JPH01311958A - Steering angle ratio control device - Google Patents

Abstract

PURPOSE:To keep the rear corner portion of a car body from coming in touch with the side wall by obtaining right and left rear wheel steering angles from the distance between the right and left side walls and the car body, a yaw angle of the car body to the side walls and the front wheel steering angle. CONSTITUTION:A yaw angle sensor detects an inclination of a car body to the right and left side walls. A distance sensor detects the distance between the right and left side walls and the car body. Rear wheel steering angle decision means are adapted to obtain a rear wheel steering angle each for turning to the right and turning to the left to keep the car body from coming in touch with the side walls even if the front wheels are steered to the maximum according to signals of the yaw angle sensor and the distance sensor. Means for setting low-speed steering angle ration are adaptec to set a low-speed steering angle ratio in which the projecting amount of the rear portion of the car body is smaller, according to signals of the rear wheel steering angle decision means and a front wheel steering angle sensor. An actuator drives a steering angle ratio control mechanism according to a signal of the low-speed steering angle ratio setting means at low speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steering angle ratio control device for a four-wheel steering vehicle.

[Prior Art] In a four-wheel steering vehicle, when the rear wheels are steered in the opposite phase to the front wheels,
The turning radius becomes smaller and the turning ability is improved. In this case, the range of motion of the rear of the vehicle is expanded compared to a normal front-wheel steering vehicle, and if there is an obstacle on the side of the road such as a side wall (hereinafter referred to as a "side wall"), the rear corner of the vehicle will touch the side wall when changing direction. There is a risk of contact.

In order to solve the above-mentioned problem, in the four-wheel steering vehicle disclosed in Japanese Patent Application Laid-open No. 61-27767, when the steering wheel is turned significantly, the rear wheel steering angle is adjusted to the target steering angle in stages for each predetermined travel distance. Approach the corner.

[Problems to be Solved by the Invention] In this four-wheel steering vehicle, the yaw angle (the angle of inclination of the longitudinal axis of the vehicle body with respect to the side wall) changes in stages according to the steering angle of the rear wheels, so that the motion of the vehicle is constant. It becomes natural and gives the driver a sense of discomfort.

The purpose of the present invention is to solve the above-mentioned problem, and to solve the above problem, below a predetermined vehicle speed,
Steering angle ratio l11111, which is determined from the distance to the side wall of the vehicle body and the yaw angle, is regulated to a rear wheel steering angle that does not contact the side wall, and allows smooth turning without causing discomfort to the driver.
1 device.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention includes a yaw angle sensor that detects the inclination of the vehicle body with respect to the left and right side walls, and a distance sensor that detects the distance between the left and right side walls and the vehicle body. Rear wheel steering angle determining means for determining, based on a signal, a rear wheel steering angle at which the vehicle body does not come into contact with a side wall even when the front wheels are turned at a maximum steering angle for right and left turning; a rear wheel steering angle determining means; and a front wheel steering angle sensor. and an actuator for driving the steering angle ratio control w+i structure at low speed based on the signal from the low speed steering angle ratio setting means. be.

[Function] In the present invention, when the vehicle starts, the yaw angle of the vehicle body with respect to the side wall and the distance between the left and right side walls and the vehicle body are detected, and based on these data, even if the front wheels are at the maximum steering angle, the vehicle body does not come into contact with the side wall. Rear wheel steering angle when turning right and left (regarding turning to the right as 10 and specifying when turning left) A low speed steering angle ratio corresponding to the smaller rear wheel steering angle is determined.

As a result, the rear wheel steering angle changes continuously in accordance with the driver's steering without the rear corner of the vehicle body coming into contact with the side wall, and smooth running is realized.

Minimum rear wheel steering angle when turning right (large rear wheel steering angle when turning left) θ
Find Rmin-f(ψ, S). Among the minimum rear wheel steering angle θRFI II i n when turning right and the minimum rear wheel steering angle θ when turning left, reverse the sign of θplain and change the signs of θFIF+ and θ in in-phase and anti-phase. Unify, θ
Select the one with the smaller absolute value of R.

Based on the current absolute value θF of the front wheel steering angle and the minimum rear wheel steering angle θR selected as described above, a steering angle ratio kL for preventing the vehicle body from contacting the side wall is determined.

On the other hand, the steering angle ratio k during normal driving is determined in relation to the vehicle speed.

Compare the low speed steering angle ratio kL and the normal steering angle ratio corresponding to the vehicle speed, and if the normal steering angle ratio k is larger than the low speed steering angle ratio kL, substitute kL for the target steering angle kt, If the normal steering angle ratio k is smaller than the low speed steering angle ratio kL, k is substituted into the target steering angle k[.

After starting, check whether the vehicle speed V is greater than the predetermined value V2 or the steering angle ratio k
When the steering angle ratio kL becomes larger than the low speed steering angle ratio kL, steering angle ratio control corresponding to the vehicle speed is performed.

[Embodiment of the Invention] As shown in FIG. 1, a knuckle arm 3 that supports each of the left and right front wheels 2 is rotatably supported on the vehicle body by a support shaft 3a, and is operatively connected by a tie rod 4. An arm of the right knuckle arm 3 is connected to the front wheel steering mechanism 7 via a drag link 10. The front wheel steering mechanism 7 is a handle 5
When the steering shaft 6 is rotated, the output shaft 7a is rotated,
The drop arm 8 coupled to this swings, and the drag link 10 moves back and forth. A rod 12 is connected to a pin 9 connected to the middle part of the drop arm 8, and the rear end of the rod 12 is connected to the input link 1 of the steering angle ratio control al1 mechanism A by the pin 13.
Connected with 4.

The input link 14 is connected to the end of the control lever 30 by a pin 15. A control lever 30 rotatably supported on the vehicle body by a support shaft 23 is connected to an output link 2 by a connecting pin 28.
7 is connected. The output link 27 is connected to a rod 31 that moves back and forth through a bin 27a. Rod 31 is coupled to one valve element of servo control valve 32 of rear wheel steering gear #134.

The rear wheel steering mechanism 34 is integrally constructed of a servo control valve 32 and seven actuators. Actuator is cylinder 3
A piston 35 is fitted into the rod 3, and the outer end of the rod connected to the piston 35 is supported by the vehicle body. Servo control valve 3
The other valve element of 2 is integral with the cylinder 33 and the rod 3
Combine 6.

A rod 36 is connected to one end of a lever 37 supported by a support shaft 38 on the vehicle body, and a rod 39 that moves back and forth is connected to the other end. The rear end of the rod 39 is connected to an arm of a knuckle arm 41 that supports a rear wheel 40. The left and right knuckle arms 41 are interlocked and connected by tie rods 42.

III control lever 30 of steering angle ratio i control mechanism A 27a
An arc-shaped groove 29 centered at is provided, and the connecting pin 28 is slidably engaged along this groove 29. In order to slide the connecting bin 28, an arc-shaped partial gear 22 is integrally formed at the end of the output link 27, and the gear 17 that meshes with this gear has a steering angle ratio of 11Jffll as an actuator.
It is driven by a motor 18. Therefore, the worm shaft 21 of the steering angle ratio III l motor 18 is meshed with the gear 16 coaxially connected to the gear 17. Steering angle ratio control motor 18
The gear 17 and gear 17 are integrally supported by a frame, and this frame is opened and moved by an actuator 19 along a guide groove 201 of the vehicle body. The actuator 19 is made up of a cylinder fitted with a piston, and this piston is connected to the frame of the steering angle ratio control motor 18 by a rod, and is normally moved forward (to release the mesh between the gear 17 and the partial gear 22) by the force of a spring. direction).

The support shaft 23 of the control lever 30 has a groove continuous with the groove 29. When the lever 24 connected to the control lever 30 is rotated clockwise by the actuator 25, the groove of the support shaft 23 is cut off from the full 29 of the fri control lever 30. The actuator 25 is formed by fitting a screw into a cylinder,
The piston and lever 24 are connected by a rod. Normally, the lever 24 is pressed against the stopper 26 by the spring force of the actuator 25, so that the groove of the support shaft 23 and the groove 29 of the control lever 30 are continuous.

Now, when the steering wheel 5 is turned to the right, the drag link 10 of the front wheel steering mechanism 7 moves forward t\, the knuckle arm 3 rotates clockwise around the support $j3a, and the front wheel 2
is deflected to the right. At the same time, the rod 12 also moves forward, and the υVm lever 30 rotates counterclockwise about the support shaft 23. The output link 27 pulls the rod 31 forward, and the action of the servo valve 32 supplies pressurized oil to the chamber on the side of the actuator. The cylinder 33 moves forward, the rod 39 moves backward via the lever 37, the knuckle arm 41 rotates counterclockwise around the support shaft 41a, and the rear wheel 40 moves to the left (in opposite phase to the front wheel). deflected to Therefore, the turning radius of the vehicle becomes smaller, and the turning ability at low speed fr is improved.

When the gear 17 is rotated by the steering angle ratio control motor tacho 8 in relation to the vehicle speed and the output link 27 is rotated counterclockwise about the pin 27a, the connecting pin 28 moves to the left side of the support shaft 23. At this time, the rear wheels 40 are deflected in the same phase as the front wheels 2 (see FIG. 4), improving steering stability when changing lanes at high speeds.

According to the present invention, when the vehicle starts or changes direction on a narrow road, by steering the rear wheels in a phase opposite to the front wheels, the rear corners of the vehicle body are prevented from protruding from the road and coming into contact with the left and right side walls. In order to , which is minimum when turning to the right and maximum when turning to the left), and then selects the rear wheel steering angle that has the smallest amount of protrusion of the rear corner of the vehicle body. By determining the low-speed steering angle ratio from the selected minimum rear wheel steering angle and front wheel steering angle, contact with the side wall of the vehicle body is avoided.

If the front wheel steering angle is θF1 and the steering angle ratio is k, then the rear wheel steering angle θR is θ, -k·θF.Now, let us consider a right turn of the vehicle. In FIG. 2, the center of the rear wheel support shaft 41a (the support shaft 41a is located at the center of the rear wheel 40) is the origin 0, and the support shaft 3a of the front wheel 2 (the support shaft 3a is located at the center of the front wheel 2). Let the coordinates of P(
x, y), a straight line A that is perpendicular to the direction of movement of the front wheel 2 and passes through point P
Let Q (XO, yO) be the intersection of the line B and the straight line B that is perpendicular to the traveling direction of the rear wheel 40 and passes through the point O. Further, the yaw angle of the vehicle body with respect to the side wall 80 is ψ, and the wheel base (the distance between points P and 0) is W.

If the slope of straight line A is a and the slope of straight line B is b, then a-j
an (θF + ψ) b - tan (OR + ψ) The equation of straight line A is 'y' - a
sinψ (2)y-WCO8ψ
(3) (2>, Substituting equation (3) into equation (1) gives 1,', W CO3ψ−a・(−Wsinψ
) + cC-W (cos ψ + a sin ψ) ;, Y-aX + W (cos ψ ten a sin ψ) (4)
The equation of straight line B is Y-bX (5) Therefore, the coordinates Q (xo, yo) of the turning center of the vehicle are (
4) From equations (5), y-ax+W (cos ψ+a sin ψ)y=bx,', X0=W (cos φ+a sin ψ) (6)-
a As shown in Fig. 3, the coordinates of the left rear corner R of the vehicle body are e: the distance between point O and the rear corner R α: the distance between point 0 and the rear corner R with respect to the longitudinal axis G of the vehicle body; Assuming that the angle formed by the line T connecting is x=esin(ψ+α) (8
)y=acos(φ+α) (9) Therefore, the turning radius of the vehicle is on the distance between point Q and point R, and <6
), (7) and (8), (9), (QR)2− [xo−e 5in(ψ1α)]2+
[yo-e cos (ψ ten (2) 12 (10)
It is.

Since the distance between the center of the car body and the side wall is ×0, the condition that the rear corner of the car body does not touch the side wall is QR<XO+S (11) S:
The distance between the support shaft 41a and the side wall 8o can be similarly determined when the vehicle is turning left.

From the above, the steering angle ratio when starting or at low speed is -f
It can be found from the relationship '(ψ, W). The minimum rear wheel steering angle θRtllin that satisfies the above conditions is θFmax(θFsa
x>O), θR+e is a value specific to the vehicle, so θR
I! 1 in-f (ψ·S>). Therefore, by detecting the yaw angle ψ and the distance S between the side wall and the vehicle body, the minimum rear wheel steering angle θR1 group is found, and the low speed steering angle ratio kL is found.

As a result, even if the vehicle starts with the front wheel steering angle θF at its maximum, the rear corner of the vehicle body will not come into contact with the side wall.

Additionally, collisions are prevented even if the vehicle leans too close to the side wall and attempts to turn right or left while driving.

For example, a distance sensor 62a disposed adjacent to the rear wheels of the vehicle body that detects the distance S by reflected waves of ultrasonic waves, and a pair of distance sensors 62a disposed adjacent to the front and rear wheels of the vehicle body, for example.
If the yaw angle detection means 62 consisting of 62b is provided, the minimum rear wheel steering angle θR at which the rear corner of the vehicle body does not come into contact with the left and right side walls can be determined based on the signals from both of them. Based on this, a low-speed steering angle ratio kL at which the vehicle body does not come into contact with the side wall is determined in relation to the actual front wheel steering angle θF at that time.

On the other hand, during normal driving, the steering angle ratio is controlled according to the vehicle speed V (see FIG. 4). For example, a target steering angle ratio kt corresponding to the vehicle speed is determined by the steering angle ratio setting means based on a signal from a vehicle speed sensor 55 disposed opposite to the output shaft of the transmission, and the steering angle ratio is controlled based on this. The steering angle ratio control motor 18 is driven by the means. For example, the partial gear 22
The steering angle ratio control motor 18 is stopped when the actual steering angle ratio ks obtained by the steering angle ratio sensor 56 disposed opposite to the steering angle ratio ks matches the target steering angle ratio kt.

FIG. 6 is a flowchart of a program in which the above-mentioned control is performed by an electronic control unit 51 consisting of a microcomputer.

This program starts with pll, initializes with p12, and sets the steering angle ratio kt to a predetermined value kaki in p13.
Substitute n. At p14, the start mode flag is turned ON. At p15, the vehicle speed ■ is read by the vehicle speed sensor 55. p
At 16, the front wheel steering angle sensor 59 determines the front wheel steering angle θFf. At p17, it is determined whether the absolute value of the vehicle speed V is smaller than a value 2 (for example, 51 v/h for Pi4) that requires care for contact with the side wall.

If the vehicle speed ■ is greater than the value ■2, the start mode flag is turned OFF in p18, and the process proceeds to p29.

If the absolute value of vehicle speed ■ is smaller than ■2 in p17, p
19, the value Vl at which the vehicle speed ■ is at a low level (for example, 0 to 2
km/b> is determined.

If the vehicle speed Vtfi (aVl) is greater, proceed to p23; if the vehicle speed V is smaller than the value ■1, proceed to p20 to determine the right and left yaw angle ψR obtained from the signals of the distance sensors 62a and 62b.
Read 0ψL.

At p21, the distance sensor 62b reads the distances SR and SL between the rear side of the vehicle body and the right and left side walls. Yaw angle ψ at p22
The minimum steering angles θHFIa+in and θ−10 of the right and left rear wheels are determined from R9ψL and the distances SR and SL between the left and right side walls and the vehicle body. At p23, the sign of the minimum steering angle θRR10in of the right rear wheel is converted. Minimum steering angle θRLmi of left rear wheel in p24
It is determined whether n is larger than the minimum steering angle θRFI II i n of the right rear wheel. Minimum steering angle θRa5 of left rear wheel
If in is smaller than the minimum steering angle θpRmin of the right rear wheel, in p25, θFIRmin is set as the minimum rear wheel steering angle θRmin, and the process proceeds to p27.

If the minimum steering angle θRLsin of the left rear wheel is larger than the minimum steering angle θBB min of the right rear wheel in p24, p2
In step 6, θBLain is set to the minimum steering angle θRWin of the rear wheels.

At p27, it is determined whether the front wheel steering angle is not θFI'fiO, that is, whether the vehicle is not in a straight-ahead state. Front wheel steering angle θF is O
If so, proceed to p35, and if the front wheel steering angle θF is not O, calculate the low speed steering angle ratio kL in p2B. In other words, the minimum steering angle θRSin of the rear wheels is reduced by the absolute value of the front wheel steering angle θF.

In p29, the steering angle ratio k corresponding to the vehicle speed ■ is set by the steering angle ratio setting means (
(control map stored in the RAM of the microcomputer). At p30, it is determined whether the start mode flag is ON. If the launch mode flag is OFF, p3
Set the start mode flag to OFF with 1, and set the steering angle ratio k with p32.
Set this as the target steering angle ratio kt and proceed to p35.

If the start mode flag is ON in p30, it is determined in p33 whether the steering angle ratio k is smaller than the low speed steering angle ratio kL. This is because the low-speed steering angle ratio kL may be larger than the steering angle ratio corresponding to the vehicle speed depending on the starting conditions of the vehicle.

If the steering angle ratio k is larger than the low speed steering angle ratio kL in p33, the process advances to p31. If the steering angle ratio k is smaller than the low speed steering angle ratio kL in p33, the low speed steering angle ratio kL is set as the target steering angle ratio kt in p34, and the steering angle ratio control motor 18 is set in p35 based on the interrupt program shown in FIG. to drive.

The interrupt program shown in FIG. 7 drives the steering angle ratio control motor 18 so that the steering angle ratio reaches the target steering angle ratio kt at p41 and at p42. The actual steering angle ratio ks is detected in p43, and it is determined in p44 whether the actual steering angle ratio ks is equal to the target steering angle ratio ks. If the actual steering angle ratio kS is not equal to the target steering angle ratio kt, the process returns to p42.

If the actual steering angle ratio ks is equal to the target steering angle ratio k, p45
The steering angle ratio control motor 18 is stopped at step p46, and the program returns to the program shown in FIG. 6 at step p46. The above program is repeatedly executed at predetermined time intervals.

In the actual droplet example described above, a step motor was used as the actuator 18 that drives the steering angle ratio control mechanism, but the present invention is not limited to this, and a rotary hydraulic motor or a reciprocating hydraulic cylinder may be used. be able to.

[Effects of the Invention] As described above, the present invention adjusts the front wheels to the maximum steering angle based on the signals from the yaw angle sensor that detects the inclination of the vehicle body with respect to the left and right side walls and the distance sensor that detects the distance between the left and right side walls and the vehicle body. Even if the vehicle body does not touch the side wall, the rear wheel steering angle determining means determines the rear wheel steering angle when turning right and when turning left, and the amount of protrusion of the rear of the vehicle body is determined from the signals from the rear wheel steering angle determining means and the front wheel steering angle sensor. Since it is equipped with means for setting a smaller low-speed steering angle ratio and an actuator that drives the steering angle ratio control mechanism at low speed based on a signal from the low-speed steering angle ratio setting means, when changing direction on a narrow road, At the same time as the vehicle starts, the distance between the left and right side walls and the vehicle body and O! From the yaw angle of the vehicle body with respect to one wall and the front wheel steering angle, the left and right rear wheel steering angles are determined so that the rear corner of the vehicle body does not come into contact with the left and right side walls, and the rear wheel steering angle, whichever is smaller, is determined. The low speed steering angle ratio is determined from therefore,
In order to prevent the rearward corner of the vehicle body from contacting the side wall below a predetermined vehicle speed, the rear wheel steering angle is continuously adjusted to 1jlI by the low-speed steering angle ratio.
Therefore, the driver can obtain circular if I steering that does not feel strange to the driver.

The rear wheel steering angle is limited to a predetermined value or less to prevent the vehicle from coming into contact with the side wall, so even if the driver turns the steering wheel sharply as if it were a normal bamboo wheel steered vehicle, there will be no contact with the side wall of the vehicle. accidents are avoided,

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a schematic configuration of a four-wheel steering vehicle equipped with a steering angle ratio control device according to the present invention, FIG. 2.3 is an explanatory diagram showing the relationship between front and rear wheel steering angles and turning radius, Figure 4 is a characteristic diagram of the steering angle ratio setting means, Figure 5 is a block diagram showing the configuration of the steering angle ratio III control device, and Figure 6.7 is a flowchart of the program that controls the steering angle ratio control @ device. be. 2: Front wheel 6: Steering shaft 7: Front wheel steering mechanism 14: Input link 18: Steering angle ratio III control motor as actuator 23: Support shaft 27: Output link 28: Connection pin 30: Control lever 34: Rear wheel steering Mechanism 40: Rear wheel 51: Electronic control I] II 55: Vehicle speed sensor 56:
Steering angle ratio sensor 59: Front wheel steering angle sensor 62a, 62b
: Distance sensor 62; Yaw angle detection means patent applicant Isuzu Motors Co., Ltd.

Claims (1)

[Claims] Based on signals from a yaw angle sensor that detects the inclination of the vehicle body relative to the left and right side walls, and a distance sensor that detects the distance between the left and right side walls and the vehicle body, the rear wheel steering angle is determined so that the vehicle body does not touch the side walls even when the front wheels are steered at the maximum angle. Rear wheel steering angle determination means for determining when turning right and left turning; means for setting a low speed steering angle ratio that causes a smaller amount of protrusion of the rear of the vehicle body from signals from the rear wheel steering angle determining means and the front wheel steering angle sensor; A steering angle ratio control device comprising: an actuator that drives a steering angle ratio control mechanism at low speed based on a signal from a low-speed steering angle ratio setting means.