JP2012025218A - Motor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability on operation of a motor control circuit at a low temperature by preventing wrong detection of the lock current at a low temperature.SOLUTION: A selector switch 33 is provided between a battery 32 and an electric motor 21. An FET 43 and a PTC thermistor 44 are connected in series to each other between one power source side terminal 35a connected to the selector switch 33 and one motor terminal 21a of the electric motor 21, and a starting capacitor 52 is connected in parallel with the FET 43 and the PTC thermistor 44. A collector C of a normal rotation side transistor 62 is connected to the one power source side terminal 35a through a gate G of the FET 43, and an emitter E is connected to the other power source side terminal 35b and a base B is connected between the PTC thermistor 44 and the one motor terminal 21a.

Description

  The present invention relates to a motor control circuit used for controlling a driving device in which a driving body such as an electric retractable door mirror provided in an automobile is driven from a first position to a second position by an electric motor. .

  Conventionally, as a door mirror provided at the front end of a door of an automobile, it is automatically stored from the use position to the storage position by operating a switch provided in the vehicle interior, and automatically from the storage position to the use position. An electric retractable type that can be restored is known. Such an electric retractable door mirror is provided with an electric motor for driving the door mirror, and the operation control of the electric motor is performed by a motor control circuit.

  The motor control circuit is a contact type that uses a relay as a driving electronic component for controlling the drive current to the electric motor, or a non-contact type that uses a semiconductor element such as an FET (field effect transistor). However, in recent years, durable non-contact types are becoming mainstream.

  In such a motor control circuit, in order to facilitate the door mirror retracting / returning operation, the electric motor is activated by one-touch operation of the switch, and when the door mirror reaches the storage position from the use position or from the storage position to the use position. An operation stop function is provided in which the electric motor is automatically stopped without performing the switch operation again.

  For example, in Patent Document 1, a PTC thermistor is connected to a motor drive circuit in series with a motor drive FET, and the door mirror reaches from the use position to the storage position or from the storage position to the use position, and a lock current flows to the electric motor. Sometimes, a motor control circuit is described in which the lock current is detected as an increase in the resistance value of the PTC thermistor and the electric motor is automatically stopped.

JP 2002-347522 A

  However, in the motor control circuit disclosed in Patent Document 1, an increase in the resistance value generated by the PTC thermistor when a lock current flows is taken into the off circuit of the motor drive FET as a voltage drop by the thermistor, and the motor drive is performed by this off circuit. Since the motor drive FET is turned off by short-circuiting the gate and source of the FET for use, there is a problem that erroneous detection of the lock current is likely to occur at low temperatures.

  That is, normally, since the PTC thermistor has a response delay characteristic with respect to an overcurrent, if the PTC thermistor is set appropriately, the inrush current generated at the initial start-up of the electric motor will not be erroneously detected as a lock current immediately. However, when the ambient temperature is lowered, the resistance value of the PTC thermistor may become two to three times higher than that at room temperature, and the inrush current also increases in inverse proportion to the ambient temperature, so that the voltage drop of the PTC thermistor increases at room temperature. Bigger than. As a result, at low temperatures, the inrush current generated at the initial start-up of the electric motor is easily detected as a lock current, and the electric motor may stop immediately after the start-up.

  Further, when the temperature is low, the sliding resistance of the gear portion of the actuator for driving the door mirror increases, and the motor driving current increases. When the increase in the resistance value of the PTC thermistor at the low temperature described above overlaps with this, the voltage drop of the PTC thermistor becomes larger than that at the normal temperature, and it becomes easy to erroneously detect the increase in the motor driving current as the lock current at the low temperature.

  As described above, in the configuration of Patent Document 1 in which the voltage drop generated in the PTC thermistor is taken into the off circuit as a signal and the motor driving FET is turned off, erroneous detection of the lock current is likely to occur at low temperatures, and the electric motor is unexpected. There was a risk of stopping.

  An object of the present invention is to prevent erroneous detection of a lock current at a low temperature and to improve the operation reliability of a motor control circuit at a low temperature.

  A motor control circuit of the present invention is a motor control circuit that is connected to an electric motor that drives a driven body from a first position to a second position, and that controls the operation of the electric motor. A starting switch connected between a DC power source, a motor driving FET connected in series with the starting switch between one pole of the DC power source and one terminal of the electric motor; A starting capacitor connected in parallel with the motor driving FET between one pole of a DC power source and one terminal of the electric motor, and between the motor driving FET and one terminal of the electric motor And a PTC thermistor connected in series with the motor driving FET and in parallel with the starting capacitor, and a base is connected between the PTC thermistor and one terminal of the electric motor. A switching transistor in which a inductor is connected to one pole of the DC power supply via a gate of the motor driving FET, and an emitter is connected between the other pole of the DC power supply and the other terminal of the electric motor It is characterized by having.

  In the motor control circuit of the present invention, the driven body is an electrically retractable door mirror provided in a vehicle, and the electric motor drives the door mirror between a use position and a retracted position.

  According to the present invention, the lock current is detected by the decrease in the voltage applied to the electric motor and the motor driving FET is turned off. Therefore, even if the resistance value of the PTC thermistor increases compared to the normal temperature at low temperatures. Without being affected by this, the lock current can be accurately detected based on the voltage drop applied to the electric motor. As a result, erroneous detection of the lock current at a low temperature can be prevented, and the operation reliability of the motor control circuit can be improved.

It is a figure which shows the outline of the electrically-driven retractable door mirror of a motor vehicle. It is a circuit diagram of the motor control circuit which is one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An electric retractable door mirror (driven body) 11 shown in FIG. 1 is provided on the left door 13 of the automobile 12 and is used for driver's rear confirmation. The door mirror 11 is rotatably supported on a stay 14 fixed to the door 13 by a support shaft 15, and as shown by a solid line in the figure, a use position that protrudes to the side of the vehicle body and as indicated by a one-dot chain line in the figure. And a storage position folded in a direction along the vehicle body, the support shaft 15 is rotatable (movable) with respect to the stay 14 around the support shaft 15. When the vehicle is traveling, the door mirror 11 is set to the use position and is used for confirming the rear view of the driver. When the vehicle is not used such as parking, the door mirror 11 can be stored in the storage position. Yes.

  The door mirror 11 includes a cover body 16 that opens on the vehicle rear side, and a mirror plate 17 is attached to the opening of the cover body 16. Although not shown in detail, this mirror plate 17 is supported by a remote control unit 18, and the driver can adjust the angle of the mirror plate 17 by remote operation by operating an adjustment switch (not shown) provided in the passenger compartment. It is like that.

  The remote control unit 18 may not be provided, and the mirror plate 17 may be manually adjusted in angle.

  Inside the cover body 16, the door mirror 11 is driven from the use position (first position) to the storage position (second position), and from the storage position (first position) to the use position (second position). ), A retractable drive electric motor 21 is provided. As the electric motor 21, a brushed DC motor that can be operated in both forward and reverse directions by a DC current is used.

  The electric motor 21 has an output shaft (not shown) in a direction parallel to the support shaft 15 and is fixed inside the cover body 16 adjacent to the support shaft 15, and the output shaft is connected via a speed reduction mechanism (not shown). It is connected to the support shaft 15. As a result, when the electric motor 21 operates in the forward rotation direction, the door mirror 11 is driven by the electric motor 21 and rotates from the use position toward the storage position around the support shaft 15, and when the electric motor 21 reverses, the door mirror 11 is It is driven by the electric motor 21 so as to rotate from the storage position toward the use position around the support shaft 15.

  FIG. 2 is a circuit diagram of a motor control circuit according to an embodiment of the present invention.

  As shown in FIG. 2, a motor control circuit 31 is connected to the electric motor 21 in order to control the operation of the electric motor 21. The motor control circuit 31 includes a battery 32 as a DC power source mounted on the automobile 12, a changeover switch 33 as a start switch provided in the vehicle interior for selectively switching the door mirror 11 to a use position or a storage position, And a control unit 34 disposed inside the cover body 16 of the door mirror 11, and controls the operation of the electric motor 21 in accordance with the operation of the changeover switch 33 by a driver or the like.

  The control unit 34 is housed in a case and is configured as a single unit. The control unit 34 is connected to the motor terminals 21a and 21b of the electric motor 21 by a connector (not shown) and is connected to the power supply terminals 35a and 35b drawn from the door mirror 11. To the change-over switch 33.

  A main switch (accessory switch) 36 is provided between the changeover switch 33 and the positive electrode of the battery 32. The main switch 36 is provided in the passenger compartment and is operated by an engine key. When the main switch 36 is turned on, the motor control circuit 31 is turned on together with other electric systems, and the door mirror 11 is retracted. The return operation is possible.

  The changeover switch 33 includes a first switch 33a connected to one power supply side terminal 35a of the control unit 34 and a second switch 33b connected to the other power supply side terminal 35b. The 2 switch 33b is structured to be interlocked. When the changeover switch 33 is operated to the storage side, one power supply side terminal 35a of the control unit 34 is connected to the positive electrode (positive electrode) of the battery 32 via the first switch 33a, and the other power supply side of the control unit 34 is connected. The terminal 35b is connected to the negative electrode (negative electrode) of the battery 32 through the second switch 33b. Conversely, when the changeover switch 33 is operated to the return side, one power supply side terminal 35a of the control unit 34 is connected to the negative electrode (negative electrode) of the battery 32 via the first switch 33a, and the other side of the control unit 34 is connected. Is connected to the positive electrode (positive electrode) of the battery 32 via the second switch 33b.

  Reference numeral 37 denotes a ground terminal for grounding the negative pole of the battery 32.

  Between one power supply side terminal 35a of the control unit 34 connected to the first switch 33a and one motor terminal 21a of the electric motor 21, a motor forward rotation side series circuit 41 and a motor reverse rotation side series circuit 42 are provided. The first switch 33a and the second switch 33b are connected in parallel with each other in series.

  The motor forward rotation side series circuit 41 has a structure in which a forward rotation side motor drive FET 43, a forward rotation side PTC thermistor 44, and a forward rotation side diode 45 are connected in series. In the illustrated case, the drain D of the FET 43 is connected to the power supply side terminal 35a, the source S is connected to one end of the PTC thermistor 44, the gate G is connected to the power supply side terminal 35a via the resistor 46, and the PTC thermistor The other end of 44 is connected to the anode A of the diode 45, and the cathode K of the diode 45 is connected to the motor terminal 21a. On the other hand, the motor reverse rotation side series circuit 42 has a structure in which a reverse rotation motor drive FET 47, a reverse rotation PTC thermistor 48, and a reverse rotation diode 49 are connected in series. In the illustrated case, the source S of the FET 47 is connected to the power supply side terminal 35a, the drain D is connected to one end of the PTC thermistor 48, the gate G is connected to the power supply side terminal 35a via the resistor 51, and the PTC thermistor. The other end of 48 is connected to the cathode K of the diode 49, and the anode A of the diode 49 is connected to the motor terminal 21a.

  Note that the PTC thermistors 44 and 48 are thermistors having a non-linear resistance value characteristic (positive characteristic) in which the resistance value is small at normal temperature, but the resistance value rapidly increases when the temperature exceeds a certain temperature due to heat generation during energization. It is.

  As described above, the motor control circuit 31 is provided with two motor drive circuits on the forward rotation side and the reverse rotation side by the changeover switch 33 and the series circuits 41 and 42, and the motor control of the battery 32 is performed by operating the changeover switch 33. When the connection direction to the circuit 31 is switched, the drive current flows to the electric motor 21 through one of the series circuits 41 and 42 by the diodes 45 and 49 provided in the series circuits 41 and 42. That is, when the changeover switch 33 is operated to the storage side and the FET 43 is turned on, a drive current flows to the electric motor 21 via the motor forward rotation side series circuit 41, and the electric motor 21 operates in the forward rotation direction. On the contrary, when the changeover switch 33 is operated to the return side and the FET 47 is turned on, a drive current flows to the electric motor 21 through the motor reverse rotation side series circuit 42, and the electric motor 21 operates in the reverse rotation direction.

  A starting capacitor 52 is connected in parallel with the motor forward rotation side series circuit 41 and the motor reverse rotation side series circuit 42 between one power supply side terminal 35 a of the control unit 34 and one motor terminal 21 a of the electric motor 21. It is connected. A resistor 53 is connected between both terminals of the starting capacitor 52 in parallel with the starting capacitor 52, and between the starting capacitor 52 and the motor terminal 21a in series with the starting capacitor 52 and on the motor forward side. A resistor 54 is connected in parallel to the series circuit 41 and the motor reverse rotation side series circuit 42.

  Further, the control unit 34 is provided with a motor operation circuit 61 in order to switch on and off the forward rotation side FET 43 and the reverse rotation side FET 47.

  The motor operation circuit 61 includes a forward rotation transistor 62 as a switching transistor corresponding to the forward rotation FET 43 and a reverse rotation transistor 63 as a switching transistor corresponding to the reverse rotation FET 47.

  The base B of the forward-rotation transistor 62 is connected between the starting capacitor 52 and the resistor 54 via the resistor 64, that is, between the PTC thermistor 44 and the motor terminal 21a via the resistors 54 and 64, and the resistor B. 65 is connected to the other power supply side terminal 35 b of the control unit 34. Further, the collector C of the forward rotation side transistor 62 is connected to the gate G of the forward rotation side FET 43 via a diode 66 and a resistor 67. In other words, the collector C of the forward rotation side transistor 62 is connected to the power supply side terminal 35 a via the gate G of the forward rotation side FET 43. Further, the emitter E of the forward rotation side transistor 62 is connected to the other power supply side terminal 35 b of the control unit 34.

  On the other hand, the base B of the reverse side transistor 63 is connected between the PTC thermistor 48 and the motor terminal 21a via resistors 54 and 64, and connected to the other power source side terminal 35b of the control unit 34 via the resistor 65. It is connected. The emitter E of the reverse transistor 63 is connected to the gate G of the FET 47 on the reverse side via a diode 68 and a resistor 69. That is, the emitter E of the reverse side transistor 63 is connected to the power supply side terminal 35 a via the gate G of the reverse side FET 47. Further, the collector C of the reverse side transistor 63 is connected to the other power supply side terminal 35 b of the control unit 34.

  As described above, the forward rotation-side transistor 62 and the reverse rotation-side transistor 63 take on the voltage between the motor terminals of the electric motor 21 into the base B, respectively, so that the on / off control is performed according to the change in the voltage between the motor terminals of the electric motor 21. It has come to be.

  The diodes 66 and 68 are provided for circuit protection, and reference numerals 71 and 72 are Zener diodes for circuit protection.

  Next, the operation control of the electric motor 21 by the motor control circuit 31 having such a circuit configuration will be described.

  When the door switch 11 is in the use position, the main switch 36 is turned on, and the FETs 43 and 47 are turned off, when the changeover switch 33 is operated to the storage side by the driver or the like, the storage operation of the door mirror 11 is started. The

  That is, when the changeover switch 33 is operated to the storage side, one power supply side terminal 35a of the control unit 34 is connected to the positive electrode of the battery 32, and the other power supply terminal 35b is connected to the negative electrode of the battery 32. A charging current flows through the starting capacitor 52.

  When the start-up capacitor 52 is charged, the base voltage of the normal rotation side transistor 62 rises, and the normal rotation side transistor 62 is turned on. When the forward side transistor 62 is turned on, a current flows through the path of the resistors 46 and 67, the diode 66, and the forward side transistor 62, and a voltage is applied to the gate G of the forward side FET 43. Side FET 43 is turned on. As a result, the drive current from the battery 32 is supplied to the electric motor 21 via the FET 43 on the forward rotation side, the electric motor 21 operates in the forward rotation direction, and the door mirror 11 is driven by the electric motor 21 from the use position. The storage operation is performed up to the storage position.

  Here, during the operation of the electric motor 21, the voltage at the motor terminal 21 a of the electric motor 21 becomes the power supply voltage. Therefore, the forward-side transistor 62 having the base B connected to the motor terminal 21 a operates the electric motor 21. The inside will be kept on. When the starting capacitor 52 is charged, the reverse-side transistor 63 is turned on together with the forward-side transistor 62, but the reverse-side FET 47 is not turned on by the action of the diode 68. .

  Next, the operation stop function of the electric motor 21 by the motor control circuit 31 will be described.

  When the door mirror 11 driven by the electric motor 21 reaches from the stop position to the retracted position, that is, the stroke end, the load applied to the electric motor 21 suddenly increases, and a lock current is applied to the electric motor 21 and the motor forward rotation side series circuit 41. Flowing. When the lock current flows, the temperature of the PTC thermistor 44 rises due to self-heating due to the flow of the lock current, and the resistance value of the PTC thermistor 44 rapidly increases as compared to the normal temperature. When the resistance value of the PTC thermistor 44 is rapidly increased, the voltage between the terminals of the PTC thermistor 44, that is, the voltage drop due to the PTC thermistor 44 is rapidly increased, and the voltage between the motor terminals of the electric motor 21 is narrowed accordingly. . When the voltage between the motor terminals decreases to a predetermined value or less, the forward-rotation transistor 62 having the base B connected to the motor terminal 21a cannot be maintained in the on state and is turned off. When the forward rotation side transistor 62 is turned off, the voltage applied to the gate G of the forward rotation side FET 43 is lowered, and the FET 43 is turned off, whereby the electric motor 21 is stopped. When the electric motor 21 is stopped, the starting capacitor 52 is maintained at the power supply voltage, so that the normal rotation side transistor 62 is not turned on again by the starting capacitor 52.

  In contrast, when the door switch 11 is in the retracted position, the main switch 36 is turned on, and the FETs 43 and 47 are turned off, when the changeover switch 33 is operated to the return side by the driver or the like, the return operation of the door mirror 11 is performed. Is started.

  That is, when the changeover switch 33 is operated to the return side, one power supply side terminal 35a of the control unit 34 is connected to the negative pole of the battery 32, and the other power supply side terminal 35b is connected to the positive pole of the battery 32. A charging current flows through the starting capacitor 52. When the starting capacitor 52 is charged, the base voltage of the reverse-side transistor 63 increases, and the reverse-side transistor 63 is turned on. At this time, since the starting capacitor 52 has already been charged during the storing operation, a voltage that is twice the power supply voltage obtained by adding the power supply voltage of the battery 32 to the charging voltage of the starting capacitor 52 serves as a base voltage of the base B of the transistor 63. To be applied. When the reverse-side transistor 63 is turned on, a current flows through the path of the transistor 63, the diode 68, and the resistors 69 and 51, a voltage is applied to the gate G of the reverse-side FET 47, and the reverse-side FET 47 is turned on. . As a result, the drive current from the battery 32 is supplied to the electric motor 21, the electric motor 21 is operated in the reverse direction, and the door mirror 11 is driven by the electric motor 21 to return from the storage position to the use position.

  On the other hand, when the door mirror 11 driven by the electric motor 21 reaches the use position, that is, the stroke end from the retracted position, the load applied to the electric motor 21 rapidly increases, and a lock current is applied to the electric motor 21 and the reverse-side series circuit 42. Flowing. When the lock current flows, the temperature of the PTC thermistor 48 rises due to self-heating due to the flow of the lock current, and the resistance value of the PTC thermistor 48 increases rapidly compared to the normal temperature. When the resistance value of the PTC thermistor 48 increases abruptly, the voltage between the terminals of the PTC thermistor 48, that is, the voltage drop due to the PTC thermistor 48 increases rapidly, and accordingly, the voltage between the motor terminals of the electric motor 21 is reduced. . When the voltage between the motor terminals drops below a predetermined value, the reverse-side transistor 63 can no longer maintain the on state and is turned off. When the reverse-side transistor 63 is turned off, the voltage applied to the gate G of the reverse-side FET 47 is lowered, and the FET 47 is turned off, whereby the electric motor 21 is stopped.

  Thus, in the motor control circuit 31 of the present invention, the transistors 62 and 63 for ON / OFF control of the FETs 43 and 47 are configured to be ON / OFF controlled by the voltage change between the motor terminals of the electric motor 21, respectively. When the lock current flowing through the electric motor 21 is detected by the increase in the resistance value of the PTC thermistors 44, 48, the electric motor generated by the increase in the resistance value of the PTC thermistors 44, 48, not the voltage drop generated in the PTC thermistors 44, 48. Accordingly, the transistors 62 and 63 are turned off by lowering the voltage between the motor terminals 21 to turn off the FETs 43 and 47 for driving the motor. Thereby, even if the resistance values of the PTC thermistors 44 and 48 are larger than those at the normal temperature at low temperatures, the lock current is accurately detected based on the voltage between the motor terminals of the electric motor 21 without being affected by the resistance value. The operational reliability of the motor control circuit 31 can be improved.

  Further, according to the present invention, the FETs 43 and 47 for driving the motor are turned off not based on the voltage drop generated in the PTC thermistors 44 and 48 but based on the decrease in the voltage between the motor terminals of the electric motor 21 caused by the increase in the resistance value of the PTC thermistors 44 and 48. Therefore, the rotation resistance of the support shaft 15 and the sliding resistance of the speed reduction mechanism increase at low temperatures, the resistance of the motor coil of the electric motor 21 decreases, the posture of the vehicle, and the load when the door mirror 11 rotates. Even if the drive current flowing through the electric motor 21 changes due to fluctuations or the like, the lock current can be accurately detected.

  Furthermore, it is possible to prevent the inrush current flowing in the electric motor 21 immediately after startup from being erroneously detected as the lock current.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the present invention is applied to the motor control circuit 31 used for controlling the operation of the electrically retractable door mirror 11, but the present invention is not limited thereto, and the driven body is moved to the first position. The present invention may be applied to a motor control circuit of an electric motor used for other purposes as long as it is a motor control circuit used for an electric motor that is driven to the second position.

  In the embodiment, the electric motor 21 drives the door mirror 11 from the use position to the storage position and from the storage position to the use position, and the motor control circuit 31 controls the electric motor 21 in the normal rotation direction. However, the present invention is not limited to this, and the present invention is applied to an electric motor that drives a driven body only in one direction. May be.

11 Door mirror (driven body)
DESCRIPTION OF SYMBOLS 12 Car 13 Door 14 Stay 15 Support shaft 16 Cover body 17 Mirror plate 18 Remote control unit 21 Electric motor 21a, 21b Motor terminal 31 Motor control circuit 32 Battery (DC power supply)
33 changeover switch (startup switch)
33a 1st switch 33b 2nd switch 34 Control unit 35a, 35b Power supply side terminal 36 Main switch 37 Ground terminal 41 Motor forward rotation side series circuit 42 Motor reverse rotation side series circuit 43 Forward rotation side motor drive FET
44 PTC thermistor on the forward rotation side 45 Diode on the forward rotation side 46 Resistance 47 Motor drive FET on the reverse rotation side
48 PTC thermistor on the reverse side 49 Diode on the reverse side 51 Resistor 52 Capacitor for starting 53, 54 Resistor 61 Motor operation circuit 62 Transistor on the normal rotation side (switching transistor)
63 Reverse-side transistor (switching transistor)
64,65 Resistor 66 Diode 67 Resistor 68 Diode 69 Resistor 71,72 Zener diode

Claims (2)

A motor control circuit connected to an electric motor for driving a driven body from a first position to a second position and controlling the operation of the electric motor;
A start switch connected between the electric motor and a DC power source;
A motor driving FET connected in series with the activation switch between one pole of the DC power source and one terminal of the electric motor;
A starting capacitor connected in parallel with the motor driving FET between one pole of the DC power source and one terminal of the electric motor;
A PTC thermistor connected in series with the motor driving FET and in parallel with the starting capacitor between the motor driving FET and one terminal of the electric motor;
The base is connected between the PTC thermistor and one terminal of the electric motor, the collector is connected to one pole of the DC power supply via the gate of the motor driving FET, and the emitter is the other terminal of the DC power supply. And a switching transistor connected between the other electrode and the other terminal of the electric motor.   2. The motor control circuit according to claim 1, wherein the driven body is an electric retractable door mirror provided in a vehicle, and the electric motor drives the door mirror between a use position and a retracted position. Motor control circuit.

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