JPH05213029A - Caster angle control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent steering response from changing, even if the center of gravity of a body changes due to the control of a caster angle, by setting the caster angle in such a way as offsetting a pneumatic trail change generated depending upon a difference in the center of gravity, on the basis of information from a gravity center information detecting means. CONSTITUTION:A controller 26 takes in information from a body gravity center sensor 29F, and controls an actuator 25. This actuator 25 drives each slider plate 13 in a front and a rear direction, and a caster angle is so set as to offset a change in pneumatic trail. As a result, a change in the magnitude of a steering force does not occur very much, and steering response can be kept approximately constant, even when there occurs a change in the center of gravity of a body and in a longitudinal force acting on wheels due to a phenomenon such as a change in driving and braking forces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a caster angle in a vehicle suspension, and more particularly to a caster for a vehicle which can control the caster angle so that a pneumatic trail change does not occur much in response to a change in vehicle weight. The present invention relates to a corner control device.

[0002]

2. Description of the Related Art In automobiles, it is known that the running characteristics of the vehicle can be changed by adjusting the alignment of the suspension, and the caster angle (hereinafter also simply referred to as the caster) which is one of the suspension elements.
Is also proposed to improve the running performance of the vehicle.

The caster angle affects the straight running stability and steering performance of the vehicle. Generally, for example, when the caster angle is small, the steering force required for steering is large, and when the caster angle is large, the steering force required for steering is small.

[0004]

By the way, it is known that when the vehicle weight changes due to a change in the weight loaded on the vehicle, the feeling of steering force (steering response) also changes. For example, when the vehicle weight increases, the vehicle height becomes lower, and the steering feel is reduced. Such a change in steering response in the same vehicle is not preferable in terms of driving feeling.

The present invention has been devised in view of the above problems, and provides a caster angle control device for a vehicle in which the steering response does not change even if the vehicle weight changes due to the control of the caster angle. The purpose is to do.

[0006]

Therefore, the caster angle control device for a vehicle according to the present invention has a caster angle adjusting mechanism capable of adjusting the caster angle by driving the constituent elements of the suspension of the vehicle, and the traveling of the vehicle. The caster angle is set according to the state, and the control unit controls the caster angle adjusting mechanism so that the caster angle of the vehicle takes the set caster angle, and detects a change in the vehicle weight of the vehicle. With the possible vehicle weight information detecting means, the control means,
It is characterized in that the caster angle is set so as to cancel the change of the pneumatic trail caused by the change of the vehicle weight based on the information from the vehicle weight information detecting means.

[0007]

In the above-described caster angle control device for a vehicle of the present invention, the control means, based on the information from the vehicle weight information detecting means, controls the caster so as to cancel the change of the pneumatic trail caused by the change of the vehicle weight. The angle is set, and the caster angle adjustment mechanism is controlled so that the set caster angle is obtained. Therefore, the trail of the wheels is kept substantially constant.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A caster angle control device for a vehicle as an embodiment of the present invention will be described below with reference to the drawings.
2 is a block diagram showing the configuration of essential parts thereof, FIG. 2 is a perspective view showing a suspension provided with the caster angle adjusting mechanism, FIG. 3 is an exploded perspective view showing the caster angle adjusting mechanism, and FIG. 4 is a view showing the caster angle adjusting mechanism. FIG. 5 is a hydraulic circuit configuration diagram, FIG. 5 is a flow chart for explaining the operation, and FIGS.
FIG. 13 is a schematic side view of a wheel portion for explaining the operation, and FIG. 14 is a schematic plan view of the wheel portion for explaining the operation.

First, the suspension of a vehicle equipped with the present device will be described. The suspension of this embodiment is a strut-type front suspension for passenger cars, as shown in FIG.
As is well known, each is configured by combining a coil spring 3 with a shock absorber 2, and the heads of the struts 1 and 1 are fixed to the vehicle body 4 side. A front wheel 7 is rotatably attached to the lower ends of the struts 1, 1 via a knuckle 5 and a hub 6.

The lower end of the strut 1 is connected via a lower arm 8 to a cross member 9 provided between the front wheels so as to also serve as a sub-frame, and the shock absorber 2 is used as a part of a suspension link. Is composed of. Incidentally, 10 is a center member provided on the cross member 9, and 11 is a disc brake.

Then, the caster angle can be freely adjusted by sliding the heads 1A and 1A on the mounting portions of the heads 1A and 1A of the struts 1 and 1 in the front-rear direction of the vehicle body 4, respectively. Mechanisms 12 and 12 are provided. In addition, 27 is a drive shaft and 28 is a stabilizer. This caster angle adjusting mechanism 12, 12
Each of the wheels has the same structure, and as shown in FIG. 3, the slide base 14 attached to the vehicle body 4 side of the upper surface of the strut tower and the slide base 14 attached to the upper end of the strut 1 with respect to the slide base 14. And a slide plate 13 that can slide.

The slide base 14 has a structure in which a substantially rectangular through hole 16 parallel to the longitudinal direction of the vehicle body is provided in the center of a plate member 15 whose longitudinal side faces the longitudinal direction of the vehicle body. A pair of rail portions 17, 17 formed of walls having a substantially triangular cross section are erected in parallel on the entire two sides corresponding to the vehicle width direction side of 16. The rail portions 17, 17 are arranged inward, and the head portion 1A of the strut 1 penetrates between the rail portions 17, 17 facing each other and the inside of the through hole 16. In addition, 17a is a rib for supporting the rail portion 17.

On the other hand, the slider plate 13 has a substantially rectangular plate member 18 having a size corresponding to the distance between the rail portions 17 of the slide base 14, and two parallel sides of the plate member 18 on the rail portion side. The rail part 17 provided on the whole,
17 and sliding wall portions 19, 19 each having a wedge shape that can be inserted and inserted. The sliding wall portions 19 and 19 have a wedge-shaped cross section, and for example, a symmetrical triangular wall having a side of the plate member 18 as a top is integrally provided on a side portion of the plate member 18. The slide plates 13 are in slidable contact with the rails 17, 17 without rattling.
The rails 17, 17 are guided between the rails 17 and 17 so that they can slide in a fixed direction.

A needle roller bearing 20 having, for example, a plurality of roller bearings arranged in parallel is interposed between each sliding wall portion 19 and the rail portion 17 facing the sliding wall portion 19 along the sliding direction, and the slider plate 13 is provided. Is stabilized along the longitudinal direction of the vehicle body so that it can slide smoothly. Further, in FIG. 3, reference numeral 21 denotes a bearing rolling surface provided on each of four outer surfaces of the sliding wall portion 19, which is a rectangular recess.

The upper end of the strut 1 penetrates the slide base 14 and is fitted into a circular opening 13a provided at the center of the slide plate 13. Further, while fixing holes 22 and 22 are provided in front of and behind the opening 13a, a pair of (two) mounting bolts 23 and 23 are projectingly provided on, for example, an insulator portion 1a of the head 1A of the strut 1 to fix the fixing holes 22 and The head portion 1A of the strut 1 is integrated with the slider plate 13 by fastening these mounting bolts 23, 23 to each other. As a result, the casters of the front suspension can be changed by sliding the slider plate 13 in the front-rear direction.

Reference numeral 24 denotes a nut for fastening the strut head. And such a slide mechanism 1
An actuator (driving device) 25 for moving the strut head in the vehicle front-rear direction is directly connected to each of the slide plates 13 and 12. As the actuator 25, for example, as shown in the figure, a hydraulic cylinder 25B is a hydraulic pressure supply / discharge system 2 having a hydraulic switching valve such as a solenoid valve.
A hydraulic type that is driven through 5A is conceivable.

In this case, for example, a hydraulic circuit configuration as shown in FIG. 4 can be considered. 4, 25a is a tank for storing hydraulic oil, 25b is a pump, 25c is a pump accumulator, 25d and 25e are main accumulators, 25f is a filter, 25g is a relief valve, 25
h is a check valve, 25i, 25j, 25k, 25l
Is a control valve, 25m and 25n are position sensors, and other symbols are the same as those described above.

A controller (consisting of a microcomputer and its peripheral circuits) 26 as control means is connected to the actuator 25, and the controller 26 operates the actuator 25 based on information information from various sensors 29. To adjust the caster angle. That is, as shown in FIG.
The controller 26 includes correction amount setting units 26B, 26C and 26E for setting a correction amount relating to a control amount for each wheel,
A pneumatic trail change calculation unit 26G that calculates the pneumatic trail change ΔN ₀ , a pneumatic trail change correction amount setting unit 26H that sets the pneumatic trail change correction amount ΔN ′, and these calculation units 26
G, correction amount setting unit 2 for setting a correction amount for the control amount for each wheel from the values ΔN ₀ , ΔN ′ determined by the setting unit 26H
It is equipped with 6I.

These correction amount setting sections 26B, 26C, 2
The vehicle weight sensor 29F, the steering angle sensor (steering angle sensor) 29B, the vehicle speed sensor 29C, the lateral acceleration sensor 29D, the longitudinal acceleration, and the longitudinal acceleration are provided in the 6E and the calculation units 26G and 26H as vehicle weight information detecting means capable of detecting a vehicle weight change. Information from various sensors 29 such as the sensor 29E is taken in. A well-known vehicle height sensor is used as the vehicle weight sensor 29F, and the vehicle weight value is converted from the vehicle height value. The longitudinal acceleration sensor 29E is configured as a longitudinal force detecting means capable of detecting the longitudinal force acting on the wheels of the vehicle.

First, the pneumatic trail change calculation unit 26G and the pneumatic trail change correction amount setting unit 26
The H and correction amount setting unit 26I will be described. As shown in FIG. 13, the pneumatic trail N is the distance between the tire center line and the force application point when the self-aligning torque acts on the tire T, the tire rolling radius R, the tire contact load W, and the tire generation. It can be calculated from the longitudinal force (driving force or braking force) F by the following formula.

N = RF / W Here, when the pneumatic trail N'when the wheel load changes by ΔW is obtained, N '= RF' / (W + ΔW) is obtained.

The pneumatic trail change ΔN ₀ is the rate of change from the above-mentioned pneumatic trail N to the pneumatic trail N ′ and is defined by the following equation. ΔN ₀ = N ′ / N = (F · (W + ΔW)) / (F ′ ·
W) Here, the wheel load W and the variation ΔW of the wheel load are obtained from the vehicle height sensor 29F. That is, there is a substantially linear relationship between the vehicle height value (vehicle height sensor value) and the wheel load W, and the pneumatic trail change calculation unit 26G calculates each wheel based on the map shown in FIG. The wheel load W or W + ΔW can be obtained from the vehicle height sensor value detected each time. In the map shown in FIG. 6, the reference line indicated by the broken line is each value when the vehicle is stopped in an empty vehicle.

Further, the tire generated longitudinal forces F and F'can be calculated from the following equations. F = m · a + F ₀ (V) In the above equation, m corresponds to the wheel load W on each wheel, so it is obtained from the vehicle height sensor value based on the map shown in FIG. Acceleration sensor 29E
Required from. Then, F ₀ (V) is a tire generated longitudinal force when there is no change in vehicle weight. For example, by preparing a map as shown in FIG. 7, the vehicle speed V can be calculated from this map.
Can be obtained in response to.

Note that the pneumatic trail change ΔN ₀
It is also conceivable to define as the amount of change as in the following equation. ΔN ₀ = N′−N = R · F / (W + ΔW) −R · F / W = R · F (1 / (W + ΔW) −1 / W) In the correction amount setting unit 26I, this pneumatic trail change ΔN _0. Parameter ΔN obtained by appropriately correcting
Based on the above, the caster angle correction amount K'is set from a map as shown in FIG. 12, for example. As shown in FIG. 12, here, the correction amount K ′ is increased in proportion to the increase of the parameter ΔN.

Such a correction amount K'is intended to cancel the amount of the pneumatic trail change ΔN ₀ caused by the change of the vehicle weight by changing the caster trail N _C. That is, as shown in FIGS. 13 and 14, when the tire generated longitudinal force F, the ground kingpin offset, the tire generated lateral force Fy, the pneumatic trail N, and the caster trail N _C are provided, the moment M about the kingpin axis is provided.
_K is given by the following equation.

M _K = F × α + Fy × (N + N _C ) The self-aligning torque SAT is expressed by the following equation. SAT = M _K −Fy × N Then, the steering force required by the driver during the steering operation is basically determined by the magnitude of the moment M _K about the kingpin axis.

If the change of the pneumatic trail N is offset by changing the caster trail N _C so that the value of N + N _C is always almost constant, the moment M _K about the kingpin axis does not change, The steering force required by the driver during the steering operation also does not change. The correction amount K'uses this. Although the parameter ΔN is not corrected to ΔN = ΔN ₀ when traveling straight ahead, it is subtracted and corrected by the correction amount ΔN ′ set by the pneumatic trail change correction amount setting unit 26H as shown in the following equation when turning. It

ΔN = ΔN ₀ −ΔN ′ Incidentally, the pneumatic trail change correction amount setting unit 26H
Then, the correction amount ΔN ′ is set corresponding to the lateral acceleration G _Y during turning. This correction amount ΔN ′ is intended to improve the steerability, and is set such that the correction amount ΔN ′ increases as the lateral acceleration G _Y increases according to the map shown in FIG. 11, for example. Since the pneumatic trail change ΔN ₀ is subtracted and corrected by the correction amount ΔN ′, the caster angle becomes smaller as the correction amount ΔN ′ becomes larger, so that the steerability can be improved.

Information from the steering angle sensor 29B is taken into the correction amount setting section 26B for setting the correction amount K ₂ corresponding to the steering angle (steering wheel angle) θ, and the map as shown in FIG. According to the magnitude of the steering angle θ, the correction amount K
_It is set to ₂ . In the map of FIG. 8, the correction amount K ₂ decreases in proportion to the magnitude of the steering angle θ, but this is because the smaller the caster angle is, the better the steering performance is. The negative correction amount K ₂ is set so as to gradually reduce the caster angle in response to the above. Incidentally, the correction amount K ₂ is for the cornering stability, the correction amount K ₂ to reduce the caster angle is set only when turning, the K ₂ to 0 in the straight running.

Information from the vehicle speed sensor 29C is fetched into the correction amount setting section 26C for setting the correction amount K ₃ corresponding to the vehicle speed V, and the magnitude of the vehicle speed V is calculated in accordance with a map as shown in FIG. 9, for example. The correction amount K ₃ is set according to In the map of FIG. 9, the correction amount K ₃ increases so as to be proportional to the magnitude of the vehicle speed V.
This is because, generally, the larger the caster angle, the better the running stability (straightness stability), and the higher the speed, the more the running stability is required. Incidentally, the correction amount K ₃ is intended for straight running stability, the correction amount K ₃ to increase the caster angle is set only during straight, the K ₃ to 0 at the time of turning.

Information from the longitudinal acceleration sensor 29E is fetched into the correction amount setting unit 26E for setting the correction amount K ₅ corresponding to the longitudinal acceleration (front and rear G) G _F , and as shown in FIG. 10, for example. The correction amount K ₅ is set according to the magnitude of the longitudinal acceleration G _F according to the map.
In the map of FIG. 10, the correction amount K ₅ increases in proportion to the magnitude of the longitudinal acceleration G _F (= | G _F |).
This is because it is desired to secure running stability (straight running stability) and steering response (steering feeling of stability) during acceleration / deceleration. As described above, generally, the larger the caster angle, the running stability (straight running stability). Is utilized and the steering response (the sense of stability of the steering wheel) is secured.

The controller 26 receives the correction amounts K ₂ , K ₃ , K ₅ and K'set by the correction amount setting sections 26B, 26C, 26E and 26I to correct the initial caster angle φ ₀ . A caster angle setting unit 26F for setting the target caster angle φ is provided. The caster angle setting unit 26F is adapted to set the caster angle φ based on the following equation.

Φ = (1 + K ₂ + K ₃ + K ₅ + K ′) φ ₀ (1) Since the caster angle control device for a vehicle as one embodiment of the present invention is configured as described above, for example, FIG. As shown in FIG. 5, the caster angle is set for each wheel. That is, first, immediately after the ignition switch of the automobile is turned on, parameters related to the control are initially set (step S1), and the presence of the road surface unevenness K, the steering angle θ, the vehicle speed V, the lateral acceleration G _Y, and the longitudinal acceleration G _{F are} related. The detection signal is read from each of the sensors 29A to 29E (step S
2).

In the next step S3, the vehicle height sensor value is converted into a wheel load W based on the map shown in FIG. 6, and this wheel load W and the longitudinal force acting on the wheel obtained from the longitudinal acceleration sensor 29E. From F, pneumatic trail N
To calculate. Furthermore, in step S4, the steering angle theta threshold near 0 | determines whether less than the steering angle theta threshold | | θ ₀ θ ₀ | is smaller than, as is running straight, to step S5 If the steering angle θ is not smaller than the threshold value | θ ₀ |, it is determined that the vehicle is turning and the process proceeds to step S8.

When the process proceeds to step S5, the correction amount K ₂ is set according to the steering angle θ using the map shown in FIG. 8 and the correction amount K ₃ is set to 0. Further, in step S6, the pneumatic trail N calculated in the previous control cycle and the pneumatic trail N (here, N ') calculated in the current control cycle are determined by N' / N or N'-N. , The pneumatic trail change ΔN ₀ is calculated. Then, in step S7, a pneumatic trail change correction amount ΔN 'is set corresponding to the lateral acceleration G _Y.

On the other hand, when the process proceeds to step S8, the correction amount K ₃ is set according to the vehicle speed V using the map as shown in FIG. 9 and the correction amount K ₂ is set to 0. Further, in step S9, the pneumatic trail change ΔN ₀ is calculated as in step S6. Then, in step S10, the pneumatic trail change correction amount ΔN 'is set to zero.

Steps S5 to S7 or Steps S8 to S
When the correction amounts K ₂ and K ₃ are set and the pneumatic trail change ΔN ₀ and the pneumatic trail change correction amount ΔN ′ are set in step 10, the routine proceeds to step S11, where the pneumatic trail change ΔN _{0 is} changed to the new one. The dynamic trail change correction amount ΔN ′ is subtracted and corrected to obtain the pneumatic trail change ΔN, and the correction amount K ′ for suppressing the change in the steering force is set based on ΔN.

Then, in step S12, the correction amount K ₅ is set according to the longitudinal acceleration G _F using the map shown in FIG. Further, in step S13, the caster angle setting unit 26F corrects the initial caster angle φ ₀ according to the above equation (1) based on these correction amounts K ₂ , K ₃ , K ₅ , and K ′. Set the target caster angle φ.

The operations of steps S2 to S13 are carried out every predetermined control cycle, and the caster angle is sometimes properly controlled according to the traveling state of the vehicle and the state of the road surface on which the vehicle is traveling. Then, the controller 26 controls the actuator 25 so that the actual caster angle becomes the target caster angle φ set in this way, and the slider plates 13, 13 are driven forward or backward by the actuator 25. The casters are adjusted.

Therefore, even if the vehicle weight changes due to the correction amount K ', or the longitudinal force generated on the wheels changes due to changes in the driving force and the braking force, the magnitude of the steering force is changed. Changes less often, and the steering response is maintained almost constant. As a result, the driver can drive with a stable steering feeling, and the driving feeling of the vehicle is improved.

Since the correction amount K'is set for each wheel, the caster adjustment for each wheel can be made even when the load of the vehicle is accelerated or decelerated even if the total weight of the vehicle does not change. Done. Therefore, there is also an effect of reducing a change in posture of the vehicle during acceleration or deceleration (for example, nose dive or nose squat). Further, the correction amount K ₂ improves the steering performance during steering, and the correction amount K ₃ improves the running stability (straight running stability) during straight running.

Further, the correction amount K ₅ ensures traveling stability (straightness stability) and steering response (stability of steering wheel) during acceleration / deceleration. Note that each of the above maps (Figs. 6 to 12)
The reference) is an example, and various map modes can be considered based on the characteristic tendency of each map. It is also conceivable to calculate the pneumatic trail change ΔN ₀ by paying attention to only the change in the vehicle weight component and not the change in the longitudinal force of the wheels.

[0043]

As described above in detail, according to the caster angle control device for a vehicle of the present invention, the caster angle adjusting mechanism capable of adjusting the caster angle by driving the components of the suspension of the vehicle, and the vehicle. A caster angle according to the traveling state of the vehicle, and a control means for controlling the caster angle adjusting mechanism so that the caster angle of the vehicle takes the set caster angle, and the change of the vehicle weight of the vehicle. With a vehicle weight information detecting means capable of detecting, the control means adjusts the caster angle so as to cancel the change of the pneumatic trail caused in accordance with the vehicle weight change based on the information from the vehicle weight information detecting means. With this configuration, even if the vehicle weight changes, the magnitude of the steering force does not change much, and the steering response is maintained almost constant. Drive feeling of the vehicle can be improved including the ring.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a caster angle control device for a vehicle as an embodiment of the present invention.

FIG. 2 is a perspective view showing a suspension provided with a caster angle adjusting mechanism of a vehicle caster angle control device as one embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a caster angle adjusting mechanism of a vehicle caster angle control device as one embodiment of the present invention.

FIG. 4 is a hydraulic circuit configuration diagram of a caster angle adjusting mechanism of a vehicle caster angle control device as one embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation of the caster angle control device for a vehicle as an embodiment of the present invention.

FIG. 6 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 7 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 8 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 9 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 10 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 11 is a map relating to setting of a control amount (correction amount) in the vehicle caster angle control device as one embodiment of the present invention.

FIG. 12 is a map relating to setting of a control amount (correction amount) in a vehicle caster angle control device as one embodiment of the present invention.

FIG. 13 is a schematic side view of a wheel portion for explaining the operation of the vehicle caster angle control device as one embodiment of the present invention.

FIG. 14 is a schematic plan view of a wheel portion for explaining the operation of the vehicle caster angle control device as one embodiment of the present invention.

[Explanation of symbols]

1 strut 1A head of strut 1 1a insulator part 2 shock absorber 3 coil spring 4 vehicle body 5 knuckle 6 hub 7 front wheel 8 lower arm 9 cross member 10 center member 11 disc brake 12 caster angle adjusting mechanism (slide mechanism) 13 slide plate 13a opening 14 Slide Base 15 Plate Member 16 Through Hole 17 Rail Part 17a Rail Part 18 Plate Member 19 Sliding Wall Part 20 Needle Roller Bearing 22 Fixing Hole 23 Mounting Bolt 24 Nut 25 Actuator (Drive Device) 25A Hydraulic Supply / Discharge System 25B Hydraulic Cylinder 25a Tank 25b Pump 25c Pump accumulator 25d, 25e Main accumulator 25f Filter 25g Relief valve 25h Check valve, 25i, 25j, 5k, 25l Control valve 25m, 25n Position sensor 26 Controller 26B, 26C, 26E Correction amount setting unit 26G Pneumatic trail change calculation unit 26H Pneumatic trail change correction amount setting unit 26I Correction amount setting unit 27 Drive shaft 28 Stabilizer 29 Sensor 29B Steering angle sensor (rudder angle sensor) 29C vehicle speed sensor 29D lateral acceleration sensor 29E longitudinal acceleration sensor 29F vehicle weight sensor (vehicle height sensor) as vehicle weight information detecting means

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takao Morita 5-3-8, Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A caster angle adjusting mechanism capable of adjusting a caster angle by driving a constituent element of a vehicle suspension, and a caster angle set according to a running state of the vehicle so that the caster angle of the vehicle is set to this value. And a vehicle weight information detecting means capable of detecting a change in vehicle weight of the vehicle, wherein the control means controls the caster angle adjusting mechanism to control the caster angle adjusting mechanism. A caster angle control device for a vehicle, which is configured to set the caster angle so as to cancel a change in the pneumatic trail caused in accordance with a change in the vehicle weight based on the information from the information detecting means. ..