JPS6237207A - Leaf spring suspension - Google Patents

Abstract

PURPOSE:To cancel vibration in differential noise are positively by forming mass members while projecting the opposite ends of subleaf to the outside of the opposite ends of main lead. CONSTITUTION:A leaf spring 3 is constructed with main leaf 1 and sub leaf 2 where subleaf 2 has longer span than main leaf 1 and projects to the outside and to form mass members 17;, 17 at the free end. Eye sections 4, 6 provided at the opposite ends of main leaf 1 are fixed through rubber bushes 5, 7 to the body bracket. In such structure, the opposite ends of main leaf 1 are positioned at the inner side than the nodes of double node bending vibration under freely supported condition of the opposite ends of subleaf 2. Consequently, the vibration levels of bouncing and bending of leaf spring 3 can cancelled at the supporting points 4, 6 to reduce transmission of vibration to the body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a leaf spring spring suspension.

As shown in Fig. 6, the conventional leaf spring type suspension has a main leaf 1 (No. 1 leaf), and No. 2 leaves, No. 3 leaves, etc., which are superimposed on the lower part of the main leaf 1. Leaf spring 3 consisting of
The centerpiece 4 of one end (front end) of the main leaf l is attached to a bracket of the vehicle body (not shown) via a bushing 5, and the other end (
The centerpiece 6 (at the rear end) is attached to a hanger bracket (not shown) on the vehicle body via a bush 7 and a shackle 8. 9 is an axle housing fixed to the center of the leaf spring 3, and 10 is a shock absorber.

By the way, the leaf spring 3 has a characteristic that it cannot absorb minute vibrations, so bounce vibrations and bending vibrations generate muffled noise inside the vehicle. The bounce vibration is a relatively low frequency vibration, and the bending vibration is a high frequency vibration.

Therefore, in the leaf spring type suspension, so-called rubber bushings are used for the bushings 5.7 to absorb the slight vibrations as much as possible. There are two types of rubber bushings: one with a so-called heavy vibration isolation structure in which one rubber bushing is provided at the front end and one on the rear end of the leaf spring, and the other with a double vibration isolation structure in which two rubber bushings are provided at the front end. There is.

Among these, leaf springs with heavy vibration isolation structure are mentioned above),
It has a structure as shown in Figure 6. In addition, the front end side of the leaf spring with the double vibration-proof structure is located between the upper bracket 15a fixed to the vehicle body and the centerpiece 4 of the first frame, as shown in FIG.
b, and two types of rubber bushings 5.5 are interposed between the spring bracket 15b and the centerpiece 4 and between the upper bracket 15a and the spring bracket 15b. this is,
Nissan Service Bulletin No. 204 allows a certain amount of longitudinal movement and absorbs longitudinal vibrations (harshness countermeasures) to prevent a rough ride and noise from entering the passenger compartment.
(Refer to pages 87 to 89 of the issue ``Introduction of the New Nissan Sedrick Gloria'' published in February 1946).

However, this not only increases the number of parts and complicates assembly, but also reduces the lateral stiffness and roll stiffness of the suspension system, impairing handling stability. Also,
- Another example of a heavy vibration isolation structure is disclosed in Japanese Patent Application Laid-Open No. 12323/1983.

This invention provides a leaf spring 3 as shown in FIG.
An axle fixing part 11 to which an axle nozzle is attached is provided in the center of the frame, and a cantilever type auxiliary leaf spring 12 is fixed to the fixing part 11 and extends rearward. The mass body 13 attached to the free end constitutes a drive shaft vibration prevention device 14, and when the automobile is accelerated while driving at low speed, the front side of the axle 9 is lifted by the reaction force of the drive torque. As shown, the free end 16 of the auxiliary leaf spring 12 separates from the leaf spring 12, and the free vibration length d1 becomes significantly larger than the contact length DI, making it possible to absorb relatively low-frequency vibrations. On the other hand, when driving at medium and high speeds, the axle fixing part 11
Since the reaction force exerted on the spring is relatively small, the contact length D' of the auxiliary leaf spring 12 becomes significantly larger than the free vibration length d'', as shown in FIG. 9B, and relatively high-frequency vibrations can be absorbed. This is how it was done.

Problems to be Solved by the Invention By the way, the vibration transmission characteristics of a leaf spring type suspension with heavy vibration isolation structure include bounce vibration that forms a peak on the low frequency side and bounce vibration that forms a peak on the high frequency side, as shown by the broken line in Figure 10. Bending vibration that forms a mountain occurs, and between the bounce resonance point, which is the bead point of both vibrations, and the bending resonance point, both bounce vibration and bending vibration overlap, and the vibration transmissibility increases as both vibrations influence each other. It shows a vibration transmission characteristic in which the value decreases.

On the other hand, in addition to vibrations from the road surface, vibrations from the drive system (powertrain system) are transmitted to the vehicle body via the leaf spring suspension. In the case of a rear stiffness spring type suspension, differential noise generated from a differential gear etc. is applied to the leaf spring via the axle and is excited.

Since this differential noise frequency range is often on the bounce vibration side, mass bodies (so-called mass dampers) are installed at appropriate locations on the leaf spring type suspension, as shown by the solid line in Figure 10, so that the differential noise frequency range is on the bounce vibration and bending side. C:, so that it is located in the valley of vibration, the position of the peak of bounce resonance is set from the def noise frequency range to the low circle store/fil
l 1m Zurao is doing one song Su2bo opening 1986-
The drive shaft vibration prevention device 14 of Publication No. 12323 is as described above, but the mass body 13 of the drive shaft vibration prevention device 14 has the 10th vibration prevention device as described above, as in the general single vibration prevention structure.
As shown in the vibration transfer characteristic diagram in the figure, it only shifts the bounce vibration to the lower frequency side so that the differential noise area is located between the bounce vibration and the bending vibration. I couldn't cancel it out.

An object of the present invention is to provide a leaf spring type suspension that not only shifts bounce vibration relative to the differential noise region, but also can actively cancel vibrations in the differential noise region.

Means for Solving the Problems The eye portions at both ends of the main leaf of the leaf spring are supported on the vehicle body via bushings, and at least one of the sub-leaves is formed to have a longer span than the main leaf, and both ends of the sub-leaf are formed to have a longer span than the main leaf. was made into a mass member at the free end.

The support point of the leaf spring relative to the vehicle body (both ends of the main leaf) is located inside the two nodes of the two-node mode bending vibration under the free support state of both ends of the leaf spring (both ends of the sub-leaf). Therefore, the vibration levels of the leaf spring's bounce vibration and bending vibration are canceled out at the support point. Therefore, transmission of vibration input applied to the center of gravity of the leaf spring to the vehicle body can be reduced.

Embodiment Next, an embodiment of the leaf spring type suspension of the present invention will be described with reference to FIGS. 1 to 5.

1 is the main leaf which is the first leaf, 2 is the subleaf which is the second leaf superimposed on the lower part of the main leaf L, 3 is a leaf spring consisting of the main leaf L and the subleaf 2, and the subleaf 2 is It is formed to have a longer span than the main leaf 1, and its both ends protrude outward from both ends of the main leaf 1, so that mass members 17 and 17 in a so-called freely supported state are protruded.

The leaf spring 3 connects the eyelet 4 at one end (face end) of the main leaf I to a bracket of the vehicle body (not shown) via a rubber bushing 5, and the eyelet 6 at the other end (rear end) of the leaf spring 3.
It is supported by the vehicle body by attaching it to a hanger bracket (not shown) on the vehicle body via a rubber bush 7 and a knot 8.

Since the leaf spring type spring/yeon of the embodiment has the above-mentioned configuration, if this is shown as a vibration model diagram, as shown in FIG. 2, the support point A1 of the leaf spring 3 by the rubber bush 5.7 is゜A, Kari-Maspring 3
This is a vibration model diagram in which the excitation force F is input to the center of gravity of the leaf spring 3, which is located inside both free ends of the leaf spring 3.

FIG. 3 shows the mode of bounce vibration of the leaf spring 3 caused by the bush 5°7 that occurs when the excitation force F is input to the leaf spring 3 while the leaf spring 3 is supported with both ends free. Figure 4 also shows the mode of bending vibration. In the leaf spring 3, bounce vibration due to vertical vertical vibration shown in FIG. 3 and bending vibration shown in FIG. 4 are transmitted to the vehicle body as individual or combined vibrations. In addition, Figure 5 shows the characteristics of the vibration transmissibility, and shows the + (plus) of the vibration transmissibility.
This indicates that vibration is amplified on the side, attenuated on the - (minus) side, and transmitted without being amplified or attenuated on the 1 side. Here, the position of Bush 5.7 (
The supporting points A,, A,) are connected to the two nodes N1. Nt
In a specific frequency range, for example, 300 to 500 Hz in the valley between the bounce resonance point and the bending resonance point in FIG. Reverse phase (+),
(-), the vibration levels of the bounce vibration and the bending vibration cancel each other out, and the vibration transmitted to the vehicle body by the excitation force F can be significantly reduced. In particular, support point AI is placed at a position where bounce vibration and bending vibration are at the same level and in opposite phases.

By setting A2, the transmission rate of vibration to the vehicle body can be made almost zero. In addition to the vibrations from the road surface, as mentioned above, vibrations are caused by differential noise, and this differential noise frequency (usually 400 to 500H2
) The differential noise frequency can be adjusted by adjusting the length of the sub-leaf that protrudes outward from both ends of the main leaf and the weight of the mass member so that the attenuation side (minus side) in Fig. It can be made to have anti-vibration performance in the range. In particular, the superposition of the bounce vibration mode and the bending vibration mode makes the vibration transmissibility negative, creating a frequency range that is an anti-resonance point (point [F] in Figure 5). The vibration level can be further reduced by matching the frequency at which anti-resonance occurs with the frequency at which the peak occurs.

In addition, in the embodiment shown in the drawings, both ends of the sub-leaf 2 are rounded to form a so-called eyeball, and this is shown as a mass member 17.17, but this is to increase the mass of the mass member 17.17. Alternatively, the mass member 17.17 may simply be one in which both ends of the sub-leaf 2 protrude outward from both ends of the main leaf 1.

Moreover, it goes without saying that a mass member 17.17 which is made of a separate member and has a large specific gravity may be attached.

Further, in this embodiment, the sub-leaf 2 is only the second leaf, but if the sub-leaf is composed of a plurality of leaves, such as the second, third, fourth...N leaves, for example, two It is sufficient that at least one of the sub-leaves 2 is formed to have a longer span than the main leaf J, such as the No. 1 leaf being formed to have a longer span than the main leaf L which is the No. 1 leaf.

Effects of the Invention As explained above, in the present invention, the eye portions at both ends of the main leaf of a leaf spring are supported by the vehicle body via bushings, and at least one of the sub-leaves is formed to have a longer span than the main leaf. Since it is a leaf spring type suspension characterized by having both ends protruding outward from both ends of the main leaf and being free ends, it has the following effects.

(1) By setting the support point of the bushing at a position where bounce vibration and bending vibration are at the same level and in opposite phases, bounce vibration and bending vibration are canceled out, and the transmission rate of vibration to the vehicle body is approximately reduced. Can be set to zero.

(2) The bounce resonance point and bending resonance point can be controlled by adjusting the length of the subleaf and the mass (weight) of the mass member, making it easy to tune the vibration characteristics of the leaf spring.

(3) By adjusting the length of the subleaf and the mass (weight) of the mass member, the distance between parts for bending vibration can be changed, so the degree of freedom in support and layout of bushes etc. can be expanded.

(4) The bushes are provided and supported by the car body at the eyelids at both ends of the main leaf, so there is no reduction in lateral stiffness or roll stiffness unlike with leaf spring suspensions with a double anti-vibration structure. .

(5) The vibration transmissibility becomes negative due to the superposition of the bounce vibration mode and the bending vibration mode, and a frequency range that becomes an anti-resonance point occurs, so this frequency range should be adjusted to match the vibration from the drive system, such as the differential noise frequency range. The vibration level can be reduced by adjusting the length of the subleaf and the mass of the mass member.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the leaf spring type suspension of the present invention, Fig. 2 is its vibration model diagram, Fig. 3 is a bounce vibration mode diagram, Fig. 4 is a bending vibration mode diagram, and Fig. 5 is a vibration transmissibility diagram. Characteristics diagram, Fig. 6 is a perspective view of a conventional leaf spring type suspension, Fig. 7 is a sectional view of a double vibration isolation structure, and Fig. 8 is a schematic illustration of the vibration isolation device disclosed in Japanese Patent Application Laid-open No. 12323/1983. Side view, FIG. 9(A) and FIG. 9(B)
is a partial side view showing its operating state, and FIG. 10 is its vibration transmission characteristic diagram. l...Main leaf, 2...Sub leaf, 3...
Leaf spring, 17...mass member. ＋ Shōkōkyō 1

Claims (1)

[Claims] (1) Eyes at both ends of the main leaf of the leaf spring are supported by the vehicle body via bushes, at least one of the sub-leaves is formed with a longer span than the main leaf, and both ends thereof are longer than both ends of the main leaf. A leaf spring type suspension that is characterized by a mass member that protrudes outward and has a free end.