JPH04138972A - Neutral position regulating method of rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To perform high-precise regulation of a neutral position by computing an average coordinate value of four polarization points at the dead zone of the stroke characteristics of a rear wheel steering shaft in relation to displacement of a support member, and setting the computing value as the neutral position of the support member. CONSTITUTION:A displacement gauge 61 to detect a displacement amount in the axial direction of a rear wheel steering shaft 13 is located at the end part of the rear wheel steering shaft 13. Meanwhile, a locking member 62 to which a support 38 is locked is displaceably arranged through a ball screw means 63. A screw rod 63a of the ball screw means 63 is rotatable through a coupling 64 with the aid of a stepping motor 65. A rotation amount of the stepping motor 65 is measured by a rotary encoder 66, and a displacement amount of the locking member 62 is detected by a non-contact distance sensor 67. When the stroke of the rear wheel steering shaft 13 responding to displacement of the support 38 is measured, an average coordinate value of four polarization points at a dead zone where the output shaft 13 is not displaced in response to displacement of the support 38 is computed, and the computing value is set as the neutral position of the support 38.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a neutral adjustment method for a vehicle rear wheel steering system in which a rear wheel steering shaft for steering the rear wheels is controlled by two systems, a mechanical system and a hydraulic system. It is related to.

L Conventional technology J Conventionally, as a rear wheel steering device of a vehicle, for example,
As described in Publication No. 273772, a mechanical system that displaces a rear wheel steering shaft that steers the rear wheels includes an input shaft that inputs the amount of steering angle of the front wheels, and an input shaft that receives input from the input shaft and moves the rear wheel steering shaft in the axial direction. comprising a stroke output rod member, and a yoke assembly that is linked to and swingably supported by the output rod member and controls the stroke amount of the output rod member due to the rotation of the input shaft according to the swing angle of the yoke assembly; The stroke amount of the output rod member is transmitted to the rear wheel steering shaft by a displacement transmitting means linked to the output rod member, the rear wheel steering shaft, and the vehicle body. The hydraulic system for assisting the displacement includes a power steering means for hydraulically assisting the displacement of the rear wheel steering shaft, and a hydraulic switching valve for controlling the power steering means, and the hydraulic switching valve is linked to the displacement transmitting means. , a system in which the mechanical system and the hydraulic system are connected is known.

[Problems to be Solved by the Invention] In such a rear wheel steering device, in the mechanical system, the stroke amount of the output rod member and the displacement amount of the rear wheel steering shaft are determined by the rotation angle of the input shaft and the swing angle of the yoke assembly. In the hydraulic system I, the power steering means hydraulically assists the rear wheel steering shaft by an amount corresponding to the displacement amount.

Therefore, in order to accurately control the rear wheel steering axis, that is, the rear wheel steering axis, it is necessary to use a neutral (neutral) It is necessary to connect the two C systems so that the neutral (zero phase) of the hydraulic system that hydraulically assists the displacement of the rear wheel steering shaft coincides with the zero phase).

By the way, when connecting both systems, the mechanical system (input shaft and yoke assembly) must be neutrally adjusted, and then the displacement transmission means must be connected to the wR thread system (that is, the output rod member and the rear wheel steering shaft). By determining the supporting portion of the displacement transmitting means on the vehicle body side, one of the hydraulic switching valves is linked so that the neutral position of both systems coincides when the hydraulic switching valve is assembled and hydraulic pressure is applied. !
! It is possible to eliminate deviations in the neutral position of the valve itself due to machining errors and the like, and to absorb deviations between the neutral position of the mechanical system and the neutral position of the hydraulic system.

In other words, when measuring the stroke of the rear wheel steering shaft (exit shaft) with respect to the displacement of the support part with hydraulic pressure applied, there is a dead zone in which the output shaft does not displace with respect to the displacement of the support part. By fixing the support portion at a position corresponding to the dead zone as a neutral position, it is possible to absorb the deviation between the neutral position of the mechanical system and the neutral position of the hydraulic system.

However, the rear wheel steering axis (
When measuring the stroke of the output shaft (output shaft), due to the spring characteristics of the centering spring of the rear wheel steering shaft and the disc springs provided on both sides of the spring, hysteresis actually appears in the stroke characteristics, resulting in a width difference in the dead zone. occurs, and a total of four inflection points appear on the stroke characteristic curve, two each on the outward and return strokes.

Therefore, by setting the centers of these four inflection points as the neutral positions of the support portion, the deviation between the neutrals of the mechanical system and the hydraulic system can be further reduced, and highly accurate neutral adjustment can be performed.

Therefore, in the vehicle rear wheel steering device, the present invention assists the mechanical system for displacing the rear wheel steering shaft and the displacement of the rear wheel steering shaft by accurately performing neutral adjustment of the support portion of the displacement transmitting means. It is an object of the present invention to provide a method for neutrally adjusting a vehicle rear wheel steering system without deviation in control of a rear wheel steering axis between the hydraulic system and the hydraulic system.

[Means for Solving the Problems] Therefore, the first invention of the present application is such that a mechanical system for displacing a rear wheel steering shaft for steering rear wheels includes an input shaft for inputting a steering angle amount of the front wheels, and an input shaft for inputting a steering angle amount of the front wheels; An output rod member that receives input from the shaft and strokes in the axial direction, and is linked to the output rod member and supported so as to be swingable, and the amount of stroke of the output rod member due to the rotation of the input shaft is determined by the swing angle of the output rod member. and a yoke assembly configured to transmit the stroke amount of the output rod member to the rear wheel steering shaft by a displacement transmitting means linked to the output rod member, the rear wheel steering shaft, and the vehicle body side. On the other hand, the hydraulic system for assisting the displacement of the rear wheel steering shaft is a power steering means for hydraulically assisting the displacement of the rear wheel steering shaft;
A vehicle rear wheel steering system comprising a hydraulic switching valve for controlling the power steering means, the hydraulic switching valve being linked to the displacement transmitting means to connect the mechanical system and the hydraulic system, the displacement transmitting means When adjusting the neutral position of the support member that supports one end of the
The average coordinate value of four inflection points in the dead zone in the stroke characteristic of the rear wheel steering shaft with respect to the displacement of the support member is calculated, and the calculated value is set as the neutral position of the support member.

Further, the second invention of the present application is the first invention,
Each of the above inflection points is obtained by calculating the intersection of six straight lines obtained by linear approximation of the above stroke characteristics, and the two straight lines indicating the dead zone are obtained from the coordinate values when the above hydraulic switching valve is OFF. .

[Effect of the Invention] According to the first invention of the present application, the average coordinate value of the four inflection points in the dead zone portion is calculated, and the calculated value is set as the neutral position of the support member, so that it is easy and accurately,
The neutral position (the center of the dead zone) of the support member can be determined, the deviation between the neutrals of the mechanical system and the hydraulic system can be further reduced, and highly accurate neutral adjustment can be performed.

Further, according to the second invention of the present application, each of the inflection points is determined by calculating the intersection points of six straight lines obtained by linear approximation of the stroke characteristics, so that the average of the four inflection points is Coordinate values can be calculated automatically. In addition, the straight line indicating the above-mentioned fuwazai is connected to the above-mentioned hydraulic switching valve OFF.
Since the calculation is made from the coordinate values at the time, the straight line indicating the dead zone can be determined with a simple operation.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

The vehicle rear wheel steering device l, which is the premise of the present invention, as shown in the schematic configuration in FIG. and a hydraulic switching valve 1 as a hydraulic assist means.
5, the rear wheel steering device l steers the rear wheels (not shown) according to a predetermined steering ratio characteristic, that is, according to the front wheel steering angle, and changes the steering ratio according to the vehicle speed. configured to change.

The rear wheel steering shaft 13 extends in the vehicle width direction, and has both ends connected to the left and right sides via a pair of left and right tie rods and knuckle arms.
It is connected to a pair of rear wheels, and the rear wheels are steered by stroke displacement of the rear wheel steering shaft 13 in the vehicle width direction.

The stroke displacement of the rear wheel steering shaft 13 in the vehicle width direction is performed by the steering ratio variable means 11 and the power steering means 12.

The steering ratio variable means 11 changes the steering ratio when steering the rear wheels, and has an output rod member 16 that is stroke-displaced in the vehicle width direction according to the amount of steering angle of the front wheels.

As will be described later, the ratio of the displacement amount of the output rod member 16 to the steering angle amount of the front wheels (corresponding to the steering ratio) changes depending on the swing angle of the yoke assembly 18 that is swing-driven by the stepping motor 17. It is configured as follows. The amount of rotation of the stepping motor 17 is appropriately controlled based on a vehicle speed signal output from a vehicle speed sensor (not shown), and the actual amount of rotation of the stepping motor 17 is detected by a steering ratio sensor (not shown). and is feedback-controlled by the detection signal.

Power steering means that controls switching of the hydraulic switching valve 15 according to the stroke displacement amount of the output rod member 16 in the steering ratio variable means 11, and generates a steering force using hydraulic pressure by the hydraulic switching valve 15. 12, the displacement of the rear wheel steering shaft 13, and therefore the steering of the rear wheels, is hydraulically assisted.

The steering ratio variable means 11 includes the output rod member 16,
Stepping motor 17 and yoke assembly 18 (
In addition to the swing shaft member 22, the pendulum arm 23, and the swing gear 31), it also includes a bevel gear 21 and a connecting rod 24. As shown in detail in FIG. 7, it is housed in a casing 25.

The output rod member 16 of the steering ratio variable means 11 is supported by the casing 25 so as to be slidable in the axial direction, and by making a stroke displacement in the axial direction, the output rod member 16 transmits the displacement transmitting means 14 as described later. Through the rear wheel steering shaft 13
is displaced in its axial direction (*width direction), thereby steering the rear wheels linked to both ends of the rear wheel steering shaft 13.

The bevel gear 21 is connected to the lever 2 of the output rod member 16.
8 toward the output rod member 16, it is supported by the output rod member 16 via a cylindrical support member 52 so as to be rotatable along with the output rod member 16 and about an axis coaxial with the output rod member 16. A pinion 27 at the rear end of the input shaft 26 that meshes with the bevel gear 21 and inputs the amount of steering angle of the front wheels.
is adapted to rotate around the axis as the handle is rotated.

The swing shaft member 22 has an axis that can be positioned coaxially with the output rod member 16, and is fixed to the swing gear 31. This swing gear 31 is connected to the stepping motor 17
The swing shaft 3 is perpendicular to the plane of the paper and intersects with the axis 121 of the swing shaft member 22, meshing with the worm 32 that rotates by the drive of the
1a (see FIG. 4), which causes the swing shaft member 22 to rotate at the same time. Note that the shaft 32a of the worm 32 is coupled to the motor shaft 17a of the stepping motor 17 via a coupling 54 (see FIG. 6).

The pendulum arm 23 is connected to the swing shaft member 22 so as to be swingable about the axis Q1 of the swing shaft member 22, and the axis Q2 of the pendulum arm 23 is the pivot axis of the swing shaft member 22. The connection position to the swing shaft member 22 is determined so as to pass through the intersection of the axis Ql of the swing shaft member 22 and the axis Ql of the swing shaft member 22.

Like the rear wheel steering shaft 13, the connecting rod 24 has an axis parallel to the axis a3 of the output rod member 16,
It is connected to the output rod member 16, the bevel gear 21, and the pendulum arm 23, and links the output rod member 16 and the yoke assembly 18. Connection to the output rod member 16 is achieved by splitting and coupling the intermediate portion of the connecting rod 24 to a lever 28 fixed to the end of the output rod member 16, and connection to the bevel gear 21 is achieved by connecting the connecting rod 24 to a lever 28 fixed to the end of the output rod member 16. The connecting rod 24 is connected to the pendulum arm 23 by inserting one end of the connecting rod 24 into an insertion hole formed in the extension 52a of the supporting member 52, and the connecting rod 24 is connected to the other end of the connecting rod 22 so as to be rotatable in all directions. t: This is done by inserting the pendulum arm 23 through the insertion hole of the pole joint member 33.

Therefore, the connecting rod 24 is connected to the output rod member 16.
Although it is fixed to the bevel gear 21, it is slidable relative to the bevel gear 21 in the direction of the axis line a4, and is slidable relative to the pendulum arm 23 in the direction of the axis line Q2. Note that the axis Q2 of the pendulum arm 23 is tilted with respect to the direction orthogonal to the axis Q3 due to the rotation of the swing shaft member 22, and the pendulum arm 23 slides in this tilted direction. Since the included angle change between the axis Q2 and the axis Q4 is absorbed, the component of the force transmitted from the pendulum arm 23 to the connecting rod 24 in the direction orthogonal to the axis Q3 of the output rod member 16 is absorbed at the connecting point. , relative movement in the orthogonal direction is possible.

In this way, the pendulum arm 2 in the steering ratio variable means 11
3 (yoke assembly 18) and the connecting rod 24 are connected so that they can move relative to each other in the direction orthogonal to the axis I13, so that when the pendulum arm 23 rotates, the The locus of the connecting rod 24 and the connecting point is a circular locus or an elliptical locus on the outer peripheral surface of a cylinder having a predetermined radius and centered on the axis Q3.

As described above, by connecting the pendulum arm 23 and the connecting rod 24 so that they can move relative to each other in the direction orthogonal to the axis Q3 of the output rod member 16, the axis Q4 of the connecting rod 24 and the output rod member The angle between the output rod member 16 and the axis 123 can be made constant, and thereby it is possible to prevent left-right deviation from occurring in the displacement of the output rod member 16.

Further, in the output rod member 16, one end of the output rod 36 is connected to the connecting rod 24 via the lever 28, and the other end of the output rod 36 is fitted into the cylindrical rod guide 35 so as to be displaceable in the direction of the axis Q3. The ends of the rod guide 35 and the output port 36 are supported by the casing 25.

The rod guide 35 includes a first cylindrical member 35b having a retaining portion 35a that engages with the engaging end A of the displacement transmitting means 14, and a second cylindrical member 35c screwed onto the first cylindrical member 35b. A spring 37 is interposed between the output rod 36 and the output rod 36.

Therefore, the output port/end 36 is connected by the connecting rod 24.
When a displacement in the direction of the axis a3 is transmitted to , it is normally transmitted from the output rod 36 to the mouth/rad guide 35 via the spring 37, and from the rod guide 35 to the displacement transmitting means 14 engaged with the engaging portion 35a. is transmitted to the engaging end A of.

However, if the movement of the engagement end A of the displacement transmitting means 14 is restricted and a load greater than the spring force of the spring 37 acts on the rod guide 35 when the output rod 36 is displaced, then the output rod 36 The displacement is absorbed by the contraction of the spring 37 and is not transmitted to the rod guide 35.

Further, the hydraulic switching valve 15 is connected to the valve housing 4.
1 and the valve housing 4 in the valve housing 41.
1, the valve spool 4 is housed so as to be displaceable in an axis Q5 direction parallel to the axis C3 of the output rod member 16.
It consists of 2. The valve spool 42 is displaced by the output rod member 16 and the rear wheel steering shaft 13 via a displacement transmission means 14, which will be described in detail below. The supply of hydraulic pressure to the power steering means 12 is controlled by this displacement of the valve spool 42.

In addition, a centering spring 45 is provided on this rear wheel steering shaft 13, and if the hydraulic pressure in the hydraulic switching valve 15 or the power steering means 12 disappears, or if the mechanical system of this rear wheel steering device l is damaged or malfunctions. When the hydraulic system is drained and the hydraulic pressure in the cylinder of the power steering means 12 disappears, the centering spring 45 moves the rear wheel steering shaft 13 to the neutral position, that is, the rear wheels are not steered and are traveling straight. It is configured to be positioned in a certain position and to provide a so-called fail-safe.

The cylinder of the power steering means 12 displaces the rear wheel steering shaft 13 in the vehicle width direction by hydraulic pressure, and the piston 46 is directly fixed to the rear wheel steering shaft 13.
Left and right oil chambers 44 and 43 are formed on the left and right sides of this piston 46.

In addition to the output rod member 16 (rod guide 35), the displacement transmission means 14 engages with the valve spool 42, the rear wheel steering shaft 13, and the vehicle body (support support 38), and is caused by the displacement of the output rod member 16. Above valve spool 4
2 in a predetermined direction, and is also actuated in a direction to displace the valve spool 42 in the opposite direction due to the displacement of the rear wheel steering shaft 13 caused by the displacement of the valve spool 42. It is structured as follows.

Specifically, the displacement transmitting means 14 has a cross lever 14a consisting of a vertical lever and a horizontal lever, and the engagement end A, which is one end of the vertical lever, is connected to the rod guide 35 of the output rod member 16, and the other end is connected to the rod guide 35 of the output rod member 16. The engagement end B, which is the end, is connected to the rear wheel steering shaft 13,
Further, one end of the horizontal lever, which is an engaging end C, is engaged with a supporting support 38 fixed to the vehicle body, and the other end, which is a retaining end, is engaged with the valve spool 42, respectively.

A sealing member 56 is attached to a portion of the housing 25 through which the cross lever 14a is inserted. Further, the port insertion hole 38h of the support support 38 is formed in the shape of a long hole, and the support support 38 can be fastened and fixed to the vehicle body while adjusting the slide within the range of the long hole 38h. There is.

The engaging ends A, B, and D are each connected to the output rod member 16.
The rod guide 35 of the rear wheel steering shaft 13 and the valve spool 42 are immovably engaged with the rear wheel steering shaft 13 and the valve spool 42 in the axial direction, but movable and rotatable in other directions. It is engaged for rotation and non-movement by an inlet (not shown).

Therefore, if the output rod member 16 is displaced to the right from a state where both the valve spool 42 and the rear wheel steering shaft 13 are in the neutral position, the engagement end A of the cross lever 14a
is displaced to the right together with the output rod member 16, and since tire reaction force and reaction force from the centering spring 45 are acting on the rear wheel steering shaft 13 when the engagement end A is displaced, this engagement end B is immovable in the axial direction, and the engaging end C is also fixed to the support 1-38 (vehicle body) and is immovable. Therefore, this cross lever 14a is connected to the engaging end B and the engaging end C. In other words, the cross lever 14a is operated in a direction to displace the valve spool 42 to the right, which is a predetermined direction, and the engagement end portion displaces the valve spool 42 to the right.

When the valve spool 42 is displaced rightward from the neutral position in this way, the oil pressure in the right oil chamber 43 increases, and the left oil chamber 4
4 decreases, and a hydraulic pressure is generated in the power steering means 12 that pushes the rear wheel steering shaft 13 to the left. The hydraulic pressure that pushes the rear wheel steering shaft 13 leftward increases in accordance with the increase in the rightward displacement of the valve spool 42, resulting in a balance position.

When the valve spool 42 is displaced to the right by a predetermined amount from the neutral position to the balance position, the hydraulic pressure of the power steering means 12 generated thereby causes an external force (centering spring force or tire (reaction force, etc.).

When the valve spool 42 is further displaced to the right from this state, the hydraulic pressure generated in the power steering means 12 becomes larger than the external force acting on the rear wheel steering shaft 13, and the rear wheel steering shaft 13 is moved to the right. It is displaced to the left by hydraulic pressure.

Then, when the rear wheel steering shaft 13 is displaced to the left, the engagement end B of the cross lever 14a is connected to the rear wheel steering shaft 13.
At this time, the output rod member 16 is affected by the steering force of the steering wheel, the tire reaction force of the front wheels, etc., so the engaging end A is immobile and the retaining end C is also displaced. Since it is stationary, the cross lever 14a tilts about the straight line connecting the engagement end A and the engagement end C, and when it returns to the balance position, the displacement of the rear wheel steering shaft 13 stops.

From this state, when the output rod member 16 is further displaced to the right and the valve spool 42 is displaced to the right, the rear wheel steering shaft 13 is displaced to the left in the same manner as above, and the valve spool 42 is returned to the balance position. However, by stopping and repeating this operation, the rear wheel steering shaft 13 is displaced by an amount corresponding to the amount of displacement of the output rod member 16, and the rear wheels are steered according to the amount of displacement.

When the output rod member 16 is displaced to the left, the cross lever 14a, the valve spool 42 and the rear wheel steering shaft 1
3 is simply reversed from the above case, and the operating principle is the same, so the explanation will be omitted. The movement of this valve spool is described in the prior art (Japanese Patent Application Laid-Open No. 1-273
It is basically the same as that of Publication No. 772).

The steering ratio changing control by the steering ratio variable means 11 can be performed based on various factors, and various changing control patterns can be considered.

In this example, based on a single chain, the rear wheels are steered in the opposite phase to the steering wheel and front wheels in low speed ranges to improve turning performance, and in high speed ranges, they are steered in the same phase to improve running stability. control to improve performance. Note that in this case, the bundle steering and the front wheel steering are always in the same phase.

Next, in the above-mentioned rear wheel steering system 1, a method of neutral adjustment between the mechanical system and the hydraulic system that affects the accuracy of the controlled steering amount of the rear wheels, that is, a method of connecting both systems while absorbing the deviation between the neutrals of both systems. I will explain about it. Note that this includes the mechanical system (input shaft 26 and yoke assembly 18
), the cross lever 14a is connected to the mechanical system (that is, the output rod member 16 and the rear wheel steering shaft 13), the support support 38 is temporarily assembled, and the hydraulic switching valve 15 is adjusted to the neutral position. This is done with the parts assembled and hydraulic pressure applied. By making adjustments in this state, deviations in the neutrality of the pulp 15 itself due to errors in the machining of the hydraulic switching valve 15 can be eliminated, and deviations between the neutrality of the mechanical system and the neutrality of the hydraulic system can be eliminated. Can be absorbed.

That is, when measuring the stroke of the rear wheel steering shaft 13 (output shaft) with respect to the displacement of the support support 38 in the above state, there is a dead zone in which the output shaft 13 does not displace with respect to the displacement of the support support 38, and in this dead zone, By fixing the support support 38 at the corresponding position as the neutral position, it is possible to absorb the deviation between the neutral position of the mechanical system and the neutral position of the hydraulic system.

That is, the specific measurement system is as shown in FIGS. 7 and 8, in which a displacement meter 61 that detects the amount of displacement in the axial direction of the rear wheel steering shaft 13 is applied to the end of the rear wheel steering shaft 13. On the other hand, a locking member 62 that locks (temporarily assembles) the support support 38 is displaceably attached via a pole screw means 63. The threaded rod 63a of the pole screw means 63 is connected to the steering motor 65 via a coupling 64 and rotated, and the rotation of the threaded rod 63a causes the locking member 62 to engage the threaded rod 63.
It is designed to move in the axial direction of a.

The amount of rotation of the stepping motor 65 is measured by a rotary encoder 66, and the amount of displacement of the locking member 62 is detected by a non-contact distance sensor 67. encoder 6
5 are all connected to a microcomputer.

A method for determining the neutral position of the support support 38 using the measurement system configured as described above will be explained with reference to the flowchart of FIG. 9 and the graph of FIG. 1O.

When the measurement starts, first in step l#, the stepping motor 65 that drives the support 38 is rotated, for example, in the clockwise direction (CW force direction) by θ [deg,]. 13 (output shaft)
Store the displacement position X1 of (step #2), and then:
The motor 65 is further rotated by θ+[deg-] in the CW force direction, and the displacement position X of the output shaft 13 at that time is stored (steps #3 and #4). These two points X r ,
X! The first straight line of the stroke characteristic is determined by .

Next, the motor 65 is moved further in the CW force direction by θ2 [deg
, ], then reverse the direction of rotation of the motor 65 from that point and rotate it counterclockwise (CCW direction) by 02[
degree and the displacement position X of the output shaft 13 at this time is stored (steps #5 and #6). Subsequently, the motor 65 is further rotated by θ1 [degl] in the CCW direction, and the displacement position X of the output shaft 13 at that time is stored (steps #7 and #8). These two points X,,X,
The second straight line of the stroke characteristic is determined.

After this, the output shaft 13 of the power steering means 12
The solenoid valve A connected to the oil chamber 43 or 44 on the side corresponding to the displacement direction is turned off, and the displacement position X5 of the output shaft 13 when the oil pressure is turned off is stored (steps #9 and #lO). At this time, in the case of this embodiment,
The same value was obtained for the displacement position XI even if the same operation was repeated, and the third straight line, that is, the straight line indicating the dead zone, could be determined at this minus point X.

Then, in step #11, the absolute value of the difference between the displacement positions X, , Xs before and after turning off this hydraulic pressure is determined to be a predetermined value δ[
It is determined whether the value exceeds lllll111.

If this judgment result is No, there is some kind of abnormality in the hydraulic system including the solenoid valve A, so step #
At step 12, the measurement is stopped and the hydraulic system is inspected.

On the other hand, if the determination result in step #11 is YES, the measurement is continued, and in step #13, the motor 65 is rotated by 2θo [deg-] in the CCW direction, and the displacement of the output shaft 13 at that time is measured. Store position X6 (step #
14).

Hereinafter, in steps #15 to #20, measurements are performed in the same manner as in steps #3 to #8 above, except that the rotation direction of the motor 65 is different, and the output shaft 13 is
The respective displacement positions X y , X a , and X s are stored. As a result, the fourth and fifth stroke characteristics
A straight line is obtained.

Then, in step #21, the power steering means 1
2, an oil chamber 44 on the side corresponding to the displacement direction of the output shaft 13
Alternatively, the solenoid valve B connected to 43 is turned off, and the displacement position X10 of the output shaft 13 when the oil pressure is turned off is stored (step #22). In this case, as in the case of steps #9 and #lO above, this - point x
At 1o, we were able to determine the sixth straight line, that is, the straight line indicating the dead zone. As a result, a characteristic curve having four inflection points a, b, c, and d is obtained, as shown in the graph of FIG. 1O.

Then, in step #23, the absolute value of the difference between the displacement positions Xs and X+o before and after turning off this hydraulic pressure is determined to be a predetermined value δ.
It is determined whether it exceeds [mm].

If the judgment result is No, there is some kind of abnormality in the hydraulic system including the solenoid valve B, so step #
At step 24, the measurement is stopped and the hydraulic system is inspected.

On the other hand, if the determination result in step #23 is YES, the angular position θ determined by the following formula (■) is calculated, and the motor 65 is rotated in the CW direction by the calculated value 8 [deg, #25). This position is the neutral position of the support 38 corresponding to the center of the four inflection points a, b, c, and d of the dead zone.

θ= θ r74- [(Xl 0-XI)/(X2-
Xl)+(L-Xa)/(Xl-Xa)+(Xs-Xs
)/(Xa-Xy)+(L o-Xa)/(Xs-L)
]...■ Then, in step #26, by pressing and fastening the support support 38 against the vehicle body side seat surface at the above position, the support support 38 can be positioned at the center of the above-mentioned fuwazai, and the rear The mechanical system and hydraulic system of the wheel steering device 1 can be connected so that there is no deviation between neutrals.

As described above, according to this embodiment, the average coordinate values of the four inflection points a, b, c, and d in the dead zone are calculated, and the calculated values are taken as the neutral position of the support 38. As a result, the neutral position (the center of the dead zone) of the supporting support 38 can be easily and accurately determined.
The deviation between the neutrals of the mechanical system and the hydraulic system can be further reduced, and highly accurate neutral adjustment can be performed.

In addition, the above-mentioned inflection points a, b, c, and d are determined by calculating the intersection points of six straight lines obtained by linear approximation of the above-mentioned stroke characteristics, so the above-mentioned four inflection points a, b, c
, d can be calculated automatically. In addition, the straight line indicating the dead zone is expressed by the coordinate values X,,X□ when the hydraulic pressure switching valve is OFF. Since it is calculated from , the straight line indicating the dead zone can be calculated with a simple operation.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram of a rear wheel steering device of a vehicle, FIG. 2 is a sectional view of a steering ratio variable means,
Figure 3 is a sectional view taken along line ■-■ in Figure 2, Figure 4 is a sectional view taken along line IV-IV in Figure 2, Figure 5 is a sectional view taken along line V-v in Figure 2, and Figure 6 is a sectional view taken along line IV--IV in Figure 2. The figure shows Vl in Figure 2.
7 is a schematic diagram showing the relationship between the support support and the rear wheel steering device, and FIG. 8 is a sectional view taken along the line S-Vl of FIG.
9 is a flowchart for explaining the neutral position adjustment method of the support, and FIG. 10 is a graph showing the relationship between the displacement of the support and the displacement of the output shaft. l... Rear wheel steering device 13... Rear wheel steering shaft (output shaft) 12...
- Power steering means 14... Lever assembly (displacement transmission means) 15... Hydraulic switching valve 16... Output rod member 18... Yoke assembly 26... ...Input shaft 38...Support supports a, b, c, d...Inflection points Fig. 3 Fig. 4 Fig. 1 Fig. 5 Fig.

Claims (2)

[Claims] (1) A mechanical system that displaces a rear wheel steering shaft that steers the rear wheels includes an input shaft that inputs the amount of steering angle of the front wheels, an output rod member that receives input from the input shaft and strokes in the axial direction, and a yoke assembly that is linked to and swingably supported by the output rod member, and controls the stroke amount of the output rod member due to the rotation of the input shaft according to the swing angle of the yoke assembly; The stroke amount of the output rod member is transmitted to the rear wheel steering shaft by a displacement transmitting means connected to the vehicle body, while the hydraulic system that assists the displacement of the rear wheel steering shaft is configured to transmit the stroke amount of the output rod member to the rear wheel steering shaft. A power steering means for hydraulically assisting the displacement of the shaft, and a hydraulic switching valve for controlling the power steering means, the hydraulic switching valve being linked to the displacement transmitting means to connect the mechanical system and the hydraulic system. In a vehicle rear wheel steering system, when adjusting the neutral position of a support member that supports one end of the displacement transmitting means with respect to the vehicle body, 4 in a dead zone portion of the stroke characteristic of the rear wheel steering shaft with respect to displacement of the support member is adjusted. A neutral adjustment method for a rear wheel steering system of a vehicle, comprising calculating an average coordinate value of two inflection points, and setting the calculated value as a neutral position of the support member. (2) Each of the above inflection points is obtained by calculating the intersection points of six straight lines obtained by linear approximation of the above stroke characteristics, and the two straight lines indicating the dead zone are
2. The neutral adjustment method for a vehicle rear wheel steering system according to claim 1, wherein the neutral adjustment method is determined from coordinate values at the time of FF.