JPS5981264A - Four-wheel steering gear for vehicle - Google Patents

Abstract

PURPOSE:To allow a control mode to be selected only at a speed less than a set speed, by providing a switch means for inputting an output from a mode selection means to a controller. CONSTITUTION:A steering direction of front wheels 1 and magnitude of a steering angle thereof are inputted as an output 4a from a front wheel steering angle sensor 4 to a controller 10, and whether a phase of rear wheels 2 is to be the same phase or reverse phase relative to the front wheels 1 is determined by the controller 10 in dependent upon a vehicular speed detected by a vehicular speed sensor 12 and in accordance with a predetermined vehicular speed corresponding pattern. In this case, a same phase fixed mode is allowed to be selected by a mode selector switch at low speed, and it is possible to obliquely move a vehicle in this mode, thereby permitting the vehicle to be easily parked in a column or adjacent to another vehicle as closely as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a device for steering not only the front wheels but also the rear wheels of a four-wheeled vehicle such as an automobile, that is, by steering the front wheels, which are steering wheels, the rear wheels are steered along with the front wheels. This invention relates to a four-wheel steering device.

Conventionally, steering devices in four-wheeled vehicles steer only the front wheels, and although the rear wheels may toe in or out to some extent depending on the driving situation, regardless of the steering of the front wheels, they do not actively steer the rear wheels. is not. However, recently, a four-wheel steering device has been proposed in which both the front wheels and the rear wheels are steered, and research on this type of device is being carried out (for example, in Japanese Patent Application Laid-Open No. 55-91458).

The four-wheel steering system enables convenient maneuvering that was previously impossible, as well as driving with improved steering performance, depending on the various driving conditions of the vehicle. For example, when maneuvering a vehicle at extremely low speeds such as parallel parking or parking in a garage, it is possible to significantly change the direction of the vehicle by steering the rear wheels in the opposite direction to the front wheels (this is called anti-phase). This makes it possible or easy to park in tight spaces, which was previously impossible or extremely difficult. Further, in a U-turn, the minimum turning radius can be made small, which is advantageous. Furthermore, by steering the rear wheels in a phase opposite to that of the front wheels, the difference between the inner wheels can be extremely reduced or eliminated, which is advantageous when turning a narrow corner. In addition, when maneuvering a heavy vehicle at extremely low speeds, if the rear wheels are steered in the same direction as the front wheels (this is called co-phasing), it is possible to move the vehicle in parallel as a whole, making it easier to park. It is often convenient when parking or parking.

On the other hand, when changing lanes while driving at medium to high speeds,
By performing four-wheel steering in the same phase, lateral force is applied to the front and rear wheels at the same time, making it possible to change lanes smoothly without phase lag.At this time, yaw ink is suppressed, so you can change lanes at high speed without fear. can be done. Furthermore, when cornering, the direction of the vehicle can be effectively changed by steering the rear wheels in opposite phases.

Furthermore, when driving straight ahead, if the rear wheels are steered in a direction that counteracts the effects of external disturbances such as crosswinds, stable driving can be maintained against external disturbances, resulting in stable driving. Achieving fast straight-line performance also means that even if you accelerate and decelerate while keeping the steering angle of the front wheels constant during a turn, the steering angle of the rear wheels changes according to the acceleration and deceleration, so that you do not deviate from the course. It is also possible to make a stable turn by using

In other words, in conventional vehicles, the steering characteristics are adjusted to slightly understeer in order to maintain straight-line stability, and when accelerating during a turn, there is a tendency for the vehicle to deviate outward from the course. By doing so, the deviation can be corrected and stable turning can be realized.

In terms of comfort, it is possible to obtain a small minimum turning radius with the same wheelbase, so the wheelbase can be increased, and this model also allows the actual steering angle of the front wheels to be reduced. There are a number of advantages that can be cited, such as the ability to make new experiments possible in terms of design.

As described above, the four-wheel rudder has many practical advantages and is extremely useful.

Regarding this four-wheel steering, various specific configurations have been proposed in order to effectively steer the rear wheels. For example, 3-4 wheel steering is performed in opposite phases at low speeds and in the same phase at high speeds (Japanese Patent Laid-Open No. 55-9145).
(No. 7), when the steering angle of the front wheels is in a small to medium range, the phase is the same, and when it is large, the phase is opposite. (, Japanese Patent Application Laid-open No. 56-5270) The rear wheels are steered in proportion to the steering angle of the front wheels. 1. In the area beyond the window, the steering angle of the rear wheels is kept constant regardless of the steering angle of the front wheels. (Unexamined Japanese Patent Publication No. 163969/1983)
.

etc. are known. These four-wheel steering devices are used when the vehicle speed is low or when the front wheel steering angle is large, and when the steering angle is large, the steering is often used when the direction of the vehicle needs to be changed significantly. Based on the empirical rule that when the steering angle is small, it is often desirable to make a slight lateral movement, the rear wheels are always steered in the desired direction.
However, when a vehicle is actually running, it may be necessary to steer the rear wheels at an angle that is different from the angle determined automatically depending on the speed of the vehicle and the front wheel steering angle. For example, when parking in a garage or parallel parking, the vehicle speed is extremely low when using four-wheel steering as described above, or the front wheel steering angle is extremely large, so the rear wheels are very slow. In some cases, the wheels are not steered, or they are steered only in the opposite phase, but depending on the situation, it may be desirable to steer them largely in the same phase. In other words, in such a case, if the rear wheels are steered largely in the same phase as the front wheels (by an angle equal to the steering angle of the front wheels), the vehicle will move diagonally in parallel, making it difficult to parallel park or narrow garages. This is extremely convenient when you want to move the vehicle laterally or in the same direction. In addition, when parking close to a wall in a narrow alley, or when driving in a narrow alley, it is necessary to repeatedly turn the steering wheel if the rear wheels are steered in the same phase as the front wheels. It is extremely easy to use, convenient and convenient. In this case, there is no need to worry about the vehicle touching or coming into contact with a wall, etc., and the vehicle can be parked very easily, and it can also be moved away from the wall. This is a common occurrence in actual driving, and it would be convenient if the entire vehicle body could be moved laterally, especially when parking in a busy area in a city. Conversely, there are times when it is desired to steer the rear wheels in the opposite phase. That is, if the rear wheels can be steered in opposite phases, the minimum turning radius can be reduced, making it easier to park the vehicle, etc., and the difference between the inner and outer wheels when turning can be reduced, making it easier to turn around narrow corners, which is convenient.

Furthermore, in the past, with the exception of special vehicles, cars were usually steered by steering only the front wheels, and the driver suddenly felt the need to drive a car with four-wheel steering due to the trajectory of the rear wheels when steering. As the vehicle's behavior changes to a certain extent, the driving sensation may become unfamiliar and may feel strange at first, and some people may prefer conventional front-wheel-only steering. Therefore, if the driver can freely select either the four-wheel steering mode or the two-wheel (front wheel) steering mode, that is, the zero-phase mode, it would be convenient for the driver, and it would also be possible to avoid unfamiliar modes. It also reduces psychological burden and is favorable from a safety standpoint.

Taking the above points into consideration, a four-wheel steering system that allows the driver to arbitrarily select automatic control mode, same-phase fixed mode, opposite-phase fixed mode, two-wheel steering mode, etc. is conceivable. can be selected arbitrarily, while driving, especially when driving at medium to high speeds, for example when changing from automatic control mode or two-wheel steering mode to fixed mode, if the fixed mode is in the opposite phase, a little front wheel steering will be applied. The vehicle body is largely steered with respect to corners, and if the fixed modes are in the same phase, there is a problem in that the vehicle also moves laterally during cornering, which is an undesirable characteristic for vehicle driving.

In view of the above-mentioned problems, the present invention has developed a control mode (same-phase fixed mode or anti-phase fixed mode) that fixes the rear wheel turning angle characteristics with respect to the front wheel turning angle in a specific pattern of the same phase or opposite phase regardless of the driving condition. To provide a four-wheel steering device in which a control mode can be freely selected by a driver and a control mode can be selected only at a set vehicle speed or lower.

The four-wheel steering device according to the present invention includes a steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a rear wheel steering angle characteristic relative to the front wheel steering angle in a specific pattern regardless of the driving condition. A control roller that controls the rear wheel steering device according to the set control mode, a mode selection means that generates a signal to operate the rear wheel steering control according to the control mode in response to the input of the controller, a vehicle speed sensor, and a combination of the mode selection means and the controller. The present invention is characterized by comprising a switch means which is connected to the output of the high speed sensor in between and inputs the output of the mode selection means to the controller only when the vehicle speed is below a set vehicle speed.

7- According to the four-wheel steering device configured as described above, the mode is switched even if the driver accidentally or intentionally operates the mode selection means while driving at medium to high speeds (vehicle speed above a predetermined value). Therefore, it is possible to perform four-wheel steering control that is preferable from a safety standpoint.

In the fixed mode, which is a control mode, for example, it is possible to perform control such as moving the vehicle laterally by steering the rear wheels largely in the same phase with a constant steering ratio (for example, 1) regardless of the vehicle speed. In the control mode, for example, the ratio of the rear wheel steering angle to the front wheel steering angle (steering ratio) is increased as the vehicle speed increases, and lateral acceleration is sensitively and responsively obtained at high vehicle speeds. It enables quick lane changes, and at low speeds, this steering ratio is set to negative and the rear wheels are steered in the opposite phase.This enables automatic four-wheel steering according to the vehicle speed. In steering mode, the vehicle can be steered using only the front wheels, just like a conventional vehicle.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 1 and 2 are graphs showing the characteristics of the front wheel steering angle (θF) and the rear wheel 8-turning angle (θR) in an embodiment of the four-wheel steering system of the present invention.

In the example of FIG. 1, an example of a fixed mode as a control mode is shown by a solid line, and an example of an automatic control mode is shown by a chain line. In this fixed mode, the rear wheel steering angle θR is shown to increase at a constant rate as the front wheel steering angle θF increases.
Of course, it is also possible to reduce the rear wheel turning angle θR at a constant rate. In the automatic control mode, the ratio of the rear wheel steering angle θR to the front wheel steering angle θF (steering ratio θR/θF) generally increases as the vehicle speed increases, decreases as the vehicle speed decreases, and decreases at very low speeds. It is made to be negative (opposite phase). In addition, in this example, in the medium and high speed range,
When the front wheel steering angle θF becomes larger than a predetermined value, the front wheel steering angle θ
Even if F increases, the rear wheel turning angle θR does not increase and remains constant at each vehicle speed. That is, the steering angle θR of the rear wheels becomes constant after the front wheels are turned to a certain extent, and is not turned any further. this is,
Based on the empirical rule that the front wheel turning angle θF is large when the direction of the vehicle is to be changed, the steering angle of the front wheels is suppressed in the same phase of the rear wheels, and the front wheels are turned largely relative to the rear wheels. This is to make it easier to change the direction of the vehicle. In the case of the embodiment shown in this figure, the same phase fixed mode can be selected using the mode selection switch at low speeds, and in this mode, the vehicle can move diagonally, making it very easy to cross over or parallel park. become.

In Fig. 2, an example of the same phase locking mode as one of the control modes is shown with a dashed line, an example of the two-wheel steering mode is shown with a solid line, and an example of the opposite phase locking mode is shown as one of the control modes with a broken line. In the same phase fixed mode example, the rear wheel steering angle θR increases at a constant rate as the front wheel steering angle θ increases.
In the case of the two-wheel steering mode example, the rear wheel turning angle θR is always zero regardless of the magnitude of the front wheel turning angle θF, and in the case of the anti-phase fixed mode example, as the front wheel turning angle θF increases. As a result, the rear wheel turning angle θR decreases. Figure 2 shows two control types, Type IIA and Type ■B. In the case of Type IIA, the same phase fixed mode (control mode) and two-wheel steering mode can be selected by the second mode selection switch, and the set value At vehicle speeds exceeding 2-wheel steering mode, Type I
1. In case of B, reverse phase fixed mode (control mode) and 2
The relationship between the front wheel and rear wheel turning angles is shown in an example in which the wheel steering mode is selectable, and when the vehicle speed exceeds a set value, the two-wheel steering mode is always used. In Type IIA, by selecting the same phase locking mode only at low speeds, the vehicle can move diagonally, making it easier to cross the road and parallel parking.
In IA, by selecting the anti-phase fixed mode at low speeds, the turning radius becomes smaller, making it easier to park the vehicle, etc.
All types are designed to automatically switch to two-wheel steering mode at medium to high speeds by operating a switch at low speeds.

Next, with reference to FIGS. 3 and 4, a specific configuration of the four-wheel steering system having two modes as in the above embodiment will be explained. Figure 3 shows an example using a hydraulic system, Figure 4
The figure shows an example using a link mechanism.

In the configuration shown in FIG. 3, the front wheels 1.1 and the rear wheels 2.2 are mechanically separated, and the output 4a of the front wheel steering angle sensor 4 that detects the steering angle θH of the steering wheel 3 is transmitted to the rear wheel steering device. This input signal is input to the controller 10, and the rear wheels 2.
I am trying to steer 2. As is well known, the front wheel steering device moves the rack 6 in the width direction of the vehicle 11 (indicated by the arrow) by means of a pinion 5, which is fixed to a steering shaft 3A to which a steering wheel 3 is fixed. 1. This rack 6
The knuckle arms 8.8 of the left and right front wheels 1.1 are connected to their shafts 8a through tie rods 1, 1 continuous to both ends of the knuckle arms 8.8 of the left and right front wheels 1.1.

It is configured to turn and move around 8a to steer the front wheels 1.1 left and right. In other words, when the steering wheel 3 in the figure is rotated in the direction of the arrow, the steering shaft 3A is rotated in the direction of the arrow, the binion 5 is also rotated in the L direction, and the rack 6, , is moved in the L direction. Due to this, the knuckle arms 8.8 of the left and right front wheels 1.1 are rotated in the L direction via the beams 7, 1, and the front wheels 1.1 are rotated in the L direction through the shafts 8a, 8 of the knuckle arms 8.
Rotate in the direction centered on a and steer to the left.

At this time, the steering angle sensor 4 outputs an output signal 4a indicating that the steering wheel 3 has rotated by an angle θH in the L direction, and inputs this to the front wheel steering angle input 10A of the controller 10 of the rear wheel steering device.

The controller 10 is powered by a power source 11,
In addition to the front wheel turning angle input 10A, a control mode signal input 10B and a feedback input 10G connected to the first rear wheel turning angle sensor 13 are provided to further control the turning direction of the rear wheels. It includes a steering direction output 10D connected to the solenoid 2012- and a hydraulic pump motor output 10E connected to the motor 21A of the hydraulic main pump 21 that controls the steering angle θk of the rear wheels. The output from the vehicle speed sensor 12 and the output adjusted to the set speed level by the variable resistor 50B are compared by the comparator 50A, and when the output from the vehicle speed sensor 12 is smaller than the set speed level, that is, the vehicle speed is below the set speed. When the output from the vehicle speed sensor 12 is higher than the set speed level, that is, when the vehicle speed is the set speed r
! When the value is 1 or more, the LOW level signal is sent to the comparator 50A.
This signal and the signal from the mode selection switch 14 enter the AND gate 50C.
A control mode signal 10B as shown in Table 1 is sent from 0C to the controller 10.

1 Table 1 The hydraulic main pump 21 includes a pump 21B that discharges oil (hydraulic oil), and this pump 21B is connected to a hydraulic actuator 23 via a steering direction switching valve 22, and this valve 22 and the pump 21B, an orifice path 24B is provided which short-circuits the oil outgoing path 24A and the oil outgoing path 24G, and has an orifice 24b in the middle, and an oil reservoir 25 is arranged in the middle of the oil outgoing path 24C.

The steering direction switching valve 22 has two inlets connected to an oil outgoing path 24A and an oil outgoing path 24G, and two inlets communicating therewith.
The valve part consisting of two outlets is
Three stop valves 22C are switchably provided in parallel, and by operating the solenoid 20, these three valve parts 2
2A, 22B.

Either one of 22G is the above oil outgoing path 24A1 return path 2
It is designed to be connected to 4C. The two outlets of this valve 22 are connected to the right oil passage 23R and the left oil passage 23L of the hydraulic actuator 23, respectively.
These right oil passage 23R and left oil passage 23[
The outgoing path 24A and the outgoing path 24 are connected via this valve 22.
It is connected to G.

The hydraulic actuator 23 has right and left oil passages 23R.
, 23m causes the rod 26, which is the output shaft, to move in the width direction of the vehicle (indicated by arrow B), and the knuckle arms 28, 28 of the rear wheels 2.2 are moved through the tie rods 27.27. It rotates around the shafts 28a, 28a, thereby steering the rear wheels 2.2 from side to side.

In the illustrated example, the front wheels 1.1 are steered to the left,
When steering the rear wheels 2.2 in the same phase as the front wheels 1.1, the steering direction switching valve 22 is set to the positive 22A position, and the oil is routed from the outgoing path 24A to the return path 2 through the orifice path 24B.
4C and returns to pump 21B via reservoir 25.

As a result, the front of the orifice 24b, that is, the outward path 24
The pressure on the A side increases, and the pressure on the rear side of the orifice 24b, that is, on the far path 24C side, decreases, causing the positive 2 side of the valve 22 to decrease.
Through the portion 2A, the pressure in the right oil passage 23R becomes higher than the pressure in the left oil passage 23L, and the operating rod 26 of the hydraulic actuator 23 is driven rightward. The drive ω at this time is determined by the amount of current input to the main pump motor 21A. As a result, the rear wheels 2, 2
is steered to the left via tie rods 21°27,
The rear wheels 2.2 are steered in the same phase as the front wheels 1.1.

Steer the front wheel 1.1 to the right, and turn the rear wheel 2.2 to the front wheel 1°1.
When steering in the same phase as the steering direction switching valve 22
is set to the reverse position 22B, the pressure relationship between the right oil passage 23R and the left oil passage 23L is reversed to that described above, and the actuating rod 26 is driven rightward.

In addition, when steering the rear wheels 2, 2 in the opposite phase to the front wheels 1, 1, the steering direction and the steering direction switching valve 22 are
The correspondence of 2A1 inverse 22B is opposite to the case of same phase as above,
In other words, when steering the front wheels 1.1 to the left, reverse 22
B, when steering the front wheel 1.1 to the right, use the positive 22A.
Set to .

Further, when the steering angle θR of the rear wheels 2, 2 is set to zero, the stop 22C portion of the valve 22 is connected to the aisle passage to cut off the communication between the pump 2IC and the hydraulic actuator 23,
Left and right oil passages 23L, 2 of the hydraulic actuator 23
Eliminate the pressure difference between 3R and set the operating rod 26 to the neutral position. At this time, in order to ensure that the actuating rod 26 is set at the neutral position, it is desirable to apply a set load to the actuating rod 26 so that it is mechanically biased to the neutral position.

The steering direction and the magnitude of the steering angle of the front wheels 1, 1 are inputted to the engine controller 10 by the output 4a of the front wheel steering angle sensor 4, and the rear wheels 2.2 are inputted to the front wheel 1.1. The vehicle speed sensor 12 determines whether to set the same phase or opposite phase.
The controller 10 determines the vehicle speed according to the vehicle speed detected by the controller 10 according to a preset vehicle speed correspondence pattern.

According to the four-wheel steering device using the hydraulic actuator as described above, the rear wheels can be steered smoothly and without applying any special load to the steering wheel for four-wheel steering, which is advantageous in practice. be.

However, hydraulic systems require heavy and costly parts such as motors, pumps, hydraulic actuators, and control valves, which increases the number of vehicles stacked on top of each other.
It is not suitable for relatively small vehicles because it complicates manufacturing assembly and causes high costs. Therefore, a four-wheel steering system using a simple link mechanism may be advantageous in practice.

An example of this type of link type mechanism will be explained below with reference to FIG. In the configuration of FIG. 4, the same members as those in the configuration of FIG. 3 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the link type configuration shown in FIG. 4, a slot 6A for sliding engagement is provided in a part of the rack 6 that is moved in the width direction of the vehicle by the steering wheel 3, and the rear wheels 2.2 are steered from this slot 6A. A link mechanism connects the rod 41 up to the sliding engagement slot 41A,
The rear wheels 2.2 are steered in a desired direction by a desired magnitude of the steered angle θR in accordance with the steered angle θF of the front wheels 1.1.

This link mechanism includes a first L-shaped lever 31 having one end 31A slidably engaged with a sliding engagement slot 6A on the front wheel side and pivotally supported by a fixed shaft 31a; A connecting lever 32 with one end 32A rotatably connected to the other end 31B of the connecting lever 31, a swinging lever 33 with one end 33A connected to the other end 32B of this connecting lever 32, and the other end 33B being pivotally supported on a fixed shaft 33a. The one end 3 of this swing lever 33
A control lever 34 whose one end 34A is rotatably connected to a connecting shaft between the intermediate lever 3A and the other end 32B of the intermediate lever 32.
The sleeve 35 and the screw rod 37 are slidably engaged in the vicinity of the free end of the control lever 34 and are pivotally supported with a rotation shaft 35A on a feed sleeve 36 screwed onto the screw rod 37. a motor 38 for rotating the control lever 34, and a connecting lever 39 whose one end 39A is pivotally supported by a shaft support 34A provided at an intermediate position of the control lever 34.
, and the other end 39B of this connecting lever 39 has one end 40A.
The second L-shaped lever 40 has its other end 40B slidingly engaged with the sliding engagement slot 41A on the rear wheel side.

The motor 38 is connected to a controller 50 and driven by the output of the controller 50.

This controller 50 is supplied with power from an electric power source 51,
The output of AND gate 50C is input.

A signal obtained by comparing the output of the vehicle speed sensor 52 and the output of the variable resistor 50B for adjusting the set speed level by a comparator 50A and a signal from the mode selection switch 54 are input to this AND gate 50C.
The control signal shown in Table 1 above is sent from C to the controller 50. Further, a potentiometer 53 is disposed near the screw rod 37, which feeds back the position of the feed sleeve 36 screwed onto the screw rod 37 to the input of the motor 19-138, and controls the position of the feed sleeve 9-136. It is meant to be controlled.

According to the four-wheel steering device equipped with the link mechanism as described above, the steering wheel 3 is moved to the left (in the direction of the arrow).
When rotated, pinion 5, rack 6, tie rod 1.7
, Naoto Kuru Arm, 8,8. , all of the front wheels 1 and 1 are rotated or moved in the direction of the arrow, and at the same time the front wheels 1 and 1 are steered to the left, the first L-shaped lever 31 is rotated to the fixed shaft 31ap.
The swinging lever 33 is rotated to the left around the fixed shaft 33a via the intermediate lever 32, and the control lever 34 is rotated to the left around the lever 35. At the same time, the second L-shaped lever 40 is rotated to the left to move the steering rod 41 of the rear wheel 2.2 in the direction. , the rear wheels 2.2 are steered to the left in the same phase. , the motor 38 is driven by the controller 50 which has selected the control mode shown in Table 1, and the feed sleeve 36 in the figure moves downward (to the left of the vehicle). is one end 39A of the connecting lever 39
When the control lever 34 reaches the position shown in FIG.
Since the connecting lever 39 does not move forward 1 (in the left-right direction in the figure) even when it swings around A, the rear wheels 2.degree. 2. are not steered. - When the sleeve 35 is further moved downward by the motor 38 (D drive) and exceeds the position 3.9A at one end of the connection lever 39, the control lever moves in the same direction as above (upward direction). 34
The swing moves the connecting lever 39 forward in the opposite direction to that described above. This is because the control lever 34 swings around the pivot shaft 3, 5A of the sleeve 35. Therefore, in this case, the third wedge-shaped lever 40 rotates in the direction of the arrow R, the steering rod 41 of the rear wheels 2.2 moves in the direction of the arrow R, and the rear wheels 2.2 move to the right. was steered,
Four-wheel steering with opposite phases will be performed.

- In this way, by driving and controlling the motor 38 by the output of the controller 50, the feed slip, -13
6, the receiver moves the sleeve 35, thereby changing the position of the axis of oscillation of the control lever 34 and, as a result, changing the direction of movement of the coupling lever 39, so that the rear wheel 2.2
The direction of steering can be changed. Furthermore, by controlling the distance of movement of the sleeve 35, the receiver can also change the magnitude of the steering angle θR of the rear wheels 2, 2 in the same phase and in the opposite phase.
The output of the controller 50 makes it possible to arbitrarily control the direction and magnitude of steering of the rear wheels 2.2 in response to the steering of the front wheels 1.1.

For example, in the case of type I shown in FIG.
Since the output from the vehicle speed sensor 52 is input to 0, when the automatic control mode is selected, steering is performed via the above link according to the magnitude of the steering angle θF of the front wheels 1.1. (including the magnitude and direction of the steering angle θR of the rear wheels 2, 2) can be controlled according to the characteristics of the steering ratio in the automatic control mode described in the above embodiment.

Also, when the same phase fixed mode is selected, only at low speeds,
For example, the steering angle θ is equal to the steering angle θF of the front wheels 1.1.
By steering the rear wheels 2.2 by R, it becomes possible to move the vehicle laterally regardless of the vehicle speed.

Note that the control characteristics in the in-phase and anti-phase fixed modes are not necessarily limited to a straight line to the in-phase side as shown in Figures 1 and 2, but rather a certain curved line. It may be a pattern of Furthermore, the control characteristic pattern in the automatic control mode is not limited to the example shown in Fig. 1, but may also be of a type in which the phase of the rear wheel steering angle is changed depending on the magnitude of the front wheel steering angle. Various deformation patterns are conceivable, such as one in which this is further changed according to the vehicle speed, and it goes without saying that automatic control based on these various patterns may also be adopted in the apparatus of the present invention.

In this way, even with the link type configuration shown in FIG.
It is possible to realize the rear wheel turning angle characteristics with respect to the front wheel turning angle as in the above-described embodiments. In particular, this link type mechanism has a smaller weight and simpler structure than a hydraulic type.
It is easy to assemble and can be manufactured at low cost, making it suitable for small vehicles.

As explained in detail above, the four-wheel steering system of the present invention has a control mode (same phase fixed mode or opposite phase fixed mode) that fixes the above characteristics regardless of the driving state, and has a control mode (same phase fixed mode or opposite phase fixed mode) that Since the rear wheel steering is controlled using the control mode only, even if the mode selection switch is operated by mistake when driving at medium to high speeds, the control mode will not change to the control I (fixed) mode, and four-wheel steering control that is preferable for safety will be performed. I can do it.

[Brief explanation of the drawing]

1 and 2 are characteristic curves showing the relationship between the front wheel steering angle and the rear wheel steering angle in the four-wheel steering system of the present invention. Figure 2 shows an example of type IIA, which allows selection of two-wheel steering mode and same-phase locking mode, and an example of type IIB, which allows selection of two-wheel steering mode and anti-phase locking mode. An example is given for each. FIG. 3 is a schematic diagram showing an example of the four-wheel steering device of the present invention using hydraulic pressure, and FIG. 4 is a schematic diagram showing an example of the four-wheel steering device of the present invention using a link mechanism. 1...Front wheel 2...Rear wheel 3
...Steering wheel 4...Steering angle sensor 5.
・・Vinion 6・・ra
Tsuri 1.27... Tie rod 8.28...
Knuckle arm 10.50...controller 12.
52... Vehicle speed sensor 14... Second mode selection switch 20... Solenoid 21... Main pump 22... Rear wheel steering direction switching valve 24- 23... Hydraulic actuator 25... Reservoir 26 ... Rear rotary marine rod 31 ... First L-shaped arm 32 ... Intermediate lever 33 ... Rocking lever 34 ... Control lever 34A ... Shaft support part 35 ... Support is sleeve 35A... Rotating shaft 36... Feed sleeve 37... Screw rod 38... Drive motor 39... Connection lever 40... Second L-shaped lever 41... Rear wheel steering rod 50A ...Comparator SOB...Variable resistor 5
0G...AND gate (voluntary) procedure Ne City Paperback December 22, 1981 Commissioner of the Patent Office Sir 2. Title of invention 4-wheel steering device for vehicles 3. Relationship with the person making the amendment case Patent applicant 4 , Agent 5, Date of amendment order 9, Attached documents Type-coated specification
1 letter 371-

Claims (1)

[Claims] A steering device that steers the front wheels, a rear wheel steering device that steers the wheels in contact, and a rear wheel steering device that uses a control mode that sets the characteristics of the rear wheel steering angle relative to the front wheel steering angle in a specific pattern, regardless of the driving condition. a controller for controlling the controller, a mode selection means for issuing a signal to the input of the controller to activate the rear wheel steering control according to the control mode, a vehicle speed sensor, and a vehicle speed sensor located between the mode selection means and the controller and connected to the output of the vehicle speed sensor. A four-wheel steering system for a vehicle, comprising a switch means for inputting the output of the mode selection means to a controller only when the vehicle speed is below a set vehicle speed.