JPH0732335Y2 - Front and rear wheel steering system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a front and rear wheel steering device for a vehicle, which is suitable for use in vehicles such as automobiles, in particular, four-wheeled vehicles, and more particularly to an actuator for steering the rear wheels. A front and rear wheel steering device for a vehicle provided with a relief valve that operates by receiving fluid pressure and receives the fluid pressure generated by a fluid pressure type power steering device for the front wheels to open a fluid pressure supply flow path to the rear wheels Regarding

[Conventional technology]

In recent years, front and rear wheel steering devices such as a four-wheel steering device have been considered in which not only the front wheels but also the rear wheels are steered when steering a vehicle such as an automobile.

In this four-wheel steering system, the rear wheels are steered in the opposite direction (reverse phase) to the front wheels in order to improve the small turning performance (hereinafter referred to as reverse phase steering), and the steering response is improved. There is a case where it is performed in the same direction (same phase) as the front wheels (hereinafter referred to as in-phase steering), and the ratio of the size of the rear wheel steering angle to the front wheel steering angle (steering wheel steering angle) (steering The problem is how to adjust the ratio) according to the running state of the vehicle.

By the way, generally, a small turning performance is required when the vehicle is running at a low speed, and steering response is required when the vehicle is running at a high speed. Therefore, based on the vehicle speed,
A means for adjusting the steering ratio of the rear wheels to the steering angle of the steering wheel has been considered.

For example, a vehicle steering system disclosed in Japanese Patent Laid-Open No. 55-91457 discloses a steering wheel, a gear box for converting rotational movement of the steering wheel into a linear motion, and a linear motion converted by the gear box. A first connecting rod that steers the front wheels, and further, for steering the rear wheels, a moving arm that rotates by receiving the linear motion converted by the gear box; and this moving arm and the rear wheels. The second connecting rod is interposed between the two, and the rear wheel is steered through the second connecting rod by the rotation of the moving arm. The fulcrum of the moving arm is movable, and the movable fulcrum moves on the moving arm according to the vehicle speed. The movement of the movable fulcrum changes the arm length of the moving arm. The steering ratios of the front wheels and the rear wheels are thereby adjusted.

That is, the tip of the moving arm is connected to the gear box, the second connecting rod is pivotally attached to the middle part of the moving arm, and the fulcrum of the moving arm is located before and after the pivoting point with the second connecting rod. It is able to move on the arm. Then, for example, when the movable support point is located before the pivot point with the second connecting rod, the front wheel and the rear wheel are in the same phase (or opposite phase) at a turning ratio according to the length of the arm. When the movable support point is located behind the pivot point, on the contrary, the front wheel and the rear wheel are steered in opposite phases (or the same phase) at a steering ratio according to the length of the arm.

Further, the four-wheel steering system for a vehicle disclosed in Japanese Patent Laid-Open No. 60-193770 is interposed between a rear wheel steering mechanism and a steering mechanism linked to the front wheel steering mechanism, and the rear wheels with respect to the steering angle of the steering wheel. Is a four-wheel steering system for a vehicle equipped with a turning ratio changing device for changing the turning ratio of the steering ratio changing device, wherein the turning ratio changing device is rotated in accordance with the steering wheel steering angle and The rotary member is provided with a rotary member whose tilt angle with respect to a predetermined reference plane is variable, and tilt angle changing means for changing the tilt angle of the rotary member. In cooperation with the rear wheel steering mechanism, the steered angle of the rear wheel is controlled according to the displacement of the rotational eccentric position determined according to the rotational angle and the inclination angle of the rotational member. Has become.

That is, if the rotation track surface of the rotation member has an appropriate inclination angle with respect to a predetermined reference plane, the rotation eccentric position of the rotation member becomes the reference plane according to the rotation of the rotation member. Contact and separate from each other. Therefore, for example, if the rear wheel steering mechanism is driven only in the direction perpendicular to the predetermined reference plane, the rotational eccentric position associated with the rear wheel steering mechanism will move away from or contact the reference plane. The rear wheel steering mechanism steers the rear wheels accordingly.

Therefore, when the inclination angle of the turning track surface of the turning member with respect to the reference surface is adjusted, the relationship between the steering angle of the steering wheel and the separation / contact of the turning eccentric position with respect to the reference surface, that is, the turning ratio of the rear wheels is controlled. Will be done. For example, when the inclination angle is 0, the rotational eccentric position moves on the reference plane and does not come into contact with or separate from the reference plane depending on the steering angle of the steering wheel, and therefore the rear wheels are not steered. Then, depending on the direction of inclination of the turning track surface (positive or negative of the inclination angle), the rear wheels are in a neutral state, or depending on the magnitude of the inclination angle in one of the same phase and the opposite phase as the front wheels. It is steered at the steering ratio.

As the rear wheel steering means of this conventional example, a fluid pressure type rear wheel steering means that uses hydraulic pressure is considered.

[Problems to be solved by the invention]

By the way, when it is desired to steer not only the front wheels but also the rear wheels by the front-rear wheel steering device as described above, the rear wheel steering means by the fluid pressure facilitates the rear wheel steering control and the rear wheel steering mechanism. This is advantageous in that the front wheel steering mechanism is less likely to be affected by this failure when the rear wheel steering mechanism fails because the front wheel steering mechanism is not directly connected.

When the rear wheel steering mechanism fails, it suffices that the vehicle can be steered only by the front wheel steering mechanism. Therefore, it is necessary to ensure the steering performance of the vehicle only by the front wheel steering mechanism when the rear wheel steering mechanism fails. There is.

For this purpose, it is only necessary to complanance steer the rear wheels when the rear wheel steering mechanism fails. As a means for complanance steering the rear wheel, a means for biasing the rear wheel toward its neutral position by means of an elastic material such as a spring (rear wheel neutral biasing means) can be considered.

Therefore, the fluid pressure supplied from the fluid pressure pump is adjusted by the control valve that operates according to the steering angle of the front wheels, and the rear wheels are steered by supplying this fluid pressure to the actuator for steering the rear wheels. A configuration in which the rear wheel neutral biasing means is provided in the front and rear wheel steering device is conceivable.

However, when the rear-wheel steering actuator by fluid pressure is provided and the rear-wheel neutral urging means is provided as described above, the urging force of the rear-wheel neutral urging means needs to be increased to some extent to ensure that the rear wheel is neutrally held. Therefore, the above actuator turns the rear wheels against the biasing force. When the vehicle is stopped while the steering wheel (steering wheel) is in the steering state (all positions except neutral), the rear wheels are steered according to the steering state of the steering wheel. Fluid pressure sufficient to oppose the urging force of the wheel neutral urging means will continue to be applied.

Therefore, if the vehicle is stopped for a long time, the compressed fluid supplied to the actuator may be heated, and seizure may occur in the fluid pressure pump or the like. Further, since the fluid pressure pump and the like are always operated, the energy of the vehicle is lost by the amount of the operation of the fluid pressure pump and the like, which is not preferable.

The present invention is intended to solve such a problem, and pays attention to the fact that the power steering fluid pressure in the power steering device of the front wheel steering mechanism is not supplied unless steering force is applied to the steering wheel. , By providing a relief valve that operates in response to the power steering fluid pressure and can stop the supply of hydraulic pressure to the rear wheel steering actuator when the power steering fluid pressure is not being applied to the power steering, An object of the present invention is to provide a front and rear wheel steering device for a vehicle, which is capable of preventing damage to a fluid pressure pump and the like and energy loss when the vehicle is stopped.

[Means for solving problems]

Therefore, the vehicle front and rear wheel steering system of the present invention includes a front wheel steering mechanism connected to the steering mechanism and a rear wheel steering mechanism that is interlocked with the steering mechanism, and the front wheel steering mechanism is connected to the steering wheel. A fluid pressure type front power steering device that operates by supplying fluid pressure according to the applied force is provided, and a rear wheel steering actuator that operates by receiving fluid pressure from a fluid pressure supply system is provided in the rear wheel steering mechanism. Provided, the fluid pressure supply system comprises a fluid pressure pump for sucking and discharging the fluid in the reservoir and a fluid pressure supply flow passage for supplying fluid pressure from the fluid pressure pump, wherein the flow passage, A control valve that regulates the supply of fluid pressure from the fluid pressure pump to the actuator according to the steering angle of the front wheels to control the operation of the actuator, and is located upstream of the control valve. When the fluid pressure from the fluid pump is urged to relieve the reservoir side and the fluid pressure generated by the front power steering device is received as pilot pressure, the fluid pressure from the fluid pressure pump is resisted against the urging force. Is provided to the control valve side, and a front wheel steering mechanism interlocking relief valve is interposed.

[Action]

In the above-described vehicle front and rear wheel steering device of the present invention, when the steering mechanism is operated, the front wheel steering mechanism and the rear wheel steering mechanism operate to steer the front wheels and the rear wheels. At this time,
In the front wheel steering mechanism, the front wheels are steered by being urged by the power steering device, and in the rear wheel steering mechanism, the rear wheel steering actuator controls the fluid pressure from the fluid pressure pump of the fluid pressure supply system by the control valve. After being adjusted, the fluid is supplied through the fluid pressure supply flow path, and appropriately operates in conjunction with the steering mechanism, and the rear wheels are steered by the operation of the actuator.

At this time, the front wheel steering mechanism interlocking type relief valve interposed upstream of the control valve of the fluid pressure supply passage receives the fluid pressure generated by the front power steering device as pilot pressure from the fluid pressure pump. Is supplied to the control valve side, but if the fluid pressure is not generated in the front power steering device, the pilot pressure is not received and the fluid pressure from the fluid pump is relieved to the reservoir side by the biasing force.

By the way, in the front power steering device, for example, pressure is generated when steering force is applied during operation of the steering wheel, but steering force is applied even if a steering angle is applied to the steering wheel (even if it is not neutral). If not, pressure will not be generated.

Therefore, when no force is applied to the steering wheel, no fluid pressure is generated in the power steering device, and pilot pressure is not supplied to the front wheel steering mechanism interlocking relief valve. The interlocking relief valve is driven by an urging force to relieve the fluid pressure from the fluid pump to the reservoir side, and the flow path is closed. As a result, the supply of fluid pressure to the rear wheel steering actuator is stopped, and the fluid pressure load on the rear wheel steering actuator is removed.

〔Example〕

A front and rear wheel steering system for a vehicle will be described below as an embodiment of the present invention with reference to the drawings. FIG. 1 is a system diagram of a fluid pressure supply system for supplying a fluid pressure to a rear wheel steering actuator, and FIG. FIG. 3 is a vertical cross-sectional view of the valve, FIG. 3 is a schematic perspective view showing the entire structure thereof, FIG. 4 is a vertical cross-sectional view showing the bevel gear assembly thereof, and FIG. 5 is a perspective view showing the cylindrical cam mechanism thereof. FIG. 6A is a longitudinal sectional view of the cylindrical cam mechanism, FIG. 6B is a lateral sectional view of the cylindrical cam mechanism, and FIG. 7 is a power transmission state of the cylindrical cam mechanism. Graphs and Figs. 8 and 9 are graphs showing the rear wheel steering characteristics of the cylindrical cam mechanism, Fig. 10 (a) is a vertical longitudinal sectional view of the rotary valve, and Fig. 10 (b) is the rotary valve. Part 11 of the horizontal vertical section
FIG. 10A is a sectional view taken along the line XIa-XIa of FIG. 10A, FIG. 11B is a sectional view taken along the line XIb-XIb of FIG. 10A, and FIG. FIG. 10 (a) is a sectional view taken along the line XIc-XIc, FIG. 11 (d) is a sectional view taken along the line XId-XId of FIG. 10 (a), and FIGS. 12 (a) and 12 (b) are the rotary valves thereof. The operating state of the 11th
FIG. 12 (c) is a cross-sectional view shown in correspondence with FIG. 11 (a), FIG. 12 (c) is a cross-sectional view showing the operating state of the rotary valve in correspondence with FIG. 11 (b), and FIG. Fig. 11 (c) is a cross-sectional view showing the operating state of the rotary valve in correspondence with Fig. 11 (c).
FIG. 13 is a longitudinal sectional view of the rear power cylinder, FIG. 14 is a graph showing assembly characteristics of the nonlinear spring mechanism of the rear power cylinder, FIG. 15 is a graph showing output characteristics of the rear power cylinder, and FIG. 16 is FIG. 17 (a) is a schematic perspective view showing the rear suspension part as a center, FIG. 17 (a) is a sectional view taken along the arrow XVIIa-XVIIa in FIG. 16 showing the parallel link mechanism, and FIG. a) XVIIb-XVIIb arrow sectional view, FIGS. 18 (a) to 18 (c) are schematic operation diagrams showing the operation of the parallel link mechanism in comparison with other mechanisms, and FIG. 19 (a) is 19 (b) is a plan view showing a partially broken in-phase / reverse-phase conversion mechanism provided in the wheel turning ratio adjusting mechanism thereafter.
Is a side view showing a part of the in-phase and anti-phase conversion mechanism in a broken manner,
FIG. 19 (c) is a rear elevational view showing a part of the in-phase anti-phase conversion mechanism cut away, and FIGS. 20 (a) to 20 (c) are all for explaining the operation of the in-phase anti-phase conversion mechanism. Perspective view of the 21st
The drawing is a system diagram of a fluid pressure supply system that supplies a fluid pressure to a rear wheel steering actuator showing a modified example of the relief valve. The front / rear wheel steering system for a vehicle according to this embodiment is provided for a four-wheeled vehicle.

As shown in FIG. 3, the front-rear wheel steering system for a vehicle includes a steering mechanism ST, a front-wheel steering mechanism FM, a rear-wheel steering ratio adjusting mechanism RC, and a rear-wheel steering mechanism RM.

The steering mechanism ST is composed of a steering wheel 1, a steering shaft 1b, other shafts and joints, and the lower end portion thereof is connected to the bevel gear assembly 3.

A front power steering gear box 1a of a front power steering device FP provided in the front wheel steering mechanism FM is interposed between the bevel gear assembly 3 and the steering shaft 1b.
By operating a front power cylinder (not shown) of the front power steering device FP, the tie rods 1c, 1c can be driven and the front wheels 2a, 2a can be steered while being biased by the front power steering device FP.

The bevel gear assembly 3 is connected to the cylindrical cam mechanism 5 of the rear wheel steering ratio adjusting mechanism RC via the control shaft 4.

The rear wheel turning ratio adjusting mechanism RC is composed of a cylindrical cam mechanism 5 and an in-phase reverse phase converting mechanism 6 interposed between the cylindrical cam mechanism 5 and the rear wheel turning mechanism RM. The in-phase / negative-phase conversion mechanism 6 is provided with a stepping motor assembly 7 as an actuator. A controller C that controls the vehicle speed sensor S is connected to the stepping motor assembly 7.

Further, the rear wheel steering mechanism connected to the in-phase / reverse-phase conversion mechanism 6
RM is a rotary valve 8 controlled and operated by the in-phase / reverse-phase conversion mechanism 6, a hydraulic pressure generation pump (engine pump in this embodiment) 74 as a fluid pressure pump, and a hydraulic pressure supply passage as a fluid pressure supply passage. Fluid pressure supply system FS consisting of 77a etc.,
A fluid pressure discharge system FD including a rotary valve 8, a drain tank (reservoir tank or reservoir) 76, a hydraulic pressure discharge passage 77a, etc., a rear power cylinder 9 connected to the rotary valve 8, and a rear power cylinder 9 connected to the rear power cylinder 9. And a rear suspension 10 that steers the rear wheels 2b while being driven by the power cylinder 9.

The tie rods (piston rods) 92, 92 protruding from the rear power cylinder 9 are connected to the trailing arm 10a of the rear suspension 10, and when the trailing arm 10a turns as the rear power cylinder 9 expands and contracts, Rear wheel 2b via this trailing arm 10a
Is being steered.

Next, the characteristic parts of the front and rear wheel steering system for a vehicle of this embodiment will be described in detail.

First, the front wheel steering mechanism FM and the steering shaft 1b
The bevel gear assembly 3 that connects the control shaft 4 with the control shaft 4 will be described with reference to FIG.

The front wheel steering mechanism FM is composed of a rack and pinion device RP and a front power steering device FP.

The rack and pinion device RP is a pinion 31 provided on a first shaft 31 that is directly connected to the steering wheel 1.
The a and the tooth surface 21a formed on the front wheel steering shaft (rack) 21 that is connected to the tie rods 1c, 1c are in mesh with each other, and the rack and pinion device RP allows the front wheel 2
A and 2a are steered.

Further, the front power steering device FP uses a power cylinder (front power cylinder) (not shown) that operates by hydraulic pressure as a fluid pressure. As shown in FIG. 3, a front power steering hydraulic supply pump (hydraulic pump) is used. ) A hydraulic pressure from 75 is applied to operate a piston (not shown) mounted on the front power cylinder. By driving this piston, steering of the front wheels 2a, 2a is urged.

Next, the bevel gear assembly 3 will be described.
As shown in FIG. 4, in the bevel gear assembly 3,
A first bevel gear 32 is attached to the lower end of the first shaft (pinion shaft) 31. The first shaft is connected to the steering shaft 1b and is provided so as to pass through the inside of the front power steering gear box 1a. A resin pin 37 for preventing rotation is interposed between the first shaft 31 and the first bevel gear 32, and the resin pin 37 is destroyed in an emergency, so that the first shaft 31 and The connection with the first bevel gear 32 is released.

Then, below the first bevel gear 32, a second shaft 33 having a second bevel gear 34 that meshes with the first bevel gear 32 is provided in a direction substantially orthogonal to the first shaft 31. . Further, the rear end of the second shaft 33 is connected to the control shaft 4 via a universal joint 35.

Each shaft 31, 33, 21 and bevel gear 32, 34 is covered by a casing 30, and at the end of the casing 30, the casing 30 and the first and second shafts 31, 33.
A seal 38 is interposed between the and. Also the casing
Bearings 36a, 36b, 36c and 36d are interposed between the 30 and the first and second shafts 31 and 32 at important points.

Reference numeral 38a in FIG. 4 indicates a sealer for sealing the joint portions of the casing portions forming the casing 30, and reference numeral 35a indicates a dust cover for covering the universal joint.

Next, the cylindrical cam mechanism 5 and the forward / reverse rotation converting mechanism 6 which constitute the rear wheel turning ratio adjusting mechanism RC will be described.

First, the cylindrical cam mechanism 5 that converts the rotational movement of the control shaft 4 into a linear movement will be described.
As shown in the figure, the cylindrical cam mechanism 5 has a casing
Cylindrical cam 51 supported by 50 through bearings 56, 56
And a slider 52 mounted on the outer periphery of this cylindrical cam 51.
And a slide rod 54 whose front end is connected to the slider 52 and whose rear end is connected to the in-phase / reverse-phase converting mechanism 6.

That is, as shown in FIGS. 6A and 6B, the cylindrical cam
51 is the control shaft 4 by the spring pin 55
Is coaxially connected to the control shaft 4 and can rotate integrally with the control shaft 4 inside the casing 51. A cam groove 53 is formed on the outer circumference of the cylindrical cam 51, and a slider 52 is slidably mounted inside the cam groove 53. This cam groove 53 is a spiral groove for sliding.
53a and arcuate grooves 53b and 53c formed continuously at the front and rear ends of the spiral groove 53a. The arcuate grooves 53b, 53c are formed along a plane orthogonal to the rotation axis of the cylindrical cam, and serve as a limit output mechanism 5A that stops the slider 52 from sliding and suppresses an increase in output to the rear wheels. Has been formed.

Further, in the neutral position of the steering wheel 1, the slider 52
However, as shown in FIG. 5, it is set to be located at the midpoint of the spiral groove 53a.

In addition, between the outer circumference of the slider 52 and the inner circumference of the cam groove 53,
A bearing 59 is provided so that the slider 52 can be easily slid by the bearing 59. Also,
The rear end of the control shaft 4 is supported by the casing 50 by a bearing 57.

The tip of a slide rod 54 is inserted into the base portion 52a of the slider 52, and the slider 52 is fixed to the slide rod 54 by nuts 58, 58 screwed onto the slide rod 54. Further, the slider 52 is such that a cylindrical sliding member 52b mounted on the base portion 52a is brought into sliding contact with an inner wall of a slide chamber 50a formed in a lower portion of the casing 50, and is guided by the inner wall of the slide chamber 50a. It can slide back and forth smoothly.

Therefore, the relationship between the operation amount of the steering wheel 1, that is, the steering wheel angle, and the amount of advance / retreat of the slide rod 54, that is, the output of the rear wheels is as shown in the graph of FIG. 7, and the slider 52 spirals around its neutral position. When sliding in the groove 53a, the output to the rear wheel increases and decreases linearly according to the steering wheel angle, the steering wheel angle increases, and the slider 52 moves in the arc-shaped groove 53a.
As it slides in b, a constant (or almost constant) output to the rear wheels can be obtained regardless of the steering wheel angle.

Next, the in-phase reverse layer converting mechanism 6 will be described. The in-phase reverse layer converting mechanism 6 is shown in FIGS. 19 (a) to (c) and FIG.
As shown in FIG. (A), a slide direction conversion portion 6A for converting the slide movement of the slide rod 54 of the cylindrical cam mechanism 5 in the front-rear direction into a lateral slide movement at an appropriate ratio by the disc-shaped cam 61, and a slide direction conversion portion 6A. A rear wheel steering force transmission unit that receives a lateral slide movement generated in the slide direction conversion unit 6A and transmits this movement to a rotary valve 8 for rear wheel hydraulic steering.
6B and the disc type cam 61 are rotated to rotate the disc groove of the disc type cam 61.
By changing the direction of 61a, the slide direction conversion unit 6
And a cam groove direction adjusting portion 6C capable of adjusting the conversion ratio at A.

Of these, the slide direction conversion portion 6A is the cylindrical cam mechanism 5
A slide pin 62 fixed to the rear end of the slide rod 54 via a pin mounting member 62b, a guide member 63 fixed to a casing 60 having a guide elongated hole 63a into which the slide pin 62 is fitted, and a slide pin A disc-shaped cam 61 having a cam groove 61a on the upper surface to which the lower end of 62 fits, and a casing 6
A slide plate (slide member) 64 is mounted on the shaft 0 so as to be slidable in the lateral direction via a sliding bearing 64b, and rotatably supports a disk-shaped cam 61 via a bearing 64c.

The cam groove 61a of the present embodiment is set to be a straight line passing through the center of the disc-shaped cam 61.

Therefore, the slide pin 62 is guided by the elongated hole 63a and can slide only in the front-rear direction, and the disc-shaped cam 61 receives the movement of the pin 62 via the cam groove 61a. When the cam groove 61a has an angle with respect to the sliding direction of the pin 62 as shown by a chain line in FIG. 19 (a), the disc-shaped cam 61 and the slide are moved along with the sliding of the pin 62 in the front-rear direction. The plate 64 can slide laterally.

A slide ring 62a is attached to the outer periphery of the slide pin 62 to smooth the movement of the pin 62 in the cam groove 61a.

Further, the pin 62 is arranged so as to be positioned at the center of the cam groove 61a, that is, at the center of the disk-shaped cam 61 at the neutral position of the slide rod 54. The rear end of the slide rod 54 provided through the casing 60 has bearings 60a,
It is pivotally supported by the casing 60 via 60a.

Next, the rear wheel steering force transmission portion 6B will be described. The rear wheel steering force transmission portion 6B includes a rack 64a provided on the lower surface of the rear portion of the slide plate 64, a pinion 69 meshing with the rack 64a, and a rear end. It is composed of a pinion shaft 69a connected to the rotary valve 8. Therefore, as the slide plate 64 slides in the horizontal direction, the pinion shaft 69a rotates via the rack 64a and the pinion 64.

Further, the cam groove direction adjusting unit 6C will be described. The cam groove direction adjusting unit 6C includes a stepping motor assembly 7 controlled by a controller C that sends a control signal based on a signal from a vehicle speed sensor S, and the stepping motor assembly 7. 7, a spline shaft 66 connected to the motor shaft of the stepping motor 7b, and a bevel gear 67 on the stepping motor side mounted on the spline shaft 66 so as to be able to move forward and backward.
And a cam-side bevel gear 65 that is attached to the lower part of the disk-shaped cam 61 and meshes with the bevel gear 67.

A key groove 67a is formed in the bevel gear 67 on the stepping motor side, and the key groove 67a is slidably engaged with a key 66a formed on the spline shaft 66, and the bevel gear 67 is connected to the spline shaft 66. And it can always rotate together. In addition, the bevel gear 67 is mounted on the mounting plate 64d provided at the bottom of the slide plate 64 with the bearing 6
Bevel gear 67 is slide plate supported by 7b.
With 64, it can slide in the axial direction of the spline shaft 66.

Further, the stepping motor assembly 7 is provided with an encoder 7a connected to the controller C, and the stepping motor 7b is feedback-controlled.

Next, a rear power cylinder 9 as a rear wheel steering actuator constituting the rear wheel steering mechanism RM, a hydraulic pressure supply system (fluid pressure supply system) FS for supplying hydraulic pressure as a fluid pressure to the rear power cylinder 9, and a rear power The hydraulic pressure discharge system (fluid pressure discharge system) FD for discharging the hydraulic pressure from the cylinder 9 and the rear suspension 10 will be described.

First, the hydraulic pressure supply system FS and the hydraulic pressure discharge system FD will be described.

As shown in FIGS. 1 and 3, the hydraulic pressure supply system FS includes a hydraulic pressure supply pump (engine pump) 74 as a fluid pressure pump, a hydraulic pressure supply pump (hereinafter referred to as a hydraulic pump) 74, and a rear power cylinder 9. And a rotary valve 8 as a control valve for controlling the operation of the repower cylinder 9.

The hydraulic pressure discharge system FD includes a drain tank (reservoir) 76, a hydraulic pressure discharge oil passage 77 b interposed between the drain tank 76 and the rear power cylinder 9, and a rotary valve 8.

The rotary valve 8 is provided near the rear power cylinder 9 on the downstream side of the oil passage 77a, receives the steering force from the rear wheel steering force transmission section 6B of the in-phase / reverse-phase conversion mechanism 6, and receives the front wheel 2a. It operates according to the steering angle and adjusts the supply of hydraulic pressure from the hydraulic pump 74 to the repower cylinder 9, whereby the operation of the rear power cylinder 9 can be controlled.

Then, in the hydraulic pressure supply oil passage 77a, the hydraulic pressure generated by the front power steering device FP of the front wheel steering mechanism FM, that is, the hydraulic pump 75 to the front power steering device FP.
A front wheel steering mechanism interlocking type relief valve 179 which operates so as to open the oil passage 77a by receiving a pilot hydraulic pressure (fluid pressure) supplied from In addition, between the front power steering device FP and the relief valve 179,
An oil passage 179a for guiding the pilot oil pressure supplied to the front power steering device FP to the relief valve 179 is arranged.

Further, the hydraulic pressure from the hydraulic pump 74 is kept constant between the hydraulic supply oil passage 77a and the hydraulic discharge oil passage 77b which are closer to the hydraulic pump 74 and the drain tank (reservoir) 76 than the relief valve 179 is interposed. In order to maintain the above, an oil pressure adjusting relief valve 180 that returns excessive oil pressure to the drain tank 76 is interposed.

The front wheel steering mechanism interlocking relief valve 179 and the rotary valve 8 provided in the hydraulic pressure supply system FS and the hydraulic pressure discharge system FD will be further described.

As shown in FIG. 2, the front wheel steering mechanism interlocking type relief valve 179 includes a spool valve 181 which is provided in a housing 179A and a tubular valve chamber 182 formed inside the housing 179A so as to be able to move forward and backward. And a return spring 183 that biases the spool valve 181 in one direction.

The housing 179A has a first port P ₁ leading to the valve chamber 182,
Four ports, that is, a second port P ₂ , a third port P ₃ and a fourth port P ₄ , are formed. Of these, the first port P ₁ is an oil for guiding the pilot oil pressure of the front power steering device FP to the relief valve 179. In the path 179A, the second port P ₂ is upstream of the hydraulic pressure supply oil passage 77a, the third port P ₃ is downstream of the hydraulic pressure supply oil passage 77a, and the fourth port P ₄ is the hydraulic pressure discharge oil passage 77b. Are connected to the return oil passages 77c communicating with each.

The outer circumference of the spool valve 181 is provided with a first small diameter portion 181a formed at the tip thereof, a first large diameter portion 181b formed behind the first small diameter portion 181a, and a rear side of the first large diameter portion 181b. The second small diameter portion 181c is formed, and the second large diameter portion 181d is formed behind the second small diameter portion 181c.

A recess 181e is formed at the rear end of the spool valve 181, and the return spring 183 has an inner end surface of the cap 184 that closes the inner end surface of the recess 181e and the hole formed when the valve chamber 182 is processed. It is interposed between and.

Further, inside the spool valve 181, hollow hole portions 181f are formed along the axis of the spool valve 181 so as to open in the first large diameter portion 181b, the second small diameter portion 181c, and the concave portion 181e, respectively.

On the other hand, the valve chamber 182, a first oil chamber communicated with the first port P ₁ and 1
82a, a second oil chamber 182b that communicates with the second port P ₂ and the third port P ₃ , a third oil chamber 182c that communicates with the fourth port P ₄ , a rear end of the spool valve 181 and the cap 184. 4th oil chamber between
182d and a fifth oil chamber 182e between the first oil chamber 182a and the second oil chamber 182b are formed.

A reduced diameter portion is formed between the oil chambers. That is, between the first oil chamber 182a and the fifth oil chamber 182e, the first reduced diameter portion 182f with which the O-ring 185a attached to the first small diameter portion 182a on the outer periphery of the spool valve 181 can always slide is provided. 5 oil chambers
Between the 182e and the second oil chamber 182b, a second reduced diameter portion 182g with which the first large diameter portion 181b of the spool valve 181 can always slide is provided.
A third reduced diameter portion 182h capable of sliding contact with the first large diameter portion 181b of the spool valve 181 is provided between the 182b and the third oil chamber 182c, and further, a third reduced diameter portion 182h.
A fourth reduced diameter portion 182i is formed between the oil chamber 182c and the fourth oil chamber 182d so that the second large diameter portion 181d of the spool valve 181 can always be in sliding contact therewith.

The spool valve 181 is adapted to be able to retract between the forward position shown by the solid line in FIG. 2 and the retracted position shown by the chain line, and from the first port P ₁ into the first oil chamber 182a. When the hydraulic pressure is supplied, the return pulling 183 contracts to take the retracted position, and when the hydraulic pressure is not supplied from the first port P ₁ into the first oil chamber 182a, the return pulling 183 extends to take the forward moving position. Becoming

At the forward position of the spool valve 181, the first large diameter portion 181b of the spool valve 181 is separated from the third reduced diameter portion 182h of the valve chamber 182, and the second
The second through the gap between the small diameter portion 181c and the third reduced diameter portion 182h
The oil chamber 182b and the third oil chamber 182c communicate with each other, and when the spool valve 181 is in the retracted position, the first large diameter portion 181b of the spool valve 181 has the valve chamber 1
The third reduced diameter portion 182h of 82 is brought into sliding contact with the second small diameter portion 181c and the third reduced diameter portion 182h to be closed, and the second oil chamber 182b and the third oil chamber 18
The phase shape of the spool valve 181 and the valve chamber 182 is set so as not to communicate with 2c.

In addition, in the hollow hole 181f of the spool valve 181, the second small diameter portion 1
Oil is supplied through an opening portion with respect to 81c, and further, from this hollow hole portion 181f to the fifth oil chamber 182e through an opening portion to the first large diameter portion 181b, and a fourth oil chamber 182d through an opening portion to the recess 181e. Oil is supplied to each. The oil supplied to the fifth oil chamber 182e slides between the O-ring 185a attached to the first small diameter portion 182a on the outer circumference of the spool valve 181 and the first reduced diameter portion 182f of the valve chamber 182. The oil supplied to the fourth oil chamber 182d is the O-ring 1 mounted on the outer circumference of the cap 184.
This is for smooth sliding contact between 85b and the inner peripheral surface of the fourth oil chamber 182d of the valve chamber 182.

Further, reference numeral 185 in FIG. 2 indicates a mounting hole portion such as a bolt hole for mounting the spool valve 179 to a predetermined position of the vehicle.

Next, the rotary valve 8 will be described.

As shown in FIGS. 10 (a), (b), and FIGS. 11 (a) to (d), the rotary valve 8 includes a housing 80 and a housing 80 in which a longitudinal axis is relative to the housing 80. A spool 81 rotatably mounted, a rotary shaft 82 rotatably mounted in the spool 81 with respect to the spool 81 via a first ring 84a and a second ring 84b, and a spool 81 by a pin 83a. And a follow-up shaft 83 mounted so as to rotate integrally with the rotary shaft 82, and an inner shaft 85 provided in hollow portions 82g and 83b formed inside the follow-up shaft 83.

The housing 80 includes a front housing 80a, an intermediate housing 80b, and a rear housing 80c, which are oil-tightly fitted to each other via an O-ring 88c, respectively, and further a bolt / nut 80e.
And a valve chamber 80d is formed inside the housing 80. In addition, the intermediate housing 80b
X port (port leading to the right oil chamber 90b of the rear power cylinder 9 described later) P _P and Y port (port leading to the left oil chamber 90a of the rear power cylinder 9) P _Y are formed in the upper part of the A P port (pressure port) P _P is formed, and an R port (return port) P _R is formed in the lower portion of the rear housing 80c. Further, annular recesses 80f and 80g are formed in the front and rear portions of the intermediate housing 80b, respectively. In addition, P port P _P and R port P _R are both connected to an external oil tank (not shown),
In particular, a pump (not shown) is interposed in the oil flow path to the P port P _P.

Spool provided inside such housing 80
The front part of 81 is rotatably supported by the front housing 80a by a bearing 87b, and the rear part thereof is rotatably supported by the rear housing 80e by a bearing 87b. A first annular oil chamber 89a is formed by the outer peripheral surface of the spool 81, the front housing 80a, and the annular recess 80f of the intermediate housing 80b, and the outer peripheral surface of the spool 81, the rear housing 80c, and the intermediate housing 80b. From the annular recess 80f to the second annular oil chamber 89
b is formed.

Then, in the lower portion of the spool 81, a first opening 81a for communicating the inside of the spool with the first annular oil chamber 89a and a second opening 81b for communicating the inside of the spool with the second annular oil chamber 89b.
And are provided. An annular groove 81c communicating with the P port P _P is formed in the middle of the first and second openings 81a, 81b on the outer circumference of the spool 81, and a third opening 81d is provided in the annular groove 81c. Has been. Spool 8
At the outer circumference before and after the first annular groove 81c, the intermediate housing 80b
O-rings 88d, 88d for sealing that are in close contact with are attached.

A follow-up shaft 83 is fitted inside the rear end of the spool 81, and the two 81, 83 are connected by a pin 83a so as to rotate integrally. The follow-up shaft 83 is axially supported by the rear housing 80c by a bearing 87c, and a seal ring 88 that seals between the housing 80 and the follow-up shaft 83 is mounted behind the bearing 87c.

Further, an annular oil chamber 89c is formed in front of the bearing 87c of the rear housing 80c, and the spool 81 and the follower shaft 83 have the annular oil chamber 89c and the follower shaft 83c.
An opening 83c is formed to communicate with the inside of the. The annular oil chamber 89c communicates with the R port P _R.

Furthermore, inside the spool 81, the rotary shaft 82
Are provided via a first ring 84a and a second ring 84b. At the front end of this rotary shaft 82,
A pinion shaft 69a of the in-phase / reverse-phase conversion mechanism 6 is formed, and a pinion 69 that meshes with the rack 64a is mounted on the pinion shaft 69a. The front portion of the pinion shaft 69a is supported by the front housing 80a via a bearing 87a. At the same time, the rear portion is pivotally supported by the follow-up shaft 83 via the bearing 87a.
The outer peripheral surface of the rotary shaft 82 can be brought into slidable contact with the inner peripheral surfaces of the spool 81 or the first and second rings 84a and 84b.
When the rotary shaft 82 is in the neutral state as shown in Fig. 5, a gap is created between the outer peripheral surface of the rotary shaft 82 and the inner peripheral surfaces of the spool 81 or the first and second rings 84a, 84b. ing.

In the present embodiment, the rotary shaft 82 and the pinion shaft 69a are coaxially and integrally formed, but a universal joint or another shaft is interposed between the rotary shaft 82 and the pinion shaft 69a. May be.

Further, on both sides of the rotary shaft 82, a first recess 82a, a second recess 82d, and a first communication port are formed.
82c and a second communication port 82d are provided, and the first and second communication ports 82c and 82d are both rotary shafts 82.
A hollow portion 82g formed along the axis of the rotary shaft 82 communicates with the outside of the rotary shaft 82. A first partition wall 82e and a second partition wall are provided between the first recess 82a and the first communication port 82c and between the second recess 82b and the second communication port 82d, respectively. It is separated from each other by 82f.

The first ring 84a and the second ring 84b are both fitted into the recess 81e formed in the inner peripheral surface of the spool 81 by press fitting or the like, and are appropriately separated from each other. In this separated portion, the first recess 82 of the rotary shaft 82 is
A communication chamber 84c capable of communicating the a with the second recess 82b is formed. Further, the upper and lower parts of the first ring 84a and the second ring 84b have respective rings 84a, 84b.
84d, 84e, 84f, 84g are formed to connect the inside and the outside of the.

Of these, the opening 84e of the first ring 84a is located at the front part of the rotary shaft 82 and communicates with the first opening 81a of the spool 81. The opening 84g of the second ring 84b is located at the rear of the rotary shaft 82 and communicates with the second opening 81b of the spool 81.

On the outer circumference of the rotary shaft 82, O-rings 88a, 88b, 88c that seal between the front casing 80a, the first ring 84a and the second ring 84b are mounted. Further, the pinion 69 and the pinion shaft 69a of the rotary shaft 82 are coupled by a pin 69b so as to be integrally rotatable.

An inner shaft 85 is provided inside the hollow portion 82g of the rotary shaft 82 and the hollow portion 83b formed in the follow-up shaft 83. This inner shaft 85
A front end of the pin 85a is fixed to the rotary shaft 82, and an appropriate gap is formed between the outer peripheral surface of the inner shaft 85 and the inner peripheral surface of the hollow portion 82g of the rotary shaft 82.

An O-ring 88f is attached to the rear end of the inner shaft 85 to seal the rotary sliding portion between the inner shaft 85 and the follow-up shaft 83.

The internal shaft 85 is once fixed and positioned on the follow-up shaft 83 by the pin 83a and then assembled, but the pin 83a is removed after the assembly.

The rotary shaft 82 is shown in FIGS. 11 (a) to 11 (c).
As shown in, the first recess 82a and the second recess 8 are provided on the left and right.
The state in which 2b is positioned is a neutral state, and when the pinion 69 that rotates by receiving the steering force from the rear wheel steering force transmission unit 6B of the in-phase / negative-phase conversion mechanism 6 by the pinion 69 that meshes with the rack 64a, The rotary shaft 82 is designed to rotate. The rotation angle θ of the rotary shaft 82 [see FIG. 12 (a)] is θ = −150 ° to +150.
It is set within the range of °.

Further, an unillustrated interlocking mechanism such as a rack and pinion is provided between the follow-up shaft 83 and a piston 91 or a piston rod 92 of a rear power cylinder 9 described later, and the follow-up shaft 83 is operated by the rotary valve 8. The rear power cylinder 9 rotates according to the movement of the piston rod 92.

That is, the follow-up shaft 83 follows the movement of the rotary shaft 82 and rotates in the same direction by the same angle as the rotation angle θ of the rotary shaft 82.

Next, the rear power cylinder 9 that drives the rear wheel by advancing and retracting the trailing arm 10a of the rear suspension 10 while expanding and contracting under the hydraulic pressure from the rotary valve 8 will be described.

This rear power cylinder 9 is, as shown in FIG. 13, a cylinder body 90 having a left oil chamber 90a and a right oil chamber 90b to which hydraulic pressure is supplied or discharged by the operation of a rotary valve.
And a piston 91 which is provided inside the cylinder body 90 so as to be able to move forward and backward and divides the inside of the cylinder body 90 into a left oil chamber 90a and a right oil chamber 90b; It is composed of piston rods (tie rods) 92, 92 penetrating left and right.

Caps 93a and 93b are mounted on the left and right of the cylinder body 90, and the piston rods 92 and 92 are mounted on the caps 93a and 93b.
Penetrates through the hole provided in the. Also, the cylinder body
An annular convex portion 90c protruding inward is formed at the center of the inner peripheral surface of 90, and the piston 91 is configured to move forward and backward while sliding left and right inside the annular convex portion 90c via a pipe 94. Is attached to.

Annular rubber springs 95a, 9ab are provided between the left and right piston rods 92, 92 of the piston 91 and the pipe 94. Further, the outer sides of the rubber springs 95a, 95b are directed outward. Protruding stoppers 96a, 96
Annular plates 97a, 97b provided with b are provided so as to be slidable inside the left oil chamber 90a or the right oil chamber 90b.

Coil springs 98a and 98b are provided between the outer surfaces of the plates 97a and 97b and the inner surfaces of the caps 93a and 93b, respectively.
Is installed. The coil springs 98a and 98b are softer and have a lower spring constant than the rubber springs 95a and 95b, and two types of springs 98a and 98 having different spring characteristics are used.
The nonlinear spring mechanism 9A is configured by mounting b and 95a, 95b in series with the piston 91.

When the piston 91 is in the neutral state, the left and right end surfaces of the annular convex portion 90c and the left and right end surfaces of the pipe 94 and the rubber springs 95a and 95b are set to be flush with each other, and
Since an appropriate preload (compressive load in this embodiment) F ₁ is applied to the coil springs 98a and 98b, the plates 97a and 97b are urged by the coil springs 98a and 98b when the piston 91 is in the neutral position. The annular projection 90c and the pipe 9
4, It is in contact with each end surface of the rubber springs 95a, 95b.

Therefore, the hydraulic pressure inside the left oil chamber 90a and the right oil chamber 90b is adjusted, and the piston 91 exerts a force on the hydraulic pressure to the left or right, and the force due to this hydraulic pressure is applied to the coil springs 98a, 98a.
When the preload F ₁ on b is exceeded, the coil springs 98a, 98b are also deformed for the first time.

It should be noted that, as shown in the graph of FIG. 14, the magnitude of this preload is such that when the stroke of the piston 91 exceeds (+ S ₁ ) or (−S ₁ ), the coil springs 98a, 98 are not for the first time.
b is set to be deformed. Within the stroke of the piston in the opposite of _{(-S 1 ~ + S 1)} , is adapted to exert a spring reaction force to deform rubber spring 95a, 95b is, the non-linear spring mechanism 9A is a rear power cylinder When the hydraulic pressure to 9 fails, it is possible to secure a certain steering rigidity by the action of the rubber springs 95a and 95b having high rigidity, and to reduce the steering force required at a large steering angle. Range of the stroke (-S ₁ ~ + S _1), at the time of hydraulic failure, even if an attempt is steered rear wheel 2b and lateral force is applied to the rear wheel 2b by the body of the swing, etc., the rubber spring 95a, 95b is reliably It is set as a range that can work to return the rear wheel 2b to the neutral state.

And the assembly characteristics of such a non-linear spring mechanism 9A (characteristics of spring reaction force with respect to cylinder stroke)
Is a rubber spring 95a, 95b, a coil spring 98a, 9
The action of 8b and stoppers 96a, 96b is shown by the solid line in FIG.

The output characteristic of the rear power cylinder 9 corresponding to this is shown by the solid line in FIG.

Next, the rear wheel 2b is driven by the rear power cylinder 9.
Explaining the rear suspension 10 that steers
As shown in FIGS. 3 and 16, the hub carrier 2b 'of the rear wheel 2b is
Chassis member 12 via upper and lower lateral links 10b, 10b
It is supported so that it can be steered. Although not shown, the lateral links 10b, 10b are pivotally attached to the chassis member 12 at their circular ends.

Further, one end of a trailing arm 10a is coupled to the hub carrier 2b 'of the rear wheel 2b, and the rear wheel 2b is steered according to the movement of the trailing arm 10a.

The front end of each trailing arm 10a is coupled to and supported by a chassis member 12 via a parallel link mechanism 11. Further, since the base end of the parallel link mechanism 11 is pivotally supported by the chassis member 12 and the tip end thereof is rotatable within a certain range, the trailing arm 10a pivots the tip end of the parallel link mechanism 11 appropriately. While making it possible, it is possible to turn around one end on the rear wheel 2b center.

The parallel link mechanism 11 will be described in more detail.
As shown in the drawings and FIGS. 17 (a) and 17 (b), the parallel link mechanism 11 includes a pair of first rotary shafts 11d and 11d on the base end side pivotally attached to the chassis member 12 via a pipe 11g, A pair of parallel link uppers 11a, 11 mounted above and below the rotating shafts 11d, 11d and projecting rearward of the chassis member 12 are provided.
a and a pair of parallel link lowers 11b, 11b, and a pair of second rotating shafts provided so as to couple the tip ends of the parallel link uppers 11a, 11a and the parallel link lowers 11b, 11b.
It is composed of 11e and 11e.

Then, a pair of adapters 11c, 11c is provided rotatably around the pair of rotary shafts 11e, 11e on the tip side, and the adapters 11c, 11c are mutually supported and the tray link arm support pin 11f is mounted. Has been done. Therefore, the support pin 11f can be moved in parallel with the chassis member 12 substantially in the longitudinal direction. The tip of the trailing arm 10a is rotatably coupled to the support pin 11f via an elastic bush 11i made of a rubber material or the like with respect to the vertical stroke. Incidentally, in FIG. 17, reference numeral 11h indicates each rotary shaft 11
The nut for mounting d and 11e is shown.

And the piston rods 92, 92 of the rear power cylinder 9
Is extended as it is and is connected to the tip portion of each trailing arm 10a as a tie rod. Therefore, the trailing arms 10a are respectively driven in the vehicle width direction according to the sliding of the tie rods 92, 92 as the piston rods.

The front and rear wheel steering system for a vehicle as one embodiment of the present invention is configured as described above, and therefore the rear wheel 2b is configured as follows.
Is steered.

That is, as shown in FIG. 3, the steering wheel 1
When you rotate the
Front power steering gearbox 1a through 1b
Is transmitted to the cam mechanism 5 of the rear wheel steering ratio adjusting mechanism RC via the bevel gear assembly 3 and the control shaft c from the gear box 1a.

When the steering wheel 1 is rotated right, the control shaft 4 rotates right when viewed from the rear, and when the steering wheel 1 is rotated left, the controllable shaft 4 rotates left when viewed from the rear.

When the steering wheel 1 is rotated, the front wheel steering mechanism FM moves the front wheels 2 through the rack and pinion RP.
a and 2a are steered. That is, when the pinion 31a of the first shaft 31 directly connected to the steering wheel 1 is rotated, the tooth surface 21a of the front wheel steering shaft (rack) 21 meshing with the pinion 31a is moved in the vehicle width direction for front wheel steering. Tie rods 1c, 1c to which the shaft (rack) 21 is connected
The front wheels 2a, 2a are steered through the front power steering gear box 1a by meshing.

At this time, the front power steering device FP drives the front wheel steering by the rack and pinion RP.

The front wheel steering mechanism FM is composed of a rack and pinion device RP and a front power steering device FP.
In other words, in the front power steering device FP,
As shown in FIG. 3, a power cylinder (front power cylinder) FP, which operates by hydraulic pressure as fluid pressure, receives hydraulic pressure from the hydraulic pump 75 and receives the front power cylinder.
A piston (not shown) mounted inside the FP is designed to move. Then, the moving piston urges the steering of the front wheels 2a, 2a through the front wheel steering shaft 21 and the tie rods 1c, 1c.

When the front wheels are steered, the rotating force of the pinion shaft 31 of the pinion 31a is constantly kept by the bevel gear assembly 3
It is transmitted to the control shaft 4 after being changed in direction through the bevel gears 32 and 34.

In addition, for example, the bevel gear assembly 3 may be overloaded due to a deformation of the control shaft 4 or a malfunction of the rear wheel steering ratio adjusting mechanism RC, the rear wheel steering mechanism RM, etc. At times, the resin pin 37 interposed between the pinion shaft 31 and the first bevel gear 32 is broken by an excessive load. As a result, the connection between the pinion shaft 31 and the first bevel gear is released, the steering force to the rear wheel steering ratio adjustment mechanism RC and the rear wheel steering mechanism RM is cut off, and the front wheel steering only is changed to two-wheel steering. It is like this. Therefore, even in an emergency, there is an advantage that the front wheel steering ability is secured and a constant steering ability is maintained.

When the control shaft 4 rotates, the cylindrical cam mechanism 5 provided at the rear end of the control shaft 4 converts the rotational movement into a linear movement.

That is, as shown in FIG. 5, the control shaft 4
When is rotated, the cylindrical cam 51 integrally connected to the rear end of the control shaft 4 is rotated. By this, it is slidably mounted in the cam groove 53 of the cylindrical cam 51,
As shown in FIG. 6, the slider 52, whose base portion 52a is slidable by being guided by the inner wall of the slide chamber 51a of the casing 50, slides in the cam groove 53 and moves forward and backward together with the slide rod 54. Move forward and backward.

At this time, the limit output mechanism 5A in which the cam groove 53 is composed of the spiral groove 53a in the middle portion and the front and rear circular arc grooves 53b, 53c.
The degree of rotation of the control shaft 4 (hence the steering wheel angle of the steering wheel 1)
The relationship between the slider 52 and the slide rod 54 advancing and retracting (and hence the output to the rear wheels) is shown in the graph of FIG.

That is, with the steering wheel 1 centered at the neutral position, the slider 52 slides in the spiral groove 53a to move back and forth within a certain steering wheel angle to the left and right, and when the steering wheel angle exceeds a certain value, the slider 52 circles. It slides in the arcuate groove 53b and stops at the forward position or the backward position.

Such forward / backward movement of the slide rod 54 is appropriately adjusted and transmitted to the rotary valve 8 via the in-phase / reverse-phase conversion mechanism 6. At this time, in the in-phase / reverse-phase conversion mechanism 6 which is a feature of the present invention. , Each part operates as follows.

That is, first, in the cam groove direction adjusting portion 6C, the direction of the cam groove 61a of the disk-shaped cam 61 is always adjusted according to the speed of the vehicle, and then an appropriate conversion ratio according to the adjusted cam groove 61a. The slide direction conversion section 6A switches the slide movement of the slider 52 in the front-back direction to the movement in the left-right direction (lateral slide movement), and this transverse slide movement is performed by the rotary valve in the rear wheel steering force transmission section 6B. 8 and the rotary valve 8 is controlled.

The operation of the in-phase / negative-phase conversion mechanism 6 will be described in more detail.

In the cam groove direction adjusting unit 6C, the controller C that receives the vehicle speed detection signal detected by the vehicle speed sensor S sends a control signal based on the vehicle speed signal to the stepping motor assembly 7 to drive the stepping motor 7b of the stepping motor assembly 7. Is controlled.

For example, when the vehicle speed is the reference value M, the stepping motor 7b operates so that the cam groove 61a is in a neutral state in which the cam groove 61a is oriented along the front-rear direction of the vehicle body [horizontal state in FIG. 1 (a)]. Drive the spline shaft 66 connected to the motor shaft of the motor 7b, and rotationally adjust the cam 61 via the bevel gears 65 and 67. At this time, in the stepping motor assembly 7, since feedback control is performed by the encoder 7a, the rotation of the cam 61 is appropriately adjusted according to the vehicle speed.

Then, for example, when the vehicle speed is lower than the reference value M and at a medium or low speed, the stepping motor 7b moves the cam 61 so that the cam groove 61a is in the reverse phase inclination state as indicated by reference numeral 61a ″ in FIG. 1 (a). At this time, the degree of inclination of the cam groove 61a is adjusted according to the vehicle speed.

When the vehicle speed is higher than the reference value M, the cam groove is
The stepping motor 7b rotationally adjusts the cam 61 so that 61a is in the in-phase inclining state opposite to that in the middle and low speeds, as indicated by reference numeral 61a 'in FIG. 1 (a). Also at this time, the inclination degree of the cam groove 61a is adjusted according to the vehicle speed.

At this time, the rotational force of the spline shaft 66 depends on the key 66a of the spline shaft 66 and the bevel gear 67 on the stepping motor side.
Bevel gear 6 through the spline engagement part with key groove 67a of
Transmitted to 7.

Next, the slide direction conversion unit 6A will be described. In the slide direction conversion unit 6A, the slide direction is converted via the cam groove 61a that is appropriately adjusted according to the vehicle speed.

For example, as shown in FIG. 2A, when the vehicle speed is the reference value M and the cam groove 61a is in the neutral state, the pin 62 slides back and forth in the cam groove 61a together with the slide rod 54. However, since the cam groove 61a is in the direction coinciding with the sliding direction of the pin 62, the pin 62 does not exert a force on the side wall of the cam groove 61a. Therefore, even if the steering wheel 1 is operated to move the pin 62 forward and backward through the cam mechanism 5, the lateral sliding force is not generated in the cam 61 and the slide plate 64.

Further, as shown in FIG. 2 (b), when the cam groove 61a is in the reverse phase inclination state at a medium or low speed when the vehicle speed is lower than M, the cam 61 and the cam 61 are moved in accordance with the forward / backward movement of the pin 62. The lateral sliding force is transmitted to the slide plate 64. For example,
When the pin 62 moves forward, the cam 61 and the slide plate 64 slide leftward, and when the pin 62 moves backward, the cam 61 and the slide plate 64 slide rightward. In response to this, in the rear wheel steering force transmission section 6B, power is transmitted to the pinion shaft 69a of the rotary valve 8 while converting the sliding motion in the lateral direction into rotational motion.

On the other hand, as shown in FIG. 2 (c), when the cam groove 61a is in the in-phase inclination state at a high speed when the vehicle speed is higher than M, the cam 61 and the slide plate move in accordance with the forward / backward movement of the pin 62. The sliding force in the lateral direction opposite to that at the time of medium and low speed is transmitted to 64. For example, when the pin 62 advances, the cam 61 and the slide plate 64 slide to the right,
When moves backward, the cam 61 and the slide plate 64 slide leftward. In response to this, in the rear wheel steering force transmission section 6B, power is transmitted to the pinion shaft 69a of the rotary valve 8 while converting the sliding motion in the lateral direction into rotational motion.

In the rear wheel steering force transmission portion 6B, the rotary shaft 82 of the rotary valve 8 and the rack 64a of the slide plate 64 are arranged so that the rotary shaft 82 of the rotary valve 8 takes a rotational phase according to the position of the pin 62, that is, the steering wheel angle based on the direction of each cam groove 61a. Pinion 69 mounted on the pinion shaft 69a at the front end of the rotary shaft 82
Power is transmitted through engagement with.

For example, when the vehicle speed is the reference value M, the cam groove 61a is always kept in the neutral state as shown in FIG. 2 (a) regardless of the forward / backward movement of the pin, and the cam 61, the slide plate 64, and the rack 64a.
The pinion shaft 69a is also held in the neutral state through the pinion 69 and the pinion 69. Therefore, the rotary shaft 82 is also in the neutral state as shown in FIGS. 11A to 11C, and the rear wheel 2b is also in the neutral state.

Further, when the vehicle speed is low or medium, the cam groove 61a is shown in FIG. 2 (b).
When the steering wheel 1 is rotated to the right and the pin 62 is moved forward as shown in Figure 5, the slide plate 64 slides to the left and the rack 64a and the pinion 69.
Through the meshing part with the pinion 69 and the pinion shaft 69
a and the rotary shaft 82 are shown in FIG.
As shown in (d), it rotates counterclockwise when viewed from behind.

Conversely, when the steering wheel 1 is rotated counterclockwise and the pin 62 is retracted, the slide plate 64 slides to the right, and the pinion shaft 69a and the rotary shaft 82 together with the pinion 69 rotate clockwise when viewed from the rear.

On the other hand, when the vehicle speed is high, the cam groove 61a is tilted in the same phase as shown in FIG. 2 (c), and when the steering wheel 1 is rotated clockwise to move the pin 62 forward, the slide plate 64 slides to the right and the rack. The pinion shaft 69a and the rotary shaft 82 rotate rightward when viewed from the rear together with the pinion 69 through the 64a and the pinion 69. Conversely, when the steering wheel 1 is rotated counterclockwise and the pin 62 retracts, the slide plate 64 slides left and the pinion shaft 69
The a and the rotary shaft 82 rotate counterclockwise when viewed from the rear.

When the slide plate 64 slides, the bevel gear 67 on the stepping motor side pivotally supported by the mounting plate 64d of the slide plate 64 slides together with the slide plate 64 as shown in FIGS. 2 (a) to (c). Therefore, the mesh state of the bevel gear 67 and the cam-side bevel gear 65 is always secured.

Next, a rear power cylinder 9 as a rear wheel steering actuator that constitutes the rear wheel steering mechanism RM, a hydraulic pressure supply system (fluid pressure supply system) FS for supplying hydraulic pressure as a fluid pressure to the rear power cylinder 9, and a power cylinder. The operation of the hydraulic pressure discharge system (fluid pressure discharge system) FD for discharging the hydraulic pressure from 9 and the rear suspension 10 will be described.

First, the operation of the hydraulic pressure supply system FS and the hydraulic pressure discharge system FD will be described.

The front wheel steering mechanism interlocking relief valve 179 provided in the hydraulic pressure supply system FS and the hydraulic pressure discharge system FD is, as shown in FIGS. 1 and 3, a front power steering device for the front wheel steering mechanism FM.
When receiving the pilot hydraulic pressure (fluid pressure) from the hydraulic pump 75 supplied to the FP, the oil passage 77a is opened.

That is, when the steering wheel 1 is operated to apply a torque (steering force) to the steering wheel 1, the pilot hydraulic pressure from the hydraulic pump 75 is supplied to the front power steering device FP of the front wheel steering mechanism FM in conjunction with this. However, the oil passage 179a is only supplied when this pilot hydraulic pressure is supplied.
Through, the relief valve 179 is driven in the direction to open the oil passage 77a.

In this relief valve 179, as shown in FIG. 2, when hydraulic pressure is supplied from the first port P ₁ into the first oil chamber 182a, a return spring 183 that biases the spool valve 181 to the forward position.
Are contracted, the spool valve 181 takes the retracted position as shown by the solid line, the first large diameter portion 181b of the spool valve 181 slides into contact with the third reduced diameter portion 182h of the valve chamber 182, and the second small diameter portion 181c and the second small diameter portion 181c 3 reduced diameter part
The second oil chamber 182b and the third oil chamber 182c are not communicated with each other because the space between the second oil chamber 182b and the third oil chamber 182c is closed.

As a result, the pressure oil that has entered the second port P ₂ from the hydraulic pump 74 through the upstream side of the hydraulic pressure supply oil passage 77a is retained on the inner wall surface of the second oil chamber 182b and the outer periphery of the first large diameter portion 181b of the spool valve 181. It is supplied to the third port P ₃ side in the high pressure state via the gap between the surface and the surface. And this pressure oil is the third port
From P ₃ is guided to the downstream side of the oil pressure supply oil passage 77a, as shown in the first and third drawing, the pressure port P _P of the rotary valve 8
Is supplied to.

On the other hand, when no torque (steering force) is applied to the steering wheel 1, that is, when the driver does not apply the steering force to the steering wheel 1, the hydraulic pump 75
Pilot oil pressure from the front wheel steering mechanism FM is no longer supplied to the front power steering device FP and the relief valve
179 is driven in a direction in which the hydraulic pressure guided from the hydraulic pressure supply oil passage 77a is relieved to the hydraulic pressure discharge oil passage 77b side.

At this time, in the relief valve 179, the pilot hydraulic pressure for the front power steering device FP is not supplied from the first port P ₁ into the first oil chamber 182a through the oil passage 179a,
Since the pressure in the first oil chamber 182a decreases, the return spring 183 extends due to the restoring force and drives the spool valve 181 to the forward position.

At the forward position of the spool valve 181, the first large diameter portion 181b of the spool valve 181 is separated from the third reduced diameter portion 182h of the valve chamber 182,
The second oil chamber 182b and the third oil chamber 182c communicate with each other through the gap between the second small diameter portion 181c and the third reduced diameter portion 182h. For this reason,
The second port p ₂ communicates with the third port P ₃ via the second oil chamber 182b and the fourth port P ₄ via the third oil chamber 182c.
Communicate with.

Then, the pressure oil supplied to the second port p _2, rather than the second port p ₂ side which communicates with the larger rotary valve 8 of the load,
It is supplied to the side of the fourth port P ₄ leading to a drain tank (reservoir) 76 having no load (or an extremely small load), and is discharged to the drain tank 76 through a return oil passage 77c.

Therefore, for example, if the steering wheel angle is set to the steering state (all states except the neutral state) when the vehicle is stopped, the pilot hydraulic pressure for the front power steering device FP is not supplied, and the relief valve 179 is supplied from the hydraulic pump 74. A relief state is reached in which the hydraulic pressure is discharged to the drain tank 76.
For this reason, unnecessary hydraulic pressure supply to the rear power cylinder 9 that operates against the neutral position urging mechanism is avoided, which contributes to the suppression of energy loss and, even when the vehicle is stopped for a long time, is supplied to the rear power cylinder 9. The applied hydraulic pressure does not heat up, and seizure on the hydraulic pump 74 and the like is prevented.

The hydraulic pressure supplied from the hydraulic pump 74 to the relief valve 179 is adjusted by the hydraulic pressure adjustment relief valve 180, and is constantly maintained in a substantially constant state (constant pressure).

Next, the operation of the rotary shaft 82 when the relief valve 179 opens the hydraulic pressure supply oil passage 77a will be described.

As shown in FIGS. 11A to 11C, when the rotary shaft 82 is in the neutral state, the outer peripheral surface of the rotary shaft 82, the spool 81, or the first and second rings 84a, 84 are formed.
Since there is a gap between the inner peripheral surface of b and the inner peripheral surface of b, the pressure putt P _P communicates with the inside of the first recess 82a and the inside of the second recess 82b of the rotary shaft through these gaps [Fig. a)], and further, from the inside of each of the first and second recesses, the respective gaps and the first and second annular oil chambers 89a, 89a,
The X port P _X and the Y port P _Y communicate with each other through 89b [see respective arrows in FIGS. 11 (b) and 11 (c)]. Also,
The pressure port P _P also communicates with the return port P _R through the hollow portions 82g and 83b [see the arrow in FIG. 11 (d)].

Therefore, the left oil chamber 90a and the right oil chamber of the rear power cylinder 9 are
90b becomes the same pressure, the rear power cylinder 9 is kept in the neutral state, and the rear wheel 2b is also kept in the neutral state.

Then, for example, as shown in FIGS. 12A, 12C, and 12D, considering the case where the rotary shaft 82 rotates counterclockwise by the angle θ, the outer peripheral surface of the rotary shaft 82 is the spool 81 or the first surface. Also, the rotary shaft 82 is in close contact with the inner peripheral surfaces of the second rings 84a and 84b to close the space between the first recess 82a and the second recess 82b of the rotary shaft 82. This allows
The pressure port P _P communicates with the inside of the second recess 82b [see the arrow in FIG. 12 (a)], and communicates with the inside of the second recess 82b through the openings 84e, 81a. It communicates with the Y port P _Y through the annular oil chamber 89a (see the arrow in FIG. 12 (c)). Therefore, the pressure oil from the pressure port P _P is Y
It is supplied from the port P _Y into the left oil chamber 90a of the rear power cylinder 9.

On the other hand, the return port P _R has hollow portions 82g and 83b which are in communication with the return port P _R via the third annular oil chamber 89c and the opening 83c, and the hollow portions 82g and 83b and the second communication portion. Aisle 82d
And the second annular oil chamber 89b communicating with each other through the openings 84g and 81b.
It communicates with and [see the arrow in FIG. 12 (d)]. Therefore, the pressure oil in the right oil chamber 90b of the rear power cylinder 9 is discharged from the X port P _X to the return port P _R.

In this way, since the pressure oil is supplied to the left oil chamber 90a of the rear power cylinder 9 and the pressure oil is discharged from the right oil chamber 90b, the piston 91 in the rear power cylinder 9 is, for example, shown in FIG. 2 (c). It is driven to the right as indicated by an arrow a in the middle.

At this time, the follow-up shaft 83 that follows the rotary shaft 82 while being feedback-controlled by an interlocking mechanism (not shown) moves only in the same phase as the rotary shaft 82 when the piston 91 moves by a required amount, as shown in FIG. 12 (b). It rotates and the supply / discharge of hydraulic pressure to / from the rear power cylinder 9 is stopped.

Then, at this time, the non-linear spring structure 9A provided in the rear power cylinder 9 operates. In other words, as shown in Fig. 14, when the steering wheel angle is large, the coil spring
It suffices if the rear wheel steering force is exerted against 98a, the spring constant of the coil spring 98a is small, and the increase of the spring reaction force is suppressed, so that the rear wheel steering force shown in FIG. The increase in hydraulic pressure supply is suppressed.
Since the non-linear spring structure 9A is provided with stoppers 96a and 96b, the rear wheel steering angle amount is limited as shown in FIG.

When the piston rods (tie rods) 92, 92 are driven rightward together with the piston 91, the left and right trailing arms 1 are moved by the piston rods 92, 92.
Both 0a and 10a drive to the right.

For example, when the steering wheel 1 is rotated to the right at high speed, the control shaft 4 is also rotated to the right when viewed from the rear, which causes the slide pin 62 to slide forward together with the slide rod 54, as shown in FIG. 2 (c). Thus, the pinion 69 rotates counterclockwise through the in-phase / negative-phase conversion mechanism 6 when viewed from the rear, and as shown in FIGS. 12 (a) to (c),
The rotary valve 8 operates and the trailing arm 10
The a and 10a are driven rightward, and the rear wheels 2b are steered rightward in the same phase (in phase) as the front wheels 2a.

Further, when the steering wheel 1 is rotated counterclockwise and the slide pin 62 is retracted in the middle and low speeds, the pinion 69 is rotated counterclockwise and the rear wheels 2b are in the opposite phase to the front wheels 2a steered to the left ( It is steered to the right (in reverse phase).

At the time of steering the rear wheels, the front end of each trailing arm 10a is coupled to the chassis member via the parallel link mechanism 11 so as to be movable in parallel, so that the trailing arm 10a easily moves laterally.

That is, the trailing arm as shown in Fig. 18 (a).
When turning 10a, bushing 11 of trailing arm 10a
The angles between the axis of i and the axis of the pin 11f in the bush 11i (bushing twist angles) α and β are, for example, the twist angles α and β of the single link shown in FIG. 18 (b). The trailing arm 10a moves laterally, that is, the rear wheel 2b, because it is much smaller than that of the power cylinder shown in FIG. The steering will be done smoothly.

Further, in the parallel link mechanism 11, the Z point (support pin 11f
The imaginary turning radius R'of the center point of) is the parallel link length (the length of the parallel link upper 11a and the parallel link lower 11b) R
Therefore, the arc drawn by the Z point can be increased when steering the rear wheels. Therefore, it is possible to reduce the displacement of the point E (the connecting point to the rear wheel 1b of the trailing arm 10a), that is, the change of the wheel base and the tread. Further, even if the stroke of the rear power cylinder 9 is small, the required rear wheel steering angle (θ) can be obtained.

Furthermore, by adjusting the length of the two links appropriately,
IN side or OUT for stroke of power cylinder 9
There is also an advantage that the rear-wheel steering angle characteristic to the side can be changed and the degree of freedom in design is large.

In this way, the rear wheels 2b are steered by the required angle in accordance with the operation amount (steering wheel angle) of the steering wheel 1 based on the rear wheel steering ratio corresponding to the vehicle speed.

The size of the rear wheel steering angle with respect to the steering wheel angle is
As shown in the figure, it changes linearly up to a certain steering wheel angle depending on the angular vehicle speed. For example, at medium and low speeds, the cam groove 61a of the in-phase / out-of-phase converting mechanism 6 is in a reverse phase inclination state according to the size of the steering wheel angle as shown in FIG. 2 (b), and the rear wheels 2b and the front wheels 2a. It is steered by the required angle in the opposite phase direction. The steering ratio at this time increases as the vehicle speed decreases.

On the other hand, at high speed, the cam groove 61a of the in-phase / out-of-phase converting mechanism 6 is in the in-phase inclination state as shown in FIG. 2 (c), and the rear wheel 2b is the same as the front wheel 2a depending on the size of the steering wheel angle. It is steered by the required angle in the phase direction. The steered ratio at this time increases as the vehicle speed increases.

When the steering wheel angle exceeds a certain value, the limit output mechanism 5A of the cam mechanism 5 operates, that is, the cam mechanism 5
The slider 52 slides in the arcuate grooves 53b and 53c, and the rear wheel steering amount is kept constant regardless of the steering wheel angle.

As a result, during reverse phase steering of the rear wheels in the medium and low speed range,
The reduction in the grip force of the rear wheels is prevented, and the strong understeer characteristic is suppressed when the rear wheels are steered in phase in the high speed range. Therefore, steering can be performed more reliably in a stable vehicle speed posture, and the steering operation can be performed softly, which improves the steering feeling.

In addition, in FIG. 8, the curves shown with 0.5g, 0.7g, and 0.9g are
The relationship between the steering wheel angle and the lateral G (lateral acceleration) during steady rotation at each vehicle speed is shown.

As described above, in this embodiment, the rear wheel steering ratio adjusting mechanism RC allows the rear wheel 2b to be steered linearly with respect to the steering wheel angle while changing the rear wheel steering ratio according to the vehicle speed by the in-phase / reverse-phase conversion mechanism 6. In combination with the function of the limit output structure 5A of the cam mechanism 5, as shown by the solid line in FIG. 9, the characteristics of the front-rear wheel steering angle ratio k with respect to the vehicle speed v are shown in FIG.
_It can be set so that _G = 0. As a result, the steering performance of the vehicle body can be greatly improved.

When the rear wheel steering mechanism RM fails, the non-linear spring structure 9A as the neutral position urging mechanism incorporated in the rear power cylinder 9 has its rubber springs 95a and 95a.
The rear wheel 2b is held in the neutral state by the urging force of b and the coil springs 98a, 98b to the neutral position. At this time, since a large spring straightness can be set in the rubber springs 95a and 95b, sufficient neutral position biasing force for the rear wheels can be obtained.

The broken line in FIG. 9 shows the characteristics of a conventional example (four-wheel steering system disclosed in Japanese Patent Laid-Open No. 60-193770), in which case the front and rear wheels are steered especially in the reverse phase region at low speed. The angular ratio is too small to control β _G = 0.

In addition, in this embodiment, the disk-shaped cam of the in-phase / reverse-phase conversion mechanism 6 is used.
Although the cam groove 61a of 61 is set on a straight line, it is also possible to set it to another suitable curved shape.By setting the shape of this cam groove 61a, the relationship between the steering angle and the rear wheel steering angle can be linearly set. It can also be set to be non-linear. Further, the cam 61 is not limited to the disc type.

Next, a modified example of the front wheel steering mechanism interlocking type relief valve will be described based on the system diagram of the fluid pressure supply system in FIG. Note that, in FIG. 21, the same reference numerals as those in FIG. 1 indicate the same members, and thus the description thereof will be omitted.

In this modification, the relief valve 179 itself is configured in the same manner as in the embodiment, in the first oil chamber 182a of the valve chamber 182 through the first port P ₁ of the relief valve 179, a front power steering from the hydraulic pump 75 Not only the pilot oil pressure supplied to the device FP is introduced, but the oil pressure from the vehicle speed corresponding oil pressure source 186 that generates the oil pressure proportional to the vehicle speed is also introduced through the oil passage 179b. The other parts are configured in the same manner as the embodiment.

As the vehicle speed corresponding hydraulic power source 186, a vehicle speed sensitive hydraulic pump such as a transmission pump or a differential pump that generates hydraulic pressure proportional to the vehicle speed is used.

Then, when one of the pilot oil pressure supplied to the front power steering device FP and the oil pressure corresponding to the vehicle speed enters the first oil chamber 182a of the valve chamber 182, the spool valve body 181
Are configured to retract.

With the above configuration, the spool valve element 181 moves forward and the hydraulic pressure from the hydraulic pump 74 is discharged to the drain tank 76 only when both the pilot hydraulic pressure of the front power steering and the hydraulic pressure corresponding to the vehicle speed become zero.

As a result, even when the pilot hydraulic pressure becomes 0 during traveling, the relief valve 179 opens the hydraulic pressure supply oil passage 77a, the control of the rear power cylinder 9 by the rotary valve 8 is performed, and the rear wheel steering function is performed. Is secured.

It is also conceivable that the spool valve body 181 retracts when both the pilot oil pressure supplied to the front power steering device FP and the vehicle speed corresponding oil pressure enter the first oil chamber 182a of the valve chamber 182. In this case, the relief function is prioritized, and when one of the pilot hydraulic pressure and the vehicle speed corresponding hydraulic pressure becomes 0, the spool valve body 181 moves forward and the hydraulic pressure from the hydraulic pump 74 is discharged to the drain tank 76.

Although hydraulic pressure is used as the fluid pressure of the actuator 7 in this embodiment, it is also possible to use other fluid pressure such as air pressure.

[Effect of device]

As described in detail above, according to the front and rear wheel steering system for a vehicle of the present invention, the front wheel steering mechanism is provided with the fluid pressure type front power steering system which is operated by supplying the fluid pressure in accordance with the force applied to the steering wheel. And a rear wheel steering actuator that operates by receiving fluid pressure from the fluid pressure supply system in the rear wheel steering mechanism, and the fluid pressure supply system sucks and discharges the fluid in the reservoir. A fluid pressure supply passage for supplying a fluid pressure from the fluid pressure pump, wherein the fluid pressure supply from the fluid pressure pump to the actuator is adjusted in the passage according to the steering angle of the front wheels. A control valve for controlling the operation of the actuator,
If the fluid pressure from the fluid pump located upstream of the control valve is urged to relieve the reservoir side and the fluid pressure generated by the front power steering device is received as pilot pressure, the urging force is resisted. Unnecessary fluid to the rear-wheel steering actuator by a configuration in which a front-wheel steering mechanism interlocking relief valve configured to supply the fluid pressure from the fluid pressure pump to the control valve side is interposed. The pressure supply is avoided, which contributes to the suppression of energy loss, and even when the vehicle is stopped, the pressure fluid supplied to the rear wheel steering actuator does not heat up and rise in temperature. Burn-in is prevented. Therefore, even if a fail-safe device for a rear-wheel steering mechanism, such as a rear-wheel neutral position urging mechanism that increases the load on the rear-wheel steering actuator, is provided, a problem in the fluid pressure pump or the like is solved, and It is possible to greatly improve the overall steering performance. Further, since the relief valve is driven by effectively utilizing the fluid pressure generated in the front power steering device,
There is also an advantage that the relief valve does not require electrical control, is highly reliable, and has a simple structure.

[Brief description of drawings]

1 to 21 show a front and rear wheel steering device for a vehicle as an embodiment of the present invention, and FIG. 1 is a system diagram of a fluid pressure supply system for supplying a fluid pressure to a rear wheel steering actuator,
FIG. 4 is a vertical cross-sectional view of the relief valve, FIG. 3 is a schematic perspective view showing the overall structure, FIG. 4 is a vertical cross-sectional view showing the bevel gear assembly, and FIG. 5 is a perspective view showing the cylindrical cam mechanism. FIG. 6 (a) is a longitudinal sectional view of the cylindrical cam mechanism, FIG. 6 (b) is a lateral sectional view of the cylindrical cam mechanism, and FIG. 7 is a power transmission state by the cylindrical cam mechanism. Graphs for explanation, FIGS. 8 and 9 are graphs showing the rear wheel steering characteristics of the cylindrical cam mechanism, and FIG. 10 (a) is a vertical longitudinal sectional view of the rotary valve, and FIG. 10 (b). ) Is a horizontal vertical sectional view of the main part of the rotary valve, and FIG.
FIG. 10 (a) is a sectional view taken along the line XIa-XIa, and FIG.
11A is a sectional view taken along the line XIb-XIb in FIG. 11, FIG. 11C is a sectional view taken along the line XIc-XIc in FIG. 10A, and FIG. 11D is a line XId in FIG. 10A. -XId is a cross-sectional view taken in the direction of the arrow, Figs. 12 (a) and 12 (b) are cross-sectional views showing the operating state of the rotary valve in correspondence with Fig. 11 (a), and Fig. 12 (c) is the rotary valve. FIG. 11 (b) is a cross-sectional view showing the operating state of FIG.
FIG. 12 (d) shows the operating condition of the rotary valve.
FIG. 13 is a longitudinal sectional view of the rear power cylinder, FIG. 14 is a graph showing assembly characteristics of the nonlinear spring mechanism of the rear power cylinder, and FIG. Fig. 16 is a graph showing the output characteristics of the rear power cylinder, Fig. 16 is a schematic perspective view showing the rear suspension part as a center, and Fig. 17 (a) is a view showing the parallel link mechanism of the rear power cylinder, as viewed in the direction of arrows XVIIa-XVIIa in Fig. 16. Sectional view, FIG. 17 (b) is a sectional view taken along line XVIIb-XVIIb in FIG. 17 (a), FIG.
Figures (a) to (c) are schematic operation diagrams showing the operation of the parallel link mechanism in comparison with other mechanisms, and Figure 19 (a) is an in-phase reverse phase conversion provided to a rear wheel steering ratio adjusting mechanism. FIG. 19 (b) is a plan view showing a part of the mechanism in a broken view, FIG. 19 (b) is a side view showing a part of the in-phase / inverting conversion mechanism in a broken view, and FIG. 19 (c).
Is a rear elevational view showing a part of the in-phase / inverted-layer conversion mechanism in a cutaway manner, and FIGS. 20 (a) to 20 (c) are perspective views for explaining the operation of the in-phase / inverted-phase conversion mechanism. The drawing is a system diagram of a fluid pressure supply system that supplies a fluid pressure to a rear wheel steering actuator showing a modified example of the relief valve. 1 ... Steering wheel, 1a ... Front power steering gear box, 1b ... Steering shaft, 1c ... Tie rod, 2a ... Front wheel, 2b ... Rear wheel, 2b '
...... Hub carrier, 3 ... Bevel gear assembly, 4 ...
... Control shaft, 5 ... Cam mechanism, 5A ... Limit output mechanism, 6 ... In-phase / reverse-phase conversion mechanism, 6A ... Sliding direction conversion section, 6B ... Rear wheel steering force transmission section, 6C ... Cam groove direction Adjustment unit, 7 ... Stepping motor assembly, 7a
...... Encoder, 7b ...... Stepping motor, 8 ...... Rotary valve as control valve, 9 ...... Rear power cylinder as rear wheel steering actuator, 9A ...... Nonlinear spring mechanism (rear wheel neutral position urging device) , 9a, 9b …… Rear power cylinder rod, 10 …… Rear suspension,
10a …… Trailing arm, 10b …… Lateral rod,
11a …… Parallel link upper, 11b …… Parallel link lower, 11
c …… adapter, 11d …… first rotary shaft, 11e …… second rotary shaft, 11f …… trailing arm support pin, 11g …… pipe, 11h …… nut, 11i …… bush, 12 …… chassis member , 21 ... Shaft for steering front wheels, 21a ... Rack, 30 ... Casing, 31 ... First shaft (pinion shaft), 32 ... First bevel gear, 33 ... Second shaft, 34 ... … Second bevel gear, 35 …… Universal joint, 35a …… Dust cover, 36a, 36b, 36c, 36d …… Bearing, 37 …… Resin pin, 38a …… Sealer, 50 …… Casing, 50a …… Sliding chamber , 51 …… Cylindrical cam, 52…
... Slider, 52a ... Slider base, 52b ... Cylindrical sliding member, 53 ... Groove (cam groove), 53a ... Helical groove (spiral cam groove), 53b, 53c ... Arc groove ( Cam groove of arcuate groove),
54 …… Slide rod, 55 …… Spring pin, 56 ……
Bearing, 57 …… Bearing, 58 …… Nut, 59 ……
Bearing, 60 …… Casing, 60a …… Bearing, 61 ……
Disc type cam, 61a …… Cam groove, 62 …… Slide pin, 62a
…… Sliding ring, 62b …… Pin mounting member, 63 …… Guide member, 63a …… Slot for guide, 64 …… Slide plate (slide member), 64a …… Rack, 64b …… Slide bearing, 64c ...... Bearing, 64d ... Mounting plate, 65 ...
… Bevel gear on the cam side, 66 …… Spline shaft, 66a ……
Key, 67 …… Bevel gear on the stepping motor side, 67a
...... Keyway, 67b …… Bearing, 69 …… Pinion, 69a
...... Pinion shaft, 69b ...... Pin, 74 ...... Hydraulic supply pump [hydraulic pump (engine pump)] as a fluid pressure pump, 75 …… Front power steering hydraulic supply pump (hydraulic pump), 76 …… Reservoir Drain tank (reservoir tank), 77a ... Oil passage for hydraulic pressure (flow passage for fluid pressure), 77b ... Oil passage for hydraulic discharge, 77c ...
… Hydraulic return oil passage, 80 …… Housing, 80a …… Front housing, 80b …… Middle housing, 80c …… Rear housing, 80d …… Valve chamber, 80e …… Bolts and nuts, 81
...... Spool, 81a ...... first opening, 81b ...... second opening, 81c ...... annular groove, 81d ...... third opening, 81e ...... recess, 82 ...... rotary shaft, 82a ...... first 1 recess, 8
2b ... second recess, 82c ... first contact, 82d ... second
, 82e ... first partition wall, 82f ... second partition wall, 82g ... hollow part, 83 ... following shaft, 83a ... pin, 83b ... hollow part, 83c ... opening, 84a ... first ring, 84b ... second ring, 84c ... communication chamber, 84d-84g ...
… Aperture, 85 …… Internal shaft, 86 …… Pin, 87a, 87b, 87
c …… Bearing, 88 …… Seal ring, 88a, 88b, 88c, 8
8d, 88e, 88f …… O-ring, 89a …… First annular oil chamber, 89b
...... Second annular oil chamber, 89c …… Third annular oil chamber, 90 ……
Cylinder body, 90a ... left oil chamber, 90b ... right oil chamber, 90c ...
… Annular convex part, 91 …… Piston, 92a, 92b …… Piston rod (tie rod), 93a, 93b… Cap, 94… Pipe, 95a, 95b… Rubber spring, 96a, 96b… Stopper, 97a, 97b …… Plate, 98 …… Coil spring, 179 …… Front wheel steering mechanism interlocking relief valve, 179a, 179b
…… Oil passage, 179A …… Housing, 180 …… Relief valve for hydraulic pressure adjustment, 181 …… Spool valve body, 181a …… First small diameter part, 181b …… First large diameter part, 181c …… Second small diameter part , 181d ...
… Second large diameter part, 181e… Concave part, 181f… Hollow hole part, 182
...... Valve chamber, 182a ...... First oil chamber, 182b ...... Second oil chamber, 182c
...... Third oil chamber, 182d ...... Fourth oil chamber, 182e ...... Fifth oil chamber,
182f ... 1st reduced diameter part, 182g ... 2nd reduced diameter part, 182h ... 3rd reduced diameter part, 182i ... 4th reduced diameter part, 183 ... Return spring, 184 ... Cap, 185 ... Mounting holes, 185a, 1
85b ... O-ring, 186 ... Transmission pump or differential pump as a hydraulic source for vehicle speed,
C: Controller, FD: Hydraulic pressure discharge system (fluid pressure discharge system), FM: Front wheel steering mechanism, FP: Front power steering device, FS: Hydraulic pressure supply system (fluid pressure supply system), RC
…… Rear wheel steering ratio adjustment mechanism, RM …… Rear wheel steering mechanism, P ₁ ……
1st port, P ₂ ... 2nd port, P ₃ ... 3rd port, P ₄
... 4th port, P ... pressure port (P port), P ... return port (R port), P ... X port, P ... Y port, S ... vehicle speed sensor, ST ... steering mechanism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Masuda, Inventor, Nakashiniri, Hashime-cho, Okazaki-shi, Aichi Japan Automotive Engineering Co., Ltd. Okazaki Plant (56) References JP 62-34859 (JP, A) JP-A-61-200064 (JP, A) JP-A-58-170668 (JP, A) Actually open 62-139783 (JP, U) Actually open 61-24276 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A front wheel steering mechanism connected to a steering mechanism and a rear wheel steering mechanism interlocked with the steering mechanism, wherein fluid pressure is applied to the front wheel steering mechanism in accordance with a force applied to a steering wheel. A fluid pressure type front power steering device that is supplied and operates is provided, and a rear wheel steering actuator that operates by receiving fluid pressure from the fluid pressure supply system is provided in the rear wheel steering mechanism, and the fluid pressure supply system is provided. Has a fluid pressure pump for inhaling and discharging the fluid in the reservoir and a fluid pressure supply passage for supplying the fluid pressure from the fluid pressure pump, and the fluid is supplied to the passage according to the steering angle of the front wheels. A control valve that regulates the supply of fluid pressure from the pressure pump to the actuator and controls the operation of the actuator; and a fluid from the fluid pump that is located upstream of the control valve. When the fluid pressure generated by the front power steering device is urged to relieve the fluid to the reservoir side as pilot pressure, the fluid pressure from the fluid pressure pump is supplied to the control valve side against the urging force. A front / rear wheel steering system for a vehicle, characterized in that a front wheel steering mechanism interlocking type relief valve configured as described above is interposed.