JPH0461976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an FRP tapered leaf spring used, for example, in a vehicle suspension spring.

[Prior Art] A major advantage of FRP leaf springs is that they are lightweight. However, if the width and thickness are made the same over the entire length of the leaf spring, the stress at each part in the length direction becomes uneven, reducing the efficiency of material usage, and therefore, sufficient weight reduction cannot be achieved.

Therefore, it is desirable to equalize stress by creating a shape in which the thickness of the plate is thick at the central portion in the length direction, and the thickness of the plate is tapered and thinned at the end sides.
Conventionally, tapered leaf springs have been developed for steel springs from the above viewpoints. But FRP
There is little prior art disclosing tapered leaf springs made by.

For example, in the prior art illustrated in FIGS. 3 and 4, the leaf spring 1 consists of an outer layer 2 and a core 3. In the case of this leaf spring 1, the plurality of unidirectional reinforcing fiber bundles 4 constituting the outer layer portion 2 and the plurality of reinforcing fiber bundles 5 constituting the core 3 are impregnated with resin and stacked on each other, so that the tapered plate Spring 1 is obtained. Further, after the reinforcing fiber bundles 4 and 5 are wound up in a mold, they are pressed down in the thickness direction and squeezed to remove excess resin before hardening.

[Problems to be Solved by the Invention] When a plurality of reinforcing fiber bundles 5 constituting a core are stacked together as in the prior art shown in FIG. Because the reinforcing fiber bundles are squeezed in the process of squeezing the reinforcing fiber bundles to remove excess resin, the resin cannot be squeezed out sufficiently because the fiber bundles tend to move at the ends 3a of the core. Through research conducted by the present inventors, it has been found that this causes a decrease in the strength of the leaf spring due to the formation of local areas with a high resin content or the inclusion of air bubbles.

In addition, as shown in FIG. 5, a plurality of fiber bundles 6 and a plurality of intermediate fiber bundles 7 having mutually different lengths
It is also possible to alternately overlap, but in this case,
Near the leaf spring surface layer 8 on the lower side of the figure, there is a fiber bundle 7a that is extremely shorter than the entire length of the leaf spring, so when the leaf spring is deformed under load, a large deflection occurs near the surface layer 8. The ends of the shortest fiber bundles 7a embedded in the fiber bundles 7a tend to lift up, which tends to cause delamination, resulting in a decrease in strength.

Accordingly, an object of the present invention is to provide an FRP tapered leaf spring that can prevent the formation of local areas with a high resin content, is resistant to delamination, and has high strength.

[Means for Solving the Problems] The present invention, which was developed to achieve the above object, has the following features:
A first continuous unidirectional reinforcing fiber bundle having a length spanning the entire length of the leaf spring, having equal lengths and impregnated with a resin; A plurality of second unidirectional reinforcing fiber bundles, each of which is continuous from one end side of the leaf spring to the other end side through the longitudinal center portion of the leaf spring and impregnated with resin, are inserted in the thickness direction of the leaf spring. An FRP tapered leaf spring in which the first and second reinforcing fiber bundles are integrally hardened by stacking them alternately and such that the positions of both ends of the second unidirectional reinforcing fiber bundles are staggered in each part in the plate thickness direction. And,
The second reinforcing fiber bundles are arranged such that the shortest length is arranged at the center in the thickness direction, and the length of the second reinforcing fiber bundle becomes longer as it is closer to the upper surface layer and the lower surface layer of the leaf spring. There is.

[Function] The above FRP tapered leaf spring has the first and second
The resin is reinforced by the unidirectional reinforcing fiber bundle.
In the FRP leaf spring of the present invention, the first unidirectional reinforcing fiber bundles made of long fibers and the second unidirectional reinforcing fiber bundles made of short fibers are alternately stacked in the plate thickness direction. Since the fibers are dispersed in the board thickness direction, when removing excess resin after wrapping each unidirectional reinforcing fiber bundle around a mold, make sure to squeeze the resin-impregnated fiber bundles. This allows you to remove excess resin and air bubbles. Therefore, it is effective in preventing a decrease in strength of the FRP tapered leaf spring.

Furthermore, in the present invention, the shortest reinforcing fiber bundle among the second reinforcing fiber bundles is arranged at the center in the plate thickness direction, and even if the plate spring deforms under load, the deflection and shear stress in this area are small. , short reinforcing fiber bundles no longer float up, and the occurrence of delamination is avoided.

[Example] In an example shown in FIGS. 1 and 2, the FRP tapered leaf spring 10 has the thickest plate thickness near the central part in the length direction, and the plate thickness decreases toward the plate ends. It has a tapered shape that gradually decreases. The plate width of this plate spring 10 is uniform over the entire length.

The leaf spring 10 has a first continuous unidirectional reinforcing fiber bundle 11 that is continuous over the entire length of the leaf spring and has the same length as that of the leaf spring 10. It is formed using a second unidirectional reinforcing fiber bundle 12 that continues from one end side of the leaf spring 10 to the other end side through the longitudinal center portion of the leaf spring 10 .

A second reinforcing fiber bundle 12 as shown in FIG.
are stacked on the first reinforcing fiber bundle 11 in such a way that the shortest length is placed at the center in the plate thickness direction, and the length becomes longer as the fibers are closer to the top and bottom sides of the leaf spring 10. It is being

These unidirectional reinforcing fiber bundles 11 and 12 are both made by impregnating, for example, glass fiber bundles along the longitudinal direction of the leaf spring 10 with a matrix resin, and these are alternately stacked in the thickness direction and cured. As a result, a tapered FRP leaf spring 10 is obtained. That is, the second reinforcing fiber bundle 12 becomes a core. The fibers and resin used in the second reinforcing fiber bundle 12 may be the same as those in the first reinforcing fiber bundle 11, but the second reinforcing fiber bundle 12 is cut into a predetermined length in advance. These unidirectional reinforcing fiber bundles 11,
12 may be made of a material other than glass fiber.

The FRP tapered leaf spring 10 having the above structure can be formed by a filament winding method. For example, in FIG. 1, a predetermined amount of the first continuous unidirectional reinforcing fiber bundle 11 is wound around a mold (not shown) located on the upper side of the drawing, and then the second unidirectional reinforcing fiber bundle 12 is cut in advance. Overlap. Next, the first continuous unidirectional reinforcing fiber bundle 11 is wound again, and then the second unidirectional reinforcing fiber bundle 12, which has been cut in advance, is overlapped. In this way, reinforcing fiber bundles 11 and 12 are alternately stacked. These reinforcing fiber bundles 1
It goes without saying that 1 and 12 are impregnated with resin in advance. After it is rolled up into a mold, it is squeezed from the outside to remove excess resin and allowed to harden.

The FRP tapered leaf spring 10 having the above configuration is used, like a general leaf spring, with the leaf end portion attached to the vehicle body side and the longitudinally intermediate portion attached to the axle side, for example.

According to the above configuration, the first continuous unidirectional reinforcing fiber bundles 11 that form the main body of the leaf spring 10 and the second unidirectional reinforcing fiber bundles 12 that form the core are alternately stacked, which is different from the conventional method. Compared to the (see Figure 4), it is easier to extrude excess resin when pressing the end. Therefore, it is possible to avoid or reduce the occurrence of local areas with a large resin content or the formation of bubbles, which is effective in preventing a decrease in strength.

Further, the shortest reinforcing fiber bundle is disposed at the center in the thickness direction of the leaf spring 10, and relatively long second reinforcing fiber bundles 12 are buried near the upper and lower surface layers of the leaf spring 10. Therefore, leaf spring 10
Even if it deforms under load, problems such as delamination of the short fiber bundles buried in the central part in the thickness direction, where there is less deformation, do not occur.

[Effects of the Invention] According to the present invention, in an FRP leaf spring in which short fiber bundles are embedded in order to taper it, both ends of the short fiber bundles are no longer gathered at the center in the thickness direction. In addition to effectively performing the process of removing excess resin before curing the resin,
It is possible to prevent localized areas with a large resin content from occurring. Further, even if the leaf spring is repeatedly bent, problems such as delamination between layers will not occur, and a decrease in strength can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a leaf spring showing an embodiment of the present invention, FIG. 2 is a side view schematically showing the arrangement of unidirectional reinforcing fiber bundles used in the leaf spring of FIG. 1, and FIG. A cross-sectional view showing a conventional FRP tapered leaf spring, Fig. 4 is a side view schematically showing the arrangement of the reinforcing fiber bundles shown in Fig. 3, and Fig. 5 shows a short fiber bundle arranged on one side of the leaf spring. FIG. DESCRIPTION OF SYMBOLS 10... FRP taper leaf spring, 11... First continuous unidirectional reinforcing fiber bundle, 12... Second unidirectional reinforcing fiber bundle.

Claims (1)

[Scope of Claims] 1. A first continuous unidirectional reinforcing fiber bundle having a length spanning the entire length of the leaf spring and having equal lengths and impregnated with resin; and a first continuous unidirectional reinforcing fiber bundle having a length shorter than that of the reinforcing fiber bundle. Moreover, the plurality of second unidirectional reinforcing fiber bundles are different in length from one another and are continuous from one end side of the leaf spring to the other end side through the longitudinal center portion of the leaf spring, and are impregnated with resin. These first and second reinforcing fiber bundles are integrated by stacking them alternately in the thickness direction and such that the positions of both ends of the second unidirectional reinforcing fiber bundle are staggered in each part in the thickness direction. In a hardened FRP tapered leaf spring, the second reinforcing fiber bundle has its shortest length arranged at the center in the thickness direction and close to the upper surface layer and the lower surface layer of the leaf spring. An FRP tapered leaf spring characterized by an arrangement in which the length becomes longer.