Electromagnetic brake for motor and motor

Abstract

To detect timing of re-sucking operation using no sensor to provide an inexpensive configuration.SOLUTION: A controller 15 of an electromagnetic brake for a motor supplies a brake current to a brake coil 17 with a predetermined attraction voltage for moving an armature from a braking position to a braking release position when the motor is started, and supplies the brake current to the brake coil 17 with a predetermined holding voltage lower than the attraction voltage after the motor is started. The controller 15 includes a current detection unit 26 that detects the brake current supplied to the brake coil 17, and a braking detection unit 27 for detecting change in the brake current being accompanied by movement of an armature 12 to the braking position through the current detection unit 26 while a holding voltage is being applied. When change in the brake current is detected by the braking detection part 27, the controller supplies the brake current to the brake coil 17 by the attraction voltage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electromagnetic brake for a motor that is attached to a motor to brake the motor shaft, and a motor to which the electromagnetic brake for a motor is attached. [Background technology]

[0002] As disclosed in Patent Document 1, a known electromagnetic brake for a motor includes a field attached to the non-load side of the motor, which has a brake coil, and an armature that is attracted when the brake coil is energized. In this electromagnetic brake for a motor, when the motor is stopped, the armature is in a braking position where it presses against a brake lining that is integral with the motor shaft due to the biasing force of a spring or the like provided in the field. When the motor starts from this position, a brake current is supplied from an electrical quantity control unit (energization control unit) to the brake coil, and the armature is attracted by the brake coil and moves to a brake release position where it is separated from the brake lining.

[0003] In such an electromagnetic brake for a motor, when the motor is started, the current control unit applies the maximum attraction voltage to attract the armature to the brake release position against the bias of a spring, etc. On the other hand, after the brake is released, the armature is close to the brake coil, so the current control unit applies a holding voltage lower than the attraction voltage, thereby saving energy. However, if an external force is applied to the electromagnetic brake due to an impact or the like, there is a risk that the attraction of the armature will be released and braking will be applied at a low holding voltage.For this reason, Patent Document 2 discloses an invention in which an acceleration sensor, speed sensor, or the like is provided in the electromagnetic brake, and when the sensor detects that an external force has been applied to the electromagnetic brake, the current control unit applies the same attraction voltage as when the brake was released, causing the brake to perform the attraction operation again. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-272057 [Patent Document 2] Patent No. 6851229 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if a sensor is used to detect the timing of the re-suction operation as in Patent Document 2, the cost of the current control unit will increase.

[0006] Therefore, an object of the present disclosure is to provide an electromagnetic brake for a motor and a motor that can detect the timing of the re-suction operation without using a sensor and that have an inexpensive configuration. [Means for solving the problem]

[0007] In order to achieve the above object, a first configuration of the present disclosure includes: a field attached to a motor and having a brake coil; an armature movable between a braking position where a motor shaft of the motor is braked and a brake release position where the braking of the motor shaft is released; biasing means for biasing the armature toward the braking position; and an energization control unit that supplies a brake current to the brake coil when the motor is started to move the armature to the brake release position, and stops supplying the brake current when the motor is stopped; the current supply control unit supplies the brake current to the brake coil at a predetermined attraction voltage that moves the armature from the braking position to the brake release position when the motor is started, and supplies the brake current to the brake coil at a predetermined holding voltage that is lower than the attraction voltage after the motor is started, The current control unit includes a current detection unit that detects the brake current supplied to the brake coil; a braking detection unit that detects a change in the brake current associated with movement of the armature to the braking position via the current detection unit while the holding voltage is being applied, The current control unit supplies the brake current to the brake coil at the attraction voltage when the braking detection unit detects a change in the brake current. Another aspect of the first configuration is characterized in that, in the above configuration, the braking detection unit detects a change in the braking current based on a value obtained by differentiating the braking current detected by the current detection unit. Another aspect of the first configuration is that, in the above configuration, the braking detection unit detects a change in the braking current based on a value obtained by integrating the differentiated value. In order to achieve the above object, a second aspect of the present disclosure is a motor equipped with an electromagnetic brake for a motor according to any one of the first aspects. [Effects of the Invention]

[0008] According to the present disclosure, when the braking detection unit detects a change in the brake current, the current supply control unit supplies the brake current to the brake coil at an attraction voltage, so that the timing of the re-attraction operation can be detected without using a sensor, resulting in an inexpensive configuration. Furthermore, since the re-attraction operation is performed only when the brake current changes, it also leads to energy savings. According to another aspect of the present disclosure, in addition to the above effects, the braking detection unit detects changes in the braking current based on a value obtained by differentiating the braking current detected by the current detection unit, making it possible to easily detect changes in the braking current when the armature moves to the braking position. According to another aspect of the present disclosure, in addition to the above effects, the braking detection unit detects changes in the brake current based on a value obtained by integrating the differentiated value, thereby making it possible to accurately detect changes in the brake current. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram of an electromagnetic brake for a motor and a motor. [Figure 2] FIG. 2 is a block diagram showing the configuration of a controller. [Figure 3] 10 is a graph showing a change in brake current. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a motor 1 equipped with an electromagnetic brake 10 for a motor (hereinafter simply referred to as an "electromagnetic brake"). First, the motor 1 has a cylindrical motor frame 2. Inside the motor frame 2, a motor consisting of a stator and a rotor (not shown) is housed. Within the motor frame 2, on the load side of the motor (the right side of FIG. 1 when viewed sideways), a reduction mechanism (not shown) is housed, with an output shaft 3 protruding from the motor frame 2. A motor shaft 4 attached to the rotor is engaged with the input side of the reduction mechanism. A terminal block 5 is installed on the top surface of the motor frame 2. A cover 7 is attached via a motor bracket 6 to the anti-load side of the motor frame 2 (the left side in FIG. 1 when viewed sideways). An end 8 of the motor shaft 4 protrudes into the cover 7. An electromagnetic brake 10 is attached to the motor bracket 6 within the cover 7, and brakes the motor shaft 4 via the end 8.

[0011] The electromagnetic brake 10 includes a field 11, an armature 12, a coil spring 13, an outer disc 14, and a controller 15. The field 11 is fixed to the motor bracket 6 with bolts 16 and houses a brake coil 17 on the anti-load side. The brake coil 17 is electrically connected to the terminal block 5 by lead wires (not shown). The armature 12 is supported so as to be movable in the axial direction while being engaged with a bolt 16 and restricted from rotation. A coil spring 13 biases the armature 12 toward the anti-load side.

[0012] The outer disc 14 is key-coupled so as to rotate integrally with the end portion 8 and move axially. A star washer nut 18 is threadedly engaged with the end portion 8 to prevent the outer disc 14 from coming off. A coil spring 19 is fitted to the end portion 8 between the motor bracket 6 and the outer disc 14, and biases the outer disc 14 to its outermost position where it abuts against the star washer nut 18. A brake disc 20 is provided on the surface of the outer disc 14 facing the armature 12. Therefore, the armature 12 can move between a braking position where it abuts against the brake disc 20 of the outer disc 14 at the outermost position, and a braking release position where it is attracted by the brake coil 17 and moves away from the brake disc 20, and is normally biased toward the braking position by the coil spring 13.

[0013] The controller 15 is electrically connected to the terminal block 5 outside the motor 1. As shown in FIG. 2, the controller 15 includes a voltage control unit 25, a current detection unit 26, and a braking detection unit 27, and controls the supply of electricity to the brake coil 17. The voltage control unit 25 controls the power supplied from the power source 28 to supply a brake current of a predetermined voltage to the brake coil 17 . The current detection unit 26 detects the brake current supplied to the brake coil 17 and outputs the detected brake current to the braking detection unit 27 .

[0014] The braking detection unit 27 includes a differentiation circuit 30 including an operational amplifier 31, a resistor 32, and a capacitor 33, and an integration circuit 40 including a capacitor 41, a resistor 42, and a comparator 43. That is, the brake current input from the current detection unit 26 is amplified by the operational amplifier 31 and differentiated by the differentiation circuit 30, thereby determining the amount of change in the brake current. As shown in FIG. 3 , when the armature 12, which is attracted to the brake release position by the holding voltage, starts to move to the braking position at time t1 due to an external force or the like, the inductance of the brake coil 17 decreases, causing the brake current to increase rapidly, and this increase is extracted by the differentiation circuit 30. The extracted differential value is then integrated by the integrating circuit 40, and when the integrated value exceeds a predetermined threshold value, a signal indicating a change in the brake current is output from the comparator 43 to the voltage control unit 25.

[0015] In the motor 1 and electromagnetic brake 10 configured as described above, when the motor 1 is stopped, the armature 12 moves to the braking position due to the bias of the coil spring 13 as described above and presses the brake disc 20 of the outer disc 14. Therefore, the motor shaft 4 is braked via the outer disc 14. When the motor 1 is turned on by power supply 28, the voltage control section 25 of the controller 15 supplies a brake current to the brake coil 17 at a predetermined attraction voltage that moves the armature 12 to the brake release position. Then, an attractive force is generated in the brake coil 17 by electromagnetic force, and the armature 12 moves to the brake release position against the bias of the coil spring 13 and moves away from the brake disc 20. As a result, the rotor of the motor shaft 4 is released from the brake and rotates, causing the output shaft 3 to rotate at a reduced speed via the reduction mechanism.

[0016] After the motor 1 is started, the voltage control unit 25 supplies a brake current to the brake coil 17 at a predetermined holding voltage that is lower than the attraction voltage. This holding voltage may be a steady voltage or a pulse voltage. Therefore, the armature 12 is maintained in the brake release position. While the motor 1 is running, the braking detection unit 27 differentiates the braking current input from the current detection unit 26 in the differentiation circuit 30 to determine the amount of change in the braking current, and integrates the extracted differentiated value in the integration circuit 35. If the armature 12 is maintained in the brake release position, the integrated value does not reach a predetermined threshold value, and therefore no braking current change detection signal is output. On the other hand, when an external force or the like causes the armature 12 to start moving toward the braking position, the brake current increases rapidly and a change detection signal is output from the braking detection unit 27. Upon receiving this change detection signal, the voltage control unit 25 returns the output voltage of the brake current to the attraction voltage. As a result, the armature 12 is attracted again by the brake coil 17 and remains in the brake release position. When the motor 1 stops, the voltage control unit 25 stops supplying the brake current to the brake coil 17.

[0017] In this way, the electromagnetic brake 10 and motor 1 of the above-described form comprise a field 11 attached to the motor 1 and having a brake coil 17, an armature 12 movable between a braking position where the motor shaft 4 of the motor 1 is braked and a brake release position where the braking of the motor shaft 4 is released, a coil spring 13 (an example of a biasing means) that biases the armature 12 toward the braking position, and a controller 15 (an example of a current control unit) that supplies a brake current to the brake coil 17 when the motor 1 is started to move the armature 12 to the brake release position, and stops supplying the brake current when the motor 1 is stopped. In addition, when the motor 1 is started, the controller 15 supplies a brake current to the brake coil 17 at a predetermined attraction voltage that moves the armature 12 from the braking position to the brake release position, and after the motor 1 is started, supplies a brake current to the brake coil 17 at a predetermined holding voltage that is lower than the attraction voltage.

[0018] The controller 15 has a current detection unit 26 that detects the brake current supplied to the brake coil 17, and a braking detection unit 27 that detects a change in the brake current associated with movement of the armature 12 to the braking position via the current detection unit 26 while the holding voltage is being applied.When the braking detection unit 27 detects a change in the brake current, it supplies the brake current to the brake coil 17 at an attraction voltage. This configuration allows the timing of the re-suction operation to be detected without using a sensor, resulting in an inexpensive configuration. Also, since the re-suction operation is performed only when the brake current changes, it also leads to energy savings.

[0019] The braking detection unit 27 detects changes in the braking current based on the value obtained by differentiating the braking current detected by the current detection unit 26 using the differentiation circuit 30, so that it is possible to easily detect changes in the braking current when the armature 12 moves to the braking position. The braking detection unit 27 detects the change in the braking current based on the value obtained by integrating the differentiated value in the integrating circuit 40, and therefore the change in the braking current can be detected accurately.

[0020] Modifications of the present disclosure will be described below. The differential circuit and the integrating circuit in the braking detection unit may have a circuit configuration other than that described above. Also, in the above-described embodiment, the differential circuit and the integrating circuit are provided in the braking detection unit, but the integrating circuit may be omitted and only the differential circuit may be provided, and the change in the braking current extracted by the differential circuit may be output to the voltage control unit. The configuration of the motor is not limited to the above-described embodiment, and can be modified as appropriate, for example, to have a fan attached to the end of the motor shaft, or to have the motor frame divided into a housing section for the motor and a housing section for the reducer, etc. [Explanation of symbols]

[0021] 1·· Motor, 2·· Motor frame, 3·· Output shaft, 4·· Motor shaft, 5·· Terminal block, 6·· Motor bracket, 8·· End, 10·· Electromagnetic brake for motor, 11·· Field, 12·· Armature, 13, 19·· Coil spring, 14·· Outer disc, 15·· Controller, 17·· Brake coil, 25·· Voltage control section, 26·· Current detection section, 27·· Braking detection section, 28·· Power supply, 30·· Differentiation circuit, 40·· Integration circuit.

Claims

1. a field attached to a motor and having a brake coil; an armature movable between a braking position for braking a motor shaft of the motor and a brake release position for releasing the brake on the motor shaft; biasing means for biasing the armature to the braking position; and an energization control unit for supplying a brake current to the brake coil when the motor is started to move the armature to the brake release position and for stopping the supply of the brake current when the motor is stopped, the current supply control unit supplies the brake current to the brake coil at a predetermined attraction voltage that moves the armature from the braking position to the brake release position when the motor is started, and supplies the brake current to the brake coil at a predetermined holding voltage that is lower than the attraction voltage after the motor is started, The current control unit includes a current detection unit that detects the brake current supplied to the brake coil; a braking detection unit that detects a change in the brake current associated with movement of the armature to the braking position via the current detection unit while the holding voltage is being applied, The electromagnetic brake for a motor, wherein the current control unit supplies the brake current to the brake coil at the attraction voltage when the braking detection unit detects a change in the brake current.

2. 2. The electromagnetic brake for a motor according to claim 1, wherein the braking detection unit detects a change in the brake current based on a value obtained by differentiating the brake current detected by the current detection unit.

3. 3. The electromagnetic brake for a motor according to claim 2, wherein the braking detection unit detects the change in the brake current based on a value obtained by integrating the differentiated value.

4. A motor equipped with the electromagnetic brake for a motor according to any one of claims 1 to 3.

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