JPS60208642A - Frp leaf spring - Google Patents

Abstract

PURPOSE:To eliminate a problem of interference of a leaf spring with the other component parts, by increasing the widthwise spring constant of the leaf spring to prevent the leaf spring from being displaced widthwise to a large degree due to vibration, etc. CONSTITUTION:Since reinforcing fibers having a highly elastic constant are laid in only sections 6a, 6b in the vicinity of the neutral axis O-O in both widthwise sections 6, 6 of a leaf spring 2, the affection of the highly elastic reinforcing fibers laid in the sections 6a, 6a in the vicinity of the neutral axis O-O is relatively small to prevent the spring constant of the leaf spring 2 from excessively increasing when the leaf spring 2 flexes thicknesswise. Meanwhile the tensile strength of the highly elastic fibers greately affect to increase the widthwise spring constant when the leaf spring 2 flexes withwidth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field of the invention] The present invention relates to a suspension mechanism for a vehicle, for example.
Regarding RP leaf springs.

[Technical background of the invention and its problems]

The leaf springs that have been used in practical use are generally made of steel, but
Some products made of FRP are also in the practical stage for the purpose of reducing weight. When using FRP instead of steel, if the spring constant in the plate thickness direction is the same as a steel plate spring, the Young's modulus E and working stress σ are different between steel and FRP, so the spring constant in the plate width direction is the same as that of steel plate springs. The spring constant of FRP leaf springs is generally lower. (Generally, the Young's modulus E8 of steel is 21000
K9/mtn.

Maximum stress σ = 90 kg/f, Young's modulus E1 of FRP is 4
20 ON! / s, maximum stress = about 5SR'j/s) However, leaf springs are often used in such a way that they are not only loaded in the thickness direction, but also loaded in the width direction, so the above-mentioned The spring constant in the plate width direction is m1l
l If the plate is lower than the spring, the vibration mode in the plate width direction changes or resonance occurs at an inconvenient frequency, resulting in a large displacement in the plate width direction and interference with other parts in the suspension mechanism. Various inconveniences may occur.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and an object thereof is to provide an FRP leaf spring that can increase the spring constant in the width direction of the leaf.

[Summary of the invention]

The gist of the present invention is that in an FRP leaf spring reinforced with resin reinforced llft, the strength of the parts on both end sides in the board width direction is increased compared to the parts on the middle side in the board width direction.

According to the above configuration, the spring constant in the plate width direction can be increased compared to a normal FRP leaf spring without substantially increasing the spring constant in the plate thickness direction.

Therefore, problems such as the FRP leaf spring being largely displaced in the width direction due to vibration or other causes and interfering with other parts can be prevented.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. A stacked leaf spring device 1 shown in FIG. 1 includes a plurality of FRP leaf springs 2 . Each of these FRP leaf springs 2 is formed into a band shape by reinforcing resin with reinforcing fibers. The main plate spring 2a located at the top is attached to the vehicle body via eyepiece members 3.3 attached to both ends thereof. Further, each FRP leaf spring 2 is restrained to each other by a center bolt 4 at an intermediate portion in the longitudinal direction.

All or part of each of the FRP leaf springs 2 . . . has higher strength at the portions 6, 6 on both end sides in the plate width direction than the portion 5 on the intermediate side in the plate width direction. As an example, the second
As shown in the figure, near the neutral axis 0-0 at both ends 6.6 in the plate width direction (portion shown with dense hatching) 6
Reinforcing fibers with a higher elastic modulus than other parts are arranged at a and 6a.

To be more specific, the above parts 5a and 5a are made of, for example, Kevlar! Aromatic polyamide fibers such as L-fiber (du Pont, trade name), or relatively expensive highly elastically reinforced msi with a high elastic modulus (Young's modulus E) such as carbon fibers are used; For most parts, ordinary glass fibers, which are inexpensively available, are used. Therefore, the cost will not increase significantly.

As described above, the neutral axis 0 at both ends 6, 6 in the plate width direction
Since reinforcing fibers with a high elastic modulus are arranged only in the vicinity of -0 6a, 6a, when the leaf spring 2 is bent in the thickness direction (centered on the neutral axis 0-0), the neutral axis 6a, 6a is in the vicinity of the neutral axis 0-0. The influence of the high elasticity reinforcement am placed in the spring is relatively small, and it is possible to prevent the spring constant from becoming too large. On the other hand, when the plate spring 2 is bent in the plate width direction, the vicinity of both ends 6a in the plate width direction.

The tensile strength of the high elasticity reinforcing fibers arranged in 6a has a large effect, and the spring constant in the plate width direction can be increased compared to a normal FRP plate spring.

Therefore, even if the leaf spring is used in such a way that loads are applied not only in the thickness direction but also in the width direction of the plate, the force generated in the width direction of the plate, such as centrifugal force or vibration that occurs when the vehicle curves, will cause the plate spring to change in width. It is possible to prevent problems such as large displacement in the direction and interference with other parts. Furthermore, since it is possible to secure a spring constant in the plate width direction equivalent to that of a steel plate spring without increasing the plate width, the same mounting as a conventional ML plate spring can be done.

As shown in FIG. 3 as a second embodiment of the present invention, a protrusion 10.10 along the longitudinal direction is formed near the neutral axis 0-0 at both ends 6, 6 in the width direction of the plate. Part 10.
10 may contain reinforced tBlfl having a higher elastic modulus than other parts as in the first embodiment. Also in this case, the spring constant in the plate width direction can be increased without substantially changing the spring constant in the plate thickness direction.

Or as another example, near the neutral axis 6a.

6a or the convex portion 10.10, for example, 85 to 90% by weight, which is higher than the reinforcing fiber content in other parts (approximately 55 to 75%). The tensile strength of the parts on both ends in the board width direction may be increased compared to the parts. Even with such means, the spring constant in the plate width direction can be increased.

Alternatively, as in the third embodiment shown in FIG. 4, in a part or all of the longitudinal direction of the leaf spring, the thickness of both ends 6. By increasing the strength of the plate, the strength of the portions on both end sides in the plate width direction may be made higher than the portions on the intermediate side in the plate width direction. In this case, the stiffness in the sheet width direction E・1 (E=Young's modulus of FRP, I, − second moment of inertia in the sheet width direction 1~) is replaced by the stiffness in the sheet thickness direction E・
It has been found through experiments by the present inventors that it is preferable to set it to 40 times or more of Ix (l = second moment of inertia in the plate thickness direction) (conventionally, it is generally 20 times or less).

Furthermore, as shown in FIG. 5, the leaf spring 2 is constituted by leaf spring components 11.11 divided into two in the width direction, and these leaf spring components 11.11 are integrated at both ends thereof. A centerpiece 3.3 may also be attached.

In this case, a gap 12 extending along the longitudinal direction of the leaf spring is formed in the middle part in the width direction of the leaf. Said leaf spring component 11.11
As schematically shown in FIG.
By intersecting each other, it is desirable to be able to prevent the occurrence of cracks and the propagation of cracks when a hole is made to attach the eyepiece member 3.

In this example, the continuous reinforcing fibers 20 are arranged biased toward both ends in the board width direction, and the intermediate part 5 in the board width direction is made of only resin or resin containing short m fibers,
To prevent the spring constant in the plate thickness direction from increasing unnecessarily.

In any of the examples below, the rigidity in the plate width direction E・1
It has been found from experiments conducted by the present inventor that it is preferable to make the stiffness in the thickness direction E.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to increase the spring constant in the width direction of an FRP leaf spring without substantially increasing the spring constant in the thickness direction, which solves the problem in the case of FRP. This is extremely effective in suppressing problems such as changes in the vibration mode and preventing interference with other parts.

[Brief explanation of the drawing]

Fig. 1 is a front view of an FRP stacked leaf spring device, Fig. 2 is a sectional view in the board width direction of an FRP leaf spring showing a first embodiment of the present invention, and Figs. A cross-sectional view in the plate width direction of an FRP leaf spring showing the second embodiment and the third embodiment, the fifth
The figure is a perspective view showing the fourth embodiment of the present invention, FIG. 6 is a sectional view taken along the line Vl-Vl in FIG. 5, and FIG. It is a schematic diagram showing an example of a constituent member. 2...FRP leaf spring, 5...Part on the middle side in the board width direction, 6...Parts on both end sides in the board width direction. Applicant's agent Patent attorney Takehiko Suzue

Claims (6)

[Claims] (1) An FRP leaf spring made of resin reinforced with reinforcing fibers, characterized in that the strength of the parts on both end sides in the width direction of the plate is higher than the parts on the middle side in the width direction of the plate. (2) The FRP leaf spring according to claim 1, characterized in that reinforcing fibers having a higher modulus of elasticity than other parts are arranged near the neutral axis at both ends in the board width direction. (3) F according to claim (1), characterized in that the content of reinforcing fibers at both ends in the board width direction is higher than the content of reinforcing fibers in the middle part in the board width direction.
RP leaf spring. (4) Claim (1) characterized in that the plate thickness at both ends in the plate width direction is greater than the plate thickness at the middle part in the plate width direction.
FRP leaf spring described in section. (5) A leaf spring is constituted by a pair of leaf spring components divided into two in the leaf width direction, and between these leaf spring components,
The FRP leaf spring according to claim 1, characterized in that a cavity is formed along the longitudinal direction of the leaf spring. (6) The FRP board according to any one of claims (1) to (5), characterized in that the rigidity in the board width direction is 40 times or more the rigidity in the board thickness direction. Spring.