JP2582291B2 - Leaf spring - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated leaf spring used in a vehicle suspension or the like, which is configured by laminating a parent leaf spring having a Berlin-shaped eyeball and a child leaf spring.

[Prior Art] In general, in a laminated leaf spring, the parent leaf spring having a Berlin-shaped eye, that is, a Berlin-shaped eye, has a moment exerted on the eye due to the center of the eye being located on the center line of the parent leaf spring. This is a small structure, which is preferable for reducing the stress generated in the main leaf spring due to the horizontal force of the vehicle when the vehicle is suddenly stopped and preventing the eyeball from being broken.

[Problems to be solved by the invention]

However, the diagonal spring constant of the leaf spring, so-called,
Dynamic spring constant (appropriate spring constant during vibration of a leaf spring)
As shown by the one-dot chain line in FIG. 6, the diagonal spring constant is high in the range where the amplitude is small, and the diagonal spring constant decreases as the amplitude increases, approaching the static spring constant. In other words, during the vibration of the leaf spring, a change in the spring span (the distance between the center and both ends of the main leaf spring), that is, a change in camber (warpage) due to the bending of the spring causes slippage between the plates, thereby generating a frictional force. . This frictional force has a small change in span in the small amplitude range, so that static friction until slippage is dominant, and in the large amplitude range, dynamic friction due to slippage is dominant because the span change is large, The friction force is lower than in the small amplitude range. Therefore, the dynamic spring constant, which is the spring constant during vibration, is large in the small amplitude range and small in the large amplitude range.

By the way, as the suspension of the vehicle, it is desirable to use a spring having a low spring constant so that a soft ride can be obtained with a small amplitude, and a spring constant having a high spring constant and a highly stable rigidity can be obtained with a large amplitude. From this viewpoint, the conventional leaf spring has completely opposite characteristics, which is disadvantageous in terms of performance.

For this reason, in the conventional laminated leaf springs, as a means for obtaining a soft ride comfort, the number of springs constituting the laminated leaf spring is reduced or the end of the leaf is reduced in order to keep the diagonal spring constant at a small amplitude low. Means for reducing friction by inserting a friction material is also performed, but in such a configuration, as shown by the dotted line in FIG. 6, the friction is reduced over the entire amplitude, so that the friction at large amplitude is also reduced. As a result, the spring constant decreases, and there is a possibility that the suspension will not have a rigidity and a poor stability.

An object of the present invention is to solve the above-mentioned problem, and in a laminated leaf spring composed of a parent leaf spring having a Berlin-shaped eyeball and a number of child leaf springs, the friction state between the eyeball and the child leaf spring is changed. As a result, the dynamic spring constant characteristic of the leaf spring is set to the ideal shape, and a low amplitude provides a low spring constant and a soft ride comfort at small amplitudes. The present invention is to provide a laminated leaf spring.

JP-A-56-167938 discloses that in which the plate width is substantially constant and the plate thickness has a tapered portion that gradually decreases in the plate edge direction, and a concentrated load in the thickness direction is applied to the plate edge, The tapered portion has a thickness set so that the section modulus is substantially proportional to the distance from the end near the end of the plate, and the cross-section at both ends in the width direction has an arc shape having a predetermined curvature related to the set thickness. In Japanese Patent Publication No. 48-14968, the distance between the leaf springs which interfere with each other and are in contact with each other due to the displacement of the leaf springs in the longitudinal direction caused as the overlapping leaf springs flex. Laminated leaf springs having varying load characteristics provided with abutting portions arranged so as to be changed are disclosed, but in each of the laminated leaf springs composed of a parent leaf spring and a child leaf spring having a Berlin-shaped eyeball. Nothing is said about the spring characteristics.

[Means for solving the problem]

To achieve the above object, the present invention is configured as follows. That is, the present invention comprises a main leaf spring having Berlin-shaped eyeballs at both ends and a child leaf spring fixed to the center of the main leaf spring by bolts, and the child leaf spring is brought into relative displacement contact with the eyeball. At the same time, a thin portion having a locally reduced plate thickness is formed at a predetermined distance from the centerpiece of the master leaf spring, and in the small amplitude region, the master leaf spring is bent at the thin portion, and the centerpiece is bent. Are arranged to make rotational contact with the child leaf spring.

[Action]

In an overlapped leaf spring having a parent leaf spring having a Berlin-shaped eyeball and a child leaf spring that comes into contact with the eyeball, the load fluctuates, the bending state of the spring changes, and the vibration begins, and FIG. As shown, the static friction FS acts on the contact portion and causes the eyeball to rotate. With the rotation of the centerpiece, the main leaf spring is inflected in the vicinity of the centerpiece and generates an inflection point K. However, this inflection is usually a slight amount, and a slip occurs immediately in the contact portion of the mutual feeling of the board. Then the inflection returns and the inflection point disappears.

The laminated leaf spring according to the present invention forms a thin portion in which the thickness of a portion at a predetermined distance from the Berlin-shaped eyeball of the parent leaf spring is locally reduced, so that inflection easily occurs in the thin portion. As a result, the period in which the eyeball and the child leaf spring are in rotational contact with each other without slipping also becomes longer. That is, in the small amplitude region (the load fluctuation is small), the rotational contact continues, and a state in which the slip does not substantially occur. Then, a spring action is generated by the inflection of the inflection point, and the plate-to-plate frictional force does not work, so that the spring constant is low, and when used in a vehicle, the riding comfort is soft in a small amplitude region.

Also, in the large amplitude (large load variation) region of the laminated leaf spring, the eyeball of the parent leaf spring and the child leaf spring in contact with the eyeball come into sliding contact with each other, generating a large frictional force and improving steering stability. .

〔Example〕

Hereinafter, an embodiment of a leaf spring according to the present invention will be described with reference to the drawings.

A leaf spring having a Berlin-shaped eyeball shown in FIG.
A main leaf spring 1 having Berlin-shaped eyeballs 2 at both ends and one or more (two in the figure) child leaf springs 3 are overlapped over the entire length while both ends are brought into contact with the lower surface of the eyeballs 2, and a center bolt 4 at the center is provided. And a clip (not shown) arranged at a predetermined position.

In the leaf spring according to the present invention, as shown in an enlarged view in FIG. 2, a notch portion, an inclined surface, etc., in which the thickness of a part of the parent leaf spring 1 at a predetermined distance from the Berlin-shaped eyeball 2 is locally reduced. The thin-walled portion 5 is formed, and the rotation behavior of the Berlin-shaped eyeball is efficiently generated.

The movement of the master leaf spring 1 in the small amplitude region including the rotation behavior of the eyeball 2 in the master leaf spring 1 is as shown in FIG. In FIG. 3, reference symbol A denotes the center position of the centerpiece 2 when the load of the stacked leaf spring is loaded, reference sign B denotes the center position of the centerpiece 2 when the conventional stacked leaf spring is not loaded, and reference symbol C denotes the deformation at the inflection point. The center position of the centerpiece 2 receiving the mark, the reference symbol D is an inflection point, the reference symbol E is the center of the center of the centerpiece track of the weight leaf spring, the reference symbol F is the contact point between the centerpiece 2 and the child leaf spring 3, and the reference symbol R is the centerpiece of the weight leaf spring. Of the trajectory center E of the eyeball 2 and the turning radius of the centerpiece 2.

As can be seen from FIG. 3, in the weight leaf spring of the present invention, since the thin portion 5 is formed in which the thickness of the portion of the main leaf spring 1 at a predetermined distance from the eyeball 2 is locally reduced, the weight leaf spring acts on the weight leaf spring. When the applied load changes, the thin portion 5 becomes an inflection point D, and a large inflection occurs in the master leaf spring 1. As a result of this inflection, a spring action is generated in the master leaf spring 1 and, at the same time, the eyeball 2 comes into rotational contact with the child leaf spring 3 (θ ₁ , θ _{2 in} FIG. ₂ ), and the center A shifts to C. In addition, in the large amplitude region (where the load variation is large), it is impossible to follow the deflection only by the rotation of the eyeball portion, and the eyeball 2 and the child leaf spring 3 are in a sliding contact state.

That is, in the small-amplitude region, static friction hardly occurs due to the rotation behavior of the eyeball, and the rotation friction of the pin around the point A, that is, the pin supporting the eyeball 2 becomes dominant.
In the large-amplitude region where the friction is small and the span change is large, it is possible to obtain the characteristic governed by the normal sliding friction between plates.

Looking at the above characteristics in terms of load-deflection characteristics, FIG. 5 (A)
As shown in (2), the load transfer portion draws a smooth hysteresis curve starting from the rotational friction. FIG. 5 (B) is a diagram showing characteristics of the conventional leaf spring, in which the inclination in the small amplitude portion is increased due to the effect of static friction.

FIGS. 4 (A) and 4 (B) show different structures of the thin-walled portions formed on the parent leaf spring 1 in the laminated leaf spring according to the present invention.

That is, the notch or thin portion 5A formed in the master leaf spring 1 shown in FIG. 4 (A) is formed by notching flatly over a predetermined length in the longitudinal direction of the spring plate. is there. Also, the thin portion 5B formed on the main leaf spring 1 shown in FIG. 4 (B) has an inclined surface which is inclined from both sides so that the central portion becomes deepest over a predetermined length in the longitudinal direction of the spring plate. It is formed by.

In order to enhance the effect of the load-displacement characteristic of the leaf spring according to the present invention, the ratio t ₂ / t _{1 is set} to 10% or more, and L is set to 70 mm.
It is preferable to set the following.

〔The invention's effect〕

The leaf spring according to the present invention is configured as described above, and has the following effects. That is, this laminated leaf spring comprises a parent leaf spring having Berlin-shaped eyelets at both ends and a child leaf spring fixed to the center of the parent leaf spring with bolts, and the child leaf spring is relatively displaceable from the eyeball. Along with the contact, a thin portion in which the plate thickness is locally reduced is formed at a position at a predetermined distance from the eyeball of the master leaf spring, and the master leaf spring is bent at the thin portion in the small amplitude region, Since the eyeball is configured to be brought into rotational contact with the child leaf spring, when the parent leaf spring bends by receiving an external force, the eyeball of the parent leaf spring in a small amplitude (small load fluctuation) region. And the child leaf spring in contact with the eyeball is in a rotational contact state, and in a large amplitude (large load vibration) region, the eyeball of the parent leaf spring and the child leaf spring in contact with the eyeball are in a sliding contact state. , In the small amplitude region, the friction is reduced, One span change is large in the large amplitude region can be obtained characteristics that are governed by normal plates sliding friction.

Therefore, by applying the leaf spring according to the present invention to a vehicle, the ride comfort characteristics of the vehicle, in particular, the frictional force between the plates in a small amplitude region can be reduced to obtain an ideal friction characteristic. It is not necessary to control the damping force in the area, and in the large amplitude range, it is possible to increase the friction more than before, so that the steering stability is improved and the need for a stabilizer during rolling is reduced. Effects can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a leaf spring, FIG. 1 (A) is an explanatory view showing an inflection of the parent leaf spring, and FIG. 2 is an explanation showing a part of the parent leaf spring in the leaf spring according to the present invention. FIG. 3 is an explanatory view showing an operation state of the parent leaf spring of the laminated leaf spring. FIG. 4 (A) is an explanatory view showing an example of the parent leaf spring in the laminated leaf spring according to the present invention, and FIG. ) Is an explanatory view showing another example of the parent leaf spring in the laminated leaf spring according to the present invention, FIG. 5 (A) is a graph showing the load-deflection characteristics of the laminated leaf spring according to the present invention, and FIG. 5 (B) is FIG. 6 is a graph showing the load-deflection characteristics of the conventional leaf spring, and FIG. 6 is a graph showing the relationship between the amplitude of the conventional leaf spring and the diagonal spring constant. 1 ... leaf spring, 2 ... eyeball, 3 ... child leaf spring, 4 ... center bolt, 5,5A, 5B ... thin part.

Claims (1)

(57) [Claims] 1. A main leaf spring having Berlin-shaped eyelets at both ends and a child leaf spring fixed to a center portion of the main leaf spring by bolts, wherein the child leaf spring is brought into contact with the eyeball so as to be relatively displaceable. Forming a thin portion having a locally reduced thickness at a portion of the main leaf spring at a predetermined distance from the eyeball, and in the small amplitude region, the main leaf spring is bent at the thin wall portion, and the eyeball is A laminated leaf spring, wherein said leaf spring is in rotational contact with said child leaf spring.