JPH0948356A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a kick back generated after a key switch is turned off, by feeding a power to a motor, and after that, reducing the power gradually, and cutting off the power fed to the motor, when the relative torsion of a torsion bar is detected in the cutting off condition of the key switch. SOLUTION: When a key switch 2 to convert feeding and cutting-off of a power source from a battery 1 to a motor 9 is made in a cutting off condition, a sensor 6 detects the relative torsion of a torsion bar, a steering torque, a car speed, and the like, through a control circuit 10. In this case, when the relative torsion is detected by the sensor 6, a motor driver 8 feeds a power to the motor 9. And after that, power feeding to the motor 9 from the motor driver 8 is reduced gradually, and the power feeding to the motor 9 from the motor driver 8 is cut off. Consequently, a kick back generated after the key switch 2 is turned off can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing kickback of an electric power steering device when a key switch is turned off.

[0002]

2. Description of the Related Art A power steering device for a vehicle is a device for assisting a steering force necessary for a driver to rotate a steering wheel and reducing a burden on the driver.

Conventionally, the power steering device is generally of a hydraulic type, but it is difficult to reduce the size, weight and cost of the power steering device. It is becoming more and more popular.

In an electric power steering system, an input shaft connected to a steering wheel and an output shaft connected to an operating portion for turning a wheel via a pinion gear or the like are connected via an elastic member such as a torsion bar. There is. Further, the electric power steering apparatus includes an electric motor that assists the rotational force of the output shaft, and a switch circuit that switches the rotational direction of the electric motor according to the rotational direction of the input shaft.

The electric motor used in the power steering device is driven by a battery as a power source. When the key switch is turned off, the electric power supplied from the battery to the electric motor is cut off. At this time, if the steering wheel is steered, elastic force that resists the steering force is accumulated in the mechanism such as the wheel and the torsion bar, and the steering wheel is restored to the neutral state at the moment when the assist force of the electric motor is lost. The force acts and so-called kickback occurs.

As a conventional technique for solving such a problem, there are those described in Japanese Utility Model Publication No. 6-1901 (Japanese Utility Model Publication No. 64-1055) and Japanese Patent Application Laid-Open No. 3-287467.

By the way, Jpn.
In the device described in Japanese Patent Application Laid-Open No. 4-1055), after the key switch is turned off, electric power is supplied to the electric motor until the steering torque becomes zero. Therefore, the driver is turned off after the key switch is turned off. If the vehicle continues to steer the steering wheel, there is a problem that the vehicle-mounted battery is over-discharged.

On the other hand, in the device disclosed in Japanese Patent Laid-Open No. 3-287467, after turning off the key switch, the conductors are switched to short-circuit both ends of the motor (or short-circuit via a resistor) to rotate the rotary shaft of the motor. The kickback is prevented by generating a braking force on the. However, since the circuit configuration is switched when the conductor is switched, a shock at that time may occur as kickback.

[0009]

Therefore, the present invention has been made in view of the above-mentioned problems, and in an electric power steering apparatus, prevents kickback that occurs after the key switch is turned off. It is an object to provide a technique for suppressing over-discharge of a battery.

[0010]

The present invention employs the following configurations in order to solve the above problems. (1) In an electric power steering device that connects a steering input shaft and an output shaft via a torsion bar and drives a motor connected to the output shaft according to a relative twist angle of the input / output shaft, a power source is supplied to the motor. A battery for supplying electric power, a key switch for switching supply / interruption of power supply from the battery to the motor, a relative twist detecting means for detecting relative twist of the torsion bar, and a key switch when the key switch is in an off state. When the torsion bar is relatively twisted, the electric power supply means for supplying electric power to the motor and the electric power supplied from the electric power supply means to the motor are gradually reduced, and the electric power is supplied from the electric power supply means to the motor. And a control means for shutting off power supply to the device (corresponding to claim 1).

(2) In the configuration of the above (1), the control means has an assist amount determination unit that determines a designated current value to be supplied to the motor based on the relative twist amount or the traveling state of the vehicle, The assist amount determination unit gradually reduces the command current value to be supplied from the power supply unit to the motor after the key switch is turned off, and when the command current value decreases to a constant value. The command current value may be set to zero (corresponding to claim 2).

(3) In addition to the configuration of (1) above, a motor driver means for driving the motor is provided, and the control means starts the motor driver means after the key switch is turned off. You may make it characterized by having a driver control part which reduces time gradually (corresponding to Claim 3).

(4) In the configuration of (1) above, the output from the key switch and the output from the power supply means are connected to a device for driving the drive source of the vehicle, and the key switch is turned off. After that, while the relative twist is generated, electric power is supplied from the power supply means to the device to continue driving the drive source (corresponding to claim 4).

(5) In addition to the configuration of (1) above, a power holding means for taking in the input side power of the power supply means as the operating power of the control means is provided (claim 5). Correspondence).

According to the above configuration (1), when the driver turns off the key switch while steering the steering wheel, the control means detects the off state of the key switch and the detection signal of the relative twist detection means. It is detected that the torsion bar is relatively twisted, that is, the steering wheel is in the steering state by referring to.

Then, the control means inputs a command value of electric power to be supplied to the electric motor to the electric power supply means.
Furthermore, the control means gradually reduces the command value,
Finally, the command value is set to zero. At this time, the driving force of the electric motor gradually decreases, while the elastic force applied to the steering wheel gradually increases. That is, the elastic force that causes kickback does not rise sharply but gradually increases (corresponding to claim 1).

Further, according to the above configuration (2), the control means gradually reduces the electric power command value to be supplied from the electric power supply means to the electric motor, and when it decreases to a constant value,
Set the command value to zero. The constant value can be, for example, a minimum current value required to drive the electric motor.

Further, according to the above configuration (3), when the key switch is in the ON state, the assist current determining section of the control means indicates the detection signal of the relative twist amount detecting means or the running state of the vehicle. The supply current value is determined by referring to the detection signal from the detecting sensor, and the value is notified to the motor driver unit.

The motor driver means supplies a current designated by the supply current value to the motor. Further, when the key switch is turned off, the driver control unit gradually reduces the activation time of the motor driver means. At this time, the current value supplied from the motor driver to the motor gradually decreases.

Further, according to the above configuration (4), by continuously supplying the electric power to the equipment necessary for driving the drive source of the vehicle, the drive source is the drive source even after the key switch is turned off. Will continue to drive. At this time, the charger using the driving force of the driving source continues to operate and charges the battery.

Further, according to the above configuration (5), the fail-safe effect can be made more reliable even during normal traveling with the key switch turned on.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

[0023]

[First Embodiment] FIG. 1 is a diagram showing an embodiment of an electric power steering apparatus. This electric power steering apparatus includes an electric motor 9 that generates a steering assist force and a motor driver 8 that drives the electric motor 9.
To the motor driver 8, the output of the fail-safe relay 3 that realizes the power supply means of the present invention and the gate signal from the control circuit 10 corresponding to the control means of the present invention are input. A current detector 7 including a shunt resistor and a differential amplifier is provided between the fail-safe relay 3 and the motor driver 8, and a detection signal of the current detector 7 is input to the control circuit 10.

The motor driver 8 is an H-bridge composed of FETs, and the electric motor 9 is switched by switching the gate according to the gate signal from the control circuit 10.
Is driven.

The fail safe relay 3 has a battery 1
Power is input, and the relay is turned on / off, that is, power supply / interruption is switched in accordance with a command value from the relay driver 16.

The relay driver 16 is composed of an FET and an AND circuit, and outputs an ON / OFF switching signal for the fail-safe relay 3 according to a command value from the control circuit 10.

Furthermore, the output from the battery 1 is input to the fail-safe relay 3 as described above, and
Input to key switch 2. The power input to the key switch 2 is branched into two, and one output is input to the controller power supply circuit 5 via the diode 14. The other output of the key switch 2 is input to the control circuit 10. Further, the output of the fail-safe relay 3 is connected to the controller power supply circuit 5 via the diode 15 so that power can be supplied to the vehicle-mounted ECU or the like even after the key switch 2 is turned off. Has become.

Further, the detection signal of the sensor section 6 which realizes the relative twist detecting means of the present invention is connected to the control circuit 10. The sensor unit 6 detects relative twist of the torsion bar, steering torque, vehicle speed, and the like.

Here, the internal configuration of the control circuit 10 will be described. The control circuit 10 includes a fail safe determination unit 10
0, comparator 101, NOR circuit 102, assist amount calculation unit 103, subtractor 106, error amplifier 104, P
A WM (PLUS WIDE MOFULATION) calculator 105 is provided.

The fail discriminating section 100 sends an instruction to switch the fail-safe relay 3 on / off to the relay driver 16
To enter. The comparator 101 and the assist amount calculation unit 103 are one embodiment of the assist amount determination unit of the present invention. The comparator 101 compares the detection signal from the current detection circuit 9 with a preset specific value, Only when the detection signal exceeds a specific value, the NOR circuit 10
Input the command value to 2. The NOR circuit 102 has two input terminals. One input terminal is connected to the comparator 101 as described above, and the other input terminal is connected to the output from the key switch 2. The output of the NOR circuit 102 is input to the relay driver 16. Here, AND of the relay driver 16
The circuit includes an output signal of the fail-safe determination unit 100 and N
The output signal of the OR circuit 102 is input. Then, the AND circuit performs a logical product operation of the two input signals and inputs the operation result to the FET. The FET outputs a signal designating ON / OFF of the fail safe relay 3 based on the input calculation result.

On the other hand, the assist amount calculation unit 103 calculates the current command value “I ^* ” based on the detection signal of the sensor unit 6, and outputs from the key switch 2 and the sensor unit 6.
The detection signal from is input. The output of the assist amount calculation unit 103 is input to the subtractor 106.

The subtractor 106 has two input terminals,
As described above, the assist amount calculation unit 1 is provided at one of the input terminals.
03 output signal is input, and the output of the current detector 7 is input to the other input terminal. Then, the subtractor 106 subtracts the signal value input from the current detector 7 from the signal value input from the assist amount calculation unit 103.

The subtraction result of the subtractor 106 is the error amplifier 1
It is input to the PWM calculation unit 105 via 04. PWM
The output of the calculation unit 105 is input to the motor driver 8.

The operation of this embodiment will be described below with reference to FIG. In a normal state, that is, in a state where the key switch 2 is on, the assist amount calculation unit 10 of the control circuit 10
3 calculates the current command value “I ^* ” corresponding to the detection signal from the sensor unit 6.

The subtractor 106 includes a current detector 7
The detected current value "I '" from the above and the current command value "I ^* " from the assist amount calculation unit 103 are input. Subtractor 106
Outputs the current value "I" by subtracting the detected current value "I '" from the current command value "I ^* ".

The current value "I" output from the subtractor 106
Are input to the error amplifier 104. Error amplifier 10
4 amplifies the current value "I" and outputs it as a voltage command value "V ^* " to be supplied to the electric motor. This voltage command value ”
V ^* ″ is input to the PWM calculation unit 105.

The PWM calculation unit 105 includes an error amplifier 104.
The ON time of the FET of the motor driver 8 is calculated based on the voltage command value "V ^* " input from the. The motor driver 8 turns on the FET according to the on-time input from the PWM calculation unit 105, and the voltage is applied to the electric motor 9.
V ^* "is input to drive the electric motor 9.

On the other hand, when the key switch 2 is turned off, the assist amount calculation section 103 refers to the detection signal of the sensor section 6 to determine whether or not the steering wheel is in the steering state. Then, if the steering wheel is in the steering state, the assist amount calculation unit 103 shifts to the calculation for kickback prevention, and increases per hour from the current command value “I ^* ” calculated based on the detection signal of the sensor unit 6. The variable “ΔI ^* ” is subtracted, and the subtraction result “I ^* ” is subtracted by the subtracter 1.
Input to 06.

The subtractor 106 includes an assist amount calculator 103.
The detected current value "I '" input from the current detector 7 is subtracted from the current value "I ^* " input from to calculate the current value "I".

As a result, the motor driver 8 supplies the electric current value "I" to the electric motor 9 to drive the electric motor 9. By this processing, the current value "I" gradually decreases with time. When the detected current value “I ′” of the current detector 7 becomes equal to or less than the set value of the comparator 101, the relay driver 16 causes the fail safe relay 3
To switch from the on state to the off state. At this time, the current supply to the electric motor 9 is also stopped and the electric motor 9 is stopped.

After that, when the key switch 2 is switched from the off state to the on state, power is supplied to the controller power supply circuit 5 and the apparatus is restarted. According to the first embodiment, the electric motor 9 is maintained even after the key switch is turned off.
The power is supplied to the power source, and the power gradually decreases with time. In response to this, the assist torque of the electric motor will gradually decrease,
It is possible to prevent the elastic force accumulated in the torsion bar or the like from suddenly acting, and thus to prevent kickback.

Further, according to this embodiment, when the key switch is turned off, it is not affected by the fluctuation of the battery voltage due to the engine stop.

[0043]

[Second Embodiment] FIG. 3 shows the configuration of an electric power steering apparatus according to the second embodiment. The electric power steering apparatus of this embodiment is different from the structure of the first embodiment described above in the structure of the control circuit 10 and is the same in other structures. Here, the same configuration as that of the first embodiment will be omitted and described.

The control circuit 10 of this embodiment comprises a fail-safe judgment section 100, an assist amount calculation section 103, an error amplifier 104, a PWM calculation section 105, and a subtractor 106.

The fail discriminating section 100 sends an instruction to switch the fail-safe relay 3 on / off to the relay driver 16
To enter. The detection signal of the sensor unit 6 is input to the assist amount calculation unit 103, and the current command value “I ^* ” is calculated based on this detection signal. The output of the assist amount calculation unit 103 is input to the subtractor 106.

The subtractor 106 includes an assist amount calculation unit 10
3, the output of the current detector 7 is input. Then, the output of the subtractor 106 is input to the error amplifier 104.

The output of the error amplifier 104 is input to the PWM calculator 105. Further, the PWM calculation unit 105
The output of the key switch 2 is input to. The output of the PWM calculation unit 105 is the relay driver 16
Is input to the AND circuit and the motor driver 8. The PWM calculation unit 105 in the present embodiment is an embodiment of the driver control unit of the present invention, and reduces the ON time of the FET of the motor driver 8.

The operation of this embodiment will be described below with reference to FIG. In the normal state, that is, when the key switch 2 is in the ON state, the fail-safe determination unit 100 and the PWM calculation unit 105 of the control circuit 10 input the “H level” relay drive signal to the AND circuit of the relay driver 16. Then, the fail safe relay 3 is turned on.

Further, the assist amount calculator 103 calculates the current command value “I ^* ” based on the detection signal from the sensor unit 6 and inputs it to the subtractor 106. The subtractor 106 uses the current command value “I ^* ” input from the assist amount calculation unit 103.
Is subtracted by the detected current value "I '" input from the current detector 7 to calculate the current value "I". This current value “I” is input to the error amplification unit 104.

The error amplifier 104 amplifies the current value "I" and outputs it as a voltage command value "V ^* " to be supplied to the electric motor 9. The voltage command value “V ^* ” is input to the PWM calculation unit 105.

The PWM calculation unit 105 determines the voltage command value "
On time of FET of motor driver 8 according to V ^* "
The motor driver 8 turns on the FET according to the on-time “ton” input from the PWM calculation unit 105, and supplies the voltage “V ^* ” to the electric motor 9.

On the other hand, when the key switch 2 is turned off, the assist amount calculation unit 103 refers to the detection signal of the sensor unit 6 to determine whether or not the steering wheel of the vehicle is in the steering state. When the steering wheel is in the steering state, the assist amount calculation unit 103 calculates the current command value “I ^* ” corresponding to the detection signal of the sensor unit 6 and inputs it to the subtractor 106.

The subtractor 103 subtracts the detected current value "I '" of the current detector 7 from the current command value "I ^* " to obtain the current value "
I "is calculated. This current value" I "is calculated by the error amplifier 10
4 is converted into the voltage command value “V ^* ” and the PWM calculation unit 10
5 is input.

The PWM calculation unit 105 shifts to a calculation for kickback prevention, and a variable "Δton" that increases the on-time command value "ton" calculated based on the voltage command value "V ^* " with the passage of time. To calculate the on-time command value "ton" for kickback prevention. The on-time command value “ton” is input to the motor driver 8.

The motor driver 8 has an on-time command value "t".
During "on", the FET is turned on and the voltage command value "
The voltage of V ^* "is supplied to the electric motor 9. As a result, the on-time command value decreases with the passage of time, and the voltage value supplied to the electric motor 9 also gradually decreases. Becomes 0, the detected current value “I ′” also becomes 0. At this time, the PWM calculation unit 105 sets the relay drive signal to “L level” and the fuel safe relay is turned off.

According to the present embodiment, the starting power of the electric motor 9 can be reduced by gradually shortening the ON time of the FET. Therefore, the assist motor of the electric motor 9 gradually decreases, and in response to this, the elastic force of the torsion bar or the like gradually rises. That is, it is possible to prevent the reaction force acting on the steering wheel from rising rapidly, and to prevent kickback.

Further, in contrast to the first embodiment described above, the kickback prevention mechanism can be operated even if the current detector 7 fails.

[0058]

[Third Embodiment] An electric power steering apparatus according to the present embodiment will be described with reference to FIG. As shown in the figure, the electric power steering apparatus of this embodiment branches the output of the fail-safe relay 3 into two, connects one output to the current detector 7, and outputs the other output to the controller power supply circuit. 5 and other electrical components. The electrical component here means at least a component necessary for maintaining driving of the internal combustion engine of the vehicle. Other configurations are similar to those of the above-described first embodiment or second embodiment, and description thereof will be omitted.

According to the present embodiment, even after the key switch 2 is turned off, power is supplied from the fail-safe relay 3 to the electric components, and the internal combustion engine continues to be driven without stopping. Become. Then, when the power supply to the electric motor 9 is stopped and the failsafe relay 3 is turned off, the internal combustion engine stops.

Therefore, according to the present embodiment, by continuing to operate the internal combustion engine even after the key switch is turned off, in addition to the effect of the first embodiment or the second embodiment described above, the overdischarge of the battery is further suppressed. It can be effectively prevented.

[0061]

[Fourth Embodiment] FIG. 6 shows the configuration of an electric power steering apparatus according to the present embodiment. As shown in the figure, the electric power steering apparatus of this embodiment is provided with a relay 17 corresponding to the motor power supply means of the present invention. Corresponding to this, the electric power input to the fail-safe relay 3 is branched so that one is connected to the fail-safe relay 3 and the other is connected to the newly provided relay 17. The output of the relay 17 is connected to the rear of the controller power supply circuit. Further, the relay driver 16 is composed of an FET for the fail safe relay 3, an FET for the relay 17, and a single AND circuit. A
The output of the ND circuit is branched into two, one of which is connected to the FET for fail safe relay 3 and the other of which is connected to the FET for relay 17. As a result, the two relays can be controlled in the same procedure as in the first embodiment described above.

According to the configuration of this embodiment, in addition to the effects of the first or second embodiment described above, the fail safe relay 3 is caused by some cause during normal traveling with the key switch 2 in the ON state. When switching to the off state,
It is possible to reliably stop the power supply to the motor driver. That is, if the diodes 14 and 15 fail and are short-circuited, power may be supplied from the key switch 2 to the motor driver 8 via the diodes 14 and 15 in the first and second embodiments. According to the present embodiment, even if the diode 14, the diode 15, or the relay 16 fails, it is possible to prevent the fail-safe relay 3 that is turned off from supplying power to the motor driver.

In the present embodiment, the relay 17 is taken as an example of the motor power supply means, but a switching element having the same function may be used.

[0064]

According to the configuration of (1) of the present invention, when the driver turns off the key switch while steering the steering wheel, the electric power is continuously supplied to the electric motor and the electric power is gradually reduced. As a result, the assist torque of the electric motor can be gradually reduced, and in response to this, the elastic force accumulated in the torsion bar or the like gradually rises and kickback can be suppressed. (Corresponding to item 1).

According to the configuration (2) of the present invention, the same effect as the above (1) can be obtained, and at the same time, the power supply is stopped when the power command value decreases to a certain value. It is possible to suppress waste of electric power and suppress over-discharge of the battery (corresponding to claim 2).

Further, according to the configuration (3) of the present invention,
By controlling the startup time of the motor driver means,
The same effect as the above (1) can be obtained. further,
According to the configuration (4) of the present invention, the same effect as that of the above (1) can be obtained, and at the same time, the battery is charged by continuing to drive the drive source even after the key switch is turned off, and the overdischarge is prevented. Can be prevented.

Further, according to the configuration (5) of the present invention, the same effect as that of the above (1) can be obtained, and the fail-safe effect can be ensured even during normal running with the key switch turned on. can do.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric power steering device according to a first embodiment.

FIG. 2 is an operation flowchart of a control circuit

FIG. 3 is a configuration diagram of an electric power steering device according to a second embodiment.

FIG. 4 is an operation flowchart of the control circuit.

FIG. 5 is a configuration diagram of an electric power steering device according to a third embodiment.

FIG. 6 is a configuration diagram of an electric power steering device according to a fourth embodiment.

[Explanation of symbols]

 1 ... Battery 2 ... Key switch 3 ... Failsafe relay 5 ... Controller power supply circuit 6 ... Sensor unit 7 ... Current detector 8 ... Motor driver 9 ... Electric motor 10 ... Control circuit 14 ...・ Diode 15 ・ ・ Diode 16 ・ ・ Relay driver 17 ・ ・ Relay 100 ・ ・ Fail-safe judgment unit 101 ・ ・ Comparator 102 ・ ・ NOR circuit 103 ・ ・ Assistance amount calculation unit 104 ・ ・ Error amplifier 105 ・ ・ PWM calculation unit 106 ..Subtractors

Claims (5)

[Claims] 1. An electric power steering apparatus that connects a steering input shaft and an output shaft via a torsion bar, and drives a motor connected to the output shaft according to a relative twist angle of the input / output shaft. A battery that supplies power to the motor, a key switch that switches between supply and cutoff of power from the battery to the motor, relative twist detection means that detects relative twist of the torsion bar, and the key switch is in a cutoff state. When a relative twist occurs in the torsion bar, the power supply means for supplying power to the motor and the power supplied from the power supply means to the motor are gradually reduced from the power supply means. An electric power steering apparatus, comprising: a control unit that shuts off power supply to the motor. 2. The control means includes an assist amount determination unit that determines a designated current value to be supplied to the motor based on the relative twist amount and / or the traveling state of the vehicle, and the assist amount determination unit is the After the key switch is turned off, the command current value to be supplied to the motor from the power supply means is gradually reduced, and when the command current value decreases to a constant value, the command current value is set to zero. The electric power steering apparatus according to claim 1, wherein 3. Further, there is provided a motor driver unit for driving the electric motor, wherein the control unit gradually reduces a starting time of the motor driver unit after the key switch is turned off. The electric power steering apparatus according to claim 1, further comprising a portion. 4. The output from the key switch and the output from the power supply means are connected to a device that drives a driving source of the vehicle, and the relative twist occurs after the key switch is in a cutoff state. 2. The electric power steering apparatus according to claim 1, wherein electric power is supplied from the electric power supply means to the device and the drive source is continuously driven while the power supply means is in operation. 5. An electric power holding means for taking in the electric power on the input side of the electric power supply means is provided, and an electric power holding means for taking the output from the electric power holding means as the output from the key switch and the operating power of the control means The electric power steering apparatus according to claim 1, further comprising means.