JPH0694246B2 - Car suspension - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle suspension adapted to perform wheel toe control.

(Prior Art) In recent years, in suspensions of automobiles, there have been many intentions of performing toe control of wheels, particularly rear wheels, so that a vehicle body exhibits preferable behavior according to a running state.

Among those that control the toe of the rear wheel, in relation to the lateral force acting on the rear wheel from the outside in the vehicle width direction (hereinafter also simply referred to as lateral force), when the lateral force is large, Then, there has been an increase in the rate of change in the toe-in direction of the rear wheels due to an increase in lateral force (Japanese Patent Laid-open No. Sho 61-96
60-148708 gazette). By doing so, when the lateral force becomes extremely large, such as when making a sharp turn or when changing lanes at high speeds, the rear wheels are set relatively in the toe-in direction to enhance the grip force of the rear wheels. While improving the stability, the turning ability (turning ability) is ensured when the lateral force is small, that is, at low and medium speeds.
In this case, the characteristic line showing the toe change amount of the wheel with respect to the lateral force is set to have one break point (characteristic change point).

As described above, the conventional toe control for the rear wheels according to the lateral force is toe-controlled in the direction in which the steering stability improves as the lateral force increases, that is, in the toe-in direction. In addition, it is also based on the idea that ensuring steering stability also leads to ensuring straight running stability. That is, both straight running stability and steering stability are obtained by increasing the grip force of the rear wheel by relatively toeing in the rear wheel and making the vehicle body hard to bend due to the increase in the grip force. There are some common points.

(Problems to be Solved by the Invention) However, the straight running stability when the toe control of the rear wheels is performed according to the lateral force as in the conventional case, particularly, the straight running stability at high speed is not always satisfactory. It didn't work.

By pursuing the reason why this straight running stability is not sufficiently satisfied, it acts on the rear wheel in a region where the steering stability is secured with a large change in the behavior of the vehicle body, such as during a sharp turn or a lane change. It has been found that the lateral force that exists is far from the magnitude of the lateral force when the vehicle is simply traveling straight at high speed. That is, it was found that the lateral force acting on the rear wheels is in a region smaller than the lateral force when turning is required when traveling straight at high speed.

The present invention has been made in consideration of the above circumstances,
In the one that controls the rear wheel toe according to the lateral force, while improving the turning performance when the lateral force is relatively small and securing the steering stability when the lateral force is relatively large, as in the past,
It is an object of the present invention to provide a vehicle suspension that can improve the straight running stability even when the lateral force is extremely small when performing high-speed straight running.

(Means and Actions for Solving Problems) In order to achieve the above-mentioned object, according to the present invention, as described above, the lateral force acting on the rear wheels in a driving state in which straight running stability is particularly required. Considering that the force is smaller than the lateral force that acts on the rear wheel in the driving state where turning is required, the toe control of the rear wheel by the magnitude of this lateral force is increased from the side with the smaller lateral force. In order from the side, it is divided into three regions, a region for straight running stability, a region for turning ability, and a region for steering stability. Specifically, the rear wheel is supported by the vehicle body so as to be movable up and down via a pair of lateral links arranged in front and back of the center of rotation.
In a suspension of an automobile in which elastic bushes are respectively interposed between the lateral links and the vehicle body, the front and rear elastic bushes are respectively arranged with respect to a direction in which a lateral force from the vehicle width direction outer side is input. The axial center is inclined and the stopper is arranged at a predetermined side end in the axial direction with a small gap from the elastic bush, so that the bending characteristic against the lateral force is applied to the stopper. It is set so that the rate of increase in the amount of deflection with respect to the increase in lateral force is greater than that after abutting until contacted, and the deflection characteristics of the front and rear elastic bushes with respect to the lateral force are set to be different. When the lateral force is smaller than the first predetermined value, the characteristic line showing the toe change amount of the rear wheel with respect to the lateral force is
When the lateral force is larger than the second predetermined value that is larger than the predetermined value, the lateral force of the rear wheel accompanying the increase of the lateral force is larger than when the lateral force is larger than the first predetermined value and smaller than the second predetermined value. The configuration is such that the rate of change in the toe-in direction is set to be large.

As described above, in summary, the characteristic line showing the toe change amount of the rear wheel with respect to the lateral force has only one break point in the past, but the present invention has two break points. By satisfying the turning ability when the force is moderate, the grip force of the rear wheel is relatively increased regardless of the region where the lateral force is smaller or larger than this, and the straight running stability is achieved. And controllability are obtained. That is, the break point on the side with the smaller lateral force is the first break point,
If the breaking point on the side where the lateral force is large is taken as the second breaking point, the straight-line stability is ensured when the lateral force until reaching the first breaking point is small as the lateral force increases. The control area is defined as a toe control area that ensures turning when the lateral force from the first break point to the second break point is medium, and when the lateral force after the second break point is large. This is the toe control area where steering stability is ensured.

More specifically, when the lateral force required for straight running is small (for example, 0.2 to 0.3G) and when the lateral force required for turning is moderate (for example, 0.4 to 0.5G), When large lateral force is required for stability (for example, 0.5 G or more)
Since the rate of change of the rear wheels in the toe-in direction is large with an increase in lateral force, it is possible to ensure straight running stability and steering stability while ensuring turning performance when the lateral force is moderate.

Further, in the present invention, the characteristic line indicating the toe change of the rear wheel as described above is set by the difference in the deflection characteristics of the front and rear bushes interposed between the front and rear lateral links and the vehicle body side. However, the two break points of the characteristic line are obtained at the time when the hard and soft boundaries of the bushes are reached, that is, when the bushes come into contact with the stopper.
In other words, the bush becomes soft until it comes into contact with the stopper due to its shearing action, and becomes hard due to its compression action after coming into contact with the stopper.
As described above, in order to obtain the breaking point of the characteristic line having two breaking points, it is set as the time when the bush comes into contact with the stopper, so that the vehicle body side is moved along with the vertical movement of the lateral link. This is preferable in that the effect of the torsional force acting on the bush is minimized and the desired characteristic line is easily and surely obtained.

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

FIG. 1 shows an example in which the present invention is applied to the rear wheels of an FF vehicle, but the suspensions for the left and right rear wheels have the same structure. Therefore, in the following description, the suspension for the right rear wheel will be described. For the left rear wheel suspension, the subscript "L" is used instead of the subscript "R" attached to the components for the right rear wheel, and the duplicated description is omitted.

In FIG. 1, reference numeral 1 denotes a sub-frame fixed to the vehicle body as a sprung weight, and the sub-frame 1 is provided with a swing arm type right suspension 2R and a right rear wheel.
3R is held vertically movable.

The suspension 2R includes a front lateral link 4R and a rear lateral link 5R extending in the vehicle width direction, and a hub 6R as a wheel support member extending in the vehicle longitudinal direction.
And have. The inner end of the front lateral link 4R (the inner end in the vehicle width direction) has a bush 8R with respect to a support shaft 7R held by a bracket 28R protruding from the subframe 1.
Is rotatably connected via. Similarly, the inner end portion (the inner end portion in the vehicle width direction) of the rear lateral link 5R is also rotatable via the bush 10R with respect to the support shaft 9R held by the bracket 29R protruding from the subframe 1. It is connected. The outer end of the front lateral link 4R is the same as the hub 6R.
Is rotatably connected via a bush 12R to a support shaft 11R projecting from the front end of the rear lateral link 5R, and an outer end of the rear lateral link 5R is supported by a support shaft 13R projecting from the rear end of the hub 6R. Rotatably connected via a bush 14R. And
A spindle 15R is provided on the outer end of the hub 6R so that the right rear wheel 3
R is rotatably held around the spindle 15R.

The front and rear lateral links 4R and 5R are arranged substantially parallel to each other, and a spindle 15R is arranged in the front-rear direction intermediate portion between the bushes 12R and 14R on the outer end side thereof. Further, the support shafts 7R, 9R, and hence the bushes 8R, 10R,
The shafts 11R and 13R, and hence the bushes 12R and 14R, are arranged to be inclined with respect to the vehicle body front-rear direction, and the axes thereof extend in the vehicle body front-rear direction. Then, a rear end of a tension rod 17R extending substantially in the vehicle front-rear direction is rotatably connected to a support shaft 16R protruding from an inner end of the hub 6R via a bush 18R, and the tension rod 17R The front end portion is rotatably connected to a support shaft 20R protruding from the vehicle body via a bush 19R. Of course, both the bushes 18R and 19R extend in the vehicle width direction, and the tension rod 17R ensures the rigidity of the hub 6R in the front-rear direction.

The hub 6R is connected to the lower end of a strut 27R including a hydraulic shock absorber and a coil spring as is known.

The bush 8R and the bush 10R are set so that their flexural characteristics are different as will be described later.
An example of the relationship between the amount of lateral force acting on 3R and the amount of deflection of the bushes 8R and 10R is shown in FIG. That is,
The bush 10R located on the rear side of the vehicle body has one breaking point α1 as shown by the R1 line in FIG. 4, and the load (lateral force) is α.
The deflection is set to be large (soft) when it is smaller than 1, and is set to be small (hard) after α1 is exceeded. The bush 8R located on the front side of the vehicle body also has one bending point β1 as shown by the F1 line in FIG.
Is set so that the deflection is large (soft) while the load is smaller than β1, and the deflection is small (hard) after the load exceeds β1. The characteristic lines R1 and F1 change at two points, γ1 and γ2, and the load is γ1.
Bush 8R when smaller than and when larger than γ2
The deflection amount of the bush 8R is made larger than that of the bush 10R, and the deflection amount of the bush 8R is made smaller than that of the bush 10R when the load is between γ1 and γ2. Of course,
Bushing 8L and 10L of the left rear wheel suspension have the same flexural characteristic relationship (bush 8L corresponds to 8R, bush 10L corresponds to 10R). The flexural characteristics of the bushes 12R (12L) and 14R (14L) are set to be the same as each other.

Next, due to the difference in the deflection characteristics of the bushes 8R and 10R described above, the relationship between the amount of lateral force acting on the right rear wheel 3R and the toe change amount of the right rear wheel 3R is shown by the characteristic line X in FIG. Yes, α1, β1, γ1, and γ2 in FIG. 2 correspond to those in FIG. 4, respectively.

The behavior change of the right rear wheel 3R based on the characteristic line X will be described with reference to FIG. In Fig. 3, the lateral force is indicated by F, and the posture change of the right rear wheel 3R is shown by a solid line when the lateral force F is "0" and by a chain line when the lateral force F is "small". , The lateral force F is “medium” by a two-dot chain line, and the lateral force F is “large” by a broken line. Also, O ₁ ~ O
₄ is the center line in the width direction of the right rear wheel 3R, and O ₁ is the lateral force “0”.
, O ₂ is when the lateral force is “small”, O ₃ is when the lateral force is “medium”, and O ₄ is when the lateral force is “large”. The bushes 8R and 10R are each schematically shown in the shape of a spring. In the embodiment, the dimensions of each member are set so that the lateral force F acts evenly on the bushes 8R and 10R. There is.

As is apparent from FIG. 3, when the lateral force F is 0,
The right rear wheel 3R faces straight ahead. When the lateral force F is small, the amount of deflection of the bush 8R on the front side is larger than the amount of deflection of the bush 10R on the rear side, so the right rear wheel 3R is toe-in, and straight running stability is ensured. When the lateral force F is "medium", the amount of deflection of the rear bush 10R is larger than the amount of deflection of the front bush 8R, so the right rear wheel 3
In R, the toe-in amount is relaxed (reduced) compared to when the lateral force F is “small”, and the turning performance, that is, the maneuverability is improved. That is, when the toe-in amount is relaxed, the understeering characteristic is weakened more than when the toe-in amount is "large", and the directional followability of the vehicle with respect to the turning of the steering wheel is improved. In addition, when the lateral force is “large”, the right rear wheel 3R is displaced in the toe-in direction again, strengthening the understeering tendency at the time of a sharp turn or a high-speed lane change to ensure steering stability. It

Of course, the behavior of the left rear wheel 3L when a lateral force, that is, a lateral force from the outside in the vehicle width direction acts on the left rear wheel 3L, is the same as the behavior of the right rear wheel described above.

Here, the movement of the left and right rear wheels when a lateral force acts from the inner side in the vehicle width direction is different from that in the above description, that is, an explanation assuming that the lateral force from the outer side in the vehicle width direction acts. The opposite is true. However, when turning, the centrifugal force acts on the inner wheels of the turning inner wheel in which the lateral force acts from the inner side in the vehicle width direction to the rear wheel on the outer turning wheel side in which lateral force acts from the outer side in the vehicle width direction. Since the load acts more than the rear wheel on the side,
The rear wheel on the turning outer wheel side controls the steering characteristics. That is, the steering characteristic is determined by how the rear wheels move with respect to the lateral force on the outer side in the vehicle width direction. In addition, straight running is a state in which a slight left turn and a right turn are repeatedly performed within an extremely short time.The steering characteristic during straight running is also the lateral force from the outside in the vehicle width direction. Will depend on the movement of the rear wheels based on.

Bushing 8R (8
L), 10R (10L) part is shown in Fig. 5 as a concrete example, and since each part of the bushes 8R and 10R has substantially the same structure, the bush 8R will be referred to in the following description. The explanation will focus on this.

First, the bush 8R includes an inner cylinder 21 into which the support shaft 7R is inserted, an outer cylinder 22 to which the front lateral link 4R is coupled, and both cylinders 21 and 22.
And a rubber material 23 filled between and. This outer cylinder 22
Has a flange portion 22a in the direction in which a component of lateral force input to the bush 8R via the front lateral link 4R is generated with respect to the support shaft 7R. Further, the rubber material 23 has a large diameter portion 23a which is further seated on the flange portion 23a and which extends further outward in the rear direction than the inner diameter of the outer cylinder 22. And
A portion of the bracket 28R that faces the large diameter portion 23a of the rubber member 23 in the axial direction of the support shaft 7R is a stopper 41. The gap between the stopper 41 and (the large diameter portion 23a of) the bush 8R when not receiving an external force is indicated by l1, and the gap in the bush 10R is indicated by l2.

Due to the inclination relationship of the support shafts 7R and 9R with respect to the lateral force input direction and the arrangement relationship of the stopper 41, the bushes 8R and 10R are
R has a flexure characteristic as shown in FIG. That is, when a lateral force is input to the bush 8R (10R) via the lateral link 4R (5R), the rubber material 23 is initially deformed by the shearing action and becomes relatively soft. After the shear deformation progresses and the large-diameter portion 23a of the rubber material 23 comes into contact with the stopper 41, the rubber material 23 is subjected to a compression action and becomes hard. Of course, the deflection of the bush 8R at the time of the break point β1 in Fig. 4 is shown in Fig. 5.
Almost equal to l1 and bush at the time of break point α1 in Fig. 4
The deflection of 10R is almost equal to 12 in Fig. 5. In this way, the bending points α1 and β1 are obtained by setting l1 and l2, but this depends on the bending deformation amount of the bushes 8R and 10R in the axial direction, and the lateral link 4R. , 5R is almost unrelated to the torsional force associated with vertical movement around the 7 or 9R support shaft, so there is almost no effect of this torsional force, and the break points α1 and β1 can be easily and securely set to the prescribed ones. Can be set to.

Here, the characteristic line X indicating the amount of change in the toe of the rear wheel 3R (3L) with respect to the lateral force F can be variously changed according to the vehicle type, as shown by the broken line in FIG. Each dot is indicated by a black circle. Even in the characteristic lines shown by these dashed lines, the rate of change in the toe-in direction with an increase in lateral force (toe-out can be regarded as negative toe-in) is
It is made smaller than the other part between the two break points.

Although the embodiments have been described above, the present invention can be similarly applied to a rear-wheel drive vehicle. Further, the present invention can be similarly applied to an appropriate type of suspension as long as it has front and rear lateral links. For example, the front and rear lateral links 4R and 5R shown in FIG. 1 are wider at their inner ends in the vehicle width direction than their outer ends, and the upper arms (rod-shaped or A-shaped) extending further in the vehicle width direction with respect to the hub 6R.
The present invention can be similarly applied to a so-called double wishbone type (multi-link type) in which molds and the like are connected in any shape. In the above multi-link type, the tension rod 17R (trailing arm) extending in the front-rear direction of the vehicle body is formed into a plate shape so that the rigidity in the vehicle width direction is small and the rigidity in the up-down direction is high. May be.

(Effects of the Invention) As is apparent from the above description, the present invention ensures straight running stability when lateral force is small, turning ability when lateral force is medium, and steering stability when lateral force is large. By satisfying all of the three conditions of securing, the behavior of the vehicle can be optimized according to the traveling state.

Further, in order to obtain the above-mentioned characteristics, since the deflection characteristic of the conventional bush interposed between the lateral link and the vehicle body is set to a predetermined value, the structure becomes simple.

Further, the bush interposed between the lateral link and the vehicle body side is provided with two break points which are characteristic change points in the desired characteristic line without being affected by the torsional force caused by the vertical movement of the lateral link. Because it is done
It is also preferable for easily and surely obtaining the desired characteristic line.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a suspension to which the present invention is applied. FIG. 2 is a graph showing an example of characteristic lines according to the present invention. FIG. 3 is a plan view showing a behavior change of a rear wheel based on a characteristic according to the present invention. FIG. 4 is a graph showing an example of the bending characteristics of the bush for obtaining the characteristics shown in FIG. FIG. 5 is a cross-sectional plan view showing in detail the portion of the bush interposed between the lateral link and the vehicle body side. 1: Subframe 2R, 2L: Suspension 3R, 3L: Rear wheel 4R, 4L: Front lateral link 5R, 5L: Rear lateral link 6R, 6L: Hub 7R, 7L: Spindle 8R, 8L: Bush (vehicle body side) 9R , 9L: Support shaft 10R, 10L: Rear bush (vehicle body side) 15R, 15L: Spindle (center of rotation) 41: Stopper α1, β1: Break points l1, l2: Small gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-36006 (JP, A) JP-A-61-285108 (JP, A) Actual development: JP-A-61-146407 (JP, U) Japanese Patent Publication 3- 73483 (JP, B2)

Claims (1)

[Claims] 1. A rear wheel is vertically movably supported by a vehicle body via a pair of lateral links arranged in front and back with a center of rotation as a boundary, and elastic bushes are respectively provided between the lateral links and the vehicle body. In the interposed vehicle suspension, the front and rear elastic bushes are arranged such that their axial centers are inclined with respect to the direction in which the lateral force from the vehicle width direction outer side is input. By disposing the stopper at a predetermined side end in the axial direction with a small gap from the elastic bush, the flexural characteristic against the lateral force is greater than that after the contact until the contact with the stopper. It is set so that the increasing rate of the flexure amount with respect to the force increase becomes large, and the flexural characteristics of the front and rear elastic bushes with respect to the lateral force are set to be different. Characteristic line showing the toe change of the rear wheel with respect to the lateral force when lateral force is smaller than the first predetermined value and the first
When the lateral force is larger than the second predetermined value that is larger than the predetermined value, the lateral force of the rear wheel accompanying the increase of the lateral force is larger than when the lateral force is larger than the first predetermined value and smaller than the second predetermined value. An automobile suspension characterized in that the change rate in the toe-in direction is set to be large.