JPH0263975A - Rear-wheel steering angle slow variable mechanism - Google Patents

Abstract

PURPOSE:To adjust the width of a dead zone by installing a wedgelike notch, capable of contacting with a driving member reciprocating a projecting piece on a valve element of a differential control valve at a moving area of this piece, in an input shaft which reciprocates in response to a wheel steering angle. CONSTITUTION:A projecting piece 22 is installed in an input shaft 19 being reciprocated in response to a steering angle out of the central position of a steering wheel 41 in both reciprocating and rectangular directions. In addition, a cylinder member 21, provided with a wedge type notch 21a contractible within the range of the projecting piece 22 moving, is installed in a drive shaft 24 reciprocating a valve element 126 of a differential control valve B controlling a hydraulic circuit of a rear-wheel actuator F. At the time of low speed running, a rod of an actuator 9D is operated to the right by hydraulic operation, the projecting piece 22 is moved to the left, whereby play between the projecting piece 22 and the notch 21a comes smaller and response motion to the rear-wheel steering actuator is speeded up. At the time of high speed, the projecting piece 22 is moved to the right and thereby the play grows larger, so that the response motion comes slow. Therefore rear wheels are steered safely and effectively at an operating area of the steering wheel conformed to a running condition.

Description

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

[Conventional VL Technique] A four-wheel steering vehicle that steers the rear wheels in the opposite phase to the front wheels is
From the viewpoint of safety, it is preferable that the rear wheel steering angle ratio (the ratio of the rear wheel steering angle to the front wheel steering angle) is large when traveling at low speeds, and that the rear wheel steering angle ratio gradually decreases at high speeds.

For example, in a four-wheel steering vehicle disclosed in Japanese Unexamined Patent Publication No. 59-77972@, an electronic i
, a rear wheel steering angle ratio preset in the II control device is selected,
Based on this, the electromagnetic directional control valve that controls the hydraulic circuit of the rear wheel steering actuator is driven.

However, in the above-mentioned four-wheel steering vehicle, as shown in FIG. 4, when the steering wheel is turned even slightly from the neutral position, the rear wheels are also steered in the opposite phase to the front wheels. With this steering angle characteristic, when driving at medium or high speeds, there is a tendency for the steering wheel to turn a little too much (the direction of the vehicle body changes suddenly), which is unfavorable from a safety standpoint. It is preferable that the rear wheels have a dead zone characteristic in which the rear wheels are not steered.

To obtain this dead zone, it is common to install an electromagnetic clutch or the like between the input member that reciprocates in relation to the steering wheel and the driving vJpH5 material that steers the rear wheels, and disconnect and connect the electromagnetic clutch at the required times. However, this is due to the clutch mechanism and the mechanism that controls the disconnection and engagement times! l, the cost increases.

[Problems to be Solved by the Invention] An object of the present invention is to provide a rear wheel steering angle characteristic gradual change mechanism that is simple in structure and reliable in operation.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention controls an input member that reciprocates in response to the turning angle from the neutral position of the steering wheel and a hydraulic circuit of a rear wheel steering actuator. One of the driving members for reciprocating the valve element of the differential control valve supports a protrusion movable in a direction substantially perpendicular to the direction of reciprocating movement, and the other member supports a protrusion in the movement area i11 of the protrusion. A notch is provided that can be brought into contact with the protruding piece, and the clearance between the notch and the protruding piece in the motion transmission direction changes in relation to the moving direction of the protruding piece.

[Function] When one of the contact members is moved in a direction perpendicular to the interlocking transmission direction at the contact portion between the input member and the drive member, the amount of play in the contact portion changes, so the width of the dead zone is adjusted. Ru.

The input member reciprocates (including reciprocating rotation) in response to the steering angle of the handle, and when the steering angle of the handle exceeds the dead zone, the drive member also reciprocates.

Embodiment 1 of the Invention FIG. 1 is a schematic diagram of a four-wheel steered vehicle equipped with a steering angle characteristic gradual change mechanism according to the present invention. The rear wheel steering mechanism includes a steering angle characteristic gradual change mechanism A that transmits the rotation of one input shaft interlocked with the output shaft 29 of the front wheel steering gear l1iI30 to the differential control valve B in relation to the vehicle speed, and a rear wheel steering actuator F. A differential 1liIitiII valve B that controls the hydraulic circuit to the rear wheel 71, a rear wheel steering actuator F that drives the rear wheels 71, and a steering angle characteristic gradual change mechanism A
A dead zone control means C for controlling the control member 20 is provided.

The steering angle characteristic gradual change mechanism Δ consists of a control member 2o spline-fitted to one input shaft and a cylindrical member 21 connected to a drive shaft 24 that drives the differential control valve B.

The drive shaft 24 is aligned coaxially with one input shaft. A projecting piece 22 extending in the radial direction from the control member 20 is configured to be able to engage with a horizontal notch 21 a formed in the circumferential surface of the cup-shaped cylindrical member 21 . The control lever 18 of the shaft 17 is engaged with the annular groove of the control member 20, and the rotation of the control lever 18 causes the control member 20 to slide in the axial direction. 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 is partitioned into an end where hydraulic pressure is introduced and the atmosphere by a piston fitted inside the cylinder. The lever 18a and the control lever 18 are rotationally biased by the spring 13 housed in the atmosphere, and the projecting piece 22 of the j11 member 20 is moved away from the notch 21a of the cylindrical member 21 in the axial direction.

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 the pipe 72.75 to one of the pipes 7680, and oil from the other pipe is supplied to the oil tank 28 via pipe 79.77.
be returned to. Pipe 76.80 is rear wheel steering actuator F
The end chambers 89 and 91 are connected to each other.

The rear wheel steering actuator F has a cylinder 57 fitted with a screw 56 to define end chambers 89 and 91, and a piston 5.
Tie rod 65 connected to G is both cylinder/157 OM
It projects outward from m. The tie rod 65 is connected to the end chamber 89.
The rear wheel 71 is returned to the neutral position by the force of the return spring 55 housed in the rear wheel 91, and the rear wheel 71 is held in the straight-ahead position. Both ends of the tie rod 65 are connected to the rear wheel knuckle 6 via auxiliary rods 67, respectively.
9. Rear wheel knuckle 69 supporting rear wheel 71
is rotatably supported on 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 a locking member 59 that can be engaged with the receiving member 58. Actuator G
When pressure oil is supplied to the cylinder 63 to 96, the locking 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 sprue 126 to the neutral position.

FIG. 2 is a perspective view showing the relationship between the front wheel steering mechanism 30, the steering angle characteristic gradual change F3 structure A, and the differential control valve B.

In order to simplify the explanation, FIG.
The lever 18 is connected to the actuator D, and the spring 13 is disposed outside. Further, an electromagnetic clutch 11 is provided between the slave CJ shaft 6 and the lever 9a. When the electromagnetic coil 8 is excited, a! which is coupled to the driven shaft 6! A friction plate 9 integrated with a lever 9a is engaged with the friction root 7, and rotation of the lever 9a is transmitted to the driven shaft 6. When the electromagnetic 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, the cable 50 is actually slidably inserted into an outer tube that has one end fixed to the vehicle body and the other end fixed to the housing of the rear wheel steering actuator F.

As shown in FIG. 1, the dead zone control means C moves the 1iil1211 member 20 in the axial direction in the steering angle characteristic gradual change mechanism A, and controls the gap in the circumferential direction between the protrusion 22 and the notch 21a in relation to the vehicle speed. do. Therefore, the dead zone control means C includes an actuator D that drives the control lever 18 that engages the control member 20, an oil amount adjustment valve E that adjusts the stroke of the actuator D, that is, the amount of oil to the actuator D, and an oil amount adjustment valve. The vehicle is equipped with a current subtraction converter 45 that controls the current to the electromagnetic coil 47 that drives E in relation to the vehicle speed.

The oil amount adjusting valve E is constructed by fitting a spool 48 having two annular grooves into a housing 46 having three boats, an end chamber 49 housing a spring 49a, and a central boat 1 to 1.
is communicated with the end chamber of actuator D. In the neutral position, the boat on the right that communicates with the annular groove of the spool 48 is the pipe 78.
．． 72 is the light hydraulic pump 26, and the boat on the left is the pipe 73.
．． 77 to the oil tank 28, respectively. A rod 48a connected to the spool 48 projects to the outside of the housing 46 to constitute an armature, and is biased to the left by the electromagnetic coil 47 against the spring 49a in response to the 'Fi flow. 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-like M is attached to the 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 442 .

Both terminals of the vehicle speed proportional current generator 44 are connected to a current subtraction converter 45.
connected to.

Next, the operation of the four-wheel steered vehicle equipped with the steering angle characteristic gradual change column 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 2 of the front wheel steering mechanism 30
9 is rotated, the redrag link 33 is pulled forward by the arm 32, the front wheel knuckle 38 is rotated clockwise about the support shaft 34, and the front wheel 40 is deflected to the right. At the same time, the rotation of the output shaft 29 is transmitted to the input shaft 19, and when the vehicle speed is below a predetermined value and the steering angle or front wheel steering angle exceeds a predetermined value, the protrusion 22 of the control member 20 moves toward the cylindrical member 21. The drive shaft 24 is rotated.

At this time, the cylindrical member 21 moves very slightly in the axial direction, the switch 23 moves, the actuator G of the neutral lock 1 structure H is driven, and the lock member 59 is separated from the receiving member 58.

The driven shaft 6 does not rotate with respect to the rotation of the drive shaft 24 and prevents the screw shaft 130 from rotating.
0, a relative rotational phase difference occurs, and the screw shaft 130 moves to the right together with the spool 126 according to the lead angle of the screw groove. As the axis of the spool 126 moves, the hydraulic pump 26
Pressure oil is supplied to the end chamber 89 of the actuator F via the pipes 72, 75, the differential control valve B, and the pipe 76. piston 5
6, the tie rod 65 is pushed to the right, and the rear wheel suspension 69 is rotated counterclockwise about the support shaft 70.
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 exhibited. 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 mentioned above, a large current flows from the power supply battery 51 to the electromagnetic coil 47 via the current subtraction converter 45, so that the spool 48 of the oil m:l valve E reaches a position where it balances the force of the spring 49. Pushed to the left. Pressure oil from the hydraulic pump 26 passes through pipes 72, 78 and is supplied from the annular groove on the right side of the spool 48 to the end chamber of the actuator D via the pipe 49b. The oil pressure at the end W49 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 Drad 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 gap in the circumferential direction between the protrusion 22 of the control member 20 and the notch 21a of the cylindrical member 21 increases. It gets 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 operates, and the front and rear wheel steering actuators F
The rear wheels 71 are steered by.

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 the pipe 49b flows into the annular groove on the left side of the spool 48. It is returned to the oil tank 28 via pipes 73,77.

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 the actuator D decreases, and the force of the spring 13 causes the Orad to return to the left. As a result, the control 11 member 20 moves to the right with respect to the input shaft 19. The protruding piece 2 that has been in contact with the notch 21a until now
2 is separated from the notch 21a, and the cylindrical member 21 is rotated to return to the neutral position by the action of a neutral return spring (not shown) provided in the cylindrical member 21.

In reality, the drive shaft 2 is rotated by the amount by which the cylindrical member 21 is returned to the neutral position while remaining in contact with the protruding piece 22 in the notch 21a.
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
9 are connected to the 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.
0, the tie rod 65 is held at that position when the screw shaft 130 returns to the right to the neutral position.

To explain the above operation with reference to FIG. 3, when the vehicle speed is as shown 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 further turned while the vehicle speed remains constant, the rear wheel steering angle gradually increases along 1ia1. If the front wheel steering angle becomes θ3 and the rear wheel steering angle becomes α1, and the vehicle speed increases, the dead zone increases from the front wheel steering angle equivalent to θ1 to the front wheel steering angle θ2 equivalent, corresponding to the vehicle speed, and the front wheel steering angle remains constant. (remains θ3), but as the vehicle speed increases, the rear wheel steering angle changes to α
It decreases from 1 to α2. The ratio of the rear wheel steering angle to the front wheel steering angle moves above the line a2 corresponding to the vehicle speed at that time,
It changes along line a2 depending on the turning angle of the handle.

In the embodiment shown in FIG. 4, a disk 82 instead of the cylindrical member is coupled to one end of an input shaft that rotates back and forth in accordance with the turning angle of the handle. A wedge-shaped notch 21 is formed on the periphery of the disc 82.
a is provided. On the other hand, a drive shaft 24 that drives the valve element of the differential control valve B is disposed coaxially with the input shaft 19 and is connected to a shaft 81 that extends in the radial direction. A protruding piece 22 protrudes parallel to the drive shaft 24 from a cylindrical control member 20 that is slidably spline-fitted to the shaft 81 and can abut on the notch 21a. Although not shown, the υ control member 20 is driven in the axial direction by the aforementioned hydraulic actuator D supported on the shaft 81, thereby controlling the width of the dead zone.

In the embodiment shown in FIG. 5, a fan-shaped plate 82 is coupled to the end of the input shaft 19 that reciprocates in response to the turning angle of the handle, and a horizontal notch 21a is provided at the periphery of the fan-shaped plate 82. A drive shaft 24 that drives the valve element of the differential control valve B is arranged coaxially with the input shaft 19. A bell crank 83 is rotatably supported by a bifurcated bracket 85 connected to the end of the input shaft 19 by a shaft 84 orthogonal to the drive shaft 24, and a spherical protrusion 22 formed at the end of the bell crank 83 can come into contact with the notch 21a. End 8 of bell crank 83
3a is rotated by the aforementioned actuator D disposed on the drive shaft 24, for example, the protruding piece 22 moves in the longitudinal direction of the notch 21a, that is, in the radial direction with respect to one input shaft, and the width of the dead zone is controlled. be done.

In the embodiment shown in FIG. 6, an arm 85 coupled to the drive shaft 24
An arm 87 is rotatably supported by a shaft 86 at the end of the arm 85, and a roller 22a supported at the end of the arm 85 can come into contact with the notch 21a. The notch 21a of the fan-shaped plate 82 connected to the input shaft is I! The locus of movement of the roller 22a as the arm 87 rotates at the neutral position of the roller 85a expands in an arc shape to have the same width in both circumferential directions. For example, when the shaft 86 of MB2 is driven by an electric motor supported by an arm 85a via a worm gear rock structure, the width of the dead zone is controlled.

In each of the embodiments shown in FIG. 4.5.6, the horizontal notch 21a is provided at the peripheral edge of the disk 82, but even if the notch has parallel side edges, the position of the protruding piece 22 in the radial direction Since the center angle at which the disk 82 can freely rotate changes in relation to can get.

In the embodiment shown in Fig. 7.8, a cylindrical control member 20 supporting a protrusion 22 is rotatable and movable in the axial direction on an input shaft 19 that reciprocates in the axial direction in accordance with the turning angle of the handle. Impossibly supported. On the other hand, drive shaft 2 parallel to one input shaft
A horizontal notch 21a is formed in 4, and in this notch 21a,
The spherical end portion 21b of the projecting piece 22 is allowed to come into contact with it. A rack of a rond 13a of an actuator D for rotating the control member 20 is engaged with a partial gear 20b formed on the control member 20.

As shown in FIG. 8, a screw shaft 24a is attached to the end of the drive shaft 24.
is formed and screwed into the threaded hole 128a of the inner valve element 128 of the differential control valve B. The differential control valve B is configured as a rotary directional valve. A cylindrical outer valve element 127 is rotatably fitted within the housing 122, and a cylindrical inner valve element 128 is rotatably housed therein.

Valve grooves are formed on the contact surfaces of the outer valve element 127 and the inner valve element 128, and the communication relationship of the valve grooves is switched by differential rotation between the two. Such a control valve is well known in power steering systems, so a description thereof will be omitted.

The driven shaft 6 is connected to the end of the outer valve element 127, and the cable 50 is connected to the end of the lever 9a of the driven shaft 6.

When the rod 13a of the actuator D is driven in relation to the vehicle speed, the control member 20 is rotated relative to the input shaft 19, and the projecting piece 22 moves in the longitudinal direction of the notch 21a together with the input shaft 19, thereby creating a dead zone. is controlled.

When the input shaft 19 moves, for example, to the right, corresponding to the turning angle of the handle, beyond the dead zone, the protruding piece 22 comes into contact with the notch 21a, and the drive shaft 24 moves to the right.

The rightward movement of the screw shaft 24a rotates the inner valve element 128, creating a rotational differential with the outer valve element 127, switching the communication state of the valve groove, and driving the rear wheel steering actuator F. When the tie rod is driven by the rear wheel steering actuator F, the rear wheels are steered and the cable 5o is pushed back, and the lever 9a moves the outer valve latch li'+27 together with the driven shaft 6 to the inner valve that was rotated earlier. Element 1
28 and the communicating state of the valve groove becomes the neutral position.

At this time, the rear wheel steering actuator F holds the rear wheels in their steered position.

In each of the above embodiments, the protruding piece that engages with the cylindrical member having the horizontal notch or the sector-shaped plate recess has the same effect whether it is supported on either the input shaft or the drive shaft.

[Effects of the Invention] As described above, the present invention includes an input member that reciprocates in response to the turning angle from the neutral position of the steering wheel, and a valve element of a differential control valve that controls the hydraulic circuit of the rear wheel steering actuator. One of the drive members for reciprocating motion supports a protrusion movable in a direction substantially perpendicular to the direction of reciprocating movement, and the other member is provided with a notch that can come into contact with the protrusion in the movement region G, Since the play in the motion transmission direction between the notch and the protruding piece is made to change in relation to the moving direction of the protruding piece, the gap between the notch provided on one side of the drive member of the input member and the protruding piece provided on the other side is The play creates a dead zone from the neutral position of the steering wheel (the front wheels go straight) until the rear wheels begin to be steered, and the play between the notch and the protrusion allows the protrusion to move in the longitudinal direction of the notch! 7J will add or subtract.

According to the steering angle characteristic gradual change mechanism of the present invention, by adjusting the play between the notch and the protrusion in relation to the vehicle speed, the rear wheels can be largely steered in accordance with the steering angle during low-speed driving, while When driving at high speeds, the rear wheels are hardly steered at the normal steering angle, and the rear wheels are steered safely and effectively within the steering wheel operating range that corresponds to the iM I-5 driving conditions.

The steering angle characteristic gradual change mechanism according to the present invention does not use an electronic control device and has a simple structure, and there is no adverse effect of backlash in the operating section, and a highly accurate steering angle υI11] can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a four-wheel steering vehicle equipped with a steering angle characteristic gradual change mechanism according to the present invention, FIG. 2 is a perspective view showing the main parts of the steering angle characteristic gradual change column, and FIG. Figures 4 and 5 are diagrams showing the steering angle characteristics in the column for gradual change in steering angle characteristics. A perspective view of the steering angle characteristic gradual change mechanism according to the third embodiment, FIG. 6 is a front view of the eleven steering angle characteristic gradual change mechanisms according to the fourth embodiment of the present invention, and FIG. 7 is a fourth embodiment of the present invention. A perspective view of a steering angle characteristic gradual change mechanism according to an example,
FIG. 8 is a sectional view of the same plane, and FIG. 9 is a diagram showing steering angle characteristics of a conventional four-wheel steering vehicle. A: Gradual change in steering angle characteristics B: Differential control valve F: Rear wheel steering actuator 18: Control lever 19: Input shaft 2
0: Control member 21: Cylindrical member 21a: Notch 22:
Protruding piece 24: Drive shaft 30: tFi steering structure 41:
Handle 82: Fan plate 83: Bell crank 87:
lever

Claims (1)

[Claims] an input member that reciprocates in response to the steering angle from a neutral position of the steering wheel; and a drive member that reciprocates a valve element of a differential control valve that controls a hydraulic circuit of a rear wheel steering actuator. A protrusion movable in a direction substantially perpendicular to the direction of reciprocating motion is supported, and the other member is provided with a notch that can come into contact with the protrusion in the moving area of the protrusion, so that the play between the notch and the protrusion in the direction of motion transmission is reduced. A rear wheel steering angle characteristic gradual change mechanism, characterized in that the rear wheel steering angle characteristic is changed in relation to the moving direction of one wheel.