GB2545721A

GB2545721A - Vibration damping component, assembly and method

Info

Publication number: GB2545721A
Application number: GB1522776.2A
Authority: GB
Inventors: David Fairbrother Michael; Denzil Pryce Timothy; Heslop Michael
Original assignee: ICON POLYMER Ltd
Current assignee: ICON POLYMER Ltd
Priority date: 2015-12-23
Filing date: 2015-12-23
Publication date: 2017-06-28
Also published as: GB201522776D0

Abstract

The invention relates to a vibration damping component 10 that comprises a first member 11, a second member 12, and an elastomeric material e.g. rubber 13 disposed between the first and second members such that the elastomeric material damps or attenuates vibrations of the first and/or second members. The thermal conductivity of the first member is higher than the thermal conductivity of the second member such that, during use of the vibration damping component, heat generated in the elastomeric material by the damping is conducted or dissipated away from the elastomeric material through the first member in preference to the second member. The second member 12 may comprise an insulating material or coating. The first component may be a shaft and the second component may be a housing. Alternatively, both components may be plates.

Description

Vibration Damping Component, Assembly and Method Field

The invention relates to a vibration damping component comprising an elastomeric material, for example mounts or bushings having a rubber material that attenuates vibrations. Further aspects of the invention relate to an assembly that includes a vibration damper, and to a method of damping vibrations.

Background

In some mechanical applications it is important to damp or isolate vibrations or other movements that maybe transferred between components. For example, a mount used to attach an engine to a frame may have a rubber material that damps vibratory motions to attenuate transmission of vibrations from the engine to the frame.

In such applications the kinetic energy of the vibrations is converted into thermal energy within the rubber. However, high temperatures can damage rubber materials and/or change their properties, resulting in a loss of performance or operational lifetime of the material. In particular, high temperatures can cause scission of the polymer chains within the rubber, leading to reduced damping performance (loss of stiffness) and a reduced operational lifetime. WO94/15113 discloses a tubular elastomer damper than includes rubber material to damp vibrations. The rubber material is arranged between a shaft and a cylindrical housing that surrounds both the shaft and the rubber material. The rubber material is attached to both the shaft and the housing. To try to prevent overheating of the rubber material it is arranged so that channels are formed that extend lengthwise along the shaft between sections of rubber material to increase the surface area of the rubber material and to permit air flow along the channels. The channels are intended to increase dissipation of the heat from the rubber material by convection into the air in the channels.

However, convection is an inefficient process of heat dissipation because air is an effective insulator, with a very low thermal conductivity. Further, as there is less rubber material in the damper, the damping performance is reduced or the size of the damper has to be increased to compensate.

Summary

The present invention seeks to provide a vibration damping component that effectively dissipates heat away from the elastomeric material.

In accordance with one aspect of the invention, there is provided a vibration damping component comprising: a first member, a second member, and an elastomeric material disposed between the first and second members to damp vibrations of the first and/or second members, wherein the thermal conductivity of the first member is higher than the thermal conductivity of the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.

The elastomeric material may be attached to the first member. For example, the elastomeric material may be attached by means of an adhesive or a fastener or chemical bond.

The second member maybe arranged adjacent to the elastomeric material such that an air gap is formed between the elastomeric material and the second member. Such an air gap will help to reduce heat transfer from the elastomeric material to the second member.

In one embodiment the second member comprises an insulative material.

Alternatively, the second member may comprise an insulative coating. In each case, heat transfer from the elastomeric material to the second member is reduced.

The thermal conductivity of the first member may be at least 10 watts per metre Kelvin when measured at 25 degrees Celsius, preferably at least 15 watts per metre Kelvin when measured at 25 degrees Celsius, more preferably at least 40 watts per metre Kelvin when measured at 25 degrees Celsius.

The thermal conductivity of the second member may be less than 1.0 watt per metre Kelvin when measured at 25 degrees Celsius, preferably less than 0.5 watts per metre Kelvin when measured at 25 degrees Celsius, more preferably less than 0.2 watts per metre Kelvin when measured at 25 degrees Celsius.

The ratio of the thermal conductivity of the first member to the thermal conductivity of the second member may be at least 10:1, preferably at least 30:1, more preferably at least 50:1, more preferably at least 100:1.

The ratio of the thermal conductivity of the first member to the thermal conductivity of the second member may be between 100:1 and 200:1.

The elastomeric material may comprise rubber.

In some embodiments, the first component comprises a shaft that is at least partially surrounded by the elastomeric material, and the second component comprises a housing that surrounds the shaft and the elastomeric material.

In these embodiments, the housing may comprise an insulative material disposed against the elastomeric material and a sheath that surrounds the insulative material of the housing.

The sheath maybe arranged such that an air gap is formed between the insulative material and the sheath.

In other embodiments, the second component comprises a shaft that is at least partially surrounded by the elastomeric material, and the first component comprises a housing that surrounds the shaft and the elastomeric material.

The shaft of any embodiment may comprise a partially spherical portion around which the elastomeric material is disposed.

In other embodiments, the first member comprises a first plate and the second member comprises a second plate, and wherein the elastomeric material is disposed between the plates.

In these embodiments, an intermediate plate may be disposed between the first and second plates and the elastomeric material may be disposed on both sides of the intermediate plate, and wherein the intermediate plate comprises a conductive material.

In some examples, the first and second plates are substantially planar. In other examples, at least one of the first and second plates is conically shaped.

In any example, the elastomeric material may be conically shaped.

In further embodiments, the first and second members are each U-shaped brackets arranged such that arms of the first and second members overlap, and wherein the elastomeric material is disposed between the arms of the first and second members.

In further embodiments, one of the first and second members is a bracket and the other of the first and second members is a block adapted to be received within the bracket with the elastomeric material disposed therebetween.

According to a further aspect of the invention, there is provided an assembly comprising a first member, a second member, and an elastomeric material disposed between the first and second members to damp vibrations of the first and/or second members, wherein the thermal conductivity of the first member is higher than the thermal conductivity of the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.

The assembly may comprise first and second components, the first component comprising the first member and the elastomeric material and the second component comprises the second member.

The first member may be attached to the elastomeric material, for example, by means of an adhesive or a fastener or chemical bond.

According to a further aspect of the invention, there is provided a method of damping vibrations comprising arranging a first member, a second member, and an elastomeric material such that the elastomeric material is disposed between the first and second members and damps vibrations of the first and/or second members, and wherein the method includes providing the first member with a higher thermal conductivity than the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.

In some examples, the step of providing the first member with a higher thermal conductivity than the second member comprises selecting materials such that the material of the first member has a higher thermal conductivity than the material of the second member.

In other examples, the step of providing the first member with a higher thermal conductivity than the second member comprises insulating the second member from the elastomeric material.

The method may further comprise attaching the elastomeric material to the first member. The first member may be attached to the elastomeric material, for example, by means of an adhesive or a fastener or by chemical bonding.

Brief Description of the Drawings

Embodiments of the invention will now be described, byway of example only, with reference to the accompanying drawings, in which: FIG. l shows a perspective view of a vibration damping bushing; FIG. 2 shows a cross-sectional view of the vibration damping bushing of FIG. 1; FIG. 3 shows a perspective view of another vibration damping bushing; FIG. 4 shows a cross-sectional view of the vibration damping bushing of FIG. 3; FIG. 5 shows a perspective view of a vibration damping machine mount; FIG. 6 shows a cross-sectional view of the vibration damping machine mount of FIG. 5; FIG. 7 shows a perspective view of another vibration damping machine mount; FIG. 8 shows a cross-sectional view of the vibration damping machine mount of FIG. 7; FIG. 9 shows a perspective view of a vibration damping sandwich mount; and, FIG. 10 shows a cross-sectional view of the vibration damping sandwich mount of FIG. 9·

Detailed Description

The vibration damping bushing 10 of FIG. 1 and FIG. 2 has a shaft 11, a housing 12, and an elastomeric material 13 disposed between the shaft 11 and the housing 12.

In this example the shaft 11 has a partially spherical enlarged portion 14 around which the elastomeric material 13 is disposed, and the elastomeric material 13 is a rubber material. However, it will be appreciated that the shaft 11 may have a differently shaped enlarged portion, or no enlarged portion at all, depending on the particular application of the vibration damping bushing 10.

Each of the shaft 11 and the housing 12 comprises means for attaching them to further components.

For example, as shown in FIG. 1 and FIG. 2, the shaft 11 comprises mounting holes 15 that allow the shaft 11 to be bolted or otherwise attached to a further component. Optionally, the mounting holes 15 may be threaded to receive a bolt or screw. Alternatively, the shaft 11 may be adapted to be received in a bore of a further component where it can be secured by a clamp, plate, circlip, retaining pin or any other suitable means of attachment. In another example, the shaft 11 is an interference fit within the bore of another component.

Moreover, in this example the housing 12 comprises an outer surface adapted to be received in a bore of a further component where it can be secured by a clamp, plate, circlip or any other suitable means of attachment. In another example, the housing 12 may be an interference fit within the bore of the further component. The housing 12 may comprise one or more protruding parts that provide the means for attaching the housing to a further component, for example a mounting hole, threaded hole, or bracket.

The function of the vibration damping bushing is to attenuate transmission of vibrations. For example, if the housing 12 were attached to an engine and the shaft 11 to a frame, then the function of the vibration damping bushing is to reduce the magnitude of vibrations transferred from the engine to the frame, i.e. to damp the vibrations.

In use, one or both of the shaft 11 and housing 12 is caused to vibrate by the component to which they are attached. These vibrations cause compression and extension of the elastomeric material 13, which damps (i.e. attenuates) the vibrations. The energy of the vibrations is at least partially converted into thermal energy within the elastomeric material 13, and thus the magnitude of the transmitted vibrations is reduced.

It is desirable to maintain an optimal temperature in the elastomeric material 13 by ensuring that the thermal energy is effectively dissipated from the elastomeric material 13. Optimal temperature helps to avoid thermal degradation of the elastomeric material 13, which can reduce the performance and operational lifetime of the elastomeric material 13.

Thermal energy can be dissipated from the elastomeric material 13 via radiation, convection and conduction. However, opportunities for convective dissipation are often limited by the application (enclosed spaces, no air flow) and convection is not an efficient mechanism for heat dissipation because of the insulative properties of air. Furthermore, radiation can only dissipate a limited amount of thermal energy. Therefore, conduction of thermal energy away from the elastomeric material 13 is the most significant form of heat dissipation in most vibration damping applications.

In the example vibration damping bushing of FIG. 1 and FIG. 2, there are two conductive routes from the elastomeric material 13 along which the thermal energy can be dissipated: 1. from the elastomeric material 13, through the shaft 11, into any further component to which the shaft 11 is attached, and onwards; and 2. from the elastomeric material 13, through the housing 12, into any further component to which the housing 12 is attached, and onwards.

It has been found that if the one of the conductive routes were significantly less efficient than the other conductive route then the temperature of the component (i.e. the shaft 11 or the housing 12) in the less conductive route would increase. As this component is immediately next to the elastomeric material 13 it will reduce the effectiveness of heat dissipation from the elastomeric material 13 and result in a higher temperature in the elastomeric material 13. Such a higher temperature is not optimal for the damping performance of the elastomeric material 13.

In one example, the conductive route via the housing 12 is significantly less efficient than the conductive route via the shaft 11 for any of a variety of reasons. For example, if the housing 12 were loosely mounted to the further component, thereby providing air gaps in the route, or if the further component were made from a material with low conductivity, for example a fibre reinforced polymer material. Additionally, if the housing 12 were mounted to a component having a low mass or low exposed surface area then heat dissipation via this component is also inefficient.

It has surprisingly been found that insulating the housing 12 from the elastomeric material to close off the less efficient conductive route results in the housing 12 remaining at a normal or only slightly increased temperature, and also the operating temperature of the elastomeric material 13 is reduced. In this case, heat is dissipated from the elastomeric material 13 via conduction through the shaft 11, which in this example is a more efficient conductive route. Therefore, the temperature increase of the housing 12 is reduced, resulting in an overall lower temperature in the elastomeric material 13.

To achieve this, in a first embodiment of the vibration damping bushing 10 of FIG. 1 and FIG. 2, the shaft 11 is made from a material having a higher thermal conductivity than the housing 12. For example, the shaft 11 maybe made from a conductive material and the housing 12 maybe made from an insulative material.

Therefore, as the elastomeric material 13 heats up during use the thermal energy will be dissipated primarily via conduction through the shaft 11, and significantly less thermal energy will be dissipated via conduction through the housing 12, resulting in a lower temperature in the elastomeric material 13.

In another embodiment of the vibration damping bushing 10 of FIG. 1 and FIG. 2, the housing 12 may be made from a material having a higher conductivity than the shaft 11. This would be appropriate if the conductive route via the housing 12 were more efficient than the conductive path via the shaft 11. This may occur, for example, if the shaft 11 were loosely mounted to the further component, thereby providing air gaps in the route, or if the further component were made from a material with low conductivity, for example a fibre reinforced polymer material.

The choice of which of the shaft 11 and the housing 12 to make from more or less conductive materials depends on the further components to which they are attached, and the type of connection used to attach them to the further components.

Generally, a close fitting connection (e.g. an interference fit) with a component made of a highly conductive material will result in efficient conductive transfer, whereas a loose fitting connection to a material having low thermal conductivity will provide an inefficient conductive transfer and thus the temperature of that component may increase during use, as explained above. Furthermore, any kind of air gap or material having low thermal conductivity in the conductive path will result in decreased conductive efficiency. Such an air gap may not be apparent when the vibration damping component 10 is in a natural, rest position, but may appear during use of the component as the components move relative to each other and the vibrations are absorbed by deforming the elastomeric material 13.

In some embodiments, the shaft 11 and housing 12 may be made from different materials, one having a higher thermal conductivity than the other.

In other embodiments, such as that illustrated in FIG. 1 and FIG. 2, the vibration damping bushing 10 may have an insulative layer 16a and 16b disposed between the elastomeric material 13 and one of the shaft 11 and housing 12, to prevent or severely reduce conduction to one of the shaft 11 and housing 12.

As shown in FIG. 2, in one embodiment where the conductive route via the shaft 11 is the more efficient and therefore desirable conductive route, the housing 12 comprises two insulative half-cups 16a, 16b and a sheath 17. The two insulative half-cups 16a, 16b are positioned against the elastomeric material 13 and separate the elastomeric material 13 from the sheath 17 that surrounds the half-cups 16a, 16b and provides the housing 12 of the vibration damping bushing 10. In this example, the insulative halfcups 16a, 16b reduce heat conduction from the elastomeric material 13 to the sheath 17, which would otherwise result in the temperature of the half-cups 16a, 16b and/or sheath 17 increasing during use. In this way, heat is effectively conducted away from the elastomeric material 13 via the shaft 11.

Moreover, as the half-cups 16a, 16b are made from an insulative material they will not themselves be significantly heated by the elastomeric material 13.

Providing the insulative layer as two half-cups 16a, 16b allows the half-cups 16a, 16b to move relative to one another during use, as the elastomeric material 13 is deformed. This helps to insulate the elastomeric material 13 from the sheath 17, as there will be less contact between the components.

In other examples, where the conductive route via the housing 12 is more efficient than the conductive route via the shaft 11, an insulative liner may be disposed between the shaft 11 and the elastomeric material 13 to reduce heat conduction from the elastomeric material 13 to the shaft 11 and thereby reduce the operating temperature of the elastomeric material 13.

In each of these embodiments the elastomeric material 13 may be attached to whichever of the shaft 11 or housing 12 has the greater thermal conductivity, rather than just being positioned adjacent to it. In this way, air gaps between the two are avoided, which provides for greater thermal conduction across the boundary between the two components.

Conversely, the elastomeric material 13 may not be adhered to the less thermally conductive component, so that air gaps between the elastomeric material 13 and the less thermally conductive component further reduce conduction along that route.

In some examples, the component adjacent to the elastomeric material 13 on the less thermally conductive route may be provided with a relief surface that only contacts the elastomeric material 13 in some places, or a spacer to separate them providing air gaps in other places. This further reduces the thermal conductivity between the two components.

In tests of the vibration damping bushing of FIG. 1 and FIG. 2 it has been observed that the operating temperature of the rubber material 13 is significantly reduced compared to a similar vibration damping bushing that does not include the insulative half-cups 16a, 16b and is subjected to the same vibrations. That is, when the thermal conductivity through the shaft 11 is higher than the thermal conductivity through the housing 12, the operating temperature of the rubber material 13 is reduced. This is because the housing 12 is insulated from the rubber material 13 and so the temperature of the housing 12 cannot increase greatly.

The particular operating temperature of the rubber material depends on a number of variables, such as the amplitude, frequency and mode of vibrations, as well as the mass and arrangement of the rubber material and other components of the vibration damper, and the composition of the rubber material.

It will be appreciated that the invention may be applied to other kinds of vibration damping components that have an elastomeric material, examples of which are described hereinafter.

In each of these examples, the vibration damping component has a first member, a second member, and an elastomeric material disposed between the first and second members. In the examples of FIG. 1 and FIG. 2 the first and second members are the shaft 11 and housing 12, and, as previously explained, one of these has a higher thermal conductivity than the other so that, during use, heat generated in the elastomeric material 13 by the damping is conducted away from the elastomeric material 13 through the member having a higher thermal conductivity, resulting in a lower operating temperature in the elastomeric material 13.

The vibration damping bushing 20 of FIG. 3 and FIG. 4 has a housing 22, an inner race 21, and an elastomeric material 23 disposed between the housing 22 and inner race 21. In this example, the inner race 21 and housing 22 are also referred to as the first and second members.

In this example, the housing 22 is similar to that of the embodiment of FIGS. 1 and 2, but the vibration damping bushing 20 has a cylindrical inner race 21 instead of a shaft. The inner race 21 has a bore 24 to receive a shaft or pin for attaching the inner race 21 to a further component. The inner race 21 may optionally have a partly spherical portion about which the elastomeric material 23 is disposed - similar to the shaft 21 of the example of FIG. 1 and FIG. 2.

In a first example, the inner race 1 has a higher thermal conductivity than the housing 22, and in a second example the housing 22 has a higher thermal conductivity than the inner race 21. The selection of which member 21, 22 has a higher thermal conductivity depends on the same factors as previously discussed with reference to the examples of FIG. 1 and FIG. 2 - i.e. the further components to which they are attached, and the type of connection used to attached them to the further components. The thermal conductivities of the housing 22 and inner race 21 should be selected such that heat is conducted away from the elastomeric material 23 along the more favourable conductive route, and prevented from being conducted along the least favourable conductive route.

This will prevent any of the temperature of the members 21, 22 increasing, which would increase the operating temperature of the elastomeric material 23.

The thermal conductivity of each member 21, 22 may be achieved by selecting materials based on their thermal conductivity. For example, one member maybe made from a material having a high thermal conductivity, and the other member may be made from a material having a low thermal conductivity.

Alternatively, one of the members 21, 22 may comprise an insulative material disposed between it and the elastomeric material 23 to reduce thermal conduction into that member. In the example of FIGS. 3 and 4, either the inner surface of the housing 22 or the outer surface of the inner race 21 maybe provided with a liner or covering made from an insulative material that separates that member 21, 22 from the elastomeric material 23, thereby giving that member 21, 22 an overall lower thermal conductivity.

The elastomeric material 23 can be adhered or otherwise attached to both the inner race 21 and the housing 22, to hold the vibration damping bushing 20 together. Alternatively, if such an adhesive is not required to hold the vibration damping bushing 20 together, then the elastomeric material 23 may be adhered to only one of the housing 22 or the inner race 21, whichever lies on the preferred route for thermal conduction (i.e. whichever has the higher thermal conductivity). An air gap maybe provided between the other member (of the inner race 21 and housing 22) to reduce thermal conduction through that member 21,22. The air gap maybe provided by shaping that member 21,22 or the elastomeric material 23 such that at least a part of the elastomeric material 23 is spaced from the member 21, 22. Such an air gap would provide effective insulation against heat transfer from the elastomeric material 23 to the member 21, 22.

The vibration damping mount 30 of FIG. 5 and FIG. 6 has a first part 32, a second part 31, and an elastomeric material 33 disposed between the first and second parts 32,31.

In this example, the first and second parts 32,31 are also referred to as the first and second members.

In this example, the first and second parts 32,31 are each conical or dish-shaped, with the elastomeric material 33 disposed therebetween. The shape of the elastomeric material 33 is such that the vibration damping mount 30 can damp vibrations in any direction.

In this example, the first part 32 has a threaded mounting hole 34 for attaching the first part 32 to a further component, but it will be appreciated that the first part 32 may be provided with other means for attaching the first part 32 to a further component, for example an unthreaded hole, a protrusion, clamp, or mounting bracket. Similarly, the second part 31 has a series of mounting holes 35 for attaching the second part 31 to a further component, but it will be appreciated that the second part 31 maybe provided with other means for attaching the second part 31 to a further component, for example protrusions, clamps, or mounting brackets.

In a first example, the first part 32 has a higher thermal conductivity than the second part 31, and in a second example the second part 31 has a higher thermal conductivity than the first part 32. The selection of which member has a higher thermal conductivity depends on the same factors as previously discussed with reference to the examples of FIG. 1 and FIG. 2 - i.e. the further components to which they are attached, and the type of connection used to attached them to the further components. The thermal conductivities of the first and second parts 32,31 should be selected such that heat is conducted away from the elastomeric material 33 along the more favourable conductive route, and prevented from being conducted along the least favourable conductive route. This will prevent the temperature of the members 31,32 increasing, which would increase the operating temperature of the elastomeric material 33.

The thermal conductivity of each member 31,32 maybe achieved by selecting materials based on their thermal conductivity. For example, one member may be made from a material having a high thermal conductivity, and the other member may be made from a material having a low thermal conductivity.

Alternatively, one of the members 31,32 may comprise an insulative material disposed between it and the elastomeric material 33 to reduce thermal conduction into that member. In the example of FIGS. 5 and 6, the inner surface of either the first part 32 or the second part 31 maybe provided with a liner or covering made from an insulative material that separates that member 32,31 from the elastomeric material 33, thereby giving that member an overall lower thermal conductivity.

The elastomeric material 33 can be adhered or otherwise attached to both the first and second parts 32, 31, to hold the vibration damping mount 30 together. Alternatively, if such an adhesive is not required to hold the vibration damping mount together 30, then the elastomeric material 33 maybe adhered to only one of the first or second parts 32, 31, whichever lies on the preferred route for thermal conduction (i.e. whichever has the higher thermal conductivity). An air gap maybe provided between the other member (of the first and second parts 32,31) to reduce thermal conduction through that member. The air gap maybe provided by shaping that member or the elastomeric material 33 such that at least a part of the elastomeric material 33 is spaced from the member 32, 31, or by providing a spacer in between. Such an air gap would provide effective insulation against heat transfer from the elastomeric material 33 to the member 32, 31.

The vibration damping mount 40 of FIGS. 7 and 8 has a first part 41, a second part 42, and an elastomeric material 43 disposed between the first and second parts 41,42. In this example, the first and second parts 41,42 are also referred to as the first and second members.

In this example, the elastomeric material 43 forms a hollow body, with the first and second parts 41,42 disposed at opposite ends of the elastomeric material 43. The elastomeric material 43 is shaped such that it can deform in any direction and so provide damping of any form of vibration. In particular, the elastomeric material 43 may have a cylindrical or conical shape.

In this example, the first part 41 has a threaded mounting hole 44 for attaching the first part 41 to a further component, but it will be appreciated that the first part 41 may be provided with other means for attaching the first part 41 to a further component, for example an unthreaded mounting hole, a protrusion, clamp or bracket. Similarly, the second part 42 has a flange 45 with a series of mounting holes 46 for attaching the second part 42 to a further component, but it will be appreciated that the second part 42 or the flange 45 maybe provided with other means for attaching the second part 42 to a further component, for example protrusions, clamps or brackets.

In a first example, the first part 41 has a higher thermal conductivity than the second part 42, and in a second example the second part 42 has a higher thermal conductivity than the first part 41. The selection of which member 41,42 has a higher thermal conductivity depends on the same factors as previously discussed with reference to the examples of FIG. 1 and FIG. 2 - i.e. the further components to which they are attached, and the type of connection used to attached them to the further components. The thermal conductivities of the first and second parts 41,42 should be selected such that heat is conducted away from the elastomeric material 43 along the more favourable conductive route, and prevented from being conducted along the least favourable conductive route. This will prevent the temperature of the members 41,42 increasing, which would increase the operating temperature of the elastomeric material 43.

The thermal conductivity of each member 41,42 may be achieved by selecting materials based on their thermal conductivity. For example, one member maybe made from a material having a high thermal conductivity, and the other member may be made from a material having a low thermal conductivity.

Alternatively, one of the members 41,42 may comprise an insulative material disposed between it and the elastomeric material to reduce thermal conduction into that member. In the example of FIGS. 7 and 8, either the surface of the first part 41 to which the elastomeric material 43 is attached, or the surface of the second part 42 to which the elastomeric material 43 is attached, may be provided with a liner or covering made from an insulative material that separates that member 41,42 from the elastomeric material 43, thereby giving that member 41,42 an overall lower thermal conductivity.

The elastomeric material 43 can be adhered or otherwise attached to both the first and second parts 41,42, to hold the vibration damping mount 40 together. Alternatively, if such an adhesive is not required to hold the vibration damping mount 40 together, then the elastomeric material 43 may be adhered to only one of the first part 41 or the second part 42, whichever lies on the preferred route for thermal conduction (i.e. whichever has the higher thermal conductivity). An air gap may be provided between the other member (of the first and second parts 41,42) to reduce thermal conduction through that member. The air gap may be provided by shaping that member 41,42 or the elastomeric material 43 such that at least a part of the elastomeric material 43 is spaced from the member, or by providing a spacer in between. Such an air gap would provide effective insulation against heat transfer from the elastomeric material 43 to the member 41,42.

The vibration damping mount of FIGS. 9 and 10 has a first plate 51, a second plate 52, and an elastomeric material 53 disposed between the first and second plates 51,52. In this example, the first and second plates 51,52 are also referred to as the first and second members.

In this example, at least one intermediate plate 54 is provided between the first and second plates 51,52 such that the elastomeric material 53 is divided into several parts. That is, intermediate plates 54 and parts of elastomeric material 53 are layered between the first and second plates 51,52 like a sandwich. The intermediate members 54 reduce the size of each layer of elastomeric material 53, which reduces the overall deflection of the vibration damping mount 50.

In the illustrated example, each of the first plate 51, second plate 52, and intermediate plates 54 is a planar member. However, it will be appreciated that the plates 51,52,53 may have various shapes, for example they maybe curved or conical.

Each of the first and second plates 51,52 may have a flange 55 with a series of mounting holes 53 for attaching the first and second plates 51,52 to further members, but it will be appreciated that the first and second plates 51,52 may be provided with other means for attaching them to further components, such as brackets, clamps or protrusions.

In a first example, the first plate 51 has a higher thermal conductivity than the second plate 52, and in a second example the second plate 52 has a higher thermal conductivity than the first plate 51. The selection of which member 51,52 has a higher thermal conductivity depends on the same factors as previously discussed with reference to the examples of FIG. 1 and FIG. 2 - i.e. the further components to which they are attached, and the type of connection used to attached them to the further components. The thermal conductivities of the first and second plates 51, 52 should be selected such that heat is conducted away from the elastomeric material 53 along the more favourable conductive route, and prevented from being conducted along the least favourable conductive route. This will prevent the temperature of the members 51,52 increasing, which would increase the operating temperature of the elastomeric material 53.

The thermal conductivity of each member 51,52 maybe achieved by selecting materials based on their thermal conductivity. For example, one member maybe made from a material having a high thermal conductivity, and the other member may be made from a material having a low thermal conductivity.

Alternatively, one of the members 51,52 may comprise an insulative material disposed between it and the elastomeric material 53 to reduce thermal conduction into that member 51,52. In the example of FIGS. 9 and 10, the inner surface of either the first plate 51 or the second plate 52, to which the elastomeric material 53 is attached, may be provided with a liner or covering made from an insulative material that separates that member 51,52 from the elastomeric material 53.

The elastomeric material 53 can be adhered or otherwise attached to both the first and second plates 51,52, to hold the vibration damping mount 50 together. Alternatively, if such an adhesive is not required to hold the vibration damping mount 50 together, then the elastomeric material 53 may be adhered to only one of the first plate 51 or the second plate 52, whichever lies on the preferred route for thermal conduction (i.e. whichever has the higher thermal conductivity). An air gap may be provided between the other member (of the first and second plates 51,52) to reduce thermal conduction through that member. The air gap maybe provided by shaping that member or the elastomeric material 53 such that at least a part of the elastomeric material 53 is spaced from the member, or by providing a spacer in between. Such an air gap provides effective insulation against heat transfer from the elastomeric material 53 to the member.

In this example, in order to allow conductive heat transfer from all parts of the elastomeric material 53 to the plate 51,52 having a higher thermal conductivity, each of the intermediate plates 54 must permit heat transfer from one side to the other. This could be achieved by making the intermediate plates 54 from a thermally conductive material, or by providing further thermal conducting members that cross over, through or around the intermediate plates 54. For example, such conducting members may comprise metallic strips that are folded over an edge of the intermediate plate 54 and contact the elastomeric material 53 on each side of the intermediate plate 54, such that thermal energy is conducted from one side of the intermediate plate 54 to the other.

It will be appreciated that many other forms and shapes of vibration damping components having first and second members with an elastomeric material disposed in between are possible, and in each case it is possible to arrange the members to promote thermal conductivity in a favourable direction to reduce the operating temperature of the elastomeric material.

In each of the examples of FIGS. 1 to 10 at least one of the members is made from a thermally conductive material. Examples of potentially suitable thermally conductive materials are carbon steel, stainless steel, titanium, brass and aluminium.

The thermally conductive material may have a thermal conductivity of at least 10 watts per metre Kelvin (W/ (mK)) when measured at 25 degrees Celsius. Alternatively, the thermally conductive material may have a thermal conductivity of at least 15 W/ (mK) when measured at 25 degrees Celsius, preferably at least 40 W/ (mK) when measured at 25 degrees Celsius.

In specific examples, the thermal conductivity of a typical stainless steel is approximately 16 W/ (mK) when measured at 25 degrees Celsius, for 1% carbon steel it is approximately 43 W/ (mK) when measured at 25 degrees Celsius, for titanium it is approximately 22 W/ (mK) when measured at 25 degrees Celsius, for a typical brass it is approximately 109 W/ (mK) when measured at 25 degrees Celsius, and for a typical aluminium it is approximately 205 W/ (mK) when measured at 25 degrees Celsius.

In addition, in many of the examples of FIGS. 1 to 12 there is at least a part made from an insulative material, or from a material having a lower thermal conductivity than the thermally conductive part. Examples of material having a low thermal conductivity, and are therefore generally described as insulative, are phenolics, nylon, PTFE (polytetrafluoroethylene), acetals (e.g. Delrin), UHMWPE (ultra-high molecular weight polyenylene), polyimide, polysulfone, and polyphenylene sulphide.

The material having a lower conductivity, the insulative material, may have a thermal conductivity of less than 1.0 watt per metre Kelvin (W/ (mK)) when measured at 25 degrees Celsius. Alternatively, the thermally conductive material may have a thermal conductivity of less than 0.5 W/ (mK) when measured at 25 degrees Celsius, preferably less than 0.2 W/ (mK) when measured at 25 degrees Celsius.

In specific examples, the thermal conductivity of a phenolic cast resin is approximately 0.15 W/ (mK) when measured at 25 degrees Celsius, for a nylon is approximately 0.25 W/ (mK) when measured at 25 degrees Celsius, for PTFE (polytetrafluoroethylene) is approximately 0.25 W/ (mK) when measured at 25 degrees Celsius, and for acetals is approximately 0.23 W/ (mK) when measured at 25 degrees Celsius.

Therefore, the ratio of the thermal conductivity of the thermally conductive material to the thermal conductivity of the thermally insulative material is at least 10:1, more preferably at least 30:1, more preferably at least 50:1, more preferably at least 100:1, and may be any ratio up to 200:1.

The elastomeric materials used in the vibration damping components are typically rubbers.

In each of the examples described herein, the member having a lower thermal conductivity may be made from an insulative material or coated with an insulative material. A member with a low thermal conductivity may be positioned against the elastomeric material, with a thermally conductive material on the opposite side so that the low thermal conductivity material insulates the rubber from the thermally conductive material. This may be appropriate where the application requires a hard or rigid outer part, for example for mounting or protection. In this case, the outer part may be a metal housing, with an insulator disposed between the housing and the elastomeric material to prevent thermal conduction from the elastomeric material to the metal housing, as described with reference to the examples of FIG. 1 and FIG. 2.

In other examples, an insulative liner may be positioned between the elastomeric material and a shaft, to prevent thermal conduction from the elastomeric material to the shaft.

In each of the above-described examples the vibration damping components have a first member, a second member, and an elastomeric material disposed therebetween. However, in some applications it maybe more appropriate for the vibration damping arrangement to be integral with a larger assembly, rather than a stand-alone component.

For example, the first member maybe an integral part of a further component or assembly to which the second member and elastomeric material are mounted. In this case, the vibration damping assembly comprises a first member, a second member, and an elastomeric material positioned therebetween, but the first and second members are not necessarily attached to each other.

In one example, similar to the vibration damping bushing of FIGS. 1 and 2, the shaft maybe a component of a further assembly, and the housing and elastomeric material may be attached to the shaft during assembly of the overall assembly. Therefore, the shaft and the housing are arranged in a vibration damping assembly.

The skilled person would appreciate that a similar arrangement is possible for each of the examples described - that is, the first member, second member, and elastomeric material may form a vibration damping assembly within a larger assembly, and do not necessarily form a stand-alone vibration damping component.

It will be appreciated that the specific embodiments described with reference to the drawings are mere examples, and the skilled person would understand that it is possible to arrange components and materials in other configurations within the scope of the claimed invention to achieve the same effect - of directing the thermal conduction along a preferable route. Therefore, the skilled person would understand that the invention defined in the claims may be applied to a great variety of vibration damping components or assemblies, and so the invention defined in the claims is not limited only to those embodiments described in detail above.

Claims

Claims

1. A vibration damping component comprising: a first member, a second member, and an elastomeric material disposed between the first and second members to damp vibrations of the first and/or second members, wherein the thermal conductivity of the first member is higher than the thermal conductivity of the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.
2. A vibration damping component according to claim l, wherein the elastomeric material is attached to the first member.
3. A vibration damping component according to claim 1 or claim 2, wherein the second member is arranged adjacent to the elastomeric material such that an air gap is formed between the elastomeric material and the second member.
4. A vibration damping component according to any of claims 1 to 3, wherein the second member comprises an insulative material.
5. A vibration damping component according to any of claims 1 to 3, wherein the second member comprises an insulative coating.
6. A vibration damping component according to any of claims 1 to 5, wherein the thermal conductivity of the first member is at least 10 watts per metre Kelvin when measured at 25 degrees Celsius, preferably at least 15 watts per metre Kelvin when measured at 25 degrees Celsius, more preferably at least 40 watts per metre Kelvin when measured at 25 degrees Celsius.
7. A vibration damping component according to any of claim 1 to 6, wherein the thermal conductivity of the second member is less than 1.0 watt per metre Kelvin when measured at 25 degrees Celsius, preferably less than 0.5 watts per metre Kelvin when measured at 25 degrees Celsius, more preferably less than 0.2 watts per metre Kelvin when measured at 25 degrees Celsius.
8. A vibration damping component according to any of claims 1 to 7, wherein the ratio of the thermal conductivity of the first member to the thermal conductivity of the second member is at least 10:1, preferably at least 30:1, more preferably at least 50:1, more preferably at least 100:1.
9. A vibration damping component according to any of claims 1 to 8, wherein the ratio of the thermal conductivity of the first member to the thermal conductivity of the second member is between 100:1 and 200:1.
10. A vibration damping component according to any of claims 1 to 9, wherein the elastomeric material comprises rubber.
11. A vibration damping component according to any of claims 1 to 10, wherein the first component comprises a shaft that is at least partially surrounded by the elastomeric material, and the second component comprises a housing that surrounds the shaft and the elastomeric material.
12. A vibration damping component according to claim 11, wherein the housing comprises an insulative material disposed against the elastomeric material and a sheath that surrounds the insulative material of the housing.
13. A vibration damping component according to claim 12, wherein the sheath is arranged such that an air gap is formed between the insulative material and the sheath.
14. A vibration damping component according to any of claims 1 to 10, wherein the second component comprises a shaft that is at least partially surrounded by the elastomeric material, and the first component comprises a housing that surrounds the shaft and the elastomeric material.
15. A vibration damping component according to any of claims 11 to 14, wherein the shaft comprises a partially spherical portion around which the elastomeric material is disposed.
16. A vibration damping component according to any of claims 1 to 10, wherein the first member comprises a first plate and the second member comprises a second plate, and wherein the elastomeric material is disposed between the plates. 17· A vibration damping component according to claim 16, wherein an intermediate plate is disposed between the first and second plates and the elastomeric material is disposed on both sides of the intermediate plate, and wherein the intermediate plate comprises a conductive material.
18. A vibration damping component according to claim 16 or claim 17, wherein the first and second plates are substantially planar.
19. A vibration damping component according to any of claims 16 to 18, wherein at least one of the first and second plates is conically shaped.
20. A vibration damping component according to any of claims 16 to 19, wherein the elastomeric material is conically shaped.
21. A vibration damping component according to any of claims 1 to 10, wherein the first and second members are each U-shaped brackets arranged such that arms of the first and second members overlap, and wherein the elastomeric material is disposed between the arms of the first and second members.
22. A vibration damping component according to any of claims 1 to 10, wherein one of the first and second members is a bracket and the other of the first and second members is a block adapted to be received within the bracket with the elastomeric material disposed therebetween.
23. An assembly comprising a first member, a second member, and an elastomeric material disposed between the first and second members to damp vibrations of the first and/or second members, wherein the thermal conductivity of the first member is higher than the thermal conductivity of the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.
24. An assembly according to claim 23, wherein the assembly comprises first and second components, the first component comprising the first member and the elastomeric material and the second component comprises the second member.
25- A method of damping vibrations comprising arranging a first member, a second member, and an elastomeric material such that the elastomeric material is disposed between the first and second members and damps vibrations of the first and/or second members, and wherein the method includes providing the first member with a higher thermal conductivity than the second member such that, during use, heat generated in the elastomeric material by said damping is conducted away from the elastomeric material through the first member in preference to the second member.
26. A method of damping vibrations according to claim 25, wherein the step of providing the first member with a higher thermal conductivity than the second member comprises selecting materials such that the material of the first member has a higher thermal conductivity than the material of the second member.
27. A method of damping vibrations according to claim 25 or claim 26, wherein the step of providing the first member with a higher thermal conductivity than the second member comprises insulating the second member from the elastomeric material.
28. A method of damping vibrations according to any of claims 25 to 27, further comprising attaching the elastomeric material to the first member.
29. A vibration damping component substantially as hereinbefore described with reference to the accompanying drawings.
30. A vibration damping assembly substantially as hereinbefore described with reference to the accompanying drawings.