Rotation braking device

Abstract

To prevent wear of a friction member and a friction surface part provided in a non-excitation operation type rotation braking device.SOLUTION: A retainer 7 arranged movably between an engagement position where an engaging element 6 held between an inner member 1 and an outer member 2 is engaged with both members 1, 2 and a release position where the engagement is released, a centering spring 8 locked to the retainer 7, a friction member 10 locked to the retainer 7 and arranged movably in the axial direction, and a separating spring 12 for energizing the friction member 10 away from the electromagnet 9 through an armature 11 axially opposed to the electromagnet 9; And a frictional surface part 2b which receives the energized friction member 10 in the axial direction and applies circumferential force to the friction member 10 so as to move the retainer 7 to the engagement position, wherein the friction member 10 is provided so as to be attracted to the armature 11 when the electromagnet 9 is excited, and at least one of mutual contact surfaces of the friction member 10 and the armature 11 is subjected to surface treatment for reducing frictional resistance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-excitation actuated rotary braking device. [Background technology]

[0002] Conventionally, a non-excitation operated rotary braking device used to brake a rotating shaft has been configured such that an engaging element is disposed between an inner member and an outer member surrounding the inner member, the engaging element is held by a cage, and when an electromagnet is de-energized, the cage is moved to an engaged position so that the engaging element engages with the inner member and the outer member, thereby stopping relative rotation between the inner member and the outer member, and when the electromagnet is energized, the cage is moved to a released position so that the aforementioned engagement is released, allowing relative rotation between the inner member and the outer member.

[0003] For example, Patent Document 1 discloses a non-excitation actuation type rotary braking device in which an inner member is connected to a rotating shaft of another machine and an outer member is prevented from rotating relative to a case. The case is attached to a stationary system. A cage is elastically held in a released position by a centering spring. The centering spring is prevented from rotating by the inner member and the cage so as to rotate integrally with the inner member. A friction member and an armature are arranged axially opposite the electromagnet. The friction member is prevented from rotating relative to the cage and is arranged axially movable. The armature is arranged between the electromagnet and the friction member. A separation spring is arranged to axially urge the friction member away from the electromagnet via the armature. A friction surface portion is provided that axially receives the friction member urged by the separation spring and applies a circumferential force (friction torque) to the friction member to move the cage to the engaged position. When the electromagnet is excited, the friction member is not pressed against the friction surface portion because the biasing force of the retraction spring is not applied to the friction member. Therefore, even if the inner member and the outer member rotate relative to each other when the electromagnet is excited, the centering spring elastically holds the cage in the released position, preventing the engagement of the engaging elements with the inner member and the outer member. The inner member and the outer member are maintained in a free state in which relative rotation is permitted. On the other hand, when the electromagnet is de-energized, the friction member is biased axially away from the electromagnet by the retraction spring via the armature, so that the friction member is pressed against the friction surface portion. Therefore, when the inner member rotates relative to the outer member when the electromagnet is de-energized, the friction surface portion that receives the friction member in the axial direction brakes the rotation of the friction member at the axial contact portion with the friction member and applies a circumferential force to the friction member so as to move the cage, which is prevented from rotating relative to the friction member, to the engaged position. As a result, the centering spring is elastically deformed and the cage is moved to the engagement position, so that the engaging elements engage with the inner and outer members, thereby creating a braking state in which relative rotation between the inner and outer members is stopped via the engaging elements. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-45468 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a non-excitation actuation type such as the rotary braking device of Patent Document 1, in which the movement of the cage that holds the engaging element between the engaged position and the released position is achieved by the cooperation of a centering spring, friction member, armature, friction surface portion, electromagnet, and separation spring, when the electromagnet is excited, the armature is attracted axially by the electromagnet and the separation spring is compressed, allowing the friction member to separate from the friction surface portion. If the position of the friction member is not maintained and the state is unstable when the electromagnet is excited and the inner member and outer member are rotating relative to each other, vibrations or the like may cause axial contact between the friction member and the friction surface portion, raising concerns that wear may occur at the contact point between the friction member and the friction surface portion.

[0006] To address the above concerns, the inventors of the present invention came up with the idea of ​​magnetically attracting the friction member to the armature when the electromagnet is excited, which would stabilize the position of the friction member when the electromagnet is excited.

[0007] However, as the inventors of the present application further investigated countermeasures, they realized that if the magnetic attraction force acting on the friction member from the armature, which is attracted to a specific part of the static system by the magnetic force of the electromagnet, is too strong, the frictional resistance from the static system acting on the friction member will become large, and a problem may arise in which the retainer, which is prevented from rotating relative to the friction member, will not be able to return to the released position by the spring force of the centering spring.

[0008] In view of the above background, the problem to be solved by the present invention is to stabilize the position of a friction member when an electromagnet provided in a non-excitation operated rotary braking device is excited, while facilitating the return of a cage to a release position when the electromagnet is excited from a non-excitation state. [Means for solving the problem]

[0009] As a first means for achieving the above object, the present invention provides a rotor comprising an inner member, an outer member surrounding the inner member, an engaging element disposed between the outer member and the inner member, a retainer disposed so as to be movable in a circumferential direction between an engaging position where the engaging element is held and engaged with the outer member and the inner member, and a releasing position where the engagement is released, a centering spring which elastically holds the retainer at the releasing position and is prevented from rotating by the retainer, an electromagnet, a friction member which is prevented from rotating relative to the retainer and is disposed so as to be movable in the axial direction, and a centering spring which faces the electromagnet in the axial direction between the electromagnet and the friction member. a friction surface portion that axially receives the friction member biased by the separation spring and applies a circumferential force to the friction member to move the cage to the engagement position, the friction member is arranged to be attracted to the armature when the electromagnet is excited, and at least one of the contact surfaces of the friction member and the armature is subjected to a surface treatment that reduces frictional resistance.

[0010] According to the above-mentioned configuration 1, when the electromagnet is excited, the friction member is attracted to the armature, thereby stabilizing the position of the friction member. Furthermore, even if the friction member is attracted to the armature when the electromagnet is excited from a non-excited state, the friction resistance at the contact surface between the friction member and the armature is reduced by the surface treatment, so that the friction resistance from the stationary system acting on the friction member is reduced, and it becomes possible to easily return the cage to the release position by the spring force of the centering spring.

[0011] As a second means for achieving the above object, the present invention provides a rotor assembly including an inner member, an outer member surrounding the inner member, an engaging element disposed between the outer member and the inner member, a retainer disposed so as to be movable in a circumferential direction between an engaging position where the engaging element is held and engaged with the outer member and the inner member, and a releasing position where the engagement is released, a centering spring which elastically holds the retainer at the releasing position and is prevented from rotating by the retainer, an electromagnet, a friction member which is prevented from rotating relative to the retainer and is disposed so as to be movable in the axial direction, an armature which faces the electromagnet in the axial direction between the electromagnet and the friction member, and a force which biases the friction member in the axial direction away from the electromagnet via the armature. and a friction surface portion that axially receives the friction member biased by the separation spring and applies a circumferential force to the friction member to move the cage to the engagement position, wherein the friction member is arranged to be attracted to the armature when the electromagnet is excited, at least one of the opposing surfaces of the friction member and the armature includes a raceway groove portion extending in the circumferential direction, a plurality of rolling elements that can roll in the raceway groove portion in the circumferential direction are arranged between the opposing surfaces, and the friction member and the armature are arranged to be supported by the plurality of rolling elements in a state where they can rotate freely relative to each other when the electromagnet is excited.

[0012] According to the above-mentioned configuration 2, when the electromagnet is excited, the friction member is attracted to the armature and supported via the plurality of rolling elements, thereby stabilizing the position of the friction member. Furthermore, when the electromagnet is excited from a de-excited state, even if the friction member is attracted to the armature, the friction member is supported in a rotatable state relative to the armature by the plurality of rolling elements that can roll in the circumferential direction along the raceway grooves. This reduces the friction resistance from the stationary system acting on the friction member, and makes it possible to easily return the cage to the release position by the spring force of the centering spring.

[0013] In the above configuration 1 or 2, a configuration 3 can be adopted in which the friction member and the armature are each made of a magnetic material.

[0014] According to the above configuration 3, a magnetic circuit can be generated that attracts both the friction member and the armature with the magnetic force of the electromagnet.

[0015] In any one of the above configurations 1 to 3, a configuration 4 can be adopted in which the friction member and the armature are subjected to a heat treatment to increase the surface hardness.

[0016] According to the above-mentioned configuration 4, wear of the sliding parts of the friction member and the armature can be prevented, and when a plurality of rolling elements according to the second means described above are employed, surface damage to the raceway groove can be prevented. [Effects of the Invention]

[0017] As described above, by adopting the above configuration 1 or 2, the present invention can prevent wear of the friction members and friction surfaces provided in the non-excitation actuation type rotary braking device. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing a non-excited state of a rotation braking device according to a first embodiment of the present invention; [Figure 2] A cross-sectional view showing the cross section of line II-II in Figure 1. [Figure 3] An enlarged cross-sectional view showing the contact surface between the friction member and the armature when the electromagnet is excited, as shown in Figure 1. [Figure 4] FIG. 10 is a cross-sectional view showing a non-excited state of a rotation braking device according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing a non-excited state of a rotation braking device according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view showing a non-excited state of a rotation braking device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] A rotary braking device according to a first embodiment (hereinafter simply referred to as "this rotary braking device") as an example of employing a first aspect of the present invention will be described with reference to the accompanying drawings, FIGS. 1 to 3. FIG.

[0020] The rotational braking device shown in Figure 1 comprises an inner member 1, an outer member 2 surrounding the inner member 1, a clutch mechanism that transmits and cuts off rotational torque between the inner member 1 and the outer member 2, and a case 3 that surrounds the outer member 2 and houses the clutch mechanism.

[0021] Here, the direction along the central axis of relative rotation of the inner member 1 and the outer member 2 is referred to as the "axial direction," and the direction perpendicular to that central axis is referred to as the "radial direction." Furthermore, the circumferential direction centered on that central axis is referred to as the "circumferential direction." Furthermore, in the description of this first embodiment, one axial direction will be simply referred to as the "right side" based on FIG. 1, and the other axial direction opposite to the one axial direction will be simply referred to as the "left side" based on FIG. 1.

[0022] The inner member 1 is connected to a rotating shaft (not shown) of another device, thereby becoming a part of the rotating system. The case 3 is a shell including a cylindrical part that surrounds the outer member 2 and the clutch mechanism, and becomes a part of the stationary system by being fixed to a stationary part (not shown) that is stationary with respect to the rotating shaft of the other device. The outer member 2 is fitted inside the case 3, and is prevented from rotating in the circumferential direction relative to the case 3 by an appropriate structure such as a key, and its axial movement relative to the case 3 is restricted by a snap ring or the like.

[0023] The other device into which this rotational braking device is incorporated is, for example, a drive system or steering device provided on a vehicle, ship, or construction machine. The rotational braking device is used, for example, as a brake to prevent steering or rear-wheel steering tires from moving, or a brake to prevent the rotation axis of a steering wheel from turning. The stationary part to which case 3 is fixed is, for example, fixed to the body of the vehicle or the housing of a reaction motor provided on the steering device.

[0024] The case 3 is cup-shaped and has a cylindrical portion that opens to the left and a bottom portion that closes the right end, all of which are seamlessly integrated. A rolling bearing 4 is disposed between the inner periphery of the case 3 and the inner member 1, supporting the right end of the inner member 1 so that it can rotate freely relative to the case 3. A rolling bearing 5 is disposed between the inner periphery of the outer member 2 and the inner member 1, supporting the left end of the inner member 1 so that it can rotate freely relative to the outer member 2. The inner member 1 and the outer member 2 are disposed in a state that allows relative rotation with a predetermined degree of coaxiality by the rolling bearings 4, 5. The inner member 1, outer member 2, and case 3 may each be formed from a single member or a combination of multiple members, as appropriate.

[0025] Each of the rolling bearings 4, 5 is a non-separable radial bearing capable of bearing axial loads in both directions. In the illustrated example, each of the rolling bearings 4, 5 is configured as a deep groove ball bearing.

[0026] The clutch mechanism includes a cam surface 1a formed on the outer periphery of the inner member 1, a cylindrical surface 2a formed on the inner periphery of the outer member 2, an engaging element 6 arranged between the cam surface 1a and the cylindrical surface 2a, a retainer 7 that holds the engaging element 6, a centering spring 8 that is prevented from rotating by the inner member 1 and the retainer 7, an electromagnet 9 attached to the case 3, a friction member 10 that is prevented from rotating relative to the retainer 7 and is arranged so as to be movable in the axial direction, an armature 11 that is arranged between the electromagnet 9 and the friction member 10, a separation spring 12 that biases the friction member 10 via the armature 11, and a friction surface portion 2b provided on the right side surface of the outer member 2.

[0027] As shown in FIG. 2, the cylindrical surface 2a of the clutch mechanism extends circumferentially. The cam surface 1a forms a wedge space between the cylindrical surface 2a and the cam surface 1a. The wedge space gradually narrows from the circumferential center of the cam surface 1a toward both ends in the circumferential direction. That is, the radial distance between the cam surface 1a and the cylindrical surface 2a gradually decreases from the position of the engaging element 6 in FIG. 2, which is located at the circumferential center of the cam surface 1a, toward one circumferential direction (counterclockwise in FIG. 2), and also gradually decreases from the position of the engaging element 6 toward the other circumferential direction (clockwise in FIG. 2). Multiple cam surfaces 1a are formed on the outer periphery of the inner member 1 at intervals in the circumferential direction. That is, multiple wedge spaces are formed, and an engaging element 6 is disposed in each wedge space. Note that, although an example in which the cam surface 1a is configured as a single plane has been shown, the cam surface may be configured as a multiple-surface or single-curved surface.

[0028] As shown in Figures 1 and 2, the inner member 1 has, seamlessly and integrally, a plurality of cam surfaces 1a, a central shaft portion 1b extending in the axial direction, end surface portions 1c located around the central shaft portion 1b, an arc-shaped recess 1d extending in the circumferential direction between the central shaft portion 1b and the end surface portion 1c, a through groove portion 1e extending in a radial direction from both circumferential ends of the arc-shaped recess 1d to the outer periphery of the inner member 1, and a joint portion 1f formed on the inner circumference.

[0029] The multiple cam surfaces 1a are located at a position that protrudes radially higher than the central shaft portion 1b toward the outer member 2, and an end surface portion 1c, an arc-shaped recessed portion 1d, and a through groove portion 1e are formed on the right side of the protruding portion. The end surface portion 1c is formed as a flat surface that extends radially. The arc-shaped recessed portion 1d and the through groove portion 1e are open to the right and have a shape that is recessed from the end surface portion 1c to the left. The joint portion 1f is connected to a rotating shaft of another device by spline fitting.

[0030] As shown in Figure 1, the outer member 2 is a ring-shaped body that opens to the right and left. The right opening of the outer member 2 has a larger diameter than the left opening of the outer member 2. The outer member 2 has a cylindrical surface 2a formed on its inner periphery and a friction surface portion 2b formed on its right end face, which are seamlessly integrated. The friction surface portion 2b is a flat surface that extends in the radial direction.

[0031] As the cage 7 rotates relative to the inner member 1, the engaging elements 6 engage with the cylindrical surface 2a and the cam surface 1a, transmitting rotational torque between the inner member 1 and the outer member 2. The engaging elements 6 are formed in the shape of cylindrical rollers.

[0032] As shown in Figure 2, the cage 7 is an annular member in which a plurality of pockets for accommodating the engaging elements 6 are formed at intervals in the circumferential direction. The engaging elements 6 come into circumferential contact with the cage 7, thereby restricting their circumferential position relative to the cam surface 1a and forcing them to rotate together with the cage 7. As shown in Figure 1, the inner flange of the cage 7 is supported radially by the inner member 1. Axial movement of the cage 7 is restricted by a snap ring 13 attached to the inner member 1 so as to be located to the left of the inner flange of the cage 7, and a step of the inner member 1 located to the right of the inner flange of the cage 7.

[0033] Cage 7 can move coaxially in the circumferential direction relative to inner member 1 between a predetermined engagement position and a release position. The engagement position is a position where engaging element 6 is moved circumferentially from the circumferential center of cam surface 1a to engage cam surface 1a with cylindrical surface 2a. The release position is a position where engaging element 6 is moved toward the circumferential center of cam surface 1a to release engagement of engaging element 6 with cam surface 1a and cylindrical surface 2a.

[0034] The centering spring 8 is a spring member that elastically holds the cage 7 in the released position and transmits the rotational torque of the inner member 1 to the cage 7. As shown in Fig. 2, the centering spring 8 is composed of an arc-shaped spring portion 8a in which a steel wire is wound in an arc shape extending in the circumferential direction, and a pair of extension portions 8b that extend radially outward from both circumferential ends of the arc-shaped spring portion 8a.

[0035] The arc-shaped spring portion 8a is fitted into the arc-shaped recess 1d. The pair of extension portions 8b are inserted into the through groove 1e, with their tips protruding from the through groove 1e. The tips of the pair of extension portions 8b are inserted into the engagement groove 7a formed in the annular portion on the right side of the cage 7. The pair of extension portions 8b can contact both circumferential ends of the through groove 1e and both circumferential ends of the engagement groove 7a. As a result, the centering spring 8 is prevented from rotating by the inner member 1 so as to rotate integrally with the inner member 1, and is also prevented from rotating by the cage 7. Furthermore, the centering spring 8 applies a circumferential spring force from its extension portion 8b to the engagement groove 7a, thereby elastically holding the cage 7 in the released position.

[0036] As shown in FIG. 1, a spring holder 14 for restricting rightward movement of the centering spring 8 is disposed inside the cage 7. The spring holder 14 is a ring member that is passed through the central shaft portion 1b. The left side surface of the spring holder 14 is adjacent to the centering spring 8 and the end face portion 1c. A retaining ring 15 is attached to the central shaft portion 1b so as to be adjacent to the right side surface of the spring holder 14. Axial movement of the spring holder 14 is restricted by the retaining ring 15 and the end face portion 1c.

[0037] The electromagnet 9 has an annular core 9a with a C-shaped cross section that opens axially toward the armature 11, and a solenoid coil 9b wound around the core 9a. The core 9a is a bobbin made of a ferromagnetic material that functions as a yoke. The core 9a is fixed to the bottom of the case 3. A through hole is formed in the case 3 for passing a lead wire that supplies power to the solenoid coil 9b. A rubber grommet 16 is attached to the case 3 to fill the gap between the through hole and the lead wire. The electromagnet 9 switches from a non-excited state to an excited state when current is applied to the solenoid coil 9b.

[0038] The friction member 10 is made of a magnetic material such as a steel plate. The friction member 10 is annular and passed between the inner periphery of the case 3 and the cage 7, and faces the friction surface portion 2b and the left side surface of the armature 11 in the axial direction. The friction member 10 is guided in the radial and axial directions by the inner periphery of the case 3 or the outer periphery of the cage 7. Therefore, the friction member 10 can move in the axial direction between the friction surface portion 2b and the left side surface of the armature 11 while being maintained at a predetermined coaxiality with the inner member 1 and the outer member 2.

[0039] The friction member 10 has an inner end portion 10a that fits axially slidably on the central shaft portion 1b, and an engaging protrusion 10b that protrudes radially from the inner end portion 10a toward the central shaft portion 1b. The engaging protrusion 10b fits into a notch 7b formed on the right side of the cage 7 and can engage with the notch 7b on either side in the circumferential direction. The friction member 10 is prevented from rotating relative to the cage 7 by the circumferential engagement between the engaging protrusion 10b and the notch 7b. The axial widths of the engaging protrusion 10b and the notch 7b are set to lengths that allow constant circumferential engagement throughout the entire reciprocating stroke of the friction member 10 that moves axially between the friction surface portion 2b and the armature 11.

[0040] It is also possible to omit the spring retainer member 14 and employ a rotation-preventing structure in which the flange of the retainer restricts the rightward movement of the centering spring from the recess and the protrusion of the retainer is inserted axially into the engagement window of the friction member.It is also possible to employ a well-known structure in which the spring retainer member or a different connecting member is engaged with the retainer and friction member in the circumferential direction and the retainer and friction member are prevented from rotating via the spring retainer member or connecting member.

[0041] The armature 11 is made of a magnetic material such as a steel plate and faces the electromagnet 9 in the axial direction. The armature 11 is an annular member slidably fitted onto the outer periphery of the central shaft portion 1b. The armature 11 does not have a portion that engages with the inner member 1 in the circumferential direction and cannot rotate integrally with the inner member 1. The armature 11 has an outer diameter equal to that of the friction member 10, and is shaped so that its outer diameter side can contact the friction member 10 in the axial direction, but its inner diameter side cannot contact the friction member 10. When the electromagnet 9 is not excited, the armature 11 is elastically held in a predetermined set position (the position shown in FIG. 1) by a separation spring 12, and is magnetically attracted from that set position when the electromagnet 9 is excited. The set position is set to a position where the friction surface portion 2b, the friction member 10, and the armature 11 butt against each other in the axial direction so that a predetermined or greater friction torque is applied between them.

[0042] The separation spring 12 is a spring member that urges the armature 11 leftward and also urges the friction member 10 leftward via the armature 11. The separation spring 12 is disposed between the right side surface of the armature 11 and the left end surface of the core 9a. The separation spring 12 stores energy when the armature 11 is moved rightward from the set position. The separation spring 12 is, for example, a wave washer-shaped or coil-shaped metal spring.

[0043] When the electromagnet 9 is not excited, the inner member 1 belonging to the rotating system rotates relative to the outer member 2 belonging to the stationary system, and the friction surface portion 2b belonging to the stationary system can apply a circumferential force (friction torque) as friction resistance to the left side surface of the friction member 10 belonging to the rotating system together with the inner member 1, the engaging element 6, and the retainer 7 at the set position.

[0044] When the electromagnet 9 is excited, a magnetic circuit is generated in which the magnetic flux of the electromagnet 9 enters the armature 11 made of a magnetic material, then enters from the armature 11 into the friction member 10 made of a magnetic material, and then returns from the friction member 10 to the electromagnet 9 via the armature 11. As a result, the generation of the magnetic circuit magnetically attracts the armature 11 and the friction member 10 to the right from the set position, and the right side surface of the armature 11 is attracted to the electromagnet 9 against the biasing force of the separation spring 12, and the right side surface of the friction member 10 is attracted to the left side surface of the armature 11. As a result, when the electromagnet 9 is excited, the friction member 10 attracted to the armature 11 is stabilized in a position where it is not pressed against the friction surface portion 2b.

[0045] When the electromagnet 9 is in an excited state, the retainer 7 is held in the released position by the spring force of the centering spring 8, and the engaging element 6 is held in a position where it does not engage with the cylindrical surface 2a and the cam surface 1a, so that even when the inner member 1 rotates in either the forward or reverse direction relative to the outer member 2, the rotational torque is not transmitted between the inner member 1 and the outer member 2, and the inner member 1 can rotate freely relative to the outer member 2. For example, when the inner member 1 rotates forward relative to the outer member 2, both the inner member 1 elastically connected by the centering spring 8 and the retainer 7 in the released position rotate forward, and the engaging element 6 held by the retainer 7 also moves in the forward rotation direction, and the friction member 10, which is prevented from rotating by the retainer 7, rotates forward together with the retainer 7 without being pressed against the friction surface portion 2b.

[0046] When the electromagnet 9 switches from an excited state to a de-excited state, the biasing force of the separation spring 12 moves the armature 11 to the left, away from the electromagnet 9, and the armature 11 and the friction member 10 are quickly returned to their set positions. When the electromagnet 9 is in a de-excited state and the inner member 1 rotates relative to the outer member 2, the circumferential force (friction torque) applied to the friction member 10 from the friction surface portion 2b at the contact portion between the friction member 10 and the friction surface portion 2b becomes a rotational resistance for the friction member 10, which rotates relative to the outer member 2 together with the inner member 1, the cage 7, etc. This circumferential force (friction torque) is preset to a value greater than the spring force of the centering spring 8. As a result, the rotation of the cage 7 lags behind the inner member 1, elastically deforming the centering spring 8, which is prevented from rotating by the inner member 1, causing the cage 7 to rotate relatively to the inner member 1 and forcing the engaging element 6 toward the narrow portion of the wedge space between the cylindrical surface 2a and the cam surface 1a. As a result, the cage 7 moves to the engaging position, causing the engaging element 6 to engage with the cylindrical surface 2a and the cam surface 1a. This puts the clutch mechanism in a state in which it transmits the rotational torque of the inner member 1 to the outer member 2 via the engaging element 6. In this state, this rotation braking device receives rotational torque from the engaging element 6 at the cylindrical surface 2a, which belongs to the stationary system, and can stop the rotation of the inner member 1 by the engaging element 6 engaged between the cylindrical surface 2a and the cam surface 1a.

[0047] When the electromagnet 9 switches from a non-excited state to an excited state, the armature 11 and friction member 10 are attracted to the right by the magnetic force of the electromagnet 9, the circumferential force applied to the friction member 10 from the friction surface portion 2b weakens, and the spring force of the centering spring 8 causes the retainer 7 to rotate relative to the inner member 1 in the opposite direction to that during engagement. As a result, the retainer 7 moves to the release position, releasing the engagement of the engaging elements 6 with the cylindrical surface 2a and cam surface 1a. This returns the clutch mechanism to a state in which the rotational torque of the inner member 1 relative to the outer member 2 is blocked. In this state, this rotation braking device can allow the inner member 1 to rotate relative to the outer member 2.

[0048] When the electromagnet 9 is excited from a non-excited state, the armature 11 attached to the electromagnet 9 belonging to the stationary system is not structured to engage with the inner member 1 in the circumferential direction, and remains stationary while being attached to the electromagnet 9 even when the inner member 1 rotates relative to the outer member 2. At this time, the friction member 10, which is rotated together with the inner member 1 via the centering spring 8 and the cage 7, is attracted to the armature 11 attached to the stationary system, and frictional resistance is generated at the contact point with the armature 11. This frictional resistance acts in a direction that retards the rotation of the friction member 10 and the cage 7 relative to the rotation of the inner member 1, and therefore counters the spring force of the centering spring 8 that attempts to hold the cage 7 in the released position. If this frictional resistance becomes larger than the spring force of the centering spring 8, the spring force of the centering spring 8 cannot return the cage 7, which is prevented from rotating relative to the friction member 10, to the released position, raising concerns about unstable performance of this rotation braking device.

[0049] To eliminate this concern, as shown in FIG. 3, the contact surfaces 10c and 11a of the friction member 10 and the armature 11 are subjected to a surface treatment to reduce the above-mentioned frictional resistance.

[0050] The contact surface 10c of the friction member 10 is a surface region of the right side surface of the friction member 10 that comes into axial contact with the left side surface of the armature 11 when the electromagnet 9 is excited. The contact surface 11a of the armature 11 is a surface region of the left side surface of the armature 11 that comes into axial contact with the contact surface 10c of the friction member 10 when the electromagnet 9 is excited.

[0051] The coatings forming the contact surfaces 10c, 11a are adhered to the required surface areas of the magnetic materials 10d, 11b of the corresponding friction member 10, respectively, filling in the recesses and covering the protrusions in the surface roughness of the corresponding materials 10d, 11b. This prevents direct contact between the materials 10d, 11b, allowing the contact surfaces 10c, 11a to slide easily against each other in the circumferential direction. Note that the thickness of the coatings forming the contact surfaces 10c, 11a is exaggerated in Figure 3.

[0052] As the surface treatment for forming the contact surfaces 10c, 11a, for example, molybdenum disulfide coating or DLC (Diamond-Like-Carbon) coating can be adopted.

[0053] In the case of molybdenum disulfide coating, the film is made up of layers of molybdenum disulfide as the main material, with solid lubricants such as fluororesin and graphite dispersed as needed, resulting in excellent lubrication.

[0054] In the case of DLC coating, it is possible to create a film consisting of a non-crystalline amorphous carbon layer made up of an SP2 structure, which is a graphite bond, and an SP3 structure, which is a diamond bond, and excellent lubricity can be obtained, especially when there is a large amount of graphite structure.

[0055] Even if only one of the contact surface 10c of the friction member 10 and the contact surface 11a of the armature 11 is subjected to the above-mentioned surface treatment, the coating forming one contact surface will adhere to the other contact surface, preventing adhesion between the two contact surfaces, improving the sliding properties between the two contact surfaces, and thereby achieving the effect of reducing the above-mentioned frictional resistance.

[0056] As described above, this rotation braking device (see FIGS. 1 and 3) comprises the inner member 1, the outer member 2 surrounding the inner member 1, the engaging element 6 arranged between the outer member 2 and the inner member 1, the retainer 7 arranged to be movable in the circumferential direction between an engaging position where the engaging element 6 is held and engaged with the outer member 2 and the inner member 1, and a releasing position where the engaging element 6 is released, the centering spring 8 that elastically holds the retainer 7 at the releasing position and is prevented from rotating by the retainer 7, the electromagnet 9, and the retainer 7. a friction member 10 that is prevented from rotating relative to the electromagnet 9 and that is arranged to be movable in the axial direction; an armature 11 that faces the electromagnet in the axial direction between the electromagnet 9 and the friction member 10; a separation spring 12 that urges the friction member 10 in the axial direction away from the electromagnet 9 via the armature 11; and a friction surface portion 2b that receives the friction member 10 urged by the separation spring 12 in the axial direction and applies a circumferential force to the friction member 10 that moves the retainer 7 to the engagement position.

[0057] This rotation braking device is provided so that the friction member 10 is attracted to the armature 11 when the electromagnet 9 is excited, and therefore the position of the friction member 10 can be stabilized when the electromagnet 9 is excited.

[0058] Furthermore, in this rotary braking device, at least one of the contact surfaces 10c, 11a of the friction member 10 and the armature 11 is subjected to a surface treatment that reduces frictional resistance. Therefore, even if the friction member 10 is attracted to the armature 11 when the electromagnet 9 is excited from a de-energized state, the frictional resistance at the contact surfaces 10c, 11a of the friction member 10 and the armature 11 is reduced by the surface treatment. This reduces the frictional resistance from the armature 11 (stationary system) acting on the friction member 10, and makes it easier for the retainer 7 to return to the released position by the spring force of the centering spring 8.

[0059] Furthermore, in this rotary braking device, since the friction member 10 and the armature 11 are both made of magnetic materials, a magnetic circuit can be generated in which the magnetic force of the electromagnet 9 attracts both the friction member 10 and the armature 11 .

[0060] In this rotary braking device, an example has been shown in which the friction member 10 and the armature 11 are made of a single seamless magnetic member, but the friction member and the armature do not need to be made of a single member. For example, the friction member can be made by bonding together a first member made of a magnetic material facing the armature and a second member made of a magnetic material or a non-magnetic material facing the friction surface, and the surface of the second member can be made to have properties that make it less slippery when pressed against the friction surface.

[0061] In this rotation braking device, a structure in which the inner member 1 is connected to a rotating shaft of another device has been exemplified, but a structure in which the outer member is connected to the rotating shaft is also possible. One such example is shown in Fig. 4, which illustrates a second embodiment. Note that, in the following, only the differences from the first embodiment will be described, and the same reference numerals will be used appropriately for corresponding components.

[0062] The rotation braking device shown in Figure 4 has an inner member 21 and an outer member 22, with the outer member 22 being connected to a rotation shaft of another device (not shown), the outer member 22 being arranged to be freely rotatable relative to the case 23, and the inner member 21 being prevented from rotating relative to the case 23.

[0063] The case 23 has a cylindrical member 24 that surrounds the clutch mechanism and a cover member 25 that is connected to the cylindrical member 24. The cylindrical member 24 has a shape that opens to the left and opens to the right with a larger diameter than the left opening. The cover member 25 has a flat plate shape that is straight in the radial direction. The cylindrical member 24 and the cover member 25 are each made of a single seamless member. The right end face of the cylindrical member 24 and the left end face of the cover member 25 are fastened in the axial direction by a plurality of male screw members 26. The joint between the cover member 25 and the cylindrical member 24 is sealed with a sealant 27.

[0064] A rolling bearing 28 is disposed between the outer member 22 and the cylindrical member 24. A retaining ring 29 is attached to the inner periphery of the cylindrical member 24. Axial movement of the outer ring of the rolling bearing 28 is restricted by the cylindrical member 24 and the retaining ring 29.

[0065] The outer member 22 has a shape that opens to the left and has a larger diameter opening to the right than the left opening. A rolling bearing 30 is disposed between the inner periphery of the outer member 22 and the inner member 21. A retaining ring 31 is attached to the inner periphery of the outer member 22. Axial movement of the outer ring of the rolling bearing 30 is restricted by the outer member 22 and the retaining ring 31.

[0066] The outer member 22 has a joint portion 22a that protrudes leftward beyond the rolling bearings 28 and 30. The joint portion 22a and a rotating shaft of another device are connected by spline fitting.

[0067] The electromagnet 32 ​​is fixed to the cover member 25. The core 32a has a spline hole 32c that penetrates axially between the left and right side surfaces of the core 32a on the radially opposite side from the side on which the solenoid coil 32b is wound. The central shaft 21a of the inner member 21 is a spline shaft that is fitted into the spline hole 32c. The inner member 21 is prevented from rotating relative to the case 23, which belongs to the stationary system, via the core 32a.

[0068] The central shaft portion 21a has an open end portion 21b that opens toward the right. The open end portion 21b holds an elastic member 33. A compression coil spring is used as the elastic member 33. The elastic member 33 is compressed in the axial direction by the open end portion 21b and the cover member 25. The elastic member 33 pushes the inner member 21 toward the left. The leftward pushing force based on the elastic rebound of the elastic member 33 is received by the tubular member 24, passing from the inner member 21 through the rolling bearing 30, the outer member 22, and the rolling bearing 28 in that order.

[0069] The spring presser member 34 is prevented from rotating by the cage 35 and the friction member 36. The spring presser member 34 has an engagement portion 34a that fits into a notch 35a formed on the right side of the cage 35 and an engagement window 36a formed in the friction member 36, and has a well-known structure that can engage with the cage 35 or the friction member 36 in the circumferential direction at the engagement portion 34a, and this engagement allows the spring presser member 34 to move circumferentially integrally with the cage 35 and also move circumferentially integrally with the armature 37 over the entire range of the reciprocating stroke of the armature 37 in the axial direction.

[0070] When the electromagnet 32 ​​is in a de-energized state, the armature 37 is supported at a set position away from the electromagnet 32 ​​by the separation spring 38, and the friction member 36 is pressed against the friction surface portion 22b of the outer member 22 by the biasing force of the separation spring 38. This allows the rotational torque of the outer member 22 to be transmitted between the friction member 36 and the friction surface portion 22b. When the electromagnet 32 ​​is in a de-energized state and the outer member 22 is in a stationary state, the retainer 35 is elastically held in a released position by the centering spring 39. When the outer member 22 rotates, the centering spring 39, retainer 35, spring presser member 34, and friction member 36 are also rotated together. In other words, the retainer 35 is rotated relative to the inner member 21, which belongs to the stationary system, and the engaging element 40 is forced toward the narrow portion of the wedge space between the cylindrical surface 22c of the outer member 22 and the cam surface 21c of the inner member 21. As a result, the retainer 35 moves to the engagement position, and the engaging element 40 held by the retainer 35 engages with the cam surface 21c and the cylindrical surface 22c. As a result, the clutch mechanism switches to an engagement state in which rotational torque is transmitted between the inner member 21 and the outer member 22, and the rotational torque is received by the inner member 21, which belongs to the stationary system, so that the rotation braking device shown in FIG. 4 can stop the rotation of the outer member 22.

[0071] In this engaged state, when the electromagnet 32 ​​is switched from a de-energized state to an energized state, the armature 37 is attracted to the right against the biasing force of the separation spring 38, compressing the separation spring 38 in the axial direction and weakening the pressure of the friction member 36 against the friction surface portion 22b, until a state in which rotational torque cannot be transmitted between the friction member 36 and the friction surface portion 22b is reached. In this state, the spring force of the centering spring 39 causes the retainer 35 to rotate relative to the inner member 21 in the opposite direction to that in the engaged state. As a result, the retainer 35 moves to the release position, disengaging the engaging element 40 from the cylindrical surface 22c and the cam surface 21c. This switches the clutch mechanism to a disengaged state in which transmission of rotational torque is interrupted between the inner member 21 and the outer member 22. While the electromagnet 32 ​​is in an excited state in the disengaged state, regardless of whether the outer member 22 rotates forward or backward relative to the case 23 and the inner member 21, the rotational torque is not transmitted between the inner member 21 and the outer member 22, and the outer member 22 can rotate freely relative to the inner member 21.

[0072] Here, when the electromagnet 32 ​​is excited from a non-excited state, the armature 37 attracted to the electromagnet 32 ​​belonging to the stationary system is not structured to engage with the outer member 22 in the circumferential direction, and remains stationary in a state attracted to the electromagnet 32 ​​even if the outer member 22 rotates relative to the inner member 21. At this time, the friction member 36, which is rotated together with the outer member 22 via the centering spring 39, the cage 35, and the spring pressing member 34, is attracted to the armature 37 attracted to the stationary system, and therefore frictional resistance is generated at the contact point with the armature 37.

[0073] The contact surfaces 36b and 37b of the friction member 36 and the armature 37 are subjected to the above-mentioned surface treatment for reducing the frictional resistance.

[0074] The friction member 36 and the armature 37 are made of a magnetic material such as a steel plate and are formed into a simple circular plate shape along the radial direction. The inner and outer diameters of these materials are set to be equal. Therefore, the contact surfaces 36b and 37b are formed entirely on the right side surface of the friction member 36 and the left side surface of the armature 37, respectively.

[0075] A rotation braking device according to a third embodiment, which is an example of the second aspect of the present invention, will be described with reference to Fig. 5. Since the third embodiment is a modification of the first embodiment, only differences from the first embodiment will be described here, and the same reference numerals will be used for corresponding components as appropriate.

[0076] In the rotation braking device shown in FIG. 5, opposing surfaces 50a, 51a of a friction member 50 and an armature 51 include raceway grooves 50b, 51b extending in the circumferential direction, respectively. The raceway groove 50b located on the right side of the friction member 50 and the raceway groove 51b located on the left side of the armature 51 face each other in the axial direction over the entire circumferential circumference, and have groove cross-sectional shapes that are symmetrical in the axial direction. A plurality of rolling elements 52 are arranged between these raceway grooves 50b, 51b, capable of rolling in the circumferential direction in both raceway grooves 50b, 51b. Balls are used as the rolling elements 52. The friction member 50 and the armature 51 are supported by the plurality of rolling elements 52 in a state in which they can rotate freely relative to each other when the electromagnet 9 is excited. For this reason, the friction member 50 and the armature 51 cannot come into direct contact with each other, and a gap is maintained between the friction member 50 and the armature 51 when the electromagnet 9 is excited. Therefore, the friction member 50 cannot be attracted to the armature 51. However, it is possible to attract the friction member 50 by the magnetic flux emitted from the armature 51 toward the friction member 50, thereby stabilizing the position of the friction member 50.

[0077] Here, in order to facilitate magnetic attraction between the friction member 50 and the armature 51, it is preferable that the rolling elements 52 are made of a magnetic material, and that when the electromagnet 9 is excited, a magnetic path is generated that passes through the armature 51, the plurality of rolling elements 52, and the friction member 50. In order to increase the magnetic path, it is also preferable to increase the total number of rolling elements 52 disposed between both raceway groove portions 50b, 51b as much as possible.

[0078] Specifically, steel balls are used as the rolling elements 52, and the rolling elements 52 are arranged to the maximum extent possible within the circumferential length of the raceway grooves 50b, 51b. In other words, no cage is used to maintain the circumferential spacing between the rolling elements 52, and multiple rolling elements 52 are arranged so that no circumferential gaps larger than the diameter of the rolling elements 52 are formed between the rolling elements 52.

[0079] It is also possible to use rollers such as needles as the rolling elements 52, but the thrust load received by the rolling elements 52 is the biasing force of the separation spring 12 and the attractive force of the electromagnet 9, which is sufficient to brake the cage 35, so steel balls can adequately receive the load. For this reason, there is little need to use rollers with a relatively large rolling resistance as the rolling elements.

[0080] Furthermore, since there is no cage to hold the rolling elements 52, it is necessary to set the diameter of the rolling elements 52 so that the rolling elements 52 do not escape from the raceway grooves 50b, 51b due to their own weight or the like when the armature 51 moves axially when the electromagnet 9 is excited. In the illustrated example, the axial movement stroke of the armature 51 when the electromagnet 9 is excited corresponds to the air gap t, which is the axial distance between the armature 51 and the electromagnet 9 when the electromagnet 9 is in a de-excited state and the friction member 50 is pressed against the friction surface portion 2b by the separating spring 12. Therefore, the diameter of the rolling elements 52 is set to be greater than t.

[0081] Furthermore, although an example has been shown in which the raceway groove portions 50b and 51b are formed in the friction member 50 and the armature 51, respectively, it is sufficient that the raceway groove portions are capable of guiding the multiple rolling elements so that they roll in the circumferential direction, and it is also possible to form the raceway groove portions in only one of the friction member and the armature, and to form the raceway surface on which the multiple rolling elements roll in the other member as a flat surface extending in the radial direction.

[0082] As described above, the rotation braking device shown in FIG. 5 includes the inner member 1, the outer member 2 surrounding the inner member 1, the engaging element 6 arranged between the outer member 2 and the inner member 1, the retainer 7 arranged to be movable in the circumferential direction between an engagement position where it holds the engaging element 6 and engages the outer member 2 with the inner member 1, and a release position where it releases the engagement, the centering spring 8 that elastically holds the retainer 7 at the release position and is prevented from rotating by the retainer 7, an electromagnet 9, a friction member 50 that is prevented from rotating with respect to the retainer 7 and is arranged to be movable in the axial direction, an armature 51 that faces the electromagnet in the axial direction between the electromagnet 9 and the friction member 50, a separation spring 12 that urges the friction member 50 in the axial direction away from the electromagnet 9 via the armature 51, and the friction surface portion 2b that axially receives the friction member 50 urged by the separation spring 12 and applies a circumferential force to the friction member 50 to move the retainer 7 to the engagement position.

[0083] In the rotation braking device shown in FIG. 5, a friction member 50 is provided so as to be attracted to an armature 51 when an electromagnet 9 is excited, and at least one of opposing surfaces 50a, 50b of the friction member 50 and the armature 51 includes raceway groove portions 50b, 51b extending in the circumferential direction, and a plurality of rolling elements 52 that can roll in the raceway groove portions 50b, 51b in the circumferential direction are disposed between the opposing surfaces 50a, 50b, and the friction member 50 and the armature 51 are disposed so as to be supported in a relatively rotatable state by the plurality of rolling elements 52 when the electromagnet 9 is excited. Since the friction member 50 is attracted to the armature 51 and supported via the plurality of rolling elements 52, the position of the friction member 50 can be stabilized. Furthermore, even if the friction member 50 is attracted to the armature 51 when the electromagnet 9 is excited from a de-energized state, the friction member 50 is supported in a rotatable state relative to the armature 51 by the plurality of rolling elements 52 that can roll in the circumferential direction along the raceway groove portions 50 b, 51 b. This reduces the frictional resistance from the stationary system acting on the friction member 50, and makes it easier for the retainer 7 to return to the released position by the spring force of the centering spring 8.

[0084] In addition, in the rotary braking device shown in FIG. 5, the friction member 50 and the armature 51 are each made of a magnetic material, so that a magnetic circuit can be generated that attracts both the friction member 50 and the armature 51 with the magnetic force of the electromagnet 9.

[0085] A rotation braking device according to a fourth embodiment, which is another application example of the second aspect of the present invention, will be described with reference to Fig. 6. Note that the fourth embodiment is a modification of the second embodiment, and therefore only differences from the second embodiment will be described here, with the same reference numerals being used appropriately for corresponding components.

[0086] 6, at least one of the opposing surfaces 60a, 61a of a friction member 60 and an armature 61 includes raceway grooves 60b, 61b extending in the circumferential direction, a plurality of rolling elements 62 that can roll in the raceway grooves 60b, 61b in the circumferential direction are disposed between the opposing surfaces 60a, 61a, and the friction member 60 and the armature 61 are disposed so as to be supported in a relatively rotatable state by the plurality of rolling elements 62 when the electromagnet 32 ​​is excited. The specific configurations and effects of the raceway grooves 60b, 61b and the rolling elements 62 are the same as those of the third embodiment, and therefore detailed description thereof will be omitted.

[0087] In each of the above-described embodiments, it is preferable that the friction members 10, 36, 50, 60 and armatures 11, 37, 51, 61 (see FIGS. 1, 4, 5, and 6) are subjected to heat treatment to increase the surface hardness.

[0088] The heat treatment may be selected as appropriate depending on the material of the friction member and the armature. For example, when the material is steel, examples of heat treatment that can be used include carburizing and quenching, nitriding, soft nitriding, and induction hardening.

[0089] 1 and 3, for example, materials 10d and 11b are heat-treated, and the heat-treated surfaces are then subjected to a surface treatment to reduce friction, forming contact surfaces 10c and 11a. This prevents wear of the sliding portions even if materials 10d and 11b slide against each other due to wear of contact surfaces 10c and 11a, or even if friction member 10, armature 11, etc. are tilted improperly, causing materials 10d and 11b other than contact surfaces 10c and 11a to slide against each other.

[0090] 5, the materials of the friction member 50 and armature 51 on which the raceway groove portions 50b and 51b are formed are subjected to heat treatment. This makes it possible to prevent surface damage to the raceway groove portions 50b and 51b.

[0091] In the above-described embodiments, the outer member has a cylindrical surface and the inner member has a cam surface. However, it is also possible to form the cylindrical surface on the inner member and the cam surface on the inner periphery of the outer member. Furthermore, sprags may be used as the engaging elements, and the tilting position of the sprags may be controlled by the relative rotation of the cage.

[0092] Furthermore, in each of the above-described embodiments, the friction surface portion is formed on the end face of the outer member, but it is also possible to form a friction surface portion on another member that is connected to the outer member.

[0093] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0094] 1, 21 Inner member 2, 22 Outer member 2b, 22b Friction surface part 6, 40 Engagement element 7, 35 retainer 8, 39 Centering spring 9, 32 Electromagnet 10, 36, 50, 60 Friction material 11, 37, 51, 61 Armature 10c, 11a, 36b, 37b contact surface 12, 38 Breakaway spring 50a, 60a, 51a, 61a Opposing surfaces 50b, 60b, 51b, 61b Raceway groove 52, 62 rolling elements

Claims

1. a friction member that is prevented from rotating relative to the cage and is arranged to be movable in the axial direction; an armature that faces the electromagnet in the axial direction between the electromagnet and the friction member; a separation spring that axially urges the friction member away from the electromagnet via the armature; and a friction surface that axially receives the friction member urged by the separation spring and applies a circumferential force to the friction member to move the cage to the engagement position, the friction member is provided so as to be attracted to the armature when the electromagnet is excited, A rotary braking device, characterized in that at least one of the contact surfaces of the friction member and the armature is subjected to a surface treatment for reducing frictional resistance.

2. a friction member that is prevented from rotating relative to the cage and is arranged to be movable in the axial direction; an armature that faces the electromagnet in the axial direction between the electromagnet and the friction member; a separation spring that axially urges the friction member away from the electromagnet via the armature; and a friction surface that axially receives the friction member urged by the separation spring and applies a circumferential force to the friction member to move the cage to the engagement position, the friction member is provided so as to be attracted to the armature when the electromagnet is excited, At least one of the opposing surfaces of the friction member and the armature includes a raceway groove portion extending in a circumferential direction, a plurality of rolling elements that can roll in the raceway groove portion in a circumferential direction are disposed between the opposing surfaces, A rotary braking device characterized in that the friction member and the armature are arranged so as to be supported by the plurality of rolling elements in a relatively rotatable state when the electromagnet is excited.

3. 3. A rotary braking device according to claim 1, wherein the friction member and the armature are each made of a magnetic material.

4. 3. The rotary braking device according to claim 1, wherein the friction member and the armature are subjected to a heat treatment to increase the surface hardness.

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