JPS60148770A - Steering device for vehicles - Google Patents

Abstract

PURPOSE:To secure stable turning performance, by deriving the cornering power of a tire according to a detection value of a factor showing a running state, while controlling rear wheel turn-steering operations according to the said power, in a steering device which makes a turn-steering angle for rear wheels controllable. CONSTITUTION:In case of a device which operates rear wheel turn-steering information at a computer 12 in which each output signal out of a lateral acceleration sensor 13 and a front wheel turn-steering angle sensor 14, etc., is inputted, and turns and steers each rear wheel through a servo actuator 8 according to the operation result, plural numbers of cornering power C1-Cn are found according to a front actual steering angle by the said sensor 14. In addition, a portion for variations in the lateral acceleration commensurate to each power aforesaid and furthermore each of estimated lateral acceleration data alpha1-alphan is found from a portion for variations in the front wheel actual steering angle. And, among them, such estimated lateral acceleration data as being most approximate to the measured lateral acceleration data alpha0 by the said sensor 13 is selected and corresponding cornering power is derived out, controlling the rear wheel turn-steering by the control information calculated on the basis of the said power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering system for a vehicle such as a four-wheeled vehicle. A vehicle steering device that can also steer the rear wheels depending on the conditions, dramatically improving the vehicle's maneuverability, steering response, and performance (patent application J1.5)
7. , 1a48B8, etc.) are proposed.
, l:: , 5 The magnitude of the cornering power that acts on the tires and tires of each wheel when a vehicle makes a turning motion is generally expressed as the ratio of increase in lateral force to a change in the tire's sideslip angle,
It varies depending on various conditions such as air pressure in the ears, ground load, and road surface conditions.

4. Cornering power decreases when the ground load increases due to bumps, tire air pressure decreases, or loaded cargo, etc. In particular, when the cornering power of the rear tires decreases, the vehicle body may tilt while turning. It becomes easier to swing, reducing turning performance and making it difficult for the driver to operate the steering wheel stably. On the other hand, if the cornering power of the rear tires increases, on the other hand, the vehicle will have a strong tendency to understeer. For example, at medium speeds, it will be difficult to respond to the cornering power, resulting in a decrease in turning performance and the driver will have to operate the steering wheel normally. It needs to be larger than . In this case, if the rear wheels are steered in a direction that reduces such adverse effects, the adverse effects can be effectively eliminated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle steering system that allows stable steering operation at all times even when cornering and improves cornering performance, without causing vehicle running to be adversely affected by fluctuations in cornering power. .

In order to achieve the above object, the present invention is applied to a steering system for a vehicle that can variably control the steering angle of the rear wheels according to certain conditions, and its main components include factors indicating the running state of the vehicle, such as: a deriving means for predicting and deriving tire cornering power by detecting steering wheel steering angle, lateral acceleration, etc., and a processing means for outputting control information for controlling rear wheel steering in response to the deriving result from the deriving means; The control means is equipped with a control means that controls the rear wheels to be additionally steered by a predetermined steering angle based on the control information, and by predicting the cornering power, for example, if the cornering power is larger than a reference setting value or The present invention is characterized in that when the cornering power becomes smaller, the rear wheels are steered in a direction in which the cornering power is corrected to the reference setting value.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, in order to clarify the present invention, a schematic configuration of a vehicle steering system will be explained based on FIG. This figure is a schematic plan view showing the basic structure of a vehicle equipped with a steering device according to the present invention. In the figure, (1) is a steering handle, and the steering shaft (2) of this handle (1) is connected to a steering gear mechanism, for example, a rack and pinion type, installed in a gear box (3). The steering rotation is converted into a movement of the tie rod (4) in the width direction of the vehicle body. Both ends of this tie rod (4) are connected to the front wheel (5),
The tie rod (4) is connected to the knuckle arms (8), (8) that support the tie rod (5), and is supported rotatably in the left and right direction.
) in the vehicle width direction causes the front wheels (5) and (5) to be steered in the steering direction of the steering wheel (1).

On the other hand, (7) is a rear wheel side gearbox, and the direction change means such as a rack & binion system installed in this gearbox (7) has a shaft (8) extending rearward from the rear wheel steering servo actuator (8). Connect 8a). In addition, a tie rod (
9) have knucks on both ends of the arm (!0), (10
) are rotatably connected, and this knuckle arm (lO),
(lO) supports the rear wheels (11), (11).

hold This allows the shaft (8a
) rotation displaces the tie rod (9) in the width direction of the vehicle body, further steering the rear wheels (!l) and (l) in a predetermined direction.

On the other hand, the vehicle is equipped with an on-board computer (12), and this computer (12) is, for example, a lateral acceleration sensor (or yaw rate sensor) that detects acceleration in the lateral direction of the vehicle.
(13) Receives detection signals from a front wheel steering angle sensor (14) that detects the steering angle of the front wheels, a vehicle speed sensor (not shown) that detects vehicle speed, etc., and sends a corresponding control signal to the rear wheel steering. Steering control is performed in the same phase direction when the servo actuation speed is high, and in the opposite phase direction when the speed is low.

Next, the configuration and functions of the main parts of the present invention will be specifically explained with reference to FIGS. 2 to 4. FIG. 2 is a functional block diagram of the rear wheel steering system, FIG. 3 is a diagram for explaining the operation, and FIG. 4 is a characteristic diagram for explaining the principle.

First, in FIG. 2, the computer (12) has a first
Various sensors such as the lateral acceleration sensor (13) shown in the figure or the front wheel steering angle sensor (14) are connected, and the detection results are stored in the computer (12) with preset data (i.e. ) to obtain rear wheel steering information (dO) corresponding to the detection result. This information (dO
) is added to the servo accutator (8) by +1,
For example, zero or more configurations and functions for rotating the shaft (8a) and steering the rear wheels (11) by digital-to-analog conversion, amplification, motor drive, etc., or operation of mechanical means such as a hydraulic cylinder, etc. This has already been proposed by the applicant and is the underlying technology of the present invention.

On the other hand, in the computer (12), the front wheel actual steering angle (dO), which is a factor indicating the driving state detected by the front wheel steering angle sensor (14), is determined by the conversion process (d). Power (cl), (C2), (
C3)...(Cn), respectively. To explain the principle of this conversion, generally speaking, the tire sideslip angle (β
) and the lateral force (F) are shown in FIG.

As mentioned above, the cornering power (C) can be expressed as C-ΔF/Δβ in the figure. On the other hand, the front wheel steering angle (
The relationship between the front wheel actual steering angle (dO) and sideslip angle (β) is expressed as β = f (u)・δ, where f (u) is the function for heavy speed (u). ) are almost proportional. Further, the lateral force (F) and the lateral acceleration (α) are approximately proportional. Therefore, in Fig. 4, the sideslip angle (β
) is the actual front wheel steering angle (C0), and the lateral force (F) is the lateral acceleration (
α) can be replaced respectively.

Therefore, each cornering power (CI), (C2)...(C
The change in lateral acceleration (Δα) corresponding to n), as well as predicted lateral acceleration data (C1), (C2), . . . (Cn) can be calculated.

On the other hand, the magnitude of the actual lateral acceleration, which is a factor indicating the running condition of the vehicle, can be detected from the lateral acceleration sensor (13) as actually measured lateral acceleration data (C0).

Then, this measured lateral acceleration data (C0) is compared with the predicted lateral acceleration data (C1), (C2)...(Cn). cl), (C2)...(Cn), the corresponding cornering power (C1) (C2)...(
, Cn), and the actual cornering power can be predicted.

This derived cornering power is the control data 0 "1)
'Lr, -7'''＞=4"idL, f=F-1("9°
゛1. : Through the calculation process described in detail later, necessary control information (C2) corresponding to the control data (d) is obtained.Then, this control information (C2) is subjected to addition/subtraction processing (c) to obtain the necessary control information (C2). Information (:d 6+
, d 2 ) or (do-C2).゛Next 6゛Arithmetic processing ()) G: Q°
That's my theory.

This calculation process (g) is performed when the tire air pressure decreases.
Or, when the ground load becomes large due to loaded cargo, etc., and the cornering power becomes less than or equal to the value, the rear wheels are steered according to the rear wheel steering information (dO). Further, the front wheels are additionally steered by a predetermined steering angle in the steering direction (in the same phase direction). That is, as shown in FIG. 3, control information (C2) for steering the rear wheels (11), (11) shown by solid lines to the rear wheels (lla), (lla) shown by virtual lines is generated. The width of the steering angle to be added is selected to be such that the steering angle of the entire rear wheel prevents the vehicle body from swaying, and the setting is stored as data 1.
(It has been.

On the other hand, when the cornering power becomes larger than the set value, the front wheels are steered in the opposite direction (one direction) with respect to the rear wheel steering state based on the rear wheel steering information (d o).
(in the opposite phase direction) by a predetermined steering angle. In other words, the rear wheel (11) shown by the solid line as shown in Figure 3,
The rear wheel (ttb) showing the virtual line ze for (11), (
ttb) to generate control information (C2) for steering the vehicle, and the magnitude of this steering angle is selected to be such that a normal turning trajectory can be obtained based on the steering wheel operation.

In addition, as mentioned at the beginning, the magnitude of cornering power fluctuates in relation to tire air pressure and ground load, so by directly detecting these, each detection result is sent to the computer (12) as described above. It is also possible to generate control information by combining the predicted coater power in parallel with the predicted result of the coater power that has been calculated, thereby improving the reliability of the control.

Therefore, the computer (12) predicts the cornering power of the tires while the vehicle is turning, that is, when the front wheels are being steered, and controls the steering angle of the rear wheels in a 4-1 additive manner. This allows you to set the rear wheel steering angle most suitable for the driving conditions. ] Computer (12)
Each process in is executed according to a control program (software) stored in memory in advance. Note that an electric circuit or the like having the same function may be used instead of the computer (I2).

As described above, the front and rear wheel steering system y1 of the vehicle according to the present invention can prevent vehicle running from being adversely affected by fluctuations in tire cornering power due to changes in tire air pressure, ground load, road surface conditions, etc., even when cornering. The steering wheel can be operated stably at all times, and the turning performance of both vehicles can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view showing the basic structure of a vehicle equipped with a steering system according to the present invention, Fig. 2 is a functional block diagram of the rear wheel steering system, Fig. fiS3 is an explanatory diagram of the operation, and Fig. 4 is an explanation of the principle. FIG. In the drawings, (II), (II), (Ifa), (Il
a) (Ilb) and (llb) are the rear wheels, (12) is the on-board computer, (13) is the lateral acceleration sensor, (14) is the front wheel steering angle sensor, (a) and (f) are the data, (b)
, (g) is arithmetic processing, (c) is addition/subtraction processing, (d).
... is conversion processing, (e) is comparison processing, (d o) is rear wheel steering information, and (d2) is control information. Patent Applicant Honda Motor Co., Ltd. Agent Patent Attorney 2 1) Yo-Buma Patent Attorney Kunihiko Ohashi Patent Attorney Yu Koyama

Claims (3)

[Claims] (1) A vehicle steering device capable of variably controlling the steering angle of rear wheels according to certain conditions, characterized by comprising the following means. (a) Derivation means for deriving tire cornering power by detecting factors indicating driving conditions; (b) Process for outputting control information for steering the rear wheels in response to the derivation result from the derivation means. (c) control means for controlling steering of the rear wheels based on the control information; (2) When the cornering power becomes smaller than the reference setting value, the processing means outputs control information for turning the rear wheels by a predetermined steering angle in the steering direction (same phase direction) of the front wheels. A vehicle steering system according to claim 1, characterized in that: (3) When the steering power becomes larger than the reference setting value, the processing means moves the rear wheels by a predetermined steering angle in a direction opposite to the steering direction of the front wheels (in an opposite phase direction). 2. The vehicle steering device according to claim 1, wherein the vehicle steering device outputs control information for causing steering.