JPH0737919B2 - Vehicle 4-wheel steering characteristics inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has made it possible to steer the rear wheels in response to steering of the front wheels by operating the steering wheel.
The present invention relates to a vehicle having a wheel steering device, and more particularly, to a method for inspecting the characteristics of the four-wheel steering device.

(Prior Art) Conventionally, in steering a four-wheel vehicle, only the front wheels were normally steered by a steering wheel. However, if only the front wheels are steered, side slippage may occur in the rear wheels or the turning radius depending on the driving situation. However, there is a problem in terms of maneuverability and steerability, such as the fact that there is a limit to the effect of small turns, and in view of this point, a four-wheel steering system has recently been proposed that steers both the front wheels and the rear wheels.
Being researched.

That is, in a four-wheel steering system, if the rear wheels are steered in the same direction as the steering direction of the front wheels when traveling at a relatively high speed (this is referred to as in-phase steering), the front and rear wheels are simultaneously subjected to lateral force. Because of the addition of the steering wheel, there is no phase shift from the steering wheel steering, and the posture of the vehicle can be maintained almost on the tangent of the turning circle, and for example, lane changes during high-speed traveling can be performed smoothly. Further, when the rear wheels are steered in the opposite direction to the steered direction of the front wheels at the time of extremely low speed traveling (this is referred to as antiphase steering), the direction of the vehicle can be greatly changed, which is convenient for parallel parking and garage parking.

Considering that the front wheels are not steered largely at relatively high speeds, and that the front wheels are largely steered when traveling at relatively low speeds, the rear wheels are also steered in the range where the front wheels are steered small. It can be seen that a four-wheel steering device that steers the rear wheels in the opposite direction is required when the steering wheels are steered in the same direction and largely steered.

For this reason, a mechanism that can arbitrarily and variably control the ratio of the steered angle of the rear wheels to the steered angle of the front wheels, that is, the steered ratio, is provided. It has been proposed to variably control the vehicle to improve maneuverability and running stability. For example, as disclosed in Japanese Unexamined Patent Publication No. 61-108070, there is a four-wheel steering system in which the steering phase and the steering ratio are variably controlled according to the vehicle speed.

(Problems to be Solved by the Invention) In a conventional vehicle that steers only two wheels, the front wheels are steered in proportion to the operation of the steering wheel. In the four-wheel steering system, the front wheels are steered proportionally in response to the operation of the steering wheel, but the rear wheels are steered according to the steering angle of the front wheels and the vehicle speed. Since the steering is performed based on the rudder characteristics, the inspection of the steered characteristics of the rear wheels with respect to the front wheels is insufficient with conventional adjustments alone, and there is a problem that the running stability of the vehicle cannot be sufficiently guaranteed if this is left as it is. . In particular, when the steered angle of the rear wheels is not zero when the steered angle of the front wheels is zero, the direction of the rear wheels deviates from the predetermined direction with respect to the operation of the steering wheel, and the steering feeling is impaired. There is a problem that there is a risk of being. In addition, backlash often occurs in the transmission system that transmits the steering of the front wheels to the rear wheels.In this case, the steering angle of the rear wheels is equal to the backlash by the right steering and the left steering of the front wheels. It will shift. When there is such backlash deviation, there is a problem in adjusting the rear wheel steering angle to zero when the front wheel steering angle is zero.

(Means for Solving the Problems) In view of the above problems, the present invention intends to solve the above problems by providing a method capable of accurately and quickly inspecting the characteristics of a four-wheel steering system. As a means therefor, the inspection method of the present invention causes the front wheels to be steered by operating a steering wheel or the like, and steered according to the steered angle of the front wheels and the steered front wheels at this time. The turning angle of the rear wheel is measured to detect the change characteristic of the turning angle of the rear wheel with respect to the turning angle of the front wheel, and it is inspected whether this characteristic is a desired characteristic. In particular, in the present invention, whether the steering angle of the rear wheels is also zero when the steering angle of the front wheels is zero is determined by the back of the steering transmission system between the front wheels and the rear wheels in the device that performs the steering. It is an object of the present invention to provide a method that can be accurately inspected in consideration of rush and the like.Therefore, in the present invention, one axis of the orthogonal coordinates indicates the front wheel steering angle and the other axis indicates the rear wheel steering angle. The characteristic of the change in the turning angle of the rear wheel with respect to the change in the turning angle of the front wheel is shown on the coordinates, and the curve showing the above characteristic when the front wheel is turned to the right and the front wheel is turned to the left. In this case, it is inspected whether or not the curve representing the above characteristics is substantially point-symmetric with respect to the origin of coordinates.

(Operation) According to the above method, the steering characteristics of the rear wheels with respect to the front wheels can be accurately and quickly detected, and when the front wheel steering angle becomes zero, that is, when the front wheels are directed straight ahead, In consideration of the backlash of the steering transmission system, it is possible to reliably check whether the steering angle of the rear wheels is also zero. Therefore, in a vehicle having a four-wheel steering system, the steering wheel can be operated in the left-right direction. It is possible to check whether the rear wheels are properly steered by following this.
By adjusting the wheel steering device, it is possible to improve the feeling of four-wheel steering with respect to the operation of the steering wheel to the left and right.

(Examples) Hereinafter, preferred examples of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view schematically showing a four-wheel steering system for a vehicle, in which front wheels 1a and 1b are steered by front wheel steering means 4 in response to an operation of steering wheel 3, and rear wheels 2a and 2b are rear. It is adapted to be steered by the wheel steering means 10. In this rear wheel steering means 10, the steering amount of the front wheel steering means 4 is transmitted to the transmission bodies 5a, 5b.
The steering phase and the steering ratio are variably controlled according to the steering amount, the vehicle speed, etc.
The rear wheel steering means 10 controls the steering of the rear wheels 2a and 2b on the basis of the steering ratio to perform four-wheel steering.
The transmission bodies 5a, 5b are connected via the connection means 6, but the transmission bodies 5a, 5b are shafts for mechanically transmitting the steering of the front wheels 1a, 1b to the rear wheel steering means 10. Alternatively, it may be a cable for transmitting the steering of the front wheels 1a, 1b as an electric signal.

Here, first, a method for performing a characteristic inspection of the above-described four-wheel steering device will be schematically described. In order to perform this characteristic inspection, first, the steering wheel 3 is operated to operate the front wheel steering means 4
The left and right front wheels 1a, 1b are steered by the
Measure the steered angle of 1b2. When the front wheels 1a, 1b are steered in this way, the steering of the front wheels 1a, 1b is transmitted to the rear wheel steering means 10 via the transmission bodies 5a, 5b connected by the connection means 6, and the rear wheel rotations are performed. Since the rudder means 10 steers the rear wheels 2a, 2b in accordance with the turning amount of the front wheels 1a, 1b, the vehicle speed, etc., the rear wheels 2
The steering angles of a and 2b are also measured. Then, the change characteristics of the steered angles of the rear wheels 2a, 2b with respect to the steered angles of the front wheels 1a, 1b obtained by these measurements show the front wheel steered angle on the horizontal axis and the rear wheel steered angle on the vertical axis. A curve representing the steering characteristic when the front wheel is steered to the right and a curve representing the steering characteristic when the front wheel is steered to the left are obtained. Then, it is inspected whether or not both curves are substantially point-symmetrical with respect to the origin of coordinates. Here, the characteristics are different between the case where the front wheels are steered to the right and the case where they are steered to the left because the transmission system that transmits the steering of the front wheels to the rear wheels has backlash and the like. If there is no such play, the above two curves will coincide and become one curve. In this case, it is inspected whether or not this curve passes through the coordinate origin. If the two curves are not point-symmetric in this inspection, the four-wheel steering system is adjusted so that they are point-symmetrical.

In general, the characteristic inspection is performed as described above. A specific example of the four-wheel steering device will be shown below, and toe-in adjustment of front and rear wheels in a vehicle having this device and characteristic inspection of this device will be performed. A specific method and apparatus to be performed will be described.

FIG. 2 is a schematic plan view showing an example of a four-wheel steering system.
The front wheel steering means 4 includes a front wheel steering rod 4a having a first rack that meshes with a first pinion 3a formed at a lower end of the steering wheel 3, and tie rods 4b and 4b connected to both ends of the rod 4a. Steering wheel 3 consisting of knuckles 4c and 4c connected to the outer ends of tie rods 4b and 4b.
The front wheel steering rod 4a is moved in the vehicle width direction in response to the operation of the knuckles 4c, 4c via the tie rods 4b, 4b.
The front wheels 1a and 1b are steered. Further, the front wheel steering rod 4a is formed with a second rack with which a second pinion 5c provided at the front end of the rotation transmission shaft (transmission body) 5a meshes, and the front wheel steering rod 4a is operated by operating the steering wheel 3. When is moved in the vehicle width direction, the rotation transmitting shaft 5a is simultaneously rotated via the second pinion 5c. This rotation is transmitted to the steering ratio variable mechanism 20 of the rear wheel steering means 10 via the connecting means 6 and the other transmission shaft 5b, and the rear wheels are moved in accordance with the steering phase and the steering ratio adjusted here. It is steered as described below.

On the other hand, the rear wheel steering means 10 is connected to the rear wheel steering rod 15 extending in the vehicle width direction, the tie rods 16 and 16 connected to both ends of the rod 15, and the outer ends of the tie rods 16 and 16. And knuckles 17 and 17 that have knuckle arms and support the rear wheels 2a and 2b so that they can be steered. The rear wheels 2a and 2b are steered by moving the rear wheel steering rod 15 in the vehicle width direction. The rear wheel steering rod 15 has a cylinder 11 that is fixed to the vehicle body and that supports the rear wheel steering rod 15 movably in the vehicle width direction.
And a piston which is divided into two parts in the cylinder 11 and is fixed to the rear wheel steering rod 15 and slidable in the cylinder 11.
A hydraulic actuator consisting of 12 and neutral return springs 14a, 14b arranged in left and right hydraulic chambers 13a, 13b divided by the piston 12 is attached. Hydraulic lines 39a and 39b from the control valve 38 are connected to the left and right hydraulic chambers 13a and 13b of the hydraulic actuator, and the hydraulic actuator is actuated by the hydraulic pressure supplied from the control valve 38 so that the rear wheel steering rod 15 has a vehicle width direction. The rear wheels are steered. The hydraulic oil in the tank 35 is pressurized and supplied to the control valve 38 by the pump 36. This control valve 38
Is a known spool valve type,
It comprises a tubular valve housing 38a integrally connected to the rear wheel steering rod 15 via an arm 15a, and a spool valve 38b fitted in the valve housing 38a. The spool valve 38b has a vehicle width direction. The valve housing along with the rear wheel steering rod 15
38a of hydraulic actuator to move 38a
Supply of hydraulic pressure to a and 13b is selectively controlled. That is, by moving the spool valve 38b in the vehicle width direction, the rear wheel steering rod 15 is moved following the spool valve 38b, and the rear wheels are steered.

The hydraulic lines 39a and 39b are respectively the hydraulic lines 37
It is connected to the normally-closed fail-safe solenoid valve 37 via a and 37b.
When 37c is energized and this valve 37 is opened, the hydraulic pressures in both hydraulic chambers 13a and 13b of the hydraulic actuator become equal, and the piston 12 is positioned in the neutral position by the biasing force of the neutral return springs 14a and 14b, and the rear wheel A fail-safe mechanism works so that the steering angles of 2a and 2b are always zero and the steering characteristics of the vehicle are in a two-wheel steering state.

The movement of the spool valve 38b in the vehicle width direction is performed by the turning ratio variable mechanism 20 which receives the rotation from the rotation transmission shaft 5b.
A description will be given in combination with the drawings. The variable steering ratio mechanism 20 includes a swing arm 22 whose base end is swingably supported by a U-shaped holder 21 via a support pin 22a, and the holder 21 is a casing fixed to the vehicle body (not shown). Above) spool valve 38b
Is rotatably supported via a support shaft 21a having a rotation axis l ₂ orthogonal to the movement axis l ₁ . The support pin 22a of the swing arm 22 is located at the intersection of the _two axes l ₁ and l ₂ and extends in a direction orthogonal to the rotation axis l ₂ and rotates the holder 21 around the support shaft 21a rotation axis l ₂ ). By rotating the support pin 22a at the tip end thereof and the moving axis l ₁ of the spool valve 38b, the swing locus surface of the swing arm 22 around the support pin 22a becomes the moving axis l _1. The angle of inclination with respect to a plane orthogonal to (hereinafter referred to as a reference plane) is changed.

Also, a ball joint is attached to the tip of the swing arm 22.
One end of the connecting rod 23 is connected to the other end of the connecting rod 23 via 23a, and the other end of the connecting rod 23 is connected to the other end of the spool valve 38b via a ball joint 23b. The spool valve 38b is displaced in the left-right direction in accordance with the displacement of the tip of the arm 22 in the left-right direction in FIG.

The connecting rod 23 has its ball joint 23a.
Is supported slidably on the rotation imparting arm 24 via a ball joint 23c at a position close to the position. The rotation imparting arm 24 is composed of a large-diameter bevel gear rotatably supported on the moving axis l ₁ via a support shaft 24a, and the bevel gear has a bevel gear attached to the rear end of the rotation transmission shaft 5b. The gear 5d is meshed with each other, and the rotation of the steering wheel 3 is transmitted to the rotation imparting arm 24. Therefore, the rotation imparting arm 24 and the connecting rod 23 rotate about the movement axis l _{1 by} an amount corresponding to the rotation angle of the steering wheel 3, and the swing arm 22 swings about the support pin 22a accordingly. When the pin 22a is moved, when the axis of the pin 22a coincides with the moving axis l ₁ of the spool valve 38b, the ball joint 23a at the tip of the swing arm 22 only swings on the reference plane, and the spool valve 38b moves. The pin 22a is held stationary, but the axis line of the pin 22a is inclined with respect to the moving axis line l _{1 so} that the swing locus surface of the swing arm 22 is displaced from the reference plane. The ball joint 23a is displaced in the left-right direction in FIG. 3 in accordance with the swing, and this displacement is caused via the connecting rod 24.
38b, the spool valve 38b moves along the moving axis l ₁ . That is, even if the swinging angle of the swinging arm 22 about the axis of the support pin 22a is the same, the displacement of the spool valve 38b in the left-right direction causes a change in the tilt angle of the pin 22a, that is, the rotation angle of the holder 21. It changes with it.

Then, in order to change the rotation angle of the holder 21, a sector gear 25a as a worm wheel is attached to the support shaft 21a of the holder 21, and a worm gear 25b is meshed with the sector gear 25a. A bevel gear 25c is mounted on the shaft of the worm gear 25b, and a bevel gear 25d mounted on the output shaft of a stepping motor 26 as an actuator is meshed with the bevel gear 25c. By rotating the sector gear 25a, the inclination angle of the holder 21 with respect to the reference plane can be changed.
The steering angle of 2a, 2b, that is, the steering ratio and the steering phase of front and rear wheels 1a, 1b, 2a, 2 are controlled. Further, on the support shaft 21a of the holder 21, a turning ratio sensor including a potentiometer as a turning ratio detecting means for detecting the turning angle of the sector gear 25a corresponding to the actual turning ratio controlled by the stepping motor 26. 27 are provided.

The control of the turning ratio and the turning phase by the stepping motor 26 is performed by a controller 33 which receives a vehicle speed signal from a vehicle speed sensor 34 and is supplied with power from a battery 31. For example, as shown in FIG. 4, when the vehicle speed is zero. The steering ratio is maximized in the opposite phase, the two-wheel steering state is achieved in the zero phase when the vehicle speed is 30 km / h, and the steering ratio is maximized in the same phase when the vehicle speed is 120 km / h.

Next, an apparatus for inspecting the four-wheel steering characteristics of a vehicle having the above-described four-wheel steering apparatus will be shown, and its structure and characteristic inspection method will be described.

FIG. 5 is a plan view showing an inspection device 40 for toe-in adjustment and four-wheel steering characteristic inspection. This device 40 includes a front wheel static tester 41 for measuring front wheel toe-in angle, steered angle, etc. A front wheel guide 43 that guides the left and right front wheels to the front wheel static tester 41, a rear wheel static tester 45 that measures the rear wheel toe-in angle, a steering angle, etc., and a rear wheel static tester 45 that guides the left and right rear wheels. The rear wheel guide 47 and the rear wheel guide 47 are arranged side by side in a line as shown in the figure. The vehicle is transported in the direction of arrow A and the front and rear wheels are guided by the front wheel and rear wheel guides 43 and 47, respectively. It is designed to be positioned above the wheel static testers 41, 45. The device 40 includes a signal sending means 105 for sending a fail signal, a vehicle speed signal, etc. to a vehicle to be inspected, and a comparison test for comparing the four-wheel steering characteristic measured by the device 40 with a preset basic characteristic. Means 100
have. Therefore, the comparison inspection means 100 is connected to the lines 100a to 100d for inputting the front and rear wheel turning angle measurement values, and the signal transmission means 105 is provided with a line 105a having a connector 105b connected to the vehicle controller. It is connected.

A front view of FIG. 6 shows the front wheel static tester 41 in detail along arrow VI-VI, and a detailed plan view of this static tester 41 is FIG. The static tester 41 consists of a pair of left and right testers that are line-symmetrical in order to measure the toe-in angle and steered angle of the left and right front wheels, as shown in the figure. Are given the same numbers, and only one of them will be described. The static tester 41 includes a full-float type turntable 50 that is mounted on a support base 41a and supports the front wheels so that they can be steered and move left and right and front and rear, and the tires of the front wheels placed on the turntable 50. Front wheel angle measuring means 60 for contacting the side surface to measure the toe-in angle, steered angle, etc. of the front wheels, and a tester moving means mounted on the support base 41a for moving the front wheel angle measuring means 60 in the vehicle width direction. Composed of 70 and. The front wheel angle measuring means 60 has a measuring plate 61 which comes into contact with the tire side surface of the front wheel, and the measuring plate 61 is brought into contact with the tire side surface of the front wheel placed on the turntable 50 by the movement by the tester moving means 70. The inclination of the measuring plate 61 is measured to measure the toe-in angle and the steered angle.

The turntable 50 will now be described in detail with reference to FIGS. 8 and 9 and the structure of the turntable 50 will be described. The turntable 50 has a frame 51 made of a plurality of members fixedly mounted on the support base 41a, and a plurality of bearings 52 are fixedly mounted on the upper surface of the frame 51 side by side on the same circumference. The bearing 52 has a rotatable ball 52a, and the ball 52a supports the table 53 so as to be rotatable and movable in the front, rear, left and right directions. This table 53
The front wheel is placed on and supports the front wheel, and front and rear guides 53a and 53b for positioning the front wheel in the front-rear direction are provided. Left and right guide plates 53b for positioning
Is provided. Further, a rotary shaft 54 extending downward from the center thereof is attached to the table 53, and an encoder 55 for detecting a rotation angle of the table 53 is attached to a lower end of the rotary shaft 55. Table on frame 51 above
Conveyor plate to smoothly convey the front wheels to 53
51b and 51b are attached with the table 53 sandwiched in the front and back. Further, a shaft holding plate 56 is disposed on the frame 51 so as to face the rotary shaft 54 so as to sandwich the rotary shaft 54 in the front-back direction and to be movable in the front-back direction.
Each of them is connected to the upper end of an arm 58 rotatably attached to 51. The lower end 58c of the arm 58 is connected to both ends of the cylinder 59.
58 is rotated so that the shaft holding plate 56 can be moved back and forth.
Approach each other and move away from each other when they shrink. FIG. 8A is a cross-sectional view of the shaft holding plates 56, 56 and the rotary shaft 54 taken along arrows VIII-VIII, and as can be seen from this figure, the end portions of the shaft holding plates 56, 56 facing each other. Is provided with a notch 56a in the shape of a right triangle, and a portion 54a of the rotary shaft 54 facing the notch 56a has a square cross section in conformity with the notch. Therefore, when the cylinder 59 is extended and both shaft holding plates 56, 56 approach, the cuts 56a, 56a
Holds the square portion 54a, and holds the rotating shaft 54 in a fixed manner. For this reason, in the above state, the table 53 also
It is fixedly held with a facing forward and backward.

Next, using FIG. 10 to FIG. 12, the front wheel angle measuring means 60
The structure of the tester moving means 70 will be described. The front wheel angle measuring means 60 extends forward on a frame 65 and has a support shaft 62 attached thereto, and a measurement plate 61 is rotatably attached to the front end of the support shaft 62 via a ball joint 62a.
Is installed. In this state, the measuring plate 61 is rotatable around the ball joint 62a, but is held vertically with respect to the frame 65 by the compression spring 63a, the tension spring 63b and the link 63c as shown in the figure. It is to be noted that such an upright state is maintained when no external force acts on the measurement plate 61, and when the measurement plate 61 receives an external force, the springs 63a and 63b are bent and the link 63c is deformed. The measuring plate 61 is rotated around the ball joint 62a according to an external force. Therefore, when the measurement plate 61 is brought into contact with the tire side surface of the front wheel, the measurement plate 61 is tilted according to the tire inclination.Therefore, if the measurement plate inclination is measured, the toe-in angle and the steering angle of the front wheel are measured. , The camber angle, etc. can be measured. In order to measure the inclination angle of the measuring plate 61, three displacement measuring devices 64 are attached to the frame 65. This displacement measuring device 64 is a probe 64a that projects forward and is movable back and forth.
And attached to the left and right and above the ball joint 62a as shown in FIG. This probe 64a measures the measurement plate 61 when the measurement plate 61 is brought into contact with the side surface of the tire.
Abutting seat 61a fixed to the
When the measuring plate 61 is tilted, a difference occurs in the amount of movement of each probe 64a in the front-back direction (the amount of movement in the displacement measuring device 64 in the front-back direction). From this difference, the toe-in angle, steering angle, camber angle Etc. can be detected. Specifically, the probes 64a of the displacement measuring device 64 arranged on the left and right of the ball joint 62a.
The toe-in angle and the steered angle can be measured from the difference in the amount of movement before and after, and the camber angle can be calculated from the average value of both the amounts of movement and the amount of movement of the displacement measuring device 64 arranged above the ball joint 62a. Can be measured. Therefore, if it is only necessary to adjust the toe-in angle and measure the steering angle as in the present invention, the ball joints 62a are arranged on the left and right sides.
Only one displacement measuring device 64 may be used. The displacement measuring device 64 and the like are covered with a cover 60a as shown by a chain double-dashed line in FIG.

The front wheel angle measuring means 60 having the above structure is supported by the tester moving means 70 via the frame 65 so as to be movable in the front-rear direction. Regarding the structure of the tester moving means 70 and the support of the front wheel angle measuring means 60 by the structure explain. The tester moving means 70 has a frame 71 fixedly mounted on the support base 41a, and a pair of left and right guide rods 72, 72 extending forward and backward by the frame 71 and a transport rod extending forward and backward between the guide rods 72, 72. 74 are supported. Two guide legs 67, 67 fixed to the lower surface of the frame 65 of the front wheel angle measuring means 60 are slidably fitted on the respective guide rods 72, whereby the front wheel angle measuring means 60 is It is supported by tester moving means 70 so as to be movable back and forth. Further, a screw is formed on the outer periphery of the transport rod 74, and the screw bush 66a of the transport leg 66 fixedly mounted on the lower surface of the frame 65 of the front wheel angle measuring means 60 is screw-engaged with the transport rod 74. There is. The transport rod 74 is rotatably supported by the frame 71, and the first sprocket 75a attached to the end of the transport rod 74 meshes with the second sprocket 75c attached to the shaft of the motor 76 via the chain 75b. By rotating the transport rod 74 by driving the motor 76, the entire front wheel angle measuring means 60 can be moved back and forth via the transport leg 66. In order to set the front and rear movement positions at this time, two limit switches 73, 73 spaced apart in the front and rear direction are attached to the frame 71 of the tester moving means 70, and the frame 65 of the front wheel angle detecting means 60 has the above-mentioned structure. A pair of switch plates 68, 6 facing the limit switch 73
8 is attached, the drive control of the motor 76 is performed by the operation of the limit switch 73 by the contact between the switch plate 68 and the limit switch 73, and the front wheel angle measuring means 60 is moved and positioned forward and backward.

Although the front wheel static tester 41 has been described above, the rear wheel static tester 45 will be described next. Similarly to the front wheel static tester 41, the rear wheel static tester 45 is composed of a pair of left and right testers, and each tester is composed of a full float type turntable 150, a rear wheel angle measuring means 160, and a tester moving means 170. There is.
The turntable 150 has a frame 151, as shown in FIG.
And a plurality of bearings (not shown) attached to the frame 151, and a table 153 rotatably supported by the bearings so as to be movable in the front, rear, left and right directions. These are turntables 50 for the front wheels. Although its shape is slightly different from the above, its function and essential structure are the same, and therefore their explanation is omitted. On the other hand, the rotary shaft 154 extending downward from the table 153 is the rotary shaft 5 of the front wheel table 53.
The extension amount to the lower side is smaller than that of 4, and only the square section 154a is provided at the lower end thereof, and an encoder for detecting the rotation of this shaft is not attached. This is because the steered angle of the front wheels is large in a four-wheel steering vehicle.
Since the turning angle cannot be measured only by itself, the front wheel angle measuring means 60 measures the turning angle within a range of ± 5 ° around the straight traveling direction with high accuracy, and the angle exceeding the above range is encoded. The measurement is made by 55, but since the steering angle of the rear wheels is within ± 5 ° centering on the straight traveling direction, it can be sufficiently measured only by the rear wheel angle measuring means 160. Is. The square cross section 154a at the lower end of the rotating shaft 154 is
A pair of shaft holding plates 156, 156 are arranged so as to sandwich the front and rear, and both shaft holding plates 156, 156 are normally expanded by a spring 157. By holding the square cross section 154a by the shaft holding plates 156, 156, the rotating shaft 15
4 is fixedly held. The rear wheel angle measuring means 160 for measuring the toe-in angle, the turning angle, etc. of the rear wheels and the tester moving means 170 for moving the rear wheel angle measuring means 160 in the vehicle width direction (left and right direction) are the front wheel static tester 41.
Since the function and the essential structure are the same as those in the case, the description thereof will be omitted.

Next, a front wheel guide that guides the front wheel and the rear wheel to the front wheel static tester 41 and the rear wheel static tester 45, respectively.
The 43 and the rear wheel guide 47 will be described. Since both guides 43 and 47 have the same shape, the front wheel guide 43 is shown in FIG. 14 and will be described based on this. The front wheel guide 43 has a pair of guide bodies 90, 90 each having a guide groove 90a for guiding the left and right front wheels toward the static tester 41, and these guide bodies 90, 90 are in the vehicle width direction (left and right direction). It is freely movable to. In addition, guide plates 91, 91 that are opened rearward in a "C" shape are attached to the guide groove 90a so as to guide the front wheel properly. Frames 96 and 97 facing the outer side surfaces of both guide bodies 90 and 90 are provided with rotatable first and second arms 92a and 92b extending rightward in the drawing.
Both arms 92a and 92b (3) are connected by a first connecting rod 93. The first arm 92a is connected to the guide body 90 that supports the right front wheel by the second connecting rod 95 as shown in the drawing.
On the frame 97 facing the outer surface of the guide body 90 that supports the left front wheel, a third arm 92c extending forward (to the left in the drawing) from the mounting portion of the second arm 92b rotates together with the second arm 92b. The third arm 92c is movably mounted, and is connected to a guide body 90 supporting the left front wheel by a third connecting rod 94 as shown in the drawing. Therefore, the first connecting rod
If 93 is moved in the vehicle width direction by a cylinder (not shown) or the like, both guide bodies 90, 90 can be moved in opposite directions in the vehicle width direction, and even if the treads of the front wheels are different, Both guides 90,90 according to the tread
The distance can be adjusted.

Further, lifters 48 and 49 for raising and supporting the vehicle body are arranged in front of and behind the front wheel guide 43 (see FIG. 5). As shown in FIG. 15 showing a cross section taken along the arrow XV-XV in FIG. 5, this lifter comprises a frame 105 and a cylinder 102 fixed to the frame 105 and extending vertically.
The rod 101 of 02 is projectable upward and has a groove 1 at its upper end.
A head 101a having 01b is attached. Therefore, when the rod 101 of the cylinder 102 is extended upward, the groove 101b of the head 101a receives the side sill of the vehicle body and lifts the vehicle body. When the front and rear wheels are placed on the full-float type turntable, when the external force is applied to the vehicle body in the horizontal direction, the turntable is moved and the vehicle body is moved, and the measurement by the front wheel and rear wheel angle measuring means becomes inaccurate. However, by supporting the vehicle body by raising it by the lifter, it is possible to prevent the vehicle body from being moved even when an external force in the horizontal direction is applied to the vehicle body. Furthermore, by lifting the vehicle body with the lifter, the weight of the vehicle body applied to the tire mounted on the turntable can be reduced, which can reduce the deformation of the tire and reduce the load on the turntable. It is made smaller so that the turntable can rotate smoothly.

A method of inspecting the four-wheel steering characteristics of a vehicle equipped with a four-wheel steering device using the above-described inspection device 40 will be described by taking the four-wheel steering vehicle shown in FIG. 2 as an example. First, the cylinders 59, 158 and 158 of the front wheel turntable 50 and the rear wheel turntable 150 are extended to extend the shaft holding plates 56, 56 and 1
After the rotary shafts 54, 154 are fixedly held by 56, 156, the vehicle is transported onto the device 40 from the right side in the drawing in FIG. 5 in the direction of arrow A, and the front and rear wheel guides 43, 47 guide the front wheels 1a, 1b and the rear wheels. The wheels 2a and 2b are placed on the front and rear wheel static testers 41 and 45, respectively. Next, the heads 101a of the lifters 48, 49 are moved upward to raise the side sill portion of the vehicle body by the heads 101a to reduce the load from the front and rear wheels to the turntables 50, 150, and to hold the vehicle body in the horizontal direction of the vehicle body by an external force. To move to.
The lifting force of the vehicle body by the lifters 48, 49 is set so that the table 53, 153 has a load enough to smoothly rotate the tables 53, 153 in accordance with the turning of the front wheels and the rear wheels. Next, the cylinders 59, 158, 158 of the front wheel turntable 50 and the rear wheel turntable 150 are contracted to release the fixed holding of the rotary shafts 54, 154 by the shaft holding plates 56, 56 and 156, 156, and the tables 53, 153 are brought into a full float state.

From this state, first, the toe-in adjustment of the front wheels and the rear wheels is performed. This toe-in adjustment is performed by steering means for the front and rear wheels.
The front and rear wheels are separately carried out in a state where the connection of the connecting means 6 of 4, 10 is released. In this case, the toe-in angle is measured by the angle measuring means 60, 160 of the front and rear wheel static testers 41, 45, and the toe-in angle when the front and rear wheels are in a straight-ahead state and the steering wheel is in a horizontal direction is a predetermined value. And the connection means 6 is then adjusted.
Although the front wheels and the rear wheels steering means are connected by means of, the description of the specific adjusting method will be omitted. The toe-in adjustment mentioned here includes not only so-called wheel toe-in adjustment but also adjustment in the toe-out direction.

After the toe-in adjustment, the four-wheel steering characteristic is inspected. The adjustment of the four-wheel steering characteristics is performed by measuring and inspecting the relationship between the steered angles of the front wheels 1a and 1b and the steered angles of the rear wheels 2a and 2b due to the operation of the steering wheel 3. However, only the method for inspecting the four-wheel steering characteristics relating to the method of the present invention will be described here. For this inspection, the steering wheel 3 is reciprocated left and right around the horizontal direction, and the front wheels 1a, 1b
Is reciprocally steered within a predetermined range around the straight traveling direction. In this case, the front wheel turning angle range may be small, for example, about ± 3 ° in this example. Since the rear wheels 2a, 2b are also steered by the steering of the front wheels, the steering angle of the front and rear wheels at this time is measured to perform the characteristic inspection. It is preferable to input a vehicle speed signal that maximizes the turning ratio to the controller 33 so that the rudder can be easily measured. Therefore, the connector 105b of the signal transmission means 105
Is connected to the controller 33 in place of the vehicle speed sensor of the vehicle to be inspected, and a vehicle speed signal (corresponding to a vehicle speed of 0 Km / H or 120 Km / H that maximizes the turning ratio from this signal transmission means 105 via the line 105a. The vehicle speed signal) is sent to the controller 33.

The steering angle of the front wheels and the rear wheels when the front wheels are steered by operating the steering wheel under the above conditions, the angle measuring means 60,16 of the front wheel and rear wheel static testers 41,45
Measured by 0. An example of this measurement result is shown in which the vertical axis represents the rear wheel steering angle and the horizontal axis represents the front wheel steering angle.
As shown by the solid line in the graph of Fig. 16, a locus with constant hysteresis is obtained. The reason why the locus having hysteresis is obtained is that there is backlash in the connection system between the front wheel steering means and the rear wheel steering means. In this case, the adjustment of the rear-wheel steering angle when the front-wheel steering angle is zero is based on the steering of either the left or right direction of the front wheels. Since the steered angle of the rear wheels is deviated and the running stability is impaired, in the present invention, the curve β representing the midpoint of both trajectories is the origin on the graph in the comparison inspection means 100 that receives the measurement signal. It is configured to detect whether or not the vehicle passes. That is, it is inspected whether or not the trajectory curve obtained by turning the steering wheel to the right and the trajectory curve obtained by turning the steering wheel to the left are substantially point-symmetrical with respect to the origin. Then, the rear wheel steering means is adjusted so that the curve β passes through the origin.

In addition, in the vehicle using the four-wheel steering means shown in FIGS. 2 and 3, the neutral return springs 14a, 14b are pre-compressed, so that the rear wheels 2a, 2b are in the straight traveling position (the steering angle is When the steering wheel is steered to the left or right from the zero position, the trailing curve is almost zero in the dead zone where the rear wheels are not steered relative to the steered front wheels (the front wheel steering angle in the graph is zero). (Horizontal part) occurs. Therefore, for example, the front wheel steering angles α ₁ and α ₂ when this dead zone occurs are read, and whether or not the median value of both the steering angles α ₁ and α ₂ becomes zero, that is, both dead zones are centered on the origin. It may be possible to inspect whether or not it is a point target.

In the above description, the method for inspecting the four-wheel steering characteristic has been described by taking a vehicle having an electrohydraulic four-wheel steering mechanism that controls the steering ratio and the steering phase according to the vehicle speed as an example. Is not limited to this, the same applies to a vehicle having a mechanical mechanism that mechanically transmits the steering of the front wheels to the rear wheels and controls the steering of the rear wheels according to the steering of the front wheels. is there.

(Effects of the Invention) As described above, according to the present invention, the front wheels are steered by operating the steering wheel or the like and the rear wheels are accordingly steered, and the front wheels are steered to one axis of the orthogonal coordinates. Angle is shown and the rear wheel turning angle is shown on the other axis, and the characteristics of the turning angle change of the rear wheels with respect to the turning angle change of the front wheels are shown on the coordinates, and the above characteristics when the front wheels are turned to the right And the curve representing the above characteristics when the front wheels are steered to the left are inspected to see if they are substantially point-symmetrical with respect to the origin of coordinates, and the front wheel steering angle is zero. In other words, when the front wheels face straight ahead, it is possible to reliably check whether the steering angle of the rear wheels is zero in consideration of the backlash of the steering transmission system.
In a vehicle having a wheel steering device, it is possible to inspect whether or not the rear wheels are properly steered by following the operation of the steering wheel in the left-right direction, and in response to this inspection, the four-wheel steering device Can be adjusted to improve the feeling of four-wheel steering with respect to the left and right operations of the steering wheel.

[Brief description of drawings]

1 is a plan view schematically showing a vehicle four-wheel steering system, FIG. 2 is a schematic plan view of the four-wheel steering system, FIG. 3 is a perspective schematic view showing a turning ratio varying mechanism, and FIG. A graph showing the relationship between the vehicle speed and the turning angle, Fig. 5 is a plan view showing the inspection device, Figs. 6 and 7 are front views and plan views of the front wheel static tester, and Figs. 8 and 9 are front wheels. FIG. 8A shows a front wheel angle measuring means and a tester moving means, and FIG. 8A shows a sectional view showing the turntable along arrow VIII-VIII. Front view, plan view and side view, FIG. 13 is a front view showing a turntable for rear wheels, FIG. 14 is a plan view showing a front wheel guide, FIG. 15 is a sectional view showing a lifter, and FIG. 16 is a front view. It is a graph which shows an example of the measurement result of the rear wheel turning angle change with respect to the wheel turning angle. 4 ... Front wheel steering means, 6 ... Connecting means 10 ... Rear wheel steering means, 14a, 14b ... Neutral return spring 20 ... Steering ratio variable mechanism, 26 ... Stepping motor 27 ... Steering ratio sensor , 33 …… Controller 34 …… Vehicle speed sensor, 38 …… Control valve 40 …… Inspection device, 41,45 …… Static tester 43,47 …… Guide, 48,49 …… Lifter 50,150 …… Turntable, 60,160… … Angle measuring means 70,170 …… Tester moving means

Claims (1)

[Claims] 1. A method for inspecting a four-wheel steering characteristic of a vehicle having a four-wheel steering device in which rear wheels are steered in accordance with steering of front wheels, the front wheels being reciprocally steered left and right. At this time, the steering angles of the front wheels and the rear wheels are measured, and the front wheel steering angle is shown on one axis of the orthogonal coordinates and the rear wheel steering angle is shown on the other axis of the rear wheels with respect to the change in the front wheel steering angle. The characteristic of the change in the turning angle is represented on the coordinates, and the curve representing the above characteristics when the front wheels are steered to the right and the curve representing the above characteristics when the front wheels are steered to the left are the coordinate origin. A method for inspecting a four-wheel steering characteristic of a vehicle, characterized in that it is inspected whether or not it is substantially point-symmetrical with respect to.