GB2041487A

GB2041487A - Elastomeric mountings with friction damping of high amplitude movements

Info

Publication number: GB2041487A
Application number: GB7928882A
Authority: GB
Original assignee: Societa Applicazioni Gomma Antivibranti SAGA SpA
Current assignee: Societa Applicazioni Gomma Antivibranti SAGA SpA
Priority date: 1979-02-09
Filing date: 1979-08-20
Publication date: 1980-09-10
Also published as: IT1110772B; IT7920033A0; FR2448660B1; ES483521A1; GB2041487B; FR2448660A1; DE2937053A1

Abstract

A damping support for suspending a body on a support structure comprises a tubular mounting body 10 for fixing to the support structure, an attaching body 26 for fixing to the body, connected between them an annular elastomeric element 20. The attaching body 26 is provided with a shank 34 which supports a pair of transverse arresting plates 38, 40. The tubular mounting body 10 supports internally an intermediate plate 48. The intermediate plate 48 has a central passage 50 through which the shank 34 is slidable axially with play and a plurality of axially extending holes 52 in each of which a pin 54 is slidably received in a friction fit. If used to mount a vehicle engine, high frequency low amplitude movements of the engine are isolated by the elastomeric spring, but low frequency high amplitude movements from the suspension or the engine starting up are frictionally damped by movement of the pins. <IMAGE>

Description

SPECIFICATION Damping support for suspending an oscillating body on a support structure The invention relates to a damping support for suspending an oscillating body on a support structure, in particular for suspending an engine on a chassis of a motor vehicle.

Damping supports of the type referred to above make it possible to dissipate part of the energy of the oscillating body and consequently to damp down the vibrations of this body to a degree which is sufficient to prevent oscillations occuring having excessive magnitude as could otherwise exist for example, in the case where the frequency of vibration of the oscillating body is close to its natural frequency of vibration. In some applications it is desirable to obtain a high damping action when large amplitude oscillations of the oscillating body occur, and an extremely reduced damping action where oscillations of small amplitudes are present.In particular, in the case of the suspension of the engine on the chassis of a motor vehicle it is necessary to provide shock absorbing supports which are in a position to damp down effectively the, normally low frequency, oarge amplitude oscilla- tions of the engine when it is running at low speed and in the case where the vehicle is subject to sharp jolts caused by irregularities in road surface, whilst, on the other hand, when the engine is turning at a high speed it is necessary for the damping action of the supports to be reduced as much as possible so as to isolate the engine from the chassis and ensure smooth running conditions.

In accordance with the present invention a damping support for suspending a body on a support structure comprises a tubular mounting body for fixing to the support structure; an attaching body for fixing to the body, the attaching body being coaxial with the tubular mounting body and connected thereto by means of a annular elastomeric element, the radially outer surface of which is fixed to the tubular body and the radially inner surface of which is fixed to the attaching body; wherein the attaching body is provided with a shank which extends along the axis of the tubular mounting body and which supports a pair of transverse arresting plates which are axially spaced with respect to each other, the tubular mounting body supporting internally an intermediate plate which is interposed between the two arresting plates and which has an axial thickness which is less than the axial distance between the two arresting plates, and the intermediate plate having a central passage through which the shank of the attaching body is slidable axially with play and a plurality of axially extending holes in each of which a pin is slidably received in a friction fit, each pin having a length which is greater than the axial thickness of the intermediate plate and less than the distance between the two arresting plates.

With this arrangement a damping support is provided in which a shock absorber employing friction only comes into operation when the amplitude of the vibrations of the suspended body exceed a given value, and which is also particularly robust and reliable and has a high operating efficiency.

An example of a damping support constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is an axial cross-section through the damping support; Figure 2 is a part axial cross-section of a modification of the damping support shown in Fig. 1; and, Figure 3 is a plan view of Fig. 2.

The damping support shown in Fig. 1 comprises a tubular metal mounting body 10 having a peripheral annular flange 1 2 at one end which allows it to be fixed, using bolts 14 extending parallel to the axis of the body 10, to a portion 1 6 of the frame of a motor vehicle. The internal surface of the tubular mounting body 10 has, at the end remotre from the flange 12, an inclined annular portion 1 8 to which, in a known manner, part of the external surface of an annular element 20 is fixed. The element 20 is made from an elastomer material having extremely low internal damping action, or in other words a very low elastic hysteresis. The annular element 20 has substantially parallel, planar, outer surfaces 22, 24, and supports a metal attaching body 26 which is arranged coaxially with respect to the element.The attaching body 26 has a central, frusto-conical portion 28, the outer surface of which is moulded in a known manner to the internal surface of the annular element 20. The frusto-conical portion 28 joins up, at its outer end, to a cylindrical portion 30. An axial, screw-threaded hole 32 is provided inside the cylindrical portion 30 into which a correspondingly screw-threaded element (not shown) may be screwed, the screw-threaded element being rigidly fixed to a portion of, for example, the engine to be suspended. The axially inner end of the frustoconical portion 28 is connected to a cylindri- cal shank 34 which extends axially inside the tubular mounting body 10 and has an externally screw-threaded end portion 36.

Two transverse arresting plates 38, 40 are provided through which the cylindrical shank 34 passes centrally. The arresting plates 38, 40 are axially spaced with respect to each other by means of a sleeve 42 which is arranged coaxially with the shank 34. The plates 38, 40 are rigidly fixed in the axial sense with respect to the shank 34 by means of a nut 44 which is screwed onto the screwthreaded end portion 36 of the shank 34 in order to urge the plate 40, the sleeve 42 and the plate 38 towards the frusto-conical portion 28 of the attaching body 26.

A metal support plate is shown at 46 and this is inserted between the flange 1 2 and the portion 1 6 of the vehicle frame and carries in its centre an intermediate plate 48 which is interposed between the two arresting plates 38, 40 and which has an axial thickness which is less than the axial spacing between the arresting plates 38, 40. The intermediate plate 48 comprises an elastomer material having a hardness greater than 85 shore, for example a nitrile rubber. The intermediate plate 48 is welded to support 46 using a conventional moulding process.

The support plate 46 and the intermediate plate 48 have a central passage 50 in which the portion of the shank 34 carrying sleeve 42 is axially slidable with play, and a plurality of holes 52 extending axially through the plates 46, 48 and into each one of which a metal pin 54 is forced. The pins 54 are held by a friction fit but are able to slide axially against friction. The metal pins 54, which may have a circular or polygonal cross-section, are inserted under force in the corresponding holes 52 which in their turn may have a circular or polygonal cross-section, and have a length which is greater than the axial thickness of the intermediate plate 48 and less than the distance between the arresting plates 38, 40.

In the example shown in Fig. 1, the support plate 46 and the intermediate plate 48 each have a rectangular shape and the pins 54 are aligned parallel to the major sides of the plates. The pins 54 may furthermore be all of the same length or have differring lengths: in the latter case the pins which are located close to the central portion of intermediate plate 48 may, for example, have a length which is greater than that of the pins 54 which are located close to the peripheral portion of the plate 48 and pins 54 which lie between the central ones and the peripheral ones may have intermediate lengths.

In use, the damping support which is fixed in the manner described above to the frame 1 6 and to a portion of the engine of the motor vehicle, performs a high damping action when large amplitude oscillations of the engine occur, which for example are present when the motor is turning at low r.p.m. and also when the vehicle is subjected to sharp jolts caused by irregularities in the road surface, and perform an extremely reduced damping action when oscillations of small amplitude are present in the engine, corresponding, for example in the case where the engine is turning at high r.p.m.

In the case of large amplitude oscillations, as a result of axial displacement of the attach ing body 26 which is greater than the axial distance between the end of pins 54 and respective plates 38, 40, the pins 54 are alternatively thrust axially in the two senses by plates 38, 40 along the holes 52, and in this way give rise to a frictional reaction which produces a damping action which is able to provide a high degree of dissipation of the energy of the oscillating body. When the pins 54 have differing lengths it is possible to obtain a progressive frictional reaction and a consequent damping action which increases as the amplitude of the oscillations of the engine increase.It will be noted that possible variations in the loading on attaching body 26 or permanent yielding of annular element 20 do not alter the damping characteristics of the damping support, since these are automatically compensated for by a fresh axial positioning of the pins 54 with respect to the intermediate plate 48.

In the latter case referred to above, in other words when the amplitude of the oscillations is less than the actual distance between the ends of pins 54 and the corresponding plates 38, 40, the damping action of the damping support is restricted to the extremely reduced internal damping provided by the elastomer material forming the annular element 20.

Figs. 2 and 3 show a modification in the support plate 46 and the intermediate plate 48 of the damping support shown in Fig. 1.

In this variation, both the support plate, indicated by reference numeral 46a, and the intermediate plate indicated at 48a, have a circular shape and are provided centrally, as in the case described above, with a passage 50a, which provides for sliding with play of the shank 34. The holes, shown at 52a, in which the pins 54 are mounted so as to slide with friction, are arranged along the circumferences of two imaginary circles which are concentric with respect to the passage 50a.

The axes of the holes positioned on the same circumference are equidistantly spaced with respect to each other along the circumference.

In this case as well, the pins 54 may all be of the same length, or may have differing lengths. For example, pins 54 which make up the inner circle of the pins which make up the outer circle.

Claims

1. A damping support for suspending a body on a support structure, the support comprising a tubular mounting body for fixing to the support structure; an attaching body for fixing to the body, the attaching body being coxial with the tubular mounting body and connected thereto by means of annular elastomeric element, the radially outer surface of which is fixed to the tubular body and the radially inner surface of which is fixed to the attaching body; wherein the attaching body is provided with a shank which extends along the axis of the tubular mounting body and which supports a pair of transverse arresting plates which are axially spaced with respect to each other, the tubular mounting body supporting internally an intermediate plate which is interposed between the two arresting plates and which has an axial thickness which is less than the axial distance between the two arresting plates, and the intermediate plate having a central passage through which the shank of the attaching body is slidable axially with play and a plurality of axially extending holes in each of which a pin is slidably received in a friction fit, each pin having a length which is greater than the axial thickness of the intermediate plate and less than the distance between the two arresting plates.

2. A support according to claim 1, wherein the pins are made of a metallic material and are force-fitted in the axially extending holes in the intermediate plate.

3. A support according to claim 2, wherein the intermediate plate is made from an elastomeric material having a hardness within the range 85 to 90 shore.

4. A support according to claim 3, wherein the elastomeric material is nitrile rubber.

5. A support according to any one of claims 1 to 4, wherein the pins are all substantially the same length.

6. A support according to any one of claims 1 to 4, wherein at least some of the pins have different lengths.

7. A support according to claim 6, wherein the pins located in a central portion of the intermediate plate each have a length with is different from that of the pins located in a peripheral region of the intermediate plate, and pins lying between those in the central and the peripheral portions have intermediate lengths.

8. A support according to any one of the preceding claims, wherein the two arresting plates and the intermediate plate are each circular, the pins being positioned on circles concentric with the intermediate plate.

9. A support according to claim 1, substantially as described with reference to Fig.

1, or Fig. 1 as modified by Figs. 2 and 3 of the accompanying drawings.

10. A motor vehicle comprising a chassis and an engine, the engine being suspended on the chassis by at least one damping support constructed according to any of the preceding claims.