JPH078355Y2 - Steering ratio control mechanism of front and rear wheel steering system for vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a steering ratio control mechanism for a steering device, which is suitable for use in vehicles such as automobiles, and particularly in four-wheeled vehicles. The present invention relates to a steering ratio control mechanism for a front / rear wheel steering device for a vehicle that can steer the front and rear wheels while controlling the steering angle ratio according to the vehicle speed.

[Prior Art] In recent years, a four-wheel steering system has 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 a 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 rear wheel steering ratio adjusting mechanism for a vehicle steering system disclosed in Japanese Patent Publication No. 60-44185 discloses a gear box for converting the rotational motion of the steered wheels into a linear motion, and a linear motion converted by the gear box. And a connecting arm that steers the front wheels by means of a moving arm that is connected to a force point at one end of the connecting rod and that rotates by receiving a linear motion converted by a gear box for steering the rear wheels. , One end of which is connected to this moving arm at the point of action and the other end of which is connected to the rear wheel, and a link mechanism is formed from these respective rods and arms, and the arm rod is rotated by the rotation of the moving arm. The rear wheels are steered through.

In this link mechanism, the movable arm is supported by a movable fulcrum, and the movable fulcrum is driven by the control / drive device according to the vehicle speed, and moves around the point of action around the point of action. The link ratio can be controlled. In particular, the control / drive device positions the movable fulcrum behind the action point and arranges the force point, the action point, and the fulcrum in this order, and then positions the movable fulcrum on the action point to match the fulcrum with the action point. In addition, the movable fulcrum can be continuously moved to a state in which the movable fulcrum is located between the force point and the action point and the force point, the fulcrum, and the action point are arranged in this order.

As a result, for example, when the movable fulcrum is located behind the point of action, the rear wheel rolls relative to the front wheel according to its link ratio (distance between the fulcrum and the force point and distance between the fulcrum and the point of action). When the steering wheel is steered to the opposite phase (or the same phase) and the movable holding point is located rearward of the point of action, the rear wheel has the same phase (or the same phase) to the front wheel at the steering ratio corresponding to the link ratio. It is steered to the opposite phase).

[Problems to be Solved by the Invention] However, in the above-described conventional steering ratio control mechanism of the vehicle steering system, the fulcrum is moved to control the steering ratio, and a large load is applied to this fulcrum. Because I will concentrate and join,
In order to secure sufficient strength and reliability of the steering ratio control mechanism, the mechanism has to be increased in size around the fulcrum, and there is a problem in mountability in an actual vehicle.

The present invention is intended to solve such a problem, and a steering ratio of a front / rear wheel steering device for a vehicle, which has a simple structure and has sufficient strength and reliability and improved mountability in an actual vehicle. The purpose is to provide a control mechanism.

[Means for Solving Problems] Therefore, the steering ratio control mechanism of the front and rear wheel steering device for a vehicle of the present invention has a front wheel steering mechanism and a rear wheel steering mechanism connected to a steering handle mechanism. In a steering ratio adjusting mechanism of a front and rear wheel steering device for a vehicle, which is interposed between the steering wheel mechanism and the rear wheel steering mechanism, for controlling a ratio of a steering angle of a rear wheel to a steering angle of a front wheel. , A displacement input section for inputting a displacement according to the front wheel turning angle is provided on one end side, and a displacement output section for outputting a displacement for controlling the rear wheel turning angle to the rear wheel turning mechanism on the other end side. An input / output arm, a support arm having one end pivotally attached to the first point of the input / output arm and the other end pivotally attached to a fixed fulcrum of the base body, and one end pivotally connected to the second point of the input / output arm. And a vehicle speed input arm that is attached to the other end of the vehicle In addition, a four-bar link having the above four points as a node is constituted by the input / output arm, the support arm, and the vehicle speed input arm, and the first and second points are intermediate portions of the input / output arm. And a vehicle speed responsive driving means for moving the moving fulcrum in accordance with the vehicle speed to change the distance between the fixed fulcrum and the moving fulcrum.

[Operation] In the steering ratio control mechanism of the vehicle front / rear wheel steering system of the present invention described above, when the steering handle mechanism is operated, the displacement corresponding to the front wheel steering angle is input to the displacement input portion of the input / output arm, and the movement fulcrum is moved. And the fixed fulcrum, the displacement output unit moves in accordance with the movement of the four-bar linkage fixed at two points, and this displacement output unit outputs the displacement for controlling the rear wheel steering angle. At this time, the moving fulcrum is moved to a position corresponding to the vehicle speed while changing the distance from the fixed fulcrum by the vehicle speed responsive driving means, and the movement of the four-section link is determined according to the position of the moving fulcrum. As a result, the characteristic of the movement of the input / output arm that operates via the movement of the four-bar linkage is also set to correspond to the vehicle speed.
The ratio of the displacement amount of the displacement output unit that is output to control the rear wheel steering angle is set with respect to the displacement amount of the displacement input unit that receives the displacement according to the front wheel steering angle and moves. In this way, the ratio of the turning angle of the rear wheels to the turning angle of the front wheels, that is, the turning ratio is adjusted by the operation of the vehicle speed responsive driving means.

[Embodiment] A steering ratio control mechanism of a front and rear wheel steering device for a vehicle according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a state in which the vehicle front / rear wheel steering device is equipped, FIG. 2 is a configuration diagram of a main portion showing the in-phase control state, and FIG. 3 is a configuration of a main portion showing the anti-phase control state. Figure, 4th
FIG. 5 is a graph showing the ratio of the output to the input with respect to the displacement of the movement fulcrum, and FIG. 5 is a schematic configuration diagram showing another vehicle front / rear wheel steering system equipped with the present turning ratio control mechanism. 6 to 8 show a modified example of the hydraulic pressure supply system of the vehicle speed responsive drive means, and FIG. 6 is a schematic configuration diagram thereof,
FIG. 7 is a graph showing the displacement characteristic of the movement fulcrum, FIG. 8 is a graph showing the rear wheel turning ratio characteristic adjusted by the vehicle speed responsive driving means, and FIGS. 9 to 11 are main turning ratio control mechanism. Fig. 9 shows a modified example of the rear power cylinder of Fig. 9, Fig. 9 is a longitudinal sectional view of the rear power cylinder, Fig. 10 is a graph showing the assembly characteristics of the nonlinear spring mechanism of the rear power cylinder, and Fig. 11 is its rear. It is a graph which shows the output characteristic of a power cylinder. Note that, in FIGS. 1 and 5, a perspective view is partially shown, and a characteristic portion is enlarged or cut away. Further, among the reference numerals shown in FIGS. 5, 6, and 9, the same reference numerals as those in FIG. 1 indicate the same members.

The steering ratio control mechanism according to the present embodiment and the front and rear wheel steering device for a vehicle equipped with this mechanism relate to a four-wheeled vehicle.

As shown in FIG. 1, the front and rear wheel steering system for a vehicle includes a steering handle mechanism (hereinafter also referred to as a steering mechanism) ST, a front wheel steering mechanism FM, a rear wheel steering ratio adjusting mechanism (a steering ratio control mechanism). ) RC and rear wheel steering mechanism RM.

The steering mechanism ST is composed of a steering wheel (steering handle) 1, a steering shaft 1b, other shafts and joints, and the lower end portion thereof is a front power steering gear box 1a and a bevel gear assembly 3 of the front wheel steering mechanism FM. Are linked to.

Then, the front wheel steering mechanism FM can steer the front wheels 2a by driving the tie rods 1c, 1c while applying a hydraulic biasing force through the front power steering gear box 1a in addition to the steering force through the rack and pinion (not shown). It is like this.

In addition, the bevel gear assembly 3 includes a rear wheel steering ratio adjustment mechanism R via a conversion mechanism 150 that converts rotational movement into linear movement.
Connected to C.

The bevel gear assembly 3 is attached to a first bevel gear 32 mounted on a first shaft 31 which is connected to the steering shaft 1b and extends substantially vertically, and a second shaft 33 which is oriented substantially horizontally. Second bevel gear 34
Are engaged with each other, and the bevel gear assembly 3 converts the rotational movement about the vertical axis into the rotational movement about the horizontal axis. Also, the conversion mechanism
150 is a screw nut 1 connected to the second shaft 33.
51 and a forward / backward screw 152 that meshes with the screw nut 151.
The rotary motion about the horizontal axis input from the second shaft 33 is converted into a horizontal forward / backward motion and output from the forward / backward screw 152.

The rear wheel steering ratio adjustment mechanism RC is a 4-point link (4-section link) 10
A link portion 100 having 0R and a vehicle speed responsive hydraulic cylinder 110 connected to a vehicle speed input arm 102 of the link portion 100.
And a vehicle speed proportional hydraulic supply system PS1 for supplying hydraulic pressure proportional to the vehicle speed to the vehicle speed responsive hydraulic cylinder 110.

Furthermore, the rear wheel steering mechanism RM is the rear wheel steering ratio adjustment mechanism RC.
Of the spool 121, the shaft 127 of the spool 121 is connected to the input / output arm 101, the hydraulic cylinder 130 hydraulically controlled by the spool valve 120, and the shaft 147 of the spool 141 on the piston rod 136 of the hydraulic cylinder 130. And a constant hydraulic pressure supply system PS2 that supplies a constant hydraulic pressure to the servo type spool valve 140,
A rear power cylinder 9 hydraulically connected to the servo spool valve 140, and a rear suspension 10 connected to the rear power cylinder 9 and driven by the rear power cylinder 9 to steer the rear wheels 2b. It is configured.

The tie rods (piston rods) 92a, 92b protruding from the rear power cylinder 9 are the rear suspension 10
Is connected to the trailing arm 10a of the rear power cylinder 9, and together with the piston 91 of the rear power cylinder 9, a piston rod 92a,
When 92b moves, the trailing arms 10a, 10a turn, and the rear wheels 2b, 2b pass through the trailing arms 10a, 10a.
Is being steered.

Next, each characteristic part of the vehicle front and rear wheel steering system of the present embodiment will be described in detail.

First, the rear wheel steering ratio adjusting mechanism RC will be described. The link portion 100 of the rear wheel steering ratio adjusting mechanism RC includes an input / output arm 101, a support arm 103, and a vehicle speed input as shown in FIGS. It is composed of an arm 102.

The input / output arm 101 includes a main arm portion 101A and a sub arm portion 101B protruding laterally from the main arm portion 101A. The main arm portion 101A has a displacement input portion 101a at one end (upper end in the figure) side for inputting a displacement according to a front wheel turning angle at an input point 108A, and at the other end (lower end in the figure) side, a rear Outputs the displacement for controlling the rear wheel steering angle to the wheel steering mechanism RM.
It has a displacement output unit 101c for outputting in 8D.

The head of the forward / backward screw 152 is pivotally attached to the input point 108A, and the rod 128 connected to the shaft 127 of the spool valve 120 is pivotally attached to the output point 108D (see FIG. 1). Also,
A first point 108C pivotally attached to one end of the support arm 103 is provided in the middle of the main arm portion 101A. Further, a second point 108B pivotally attached to one end of the vehicle speed input arm 102 is provided at the tip of the sub arm 101B.

Of these, input point 108A, output point 108D and first point 108C
Are arranged so as to be located on the axis of the main arm portion 101A, and in this embodiment, a particularly large distance is set between the output point 108D and the first point 108C.

The support arm 103 and the vehicle speed input arm 102 are set to have substantially the same length, the other end of the support arm 103 is pivotally attached to the base body (base member) 107 at a fixed fulcrum 106, and the other end of the vehicle speed input arm 102 is A piston rod 112 of a vehicle speed responsive hydraulic cylinder 110 as vehicle speed responsive driving means is pivotally attached at a movement fulcrum 105.

The 4-point link 100R has such a moving fulcrum 105 and a fixed fulcrum 10
6, 4 points of the 1st point 108C and the 2nd point 108B are constituted as a node.

The distance between the pivot points at both ends of the support arm 103, that is, the distance between the fixed fulcrum 106 and the first point 108C, and between the pivot points at both ends of the vehicle speed input arm 102, that is, the movement fulcrum 105 and the second point. The distance to 108B is the same as each other, and both are set shorter than the distance between the output point 108D and the first point 108C.

When the moving fulcrum 105 moves, the distance to the fixed fulcrum 106 can be changed by driving the vehicle speed responsive hydraulic cylinder 110. However, when the moving fulcrum 105 moves and overlaps the fixed fulcrum 106, the supporting arm 103 and the vehicle speed Each link of the input arm 102 becomes two equal sides of an isosceles triangle, and a link (a line segment between the first point 108C and the second point 108B) of the sub arm portion 101B of the input / output arm is formed. , So that it is at the bottom
A straight main arm 10 formed by the first point 108C and the second point 108B
The angle with respect to the axis of 1A is set.

Further, the distance of the second point 108B from the first point 108C becomes equal to the distance between the moving fulcrum 105 and the fixed fulcrum 106 when the moving fulcrum 105 moves and is largely separated from the fixed fulcrum 106. The four-point link 100R is set so as to form a parallelogram.

The pivot points 105, 106, 108A, 108B, 108C and 108D are pivotally attached through the pivot pins 104a, 104b, 104c, 104d, 104e and 104f.

Next, the vehicle speed-responsive hydraulic cylinder 110 will be described.This cylinder 110 has a piston 114 inside a cylinder body 110a, and a piston rod 112 of the piston 114 projects from one end of the cylinder body 110a.
The tip of this piston rod 112 is the fulcrum 105 and the link
It is pivotally connected to a vehicle speed input arm 102 of 100.

Further, the sliding stroke of the piston 114 is at least the position where the movement fulcrum 105 at the tip of the piston rod 112 coincides with the fixed fulcrum 106 as shown in FIG. 3, and the four-point link 100R as shown in FIG. It is set so that it can move to a position where a parallelogram is formed.

Inside the cylinder body 110a, a portion of the piston chamber 112 closer to the piston rod 112 than the piston 114 is the oil chamber 1 in which pressurized oil is supplied and discharged.
10b is provided and the cylinder body 11 opposite the piston 114 is provided.
A return spring 113 is interposed between the inner end wall of 0a and the piston 114.

The vehicle speed responsive hydraulic cylinder 110 is
10a is pivotally supported by a bracket 111 fixed to the vehicle body via a pin 111a.

Next, a vehicle speed proportional hydraulic supply system PS1 that supplies hydraulic pressure proportional to the vehicle speed to the vehicle speed responsive hydraulic cylinder 110 will be described.The hydraulic supply system PS1 includes a transmission pump 72 that generates hydraulic pressure proportional to the vehicle speed, The oil supply passage 72j provided from the drain tank 76 to the transmission pump 72 and the transmission pump 72
To a vehicle speed responsive hydraulic cylinder 110, a hydraulic pressure supply path 72c and a hydraulic pressure supply / discharge path 119, and a hydraulic pressure discharge path provided from an end of the hydraulic pressure supply / discharge path 119 to a drain tank 76.
72d and a hydraulic pressure sudden change prevention device 115 provided in the middle of the hydraulic pressure supply / discharge passage 119.

Of these, the hydraulic pressure sudden change prevention device 115 is a check valve (check valve) provided in an orifice 118 provided in a hydraulic pressure supply / discharge passage 119 and an oil passage 117a provided in parallel with the hydraulic pressure supply / discharge passage 119. 11
It is configured to prevent rapid discharge of pressure oil from the oil chamber 110b of the vehicle speed responsive hydraulic cylinder 110.

An orifice 72f is also provided in the hydraulic pressure discharge path 72d.

Next, the rear wheel steering mechanism RM will be described.

The spool valve 120 connected to the input / output arm 101 of the rear wheel steering ratio adjusting mechanism RC includes the casing 121a and the casing 121a.
Spool 120 slidably equipped inside 20a,
It is composed of return springs 122a and 122b.

The casing 120a has a spool chamber 124 formed mainly of a cylindrical surface inside. This spool room 124
The inner wall is formed with annular recesses 123c, 123a, 123b having substantially the same diameter in the axial center and on the left and right sides thereof. Of these, the annular recesses 123a and 123b are set to have equal lengths and shorter than the length of the annular recess 123c, and are formed symmetrically with respect to the annular recess 123c.

By these annular recesses 123c, 123a, 123b, the spool chamber
The inner wall surface of 124 is four inner wall surface portions 123d, 123e, 1 in the axial direction.
It is divided into 23f and 123g.

Then, in the annular recesses 123a and 123b, the hydraulic pressure supply passage 1 is provided, respectively.
26a and 126b are communicatively connected, and the annular recess 123c is communicatively connected to a hydraulic discharge passage 126c. Then, the hydraulic pressure supply path 126
a and 126b are both branched from the hydraulic discharge passage 146c of the servo type spool valve 140.
The hydraulic pressure discharged from the spool valve 120 can be supplied to the spool valve 120. The tip of the hydraulic pressure discharge path 126c is guided to the inside of the drain tank 76.

The spool 121 has shafts 127, 127 projecting from both ends of the casing 120a at both ends thereof, and has a cylindrical outer surface which is enlarged in the middle portion thereof and slidably contacts the cylindrical inner wall surface of the spool chamber 124 or is extremely close to the inner wall surface. Valve body portions 121a, 121 having
It has c and 121b. Inside the spool chamber 124, a first oil chamber 124a is formed between the valve body portions 121a and 121c, and a second oil chamber 124b is formed between the valve body portions 121c and 121b. Then, an inner wall surface portion 123e which is a wall portion of the first oil chamber 124a and an inner wall surface portion which is a wall portion of the second oil chamber 124b.
Hydraulic supply / discharge passages 135a and 135b, which communicate with the inside of the hydraulic cylinder 130, are connected to 123f.

Further, among these valve body portions, the valve body portion 121c is provided at the central portion in the axial direction, and the valve body portions 121a and 121b are provided symmetrically with respect to the valve body portion 121c. And spool 12
In the neutral position of 1, that is, when the valve body portion 121c is in the same axial position as the annular recess 123c, the valve body portion 121c.
The valve body portions 121a and 121b are arranged such that the a and 121b are located slightly outward of the annular recesses 123a and 123b, respectively. Further, the length of the valve body portion 121c is determined by the annular recess 123c.
Is set appropriately shorter than the length of
The lengths of a and 121b are equal to each other and annular recesses 123a and 123b.
It is set to almost the same length as.

Further, one shaft 127 of the spool 121 is pivotally attached at one end thereof to a rod 128 pivotally attached to the link portion 100 by a pivot pin 127a, whereby the output point 108D of the link portion 100 is displaced. The spool 121 is slidable.

The slide stroke range of this spool 121 is
The outer peripheral surface of the valve body portion 121c is the inner wall surface portion 123 of the spool chamber 124.
The outer peripheral surface of the valve body portion 121c is the inner wall surface of the spool chamber 124 from a position in which it is in sliding contact with e (or is in a state of facing very closely to the inner wall surface portion 123e) (this is the leftward moving position). It is set so as to extend to a position in which it is in sliding contact with the portion 123f (or is in a state of facing very closely to the inner wall surface portion 123f) (this is the rightward movement position).

Then, at the leftward position of the spool 121, the outer peripheral surface of the valve body portion 121b is in sliding contact with the inner wall surface portion 123f of the spool chamber 124 (or is in a state of facing very closely to the inner wall surface portion 123f), and the valve body portion The outer peripheral surface of 121a is separated from the inner wall surface portion 123e of the spool chamber 124.

Further, in the rightward position of the spool 121, the outer peripheral surface of the valve body portion 121a is in sliding contact with the inner wall surface portion 123e of the spool chamber 124 (or is in a state of facing very closely to the inner wall surface portion 123e), and the valve body portion The outer peripheral surface of 121b is separated from the inner wall surface portion 123f of the spool chamber 124.

The return springs 122a and 122b have the same shape and the same elastic characteristic, and are respectively interposed between the inner walls of both ends of the casing 120a and the valve body portions 121a and 121b, and the spool 121 is attached to its neutral position. I am energetic.

Next, the hydraulic cylinder 130 hydraulically controlled by the spool valve 120 will be described.
A piston 131 is slidably provided inside the cylinder body 130a, and the inside of the cylinder body 130a is partitioned by the piston 131 into a left oil chamber 133a and a right oil chamber 133b. In each of the oil chambers 133a and 133b, return springs 134a and 134b for biasing the piston 131 to a neutral position are provided between the end wall of the oil chamber and the piston 131.

Then, in the opening 132a formed at the left end of the left oil chamber 133a,
Hydraulic supply / discharge passage 1 communicating with the first oil chamber 124a of the spool valve 120
35a is connected, and a hydraulic supply / discharge passage 135b communicating with the second oil chamber 124b of the spool valve 120 is connected to an opening 132b formed at the right end of the right oil chamber 133b.

The piston rod 136 of the piston 131 has both ends projecting from each end wall of the cylinder body 130a, and one end of the piston rod 136 is integrated with the shaft 147 of the spool 144 protruding from the casing 140a of the servo spool valve 140. Is bound to. However, in this embodiment, the piston rod 136 and the shaft 147 are made of the same rod.

The servo type spool valve 140 includes a casing 140a, a spool 141 slidably mounted inside the casing 140a, and return springs 142a and 142b.

The casing 140a has a spool chamber 144 formed mainly of a cylindrical surface inside. This spool room 144
On the inner wall of the, the annular recesses 143c, 143a, 143b having substantially the same diameter are formed at the center in the axial direction and at the left and right thereof. Of these, the annular recesses 143a and 143b are set to have the same length and shorter than the length of the annular recess 143c, and are formed symmetrically with respect to the annular recess 143c.

By these annular recesses 143c, 143a, 143b, the spool chamber
The inner wall surface of 144 has four inner wall surface portions 143d, 143e, 1 in the axial direction.
It is divided into 43f and 143g.

Then, in the annular recesses 143a and 143b, the hydraulic pressure supply passage 1 is provided, respectively.
46a and 146b are communicatively connected, and the annular recess 143c is communicatively connected to a hydraulic pressure discharge passage 146c. Hydraulic supply path 146a, 146b
Are all hydraulic supply lines connected to the engine pump 74.
It is branched from 77a, and the hydraulic pressure from the engine pump 74 can be supplied to the spool chamber 144 inside the spool valve 140. The hydraulic pressure discharge passage 146c is guided to the spool valve 120 described above.

The spool 141 has shafts 147, 147 projecting from both ends of the casing 140a at both ends thereof, and has a diameter enlarged in the middle portion thereof so as to be in sliding contact with the cylindrical inner wall surface of the spool chamber 144 or a cylindrical outer surface extremely close to the inner wall surface. Valve body portions 141a, 141 having
It has c, 141b.

Inside the spool chamber 144, a first oil chamber 144a is provided between the valve body portions 141a and 141c, and a second oil chamber 1 is provided between the valve body portions 141c and 141b.
44b are formed respectively. And the first oil chamber 1
An inner wall surface portion 143e which is a wall portion of 44a and a second oil chamber 144b
Hydraulic pressure supply / discharge passages 148a and 148b, which communicate with the inside of the rear power cylinder 9, are connected to an inner wall surface portion 143f, which is a wall portion of the vehicle.

Further, among these valve body portions, the valve body portion 141c is provided at the central portion in the axial direction, and the valve body portions 141a and 141b are provided symmetrically with respect to the valve body portion 141c. And spool 14
In the neutral position of 1, that is, when the valve body portion 141c is in the same axial position as the annular recess 143c, the valve body portion 141c
The valve body portions 141a and 141b are arranged so that the a and 141b are located slightly outward of the annular recesses 143a and 143b, respectively. Further, the length of the valve body portion 141c is determined by the annular recess 143c.
The length of the valve body 141
The lengths of a and 141b are equal to each other and are annular recesses 143a and 143b.
It is set to almost the same length as.

Then, one shaft 147 of the spool 141 is integrally connected to the piston rod 136 of the piston 131. As a result, the spool 141 can slide as the piston 131 slides.

The slide stroke range of this spool 141 is
The outer peripheral surface of the valve body portion 141c is the inner wall surface portion 143 of the spool chamber 144.
The outer peripheral surface of the valve body portion 141c is the inner wall surface of the spool chamber 144 from a position in which it is in sliding contact with e (or is in a state of facing the inner wall surface portion 143e very closely) (this is the leftward moving position). It is set so as to extend to a position in which it is in sliding contact with the portion 143f (or is in a state of facing very closely to the inner wall surface portion 143f) (this is the rightward movement position).

At the leftward position of the spool 141, the outer peripheral surface of the valve body portion 141b is in sliding contact with the inner wall surface portion 143f of the spool chamber 144 (or is in a state of facing very close to the inner wall surface portion 143f), and the valve body portion 141a The outer peripheral surface is separated from the inner wall surface portion 143e of the spool chamber 144.

Further, when the spool 141 moves to the right, the outer peripheral surface of the valve body portion 141a is in sliding contact with the inner wall surface portion 143e of the spool chamber 144 (or in a state of facing very closely to the inner wall surface portion 143e), and the valve body portion The outer peripheral surface of 141b is separated from the inner wall surface portion 143f of the spool chamber 144.

The return springs 142a and 142b have the same shape and the same elastic characteristics, and are respectively interposed between the inner walls at both ends of the casing 140a and the valve body portions 141a and 141b, and the spool 141 is attached to its neutral position. I am energetic.

Further, the other end of the interlocking rod 149, which has one end pivotally attached to the piston rod 92a of the rear power cylinder 9 by the pivot pin 149c, is pivotally attached to one end of the casing 140a by the pivot pin 149a. This interlocking rod 149 has a fixed fulcrum 1 at the middle part.
It is pivotally attached to 49B with a pivot pin 149b, and the piston rod 9
The casing 140a itself can slide in association with the movement of 2a.

A constant hydraulic pressure supply system PS2 that supplies a constant hydraulic pressure to the oil chambers 144a and 144b of the servo type spool 140 is provided between the engine pump 74 that generates a substantially constant hydraulic pressure and the drain tank 76 to this engine pump 74. Oil supply passage 74b, hydraulic supply passages 74a and 77a provided from the engine pump 74 to the servo spool valve 140, and a hydraulic discharge passage 72d provided from the tip of the hydraulic supply passage 74a to the drain tank 76. , Relief valve 74 installed in this hydraulic discharge passage 72d
It consists of c and.

Of these, the relief valve 74c is designed to be opened according to the hydraulic pressure so that the hydraulic pressure output from the engine pump 74 can always be maintained at a constant pressure.

Next, the rear power cylinder 9 which receives hydraulic pressure from the servo type spool valve 140 and operates to move the trailing arm 10a of the rear suspension 10 to steer the rear wheels 2b will be described.

This rear power cylinder 9 is a servo type spool valve 140.
The cylinder main 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 the cylinder main body 90 and the cylinder main body 90 so as to be able to move back and forth. 90a and a right oil chamber 90b are divided into a piston 91, piston rods (tie rods) 92a and 92b protruding left and right from the piston 91 and penetrating left and right of the cylinder body 90, and a return for biasing the piston 91 to a neutral position. It is composed of springs 98a and 98b.

The return springs 98a, 98b have the same shape and the same elastic characteristic, and are interposed between the oil chamber end wall in each oil chamber 90a, 90b and the piston 91.

The opening 99a formed at the left end of the left oil chamber 90a is connected to the hydraulic pressure supply / discharge passage 148a communicating with the first oil chamber 144a of the servo spool valve 140, and the right end of the right oil chamber 90b is connected to the right end. A hydraulic pressure supply / discharge passage 148b communicating with the second oil chamber 144b of the servo spool valve 140 is connected to the formed opening 99b.

A steering ratio control mechanism for a vehicle front / rear wheel steering apparatus and a vehicle front / rear wheel steering apparatus having this mechanism as one embodiment of the present invention are configured as described above, and therefore the front wheel 2a and rear wheels 2b are steered.

When the steering wheel 1 is rotated, this rotational force is transmitted to the front power steering gear box 1a through the steering shaft 1b, and the front wheel steering mechanism is rotated.
The FM is operated and is further transmitted from the gear box 1a through the bevel gear assembly 3 and the conversion mechanism 150 to the link portion 100 of the rear wheel steering ratio adjustment mechanism RC.

At this time, in the front wheel steering mechanism FM, the tie rods 1c, 1c are driven to the left and right by applying a hydraulic biasing force through the front power steering gear box 1a in addition to the steering force through the rack and pinion (not shown).
Steer a, 2a.

On the other hand, the steering force from the gear box 1a is transmitted from the first bevel gear 32 mounted on the first shaft 31 of the bevel gear assembly 3 to the second bevel gear 34 mounted on the second shaft 33. , The rotary motion about the vertical axis is converted into the rotary motion about the horizontal axis. Then, in the conversion mechanism 150, the steering force is transmitted from the screw nut 151 that rotates integrally with the second shaft 33 to the advancing / retreating screw 152, and the rotational movement about the horizontal axis is converted into the advancing / retreating movement in the horizontal direction.

As a result, the link portion 100 of the rear wheel turning ratio adjustment mechanism RC operates.

In the link portion 100, the input point 108 is changed according to the position of the movement fulcrum 105 driven by the vehicle speed responsive hydraulic cylinder 110.
Ratio of movement of output point 108D to movement of A (output
Input ratio = output point movement amount / input point movement amount) is set,
The shaft 121 of the spool valve 120 is driven based on this output / input ratio. Regarding the operation of this rear wheel steering ratio adjustment mechanism RC,
It will be described in detail later.

In the spool valve 120, when the output point 108D of the link portion 100 moves by a certain amount or more, the shaft 127 is driven left and right via the rod 128.

Then, for example, when the shaft 127 is driven to the left and right, the spool 121 inside the spool valve 120 is also driven to the left, and the first oil chamber 124a communicates with the hydraulic pressure supply passage 126a and the second oil chamber 124b is formed. It communicates with the hydraulic pressure discharge path 126c. Then, the servo type spool valve
The pressure oil from the hydraulic discharge passage 146c of 140 is supplied into the left oil chamber 133a of the hydraulic cylinder 130 through the hydraulic supply passage 126a, the first oil chamber 124a, and the hydraulic supply / discharge passage 135a, and the right oil of the hydraulic cylinder 130 is discharged. The pressure oil in the chamber 133b is supplied to the hydraulic pressure supply / discharge passage 135b and the second oil chamber 124.
It is discharged to the drain tank 76 through b and the hydraulic pressure discharge path 126c.

As a result, the piston 131 in the hydraulic cylinder 130 is driven to the right. This piston 131 piston rod 136
The spool 14 via the shaft 147 of the servo type spool valve 140
Spool with piston 131 because it is connected with 1.
141 is also driven to the right.

Therefore, in the servo type spool valve 140, the first oil chamber 144
a communicates with the hydraulic pressure discharge passage 146c, and the second oil chamber 144b communicates with the hydraulic pressure supply passage 146b. Then, the pressure oil supplied from the engine pump 74 through the hydraulic pressure supply passage 77a is changed to the hydraulic pressure supply passage 146.
b, through the second oil chamber 144b and the hydraulic pressure supply / discharge passage 148b, the pressure oil in the left oil chamber 90a of the rear power cylinder 9 is supplied to the right oil chamber 90b of the rear power cylinder 9, 148
a, through the first oil chamber 144a and the hydraulic pressure discharge passage 146c to the spool valve 120 side.

As a result, the piston 91 of the rear power cylinder 9 is driven leftward together with the piston rods 92a, 92b, and the trailing arms 10a, 10a of the rear suspension 10 connected to the piston rods 92a, 92b are swiveled leftward. , Rear wheels 2b, 2b via this trailing arm 10a, 10a
Is steered to the left.

The amount of hydraulic pressure supplied to and discharged from the hydraulic cylinder 130 is determined by the output point 108.
It is almost proportional to the moving amount of D and increases as the moving amount of the output point 108D increases. Therefore, the piston 131 in the hydraulic cylinder 130 is driven by an amount corresponding to the steering amount, and the spool 141 of the servo type spool valve 140 is also driven in accordance with the steering amount.

In the servo type spool valve 140, the casing 140a
However, since it can slide in conjunction with the piston rods 92a, 92b via the rod 149, when the piston rods 92a, 92b slide leftward while driving the rear wheel 2b, the rod 149 , And rotates clockwise around the fixed fulcrum 149B to slide the casing 140a to the right through the pivot pin 149a.

As a result, the casing 140a follows the spool 141 that has slid to the right, and when the casing 140a slides by the same amount as the spool 141, the servo spool valve 140 is in a neutral state and the steering amount (steering wheel 1 The steering state of the rear wheels corresponding to the operation angle) is maintained.

On the other hand, when the shaft 127 is driven to the right, the spool valve 1
20, each part of the hydraulic cylinder 130, the servo spool valve 140, the rear power cylinder 9, and the rear suspension 10 is driven in the opposite direction to the above, and the rear wheels 2b, 2b are steered to the right.

Next, the operation of the rear wheel turning ratio adjustment mechanism RC will be described.

First, the vehicle speed responsive hydraulic cylinder 110 and the vehicle speed proportional hydraulic pressure supply system PS1 will be described. The transmission pump 72 of the vehicle speed proportional hydraulic pressure supply system PS1 outputs a hydraulic pressure proportional to the vehicle speed. The oil is supplied into the oil chamber 110b of the vehicle speed responsive hydraulic cylinder 110 through the supply path 72c and the hydraulic pressure supply / discharge path 119.

The hydraulic pressure supplied to the oil chamber 110b is applied to the return spring 11
While pressing 3, the piston 114 is driven in the contracting direction of the hydraulic cylinder 110 (leftward in FIG. 1). This piston
The driving amount of 114 is proportional to the hydraulic pressure supplied into the oil chamber 110b, and therefore proportional to the vehicle speed.

Therefore, when the vehicle is stopped or the vehicle speed is extremely close to 0, the piston 114 takes the extended position of the hydraulic cylinder 110 as shown in FIG. Then, as the vehicle speed increases, the piston 114 is positioned in the contracting direction (left direction) of the hydraulic cylinder 110.

Therefore, the moving fulcrum 105 of the vehicle speed input arm 102 connected to the tip of the piston rod 112 has a fixed fulcrum 106 of the support arm 103 when the vehicle is stopped (low speed etc.) or when the vehicle speed is very close to zero. It is located on the upper side, and is separated from the fixed fulcrum 106 to the left as the vehicle speed increases.

Furthermore, since the hydraulic cylinder 110 is pivotally supported by the bracket 111, even when the piston rod 112 moves back and forth, the cylinder body 110a interferes with the piston 114 and the piston rod 112, and the link portion 100 connected to the piston rod 112.
Unnecessary load on each of the pivot joints is prevented.

Next, the operation of the link portion 100 will be described. In this link portion 100, the rear wheel 2b is moved to the front wheel according to the position of the movement fulcrum 105.
Rear wheel 2b and the state of steering in the same phase as 2a (in-phase state)
A state in which the front wheel 2a is steered in the opposite phase direction (reverse phase state),
Even if the front wheels 2a are steered, the rear wheels 2b are not steered, and there is a boundary state between the in-phase state and the in-phase state.

FIG. 3 shows the reversed phase state, in which the vehicle is stopped or the vehicle speed is extremely low (low speed state), and the piston 114 has the hydraulic cylinder 1 as shown in FIG.
The extension position of 10 and the movement fulcrum 1 of the vehicle speed input arm 102
05 is located on the fixed fulcrum 106 of the support arm 103 so as to overlap.

Therefore, the first point 108C, the second point 108B, the movement fulcrum 105
The 4-node link 100R itself, which is composed of the fixed fulcrum 106 and the fulcrum 106, is fixed so as not to move, and the input / output arm 101
Will rotate about the fulcrums 105 and 106.

That is, when the input point of the input / output arm 101 is driven rightward from the position shown by reference numeral 108A 'in FIG. 3 to the position shown by reference numeral 108A, the first point is at the position shown by reference numeral 108C'. From the position shown by the reference numeral 108C to the position shown by the reference numeral 108D, the second point moves from the position shown by the reference numeral 108B 'to the position shown by the reference numeral 108B, and the output point changes from the position shown by the reference numeral 108D' to the position shown by the reference numeral 108D. And moves to the left, which is the opposite of the input point 108A.

Therefore, when the steering wheel 1 is rotated to the right when the vehicle is stopped or traveling at a low speed, the front wheels 2a are steered to the right, whereas the rear wheels 2b are steered to the left.

That is, when the steering wheel 1 is rotated to the right, the rotational force is converted by the conversion mechanism 150 into the sliding movement of the advancing / retreating screw 152 to the right in FIG. 1, and the link portion 100 is turned on as shown in FIG. Output arm 101 rotates to the right and output point 1
The shaft 127 of the spool valve 120 is driven leftward through 08D. As a result, as described above, the spool valve 120, the hydraulic cylinder 130, the servo type spool valve 140, the rear power cylinder 9, and the rear suspension 10 operate,
The rear wheels 2b are steered to the left, contrary to the front wheels 2a.

Conversely, if the steering wheel 1 is rotated counterclockwise, the front wheels
2a is steered to the left and rear wheels 2b are steered to the right.

On the other hand, FIG. 2 shows the in-phase state of the link portion 100, in which the vehicle is in a high speed state (a state in which the vehicle speed is equal to or higher than a predetermined vehicle speed), the piston 114 is in the contracted position of the hydraulic cylinder 110, and the vehicle speed input is performed. The movement fulcrum 105 of the arm 102 is a support arm 103.
The fixed fulcrum 106 is located at a position far left to the left.

In particular, in FIG. 2, the distance between the moving fulcrum 105 and the fixed fulcrum 106 becomes substantially equal to the distance between the first point 108C and the second point 108B, and the first point 108C, 2 point 108B, movement fulcrum
The four-bar link 100R composed of 105 and fixed fulcrum 106 forms a substantially parallelogram. Therefore, the input / output arm 10
1 does not rotate as a whole, and only slides in the lateral direction.

Therefore, in the input / output arm 101, its input point is the second
When driven rightward from the position shown by reference numeral 108A 'to the position shown by reference numeral 108A, the first point changes from the position shown by reference numeral 108C' to the position shown by reference numeral 108C, and the second point shows the reference code. 108B ′
From the position indicated by reference numeral 108D ′ to the position indicated by reference numeral 108D ′.
It moves to the position indicated by 8D in the right direction similar to the input point 108A.

Therefore, when the steering wheel 1 is rotated to the right during high-speed traveling, the front wheels 2a are steered to the right and the rear wheels are rotated.
2b is also steered to the right.

That is, when the steering wheel 1 is rotated to the right, the rotational force is converted by the conversion mechanism 150 into the sliding movement of the advancing / retreating screw 152 in the right direction in FIG. 1, and the link portion 100 is turned on as shown in FIG. The output arm 101 slides to the right,
The shaft 127 of the spool valve 120 is driven to the right through the output point 108D. As a result, the spool valve
Each part of the 120, the hydraulic cylinder 130, the servo type spool valve 140, the rear power cylinder 9 and the rear suspension 10 operates, and the rear wheel 2b is steered to the right like the front wheel 2a.

Conversely, if the steering wheel 1 is rotated counterclockwise, the rear wheels
2b is steered to the left along with the front wheels 2a.

Further, the vehicle speed is an intermediate size (vehicle speed = M), and the moving fulcrum 105 of the vehicle speed input arm 102 is separated from the fixed fulcrum 106 of the support arm 103 to the left by an appropriate amount (see FIG. 2). If the position is appropriately closer to the fixed fulcrum 106 than in the state shown, the rear wheel 2b will not be steered even if the front wheel 2a is steered, and there will be a boundary state between the in-phase state and the in-phase state.

That is, the input / output arm 101 rotates around the output point 108D, and even if the input point 108A is driven to the left or right, the output point 108D does not move.

The relationship between the displacement of the movement fulcrum 105 (displacement of the vehicle speed input arm 102) and the output / input ratio is shown by a straight line L in FIG. 4, and the output / input ratio increases in proportion to the vehicle speed. I understand that I will do it.

As described above, in this steering ratio control mechanism, the four-bar link 100R
Since it is configured to adjust the steering ratio of the rear wheels while driving the moving fulcrum 105, which is one of the nodes, the load applied to the link portion 100 is distributed to each point and is large at one point. No load is applied. Therefore, it is possible to reduce the size of the entire mechanism while ensuring sufficient strength and reliability, and there is an advantage that the mounting performance in an actual vehicle is significantly improved. In addition to this, since this mechanism has a simple structure, in this respect as well, the reliability is improved and the cost is reduced.

Further, in the vehicle front / rear wheel steering system according to the present embodiment, four oil passages 77a are provided between the front wheel side (engine side) F and the rear wheel side R.
Since only the 135a, 135b and 146c are connected, the device can be easily and compactly installed in the vehicle.

On the other hand, as shown in FIG. 5, the spool valve 120, the hydraulic cylinder 130 and the oil passages associated with them of the vehicle front / rear wheel steering system of the present embodiment are omitted, and the output point 108D of the link portion 100 is omitted.
The rod 128 connected to the shaft of the servo spool valve 140
141 may be coupled with the interlocking rod 160 so that the movement of the output point 108D is directly transmitted to the shaft 141.

In this case, both ends of the interlocking rod 160 are in rigid contact with the rod 128 and the shaft 141, and the end of the hydraulic pressure discharge passage 146c is guided to the drain tank 76.

With such a configuration, the servo type spool valve 1 can be used even with the advantage that the device is simplified and the minute movement of the link portion 100.
Since 40 is responsive, there is an advantage that the steering response of the rear wheel 2b to the operation of the steering wheel 1 is good.

The hydraulic cylinder 110 may be configured as shown in FIG.

This hydraulic cylinder 110 includes a cylinder body 110a and a piston 114 that is provided inside the cylinder body 110a so as to be able to move forward and backward.
A piston rod 112 that is connected to the piston 114 and has a tip portion protruding to the outside of the cylinder body 110a; a piston side (rear) first coil spring 70e that biases the piston 114 to a retracted position; The second coil spring 70f, the spring contact member 70d interposed between the first and second coil springs 70e, 70f, and the spring contact member 70d by contacting the spring contact member 70d. A stopper 70c that restricts the backward movement of the piston to the piston 114 side, a rubber stopper 70g as an elastic body that abuts the spring abutting member 70d to elastically restrain the forward movement of the spring abutting member 70d, and the cylinder body 110a.
And an oil chamber 110b formed by the piston 114 and the opening 110 thereof.
It consists of c and.

An appropriate preload (compression load) is applied to the front second coil spring 70f in a state where the spring contact member 70d contacts the stopper 70c and is most extended. The second coil spring 70f is set to have a larger spring constant and a higher rigidity than that of the first coil spring 70e. The rubber stopper 70g is
The second coil spring 70f has a larger spring constant and a higher rigidity.

In addition, each oil passage of the transmission pump 72 has a sixth
As shown in the figure, a pressure oil supply / discharge passage 7 connecting the transmission pump 72 and the oil chamber 110b of the hydraulic cylinder 110.
2b, a pressure oil supply passage 72c and a pressure oil discharge passage 72d connected to the pressure oil supply / discharge passage 72b, an oil passage 72j provided between the transmission pump 72 and the reservoir tank 72g, and a pressure oil supply passage 72c. And the oil passage 72j between the transmission pump 72
Oil passage 72i with check valve 72e installed in parallel with a
And an orifice 72f interposed in the pressure oil discharge passage 72d, and a relief valve 72h provided in parallel with the orifice 72f between the pressure oil supply passage 72c and the pressure oil discharge passage 72d.

The relief valve 72h is opened when a hydraulic pressure equal to or higher than a predetermined value is generated in the pressure oil supply passage 72c, and the relief oil 72h is released from the pressure oil supply passage 72c.
It is designed to relieve pressure oil.

With such a configuration, when the hydraulic pressure proportional to the vehicle speed is supplied from the transmission pump 72 into the oil chamber 110b, an appropriate preload (compression load) is applied to the second coil spring 70f. If the hydraulic pressure level supplied in 110b is lower than the above preload value,
Since the hydraulic pressure receives only the drag force of the first coil spring 70e, the piston rod 112 advances relatively rapidly as indicated by a straight line l ₁ shown in FIG. 7 (this state is referred to as a first drive state). ).

When the oil pressure level exceeds the above preload value,
The hydraulic pressure receives not only the drag force of the first coil spring 70e but also the larger drag force of the second coil spring 70f, so that the drive rack 70b is relatively gentle as indicated by a straight line l ₂ shown in FIG. Forward (this state is referred to as a second drive state).

When the hydraulic pressure level further increases and the drive rack 70b moves forward greatly, the second coil spring 70f contracts accordingly, and the spring contact member 70d moves to the rubber spring 70g.
The drive rack 70b contacts the first coil spring 70e and the second coil spring 70f.
In addition to the drag, will receive a greater force of the rubber spring 70 g, driving rack 70b, as in the straight line l ₃ shown in FIG. 7, a more gradual advancement state (this state the 3 driving state).

Therefore, while the supplied hydraulic pressure increases in proportion to the vehicle speed, the forward movement state of the piston rod 112 changes in three stages according to the increase in hydraulic pressure as described above.

Therefore, when the front-rear wheel turning ratio is set to 0 at the vehicle speed reference value M, the front-rear wheel turning ratio characteristic shows a bending line that is combined with straight lines L ₁ , L ₂ and L ₃ shown by broken lines and solid lines in FIG. become that way. The straight line L ₁ corresponds to the above-mentioned first driving state (see the straight line l _{1 in} FIG. 7), and the straight line L ₂ corresponds to the above-mentioned second driving state (see the straight line l _{2 in} FIG. 7). Corresponding to a straight line
L ₃ corresponds to the above-mentioned third driving state (see the straight line l _{3 in} FIG. 7). The curve indicated by a chain line in FIG. 8 is a front-rear wheel turning ratio characteristic curve that makes the center-of-gravity slip angle zero.

In this way, by simply arranging a plurality of springs 70e, 70f, and 70g having appropriate elasticity (spring constant) inside the hydraulic cylinder 110 so as to resist the hydraulic pressure, the front-rear wheel steering ratio can be extremely easily adjusted. The characteristic can be set to be similar to the front-rear wheel turning ratio characteristic in which the center-of-gravity slip angle is zero.

Further, the rear power cylinder may be configured as shown in FIG.

The rear power cylinder 9 is provided with 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 cylinder body 90 which can move forward and backward. , A piston 91 that divides the inside of the cylinder body 90 into a left oil chamber 90a and a right oil chamber 90b, and piston rods (tie rods) 92a and 92b that project from the piston 91 to the left and right and penetrate the left and right of the cylinder body 90. Has been done.

Caps 93a, 93b are mounted on the left and right of the cylinder body 90, and the piston rods 92a, 92b are mounted on the caps 93a, 9b.
It penetrates the hole provided in 3b. In addition, in the center of the inner peripheral surface of the cylinder body 90, an inwardly projecting annular protrusion 90c
The piston 91 is slidably attached to the inside of the annular convex portion 90c so as to be able to advance and retreat while sliding left and right via the pipe 94.

The left and right piston rods 92a and 92b of the piston 91 and the pipe 94
An annular rubber spring 95a, 95b is provided between and, and further, outside of the rubber spring 95a, 95b, a stopper 96a, which protrudes outward, respectively.
The annular plates 97a and 97b provided with 96b are the left oil chamber 90a.
Alternatively, it is provided so that it can slide inside 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 structure 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 oil chambers inside the left oil chamber 90a and the right oil chamber 90b are adjusted, and a force acts on the piston 91 for 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.

The magnitude of this preload is, as shown in the graph of FIG. 10, only when the stroke of the piston 91 exceeds (+ S ₁ ) or (−S ₁ ), the coil springs 98a, 98 are not shown.
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 structure 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
By the action of 8b and stoppers 96a and 96b, the solid line is shown in FIG.

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

With such a configuration, the non-linear spring structure 9A provided in the rear power cylinder 9 operates as follows.

That is, when the steering wheel angle is large, the rear wheel steering force may be exerted against the coil spring 98a, the spring constant of the coil spring 98a is small, and the increase of the spring reaction force is suppressed. The increase in the rear wheel steering force, that is, the amount of hydraulic pressure supplied to the rear power cylinder, is suppressed. The nonlinear spring structure 9A includes stoppers 96a, 96
Since b is provided, the rear wheel steering angle amount is limited as shown in FIG.

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.

[Advantages of the Invention] As described in detail above, according to the steering ratio control mechanism of the front and rear wheel steering device for a vehicle of the present invention, the front wheel steering mechanism and the rear wheel steering mechanism connected to the steering handle mechanism are provided. A steering ratio adjusting mechanism for controlling the ratio of the steering angle of the rear wheels to the steering angle of the front wheels, which is provided between the steering handle mechanism and the steering mechanism for the rear wheels of the front and rear wheel steering device for a vehicle. At one end side, a displacement input section for inputting a displacement according to the front wheel steering angle is provided, and at the other end side a displacement output section for outputting a displacement for controlling the rear wheel steering angle to the rear wheel steering mechanism is provided. An input / output arm, a support arm having one end pivotally attached to a first point of the input / output arm and the other end pivotally attached to a fixed fulcrum of the base body, and one end to a second point of the input / output arm. With a vehicle speed input arm that is pivotally attached and the other end is pivotally attached to the movement fulcrum. In addition, a four-bar link having the above four points as a node is constituted by the input / output arm, the support arm, and the vehicle speed input arm, and the first and second points are intermediate portions of the input / output arm. And a vehicle speed responsive drive means for moving the moving fulcrum in accordance with the vehicle speed to change the distance between the fixed fulcrum and the moving fulcrum, while ensuring sufficient strength and reliability. It has the advantage that it can be miniaturized and that its performance in actual vehicles can be greatly improved. In particular, the vehicle speed responsive driving means moves the movement fulcrum of the vehicle speed input arm in accordance with the vehicle speed to change the distance between the fixed fulcrum and the movement fulcrum of the support arm. There is also an advantage that the displacements of the other nodes constituting the above are small and the displacements are secondary, so that the movable space of the steering ratio control mechanism can be small. In addition to this, since this mechanism has a simple structure, in this respect as well, the reliability is improved and the cost is reduced.

[Brief description of drawings]

1 to 11 show a steering ratio control mechanism of a front and rear wheel steering device for a vehicle as an embodiment of the present invention, and FIG. 1 is a schematic diagram showing an equipment state of the front and rear wheel steering device for a vehicle. 2 is a main part configuration diagram showing the in-phase control state, and FIG.
FIG. 4 is a configuration diagram of a main part showing the reversed phase control state, FIG. 4 is a graph showing a ratio of output and input with respect to displacement of the movement fulcrum, and FIG. FIG. 6 is a schematic configuration diagram showing the vehicle front and rear wheel steering device,
FIG. 8 shows a modified example of the hydraulic pressure supply system of the vehicle speed responsive drive means, FIG. 6 is its schematic configuration diagram, FIG. 7 is a graph showing the displacement characteristics of its movement fulcrum, and FIG. It is a graph which shows the rear wheel turning ratio characteristic adjusted by a vehicle speed response drive means, FIGS. 9-11 shows the modification of the rear power cylinder of this turning ratio control mechanism, and FIG. 9 shows the rear power. FIG. 10 is a longitudinal sectional view of the cylinder, and FIG. 10 is a graph showing the assembly characteristic of the nonlinear spring mechanism of the rear power cylinder.
FIG. 11 is a graph showing the output characteristic of the rear power cylinder. 1 ... Steering wheel (steering handle), 1a ... Front power steering gear box, 1b ... Steering shaft, 1c ... Tie rod,
2a ...... front wheel, 2b ... rear wheel, 3 ... bevel gear assembly, 6 ... in-phase / reverse-phase conversion mechanism, 9 ... rear power cylinder, 9A ... nonlinear spring structure, 10 ... rear suspension, 10a ... tray Ring arm, 12 ... Suspension cross member, 31 ... First shaft, 32 ... First bevel gear 32, 33 ... Shaft, 34 ... Second bevel gear, 70c
...... Stopper, 70d ...... Spring contact member, 70e ...... First coil spring, 70f ...... Second coil spring, 70g ...... Rubber stopper as elastic body, 70h ...... Sensor rod, 70i ...... Casing, 71 ... Potentiometer, 71a ... Signal line, 71b ... Power supply line, 72 ...
… Transmission pump (or differential pump), 72b …… Pressure oil supply / discharge path, 72c …… Pressure oil supply path, 72
d ... Pressure oil discharge path, 72e ... Check valve, 72f ... Orifice, 72g ... Reservoir tank, 72h ... Relief valve, 72j
…… Oil passage, 74 …… Engine pump, 74a …… Hydraulic supply passage, 74b …… Oil supply passage, 74c …… Relief valve, 74d …… Hydraulic discharge passage, 76 …… Drain tank (reservoir), 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, 98a, 98b …… Coil spring (return spring), 99a, 99b …… Opening, 100 ……
Link section, 100R ... 4-point link (section 4 link), 101 ...
Input / output arm, 101a ... Displacement input section, 101c ... Displacement output section, 101A ... Main arm section, 101B ... Sub arm section, 102
...... Vehicle speed input arm, 103 …… Support arm, 104a, 104b, 1
04c, 104d, 104e, 104f …… Pivot pin, 105 …… Movement fulcrum, 1
06 …… Fixed fulcrum, 107 …… Base body (base member), 108A…
… Input point, 108B …… Second point, 108C …… First point, 108D
...... Output point, 110 …… Vehicle speed responsive hydraulic cylinder as vehicle speed responsive driving means, 110a …… Cylinder body, 110b …… Oil chamber, 111 …… Bracket, 111a …… Pin, 111 …… Bracket, 111a …… Pin, 112 …… Piston rod, 113 ……
Return spring, 114 ...... Piston, 115 ...... Prevention of sudden change in hydraulic pressure, 117 ...... Check valve (check valve), 117a ......
Oil passage, 118 ... Orifice, 119 ... Hydraulic pressure supply / discharge passage, 120 ...
… Spool valve, 120a …… Casing, 121 …… Spool, 121a, 121b, 121c …… Valve body part, 122a, 122b …… Return spring, 123a, 123b, 123c …… Annular recess, 123d, 1
23e, 123f, 123g …… Inner wall surface part, 124 …… Spool chamber, 12
4a ... first oil chamber, 124b ... second oil chamber, 126a, 126b ...
… Hydraulic supply path, 126c …… Hydraulic discharge path, 127 …… Spool valve shaft, 128 …… Rod, 130 …… Hydraulic cylinder, 130a…
… Cylinder body, 131 …… Piston, 132a, 132b …… Opening, 133a …… Left oil chamber, 133b …… Right oil chamber, 134a, 134b ……
Return springs, 135a, 135b ...... hydraulic pressure supply / discharge paths, 136 ...
… Piston rod, 140… Servo type spool valve, 140a
... Casing, 141 ... Spools, 141a, 141b, 141c ...
… Valve disc part, 142a, 142b …… Return spring, 143a,
143b, 143c ... annular recess, 143d, 143e, 143f, 143g ... inner wall surface portion, 144 ... spool chamber, 144a ... first oil chamber, 144
b …… second oil chamber, 146a, 146b …… hydraulic supply path, 146c ……
Hydraulic discharge path, 147 …… Spool valve shaft, 148a, 148b …… Hydraulic supply / discharge path, 149 …… Interlocking rod, 149a, 149b, 149c …… Pivoting pin, 149B …… Fixed fulcrum, 150 …… Conversion mechanism , 151 ……
Screw nut, 152 …… Advancing / retreating screw, 160 …… Interlocking rod, PS1 …… Vehicle speed proportional hydraulic supply system, RC …… Rear wheel steering ratio adjusting mechanism, RM …… Rear wheel steering mechanism, FM …… Front wheel steering mechanism , ST …… Steering handle mechanism.

Front page continuation (72) Creator Tadahiro Otsuka 10 Oe-cho, Minato-ku, Aichi Prefecture Nagoya Aircraft Manufacturing Co., Ltd. (72) Creator Tsujide Shin-Aichi Prefecture, 10 Oe-cho, Minato-ku Nagoya Mitsubishi Heavy Industrial Co., Ltd. Nagoya Aircraft Works (72) Inventor Teruo Nakanishi 10 Oe-cho, Minato-ku, Nagoya-shi, Aichi Mitsubishi Heavy Industries, Ltd. Nagoya Aircraft Works (56) Reference JP-A-60-193770 (JP, A) Open Sho 59-92261 (JP, A) Actual Open Sho 62-38782 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A front / rear wheel steering device for a vehicle, comprising a front wheel steering mechanism and a rear wheel steering mechanism connected to a steering handle mechanism, which is interposed between the steering wheel mechanism and the rear wheel steering mechanism. In the steering ratio adjusting mechanism that controls the ratio of the steering angle of the rear wheels to the steering angle of the front wheels, one end has a displacement input section for inputting the displacement according to the steering angle of the front wheels and the other end side. An input / output arm having a displacement output section for outputting a displacement for controlling the rear wheel steering angle to the rear wheel steering mechanism, one end of which is pivotally attached to a first point of the input / output arm and the other end of which is a base body. A support arm pivotally attached to a fixed fulcrum of the vehicle and a vehicle speed input arm pivotally attached at one end to a second point of the input / output arm and at the other end to a moving fulcrum. From the support arm and the vehicle speed input arm, A four-joint link serving as a joint is formed, and the first and second points are provided in an intermediate portion of the input / output arm, and the movement fulcrum is moved in accordance with the vehicle speed to move the fixed fulcrum and the movement. A steering ratio control mechanism for a front / rear wheel steering device for a vehicle, comprising vehicle speed responsive driving means for changing a distance from a fulcrum.