GB2211580A

GB2211580A - Rubber sleeve spring

Info

Publication number: GB2211580A
Application number: GB8824736A
Authority: GB
Inventors: Giacomo Sciortino
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1987-10-26
Filing date: 1988-10-21
Publication date: 1989-07-05
Anticipated expiration: 2008-10-21
Also published as: FR2622269A1; JPH01153833A; DE8714241U1; GB2211580B; DE3736162A1; GB8824736D0

Description

1 Rubber sleeve sprin 2211580 The invention relates to a rubber sleeve

spring for mounting an internal combustion engine, comprising an outer tube and an inner tube, which are supported on one another by an elastic body of elastomeric material, the elastic body containing two chambers which are located one behind the other in the direction of the vibrations introduced and are connected by an opening and filled with fluid, and at least one of the chambers being bounded in at least one subregion of its axial boundary by an axially displaceable front wall which forms a single piece with the elastic body.

Such a rubber sleeve spring is known from DE-OS 3,531,182. The isolation of engine-induced, high-frequency vibrations thereby achieved is not very satisfactory.

The present invention seeks to develop such a rubber sleeve spring further so that, while a good damping of lowfrequency vibrations of up to at most 30Hz is maintained, there is an improved isolation of high- frequency vibrations of at least 50Hz.

According to the present invention there is provided a rubber sleeve spring for mounting an internal combustion engine, comprising an outer tube and an inner tube, which are supported on one another by an elastic body of elastomeric material, the elastic body containing two chambers which are located one behind the other in the direction of the vibrations introduced and are connected by an opening and filled with fluid, and at least one of the chambers being bounded in at least one subregion of its axial boundary by an axially displaceable front wall which forms a single piece with the elastic body, wherein by virtue of a diaphragm-like design the front wall is shaped to be easily-moveable and is so dimensioned that upon the introduction of vibrations of a frequency of at least 50Hz

2 no significant change occurs in the pressure in the chambers.

Because of the design of the rubber sleeve spring of the invention the forces transferred to the foundation upon the introduction of the corresponding vibrations are balanced, and the vibrations are not perceptible here as such. They therefore also cannot make themselves felt disadvantageously in attached units, for example in the interior cabin area of a motor vehicle.

By contrast, vibrations of a lower frequency are accompanied by a comparatively large amplitude of the relative displacements of the inner tube with respect to - the outer tube..

The change in the volumes of the two chambers is correspondingly large, and, as early as the introduction of vibrations of a frequency of less than 30Hz and especially with the introduction of vibrations of less than 20Hz, it reaches an order of magnitude which it is no longer possible to counterbalance, with zero pressure, while avoiding a build-up of pressure in the chambers, by a simple displacement of their front wall. The consequence is an alternative displacement of fluid components from the chamber at higher pressure into the chamber at lower pressure through the opening connecting the two chambers, which is so shapgd that during this process there is a dispersion of energy and especially a good damping effect. Accordingly, the opening can be shaped as a throat, although it is more expedient in most cases for it to be shaped as a channel, in which the fluid- column contained experiences a resonance movement in the zone of the vibrations to be damped.

In the vibration-free state of the rubber sleeve spring under statically prescribed loading, the front wall is required to have a profile curved slightly outwards in 3 the axial direction in order to guarantee for it an appropriate mobility. Upon the introduction of high frequency vibrations, this profile can easily be filled out until it reaches a profile with a semicircular curvature, without this requiring a particular expenditure of energy. Consequently, the isolation of appropriate vi brations thereby achieved is excellent.

The external contour of the axially displaced part of the front wall can, for its part, have an arbitrary, for example circular, shape. However, with regard to the consideration of forming the front wall in one piece with the elastic body it has proved to be expedient to choose the contour to be as large as possible, avoiding sharpedged corners, and to give the front wall a kidney-shaped contour.

As far as the elastomeric parts are concerned, it is advantageous for the rubber sleeve spring according to the invention to have a specular shape in the axial direction. In this way, the forces introduced into the zone of the two faces of the rubber sleeve spring by virtue of the operational conditions are absorbed in the same way by the elastic parts fitted there, which as far as possible excludes operationally conditioned tilting phenomena of the inner tube with respect to the outer tube, and makes it simpler to mount the rubber sleeve spring in the proper way. Moreover, when the elastic parts of the rubber sleeve spring are designed to be identical on both sides, it is possible that certain simplifications regarding their ease of production will arise.

Generally speaking, the rubber sleeve spring is applied in cases where a certain static initial load is to be absorbed. Such an instance occurs, for example, in the mounting of an internal combustion engine, and in this case front walls designed to be as large as possible and having a kidney-shaped contour are located advantageously in the 4 region of the upper chamber. As a consequence of the static initial load, there arises in this case a certain flattening of the profile of the front walls, which by virtue of the manufacturing conditions project convexly outwards. However, these can be absorbed by the body of the material forming them, avoiding internal tensile stresses of the front walls, and this is decisively advantageous for the fatigue limit of the rubber sleeve spring. At the same time, the possibility arises of designing the axially moveable front wall to be as large as possible with respect to the total size of the rubber sleeve spring, and thereby of achieving a satisfactory isolation of high-frequency vibration.

The present -invention is further described below with reference to the accompanying drawings, in which Figure 1 shows a rubber sleeve spring according to the invention in an unloaded state in longitudinal section; Figure 2 shows the rubber sleeve spring according to Figure 1 in crosssection along the plane A-A of Figure 1; and Figure 3 shows a side view of the rubber sleeve spring shown in Figure 1.

The rubber sleeve spring shown in Figure 1 comprises an outer tube 1 and an inner tube 2, which are supported on one another by an elastic body 3 of elastomeric material. The elastic body 3 has two chambers 4, 5, which are located one behind the other in the direction of the vibrations introduced and are connected with one another by an opening 6 and filled with fluid, for example with a mixture of glycol and water.

In the axial direction, the upper chamber 4 is bounded at both ends by axially displaceable front walls 7, which are formed in a single piece with the elastic body 3. and by virtue of a diaphragm-like design are shaped to be easily moveable and are so dimensioned that, upon the introduction of vibrations of a frequency of at least 50Hz, no significant change occurs in the pressure in the chambers 4, 5.

If, by contrast, vibrations of a frequency of less than 50Hz, and, especially, of a frequency of less than 30Hz, are introduced into the rubber sleeve spring shown, the limit of elasticity of the front walls 7 is exceeded, and a differential pressure arises between the chambers 4 and 5. This leads to fluid components being pressed through the channel-like openings, and this in turn is associated with a large damping effect. In this way, the resonance sharpness of the engine mounted on the rubber sleeve spring is effectively suppressed.

In the cross-section of the rubber sleeve spring shown in Figure 2 it can be seen that the opening 6 connecting the two chambers 4, 5 is designed to be channel-like. In this connection, the cross-section is so dimensioned that upon the introduction of vibrations of a frequency of 5 to 20Hz the fluid column contained experiences a resonance movement. -As a result there is a good damping effect with respect to the introduction of appropriate vibrations.

In the side view of the previously described rubber sleeve spring shown in Figure 3 it canbe seen that the front wall 7 is located in the intermediate zone between the outer tube 1 and the inner tube 2, the contour being essentially kidney-shaped and the arrangement essentially concentric. The area enclosed by the contour line is therefore large, and dispenses with the need to use strengthening inserts in the front wall. The latter can be manufactured in a single piece with the elastic body 3, and therefore in an especially economical way.

6

Claims

1. A rubber sleeve spring for mounting an internal combustion engine, comprising an outer tube and an inner tube, which are supported on one another by an elastic body of-elastomeric material, the elastic body containing two chambers which are located one behind the other in the direction of the vibrations introduced and are connected by an opening and filled with fluid, and at least one of the chambers being bounded in at least one subregion of its axial boundary by an axially displaceable front wall which forms a single piece with the elastic body, wherein by virtue of a diaphragm-like design the front wall is shaped to be easily moveable and is so dimensioned that upon the - introduction of vibrations of a frequency of at least 50Hz 15 no significant change occurs in the pressure in the chambers.

2. A rubber sleeve spring according to claim 1, wherein in the vibrationfree state of the statically prescribed loading the front wall has a profile curved slightly outwards.

3. A rubber sleeve spring according to claim 1 or 2, wherein the front wall has a kidney-shaped contour.

4. A rubber sleeve spring substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

Published 1989 atThePatentOftice, State House, 66P7lriighHolburn,Londen WC1R4TP. Further copies maybe obtainedfrom The Patentomce. Sales Branch, St Maxy Cray. Orpington, Kent BRI5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1187