JPH03148375A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To secure stable running at the time of cornering by providing a control map which changes subsidiary steering angles of subsidiary steering wheels in response to main steering angles of main steering wheels, and also changing the phase of the subsidiary steering angle in the control map when a brake switch is turned on. CONSTITUTION:A vehicle 2 is equipped with a main steering means 8 for steering front wheels 10 acting as main steering wheels and subsidiary steering means 12 for steering rear wheels 14 acting as subsidiary steering wheels. And the subsidiary steering means 12 is driven by a motor which is not shown. In the above-said constitution, the aforesaid motor is controlled by a control means 46 based on respective detected signals from a brake switch 44 and a front and a rear wheel steering angle sensor 48 and 50. And the control means 46 is provided with a control map which changes steering angle of rear wheels 14 in response to steering angle of the front wheels 10, and when the brake switch 44 is turned on, the rear wheels 14 are drivingly controlled in such a way that the phase of rear wheel steering angles are changed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a four-wheel steering system, and in particular, a four-wheel steering device that steers a main steering wheel by a main steering means, and steers a sub-steering wheel by a sub-steering means, The present invention relates to a four-wheel steering device that drives and controls slave steering means using an electric motor that supplies pulsed power. [Prior Art] In a vehicle, normally, front wheels, which are main steering wheels, are provided so as to be steerable in a desired direction of travel of the vehicle, and rear wheels, which are secondary steering wheels, are provided parallel to the longitudinal direction of the vehicle. . When a vehicle that steers two front wheels is turned by steering the front wheels, the front wheels and rear wheels do not match the turning circle, and at low vehicle speeds, the rear wheels end up inside the turning circle due to the difference between the inner wheels. The vehicle turns in this position, and at high vehicle speeds, the centrifugal force causes the vehicle to turn in such a position that the front wheels are inside the turning circle. For this reason, there is a problem in that even if the front wheels are steered in the turning direction, which is the traveling direction of the vehicle, the attitude of the vehicle cannot be made to match the turning direction. Therefore, a vehicle has been proposed that includes a steering device that improves running performance by steering not only the front wheels but also the rear wheels. That is, this steering system is equipped with a main steering means, which is a steering device that steers the front wheels, and a slave steering device, which is a rear wheel steering device that steers the rear wheels. While improving the maneuverability of the vehicle when driving on the road, it can also improve the steering stability during lane check at medium and high speeds. As this steering device, for example, the Japanese Patent Publication No. 60-44186
There is something disclosed in the publication No. The vehicle steering method disclosed in this publication steers the rear wheels in the same phase as the front wheels in a range where the detected amount of front wheel steering is smaller than a predetermined value, and
In the range where the detected amount is greater than a predetermined value, the rear wheels are steered in the opposite phase to the front wheels, eliminating the delay in steering response that is a problem with conventional devices when steering at medium and high speeds, and improving the ease of steering. Stability is ensured. Further, the steering device includes a front wheel steering angle responsive type four-wheel steering device that controls the rear wheel steering angle in accordance with the front wheel steering angle. As shown in Fig. 11, this front wheel steering angle responsive type four-wheel steering system sets the rear wheel steering angle to the in-phase region when the front wheel steering angle becomes slightly large from 0, and starts rear wheel steering from around 10 degrees. It has a control map of a control curve in which the angle is in the opposite phase region, and the rear wheel steering angle is controlled along this control map. [Problems to be Solved by the Invention] By the way, in the conventional four-wheel steering system, when a front-wheel steering-responsive four-wheel steering system is used for a dirt trial vehicle that runs off-road with the rear wheels sliding, It is said that oversteer becomes stronger when braking, and when the steering wheel is turned sharply, the rear wheel steering angle becomes in the opposite phase range, making it easier to spin around corners in tight hairpin curves, as shown in Figure 12. There is an inconvenience. Also, when exiting a tight hairpin curve, although it is accelerating, the dirt trial vehicle may exhibit strong understeer and may not be able to complete the hairpin curve, so the rear wheel steering angle must be in the opposite phase range. It is something. [Object of the Invention] Therefore, in order to eliminate the above-mentioned disadvantages, the object of the present invention is to provide a brake switch that is turned on during braking operation, and to adjust the auxiliary steering angle of the auxiliary steering wheel according to the main steering angle of the primary steering wheel. By having a control map for changing the slave steering angle and a control means for controlling the slave steering wheels to change the phase of the slave steering angle of the control map when the brake switch is turned on, the slave steering angle is changed during the braking operation. Our goal is to realize a four-wheel steering system that changes the phase of the four-wheel steering system to ensure stable driving when cornering, as well as reliably prevent spins during cornering. Ru. [Means for Solving the Problem] In order to achieve this object, the present invention provides a main steering means for steering a main steering wheel, a sub-steering means for steering a sub-steering wheel, and a pulse power source to drive the above-mentioned In a four-wheel steering system having an electric motor that drives and controls a slave steering means, a brake switch that is turned on during a braking operation is provided, and the slave steering angle of the slave steering wheel is changed according to the master steering angle of the master steering wheel. The present invention is characterized in that it is provided with a control means for controlling the steering of the slave steering wheel so as to develop a control map that causes the brake switch to turn on, and to change the phase of the slave steering angle of the control map when the brake switch is turned on. Effect] With the above-described configuration, when the brake switch is turned on due to braking operation, the phase of the slave steering angle of the control map is changed to ensure stable running during cornering, and Prevents spin when cornering. [Examples] Examples of the present invention will be described in detail below based on the drawings. 1 to 10 show embodiments of this invention. In Figure 2, 2 is a vehicle, 4 is a steering wheel, 6 is a steering shaft, 8 is a main steering means which is a steering device, 10.10 is a front wheel which is a main steering wheel, and 12 is a rear vehicle. The slave steering means is a wheel steering device, and 14.14 is a rear wheel that is a slave steering wheel. The main steering means 8 includes a front pinion (not shown) fixed to the tip side of the steering shaft 6 and a front rack (not shown) provided on a front rack bar (not shown) to mesh with the front pinion (not shown). (not shown), and the front gear box 1
6 housed in the front rack and pinion mechanism 18, and front tie rods 20 and 20 connected to each end of the front rack bar.
and a front knuckle arm 22.2 connected to the front tie rod 20.20 and connected to the front wheel 10.10.
Consisting of 2. As shown in FIG. 3.4, the slave steering means 12 is connected to a rear rack 28 and a rear rack 28 provided on a rear rack bar 26 to mesh with the rear binion 24. a hypoid gear 30 provided coaxially with the motor pinion gear 32 meshing with the hypoid gear 30;
It consists of a rear rack and pinion mechanism 36 housed in the rear gear box 34, a rear tie rod 38.38 connected to each end of the rear rack bar 26, and a rear tie rod 38.38 connected to the rear tie rod 38.38. The rear knuckle arm 40.40 is connected to the rear wheel 14.14. The rear pinion 24 of the rear rack and pinion mechanism 36 is connected to an electric motor 42 that is a DC motor that drives and controls the slave steering means 12. When no pulse current is supplied to the electric motor 42 and the rear rack bar 26 freely moves in the left-right direction of the vehicle 2 and the rear wheels 14.14 are in a free state, the rear rack bar 26 is preset. The rear wheels 14, 14 are held in a neutral position by a return spring (not shown), and the steering angle of the rear wheels 14, 14 is maintained at zero. A brake i-pedal (not shown) near the steering shaft 6 is provided with a brake switch 44 that is turned on during a braking operation. The electric motor 42 is configured to be driven by pulses, and its operation is controlled by a duty ratio that is a ratio of pulse widths of pulse currents from a control means 46. This control means 46 has a device that detects the amount of rotation of the steering shaft 6 as a steering angle of the front wheels 10. a rear axle steering angle sensor 50 provided in the rear gearbox 34 to detect the operating amount of the slave steering means 12 as the steering angle amount of the rear wheels 14.14;
It is in communication with the brake switch 44. Further, the control means 48 has a control map that changes the steering angle of the rear wheels 14.14, which are the subordinate steering wheels, in accordance with the steering angle of the front wheels 10.10, which are the main steering wheels, and the brake switch 44. When turning on the rear wheels 14.14, the rear wheels 14.14 are steered to change the phase of the steering angle of the rear wheels 14.14 in the control map. More specifically, the control means 46 has a control map l which is a basic control map as shown in FIG. 14. In order to set the phase of the steering angle of 14 to control map 2 as shown in FIG.
．． This is to shift the phase of the rear wheel steering angle, which is the steering angle of No. 14, to the right. Next, the operation will be explained along with the flowchart for steering control of the four-wheel steering system shown in FIG. The program of the control means 46 starts (step 1)
00), first, the front wheel steering angle of the front wheels 10.10 is input (step 102). Next, an on/off signal for the brake switch 44 is input (step 104), and it is determined whether or not the brake switch 44 is in an on operation (step 106). If this judgment (step 10B) is No, the process moves to judgment (step 108) as to whether or not the brake switch 44 has been turned on, and the judgment (step 10B) is YES.
In the case of S, control is performed using control map 2, that is, the phase of the rear wheel steering angle of control map 1 is moved to the right to change the phase (step 110). That is, as shown in FIG. 8, by turning on the brake switch 44 when the front wheel steering angle is a degree, the phase of the rear wheel steering angle is shifted to the right as shown in FIG. Change the phase of the angle from the anti-phase region to the in-phase region. If the above judgment (step 108) is No, no brake operation is performed and conventional four-wheel steering (4WS) control is performed according to control map 1 (step 112). If the determination (step 108) is YES, since the brake switch 44 has been turned on, the rear wheels 14, 14 are operated to achieve the steering angle of the control map 1 (step 114). In other words, when the determination (step 108) is YES, the rear wheel steering angle is in the same phase range as shown in FIG. Change the wheel steering angle from the in-phase region to the anti-phase region. After each control, the process returns to step 116. This will make it easier for the vehicle 2 to turn when the accelerator switch (not shown) exits the on-operation range A and enters the braking operation range B, as shown in FIG. 7, during tight cornering during a dirt trial or the like. In order to do this, the driver consciously performs a feint by slightly rotating the steering wheel 4 outward. Thereafter, when the steering wheel 4 is largely rotated inward, the phase of the rear wheel steering angle moves from the opposite phase range to the in-phase range due to the ON operation of the brake switch 44, resulting in an understeer state. Also, from the braking operation range B to the brake switch 44
When the vehicle enters acceleration range C, in which the accelerator switch is turned off and the accelerator switch is turned on, the phase of the rear wheel steering angle slowly moves from the in-phase range to the opposite-phase range, allowing the vehicle to easily pass through corners. -Thus, when cornering, the phase of the gripping wheel steering angle can be changed from an anti-phase region to an in-phase region, and from an in-phase region to an anti-phase region by on/off operation of the brake switch 44, resulting in stable cornering. can be secured. Furthermore, since it is possible to reliably prevent the vehicle from spinning near a corner during cornering, it improves the maneuverability of the vehicle and contributes to improved safety. [Effects of the Invention] As described in detail above, according to the present invention, a brake switch that is turned on during a braking operation is provided, and control is performed to change the sub-steering angle of the sub-steering wheels in accordance with the main steering angle of the main-steering wheels. In addition to having a control map, the control means for controlling the steering of the slave steering wheel to change the phase of the slave steering angle of the control map when the brake switch is turned on is provided, so that the phase of the slave steering angle is changed during cornering. It can be changed by turning on and off the switch.
Stable cornering can be ensured. Further, by being able to reliably prevent the vehicle from spinning near the corner during cornering, the maneuverability of the vehicle can be improved, contributing to improved safety.

[Brief explanation of the drawing]

1 to 10 show embodiments of the present invention, FIG. 1 is a flowchart for steering control of a four-wheel steering device, FIG. 2 is a schematic diagram of a vehicle equipped with a four-wheel steering device, and FIG. 3 is a rear side 4 is a schematic enlarged perspective view of the slave steering means; FIG. 5 is a schematic diagram showing control map 1; FIG. 4 is a schematic diagram showing control map 2; FIG. 6 is a schematic diagram showing the cornering driving state, FIG. 6 is a diagram showing the control curve during normal driving, FIG. 7 is a diagram showing the control curve when the brake switch is turned on by braking operation, and FIG. It is a figure which shows the control curve at the time of OFF operation|movement of a switch. 11 and 12 show the prior art of the present invention, FIG. 11 is a schematic diagram showing a control map, and FIG. 12 is a schematic diagram showing a cornering running state. In the figure, 2 is the vehicle, 4 is the steering wheel, 8 is the steering shaft, 8 is the main steering means, 10.10 is the front wheel, 12 is the slave steering means, 14.14 is the rear wheel, and 16 is the front side. Gear box, 18 is the front side, the coupling mechanism, 20.20 is the front tie rod, 22.22 is the front knuckle arm, 24 is the rear pinion, 26 is the rear rack bar, 28 is the front rack, 30 is the hypoid gear, 32 is 34 is a rear gear box, 36 is a rear rack and pinion mechanism, 38.38 is a rear tie rod, 40.40 is a rear knuckle arm, 42 is an electric motor, 44 is a brake switch, 46 is a control means, 48 is a front axle steering angle sensor, 5
0 is the rear axle steering angle sensor. Patent Applicant Suzuki Automobile Industry Co., Ltd. Representative Patent Attorney Yoshimi Saigo Figure 6 Rear wheel steering angle Rear wheel steering angle Figure 7 1 τ \ ,, 1 Hei 1-283453 2. Name of the invention Four-wheel steering device 3. Relationship with the case of the person making the amendment Patent applicant address 300 Takatsuka, Kamimura, Hamana-gun, Shizuoka Prefecture Name (20)
B) Suzuki Motor Co., Ltd. Representative - Osamu Suzuki 4, Agent Address: 101 ()3-292-441
1 (Representative) Address: 2-8 Kanda Ogawamachi, Chiyoda-ku, Tokyo
Address Name (8005) Patent attorney Yoshimi Saigo 5, Date of amendment order Voluntary 8, Subject of amendment (1) Brief explanation of drawings column 417, Contents of amendment (1) Specification, page 14 4 lines of “Figure 4” to “Figure 6”
Correct to. (2) "Figure 5" on page 14, line 5 of the specification has been changed to "Figure 7"
Correct to. (3) "Figure 6" on page 14, line 6 of the specification has been changed to "Figure 8"
Correct to. (4) "Figure 7" on page 14, line 7 of the specification is replaced with "Figure 2"
Correct to. (5) “Figure 8” on page 14, lines 8-9 of the specification
Corrected to ``Figure 0''. (6) The sentences from page 14, line 14 to page 15, line 8 of the specification are corrected as follows. "In Figure 2, 2 is the vehicle, 4 is the steering wheel, 6 is the steering shaft, 8 is the main steering means, 10.1
0 is the front wheel, 12 is the slave steering means, 14.14 is the rear wheel,
16 is a front gear box, 18 is a front rack and pinion mechanism, 20, 20 is a front tire roller F, 22, 22 are front gear arms, 24 is a rear binion, 26 is a rear rack bar, 28 is a front rack, 30 is a Hypoid gear, 3
2 is a motor pinion gear, 34 is a rear gear box, 3
6 is a rear rack and pinion mechanism, 38.38 is a rear tie rod, 40.40 is a rear knuckle arm, 42 is an electric motor, 44 is a brake switch, 46 is a control means, 48
50 is a front axle steering angle sensor, and 50 is a rear axle steering angle sensor. ”

Claims (1)

[Claims] 1. A four-wheel steering system having a main steering means for steering a main steering wheel, a slave steering means for steering a slave steering wheel, and an electric motor that is driven by a pulse power source to drive and control the slave steering means, including a brake. a brake switch that is turned on when the brake switch is turned on, and has a control map that changes the slave steering angle of the slave steering wheel according to the master steering angle of the master steering wheel, and the control map that is turned on when the brake switch is turned on. A four-wheel steering system, comprising: a control means for controlling the steering of the slave steering wheels to change the phase of the slave steering angle.