JPH0263976A - Steering angle ratio controller for four-wheel steered vehicle - Google Patents

Abstract

PURPOSE:To make improvements in rectilinearity at the time of high speed, by making a fluid quantity to be fed to an actuator pushing a control member in a direction making a rear-wheels steering angle ratio of a four-wheel steered vehicle larger against a spring, so as to be decreased according to an increases in car speed. CONSTITUTION:A piston 56 of a rear-wheels steering actuator F operates through hydraulic pressure being controlled by a spool 126 axially moved with rotation of a drive shaft 24 of a differential control valve B. A notch member 21 connected to this drive shaft 24 formes a steering angle ratio control mechanism A together with a control member 20 being engaged with this notch member, and when speed is less than the specified one, the control member 20 and the notch 21 are made contact with each other by an input shaft 19, and the hydraulic pressure is transmitted to the piston 56 by operation of the spool 126. At the time of high speed, a current of a solenoid valve 47 is decreased by action of a current subtracter 45, while an oil regulating valve E checks an oil quantity for an actuator D and it separates the control member 20 from the notch 21 by a control lever 18. Consequently, the spool 126 is restored and hydraulic supply to the piston 56 decreases, thereby making a steering angle ratio smaller, so that rectilinearity at high speed is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steering angle ratio control mechanism for a four-wheel steering vehicle.

[Prior Art] As shown in Fig. 5, in the four-wheel steering vehicle disclosed in Japanese Utility Model Application Publication No. 5'l-77969, the rear wheels are By steering the front wheels in the same phase as the front wheels, and narrowing the control range in which the rear wheels are steered in response to the front wheels as the vehicle speed increases, sudden changes in vehicle body posture at high speeds can be suppressed, and at the same time the vehicle speed increases. By gradually increasing the rear wheel steering angle ratio, the lateral acceleration of the vehicle body is increased to a certain extent, improving steering response. According to the four-wheel steering vehicle described above, when driving at high speed, if the steering wheel is turned even slightly to the left or right from the neutral position, the rear wheels are also sharply steered in the same phase as the front wheels, so if the steering wheel wobbles, straight-line driving performance is impaired. There is a fear.

On the other hand, even in a four-wheel steering vehicle that improves turning ability by steering the rear wheels in the opposite phase to the front wheels when driving at low speeds, reducing the rear wheel steering angle ratio as the vehicle speed increases does not improve straight-line driving ability at high speeds. Therefore, when the steering wheel turning angle is below a predetermined value (l11), only the front wheels are steered and the rear wheels are returned to the neutral position (straight-ahead position) or locked.
Required to maintain straight running performance.

[Problems to be Solved by the Invention] In a four-wheel steering vehicle with such steering angle characteristics, even if the steering angle is constant, the rear wheel steering angle gradually decreases as the vehicle speed increases. There is less discomfort in maneuverability than when the rear wheels are suddenly returned to the neutral position.

However, in a four-wheel steered vehicle having such steering angle characteristics, the configuration of the electric/hydraulic control device is complicated, and because of the complexity of the configuration, the reliability of the 111111 is also inferior to that of the latter.

The object of the present invention is that normally, as the vehicle speed increases, the rear wheel steering angle ratio gradually decreases, and when the electric/hydraulic control device fails,
To provide a steering angle ratio control 189 structure for a four-wheel steering vehicle, which allows rear wheels to be safely returned to a neutral position and has excellent straight running performance.

[Means for solving the problem] In order to achieve the above object, the configuration of the present invention includes a spring that biases the control member in a direction where the rear wheel steering angle ratio becomes O, and a spring that biases the control member in the direction where the rear wheel steering angle ratio becomes O, It consists of a rear wheel steering actuator that pushes a member in a direction that increases the rear wheel steering angle ratio, and the amount of fluid supplied to the rear wheel steering actuator is reduced as the medium speed increases.

[Operation] As long as the steering angle is small, even if the front wheels are steered, the rear wheels are not steered.

A protrusion or notch on the input shaft that rotates in response to the steering angle engages with a cutout or protrusion on the drive shaft of the differential IIJtIII valve that controls the rear wheel steering actuator, and the drive shaft is rotated. The width of the dead zone (play) from the neutral position of the steering wheel until the rotation is transmitted is controlled in relation to the vehicle speed, so the rear wheel steering angle ratio gradually decreases as the vehicle speed increases.

The control member that controls the position of the protrusion II'rj with respect to the notch member is biased by the spring force to remove the protrusion from the notch to the disengaging position, so that the electric power
If the hydraulic control device fails, the engagement between the notch member and the protruding piece is automatically released, and the rear wheel is returned to the neutral position.

[Practical Example of the Invention] FIG. 1 is a schematic diagram of a four-wheel steered vehicle equipped with a steering angle ratio control mechanism according to the present invention. , the four-wheel steering vehicle includes a steering angle ratio control mechanism A that transmits the rotation of the input shaft 19 interlocked with the output shaft 29 of the front wheel steering mechanism 30 to the differential control valve B in relation to the vehicle speed, and a rear wheel steering actuator F. A differential control valve B that controls the hydraulic circuit to the steering wheel, a rear wheel steering actuator F that drives the rear wheels 71, and an electric/hydraulic tiog device C that drives the control member 20 of the steering angle ratio control mechanism A. ing.

Steering angle ratio control 11151 structure A is υ1 spline-fitted to input shaft 19! It consists of a JO member 20 and a cup-shaped slot member 21 connected to a drive shaft 24 that drives the differential control valve B. The drive shaft 24 is aligned coaxially with the input shaft 19.

A projecting piece 22 extending in the radial direction from the a control member 2o is configured to be able to engage with a notch 21a formed in the circumferential surface of the notch member 21 in the radial direction.

In order to control the position of the notch member 21 of the projection piece 22, the control lever 18 of the shaft 17 is engaged with the annular groove of the control member 2o, and the control member 20 is slid in the axial direction by rotation of the control lever 18. Ru. A lever 18a of a shaft 17 rotatably supported on the vehicle body side is connected to a piston rod of an actuator D and rotated.

The actuator D that drives the control member 20 is driven by an electric/hydraulic control device C that will be described later.

The actuator D is partitioned into an end where hydraulic pressure is introduced and the atmosphere by a piston fitted inside the cylinder. The spring 13 housed in the atmosphere is the lever 18a! 1il
A rotational force is applied to the IlIl lever 18, which acts to move the I+1 member 20 in the axial direction and remove the protruding piece 22 to a position where it cannot engage with the notch 21a.

The differential control valve B is a four-bottom neutral position open type or block type directional switching valve, and has a spool 126 fitted inside the valve housing 122 so as to be movable in the axial direction against the force of a neutral return spring. , are coupled to the screw shaft 130 by a coupling means 136a so as to move together in the axial direction. Screw shaft 1
The right end of the lead 30 is screwed into a screw hole 131 having a large lead thread groove formed at the end of the drive shaft 24. The driven shaft 6 is spline-fitted into a spline hole 132 formed at the left end of the screw shaft 130. When the spool 126 undergoes axial movement as the drive shaft 24 rotates, the hydraulic pump 26
Pressure oil is supplied from pipe 72.75 to one of pipes 76.80, and oil from the other pipe passes through pipe 79.77 to oil tank 2.
Returned to 8. The tube 76.80 communicates with the end chamber 89.91 of the rear wheel steering actuator F.

The rear wheel steering actuator F has a piston 5 in a cylinder 57.
6 is fitted to define end chambers 89 and 91, and the piston 56
A tie rod 65 coupled to the cylinder 57 projects outward from both terminals of the cylinder 57. The tie rod 65 is returned to the neutral position by the force of the return spring 55 housed in the end chamber 89, 91, and holds the rear wheel 71 in the straight-ahead position. Both ends of the tie rod 65 are connected to rear wheel knuckles 69 via auxiliary rods 67, respectively. A rear wheel knuckle 69 that supports the rear wheel 71 is rotatably supported by the vehicle body by a vertical support shaft 70.

In order to more reliably maintain the neutral position of the tie rod 65, a neutral locking mechanism H is provided which includes a receiving member 58 having a conical hole or groove coupled to the tie rod 65, and five locking members that can be engaged with the receiving member 58. Actuator G
When pressure oil is supplied to all 96 of the cylinders 63, the lock member 59 is separated from the receiving member 58 by the piston 64 against the force of the spring 61.

The movement of the tie rod 65 is transmitted as rotation to the driven shaft 6 via the cable 50 connected between the receiving member 58 and the lever 9a. The driven shaft 6 acts independently of the drive shaft 24 to rotate the screw shaft 130 and return the spool 126 to the neutral position.

FIG. 2 is a perspective view showing the relationship between the front wheel steering mechanism 30, the steering angle ratio control @JRmA, and the differential control valve B. In FIG. 2, for ease of explanation, an actuator D is connected to a control lever 18 of a shaft 17, and a spring 13 is disposed externally.

Further, an electromagnetic clutch 11 is provided between the driven shaft 6 and the lever 9a.
is provided.

When the electromagnetic coil 8 is excited, the friction plate 9 integrated with the lever 9a is frictionally engaged with the friction plate 7 coupled to the driven shaft 6.
The rotation of the lever 9a is transmitted to the driven shaft 6. 1. When the magnetic clutch 11 is disconnected, the lever 9a is freely rotated by the spring 5 hooked between the lever 9a and the bell crank 10, and the slack in the cable 50 is removed. As is well known, in reality, the cable 50 is inserted movably through an outer tube having one end fixed to the vehicle body side and the other end fixed to the housing side of the rear wheel steering actuator F.

As shown in FIG. 1, the electric/hydraulic control device C moves the control member 20 of the steering angle ratio control mechanism A in the axial direction, and adjusts the gap in the circumferential direction between the protrusion 22 and the notch 21a in relation to the vehicle speed. and control. For this reason, the electric/hydraulic control device C
Current flows to the actuator D that drives the control lever 18 that engages with 0, the oil amount adjustment valve E that adjusts the stroke of the actuator D, that is, the amount of oil to the actuator D, and the electromagnetic coil 47 that drives the oil amount adjustment valve E. A current subtracting converter 45 is provided which calculates 1ill'm in relation to the vehicle speed.

Oil Llfl Regulator E Housing 4 with 3 Boats
A spool 48 having two annular grooves is fitted into the inside of the actuator D, and the four end chambers housing the springs 49a and the center boat communicate with the RA of the actuator D. The right-hand boat, which in the neutral position communicates with the annular groove of the spool 48, communicates with the hydraulic pump 26 via a pipe 78.72, and the left-hand boat communicates with the oil tank 28 via a pipe 73.77.

A rod 48a connected to the sprue 48 protrudes outside the housing 46 to form an armature, and is biased to the left by the electromagnetic coil 47 against the spring 49a in response to the current. The electromagnetic coil 47 is connected to the power source battery 51 in series with a current subtraction converter 45, which has a large current when the vehicle speed is low, and a current decreases as the vehicle speed increases. A gear 4 is attached to a flexible shaft 43 that transmits the rotation of the output shaft of the transmission to the speedometer 15.
A vehicle speed proportional current generator 44 is coupled via 2. Both terminals of the vehicle speed proportional current generator 44 are connected to the current converter 45.
connected to.

Next, the operation of the four-wheel steered vehicle equipped with the steering angle ratio control mechanism according to the present invention will be explained. In FIG. 1, for example, when the steering wheel 41 is turned to the right, the output shaft 29 of the front wheel steering mechanism 30
is rotated, the drag link 33 is pulled forward by the arm 32, the front wheel knuckle 38 is rotated clockwise around the support shaft 34, and the front wheel 40 is moved to the right (-direction. At the same time, the output shaft 29 is transmitted to the input shaft 19, and when the vehicle speed is below a predetermined value and the steering wheel turning angle or front wheel steering angle exceeds a predetermined value, the protruding piece 22 of the control member 20 engages the cylindrical member 2.
1, and the drive shaft 24 is rotated. At this time, the notch member 21 moves very slightly in the axial direction, the switch 23 is activated, and the actuator G of the neutral locking mechanism H is activated.
is driven, and the locking member 59 is separated from the receiving member 58.

The driven wheel 6 does not rotate with respect to the rotation of the drive shaft 24 and prevents the rotation of the screw shaft 130. Therefore, a axial thrust commensurate with the lead angle of the screw hole 131 is generated on the screw shaft 130, and the screw shaft 13
0, the spool 126 moves to the right. As the axis of the spool 126 moves, pressure oil is pumped from the hydraulic pump 26 to the pipe 7.
2.75, the differential control valve B is supplied to the end chamber 89 of the actuator F via the pipe 76. The tie rod 65 is pushed to the side together with the piston 56, and the six rear wheel knuckles are pushed to the support 17.
The rear wheel 71 is rotated counterclockwise around 0, and the rear wheel 71 is deflected to the left (in the opposite phase to the front wheel 40).

In this way, the vehicle's ability to turn in a tight corner while traveling at low speeds is demonstrated.

The oil in the end chamber 91 is returned to the oil tank 28 via the pipe 80, the differential control valve B, and the pipe 77.

When the vehicle speed is low, as described above, a large current flows from the N'FA battery 51 to the electromagnetic coil 47 via the current subtraction converter 45. Pushed to the left. Hydraulic pump 26
Pressure oil passes through pipes 72, 78 and is supplied from the annular groove on the right side of spool 48 to the end chamber of actuator D via pipe 49b. The oil pressure at the end v49 increases and the spool 48 is returned to the right. In this way, the amount of oil sent to actuator D is controlled in proportion to the current of electromagnetic coil 47.

When the rod of the actuator D moves to the right, the control member 20 moves to the left with respect to the input shaft 19, so that the circumferential gap between the protrusion 22 of the control member 20 and the notch 21a of the notch member 21 increases. becomes narrower. Therefore, when the handle 41 is slightly rotated from the neutral position, the protruding piece 22 moves into the notch 21.
a, the rotation of the input shaft 19 is transmitted to the drive shaft 24, the differential control valve B is operated, and the rear wheel steering actuator F steers the rear wheels 71.

When the vehicle speed increases, the current in the electromagnetic coil 47 decreases, and the spool 48 of the oil amount control valve E is temporarily returned to the right by the force of the spring 49a, and the oil in W49b flows into the annular groove and pipe on the left side of the spool 48. It is returned to the oil tank 28 through 73 and 77.

In this way, as the vehicle speed increases, the current flowing to the electromagnetic coil 47 decreases, and the spool 48 of the oil amount regulating valve E decreases.
temporarily returns to the right, the amount of oil to actuator D decreases, and the rod is returned to the left by the force of the spring 130. As a result, the control member 20 also moves toward one input shaft. The protruding piece 22 that has been in contact with the notch 21a until now is separated from the notch 21a, and the notch member 21 is rotated so as to return to the neutral position by the action of a neutral return spring (not shown) attached to the notch member 21. Ru.

In reality, the notch 21a remains in contact with the protruding piece 22, and the drive shaft 2 is rotated by the amount by which the notch member 21 is returned to the neutral position.
A screw movement occurs between the screw hole 131 of No. 4 and the screw shaft 130, the spool 126 is returned to the left, and the tube 75 is connected to the tube 80, and the tube 7
are connected to tubes 76, respectively. The piston 56 of the rear wheel steering actuator F is returned to the left, and the steering angle of the rear wheel 71 is reduced. Cable 5 moves tie rod 65 to the left.
Since the driven shaft 6 is rotated through 0, when the screw shaft 130 returns to the rightward neutral position, the tie rod 65 is held at that position.

To explain the above operation with reference to FIG. 3, when the vehicle speed is reduced by line a1, the steering wheel is moved from the neutral position to the front wheel steering angle θ.
There is a dead zone until the angle corresponding to 1 is reached, and the rear wheels are not steered. When the steering wheel is roughly turned while the vehicle speed remains constant, the rear wheel steering angle gradually increases along line a1. When the front wheel steering angle reaches 193 on the slope and the rear wheel steering angle reaches α1, the vehicle speed increases (as the vehicle speed increases, the dead zone increases from the front wheel steering angle equivalent to θ1 to the front wheel steering angle equivalent to θ2, and the front wheel steering angle increases. Even if is constant (remains 03), the rear wheel steering angle increases as the vehicle speed increases.
It decreases from 1 to a2. The steering angle ratio (ratio of the rear wheel steering angle to the front wheel steering angle) moves onto the line a2 corresponding to the vehicle speed at that time, and changes along the line a2 according to the steering wheel turning angle. Therefore, as shown in FIG. 4, the steering angle ratio gradually decreases as the vehicle speed increases.

[Effects of the Invention] As described above, the present invention includes a spring that urges a control member in a direction in which the rear wheel steering angle ratio becomes 0, and a spring that urges the control member in a direction where the rear wheel steering angle ratio is large. Since the amount of fluid supplied to the rear wheel steering actuator is reduced as the vehicle speed increases, the projecting piece of the input shaft that rotates in accordance with the steering wheel turning angle or The dead zone (play) of the handle from the neutral position until the cutout member engages with the cutout member or protrusion on the drive shaft of the differential control valve that controls the rear wheel steering actuator and transmits rotation to the drive shaft. The width is controlled in relation to the vehicle speed, so that the rear wheel steering angle ratio becomes progressively smaller as the vehicle speed increases.

Therefore, when driving at low speeds, the rear wheels are relatively largely steered in the opposite phase to the front wheels, demonstrating tight turning ability, while when driving at medium speeds, the rear wheels are hardly steered within the normal steering angle range, and when driving at high speeds, Since the projecting piece is in a state where it cannot engage with the notch member, the rear wheels are not steered at all, and straight-line running performance is improved.

Further, since the control member that controls the relative position of the notch member and the protruding piece is biased by the spring force so as to remove the protruding piece from the notch to a position where it cannot be engaged, the electric
Even if the hydraulic control I device fails, the engagement between the notch member and the protruding piece is automatically released and the rear wheel is returned to the neutral position.
There is no risk that the rear wheel steering angle will change irregularly or the vehicle body posture will change suddenly, ensuring operational safety.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a four-wheel steering vehicle equipped with a steering angle ratio control mechanism according to the present invention, FIG. 2 is a perspective view showing the main part of the steering angle ratio control 11R bridge, and FIG. FIG. 5 is a diagram showing the steering angle characteristics of the steering angle ratio control 11R bridge, and is a miniature diagram showing the steering angle characteristics of the conventional steering angle ratio control mechanism. A: Steering angle ratio 1IiIIIIIR structure B: Differential control valve C
: Electric/hydraulic control system M D: Actuator E: Oil
Adjustment valve F: Rear wheel steering actuator 13: Spring 1
8:lll1l lever 1g, input shaft 2o: control member 21: notch member 22: protruding piece 24: drive shaft
44: Vehicle speed proportional current generator 45 Two current subtraction converter

Claims (1)

[Claims] It consists of a spring that urges the control member in the direction where the rear wheel steering angle ratio becomes 0, and a rear wheel steering actuator that pushes the control member in the direction where the rear wheel steering angle ratio increases against the spring. A steering angle ratio control mechanism for a four-wheel steering vehicle, characterized in that the amount of fluid supplied to a rear wheel steering actuator is reduced as the vehicle speed increases.