GB2068079A

GB2068079A - Fluid damped elastomeric mounting with high frequency movements accommodated by diaphragm

Info

Publication number: GB2068079A
Application number: GB8038934A
Authority: GB
Original assignee: Continental Gummi Werke AG
Current assignee: Continental AG
Priority date: 1979-12-13
Filing date: 1980-12-04
Publication date: 1981-08-05
Also published as: DE2950109A1; JPH025936B2; GB2068079B; FR2472116A1; FR2472116B3; JPS5694047A; DE2950109C2

Abstract

A resilient mounting, more especially for engines in automotive vehicles, having elastomeric spring elements 6, 7 defining a cavity filled at least partly with a damping liquid or composition, includes a flexible diaphragm 30 and associated therewith a rigid stop plate 3 having apertures 23 formed therein. High frequency low amplitude movements are accommodated by the diaphragm which can move freely until it abuts the plate. Low frequency high amplitude movements cause liquid to flow from one chamber to the other. The diaphragm and its stop plate may be located in a partition between the chambers. <IMAGE>

Description

SPECIFICATION Resilient mounting The present invention relates to resilient mountings, more especially for engines in automotive vehicles, having spring elements of rubber or rubber-like plastics material, inserted with adhesive bonding between rigid connecting members, a shockabsorbing or damping device in the shape of a cavity defined by an external connecting member and the spring elements and filled at least partly with a damping fluid or composition, and open through overflow bores in an internal connecting member and a flexible diaphragm spanning the cavity deformable under the pressure action of the damping fluid.

Engine mountings of this kind, which are also frequently made double-symmetrically and have two sets of spring elements located opposite one another and between two external connecting members, are known, for example from German Gebrauchsmuster No.7 616 276. The diaphragms are thus impacted on one side by the damping medium, mainly water or another liquid containing an antifreeze agent, and on the other side by an air cushion.

For absorbing and damping low frequency vibrations with relatively large amplitudes, known mounting structures have generally proved to be good. It has, however, been shown that relative to high frequency vibrations and only small vibration amplitudes they harden to an undesired extent; since in this case the high throttle or restrictive effect of the overflow bores results for the damping liquid such that the air cushions of the overall rubber spring are added thereto in parallel and thereby unfavourably influence the resilience of the mounting system in this restricted region.The object, moreover, of the invention is based on eliminating the influencing of the resilience of elastic or resilient engine mountings by damping in the region of the lesser vibration amplitudes typical to normal driving operation and to retain the desired high soft deflection substantially undampened without the otherwise unavoidable hardening phenomena.

According to the present invention there is provided a resilient mounting, more especially for engines in automotive vehicles having spring elements of rubber or rubber-like plastics material inserted with adhesive bonding between rigid stop plates, a damping device in the shape of a cavity defined by an external connecting member and the spring elements, filled at least partly with a damping liquid or composition, and open through overflow bores in an internal connecting member, and a flexible diaphragm spanning the cavity and deformable subject to the pressure action of the damping liquid, in which the diaphragm on its side remote from the damping liquid has associated therewith a rigid stop plate having apertures formed therein, which in the deformed state of the diaphragm hermetically seal it therefrom.

As stop plate an already existing external connecting member may be used. It is within the scope of the invention, in the case of the frequent embodiment in practice of the mounting as a double element having two sets of rubber springs located opposite each other between two connecting members, to associate a diaphragm each therewith. Then with every half vibration pressure is exerted in one direction on the damping fluid and consequently the occurrence of a negative pressure with vapor or vacuum foam formation diminishing the spring action is avoided. Subject to conditions of the double embodiment of the mounting, it is also possible in accordance with an alternative embodiment of the invention to provide only a single diaphragm and the latter is then located centrally between the two sets of rubber springs and is associated with a rigid stop plate on both sides thereof.

The invention provides, with surprisingly simple means, a reciprocating amplitude-dependent damping arrangement which does not have the disadvantages of known systems operating pneumatic or hydraulic flow-compression of the air in front of the narrow nozzles and hardening, vacuum formation over liquid during deflection, generating additional vibrations and noises by special flutter valves and the like.Since the diaphragms impacted on one side by the damping medium contrary to known engine mountings is not supported against an air cushion but, due to the apertures formed in the associated stop plates, is free to become deformed and able to yield to an increasing pressure drop initially unhindered up to stopping against the rigid plate, the damping effect is chiefly cancelled in the critical amplitude region and consequently the overall suspension system is not subjected to any interfering hardening. The vibration width embraced thereby depends upon the spacing of the diaphragms in the tension free state upon the stop plate and may therefore from the start be adjusted very accurately, for example, of the order of magnitude of one or a few millimetres.Only when the predetermined dimensional size has been exceeded and the diaphragm covers the whole surface of the stop plate does damping set in and then acts additionally to the suspension of the mounting. The elasticity of the diaphragms renders the transition to the greater dampened amplitudes vibration-free and does not permit any noises to occur. In consideration of the high tensions produced locally during abutment against the perforated stop plates it is advisable to provide the diaphragms with textile reinforcing plies.

The invention is not limited alone to the resilient mounting of driving units in automotive vehicles, but is applicable with advantage also in other fields of vibration and mounting technology, for example, for mounting fixed machine sets and motor units of all kinds and for similar purposes.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which Figure 1 schematically shows an angled axial section through an engine mounting of double symmetrical development having two diaphragms; and Figure 2 schematically shows an angled axial section through an engine mounting of identical development having only a single diaphragm mounted centrally.

The mounting shown in Figure 1 contains two cup-shaped or bell-shaped external metal connecting members 3,4 with their openings facing each other which members, by means of spacer sleeves 5 and connecting screws, not further shown, are mutually braced in a fixed spacing opposite one another and resiliently supported, via two hollow frusto-conically shaped rubber spring elements 6,7 against two similarly geometrically shaped, but smaller, internal metal connecting members 8, 9.

The internal connecting members 8, 9, with their edge faces abutting directly with one another form a unitary structural unit which, in turn, by means of lateral extensions 18, 19 and a yoke-shaped cranked supporting arm 20 is secured to the chassis, not shown, of an automotive vehicle. The engine, also not shown, is supported against the upper external connecting member 3, and to secure the bonding this external connecting member 3 is provided with a securing bolt 10. The rubber spring elements 6,7 are fabric bonded with the metal connecting members 3,4 and 8,9 and vulcanized together.The spring values of the elements 6,7 in the three different directions of vibration may be influenced by their configuration and by adjustment of the amounts of the ingredients of the rubber mixture and by the provision of recesses in the desired mannerforthe purpose intended.

The structure, mounting and method of operation of such engine mountings are known perse, and it is therefore believed that illustration of further details and detailed description not appertaining to the invention may be dispensed with.

The cavities 13, 14 formed between the inside surface of the external connecting members 3,4 and the trough-like indented surface of the spring elements 6,7 are filled with damping fluid comprising liquid or plastics materials having absorbing properties which, in the course of the suspension movements may overflow through relatively narrow, constantly open overflow bores 28, 29 into the displacement space 11 formed between the internal connecting members 8, 9. With minimal spacing, e.g. of the order of magnitude of 1 mm from the inside surface of the external connecting members, each of the cavities 13, 14 is spanned by a flexible diaphragm 30, 31, each diaphragm being reinforced with textile plies.In the expanded rest position illustrated in the drawings, the diaphragms 30, 31 over their whole flat effective surface are uniformly spaced from and parallel to the inside surface of the external connecting members 3,4 said members 3,4 being provided with a plurality of relatively wide apertures 23, 24.On the other hand, as soon as the internal connecting members 8,9 move upwardiy relative to the external connecting members 3,4 upon deflection together with the volumetric changes caused thereby, the static pressure of the damping fluid in the upper cavity 13 on the diaphragm 30 increases which, due to the lack of counter pressure on the opposite side, the diaphragm 30 can yield unhindered and bend until it abuts against the inside surface of the external connecting member 3. Only on reaching this state does the damping effect occur.At the other side the delayed pressure compensation under the lower diaphragm 31 may be readily adaptable to the restrictive action of the overflow bore 29 under the influence of the atmospheric pressure resting thereagainst on its opposite side, so that adverse occurrence of negative pressure in the lower cavity 14 is avoided right from the start.

With reversal of the movement cycle during deflection, the operations described above are also reversed.

The engine mounting shown in Figure 2 with regard to its essential components is built up in the same manner as the mounting described above, and accordingly the same reference numerals as used in Figure 1 also apply thereto. However, the difference between Figure 1 and Figure 2, is that in the arrangement of Figure 2 the internal connecting members 8,9 have apertures 28,29 formed therein for the unrestricted passage of the damping fluid, and in place of two diaphragms a single diaphragm 50 extends in symmetrical arrangement through the cavity 11 acting as the displacement space. The diaphragm 50 is framed on both sides, with slight spacing therefrom, by rigid stop plates 51,52 which, in turn, are provided with apertures 53, 54 formed therein. A narrow overflow bore 55 penetrating the assembled members 50, 51, 52 produces the restricted communication between the chamber sections 11 on both sides of the diaphragm 50 for the transfer of the damping liquid in course of the deflection movements.

The mode of operation of this alternative embodiment of the invention is as described for Figure 1.

Depending upon the direction of the spring stroke, the diaphragm 50 abuts alternately against one of the rigid stop plates 51,52 whereby the apertures 53, 54 formed therein permit it to bend in both directions unobstructed by air or liquid cushions.

Claims

1. A resilient mounting, more especially for engines in automotive vehicles having spring elements of rubber or rubber-like plastics material inserted with adhesive bonding between rigid stop plates, a damping device in the shape of a cavity defined by an external connecting member and the spring elements, filled at least partly with a damping liquid or composition, and open through overflow bores in an internal connecting member, and a flexible diaphragm spanning the cavity and deformable subject to the pressure action of the damping liquid, in which the diaphragm on its side remote from the damping liquid has associated therewith a rigid stop plate having apertures formed therein, which in the deformed state of the diaphragm hermetically seal it therefrom.

2. A mounting as claimed in claim 1, in which the stop plate is an external connecting member.

3. A mounting as claimed in claim 2, having two sets of spring elements located opposite to one another between two external connecting members, in which the two external connecting members each have a diaphragm associated therewith.

4. A mounting as claimed in claim 1, having two sets of spring elements located opposite to one another between two external connecting members in which one diaphragm is located centrally between the two sets of spring elements and a stop plate being associated on both sides thereof.

5. A mounting as claimed in claim 4, in which constantly open overflow bores penetrate the diaphragm and the two stop plates.

6. A mounting as claimed in any preceding claim, in which the diaphragms in the undeformed state are located with a slight spacing of the order of magnitude of one or a few millimetres in front of the stop plates.

7. A mounting as claimed in any preceding claim in which the diaphragms are provided with textile reinforcing plies.

8. A resilient mounting, substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.