JPH01223078A - Steering device for vehicle - Google Patents

Abstract

PURPOSE:To reduce the operation delay of a steering rod by providing a displacement transmitting means expanding the displacement of the output displacement member of a steering ratio variable means and transmitting it to the valve member of a hydraulic transfer valve. 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 motor 44. A hydraulic transfer valve 22 controlling the feeding and discharging of the oil pressure to a power cylinder 54 displacing a steering rod 24 is provided. The output displacement member 30, the valve member 22 of the hydraulic valve 22 and the steering rod 24 are connected by a displacement transmitting means 26. This displacement transmitting means 26 is formed in a cross lever structure, it expands the displacement of the output displacement member 30 and transmits it to the valve member 52.

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 the above-mentioned steering ratio variable means 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. 82-37283 discloses A rear wheel steering device for four-wheel steering as described in the 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 steering ratio variable means 5 has an output displacement section 5a, and the output displacement section 5a is stroke-displaced in the vehicle width direction in response to the input steering amount of the steering wheel 1. The ratio of the amount of displacement of the portion 5a (as 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 is also referred to as the steering ratio) is the ratio of the amount of displacement of the stepping motor 6. It is configured to change depending on the amount of rotation. 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 amount of steering of the handle 1, the amount of displacement of the output displacement portion 5a, and the amount of rotation of the stepping motor 6 are not only the absolute amounts of steering, displacement, and rotation, but also their directions (
+) and (-).

The displacement of the output displacement section 5a in the steering ratio variable means 5 is determined by the displacement transmission means 1 integrally formed with the output displacement section 5a.
6 to the spool loa, which is the valve member of the hydraulic switching valve IO, and the hydraulic switching valve IO
By the displacement of this spool 10a, appropriate oil pressure is supplied to the hydraulic power cylinder 11, and the rear wheel steering rod 12 is moved to the output displacement portion 5a by the hydraulic pressure of the hydraulic power cylinder U.
It is configured to steer the rear wheels 13 by displacing them in the vehicle width direction by an amount corresponding to the amount of displacement.

That is, in the hydraulic switching valve IO, the spool lOa is accommodated in the valve housing 10b so as to be displaceable in the vehicle width direction, and the valve housing 10b is connected to the rear wheel steering rod 12 at the connecting portion 10c so as to be displaced in the vehicle width direction. When the spool 10a is displaced, for example, to the right from the illustrated neutral position, hydraulic pressure is supplied from the oil pump 14 to the left oil chamber 11a of the hydraulic power cylinder, and the piston ub fixed to the rear wheel steering rod 12 is fixed to the rear wheel steering rod 12. , the rod 12 is displaced to the right, and accordingly the valve housing lOb is also displaced to the right, and the position of the spool 10a with respect to the housing 10b is approximately the neutral position (more precisely, the balance position rIl described below). ), the supply of hydraulic pressure to the hydraulic power cylinder 11 is stopped, and if the spool 10a is further displaced to the right from that state, the rear wheel steering rod 12 is moved to the right by the amount of displacement of the spool 10a in the same manner as above. It is forced to move in the opposite direction. Of course, when the spool loa is displaced to the left, hydraulic pressure is supplied to the oil chamber 11c of the hydraulic power cylinder, and the spool loa
The rear wheel steering rod 12 is displaced leftward by a leftward displacement amount of .

(Problems to be Solved by the Invention) However, in the conventional steering system described above, there is a problem in that the operation of the rear wheel steering rod 12 is delayed due to the dead zone of the hydraulic switching valve 10.

In other words, hydraulic switching valves generally have a dead zone (from the neutral position to the balance position described below) in which the valve does not operate even if there is relative displacement between the valve member and the housing.
Therefore, even if the output displacement portion 5a is displaced, the rear wheel steering rod 12 is not immediately displaced, and an operation delay occurs in which the rear wheel steering rod 12 starts to be displaced after the output displacement portion 5a has been displaced to some extent.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a vehicle steering system that can reduce the delay in operation of a steering rod caused by the dead zone of the hydraulic switching valve.

(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 portion of the steering ratio variable means to the valve member of the hydraulic switching valve. is configured to magnify the displacement of the output displacement section and transmit it to the valve member.

(Function) According to the above configuration, the amount of displacement of the valve member is larger than the amount of displacement of the output displacement portion, and therefore, the displacement speed of the valve member is such that the displacement of the output displacement portion is directly transferred to the valve member as in the conventional example. This is faster than when the signal is transmitted, and the time required to clear the dead zone is correspondingly shortened, reducing delay in operation.

(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, and the rear wheel steering device is a hydraulic switching valve related part of the conventional rear wheel steering device in order to reduce the size and weight of the device. This type is an improved version of .

This rear wheel steering device includes a steering ratio variable means 20, a hydraulic switching valve 22, a rear wheel steering rod 24, and a displacement transmitting means 2.
B, and a hydraulic power cylinder 54.

Steering (rotation) of the steering wheel is inputted to the steering ratio variable means 20 using a configuration similar to that of the conventional example. That is, by steering a handle (not shown), the front wheel steering rod is displaced in the vehicle width direction, and 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. This is inputted to the steering ratio variable means 20 as a result.

This steering ratio variable means 20 has an output displacement section 30 that is displaced in response to the input steering of the steering wheel, and the steering ratio, that is, the amount of displacement of the output displacement section with respect to the steering amount of the steering wheel (in this case, Not only the absolute amount but also the direction of the steering amount and displacement amount (+) and (-> are included) can be changed. The bevel gear 32 meshes with the provided pinion 28a and rotates around a rotation axis 9.z extending in the vehicle width direction orthogonal to the rotation axis 1 of the pinion 28a. A rod support hole 32a is formed at a position offset from the
A connecting rod 34 is inserted into the rod support hole 32a so as to be rotatable relative 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 section 30 via a ball joint. Output displacement part 3
0 is supported by a support member 3B and guided so as to be slidable only in three axial directions 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. Axis line QJa of the swing shaft 40 of the lever
It is configured to be rotatable around the center. Note that the axis 1 of the swing shaft 40, the rotation axis 2 of the bevel gear 32, and the axis 9 extending in the slidable direction of the output displacement section 30
．． 3 are all located on a single straight line extending in the vehicle width direction. The swing shaft 40 is a swing gear 42
The swing gear 42 has a gear portion 42a that meshes with a worm 4B rotated by a stepping motor 44, and has an axis 9Js that coincides with the axes Q and 5 of the pendulum arm 38 due to the rotation of the worm 46. It is rotated around the central axis 42b.

The steering of the above-mentioned handle is carried out from the transmission shaft 28 to the pinion 2.
The rotation of the bevel gear 32 causes the output displacement portion 30 to undergo a stroke displacement in the vehicle width direction. When the amount of steering of the steering wheel is constant, the rotation angle of the bevel gear 32 is also constant, but even in that case, the swing shaft 40 becomes an axis.

When the output displacement section 30 rotates and tilts around , the absolute amount and direction of the stroke displacement of the output displacement section 30 change depending on the tilt angle. That is, when the swing shaft 40 is tilted, the ratio of the stroke displacement amount of the output displacement section 30 to the steering amount of the steering wheel, that is, the steering ratio changes. In this case, both the steering amount of the steering wheel and the displacement amount of the output displacement section 30 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 the case where the swing shaft 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 located overlapping the rotational axis of the bevel gear 32 in FIG. The pendulum 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 in the figure, the rotating surface of the pendulum arm 38 is also tilted by "θ2" with respect to the bottom surface of the cone. Therefore, 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 be α1, the other end 34b of the connecting rod 34 will move to the position 34b' by a distance d, 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 section 30 to be displaced leftward. Also,
When the bevel gear 32 rotates in the opposite direction so that the angle between the connecting rod 34 and the rotation axis of the bevel gear 32 becomes α2, the other end 34b of the connecting rod moves to the position 34b'' by a distance d2, and thus One end 34a also moves to the right by approximately the same distance to the position 34a'.
The distance d1+d2 is the same 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.
It changes depending on the size of θ. Therefore, the steering ratio, which is the ratio of the displacement amount of the output displacement section 30 to the steering amount of the steering wheel, 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.
At this time, the connecting rod 3 for the rotation of the bevel gear 32
The moving direction of one end 34a of 4 is opposite to that in the above case. 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, in low speed ranges, the rear wheels are steered in the opposite phase to the steering wheel and front wheels to improve maneuverability, and in high speed ranges, they are steered in the same phase to improve driving stability. Control is performed in a pattern as shown in FIG. 3 in order 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 stepping motor 44 is rotated by a predetermined amount in a predetermined direction by a control circuit 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 50 and a spool 52 which is a valve member housed in the housing 50 so as to be displaceable in an axis 9J7 direction parallel to the axis 3 of the output displacement section 30 with respect to the housing 50. It consists of The spool 52 is connected to the output displacement section 30 and the rear wheel steering rod 24 via a displacement transmission means 26, which will be described in detail below.
Displaced by The supply of hydraulic pressure to the hydraulic power cylinder 54 is controlled by this displacement of the spool 52. In other words, when the spool 52 is displaced from the neutral position relative to the illustrated housing 50 in one direction, for example, in the right direction, it is transferred to the right oil chamber 56, which is one of the hydraulic power cylinders. When hydraulic pressure is supplied and the cylinder is displaced in the other direction, that is, to the left, 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 24 extends in the vehicle width direction parallel to the axis 3 of the output displacement section 30, is displaced in that direction, and is connected to both left and right ends via tie rods and knuckle arms (not shown). The wheels are steered, and the above displacement is performed by the hydraulic pressure of the hydraulic power cylinder 54. In addition, this rear wheel steering rod 24 is provided with a centering spring BO, and if the hydraulic system of the hydraulic switching valve 22 or the hydraulic power cylinder 54 is damaged or malfunctions and the hydraulic pressure in the hydraulic power cylinder 54 is lost, If the mechanical system of the rear wheel steering device is damaged or malfunctions, the hydraulic system is opened to drain and the hydraulic power cylinder 5
When the hydraulic pressure at 4 is eliminated, this centering spring 6o 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. .

The hydraulic power cylinder 54 displaces the rear wheel steering rod 24 in the vehicle width direction using hydraulic power. 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 58.5G
A sealing member 64.6G is provided to form a seal member 64.6G. This seal member [i4. (i6 is fixed to the housing 68 of the hydraulic power cylinder and is slidable on the rear wheel steering rod 24.

The displacement transmission means 26 includes an output displacement section 30 and a spool 5.
2 and the rear wheel steering rod 24, and the output displacement portion 3
A displacement of 0 causes the spool 52 to be operated in a predetermined direction, and a displacement of the rear wheel steering rod 24 caused by the displacement of the spool 52 causes the spool 52 to be displaced in the opposite direction. When activated, the steering rod 24 is displaced by the displacement of the output displacement section 30, but the valve member 52 is configured so as to be hardly displaced. Further, the displacement transmission means 26 includes an output displacement section 30
In order to transmit the displacement of the output displacement section 30 to the spool 52, the displacement of the output displacement section 30 can be magnified and transmitted to the spool 52.
It has a transmission displacement amplifying mechanism.

The displacement transmitting means 26 in this embodiment consists of a cross lever consisting of a vertical lever and a horizontal lever, as shown in FIG.
One end A of the vertical lever is attached to the output displacement part 30, the other end B is attached to the rear wheel steering rod 24, one end C of the horizontal lever is attached to the case of the rear wheel steering device fixed to the vehicle body, and the other end is attached to the spool 52. is engaged with. The engaging ends A, B, and D engage with the output displacement portion 30, the rear wheel steering rod 24, and the spool 52, respectively, so that they cannot move in the axial direction but are movable and rotatable in other directions. The engaging end C is engaged by a ball joint so that it can rotate but cannot move.

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 portion 30 is displaced rightward from this state. Then, the A end of the cross lever 26 is displaced to the right together with the output displacement part, and since tire reaction force and reaction force from the centering spring 60 are acting on the rear wheel steering rod 24 when the A end is displaced, this B end is axially stationary;
In addition, since the C end is also attached to the case and is immovable, the cross lever 2B is tilted as shown in FIG. 4B about the straight line connecting the C end and the B end. The spool 52 is actuated in a certain direction to the right, and the D end displaces the spool 52 to the right.゛In the neutral state shown in FIG. 4A above, the valve housing 50 and the spool 52
The tank return oil passage gap between the left and right oil chambers 58.5 of the power cylinder 54 [I side was 0 for both sides, but when the spool 52 is displaced from the middle position to the right in this way, the right oil chamber 56 The tank return oil passage gap on the side becomes narrower and that on the left oil chamber 58 side becomes wider, so the oil pressure in the right oil chamber 56 increases, the oil pressure in the left oil chamber 58 decreases, and the oil pressure in the hydraulic power cylinder 54 increases. Hydraulic pressure is generated that pushes the wheel steering rod 24 to the left. The hydraulic pressure that pushes the rear wheel steering rod 24 leftward increases as the rightward displacement of the spool 52 increases.

The spool 52 moves from the neutral position shown in FIG. 4A to the balanced position shown in FIG. 4B (balance position means that when the spool 52 is in that position, the centering spring
This refers to the position where the hydraulic per cylinder 54 generates a hydraulic pressure sufficient to balance the external force acting on the rear wheel steering rod 24 such as the force caused by the rear wheel steering rod 24 and the tire reaction force. The period from the neutral position to the balance position is a so-called valve dead zone, and the rear wheel steering rod 24 is not displaced by displacement of the spool 52 within this dead zone. Of course, the range of this dead zone is extremely small), and when it is displaced 52.1 to the right, the tank return oil passage gap on the right oil chamber 56 side narrows to Q, z-9, o-min 1. , that on the left oil chamber 58 side widens to QJ3 = lo "Qrt, and the resulting 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. and balance it out.

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 56 side becomes even narrower than the 9Jz, and that on the left oil chamber 58 side becomes narrower than the above 9Jz. 9. ．． 3, so that the hydraulic pressure generated in the hydraulic power cylinder 54 is greater 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. .

Then, when this rear wheel steering rod 24 is displaced to the left, the B end of the cross lever is displaced to the left together with this steering rod 24, and at that time, the output displacement portion 80 is used to control the steering force of the steering wheel and the tire reaction of the front wheels. A because a force, etc. is acting on it.
Since the end is immovable and the C end is also immovable, this cross lever 2B moves to the 4th C end with the straight line connecting the A end and C end as the center.
As shown in the figure, the Dobe lever 26 is tilted to the spool 5.
2 to the left, which is the opposite direction to the above, and the D end displaces the spool 52 to the left. When the spool 52 returns to the balance position as shown in FIG. 4C, the rear wheel The displacement of the steering rod 24 stops.

From this state, when the output displacement part 3o 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 section 30, and the rear wheels are steered according to the amount of displacement. The balance position described above changes depending on the magnitude of the external force. For example, when the rear wheel steering rod 24 is displaced to the left as described above, the centering spring 60 is deflected accordingly.
As a result, the force (external force) exerted by the centering spring increases, and the balance position moves to the right from the position shown in FIG. 4B. 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 moved from the neutral position to the left and right as much as possible.
The balance position at the time of maximum displacement is only about ±1al11 from the neutral position shown in FIG. 4A.

When the output displacement section 30 is displaced to the left, the movements of the cross lever 26, spool 52, and rear wheel steering rod 24 are simply reversed from the above case, and the operating principle is the same, so a description will be omitted. do.

By the way, the cross lever 281 which is the displacement transmission means mentioned above!
It has a transmission displacement amplifying mechanism consisting of a horizontal lever 28b. That is, the cross lever 2B is supported at one end C in a non-displaceable but rotatable manner by a ball joint in the case, and is connected to the vertical lever 26a at a point E in the middle, and the other end is connected to the spool. and a transmission displacement amplifying mechanism consisting of a horizontal lever 26b set so as to be 100 B CD AB CE , and by this mechanism, the output displacement S of the steering ratio variable means 20 is increased as shown in FIG. and is transmitted to the spool 52, that is, the displacement S2 of the spool 52 is S2>
It is configured to be sl.

Generally, hydraulic switching valves have a dead zone (dead zone) in which the valve does not operate even if there is relative displacement between the valve member and the housing.
from the neutral position to the balance position).

Therefore, in this device as well, even if the output displacement section 30 is displaced, the rear wheel steering rod 24 is not immediately displaced, and the output displacement section 30 is not displaced immediately.
An operation delay occurs in which the rear wheel steering rod 24, which has been displaced to some extent, starts to be displaced.

This delay in operation can be reduced by the transmission displacement amplifying mechanism as described above. That is, due to the transmission displacement amplifying mechanism as described above, the displacement speed of the spool 52 becomes faster than when the displacement of the output displacement section 30 is directly transmitted to the spool, and the scream when clearing the dead zone is correspondingly shortened, reducing the delay in operation. can do.

In addition, in the conventional steering device shown in FIG. 16,
There is a problem in that the hydraulic switching valve portion is large and heavy, which hinders miniaturization and weight reduction of the entire steering system.

That is, in the conventional hydraulic switching valve, the valve housing is integrally provided with a connecting portion for fixing the housing to the rear wheel steering rod, and this valve housing is integrally formed with the rear wheel steering rod. For example, from the neutral position shown in the figure to the left or right (
Since the housing is configured to be displaced by about ±low in the vehicle width direction, it is large and heavy due to the connection part, and it is necessary to secure a space around the housing to allow displacement for the widthwise displacement of the housing. Therefore, there is a problem in that this hydraulic switching valve increases the size and weight of the entire steering system.

However, as understood from the above operation description, in the steering system according to the present embodiment, the valve housing 50 of the hydraulic switching valve 22 is immovable, and therefore the housing 50
This does not require a connecting part or the like for fixing to the rear wheel steering rod 24 as in the conventional case. Further, the spool 52 is displaced by the output displacement section 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 24 is displaced. It is returned to the balance position and this operation is repeated, so eventually the spool 5
The movement of No. 2 is as far as possible from the neutral position to the above-mentioned balance position in the left-right direction, for example, by only about ±1 margin left and right from the neutral position.

Therefore, in the steering system having the above configuration, there is no need for a conventional connecting part that connects the housing 50 of the hydraulic switching valve to the steering rod 24, and the spool can be moved from the maximum neutral position to the balance position left and right with a very small amount of movement. Since the displacement is only by the amount, for example ±l0JII from the neutral position as in the conventional
There is no need to secure a large displacement permissible space such as II+, and therefore the device can be made smaller and lighter.

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 cross lever 2B tilts (operates) 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 oil pressure in the right oil chamber 56 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. That is, 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. A predetermined steering condition is automatically maintained without any change.

Next, a more specific example will be described with reference to FIGS. 5 to 7. FIG. 5 is a sectional view, and FIGS. 6 and 7 are sectional views taken along lines Vl-Vl and ■-■ in FIG. 5.

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 device is provided, and this case 70 is fixed to the vehicle body (not shown).
, a hydraulic switching valve 22, a rear wheel steering rod 24, a displacement transmitting 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, so that the valve housing 50 is formed by the case 70 itself. Further, the rear wheel steering rod 24 is also disposed in a hole formed in the case 70, and the hydraulic power cylinder 54 also has its cylinder nose and housing 68 formed by the case 70 itself.

The spool 52 is moved, for example, by ±1 from the neutral position as described above.
Therefore, as shown in FIG. 7, the hydraulic switching valve 22 is capable of displacing the spool 52 within its housing 50 by an extremely small amount from the neutral position to the balance position. By configuring it in this manner, 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. However, in this embodiment, the valve housing 50 of the hydraulic switching valve 22 is stationary as described above, and therefore the housing 50
can be formed from a case 700, and the hydraulic switching valve 22 can be disposed at a position facing the hydraulic power cylinder 54. Therefore, as shown in FIG. 5, the hydraulic switching valve 22 and the hydraulic power cylinder 54 are disposed facing each other, and their housing 50.68 is formed by the case 70 itself, and the hydraulic power cylinder 22.54 is connected to the hydraulic power cylinder 54. The passages are also formed directly on the case 70, thereby making the device more compact and facilitating the formation of the oil passages.

The cross lever 2B, which is the displacement transmitting means, is made up of a vertical lever 28a and a horizontal lever 28b which are separate members and are connected in a cross shape, as shown in FIG. The connection is made by inserting the horizontal lever 26b into the hole of the vertical lever 28a.
This is done by fitting and inserting the levers 26a and 28b, and the fitting may be such that both levers 26a and 28b are completely fixed, or the horizontal lever 26b is rotatable around its axis relative to the vertical lever 26a and the It may be movable in the direction.

Further, the cross lever 2B has both levers 26a, 26
If the connection point of b is E, as shown in Figure 6, AE<E
It is set to be B. By making the lever length EB larger than the lever length AE, 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 cross lever 26, from the state where the cross lever 26 is in the balance position shown by the solid line, the output displacement section moves the A end to A'.
When it is displaced to the right by a distance of 111s1 to the position,
The cross lever 2B is in the state shown by the two-dot chain line, and the D end is displaced to the right by a distance S2 to the D' position, and the spool is accordingly displaced to the right by a distance S1. 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. ' Distance S to position
Displaced by 3. In this case, Sl: S3-AE
: EB, so by making EB larger than AE, S! A large S3 can be obtained.

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 section 30, the output displacement section 30 necessary to obtain a predetermined stroke displacement of the rear wheel steering rod 24 is adopted. If the amount of displacement of the steering ratio variable means 20 can be reduced, the steering ratio variable means 20
Since the output displacement amount may be small, the steering ratio variable means 20
For example, in the illustrated type of variable steering ratio means, the diameter of the bevel gear 32 can be reduced.

Further, in the embodiment shown in FIG. 5, the output displacement section 30 is provided with a transmission displacement absorption mechanism.

Figure 9 shows an output displacement section 3 equipped with an example of a transmission displacement absorption mechanism.
FIG. This output displacement section 30 is a transmission displacement absorption mechanism itself, and a shaft member 74 is supported by a support member 36 that is integral with the case 70 so as to be displaceable in the axial direction.
and a cylindrical member 76, the shaft member 74 is connected to the connecting rod 34 via a ball joint and is fitted into the cylindrical member 76 so as to be displaceable in the axial direction. A first cylindrical portion 76b having an engaging portion 7 (ia) that engages with the A end of the transmission means 26;
It consists of a second cylindrical portion 78c and a lock nut 76d which are screwed together.

A large-diameter hole 78c is formed inside the cylindrical member 76, and the shaft member 74 has spring seats 74a, 74b whose movement in the axial direction outward is restricted by a step and a retainer, and both spring seats 74a.
, 74b are provided, and both spring seats 74a, 74b are pushed axially outward by the spring 74c as shown in the figure, and abut against the stepped portion of the shaft member 74 and the retainer, as well as against the cylindrical member. It is brought into contact with the stepped portions at both axial ends of the large diameter hole 7 (ie).

Therefore, when an axial displacement is transmitted to the shaft member 74 by the connecting rod 34, the shaft member 74 normally
4a, 74b, large diameter hole 760 of spring 74c1 cylindrical member
is transmitted to the cylindrical member 76 via the stepped portion of the cylindrical member 7B.
From there, it is transmitted to the A end of the displacement transmitting means 2G 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 74e set to a predetermined value is applied to the cylindrical member 7θ 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 713.

In the steering system of this embodiment, as mentioned above, a centering spring 80 is provided for the purpose of achieving a seven-fail safety, and in the event of a failure, the hydraulic pressure of the hydraulic power cylinder is removed, and this centering spring 60 applies a force of several hundred kilograms to the rear wheel steering rod. 24 to the neutral position, and in the hydraulic switching valve z2, the spool 52 is configured to be able to move only about ±1jllI from the neutral position,
Furthermore, a mechanical steering transmission system connects the handle to the spool 52 via the variable steering ratio means 20. Therefore, in the event of a failure, the spool 52 is displaced by steering wheel steering, but the rear wheel steering rod 24 is not displaced, so that the spool 52 is not returned to the balanced position by the rear wheel steering rod 24, and as a result, further steering wheel steering causes the spool 52 to be displaced. will be displaced beyond the allowable displacement of about ±1 s, resulting in problems such as damage to the mechanical steering transmission system such as the steering ratio variable means 20, displacement transmission means 26, etc. or the hydraulic switching valve 22 due to overload. occurs.

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. This is to prevent damage to the system or hydraulic switching valve.

Further, in the embodiment shown in FIG. 5, as shown in FIG. 6, a long groove 78 extending in the axial direction is formed in the rear wheel steering rod 24, and a screw 80 is screwed into the long groove 78 and screwed into the case 70. is configured to allow displacement of the rear wheel steering rod 24 in the axial direction while preventing rotation about the axis. Further, the output displacement section 30 is also configured to slide in a plane between the inner surface of the case 70 and allow displacement in the axial direction while preventing rotation around the axis.

In the embodiment shown in FIG. 5, the A, B, and D ends of the cross lever 26, which is the displacement transmitting means, are formed into spherical shapes, and the spherical A, B, and D ends are connected to the output displacement portion 30,
The rear wheel steering rod 24 and the spool 52 are fitted into holes formed therein, which are directed to the connection point E perpendicular to the axial direction, so that they are immovable in the axial direction but movable in the direction toward the connection point E. and are pivotally and rotatably engaged.

In addition to the above-mentioned engagement mode, the cross lever 26 has, for example, a ball joint at the A, B, and D ends similar to the C end, which engages the members 30, 24, and 52 only in a rotatable manner, and The vertical and horizontal levers 28a and 2[ib may be configured to be telescopic, for example, and extendable and retractable.

In addition, as shown in FIG. 1O, 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 cross lever 26 are engaged between the two collars 82 so that their both sides abut against 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.

Furthermore, as shown in FIG. 11 and FIG. 12 when viewed from the direction of arrow X and the force 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 to slide on a plane, and the spherical ends A and B are engaged with this sliding contact piece 84 in a ball joint type. It's okay.

Further, the cross lever 2B in the embodiment shown in FIG.
Although the lever is a split type consisting of a combination of a vertical lever 28a and a horizontal lever 28b, it may also be an integrated cross lever in which both levers 26a and 28b are integrally formed as shown in FIG. 1O.

In addition to the above-mentioned cross lever, the displacement transmitting means 2B includes a thirteenth lever.
As shown in the figure, it may be a single-character lever. This 1-shaped lever 26 engages one end C of the horizontal lever 26b with the case 70 and the other end with the spool 52 of the hydraulic switching valve.
A connecting point E with the vertical lever 26a is set in the middle of the horizontal lever 28b, and at the connecting point E, one end of the vertical lever 28a is connected to the horizontal lever 28b, and the other end B is connected to the rear wheel steering rod 26a.
, and an engaging portion A with the output displacement portion 30 is set in between. The above-mentioned engaging end or engaging portion A, B,
The manner of engagement of C and D is the same as in the case of FIG. 11.12.

If the displacement transmitting means 2B is formed in this way and the output displacement section 30 is positioned between the spool 52 and the rear wheel steering rod 24, the displacement of the output displacement section 30 can be transmitted to the vertical lever 26a and the horizontal lever 26a. The increased pressure can be transmitted to the spool 52 by both levers 26b, and the delay in operation due to the dead zone of the hydraulic switching valve can be more effectively reduced. In each of the embodiments described above, the direction of displacement of the rear wheel steering rod 24 is opposite to that of the output displacement section 30.

However, in this embodiment, the spool 52 can be returned to the balanced position by displacing the rear wheel steering rod 24 in the same direction with respect to the output displacement section 30.

The displacement transmitting means in the vehicle steering device according to the present invention includes:
In addition to the lever type described above, the type shown in FIG. 14 can also be adopted.

The displacement transmitting means 2B shown in FIG. 14 is of a gear type using gears, and has rack parts 88,90 formed on the output displacement part 30 and the rear wheel steering rod 24, and both rack parts 88,90. A gear 92 is meshed between them, a lever 94 is inserted into the center of the gear 92, one end C of the lever 94 is supported by a ball joint in a non-displaceable but rotatable manner on the case 70, and the other end is supported by a ball joint. is engaged with the spool 52 of the hydraulic switching valve in the same manner as in FIG.

In this example, if the Kanayama force displacement part 30 is displaced to the right in the figure, the tire reaction force etc. acts on the rear wheel steering rod 24 as described above, and the rod 24 remains immobile.
The gear 92 rotates clockwise and is displaced rightward by the displacement amount of the output displacement section 30. Then, the lever 94 is tilted with the C end as a fulcrum, and the D end is displaced to the right and the spool 5
2 from the neutral position to the right beyond the balance position. This rightward displacement of the spool 52 supplies hydraulic pressure to the right oil chamber 56 of the hydraulic power cylinder 54, and the hydraulic pressure in the left oil chamber 58 is discharged, thereby causing the rear wheel steering rod to
4 is displaced to the left in the figure. Then, when this rear wheel steering rod 24 is displaced to the left, the output displacement portion 301;
As mentioned above, since the part 30 remains stationary due to the reaction force caused by the steering force, the gear 92 is displaced to the left while rotating clockwise, and thereby the D end of the lever 94 is also displaced to the left. The spool 52 is then displaced until it returns to the balanced position. Therefore, by repeating this operation, the spool 52 responds to the displacement of the output displacement section 30 by only making a slight displacement from the neutral position to the balance position, as in the case of the lever-type displacement transmission means described above. The displacement of the wheel steering rod 24 can be obtained.

Of course, the displacement transmitting means 2B of this embodiment also uses the lever 94 to magnify the displacement of the output displacement part 30 and transmits it to the valve member 52, that is, the connection point between the gear 92 and the lever 94 is
In this case, the displacement of the output displacement section 30 is multiplied by CD/CE and transmitted to the valve member 52, thereby reducing the delay in the operation of the rear wheel steering rod 24 caused by the dead zone of the hydraulic switching valve 22. It is configured.

In each of the embodiments described above, the valve housing 50 of the hydraulic switching valve 22 is immovable, and the spool 52 is also relatively displaced only from the neutral position to the balance position in both directions. The present invention is applicable not only to such a steering device, but also to a type of steering device in which the valve housing of the hydraulic switching valve is fixed to a steering rod and is displaced together with the steering rod, as in the conventional example. is shown in FIG.

The basic structure of the embodiment shown in FIG. 15 is exactly the same as the conventional example described above, and the basic structure of the steering ratio variable means, which is not explained in the conventional example, is also shown in FIGS. 1 to 3 above. Same as described. Therefore, the displacement transmitting means 26, which is the main part of this embodiment, will be explained below.

The steering ratio variable means 20 in this embodiment includes a stepping motor 44, a worm 4,
6, swing gear 42, swing shaft 40. Consisting of a pendulum arm 88, a connecting rod 34, a bevel gear 32, etc., the connecting rod 3
4 is formed as an output displacement section 30, and this output displacement section 30 is connected to the hydraulic switching valve 2 via the displacement transmission means 2B.
It is connected to a spool 52 which is the second valve member.

The displacement transmission means 26 includes a support arm 110 fixed to the case 70 of the steering device, a transmission rod 112 connected to the spool 52, and a transmission rod 112 at both ends 1. J is connected to the support arm 11G and the transmission rod 112 by a ball joint, and a lever l14 is connected to the output displacement part 30 by a ball joint at a point in between.

In such a displacement transmitting means 2B, the displacement of the output displacement section 30 is increased by the lever 114 that rotates about the I end as a fulcrum and is transmitted to the spool 52. That is, the displacement amount of the output displacement section 30 is multiplied by IJ/IK. Spool 5
2 and thereby hydraulic switching valve 2.
The delay in actuation of the rear wheel steering rod 24 due to the dead zone of No. 2 is reduced.

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.

Additionally, a hydraulic switching valve can supply hydraulic pressure by displacing a valve member such as a spool from a neutral position with respect to the valve housing, and can switch the supply of hydraulic pressure to a hydraulic power cylinder depending on the direction of displacement. Any type of displacement from the neutral position of the valve member may be used, and the displacement of the valve member from the neutral position may be stroke displacement, rotational displacement, or other types of displacement.

Further, although the displacement of the output displacement portion is a stroke displacement in the embodiment, it may be other displacement such as a rotational displacement depending on the form of the hydraulic switching valve.

Further, the displacement transmitting means may be of any type as long as it is configured to magnify the displacement of the output displacement section and transmit it to the valve member of the hydraulic switching valve.

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 section with respect to the steering amount of the steering wheel.

Further, each of the above-mentioned embodiments was of a so-called full power type in which the steering rod was displaced only by a hydraulic power cylinder, but in the present invention, the steering rod is displaced by being assisted by the hydraulic pressure of a hydraulic power cylinder. It is also applicable to so-called assist type devices. The steering wheel is equipped with a displacement transmitting means as shown in the embodiments shown in FIGS. 1 to 14, so that the valve housing of the hydraulic switching valve is immovable and the valve member can only be displaced from the neutral position to the balance position in both directions. The device is also applicable to the above-mentioned assist type.

(Effects of the Invention) As explained above, the vehicle steering device according to the present invention includes a displacement transmitting means that engages the output displacement portion of the steering ratio variable means and the valve member of the hydraulic switching valve, and The means is configured to magnify and transmit the displacement of the output displacement portion to the valve member.

Therefore, in the present invention, the displacement speed of the valve member of the hydraulic switching valve is faster than when the displacement of the output displacement section is directly transmitted to the valve member, and as a result, the time to clear the dead zone of the hydraulic switching valve is shortened. , the delay in operation of the steering rod can be reduced.

[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 40 shows the displacement transmitting means in the embodiment shown in Figure 1;
A diagram for explaining the operation of the output displacement member, hydraulic switching valve, and steering rod. FIG. 5 is a sectional view showing the main parts of another embodiment in detail. FIGS. 6 and 7 are ■
8 is a perspective view showing the movement of the displacement transmitting means of the embodiment shown in FIG. 5, and FIG. 9 is a transmission displacement absorption mechanism provided in the embodiment shown in FIG. 5. 10 is a sectional view similar to FIG. 6 showing another embodiment, FIG. 11 is a sectional view similar to FIG. 6 showing another embodiment, and FIG. 12 is a sectional view similar to FIG. 6 showing another embodiment. Fig. 11 is a view of the main part of the embodiment shown in the direction of arrow X and force; Fig. 13 is a sectional view similar to Fig. 6 showing another embodiment; FIG. 15 is a schematic perspective view similar to FIG. 1; FIG. 15 is a schematic partial cross-section showing main parts of another embodiment; FIG. 16 is a schematic partial cross-section showing an example of a conventional vehicle steering system. 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...Housing 70 of the hydraulic power cylinder...
Steering device case Fig. 8 Fig. 7 Fig. 10 Fig. 11.

Claims (1)

[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 section that is displaced in response to the steering of the steering wheel, the steering ratio variable means being capable of changing the ratio of the displacement amount of the output displacement section to the steering amount of the steering wheel. A steering system for a vehicle, comprising: a displacement transmitting means for magnifying the displacement of the output displacement portion of the steering ratio variable means and transmitting the expanded displacement to a valve member of the hydraulic switching valve.