JPH0220472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to vehicles in which the rear wheels are steered in addition to the front wheels, especially four-wheeled vehicles such as passenger cars that run at high speeds.
The front wheels are steered by steering wheel operation, the rear wheels are steered in conjunction with the steering of the front wheels, and changes in the steering ratio and phase between the front wheels and the rear wheels are controlled by the vehicle speed. This invention relates to a front and rear wheel steering system for a vehicle that further improves responsiveness and stability at high speeds, and that allows for a wide range of signal settings to control the steering of the rear wheels in accordance with various required characteristics such as the size and weight of the vehicle. .

(Prior Art) Steering in a four-wheeled vehicle is generally performed by steering only the front wheels. In the case of steering only the front wheels, the driver first operates the steering wheel, and when the front wheels are steered, the front wheels create a sideslip angle with respect to the direction of travel, and the force that tries to go in the steered direction, that is, cornering. A force is generated. This creates a force that tries to rotate the car body around its center of gravity, or a yawing moment, causing the car body to change direction. Subsequently, the rear wheels fixed to the vehicle body also develop a sideslip angle, a cornering force is generated, and the vehicle body begins to turn. Therefore, since there is a phase lag in the cornering force generated by the rear wheels compared to the front wheels, the vehicle body will not move until the resultant force of the cornering forces of the front and rear wheels reaches the value intended by the driver, that is, after operating the steering wheel. There is always a slight time delay before the direction of the vehicle changes, and this requires skill in steering a four-wheeled vehicle.

Furthermore, while a four-wheeled vehicle is turning by steering the front wheels, the wheels are turning by balancing the cornering force generated and the centrifugal force exerted on the vehicle body, but the tangent to the turning trajectory and the vehicle axis are Due to the difference in the magnitude of the yawing moment and the difference in the phase delay time due to speed, the vehicles do not always travel in unison, and this is another reason why the steering of a four-wheeled vehicle requires skill.

Therefore, the driver of a four-wheeled vehicle is concerned about the turning trajectory of the vehicle and the vehicle axis caused by the time delay between the front wheels being steered, the cornering force generated by the rear wheels, and the vehicle changing direction, and changes in vehicle speed. angular deviation,
In other words, accurate steering requires empirical recognition of changes in the attitude of the vehicle during turning, and a certain amount of driving experience is required to drive a four-wheeled vehicle.

As a means to solve the problems with such conventional steering devices, it has been proposed to steer not only the front wheels but also the rear wheels. For example, the special public relations system in the 1970s
No. 10728 discloses a method for generating a steering angle in the rear wheels by the moment of the caster rail caused by the cornering force of the rear wheels when the vehicle body turns using the front wheel steering in a vehicle steered by a front wheel steering device. is disclosed and also U.S. Patent No.
No. 2910131 discloses a method for controlling the amount of steering of the rear wheels by detecting G that is generated in the lateral direction on the vehicle body due to the centrifugal force generated when the vehicle turns.

(Problems to be Solved by the Invention) However, these known techniques not only have technical problems such as accuracy in the sideslip angle detection method or G detection sensor that controls rear wheel steering, but also This method corrects the steering of the rear wheels based on the indirect control factor generated by the steering of the front wheels, that is, the control is performed after the change in the direction of the vehicle body due to the steering of the front wheels. A response delay occurs when steering the rear wheels.

In addition, although technology for steering the front and rear wheels together, for example by mechanically coupling them, has been used in special vehicles, the purpose of both is to reduce the turning radius and improve the maneuverability of the vehicle. This purpose is simply achieved by switching the control mode for the front and rear wheels using a control lever (for example, British Patent No. 523656, Japanese Patent Publication No. 53-26732).

Furthermore, JP-A No. 52-61024 discloses a method in which the rear wheels are steered in the opposite phase to the front wheels when driving at low speeds, but only the front wheels are steered without steering the rear wheels when driving at high speeds. However, this approach focuses only on the maneuverability of the vehicle when running at low speeds, and cannot improve the ease and stability of steering when running at high speeds by in-phase steering of the rear wheels.

Therefore, it is an object of the present invention to eliminate the delay in the response of rear wheel steering due to the follow-up correction performed by the indirect control factor, which was a disadvantage of the conventional device, by simultaneously steering the front and rear wheels by steering wheel operation. By steering the rear wheels in the opposite phase to the front wheels at low speeds based on the vehicle speed, it reduces the turning radius and improves the maneuverability of the vehicle. By steering the wheels in the same phase, it is possible to obtain ease and stability of steering at high speeds, thereby achieving a good balance of responsiveness and stability of steering at high speeds, and furthermore, by steering the wheels in the same phase. Wheel control is based on the front wheel turning amount and turning direction signals from the front wheel turning amount and turning direction detection means, and the rear wheel phase setting signal from the rear wheel phase control device. The system is configured to set the steering ratio and perform the steering based on the steering signal to the rear wheels from the steering angle function generator that determines the steering amount and phase of the rear wheels, and calculates the size, weight, etc. of the vehicle. To provide a front and rear wheel steering device which can perform a wide range of signal settings for steering control of rear wheels in accordance with various characteristics and can be easily realized with a simple device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides front wheel turning amount and turning direction detection means for detecting the turning amount and turning direction of the front wheels in conjunction with steering wheel operation. , a front wheel steering device that steers the front wheels based on a signal from the detection device, a vehicle speed detection device that detects the vehicle speed, a rear wheel steering device that steers the rear wheels, and a vehicle speed from the vehicle speed detection device. Based on the signal, when the vehicle speed is smaller than a predetermined value, the rear wheels are steered in a phase opposite to the front wheels, and when the vehicle speed is larger than the predetermined value, the rear wheels are steered to the front wheels. a rear wheel phase control device configured to steer within the same phase range as the front wheel, and a front wheel turning amount and steering direction signal from the front wheel turning amount and steering direction detection means, and the rear wheel phase. The steering angle function generator is configured to set the steering ratio between the front wheels and the rear wheels based on the rear wheel phase setting signal from the control device, and determine the steering amount and phase of the rear wheels. The present invention is characterized in that the front and rear wheel steering devices of the vehicle are configured to control the steering of the rear wheels based on the steering signals sent to the rear wheels from the generator.

(Function) The present invention steers the rear wheels simultaneously in conjunction with steering of the front wheels by steering wheel operation, and when the vehicle is running at low speed, the front and rear wheels are steered in opposite phases, and when the vehicle is running at high speed, the front and rear wheels are steered in opposite phases. The front and rear wheels are steered in the same phase, and the steering ratio of the front and rear wheels is changed depending on the vehicle speed. Furthermore, when the vehicle speed changes from a low speed region to a high speed region, or vice versa, it is possible to continuously change the phase of the front and rear wheels when the vehicle speed changes from a high speed region to a low speed region.

First, the method of reducing the minimum turning radius according to the present invention will be explained.

In other words, when only the front wheels are steered, the turning radius of the vehicle decreases as the steering angle of the steered wheels increases. The maximum steering angle is limited due to size constraints and, if the steered wheels are also drive wheels, the flexibility angle of the shaft coupling, etc., and therefore there is a limit to the minimum turning radius.

However, with the present invention, by steering the front and rear wheels in opposite phases at low speeds, the minimum turning radius and the difference between the inner wheels are significantly reduced, making it easier to drive even on narrow curved roads and to park in narrow spaces. .

Particularly when steering at high speeds, the front and rear wheels are steered in the same phase, and the rear wheels are simultaneously steered in conjunction with the steering of the front wheels, so even immediately after the start of steering, the rear wheels are steered at the same time as the front wheels. Cornering force is generated, the vehicle's lateral acceleration reaches the intended value in a very short time, and the vehicle's responsiveness is significantly improved.
In other words, there is no time delay between turning the steering wheel and changing the direction of the vehicle, making steering easier and more stable.

Further, according to the present invention, the control factor for rear wheel steering can be easily and accurately set, and it is possible to widely correspond to various required rear wheel steering characteristics.

That is, the above control factors are combined with the front wheel turning amount and steering direction signal, which are set based on the steering wheel operation based on the driver's will, and the rear wheel phase, which is set based on the vehicle speed, which can be easily and accurately detected. The steering ratio between the front wheels and the rear wheels is set based on the setting signal, and the steering ratio is set based on the steering signal to the rear wheels from the steering angle function generator that determines the steering amount and phase of the rear wheels. By setting the value of each control factor, the steering control can be broadly adapted to the required steering characteristics.

Next, the relationship between the direction of the vehicle and the turning locus when the steering system according to the present invention is used will be explained with reference to FIGS. 2 to 5. Although all the figures are shown with two wheels, there is no risk of impairing the validity of the explanation if the turning radius is sufficiently large compared to the wheel width, such as in a normal four-wheeled vehicle.

FIGS. 2 and 3 show the orientation and turning locus of a vehicle in a conventional steering system that steers only the front wheels.

In the case of a turn at low speed, the direction of movement of the vehicle coincides with the direction of the tires, so the direction of the vehicle faces outward from the tangent to the turning trajectory, as shown in FIG. When the vehicle speed increases, a slip angle occurs in the front and rear wheels, and the direction of motion of the front and rear wheels points outward from the plane of the tires. Therefore, the turning center of the vehicle gradually moves forward, and the tangent to the turning locus begins to point outward with respect to the vehicle axis. That is, as shown in FIG. 3, the direction of the vehicle body is directed inward from the tangent to the turning trajectory.

In the case of the steering system according to the present invention, the steering of the front and rear wheels is in opposite phases at low speeds, and if the steering ratio of the front and rear wheels is determined to suit the characteristics of the vehicle, the direction of the vehicle can be adjusted as shown in FIG. and the tangent line of the turning trajectory can be made to match. Furthermore, when the vehicle speed is increased, by steering the rear wheels in the same phase as the front wheels, it is possible to match the direction of the vehicle with the turning locus, as shown in FIG. 5, even at high speeds.

In other words, at low speeds when the rear wheels are steered in the opposite phase to the front wheels, the steering ratio of the front and rear wheels is controlled to approach -1 as the vehicle speed decreases, in other words, the rear wheel steering angle is controlled as the vehicle speed decreases. At the same time, since the steering angle of the front wheels is brought close to that of the front wheels, the straight line connecting the turning center and the center of the vehicle body at low speeds becomes almost perpendicular to the direction of the vehicle, as shown in FIG. 4, and the occurrence of sideslip of the rear wheels is almost eliminated. Similarly, at high speeds when the rear wheels are steered in the same phase as the front wheels, the steering ratio of the front and rear wheels is controlled to approach +1 as the vehicle speed increases,
In other words, the rear wheel steering angle is brought closer to the front wheel steering angle as the vehicle speed increases, so the higher the speed, the more the straight line connecting the turning center and the center of the vehicle body maintains almost a right angle to the direction of the vehicle. The occurrence of sideslip can be almost eliminated.

Front and rear wheel steering that follows the vehicle speed can be performed while simultaneously steering the rear wheels in conjunction with steering of the front wheels by steering wheel operation, and furthermore, the steering ratio of the front and rear wheels can be changed according to the vehicle speed. It is something that makes you

Furthermore, the above-mentioned rear wheel control is performed based on the front wheel turning amount and steering direction signals from the front wheel turning amount and steering direction detection means, and the rear wheel phase setting signal from the rear wheel phase control device. The steering ratio with the rear wheels is set, and the steering is performed based on the steering signal to the rear wheels from the steering angle function generator, which determines the steering amount and phase of the rear wheels, so the vehicle size, weight, etc. , it is possible to perform a wide range of signal settings for steering control of the rear wheels in accordance with various required characteristics, and it can be easily realized with a simple device.

(Example) Examples will be described below based on the accompanying drawings.

FIG. 1 shows a first embodiment of the steering system of the present invention, and shows only the left wheel, but the right wheel, which is not shown in the figure, is connected to the left wheel by a known method. be done.

In FIG. 1, a known gear box 2 incorporating a rack and pinion or the like for converting the rotational motion of the steered wheel 1 into reciprocating motion is disposed at the end of a shaft 1a extending from a steered wheel 1 forming a handle. The linear motion converted within the gearbox 2 is guided to the differential gear 3 by the arm rod 2a, and is transferred to the differential gear 3 by the pinion 3c and the rack 3.
It is divided into two displacements in different directions at a and 3b. The displacement of the left rack 3a of the differential gear 3 is configured to steer the front wheels 6 from one end of the arm rod 4 via the connecting rod 5. Gearbox 2 like this
from the mechanism to the rack 3 of the differential gear 3 via the arm rod 2a.
A, 3b, pinion 3c, and arm rod 4 form a front wheel turning amount and steering direction detection means, and the arm rod 4 is connected to a connecting rod 5 of the front wheel steering device. The other end of the arm rod 4 is connected via a connecting rod 7 to a movable arm 8 that rotates about a fulcrum 9.

On the other hand, the displacement of the right rack 3b of the differential gear 3 steers the rear wheel 14 via the arm rod 10, the movable arm 11 having a fulcrum in the center, the arm rod 12, and the arm rod 13. A connecting portion 18 of the arm rods 12 and 13 is fixed on the movable arm 8. The fulcrum 9 of the movable arm 8 is fixed to a screw piece 17 that can move on a screw rod 16 connected to a motor 15. Therefore, the fulcrum 9 moves on the movable arm 8 by the rotation of the screw rod 16 by the motor 15, and rotates the front and rear wheels. The steering ratio is determined by the position of the fulcrum 9 of the movable arm 8. In this way, the fulcrum 9
A steering angle function generating device is formed by the movable arm 8 having a coupling portion 18, and the coupling portion 18 is connected to the arm rod 13 of the rear wheel steering device. A connecting rod 7, an arm rod 10, a moving arm 11, and an arm rod 12 are connected between the moving arm 8 and the front wheel turning amount and steering direction detecting means.
is interposed. The motor 15 is controlled by a controller 19 which receives a signal from a vehicle speed sensor 20, which is a vehicle speed detection means, to control the motor. Therefore, the position of the fulcrum 9 is determined by the vehicle speed.

That is, the controller 1 receives a signal from the vehicle speed sensor 20.
9, a motor 15 that receives a drive signal from this controller 19, a screw rod 16 connected to this motor 15, and a screw piece 17 that can be moved by rotation of the screw rod 16. There is. A screw top 17 on the screw rod 16 makes the fulcrum 9 of the movable arm 8 of the steering angle function generator variable.

The controller 19 described above is configured such that in a range where the vehicle speed is greater than a predetermined value, that is, when traveling at high speeds above a certain speed, the steering of the front and rear wheels is at the same position, and as the speed increases, the steering ratio of the front and rear wheels increases by +1. When driving at low speeds in a range where the vehicle speed approaches 100, and the vehicle speed is smaller than the predetermined value, the steering of the front and rear wheels will be in opposite phases, and as the speed decreases, the specifications should be set so that the steering ratio of the front and rear wheels approaches -1. desirable.

Since the steering device according to the present invention has the above configuration, the ratio between the steering angle of the steered wheels and the difference between the front wheel steering angle and the rear wheel steering angle is always kept constant, and the ratio of the steering angles of the front and rear wheels, that is, the steering angle of the front and rear wheels is maintained constant. The steering ratio is determined by the position of the fulcrum 9 of the movable arm 8.
This position can be arbitrarily selected according to the specifications of the controller 19 with respect to the vehicle speed. When the fulcrum 9 is located to the right of the joint 18 of the arm rods 12 and 13, the front and rear wheels are steered in the same phase, and when the fulcrum 9 is on the joint 18, the rear wheels 14 are not steered. First, only the front wheels 6 are steered. When the fulcrum 9 is on the left side of the joint 18, the front and rear wheels are steered in opposite phases.

In this way, the front and rear wheel steering system of the vehicle is controlled by the front wheel turning amount and steering direction detecting means which detects the turning amount and turning direction of the front wheels in conjunction with the steering wheel operation, and the signal from the front wheel turning direction. , a front wheel steering device that steers the front wheels, a vehicle speed detection device that detects the vehicle speed, a rear wheel steering device that steers the rear wheels, and a vehicle speed signal from the vehicle speed detection device. When the vehicle speed is smaller than a predetermined value, the rear wheels are steered within a range opposite to the front wheels, and when the vehicle speed is greater than the predetermined value, the rear wheels are steered within a range where the rear wheels are in the same phase as the front wheels. a rear wheel phase control device that sets the front wheel to be steered by the front wheel, a front wheel turning amount and a turning direction signal from the front wheel turning amount and turning direction detection means, and a rear wheel phase setting from the rear wheel phase control device; Based on the signal, the steering ratio between the front wheels and the rear wheels is set,
The steering wheel includes a steering angle function generator that determines the steering amount and phase of the rear wheels, and is configured to control the steering of the rear wheels based on a steering signal sent to the rear wheels from the steering angle function generator.

Note that the steering angle function generator is capable of phase control such that if the steering ratio of the front and rear wheels is positive, the phase is the same, and if the steering ratio is negative, the steering ratio is opposite.

FIG. 6 shows a second embodiment of the steering system of the present invention.

Although only the left wheel is shown in this figure, the relationship with the right wheel is exactly the same as that described in the first embodiment.

In FIG. 6, the rotational force applied to the steered wheels 101 is converted by the gearbox 102 into a linear motion of the arm rod 103, and the front wheels 104 are steered. In this way, the mechanism of the gearbox 102 and the arm rod 10
A front wheel turning amount and turning direction detecting means according to No. 3 is formed, and an arm rod 103 is connected to the front wheel steering device. Furthermore, the arm rod 103 is connected via an arm rod 105 to an end of a movable arm 106 that rotates about a fulcrum 107. Therefore, the movement of the arm rod 103 is the same as that of the moving arm 106.
is rotated around the fulcrum 107, and the movable arm 106
The rear wheel 109 is steered via the arm rod 108 connected to the upper joint 113. The fulcrum 107 of the movable arm 106 is fixed to a screw piece 112 that is screwed into a screw rod 111 extending from a motor 110 so as to rotate the screw rod 111, and is connected to a vehicle speed sensor 115 as a vehicle speed detection means and a controller. 1
It moves on the movable arm 106 by the rotation of the motor 110 controlled by the motor 14.

As described above, a steering angle function generator is formed from the movable arm 106 having the fulcrum 107 and the connecting portion 113, and a rear wheel phase control device is formed from the controller 114, the motor 110, the screw rod 111, and the screw top 112. There is. A coupling portion 113 of the movable arm 106 forming the steering angle function generator is connected to the arm rod 108' of the rear wheel steering device, and there is a connecting portion 113 between the movable arm 10 and the front wheel turning amount and steering direction detecting means. An arm rod 105 is provided. A screw top 112 on the screw rod 111 makes the fulcrum 107 of the movable arm 106 of the steering angle function generator variable.

With the above configuration, as in the first embodiment, the ratio between the steering angle of the steered wheels and the difference between the front and rear wheel steering angles is always kept constant depending on the vehicle speed, and the steering ratio of the front and rear wheels is It is determined by the position of the fulcrum 107 of 106. It is preferable that the specifications of the controller 114 are also determined in the same manner as described above.

Incidentally, for the vehicle speed detection means, the connection path between the front wheel steering device and the rear wheel steering device, etc., publicly known devices can be appropriately adopted.

(Effects of the Invention) As described above, according to the present invention, by simultaneously steering the rear wheels in conjunction with the front wheels by steering wheel operation, the rear wheels can be steered by an indirect control factor, which has been a problem with conventional devices. In addition to eliminating the response delay in rear wheel steering due to the correction, front and rear wheel steering can be performed reliably even on low μ roads where accurate lateral force cannot be detected. In addition, based on easily sensed vehicle speed, the rear wheels are steered in the opposite phase to the front wheels at low speeds, reducing the turning radius and improving vehicle maneuverability. On the other hand, by steering the rear wheels to the same position, it is possible to obtain easier steering and stability at high speeds.

Furthermore, the above-mentioned rear wheel control is performed based on the front wheel turning amount and steering direction signals from the front wheel turning amount and steering direction detection means, and the rear wheel phase setting signal from the rear wheel phase control device. The steering ratio with respect to the rear wheels is set, and the steering is performed based on the steering signal to the rear wheels from the steering angle function generator, which determines the amount and phase of steering of the rear wheels. It is possible to perform a wide range of signal settings for controlling the steering of the rear wheels in accordance with various required characteristics, and it can be easily realized using a simple device.

Therefore, according to the present invention, rear wheel steering with excellent steering response can be easily and accurately performed.

That is, low-speed anti-phase steering and high-speed in-phase steering of the front and rear wheels that follow the vehicle speed that can be easily and accurately detected can be performed with good responsiveness.

In particular, the responsiveness of the rear wheel turning to the rear wheel steering can be significantly improved in the same phase steering of the front and rear wheels during high speed driving where responsiveness is required, and the rear wheel turning can be accurately controlled.

It also facilitates the control factor for rear wheel steering,
Moreover, it can be set accurately and widely corresponds to various required rear wheel steering characteristics.

That is, the above control factors are combined with the front wheel turning amount and steering direction signal, which are set based on the steering wheel operation based on the driver's will, and the rear wheel phase, which is set based on the vehicle speed, which can be easily and accurately detected. The steering ratio between the front wheels and the rear wheels is set based on the setting signal, and the steering ratio is set based on the steering signal to the rear wheels from the steering angle function generator that determines the steering amount and phase of the rear wheels. By setting the value of each control factor, the steering control can be broadly adapted to the required steering characteristics.

In addition, front and rear wheels can be steered in a well-balanced manner for precise steering, including ease of handling and stability of the vehicle body, from low speed ranges where anti-phase steering is performed to high speed ranges where in-phase steering is performed. The front and rear wheels can be steered from low speeds to high speeds without any discomfort for the driver.

In other words, by making the steering ratio between the front wheels and the rear wheels variable according to the vehicle speed, which can be easily detected, the required amount of rear wheel steering can be optimally controlled by changing it moment by moment according to the traveling speed. , it is possible to suppress unnecessary changes in vehicle body posture from low speeds, where maneuverability is required, to high speeds, where stability is required, and to significantly reduce the difficulty of steering a four-wheeled vehicle.

Further, since the phase change is automatically controlled according to the vehicle speed without requiring any switching operation of the device, it is possible to easily perform front and rear wheel steering without causing any discomfort to the driver.

In addition, the front and rear wheels can be steered accurately and reliably under any road surface conditions or vehicle posture conditions.

In other words, since rear wheel steering is performed simultaneously and in conjunction with front wheel steering by steering wheel operation, the control factor is not affected by external forces such as low μ roads such as snowy roads or wet roads, or crosswinds. This allows accurate, reliable and stable rear wheel steering at all times.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing a first embodiment of the steering device of the present invention, FIGS. 2 and 3 are schematic diagrams pointing out the problems of the conventional technology, and FIGS. 4 and 5 are advantages of the present invention. FIG. 6 is a schematic plan view of the second embodiment. In addition, in the drawing, 1,101 is a handle, 1,10
2 is the gear box, 2a, 103 is the arm lever, 6, 1
04 is the front wheel, 8,106 is the moving arm, 9,107 is the fulcrum, 13,108 is the arm rod, 14,109 is the rear wheel,
15, 110 are motors, 16, 111 are screw rods, 17, 112 are screw pieces, 18, 113 are coupling parts, 19, 114 are controllers, and 20, 115 are vehicle speed detection means.

Claims (1)

[Scope of Claims] 1. Front wheel turning amount and steering direction detection means for detecting the amount and direction of turning of the front wheels in conjunction with steering wheel operation; and a signal from the detection means to steer the front wheels. a front wheel steering device that detects vehicle speed; a rear wheel steering device that steers rear wheels; In a small range, the rear wheels are steered within a range in opposite phase to the front wheels, and in a range where the vehicle speed is greater than the predetermined value, the rear wheels are steered within a range in the same phase as the front wheels. a rear wheel phase control device that sets a rear wheel phase control device based on a front wheel turning amount and steering direction signal from the front wheel turning amount and steering direction detection means and a rear wheel phase setting signal from the rear wheel phase control device. , a steering angle function generator that sets the steering ratio between the front wheels and the rear wheels, and determines the steering amount and phase of the rear wheels, and a steering signal to the rear wheels from the steering angle function generator, A front and rear wheel steering device for a vehicle, characterized in that the rear wheels are controlled to steer.