Motor drive device having brake device

Abstract

To realize a motor drive device that is easily constructed and inexpensive with fewer wires related to a brake device.SOLUTION: A motor drive device 1 comprises an inverter 11 that converts an input DC voltage into an AC voltage and outputs the AC voltage to a motor power line 13 to which a motor 3 is connected, and a brake device 12 that is connected to the motor power line 13 and locks the motor 3 when a predetermined voltage is not supplied from the inverter 11 and unlocks the motor 3 when the predetermined voltage is supplied from the inverter 11 via the motor power line 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor drive device having a brake device. [Background technology]

[0002] Motor drive devices that drive motors in robots and machine tools are equipped with friction-type brake devices that apply brakes to the motor by frictional force by sandwiching a friction plate between an armature and an end plate. In such brake devices, the motor is locked by pressing the armature against the friction plate connected to the motor shaft using the elastic force of a spring, and the motor is unlocked by pulling the armature away from the friction plate using electromagnetic force generated by applying a brake coil voltage to the brake coil.

[0003] For example, a variable speed hoist is known that is characterized by comprising an electric motor that drives the variable speed hoist, an inverter that supplies current to the electric motor to drive it and control the speed of the electric motor, and a brake circuit that is inserted in series between the output of the inverter and the electric motor, and that locks the electric motor when no current is applied and releases the electric motor when current is applied (see, for example, Patent Document 1).

[0004] For example, in a simultaneous opening and closing power module of a DC non-excitation operating type electromagnetic brake, a detection circuit is known which is equipped with a three-phase full-wave rectifier circuit and a cutoff type constant voltage circuit, and by combining these circuits, detects the energization and interruption of three-phase AC as a signal at high speed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-97399 [Patent Document 2] Utility Model Registration No. 3013113 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, in a motor drive device, a brake coil voltage for unlocking a motor is supplied to a brake device via a power line (brake power line) separate from a motor power line for supplying drive power to the motor. That is, a power line from an AC power source to the motor drive device and a power line from an AC power source to the brake device are provided separately. Furthermore, a brake control unit for controlling the supply of the brake coil voltage is provided on the power line from the AC power source to the brake device. For this reason, when constructing a system of a motor drive device having a brake device, there is a problem that the wiring work related to these power lines becomes complicated. For example, a general articulated robot is equipped with six or more motors, and a brake device is provided for each motor, so the number of power lines is enormous, and the wiring work becomes even more complicated. Therefore, a motor drive device with a small number of wires related to the brake device, an easy-to-construct and low-cost motor drive device is desired. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a motor drive device includes an inverter that converts an input DC voltage into an AC voltage and outputs the AC voltage to a motor power line to which a motor is connected, and a brake device that is connected to the motor power line and locks the motor when a predetermined voltage is not supplied from the inverter and unlocks the motor when the predetermined voltage is supplied from the inverter via the motor power line. The brake device locks the motor by pressing an armature against a friction plate to which a shaft of the motor is connected using the elastic force of a spring, and an electromagnetic force generated by applying the AC voltage output from the inverter to a brake coil via the motor power line. and an electromagnetic force based on residual magnetic flux, which is an electromagnetic force held in a core provided with a brake coil by residual magnetic flux. the armature is separated from the friction plate to release the lock of the motor, the inverter outputs to the motor power line an AC voltage for causing an AC current to flow through the brake coil, the AC current generating an electromagnetic force exceeding the elastic force of the spring, and the maximum amplitude of the AC current flowing through the brake coil exceeds the current value when the electromagnetic force generated in the core in which the spring and the brake coil are provided exceeds the elastic force of the spring, The maximum absolute value of the electromagnetic force based on the application of an AC voltage exceeds the absolute value of the elastic force of the spring, and the absolute value of the electromagnetic force based on the application of an AC voltage due to a change in the phase of the AC voltage The length of time when is the absolute value of the electromagnetic force based on the application of AC voltage and the absolute value of the electromagnetic force based on the residual magnetic flux. Elastic force of a spring Absolute value of Exceeds This keeps the motor unlocked. The electromagnetic force retention time is not exceeded. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to realize a motor drive device that has a small number of wirings related to a brake device, is simple in structure, and is low in cost. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a motor drive device (first mode) according to an embodiment of the present disclosure. [Diagram 2] 1A and 1B are cross-sectional views showing the structure of a brake device in a motor drive device (first and second forms) according to one embodiment of the present disclosure, in which (A) shows a state in which the motor 3 is locked, and (B) shows a state in which the motor 3 is unlocked. [Diagram 3] 4 is a diagram illustrating an example of the relationship between an AC current flowing through a brake coil and an electromagnetic force generated in a core. FIG. [Figure 4] 4 is a diagram illustrating an example of a waveform of an AC current flowing through a brake coil. FIG. [Diagram 5] FIG. 2 is a diagram illustrating an example of on / off driving of a switching element of an inverter for applying a DC brake coil voltage to a brake coil in a motor drive device (first mode) according to an embodiment of the present disclosure. [Figure 6] 5 is a flowchart showing an operation flow when a DC brake coil voltage is applied to a brake coil in a motor drive device (first and second modes) according to an embodiment of the present disclosure. [Figure 7] FIG. 2 is a diagram showing a motor driving device (second mode) according to an embodiment of the present disclosure. [Figure 8] FIG. 11 is a diagram illustrating an example of on / off driving of a switching element of an inverter for applying a DC brake coil voltage to a brake coil in a motor drive device (second mode) according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A motor drive device having a brake device will be described below with reference to the drawings. In each drawing, the same reference numerals are used for the same components. In addition, the scale of these drawings is appropriately changed to facilitate understanding. In addition, the embodiment shown in the drawings is one example for carrying out the invention, and the invention is not limited to the illustrated embodiment.

[0011] 1 is a diagram showing a motor drive device (first mode) according to an embodiment of the present disclosure. Note that, although details will be described later, a brake device 12 is connected in parallel or in series to a motor 3 via a motor power line 13. A mode in which the brake device 12 is connected in parallel to the motor 3 via the motor power line 13 is referred to as a first mode, and a mode in which the brake device 12 is connected in series to the motor 3 via the motor power line 13 is referred to as a second mode. The first mode and the second mode differ in whether the brake device 12 is connected in parallel to the motor 3 or in series to the motor 3 via the motor power line 13.

[0012] As an example, a case where a motor 3 is controlled by a motor drive device 1 connected to an AC power source 2 is shown. In this embodiment, the type of the motor 3 is not particularly limited, and may be, for example, an induction motor or a synchronous motor. The number of phases of the AC power source 2 and the motor 3 is not particularly limited in this embodiment, and may be, for example, three-phase or single-phase. In the illustrated example, the AC power source 2 and the motor 3 are each three-phase. Examples of the AC power source 2 include a three-phase 400V AC power source, a three-phase 200V AC power source, a three-phase 600V AC power source, and a single-phase 100V AC power source. Machines in which the motor 3 is provided include, for example, robots and machine tools.

[0013] As shown in FIG. 1, a motor drive device 1 according to an embodiment of the present disclosure includes an inverter 11, a braking device 12, a motor power line 13, a converter 14, a capacitor 15, and a control unit 16.

[0014] The converter 14 converts the AC voltage input from the AC power source 2 into a DC voltage and outputs the DC voltage to a DC link, which is the DC output side of the converter 14. The DC link refers to a circuit portion that electrically connects the DC output side of the converter 14 and the DC input side of the inverter 11, and may also be called a "DC link section," a "DC link," a "DC link section," or a "DC intermediate circuit." The converter 14 is configured with a three-phase bridge circuit when the AC power source 2 is a three-phase AC power source, and is configured with a single-phase bridge circuit when the AC power source 2 is a single-phase AC power source. In the example shown in FIG. 1, the AC power source 2 is a three-phase AC power source, so the converter 14 is configured with a three-phase bridge circuit. Examples of the converter 14 include a diode rectifier, a 120-degree conduction type rectifier, and a PWM switching control type rectifier. For example, when the converter 14 is configured with a diode rectifier, it is configured with a diode bridge circuit. For example, when converter 14 is composed of a 120-degree conduction type rectifier and a PWM switching control type rectifier, it is composed of switching elements and a bridge circuit of diodes connected in inverse parallel to the switching elements, and performs power conversion in both directions, AC and DC, by driving each switching element on and off in response to a switching command received from control unit 16. In this case, examples of switching elements include FETs, IGBTs, thyristors, GTOs (Gate Turn-OFF thyristors), transistors, etc., but other semiconductor elements may also be used.

[0015] Capacitor 15 is provided in a DC link, which is the DC output side of converter 14. Capacitor 15 may also be called a "DC link capacitor" or a "smoothing capacitor." Capacitor 15 has a function of suppressing pulsation in the DC output of converter 14 and a function of storing DC power used by inverter 11 to generate AC power. Examples of capacitor 15 include an electrolytic capacitor and a film capacitor.

[0016] The inverter 11 is connected to the DC output side of the converter 14 via a capacitor 15. The inverter 11 has a bridge circuit in which switching elements, each of which has a diode connected in inverse parallel, are provided on an upper arm on the high potential side and a lower arm on the low potential side. Examples of the switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other semiconductor switching elements may also be used. The inverter 11 is configured as a three-phase bridge circuit when the motor 3 is a three-phase AC motor, and is configured as a single-phase bridge circuit when the motor 3 is a single-phase AC motor. In the example shown in FIG. 1, the motor 3 is a three-phase AC motor, so that the inverter 11 is configured as a three-phase bridge circuit. The inverter 11 converts a DC voltage input from a DC link on the DC input side into an AC voltage by driving the switching elements on and off in response to a switching command based on a PWM control method from the control unit 16, and outputs the AC voltage to the motor power line 13 on the AC output side. In addition, the inverter 11 can also output a motor lock release DC voltage to the motor power line 13 under the control of the control unit 16, as will be described in detail later.

[0017] The control unit 16 generates switching commands for controlling the on / off drive of the switching elements in the inverter 11. In addition, when the converter 14 is configured with a 120-degree conduction type rectifier and a PWM switching control type rectifier, the control unit 16 also generates switching commands for controlling the on / off drive of the switching elements in the converter 14. The control unit 16 may be configured with a combination of an analog circuit and a processor, or may be configured with only a processor, or may be configured with only an analog circuit. Examples of processors that can configure the control unit 16 include IC, LSI, CPU, MPU, DSP, etc. For example, when the control unit 16 is constructed in the form of a software program, the function of the control unit 16 can be realized by operating the processor in accordance with the software program. Alternatively, a semiconductor integrated circuit or a storage medium in which a software program for realizing the function of the control unit 16 is written may be constructed. Alternatively, the control unit 16 may be provided, for example, in a robot controller that controls a robot, or in a numerical control device of a machine tool.

[0018] The inverter 11 and the motor 3 are connected via a motor power line 13. The voltage output from the inverter 11 is applied to the input terminal of the motor 3 via the motor power line 13. As a result, an AC driving current is supplied to the motor 3 from the inverter 11 via the motor power line 13. The motor 3 is rotationally driven by the supplied AC driving current.

[0019] The brake device 12 is connected to a motor power line 13. In particular, in the first embodiment, the brake device 12 and the motor 3 are connected in parallel via the motor power line 13 so that the brake coil and its resistance component in the brake device 12 and the motor coil and its resistance component of the motor 3 are parallel to each other. No circuit components other than the motor power line 13 are provided between the inverter 11 and the brake device 12. In the example shown in FIG. 1, the motor 3 is a three-phase AC motor, so that the motor power line 13 is provided for three phases, but the input terminals of the brake device 12 are connected to any two phases of the three phases of the motor power line 13. If the motor 3 is a single-phase AC motor, the input terminals of the brake device 12 are connected to each of the two phases of the motor power line 13. Note that the inductance component and the resistance component of the brake coil in the brake device 12 and the inductance component and the resistance component of the motor coil of the motor 3 are relatively small values.

[0020] In the braking device 12, a brake coil voltage is applied to the brake coil to unlock the motor 3, and is supplied from the inverter 11 via the motor power line 13. When a predetermined voltage, i.e., the brake coil voltage, is not supplied from the inverter 11 via the motor power line 13, the braking device 12 locks the motor 3 to apply the brakes, and when the brake coil voltage is supplied from the inverter 11 via the motor power line 13, the braking device 12 unlocks the motor and releases the brake.

[0021] 2 is a cross-sectional view showing the structure of a brake device in a motor drive device (first and second modes) according to an embodiment of the present disclosure, where (A) shows a state in which the motor 3 is locked, and (B) shows a state in which the motor 3 is unlocked. The brake device shown in FIG. 2 is also applicable to the second mode described below.

[0022] In the brake device 12, a friction plate 111 is disposed between an armature 112 and an end plate 113. A hub 122 is splined to the friction plate 111, and the hub 122 and the shaft 121 of the motor 3 are integrated by shrink fitting, so that the friction plate 111 also rotates in conjunction with the rotation of the shaft 121 of the motor 3. The end plate 113 and a spacer 117 are connected by a bolt 118, and the armature 112 is connected to the spacer 117 so as to be movable toward and away from the friction plate 111. A spring 114 and a brake coil 115 are provided in the core 116. As shown in FIG. 2(A), when the brake coil voltage from the inverter 11 is not applied to the brake coil 115 via the motor power line 13, the armature 112 is strongly pressed against the friction plate 111 by the elastic force of the spring 114, and the friction plate 111 is sandwiched between the armature 112 and the end plate 113 and cannot rotate. As a result, the shaft 121 coupled to the friction plate 111 cannot rotate either, and the motor 3 is locked, i.e., the motor 3 is braked. On the other hand, as shown in Fig. 2(B), when the brake coil voltage from the inverter 11 is applied to the brake coil 115 via the motor power line 13, an electromagnetic force that overcomes the elastic force of the spring 114 that has been pressing the armature 112 against the friction plate 111 is generated in the core 116, and this attracts the armature 112 to the core 116, and the friction plate 111 is released from contact with the armature 112 and the end plate 113. As a result, the friction plate 111 and therefore the shaft 121 can rotate freely, and the motor 3 is unlocked, i.e., the brake of the motor 3 is released.

[0023] As described above, the inverter 11 converts a DC voltage input from a DC link, which is a DC input side, into an AC voltage and outputs this AC voltage to the motor power line 13 connected to the AC output side. The motor 3 and the brake device 12 are connected to the inverter 11 via the motor power line 13. The AC voltage supplied from the inverter 11 to the motor 3 via the motor power line 13 is used as a drive voltage for the motor 3. On the other hand, the voltage supplied from the inverter 11 to the brake device 12 via the motor power line 13 is used as a brake coil voltage applied to a brake coil in the brake device 12 to unlock the motor 3.

[0024] In the motor drive device 1 according to the first embodiment in which the brake device 12 is connected in parallel to the motor 3 via the motor power line 13, the voltage supplied as a brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 may be either an AC voltage or a DC voltage. Below, an example in which the brake coil voltage is an AC voltage and an example in which the brake coil voltage is a DC voltage will be described separately.

[0025] First, an example will be described in which the voltage supplied as the brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 is an AC voltage.

[0026] Since both the motor 3 and the brake device 12 are connected to the inverter 11 via the motor power line 13, the AC voltage output from the inverter 11 to the motor power line 13 is used as a drive voltage for the motor 3 and a brake coil voltage for unlocking the motor 3 (releasing the brake) by the brake device 12. In other words, when the motor 3 is driven in a state in which the motor 3 is unlocked, an AC current having a magnitude according to the input impedance of the motor 3 and the brake device 12 flows through each of the motor 3 and the brake device 12 via the motor power line 13 due to the AC voltage output from the inverter 11.

[0027] In order to unlock the motor 3 (to release the brake of the motor 3), the inverter 11 needs to output, as a brake coil voltage, to the motor power line 13, an AC voltage for passing an AC current to the brake coil 115, which generates an electromagnetic force in the core 116 that exceeds the elastic force of the spring 114. When the brake coil voltage is not supplied from the inverter 11 via the motor power line 13, there is a void between the armature 112 and the core 116 in the brake device 12, and magnetic flux leaks from this void. For this reason, in order to unlock the motor 3 by supplying a brake coil voltage to the brake device 12 to bring the armature 112 into contact with the core 116 and releasing the friction plate 111 from contact with the armature 112 and the end plate 113, a brake coil voltage for passing a large AC current to the brake coil 115 is required. However, once the armature 112 and the core 116 come into contact with each other, the void between the armature 112 and the core 116 disappears and the armature 112 and the core 116 form an integrated magnetic body, so that magnetic flux leakage is almost eliminated. Therefore, after the armature 112 and the core 116 have come into contact with each other, even if an AC current smaller than the AC current passed through the brake coil 115 to initially bring the armature 112 and the core 116 into contact flows through the brake coil 115, the contact between the armature 112 and the core 116 can be maintained (i.e., the unlocking of the motor 3 can be maintained).

[0028] The magnitude and the positive and negative polarities of the AC voltage and AC current change periodically over time. Now, how the motor 3 is kept unlocked by the AC current flowing through the brake coil 115 will be described in more detail with reference to FIGS. 3 and 4.

[0029] Fig. 3 is a diagram illustrating the relationship between the AC current flowing through the brake coil and the electromagnetic force generated in the core. In Fig. 3, the horizontal axis indicates the AC current I flowing through the brake coil 115, and the vertical axis indicates the electromagnetic force F generated in the core 116. The relationship between the AC current I flowing through the brake coil 115 and the electromagnetic force F generated in the core 116 is expressed by a hysteresis curve as shown in Fig. 3. The elastic force of the spring 114 is F bThe electromagnetic force generated in the core 116 is expressed by the elastic force F of the spring 114. b If the load exceeds F, the lock on motor 3 can be released (the brake on motor 3 can be released). b can be rephrased as the magnitude of the force required to unlock the motor 3.

[0030] As shown in FIG. 3, the AC current flowing through the brake coil 115 increases from 0 to I a Until this occurs, the electromagnetic force generated in the core 116 is equal to the elastic force of the spring 114 (in other words, the force required to unlock the motor 3) F b The AC current flowing through the brake coil 115 further increases and the motor 3 remains locked. a Then, the electromagnetic force generated in the brake coil 115 is F b Since there is a hysteresis, the AC current flowing through the brake coil 115 becomes I a It further increases to a maximum value and then decreases to I a Less than I b Until then, the electromagnetic force generated in the core 116 is F b The AC current flowing through the brake coil 115 is further reduced to I b When the electromagnetic force generated in the core 116 is F b However, the electromagnetic force generated in the core 116 does not disappear immediately due to the residual magnetic flux, but is maintained for a certain period of time. In this specification, the maximum time during which the core 116 can maintain the electromagnetic force based on the residual magnetic flux exceeding the elastic force of the spring 114 is defined as the "electromagnetic force maintenance time t b The AC current flowing through the brake coil 115 is further reduced to -I a Then, the electromagnetic force generated in the core 116 is -F b Therefore, the AC current flowing through the brake coil 115 reaches I b From-I a Time until it decreases to t sEven during this period, if the electromagnetic force based on the residual magnetic flux generated in the core 116 exceeds the elastic force of the spring 114, the motor 3 can be kept unlocked.

[0031] The AC current flowing through the brake coil 115 is -I a It further falls below this value to a minimum value and then increases to -I a Greater than -I b Until then, the electromagnetic force generated in the core 116 is F b The AC current flowing through the brake coil 115 further increases to -I b Then, the electromagnetic force generated in the core 116 is -F b However, the electromagnetic force generated in the core 116 does not disappear immediately due to the residual magnetic flux, and the electromagnetic force is maintained for at least the electromagnetic force retention time t b The AC current flowing through the brake coil 115 is further increased and maintained at I a When the electromagnetic force generated in the core 116 is F b Therefore, the AC current flowing through the brake coil 115 becomes -I b From I a Time it takes to increase to t s Even during this period, if the electromagnetic force based on the residual magnetic flux generated in the core 116 exceeds the elastic force of the spring 114, the motor 3 can be kept unlocked.

[0032] Fig. 4 is a diagram illustrating an example of the waveform of the AC current flowing through the brake coil. As shown in Fig. 4, the AC current supplied from the inverter 11 to the brake coil 115 via the motor power line 13 periodically changes in magnitude and sign over time. As described with reference to Fig. 3, when the AC current flowing through the brake coil 115 is I a It increases to a maximum value beyond I b Until and -I a It then decreases to a minimum value below -I bUntil this occurs, the absolute value of the electromagnetic force generated in the core 116 is greater than the absolute value of the elastic force of the spring 114 (in other words, the force required to unlock the motor 3), so the unlocking of the motor 3 is reliably maintained. b From-I a Time until it decreases to t s Between and -I b From I a Time it takes to increase to t s If the absolute value of the electromagnetic force held by the core 116 due to the residual magnetic flux is set to be greater than the absolute value of the elastic force of the spring 114 even during this period, the motor 3 can be kept unlocked throughout all periods of the AC current flowing through the brake coil 115. In other words, when the AC current flowing through the brake coil 115 is I b From-I a Time until it decreases to t s The length of -I b From I a Time it takes to increase to t s Each of the lengths corresponds to an electromagnetic force holding time t b If the voltage Vcc does not exceed 1, the motor 3 can be kept unlocked over all periods of the AC current flowing through the brake coil 115.

[0033] The type of AC current that can be applied to the brake coil 115 to keep the motor 3 unlocked throughout all cycles can be determined by plotting the hysteresis curve shown in FIG. 3 and the force F required to unlock the motor 3. b For example, the hysteresis curve may be measured by operating the brake device 12 in the motor drive device 1 through an experiment, or a hysteresis curve specified in a specification table for the core 116 may be used, or a hysteresis curve provided as data by the manufacturer of the core 116 may be used. bSince is the elastic force of the spring 114, it can be obtained in advance from the spring constant k of the spring 114 and the contraction length x of the spring 114 when the motor 3 is unlocked. b Once this is determined, I a and I b is also determined.

[0034] As described above, when the motor 3 is driven in an unlocked state, an AC current having a magnitude corresponding to the input impedance of the motor 3 and the brake device 12 flows through the motor power line 13 to each of the motor 3 and the brake device 12 due to the AC voltage output from the inverter 11. For example, a hysteresis curve is obtained by operating the motor drive device 1 through an experiment and measuring the AC current flowing through the brake coil 115 of the brake device 12, and this hysteresis curve and the force F required to unlock the motor 3 are compared. b From I a and I b "The AC current flowing through the brake coil 115 is such that the electromagnetic force generated in the core 116 exceeds the elastic force of the spring 114. a (the first requirement) and "the said AC current has an amplitude exceeding I b From-I a Time until it decreases to t s The length of the electromagnetic force is the retention time t b (2nd requirement)," "-I b From I a Time it takes to increase to t s The length of the electromagnetic force is the retention time t b (third requirement)” is satisfied, the motor 3 can be kept unlocked throughout all periods of the AC current, and therefore the AC current can be used as a current for unlocking the motor 3 by the brake device 12.

[0035] On the other hand, if the AC current flowing through the brake coil 115 measured in an experiment does not satisfy any of the first, second, and third requirements, it is sufficient to adjust the AC current flowing through the brake coil 115 so as to satisfy all the requirements, or to select the spring 114 and the core 116 in the brake device 12 so as to satisfy all the requirements. Some specific examples are as follows.

[0036] For example, if the frequency of the AC current flowing through the brake coil 115 is increased, the AC current I b From-I a Time until it decreases to t s Length of -I b From I a Time it takes to increase to t s Since the length of the second and third requirements is shortened, it becomes easier to satisfy the second and third requirements.

[0037] For example, if a spring with a small spring constant k or a spring with a short contraction length x of the spring 114 when the motor 3 is unlocked is selected as the spring 114 in the brake device 12, F b Since becomes smaller, I a and I b becomes smaller, making it easier to satisfy the first requirement. a and I b As a result, the AC current flowing through the brake coil 115 becomes I b From-I a Time until it decreases to t s Length of -I b From I a Time it takes to increase to t s Since the length of the second and third requirements is shortened, the second and third requirements are also easily satisfied.

[0038] For example, as the core 116 in the brake device 12, the electromagnetic force holding time t b If a core made of a magnetic material with a long electromagnetic force retention time t is selected, the second and third requirements can be easily met. bExamples of magnetic materials with long lengths include ferromagnetic materials such as iron, cobalt, and nickel, and permanent magnets such as neodymium and ferrite.

[0039] For example, by selecting a core 116 in the brake device 12 made of a magnetic material having a large hysteresis width in the relationship between the AC current I flowing through the brake coil 115 and the electromagnetic force F generated in the core 116, I b If the value is reduced, the AC current flowing through the brake coil 115 will be I b From-I a Time until it decreases to t s Length of -I b From I a Time it takes to increase to t s Since the length of the magnetoresistance is shortened, it becomes easier to satisfy the second and third requirements. Examples of magnetic materials with a large hysteresis width include ferromagnetic materials such as iron, cobalt, and nickel, and permanent magnets such as neodymium and ferrite.

[0040] Furthermore, when the motor 3 is driven in an unlocked state, an AC current having a magnitude according to the input impedance of each of the motor 3 and the brake device 12 flows through the motor power line 13 to each of the motor 3 and the brake device 12 due to the AC voltage output from the inverter 11. Therefore, the input impedance of each of the motor 3 and the brake device 12 can be adjusted so as to satisfy the first, second and third requirements.

[0041] Next, an example will be described in which the voltage supplied as the brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 is a DC voltage.

[0042] 5 is a diagram illustrating an example of on / off driving of a switching element of an inverter for applying a DC brake coil voltage to a brake coil in a motor drive device (first mode) according to an embodiment of the present disclosure. In FIG. 5, the AC power supply 2 and the converter 14 are omitted.

[0043] By appropriately controlling the on / off driving of the switching elements provided on the upper and lower arms of the inverter 11, a "motor unlocking DC voltage" which is a DC voltage for passing a DC current through the brake coil 115, which generates an electromagnetic force in the core 116 that exceeds the elastic force of the spring 114, can be output from the inverter 11 to the motor power line 13.

[0044] The motor unlocking DC voltage output from the inverter 11 to the motor power line 13 is applied to both the motor coil of the motor 3 connected to the motor power line 13 and the brake coil 115 of the brake device 12. However, since the motor 3 is an AC motor, the motor unlocking DC voltage does not rotate the motor 3. On the other hand, in the brake device 12, when the motor unlocking DC voltage that generates an electromagnetic force in the core 116 exceeding the elastic force of the spring 114 is applied to the brake coil 115, an electromagnetic force that overcomes the elastic force of the spring 114 that has been pressing the armature 112 against the friction plate 111 is generated in the core 116, and this attracts the armature 112 to the core 116, and the friction plate 111 is released from contact with the armature 112 and the end plate 113. As a result, the friction plate 111 and therefore the shaft 121 become freely rotatable, and the motor 3 is unlocked, i.e., the brake of the motor 3 is released. Once the armature 112 and the core 116 come into contact with each other, there is no gap between the armature 112 and the core 116, and the armature 112 and the core 116 form an integrated magnetic body. Therefore, even if an AC voltage for driving the motor 3 is applied to the brake coil 115 instead of the DC voltage for unlocking the motor, the contact between the armature 112 and the core 116 can be maintained (i.e., the unlocking of the motor 3 can be maintained). In order to be able to continue to maintain the unlocking of the motor 3 while the AC voltage for driving the motor 3 is being applied to the brake coil 115, it is preferable to satisfy all of the first, second and third requirements described with reference to Figs. 3 and 4. After a predetermined time has elapsed since the DC voltage for unlocking the motor output from the inverter 11 is applied to the brake coil 115 to bring the armature 112 and the core 116 into initial contact with each other, the voltage output from the inverter 11 to the motor power line 13 is switched from the DC voltage for unlocking the motor to the AC voltage for driving the motor 3 under the control of the control unit 16.

[0045] The control unit 16 starts measuring the "predetermined time" from the timing when the inverter 11 starts to output the motor unlocking DC voltage. When the motor unlocking DC voltage is applied to the brake coil 115, the armature 112 and the core 116 immediately come into contact with each other. The "predetermined time" may be set to a length sufficient to ensure the initial contact between the armature 112 and the core 116 caused by the application of the motor unlocking DC voltage to the brake coil 115, and may be set to, for example, several milliseconds to several seconds. The "predetermined time" is defined in a software program that constitutes the control unit 16. Alternatively, the value of the "predetermined time" may be stored in, for example, a storage unit (not shown) in the control unit 16, and the control unit 16 may read the stored "predetermined time" to measure the time. The storage unit is composed of an electrically erasable and recordable non-volatile memory such as an EEPROM (registered trademark), or a high-speed readable and writable random access memory such as a DRAM or SRAM. If the storage unit is realized by a rewritable memory, even after the "predetermined time" has been set, it can be changed to an appropriate value as necessary.

[0046] The motor unlocking DC voltage can be output from the inverter 11 by controlling the control unit 16 to turn on the upper arm switching element and the lower arm switching element in the inverter 11 connected to the brake device 12 via the motor power line 13 and to turn off all other switching elements. In the example shown in FIG. 5, the brake coil 115 of the brake device 12 is connected to the v-phase and the w-phase, so that the control unit 16 controls, for example, the upper arm switching element S v1 and the lower arm switching element S of the w-phase w2 At the same time, the switching element S u1 , S u2 , S v2 , and S w1 By turning off the switching element S of the lower arm of the v-phase, a DC voltage for unlocking the motor can be output from the inverter 11. Alternatively, although not shown in the figure, the control unit 16 controls the switching element S of the lower arm of the v-phase to v2and the upper arm switching element S of the w-phase w1 At the same time, the switching element S u1 , S u2 , S v1 , and S w2 By turning off the inverter 11, a similar motor unlocking DC voltage can be output.

[0047] 5 shows an example in which the brake coil 115 of the brake device 12 is connected to the v-phase and the w-phase. Although not shown here, when the brake coil 115 of the brake device 12 is connected to the u-phase and the v-phase, the switching element S of the upper arm of the u-phase is turned on by the control of the control unit 16. u1 and the v-phase lower arm switching element S v2 At the same time, the switching element S u2 , S v1 , S w1 , and S w2 or the lower arm switching element S of the u-phase u2 and the v-phase upper arm switching element S v1 At the same time, the switching element S u1 , S v2 , S w1 , and S w2 By turning off the inverter 11, a DC voltage for unlocking the motor is output.

[0048] In addition, when the brake coil 115 of the brake device 12 is connected to the u-phase and w-phase, the control unit 16 controls the switching element S u1 and the lower arm switching element S of the w-phase w2 At the same time, the switching element S u2 , S v1 , S v2 , and S w1 or the lower arm switching element S of the u-phase u2 and the upper arm switching element S of the w-phase w1 At the same time, the switching element S u1 , S v1 , Sv2 , and S w2 By turning off the inverter 11, a DC voltage for unlocking the motor is output.

[0049] Furthermore, when the motor 3 is a single-phase AC motor, the input terminals of the brake device 12 are connected to each of the two phases of the motor power line 13. Therefore, under the control of the control unit 16, the upper arm of one phase is switched on and the other phase is switched off, causing the inverter 11 to output a motor lock release DC voltage.

[0050] 6 is a flowchart showing an operation flow when a DC brake coil voltage is applied to the brake coil in the motor drive device (first and second modes) according to an embodiment of the present disclosure. The flowchart shown in FIG. 6 is also applicable to the second mode described later.

[0051] In step S101, the brake coil voltage from the inverter 11 is not applied to the brake coil 115. Therefore, the armature 112 is pressed strongly against the friction plate 111 by the elastic force of the spring 114, and the friction plate 111 is sandwiched between the armature 112 and the end plate 113 and cannot rotate, and the motor 3 having the shaft 121 connected to the friction plate 111 is in a locked state.

[0052] In step S102, the control unit 16 judges whether or not an unlock command for unlocking the motor 3 has been received from a host control device (not shown). The host control device may be provided in a robot controller that controls the robot, or may be provided in a numerical control device of the machine tool. If it is judged in step S102 that an unlock command has been received, the process proceeds to step S103.

[0053] In step S103, under the control of the control unit 16, the inverter 11 outputs, as a brake coil voltage, a motor unlocking DC voltage to the motor power line 13, for causing a DC current to flow through the brake coil 115, which generates in the core 116 an electromagnetic force exceeding the elastic force of the spring 114 in the brake device 12.

[0054] In step S104, a motor unlocking DC voltage, which is a brake coil voltage, is applied to the brake coil 115 of the brake device 12, causing an electromagnetic force to be generated in the core 116 that overcomes the elastic force of the spring 114 that has been pressing the armature 112 against the friction plate 111, and this attracts the armature 112 to the core 116, releasing the friction plate 111 from contact with the armature 112 and the end plate 113. As a result, the friction plate 111 and therefore the shaft 121 become able to rotate freely, and the motor 3 is unlocked, i.e., the brake of the motor 3 is released.

[0055] In step S105, the control unit 16 determines whether or not a predetermined time has elapsed since the timing in step S103 when the motor lock release DC voltage started to be output from the inverter 11. If it is determined in step S105 that the predetermined time has elapsed, the process proceeds to step S106.

[0056] In step S106, the inverter 11 outputs an AC voltage for driving the motor 3 to the motor power line 13 under the control of the control unit 16. As a result, the motor 3 is driven to rotate.

[0057] The configuration and operation of the motor drive device 1 in the first embodiment in which the brake device 12 is connected in parallel to the motor 3 via the motor power line 13 have been described above. Next, a description will be given of the motor drive device 1 in the second embodiment in which the brake device 12 is connected in series to the motor 3 via the motor power line 13.

[0058] FIG. 7 is a diagram showing a motor driving device (second mode) according to an embodiment of the present disclosure.

[0059] In the second mode, the brake device 12 and the motor 3 are connected in series via the motor power line 13 so that the brake coil 115 and its resistance component in the brake device 12 and the motor coil and its resistance component of the motor 3 are connected in series. When the motor 3 is a three-phase AC motor as shown in FIG. 7, one end of the motor coil opposite to the end to which the motor power line 13 is connected is connected to a neutral point. As shown in FIG. 7, the input terminal of the brake device 12 and the motor coil of the motor 3 are connected so that the brake coil 115 and its resistance component of the brake device 12 are inserted between the neutral point of the motor 3 and one end of the motor coil of one phase opposite to the end to which the motor power line 13 is connected. Although not shown here, when the motor 3 is a single-phase AC motor, the input terminal of the brake device 12 is connected to each of the ends of the motor coil opposite to the end to which the motor power line 13 is connected for the motor coil of two phases. The configuration inside the brake device 12 is as described with reference to FIG. 1. Moreover, since the circuit components other than the brake device 12 are similar to the circuit components shown in FIG. 1, the same circuit components are given the same reference numerals and detailed description of these circuit components is omitted.

[0060] Even in the motor drive device 1 of the second form in which the brake device 12 is connected in series to the motor 3 via the motor power line 13, the voltage supplied as a brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 may be either an AC voltage or a DC voltage.

[0061] In the second embodiment, when the voltage supplied as the brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 is an AC voltage, the operation of the inverter 11 is the same as that of the first embodiment described with reference to Figures 3 and 4, and therefore will not be described.

[0062] 8 is a diagram illustrating an example of on / off driving of a switching element of an inverter for applying a DC brake coil voltage to a brake coil in a motor drive device (second mode) according to an embodiment of the present disclosure. In FIG. 8, the AC power supply 2 and the converter 14 are omitted from the illustration.

[0063] In the second embodiment, even when the voltage supplied as the brake coil voltage from the inverter 11 to the brake device 12 via the motor power line 13 is a motor lock release DC voltage, as in the first embodiment, by appropriately controlling the on / off driving of the switching elements provided on the upper arm and the lower arm of the inverter 11, it is possible to output the motor lock release DC voltage from the inverter 11 to the motor power line 13, for causing a DC current to flow through the brake coil 115, which generates an electromagnetic force in the core 116 that exceeds the elastic force of the spring 114.

[0064] The motor unlocking DC voltage can be output from the inverter 11 by controlling the control unit 16 to turn on the upper arm switching element and the lower arm switching element in the inverter 11 connected to the brake device 12 via the motor power line 13 and to turn off all other switching elements. In the example shown in FIG. 8, the brake coil 115 of the brake device 12 is connected to the v-phase and w-phase via the motor coil, so that the control unit 16 controls, for example, the upper arm switching element S v1 and the lower arm switching element S of the w-phase w2 At the same time, the switching element S u1 , S u2 , S v2 , and S w1 By turning off the switching element S of the lower arm of the v-phase, a DC voltage for unlocking the motor can be output from the inverter 11. Alternatively, although not shown in the figure, the control unit 16 controls the switching element S of the lower arm of the v-phase to v2 and the upper arm switching element S of the w-phase w1 At the same time, the switching element S u1 , S u2 , S v1, and S w2 By turning off the inverter 11, a similar motor unlocking DC voltage can be output.

[0065] In FIG. 8, an example is shown in which the brake coil 115 of the brake device 12 is connected to the v-phase and w-phase via a motor coil. Although not shown here, when the brake coil 115 of the brake device 12 is connected to the u-phase and v-phase via a motor coil, the switching element S of the upper arm of the u-phase is switched by the control of the control unit 16. u1 and the v-phase lower arm switching element S v2 At the same time, the switching element S u2 , S v1 , S w1 , and S w2 or the lower arm switching element S of the u-phase u2 and the v-phase upper arm switching element S v1 At the same time, the switching element S u1 , S v2 , S w1 , and S w2 By turning off the inverter 11, a DC voltage for unlocking the motor is output.

[0066] In addition, when the brake coil 115 of the brake device 12 is connected to the u-phase and w-phase via a motor coil, the control unit 16 controls the switching element S of the upper arm of the u-phase. u1 and the lower arm switching element S of the w-phase w2 At the same time, the switching element S u2 , S v1 , S v2 , and S w1 or the lower arm switching element S of the u-phase u2 and the upper arm switching element S of the w-phase w1 At the same time, the switching element S u1 , S v1 , S v2 , and S w2By turning off the inverter 11, a DC voltage for unlocking the motor is output.

[0067] Furthermore, when the motor 3 is a single-phase AC motor, the input terminals of the brake device 12 are connected to the ends of the motor coils for two phases, one end opposite to the end to which the motor power line 13 is connected. Therefore, under the control of the control unit 16, the upper arm of one phase is switched on and the other phase is switched off, thereby causing the inverter 11 to output a motor lock release DC voltage.

[0068] In the motor drive device 1 according to the second form in which the braking device 12 is connected in series to the motor 3 via the motor power line 13, the operation flow when the voltage supplied as the brake coil voltage from the inverter 11 via the motor power line 13 to the braking device 12 is a motor lock release DC voltage is as shown in FIG. 6.

[0069] As described above, according to the motor drive device 1 of an embodiment of the present disclosure, the brake device 12 is connected to the motor power line 13 connecting the inverter 11 and the motor 3, and the on / off drive of the switching element of the inverter 11 is appropriately controlled, thereby allowing the motor 3 to be locked and unlocked by the brake device 12. In the motor drive device 1 of an embodiment of the present disclosure, it is not necessary to provide a brake power supply as in the conventional case, so the number of wirings related to the brake device is small, and the structure is simple and low cost. Furthermore, in the motor drive device 1 of an embodiment of the present disclosure, it is not necessary to provide an independent brake control unit as in the conventional case, and the motor 3 can be locked and unlocked by the brake device 12 through the operation of the control unit 16 that controls the inverter 11, so the number of wirings is small, and the structure is simple and low cost. [Explanation of symbols]

[0070] 1 Motor drive unit 2 AC power supply 3 Motor 11 Inverter 12 Brake system 13 Motor power line 14 Converter 15 Capacitor 16 Control section 111 Friction plate 112 Amateur 113 End plate 114 Spring 115 Brake coil 116 cores 117 Spacer 118 Volts 121 Shaft 122 Hub

Claims

1. an inverter that converts an input DC voltage into an AC voltage and outputs the AC voltage to a motor power line to which a motor is connected; a brake device connected to the motor power line, locking the motor when a predetermined voltage is not supplied from the inverter, and unlocking the motor when the predetermined voltage is supplied from the inverter via the motor power line; Equipped with the brake device locks the motor by pressing an armature against a friction plate connected to the motor shaft with the elastic force of a spring, and unlocks the motor by pulling the armature away from the friction plate with at least one of an electromagnetic force based on application of an AC voltage, which is an electromagnetic force generated when an AC voltage output from the inverter is applied to a brake coil via the motor power line, and an electromagnetic force based on residual magnetic flux, which is an electromagnetic force held in a core in which the brake coil is provided by residual magnetic flux; the inverter outputs, to the motor power line, an AC voltage for causing an AC current to flow through the brake coil, the AC current generating the electromagnetic force exceeding the elastic force of the spring; a maximum amplitude of the AC current flowing through the brake coil exceeds a current value when an electromagnetic force generated in a core to which the spring and the brake coil are provided exceeds an elastic force of the spring, a maximum absolute value of the electromagnetic force based on the application of the AC voltage exceeds an absolute value of the elastic force of the spring, a length of time during which the absolute value of the electromagnetic force based on application of the AC voltage does not exceed the absolute value of the elastic force of the spring due to a change in the phase of the AC voltage does not exceed an electromagnetic force retention time during which the absolute value of the electromagnetic force based on application of the AC voltage and the absolute value of the electromagnetic force based on the residual magnetic flux exceed the absolute value of the elastic force of the spring, thereby maintaining the unlocking of the motor.

2. an inverter that converts an input DC voltage into an AC voltage and outputs the AC voltage to a motor power line to which a motor is connected; a brake device connected to the motor power line, locking the motor when a predetermined voltage is not supplied from the inverter, and unlocking the motor when the predetermined voltage is supplied from the inverter via the motor power line; Equipped with The inverter includes a bridge circuit in which switching elements with diodes connected in inverse parallel are provided on an upper arm on a high potential side and a lower arm on a low potential side, The brake device locks the motor by using the elastic force of a spring to press an armature against a friction plate connected to the motor shaft, and unlocks the motor by pulling the armature away from the friction plate with electromagnetic force generated by applying a motor unlocking DC voltage to the brake coil caused by turning on the switching element of the upper arm and the switching element of the lower arm of a phase connected to a brake coil of the brake device via the motor power line.

3. 3. The motor drive device according to claim 2, wherein the inverter outputs the motor unlocking DC voltage to the motor power line so as to cause a DC current to flow through the brake coil, the DC current generating the electromagnetic force exceeding the elastic force of the spring, and after a predetermined time has elapsed, outputs an AC voltage to the motor power line for driving the motor.

4. 4. The motor drive device according to claim 1, wherein the brake coil and the motor are connected in parallel via the motor power line.

5. 4. The motor drive device according to claim 1, wherein the brake coil and the motor are connected in series via the motor power line.

Images