JPS5977970A - Four-wheel steering gear for vehicle - Google Patents

Abstract

PURPOSE:To enhance operability of a four-wheel steering gear at intermediate and high vehicle velocities, by providing a controller for controlling a rear-wheel steering gear in accordance with rear-wheel steering angle characteristics relative to a front-wheel steering angle. CONSTITUTION:Front wheels 1, 1 and rear wheels 2, 2 are mechanically separated from each other, an output 4a from a front-wheel steering angle sensor 4 detecting a steering angle thetaH of a steering wheel 3 is inputted into the controller 10 for the rear-wheel steering gear, and the rear wheels 2, 2 are steered by the input signal. The rear-wheel steering angle thetaR is increased at a predetermined ratio to the front-wheel steering angle thetaF when the vehicle velocity is the highest V1, and becomes thetaR1 at a point of inflection P1, and beyond this point, the angle thetaR is maintained at a fixed value even when the front-wheel steering angle thetaF is increased. When the vehicle velocity is V2 or V3, thetaR is increased at a predetermined ratio to thetaF, and beyond the point of inflection P2 or P3, the rear-wheel steering angle thetaR is maintained to be constant even when the front-wheel steering angle thetaF is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for steering both the front wheels and the rear wheels of a four-wheel vehicle such as an automobile, that is, a four-wheel steering system that steers the rear wheels as well as the front wheels by steering the front wheels, which are steering wheels. It is related to the device.

Conventionally, steering devices for four-wheeled vehicles steer only the front wheels, and the rear wheels undergo some toe-in depending on the driving situation, regardless of the steering of the front wheels.

Although it toes out, it is not designed to steer in a seed-like manner. However, recently, a four-wheel steering device has been proposed that steers both the front wheels and the rear wheels (for example, in Japanese Patent Laid-Open No. 55-91458), and research on this type of device is being conducted.

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 minimized or eliminated, which is advantageous when turning a narrow corner. In addition, when steering a vehicle at extremely low speeds, if the rear wheels are steered in the same direction as the front wheels (this is called in-phase), it is possible to move the entire vehicle in parallel, making it easier to park and park. It is often convenient when parking in the garage.

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, yawing 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 effect of external disturbances such as crosswinds, stable driving can be maintained against external disturbances, and stable high speeds can be maintained. It is also possible to obtain straightness.

Also, during a turn, even if force U decelerates while keeping the front wheel steering angle constant, the rear wheel steering angle changes in accordance with the force N deceleration, ensuring a stable turn without deviating from the course. You can also do it. In other words, in conventional vehicles, the steering characteristics are adjusted to have a slight understeer tendency for straight-line stability, and when accelerating during a turn, there is a tendency for the vehicle to deviate outward from the course. By steering, the deviation can be corrected and stable turning can be achieved.

In terms of comfort, it is the smallest with the same wheelbase.
Since it is possible to obtain a large turning radius, the wheelbase can be made thicker, and in addition to this, the actual steering angle of the front wheels can be reduced, which makes it possible to create new designs in terms of design. There are many advantages such as being able to

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

Regarding this four-wheel steering, various specific configurations have been proposed so far to effectively steer the rear wheels. For example, one in which the four wheels are steered in opposite phases at low speeds and in the same phase at high speeds (% Kai No. 55-91457), and one in which the front wheels are in the same phase when the steering angle is small, and in opposite phases when the steering angle is wide. (Japanese Patent Laid-open No. 56-5270), the rear wheels are steered in proportion to the front wheel steering angle only when the front wheel steering angle is below a predetermined range, and when the front wheel steering angle is above the predetermined range, the front wheels are steered in proportion to the front wheel steering angle. The steering angle of the rear wheels is kept constant regardless of the
63969) etc. are known.

These four-wheel steering devices often require a large change in the direction of the vehicle when the vehicle speed is low or the front wheel steering angle is large, but only slightly when the vehicle speed is high or the front wheel steering angle is small. This system always steers the rear wheels in the desired direction, based on the empirical rule that there are many cases where a vehicle wants to move laterally.

However, in actual driving of a vehicle, sufficient maneuverability and driving stability cannot be obtained simply by considering the vehicle speed and the front wheel steering angle independently. For example, when turning with a constant front wheel steering angle, even if the rear wheels are steered with the desired steering ratio corresponding to this steering angle, if you accelerate or decelerate during the turn, you will deviate from the course or go round.・＼There is a mark when it comes off. This is because centrifugal force (lateral force) changes as the vehicle speed changes, but in order to avoid going off course, the front and rear wheels must be adjusted according to the change in vehicle speed. Is it necessary to change the steering ratio? Therefore, it is desirable to change the rear wheel steering angle (steering ratio) with respect to the front wheel steering angle depending on the vehicle speed. In addition, in the medium to high speed range, the higher the vehicle speed, the larger the steering ratio in the same phase, and the larger the lateral acceleration (q) to enable smooth lane changes and improve maneuverability. It is desirable to reduce the steering ratio and the lateral acceleration as the vehicle speed decreases to medium speed.

SUMMARY OF THE INVENTION In response to the above-mentioned needs, the present invention aims to provide a four-wheel steering system that has improved maneuverability at medium and high speeds.

A four-wheel steering device according to the present invention includes a steering device that steers front wheels, a rear wheel steering device that steers rear wheels, and a controller that controls the rear wheel steering device according to the steering angle of the front wheels. In the device, when the front wheel steering angle is less than a set value, the rear wheel steering angle is increased in accordance with the increase in the front wheel steering angle,
Above this set value, control is performed to have an inflection point that reduces the rate of increase, and control is performed to change this inflection point to the side where the rear wheel steering angle is smaller as the vehicle speed decreases. It is characterized by:

According to the four-wheel steering system of the present invention, in a small range where the front wheel steering angle is less than or equal to the set value, the rear wheel steering angle increases in accordance with the increase in the front wheel steering angle, so that G is less likely to occur. In the range where the front wheel steering angle is larger than this set value, the rate of increase decreases), and the yaw area (ψ area) in which yawing does not occur is obtained, and the front wheel steering angle, that is, the steering Desire in response to changes in the steering angle! In addition, the inflection point changes to the smaller rear wheel steering angle as the vehicle speed decreases, so at high speeds, the lateral direction that acts on the rear wheels during steering is In addition to increasing acceleration and decreasing speed, this lateral acceleration can be decreased to increase turning performance.

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

Figures 1, 2, and 3 show the rear wheel steering angle (θF) relative to the front wheel steering angle (θF) in the four-wheel steering system of the present invention.
Examples of the characteristics are shown below. In the characteristic curve of ■1, which is the highest speed, the inflection point P1 is at the point where the steering angle θR is wide (θ'R1), and this $ speed V is lower than the vehicle speed. In the characteristic curve of V2, the inflection point P2 is at a relatively small point (θT) where the rear wheel turning angle θR is relatively small (θT), and in the characteristic curve for a lower vehicle speed v3, the inflection point P3 is at the point where the rear wheel turning angle θR is the smallest (
θF3). FIG. 3 shows a characteristic curve for an even lower vehicle speed ■4.

In the example shown in Figure 1, the rear wheel steering angle θF increases at a constant rate with respect to the front wheel steering angle θF when the vehicle speed is extremely high at 710, and at the inflection point P□ it becomes θF7. Thereafter, even if the front wheel steering angle increases, it is maintained at one minus foot, that is, θF1. Vehicle speed is V2 KV+ ) and V3 (<V2 <
When 'V+>, the rear wheel steering angle θR is the front wheel steering angle θFK.
On the other hand, the power is increased at the same constant rate as when the vehicle speed is 1, and at the inflection point P2 it becomes θF2 (when the vehicle speed is V2) and at the inflection point P3 it becomes θF3 (when the vehicle speed is 3). Even if the wheel steering angle θF increases, the rear wheel steering angles θ and R each increase by θ.
It is held at F2 (when the vehicle speed is v2) and θ·R3 (when the vehicle speed is v3). The magnitude of these θ'R+ r θ'R2 and θF3 is θ・R1>θF2>θ'Rs
As the vehicle speed decreases, turning performance improves. Conversely, as the vehicle speed increases, the lateral acceleration acting on the rear wheels during steering increases.

In the example of Fig. 2, the vehicle speeds V,, V, , and Vs
(In each case, V+ > V2 >'Vs), until reaching P2 and P3, the rear wheel steering angle θ゛R is the front wheel steering angle, as in the embodiment shown in Fig. 1. The force is increased a at a constant rate with respect to θF, but after the inflection point, when the vehicle speed is V□, the rear wheel steering angle θ1 is held constant at θF5, and when the vehicle speed is v2, the rear wheel steering angle θR is kept constant at the front wheel rotation. On the contrary, it decreases as the steering angle IθF increases, and when the vehicle speed is v3, the rear wheel steering angle θF decreases at a larger decreasing rate than when the vehicle NVsO increases as the front wheel steering angle θ・F increases. That is, as the front wheel turning angle .theta.F increases, the rear wheel turning angle .theta.R increases until it reaches an inflection point, but after that, it decreases at a constant rate or at a steep decreasing rate with a slow vehicle speed.

In the example of FIG. 3, vehicle speeds V, , V2. V3 and V.

(V, > V2 > V3 > V, ) Compare the inflection points 1, I+, P2, PR+ and P4 with the example shown in Fig. 1 by changing the other three points according to the decrease in vehicle speed while leaving P as is. The steering angle θF of the front wheels is shifted to the larger side.

In other words, compared to the embodiment shown in FIG. 1, by narrowing the yaw area until reaching the inflection point (widening the G area) as the vehicle speed decreases, the turning performance until reaching the inflection point also improves at low speeds. I'm doing reasonably well.

According to each of these embodiments of the present invention, the steering ratio θR/θF
is an inflection point P,, P2. As the vehicle speed decreases, the rear wheel turning angle θR decreases, the lateral acceleration decreases, and turning performance can be improved.

Next, with reference to FIGS. 4 and 5, a specific configuration of a four-wheel steering system that achieves the characteristics as in the above embodiment will be explained.

FIG. 4 shows an example using hydraulic pressure, and FIG. 5 shows an example using links.

In the configuration shown in FIG. 4, the front wheels 1, 1 and the rear wheels 2, 2 are mechanically molecular IMed, and the output 4a of the front wheel steering angle sensor 4 that detects the steering angle θH of the steering wheel 3 is applied to the rear wheels. This input signal is input to the controller 10 of the steering device, and the rear wheels 2, 2 are steered by this input signal. As is well known, the front wheel steering device moves a rack 6 in the width direction of the vehicle (indicated by arrow A) by means of a pinion 5 fixed to a steering shirt l-3A to which a steering wheel 3 is fixed. 60 Tie rods connected to both ends 7.7
jr and left and right front wheels], 10 knuckle arms 8, 8 II! lI]8a, 8a0) to steer the front wheels 1, 1 left and right. That is, 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 rotated.
move in the L direction. As a result, the knuckle arms 8, 8 of the left and right front wheels 1, 1 are connected via the tie rods 7.7]J
10,000"J fc rotate, knuckle arm 8 front wheels 1,1
．． Rotate in the L direction around the 80 shafts 8a, 8a and steer to the left. At this point, 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 steering angle input 10A, a vehicle speed input 10B connected to the vehicle speed sensor 12 and a feed hack human power 10C connected to the rear wheel steering angle sensor 13 are provided, and furthermore, it is provided with a vehicle speed input 10B connected to the vehicle speed sensor 12, and a human power input 10C for feed hacking connected to the rear wheel steering angle sensor 13. 11'e direction output 101] connected to the solenoid 20 on the side 1) and controlling the steering angle θR of the rear wheels (
It is equipped with a hydraulic pump motor output 101 connected to the motor 21A of the hydraulic main pump 21.

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 pulp 22. In between, there is an oil outbound path 24. Short circuit A and oil return path 24C'
and an orifice path 24 with an orifice 24b in the middle.
B is provided, and an oil reservoir 25 is arranged in the middle of the oil return path 24C.

The steering direction switching valve 22 is connected to the oil outgoing path 24 and the oil return path 24CK.
The pulp part consisting of two outlets: forward 22A, reverse 221:
(, 3III!iI of the stop 22C can be freely switched in parallel, and by operating the solenoid 20, any one of these three valve parts 22A, 22B, 22C is brought into contact with the oil outgoing path 24A and return path 24C. The two outlets of this pulp 220 are respectively connected to the right oil passage 23R and left oil passage 23.L of the hydraulic actuator 23, and these right oil passage 231t and left oil passage 23L are connected to this oil passage 23.L. pulp 22
The outgoing route 24A and the returning route 24C are connected to each other via the outgoing route 24A and the return route 24C.

The hydraulic actuator 23 has right and left oil passages 2:3.
Due to the pressure difference applied to JL, 23LK, the rod 26, which is the output shaft, is moved in the width direction of the vehicle (indicated by arrow B), the tie rods 27 and 27 are valved, and the knuckle arms 28 and 28 of the rear wheels 2.2 are moved. Its axis 28a, 28a 117)
'! Instead, the rear wheels 2.2 are rotated, thereby steering the rear wheels 2.2 left and right.

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! ; The rJ exchange valve 22 is set to the positive 22A position, and the oil is transferred from the outgoing path 24A to the return path 24. through the orifice path 2413. C, passes through reservoir 25 to pump 2
Return to 1B.

This causes the orifice 24. The pressure in g4IJ increases and the orifice 24
The pressure in the rear passage 24CIII of the pulp 22 becomes lower, and the pressure in the right oil passage 23K becomes higher than the pressure in the left oil passage 23J through the positive 22A portion of the pulp 22, and the hydraulic actuator 23 operating rod 2
0baJ.

driven in the direction. The amount of drive of this crest is determined by the amount of current input to the main pump motor 2]A. As a result, the rear wheels 2, 2 are steered in the left direction 1. via the tie rods 27.27, and the rear wheels 2, 2 are steered in the same phase as the front wheels 1.1.

The front wheels 1, 1 are steered to the right, and the rear wheels 2, 2 are steered to the right. l
When steering in the same phase as the steering direction switching pulp 22
Set it in the reverse 22B position, and open the right oil passage 23.
J (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 positive 2.2 of the steering direction switching pulp 22 are
The correspondence between 2A and reverse 22B is opposite to the case of same phase as above.
In other words, when steering the front wheels 1 and j to the left, reverse 22
B, when steering the front wheel 1.1 to the right, use the positive 22A.
to cents.

The pulp 22 makes the steering angle θR of the rear wheels 2, 2 zero.
Connect the stop 22C part of the pump 2 to the oil passage.
Communication between the IC and the hydraulic actuator 23 is cut off, and the pressure difference between the left and right oil passages 23L, 23a of the hydraulic actuator 23 is eliminated, and the S1 operating rod 26 is set to a neutral position. At this time, in order to ensure that the actuating rod 26 is set in the neutral position, a set load is applied to the actuating rod 26 so that it is mechanically urged to the neutral position. desirable.

The steering direction of the front wheels 1 and 10 is determined by the output 4 of the front wheel steering angle sensor 4.
a to the controller 1o, and the rear wheels 2,
2 to front wheel 1. Depending on the vehicle speed detected by the vehicle speed sensor 12, the controller 10 determines whether to set it in the same phase or in the opposite phase with respect to IK, according to a preset vehicle speed correspondence pattern.

The controller 10 receives input θ・H from the steering angle sensor 4.
(This is proportional to the steering angle θF of the front wheels 1 and 10) and the input ■ from the vehicle speed sensor 12, a control signal is output according to the characteristics shown in FIGS. 2
, 2.

The four-wheel steering system using a hydraulic actuator as described above is advantageous for practical use because the rear wheels can be steered smoothly and without any special load on the steering wheel for four-wheel steering. .

However, hydraulic systems require heavy and costly parts such as motors, pumps, hydraulic actuators, and pulp for control, which increases the amount of nitrogen in the vehicle.
It is not suitable for relatively small vehicles because it complicates manufacturing assembly and causes cost constraints. Therefore, a four-wheel steering system that uses a simple link mechanism may be advantageous in practice.

Hereinafter, an example of this type of link type mechanism will be explained with reference to FIG. In the configuration of FIG. 5, the same members as those in the configuration of FIG. 4 are designated by the same reference numerals, and their explanations will be omitted.

In the link type configuration shown in FIG. 5, 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 slot for sliding engagement provided in the rod 41 [up to 41A is connected to the link mechanism,
The rear wheels 2 and 2 are steered in a desired direction by a desirable magnitude of the steered angle θR in accordance with the steered angle θF of the front wheels 1 and 10.

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 member 31a; A connecting lever 32 whose one end 32A is rotatably connected to the other end 31B of the connecting lever 31, and the other end 32B of this connecting lever 32.
A swinging lever 33 has one end 33A connected to the other end 3313, and the other end 3313 is pivotally supported on a fixed shock shaft 33a. The control lever 34 is rotatably connected, and the feed sleeve 36 is slidably engaged near the free end of the control lever 34 and is screwed onto the screw rod 37. The supported receiver is the sleeve 35, the screw rod 37 is connected to the rotary sacel motor 38, and the connecting lever 39 has one end 39A pivotally supported by the shaft support 3/IA provided at an intermediate position of the control lever 34. 39 other end 3
One end 40A is connected to 9B, and the other end 40B is connected to the second L that is dynamically engaged with the sliding engagement slot h4zAKff on the rear wheel side.
It consists of a glyph-shaped lever 40.

The motor 38 is connected to a controller 50 and driven by the output of the controller 5o. This controller 5o is supplied with power from a power source 5■, and a vehicle speed sensor 52
The output of is input. Further, a bottom meter 53 is arranged near the screw rod 37 to feed back the position of the feed sleeve 36 screwed onto the screw rod 37 to the input of the motor 38.
It is designed to control the position of 6.

In a four-wheel steering system equipped with the link mechanism described above, when the steering wheel 3 is rotated to the left (in the direction of arrow J), the pinion 5° rack 6, the tyron door, 7. Knuckle arm 8.8. Front wheel 1. (3) all rotate or move in the direction of the arrow, steer the front wheels 1.1 to the left, and at the same time rotate the J-shaped lever 31 in the L direction around the fixed shaft 31a, and turn the intermediate lever 32. The swing lever 33 is rotated in the J direction around the fixed shaft 33a, and the control lever 34 is rotated around the sleeve 35 in the L direction.
direction to move the connecting lever 39 in the JJ direction, and simultaneously rotate the second L-shaped lever 40 in the L direction to move the steering rod 41 of the rear wheel 2.2 in the L direction, As a result, the rear wheels 2, 2 are steered to the left in the same phase.

When the motor 38 is driven by the controller 50 and the feed sleeve 36 moves downward (to the left of the vehicle) in the figure, and the feed sleeve 36 reaches the position of one end 39A of the connecting lever 39, the control lever 34 Since the connecting lever 39 does not move back and forth (in the left-right direction in the drawing) even if it swings relative to the rotation axis 35A0) of 35, the rear wheels 2, 2 are not steered.

When the sleeve 35 is moved further downward by the drive of the motor 38 and passes the position of one end 39A of the connecting lever 39, the swinging of the control lever 34 in the same direction as above (in the L direction ril causes the connecting lever 39 to move downward). Contrary to the above, the cell moves forward. This is because the control lever 34 is oscillating around the rotation of the sleeve 35 @ 35A. Therefore, in this case, the second ""-shaped lever 40 rotates in the direction of arrow 1, the steering rods 41 of the rear wheels 2, 2 move in the direction of arrow 1, the rear wheels 2, 2 are steered to the right, and four-wheel steering with opposite phases is performed. It will be.

In this way, the output of the controller 50 causes the remoter 38 to
By driving and controlling the feed sleeve 36, the receiver moves the sleeve 35, thereby changing the position of the swing axis of the control lever (-34) and changing the direction of movement of the connecting lever 39. The direction of steering of the rear wheels 2, 2 can be changed by changing the steering direction of the rear wheels 2, 2.Furthermore, by controlling the distance of movement of the sleeve 35, the receiver can steer the rear wheels 2 in the same phase or in the opposite phase. , 2 steering angle θR
Therefore, by the output of the controller 50, it is possible to arbitrarily change the direction and thickness of the steering of the rear wheels 2 and 20 according to the steering of the front wheels 1 and 10 to the open side 1. becomes.

Since the output from the vehicle speed sensor v52 is input to the controller 50, the rear wheels 2 and 2 are steered according to the width of the front wheels 1 and 10 and the steering angle θF via the above link.
(including the direction in which the steering angle θR is increased) can be controlled according to the characteristics of the steering ratio explained in the above-mentioned valley embodiment.

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

As described above in detail, the four-wheel steering system of the present invention increases the rear wheel steering angle in accordance with the increase in the front wheel steering angle when the front wheel steering angle is below a set value (inflection point), and Above this value, the rate of increase is reduced, and the inflection point is changed to the side where the rear wheel steering angle is smaller as the vehicle speed decreases, thereby improving maneuverability such as lane changes at high speeds. As the vehicle speed improves and the vehicle speed decreases, the turning performance increases, making it possible to realize practically preferable four-wheel steering.

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of a characteristic curve 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, and FIGS. 2 and 3 are the other sides of the same characteristic curve. FIG. 4 is a schematic diagram showing an example of the four-wheel steering device of the present invention using hydraulic pressure. FIG. 5 is a schematic diagram showing an example of the four-wheel steering device of the present invention using a link mechanism. It is. 1...Front wheel 2...Rear
Wheel 3... Steering wheel 4...
・・Steering angle sensor 5・・・・Vinion 6・
...Rat 7.27...Tyron 8.28...Narecle arm 10.5 type...Controller 12,52. ...Vehicle speed sensor 20...
...Nrenoid 21...Main pong 22
......Rear wheel steering direction switching pulp 23...
Hydraulic actuator 25... Reservoir -
Bar 26... Rear wheel steering rod 31... First IJ-shaped arm 32... Intermediate lever 33... Rocking bar - 34
...Control lever 34A...shaft support
Part 35...The receiver is sleeve 35A...times
Moving shaft 36...Feed sleeve 37...
...Screw rod 38...Drive motor 39...Connection lever 4.0...Second L-shaped lever 41...Rear wheel steering rondo (spontaneous) procedure Hosei sho December 20, 1980 Commissioner of the Japan Patent Office 1. Indication of Matter A' [Patent Application No. 189447 1987 2. Name of Invention 4-wheel Steering Device for Vehicles 3. Relationship with the Ministerial Case for Amendment Patent applicant 4, agent 5-2-1-7 Roppongi, Minato-ku, Tokyo, subject of amendment "Detailed description of the invention" in the specification
Column 8, Contents of amendment 1) Specification, page 8, line 16 and page 11, lines 17-18
Line ``Delete J that acts on the rear wheel.'' 2) Correct ``large'' to ``secure'' in lines 16-17 of page 8. 3) Page 8, line 17 and page 11, line 19, ``Correct 1 to `` and J. Page 10, line 7, insert ``As the difference between the front wheel turning angle and the rear wheel turning angle increases'' between ``and J''. 6) Delete "On the contrary, it becomes larger." in lines 7 to 9 of the same page. 7) Insert "Small the inclination" between "Until reaching" and "Yaw area" in the 10th line of page 11. 8) Correct the 11th line of the same page to read ``Narrow < (G area wide <)'' to 1 and θR smaller.'' 9) On the same page, lines 11-12 [inflection point...lower speed] should be corrected to "turning performance." 10) In the 19th line of the same page, correct "to become smaller" to "to suppress."

Claims (1)

[Scope of Claims] A steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, a vehicle speed sensor, and when the front wheel steering angle is less than a set value, the rear wheel steering angle is adjusted as the front wheel steering angle increases. has an inflection point that increases the rate of increase and reduces the rate of increase above this set value, and this inflection point changes to the smaller side of the rear wheel steering angle as the vehicle speed decreases. A four-wheel steering system for a vehicle, comprising a controller that controls a rear wheel steering system based on characteristics of a rear wheel steering angle with respect to a front wheel steering angle.