JPH0651475B2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has an electric power steering apparatus which has a two-system configuration of a torque direction determination circuit section in a torque detection circuit section of a motor to improve the safety thereof. It is about.

[Conventional technology]

A conventional electric power steering device using a motor is provided with a torque detector for steering torque control, and an auxiliary torque that is approximately proportional to the output of this torque detector is generated by the motor and supplied to the steering shaft. The steering force is assisted to reduce the steering force of the steering wheel.

FIG. 3 is a block diagram of a conventional electric power steering apparatus, in which 1 is a steering torque detector (hereinafter referred to as torque detector), 16 is a motor control circuit section, and 15A,
Reference numeral 15B is an input terminal of the motor control circuit unit 2, 2 is an interface circuit of the torque detector, and the output of the torque detector 1 is a CPU via the interface circuit 2.
(Microcomputer, hereinafter referred to as microcomputer) 3 is input.

The output of the CPU 3 is the motor right direction drive interface circuit 4, the motor left direction drive interface circuit 5, D /
The signal is sent to the A (digital / analog) conversion circuit 6, and the rightward drive signal of the CPU 3 is passed through the rightward drive interface circuit 4 to the motor drive circuit 10.
It is designed to be input to.

Similarly, the leftward drive signal of the CPU 3 is input to the motor drive circuit 10 via the leftward drive interface circuit 5.

Reference numerals 13A and 13B denote output terminals of the motor drive circuit 10, through which the motor 14 is drive-controlled. Motor 14
Is a motor that is coupled to the steering shaft via coupling means (not shown) and that applies a steering assist force to the steering shaft.

On the other hand, 7 is an error amplifier for motor control, and the torque signal of the CPU 3 is input to one of its input terminals as an analog signal D / A converted by the D / A conversion circuit 6.

The output signal of the motor current detection circuit 11 is input to the other input terminal of the error amplifier 7. The error amplifier 7 is D /
The error between the output signal of the A conversion circuit 6 and the output of the motor current detection circuit 11 is amplified, and PWM (pulse width modulation) of the next stage is amplified.
The signal is output to one input terminal of the modulator 8.

The output of a pulse width modulation (referred to as PWM) oscillation circuit 9 as a reference oscillator is input to the other input terminal of the PWM modulator 8. The PWM modulator 8 outputs the output of the error amplifier 7 and the PWM oscillation circuit. The PWM signal of the motor 14 is generated by the motor drive circuit 10 by comparing the output of the motor drive circuit 9.

Further, a detection resistor 12 is provided between the motor drive circuit 10 and the ground.
Are connected, and a voltage corresponding to the current detected by the detection resistor 12 is applied to the motor current detection circuit 11.

Next, an example of motor control in the conventional example will be described.
The figure shows an example of the output characteristics of the torque detector 1.
The horizontal axis shows the (left / right) steering torque, and the vertical axis shows the torque signal output. T ₀ shows the neutral point (zero torque point) of the steering torque. From this point, the right rotation steering torque is shown. To
The left rotation steering torque is shown in the left direction. T ₂ indicates the steering torque at the control start point in the right direction, T ₁ indicates the steering torque at the control start point in the left direction, the vertical axis indicates the torque output corresponding to the steering torque, and V ₀ is neutral. Point output, V ₂ indicates the rightward control start point output, and V ₁ indicates the leftward control start point output, and the torque output characteristic is almost linear within the control range.

In addition, the dead zone of control is between the neutral points T ₀ and T _{1 of} the steering torque between T _{1 and} T ₂ .

FIG. 5 shows an example of the control output characteristics of the motor.
The horizontal axis shows the torque signal output and the vertical axis shows the motor output. V ₀ is the neutral point output of the torque detector, V ₂ is the right direction control start point output, and V ₃ is the right direction saturation point torque output. , the torque output signal is the motor output between V ₂ ~V ₃ is almost linear control over the torque output is made.

The motor output is zero between the torque outputs V _{0 and} V ₂ , and when the torque output exceeds V ₃ , the motor output is controlled to a constant value (Pmax). Similarly, V ₁ is the left-direction control start point torque, V ₄ is the left-direction saturation point torque, and when the steering torque is between V _{1 and} V ₄ , the motor output is linearly controlled almost symmetrically to the right rotation. Is done and V
₀ ~V ₁ between the motor output zero, exceeds V _4, the motor output control is performed at a constant value (Pmax).

Next, the overall flow of motor torque control will be described with reference to FIG. 3. A torque signal proportional to the steering torque is output from the torque detector 1 and input to the CPU 3 via the torque signal interface circuit 2. .

The CPU 3 outputs the torque signal as a digital signal, and the D / A converter 6 at the next stage converts the torque signal into an analog signal again.

The torque signal output is level-determined in the CPU 3, the right rotation drive signal is input to the motor right direction drive interface circuit 4, and the left rotation drive signal is input to the motor left direction drive interface circuit 5.

The (left / right) rotation drive signals are respectively input to the motor drive circuit 10, the rotation direction of the motor 14 is instructed, and the torque signal is analogized by the D / A converter 6 and input to the error amplifier 7. To be done. This output is further input to the PWM converter 8 of the next stage, modulated by the output of the oscillation circuit 9 for PWM, and supplied to the motor drive circuit 10 of the next stage as a control signal having a pulse width proportional to the output of the torque detector 1. The torque is output from the motor 14, and the torque of the motor 14 connected to the output terminals 13A and 13B is controlled.

The motor current is detected by the detection resistor 12 and its level is limited or cut off by the motor current detection circuit 11.
Is done.

By the way, the rotation direction of the motor is determined by receiving the output of the torque detector 1 and determining the level in the CPU 3 (microcomputer) of the motor control circuit unit 16 to determine the rotation direction of the motor.

[Problems to be Solved by the Invention]

Therefore, when the CPU loses its rotation direction determination function due to external noise or the like, the rotation direction of the motor is not fixed, and a very dangerous state is exhibited.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an electric power steering apparatus capable of avoiding an uncontrollable state when a CPU malfunctions and increasing its safety.

[Means for Solving the Problems]

An electric power steering apparatus according to the present invention includes a CPU that outputs a motor rotation direction signal, a left rotation drive signal, and a torque signal based on an output signal of a torque detector,
A motor rotation drive direction determination block that outputs a rightward drive signal and a leftward drive signal based on the output signal of the torque detector is provided.

[Work]

According to the present invention, the CPU outputs the right rotation direction drive signal and the left rotation direction drive signal of the motor based on the output signal of the torque detector to drive the motor drive circuit, and the motor rotation drive based on the output signal of the torque detector. A rightward drive signal and a leftward drive signal are output from the direction discriminating block, and only when the direction of the drive signal from the CPU coincides with the direction of the signal from the discriminating block, the drive signal of the motor drive circuit is obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, reference numerals 1 to 16 are the same as in the conventional example of FIG. 3, and the description of the configuration is omitted. Reference numeral 17 is a portion newly added according to the present invention, which is a motor rotation drive direction determination block. The output signal from the torque detector 1 is input to the torque signal direction determination circuit 17A, and the rightward drive signal 1 is input.
7B and a leftward drive signal 17C are output.

The rightward drive signal 17B is input to the first input terminal of the AND circuit 20A, and the first input terminal of the AND circuit 20A is
The output signal of the motor right direction drive interface circuit 4 is introduced. The output of the AND circuit 20A is sent to the motor drive circuit 10.

Similarly, the leftward drive signal 17C is applied to the AND circuit 20B.
Is input to the second input end of the AND circuit 20B, and the first input end of the AND circuit 20B is connected to the motor leftward drive output interface circuit 5
The output of is input. AND circuit 20
The output of B is sent to the motor drive circuit 10. Other configurations are the same as those in FIG.

Next, the operation will be described. The output signal of the torque detector 1 is input to the CPU 3 and also input to the torque signal direction determination circuit 17A of the motor rotation drive direction determination block 17 to output the rightward drive signal 17B and the leftward drive signal 17C, respectively. AND circuit 20A, 20B
Is applied to the second input terminal of.

Further, a rightward drive signal from the CPU 3 is sent to the AND circuit 20A via the motor rightward drive output interface circuit 4.
And the motor leftward drive signal is applied to the first input end of the AND circuit 20B via the motor leftward drive output interface circuit 5.

As a result, the AND circuits 20A and 20B take AND inputs of both inputs to determine the coincidence, and only when the signals are determined to coincide with each other, the AND circuits 20A and 20B output the left and right rotation drive outputs to the motor drive circuit 10 to rotate the motor 14. The drive direction is specified.

FIG. 2 shows an embodiment of the torque signal direction discriminating circuit 17A composed of two comparators.

In FIG. 2, resistors 33 to 35 for creating a reference voltage are connected in series between a positive voltage 36 and a ground 37, and the voltage E _{1 at} the connection point between the resistors 33 and 34 is the right direction signal detection circuit. It is added to the (+) input terminal of 31 and resistor 34
The voltage E _{2 at} the connection point between
Has been added to the (-) input end of.

Reference numeral 30 is an input end to which the output signal of the torque detector 1 of FIG. 1 is input, and this input end 30 is the right direction signal detection circuit 3
It is connected to the (-) input end of 1 and the (+) input end of the leftward signal detection circuit 32.

Next, the operation will be described. First, the output signal from the torque detector 1 is input to the input terminal 30 and also input to the comparison terminals of the right direction signal detection circuit 31 and the left direction signal detection circuit 32, and the reference voltages E ₁ and E having different levels are provided. ₂ and the reference voltage E _{1 is} greater than the reference voltage E _{1, the} rightward drive signal EX is used, and when the voltage is less than the reference voltage E _{2, the} leftward drive signal EY is used and the AND circuits 20A and 20B of the next stage are used.
Is input to the CPU 3, and the CPU 3 determines that the driving direction signal is the same.

The dead zone width E ₀ is E ₀ = E ₁ −E ₂ .

Next, the advantages of the embodiment of the present invention over the prior art will be listed below.

(1) Non-steering (output of torque detector 1 ≈ neutral point output V ₀ )
In this state, even if the CPU 3 outputs the left and right erroneous drive signals, the second drive direction signal is not output, so that neither the drive signal (left / right) is output, and the motor 14
Is not driven.

(2) The motor 14 is not driven to the left or right even if the CPU 3 generates a drive signal in the left direction during steering to the right or the CPU 3 generates a drive signal in the right direction during steering to the left.

〔The invention's effect〕

As described above, according to the present invention, based on the output signal from the torque detector, the CPU determines whether the left / right rotation direction drive signal of the motor matches the left / right direction drive signal output from the motor rotation drive direction determination block. Since the presence and absence is discriminated by the AND circuit and output as the left and right rotation drive signals of the motor drive circuit when both signals match, the rotation drive direction of the motor is designated, and the CPU is affected by external noise or the like. Even if the function of discriminating the direction of rotation is lost, the motor is prevented from rotating in an unexpected direction, the safety of the motor is remarkably improved as compared with the conventional example, and its practical advantage is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric power steering apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a concrete configuration of a torque signal direction discriminating circuit in the same embodiment, and FIG. FIG. 4 is a block diagram of a conventional electric power steering device, FIG. 4 is an output characteristic diagram of a torque detector for explaining a conventional electric power steering device, and FIG. 5 is a diagram for explaining the operation of the conventional electric power steering device. It is a control output characteristic view of a motor. 1 ... Torque detector, 3 ... CPU, 10 ... Motor drive circuit, 14 ... Motor, 16 ... Motor control circuit section,
17 ... Motor rotation drive determination block, 17A ... Torque signal direction determination circuit, 20A, 20B ... AND circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A motor that is coupled to a steering shaft via coupling means and that applies a steering assist force to the steering shaft, a steering torque detector that determines the steering assist force of the motor, and In an electric power steering apparatus comprising a motor control circuit unit that controls the torque of the motor by the output of a steering torque detector, a right drive signal and a left drive signal of the motor based on the output of the steering torque. And a motor rotation drive direction determination block which outputs a rightward drive signal and a leftward drive signal from the output of the steering torque detector, which is provided in the motor control circuit section, the microcomputer and the motor. Only when the rotation drive direction determination block and the right drive signal are both output, Rightward drive a first AND circuit for performing designated, the microcomputer and the motor rotational drive direction detection block and the second together for specifying the leftward drive of the motor only when outputting a leftward drive signal
And an AND circuit of the electric power steering device.