JPH0445388B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a steering device that automatically returns the steering system to the intermediate position using the power of an electric motor when the steering system is desired to return to the intermediate position. This invention relates to an intermediate position return device.

(Prior Art) A steering device converts the rotation of the steering wheel into a rocking motion of the wheels to enable steering of the vehicle.While the vehicle is running, the rotation of the steering wheel causes the vehicle to be steered. There is a patent in which the device itself attempts to return to the intermediate position using a caster trail or the like. Therefore, generally, when the steering wheel is released or the steering force is weakened, the steering wheel (steering system) is returned to the intermediate position.

(Problem to be Solved by the Invention) However, in the conventional steering device described above, when the vehicle is stopped, there is no force to return the steering wheel to the middle position, so even when parking on a narrow road or in a bad garage environment, It may be difficult to park the vehicle in a garage, etc., and it requires considerable driving experience, especially before the vehicle can be stopped straight. Furthermore, even when the vehicle starts from a state where the steering wheel has not returned to the middle position, it may be difficult to start the vehicle smoothly on a narrow road or in a poor garage environment.

(Purpose of the Invention) Therefore, the present invention enables smooth stopping and starting even on narrow roads or garages with poor garage environments by automatically returning the steering device to the middle position when the steering device is desired to return to the middle position. It is an object of the present invention to provide an intermediate position return device for a steering device that can be expected to perform a smooth return operation regardless of the size of the steering device.

(Means for Solving Problems and Their Effects) The intermediate position return device of the present invention includes a position detecting means for detecting the steering position of the steering system, a rotation detecting means for detecting the rotational speed of the electric motor, a switch means,
The motor control means determines and outputs a motor control signal for driving and controlling the electric motor based on the output signal from the position detecting means when the switch means is turned on. At the same time, the steering system is returned to the neutral position by controlling the drive of the electric motor based on the deviation between the electric motor control signal and the output signal from the rotation detection means. Therefore, regardless of the magnitude of the load on the road surface, it is possible to return the steering system to the intermediate position at any set return speed, thereby making the return operation smooth.

(Embodiment) A preferred embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1a is a schematic longitudinal cross-sectional view of a steering device equipped with the intermediate position return device of this embodiment, FIG. 1b is a plan view of a potentiometer, FIG. 2 is a control device thereof, and FIG. Shows control processing.

In Figure 1a, 1 is the steering shaft;
A steering wheel is fixed above the steering shaft 1 in the figure via a first universal joint, a first shaft, a second universal joint, and a second shaft (not shown). The steering shaft 1 is connected to the cap 2 of the case 2.
It is rotatably supported by angular contact bearings 4A and 4B, which are pressed by disc springs 3 to a, with play in the axial direction removed. Furthermore, the opening of the case 2 of the steering shaft 1 is provided with a sealing member 5.
A and a dust seal 5B are provided. Further, a pinion gear 1a is integrally provided on the steering shaft 1, and a rack 6a of a rack shaft (shaft-like member) 6 is meshed with the pinion gear 1a. Convert it into exercise. Furthermore, tie rods and knuckles (not shown) are connected to both ends of the rack shaft 6, respectively, so that the swinging motion of the wheels is converted to enable steering of the vehicle.

Further, a small-diameter toothed pulley 1b is pivotally attached to the other end of the steering shaft 1. Correspondingly, a potentiometer 7 is fixed to the case 2 substantially parallel to the steering shaft 1, and a first
As shown in FIG. b, a large-diameter toothed pulley 7a is pivotally mounted, and a timing belt 7b is wound between the large-diameter pulley 7a and the small-diameter pulley 1b. Therefore, the rotation of the steering shaft 1 is decelerated and transmitted to the potentiometer 7, and the rotation angle of the steering shaft 1 is converted into a resistance value of the potentiometer 7. This potentiometer 7 constitutes an intermediate position sensor.

A ball screw 8 is provided at the left end of the rack shaft 6 in FIG. 1a. This ball screw 8 has a spiral groove 6b formed on the outer peripheral surface of the rack shaft 6, a nut portion 8a having a spiral groove 8b on the inner peripheral surface and spiraled around the outer periphery of the spiral groove 6b, and a spiral groove 6b. It consists of a plurality of balls 8c surrounded by a ring 8b. Also,
The nut portion 8a is rotatably supported by the case 2 with angular contact bearings 9A and 9B pressed through disc springs to eliminate play in the axial direction, and is integrally provided with a large-diameter toothed pulley 8d on the outer periphery. ing. Corresponding to the large-diameter pulley 8d, an electric motor 9 is fixed to the case 2 substantially parallel to the rack shaft 6, and a small-diameter toothed pulley 9a is attached to the rotating shaft of the electric motor 9. Large diameter pulley 8d
A timing belt 11 is wound between the two. Therefore, the rotation of the electric motor 9 is caused by the rotation of the nut member 8 of the bolt screw 8 via the timing belt 11.
The rotation is transmitted to the shaft a, and converted into linear motion of the rack shaft 6 by the ball screw 8. In addition, 12,
12 is a sealing member.

Furthermore, a DC generator (tachogenerator) 13 is connected to the rotating shaft of the electric motor 9. Also,
There is a manual switch 2 near the steering wheel.
0 is set. These potentiometer 7, electric motor 9, switch 20, and exercise machine 13 are electrically connected to a control device 10.

Next, the control device 10 will be explained.

In FIG. 2, the intermediate position detection means (position detection means) 16 includes a potentiometer 7, a low-pass filter 23, and an operational amplifier 25. The potentiometer 7 consists of a resistor 17 and a contact piece 18. One end of the resistor 17 is connected to a constant voltage power supply A of a constant voltage circuit 46 (described later) through a resistor 21, and the other end is connected to a common side ( connected to ground). The contact piece 18 is input to a low-pass filter 23, and this circuit 23 removes noise caused by movement of the contact portion between the contact piece 18 and the resistor 17. The output of the low-pass filter 23 is connected to the inverting terminal of an operational amplifier 25 via a resistor 24. The voltage of power supply A is connected to the non-inverting terminal of the operational amplifier 25 through a resistor 26.
The voltage is divided into 1/2 by 27 and input through the resistor 28, and the divided voltage is directly input to the A/27.
It is input to the D converter 29 and becomes the reference voltage _S3 . Inverting terminal of operational amplifier 25 and operational amplifier 25
A negative feedback circuit is formed by the resistor 30 connected between the output terminal of the operational amplifier 25 and the output terminal of the operational amplifier 25 is connected to the input side of the A/D converter 29, and the intermediate position detection signal _S2 is output. The output of the A/D converter 29 is sent to the microcomputer unit 32.
The position detection signal is read based on the control described later.

The switch means 19 includes a manual switch 20 installed near the steering wheel, a low-pass filter 34, and a waveform shaping circuit 35. One end of the switch 20 is connected to the common side (ground), and the other end is connected to a constant voltage power supply A via a resistor 33 and is input to a low pass filter 34. low pass filter 3
4, the noise accompanying the opening and closing of the switch 20 is removed, and the output of the low-pass filter 34 is sent to the microcomputer unit 32 via the waveform shaping circuit 35.
The waveform shaping circuit 35 shapes _the waveform into a rectangular wave and outputs the output signal S ₁ when the switch is turned on.
is read based on the control described later.

The microcomputer unit 32 includes a CPU,
Reference clock, clock generator, ROM,
It is composed of RAM, I/O ports, etc., and operates according to a ROM in which control software, which will be described later, is written. The output side of this microcomputer unit 32 is connected via a D/A converter 36 to a motor drive means 44, which will be described later. Then, in _the microcomputer unit ₃₂ , motor control signals _T3 , _T4 ( _T3 :
A direction control signal ( _T4 : rotational speed control signal) is determined and output. Of the control signals, _T3 is sent to the drive unit 43 of the motor drive means 44, and _T4 is sent to the differential amplifier circuit 4 through the D/A converter 36.
It is output to the (+) input terminal of 0. Furthermore, the microcomputer unit 32 and the A/D converter 29
The D/A converter 36 constitutes a motor control signal generating means 37.

In FIG. 2, 38 is a rotation detection means, and this rotation detection means 38 includes the generator 13 and an absolute value amplification circuit 39 that amplifies the absolute value of the output voltage.
Therefore, a detection signal _S4 corresponding to the rotational speed of the electric motor 9 is obtained from the absolute value amplification circuit 39, and is input to the (-) input terminal of a differential amplification circuit 40, which will be described later.

The motor driving means 44 is composed of a differential amplifier circuit 40, a triangular wave generating circuit 41, a comparator circuit 42, a drive unit 43, and a bridge circuit consisting of FETs _Q1 to _Q4 .

The differential amplifier circuit 40 calculates and outputs a deviation ΔC between the rotation speed control signal T ₄ and the rotation speed detection signal S ₄ of the electric motor 9. Therefore, the differential amplifier circuit 4
0, it is output as the deviation ΔC between the motor control signal T ₄ and the current rotational speed of the motor 9. The output ΔC of the differential amplifier circuit 40 is input to the (+) input terminal of the comparison circuit 42, and the (-) input terminal of the comparison circuit 42 is connected to the triangular wave generation circuit 41. Therefore, in the comparator circuit 42, the level of the deviation output ΔC from the differential amplifier circuit 40 with respect to the triangular wave is compared and outputted to the drive unit 43 as a PWM signal C having a duty ratio corresponding to the deviation output ΔC.

The drive unit 43 uses a booster circuit for driving FETs Q ₁ and Q ₄ and a control signal T ₃ from the microcomputer unit 32 to drive the FETs Q 1 and Q 4 .
It consists of a circuit etc. that enables operation by switching Q ₁ , Q ₃ or FETQ ₂ , Q ₄ . The output of the drive unit 36 is connected to the respective gate terminals of FETQ ₁ and Q ₄ ,
The drain terminals of FETQ ₁ and Q ₄ are connected to the positive side of battery 45 .
The source terminals of FETQ ₁ and Q ₄ and the drain terminals of FETQ ₂ and Q ₃ are connected respectively to the source terminal of FETQ ₄ .
A connection portion between the drain terminal of FETQ ₃ and a connection portion between the source terminal of FETQ ₁ and the drain terminal of FETQ ₂ are connected to an electric motor 9. The respective drain terminals of FETQ ₂ and Q ₃ are connected to the common side.

Further, a constant voltage circuit 46 is connected to the positive terminal of the battery 45. The output A of the constant voltage circuit 46 is a constant voltage lower than the battery voltage 45, and is supplied to control circuits such as the low-pass filters 23 and 34, the waveform shaping circuit 35, the operational amplifier 25, and the microcomputer unit 32. The motor control signal generating means 37 and the motor driving means 44 constitute a motor control means.

In this embodiment, the microcomputer unit is controlled according to the flowchart shown in FIG. Note that P ₁ to _{P 23} in FIG. 3 indicate each step.

First, when the power is turned on, control starts,
In step _P1 , the registers in the CPU and the data in the RAM are cleared. In step _P2 , the output signal _S1 of the switch 20 is read. Here, if the switch 20 is turned ON, S ₁ is 0.
Therefore, when the switch 20 is OFF, _S1 becomes almost equal to the output voltage A of the constant voltage circuit 45 and becomes "1".
becomes. At step _P3 , it is determined whether the output signal _S1 of the switch 20 is "0", that is, whether it is ON. If it is OFF, _S1 = 1, so step _P2
It jumps to the switch 20 and waits for the input of the output signal from the switch 20.

If the switch 20 is ON, S ₁ = 0, so proceed to step P ₄ , read the detection signal S ₂ of the intermediate position detection means 16, and then, in step P ₅ , set the reference voltage.
Enter _S3 . At this time, the detection signal S ₂ and the reference voltage S ₃
is expressed as shown in FIG. Step P ₆ and S ₂
The difference between S3 and _S3 is processed to be S, and the amount and direction of deviation of the steering device from the middle position are calculated and stored in the S register. In step _P7 , it is determined whether the value of the S register is 0, and if it is 0, the step
Proceed to P ₈ , direction control signal T ₃ consisting of R=L=0
is output to the motor drive means 44, and all FETs (Q ₁ to Q ₄ ) of the motor drive means 44 are turned off. and,
In step _P9 , the value of the duty D, which is the rotational speed control signal _T4, is set to 0 and is output to the motor drive means 44 through the D/A converter 36. The program then jumps to step _P2 and waits for switch input.

If the value of the S register is positive or negative, its sign is determined in step _P10 . If the value in the S register is negative, step _P12 sets R to 0;
After setting L to 1, in step _P13 , the value in the S register is converted to sign S←-S, and the process proceeds to step _P14 . Step if the value in the S register is positive
Set R to 1 and L to 0 with P ₁₁ . In step _P14 , in order to provide a dead zone A for the value in the S register, the S-
Perform the operation A and store the subsequent value as S in the S register. Then, in step _P15 , the sign of the value S in the S register is determined. If it is negative, it is determined that the position is in the middle position since it is within the dead zone A, and the process jumps to step _P8 , where the operation of the motor drive means 44 is stopped.

On the other hand, if the value of S is positive, it is larger than the value of dead zone A, and therefore it is necessary to return to the middle position. Therefore, the process advances to step _P16 , and the data K and N values whose address is S in the S register are read out. That is, the ROM is configured with a table storing the data shown in FIG. 5, and this table uses the absolute value of the detection signal S ₂ −S ₃ as an address.
In the ROM, there is data that determines the rotation speed of the motor 9, that is, the armature voltage V corresponding to the duty value obtained by dividing the product of the motor's induced electromotive force constant k and the rotation speed N by the battery voltage V. Stored. Therefore, this duty value determines the rotation speed of the rotating machine of the electric motor. In step _P16 , the data in the ROM whose address is the data in the S register, that is, the speed duty, that is, the K·N value is called out, and in step _P17 , the read K·N value is set as the control duty value D. Store in register. And the steps
At step _P18 , the direction control signal _T3 consisting of R and L is outputted to the drive unit 43 of the motor drive machine 44, and at step _P19 , the rotational speed control signal _T4 consisting of the control duty value D in the D register is outputted to the drive unit 43 of the motor drive machine 44. /A converter 36, and from the D/A converter 36
T ₄ is output to differential amplifier 40 as an analog signal. In the microcomputer unit 32, this process is repeated until the detection signal S=S ₂ -S ₃ from the intermediate position detection means 16 enters the insensitive body A.

Further, the differential amplifier circuit 4 of the motor drive means 44
0, the deviation ΔC between the torque signal T ₄ converted into an analog signal by the D/A converter 36 and the detection signal S ₄ detected by the rotation detection means 38 is output. This deviation output ΔC is the deviation between the set rotational speed requested of the electric motor 9 and the actual rotational speed of the electric motor. This deviation output ΔC is then outputted to the drive unit 43 as a PWM signal C in the comparator circuit 42. In the drive unit 43, the above-mentioned direction control signal
FETQ ₁ ~ by PWM signal C of T ₃ and deviation output ΔC
The electric motor 9 is driven by controlling Q ₄ ,
As a result, the steering system is returned to the intermediate position at the set rotational speed.

Therefore, in this embodiment, as shown in FIG. 5, the return speed is arbitrarily set to be constant up to the vicinity of the middle position, or to a return speed that gradually decreases from the vicinity of the middle position to the middle position. If this is done, the PWM signal C that drives and controls the electric motor 9 is formed by the deviation ΔC from the rotational speed of the electric motor 9, so the steering system can be returned to the desired speed regardless of the magnitude of the road load. Therefore, smooth differential movement can be expected. It also controls the drive of the electric motor 9.
Since the PWM signal is obtained from the deviation from the rotational speed of the electric motor 9, it has the advantage of high responsiveness.

Next, steps P ₁₄ to _{P 32} that are different from the previous embodiment regarding control processing according to another embodiment of the present invention will be explained.

In this embodiment, the control of the electric motor 9 for returning the steering system to the middle position is as shown in FIG. at speed,
Control is performed so that it gradually decreases in the range a near the middle position.

In Fig. 6, at step _P15 , S-(a+c)
Calculate this and call it b. a and c are constants consisting of integers arbitrarily set by initial setting. Next, in step _P15 , it is determined whether b>0, and if b>0, it is assumed that the displacement from the middle position is within dead zone A, and step P15 is performed.
Proceeding to _P8 , the electric motor 9 is not driven. b
>0, proceed to step _P16 , where it is determined whether c=0, and if c=0, proceed to step _P17
~ Perform the processing on _P21 . In step _P17 , c is decremented by one, in step _P18 a direction control signal _T3 consisting of R and L is output, in step _P19 a rotational speed control signal _T4 consisting of a control duty D is output, and in step D is incremented by one at step _P20 , and this process is repeated at the repetition period set at step _P21 until c=0. Therefore, as shown in FIG. 7, in the range c, the electric motor 9
The torque of the steering system is increased, and the return speed of the steering system is increased.

Next, if c is zero at step _P16 , the process proceeds to step _P22 , where it is determined whether b=0. If b=0, step P ₂₃ to _{P 26}
Process. In step _P23 , b is decremented by one, and the same processing as in the previous steps _P16 , _P19 , and _P21 is performed in steps _P24 to _P26 ,
Repeat this until b=0. Therefore, b
In the range of , the return speed is constant as shown in FIG.

If b is zero at step _P22 , the process advances to step _P27 , where it is determined whether a=0.
If a=0, then steps _P28 to _P32 are performed. In step _P28 , a is decremented by one, the same processing as in the previous steps _P18 to _P19 is performed in steps _P29 to _P30 , D is decremented by one in step _P31 , and in step _P32 , This process is repeated at the set period until a=0. Therefore, in the range a, as shown in FIG. 7, the return speed gradually decreases near the middle position of the steering system and becomes zero at the middle position. step
Return to step _P2 where a=0 at _P27 . Therefore, in this embodiment, in addition to the effects of the above embodiments, each detection signal does not have to be read every time it is processed, so
This has the advantage of increasing control speed and eliminating the need for position detection upon return.

In the above two embodiments, the switch means is a manual switch that is turned on by the driver's will, but the switch means is not limited to this, and the switch means may be linked to the ignition key. The steering wheel may be configured to automatically return the steering wheel to the middle position when the engine is started. Further, since the electric motor is also used as an electric motor for electric power steering to reduce the steering force of the steering system, it is advantageous in terms of cost and space.

(Effects of the Invention) As explained above, according to the present invention, since the motor is configured to return to its original state using a detection signal corresponding to the motor rotation speed, the steering system can be set regardless of the magnitude of the road surface load. It can be returned to the intermediate position at the return speed. In addition, it is possible to gradually reduce the return speed near the middle position, preventing the occurrence of hunting near the middle position, allowing the return operation of the steering system to operate smoothly, and improving marketability. I can do it.

[Brief explanation of drawings]

1a to 5 show an embodiment of the intermediate position return device according to the present invention, FIG. 1a is a longitudinal sectional view showing the steering system, and FIG. 1b is a plan view showing the potentiometer. , FIG. 2 is a schematic configuration diagram showing the intermediate position return device, FIG. 3 is a flowchart showing an outline of its control processing, and FIG. 4 is a diagram showing displacement and detection signals S ₂ and S ₃
FIG. 5 is a diagram showing the relationship between displacement and return speed, FIGS. 6 and 7 show other embodiments of the present invention, and FIG. 6 shows an outline of the control process. The flowchart shown in FIG. 7 is a diagram showing the relationship between the displacement and the return speed. In the drawings, 9... electric motor, 10... motor control means (control device), 16... position detection means, 19...
...Switch means, 38...Rotation detection means, ΔC...
...It is a deviation.

Claims (1)

[Scope of Claims] 1. Position detection means for detecting the steering position of the steering system, rotation detection means for detecting the rotational speed of the electric motor, switch means, and an output signal from the position detection means when the switch means is turned on. an electric motor that determines and outputs a motor control signal based on the motor control signal, and drives and controls the electric motor based on a deviation between the motor control signal and the output signal from the rotation detection means to return the steering system to a neutral position. What is claimed is: 1. An intermediate position return device for a steering device, comprising a control means. 2. The intermediate position return device for a steering device according to claim 1, wherein the switch means is a manual switch provided in the vehicle interior near the driver's seat.