JPS62268717A - Link type suspension device - Google Patents

Abstract

PURPOSE:To reduce vibration of a vehicle body in front and rear directions, by connecting the vehicle body with an axle case through upper, lower links and providing bushed with respective connecting portions and setting a ratio of rigidity of the bushes on the upper and lower link sides at a specific value. CONSTITUTION:A rear axle case 2 integral with a differential gear case 1 has upper and lower portions with upper and lower brackets fixed thereto and the rear ends of a upper link 6 and a lower link 12 are axially supported by the brackets 3, 4 through bushes 5, 11 of an elastic material. The front ends of the respective links 6, 12 are swingingly supported by upper and lower brackets 10, 14 on the side of a vehicle body fixed to the vehicle body 9 through bushes 8, 13 which are identical with the bushes 5, 11. As a result, an accelerator case 2 is swingingly supported with respect to the vehicle body 9. The rigidity of the respective bushes 5, 8, 11, 13 are set in such a manner that a ratio of the rigidity KU of the bushes 5, 8 on the side of the upper link to the rigidity KL is approximately KU/KL<=1/4.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the improvement of a link type suspension device, and in particular, by specifying the stiffness of the bushings of each connecting part of the link, engine The present invention relates to a link type suspension device that reduces the amount of longitudinal movement of a differential and the longitudinal vibration of a vehicle body when torque changes in a stepwise manner.

[Conventional technology]

Examples of conventional link suspension devices include:
"Laurel 1984 Maintenance Manual".

Published by Nissan Motor Co., Ltd. on October 1, 1981, No. C-7
The one disclosed on page 2 is known.

This conventional device connects the vehicle body and the rear axle case with a total of five links: two upper links and two lower links placed in the longitudinal direction of the vehicle, and one Panhard rod placed in the lateral direction of the vehicle. However, a bushing made of an elastic material is interposed at each connecting portion at both ends of these five links.

[Problem that the invention seeks to solve]

However, in such a conventional link type suspension device, the rigidity of the bushing on the upper link side was slightly larger than that of the bushing on the lower link side, so the engine When the torque changes in a stepwise manner, the amount of movement of the differential in the longitudinal direction of the vehicle and the accompanying longitudinal vibration of the vehicle body become large, which poses a problem in that drivability is impaired.

This invention was made by focusing on such conventional problems, and the amount of longitudinal movement of the differential and the longitudinal movement of the vehicle body when the engine torque changes stepwise, such as when the accelerator is turned on and off. It is an object of the present invention to provide a link type suspension device that can reduce vibration.

[Means for solving problems]

Therefore, in the link type suspension device of the present invention, the vehicle body and the axle case are connected by an upper link and a lower link, and a bushing is interposed in each connecting portion. It is characterized in that the ratio of the stiffness kL of the bushing on the lower link side is approximately ≦1/4.

[Effect]

In a link type suspension device in which the vehicle body and the axle case are connected by an upper link and a lower link, and a bushing is interposed in each connecting part, the stiffness of the bushing on the upper link side and the stiffness of the bushing on the lower link side kLO ratio ku If /kL is large, the reaction force of the driving force and the windup torque around the axle of the vehicle body are added together in the same direction, so the amount of longitudinal movement of the differential and the longitudinal vibration of the vehicle body become large. However, when the rigidity ratio ku/kL is reduced, the directions of the reaction force of the driving force and the windup torque become opposite directions and cancel each other out, so that the amount of longitudinal movement of the differential and the longitudinal vibration of the vehicle body become smaller.

In the range of ratio ku/kL≦1/4, the amount of longitudinal movement of the differential and the degree of reduction in longitudinal vibration of the vehicle body become remarkable.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

First, to explain the configuration, in Fig. 1, differential case 1
A rear axle case 2 is integrally fixed to the rear axle case 2, and an axle-side upper bracket 3 and an axle-side lower bracket 4 are integrally fixed to the upper and lower parts of the rear axle case 2, respectively.

The upper end of the axle side upper bracket 3 sandwiches the rear end of the upper link 6 via an upper link rear bush 5 made of an elastic material, and these are tightened and connected by bolts 7, and the upper link 6 is connected to the axle side upper bracket. 3, the bolt 7 is used as a swing axis to swing freely.

The upper link 6 is arranged in the longitudinal direction of the vehicle,
Its front end is connected to the vehicle body side upper bracket 10 fixed to the vehicle body 9 via an upper link front bushing 8 and bolts 7, which are also made of an elastic material, and the upper link 6 is connected to the vehicle body side upper bracket 10 by the bolts 7. It can be freely swung using the oscillation axis.

On the other hand, the rear end of a lower link 12 is swingably connected to the lower end of the axle-side lower bracket 4 via a lower link rear bushing 11 made of an elastic material and a bolt 7. A lower link front bushing 13 is arranged in the front-rear direction and the front end thereof is also made of an elastic material.
It is swingably connected to a vehicle body side lower bracket 14 fixed to the vehicle body 9 via bolts 7 .

Then, the sum of the rigidity of the upper link rear bushing 5 and the rigidity of the upper link front bushing 8, that is, the rigidity of the upper link side bushing, is ku, and the lower link rear bushing 1 is
1 and the rigidity of the lower link front bushing 13, that is, the stiffness of the lower link side bushing is kL, each bushing is set at 5°8.11 so that the stiffness ratio of both is ku/kL≦1/4. A stiffness of .13 is set.

Next, to explain the operation, in the schematic diagram of the link type suspension device shown in FIG. If the distance from the swing axis of the lower bracket 14 on the vehicle body side is l, the displacement α of the elastic principal axis B of the differential (i.e., the center around the axle shaft) with respect to the differential center A is determined by the stiffness ratio ku/kt of the bushing. Change.

Figure 3 shows the change in displacement α when i/kL is changed in the stiffness ratio, and as is clear from the figure, ka/k
As L increases, the elastic principal axis B moves above the differential center A, and as ku/kL decreases, the elastic principal axis B moves below the differential center B.

When ku/kL≧1, the elastic principal axis B is above the differential center A, and in this case, as shown in Fig. 4, the direction of the reaction force FII of the driving force F and the windup torque W are the same. As a result, the amount of movement of the differential case 1 in the longitudinal direction of the vehicle increases, and the longitudinal vibration of the vehicle body increases.Therefore, the longitudinal vibration of the vehicle body becomes worse.

In the conventional device, the stiffness ratio ku/kL was set to be slightly larger than 1, so the amount of longitudinal movement of the differential and the longitudinal vibration of the vehicle body were large, impeding drivability.

On the other hand, when kn/kt≦1, the elastic principal axis B is below the differential center A, and in this case, as shown in FIG.
Since the reaction force F of the driving force F and the direction of the windup torque W are opposite to each other and they cancel each other out, the differential case 1
The amount of longitudinal movement of the vehicle and the longitudinal vibration of the vehicle body are reduced.

In particular, in the range of ku/kt≦1/4, the elastic principal axis B drops rapidly downward, and the degree of reduction in the longitudinal movement of the differential and the longitudinal vibration of the vehicle body becomes remarkable.

In this invention, the rigidity ratio is thus set to be smaller than 1, particularly to 1/4 or less.

Figure 6 shows the acceleration amplitude gp (unit gravitational acceleration G) of the vehicle body longitudinal vibration when suddenly accelerating during driving, and the stiffness ratio k
Actual measurements with various values of u/kt are shown. The vehicle body longitudinal vibration acceleration amplitude gp is obtained from the detection signal waveform of the acceleration of the vehicle body longitudinal vibration, as shown in FIG. As shown by diagonal lines in FIG. 6, it can be seen that the longitudinal vibration of the vehicle body is significantly reduced in the range of ku/kL≦1/4.

Further, FIG. 8 shows actual measurements of the amount of longitudinal movement of the differential case 1 when the vehicle suddenly accelerates while driving.

It can also be seen from the shaded area in this figure that the amount of longitudinal movement of the differential case 1 is reduced within the range of ku/kL≦1/4.

In addition, in the above-mentioned embodiment, a four-link suspension device was illustrated in which the upper link and the lower link were arranged in the longitudinal direction of the vehicle, but the present invention is not limited to this. Applicable to the upper link side bushings and lower link side bushings in a 5-link suspension device with a banal rond arrangement, or a 4-link suspension device with the upper link arranged diagonally so that it can also receive lateral loads. It is something that can be done.

[Effects of the Invention] As explained above, in the link type suspension device of the present invention, the stiffness of the bushings of each connecting portion of the upper link and the lower link is determined by the stiffness ku of the bushing on the upper link side and the stiffness kL of the bushing on the lower link side. The ratio of approximately ku/+,
≦1/4, it is possible to reduce the amount of longitudinal movement of the differential case and therefore the longitudinal vibration of the vehicle body when the engine torque changes stepwise, such as when the accelerator is turned on or off. Since the rigidity of the upper link side bushing is reduced, noise characteristics such as road noise can be improved.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the configuration of an embodiment of the link type suspension device of the present invention, Fig. 2 is a diagram schematically showing the link type suspension device, and Fig. 3 is the relationship between the rigidity ratio and the elastic principal axis displacement. FIG. 4 and FIG. 5 are diagrams showing the operation of the present invention. FIG. 6 is a diagram showing the actual measurement results of the relationship between the rigidity ratio and the longitudinal vibration acceleration amplitude of the vehicle body. FIG. 7 is a diagram showing the longitudinal vibration acceleration amplitude of the vehicle body. FIG. 8 is a diagram showing actual measurement results of the relationship between the stiffness ratio and the amount of longitudinal movement of the differential. 1... Differential case, 2... Rear axle case, 5
...Upper link rear bushing, 6...Upper link, 8...Upper link front bushing, 9...Vehicle body, 11...Lower link rear bushing, 12...Lower link, 13...・Lower link front bushing.

Claims (1)

[Claims] In a link type suspension device in which the vehicle body and the axle case are connected by an upper link and a lower link, and a bush is interposed in each connection part, the ratio of the stiffness k_U of the upper link side bush to the stiffness k_L of the lower link side bush is , approximately k_U/k_L≦1/4.