JPH0788130B2 - Vehicle suspension - Google Patents

Description

TECHNICAL FIELD The present invention relates to a suspension system for a vehicle used in a suspension system of a vehicle.

[Prior Art] Various types of vehicle suspension devices have been known. For example, a traditional suspension device using a vertical steel spring plate is one in which eyeball parts are provided at both ends of the spring plate, and these eyeball parts are connected to the vehicle body side. The axle housing is fixed to the section.

In addition, in suspensions of an independent suspension system, a suspension spring using a steel coil spring is widely used as represented by, for example, a MacPherson strut or a double wishbone type suspension.

[Problems to be Solved by the Invention] In order to improve the riding comfort, it is desired to increase the vertical stroke of the wheel. However, in the conventional suspension system using the steel spring plate, the spring plate needs to be considerably long in order to increase the vertical deflection. However, since the mounting space of the spring plate is naturally limited, the spring plate cannot be lengthened unnecessarily, and the weight is considerably heavy.

On the other hand, the height of the coil spring is large in order to increase the vertical stroke of the suspension system using the coil spring. However, since there are restrictions on the space for accommodating the springs of the vehicle body frame and the suspension mechanism, the height at which the coil spring can be incorporated is naturally limited.

Under these circumstances, it has been desired to develop a suspension device that has a suspension spring that can be accommodated in a relatively narrow space and that can obtain sufficient bending.

Therefore, the inventors of the present invention focused on adopting a FRP belt-shaped spring for the suspension mechanism unit, and suspended the belt-shaped spring in order to store the FRP belt-shaped spring in a narrow space of the suspension mechanism unit. I thought about making it a shape that follows the link for use. However, in such a shape of the spring, it is necessary to provide a curved portion at an intermediate portion in the longitudinal direction, and the smaller the radius of curvature of the curved portion, the larger the strain on the inside of the curve as compared with the strain on the outside of the curve. It was found that the inner side of the curve becomes a weak point depending on the direction of the load.

[Means for Solving Problems] A vehicle suspension system of the present invention developed to solve the above problems is pivotally attached to a member on a vehicle body side in a vertically swingable manner around a pivot. A suspension link and a FRP belt-shaped spring formed in a U-shaped, V-shaped, or "V" -shaped curved shape. The belt-shaped spring has a curved inner side when a vehicle body load is applied. Is connected to the link so that the one end side is connected to the member on the vehicle body side so that the curved outside is the compression side and the other end side of the strip spring is biased to rotate the link downward. It is characterized by having done.

The suspension link is, for example, an upper link (upper arm) or a lower link (lower arm). The FRP strip-shaped spring is one in which unidirectional continuous reinforcing fibers such as glass fibers or carbon fibers are embedded mainly in the longitudinal direction of the spring to cure the matrix resin.

[Operation] In the suspension device having the above configuration, when the suspension link swings in the vertical direction as the wheel moves up and down, the band-shaped spring bends with this movement. The strip-shaped spring can be arranged generally along the member on the vehicle body side along the link, and can be incorporated in the suspension mechanism section having severe space constraints. However, this kind of belt-shaped spring requires a considerably large amount of bending in order to ensure the vertical stroke of the wheel.

Here, when the strip-shaped spring is made of steel, it is not suitable for practical use because a large amount of bending cannot be obtained due to the relationship between the bending elastic modulus of steel and the magnitude of allowable strain.

However, an FRP material in which a unidirectional continuous reinforcing fiber bundle such as glass fiber or carbon fiber is embedded in a matrix resin can be flexed about twice as much as steel because of the relationship between the flexural modulus and the magnitude of strain. In terms of material mechanics, the maximum allowable deflection when a constant load is applied to a plate of constant width and constant length is Proportional to. E is the flexural modulus, and ε is the strain that can withstand repeated use. In other words, since the FRP that can withstand repeated bending and the amount of flexure are sufficiently larger than steel, the U-shape that is connected to the link and the member on the vehicle body side and bends like the strip-shaped spring described above. Through the V-shaped strip spring, sufficient bending can be obtained for practical use.

Moreover, the strip-shaped spring according to the present invention has the tension side on the curved inner side where a large strain is generated as compared with the curved outer side, so that the characteristic of the FRP material that is strong against tension can be utilized,
It is effective in increasing durability.

[Embodiment] In the suspension system for a vehicle shown in FIG. 1, a member 1 (only a part of which is shown) on the vehicle body side is provided with pivots 2 and 3 at two upper and lower positions. The member 1 on the vehicle body side is a vehicle body frame, a subframe, or the like.

A link mechanism 5 for suspension is provided on the member 1 on the vehicle body side. That is, the upper link 6 is attached to the upper pivot 2.
However, lower links 7 are pivotally attached to the lower pivots 3 so as to be vertically swingable. These links 6,7
Like the well-known double wishbone type, is projected in the vehicle width direction, and the knuckle 8 is attached to the tip ends of the links 6 and 7. Wheels 10 are rotatably supported on the knuckle 8. A shock absorber (not shown) is provided between the lower link 7 and the member 1 on the vehicle body side. Also,
A similar link mechanism for suspension is also provided on the right side of the member 1 on the vehicle body side in the drawing.

The link mechanism 5 is provided with a FRP belt-shaped spring 11. This strip-shaped spring 11 is obtained by impregnating a matrix resin into a unidirectionally reinforced fiber bundle such as a well-known glass fiber or carbon fiber which is mainly continuous in the longitudinal direction, and then cured.
It is shaped like a dogleg. That is, it has a curved portion 12 located at the middle portion in the longitudinal direction and a pair of arm portions 13 and 14 located on both sides of the curved portion 12.

One end side of the strip-shaped spring 11 is connected to the upper link 6 via the connecting portion 20, and the other end side is connected to the member 1 on the vehicle body side by the connecting portion 21. The curved portion 12 is arranged near the pivot 2, and the intermediate portion in the longitudinal direction is supported by the intermediate support portion 22.

In the embodiment having the above configuration, the lower link 7 is loaded by the load.
When is pivotally displaced upward, both arm portions 13 and 14 of the strip-shaped spring 11 are elastically deformed in a direction in which the angle formed by each other expands, and the repulsive force urges the upper link 6, that is, the wheel 10 downward. Therefore, in the strip-shaped spring 11 of this embodiment, when the load is applied, the inner side of the curve of the bending portion 12 becomes the tension side and the outer side of the curve becomes the compression side, which is preferable for improving durability.

That is, in a curved portion such as the curved portion 12, generally, the smaller the radius of curvature, the larger the strain inside the curve becomes compared to the strain outside the curve. By the nature of the FRP material, the strength of the reinforcing fiber in the tensile direction, that is, the tension side is higher than that in the compression direction, that is, the compression side. For this reason, when using a FRP material that is weak in compression, it is more advantageous in strength to use it so that the inside of the bend becomes the tension side. Note that, as shown in FIG. 2, a strip-shaped spring 11 formed in a generally V-shape or U-shape may be adopted. The arms 13 and 14 are substantially straight or slightly curved.

As mentioned above, when a constant load is applied to a plate of constant width and constant length, the maximum amount of bending that can be repeatedly used is Proportional to. Table 1 below shows experimental results comparing the conventional spring steel with the test pieces of the glass fiber reinforced synthetic resin (GFRP) and the carbon fiber reinforced synthetic resin (CFRP) developed by the present inventors.

From Table 1, GFRP Is 2.4 times that of spring steel and CFRP is 1.6 times that of spring steel, and under the same load, GFRP can withstand the largest cyclic deformation.

A shape model of the strip spring 11 is shown in FIG. In the figure, the length L of the arm portions 13 and 14 is 350 mm, the angle θ between the arm portions 13 and 14 is 45 °, the radius of curvature r of the curved portion 12 is 75 mm, and the plate width is practical. There are two types, 70 mm and 100 mm.

The following Table 2 shows GFRP for the strip-shaped spring 11 with the above-mentioned shape and size.
It is the result of comparing the one made of CFRP with the one made of spring steel. The load P is 400 kgf and the maximum deflection δmax is both arms 13,1.
This is the sum of four.

When the strip-shaped spring having the above-described shape and size is used in a suspension device, a maximum deflection δmax of 150 mm or more is practically desired. As can be seen from Table 2, the strip-shaped springs made of GFRP and CFRP satisfy this condition, but the spring made of steel lacks bending. According to the research conducted by the present inventors, in order to obtain the bending that can be mounted on an actual vehicle by the band-shaped spring It is necessary to use the above materials. Such values are not possible with steel springs, but can be achieved by using FRP.

As in the strip-shaped spring 11 shown in FIG. 3, by changing the plate thickness or the plate width of the curved portion 12 or the arm portions 13 and 14 so that the sectional area on the plate end side gradually decreases, It is also possible to achieve equal stress in the direction. In particular, since the strain ε is maximized in the curved portion 12, it is desirable to increase the second moment of area of this portion. By doing so, it is possible to further reduce the weight as compared with the strip-shaped spring having the same thickness over the entire length.

Alternatively, as shown in FIG. 4, a substantially V-shaped strip-shaped spring 11 having a curved portion 12 'wound in a loop may be used. In this case, by assembling the arms 13 and 14 so that a load in the direction of the arrow shown in the drawing acts, the inside of the bend of the bend 12 'can be made a tension side.

The present invention can also be applied to a suspension device using a link other than the double wishbone type. Further, the cross-sectional shape of the strip-shaped spring 11 may be circular, oval, oval-shaped or the like other than rectangular.

[Advantages of the Invention] According to the present invention, a sufficient vertical stroke can be obtained even when a suspension spring having a shape that can be incorporated into a suspension mechanism section having severe space constraints is used, and the suspension spring is an FRP.
Combined with the fact that it is made, it has a great effect on making the suspension mechanism part compact and lightweight. And by making the curved inside of the FRP belt-shaped spring the tension side,
On the inside of the curved surface where a large amount of strain occurs, the characteristics of the FRP material, which is strong in tension, can be utilized, which contributes to the improvement of durability.

[Brief description of drawings]

FIG. 1 is a schematic front view of a part of a suspension system showing an embodiment of the present invention, and FIGS. 2 to 4 are front views showing modified examples of strip springs. 1 ... Vehicle side member, 2,3 ... Axis, 6,7 ... Suspension link, 10 ... Wheel, 11 ... Band spring, 12,12 '... Bending part, 13,14 ... Arm Department.

Claims (2)

[Claims] 1. A suspension link pivotally attached to a member on the vehicle body side in a vertically swingable manner about a pivot, and an FRP formed in a U-shaped, V-shaped or "V" -shaped curved shape. And a belt-shaped spring made of steel, and the belt-shaped spring has one end side connected to the member on the vehicle body side so that the inner side of the curve is the tension side and the outer side of the curve is the compression side when a vehicle load is applied. The suspension device for a vehicle, wherein the other end of the strip-shaped spring is connected to the link so as to urge the link to rotate downward. 2. The suspension system for a vehicle according to claim 1, wherein the strip-shaped spring has a cross-sectional shape changed in the longitudinal direction so that stress distributions at respective portions in the longitudinal direction are substantially equal.