JPH0694244B2 - 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 many suspensions of automobiles, the toe control of the rear wheels is performed after the wheels so that the vehicle body behaves in a preferable manner according to the 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).

Further, as one type of the toe control of the rear wheels according to the lateral force, a sensor for detecting a lateral G (lateral acceleration) generated in response to the lateral force acting on the rear wheels is provided.
When the value exceeds a predetermined value, the hydraulic cylinder connected to the rear wheel suspension is operated to force the rear wheel to move in the toe-in direction within the elastic deformation range of the elastic member incorporated in the suspension. Some have been proposed. Also in this case, the characteristic line showing the toe change amount of the rear wheel with respect to the lateral force is set as having one break 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 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 at the rear wheel side and the vehicle body side connecting portions of the lateral links, a lateral direction from the vehicle width direction outer side of each of the front and rear elastic bushes on the vehicle body side is provided. Deflection characteristics indicating the amount of deflection with respect to force are set such that the increase rate of the deflection amount with the increase of the lateral force is different when the lateral force is larger than a predetermined value and when the lateral force is smaller than the predetermined value. Values are set to be different from each other in the front and rear elastic bushes, and due to the difference in the flexural characteristics of the front lateral link system and the rear lateral link system including the elastic bushes against the lateral force, The characteristic line indicating the amount of change in toe of the rear wheel is such that the lateral force is smaller than the smaller first predetermined value of the two different predetermined values and the larger second line thereof. When the lateral force is larger than the constant value, the rate of change of the rear wheels in the toe-in direction due to 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 it 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 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.

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. 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 protruding from the subframe 1 via a bush 8R,
The inner end of the rear lateral link 5R (the inner end in the vehicle width direction) has a bush 10R with respect to the support shaft 9R protruding from the subframe 1.
Is rotatably connected via. The outer end of the front lateral link 4R is rotatably connected to the support shaft 11R projecting from the front end of the hub 6R via a bush 12R, and the outer end of the rear lateral link 5R is It is rotatably connected to a 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. Further, the support shafts 7R, 9R, 11R, 13R and the bushes 8R, 10
The axes of R, 12R, and 14R extend in the front-rear direction of the vehicle body, respectively. Therefore, the right rear wheel 3R can swing vertically about the support shafts 7R and 9R. And hub 6R
On the support shaft 16R projecting from the inner end of the, the rear end of the tension rod 17R that extends almost in the longitudinal direction of the vehicle body
The tension rod 17R is rotatably connected via
The front end portion of 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 bushes 8R and 10R have different flexural characteristics, and an example of the relationship between the magnitude of the lateral force acting on the rear wheel 3R and the flexure amounts of the bushes 8R, 10R is shown in FIG. That is, the bush 10R located on the rear side of the vehicle body
Has one break point α1 as shown by line R1 in Fig. 4, and its deflection is large (soft) while the load (lateral force) is smaller than α1, and the deflection is small after α1. It is set to be (hard). In addition, the bush 8R located on the front side of the vehicle body and one bending point β1 as shown by the F1 line in FIG. The flexure is set to be small (hard) from the beginning. The characteristic lines R1 and F1 change at two points of γ1 and γ2. When the load is smaller than γ1 and larger than γ2, the amount of deflection of the bush 8R is made larger than that of the bush 10R, and the load is Between γ1 and γ2, the amount of deflection of the bush 8R is made smaller than the amount of deflection of the bush 10R. Of course, the bush 8 of the left rear wheel suspension
The flexural characteristics of L and 10L are similar (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 flexural 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, this second
Α1, β1, γ1, and γ2 in the figure 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.

Bushings 8R (8L), 10 with the above-mentioned flexibility characteristics
Specific configuration example of R (10L) bush 12R (12L), 14R (1
4L). The following description focuses on the right rear wheel 3R.

Each bush 8R, 10R, 12R, 14R is shown in FIG. 6 and FIG.
As shown in FIG. 13, an inner cylinder 21 into which the support shafts 7R, 9R, 11R or 13R are fitted, an outer cylinder 22 into which the lateral links 4R or 5R are joined, and between the both 21 and 22. Although the rubber material 23 is inserted, the structure of the rubber material 23 is different in detail.

First, the bushes 12R, 1 at the outer ends of the lateral links 4R, 5R
As shown in FIG. 8 and FIG. 9, 4R is filled with a rubber material 23 having the same hardness between the inner cylinder 21 and the outer cylinder 22, respectively. The relationship between the lateral force and the amount of deflection in 12R and 14R is equal to each other.

The bush 8R at the inner end of the front lateral link 4R is
As shown in FIG. 11 and FIG. 11 (see also FIG. 6), the outer circumference of the rubber material 23 is positioned on the line of action of lateral force, and is separated from the inner cylinder 21 by 180 ° in the circumferential direction. Two first hollow portions 24 (cutout grooves) having a circular arc shape in cross section are formed, and a second hollow portion 25 continuous with the first hollow portion 24 is formed in an axially intermediate portion thereof. And this second hollow part
Similarly to the first hollow portion 24, the reference numeral 25 extends in an arc in the circumferential direction of the inner cylinder 21. Therefore, when the lateral force (acting in the vertical direction in Fig. 10) is small, the
Due to the presence of the hollow portion 24, the deflection thereof becomes sufficiently large, and after the lateral force becomes large and the first hollow portion 24 is crushed, the deflection becomes small. However, due to the presence of the second hollow portion 25, the lateral force is increased. The increase in the amount of deflection with respect to the increase is considered to be relatively large (Fig. 4, line F1).

The bush 10R at the inner end of the rear lateral link 5R is
As shown in FIG. 13 and FIG. 13 (see also FIG. 6), the bush 8R is configured to be the same as the bush 8R except that the bush 8R does not have the second hollow portion 25. . Since the second hollow portion 25 does not exist, the bending characteristic of the bush 10R is as shown by the R1 line in FIG.
The amount of deflection until the first hollow portion 24 is crushed is made smaller than that of the bush 8R, and the amount of deflection after the first hollow portion 24 is crushed is made extremely small.

Of course, the bush for the left rear wheel 3L is set in the same way as the right rear wheel 3R.

FIG. 5 is another modified example corresponding to FIG. 4 for obtaining the characteristic line X as shown in FIG. 2, in which the deflection characteristic of the front lateral link 4R system including the bushes 8R and 12R is F2 line, In addition, the flexural characteristics of the rear lateral link 5R system including the bushes 10R and 14R are shown by the R2 line. Note that α1, β1, γ1, and γ2 are set corresponding to FIG. In this embodiment, as shown in FIG. 7, both the bushes 8R and 10R are made of rubber material 2
A thick plastic plate 26 is press-fitted into the hollow portion 24 'of the third member in the radial direction of the inner cylinder 21 relative to the hollow portion 24' so that a lateral force acts on the rubber material 23. On the other hand, a pre-compression force is applied. The pre-compression force of the bush 10R is smaller than that of the bush 8R. Further, the hardness of the rubber material 23 in each bush 8R, 10R, 12R, 14R is changed. This allows the F2
As shown by the line and R2 line, the amount of deflection with respect to the load decreases until the lateral force reaches a value equivalent to the precompression force, but when the force exceeds this precompression force, the amount of deflection increases. . Even in the case of this embodiment, the behavioral change of the rear wheel 3R (3L) with respect to the magnitude of the lateral force is as shown in FIG. 3 (behavioral change according to the characteristic line X in FIG. 2).

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.

FIGS. 14 to 16 are examples in which the present invention is applied to a suspension of a type different from that of FIG. 1, and the same components as those of FIG. 1 are designated by the same reference numerals and their description is omitted. To do.

Fig. 14 shows the left rear wheel 3L side as an example. Compared with the one in Fig. 1, the distance between the front and rear lateral links 4L, 5L is
This is a so-called trapezoidal link type in which the inner side end of the vehicle body is larger than the outer side end of the vehicle body.

FIG. 15 shows a rod-shaped upper arm 31L extending linearly in the vehicle width direction, which is further added to that of FIG. 1, and the hub 6L and the vehicle body (subframe 1) are added by the upper arm 31L. And the tension rod
17L is plate-shaped.

FIG. 16 shows the linear upper arm in FIG.
Instead of 31L, type A upper arm 32R (Fig. 16 shows the right rear wheel)
3R) is used.

In addition, in the suspensions shown in FIGS. 14, 15 and 16, the bushes 8R (8L) and 10R (10L) provided at the inner ends of the pair of front and rear lateral links 4R (4L) and 5R (5L) are used. Due to the deflection characteristics, the behavior change of the rear wheel 3R (3L) as shown in FIG. 3 can be obtained.

Although the embodiments have been described above, the present invention can be similarly applied to a rear-wheel drive vehicle. Further, the characteristic according to the present invention is that at least an arbitrary pair of front and rear bushes (elastic member) of the front side bush 8R (8L) or 12R (12L) and the rear side bush 10R (12L) or 14R (14L). It can be obtained by a combination of the bending characteristics of

(Effects of the Invention) As is apparent from the above description, the present invention ensures straight-line stability when lateral force is small, secures swivelability when lateral force is moderate, 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 the present invention, the elastic member itself, which is interposed between the rear wheel and the vehicle body, is elastically deformed when a lateral force is applied from the outside in the vehicle width direction. Since the toe change is obtained, it can be implemented inexpensively and easily, and the followability of the toe change of the rear wheel to the change in the lateral force is also high.

[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 and FIG. 5 are graphs showing examples of deflection characteristics for obtaining the characteristics shown in FIG. 2, respectively. 6 and 7
The figure is a perspective view showing an example of a bush for obtaining the characteristics according to the present invention together with a state of being coupled with a lateral link. FIGS. 8 to 13 show examples of bushes for obtaining the characteristics of the present invention. FIGS. 8, 10, and 12 are radial cross-sectional views thereof, and FIG. 9 is FIG. 11 is a sectional view taken along line IX-IX of FIG. 11, FIG. 11 is a sectional view taken along line XI-XI of FIG. 10, and FIG. 13 is a sectional view taken along line XIII-XIII of FIG. 14th
FIGS. 15, 15 and 16 are views showing other examples of suspensions to which the present invention is applied. 1: Subframe 2R, 2L: Suspension 3R, 3L: Rear wheel 4R, 4L: Front lateral link 5R, 5L: Rear lateral link 6R, 6L: Hub 8R, 8L: Front side bush 12R, 12L: Front side bush 10R, 10L: Rear bush 14R, 14L: Rear bush α1, β1: Break point

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography SHO 61-201911 (JP, U) RIE 62-28604 (JP, U) JP-B 3-73483 (JP, B2) JP 61- 44881 (JP, Y1)

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 a connecting portion of each of the lateral links on the rear wheel side and the vehicle body side. In the suspension of the automobile in which the elastic bushes are respectively interposed, the deflection characteristics indicating the amount of deflection with respect to the lateral force from the vehicle width direction outer side of the front and rear elastic bushes on the vehicle body side are respectively the lateral force. Is set to be larger than and smaller than a predetermined value so that the increasing rate of the flexure amount with the increase of the lateral force is different, and the predetermined value is set to be different between the front and rear elastic bushes. Due to the difference in the flexural characteristics of the front lateral link system and the rear lateral link system including the elastic bushes against the lateral force, the toe change of the rear wheel with respect to the lateral force. When the lateral force is smaller than the smaller first predetermined value of the two different predetermined values and larger than the larger second predetermined value of the two different predetermined values, the lateral force is the first It is set so that the rate of change of the rear wheels in the toe-in direction due to the increase of the lateral force is larger than that when the lateral force is larger than a predetermined value and smaller than the second predetermined value. Car suspension to do.