JPH01115772A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To improve maneuverability, by a method wherein two mode switching valves are provided, front and rear wheels can be switched by means of an isophase mode and a reverse phase mode, and according to a steering angle, automatic switching from an isophase to a reverse phase or from a reverse phase to an iso-phase can take place. CONSTITUTION:A worm shaft is rotated through the working of a cylinder for front wheels by means of working oil flowing through a rotary valve 22 actuated in linkage with control of rotation of a handle 25 and steers front wheels. In this device, a control valve 56 for rear wheels is linked to the worm shaft, and the valve 56 is connected to the one pressure chamber of a servo cylinder C. A first mode switching valve 33 having a port to which the rotary valve 22 and a cylinder 87 for rear wheels are connected and a second mode switching valve 76 having a port connected to the other pressure chamber of the servo cylinder C and the control valve 56 for rear wheels are provided. Further, a correction valve 101 is provided for correcting the errors of front and rear wheels according to a deviation between output signals from steering angle sensors 96 and 97 for front wheels and a steering angle sensor 99 for rear wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering device that switches front and rear wheels in an in-phase mode or in an anti-phase mode depending on the steering angle of a steering wheel.

(Prior Art) FIG. 8 shows a conventional four-wheel steering system, in which a handle l is linked to an input shaft 2 of an integral type power steering system PS for steering the front wheels. When the input shaft 2 rotates together with the handle 1, the control valve (
(not shown) is switched. When the control valve is switched in this way, the pressure oil from the pump P1, which is the oil pressure source, acts on the power steering device P'3, and rotates the pitman arm 4 linked thereto.

The rotational force of the pitman arm 4 is transmitted to the front wheel 7 via the drag link 5 and the knuckle arm 6, and the front wheel 7 is steered.

Further, a fully hydraulic steering unit SU is provided separately from the power steering system PS, and this steering unit SU mainly includes a rotary valve and a control pump (not shown). A pulley 9 is provided at the tip of the input shaft 8 linked to this rotary valve, and a pulley 10 is also provided on the input shaft 2 of the power steering device PS for the front wheels. are linked.

Fully hydraulic power steering unit S like this
A supply line 12 and a tank line 13 are connected to U, the supply line 12 is communicated with the pump P2, and the tank line 13 is communicated with the tank T.

In addition, in addition to the above-mentioned both lines 12 and 13, a hydraulic line 14 is also provided.
．． 15, and the fully hydraulic power steering unit SU is connected to the power cylinder S for the rear wheels via these hydraulic lines 14 and 15.

Now, when the steering wheel 1 is turned, the input shaft 2 is rotated, the power steering device PS for the front wheels is operated, and the front wheels are steered according to the direction of rotation of the steering wheel. When the input shaft 2 rotates as described above, its rotational force is transmitted to the input shaft 8 of the fully hydraulic steering unit SU via the pulley 10, belt 11, and pulley 9.

When the input shaft 8 rotates in this manner, the rotary valve is switched in accordance with the direction of rotation of the handle 1, and the oil discharged from the pump P2 flows into the control pump via this rotary valve. . This control pump discharges a flow rate corresponding to the rotational speed of the handle l, and this discharged oil is supplied to either one of the hydraulic lines 14 or 15 depending on the switching position of the control valve. be done. Further, either the other hydraulic line 15 or 14 communicates with the tank T.

Therefore, when the front wheels 7 are steered by switching the steering wheel l, the fully hydraulic power steering unit SU operates accordingly, and the flow rate corresponding to the rotational speed of the steering wheel 1 is directed to either chamber 18 of the power cylinder S. Alternatively, the other chamber 17 or 16 is connected to the tank T.

This causes the rear wheels 18 to be steered in the same direction as the front wheels 7.

(Problems to be Solved by the Invention) The conventional device as described above has a problem in that when the relative relationship between the front and rear wheels shifts due to an internal leak in the hydraulic circuit, it cannot be corrected. Ta.

Furthermore, this conventional device cannot control the turning angle of the rear wheels according to the steering conditions, so there is a problem in that it is not possible to perform steering according to the conditions.

An object of the present invention is to provide a device that can correct even if the relative relationship between the front and rear wheels deviates, and can also change the steering mode according to steering conditions.

(Means to solve problems).

This invention links an input shaft and a worm shaft via a torsion bar, switches a rotary valve according to the amount of relative rotation between the input shaft and the worm shaft, and moves the piston of the front wheel cylinder while moving the worm shaft. This system is based on a four-wheel steering system that rotates the front wheel and drives the front wheels, while steering the rear wheels in conjunction with the operation of the front wheel cylinder.

Based on the premise of the above device, the present invention provides a rear wheel control valve that switches according to the movement locus of the inner rotor of the trochoid gear mechanism linked to the worm shaft, and a rear wheel control valve that connects one pressure chamber to the rear wheel control valve. One port on the upstream side is connected to one pressure chamber of the cylinder for the front wheels, the other port is connected to the rotary valve, and the port on the downstream side is connected to the pressure chamber of the cylinder for the front wheels. A first mode switching valve is connected to a pressure chamber, and a second mode is formed by connecting one upstream port to the other pressure chamber of the servo cylinder and connecting the other port to a rear wheel control valve. a switching valve, a first front wheel steering angle sensor provided on the front wheel cylinder, a second front wheel steering angle sensor provided on the piston rod of the servo cylinder, and a rear wheel steering angle sensor provided on the rear wheel cylinder rod. The present invention is characterized in that it includes a controller that calculates errors in the output signals of these sensors, and a correction valve that switches according to the output signals of the controller to correct errors in the front and rear wheels.

(Operation of the present invention) Since the present invention is configured as described above, by switching the first mode switching valve and the second mode switching valve, the
The front and rear wheels can be switched in in-phase mode or in anti-phase mode, and can also be automatically switched from in-phase to anti-phase or from anti-phase to in-phase depending on the steering angle.

Further, when a relative error occurs in the steering angles of the front and rear wheels, the controller calculates the error based on the output signal from the sensor, and according to the result of the calculation, the correction valve can be switched to correct the error.

(Effects of the Present Invention) According to the device of the present invention, the phase mode of the front and rear wheels can be freely selected by switching the 1.2 mode switching valve. Moreover, even if an error such as advance or delay occurs in the steering of the front and rear wheels due to internal leakage of fluid or the like, the correction valve operates to correct the error.

Also, depending on the steering angle of the steering wheel, the front and rear wheels can be switched to in-phase mode or reverse-phase mode.

(Effects of the present invention) The four-wheel steering system of the present invention can control the switching direction of the rear wheel control valve according to the steering angle of the steering wheel by switching the second steering switching valve, so the steering angle is small. In medium and high speed ranges, the front and rear wheels are steered in the same phase mode to maintain steering stability, and in low speed ranges where the steering angle is large, it is possible to improve turning ability. Switching can be done automatically according to the steering angle, so
Its accuracy is also maintained sufficiently.

In addition, by switching the first mode switching valve, the front and rear wheels can be steered at the same steering angle, and can also be switched to the same phase or opposite phase, which improves the ability to turn around in narrow areas, etc. etc., is also possible.

(Embodiment of the present invention) The embodiment of the present invention shown in Figs.
A valve case 20 is provided at one end of the input shaft 9, and a rotary valve 22 that is switched in relation to the rotation of the input shaft 21 is housed in the valve case 20. and,
One of the upstream ports 23 and 24 connected to the upstream side of the rotary valve 22 is connected to the front wheel pump P1, and the other port 24 is connected to the tank T.

Further, the input shaft 21 has one end connected to the nodle 25, and the other end connected to the worm shaft 27 via a torsion bar 26.

A piston 29 of a front wheel cylinder 28 is slidably housed in the gear case 19, and a pressure chamber 30.31 is defined within the case 19. The worm shaft 27 is mounted in the center of the piston 29. It penetrates. Furthermore, if the piston 28 and the worm shaft 27 are worm-coupled, and the worm shaft 27 rotates, the piston 2
9 moves, and if the piston 29 moves, the worm shaft 27 also rotates.

One pressure chamber 30 configured as described above is connected to one downstream port 32 of the rotary valve 22, and the other pressure chamber 31 is connected to one upstream port 32 of the first mode switching valve 33.
Connected to 4. This first mode switching valve 33
The other upstream port 35 of is connected to the other downstream port 36 of the rotary valve 22 . Further, a gear 37 is formed on the piston 29, and a sector gear 38 is engaged with this gear 37. The sector gear 38 meshed with the gear 37 rotates as the piston 29 reciprocates, and in conjunction with the rotation, rotates the pitman arm and steers the front wheels.

Gear case 1 provided on the opposite side of the valve case 20
A control case 39 is provided outside the worm shaft 9, and the tip of the worm shaft 27 projects into the control case 39. A pinion 40 is integrally formed on the protruding end of the worm shaft 27.
is engaged with an internal gear 41 rotatably provided on the inner periphery of the control case 39. And the internal gear 41
An output shaft 42 that rotates integrally with the output shaft 42 is connected to the output shaft 42, and one end of a transmission shaft 43 is connected to the output shaft 42. The transmission shaft 43 has a gear 44 formed at its tip, is swingable around a pin 45 at a connecting portion with the output shaft 42, and is configured to rotate integrally with the output shaft 42.

The pinion 40, internal gear 41, output shaft 42, and transmission shaft 43 constitute the speed reduction mechanism °r of the present invention.

The transmission shaft 43 configured as described above has a trochoid gear mechanism g
This trochoid gear mechanism g has an outer rotor 46 and an inner rotor 47 as main elements. In other words, the outer rotor 46 is connected to the bolt 48
is fixed to the control case 39, and the rotor 50 is fitted into a recess 49 formed on the inner periphery thereof. Further, the inner rotor 47 has tooth grooves 51 formed on its outer periphery, and the radii of curvature of the tooth grooves 51 and the rotor 50 of the outer rotor 46 are made equal. The number of tooth spaces 51 on the inner rotor 47 is equal to the number of tooth spaces 51 on the outer rotor 46.
The number of inner rotors 47 is smaller than the number of rotors 50 in
When the inner rotor 47 is engaged with the outer rotor 48, the inner rotor 47 is eccentric with respect to the outer rotor 46 by an amount e, as shown in FIG.

The inner rotor 47 configured as described above has an internal gear 52 formed in its center portion, and the gear 44 of the transmission shaft 43 is meshed with the internal gear 52. A connecting plate 53 is fixed to the outside of this inner rotor 47, and the base end of a connecting rod 55 is connected to the outside of this connecting plate 53 via a spherical bearing 54.

The tip of the connecting rod 55 is connected to a spool 57 of a rear wheel control valve 58.
7 is slidably installed inside the valve sleeve 58. Further, this valve sleeve 58 is slidably installed inside a valve hole 59 formed in the control case 3θ.

And a servo cylinder C provided in the control case 3θ
A piston 61 is housed in the cylinder portion 60 of. The piston 61 thus configured is provided with piston rods 62 and 63 on both sides thereof, and one piston rod 82 is made to protrude toward the valve hole 59 side, and its protruding end is connected to one end of the valve sleeve 58. are doing. ' As is clear from FIG. 3, a supply groove 64 extending in the axial direction is formed on the outer periphery of the valve sleeve 58, which constitutes the main element of the rear wheel control valve 56.

This supply groove 64 communicates with the rear wheel pump P2 via an upstream port 65 formed in the control case 33, and also communicates with the first port 64 formed on the inner periphery of the valve sleeve 58.
It also communicates with two annular grooves 68 and 67.

Furthermore, a tank passage 69 that is constantly connected to the tank port 88 is formed on the outer periphery of this valve sleeve.

This tank passage 89 communicates with a third annular groove 70 formed between the first and second annular grooves 6B and 67.

Further, the spool 57, which also constitutes the main element of the rear wheel control valve 56, is formed with a 1.2 annular surrounding portion 71.72. When in the illustrated neutral position, it communicates with downstream ports 73 and 74 of the rear wheel control valve 58. This one downstream port 73 is connected to one upstream port 77 of the second mode switching valve 78 via a passage 75, and the other downstream port 74 is connected to the servo cylinder C via a communication passage 78.
The pressure chamber 79 is in communication with one of the pressure chambers 79 . The pressure chamber 80 on the opposite side to the one pressure chamber 78 is connected to the other upstream port 8 of the second mode switching valve 7B via a passage 81.
Connected to 2.

1. The downstream port 83 of the first mode switching valve 33
．． 84 is a rear wheel cylinder 87 via a passage 85.8B.
The pressure chamber 8th is connected to 87, but this passage 85.8
6 are connected to operating check valves 90 and 91.

When the first mode switching valve 33 is in the illustrated normal position, the first mode switching valve 33 allows the upstream ports 37 and 38 to communicate with each other. Therefore, when the first mode switching valve 33 is in the normal position, the pressure chamber 31 of the front wheel cylinder 28
is connected to rotary valve 2 via upstream ports 37 and 38.
It communicates with the downstream port 38 of No. 2.

Then, when the first mode switching valve 33 is switched to the in-phase mode position, which is the left side position in the figure, the upstream port 37 and the downstream port 83, and the upstream port 35 and the downstream port 84 are brought into communication. Further, when the first mode switching valve 33 is switched to the reverse phase mode position, which is the right side position in the figure, the upstream port 37 and the downstream port 84, and the upstream port 35 and the downstream port 83 are brought into communication.

The second mode switching valve 7B has its downstream port 92.
83 joins said passage 85.86 via passage 94.95. When the second mode switching valve 7B is in the normal position shown in the figure, its upstream port 77
．． 82 and switch to the speed compatible mode position on the right side of the drawing, the upstream port 77 and the downstream port 92, and the upstream port 82 and the downstream port S3
communicate with.

A first front wheel steering angle sensor 98 is provided on the rotating shaft of the sector gear 41 of the front wheel cylinder 28. Also,
A second front wheel steering angle sensor 97 is provided on the piston rod 63 of the servo cylinder C, and a rear wheel steering angle sensor 99 is also provided on the piston rod 98 of the rear wheel cylinder 87.

Each of the sensors 96, 97, 98 as described above is connected to a controller 100, and this controller 100 operates the 1.2 mode switching valve 33.76 and the correction valve 101 according to the input signal. It is something to control. In addition to the signals from each of the sensors described above, the signals input to this controller 100 include an output signal from the vehicle speed sensor 102, a signal from the two-wheel steering switch 103, a signal from the first four-wheel steering switch 104, and a signal from the second four-wheel steering switch 103. A signal from the steering switch 105 is input.

The correction valve 101 controlled by the controller 100 has one upstream port 106 connected to the tank T, and the other upstream port 107 connected to the shuttle valve 108 via a fuse valve 108. There is.

This shuttle valve 109 guides the fluid on the higher pressure side of the front wheel pump P1 and the rear wheel pump P2 to the correction valve 101.

Further, one downstream port 110 of the correction valve 101 is communicated with the passage 94, and the other downstream port 111 is communicated with the passage 95.

Note that reference numerals 112 and 113 in the figure indicate centering cylinders for returning the rear wheels 18 to a straight-ahead state.

When the handle 25 is rotated, the input shaft 21 rotates accordingly, but since the switching resistance at this time acts on the sector gear 3, the worm shaft 27 does not rotate. Therefore, the input shaft 21 is connected to the torsion bar 26.
Rotate while twisting to switch the rotary valve 22. At this time, the two-wheel steering switch 103 is turned on and the first
．． When the two-mode switching valves 33 and 76 are held at the two-wheel steering mode position, which is the normal position shown in the figure, the following occurs.

Now, for example, when the handle 25 is turned to the left, the rotary valve is switched, and the fluid discharged from the front wheel pump P1 passes through the upstream port 23 and the downstream port 32 of the rotary valve, and is divided by the piston 29. Pressure chamber 3
0. The fluid in the other pressure chamber 31 flows from the upstream port 34, 35 of the first mode switching valve 33 to the downstream port 36 of the rotary valve to its upstream port 2.
4, the piston 28 moves to the left in FIG. 2, rotates the sector gear 38 to the left, and steers the front wheel 7 to the left.

In this way, the fluid discharged from the front wheel pump P1 is transferred to the rotary valve 22, the front wheel cylinder 28, and the first mode switching valve 33.
and tank T, so the rear wheel cylinder 8
7, the discharge fluid of the front wheel pump P1 is not supplied, and when the handle 25 is turned, the rear wheel control valve 56 is switched accordingly, but as described above, the second mode switching valve 76 is set to normal mode. Since the rear wheel pump P2 is held in this position, the fluid discharged from the rear wheel pump P2 circulates within the rear wheel control valve 5B, the servo cylinder C, and the tank T. Therefore, the discharge fluid of this rear wheel pump P2 is also not supplied to the rear wheel cylinder 87.

Therefore, in the two-wheel steering mode in which the dual mode switching valve 33.7B is held at the normal position, no matter which direction the handlebar 25 is turned, only the front wheel cylinder 28 operates, the rear wheel cylinder 87 does not operate, and the front wheel Only 7 are steered.

In addition, if the first four-wheel steering switch 104 is operated to switch the first mode switching valve 33 to the in-phase mode position, which is the left side position in the figure, and leave the second mode switching valve 76 at the normal position shown in the drawing, As shown by the characteristic line indicated by the dashed line in Fig. 6, the front and rear wheels are steered in the same direction and by the same angle.

For example, if you turn the handle 25 to the left, the front wheel pump PI
The discharge fluid is supplied to one pressure chamber 30 of the front wheel cylinder 28 as described above, and the fluid in the other pressure chamber 31 is pushed out and supplied to the upstream port 37 of the first mode switching valve 33. Ru.

The pressure fluid thus supplied to the upstream port 37 pushes open the operating check valve 90 formed in the downstream port 83 and the passage 85, and pushes open the rear wheel cylinder 87.
The pressure chamber 88 is supplied to one of the pressure chambers 88 . At this time, the operating check valve 91 on the passage 8B side opens due to the pressure action on the opposite passage 85 side, so that the fluid in the other pressure chamber 89 of the rear wheel cylinder 87 flows from the passage 86 to the first mode switching valve. 33
Downstream port 84 → Upstream port 35 → Downstream port 36 of rotary valve 22 → Upstream port 24
It is returned to Tank T via . Therefore, the piston 115 of this rear wheel cylinder 87 moves to the right, steering the rear wheel to the left, which is the same direction as the front wheel 7.

The volume change of the pressure chamber 30.31 when the piston 28 of the front wheel cylinder 28 moves, and the pressure chamber 88 when the piston 115 of the rear wheel cylinder 87 moves.
．． Since the volume changes of the wheels 89 are set to be equal to each other, in this case, the steering angles of the front wheels 7 and the rear wheels are also equal.

However, in the above embodiment, the volumes of the pressure chambers of the front wheel cylinder 2 and the rear wheel cylinder 87 are made equal to equalize the steering angles of the front and rear wheels. The steering angle may be adjusted to make the steering angles of the front and rear wheels the same.

In addition, if the steering wheel 25 is turned to the right in the above state, the rotary valve 22 is switched in the opposite direction to the above, and the front wheels 7 are steered to the right, and the rear wheels are also steered to the right accordingly. It is.

Also, by switching the first four-wheel steering switch 104,
When the first mode switching valve 33 is switched to the reverse phase mode position, which is the right side position in the drawing, while the mode switching valve 76 is held at the normal position shown in the figure, the flow path relationship downstream of the first mode switching valve 33 is reversed. The front and rear wheels will be steered in opposite directions. Also at this time, as is clear from the characteristic line indicated by the two-dot chain line in FIG. 6, the steering angles of the front and rear wheels are equal.

In any case, if the second mode switching valve 76 is held at the normal position shown in the figure, no matter how the rear wheel control valve 56 is switched, the fluid discharged from the rear wheel pump P2 will be switched to the rear wheel pump P2. Since it is not supplied to the cylinder 87, the rear wheel pump P2
The steering characteristics of the rear wheels are not affected by the discharged fluid.

In other words, if the second mode switching valve 7B is set to the normal position, the steering mode is determined only by the first mode switching valve 33.

Also, by switching the second four-wheel steering switch 105,
The mode switching valve 33 is held at the normal position shown in the figure, and the second
When only the mode switching valve 78 is switched from the illustrated normal position to the steering angle corresponding mode position, the in-phase mode or anti-phase mode is established depending on the rotation angle of the steering wheel.

That is, when the piston 28 is moved by turning the handle 25 to the left as described above, the worm shaft 2
7 also rotates, and its rotational force is transmitted to the internal gear 41 via the pinion 40, causing the internal gear 41 to rotate. The rotational force of the worm shaft 27 is decelerated in the process of being transmitted to the internal gear 41, and the internal gear 41
The rotational force is transmitted to the inner rotor 47 of the trochoid gear mechanism g via the transmission shaft 43.

When the rotational force is transmitted to the inner rotor 47, each inner rotor 4 revolves while rotating on its own axis. For example, if the inner rotor rotates to the left, which is the direction of arrow 114 in FIG. It will be on the opposite side, to the right. Therefore, the movement locus of the center portion 01 of the inner rotor 47 at this time is as follows.

That is, the vertical axis direction shown in FIG. 4 is Y, and the horizontal axis direction is X, and the center 01 of the inner rotor when the handle is held in the neutral position is - with respect to the center Oo of the outer rotor 46. If it is eccentric by e in the Y direction, the movement locus of the center O1 will be as shown by curve a in FIG. 5. That is, during the initial rotation of the worm shaft 27, in other words, when the rotation angle is small, the center 0
1 moves in the negative direction of the X-axis, but when the rotation angle increases and the movement locus exceeds the X-axis, the direction of movement with respect to the X-axis is reversed to the positive direction. Furthermore, as the rotation angle of the worm shaft 27 increases, the center O1 moves beyond the Y-axis to the positive direction of the X-axis.

Since a connecting rod 55 is connected to the center 01 of the inner rotor 47 via a spherical bearing 54, the movement of the center 01 in the X-axis direction is as follows.
This reciprocating motion of the connecting rod is converted and transmitted to the spool 57 of the rear wheel control valve 56.

Therefore, as described above, depending on the steering angle of the handle 25, the spool 57 is switched in the positive direction of the X-axis or in the negative direction.

When the handle is slightly turned to the left, the connecting rod 55 is pulled upward in FIG. 2, so the spool 57 also moves upward, and the rear wheel control valve 56 is switched. When the rear wheel control valve 56 is switched to the left side position, the discharge fluid of the rear wheel pump P2 is transferred from the upstream port 65 of the control valve 5B to its downstream port 73 to the upstream side of the second mode switching valve 7B. It is supplied to the pressure chamber 88 of the rear wheel cylinder 87 via the port 77 → downstream port 92 → passage 95 → passage 86 → operating check valve 91.

At this time, the pressure on the passage 86 side opens the operating check valve 80 provided in the passage 85 on the opposite side, so that the fluid in the pressure chamber 88 on the opposite side of the rear wheel cylinder 87 is
It is supplied to the pressure chamber 80 of the servo cylinder C via the passage 85 → passage 94 → downstream port 83 of the second mode switching valve 76 → its upstream port 82 → passage 81. Further, the fluid in one pressure chamber 78 of this servo cylinder C is supplied to the downstream port 74 and the upstream port 8 of the rear wheel control valve 56.
8 and is returned to tank T.

Therefore, the piston 61 of the servo cylinder C moves upward in FIG. 2 and pushes the sleeve 58 upward in FIG. 2, so that the relative relationship between the sleeve 58 and the spool 57 is returned to the neutral state shown in the figure. Then, the piston 61 stops.

When the relative relationship between the sleeve and the spool returns to the above-mentioned neutral state, the fluid discharged from the rear wheel pump P2 is returned to the tank T, so that no pressure fluid is supplied to the rear wheel cylinder, and the rear wheel pump P2 is returned to the tank T. The cylinder is operated check valve 90
．． The movement position is maintained by the action of 91.

Then, when the handle is further rotated from the above state and the rotation angle is increased, the direction of movement of the center O1 of the inner rotor 47 of the trochoid gear mechanism g is reversed, and
Shift in the positive direction of the axis. Therefore, at this time, the connecting rod 55 is lowered, the spool 57 is moved downward, and the rear wheel control valve 5S is switched to the right position in FIG. 1.

When the rear wheel control valve is switched to the right position in this way, the discharge fluid of the rear wheel pump P2 is supplied to one pressure chamber 79 of the servo cylinder C via the upstream port 65 and the downstream port 74. be done. Then, the fluid in the other pressure chamber 80 at this time is pushed out to the passage 81 side, and
It is supplied to the pressure chamber 88 of the rear wheel cylinder 87 via the upstream port 82 of the second mode switching valve 76 → its downstream port 93 → passage 94 → passage 85 through the operating check valve 90.

At this time, due to the pressure in the passage 85, the operating check valve 91 provided in the passage 86 on the opposite side opens, so that the fluid in the pressure chamber 89 of the rear wheel cylinder 87 is
Returned to tank T via passage 86 → passage 95 → downstream port 92 of second mode switching valve 78 → its upstream port 77 → downstream port 73 of rear wheel control valve 58 → its upstream port 88 .

Therefore, according to this embodiment, as is clear from the characteristic line shown by the solid line in FIG. It is possible to improve steering stability by steering in the same direction. On the other hand, when driving at low speeds with a large turn of the steering wheel, the front and rear wheels are steered in opposite directions, making it possible to maintain tight turning performance.

By changing the connecting position of the connecting rod 55 with respect to the inner rotor 47, the movement locus drawn by the connecting portion can be varied, and this situation is shown by curves 5 and 5 in Figure 5. . In other words, the curved line is a movement locus when the connecting rod 55 is connected to the P1 position shown in FIG. 5 and eccentric by el with respect to the center 00 of the outer rotor 46. Curve C is a locus of movement when connecting rod 55 is connected to position P2 and eccentric by e2. Therefore, if the connection position of the connecting rod 55 to the inner rotor 47 is adjusted in consideration of the characteristics of the vehicle,
You can select your preferred steering characteristics.

As is clear from the above, according to this embodiment, when the 1.2 mode switching valve 33.76 is held at the normal position, the two-wheel steering mode is established in which only the front wheels 7 can be steered.

Furthermore, if only the first mode switching valve 33 is switched to the in-phase or anti-phase mode position while the second mode switching valve 7B is held at the normal position, the front and rear wheels are switched to the in-phase or in-phase mode depending on the switching mode. However, the steering angles of the front and rear wheels at that time are equal to each other.

Furthermore, if the first mode switching valve 33 is held at the normal position and only the second mode switching valve 7B is switched, the front and rear wheels can be steered in the same direction or in the opposite direction depending on the rotation angle of the steering wheel. It is something that is steered in the same direction.

Furthermore, when the relative steering angle between the front wheels 7 and the rear wheels 18 becomes out of order due to internal leakage or the like while the steering device is being driven, the following will occur. That is, when an error occurs between the front and rear wheels when the first four-wheel steering switch 104 is operated to switch the first mode switching valve 33, the first front wheel steering angle sensor 8B and the rear wheel steering angle The controller 100 calculates based on the output signal from the sensor 88, switches the correction valve 101 according to the error, and corrects the error.

FIG. 7 shows a flowchart regarding this correction.

For example, if it is assumed that in Step E, the first mode switching valve 33 is switched to the in-phase mode position, which is the left side position in the figure, and in that state, pressure fluid is supplied to the pressure chamber 89 of the rear wheel cylinder 87. In step (2), the steering angle θf of the front wheels is detected by the second steering angle sensor 97, and in step (2), the steering angle θf of the rear wheels is detected.

is detected by the rear wheel steering angle sensor 87. Then, in step (2), it is determined whether the steering speed of the steering wheel 25 is above or below a set value and the vehicle is in a stopped state. If it is in the stopped state, the process moves to step (3), and the correction valve 101
keep it off. Further, if the steering speed is equal to or higher than the setting in step (2) above, the process moves to step (2) and it is determined whether the error in the steering angle between the front wheels and the rear wheels is within the setting range. If the error is within the set range, the error is considered to be small, and the process proceeds to step (2), where the correction valve 101 is kept in the OFF state.

If the error in the steering angle between the front wheels and the rear wheels exceeds the set range, the process moves to step (2) to correct the error, and the difference in steering angle between the front wheels and the rear wheels is detected. As a result, if the steering angle of the front wheels 8 is too advanced, the process moves to step (2) and the correction valve 101 is switched to the right position in the figure. When the correction valve 101 is switched to the right position, the pressure fluid from the shuttle valve 109 is transferred from the fuse valve 108 to the correction valve 1.
It is supplied to the pressure chamber 89 on the high pressure side of the rear wheel cylinder 87 via the upstream port 107 of 01 → downstream port 111 → passage 85 → passage 86. Also, at this time, the fluid in the pressure chamber on the low pressure side of the rear wheel cylinder 87 is returned to the tank T via the passage 94 and the correction valve 101, so that the delay in the rear wheel cylinder 87 is corrected. It turns out.

Contrary to the above, if the front wheels are lagging behind, the process moves to step It is returned to the tank T to correct excessive advance of the rear wheel cylinder.

Further, when the second four-wheel steering switch 105 is turned on and the second mode switching valve 76 is switched to the steering angle corresponding mode, the controller 100 controls the second front wheel steering angle sensor 9.
7 and the rear wheel steering angle sensor 98, the error is calculated, and the correction valve 10 is operated in the same manner as above according to the error.
1 to correct the error.

Note that when an error occurs in the relative relationship between the front and rear wheels as described above, it can be corrected by switching the correction valve 101. However, by actively switching the correction valve, its control characteristics can be changed.
For example, it is possible to change the characteristic line as shown by the dotted line in FIG.

[Brief explanation of the drawing]

Drawings 1 to 7 show embodiments of this invention.
The figure is a circuit diagram, Figure 2 is a sectional view of the main parts of the device, Figure 3 is a diagram of the internal gear of the reduction mechanism as seen from inside, Figure 4 is a side view of the trochoid gear mechanism, and Figure 5 is a side view of the trochoid gear mechanism. The figure is a diagram showing the movement locus of the connecting portion of the connecting rod with respect to the inner rotor, Figure 6 is a graph showing the steering angle characteristics of the front and rear wheels, and Figure 7 is a flowchart showing the process of correcting the relative error of the front and rear wheels. FIG. 8 is a circuit diagram of a conventional device. 7...Front wheel, 18...Rear wheel, 21...Input shaft, 2
2...Rotary valve, 26...Torsion bar,
27... Worm shaft, 28... Front wheel cylinder, 3
3... First mode switching valve, g... Trochoid gear mechanism, 47... Inner rotor, 56... Rear wheel control valve, C... Servo cylinder, 62.63... Piston rod , 76... Second mode switching valve, 87... Rear wheel cylinder, 88.89... Pressure chamber, 96.97...
1.2 front wheel steering angle sensor, 99... rear wheel steering angle sensor, 100... controller, 101... correction valve.

Claims (1)

[Claims] The input shaft and the worm shaft are linked via a torsion bar, and a rotary valve is switched according to the amount of relative rotation between the input shaft and the worm shaft, and the worm shaft is rotated while moving the piston of the front wheel cylinder. In a four-wheel steering device that drives the front wheels and steers the rear wheels in conjunction with the operation of the front wheel cylinder, the rear wheels are switched according to the movement locus of an inner rotor of a trochoid gear mechanism linked to the worm shaft. A control valve, a servo cylinder with one pressure chamber connected to the rear wheel control valve, one upstream port communicating with one pressure chamber of the front wheel cylinder, and the other port connected to the rotary valve. Along with communicating,
A first mode switching valve has a downstream port connected to the pressure chamber of the rear wheel cylinder, one upstream port is connected to the other pressure chamber of the servo cylinder, and the other port is connected to the rear wheel cylinder. a second mode switching valve connected to a control valve; a first front wheel steering angle sensor provided on the front wheel cylinder; a second front wheel steering angle sensor provided on the piston rod of the servo cylinder; and a rear wheel cylinder. It is equipped with a rear wheel steering angle sensor provided on the rod, a controller that calculates the error in the output signals of each of these sensors, and a correction valve that switches according to the output signal of this controller to correct the error of the front and rear wheels. four-wheel steering system.