JPH0776280A - Motor-driven power steering device equipped with power source voltage controller - Google Patents

Abstract

PURPOSE:To improve the reduction of the electric conduction efficiency in the increase of a load, by boosting the electric power source voltage according to the reduction of the car speed, when the electric power source voltage of an on-vehicle battery which is supplied to the motor for steering assistance is controlled on the basis of the control signal applied with the car speed correspondence characteristic. CONSTITUTION:The flip flop FF of an electric power source voltage control circuit 20 receives the output signal of an oscillation circuit OSC and outputs the ac pulse signal. Each pulse width modulation circuit PWN1, PWM2 receives the car speed signal of a car speed sensor 9 as the output signal of each frequency-voltage converter FV, and converts the ON/OFF duty ratio of the ac pulse signal. Accordingly, the car speed correspondence characteristic is applied to the ac pulse signal, and each pulse turning-ON time is increased, accompanied kith the reduction of the car speed. Further, the ac pulse signal is inputted into each transistor T1, T2 of a boosting voltage circuit through each electric power source driving circuit DV1, DV2. A boosting voltage circuit boosts the electric power source voltage of an on-vehicle battery 7 according to the ac pulse signal.

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 system for a vehicle equipped with a power supply voltage control system for controlling power supply from a power source which is an on-vehicle battery to a steering assisting motor.

[0002]

2. Description of the Related Art Generally, in an electric power steering apparatus using a steering assisting motor, a power supply voltage of an on-vehicle battery is supplied to the motor via an electronic control circuit according to a driving state of the vehicle. Specifically, the electronic control circuit outputs a control signal to which a vehicle speed response characteristic according to the detected vehicle speed and a steering response characteristic according to the detected steering (steering speed, steering torque) are added, and The electric power steering device is configured to decrease the steering assist force as the vehicle speed increases, or increase the steering assist force as the steering speed and the steering torque increase.

In such a conventional electric steering system, a current of several tens of amperes flows through a vehicle battery of, for example, 12 volts at the maximum load of the steering assist (during dry parking and running at an extremely low speed). There will be a considerable voltage drop due to the resistance, thus reducing the voltage input to the electronic control circuit. Furthermore, this input voltage also receives the voltage drop of the semiconductor element (for example, MOSFET) in the electronic control circuit and the voltage drop of the wire cable connecting the electronic control circuit and the motor, and the voltage actually supplied to the motor is about 7 volts. However, there is a drawback that the current-carrying efficiency is significantly reduced.

[0004]

The problem to be solved by the present invention is that the energization efficiency from the on-vehicle battery to the motor is significantly reduced at the maximum load of steering assist.

Further, in the conventional electric power steering apparatus, since a relatively large current is supplied to the motor winding, electromagnetic noise caused by the exciting current is generated.

Further, in the conventional electric power steering apparatus, it is inevitable to use a semiconductor element having an appropriate large current capacity so as to withstand a large current at the time of the maximum steering load, and the electronic control circuit section associated therewith is required. There were also problems of large size and high cost.

Generally, it is well known that the voltage drop and the electromagnetic noise as described above are both proportional to the square of the current value. Therefore, if such a reduction in current value is possible, extremely good results can be expected.

[0008]

SUMMARY OF THE INVENTION The present invention provides a high-voltage electronic control circuit and a motor by providing a power supply voltage control device that boosts the power supply voltage of an on-vehicle battery in response to a decrease in vehicle speed during steering assistance. This has made it possible to reduce the resistance loss of the entire electric system.

Further, the present invention provides a power supply voltage control device for boosting the power supply voltage of a vehicle-mounted battery in response to a decrease in vehicle speed and an increase in steering speed during steering assistance.

[0010]

1 is a schematic diagram of an electric power steering apparatus of the present invention to which a power supply voltage control apparatus can be applied.

The operation of the electric power steering system will be described with reference to FIG. The steering of the steering wheel 1 moves the rack bars at both ends of the rack gear in the axial direction via the rack and pinion gear 2 and the rack gear in the housing 3. The axial movement of the rack bar is further transmitted to the wheel 5 via the tie rod 4. A motor 6 for steering assistance is connected to the rack gear in the housing 3, and the rotation of the motor 6 assists the axial movement of the rack bar. The power supply voltage of the vehicle-mounted battery 7 is supplied to the motor 6 via the electronic control circuit 8. Electronic control circuit 8
Is the vehicle speed signal detected by the vehicle speed sensor 9, the steering speed sensor 1
The steering speed signal detected at 0 and the steering torque signal detected by the steering torque sensor 11 are input, and a control signal indicating the vehicle speed sensitive characteristic and the steering sensitive characteristic is output. Therefore, the motor 6 is rotationally controlled according to the control signal output from the electronic control circuit 8 to achieve a desired steering assist force.

FIG. 2 is a block circuit diagram of an electric power steering apparatus equipped with the power supply voltage control apparatus of the present invention.
It is composed of an on-vehicle battery 7, a power supply voltage control device 20, a vehicle speed sensor 9, a steering torque sensor 11, a power drive circuit 21, a power output circuit 22, and a three-phase motor 6.

As will be described later with reference to FIG. 3, the power supply voltage control device 20 includes a voltage doubler circuit, and receives a speed signal from the speed sensor 9, and thereby a power supply voltage according to a speed-sensitive boost characteristic, that is, a decrease in speed. Is configured to boost.

The power drive circuit 21 is a three-phase step pulse signal generation circuit, and controls the firing of the power output circuit 22 according to the steering signal detected by the steering torque sensor 11. That is, the three-phase step signal output from the power drive circuit 21 is subjected to pulse width modulation (PWM) control in which the ON-OFF duty ratio is changed according to the magnitude of the steering torque when the steering wheel 1 is rotated,
Also steering. This is a three-phase step pulse signal with polarity discrimination according to the steering rotation direction when the wheel 1 is rotated. Therefore, the power drive circuit 21 has a steering torque sensitive characteristic and is configured to sequentially output the three-phase step pulse signals in accordance with the magnitude and polarity of the steering torque.

The power output circuit 22 supplies the control power supply voltage from the power supply voltage control device 20 having the speed sensitive boosting characteristic as described above to each winding of the three-phase motor. At this time, power supply to each winding is sequentially performed by firing control of the three-phase step pulse signal from the power drive circuit 21 having the steering torque sensitive characteristic as described above.

FIG. 3 is a detailed view of the block circuit diagram of FIG. 2, and particularly shows details of the power supply voltage control device 20.

The power supply voltage controller 20 includes MOS field effect transistors T1 and T2, reverse current blocking diodes D1 and D2, boost capacitors C1 and C2, an oscillation circuit OSC, a flip-flop FF, and a pulse width modulation circuit P.
It is composed of WM1 and PWM2, and power supply drive circuits DV1 and DV2. In the power supply voltage control circuit 20, the transistors T1 and T2, the diodes D1 and D
2. The boost capacitors C1 and C2 form a voltage doubler circuit that functions as a D-D converter, and the remaining circuit elements form a drive circuit for the voltage doubler circuit.

The operation of the circuit of FIG. 3 will be described below.

The flip-flop FF is an oscillator circuit OS.
Upon receiving the output signal of C, the alternating pulse signal is sequentially given to the pulse width modulation circuits PWM1 and PWM2. The pulse width modulation circuits PWM1 and PWM2 respectively input the vehicle speed signal detected by the vehicle speed sensor 9 as an output signal of the frequency-voltage converter F / V, and turn on / off the alternating pulse signal from the flip-flop FF. Change the duty ratio. Therefore, a vehicle speed response characteristic is added to the alternating pulse signals output from the pulse width modulation circuits PWM1 and PWM2, and the ON period of each pulse increases as the vehicle speed decreases.
Such an alternating pulse signal is transmitted through the power supply drive circuits DV1 and DV2 respectively to the transistor T of the voltage doubler circuit.
It is applied to its terminals G1 and G2 as gate signals of 1 and T2.

The voltage doubler circuit boosts the power supply voltage of the vehicle battery 7 in response to the alternating pulse signal as the gate signal. That is, when the first alternating pulse output from the pulse width modulation circuit PWM1 makes the transistor T1 conductive,
First, battery 7, transistor T1, capacitor C
1, a closed circuit of the diode D1 and the battery 7 is formed, the capacitor C1 is filled up to the power supply voltage,
Then, when the second alternating pulse outputted from the pulse width modulation circuit PWM2 turns on the transistor T2, a closed circuit of the battery 7, the diode D2, the capacitor C2, the transistor T2 and the battery 7 is formed, and the capacitor C2 is connected to the capacitor C1. It is charged up to the power supply voltage with the same polarity as. Therefore, as a result, a voltage twice the power supply voltage is obtained across the capacitors C1 and C2 connected in series.

The output characteristic of the voltage doubler circuit is determined by the vehicle speed response characteristic as shown in FIG. 4. Specifically, when the speed is low, for example, 10 km / H or less, it is twice the power supply voltage. Is determined so as to obtain the maximum voltage, and is gradually decreased with an increase in vehicle speed.

The voltage doubler circuit to which the speed sensitive characteristic is added, that is, the output of the power supply voltage controller 20, is the power output circuit 2.
Each winding Lu of the three-phase motor 6 under the control of 2 (FIG. 2),
It is sequentially supplied to Lv and Lw. In the phase rotation control of the three-phase motor 6, as described with reference to FIG. 2, the three-phase step pulse signal output from the power drive circuit 21 to which the steering torque characteristic is added is the MOS of the power output circuit 22. -Shaped field effect transistors Tu, Tv and Tw each gate G
This is done by sequentially triggering u, Gv and Gw. The steering rotation direction is determined by the polarity discrimination of the steering torque signal and the phase conversion of the three-phase step pulse signal.

In the above description of the embodiment, in order to boost the power supply voltage in response to an increase in the load of steering assistance, the vehicle speed is monitored and the power supply voltage control device 20 is provided with a vehicle speed response characteristic. Occurs not only when the vehicle is stopped or running at an extremely low speed, but also as the operation speed of the steering wheel increases. Therefore, it is effective to monitor the vehicle speed as well as the steering speed.

In this case, as indicated by the broken line in FIG.
The steering speed sensor 1 is attached to the pulse width modulation circuits PWM1 and PWM2.
The steering speed signal detected at 0 is input, and the steering speed response characteristic is added to the alternating pulse signal together with the vehicle speed response characteristic. When the steering speed response characteristic is reflected in the power supply voltage-vehicle speed characteristic curve of FIG.
It can be understood as the difference between the broken line and the solid line.

[0025]

As described above, according to the present invention,
By using the DC-DC conversion function, by boosting the power supply voltage of the vehicle-mounted battery at the time of assisting steering with a decrease in vehicle speed and with a decrease in vehicle speed and an increase in steering speed,
Since the load current is substantially reduced, resistance loss can be reduced throughout the electric system of the electric power steering system. Therefore, it is possible to improve the efficiency of energization from the vehicle-mounted battery to the steering assist motor.

Further, according to the present invention, the semiconductor element which constitutes the electronic control circuit due to the reduction of the load current, and further the motor itself can be constituted by a high voltage device having a relatively small current capacity, and therefore, the electronic control circuit. In particular, it is possible to reduce the size of the electric power unit and reduce electromagnetic wave noise leaking from the wire cable connecting the electronic control circuit and the motor.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electric power steering apparatus of the present invention to which a power supply voltage control circuit can be applied.

FIG. 2 is a block circuit diagram of an electric power steering device including a power supply voltage control device of the present invention.

FIG. 3 is a detailed view of the block circuit of FIG.

FIG. 4 is a diagram showing an operating characteristic curve of the present invention.

[Explanation of symbols] 1 steering wheel 2 rack and pinion gear 3 housing 4 tie rod 5 wheel 6 (three-phase) motor 7 vehicle battery 8 electronic control circuit 9 vehicle speed sensor 10 steering speed sensor 11 steering torque sensor 20 power supply voltage control Device 21 Power drive circuit 22 Power output circuit T1, T2, Tu, Tv, Tw MOS type field effect transistor D1, D2 Backflow prevention diode C1, C2 Boost capacitor OSC Oscillation circuit FF flip-flop PWM1, PWM2 Pulse width modulation circuit DV1, DV2 Power supply drive circuit F / V frequency-voltage converter

[Procedure amendment]

[Submission date] November 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering system for a vehicle equipped with a power supply voltage control system for controlling power supply from a power source which is an on-vehicle battery to a steering assisting motor.

[0002]

2. Description of the Related Art Generally, in an electric power steering apparatus using a steering assisting motor, a power supply voltage of an on-vehicle battery is supplied to the motor via an electronic control circuit according to a driving state of the vehicle. Specifically, the electronic control circuit outputs a control signal to which a vehicle speed response characteristic according to the detected vehicle speed and a steering response characteristic according to the detected steering (steering speed, steering torque) are added, and The electric power steering device is configured to decrease the steering assist force as the vehicle speed increases, or increase the steering assist force as the steering speed and the steering torque increase.

In such a conventional electric steering system, a current of several tens of amperes flows through a vehicle battery of, for example, 12 volts at the maximum load of the steering assist (during dry parking and running at an extremely low speed). There will be a considerable voltage drop due to the resistance, thus reducing the voltage input to the electronic control circuit. Furthermore, this input voltage also receives the voltage drop of the semiconductor element (for example, MOSFET) in the electronic control circuit and the voltage drop of the wire cable connecting the electronic control circuit and the motor, and the voltage actually supplied to the motor is about 7 volts. However, there is a drawback that the current-carrying efficiency is significantly reduced.

[0004]

The problem to be solved by the present invention is that the energization efficiency from the on-vehicle battery to the motor is significantly reduced at the maximum load of steering assist.

Further, in the conventional electric power steering apparatus, since a relatively large current is supplied to the motor winding, electromagnetic noise caused by the exciting current is generated.

Further, in the conventional electric power steering apparatus, it is inevitable to use a semiconductor element having an appropriate large current capacity so as to withstand a large current at the time of the maximum steering load, and the electronic control circuit section associated therewith is required. There were also problems of large size and high cost.

Generally, it is well known that the voltage drop and the electromagnetic noise as described above are both proportional to the square of the current value. Therefore, if such a reduction in current value is possible, extremely good results can be expected.

[0008]

SUMMARY OF THE INVENTION The present invention provides a high-voltage electronic control circuit and a motor by providing a power supply voltage control device that boosts the power supply voltage of an on-vehicle battery in response to a decrease in vehicle speed during steering assistance. This has made it possible to reduce the resistance loss of the entire electric system.

Further, the present invention provides a power supply voltage control device for boosting the power supply voltage of a vehicle-mounted battery in response to a decrease in vehicle speed and an increase in steering speed during steering assistance.

[0010]

1 is a schematic diagram of an electric power steering apparatus of the present invention to which a power supply voltage control apparatus can be applied.

The operation of the electric power steering system will be described with reference to FIG. The steering of the steering wheel 1 moves the rack bars at both ends of the rack gear in the axial direction via the rack and pinion gear 2 and the rack gear in the housing 3. The axial movement of the rack bar is further transmitted to the wheel 5 via the tie rod 4. A motor 6 for steering assistance is connected to the rack gear in the housing 3, and the rotation of the motor 6 assists the axial movement of the rack bar. The power supply voltage of the vehicle-mounted battery 7 is supplied to the motor 6 via the electronic control circuit 8. Electronic control circuit 8
Is the vehicle speed signal detected by the vehicle speed sensor 9, the steering speed sensor 1
The steering speed signal detected at 0 and the steering torque signal detected by the steering torque sensor 11 are input, and a control signal indicating the vehicle speed response characteristic and the steering response characteristic is output. Therefore, the motor 6 is rotationally controlled according to the control signal output from the electronic control circuit 8 to achieve a desired steering assist force.

FIG. 2 is a block circuit diagram of an electric power steering apparatus equipped with the power supply voltage control apparatus of the present invention.
It is composed of an on-vehicle battery 7, a power supply voltage control device 20, a vehicle speed sensor 9, a steering torque sensor 11, a power drive circuit 21, a power output circuit 22, and a three-phase motor 6.

As will be described later with reference to FIG. 3, the power supply voltage control device 20 includes a voltage doubler circuit, and receives a speed signal from the speed sensor 9, and thereby a power supply voltage according to a speed-sensitive boost characteristic, that is, a decrease in speed. Is configured to boost.

The power drive circuit 21 is a three-phase step pulse signal generation circuit, and controls the firing of the power output circuit 22 according to the steering signal detected by the steering torque sensor 11. That is, the three-phase step signal output from the power drive circuit 21 is subjected to pulse width modulation (PWM) control in which the ON-OFF duty ratio is changed according to the magnitude of the steering torque when the steering wheel 1 is rotated,
Also steering. This is a three-phase step pulse signal with polarity discrimination according to the steering rotation direction when the wheel 1 is rotated. Therefore, the power drive circuit 21 has a steering torque sensitive characteristic and is configured to sequentially output the three-phase step pulse signals in accordance with the magnitude and polarity of the steering torque.

The power output circuit 22 supplies the control power supply voltage from the power supply voltage control device 20 having the speed sensitive boosting characteristic as described above to each winding of the three-phase motor. At this time, power supply to each winding is sequentially performed by firing control of the three-phase step pulse signal from the power drive circuit 21 having the steering torque sensitive characteristic as described above.

FIG. 3 is a detailed view of the block circuit diagram of FIG. 2, and particularly shows details of the power supply voltage control device 20.

The power supply voltage controller 20 includes MOS field effect transistors T1 and T2, reverse current blocking diodes D1 and D2, boost capacitors C1 and C2, an oscillation circuit OSC, a flip-flop FF, and a pulse width modulation circuit P.
It is composed of WM1 and PWM2, and power supply drive circuits DV1 and DV2. In the power supply voltage control circuit 20, the transistors T1 and T2, the diodes D1 and D
2. The boost capacitors C1 and C2 form a voltage doubler circuit that functions as a D-D converter, and the remaining circuit elements form a drive circuit for the voltage doubler circuit.

The operation of the circuit of FIG. 3 will be described below.

The flip-flop FF is an oscillator circuit OS.
Upon receiving the output signal of C, the alternating pulse signal is sequentially given to the pulse width modulation circuits PWM1 and PWM2. The pulse width modulation circuits PWM1 and PWM2 respectively input the vehicle speed signal detected by the vehicle speed sensor 9 as an output signal of the frequency-voltage converter F / V, and turn on / off the alternating pulse signal from the flip-flop FF. Change the duty ratio. Therefore, a vehicle speed response characteristic is added to the alternating pulse signals output from the pulse width modulation circuits PWM1 and PWM2, and the ON period of each pulse increases as the vehicle speed decreases.
Such an alternating pulse signal is transmitted through the power supply drive circuits DV1 and DV2 respectively to the transistor T of the voltage doubler circuit.
It is applied to its terminals G1 and G2 as gate signals of 1 and T2.

The voltage doubler circuit boosts the power supply voltage of the vehicle battery 7 in response to the alternating pulse signal as the gate signal. That is, when the first alternating pulse output from the pulse width modulation circuit PWM1 makes the transistor T1 conductive,
First, battery 7, transistor T1, capacitor C
1, a closed circuit of the diode D1 and the battery 7 is formed, the capacitor C1 is filled up to the power supply voltage,
Then, when the second alternating pulse outputted from the pulse width modulation circuit PWM2 turns on the transistor T2, a closed circuit of the battery 7, the diode D2, the capacitor C2, the transistor T2 and the battery 7 is formed, and the capacitor C2 is connected to the capacitor C1. It is charged up to the power supply voltage with the same polarity as. Therefore, as a result, a voltage twice the power supply voltage is obtained across the capacitors C1 and C2 connected in series.

The output characteristic of the voltage doubler circuit is determined by the vehicle speed response characteristic as shown in FIG. 4. Specifically, when the speed is low, for example, 10 km / H or less, it is twice the power supply voltage. Is determined so as to obtain the maximum voltage, and is gradually decreased with an increase in vehicle speed.

The voltage doubler circuit to which the speed sensitive characteristic is added, that is, the output of the power supply voltage controller 20, is the power output circuit 2.
Each winding Lu of the three-phase motor 6 under the control of 2 (FIG. 2),
It is sequentially supplied to Lv and Lw. In the phase rotation control of the three-phase motor 6, as described with reference to FIG. 2, the three-phase step pulse signal output from the power drive circuit 21 to which the steering torque characteristic is added is the MOS of the power output circuit 22. -Shaped field effect transistors Tu, Tv and Tw each gate G
This is done by sequentially triggering u, Gv and Gw. The steering rotation direction is determined by the polarity discrimination of the steering torque signal and the phase conversion of the three-phase step pulse signal.

In the above description of the embodiment, in order to boost the power supply voltage in response to an increase in the load of steering assistance, the vehicle speed is monitored and the power supply voltage control device 20 is provided with a vehicle speed response characteristic. Occurs not only when the vehicle is stopped or running at an extremely low speed, but also as the operation speed of the steering wheel increases. Therefore, it is effective to monitor the vehicle speed as well as the steering speed.

In this case, as indicated by the broken line in FIG.
The steering speed sensor 1 is attached to the pulse width modulation circuits PWM1 and PWM2.
The steering speed signal detected at 0 is input, and the steering speed response characteristic is added to the alternating pulse signal together with the vehicle speed response characteristic. When the steering speed response characteristic is reflected in the power supply voltage-vehicle speed characteristic curve of FIG.
It can be understood as the difference between the broken line and the solid line.

Further, in the above description of the embodiments, a three-phase motor is exemplified as an electric motor for assisting steering, but a multi-phase stepping motor such as a three-phase or four-phase motor,
It is also possible to use a general DC motor, AC servo motor, or the like.

Further, in the description of the embodiments, an electric power steering device of the type in which a rack shaft is directly driven by an electric motor to apply a steering assist force is exemplified.
It goes without saying that the electric power steering device includes a hydraulic type device in which a hydraulic pump is driven by an electric motor and a steering assist force is hydraulically applied.

[0027]

As described above, according to the present invention,
By using the DC-DC conversion function, by boosting the power supply voltage of the vehicle-mounted battery at the time of assisting steering with a decrease in vehicle speed and with a decrease in vehicle speed and an increase in steering speed,
Since the load current is substantially reduced, resistance loss can be reduced throughout the electric system of the electric power steering system. Therefore, it is possible to improve the efficiency of energization from the vehicle-mounted battery to the steering assist motor.

Further, according to the present invention, the semiconductor element which constitutes the electronic control circuit by reducing the load current, and further the motor itself can be constituted by a high voltage device having a relatively small current capacity. In particular, it is possible to reduce the size of the electric power unit and reduce electromagnetic wave noise leaking from the wire cable connecting the electronic control circuit and the motor.

Claims (3)

[Claims] 1. A power supply voltage of an on-vehicle battery supplied to a steering assisting motor, comprising an electronic control circuit for outputting a control signal to which a vehicle speed sensitive characteristic is added in response to a vehicle speed signal detected by a vehicle speed sensor. In the electric power steering device configured to be controlled according to the control signal, the electronic control circuit includes a power supply voltage control device that boosts the power supply voltage of the vehicle-mounted battery in response to a decrease in vehicle speed. An electric power steering device comprising: 2. The power supply voltage control device is configured to respond to a steering speed signal detected by a steering speed sensor, and further increase the power supply voltage of the vehicle-mounted battery according to an increase in the steering speed. The electric power steering device according to claim 1, wherein: 3. The power supply voltage control device is configured to boost up to a voltage approximately twice as high as a power supply voltage of the vehicle-mounted battery at maximum when the vehicle speed is equal to or lower than a predetermined speed. Alternatively, the electric power steering device according to item 2.