GB2037398A

GB2037398A - Vibration proof bushed mounting

Info

Publication number: GB2037398A
Application number: GB7938484A
Authority: GB
Original assignee: Sumitomo Riko Co Ltd; Nissan Motor Co Ltd
Current assignee: Sumitomo Riko Co Ltd; Nissan Motor Co Ltd
Priority date: 1978-11-09
Filing date: 1979-11-07
Publication date: 1980-07-09
Also published as: JPS5570636U; FR2441101A1; FR2441101B1; GB2037398B; DE2945323A1

Abstract

A bushed mounting comprises co-axially disposed inner and outer tubes 11, 12, a bush 13 of resilient material and of hollow cylindrical shape adapted to be disposed between the inner and outer tubes, and having an annular groove 14 formed in each axial end surface. <IMAGE>

Description

SPECIFICATION Vibration proof bushed mounting The present invention relates to a vibration proof bushed mounting, and more particularly to a vibration proof bush applicable to a suspension mechanism of an automobile.

This kind of a vibration proof bushing widely used in, for instance, rear suspension linkages, transverse linkages, and shock absorber mountings. A conventional bush is designed to improve the vibration proof effect, as shown in Fig. 1.

In the event that a load in the direction of P is applied perpendicularly to the axis of the bush, it is required that when the deformation of the bush due to the applied load is small, the bush has a low modulus of elasticity in order to lessen noise and vibration, while when the deformation of the bush exceeds a predetermined value, the bush has a higher modulus of elasticity so as not to generate secondary interference vibration in the linkage.

Accordingly, in a conventional bushed mounting, a rubber bush may be used, for example, which has a cross-section of dimpled shape, as shown in Fig. 1. In this way, the stress strain relationship when a load is applied in the orientation of arrow P is made non-linear.

The bushed mounting shown in Fig. 1 comprises a resilient member 3, such as of rubber, interposed between an internal tube 1 and a coaxial outer tube 2, a pair of dimpled portions 3a, 3a being formed in the resilient member 3 opposite each other in the direction of P, and a pair of metal stop means 4, 4 provided on the inner circumferential surface of the outer tube 2 so as to face the dimpled portions 3a, 3a respectively. Suppose that now a predetermined load in the direction of P is applied to the inner tube 1.

At the initial application of a load, the resilient member 3 first compresses until one of the dimpled portions comes in contact with the inner surface of the outer tube 2. During this time, only a portion of the resilient member is bearing any load so that the overall apparent modulus of elasticity of the resilient member is low.

On the other hand, after the dimpled portion has contacted the inner surface of the outer tube 2, the whole bush bears a load increase, so that the overall modulus of elasticity of the resilient member is now high. Unfortunately, however, when a load in the direction of arrow P or a rotation load is applied to the outer tube 2, fatigue is apt to occur around the edges 3b of the dimpled portions 3a of the bush tending to reduce the durability of the mounting. Since the deformation of the bush and the vibration proof effect depend on directional properties of the bush, extra work is involved in mounting the bush to ensure that it is correctly oriented. A metal stop means is also required within the mounting, thus increasing the cost. Another drawback is that the deformation characteristic changes, should the metal stop means become detached accidentally.

With the above in mind, an object of the present invention is to provide a vibration-proof bushed mounting which eliminates directionality in the vibration proof characteristics thereof.

Another object of the present invention is to provide a vibration proof bushed mounting which avoids the tendency of fatigue and cracking which a bush of irregular cross-section is prone to.

A further object of the present invention is to provide a vibration proof bushed mounting which reduces the number of parts, by eliminating the use of a metal stop means.

According to the present invention, there is provided a bushed mounting comprising co-axially disposed inner and outer tubes, a bush of resilient material and of hollow cylindrical shape adapted to be disposed between the inner and outer tubes, and having a circumferential groove formed in each axial end surface.

A vibration proof mounting according to the present invention will now be described in greater detail with reference to the accompanying drawings, in which: Fig. 1 as explained above, is a side view of a conventional rubber bush, partly cut away, Fig. 2 is a longitudinal section of a vibration proof bush according to the present invention, Fig. 3 is a side view of Fig. 2, and Fig. 4 is a graph illustrating a desired characteristic.

In all the drawings, the same reference numeral indicates the same or a corresponding element.

A preferred embodiment will now be described with reference to Figs. 2 and 3.

Fig. 2 is an elevational longitudinal section showing a vibration-proof, bushed mounting 10 according to the present invention, and Fig. 3 is a side view thereof. Reference numeral 11 denotes an inner tube, 12 an outer tube disposed coaxially outside the inner tube 1 and 13 a substantially cylindrical resilient bush interposed between the inner tube 11 and the outer tube 12.

The two elements to be linked by the mounting are fixed one to the inner tube 11 and one to the outer tube 12. If, for example, the vibration-proof bushed mounting 10 is used in a rear suspension linkage, a rod (not shown), serving as a pivotal axle, is inserted through the inner tube 11 and a suspension arm (not shown) is fixed to the outer tube 12.

As stated above, the resilient bush 1 3 is interposed between the inner tube 11 and the outer tube 12 wherein inner and outer circumferential surfaces thereof are welded to the inner tube 11 and the outer tube 12, respectively.

The bush 13 is vulcanized and annular grooves 14 are formed around each axial end of the bush 13.

In this embodiment, the depth I of each groove 1 4 is approximately one third of the overall length lo of the bush 1 3 at its outer portion, and the width H of the groove 14 is selected to obtain a predetermined ratio with respect to the total thickness I of the bush 1 3. It is preferable to provide the grooves 14 closer to the outer circumferential surface of the bush 1 3 in view of vibration proof characteristic. H/I is preferably between 1/4 and 1/2, and a/b is preferably between 1/5 and 2/3, where a and b are the thicknesses of the outer and inner portions respectively of the bush 13 separated by the groove.

In this embodiment, the grooves are of Ushaped cross-section with the above construction, when'a load is applied to the inner tube 11 relative to the outer tube 12, the bush 13 is deformed in the radial direction.

More particularly, since the bush 1 3 is provided with the annular grooves 14, when a load perpendicular to the axial direction is applied, the bush 1 3 is deformed in the radial direction until the portions 13' around the outer periphery of the grooves 14 come in contact with the portions 1 3b around the inner periphery of the grooves 14. During this first stage of deformation of the bush the axially outer portions of the bush 13 which surround the grooves 14 have substantially no effect on relative movement of the inner and outer tubes.The modulus of elasticity of the bush is effectively the same as that of a bush of the size of the axially centre portion of the bush 1 3 (at length 10-21) and is substantially small in comparison with that of solid bush without provision of the grooves.

On the other hand, when the portions 13' come into contact with and are further pressed against the portion 1 3h i.e. the amount of deformation is equal to or larger than the width H of the grooves 14, at the compression side of the bush there are no gaps formed by the grooves 14, so that the entire axial length of the bush 1 3 is resisting further movement. Accordingly the modulus of elasticity of the bush becomes effectively the same as that of a solid bush and is, compared with the previous value, relatively high.

As will be seen from Fig. 4 illustrating this characteristic, the gradient at the time of low load is different from that at the time of intermediate or high load, so that the overall stress-strain characteristic in non-linear.

Since this bush 1 3 has the same sectional structure with respect to any radial direction stress and strain are distributed uniformly over the radial directions with respect to a load applied in a direction perpendicular to the axis of the bush or an angular load about the axis. As shown in Fig. 2, the boundary region between the grooved and non-grooved portion is in the plane G perpendicular to the axis of the bush. Accordingly, there is little possibility that cracks will occur in this plane of the rubber bush, so that the deterioration of the bush cannot be expected.

Since the sectional construction of the bush is the same in all radial directions, the stress-strain relationship is independent of direction, so that mounting the bush is easier since it does not have to be oriented.

As will be clear from the foregoing description, a vibration proof rubber bush according to the present invention is constituted so that annular grooves are formed in the axial ends thereof.

Accordingly, the dependence on direction of the vibration proof characteristics of the bush is eliminated, thereby facilitating the mounting work, and preventing the breakage of the bush.

Further, the need for a metal stop means as used in a conventional vibration proof bushed mounting is obviated thus reducing the number of parts. While the present invention has been described in terms of a preferred embodiment, and with reference to the drawings, this is not to be taken as limitative of the present invention which is rather to be defined by the appended claims. In particular, various materials may be used for the bush 1 3, and the size and shape of the annular grooves may be varied to suit the particular application.

Claims

1. A bushed mounting including co-axially disposed cylindrical inner and outer tubes so as to form an annular space therebetween, and a bush of resilient material filling the space, wherein said bush having the same sized annular groove concentrically formed in each axial end surface.

2. A bush as defined in either claim 1 or 2 in which a groove cross-section is substantially Ushaped.

3. A bush as defined in claim 5 in which depth of a groove is substantially one third of the axial length of the bush.

4. A bush as claimed in claim 5 in which the ratio of the radial thickness of the portion of the bush circumferentially outside the groove to the radial thickness of the portion circumferentially inside the groove is between 1:5 and 2:3.

5. A bush as defined in claim 5 in which the ratio of the width of a section of a groove to the overall width of a section of the bush is in the range 1:4 to 1:2.

6. A bushed mounting substantially as herein described with reference to and as illustrated by Figs. 2, 3 and 4 of the accompanying drawings.