JP2025086638A - Frictional engagement device - Google Patents

Abstract

A friction engagement device capable of saving power is provided.
The friction engagement device includes an armature, a friction disk, a permanent electromagnet, and a support member. The armature is arranged to be movable in the axial direction. The friction disk is arranged to be rotatable relative to the armature. The friction disk faces the armature in the axial direction. The permanent electromagnet is configured to move the armature in the axial direction. The support member supports the permanent electromagnet.
[Selected figure] Figure 2

Description

The present invention relates to a friction engagement device.

Electromagnetic brakes and electromagnetic clutches that utilize electromagnetic force are widely used as friction engagement devices such as brake devices and clutch devices. For example, an excitation-type electromagnetic brake is configured so that the brake operates while current is flowing through the coil. Also, a non-excitation-type electromagnetic brake is configured so that the brake operates when current is not flowing through the coil (Patent Document 1).

JP 2023-120788 A

The above-mentioned excitation-type electromagnetic brakes must be energized while the brake is activated, and the non-excitation-type electromagnetic brakes must be energized while the brake is not activated. In other words, they must be energized while the armature is attracted by the electromagnetic brake.

The objective of the present invention is to provide a friction engagement device that can reduce power consumption.

The friction engagement device according to the first aspect includes an armature, a friction disk, a permanent electromagnet, and a support member. The armature is arranged so as to be movable in the axial direction. The friction disk is arranged so as to be rotatable relative to the armature. The friction disk faces the armature in the axial direction. The permanent electromagnet is configured to move the armature in the axial direction. The support member supports the permanent electromagnet.

According to this configuration, the armature is moved in the axial direction by the permanent electromagnet. Here, the permanent electromagnet is energized only when switching between the attracted state and the non-attached state, thereby moving the armature in the axial direction, thereby enabling power saving.

The friction engagement device according to the second aspect is configured as follows in the friction engagement device according to the first aspect. The permanent electromagnet has a pair of yokes, a first magnet, a second magnet, and a coil. The pair of yokes are arranged at a distance from each other. The first magnet is arranged between the pair of yokes. The second magnet is arranged between the pair of yokes. The second magnet has a weaker coercive force than the first magnet. The coil is wound around at least the second magnet. Note that the coil may be wound around both the first magnet and the second magnet.

The friction engagement device according to the third aspect is configured as follows in the friction engagement device according to the second aspect: The pair of yokes are spaced apart in the circumferential direction.

The friction engagement device according to the fourth aspect is configured as follows in the friction engagement device according to the second or third aspect: The first magnet and the second magnet are arranged in the radial direction.

The friction engagement device according to the fifth aspect is a friction engagement device according to any one of the second to fourth aspects, and is configured as follows. The friction engagement device includes a plurality of permanent electromagnets arranged in a circumferential direction. The magnetization direction of each first magnet is along the circumferential direction. In a pair of adjacent permanent electromagnets, the first magnets are arranged so that their magnetization directions are different from each other. In other words, the magnetization directions of the first magnets are either facing each other or moving away from each other.

The friction engagement device according to the sixth aspect is a friction engagement device according to any one of the second to fifth aspects, and is configured as follows: The armature is disposed between the electro-permanent magnet and the friction disk in the axial direction. The yoke protrudes from the support member in the axial direction.

The friction engagement device according to the seventh aspect is the friction engagement device according to any one of the first to sixth aspects, further including a biasing member. The biasing member biases the armature toward the friction disc in the axial direction. The armature is disposed between the electro-permanent magnet and the friction disc in the axial direction.

The friction engagement device according to the eighth aspect is the friction engagement device according to the seventh aspect, and is configured as follows. The friction engagement device includes a plurality of electro-permanent magnets arranged in the circumferential direction. The biasing member is disposed between a pair of adjacent electro-permanent magnets in the circumferential direction.

The friction engagement device according to the ninth aspect is the friction engagement device according to the seventh or eighth aspect, and is configured as follows. The support member has a first accommodating recess and a second accommodating recess. The first accommodating recesses are arranged at a distance from each other in the circumferential direction. The second accommodating recesses are arranged between the first accommodating recesses in the circumferential direction. The permanent electromagnet is arranged in the first accommodating recess. The biasing member is arranged in the second accommodating recess.

The friction engagement device according to the tenth aspect is the friction engagement device according to any one of the second to sixth aspects, further comprising a non-magnetic friction material and a magnetic friction material. The non-magnetic friction material is attached to the friction disk. The magnetic friction material is attached to the tip surface of the yoke. The friction disk is disposed between the electro-permanent magnet and the armature in the axial direction. The friction disk has a through hole extending in the axial direction. The yoke is exposed toward the armature through the through hole.

The friction engagement device according to the eleventh aspect is the friction engagement device according to any one of the first to tenth aspects, further comprising a biasing member. The biasing member biases the armature in the axial direction so as to move it away from the friction disk. The friction disk is disposed between the electro-permanent magnet and the armature in the axial direction.

The friction engagement device according to the twelfth aspect is a friction engagement device according to any one of the first to eleventh aspects, and is configured as follows: The armature and the friction disc are rotatably arranged.

The friction engagement device according to the thirteenth aspect is configured as follows in the friction engagement device according to the twelfth aspect. The permanent electromagnet is disposed radially outward from the friction disk. The permanent electromagnet is disposed on the same side as the friction disk in the axial direction relative to the armature.

The friction engagement device according to the fourteenth aspect is a friction engagement device according to any one of the first to thirteenth aspects, and is configured as follows: The friction disc has a boss portion and a disc body portion. The disc body portion is disposed radially outward from the boss portion. The disc body portion is attached to the boss portion so as to be movable in the axial direction.

The present invention makes it possible to save power.

FIG. Cross-sectional view taken along line II-II in FIG. FIG. 4 is a plan view of the friction engagement device with some components removed. FIG. 11 is a cross-sectional view of a friction engagement device according to a modified example. FIG. 13 is a plan view of a friction engagement device according to a modified example with some components removed. FIG. 11 is a cross-sectional view of a friction engagement device according to a modified example. FIG. 11 is a cross-sectional view of a friction engagement device according to a modified example.

The friction engagement device 100 according to this embodiment will be described below with reference to the drawings. In the following description, the axial direction is the direction in which the rotation axis O of the friction engagement device 100 extends. Additionally, the circumference is the circumference of a circle centered on the rotation axis, and the diameter is the diameter of a circle centered on the rotation axis.

<Frictional engagement device>
1 and 2 , the friction engagement device 100 includes an armature 2, a friction disc 3, a plurality of electro-permanent magnets 4, a support member 5, a side plate 6, a plurality of biasing members 7, and a plurality of collars 8. In this embodiment, the friction engagement device 100 is used as a brake device.

<Armature>
The armature 2 is disk-shaped. The armature 2 has a plurality of cutouts 21 on its outer periphery. The cutouts 21 are arranged at intervals in the circumferential direction. Each cutout 21 opens radially outward.

The armature 2 is arranged so as to be movable in the axial direction. Specifically, the armature 2 moves toward the friction disc 3 and away from the friction disc 3. The armature 2 is arranged so as not to rotate. More specifically, the armature 2 is arranged so as not to rotate with respect to the support member 5. The armature 2 is arranged between the friction disc 3 and the permanent electromagnet 4 in the axial direction.

The armature 2 is made of a magnetic material. In particular, the armature 2 is made of steel. More particularly, the armature 2 is made of carbon steel for mechanical construction (e.g., S45C), rolled steel for general construction (e.g., SS400), or cold-rolled steel (e.g., SPCC).

<Friction disc>
The friction disc 3 is disk-shaped. The friction disc 3 is rotatably arranged. That is, the friction disc 3 is arranged to be rotatable relative to the armature 2. The friction disc 3 is configured to rotate together with a rotating member (not shown) to be braked. The friction disc 3 faces the armature 2 in the axial direction.

The friction disk 3 is made of a non-magnetic material. In particular, the friction disk 3 is made of stainless steel. More particularly, the friction disk 3 is made of austenitic stainless steel (e.g., SUS303, SUS304, SUS316) or the like.

The friction disc 3 has a boss portion 31 and a disc body portion 32. The boss portion 31 is cylindrical. The rotating member fits into the boss portion 31. For example, the rotating member fits into the boss portion 31 and rotates integrally with the boss portion 31 by a key and a key groove.

The disk body 32 is disposed radially outward from the boss 31. The disk body 32 is attached to the boss 31 so as to be movable in the axial direction. In particular, the boss 31 is spline-fitted to the disk body 32. Therefore, the disk body 32 rotates integrally with the boss 31 and is movable in the axial direction relative to the boss 31.

<Support Member>
Fig. 3 is a plan view of the friction engagement device 100 with the armature 2, the friction disc 3, and the side plate 6 removed. As shown in Figs. 2 and 3, the support member 5 supports the permanent electromagnet 4. In detail, the support member 5 has a plurality of first accommodating recesses 51 and a plurality of second accommodating recesses 52. The support member 5 supports the permanent electromagnet 4 by accommodating the permanent electromagnet 4 in the first accommodating recess 51. In addition, the support member 5 supports the biasing member 7 by accommodating the biasing member 7 in the second accommodating recess 52.

The first accommodating recesses 51 are arranged at intervals from each other in the circumferential direction. The second accommodating recesses 52 are arranged between a pair of adjacent first accommodating recesses 51 in the circumferential direction. In this embodiment, a plurality of first accommodating recesses 51 and a plurality of second accommodating recesses 52 are arranged alternately in the circumferential direction.

The first accommodating recess 51 opens toward the armature 2 in the axial direction. The first accommodating recess 51 also opens toward the radially inward side. The second accommodating recess 52 opens toward the armature 2 in the axial direction.

The support member 5 is fixed to a fixed member. The fixed member is a member that does not move easily, such as a vehicle body frame. The support member 5 is fixed to the fixed member by a bolt 13. Therefore, the support member 5 cannot rotate. Furthermore, the support member 5 cannot move in the axial direction.

The support member 5 is made of a non-magnetic material. For example, the support member 5 is made of stainless steel, aluminum, an aluminum alloy, or the like.

<Side plate>
2, the side plate 6 is disposed axially apart from the support member 5. The armature 2 and the friction disc 3 are disposed between the side plate 6 and the support member 5 in the axial direction.

The side plate 6 is disk-shaped. The side plate 6 is fixed to the support member 5. For example, the side plate 6 is fixed to the support member 5 by a plurality of bolts 9. Therefore, the side plate 6 cannot rotate relative to the support member 5 and cannot move in the axial direction.

The side plate 6 is made of a magnetic material. In particular, the side plate 6 is made of steel. More particularly, the side plate 6 is made of carbon steel for mechanical construction (e.g., S45C), rolled steel for general construction (e.g., SS400), or cold-rolled steel (e.g., SPCC). The side plate 6 may be made of a non-magnetic material. In this case, the side plate 6 may be made of stainless steel. In particular, the friction disc 3 may be made of austenitic stainless steel (e.g., SUS303, SUS304, SUS316), etc.

<Color>
The collar 8 is disposed between the side plate 6 and the support member 5 in the axial direction. The collar 8 is cylindrical. The bolt 9 extends through the collar 8. The collar 8 maintains the distance between the side plate 6 and the support member 5. The collar 8 is also disposed in the cutout portion 21 of the armature 2. Therefore, the armature 2 interferes with the collar 8 and cannot rotate.

<Using Member>
2 and 3 , the biasing member 7 biases the armature 2 toward the friction disc 3 in the axial direction. The biasing member 7 is, for example, a coil spring. The biasing member 7 is disposed between a pair of electro-permanent magnets 4 adjacent to each other in the circumferential direction. In detail, the biasing member 7 is disposed in the second accommodating recess 52 of the support member 5. A portion of the biasing member 7 protrudes from the second accommodating recess 52 toward the armature 2.

The biasing member 7 is disposed radially inward relative to the bolt 9 for fixing the side plate 6 and the bolt 13 for fixing the support member 5. When viewed radially, the biasing member 7 overlaps with the bolt 9 or the bolt 13.

The biasing member 7 is preferably made of a magnetic material. The biasing member 7 may also be made of a non-magnetic material.

<Permanent electromagnet>
The electro-permanent magnet 4 is configured to move the armature 2 in the axial direction. The electro-permanent magnet 4 is switched between an attracted state and a non-attached state. That is, the electro-permanent magnet 4 can be put into an attracted state or a non-attached state by applying a signal from the outside. The electro-permanent magnet 4 is configured to attract the armature 2 and move it in the axial direction by being in the attracted state. In this embodiment, the electro-permanent magnet 4 moves the armature 2 in the axial direction so as to move it away from the friction disc 3.

The permanent electromagnets 4 are arranged in the circumferential direction. The permanent electromagnets 4 are disposed in the first accommodating recess 51 of the support member 5.

The electro-permanent magnet 4 has a first magnet 41, a second magnet 42, a pair of yokes 43, and a coil 44. The pair of yokes 43 are arranged at a distance from each other. In detail, the pair of yokes 43 are arranged at a distance from each other in the circumferential direction. Each yoke 43 is plate-shaped. Each yoke 43 is arranged to face in the circumferential direction.

The yoke 43 protrudes from the support member 5 toward the armature 2 in the axial direction. Although not particularly limited, the amount of protrusion of the yoke 43 from the support member 5 is, for example, about 0.1 to 0.2 mm. The yoke 43 may not protrude from the support member 5 and may be flush with the support member 5.

The yoke 43 protrudes radially inward from the first accommodating recess 51. Although not particularly limited, the amount of protrusion of the yoke 43 from the first accommodating recess 51 is, for example, about 2 to 3 mm. Note that the yoke 43 does not have to protrude radially inward from the first accommodating recess 51.

The yoke 43 is made of a magnetic material. For example, the yoke 43 is made of steel. More specifically, the yoke 43 is made of carbon steel for mechanical construction (e.g., S45C, S50C) or rolled steel for general construction (e.g., SS400).

The first magnet 41 is disposed between a pair of yokes 43. The first magnet 41 is in contact with each yoke 43. The first magnet 41 has a greater coercive force than the second magnet 42. The first magnet 41 is configured so that magnetization does not reverse even when a pulse current is passed through the coil 44. The first magnet 41 is, for example, a neodymium magnet or a samarium-cobalt magnet.

The magnetization direction of the first magnet 41 is along the circumferential direction. That is, the magnetization direction of the first magnet 41 is from one yoke 43 of the pair of yokes 43 to the other yoke 43. In a pair of adjacent permanent electromagnets 4, the first magnets 41 are arranged so that their magnetization directions are different from each other. For example, the magnetic pole of one first magnet 41 close to the other first magnet 41 is a north pole, and the magnetic pole of the other first magnet 41 close to the one first magnet 41 is a north pole. By arranging in this way, it is possible to suppress the flow of magnetic flux between a pair of adjacent permanent electromagnets 4.

The second magnet 42 is disposed between a pair of yokes 43. The second magnet 42 is in contact with each yoke 43. The second magnet 42 has a weaker coercive force than the first magnet 41. The second magnet 42 is configured so that its magnetization is reversed by passing a pulse current through the coil 44. The second magnet 42 is, for example, an alnico magnet.

The first magnet 41 and the second magnet 42 are arranged in the radial direction. In this embodiment, the first magnet 41 is arranged radially inward relative to the second magnet 42. The first magnet 41 may also be arranged radially outward relative to the second magnet 42.

The coil 44 is wound around the first magnet 41 and the second magnet 42. Note that the coil 44 may be wound only around the second magnet 42 and not around the first magnet 41. The coil 44 is disposed between a pair of yokes 43.

The coil 44 is completely housed in the first housing recess 51 in the axial direction. On the other hand, in the radial direction, the coil 44 protrudes radially inward from the first housing recess 51. Note that the coil 44 may be completely housed in the first housing recess 51 in the radial direction.

The coil 44 is connected to an external power source. It is configured to pass a pulse current through the coil 44 to reverse the magnetization of the second magnet 42. Note that the magnetization of the first magnet 41 does not reverse even when a pulse current is passed through the coil 44.

<Operation>
The friction engagement device 100 configured as above operates as follows: First, in the permanent electromagnet 4, when the magnetization direction of the first magnet 41 differs from the magnetization direction of the second magnet 42, a magnetic circuit is formed between the pair of yokes 43, the first magnet 41, and the second magnet 42. As a result, the permanent electromagnet 4 is in a non-attracted state.

When the permanent electromagnet 4 is in a non-adsorbed state, the armature 2 is pressed against the friction disk 3 by the biasing force of the biasing member 7. As a result, the friction disk 3 is sandwiched between the armature 2 and the side plate 6, and rotation is stopped.

Next, a pulse current is passed through the coil 44 of the permanent electromagnet 4 to reverse the magnetization of the second magnet 42 and make the magnetization direction of the second magnet 42 the same as that of the first magnet 41, thereby placing the permanent electromagnet 4 in an attracted state. That is, a magnetic circuit is formed between the pair of yokes 43, the first magnet 41, the second magnet 42, and the armature 2. As a result, the armature 2 moves in the axial direction away from the friction disk 3 against the biasing force of the biasing member 7. The friction disk 3 is released from being sandwiched between the armature 2 and the side plate 6, and is thus in a rotatable state. After the magnetization of the second magnet 42 is reversed, there is no need to pass a current through the coil 44. That is, no power is consumed while the permanent electromagnet 4 is attracting the armature 2.

Next, a pulse current is passed through the coil 44 of the permanent electromagnet 4 in the opposite direction to the above, reversing the magnetization of the second magnet 42 and reversing the magnetization direction of the second magnet 42 from that of the first magnet 41, thereby placing the permanent electromagnet 4 in a non-attached state. That is, a magnetic circuit is formed within the first magnet 41, the second magnet 42, and the pair of yokes 43, and no magnetic flux flows to the armature 2. Since the armature 2 is not attracted by the permanent electromagnet 4, it moves toward the friction disk 3 by the biasing force of the biasing member 7. As a result, the friction disk 3 is sandwiched between the armature 2 and the side plate 6 and cannot rotate. In this case, there is also no need to pass a current through the coil 44 after the magnetization of the second magnet 42 is reversed.

[Modification]
Although the embodiment of the present invention has been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. Note that the following modifications can basically be applied simultaneously.

(a) In the above embodiment, the armature 2 is attracted to the permanent electromagnet 4, thereby separating the armature 2 from the friction disc 3, but the configuration of the friction engagement device 100 is not limited to this.

For example, as shown in FIG. 4, the friction engagement device 100 may be configured to press the armature 2 against the friction disk 3 by attracting the armature 2 with a permanent electromagnet 4. This modification will be described in detail below. Note that a description of the configuration that is substantially the same as the above embodiment will be omitted.

The armature 2 is arranged to be rotatable. A rotating member 101, which is the object to be braked, is attached to this armature 2. The armature 2 rotates integrally with the rotating member 101. The biasing member 7 is arranged between the armature 2 and the rotating member 101. The biasing member 7 is attached to the armature 2 and the rotating member 101. The biasing member 7 biases the armature 2 in the axial direction so as to move it away from the friction disc 3. For example, the biasing member 7 is a leaf spring or the like.

The friction disc 3 is arranged so that it cannot rotate. More specifically, the friction disc 3 is fixed to the support member 5. For example, the friction disc 3 is fixed to the support member 5 by a bolt or the like. The friction disc 3 may be formed integrally with the support member 5 by a single member.

The armature 2 is disposed between the rotating member 101 and the friction disk 3 in the axial direction. The friction disk 3 is disposed between the armature 2 and the permanent electromagnet 4 in the axial direction.

Figure 5 is a plan view of the friction engagement device 100 with the rotating member 101, the biasing member 7, and the armature 2 removed. As shown in Figure 5, the friction disc 3 has multiple through holes 33 extending in the axial direction.

A pair of yokes 43 of the electro-permanent magnet 4 extend through the through-hole 33 of the friction disk 3. The tip surface (upper end surface in FIG. 4) of each yoke 43 is exposed toward the armature 2 through the through-hole 33.

A non-magnetic friction material 11a is attached to the upper surface of the friction disc 3 (the surface facing the armature 2). For example, the non-magnetic friction material 11a is attached to the friction disc 3 by an adhesive or the like. The non-magnetic friction material 11a is a friction material that does not have magnetic properties.

A magnetic friction material 11b is attached to the tip surface of the yoke 43 (the surface facing the armature 2). For example, the magnetic friction material 11b is attached to the yoke 43 by an adhesive or the like. The magnetic friction material 11b is a friction material that has magnetic properties.

In the friction engagement device 100 configured in this manner, when the permanent electromagnet 4 is in a non-attached state, the armature 2 is separated from the friction disc 3 by the biasing force of the biasing member 7, and therefore the armature 2 can rotate. On the other hand, when the permanent electromagnet 4 is in an attracted state, the armature 2 is pressed against the friction disc 3, and therefore cannot rotate. In this case as well, there is no need to pass a current through the coil 44 after the magnetization of the second magnet 42 has been reversed. In other words, no power is consumed while the armature 2 is attracted by the permanent electromagnet 4.

(b) In the above embodiment, the friction engagement device 100 has been described as a brake device, but the friction engagement device 100 can also be used as a clutch device. This modification will be described in detail below. Note that a description of the configuration that is substantially the same as the above embodiment will be omitted.

As shown in FIG. 6, the armature 2 is disposed between the electro-permanent magnet 4 and the first rotating member 101 in the axial direction. The electro-permanent magnet 4 is disposed radially outward from the friction disc 3. The electro-permanent magnet 4 faces the armature 2 in the axial direction.

The armature 2 is arranged to be rotatable. A first rotating member 101 is attached to the armature 2, and the armature 2 and the first rotating member 101 rotate together.

The biasing member 7 is disposed between the armature 2 and the first rotating member 101. The biasing member 7 is attached to the armature 2 and the first rotating member 101. The biasing member 7 biases the armature 2 in the axial direction so as to move it away from the friction disc 3. For example, the biasing member 7 is a leaf spring.

The friction disc 3 is arranged to be rotatable. The second rotating member 102 is attached to this friction disc 3.

The electro-permanent magnet 4 is disposed on the same side of the armature 2 as the friction disk 3 in the axial direction. That is, as shown in FIG. 6, the electro-permanent magnet 4 and the friction disk 3 are disposed below the armature 2.

In the friction engagement device 100 configured in this manner, when the permanent electromagnet 4 is in a non-adsorbed state, the armature 2 is separated from the friction disc 3 by the biasing member 7, and therefore no torque is transmitted between the armature 2 and the friction disc 3. That is, torque transmission between the first rotating member 101 and the second rotating member 102 is blocked. On the other hand, when the permanent electromagnet 4 is in an attracted state, the armature 2 is pressed against the friction disc 3, and therefore the armature 2 and the friction disc 3 rotate together. That is, torque is transmitted between the armature 2 and the friction disc 3. Therefore, torque is transmitted between the first rotating member 101 and the second rotating member 102.

As described above, the friction engagement device 100 according to this modified example can block the transmission of torque between the armature 2 and the friction disk 3 by setting the permanent electromagnet 4 in a non-adherent state, and can transmit torque between the armature 2 and the friction disk 3 by setting the permanent electromagnet 4 in an attracted state. In other words, the friction engagement device 100 can be used as a clutch device. In this case as well, there is no need to pass a current through the coil 44 after the magnetization of the second magnet 42 has been reversed. In other words, no power is consumed while the armature 2 is being attracted by the permanent electromagnet 4.

In this modified example, as shown in FIG. 7, the pair of yokes 43 of the permanent electromagnet 4 may have protrusions 431. The protrusions 431 protrude toward the armature 2 at the outer periphery. This allows the friction disc 3 to be positioned above the yoke 43 excluding the protrusions 431, thereby increasing the diameter of the friction disc 3. As a result, the contact area between the armature 2 and the friction disc 3 can be increased.

The friction engagement device 100 can also be configured to block torque transmission between the armature 2 and the friction disk 3 by setting the permanent electromagnet 4 in an attracted state, and to transmit torque between the armature 2 and the friction disk 3 by setting the permanent electromagnet 4 in a non-attached state. In this case, the axial positions of the armature 2 and the friction disk 3 are swapped. The biasing member 7 also biases the armature 2 so as to press it against the friction disk 3.

(c) The friction engagement device 100 according to the above embodiment or the friction engagement device 100 according to the modified example (a) can also be attached to a motor. In other words, the friction engagement device 100 can be used as a brake for a motor with a brake.

2: Armature 3: Friction disk 31: Boss portion 32: Disk body portion 4: Permanent electromagnet 41: First magnet 42: Second magnet 43: Yoke 44: Coil 5: Support member 51: First accommodating recess 52: Second accommodating recess 7: Urging member 11a: Non-magnetic friction material 11b: Magnetic friction material 100: Friction engagement device

Claims (14)

an armature arranged to be movable in an axial direction;
a friction disk disposed so as to be rotatable relative to the armature and facing the armature in the axial direction;
an electro-permanent magnet configured to move the armature axially;
A support member for supporting the electro-permanent magnet;
A friction engagement device comprising:
The permanent electromagnet is
A pair of yokes spaced apart from each other;
A first magnet disposed between the pair of yokes;
a second magnet disposed between the pair of yokes and having a coercive force weaker than that of the first magnet;
A coil wound around at least the second magnet;
having
The friction engagement device according to claim 1 .
The pair of yokes are arranged at intervals in the circumferential direction.
The friction engagement device according to claim 2 .
The first magnet and the second magnet are arranged in a radial direction.
The friction engagement device according to claim 2 .
The friction engagement device includes a plurality of the electro-permanent magnets arranged in a circumferential direction,
Each of the first magnets has a magnetization direction along a circumferential direction,
In the pair of adjacent permanent electromagnets, the first magnets are arranged so that their magnetization directions are different from each other.
The friction engagement device according to claim 2 .
the armature is disposed between the electro-permanent magnet and the friction disk in the axial direction;
The yoke protrudes from the support member in an axial direction.
The friction engagement device according to claim 2 .
a biasing member that biases the armature toward the friction disk in an axial direction;
The armature is disposed between the electro-permanent magnet and the friction disk in the axial direction.
The friction engagement device according to claim 1 .
The friction engagement device includes a plurality of the electro-permanent magnets arranged in a circumferential direction,
The biasing member is disposed between a pair of adjacent electro-permanent magnets in the circumferential direction.
The friction engagement device according to claim 7.
The support member has first accommodating recesses arranged at intervals in a circumferential direction and second accommodating recesses arranged between the first accommodating recesses in the circumferential direction,
the electro-permanent magnet is disposed in the first accommodating recess,
The biasing member is disposed in the second accommodating recess.
The friction engagement device according to claim 7.
a non-magnetic friction material attached to the friction disc;
A magnetic friction material attached to a tip surface of the yoke;
Further equipped with
The friction disk is disposed between the electro-permanent magnet and the armature in the axial direction,
The friction disk has an axially extending through hole,
The yoke is exposed toward the armature through the through hole.
The friction engagement device according to claim 2 .
a biasing member configured to bias the armature away from the friction disk in an axial direction;
The friction disk is disposed between the electro-permanent magnet and the armature in the axial direction.
The friction engagement device according to claim 1 .
The armature and the friction disk are rotatably arranged.
The friction engagement device according to claim 1 .
The electro-permanent magnet is disposed radially outward from the friction disk,
The electro-permanent magnet is disposed on the same side of the armature as the friction disk in the axial direction.
The friction engagement device according to claim 12.
The friction disk has a boss portion and a disk body portion disposed radially outward from the boss portion,
The disk body is attached to the boss so as to be movable in the axial direction.
The friction engagement device according to claim 1 .

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