阅读说明：本技术 Dc有刷马达的驱动装置以及驱动方法 (Drive device and drive method for DC brush motor ) 是由 木村秀树 于 2020-09-02 设计创作，主要内容包括：本发明的实施方式整体式涉及DC有刷马达的驱动装置以及驱动方法。根据实施方式,DC有刷马达的驱动装置具备：驱动电路,向DC有刷马达的线圈供给马达电流；以及控制电路,在启动上述DC有刷马达之后,在经过了规定的期间之后,使对上述马达电流的上限进行设定的限制值阶段性地降低,并对成为了上述马达电流由上述限制值限制的状态的情况进行检测。(Embodiments of the present invention relate generally to a drive device and a drive method for a DC brushed motor. According to an embodiment, a drive device for a DC brushed motor includes: a drive circuit that supplies a motor current to a coil of the DC brushed motor; and a control circuit that, after a predetermined period of time has elapsed after the DC brushed motor is started, gradually reduces a limit value that sets an upper limit of the motor current, and detects that the motor current is limited by the limit value.)

1. A drive device for a DC brush motor includes:

a drive circuit that supplies a motor current to a coil of the DC brushed motor; and

and a control circuit that, after a predetermined period of time has elapsed after the DC brushed motor is started, gradually reduces a limit value that sets an upper limit of the motor current, and detects that the motor current is limited by the limit value.

2. The drive device of a DC brushed motor according to claim 1,

the predetermined period is a period until a motor current at the time of starting the DC brushed motor is reduced to a preset threshold value.

3. The drive device of a DC brushed motor according to claim 1,

the limit value at the time of starting the DC brushed motor is set to a value larger than an upper limit value of an impact current.

4. The drive device of a DC brushed motor according to claim 1,

the drive circuit includes a PWM control circuit that supplies a PWM signal for controlling on/off of a switching element of the drive circuit.

5. The drive device of a DC brushed motor according to claim 4,

the control circuit detects the motor current based on a value of a voltage drop generated in a switching element of the drive circuit.

6. The drive device of a DC brushed motor according to claim 1,

the control circuit detects the motor current based on a value of a voltage drop generated in a resistor connected to the drive circuit.

7. The drive device of a DC brushed motor according to claim 1,

the timing controller controls the timing at which the limit value is lowered in a stepwise manner.

8. The drive device of a DC brushed motor according to claim 4,

the control circuit adjusts the duty ratio of the PWM signal according to the control value.

9. The drive device of a DC brushed motor according to claim 1,

after the motor current is controlled by the limit value, the control circuit performs control to increase the limit value.

10. The drive device of a DC brushed motor according to claim 1,

the control circuit outputs a detection signal indicating that the motor current is limited by the limit value,

the drive device for the DC brush motor includes a display device that responds to the detection signal.

11. The drive device of a DC brushed motor according to claim 1,

the control circuit stores, as basic data, timings at which the limit values are lowered in stages and values of the limit values at the timings.

12. The drive device of a DC brushed motor according to claim 1,

the basic data includes a limit timing at which the motor current is limited and initial data of a limit value at that time.

13. The drive device of a DC brushed motor as defined in claim 12,

the control circuit is provided with a control circuit,

outputting a detection signal indicating a state in which the motor current is limited by the limit value,

the state of the DC brushed motor is determined based on a front-rear relationship between a timing of outputting the detection signal and the limit timing of the initial data.

14. A method of driving a DC brush motor includes:

starting a DC brush motor;

a step of gradually decreasing a limit value set for an upper limit of a motor current supplied to a coil of the DC brushed motor after a predetermined period has elapsed from the start of the DC brushed motor; and

and detecting that the motor current is limited by the limit value.

15. The driving method of a DC brushed motor according to claim 14,

the method includes a step of storing, as basic data, timings at which the limit values are to be lowered in stages and values of the limit values at the timings.

16. The driving method of a DC brushed motor according to claim 15,

the method includes a step of storing initial data of a limit timing and a limit value at the time when the motor current is limited as the basic data.

17. The driving method of the DC brushed motor according to claim 16, comprising:

outputting a detection signal indicating that the motor current is limited by the limit value; and

and comparing a timing of outputting the detection signal with the limit timing of the initial data to determine a state of the DC brushed motor.

18. The driving method of the DC brushed motor according to claim 16, comprising:

outputting a detection signal indicating that the motor current is limited by the limit value; and

and comparing a limit value of the output detection signal with a limit value of the limit timing of the initial data to determine a state of the DC brushed motor.

19. The driving method of the DC brushed motor according to claim 14, having:

outputting a detection signal indicating that the motor current is limited by the limit value; and

and displaying a state in which the motor current is limited by the limit value in response to the detection signal.

20. A method of driving a DC brush motor includes:

limiting a motor current to a predetermined limit value when the DC brushed motor is started;

detecting a time during which the motor current decreases from a current value limited by the limit value to a predetermined reference value; and

and comparing the time until the reference value is reduced with a predetermined reference time.

Technical Field

Embodiments generally relate to a driving apparatus and a driving method of a DC brushed motor.

Background

Conventionally, the following techniques have been disclosed: the output current supplied to the motor is detected, and an abnormality due to deterioration of the motor and the load machine is detected. The abnormality of the motor is often deterioration due to aging over a long period of time. It is sometimes difficult for a user to determine degradation of the motor. On the other hand, by appropriately showing the deterioration of the motor to the user, the convenience can be improved. The DC brush motor has a characteristic feature of generating a rush current at the time of starting. A driving device and a driving method for a DC brushed motor are desired, which can easily detect an abnormal state associated with deterioration from characteristics of the DC brushed motor.

Disclosure of Invention

Embodiments provide a driving device and a driving method for a DC brush motor, which can easily detect the deterioration of the DC brush motor.

A drive device for a DC brush motor according to an embodiment includes: a drive circuit that supplies a motor current to a coil of the DC brushed motor; and a control circuit that, after a predetermined period of time has elapsed after the DC brushed motor is started, gradually reduces a limit value that sets an upper limit of the motor current, and detects that the motor current is limited by the limit value.

Drawings

Fig. 1 is a diagram showing a driving device of a DC brushed motor according to embodiment 1.

Fig. 2A and 2B are diagrams for explaining a driving method of the driving device of the DC brush motor.

Fig. 3 is a flowchart for explaining a driving method of the DC brushed motor.

Fig. 4 is another flowchart for explaining a driving method of the DC brushed motor.

Fig. 5 is a diagram showing an embodiment of detecting a motor current of a DC brushed motor.

Fig. 6 is a diagram for explaining another driving method for detecting a deterioration state of the driving device of the DC brushed motor.

Detailed Description

Hereinafter, a driving device and a driving method of a DC brushed motor according to an embodiment will be described in detail with reference to the drawings. The present invention is not limited to these embodiments.

(embodiment 1)

Fig. 1 is a diagram showing a configuration of a drive device for a DC brush motor according to embodiment 1. The driving device of fig. 1 includes a driving circuit 10, voltage detection circuits 20 and 30, reverse voltage detection circuits 21 and 31, a PWM control circuit 40, a control logic circuit 50, timing controllers 60 and 70, and current direction selection circuits 61 and 71.

The drive circuit 10 supplies a motor current I to a coil 101 provided in the rotor 100 via brushes 102 and 103_M. Motor current I of fig. 1_MThis shows a case where the brush 102 side is supplied to the brush 103 side. The driver circuit 10 includes PMOS transistors 11 and 13 and NMOS transistors 12 and 14 constituting an H-bridge circuit. The transistors 11 to 14 have parasitic diodes 11D to 14D, respectively. The connection point between the drain of the transistor 11 and the drain of the transistor 12 is connected to the brush 102. The connection point between the drain of the transistor 13 and the drain of the transistor 14 is connected to the brush 103. The motor voltage VM is supplied to the drive circuit 10 by the power supply 110.

The control logic circuit 50 controls the PWM control circuit 40 in response to signals supplied from the current direction selection circuits 61 and 71 and the timing controllers 60 and 70. The control logic circuit 50 generates a reference voltage Vref supplied from the voltage circuit 111 to the motor current I_MThe upper limit value of (3) is set as a limit value. The control logic circuit 50 performs, for example, a/D conversion on the value of the reference voltage Vref, and generates a voltage corresponding to the limit value by performing an operation based on a predetermined coefficient. The limit value and the value of the voltage generated in accordance with the limit value are stored in a memory (not shown) incorporated therein. The control logic circuit 50 compares the detection voltages of the voltage detection circuits 20 and 30 and the reverse voltage detection circuits 21 and 31 supplied via the current direction selection circuits 61 and 71 with the voltages corresponding to the limit values. The control logic circuit 50 supplies a signal for controlling the duty ratio of the PWM signal to the PWM control circuit 40 based on the comparison result. The control logic circuit 50 may be constituted by a microcomputer (microcomputer), for example.

When a control signal is supplied from the control logic circuit 50, the PWM control circuit 40 outputs a PWM signal whose duty ratio is adjusted in accordance with the control signal. The PWM control circuit 40 supplies PWM signals to the gates of the transistors 11-14, and turns on/off the transistors 11-14And (5) controlling. Thus, the PWM control circuit 40 performs the motor current I_MThe rotational direction and rotational speed of the rotor 100 are controlled.

The voltage detection circuits 20 and 30 detect source-drain voltages of the transistors 12 and 14 with reference to the source voltages. The source-drain voltage of the transistors 12, 14 is dependent on the motor current I_MBut the voltage drop due to the on-resistance of transistors 12, 14. Therefore, voltage detection circuit 20 detects motor current I flowing from brush 103 side to brush 102 side_MAnd the resulting voltage drop of transistor 12 is detected. Further, voltage detection circuit 30 detects a motor current I flowing from brush 102 side to brush 103 side_MAnd the resulting voltage drop of transistor 14 is detected. Dependent on the motor current I due to the voltage drop in the transistors 12, 14_MAnd therefore the motor current I can be detected based on the value of the voltage drop in the transistors 12, 14_M。

The reverse voltage detection circuits 21 and 31 detect source-drain voltages of the transistors 12 and 14 with the drain side as a reference. That is, the reverse voltage detection circuits 21 and 31 detect a reverse voltage generated between the source and the drain by a drain current flowing in a reverse direction from the source to the drain. For example, in the case of motor current I_MIn the control for limiting the upper limit value of (3), there is a motor current I_MBelow zero and the rotation of the rotor 100 is accelerated in the opposite direction. When the reverse voltage detection circuits 21 and 31 detect the reverse voltage, the control logic circuit 50 controls the PWM control circuit 40 to prevent the rotation of the rotor 100 from being accelerated in the reverse direction. Hereinafter, the rotation speed of the rotor 100 may be referred to as the rotation speed of the motor.

The current direction selection circuits 61 and 71 supply the detection voltages of the voltage detection circuits 20 and 30 and the reverse voltage detection circuits 21 and 31 to the control logic circuit 50 under the control of the timing controllers 60 and 70. The timing controllers 60 and 70 select the voltage detection circuits 20 and 30 when detecting a voltage with the source sides of the transistors 12 and 14 as a reference, and select the reverse voltage detection circuits 21 and 31 when detecting a voltage with the drain sides of the transistors 12 and 14 as a reference.

The timing controller 60 supplies the control logic circuit 50 with the timings of the voltages detected by the voltage detection circuit 20 and the reverse voltage detection circuit 21 to the current direction selection circuit 61, and controls the control logic circuit 50 to make the motor current I_MThe timing of the change in the limit value of (b) is controlled. Similarly, the timing controller 70 supplies the control logic circuit 50 with the timings of the voltages detected by the voltage detection circuit 30 and the reverse voltage detection circuit 31, and the timing of the motor current I caused by the control logic circuit 50, to the current direction selection circuit 71_MThe timing of the change in the limit value of (b) is controlled. For example, the display device 120 displays the deterioration state of the motor detected by the control logic circuit 50. In addition, the control logic circuit 50 may set the motor current I_MTiming of the change in the limit value of.

The driving method according to the present embodiment will be described with reference to fig. 2A and 2B. Fig. 2A is a diagram for explaining a driving method in an initial stage in which deterioration of the DC brushed motor is not generated. For example, the basic data is acquired at the time of shipment without deterioration. Hereinafter, the DC brushed motor may be simply referred to as a motor. The horizontal axis represents time. The solid line 130 represents the limit value of the motor current, the solid line 140 represents the motor speed, and the solid line 150 represents the motor current I_M. At the time of motor startup, since no counter electromotive force is generated in the coil 101, the power supply voltage VM is directly applied to the coil 101 and a rush current flows. Then, the motor current I is generated due to the counter electromotive force generated in the coil 101 in accordance with the rotation speed of the motor_MThe value of (c) decreases and stabilizes. The limit value at the time of starting the motor is set to a reference value higher than the upper limit value of the assumed rush current, for example.

At motor current I_MAt a stable timing t1, the limit value is lowered from the reference value to V3. That is, the motor current I is limited by the limit value V3_MThe upper limit value of (2). The period of the rush current can be, for example, a motor current I_MFrom the start-up time, the threshold value is lower than a predetermined threshold value Ith indicated by a broken line 155. The voltage corresponding to the threshold value Ith is stored in the control logic circuit 50 in advance, and the voltage is detectedThe pressures were compared. Thus, the motor current I can be detected_MThe timing t1 of lowering to the threshold Ith. In addition, at the motor current I_MIn the stabilized state, the rotation speed of the motor is also stabilized. Therefore, the motor current I or the timing at which the rotational speed of the motor is stabilized can be used_MThe timing at which both the motor rotation speed and the motor rotation speed are stabilized is set as timing t 1. The structure can be as follows: the rotational speed of the motor is detected using a tachometer (not shown) and the detection result is supplied to the control logic circuit 50.

The control logic circuit 50 compares the detected voltage with a voltage value corresponding to the limit value V3 to detect the motor current I_MWhether limit value V3 is reached. As a result of the comparison, the current I due to the motor_MThe limit value V3 is not reached, so the control logic circuit 50 falls to the limit value V2 at the timing t 2. Due to motor current I_MThe limit value V2 is not reached, so the control logic circuit 50 falls to the limit value V1 at the timing t 3. As a result of the comparison, the current I due to the motor_MSince the limit value V1 is reached, the limit detection signal shown in the lower stage becomes H level. The control logic circuit 50 controls the PWM control circuit 40 so as to become the motor current I_MConstant current operation limited by limit value V1.

The control logic circuit 50 supplies a control signal for adjusting the duty ratio of the PWM signal in accordance with the limit value V1 to the PWM control circuit 40. The PWM control circuit 40 supplies the PWM signal whose duty ratio is adjusted according to the limit value V1 to the drive circuit 10. The on/off of the transistors 11 to 13 of the drive circuit 10 is controlled by the PWM signal whose duty ratio is adjusted in accordance with the limit value V1. Thereby, a constant current operation controlled by limit value V1 is performed. By comparing the detection voltage with the voltage corresponding to limit value V1, control logic circuit 50 can detect that the constant current operation is being performed by limit value V1. The rotational speed of the motor and the motor current I limited by the limiting value V1_MChange in linkage.

Then, at timing t4, the value is raised to limit value V2. Due to motor current I_MSince it is lower than the limit value V2, the detection signal is limited to the L level at the timing t4, and the constant current is controlled by the limit value V1The action is ended. Then, at timing t5, the value is raised to limit value V3. By setting the limit value relative to the motor current I_MLimit value V3 with sufficient margin to allow motor current I due to load variations_MA variation of (c). This enables stable motor driving in which the number of rotations of the motor follows the load fluctuation.

The limit value V1 for the constant current operation and the timing t3 are basic data indicating the driving state of the motor in which no deterioration occurs. When the end of the constant current operation is detected at the timing t4, it can be understood that the actual current used by the motor in the no-load state is between the limit values V1 and V2, for example. The current is used as the basic data of the actual current of the motor without deterioration.

Fig. 2B is a diagram for explaining a driving method for detecting a deterioration state of the motor by comparing with basic data acquired by the driving method of fig. 2A. Solid line 131 represents motor current I_MSolid line 141 represents the motor speed, and solid line 152 represents the motor current I_M. Dashed line 151 corresponds to solid line 150 in fig. 2A. The timings t1 to t5 correspond to the timings t1 to t5 in fig. 2A.

Similarly to fig. 2A, at a timing t1 when the rotation speed of the motor is stable, the limit value is decreased from the reference value to V3. In the state of limit value V3, control logic circuit 50 detects whether or not constant current operation is being performed in drive circuit 10. Due to motor current I_MSince it is smaller than limit value V3, it is determined that the constant current operation is not performed by limit value V3. Therefore, the limit detection signal shown in the lower stage becomes L level.

Then, at timing t2, it decreases to limit value V2. In the illustrated example, the motor current I is due to degradation_MIncrease, therefore, the motor current I_MThe limit value V2 is reached. Therefore, a constant current operation is performed by the limit value V2, and the motor current I_MAnd (4) reducing. At timing t2, the detection signal is restricted to the H level. That is, the constant current operation is performed at a timing t2 before a timing t3 at which the constant current operation is performed in the motor in which deterioration does not occur. By comparing the timing t2 of outputting the detection signal with the timing t3 of the basic dataThe deterioration state of the motor can be determined.

Then, at timing t3, it decreases to limit value V1. Due to motor current I_MSince limit value V1 is reached, a constant current operation is performed based on limit value V1. The limit detection signal maintains the H level. Then, at timing t4, the value rises to limit value V2. Due to motor current I_MSince limit value V2 is reached, a constant current operation is performed based on limit value V2. The limit detection signal maintains the H level. Then, at timing t5, the value rises to limit value V3. Due to motor current I_MSince the detection signal does not reach the limit value V3, the constant current operation is not performed by the limit value V3, and the detection signal is limited to the L level. The motor speed and the motor current I limited by the limit values V1 and V2_MChange in linkage.

Motor current I in case of motor deterioration_MAnd (4) increasing. Therefore, the degree of deterioration of the motor can be grasped by comparison with the basic data indicating the driving state of the motor in which deterioration has not occurred. For example, in the case of a state without deterioration, the motor does not perform the constant current operation at limit value V2. On the other hand, when the deterioration progresses, the motor performs a constant current operation at limit value V2. Therefore, by comparing limit value V1, which is the basic data of the constant current operation without degradation, with limit value V2, which performs the constant current operation from the start of use, the degradation state of the motor can be grasped. Further, whether or not the limit value is reached can be digitally determined based on whether or not the limit detection signal is at the H level, and therefore, the deterioration state of the motor can be easily determined. Further, by displaying the limit detection signal on the display device 120, the user can be notified of the deterioration state of the motor.

In the embodiment, the limit value is lowered stepwise from the reference value, but the versatility can be improved by appropriately setting the limit value, the number of stages in which the limit value is changed stepwise, or the timing at which the limit value is changed. Further, by automatically comparing the data with the basic data at the time of starting the motor and displaying the result on the display device 120, the user can be notified of the degradation information of the motor in real time.

Fig. 3 is a flowchart for explaining a driving method of the motor shown in fig. 2A. The motor is started (S301). When the period of the rush current generated at the time of starting has elapsed (YES in S302), it is determined whether or not the rotation speed of the motor is stable (S303). For example, it is determined whether or not the rotation speed of the motor is stable based on a signal from a not-shown tachometer. If the rush current period has not elapsed (no in S302), the period of waiting for the rush current to elapse.

When the rotational speed of the motor is stable (YES in S303), the motor current I is determined_MWhether the limit value is reached (S304). When the rotation speed of the motor is unstable (S303: NO), the control device waits until the rotation speed of the motor is stable. At motor current I_MWhen the limit value is reached (no in S304), the process waits until the limit value is not reached.

At motor current I_MIf the limit value is not reached (YES in S304), the limit value is lowered (S305). Using the reduced limit value for the motor current I_MAnd determines that there is an unlimited detection signal output (S306). In the case where the limit detection signal is not output (S306: No), that is, in the case where the limit detection signal is at the L level, the limit value is lowered (S305).

When the limit detection signal is output (YES in S306), that is, when the limit detection signal is at H level, it is determined whether or not a constant current operation is performed based on the limit value (S307). When the constant current operation is not performed based on the limit value (S307: NO), the limit value is decreased (S305). When the constant current operation is performed based on the limit value (S307: YES), the limit value V1 at that time is recorded (S308).

Next, the limit value is increased (S309), and it is determined that there is an unlimited detection signal output (S310). When the limit detection signal is not output (no in S310), limit value V2 at this time is recorded (S311). When the limit detection signal is output (S310: YES), the limit value is raised (S309).

After recording limit value V2(S311), the limit value is further increased (S312). As already mentioned, the limit value V3 is increased to a sufficient margin with respect to the limit value V2. Thereby, the motor can be transferred toCurrent I_MA normal driving state not limited by the limit value.

In addition, the limit value may be reduced in an analog manner after the period of the rush current has elapsed, and the motor current I may be recorded_MThe limit value in the reaction was reached. The control logic circuit 50 compares the detection voltage with a voltage corresponding to the limit value and detects the limit detection signal, thereby detecting the motor current I_MThe limit of the reaction was reached.

Fig. 4 shows a flow of the driving method based on fig. 2B. The data of the limit values V1 to V3 and the timings t1 to t5 obtained by the driving method of fig. 3 are stored in the control logic circuit 50, for example. The motor is started (S401), and it is determined whether or not a period of inrush current has elapsed (S402). When the rush current period has elapsed (S402: YES), it is determined whether or not the rotation speed of the motor is stable (S403). If the rush current period has not elapsed (no in S402), the period of waiting for the rush current to elapse.

When the rotational speed of the motor is stable (S403: YES), the motor current I is determined_MWhether the limit value is reached (S404). The limit value at the time of starting the motor is set to a reference value, for example. At motor current I_MWhen the limit value is reached (NO in S404), the process waits until the limit value is not reached. When the rotational speed of the motor is unstable (S403: NO), the control device waits until the rotational speed of the motor is stable.

At motor current I_MIf the limit value is not reached (yes in S404), the limit value is lowered to V3 and V2 in stages at timings t1 and t2, and limit value V1 is set at timing t3 (S405). When the restriction detection signal is detected (YES in S406) and the constant current operation is performed based on the restriction value V1 (YES in S407), the operation is raised to the restriction value V2 (S408). By raising the limit value to V2 and detecting whether or not the limit detection signal is output, the deterioration state of the motor can be determined. When the limit detection signal is not detected (NO in S406) and when the constant current operation is not performed (NO in S407), a notification is made that the state is in a non-degraded state (S411).

When the limit detection signal is output (YES in S409), a notification is made that the state is degraded (S410). For example, the display device 120 displays that the deterioration has occurred. If the limit detection signal is not detected (S409: NO), a notification is made that the state is not degraded (S411).

Subsequently, the limit value is increased (S412). The limit value is raised to limit value V3 with a sufficient margin with respect to limit value V2. Thereby, the motor current I can be transferred_MA normal driving state not limited by the limit value.

It is to be noted that, instead of the determinations at S402 to S404, a determination may be made at timing t1 as to whether or not the limit detection signal is output at the limit value V3 (S406). Further, the determination may be performed not always but in a steady state at the time of starting the motor with little load variation. For example, the deterioration state of the motor may be effectively determined in a short time from the start to the timing t 5.

In the case of a motor in which no deterioration occurs, the limit detection signal is detected at the limit value V1, whereas in the case of a motor in which deterioration has progressed, the limit detection signal is output at the limit values V1 and V2. The control logic circuit 50 determines the deterioration state of the motor by comparing the basic data with the detection data. By automatically comparing the basic data with the detection data at the time of starting the motor and displaying the result on the display device 120, the user can be notified of the deterioration state of the motor in real time.

When the limit detection signal is output (yes in S409), the deterioration may be notified (S410), and the control for stopping the driving operation of the motor may be performed. By automatically stopping the motor drive, it is possible to suppress an increase in power consumption due to the use of a deteriorated motor. Further, a case where maintenance of the motor is required may be displayed on the display device 120 to call the attention of the user.

Fig. 5 is a diagram showing another configuration example of the drive circuit 10. The driver circuit 10 of fig. 5 has a resistor 80 connected between the sources of the transistors 12, 14 and ground. Supplying a motor current I to a resistor 80 via a transistor 12 or 14_M. Thus, produced in resistor 80The generated voltage drops to the motor current I_MThe corresponding voltage. The motor current I can be detected by supplying the value of the voltage drop generated in the resistor 80 to the control logic circuit 50_M。

Fig. 6 is a diagram for explaining another driving method for detecting the deterioration state of the motor. The horizontal axis represents time, and the vertical axis represents limit value and motor current I_M. The broken line 132 indicates a reference value of the limit value, corresponding to the reference value of fig. 2. The broken line 153 corresponds to the solid line 150 in fig. 2(a), and indicates the motor current I of the motor in which no deterioration occurs_M. The solid line 154 corresponds to the solid line 152 in fig. 2(B), and represents the motor current I of the motor in which the deterioration has progressed_M。

In fig. 6, at the time of start-up, limit value V10 indicated by solid line 133 lower than the reference value is set. That is, the rush current is limited by the limit value V10.

Motor current I limited by limit value V10_MAnd is reduced by the back electromotive force of the coil 101. When the deterioration of the motor progresses, the motor current I is larger than that when the deterioration does not progress_MBecomes larger. Thus, depending on the state of the degradation of the motor, the current I is applied to the motor_MThe time until the reference value V11 set for comparison shown by the solid line 134 is reduced and becomes different. For example, when the motor is deteriorated, the timing to be lowered to the reference value V11 is delayed as compared with the case where the deterioration is not caused. Therefore, the motor current I is measured by the control logic circuit 50_MWhen the timing falls to the reference value V11, the deterioration state of the motor can be detected. For example, the control logic circuit 50 determines that the deterioration of the motor has progressed when the timing t10 is set as the reference time of the basic data and the time difference between the timing t10 and the timing t11 is longer than a predetermined threshold time.

Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope equivalent thereto.