JP2009240136A - Device and method for controlling motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling a motor that protects overheating of the motor, on the basis of a motor heating temperature obtained by arithmetic processing and is capable of surely protecting overheating of the motor, even under the condition where arithmetic processings cannot be conducted in a normal manner. <P>SOLUTION: The device 10 for controlling the motor has an overheat protective circuit 15 for stopping the supply of a drive current to the motor M, independently of a control section 13, on the basis of the changes of the output characteristics of circuit elements (such as, a comparator 16 and transistors Tr11, Tr12) due to change in a temperature-detecting voltage, when a temperature-detecting voltage output from a heating-temperature detecting section 14 reaches a voltage which is equivalent to a second temperature (such as, 120°C) higher than a first temperature (such as, 110°C) overheat protective control by the control section 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor control device having an overheat protection function for protecting a motor from burning and the like, and a motor control method.

  A wiper motor mounted on a vehicle has a structure in which a wiper performs a reciprocating wiping operation within a predetermined angle range and wipes raindrops and the like on the wiping surface by a reciprocating wiping operation by the wiper. When this occurs, the load on the wiper motor increases. If the amount of snow increases, the wiper cannot push the snow outside the wiping range, and the wiping operation may be restricted before the reverse position, and the wiper motor may be forcibly stopped. Overcurrent flows through the motor and eventually burns out. Therefore, such a wiper motor is provided with an overheat protection function in the motor itself and its control device.

  For example, in the technique disclosed in Patent Document 1, a bimetallic overheat protection element is mounted in the motor, and when an overcurrent occurs, the contact is separated by heat generation, thereby supplying current to the motor. It is to stop. However, since the bimetal-type overheat protection element has a configuration in which the motor drive current flows directly through the bimetal type overheat protection element, the larger the current value of the drive current handled, the larger the element, and it becomes difficult to secure a mounting space in the motor. . Among them, the reverse drive type wiper motor is particularly problematic because it requires a larger drive current than the one-way rotation type wiper motor using the link.

A technique that does not cause this problem is disclosed in Patent Document 2, for example. In Patent Document 2, a thermistor whose resistance value changes with temperature and output voltage changes is used to detect the heat generation temperature of the motor. The voltage value of the output voltage of the thermistor is binarized by an A / D converter in the microcomputer, and the motor heat generation temperature is calculated by calculation by the CPU. Based on the motor heat generation temperature calculated in this way, if the current supply to the motor is stopped when an overheat state exceeds a predetermined temperature, it is possible to prevent further motor heat generation. is there.
JP-A-8-9613 Japanese Utility Model Publication No. 5-28946

  However, as in Patent Document 2, in the case of performing motor control by a microcomputer, there is a case where accurate motor control cannot be performed when the microcomputer runs out of control, and current supply to the motor is not possible even if the motor is overheated. There was a possibility that the motor could not be stopped and the heat generation of the motor beyond that could not be suppressed.

  The present invention has been made to solve the above-described problems, and its purpose is to protect the motor from overheating based on the motor heat generation temperature obtained by the arithmetic processing, and the arithmetic processing is normally performed. It is an object of the present invention to provide a motor control device and a motor control method capable of reliably performing overheat protection of a motor even in a situation where it cannot be performed.

  In order to solve the above-mentioned problem, the invention according to claim 1 performs a drive control of the motor, and a heat generation temperature detection unit that outputs a temperature detection voltage corresponding to the heat generation temperature associated with the drive of the motor to be controlled. The motor heat generation temperature is calculated from the voltage value of the temperature detection voltage output from the heat generation temperature detection unit, and when the motor is in a predetermined overheat state based on the calculated motor heat generation temperature, the motor And a control unit that performs overheat protection control to stop the supply of drive current to the temperature detection voltage output from the heat generation temperature detection unit, the overheat protection control by the control unit When the voltage corresponding to the second temperature higher than the first temperature is reached, independent of the control unit based on the output characteristic change of the circuit element accompanying the change of the temperature detection voltage Further comprising an overheat protection circuit performs an overheat protection circuit operates to stop the supply of the drive current to the serial motor as its gist.

  In the present invention, by providing the overheat protection circuit, the temperature detection voltage output from the heat generation temperature detection unit reaches a voltage corresponding to the second temperature higher than the first temperature at which the overheat protection control by the control unit is performed. Then, an overheat protection circuit operation for stopping the supply of the drive current to the motor is performed independently of the control unit based on the change in the output characteristic of the circuit element accompanying the change in the temperature detection voltage. As a result, when the software overheat protection by the control unit becomes ineffective due to runaway of the control unit, etc., hardware overheat protection is performed by the overheat protection circuit independent of the control unit, so the motor overheat protection Can be reliably performed.

  According to a second aspect of the present invention, in the motor control device according to the first aspect, when the control unit performs the overheat protection control, the motor heat generation temperature is equal to or lower than a third temperature lower than the first temperature. The gist of this is to continue the overheat protection control until the temperature drops.

  In this invention, when the control unit performs the overheat protection control, the control unit continues the overheat protection control until the motor heat generation temperature falls below a third temperature lower than the first temperature at which the overheat protection control is performed. In other words, by providing hysteresis to the overheat protection control, it is possible to reliably reduce the motor heat generation temperature and to ensure a certain degree of continuous driving when the next motor is driven.

  According to a third aspect of the present invention, in the motor control device according to the first or second aspect, the overheat protection circuit is configured such that the temperature detection voltage is based on a comparison between the temperature detection voltage and a threshold voltage. And a switching element that cuts off a current supply path to the motor based on a change in the logic of the output signal of the comparator. And

  In this invention, the overheat protection circuit includes a comparator that changes the logic of the output signal when the temperature detection voltage becomes higher than the voltage corresponding to the second temperature based on the comparison between the temperature detection voltage and the threshold voltage, and the output signal of the comparator. And a switching element that cuts off a current supply path to the motor based on a change in logic. That is, the overheat protection circuit can be configured with a simple circuit using a comparator and a switch element.

  According to a fourth aspect of the present invention, in the motor control device according to the third aspect of the present invention, the overheat protection circuit may operate at a temperature at which the motor heat generation temperature is normally operable when the overheat protection circuit is operated. The gist of the invention is that it includes a threshold voltage changing unit that changes the voltage value of the threshold voltage so as to maintain the supply stop state of the drive current to the motor.

  In this invention, the overheat protection circuit is provided with a threshold voltage changing unit, so that when the overheat protection circuit is operated, the supply current of the drive current to the motor is stopped even if the motor heat generation temperature reaches a normal operating temperature. Thus, the voltage value of the threshold voltage is changed. In other words, the hardware overheat protection by the overheat protection circuit means that the software overheat protection by the control unit has become ineffective due to the runaway of the control unit. By adopting a configuration that requires some kind of reset processing such as returning to the current voltage value, it is possible to prevent repeated overheating protection in hardware by the overheating protection circuit.

The gist of a fifth aspect of the present invention is the motor control device according to any one of the first to fourth aspects, wherein the controlled object is a wiper motor of a vehicle.
In this invention, the control object of the motor control device is the wiper motor of the vehicle. In this wiper motor, for example, the wiping operation of the wiper is hindered due to the placement of foreign matter such as snow on the wiping surface, thereby causing the motor driving current to be excessive. Since the motor heat generation temperature often increases greatly, it has great significance to have the overheat protection function as described above.

  The invention according to claim 6 detects the heat generation temperature associated with driving of the motor to be controlled, calculates the motor heat generation temperature from the voltage value of the temperature detection voltage corresponding to the heat generation temperature, and calculates the calculated motor heat generation. A motor control method for performing overheat protection control for stopping the supply of drive current to the motor when the motor is in a predetermined overheat state based on temperature, wherein the temperature detection voltage is determined by the overheat protection control. When the voltage corresponding to the second temperature higher than the first temperature to be implemented is reached, the motor is driven independently of the overheat protection control based on the output characteristic change of the circuit element accompanying the change of the temperature detection voltage. The gist is that the overheat protection circuit operation for stopping the supply of current is performed.

  In the present invention, similarly to the first aspect, when the soft overheat protection by the control unit becomes ineffective due to the runaway of the control unit, etc., the hardware overheat protection by the overheat protection circuit independent of the control unit. Therefore, it is possible to reliably protect the motor from overheating.

  According to the present invention, the motor overheat protection is performed based on the motor heat generation temperature obtained by the arithmetic processing, and the motor can reliably perform the overheat protection of the motor even in the situation where the arithmetic processing cannot be performed normally. A control device and a motor control method can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is an electrical configuration diagram of a motor control device 10 that controls the wiper motor M. The wiper motor M causes the wiper 2 that wipes the windshield 1 of the vehicle to reciprocate within a predetermined angle range, and wipes raindrops and the like on the wiping surface 1a of the glass 1 by the reciprocating wiping operation by the wiper 2. . The wiper motor M is reversely driven by the motor control device 10, and the wiper 2 is wiped back and forth based on the reverse drive.

  The motor control device 10 includes a motor drive unit 11 that generates drive power to be supplied to the wiper motor M from an in-vehicle battery (not shown). The motor drive unit 11 is composed of an H bridge circuit using four switching elements Tr1 to Tr4 made of MOSFETs, the positive power supply terminal is connected to the power supply line L0 receiving the supply of battery power + B, and the negative power supply terminal is It is connected to the ground GND (vehicle body ground) via a shunt resistor R0. Each of the switching elements Tr1 to Tr4 has a gate connected to an output terminal of the drive signal output unit (predriver IC) 12 via resistors R1 to R4, respectively, and from the drive signal output unit 12 input to the gate. Based on the drive signal, each set for forward rotation or reverse drive is turned on / off, and drive power for forward / reverse rotation is generated in the wiper motor M. Further, in order to perform speed control and torque control of the wiper motor M in addition to forward / reverse drive, the switching elements Tr1 to Tr4 are subjected to PWM control. The drive signal output unit 12 that outputs the drive signal has an input terminal connected to the control unit 13 via the resistor R5, and outputs the drive signal based on the input of the control signal from the control unit 13. .

  Although not shown, the control unit 13 is configured by a microcomputer including an A / D converter, a CPU, and the like. A temperature detection voltage corresponding to the heat generation temperature of the wiper motor M is input from the heat generation temperature detection unit 14 to the control unit 13. The heat generation temperature detector 14 includes a resistor R10 and a thermistor Rth connected in series between a power supply line L1 to which a DC voltage of 5V is applied and the ground GND. The thermistor Rth is an NTC thermistor (Negative Temperature Coefficient Thermistor), and has a characteristic that the resistance value decreases as the ambient temperature increases. Therefore, when the ambient temperature of the thermistor Rth increases, the resistance value of the thermistor Rth decreases and the potential of the node N1 gradually decreases, and the potential of the node N1 thus changing is input to the control unit 13 as a temperature detection voltage. The

  The thermistor Rth is installed in the vicinity of the shunt resistor R0 of the motor drive unit 11 through which a motor drive current having a correlation with the heat generation (mainly winding temperature) of the wiper motor M flows. In other words, since the heat generation of the wiper motor M increases as the motor drive current increases, the shunt resistor R0 whose heat generation similarly increases due to the increase in the drive current is set as the detection target. When the heat generation of the shunt resistor R0 increases due to the increase of the motor drive current, the ambient temperature of the thermistor Rth increases, and the resistance value of the thermistor Rth decreases accordingly, and the temperature detection voltage output from the node N1 decreases. It is like that.

  The control unit 13 binarizes the voltage value of the temperature detection voltage with the A / D converter (not shown), and calculates the heat generation temperature of the wiper motor M (motor heat generation temperature) by calculation with the CPU. When the calculated motor heat generation temperature is equal to or lower than the first temperature B (for example, 110 ° C.), the control unit 13 determines that the motor heat generation temperature is within the normal range, and outputs a control signal for performing a normal wiper operation as a drive signal. To the unit 12. The drive signal output unit 12 outputs a drive signal based on the control signal to each of the switching elements Tr1 to Tr4 to turn it on and off, thereby causing the wiper motor M to normally operate.

  On the other hand, when the motor heat generation temperature based on the temperature detection voltage becomes higher than the first temperature B (110 ° C.), the control unit 13 determines that the wiper motor M has become a medium overheated state and stops the wiper operation. The control signal is output to the drive signal output unit 12. The drive signal output unit 12 turns off the switching elements Tr1 to Tr4, stops the supply of the drive current to the wiper motor M, and stops its drive.

  In other words, when a foreign object such as snow that is placed on the wiping surface 1a interferes with the normal wiping operation of the wiper 2, the wiping operation of the wiper is restricted before the reversing position of the wiper. The current becomes overcurrent and the motor heat generation temperature rises. If the controller 13 determines that the motor heat generation temperature is higher than the first temperature B (110 ° C.) and thus the wiper motor M has become a medium overheated state, the controller 13 stops the supply of drive current to the motor M and the motor Overheat protection control is performed to reduce the heat generation temperature and prevent the motor M from being burned out.

  When it is determined once that the wiper motor M is in the intermediate overheat state, the control unit 13 determines that the motor heat generation temperature based on the temperature detection voltage is lower than the first temperature B (110 ° C.). Hysteresis is provided so that the drive current to the wiper motor M is stopped and the drive stop state is continued until the temperature drops below the temperature C (for example, 100 ° C.).

  In addition to the software overheat protection control by the control unit 13, the motor control device 10 is additionally provided with an overheat protection circuit 15 that performs hardware overheat protection circuit operation not controlled by the control unit 13. .

  More specifically, the overheat protection circuit 15 includes a determination switching unit 15a, and the plus side input terminal of the comparator 16 constituting the determination switching unit 15a is connected to the resistor R10 and the thermistor Rth constituting the exothermic temperature detection unit 14. And a temperature detection voltage generated at the node N1 is applied to the input terminal. The threshold voltage generated by the threshold voltage generator 15b is applied to the negative input terminal of the comparator 16. The threshold voltage generator 15b includes two resistors R11 and R12 connected in series between a power supply line L1 to which a DC voltage of 5V is applied and the ground GND. The negative input terminal of the comparator 16 is connected to a node N2 between the resistors R11 and R12, and the potential of the node N2 is applied to the input terminal as a threshold voltage. The resistance values of the resistors R11 and R12 are set such that a threshold voltage corresponding to a second temperature A (for example, 120 ° C.) higher than the first temperature B (110 ° C.) is generated.

  In the comparator 16, a pair of power supply terminals are respectively connected to the power supply line L1 to which a DC voltage of 5V is applied and the ground GND. The comparator 16 compares the temperature detection voltage with the threshold voltage, and outputs an H level output signal when the temperature detection voltage is lower than the threshold voltage, that is, when the motor heat generation temperature is lower than the second temperature A (120 ° C.). To do. The motor heat generation temperature is not more than the second temperature A (120 ° C.), in particular, the first temperature B (110 ° C.) or less, and is within the normal range, and is higher than the first temperature B (110 ° C.) and the second temperature A (120 ° C.). ) In the following, it means a moderate overheating state, and the output signal of the comparator 16 becomes H level. On the other hand, when the temperature detection voltage exceeds the threshold voltage, that is, the motor heat generation temperature becomes higher than the second temperature A (120 ° C.), the comparator 16 sets the output signal to the L level (internally, the output terminal is connected to the ground GND). . The L level output signal of the comparator 16 means an overheated state in which the motor heat generation temperature is high.

  The output terminal of the comparator 16 is connected to a power supply line L1 to which a DC voltage of 5V is applied via a resistor R13, and is connected to the base of the NPN transistor Tr11 via a resistor R14. The collector of the transistor Tr11 is connected to a power supply line L1 to which a DC voltage of 5V is applied via a resistor R15, is connected to the base of the NPN transistor Tr12, and the emitter is connected to the ground GND. The collector of the transistor Tr12 is a diode connected to the input terminal of the drive signal output unit 12 to which a control signal is input from the control unit 13 and the gates of the two switching elements Tr3 and Tr4 on the low potential side of the motor drive unit 11. D1 to D3 are connected to each other, and the emitter is connected to the ground GND.

  The output terminal of the comparator 16 is connected to the control unit 13 via a resistor R16, and is connected to the base of a PNP transistor Tr13 constituting the threshold voltage changing unit 15c via a resistor R17. The emitter of the transistor Tr13 is connected to the power supply line L1 to which a DC voltage of 5V is applied, and is connected to the base via the resistor R18, and the collector is connected between the resistors R11 and R12 constituting the threshold voltage generator 15b. Is connected to the node N2 via a resistor R19. The overheat protection circuit 15 having such a configuration is provided on one circuit board (not shown) together with the motor drive unit 11, the drive signal output unit (pre-driver IC) 12, the control unit 13, and the heat generation temperature detection unit 14. It is configured.

  In the overheat protection circuit 15 having such a configuration, the motor heat generation temperature becomes higher than the first temperature B (110 ° C.), and the overheat protection control (wiper motor M stop control) by the control unit 13 cannot be performed. It operates by becoming higher than the second temperature A (120 ° C.).

  That is, below the second temperature A (120 ° C.), an H level output signal is output from the comparator 16 of the determination switching unit 15a, and the transistor Tr11 is on and the transistor Tr12 is off. Thus, the input terminal of the drive signal output unit 12 to which the control signal is input from the control unit 13 and the gates of the switching elements Tr3 and Tr4 are not connected to the ground GND, and the control signal to the drive signal output unit 12 is not transmitted. Input is possible, and a drive signal can be output from the drive signal output unit 12 to the switching elements Tr3 and Tr4. That is, the wiper motor M can be controlled by the control unit 13 via the drive signal output unit 12 and the motor drive unit 11.

  Since the output signal of the comparator 16 is at the H level, the transistor Tr13 of the threshold voltage changing unit 15c is turned off, and the voltage is supplied to the comparator 16 only by the voltage division of the resistors R11 and R12 of the threshold voltage generating unit 15b. A threshold voltage is generated. The output signal of the comparator 16 is also output to the control unit 13.

  On the other hand, a foreign matter such as snow that is placed on the wiping surface 1a interferes with the normal wiping operation of the wiper 2, and the wiping operation is restricted before the wiper is in the reverse position. If the overheat protection control described above cannot be performed, the motor heat generation temperature rises and eventually becomes higher than the second temperature A (120 ° C.). Then, in the overheat protection circuit 15, it is assumed that the overheat protection control cannot be performed by the control unit 13, and the output signal of the comparator 16 is switched from the H level to the L level, the transistor Tr11 is turned off, and the transistor Tr12 is turned on.

  As a result, the input terminal of the drive signal output unit 12 to which the control signal is input from the control unit 13 is connected to the ground GND, and the gates of the switching elements Tr3 and Tr4 are connected to the ground GND, and the switching elements Tr3 and Tr4 are connected. Is fixed off. That is, the overheat protection circuit 15 stops the supply of the drive current to the motor M in this way, lowers the motor heat generation temperature, and performs the hardware overheat protection circuit operation without using the control unit 13 for the motor M. It has become.

  When the output signal of the comparator 16 becomes L level, the transistor Tr13 of the threshold voltage changing unit 15c is turned on and supplied to the comparator 16 by the divided voltage of the combined resistance of the resistors R11 and R19 and the resistor R12 connected in parallel. A threshold voltage is generated. Accordingly, the potential of the node N2 that generates the threshold voltage increases, and in this embodiment, even if the motor heat generation temperature decreases and returns to the normal range of the first temperature B (110 ° C.) or less, the overheat protection circuit 15 When the overheat protection circuit operation is performed once, the resistance value of the resistor R19 is set so that the output signal of the comparator 16 is maintained at the L level, and the control of the wiper motor M by the control unit 13 is impossible. The state is maintained. Thereafter, in order to perform normal control of the wiper motor M by the control unit 13, it is necessary to perform a reset process for turning off the transistor Tr13 from the outside. In the present embodiment, the vehicle ignition switch (IG ) Is switched from off to on so that the reset process is possible.

Next, the overheat protection function of the motor control device 10 in the present embodiment will be described using the operation flow of FIG.
In step S1, the heat generation temperature detector 14 detects the motor heat generation temperature. In step S2, the overheat protection circuit 15 (comparator 16) determines whether the motor heat generation temperature is higher than the second temperature A (120 ° C.). Determined. When the motor heat generation temperature is equal to or lower than the second temperature A (120 ° C.), the process proceeds to step S3.

  In step S3, it is determined by the control unit 13 (microcomputer) whether or not the motor heat generation temperature is higher than the first temperature B (110 ° C.). When the motor heat generation temperature is equal to or lower than the first temperature B (110 ° C.), the process proceeds to step S4. In step S4, it is determined by the control unit 13 (microcomputer) whether the motor heat generation temperature is higher than a third temperature C (for example, 100 ° C.). When the motor heat generation temperature is equal to or lower than the third temperature C (for example, 100 ° C.), the process proceeds to step S5, and normal control of the wiper motor M by the control unit 13 is performed.

  Further, even when the motor heat generation temperature is lower than the first temperature B (110 ° C.) and higher than the third temperature C (for example, 100 ° C.), the control is performed on the condition that the overheat protection control by the control unit 13 is not currently performed. The normal control of the wiper motor M by the unit 13 is performed.

  That is, in step S3, when the motor heat generation temperature becomes higher than the first temperature B (110 ° C.), the process proceeds to step S6, overheat protection control is performed by the control unit 13 to drive the wiper motor M in order to lower the motor heat generation temperature. The current supply is stopped (wiper motor M is stopped). When the motor heat generation temperature falls below the first temperature B (110 ° C.) but is higher than the third temperature C (eg 100 ° C.), the process proceeds from step S4 to step S7, and overheat protection control is currently performed by the control unit 13. Is determined. If overheat protection control is not currently performed, the process proceeds to step S5, and normal control of the wiper motor M by the control unit 13 is performed.

  On the other hand, if overheat protection control is being performed by the control unit 13, the process proceeds to step S8, and the supply of the drive current to the wiper motor M is continued. That is, once the motor heat generation temperature becomes higher than the first temperature B (110 ° C.) and the overheat protection control is performed by the control unit 13, the control unit until the motor heat generation temperature becomes the third temperature C (for example, 100 ° C.) or less. Hysteresis is provided so that normal control of the wiper motor M by 13 can not be performed, and the motor heat generation temperature is surely lowered so that a certain amount of continuous drive can be secured when the next wiper motor M is driven.

  In step S2, when the motor heat generation temperature becomes higher than the second temperature A (120 ° C.), the overheat protection circuit 15 (comparator 16) is activated, and the process proceeds to step S9. That is, when the motor heat generation temperature becomes higher than the second temperature A (120 ° C.), some abnormality occurs in the control unit 13 composed of a microcomputer, and the software overheat protection control by the control unit 13 is not performed. Therefore, the hardware overheat protection circuit operation by the overheat protection circuit 15 (comparator 16) is performed. When the overheat protection circuit 15 (comparator 16) is activated, the gates of the switching elements Tr3 and Tr4 of the motor drive unit 11 are connected to the ground GND, and the switching elements Tr3 and Tr4 are turned off. Thereby, the supply of the drive current to the motor M is stopped, and the motor heat generation temperature is lowered.

  When the hardware overheat protection circuit operation by the overheat protection circuit 15 is performed as described above, the process proceeds to step S10, and if the operation of switching the ignition switch (IG) of the vehicle from OFF to ON is not performed, the motor heat generation temperature is increased. Even when the temperature is equal to or lower than the first temperature B (110 ° C.) or the third temperature C (for example, 100 ° C.), the control unit 13 cannot perform normal control of the wiper motor M.

  Incidentally, in the overheat protection function of the motor control device 10 as described above, the change in the motor heat generation temperature at which the soft overheat protection by the control unit 13 is effective increases the load on the wiper motor M as shown by the solid line in FIG. When the motor heat generation temperature rises, supply of the drive current to the wiper motor M is stopped at the first temperature B (110 ° C.), and the motor heat generation temperature is lowered, and the temperature becomes the third temperature C (100 ° C.) or less. This is continued until the first temperature B (100 ° C.) is reached, so that the normal control of the wiper motor M is possible and the supply of the drive current to the motor M is resumed when the temperature is lower than the third temperature C (100 ° C.). 110 ° C.) and the third temperature C (100 ° C.).

  On the other hand, when the motor heat generation temperature rises to the second temperature A (120 ° C.), since the soft overheat protection by the control unit 13 is not effective, the hardware overheat protection by the overheat protection circuit 15 is activated. When the motor heat generation temperature becomes higher than the second temperature A (120 ° C.), the overheat protection circuit 15 directly stops the supply of drive current to the wiper motor M, and the motor heat generation temperature is reduced. When the hardware overheat protection by the overheat protection circuit 15 is performed, even if the motor heat generation temperature falls below the first temperature B (110 ° C.) or the third temperature C (eg 100 ° C.), the ignition switch ( If the operation of switching IG) from OFF to ON is not performed, normal control of the wiper motor M cannot be performed, so that the drive current is not supplied to the motor M, and the motor heat generation temperature continues to decrease.

Next, characteristic effects of the present embodiment will be described.
(1) The motor control device 10 of the present embodiment includes an overheat protection circuit 15 that performs hardware overheat protection separately from the control unit 13 that performs software overheat protection. And the temperature detection voltage output from the exothermic temperature detection part 14 becomes a voltage equivalent to 2nd temperature A (120 degreeC) higher than 1st temperature B (110 degreeC) in which the overheat protection control by the control part 13 is implemented. When it reaches, overheating that stops the supply of the drive current to the motor M independently of the control unit 13 based on the change in the output characteristics of the circuit elements (comparator 16, transistors Tr11, Tr12, etc.) accompanying the change in the temperature detection voltage. Protection circuit operation is performed. Thereby, when the soft overheat protection by the control unit 13 is not effective due to the runaway of the control unit 13 or the like, the hardware overheat protection by the overheat protection circuit 15 independent of the control unit 13 is performed. The overheating protection of the motor M can be reliably performed. In particular, in the wiper motor M as in the present embodiment, the wiping operation of the wiper 2 is hindered due to the placement of foreign matters such as snow on the wiping surface 1a, thereby causing excessive motor drive current and a large increase in motor heat generation temperature. In many cases, the significance of having such an overheat protection function is great.

  (2) When the control unit 13 of the present embodiment performs the overheat protection control, the motor heat generation temperature is lower than the first temperature B (110 ° C) at which the overheat protection control is performed. ) Continue overheat protection control until it drops below. In other words, by providing hysteresis to the overheat protection control, it is possible to reliably reduce the motor heat generation temperature and to ensure a certain degree of continuous driving when the next wiper motor M is driven.

  (3) The overheat protection circuit 15 of the present embodiment is configured such that the temperature detection voltage is the second temperature A based on the comparison between the temperature detection voltage from the heat generation temperature detection unit 14 and the threshold voltage generated by the threshold voltage generation unit 15b. A comparator 16 that changes the logic of the output signal when it becomes higher than the voltage corresponding to (120 ° C.), and a transistor Tr11 as a switch element that cuts off the current supply path to the wiper motor M based on the change of the logic of the output signal of the comparator 16 , Tr12. That is, the overheat protection circuit 15 can be configured with a simple circuit using the comparator 16 and the transistors Tr11 and Tr12.

  (4) The overheat protection circuit 15 of this embodiment includes a threshold voltage changing unit 15c, and when the overheat protection circuit is operated by the overheat protection circuit 15, the first temperature B (110 Or the third temperature C (100 ° C.) or less, the threshold voltage is changed so as to maintain the drive current supply stop state to the wiper motor M. In other words, the fact that the hardware overheat protection by the overheat protection circuit 15 is performed means that the software overheat protection by the control unit 13 has become ineffective due to the runaway of the control unit 13, and so on. By adopting a configuration that requires some reset processing from the outside, such as switching the ignition switch from OFF to ON as described above, it is possible to prevent repeated overheating protection by hardware by the overheating protection circuit 15.

In addition, you may change embodiment of this invention as follows.
In the above embodiment, the motor drive unit 11 is configured with an H bridge circuit of the switching elements Tr1 to Tr4, but may be configured with a drive circuit other than the bridge circuit.

  In the above embodiment, the overheat protection circuit 15 includes the determination switching unit 15a, the threshold voltage generation unit 15b, and the threshold voltage change unit 15c. However, the overheat protection circuit 15 may be appropriately changed, for example, by omitting the threshold voltage change unit 15c. . The configuration of each circuit unit may be changed as appropriate.

  For example, in the determination switching unit 15a, the transistors Tr11 and Tr12 are used as switching elements that block the current supply path to the wiper motor M. However, one transistor may be used. The transistors Tr11 and Tr12 are bipolar transistors, but other semiconductor switch elements such as MOSFETs may be used. In addition to the semiconductor switch element, a relay or the like may be used. Further, the determination switching unit 15a turns off the switching elements Tr1 to Tr4 of the motor driving unit 11 to cut off the current supply path to the wiper motor M. However, a switching element is separately provided on the current supply path, and the switching element is switched. It is good also as a structure.

  Further, when overheat protection is performed by the overheat protection circuit 15, the threshold voltage input to the comparator 16 of the determination switching unit 15a is changed by the threshold voltage changing unit 15c to fix the output signal of the comparator 16. However, for example, without changing the threshold voltage, a signal (voltage) indicating that the overheat protection is performed in the overheat protection circuit 15 is added to the input or output of the comparator 16 to fix the output signal of the comparator 16. Also good.

  Further, when the overheat protection is performed by the overheat protection circuit 15, the control unit 13 allows the normal control of the motor M by switching the ignition switch from OFF to ON. However, the present invention is not limited to this. However, the operation may be appropriately changed to other operations.

  In the above embodiment, in the overheat protection control by the control unit 13, when the motor heat generation temperature becomes the first temperature B and the overheat protection is effective, until the temperature becomes equal to or lower than the third temperature C lower than the first temperature B. Although the hysteresis that normal control cannot be performed is provided, the hysteresis may not be provided.

  In the above embodiment, the NTC thermistor is used as the thermistor Rth. However, a PTC thermistor (Positive Temperature Coefficient Thermistor) whose resistance value increases as the ambient temperature increases may be used. Further, other temperature sensitive elements may be used.

  In the above embodiment, the present invention is applied to the control of the wiper motor M, but may be applied to other motor controls.

It is a circuit diagram of the motor control device in the present embodiment. It is an operation | movement flowchart for demonstrating the overheat protection function of a motor control apparatus. It is a wave form diagram which shows the temperature change at the time of the motor heating temperature rise by overheat protection.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Motor control apparatus, 13 ... Control part, 14 ... Exothermic temperature detection part, 15 ... Overheat protection circuit, 15c ... Threshold voltage change part, 16 ... Comparator, M ... Wiper motor (motor), Tr11, Tr12 ... Transistor (switch element) ), A ... second temperature, B ... first temperature, C ... third temperature.

Claims (6)

A heat generation temperature detection unit that outputs a temperature detection voltage corresponding to the heat generation temperature associated with driving of the motor to be controlled;
While controlling the drive of the motor, the motor heat generation temperature is calculated by calculation from the voltage value of the temperature detection voltage output from the heat generation temperature detection unit, and the motor is heated to a predetermined overheat based on the calculated motor heat generation temperature. A motor control device including a control unit that performs overheat protection control to stop the supply of drive current to the motor in a state,
When the temperature detection voltage output from the heat generation temperature detection unit reaches a voltage corresponding to a second temperature higher than the first temperature at which the overheat protection control is performed by the control unit, the temperature detection voltage changes. A motor control apparatus comprising: an overheat protection circuit that performs an overheat protection circuit operation that stops supply of a drive current to the motor independently of the control unit based on a change in output characteristics of a circuit element involved. The motor control device according to claim 1,
The control unit, when performing the overheat protection control, continues the overheat protection control until the motor heat generation temperature falls below a third temperature lower than the first temperature. In the motor control device according to claim 1 or 2,
The overheat protection circuit is
A comparator that changes a logic of an output signal when the temperature detection voltage becomes higher than a voltage corresponding to the second temperature based on a comparison between the temperature detection voltage and a threshold voltage;
A motor control device comprising: a switching element that cuts off a current supply path to the motor based on a change in logic of an output signal of the comparator. The motor control device according to claim 3,
When the overheat protection circuit operates, the overheat protection circuit is configured to maintain the drive current supply stop state to the motor even when the motor heat generation temperature reaches a normal operating temperature. A motor control device comprising a threshold voltage changing unit for changing a value. In the motor control device according to any one of claims 1 to 4,
A motor control device characterized in that a controlled object is a wiper motor of a vehicle. The heat generation temperature associated with the drive of the motor to be controlled is detected, the motor heat generation temperature is calculated from the voltage value of the temperature detection voltage corresponding to the heat generation temperature, and the motor is set to a predetermined value based on the calculated motor heat generation temperature. A motor control method for performing overheat protection control for stopping the supply of drive current to the motor when an overheat state occurs,
When the temperature detection voltage reaches a voltage corresponding to a second temperature higher than the first temperature at which the overheat protection control is performed, the overheat protection is performed based on a change in output characteristics of the circuit element accompanying a change in the temperature detection voltage. A motor control method characterized in that an overheat protection circuit operation for stopping the supply of drive current to the motor is performed independently of the control.

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