GB2193553A

GB2193553A - Vibration absorbing mountings

Info

Publication number: GB2193553A
Application number: GB08715716A
Authority: GB
Inventors: Peter Thomas Court
Original assignee: BTR PLC
Current assignee: BTR PLC
Priority date: 1986-07-08
Filing date: 1987-07-03
Publication date: 1988-02-10
Also published as: GB8715716D0; GB8616572D0

Abstract

A rubber/hydraulic vibration absorbing mounting (10) for a shaft bearing, particularly for a vehicle propellor shaft, comprises outer and inner members (12 and 14) between which liquid-filled segmental chambers (32-37) are provided. The chambers are separated by rubber partition members (24-29) and communication is established between chambers via annular passages (e.g. 71), formed in the outer member between a rigid intermediate sleeve (43) and an outer casing (62), the annular passage communicating with respective chambers through apertures (57, 58) formed in the intermediate sleeve. <IMAGE>

Description

SPECIFICATION Vibration absorbing mountings This invention relates to vibration absorbing mountings, and particularly, but not exclusively, to vibration absorbing mountings for shaft bearings.

A propellor shaft for a front-engined rear wheel driven motor car may be supported on a vehicle body in a central bearing. This may comprise a bearing having an inner race fitted around the propellor shaft and an outer race mounted, usually in a rubber-lined bush, on the body of the vehicle. Whilst a rubber lining has been found to provide reasonably good insulating properties to reduce the transmission of propellor shaft vibrations to the vehicle body, this known device has limitations to its vibration-insulating qualities and for certain applications,particularly for high-quality cars in which great efforts are made to reduce noise and vibration,a better form of mounting has been sought.

According to the invention, a vibration absorbing mounting comprises coaxial inner and outer annular members having an annular space therebetween arranged to contain a liquid, a plurality of imperforate flexible partition members being arranged to extend between the inner and outer annular members to divide the annular space into a plurality of separate segmental chambers, at least two of said chambers being inter-connected to permit liquid to flow from one of said chambers to the other in order to accommodate relative movement of the inner and outer members in a radial direction relative to the axis of the mounting, wherein the outer member comprises an outer casing and a rigid intermediate sleeve extending around the partition members and side flanges to form said chambers between the partition members, apertures being formed in the sleeve to provide communication between chambers via an annular passage provided between the sleeve and the outer casing.

Preferably, the flexible partition members are of rubber (the term "rubber" includes natural and synthetic elastomeric materials) and extend generally radially between the inner and outer members providing a required radial stiffness normally to hold the inner member coaxially within the outer member whilst having sufficient elastic compliance to permit relative radial movements of the inner and outer members to absorb vibrations of a vibrating component carried either by the inner or the outer member.

In a preferred form, the mounting in accordance with the invention comprises an inner member having a rubber lining moulded integrally with radially-extending rubber partition members and side flanges. A rigid intermediate sleeve extends in fluid-tight engagement around the partition members and side flanges to form closed chambers between the partition members, and apertures are formed in the sleeve to provide communication between diametrically opposite chambers via an annular passage provided between the sleeve and an outer casing.The outer surface of the sleeve may contain grooves, or annular ribs may be provided within the spaces between the sleeve and the outer casing, so as to provide a plurality of separate annular passages, and the apertures are formed in the sleeve in appropriate positions to enable separate pairs of chambers to be put in communication via the annular passages.

Two embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a radial cross-section on the line I-I of Figure 2 through a vibration absorbing mounting in accordance with the invention; Figure 2 is an axial section on the line ll-ll of Figure 1; Figure 3 is an axial section on the line Ill-Ill of Figure 1; Figure 4 is a side view of an intermediate sleeve forming part of the mounting shown in Figures 1-3; Figure 5 is a similar view to Figure 1, taken on the line V-V of Figure 6, showing an alternative vibration absorbing mounting in accordance with the invention; Figure 6 is an axial section on the line VI-VI of Figure 5, and Figure 7 is an axial section on the line VII VII of Figure 5.

The mounting 10 illustrated in Figures 1-4 is intended to support a rotatable propellor shaft connecting the gearbox of a front-engined motor car to the driven rear axle. An outer member 12 is arranged to be fastened by a U-shaped clamp or other means (not shown) to the bodywork of the car, and an inner member 14 is arranged to support a ball bearing assembly (not shown) which encircles and rotatably supports the propellor shaft (also not shown).

The inner member 14 comprises a steel tube 15 having an integral flange 16 and formed with holes 17 to assist in the moulding and subsequent retention of a rubber lining 18 formed on the tube 15 and covering its radially outer, and part of its radially inner, surface. On the inner side of the tube, the portion 19 of the lining 18 forms a cushioned seating for the ball bearing, and on the radially outer side of the tube 10 it is formed as a continuous moulding which covers the radially outer surface of the tube 15 and extends to form integral side flanges 20, 21 (see Figure 3) and six radially extending imperforate partition members 24 to 29.

The lining 18 forms a cylindrical wall which seals the inner boundaries of six segmental chambers 32 -37 formed between the succes sive partition members 24 to 29, the side flanges 20, 21 forming side walls which seal the axial ends of the segmental chambers.

The radially outer edges 40 of the partition members are rounded and are compressed in engagement with the inner surface 42 of a rigid (steel) intermediate sleeve 43 which forms part of the outer member 12.

Sealing of the joints between the side flanges 20, 21 and the intermediate sleeve 43 is effected by the provision of rebated edges 46, 47 on the side flanges 20, 21 respectively to receive the sleeve 43, an axial compressive loading being provided by annular side plates 49, 50 which are secured by six rivets 52 passing axially through holes in side plates 49, 50 and corresponding openings 53 formed axially through the respective partition members 24-29.

The intermediate sleeve 43 is formed, as shown in Figure 4, with pairs of apertures 55, 56; 57, 58; 59, 60. The outer member 12 also comprises a cylindrical outer casing 62 having a pair of side flanges 63, 64 and internal annular ribs 65, 66. The outer casing 62 fits closely around the intermediate sleeve 43, thus providing three separate annular passages 70, 71 and 72 around the circumference of the mounting 10. The side joints between the intermediate sleeve 43 and the outer casing 62 are also sealed by the rebated outer edges 46, 47 of the side flanges 20, 21 under the axial compressive loading from the side plates 49, 50.

Apertures 57 and 58 establish communication between the segmental chambers 34 and 37 (as shown in Figure 1) via the annular passage 7 1 as shown in Figure 3. Similarly, apertures 59 and 60 establish communication between segmental chambers 32 and 35 via the annular passage 72, and apertures 55 and 56 establish communication between segmen tal chambers 33 and 36 via the annular passage 70.

On assembly of the mounting 10- the segmental chambers and the three annular passages are filled with ethylene glycol.

In operation, the propeller shaft supported by the mounting 10 may vibrate or be subject to transverse shocks which need to be absorbed by the mounting to avoid transmission of noise or vibration to the vehicle body.

When the shaft moves transversely it tends to reduce the volume of at least one of the segmental chambers 32-37 and this causes liquid to flow from each compressed chamber to the diametrically opposite chamber via the respective annular passage or passages.

The annular passages are each arranged to have a smaller cross-sectional area than that of the associated segmental chambers, and this results in the velocity of the liquid flowing through the passages being greater than the velocity of liquid flow in the chambers themselves. Consequently, the effective mass of the liquid contained in the passages is increased (when considering its effect on the resonant frequency of the system).

Cushioning of shocks and vibrations is achieved by movement of the propellor shaft transversely within the mounting, deforming the opposed segmental chambers and causing the flow of liquid from one side to the other.

By suitable choice of the stiffnesses of the partition members and the side flanges, and the areas of the chambers and their connecting passages the resonant frequency and thus the cushioning characteristics of the system can be tailored to suit particular applications.

In alternative constructions other numbers of segmental chambers may be provided, normally at least four but preferably six or more.

Odd numbers of chambers may be provided and communication does not necessarily need to be between opposite chambers : for some applications the connecting passages may link adjacent chambers.

The partition members may be of uniform thickness, extending radially as illustrated, or may be of arcuate cross-section to provide enhanced fatigue resistance, or of wedgeshaped cross-section to provide rising stiffness characteristics, or of other forms as may be required for particular applications. Similarly the rubber side flanges may be designed to be of suitable thickness for particular requirements.

The mounting 110 illustrated in Figures 5-7 comprises an outer member 112 and an inner member 114 which are functionally similar to the outer member 12 and the inner member 14 of the embodiment shown in Figures 1-4.

The inner member 114 comprises a steel tube 115 having an integral crimped flange 116 and formed with holes 117, a rubber lining 118 being provided. The lining 118 extends to form integral side flanges 120 and 121 and six radially extending imperforate partition members 124 to 129.

Six segmental chambers 132-137 are thus formed as in the embodiment described above, and the radially outer edges 140 of the partition members are rounded and compressed in engagement with the inner surface 142 of a steel intermediate sleeve 143 which forms part of the outer member 112. It will be noted that the partition members 124-129 are of arcuate cross-section, providing improved flexibility.

The side flanges 120, 121 of the rubber moulding have rebated edges 146, 147 to receive the intermediate sleeve 143 and annular side plates (not shown) are arranged to be secured by six rivets 152, passing axially through the holes in the side plates and corresponding openings 153 formed axially through the partition members 124-129.

The intermediate sleeve 143 is formed with pairs of apertures (not shown) providing com munication between pairs of the chambers 132 to 137 with respective grooves 170, 171 and 172 formed in the outer periphery of the intermediate sleeve 143.

The grooves 170, 171 and 172 thus constitute three separate annular passages which provide communication between opposite segmental chambers as in the embodiment previously described, an outer casing 162 fitting closely around the intermediate sleeve 143 to define the outer wall of the passages.

The segmental chambers 132-137 and annular passages 170-172 are fIlled with ethy lene glycol and the operation of the mounting 110 is similar to that of the mounting 10 described above; the use of communicating passages of smaller cross section as shown in Figures 6 and 7 provides a greater damping effect than the larger passages shown in Figures 2 and 3, and this effect is also enhanced by the smaller apertures which are provided to communicate with the segmental chambers.

The embodiment of Figures 5-7 has improved durability by virtue of the curved partition walls which reduce the stress in the rubber on deflection, and is more economically manufactured since the machining of the grooves 170-172 in the outer surface of the intermediate sleeve 143 is readily accomplished.

Advantages of the mounting designs illustrated include the provision of communicating channels of easily predetermined and maintained dimensions, the thin walls of the partition members and side members providing low static stiffness, giving good high frequency insulation and avoiding the need for pre-compression of the rubber components which tends to worsen the high-frequency insulation properties. Also, the mechanical structure securing together the rubber and metal components is particularly effective against leakage of the liquid contained in the mounting.

Claims

1. A vibration absorbing mounting comprising coaxial inner and outer annular members having an annular space therebetween arranged to contain a liquid, a plurality of imperforate flexible partition members being arranged to extend between the inner and outer annular members to divide the annular space into a plurality of separate segmental chambers, at least two of said chambers being interconnected to permit liquid to flow from one of said chambers to the other in order to accommodate relative movement of the inner and outer members in a radial direction relative to the axis of the mounting, wherein the outer member comprises an outer casing and a rigid intermediate sleeve extending around the partition members and side flanges to form said chambers between the partition members, apertures being formed in the sleeve to provide communication between chambers via an annular passage provided between the sleeve and the outer casing.

2. A vibration absorbing mounting according to Claim 1 wherein annular ribs are provided within the spaces between the sleeve and the outer casing so as to provide a plurality of separate annular passages, and apertures are formed in the sleeve in appropriate positions to enable separate pairs of chambers to be put in communication via the annular passages.

3. A vibration absorbing mounting according to Claim 1 wherein the outer periphery of the intermediate sleeve is provided with grooves to constitute annular passages to provide communication between chambers.

4. A vibration absorbing mounting according to any of Claims 1-3 wherein the flexible partition members are of rubber and extend generally radially between the inner and outer members, providing a required radial stiffness normally to hold the inner member coaxially within the outer member whilst having sufficient elastic compliance to permit relative radial movements of the inner and outer members to absorb vibration.

5. A vibration absorbing mounting according to any of Claims 1-4 wherein the inner member has a rubber lining moulded integrally with radially-extending rubber partition members and side flanges.

6. A vibration absorbing mounting according to Claim 5 wherein the side flanges of the rubber lining are rebated to receive the intermediate sleeve, and side plates provided to apply an axial compressive load to assist in sealing the joints between the side flanges and the intermediate sleeve.

7. A vibration absorbing mounting according to any of Claims 1-6 wherein the flexible partition members are of arcuate cross-section.

8. A vibration absorbing mounting according to any of Claims 1-7 wherein said communication is provided between diametrically opposite chambers.

9. A vibration absorbing mounting according to any of Claims 1-8 wherein the inner member is arranged to support a rotatable shaft.

10. A vibration absorbing mounting according to Claim 9 wherein the inner member is arranged to support a propellor shaft of a motor vehicle and the outer member is arranged to be secured to the vehicle body.

11. A vibration absorbing mounting constructed and arranged substantially as described in the accompanying Description and illustrated in Figures 1-4 or Figures 5-7 of the accompanying drawings.