JPS5854241A - Leaf spring of fiber reinforced plastics - Google Patents

Abstract

PURPOSE:To relatively increase compressive strength, by shifting the neutral axis of bending of a fiber reinforced plastic (FRP) leaf spring to a surface side, caused with maximum compressive stress, and arranging the maximum compressive stress, generated at a bending load, smaller than maximum tensile stress. CONSTITUTION:A surface 1a in a receiving side of tensile stress is hollowed to a circular arc shape, while a surface 1b in a receiving side of compressive stress is expanded to a circular arc shape. When a bending load is applied to the central part toward the upper side of a leaf spring 1, maximum tensile stress is generated in angular parts 1c of the leaf spring 1, while maximum compressive stress is generated in a vertex of the surface 1b, however, a neutral axis X of bending is considerably shifted to a side of the surface 1b, and the maximum compressive stress at a bending load becomes smaller than the maximum tensile stress.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber-reinforced resin leaf spring, and in particular, a fiber-reinforced leaf spring that improves compressive strength by taking advantage of the characteristics of a fiber-reinforced resin leaf spring that is strong in tension and weak in compression. Regarding resin leaf springs.

Conventionally, various proposals have been made regarding leaf springs made of fiber-reinforced resin, but leaf springs made of fiber-reinforced resin have the advantage of being extremely lightweight and having high tensile strength compared to steel plate springs. It had the disadvantage of low strength.

The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to move the neutral axis of bending of a fiber-reinforced resin leaf spring toward the surface where the maximum compressive stress occurs. By doing so, the maximum compressive stress generated during bending load is made smaller than the maximum tensile stress to increase the compressive strength, and thereby, it is an object of the present invention to provide a fiber-reinforced resin plate spring that can be put to practical use.

In short, the cross section of the line of the present invention in a plane perpendicular to the longitudinal direction of the leaf spring is formed so that a part of the wall thickness on the side that receives tensile stress during bending load is less, and the neutral axis of bending receives compressive stress during bending load. A part of the wall thickness on the side is formed to be smaller, and the neutral axis of bending is moved to the side that receives compressive stress during bending load, so that the maximum compressive stress during bending load is smaller than the maximum tensile stress. It is characterized by:

The present invention will be explained below based on embodiments shown in the drawings. 1st
In the figure, the cross section of a leaf spring made of fiber-reinforced resin (hereinafter referred to as FRP) in a plane perpendicular to its longitudinal direction shows that part of the wall thickness on the side that receives tensile stress during bending load, that is, on the upper side in the figure, is smaller. As shown in Figure 4, the neutral axis of bending moves to the side that receives compressive stress during bending load, that is, to the lower side in the figure, and the maximum compressive stress during bending load is equal to the maximum tensile stress. It is also configured to have a small size.

Various shapes can be considered to reduce the cross section of a part of the wall thickness on the side that receives tensile stress during bending load, but in the first embodiment shown in FIGS. 1 to 4, the surface 1a on the side that receives tensile stress is concave in a circular arc shape, and the surface 1b on the side receiving compressive stress is bulged in a circular arc shape.In short, the cross section in the plane perpendicular to the longitudinal direction of the plate spring 1 is an arc-shaped cross section concave upward in the figure. It has become.

Furthermore, when the FRP leaf spring 1 with the arc-shaped cross section shown in FIG. 1 is used as the stacked leaf spring 2, there is a gap between each FRP leaf spring 1 as shown in FIGS. C is formed. That is, if the radius of curvature of the concave arc is made smaller than the radius of curvature of the bulged arc, a gap C will inevitably be formed and a favorable result will be obtained. The pad 3 has a radius of curvature equal to the radius of curvature of the circular arc in which the lower side bulges out into a concave shape, and is fastened to the axle 5 by a U bolt 4. The upper side of the pad 6 is recessed in an arc shape so as to match the radius of curvature of the lowermost plate 1.

Carbon fiber reinforced resin (hereinafter referred to as CFRP) and glass fiber reinforced resin (hereinafter referred to as GFRP) are mainly used as the F-P.

The present invention is configured as described above, and its operation will be explained below. In Figures 1 to 4, when a bending load l is applied to the center part of the plate l or stacked plate 2 from the bottom to the top in the figure, the maximum tensile stress of the plate 1 is The maximum compressive stress occurs at the corner 1c, and the maximum compressive stress occurs at the apex of the surface 1b, but since the neutral axis X of bending has moved considerably toward the surface 1b, the maximum compressive stress is considerably smaller than the maximum tensile stress. The ridge spring 1, especially the strength of CFRP that is strong in tension and weak in compression, is utilized, and the overall strength is well-balanced.

The FRPjQ leaf spring 21 shown in FIG. 5 is a second embodiment of the present invention, in which the side receiving tensile stress is recessed in a U-shape and the neutral axis of bending X is moved to the compression side. Yes, it is also possible to overlap the board with a ridge that increases the width.

Moreover, the FRP leaf spring 31 shown in FIG.
This is an example in which the cross section is formed into a dogleg shape so that it is concave on the tensile stress side, and the neutral axis X of bending is moved to the compression side.

The FRP leaf spring 41 shown in FIG. 7 is the fourth embodiment of the present invention, and both corners in the width direction on the tensile stress side are FII.
Jp is taken, and the neutral axis of bending X is moved to the compression side.

These FRP plate springs 21, 31, and 41 of the second to fourth embodiments also function in the same manner as the FRP plate spring 1 of the first embodiment, so a description thereof will be omitted.

Since the present invention is constructed and operates as described above, the neutral axis of bending of the FRP leaf spring is moved toward the surface where the maximum compressive stress occurs, so that the maximum compressive stress that occurs during bending load is reduced. The stress can be made smaller than the maximum tensile stress, the compressive strength of the FRP leaf spring can be relatively increased, and as a result, it is possible to provide a practically usable F) LP leaf spring. This is an extremely effective invention.

[Brief explanation of the drawing]

The drawings are 9F and 9 showing an embodiment of the present invention, FIG. 1 is a perspective view of an FRP leaf spring, FIG. 2 is a partially cutaway perspective view of an FRP leaf spring with stacked leaf springs, and FIG. Figure 2 is an enlarged vertical cross-sectional view taken along arrows 1-1 in Figure 1;
The figure is a longitudinal cross-sectional view of a FRP leaf spring according to the second embodiment of the present invention, FIG. 6 is a longitudinal cross-sectional view of a FRP leaf spring according to the third embodiment, and FIG. l” according to 4 embodiments
i (This is a vertical cross-sectional view of a leaf spring made of P. 1.21 and 31.41 are leaf springs made of FRP, 1a is the surface on the side that receives tensile stress during bending load, 1b is the surface on the side that also receives compressive stress, X is the neutral axis of bending. Patent applicant: Hino Motors Co., Ltd., Agent
Patent Attorney 1) Japanese Male Figure 1 Figure 3 Figure 4 b Figure 5 1 Figure 6 f Figure 7 1

Claims (1)

[Claims] A cross section in a plane perpendicular to the longitudinal direction of the leaf spring is formed so that a portion of the wall thickness on the side receiving tensile stress during bending load is less, and the neutral axis of bending is moved to the side receiving compressive stress during bending load, A fiber-reinforced resin leaf spring characterized in that the maximum compressive stress under bending load is smaller than the maximum tensile stress.