JP2020118214A - Electromagnetic brake - Google Patents

Abstract

To provide an electromagnetic brake capable of improving braking force while suppressing the enlargement of a device.SOLUTION: An electromagnetic brake 10 applying braking force to rotary shaft 20, includes an armature 30 coupled to the rotary shaft 20 so as to move in an axial direction and integrally rotate, a yoke 40 fixedly disposed so as to align with the armature 30 in the axial direction, and a coil 50 that is assembled in the yoke 40, and generates a magnetic field attracting the armature 30 to the yoke 40. The armature 30 has a first armature 31 and a second armature 32 disposed across the yoke 40 in the axial direction. The yoke 40 has a first friction surface 421 opposite to the first armature 31 in the axial direction, and a second friction surface 422 opposite to the second armature 32 in the axial direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electromagnetic brake.

Patent Document 1 describes an electromagnetic brake that applies a braking force to an object to be braked by moving an armature by a magnetic flux generated by energizing an exciting coil.

JP, 2003-106354, A

However, there is still room for improvement in the electromagnetic brake as described above in terms of achieving both downsizing of the device and improvement of the braking force. An object of the present invention is to provide an electromagnetic brake that can improve the braking force while suppressing an increase in the size of the device.

Hereinafter, the means for solving the above problems and the operation effects thereof will be described.
An electromagnetic brake that solves the above problem is an electromagnetic brake that applies a braking force to a rotating shaft, and an armature that is axially movable and integrally rotatable with respect to the rotating shaft, and the armature. The armature includes a yoke fixedly arranged so as to be aligned in the axial direction, and a coil incorporated in the yoke and generating a magnetic field that attracts the armature to the yoke, and the armature sandwiches the yoke in the axial direction. A first friction surface that is axially opposed to the first armature, and a second friction surface that is axially opposed to the second armature. And a surface.

The electromagnetic brake configured as described above attracts the first armature to the first friction surface of the yoke and the second armature to the second friction surface of the yoke when the coil is energized. Therefore, the electromagnetic brake can apply the braking force due to the contact between the first armature and the first friction surface and the braking force due to the contact between the second armature and the second friction surface to the rotating shaft as the braking target. Therefore, the electromagnetic brake can increase the braking force to be applied to the braking target while suppressing the size increase of the device, as compared with the electromagnetic brake having the same size of the device and having only one armature.

The electromagnetic brake urges the first armature toward the first friction surface of the yoke, and the second armature toward the second friction surface of the yoke. And a second biasing member.

In the electromagnetic brake configured as described above, the distance between the first armature and the first friction surface of the yoke and the distance between the second armature and the second friction surface of the yoke are likely to be small when the coil is not energized. Therefore, an air gap is less likely to occur in the magnetic circuit when the energization of the coil is started. Therefore, the electromagnetic brake can shorten the time from when the coil is energized until the armature is attracted to the yoke.

The electromagnetic brake includes a first biasing member that biases the first armature toward the first friction surface of the yoke, and a biasing force of the second armature away from the second friction surface of the yoke. A second urging member, the inner peripheral wall disposed between the rotary shaft and the coil in the radial direction of the rotary shaft, and the coil together with the inner peripheral wall in the radial direction. An outer peripheral wall arranged so as to sandwich it, and a bottom wall having a plate thickness smaller than that of the inner peripheral wall and the outer peripheral wall and connecting the inner peripheral wall and the outer peripheral wall in the radial direction so as to face the second armature. And a first magnetic circuit including the inner peripheral wall, the outer peripheral wall and the bottom wall of the yoke, and the first armature, the inner peripheral wall and the outer peripheral wall of the yoke, and the first magnetic circuit. An armature and a second magnetic circuit including the second armature are preferably configured.

In the electromagnetic brake configured as described above, when the current flowing through the coil is small, magnetic flux is more likely to be generated in the first magnetic circuit having a smaller magnetic resistance than the second magnetic circuit. That is, when the current flowing through the coil is small, the first armature is attracted to the first friction surface, and the braking force due to the contact between the first armature and the first friction surface is applied to the rotating shaft. When the current flowing through the coil increases, magnetic flux saturation occurs on the bottom wall of the yoke forming the first magnetic circuit, and the magnetic flux generated in the second magnetic circuit gradually increases. That is, the second armature is attracted to the second friction surface, and the braking force due to the contact between the second armature and the second friction surface is applied to the rotating shaft. In this way, the electromagnetic brake can gradually change the braking force applied to the braking target according to the value of the current flowing through the coil.

In the electromagnetic brake, it is preferable that each of the second friction surface of the yoke and the second armature has tooth portions that mesh with each other.
The electromagnetic brake configured as described above can improve the braking force due to the contact between the second armature and the second friction surface. That is, the electromagnetic brake can more rapidly change the braking force applied to the braking target according to the value of the current flowing through the coil.

The electromagnetic brake includes the rotating shaft, and a bearing that allows relative rotation of the yoke and the rotating shaft. The rotating shaft and the bearing are magnetic bodies, and together with the yoke and the armature, a magnetic circuit. Are preferably formed.

In the electromagnetic brake configured as described above, since the rotating shaft and the bearing form a magnetic circuit, the attraction force of the armature to the yoke can be changed by changing the shaft diameter of the rotating shaft. As a result, the electromagnetic brake can change the torque applied to the braking target according to the shaft diameter of the rotating shaft.

The electromagnetic brake configured as described above can improve the braking force while suppressing an increase in the size of the device.

The side view of the electromagnetic brake of 1st Embodiment. The end view of the electromagnetic brake of 1st Embodiment. The side view of the electromagnetic brake of 2nd Embodiment. The end view of the electromagnetic brake of 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the electromagnetic brake will be described with reference to the drawings. The electromagnetic brake of the first embodiment is a device for applying a braking force (braking torque) to a rotating braking target. Therefore, the electromagnetic brake is usually arranged on the axis of the braking target.

As shown in FIGS. 1 and 2, the electromagnetic brake 10 includes a rotating shaft 20 connected to an object to be braked, an armature 30 assembled to the rotating shaft 20, and an armature 30 and the rotating shaft 20, which are arranged side by side in the axial direction. And a yoke 40 that is formed. The electromagnetic brake 10 includes a coil 50 incorporated in the yoke 40, a bobbin 60 holding the coil 50, a biasing member 70 for biasing the armature 30, a pedestal 80 fixed to the rotary shaft 20, and a rotary shaft. 20 and a bearing 90 that allows relative rotation of the yoke 40.

The rotating shaft 20 is made of a magnetic material. The rotating shaft 20 is formed with a spline shaft portion 21 in which a plurality of teeth are arranged in the circumferential direction. The spline shaft portion 21 is formed so as to make a pair with the first end portion and the second end portion in the axial direction of the rotating shaft 20. A circumferential groove 22 is formed on the rotary shaft 20 in the circumferential direction. The circumferential groove 22 is formed so as to form a pair at a position closer to the end than the spline shaft portion 21 in the axial direction of the rotary shaft 20. A pedestal 80 is fixed to the circumferential groove 22.

The armature 30 has a first armature 31 and a second armature 32 which are arranged so as to sandwich the yoke 40 in the axial direction with respect to the rotating shaft 20. The first armature 31 and the second armature 32 have a disc shape and are made of a magnetic material. On one surface in the axial direction of the first armature 31 and the second armature 32, an annular wall 33 having a height direction in the axial direction is provided in the circumferential direction. The tip surface 34 of the annular wall 33 is a portion that contacts the yoke 40. A spline hole 35 in which a plurality of teeth are arranged in the circumferential direction is formed in the central portions of the first armature 31 and the second armature 32. In the first armature 31, the spline shaft portion 21 near the first end of the rotary shaft 20 is inserted into the spline hole 35, and in the second armature 32, the spline shaft 35 near the second end of the rotary shaft 20 is inserted into the spline hole 35. The part 21 is inserted. In this way, the first armature 31 and the second armature 32 are connected to the rotating shaft 20 so as to be movable in the axial direction and integrally rotatable around the axis. In the state where the first armature 31 and the second armature 32 are connected to the rotating shaft 20, the annular wall 33 of the first armature 31 and the annular wall 33 of the second armature 32 face each other in the axial direction of the rotating shaft 20. Is arranged as.

The yoke 40 is made of a magnetic material. The yoke 40 has an inner peripheral wall 41 and an outer peripheral wall 42 that are substantially cylindrical. The inner diameter of the inner peripheral wall 41 is substantially equal to the outer diameter of the bearing 90, and the outer diameter of the inner peripheral wall 41 is smaller than the inner diameter of the outer peripheral wall 42. In the axial direction, the length of the inner peripheral wall 41 is shorter than the length of the outer peripheral wall 42.

The rotary shaft 20 is inserted through the inner peripheral wall 41. A bearing 90 is arranged between the inner peripheral wall 41 and the rotary shaft 20. The inner peripheral wall 41 is arranged between the first armature 31 and the second armature 32 in the axial direction of the rotating shaft 20. At this time, in the axial direction of the rotary shaft 20, a gap is formed between the first end surface of the inner peripheral wall 41 and the first armature 31, and between the second end surface of the inner peripheral wall 41 and the second armature 32. A gap is formed.

The outer peripheral wall 42 is configured by combining three tubular members. The outer peripheral wall 42 slides on the first friction surface 421 that gives a braking force (braking torque) to the first armature 31 by sliding on the tip surface 34 of the first armature 31, and the tip surface 34 of the second armature 32. And a second friction surface 422 that applies a braking force (braking torque) to the second armature 32 by moving. The first friction surface 421 is formed on a first end portion of the outer peripheral wall 42 in the axial direction, and the second friction surface 422 is formed on a second end portion of the outer peripheral wall 42 in the axial direction. It is preferable that the first friction surface 421 and the second friction surface 422 have a surface roughness such that a required braking force can be obtained when sliding with the tip surface 34 of the armature 30. Further, the outer peripheral wall 42 has a flange 423 fixedly arranged in a housing or the like that houses the braking target. The flange 423 is formed with an insertion hole 424 into which a fastening member such as a bolt can be inserted.

Further, the outer peripheral wall 42 is arranged outside the inner peripheral wall 41 in the radial direction of the rotating shaft 20, and is arranged between the first armature 31 and the second armature 32 in the axial direction of the rotating shaft 20. That is, in the axial direction of the rotating shaft 20, the first friction surface 421 faces the annular wall 33 of the first armature 31, and the second friction surface 422 faces the annular wall 33 of the second armature 32. At this time, the first friction surface 421 of the outer peripheral wall 42 is located closer to the first end of the rotary shaft 20 than the first end surface of the inner peripheral wall 41, and the second friction surface 422 of the outer peripheral wall 42 is the second end of the inner peripheral wall 41. It is located closer to the second end of the rotary shaft 20 than the end surface.

The coil 50 generates a magnetic field that attracts the armature 30 to the yoke 40 when energized. The bobbin 60 is a tubular member provided with flanges at both ends in the axial direction. The inner diameter of the bobbin 60 is substantially equal to the outer diameter of the inner peripheral wall 41 of the yoke 40. The bobbin 60 is arranged between the inner peripheral wall 41 and the outer peripheral wall 42 in the light direction of the rotating shaft 20. Therefore, the coil 50 and the bobbin 60 are arranged between the first armature 31 and the second armature 32 in the axial direction of the rotary shaft 20.

The biasing member 70 is a coil spring that can be inserted into the rotating shaft 20 in the present embodiment. The biasing member 70 includes a first biasing member 71 that biases the first armature 31 and a second biasing member 72 that biases the second armature 32. The first biasing member 71 is arranged between the first armature 31 and the pedestal 80 fixed to the circumferential groove 22 of the rotary shaft 20, and the second biasing member 72 is provided between the second armature 32 and the rotary shaft 20. It is arranged between the base 80 fixed to the circumferential groove 22 and the base 80. Thus, the first biasing member 71 biases the first armature 31 toward the first friction surface 421 of the yoke 40, and the second biasing member 72 causes the second armature 32 to move the second armature 32 to the second friction surface of the yoke 40. Urge toward 422. However, it is preferable that the urging force of the urging member 70 be such that the armature 30 is in slight contact with the yoke 40.

The bearing 90 has a tubular shape and is made of a magnetic material. The bearing 90 is arranged between the rotary shaft 20 and the yoke 40.
As described above, in the electromagnetic brake 10, the rotating shaft 20 is a part connected to the braking target, and the outer peripheral wall 42 of the yoke 40 is a part fixed to a housing or the like that houses the braking target. Therefore, in the electromagnetic brake 10, the armature 30, the urging member 70, and the pedestal 80 are parts that rotate together with the rotating shaft 20, and the yoke 40, the coil 50, and the bobbin 60 are parts that do not rotate together with the rotating shaft 20.

The operation and effect of the first embodiment will be described.
(1) As shown in FIG. 2, in the electromagnetic brake 10, when the coil 50 is energized, a magnetic flux is generated in the magnetic circuit Mg passing through the yoke 40 and the armature 30. Therefore, the electromagnetic brake 10 attracts the first armature 31 and the second armature 32 to the yoke 40. As a result, in the electromagnetic brake 10, the braking force due to the contact between the tip surface 34 of the first armature 31 and the first friction surface 421 of the yoke 40, and the tip surface 34 of the second armature 32 and the second friction surface 422 of the yoke 40. The braking force due to the contact is applied to the rotating shaft 20 as the braking target. Therefore, the electromagnetic brake 10 suppresses an increase in the size of the device while increasing the braking force applied to the braking target, as compared with the electromagnetic brake of the comparative example in which the devices have the same size and have only one armature 30. it can.

(2) The first armature 31 is lightly contacted with the first friction surface 421 of the yoke 40 by being biased by the first biasing member 71, and the second armature 32 is biased by the second biasing member 72. By being urged, the second friction surface 422 of the yoke 40 is slightly contacted. Therefore, when the coil 50 is energized, an air gap is unlikely to occur in the magnetic circuit Mg. Therefore, the electromagnetic brake 10 can shorten the time from when the coil 50 is energized until the armature 30 is attracted to the yoke 40.

(3) Since the rotary shaft 20 and the bearing 90 form a part of a magnetic circuit in the electromagnetic brake 10, the attraction force of the armature 30 to the yoke 40 can be changed by changing the shaft diameter of the rotary shaft 20. As a result, the electromagnetic brake 10 can change the torque applied to the braking target according to the shaft diameter of the rotating shaft 20.

(4) The first armature 31 contacts the yoke 40 at the annular wall 33 at the radially outer portion, but does not contact the yoke 40 at the radially inner portion. Similarly, the second armature 32 makes contact with the yoke 40 at the annular wall 33 at the outer portion in the radial direction, but does not make contact with the yoke 40 at the inner portion in the radial direction. That is, the part where the first armature 31 and the second armature 32 slide on the yoke 40 is a part away from the center of rotation of the first armature 31 and the second armature 32. Therefore, the electromagnetic brake 10 can efficiently apply the braking force to the rotating shaft 20 as the braking target.

(Second embodiment)
Hereinafter, a second embodiment of the electromagnetic brake will be described with reference to the drawings. The electromagnetic brake of the second embodiment differs from the electromagnetic brake of the first embodiment in the configuration related to the second armature. In the following description, the same members as those in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the description will be omitted or simplified.

As shown in FIGS. 3 and 4, the electromagnetic brake 10A is arranged so that the rotary shaft 20 connected to the braking target, the armature 30A assembled to the rotary shaft 20, and the armature 30A and the rotary shaft 20 are aligned in the axial direction. And a yoke 40A that is formed. The electromagnetic brake 10A includes a coil 50 incorporated in the yoke 40A, a bobbin 60 holding the coil 50, a biasing member 70 for biasing the armature 30A, a pedestal 80 fixed to the rotary shaft 20, and a yoke 40A. And a bearing 90 that allows relative rotation between the rotary shaft 20 and the rotary shaft 20.

The armature 30A has a first armature 31 and a second armature 32A that are arranged axially with respect to the rotation shaft 20. The annular wall 33 of the second armature 32A is provided with a tooth portion 36 in which the tooth depth changes periodically in a wavy manner in the circumferential direction of the second armature 32A. In the second embodiment, the surface of the tooth portion 36 serves as the tip surface 34 of the annular wall 33.

The yoke 40A is made of a magnetic material. The yoke 40A has an inner peripheral wall 41 and an outer peripheral wall 42A each having a substantially cylindrical shape, and a bottom wall 43A having a substantially disk shape.
The outer peripheral wall 42A has a first friction surface 421 at a first end portion in the axial direction of the outer peripheral wall 42A. On the other hand, the outer peripheral wall 42A is provided with a tooth portion 425 at the second end portion in the axial direction of the outer peripheral wall 42A, the tooth portion 425 having a toothbrush that periodically changes in a wave shape in the circumferential direction of the outer peripheral wall 42A. The tooth portion 425 of the outer peripheral wall 42A can mesh with the tooth portion 36 of the second armature 32A. In the second embodiment, the surface of the tooth portion 425 of the outer peripheral wall 42A serves as a second friction surface 422 that applies a braking force (braking torque) to the second armature 32A by sliding on the second armature 32A. That is, in the second embodiment, the tooth portion 36 of the armature 30A and the tooth portion 425 of the outer peripheral wall 42A have a shape and a structure that are supposed to relatively rotate in the circumferential direction of the rotating shaft 20 unlike the configuration of the dog clutch and the like. It is preferable to have.

The thickness of the bottom wall 43A is smaller than the thickness of the outer peripheral wall 42A and the inner peripheral wall 41, and smaller than the thickness of the first armature 31. The bottom wall 43A connects the second end of the outer peripheral wall 42A in the axial direction and the second end of the inner peripheral wall 41 in the axial direction in the radial direction of the rotary shaft 20. Therefore, the bottom wall 43A faces the second armature 32A in the axial direction of the rotary shaft 20.

The biasing member 70 includes a first biasing member 71 that biases the first armature 31 and a second biasing member 72A that biases the second armature 32A. The first urging member 71 is arranged between the first armature 31 and the pedestal 80 fixed to the circumferential groove 22 of the rotary shaft 20, and the second urging member 72A includes the second armature 32A and the yoke 40A. It is arranged between the second end surface of the peripheral wall 41. Thus, the first biasing member 71 biases the first armature 31 toward the first friction surface 421 of the yoke 40A, and the second biasing member 72A moves the second armature 32A to the second friction surface of the yoke 40A. Bias in a direction away from 422. That is, the second biasing member 72A biases the second armature 32A toward the pedestal 80 fixed to the second end of the rotary shaft 20. Therefore, in the second embodiment, the tip surface 34 of the first armature 31 slightly contacts the first friction surface 421 of the yoke 40A while the coil 50 is not energized, while the tooth portion of the second armature 32A is in contact. 36 does not contact the tooth portion 425 of the yoke 40A.

In addition, in FIG. 4, the gap between the second armature 32A and the yoke 40A is shown too large. In reality, the gap between the second armature 32A and the yoke 40A is narrower than the gap shown.

The operation and effect of the second embodiment will be described.
(5) As shown in FIG. 4, in the electromagnetic brake 10A, when a relatively small current is applied to the coil 50, the first magnetic circuit Mg1 passing through the first armature 31, the outer peripheral wall 42A, the inner peripheral wall 41, and the bottom wall 43A. Magnetic flux is generated in the. In other words, a larger magnetic flux is generated by the first magnetic circuit Mg1 having a smaller magnetic resistance than the second magnetic circuit Mg2. Therefore, the first armature 31 is attracted to the yoke 40A, and the electromagnetic brake 10A applies a braking force to the rotating shaft 20 by the contact between the tip end surface 34 of the first armature 31 and the first friction surface 421 of the yoke 40A.

Thereafter, when the current flowing through the coil 50 increases, magnetic flux saturation occurs in the bottom wall 43A of the yoke 40A, which is the smallest cross-sectional area among the constituent members of the first magnetic circuit Mg1. Then, the magnetic flux generated in the second magnetic circuit Mg2 passing through the first armature 31 and the second armature 32A and the outer peripheral wall 42A and the inner peripheral wall 41 gradually increases. Therefore, the second armature 32A is attracted to the yoke 40A, and the electromagnetic brake 10A applies a braking force to the rotating shaft 20 by the contact between the tip end surface 34 of the second armature 32A and the second friction surface 422 of the yoke 40A.

In this way, the electromagnetic brake 10</b>A can change the braking force applied to the braking target stepwise according to the value of the current flowing through the coil 50. For example, when the current value flowing through the coil 50 when the second armature 32A is attracted to the yoke 40A is used as the reference current value, the electromagnetic brake 10A can be used as follows. Specifically, when the braking force applied to the braking target may be weak, such as in normal times, the electromagnetic brake 10A needs to make the current value flowing through the coil 50 less than the reference current value and suddenly stop the braking target in an emergency. In some cases, the value of the current flowing through the coil 50 can be made higher than the reference current value.

(6) Each of the second friction surface 422 of the yoke 40A and the second armature 32A has teeth 36 and 425 that mesh with each other. Therefore, the electromagnetic brake 10A can improve the braking force due to the contact between the second armature 32A and the second friction surface 422. That is, the electromagnetic brake 10A can change the braking force applied to the braking target more rapidly in accordance with the value of the current flowing through the coil 50.

The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the first embodiment, the electromagnetic brake 10 does not have to include the first biasing member 71 and the second biasing member 72. In this case, it is preferable that the electromagnetic brake 10 be configured so that the distance between the first armature 31 and the first friction surface 421 of the yoke 40 is as narrow as possible. The same applies to the distance between the second armature 32 and the second friction surface 422 of the yoke 40.

In the second embodiment, the inner peripheral wall 41, the outer peripheral wall 42A, and the bottom wall 43A forming the yoke 40 may be formed separately or integrally.
-In 2nd Embodiment, each of the armature 30A and the yoke 40A does not need to have the tooth parts 36 and 425. Also in the electromagnetic brake 10 having this configuration, the braking force can be varied stepwise according to the current flowing through the coil 50.

-In both embodiments, you may arrange|position a brake material in the both ends in the axial direction of the outer peripheral wall 42 of yoke 40,40A.
-In both embodiments, the rotating shaft 20 and the bearing 90 do not need to be magnetic materials. In this case, the inner peripheral wall 41 of the yokes 40, 40A is preferably shaped so that no air gap is formed between the first armature 31 and the second armatures 32, 32A.

-In both embodiments, the electromagnetic brake 10 does not need to have the rotating shaft 20. In this case, the electromagnetic brake 10 is attached to the shaft to be braked.

10, 10A... Electromagnetic brake, 20... Rotating shaft, 21... Spline shaft part, 22... Circumferential groove, 30... Armature, 30A... Armature, 31... First armature, 32, 32A... Second armature, 33... Annular wall, 34... Tip surface, 35... Spline hole, 36... Tooth portion, 40, 40A... Yoke, 41... Inner peripheral wall, 42, 42A... Outer peripheral wall, 421... First friction surface, 422... Second friction surface, 423... Flange 424... Insertion hole, 425... Tooth portion, 43A... Bottom wall, 50... Coil, 60... Bobbin, 70... Biasing member, 71... First biasing member, 72, 72A... Second biasing member, 80... Base, 90... Bearing, Mg... Magnetic circuit, Mg1... First magnetic circuit, Mg2... Second magnetic circuit.

Claims (5)

An electromagnetic brake that applies a braking force to a rotating shaft,
An armature that is axially movable and integrally rotatable with respect to the rotation shaft;
A yoke fixedly arranged so as to be lined up in the axial direction with the armature,
A coil that is incorporated in the yoke and that generates a magnetic field that attracts the armature to the yoke;
The armature has a first armature and a second armature arranged so as to sandwich the yoke in the axial direction,
The yoke includes a first friction surface that faces the first armature in the axial direction, and a second friction surface that faces the second armature in the axial direction. A first biasing member that biases the first armature toward the first friction surface of the yoke;
The electromagnetic brake according to claim 1, further comprising a second biasing member that biases the second armature toward the second friction surface of the yoke. A first biasing member that biases the first armature toward the first friction surface of the yoke;
A second biasing member that biases the second armature in a direction away from the second friction surface of the yoke,
The yoke has an inner peripheral wall arranged between the rotary shaft and the coil in a radial direction of the rotary shaft, an outer peripheral wall arranged so as to sandwich the coil together with the inner peripheral wall in the radial direction, A plate having a smaller thickness than the inner peripheral wall and the outer peripheral wall, and connecting the inner peripheral wall and the outer peripheral wall in the radial direction so as to face the second armature,
A first magnetic circuit including the inner peripheral wall, the outer peripheral wall, and the bottom wall of the yoke, and the first armature, the inner peripheral wall and the outer peripheral wall of the yoke, the first armature, and the first armature. The electromagnetic brake according to claim 1, wherein a second magnetic circuit including two armatures is configured. The electromagnetic brake according to claim 3, wherein each of the second friction surface of the yoke and the second armature has teeth that mesh with each other. The rotary shaft, and a bearing that allows relative rotation of the yoke and the rotary shaft,
The electromagnetic brake according to any one of claims 1 to 4, wherein the rotating shaft and the bearing are magnetic bodies and form a magnetic circuit together with the yoke and the armature.