Electromagnetic brake

Abstract

To compactly configure an electromagnetic brake having an overexcitation circuit while taking heat radiation into consideration.SOLUTION: In adopting a configuration for energizing a coil 2 through an overexcitation circuit 7 to excite a yoke 1, a substrate 7x, on which the overexcitation circuit 7 is mounted, is resin-molded on the yoke 1 together with the coil 2, so that the overexcitation circuit 7 is integrally formed with the yoke 1 to compactify the electromagnetic brake MB. By resin-molding the overexcitation circuit 7 on the yoke 1 together with the coil 2, a heat load received by the overexcitation circuit 7 can be reduced by heat radiation through a resin mold layer 8.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electromagnetic brake that receives power through an overexcitation circuit. [Background technology]

[0002] An electromagnetic brake is known which has a yoke, a coil which excites the yoke by receiving power from an external source via a power supply path, and braking means, and which also has an over-excitation circuit in the power supply path which temporarily puts the excitation to the yoke into an over-excitation state, and which is configured to switch the ON / OFF state of the brake by the braking force of the braking means and the excitation force through the power supply path (for example, Patent Document 1).

[0003] FIG. 8 shows an electromagnetic brake MB whose basic operation is substantially the same as that of the above-mentioned Patent Document 1.

[0004] This electromagnetic brake MB comprises a yoke 1, a coil 2 attached to the yoke 1, and a coil spring 3 serving as a braking means, and is configured so that an armature 4 can be driven back and forth by the excitation force of the coil 2 and the spring force of the coil spring 3, and when de-excited, the coil spring 3 moves the armature 4 and sandwiches a disc 6 between it and a side plate 5, thereby transmitting the braking force of the disc 6 to the motor shaft 10, and when excited, the electromagnetic force moves the armature 4 away from the side plate 5 and attracts it to the attraction surface 1a of the yoke 1, thereby releasing the braking state applied to the motor shaft 10 by the disc 6.

[0005] In this case, an over-excitation circuit 7 as shown in FIG. 8 is attached externally to the current path L, and the excitation to the yoke 1 is temporarily put into an over-excitation state, thereby increasing the excitation force at the initial movement when the brake is released, thereby making it possible to drive the armature 4 more effectively, and after the armature 4 is attracted to the yoke attraction surface 1a, the excitation is switched to normal excitation to appropriately maintain the attracted state.

[0006] In Patent Document 1, a permanent magnet is used as the braking means instead of a coil spring, but the basic operation is the same as in FIG. 8, and other suitable devices such as a leaf spring can also be used as the braking means. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-273577 Summary of the Invention [Problem to be solved by the invention]

[0008] However, conventionally, this type of over-excitation circuit 7 has been attached externally to the yoke 1 as an over-excitation circuit component 70, as shown in Figures 9 and 10. For this reason, when attempting to configure an electromagnetic brake as shown in Figure 8 using this yoke 1, the over-excitation circuit component 70 also has to be attached externally to the electromagnetic brake MB, which results in the need for additional space for the over-excitation circuit component 70, making it difficult to make the electromagnetic brake MB compact and imposing many constraints on its assembly to a motor, etc.

[0009] Therefore, it is considered to be an effective measure to incorporate the over-excitation circuit 7 into the electromagnetic brake MB. In that case, however, it is necessary to take appropriate measures in consideration of the fact that this type of over-excitation circuit 7 is made up of electronic components and is therefore susceptible to thermal and electromagnetic influences.

[0010] The present invention aims to realize a new electromagnetic brake based on this idea. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides the following means.

[0012] In other words, the electromagnetic brake of the present invention has a yoke, a coil which excites the yoke by receiving power from the outside via a power supply path, and braking means, and is further provided with an over-excitation circuit in the power supply path which temporarily puts the excitation to the yoke into an over-excitation state, and is configured so that the ON / OFF state of the brake is switched by the braking force by the braking means and the excitation force through the power supply path, and is characterized in that a board carrying the over-excitation circuit is integrated into the yoke together with the coil by resin molding.

[0013] In this way, the over-excitation circuit can be integrated into the yoke, making it possible to make the electromagnetic brake more compact. Moreover, since the over-excitation circuit includes electronic components and is therefore susceptible to thermal effects, by resin molding it into the yoke together with the coil, the heat can be dissipated through the resin mold layer, reducing the thermal load on the over-excitation circuit.

[0014] It is preferable that the substrate is in close contact with the yoke via a heat dissipation sheet.

[0015] When continuous current is applied to release the brake, it is thought that the heat dissipation effect from the resin molded layer alone may be insufficient. However, by attaching the base to the yoke via a heat dissipation sheet, it is possible to dissipate heat to the yoke. This ensures that, in addition to the heat dissipation from the resin molded layer, another heat dissipation path with a higher heat dissipation effect is provided, so that the impact of thermal load can be more effectively reduced even if the base is integrated into the yoke.

[0016] In this case, it is preferable that the base is fixed to the yoke via a fastener having high thermal conductivity.

[0017] Resin molding is prone to losing its adhesion to the yoke due to shrinkage of the resin when cooled. By using the above-mentioned highly heat-conductive fastener, on the other hand, it is possible to ensure proper adhesion after resin molding and also to create a new heat dissipation route through the fastener.

[0018] It is also preferable that a recess be provided in the yoke at the outer periphery of the coil, and that the base be disposed within the recess.

[0019] When an over-excitation circuit is exposed to electromagnetic waves, the circuit acts as an antenna and receives the electromagnetic waves, which can easily have a negative effect on the function of the over-excitation circuit. In response to this, by providing a recess around the outer periphery of the coil and placing the board on it, it is possible to ensure that electromagnetic waves are less likely to reach the board.

[0020] It is also preferable that an electromagnetic wave shielding wall is disposed between the coil and the base.

[0021] By disposing such an electromagnetic wave blocking wall, it is possible to block electromagnetic waves emitted from the coil winding portion (core portion) around the yoke, and more effectively reduce the influence of the electromagnetic waves on the over-excitation circuit.

[0022] The present invention is particularly effective when the overexcitation circuit is configured to create a normal excitation state by PWM control.

[0023] If digital components are used in such an over-excitation circuit, they are particularly susceptible to the effects of electromagnetic waves, so measures against electromagnetic waves are particularly effective. Effect of the Invention

[0024] According to the present invention as described above, it is possible to provide a new electromagnetic brake which can be made compact by integrally assembling the over-excitation circuit into the yoke and which also deals well with thermal loads. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a perspective view showing a yoke portion of the electromagnetic brake according to the embodiment of the present invention. [Diagram 2] FIG. 2 is a partial longitudinal sectional view of FIG. [Diagram 3] FIG. 2 is an explanatory diagram of an over-excitation circuit constituting the embodiment. [Figure 4] FIG. 3 is a partial cross-sectional view corresponding to FIG. 2 and showing a modified example of the present invention. [Diagram 5] FIG. 3 is a partial cross-sectional view corresponding to FIG. 2 and showing a modified example of the present invention. [Figure 6] 3 is an explanatory diagram including a partial sectional view and a plan view corresponding to FIG. 2, showing a modified example of the present invention. [Figure 7] 3 is an explanatory diagram including a partial sectional view corresponding to FIG. 2 and a perspective view of a coil bobbin, showing a modified example of the present invention. FIG. [Figure 8] FIG. 1 is a diagram showing the configuration of a conventional electromagnetic brake. [Figure 9] FIG. 1 is a diagram showing a conventional electromagnetic brake with an external over-excitation circuit. [Figure 10] FIG. 1 is a diagram showing a conventional electromagnetic brake with an external over-excitation circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] Figures 1 and 2 show a yoke 1 portion of the configuration of the electromagnetic brake shown in Figure 8. In explaining this embodiment, Figure 8 will be used as appropriate because it is the premise of the configuration of the electromagnetic brake.

[0028] The yoke 1 is cylindrical with a bottom, has an annular gap 13 between an inner circumferential wall 11 and an outer circumferential wall 12, and has a through hole 14 for inserting a shaft inside the inner circumferential wall 11. A coil bobbin 20 around which a copper wire coil 2 is wound is housed in the annular gap 13, and a rotating shaft is inserted into the through hole 14. The coil bobbin 20 is annular with a U-shaped opening on the outer circumferential side, and is made of a resin material.

[0029] The inner peripheral wall 11 and the outer peripheral wall 12 of the yoke 1, including the bottom wall 15, are made of an iron core material and form a magnetic path through which magnetic flux passes. The end face (top face) opposite the bottom wall 15 serves as the attraction surface 1a of the armature 4 shown in Figure 8, and the armature 4 is attracted to the attraction surface 1a by connecting the magnetic path through the armature 4.

[0030] In order to supply power to the coil 2 from the outside, a lead-in portion 12a of the power supply path L is provided on the outer wall 12 of the yoke 1, and the power supply wiring 2a is led in from here. The illustrated lead-in portion 12a utilizes a groove provided to avoid interference with other components, but if such grooves are provided in multiple locations, an appropriate groove may be used, or there may be no such groove at all, and only a hole may be provided in the outer wall 12 as the wiring lead-in portion.

[0031] An over-excitation circuit 7 shown in Fig. 3 is provided in the power supply path L. This over-excitation circuit 7 enables the armature 4 to properly start moving when the brake is released by temporarily putting the excitation of the yoke 1 into an over-excitation state, and includes a voltage conversion unit 7a and a voltage switching timing control unit 7b.

[0032] The voltage conversion unit 7a converts the input voltage into a lower output voltage and energizes the coil. It is configured to include a PWM control circuit using an operational amplifier or the like, and creates an output voltage that is artificially lower than the input voltage through pulse width conversion of a stepped input voltage. In the illustrated example, 24V is converted to 5V, but the input voltage may be other than 24V, and the output voltage may be, for example, 5 to 12V. The voltage switching timing control unit 7b performs a switching operation to output the input voltage (e.g., 24V) for a predetermined overexcitation period after the voltage is applied, and switch to the voltage (e.g., 5V) converted by the voltage conversion unit 7a after the overexcitation period has elapsed, and outputs the voltage. It is configured using a time constant of an RC circuit or the like.

[0033] In the past, this over-excitation circuit 7 was attached externally to the electromagnetic brake MB as shown in Figures 8 to 10, which caused problems with the space required for installation, so in this embodiment, a board 7x carrying this over-excitation circuit 7 is integrated into the yoke 1 as shown in Figures 1 and 2. At that time, the over-excitation circuit 7 is easily affected by thermal and electromagnetic influences, and so the circuit is incorporated into the yoke 1 in a creative way.

[0034] Specifically, a portion of the outer peripheral wall 12 of the yoke 1 is removed from the suction surface 1a toward the bottom wall 15 to form a notched recess 16, and a substrate 7x carrying an over-excitation circuit 7 is attached to the bottom surface 16a of the recess 16 by stacking it flat so that it is in close contact with the yoke 1, via a heat dissipation sheet 17 made of a common heat dissipation material.

[0035] In this state, a pair of input ends of the over-excitation circuit 7 shown in Figure 3 are connected to 24V wiring 2a drawn in from an external power source, for example, part of the driving power source of a motor (e.g., the driving power source of a robot), which is the equipment to which this electromagnetic brake is applied, and a pair of output terminals are connected to the coil 2 housed in the coil bobbin 20.

[0036] Then, in this state, resin made of a common material used for molding purposes is poured into the annular gap 13 and the recess 16, thereby forming a resin molded layer 8 (see Figure 1 (b)), which integrates the base 7x and the coil 2 into the yoke 1.

[0037] The electromagnetic brake MB equipped with the yoke 1 constructed in this manner operates as a non-excitation actuated electromagnetic brake in that when not excited, it biases the armature 4 shown in Fig. 8 in a direction away from the yoke 1 using braking means 3 such as a coil spring to actuate the brake, and when voltage is applied to the coil 2 to release the brake, it increases the initial excitation force at the time of brake release to effect the initial movement of the armature 4, and after the armature 4 is attracted to the attraction surface 1a, it switches to normal excitation to appropriately maintain the attracted state of the armature 4, thereby operating as a non-excitation actuated electromagnetic brake. This switching of operating states is repeated each time the 24V brake release command is turned ON / OFF.

[0038] As described above, in the electromagnetic brake of this embodiment, in adopting a configuration in which current is passed through the coil 2 via the over-excitation circuit 7 to excite the yoke 1, the board 7x on which the over-excitation circuit 7 is mounted is resin-molded to the yoke 1 together with the coil 2. By integrating the over-excitation circuit 7 with the yoke 1 in this manner, it is possible to make the electromagnetic brake MB more compact. Moreover, since the over-excitation circuit 7 includes electronic components and is therefore susceptible to thermal effects, by resin-molding the board 7x on which it is mounted together with the coil 2 to the yoke 1, it is possible to reduce the thermal load received by the over-excitation circuit 7 by dissipating heat through the resin mold layer 8.

[0039] Furthermore, in this embodiment, taking into consideration the fact that the heat dissipation effect from the resin molded layer 8 alone may be insufficient when continuous current is applied to release the brake, the base 7x is attached to the yoke 1 (specifically, the bottom surface 16a of the recess 16 provided in the yoke 1) via a heat dissipation sheet 17, thereby dissipating heat to the yoke 1. Since this ensures another heat dissipation path with a higher heat dissipation effect in addition to the heat dissipation from the resin molded layer 8, the effects of thermal load can be more effectively reduced even if the base 7x is provided integrally with the yoke 1.

[0040] In addition, in this embodiment, in consideration of the fact that when the over-excitation circuit 7 is exposed to electromagnetic waves, the circuit acts as an antenna to receive the electromagnetic waves, which can adversely affect the function of the over-excitation circuit, a recess 16 is provided in the outer wall 12 of the yoke 1 at the outer periphery of the coil 2, and a base 7x is placed within the recess 16, thereby ensuring that electromagnetic waves are less likely to reach the base 7x.

[0041] In particular, the over-excitation circuit 7 of this embodiment creates a normal excitation state by PWM control, and since it uses digital components and is susceptible to the effects of electromagnetic waves, the above-mentioned electromagnetic wave countermeasures are particularly effective.

[0042] Although an embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above-described embodiment. Modifications of the present invention will be described below.

[0043] In the above embodiment, a recess 16 is provided in the outer peripheral wall 12 of the yoke 1 located around the outer periphery of the coil 2, and the base 7x is placed flat. However, as shown in FIG. 4(a), a vertical hole-shaped recess 116 may be provided in the outer periphery 12 of the yoke 1 located around the outer periphery of the coil 2, and the base 7x may be inserted vertically together with the heat dissipation sheet 17 to be closely attached to the outer peripheral wall 12 of the yoke 1.

[0044] Alternatively, as shown in FIG. 4(b), a recess 216 may be provided in the bottom wall 15 of the yoke 1 below the coil 2 (coil bobbin 20), and the base 7x may be attached to the recess 216 together with the heat dissipation sheet 17 in a flat state by being in close contact with the bottom wall 15.

[0045] Alternatively, as shown in FIG. 4(c), a vertical hole-shaped recess 316 may be provided in the inner wall 11 of the yoke 1 located at the inner circumference of the coil 2, and the base 7x may be inserted vertically together with the heat dissipation sheet 17 to be closely attached to the inner wall 11 of the yoke 1.

[0046] In either case, in addition to the heat dissipation effect by the resin molding that is performed afterwards, a heat dissipation effect from the part that is in close contact with the yoke 1 to the yoke 1 can be expected.

[0047] 5(a), the base 7x may be fixed to the yoke 1 via a fastener 71 made of metal or the like and having high thermal conductivity. Specifically, a recess 16 is provided on the top surface of the yoke 1 and the fastener 71 is press-fitted into the yoke 1, while a hole 72 is provided in the base 7x and the large diameter part of the hole 72 is passed over the head of the fastener 71 so that the base 7x is placed flat on the yoke 1 together with the heat dissipation sheet 17, and then the base 7x is slid to move the fastener 71 relatively toward the small diameter part, thereby preventing the base 7x from coming off.

[0048] In resin molding, the shrinkage of the resin during cooling can easily cause the adhesion of the base 7x to the yoke 1 via the heat dissipation sheet 17 to be compromised. However, by using the above-described highly heat-conductive fastener 71, it is possible to ensure adhesion of the base 7x to the yoke 1 after resin molding and also to form a new heat dissipation route to the yoke 1 via the fastener 71.

[0049] In this case, one end of the base 7x may be fixed in contact with the side wall 16a of the recess 16, and the other end of the base 7x may be fixed at one point by a fastener. Also, as shown in Fig. 5(b), two or more points of the base 7x may be fixed to the yoke 1 by fasteners 71 in the form of screws. Alternatively, the fasteners 71 in Fig. 5(a) and the fasteners 71 in Fig. 6(a) may be combined.

[0050] As shown in FIG. 6, it is also effective to place an electromagnetic wave shielding wall 9 made of a material that shields electromagnetic waves between the coil 2 and the base 7x.

[0051] By disposing such an electromagnetic wave shielding wall 9, the electromagnetic waves emitted from the winding part (core part) of the yoke 1 and the coil 2 can be blocked by the electromagnetic wave shielding wall 9, and the influence of the electromagnetic waves on the over-excitation circuit 7 mounted on the board 7x can be effectively reduced. In this case, the board 7x may be stacked flat in a recess 16 provided in the outer peripheral wall 12 of the yoke 1 as shown in Fig. 6(a), or may be attached to its outer peripheral surface by using the electromagnetic wave shielding wall 9 as shown in Fig. 6(b). In either case, it is effective to set the upper end of the electromagnetic wave shielding wall 9 to be higher than the board 7x.

[0052] Alternatively, even when the base 7x is placed in close contact with the bottom wall 15 of the yoke 1 via a heat dissipation sheet 17 as shown in FIG. 6(c), the heat dissipation effect can be improved by fixing the base 7x to the bottom wall 15 of the yoke 1 via a highly heat-conductive fastener 71 such as metal, and measures against electromagnetic waves can be taken by providing an electromagnetic wave shielding wall 9 wider than the base 7x under the coil bobbin 20 to block electromagnetic waves.

[0053] Alternatively, in the above embodiment, the base 7x is attached to the yoke 1 via the heat dissipation sheet 17, but if, for example, the electromagnetic brake is not frequently switched on and off and high heat dissipation is not required, a flange 20a may be provided on the coil bobbin 20, this flange 20a may be placed in the recess 16 of the yoke 1, and the base 7x may be attached to this flange 20a via a foamed double-sided tape 117, as shown in Figures 7(a) and (b). Even in this case, heat dissipation from the resin mold layer 8 can be expected by subsequently performing resin molding.

[0054] However, doing so would result in the coil bobbin 20 becoming irregular in shape, which would increase the amount of resin used during molding and the associated costs, so in terms of moldability, ease of quality control of the bobbin, and the like, it is preferable to attach the board 7x without changing the shape of the coil bobbin 20 as in the above embodiment, etc. If there is a protrusion such as the flange 20a at the board attachment location, it could be a cause of winding problems (scratches or breaks) in the coil 2.

[0055] Other configurations can also be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0056] 1. York 2. Coil 3... Braking means (coil spring) 7...Overexcitation circuit 8…Resin mold layer 9. Electromagnetic shielding wall 16…Recess 17...Heat dissipation sheet 71...Clasp L…Power supply path

Claims

1. A brake device comprising: a yoke; a coil for exciting the yoke by receiving power from an external source via a power supply path; and a braking means, and further comprising an over-excitation circuit in the power supply path for temporarily over-exciting the yoke, the over-excitation circuit being provided in the power supply path, and configured to switch between ON / OFF states of a brake by a braking force by the braking means and an excitation force through the power supply path, an electromagnetic brake, characterized in that a board on which the over-excitation circuit is mounted is integrated with the yoke together with the coil by resin molding.

2. 2. The electromagnetic brake according to claim 1, wherein the base is in close contact with the yoke via a heat dissipation sheet.

3. 3. The electromagnetic brake according to claim 2, wherein the base is fixed to the yoke via a fastener having high thermal conductivity.

4. 4. The electromagnetic brake according to claim 1, wherein a recess is provided in said yoke at an outer periphery of said coil, and said base is disposed within said recess.

5. 5. The electromagnetic brake according to claim 1, further comprising an electromagnetic wave blocking wall disposed between said coil and said base.

Images