JPS6137484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leaf spring for a vehicle, and more particularly to a leaf spring for a vehicle made of fiber-reinforced resin that is lighter in weight, lower in price, and has improved torsional strength.

Conventionally, steel plates have been used for leaf springs for vehicles, but the specific gravity of steel plates is high, which increases the weight of the vehicle.Especially in large vehicles, the weight of leaf springs is quite large, resulting in increased fuel consumption and poor acceleration performance. This causes deterioration and increases worker fatigue during the assembly process, and there is a desire to reduce the weight.

In order to eliminate the drawbacks of the conventional steel plate springs, various vehicle leaf springs made of composite materials, particularly fiber-reinforced resins reinforced with carbon fibers or glass fibers, have been proposed. However, in this conventional example, the area near the neutral axis of bending where almost no stress is applied is also solid, so it is not possible to achieve sufficient weight reduction, and very expensive reinforcing fiber material is wasted, so There was a drawback that it was not possible to reduce costs.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and its purpose is to create a cavity near the center of the plate thickness, which is the neutral axis of bending, in a fiber-reinforced resin leaf spring. The objective is to sufficiently reduce the weight by forming the reinforcing fiber material, and also to save the very expensive reinforcing fiber material and reduce the price. Another object is to particularly increase torsional strength by using reinforcing fiber materials with a structure suitable for each part on which tensile stress, compressive stress and torsional stress act.

In short, the present invention provides a fiber-reinforced resin leaf spring in which a cavity is formed near the center of the plate thickness, which is the neutral axis of bending, and the upper and lower surface layers are formed using directional long fibers. The surface layer of the leaf spring is formed by laminating cross-woven fiber materials in the width direction of the leaf spring.

The present invention will be explained below based on embodiments shown in the drawings. In FIGS. 1 and 2, the leaf spring 1 made of fiber-reinforced resin (hereinafter referred to as FRP) may be flat, but it may also be formed curved as shown, and the shapes of both ends 1a and 1b are as shown in the drawings. It has been omitted. As the resin, thermosetting resins such as epoxy resins, unsaturated polyester resins, and phenol resins, and thermoplastic resins such as polyester resins, polyamide resins, polyimide resins, and polyamide-imide resins are selected. In addition, as a reinforcing fiber material, specific strength,
Carbon fibers with excellent specific rigidity, weather resistance, and oil resistance, glass fibers with excellent abrasion resistance, boron fibers, silicone carbide fibers, or organic high modulus fibers are selected.

When the FRP leaf spring 1 is actually used, tensile stress is applied to the upper surface layer 1c, and tensile stress is applied to the lower surface layer 1d.
Compressive stress mainly acts on the plate, and in the case of a bending load, the stress generated at the bending neutral axis 2 is 0, and the stress near the center of the plate thickness is also extremely small.

Therefore, in the present invention, referring also to FIGS. 3, 5, and 6, the upper and lower surface layer parts 1c and 1d are formed using directional long fibers 3, and the surface layer parts 1e on both side surfaces are formed using directional long fibers 3. is formed by laminating cross-woven fiber materials 4 in the width direction of the leaf spring 1, and a cavity 5 is formed near the center of the plate thickness, which is the neutral axis 2 of bending. The long fibers 3 are preferably carbon fibers, glass fibers, or a mixture thereof. Further, since glass fiber has high abrasion resistance, it is desirable to arrange a large amount of glass fiber on the outermost side. There are various weaving methods for the cross-woven fiber material 4, but plain weave is preferable because it has the highest number of intersecting warp and weft fibers and the strongest structure, and the direction of the warp and weft fibers is shown in Figure 5. It is best to use the leaf spring 1 at an angle of 45° to the longitudinal direction or thickness direction of the leaf spring 1.

The one shown in FIG. 4 is another embodiment of the present invention, in which a reinforcing rib 6 in the thickness direction is formed in a part of the cavity 5,
It has increased bending and torsional strength.

The present invention is configured as described above, and its operation will be explained below. In Fig. 1 to Fig. 3 and Fig. 5 to Fig. 6, FRP leaf spring 1
When a force is applied upward from the lower center of the fiber, compressive stress is generated in the lower surface layer 1d, and tensile stress is generated in the upper surface layer 1c, but these stresses are caused by the directional long fibers 3. Absorb.

Next, when a torsional force is applied to the FRP leaf spring 1, torsional stress is generated in the leaf spring, but this stress is mainly absorbed by the cross-woven fiber material 4 of the surface layer 1e on both sides.

In the embodiment shown in FIG. 4, since the reinforcing ribs 6 are present, the strength is greater than in the above case, but the degree of weight reduction is small. If this point is hollow 5
If this were achieved at the ratio shown in Figure 3, the weight would be reduced by approximately 47% compared to the case of solid material.

Since the present invention is constructed and operates as described above, the weight of the FRP leaf spring can be sufficiently reduced by forming a cavity near the center of the plate thickness, which is the neutral axis of bending. At the same time, very expensive reinforcing fiber materials can be saved,
The effect of reducing the price can be obtained. In addition, since a fiber material with a structure suitable for areas where tensile stress, compressive stress, and torsional stress act, especially a cross-woven material for the surface layer of the side surface, is used, it is possible to increase the torsional strength.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and Figure 1 is an FRP
The front view of the plate spring, Figure 2 is also a plan view, Figure 3 is
The figures are a vertical cross-sectional view taken in the direction of the − arrow in FIG. 1, FIG. 4 is a vertical cross-sectional view similar to FIG. 3 according to another embodiment, FIG. 5 is a partially enlarged perspective cross-sectional view showing the structure of the reinforcing fiber material, FIG. 6 is a vertical sectional view taken along the - arrow direction in FIG. 2. 1 is an FRP leaf spring, 1c is the upper surface layer, 1
d is the lower surface layer, 1e is the surface layer on both sides, 2 is the neutral axis of bending, 3 is a directional long fiber, 4 is a cross-woven fiber material, and 5 is a cavity.

Claims (1)

[Claims] 1. In a fiber-reinforced resin leaf spring, a cavity is formed near the center of the plate thickness, which is the neutral axis of bending, and the upper and lower surface layers are formed using directional long fibers,
A leaf spring for a vehicle, characterized in that the surface layer portions of both sides are formed by laminating cross-woven fiber materials in the width direction of the leaf spring.