JPS5943655B2 - Fiber reinforced plastic leaf spring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber-reinforced plastic leaf spring that uses a three-dimensional fabric and a group of roping as reinforcing materials, and has high strength in the longitudinal direction such as tensile strength. ,
The object of the present invention is to provide a fiber-reinforced plastic leaf spring that does not cause cracks in the thickness direction of the leaf spring or interlayer shear failure, has a high so-called shear strength, and is relatively easy to manufacture.

This type of fiber-reinforced plastic leaf spring is generally required to have high strength in the longitudinal direction, such as tensile strength, so conventionally, glass fiber, carbon fiber, aramid fiber, etc. The so-called unidirectionally reinforced structure is obtained by arranging the stretched ropes in the length direction of the leaf spring as reinforcing fibers, impregnating them into a plastic matrix, and hardening them.

As shown in FIG.
When a load P parallel to the reinforcing fiber direction B is applied,
This results in the following drawbacks.

That is, the first drawback is that under a relatively small load, and when the load is a repeated load, with a small number of repetitions, the reinforcing fiber direction B
The crack C tends to be deep in the thickness direction along the thickness D direction. The second drawback is that, as shown in Fig. 2, in the direction of the thickness D of the leaf spring A, a shear stress f occurs that is maximum at the neutral axis (O-O), and when the span is short, , particularly along the direction B of the reinforcing fibers, resulting in interlaminar shear failure or delamination phenomena.

The first means conventionally adopted to eliminate the first drawback described above is to strengthen the unidirectional reinforced structure described above by stacking multiple layers of two-dimensional non-directional materials such as chopped strand mats and continuous strand mats. The second method is to stack two-dimensional orthotropic materials such as roping cloth in multiple layers and use them together with the reinforcing fibers of the unidirectional reinforcing structure described above. When using the above-mentioned combinations, from the viewpoint of the distribution of shear stress f shown in FIG. 2, as shown in FIG. A structure in which reinforcing fiber layers F and G of a directional reinforcing structure are arranged is adopted.

If the structure shown in FIG. 3 is adopted, the first defect C shown in the above-mentioned FIG. It stops at the interface with the material layer E and does not advance into the material layer E, but since the material layer E is stacked in multiple layers, there is a risk of interlayer shear failure within the material layer E. exists,
Interlaminar shear failure often occurs.

On the other hand, conventional methods for manufacturing a fiber-reinforced plastic leaf spring having the structure shown in FIG. 3 include press molding means, filament winding molding means, and pull-forming molding means.

Assuming that the shape of the leaf spring is constant in the length direction, the press forming means produces glass fibers aligned in the length direction of the leaf spring, which form the reinforcing fiber layer G of the unidirectional reinforced structure. A roping etc. impregnated with plastic matrix or a prepreg state of this is set in a press mold L. On top of it, a two-dimensional non-directionally oriented material layer or a two-dimensional orthotropic material layer E A layer F impregnated with a plastic matrix is laminated, and on top of that, a reinforcing fiber layer F having a unidirectional reinforced structure impregnated with a plastic matrix is laminated, the mold is closed, pressure is applied and heated It is molded using

This method has the disadvantage that the number of processing steps is large and the unit price of the product is high. Further, in the filament winding forming means for the leaf spring, as shown in FIG. 4, glass fiber roping or the like forming the reinforcing fiber layer H of the unidirectional reinforcing structure is impregnated with a plastic matrix; A two-dimensional non-directionally oriented material layer or a two-dimensional orthotropic material layer 1 impregnated with a plastic matrix is simultaneously supplied and wound multiple times on a mandrel,
The laminated structure shown in FIG. 4 is formed, and since the molding is continuous, the number of processing steps is small, and although the occurrence of cracks can be prevented, the structure is unfavorable in terms of interlaminar shear failure.

Although there is no problem in the forming process with the above-described pull-forming forming means for leaf springs, the obtained product is not preferable in terms of interlaminar shear failure.

On the other hand, when the shape of the leaf spring changes continuously in the length direction, the two-dimensional non-directionally oriented material layer or the two-dimensional orthotropic material layer is adjusted in advance to match the change in the shape of the leaf spring. It is cut into pieces and subjected to the molding process.

The press forming means has the same drawbacks as mentioned above, but the filament winding forming means and the preforming forming means have the above-mentioned pre-cut two-dimensional non-directionally oriented material layer or two-dimensional orthogonal material layer. If the supply position of the anisotropic material is not strictly and accurately controlled, it will not be possible to form the anisotropic material, making the manufacturing process even more difficult than in the case where the shape of the leaf spring remains unchanged.

Moreover, the resulting product still has the drawback of being susceptible to interlaminar shear failure.

The present invention has the structure described in the claims.
Because of this, both the strength in the length direction and the so-called shear strength are high, and the fabrication is relatively easy.The fiber has a shape in which the cross-sectional area perpendicular to the length direction is constant and the width and thickness change continuously. This is a plate spring made of reinforced plastic.

The configuration of the illustrated example will be explained below.

In the present invention, the above-mentioned two-dimensional non-directionally oriented material or two
It is characterized by the use of a three-dimensional fabric instead of a six-dimensional orthotropic material. The three-dimensional fabric used in the present invention is
This is a well-known woven fabric as disclosed in US Pat. No. 4,312,261, and can be made into a woven fabric with an extremely large degree of freedom of deformation in three-dimensional directions by selecting a weaving pattern.

In the present invention, the weaving pattern of the three-dimensional fabric shown in U.S. Pat.
10, preferably woven in a size of 1 x 1 x 5. Given the weaving pattern,
The resulting three-dimensional fabric has a significantly increased degree of freedom in changing its shape in three-dimensional directions. Figures 5A to 5E use 62 roping Y formed by bundling 4000 long glass fibers of 23.5μ, and the U.S. Patent No. 4
312261 shows the roping process when weaving according to the method of No. 312261;

In other words, each roping is stretched from the bottom to the top of the paper in FIG. b
Each row is inserted through a roping guide so as to move in the same direction.

Now, assuming that the valley roping is in the arrangement shown in Figure 5 A, the first step is to move each column from lower a to upper c one pitch in the direction shown by arrow e in Figure 5, c.Move each row of the top a one pitch in the direction of arrow f toward the exit in Figure 5.

Next, as a second step, the column from left b to right d is moved one pitch in the direction shown by arrow g in FIG. 5C, and the column from left d to right b is moved in the direction G shown by arrow h in FIG. Move this one pitch0
Next, in the third step, each column of lower a and upper c is moved one pitch in the direction shown by arrow 1 in Fig. 5 2, and each column of lower c and upper a is moved in the direction shown by arrow j in Fig. 5 2. 1 pitch.

As the fourth step, move the column from left b to right d one pitch in the direction shown by arrow k in Fig. 5E, and move the column from left d to right b by one pitch in the direction shown by arrow 1 in Fig. 5E. move it.

Through the above-mentioned four steps, the roping that was at the position indicated by the symbol X in FIG. 5A occupies the position indicated by the symbol Move to the position indicated by .

After completing the four strokes described above, the roping Y group is combed once upwards on the paper, and the above-mentioned four strokes are repeated again, thereby weaving upward on the paper.

By repeating the above-mentioned four-stroke movement, the roping at the position indicated by the symbol X in Fig. 5A moves along the trajectory indicated by the arrow in Fig. All the ropings Y also move sequentially while drawing the same locus, and due to this movement, the roping group is intertwined and woven like a braided cord structure, resulting in a three-dimensional fabric with a large width and thickness.

In the leaf spring according to the present invention, a group of ropings that are continuous in the length direction of the leaf spring are arranged on both the front and back surfaces of the above-mentioned three-dimensional fabric. The reinforcing fibers are sandwiched in a three-dimensional fabric structure in the form of a three-sand beach.

Each of the front and back roping groups constituting the reinforcing fibers and the three-dimensional fabric are integrally bonded by a plastic matrix to form a plate spring 1 as a combined body as shown in FIG.

In the embodiment shown in FIG. 6, both the front and back outer layers 2, 3
are respectively continuous in the length direction l-l of the leaf spring 1.
The intermediate layer 4, which is composed of a roping group consisting of 90 ropings made of 4,000 long glass fibers of 3.5 μm and is sandwiched between both outer layers 2 and 3, is as described in Fig. 5 A to E. , is composed of a three-dimensional fabric using 62 ropings made of 4,000 long glass fibers of 23.5μ that are continuous in the length direction l-l of the leaf spring 1.

Each of the roping groups and the three-dimensional fabric has a constant cross-sectional area Sl, S2, S3 at any position J, K, L perpendicular to the length direction l-l of the leaf spring 1. In addition, the leaf spring 1 itself has a cross section S perpendicular to its length direction l-l, which is always constant, and a width W.
and the thickness V continuously change.

The leaf spring 1 having the above-described structure is formed into a continuous shape by the apparatus shown in FIGS. 7 to 11, and then cut into individual pieces.

In FIG. 7, roping groups 7 and 8 of long glass fibers drawn from glass fiber roping cakes 5 and 6 are as follows:
The three-dimensional fabric 10 that has been unrolled from the wrapping roll 9 forms the above-mentioned intermediate layer 4, which forms the above-mentioned front side outer layer 2 and back side outer layer 3. The roping groups 7, 8 and the three-dimensional fabric 10 are connected to the guides 11, 12, 1.
After passing through 3 groups, impregnation tank 15 for plastic matrix 14
A plastic matrix 14 of unsaturated polyester resin, epoxy resin, etc. is impregnated with the plastic matrix 14.

Thereafter, the roping groups 7, 8 and the three-dimensional fabric 10 are processed by dies 16, 17, and 18 to remove excess plastic matrix 14, and further by a die 19 to the maximum height of the recess, which will be described later. After the base material 20 is preformed into a substantially matching shape, the introduction guide 21 molds the base material 20 into an infinite recess 23 recessed in the circumferential surface of the rotating body 22. will be introduced in

The rotating body 22 is continuously rotated in the direction of arrow Z so that the base material 20 can be rolled into the recess 23 from a substantially tangential direction.

The recesses 23 provided infinitely on the circumferential surface of the rotary body 22 have a cross-sectional area of a longitudinal section passing through the center of the rotation axis 24 of the rotary body 22, which is the same regardless of the position on the entire circumferential surface, and Figure 10,
Height M, M' and depth N, N' as shown in Figure 11.
are continuously changed, and the shape is a repeating shape in which a plurality of individual elongated leaf springs 1 to be molded are successively formed.

On the outer circumferential surface of the rotating body 22, facing the concave 23, extending from the installation position of the introduction guide 21 until the plastic matrix impregnated in the base material 20 is hardened,
A pressing shoe 25 defining the outer surface of the recess 23 is provided.

As shown in FIGS. 8, 10, and 11, the introduction guide 21 described above has a vertical rod 28 that is connected to a spring 27 compressed to a base plate 26 fixed to a machine frame (not shown). It is attached by being constantly biased by a force in the advancing direction from the base plate 26, and above and below the vertical rod 28, horizontal rods 29 and 30 are installed.
They extend parallel to each other in the same direction so as to be slidable in the vertical direction, and a spring 31 is compressed between the horizontal rods 29 and 30, so that the horizontal rods 29 and 30 always move in opposite vertical directions. They are urged to move away from each other.

The above-mentioned horizontal rods 29 and 30 cross the base material 20 introduced into the recess 23 so as to sandwich it from above and below, and their tips 32 and 33 are inserted into the recess 23, and the upper and lower end walls 34 of the recess 23 are inserted into the recess 23. ,3
5.

This contact is an elastic contact based on the elasticity of the spring 31, and since both horizontal rods 29 and 30 are vertically slidable with respect to the vertical rod 28, rotation of the rotating body 22 in the direction of arrow Z is prevented. Accordingly, both horizontal rods 29 and 30 move up and down following changes in the heights M and M' of the recess 23, compressing and releasing the base material 20. That is, by vertically moving the horizontal rods 29 and 30, the base material 2
0, immediately before being introduced into the concave 23, its height is changed to the first
While being pressed and deformed from the state shown in Fig. 0 to the state shown in Fig. 11, or deformed from the state shown in Fig. 11 to the state shown in Fig. 10 due to restoring elasticity, the entire amount of the base material 20 is smooth. This is introduced into the recess 23.

Considering the above effects, the roping groups 7 and 8 have no constraints other than being continuous in the length direction, and
In the case of three-dimensional fabrics as well, when the weaving pattern is as explained with reference to FIGS. .

The leaf spring 1 according to the present invention is formed by cutting a leaf spring formed by the above-described apparatus and means into unit lengths.

Then, both outer layers 2 and 3 on the front and back sides are composed of 90 ropings made of 4,000 long glass fibers of 23.5μ, and the intermediate layer 4 is composed of 62 ropings, as described in U.S. Pat.
It is composed of a three-dimensional fabric woven with a weaving pattern in which the pitch in the width direction: the pitch in the thickness direction: the pitch in the length direction is 1:1:5 by the means shown in the specification of No. 312261, and vinyl ester is used as the plastic matrix. Using a resin, the thickness is 1 mm using the apparatus shown in FIGS.
2.5m7n1 width 60m! From the part, thickness 30m1L
1 width 25m7! Sequentially deform the L part, again to a thickness of 12
．． 5m! , the thickness is 12.5 m7 when the plate spring is formed by sequentially deforming the parts with a width of 6011 mI! L1 width 6
The strength of the 0mm portion is as shown in column A of the table below.
On the other hand, a plate spring of the same shape was made of 23.5μ long glass fiber 4.
242 ropings consisting of ,000 pieces in the length direction of the leaf spring! The thickness when aligned and molded using the same plastic matrix is 12.5m7! L1 width 60
The strength of the 1Lm portion was as shown in column B of the following table.

Note that the weight ratio of reinforcing fiber and plastic matrix was 75:25. As is clear from the results in this table,
In the leaf spring according to the present invention, the shear strength is 1.63 times higher than that of a so-called unidirectional reinforced structure in which the ropings are aligned in one direction. This makes it possible to effectively prevent cracks that occur in the thickness direction along reinforcing fibers, interlayer shear failure, or interlayer peeling phenomenon.

The fiber-reinforced plastic leaf spring according to the present invention has the structure described above, and has high strength in the longitudinal direction such as tensile strength, and also prevents cracks in the thickness direction of the leaf spring and interlaminar shear failure. This has the effect of exhibiting good spring characteristics over a long period of time without causing problems such as the above. In addition, a leaf spring has a shape in which the cross-sectional area perpendicular to the length direction is constant, and the width and thickness change continuously. It has the effect that a single leaf spring can perform the same function as a so-called stacked leaf spring in which a plurality of leaf springs are stacked with different lengths.

Furthermore, both the front and back outer layers of the leaf spring are composed of groups of ropings that are continuous in the length direction of the leaf spring, and only the middle layer is composed of a three-dimensional fabric, so when a bending load is applied, both outer layers will absorb tensile stress. , which takes on compressive stress and has a single structure because the intermediate layer is a single structure.
This has the effect of preventing interlayer shear failure and also blocking cracks that develop from the outer layer, and each roping group and three-dimensional fabric are The cross-sectional area of each of the leaf springs is constant, the amount of reinforcing fibers supplied is constant at each position, and the content of reinforcing fibers is one pair for each cross-section. It also has the effect of making the physical properties constant over the entire length.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing how to crack a conventional fiber-reinforced plastic spring with one-way reinforced structure, and Figure 2
FIGS. 3 and 4 are enlarged cross-sectional views showing the layered structure of a conventional fiber-reinforced plastic leaf spring, and FIGS. An explanatory diagram of each step of the weaving pattern of the three-dimensional fabric used in the invention, FIG. 6 is a perspective view of an example of the implementation of the present invention, and FIG. 7 is a diagram showing the production of a fiber-reinforced plastic leaf spring according to the present invention. A schematic side view of one example of the device, FIG.
9 is a plan view thereof, and FIGS. 10 and 11 show different operating states of the recess 23 and introduction guide 21 shown in FIG. 8. It is an enlarged sectional view. 1: leaf spring, 2, 3: outer layer, 4: middle layer, 7, 8: roping group, 10: three-dimensional fabric, 14: plastic matrix.

Claims (1)

[Claims] 1 In a leaf spring, both the front and back outer layers are each composed of a group of rovings that are continuous in the length direction of the leaf spring, and the intermediate layer sandwiched between the two outer layers is a three-dimensional fabric that is continuous in the length direction of the leaf spring. The roving group and the three-dimensional fabric are integrally connected with a plastic matrix to form one combined body, and each of the roving groups and the three-dimensional fabric are connected in the longitudinal direction of the leaf spring. The cross-sectional area of each orthogonal cross section is constant, and the cross-sectional area perpendicular to the length direction of the leaf spring is constant, and the width and thickness of the leaf spring change continuously. A fiber-reinforced plastic leaf spring characterized by having a shape that