear actuator 9 that is an actuator to be driven.

  The brake caliper 7 includes a pair of brake pads 8a and 8b at the front and rear, and a pair of brake disks 1a and 1b that are separated from each other between the brake pads 8a and 8b. In a state in which the gap is provided, the bracket 17 is urged and supported by a bolt or the like on which a spring is mounted. The bracket 17 is attached to a non-rotating part of the vehicle.

  The bracket 17 is rotatably supported by a sleeve 13 integrated with the rotary shaft 11 via a bearing 18. However, in the case of a reduction gear mounted on the output side of the transmission of the vehicle, the bracket 17 does not need to be supported via the bearing 18 if it is fixed to the transmission cover (non-rotating portion). This is because the transmission cover is supported via a bearing.

  An actuator 9 is fixed to the brake caliper 7 with a bolt or the like. The actuator 9 is driven by the electric motor 10, converts the rotational motion of the electric motor 10 into a linear motion, and linearly moves the rear brake pad 8b toward the rear brake disk 1b. Thereby, the rear brake pad 8b is pressed against the rear brake disk 1b, and the front brake pad 8a moves toward the front brake disk 1a by the action of the reaction force associated therewith. As a result, although the details will be described later, a pressing force is applied to each brake disk 1a, 1b from the brake pads 8a, 8b, whereby the brake disks 1a, 1b move closer to each other and are closest to each other. In this state, the whole is strongly sandwiched between the front and rear brake pads 8a and 8b.

  6A and 6B are schematic diagrams for explaining the operation of the synchronous rotation speed reduction device according to the embodiment of the present invention. Among these, FIG. 6A shows a state during non-braking, and FIG. 6B shows a state during braking.

  As shown in FIG. 6A, the friction brake is not operated during non-braking. The brake disks 1a and 1b are separated from each other by the elastic force of the compression coil spring 21 and are in the most separated state by abutting against the first ring members 22a and 22b. At this time, as the magnet holding disk 4 rotates integrally with the rotating shaft 11, each brake disk 1 a, 1 b has a magnetic attraction action with the permanent magnet 5 held by the magnet holding disk 4 (the brake disks 1 a, 1 b are It rotates in synchronization with the magnet holding disk 4 by the action of a magnetic material) or by the action of a magnetic field (when the braking disks 1a, 1b are non-magnetic materials). For this reason, since a relative rotational speed difference does not occur between the brake disks 1a and 1b and the permanent magnet 5 in the magnet holding disk 4, no braking force is generated.

  On the other hand, during braking, the friction brake is operated. Then, as shown in FIG. 6B, the brake pads 8a and 8b move so as to sandwich the entire pair of brake disks 1a and 1b, and a pressing force is applied to each brake disk 1a and 1b from the brake pads 8a and 8b. The Due to this pressing force, the brake disks 1a and 1b move closer to each other while resisting the elastic force of the compression coil spring 21, and the second ring members 23a and 23b abut against each other, so that they are closest. It will be in the state. Since the pressing force from the brake pads 8a and 8b continues to be applied to the brake disks 1a and 1b, the entire brake disks 1a and 1b are strongly sandwiched between the brake pads 8a and 8b. Thereby, rotation of each brake disk 1a, 1b stops, and brake disk 1a, 1b stops.

  When only the brake disks 1a and 1b are stationary while the magnet holding disk 4 is rotating, a relative rotational speed difference is generated between the brake disks 1a and 1b and the permanent magnet 5 in the magnet holding disk 4. Eddy currents are generated on the inner surfaces of the brake disks 1a and 1b. Then, in accordance with Fleming's left-hand rule due to the interaction between the eddy currents generated on the inner surfaces of the respective brake disks 1a and 1b and the magnetic flux density from the permanent magnet 5, a braking force in the direction opposite to the rotation direction is applied to the rotating magnet holding disk 4. And the rotation of the rotating shaft 11 can be decelerated via the magnet holding disk 4. In the present embodiment, since eddy currents are generated on the inner surfaces of the brake disks 1a and 1b, the braking force is generated from the two surfaces, and the braking efficiency can be remarkably improved. At this time, each brake disk 1a, 1b generates heat due to an eddy current generated on the inner surface.

  After such braking, the operation of the friction brake is stopped when shifting to non-braking. As a result, as shown in FIG. 6A, the brake pads 8a and 8b are separated from the respective brake disks 1a and 1b. That is, the pressing force from the brake pads 8a and 8b to the brake disks 1a and 1b is unloaded. Then, each brake disk 1a, 1b moves away from each other by the elastic force of the compression coil spring 21, and comes into the most separated state by abutting against the first ring members 22a, 22b. Since each of the brake disks 1a and 1b has not received a pressing force from the brake pads 8a and 8b, the brake disks 1a and 1b start to rotate again in synchronization with the magnet holding disk 4 that rotates together with the rotating shaft 11.

  Thus, during braking, the brake disks 1a and 1b are brought close to each other, and the magnet 5 and the brake disks 1a and 1b are kept in close proximity, so that braking force is effectively generated. On the other hand, at the time of non-braking after braking, the respective braking disks 1a, 1b are separated from each other, and the gap between the magnet 5 and each braking disk 1a, 1b is enlarged. The amount of heat transfer from the heat generation area (inner surface) to the magnet 5 is reduced. Thereby, at the time of non-braking, cooling of the magnet 5 is accelerated | stimulated and the temperature rise of the magnet 5 can be suppressed effectively.

  Here, in realizing the above-described operation by the speed reducer of the present embodiment, it is necessary to consider the following conditions.

  FIG. 7 is a schematic diagram for explaining conditions for realizing the operation of the speed reducer according to the embodiment of the present invention. This figure shows a state during braking.

  First, let us consider a situation where the friction brake is operated from the non-braking state to shift to braking. As shown in FIG. 7, the brake disks 1a and 1b approach each other and move a distance of Δx by the load of the pressing force F from the brake pads 8a and 8b. At this time, the following forces are acting on each brake disk 1a, 1b.

F: Pressing force from the brake pad F1: (braking torque generated when the brake disk stops rotating) / {(coefficient of friction μ between the brake brake pad and the brake disk) × (brake pad from the center of the rotating shaft Radius to center r)}
F2: Elastic force (= spring constant k × Δx) of compression coil springs (all plural)
F3: Magnetic attraction force by permanent magnets (all multiple) (however, only when the brake disk is made of magnetic material)
F4: Sliding resistance between the bushing on the inner periphery of the brake disc and the outer ring of the bearing (however, it reaches 0 when it reaches a fixed position)

Between these forces, the condition of the following formula (1) must be satisfied.
F ≧ F1 + F2−F3 + F4 (1)

  Next, a situation is considered in which the operation of the friction brake is stopped from the braking state and the state is shifted to non-braking. At this time, the pressing force F from the brake pads 8a and 8b is unloaded from each brake disk 1a and 1b, and F = 0. Accordingly, each brake disk 1a, 1b starts to rotate in synchronization with the magnet holding disk 4, and the braking force disappears, so that F1 = 0. For this reason, the force which acts on each brake disk 1a, 1b becomes only F2, F3, and F4.

In order for each of the brake disks 1a and 1b to move the distance Δx by receiving the elastic force F2 of the compression coil spring 21, the condition of the following equation (2) must be satisfied.
F2> (F3 + F4) (2)

From the condition of the expression (2), the spring constant k of the compression coil spring 21 needs to satisfy the condition of the following expression (3).
k> {(F3 + F4) / Δx} (3)

  When the brake disks 1a and 1b are made of a non-magnetic material, the magnetic attractive force by the permanent magnet 5 does not act on the brake disks 1a and 1b, so that F3 = 0 in the above formulas (1) to (3). .

  In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  The eddy current type speed reducer of the present invention is useful as an auxiliary brake for any vehicle.

1a, 1b: braking disk, 4: magnet holding disk, 5: permanent magnet,
7: Brake caliper, 8a, 8b: Brake pad,
9: Electric linear actuator 10: Electric motor
11: Rotating shaft, 12: Connection shaft, 13: Sleeve,
15a, 15b: bearing, 17: bracket, 18: bearing,
20a, 20b: bush, 21: compression coil spring,
22a, 22b: first ring member, 23a, 23b: second ring member,
24: Cover

Claims (6)

A magnet holding disk that holds a plurality of permanent magnets arranged with magnetic poles alternately different over the circumferential direction, and is fixed to the rotating shaft of the vehicle;
A pair of braking disks disposed opposite to both surfaces of the magnet holding disk and supported so as to be rotatable about the rotation axis and movable in the axial direction;
A brake caliper having a pair of brake pads sandwiched between the pair of braking discs and fixed to a non-rotating portion of the vehicle;
An actuator that drives the brake caliper at the time of braking, moves the pair of brake pads toward the braking disk, presses the brake caliper, and stops the braking disk;
The braking disks are connected via an elastic member, and are urged in directions away from each other along the axial direction,
The braking disk is subjected to a pressing force accompanying the movement of the brake pad during braking and approaches the elastic member against the elastic force of the elastic member, and the pressing force is unloaded during non-braking. An eddy current reduction device that is separated from each other by the elastic force of the elastic member. The eddy current type speed reducer according to claim 1,
An eddy current type speed reducer, wherein the elastic member is a compression coil spring. The eddy current type speed reducer according to claim 1 or 2,
A first restricting member that restricts the spaced position of each of the braking disks during non-braking;
An eddy current reduction device comprising: a second restriction member that restricts a position where each of the braking disks approaches during braking. The eddy current type reduction device according to claim 3,
The first restricting member is a first ring member that is disposed outside the brake disks and is fixed to the rotating shaft. The first ring members are arranged on the inner surfaces of the brake disks during non-braking. Eddy current type speed reducer that hits the periphery. The eddy current type speed reducer according to claim 3 or 4,
The second limiting member is a second ring member that protrudes from an outer peripheral portion of an inner surface of each braking disk, and the second ring members abut against each other during braking. An eddy current type reduction gear according to any one of claims 1 to 5,
An eddy current reduction device comprising an extendable cover that surrounds the space between the brake disks from the outer peripheral side.

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