JPH01223077A - Steering device for vehicle - Google Patents

Abstract

PURPOSE:To make the whole steering device simple and small-sized by providing a displacement transmitting means coupled with the output displacement member of a steering ratio variable means, the valve member of a hydraulic transfer valve and a steering rod and constituting this means with a lever member. CONSTITUTION:A steering ratio variable means 20 using a transmitting shaft 28 inputted with the steering force of a handle as an input shaft is provided, and it changes the absolute quantity and direction of the stroke displacement of an output displacement member 30 with the tilt angle when a sway shaft 40 is rotated centering axes l5 and l6 by the operation of a stepping motor 44. A displacement transmitting means 26 constituted of one vertical lever is operated in the direction to displace a spool 52 which is a valve member in the preset direction by the displacement of the output displacement member 30. The spool 52 is also operated to be displaced in the opposite direction to the above by the displacement of a rear wheel steering rod 24 generated by the displacement of the spool 52. The steering rod 24 is displaced by the displacement of the output displacement member 30, but the valve member is hardly displaced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a steering device that includes a hydraulic power cylinder controlled by a hydraulic switching valve and performs steering using the hydraulic pressure of the hydraulic power cylinder. The present invention relates to a steering device for a vehicle, such as a rear wheel steering device in a four-wheel steering vehicle, which is equipped with a steering ratio variable means capable of changing the steering ratio, that is, the ratio of the steering amount of the wheels to the amount of steering of the steering wheel.

(Prior Art) Conventionally, as a steering device for a vehicle that has a steering ratio variable means as described above and performs steering using the hydraulic pressure of a hydraulic power cylinder controlled by a hydraulic switching valve, for example, Japanese Patent Application Laid-Open No. 12-37283 A rear wheel steering device for four-wheel steering as described in the above publication is known.

An outline of this steering device is shown in FIG. 16. As shown in the figure, in this steering device, the front wheel steering rod 2 is stroke-displaced in the vehicle width direction by steering (rotation) of the handle 1, and the front wheels 3 are steered. The signal is input to the variable steering ratio means 5 via the shaft 4.

The variable steering ratio means 5 uses an output displacement member 5a, which is stroke-displaced in the vehicle width direction in response to the input steering amount of the steering wheel 1.
Change of output displacement member 5a (ratio of M, H (ratio of M, H) with respect to the steering amount of
As will be understood from the following explanation, this ratio corresponds to the ratio of the amount of steering of the rear wheels to the amount of steering of the steering wheel, so this ratio (also referred to as the steering ratio) changes depending on the amount of rotation of the stepping motor 6. It is composed of In this example, the amount of rotation of the stepping motor 6 is appropriately controlled by a control circuit 8 based on a vehicle speed signal output from a vehicle speed sensor 7, and the actual amount of rotation of the stepping motor 6 is detected by a steering ratio sensor 9. , and is configured to be feedback-controlled by the detection signal.

Note that the steering amount of the handle 1, the displacement amount of the output displacement member 5a, and the rotation amount of the stepping motor 6 are expressed not only as the absolute amounts of the steering, displacement, and rotation, but also their directions as (+) and (-). Contains m tear; E,.

The displacement of the output displacement 1445a in the steering ratio variable means 5 is determined by the displacement of the spool 1 which is the valve member of the hydraulic switching valve lO.
0a, and the hydraulic pressure switching valve 1o appropriately supplies hydraulic pressure to the hydraulic power cylinder 11 by the displacement of the spool 10a.1. It is configured to steer the rear wheels 13 by displacing the rear wheel steering rod 12 in the vehicle width direction by an amount corresponding to the displacement amount of the output displacement member 5a by the hydraulic pressure of the hydraulic power cylinder 11.

That is, in the hydraulic switching valve 10, the spool lOa is housed in the valve housing tob so as to be displaceable in the vehicle width direction, and the valve housing tab is fixed to the rear wheel steering rod 12 so as to be displaced in the vehicle width direction together with the rear wheel steering rod 12. When the spool lOa is displaced, for example, to the right from the illustrated neutral position, oil pressure is supplied from the oil pump 14 to the left oil chamber 11a of the hydraulic power cylinder, and the rod 12 is supplied via the piston ub fixed to the rear wheel steering rod 12. is displaced to the right, and accordingly, the valve housing lOb is also displaced to the right, and when the position of the spool lOa with respect to the housing tab returns to the approximately neutral position (strictly speaking, the balance position described below), the hydraulic power cylinder The supply of hydraulic pressure to 11 is stopped, and when the spool loa is further displaced to the right from this state, the rear wheel steering rod 12 is displaced to the right by the amount of displacement of the spool loa in the same manner as described above. Of course, when the spool 10a is displaced to the left, hydraulic pressure is supplied to the oil chamber lie of the hydraulic power cylinder, and the rear wheel steering rod 12 is displaced to the left by the amount of leftward displacement of the spool LOa.

(Problems to be Solved by the Invention) However, in the above conventional steering system, there is a problem in that the hydraulic switching valve 10 portion is large and heavy, which hinders miniaturization and weight reduction of the entire steering system.

That is, in the hydraulic switching valve 10, the valve housing lOb is integrally provided with a connecting portion 10c for fixing the housing 10b to the rear wheel steering rod 12, and this valve housing lOb is connected to the rear wheel steering rod 12. Together with the steering rod 12, the rear wheel steering rod is displaced by the amount of displacement, for example, ±10 from the neutral position shown in the figure to the left and right (vehicle width direction).
Since it is configured to be displaced by about mm, the connecting portion 10c
In addition, it is necessary to secure a space around the housing 10b that allows displacement for the widthwise displacement of the housing 10b, and therefore, this hydraulic switching valve lO increases the size and weight of the entire steering system. There's a problem.

In view of the above-mentioned circumstances, an object of the present invention is to provide a vehicle steering system in which the structure of the hydraulic switching valve-related portion is improved and the entire system can be significantly reduced in size and weight.

(Means for Solving the Problems) In order to achieve the above object, the vehicle steering system according to the present invention includes a displacement transmitting means for transmitting the displacement of the output displacement member of the steering ratio variable means to the valve member of the hydraulic switching valve. A vehicle steering device that displaces a steering rod by using the hydraulic pressure of a hydraulic power cylinder due to displacement of the valve member, wherein the displacement transmitting means transmits only the output displacement member, the valve member, and the steering rod. The valve member is actuated in a direction to displace the valve member in a predetermined direction by the displacement of the output displacement member, and the valve member is moved in the predetermined direction by the displacement of the steering rod caused by the displacement of the valve member. The steering rod is operated in a direction opposite to that of the output displacement member, so that displacement of the output displacement member causes the steering rod to be displaced, but the valve member is hardly displaced.

The vehicle steering device according to the present invention is of a so-called full power type in which the steering rod is displaced only by the hydraulic pressure of the hydraulic power cylinder, and the steering device is of a so-called full power type in which the steering rod is assisted by the hydraulic pressure of the hydraulic power cylinder. This is applicable to both so-called assist type devices in which displacement is caused by In addition, in the case of the above-mentioned assist type, the hydraulic pressure of the hydraulic power cylinder generated by the displacement of the valve member is an assist force for displacing the steering rod, and therefore the steering rod is not displaced only by the displacement of this valve member. , at least the displacement of the steering rod is also due to the hydraulic assist force caused by the displacement of the valve member, and therefore, from this meaning, the above expression "displacement of the steering rod caused by the displacement of the valve member" includes the above-mentioned assist type. It should be understood as meaning.

(Function) In the above configuration, it is assumed that the Kanayama force displacement member is displaced, thereby activating the displacement transmission means, and the valve member is displaced by a predetermined amount in one direction from the neutral position due to the operation of the displacement transmission means. .

In this case, first, the period between the neutral position and the balance position of the valve member is a so-called valve dead zone, and the interval between the two positions is, of course, extremely small. In addition, the balance position means the position where the hydraulic power cylinder generates enough hydraulic pressure to balance the external forces acting on the steering rod, such as the force from the centering spring and tire reaction force when the valve member is in that position.) The steering rod will not be displaced until it is displaced.

Subsequently, when the valve member is displaced in one direction beyond the balance position by the displacement of the output displacement member, the displacement of the valve member causes the hydraulic power cylinder to generate a hydraulic pressure that overcomes the external force acting on the steering rod. occurs,
The steering rod is displaced by the hydraulic pressure. As described above, this displacement of the steering rod operates the displacement transmission means in a direction that displaces the valve member in the opposite direction (other direction), and therefore the steering rod operates the displacement transmission means. via until the valve member is returned to the balance position and then stopped. When the output displacement member is further displaced from this state and the valve member is again displaced in one direction beyond the balance position, the steering rod is thereby displaced via the hydraulic power cylinder, and the displacement of the steering rod causes the above-mentioned displacement. Like (
The valve member is returned to the balance position again, and by repeating this, the steering rod is displaced in accordance with the direction and amount of displacement of the output displacement member, and the wheels are steered.

That is, according to the above configuration, the steering rod is displaced in accordance with the displacement of the output displacement member, but the valve member is only displaced from the neutral position to the balance position with an extremely small ileum, and therefore almost no displacement occurs. It does not displace. In addition,
The above balance position changes depending on the magnitude of the external force. For example, if the displacement of the steering rod becomes large (the centering spring will bend accordingly, the force (external force) exerted by the centering spring will increase, and the balance position will be neutral accordingly) Although it moves in a direction further away from the position, the amount of movement is, of course, extremely small compared to the amount of displacement of the output displacement member.

Therefore, according to the above configuration, the valve housing does not displace at all, and the valve member also displaces only a small amount from the neutral position to the balance position in both directions, so that the connection connecting the valve housing to the steering rod as in the conventional case In addition, there is no need to secure a space for allowing displacement of the hydraulic switching valve, and therefore the steering device can be made smaller and lighter.

Further, although various structures are conceivable as a displacement transmitting means that performs the above-mentioned action, the displacement transmitting means according to the present invention has the minimum required output displacement member and hydraulic pressure to perform the above-mentioned action. It engages only the valve and the steering rod, and is formed by a lever member, which is the simplest form. Therefore, the displacement transmitting means itself can be formed into an extremely simple and compact structure, and from this point of view, it is a steering device. The overall size and weight can be reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic perspective view showing essential parts of an embodiment of a vehicle steering system according to the present invention.

In this embodiment, the present invention is applied to a rear wheel steering device in four-wheel steering as described above, and the steering ratio is as follows.

Variable means 20, hydraulic switching valve 22, rear wheel steering rod 24, displacement transmitting means 26, and hydraulic power cylinder 5
4.

The steering ratio variable means 20 has a configuration similar to that of the conventional example, and the steering (rotation) of the steering wheel is manually operated. That is, the front wheel steering rod is displaced in the vehicle width direction by steering a handle (not shown), the front wheels are steered by the displacement of the rod, and the displacement of the rod is transmitted via the transmission shaft 28 to the rotation of the shaft 28 to change the steering ratio. It is input to the variable means 20.

This steering ratio variable means 20 has an output displacement member 30 that is displaced in response to the input steering of the steering wheel, and the steering ratio, that is, the displacement ff1 of the output displacement member with respect to the steering amount of the steering wheel (in this case, The amount of steering and displacement is not only the absolute amount but also the direction (+).

It is possible to change the ratio of (the amount included as (-)), and specifically, it meshes with the pinion 28a provided at the rear end of the transmission shaft 28 and changes the rotational axis of the pinion 28a. A rotational axis 9 extending in the vehicle width direction perpendicular to 9. ．． 2
The bevel gear 32 has a bevel gear 32 that rotates around the rotation center, and a rod support hole a2a is formed in the bevel gear 32 at a position offset from the rotation center.
A connecting rod 34 is inserted therein so as to be rotatable with respect to the bevel gear 32 and slidable in the axial direction of the rod 34 .

One end 34a of the rod 34 is connected to the output displacement member 30 via a ball joint. The output displacement member 30 is supported by a support member 36 and guided so as to be slidable only in an axis 9J3 direction extending in the vehicle width direction. The other end 34b of the rod 34 is connected to one end of a pendulum arm 38 via a ball joint, and the other end of the pendulum arm 38 is fixed to a swing shaft 40 extending in a direction perpendicular to the arm 38. The lever is configured to be rotatable around the axis of the swing shaft 40. Note that the axis 4 of the swing shaft 40, the rotation axis Q, 2 of the bevel gear 32, and the axis 3 extending in the slidable direction of the output displacement member 30 are all on one straight line extending in the vehicle width direction. It is configured to be located in The swing shaft 40 is fixed to a swing gear 42, and the swing gear 42 has a gear portion 42a that meshes with a worm 46 rotated by a stepping motor 44. It is rotated around a central shaft 42b having an axis 9J6 that coincides with the axis z5.

The steering of the above handle is carried out from the transmission shaft 28 to the pinion 2.
The rotation of the bevel gear 32 causes the output displacement member 30 to undergo a stroke displacement in the vehicle width direction. When the steering amount of the steering wheel is constant, the rotation angle of the bevel gear 32 is also constant, but even in that case, when the swing shaft 40 rotates and tilts around the axis QJ519J6, the stroke of the output displacement member 30 is determined by the tilt angle. The absolute amount and direction of displacement changes. That is,
When the swing shaft 40 is tilted, the ratio of the stroke displacement amount of the output displacement member 30 to the steering amount of the handle, that is, the steering ratio changes. Note that both the steering amount of the steering wheel and the displacement amount of the output displacement member 30 in this case include not only the absolute amount but also the direction thereof as (+) and (-).

This point will be explained in detail with reference to FIG. 2, which is a schematic plan view of the steering ratio variable means.

First, consider a case where the swing wheel 40 extends in the vehicle width direction (left-right direction in the figure) and its axis is located on the same straight line as the rotation axis of the bevel gear 32. At this time, when the bevel gear 32 is rotated, the connecting rod 34, which is positioned overlapping the rotational axis of the bevel gear 32 in FIG. Arm 38 rotates on the base of this cone. Therefore, even if the bevel gear 32 rotates, the one end 34a does not move. That is, at this time, even if the steering wheel is turned, the front wheels are steered, but the rear wheels are not steered. From this state, when the stepping motor 44 is rotated and the swing shaft 40 is tilted counterclockwise by "θ" as shown, the rotating surface of the pendulum arm 38 is also tilted by "θ" with respect to the bottom surface of the cone. For this reason, for example, by rotating the bevel gear 32,
In FIG. 2, if the angle between the connecting rod 34 and the rotational axis of the bevel gear 32 is set to αl, the other end 34b of the connecting rod 34 will move a distance d to the position 34b', and therefore the one end 34a will also move to the position 34b'. It moves to the left by approximately the same distance to the position 34a'. This movement similarly causes the output displacement member 30 to be displaced leftward. Also, the bevel gear 32 rotates in the opposite direction and the connecting rod 34
When the angle between the axis of rotation and the rotational axis of the bevel gear 32 is set to α2, the other end 34b of the connecting rod moves to the position 34b' by a distance mdz, so that one end 34a is moved by a distance mdz.
Move to the right by approximately the same distance to position a'.

The distances fidt and dz change depending on the magnitude of θ even if the steering amount of the steering wheel is the same and therefore the amount of rotation of the bevel gear 32 is the same. Therefore, the steering ratio, which is the ratio of the displacement amount of the output displacement member 3o to the steering amount of the handle, can be changed depending on the magnitude of the inclination θ of the swing shaft 40. Furthermore, the swing shaft 40 can be tilted not only counterclockwise as described above, but also clockwise, and in this case, the direction of movement of the one end 34a of the connecting rod 34 with respect to the rotation of the bevel gear 32 is different from the case described above. It will be the opposite. Thereby, the rear wheels can be steered in the same phase or in the opposite phase with respect to the steering wheel or the front wheels.

The above-mentioned steering ratio can be changed and controlled based on various factors, and various change control patterns can be considered. In this embodiment, based on the vehicle speed, the rear wheels are steered in the opposite phase to the steering wheel and front wheels in the low speed range to improve turning performance, and in the high speed range they are steered in the same phase to improve driving stability. Control is performed in a pattern as shown in FIG. 3 to improve the performance. In this case, the steering wheel steering and the front wheel steering are always in the same phase. This control is performed by storing the above-mentioned steering ratio control pattern in a control circuit (not shown) as explained in the conventional example, and by storing a vehicle speed sensor (
(not shown), and the control circuit rotates the stepping motor 44 by a predetermined amount in a predetermined direction in order to realize a steering ratio determined by the vehicle speed signal and a steering ratio control pattern, and The actual steering ratio set by the rotation of the stepping motor 44 is detected from the rotation angle of the central shaft 42b of the swing gear by a steering ratio detection sensor (not shown), and the detection signal is input to the control circuit. It is configured to perform feedback control.

The hydraulic switching valve 22 includes a valve housing 5° and a spool which is a valve member housed in the housing 50 so as to be displaceable in the direction of an axis 9J7 parallel to the axis z3 of the output displacement member 30 with respect to the housing 50. It consists of 52. The spool 52 is displaced by the output displacement member 3o and the rear wheel steering rod 24 via a displacement transmission means 26, which will be explained in detail below.

Due to this displacement of the spool 52, the hydraulic power cylinder 5
4 is controlled, that is, when the illustrated valve housing 50 is displaced from the neutral position in one direction, for example, to the right, hydraulic pressure is supplied to the right oil chamber 5G, which is one of the hydraulic power cylinders, and in the other direction. When displaced in a certain left direction, hydraulic pressure is supplied to the left oil chamber 58, which is the other side of the hydraulic power cylinder.

The rear wheel steering rod z4 extends in the vehicle width direction parallel to the axis QJ3 of the output displacement member 30, and is displaced in that direction to connect rear wheels (not shown) to both left and right ends via tie rods and knuckle arms (not shown). The displacement is performed by the hydraulic pressure of the hydraulic power cylinder 54. Further, a centering spring 60 is provided on this rear wheel steering rod 24, and a centering spring 60 is provided on the rear wheel steering rod 24.
If the hydraulic system of the hydraulic power cylinder 54 is damaged or malfunctions and the hydraulic pressure in the hydraulic power cylinder 54 disappears, or if the mechanical system of this rear wheel steering device is damaged or malfunctions, the hydraulic system is opened to drain. When the oil pressure in the hydraulic power cylinder 54 disappears, the centering spring 60 positions the rear wheel steering rod 24 at a neutral position, that is, a position where the rear wheels are not steered and are traveling straight, so as to provide a so-called fail-safe. It is configured.

The hydraulic power cylinder 54 displaces the rear wheel steering rod 24 in the vehicle width direction by hydraulic pressure. In this embodiment, a piston 62 is directly fixed to the rear wheel steering rod 24, and a piston 62 is installed on the left and right sides of the piston 62. Left and right oil chambers 58.5B
Seal members θ4 and 6B are provided. This seal member 84 , 86 is fixed to the housing 68 of the hydraulic power cylinder and is slidable with respect to the rear wheel steering rod 24 .

The displacement transmitting means 2B is composed of an output displacement member 30, a spool 52, and a lever member that engages only with the rear wheel steering rod 24, and is actuated in a direction to displace the spool 52 in a predetermined direction by displacement of the output displacement member 3o. The spool 52 is moved in the opposite direction by the displacement of the rear wheel steering rod 24 caused by the displacement of the spool 52.

The displacement transmitting means 2B in this embodiment consists of one vertical lever, as shown in FIG.
A predetermined point between them is engaged with the spool 52. The engagement ends A and B are engaged with the output displacement member 30 and the rear wheel steering rod 24 so that they cannot move in the axial direction, but are movable and rotatable in other directions, and the engagement ends The spool 52 is rotatably but immovably engaged to the spool 52 by a ball joint.

Next, the operating principle of this steering system will be explained with reference to FIGS. 4A to 40.

FIG. 4A is a schematic cross-sectional view showing a state in which the spool 52 and the rear wheel steering rod 24 are both in the neutral position as shown in FIG. 1, and it is assumed that the output displacement member 30 is displaced rightward from this state. Then, the A end of the vertical lever 2B is displaced to the right together with the output displacement member, and when the A end is displaced, tire reaction force and reaction force from the centering spring 60 are acting on the rear wheel steering rod 24, so this B end is displaced. is immovable in the axial direction, and therefore, this vertical lever 26 is tilted with the B end as a fulcrum as shown in FIG. , the spool 52 is displaced to the right by point D.

In the neutral state shown in FIG. 4A, the tank return oil passage gap between the valve housing 50 and the spool 52 is visible on both the left and right oil chambers 58.5B of the power cylinder 54. However, when the spool 52 is displaced from the neutral position to the right in this manner, the tank return oil passage gap on the right oil chamber 56 side narrows, and that on the left oil chamber 58 side widens, so that the right oil chamber 5B increases, the oil pressure in the left oil chamber 58 decreases, and a hydraulic pressure is generated in the hydraulic power cylinder 54 that pushes the rear wheel steering rod 24 to the left. This rear wheel steering rod 24
The hydraulic pressure pushing the spool 52 to the left increases as the displacement of the spool 52 to the right increases.

The spool 52 then moves from the neutral position shown in FIG. 4A to the balanced position shown in FIG. 4B! When the oil chamber 56 side is displaced to the right, the tank return oil passage gap on the oil chamber 56 side narrows to Q, 2-Q, o-Ll, and that on the left oil chamber 58 side widens to 9J3-Lo +it, thereby The generated hydraulic pressure of the hydraulic power cylinder 54 is balanced with the external force (centering spring force, tire reaction force, etc.) acting on the rear wheel steering rod 24.

When the spool 52 is further displaced to the right from the state shown in FIG. 4B, the tank return oil passage gap on the right oil chamber 5B side becomes even narrower than z2, and that on the left oil chamber 58 side becomes smaller than the above. Q, becomes wider than 3, and as a result, the hydraulic pressure generated in the hydraulic power cylinder 54 becomes larger than the external force acting on the rear wheel steering rod 24, and the rear wheel steering rod 24 is displaced to the left by the hydraulic pressure. I am forced to do it.

Then, when this rear wheel steering rod 24 is displaced to the left, the B end of the vertical lever is displaced to the left together with this steering rod 24, and at this time, the output displacement member 30 is affected by the steering force of the steering wheel and the tire reaction of the front wheels. A because a force, etc. is acting on it.
The end is immovable, so this vertical lever 2G is tilted with the A end as a fulcrum as shown in FIG. The spool 52 is pressed by point D.
is displaced to the left, and when the spool 52 returns to the balanced position as shown in FIG. 4C, the displacement of the rear wheel steering rod 24 stops.

From this state, when the output displacement member 30 is further displaced to the right and the spool 52 is displaced to the right, the rear wheel steering rod 24 is displaced to the left in the same manner as above, and when the spool 52 returns to the balance position. By stopping and repeating this operation, the rear wheel steering rod 24 is displaced by an amount corresponding to the amount of displacement of the output displacement member 30, and the rear wheels are steered according to the amount of displacement. Note that the above-mentioned balance position changes depending on the magnitude of the external force as described above. For example, when the rear wheel steering rod 24 is displaced to the left as described above, the centering spring 60 is deflected accordingly, whereby the force by the centering spring (external force) ) becomes larger, so the balance position becomes 4th.
Move to the right from the position shown in Figure B. However, of course, the amount of movement of this balance position is extremely small; for example, in this embodiment, the rear wheel steering rod 24 is displaced from the neutral position to the left and right by about 10 degrees; The balance position at the time it is set is only about ±1 m away from the neutral position shown in FIG. 4A.

When the output displacement member 30 is displaced to the left, the movements of the vertical lever 2B, spool 52, and rear wheel steering rod 24 are simply reversed from the above case, and the operating principle is the same, so the explanation is omitted. do.

As can be understood from the above description of operation, in this steering system, the valve housing 50 of the hydraulic switching valve 22 is immovable, and therefore, the housing 50 is a connecting part for fixing to the rear wheel steering rod 24 as in the conventional case. does not require.

Further, the spool 52 is displaced by the output displacement member 30, and the spool 52 is displaced from the neutral position to the above-mentioned balance position, and as soon as the spool 52 is displaced beyond the balance position, the rear wheel steering rod 2
4 is displaced and returned to the balance position, and this operation is repeated, so the movement of the spool 52 is as much as possible from the neutral position to the balance position in the horizontal direction, for example, from the neutral position to the left and right by about ±1#. No displacement.

Therefore, in the steering system having the above configuration, since the housing 50 of the hydraulic switching valve is immovable, there is no need for a conventional connection part for connecting the housing 50 to the steering rod 24, and the structure is made into a bamboo skewer shape and lightweight. In addition, since the spool can only be displaced from the neutral position to the left and right to the balance position, the displacement is extremely small.
It is not necessary to secure a large displacement permissible space of 1, and it is possible to achieve a regenerative type.

Note that even in a steering system using the hydraulic switching valve and displacement transmission means configured as described above, a predetermined steering state is maintained in response to changes in external force acting on the rear wheel steering rod, as in the case of conventional steering systems. be able to. For example, in a steering state as shown in FIG. 4C (of course, in this steering state, the external force acting on the rear wheel steering rod 24 and the hydraulic pressure generated by the hydraulic power cylinder are balanced),
For example, assume that a new external force F in the right direction in the figure acts on the rear wheel steering rod 24 from the rear wheels, and the rod 24 is displaced to the right. Then, the vertical lever 26 is tilted (actuated) in a direction to displace the D end to the right with the A end as a reference, thereby displacing the spool 52 to the right and increasing the hydraulic pressure in the right bending chamber 5G of the hydraulic power cylinder. As the pressure increases, the oil pressure in the left oil chamber 58 decreases, and as a result, the rear wheel steering rod 24 is returned to its original position. In other words, in response to the displacement of the rear wheel steering rod 24 due to a change in external force, the hydraulic pressure of the hydraulic power cylinder 54 is automatically corrected to displace the rod 24 in the opposite direction, so that the output displacement member 30 and the steering wheel are A predetermined steering condition is automatically maintained without any change.

Furthermore, in order for the displacement transmitting means 2B to perform the above-mentioned action, it is necessary to engage at least the output displacement member 30°, the valve member 52, and the steering rod 24, but it is not limited to these. Furthermore, it may also be engaged with other things. For example, as shown in FIG. 5, the displacement transmitting means 26 is formed by a cross lever consisting of a vertical lever 26a and a horizontal lever 26b, and one end C of the horizontal lever 20b is connected to a case of a steering device fixed to the vehicle body. It is rotatably and immovably engaged and supported by a ball joint, and the other end and both ends A and B of the vertical lever 2Ga are engaged with the valve member 52, the output displacement member 30, and the steering rod 24, respectively. You can also. Furthermore,
The displacement transmitting means 26 is not limited to a lever member, and may have various other structures.

However, the displacement transmitting means 26 according to the present invention consists of the simplest lever member as described above, and engages only the minimum required output displacement member 30, valve member 52, and steering rod 24. Therefore, the displacement transmitting means itself is extremely simple and compact in structure compared to cases where it is made up of something other than the lever member or when it is engaged with something other than the output displacement member, valve member, and steering rod. This also facilitates the assembly of the displacement transmitting means.

The displacement transmitting means shown in FIG. 5 is supported by a ball joint on the case of the steering device at the C end, but the displacement transmitting means 2B according to the present invention includes the output displacement member 30, the valve member 52, and the steering rod 24. These 3 parts are not supported by the case.
It is necessary to take measures to prevent withdrawal from 0.52.24. For example, in the embodiment shown in FIG. 1, this separation is prevented by engaging the 0 point with the valve member 52 in the form of a ball joint, but other methods, such as the output displacement member 30 or the steering rod 24 This may be done by engaging them in a ball joint type, or by engaging both of them in a ball joint type and forming the vertical lever 26 itself as a telescopic type so that it is telescopic. good.

Next, a more specific example will be described with reference to FIGS. 6 and 7. Figure 6 is a cross-sectional view, Figure 7 is the ■ of Figure 6.
It is a sectional view taken along the line -■.

Since the basic configuration of this embodiment is the same as that of the embodiment shown in FIG. 1, similar components are given the same numbers and detailed explanations will be omitted.

In this embodiment, as shown in the figure, a case 70 of the rear wheel steering system is provided, and this case 70 is fixed to the vehicle body (not shown). A valve 22, a rear wheel steering rod 24, a displacement transmission means 26 and a hydraulic power cylinder 54 are incorporated. The hydraulic switching valve 22 is formed by forming a hole in the case 70 and disposing the spool 52 therein, and therefore, the valve housing 50 is formed by the case f 0 itself. Further, the rear wheel steering rod z4 is also disposed in a hole formed in the case 70, and the cylinder housing 68 of the hydraulic power cylinder 54 is also formed by the case 70 itself.

The spool 52 is moved, for example, by ±1 from the neutral position as described above.
Only a very small displacement of the melon up to the balance position of about mm is possible, so the hydraulic switching valve 22
The spool 52 is configured to be able to move only a very small amount from the neutral position to the balance position, and by such a configuration, the hydraulic switching valve 22 portion can be made smaller.

It is desirable that the hydraulic switching valve and the hydraulic power cylinder are arranged as close as possible, preferably facing each other. This is because the device can be made smaller and the oil passage connecting the two can be easily formed.

In this embodiment, as described above, the valve housing 50 of the hydraulic switching valve 22 is immovable, so the housing 50 can be formed by the case 70 itself, and the hydraulic switching valve 22 can be positioned opposite the hydraulic power cylinder 54. can be placed. Therefore, as shown in FIG. 6, the hydraulic switching valve 22 and the hydraulic power cylinder 54 are arranged facing each other, and their housings 50.
8 formed by the case 70 itself, and both 22.5
The oil passages connecting the oil passages 4 and 4 are also formed directly in the case 70, thereby reducing the size of the device and making the oil passages more compact.

The vertical lever 26, which is the displacement transmitting means, is set so that AD<DB as shown in FIG. By making the long surface of the lever larger than the lever length (2), the stroke displacement of the rear wheel steering rod 24 can be made larger than the stroke displacement of the output displacement member 30.

That is, as shown in FIG. 8, which conceptually and exaggerates the operation of the vertical lever 26, from the state where the vertical lever 26 is in the balance position shown by the solid line, the output displacement member moves the A end to A'.
When the vertical lever 26 is displaced to the right by a distance S1 to the position D, the vertical lever 26 is in the state shown by the two-dot chain line, and the point D is displaced to the right by a distance S2 to the D' position, and the spool is also displaced by a distance S1 to the right. is displaced to the right. Then, the rear wheel steering rod moves this spool to the balance position (this balance position and the above first balance position are not strictly the same as mentioned above, but the difference between the two positions is due to the output displacement member and rear wheel steering discussed here). Since the amount of displacement of the rod is sufficiently small compared to the amount of displacement of the rod, both positions are shown as being the same in Figure 8. ' is displaced by a distance S3.

In this case, Sl: S3-AD: DB,
Therefore, by making DB larger than AD, a larger S3 can be obtained with a smaller Sl.

In this way, by adopting a configuration in which the stroke displacement of the rear wheel steering rod 24 is made larger than the stroke displacement of the output displacement member 30, the output displacement member 30 necessary to obtain a predetermined stroke displacement of the rear wheel steering rod 24 is adopted. If this is the case, the output displacement amount of the variable steering ratio means 20 may be small, so that the variable steering ratio means 20 can be miniaturized, for example, the variable steering ratio means of the type shown in the drawing. In this case, advantages such as being able to reduce the diameter of the bevel gear 32 can be obtained.

Further, in the embodiment shown in FIG. 6, the output displacement member 30 is provided with a transmission displacement absorption mechanism.

FIG. 9 is a sectional view of an output displacement member 30 including an example of a transmission displacement absorption mechanism. This output displacement member 30 is a transmission displacement absorption mechanism itself, and includes a shaft member 74 and a cylindrical member 7B that are supported so as to be displaceable in the axial direction by a support member 3G that is integrated with the case 70, and the shaft member 74 is a ball joint. connected to the connecting rod 34 via the int and fitted into the cylindrical member 7B so as to be displaceable in the axial direction;
The cylindrical member 7B includes a first cylindrical portion 78b having an engaging portion 76a that engages with the A end of the displacement transmitting means 2B, and the first cylindrical portion 7B.
6b and the second cylinder portion 78c and lock nut 78d
It consists of. Further, a large diameter hole 78e is formed inside the cylindrical member 78, and the shaft member 74 has spring seats 74a, 74 whose movement in the axial direction outward is restricted by a step and a retainer.
b and a spring 74c disposed between both spring seats 74a and 74b.
As shown in the figure, both spring seats 74a and 74b are pushed outward in the axial direction by a spring 74c, and abut against the stepped portion of the shaft member 74 and the retainer, as well as the large diameter hole 7 of the cylindrical member.
It is brought into contact with the step portions at both axial ends of 6e.

Therefore, when an axial displacement is transmitted to the shaft member 74 by the connecting rod 34, the shaft member 74 normally moves to the spring seat 7.
4a, 74b, large diameter hole 76e of spring 74c1 cylindrical member
is transmitted to the cylindrical member 76 via the stepped portion of the cylindrical member 76.
From there, it is transmitted to the A end of the displacement transmitting means 26 that is engaged with the engaging portion 70a. However, if the movement of the A end of the displacement transmitting means 26 is restricted and a load greater than the spring force of the spring 74c set to a predetermined value is applied to the cylindrical member 76 when the shaft member 74 is displaced, The displacement of the member 74 is absorbed by the contraction of the spring 74c and is not transmitted to the cylindrical member 7B.

In the steering system of this embodiment, as described above, the centering spring 60 is provided for fail-safe purposes, and in the event of a failure, the hydraulic pressure of the hydraulic power cylinder is removed and the centering spring 80 applies a force of several hundred parts to the rear wheel steering rod. 24 to a neutral position, and in the hydraulic switching valve 22, the spool 52 is configured so that it cannot move within ±1 mm from the neutral position. are connected by a mechanical steering transmission system. Therefore, in the event of a failure, the spool 5 is
2 is displaced, but the rear wheel steering rod 24 is not displaced. Therefore, the spool 52 is not returned to the balance position by the rear wheel steering rod 24, and as a result, the spool 52 can be displaced by an amount of about ±1 mm by further steering the handle. This causes problems such as damage to the mechanical steering transmission system such as the variable steering ratio means 20 and the displacement transmission means 26 or the hydraulic switching valve 22 due to overload.

In order to solve this problem, the transmission displacement absorption mechanism absorbs the displacement to be transmitted when an overload of a predetermined value or more occurs in the steering transmission system up to the hydraulic switching valve 22, and thereby Alternatively, this is to prevent damage to the hydraulic switching valve.

Further, in the embodiment shown in FIG. 6, as shown in FIG. 7, a long groove 78 extending in the axial direction is formed in the rear wheel steering rod 24, and a screw threaded into the long groove 78 is screwed into the case 7°. 80 is fitted, thereby allowing displacement of the rear wheel steering rod 24 in the axial direction and preventing rotation about the axis. Further, the output displacement member 30 is also configured to plane-slide with the inner surface of the case 70, allowing displacement in the axial direction and preventing rotation about the axis.

Further, in the embodiment shown in FIG. 6, the A and B ends of the vertical lever 2B, which is the displacement transmitting means, are formed into spherical shapes.
The spherical ends A and B are fixed to the output displacement member 30 and the rear wheel steering rod 24 by fitting into holes perpendicular to the axis formed therein so as to be immovable in the axial direction. It is movably and rotatably engaged in the direction in which the hole extends, and point D is rotatably and immovably engaged with the spool 52 by a ball joint.

In addition to the above-mentioned engagement mode, the vertical lever 26 can be configured such that, for example, the A and B ends are ball joints similar to the D end so that the output displacement member 30 and the rear wheel steering rod 24 can only rotate.
In addition, the vertical lever 26 itself may be configured to be telescopic, for example, so as to be telescopic.

Further, as shown in FIG. 10, two collars 82 (both members 30
．． 24 (only one collar is shown in the figure) is fixed, and the spherical A and B ends of the vertical lever 2B are engaged between the two collars 82 so that both sides thereof are in contact with the two collars 82, respectively. You can also match them. This engagement mode is the same as that shown in FIGS. 1 and 4 described above.

In addition, as shown in FIG. 11 and FIG. 12 when viewed from the arrow X-- force direction in FIG. A sliding contact piece 84 is provided between the two flanges 82 and the two flanges 82 and both sides thereof are in contact with each other and slide on a plane, and the spherical ends A and B are engaged with the sliding contact piece 84 in a ball joint type. It's okay.

In addition to the above-mentioned lever, the displacement transmitting means 26 also includes a first
It may also be a vertical lever as shown in Figure 3. This vertical lever 26 has one end engaged with the spool 52 of the hydraulic switching valve, the other end B engaged with the rear wheel steering rod 24, and the output displacement member 30 engaged with a point A between the two. It is something. The manner of engagement of the above-mentioned engagement ends or engagement points A, B, and D is the same as in the case of FIG. 11.12.

In this embodiment, as shown in FIG. 14, when point A is displaced to the right by the output displacement member to A', the D end or spool is thereby displaced to the right to position D'. As a result, the B end, ie, the rear wheel steering rod, is displaced to the right to the B' position, and the D end, ie, the spool, is returned to the balance position.

In this embodiment, as can be seen from FIG.
8, the displacement amount S3 of the rear wheel steering rod 24 corresponding to the displacement amount 81 of the output displacement member 30 is always larger than the displacement amount 81 of the output displacement member 30. Therefore, as described above, the steering ratio variable means can be downsized. It becomes possible.

Further, in this embodiment, as can be seen from FIG. 14, the displacement amount S2 of the spool is larger than the displacement amount S of the output displacement member. Generally, a hydraulic switching valve has a dead zone (between the neutral position and the balance position) in which the valve does not operate even if there is a relative displacement between the valve member and the housing. Therefore, in this device as well, even if the output displacement member 30 is displaced, the rear wheel steering rod 24 is not immediately displaced, and there is an operation delay in which the rear wheel steering rod 24 starts to be displaced after the output displacement member 30 has been displaced to some extent.

However, by setting <sl<s2 as described above, the displacement speed of the spool 52 becomes faster than when the displacement of the output displacement member 30 is directly transmitted to the spool 52, and the time to clear the dead zone is correspondingly shortened. Delays can be reduced.

In each of the above embodiments, the spool 52 is returned to the balance position by reversing the displacement direction of the rear wheel steering rod 24 with respect to the output displacement member 30, but in this embodiment, the output displacement By displacing the rear wheel steering rod 24 in the same direction relative to the member 30, the spool 5
2 can be returned to the neutral position.

FIG. 15 is a schematic perspective view showing another embodiment of the displacement transmitting means. While the embodiment shown in FIG. 1 consists of only one vertical lever, this displacement transmitting means 2e has a vertical lever 28a.
and a horizontal lever 28b, one end of which is fixed between the A end and the B end of the vertical lever 26a, and a spool 52 is engaged with the other end of the horizontal lever 2Bb. The prevention of disengagement of the displacement transmitting means 26 is the same as in the example shown in FIG. 1 above, but in the case of this embodiment, the spool 52 is also It is necessary to take appropriate measures, such as providing a means to prevent the vertical lever 26a from rotating in the direction of arrow G, so that the vertical lever 26a is displaced correctly.

The vehicle steering system according to the present invention can be modified in various ways without departing from the gist thereof.

For example, although the above embodiment applies the present invention to a rear wheel steering device of a four-wheel steering vehicle, it may also be applied to a rear wheel steering device that steers the rear wheels independently of the front wheels, or a rear wheel steering device that steers the rear wheels independently of the front wheels. It can also be applied to a front wheel steering device that steers a vehicle.

In addition, the displacement transmitting means is basically composed of an output displacement member, a valve member of the hydraulic switching valve, and a lever member that engages only with the steering rod as described above, and the displacement of the output displacement member displaces the valve member in a predetermined direction. and the valve member is operated in a direction opposite to the above direction by the displacement of the steering rod caused by the displacement of the valve member, so that the steering rod is displaced by the displacement of the output displacement member. The above-mentioned valve member may be of any type as long as it is configured so that it is hardly displaced.

Further, the steering ratio variable means may be any type as long as it can change the displacement amount, displacement direction, and displacement amount of the output displacement member with respect to the steering amount of the steering wheel.

(Effects of the Invention) As explained above, the vehicle steering system according to the present invention includes a displacement transmitting means that engages with the output displacement member of the steering ratio variable means, the valve member of the hydraulic pressure switching valve, and the steering rod, The displacement transmitting means is actuated in a direction to displace/displace the valve member in a predetermined direction by the displacement of the output displacement member, and also displaces the valve member in the opposite direction by the displacement of the steering rod caused by the displacement of the valve member. The valve member is operated in a direction in which the output displacement member displaces the steering rod, but the valve member is hardly displaced.

Therefore, in the present invention, the housing of the hydraulic switching valve does not displace at all, and the valve member also displaces only a small amount from the neutral position to the balance position in both directions.
There is no need for a connecting part that connects the valve housing to the steering rod as in the past, making it possible to make the hydraulic switching valve lighter and more compact.In addition, the hydraulic switching valve housing and spool can have a large displacement space. There is no need to secure the valve, and the area around the hydraulic switching valve can be made smaller, thereby making it possible to significantly reduce the size and weight of the steering device.

In addition, the displacement transmitting means in the present invention is formed by engaging only the output displacement member, the valve member, and the steering rod that must be engaged with the minimum in order to perform the function, and is a lever member in the simplest form. Therefore, the displacement transmitting means itself can be made extremely simple and compact in structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing essential parts of an embodiment of a vehicle steering system according to the present invention; FIG. 2 is a diagram showing the operating principle of the variable steering ratio means of the embodiment shown in FIG. 1; The figure is a diagram showing an example of a steering ratio control pattern, No. 4A.
- Figure 4C shows the displacement transmitting means in the embodiment shown in Figure 1;
FIG. 5 is a perspective view showing a comparative example to explain the present invention in detail; FIG. 6 is a main part of another embodiment. FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6, FIG. 8 is a diagram showing the movement of the displacement transmitting means of the embodiment shown in FIG. 6, and FIG. FIG. 10 is a sectional view similar to FIG. 7 showing another embodiment; FIG. 11 is FIG. 7 showing another embodiment. 12 is a view of the main part of the embodiment shown in FIG. 11 as seen from the direction of arrow X and force; FIG. 13 is a sectional view similar to FIG. 14 is a diagram showing the movement of the displacement transmitting means of the embodiment shown in FIG. 13, FIG. 15 is a schematic perspective view similar to FIG. 1 showing the main parts of another embodiment, and FIG. FIG. 1 is a schematic partial cross-sectional view showing an example of a steering device for a vehicle. 20... Steering ratio variable means 22... Hydraulic switching valve 24... Steering rod 26... Displacement transmitting means 30... Output displacement member 50 of the steering ratio variable means... Housing 52 of the hydraulic switching valve ... Valve member 54 of the hydraulic switching valve ... Hydraulic power cylinder 68 - ... /% Uzing 70 of the hydraulic power cylinder...
・Steering device case Fig. 3 Fig. 5 Fig. 10 Fig. 11 Fig. 1'1 prong 1 Fig. 13

Claims (1)

[Scope of Claims] A steering rod that steers wheels by being displaced; a hydraulic power cylinder that displaces the steering rod by hydraulic pressure; a valve housing; and a valve housing disposed within the valve housing so as to be displaceable with respect to the valve housing. displacement of the valve member relative to the valve housing from a neutral position in one direction supplies hydraulic pressure to one of the hydraulic power cylinders, and displacement in the other direction supplies hydraulic pressure to the other hydraulic power cylinder. a hydraulic switching valve that operates to supply a hydraulic pressure, and an output displacement member that is displaced in response to the steering of a steering wheel, and is capable of changing the ratio of the displacement amount of the output displacement member to the steering amount of the steering wheel. and a lever member that engages only with the output displacement member of the steering ratio variable means, the valve member of the hydraulic switching valve, and the steering rod, and a direction in which the valve member is displaced in a predetermined direction by displacement of the output displacement member. and the valve member is operated in a direction opposite to the above direction due to the displacement of the steering rod caused by the displacement of the valve member, so that the steering rod is displaced by the displacement of the output displacement member. 2. A steering system for a vehicle, comprising: a displacement transmitting means configured to cause the valve member to move, but hardly displace the valve member.