GB2402184A

GB2402184A - Bush made from bearing foil

Info

Publication number: GB2402184A
Application number: GB0410690A
Authority: GB
Inventors: Lucchetti Werner; Wilhelm Maik
Original assignee: Federal Mogul Wiesbaden GmbH
Current assignee: Federal Mogul Wiesbaden GmbH
Priority date: 2003-05-13
Filing date: 2004-05-13
Publication date: 2004-12-01
Anticipated expiration: 2024-05-13
Also published as: FR2858670A1; DE10322249A1; FR2858670B1; GB2402184B; DE10322249B4; GB0410690D0

Abstract

A bearing bush 6 which is produced from a bearing foil comprises a sliding surface and at least one collar 7 wherein the sliding surface is provided on the inner surface of the bush 6 and the at least one collar 7 is directed radially inwards. Preferably the bush 6 has a collar 7, at each end face 12, 13 and the bearing foil comprises a support fabric which is covered at least on one side by a sliding layer which preferably contains PTFE and at least one polymer that is resistant to high temperatures. The bush 6 preferably has an open butt joint 14 which makes an acute angle with the end faces 12, 13 of the bush 6. The bush 6 can be produced by providing a sheet-like blank or bearing foil which has a length which corresponds to the circumferential length of the finished bush 6, rolling up the blank to give a cylindrical bush 6, bending over the strip at the edge of the bush to form a collar 7 that is directed radially inwards.

Description

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1 24021 84 ! Bush produced from bearing foil

Description

The invention relates to a bush which is produced from a bearing foil having a sliding surface and is equipped with a collar.

The invention furthermore relates to a method for the production of a bush produced from bearing foil, namely a method in which the following method steps are provided: À provision of a sheet-like blank of bearing foil which has a length which corresponds substantially to the circumferential length of the finished bush; À rolling up of the blank to give a cylindrical bush;

À introduction of at least one collar by bending

over an annular strip at one edge of the bush.

The invention furthermore relates to the use of such a bush.

In the context of the present invention, bearing foil is understood as meaning a strip-like bearing material which can be shaped by hand and is composed of an expanded metal or preferably metallic fabric as a carrying or support body and a sliding layer applied to this carrying or support body. The sliding layer preferably contains plastics, in particular polytetrafluoroethylene (PTFE). In particular, bearing foils are to be understood as meaning bearing materials as described in German Laid-Open Applications DE 101 47 292 Al and DE 101 47 303 Al. As is evident from the present invention itself, however, it is also possible to use bearing foils having a similar shapeability since, in the context of the present invention, the shapeability of the bearing foils under discussion is the technical feature which is of primary importance.

Figure 1 shows, by way of example, an embodiment of a bearing foil. The bearing material shown schematically in cross-section in Figure 1 and denoted as a whole by 1 has a first filament system 3 and a second filament system 2 perpendicular thereto, the filament systems 2 and 3 being composed of metal wires and together forming the support fabric, i. e. the support body. On its top, this support fabric is provided with a sliding layer 4, the sliding layer 4, which preferably predominantly contains polytetrafluoroethylene, covering the support fabric on its surface on one side and projecting beyond said support fabric. The bottom which is opposite this, i.e. facing away from this, is partly provided with a sliding layer 5 which is composed of identical material and, in contrast to the sliding layer 4, does not cover the surface of the support fabric on the bottom, so that parts of the filament systems 3a, 2a and 3b form the outer bottom of the bearing material 1.

Bushes produced from bearing foil are used according to the prior art in particular for vehicle door hinges and are positioned between hinge hole and hinge spindle. In this way, good and easy mobility of the spindle in the hole is ensured.

However, suitable mounting with good sliding properties is required in a large number of applications in particular in the case of shafts.

The shaft is one of the most frequently used machine elements and is also used in vehicle construction and, in a special design, in engine construction, namely in the form of a crankshaft and a camshaft. In principle, shafts must be mounted in some way as moveable, i.e. revolving, components, this bearing on the one hand supporting the shaft but on the other hand allowing it the possibility of movement which it requires in order to perform its function.

According to the prior art, camshafts are

received and mounted directly in bearing saddles and bearing covers which were incorporated into the cast cylinder head, i.e. in its lower and upper housing halves, in the course of subsequent processing. The arrangement of bearing, roller bearings or sliding bearings is in principle dispensed with in the mounting of camshafts. Mounting of the camshaft in sliding bearing bushes or roller bearing is also not possible in principle since camshafts are shafts which do not permit annular bearings closed at their circumference to be pushed on over their free end. This is prevented by the cams which are arranged on the shaft and the dimensions of which are greater than the diameter of the required bearings. Theoretically, it would be possible to mount camshafts in bearing half-shells, but this is regarded as being too complicated. Exceptions are assembled camshafts which permit mounting by means of sliding bearing bushes or roller bearings but are too expensive for mass production.

Crankshafts on the other hand are mounted in two bearing half-shells which, during assembly of crankshafts in the crank case, are arranged in holders r, provided for this purpose in the upper and the lower halves of the crank case. The use of sliding bearing bushes is not possible since the crankshaft is a shaft bent at right angles and the bushes closed over their circumference cannot be pushed over the free ends of the crankshaft and positioned on the intended shaft sections. A problem exists which is similar to that already described above for the camshafts.

As in the case of the camshaft, expedient mounting, particularly from points of view of costs, can also be effected in the case of the crankshaft only by means of bearing shells. Alternatively, however, these shafts could also be mounted in a bush of bearing foil which can be shaped by hand. However, this leads to another set of problems. Since the suppliers are increasingly keen to provide their customers with complete modules, which have already been preassembled, for the final assembly, it is also desired with respect to the shafts to provide preassembled shafts, i.e. shafts which have already been provided with bearings.

In the case of shafts which are expediently mounted by means of bearing shells or bearings comprising bearing foil, as described above for camshaft and crankshaft, the problem of fixing loose bearing half-shells or bearings to the respective shaft therefore arises.

Against this background, it is the object of

the present invention to provide a bearing by means of which the disadvantages known from the prior art are overcome and by means of which in particular fixing of the bearings is permitted.

A further partial object of the present invention is to provide a method for the production of such a bearing.

A further partial object of the invention is to provide potential uses of such a bearing.

The first partial object is achieved by a bush which is produced from a bearing foil and is equipped with at least one collar, and which is characterized in that the sliding surface is provided on the inside of the bush and in that the at least one collar is a collar directed inwards.

By means of the at least one collar which is directed inwards, the bush according to the invention can easily be fixed to a shaft shoulder provided on the shaft for it.

The first partial object of the invention is thus achieved. It is possible to provide preassembled shafts, i.e. shafts which are already provided with bearings.

Embodiments of the bush in which the bush is equipped with a collar at each end face are advantageous. In this way, the bush is secured in both directions to prevent axial displacement.

Embodiments of the bush in which the bearing foil contains a support fabric which is covered at least on one side by a sliding layer are advantageous.

This ensures that at least one side of the bush has a completely closed sliding layer. This is then mounted facing the shaft, while the side which is not completely covered by sliding material is provided for holding, for example, in the bearing saddle or bearing cover.

Embodiments of the bush in which the sliding layer contains polytetrafluoroethylene (PTFE) are advantageous. Such a sliding layer is hardwearing, has a long service life and can be reworked if necessary. l 1.

Moreover, it has the necessary shapeability.

Embodiments of the bush in which the sliding layer also contains at least one polymer resistant to high temperatures in addition to polytetrafluoroethylene (PTFE) are advantageous.

Embodiments of the bush in which the bush has an open butt joint are advantageous. The bush inevitably requires an open butt joint for mounting on shafts which are bent at right angles or other shafts not accessible via their free ends. However, the butt joint should preferably not be closed after mounting since this complicates dismantling and is not necessary from technical points of view.

Embodiments of the bush in which the butt joint makes an acute angle with the end faces of the bush are advantageous, the acute angle preferably being greater than 50 and less than 80 . A butt joint is defined as the connecting point of the two short sides of the sheet which come to rest against one another when the blank is rolled up to give a cylindrical bush.

Since the bush is produced from easily shapeable bearing foil, it cannot be fixed by means of a press fit in the bearing. For this reason, the bush may migrate in the bearing hole, and it therefore cannot be ruled out that the butt joint will also come to lie in regions of high bearing load. Owing to the oblique design of the butt joint, i.e. an arrangement of the butt joint in such a way that it is not parallel to the bush axis but makes an acute angle with the end faces of the bush, the butt joint is distributed over the circumference of the bush in the circumferential direction. In this way, it is ensured that - if at all - at least only a section comes to rest in regions of l high bearing load.

The collar preferably has at least two slots extending in the radial direction. By means of the slots extending in the radial direction, a planar sliding surface without distortion is created on the inside of the collar since, for the formation of the slots in this region, material which would have led to waviness of the sliding surface and of the collar during shaping is removed. Depending on the diameter of the bush, it is advantageous also to provide a plurality of slots. Four to six slots have proved advantageous.

The slots preferably extend over the total width of the collar. This has the advantage that a planar sliding surface is created over the total radial width of the collar.

The slots are preferably closed. Closed slots have the advantage that a closed collar surface is created.

Closing of the slots can be achieved if the recesses, which are explained in association with the method, are appropriately formed so that the slots are closed on shaping.

Embodiments of the bush in which the at least one collar has an annular, closed collar surface are advantageous. If the collar is required or used for axial mounting, for example in the form of a butting ring, this is the advantageous embodiment of the bush since in this way optimum axial mounting can be ensured. However, this requires a blank cut to size in a very specific manner, as will be explained further

below in association with the description of the

figures. -\ 8

Embodiments of the bush in which the at least one collar has partly overlapping sections of bearing material are advantageous. This bush requires no blank cut to size in a very specific manner, as in the case of the embodiment described above, and this bush variant is therefore preferable from points of view of costs if no axial mounting via this at least one collar is required.

The second partial object, namely the provision of a method for the production of such a bearing, is achieved by a method in which the following method steps are provided: À provision of a sheet-like blank of bearing foil which has a length which corresponds substantially IS to the circumferential length of the finished bush; À rolling up of the blank to give a cylindrical bush;

À introduction of at least one collar by bending

over an annular strip at one edge of the bush; and which is characterized in that À the annular edge strip of the bush is bent inwards.

Embodiments of the method in which a sheet-like blank which has a width which substantially corresponds to the width of the finished bush together with the width of the at least one collar is provided are advantageous. In this way, the sheet shaped to give a bush need not be subsequently processed. A finished bush which has the desired dimensions is already present.

Embodiments of the method in which the sheet- like blank is cut to length from a bearing foil strip

I

are advantageous. This variant permits automated production in large quantities, it being possible to integrate the cutting to length of the sheet into the production process, and the starting material being stored on rolls.

Embodiments of the method in which a bearing foil strip which has a width which substantially corresponds to the width of the finished bush together with the width of the at least one collar is used are advantageous. Processing of the width of the sheet is therefore necessary neither before rolling up nor before cutting for length.

Embodiments of the method in which a sheet-like blank having a substantially parallelogram-shaped base form is provided are advantageous. This makes it possible to realize an oblique butt joint, as preferred, when rolling up the sheet to give a bush.

Embodiments of the method in which parts of the bearing foil are removed from the sheet-like blank at the ends of the longitudinal side on which a collar is provided are advantageous. This makes it possible to produce bushes in which the collar has an annular, closed collar surface. The advantages of these bushes has already been explained in detail above.

Embodiments of the method which is characterized in that recesses are provided in the bearing foil in the case of the sheet-like blank at the longitudinal side at which a collar is provided are advantageous. This likewise serves for the production of bushes in which the collar has an annular, closed collar surface.

Embodiments of the method in which the recesses in the bearing foil have a V-shape are advantageous.

The removal of bearing material at the longitudinal sides of the sheet serves in principle for removing excess material which is not required in the production of the collar and may even be a hindrance.

Embodiments of the method in which the production of the at least one collar is effected together with the mounting of the bush are advantageous. The bending over of the collar then simultaneously performs the function of fixing the bush. A collar which has already been produced and is directed inwards must in any case be opened once again for mounting.

Uses of the bush as a sliding bearing are advantageous.

Uses in which the bush is used as a sliding bearing for camshafts are advantageous. Together with the bush according to the invention, preassembled camshafts, i.e. camshafts equipped with bearings, can be provided.

Uses in which the bush is used as a sliding bearing for crankshafts are advantageous. The advantages are those described for the camshaft.

The use in which the bushes are used as sliding bearings for eccentric shafts of a variable valve drive as so-called auxiliary camshafts is also advantageous.

This particular use will be discussed below.

A possibility of optimizing the combustion process of a petrol engine consists in the use of a variable valve drive. In contrast to conventional valve drives in which both the stroke of the valve and the control times, i.e. the opening and closing times of the intake and exhaust valves, are predetermined as invariable parameters owing to the fact that the ) 11 mechanism of the valve drive is inflexible since it is not adjustable, these parameters influencing the combustion process and hence the fuel consumption can be varied to a lesser or greater extent by means of variable valve drives. The ideal solution would be a completely variable valve control which permits specially tailored values for the stroke and the control times for any desired operating point of the petrol engine.

Noticeable fuel savings can, however, also be achieved with only partly variable valve drives. Such a (ert4) valve drive is, for example, the VALVETRONIC valve drive of BMWas described in the Motortechnische Zeitung [Motor newspaper], year 2001, Issue 6, page 18.

In the case of this valve drive, the closing time of the intake valve and the intake valve stroke can be varied. This permits throttle-free and hence loss-free load control.

The mass of the mixture flowing into the combustion chamber during the intake process is thus not controlled, i.e. metered, by means of a throttle valve arranged in the intake tract as in the case of conventional petrol engines, but via the intake valve stroke and the duration of opening of the intake valve.

For this purpose, the valve drive is equipped with an eccentric shaft as an auxiliary camshaft. This eccentric shaft can be adjusted, i.e. rotated, by means of a drive via a screw, this rotation of the eccentric shaft producing a change in the valve stroke of the intake valve.

The eccentric shaft itself is mounted in the cylinder head between the two top camshafts. This

mounting is effected according to the prior art by I, t.

means of roller bearings, the mounting being formed specifically as follows. Incorporated into the cylinder head are bearing saddles into which first metal shells are inserted which form a half of the outer roller bearing ring. The metal shells generally have a lug which is received by a hole in the bearing saddle and by means of which the shell is secured to prevent rotation. As a result of this securing to prevent rotation, the outer ring consisting of a first and a second metal shell is prevented from migrating and one of the two butt joints, located opposite to which are the parting surfaces of the two metal shells, from coming to rest in a high-load region of the bearing.

The eccentric shaft, which has at least two thicker shaft shoulders for holding the bearing, is provided at these shaft shoulders with an annular band open on one side comprising needles running in a cage and serving as a roller body and is arranged in the already mounted first metal shells. A corresponding number of bearing covers is arranged together with second metal shells, which form the other half of the outer roller bearing ring opposite the bearing saddles and is screwed thereto. The two metal shells thus form the outer ring of the roller bearing, and the eccentric shaft itself forms the inner ring of the roller bearing, the needles serving as a roller body and running between metal shells and eccentric shaft.

Owing to the large number of components of which the roller bearings are composed, a predetermined bearing play is difficult to realize. On the one hand, the tolerances of the individual components are additive and, on the other hand, the number of joints between the components increases with an increasing al al number of components. The result is a bearing play which varies very greatly, is difficult to control and can therefore lead to undesired noises during operation of the valve drive.

Owing to the auxiliary cams of the eccentric shaft, sliding bearing bushes cannot be used since the bearing holders are not accessible via the free ends of the shaft. In the case of bearing shells, the necessary l fixing is lacking. On the other hand, the bush produced from bearing foil can readily be fixed on the bearing shoulder by means of its at least one collar which is directed inwards.

Below, the invention is explained in more detail with reference to four embodiments according to Figures 2a, 2b, 3, 4 and 5. Here: Fig. 1 schematically shows an embodiment of a bearing foil, Fig. 2a schematically shows, in a perspective view, a first embodiment of the bush, looking onto that side of the bush which is provided with a collar, Fig. 2b schematically shows, in a perspective view, the bush shown in Figure 2a, on that side of the bush which is not provided with a collar, Fig. 3 schematically shows a second embodiment of the bush in the assembled state, Fig. 4 schematically shows a sheet-like blank of a third embodiment of the bush, Fig. 5 schematically shows a sheet-like blank of a fourth embodiment of the bush, and Fig. 6 shows a perspective view of a flanged bush according to the fourth embodiment.

Figure 1 has already been explained in detail in association with the description of the prior art, in particular with the description of bearing foils.

Figures 2a and 2b schematically show a first embodiment of the bush 6. This bush 6 does not have a collar at its first end face 12 but only has a collar 7 which is arranged at the second end face 13. Figure 2a shows the bush 6 in a perspective view, looking onto that end face 13 of the bush 6 which is provided with a collar 7. Figure 2b shows the same bush 6 in a perspective view, looking onto the end face 12 of the bush 6 which does not have a collar.

The oblique butt joint 14 which makes an acute angle with both end faces 12, 13 is evident. By means of an oblique design of the butt joint 14, i. e. an arrangement of the butt joint 14 in such a way that it is not parallel to the bush axis but makes an acute angle with the end faces 12, 13 of the bush 6, the butt joint 14 is distributed over the circumference of the bush 6 in the circumferential direction. In this way, it is ensured that - if at all - at least only a section comes to rest in regions of high bearing load.

Figure 3 schematically shows a second embodiment of the bush 6 in the assembled state. The bush 6 is mounted on a shaft shoulder 11 of a shaft 9.

Said bush has two collars 7, 8 which are directed inwards and by means of which it is fixed on the shaft 9. It is thus secured to prevent axial displacement in both directions of the shaft axis 10.

Figure 4 schematically shows a sheet-like blank 15 of a third embodiment of the bush. The basic shape of the blank 15 is a parallelogram. An oblique butt joint of the bush to be produced is thus generated. The short sides of the blank 15 make, with the longitudinal sides 16', 16'', the future end faces of the bush, an acute angle 0, namely exactly the angle which the butt joint arranged on the circumference subsequently makes with the end faces. Parts 17a, 17b, 17c, 17d of the bearing material or of the blank 15 are removed (shown by means of a dashed line) at the ends of the longitudinal sides 16', 16''. This serves for producing a bush whose collar has an annular, closed collar surface, but at least no overlaps of bearing material in the collar region.

Figure 5 schematically shows the sheet-like blank 15 of a fourth embodiment of the bush, which corresponds substantially to Figure 4. In addition, V-shaped recesses 18a-d are provided in order to create an annular, closed collar surface after the edge has been turned over.

Figure 6 shows a perspective view of a bush 6 which has a radial bearing part 19 and a collar 7 which is directed inwards. The sliding surface is present in the interior of the bush, i.e. on the inside of the radial bearing part 19 and on the inside of the collar 7. The butt joint 14 extends into the region of the collar 7 and forms a slot 20' there. The V-shaped recesses 18a-d according to Figure 5 lead to further slots 20 after the collar 7 has been bent over. Owing to the design as a V-shape, the slots are closed after the edge region of the blank 15 has been bent over.

J

Reference numerals 1 Bearing material, bearing foil 2 Filament system 2a Part of the filament system 3 Filament system 3a Part of the filament system 3b Part of the filament system 4 Sliding layer 5 Sliding layer 6 Bush 7 First collar 8 Second collar 9 Shaft 10 Shaft axis 11 Shaft shoulder 12 First end face 13 Second end face 14 Butt joint 15 Blank 16' Longitudinal side 16'' Longitudinal side 17a Parts of the bearing foil 17b Parts of the bearing foil 17c Parts of the bearing foil 17d Parts of the bearing foil 18a Recess 18b Recess 18c Recess 18d Recess 20, 20' Slots Angle between butt joint and end face of the bush

Claims

Claims 1. Bush (6) which is produced from a bearing foil (1) having a

sliding surface and is equipped with at least one collar (7, 8), characterized in that the sliding surface is provided on the inside of the bush and in that the at least one collar (7, 8) is a collar (7, 8) which is directed inwards.
2. Bush (6) according to Claim 1, characterized in that the bush (6) is equipped with a collar (7, 8) at each end face (12, 13).
3. Bush (6) according to Claim 1 or 2, characterized in that the bearing foil (1) contains a support fabric which is covered at least on one side by a sliding layer (4).
4. Bush (6) according to Claim 3, characterized in that the sliding layer (4) contains polytetrafluoroethylene (PTFE).
5. Bush (6) according to Claim 4, characterized in that the sliding layer (4) also contains at least one polymer resistant to high temperatures in addition to polytetrafluoroethylene (PTFE).
6. Bush (6) according to any of the preceding Claims, characterized in that the bush (6) has an open butt joint (14).
7. Bush (6) according to Claim 6, characterized in that the butt joint (14) makes an acute angle with the end faces (12, 13) of the bush (6).
8. Bush (6) according to Claim 7, characterized in that the acute angle is greater than 50 and less than 80 .
9. Bush according to any of Claims 1 to 8, characterized in that the collar has at least two slots (20, 20') extending in the radial direction.
10. Bush according to Claim 9, characterized in that the slots (20) extend over the total width of the collar.
11. Bush according to Claim 9 or 10, characterized in that the slots (20) are closed.
12. Bush (6) according to any of the preceding Claims, characterized in that the at least one collar (7, 8) has an annular, closed collar surface.
13. Bush (6) according to any of Claims 1 to 12, I characterized in that the at least one collar (7, 8) has partly overlapping sections of bearing material (1) .
14. Method for the production of a bush (6) according to any of the preceding Claims, in which the following method steps are provided: À provision of a sheet-like blank (15) of bearing foil (1) which has a length which corresponds substantially to the circumferential length of the finished bush (6); À rolling up of the blank (15) to give a cylindrical bush;

À introduction of at least one collar (7, 8) by

bending over an annular strip at the edge of the bush; characterized in that À the annular edge strip of the bush is bent inwards.
15. Method according to Claim 14, characterized in that a sheet-like blank (15) is provided which has a width which substantially corresponds to the width of the finished bush (6) together with the width of the at least one collar (7, 8).
16. Method according to Claim 14 or 15, characterized in that the sheetlike blank (15) is cut to length from a bearing foil strip.
17. Method according to Claim 15, characterized in that a bearing foil strip is used which has a width which substantially corresponds to the width of the finished bush together with the width of the at least one collar.
18. Method according to any of Claims 14 to 17, characterized in that a sheet-like blank (15) having a substantially parallelogram-shaped base form is I provided.
19. Method according to any of Claims 14 to 18, characterized in that parts (17a, 17b, 17c, 17d) of the bearing foil (1) are removed from the sheet-like blank (15) at those ends of the longitudinal side (16', 16 ") at which a collar is provided.
20. Method according to any of Claims 14 to 19, characterized in that recesses (18a, lab, 18c, led) are provided in the bearing foil (1) in the sheet-like blank (15) at the longitudinal side (16', 16'') on which a collar is provided.
21. Method according to Claim 20, characterized in that the recesses (18a, lab, 18c, led) in the bearing foil (1) have a V-shape.
22. Method according to any of Claims 14 to 21, characterized in that the production of the at least one collar (7, 8) is effected together with the mounting of the bush (6).
23. Use of a bush (6) according to any of Claims 1 to 13 as a sliding bearing.
24. Use according to Claim 23, characterized in that the bush (6) is used as a sliding bearing for camshafts.
25. Use according to Claim 23, characterized in that the bush (6) is used as a sliding bearing for crankshafts.
26. Use according to Claim 23, characterized in that the bush (6) is used as a sliding bearing for auxiliary camshafts of a variable valve drive.