JPH01301471A - Four-wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To secure starting stability of a vehicle on a low mu road by correcting a steering ratio characteristic in a four-wheel steering device to the running stable side of a vehicle when a traction control device is operated. CONSTITUTION:As excessive slip is caused in front wheels when a vehicle runs on a low mu road, a controller 130 of a braking control device conducts traction control to prevent slip. Previously to the traction control, a signal is output from the controller 130 to a controller 60 for four-wheel steering control. In the controller 130, traction operation detecting means 64 receive an output signal from the controller 130 for braking control to detect that the braking control device is in the course of traction control operation, and a correction command signal is output from correction means 65 adapted to receive a signal from detecting means 64 to steering ratio setting means 63.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a four-wheel steering device that steers both the front wheels and the rear wheels of a vehicle in accordance with the operation of a steering wheel. The present invention relates to a four-wheel steering system for a vehicle equipped with a traction control system that applies 49 degrees of torque to the drive wheels to prevent excessive slippage.

(Prior art) Conventionally, as a four-wheel steering system for vehicles, for example, the
As disclosed in Japanese Patent No. 0-44185, the front wheels and the rear wheels are steered in accordance with the operation of the steering wheel, and the steering ratio of the front and rear wheels is determined based on a predetermined steering ratio characteristic set in advance. It is known that the vehicle speed is changed according to the vehicle speed. In this case, the above-mentioned steering ratio characteristics are basically such that the front and rear wheels are set in opposite phases at low vehicle speeds to improve the turning performance of the vehicle, and at high vehicle speeds, the front and rear wheels are set in the same phase to improve the running stability of the vehicle. is set to .

On the other hand, in recent years, traction control has been put into practical use in vehicles to prevent excessive slip of the drive wheels on so-called low-μ roads where the frictional resistance of the road surface is low, such as on snowy roads (especially (See JP-A-58-16948 and JP-A-60-56662). The reason for the excessive slip of the driving wheels is that the torque applied to the driving wheels is too large. Therefore, in traction control, the slip state of the drive wheels with respect to the road surface is detected, and when the slip rate exceeds a predetermined value, the torque applied to the drive wheels is reduced by reducing engine output or applying braking force to the drive wheels using the brake. The system that performs such control is collectively called traction control tIlia.

(Problems to be Solved by the Invention) Incidentally, in the above-mentioned four-wheel steering device, in order to improve running stability on low μ roads where the wheels tend to slip, a steering ratio preset for normal road surfaces is used. The characteristics may be corrected to make the vehicle run more stable, such as by shifting the characteristics by a predetermined width in the same phase direction, and the steering ratios of the front and rear wheels may be controlled based on the corrected steering ratio characteristics.

In this case, it is necessary to detect whether or not the road surface is a low μ road. Conventionally, this detection has been made based on the slip state of the wheels, etc., but the configuration of the detection means is complicated and costly. It had drawbacks such as being expensive.

The present invention has been made in view of this point, and its purpose is to specifically focus on the fact that the above-mentioned traction control device is activated when the road surface is a low μ road.
When this traction control device is activated, the steering ratio characteristics of the four-wheel steering device are corrected to the side that will stabilize the vehicle's running, thereby simplifying the configuration of the detection means and effectively improving running stability on low μ roads. It is an object of the present invention to provide a four-wheel steering system for a vehicle that can be used as a vehicle.

(Means for Solving the Problems) In order to achieve the above object, one solution of the present invention is to steer the front wheels and rear wheels according to the operation of the steering wheel, and to adjust the steering ratio of the front and rear wheels. A four-wheel steering device that changes according to vehicle speed based on a preset steering ratio characteristic, and a traction control device that controls torque applied to the drive wheels so that the drive wheels do not cause excessive slip on the road surface. Vehicles with

The four-wheel steering system of this vehicle includes a steering ratio changing means that controls the steering ratio of the tfJ rear wheels according to the steering ratio characteristic, and a traction operation that detects that the traction control system is in operation. The present invention is configured to include a detection means and a correction means that receives a signal from the traction actuation means and corrects the steering ratio characteristic to a side where the vehicle runs more stably when the traction device is actuated.

(Function) With the above configuration, in the present invention, when the vehicle runs on a low μ road, the traction control device operates to prevent the drive wheels from slipping, but the four-wheel steering device In this case, the traction operation detection means detects that the road surface is a low μ road by the operation of the 1-traction control device. Then, the steering ratio characteristic is corrected to the vehicle running stability side by the correction means receiving the signal from the traction operation detection means, and the steering ratio of the FFJ rear wheels is adjusted based on the corrected steering ratio characteristic. This is controlled by the ratio changing means, thereby improving the running stability of the vehicle.

Moreover, the traction operation detection means detects whether the traction control tIII device is in operation or not.
It only detects whether the vehicle is in the N or OFF state, and the configuration of the detection means is simpler than that of a detection means that detects whether the road is low μ based on the slip state of the wheels, etc. Also, the risk of erroneous detection or erroneous control is reduced.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIGS. 1 and 2 show four diagrams of a vehicle according to an embodiment of the present invention.
The wheel steering device is shown, IL, IR, 2L.

2R are the four wheels of the vehicle, including the left and right front wheels 1L, I
R is the front wheel steering mechanism 3, and the left and right rear wheels 2m, 2R
are linked to each other by a rear wheel steering mechanism 12.

The front wheel steering mechanism 3 includes a pair of left and right knuckle arms 4L.
, 4R, tie rods 5L, 5R, and a relay rod 6 that connects the left and right tie rods 5L, 5R. Furthermore, a steering wheel 10 is connected to this front wheel steering mechanism 3 via a rack vinyl 32 type steering mechanism 7.
are linked. The steering mechanism 7 has a rack 8 formed on the relay rod 6, a steering wheel 10 connected to the upper end, and the rack 8 formed at the lower end.
A steering shaft 11 to which a pinion 9 that meshes with the steering shaft 11 is attached, and the left and right front wheels IL and IR are steered in accordance with the operation of the steering wheel 10.

On the other hand, similarly to the front wheel steering mechanism 3, the rear wheel steering mechanism 12 includes left and right knuckle arms 13L, 13R and tie rods 14L, 14R.
It has a relay rod 15 that connects them together, and is further provided with a hydraulic power steering mechanism 16. The power steering mechanism 16 includes a power cylinder 17 that is fixed to the vehicle body and has the relay rod 15 as a piston rod. It is divided into hydraulic chambers 17b and 17c, and these hydraulic chambers 17b and 17c are connected to a control valve 20 via pipes 18 and 19, respectively. Furthermore, two pipes, an oil supply pipe 22 and an oil discharge pipe 23, leading to a reserve tank 21 are connected to the control valve 20, and a hydraulic pump 24 driven by an engine (not shown) is arranged in the oil supply pipe 22. It is set up. The control valve 20 is a known spool valve type, and includes a cylindrical valve casing 20a integrally attached to the relay rod 15 via a connecting member 25, and a valve casing 20a fitted into the valve casing 2Oa. The hydraulic pump 24 supplies pressure oil from the hydraulic pump 24 to one hydraulic chamber 17b (170) of the power cylinder 17 according to the movement of the spool valve to assist the driving force for the relay rod 15. It is something.

In addition, return springs 17d and 17d are provided in the power cylinder 17 to urge the relay rod 15 to a neutral position (a position where the steering angle θR of the rear wheels 2L and 2R is zero).
is installed.

A rack 2 is attached to the relay rod 6 of the front wheel steering mechanism 3 at a position different from the rack 8 constituting the steering mechanism 7.
6 is formed, and a pinion 27 attached to the front end of a rotating shaft 28 extending in the longitudinal direction of the vehicle body is engaged with the rack 26, and the rear end of the rotating shaft 28 is connected to the rear wheel steering system via a steering ratio control mechanism 29. It is linked to mechanism 12.

The steering ratio control mechanism 29, as shown in FIG. Connected to the spool valve. The steering ratio control mechanism 29 also includes a swing arm 33 whose base end is swingably supported by a U-shaped holder 31 via a support pin 32, and the holder 31 is a casing fixed to the vehicle body. A support shaft 35 (not shown) has a rotating wheel line perpendicular to the movement axis of the control rod 30.
It is rotatably supported via.

The support pin 32 of the swing arm 33 is located at the intersection of the two axes (the movement axis of the control rod 30 and the rotation axis of the support shaft 35) and extends in a direction perpendicular to the rotation wheel line. By rotating around the support shaft 35, the support pin 32 and control rod 3 at the tip thereof are
0, that is, the angle of inclination that the swing locus plane of the swing arm 33 centered on the support bin 32 makes with respect to a plane perpendicular to the movement axis (hereinafter referred to as the reference plane). It looks like this.

Further, one end of a connecting rod 37 is connected to the tip of the swing arm 33 via a ball joint 36, and the other end of the connecting rod 37 is connected to the other end of the control rod 30 via a ball joint 38. The control rod 30 is connected to the end of the swing arm 33, and is configured to displace the control rod 30 in the vehicle width direction in accordance with the displacement of the tip of the swing arm 33 in the vehicle width direction.

The connecting rod 37 is slidably supported by the rotation imparting arm 40 at a portion near the ball joint 36 via a ball joint 1-41.

The rotation imparting arm 40 is connected to the control rod 3.
The bevel gear 43 is provided integrally with a large-diameter bevel gear 43 rotatably supported via a support shaft 42 on the movement axis of 0, and the bevel gear 44 attached to the rear end of the rotating shaft 28 is attached to the bevel gear 43 The rotational motion of the steering wheel 10 is transmitted to the rotation imparting arm 40. Therefore, the rotation imparting arm 40 and the connecting rod 37 rotate around the movement axis of the control rod 30 by an amount corresponding to the rotation angle of the steering wheel 10, and accordingly, the swing arm 33 rotates around the support bin 32. When the axis of the support bin 32 is swung by the control rod 30
When the axis of movement of the support bin 32 coincides with the axis of movement, the ball joint 36 at the tip of the swing arm 33 only swings on the reference plane, and the control rod 30 is held stationary. If the swinging locus plane of the swinging arm 33 deviates from the reference plane by tilting with respect to the moving wheel line, the ball joint 36 will move against the vehicle as the swinging arm 33 swings about the support bin 32. is displaced in the width direction, and this displacement is transmitted to the control rod 3o via the connecting rod 37, so that the control rod 30 moves along the movement axis to actuate the spool valve of the control valve 20. It is composed of That is, the swinging arm 3 centered on the axis of the support bin 32
Even if the swing angles of the control rods 30 and 3 are the same, the control rods 30
The displacement in the left-right direction changes with the change in the tilt angle of the support bin 32, that is, the rotation angle of the holder 31.

In order to change the inclination angle of the support bin 32 with respect to the movement axis, that is, the inclination angle of the holder 31 with respect to the reference plane, a sector arm 45 as a worm wheel is attached to the support shaft 35 of the holder 31. A worm gear 47 on a rotating shaft 46 is meshed with the sector gear 45 . Further, a bevel gear 48 is attached to the rotating shaft 46, and a bevel gear 49 attached to the output shaft 50a of a stepping motor 50 is meshed with the bevel gear 48. When the stepping motor 50 is operated, the sector gear 45 By rotating the holder 31, the inclination angle with respect to the reference plane is changed to control the steering angle θR of the rear wheels 2L and 2R, and the sector gear 45 is rotated so that its center line is aligned with the center line of the rotating shaft 46 of the worm gear 47. When the vehicle is rotated clockwise from the neutral position at right angles when viewed from above, the steering ratio is set to 2L for the rear wheels.

While the rear wheels 2R and 2R are controlled in the opposite phase to face in the opposite direction to the front wheels IL and IR, when they are rotated counterclockwise, the rear wheels 2L and 2R are controlled to have the same steering ratio as the front wheels IL.

It is configured to be controlled to be in the same phase and in the same direction as 1R.

Further, on the casing that supports the holder 31, stopper members 51 and 52 on the opposite phase side and the same phase side, which are made of pins that restrict the rotation range of the sector gear 45, are attached on both left and right sides of the sector gear 45. When the sector gear 45 rotates to the opposite phase side, if the rotation angle from the neutral position reaches, for example, -17.5 degrees, the sector gear 45 will come into contact with the opposite phase side stopper member 51 and will not rotate further. When the sector gear 45 rotates toward the same phase side, when the rotation angle from the neutral position reaches, for example, 20 degrees, the sector gear 45 comes into contact with the stopper member 52 on the same phase side, and the movement is restricted. It looks like this. and,
The sector gear 45 is connected to the stopper member 51 on the opposite phase side.
The control position of the stepping motor 5o when the stepping motor 5o comes into contact with the motor 5o is set as its initial position. Note that 3 is a rod stopper that restricts the maximum movement range of the relay rod 15 in the rear wheel steering mechanism 12.

The stepping motor 50 functions as a steering ratio changing means, and is configured so that its operation is controlled by an output from a four-wheel steering controller 60 having a built-in microcomputer shown in FIG. The controller 60 includes a vehicle speed detecting means 62 that detects the vehicle speed according to a detection signal from the vehicle speed sensor 61, and receives a signal from the vehicle speed detecting means 62 and adjusts the vehicle speed based on pre-stored steering ratio characteristics. A steering ratio setting means 63 that determines the steering ratio of the front and rear wheels, and a 1-traction control device that detects that the brake control device is in traction control operation based on a signal from a controller 130 of the brake control device (traction control device), which will be described later. The operation detection means 64 receives a signal from the traction operation detection means 64, and when the traction control device is activated, corrects the steering ratio characteristic by changing it in the same phase direction, that is, in a direction that improves the running stability of the vehicle. A correction means 65 outputs a correction command signal to the steering ratio setting means 63, and the operation of the stepping motor 50, which acts as a steering ratio changing means, is controlled in accordance with the output signal from the steering ratio setting means 63. A motor control means 66 is provided.

FIG. 4 shows the configuration of a brake control device as a traction control device installed in a vehicle together with a four-wheel steering device. still,
In the case of the embodiment shown in the drawings, an example in which the present invention is applied to an FF (front engine/front drive) type vehicle is shown.

In addition, the braking control device also controls the drive wheels IL,
In addition to traction control that controls the torque applied to IR, 11. prevents each wheel IL, IR, 2L, and 2R from locking during braking. The so-called A that controls lj initial power
An example is shown in which the system also controls the B S 1lIIJ.

In FIG. 4, reference numeral 71 is an engine mounted horizontally on the front of the vehicle body, and the output from the engine 71 is transmitted to the left and right sides via axle shafts 74 and 75 after passing through a transmission Ia 72 and a differential device 73. The power is transmitted to the front wheels IL and 1R.

76, 77, 78 and 79 are each wheel 1L, I
The brakes (disc brakes in the drawing) provided at R, 2L, and 2R, and the mask cylinder 81 as a brake fluid pressure generation source, the mask cylinder 81 releases brake fluid when the driver depresses the brake pedal 82. Generates pressure. The mask cylinder 81 is the first.
It is a tandem type having two second discharge ports 81a and 81b, and the brake pipe tR83 extending from the first discharge port 81a is branched into two in the middle, and the negative branch pipe 83a is for the front right wheel. The other branch pipe 83b is connected to the brake 77 of 1R (more specifically, its wheel cylinder), and the other branch pipe 83b is connected to the left rear wheel 2.
The L brakes 78 are connected to the L brakes 78, respectively. Further, the brake pipe 84 extending from the second discharge port 81b is also branched into two parts in the middle, one branch pipe 84a is connected to the brake 76 of the left front wheel 1L, and the other branch pipe 84b is connected to the right rear wheel 2R. The brakes 79 are respectively connected to the brakes 79 .

Therefore, the brake piping system is a so-called two-system X piping system.

The front wheel brake pipe 83a (84a) includes:
ABS hydraulic control valve 85F sequentially from the upstream side to the downstream side
R (85FL) and a traction 1IIJ till hydraulic pressure control valve 86R (86L) are connected. In addition, the brake piping 83b (84b) for the rear wheel is equipped with blow-off valves 87L sequentially from the upstream side to the downstream side.
(87R), ABS hydraulic control valve 85RL (85R
R) is connected. That is, each brake pipe 83
A, 83b, 84a, 84b each have ABS
Hydraulic pressure control valve 85FR, 85RL, 85FL or 85R
R is connected to, in addition to this, a front wheel brake pipe 83a which becomes a driving wheel.

84a each has a hydraulic pressure control valve 86 for traction control.
R or 86L is connected to the rear wheel brake pipes 83b and 84b, respectively, and a blobbing valve 87L or 87R is connected to the rear wheel brake pipes 83b and 84b, respectively, for reducing the brake fluid pressure at a predetermined rate to the front wheel side.

Although not shown, the rear wheel brakes 78 and 79 have a built-in parking brake as is known. That is, when the driver operates the parking lever 88, braking force is applied only to the rear wheels 2L and 2R.

The Al3S hydraulic circuit HCI that performs ABS control is shown surrounded by a dashed line in FIG.

In this ABS hydraulic circuit HC1, 91 is a pump, and the pump 91 is driven by a motor 92.
The brake fluid in the reservoir 93 is discharged toward the accumulator 94. When the hydraulic pressure stored in the accumulator 94 exceeds a predetermined pressure, the relief valve 95 listens, and when the pressure falls below the predetermined pressure, the pressure switch 96 is closed and the motor 92 or the pump 91 is activated. A predetermined hydraulic pressure is always stored. 97 is a check valve.

The accumulator 94 is connected to each of the ABS hydraulic pressure control valves 85 (85FR, 85RL, 85
RR, 85FL), and each ABS hydraulic pressure control valve 85 is independently connected to a reservoir 93 via a relief pipe 99 (in the drawing, for simplicity, each ABS hydraulic pressure control valve 85 is (I omit the connection)
. Each of the ABS hydraulic pressure control valves 85 is of an electromagnetically operated type and is of a known circulation type. That is, when the wheels 1L, 1R, 2L, and 2R are about to lock under the control of the braking control controller 130, which will be described later, during braking when the brake pedal 82 is depressed,
Brake fluid pressure is released to the reservoir 93 to weaken the braking force, and when this near lock is interrupted, high fluid pressure from the accumulator 94 is transferred to the brake distribution W83a, 83.
b, 84a.

84b to increase braking force. Furthermore, the brake fluid pressure for the rear wheels 1L and 1R is adjusted independently for the left and right wheels, while the brake fluid pressure for the rear wheels 2L and 2R is adjusted for both the left and right wheels using a so-called 4-sensor, 3-channel system.

On the other hand, the traction control hydraulic circuit HC2 that performs traction control is shown surrounded by a two-dot chain line in FIG. This]・Hydraulic pressure circuit for traction control [1C
2, first, the hydraulic pressure control valves 86L and 86R for controlling the first helix will be explained with reference to FIG. . The hydraulic pressure control valve 86L has a casing 101 and a piston 102 slidably inserted into the casing 101, and the piston 1
02 defines the inside of the casing 101 into a liquid passage chamber 103 and a control liquid chamber 104. An inlet 105 and an outlet 106 that open into the liquid passage chamber 103 are formed in one end wall of the casing 101, and the inlet 105, the liquid passage chamber 103, and the outlet 106 are part of the brake pipe 84a. It consists of

A pair of guides 107 and 108 are disposed within the liquid passage chamber 103 and are spaced apart in the circumferential direction of the piston 102, and both guides 107 and 108 are biased in the direction of separation by a spring 109. . As a result, one guide 107 is always seated on one end wall of the casing 101 where the inlets 105 and 106 are present, and the other guide 108 is always seated on the piston 102. This-
The check valve 11 is straddled between the pair of guides 107 and 108.
0 in the fast moving direction of the piston 10.2). The check valve 110 includes a valve body 110a facing the inlet 105, and a valve stem 110b that is integrated with the valve body 110a and slidably passes through the guides 107 and 108.
and a spring 110d that is compressed between the end of the valve stem 110b and the guide 107 and biases the valve body 110a to seat on a valve seat 110C formed around the inlet 103. are doing. The valve body 110a is the valve seat 11
A displacement of more than a predetermined value in the direction approaching 0C causes the valve stem 110b to
The stopper 110e formed in the guide 108 is regulated by coming into contact with the guide 108. When the piston 102 is in the rightward stroke position in FIG. 5, the valve body 110a
is slightly separated from the valve seat 110C, and brake fluid pressure from the inlet 105 is propagated to the outlet 106 via the fluid passage chamber 103. Further, as the piston 102 is displaced to the left, the valve body 110a is seated on the valve seat 110C, and the inlet 1
05 is closed, the brake fluid in the liquid passage chamber 103 that is pressurized as the piston 102 is displaced to the left flows out from the outlet 106.

In this way, the brake fluid pressure that has passed through the ABS fluid pressure control valve 85FL is freely supplied to the outlet 106-1 and the brake 76 in accordance with the displacement of the piston 102 in the left direction. The brake fluid pressure in the fluid passage chamber 103 is increased while preventing backflow to the ABS fluid pressure control valve 85FL side.
A state is obtained in which the brake 76 generates a braking force. Of course, to prevent excessive slip of the front wheels IL and 1R as driving wheels during traction $1 till, the piston 102 is displaced to the left in FIG. 5, and when this excessive slip no longer occurs, the piston 102 will be displaced to the right in Figure 5.

The piston 102 is displaced by controlling the supply of hydraulic pressure to the control liquid chamber 104 through an opening 111 formed in the casing 101. 94 and the hydraulic pressure is utilized. To explain this point in detail, a supply pipe 98 extending from the accumulator 94
and the relief pipe 99 communicating with the reservoir 93 are connected by a pipe 121, and the middle part of the pipe 121 forms two branch pipes 121a and 121b parallel to each other. An opening 111 (control liquid chamber 104) of a hydraulic pressure control valve 86L is connected to this one branch pipe 121a, and electromagnetic on-off valves 122L are provided upstream and downstream of the opening 111, respectively. Or 123L is connected. Further, an opening 111 (control liquid chamber 104) of a hydraulic pressure control valve 86R is connected to the other branch pipe 121b, and an electromagnetic opening/closing mechanism 122R is connected to the upstream and downstream sides of the opening 111, respectively. Or 123R is connected. Then, when the supply on-off valve 122m (122R) is opened and the relief on-off valve 123L (123R) is closed, the control liquid chamber 104 is filled with water from the accumulator 94.
pressure is supplied, and the hydraulic pressure control valve 86L (86K>
The piston 102 is displaced in a direction that compresses the liquid passage chamber 103, and the brake 76 (77) is activated (braking force applied). On the contrary, supply on-off valve 122L (122R)
When the relief on-off valve 123m (123R) is opened, the hydraulic pressure in the control liquid chamber 104 is released to the reservoir 93, the piston 102 is returned to the direction of expanding the liquid passage chamber 103, and the brake 76 ( 77) is reduced or canceled. The above on-off valve 122L, 123m <12
2R, 123R> is the brake & lJ I! described later. When the slip of the front wheels IL and IR becomes large, the hydraulic pressure is supplied to the control liquid chamber 104, and when the slip becomes small, the hydraulic pressure of the control liquid chamber 104 is controlled by the controller 130 for the control liquid chamber 104. You will have to run away.

Furthermore, in FIG. 4, 130 is a control system configured by, for example, a microcomputer! II i control controller, the controller 130 is not shown, but
It is equipped with CPLllROM, RAM and CLOCK. The controller 130 includes each wheel IL, 1R,
Rotation speed signals from pick-up type rotation speed sensors 13.1, 132, 133, and 134 that detect the rotation speed of 2L and 2R, vehicle speed signals from the vehicle speed sensor 61, and an opening sensor that detects the operation amount of the accelerator pedal 136. An accelerator opening signal from 137, a parking brake signal from a brake sensor 138 that detects that the parking brake lever 88 has been operated, and a steering angle signal from a steering angle sensor 139 that detects the amount of steering of the steering wheel 10 are input, respectively. has been done.

Further, from the controller 130, the ABS hydraulic pressure control valve 85 and the on-off valves 122L, 122R, 1231, 12
In addition to 3R, there is a valve for driving the throttle valve 142 disposed in the intake passage 141 of the engine 71. ! A control signal is output to the magnetic actuator 143 to control its operation. Furthermore, when performing traction control in the braking control controller 130, the control I/roller 13
0, a signal is output to the traction operation detection means 64 of the four-wheel steering control controller 60, and the traction operation detection means 64 detects that the brake control device is operating the traction 1IIl til1. There is.

In the above configuration, the control operation by the controller 130 of the brake 11JJ III device will be explained based on the flowchart shown in FIG.

First, in step S+, each sensor 61.131-134.
After reading the signals from 137 to 139, step S2
The ABS slip rate R1 is calculated by '. This ABS slip rate R1 is determined by vehicle body speed Vo and wheel rotation speed Vw.
Then, it is calculated by the formula: R+ = (Vs - Vw)/Va.

Next, in step S3, it is determined whether the ABS slip ratio R1 is smaller than a predetermined value α, and this determination is YES.
In this case, the wheels are likely to lock, so ABS control is performed in step S4. This ABS control is △[
A control signal is output to the 3S hydraulic pressure control valve 85 to automatically adjust the brake hydraulic pressure so that the wheels do not lock during full braking. On the other hand, the determination in step S3 is N.
If o, the traction control slip rate R2 is calculated in step S5. This slip ratio R2 for traction control is determined by the rotational speed of the drive wheels (front wheels 1L, IR)
, where WL is the rotational speed of the driven wheels (rear wheels 2L, 2R), R2-(Wo-WL)/W.

It is calculated by the following formula.

After that, in step S6, it is determined whether the traction control slip ratio R2 is larger than the predetermined value β. If this determination is No, it means that no excessive slip has occurred on the drive shaft, so the traction control is performed. Return without doing anything. On the other hand, when the determination in step S6 is YES, it is determined in step $7 whether or not the steering angle of the steering wheel 10 is equal to or greater than a predetermined value, and step S
8, it is determined whether the parking brake lever 88 is being operated. The determination in steps S7 and S8 is as follows:
This is to determine whether the driver intends to cancel traction control and perform a spin turn.

Then, the determinations in steps S7 and S8 are both YES.
The next step is when you have the intention to perform a spin turn;
In this case, the vehicle returns without performing traction control. On the other hand, if either of the determinations in steps S7 and S8 is N
When O, there is no intention to perform a spin turn, so in this case, it is determined in step S9 whether the slip ratio R2 is greater than a predetermined value T set as a condition for distinguishing the modes of traction control. do. When the determination in step S9 is YES, a signal is output to the four-wheel steering controller 60 in step S1o, and then traction control is performed using both the brake and the engine in step Sn.

That is, on-off valves 122L, 122R, and 123L.

A control signal is output to the actuator 123R to control the braking force, and a braking signal is output to the actuator 143 to control the opening degree of the throttle valve 142, that is, the engine output, thereby preventing excessive slip of the drive wheels. do. Also,
When the determination in step S9 is No, step S12
After outputting a signal to the four-wheel steering controller 60 in step S13, traction control is performed using only the brakes to prevent excessive slip of the drive shaft.

Next, to explain the operation of the four-wheel steering system in the above embodiment, especially the steering ratio control of the front and rear wheels by the controller 60, when the vehicle runs on a general road, the controller 60 sets the steering ratio. Based on the basic steering ratio characteristics stored in advance by means 63? The steering ratio of the front and rear wheels corresponding to Jl″a is determined, and the steering ratio setting means 6
The stepping motor 5o, which serves as a steering ratio changing means, is operated and controlled by the motor control means 66 that receives the output signal from the steering ratio control means 66 to perform normal steering ratio control according to the above-mentioned basic steering ratio characteristics. . Here, the basic steering ratio characteristic is that the steering ratio of the front and rear wheels changes depending on the vehicle speed, as shown by @a in Fig. 7, and at low vehicle speeds, the rear wheels 2L and 2R are 1L front wheels.

The front wheels are steered in the opposite direction to 1R, and the steering ratio of the front and rear wheels becomes negative. At high vehicle speeds, the rear wheels 2L and 2R are turned to the front wheels 1L in order to improve the wheel grip when turning and increase running stability.
, are set so that they are steered in the same direction as IR and the steering ratio of the front and rear wheels is positive.

On the other hand, when the vehicle runs on a low μ road, the front wheel I, which is the drive shaft,
Since L and IR cause excessive slip, the controller 130 of the brake control device performs traction control to prevent such excessive slip except in special cases when the driver performs a spin turn. Furthermore, prior to this traction control, a signal is output from the controller 130 to the four-wheel steering controller 60. and,
In the four-wheel steering control controller 130, the traction operation detection means 64 is connected to the four-wheel steering control controller 1.
30, the braking control device detects that traction control is in operation, and a correction command signal is sent to the steering ratio setting means 63 from the correction means 65, which receives the signal from the traction operation detection means 64. By outputting the steering ratio characteristic, the steering ratio characteristic is sent to the steering ratio setting means 63, as shown by the broken line in FIG. The displacement is corrected to the same phase side, which is the stable running side of the vehicle, and the operation of the stepping motor 50 is controlled based on the corrected steering ratio characteristic.

In this way, when driving on low-μ roads where the wheels are prone to slippery, the steering ratio of the front and rear wheels is controlled to stabilize the vehicle's running, which effectively improves driving stability on low-μ roads. You can

Moreover, the traction operation detection means 64 merely detects that the brake control device is in traction control operation upon receiving a signal from the brake control controller 130; This is much simpler than a detection means that detects and determines whether or not it is a low μ road based on the state or the like. Moreover, there is no fear of erroneous detection, and it can contribute to prevention of erroneous control.

It should be noted that the present invention is not limited to the above embodiments, but includes various other modifications.

For example, in the above embodiment, when the traction control of the brake control device i (traction control device) is activated, the correction means 65
As a method of correcting the basic steering ratio characteristics to the side of vehicle running stability, the above steering ratio characteristics are adjusted by a predetermined width α in the same phase direction.
However, instead of this, for example, as shown by the dashed line C in Fig. 6, the steering ratio of the front and rear wheels is controlled in accordance with the steering ratio characteristic corrected to eliminate the antiphase region. You may also do so. In addition, when it is detected that the traction control device is operating, the steering characteristics are adjusted so that the steering angle θR of the rear wheels 2L and 2R is always zero, resulting in a two-wheel steering state regardless of the vehicle speed. may be corrected.

(Effects of the Invention) As described above, according to the four-wheel steering system for a vehicle according to the present invention, it is possible to detect that the road surface is a low μ surface by the operation of the traction control device that operates on a low μ road, and to adjust the steering ratio characteristic. is corrected to the side of vehicle running stability, resulting in low μ.
It is possible to improve running stability on roads, simplify the detection means, and prevent erroneous control.
This has excellent practical effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram showing the overall configuration of a four-wheel steering device, FIG. 2 is a perspective view of the same,
FIG. 3 is a block diagram of the controller of the four-wheel steering system. Fig. 4 is an overall configuration diagram of the 11-movement 11jiill device, Fig. 5 is an enlarged sectional view of the hydraulic pressure control valve for traction control, Fig. 6 is a flowchart showing the control operation by the brake control controller, and Fig. 7 is a flowchart showing the control operation by the brake control controller. FIG. 3 is a characteristic diagram showing steering ratio characteristics. 50...Stepping motor (steering ratio changing means), 6
4... Traction operation detection means, 65... Correction means. Patent applicant: Mazda Motor Corporation, “゛3rd
Figure 5] 10

Claims (1)

[Claims] (1) A four-wheel steering device that steers the front wheels and rear wheels according to the operation of a steering wheel, and changes the steering ratio of the front and rear wheels according to the vehicle speed based on a preset steering ratio characteristic; In a vehicle equipped with a traction control device that controls the torque applied to the drive wheels so that the drive wheels do not cause excessive slip on the road surface, the steering ratio of the front and rear wheels is controlled according to the above-mentioned steering ratio characteristics. steering ratio changing means; traction operation detection means for detecting that the traction control device is in operation; and receiving a signal from the traction operation detection means to determine the steering ratio characteristic when the traction control device is operating. A four-wheel steering device for a vehicle, comprising a correction means for correcting the vehicle to a stable running side.