Supporting bearing

A supporting bearing for resiliently supporting parts to be connected to one another, such as the body and rear axle housing of a motor vehicle, includes two bearing parts to be arranged on mutually opposite bearing surfaces of one part, coaxially to a bore traversing the latter. These bearing parts are each equipped with an annular elastomer element arranged between two supporting parts and can be clamped to the part in which the bore has been made using a clamping bolt traversing the bearing parts and the bore with radial clearance. The elastomer elements of the two bearing parts are, on the one hand, vulcanized to one of the supporting parts accommodating them between them and, on the other hand, rest on the other supporting part by an integrally formed surface region projecting at their free front face.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to a supporting bearing for resiliently supporting 
parts to be connected to one another, such as the body or rear axle 
support and rear axle gear unit of a motor vehicle. 
A supporting bearing of this type is known in which the supporting parts of 
the two bearing parts which rest against mutually opposite bearing 
surfaces of a crossmember of a vehicle body in order to support a rear 
axle gear unit, said bearing parts accommodating the cross-member between 
them, are of cup-like design. The clamping bolt, which also passes through 
the crossmember, being passed through the base of the bearing parts. 
With the aid of the clamping bolt, the rear axle gear unit is supported in 
a resiliently complaint manner on the crossmember in the axial direction 
of the bolt via the two bearing parts. 
In this arrangement, the annular elastomer element of each bearing part is 
vulcanized by flat front faces both to the base of the cup-like supporting 
part and to the flange of the pressure piece fitting over the latter, the 
pressure piece traversing with a neck with radial clearance the central 
opening of the elastomer element and the bore in the base of the 
associated supporting part and protruding into the crossmember bore. The 
annular elastomer element likewise has a radial clearance with respect to 
the wall of the vulcanized-on supporting part. 
The fabrication of this supporting bearing is complicated since supporting 
part and pressure piece are to be jointly vulcanized to the elastomer 
element, this being possible only with the aid of a correspondingly 
expensive vulcanizing mould. 
It is furthermore disadvantageous that the elastomer element must be highly 
prestressed in order to avoid one of its two bearing parts being able to 
lift off from its bearing surface of the part supporting the supporting 
bearing in the event of compressive loading of the supporting bearing. 
However, this cannot be avoided in the case of very high supporting forces 
because in this case, due to its connection to the flange of the 
associated pressure piece, established via the elastomer element, the 
cup-shaped supporting part of the relieved bearing part is lifted off, for 
example, from the crossmember, this causing troublesome knocks. It is also 
easily possible, if extreme supporting forces occur, that the collar of 
the supporting part will jump out of the crossmember bore, and this can 
lead to the collar tilting in the bore when this bearing part is loaded 
and the supporting part thereby being damaged or the entire bearing part 
no longer being able to return to its intended design position. 
The necessity of highly prestressing the supporting bearing is here to the 
detriment of bearing softness and at the expense of the desire acoustic 
decoupling, which can in any case only be achieved to an unsatisfactory 
degree due to the relatively large contact areas between the elastomer 
elements and the supporting parts and pressure pieces associated with 
them. 
The necessary axial prestressing of the elastomer elements, correspondingly 
hardening the supporting bearing and leading to a correspondingly steep 
characteristic, also lead to its inner and outer circumferential surfaces 
arching outwards. As a result, stress peaks occur in the elastomer 
material at the edge regions of the vulcanization faces, prejudicing their 
strength and ability to withstand sustained loading. 
Finally, the bonding of the elastomer elements at both front faces by 
vulcanization has the consequence that the supporting bearing is only 
unsatisfactorily fixed in the radial direction. 
An object on which the invention is based is to improve supporting bearings 
of the above-noted type in such a way that, in addition to a considerable 
simplification of their fabrication, a longer spring excursion, improving 
acoustic decoupling, is achieved and damaging overloading of the elastomer 
elements due to stress and a lifting off of the bearing part relieved 
during the occurrence of high supporting forces from its supporting 
surface are effectively prevented. 
These objects are achieved according to preferred embodiments of the 
invention by providing an arrangement wherein a clamping bolt is provided 
for clamping the two bearing parts together, said clamping bolt 
simultaneously receiving one of the parts to be connected and traversing 
the bore of the other part to be connected with radial clearance so as to 
mutually clamp the parts to be supported resiliently relative to one 
another, 
wherein a free front face of the elastomer element has a part-region which 
projects towards the front face facing it of one of the supporting part 
and the pressure piece to which it is not vulcanized and rests against 
said front face. 
With this bearing construction according to the invention, the elastomer 
elements of the two bearing parts are thus in each case now only 
vulcanized by one of their front faces to the supporting part or pressure 
piece. These parts are therefore separated from one another and, during 
bearing assembly, have only to be fitted together. This separate 
association offers the further advantage that, in the case of very 
powerful jolts, the pressure piece of the bearing part experiencing relief 
during this process can, if its elastomer element is vulcanized to the 
supporting part, lift off from the elastomer element and the supporting 
part can thus remain on its bearing surface. A similar result is obtained 
if the elastomer element is vulcanized to the pressure piece. In this 
case, it is lifted off from the supporting part by the pressure piece. 
In the intended design position, the area of contact between the elastomer 
elements and the supporting part or pressure piece resting against the 
latter is here at a minimum, this guaranteeing optimum soundproofing; not 
least due to the possibility of designing the bearing surface of 
supporting part or pressure piece in such a way that the spring excursion 
is long and the prestressing force correspondingly small. This offers the 
particular advantage that, as the compressive loading of the supporting 
bearing increases, the spring progression over the spring excursion is 
initially gradual until, from a certain spring excursion, the supporting 
bearing is highly stiffened by correspondingly rising progression. This 
pronounced spring stiffness can replace a stop limiting the spring 
excursion, with the advantage that it does not reach its maximum value 
abruptly, rather it reaches it continuously but rapidly and noise 
generation is thereby prevented. This progression of the spring 
characteristic arises from the increasingly larger bearing surface during 
axial loading of the bearing, under compressive stress the supporting part 
or pressure piece rolling against the elastomer element, its free front 
face portion gradually decreasing as a result. This relative movement of 
the surfaces resting against one another due to corresponding extension of 
the elastomer element produces friction and hence simultaneously vibration 
damping. 
Furthermore, the arrangement of the invention also result in greater radial 
hardness of the supporting bearing, producing, under the influence of 
inertial forces, a better fixing of the supporting bearing. 
In addition to the above-mentioned construction, from which the invention 
starts, a supporting bearing in accordance with German Published 
Unexamined Patent Application (DE-OS) 3,106,690 is already known, the 
construction of the two bearing parts of which is similar to that of the 
supporting bearing according to the invention. Their annular elastomer 
elements are, however, of conical design, having, due to their larger 
diameter, radially projecting part-regions which rest in bearing recesses 
formed in the beam. 
Further, German Published Examined Patent Application (DE-AS) 1,163,165, in 
FIG. 6, discloses a supporting bearing which has two annular rubber spring 
elements which are supported opposite to one another against an 
intermediate piece and are of conical design at their front faces. The 
front faces which face away from each other taper conically inwards, these 
front faces thus each having an axially projecting outer part-region which 
rests against a counter-surface. However, here the intermediate piece does 
not form one of two parts to be supported resiliently relative to one 
another. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
According to FIG. 1, the known construction of a supporting bearing 10 of 
the generic type has an upper and a lower bearing part 12 and 14 which are 
fixed on opposite sides of a beam, for example a transverse tie-bar 16 
fixed to the body of a passenger vehicle, for supporting a rear axle gear 
unit provided underneath the transverse tie-bar 16. The only part of the 
rear axle gear unit which is shown is a mounting lug 17, which is 
traversed by the shank of a clamping bolt 18 of the supporting bearing 10. 
The clamping bolt 18 extends through the transverse tie-bar 16 and also 
through the two bearing parts 12 and 14. 
Screwed onto the clamping bolt 18 is a clamp nut 20, which is supported 
against the mounting lug 17 and clamps the mounting lug 17 to the 
supporting bearing 10 and the supporting bearing 10 to the transverse 
tie-bar 16. The two bearing parts 12 and 14 are of symmetrical 
construction. Bearing parts 12 and 14 each have a cup-shaped supporting 
part 22 which engages by a collar 24, formed integrally at the center, in 
a bore 26 traversing the transverse tie-bar 16 and rests with its base 28 
against the transverse tie-bar 16. 
Assigned coaxially to this cup-shaped supporting part 22 is a pressure 
piece 30 which fits over the supporting part 22 with a flange 32. Arranged 
between the base 28 of the supporting part 22 and the flange 32 of the 
pressure piece 30 is an annular elastomer element 34, preferably 
consisting of rubber, which is vulcanized with its front faces both to the 
base 28 and to the flange 32. The pressure piece 30 has a neck 36 which is 
traversed by the shank of the clamping bolt 18 and the outside diameter of 
which neck 36 is smaller than the inside diameter of elastomer element 34 
and bore 26 or collar 24. 
In the installed condition of the supporting bearing 10, the necks 36 of 
the pressure pieces 30 rest against one another by their front faces, the 
two elastomer elements 34 thereby receiving a defined prestress. This 
prestress is to be chosen so that, even in the case of large axial 
supporting forces, the cup-like supporting parts 22 of the bearing parts 
12 and 14, which then become relieved, cannot be lifted off from the 
bearing surface of the transverse tie-bar 16. However, this leads to a 
bearing hardness which correspondingly reduces the desired acoustic 
decoupling. 
Despite the given prestress of the elastomer element 34, it is not possible 
in the case of extremely strong supporting forces, when the pressure piece 
30 of, for example, the upper bearing part 12 is lifted off, to prevent 
the cup-shaped supporting part 22 from also being lifted off from its 
bearing surface of the transverse tie-bar 16 by the elastomer element 34 
vulcanized to the flange 32 and to the supporting part 22, and its collar 
24 from being possibly pulled out of the transverse tie-bar bore 26, as 
can be seen from FIG. 2. There is then the possibility, particularly in 
the case of a simultaneous radial loading of the supporting bearing, that 
the collar 24 will tilt on the transverse tie-bar 16 and as a result will 
no longer be able to return into its intended design position. However, in 
all cases, troublesome noises in the form of knocks occur in the event of 
such axial displacements of the supporting part 22. In addition, during 
such axial displacements the elastomer element 34 of the stressed bearing 
part 12 or 14 is highly compressed, with the result that the elastomer 
material at the outer and inner circumference arches outwards, damaging 
stress peaks occurring at the edges of the vulcanization faces. 
In the supporting bearing according t the invention, in accordance with 
FIG. 3, the elastomer element 38, which preferably likewise consists of 
rubber, is only vulcanized to the base 40 of the cup-shaped supporting 
part 42. The flange 44 of the pressure piece 46, on the other hand, rests 
on the elastomer element 38. The flange 44 rests against elastomer element 
38 only at a projecting part-region 48 at a front face facing the flange 
44. This projecting part-region 48 is integrally formed in the manner of a 
torus in the transitional region of the front face 49 facing the pressure 
piece 46 and of the inner circumferential surface 50 of the elastomer 
element 38 and rests against a mating surface portion 52 of the pressure 
piece 46 of concave crosssection. The portion 52 is situated in the 
transitional region between the inner front face 54 and the neck 56 
integrally formed on the flange 44. The elastomer element 38 is also 
vulcanized to the inner circumference of a collar 58 of the supporting 
part 42. A similar collar is shown in phantom on the pressure piece 
according to another embodiment. The advantage is thereby obtained that 
dirt and water cannot be deposited between the supporting part 42 and the 
elastomer element 38, which could lead to corrosion on the supporting part 
42. In addition, damage to the elastomer element 38 cannot be ruled out 
under the action of dirt. The outside diameter of the necks 56 of the 
pressure pieces 46 of both bearing parts 60 and 62 is slightly greater 
than the inside diameter of the toroidal part-region 48 of the associated 
elastomer element 38, with the result that, when the supporting bearing is 
installed in the corresponding elastomer element 38, the pressure pieces 
46 are radially fixed. 
Similarly to the known bearing construction, the outside diameter of the 
neck 56 is considerably smaller than the inside diameter of the 
crossmember bore 26 and the collar 64 of the supporting parts 42 engaging 
in the latter. 
As FIG. 4 shows, the pressure piece 46, which is displaced, for example 
upwards, in the event of extreme axial forces, can be displaced 
independently of the elastomer element 38 and, given appropriate 
dimensioning of the projection of part-region 48 of the elastomer element 
38, may also lift off from the elastomer element 38. The position of the 
supporting part 42 concerned remains unaffected by this axial movement. 
Troublesome noise generation is thus excluded in the case of such axial 
loads. 
However, the bearing construction offers the considerable advantage that, 
given appropriate bearing design, lifting off can be reliably prevented by 
an appropriate choice of prestressing path. This means identical spring 
characteristics during compression and rebound, given the same 
configuration of the two bearing parts 60 and 62, the progression of one 
bearing part thus theoretically preventing lifting off of the elastomer 
element 38 of the relieved bearing part, with the result that a stop can 
be dispensed with. 
In the case of two bearing parts 60 and 62 of different configuration, on 
the other hand, the progression of the harder bearing part has already 
started at a point in time at which the spring excursion of the other 
bearing part has not yet been produced, with the result that lifting off 
of the pressure piece 46 of the relieved bearing part is not possible. 
As indicated by chain lines in FIG. 4, the axial extension of the toroidal 
part-region 48 is dimensioned in such a way that the elastomer element 38 
is always guaranteed to rest against the associated pressure piece 46 even 
in the case of the maximum possible lifting path of the bearing parts 60 
or 62. 
Under compressive loading of the elastomer element 38, the flange 44 of the 
corresponding pressure piece 46 rolls against the elastomer element 38, 
the free front face part 49' gradually decreasing. The elastomer element 
38 simultaneously arches radially inwards and downwards at the inner 
circumferential region into the annular space 68 present between the 
collar 64 and the neck 56. Initially, the deformation of the elastomer 
element 38 which thus takes place produces a gently rising characteristic 
of the supporting bearing or of its two bearing parts 60 or 62 and, with 
increasing reduction of the free surface area of the loaded bearing part 
60 or 62, produces a highly progressive characteristic. The rolling of the 
front face 54 of the flange against the front face part 49' of the 
elastomer element 38 also causes friction at the outer circumference of 
the neck 56, this simultaneously having a vibration-damping effect. 
The toroidal part-region 48 of the elastomer element 38 can also be 
provided in a different radial region according to other contemplated 
embodiments. Embodiments are also contemplated with varying of the shape 
of the spring characteristic in accordance with the intended applications 
of the supporting bearing by appropriate positioning of the inner front 
face 54 relative to the elastomer element 34. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.