JPH0455908B2 - - 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. At the same time, the device itself tends to return to the intermediate position by means of 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 starting from a state where the steering wheel has not returned to the middle position, it may be difficult to start smoothly on a narrow road or in a bad garage environment.

(Object of the Invention) Therefore, the present invention provides a steering device that can smoothly stop and start even on narrow roads or in bad garages by automatically returning the steering device to the middle position when desired. The object of the present invention is to provide a position return device.

(Means for Solving the Problems and Their Effects) The intermediate position return device of the present invention includes a position detection means for detecting the steering position of the steering system, a current detection means for detecting the armature current of the electric motor, a switch means, and a switch means for detecting the armature current of the electric motor. The motor control means controls the drive of the electric motor based on the detection signals from the position detection means and the current detection means when the switch means is turned on, and controls the steering system to a preset return speed. to return to the middle position. Therefore, since the armature current corresponds to the road load, it is possible to return the steering diameter to the intermediate position at any set return speed, regardless of the magnitude of the road load.

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

FIG. 1 is a schematic longitudinal cross-sectional view of a steering device equipped with an intermediate position return device of this embodiment, FIG. 2 is a control device thereof, and FIG. 3 is a control process thereof.

In FIG. 1, 1 is a steering shaft, and a steering wheel (not shown) is integrally fixed to the right end of the steering shaft 1 in the drawing, and a universal joint (not shown), a second shaft, a universal joint, A rack and pinion, a tie rod, and a nut are connected, and the rotation of the steering shaft 1 is converted into a rocking motion of the wheels to enable steering of the vehicle. Further, the steering shaft 1 is rotatably supported by a case 4 through bearings 2 and 3. A small-diameter toothed pulley 5 is integrally provided on the outer periphery of the steering shaft 1, and a case 4 is mounted substantially in equilibrium with the steering shaft 1.
A potentiometer 6 is integrally fixed to the potentiometer 6, and a timing belt 7 is wound between a large-diameter toothed pulley 6a, which is attached to the rotating shaft of the potentiometer 6, and the small-diameter pulley 5. It's being passed around. Therefore, the rotation of the steering shaft 1 is decelerated and transmitted to the potentiometer 6, converted into a change in the resistance value of the potentiometer 6, and outputted to the control device 10 as an electrical signal.

Further, an electric motor 9 is integrally fixed to the case 4 substantially parallel to the steering shaft 1, a small-diameter toothed pulley 9a is integrally attached to the rotating shaft of the electric motor 9, and a bearing 11 is attached to the steering shaft 1. A timing belt 13 is wound around a large-diameter toothed pulley 12 that is rotatably supported through the belt. Therefore, the rotation of the electric motor 9 is reduced by the pulley ratio of the pulleys 9a and 12 and transmitted to the large diameter pulley 12. Sun gear 14 is located at the left end of the large diameter pulley 12 in the figure.
A is integrally formed, and a plurality of pinion gears 14B are externally engaged with this sun gear 14A,
These pinion gears 14B are rotatably supported by a carrier 14C. The case 4 includes a ring gear 14 that internally meshes with a pinion gear 14B.
D is fixed, and these constitute a planetary gear mechanism 14. The rotation of the large diameter pulley 12 is further decelerated by the planetary gear mechanism 14 and transmitted to the carrier 14C. carrier 14
C is a hollow shaft 15 provided integrally at the left end in the figure.
This hollow shaft 15 is provided with a taper screw and a spline on the outer periphery of the left end in the figure.
It is integrally fixed to the steering shaft 1 by a spline and a nut provided at the left end of the steering shaft 1.

In FIG. 2, the intermediate position detection means (position detection means) 16 includes a potentiometer 6, a low-pass filter 23, and an operational amplifier 25. The potentiometer 6 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 42 (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 switch 20 installed near the steering wheel and a low pass filter 3.
4 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 the constant voltage power supply A via a resistor 33, and the low pass filter 3
4 is entered. The low-pass filter 34 removes noise caused by the opening and closing of the switch 20,
The output of the low pass filter 34 is the waveform shaping circuit 35
is connected to the I/O port of the microcomputer unit 32 via the waveform shaping circuit 35, which shapes it into a rectangular wave and outputs the signal when the switch is turned on.
_S1 is output, and the signal _S1 when the switch 20 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 the microcomputer unit 32 is connected to motor drive means 37. This motor drive means 37 includes a drive unit 36 and an FET.
(Q ₁ to _{Q 4} ) bridge circuits. The drive unit 36 is driven by a booster circuit for driving FETQ ₁ and Q ₄ and a control signal from the microcomputer unit 32.
A circuit that enables operation by switching FETQ ₁ , Q ₃ or FETQ ₂ , Q ₄ , converts control signals T ₃ , T ₄ from the microcomputer unit 32 into PWM signals, and drives FETQ ₂ or Q ₃ in PWM. It consists of a programmable timer circuit, etc. The output of the drive unit 36 is connected to the gate terminals of FETQ ₁ and Q ₄ , and the drain terminals of FETQ ₁ and Q ₄ are connected to the positive side of battery 41 . Source terminals of FETQ ₁ and Q ₄ ,
The drain terminals of FETQ ₂ and Q ₃ are connected respectively.
A connection between the source terminal of FETQ ₄ and the drain terminal of FETQ ₃ , and a connection between the source terminal of FETQ ₁ and the drain terminal of FETQ ₂ are connected to the motor 9.
The respective drain terminals of FETQ ₂ and Q ₃ are connected,
It is installed on the common side via a resistor R.

The current detection means 40 includes the resistor R, a low-pass filter 38 that converts the PWM voltage across the resistor R into a DC voltage, and a DC amplification circuit 39 that amplifies this output. The current detection signal _S4 is sent to the A/D converter 2.
9 to the microcomputer unit 32.

Further, a constant voltage circuit 42 is connected to the positive terminal of the battery 41. The output A of the constant voltage circuit 42 is a constant voltage lower than the battery voltage 41, 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 50 and the motor driving means 37 constitute a motor control means.

In such a device, control processing is performed according to the flowchart shown in FIG. In addition, P ₁ to _{P 23} in Figure 3
indicates 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, and the process advances to step _P2 . In step _P2 , the output signal _S1 of the switch 20 is read. Here, when the switch 20 is turned on, _S1 is at a low level, that is, 0, and when the switch 20 is off, _S1 is at a high level, that is, almost equal to the output voltage A of the constant voltage circuit 42. becomes "1". In 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, S ₁ =1, so the process jumps to step P ₂ and waits for the output signal from switch 20 to be input.

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. Next step P ₆
The difference between S ₂ and S ₃ is processed as S, and the amount and direction of deviation from the middle position of the steering device are calculated.
Store it in the register and proceed to step _P7 . In step _P7 , it is determined whether or not the value of the S register is 0. If it is 0, the process proceeds to step _P8 , and a direction control signal _T3 consisting of R=L=0 is output to the motor drive means 37. At this time, the motor drive means 37
Turn off all FETs (Q ₁ to _{Q 4} ). Then, in step _P9 , the value of the duty D, which is the PWM signal _T4, is set to 0 and is output to the motor drive means 37. The program then jumps to step _P2 and waits for switch input.

If the value _of the S register is positive or negative, the process advances to step _P10 , where its sign is determined. If the value in the S register is negative, proceed to step _P12 , set the sign flag F to 1, then proceed to step _P13 , convert the value in the S register to sign conversion S←-S, and proceed to step _P14 . move on. If the value in the S register is positive, the code flag F is set to 0 in step _P11 , and the process advances to step _P14 . Step P ₁₄
Now, in order to provide a dead zone for the values in the S register, a predetermined value A is calculated and the subsequent value is stored in the _S1 register. Then, in step _P15 , the sign of the value _S1 of the _S1 register is determined. If it is negative, it is judged that it is in the middle position because it is within the dead zone, and step P ₈
Then, the electric motor drive means 37 stops operating.

On the other hand, if the value of S ₁ is positive, it is larger than the value of the dead zone, so it is necessary to return to the intermediate position. Therefore, the process advances to step _P16 , and the data whose address is S in the _S1 register is read out. That is,
The ROM is configured with a table in which data shown in FIG. 5 is stored. The table shows the detection signal S ₂
- In the ROM whose address is the absolute value of S ₃ , the data that determines the rotation speed of the motor 9, that is, the 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, is binarized. , the armature voltage V corresponding to the DUTY value is stored. Therefore, this
The DUTY value determines the rotation speed of the rotating machine of the electric motor. At step _P16 , data in the ROM having the data in the S register as an address, that is, speed DUTY, is called, and the process advances to step _P17 .
At step _P17 , the detected current signal _S4 from the current detecting means 40 is read. This detection current signal S ₄
is the current I flowing through the motor 9 and the PWM signal when PWM driving is performed by the motor drive means 37.
The product with the DUTY value is I x (DUTY), so in step _P18 , the value obtained by dividing the detection signal _S4 by the armature voltage V corresponding to the DUTY value called in step _P16 is stored in the _S4 register. do. At this time, the data S ₄ in the S ₄ register corresponds to the road load because the detected current S ₄ is proportional to the value of the current I of the motor 9, and this current I is proportional to the road load.
Next, in step _P19 , the data _S4 in the _S4 register,
The value D obtained by adding the DUTY value called in step _P16 is stored in the D register. The values in the D register therefore determine the rotational speed of the motor 9 and the load current, ie the power. Next step
Proceeding to P ₂₀ , the sign flag F is determined to determine the sign of the detection signals S ₂ -S ₃ from the intermediate position detecting means 16. If F=0, it is positive, so a direction control signal _T3 consisting of R=1 and L=0 is output to the motor drive means 37, FET _Q1 is turned on, _Q3 is set to a controllable state, and step P is performed. Proceed to _{step 23} and output the motor control signal _T4 based on the value D in the D register,
Drive FETQ ₃ with PWM. If F=1, it is negative, so the process proceeds to step _P22 , where a control signal consisting of R=0 and L=1 is sent to the motor drive means 37.
Outputs T ₃ , turns on FETQ ₄ , and
LETQ ₂ is brought into a drivable state, and at step _P23 a control signal _T4 consisting of data D in the D register is output for PWM driving, and the process returns to step _P4 . Then, the detection signal S from the intermediate position detection means 16 is
This process is repeated until =S ₂ -S ₃ falls within dead zone A.

Therefore, in this embodiment, if the return speed is set in advance to decrease from a constant speed to near the intermediate position as shown in the table of FIG.
It returns at a constant speed within a predetermined range, and the return speed can be reduced near the middle position, so smooth operation can be expected. Further, since the detection signal corresponding to the road surface load is used to return to the middle position, the steering system can be returned to the set speed regardless of the magnitude of the road surface load.

Next, steps Pp ₁₄ to P ₄₁ that are different from the previous embodiment regarding the 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 _P14 , 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 process on _P24 . In step _P17 , c is decremented by one, in step _P18 the current detection signal _S4 is read, and in step _P19 , the duty component of _S4 is calculated by calculating _S4 / _D1 , and this is set as _D1. Process. Next, at step P ₂₀ , D+D ₁
A process is performed in which the addition is performed and this is set as _D1 .
D is set in advance from zero to the maximum value, and is initially set to D=0. At step _P21 , a direction control signal _T3 consisting of R and L is output, at step _P22 a torque control signal _T4 consisting of a control duty _D1 is output, at step _P23 D is incremented by one, and then c with the repetition period set in P ₂₄
This process is repeated until =0. Therefore,
As shown in FIG. 7, in the range c, the torque of the electric motor 9 increases and the return speed of the steering system increases.

Next, if c is zero at step _P16 , the process proceeds to step _P25 , where it is determined whether b=0. If b=0, step P ₂₆ to _{P 32}
Process. In step _P17 , b is decremented by one, and the same processing as in the previous steps _P18 to _P24 is performed in steps _P27 to _P32 , so that b=0.
Repeat this until. However, since there is no step corresponding to step _P23 at this time, the return speed is constant in the range b as shown in FIG.

If b is zero at step _P25 , the process proceeds to step _P33 , where it is determined whether a=0.
If a=0, then steps _P34 to _P41 are performed. In step _P34 , a is decremented one by one, and the same processing as in the previous steps _P18 to _P22 is performed in steps _P35 to _P39 . In step _P40 , D is decremented one by one, and in step _P41 , 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
When a=0 at _P33 , the process returns to step _P2 . Therefore, in addition to the effects of the above-mentioned embodiments, this embodiment has the advantage that the control speed is faster because it is not necessary to read each detection signal every time it is repeatedly processed, and there is no need to perform position detection at the time of return. has.

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 an ignition key. The steering wheel may be configured to be interlocked with each other so that the steering wheel is automatically returned 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 be driven for return using a detection signal corresponding to the road load, the steering system can be set for return drive regardless of the magnitude of the road load. It can be returned to the intermediate position at speed. In addition, near the middle position, the return speed can be gradually reduced, allowing the steering system to return smoothly and improving marketability.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the intermediate position return device according to the present invention, FIG. 1 is a longitudinal sectional view showing a steering system, and FIG. 2 is a schematic configuration diagram showing the intermediate position return device. , Fig. 3 is a flowchart showing the outline of the control process, and Fig. 4 shows the 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, 40 . . . current detection means.

Claims (1)

[Scope of Claims] 1. Position detection means for detecting the steering position of the steering system, current detection means for detecting the armature current of the motor, switch means, and when the switch means is turned on, the position detection means and the current detection a medium position steering device, comprising electric motor control means for driving and controlling the electric motor based on an output signal from the means to return the steering system to the medium position at a preset return speed. Return device. 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.