VIBRATION DAMPING ASSEMBLIES

Abstract: A hydroelastic engine mount comprises a metal armature (10) which in use is bolted to the vehicle chassis. A hollow conically shaped damping member made of resilient elastomeric material (22) is moulded onto the armature (10) and supports a rigid metal fixture (26) which is bolted to the engine. A working chamber (24) is filled with hydraulic fluid and connected to a compensation chamber (40) by means of a conduit (42). Engine vibrations are partly damped by the resilient damping member (22) and also by the damping effect applied by the conduit (42) to the fluid passing oscillatingly through it between the two chambers (24, 40). The conduit (42) is integrally formed in the armature (10). The armature (10) also includes an integral extension (13) which supports abutments made of elastomeric material (e.g. 44, 56, 58) which act against the surfaces (e.g. 46) of the engine to limit its maximum movement. The damping material can be moulded onto the armature (10) at the same time as the resilient damping material (22) but can be of a different type.

Description: VTBRATTON DAMPTMΠ ABfiEMBTiTEfi The invention relates to vibration damping assemblies. Embodiments of the invention to be described in more detail below, by way of example only, are in the form of hydroelastic engine mounts for mounting and damping the vibrations of engines in motor vehicles. According to the invention, there is provided a vibration damping arrangement for damping relative vibrations between two rigid members, comprising a first rigid element for connection to one of the rigid members, a second rigid element for connection to the other rigid member, and resilient damping material interconnecting the two rigid elements for damping vibration between them, the second rigid element integrally supporting movement -limiting means for limiting the maximum relative movement between the rigid members. According to the invention, there is further provided a hydroelastic engine mount, comprising a rigid armature for connection to one of the engine and the vehicle body, a rigid fixing element for attachment to the other of the engine and the body, resilient damping material extending between the armature and the rigid fixing element for flexing in response to and for damping vibrations between them, a first chamber defined in part 2 by the resilient damping material, a second flexible-walled chamber, and a conduit interconnecting the two chambers whereby hydraulic fluid can pass through the conduit between the two chambers in response to flexing of the resilient material such that its movement through the conduit damps the vibrations, the conduit being integrally formed within the armature. Hydroelastic engine mounts embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a cross-section through one of the engine mounts; Figure 2 is a top plan view of the engine mount of Figure 1 ; Figure 3 is an underside view of the engine mount of Figures 1 and 2 but with some parts removed. As shown in Figure 1, the engine mount has a rigid metal armature 10 such as made from a light alloy or aluminium. The armature has a number of fixing holes 12 (see Figure 2 also) by means of which it can be rigidly secured to the body or chassis of the vehicle. On one side, the armature 10 has an integral extension 13 provided with preformed recesses 16,18,20. 3 During a moulding operation, elastomeric material is moulded onto the armature 10 to produce a conically shaped part 22 defining a hollow chamber 24. In addition, the moulding operation forms elastomeric material in the recesses 16,18 and 20 to form parts of an abutment portion 21 for restricting maximum movement of the engine in a manner to be described in more detail . By means of a bi-injection process, the elastomeric material forming the abutment portion 21 can be different from the material forming the conically shaped part 22, so that each part has appropriate characteristics . The conically shaped part 22 supports a rigid metal insert 26. The insert 26 carries a bolt 28 by means of which the engine mount can be rigidly attached to the engine . Part of the engine is shown diagrammatically at 29. As shown in Figure 1, the moulded elastomeric material extends over at least part of the inner and outer surfaces of the armature 10 as shown at 30 and 32. The chamber 24 is closed off by a dished metal plate 34. Below the metal plate 34 a flexible membrane 36 is supported and protected by a cover 38. A further chamber 40 is defined between the membrane 36 and the plate 34. 4 Chambers 24 and 40 are interconnected by a part -circular conduit 42. This is shown more clearly in Figure 3 where the cover 38, the membrane 36 and the plate 34 have been removed. The canal 42 extends from an end A to an end B. When the plate 34 is in position, the conduit 42 is closed, except for an opening at A which connects it with the upper or working chamber 24 and an opening at B which connects it with the lower or compensation chamber 40. As shown in Figure 1, the moulded material 32 covering the inner surface of the armature 10 ensures that the conduit 42 is sealingly closed, except at the openings A and B. In use, chambers 24 and 40 and conduit 42 are filled with a suitable liquid. The cover 38 allows access by the local atmosphere to the membrane 36. The membrane 36 is very flexible so that the pressure within the compensation chamber 40 is not effectively different from atmospheric pressure. In operation, various modes of vibration of the engine relative to the vehicle chassis or body may develop. In one mode, the mass of the engine will vibrate quite strongly in a vertical direction as the attitude of the vehicle changes because of the road profile. 5 In this mode, the vibrations of the engine are partially damped by the conically shaped part 22. In addition, however, the part 22 acts as a piston on the fluid within the working chamber 24, causing the liquid to be pumped to and fro between the working chamber 24 and the compensation chamber 40 through the conduit 42. Because the pressure in the compensation chamber 40 is maintained constant and substantially equal to atmospheric pressure, this chamber produces no resistance to liquid fluctuations. Damping is achieved by oscillation of the liquid mass in the conduit 42 which acts as a dynamic damper. Maximum damping is obtained at the resonant frequency which depends on the characteristics of the conduit 42. - The construction shown is advantageous in that the conduit 42 is formed integrally in the armature 10 itself instead of being a separate part. Not only does this significantly simplify manufacture and reduce manufacturing costs but it also enables the conduit 42 to be positioned around the outside of the widest end of the conically shaped part 22. Therefore, the conduit can have a greater length than it would have if it were made as a separate part. Its greater length means that the liquid mass in movement is correspondingly increased to produce a greater damping effect. At the idling speed of the engine, relatively low frequency and 6 low amplitude vibrations are produced. The vibrations are not sufficient to force the liquid through the conduit 42. Damping is thus carried out substantially only by the material of the conically shaped part 22. In order to provide further damping of vibrations caused by engine idling, it is possible to provide a further interconnection between the working and compensation chambers through an opening which is normally held closed by a disc-shaped valve capable of limited vibratory movement. When small -amplitude vibrations take place, such as in response to the idling speed of the engine, this valve is able to vibrate and reduces the pressure within the working chamber 24 to the atmospheric pressure in the compensation chamber 40. The effective stiffness of the engine mount is thus reduced and transmission of vibrations from the engine to the chassis is reduced . At higher engine speeds, the frequency of the vibrations is correspondingly increased. Again, the liquid is not able to pass between the chambers 24 and 40 by means of the conduit 42. The disc-shaped valve referred to above is no longer capable of following the vibrations and remains closed. Damping is achieved by means of the material of the conically shaped part 22. The foregoing explanation relates to normal damping of vibrations. However, under certain conditions, very large 7 amplitude movement of the engine can occur, and it is necessary to limit the extent of such movement. This limitation is carried out by means of the abutment portion 21 which is supported on the extension 13 of the armature 10 (see Figure 1) . When the engine mount is in position, the abutment portion 21 is located immediately adjacent specified abutment surfaces of the engine which effectively form a hollow "chamber" in which the abutment portion 21 is located with clearance. During the moulding operation, the elastomeric material becomes moulded onto the armature extension 13 to provide abutments acting along all three perpendicular axes. - Thus, as shown in the Figures, the moulding operation produces an abutment 44. Abutment 44 is normally spaced from the adjacent engine surface 46 by a clearance D. However, very substantial vibratory movements of the engine in the horizontal plane takes place, such as induced by very strong variations of engine torque, during gear changing or strong braking, are limited by abutments 48 and 50 which are formed by the elastomeric material moulded into the recess 16 (see Figure 1) . Abutments 48 and 50 are positioned adjacent surfaces 52 and 54 of the engine but spaced from them with clearance E. In response to large amplitude movements of the engine in the direction of the arrow F or the arrow G, the abutment 48 will come into limiting contact 8 with the surface 52 or the abutment 50 will come into such contact with the surface 54 depending on the direction of movement . Large amplitude movements of the engine in the perpendicular direction, but still in the horizontal plane, are limited by an abutment 44, which will come into contact with the engine surface 46 to limit undue movement. Excessive movement of the engine in the vertical direction, because of sudden changes in road profile, are limited by vertical abutments 56 and 58 (see Figure 1) . These abutments are mounted adjacent engine surfaces 60 and 62 respectively but normally spaced from them by clearance H. In the event of excessive vertical movement of the engine, one or other of these abutments 56,58 comes into contact with the relevant engine surface to limit the extent of movement. The extension 13 of the armature (see Figure 1) enables the abutments to be moulded directly onto the armature 10 at the same time as the conically shaped part 22. A separate operation to produce the abutments and to connect them suitably to the engine mount is thus avoided. It is thus relatively easy to adjust the shapes of the various abutments, by suitable changes to the moulding operation, and the stiffness of the abutments can be 9 changed by appropriately altering the injected material. In this way, therefore, the armature 10 integrates the functions of supporting the conically shaped part 22, defining the liquid conduit 42, and supporting the abutment 44, 48, 50, 56 and 58. The manufacturing process is thus simpler and less expensive.

Claims: 10 CLAIMS 1. A vibration damping arrangement for damping relative vibrations between two rigid members, comprising a first rigid element (28) for connection to one of the rigid members, a second rigid element (10) for connection to the other rigid member, and resilient damping material (22) interconnecting the two rigid elements (28,10) for damping vibration between them, characterised in that the second rigid element integrally supports movement-limiting means (21) for limiting the maximum relative movement between the rigid members. 2. An arrangement according to claim 1, characterised in that the movement limiting means comprises resilient abutment material (44,48,50) moulded onto the second rigid element (10). 3. An arrangement according to claim 2, characterised in that the resilient damping material (22) and the resilient abutment material (44,48,50) are moulded onto the second rigid element (10) during the same moulding process. 4. An arrangement according to claim 2 or 3 , characterised in that the two materials (22 ; 44 , 48 , 50) are different. 5. An arrangement according to any preceding claim, characterised in that the resilient damping material (22) defines 11 a first hollow chamber (24) , and by means defining a second hollow chamber (40), and a conduit (42) interconnecting the two chambers (24,40), the chambers (24,40) and the conduit (42) containing hydraulic fluid for damping the movement of the resilient material (22) in response to the said vibrations. 6. An arrangement according to claim 5, characterised in that vibrations at relatively low frequency and of relatively large amplitudes are at least partially damped by the resistance of the conduit (42) to oscillation of the hydraulic fluid therein between the two chambers (24,40) . 7. An arrangement according to claim 5 or 6, characterised in that the ambient pressure within the second chamber (40) is substantially atmospheric pressure. 8. An arrangement according to any one of claims 5 to 7 , characterised in that the conduit (42) is integrally formed in the second rigid element (10) . 9. A hydroelastic engine mount, comprising a rigid armature (10) for connection to one of the engine and the vehicle body, a rigid fixing element (28) for attachment to the other of the engine and the body, resilient damping material (22) extending between the armature (10) and the rigid fixing element (28) for 12 flexing in response to and for damping vibrations between them, a first chamber (24) defined in part by the resilient damping material (22) , a second flexible-walled chamber (40) , and a conduit (42) interconnecting the two chambers (24,40) whereby hydraulic fluid can pass through the conduit (42) between the two chambers (24,40) in response to flexing of the resilient material (22) such that its movement through the conduit (42) damps the vibrations, characterised in that the conduit (42) is integrally formed within the armature (10) . 10. An engine mount according to claim 9, characterised in that the resilient damping material (22) is moulded onto the armature (10) . 11. An engine mount according to claim 10, characterised in that the resilient damping material (22) integrally extends into so as to form a sealing layer in and for the conduit (42) . 12. An engine mount according to any one of claims 9 to 11, characterised in that the flexible wall (36) of the second chamber (40) is open to atmospheric pressure and is of such flexibility that the pressure within the second chamber (40) is substantially atmospheric pressure. 13. An engine mount according to any one of claims 9 to 12, 13 characterised in that the first chamber (24) is conically shaped and in that the conduit (42) at least partly surrounds the larger end of the first chamber (24) . 14. An engine mount according to any one of claims 9 to 13 , characterised in that the armature (10) carries an integral extension (13) supporting resilient abutment material (44,48,50) for limiting maximum movement of the engine relative to the vehicle body or chassis. 15. An engine mount according to claim 14, characterised in that the resilient abutment material (44,48,50) is moulded onto the integral extension of the armature (10) at the same time as the resilient damping material (22) is moulded onto the armature (10) . 16. An engine mount according to claim 15, characterised in that the resilient damping material (22) and the resilient abutment material (44,48,50) are different. 17. An engine mount according to any one of claims 9 to 16, characterised in that the outside of the resilient damping material (22) is conically shaped and in which the rigid fixing element (28) is mounted on the resilient material (22) at the peak of its conical shape.

Inventors: SOUYRI PHILIPPE, SOUYRI, PHILIPPE
Applicants: DRAFTEX IND LTD, DRAFTEX INDUSTRIES LIMITED
Application year: 1999
Main classification: F16F13
IPC codes: F16F13