JPH0115430B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rear wheel steering angle control device for a vehicle, and particularly to a device for controlling an operating mechanism that produces a steering angle on the rear wheels to produce a steering angle on the front wheels. The present invention relates to a rear wheel steering angle control device for a vehicle (hereinafter referred to as a four-wheel steering vehicle) that automatically controls the steering angle of the rear wheels in accordance with steering of a steering wheel.

[Conventional technology]

A conventional rear wheel steering angle control device for a four-wheel steered vehicle (Japanese Patent Laid-Open No. 57-44568), which is the basis of the present invention, will be explained with reference to FIG.

The shaft 2 rotates together with the rotational steering of the handle 1, and this rotation is transmitted to the gearbox 3 and converted into linear motion of the linkage 4. linkage 4
The linear motion rotates the knuckle arm 5 around the fulcrum 5a, steers the front wheels 6, and gives the front wheels 6 a steering angle δ _f
(t) (where t is time).
A sensor 15 attached to the shaft 2 detects the rotational steering angle δ _h (t) _of the steering wheel 1, and a sensor 7 detects the lateral acceleration V Detect. computer 8
actuates the actuator 9 based on detection signals from the sensors 7 and 15, and applies linear motion to the linkage 14 via the gearbox 10. The linear motion of the linkage 14 rotates the knuckle arm 13 around the fulcrum 13a, steers the rear wheel 12, and causes the rear wheel 12 to produce a steering angle δ _r (t). This rear wheel steering angle δ _r (t) is set in the computer 8 as δ _r (t) = K·V (1), which has a proportional relationship to the lateral acceleration V, or the front wheel steering angle Adding h・δ _f (t), which is obtained by multiplying the angle δ _f (t) by the proportionality constant h, to the right side of the above equation (1), δ _r (t)=h・δ _f (t)+K・V〓 …… (2) is set and controlled.

However, such conventional rear wheel steering angle control devices are not configured to take into account the steering speed of the steering wheel, and the rotational steering angle of the steering wheel is small due to the signal proportional to the rotational steering angle of the steering wheel. Even if the steering angle is large, the rear wheels are steered in the same direction as the front wheels, which has the advantage of improving the running stability of the vehicle when driving straight and making it easier to correct the steering wheel. The responsiveness of the movement is not good, and the structure is not designed to enable turning movement with a small turning radius.

In addition to the device shown in Fig. 2, conventionally, in a four-wheel steering vehicle in which a steering device for steering the front wheels and a steering device for steering the rear wheels are mechanically connected, when the rotational steering angle of the steering wheel is small, In this case, the rear wheels are steered in the same direction as the front wheel steering angle, and when the steering angle of the steering wheel is large, the rear wheels are steered in the opposite direction to the front wheel steering angle.
A device for controlling the steering angle of the rear wheels has also been proposed.

[Problem that the invention seeks to solve]

However, in such a device, the rear wheels are steered in the same direction or in the opposite direction as the front wheels depending on the magnitude of the rotational steering angle of the steering wheel, and the speed at which the driver turns the steering wheel is controlled. For example, when the driver is responding to an emergency maneuver that requires a rapid turning movement such as to avoid an obstacle or changing lanes, and when the driver is performing normal steering such as making a gentle turn while driving straight ahead. Even if you change the steering speed of the steering wheel in anticipation of different dynamic characteristics, if the rotational steering angle of the steering wheel is constant, the steering angle of the rear wheels will remain constant in the specified direction. It has a controlled configuration.

Therefore, the conventional four-wheel steering vehicle described above has a problem in that it cannot fully satisfy the motion characteristics expected by the user depending on the steering speed of the steering wheel.

The present invention has been made to solve the above-mentioned problems.It improves the responsiveness of turning movements in situations where rapid turning movements are required, and improves the responsiveness of turning movements in situations where slow turning movements are required. It is an object of the present invention to provide a rear wheel steering angle control device for a vehicle, which can improve the stabilizer to obtain the dynamic characteristics expected by a driver, and can reliably steer the rear wheels using hydraulic pressure.

[Means for solving problems]

In order to achieve the above object, the present invention provides a rear wheel steering angle control device for a vehicle that controls the steering angle of the rear wheels in accordance with the steering of a steering wheel that produces a steering angle in the front wheels.
The steering speed of the steering wheel is determined, and when the steering speed is fast, the rear wheels are caused to produce a steering angle in the opposite direction to the front wheels, and when the steering speed is slow, the rear wheels are caused to steer in the same direction as the front wheels. a rear wheel steering determining means for switching a flow path to produce a steering angle of; a cylinder arranged so that a linkage connected to the rear wheel passes through; a cylinder fixed to the linkage to divide the inside of the cylinder into two chambers; A piston to be divided, a hydraulic pressure generating device that is driven by an engine to generate hydraulic pressure, and the rear wheel steering determining means so as to communicate the hydraulic pressure generating device and two chambers in the cylinder to supply and discharge hydraulic pressure. and an actuation mechanism equipped with a control valve that switches the flow path.

[Effect]

Next, the operation of the present invention will be explained. The rear wheel determining means determines the steering speed of the steering wheel, and when the steering speed of the steering wheel is fast, the flow path of the control valve of the operating mechanism is configured to cause the rear wheels to have a steering angle in the opposite direction to that of the front wheels. When the speed of switching and engagement of the steering wheel is slow, the flow path of the control valve of the operating mechanism is switched so that the rear wheels are steered in the same direction as the front wheels. This results in
Hydraulic pressure generated by a hydraulic pressure generating device driven by an engine is supplied to and discharged from two chambers within the cylinder via a control valve, and this supply and discharge of hydraulic pressure generates a hydraulic pressure difference between the two chambers within the cylinder. 2 in the cylinder
The two chambers are divided by a piston, and since a linkage connected to the rear wheel is fixed to this piston, the piston is moved by the hydraulic pressure difference, and the rear wheel is moved via the linkage in response to switching of the control valve. Be steered. When the front and rear wheels are steered in opposite directions, the front and rear wheels produce steering angles almost simultaneously, generating force on the tires, and these forces become a yawing moment that rotates in the same direction. (In this case, the steering angle of the steering wheels is equivalently the steering angle of the front wheels and the steering angle of the rear wheels.) ), the responsiveness of the vehicle's turning motion is improved. Additionally, when the front wheels and rear wheels are steered in the same direction, steering angles are generated in the front and rear wheels almost simultaneously, generating force on the tires, and these forces become yawing moments that rotate in opposite directions. The steering gain is equivalently reduced, and the straight-line stability of the vehicle is improved.

〔Effect of the invention〕

Therefore, according to the present invention, when the steering wheel is being steered quickly, the steering gain is increased to improve the responsiveness of the vehicle's rapid turning motion, and when the steering wheel is being steered at a slow speed, the steering gain is decreased. It prevents the vehicle from wobbling or wobbling, improving running stability when the vehicle is traveling straight, and since hydraulic pressure is used, the rear wheels can be steered reliably and responsively with optimal power. ,
This effect can be obtained.

[Description of aspects of the invention]

Next, aspects of the present invention will be explained. In a first aspect, the rear wheel steering determination means includes a first member that moves in response to steering of a steering wheel, a second member that moves in a direction opposite to the movement of the first member, and a second member that moves in a direction opposite to the movement of the first member. an elastic member connected to the first member; a dart pot connected to the second member; and a dart pot connected to the elastic member and the dart pot to move in accordance with the movements of the first member and the second member. and an output shaft connected to the control valve of the operating mechanism so as to switch the flow path.

Next, the operation of the rear wheel steering determining means of the first aspect will be explained. The first member moves in response to the steering of the steering wheel when the steering wheel is steered. That is, the first member performs linear movement, rotational movement, etc. in the vehicle width direction, the vehicle longitudinal direction, or the vehicle vertical direction, for example. Along with this movement of the first member, the second member moves in a direction opposite to the movement of the first member. Further, the output shaft is connected to the first
Since the output shaft is connected to the first member and the second member via the dart pot, the output shaft also moves as the first member and the second member move.

Here, as shown in Fig. 3, with time t,
The displacement of the first member's motion is x ₁ (t), the displacement of the second member's motion is x ₂ (t), and the displacement of the output shaft is x _put
(t), the resistance F _c of the dart pot is proportional to the speed, so it can be expressed by the following equation.

F _c =C (x〓 _put (t) - x〓 ₂ (t)) ... (1) where C is the attenuation coefficient of the dart pot, and . represents the time differential.

Furthermore, when the elastic modulus of the elastic member is k, the restoring force _Fk of the elastic member is expressed by the following equation.

F _k = k (x ₁ (t) - x _put (t)) ... (2) Since these two are balanced, the following equation holds true.

C (x〓 _put (t) - x〓 ₂ (t)) + k (x _put (t) - x ₁ (t)) = 0 ... (3) Also, the first member and the second member are mutually Since it moves in the opposite direction, the following equation holds.

x ₂ (t) = -N・x ₁ (t) ...(4) (N is a positive proportionality constant) Therefore, from equations (3) and (4) above, the following equation (5) is obtained. It will be done.

x _put +C/kx〓 _put (t)=x ₁ (t)-c/k・N・x
〓 ₁ (t) ...(5) Laplace transform the above equation (5) to obtain the transfer function G(s)=
Expressed in the form x _put (s)/x ₁ (s), it becomes as follows.

G(s)=1−K ₁ TS/1+TS ...(6) However, K ₁ =N+1, T=C/k, s is σ+
Complex frequency expressed as jω (where σ is any real number unrelated to time t, ω is the angular frequency, j = √
−1).

Here, K ₁ =2, that is, the first member and the second member
When the magnitude of the displacement with the member is equal (x ₂ (t) =
−x ₁ (t)), the above equation (6) becomes as follows.

G(s)=1-TS/1+TS...(7) In the above equation (7), when the first member and the second member are displaced very slowly, that is, when the complex frequency S is close to 0, Considering this, lim s→0G(s)=1...(8). Therefore, x _put (s)/x ₁ (s) = 1,
The output shaft will be displaced with the same magnitude and in the same direction as the displacement of the first member (i.e. x _put (t) = x ₁
(t)).

On the other hand, if we consider the case where the first member and the second member are displaced extremely quickly, that is, the complex frequency S is close to infinity, lim s→∞G(s)=-1 ...(9) Become. Therefore, x _put (s)/x ₁ (s) = -1, and the output shaft is displaced in the same magnitude and opposite direction as the displacement of the first member (with the same magnitude and same displacement for the second member). x _put (t) = -
x ₁ (t) = x ₂ (t)).

Then, considering the case where the first member and the second member are displaced at a speed intermediate between the above speeds, that is, when the complex frequency S is close to 1/T, lim s→1/TG(s )=0...(10) Therefore, x _put (s)/x ₁ (s) = 0,
Even if the first member and the second member are displaced, the output shaft is hardly displaced (ie, x _put ≈0).

Considering the above points, the complex frequency S and the transfer function G are
The relationship with (s) is shown in Figure 4. As can be understood from the figure, in a region where the complex frequency S is less than 1/T, the output shaft is displaced in the same direction as the first member, and in a region where the complex frequency S exceeds 1/T, the output shaft is displaced in the same direction as the first member. When the complex frequency is 1/T, the output shaft is not displaced. Also,
The magnitude of the displacement of the output shaft at this time changes depending on the complex frequency.

Since the control valve of the operating mechanism is connected to the output shaft, the control valve is controlled according to the movement of the output shaft, and the flow path of the control valve is switched to operate the operating mechanism and handle the handle. When the steering speed of the steering wheel is fast, the rear wheels produce a steering angle in the opposite direction to the front wheels, and when the steering speed of the steering wheel is slow, the rear wheels produce a steering angle in the same direction as the front wheels. When the steering wheel is turned at an intermediate speed, almost no steering angle is generated in the rear wheels.

Therefore, the first aspect has the effect that the rear wheels can be reliably and responsively steered with optimal power using the hydraulic pressure from the operating mechanism.

Furthermore, in the first aspect, it is also possible to steer the straight rear wheels by the above-mentioned determining means;
In that case, the burden on the driver in steering the vehicle increases. However, since the rear wheels are steered with optimal power using the hydraulic energy of the operating mechanism according to the first aspect, it is only necessary to request the driver to steer the steering wheel with a small amount of power to enable the judgment function of the judgment means. This has the advantage of reducing the burden on the driver when operating the steering wheel. That is, the actuation mechanism of the first aspect has a function as a booster for the mechanical rear wheel steering mechanism.

Further, in a second aspect, the rear wheel steering determination means includes a detection circuit that detects a steering amount of the steering wheel and outputs a steering amount signal, and a detection circuit that determines the steering speed of the steering wheel based on the steering amount signal. a judgment circuit; and based on the judgment result of the judgment circuit, when the steering speed is fast, the rear wheels are caused to produce a steering angle in the opposite direction to the front wheels, and when the steering speed is slow, the rear wheels are caused to produce a steering angle in the opposite direction to the front wheels. and a control circuit that switches the flow paths of the control valves so as to produce steering angles in the same direction.

According to the second aspect, the detection circuit detects the rotational steering angle of the steering wheel or the displacement D of the steering wheel with respect to the position of the steering wheel corresponding to the straight-ahead direction of the vehicle, that is, an amount corresponding to the steering angle of the front wheels, as the steering amount of the steering wheel. is detected, and a steering amount signal is output from the detection circuit. When the rotational steering angle of the steering wheel is detected, the angular frequency ω of the steering wheel is obtained by differentiating the steering amount signal with respect to time, and when the displacement D of the steering wheel is detected, the displacement D is the angular frequency ω of the steering wheel. It is expressed as D=f(ωt) using .

Here, if the transfer function of the judgment circuit is the same as the above equation (7), the transfer function changes according to the angular frequency in the same way as shown in Fig. As a result of the judgment, if the steering speed of the steering wheel is slow, a signal that is in phase with the steering wheel steering amount signal is output, and if the steering speed of the steering wheel is fast, a signal that is in phase with the steering wheel steering amount signal is output. It is possible to output a signal that is 180° out of phase with respect to the linkage, and not output the signal when the steering speed of the linkage is an intermediate speed as described above. Based on the judgment result of the judgment circuit, the control circuit causes the rear wheels to produce a steering angle in the opposite direction to the front wheels when the steering speed of the steering wheel is fast, and the rear wheels when the steering speed of the steering wheel is slow. The flow path of the control valve of the operating mechanism is switched so that the steering angle is in the same direction as the front wheels. Then, by switching the flow path of this control valve, the rear wheels are steered similarly to the first aspect.

In the second aspect, the rear wheel steering determination means can be configured with an electric circuit, thereby simplifying the mechanical configuration.

Further, a third aspect includes a front wheel power cylinder arranged so that a linkage connected to the front wheel passes through the front wheel power cylinder, and a front wheel power piston that is fixed to the linkage and divides the inside of the power cylinder into two chambers. The vehicle is further provided with a switching valve that is switched in response to the steering of the steering wheel to communicate the hydraulic pressure generating device of the actuating mechanism with the chamber of the power cylinder to assist the steering of the front wheels.

The switching valve of this embodiment is switched in accordance with the steering of the handle, and supplies and discharges the hydraulic pressure generated by the hydraulic pressure generating device to the chamber in the cylinder, thereby creating a hydraulic pressure difference between the two chambers. As a result, the piston moves toward the low oil pressure chamber, applying force to the front wheels via the linkage and steering the vehicle.

According to the third aspect, since the steering of the front wheels is supplemented by hydraulic pressure, the steering force of the steering wheel can be reduced even when the road reaction force is large.

Therefore, according to the third aspect, there is an advantage that steering control is performed reliably and with good responsiveness using optimal power for both the front wheels and the rear wheels.

Furthermore, the third aspect has the advantage of reducing the burden of steering force on the driver even though front and rear wheel steering control is performed.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of a four-wheel steered vehicle equipped with a rear wheel steering angle control device according to an embodiment of the present invention.

A handle (steering wheel) 1 is connected to a gearbox 3 via a shaft 2. The gearbox 3 includes a first conversion mechanism that converts the rotation of the shaft 2 into a linear motion in the vehicle width direction, and a second conversion mechanism that converts the rotation of the shaft 2 into a rotational motion centered on the vehicle longitudinal direction. There is.
That is, the first conversion mechanism is composed of a rack 3A extending in the vehicle width direction and a pinion 3B connected to the shaft 2 that meshes with the rack 3A.
The rotation of the shaft 2 is converted into linear motion in the vehicle width direction. Further, the second conversion mechanism is composed of a rack 3A and a pinion 3C that meshes with the rack 3A,
The rotation of the shaft 2 is converted into rotational motion centered on the longitudinal direction of the vehicle.

A linkage 4 is connected to both ends of the rack 3A of the gearbox 3 to form an integral body.
Knuckle arms 6 are connected to each of them via tie rods 5. The knuckle arm 6 is rotatably supported by a pivot shaft 7 fixed to the vehicle body 30 via a bearing. A front wheel 8 is pivotally supported at the tip of the knuckle arm 6.

Therefore, the front wheels 8 are steered by the knuckle arm, which is rotated about the pivot shaft 7 in response to the rotational steering of the handle 1, thereby producing a steering angle.

The pinion 3C of the gearbox 3 is connected to the connecting shaft 21
The connecting shaft 21 is integrally connected to the universal joint 2.
2. It is connected to an input shaft 25 via an operating shaft 23 and a universal joint 24. The input shaft 25 is connected to the vehicle body 3
It is rotatably supported via a bearing on a bracket 31 fixed at 0, and is connected to a rear wheel steering determination mechanism. Therefore, the input shaft 25 rotates in the same direction as the steering wheel 1 in response to the steering of the steering wheel 1, and transmits this rotational movement to the rear wheel steering determination mechanism.

A linkage 14 that constitutes an operating mechanism protrudes from the rear wheel steering judgment mechanism, and a knuckle arm 16 that rotates around a pivot shaft 17 is connected to this linkage via a tie rod 15. rear wheel 1
8 is pivoted. Therefore, the linkage 1 is controlled via the rear wheel steering judgment mechanism in response to steering of the steering wheel.
4 is linearly moved in the vehicle width direction, the knuckle arm 16 is rotated about the pivot shaft 17, thereby steering the rear wheels 18.

Further, power steering fluid 66 flows into and out of the operating mechanism via a hydraulic pipe 65. Power steering fluid 66 is delivered by vane pump 61 driven via belt 41 in accordance with the rotation of engine 40, and generates hydraulic pressure.

The power steering fluid 66 sent out from the vane pump 61 has its flow rate in the oil path adjusted by a flow rate control valve 63, and the maximum oil pressure is regulated by a pressure adjustment valve 64, after which the power steering fluid 66 is connected to an operating mechanism connected to a rear wheel steering determination mechanism. supplied to The oil tank 62 returns unnecessary power steering fluid 66 from the operating mechanism, flow rate control valve 63, and pressure adjustment valve 64, and is also connected to the inlet of the vane pump 61 to provide oil for recirculating the power steering fluid 66. It is a reservoir.

Furthermore, if the target vehicle is a vehicle having a front wheel power cylinder 50 in the gear box 3 for front wheel steering (a so-called conventional vehicle equipped with front wheel power steering), these hydraulic pressure generating power devices The generating power device may also be used as a hydraulic pressure generating source for the actuating mechanism.

At that time, if larger power is required, it is also possible to provide an accumulator for accumulating hydraulic pressure in a part of the hydraulic piping 65.

Next, details of the rear wheel steering determination mechanism and operating mechanism of the first embodiment of the present invention will be explained based on FIG. 5, which is a cross-sectional view taken along the line AA in FIG. In addition, in this first embodiment, changes were made to the gearbox 3,
The pinion 3B and pinion 3C are directly engaged with each other so that the connecting shaft 25 rotates in the opposite direction to the steering wheel.

First, the rear wheel steering determination mechanism will be explained. A pinion 101 is provided at the tip of the input shaft 25.
The input shaft 25 is rotatably supported by a bracket 31 attached to the vehicle body 30 via a bearing. A rod 103 acting as a first member and a rod 113 acting as a second member are arranged symmetrically with respect to the input shaft 25. A rack 102 that meshes with the pinion 101 is formed on the input shaft 25 side of the rod 103, and a rack 112 that meshes with the pinion 101 is formed on the input shaft 25 side of the rod 113. The rod 103 is supported by the bracket 31 so as to be movable in the left-right direction in the figure, that is, in the width direction of the vehicle body, and one end is connected to the right spring seat 121. The right spring seat 121 fastens one end of the coil spring 122 with a metal fitting 121a.
It is fixed by The other end of the coil spring 122 is attached to the left spring seat 123 with a stopper 1.
It is fixed at 23a. The left spring seat 123 is attached to the output shaft 13 on which a rack 131 is formed.
It is connected to one end of 1A.

The rack 131 meshes with a pinion 132 constituting an operating mechanism, and the other end is connected to a connecting member 141.
is connected to one end of the One end of the pinion 132 is rotatably supported by the bracket 31 via a bearing.

On the other hand, the rod 113 on which the rack 112 is formed
The hydraulic oil 117 having a predetermined viscosity is coupled to a sealed cylinder 114 and is integrated with the cylinder. The cylinder 114 is supported so as to be movable in the left-right direction in the figure, that is, in the width direction of the vehicle body. Inside this cylinder 114, there is an orifice 11 having a predetermined throttle diameter so as to divide the inside of the cylinder into a left cylinder chamber 118L and a right cylinder chamber 118R.
A piston 115 having a cylinder 114 is enclosed, and one end of a piston rod 119 passing through the cylinder 114 is fixed to the piston 115. The piston rod 119 is supported so as to be movable in the width direction of the vehicle body, and its other end is connected to the other end of the connecting member 141. The above cylinder 114, hydraulic oil 1
17. Piston 115 with orifice 116
constitutes an oil damper as a dumppot.

Next, the operating mechanism will be explained. The operating mechanism is
It is equipped with a control valve, an enlarged view of which is shown in FIG. 6, and a power cylinder. The control valve has a pinion 132 at one end.
The control valve shaft 151a is fixed to a pinion 161 and the other end is rotatable, and the rotary valve 152 is fixed to a pinion 161 at one end and rotatable at the other end. One end of the torsion bar 151 is connected to the control valve shaft 151a through a pin 150A, and the other end of the torsion bar 151 is connected to the rotary valve 152 through a pin 150B. Therefore, the rotational torque is transmitted from the pinion 132 to the control valve shaft 151a to the torsion bar 1.
51 to the rotary valve 152 fixed to the pinion 161. However, when the ground resistance of the tire acts on the pinion 161 through a linkage or the like, the torsion bar 151 is twisted, and at this time, the gap between the control valve shaft 151a fixed to the pinion 132 and the rotary valve 152 fixed to the pinion 161 is Rotational displacement occurs by the amount of twist.

The housing 153 is fixed to the bracket 31 and is connected to the torsion bar 15 via a bearing.
1. Rotatably supports the control valve shaft 151a and the rotary valve 152. The opening of the housing 153 is communicated with the oil tank 62 and the vane pump 61 via a hydraulic pipe 65, and is also communicated with the left power cylinder chamber 171L and right power cylinder chamber 171R of the power cylinder 171 via the hydraulic pipe 65. ing.

Therefore, the control valve shaft 15
The control valve shaft 151a and the rotary valve 152 rotate relative to each other by the torsion angle of the torsion bar 151 connecting the pinion 1a and the pinion 161, and this rotation forms a restriction in the hydraulic circuit, thereby switching and controlling the hydraulic pressure. Let's do it.

The other end of the pinion 161 is rotatably supported by the bracket 31 via a bearing, and the pinion 161 is engaged with a rack 162. One end of the rack 162 becomes the linkage 14 and is connected to the tie rod 15. The other end of the rack 162 becomes a piston rod that passes through the power cylinder 171 and is connected to the power piston 172.

The power piston 172 is the power cylinder 17
1 and acts as a hydraulic booster having power steering fluid 66. This power cylinder 171 is fixed to the bracket 131. The piston rod in the right power cylinder chamber 171R has one end fixed to the power piston 172 and the other end connected to the tie rod 15 to form a linkage 14. The tie rod 15 is connected to the rear wheel 18 via a knuckle arm 16 (FIG. 1).

Next, the operation of the first embodiment will be explained.
The shaft 2 is rotationally displaced in accordance with the steering of the handle 1. The rotational displacement is converted into a linear displacement of the tie rod 5 via the linkage 4 by a conversion mechanism within the gearbox 3. The linear displacement causes the knuckle arm 6 to rotate around the pivot shaft 7, causing the front wheels 8 to produce a steering angle. Further, in response to the steering of the handle 1, the connecting shaft 21 is rotationally displaced by another conversion mechanism within the gearbox 3. The rotational displacement is caused by the rotational displacement of the universal joint 2
2. Input shaft 2 via operating shaft 23 and universal joint 24
5 is rotated. The rear wheel steering determination mechanism determines the rotational displacement speed of the input shaft 25, that is, the steering speed of the steering wheel 1, and also determines the speed according to the determination result and the rotational displacement of the input shaft 25, that is, the steering angle of the steering wheel 1. This determines the direction and magnitude of the steering angle of the rear wheels 18 and causes a linear displacement in the linkage 14. At this time,
The hydraulic pressure generated by the vane pump 61 assists in the operating force required to cause linear displacement of the linkage 14, thereby reducing the steering force required to steer the handle 1. Linear displacement of linkage 14 rotates knuckle arm 16 about pivot axis 17 via tie rod 15. Along with this rotation, the rear wheel 18
is steered to produce a steering angle in the rear wheels 18.

The operation of the rear wheel steering determination mechanism and the operating mechanism described above will be explained in more detail with reference to FIGS. 7A to 7C.

FIG. 7A shows the rear wheel steering determination mechanism and operating mechanism when the steering wheel is placed in a neutral state in order to keep the vehicle traveling straight without steering the steering wheel. The input shaft 25 is stationary without rotating, and the coil spring 122 is at its natural length. At this time, no relative rotation occurs between pinion 132 and pinion 161, and no twist occurs in torsion bar 151. Therefore, control valve shaft 1
51a does not rotate, so the rotary valve 152
is in a neutral state. Therefore, the power steering fluid 66 supplied from the vane pump 61 is returned to the oil tank 62 through an oil return port formed by the rotary valve 152 and the control valve shaft 151a.
Further, pressure is applied to the left power cylinder chamber 171L and right power cylinder chamber 171R of the power cylinder 171, but since oil is not fed, no pressure difference occurs and no action to move the power piston 172 occurs.

Next, consider the case where the steering wheel is slowly steered to the right to cause the front wheels to produce a rightward steering angle, as shown in FIG. 7B. In response to the slow rightward steering of the steering wheel 1, the input shaft 25 is slowly rotated in the direction of the arrow in FIG. 7B, opposite to the rotation of the steering wheel, by the conversion mechanism in the front wheel steering gear box 3, etc. and rotate. Due to this rotation, the rack 102 and rod 103 move to the left (in the direction of the arrow in the figure) via the pinion 101, and the rack 112 and rod 113 move to the left (in the direction of the arrow in the figure).
moves to the right (in the direction of the arrow in the figure). This movement causes the rod 103 to move to the right spring seat 12.
1 to the left, while the rod 113 moves the cylinder 114 to the right. Rod 103
Due to this movement, the right spring seat 121 presses the right end of the coil spring 122 to the left and tries to contract it. The coil spring 122 is compressed by the spring seat 121 and generates a restoring force, which tends to move the left coil spring seat 123 to the left. On the other hand, as the cylinder 114 moves rightward due to the movement of the rod 113, the volume of the left cylinder chamber 118L decreases and the volume of the right cylinder chamber 118R increases. Hydraulic oil 117
is the orifice 11 provided in the piston 115.
6, the hydraulic oil 11 flows from the left cylinder chamber 118L on the high pressure side to the right cylinder chamber 118R on the low pressure side.
A flow (viscous) resistance (or damping force) of 7 is generated, and the piston 115 attempts to move to the right. In this case, according to the transfer function of equation (7) above, the input shaft 25 rotates slowly, that is, the handle 1
Since the cylinder 114 slowly moves to the right in response to the slow steering, no large damping force acts on the piston 115. Therefore, the force that tries to move the rack 132 to the left due to the restoring force of the coil spring 122 is stronger than the force that tries to move the rack 132 (output shaft) to the right via the piston rod 119 and the connecting member 141 due to the damping force generated in the piston 115. The force becomes greater than the force trying to move the rack 132, and the rack 132 moves to the left. If the speed of rotation of the input shaft 25, that is, the speed of steering the handle 1, is extremely slow, the amount of movement of the rack 132 is 10.
It is approximately equal to the amount of movement to the left of 2. Rack 13
2 moves to the left, the pinion 131 attempts to rotate to the right (right-handed thread direction).

The clockwise rotation of the pinion 132 attempts to rotate the pinion 161 clockwise via the torsion bar 151, but the grounding resistance of the rear wheel acts on the pinion 161 via the tie rod 15, linkage 14 and rack 162. , the torsion bar 151 is twisted, and the control valve shaft 151a is rotated by the amount of twisting.
Rotate to the right relative to 2. This control valve shaft 151a and rotary valve 152
A hydraulic path shown in FIG. 7B is formed in the control valve by the relative rotation between the two and Oiled power piston 17
2 to the left, and assists the operation of causing the rear wheel 18 to produce a rightward steering angle.
At the same time, the power steering fluid 66 in the left power cylinder chamber 171L is returned to the oil tank 62 through the hydraulic path created by the relative rotation between the control valve shaft 151a and the rotary valve 152.

Next, consider a case where the steering wheel is rapidly steered to the right to cause the front wheels to produce a rightward steering angle, as shown in FIG. 7C. In response to a quick rightward steering of the handle 1, the input shaft 25 rotates quickly in the direction of the arrow in FIG. 7C. This rotation causes rack 102 and rod 103 to move to the left via pinion 101, and rack 112 and rod 113 to move to the right. Rod 103 is the right spring seat 121
Moving the cylinder 114 to the left while the rod 113 moves the cylinder 114 to the right is exactly the same as when the steering wheel is turned slowly in FIG. 7B. The right spring seat 121 is a coil spring 122
Press the right end to the left to compress it. The coil spring 122 is compressed and generates a restoring force, which tends to move the left coil spring seat 123 to the left. On the other hand, the cylinder 114 is connected to the input shaft 25
Since the piston 115 moves quickly to the right in response to the fast rotation of the handle 1, that is, the fast steering of the handle 1, a large damping force acts on the piston 115. The damping force is the piston 11
5, the piston rod 119 and the connecting member 14
1 to move the rack 132 to the right. The force that tries to move the rack 132 to the right due to the damping force generated in the piston 115 is
Since the restoring force is greater than the restoring force of the coil spring 122, the coil spring 122 is compressed and the rack 132 moves to the right. The amount of movement is approximately equal to the amount of movement of the rack 112 to the right when the rotation speed of the input shaft 25, that is, the speed of steering the handle 1 is extremely fast.

By moving the rack 132 to the right, pinion 1
31 rotates to the left (left-hand thread direction). As the pinion 131 rotates to the left, the torsion bar 151 is twisted, causing the pinion 161 to rotate to the left and try to move the rack 162 to the right.
The control valve shaft 151a rotates to the left by the torsion angle of the torsion bar 151. The power steering fluid 66 sent from the vane pump 61 is sent to the left power cylinder chamber 171L of the power cylinder 171 through a hydraulic path generated by the relative rotation between the control valve shaft 151a and the rotary valve 152, and moves the power piston 172 to the right. This assists the operation of causing the rear wheels 18 to turn to the left. At the same time, the power steering fluid 66 in the right power cylinder chamber 171 is returned to the oil tank 62 through a hydraulic path created by the relative rotation between the control valve shaft 151a and the rotary valve 152.

In addition, when the steering speed of the steering wheel is an intermediate speed between the above two, that is, the coil spring 122
When the restoring force of the oil damper is almost in balance with the damping force of the oil damper, the rack 132 hardly moves. Therefore, the pinion 131 hardly rotates, and the control valve shaft 15
1a also hardly rotates. In this case, Figure 7A
The state is similar to that shown in FIG. 2, and the rear wheels 18 have almost no steering angle.

When the rack 162 moves after the above-described series of operations and a steering angle is generated in the rear wheels, the pinion 161 rotates by the same amount as the pinion 131, thereby eliminating twisting of the torsion bar 151. Therefore, the relative rotation that occurs between the control valve shaft 151a and the rotary valve 152 is eliminated, and a neutral state is established, where oil supply to the left and right power cylinder chambers is stopped, and the power piston 172 does not move.

As is clear from the above description, according to the rear wheel steering determination mechanism of the first embodiment of the present invention, the steering speed of the steering wheel is determined based on the steering of the steering wheel,
The direction and magnitude of the steering angle of the rear wheels are determined according to the determination result and the steering angle of the steering wheel, and an operating mechanism that steers the rear wheels to produce a steering angle is controlled to produce a steering angle of the rear wheels. This has the effect that it can be done. Specifically, if the steering speed of the steering wheel is slow,
It is possible to cause the rear wheels to have a steering angle in the same direction as the front wheels, and also to cause the rear wheels to have a steering angle corresponding to the steering angle of the steering wheel. On the other hand, when the steering speed of the steering wheel is high, it is possible to cause the rear wheels to produce a steering angle in the opposite direction to that of the front wheels, and also to produce a steering angle in the rear wheels of a magnitude corresponding to the steering angle of the steering wheel. Further, when the steering speed of the steering wheel is intermediate between the above two speeds, the steering angle of the rear wheels can be set to zero or almost zero. In this case, the rear wheel steering judgment mechanism is equipped with an operating mechanism that uses hydraulic pressure to steer the rear wheels. This has the advantage that the steering force that must be applied to the vehicle can be reduced.

Next, a rear wheel steering determination mechanism according to a second embodiment of the present invention will be described with reference to FIG. Figure 8 shows
FIG. 8 is a cross-sectional view of the cross section indicated by diagonal lines in FIG. 8A, viewed from the direction of line BB. The rear wheel steering determination mechanism of the second embodiment differs from the mechanism of the first embodiment in that the input and output of the elastic body and the damper are both rotational displacements.

The differences will be mainly explained below. The input shaft 25 is
It is integrally coupled to one end of the input shaft 210. The input shaft 201 is rotatably supported by a case 291 fixed to the bracket 31 via a bearing, and is integrally coupled with a spur gear 221 to rotate together. The spur gear 221 meshes with the spur gear 211, which is a driven gear, and this pair of gears achieves rotation in which the respective gears have the same rotational speed and opposite rotational directions. Spur gear 211 is integrally coupled to shaft 210. The shaft 210 is rotatably supported by a case 291 via a bearing, and is integrated with a left spring seat 212 having a disc-shaped tip. The left spring seat 212 has two springs 214 and 215 fixed at one end with a stopper 213. two springs 214, 215
are torsion coil springs designed to produce equal restoring force against torsion in either the forward or reverse direction, and their other ends are attached to the right spring seat 2.
16 using a fastener 213.
The right spring seat 216 is integrated with the shaft 217. The shaft 217 is the case 29
1 is rotatably supported via a bearing, and
The spur gears 218 are coupled together and rotate together. The spur gear 218 meshes with the spur gear 234 and is set to rotate at the same number of rotations in opposite directions.

On the other hand, the other end of the input shaft 201 is connected to a cylinder cover 226 integrally with a cylinder 222 of the oil damper. As shown in FIG. 9, the inner cylindrical portion of the cylinder 222 has a cam ring shape and seals the hydraulic oil 117. Also, two narrow grooves 242L, 242R provided on the left inner wall surface of the cylinder 222, two holes 241L, 241R, and left and right bypass pipes 223L, 223R provided in the cylinder 222.
are in communication. The left bypass conduit 223L and the right bypass conduit 223R communicate with each other via an orifice 225 that can be adjusted by a control valve 224, and each bypass conduit is connected to a blind lid 240 in the outer cylindrical portion of the cylinder 222. It is closed at.

Note that the orifice 225 is preset to a predetermined gap size by the control valve 224. Further, the depth and width of the grooves 242L and 242R are also set to predetermined sizes.

The cylinder 222, the cylinder cover 226, the rotor 227, and the hydraulic oil 117 constitute an oil damper, and the rotor 227 has a pair of vanes 228 and 229 at axially symmetrical positions. At the bottom of the vanes 228, 229, a spring 230,
231 is inserted, and springs 230, 2
31 exerts a pushing force that tries to move out from the rotor 227. On the other hand, vanes 228, 22
The tip end of 9 is in contact with the inner cylindrical part of the cam ring-shaped cylinder 222 due to the pushing up force.

The rotor 227 is rotatably supported by the cylinder cover 226 and is integrated with the shaft 232. The shaft 232 is rotatably supported by the case 291 via a bearing, and the spur gear 23
3 are integrally connected and rotate together. The spur gear 233 meshes with the spur gear 234 and is set to rotate at the same number of rotations in opposite directions. Spur gear 234 is integrally connected to output shaft 235 and rotates therewith. Output shaft 2
35 is rotatably supported by the case 291 via a bearing, and includes the torsion bar 151 and the control valve shaft 1 at the tip.
51a.

The structure from the torsion bar 151 to the linkage 14 is the same as the operating mechanism of the mechanism of the first embodiment, so the same reference numerals will be used below and the explanation will be omitted.

The effects of the second embodiment having the above configuration will be explained. In the following, a case will be considered in which the steering wheel is steered to the right to produce a rightward steering angle in the front wheels, as explained in the operation and effect of the first embodiment. In this embodiment, unlike the rotation direction of the input shaft 25 in FIG. 7, which is an explanatory diagram of the effects of the first embodiment, the input shaft 25 is rotated in the direction of the arrow attached to the input shaft 25 in FIG. A conversion mechanism within the gearbox 3 is set to rotate in response to the steering of the steering wheel. In other words, gearbox 3
is constructed as shown in FIG. The input shaft 25 rotates clockwise to rotate the input shaft 201.
rotates to the right. On the other hand, the shaft 210 is
It rotates to the left (in the direction of the arrow attached to shaft 210 in FIG. 8) via a pair of spur gears 221 and 211. The left spring seat 212 also rotates to the left along with the shaft 210, and the spring 21
4, 215 to the left, the springs 214, 215 generate a restoring force and try to rotate the right spring seat 216 to the left. This rotation attempts to rotate the spur gear 218 to the left via the shaft 217.

On the other hand, due to the rightward rotation of the input shaft 210, the cylinder 222 rotates rightward from the state shown in FIG. 10A, as shown in the explanatory cross-sectional view of FIG. 10B. Rotation of the cylinder 222 in the right direction (first
0), the left cylinder chamber 222L decreases in volume and becomes high pressure, and the right cylinder chamber 222R increases in volume and becomes low pressure. Hydraulic oil 11
7 is connected to the left bypass conduit 223 via a groove 242L provided on the left inner wall surface of the cylinder 222.
L and orifice 225, right bypass line 22
3R and groove 242R, and attempts to flow from the high pressure side left cylinder chamber 222L to the low pressure side right cylinder chamber 222R. At this time, a damping force is generated according to the rotational speed of the cylinder 222, and the vanes 228, 2
29 to the right to rotate the rotor 227 to the right. The rightward rotation of the rotor 227 attempts to rotate the spur gear 233 to the right via the shaft 232. When the rotational speed of the cylinder 222, that is, the rotational speed of the input shaft 201 is high, a large damping force is generated in the oil damper, which overcomes the restoring force generated by the springs 214 and 215 and is applied to the oil damper via the spur gear 233. gear 234
rotates to the left in response to the rotation of the rotor 227 to the right. At this time, the spur gear 218 rotates to the right, and the springs 214 and 215 become largely twisted. Therefore, if the steering wheel 1 is quickly steered to the right, the output shaft 235 will be
It rotates to the left according to the steering angle of the handle 1 based on the transfer function of equation (7).

On the other hand, when the rotational speed of the cylinder 222, that is, the rotational speed of the input shaft 201 is slow, the oil damper can only generate a small damping force. The spur gear 234 rotates to the right in response to the rotation of the shaft 217 to the left. At this time, the spur gear 233 rotates to the left, and the rotor 227 only rotates largely relative to the cylinder 222. Therefore, if the steering wheel 1 is slowly steered to the right, the output shaft 235
rotates to the right according to the steering angle of the handle 1. When the cylinder 222 rotates at a speed intermediate between the two above, that is, when the input shaft 201 rotates at a speed intermediate between the two, the damping force generated by the oil damper and the spring 214,
When the restoring forces generated at 215 are almost balanced, spur gear 234 hardly rotates. Therefore, when the steering wheel 1 is steered at a speed intermediate between the above two speeds, the output shaft 235 hardly rotates.

Interlocking with the rotation of the output shaft 235, twisting occurs in the torsion bar 151, which rotates the pinion 161 and attempts to move the rack 162 in the width direction of the vehicle body. The control valve shaft 151a rotates relative to the rotary valve 152 by the angle of this twist, thereby forming a restriction in the hydraulic circuit. The power cylinder 171 performs the operation of switching and controlling the oil pressure by this throttle, moving the rack 162 in the width direction of the vehicle body, steering the rear wheels, and producing a steering angle.
The assisting action by the oil pressure difference applied to the left power cylinder chamber 171L and the right power cylinder chamber 171R is as explained in the first embodiment.

In the second embodiment, steering the steering wheel to the right,
In other words, when the front wheels are steered to the right, the output shaft 235 rotates to the right, which causes the tie rod 15 to move to the left (bottom direction in FIG. 8) via the rack 162, etc.
The rotation of the output shaft 235 to the left causes the tie rod 15 to move to the right (upward in FIG. 8) through the rack 162, etc., causing a leftward steering angle to the rear wheels. Produces a rudder angle.

As is clear from the above description, according to the second embodiment of the present invention, similarly to the first embodiment, the speed of steering of the steering wheel is determined based on the steering of the steering wheel, and the speed of steering of the steering wheel is determined based on the determination result and the steering of the steering wheel. The effect is that the direction and magnitude of the steering angle of the rear wheels can be determined according to the angle, and the operating mechanism that steers the rear wheels to generate the steering angle can be controlled to generate the steering angle of the rear wheels. has. In this case, by adding an operating mechanism that steers the rear wheels using hydraulic pressure, it is possible to reduce the steering force that the driver must apply to the steering wheel to steer not only the front wheels but also the rear wheels. It has the advantage of being possible. Furthermore, since it is composed of a rotating body whose input and output is rotational displacement, a spring, and an oil damper, by appropriately selecting and combining the speed ratios of the rotating bodies, the ratio of the steering angle of the rear wheels to the steering angle of the steering wheel can be adjusted. It has the advantage that it can be set optimally.

Next, a third embodiment of the present invention will be described. In this embodiment, the orifice of the rear wheel steering determination mechanism is made variable and the cross-sectional area of the orifice is automatically adjusted in accordance with a physical quantity related to vehicle speed. FIG. 11 shows an example in which a variable orifice is provided in the first embodiment. Therefore, parts corresponding to those in the first embodiment are designated by the same reference numerals and explanations are omitted, and since the operating mechanism is the same as in the first embodiment, illustration thereof is omitted.

As shown in FIG. 11, the cylinder 114 includes a bypass conduit 1120 that communicates the left cylinder chamber 118L and the right cylinder chamber 118R. Further, the piston 115 does not have an orifice. A control valve 1 that is movable in a direction perpendicular to the longitudinal direction of the bypass pipe is provided approximately at the center of the bypass pipe 1120 so as to protrude into the bypass pipe.
123 is inserted, and an orifice 1131 is formed by the upper outer surface of the control valve 1123 and the inner surface of the bypass conduit 1120. Orifice 1131
Control valve 1123 for adjusting the gap and therefore the cross-sectional area
is integrally coupled with the adjustment screw 1132.
The adjustment screw 1132 rotates integrally with a bevel gear 1134, and the bevel gear 1134 forms a pair of miter gears with the other bevel gear 1135 as a mating gear. The bevel gear 1135 is connected to the motor 1 so as to rotate together with the shaft of the motor 1136.
It is fixed to the 136 shaft. The motor 1136 is a reversible rotary motor whose rotation direction can be reversed, and is fixed to the outer wall of the bypass conduit 1120 with a stopper so that it can move in the left and right direction together with the cylinder 114, and is controlled by an on-vehicle microcomputer 1130. Connected as expected. A vehicle speed detector 2010 is connected to the microcomputer 1130. As shown in FIG. 12A, the vehicle speed detector 2010 includes a generator 2011 and a vehicle speed meter 2012. The generator 2011 is the transmission 201
A speedometer driven gear 2015 is attached to the outlet of the speedometer cable 2014 of the transmission extension housing 3 (transmission extension housing) and rotates within the transmission 2013 according to the vehicle speed, and transmits rotation according to the vehicle speed to the speedometer. The speedometer cable 2014 generates an alternating current voltage in response to the rotation. When the AC voltage generated by the generator 2011 is large, the vehicle speed meter 2012 lowers the voltage and rectifies the AC voltage using a full-wave rectifier circuit, and smoothes the resulting ripple voltage using a filter, as shown in FIG. 12B. A DC voltage signal such as this is output as a vehicle speed signal and supplied to the microcomputer 1130. This microcomputer 1130 determines the vehicle speed according to the vehicle speed signal,
When the vehicle speed is low, the control valve 1123 is fully closed to control the motor 1136 so that the cross-sectional area of the orifice 1131 is minimized, and when the vehicle speed is high, the control valve 1123 is fully opened to minimize the cross-sectional area of the orifice 1131. Control the motor to maximize. That is, the motor 1136 is driven according to the control signal of the microcomputer 1130, and the motor 1
The rotation of the shaft 136 is caused by a pair of bevel gears 1134,
Adjustment screw 1 through a miter gear consisting of 1135
132 and control valve 1123 to change the cross-sectional area of the orifice. Therefore, according to this embodiment, the cross-sectional area of the orifice can be automatically controlled according to the vehicle speed, so the damping force of the oil damper can be changed according to the vehicle speed.

Next, the steering angle direction of the rear wheels when the microcomputer 1130 outputs a control signal according to the vehicle speed and drives the motor 1136 will be described.

When the vehicle speed is low, the microcomputer 1130 outputs a control signal to control the motor 1136 so that the orifice 1131 is fully closed, and the damping force of the damper is restored by the coil spring 122 regardless of the rotation speed of the input shaft 25. The linkage 14 is moved almost by the damping force of the damper in the same direction as the rack 112.

As a result, when the vehicle speed is low, the rear wheels are steered in the opposite direction to the front wheels, regardless of how fast the steering wheel is turned.

On the other hand, if the vehicle speed is high, orifice 1131
The microcomputer 113
0 outputs a control signal to control the motor 1136, the damping force of the damper becomes a sufficiently small value compared to the restoring force of the coil spring 122, regardless of the rotation speed of the input shaft 25, and the linkage 14 is almost a coil spring. It moves by the restoring force of rack 122 and moves in the same direction as rack 102. As a result, when the vehicle speed is high, the rear wheels are steered in the same direction as the front wheels, regardless of how fast the steering wheel is turned.

As described above, according to this embodiment, when the vehicle is running at low speed, the rear wheels are made to have a steering angle in the opposite direction to that of the front wheels to improve the turning motion of the vehicle, and when the vehicle is running at high speed, the rear wheels are steered in the opposite direction to the front wheels. By creating steering angles in the same direction, it is possible to prevent the sensitivity of turning movements from increasing rapidly and improve steering stability. By controlling the steering angle direction of the rear wheels, when the steering speed of the steering wheel is fast, the steering gain is increased to improve the responsiveness of the vehicle's rapid turning motion, and when the steering speed of the steering wheel is slow, the steering gain is increased. By reducing the gain, it is possible to prevent the vehicle from wobbling, wandering, etc., and improve running stability when the vehicle is traveling straight.

By the way, when a vehicle is operated at high speed and the steering wheel is turned, a large yaw rate and a large lateral acceleration occur. Therefore, instead of using the vehicle speed described in the third embodiment as the physical quantity related to the vehicle speed, the cross-sectional area of the orifice can be controlled using the yaw rate or the lateral acceleration. A yaw rate detector for detecting the above yaw rate will be explained with reference to FIG. 13A. As shown in FIG. 13A, the yaw rate detector includes a rate dial 1251 and an electrical system section 12.
It consists of 52. The rate gyro 1251 is fixed at the center of gravity of the vehicle body 30 and detects the rotational angular velocity (yaw angular velocity or yaw rate r) of the vehicle body 30 about the vertical axis. Electrical system section 12
52 supplies voltage to the rate gyro 1251, amplifies the signal from the rate gyro 1251, outputs it as a yaw rate signal, and supplies it to the microcomputer 1130 (FIG. 11). The yaw rate signal is a positive voltage signal for the yaw rate r that occurs when the vehicle rotates to the right around the vertical axis as the steering wheel 1 is steered to the right, as shown in FIG. 13B. The rate gyro 125 is set so that a negative voltage signal is generated for the yaw rate r that occurs when the vehicle rotates to the left around the vertical axis as the vehicle is steered to the left.
1 and the electrical system section 1252. And the microcomputer 113
0 maximizes the cross-sectional area of the orifice when the absolute value of the yaw rate signal is large, and minimizes the cross-sectional area of the orifice when the absolute value of the yaw rate signal is small. As a result, the steering angle of the rear wheels is controlled similarly to the third embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the rear wheel steering determining means is constructed of an electric circuit, and the control valve of the actuating mechanism is switched by a signal output from the electric circuit.

The detection circuit 60 that detects the steering amount of the steering wheel is
Consists of a linear resistor 602 and a slider 604,
It consists of a linear potentiometer SP fixed to the vehicle body 30. One end of the slider 604 is locked to a gear built into the gearbox 3. When the shaft 2 rotates in accordance with the steering angle δ _h (t) of the handle 1, this rotational movement is transferred to the gear in which the slider 604 is locked by a movement converting mechanism such as a rack and pinion built in the gear box 3. is converted into linear motion. The detection circuit 60 detects this linear movement as a displacement corresponding to the steering angle δ _h (t) of the handle 1 using a linear potentiometer SP.
A corresponding voltage signal is output as a displacement signal D. Here, to simplify the explanation, assuming that the steering wheel 1 is continuously steered in a sinusoidal manner at an angular frequency ω, the rotational steering angle δ _h (t) of the steering wheel is expressed as ωt, so the straight direction is used as the reference. The displacement of the steering wheel at the rotational steering angle ωt is δ _h0・Sinωt (however, δ _h0
is the amplitude of the handle), and accordingly, the displacement signal D output from the linear potentiometer SP also has an amplitude D ₀ corresponding to the amplitude of the handle.
A sinusoidal continuous voltage signal D=D ₀ ·sinωt having an angular frequency ω is obtained.

Signal processing circuit 30 constituting rear wheel steering determination means
0 is composed of a phase shift circuit 301 connected to the slider of the detection means 60 and a coefficient multiplier 351.

The phase shift circuit 301 includes an operational amplifier 306 and a resistor 3.
02, 303, 304 and a capacitor 305, and the resistance values of the input resistor 302 and the feedback resistor 303 are set to be equal. Resistor 3 above
04 and the capacitor 305 act as a judgment circuit, and the resistors 302 and 303, the operational amplifier 306 and the coefficient multiplier 351 act as a control circuit.

In the phase shift circuit 301, when the angular frequency ω of the input displacement signal D is small and close to zero, the reactance of the capacitor 305 becomes close to infinity, and the positive terminal of the operational amplifier 306 receives the displacement signal D at one end. A signal is inputted through the resistor 304 to which is supplied. At the same time, the displacement signal D is also applied to the input resistor 302, and the input resistor 302 and the return resistor 3
Since the resistance ratio of 03 is 1, a signal input to the negative terminal of operational amplifier 306 outputs a signal with a gain of -1. On the other hand, a signal with a gain of 2 is output from the signal input to the positive terminal of the operational amplifier 306, and the gain of the entire phase shift circuit 301 is 2-1=1.
The output is obtained. Therefore, when the angular frequency of the displacement signal D is small and close to zero, an output signal D equal to the input displacement signal D is obtained.

On the other hand, when the angular frequency ω of the input displacement signal D is large and close to infinity, the capacitor 305 is almost short-circuited, and the positive terminal of the operational amplifier 306 is equivalent to being grounded. At this time,
A signal is input only to the negative terminal of the operational amplifier 306, and the phase shift circuit 301 functions only as an inverting amplifier itself. In this case, since the resistance ratio between the input resistor 302 and the feedback resistor 303 is 1, the gain is -
It becomes 1. Therefore, if the angular frequency ω of the displacement signal D is large and close to infinity, the input displacement signal D
An output signal -D is obtained by inverting the output signal -D. This output signal -D has an absolute value (amplitude D ₀ ) equal to the input,
This is a signal whose phase is delayed by 180° with respect to the input signal.

According to the operating principle as described above, the phase shift circuit 301
As the angular frequency of the displacement signal D increases,
Outputs an output signal whose phase is delayed from 0° to a maximum of 180° with respect to the displacement signal D.

The coefficient multiplier 351 amplifies the output signal from the phase shift circuit 301 by a constant value K _A and outputs a control signal Y.

The operating mechanism is a hydraulic pressure generator P and an accumulator.
AL, flow control valve SV, oil sump T connected to the suction side of hydraulic pressure generator P to return unnecessary oil, actuator AC acting as a power cylinder connected to flow control valve SV through piping, pivot shaft 17 Pin joint the knuckle arm 16 and the left and right knuckle arms 16, 16.
It is composed of steering cages 14, 14 connected via SLa, SLa.

The hydraulic pressure generator P is composed of a vane pump driven by the engine via a pulley, and stores a predetermined pressure in the accumulator AL in advance. This vane pump is driven according to the rotation of the engine.

The accumulator AL consists of a metal container 30 having a predetermined capacity.The metal container 30 is divided into two by a rubber diaphragm 32, one chamber is filled with gas such as nitrogen at a predetermined pressure, and the other chamber is filled with a gas such as nitrogen at a predetermined pressure. is configured to communicate with a discharge port of a vane pump that constitutes the hydraulic pressure generator P via piping. This accumulator AL compensates for the inoperability of the rear wheel steering angle control device when the capacity of the vane pump is insufficient to meet the requirements of the rear wheel steering angle control device of the vehicle. Further, by providing the accumulator AL, it is possible to downsize the vane pump and reduce its capacity. The accumulator AL is connected to the flow control valve SV via piping, and the hydraulic pressure accumulated in the accumulator AL is transferred to the actuator AC according to the valve opening degree of the flow control valve SV.
supply to

The flow rate control valve SV is composed of a spool valve consisting of a cylinder provided with an inflow port and a discharge port, and a spool that moves the cylinder in the axial direction. By changing the positional relationship with the discharge port, the opening area of the throttle is changed to control the discharge flow rate.

The actuator AC consists of a cylinder 34 connected to the discharge port of the flow control valve SV via piping and a piston 36 that moves in the axial direction within the cylinder 34. Both ends of the steering ring 36 are engaged with the left and right steering ring gauges 14, 14 forming the operating mechanism.

Next, the operation of the fourth embodiment will be explained.
As mentioned above, the handle 1 has an amplitude δ _h0 and an angular frequency ω
A case can be considered in which the vehicle is continuously steered in a sinusoidal manner, that is, the vehicle is steered at a rotational steering angle δ _h (t)=δ _h0 ·sinωt. In response, the detection means 60 detects the amplitude
A sinusoidal continuous displacement signal D=D ₀ ·sinωt having an angular frequency ω at D ₀ is output. Then, the signal processing circuit 300 processes the displacement signal D according to the angular frequency ω that the displacement signal D has, and outputs a control signal Y.

The flow rate control valve SV of the operating mechanism changes the aperture area of the throttle according to the control signal Y, and operates the accumulator.
Introduce AL hydraulic pressure to actuator AC. This changes the pressure in the cylinder of the actuator AC to move the piston, causing the knuckle arm 16 of the actuating mechanism to rotate around the pivot shaft 17. Since the left and right knuckle arms 16, 16 are connected to the steering linkage 14,
The left and right rear wheels 18, 18 are steered by the rotation of the knuckle arms 16, 16, and a steering angle δ _r (t) is generated. Note that, as a matter of course, the front wheels 8 are steered in accordance with the steering of the steering wheel 1, and a steering angle δ _f (t) is generated in the front wheels 8. Further, it goes without saying that the steering direction of the handle 1 and the steering direction of the front wheels 8 are the same.

The relationship between the characteristics of the signal processing circuit and the steering angle δ _r (t) of the rear wheels 18 when operated as described above will be explained in detail based on Sections 15A, B, C, and D.

FIG. 15A shows the signal processing circuit 300 of this embodiment.
This shows the characteristics of Signal processing circuit 300
is a control signal Y whose gain is always constant K _A and whose phase is delayed from 0° to a maximum of 180° as the angular frequency ω increases with respect to the input displacement signal D = D ₀ · sinωt. Output. Angular frequency ω of displacement signal D
is in the small region ω ₁ , the signal processing circuit outputs a signal obtained by multiplying the input signal by K _A as a control signal Y=K _A ·D due to the characteristics of the signal processing circuit. Therefore, the rear wheels are steered by the actuating mechanism according to the control signal Y, and the steering angle δ _r (t) of the rear wheels 18 is
As shown in , the steering angle δ _f (t) of the front wheels 8 is controlled in the same direction. The steering angle of the rear wheels at this time is proportional to the displacement of the steering wheel.

On the other hand, while the angular frequency ω of the displacement signal D is in the large region ω ₃ , due to the characteristics of the signal processing circuit, the signal processing circuit outputs a signal whose phase is delayed by 180° with respect to the input signal, that is, the displacement signal _D. The multiplied signal is output as a control signal Y=-K _A ·D. For this reason,
The rear wheels are steered by an actuating mechanism according to the control signal Y, and the steering angle δ _r (t) of the rear wheels 18 is equal to the steering angle δ _f (t) of the front wheels 8, as shown in FIG. 15D. in the opposite direction,
It is controlled in a magnitude proportional to the displacement of the handle.

Furthermore, while the angular frequency ω of the displacement signal D is in the region ω ₂ between the region ω ₁ and the region ω ₃ , the signal processing circuit changes the phase from 0° to 180° with respect to the input signal due to the characteristics of the signal processing circuit. A signal with a delay of up to .degree. is output as a control signal Y. For example, when the signal processing circuit outputs a signal whose phase is delayed by 90 degrees with respect to the input signal as the control signal Y, the rear wheels are steered by the operating mechanism with a delay in relation to the front wheels, and as shown in Fig. 15C. As shown, control is performed so that the steering angle δ _r (t) of the rear wheels 18 becomes zero at the time when the steering angle δ _f (t) of the front wheels reaches the maximum.

In the fourth embodiment of the present invention, if necessary, a means for detecting the steering angle of the rear wheels 18 is provided as appropriate, and a so-called feedback signal using a deviation signal between an output signal of this means and a control signal from the signal processing circuit 300 is provided. The rear wheels may be steered by controlling the flow rate control valve SV.

In the first and second embodiments described above, the operating mechanism using a rotary valve and a rack-and-pinion was explained, but the present invention is not limited to this, and the present invention can be applied to various control valves, exchange mechanisms, and the shape and arrangement of the power cylinder. An actuation mechanism having the following can be applied. For example, the present invention may be configured using an integral type actuation mechanism operated by a flapper valve or a physical quantity sensitive type actuation mechanism that detects a physical quantity of the vehicle and controls a solenoid valve by a computer to open and close a bypass circuit. It is possible to do so. In addition, since the operating mechanism that steers the rear wheels and generates the steering angle can be assisted by hydraulic pressure, in addition to the effects of the present invention described above, the steering force of the steering wheel can be reduced, so the steering force can be reduced. There are no restrictions on the ratio of the steering angle of the front wheels to the steering wheel angle due to restrictions, and the ratio can be freely selected.
The present invention also has secondary effects such as being able to prevent the rear wheels from kickback or shimmy motion from the road surface.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a schematic diagram of a conventional four-wheel steering vehicle, and FIG. 3 is a diagram for explaining the operating principle of the mechanical rear wheel steering determining means of the present invention. 4 is a diagram showing the transmission characteristics of FIG. 3, FIG. 5 is a cross-sectional view of the rear wheel steering judgment mechanism and operating mechanism in the first embodiment of the present invention, and FIG. 6 is a diagram showing the transmission characteristics of FIG. Enlarged view of control valve, Figure 7A, Figure 7B
and FIG. 7C is a sectional view similar to FIG. 5 for explaining the operation of the first embodiment, and FIG. 8A is a perspective view showing the rear wheel steering determination mechanism section of the second embodiment of the present invention.
Figure 8 is a cross-sectional view of the shaded area in Figure 8 A taken from the BB line direction, Figure 9 is a cross-sectional view taken along the line AA in Figure 8, and Figure 10
Figures A and 10B are sectional views similar to Figure 9 for explaining the operation of the second embodiment, and Figure 11 is a sectional view similar to Figure 5 of the third embodiment of the present invention. Figure 12A is a detailed diagram of the vehicle speed detector, Figure 12
Figure B is a diagram showing the vehicle speed signal, Figure 13A is a detailed diagram of the yaw rate detector, Figure 13B is a diagram showing the yaw rate signal, Figure 14 is a block diagram of the fourth embodiment of the present invention, and Figure 14 is a diagram showing the yaw rate signal. Figure 15A is a diagram showing the gain and phase of the signal processing circuit of the fourth embodiment, Figure 15B is a diagram showing the gain and phase of the signal processing circuit of the fourth embodiment.
FIG. 5C and FIG. 15D are explanatory diagrams showing the steering angles of the front wheels and rear wheels with respect to FIG. 15A. 1...Handle, 2...Shaft, 3...Gearbox, 8...Front wheel, 18...Rear wheel, 14...
Linkage...Rear wheel steering judgment mechanism.

Claims (1)

[Scope of Claims] 1. A rear wheel steering angle control device for a vehicle that controls a steering angle of a rear wheel according to the steering of a steering wheel that causes a steering angle of the front wheels, which determines the steering speed of the steering wheel and controls the steering angle of the steering wheel. When the steering speed is fast, the flow path is switched so that the rear wheels have a steering angle in the opposite direction to that of the front wheels, and when the steering speed is slow, the rear wheels have a steering angle in the same direction as the front wheels. Rear wheel steering determination means: a cylinder arranged so that a linkage connected to the rear wheel passes through it, a piston fixed to the linkage and dividing the inside of the cylinder into two chambers, driven by an engine to generate hydraulic pressure. hydraulic generator,
an actuating mechanism including a control valve whose flow path is switched by the rear wheel steering determining means so as to communicate the hydraulic pressure generating device and the two chambers in the cylinder to supply and discharge hydraulic pressure; A rear wheel steering angle control device for a vehicle, characterized in that: 2. The rear wheel steering determination means includes a first member that moves in response to the steering of the steering wheel, a second member that moves in a direction opposite to the movement of the first member, and a second member that moves in a direction opposite to the movement of the first member. an elastic member connected to the first member and a dart pot connected to the second member; 2. The rear wheel steering angle control device for a vehicle according to claim 1, comprising: an output shaft connected to said control valve so as to switch roads. 3. The rear wheel steering determination means includes a detection circuit that detects the steering amount of the steering wheel and outputs a steering amount signal, a determination circuit that determines the steering speed of the steering wheel based on the steering amount signal, and the Based on the judgment result of the judgment circuit, when the steering speed is fast, the rear wheels are caused to have a steering angle in the opposite direction to the front wheels, and when the steering speed is slow, the rear wheels are caused to have a steering angle in the same direction as the front wheels. 2. The rear wheel steering angle control device for a vehicle according to claim 1, further comprising a control circuit that switches the flow path of the control valve so as to cause the following. 4. A front wheel power cylinder arranged so that a linkage connected to the front wheel passes through it, a front wheel power piston fixed to the linkage and dividing the inside of the power cylinder into two chambers, and a front wheel power piston that is fixed to the linkage and divides the inside of the power cylinder into two chambers, and Claims 1 to 3 further include a switching valve that is switched to communicate the hydraulic pressure generating device of the operating mechanism with the chamber of the power cylinder to assist in steering of the front wheels. A rear wheel steering angle control device for a vehicle according to any one of the items.