JP2011173562A - Suspension device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further reduce the wobbling of a steering wheel when the input from the road surface to a wheel fluctuates. <P>SOLUTION: A suspension device for a vehicle is configured in such a way that the kingpin offset δk, kingpin inclination θk, caster offset δc, and caster angle θc satisfy a relationship: δc×tan(θk)+δk×tan(θc)≤α (where α is a value near zero set in accordance with the suspension structure), and the caster offset δc is within a range set from the ratio of the moment on the vertical axis of the wheel to the lateral force of the wheel, when the wheel is at a neutral position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle suspension apparatus for suspending a vehicle body.

In a vehicle suspension apparatus, when improving the straightness of a vehicle, the relationship between the driver's intention to trace the target line and the steering response and vehicle motion is an important factor.
Specifically, it is important that the vehicle reacts quickly to the driver's steering operation and that the steering wheel does not shake against disturbance input from the road surface.

The characteristics of such a suspension device are related to the moment fluctuation around the kingpin axis with respect to the input from the wheel side.
Patent Document 1 discloses a stabilizer link structure that can change the direction in which the moment in the steering direction acts by the stabilizer.
With such a structure, according to the technique described in Patent Document 1, at the start of turning (at the start of steering), an increased moment is generated with respect to the suspension to improve the steering feeling. Further, at the time of steady turning (at the time of steering), a moment on the back side is generated with respect to the suspension so as to cause an understeer tendency to stabilize the vehicle.

JP 2006-082790 A

However, the technique described in Patent Document 1 is intended to improve the running stability of the vehicle by turning the wheels in the toe-in direction during turning.
For this reason, when the input from the wheel side fluctuates due to road surface irregularities or the like, the moment around the kingpin axis fluctuates and the steering wheel may be shaken.
As described above, in the conventional technique, it is difficult to sufficiently reduce the shake of the steering wheel when the input from the road surface to the wheel fluctuates.
An object of the present invention is to further reduce steering wheel shake when the input from the road surface to the wheels fluctuates.

In order to solve the above problems, the suspension device for a vehicle according to the present invention is configured such that the kingpin offset δk, the kingpin offset angle θk, the caster offset δc, and the caster angle θc satisfy the relationship of the following expression. . Further, when the wheel is in the neutral position, the caster offset is within a set range (for example, within the allowable range α1 of Mz / Fy) from the ratio of the moment about the vertical axis of the wheel and the lateral force of the wheel. It was.
δc · tan (θk) + δk · tan (θc) ≤ α (where α is a value near 0 set according to the suspension structure)

  According to the present invention, when the input from the road surface to the wheel fluctuates, the moment around the kingpin axis can be suppressed, so that the steering wheel shake can be further reduced.

It is a schematic block diagram of the motor vehicle 1A provided with the suspension apparatus 1 which concerns on 1st Embodiment. 1 is a diagram illustrating a configuration example of a suspension device 1. FIG. It is a figure explaining the parameter for defining a kingpin axis. It is a figure which shows the relationship between the slip angle (beta) in the tire ground-contact surface of the wheel in a cornering state, lateral force Fy, and restoring torque Mz. It is a figure which shows the case where the lateral force Fy of a wheel and the restoring torque Mz arise in a wheel center. It is a figure which shows the relationship between the lateral force Fy and the restoring torque Mz of a wheel center position, and the moment Mk around a kingpin axis | shaft. It is a figure which shows the relationship between the up-down direction load of a wheel, and a kingpin axis surrounding moment. 2 is a diagram illustrating an example of a suspension arm in the suspension device 1. FIG. It is a figure which shows the relationship between caster offset (delta) c and a moment fluctuation amount around a kingpin axis | shaft. It is a figure which shows the relationship between kingpin offset (delta) k and a kingpin axis surrounding moment fluctuation amount. It is a figure which shows the relationship between the turning angle of a wheel, and ground camber change. 2 is a diagram illustrating a specific configuration example of the suspension device 1. FIG. It is a figure which shows an example of the state which installed the suspension arm. It is a figure which shows the state which the suspension structure shown in FIG. 13 turned to the turning inner ring | wheel side. It is a figure which shows the other example of the state which installed the suspension arm. FIG. 16 is a view showing a state where the suspension structure shown in FIG. 15 is on the turning inner wheel side. It is a figure which shows the straight line which an equation represents when the right side of (2) Formula is set to the x-axis and the left side is set to the y-axis. It is a figure which shows the state which made the kingpin offset (delta) k zero by the suspension arm of the attachment position to the knuckle 14. It is a figure which shows the state which made the kingpin offset (delta) k zero with the suspension arm of the attachment position to the knuckle 14 at two points. It is a figure which shows the other structural example of the suspension apparatus 1 which concerns on 1st Embodiment. It is a figure which shows the other structural example of the suspension apparatus 1 which concerns on 1st Embodiment. It is a figure which shows the relationship between a slip angle and the force which acts on a wheel.

Embodiments of an automobile to which the present invention is applied will be described below with reference to the drawings.
(First embodiment)
(overall structure)
FIG. 1 is a schematic configuration diagram of an automobile 1A provided with a suspension device 1 according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration example of the suspension device 1, FIG. 2A is a specific structural example of the front suspension, and FIG. 2B is a schematic diagram illustrating a state where the suspension device 1 is installed in the automobile 1 </ b> A.

1 and 2, an automobile 1A includes a suspension device 1, a steering device 2, and wheels 3FL, 3FR, 3RL, and 3RR.
The suspension device 1 includes a vehicle body attachment member 11, suspension arms 12 and 13, a knuckle 14, a damper 15, and a hub 16.
The vehicle body attachment member 11 is a member for attaching the suspension arms 12 and 13 to the vehicle body, and supports the suspension arms 12 and 13 so as to be swingable in the vertical direction of the vehicle body.
The suspension arms 12 and 13 are, for example, A-shaped suspension arms, and are connected to the vehicle body by the vehicle body attachment member 11. In the present embodiment, the suspension arm 12 is an upper arm, and the suspension arm 13 is a lower arm.

  The knuckle 14 has suspension arms 12 and 13 rotatably supported at both ends thereof. A line connecting the upper and lower support points of the knuckle 14 constitutes a kingpin axis that is a virtual rotation axis. The knuckle 14 includes a hub 16 that rotatably holds the wheel. Furthermore, the knuckle 14 has a knuckle arm that transmits a steering input from the steering device 2 via a tie rod (not shown). The knuckle 14 swings around the support points of the suspension arms 12 and 13 when the knuckle arm receives the steering input from the steering device 2.

The damper 15 is a damping device such as an oil damper, and has an upper end fixed to the vehicle body and a lower end fixed to the lower arm. The suspension device 1 includes a spring (not shown) in parallel with the damper 15.
The hub 16 is a wheel holding member installed on the knuckle 14 and holds the wheel rotatably around the rotation axis.
The steering device 2 includes a steering wheel 21, a steering column 22, a pinion gear 23, and a rack gear 24.
The steering wheel 21 is connected to the steering column 22 and transmits the steering operation by the driver as a rotational motion around the axis of the steering column 22.
The steering column 22 includes a pinion gear 23 on the other end side of the steering wheel 21. The steering column 22 rotates the pinion gear 23 by the rotational movement around the axis transmitted from the steering wheel 21.

The pinion gear 23 meshes with the rack gear 24 and moves the rack gear 24 forward and backward in the vehicle left-right direction by the rotational movement of the steering column 22.
The rack gear 24 meshes with the pinion gear 23, and both ends thereof are connected to the respective knuckle arms via tie rods. The rack gear 24 advances and retreats in the left-right direction of the vehicle by the rotation of the pinion gear 23 and transmits force to the knuckle arm. Thereby, the steering input by the driver is transmitted to the knuckle arm, and the wheels 3FL and 3FR are steered when the knuckle 14 swings.

(Configuration around the kingpin axis)
(Caster offset conditions)
3A and 3B are diagrams for explaining parameters for defining the kingpin axis. FIG. 3A is a view of the wheel as viewed from the side of the vehicle (side view), and FIG. 3B is a view of the wheel from the front of the vehicle. It is the figure (front view) which it saw.
In FIG. 3, the kingpin axis of the wheel is the kingpin axis inclination angle (hereinafter referred to as “caster angle”) θc as viewed from the side, and the longitudinal offset in the wheel center height R of the kingpin axis as viewed from the side. Amount (hereinafter referred to as “caster offset”) δc, a tilt angle of the kingpin shaft viewed from the front (hereinafter referred to as “kingpin tilt angle”) θk, a wheel center height R of the kingpin shaft viewed from the front Left and right direction offset amount (hereinafter referred to as “kingpin offset”) δk.

FIG. 4 is a diagram showing the relationship between the slip angle β, the lateral force Fy, and the restoring torque Mz on the tire ground contact surface of the wheel in the cornering state.
In FIG. 4, if a slip angle β is generated on the wheel due to a deviation between the traveling direction of the wheel (the direction of the speed vector) and the direction of the wheel, a lateral force Fy is generated on the wheel. Since this lateral force Fy is applied to the rear side of the center of the tire ground contact surface of the wheel, a restoring torque Mz is generated in a direction that reduces the slip angle β with respect to the contact center.

FIG. 5 is a diagram showing a case where the lateral force Fy and the restoring torque Mz of the wheel are generated in the wheel center, and are shown for comparison with the case shown in FIG.
As shown in FIG. 4, the lateral force Fy generated when the wheel has a slip angle β has an applied point located behind the center of the tire contact surface. For this reason, as described above, the restoring torque Mz in the direction of decreasing the slip angle β is generated around the center of contact. On the other hand, as shown in FIG. 5, when the lateral force Fy and the restoring torque Mz of the wheel are generated at the wheel center, the lateral force Fy and the restoring torque Mz are not displaced in the front-rear direction and are at the same position (wheel Detected as a force acting on the center).

  FIG. 6 is a diagram showing the relationship between the lateral force Fy and restoring torque Mz at the wheel center position and the moment Mk around the kingpin axis. FIG. 6A shows a case where the caster offset δc is positive, and FIG. FIG. 6C shows a case where the caster offset δc is zero, and FIG. 6C shows a case where the caster offset δc is negative. In addition, each figure shown in FIG. 6 has shown the state which looked at the wheel from the upper surface, and when the kingpin axis | shaft exists ahead of a vehicle with respect to a wheel center, the caster offset (delta) c shall be positive.

  In FIG. 6, the lateral force Fy acting on the wheel center position is converted into a kingpin axis moment Mk using the caster offset δc as a moment arm. On the other hand, the restoring torque Mz acting on the wheel center is directly converted into a moment Mk around the kingpin axis. At this time, the moments around the kingpin axis can be classified into the following three patterns as shown in FIGS. 6A to 6C, depending on the positional relationship between the wheel center and the kingpin axis.

(1) When the caster offset δc is positive As shown in FIG. 6A, when the caster offset δc is positive, that is, when viewed from the side, the kingpin axis is ahead of the wheel center, the lateral force Fy The moment about the kingpin axis due to is in the same direction as the moment about the kingpin axis due to the restoring torque Mz, and each promotes rotation of the wheel around the kingpin axis.
(2) When the caster offset δc is zero As shown in FIG. 6B, when the caster offset δc is zero, that is, when the kingpin axis is coincident with the wheel center position as viewed from the side, the lateral force The moment around the kingpin axis due to Fy is not generated, and only the moment around the kingpin axis due to the restoring torque Mz is generated. In this case, rotation of the wheel around the kingpin axis by the restoring torque Mz occurs.
(3) When the caster offset δc is negative As shown in FIG. 6C, when the caster offset δc is negative, that is, when the kingpin axis is behind the wheel center as viewed from the side, the lateral force Fy The moments about the kingpin axis due to are opposite to the moments about the kingpin axis caused by the restoring torque Mz, and cancel each other.

In the present invention, the property in the pattern (3) is used. That is, when the slip angle β varies due to road surface irregularities or the like, the wheel also varies in the restoring torque Mz simultaneously with the lateral force Fy. The lateral force Fy and the restoring torque Mz of the wheel constantly change according to the shape and size of the road surface irregularity, the travel speed, the lateral acceleration, and the like.
For this reason, in order to prevent the moment Mk around the kingpin axis from fluctuating even if the slip angle β of the wheel fluctuates due to these factors, the wheel center and the wheel center according to the fluctuation of the lateral force Fy and the restoring torque Mz Is made substantially equal to a value obtained by the ratio Mz / Fy of the restoring torque Mz and the lateral force Fy, it is possible to prevent unnecessary shaking of the steering wheel 21.

(Kingpin offset conditions)
FIG. 7 is a diagram showing the relationship between the wheel vertical load and the moment about the kingpin axis. FIG. 7A shows the caster angle component (corresponding to the second term of the equation (1)), and FIG. 7B shows the kingpin inclination component (corresponding to the first term of the equation (1)). Yes.
The kingpin axis moment Mk due to the vertical force of the wheel can be separated into a caster angle component and a kingpin tilt component. In FIG. 7, it is assumed that the kingpin offset δk is positive when the kingpin axis is inside the vehicle body.
As shown in FIG. 7, the caster angle component means a moment around the kingpin at a position shifted by the kingpin offset δk in a state where the kingpin inclination angle θk is zero. In general, the kingpin axis at the height of the wheel center as viewed from the front is located on the inner side of the vehicle body relative to the wheel center, and therefore the kingpin offset δk takes only a positive value. Therefore, as the kingpin offset δk increases, the moment around the kingpin axis also increases.

  On the other hand, the kingpin tilt angle component means a moment around the kingpin at a position shifted by a caster offset δc in a state where the caster angle is zero. The kingpin shaft at the height of the wheel center as viewed from the side can be disposed either in front of or behind the vehicle body relative to the wheel center. At this time, the kingpin inclination component of the vertical force input to the wheel is positive when the caster offset δc is positive, that is, when the kingpin axis at the wheel center height is ahead of the wheel center and behind the wheel center. Depending on the case, the direction of the moment around the kingpin axis will be different.

  In the present invention, the moment around the kingpin axis, which varies depending on the position of the kingpin axis at the wheel center height, is used. That is, the caster angle component when the kingpin offset δk takes a positive value is canceled by the kingpin tilt component when the caster offset δc is negative. With such a configuration, even if the vertical force input to the wheel fluctuates, the moment fluctuation around the kingpin axis is suppressed, and unnecessary shaking of the steering wheel 21 can be prevented.

(Overall conditions)
FIG. 8 is a diagram illustrating an example of the suspension arms 12 and 13 in the suspension device 1. 8A is a substantially A-shaped suspension arm and the attachment position to the knuckle 14 is one point. FIG. 8B is a substantially A-shaped suspension arm and the attachment position to the knuckle 14 is two points. The case where it is divided is shown.
Based on the above results, in the suspension device 1 according to the present embodiment, the suspension arms illustrated in FIG. 8A or FIG. 8B are arranged above and below the knuckle 14 as an upper arm and a lower arm. The position of the kingpin shaft at the wheel center height as viewed from the side is arranged behind the wheel center, and the kingpin offset δk, kingpin tilt angle θk, caster offset δc, and caster angle θc are expressed by the following equation (1). Arrange to satisfy the relationship.
δc · tan (θk) + δk · tan (θc) ≤ 0 (1)
However, δc≈Mz / Fy.

By adopting such a configuration, it is possible to further reduce the shake of the steering wheel 21 when the input from the road surface to the wheels fluctuates.
Here, the caster offset δc is effective even if it includes an error of about 20% with respect to the value obtained by the ratio Mz / Fy of the restoring torque Mz and the lateral force Fy.

FIG. 9 is a diagram showing the relationship between the caster offset δc and the moment fluctuation amount around the kingpin axis.
In FIG. 9, when the caster offset δc is substantially equal to the ratio Mz / Fy of the restoring torque Mz and the lateral force Fy as compared with the case of the caster offset δc = 0 mm, and the value is set as an allowable range α1. This shows the effect of reducing the fluctuation amount of the moment around the kingpin axis when it is varied by 20%. In any of the cases shown in FIG. 9, it can be seen that if the allowable range α1 with respect to the caster offset δc is within ± 20% from Mz / Fy, the reduction effect is at least 30% or more.
The value of α1 can be set according to the suspension structure.
Further, the kingpin offset δk is effective even when an error of about 20% is included with respect to the value determined by using the equation (1) as an equation.

FIG. 10 is a diagram showing the relationship between the kingpin offset δk and the moment fluctuation amount around the kingpin axis.
In FIG. 10, compared to the case where the kingpin offset δk = 60 mm, when the equation (1) is made substantially equal to the value determined as an equation, and the value is varied by ± 20% as the allowable range α2. This shows the effect of reducing the fluctuation of the moment around the kingpin axis. In any case shown in FIG. 10, when the allowable range α2 with respect to the equation (1) as an equation is ± 20%, it can be seen that the reduction effect is at least 48% or more.

The value of α2 can be set according to the suspension structure.
Here, the basic condition in the equation (1) is the case where the left side = 0, and in this case, the load variation input to the wheel is always canceled out by the suspension structure of a single wheel.
On the other hand, in the region where the left side <0, the suspension structures in the left and right wheels interact with each other, thereby having an effect of canceling the disturbance.
That is, on a rusty road, a repair patch road, or a road surface with undulations, different disturbances may be applied to the left and right wheels from the road surface.
At this time, in the region of the left side <0, there is an effect of canceling out the influence of the disturbance input from the left and right other wheels.

(Steering angle-ground camber characteristics)
Next, the turning angle-ground camber characteristic when the kingpin axis is set as described above will be described.
FIG. 11 is a diagram showing the relationship between the turning angle of the wheel and the ground camber change. FIG. 11A shows the characteristics when the caster angle is 3 degrees, 6 degrees, and 9 degrees when the kingpin inclination angle is 6 degrees. FIG. 11B shows the characteristics when the kingpin tilt angle is 3 degrees, 6 degrees, and 9 degrees when the caster angle is 6 degrees.
As shown in FIG. 11A, when the caster angle is increased while maintaining the same kingpin inclination angle, the negative camber for the outer ring against the vehicle body can be increased, and the positive camber for the inner ring against the vehicle body can be increased.

That is, both the inner ring and the outer ring can cause the canvas last to turn inward, and the tire lateral force of the inner and outer rings can be increased.
Further, as shown in FIG. 11B, when the king pin inclination angle is reduced while maintaining the same caster angle, the negative camber of the outer ring against the vehicle body can be increased. On the other hand, when the kingpin inclination angle is increased, the positive camber of the inner ring against the vehicle body can be increased.
That is, both the inner ring and the outer ring can cause the canvas last to turn inward, and the tire lateral force of the inner and outer rings can be increased.
As described above, by selecting the caster angle θc and the kingpin inclination angle θk at which the tire lateral force becomes larger, the driver intentionally steers the vehicle while suppressing unintentional steering wheel 21 shake due to road surface irregularities and the like. When the wheel 21 is operated, the responsiveness of the vehicle can be improved.

(Function)
Next, the operation will be described.
FIG. 12 is a diagram illustrating a specific configuration example of the suspension device 1 according to the present embodiment.
The operation of the present invention will be described below with respect to the suspension structure having the configuration example shown in FIG.
12 is a substantially A-shaped suspension arm (see FIG. 8 (b)) that is divided into two attachment positions to the knuckle 14 so that the upper and lower support points of the knuckle 14 can be freely rotated and swung. An example configured to do this is shown. In this case, the kingpin axis is defined by a straight line 14a connecting the intersections extending from the upper arm links and the intersections extending from the lower arm links.

FIG. 13 shows the suspension structure shown in FIG. 12, in which the angle A1 formed by the link X on the front side of the vehicle body and the extension line L to the front side of the vehicle body is approximately 90 °, and the link Y on the rear side of the vehicle body and the extension line L to the front side of the vehicle body. Is a diagram showing a state in which the suspension arm is installed such that the angle formed between and becomes approximately 60 °. In addition, in FIG. 13, the outer wheel side at the time of steering is shown.
In the case of the example shown in FIG. 13, the knuckle attachment position x of the link X on the front side of the vehicle body moves on the arc L1 as the wheels are steered. Further, the knuckle attachment position y of the link Y on the vehicle body rear side moves on the arc L2 as the wheels are steered. As a result, the intersection point P obtained by extending the links X and Y moves from the position P1 to the position P2.

At this time, the distance in the vehicle front-rear direction between the wheel center and the kingpin shaft passing point changes from X1 to X2, and the distance in the vehicle left-right direction changes from Y1 to Y2. And can be moved to the outside of the vehicle body.
FIG. 14 is a view showing a state in which the suspension structure shown in FIG. 13 is on the turning inner wheel side.

In the case of the example shown in FIG. 14, the knuckle attachment position x of the link X on the vehicle body front side moves on the arc L <b> 1 as the wheels are steered. Further, the knuckle attachment position y of the link Y on the vehicle body rear side moves on the arc L2 as the wheels are steered. As a result, the intersection point P obtained by extending the links X and Y moves from P1 to P2.
At this time, the distance in the vehicle front-rear direction between the wheel center and the kingpin shaft passing point changes from X1 to X2, and the distance in the vehicle left-right direction changes from Y1 to Y2. And can be moved to the outside of the vehicle body.

In the present embodiment, the position of the kingpin shaft at the wheel center height as viewed from the side is arranged behind the wheel center, and the kingpin offset δk, the kingpin inclination angle θk, the caster offset δc, and the caster angle θc are ( 1) It is comprised so that the relationship of Formula may be satisfied.
Therefore, in any of the cases shown in FIGS. 13 and 14 described above, when a lateral force is applied to the wheels by turning, the moment around the kingpin axis due to the lateral force Fy is restored depending on the caster offset condition. The direction is opposite to the moment about the kingpin axis caused by the torque Mz, and they cancel each other.

Further, the caster angle component is canceled out by the kingpin inclination component for the vehicle vertical force input to the wheel depending on the kingpin offset condition.
For this reason, moment fluctuations around the kingpin axis are suppressed even with respect to fluctuations in the vertical force input to the wheels.
Therefore, according to the suspension device 1 according to the present embodiment, it is possible to further reduce the shake of the steering wheel 21 even when the lateral and vertical forces input to the wheels fluctuate.
In the present embodiment, the knuckle 14 corresponds to a knuckle, and the suspension arms 12 and 13 correspond to support members. Further, α2 shown as the allowable range of the expression (1) corresponds to α in the claims.

(Effect of 1st Embodiment)
(1) The kingpin offset δk, the kingpin pitch angle θk, the caster offset δc, and the caster angle θc are configured so as to satisfy the relationship of the following formula, and when the wheel is in the neutral position, the caster offset is From the ratio between the moment about the vertical axis of the wheel and the lateral force of the wheel, the configuration is within a set range (for example, within the allowable range α1 of Mz / Fy).
δc · tan (θk) + δk · tan (θc) ≤ α (where α is a value near 0 set according to the suspension structure)
Therefore, when the input from the road surface to the wheel fluctuates, the moment around the kingpin axis can be suppressed, and the steering wheel shake can be further reduced.

(2) By matching the caster offset to the ratio of the moment around the vertical axis of the wheel to the lateral force of the wheel, the moment around the kingpin axis due to the lateral force input to the wheel is opposite to the moment around the kingpin axis due to the restoring torque. Each direction cancels out.
Therefore, the shake of the steering wheel can be further reduced.
(3) The kingpin offset δk, the kingpin pitch angle θk, the caster offset δc, and the caster angle θc satisfy the following relationship.
δc · tan (θk) + δk · tan (θc) = 0
Thereby, it is possible to always cancel the load fluctuation input to the wheel with the suspension structure of the single wheel.

(Application 1)
In the configuration example of FIG. 12 described in the first embodiment, the suspension arm of the suspension device 1 can be installed as follows.
FIG. 15 shows the suspension structure shown in FIG. 12, in which the angle A1 between the link X on the front side of the vehicle body and the extension line L to the front side of the vehicle body is approximately 120 °, the link Y on the rear side of the vehicle body and the extension line L to the front side of the vehicle body. The suspension arm is installed so that the angle between the angle and the angle is approximately 90 °. In addition, in FIG. 15, the outer wheel side at the time of steering is shown.

In the case of the example shown in FIG. 15, the knuckle attachment position x of the link X on the front side of the vehicle body moves on the arc L1 as the wheels are steered. Further, the knuckle attachment position y of the link Y on the vehicle body rear side moves on the arc L2 as the wheels are steered. As a result, the intersection point P obtained by extending the links X and Y moves from P1 to P2.
At this time, the distance in the vehicle front-rear direction between the wheel center and the kingpin shaft passing point changes from X1 to X2, and the distance in the vehicle left-right direction changes from Y1 to Y2. And it can be moved inside the vehicle body.

FIG. 16 is a view showing a state in which the suspension structure shown in FIG. 15 is on the turning inner wheel side.
In the case of the example shown in FIG. 16, the knuckle attachment position x of the link X on the front side of the vehicle body moves on the arc L1 as the wheels are steered. Further, the knuckle attachment position y of the link Y on the vehicle body rear side moves on the arc L2 as the wheels are steered. As a result, the intersection point P obtained by extending the links X and Y moves from P1 to P2.
At this time, the distance in the vehicle front-rear direction between the wheel center and the kingpin shaft passing point changes from X1 to X2, and the distance in the vehicle left-right direction changes from Y1 to Y2. And it can be moved inside the vehicle body.

Also in this application example, as in the first embodiment, the position of the kingpin shaft at the wheel center height as viewed from the side is arranged behind the wheel center, and the kingpin offset δk, the kingpin tilt angle θk, and the caster offset δc and caster angle θc are configured to satisfy the relationship of the expression (1).
Therefore, in any of the cases shown in FIGS. 15 and 16 described above, when a lateral force is applied to the wheels by turning, the moment around the kingpin axis due to the lateral force Fy is restored depending on the caster offset condition. The direction is opposite to the moment about the kingpin axis caused by the torque Mz, and they cancel each other.

Further, the caster angle component is canceled out by the kingpin inclination component for the vehicle vertical force input to the wheel depending on the kingpin offset condition.
For this reason, moment fluctuations around the kingpin axis are suppressed even with respect to fluctuations in the vertical force input to the wheels.
Therefore, according to the suspension device 1 according to this application example, it is possible to further reduce the shake of the steering wheel 21 even when the lateral and vertical forces input to the wheels fluctuate.

(Application example 2)
In the first embodiment, the suspension device 1 has been described as satisfying the condition of the expression (1) so as to further reduce the shake of the steering wheel 21 when the input from the road surface to the wheel fluctuates.
In this application example, the configuration of the suspension is further examined, and an additional condition is set in Equation (1).
Hereinafter, additional conditions in this application example will be described.
The left side of the equation (1) can be rewritten as the following equation (2).
δc · tan (θk) ≤-δk · tan (θc) (2)
When the right side of equation (2) is taken on the x axis and the left side is taken on the y axis, the equation of equation (2) represents one straight line.

FIG. 17 is a diagram illustrating a straight line represented by an equation when the right side of the equation (2) is the x axis and the left side is the y axis.
In FIG. 17, the region near the origin is a region where the caster angle θc and the kingpin tilt angle θk are both zero, or the caster offset δc and the kingpin offset δk are both zero.
In this region, the suspension has the following characteristics.
(1) When the caster angle θc and the kingpin inclination angle θk are both zero When such a kingpin axis is set, the camber change of the wheel accompanying the turning becomes zero, and the effect of increasing the tire lateral force during turning cannot be used. It becomes. In this case, improvement in vehicle responsiveness cannot be expected.
(2) When the caster offset δc and the kingpin offset δk are both zero When such a kingpin axis is set, there is a possibility that the suspension arm interferes or the torsional rigidity around the wheel rotation axis decreases.

FIG. 18 is a diagram showing a state (solid line in the figure) in which the kingpin offset δk is zero at a suspension arm (see FIG. 8A) whose attachment position to the knuckle 14 is one point.
As shown in FIG. 18, when the upper and lower support points of the knuckle 14 connecting the suspension arms have one ball joint, it is necessary to make the ball joint coincide with the wheel center position in order to make the kingpin offset δk zero. There is.
In this case, it is difficult to make the kingpin offset δk zero because it interferes with parts such as a brake disposed inside the wheel.

FIG. 19 is a diagram showing a state where the kingpin offset δk is zero (suspension line in the figure) at the suspension arm (see FIG. 8B) where the attachment position to the knuckle 14 is two points.
As shown in FIG. 19, in the case where the upper and lower support points of the knuckle 14 connecting the suspension arms are provided with two ball joints, in order to make the kingpin offset zero, the space secured between the ball joints is wider. It becomes.
In this case, the wind-up moment acting on the wheel during acceleration makes it easy for the links before and after the suspension arm to twist in the vehicle vertical direction.
Therefore, the kingpin offset δk is desirably set to at least 20 mm, and the caster angle θc is desirably 3 degrees or more. That is, δk · tan (θc)> 1.05 (solid line portion in FIG. 19) is a region where a higher effect can be expected.

(Application 3)
With respect to the configuration example of FIG. 12 described in the first embodiment, the suspension device 1 can be configured as follows.
FIG. 20 is a diagram illustrating another configuration example of the suspension device 1 according to the first embodiment.
The configuration example shown in FIG. 20 shows an example in which the upper and lower support points of the knuckle 14 are configured to freely support rotation and swing by a substantially A-shaped suspension arm (see FIG. 8A). Yes. In this case, the kingpin axis is defined by a straight line 14 a connecting the upper and lower support points of the knuckle 14.
The present invention can also be applied to such a suspension structure, and even when the force input to the wheels fluctuates, it is possible to further reduce the shake of the steering wheel 21.

(Application 4)
With respect to the configuration example of FIG. 12 described in the first embodiment, the suspension device 1 can be configured as follows.
FIG. 21 is a diagram illustrating another configuration example of the suspension device 1 according to the first embodiment.
In the configuration example shown in FIG. 21, a substantially A-shaped suspension arm (see FIG. 8A) and a suspension arm substantially A-shaped and attached to the knuckle 14 at two points (FIG. 8B) Reference) shows an example in which the upper and lower support points of the knuckle 14 are configured to freely support rotation and swing. FIG. 21 shows a case where the upper arm is a substantially A-shaped suspension arm, and the lower arm is a substantially A-shaped suspension arm in which the attachment position to the knuckle 14 is divided into two points. However, the upper arm and the lower arm may be replaced with each other.

In the case of the configuration example shown in FIG. 21, the kingpin axis is defined by a straight line 14 a that connects a support point on the upper side of the knuckle 14 and an intersection that extends from the link of the lower arm.
The present invention can also be applied to such a suspension structure, and even when the force input to the wheels fluctuates, it is possible to further reduce the shake of the steering wheel 21.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the present embodiment, a condition in consideration of the wheel turning time is added to the condition of the suspension device 1 in the first embodiment.
Hereinafter, the conditions of the suspension device 1 at the time of wheel steering will be specifically described.
The lateral force Fy of the tire and the moment (restoring torque) Mz around the vertical axis vary depending on the vertical load, slip angle, camber angle, etc. input to the wheel.

FIG. 22 is a diagram showing the relationship between the slip angle and the force acting on the wheel. FIG. 22A shows a change in the tire lateral force Fy with respect to the slip angle, and FIG. 22B shows a change in the moment Mz about the vertical axis with respect to the slip angle. FIG. 22C shows the change in Mz / Fy with respect to the slip angle.
As shown in FIG. 22C, the value of Mz / Fy gradually decreases as the slip angle increases. That is, in the suspension structure of the first embodiment, if the wheel is in a neutral state, that is, if the slip angle is substantially equal to the value of Mz / Fy in the vicinity of zero, the shake of the steering wheel 21 can be further reduced.

On the other hand, in the suspension structure of the present embodiment, the suspension arm is arranged so that the caster offset becomes small according to the turning of the wheel.
Specifically, suspension arms are installed at the upper and lower support points of the knuckle 14 in the form shown in FIGS.
In this case, in the turning outer wheel or the turning inner wheel, the kingpin shaft passing point viewed from the wheel center moves forward as the turning angle increases, and the caster offset can be reduced.

As described above, in this embodiment, the suspension arm is arranged so that the caster offset is reduced according to the steering of the wheel, so that the steering wheel shake can be further reduced even when the vehicle is turning. Become.
Since the fluctuation of the moment about the kingpin axis is transmitted to the steering wheel via the steering rack or the steering column, suppressing the fluctuation of the moment about the kingpin axis leads to a reduction in the shake of the steering wheel.

(Effect of 2nd Embodiment)
(1) When the wheel is steered, at least one of the first support point constituting the kingpin shaft and the second support point constituting the kingpin shaft has a caster offset of a moment around the vertical axis of the wheel. It is the structure which moves so that it may become a ratio with the lateral force of a wheel.
Therefore, even if the slip angle increases and the ratio of the moment about the vertical axis of the wheel to the lateral force of the wheel decreases, the caster offset is matched to the ratio of the moment about the vertical axis of the wheel to the lateral force of the wheel. be able to.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
In the present embodiment, a condition in consideration of the wheel turning time is added to the condition of the suspension device 1 in the first embodiment.
Hereinafter, the conditions of the suspension device 1 at the time of wheel steering will be specifically described.
In the suspension device 1 of the present embodiment, the suspension arm is arranged so that the caster angle increases according to the turning of the wheel.
Specifically, the suspension arm is arranged on the lower side (lower arm) of the knuckle 14 in the form shown in FIGS. 13 and 14, and the upper side (upper arm) of the knuckle 14 is shown in FIGS. 15 and 16. The suspension arm is arranged in the form.

In this case, the amount of forward movement of the lower portion of the knuckle 14 becomes larger than the amount of movement of the upper portion of the knuckle 14 according to the turning, and the caster angle can be gradually increased.
Thus, in this embodiment, the ground camber angle with respect to the turning of the inner and outer wheels can be set inward of the turning of the vehicle, and the tire lateral force can be increased.
In other words, it is possible to improve the responsiveness of the vehicle when the driver intentionally operates the steering wheel while suppressing unintentional steering wheel shake due to road surface irregularities and the like.

(Effect of the third embodiment)
(1) The larger the turning angle of the wheel, the larger the caster angle of the inner and outer wheels than when the wheel is in the neutral position.
Therefore, the ground camber angle with respect to the turning of the inner and outer wheels can be set inward of the turning of the vehicle, and the tire lateral force can be increased.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
In the present embodiment, a condition in consideration of the wheel turning time is added to the condition of the suspension device 1 in the first embodiment.
Hereinafter, the conditions of the suspension device 1 at the time of wheel steering will be specifically described.
In the suspension device 1 of the present embodiment, the suspension arm is disposed so that the king pin inclination angle of the outer ring becomes smaller than the king pin inclination angle of the inner ring in accordance with the steering of the wheel.

Specifically, the suspension arm is arranged on the lower side (lower arm) of the knuckle 14 in the form shown in FIGS. 15 and 16, and the upper side (upper arm) of the knuckle 14 is shown in FIGS. The suspension arm is arranged in the form.
In this case, the amount of movement in the left-right direction of the lower part of the knuckle 14 becomes larger than the amount of movement of the upper part of the knuckle 14 in the left-right direction according to the turning, and the kingpin inclination angle can be gradually reduced.

Thus, in this embodiment, the ground camber angle with respect to the turning of the inner and outer wheels can be set inward of the turning of the vehicle, and the tire lateral force can be increased.
In other words, it is possible to improve the responsiveness of the vehicle when the driver intentionally operates the steering wheel while suppressing unintentional steering wheel shake due to road surface irregularities and the like.
(Effect of 4th Embodiment)
(1) As the turning angle of the wheel increases, the king pin inclination angle of the outer ring becomes smaller than the king pin inclination angle of the inner ring.
Therefore, the ground camber angle with respect to the turning of the inner and outer wheels can be set inward of the turning of the vehicle, and the tire lateral force can be increased.

DESCRIPTION OF SYMBOLS 1 Suspension apparatus, 1A automobile, 2 Steering apparatus, 3FL, 3FR, 3RL, 3RR Wheel, 11 Car body mounting member, 12, 13 Suspension arm, 14 Knuckle, 15 Damper, 16 Hub, 21 Steering wheel, 22 Steering column, 23 Pinion Gear, 24 rack gear

Claims (6)

A knuckle that swings with the wheels during steering,
A support member for swingably supporting the knuckle,
The kingpin offset δk that is the distance between the kingpin axis and the wheel center at the wheel center height in front view, the kingpin angle θk that is the angle between the kingpin axis and the vertical line in front view, and the wheel center in side view The caster offset δc, which is the distance between the kingpin axis at the height and the wheel center, and the caster angle θc, which is the angle between the kingpin axis and the vertical line in side view, satisfy the relationship of the following equation (1):
A suspension apparatus for a vehicle, wherein when the wheel is in a neutral position, the caster offset δc is within a set range from a ratio of a moment around a vertical axis of the wheel and a lateral force of the wheel.
δc · tan (θk) + δk · tan (θc) ≤ α (1)
However, α is a value near 0 set according to the suspension structure.   2. The vehicle suspension apparatus according to claim 1, wherein the caster offset is a ratio of a moment around a vertical axis of a wheel and a lateral force of the wheel. 3. The vehicle suspension according to claim 1, wherein the kingpin offset δk, the kingpin pitch angle θk, the caster offset δc, and the caster angle θc satisfy the relationship of the following expression (2): apparatus.
δc · tan (θk) + δk · tan (θc) = 0 (2)   When the wheel is steered, at least one of the first support point constituting the kingpin axis and the second support point constituting the kingpin axis is such that the caster offset is a moment around the vertical axis of the wheel and the The vehicle suspension device according to any one of claims 1 to 3, wherein the vehicle suspension device is configured to move so as to have a ratio to a lateral force of the wheel.   5. The vehicle suspension according to claim 1, wherein the larger the turning angle of the wheel, the larger the caster angle of the inner and outer wheels than when the turning angle is in a neutral position. 6. apparatus.   The vehicle suspension device according to any one of claims 1 to 4, wherein the king pin inclination angle of the outer ring becomes smaller than the king pin angle of the inner ring as the turning angle of the wheel becomes larger.

Images