JPS5814567B2 - Layered leaf spring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stacked leaf spring device capable of increasing inter-plate friction.

In stacked leaf spring devices used in automobile suspension systems, the frictional resistance between the sheets has a large effect on riding comfort and steering stability during driving.

For example, when the frictional resistance between the plates is small, the ride comfort is improved compared to when the frictional resistance is large, but the restorability of the vehicle body tilt during turning is deteriorated.

Further, when an oil damper or the like is used, since it is viscous friction, the damping characteristics are different from the friction between solid bodies, and there are cases where vibrations with minute amplitudes cannot be effectively damped due to the mechanism.

Therefore, in a stacked leaf spring device, it is desirable to be able to set the inter-plate frictional resistance to a state corresponding to desired damping characteristics.

However, this frictional resistance between the plates is determined by various factors such as the static spring constant of the device, the number, length and surface condition of the spring plates, and the magnitude of the load acting in the thickness direction. For example, when you want to maintain the same level of frictional resistance between the plates even if you reduce the number of spring plates to reduce weight, or when you want to further increase the frictional resistance between the plates to improve handling stability. , there is a need for a means that can achieve these without regard to the above factors.

Furthermore, load fluctuations in vehicle suspension systems are relatively large;
Since the amount of deflection of the spring plates varies, it has been desired to increase the friction between the plates over a wide load range.

The present invention was made in response to the above-mentioned needs, and its purpose is to be able to arbitrarily set the frictional resistance between the plates without substantially changing the characteristics of each spring plate, and to
It is an object of the present invention to provide a stacked leaf spring device capable of increasing inter-plate friction over a wide load range.

Hereinafter, the present invention will be explained based on illustrated embodiments.

In FIGS. 1 to 3, a plurality of spring plates 1, 2, and 3 (in the case of three in the figure) overlapped in the thickness direction are formed, for example, from a spring steel material into a band shape having the same thickness and width. A centerpiece 4 is formed at the end of the first spring plate 1, and the second and third spring plates 2 and 3 are formed to have approximately the same length.

These spring plates 1, 2, and 3 are tightened in the thickness direction by a center bolt (not shown) inserted into a through hole 5 at a part of the longitudinal direction, for example, a center part in the longitudinal direction. The plate end portion is connected to the vehicle body side (not shown) via the center portion 4.

Then, a downward load is applied to the end of the spring plate in the thickness direction of the spring plate, and a tensile stress is applied to the upper surface of each spring plate 1, 2.3.
Compressive stress is also generated on each lower surface.

When the amount of deflection of the spring plate changes due to changes in load,
The end portions of the plates are configured to move relative to each other in the longitudinal direction.

In addition, the spring plates 1, 2.3 have a portion located on the plate end side excluding the joint portion between the spring plates, that is, an intermediate portion between the center portion and the plate end portion, in the direction of load application, that is, downward. Projecting convex portions 6 are formed respectively.

In the illustrated example, these convex portions 6 have substantially the same shape, and each part of the elliptical spring plates 1, 2, and 3 has a cross section from the tensile stress side plate surface to the compressive stress side plate surface. It is extruded into a ladder shape, and recesses 7 are formed on the tensile stress side plate surfaces.

Convex portions 6 formed on the first and second spring plates 1 and 2
, 6 are recesses 7 formed in the second and third spring plates 2 and 3.
, 7, respectively.

A first inclined surface 8 and a second inclined surface 9 are formed at both longitudinal ends of the convex portion 6, that is, on the fastening portion side and the plate end side of the spring plate, respectively.

These first and second inclined surfaces 8, 9 form the recessed portions 7...
It is formed so that it can be brought into close contact with a first oblique opposing surface 10 and a second oblique opposing surface 10 formed at both ends in the longitudinal direction, respectively.

Even if the spring plates 1, 2, and 3 are slightly bent, the first inclined surface 8 and the first inclined opposing surface 10, or the second inclined surface 9 and the second inclined opposing surface 11 may In order to be able to slide, the shape and dimensions of each tip of the convex part 6... are the same as that of the concave part 7.
It is formed to be equal to or slightly larger than that of the bottom of each (see Figure 3).

Next, the operation of the apparatus configured as described above will be explained.

For ease of understanding, it is assumed that each of the spring plates 1, 2, and 3 is fixed at its center, has a substantially horizontal shape, and a downward vertical load is applied to the edge of the plate via the center portion 4. .

When this load increases (or decreases), spring plates 1, 2.3
is deformed in a curve such that each plate end is displaced downward (upward), thereby causing relative displacement in the longitudinal direction between adjacent spring plates 1 and 2 and 2 and 3.

Generally, in the n-th spring plate, if the radius of curvature of the neutral axis under no load and under load is Rnf and Rn, and the thickness is tn, then the length from the center along the neutral axis is The relative displacement amount Δ in the longitudinal direction at the position ln is Δ=[ln(tn+tn+1)/2](1/Rnf-1
/Rn)......(1) It is expressed as follows.

On the other hand, the effective coefficient of friction μ1 in the horizontal direction on a sloped surface that forms an angle θ with the horizontal plane is μ1 = (μ+tanθ)/(1-μtanθ)...(
2).

Therefore, if μtanθ≪1, μ1≒μ+ta
nθ, the frictional resistance F based on the vertical load W is approximately equal to the sum of the frictional resistance μW in the direction parallel to the slope and the frictional resistance W tanθ based on the slope, as expressed as F=Wμ1≒μW+Wtanθ. is known.

That is, when the spring plates 1, 2.3 make the above-mentioned relative displacement Δ due to a change in load, the first inclined surface 8 and the first inclined opposing surface 10, or the second inclined surface 9 and the second inclined surface Slanted opposing surface 11
It is known that the frictional resistance is increased compared to that in a normal device in which these inclined surfaces are not present, and that the amount of increase is approximately equal to W tan θ.

Figure 4 shows the relationship between the vertical load W applied to the plate end and the resulting vertical displacement δ of the plate end, and shows the difference Fa between characteristic lines A and B when the load increases and decreases. Fb is the load Wa
, corresponds to the frictional resistance corresponding to Wb.

According to the inventors' experiments on a device consisting of three spring plates with a width of 60 mm, a thickness of 12 mm, and an effective length of 1140 mm between both ends, a static spring constant of 11.7 kg/mm, and a weight of 16 kg, the lower As shown in the table, the above convex portion 6...
There was a significant difference in frictional resistance between Type A with ・ and Type B without.

C in the table has the same dimensions and shape as B above, except that the thickness of the spring plate is 10 mm and the number of spring plates is 5, and has a frictional resistance similar to A above. However, the weight is 19.2 kg, which is 20% more than A and B above.

In other words, if we reduce the weight of the above C and make it like the above B, we can obtain the same static spring constant, but the frictional resistance between the plates must be significantly smaller.
By providing the convex portions 6, it is possible to achieve a significant weight reduction while keeping the static spring constant and frictional resistance between the plates substantially the same.

Note that the convex portion 6 is not limited to an elliptical shape, and may be shaped like a spring plate bent in the thickness direction, for example, as shown in FIG. It may also have any other arbitrary shape.

Further, the cross-sectional shape of the convex portions 6 is not limited to the ladder shape as shown in the drawings, and the inclined surfaces 8, 9, etc. may have an appropriate curved surface.

Furthermore, as is known from the above equation (1), since the relative displacement amount Δ is proportional to the length ln, it is desirable to provide the projections 6 at a position close to the plate end. An appropriate position may be selected depending on the frictional resistance, and in short, it may be any position on the plate end side excluding the joints between the spring plates.

Further, the convex portions 6 may be provided at multiple locations as illustrated in FIG. 6, or may be provided only on some of the spring plates as illustrated in FIG. good.

Moreover, although the case where the convex part protrudes in the direction of the surface of the compressive stress side plate has been described above, it may be formed so as to protrude in the direction of the surface of the tensile stress side plate, contrary to this.

As described above, depending on the shape, size, number, position, etc. of the convex portions, various frictional resistances can be generated for the same amount of displacement of the spring plate.

Therefore, a desired frictional resistance, that is, a desired damping characteristic, can be obtained without substantially affecting the main properties of the spring plate.

As described above, the present invention provides that, in a region on the end side of the spring plates other than the fastening part of the spring plates overlapped in the thickness direction, a first A convex portion having an inclined surface and a second inclined surface on the plate end side is integrally formed, and on the other hand, a convex portion that exactly fits into the convex portion and closely contacts the eleventh and second inclined surfaces, respectively. The present invention is characterized in that a recessed portion having first and second oblique opposing surfaces is provided.

Therefore, according to the present invention, even if a load is applied to the spring plate and the spring plate is slightly bent in either direction, the inclined surface and the inclined opposing surface are in sliding contact with each other from the initial stage of bending, and the friction between the plates can be increased. In a suspension system where load changes are relatively large and the amount of deflection of the spring plates changes in various ways, the frictional force between the plates can be increased over a wide range from a small load area to a large load area.

Therefore, even if the number of spring plates is reduced to reduce the weight, predetermined spring characteristics and damping characteristics can be obtained, and it is possible to achieve both a reduction in the weight of the vehicle body and an improvement in handling stability.

Moreover, since the inclined surface and the oblique opposing surface can be brought into sliding contact with each other even by a slight bending of the spring plate, the friction resistance characteristics between the plates can be linearized from a small load region, and therefore linear spring characteristics can be obtained. Suitable for cases where

Moreover, by appropriately setting the inclination angle, area, position, etc. of the above-mentioned inclined surface and the inclined opposing surface, the frictional force between the plates can be set arbitrarily, which has great practical effects.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a side view showing a part of the stacked leaf spring device in cross section, FIG. 2 is a plan view of the end of the spring plate, and FIG. 3 4 is a sectional view showing a concave portion and a convex portion, FIG. 4 is a spring characteristic diagram, FIG. 5 is a plan view showing a modified example of a concave portion and a convex portion, and FIGS. 6 and 7 are modified examples of a spring plate, respectively. FIG. 1, 2, 3...Spring plate, 6...Protrusion,
7... Concavity, 8... First inclined surface, 9
. . . second slanted surface, 10 . . . first slanted opposing surface, 11 . . . second slanted opposing surface.

Claims (1)

[Claims] 1. In a stacked leaf spring device in which a plurality of spring plates are overlapped and fastened to each other in the thickness direction at a part of the longitudinal direction, and the plate ends are moved longitudinally with respect to changes in load, the above-mentioned On the end side of the spring plate other than the fastening part, one of the mutually opposing surfaces of the spring plate has a first inclined surface on the fastening part side of the spring plate and a second slope on the end side of the spring plate. 2
A convex portion having an inclined surface is integrally formed, and the other side has first and second oblique opposing surfaces that exactly fit into the convex portion and are in close contact with the first and second inclined surfaces, respectively. What is claimed is: 1. A stacked leaf spring device, characterized in that it is provided with a recessed portion.