JPH0439431A - Laminated leaf spring - Google Patents

Abstract

PURPOSE:To improve riding comfortableness relating to both large and small amplitudes by extending a child leaf, adjacent to a main leaf having a dome- shaped eye, to the outside of a load point of the main leaf and forming a shape of a contact part with the main leaf into a cycloidal curve with an external diameter of the eye serving as a basic circle. CONSTITUTION:A laminated leaf spring is constituted of a main leaf 1, having a dome-shaped eye 4, and child leaves 2, 3, and the second child leaf 2, adjacent to the first main leaf 1, is formed in a span of a load point or more of the main leaf 1. A lower surface of the eye 4 is brought into contact with an upper surface of the child leaf 2 in a contact point TP. A leaf surface CS of cycloidal curvature with an external diameter R of the eye 4 serving as a basic circle is formed by a contact surface formed by the contact point TP. Thus, rolling friction is obtained without generating slip friction in small amplitude and a diagonal spring constant is prevented from decreasing by generating the slip friction in large amplitude. Accordingly, riding comfortableness of a vehicle is improved in both regions of large and small amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stacked leaf spring for vehicle suspension, which is formed by stacking a parent plate and a daughter plate.

[Conventional technology]

Conventionally, as shown in FIG. 5, as a stacked leaf spring for suspension of an automobile, the end shape of the main plate 11 is in the shape of an upturned eye, that is, the eye shape of an upturn eye 12, or
As shown in the figure, it is well known that the end shape of the main plate 13 has the shape of a Berlin eye, that is, the eye of a Berlin eye 14.

These stacked leaf springs have a structure that has friction between the plates, so the load-deflection diagram of the stacked leaf springs is as shown in the seventh figure.
As shown in the figure, the locus is different when the leaf spring is pressurized and when it is depressurized, resulting in hysteresis loss. In FIG. 7, the deflection X is plotted on the horizontal axis, and the load W is plotted on the vertical axis.

In addition, when the above-mentioned laminated leaf spring having a load-deflection diagram as shown in Fig. 7 is given a constant amplitude under a standard load state, hysteresis occurs due to pressurization and depressurization of the laminated leaf spring as shown in Fig. 8. - In Figure 8, where a loop is drawn, the deflection X is plotted on the horizontal axis and the load W is plotted on the vertical axis. That is, by applying pressure to the stacked leaf spring, an arbitrary deflection: +A1
After applying , when the pressure is reduced and the deflection is reduced to -AI, without returning to the characteristic line at the time of pressurization, that is, the line 3 + -b +, i), = (, -d, = 6□ -e, which returns along another characteristic diagram such as 0. Then, when the stacked leaf spring is pressurized, a characteristic diagram of 6.-f, -+3. is drawn, and the stacked leaf spring becomes A loop is formed with an amplitude of ±A.A similar phenomenon is observed in the case of arbitrary amplitudes At, As, etc., except in the case of extremely small amplitudes.

In addition, as a vehicle suspension system, Japanese Patent Application Laid-Open No. 62-160907
There is something disclosed in the publication No. This vehicle suspension system is composed of a stacked leaf spring consisting of several leaves and a vehicle. In addition, the group of leaves below the second leaf is housed inside the axle box under appropriate tightening force, and this axle box is placed inside the axle box with the group of leaves below the second leaf housed in the first leaf. Proper tightening is one that is attached to the axle while applying force. Furthermore, the - number leaf is fastened to the axle via the upper pad in the axle box.

[Problem to be solved by the invention]

By the way, regarding stacked leaf springs, the above characteristics &
The influence of the vehicle performance of a stacked leaf spring with Figure 1 is usually defined as the slope of the straight line connecting bl-81, bz -ez + =----, and the diagonal spring constant is regarded as the dynamic spring constant. , and "I dl + a3 - d".In addition, these characteristic values have a remarkable amplitude dependence and are closely related to vehicle performance. Hereinafter, problems with stacked leaf springs will be explained using a diagonal spring constant as an example.

Regarding the stacked leaf springs shown in Figures 5 and 6,
The amplitude dependence of the diagonal spring constant, that is, the dynamic spring constant, is shown by the solid line T in FIG. In FIG. 9, the amplitude F is plotted on the horizontal axis and the diagonal spring constant K is plotted on the vertical axis. Its major feature is that the diagonal spring constant increases rapidly at small amplitudes, decreases as the amplitude increases, and approaches a static spring constant. However, for small amplitude suspensions, the spring constant is low and provides a soft ride for the vehicle, while for large amplitudes, stacked leaf springs are used, which have a high spring constant and a rigid tube with high stability. is ideal. Therefore, it can be said that the conventional stacked leaf spring has a performance completely opposite to the ideal.

When this type of stacked leaf spring is applied to a vehicle, in order to obtain a soft ride comfort for the vehicle, that is, to suppress the increase in the diagonal spring constant of the stacked leaf spring with a small amplitude, the above-mentioned Japanese Patent Application Laid-Open No. 62 - The vehicle suspension system disclosed in Publication No. 160907, or as shown in FIG.
There is a structure in which a liner 18 made of a material with a low coefficient of friction is inserted between the child plate 16 and the child plate 17 and at the plate end between the child plate 16 and the child plate 17. The diagonal spring constant of a false lap spring having such a structure is indicated by a dotted line S in FIG. In stacked leaf springs with this structure, it is clear that the diagonal spring constant is reduced by reducing the frictional force generated between the leaves, that is, between the plates, but it is still difficult to say that the reduction has been achieved sufficiently. It is. Furthermore, in the stacked leaf spring of this structure, the diagonal spring constant at large amplitudes is also reduced at the same time, so the stacked leaf springs of this structure work disadvantageously in terms of riding comfort at large amplitudes.

Furthermore, a conventional stacked leaf spring has a structure in which a main plate having a Berlin-shaped eyeball is used as the first leaf, and a full-length plate is used as the second leaf. Usually, the purpose of a stacked leaf spring having such a structure is to protect the stacked leaf spring itself with the daughter plate when the first leaf, which is the parent plate, breaks.

The purpose of this invention is to solve the above problems,
Using a mirror plate with a Berlin-shaped eye as the first leaf,
As the second leaf, one or both sides use a child plate with a full length plate,
In particular, by specifying the shape of the contact surface between the first leaf and the second leaf, compared to conventional stacked leaf springs, the diagonal spring constant at large amplitudes is maintained, and the diagonal spring constant at small amplitudes is reduced. It is an object of the present invention to provide a stacked leaf spring that can significantly reduce the amount of vibration and improve the riding comfort of a vehicle in both large amplitude and small amplitude $1 ranges.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, in a stacked leaf spring consisting of a main plate having a Berlin-shaped eye on at least one end and at least one child plate, the second leaf of the child plate adjacent to the first leaf, which is the main plate, is A stacked leaf spring, which is extended outward from the load point of the parent plate, and the shape of the contact portion of the second leaf with the first leaf is formed into a cycloidal curved surface whose base circle is the outer diameter of the eye. Regarding.

[Effect]

The stacked leaf spring according to the present invention is constructed as described above and operates as follows. That is, this stacked leaf spring is
The second leaf of the child plate adjacent to the first leaf, which is the parent machine, is extended to the outside of the load point of the main plate, and the shape of the contact part of the second leaf is formed into a cycloidal curved surface with the outer diameter of the eyeball as the base circle. Therefore, at small amplitudes, the contact surface between the eye of the first leaf and the second leaf does not generate sliding friction.
On the contact surface, it is possible to generate a state in which the eyeball of the parent plate rolls on the child plate, that is, rolling friction, and when the amplitude is large, there is a sliding effect on the contact surface between the eyeball of the parent plate and the child plate. Friction can be generated. Therefore, without reducing the diagonal spring constant at large amplitudes, it is possible to maintain a predetermined diagonal spring constant and maintain the good ride comfort of conventional vehicles, and especially at small amplitudes, by reducing the diagonal spring constant, the vehicle The ride comfort can be improved.

〔Example〕

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

FIG. 1 is a schematic view showing an overall embodiment of a stacked leaf spring according to the present invention, and FIG. 2 is a schematic diagram showing the state of the stacked leaf spring of FIG. 1 at constant volume.

In FIG. 1, an embodiment of a stacked leaf spring according to the present invention is made up of a main plate 1 having a Berlin-shaped eye 4 at both ends and two daughter plates 2.3. It is stacked in contact with the second leaf. The second leaf daughter plate 2 adjacent to the first leaf parent plate 1 is formed to have a span greater than the load point of the parent plate 1. In this stacked leaf spring, a parent plate 1 and a daughter plate 2.3 are stacked over the entire length of the leaf, and the parent plate 1 and daughter plate 2.3 are fixed to each other by a center bolt 5 at the center of the leaf. . Further, although not clearly shown in the drawings, the stacked leaf spring consisting of the parent plate 1 and daughter plates 2.3 is configured as a Taber leaf spring. Further, regarding the child plate, a single plate or a plurality of plates may be used. Further, the child plate 2 is formed in a shape having a span longer than the load point of the parent plate 1, that is, in a shape extending outward from the load point of the parent plate 1.

In this stacked leaf spring, as shown in Fig. 2, the lower surface of the eyeball 4 provided at the end of the main plate 1 of the first leaf and the upper surface of the end of the daughter plate 2 of the second leaf are at a contact point TP. configured to make contact. The contact point TP between the lower surface of this eyeball 4 and the upper surface of the end of the child plate 2 is the point on the main plate 1 from the part where the load of the child plate 2, which is the second leaf, is zero to the part where it is maximum. It is the contact surface with the This stacked leaf spring is particularly characterized in that the contact surface is formed into a leaf surface having a cycloidal curvature with the outer diameter R of the eyeball 4 of the parent plate 1 as a base circle, that is, a cycloidal curved surface C8. . By configuring the contact surface between the eye 4 of the main board 1 and the end of the child board 2 in the above-described structure, the eye 4 of the main board 1, which is the number leaf,
The contact surface between the second leaf and the second leaf plate 2 can be configured to have rolling friction at small amplitudes and sliding friction at large amplitudes.

That is, the stacked leaf spring having the above configuration operates as follows. In this stacked leaf spring, in the diagonal spring constant characteristic diagram shown in FIG. Since the span changes are not equal, a relative displacement occurs in the contact portion TP, and sliding friction occurs. In FIG. 4, the amplitude F is plotted on the horizontal axis, and the diagonal spring constant K is plotted on the vertical axis. In other words, if the contact area TP between the eyeball 4 of the main board 1, which is the first leaf, and the end of the child board 2, which is the second leaf, is small, the eyeball 4 will be connected to the entire cycloid curve of the child board 2, which is the second leaf. - It moves relatively while rolling on the edge of the flat surface, that is, the cycloid curved surface. Therefore, at small amplitudes, no sliding friction occurs between the main plate 1 and the daughter plate 2 due to the difference in span change, but rolling friction occurs.

Also, before sliding friction occurs, static F! ! It is in a stationary state due to frictional force. This frictional force appears as a hysteresis loop shown in Figure 3, producing a rapid increase in the diagonal spring constant with small amplitude. In Figure 3, the horizontal axis plots the deflection The load W is plotted on . In other words, the stacked leaf spring configured in this way is
It has the characteristic of drawing a hysteresis loop as shown in FIG. That is, when a constant amplitude is applied to a stacked leaf spring under a standard load condition, it exhibits hysteresis loss as shown in FIG. 3.

By forming the shape of the contact portion TP between the eye 4 of the parent plate 1 of the stacked leaf spring and the daughter plate 2 in this way, a diagonal spring constant as shown in FIG. 4 can be obtained. That is, in this stacked leaf spring, when the amplitude is small, the cycloidal curved surface C8, that is, the contact surface between the center plate 4 of the main plate 1 and the child plate 2 does not generate sliding friction; 4
Since rolling on the child plate 2, that is, rolling friction occurs, the diagonal spring constant according to the present invention has a decrease, as shown by the solid line E in FIG. 4, compared to the conventional diagonal spring constant K, shown by the dotted line H. It is possible to improve the riding comfort of the vehicle. In addition, at large amplitudes, sliding friction occurs at the contact portion TP between the centerpiece 4 of the main plate 1 and the child plate 2, so as shown by the solid line G, the diagonal spring constant K can be adjusted without reducing the diagonal spring constant K as in the conventional case. Since the predetermined diagonal spring constant K equivalent to the conventional one is maintained, the good ride comfort of the conventional vehicle can be ensured.

〔Effect of the invention〕

The stacked leaf spring according to the present invention is constructed as described above and has the following effects.

That is, in a stacked leaf spring consisting of a parent plate having a Berlin-shaped eye on at least one end and at least one daughter plate, the second leaf of the daughter plate adjacent to the first leaf, which is the parent plate, is extended to the outside of the load point of the parent plate, and the shape of the contact portion of the second leaf is formed into a cycloidal curved surface with the outer diameter of the eye as the base circle, so that the diagonal spring constant characteristic can improve the ride comfort of the vehicle. can be obtained. That is, with a small amplitude, no sliding friction occurs on the contact surface between the eyeball of the first leaf and the second leaf, and a state in which the eyeball rolls on the child plate, that is, rolling** occurs on the contact surface. can be done. Further, when the amplitude is large, sliding friction is generated on the contact surface between the eyeball and the child plate.

Therefore, without reducing the diagonal spring constant at large amplitudes, it is possible to maintain the conventional good vehicle ride comfort while maintaining a predetermined diagonal spring constant.

Furthermore, when the amplitude is small, the diagonal spring constant can be reduced to improve the ride comfort of the vehicle.

That is, at large amplitudes, it generates sliding friction in the same way as conventional stacked leaf springs, and has the same friction run, so ride comfort on rough roads does not deteriorate. Furthermore, an increase in the diagonal spring constant with a small amplitude is suppressed, and a soft ride comfort of the vehicle can be provided on a good road or an ordinary road. Furthermore, at small amplitudes, movement of the contact point occurs due to the rolling of the eyeball, which does not cause slipping, so in the stacked leaf spring, l'! ! It is possible to suppress the generation of squeaking sounds.

[Brief explanation of the drawing]

1 is a schematic diagram showing an embodiment of the stacked leaf spring according to the present invention, FIG. 2 is a schematic diagram showing the state of the stacked leaf spring of FIG. 1 at constant volume, and FIG. 3 is a schematic diagram showing the stacked leaf spring according to the present invention. Spring load -
A diagram showing the deflection characteristics, FIG. 4 is a graph showing the amplitude dependence of the diagonal spring constant of the stacked leaf spring according to the present invention and a conventional stacked leaf spring, and FIG. 5 is a schematic diagram showing an example of the conventional stacked leaf spring. Figure 6 is a schematic diagram showing another example of a conventional stacked leaf spring, Figure 7 is a load-deflection diagram showing the relationship between load and deflection of a stacked leaf spring, and Figure 8 is a diagram showing the relationship between the load and deflection of a stacked leaf spring. A diagram showing the hysteresis loss when a constant amplitude is given under standard load conditions, Fig. 9 is a graph showing the amplitude dependence of the diagonal spring constant of a conventional stacked leaf spring, and Fig. 10 is a graph showing the amplitude dependence of the diagonal spring constant of a conventional stacked leaf spring. FIG. 1-・-・-Main board (first leaf), 2-・-・-・Child board (second leaf), 3-'-・Child board, 4-・・-Berlin-shaped eyeball, c 5-- −−−−−Cycloidal surface,
TP...--Contact part.

Claims (1)

[Claims] In a stacked leaf spring consisting of a parent plate having a Berlin-shaped eye on at least one end and at least one daughter plate, the second leaf of the daughter plate adjacent to the first leaf, which is the parent plate, is placed outside the load point of the parent plate. A stacked leaf spring, characterized in that the shape of the contact portion of the second leaf with the first leaf is formed into a cycloidal curved surface whose base circle is the outer diameter of the eye.