JP3891157B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor driving device having a function of limiting a current flowing to a DC motor.

  For example, some electronic throttle systems for automobiles use a DC motor as a drive source for the throttle valve. In this system, in order to speed up the responsiveness of the throttle valve, when the motor is started, current is supplied to the DC motor with 100% duty to increase the operating speed of the throttle valve. Is applied in the reverse direction to brake the DC motor so that the throttle valve is quickly stopped at the target throttle opening. Furthermore, in this system, when the DC motor is locked due to foreign matter biting into the throttle valve, etc., a large current continues to flow through the DC motor, so that the throttle valve does not approach the target throttle opening for a predetermined time. In some cases, it is determined that the motor is locked, and the DC motor is turned off to protect the switching element of the drive control circuit.

  For example, a temporary light lock state due to freezing of water adhering to the throttle valve may recover from the lock state and be able to drive normally if the drive is continued for a while. Therefore, if the time until the DC motor is turned off when the motor is started or braked (the lock judgment time) is too short, the motor will stop immediately even if it is temporarily locked. The trouble which is done occurs. Therefore, it is preferable to set the lock determination time to a certain extent. However, the longer the lock determination time, the longer the time for a large current to flow through the switching element of the drive control circuit. Or a switching element having a small on-resistance (heat generation) and a large chip size is required, which increases the manufacturing cost of the drive control circuit.

Therefore, there is one in which the switching element of the drive control circuit can be reduced in size and cost by limiting the energization current of the DC motor to a certain value or less (see, for example, Patent Document 1). However, in this case, the current is limited even when the motor is started or brakes where a relatively large torque is required, so that the driving torque and braking force are insufficient, and the driving response of the throttle valve is deteriorated. There is a drawback.
JP 9-501817 A

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to reduce the size and cost of the switching element of the drive control circuit without sacrificing the drive response at the time of starting or braking the motor. Another object of the present invention is to provide a motor drive device that can flow a current to a DC motor for a certain period of time in anticipation of recovery to a normal state when the motor is locked.

  By the way, in the normal operation state where the motor lock is not generated, the time required for starting and braking the motor is short. Even if the current flows, the power loss (heat generation) of the switching element of the drive control unit is small, and as the switching element, a large rated element that can drive a large current for a long time, or an element with a small on-resistance and a large chip size is required. And not.

Focusing on this point, according to the motor driving apparatus according to claim 1 of the present invention, in a period corresponding to the activation of the throttle valve, the activation of the throttle valve when the Hare line without limitation of the current flowing through the DC motor When the state where the current value flowing through the DC motor exceeds the first limit value continues for a predetermined time, the current value flowing through the DC motor is limited to the predetermined value. The switching element of the drive control unit can be protected by switching to the second limit value. Therefore, the first limit value can be set to a high current value that does not impair the starting performance, and the switching element can be reduced in size and cost while improving the starting performance.

Further, as in claim 2 , the DC motor may be connected to an H-bridge drive circuit. If it does in this way, the electric current sent through a direct current motor can be sent to both the forward direction and the reverse direction, and both the starting of a direct current motor and the energization of a brake can be performed.

Furthermore, as claimed in claim 3, it is preferable to provide a current detecting means for detecting a current flowing in the DC motor. In this way, it is possible to limit the current while detecting the actual current flowing through the DC motor.

Further, as in claim 4 , the determination means determines whether or not the state limited to the second limit value continues for a certain period of time, and if it is determined that the state is continued for a certain period of time or more, the direct current It is preferable to cut off the power supply to the motor. In this way, it is possible to prevent the DC motor from being energized indefinitely while the DC motor is locked.

Furthermore, as according to claim 5, the desired throttle by the throttle valve control means based on the throttle signal from throttle opening sensor connected to the accelerator signal and throttle valve from an accelerator sensor which is connected to an accelerator pedal of the vehicle You may make it control to a valve opening degree. In this way, it is possible to improve the drive response of the system in which the throttle valve is driven by a DC motor and to reduce the cost of the drive control unit of the DC motor.

In this case, when the difference between the actual throttle valve opening degree based on the desired throttle valve opening degree and the throttle signal state equal to or greater than a predetermined value has continued longer set time than than the predetermined time, the DC motor It is recommended to cut off the power to. In this way, it is possible to prevent the DC motor from being energized indefinitely while the electronic throttle is locked.

Further, as in claim 6 , as in the case of claim 1, if the current value of the brake energization is limited by the first limit value even during the period of brake energization, What is necessary is just to make it restrict | limit to the 2nd limit value lower than this limit value.
The seventh to tenth aspects are the same as the second to fifth aspects.

    [Example 1]

  Hereinafter, an embodiment (1) in which the present invention is applied to an electronic throttle system will be described with reference to FIGS. First, a schematic configuration of the entire system will be described with reference to FIG. A throttle valve 12 provided in the middle of the intake pipe 11 of the engine is driven by a DC motor 13. The throttle valve 12 is urged in a closing direction by a return spring (not shown), and is forcibly returned to a substantially closed position to the extent that the throttle valve 12 can be idle when a failure occurs. Therefore, the DC motor 13 needs a torque that can drive the throttle valve 12 in the opening direction against the return spring. Therefore, the DC motor 13 is energized at the time of start-up from the stop state or braking at the operation state. It is necessary to secure torque by increasing the current. The opening degree of the throttle valve 12 is detected by a throttle opening degree sensor 14, and the detection signal is taken into the engine control circuit 15. The engine control circuit 15 functions as throttle valve control means for controlling the ignition timing and the fuel injection amount and controlling the opening degree of the throttle valve 12.

  On the other hand, the depression amount of the accelerator pedal 16 is detected by the accelerator sensor 17, and the detection signal is taken into the engine control circuit 15. The engine control circuit 15 outputs drive command signals A1 to A4 corresponding to the accelerator depression amount taken from the accelerator sensor 17 to the drive control circuit 18, and the DC motor 13 is driven by the drive control circuit 18, whereby the throttle valve 12 is driven to a target throttle opening set according to the accelerator depression amount. The drive control circuit 18 and the engine control circuit 15 (throttle valve control means) constitute a drive control unit referred to in the claims.

  The drive control circuit 18 includes a drive logic circuit 19 to which four drive command signals A 1 to A 4 are input from the engine control circuit 15, an H-bridge type drive circuit 20 that drives the DC motor 13, and a current that flows through the DC motor 13. And a current detection circuit 21 for detecting. The drive control circuit 18 starts and brakes the current flowing to the DC motor 13 without limiting the current flowing to the DC motor 13 for a predetermined period corresponding to starting and braking. In this case, the current limit value smaller than the current flowing is limited. Therefore, if the motor is locked, the current flowing through the DC motor 13 is limited by the current limit value. If the motor lock is released during the current limit operation, the current limit is released. However, if the opening degree of the throttle valve 12 does not approach the target throttle opening degree even after the predetermined period has elapsed, the engine The control circuit 15 determines that the motor is locked and sets all the drive command signals A1 to A4 to a low level to cut off the energization to the DC motor 13.

  Next, a detailed configuration of the drive control circuit 18 will be described with reference to FIG. The drive circuit 20 is configured by connecting four switching elements, for example, MOSFETs 22 to 25 in an H-bridge type, and a direct current is connected between an intermediate connection point of the right MOSFETs 22 and 25 and an intermediate connection point of the left MOSFETs 23 and 24. A positive terminal and a negative terminal of the motor 13 are connected. The high side of the drive circuit 20 is connected to the positive terminal side of a power source 26 such as a battery, and the current detection circuit 21 (current detection means) is connected to the low side of the drive circuit 20. The current detection circuit 21 includes a current detection resistor 27 connected between the low side of the drive circuit 20 and the ground side, and a differential amplifier circuit 28 that amplifies the potential difference between both ends of the current detection resistor 27. .

  Next, a detailed configuration of the drive logic circuit 19 will be described. The output of the current detection circuit 21 (voltage corresponding to the energization current of the DC motor 13) is input to the + input terminal of the comparator 30 and compared with the reference voltage Vref input to the − input terminal. The reference voltage Vref is set to a voltage corresponding to the current limit value during the current limit operation, and this current limit value is a low current limit value that does not damage the MOSFETs 22 to 25 even if energization is continued to some extent when the motor is locked. (In other words, the current limit value is lower than the current generated by starting or braking). Each time the energization current of the DC motor 13 exceeds the current limit value, the output of the comparator 30 is inverted to a high level, and this high level signal is input to the set terminals S of the two set priority type RS latches 31 and 32. . The outputs of the timers 33 and 34 are input to the reset terminals R of the RS latches 31 and 32, respectively.

  When one of the RS latches 31 receives a high level signal indicating that the energization current of the DC motor 13 has exceeded the current limit value from the comparator 30 to the set terminal S, the RS latch 31 performs a set operation and outputs the AND gate 39 from the output terminal Q. A high level signal is output to both the timer 33 and the timer 33. The timer 33 is a timer for setting a time for temporarily turning off the energization of the DC motor 13 every time the energization current of the DC motor 13 exceeds the current limit value during the current limiting operation. When a high level signal is input to the timer 33, the count operation of the internal counter is started, and when the preset time is finished, the high level signal is output from the output terminal Q to the reset terminal R of the RS latch 31. . As a result, the RS latch 31 performs a reset operation and outputs a low level signal from the output terminal Q to both the AND gate 39 and the timer 33. When the low level signal is input, the timer 33 resets the internal counter and inverts the output of its output terminal Q to the low level.

  As described above, by forming a closed loop by the RS latch 31 and the timer 33, the output terminal Q of the RS latch 31 is connected to the DC motor 13 every time the energization current of the DC motor 13 exceeds the current limit value during the current limiting operation. A high level signal is output for a time during which the energization is temporarily turned off (see FIG. 4).

  The output of the output terminal Q of the timer 34 is input to the reset terminal R of the other RS latch 32. This timer 34 receives the output of its output terminal Q at the input terminal T via the delay circuit 35 and the inverter 36. As a result, when the output of the output terminal Q of the timer 34 is inverted to the low level, the output of the delay circuit 35 is inverted to the low level with a delay of a certain time, and at the same time, from the inverter 36 to the input terminal T of the timer 34. A high level signal is input. Along with this, the timer 34 outputs a high level signal from the output terminal Q when the internal counter starts counting and ends counting at a preset time t34. The high level signal is input to the inverter 36 with a predetermined time delay by the delay circuit 35, and the low level signal is input from the inverter 36 to the input terminal T of the timer 34. Thereby, the timer 34 resets the internal counter and inverts the output of the output terminal Q to the low level. As described above, by forming a closed loop of the timer 34, the delay circuit 35, and the inverter 36, the output terminal Q of the timer 34 is set to the high level for the delay time of the delay circuit 35 every fixed time t34 set in the timer 34. A signal is output (see FIG. 3).

  The output of the output terminal Q of the timer 34 is input to the reset terminal R of the RS latch 32 and the clock input terminal CK of the D flip-flop (DFF) 37. The output terminal Q of the RS latch 32 is connected to the data input terminal D of the D flip-flop 37.

  When the high level signal indicating that the energization current of the DC motor 13 exceeds the current limit value is input from the comparator 30 to the set terminal S, the RS latch 32 performs the set operation and the output terminal Q to the D flip-flop 37. A high level signal is output to the data input terminal D. Further, the RS latch 32 performs a reset operation by a high level signal input from the timer 34 to the reset terminal R every fixed time t34, and outputs a low level signal from the output terminal Q to the data input terminal D of the D flip-flop 37. To do.

  On the other hand, the D flip-flop 37 outputs the output level of the output terminal Q of the RS latch 32 input to the data input terminal D at the timing when the output level of the timer 34 input to the clock input terminal CK rises from the low level to the high level. Is stored and held, and a signal level corresponding to the stored level is output from the output terminal Q of the D flip-flop 37 to the input terminal T of the timer 38.

  As described above, when the RS latch 32 and the D flip-flop 37 operate, the output of the D flip-flop 37 when the energizing current of the DC motor 13 exceeds the current limit value within the time t34 set in the timer 34. A high level signal is output from the terminal Q to the input terminal T of the timer 38.

  In this case, the time t34 set in the timer 34 is a time during which the energization to the DC motor 13 is temporarily turned off when the energization current of the DC motor 13 exceeds the current limit value during the current limiting operation, and the energization is resumed after the temporary energization is turned off. The time until the current limit value is exceeded again is set to be longer than the total time. Thereby, the output of the output terminal Q of the D flip-flop 37 is maintained at a high level during the current limiting operation.

  On the other hand, when the timer 38 receives a high level signal indicating that the energization current of the DC motor 13 continues to exceed the current limit value from the output terminal Q of the D flip-flop 37, the internal counter starts counting operation. Then, the times t1a and t2a (see FIG. 3) during which the energization current continues to exceed the current limit value are counted. Thereafter, when the timer 38 finishes counting a preset time t38 (see FIG. 4), a high level signal (current limiting operation start signal) is output from the output terminal Q to one input terminal of the AND gate 39. When the timer 38 receives from the output terminal Q of the D flip-flop 37 a low level signal indicating that the energization current of the DC motor 13 is less than or equal to the current limit value, the timer 38 resets the internal counter and outputs the output terminal Q. A low level signal is output from Q to one input terminal of the AND gate 39.

  In this case, the time t38 set in the timer 38 determines the timing for starting the current limiting operation when the time for starting energization or braking of the DC motor 13 becomes longer, and the time t38 is the start during normal operation. The time is set slightly longer than the time of energization and braking. As a result, as shown in FIG. 3, in the start-up energization and braking during normal operation, the actual throttle opening approaches the target throttle opening before the count times t1a and t2a of the internal counter of the timer 38 reach the time t38. Since the start energization and the brake are finished, the current limiting operation does not work, the start and the brake are performed in a state where the energization current of the DC motor 13 is not limited, and the drive responsiveness at the start and the brake is improved.

  The AND gate 39 outputs a high level only when both the output of the timer 38 and the output of the RS latch 31 input to both terminals are at a high level. As a result, the output of the AND gate 39 is maintained at a low level during normal operation (see FIG. 3), and during the current limit operation, the energization of the DC motor 13 is temporarily performed every time the energization current of the DC motor 13 exceeds the current limit value. Therefore, the output of the AND gate 39 is inverted to the high level only during the time of turning off (see FIG. 4).

  The output of the AND gate 39 is input to the OR gates 40 and 41 and also input to the AND gates 43 and 44 via the inverter 42. Drive command signals A1 to A4 output from the engine control circuit 15 are input to the OR gates 40 and 41 and the AND gates 43 and 44, respectively. The outputs of the OR gates 40 and 41 are applied to the gates of the high-side MOSFETs 22 and 23 via the protection control circuit 45 and the pre-drivers 46 and 47. As a result, the high-side MOSFETs 22 and 23 are turned on when the high-side drive command signals A1 and A2 are at the high level, and the energization is temporarily turned off when the output of the AND gate 39 is at the high level (current limiting operation). Also, the high-side MOSFETs 22 and 23 are turned on, and the energy remaining in the coil of the DC motor 13 during the current-off operation is circulated through the circulation path 50.

  On the other hand, the outputs of the AND gates 43 and 44 are applied to the gates of the low-side MOSFETs 24 and 25 via the protection control circuit 45 and the pre-drivers 48 and 49. As a result, the low-side MOSFETs 24 and 25 are turned on when the low-side drive command signals A3 and A4 are at a high level and the output of the inverter 42 is at a high level. During normal operation, as shown in FIG. 3, since the output of the AND gate 39 is maintained at a low level, the output of the inverter 42 is maintained at a high level. As a result, during normal operation, the low-side drive command signals A3 and A4 pass through the AND gates 43 and 44 as they are, and when the low-side drive command signals A3 and A4 are at the high level, the low-side MOSFETs 24 and 25 are turned on, and the DC The motor 13 is energized.

  Further, during the current limiting operation, as shown in FIG. 4, the output of the AND gate 39 is set to the high level for the time during which the energization of the DC motor 13 is temporarily turned off whenever the energizing current of the DC motor 13 exceeds the current limit value. Therefore, every time the energization current of the DC motor 13 exceeds the current limit value, the output of the inverter 42 is inverted to a low level for a time during which the energization of the DC motor 13 is temporarily turned off. As a result, even if the low-side drive command signal A3 (or A4) is at a high level, the output of the AND gate 43 (or 44) is temporarily low every time the energization current of the DC motor 13 exceeds the current limit value. Become a level. Thereby, at the time of the current limiting operation, the low-side MOSFET 24 (or 25) is temporarily turned off every time the energization current of the DC motor 13 exceeds the current limit value, and the energization current of the DC motor 13 is suppressed below the current limit value. It is done.

  The protection control circuit 45 prevents a so-called through current in which an overcurrent flows when the high-side and low-side MOSFETs 22 to 25 connected to both terminals of the DC motor 13 are simultaneously turned on, or an overcurrent is generated. Logic such as overcurrent protection control for forcibly turning off the MOSFETs 22 to 25 when flowing is included.

  Next, the normal operation will be described with reference to FIG. During a period t0 in which the throttle opening is not changed while the throttle 12 is stopped, the engine control circuit 15 maintains the drive command signal A1 at a high level in order to hold the throttle valve 12 at a constant opening against the return spring. In addition, by switching the drive command signal A3 between a high level and a low level at a predetermined duty ratio, the low-side left MOSFET 24 is turned on / off at a predetermined duty ratio while the high-side right MOSFET 22 is kept on. Then, a current is passed through the DC motor 13 in the direction of arrow B (positive direction) in FIG. 2 at a predetermined duty ratio to keep the throttle valve 12 at a constant opening.

  During the holding energization period t0, each time the drive command signal A3 becomes low level, the drive command signal A2 is switched to high level only during the low level period, so that the high side The left MOSFET 23 is turned on, and the energy remaining in the coil of the DC motor 13 is circulated through the circulatory path 50.

  Thereafter, when the accelerator pedal 16 is depressed and the target throttle opening changes, the engine control circuit 15 starts the DC motor 13 at a 100% duty ratio as follows, and the actual throttle opening is set to the target throttle opening. Start energization to bring During the start-up energization period t1, the drive command signals A1 and A3 are held at a high level, whereby both the high-side right side MOSFET 22 and the low-side left side MOSFET 24 are held in an on state, and the direct current motor 13 receives the arrow B in FIG. A current is flowed in the direction (positive direction) at a duty ratio of 100%, and the starting torque is increased to increase the operating speed of the throttle valve 12. Therefore, the current limiting operation does not work during the startup energization period t1 during normal operation. This is because the startup count time t1a (time when the energization current exceeds the current limit value) by the internal counter of the timer 38 does not reach the time t38 when the current limit operation is started.

  When the engine control circuit 15 detects that the actual throttle opening is approaching a predetermined range preset to the target throttle opening during the start energization period t1, the engine control circuit 15 ends the start energization period t1 and Brake energization is performed to brake the throttle valve 12 and stop at the target throttle opening. During this braking period t2, the MOSFET 23 on the left side on the high side and the MOSFET 25 on the right side on the low side are both turned on, and a current is supplied to the DC motor 13 in the direction of arrow C (reverse direction) in FIG. The brake force is increased to quickly stop the throttle valve 12 at the target throttle opening. Therefore, the current limiting operation does not work during the brake period t2 during normal operation. This is because the count time t2a during braking by the internal counter of the timer 38 (the time during which the energization current exceeds the current limit value) does not reach the time t38 when the current limit operation is started. In addition, after the throttle valve 12 stops at the target throttle opening (period t3), the same holding energization control as that before the DC motor 13 is started (period t0) is performed.

  Next, the operation when the motor is locked will be described with reference to FIG. FIG. 4 shows an operation example when the motor lock is generated at the timing tx immediately after the start-up energization with the 100% duty ratio is started. When the motor lock occurs, even if the start-up energization with the 100% duty ratio is continued, the start-up energization is continued for a while because the throttle valve 12 does not approach the target throttle opening. As a result, when the count time t1a at the time of activation by the internal counter of the timer 38 (time when the energization current exceeds the current limit value) reaches the time t38 when the current limit operation is started, the current limit operation is started as follows. Is done.

  When the startup count time t1a by the internal counter of the timer 38 reaches the time t38 when the current limiting operation is started, the output of the timer 38 is inverted to a high level. The AND gate 39 to which the output of the timer 38 and the output of the RS latch 31 are input is a period during which the output of the RS latch 31 is at a high level (that is, every time the energization current of the DC motor 13 exceeds the current limit value). It is reversed to the high level only for the time when power is temporarily turned off. Thus, every time the AND gate 39 is inverted to a high level, the high level signal is inverted to a low level signal by the inverter 42 and input to the AND gate 43. For this reason, even if the low-side drive command signal A3 is at a high level, the output of the AND gate 43 temporarily becomes a low level whenever the energization current of the DC motor 13 exceeds the current limit value. As a result, during the current limiting operation, the low-side MOSFET 24 is temporarily turned off every time the energization current of the DC motor 13 exceeds the current limit value, and the energization current of the DC motor 13 is suppressed below the current limit value.

  During this current limiting operation period, the output of the OR gate 41 is inverted to a high level during the off period of the low-side MOSFET 24 (the high-level period of the AND gate 39), and the MOSFET 23 on the left side of the high-side is turned on. The energy remaining in the coil is circulated through the circulation path 50.

  During this current limiting operation period, when it is detected that the motor lock is released and the throttle valve 12 approaches the target throttle opening within a predetermined range set in advance, the process shifts to energization of the brake. When the energization of the brake is started, as shown in FIG. 3, the energization current of the DC motor 13 temporarily falls below the current limit value, so that the output of the D flip-flop 37 is inverted to a low level and the timer 38 Is reset, and the output of the timer 38 is inverted to a low level. As a result, the current limiting operation is released, and a current is supplied to the DC motor 13 in the direction of arrow C (reverse direction) in FIG. 2 at a 100% duty ratio, and the movement of the throttle valve 12 is braked.

  On the other hand, if the opening degree of the throttle valve 12 does not approach the target throttle opening degree even if the current limiting operation is continued to some extent, the energization of the DC motor 13 is cut off by the engine control circuit 15 as follows. The The engine control circuit 15 counts the time during which the state where the difference between the actual throttle opening and the target throttle opening is equal to or greater than a predetermined value at the time of start-up, and determines that the motor is locked when the time reaches a predetermined time t4. Thus, all the drive command signals A1 to A4 are set to the low level to cut off the energization to the DC motor 13.

  Alternatively, the engine control circuit 15 inputs a current limit operation monitor signal indicating that it is during the current limit operation period output from the timer 38 indicated by a broken line in FIG. The time during which the state of the high level shown is continued is counted, and when that time reaches a predetermined time t5, all the drive command signals A1 to A4 are set to the low level to cut off the energization to the DC motor 13. Anyway. The operation example in FIG. 4 is an example when the motor lock is generated during the start-up energization, but the same control is performed when the motor lock occurs during the brake.

  In the embodiment (1) described above, during the start-up energization period (brake energization period) set to a time slightly longer than the start-up energization and brake time during normal operation of the DC motor 13, the energization current of the DC motor 13 is set. Since the start (brake) is performed without restricting the current, the start torque (brake force) can be increased compared to the case where the current is limited from the start (start of braking), and the drive response of the throttle valve 12 is improved. Can do.

In addition, if the state where the energization current of the DC motor 13 is larger than the current limit value continues for a preset time t38 during the start energization period (brake energization period), it is determined that the motor may be locked. Since the energization current is limited to a low current value, the current flowing through the MOSFETs 22 to 25 can be limited to a low current value, and the heat generation of the MOSFETs 22 to 25 can be reduced. As a result, even when the motor is locked, it is possible to allow a current to flow through the DC motor 13 for a certain length of time. When the motor is temporarily locked, the driving torque can be continuously applied for a while to restore the normal state. . In addition, the MOSFETs 22 to 25 can be reduced in size and cost because the heat generation of the MOSFETs 22 to 25 is small. As a result, it is possible to satisfy the demand for cost reduction of the drive circuit 20 without sacrificing the drive responsiveness of the throttle valve 12.
[Example 2]

  Next, an embodiment (2) applied to a system in which the torque of the DC motor 13 has a margin will be described with reference to FIGS. In the embodiment (1), the current is not limited during the start-up energization period (brake energization period). In the present embodiment (2), the current passed through the DC motor 13 during the start-up energization period (brake energization period). If the start (brake) is performed with a high current value that does not impair the start performance (brake performance), and there is a possibility of motor lock, the limit value of the current that flows to the DC motor 13 after the period has elapsed Is switched to a lower current limit value. Hereinafter, a different part from the said embodiment (1) is demonstrated.

  In the embodiment (1), the reference voltage Vref (voltage corresponding to the current limit value) input to the −input terminal of the comparator 30 is a fixed value. However, in the embodiment (2), the −input terminal of the comparator 30 is used. A reference voltage switching circuit 51 is provided for switching the reference voltage Vref input to the two stages of a voltage Vref (H) corresponding to a high current limit value and a voltage Vref (L) corresponding to a low current limit value. The reference voltage switching circuit 51 has three resistors 52 to 54 connected in series between the power supply voltage Vcc side and the ground side, and a reference voltage switching circuit is connected to both ends of one resistor 54 on the ground side. The collector and emitter of the transistor 55 are connected, and the intermediate connection point of the resistors 52 and 53 is connected to the negative input terminal of the comparator 30.

  In the embodiment (1), the output of the timer 38 and the output of the RS latch 31 are input to the AND gate 39. However, in the embodiment (2), the AND gate 39 is eliminated and the output of the RS latch 31 is output. Is directly input to the OR gates 40 and 41, and the output of the RS latch 31 is also input to the AND gates 43 and 44 via the inverter 42. The output terminal Q of the timer 38 is connected to the base of the reference voltage switching transistor 55, and the reference voltage Vref (current limit value) is switched by the output of the timer 38. Other configurations are the same as those in the embodiment (1).

  Next, the normal operation will be described with reference to FIG. Usually, since the output of the timer 38 is maintained at a low level, the reference voltage switching transistor 55 is maintained in the OFF state. In this state, the reference voltage Vref input from the reference voltage switching circuit 51 to the comparator 30 is maintained at a voltage Vref (H) corresponding to a high current limit value. Here, assuming that the resistance values of the three resistors 52 to 54 of the reference voltage switching circuit 51 are R52 to R54, Vref (H) is calculated by the following equation. Vref (H) = Vcc × (R53 + R54) / (R52 + R53 + R54) This high reference voltage Vref (H) is set such that the current limit value is a high current value that does not impair the starting performance (braking performance). .

  When the accelerator pedal 16 is depressed and the target throttle opening changes, the start energization is performed, the actual throttle opening is brought close to the target throttle opening, and the brake is energized, as in the first embodiment. Then, the throttle valve 12 is stopped at the target throttle opening. At the start of the start-up energization, a current is supplied to the DC motor 13 at a 100% duty ratio. During this start-up energization period t1, the high current limit set by the reference voltage Vref (H) at which the energization current of the DC motor 13 is high. Each time the value is exceeded, the output of the RS latch 31 becomes high level for the time set by the timer 33, and this high level signal is inverted to a low level signal by the inverter 42 and input to the AND gate 43. For this reason, even if the low-side drive command signal A3 is at a high level, the output of the AND gate 43 temporarily becomes a low level every time the energization current of the DC motor 13 exceeds a high current limit value. As a result, the low-side MOSFET 24 is temporarily turned off every time the energization current of the DC motor 13 exceeds the high current limit value, and the energization current of the DC motor 13 is suppressed below the high current limit value.

  During this current limiting operation, the output of the OR gate 41 is inverted to a high level during the off period of the low-side MOSFET 24 (high level period of the RS latch 31), and the high-side left MOSFET 23 is turned on. The energy remaining in the coil is circulated through the circulation path 50.

  When it is detected by such activation energization that the throttle valve 12 has approached the target throttle opening within a predetermined range set in advance, the activation energization period t1 is terminated and the brake energization is performed. At the start of braking, a current is passed through the DC motor 13 in the reverse direction at a 100% duty ratio. During this braking energization period t2, the energizing current of the DC motor 13 is set at a high reference voltage Vref (H). Whenever the limit value is exceeded, the output of the RS latch 31 becomes a high level for the time set by the timer 33, and, similar to the start energization described above, every time the energization current of the DC motor 13 exceeds the high current limit value, And the energization current of the DC motor 13 is suppressed to a high current limit value or less.

  Note that, similarly to the embodiment (1), after the throttle valve 12 stops at the target throttle opening (period t3), the same holding energization control as that before the DC motor 13 is started (period t0) is performed.

  Next, the operation when the motor is locked will be described with reference to FIG. FIG. 7 is an operation example when the motor lock occurs at the time tx immediately after the start-up energization is started. In this case, even if the start-up energization limited by the high current limit value is performed, the start-up energization is continued for a while because the throttle valve 12 does not approach the target throttle opening. Thereby, when the count time t1a at the time of activation by the internal counter of the timer 38 (time when the energization current exceeds the high current limit value) reaches the time t38, the current limit value is lowered as follows.

  When the count time t1a at startup by the internal counter of the timer 38 reaches the time t38, a high level signal is output from the timer 38 to the base of the reference voltage switching transistor 55. Thereby, the transistor 55 is turned on, both ends of one resistor 54 of the reference voltage switching circuit 51 are short-circuited, and the reference voltage Vref input from the reference voltage switching circuit 51 to the comparator 30 corresponds to a low current limit value. The voltage is switched to Vref (L). This low reference voltage Vref (L) is calculated by the following equation.

  Vref (L) = Vcc × R53 / (R52 + R53) The low current limit value set by the low reference voltage Vref (L) is a low current that does not damage the MOSFETs 22 to 25 even if energization is continued to some extent when the motor is locked. It is set to be a value.

  In this way, when the reference voltage Vref input to the comparator 30 is switched to the voltage Vref (L) corresponding to the low current limit value, every time the energization current of the DC motor 13 exceeds the low current limit value, RS The output of the latch 31 becomes high level for the time set by the timer 33, and this high level signal is inverted to a low level signal by the inverter 42 and input to the AND gate 43. As a result, the low-side MOSFET 24 is temporarily turned off each time the energization current of the DC motor 13 exceeds a low current limit value, and the energization current of the DC motor 13 is suppressed to a value equal to or less than the low current limit value. At this time, the MOSFET 23 on the left side of the high side is turned on during the off period of the MOSFET 24 on the low side, and the energy remaining in the coil of the DC motor 13 is circulated through the circulation path 50.

  If the opening degree of the throttle valve 12 does not approach the target throttle opening degree even if the current limiting operation with such a low current limiting value is continued to some extent, the DC motor 13 is processed in the same manner as in the first embodiment (1). Shut off the power to the. The operation example of FIG. 7 is an example when the motor lock is generated during the energization of starting, but the same control is performed when the motor lock is generated during the braking. In the embodiment (2) described above, the same effects as those in the embodiment (1) can be obtained.

  In the embodiments (1) and (2), the current limiting operation is controlled by the drive logic circuit 19 configured by hardware. However, the current limiting operation is controlled by program control by a microcomputer. Also good. Further, the current limit value may be reduced to two or more levels as time elapses during the period of the current limit operation performed when there is a possibility of motor lock.

In the embodiments (1) and (2), when the motor lock occurs during the brake energization period, the current limiting operation is performed after a predetermined period of time, as in the case where the motor lock occurs during the start energization period. Although it is performed, the current limiting operation may be performed only in one of the start and the brake. Further, the H-bridge type drive circuit 20 may be configured with switching elements other than the MOSFETs 22 to 25.
In addition, the application range of the present invention is not limited to the electronic throttle system, and can be implemented by applying the present invention to various devices using a DC motor as a drive source.

Schematic configuration diagram of the entire system showing an embodiment (1) in which the present invention is applied to an electronic throttle system Electrical circuit diagram of drive control circuit of embodiment (1) The time chart which shows the signal waveform of each part at the time of normal operation of embodiment (1) The time chart which shows the signal waveform of each part at the time of the motor lock of embodiment (1) Electrical circuit diagram of drive control circuit of embodiment (2) The time chart which shows the signal waveform of each part at the time of normal operation of embodiment (2) The time chart which shows the signal waveform of each part at the time of the motor lock of embodiment (2)

Explanation of symbols

12 ... Throttle valve,
13 ... DC motor,
14 ... Throttle opening sensor,
15 ... Engine control circuit (drive control unit, throttle valve control means),
16 ... accelerator pedal,
17 ... accelerator sensor,
18 ... Drive control circuit (drive control unit),
19 ... Drive logic circuit,
20 ... Drive circuit,
21 ... Current detection circuit (current detection means),
22-25 ... MOSFET (switching element),
30 ... Comparator,
33, 34 ... timer,
35 ... delay circuit,
38 ... Timer,
51. Reference voltage switching circuit,
52-54 ... resistance,
55 ... Transistor.

Claims (10)

A drive control unit that drives the throttle valve to a desired throttle valve opening by driving a DC motor,
When the desired throttle valve opening changes in the state where the throttle valve is held at a constant opening by supplying a current to the DC motor in a stopped state, the drive control unit determines the actual throttle valve opening Driving the throttle valve so as to bring the actual throttle valve opening closer to the desired throttle valve opening by controlling the DC motor by supplying a current to the DC motor based on the deviation from the desired throttle valve opening. To do,
Further, when the drive control unit controls the DC motor and drives the throttle valve in a period corresponding to the driving of the throttle valve , a current flowing through the DC motor is first limited immediately after the start of the period. When the current value flowing through the DC motor exceeds the first limit value is detected for a predetermined time, the current value flowing through the DC motor is changed to the first value. The motor drive device is characterized by being limited to a second limit value lower than the limit value . The motor drive device according to claim 1 ,
The DC motor is connected to an H-bridge driving circuit. In the motor drive device according to claim 1 or 2 ,
A motor drive device comprising: current detection means for detecting a current flowing through the DC motor. In the motor drive unit according to any one of claims 1 to 3 ,
Comprising a determining means for determining whether current flowing to the DC motor is continuing the second limit value to Restricted is time or state, it has continued over time with this judgment means A motor drive device characterized by shutting off the energization to the DC motor when judged. In the motor drive device according to any one of claims 1 to 4 ,
The drive control unit includes a throttle for controlling a throttle valve opening to a desired throttle valve based on an accelerator signal from an accelerator sensor connected to an accelerator pedal of a vehicle and a throttle signal from a throttle opening sensor connected to the throttle valve. Valve control means are included,
The desired state in which the difference between the actual throttle valve opening based on the throttle valve opening degree and the throttle signal is greater than or equal to a predetermined value, if continued longer set time than than the predetermined time, the direct current motor The motor drive device characterized by interrupting energization to. A drive control unit that drives the throttle valve to a desired throttle valve opening by driving a DC motor,
When the desired throttle valve opening changes in the state where the throttle valve is held at a constant opening by supplying a current to the DC motor in a stopped state, the drive control unit determines the actual throttle valve opening Driving the throttle valve so as to bring the actual throttle valve opening closer to the desired throttle valve opening by controlling the DC motor by supplying a current to the DC motor based on the deviation from the desired throttle valve opening. To do,
The drive control unit applies a brake to the direct current motor when the actual throttle valve opening approaches a predetermined range set in advance with respect to the desired throttle valve opening,
Furthermore, when the drive control unit controls the DC motor and brakes the throttle valve in a period corresponding to the brake, immediately after the start of the period , the current flowing through the DC motor is set to the first limit value. When it is detected that the state where the current value flowing through the DC motor exceeds the first limit value continues for a predetermined time, the current value flowing through the DC motor is changed to the first limit value. The motor drive device is characterized by being limited to a second limit value lower than the value . In the motor drive device according to claim 6,
The DC motor is connected to an H-bridge driving circuit. In the motor drive device according to claim 6 or 7,
A motor drive device comprising: current detection means for detecting a current flowing through the DC motor. In the motor drive device according to any one of claims 6 to 8,
A determination means for determining whether or not a state in which the value of the current flowing through the DC motor is limited to the second limit value continues for a certain period of time; A motor drive device characterized by shutting off the energization to the DC motor when judged. In the motor drive device according to any one of claims 6 to 9,
The drive control unit includes a throttle for controlling a throttle valve opening to a desired throttle valve based on an accelerator signal from an accelerator sensor connected to an accelerator pedal of a vehicle and a throttle signal from a throttle opening sensor connected to the throttle valve. Valve control means are included,
When the state in which the difference between the desired throttle valve opening and the actual throttle valve opening based on the throttle signal is equal to or greater than a predetermined value continues for a set time longer than the predetermined time, the DC motor The motor drive device characterized by interrupting energization to.

Images