JP2949986B2 - Caster angle control device for automobile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caster angle control device for a vehicle for controlling a caster angle of a vehicle suspension.

[0002]

2. Description of the Related Art Generally, a vehicle undergoes a change in attitude (pitching motion) such as a nose-up during acceleration (a lift on a front side) and a nose dive (a lift on a rear side) during braking. Suspension geometry becomes unstable. By the way, depending on the setting of the suspension, it is possible to make it difficult for the posture of the vehicle to change. When setting the suspension, the instantaneous rotation center is almost determined by selecting the structure and type of the suspension. Therefore, it is difficult to set an ideal position because the degree of freedom in setting is narrow, but the anti-pitching angle (anti-nose dive angle, It is not preferable to set the anti-nose-up angle, the anti-tail lift angle, and the anti-squat angle) in a negative region, and it is preferable to set them so as to be as close as possible to an ideal region (hatched portion) as shown in FIGS. desirable.

FIG. 5 shows an anti-nose dive angle and an anti-nose up angle set for a front suspension, and FIG. 6 shows an anti-tail lift angle and an anti-squat angle set for a rear suspension. 5 and 6, the actual set values for the driven wheels are indicated by ●, the actual set values for the non-driven wheels are indicated by ○, and the ideal region is indicated by hatching.

Next, the position of the instantaneous center of rotation of the suspension at which the anti-pitching effect is 100% during acceleration or braking will be described with reference to the suspension geometry shown in FIG. In FIG. 7, G is the center of gravity of the vehicle body, F and G
Is the center of rotation of the front and rear wheels (wheel center), F
G and RG are the ground contact positions of the front and rear wheels, Rt is the tire radius, L is the wheel base, λ is the driving force distribution ratio of the front wheels, λ 'is the braking force distribution ratio of the front wheels, and MC is the instant of the vehicle during acceleration. The moment center, MC ', is the instantaneous moment center of the vehicle during braking.

[0005] During acceleration, the instantaneous rotational center of the suspension is set on the F-MC line connecting the front wheel rotational center F and the instantaneous moment center MC during acceleration on the front side, and the rear wheel rotational center on the rear side. When placed on the R-MC line connecting R and the instantaneous moment center MC, the anti-pitching effect becomes 100%. On the other hand, during braking, the instantaneous center of rotation of the suspension is set on the FG-MC 'line connecting the front wheel grounding position FG and the momentary moment center MC' during braking on the front side, and the rear wheel grounding position RG is set on the rear side. And an instantaneous moment center MC 'on the RG-MC' line connecting the
The anti-pitting effect becomes 100%.

Therefore, the instantaneous center of rotation of the suspension without any change in attitude (pitching motion) during acceleration / deceleration and braking is, as shown in FIG.
-MC and FG-MC 'at the position of the intersection M, and on the rear side, the position of the intersection N of R-MC and RG-MC'.

[0007]

However, it is difficult to configure the suspension such that the instantaneous center of rotation is located at the point M shown in FIG. 7, and the pitching motion of the vehicle body during acceleration and braking depends on the setting of the suspension. It is difficult to control. The present invention has been made in view of the above-described problems, and has been designed to improve the riding comfort by controlling the caster angle of the suspension so as to reliably suppress the change in the posture of the vehicle body during acceleration or braking. ,
It is an object of the present invention to provide a caster angle control device for an automobile.

[0008]

Therefore, a caster angle control device for a vehicle according to the present invention has a caster angle adjusting means for adjusting a caster angle of a suspension of a vehicle, and a caster angle adjusting device for adjusting the caster angle to a target caster angle. A control means for controlling an operation of the caster angle adjusting means; and an acceleration state detecting means for detecting that the vehicle is in an acceleration state, wherein the control means includes a target caster angle setting means, angle setting means is configured to set the target caster angle to suppress the pitching motion of the vehicle due to the acceleration when the vehicle is in an acceleration state based on information from the acceleration state detecting means, the second
The target caster angle setting means sets the
The pitching movement of the above-mentioned vehicle due to the acceleration of
The center of instantaneous rotation of the suspension
On a straight line connecting the heart and the moment's moment center of the car
Set the target caster angle so that it can be positioned
It is characterized by being constituted .

[0009]

[0010]

In the above-described caster angle control device for a vehicle according to the present invention, when it is detected from the acceleration state detecting means that the vehicle is in an accelerated state, the target caster angle setting means in the control means controls the acceleration. A target caster angle that can suppress the accompanying pitching movement of the vehicle is set.
At this time, the target caster angle setting means
The angle, the instantaneous center of rotation of the suspension is
Positioned on a straight line connecting the above momentary moment center of the car
Set to Then, the operation of the caster angle adjusting means is controlled by the control means, the caster angle of the suspension is adjusted to the target caster angle, and the pitching movement of the vehicle is suppressed.

[0011]

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given, with reference to the drawings, of a caster angle control device for an automobile according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram thereof, and FIG. FIGS. 3 and 4 are schematic side views of the vehicle body showing a pitching geometry for explaining the operation during acceleration and braking, respectively, for explaining a change in the center position.

In this embodiment, as shown in FIG.
Is supported on the vehicle body 1 of the vehicle by a McPherson strut type suspension 2. The suspension 2 has struts 4, a ball joint 5, and a lower arm 6. The lower end of the strut 4 and the outer end of the lower arm 6 are
The ball 3 is connected via a ball joint 5 to a knuckle (not shown) that supports the wheel 3.

The front end 6a and the rear end 6b of the inner end of the lower arm 6 are supported by the vehicle body 1 via a rubber bush (not shown) so as to be rotatable around the vehicle length direction axis. At this time, in the present embodiment, the vertical rigidity of the rubber bush supporting the front end 6a of the lower arm 6 is set to be softer than that of the rubber bush supporting the rear end 6b, and will be described later with reference to FIGS. As the strut 4 is driven forward and backward, the front end 6 of the lower arm 6
a can be displaced in the vertical direction.

Further, the upper end of the strut 4 is supported by the vehicle body 1 via a strut drive mechanism 7 as a caster adjusting means so as to be movable in the front-rear direction of the vehicle body 1.
As shown in FIGS. 1 and 2, the strut driving mechanism 7 drives the upper end of the strut 4 back and forth with respect to the vehicle body 1 so that the caster angle of the suspension 2 (the angle formed between the strut 4 and the vertical direction). The caster angle can be reduced by moving the upper end of the strut 4 forward, while the caster angle can be increased by moving the upper end of the strut 4 rearward.

On the other hand, in FIG. 1, reference numeral 8 denotes a G sensor as acceleration state detecting means for detecting an acceleration (acceleration state) of the vehicle body 1 in the front-rear direction, and 9 denotes a strut driving mechanism 7 so that the caster angle becomes the target caster angle. The controller 9 is a controller as a control means for controlling the operation of the controller. The controller 9 includes an acceleration determination unit 9a and a target caster angle setting means 9b.

Here, the acceleration determining section 9a determines whether the vehicle body 1 is in an accelerating state such as accelerating or braking (during deceleration) based on the acceleration detected by the G sensor 8. For example, the acceleration from the G sensor 8 is
If it exceeds the predetermined value for a certain period of time, it is determined that the vehicle is in an acceleration state. When the acceleration determining unit 9a determines that the vehicle body 1 is in an accelerating state, the target caster angle setting means 9b controls the instantaneous rotation of the suspension 2 in order to suppress the pitching movement of the vehicle body 1 due to the acceleration or braking. A straight line connecting the center IC (see FIGS. 2 to 4) to the center F, R of the wheel 3 (see FIGS. 3 and 4) and the momentary moment center MC or MC 'of the vehicle body 1 (see FIGS. 3 and 4). It is configured to set the target caster angle so that it can be positioned above.

The target caster angle set by the target caster angle setting means 9b is sent to the strut drive mechanism 7 as longitudinal position information on the upper end of the strut 4, and the strut drive mechanism 7 moves the upper end of the strut 4 to a predetermined position. Thus, the caster angle of the suspension 2 is adjusted to the target caster angle. Although only the front wheels 3 are shown in FIG. 1, a similar suspension 2 and strut driving mechanism 7 are provided on the rear side, and the caster angle of the suspension 2 is controlled by the controller 9 and the strut driving mechanism 7. Is to be adjusted.

Since the automobile caster angle control device according to one embodiment of the present invention is configured as described above, the acceleration judging section 9a determines whether or not the vehicle body 1 is accelerating based on the acceleration detected by the G sensor 8. If it is determined that the vehicle is in the acceleration state during braking, the instantaneous rotation center IC of the suspension 2
Is set on a straight line connecting the centers F and R of the front and rear wheels 3 and the instantaneous moment center MC during acceleration of the vehicle body 1 or the instantaneous moment center MC ′ during braking. Sets the target caster angle.

The target caster angle set by the target caster angle setting means 9b is sent to the strut drive mechanism 7 as longitudinal position information on the upper end of the strut 4, and the strut drive mechanism 7 drives the upper end of the strut 4 to a predetermined position. The caster angle of the suspension 2 is adjusted to the target caster angle. The change in the position of the instantaneous rotation center of the suspension due to such caster angle adjustment will be described with reference to FIG. In FIG. 2, A, A 'and A "denote positions of the front end 6a of the lower arm 6, and B denotes a ball joint 5
(Lower end of strut 4), C, C ', C "are upper end positions of strut 4, and D is rear end 6b of lower arm 6.
, IC, IC ′, IC ″ indicate the instantaneous rotation center of the suspension 2.

The state shown by the solid line corresponds to the normal reference position, in which the upper end of the strut 4 is located at the position C and the front end 6a of the lower arm 6 is located at the position A. Instantaneous rotation center IC of suspension 2
Is an A-D connecting a line passing through the upper end position C of the strut 4 and orthogonal to the direction in which the strut 4 is arranged, and the position A of the front end 6a and the position D of the rear end 6b of the lower arm 6.
Intersection with the line.

When the upper end position of the strut 4 is driven from the reference position C to the front position C 'by the strut driving mechanism 7, the caster angle is reduced, and the front end of the lower arm 6 supported by the soft rubber bush. 6a moves from the position A to the lower position A '. Accordingly, the instantaneous center of rotation of the suspension 2 is displaced from the position IC to the upper position IC '.

When the upper end position of the strut 4 is driven from the reference position C to the rear position C ″ by the strut drive mechanism 7, the caster angle increases, and the front end 6a of the lower arm 6 moves upward from the position A. To the position A ″. As a result, the instantaneous rotation center of the suspension 2 is displaced from the position IC to the lower position IC ". In the apparatus of this embodiment, the position of the instantaneous rotation center IC of the suspension 2 accompanying such caster angle adjustment is adjusted. The change is used to suppress the pitching movement of the vehicle body 1 due to acceleration or braking.

Next, the operating principle of the apparatus of this embodiment, that is, the instantaneous rotation center IC of the suspension 2 is defined by the center F of the wheel 3 and the instantaneous moment center MC of the vehicle body 1 during acceleration or the instantaneous moment center MC during braking. The reason why the pitching motion of the vehicle body 1 is suppressed when the vehicle body 1 is positioned on a straight line connecting the 'and' will be described with reference to FIGS. 3 and 4 show pitching geometries when the vehicle body 1 is accelerating and when braking (when decelerating), respectively. In these figures, Ff is a driving force or a braking force on the front wheel side, and Fr is a driving force or a braking force. When the total driving force is Fa and the front wheel driving force distribution ratio and the front wheel braking force distribution ratio are λ and λ ′, respectively, the front wheel driving force Ff is λ ·
Fa, the rear side driving force Fr is (1-λ) · Fa, the front side braking force Ff is λ ′ · Fa, and the rear side braking force Fr is (1−λ) · Fa.
λ ′) · Fa.

L is the wheel base, H _CG is the height of the center of gravity, Rt is the radius of the wheel 3, and G is the center of gravity of the vehicle body 1. At this time, the instantaneous moment center MC during acceleration is a point that divides the front and rear wheel centers F and R into λ: (1−λ) at a level above the radius Rt of the wheel 3 of the center of gravity G by braking. Is the point at the level of the center of gravity G that divides the center between the front and rear wheel centers F and R into λ ′ :( 1−λ ′).

Further, the symbols used in the following description will be described. W is the weight of the vehicle body 1, kf is the front wheel position spring constant, kr is the rear wheel position spring constant, and ηf is the front end of the lower arm 6 of the front suspension 2. The angle between the horizontal line and the line connecting the position A of the portion 6a and the instantaneous rotation center IC, ηr is the same angle as ηf in the rear suspension 2, and ηfo is the front wheel center F and the instantaneous moment center MC or MC. Is the angle between the horizontal line and the line connecting the rear wheel center R and the instantaneous moment center MC or MC '.

First, a description will be given of the case of acceleration of the vehicle body 1 with reference to FIG. 3. The pitching moment M around the center of gravity G due to the driving force via the suspension 2 becomes M = F · (H _CG −Rt), and the driving system torque reaction force T becomes T = F · Rt. Therefore, the pitching moment of the entire driving force around the center of gravity is M + T = F · _HCG .

At this time, the load movement amount ΔW from the front side to the rear side is as follows: ΔW = (M + T) / L = F · H _CG / L, and the extension stroke δf of the front suspension 2 is δf = (ΔW −λ · F · tanηf) / kf = (H _CG / L−λ · tanηf) · F / kf

In order to eliminate the pitching movement of the vehicle body 1, it is sufficient that the extension stroke δf becomes zero.
The condition of = 0 is H _CG / L−λ · tan ηf = 0, and tan ηf = H _CG / (λ · L) is obtained from this equation.

Similarly, tan ηr = H _CG / [(1−λ) · L] is obtained from the condition that the rear-side compression stroke δr is set to zero. As can be seen from the above equation, ηf = ηf
When o, ηr = ηro, that is, when the instantaneous rotational center IC of the suspension 2 is on a straight line connecting the front and rear wheel centers and the instantaneous moment center MC during acceleration, the longitudinal force is applied to the instantaneous rotational center direction. The vertical force, when decomposed into the vertical force and the vertical force, cancels out the load movement amount ΔW, does not cause a suspension stroke, and suppresses the pitching motion (nose-up) of the vehicle body 1 during acceleration.

On the other hand, when the vehicle body 1 is braked, all the braking force enters from the suspension 2, and as shown in FIG. 4, the pitching moment M around the center of gravity G at the time of braking is M = F · _HCG , From the front to the front side is ΔW = M / L = F · H _CG / L, and the compression stroke δf of the front suspension 2 is δf = (ΔW−λ ′ · F · tanηf) / kf = (H _CG / L−λ ′ · tanηf) · F / kf.

In order to eliminate the pitching movement of the vehicle body 1, it is sufficient that the compression stroke δf becomes zero.
The condition of = 0 is H _CG / L−λ ′ · tan ηf = 0. From this equation, tan ηf = H _CG / (λ ′ · L) is obtained.

Similarly, tanηr = H _CG / [(1−λ ′) · L] is obtained from the condition that the rear-side extension stroke δr is set to zero. As can be seen from the above-described equation, when ηf = ηfo and ηr = ηro, that is, when braking, the instantaneous rotation center IC of the suspension 2 becomes
The center of each wheel before and after and the moment moment MC 'during braking
When the longitudinal force is separated into a force in the direction of the instantaneous rotation center and a vertical force, the vertical force cancels the load movement amount ΔW, and does not cause a suspension stroke, and the vehicle body during braking The pitching movement (nose-down) of No. 1 is suppressed.

FIGS. 3 and 4 show the case where each of the front and rear wheels has a driving force, that is, the case of a four-wheel drive vehicle.
= 1 and λ = 0 for FR vehicles (rear-wheel drive vehicles). As described above, according to the vehicle caster angle control device of the present embodiment, the target caster angle setting means 9 b
Set the target caster angle to the instantaneous rotation center I of the suspension 2.
C is the wheel center and momentary moment center MC or M
By setting the upper end position of the strut 4 of each suspension 2 by the strut drive mechanism 7 so as to be located on the straight line connecting C ′ and the target caster angle, the suspension stroke is not caused. In addition, the pitching motion at the time of acceleration or braking of the vehicle is suppressed, and the riding comfort can be greatly improved.

In the above-described embodiment, the case where the device of the present invention is applied to a McPherson strut type suspension has been described. However, the present invention is not limited to this, and the wishbone type, multi-link type The same applies to other types of suspensions. Further, in the above-described embodiment, the caster angle adjusting means is configured such that the upper end position of the strut 4 is adjusted by the strut driving mechanism 7, but the apparatus of the present invention is not limited to this, and the apparatus of the present invention is not limited to this. Depending on the type, the caster angle adjusting means may be configured by rotating the arm itself or directly adjusting the mounting position of the arm.

Further, in the above-described embodiment, the case where the G sensor 8 is used as the acceleration state detecting means has been described. However, the present invention is not limited to this, and the acceleration state may be determined from the detection result of the vehicle speed sensor or the like. May be calculated and obtained.

[0037]

As described in detail above, according to the caster angle control device for a vehicle of the present invention, the caster angle adjusting means for adjusting the caster angle of the vehicle suspension, and the caster angle becomes the target caster angle. Control means for controlling the operation of the caster angle adjusting means, and acceleration state detecting means for detecting that the vehicle is in an acceleration state, and the target caster angle setting means provided in the control means, When the vehicle is in an accelerating state based on information from the acceleration state detecting means, the target caster angle is set so as to suppress the pitching movement of the vehicle due to the acceleration. Therefore, the acceleration is controlled by controlling the caster angle of the suspension. This has the advantage that the change in the attitude of the vehicle body during braking or braking can be reliably suppressed, and the riding comfort of the automobile can be greatly improved.

Further, the target caster angle setting means sets the target caster angle so that the instantaneous center of rotation of the suspension can be located on a straight line connecting the wheel center and the instantaneous moment center of the automobile. In this configuration, the suspension stroke is not caused, and the pitching motion of the vehicle is reliably suppressed, so that the riding comfort of the vehicle is greatly improved.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram for explaining a change in the position of an instantaneous rotation center of a suspension caused by adjustment of a caster angle by the device of the present embodiment.

FIG. 3 is a side view of the vehicle body showing a pitching geometry for explaining the operation of the device of the present embodiment during acceleration.

FIG. 4 is a side view of the vehicle body showing a pitching geometry for explaining an operation at the time of braking of the device of the present embodiment.

FIG. 5 is a diagram showing an anti-nose dive angle, an anti-nose up angle, and an ideal region thereof conventionally set for a front suspension.

FIG. 6 is a diagram illustrating an anti-tail lift angle, an anti-squat angle, and an ideal region thereof conventionally set for a rear suspension.

FIG. 7 is a schematic side view of a vehicle body for illustrating a conventional ideal anti-pitching suspension geometry.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 2 Suspension 3 Wheel 4 Strut 5 Ball joint 6 Lower arm 7 Strut drive mechanism as caster adjustment means 8 G sensor as acceleration state detection means 9 Controller as control means 9a Acceleration state determination unit 9b Target caster angle setting means

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takao Morita 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-60-47714 (JP, A) JP-A-61-41605 (JP, A) JP-A-2-220908 (JP, A) Japanese Utility Model Application Showa 60-69707 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60G 17 / 015

Claims (1)

(57) [Claims] A caster angle adjusting means for adjusting a caster angle of a suspension of the vehicle; a control means for controlling an operation of the caster angle adjusting means so that the caster angle becomes a target caster angle; An acceleration state detecting means for detecting that the vehicle is in a state, wherein the control means is provided with a target caster angle setting means, and the target caster angle setting means is adapted to accelerate the vehicle based on information from the acceleration state detecting means. When a state is configured to set the target caster angle to suppress the pitching motion of the vehicle due to the acceleration, the target caster angle setting means, an acceleration state of the motor vehicle
Sometimes suppresses the pitching movement of the car due to this acceleration
The suspension's instantaneous rotation center is
A straight line connecting the center of the wheel and the center of the moment of the car
Set the target caster angle so that it can be positioned above
A caster angle control device for an automobile, characterized in that it is configured as follows.