JPH0530552Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a front and rear wheel steering vehicle in which the rear wheels are also steered in response to the steering of the front wheels, and in particular the rear wheels are steered in substantially the same direction as the front wheels. The present invention relates to a rear wheel steering control device for a vehicle with front and rear wheel steering, which has a function of steering (hereinafter referred to as club steering).

[Prior art]

Conventionally, this type of rear wheel steering control device was developed in Japanese Patent Application Laid-Open No. 1983
As shown in Publication No. 81261 and Japanese Patent Application Laid-Open No. 59-81264, it is equipped with an operation switch that is selectively operated by the driving vehicle, and when the switch is operated, the operation switch is activated. An electrically connected steering control circuit responds to the switch operation,
A control signal for club-steering the rear wheels is output to the steering control mechanism, which then club-steering the rear wheels to facilitate parallel parking or side-to-side parking of the vehicle.

[Problem that the invention attempts to solve]

However, in the conventional device described above, if an abnormality occurs in the conductor connecting the operation switch and the steering control circuit, such as when the conductor is disconnected or shot to ground (vehicle body), the state of the operation switch is changed. As a result, the control circuit misjudges the operation state of the operation switch and cooperates with the steering control mechanism to cause the control circuit to misjudge the operation state of the operation switch, even though the operation switch is not operated. There is a possibility of club steering the wheels.
Such erroneous steering of the rear wheels occurs against the driver's will. For example, if the erroneous steering occurs while the vehicle is turning, the vehicle will be unable to turn, and the steering stability of the vehicle will be affected. The problem is that it gets extremely worse.

The present invention was devised in view of the above problem, and its purpose is to improve the steering stability by detecting an abnormality in the conductor and preventing the rear wheels from being club steered when the abnormality occurs. It is an object of the present invention to provide a rear wheel steering control device for a front and rear wheel steered vehicle that prevents the deterioration of the front and rear wheels.

[Means for solving problems]

In order to achieve the above object, the structural features of the present invention include an operation switch (corresponding to the switch 43a of the embodiment) that turns on and off when operated, and rear wheels 12a and 12b that respond to the on operation of the operation switch.
A steering control circuit (front wheel steering angle sensor 41, rear wheel steering angle sensor 42,
A/D converter 44a, 44b, 44f, ROM4
4g, CPU44h, RAM44i, I/O44
j, the drive circuit 44l, corresponding to steps 53 and 54), and the rear wheels 12a and 12a in response to the control signal.
2b in substantially the same direction as the front wheels 11a, 11b (corresponding to the rear wheel steering mechanism 30 of the embodiment). A first resistor 43b, a second resistor 44c connected between one end of the first resistor 43b and the voltage source 44d, and a third resistor 44c connected between the other end of the first resistor 43b and ground. Detection that detects the ON operation of the operating switch based on the magnitude of the voltage at one end or the other end of the resistor 44e and the first resistor 43b, and detects an abnormality in the conducting wires L3 and L4 that connect the operating switch and the steering control circuit. means (A/D converter 44f of the embodiment,
ROM44g, CPU44h, RAM44i, I/
O44j, corresponding to steps 51 and 53) and the rear wheel 12 in response to the detection of an abnormality by the detection means.
Prohibition means for prohibiting the steering of a and 12b (in the embodiment)
ROM 44g, CPU 44h, RAM 44i, corresponding to steps 60 to 64) are provided.

[Effect of invention]

In the present invention configured as described above, if there is no abnormality in the conductor connecting the operating switch and the steering control circuit, the voltage at one end or the other end of the first resistor is determined by the first to third resistors. Since the voltage is set to a predetermined voltage, the detection means detects the on/off operation of the operating switch without detecting the abnormality. As a result, the steering of the rear wheels is not inhibited by the inhibiting means, and the rear wheels are club-steering in response to the operation of the operating switch through cooperation between the steering control circuit and the steering control mechanism. On the other hand, if an abnormality occurs in the conductor that connects the operation switch and the steering control circuit, such as when the conductor is disconnected or shorted to ground (vehicle body), the voltage at one end or the other end of the first resistor will be lower than that of the operation switch. The value will be different from the value due to the on/off operation. Based on the different voltage values, the detection means detects an abnormality in the conductor, and the inhibiting means inhibits steering of the rear wheels. As a result, the rear wheels are no longer subject to crab steering regardless of the operation of the operating switch.

[Effect of idea]

As can be understood from the above operation explanation, the rear wheels are club steered in response to the operation of the operation switch only when there is no abnormality in the conductor connecting the operation switch and the steering control circuit.On the other hand, if an abnormality occurs in the conductor In this case, the rear wheels will not be club steered against the driver's will.
For example, when the driving vehicle is trying to turn the vehicle, the vehicle will not become unable to turn, and the deterioration of maneuverability that occurs in the conventional device described above can be prevented.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a front wheel steering mechanism 20 for steering left and right front wheels 11a, 11b, and a front wheel steering mechanism 20 for steering left and right front wheels 11a, 11b, and left and right rear wheels 12a, 12b.
2 schematically shows a vehicle equipped with a rear wheel steering mechanism 30 that steers the rear wheel steering mechanism 30, and an electric control device 40 that electrically controls the mechanism 30.

The front wheel steering mechanism 20 is a rack and pinion mechanism 2 consisting of a rack part 21a and a pinion part 21b.
1. The mechanism 21 is a pinion part 21b
It is connected to a steering handle 23 via a steering shaft 22, and converts rotational movement of the handle 23 into reciprocating movement of the rack portion 21a. This reciprocating motion is caused by the left and right relay rods 24a, 24b, and the left and right tie rods 25 connected to both ends of the rack part 21a, respectively.
a, 25b and left and right knuckle arms 26a, 26
is transmitted to the left and right front wheels 11a, 11b via b,
The front wheels 11a and 11b are steered in response to rotation of a steering handle 23.

The rear wheel steering mechanism 30 has a step motor 31, which rotates under the control of an electric control device 40 to rotationally drive a steering shaft 32 at one end thereof. A pinion portion 33a forming a rack and pinion mechanism 33 is provided at the other end of the steering shaft 32, and the mechanism 33 converts the rotational movement of the steering shaft 32 into a reciprocating movement of a rack portion 33b forming the mechanism 33. do. This reciprocating motion is caused by the left and right relay rods 34a, 3 connected to both ends of the rack portion 33b.
4b, the left and right rear wheels 1 via the left and right tie rods 35a, 35b and the left and right knuckle arms 36a, 36b.
2a, 12b, the same rear wheels 12a, 12b
is designed to be steered according to the rotation of the step motor 31. Further, a power steering switching valve 37 constituted by a four-way switching valve is attached to the middle portion of the steering shaft 32. The switching valve 37 supplies hydraulic oil from a hydraulic unit 38 consisting of a hydraulic pump and a reservoir to the power cylinder 39 and from the cylinder 39 to the unit 38 in accordance with the torque acting on the steering shaft 32 due to the rotation of the step motor 31. Switches and controls the discharge of hydraulic oil to. The power cylinder 39 accommodates a piston 39a fixed to the left relay rod 34a, and operates the left and right rear wheels 12 according to the supply of hydraulic oil.
a, 12b assists in said steering.

The electric control device 40 includes a front wheel steering angle sensor 41 attached to the steering shaft 22 of the front wheel steering mechanism 20, a rear wheel steering angle sensor 42 attached to the right relay rod 34b of the rear wheel steering mechanism 30, and a rear wheel steering angle sensor 42 attached to the right relay rod 34b of the rear wheel steering mechanism 30. An operation switch unit 43 disposed nearby, and a control circuit unit 44 disposed apart from each of these sensors 41, 42 and the operation switch unit 43.
Consisting of

The front wheel steering angle sensor 41 detects the steering angle θf of the left and right front wheels 11a, 11b by detecting the rotation angle of the steering shaft 22 from the reference direction, and generates an analog signal representing the detected steering angle θf. This analog signal is sent to the control circuit unit 44 via the conductor L1.
An analog-to-digital converter (hereinafter referred to as an A/D converter) 44 provided in the same unit 44
a is converted into digital data. The rear wheel steering angle sensor 42 detects the steering angle θr of the left and right rear wheels 12a, 12b by detecting the amount of axial displacement of the right relay rod 34b from the reference position, and outputs an analog signal representing the detected steering angle θr. occurs. This analog signal is supplied to the control circuit unit 44 via the conductor L2, and is converted into digital data by an A/D converter 44b provided in the same unit 44. In addition, each steering angle θf, θr is negative, and the left and right front wheels 11a, 11b and the left and right rear wheels 12a, 12
b respectively represents the steering to the left, positive represents the steering of the front wheels 11a, 11b and rear wheels 12a, 12b to the right, and zero represents the front wheels 11.
a, 11b and the rear wheels 12a, 12b are not steered, respectively.

The operation switch unit 43 consists of a normally open switch 43a and a resistor 43b having a resistance value r1 connected in parallel to the switch 43a. switch 43a
One end of the resistor 43b is connected to the control circuit unit 44 via a conductive wire L3, and a resistor 44c with a resistance value r2 provided in the same unit 44 is connected to the conductive wire L3.
A voltage E is applied from a voltage source 44d via. The other ends of the switch 43a and the resistor 43b are connected to a control circuit unit 44 via a conductor L4, and the conductor L4 is grounded to the vehicle body via a resistor 44e provided in the unit 44 and having a resistance value r3. The conducting wire L3 is also connected to an A/D converter 44f provided in the control circuit unit 44, and the converter 44f converts the voltage Ein determined by the resistors 43b, 44c, and 44e into digital data.

The control circuit unit 44 also includes a read-only memory (hereinafter referred to as ROM) 44g that stores a program corresponding to the flowchart shown in FIG. 2, and a central processing unit (hereinafter referred to as CPU) that executes the program.
) 44h, a writable memory (hereinafter referred to as RAM) 44i that temporarily stores data necessary for executing the program, and an input/output interface (hereinafter referred to as I/O) 44 that exchanges data.
j, these ROM44g, CPU44h,
It is equipped with a microcomputer consisting of a bus 44k that commonly connects a RAM 44i and an I/O 44j.

This microcomputer inputs various digital data from A/D converters 44a, 44b, and 44f connected to I/O 44j, and inputs various digital data to the left and right rear wheels 1.
Digital data for controlling the steering of the motors 2a and 12b is output to a drive circuit 44l connected to the I/O 44j and provided in the control circuit unit 44. The drive circuit 44l outputs a drive pulse signal according to the digital data, and the pulse signal is supplied to the step motor 31 via the conductor L5 to control the rotation of the motor 31.

The operation of the embodiment configured as above will now be described with reference to the flow chart of FIG.
First, the operation when no fault such as a break in the conductors L3 and L4 or a short circuit to the vehicle body occurs will be described. In response to the closing of the ignition switch, the CPU 44h starts the execution of a program in step 50, and in step 51, digital data representing the voltage Ein in the conductor L3 is taken in from the A/D converter 44f via the I/O, and the voltage
Ein is the voltage E1 = (r1 + r3) E/(r1 + r
If the switch 43a is currently in the open state (the state shown in FIG. 1),
The voltage Ein is equal to E1, so the CPU 44h judges "YES" in step 51, and outputs digital data representing the difference -θr between the target rear wheel steering angle θo (=0) and the rear wheel steering angle θo represented by the digital data taken in from the rear wheel steering angle sensor 42 via the A/D converter 44b and the I/O 44j to the drive circuit 44l in step 52. The circuit 44l outputs a drive pulse signal based on the digital data to the step motor 31, which rotates the steering shaft 32 and, in cooperation with the power cylinder 39, moves the left and right rear wheels 12a, 12b to the difference -θr.
As a result, if the left and right rear wheels 12a, 12b are steered leftward (or rightward) with respect to the reference direction before the control and the rear wheel steering angle θr is negative (or positive), the difference −θr becomes positive (or negative).
Since the rear wheels 12a, 12b are steered to the right (or left) by |θr|, the rear wheel steering angle θr after the control is zero. Also, if the rear wheel steering angle θr before the control is zero, the difference -θr also becomes zero, and the left and right rear wheels 12a, 12b are not steered, so the rear wheel steering angle θr after the control is also maintained at zero. In the process of step 52, the CPU 44h returns the program to step 51, and steps 51 and 52 are repeated.
In this way, if the switch 43a is in the open state, the left and right rear wheels 12a, 1
The steering angle θr of 2b is always maintained at zero, and the vehicle functions as a normal front-wheel (two-wheel) steering vehicle.

On the other hand, when the switch 43a is closed,
The voltage Ein at the conductor L3 is the voltage E2=r3・
E/(r2+r3), so the CPU 44h determines "NO" in step 51, that is, that voltage Ein is not equal to voltage E1, and determines "YES" in step 53, that is, that voltage Ein is approximately equal to voltage E2. After making a determination, the program proceeds to step 54. In this step 54, the CPU 4
4h takes in digital data representing the front wheel steering angle θf from the front wheel steering angle sensor via the A/D converter 44a and I/O 44j, and converts the front wheel steering angle θf represented by the data into the target rear wheel steering angle θo. (=θf)
from the steering angle θo (=θf) and the rear wheel steering angle sensor 42 to the A/D converter 44b and the I/O
Difference θo−θr (=θf−θr) from the rear wheel steering angle θr expressed by digital data taken in through 44j
Digital data representing the value is output to the drive circuit 44l. As a result, the drive circuit 44l, step motor 31, and power cylinder 39 move the left and right rear wheels 12a, 12b to the difference θo as in the above case.
Steering by −θr (=θf−θr). As a result, the left and right rear wheels 12a, 12b are steered to the left (or right) of the target rear wheel steering direction before the control, and the difference θo−θr (=θf−θr) is positive (or negative). If so, the rear wheels 12a and 12b are steered rightward (or leftward) by |θo−θr|(=|θf−θr|), so the rear wheel steering angle θr after the control is equal to the target rear wheel It becomes equal to the steering angle θo, that is, the front wheel steering angle θf. Also,
The rear wheel steering angle θr before the control is the target rear wheel steering angle θo
(=θf), the difference θo−θr(=θf−θr
)
becomes zero, and the left and right rear wheels 12a, 12b are not steered, so the rear wheel steering angle θr after the control is maintained at the target rear wheel steering angle θo, that is, the front wheel steering angle θf. After processing step 54, the CPU 44h returns the program to step 51 and executes steps 51, 53, and 5.
Continue executing the circular process in step 4. In this way, if the switch 43a is in the closed state, the left and right rear wheels 12a,
The steering wheel 12b is steered so that it becomes the same as the steering angle θf of the left and right front wheels 12a and 12b, that is, it is club steered. Such club steering allows the vehicle to travel in a straight line in a diagonal direction, making parallel parking and side-to-side parking easier.

Next, a case will be described in which a failure occurs in the conductors L3 and L4, such as disconnection or shot to the vehicle body. In this case, the voltage Ein at the conductor L3 has the following value depending on the type of failure.

(1) If conductor L3 or conductor L4 is disconnected, the voltage
Ein becomes the voltage E regardless of whether the switch 43a is opened or closed.

(2) When conductor L3 is grounded to the vehicle body, the voltage
Ein is 0 regardless of whether the switch 43a is opened or closed.
becomes.

(3) When the conductor L4 is grounded to the vehicle body and the switch 43a is open, the voltage Ein will be r1.
E/(r1+r2), and if the switch 43a is in the closed state, the voltage Ein becomes 0.

In this way, if a failure occurs in the conductors L3 and L4, the voltage Ein will be reduced to the voltage E1=(r1+r
3)・E/(r1+r2+r3) and the above voltage E
2=r3・E/(r2+r3), so step 51, 52 or step 5
If the failure occurs during the cyclic process consisting of steps 1, 53, and 54, the CPU 44h determines "NO" in steps 51 and 53, respectively, and advances the program to step 60. Note that the resistors 43b, 44c, 44
The resistance values r1, r2, r3 of e are set so that the voltage Ein=r1・E/(r1+r2) in the former case of (3) above is not equal to the above voltages E1, E2.
1/(r1+r2)=(r2+r3)/(r1+r
2+r3) and r1/(r1+r2)=r3/
It is set so that the relationship (r2+r3) does not hold.

At step 60, the CPU 44h takes in digital data representing the rear wheel steering angle θr from the rear wheel steering angle sensor 42 via the A/D converter 44b and I/O 44j, and calculates the rear wheel steering angle represented by the data. It is determined whether θr is approximately equal to zero. If the left and right rear wheels 12a, 12b are not currently being steered and the rear wheel steering angle θr is approximately equal to zero, the CPU 44h determines "YES" in step 60, and advances the program to step 51, and thereafter, Step 51,
53 and 60 continue to be executed. As a result, in such a case, the steering angle θr of the left and right rear wheels 12a12b is maintained at approximately zero, so that the vehicle
(wheels) function as steering vehicles.

Further, if the left and right rear wheels 12a, 12b are being steered by the processing in step 54 and the rear wheel steering angle θr is not equal to zero, the CPU 44h determines "NO" in step 60, and the program is continued from steps 61 to 60. The process proceeds to the reference direction return routine consisting of step 64. In this routine, CPU44h
At step 61, it is determined whether or not the rear wheel steering angle θr is positive based on the digital data taken in through the processing at step 60. In this judgment, if the steering angle θr is positive, the CPU 44h makes a “YES” judgment in step 61, and steers the left and right rear wheels 12a, 12b to the left by a minute steering angle Δθ in step 62. The digital data for this is output to the drive circuit 44l via the I/O 44j, and if the steering angle θr is negative, the CPU 44
h is determined to be "NO" in step 61,
At step 63, digital data for steering the left and right rear wheels 12a, 12b to the right by a minute steering angle Δθ is outputted to the drive circuit 44l via the I/O 44j. As a result, the drive circuit 44l, step motor 31, and power cylinder 39 steer the left and right rear wheels 12a, 12b leftward or rightward by a minute steering angle Δθ. Through the processing of steps 61 to 63, the left and right rear wheels 12a, 1
If the rear wheel 2b is steered rightward (or leftward) with respect to the reference direction, after the control, the rear wheel 12
The steering directions a and 12b approach the reference direction by a minute steering angle Δθ. This step 62,6
After processing step 3, the CPU 44h stops the progress of the program for a minute time ΔT in step 64, and returns the program to step 60 after the elapse of the same time ΔT.

In step 60, the CPU 44h again sends the digital data representing the rear wheel steering angle θr from the rear wheel steering angle sensor 42 to the A/D converter 44b and the I/O
44j, and based on the data, it is determined whether the rear wheel steering angle θr is approximately equal to zero. If this judgment is ``YES'', from now on,
The CPU 44h goes to step 51 as in the above case.
The circulation processes 53 and 60 are continued to maintain the steering angle θr of the left and right rear wheels 12a and 12b at zero. In addition, if the determination is "NO" in the above determination,
The CPU 44h again executes the above-mentioned reference direction return routine consisting of steps 61 to 64. The execution of this routine is based on the rear wheel steering angle θr.
is repeated until it becomes approximately equal to zero, and when the rear wheel steering angle θr becomes approximately equal to zero, the CPU 44
h then moves on to the cyclic processing of steps 51, 53, and 60 as described above. Through such processing of the reference direction return routine, the left and right rear wheels 12a, 12b are steered by a minute steering angle Δθ in the reference direction every minute time ΔT, and the absolute value |θr| of the rear wheel steering angle θr is as shown in FIG. As shown in the figure, it gradually approaches zero.

As you can understand from the above operation explanation, the conductor L
3. If a failure such as wire breakage or shot occurs in L4, the CPU 44h detects this failure and maintains the left and right rear wheels 12a, 12b in the reference direction, so the CPU 44h detects the problem caused by the failure of the conductors L3, L4. The driver may misjudge the opening/closing operation of the switch 43a, and the left and right rear wheels 12a, 12b will not be club-steering against the driver's will, for example, while the vehicle is turning, and the vehicle may be damaged due to a failure in the conductors L3, L4. It is possible to prevent deterioration of steering stability. Furthermore, if the left and right rear wheels 12a, 12b were steered to the left or right before the failure, the left and right rear wheels 12a, 12b will gradually return to the reference direction at the time of the failure. It is possible to prevent deterioration in the steering stability of the vehicle due to sudden changes in the steering angle θr of the wheels 12a and 12b.

In the above embodiment, the switch 43a is configured as a normally open type switch, and the club steering mode is selected when the switch 43a is closed, but the switch 43a is configured as a normally closed type switch. , the club steering mode may be selected when the switch 43a is opened. In this case, steps 51 and 53 (second
In the determination shown in the figure), the relationship between the values of voltages E1 and E2 may be reversed. Further, in the above embodiment, the conductor L3 is connected to the A/D converter 44f, but the conductor L4 is connected to the A/D converter 44f, and the left and right rear wheels are adjusted based on the voltage Ein* in the conductor L4.
The steering of 2a and 12b may also be controlled. In this case, the voltage Ein* is as follows depending on the state of the switch 43a and the states of the conductors L3 and L4.

(1) If the conductors L3 and L4 are normal and the switch 43a is open, the voltage Ein* will be E1*=r3・
E/(r1+r2+r3).

(2) If the conductors L3 and L4 are normal and the switch 43a is closed, the voltage Ein* will be E2*=r3・
E/(r2+r3).

(3) If conductor L3 or conductor L4 is disconnected, the voltage
Ein* becomes 0 regardless of whether the switch 43a is opened or closed.

(4) When the conducting wire L3 or the conducting wire L4 is grounded to the vehicle body, the voltage Ein* becomes 0 regardless of whether the switch 43a is opened or closed.

Using this relationship, in this case, step 5
1,53 (Fig. 2), the voltage Ein*
What is necessary is to compare the voltages E1* and E2 respectively.

Further, in the above embodiment, the switch 43a
is in the open state, that is, when the club steering mode is not selected, the left and right rear wheels 12
Although the left and right rear wheels 12a are not steered, as shown in Japanese Unexamined Patent Publication No. 59-81261 and Japanese Unexamined Patent Publication No. 59-81264 cited in the [Prior Art] section above, the left and right rear wheels 12a , 12b may be controlled in accordance with the vehicle speed V. In this case, a vehicle speed sensor for detecting the vehicle speed is provided in the above embodiment, and in the process of step 52 (FIG. 2), if the detected vehicle speed is low, the rear wheel steering angle θr is determined to have a reverse phase with respect to the left and right front wheels 11a and 11b. and if the detected vehicle speed is high, a rear wheel steering angle θr that is in phase with the left and right front wheels 11a and 11b is determined, and the left and right rear wheels 12a and 12b are steered in accordance with the determined steering angle θr. Bye.

Furthermore, a warning device is added to the above embodiment, so that when the conductor fails and/or when the left and right rear wheels 12a, 12b return to the reference direction due to the failure, the driving vehicle is alerted to the failure and/or the reference direction. A warning may be given for returning to the direction.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of a vehicle equipped with a rear wheel steering control device showing one embodiment of the present invention, FIG. 2 is a flowchart corresponding to a program executed by the microcomputer in FIG. 1, and FIG. The figure is a diagram for explaining a state in which the rear wheels are returned to steering in the reference direction. Explanation of symbols, 11a, 11b...Front wheel, 12
a, 12b...Rear wheel, 20...Front wheel steering mechanism, 3
0... Rear wheel steering mechanism, 40... Electric control device, 4
1... Front wheel steering angle sensor, 42... Rear wheel steering angle sensor, 43... Operation switch unit, 43a...
...Switch, 43b, 44c, 44e...Resistance,
44... Control circuit unit, 44d... Power supply, 4
4g...ROM, 44h...CPU.

Claims (1)

[Scope of utility model registration request] An operation switch that turns on and off depending on the operation,
a steering control circuit that outputs a control signal for steering the rear wheels in substantially the same direction as the front wheels in response to an on operation of the operating switch; and a steering control circuit for steering the rear wheels in substantially the same direction as the front wheels in response to the control signal. In the rear wheel steering control device for a front and rear wheel steered vehicle, the rear wheel steering control device includes a first resistor connected in parallel to the operation switch, and a first resistor connected between one end of the first resistor and a voltage source. A second resistor, a third resistor connected between the other end of the first resistor and the ground, and the magnitude of the voltage at one end or the other end of the first resistor control the ON operation of the operation switch. A detecting means for detecting an abnormality in a conducting wire connecting the operating switch and the steering control circuit, and a prohibiting means for prohibiting steering of the rear wheels in response to the detection of the abnormality by the detecting means. A rear wheel steering control device for a vehicle with front and rear wheel steering.