JP2538225B2 - Vehicle 4-wheel steering characteristics inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a four-wheel steering system in which the rear wheels can also be steered according to the steering angle of the front wheels and the vehicle speed by operating the steering wheel. More specifically, the present invention relates to a vehicle having a four-wheel steering system including a fail-safe mechanism that holds the rear wheels in a straight-ahead direction and holds them in a two-wheel steering state when a malfunction occurs in the rear-wheel steering means. The present invention relates to a method for inspecting the operating characteristics of the fail-safe mechanism in.

(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 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, and the steered ratio is adjusted according to the vehicle speed, the steered angle of the front wheels, and the like. 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. In such a four-wheel steering system, when the rear wheel steering means malfunctions, running stability and maneuverability are significantly impaired, which is dangerous. Therefore, when the rear wheel steering means malfunction is detected, Is often provided with a fail-safe mechanism that holds the rear wheels in a straight-ahead direction and brings the vehicle into a two-wheel steering state.

(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 characteristic, the inspection of the operating characteristics of the fail-safe mechanism is insufficient only by the conventional adjustment, and the running stability of the vehicle cannot be sufficiently guaranteed as it is. It is necessary to inspect the operating characteristics of.

The operation characteristic of the fail-safe mechanism is inspected by operating the fail-safe mechanism in a state where the rear wheels are sufficiently steered and checking whether or not the rear wheels correctly return to the straight traveling direction.

However, in the case where the rear wheel steering means for steering the rear wheels based on at least the front wheel steering angle and the vehicle speed is provided as described above, in order to steer the rear wheels sufficiently, the front wheels are simply steered. In addition to driving the vehicle, the vehicle must be brought to a predetermined vehicle speed state. Therefore, when inspecting the operating characteristics of the fail-safe mechanism, the vehicle must be actually driven (the wheels are actually rotated) and the inspection must be performed. In addition, there is a problem that it is not realistic because the time and labor required for the inspection increase significantly.

(Means for Solving the Problems) In view of the problems in the conventional method as described above, the present invention
The present invention is intended to solve the above problems by providing a method capable of accurately, easily, and quickly inspecting the characteristics of a wheel steering device, particularly the operation characteristics of a fail-safe mechanism. The inspection method of (1) is a front wheel steering means for steering the front wheels, a rear wheel steering means for steering the rear wheels according to the front wheel steering angle and the vehicle speed, and a malfunction of the rear wheel steering means. When a steering wheel is detected, a four-wheel steering characteristic of a vehicle having a four-wheel steering device including a fail-safe mechanism for stopping the steering of the rear wheels by the rear-wheel steering means and holding the rear wheels in the straight traveling direction is provided. A method of inspecting, in which the front wheels are steered by operating the steering wheel, etc., and the pseudo vehicle speed signal is input to the rear wheel steering means to steer the rear wheels, after which an operation failure signal is sent to the fail safe mechanism. Don't send To is configured to inspect the return to the straight direction of the rear wheel by the operation of the fail-safe mechanism.

(Operation) By using the above method, the operation confirmation of the fail-safe mechanism in the event of malfunction of the four-wheel steering device can be reliably grasped, and the running safety of the vehicle having the four-wheel steering device can be improved. It can be easily confirmed.

Further, in the case where the rear wheel steering means for steering the rear wheels based on at least the front wheel steering angle and the vehicle speed is provided, the front wheels should be largely steered and a predetermined vehicle speed condition should be taken when inspecting the fail-safe mechanism. As a result, it is necessary to sufficiently steer the rear wheels, but in the present invention, since the predetermined vehicle speed state is obtained by inputting the pseudo vehicle speed signal to the rear wheel steering means as described above, it is necessary to inspect the fail safe mechanism. It can be performed very easily and quickly without actually driving the vehicle.

(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, 5
The steering phase and the steering ratio are variably controlled according to the steering amount, the vehicle speed signal input from the vehicle speed sensor, etc. based on the steering phase and the steering ratio. When the rear wheels 2a, 2b are controlled to be steered by the rear wheel steering means 10 so that four-wheel steering is performed, the operating condition of the rear wheel steering means 10 is checked, and if a malfunction occurs, Is equipped with a fail-safe mechanism that holds the rear wheels in a straight ahead direction. 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 an operation inspection of the fail-safe mechanism of the four-wheel steering device will be schematically described. In order to perform this characteristic inspection, first, the steering wheel 3 is operated to steer the left and right front wheels 1a, 1b by the front wheel steering means 4, and the steering of the front wheels 1a, 1b is connected by the connecting means 6. The rear wheels 2a, 2b are also steered by transmitting them to the rear wheel steering means 10 via the transmission bodies 5a, 5b. After that, when a signal for operating this mechanism to the fail-safe mechanism of the rear wheel steering means 10, for example, an operation failure signal is input, the fail-safe mechanism operates and the rear wheels are steered so as to face the straight traveling direction. The presence or absence of steering in the straight ahead direction and whether or not the rear wheels have been steered correctly in the straight ahead direction are inspected.

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

FIG. 2 is a schematic plan view showing an example of the four-wheel steering device. The front wheel turning means 4 includes a front wheel turning rod 4a having a first rack meshing with a first pinion 3a formed at a lower end of the steering wheel 3, tie rods 4b, 4b connected to both ends of the rod 4a, Knuckles 4c, 4c connected to the outer ends of the tie rods 4b, 4b, the front wheel steering rod 4a is moved in the vehicle width direction according to the operation of the steering wheel 3, and this movement is performed via the tie rods 4b, 4b. Knuckle 4c,
It is transmitted to 4c and the front wheels 1a and 1b are steered. The front wheel steering rod 4a is formed with a second rack that meshes with a second pinion 5c provided at the front end of a rotation transmission shaft (transmission body) 5a, and the front wheel steering rod 4a is operated by operating the steering wheel 3. Is moved in the vehicle width direction, the rotation transmission 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 includes a rear wheel steering rod 15 extending in the vehicle width direction, tie rods 16, 16 connected to both ends of the rod 15, and an outer end of the tie rods 16, 16. Knuckles 17 and 17 having a knuckle arm that is provided and rotatably supporting the rear wheels 2a and 2b. 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 fixed to the vehicle body and movably supporting the rear wheel steering rod 15 in the vehicle width direction, and an inner space of the cylinder 11 is divided into two parts. A hydraulic actuator composed of a fixed piston 12 slidable in the cylinder 11 and neutral return springs 14a, 14b arranged in left and right hydraulic chambers 13a, 13b defined by the piston 12 is mounted. ing. Hydraulic lines 39a, 39b from a control valve 38 are connected to the left and right hydraulic chambers 13a, 13b of the hydraulic actuator, and the hydraulic actuator is operated by the hydraulic pressure supplied from the control valve 38, whereby the rear wheel steering rod 15 in the vehicle width direction is operated. Is performed, whereby 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. The control valve 38 is of a known spool valve type, and has a cylindrical valve housing 38a integrally connected to the rear wheel steering rod 15 via an arm 15a, and is fitted in the valve housing 38a. And a hydraulic chamber 13a of a hydraulic actuator that moves the valve housing 38a together with the rear wheel steering rod 15 following the movement of the spool valve 38b in the vehicle width direction in accordance with the movement of the spool valve 38b in the vehicle width direction. 13b is selectively supplied with hydraulic pressure. That is, by moving the spool valve 38b in the vehicle width direction, the spool valve 38b follows the spool valve 38b and the rear wheel steering rod 1
5 is moved and the rear wheels are steered.

Further, the hydraulic lines 39a and 39b are respectively the hydraulic lines 3
The valve is connected to a normally closed fail-safe solenoid valve 37 through 7a and 37b.
When this valve 37 is opened by energizing 37c, the hydraulic pressures in both hydraulic chambers 13a, 13b of the hydraulic actuator become equal, and the pinion 12 is moved to the neutral position by the urging force of the neutral return springs 14a, 14b. 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 that receives the rotation from the rotation transmission shaft 5b. explain. 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 38
It is rotatably supported via a support shaft 21a having a rotation axis l ₂ orthogonal to the movement axis l _{1 of} b. 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.

One end of the connecting rod 23 is connected to the tip end of the swing arm 22 via a ball joint 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 end of the swing arm 22 in the left-right direction in FIG.

The connecting rod 23 has its ball joint 23.
The rotation imparting arm 24 is slidably supported at a portion close to a via a ball joint 23c. 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 moving axis l _{1 by} an amount corresponding to the rotation angle of the steering wheel 3, and the swinging arm 22 moves around the support pin 22a accordingly. When the pin 22a is swung, and 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 Is held stationary, but if the axis of the pin 22a is tilted with respect to the movement axis l _{1 and} the swing locus surface of the swing arm 22 deviates from the reference plane, the swing arm 22 centered around this pin 22a The ball joint 23a is displaced in the left-right direction in FIG. 3 in accordance with the swing of the spool valve 38a through the connecting rod 24.
is transmitted to b, the spool valve 38b is moved along the movement axis l _1. That is, even if the swing angle of the swing 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 is caused by the change in the inclination angle of the pin 22a, that is, the change in 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 to operate the stepping motor 26. By turning the sector gear 25a, the tilt angle of the holder 21 with respect to the reference plane is changed to change the turning angle of the rear wheels 2a, 2b, that is, the turning ratio and the turning phase of the front and rear wheels 1a, 1b, 2a, 2b. Control. Further, a turning ratio sensor comprising a potentiometer as turning ratio detecting means for detecting a turning angle of the sector gear 25a corresponding to an actual turning ratio controlled by the stepping motor 26 is provided on the support shaft 21a of the holder 21. 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 transfer 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 performing toe-in adjustment and four-wheel steering characteristic inspection.
After measuring the front wheel static tester 41 that measures the front wheel toe-in angle and the steered angle, the front wheel guide 43 that guides the left and right front wheels to the front wheel static tester 41, and the rear wheel toe-in angle and the steered angle. The wheel static tester 45 and the rear wheel guides 47 that guide the left and right rear wheels to the rear wheel static tester 45 are arranged side by side in a line as shown in the figure, and convey the vehicle in the direction of arrow A. The front and rear wheels are guided by front and rear wheel guides 43 and 47, respectively, and are positioned above the front and rear wheel static testers 41 and 45. The device 40 includes a signal sending means 105 for sending a fail signal, a pseudo vehicle speed signal, etc. to a vehicle to be inspected and a four-wheel steering characteristic measured by the device 40 for comparison with a preset basic characteristic. Inspection means
Have 100. 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. This static tester 41 is composed of a pair of testers which are symmetrical to the left and right to measure the toe-in angle and the steering angle of the left and right front wheels as can be seen from 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. 70
It is composed of The front wheel angle measuring means 60 has a measuring plate 61 abutting on the tire side surface of the front wheel, and the tester moving means 70
The measurement plate 61 is brought into contact with the side surface of the tire of the front wheel placed on the turntable 50 by the movement by, and the inclination of the measurement plate 61 is measured to measure the toe-in angle and the steering 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 composed of a plurality of members fixed to the support base 41a.
A plurality of bearings 52 are fixedly arranged on the upper surface of the above so as to be lined up on the same circumference. This bearing 52 is a rotatable ball 52a
The table 53 is supported by the ball 52a so as to be rotatable and movable back and forth and left and right. The table 53 has front wheels placed thereon to support it, and front and rear guides 53a, 53a for positioning the front wheels in the front-rear direction.
The left and right guide plates 53 that are provided with the front wheel and contact the inner surface of the front wheel to position the front wheel in the width (left and right) direction.
b 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. Conveying plates 51b, 51b for smoothly conveying the front wheels to the table 53 are attached to the frame 51 with the table 53 sandwiched in front and rear. Further, on the frame 51, shaft holding plates 56, 56 are disposed so as to face each other so as to sandwich the rotary shaft 54 in the front and back and to be movable in the front and back. The shaft holding plates 56, 56 have a central portion 58a in the frame 51. Each of them is connected to an upper end of an arm 58 rotatably attached to the. The lower end 58c of the arm 58 is the cylinder 59
Are connected to both ends of the cylinder 59, and the arm 58 is rotated by the expansion and contraction of the cylinder 59 to move the shaft holding plate 56 back and forth.
6 approach each other and move away from each other when contracted. 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, the cylinder 59
When the shaft holding plates 56, 56 are extended and the shaft holding plates 56, 56 approach, the cuts 56a, 5
6a holds the square portion 54a and holds the rotating shaft 54 in a fixed manner. Therefore, in the above state, the table 53 also
53a is fixed and held with the front and rear facing.

Next, the front wheel angle measuring means 60 will be described with reference to FIGS.
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 measurement plate 61 is rotatable around the ball point 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 should be noted that the measurement plate 61 is held in the upright state 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 bend and the link 63c deforms. The measurement plate 61 is turned around a ball joint 62a in response 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.
As shown in FIG. 12, they are attached to the left, right, and above the ball joint 62a. This probe 64a
Is the measuring plate when the measuring plate 61 is in contact with the side of the tire.
When the measurement plate 61 is inclined, the amount of movement of each probe 64a in the front-rear direction (fore-and-aft movement in the displacement measurement device 64) is provided. amount)
, A toe-in angle, a steering angle, a camber angle, and the like can be detected from the difference. Specifically, the toe-in angle and the steering angle can be measured from the difference in the amount of movement of the probe 64a before and after the probe 64a of the displacement measuring device 64 disposed on the left and right sides of the ball joint 62a. The camber angle can be measured from the displacement of the displacement measuring device 64 disposed above the ball joint 62a. For this reason,
If only the toe-in angle is adjusted and the steered angle is measured as in the present invention, only two displacement measuring devices 64 arranged on the left and right sides of the ball joint 62a may be used. The displacement measuring device 64 and the like are covered by the cover 60 as shown by the chain double-dashed line in FIG.
covered by a.

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 is a frame 71 fixed on the support base 41a.
The frame 71 supports a pair of left and right guide rods 72, 72 extending in the front-rear direction and a transport rod 74 extending between the guide rods 72, 72 in the front-rear direction. On each guide rod 72, two guide legs 67, 67 fixedly mounted on the lower surface of the frame 65 of the front wheel angle measuring means 60 are slidably fitted respectively, whereby the front wheel angle measuring means 60 The tester moving means 70 supports the front and rear movably.
Further, a screw is formed on the outer periphery of the transfer rod 74, and a screw bush 66a of a transfer leg 66 fixed to the lower surface of the frame 65 of the front wheel angle measuring means 60 is screw-engaged with the transfer rod 74. I have. The transport rod 74 is rotatably instructed by the frame 71, and is also attached to the end of the first rod.
The sprocket 75a is meshed with the second sprocket 75c mounted on 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 6 facing the limit switch 73
8, 68 are 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 also includes a pair of left and right testers, and each tester includes a full float turntable 150, a rear wheel angle measuring unit 160, and a tester moving unit 170. I have. As shown in FIG. 13, the turntable 150 includes a frame 151, a plurality of bearings (not shown) attached to the frame 151, and a table 153 supported by the bearings so as to be rotatable and movable back and forth and left and right. Although these have a slightly different shape from the front wheel turntable 50, their functions and essential structures are the same, and therefore their explanations are omitted. On the other hand, the rotary shaft 154 extending downward from the table 153 has a smaller downward extension amount than the rotary shaft 54 of the front wheel table 53, and has a square cross section 154a at the lower end thereof to rotate the shaft. The encoder that detects is not installed. This is because the steered angle of the front wheels is large in a four-wheel steered vehicle,
Since the turning angle cannot be measured only with 60, the turning angle within a range of ± 5 ° centering on the straight traveling direction is accurately measured by the front wheel angle measuring means 60, and the angle exceeding the above range is measured. The encoder 55 makes the measurement by the encoder 55. However, since the steering angle of the rear wheels is within ± 5 ° centering on the straight traveling direction, the rear wheel angle measuring means 160 alone is sufficient for the measurement. Because you can. The pair of shaft holding plates 156, 156 are arranged so that the square cross section 154a at the lower end of the rotary shaft 154 is sandwiched in the front and rear.
The shaft holding plates 156, 156 are normally expanded by a spring 157, but the shaft holding plates 156, 1 are pushed by the cylinders 158, 158 arranged in front and rear.
By holding the square cross section 154a by 56,
The rotating shaft 154 is fixedly held. Rear wheel angle measuring means 160 for measuring the toe-in angle, steering angle, etc. of the rear wheels
The function and the essential structure of 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 same as those of the front wheel static tester 41, and the description thereof will be omitted.

Next, the front wheel guide 43 that guides the front and rear wheels to the front wheel static tester 41 and the static tester 45, respectively.
The rear wheel guide 47 will be described. Both these guides
Since 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. On the frames 96 and 97 facing the outer surface side of both guide bodies 90 and 90, a rotatable first member extending rightward in the drawing is provided.
An arm 92a and a second arm 92b are attached, and both arms 92a and 92b are connected by a first connecting rod 93. Also, the first arm 92a is connected to the second connecting rod 9 as shown.
A frame 97 connected to the guide body 90 supporting the right front wheel by 5 and facing the outer surface of the guide body 90 supporting the left front wheel.
A third arm 92c extending forward from the mounting portion of the second arm 92b (to the left in the figure) is rotatably attached to the second arm 92b integrally with the second arm 92b. As described above, the third connecting rod 94 is connected to the guide body 90 that supports the left front wheel. Therefore, if the first connecting rod 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. Even if the treads are different, the distance between the guide bodies 90, 90 can be adjusted according to the treads.

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 is capable of projecting upward, and a head 101a having a groove 101b is attached to the upper end thereof. 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 for 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 second.
The four-wheel steering vehicle shown in the figure will be described as an example. First,
After the cylinders 59, 158, 158 of the front wheel turntable 50 and the rear wheel turntable 150 are extended and the rotating shafts 54, 154 are fixed and held by the shaft holding plates 56, 56 and 156, 156, the device 40 is placed on the right side in FIG. The vehicle is transported in the direction of arrow A, and the front wheels 1a, 1b and the rear wheels 2a, 2b are placed on the front and rear static testers 41, 45 by the front and rear wheel guides 43, 47, respectively. Next, the heads 101a of the lifters 48 and 49 are moved up to move the heads 101a.
By a, the side sill portion of the vehicle body is lifted to reduce the load from the front and rear wheels to the turntables 50 and 150, and the vehicle body is held to prevent the vehicle body from moving in the horizontal direction due to an external force. 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. Then, 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 separately for the front and rear wheels in a state where the connection of the front wheel and rear wheel steering means 4 and 10 by the connection means 6 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 oriented straight and the steering wheel is oriented horizontally is a predetermined value. After that, the front wheel and the rear wheel turning means are connected by the connecting means 6, but the description of the specific adjusting method is omitted. The toe-in adjustment 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 operation of the fail-safe mechanism relating to the method of the present invention will be described here. For this inspection, first, the steering wheel 3 is steered largely to the left or right, and the front wheels and the rear wheels are steered as much as possible.
To do this, the front wheels are steered to the maximum steering angle, and the pseudo vehicle speed signal that maximizes the steered angles of the rear wheels (for example, a pseudo vehicle speed signal corresponding to a vehicle speed of 0 Km / H or 120 Km / H). To the controller 33. This pseudo vehicle speed signal is sent by connecting the connector 105b of the signal sending means 105 to the controller 33 in place of the vehicle speed sensor 34 of the vehicle to be inspected, and sending the pseudo vehicle speed signal from the signal sending means 105 through the line 105a. This is performed by sending it to the controller 33. At this time, the turning angles of the front wheels and the rear wheels are measured by the front and rear static testers 41 and 45.
In this case, since the front wheels are steered beyond the measurement range of the front wheel angle measuring means 60, the steering angle is measured by the encoder 55 attached to the lower end of the rotary shaft 54 of the turntable 50, and the rear wheels are The steered angle is measured by the rear wheel angle measuring means 160.

Then, the solenoid 37c of the fail-safe solenoid valve 37 in the rear wheel steering means 10 of the four-wheel steering vehicle is energized to open the solenoid valve 37. That is, the fail safe mechanism is activated. In this case,
The controller 33 sends a fail signal from the signal sending means 105 connected to the controller 33 to the controller 33.
The solenoid valve 37 is opened by 33. When the solenoid valve 37 is opened, the hydraulic pressures in both hydraulic chambers 13a and 13b of the hydraulic actuator become equal as described above, and the piston 12 is positioned at the neutral position by the biasing force of the neutral return springs 14a and 14b. Should be in the straight traveling state (the steering angle is zero), so that this is detected by the rear wheel angle measuring means 160, and the fail-safe mechanism operates in the comparison inspection means 100 receiving this detection signal. Inspect whether there is.

(Effects of the Invention) As described above, according to the inspection method of the present invention, the front wheels are steered and the rear wheels are steered by operating the steering wheel, and thereafter, the fail signal (operation) is sent to the fail safe mechanism. A failure signal) is sent to check the return of the rear wheels to the straight traveling direction due to the operation of the fail-safe mechanism. The operation confirmation can be reliably grasped, and the traveling safety of the vehicle having the four-wheel steering device can be easily confirmed. Further, in the case where the rear wheel steering means for steering the rear wheels based on at least the front wheel steering angle and the vehicle speed is provided, the front wheels should be largely steered and a predetermined vehicle speed condition should be taken when inspecting the fail-safe mechanism. As a result, it is necessary to sufficiently steer the rear wheels, but in the present invention, since the predetermined vehicle speed state is obtained by inputting the pseudo vehicle speed signal to the rear wheel steering means as described above, it is necessary to inspect the fail safe mechanism. It can be performed very easily and quickly without actually driving the vehicle.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a four-wheel steering system for a vehicle, FIG. 2 is a plan schematic view of the four-wheel steering system, and FIG. 3 is a perspective schematic view showing a turning ratio varying mechanism. Is 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 A front sectional view and a side view showing a turntable for the front wheels, FIG. 8A is a sectional view showing the turntable along the arrow VIII-VIII, and FIGS. 10 to 12 show front wheel angle measuring means and tester moving means. Front view, plan view and side view, FIG. 13 is a front view showing a rear wheel turntable, FIG. 14 is a plan view showing a front wheel guide, and FIG. 15 is a sectional view showing a lifter. 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)

(57) [Claims] A front wheel steering means for steering a front wheel;
When the rear wheel steering means for steering the rear wheels in accordance with the front wheel steering angle and the vehicle speed and the malfunction of the rear wheel steering means are detected, the rear wheels are steered by the rear wheel steering means. A method for inspecting a four-wheel steering characteristic of a vehicle having a four-wheel steering device including a fail-safe mechanism for stopping the suspension and holding the rear wheel in a straight traveling direction, comprising: steering front wheels; After inputting a pseudo vehicle speed signal to the rear wheel to steer the rear wheels, the fail-safe mechanism is activated, and the return of the steered rear wheels in the straight traveling direction is inspected. Method for inspecting steering characteristics of four wheels of a vehicle.