JPH0299464A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To enable reduction of a revolving radius and to improve high speed running safety by providing a means to drive a rod on the output side interlocking with rear wheels according to displacement of a rod on the input side interlocking with front wheels and a means to drive only a rod on the output side independently. CONSTITUTION:With front wheels steered, a rod 1 on the input side is moved, and a pivotal support part A between the rod 1 in the input side and a coupling rod 3 is moved. Along with the movement, the coupling rod 3 is swung around a pivotal support part B between the coupling rod 3 and a rod 2 on the output, and a pivot support member 4 through which the coupling rod 3 is coupled to a spool 6 is moved. As a result, since a relation between the spool 6 and a cylinder 8 is changed and a hydraulic switching valve 5 is switched, pressure oil is fed to and discharged from a hydraulic cylinder 13 to steer rear wheels. Meanwhile, by controlling a stepping motor 24 according to the running state of a vehicle by means of a controller 27, the hydraulic switching valve 5 is switched in a similar manner described above, and rear wheel and front wheels are steered independently from each other.

Description

[Detailed Description of the Invention] (Industrial Application Field) The four-wheel steering device according to the present invention is used as a steering device for an automobile, and when changing the course of the automobile, it is possible to use not only the front wheels but also the rear wheels. By changing the direction of the wheel, the turning radius can be made smaller and running stability can be maintained.

(Prior art) To reduce the turning radius of a car so that it can easily change course on a narrow road, or to maintain vehicle stability even when changing course while driving at high speed. Therefore, four-wheel steering devices that move not only the front wheels but also the rear wheels when the steering wheel is operated have come into use in recent years.

The structure of a four-wheel steering system has traditionally been the following (a) to (d).
) shown in 4f! I! Something like - is used numerically.

(a) A system in which a front wheel steering device and a rear wheel steering device are mechanically coupled to move the rear wheels in a fixed relationship according to the movement of the front wheels.

(b) A steering device for the front wheels and a steering device for the rear wheels are connected by a hydraulic circuit, so that the rear wheels do not move in a fixed relationship according to the movement of the front wheels.

(c) A steering device for the front wheels and a steering device for the rear wheels are coupled by a hydraulic mechanism, but the rear wheels can move independently of the front wheels.

(d) The steering device for the front wheels and the steering device for the rear wheels are only electrically connected, and the rear wheels can move independently of the front wheels.

Among these four conventionally known types of four-wheel steering devices, when it is necessary to increase the steering angle of the rear wheels in order to reduce the turning radius, either (a) or (b) is adopted. ,
If there is no need to increase the steering angle of the rear wheels, -numerically (
e) Either (cl) is adopted.

(c) (d) In the case of two types of four-wheel steering systems, the rear wheels are controlled independently from the front wheels, so if a failure occurs,
While it is dangerous if the rear wheels are steered significantly when driving at high speeds, in the case of (a) and (b) two types of four-wheel steering systems, the front and rear wheels are steered by the driver's will. This is because the two move only in relation to each other, and there is no danger as described above.

(Problem to be solved by the invention) However, the above (a), which has been used conventionally,
(b) In the case of two types of four-wheel steering devices, the front wheels and rear wheels, which are steered by the driver's will, move only in relation to each other, so stability during high-speed driving etc. is not always sufficiently improved. I can't do anything.

In other words, when the movements of the front wheels and the rear wheels are related to each other, when the steering angle of the front wheels is small, the phases of the front and rear wheels are the same (rotating the front and rear wheels in the same direction), and when driving at high speed, In addition, when the steering angle of the front wheels increases, the phase of the front and rear wheels is reversed (the front and rear wheels rotate in opposite directions), and the turning radius of the vehicle is improved. However, when driving at high speeds and factors that cannot be incorporated in advance are added, the steering system becomes much more stable than the conventional two-wheel steering system However, it may not be possible to ensure sufficient vehicle stability.

For example, if you are hit by a crosswind while driving at high speed, if the rear wheels skid while cornering at high speed, or if unexpected sudden steering is performed (sudden steering wheel) due to a jump, etc. By steering the vehicle, the stability of the vehicle can be ensured, but in this case, it is necessary to steer the rear wheels independently of the front wheels. However, the above (
a) (b) In the case of two types of four-wheel steering devices, the rear wheels cannot be steered independently of the front wheels, so it is not possible to deal with such a case.

In the case of the four-wheel steering system of the above (C) (d) Z fi type, it is possible to cope with this modest case, but from the viewpoint of safety,
As mentioned above, the steering angle of the rear wheels cannot be increased and the turning radius of the vehicle cannot be made very small.

The four-wheel steering system of the present invention was devised to eliminate such inconveniences, and the steering angle of the rear wheels can be increased only in relation to the steering angle of the front wheels. The small steering of the wheels can be done independently of the steering of the front wheels.

(Means for Solving the Problems) The four-wheel steering device of the present invention has a steering wheel! an input side rod that is displaced by an amount corresponding to the steering angle of the front wheels according to the steering angle of the front wheels;
An output rod that steers a rear wheel, a coupling means that moves the output rod in accordance with the displacement of the input rod, a drive means that moves the output rod regardless of the displacement of the input rod, and a vehicle that is detected by a sensor. and a controller that operates this drive means according to the operating conditions of the vehicle.

According to the second aspect of the present invention, the rear wheels are steered by an input rod that moves in the axial direction by a length corresponding to the steering angle of the front wheels in accordance with the movement of the steering wheel, and a B rod that extends in the axial direction. It consists of an output rod, a connecting rod whose ends are pivoted to the input rod and the output rod, respectively, and a spool built into the cylinder cylinder, and the relative displacement in the axial direction of the temperature of both the spool and the cylinder. A hydraulic switching valve that switches communication between the pressure oil supply port and the discharge port and the first port and the second port, a portion that moves in the axial direction together with the spool, and an intermediate portion of the connecting rod are swingable. a hydraulic cylinder in which a piston, which is provided at a position surrounding the output rod and is fixed to the outer peripheral surface of the intermediate portion of the output rod, is fitted in an oil-tight manner so as to be movable in the axial direction; and first and second hydraulic passages that connect the first and second chambers located on both sides of the piston in the hydraulic cylinder and the first and second ports of the hydraulic switching valve, and the hydraulic pressure It is comprised of a drive means that moves the cylinder tubes of the switching valve axially relative to each other, and a controller that moves this drive means in accordance with the driving situation of the vehicle detected by a sensor.

(Function) In the case of the four-wheel steering device of the present invention configured as described above, when steering the front wheels and rear wheels in relation to each other, it is possible to increase the steering angle of the rear wheels, If the steering angle of the wheels can be small, it is possible to steer the rear wheels independently of the front wheels.

For example, in the case of the invention described in claim 2, when steering the front wheels and rear wheels in relation to each other, the input rod moves in the axial direction as the front wheels are steered, and the input rod moves in the axial direction as the front wheels are steered. A connecting rod with one end pivoted on the side rod and the other end pivoted on the output side rod rotates tl around a pivot support member provided in the middle.
llt, move the output side rod in the axial direction.

As a result, the output rod steers the rear wheels in conjunction with the front wheels.

However, in this case, the connecting rod first swings around its pivot point with the output rod, and the spool, which moves in the axial direction together with the pivot member in the middle of the connecting rod, moves in the axial direction due to the torque applied to the connecting rod. , and the port of the hydraulic switching valve is switched. At this moment, the output rod is not moving yet.

When pressure oil is supplied to and discharged from the hydraulic cylinder via the first and second hydraulic passages, the output rod moves in the axial direction via the piston, but the direction and amount of movement are This eliminates displacement of the pivot member connecting the connecting rod and the spool. That is, by supplying and discharging pressure oil to and from the hydraulic cylinder through the hydraulic switching valve, the displacement of the pivot member due to the torque applied to the connecting rod is corrected (resolved).

This displacement correction is actually instantaneous, so the movement of the input rod is directly transmitted to the output rod, as if the connecting rod were rotating around a fixed pivot member, and the rear wheel steering This is done in conjunction with the steering of the front wheels. Therefore, in this case, the steering angle of the rear wheels can be made sufficiently large even in consideration of safety.

Next, when steering the rear wheels independently of the front wheels, the controller sends a signal to the drive means based on the signal from the sensor, and the drive means steers the cylinder of the hydraulic switching valve according to the disturbance detected by the sensor. The object is moved by an appropriate length in an appropriate direction depending on the direction and size of the object.

As a result, the port of the hydraulic switching valve is switched in accordance with the movement of the cylinder cylinder or spool, and pressure oil is supplied to and discharged from the hydraulic cylinder via the second and second hydraulic passages, and then via the piston. Since the output rod is moved in the axial direction, the rear wheels are steered independently of the front wheels.

When the output rod moves in the axial direction by an amount necessary and sufficient to properly steer the rear wheels, the spool and cylinder barrel move in the axial direction via a pivot member provided in the middle of the connecting rod. Based on the relative displacement, the port of the hydraulic switching valve is switched, supply and discharge of pressure oil to the hydraulic cylinder is stopped, and the steering angle of the rear wheels is fixed.

(Example) Next, the present invention will be explained in more detail while explaining the illustrated embodiment.

Figures 1 to 5 show an embodiment of the present invention, with Figure 1 being a sectional view showing the rear wheel steering mechanism, Figure 2 showing the neutral state of the hydraulic switching valve, and Figure 3 showing the switched state. FIG. 4 is an enlarged cross-sectional view of the X section in FIG. 1, FIG. 4 shows a case where the front wheels and rear wheels are steered in relation to each other, and FIG. 5 shows a case where the rear wheels are steered independently of the front wheels. 2 are schematic diagrams showing the movements of each part.

1 is the input side rod, which moves in the axial direction (horizontal direction in Figure 1) by a length corresponding to the steering angle of the front wheels (due to the adoption of a variable pull ratio gear, etc.) according to the movement of the steering wheel. Moving.

In addition, 2 is the output side rod, which moves in the axial direction (left and right directions). & steer the wheels.

These rods 1.2 on the input side and the output side are arranged almost parallel to each other, but in order to be able to freely move relative to the connecting rod 3 described below, at least one of the rods 1.2
(or 2) is supported by the vehicle body so as to be able to swing slightly. However, the connecting rod 3 may have a structure that can be expanded and contracted slightly while maintaining sufficient rigidity, or the connecting rod 3 may have a structure that can be freely expanded and contracted, or the pivoting portion A between both ends of the connecting rod 3 and the input side, output side, and both rods 1.2 may be used.
, B have a structure that can be slightly displaced in the axial direction of the connecting rod 3 by engagement between a long hole and a bottle, etc., then the input side,
There is no need to swingably support both rods 1.2 on the output side relative to the vehicle body.

A spool 6 of a hydraulic switching valve 5 is connected via a pivot member 4 to the intermediate portion of the connecting rod 3 whose both ends are pivotally supported by the input rod 1 and output rod 2 as described above. There is.

The cylinder tube 8 of the above hydraulic switching '#-5 is connected to the casing 7
A spool 6 is housed within the cylinder tube 8 so as to be freely movable only in the axial direction, and a spool 6 is housed within the cylinder tube 8 so as to be freely movable in the axial direction. Cylinder tube 8! -7 is
A pressure oil supply port (10) communicating with the discharge port of the pressure oil pump 9;
A discharge port 12 communicating with the oil tank 11 and first and second ports 16.17 communicating with first and second chambers 14.15 of the hydraulic cylinder 13, which will be described later, are respectively formed. Based on the relative displacement between the spool 6 and the spool 6 in the axial direction, the pressure oil supply port 10 and the discharge port 12
, the first port 16 and the second port 17 are switched.

In addition, the outer peripheral edge of the retaining ring 18.18 fitted around the base end and tip end of the protruding rod 31 protruding from one end surface of the spool 6,
A compression spring 20 is placed opposite the stepped portion 19.19 formed on the inner circumferential surface of the cylinder tube 8, and between both retaining rings 18.18.
is provided, and this spool 6 will operate as long as no external force is applied.
It is held in a neutral position (the position shown in FIGS. 1 and 2), and the pressure oil supply port lO and the discharge port 12 are in direct communication, so that pressure oil is not supplied to or discharged from any of the chambers 14 and 15 of the hydraulic cylinder 13. I am trying to prevent this from happening.

Also, a similar retaining ring 2 is installed around the middle part of the output rod 2.
8.28 and a compression spring 29 are provided, and each retaining ring 28.28
By having the outer circumferential edge of the hydraulic cylinder 13 face the stepped portion 30.30 formed on the inner circumferential surface of the hydraulic cylinder 13, the output rod 2 is held at the neutral position unless an external force is applied, and the output side rod 2 is held at the neutral position, so that the rear wheels are not steered. The corners are not added.

A hydraulic cylinder 1 is located at a position surrounding the middle part of the output rod 2.
3, and a piston 21 fixed to the outer peripheral surface of the intermediate portion of the output rod 2 is fitted into the hydraulic cylinder 13 in an oil-tight manner and movable in the axial direction.

The first and second chambers 14.15 located on both sides of the piston 21 in the hydraulic cylinder 13 and the first and second ports 16.17 of the switching valve 5 are connected to the first and second chambers 14.15 and They are connected to each other by two hydraulic passages 22, 23.

A stepping motor 24 is fixed to the end of the casing 7, and a nut piece 25 fixed to the output shaft of the stepping motor 24 and a male screw portion 26 protruding from the end surface of the cylinder tube 8 are screwed together. As the stepping motor 24 rotates, the cylinder tube 8 can be moved in the axial direction.

This stepping motor 24 is rotated by an appropriate angle (rotation speed) in an appropriate direction in response to a command signal from a controller 27. That is, the controller 27 with a built-in microcomputer controls the rotation angle of the steering wheel, the rotational angular velocity of the steering wheel, the magnitude of the reaction force generated in the front wheel steering device, the acceleration (G) applied in the lateral direction of the vehicle body, crosswinds, and running on slopes. detect one or more elements selected from among those that do not affect the operation of the vehicle, such as stress applied to the vehicle body due to
determined according to signals from one or more sensors,
Depending on the driving situation of the car, the stepping motor 24
are rotated in an appropriate direction by an appropriate angle (rotation speed) to mutually displace the cylinder tubes 8 in their axial directions.

Next, the operation of steering a vehicle using the four-wheel steering system of the present invention configured as described above will be described.

First, when steering the front wheels and rear wheels in relation to each other, the input rod 1 moves in the axial direction as the front wheels are steered, and the pivot point between the input rod 1 and one end of the connecting rod 3 is changed. Branch A moves from the A0 position in FIG. 4 to the A1 position in the same figure. Along with this, the connecting rod 3 swings around the pivot point B with the output rod 2, and the connecting rod 3, which had been in the state shown by the solid line in FIG. The middle part of the connecting rod 3 and the spool 6 are displaced as shown.
The pivot member 4 connecting the two moves from the C0 position in FIG. 4 to the C position in the same figure.

As a result, the spool 6, which had been in the state shown in FIG.
The relationship between the cylinder pipe 8 and the cylinder pipe 8 changes to the state shown in FIG.
are switched, and the pressure oil supply port 10 and the first port 16 (or the second port 17) are switched, and the discharge port 12 and the second port 17 (or the first port 16) are switched, respectively. Pressure oil is fed into the first chamber 14 (or second chamber 15) of the hydraulic cylinder 13 through the first hydraulic passage 22 (or second hydraulic passage 23), and the second chamber 15(
Alternatively, oil is discharged from the first chamber 14 through the second hydraulic passage 23 (or the first hydraulic passage 22). At the moment when the hydraulic switching valve 5 is switched in this way, the output side rod 2 is not yet moving, and the connecting rod 3 and the output side rod 2 are not moving.
The pivot point B is located at the B0 position in FIG.

As described above, as the spool 6 moves based on the swinging of the connecting rod 3, each port 10, 12, .
16 and 17 are switched, and the first and second hydraulic passages 22
．． When pressure oil is supplied to and discharged from the hydraulic cylinder 13 via the hydraulic cylinder 13, the piston 2 fitted in the hydraulic cylinder 13
The output rod 2 is moved in the axial direction via the shaft 1, and the rear wheels are steered.

As the output rod 2 moves, the pivot point B between the connecting rod 3 and the output rod 2 changes from the B0 position to B1 in FIG.
When the connecting rod 3 moves to the position indicated by the chain line in the figure, the pivot member 4 connecting the intermediate part of the connecting rod 3 and the spool 6 moves from the C1 position to the C0 position in the figure. ), and the displacement of the pivot member 4 connecting the connecting rod 3 and the spool 6 is eliminated.

This displacement correction, that is, input rod 1 and output rod 2
Due to the movement in the axial direction, the position of the pivot member 4 is changed to Ca.
= Since the operation of moving from Ct to C0 is instantaneously performed, in reality, the connecting rod 3 moves from the state shown by the solid line in Fig. 4 to the state shown by the solid line in Fig. 4, centering on the pivot member 4 fixed at the Co position. The movement of the input rod 1 is directly transmitted to the output rod 2, as if it had rotated to the state shown by the chain line in .
Steering of the rear wheels is performed in conjunction with steering of the front wheels.

Therefore, in this case, the steering angle of the rear wheels can be made sufficiently large even if safety is considered, and the turning radius of the vehicle can be made small.

Next, when steering the rear wheels independently of the front wheels, based on signals from sensors that detect the vehicle condition and steering condition,
The controller 27 sends a signal to the stepping motor 24, and the stepping motor 24 controls the cylinder tube 8 of the hydraulic switching valve 5 via the nut piece 25 and the male thread 26 according to the direction and magnitude of the disturbance detected by the sensor. The object is moved by a predetermined length in a predetermined direction.

When each port 10, 12, 16, 17 of the hydraulic switching valve 5 is switched in accordance with this wJ movement of the cylinder tube 8,
Pressure oil is supplied to and discharged from the hydraulic cylinder 13 via the first and second hydraulic passages 22 and 23, and the output rod 2 is moved in the axial direction via the piston 21. As a result, the pivot point B between the output rod 2 and the connecting rod 3, which had been at position 82 in FIG. It is performed independently of the front wheels, regardless of the movement of the front wheels.

In this way, when the output rod 2 moves in the axial direction by an amount necessary and sufficient to properly steer the rear wheels, the pivot member connecting the intermediate portion of the connecting rod 3 and the spool 6 4 moves from the 02 position in FIG. 5 to the C3 position in the same figure, and the spool 6 is pulled (or pushed) by the pivot member 4 and moves in the axial direction within the cylinder tube 8. The relative positional relationship between the spool 6 and the cylinder tube 8, which had been in the state shown in FIG. 3 until then, is now as shown in FIG. 2, and the pressure oil supply port 10 and the discharge port 12 are in direct communication. As a result, supply and discharge of pressure oil to the hydraulic cylinder 13 is stopped, the output side port ν door 2 no longer moves, and the steering angle of the rear wheels is fixed. When the disturbance is no longer present, the controller 27 rotates the stepping motor 24 in the opposite direction to return the cylinder tube 8 to its original position and eliminate the steering angle of the rear wheels. In this case, the pressure oil is supplied and discharged in the opposite direction to the direction in which the steering angle is applied.

If necessary, the movement of the input rod 1 that moves in the axial direction by operating the handle is detected by the sensor 33, and the movement of the stepping motor 24 is detected by the sensor 32, and the signals from each sensor 33 and 32 are controlled. The device 27 is manually operated to have a fail-safe function against sudden steering operations, etc.

The four-wheel steering system of the present invention does not require the use of a spool valve that is switched by a connecting rod that connects an input rod and an output rod, as in the illustrated embodiment. Using solenoid valve switched,
It can also be configured by switching the supply and discharge of pressure oil to the hydraulic cylinder, or by omitting the hydraulic cylinder and directly driving the output rod with an electric actuator that is directly driven by the signal from the sensor. I can do it.

(Effects of the Invention) The four-wheel steering device of the present invention is configured and operates as described above, and the steering angle of the rear wheels is increased only in relation to the steering angle of the front wheels. Since small steering can be performed independently of front wheel steering, it is possible to reduce the turning radius of the vehicle while ensuring safety, and it can also be used in cases such as when unexpected disturbances occur while driving at high speed. It is also possible to subtly steer the rear wheels to ensure vehicle stability.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, FIG. 1 is a sectional view showing the rear wheel steering mechanism, and FIG. 2 is a hydraulic cut-off 1! ! ! FIG. 3 shows the valve in its neutral state, and FIG. 3 shows the valve in its switched state. FIG. 4 is an enlarged sectional view of section X in FIG. The figure shows 1. when the rear wheels are steered independently of the front wheels. Each is a schematic diagram showing the movement of each part. 1. Input side rod, 2: Output side rod, 3: Connection rod, 4: Pivot support member, 5: Hydraulic switching valve, 6: Spool, 7:
Casing, 8 cylinder cylinder, 9: Pressure oil pump, 10;
Pressure oil supply port, 11: pond tank, 12: discharge port,
13: Hydraulic cylinder, 14: First chamber, 15: Second chamber, 16: First port, 17: Second port, 18: Retaining ring, 19: Step, 20: Compression spring, 21: Biston,
22: first hydraulic passage, 23 2 second hydraulic passage, 24 chipping motor, 25: nut piece, 26: female thread, 27: controller, 28: retaining ring, 29: compression spring, 3o
: Step part, 31: Projecting rod, 32.33: Sensor.

Claims (3)

[Claims] (1) An input rod that is displaced in accordance with the steering angle of the front wheels in response to the movement of the steering wheel, an output rod that steers the rear wheels, and a connecting means that moves the output rod in accordance with the displacement of the input rod. A four-wheel steering device comprising a drive means that moves an output rod regardless of the displacement of an input rod, and a controller that moves this drive means in accordance with the driving situation of the vehicle detected by a sensor. (2) In response to the movement of the steering wheel, the input rod moves in the axial direction by a length corresponding to the steering angle of the front wheels, and the output rod steers the rear wheels by moving in the axial direction. It consists of a connecting rod that is pivotally supported on the side rod and the output side rod, respectively, and a spool built into the cylinder cylinder, and the relative displacement between the spool and the cylinder cylinder in the axial direction allows the pressure oil supply port and the discharge port to be connected to each other. a hydraulic switching valve that switches communication with the first port and the second port, a pivot member that swingably connects a portion that moves in the axial direction together with the spool and an intermediate portion of the connecting rod, and the output A hydraulic cylinder is provided in a position surrounding the side rod and has a piston fixed to the outer circumferential surface of the intermediate portion of the output side rod fitted in an oil-tight manner so as to be movable in the axial direction, and a piston in the hydraulic cylinder. A first, which connects the first and second chambers located on both sides and the first and second ports of the hydraulic switching valve.
A four-wheel drive system consisting of a second hydraulic passage, a drive means for moving the cylinder cylinder of the hydraulic switching valve in the axial direction, and a controller that moves the drive means according to the vehicle operating condition detected by the sensor. Steering device. (3) The sensor is selected from among the rotation angle of the steering wheel, the rotational angular velocity of the steering wheel, the magnitude of the reaction force generated in the front wheel steering device, the acceleration applied in the lateral direction of the vehicle body, and the stress applied to the vehicle body. The four-wheel steering device according to claim 1 or 2, wherein a plurality of elements are detected.