Electromagnetic brake system

Abstract

To surely reduce impact shock caused by contact of a movable member and a rotating member in operation of a brake.SOLUTION: An electromagnetic brake device 1 includes a movable plate 4 disposed in adjacent to one side of a rotating member 2 in an axial direction, a plurality of springs 6, and an electromagnetic unit 5. The electromagnetic unit 5 has a yoke 51 having an inner cylindrical portion 53 and an outer cylindrical portion 54, a coil 52, and an end face 54b for restricting relative movement in an axial direction, of the outer cylindrical portion 54 and the movable plate 4. The end face 54b is constituted to keep an end face 22a of the rotating member 2 and an end face 4b formed on the movable plate 4 in parallel with each other in a state that the movable plate 4 is attracted to the yoke 51 by magnetic force. Magnetic resistance of a first magnetic path disposed at one side with respect to a virtual plane P is larger than magnetic resistance of a second magnetic path disposed at the other side with respect to the virtual plane P, in the magnetic path formed with the movable plate 4 and the yoke 51 in a state that the movable plate 4 is attracted to the yoke 51.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electromagnetic brake device.

Background Art

[0002] Patent Document 1 discloses an electromagnetic brake device that brakes a disk (hereinafter, a rotating member) that rotates with a predetermined axial direction as the rotation axis direction. The electromagnetic brake device includes a movable plate (hereinafter, a movable member) disposed adjacent to the rotating member in the axial direction, a spring that biases the movable member toward the rotating member in the axial direction, and an electromagnet for separating the movable member from the rotating member in the axial direction. The movable member is made of a magnetic material. The electromagnet has a yoke disposed on the opposite side of the rotating member with the movable member interposed therebetween in the axial direction, and a coil housed in the yoke. When the coil is energized, the movable member is attracted to the yoke by a magnetic attractive force (hereinafter, simply referred to as magnetic force) and is separated from the rotating member. When the energization of the coil is cut off, the magnetic force weakens in a short time. When the biasing force by the spring becomes relatively stronger than the magnetic force, the movable member moves in the axial direction and contacts the rotating member, thereby activating the brake by frictional force.

[0003] To mitigate the impact caused by contact between the movable member and the rotating member when the brake is applied, steps are formed at the yoke-side end of the movable member and the movable member-side end of the yoke, as described in Patent Document 1. More specifically, the above-mentioned end of the movable member has two semi-ring-shaped end faces divided in the circumferential direction (referred to as the first movable surface and the second movable surface for convenience of explanation). The second movable surface is positioned further from the yoke in the axial direction than the first movable surface. Similarly, the above-mentioned end of the yoke also has two end faces divided in the circumferential direction (referred to as the first yoke end face and the second yoke end face for convenience of explanation). The first yoke end face faces the first movable end face in the axial direction, and the second yoke end face faces the second movable end face in the axial direction. The axial distance between the second movable end face and the second yoke end face is greater than the axial distance between the first movable end face and the first yoke end face. As a result, the magnetic force acting between the second movable end face and the second yoke end face is weaker than the magnetic force acting between the first movable end face and the first yoke end face. This ensures that when the power to the coil is cut off, the portion of the movable member with the second movable end face formed thereon contacts the rotating member sooner than the portion of the movable member with the first movable end face formed thereon. In this way, impact is mitigated by avoiding simultaneous contact of the entire surface of the movable member with the rotating member and by gradually bringing the movable member into contact with the rotating member. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 61-88032 [Overview of the project] [Problems that the invention aims to solve]

[0005] When the coil is energized, if the end face of the movable member closer to the rotating member in the axial direction (the end face on the rotating member side) is parallel to the end face of the rotating member opposite to the end face on the rotating member side (the end face on the movable member side), then, as described above, the movable member can be gradually brought into contact with the rotating member. However, generally, electromagnetic brake devices are designed so that the attractive force of the electromagnet is much stronger than the biasing force of the spring in order to reliably switch the brake on and off. For this reason, when the coil is energized, after the first movable end face contacts the first yoke end face, the second movable end face tilts toward the second yoke end face with the boundary between the first and second movable end faces as a fulcrum, and there is a possibility that the second movable end face will also be completely attracted to the yoke. At this time, the end face of the movable member on the rotating member side will be tilted relative to the end face of the rotating member on the movable member side. If the power to the coil is cut off in this state, as described above, the second movable end face will move away from the second yoke end face quickly, and there is a risk that the movable member will come into contact with the rotating member at the moment the end face on the rotating member side returns to being approximately parallel to the end face on the movable member side. In this case, ultimately, the entire surface of the movable member will come into contact with the rotating member at the same time.

[0006] The objective of the present invention is to reliably mitigate the impact caused by contact between a movable member and a rotating member when the brake is activated. [Means for solving the problem]

[0007] The first electromagnetic brake device is an electromagnetic brake device for braking a rotating member that rotates with a predetermined axial direction as the rotation axis, and comprises: a movable member made of a magnetic material, which is disposed adjacent to one side of the rotating member in the axial direction, is configured to be movable in the axial direction, and brakes the rotation of the rotating member when in contact with an end face formed at one end of the rotating member in the axial direction; a plurality of biasing members that bias the movable member toward the other side in the axial direction; and an electromagnet unit configured to apply a magnetic force to the movable member toward the one side in the axial direction, wherein the electromagnet unit has a cylindrical inner cylinder portion extending in the axial direction and made of a magnetic material, and a cylindrical outer cylinder portion disposed radially outside the inner cylinder portion and made of a magnetic material, and a yoke disposed on one side of the movable member in the axial direction, and radially outside the inner cylinder portion and inside the outer cylinder portion The device includes a coil positioned on one side and configured to generate a magnetic flux passing through the movable member and the yoke when current is flowing, and restricting portions provided on the outer cylinder and positioned on both sides of a predetermined virtual plane including the rotational axis of the rotating member, which restrict the movement of the movable member to one side in the axial direction, wherein the restricting portions are configured to make the end face of the rotating member and a facing surface formed on the movable member that faces the end face of the rotating member in the axial direction parallel when the movable member is attracted to the yoke by the magnetic force, and the magnetic resistance of the first magnetic path positioned on one side of the virtual plane among the magnetic paths formed including the movable member and the yoke is greater than the magnetic resistance of the second magnetic path positioned on the other side of the virtual plane.

[0008] In this invention, when the coil is energized (i.e., when current flows through the coil), the movable member is attracted to the yoke by magnetic force. In this state, the restricting part makes it possible to make one end face of the rotating member in the axial direction parallel to the opposing face of the movable member. Furthermore, with the movable member attracted to the yoke, the magnetic resistance of the first magnetic path is greater than the magnetic resistance of the second magnetic path. As a result, when the power to the coil is cut off, the magnetic force acting on the portion of the movable member located on one side of the virtual plane (hereinafter referred to as the first portion) weakens faster than the magnetic force acting on the portion of the movable member located on the other side of the virtual plane (hereinafter referred to as the second portion). Therefore, when the power to the coil is cut off, the first portion leaves the yoke and contacts the rotating member before the second portion. In other words, the movable member contacts the rotating member while slightly tilted. Subsequently, the second portion contacts the rotating member slightly later than the first portion. In this way, when braking the rotation of the rotating member, the contact area between the movable member and the rotating member can be gradually increased. Therefore, the impact caused by contact between the movable and rotating members when the brakes are applied can be reliably mitigated.

[0009] The electromagnetic brake device of the second invention is characterized in that, in the first invention, the plurality of biasing members are housed in the outer cylinder portion and are arranged at different positions from each other in the circumferential direction of the movable member, and the regulating portion is arranged at least between two biasing members that are adjacent to each other in the circumferential direction among the plurality of biasing members.

[0010] For the sake of explanation, the portion of the movable member located where a biasing member is positioned in the circumferential direction is called the biased portion. The portion of the movable member located where no biasing member is positioned in the circumferential direction is called the unbiased portion. When current flows through the coil, the unbiased portion is pulled towards the yoke with a stronger force than the biased portion, and may therefore bend. In this invention, a restricting portion is provided at the position where the unbiased portion is located in the circumferential direction. Therefore, bending of the movable member can be suppressed when the movable member is attracted to the yoke, etc.

[0011] The electromagnetic brake device of the third invention is characterized in that, in the second invention, the regulating portion is provided around the entire circumference of the outer cylinder portion.

[0012] In this invention, it is possible to effectively prevent the movable member from bending when it is attracted to the yoke.

[0013] The electromagnetic brake device of the fourth invention is characterized in that, in any of the first to third inventions, the plurality of biasing members comprises one or more first biasing members arranged on one side of the virtual plane and one or more second biasing members arranged on the other side of the virtual plane, and when the movable member is pulled towards the yoke, the first biasing force by the one or more first biasing members is stronger than the second biasing force by the one or more second biasing members.

[0014] In this invention, when the power supply to the coil is cut off, the first part can be made to contact the rotating member more reliably and quickly than the second part. [Brief explanation of the drawing]

[0015] [Figure 1] This is a view of the electromagnetic brake device according to this embodiment, seen from the axial direction. [Figure 2] (a) and (b) are cross-sectional views taken along line II-II in Figure 1. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] This is a cross-sectional view of the inner cylinder portion of the yoke. [Figure 5] This is a perspective view of the inner cylinder. [Figure 6] This is an explanatory diagram showing the state of the electromagnetic brake system one hour after the power supply to the coil has been cut off. [Figure 7] This is an explanatory diagram showing the state of the electromagnetic brake system two hours after the state shown in Figure 6. [Figure 8] This is a view of the electromagnetic brake device according to a modified example, seen from the axial direction.

Best Mode for Carrying Out the Invention

[0016] Next, the electromagnetic brake device 1 according to an embodiment of the present invention will be described. For convenience of explanation, the direction perpendicular to the paper surface of FIG. 1 and the vertical direction of the paper surface of FIG. 2 are referred to as the axial direction. The axial direction is the rotational axis direction of the rotation axis RS (see FIG. 2) described later. The radial direction of the rotation axis RS is simply referred to as the radial direction. The radial direction is equal to the radial direction of the entire electromagnetic brake device 1. The circumferential direction of the rotation axis RS is simply referred to as the circumferential direction. The circumferential direction is equal to the circumferential direction of the entire electromagnetic brake device 1.

[0017] (Outline of Electromagnetic Brake Device) The outline of the electromagnetic brake device 1 will be described with reference to FIGS. 1 to 2(b). FIG. 1 is a view of the electromagnetic brake device 1 seen from the side of the fixed plate 3 described later in the axial direction. FIG. 2(a) is a sectional view taken along line II-II of FIG. 1. More specifically, FIG. 2(a) is a view showing the state of the electromagnetic brake device 1 when the coil 52 described later is energized (that is, when a current is flowing through the coil 52). FIG. 2(b) is, similarly to FIG. 2(a), a sectional view taken along line II-II of FIG. 1. More specifically, FIG. 2(b) is a view showing the state of the electromagnetic brake device 1 when no current is flowing through the coil 52.

[0018] The electromagnetic brake device 1 is a device for stopping the operation of a device (not shown) to which the rotating shaft RS is connected by braking the rotation of the rotating shaft RS (see FIG. 2). As shown in FIGS. 1 to 2(a), the electromagnetic brake device 1 includes a rotating member 2, a fixed plate 3, a movable plate 4 (the movable member of the present invention), an electromagnet unit 5, and a plurality of springs 6 (the biasing member of the present invention). The electromagnetic brake device 1 is configured to operate the brake by sandwiching the rotating member 2 attached to the rotating shaft RS between the fixed plate 3 and the movable plate 4. More specifically, when the electromagnet unit 5 pulls the movable plate 4 away from the rotating member 2, the rotation of the rotating member 2 becomes possible. Further, when the state in which the electromagnet unit 5 pulls the movable plate 4 is released (hereinafter referred to as "the electromagnet unit 5 releases the movable plate 4"), the movable plate 4 is pressed against the rotating member 2 by a plurality of springs 6 (see FIG. 2(b)). Thereby, the brake operates.

[0019] (Each component) Next, the more details of each component of the electromagnetic brake device 1 will be described while referring to FIGS. 1 to 3. FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1 when the coil 52 is energized.

[0020] The rotating member 2 has a hub 21 and a disk 22. The hub 21 is a substantially cylindrical portion fixed to the tip end portion RS1 of the rotating shaft RS. The hub 21 is, for example, a known spline collar. The hub 21 has a fitting portion 21a (see FIG. 1) that fits with the inner peripheral portion of the disk 22, for example. The disk 22 is a substantially disk-shaped member disposed outside the hub 21 in the radial direction. The inner peripheral portion of the disk 22 is fitted with the fitting portion 21a of the hub 21. Thereby, the disk 22 can rotate integrally with the hub 21. Alternatively, the hub 21 and the disk 22 may be formed of one member.

[0021] For the sake of explanation, the following definitions of one side and the other side in the axial direction are shown in Figure 2(a). The lower side of Figure 2(a) is one side in the axial direction. The upper side of Figure 2(a) is the other side in the axial direction. Although not shown in Figure 2(b), the definitions of one side and the other side in the axial direction are the same in Figure 2(a) and Figure 2(b). As shown in Figures 2(a) and 2(b), an end face 22a is formed at one end of the disk 22 in the axial direction. An end face 22b is formed at the other end of the disk 22 in the axial direction. End face 22a is a surface arranged to be in contact with the end face 4b (described later) of the movable plate 4. End face 22b is a surface arranged to be in contact with the end face 3a (described later) of the fixed plate 3.

[0022] The fixing plate 3 is, for example, a substantially disc-shaped member. As shown in Figures 2(a) to 3, the fixing plate 3 is positioned adjacent to the other side of the disk 22 in the axial direction. An end face 3a is formed at one end of the fixing plate 3 in the axial direction. The end face 3a is a surface positioned to be in contact with the end face 22b of the disk 22. As shown in Figure 3, the fixing plate 3 has multiple through holes 3b through which the shafts of multiple bolts B are inserted. The fixing plate 3 is fixed to the electromagnet unit 5 by multiple bolts B.

[0023] The movable plate 4 is, for example, a substantially disc-shaped member. The movable plate 4 is made of a magnetic material such as iron. As shown in Figures 2(a) to 3, the movable plate 4 is positioned adjacent to one side of the disk 22 in the axial direction. The movable plate 4 is positioned adjacent to the other side of the electromagnet unit 5 in the axial direction. The movable plate 4 is positioned on the radially outer side of the rotation axis RS. An end face 4a is formed at one end of the movable plate 4 in the axial direction. The end face 4a is a surface that is in contact with the end face 54b formed on the yoke 51, which will be described later. An end face 4b (the opposing surface of the present invention) is formed at the other end of the movable plate 4 in the axial direction. The end face 4b is a surface that is in contact with the end face 22a of the disk 22. The end faces 4a and 4b are substantially parallel.

[0024] As shown in Figure 3, the movable plate 4 has multiple through holes 4c through which multiple collars C are inserted. Each through hole 4c penetrates the movable plate 4 axially. Each of the multiple collars C extends axially. The multiple collars C are fixed between the fixed plate 3 and the electromagnet unit 5 by multiple bolts B. The movable plate 4 is guided axially by the multiple collars C. This makes the movable plate 4 movable in the axial direction. More specifically, the movable plate 4 is movable between a brake release position (see Figure 2(a)) and a brake activation position (see Figure 2(b)). The brake release position is the position of the movable plate 4 when it is attracted to the electromagnet unit 5 in the axial direction. The brake activation position is the position of the movable plate 4 when it is released from the electromagnet unit 5 and is fully pressed against the disc 22.

[0025] The electromagnet unit 5 is a unit for attracting and releasing the movable plate 4. As shown in Figures 2(a) to 3, the electromagnet unit 5 is positioned adjacent to one side of the movable plate 4 in the axial direction. The electromagnet unit 5 has a yoke 51 and a coil 52.

[0026] The yoke 51 is a generally cylindrical member extending along the axial direction. The yoke 51 is made of a magnetic material such as iron. The yoke 51 is positioned on the radially outer side of the rotation axis RS. The yoke 51 has an inner cylinder portion 53, an outer cylinder portion 54, and a disc portion 55. The inner cylinder portion 53, the outer cylinder portion 54, and the disc portion 55 form a coil housing groove 56 in which the coil 52 is housed. In this embodiment, the inner cylinder portion 53, the outer cylinder portion 54, and the disc portion 55 are integrally formed from a single member. However, it is not limited to this.

[0027] The inner cylinder portion 53 is a substantially cylindrical portion located immediately outside the radial axis RS. For convenience of explanation, one end of the outer cylinder portion 54 in the axial direction is shown by a dashed line in Figures 2(a) and 2(b). The inner cylinder portion 53 has an outer peripheral surface 53a formed at its radial outer end. The outer peripheral surface 53a is positioned to face the inner peripheral surface 54a, which will be described later, in the radial direction. The inner cylinder portion 53 has, for example, a ring housing groove 53b formed at the other end in the axial direction. The ring housing groove 53b extends over the entire circumference of the inner cylinder portion 53 (i.e., the entire area in the circumferential direction). An O-ring R is fitted into the ring housing groove 53b. The O-ring R is a cushioning member for suppressing shock and noise generated when the movable plate 4 and the yoke 51 come into contact. The O-ring R may be provided at a different location. Instead of the ring housing groove 53b, a ring housing groove (not shown) may be provided on, for example, the end face 54b (described later) of the outer cylinder portion 54. An O-ring R may be housed in such a ring housing groove (not shown).

[0028] The outer cylinder portion 54 is a substantially cylindrical portion located radially outside the inner cylinder portion 53. For convenience of explanation, one end of the outer cylinder portion 54 in the axial direction is shown by a dashed line in Figures 2(a) and 2(b). The outer cylinder portion 54 has an inner circumferential surface 54a formed at its radially inner end. The inner circumferential surface 54a is positioned radially, spaced apart from the outer circumferential surface 53a of the inner cylinder portion 53 and facing the outer circumferential surface 53a. An end face 54b (the restricting portion of the present invention) is formed at the other end of the outer cylinder portion 54 in the axial direction. The end face 54b is positioned to be in contact with the end face 4a of the movable plate 4. The outer cylinder portion 54 has a plurality of screw holes 54c that extend axially. A plurality of bolts B are screwed into each of the plurality of screw holes 54c. The outer cylinder portion 54 has a plurality of spring housing holes 57 that extend axially. A spring 6 is housed in each of the multiple spring housing holes 57.

[0029] The disc portion 55 is a substantially disc-shaped part. The disc portion 55 is located on one side in the axial direction of the inner cylinder portion 53 and the outer cylinder portion 54. For the sake of explanation, the boundary between the disc portion 55 and the inner cylinder portion 53 and the boundary between the disc portion 55 and the outer cylinder portion 54 are shown by dashed lines in Figures 2(a) and 2(b). An upper surface 55a is formed at the upper end of the disc portion 55. The upper surface 55a is located radially between the outer circumferential surface 53a of the inner cylinder portion 53 and the inner circumferential surface 54a of the outer cylinder portion 54. The upper surface 55a is connected to the outer circumferential surface 53a and the inner circumferential surface 54a. The coil housing groove 56 described above is formed by the outer circumferential surface 53a, the inner circumferential surface 54a and the upper surface 55a.

[0030] Coil 52 is configured to generate magnetic flux through the movable plate 4 and the yoke 51 when current is flowing. Coil 52 is located in the coil housing groove 56. Coil 52 is wound in the circumferential direction (see the symbol for coil 52 in Figure 2(a), etc.). Coil 52 is connected to a power source (not shown). The magnetic flux generated by the current flowing through coil 52 passes through, for example, the inner cylinder portion 53, the movable plate 4, the outer cylinder portion 54, and the disc portion 55 in this order (not shown). In this way, a magnetic path through which the magnetic flux passes is formed around the entire circumference of the electromagnet unit 5.

[0031] The multiple springs 6 are biasing members for biasing the movable plate 4 axially toward the other side. Each of the multiple springs 6 is, for example, a known compression coil spring. The multiple springs 6 are each housed in a plurality of spring housing holes 57. The multiple springs 6 are, for example, arranged at approximately equal intervals in the circumferential direction. In this embodiment, six springs 6 are housed in six spring housing holes 57 (see Figure 1).

[0032] (Overview of the operation of the electromagnetic brake system) The operation of the electromagnetic brake device 1 having the above configuration will now be outlined. When the coil 52 is energized, a magnetic force (magnetic attraction force) is generated between the movable plate 4 and the yoke 51 due to the magnetic flux. When the magnetic force becomes stronger than the biasing force of the spring 6 (i.e., elastic restoring force, also called spring load), the movable plate 4 moves to one side in the axial direction against the biasing force and is attracted to the yoke 51 (see Figure 2(a)). At this time, the movable plate 4 moves to the brake release position. When the movable plate 4 is in the brake release position, the rotating member 2 is slightly separated from the fixed plate 3 and the movable plate 4 in the axial direction. As a result, the rotating member 2 and the rotating shaft RS become rotatable.

[0033] On the other hand, when the power to coil 52 is cut off, the magnetic force weakens rapidly. When the biasing force from spring 6 becomes relatively stronger than the magnetic force, the movable plate 4 separates from yoke 51 (i.e., is released from electromagnet unit 5). At this time, the movable plate 4 moves to the brake operating position due to the biasing force. When the movable plate 4 is pressed against the rotating member 2, the rotating member 2 is sandwiched between the fixed plate 3 and the movable plate 4. As a result, a frictional force acts between the end face 22a of disc 22 and the end face 4b of movable plate 4, and also between the end face 22b of disc 22 and the end face 3a of fixed plate 3. As a result, the rotation of the rotating member 2 and the rotating shaft RS is braked (i.e., the brake is activated).

[0034] Here, when the movable plate 4 moves from the brake-activated position to the brake-release position, the impact can be mitigated by the O-ring R described above. However, it is not possible to provide a cushioning member such as an O-ring between the rotating member 2 and the movable plate 4 in the axial direction for the purpose of mitigating the impact when the movable plate 4 moves from the brake-release position to the brake-activated position. The reason for this is that if a cushioning member is provided, the contact area between the end face 22a of the disc 22 and the end face 4a of the movable plate 4 will decrease. In this case, there is a risk that the frictional force necessary to brake the rotating member 2 and the rotating shaft RS will not be obtained.

[0035] Therefore, in order to reliably mitigate the impact caused by contact between the movable plate 4 and the rotating member 2 when the brake is activated, the electromagnetic brake device 1 is further configured as follows.

[0036] (Detailed configuration of the electromagnetic brake system) The detailed configuration of the electromagnetic brake device 1 (in particular, the detailed configuration of the yoke 51) will be explained with reference to Figures 1 to 5. Figure 4 is a cross-sectional view of the inner cylinder portion 53 of the yoke 51. Figure 5 is a perspective view of the inner cylinder portion 53. In Figure 5, the ring housing groove 53b is not shown.

[0037] In summary, the yoke 51 is configured such that the magnetic resistances of two magnetic paths, formed on opposite sides of a predetermined virtual plane P (see Figures 1, 2(a), 2(b), and 4), are different. The virtual plane P is a predetermined virtual plane that is parallel to the axial direction and passes through approximately the center of the yoke 51 in the radial direction. The virtual plane P includes the rotational axis of the rotating member 2. For the sake of explanation, the two magnetic paths are virtually divided into two by the virtual plane P. That is, the two magnetic paths are not necessarily divided by any member or the like. Hereafter, the direction perpendicular to the virtual plane P will be referred to as the predetermined direction (see Figures 1, 2(b), and 4). For the sake of explanation, in Figures 1, 2(b), and 4, the right side of the paper is defined as one side in the predetermined direction, and the left side of the paper is defined as the other side in the predetermined direction. Although not shown in the illustration, the definition of the predetermined direction in Figure 2(a) is the same as the definition of the predetermined direction in Figure 1, etc.

[0038] For the sake of explanation, the portion of the electromagnetic brake device 1 located on one side in a predetermined direction relative to the virtual plane P will be referred to as the one-side portion. The portion of the electromagnetic brake device 1 located on one side in a predetermined direction relative to the virtual plane P will be referred to as the other-side portion.

[0039] As shown in Figure 2, the movable plate 4 is conveniently divided into a movable plate section 4R and a movable plate section 4L, separated by a virtual plane P. The movable plate section 4R (which can also be called the first section) is included in one side of the electromagnetic brake device 1. The movable plate section 4L (which can also be called the second section) is included in the other side of the electromagnetic brake device 1.

[0040] As shown in Figures 4 and 5, the inner cylinder portion 53 has a shape that is a cylinder cut at an angle (see Figures 4 and 5). An end face 53c is formed at the other end of the inner cylinder portion 53 in the axial direction. The end face 53c is, for example, generally ring-shaped overall. The end face 53c is inclined with respect to a predetermined direction as a whole. In other words, if a virtual end face 53cV is defined as a hypothetical surface whose position in the axial direction is constant (see Figures 4 and 5), then the end face 53c is inclined with respect to the virtual end face 53cV.

[0041] As shown in Figures 4 and 5, the inner cylinder portion 53 is conveniently divided into an inner cylinder portion 53R and an inner cylinder portion 53L, separated by a virtual plane P. The inner cylinder portion 53R is included in one side of the electromagnetic brake device 1. The inner cylinder portion 53L is included in the other side of the electromagnetic brake device 1. The other end face of the inner cylinder portion 53R in the axial direction is called end face 53Rc. The other end face of the inner cylinder portion 53L in the axial direction is called end face 53Lc. The axial positions of end face 53Rc and end face 53Lc are different from each other. More specifically, in the axial direction, one end of end face 53Rc in a predetermined direction is located one side further than the other end of end face 53Lc in a predetermined direction (see distance D shown in Figure 4). As a result, when the movable plate 4 is in the brake release position, the average size of the gap formed between end face 53Rc and end face 4a is greater than the average size of the gap formed between end face 53Lc and end face 4a. Therefore, when the movable plate 4 is in the brake release position, magnetic flux does not pass through as easily on one side as it does on the other side. In other words, the magnetic resistance of the magnetic path formed on one side in a predetermined direction relative to the virtual plane P (hereinafter referred to as the first magnetic path) is greater than the magnetic resistance of the magnetic path formed on the other side in a predetermined direction relative to the virtual plane P (hereinafter referred to as the second magnetic path).

[0042] Next, the shape of the outer cylinder portion 54 will be described in detail. The end face 54b of the outer cylinder portion 54 is provided around the entire circumference of the outer cylinder portion 54. In other words, the end face 54b is positioned at least between any two springs 6 that are adjacent to each other in the circumferential direction among the multiple springs 6. Furthermore, the axial position of the end face 54b is substantially constant around the entire circumference of the outer cylinder portion 54. That is, the axial position of the end face 54b is substantially the same on both sides of the virtual plane P. As a result, when the movable plate 4 moves to the brake release position, the end face 4a of the movable plate 4 reliably contacts the end face 54b of the outer cylinder portion 54 around its entire circumference. Therefore, when the movable plate 4 is in the brake release position, the end face 4b of the movable plate 4 can be made substantially parallel to the end face 22a of the disc 22.

[0043] Of the multiple spring housing holes 57, the spring housing hole 57 located on one side in a predetermined direction relative to the virtual plane P is called a spring housing hole 57R (see Figures 2(a) and 2(b)). Of the multiple spring housing holes 57, the spring housing hole 57 located on the other side in a predetermined direction relative to the virtual plane P is called a spring housing hole 57L (see Figures 2(a) and 2(b)). In this embodiment, multiple (more specifically, three) spring housing holes 57R and multiple (more specifically, three) spring housing holes 57L are provided (see Figure 1). The multiple spring housing holes 57R are shallower in the axial direction than the multiple spring housing holes 57L. In other words, the bottom surface formed at one end in the axial direction of a spring housing hole 57R is located on the other side in the axial direction than the bottom surface formed at one end in the axial direction of a spring housing hole 57L. The axial depths of the multiple spring housing holes 57R are, for example, approximately equal. The axial depths of the multiple spring housing holes 57L are, for example, approximately equal. The spring 6 housed in the spring housing hole 57R is called spring 6R (the first biasing member of the present invention). The spring 6 housed in the spring housing hole 57L is called spring 6L (the second biasing member of the present invention). The number of springs 6R and the number of springs 6L are equal. The free height of spring 6R and the free height of spring 6L are, for example, approximately equal. The spring constant of spring 6R and the spring constant of spring 6L are, for example, approximately equal. As a result, when the movable plate 4 is in the brake release position, the deformation amount of spring 6R is greater than the deformation amount of spring 6L. Therefore, when the movable plate 4 is in the brake release position, the biasing force by the multiple springs 6R (hereinafter, the first biasing force) is stronger than the biasing force by the multiple springs 6L (hereinafter, the second biasing force). The first biasing force is the sum of the spring loads (elastic restoring forces) of each of the multiple springs 6R. The second biasing force is the sum of the individual spring loads of the multiple springs 6L.

[0044] (Details of the operation of the electromagnetic brake system) The operation of the electromagnetic brake device 1 having the above configuration will now be described in detail. First, when current flows through the coil 52, the movable plate 4 is in the brake release position as described above (see Figure 2(a)). At this time, the end face 4a of the movable plate 4 is in contact with the end face 54b of the outer cylindrical portion 54 of the yoke 51 over almost the entire circumferential area. Therefore, when the movable plate 4 is in the brake release position, the end face 4b of the movable plate 4 is approximately parallel to the end face 22a of the disc 22. With the above configuration, one side of the electromagnetic brake device 1 has the following properties compared to the other side of the electromagnetic brake device 1. That is, the magnetic resistance of the first magnetic path formed in the one side is greater than the magnetic resistance of the second magnetic path formed in the other side. As a result, the magnetic force generated between the movable plate 4 (movable plate portion 4R) and the yoke 51 in the one side is weaker than the magnetic force generated between the movable plate 4 (movable plate portion 4L) and the yoke 51 in the other side. Furthermore, the first biasing force exerted by multiple springs 6R on one side is stronger than the second biasing force exerted by multiple springs 6L on the other side.

[0045] Because the electromagnetic brake device 1 has the properties described above, the movable plate 4 operates as shown in Figures 6 and 7 after the power supply to the coil 52 is cut off. Figure 6 is an explanatory diagram showing the state of the electromagnetic brake device 1 after a predetermined first time has elapsed since the power supply to the coil 52 was cut off. Figure 7 is an explanatory diagram showing the state of the electromagnetic brake device 1 after a further predetermined second time has elapsed from the state shown in Figure 6. Both the first and second times are very short periods of time.

[0046] First, when the power to the coil 52 is cut off, the magnetic force generated between the movable plate 4 and the yoke 51 weakens as described above. For example, when 1 hour has elapsed since the power to the coil 52 was cut off, the magnetic force acting between the movable plate portion 4R and the yoke 51 on one side becomes weaker than the biasing force of the spring 6R. In other words, the biasing force of the spring 6R becomes relatively stronger than the magnetic force on one side. On the other hand, at this time, due to the properties of the electromagnetic brake device 1 described above, the magnetic force acting between the movable plate portion 4L and the yoke 51 on the other side is still stronger than the biasing force of the spring 6L. For this reason, of the movable plate 4, only the movable plate portion 4R is released from the yoke 51 before the movable plate portion 4L (see arrow in Figure 6). Then, the portion of the end face 4b of the movable plate 4 that is positioned to one side of the virtual plane P in a predetermined direction comes into contact with the end face 22a of the disc 22 in that predetermined direction (see Figure 6). In other words, end face 4b is inclined with respect to end face 22a and contacts only a portion of end face 22a.

[0047] Subsequently, after a second time has elapsed, the magnetic force acting between the movable plate portion 4L and the yoke 51 becomes weaker than the biasing force of the spring 6L. In other words, the biasing force of the spring 6L becomes relatively stronger than the magnetic force on the other side. As a result, the movable plate portion 4L is also released from the yoke 51 (see arrow in Figure 7). As a result, the movable plate 4 moves with the portion that contacted the end face 22a in Figure 6 as a fulcrum, so that the inclination of the end face 4b with respect to the end face 22a decreases. In other words, the end face 4b gradually comes into contact with the end face 22a from one end to the other in a predetermined direction.

[0048] As described above, when the power to the coil 52 is cut off, the end face 4b gradually comes into contact with the end face 22a. In other words, when the power to the coil 52 is cut off, the contact area between the movable plate 4 and the rotating member 2 gradually increases. This suppresses the impact and noise when the movable plate 4 comes into contact with the disc 22.

[0049] As described above, when current flows through the coil 52, the movable plate 4 is attracted to the yoke 51 by magnetic force. In this state, the end face 54b of the outer cylinder portion 54 makes the end face 22a on one axial side of the rotating member 2 (disk 22) and the end face 4b of the movable plate 4 approximately parallel. Furthermore, with the movable plate 4 attracted to the yoke 51, the magnetic resistance of the first magnetic path is greater than the magnetic resistance of the second magnetic path. As a result, when the power to the coil 52 is cut off, the magnetic force acting on the movable plate portion 4R weakens faster than the magnetic force acting on the movable plate portion 4L. Therefore, when the power to the coil 52 is cut off, the movable plate portion 4R separates from the yoke 51 and contacts the rotating member 2 before the movable plate portion 4L. In other words, the movable plate 4 contacts the rotating member 2 while slightly tilted from the predetermined direction. Subsequently, the movable plate portion 4L contacts the rotating member 2 slightly later than the movable plate portion 4R. In this way, when braking the rotation of the rotating member 2, the contact area between the movable plate 4 and the rotating member 2 can be gradually increased. Therefore, the impact caused by contact between the movable plate 4 and the rotating member 2 when the brake is activated can be reliably mitigated.

[0050] Furthermore, the end face 54b is positioned at least between any two springs 6 that are adjacent to each other in the circumferential direction among the multiple springs 6. The portion of the movable plate 4 that is located in a position where no springs 6 are positioned in the circumferential direction is pulled towards the yoke 51 with a relatively strong force when the coil 52 is energized, and may bend. In this embodiment, however, since the end face 54b is provided in the position described above, it is possible to suppress bending of the movable plate 4 when the movable plate 4 is attracted to the yoke 51, etc.

[0051] Furthermore, the end face 54b is provided around the entire circumference of the outer cylinder portion 54. Therefore, it is possible to effectively suppress the bending of the movable plate 4 when it is attracted to the yoke 51.

[0052] Furthermore, the first biasing force provided by the multiple springs 6R is stronger than the second biasing force provided by the multiple springs 6L. This ensures that when the power to the coil is cut off, the movable plate portion 4R can be brought into contact with the rotating member 2 more reliably and quickly than the movable plate portion 4L.

[0053] Next, modified examples of the above embodiments will be described. However, components having the same configuration as the above embodiments will be denoted by the same reference numerals and their descriptions will be omitted as appropriate.

[0054] (1) In the above embodiment, the spring housing holes 57R and 57L are configured such that the deformation amount of spring 6R is greater than the deformation amount of spring 6L. More specifically, the multiple spring housing holes 57R are shallower in the axial direction than the multiple spring housing holes 57L. Also, the axial depths of the multiple spring housing holes 57R are approximately equal, and the axial depths of the multiple spring housing holes 57L are approximately equal. However, this is not limited to this. First, the axial depths of the multiple spring housing holes 57R may differ from each other depending on their position in a predetermined direction. For example, the spring housing hole 57R furthest from the virtual plane P in a predetermined direction may be even shallower in the axial direction than the spring housing hole 57R that is closer to the virtual plane P in a predetermined direction. Similarly, the axial depths of the multiple spring housing holes 57L may also differ from each other depending on their position in a predetermined direction. For example, the spring housing hole 57L furthest from the virtual plane P in a given direction may be deeper in the axial direction than the spring housing hole 57L that is closer to the virtual plane P in the given direction.

[0055] Alternatively, the multiple spring housing holes 57R do not have to be shallower than the multiple spring housing holes 57L in the axial direction. That is, in the axial direction, the bottom surface formed at one end of the spring housing hole 57R may be positioned at approximately the same location as the bottom surface formed at one end of the spring housing hole 57L. In this case, for example, the first biasing force by the multiple springs 6R may be stronger than the second biasing force by the multiple springs 6L, as follows. As a first example, the spring constant of spring 6R may be greater than the spring constant of spring 6L. As in the first example, the first biasing force can be made stronger than the second biasing force with a simple structure. As a second example, as shown in Figure 8, the number of multiple springs 6R may be greater than the number of multiple springs 6L.

[0056] (2) In the embodiments described above, the first biasing force provided by the multiple springs 6R was stronger than the second biasing force provided by the multiple springs 6L. However, this is not the case. The first biasing force and the second biasing force may be approximately the same.

[0057] (3) The number of springs 6 and bolts B provided in the electromagnetic brake device 1 is not limited to those described above. The number of springs 6 and bolts B shall be set appropriately according to the specifications of the electromagnetic brake device 1.

[0058] (4) In the embodiments described above, the end face 54b of the outer cylinder portion 54 was formed over the entire circumference (the entire area in the circumferential direction). Furthermore, the position of the end face 54b in the axial direction was assumed to be substantially constant over the entire circumference. However, it is not limited to this. As described above, at least in the circumferential direction, a plurality of restricting parts that restrict the axial movement of the movable plate 4 may be provided between any two adjacent springs 6 among the plurality of springs 6. In this case, the positions of the plurality of restricting parts in the axial direction are substantially the same. Alternatively, the plurality of restricting parts do not necessarily have to be arranged between two adjacent springs 6 in the circumferential direction.

[0059] (5) In the embodiments described above, the inner cylinder portion 53 was made to have a shape in which a cylinder was cut at an angle in order to make the magnetic resistance of the first magnetic circuit greater than the magnetic resistance of the second magnetic circuit. However, it is not limited to this. For example, the end faces 53Rc and 53Lc of the inner cylinder portion 53 may be formed in a stepped shape. That is, the end faces 53Rc and 53Lc may be formed asymmetrically with respect to the virtual plane P. In addition, the shape of the end face 4a of the movable plate 4 may be formed asymmetrically with respect to the virtual plane P in addition to the inner cylinder portion 53, or in place of the inner cylinder portion 53. In addition, some non-magnetic member may be placed in the gap formed between the end face 53c and the end face 4a in the axial direction. As described above, any means may be provided to make the magnetic resistance of the first magnetic circuit greater than the magnetic resistance of the second magnetic circuit. [Explanation of Symbols]

[0060] 1. Electromagnetic brake system 2 Rotating members 4. Movable plate (movable member) 4b End face (opposing face) 5 Electromagnet Unit 6. Spring (biasing member) 6L Spring (Second biasing member) 6R Spring (First biasing member) 22a End face 51 York 52 coils 53 Inner cylinder 54 Outer cylinder 54b End face (regulating part) P Virtual Plane

Claims

1. An electromagnetic brake device for braking a rotating member that rotates with a predetermined axial direction as the rotation axis, A movable member made of a magnetic material is positioned adjacent to one side of the rotating member in the axial direction, configured to be movable in the axial direction, and brakes the rotation of the rotating member when in contact with an end face formed on one end of the rotating member in the axial direction; A plurality of biasing members that bias the movable member toward the other side in the axial direction, The electromagnet unit is configured to apply a magnetic force to the movable member on one side in the axial direction, The electromagnet unit is, The movable member has a cylindrical inner cylinder portion extending in the axial direction and made of a magnetic material, and a cylindrical outer cylinder portion positioned radially outside the inner cylinder portion and made of a magnetic material, and a yoke positioned on one side of the movable member in the axial direction, A coil is positioned on the outside of the inner cylinder and on the inside of the outer cylinder in the radial direction, and is configured to generate a magnetic flux passing through the movable member and the yoke when current is flowing. The outer cylinder portion is provided with a restricting portion which is positioned on both sides of a predetermined virtual plane including the rotational axis of the rotating member and restricts the movement of the movable member to one side in the axial direction, The restricting portion is configured to make the end face of the rotating member and the opposing surface formed on the movable member that faces the end face of the rotating member in the axial direction parallel when the movable member is attracted to the yoke by the magnetic force, by contacting the movable member on both sides of the virtual plane. An electromagnetic brake device characterized in that, when the movable member is attracted to the yoke by the magnetic force, the magnetic resistance of the first magnetic path, which is located on one side of the virtual plane, is greater than the magnetic resistance of the second magnetic path, which is located on the other side of the virtual plane, among the magnetic paths formed including the movable member and the yoke.

2. The plurality of biasing members are housed in the outer cylinder and are arranged at different positions in the circumferential direction of the movable member. The electromagnetic brake device according to claim 1, characterized in that the restricting portion is arranged at least between two biasing members that are adjacent to each other in the circumferential direction among the plurality of biasing members.

3. The electromagnetic brake device according to claim 2, characterized in that the regulating portion is provided around the entire circumference of the outer cylinder portion.

4. The plurality of biasing members include one or more first biasing members arranged on one side of the virtual plane, and one or more second biasing members arranged on the other side of the virtual plane. The electromagnetic brake device according to any one of claims 1 to 3, characterized in that, when the movable member is pulled towards the yoke, the first biasing force provided by the one or more first biasing members is stronger than the second biasing force provided by the one or more second biasing members.

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