GB2360345A

GB2360345A - Mounting device for hydraulically damping both axial and radial vibrations

Info

Publication number: GB2360345A
Application number: GB0112466A
Authority: GB
Inventors: David Boast; Mary Louise Marfell; John Morton; Trevor Howard Johnson
Original assignee: Avon Vibration Management Systems Ltd
Current assignee: Avon Vibration Management Systems Ltd
Priority date: 1999-06-14
Filing date: 2000-06-08
Publication date: 2001-09-19
Anticipated expiration: 2020-06-08
Also published as: GB2360345B; GB2360344B; GB2360344A; GB0112466D0; GB0112464D0

Abstract

The device has a first anchor part (10) within a second anchor part (11). The anchor parts (10, 11) are interconnected by resilient walls (14, 15) spaced axially apart to define an enclosed space which is divided into two chambers (30, 31) for hydraulic fluid by axially extending walls. The chambers are interconnected by passageway (20). Resilient walls (14, 15) which are not mirror images of each other about a central radial plane so that axial movement causes the chambers to change volume and so cause fluid movement through the passageway (20). Further embodiments include various combinations of numbers of chambers and interconnections between the chambers.

Description

2360345 HYDRAULICALLY DAMPED MOUNTING DEVICE The present invention relates

to a hydraulically damped mounting device. Such a mounting device usually has a pair of chambers for hydraulic fluid, connected by a suitable passageway, and damping is achieved due to the flow of fluid through that passageway.

In EP-A-0172700, a hydraulically damped mounting device of the "bush" type was disclosed which damped vibration between two parts of a piece of machinery, e.g. a car engine and a chassis. In a bush type of hydraulically damped mounting device, the anchor for one part of the vibrating machinery is in the form of a hollow sleeve, and the other anchor part is in the form of a rod or tube extending approximately centrally and coaxially of the sleeve. Resilient walls then interconnect the central anchor part and the sleeve to act as a resilient spring for loads-applied to the mounting device. In EP-A-1072700, the resilient walls also defined one of the chambers (the "working chamber") in the sleeve, which chamber was connected via the elongate passageway to a second chamber (the "compensation chamber") bounded at least in part by a bellows wall which was effectively freely deformable so that it could compensate for fluid movement through the passageway without itself resisting that fluid movement,, -2significantly.

In GB-A-2291691, the arrangement disclosed in EP-A1072700 was modified by providing a bypass channel from the working chamber to the compensation chamber. Under normal operating conditions, that bypass channel was closed by part of the bellows wall bounding the compensation chamber. At high pressures, however, the bellows wall deformed to open the bypass channel, thereby permitting fluid from the working chamber to pass directly into the compensation chamber without having to pass through the full length of the passageway.

In both EP-A-1072700 and GB-A-2291691, the resilient walls extended generally axially along the interior of the mount. Those walls therefore formed axially elongate blocks of e.g. rubber material which were configured to achieve the desired static spring requirements. The material of the block was deformed primarily in shear, to give maximum durability. As the resilient walls also formed walls of the working chamber, the axial ends of the working chamber were closed with material being integral with the resilient walls. In practice, however, the spring effect of those ends walls was small, so that the spring characteristic of the mount could be determined by the axially extending resilient walls.

GB-A-2322427 departed from this, by locating the resilient walls at axially spaced apart locations, unlike -3the arrangements in EP-A-1072700 and GB-A-2291691, in which the main spring effect is provided by axially extending, circumferentially spaced, resilient walls. The resilient walls of GB-A-2322427 thus defined an enclosed space within the sleeve which extends circumferentially around the central anchor part, which space is axially bounded by the resilient walls.

It was then necessary to divide that space into two chambers, and connect those two chambers with a passageway, to form the hydraulic mounting device of. the bush type. To provide that division, GB-A-2322472 proposed that axially extending walls extend between the central anchor part and the sleeve. Unlike the axially extending walls of the known arrangements, those walls do not need to provide a spring effect, since the spring effect is provided by the axially spaced resilient walls. Therefore, it is not necessary for those axially extending walls to be bonded to the sleeve and/or central anchor part. Instead, they made abutting, un-bonded, contact.

This permitted a bypass to be formed between the chambers without the need for a separate bypass channel, as in GB-A-2291691. By suitably selecting the abutment force of the axial walls against the sleeve and/or central anchor part, a pressure- sens it ive seal was achieved. For pressures below a suitable level, the integrity of that seal was achieved by the force of abutment. For higher pressures, however, the seal was broken, thereby providing a path around the axial walls between the two chambers.

The present invention, in its various aspects, seeks to develop a mount of the general type shown in GB-A 2322427, in which resilient walls are at axially spaced locations and in which axially extending walls need not necessarily provide a spring effect. It should be noted, however, that the present invention is not limited to the case where those axial extending walls make unbonded contact with the sleeve and/or central anchor part, and also includes arrangements in which those axially extending walls are resilient.

The various aspects of the present invention are concerned primarily with the providing a damping effect to axial vibrations of the central anchor part relative to the sleeve. All the "bush" mounts discussed previously were concerned with damping or otherwise controlling radial vibrations. The present invention, in its various aspects, therefore seeks to provide both radial and axial damping.

In a first aspect, the present invention proposes that the axial damping is provided within the axially extending walls which divide the interior of the mount into two chambers which are filled with hydraulic fluid.

Within the wall is a body fixed to either the central anchor part or the sleeve. On the axial sides of that body are respective axially spaced pockets for hydraulic fluid, which are each partially bounded by the body, and 5 which are joined by a channel.

Assume now that the body is fixed to the central anchor part. As the central anchor part moves axially relative to the sleeve, the body moves with it, towards one axial end of the mount and away from the other. One pocket therefore reduces in volume, and the other increases. Hydraulic fluid moves from one pocket to other, via the channel, thus providing a damping action. When the central anchor part moves in the opposite axially direction, the relative change in volume of the pockets is reversed. A similar effect is achieved if the body is mounted on the sleeve.

It may be simplest for the channel to be defined between a circumferential surface of the body and the anchor part (central anchor part or sleeve) to which it is not attached. Other arrangements are possible, however, such as those in which the channel extends through the body. Note also that such an arrangement may be provided in only one of the axial walls, or in both of them.

In a second aspect of the present invention, the resilient walls are shaped so that they are not mirror -6images of each other when reflected about the central radial plane of the mount. Instead the chambers f or hydraulic fluid are shaped so that axial movement in one direction of the central anchor part relative to the sleeve causes one chamber to increase in volume, and the other to decrease in volume, with the opposite volume change occurring when the central anchor part moves in the opposite axial direction.

With such an arrangement, when axial movement occurs, the relative change in volume of two chambers (one getting larger and one getting smaller) causes hydraulic fluid to pass through the passageway, thereby providing a damping effect. Of course, as in GB- A2322427, fluid will pass through the passageway under radial vibration as well. The disadvantage of the second aspect, relative to the first, is that the damping effect in the axial and radial directions are linked, since the damping effect is provided by the same passageway, on the other hand, such.a mount may be easier to form.

Such an asymmetric mount may be provided by shaping the resilient walls so that, at one axial end, a short section of wall bounds one chamber and a long section of wall bounds the other, with the length of the walls being reversed at the opposite axial end.

It will be appreciated that an asymmetric mount will tend to cause the central anchor part to twist relative -7 to the sleeve as it moves axially. This is not always a problem; indeed there are some arrangements in which that twisting may provide steering of the vibrating parts which may be advantageous.

In a third aspect of the invention, chambers are formed by the resilient axially spaced walls and the axially extending walls (which may be resilient or not) are axially divided by a diaphragm. That diaphragm may be fixed to the central anchor part and/or the sleeve and have a flow-path therearound. Then, when there are axial vibrations, hydraulic fluid moves from one side of the diaphragm to the other, through the flow-path, thereby providing damping.

Preferably, in this third aspect, the diaphragm is fixed to one of the central anchor part and sleeve, and, makes abutting, unbonded, contact wi-th the other. The flow-path is then defined between an edge of the diaphragm and the anchor part to which it makes unbonded contact. It is also possible, either as an alternative or in addition, to provide a channel around the diaphragm. For example, such a channel may be f ormed in a flange of the central anchor part to which an edge of the diaphragm is bonded.

In a fourth aspect of the present invention, a mount is provided with a central anchor part and outer sleeve, which are interconnected by three radially extending -8resilient walls, at axially spaced apart locations, to define axially separated spaces which are filled with hydraulic fluid. By suitable shaping of the interior of those spaces, eg. by making them tapered in opposite axial directions, axial movement of the central anchor part relative to the sleeve will-cause an increase in the volume of one of the spaces, and decrease in volume in the other. If the two spaces are then connected by an elongate channel, fluid will flow between one space and another, providing a damping effect.

In this fourth aspect, the space also needs to provide damping for radial movement. In the simplest case, each space is separated into two chambers by axially extending walls. Those two chambers in each space are then connected by a passageway. The axially extending walls may be as in GB-A2322427, which make a abutting, un-bonded, contact with the sleeve or central anchor part. However, bonded contact is al'so possible.

In a further development of this fourth aspect, each space is itself divided into four chambers by axially extending walls. This then permits damping of radial vibrations in multiple directiohs.

The four aspects of the invention discussed above are all concerned with mounts in which there was both axial and radial damping. In a development of such aspects, the radial damping is different in different -9radial directions. In general, this development involves the formation of more than two chambers, and then arranging for those chambers either to deform differently under different radial vibrations, or providing passageways linking those chambers which provide different damping.

For example, in the second aspect of the invention, the two chambers may be divided into two halves by an axially extending wall, and one half of a first one of the two chambers is connected to the opposite half of the second chamber by a passageway, and the second half of the first chamber is connected to the opposite half of the second chamber by a passageway of different length and/or crosssection, to provide different damping. In the third aspect of the invention, the two chambers may similarly be divided into two axially. It has already been mentioned that the fourth aspect of the present invention may have a development in which each space is divided into four chambers. Then, by interconnecting both pairs of those four chambers with passageways with different characteristics, radial damping which is different in different directions can be achieved.

Indeed, this idea of having different damping characteristics in different radial directions may be developed in mounts which do not have axial damping. Thus, in a fifth aspect of the present invention, a mount -10has a central anchor part and a sleeve surrounding the central anchor part and forming a second anchor part, which are interconnected by both radial extending walls, and axially extending walls spaced around the central anchor part to define a plurality of chambers which are interconnected by passageways such that at least a first pair of chambers interconnected by an elongate passageway are deformed by opposite extents due to radial movement of the central anchor part relative to the sleeve in a first radial direction, and a second pair of chambers interconnected by a second elongate passageway are deformed to opposite extents by radial movement of the central anchor part relative to the sleeve in a different radial direction.

In the simplest case, this fifth aspect of the present invention may involve four chambers, at different circumferential positions around the central anchor part, with each chamber connected to a diametrically opposite chamber. Then, vibrations in one direction deform two opposed chambers such that there are corresponding changes in volume of the two chambers, so that damping occurs as fluid moves from one chamber to the other via the passageway. For movement in another direction, fluid movement is between the passageway interconnection the other two chambers.

It is possible for the four chambers to be arranged -11circumferentially around the central anchor point at a common axial position. The chambers may then be separated by axial walls spaced e.g. 900 apart around the central anchor point. However, this is not essential.

It would be possible to have the first pair of chambers at one axial position, and the second pair of chambers at a different axial position.

This idea may be developed further, by providing two sets.of two pairs of chambers, with the two sets being axially spaced along the central anchor part.

Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

1 Fig. 1 is a partial sectional view through a first embodiment of the present invention; Fig. 2 is a side view of part of the mount of Fig.

Fig. 3 is a perspective view of part of the mount of Fig. 1; Fig. 4 is a sectional view of the mount of Fig. 1, perpendicular to the view shown in Fig. 1; Fig.. 5 is a perspective sectional view, showing the relationship between the views of Fig. 1 and Fig. 4; Fig. 6 is a sectional perspective view through a second embodiment of the present invention; Fig. 7 is a transverse sectional view through the -12mount of Fig. 6; Fig. 8 is a perspective sectional view of a mount being a third embodiment of the present invention; Fig. 9 is a transverse sectional view through the 5 mount of Fig. 8; Fig. 10 is a transverse sectional view through a mount being a variant on the third embodiment; Fig. 11 is a longitudinal sectional view through a mount being a fourth embodiment of the present invention; Fig. 12 is a transverse sectional view through the mount of Fig. 11; Fig. 13 shows rubber elements of the mount of the fourth embodiment; Figs. 14a to 14d are perspective, two side, and sectional views of a mount being fifth embodiment of the present invention; Figs. 15a to 15c are side section and perspective views of a mount being a sixth embodiment of the present invention; and 20 Figs. 16 a to 16c are axial and transverse sectional views of a mount being a seventh embodiment of the present invention. As can be seen from Fig. 1, a first embodiment of the present invention is in the form of a "bush" type mount in which a central anchor part 10 is located within a sleeve 11 forming a second anchor part, to which one -13part of vibrating machinery may be attached. The central anchor part 10 has a bore 12 to which another part of the vibrating machinery may be attached. The central anchor part 10 has a projecting ridge 13 from which extend resilient walls 14,15. The resilient walls 14,15 extend circumferentially around the central anchor part 10, and thus are generally in the shape of hollow frusto-cones with their f rustums at the ridge 13 of - the central anchor part 10, and their bases in contact with rings 16,17 which are secured to the sleeve 11. The inclined shape of the resilient walls 14,15 therefore defines an enclosed space 18 within the sleeve 11. That space 18 is axially bounded by the resilient walls 14,15, radially bounded outwardly by the sleeve 11, and radially bounded inwardly by the central anchor part, including parts of the projecting ridge 13 of the central anchor part 10.

In order for the hydraulically damped mounting device to act as such, it is necessary f or the space 18 to be divided into two chambers for hydraulic fluid.

When those two chambers are connected by a suitable passageway, hydraulic fluid flows through the passageway from one chamber to the other as the mount vibrates, thereby to damp the vibration.

The mount described above is similar to that in GB-A-2322427. In both that document, and the present invention, walls extend axially between the first and -14second resilient walls 14,15 at circumferentially locations, so as to divide the space 18 into first and second chambers for hydraulic fluid. The passageway, a part of which is shown at 20 in Fig 1 and interconnects those chambers. However, in this embodiment, the structure of the deformable walls is different from that of GB-A-2322427. As shown in Fig 2, in which the sleeve 11 is removed, an axial wall 21 extends between the rings 16,17. With a similar wall on the opposite side of the mount from that shown in Fig 2, the space 18 is thus divided into two chambers, one on the left side of wall 21 in Fig 2 and one on the right. For axial vibrations, which thus move the central anchor part 10 sideways in Fig 2, relative to the sleeve,. one of those chambers will increase in size, and the other will decrease. Hydraulic f luid will pass from one chamber to the other, via the passageway 20. Consider now axial vibrations of the central anchor part 10 relative to the sleeve.. Since the two chambers are symmetric, they will not change in volume and thus there will be no damping due to f luid movement through the passageway 20. Instead, damping is provided by fluid movement within the wall 21.

The internal structure of the wall 21 is shown in more detail in Fig 3 again, the sleeve 11 is removed for ease of viewing. As shown in Fig 3, the wall 2,1 comprises axially extending diaphrams 22,23 which are -15circumferentially spaced, so that wall 21, and the similar wall on the opposite side of the mount, divide the space 18 into two chambers. Between those two diaphrams 22,23, there are two pockets 24, 25 which are spaced in the axial direction and are connected by a channel 26. The structure is shown in more detail in Fig 4 which shows that the pockets 24,25 are defined between a body 27 projecting from the central anchor part 10 and outer walls 28, 29 extending effectively between the rings 16, 17 and the central anchor part 10.

Consider now downward movement of the central anchor part 10 relative to the sleeve in Fig. 4. Although the part 28 will deform, it is attached to the ring 16 at its outer radial edge, and so as the body 27 moves downwardly, the volume of the pocket 24 will decrease. The opposite effect will happen to pocket 25; as the body 27 moves down the part 29 will deform but the effect will be to increase the volume of pocket 25. Thus, hydraulic fluid in pocket 24 will be forced through the channel 26 to the pocket 25, thus providing a damping effect. This effect is reversed if the central anchor part 10 moves upwardly in Fig. 4. For axial vibrations there is therefore a thumping action along the passageway 26, a damping effect thus provided is determined by the length and cross-section of 'the passageway 26. The hydraulic fluid in pockets 24 and 25 and passageway 26, is entirely -16 separated from the hydraulic fluid in the chambers defined within space 18, on either side of the wall 21.

Separation is provided by the diaphrams 22,23 and parts 28,29. If the outer edge of the wall 21 is in unbonded contact with the sleeve as in GB-A-2322427, then some linking of the chambers and pockets may occur, but it is also possible to bond the wall 21 (and the wall on the opposite side of the mount) to the sleeve.

Fig. 5 shows a further view of the mount to illustrate the relationship between the parts 28,29 and the resilient walls 14, 15.

It has previously been mentioned that the embodiment described above may have a structure corresponding to the axial wall 21 shown in Fig. 2 in a wall located 1801 around the mount from that wall 21. In a further development of such an arrangement, the configuration of the pockets and channel 26 may be different in the two axial walls, thereby providing two different axial damping frequencies. In the simplest case, the channel 26 in the two axial walls has different lengths or cross sectional areas.

A second embodiment of the invention will now be described with reference to Figs 6 and 7. In the mount of GB-A-2322427, the resilient walls were symmetric about the central radial plane of the mount. The resilient walls were in the shape of hollow frusto-cones.In this -17embodiment, however, walls are not circumferentially symmetric. Instead, the length of those walls as they extend between the central anchor part and the sleeve varies around the central anchor part. They are frusto- cones, but with bases inclined to the perpendicular to the axis of the cone.

Thus, referring to Figs 6 and 7, the parts which are similar to the first embodiment are indicated by the same reference numerals. However, each resilient wall comprises a short part 14a,15a and a long part 14b,15 and the walls are arranged so that the two chambers 30,31 formed by the division of the space 18 by the axial walls are bounded by one long part of a resilient wall and one short part of a resilient wall. Thus, one chamber 30 is bounded by short wall 14a and long wall 15b and the other chamber 31 is bounded by long wall 14b and short. wall 15a. It can be noted that the ridge is itself not symmetric, having one part 13a close to one axial end, and another part 13b close to the other axial end.

Again, the chambers 30, 31 are filled with hydraulic fluid.

Consider now axial movement of the sleeve 10 downwardly in Figs 6 and 7 the effect of this will be to increase the volume of chamber 30 but to decrease the volume of chamber 31. Thus, hydraulic fluid is forced in the passageway 20 from chamber 31 to the chamber 30, thus -18 providing a damping effect. If the central anchor part moves upwardly in Figs 6 and 7, the fluid flow is reversed as the chamber 30 decreases in volume and the chamber 31 increases in volume.

A third embodiment of the invention will now be described with reference to Figs 8 and 9. Again, parts which correspond to parts shown in other embodiments are indicated by the same reference numerals, and will not be discussed in detail. In this embodiment, however, each chamber formed by the division of the space 18 in Fig. 1 into two by the axial wall, contains a diaphram 41,42 extending from the ridge 13 towards the sleeve, which diaphrams extends both radially and circumferentially in the mount. Diaphrams 41,42 makes abutting, u,nbonded contact with the sleeve 11. The diaphrams thus divide the two chambers into two, with. the diaphrams 4 0 defining chamber parts 42a,42b and diaphrams 41 defining chamber parts 43a,43b. These chamber parts are all filled wit hydraulic fluid.

For radial vibrations of the mounts, any change in volume of those chamber parts will be the same-on the respective sides of the diaphrams 40,41. For axial movement, position is different. Consider.movement of the central anchor part downwardly in Figs 8 and 9. The diaphrams 40,41 slide downwardly relative to the sleeve 11, so that chamber parts 42a,43a increase in size, and -19chamber parts 42b,43b decrease in size. Since the diaphrams 40,41 are in unbonded contact. with the sleeve 11, hydraulic fluid is forced between the radially outer edges of the diaphrams 40,41 on the sleeve 11 from chamber part 42b to chamber part 42a, and from chamber part 43b to chamber part 43a. The restriction on fluid flow between the radially outer edge of the diaphrams 40,41 and the sleeve thus provides a damping effect. if the central anchor part 10 moves upwardly in Figs 8 and 9 and the fluid flow is reversed, but a similar damping action occurs.

Fig. 8 shows in more detail the axial wall 44 which separates the two chambers.. This. embodiment, the wall 44 is bonded to both the central anchor part 10 and the sleeve 11. It would also be possible, within this embodiment, to provide an unbonded contact as in GB-A 2322427.

Figs 8 and 9 also show that radially outer edges of the diap hrams 40, 41 preferably have strengthening members 45,46 therein. In this embodiment, those members 45,46 are V-shaped with the legs of the "V" abutting the sleeve 11. A channel is then defined around the radially outer edge of the diaphrams, which may permit some fluid movement under radial vibration...

A variation on this third embodiment, is shown in Fig. 10. In this embodiment, the resilient walls 50, 51 -20are different from the corresponding walls of the third embodiment. Instead of their bases being axially outwards relative to their frustums, they are axially inwards. This does not affect the behaviour of the mount. Again, the chambers formed by the division of the space within the sleeve 11 by the axial extending walls are divided into chamber parts 52a, 52b,53a,53b by respective diaphrams 54,55 which are secured to the central anchor part 10, and are in abutting, unbonded contact with the sleeve 11. However, in this fourth embodiment, there are also channels 56,57 extending axially between the chamber parts 52a,52b and 53a,53b respectively through the ridge 13. There are thus two possible fluid paths between the respective pairs of chamber parts. One of those paths is around the radially outer edges of the diaphrams 54,55, adjacent the sleeve. The other is through the channels 56,57. By suitable arrangement of the force of abutment of the diaphrams 54, 55 on the sleeve, it can be arranged that the main 20. fluid path is through the channels 56,57, thereby providing a more accurately defined damping effect.

A fourth embodiment of the present invention will now be described with reference to Figs. 11 to 13. Again, corresponding parts are indicated by the same reference numerals.

Referring first to Fig. 11, the central anchor part -2110 and sleeve are joined by three radial walls 60, 61, 62 which are spaced apart in the axial direction along the central anchor part 10 and thus form two spaces 63, 64 between the central anchor part 10 and the sleeve 11.

These spaces are then filled with hydraulic fluid. In this embodiment, the walls 60, 61, 62 extend radially perpendicular to the axis of the central anchor part 10, but the spaces 63, 64 are tapered in opposite axial directions, by shaping of the interior of the sleeve 11 so that its inner walls 65, 66 are in the shape of two frusto-cones, with a common base corresponding to the central wall 61. The spaces 63, 64 are then interconnected by channels 67, 68 which extend through -the central wall 61, and are defined by flanges 69, 70 in each space.

Consider now axial movement of -the central anchor part 10 downwardly in Fig. 11. Each of the radial extending walls 60, 61, 62 are deformed but the tapering of the spaces 63, 64 means that space 63 will increase in volume and space 64 will decrease in volume. Hydraulic fluid in those spaces will then pass through the channels 67, 68 f rom. the space 64 to the space 63, and the length of those channels due to the flanges 69, 70 will. thus provide a damping action. Movement of the central anchor part 10 relative to the sleeve.11 in the opposition axial direction, will cause a reverse movement of hydraulic 22fluid through the channels 67, 68.

In this embodiment each of the spaces 63, 64 is divided into quarters by axially extending walls. The division of the space 64 is shown in Fig. 12,but there 5 will be a similar division of space 63.

Referring now to Fig. 12, it can be seen that there are four axially extending walls 71, 72, 73, 74 spaced by approximately 901 around the central anchor part 10. In this embodiment, three of those walls 71, 72 and 73 make abutting, un-bonded contact with the sleeve 11, whereas the wall 74 is bonded to a projecting part 74a. of the sleeve. The space 64 is thus divided into four chambers 75, 76, 77 and 78. Fig 12 also shows that, in addition to the channels 67, 68 shown in Fig. 11, there are further channels 79, 80, so that each chamber 75 to 78 communicates with one of the channels 67, 68, 79, 80. Hence, each - chamber 75 to 78 of space 64 communicates with a corresponding chamber in the space 63.

A passageway 81 is formed in the sleeve.11, which passageway communicates with each of the chambers 75 to 78. Such a communication is shown in Fig. 11, in which the corresponding passageway 82 around the chamber 63 is shown opening into that space 63.

Any radial movement of the central anchor part 10 relative to the sleeve 11 in this embodiment, in any direction, will have the effect of increasing the volume -23of at least one, possibly two, of the chambers 75 to 78, and decreasing the volume of at least one of the others. If the axial movement was downward in Fig. 1, chamber 75 and 76 would increase in volume, and chamber 77 and 78 would decrease in volume. If the movement was inclined downwardly and to the left at 45o, chamber 77 would decrease in volume, chamber 75 would increase in volume, and the volume of chambers 76 and 78 would not change. Each of these movements would cause hydraulic fluid filling the chambers 75 to 78 to be forced out of any chamber decreasing in volume, and into any chamber increasing in volume, through the passageway 81. Damping would thus occur.

Moreover, since the walls 71, 72 and 73 make abutting, un-bonded, contact with the sleeve 11, over pressure would force hydraulic fluid- between the chambers 75, 78, with the fluid passing between the walls 71 to 73 and the sleeve 11.

The radial walls 60, 61 and 62, the axial walls 71 to 74 in the space 64 and the corresponding axial walls in the space 63, may be f ormed by two rubber units, mounted one on the other. The structure thus formed is shown in Fig. 3. Thus, from Fig. 13, the central wall 61 is formed by two wall parts 82, 83 which are held immediately adjacent to each other in abutting contact, by suitable clamping by the sleeve 11. It would, -24however, be possible for wall 61 to be a single rubber wall, in which case the structure shown in Fig. 3 would be formed as a single part, not as two parts located together. Fig. 13 also shows the wall 64 to 67 which 5 divide the space 63 into four chambers.

In the embodiments described above, there is only one radial mode of vibration or, where there is more than one mode, as in the f ourth embodiment of Figs. 11 to 13, the characteristics of the mount are the same in different radial directions.

Figs. 14a to 14d show a fifth embodiment of the present invention, being a mount similar to that of the embodiment of Figs. 6 and 7, but which has different damping characteristics in different radial directions.

Components which are similar to those of the embodiment of Figs. 6 and 7 are indicated by the same reference numerals. Note that the sleeve 11 is omitted from Figs. 14a to 14c for the sake of clarity.

In this embodiment, the chambers 30, 31 are separated by axial walls 90 spaced 1800 apart around the mount. The chambers 30, 31 are then mirror images of each other about the plane of those walls. 90, 91. In addition, in this fifth embodiment, each chamber 30, 31 is itself divided axially by axially extending walls 92, 93. Thus, as can be seen from Figs. 14a to 14c, the chamber 30 is divided into two part chambers 30a,30b, and -25similarly chamber 31 is divided into two part chambers which we will refer to as 31a and 31b, although chamber 31b does not appear in the drawings since it is 1801 around the mount from chamber 30b and so is not visible in the views shown. Then, two different channels 94, 95 are provided in the mount. One channel 94 interconnects chambers 30a and 31a, and the other channel 95 interconnects chambers 30b and 31b.

In such a mount, if the direction of vibration is e.g. in the plane formed by the 451 bisection of the walls 91, 92, the effect is that chambers 30a, 31a change in size under that vibration, but chambers 30b 31b do not. Thus, fluid passes through the passageway 94 been the chambers 30a and 31a. Similarly, perpendicular direction, in the plane of the 451 bisection of the walls 90, 92, chambers 30a, 31a are unaffected, and chambers 30b, 31b change in size. This time, the fluid movement is through passageway 95. Hence,: by providing different characteristics for the passageways 94, 95, for example if they have different lengths or different crosssectional areas, different damping characteristics can be provided.in mutually perpendicular radial directions.

A further embodiment of a mount in which different radial damping may be achieved in different directions is shown in the sixth embodiment of the.present invention of Figs. 15a to 15c. This is a modification of the mount -26shown in Figs. 8 and 9, and again the same reference numerals are used to indicate corresponding parts. Moreover, the sleeve 11 is omitted in Figs. 15a and 15c for the sake of clarity.

Fig. 15 is substantially the same as Fig. 9, although there is an additional passageway that will be discussed later. As in Figure 9, diaphrams 40. 41 separate chambers 42a and 42b, and chambers 43a, 43b respectively. Axial walls 44 as previously described 1800 apart then separate the chambers.

However, in this embodiment, there are additional axial walls which divide each of the chamber parts into two. Once of those walls 105 is shown in Fig. 5a, dividing chamber parts 42 into sub-parts 42aa 42ab and 42ba 42bb. The chamber parts 43a and 43b are similarly divided into two by another axial wall, which is not visible in the drawings, which divide those chambered parts into sub-parts 43ab, 43bb (which are visible in Fig. 15c) and 43aa 43ba which are not visible in the drawings.

For axial vibrations, the behaviour of this mount is exactly the same as that shown in Figs. 8 and 9. For radial vibrations, there are two different radial modes if there are passageways 106, 107 of different characteristics which provide suitable interconnections. Chamber subparts 42aa and 43aa are interconnected by -27passageway 106, and chamber sub-parts 42bb, 43bb are interconnected by passageway 107.. Note that fluid movement around diaphrams 40, 41 permit fluid movement between sub-parts 42aa, 42ba, sub-parts 42ab, 42bb, sub parts 43ab 43bb and sub-parts 43aa, 43ab respectively.

Consider now a vibration mode extending out of the plane of the drawings in Figs. 15c. Chamber sub-parts 42aa,42ba, 43aa,43ba are all affected by this vibration, and thus fluid moves through passageway 106 to damp that vibration. Chamber sub-parts 42ab,42bb, 43ab,43bb are not affected. For vibration in the radially perpendicular direction, the situation is reversed and fluid moves through passageway 107. By arranging for passageways 106, 107. to.have different characteristics, again, for example by them having different lengths or cross-sections, different radial damping characteristics can be achieved.

A further feature of the mounts of the fifth and sixth embodiments of the present invention is that they providing damping of "conical" vibrations "Conical" vibrations are those which twist the central anchor part relative to the sleeve 11 about a radial axis extending through an intermediate point (normally the centre point) of the central anchor part 10 Consider, for example, such a conical vibration of the central anchor part 10 relative to the sleeve 11 in a -28plane being at 451 to the walls 44, 105 in Fig. 15a, and extending through chamber sub-parts 42aa, 42ba. In one direction, such vibration will have the effect of decreasing the volume of chamber 42aa and increasing the volume of chamber 42ba. On the opposite side of the mount, not visible in Fig. 15a, the chamber sub-part 43ab will increase in volume, and the chamber 43bb will decrease in volume. Thus, fluid will pass from chamber 42aa to 43aa, and from chamber 43ba to chamber 42ba via 10 passageways 106, 107 respectively. Thus, there will be a damping effect. The opposite changes in chamber volume will occur for conical vibration of the central anchor part 10 relative to the sleeve 11 in the same plane, but in the opposite direction, decreasing the volume of 15 chamber 42ba and increasing the volume of chamber subpart 42aa. Similarly, if the conical vibration of the central anchor part 10 relative to the sleeve 11 is in the plane at 451 to the walls 44, 105 which intersects chambers 42ab, 42bb, then similar effects will result 20 with fluid movement moving between chambers 42ab and 43ab, and 42bb and 43bb. It should be noted that a similar effect is. achievable with mount of Figs. 14a to 14d, because the shaping of chambers 30, 31 means that their upper and 25 lower parts in those Figures can be considered to be separate chamber parts under conical vibration.

-29 A seventh embodiment of the present invention will now be described with reference to Figs. 15a to 15c. In this embodiment, there are two different radial modes of damping, but no axial damping. Again, corresponding parts are indicated by the same reference numerals.

Referring first to Fig. 16a, a central anchor part is located within a sleeve 11, and interconnected thereto by. axially extending walls 110, 111 and 112, the space -between the central anchor part 10 and the sleeve 11 is thus divided into an upper space 113 and a lower space 113a. As can be seen from Fig. 16a, the central one 111 of the three axial walls is itself divided into two parts 111a, 111b, in a similar way to the corresponding structure in Figs. 11 to 13.

Fig. 16b then shows a transverse sectional view of the mount of Fig. 16a, along the line A-A intersecting space 113. A section along the line B-B intersecting the space. 113a would be substantially the same. Fig. 16b shows that the space 113 is divided into four chambers 114, 115, 116 and 117 by axially extending walls 118, 119, 120 and 121 spaced 901 apart around the central anchor part 10. There is a similar division of space 113a. Fig. 16b also shows a passageway 122 interconnecting chambers 114 and 116.

Consider now vibration along the plane defined by arrows C to C in Fig. 16b. If the central anchor part 10 -30 moves downwardly and to the right relative to the sleeve 11 in Fig. 16b, the volume of chamber 116 decreases, and the volume of chamber 114 increases. Although chambers and 117 deform, their volumes should not change.

Then, fluid moves from chamber 116 to 114 through the passageway 122, and that fluid morement through an elongate passageway causes damping. If the movement of the central anchor part 10 relative to the sleeve 11 is upwardly and to the left in Fig. 16b, then the opposite volume changes occur in chambers 114 and 116, and again damping occurs due to movement of fluid through the passageway 112.

For such vibrations, chambers 115, 117 are not affected, and indeed those chambers could be filled with air. Then, chambers corresponding to chambers 115, 117 but in space 114 could be filled with fluid and interconnected by.a passageway 123. This passageway is shown in Fig. 16a and Fig. 16c. In.such an arrangement, the chambers in space 113a corresponding to chambers 114, 116 would also be filled with air. Then, if the plane of vibration is perpendicular to arrows C to C then it is the chambers in space 113a corresponding to chambers 115 and 116 in Fig. 1,6b that change in volume and damping occurs due to fluid movement through the passageway 123.

This direction of movement is in the plane D to D in Fig.

16c.

In such an arrangement, radial damping in one.direction is determined by fluid movement in the upper half of the mount in Fig. 16a, and damping in the mutually perpendicular radial direction is determined by fluid movement in the lower half of the mount. It would also be possible to have an arrangement in which each half of the mount provides damping in two mutually perpendicular directions. In such an arrangement, all four chambers 114, 115, 116 and 117 in Fig. 16b, would be f illed with f luid, and there would then have to be a passageway (not shown) interconnected chambers 115 and 117. That passageway would not have to intersect passageway 112, and this may make such an arrangement more difficult to manufacture. It is, however, possible by suitable arrangement of the passageways. Then, the corresponding four chambers in space 113a would similarly be interconnected by two passageways. Thus, the space 113 would provide two different radially damping modes, as would the space 113a.

In this embodiment, there is no interconnection between the spaces 113 and 113a so that axial damping does not occur. Thus, this embodiment has two radial modes of damping but no axial mode, unlike the first to sixth embodiments described previously.

Claims

Claims:

1 A hydraulically damped mounting device having a first anchor part; a second anchor part in the f orm of a hollow sleeve containing the f irst anchor part, such that the f irst anchor part extends axially of the sleeve; first and second resilient walls interconnecting the first and second anchor parts, the first and second resilient walls being spaced apart so as to define an enclosed space within the sleeve extending circumferentially around the first anchor part and axially bounded by the first and second resilient walls; and first and second axial walls, each extending axially between the first and second resilient walls at circumferentially spaced locations, so as to divide the enclosed space into first and second chambers for hydraulic fluid; and a passageway interconnecting the first and second chambers for flow of hydraulic fluid there through; wherein the resilient walls are such that the resilient wall on one side of a radial plane of the mount has a different shape from the resilient wall on the other side of said radial plane such that the resilient walls are not mirror images of each other when reflected about a radial plane of the mounting device.

2. A mounting device according to claim 1, wherein each of -33said resilient walls is of different lengths at different radial positions, such that at one axial end of said mounting device a shorter part of the first resilient wall bounds said first chamber and a longer part of the first resilient wall bounds said second chamber, and at the other axial end of said mounting device a longer part of the second resilient wall bounds the first chamber and a shorter part of said second resilient wall bounds said second chamber.

3. A mounting device according to claim 1 or claim 2, wherein the device has more than two of said chambers and the chambers are arranged to deform differently under different radial vibrations.

4. A mounting device according to claim 3, wherein the first and second chambers are each, divided into two parts by a respective axially extending wall, with each part of one chamber connected by a passageway to the opposite part of the other chamber.

5. A mounting device according to claim 4, wherein the passageways have different lengths and/or cross sections.

6. A hydraulically damped mounting device substantially as herein described with reference to and as illustrated in Figs. 6 and 7, or Figs. 14a to 14d, of the accompanying drawings.