JP3096792B2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus.

[0002]

2. Description of the Related Art An electric power steering apparatus has been put into practical use in which a steering force is detected by a torque sensor, and a steering assist force corresponding to the direction and magnitude of the detected torque is applied by a motor. In this device, a voltage suitable for each circuit such as a torque detection system and a motor drive system is required, so that a plurality of power supply circuits corresponding to each voltage are prepared.

[0003]

These power supply circuits are supplied with power from a battery mounted on a vehicle via a key switch. However, since the power supply circuits have different configurations, each power supply circuit has to be driven until the output of each power supply circuit reaches a specified voltage. Time is different for each. Then, for example, an erroneous detection signal is generated in the torque detection system, which causes a problem that unnecessary motor driving is performed. The same is true when the key switch is turned off, and the voltage drop state differs for each power supply circuit, and unnecessary motor driving may be performed. The present invention has been made to solve such a problem, and an object of the present invention is to provide an electric power steering device capable of preventing unnecessary motor driving when a key switch is turned on / off.

[0004]

SUMMARY OF THE INVENTION An electric power steering apparatus according to the present invention includes a plurality of power supply circuits which are supplied / cut off by turning on / off a key switch, and a plurality of circuits supplied by these power supply circuits. In an electric power steering apparatus that detects a steering torque and drives a steering assist motor based on the detected torque, a circuit that outputs a predetermined signal in conjunction with turning on a key switch;
It is characterized by comprising a circuit for inhibiting the driving of the motor for a predetermined period by an output signal of the circuit, and a circuit for momentarily interrupting the power supply to the motor when a key switch is turned off.

[0005]

When the key switch is turned on, the driving of the motor is prohibited for a predetermined period, and when the key switch is turned off, the power supply to the motor is momentarily interrupted.

[0006]

1 and 2 are block diagrams of an electric power steering apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a vehicle-mounted battery, which is connected via a key switch 2 to a key-on control circuit 3, a key-off control circuit 4, a 5V power circuit 5, a -5V power circuit 6, and a 26V power circuit 7. The key-on control circuit 3 outputs a reset signal and a motor prohibition signal having a predetermined time width to the fail processing circuit 9 and the motor drive prohibition circuit 14, respectively, in conjunction with the key switch-on. . The key-off control circuit 4 immediately shuts off the output of the 26V power supply circuit 7 in conjunction with the key switch-off, and the details of its configuration will be described later.

5V power supply circuit 5, -5V power supply circuit 6, 26V
The power supply circuit 7 generates voltages of 5 V, -5 V, and 26 V, respectively, and this voltage is input to the power supply monitoring circuit 8. Power supply monitoring circuit 8
Is designed to supply power to the relay coil 33 of the fail-safe relay when the power supply circuits 5, 6, and 7 are normal, and to cut off the power supply when an abnormality occurs. The relay drive circuit 15 is a circuit for controlling the energization of the relay coil 33. The +5 V and -5 V voltages generated by the 5 V power supply circuit 5 and the -5 V power supply circuit 6 are supplied to both the main current target value circuit 18 and the sub current target value circuit 19 as positive and negative power supplies. The 26V voltage generated by the 26V power supply circuit 7 is given to the motor drive circuit 31. The other circuits are supplied with the 5V voltage of the 5V power supply circuit 5.

[0008] Torque detection is performed by detecting the torsion of a torsion bar interposed between the steering wheel and the steering mechanism by a torque sensor TS.
16 and two auxiliary torque detection circuits 17 are provided. The outputs of the two detection circuits 16 and 17 are input to a main current target value circuit 18 and a sub current target value circuit 19, respectively, where a target value corresponding to a current value of a motor 32 necessary to generate a steering assist force corresponding to the detected torque is obtained. A signal is generated, and each target value signal output is input to the main limiter circuit 20 and the sub limiter circuit 21. These limiter circuits 20 and 21 suppress the target value signal to an upper limit value based on the temperature of the motor 32 detected by the motor temperature detection circuit 22.

The target value signal output from the main limiter circuit 20 is used for driving the motor 32, and the target value signal output from the sub limiter circuit 21 is used for a fail-safe circuit. The target value signal output from the main limiter circuit 20 is input to an error amplifier circuit 23, where an error between the current value of the motor 32 and the feedback value of the motor 32 detected by the current detection circuit 27 for motor drive control is amplified, and the output is amplified. This is supplied to a PWM output circuit 24 that outputs a PWM wave for controlling the drive current of the motor 32. twenty five
Is a triangular wave generation circuit used for PWM modulation.

The drive circuit 31 of the motor 32 has a voltage of 26 V as described above.
Is supplied from the battery 1 and the relay coil
Motor 32 via a normally open contact 33a actuated by 33
Power is supplied for driving. The first power supply current detection circuit 301 is connected to the positive side of the motor drive circuit 31, and supplies the detected motor drive current to the overcurrent monitoring circuit 28 and the motor terminal ground fault detection circuit 29. A similar second power supply current detection circuit 302 is connected to the negative side of the motor drive circuit 31 so that its detection output is supplied to the motor terminal ground fault detection circuit 29. In addition, a current detection circuit 26 for fail-safe control similar to the current detection circuit 27 is provided.

Reference numeral 13 denotes a fail determination time changing circuit which prevents erroneous fail-safe detection when the actual current does not follow the current target value when the steering wheel is rapidly steered. The outputs of the sub limiter circuit 21, the current detection circuit 26, and the overcurrent monitoring circuit 28 are input to the circuit 13, and based on the inputs from these circuits, the fail determination time changing circuit 13 outputs When the current detection value is equal to or less than a predetermined value and the output of the overcurrent detection circuit is normal, the clock frequency of a fail processing circuit described later is lowered so as to extend the fail-safe determination time.

Output of current detection circuit 26 and auxiliary limiter circuit 21
The output is also supplied to a differential amplifier circuit 11, and the difference between the two is amplified and supplied to a fail detection circuit 10. If the circuit operation is normal, a differential amplifier circuit is used except when the steering wheel is turned sharply.
11 inputs are equal or slightly different. The output of the motor terminal ground fault detection circuit 29 has no output when no ground fault exists. In such a case, the fail detecting circuit 10 does not output any signal.However, when an abnormality occurs in the circuit operation and the output of the differential amplifier circuit 11 increases, or when a ground fault occurs, the fail detecting circuit 10 10 outputs a predetermined signal to the fail processing circuit 9. The fail processing circuit 9 includes an oscillation circuit 12
Clocking is performed by the clock signal obtained from, and after the predetermined time is counted, a signal for inhibiting motor rotation is output to the motor drive inhibition circuit 14, and a signal for stopping the energization of the relay coil 33 is output to the relay drive circuit 15. I do.

As is apparent from the above description, since the limiter circuit for motor drive control and the one for fail-safe control are provided independently, it is necessary to always detect the abnormality even if one of them has an abnormality. Can be. That is, if the limiter circuit is shared for control and fail-safe,
If an error occurs in the limiter circuit, the output of the subsequent stage becomes the same, and it is not possible to detect an abnormality in the limiter circuit itself.
In this embodiment, such a risk is avoided.

Further, since current detection circuits for motor drive control and fail-safe control are separately provided, even if the current detection circuit 27 for motor drive control fails, the current detection circuit 26 for fail-safe control is provided. Thus, the motor current can be detected, and the fail-safe control can be performed based on the detected motor current.

FIG. 3 is a circuit diagram of the motor drive circuit 31.
The motor 32 has four bridged transistors Q _1.
To Q ₄ are connected to bridge the, now forward ON of the transistor Q _1, Q _4, the power supply from the battery 1 so as to reverse the on transistor Q _2, Q ₃ is performed ing. The transistors Q ₁ , Q ₄ (or Q ₂ ,
Q ₃ ) are simultaneously turned on by the PWM waves input to the respective drive circuits 311 and 314 (or 312 and 313). The output voltages of the 5V power supply circuit 5 and the 26V power supply circuit 7 are supplied to the drive circuits 311 to 314, respectively.

FIG. 4 is a circuit diagram showing the configuration of the key-on control circuit 3 and the key-off control circuit 4. First, the configuration of the key-on control circuit 3 will be described. The positive electrode key switch 2 of the battery 1 is connected to the emitter of PNP transistors T ₁ through a diode, it is connected to the base via a further resistor. Based transistors T ₁ resistor is grounded through a capacitor C _1. The collector of the transistors T ₁ is connected to a motor drive inhibiting circuit 14 is connected via a resistor to the base of the NPN transistor T _2. The emitter of the transistor T ₂ are connected to ground and a collector connected to a 5V power supply through a resistor.

The collector of the transistor T ₂ is also connected to the fail processing circuit 9 and sends out a reset signal. When the key switch 2 is turned on the transistor T ₁ is turned on charging of the capacitor C ₁ is started. Since the transistor T ₂ with the ON of the transistor T ₁ is turned on and the collector is given thereto becomes low level to fail processing circuit 9 as a reset signal.

The fail processing circuit 9 counts the number of pulses output from the oscillation circuit 12, and when the number of pulses reaches a predetermined number, activates the motor drive inhibition circuit 14 and the relay drive circuit 15. The counter for counting is reset by the reset signal. Keep in reset state. The motor drive inhibiting circuit 14 is configured to drop the gate voltage of the transistors Q ₃ and Q ₄ of the motor drive circuit 31 to the ground level by turning on the transistor T ₃ ,
Therefore, the configuration is such that energization of the motor 32 is prohibited.

The collectors of transistors T ₁ is connected via a resistor to the base of the transistor T _3, the transistor T ₃ by the key switch 2 ON also turned on, during which the motor 32 is not driven. That the collector potential of the transistor T ₁ is the motor inhibiting signal. Capacitor C ₁
There transistors T ₁ when being charged reaches a predetermined voltage is turned off, the transistor T _2, T ₃ With this also turned off.
As a result, the reset signal output disappears and the motor drive inhibiting circuit 14 also disconnects the gates of the transistors Q ₃ and Q ₄ from the ground potential. Thereby, transistors Q ₃ and Q
₄ is in a state where it can be turned on by the outputs of the drive circuits 313 and 314.

[0020] if that you select the value of the resistor in the charging circuit of the capacitor C ₁ and to this appropriately as understood from the above description, at the time of the key switch on the motor 32 for a predetermined time Driving is prohibited, and fail processing accompanying malfunction of each circuit due to voltage irregularity of the output of the power supply circuit can also be prohibited. In addition, as the predetermined time,
The time from when the key switch is turned on to when all the power supply circuit outputs reach a specified voltage is set.

Next, the key-off control circuit 4 will be described. The cathode of the diode connected to the key switch 2 is connected to the base of NPN transistor T ₄ via the resistor, the base is grounded through the other resistors. NP
The emitter of the N transistor T ₄ is grounded, and the collector is connected to the base of the PNP transistor T ₅ via a resistor.
It is connected to the emitter via a resistor. The emitter of the transistor T ₅ is connected to the output terminal of the 26V power supply circuit 7, and the collector is connected to the drive circuit 311-314.

When the key switch 2 is turned on, the transistor T ₄ is turned on, and accordingly, the transistor T ₅ is also turned on. Therefore, the output of the 26V power supply circuit 7 is supplied to the load. Meanwhile, the supply of power from the key switch 2 when it is off the transistor T _4, T ₅ are turned off immediately to the drive circuit 311 to 314 is cut off, thus driving the motor 32 is to be prohibited.

[0023]

According to the present invention as described above, a malfunction due to turning on / off of a key switch can be avoided, and a highly reliable and safe electric power steering apparatus can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of the device of the present invention.

FIG. 2 is a block diagram of the device of the present invention.

FIG. 3 is a circuit diagram of a motor drive circuit.

FIG. 4 is a circuit diagram of a key-on control circuit and a key-off control circuit.

[Explanation of symbols]

 2 Key switch 3 Key-on control circuit 4 Key-off control circuit 5 5V power circuit 6 -5V power circuit 7 26V power circuit 31 Motor drive circuit 32 Motor

Claims (1)

(57) [Claims] 1. A power supply / turn-on operation by turning on / off a key switch.
An electric power steering apparatus comprising a plurality of power supply circuits that are cut off from power supply, detects steering torque by a plurality of circuits supplied by these power supply circuits, and drives a steering assist motor based on the detected torque. A circuit that outputs a predetermined signal in conjunction with the circuit, a circuit that prohibits driving of the motor for a predetermined period by an output signal of the circuit, and a circuit that momentarily interrupts power supply to the motor when a key switch is turned off. An electric power steering device characterized by the above-mentioned.