GB2370338A

GB2370338A - A resilient bush for connecting parts of vehicle frames and sub-frames

Info

Publication number: GB2370338A
Application number: GB0128492A
Authority: GB
Inventors: Ian Nicholson; Trevor Howard Johnson; David John Ledwitch
Original assignee: Avon Vibration Management Systems Ltd
Current assignee: Avon Vibration Management Systems Ltd
Priority date: 2000-12-21
Filing date: 2001-11-28
Publication date: 2002-06-26
Anticipated expiration: 2021-11-28
Also published as: GB0128492D0; GB2370338B; DE10162999A1; GB0031260D0

Abstract

A bush for use in vehicle manufacture, that allows for a reduced pull-out load, to enable the whole bush to detach from the housing and thus preventing excessive deformation of the vehicle body when subjected to a large force. A lower pull-out load is achieved by forming the angle between the shoulder 22 of the lug 23 of the bush and the outer body 21 to 40 degrees or less. Alternatively, making the shape of the lug shoulder convex or concave with respect to the main body of the lug, results in a reduction of the pull-out load. In addition, making the shoulder 12 of the corresponding housing of the bush 11 convex or concave, with respect to the lug of the bush, also reduces the pull-out load.

Description

Bush This invention relates to bushes for connecting parts of an assembly

to each other. It is particularly, but not exclusively, related to bushes for connecting 5 parts of car frames and sub-frames to each other.

A typical bush of the type currently used in such applications is shown in Figure 1 of the corresponding drawings. It comprises an injection moulded outer body 2 bonded directly to the rubber sleeve 3. This rubber 10 sleeve is bonded to an inner metal core 1, which is normally steel, but may be other metals, for example aluminium. The bush is generally cylindrically symmetric about a central axis.

The advantage of using a nylon or plastics material 15 for the outer body 2 is known in that there is no requirement for any corrosion protection, and also that the bush can be inserted directly into the sub-frame without a need for post moulding contraction. This contraction is traditionally performed in order to remove 20 post-moulding stresses in the rubber sleeve 3 caused by cooling and shrinking of the rubber sleeve 3. If these stresses are not removed then the durability of the bush is greatly reduced. When a nylon or plastics outer body

2 is used, this contraction is achieved when the bush is inserted into the sub-frame.

When designing bushes, consideration must be given to the force required to insert the bush into the sub 5 frame (push-in load). The push-in load should not be too great as this will cause the assembly process to take longer, and also may result in damage to the outer body 2 during insertion.

In the bush of Figure 1, the push-in load is 10 determined by the shape of the outer body 2 relative to the sub-frame assembly into which the bush will be inserted. This is shown in more detail in Figure 2 of the accompanying drawings. Figure 2 shows the bush of Figure 1 mounted in a sub-frame assembly 10. As can be 15 seen from that figure, the outer body 2 of the bush has a main section 21 of generally uniform cross-section forming a cylinder co-axial with the rubber 3 and metal core 1. That central section 21 terminates in lugs 23 at each axial end, the lugs 23 forming a shoulder 22 which 20 abuts against a corresponding shoulder 12 of the sub-

frame 10. The part 11 of the sub-frame assembly 10 between the shoulders 12 rests on the main section 22 of the outer body 2.

The shape and size of the lugs 23, and in particular the shape of the shoulder 22 determines the push-in load.

In the known arrangements, the surface of the shoulder 22, and the surface of the shoulder 12, are both inclined S at 45 degrees to the axis of the bush. The resulting construction has been found to have a suitable push-in load when the bush is pushed into the sub-frame assembly 10, and to resist the bush coming out of that sub-frame assembly 10 once inserted.

10 However, due to changing requirements, consideration has been given to permitting the bush to Come out of the sub-frame assembly 10 under appropriate conditions. For example, in a vehicle crash, it may be preferable for the bush (to which the vehicle body is attached) to be able 15 to move relative to the sub-frame assembly to prevent excessive deformation of the vehicle body.

Therefore, consideration has been given to the force which will cause the bush to pop out of the subframe (the push-out load). In the known arrangements, described 20 above, the push-out load was sufficiently large that the bush would not push out under even the extreme forces encountered in a crash, but that the present invention seeks to provide a bush which the push-out load is smaller. Of course, the push-out load should not be too

small. During normal vehicle operating conditions, the bush should stay securely in place in the sub-frame, functioning normally. Thus, the pushout load needs to be accurately determined and within tight tolerances.

S The present invention, in its various aspects, therefore seeks to modify the known bush to provide suitable push-

out loads.

In bushes of the type described above, with reference to Figures 1 and 2, the push-out load arises 10 due to friction forces (such as those acting between the shoulder 22 of the outer body 2 of the bush (normally made of nylon or plastics material), between the lugs 23 and the main section 21 of the bush, and the corresponding shoulder 12 in the sub-frame assembly 10, 15 and between the main section 21 of the bush and the retaining portion 11 of sub-frame 10) and from the force needed to compress one of the lugs 23 of the bush so that it will pass through the retaining portion 11 of the sub-

frame assembly. In the bushes currently available, the 20 shoulder 22 is manufactured to be at an angle of 45 degrees, within a tolerance of, for example, 0.5 degrees, relative to the central axis of the bush.

According to a first aspect of the present invention, there is provided a bush comprising an

s injection moulded outer body, bonded to an inner metal core, via a rubber sleeve, said outer body having a projecting lug to retain the bush in a housing, and said lug having a shoulder connecting it to the main section 5 of the outer body, wherein the shoulder between the main section of the outer body and the interior lug of the outer is at an average angle of 40 degrees or less relative to the central axis of the bush.

By reducing the angle of the shoulder of the lug, 10 the push-out load is reduced, and can be chosen so that the bush separates from the sub-frame when it is subject to a force (in that direction) greater than the pushout load, for example in a car crash or other violent impact.

However, it is desirable that the push-out load is not 15 reduced to such an extent that the bush and sub-frame will separate when under forces that are experienced during normal motion or operation. Consequently it is preferable that the average angle of the shoulder is not less than 10 degrees.

20 Normally the shoulder of the sub-frame assembly is sloped so that it conforms with the corresponding shoulder of the lug, but this need not always be the case.

It can be noted that the bush of Figure 2 has lugs 23 at each end of the outer body 2. This may well be true in the present invention, in which case there will be two projecting lugs. However, since it is desirable 5 for push-out to occur in a preferred direction, the present invention may involve only one lug of the desired shape. In Figure 2 as described above, the bush shown has shoulders that are sharply defined. However, it is 10 usual, for production tool purposes, for bushes to be manufactured so that the shoulder(s) are blended with the main face of the lug and of the main section. This means that whilst the face of the shoulder may be substantially flat, there will be a curved portion at either end.

15 Further adjustments to the push-out load can be achieved by altering other dimensions of the interior luff of the bush.

Thus, it is preferable for the diameter of the portion of the bush forming the interior lug to be at the 20 most 120% of the diameter of the portion of the bush which does not form a lug, excluding any shoulder section between. Since if these two diameters were equal, the lug would not exist, the diameter of the portion of the bush forming the interior lug must be at least 101% of

that of a portion of the bush which does not form a lug, excluding any shoulder section between.

Reducing the diameter, or thickness, of the lug makes it easier for the lug to be compressed so that it 5 can pass through the retaining portion of the sub-frame assembly and so separate from the sub-frame assembly.

Consequently the push-out load is lower.

It is also preferable that the length of the projecting lug, not including any shoulder portion, is 10 not less then 5%, and not more than 20%, of the overall length of the bush.

Reducing the length of the interior lug has two effects on the separation of the bush and the sub-frame assembly. Firstly it means that there is less of the lug 15 to pass through the retaining portion of the sub-frame assembly before the two parts are separated. This means that separation will occur quicker for a given force.

Secondly, it means that there is less of the bush in friction contact with the retaining portion of the sub 20 frame assembly when the bush is passing through, thus reducing the push-out load.

In the prior art, and also in the first aspect of

the present invention, the shoulders of the interior lugs are substantially straight, although blended with the

main face of the lug and of the main section. However, by making the shoulder section curved, the area in contact with the corresponding shoulder of the sub-frame assembly can be reduced, thereby adjusting the push-out 5 load.

Thus, according to a second aspect of the present invention, there is provided a bush comprising an injection moulded outer body, bonded to an inner metal core, via a rubber sleeve, said outer body having a 10 projecting lug to retain the bush in a housing, and said lug having a shoulder connecting it to the main section of the outer body, wherein the central part of the shoulder between the main section of the outer body and the remainder of the lug is convex with respect to the 15 remainder of the lug. That central part of the shoulder being up to 90% of the shoulder, e.g. 80% of the shoulder. According to a third aspect of the present invention, there is provided a bush comprising an 20 injection moulded outer body, bonded to an inner metal core, via a rubber sleeve, said outer body having a projecting lug to retain the bush in a housing, and said lug having a shoulder connecting it to the main section of the outer body, wherein the central part of the

shoulder between the main section of the outer body and the remainder of the lug is concave with respect to the remainder of the lug. That central part of the shoulder being up to 90% of the shoulder, e.g. 80% of the 5 shoulder.

Preferably in these latter two aspects, the corresponding shoulder of the sub-frame assembly is kept substantially straight, or in the case of the convex shoulder, possibly curved in the opposite direction (so 10 that it does not match the shoulder of the bush), which would further adjust the push-out load.

Similar effects can be achieved by altering the shape of the shoulder of the sub-frame assembly rather than the shoulder of the lug, directly corresponding to 15 the second and third aspects of the invention above and in these cases, the corresponding shoulder of the lug is kept substantially straight, and can even be at the 45 degree angle of the prior art.

Thus, according to a fourth aspect of the present 20 invention, there is provided a bush and a corresponding housing (normally being a sub-frame assembly), into which the bush is to be inserted. The bush comprises an injection moulded outer body, bonded to an inner metal core, via a rubber sleeve, said outer body having a

projecting lug to retain the bush in a housing, and said lug having a shoulder connecting it to the main section of the outer body. The corresponding housing also has a shoulder, and the central part of the shoulder of the 5 housing is concave with respect to the lug. That central part of the shoulder being up to 90% of the shoulder, e.g. 80% of the shoulder.

According to a fifth aspect of the present invention, there is provided a bush and a corresponding 10 housing (normally being a sub-frame assembly), into which the bush is to be inserted. The bush comprises an injection moulded outer body, bonded to an inner metal core, via a rubber sleeve! said outer body having a projecting lug to retain the bush in a housing, and said 15 lug having a shoulder connecting it to the main section of the outer body. The corresponding housing also has a shoulder, and the central part of the shoulder of the housing is convex with respect to the lug. That central part of the shoulder being up to 90% of the shoulder, 20 e.g. 80% of the shoulder.

Since it will still be necessary, for production tool purposes, for the shoulder of either the bush or the sub-frame assembly to be blended to the other sections of the outer body or sub-frame assembly, it is not normally

possible for the whole of either shoulder to be convex or concave. Arrangements combining any or all of the features of the above aspects are envisaged and form part of the 5 present invention.

Embodiments of the present invention will be described in more detail, with reference to the drawings, in which: Figure 1 is a typical bush, and has already been 10 described; Figure 2 is a typical mounting of a bush in a sub-

frame assembly, and has already been described; Figure 3 is a schematic of an outer body of a bush, being an embodiment of the present invention, showing the 15 relevant dimensions; Figure 4 is an outer body of a bush according to the present invention, showing the blending of the shoulder; Figure 5 is an outer body of a bush showing a convex shoulder according to the second aspect of the present 20 invention; and Figure 6 is an outer body of a bush showing a concave shoulder according to the third aspect of the present invention.

In the embodiments of the bush of the present invention that will now be described, the general configuration of the bush similar to that of Figures l and 2. Thus, the bush has an inner metal core which is 5 connected to a outer body via a rubber sleeve. The outer body is then inserted into a sub-frame assembly. With the exception of the shaping of the mating surfaces of the outer body and of the sub-frame assembly, embodiments of the present invention may be the same as known bushes 10 and thus the detailed construction of the rubber sleeve and metal core will not be described in farther detail.

They may be, for example, identical to that shown in Figure 2.

In order to understand the changes to the known bush 15 envisaged by the embodiments of the present invention, consideration must be given to the various dimensions of the components. These are illustrated in more detail in Figure 3, which shows a schematic of an outer body 2.

The outer body 2 is defined by dimensions Dl, D2, 20 D3, Ll, L2, L3 and angle O. Dl is the diameter of the inside of outer body 2 (alternatively the diameter of the outside of rubber sleeve 3, not shown in Figure 3), as measured in a radial direction across the central axis of the cylindrical bush, D2 is the diameter of the outside

of the main section 21 of outer body 2 and D3 is the diameter of the outside of the lug 23. L2 is the overall length of the bush, measured in a longitudinal direction and L1 is the length of lug 23, not including shoulder 5 22. is the angle that shoulder 22 makes with the lug 23 and the main section 21 of the outer body 2. Several embodiments of the present invention can then be illustrated using Figure 3.

A first embodiment according to the first aspect of 10 the present invention is when shoulder 22 of lug 23 is at an angle O which is less than 40 degrees. Preferably is also greater than 10 degrees to ensure that push-out does not occur during ordinary motion.

A second embodiment according to the first aspect of 15 the present invention is when lug 23 also has a thickness, as determined by the ratio of D3 and D2 such that D3 is 101% to 120% of D2.

A third embodiment according to the first aspect of the present invention is when, in addition, the length of 20 lug 23 (L1) is 5% to 20% of the overall length of the bush (L2).

Figure 4 shows an outer body 2 of a bush which may be any of the above embodiments, with the shoulder 22 blended to the lug 23 and the main section 21 by curves R

and R2. Such blending is necessary for production tool purposes, and would normally be much smaller than illustrated in Figure 4.

Figure 5 shows a fourth embodiment of an outer body 5 2 of a bush according to the second aspect of the present invention. Shoulder 22 is curved in a convex manner (with respect to the interior end of the bush), in this case a uniform curve with radius of curvature R5. It still necessary for the ends of the shoulder 22 to be 10 blended to the lug 23 and the main section 21 of the outer body 2, although such blending is not visible in Figure 5.

Figure 6 shows a fifth embodiment of an outer body 2 of a bush according to the third aspect of the present 15 invention. Shoulder 23 is curved in a concave manner (with respect to the interior end of the bush), in this case a uniform curve with radius of curvature R6. Again, it is still necessary for the ends of the shoulder 22 to be blended to the lug 23 and the main section 21 of the 20 outer body 2, although such blending is not visible in Figure 6.

Claims

Claims:

A bush comprising: an outer body bonded to an inner core via a rubber 5 sleeve, the outer body having a projecting lug to retain the bush in a housing; said lug having an inclined surface forming a shoulder between the rest of the lug and the main section of the outer body; 10 Wherein at least the central part of the shoulder is at an angle of 40 degrees or less, to the central axis of the bush.

2. A bush according to claim 1, wherein said angle is not less than 10 degrees.

3. A bush according to claims 1 and 2, wherein the central part of the shoulder of the lug comprises up to 90% of said shoulder.

A bush comprising: an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in a housing;

said lug having an inclined surface forming a shoulder between the rest of the lug and the main section of the outer body; wherein the central part of said shoulder, between 5 the main section of the outer body, and the remainder of said lug is convex with respect to the remainder of the lug. A bush comprising: 10 an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in a housing) said lug having an inclined surface forming a shoulder between the rest of the lug and the main section 15 of the outer body; wherein the central part of said shoulder, between the main section of the outer body, and the remainder of said lug is concave with respect to the remainder of the lug. 6. A bush according to claim 4 or claim 5, wherein the central part of the shoulder of the lug comprises up to 90% of said shoulder.

25 7. A bush according to any one of the preceding claims, wherein there are two projecting lugs.

8. A bush according to any one of the preceding claims, wherein the projecting lugs are positioned at opposite ends of the outer body of said bush.

9. A bush according to any one of the preceding claims, wherein central part of the shoulder of the lug is blended to the lug and to the main section of the lug in a curved manner.

10. A bush according to any one of the preceding claims, wherein the diameter of the outside of the lug is up to 120% of the diameter of the outside of the main section of the outer body.

A bush according to any one of the preceding claims, wherein the axial length of the projecting lug, not including any shoulder portion, is not less than 5% of the overall axial length of the bush.

12. A bush according to any one of the preceding claims, wherein the axial length of the projecting lug, not including any shoulder portion, is not greater than 20% of the overall axial length of the bush.

13. The combination of a bush according to any of the preceding claims and a housing into which the bush is inserted, wherein the housing has a shoulder or shoulders conforming of the shoulder or shoulders of the bush.

A combination according to claim 13, wherein the or each shoulder of the housing has a straight central part inclined to the axis of the bush.

10 15. A combination of a bush and a housing, into which the bush is inserted, comprising: an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in a housing) 15 said lug having an inclined surface forming a shoulder between the rest of the lug and the main section of the outer body; a corresponding inclined surface forming a shoulder between the outer edge of the housing and the main 20 section of said housing; wherein the central part of the shoulder of said housing is convex.

16. A combination of a bush and a housing, into which 25 the bush is inserted, comprising:

an outer body bonded to an inner core via a rubber sleeve, having a projecting lug to retain the bush in a housing; said lug having an inclined surface forming a 5 shoulder between the rest of the lug and the main section of the outer bodyi a corresponding inclined surface forming a shoulder between the outer edge of the housing and the main section of said housing; 10 wherein the central part of the shoulder of said housing is concave.

17. A combination according to claim 15 or claim 16, wherein the central part of the shoulder of said housing 15 comprises up to 90% of said shoulder.

18. A combination according to claim 15 or claim 16, wherein the shoulders of the projecting lugs of the bush are positioned so that they abut the shoulders of the 20 housing.

19. A combination according to any one of claims 15 to 18, wherein the shoulder of the lug of the bush is curved to conform to the curvature of the shoulder of the 25 housing.

20. A bush substantially as herein described with reference to and as illustrated by Figures 1 to 4 or Figure 5 or Figure 6 of the accompanying drawings.

All Amendments to the claims have been filed as follows 1. A bush comprising: an outer body bonded to an inner core via a rubber 5 sleeve, the outer body having a projecting lug to retain the bush in a housing) said lug having an inclined surface forming a shoulder between the rest of the lug and the main section of the outer body; 10 Wherein at least the central part of the sh-o-u l-der is at an angle of 40 degrees or less, to the central axis of the bush.

2. A bush according to claim 1, wherein said angle is 15 not less than 10 degrees.

3. A bush according to claims 1 and 2, wherein the central part of the shoulder of the lug comprises up to 90% of said shoulder.

4. A bush comprising: an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in a housing;

said lug having an inclined surface forming a shoulder between the rest of the lug and the main section of the outer bodyi wherein the central part of said shoulder, between 5 the main section of the outer body, and the remainder of said lug is convex with respect to the remainder of the lug. 5. A bush comprising: 10 an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in a housing; said lug having an inclined surface forming a shoulder between the rest of the lug and the main section 15 of the outer body wherein the central part of said shoulder, between the main section of the outer body, and the remainder of said lug is concave with respect to the remainder of the lug. 6. A bush according to claim 4 or claim 5, wherein the central part of the shoulder of the lug comprises up to 90% of said shoulder.

25 7. A bush according to any one of the preceding claims, wherein there are two projecting lugs.

8. A bush according to any one of the preceding claims, wherein the projecting lugs are positioned at opposite ends of the outer body of said bush.

9. A bush according to any one of the preceding claims, wherein central part of the shoulder of the lug is blended to the lug and to the main section of the lug in a curved manner.

10. A bush according to any one of the preceding claims, wherein the diameter of the outside of the lug is up to 120% of the diameter of the outside of the main section of the outer body.

11. A bush according to any one of the preceding claims, wherein the axial length of the projecting lug, not including any shoulder portion, is not less than 5% of the overall axial length of the bush.

12. A bush according to any one of the preceding claims, wherein the axial length of the projecting lug, not including any shoulder portion, is not greater than 20% of the overall axial length of the bush.

13. The combination of a bush according to any of the preceding claims and a housing into which the bush is inserted, wherein the housing has a shoulder or shoulders conforming of the shoulder or shoulders of the bush.

14. A combination according to claim 13, wherein the or each shoulder of the housing has a straight central part inclined to the axis of the bush.

10 15. A combination of a bush and a housing, into which the bush is inserted; the bush having an outer body bonded to an inner core via a rubber sleeve, the outer body having a projecting lug to retain the bush in the housing, said 15 lug having an inclined surface forming a shoulder between , the rest of the lug and the main section of the outer .. body; and (:: the housing having a corresponding inclined surface forming a shoulder between the outer edge of the housing . 20 and the main section of said housing; At: wherein the central part of the shoulder of said housing is convex.

16. A combination of a bush and a housing, into which 25 the bush is inserted;

the bush having an outer body bonded to an inner core via a rubber sleeve, having a projecting lug to retain the bush in the housing, said lug having an inclined surface forming a shoulder between the rest of 5 the lug and the main section of the outer body; the housing having a corresponding inclined surface forming a shoulder between the outer edge of the housing and the main section of said housing) wherein the central part of the shoulder of said 10 housing is concave.

17. A combination according to claim 15 or claim 16, wherein the central part of the shoulder of said housing comprises up to 90% of said shoulder.

t i c colic 18. A combination according to claim 15 or claim 16, i<.< wherein the shoulders of the projecting lugs of the bush (,. are positioned so that they abut the shoulders of the housing. i i c ; 20

c. 19. A combination according to any one of claims 15 to 18, wherein the shoulder of the lug of the bush is curved to conform to the curvature of the shoulder of the housing.

2C 20. A bush substantially as herein described with reference to and as illustrated by Figures 3 and 4 or Figure 5 or Figure 6 of the accompanying drawings.

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