JPH03148377A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To prevent rear wheels from being abruptly steered to the opposite direction at the time of abrupt deceleration by detecting the deceleration of a vehicle at the time of deceleration, setting the steering angle ratio of front wheels to rear wheels to zero until the deceleration will be less than a set value, and thereby suspending the steering of the rear wheels to the opposite direction. CONSTITUTION:A vehicle 2 is equipped with a main steering means 8 steering front wheels 10, and a steered means 12 steering rear wheels 14 in the same phase or reverse phase with the front wheels 10. The rear wheel rack and pinion mechanism 26 of the steering means 12 is driven by an electric motor 32, and the electric motor 32 is concurrently controlled by a control means 34 based on detected signals by a vehicle speed sensor 40, and a front and a rear steering angle sensors 36 and 38. In this case, the control means 34 detects the deceleration of the vehicle at the time of deceleration, and sets the steering angle ratio of front wheels 10 to rear wheels 14 to zero until the deceleration will be less than a set value, and thereby suspends the abrupt steering of the rear wheels 14 to the opposite direction. By this constitution, the rear wheels 14 are prevented from being abruptly steered to the opposite direction at the time of deceleration.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a four-wheel steering system, and particularly to a four-wheel steering system that maintains a good driving feeling by preventing the rear wheels from suddenly turning in the opposite direction during deceleration. The present invention relates to a four-wheel steering system that can be used. [Prior Art] Vehicles such as automobiles are usually provided with front wheels that can be steered in a desired direction of travel of the vehicle, and rear wheels that are provided parallel to the longitudinal direction of the vehicle body. When the front wheels of such a vehicle are steered to turn, the traveling trajectories of the front and rear wheels do not match the turning circle, and at low vehicle speeds, due to the difference between the inner wheels, the vehicle is in a position where the rear wheels are inside the turning circle. At high vehicle speeds, centrifugal force causes the vehicle to turn with the front wheels inside the turning circle. Therefore, even if the front wheels are steered in the turning direction, which is the traveling direction of the vehicle, there is a problem in that the attitude of the vehicle cannot be made to match the turning direction. Therefore, a vehicle has been proposed in which the rear wheels are also steered when the front wheels are steered. Some vehicles that steer the rear wheels in this manner employ a four-wheel steering device that steers the rear wheels so that the actual steering angle of the rear wheels becomes the target steering angle when steering the front wheels. As such a four-wheel steering device, for example, Japanese Patent Application Laid-Open No. 63
It is disclosed in Japanese Patent Publication No. 173766 and Japanese Patent Publication No. 60-44185. The system described in JP-A-63-173766 steers the rear wheels in the same phase as the front wheels at high speeds based on the vehicle speed, and also changes the steering ratio between the front wheels and the rear wheels according to the vehicle speed. In addition, when decelerating, it has hysteresis in the same phase direction, thereby eliminating the response delay in rear wheel steering due to follow-up correction, and making steering easier and more stable at high speeds. be. Furthermore, the vehicle described in Japanese Patent Publication No. 60-44185 makes the ratio between the amount of steering of the front wheels and the amount of steering of the rear wheels (steering angle ratio) variable based on the vehicle speed, and also changes the ratio of the amount of steering of the front wheels to the amount of steering of the rear wheels at high speeds. The rear wheels are steered in the same phase as the front wheels during deceleration, and the steering angle ratio is changed according to the vehicle speed, eliminating the response delay in rear wheel steering due to follow-up correction. This provides ease and stability of steering at high speeds, and improves maneuverability of the vehicle at low speeds. [Problems to be Solved by the Invention] By the way, in the conventional four-wheel steering system, as shown in FIG. The vehicle is steered in the opposite phase, that is, in the opposite direction, and after the vehicle speed reaches vehicle speed V, two-wheel steering (2WS) is performed for T1., that is, the steering angle ratio is set to zero, Once the vehicle speed reached V. or higher, the rear wheels were in phase with the front wheels, that is, they were steered in the same direction. However, when the rear wheels suddenly decelerated from the same phase state at high speed, the rear wheels became in phase with the front wheels and two-wheel steering ( 2WS), there was a phenomenon in which the phase suddenly changed to the opposite phase.In order to eliminate this phenomenon, as in the above-mentioned Japanese Patent Laid-Open No. 63-173766, hysteresis was provided in the in-phase direction during deceleration. However, in this case, Fig. 6(a), (b), (C
As shown in Figure 6(a), during sudden deceleration, the in-phase region widens and becomes out-of-phase (Fig. 6(a)). vehicle speed V
, vehicle speed v1! During two-wheel steering, T1□ becomes narrower,
There is a sudden change from in-phase to out-of-phase when the vehicle speed decreases, so there is no problem in terms of safety, but there is an inconvenience in that the driving feeling is impaired. [Object of the invention] Therefore, the object of this invention is to eliminate the above-mentioned disadvantages.
By calculating the deceleration during deceleration, and stopping the rear wheels from turning in the opposite direction by setting the steering angle ratio to zero until the deceleration becomes less than the set value, the rear wheels will suddenly move in the opposite direction even during sudden deceleration. To provide a four-wheel steering device that can maintain a good driving feeling by preventing the vehicle from being steered. [Means for Solving the Problems] In order to achieve this object, the present invention steers the rear wheels in phase with or in phase with the front wheels depending on the vehicle speed state, and also changes the steering angle ratio between the front wheels and the rear wheels. In a four-wheel steering device that controls the steering of the rear wheels to a target steering angle by changing the steering angle, a deceleration is calculated during deceleration, and the steering angle ratio is set to zero until the deceleration becomes less than a set value. Feature *A feature characterized by the provision of a control means for stopping steering in the opposite direction] According to the configuration of the present invention, the control means calculates the deceleration while inputting the deceleration state during deceleration, and Until the deceleration becomes less than the set value, the steering angle ratio is set to zero, that is, two-wheel steering is performed, and steering of the rear wheels in the opposite direction is stopped. This prevents the rear wheels from being abruptly steered in the opposite direction even during sudden deceleration, making it possible to maintain a good driving feeling. (Example) An example of the present invention will be described below in detail and concretely based on the drawings. Figs. 1 to 4 show an example of the present invention. In Fig. 1, 2 indicates a vehicle ( (four-wheel steering vehicle), 4 is a steering wheel, 6 is a steering shaft, 8 is a main steering means,
1 G-10 front wheel, tzitma direction means, 14.1
4 is the rear wheel. The main steering means 8 includes a front pinion (not shown) fixed to the tip end of the steering shaft 6 and a front rack (not shown) provided on a front rack bar (not shown) that meshes with the front pinion. (not shown) and the front gearbox 16.
The front rack and pinion mechanism 18 housed in the front rack and pinion mechanism 18, the front tie lofts 20, 20 connected to the respective ends of the front rack bar, and the front tie lofts 20, 20 connected to the front tie lofts 7, 20, 20, and the front wheel lO
・Constructed by front knuckle arms 22 connected to IO. The sub-direction means 12 consists of a rear pinion (not shown) and a rear luff (not shown) provided on a rear rack bar (not shown) that meshes with the rear pinion. A rear rough rack mechanism 26 housed in the rear gear box 24, rear tie rods 28, 28 connected to the respective ends of the rear rack bar, and a rear wheel 14 connected to the rear tie rods 28, 28, respectively. The rear rack and binion mechanism 26 is connected to an electric motor 32 that drives and controls the driven and directed means 12, and is driven and controlled by the electric motor 32. This electric motor 32 is configured to be driven by pulses, and its operation is controlled by a duty ratio that is a ratio of the pulse width of the pulse current from the liWj means 34. The front wheel steering angle sensor 36 provided in the front gear box 16 detects the amount of rotation of the front wheels 10-10 as the steering angle of the front wheels 10-10, and the amount of operation of the slave steering means 12 due to the rotation of the electric motor 32 is detected as the steering angle of the rear wheels 14.
・Should be detected as the steering angle amount of 14 (rear gear box 2
A rear wheel steering angle sensor 38 provided at the vehicle 2 is in communication with a vehicle speed sensor 40 that detects the speed of the vehicle 2. Further, as shown in FIG. 2, the control means 34 includes a front wheel steering angle sensor 36, a rear wheel steering angle sensor 38, and a vehicle speed sensor 4.
0 and this control circuit section 42
and a motor driver 44 for driving the electric motor 32. The control means 34 receives the steering angles of the front wheels 10, 10 from the front wheel steering angle sensor 36, the actual steering angles of the rear wheels 14, 14 from the rear wheel steering angle sensor 38, and the vehicle speed state from the vehicle speed sensor 40. is input, the steering angle ratio which is the ratio of the steering angle amount of the front wheels 10, 10 and the rear wheels 14, 14 is calculated, and the target steering angle of the rear wheels 14, 14 is calculated based on this determined steering angle ratio. is determined, and the rear wheels 14, 14 are controlled to be steered to this target steering angle.The electric motor 32 is driven and controlled, thereby controlling the steering of the rear wheels 14, 14. Further, the control means 34 controls the vehicle speed sensor 40 during deceleration.
The deceleration is calculated based on the signal state from the steering angle ratio, and the steering angle ratio is set to zero until the calculated deceleration becomes less than the set value A that does not cause the rear wheels 14, 14 to be abruptly steered in the opposite direction. 2WS) and stops steering the rear wheels 14 in the opposite direction. Next, the operation of this embodiment will be explained based on the flowchart of FIG. 3 and the time chart of FIG. 4. The program of the control means 34 starts (step 101).
) Then, first, the vehicle speed V is input by the signal input from the vehicle speed sensor 40 (step 102), and the steering angle of the front wheels 10 is input by the signal from the front wheel steering angle sensor 36 (step 103), and then, The actual steering angles of the rear wheels 14 are input based on the signal from the rear wheel steering angle sensor 38 (step 104). Then, the deceleration α state is calculated from the vehicle speed V obtained this time and the fully throttled vehicle speed Vo (step 105). That is, this deceleration α is calculated as α=−(V−Vo)/t, where t: sampling time. Next, in step 106, the calculated deceleration α
is larger than a set value A. If the deceleration α> set value A and step 106 is YES, the previous vehicle speed Vo is equal to or higher than the predetermined vehicle speed and the rear wheels 14 and 14 are in phase, or two-wheel steering (two WS) is performed and the current vehicle speed V
is in the reverse phase region (step 107). If YES in step 107, the steering angle ratio is set to zero and the characteristics of the steering angle are shifted (step 10B), and two-wheel steering is executed. In other words, as shown in Fig. 4 (during deceleration, two-wheel steering is performed at a vehicle speed of Vl, and in the past, four-wheel steering was performed in the opposite phase at a vehicle speed of 2) (Fig. 4 (b)). In this embodiment, the steering angle ratio is set to zero and two-wheel steering is executed (as shown in FIG. 4(C)) until the deceleration reaches the set value A (shown in FIG. 4(a)). , compared to the past, the two-wheel steering is extended by the region Tl between vehicle speed v2 and vehicle speed v3, and the rear
This prevents the rings 14 from rapidly changing from the same phase to the opposite phase. Then, when the deceleration α becomes less than the set value A, - in the case of No in the step 106 and in the case of NO in the step 107.
In this case, the steering angle ratio is set (Step 109), and the target steering angle of the rear wheels 14, 14 is calculated (Step 1).
10), the electric motor 32 is driven so that the actual steering angle of the rear wheels 14 becomes the target steering angle (step 11).
1), as a result, the rear wheels 14 and
14 is steered in the opposite phase. As a result, during deceleration, two-wheel steering is performed until the deceleration α reaches the set value A, and the deceleration α reaches the set value A.
Since the phase is reversed after it becomes smaller than , the rear wheel 14.1
4 can be prevented from rapidly changing from the same phase to the opposite direction, that is, the opposite phase, the steering state of the vehicle 2 can be stabilized, and a good driving feeling can be maintained. [Effects of the Invention] As is clear from the above detailed description, according to the present invention,
Calculates the deceleration during deceleration, sets the steering ratio to zero and stops steering the rear wheels in the opposite direction until the deceleration becomes less than the set value.i
By providing the lm means, it is possible to prevent the rear wheels from being abruptly steered in the opposite direction even when the vehicle suddenly decreases, and it is possible to maintain a good running feeling.

[Brief explanation of the drawing]

Figures 1 to 4 show embodiments of the present invention, Figure 1 is a schematic diagram of a four-wheel steering vehicle (four WS vehicle), Figure 2 is a system block diagram of a four-wheel steering device, and Figure 3 is a schematic diagram of a four-wheel steering vehicle (four WS vehicle). A flowchart explaining the operation of this embodiment, FIGS. 4(a), (b), (C), (
d) is a time chart during deceleration. FIG. 5 is a characteristic diagram of the steering angle in the prior art. FIGS. 6(a), (b), and (C) are time charts during deceleration, which are conventionally used. In the figure, 2 is a vehicle, 8 is a main steering means, 1° and 10 are front wheels, 12 is a slave steering means, 14 and 14 are rear wheels, 32 is an electric motor, 34 is a control means, and 36 is a front wheel steering wheel. angle sensor,
38 is a rear wheel steering angle sensor, 40 is a vehicle speed sensor, 42 is a control circuit section, and 44 is a motor driver. Patent applicant Yoshimi Saigo, Patent attorney represented by Suzuki Motor Co., Ltd. - Figure 1, Figure 3 Figure 1 1 1YE Figure 4 Both speed time lapse 1 To 1 '? Lock I I Same 1 1 1 VrVz Vs Figure 5 Figure 6 (a) :j-ゝゝゝゝゝk A1 /' Director Fumi Takeshi Yoshida1, Indication of the case Patent Application No. 1-2834572, Name of the invention Four-wheel steering device3, Relationship with the person making the amendment Patent applicant address Takatsuka, Kamimura, Hamana District, Shizuoka Prefecture 300 address name (
208) Suzuki Motor Co., Ltd. Representative Osamu Suzuki 4, Agent 101 7a 03-292-44
11 (Representative) Address: 2-8-6, Kanda Ogawamachi, Chiyoda-ku, Tokyo, Subject of amendment 1), Detailed explanation of the invention column of the specification, page 7, Contents of amendment 1), Section 1 of the specification Delete "Day 1" on page 3, line 20. 2) "From vehicle speed VI2 to vehicle speed Vti*" on page 4, line 14 of the specification is corrected to "between vehicle speed v1 and vehicle speed v2." 3), "Full throttle vehicle speed V." on page 9, line 20 of the specification is corrected to "previously obtained vehicle speed VoJ." Figure 4 (
4(a)" is corrected to "as shown in FIG. 4(a)." 5) In the first line of page 11 of the specification sheet, "as shown in FIG. 4(a)" is corrected to "as shown in FIG. 4(b)". 6) The drawings in Figures 3, 5 and 6 are corrected as shown in the attached drawings. Above is Figure 3 1 1 1”

Claims (1)

[Claims] 1. In a four-wheel steering device that steers the rear wheels in the same phase or in the opposite phase as the front wheels depending on the vehicle speed state, and changes the steering angle ratio between the front wheels and the rear wheels to control the steering of the rear wheels to a target steering angle. 4, characterized in that a control means is provided which calculates a deceleration at the time of deceleration, sets the steering angle ratio to zero, and stops steering the rear wheels in the opposite direction until the deceleration becomes less than a set value. Wheel steering device.