JPH071046B2 - 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. 8, an end shape of a parent 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 leaf springs are structured to have inter-plate friction, their load-deflection diagram plots the deflection X on the horizontal axis and the load W on the vertical axis as shown in FIG. Then, the locus is different between when the pressure P is applied to the leaf spring and when it is depressurized, and a hysteresis loss occurs. First
In FIG. 10, deflection X is plotted on the horizontal axis and load W is plotted on the vertical axis.

Further, the leaf spring having a load-deflection diagram as shown in FIG. 10 has a constant amplitude in a standard load state,
As shown in FIG. 11, a hysteresis loop is drawn by pressurizing and depressurizing the leaf spring. In FIG. 11, deflection X is plotted on the horizontal axis and 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 → d ₁ → e ₂ →
We will go back along another characteristic diagram such as e ₁ . Further, 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 of the leaf spring having the above characteristic diagram on the vehicle performance is usually b ₁
-e ₁ , b ₂ -e ₂ , ... is defined as the inclination of the straight line connecting the diagonal spring constants, which are considered as the dynamic spring constants, 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. 8 and 9,
The amplitude dependence of the diagonal spring constant or dynamic spring constant is
As shown in FIG. 12, the diagram becomes as shown by the solid line T. First
In FIG. 12, the horizontal axis plots the amplitude F and the vertical axis plots the diagonal spring constant K. Its main feature is
The diagonal spring constant K is that it rapidly increases at small amplitude, decreases as the amplitude increases, and approaches the static spring constant. However, as a suspension for a vehicle, a leaf spring is ideal because it has a low spring constant at small amplitude and provides a soft ride comfort of the vehicle, and at large amplitude, a rigid tube with a high spring constant and high stability can be obtained. is there. 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. 13, 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 K of the leaf spring having such a structure is shown by the 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 having this structure, the diagonal spring constant K at a large amplitude is also reduced at the same time, which is disadvantageous to the riding comfort at a 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 leaf spring having such a structure is intended to protect the leaf spring itself when the first leaf, which is a 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 the second leaf, a child plate whose one side or both sides are full length plates is used, and in particular, by specifying the contact position between the first leaf and the second leaf, the amplitude is larger than that of the conventional leaf spring. It is an object of the present invention to provide a leaf spring for improving the riding comfort of a vehicle by significantly reducing only the diagonal spring constant with a small amplitude while maintaining the diagonal spring constant.

[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 Formed in a shape that extends outward from the load point of the main plate, and the contact portion between the end of the first leaf and the end of the second leaf is located at an angle of 15 ± 8 ° from the vertical center plane of the center of the eyeball. Relating to the leaf spring set in.

[Action]

The leaf spring according to the present invention is configured as described above and operates as follows. That is, this leaf spring is
Since the main plate having Berlin type eyeballs is used as the first leaf, and the second board as the second leaf is set to contact at a predetermined position of the inside of the eyeball, that is, at an angle of 15 ± 8 °. , With a small amplitude, a sliding friction does not occur at the contact portion between the eyeball of the first leaf and the second leaf, and the eyeball of the parent plate rolls on the child plate at the contact portion, that is, rolling. Friction can be generated. Further, with a large amplitude, sliding friction can be generated at the contact portion between the eyeball of the parent plate and the child plate. Therefore, without reducing the diagonal spring constant at large amplitude,
A good riding comfort of the conventional vehicle can be ensured while maintaining a predetermined diagonal spring constant, and in particular, at a small amplitude, the diagonal spring constant can be reduced to improve the riding comfort of the vehicle.

〔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, FIG. 2 is an explanatory view showing a force relationship due to a vertical load of the leaf spring shown in FIG. 1, and FIG. FIG. 1 is an explanatory view showing a force relationship due to a horizontal force of the leaf spring of FIG. 1, and FIG. 4 is a schematic view showing a state of the leaf spring of FIG.

FIG. 1 shows, as an example of a leaf spring according to the present invention, a leaf spring composed of a parent plate 1 having Berlin-shaped eyeballs 4 at both ends and two child plates 2 and 3. One or both sides of the second leaf sub-board 2 adjacent to the first leaf main board 1 is formed to have a span not less than the load point of the main board 1. That is, the child board 2 is formed in a shape that extends outside the load point of the parent board 1. In this leaf spring, the parent 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.

In particular, in this leaf spring, the lower surface of the eyeball 4 provided at the end of the first leaf parent plate 1 and the upper surface of the end of the second leaf child plate 2 are configured to come into contact at the contact portion TP. ing.
Contact part TP between the lower surface of this eyeball 4 and the upper surface of the edge of the child board 2
As shown in FIG. 4, is set at a position of an angle θ = 15 ± 8 ° inward from a vertical plane V passing through the center O of the eyeball 4 in a constant volume state of the vehicle. By setting the contact portion TP between the end portion of the parent board 1 and the end portion of the child board 2 at the above position, the contact portion TP between the eyeball 4 of the parent board 1 which is the most leaf and the child board 2 of the second leaf
That is, the contact surface may have rolling friction when the amplitude is small and sliding friction when the amplitude is large. The leaf spring thus constructed has the characteristic of drawing a hysteresis loop as shown in FIG. That is, when a constant amplitude is applied to the leaf springs under a standard load condition, as shown in FIG. 6, when the deflection X is plotted on the horizontal axis and the load W is plotted on the vertical axis, the hysteresis It will be an indication of loss.

In the leaf spring according to the present invention, the contact between the parent plate 1 and the child plate 2 under the above conditions causes the load 4 to be applied to or removed from the parent plate 1 when the load is applied in the constant volume state. The contact point between the leaf and the end of the child board 2 is shown in FIGS.
A force as shown in the figure is generated. Hereinafter, the relationship of forces will be described with reference to FIGS. 2 and 3.

Contact part between the eyeball 4 of the parent board 1 and the end of the child board 2 of the second leaf
In TP, a force μ · N ₁ is generated by the vertical load P as shown in FIG. _2, and a force μ · N ₂ is generated by the horizontal force Q as shown in FIG. However, P: Load sharing on one side of the leaf spring N ₁ : Vertical drag force generated on the eyeball 4 and the child board μ: Friction coefficient Q: Force generated by the difference in horizontal displacement between the eyeball 4 and the child board N ₂ : Vertical drag force generated by the force Q on the eyeball 4 and the child board 2 θ: An angle from the central vertical plane of the eyeball 4 to the inside. Also, in the figure, F ₁ and F ₂ indicate frictional force, and F ₁ =
μ · N ₁ and F ₂ = μ · N ₂ .

Therefore, the total frictional force F _t generated by these forces μ · N ₁ and forces μ · N ₂ is expressed by the following equation.

F _t = μ ・ N ₁ + μ ・ N ₂ = μ (P / cos θ + Q ・ sin θ) (1) This force F _t is the component force Q ・ cos of the horizontal force Q in the eye contact direction.
When it is smaller than θ, that is, when the following inequality is satisfied, a slip, that is, a relative displacement occurs at the contact point TP between the eyeball 4 and the child board 2.

μ (P / cos θ + Q · sin θ) <Q · cos θ (2) At this time, the rotational moment M is generated in the eyeball 4. That is, when the radius of the eyeball 4 and _{R, M = F t · R} = μ (P / cos θ + Q · sin θ) R ...... (3) Further, the sliding contact point TP between the centerpiece 4 and Coban 2 As an equation that does not occur, the following equation holds.

μ (P / cos θ + Q · sin θ) = Q · cos θ (4) At this time, the rotation moment M is generated in the eyeball 4.

M = Q · cos θ (5) Here, the total frictional force F _t and the rotation moment M of the eyeball 4 are used as variables of the angle θ at which the contact point TP is displaced inward from the central vertical plane V of the eyeball 4. , F _t = f ₁ (θ), and
Let M = f ₂ (θ). That is, f ₁ (θ) = μ (P / cos θ + Q · sin θ) f ₂ (θ) = Q · cos θ.

In FIG. 5, a graph shows the relationship between f ₁ (θ) and f ₂ (θ). In FIG. 5, the horizontal axis plots the angle θ, and the vertical axis plots the force F.

Here, the vertical load P, assuming medium truck, at this time, the horizontal force Q, spring constant, takes a value of about Q _L to Q _H in the figure from the difference of such leaf structure.

At this time, in Q _L , f ₁ (θ) and f at the angle θ = 8 °
_The intersection is with ₂ (θ). Therefore, when the angle θ = 8 ° or less, sliding friction occurs between the master plate 1 and the slave plate 2, and the angle θ = 8.
Above 0 °, rolling friction occurs between the parent plate 1 and the child plate 2. In Q _H , f ₁ (θ) and f ₂ (θ) are intersections at the angle θ = 23 °. Therefore, when the angle θ is 23 ° or less, the main plate 1
And the slave plate 2 have a sliding friction, and when the angle θ = 23 ° or more, the master plate 1 and the slave plate 2 have a rolling friction. When the contact portion TP between the eyeball 4 and the child board 2 is more than the angle θ, no slip occurs between the parent board 1 and the child board 2. Further, the moment amount M for rotating the eyeball 4 is given by the above equation (5), and the intersection has the maximum value, which is the most effective.

That is, in consideration of the above phenomenon, the optimum value of the angle θ is a position where slippage does not occur between the two and the rotation moment M of the eyeball 4 is maximized.
It can be said that the optimum range is the angle θ = 15 ± 8 °.

In this way, by setting the contact surface TP between the eyeball 4 of the parent plate 1 of the leaf spring and the child plate 2, the diagonal spring constant K as shown in FIG. 7 can be obtained. In FIG. 7, the horizontal axis plots the amplitude F and the vertical axis plots the diagonal spring constant K. That is, in this leaf spring, at a small amplitude, the contact surface between the eyeball 4 of the master plate 1 and the slave board 2 does not generate sliding friction, and the contact portion TP has the eyeball 4 of the master plate 1 at its contact portion TP.
Is rolling on the daughter plate 2, that is, rolling friction occurs, so that the diagonal spring constant K according to the present invention can be reduced as shown by the solid line E as compared with the conventional diagonal spring constant shown by the dotted line H, The riding comfort of the vehicle can be improved. Also, at a large amplitude, the contact portion TP between the center plate 4 of the master plate 1 and the slave plate 2
Since sliding friction occurs in the conventional vehicle, the diagonal spring constant K does not decrease as in the conventional case, and the predetermined diagonal spring constant K equivalent to the conventional case is maintained as shown by the solid line G. It is possible to secure a good ride comfort.

〔The invention's effect〕

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

In other words, this leaf spring is a leaf spring composed of a parent plate having at least one end with a Berlin-shaped eyeball and at least one child plate, and in the leaf spring of the parent plate and the end of the second leaf of the child plate. Since the contact part of each part is set at an angle of 15 ± 8 ° inward from the center vertical plane of the eyeball, at a small amplitude, sliding friction occurs in the contact area between the first leaf eyeball and the second leaf. Without doing so, a state in which the eyeball rolls on the child board, that is, rolling friction can be generated in the contact portion. Further, with a large amplitude, sliding friction can be generated on the contact surface between the eyeball and the child plate.

Therefore, at a large amplitude, the riding comfort of the conventional vehicle is ensured while maintaining a predetermined diagonal spring constant without lowering the diagonal spring constant. 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, at a large amplitude, sliding friction is generated between the two as in the conventional leaf spring, and since the friction is equivalent, the riding comfort on rough roads is not reduced. Further, when the amplitude is small, an increase in the diagonal spring constant is suppressed, and a soft ride comfort of the vehicle can be provided on a good road or an ordinary road.

Furthermore, with small amplitude, contact points move due to rolling of eyeballs that do not cause slippage between the parent plate and the child plate.Therefore, it is possible to suppress the generation of squeak noise, which has been a future concern in leaf springs. You can

[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 an explanatory view showing a force relationship due to a vertical load of the leaf spring shown in FIG. 1, and FIG. FIG. 4 is an explanatory view showing a force relationship due to a horizontal force of the leaf spring, FIG. 4 is a schematic view showing a state of the leaf spring of FIG. 1 at a constant volume, and FIG. 5 is a vertical direction with respect to the leaf spring according to the present invention. FIG. 6 is a graph showing the relationship between the frictional force generated by the load and the horizontal force and the angle of the contact point, and FIG. 6 is the load of the leaf spring according to the present invention.
FIG. 7 is a graph showing the deflection characteristics, FIG. 7 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. 8 is a schematic showing an example of the conventional leaf spring. FIG. 9 is a schematic view showing another example of the conventional leaf spring, FIG. 10 is a load-deflection diagram showing the relationship between the load and the deflection of the conventional leaf spring, and FIG. A diagram showing the hysteresis loss when a constant amplitude is applied to the leaf spring in the standard load state, Fig. 12 is a graph showing the amplitude dependence of the diagonal spring constant of the conventional leaf spring, and Fig. 13 is the conventional FIG. 6 is a schematic view showing still another example of the leaf spring of FIG. 1 ... Parent plate (first leaf), 2 ... Child plate (second leaf), 3 ... Child plate, 4 ... Berlin type eyeball, θ ... Angle of contact part, P ... Vertical load, Q: Horizontal force, TP
…… Contact area, R …… Radius of the eyeball.

 ─────────────────────────────────────────────────── ─── 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. It is formed in a shape that extends to the outside of the load point of the plate, and the contact portion between the end of the first leaf and the end of the second leaf is set at an angle of 15 ± 8 ° from the vertical center plane of the center of the eye. A laminated leaf spring characterized in that