JPH0529557Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a leaf having an eye at its end, constituting a stacked leaf spring used as a suspension device for a vehicle or the like.

[Conventional technology]

In recent years, vehicles have adopted cab suspensions and the like to improve riding comfort, and increased engine output has improved their ability to travel on rough roads, so vehicles are increasingly being driven on rough roads at high speeds.

At this time, a stacked leaf spring is generally used as the suspension device, and this stacked leaf spring is normally designed as shown in FIG. In the figure, suspension device A is equipped with an auxiliary spring a and a main spring b,
Each of the springs a and b is composed of a stacked leaf spring made of a plurality of stacked leaves. Both springs a and b are integrally fastened together with an axle c using U-bolts d and d. This suspension system A is attached to the vehicle body by attaching it to the center part e formed at the end of the main spring b.
It is done through. That is, the lower parts of the auxiliary spring sliding sheets f, f attached to the vehicle body frame (not shown) are brought into contact with the #1 leaf of the auxiliary spring a, and the lower part of the main spring sliding sheet g is brought into contact with the main spring b. Let it come into contact with the #1 leaf of
In this state, the suspension system A is attached to the vehicle body by inserting the spring pin h into the eyelet e of the main spring b and appropriately fixing the spring pin h to the vehicle body frame.

In the figure, i is a tire, which is attached to rotate around an axle attached to an axle c, and vibrations from the tire i are transmitted to the main spring b and the auxiliary spring a through the axle c. It's summery.

On the other hand, if the vehicle is traveling at high speed on a rough road, the tire i
The ground contact force of the tire i constantly fluctuates, and the output of the engine also fluctuates accordingly, causing the tire i to constantly vibrate in the longitudinal direction. This vibration is then transmitted to the main spring b and the auxiliary spring a. However, since the part of the car body above the frame, including the frame, tries to continue moving at a steady speed, as shown in Figure 6, the main spring b is attached to the spring pin h that fixes it to the car body in the longitudinal direction described above. A load of vibration j is applied, and this load may break the lower part k of the eyelet part (shaded area in FIG. 6) of the leaf having the eyelet part. This is because in conventional leaves, the gap w at the end of the eyeball part is small, for example w = 0 ~
Since the thickness is about 5 mm, the steel balls used in the shot peening treatment of the leaf are prevented from entering, so the lower part of the eyeball part k is not subjected to the same treatment.
This is because the fatigue strength is lower than in the shot peened area.

Therefore, conventionally, the strength has been improved by increasing the thickness of the leaf for a stacked leaf spring having an eye part to reduce the stress generated in the lower part k of the eye part.

[Problem that the invention attempts to solve]

However, increasing the thickness of the leaf not only goes against the request for weight reduction, but also increases the stress in the general part l of the leaf (see Figure 6) because the spring constant of the leaf itself hardly changes even if the thickness is increased. ,
On the contrary, there was a problem in that this portion was more likely to break.

In addition, the bushing m is fitted into the eyelet e, but the inner diameter of the eyelet and the outer diameter of the bushing are in an interference fit relationship, and even if the interference is the same, the press-fit stress of the bushing m is greatly affected by the plate thickness. . This effect becomes more noticeable as the plate thickness increases, and as the press-fit stress increases, the strength against fluctuating stress decreases, leading to the problem that breakage occurs more often at the upper part of the eye (see Figure 6). Was.

The present invention was developed in view of the above-mentioned circumstances, and the purpose is to obtain a leaf for a stacked leaf spring that has an eyelet part that increases the strength of the eyelet part and improves the leaf life without going against the weight reduction. do.

[Means for solving problems]

In order to achieve the above object, the present invention has an opening at the end of the eyeball part so that the shot peening treatment is performed at the lower part of the eyeball part, and the winding end of the eyeball part formed at the end of the leaf is opened. It is characterized by being formed obliquely at an angle of 20° to 30° so as to open outward.

[Effect]

Since the rolled end of the eyeball formed at the end of the leaf opens outward, processing steel balls can enter the eyeball during shot peening of the leaf, and may also enter the lower part of the eyeball. The same treatment is performed, and compressive residual stress is generated in the part. This increases the fatigue strength of the lower part of the eyeball.

〔Example〕

Hereinafter, the present invention will be described in more detail based on illustrated embodiments.

FIG. 1 is a partial side view of a leaf 1 for a stacked leaf spring having a center portion according to the present invention, and a general portion 3 extends from the end of the leaf 1 to form a center portion 2. As shown in FIG. A bushing 4 is fitted into this eyepiece 2, and a spring pin is inserted through the bushing 4 so that it can be attached to the vehicle body.

The eyepiece portion 2 is formed by winding in a conventional manner, but unlike the conventional structure, the winding end portion 2a is formed diagonally so as to open outward. The magnitude of the inclination angle θ of the winding end portion 2a at this time affects the compressive residual stress value generated by the shot peening process and the amount of wear of the bush 4, so it is designed within a range that satisfies both.

First, we will discuss compressive residual stress.

A plurality of leaves for stacked leaf springs each having an eyelet portion 2 formed by gradually changing the inclination angle θ of the winding end portion 2a were formed, and each leaf was shot peened under the same conditions. Thereafter, the relationship between the inclination angle θ of the winding end 2a of each leaf and the compressive residual stress was measured, and a characteristic curve shown in FIG. 2 was obtained. As can be seen from Fig. 2, as the inclination angle θ increases up to 20°, the residual stress increases proportionally;
When the angle is greater than 20°, a substantially constant high level of residual stress is obtained despite the increase in angle.

Next, the amount of wear on the bush 4 will be described.

The winding end 2a of a plurality of leaves with different inclination angles θ used in the measurement of the compressive residual stress
When the relationship between the inclination angle θ and the wear amount of the bush 4 was measured, a characteristic curve shown in FIG. 3 was obtained. As can be seen from Fig. 3, the amount of wear on the bushing 4 is maintained at an almost constant low level despite the increase in the angle of inclination θ up to 30°, but when the angle increases beyond 30°, The amount of wear on the bushing 4 also increases in proportion to this.

According to the above, the inclination angle θ of the eye roll end portion 2a is desirably designed to be 20° to 30°.

In order to form the end portion 2a of the eye roll obliquely at the desired inclination angle θ, the end portion of the leaf spring material before the eye winding is formed is cut diagonally in advance, and the said inclination angle θ is adjusted at the same time as the eye winding is formed. Alternatively, after forming the eyelet winding, the end portion of the winding may be cut so as to have the above-mentioned inclination angle θ.

The thus obtained leaf with a compressive residual stress value of 50 Kg/mm ² at the lower part of the eye can have a significantly longer leaf life than a conventional leaf with a compressive residual stress value of 0, as shown in FIG.

[Effect of idea]

As mentioned above, the present invention has an extremely simple structure in which the winding end of the eyepiece is formed diagonally at an angle of 20° to 30° so as to open outward. It has the practical effect of increasing leaf life.

Moreover, since the present invention has a simple structure, it is easy to manufacture, and the above-mentioned effects can be achieved along with weight reduction without increasing the thickness of the leaf, so the practical effects are significant. .

[Brief explanation of the drawing]

Fig. 1 is a partial side view of the leaf of the present invention, Figs. 2 to 4 are graphs showing characteristic curves of the same leaf, Fig. 5 is a schematic side view of a conventional suspension system, and Fig. 6 is a schematic side view of a conventional suspension system.
The figure is a partial side view of a conventional leaf. 1... A leaf for a stacked leaf spring having an eye portion, 2
...eyeball part, 2a... winding end part.

Claims (1)

[Scope of utility model registration request] For a stacked leaf spring having an eyelet formed at the end of a leaf, the winding end of the eyelet being formed at an angle of 20° to 30° so as to open outward. Leaf.