JPH0694247B2 - 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 sometimes 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). That is, the rear wheel is vertically movably attached to the vehicle body through a pair of lateral links arranged in front and back with the center of rotation as a boundary, and the elastic force interposed in the connecting portion of the lateral link to the vehicle body side or the rear wheel side. By setting the flexural characteristics of the bush (which may be simply referred to as a bush hereinafter) differently between the front lateral link and the rear lateral link, the above-described toe control is obtained. 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 indicating the toe change amount of the wheel with respect to the lateral force has 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 condition 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 wheels are vertically movably held on the vehicle body via a pair of lateral links arranged in front and back with the center of rotation as a boundary.
In a suspension of an automobile in which elastic bushes are respectively interposed at connecting portions of each lateral link to a vehicle body side and a rear wheel side, the rear lateral link has a divided structure of an inner link and an outer link, and A first stopper that restricts relative displacement of the inner link and the outer link in the extension direction by a predetermined amount or more, and a second stopper that restricts relative displacement in the contraction direction by a predetermined amount or more.
The front lateral is provided with a stopper, and a spring precompressed in a direction of extending the inner link and the outer link in the link longitudinal direction is interposed between the inner link and the outer link, each of which includes the elastic bush. The flexural characteristics of the link system and the rear lateral link system with respect to the lateral force from the vehicle width direction outer side are set to be different from each other, and the lateral force is different due to the difference in the flexural characteristics of the front and rear lateral link systems with respect to the lateral force. When the lateral force is smaller than the first predetermined value and is larger than the second predetermined value that is larger than the first predetermined value, the lateral force is As compared with the case where it is larger than the first predetermined value and smaller than the second predetermined value, the rate of change of the rear wheels in the toe-in direction with the increase of the lateral force is set to be larger. There as formed.

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 steering stability will be 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, according to the present invention, instead of the bushes interposed in the connecting portions of the front and rear lateral links to the vehicle body side and the wheel side, the intermediate portions of the rear lateral links, that is, the inner links and the outer links that are relatively displaceable by a predetermined amount. By using a spring separately provided in a pre-compressed state at the connecting portion with and, the breaking point of the characteristic line for the toe control as described above is obtained, in other words, mainly for the purpose of ensuring ride comfort. Since it is not necessary to make the flexure characteristic of the bush described above complicated, the setting for the toe control can be performed easily and surely, and the degree of freedom of the setting becomes high.

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 that extends in the vehicle width direction, a rear lateral link 5R that is a split type as described later, and a hub 6R that extends in the vehicle front-rear direction as a wheel support member. . An inner end portion (an inner end portion in the vehicle width direction) of the front lateral link 4R is rotatably connected to a support shaft 7R projecting from the subframe 1 via a bush 8R, and an inner end portion of the rear lateral link 5R. The end portion (the inner end portion in the vehicle width direction) is rotatably connected to a support shaft 9R protruding from the subframe 1 via a bush 10R. Also, the outer end of the front lateral link 4R has a bush 12R with respect to the spindle 11R projecting from the front end of the hub 6R.
The rear end of the rear lateral link 5R is rotatably connected to the support shaft 13R projecting from the rear end of the hub 6R via a bush 14R. A spindle 15R is provided on the outer end of the hub 6R so that the right rear wheel 3R 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. As a result, the lateral force input to the rear wheel 3R is input to the front and rear lateral links 4R and 5R after being substantially evenly divided. Further, the support shafts 7R, 9R, 11R, 13R and the bushes 8R, 10R, 12R, 14R
The shaft center of each of them extends in the front-rear direction of the vehicle body, and therefore, the right rear wheel 3R is swingable in the vertical direction about the support shafts 7R and 9R. A rear end of a tension rod 17R extending substantially in the vehicle body front-rear direction is rotatably connected to a support shaft 16R projecting from the inner end of the hub 6R via a bush 18R. The front end is
It 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 rear lateral link 5R is configured by connecting the inner link 5R.1 and the outer link 5R.2, which are formed separately from each other, as described later, and the inner and outer links 5R.1 and 5R.2 are connected. The site is shown as 5R / 3. This binding site 5R / 3
As will be described later, the pre-compressed spring is interposed, and the deflection characteristics of the front lateral link 4 system including the bushes 8R and 12R are shown in FIG. 4F, and the springs are included in addition to the bushes 10R and 14R. The flexural characteristics of the rear lateral link 5R system are shown by the R line in FIG.

The details of the binding site 5R-3 in the posterior lateral link 5R are shown in FIG.

First, the inner link 5R-1 integrally has a cylinder 41 at the outer end thereof which is open outward in the vehicle width direction. Also,
An inner end portion of the outer link 5R / 2 integrally has a large-diameter piston 42 slidably fitted in the cylinder 41. The piston 42, that is, the outer link 5R / 2 is prevented from coming off through the elastic member 44 by the plug body 43 screwed to the cylinder 41, that is, the outer link 5R / 2 is separated from the inner link 5R / 1 by a predetermined amount or more. Is prevented. In addition, the cylinder
The outer link 5R, 2 is biased toward the rear wheel 3R by a spring 45 (a coil spring in the embodiment) arranged in a compressed state in 41. In other words, the spring is adjusted by adjusting the screwing position of the plug body 43 with respect to the cylinder 41.
The compression force of 45, that is, the pre-compression force is adjusted. As a result, the spring 45 that was initially pre-compressed against the external force that tries to shorten the front lateral link 5R.
When the external force becomes larger than the pre-compression force due to the large force due to, the spring 45 is contracted (the contraction of the rear lateral link 5R) in accordance with its elastic coefficient.
Then, after the spring 45 starts to contract, the outer link 5R
When 2 is displaced relative to the inner link 5R-1 by a predetermined displacement amount 1, the piston 42 contacts the stopper 41a of the cylinder 41, and after this contact, the further reduction of the rear lateral link 5R is restricted. .

As shown in FIGS. 6 and 7, each bush 8R, 10R, 12R, 14R has an inner cylinder 21 into which a support shaft 7R, 9R, 11R or 13R is fitted, and a lateral link 4R or 5R. Outer cylinder
22 and a rubber material 23 fitted between the two 21 and 22, and the hardness of the rubber material 23 is set to a predetermined hardness. First, the bushes 12R and 14R at the outer ends of the lateral links 4R and 5R are filled with the rubber material 23 having the same hardness, and therefore, the loads (lateral force) on the bushes 12R and 14R. And the amount of deflection are equal to each other. Front lateral link 4R Bushing 8R at the inner end and rear lateral link
The bush 10R at the inner end of the 5R is such that the bush 8R on the front side is softer than the bush 10R on the rear side.

Due to the difference in the setting of the bending characteristics of the bushes 8R and 10R as described above, the rear lateral link via the spring 45
With 5R configuration, front lateral link 4R system load (lateral force)
The flexure characteristic for the is shown in FIG. 4F, and the flexure characteristic of the rear lateral link R system is shown in FIG. 4R. That is, the characteristic line R has two break points α1 and β1.
With, the deflection is small (hard) as long as the load (lateral force) is smaller than β1, the deflection is large (soft) after exceeding β1, and the deflection is small again after exceeding α1. It is set to be (hard). Also,
The characteristic line is almost linear. And both characteristic lines F
And R change at two points, γ1 and γ2, and when the load is smaller than γ1 and larger than γ2, the front lateral link
The deflection amount of the 4R system is made larger than the deflection amount of the rear lateral link 5R system, and between the loads γ1 and γ2, the deflection amount of the front lateral link 4R system is made smaller than that of the rear lateral link 5R system. It Of course, the load at the break point β1 corresponds to the precompression force of the spring 45 in the rear lateral link 5R. In addition, the break point β from the origin of the characteristic line R
Bush 12 is the inclination up to 1 and the inclination after break point α1
Depends on the characteristics of R (14R).

Due to the difference in the deflection characteristics of the front and rear lateral links 4R and 5R systems, the relationship between the magnitude of the lateral force acting on the right rear wheel 3R and the toe change amount of the right rear wheel 3R is shown in Fig. 2 as the characteristic line X. 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
₃ is the center line of the right rear wheel 3R in the width direction, 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 front lateral link 4R system is larger than the amount of deflection of the rear lateral link 5R system, so the right rear wheel 3R is toe-in, and straight running stability is ensured. Also, the lateral force F
When is "medium", the amount of deflection of the rear lateral link 5R system is larger than the amount of deflection of the front lateral link 4R system, so the right rear wheel 3R has toe-in more than when the lateral force F is "small". The amount is eased (reduced), and the turning ability, 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.

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 in FIG. 1 whose inner ends in the vehicle width direction are wider than their outer ends, and upper arms (rod-shaped or A-shaped) extending further in the vehicle width direction with respect to the hub 6R. The same can be applied to the so-called double wishbone type (multi-link type) in which objects and the like are connected in any shape. In the above multi-link type, tension rod 17R that extends in the front-back direction of the vehicle body
The (trailing arm) may be formed in a plate shape so that the rigidity in the vehicle width direction is low and the rigidity in the vertical direction is high.

(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 characteristics satisfying the above three conditions, since the rear lateral link is a split type and the pre-compressed spring interposed in this split portion is used, the vehicle side of each lateral link or It is not necessary to make the bending characteristic of the bush provided at the connecting portion to the rear wheel side particularly complicated, and it is possible to set easily and surely according to the desired characteristic and the degree of freedom of setting is high.

BRIEF DESCRIPTION OF THE 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 deflection characteristics of the lateral link system before and after to obtain the characteristics shown in FIG. FIG. 5 is an enlarged cross-sectional view showing a connecting portion between the inner link and the outer link. FIG. 6 shows an example of a bush, and is a cross-sectional view in a direction orthogonal to the axis thereof, and FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 1: Subframe 2R, 2L: Suspension 3R, 3L: Rear wheel 4R, 4L: Front lateral link 5R, 5L: Rear lateral link 5R ・ 1: Inner link 5R ・ 2: Outer link 5R ・ 3: Joining parts 6R, 6L : Hub 8R, 8L: Front bushing 12R, 12L: Front bushing 10R, 10L: Rear bushing 14R, 14L: Rear bushing 15R, 15L: Spindle (rotating shaft center) 41: Cylinder 41a: Stopper 42: Piston 45: Spring α1, β1: Break point 1: Predetermined displacement

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-234705 (JP, A) SAIKAI Sho 59-68840 (JP, U) JP-B 3-73482 (JP, B2)

Claims (1)

[Claims] 1. A rear wheel is vertically movably held on a vehicle body via a pair of lateral links arranged in front and back of a center of rotation of the rear wheel, and the lateral links are connected to the vehicle body side and the rear wheel side. In a suspension of an automobile in which elastic bushes are respectively interposed in the parts, the rear lateral link has a divided structure of an inner link and an outer link, and the inner link and the outer link are relatively displaced in a predetermined direction or more in an extension direction. The first stopper for restricting the movement and the second stopper for restricting the relative displacement in the contraction direction more than a predetermined amount
The front lateral is provided with a stopper, and a spring precompressed in a direction of extending the inner link and the outer link in the link longitudinal direction is interposed between the inner link and the outer link, each of which includes the elastic bush. The flexural characteristics of the link system and the rear lateral link system with respect to the lateral force from the vehicle width direction outer side are set to be different from each other, and the lateral force is different due to the difference in the flexural characteristics of the front and rear lateral link systems with respect to the lateral force. When the lateral force is smaller than the first predetermined value and is larger than the second predetermined value that is larger than the first predetermined value, the lateral force is As compared with the case where it is larger than the first predetermined value and smaller than the second predetermined value, the rate of change of the rear wheels in the toe-in direction with the increase of the lateral force is set to be larger. Automotive suspension for the butterflies.