JPH07165108A - Caster angle control device for variable caster suspension - Google Patents

Abstract

PURPOSE:To restrain kickback occurrence by operating a caster angle with detected vehicle height as a parameter to adjust and control the caster angle so as to become an operated caster angle. CONSTITUTION:A vehicle-height signal H, a vehicle-speed signal V, and a steering wheel steering angle signal delta are inputted into an operation part 521 respectively form a vehicle-height sensor 524, a vehicle-speed sensor 525, and a steering wheel steering angle sensor 526. The target extension/contraction position X of an actuator corresponding to an objective caster angle is operated from these input signals by the operation part 521. A caster angle at that time is operated with detected vehicle height as one parameter. The objective extension/ contraction position signal X and an extension/contraction position signal Y from a stroke sensor 509 are compared by a comparator 522 to output a comparison error signal to a drive 523. The drive 523 controls an electromagnetic switching valve 516 so as to eliminate an error based on this comparation error signal to control a caster adjustment mechanism 1 via the actuator 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caster angle controller for a vehicle such as an automobile, and more particularly to a caster angle controller for a variable caster suspension.

[0002]

2. Description of the Related Art A caster angle control device for a variable caster suspension for a vehicle such as an automobile is disclosed in, for example, Japanese Unexamined Patent Publication No. 4-87884 (invention title "Vehicle caster angle control device"). Things are known.

This caster angle control device for a vehicle is a caster angle adjusting mechanism capable of adjusting the caster angle by driving components of a suspension, a caster angle setting means for setting an optimum caster angle for a running state, and a vehicle. The caster angle setting means controls the caster angle adjusting mechanism so that the caster angle is set to the caster angle set by the caster angle setting means, and the caster angle setting means controls the desired steering according to the vehicle speed, the steering angle, and the steering angular velocity. The feature is that the caster angle is set so that force can be obtained.

[0004]

By the way, in general, since the front suspension has an anti-dive geometry, the instantaneous center in side view is located above the road surface and behind the front wheel center. In the anti-dive geometry, the carrier rotates about the instantaneous center, so that the wheels move upward and the caster angle increases. Therefore, the conventional caster angle control device for a vehicle described above has a problem that the caster angle deviates from a desired value when the vehicle height changes in accordance with changes in the number of occupants and the load capacity.

Further, since the caster angle φ is controlled as a function φ = f (V) of the vehicle speed V as shown in FIG. 15, for example, when the vehicle speed V changes and the vehicle height changes due to aerodynamic characteristics, There is a problem that the actual caster angle φ ′ deviates from φ = f (V) by Δφ as the vehicle height changes. Here, Δφ is the amount of change in the caster angle due to the change in vehicle height.

Further, since the same caster angle is set in accordance with the above-mentioned conditions without considering the forward movement and the backward movement, the action points of the tire friction force during the forward movement and the backward movement differ substantially. Even if the amount of trail is different and the steering reaction force is set so that steering is easy when moving forward, there is a problem that steering is difficult when steering backward and steering stability is deteriorated.

Further, since the caster angle is set to a large value regardless of the condition of the road surface during high speed running (see FIG. 15), when running at high speed on an uneven road surface, the trail amount is increased. There is a problem that kickback occurs because the steering reaction force is affected by the disturbance from the road surface.

An object of the present invention is to further improve the performance of a caster angle control device, in which the caster angle is calculated with the vehicle height as one parameter, or the vehicle height changes with a change in vehicle speed. Is used as a parameter to calculate the caster angle, or to calculate the caster angle so that the trail amount of the wheel when reversing is optimal, or when the road surface is uneven, the caster angle is limited to a predetermined value or less. This aims to solve the above problems.

[0009]

In order to solve the above problems, according to the invention of claim 1, a caster adjusting mechanism for adjusting a caster angle by driving a component of a suspension by an actuator, and a running state of a vehicle. In a caster angle control device for a caster variable suspension, which comprises a caster angle setting means for setting the caster angle based on the caster angle and a control means for controlling the caster adjusting mechanism so that the caster angle of the vehicle becomes the set caster angle. The setting means includes a vehicle height detecting means for detecting the vehicle height and a means for calculating the caster angle using the vehicle height detected by the vehicle height detecting means as one parameter.

According to another aspect of the invention, a caster adjusting mechanism that adjusts the caster angle by driving the components of the suspension by an actuator, and a caster angle setting means that sets the caster angle based on the running state of the vehicle, In the caster angle control device of the caster variable suspension, which comprises a control means for controlling the caster adjusting mechanism so that the caster angle of the vehicle becomes the set caster angle, the caster angle setting means, the vehicle speed detecting means for detecting the vehicle speed, and The caster angle is calculated by using the change in vehicle height due to the change in vehicle speed as one parameter.

According to another aspect of the invention, a caster adjusting mechanism that adjusts the caster angle by driving the constituent elements of the suspension by an actuator, and a caster angle setting means that sets the caster angle based on the running state of the vehicle, In a caster angle control device for a caster variable suspension, which comprises a control means for controlling the caster adjusting mechanism so that the caster angle of the vehicle becomes a set caster angle, the caster angle setting means detects a backward movement of the vehicle. When the backward movement of the vehicle is detected, the caster angle is calculated so as to optimize the trail amount of the wheels during the backward movement.

According to another aspect of the invention, a caster adjusting mechanism for adjusting the caster angle by driving the constituent elements of the suspension by an actuator, and a caster angle setting means for setting the caster angle based on the running state of the vehicle, In a caster angle control device for a caster variable suspension, which comprises a control means for controlling a caster adjusting mechanism so that a caster angle of a vehicle becomes a set caster angle, the caster angle setting means detects unevenness on a traveling road surface. And a limiting means for limiting the caster angle to a predetermined value or less when the traveling road surface is uneven.

[0013]

According to the above-mentioned structure, the caster angle is calculated by using the vehicle height as one parameter.

According to the second aspect of the present invention, the caster angle is calculated by using the change of the vehicle height accompanying the change of the vehicle speed as one parameter.

According to the third aspect of the present invention, when the backward movement of the vehicle is detected, the trailer amount of the wheel during the backward movement is set to the caster angle calculated so as to be optimum.

According to the structure of claim 4, the caster angle is set to be limited to a predetermined value or less when irregularities on the road surface are detected.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a perspective view showing a variable caster suspension (caster adjusting mechanism 1) used in the present invention,
FIG. 2 is a schematic perspective view showing the caster adjusting mechanism 1 shown in FIG. 1 as a skeleton diagram. The shock absorber and the suspension spring are omitted in these figures.

In both figures, reference numeral 10 denotes a carrier which supports a wheel 14 via a bearing 12 so as to be rotatable about a rotation axis 14A. In both figures, 16 and 18
Each show an upper arm and a lower arm which extend substantially laterally of the vehicle. The upper arm 16 is pivotally attached to the upper end of the carrier 10 by a joint 20 at an outer end, and is pivotally supported by a joint 22 at a vehicle body (not shown) at an inner end.

Similarly, the lower arm 18 is pivotally attached at its outer end to the lower end of the carrier 10 by a joint 24, and is pivotally supported at its inner end by a joint 26 on a vehicle body (not shown). The joints 22 and 26 respectively have axes 28 and 30 extending substantially in the longitudinal direction of the vehicle.
And includes a tubular rubber bushing extending along these axes.

One ends of an upper link 36 and a lower link 38 are pivotally attached to the upper arm 16 and the lower arm 18 by joints 32 and 34, respectively. Although not shown, the joints 32 and 34 each have axes that extend substantially vertically and include tubular rubber bushings that extend along those axes.
In the caster adjusting mechanism 1, the upper link 36 and the lower link 38 extend toward the front of the vehicle while inclining toward the inboard direction from one end to the other end.

The other ends of the upper link 36 and the lower link 38 are pivotally attached to the upper and lower ends of a pivot link 44 by joints 40 and 42, respectively. Although not shown, joints 40 and 42 have axes that extend substantially transversely to upper link 36 and lower link 38, respectively, and tubular rubber bushings extending along these axes. Is included.

Fixed to the pivot link 44 is a cylindrical bearing 48 having an axis 46 extending substantially transversely of the vehicle. Although not shown in the drawing, a shaft fixed to the vehicle body is inserted through the bearing 48, whereby the pivot link 44 is supported by the vehicle body so as to be pivotable around an axis 46.

In this embodiment, the pivot link 44 is pivoted and positioned by a hydraulic actuator 50. As will be described later, the actuator 50 is a cylinder piston device and is connected to the vehicle body via a rubber bush via a connecting plate 54 fixed to one end of the cylinder 52 so as to be pivotable about an axis 56 parallel to the axis 46.

The actuator 50 is pivotally attached to a portion between the upper end of the pivot link 44 and the bearing 48 by a joint 60 at the tip of the piston 58. Although not shown, the joint 60 also has an axis 62 parallel to the axis 46 and includes a tubular rubber bushing extending along the axis 62.

FIG. 3 shows the actuator 50 shown in FIG.
FIG. 3 is a diagram showing a hydraulic drive control system thereof.

As shown in FIG. 3, the actuator 50 comprises a substantially cylindrical cylinder 52 and a substantially cylindrical piston 58 which are concentric with the center line 76, and a joint is provided at one end of each. 54 and 60 are provided. An L-shaped rod 511 is arranged in the vicinity of the joint 60 of the piston 58.
A part of the stroke sensor 510 is arranged inside the main body of the stroke sensor 510. Stroke sensor 510 Main unit and rod 511 make stroke sensor 509
Is configured.

A large-diameter portion 502 is formed at the substantially central portion of the piston 58.
However, a small diameter portion 502 is arranged on the left side of the large diameter portion 502, and a small diameter portion 503 is arranged on the right side thereof. The small diameter portion 502 is fitted in the cylinder 52 and is slidable in the left-right direction. That is, the small-diameter portion 501 is fitted to the small-diameter portion 504 in the substantially central portion of the cylinder 52, the large-diameter portion 502 is fitted to the large-diameter portion 505 on the right side of the cylinder 52, and the small-diameter portion 503 is the small-diameter portion 5 at the right end of the cylinder 52.
Mating with 06.

As a result, the small diameter portion 5 inside the cylinder 52
The right side of 04 is divided into two chambers, an oil chamber 507 and an oil chamber 508. Communication holes 551 and 5 are provided at both left and right ends of the large diameter portion 505.
52 is bored, and the oil chamber 507 is connected to one end of the conduit 518 through the communication hole 551, and the oil chamber 508 is connected to one end of the conduit 519 through the communication hole 552.

The other ends of the conduits 518 and 519 are connected to the ports a and b of the electromagnetic switching valve 516, respectively. The ports c and d of the electromagnetic switching valve 516 are connected to the conduit 51.
5 and 517 are connected to one end of each.
The other end of the conduit 517 is communicatively connected to the reservoir tank 512. One end of a conduit 513 is communicatively connected to the reservoir tank 512. The other end of the conduit 513 and the conduit 51
An oil pump 514 is connected between the other end and the other end.

The solenoid 5 is provided on the left and right of the electromagnetic switching valve 516.
53 and 554 are arranged, and both solenoids are an electronic control unit (ECU) 5 described later.
It is turned on / off according to the drive signal from 20.

FIG. 4 is a block diagram showing an embodiment of the present invention.

In FIG. 4, the electronic control unit 520 is a CP
U (Central Processing Unit), ROM
(Read Only Memory) and RAM
An arithmetic unit 521 having a (Random Access Memory), a comparator 522, and a driver 52.
3 and input ports and output ports (not shown).

The calculation unit 521 has a vehicle height signal H from the vehicle height sensor 524 and a vehicle speed signal V from the vehicle speed sensor 525.
And the steering wheel steering angle signal δ from the steering wheel steering angle sensor 526 are input. The computing unit 521 computes the target expansion / contraction position X of the actuator corresponding to the target caster angle from these signals, and outputs it as described later.

The target extension / contraction position signal X and the extension / contraction position detection signal Y from the stroke sensor are input to the comparator 522, and a comparison error signal (XY) between them is output. The driver 523 sets the solenoid (553, 53, 5) of the electromagnetic switching valve 516 so that the comparison error signal becomes 0 and the expansion / contraction position of the actuator 50 becomes equal to the target expansion / contraction position X.
A drive signal is supplied to 54). As a result, the actuator 50 is driven as described later, and the actuator 50 drives the caster adjusting mechanism 1 to set the target caster angle.

Returning to FIG. 3, the solenoids 553 and 554 are both off in the illustrated state. At this time, the electromagnetic switching valve 516 is in the neutral position where the ports a and b are shut off and the ports c and d are communicatively connected.

Therefore, the oil in the reservoir tank 512 passes through the conduit 513 and is pressurized by the oil pump 514,
It is sent to the port c of the electromagnetic switching valve 516 through the conduit 515. Further, the oil discharged from the port d of the electromagnetic switching valve 516 returns to the reservoir tank 512 through the conduit 517. The other end of the conduit 518 is blocked by the port a, and the other end of the conduit 519 is blocked by the port b. Therefore, the piston 58 is stopped at the illustrated neutral position, and the volumes of the oil chamber 507 and the oil chamber 508 are substantially equal.

On the other hand, when the solenoid 553 is turned on and the solenoid 554 is turned off in response to the drive signal from the electronic control unit 520, the electromagnetic switching valve 516 is displaced rightward from the neutral position. As a result, ports a and c are connected for communication,
b and d are connected for communication.

Therefore, the oil in the reservoir tank 512 passes through the conduit 513 and is pressurized by the oil pump 514,
It is sent to the port c of the electromagnetic switching valve 516 through the conduit 515. Further, the oil discharged from the port a of the electromagnetic switching valve 516 is injected into the oil chamber 507 through the conduit 518.

As a result, the volume of the oil chamber 507 increases, the volume of the oil chamber 508 decreases, the piston 58 slides to the right, and the actuator 50 extends. Oil from the oil chamber 508 is sent to the port b of the electromagnetic switching valve 516 through the conduit 519. Further, the oil discharged from the port c of the electromagnetic switching valve 516 is injected into the reservoir tank 512 through the conduit 517.

On the other hand, the solenoid 554 is turned on in response to the drive signal from the electronic control unit 520 and the solenoid 55 is turned on.
When 3 is turned off, the electromagnetic switching valve 516 is displaced leftward from the neutral position. As a result, the ports a and d are communicatively connected, and the ports b and c are communicatively connected.

Therefore, the oil in the reservoir tank 512 passes through the conduit 513 and is pressurized by the oil pump 514,
It is sent to the port c of the electromagnetic switching valve 516 through the conduit 515. Further, the oil discharged from the port b of the electromagnetic switching valve 516 is injected into the oil chamber 508 through the conduit 519.

As a result, the volume of the oil chamber 508 increases, the volume of the oil chamber 507 decreases, the piston 58 slides to the left, and the actuator 50 contracts. Oil from the oil chamber 507 is sent to the port a of the electromagnetic switching valve 516 through the conduit 518. Further, the oil discharged from the port d of the electromagnetic switching valve 516 is injected into the reservoir tank 512 through the conduit 517.

FIG. 5 is an explanatory view showing the movement of the pivot link as a skeleton diagram as seen from the outboard side of the vehicle.

As shown in FIG. 5, the pivot link 44
The center of the bearing 48, that is, the axis 46 and the joint 42
L ₁ is the distance from the center of the bearing 48 to L ₂ is the distance from the center of the bearing 48 to the center of the joint 40. Around the center θ (ra
d) If pivoted, the joint 42 moves L ₁ θ toward the front of the vehicle and the joint 40 moves L ₂ θ toward the rear of the vehicle.

FIG. 6 is an explanatory view showing the movements of the upper arm and the upper link as a skeleton diagram as seen from above the vehicle.

[0047] Here, the joint 40 when moved rearward L ₂ theta, joint 32 as shown in FIG. 6 is also displaced to only the rear of the vehicle L ₂ theta. Joint 22
Let L ₅ be the distance between the joints 22 and 20
Let L ₆ be the distance between the joint 32 and L _2.
By displacing the joint 20 rearward of the vehicle, the joint 20 is displaced rearward of the vehicle by (L ₂ L ₆ / L ₅ ) θ.

FIG. 7 is an explanatory view showing the movements of the lower arm and the lower link as a skeleton diagram as seen from above the vehicle.

Similarly, when the joint 42 is displaced forward by L ₁ θ in the vehicle, the joint 34 is also displaced forward by L ₁ θ in the vehicle as shown in FIG. 7. Let L ₃ be the distance between the joints 26 and 34,
Assuming that the distance between L and 24 is L ₄ , the joint 34 is displaced forward by L ₁ θ and the joint 2
4 is displaced by (L ₁ L ₄ / L ₃ ) θ toward the front of the vehicle.

FIG. 8 is an explanatory view showing changes in caster angle and caster trail.

As shown in FIG. 8, the caster angle φ is the angle formed by the vertical line 92 and the kingpin shaft 94, and the caster trail T is the intersection point P between the kingpin shaft 94 and the road surface 96 and the ground contact point Q of the wheel. Is the distance between. Therefore wheel 1
4, the vertical distance between the rotation axis 14A and the joint 24 is L _7, and the vertical distance between the rotation axis 14A and the joint 20 is L ₈ , the increase amount Δφ of the caster angle φ is Given by the formula.

Δφ = (L ₁ L ₄ / L ₃ + L ₂ L ₆ / L ₅ ) / (L ₇ + L ₈ ) (1) Therefore, the change amount of the caster angle changed by pivoting the pivot link 44 Is determined by the distances L _{1 to} L ₈ described above.

A point on the carrier 10 that does not displace in the vehicle front-rear direction even when the caster angle changes, that is, a virtual pivot point is A, and a vertical direction from the wheel rotation axis 14A to the pivot point A. The distance d is given by the following equation.

[0054] _{d = (L 2 L 3 L} 6 L 7 -L 1 L 4 L 5 L 8) / (L 1 L 4 L 5 -L 2 L 3 L 6) (2) when the caster angle varies The change amount of the caster trail T is determined by the change amount Δφ of the caster angle and the position of the pivot point A, and both of them are determined by the above-mentioned distances L _{1 to} L _{8 from the} above equations (1) and (2). The amount of change of the caster trail T is also determined by these distances.

Therefore, the caster angle and the caster trail can be changed in a desired manner by appropriately setting the above distances L _{1 to} L ₈ , especially the distances L ₁ and L ₂ .

For example, the radius of the wheel 14 is R, and the vertical distance between the pivot point between the tie rod and the carrier 10 and the rotation axis 14A of the wheel (not shown) is d '.
Then, by setting the distance d to a specific value as shown in Table 1 below and setting the pivot point A to a specific position, the manner in which the suspension changes when the caster angle is changed is described. It can be set as follows.

[0057]

[Table 1]

This Table 1 is merely an example of the case in which the mode of change is characteristic. From Table 1, the caster angle and caster trail are desired by appropriately setting the value of d in accordance with the characteristics required for the suspension. Can be changed in the following manner.

FIG. 9 is a flow chart showing an example of control of the electromagnetic switching valve 516 by the electronic control unit 520.

In the flowchart of FIG. 9, X _L is a target expansion / contraction position at low speed, X _H is a target expansion / contraction position at high speed, and X _L <X _H is set. Further, X _LO is the target expansion / contraction position at low speed at the standard vehicle height, X _HO is the target expansion / contraction position at high speed at the standard vehicle height, and X _LO <X _HO
Is set to. Further, K _L is a coefficient for correcting the target expansion / contraction position at low speed due to the difference in vehicle height, and K _H is a coefficient for correcting the target expansion / contraction position at high speed due to the difference in vehicle height.

H _O is the standard vehicle height. Also, V _O
Is a threshold value of the vehicle speed for determining whether the vehicle is stopped, V ₁ is a threshold value of the vehicle speed for switching the caster angle from small to large, and V ₂ is the caster angle to be switched to large or small. Is a threshold value of the vehicle speed, and V ₁ <V ₂ is set. Further, δ _O is a threshold value of the steering wheel steering angle δ for determining whether or not the caster angle may be changed. When the steering wheel steering angle δ value is less than the threshold value δ _O , the caster angle is not changed. Done.

Further, the control according to the flowchart shown in FIG. 9 is started by opening an ignition switch (not shown), and is ended by closing the ignition switch.

[0063] First, in the first step S10 in FIG. 9, the target telescopic position X _LO during low-speed in the standard vehicle height of low speed to the target stretching position X _L, the target telescopic position X _HO fast during the standard vehicle height Fast Write in the target expansion / contraction position X _H at each time.

In the following step S20, the target expansion / contraction position X _L at low speed is output as the target expansion / contraction position X of the actuator corresponding to the target caster angle.
The process proceeds to the stop determination process.

In step S30, the vehicle speed sensor (52
The vehicle speed V is read from 5), and it is determined whether the absolute value of the vehicle speed V is less than a vehicle speed threshold V _O for determining whether the vehicle is stopped. When the absolute value of the vehicle speed V is smaller than the threshold value V _O (Yes), it is determined that the vehicle is stopped, and the process proceeds to step S40.

In step S40, the vehicle height sensor (52
The vehicle height H at the time of stop is read from 4), and
Value of difference between vehicle height H at stop and standard vehicle height H _O (H-H _O )
And a coefficient K _L for correcting the target expansion / contraction position at low speed due to the difference in vehicle height and the target expansion / contraction position X _LO at low speed at the standard vehicle height, a low speed corresponding to the caster angle optimal for the vehicle height H is obtained. target telescopic position X _L is calculated from the following equation _{X L = X LO + K L} (H-H O) (3).

[0067] Simultaneously, the value of the difference between the vehicle height H and the standard vehicle height H _O when stopping (H-H _O), and the coefficient K _H for correcting the target stretching position at high speed by the difference in height, the standard From the target expansion / contraction position X _HO at high speed in the vehicle height, the target expansion / contraction position X _H at high speed corresponding to the caster angle optimal for the vehicle height H is expressed by the following formula: X _H = X _HO + K _H (H−H _O ) ( 4) is required.

Target expansion / contraction at low speed in step S40
Position X_LAnd target expansion / contraction position X at high speed _HIs required
Then, the process returns to step S20, and the determination of step S30 is made.
In the disconnection process, the absolute value of the vehicle speed V is the threshold value V_OGreater than
Until it is determined to be (No), the processing of steps S20 to S40 is performed.
The reason is repeatedly executed.

When the absolute value of the vehicle speed V is larger than the threshold value V _O (No) in step S30, it is determined that the vehicle is stopped, and the processes of step S50 and thereafter are executed.
That is, in step S50, the vehicle speed sensor (525)
The vehicle speed V is read from and the process for determining whether or not the vehicle speed V is less than the vehicle speed threshold V ₂ for switching the caster angle from large to small is executed. Step S50
Is a process of determining whether to reduce the caster angle.

In step S50, if it is determined that the vehicle speed V is less than the vehicle speed threshold V ₂ for switching the caster angle from the larger value to the smaller value (Yes), the caster angle may be small, so that the processing in step S60 and subsequent steps is performed. move on.

In the stop determination process of step S60, the vehicle speed is
When the vehicle speed V is read from the sensor (525)
To determine whether or not the absolute value of the vehicle speed V is stopped.
Vehicle speed threshold V for_OIs less than
It The absolute value of the vehicle speed V is the threshold value V _OLess than (Yes)
If it is determined that the vehicle is stopped, step S4
The process proceeds to 0.

Steps S40 to S50 are as described above, and it is judged in the judgment processing of step S50 that the vehicle speed V is equal to or higher than the threshold value V ₂ of the vehicle speed for switching the caster angle from the larger value to the smaller value (No), In the determination process of step S60, the absolute value of the vehicle speed V is larger than the threshold value V _O (N
Until it is determined to be o), the processes of steps S20 to S60 are repeatedly executed.

When it is determined in step S60 that the absolute value of the vehicle speed V is larger than the threshold value V _O (No), in the subsequent step S70, the steering wheel steering angle δ is read from the steering wheel steering angle sensor (526). A process of determining whether or not the absolute value of the steering angle δ is less than the threshold δ _O of the steering angle δ for determining whether the caster angle may be changed is executed.

In step S70, the steering wheel steering angle δ
If the absolute value of is greater than or equal to the threshold value δ _O (No), the caster angle is not changed so that the change of the turning performance due to the change of the caster angle does not occur during turning of the vehicle.
Returning to the processing of step 50, the processing of steps S50 to S70 is repeatedly executed until it is determined in step S70 that the absolute value of the steering wheel steering angle δ is less than the threshold value δ _O (Yes).

In step S70, the steering wheel steering angle δ
If it is determined that the absolute value of is less than the threshold value δ _O (Yes), the process proceeds to step S80 to change the caster angle. That is, in step S80, the target expansion / contraction position X _L at low speed is output as the target expansion / contraction position X of the actuator corresponding to the target caster angle.

[0076] Thus, the comparator (522) compares the error signal at (X _L -Y) is zero actuator (50)
Telescopic position of the drive signal from the equal way driver and target stretching position X _L (523) to the solenoid (554) of the electromagnetic switching valve (516) is supplied. Then, as described above, the actuator (50) contracts and drives the caster adjusting mechanism (527) to set a small target caster angle at low speed.

On the other hand, if it is determined in step S50 that the vehicle speed V is equal to or higher than the vehicle speed threshold V ₂ for switching the caster angle to a larger or smaller value (No), the process proceeds to step S90 and subsequent steps. In step S90, the vehicle speed sensor (52
5) The vehicle speed V is read from the vehicle speed V and the vehicle speed threshold V ₁ for switching the caster angle from the small speed to the large speed V ₁
The determination process of whether or not is exceeded. Step S90 is a process of determining whether to increase the caster angle.

If it is determined in step S90 that the vehicle speed V is less than or equal to the vehicle speed threshold V ₁ for switching the caster angle from small to large (No), it is not necessary to change the caster angle, so that the steps after step S60 are performed. Go to processing. Step S
The processing after 60 is as described above. Originally, V ₁
<Because it is set to V _2, the vehicle speed V ≧ threshold V ₂ in the case of (No), the vehicle speed V in step S90 unless there is a sharp reduction in the vehicle speed V in step S50> threshold V ₂
(Yes)

If it is determined in step S90 that the vehicle speed V exceeds the vehicle speed threshold V ₂ for switching the caster angle from a small value to a large value (Yes), the caster angle should be changed significantly. Proceed to the subsequent processing.

In step S70, the steering wheel steering angle δ is read from the steering wheel steering angle sensor (526), and it is determined whether the absolute value of the steering wheel steering angle δ can change the caster angle. Steering angle δ
Is determined to be less than or equal to the threshold value δ _O.

In step S70, the steering wheel steering angle δ
If it is determined that the absolute value of is greater than or equal to the threshold value δ _O (No), the caster angle is not changed so that the change of the turning performance due to the change of the caster angle does not occur during turning of the vehicle. Processing returns to step S100
Until it is determined that the absolute value of the steering wheel steering angle δ is less than the threshold value δ _O (Yes) in steps S90 to S100.
The process of is repeatedly executed.

If it is determined in step S100 that the absolute value of the steering wheel steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S110 to change the caster angle. That is, in step S110, the target expansion / contraction position X _H at high speed is output as the target expansion / contraction position X of the actuator corresponding to the target caster angle.

As a result, the comparison error signal (X _H -Y) in the comparator (522) becomes 0, and the actuator (50)
A drive signal is supplied from the driver (523) to the solenoid (553) of the electromagnetic switching valve (516) so that the expansion / contraction position of (1) becomes equal to the target expansion / contraction position X _H. Then, as described above, the actuator (50) extends and drives the caster adjusting mechanism (527) to set a large target caster angle at high speed.

As described above, according to the control according to the flowchart shown in FIG. 9, the caster angle can be appropriately set according to the vehicle speed, and the caster angle is reduced at a low speed to reduce the steering force of the steering wheel, and at the high speed. The caster angle can be increased to improve the straight running stability of the vehicle.

By comparing the vehicle height H at the time of stop and the standard vehicle height H _O and correcting the caster angle, the desired vehicle height can be obtained even when the number of passengers or the load of luggage changes. Caster angle can be obtained. Further, since the caster angle at low speed and the caster angle at high speed are corrected by different coefficients, it is possible to set the fine caster angle.

FIG. 10 is a flow chart showing another example of control of the electromagnetic switching valve 516 by the electronic control unit 520. Here, the calculation unit 521 of the electronic control unit 520 calculates a target expansion / contraction position X of the actuator 50 corresponding to a predetermined caster angle corresponding to the vehicle speed V, in consideration of a change in the caster angle accompanying the change of the vehicle speed V in advance. It is configured to do.

The control according to the flow chart shown in FIG. 10 is started by opening an ignition switch (not shown) and is ended by closing the ignition switch.

In FIG. 10, the first step S21.
At 0, the steering wheel steering angle δ is read from the steering wheel steering angle sensor (526), and the steering wheel steering angle δ for determining whether or not the absolute value of the steering wheel steering angle δ may change the caster angle. Is determined to be less than or equal to the threshold value δ _O.

In step S210, when the absolute value of the steering wheel steering angle δ is equal to or greater than the threshold value δ _O (No), the caster angle is set so that the change of the turning performance due to the change of the caster angle does not occur during turning of the vehicle. Since it is not changed, the process of step S210 is executed again. That is, step S
The process of step S210 is repeatedly executed until it is determined at 70 that the absolute value of the steering wheel steering angle δ is less than the threshold value δ _O (Yes).

When it is determined in step S210 that the absolute value of the steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S220 to set the caster angle. After setting the caster angle to the ideal value in step S220, the process returns to step S220.

That is, in step S220, the target expansion / contraction position X of the actuator 50 corresponding to the caster angle φ is calculated from the following equation φ = f ′ (V) = φ _V + Δφ (5).

In the equation (5), φ _V is a caster angle set in advance in consideration of a change in vehicle height due to a change in aerodynamic characteristics accompanying a change in vehicle speed V, and Δφ is a vehicle angle due to a change in aerodynamic characteristics accompanying an increase in vehicle speed V. It is the amount of decrease in the caster angle due to the increase in height.

Therefore, the map for obtaining the ideal caster angle φ considering the change in vehicle height from the vehicle speed V is shown in FIG.
It is expressed as 1. In this way, it is possible to set the ideal caster angle φ corresponding to the change in vehicle height due to the change in vehicle speed V, and it is possible to obtain stable maneuverability even at high speeds.

FIG. 12 is a flowchart showing still another example of control of the electromagnetic switching valve 516 by the electronic control unit 520. The control according to the flowchart shown in FIG. 12 is started by opening an ignition switch (not shown), and is ended by closing the ignition switch.

First step S31 in FIG.
At 0, it is determined whether or not the gear is in reverse. If the gear is not in reverse (No)
Since the vehicle is moving forward, steps S330 to S3 will be performed as described later.
The target expansion / contraction position setting process for forward movement according to the vehicle speed V of 80 and the steering angle δ is executed.

If it is determined in step S310 that the gear is in reverse (Yes), the extension / contraction position for reverse is set in step S320. Here, the target expansion / contraction position of the actuator corresponding to a predetermined caster angle that sets the trail amount of the wheel to an optimum value is set so that a steering reaction force that facilitates steering even when moving backward is obtained. After setting the target expansion / contraction position, the process returns to the determination process of step S310.

By the processes of steps S310 to S320, the trailer amount can be set to the optimum caster angle which is different from that when the vehicle is moving forward, so that the substantial trail amount can be set to be the same as when the vehicle is moving forward. It is easy to improve the steering stability when moving backward.

On the other hand, to briefly describe the processing at the time of forward movement, the processing of steps S330 to S380 is the same as the processing of steps S50 to S110 in FIG. That is, in step S330, the vehicle speed sensor (525)
The vehicle speed V is read from the vehicle speed V and the processing for determining whether or not the vehicle speed V is less than the vehicle speed threshold V ₂ for switching the caster angle from large to small is executed in step S330.
If V <V ₂ (Yes) in step S34, the following step S34
In step 0, the steering wheel steering angle δ is read from the steering wheel steering angle sensor (526), and the steering wheel for determining whether or not the absolute value of the steering wheel steering angle δ may change the caster angle. A process of determining whether or not the steering angle δ is less than the threshold value δ _O is executed. Step S340
At steering wheel steering angle δ, the absolute value is equal to or greater than threshold value δ _O (N
In the case of o), since the caster angle is not changed so that the change of the turning performance due to the change of the caster angle does not occur during the turning of the vehicle, the process returns to the first step S310.

When it is determined in step S340 that the absolute value of the steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S350 to calculate the target expansion / contraction position and change the caster angle to a small value. That is, the caster angle is set to a predetermined value at low speed. When the caster angle is set, the process returns to the first step S310.

On the other hand, in step S330, V ≧ V₂
In the case of (No), in the subsequent step S360, the handle
Read steering wheel steering angle δ from steering angle sensor (526)
And the vehicle speed V increases the caster angle from small to large
Vehicle speed threshold V for switching ₁Judgment of whether or not
The disconnection process is executed, and the process proceeds to step S370.

When the absolute value of the steering wheel steering angle δ is equal to or greater than the threshold value δ _O (No) in step S370, the caster angle is set so that the change in the turning performance due to the change in the caster angle does not occur during turning of the vehicle. Since no change is made, the process returns to step S360.

If it is determined in step S370 that the absolute value of the steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S380 to calculate the target expansion / contraction position and greatly change the caster angle. That is, the caster angle is set to a predetermined value at high speed. When the caster angle is set, the process returns to step S360.

FIG. 13 is a block diagram showing another embodiment of the present invention.

In FIG. 13, the electronic control unit 520a is
An arithmetic unit 521a having a CPU, a ROM and a RAM;
It comprises a comparator 522, a driver 523, and an input port and an output port (not shown).

The vehicle speed signal V from the vehicle speed sensor 525, the steering wheel steering angle signal δ from the steering wheel steering angle sensor 526, and the unevenness detection signal R from the preview sensor 527 are input to the calculation unit 521a. Preview sensor 52
Reference numeral 7 detects irregularities on the road surface during traveling. Operation unit 521a
Calculates the target expansion / contraction position X of the actuator corresponding to the target caster angle from these signals, and outputs it.

The target expansion / contraction position signal X and the expansion / contraction position detection signal Y from the stroke sensor are input to the comparator 522, and a comparison error signal (XY) between them is output. The driver 523 sets the solenoid (553, 53, 5) of the electromagnetic switching valve 516 so that the comparison error signal becomes 0 and the expansion / contraction position of the actuator 50 becomes equal to the target expansion / contraction position X.
A drive signal is supplied to 54). As a result, the actuator 50 is driven as described above, and the actuator 50 drives the caster adjusting mechanism 1 to set the target caster angle.

FIG. 14 is a flow chart showing an example of control of the electromagnetic switching valve 516 by the electronic control unit 520a. Here, the electronic control unit 520a is configured to set the caster angle to a small predetermined value regardless of the vehicle speed when detecting the unevenness of the road surface.

The control according to the flow chart shown in FIG. 14 is started by opening an ignition switch (not shown), and is ended by closing the ignition switch.

In FIG. 14, the first step S41.
At 0, the vehicle speed V is read from the vehicle speed sensor (525), and a process of determining whether or not the vehicle speed V is less than a vehicle speed threshold V ₂ for switching the caster angle from large to small is executed. V <V in S410
_In the case of ₂ (Yes), the process proceeds to the subsequent step S420, the steering wheel angle δ is read from the steering wheel angle sensor (526), and the caster angle may be changed by the absolute value of the steering wheel angle δ. Whether or not the steering wheel steering angle δ is less than a threshold value δ _O for determining whether or not is executed.

In step S420, when the absolute value of the steering wheel steering angle δ is equal to or greater than the threshold value δ _O (No), the caster angle is set so that the change of the turning performance due to the change of the caster angle does not occur during turning of the vehicle. Since no change is made, the process returns to the first step S410.

If it is determined in step S420 that the absolute value of the steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S430 to calculate the target expansion / contraction position and change the caster angle to a small value. That is, the expansion / contraction position of the actuator is controlled so that the predetermined caster angle φ = φ _L (see FIG. 15) at low speed. When the caster angle φ is set, the process returns to the first step S410.

In step S410, V ≧ V ₂ (No)
When the vehicle is traveling at a high speed, the processing proceeds to step S440,
From the steering wheel angle sensor (526) to the steering wheel angle δ
Is read, and a determination process is performed to determine whether or not the absolute value of the steering angle δ is less than the threshold δ _O of the steering angle δ for determining whether the caster angle may be changed. To be done.

In step S440, when the absolute value of the steering angle δ is equal to or greater than the threshold value δ _O (No), the caster angle is set so that the change in the turning performance due to the change in the caster angle does not occur during turning of the vehicle. Since no change is made, the process of step S440 is repeatedly executed.

When it is determined in step S440 that the absolute value of the steering wheel steering angle δ is less than the threshold value δ _O (Yes), the process proceeds to step S460 and it is determined whether road surface irregularities are detected. Here, the preview sensor (5
The presence or absence of unevenness is determined by comparing the unevenness detection signal R (indicated as the degree of unevenness per unit time) input from 27) with a threshold value.

No unevenness in step S440 (No)
If it is determined that the caster angle φ is controlled as a function f (V) of the vehicle speed V in the process of the subsequent step S450 (see FIG. 15). Therefore, the caster angle φ is controlled to a greater extent when traveling at a higher speed.

On the other hand, when it is determined in step S440 that there is unevenness (Yes), the caster angle φ is determined according to the vehicle speed.
When is set to a large value, as described above, kickback occurs because the amount of increase in the trail affects the steering reaction force due to the disturbance from the road surface.

Then, in the following step S470,
The expansion / contraction position of the actuator is controlled so that the caster angle φ _L becomes the same as the predetermined caster angle φ _L during low speed traveling even during high speed traveling, and the caster angle φ is set to φ _L.

Then, in step S480, the set caster angle φ _L is held for a predetermined time t ₁ . This is to keep the caster angle small during that time even if the unevenness detection position on the road surface has some distance.
After the caster angle is maintained for the predetermined time t ₁ , the process returns to step S440.

According to the control of the flow chart, since the small caster angle is set when the unevenness of the road surface is detected during the high speed running, the trail amount is reduced and the disturbance from the road surface hardly affects the steering reaction force. Therefore, the occurrence of kickback can be reduced.

[0120]

As described above, according to the first aspect of the invention, since the caster angle is calculated by using the vehicle height as one parameter, the vehicle height is changed according to the change in the number of passengers or the load of luggage. The desired caster angle can be obtained even when is changed, and fine caster angle can be set.

According to the second aspect of the invention, since the caster angle calculated with one change in the vehicle height due to the change in vehicle speed is set, the change in vehicle height due to the change in vehicle speed can be dealt with. The caster angle can be set to an ideal value, and stable maneuverability can be obtained at both low speed and high speed.

Further, according to the third aspect of the present invention, when the backward movement of the vehicle is detected, the trailer amount of the wheel during the backward movement is set to the caster angle which is calculated so as to be optimum. By setting the caster angle to be different from the optimum time, the substantial trail amount can be set to be the same as when moving forward, and it is easy to steer both forward and backward, and steering stability during backward can be improved.

According to the invention as set forth in claim 4, the caster angle is limited to a predetermined value or less when unevenness of the road surface is detected, so that when unevenness of the road surface is detected during high speed running, it is small. By setting the caster angle, the trail amount is reduced, and it is less affected by the steering reaction force due to the disturbance from the road surface, and it is possible to reduce the occurrence of kickback.

[Brief description of drawings]

FIG. 1 is a perspective view showing a variable caster suspension (caster adjusting mechanism 1) used in the present invention.

FIG. 2 is a schematic perspective view showing the caster variable suspension shown in FIG. 1 as a skeleton diagram.

FIG. 3 is a diagram showing an actuator 50 shown in FIG. 1 and a hydraulic drive control system thereof.

FIG. 4 is a block diagram showing an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the movement of the pivot link as a skeleton diagram viewed from the outboard side of the vehicle.

FIG. 6 is an explanatory diagram showing movements of an upper arm and an upper link as a skeleton diagram viewed from above the vehicle.

FIG. 7 is an explanatory diagram showing movements of a lower arm and a lower link as a skeleton diagram viewed from above the vehicle.

FIG. 8 is an explanatory diagram showing changes in caster angle and caster trail.

9 is a flowchart showing an example of control of an electromagnetic switching valve 516 by an electronic control device 520. FIG.

FIG. 10 is an electromagnetic switching valve 516 by an electronic control unit 520.
6 is a flowchart showing another example of the control of FIG.

FIG. 11 is a diagram showing a map for obtaining an ideal caster angle in consideration of a vehicle height change from a vehicle speed.

FIG. 12: Electromagnetic switching valve 516 by electronic control unit 520
6 is a flowchart showing still another example of the control of FIG.

FIG. 13 is a block diagram showing another embodiment of the present invention.

FIG. 14 is an electromagnetic switching valve 51 by an electronic control unit 520a.
6 is a flowchart showing an example of control of No. 6.

FIG. 15 is a diagram showing a caster angle φ as a function φ = f (V) of a vehicle speed V.

[Explanation of symbols]

 1 Caster adjustment mechanism 50 Actuator 509 Stroke sensor 516 Electromagnetic switching valve 520, 520a Electronic control unit 521, 521a Calculation unit 522 Comparator 523 Driver 524 Height sensor 527 Preview sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Kobayashi 1 Toyota-cho, Toyota-shi, Aichi Toyota Automobile Co., Ltd.

Claims (4)

[Claims] 1. A caster adjusting mechanism for adjusting a caster angle by driving a component of a suspension by an actuator, a caster angle setting means for setting a caster angle based on a traveling state of the vehicle, and a caster angle of the vehicle being set as described above. In a caster angle control device for a caster variable suspension, which comprises a control means for controlling a caster adjusting mechanism so that the caster angle becomes a fixed caster angle, the caster angle setting means detects a vehicle height, and a vehicle height detecting means for detecting the vehicle height. A caster angle control device for a variable caster suspension, comprising means for calculating a caster angle using the vehicle height detected by the detection means as one parameter. 2. A caster adjusting mechanism for adjusting a caster angle by driving a component of a suspension by an actuator, a caster angle setting means for setting a caster angle based on a running state of the vehicle, and a caster angle of the vehicle being set as described above. In a caster angle control device for a caster variable suspension, which comprises a control means for controlling a caster adjusting mechanism so as to achieve a fixed caster angle, the caster angle setting means detects a vehicle speed, A caster angle control device for a caster variable suspension, comprising means for calculating a caster angle using a change in vehicle height as one parameter. 3. A caster adjusting mechanism for adjusting a caster angle by driving a constituent element of a suspension by an actuator, a caster angle setting means for setting a caster angle based on a traveling state of the vehicle, and a caster angle of the vehicle being set as described above. In a caster angle control device for a variable caster suspension, which comprises a control means for controlling the caster adjusting mechanism so that the caster angle becomes a fixed caster angle, the caster angle setting means detects a backward movement of the vehicle and a backward movement of the vehicle. And a means for calculating the caster angle so that the trail amount of the wheel at the time of retreat is optimized when is detected. 4. A caster adjusting mechanism for adjusting a caster angle by driving a component of a suspension by an actuator, a caster angle setting means for setting a caster angle based on a traveling state of the vehicle, and a caster angle of the vehicle being set as described above. In a caster angle control device for a caster variable suspension, which comprises a control means for controlling a caster adjusting mechanism so that the caster angle becomes a fixed caster angle, the caster angle setting means comprises an unevenness detecting means for detecting unevenness of a traveling road surface, and a traveling road surface. A caster angle control device for a caster variable suspension, comprising: a limiting means for limiting the caster angle to a predetermined value or less when the unevenness is formed.