JPH071045B2 - Leaf spring - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a leaf spring for vehicle suspension, which is formed by stacking a parent plate and a child plate.

[Conventional technology]

2. Description of the Related Art Conventionally, as a leaf spring for suspension of an automobile, as shown in FIG. 5, an end shape of a main plate 11 has an upper winding eyeball, that is, an eyeball shape of an upturned eye 12, or as shown in FIG. As described above, it is well known that the end portion of the main plate 13 has the shape of a Berlin eye, that is, the shape of a Berlin eye 14. Since these laminated leaf springs are structured to have inter-plate friction, the load-deflection diagram of the laminated leaf springs is
As shown in FIG. 7, the loci differ between the time P when the leaf spring is pressed and the time D when the leaf spring is depressed, and a hysteresis loss occurs. In FIG. 7, deflection X is plotted on the horizontal axis and load W is plotted on the vertical axis.

Further, in the above-mentioned leaf spring having a load-deflection diagram as shown in FIG. 7, when a constant amplitude is applied in a standard load state, hysteresis is generated by pressurizing and depressurizing the leaf spring as shown in FIG.・ Draw a loop. In FIG. 8, the flexure X is plotted on the horizontal axis and the load W is plotted on the vertical axis. That is, when the leaf spring is pressed to give an arbitrary deflection; + A ₁ is applied, and then depressurized to bend; and when reduced to −A ₁ , the characteristic diagram at the time of pressurization, that is, the line of a ₁ → b ₁ Without returning, b ₁ → c ₁ →
It returns along another characteristic diagram such as d ₁ → e ₂ → e ₁ . Then, when the leaf spring is pressed, a characteristic diagram of e ₁ → f ₁ → a ₁ is drawn, and the leaf spring forms a loop with an amplitude of ± A ₁ . This phenomenon is also observed in the case of arbitrary amplitudes A ₂ , A _3, etc., except in the case of extremely small amplitudes.

Further, as a vehicle suspension device, there is one disclosed in JP-A-62-160907. The vehicle suspension system is composed of a leaf spring composed of several leaves and a vehicle, and the first leaf of the leaf spring is placed on the outer top surface or bottom surface of the hollow box-shaped axle box. The leaf group of the second leaf or less is accommodated inside the axle box under an appropriate tightening force, and this axle box is suitable for the first leaf while accommodating the leaf group of the second leaf or less. It is attached to the axle while giving a tightening force. Further, the first leaf is fastened to the axle box via the upper pad on the axle box.

[Problems to be Solved by the Invention]

By the way, regarding the leaf spring, the degree of influence on the vehicle performance of the leaf spring having the above characteristic diagram is usually
It is defined as the slope of a straight line connecting b ₁ -e ₁ , b ₂ -e ₂ ,
The diagonal spring constant, which is regarded as the dynamic spring constant, and a ₁ -d ₁ , a ₃
It is mostly determined by the friction defined as the width of -d ₃ . Further, these characteristic values have a remarkable amplitude dependency and have a close relationship with vehicle performance. The problem of the leaf spring will be described below by taking the diagonal spring constant as an example.

Regarding the leaf springs as shown in FIGS. 5 and 6,
The amplitude dependence of the diagonal spring constant, that is, the dynamic spring constant, is as shown by the solid line T in FIG. In FIG. 9, the horizontal axis represents the amplitude F and the vertical axis represents the diagonal spring constant K. The major feature is that the diagonal spring constant K rapidly rises at a small amplitude, decreases as the amplitude increases, and approaches the static spring constant. However, as a suspension of a vehicle, a leaf spring that has a small spring constant and a soft ride comfort of the vehicle at a small amplitude and a rigid pipe with a high spring constant and a high stability at a large amplitude is ideal. Is. Therefore, it can be said that the conventional leaf spring has a performance completely opposite to the ideal.

When this type of leaf spring is applied to a vehicle, in order to obtain a soft riding comfort for the vehicle, that is, in order to suppress an increase in the diagonal spring constant with a small amplitude of the leaf spring, the above-mentioned JP-A-62-62 Suspension device disclosed in Japanese Patent Publication No. 160907, or, as shown in FIG. 10, between a parent board 15 and a child board 16 and a child board
There is a structure in which a liner 18 made of a material having a low friction coefficient is inserted at the plate end between the 16 and the child plate 17. The diagonal spring constant of the leaf spring having such a structure is shown by a dotted line S in FIG. In the leaf spring having this structure, the effect of reducing the diagonal spring constant K is clear by reducing the frictional force generated between the leaves, that is, between the plates, but it cannot be said that it has been sufficiently reduced. Is. Further, in the leaf spring of this structure, the diagonal spring constant K at large amplitude is also reduced at the same time, so that the leaf spring of this structure is disadvantageous for the riding comfort at large amplitude.

Further, a conventional leaf spring having a structure in which a parent plate having a Berlin-shaped eyeball is used as the first leaf and a child plate is a full length plate as the second leaf is disclosed. Usually, the laminated leaf spring having such a structure is intended to protect the laminated leaf spring itself by the child plate when the first leaf, which is the parent plate, is broken.

An object of the present invention is to solve the above problems,
Using the main board with Berlin-shaped eyeballs as the first leaf,
As a second leaf, one side or both sides use a full length board,
In particular, by specifying the shape of the contact surface between the first leaf and the second leaf, the diagonal spring constant at a small amplitude is maintained while maintaining the diagonal spring constant at a large amplitude compared to the conventional leaf spring. It is intended to provide a leaf spring for significantly reducing the vehicle load and improving the riding comfort of the vehicle in both the large amplitude region and the small amplitude region.

[Means for Solving the Problems]

The present invention is configured as follows to achieve the above object. That is, in the present invention, in a laminated leaf spring consisting of a parent plate having at least one end with a Berlin-shaped eyeball and at least one child plate, the second leaf of the child plate adjacent to the first leaf which is the parent plate is The leaf spring, which is extended to the outside of the load point of the main plate, and the shape of the contact portion of the second leaf with the first leaf is formed in a cycloidal curved surface having the outer diameter of the eyeball as a base circle. Regarding

[Action]

The leaf spring according to the present invention is configured as described above and operates as follows. That is, this leaf spring is
The second leaf of the child 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 curved surface of a cycloid whose base circle is the outer diameter of the eyeball. Therefore, at a small amplitude, the contact surface between the eyeball of the first leaf and the second leaf does not generate sliding friction,
A state where the eyeballs of the master plate roll on the daughter plate, that is, rolling friction can be generated on the contact surface, and when the amplitude is large, a slip occurs on the contact surface between the eyeballs of the master plate and the daughter plate. Friction can be generated. Therefore, a good riding comfort of a conventional vehicle is ensured while maintaining a predetermined diagonal spring constant without lowering the diagonal spring constant at a large amplitude. You can improve the riding comfort of the car.

〔Example〕

An embodiment of a leaf spring according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of a leaf spring according to the present invention as a whole, and FIG. 2 is a schematic view showing a state of the leaf spring of FIG.

In FIG. 1, as one embodiment of a leaf spring according to the present invention, a parent plate 1 having Berlin-shaped eyeballs 4 at both ends and two child boards 2 and 3 are provided. It is stacked in contact with the second leaf. The second leaf child plate 2 adjacent to the first leaf parent plate 1 is formed in a span equal to or larger than the load point of the parent plate 1. This leaf spring is the main plate 1
And the child plates 2 and 3 are overlapped over the entire length of the leaf, and the parent plate 1 and the child plates 2 and 3 are fixed to each other by a center bolt 5 at the center of the leaf. Further, although not clearly shown in the drawing, the laminated leaf spring including the parent plate 1 and the child plates 2 and 3 is configured as a taper leaf spring. Also,
As for the child board, a single board or a plurality of boards are used.
Further, the child board 2 is formed in a shape having a span equal to or larger than the load point of the master board 1, that is, a shape extending to the outside of the load point of the master board 1.

In this leaf spring, as shown in FIG. 2, the lower surface of the eyeball 4 provided at the end of the parent plate 1 of the first leaf and the upper surface of the end of the secondary plate 2 of the second leaf are contact points TP. Configured to contact. The contact point between the lower surface of the eyeball 4 and the upper surface of the end portion of the child board 2, that is, the contact portion TP, is the parent board 1 from the portion where the load load of the child plate 2 which is the second leaf becomes zero to the portion where it becomes the maximum. It is the contact surface with. In this leaf spring,
The contact surface is characterized by being formed on a leaf surface having a cycloid curvature with the outer diameter R of the eyeball 4 of the main plate 1 as a base circle, that is, a curved surface CS of the cycloid. By configuring the contact surface between the eyeball 4 of the parent board 1 and the end of the child board 2 with the above structure, the eyeball 4 of the parent board 1 which is the most leaf and the child board 2 of the second leaf contact The surface can be configured to have rolling friction at small amplitudes and sliding friction at large amplitudes.

That is, the leaf spring having the above-described structure operates as follows. In this leaf spring, in the diagonal spring constant characteristic diagram shown in FIG. 4, when a load is applied in the constant volume state or when the load is released, it occurs in each leaf of the master plate 1 and the slave plate 2. Since the span changes are not equal, relative displacement occurs at the contact portion TP and sliding friction occurs. In FIG. 4, the horizontal axis plots the amplitude F and the vertical axis plots the diagonal spring constant K. That is, if the contact point TP between the eye 4 of the parent board 1 which is the most leaf and the end of the child board 2 that is the second leaf has a small amplitude, the leaf 4 of the cycloid curve of the child board 2 whose eyeball 4 is the second leaf. It moves relatively while rolling on the plate, that is, the plate edge of the cycloid curved surface.
Therefore, at a small amplitude, sliding friction does not occur between the master plate 1 and the slave plate 2 due to the difference in span change, and rolling friction occurs. Further, before the sliding friction occurs, it is in a stationary state due to the static friction force. This frictional force appears as a hysteresis loop shown in FIG. 3, and causes a sharp increase in the diagonal spring constant with a small amplitude. In FIG. 3, the deflection X is plotted on the horizontal width, and the load W is plotted on the vertical axis. In other words, the leaf springs constructed in this way are
It has the characteristic of drawing a hysteresis loop as shown in FIG. That is, when a constant amplitude is applied to the leaf spring in the standard load state, it exhibits the hysteresis loss as shown in FIG.

In this way, by forming the shape of the contact portion TP between the eyeball 4 of the parent plate 1 of the leaf spring and the child plate 2, the diagonal spring constant as shown in FIG. 4 can be obtained. That is, in this leaf spring, at a small amplitude, the cycloidal curved surface CS of the master plate 1 and the slave plate 2, that is, the contact surface does not generate sliding friction, and the contact surface of the master plate 1 has no sliding friction. 4 is a state of rolling on the daughter plate 2, that is, rolling friction occurs, so that the diagonal spring constant K according to the present invention is compared with the conventional diagonal spring constant K shown by the dotted line H as shown by the solid line E in FIG. It is possible to reduce the ride comfort of the vehicle. Further, at a large amplitude, sliding friction occurs in the contact portion TP between the eyeball 4 of the parent board 1 and the child board 2, so as shown by the solid line G, the diagonal spring constant K does not decrease as in the conventional case, Since the predetermined diagonal spring constant K equivalent to that of the conventional one is maintained, it is possible to secure the good ride comfort of the conventional vehicle.

〔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 leaf spring is a leaf spring having a parent plate having a Berlin-shaped eyeball at least one end and at least one child plate, and the second leaf of the child plate adjacent to the first leaf which is the parent plate. Is extended to the outside of the load point of the main plate, and the shape of the contact portion of the second leaf is formed into a curved surface of a cycloid whose basic circle is the outer diameter of the eyeball, so that the riding comfort of the vehicle can be improved. Can be obtained. That is, with a small amplitude, sliding friction does not occur on the contact surface between the first leaf eyeball and the second leaf, and the eyeball rolls on the contact plate, that is, rolling friction occurs on the contact surface. be able to. Further, when the amplitude is large, sliding friction is generated on the contact surface between the eyeball and the child board.

Therefore, it is possible to secure the conventional good ride comfort of the vehicle while maintaining the predetermined diagonal spring constant without lowering the diagonal spring constant at a large amplitude. Further, when the amplitude is small, the diagonal spring constant can be reduced and the riding comfort of the vehicle can be improved.

That is, with a large amplitude, sliding friction is generated as in the conventional leaf spring, and since it has the same friction, the riding comfort on rough roads is not reduced. Further, the rise of the diagonal spring constant with a small amplitude can be suppressed, and a soft ride comfort of the vehicle can be provided on a good road or a general road. Further, at a small amplitude, the contact point moves due to rolling of the eyeball that does not cause slippage, so that it is possible to suppress the generation of squeak noise, which has been a future concern in the leaf spring.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a leaf spring according to the present invention, FIG. 2 is a schematic view showing a state of the leaf spring shown in FIG. 1 at a constant volume, and FIG. 3 is a leaf plate according to the present invention. Spring load −
FIG. 4 is a graph showing the bending characteristic, FIG. 4 is a graph showing the amplitude dependence of the diagonal spring constant between the leaf spring according to the present invention and the conventional leaf spring, and FIG. 5 is a schematic showing an example of the conventional leaf spring. FIG. 6 is a schematic view showing another example of a conventional leaf spring, FIG. 7 is a load-deflection diagram showing the relationship between load and deflection of the leaf spring, and FIG. 8 is a leaf spring. A diagram showing hysteresis loss when a constant amplitude is applied under standard load condition, Fig. 9 is a graph showing amplitude dependence of diagonal spring constant of a conventional leaf spring, and Fig. 10 is a conventional leaf spring. It is a schematic diagram showing another example of. 1 ... Parent plate (first leaf), 2 ... Child plate (second leaf), 3 ... Child plate, 4 ... Berlin type eyeball, CS ... Cycloid curved surface, TP ... Contact part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fusao Wakabayashi No. 8 Tsutana, Fujisawa City, Kanagawa Prefecture Isuzu Motors Co., Ltd. Fujisawa Plant (72) Inventor Ikuo Numazaki No. 8 Shelf, Fujisawa City, Kanagawa Isuzu Motors Co., Ltd. Within

Claims (1)

[Claims] 1. A laminated leaf spring comprising a parent plate having at least one end having a Berlin-shaped eyeball and at least one child plate, wherein the second leaf of the child plate adjacent to the first leaf which is the parent plate is the parent plate. A leaf spring, wherein the leaf is extended to the outside of the load point, and the shape of the contact portion of the second leaf with the first leaf is formed into a cycloid curved surface having the outer diameter of the eyeball as a base circle.