JPS62251215A - Suspension of automobile - Google Patents

Abstract

PURPOSE:To secure stability in straight advancing particularly at the time of high speed by differentiating the precompressing forces and elastic moduli of springs as well as the hardness of bushes from each other to differentiate the deflecting characteristics between front and rear lateral links and adjusting the rate of change in the toe-in of a rear wheel accompanying increase in a lateral force. CONSTITUTION:A right rear wheel 3R, for example, is supported vertically movably by a sub-frame 1 via a right side suspension 2R. The suspension 2R has front and rear lateral links 4R, 5R and a hub 6R. And, the inner end parts of the front and rear lateral links 4R, 5R are rotatably connected to supporting shafts 7R, 9R via bushes 8R, 10R respectively. In this case, springs are installed in the middle connecting parts 4R3, 5R3 of the front and rear lateral links 4R, 5R respectively,and the precompressing forces and elastic moduli of the springs are differentiated from each other. And, the hardness of the bushes 8R, 10R are also differentiated from each other. Thereby, the deflecting characteristics of the front and rear lateral links 4R, 5R are differentiated from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automobile suspension that performs toe control of wheels.

(Prior Art) In recent years, many suspensions for automobiles are designed to perform toe control on the wheels, particularly the rear wheels, so that the vehicle body exhibits preferable behavior depending on the driving conditions.

Some devices that control the toe of the rear wheels are designed to increase the rate of change in the toe-in direction of the rear wheel when the lateral force is large, compared to when the lateral force is small, in relation to the lateral force acting on the rear wheel. There is something that was done (Japanese Patent Publication No. 1983
In other words, the rear wheel is attached to the vehicle body so as to be movable up and down via a pair of lateral links arranged front and rear with respect to its center of rotation, and the rear wheels are attached to the vehicle body side or the rear wheel side of the lateral links. By setting the deflection characteristics of the bushing interposed in the connecting portion to be different between the front lateral link and the rear lateral link, the above-mentioned toe control I-roll can be obtained. By doing this, when the special lateral force required for lane change during sharp turns or high-speed driving becomes extremely large, the rear wheels are relatively set in the toe-in direction, increasing the grip force of the rear wheels and stabilizing the steering. While improving performance, turning performance (turning performance) is ensured when lateral force is small, that is, at low and medium speeds. In this case, the characteristic line indicating the amount of change in wheel toe with respect to lateral force has one bending point (characteristic change point).

As mentioned above, in conventional systems that perform toe control of the rear wheels according to lateral force, the greater the lateral force, the more the toe control is performed in the direction that improves steering stability, that is, in the toe-in direction. It is also based on the idea that ensuring steering stability also leads to ensuring straight-line stability. In other words, both straight-line stability and handling stability are achieved by increasing the grip of the rear wheels by relatively toe-in the rear wheels, and this increased grip makes it difficult for the vehicle to bend. There are some things in common.

(Problems to be Solved by the Invention) However, when the toe control of the rear wheels is performed according to the lateral force as in the conventional method, the straight-line stability, especially the straight-line stability at high speeds, is not always fully satisfactory. It didn't turn out to be anything.

After investigating the cause of insufficient straight-line stability, we found that the rear wheels are affected by large changes in the behavior of the vehicle, such as when making sharp turns or changing lanes, in order to maintain steering stability. It has been found that the lateral force that occurs is far different from the lateral force that occurs when the vehicle is simply continuously traveling in a straight line at high speed. That is, it has been found that when the vehicle is traveling straight at high speed, the lateral force acting on the rear wheels is in a region that is even smaller than the magnitude of the lateral force when turning performance is required.

The present invention was made in consideration of the above circumstances, and
In a vehicle that toe-controls the rear wheels in response to lateral force, it improves turning performance when lateral force is relatively small and maintains steering stability when lateral force is relatively large, while driving in a straight line at high speed. It is an object of the present invention to provide a suspension for an automobile that can improve straight-line stability even when the lateral force is extremely small.

(Means and Actions for Solving the Problems) In order to achieve the above-mentioned object, the present invention has the following features: Considering that the force is smaller than the lateral force acting on the rear wheels in driving conditions that require unidirectionality, the toe control of the rear wheels due to the magnitude of this lateral force is increased from the side with the smallest lateral force. In order of side, the vehicle is divided into three regions: a region for straight-line stability, a region for one-time turning stability, and a region for steering stability. Specifically, the rear wheels are held on the vehicle body through a pair of lateral links arranged in front and behind the center of rotation, allowing them to move up and down.
In an automobile suspension in which bushings are interposed at the connecting portions of each lateral link to the vehicle body side and the rear wheel side, each of the lateral links has an inner link and an outer link each having a precompressed spring. The front lateral link system and the rear lateral link system, each including the bush, are configured to have different deflection characteristics against a lateral force.

Due to the difference in the deflection characteristics of the front and rear lateral link systems, the characteristic line showing the amount of rear wheel toe change in response to lateral force will change when the lateral force is small, when the lateral force is large, and when the lateral force is medium. In comparison, the configuration is such that the rate of change of the rear wheels in the toe-in direction increases as the lateral force increases.

In this way, the characteristic line that shows the amount of rear wheel toe change with respect to lateral force conventionally had only one bending point, but in the present invention it has two bending points, so it can be used even when the lateral force is moderate. In some cases, by making the turning ability more cat-like, the grip force of the rear wheels is relatively increased even in areas where the lateral force is smaller or larger than this, which improves straight-line stability and handling stability. will be obtained. In other words, if the bending point on the side where the lateral force is small is the first bending point, and the bending point on the side where the lateral force is large is the second bending point, as the lateral force increases, the When the lateral force is small, the toe control area is such that straight-line stability is ensured, and when the lateral force from the first bending point to the second bending point is moderate, the toe control area is such that turning performance is ensured. When the lateral force after the second bending point is large, the toe control region occurs, where steering stability is ensured.

More specifically, when the lateral force that requires straight-line stability is small (for example, 0.2 to 0.5 G) than when the lateral force that requires turning ability is moderate (for example, 0.4 to 0.5 G), 0.3G)
When the lateral force is large and requires steering stability (for example, 0.5 G or more), the rate of change in the rear wheel toe-in direction is large as the lateral force increases, so turning when the lateral force is moderate It is possible to ensure straight-line stability and steering stability while ensuring stability.

Furthermore, in the present invention, instead of the bushings interposed between the front and rear lateral links connecting to the vehicle body side and the wheel side, the intermediate part of the front and rear lateral links, that is, the joint part between the inner link and the outer link, is in a pre-compressed state. By using a separately provided spring, the bending point of the characteristic line for toe control as described above can be obtained. Since there is no need to make it complicated, setting for toe control can be done easily and reliably, and the degree of freedom in the setting is also high.

(Example) Examples of the present invention will be described below based on the attached drawings.

Figure 1 shows an example in which the present invention is applied to the rear wheels of a front-wheel drive vehicle.Since both the left and right rear wheel suspensions have the same structure, the following explanation will focus on the right rear wheel suspension. Regarding the suspension for the left rear wheel, the suffix rLJ will be used in place of the suffix "R" attached to the component for the right rear wheel, and a redundant explanation thereof will be omitted.

In FIG. 1, l is a sub-frame fixed to the vehicle body as a sprung mass, and the sub-frame 1 is connected to a right rear wheel 3R which can freely move downward via a swing arm type right suspension 2R. is maintained.

The suspension 2R includes a front lateral link 4R and a rear lateral link 5R that extend in the vehicle width direction and are split as described below, and a wheel support that extends in the longitudinal direction of the vehicle body; and a hub 6R as a member. are doing. The inner end (inner end in the vehicle width direction) of the front lateral link 4R is rotatably connected via a bushing 8R to a support shaft 7R protruding from the subframe l, and the inner end of the rear lateral link 5R The end portion (inner end portion in the vehicle width direction) is rotatably connected to a support shaft 9R protruding from the subframe l via a bush lOR. The outer end of the front lateral link 4R is rotatably connected via a bushing 12R to a support shaft 11R protruding from the front end of the hub 6R, and the outer end of the rear lateral link 5R is The hub 6R
A bushing 14R is attached to the support shaft 13R protruding from the rear end.
are rotatably connected via the And hub 6R
A spindle 15R is protruded from the outer end, and 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 bushes 12R and 14 at their respective outer ends are arranged substantially parallel to each other.
A spindle 15R is arranged at an intermediate portion between the spindle 15R and R in the front-rear direction. Thereby, the lateral force input to the rear wheel 3R is almost equally divided and input to the front and rear lateral links 4R15R. Further, the axes of the support shafts 7R19R1IIR, 13R and the bushes 8R1IOR, 12R, 14R extend in the longitudinal direction of the vehicle body, so that the right rear wheel 3R can freely swing in the vertical direction about the support shaft 7R19R. It becomes. A rear end bush of a tension rod 17R extending in the longitudinal direction of the vehicle body is rotatably connected to a support shaft 16H protruding from the inner end of the hub 6R via a bush 18R. The spigot end of 17R is rotatably connected to a support shaft 20R protruding from the vehicle body via a bush 19R. Of course, these bushings 18R and 19R extend in the vehicle width direction, and the tension rod 17H ensures the rigidity of the hub 6H in the longitudinal direction.

Note that the lower end portion of a strut 27H consisting of a hydraulic shock absorber and a coil spring is connected to the hub 6R as is known.

The front lateral link 4R is constructed by connecting the inner link 4R.l and the outer link 4R.2, which are formed separately from each other, as described below, and the inner and outer links 4R.l and 4R
・The binding site with 2 is shown as 4R・3. Similarly, the rear lateral link 5R is also configured by connecting the inner link 5R-1 and the outer link 5R@l at the bonding site 5R.3. As will be described later, pre-compressed springs are interposed between the two connecting portions 4R.3 and 5R.3, and the deflection characteristics of the front lateral link 4 system including these springs and bushes 8R and 12R are shown in Figure 4. The deflection characteristics of the rear lateral link 5R system including the spring and bushing IOR, 14R are shown by line F, and line R in FIG. 4.

Details of the binding sites 4R, 3.5R, and 3 in each of the front and rear lateral links 4R15R are shown in FIG. 5. The binding sites 4R-3 and 5R-3 have the same structure except for the details, so the common parts will be explained focusing on the binding site 4R-3, and then the different parts will be explained. We will do so.

First, the inner link 4R@1 integrally has a cylinder 41 that opens outward in the vehicle width direction at its outer end. Further, the inner end of the outer link 4R.2 integrally includes a large diameter piston 42 that is slidably fitted into the cylinder 41. This piston 42, that is, the outer link 4R.2 is prevented from being removed via the elastic member 44 by a plug 43 screwed into the cylinder 41, that is, the outer link 4R.2 is separated from the inner link 4R-1 by a predetermined amount or more. are being prevented. The outer link 4R.2 is biased toward the rear wheel 3R by a spring 45 (a coil spring in the embodiment) disposed in a compressed state within the cylinder 41. In other words, the compression force of the spring 45, that is, the precompression force, is adjusted by adjusting the screwing position of the stopper 43 with respect to the cylinder 41. As a result, the external force that attempts to retract the front lateral link 4R is initially countered with a large force by the pre-compressed spring 45, and when the external force becomes larger than the pre-compressed force, the spring 45 increases its elastic modulus. It will be shortened (reduction of the front lateral link 4R) in accordance with the following.

The coupling portions 4R-3 and 5R-3 configured as described above are set so that the precompression force and elastic modulus of the spring 45 are different from each other. That is, the precompression force is larger on the front lateral link 4R side, and conversely, the elastic modulus is smaller on the front lateral link 4R side.

Each bush 8R, IOR, 12R, 14R is the 6th ry
J, as shown in FIG. 7, the inner cylinder 21 into which the support shaft 7R19R111R or 13R is fitted, and the lateral link 4
It consists of an outer cylinder 22 to which R or 5R is coupled, and a rubber material 23 inserted between the two 21 and 22, and the hardness of this rubber material 23 is set to a predetermined value. There is. First, the bushes 12R and 114R at the outer ends of the lateral links 4R and 5R are filled with rubber material 23 having the same hardness, so that the load (lateral force) on both bushes 12R and 14H is
The relationships between and the amount of deflection are made equal to each other. Regarding the bushing 8R at the inner end of the front lateral link 4R and the bushing IOR at the inner end of the rear lateral link 5R, the front bushing 8H is harder than the rear bushing IOR.

Due to the difference in the settings of the deflection characteristics of the bushings 8R1IOH as mentioned above, and the differences in the settings of the springs 45 of the front and rear lateral links 4R15R, the deflection characteristics of the front lateral link 4R system against the load (lateral force) are as shown in Figure 4, line F. and the deflection characteristic of the rear lateral link R system is the fourth
It will look like line R in the figure. In other words, the characteristic line F has one bending point αl, and the deflection is small (hard) while the load (lateral force) is smaller than αl, and becomes large (softer) after exceeding α1. It is set as follows. Further, the characteristic line R also has one bending point βl, and the load is βl.
When it is smaller than , the deflection is small (hard) and β1
The deflection is set so that it becomes larger (softer) after exceeding . Both characteristic lines F and R change at two points, γl and γ2, and when the load is smaller than γl and larger than γ2, the amount of deflection of the front lateral link 4R system is greater than the amount of deflection of the rear lateral link 5R system. When the load is between γ1 and γ2, the amount of deflection of the front lateral link 4R system is made smaller than the amount of deflection of the rear lateral link 5R system. Of course, the load PF at the bending point α1 corresponds to the precompression force of the spring 45 in the front lateral link 4R, and the load PR at the bending point β1 corresponds to the precompression force of the spring 45 in the rear lateral link 5R. There is. Furthermore, the slope from the origin of characteristic line H to bending point αl depends on the characteristics of bush 8R (12R), and the slope from the origin of characteristic line H to bending point αl depends on bushing 12R (14R).
It depends on the properties of R).

Due to the difference in the deflection characteristics of the front and rear lateral links 4R15R mentioned above, the relationship between the amount of toe change of the right rear wheel 3R and the magnitude of the lateral force acting on the right rear wheel 3R is expressed by the characteristic line X in Figure 2.
αl, β1, γ1,
γ2 correspond to those in FIG. 4, respectively.

Changes in the behavior of the right rear wheel 3R based on such characteristic line X will be explained with reference to FIG. 3. In this @3 diagram, the lateral force is indicated by F, and the attitude change of the right rear wheel 3R is expressed by the lateral force F.
is rOJ with a solid line, when the lateral force F is "small" with a dashed-dot line, when the lateral force F is "medium" with a double-dashed line, and when the lateral force F is "large" with a dashed line. This is an indication. Also, O1~
04 is the center line in the width direction of the right rear wheel 3R, 01 indicates when the lateral force is "O", 02 indicates when the lateral force is "small", 03 indicates when the lateral force is "medium", and 04 indicates when the lateral force is "medium". This shows when the lateral force is "large". Note that each bushing 8R1IOR is schematically shown in the shape of a spring, and in the example, this bushing 8R1IOR is shown schematically in the shape of a spring.
The dimensions of each member are set so that the lateral force F acts equally on 1IOH.

As is clear from Fig. 3, when the lateral force F is 0,
The right rear wheel 3R is pointing straight ahead. When the lateral force F is small, the amount of deflection of the front lateral link 4R system is greater than the amount of deflection of the rear lateral link 5R system, so the right rear wheel 3R becomes toe-in, ensuring straight-line stability. Also, when the lateral force F is R, the deflection amount of the rear lateral link 5R system is larger than the deflection amount of the front lateral link 4R system, so the lateral force F of the right rear wheel 3R is "small". The amount of toe-in is relaxed (reduced) compared to when the vehicle is in use, and the turning performance, that is, the maneuverability is improved. That is, when the amount of toe-in is reduced, the understeering characteristic is weakened compared to when the amount of toe-in is "large", and the direction followability of the vehicle in response to the steering wheel is improved. Furthermore, when the lateral force is "large", the right rear wheel 3R is again displaced in the toe-in direction, which strengthens the tendency to understeering during sharp turns or high-speed lane changes, ensuring steering stability. Ru. Of course, all of the above also applies to the left rear wheel 3L.

Here, the characteristic line X indicating the amount of toe change of the rear wheels 3R (3L) with respect to the lateral force F, as shown by the broken line in Figure 2, can be changed in various ways depending on the vehicle type, etc. Each point is indicated by a black circle. Even in the characteristic lines shown by these broken lines, the rate of change in the toe-in direction as the lateral force increases (toe-out can be seen as negative toe-in)
is made smaller between the two bending points than in other parts.

Although the embodiments have been described above, the present invention can be similarly applied to rear-wheel drive vehicles. Further, the present invention can be similarly applied to any appropriate type of suspension as long as it has front and rear lateral links.For example, the front and rear lateral links 4R15R in FIG. The so-called double wishbone type (multi-link) is made wider than the end, and connects the upper arm (the shape does not matter, such as rod-shaped or A-shaped) that extends further in the vehicle width direction to the hub 6R. It can be similarly applied to the equation (2) and the like.

In the multi-link type mentioned above, the tension rod 17R (railing arm) that extends in the longitudinal direction of the vehicle body is made into a plate shape so that the rigidity in the vehicle width direction is small and the rigidity in the vertical direction is high. There may be.

(Effects of the Invention) As is clear from the above description, the present invention ensures straight-line stability when the lateral force is small, ensures turning performance when the lateral force is moderate, and provides steering stability when the lateral force is large. It is possible to satisfy all three conditions of ensuring that the vehicle behaves optimally according to the driving condition IEi.

In addition, in order to obtain the characteristics that satisfy the above three conditions, each lateral link is split and a pre-compressed spring interposed in this split part is used. There is no need to make the bending characteristics of the bushing provided at the connecting portion to the rear wheel side particularly complicated, and it is possible to easily and reliably set the bushing to the desired characteristics, and the degree of freedom in setting is also high.

[Brief explanation 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 a characteristic line according to the present invention. FIG. 3 is a plan view showing changes in rear wheel behavior based on characteristics according to the present invention. FIG. 4 is a graph showing an example of the deflection characteristics of the front and rear lateral link systems to obtain the characteristics shown in FIG. 2, respectively. FIG. 5 is an enlarged cross-sectional view showing a connecting portion between an inner link and an outer link. Fig. 6 shows an example of a bushing, and is a sectional view taken in a direction perpendicular to its axis, and Fig. 7 is a sectional view taken along the line ■-■ in Fig. 6. l: Subframe 2R12L: Suspension 3R, 3L: Rear wheel 4R14L: Front lateral link 4R@1: Inner link 4R・2: Outer link 4R・3: Connection part 5R15L: Rear lateral link 5R・1: Inner link 5R・2 :Outer link 5R cloud 3=Connection part 6R16L:Hub 8R18L:Front bushings 12R, 12L:Front bushings 10R,IOL:Rear bushings 14R14L:Rear bushings 15R115LNissing spindle (rotation center) 45 Nispring αl, βl: Breaking point Figure 2

Claims (1)

[Claims] (1) The rear wheel is held vertically movably on the vehicle body via a pair of lateral links arranged in front and behind the center of rotation, and each lateral link is connected to the vehicle body side and the rear wheel side, respectively. In an automobile suspension in which a bush is interposed, each of the lateral links is configured by coupling an inner link and an outer link via a precompressed spring, and each of the front lateral links including the bush The deflection characteristics of the link system and the rear lateral link system with respect to lateral force are set to be different from each other, and due to the difference in the deflection characteristics of the front and rear lateral link systems, a characteristic indicating the amount of toe change of the rear wheel in response to lateral force is obtained. When the lateral force is small and when the lateral force is large, the rate of change of the rear wheel in the toe-in direction as the lateral force increases is larger than when the lateral force is moderate. An automobile suspension characterized by: