JP3542290B2 - Drive control device for DC motor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drive control device for a DC motor.
[0002]
[Prior art]
Conventionally, a drive control device capable of detecting a locked state of a DC motor that drives a pump used in an anti-lock brake control device of a vehicle is disclosed in Japanese Patent No. 2513323, in which a DC motor is operated. In such a case, the current is continuously supplied from the drive circuit to the DC motor, and based on the speed of the decrease in the voltage between the terminals of the motor immediately after the drive of the DC motor is stopped, the lock of the motor due to the fixation of the pump is performed. It is determined whether or not a state has occurred.
[0003]
That is, when the pump is not stuck and the DC motor is normal, the voltage between the terminals of the motor is saturated to a certain value according to the start of the operation of the DC motor by the drive circuit, and the driving of the motor is stopped. In response to the termination, the voltage between the terminals drops with a certain constant. On the other hand, when the DC motor is locked due to the fixation of the pump, the voltage between the terminals of the motor is changed according to the start of operation of the DC motor. The lock state of the motor is detected based on the fact that the voltage saturates to a certain constant value as in the normal state, and the voltage between the terminals drops in a shorter time than the normal state in response to the end of driving of the motor. It is possible.
[0004]
[Problems to be solved by the invention]
In the above-described conventional motor, even if the DC motor is in an abnormal state, the locked state of the DC motor cannot be determined until the drive is completed, and the drive circuit supplies a drive current to the DC motor until the determination of the locked state is completed. It will continue to be supplied. Further, in the locked state of the DC motor, as shown by the broken line in FIG. 5, several tens of times of the current flows compared to the normal operation indicated by the solid line. Overcurrent will be imposed on itself and the drive circuit. Even if the DC motor is normal, an inrush current of several tens of times is generated at the start of driving the DC motor. Therefore, it is necessary to use an element having a large current capacity to withstand the overcurrent in the drive circuit.
[0005]
By the way, the suppression of the overcurrent and the rush current in the lock state can be achieved by controlling the drive circuit so as to repeat on / off in a minimum time, but the on / off duty of the drive circuit is fixed. If the upper limit value of the current is kept low, the start-up characteristics of the DC motor deteriorate.
[0006]
The present invention has been made in view of the above circumstances, and suppresses a peak current flowing through a DC motor while avoiding deterioration of the start-up characteristics of the DC motor at the start of driving of the DC motor. It is an object of the present invention to provide a drive control device for a DC motor capable of reducing the size and cost.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a drive control device for a DC motor, wherein duty control of a drive circuit for driving the DC motor is performed at the start of driving of the DC motor. current detecting means for detecting a current calculated from a preset constant target current, the current difference by subtracting the current detected by said current detecting means as a target value of the inrush current at the start of driving of the direct current motor Difference calculating means, duty calculating means for calculating the on / off duty of the drive circuit based on the current difference calculated by the current detecting means, and duty control of the drive circuit based on the calculation result of the duty calculating means. And a constant lock detection current preset as a value lower than the target current and a current detected by the current detection means. A comparison means for outputting a measurement start signal in response to the detection current being equal to or greater than the lock detection current; a time measurement means for measuring a time from when the measurement start signal is output from the comparison means; DC motor according to the measurement time is preset lock detection time or more by the time measuring means has a determining lock determination means and a locked state, the lock detection time, the start of driving of the DC motor In order to reduce the load on the drive circuit by judging in a short time that the DC motor is in the locked state, the current exceeds the lock detection current and reaches the target current once at the start of normal operation of the DC motor. , Is set slightly longer than the time when the current becomes less than the lock detection current again .
[0008]
According to such a configuration, by controlling the duty of the drive circuit at the start of driving of the DC motor , the peak current flowing to the motor at the start of drive can be suppressed to a relatively low level. Since the use of an element is not required, the size and cost of the driving circuit can be reduced. Moreover, the on / off duty of the drive circuit is based on a current difference obtained by subtracting the current detected by the current detection means from a predetermined target current set as a target value of the inrush current at the start of driving of the DC motor. Therefore, it is possible to prevent the rising characteristics of the DC motor from deteriorating.
[0009]
In addition, when the DC motor is started to drive, if the DC motor is normal, the peak current flows for a certain period of time from the start of the operation of the DC motor, whereas in the locked state of the DC motor, the peak current continues until the drive ends. since, predetermined constant lock detection current or currents, by determining that the flow persisted predetermined lock detection time or more, Ru can detect the locked state of the direct current motor . In particular, the lock detection time is set slightly longer than the time when the current exceeds the lock detection current, once reaches the target current, and once again becomes less than the lock detection current at the start of driving of the DC motor in a normal state. since you are, dc motor at the start of driving of the DC motor becomes possible to reduce the load of the relatively short period of time determined by the drive circuit to be in a locked state, further cost by unloading of the driving circuit Down can be planned.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on an embodiment of the present invention shown in the accompanying drawings. 1 to 4 show an embodiment of the present invention. FIG. 1 is a circuit diagram showing a configuration of an antilock brake control device for a vehicle to which the present invention is applied, and FIG. 2 is a drive control system of a DC motor. FIG. 3 is a block diagram showing the configuration, FIG. 3 is a flowchart showing a drive control procedure of the DC motor, and FIG. 4 is a current waveform diagram showing a normal state and a locked state of the DC motor in comparison.
[0011]
First, in FIG. 1, a master cylinder M is provided with an output port 2 for outputting a brake fluid pressure according to the depression of a brake pedal 1, and an antilock brake control device is provided between the output port 2 and a wheel brake B. 3 are provided.
[0012]
The antilock brake control device 3 includes a reservoir 4, a pump 5 provided between the reservoir 4 and the output port 2, and a switching valve means 6 capable of switching and connecting the wheel brake B to the output port 2 and the reservoir 4. And a damper 7 and an orifice 8 provided between the output port 2 and the pump 5.
[0013]
The switching valve means 6 includes a normally-open solenoid valve 9 provided between the output port 2 and the wheel brake B, and a normally-closed solenoid valve 10 provided between the wheel brake B and the reservoir 4. 9 is connected in parallel to a one-way valve 11 that allows the flow of brake fluid from the wheel brake B side to the master cylinder M side when the hydraulic pressure on the wheel brake B side is higher than the master cylinder M side.
[0014]
The pump 5 has a built-in suction valve 12 and a discharge valve 13. The pump 5 is driven by a DC motor 14.
[0015]
In FIG. 2, the drive circuit 15 for driving the DC motor 14 is duty- controlled by the control unit 16 at the start of driving of the motor 14 so as to keep the peak current relatively low while avoiding deterioration of the rising characteristics of the motor 14. The detection value of the current detection means 17 for detecting the current flowing through the DC motor 14 is input to the control unit 16.
[0016]
The control unit 16 is capable of switching control of demagnetization / excitation of the normally-open solenoid valve 9 and the normally-closed solenoid valve 10 in the switching valve means 6 and is capable of controlling the drive circuit 15. The part related to the operation control of the DC motor 14 of the unit 16 includes a current difference calculating means 18 for calculating a current difference by subtracting the current detected by the current detecting means 17 from a preset target current; Duty calculating means 19 for calculating the on / off duty of the driving circuit 15 based on the current difference calculated by the difference calculating means 18; and a duty for controlling the driving circuit 15 based on the calculation result of the duty calculating means 19. The control means 20 compares the current detected by the current detection means 17 and a preset lock detection current, A comparison unit 21 that outputs a measurement start signal in response to the above, a time measurement unit 22 that measures the time from when the measurement start signal is output from the comparison unit 21, and a measurement time that is measured by the time measurement unit 22 in advance. A lock determination unit that determines that the DC motor is in a locked state when the lock detection time is equal to or longer than a set lock detection time;
[0017]
The control procedure of the control unit 16 having such a configuration is set as shown in FIG. 3. In step S <b> 1, the first drive duty by the duty control unit 20 is provisionally set to start driving the DC motor 14. Then, in step S3 after confirming in step S2 that the driving of the DC motor 14 is not terminated is set to a certain constant value, the DC motor 14 is controlled by the duty control of the drive circuit 15 by the duty control means 20. Drive.
[0018]
In a step S4, a current rising characteristic based on the current I detected by the current detecting means 17, for example, a rising gradient of the current is measured. In a step S5, the detected current I is subtracted from a predetermined target current IO to obtain a current difference ΔI. Is calculated. Further, in step S6, the duty calculation means 19 calculates the next on / off duty of the drive circuit 15 based on the current rise characteristic in step S4 and the current ΔI in step S5.
[0019]
At step S7, comparison between the detected current I detected by the current detecting means 17, and a lock detection current IL over which is predetermined as a value lower than the target current IO by comparison means 21 was I <I L Sometimes, the process returns to step S2. When I ≧ IL, the process proceeds from step S7 to step S8 in response to the output of the measurement start signal from the comparison means 21. In this step S8, the time T from the start of the output of the measurement start signal is measured by the time measurement means 22. Time by
[0020]
In step S9, the lock determination unit 23 determines whether or not the time T measured by the timer 22 is equal to or longer than a predetermined lock detection time TL. If T <TL , the process returns to step S2. If ≧ TL, the determination means 23 determines in step S10 that the DC motor 14 is in the locked state. The signal from the lock determining means 23 when it is determined in step S9 that the DC motor 14 is in the locked state is input to the duty control means 20, and the duty control is performed when it is determined that the DC motor 14 is in the locked state. The means 20 outputs a signal for stopping the operation of the DC motor 14, and the drive circuit 15 stops the operation of the DC motor 14 accordingly. Further, a warning lamp or the like (not shown) may be operated when the lock state of the DC motor 14 is determined.
[0021]
By the way, the lock detection time TL is longer than the time when the current I once exceeds the lock detection current IL and reaches the target current IO once and then becomes lower than the lock detection current IL again at the start of driving of the DC motor 14 in a normal state. Is also set slightly larger.
[0022]
Next, the operation of this embodiment will be described. When the driving of the DC motor 14 is started , the duty control of the driving circuit 15 for driving the DC motor 14 is performed by the duty control means 20. The peak current that flows can be kept relatively low, and it is not necessary to use an element having a large current capacity in the drive circuit 15, so that downsizing and cost reduction of the drive circuit can be achieved.
[0023]
Moreover, the on / off duty of the drive circuit 15 is calculated by the duty calculating means 22 based on the current difference ΔI obtained by subtracting the current I detected by the current detecting means 17 from the preset target current IO. As shown by the solid line in FIG. 4, the rush current at the start of driving of the DC motor 14 can be quickly started until the DC current 14 reaches the target current IO. it can.
[0024]
When the DC motor 14 is normal at the start of driving of the DC motor 14, as shown by a solid line in FIG. In the locked state of the motor 14, the peak current continues until the drive ends, as indicated by the broken line in FIG. As a result of comparing the detection current I detected by the current detection means 17 with the preset lock detection current IL, the time T at which the measurement was started in response to the detection current I being equal to or greater than the lock detection current IL is: The DC motor 14 is determined to be in a locked state when the lock detection time TL becomes equal to or longer than a preset lock detection time TL , and the lock detection time TL is determined as described above. Is set slightly longer than the time when the current I exceeds the lock detection current IL and once reaches the target current IO and then becomes lower than the lock detection current IL at the start of driving of the DC motor 14, that dc motor 14 is determined in a relatively short time that it is in the locked state can reduce the load of the driving circuit 15, achieving a further cost reduction That.
[0025]
As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is possible.
[0026]
For example, in the above-described embodiment, the description has been given in relation to the DC motor used in the antilock brake control device of the vehicle. However, the present invention can be widely applied as a drive control device of the DC motor.
[0027]
【The invention's effect】
As described above, according to the present invention, by controlling the duty of the drive circuit at the start of driving of the DC motor, the peak current flowing to the motor at the start of drive is suppressed relatively low, and an element having a large current capacity is used in the drive circuit. This makes it possible to reduce the size and cost of the drive circuit, and to set the ON / OFF duty of the drive circuit to a constant target current preset as a target value of the inrush current at the start of driving of the DC motor. Since the calculation is performed based on the current difference obtained by subtracting the current detected by the current detection means from the above, deterioration in the startup characteristics of the DC motor can be avoided.
[0028]
In addition, when the DC motor is started to drive, if the DC motor is normal, the peak current flows for a certain period of time from the start of the operation of the DC motor, whereas in the locked state of the DC motor, the peak current continues until the drive ends. Therefore, by determining that a current equal to or greater than a predetermined lock detection current that is lower than the target current and flowing continuously for a predetermined lock detection time or longer, it is possible to lock the DC motor. Ru can be used to detect the state. In particular, the lock detection time is set slightly longer than the time when the current exceeds the lock detection current, once reaches the target current, and once again becomes less than the lock detection current at the start of driving of the DC motor in a normal state. As a result, it is possible to reduce the load on the drive circuit by quickly determining that the DC motor is in the locked state at the start of driving the DC motor, and to further reduce costs by reducing the load on the drive circuit. Can be.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a vehicle antilock brake control device. FIG. 2 is a block diagram showing a configuration of a DC motor drive control system. FIG. 3 is a flowchart showing a DC motor drive control procedure. FIG. 5 is a current waveform diagram showing a normal state and a locked state of a DC motor in comparison. FIG. 5 is a current waveform diagram showing a normal state and a locked state of a DC motor in the prior art.
14 DC motor 15 Drive circuit 17 Current detection means 18 Current difference calculation means 19 Duty calculation means 20 Duty control means 21 Comparison means 22 .Timekeeping means 22: lock determination means

Claims (1)

A drive control device for a DC motor for performing duty control of a drive circuit (15) for driving the DC motor (14) at the start of driving of the DC motor (14) ,
A current detecting means (17) for detecting a current flowing through the DC motor (14), and a current target (IO) preset as a target value of the inrush current at the start of driving of the DC motor (14), the current being obtained from the current A current difference calculating means (18) for calculating a current difference (ΔI) by subtracting the current (I) detected by the detecting means (17); and a current difference calculating means (18) at the start of driving of the DC motor (14). ), A duty calculating means (19) for calculating the on / off duty of the driving circuit (15) based on the current difference (ΔI) calculated based on the current difference (ΔI), and the driving based on the calculation result of the duty calculating means (19). A duty control means (20) for duty-controlling the circuit (15); a constant lock detection current (IL) preset as a value lower than the target current (IO); ) And a comparison means (21) for outputting a measurement start signal in response to the detection current (I) being equal to or greater than the lock detection current (IL), and the comparison means (21). ), A time measuring means (22) for measuring the time from the output of the measurement start signal, and a DC motor (14) in response to the time measured by the time measuring means (22) being longer than a preset lock detection time. ) Is provided with a lock determining means (23) for determining that the lock state is established.
The lock detection time (TL) is set to a normal value in order to reduce the load on the drive circuit (15) by quickly determining that the DC motor (14) is in a locked state at the start of driving of the DC motor (14). At the start of driving of the DC motor (14) in the state, the current (I) exceeds the lock detection current (IL) and reaches the target current (IO) once, and is slightly shorter than the time when the current (I) again becomes lower than the lock detection current (IL). A drive control device for a DC motor, which is set to be large .

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