JP5966605B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus including an electric motor that applies a steering assist force to a steering mechanism to reduce a driver's steering burden.

Conventionally, as a steering device, a driver calculates a current command value based on a steering torque for steering a steering wheel, and performs feedback control based on a deviation between the calculated current command value and a drive current detection value of an electric motor. 2. Description of the Related Art An electric power steering apparatus that gives steering assist force to a steering mechanism by driving and controlling an electric motor has been widespread.
As a control device for such an electric power steering device, for example, there is a technique described in Patent Document 1. In this technique, when it is detected that the power supply voltage of the MCU that calculates the current command value is low, a reset signal is output to the MCU and the operation of the MCU is automatically stopped. As a result, the MCU is prevented from operating outside the guaranteed operating voltage range, and the system operation is prevented from becoming unstable due to the MCU operation becoming unstable.

JP 2008-13146 A

However, in the technique described in the above-mentioned Patent Document 1, when a failure occurs in the reset signal, or when a normal reset signal can be generated, a signal fixing failure occurs on the side where the MCU operation cannot be stopped. In such a case, the MCU operation cannot be stopped.
Therefore, an object of the present invention is to provide an electric power steering apparatus that can appropriately shift the system to the safe side when an abnormality occurs in the power supply voltage.

  In order to solve the above problems, an electric power steering apparatus according to the present invention includes an electric motor that applies a steering assist force to a steering system, and a control calculation that calculates a current command value for driving and controlling the electric motor. An electric power steering apparatus comprising: a circuit; and a drive circuit that drives the electric motor based on a current command value calculated by the control arithmetic circuit, wherein the power supply voltage supplied to the control arithmetic circuit is monitored When the power supply voltage monitoring means and the power supply voltage monitoring means detect that the power supply voltage is out of a predetermined set voltage range, the control operation circuit and the drive circuit are stopped. And a stop signal output means for outputting different stop signals.

  Thus, when an abnormality in the power supply voltage is detected, different stop signals are output to the control arithmetic circuit (microcomputer) and the drive circuit (gate drive circuit). Therefore, for example, even when the control arithmetic circuit cannot be stopped normally by the stop signal output to the control arithmetic circuit, the drive circuit can be stopped by the stop signal output to the drive circuit, and the system is shifted to the safe side. be able to.

In the above, the set voltage range is an operation guarantee voltage range in which the control arithmetic circuit can operate normally.
As a result, when the power supply voltage deviates from the guaranteed operation voltage range in which the control arithmetic circuit can operate normally, it can be determined that an abnormality in the power supply voltage has occurred and a stop signal can be output. it can. Therefore, it is possible to reliably prevent the control arithmetic circuit from operating outside the guaranteed operating voltage range.

Further, in the above, the power supply generating means for generating a stabilized power supply voltage having a preset set voltage value from an input power supply and supplying the stabilized power supply voltage to the control arithmetic circuit as the power supply voltage is provided, and the upper limit of the guaranteed operation voltage range The voltage value is set to a predetermined voltage value on a higher voltage side than the set voltage value.
Thereby, even when the power supply voltage becomes abnormal toward the high voltage side, the control arithmetic circuit and the drive circuit can be appropriately stopped. In addition, since the upper limit voltage value of the guaranteed operation voltage range is set with reference to the set voltage value of the stabilized power supply voltage, a voltage abnormality can be detected appropriately.

Further, in the above, a power supply generating means for generating a stabilized power supply voltage having a preset set voltage value from an input power supply and supplying the power supply voltage to the control arithmetic circuit as the power supply voltage is provided, and the lower limit of the guaranteed operation voltage range The voltage value is set to a predetermined voltage value on a lower voltage side than the set voltage value.
Thereby, even when the power supply voltage becomes abnormal toward the low voltage side, the control arithmetic circuit and the drive circuit can be appropriately stopped. In addition, since the lower limit voltage value of the guaranteed operation voltage range is set with reference to the set voltage value of the stabilized power supply voltage, a voltage abnormality can be detected appropriately.

  In the electric power steering apparatus of the present invention, when an abnormality in the power supply voltage is detected, different stop signals are output to the control arithmetic circuit and the drive circuit, respectively, so that the control arithmetic circuit and the drive circuit are stopped. Therefore, it is possible to improve the reliability of the operation stop function when the power supply voltage is abnormal. In this way, the system can be appropriately shifted to the safe side.

1 is an overall configuration diagram showing an electric power steering apparatus according to the present invention. It is a block diagram which shows the structure of a control unit. It is a block diagram which shows the specific structure of a control arithmetic unit and a power supply circuit part. It is a block diagram which shows the modification of a power supply circuit part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an electric power steering apparatus according to the present invention.
In the figure, reference numeral 1 denotes a steering wheel, and a column shaft 2 of the steering wheel 1 is connected to a tie rod 6 of a steering wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5.

The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering wheel 1, and a motor 40 that assists the steering force of the steering wheel 1 is connected to the column shaft 2 via the reduction gear 3. . The motor 40 is an electric motor, and a three-phase brushless motor is applied here.
The control unit 30 operates when power is supplied from a vehicle-mounted battery 14 (for example, the rated voltage is 12V). The negative electrode of the battery 14 is grounded, and the positive electrode thereof is connected to the control unit 30 via the ignition key 11 for starting the engine, and is directly connected to the control unit 30 without passing through the ignition key 11.
As described above, the control unit 30 is supplied with electric power from the battery 14 and also receives the ignition key signal IGN via the ignition key 11.

Further, the control unit 30 inputs the steering torque Ts detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and calculates a steering assist command value (current command value) I based on these. . Based on the calculated steering assist command value I, the current supplied to the motor 40 is controlled.
FIG. 2 is a block diagram showing the configuration of the control unit 30.
In the three-phase brushless motor 40, as shown in FIG. 2, one end of each of the a-phase, b-phase, and c-phase coils is connected to each other to form a star connection, and the other end of each coil is connected to the control unit 30. The motor drive currents ia, ib and ic are supplied individually.
The steering torque Ts detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12 are input to a control arithmetic device (control arithmetic circuit) 50.

  Each phase current of the three-phase brushless motor 40 is detected by a current detection circuit 45, and the detected three-phase motor currents ia to ic are input to the control arithmetic device 50 as feedback currents. Further, a rotation sensor 41 such as a hall sensor is attached to the three-phase brushless motor 40. A rotation signal RT from the rotation sensor 41 is input to the rotor position detection circuit 46, and the detected rotation position θ is a control arithmetic unit. 50.

The control arithmetic device 50 calculates a steering assist command value I based on these input signals and outputs it to the gate drive circuit (drive circuit) 43.
Based on the input steering assist command value I, the gate drive circuit 43 executes PWM control processing to form a gate drive signal, and controls the gate current of the FET constituting the inverter circuit 44 by the gate drive signal. .

  The inverter circuit 44 drives the three-phase brushless motor 40 through the emergency stop circuit 42. The inverter circuit 44 is composed of six FETs Tr1 to Tr6 constituting a three-phase bridge, and the interrupting device 42 is composed of relay contacts 421 and 422 that interrupt two phases. The relay contacts 421 and 422 are normally turned on, and in this example, the a and b phases are cut off in an emergency, but a combination of other phases may be used.

  Further, the ignition key signal IGN from the ignition key 11 is input to the ignition voltage monitor unit 15 and the power supply circuit unit 60. The power supply circuit unit 60 generates a power supply voltage Vdd from the input voltage and outputs the power supply voltage Vdd to the control arithmetic device 50, and outputs a reset signal RS1 described later to the control arithmetic device 50. Further, the power supply circuit unit 60 outputs a drive stop signal RS2 described later to the gate drive circuit 43.

FIG. 3 is a diagram illustrating a specific configuration of the control arithmetic device 50 and the power supply circuit unit 60.
The control arithmetic device 50 is a microcomputer, and includes a CPU 51 that performs overall control, a ROM / RAM unit 52 that stores data, programs, and the like, and a peripheral circuit 53 that serves as an interface with peripheral devices.
The power supply voltage Vdd from the power supply circuit unit 60 is supplied to the CPU 51, the ROM / RAM unit 52, and the peripheral circuit 53, respectively. Further, the steering torque Ts, the vehicle speed V, the motor currents ia to ic, and the rotor rotational position θ are input to the peripheral circuit 53.
Based on the ignition key signal IGN, the power supply circuit unit 60 outputs a stabilized power supply voltage Vdd having a set voltage value of 5 V, and a voltage monitoring unit 62 that monitors an abnormality of the power supply voltage Vdd. With. Here, the power supply generation unit 61 is configured to output the power supply voltage Vdd with an accuracy of 5V ± 0.15V in a normal state.

In addition, the voltage monitoring unit 62 monitors the power supply voltage Vdd and detects that the power supply voltage Vdd is in an abnormal state that deviates from a predetermined set voltage range, and detects a voltage abnormality. And a reset generation circuit 622 that outputs a reset signal RS1 and a drive stop signal RS2.
The voltage detection circuit 621 has thresholds Th1 and Th2 for defining the set voltage range. When the power supply voltage Vdd is equal to or lower than the threshold Th1 or higher than the threshold Th2, the power supply voltage Vdd is in an abnormal state. It is determined that This voltage detection circuit 621 always monitors the power supply voltage Vdd immediately after the ignition is turned on.

The reset generation circuit 622 outputs a reset signal RS1 to the CPU 51 and the peripheral circuit 53 to stop the CPU 51 and the peripheral circuit 53 when the voltage abnormality of the power supply voltage Vdd is detected, and outputs a drive stop signal RS2. An output is made to the gate drive circuit 43 to stop the gate drive circuit 43.
Here, it is assumed that the set voltage range is set to an operation guarantee voltage range in which the control arithmetic device 50 can operate normally. For example, the threshold (lower limit voltage value) Th1 is higher than the set voltage value (5 V). The low voltage side 4.5V and the threshold (upper limit voltage value) Th2 are set to 5.5V higher than the set voltage value (5V). That is, 5 V ± 0.5 V is set as the operation guarantee voltage range, and when the power supply voltage Vdd is out of this range, it is determined that the power supply voltage Vdd is in an abnormal state.

In FIG. 3, the power generation unit 61 corresponds to the power generation unit, the voltage detection circuit 621 corresponds to the power supply voltage monitoring unit, and the reset generation circuit 622 corresponds to the stop signal output unit.
In this way, the power supply voltage Vdd is constantly monitored, and when a voltage abnormality occurs in the power supply voltage Vdd for some reason, the control arithmetic device 50 and the gate drive circuit 43 are stopped in order to stop their operations. Since different stop signals are output, the system can be appropriately stopped.

If the configuration is such that only the reset signal RS1 is output to the control arithmetic unit 50 and the drive stop signal RS2 is not output to the gate drive circuit 43 when an abnormality occurs in the power supply voltage Vdd, the following problem occurs. . That is, when the reset signal RS1 itself is abnormal, or when an abnormality occurs in the stop operation function on the control arithmetic device 50 side even if the normal reset signal RS1 is output (to the side where the operation cannot be stopped). When the signal is stuck, the control arithmetic device 50 cannot be stopped by the reset signal RS1.
This problem similarly occurs when only the drive stop signal RS2 for the gate drive circuit 43 is output and the reset signal RS1 for the control arithmetic device 50 is not output.

On the other hand, in the present embodiment, when a voltage abnormality of the power supply voltage Vdd occurs, a stop signal is output to each so that not only the control arithmetic device 50 but also the gate drive circuit 43 is stopped. The stop signal is different between the control arithmetic device 50 and the gate drive circuit 43 (reset signal RS1 and drive stop signal RS2). Therefore, even when either one of the reset signal RS1 and the drive stop signal RS2 becomes abnormal or when the stop operation function of any one of the control arithmetic device 50 and the gate drive circuit 43 becomes abnormal, It is possible to stop the system operation and shift to the stable side.
That is, the fail-safe function can be duplicated when a voltage abnormality of the power supply voltage Vdd occurs.

  Incidentally, there is a general-purpose integrated circuit incorporating a 5V constant voltage power supply and a low voltage monitoring function of the power supply voltage Vdd as a power supply voltage Vdd supply and voltage abnormality monitoring. This circuit is configured to immediately output a reset signal when the power supply voltage Vdd decreases and falls below the threshold value VTH. As described above, in this circuit, the threshold value VTH is set only on the low voltage side to monitor the voltage abnormality, and the threshold value is not set on the high voltage side.

  However, the operation guarantee voltage range of the control arithmetic device 50 has a range not only on the low voltage side but also on the high voltage side with respect to 5 V, for example, 5 V ± 0.5 V. This is because when the power supply voltage Vdd rises and the voltage becomes abnormal toward the high voltage side, an internal failure of the IC occurs, and there is a risk of runaway due to fixing with the high voltage. In the above-described general-purpose integrated circuit with a low voltage monitoring function, since the reset signal is not output even if the power supply voltage Vdd becomes abnormal on the high voltage side, the control arithmetic device 50 cannot be stopped appropriately by the reset signal.

  On the other hand, in this embodiment, not only the voltage abnormality on the low voltage side but also the voltage abnormality on the high voltage side is monitored, so when the power supply voltage Vdd rises and becomes a voltage abnormality on the high voltage side. Can appropriately output the reset signal RS1 and the drive stop signal RS2. Therefore, the control arithmetic device 50 and the gate drive circuit 43 can be appropriately stopped by these signals, and the system can be shifted to the safe side.

  Further, the lower limit voltage value of the guaranteed operation voltage range in which the control arithmetic device 50 can operate normally is set as the threshold Th1, and the upper limit voltage value of the guaranteed operation voltage range is set as the threshold Th2, and the power supply voltage Vdd is monitored. Therefore, it is possible to appropriately detect that the power supply voltage Vdd has deviated from the operation guarantee voltage range, and to stop the control arithmetic device 50 and the gate drive circuit 43. Therefore, it is possible to prevent the system from operating in a state where the power supply voltage Vdd deviates from the guaranteed operation voltage range.

(Modification)
In the above embodiment, a general-purpose regulator with a low voltage monitoring function may be used as the power supply circuit unit 60. In this case, as shown in FIG. 4, the voltage monitoring circuit 62 of the power supply circuit unit 60 includes a low voltage detection circuit 621 that detects only an abnormality on the low voltage side of the power supply voltage Vdd, and an abnormality on the low voltage side of the power supply voltage Vdd. And a reset generation circuit 622 that outputs a reset signal RS1 to the control arithmetic unit 50 and outputs a drive stop signal RS2 to the gate drive circuit 43.

  A voltage monitoring circuit 63 is provided separately from the voltage monitoring circuit 62. The voltage monitoring circuit 63 detects a high voltage side abnormality of the power supply voltage Vdd, and detects a high voltage side abnormality of the power supply voltage Vdd. The reset generation circuit 632 outputs RS1 ′ and outputs a drive stop signal RS2 ′ to the gate drive circuit 43. Also in this case, the same effect as the above-described embodiment can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Column shaft, 3 ... Reduction gear, 4A, 4B ... Universal joint, 5 ... Pinion rack mechanism, 6 ... Tie rod, 10 ... Torque sensor, 11 ... Ignition key, 12 ... Vehicle speed sensor, 14 ... Battery , 15 ... IGN voltage monitor unit, 30 ... control unit, 40 ... motor (three-phase brushless motor), 41 ... rotation sensor, 42 ... shut-off device, 43 ... gate drive circuit (drive circuit), 44 ... inverter circuit, 45 ... Current detection circuit, 46 ... rotor position detection circuit, 50 ... control arithmetic unit, 51 ... CPU, 52 ... ROM / RAM section, 53 ... peripheral circuit, 60 ... power supply circuit section, 61 ... power generation section, 62 ... voltage monitoring section 621 ... Voltage detection circuit 622 ... Reset generation circuit 63 ... Voltage monitoring unit 631 ... High voltage detection circuit 632 ... Tsu door generating circuit

Claims (4)

A three-phase electric motor for applying a steering assist force to the steering system, a control arithmetic circuit for calculating a current command value for driving and controlling the three-phase electric motor, and a current command value calculated by the control arithmetic circuit An electric power steering device comprising: a drive circuit that drives the three-phase electric motor based on
The drive circuit includes an inverter circuit composed of six field effect transistors constituting a three-phase bridge, and a gate drive circuit that forms a gate drive signal of the field effect transistor based on the current command value,
A breaker configured by relay contacts individually inserted in any two-phase connection line among the three-phase connection lines of the inverter circuit and the three-phase electric motor;
Power supply voltage monitoring means for monitoring the power supply voltage supplied to the control arithmetic circuit;
When the power supply voltage monitoring means detects that the power supply voltage is out of a predetermined set voltage range, a different stop signal is used to stop the operation of the control arithmetic circuit and the drive circuit. and a stop signal output means for outputting,
The shut-off device is controlled to be normally turned on and shut off in an emergency,
The electric power steering apparatus characterized in that the stop signal output means stops the operation of the drive circuit by outputting a stop signal to the gate drive circuit and setting the gate drive circuit to a stop operation .   The electric power steering apparatus according to claim 1, wherein the set voltage range is an operation guarantee voltage range in which the control arithmetic circuit can operate normally. A power supply generating means for generating a stabilized power supply voltage having a preset set voltage value from an input power supply and supplying the stabilized power supply voltage to the control arithmetic circuit as the power supply voltage;
The electric power steering apparatus according to claim 2, wherein the upper limit voltage value of the operation guarantee voltage range is set to a predetermined voltage value on a higher voltage side than the set voltage value. A power supply generating means for generating a stabilized power supply voltage having a preset set voltage value from an input power supply and supplying the stabilized power supply voltage to the control arithmetic circuit as the power supply voltage;
4. The electric power steering apparatus according to claim 2, wherein the lower limit voltage value of the operation guarantee voltage range is set to a predetermined voltage value on a lower voltage side than the set voltage value. 5.

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