WO2008128833A1

WO2008128833A1 - Device for compensating thermally induced axial relative displacements

Info

Publication number: WO2008128833A1
Application number: PCT/EP2008/053270
Authority: WO
Inventors: Tomas Smetana; Thorsten Biermann
Original assignee: Schaeffler Kg
Priority date: 2007-04-21
Filing date: 2008-03-19
Publication date: 2008-10-30
Also published as: DE102007018929A1

Abstract

The invention relates to a device for compensating thermally induced axial relative displacements between two components having two compensating parts (12, 18), which convert a thermally induced radial movement of the effective surfaces (15, 40) into an axial temperature-compensating movement of at least one compensating part (18) via the cooperating effective surfaces (15, 40). In order to impart a comparatively large thermal compensation capacity upon the device with a very small axial spatial requirement, and using simple means, a compensating part (18) comprising a drive element (22) having a higher thermal expansion coefficient than the compensating part (18) is coupled such that the drive element (22) applies the thermally induced geometric changes thereof onto the compensating part while increasing the radial movement thereof.

Description

Device for compensation of thermally induced axial

relative displacements

description

Field of the invention

The invention relates to a device for compensating for thermally induced relative axial displacements between two components with two compensating parts which convert a thermally induced relative radial movement of the active surfaces in an axial temperature compensating movement of at least one compensating part on cooperating active surfaces.

In devices or machines whose individual components consist of materials with different thermal expansion (different temperature coefficients) occurs at varying operating temperatures, a different relative change in length of the components. This phenomenon is undesirable or even unacceptable, especially in high-speed machines or arrangements in which a precise storage is required - such as motor vehicle differentials or transfer cases. Thus, in a motor vehicle transmission, the gearbox housing is generally made in aluminum diecasting and the gearbox shafts are made of steel and mounted by means of an engaged cone roller bearing. Here, the approximately twice as high thermal expansion of the aluminum housing in comparison to the steel shafts significantly noticeable and changes the set preload or the set clearance of the tapered roller bearing. This leads to a significantly reduced bearing life, at worst to an axial Wei- and not ideal meshing with appropriate noise.

To compensate for these effects, devices have been proposed in which the outer ring of the tapered roller bearing is supported on the machine or transmission housing via a thermal expansion compensation ring (US Pat. No. 5,028,152). The thermal expansion compensating ring is made of a material - e.g. the elastomer marketed under the trade name VITON® by Dupont - with a significantly higher temperature coefficient than the components subjected to thermal fluctuations. The thermal expansion compensating ring transmits the required axial prestressing to the bearing outer ring and is thus exposed to a considerable mechanical load leading to a long-term unstable setting behavior.

Since the thus achievable axial compensation lengths are relatively low, DE 42 21 802 A1 proposes a compensation device in which two concentric Wärmedehnungsausgleichsringe be serially connected in a mounting ring with a partial longitudinal section approximately S-shaped in shape.

Another approach followed by the aforementioned generic and known from DE 41 18 933 A1 known device. This consists of at least two balancing parts, of which the first is guided with a conical sliding surface in a corresponding recess of the second compensating part. The first balancing part is made of aluminum and has a higher temperature coefficient than the second balancing part made of steel. The two balancing parts are used directly to produce a temperature-compensating axial displacement for maintaining the prestressing of a tapered roller bearing by the first expansion part in the radial direction significantly more expands as the second and over the cooperating conical sliding surfaces causes axial movement of at least one of the compensation parts with increasing temperature. Although this arrangement is relatively robust and durable, as can be found in contrast to the aforementioned devices compensating metal parts use. However, only a comparatively small temperature-compensating axial movement of the compensating part can be realized with this known device with limited axial space. Therefore, it is proposed in DE 41 18 933 A1, if appropriate, to arrange further such balancing parts in series. But this increases the need for - in many applications very limited - axial space and increases the cost of manufacturing costs.

Against this background, an object of the present invention is to provide a device for the compensation of thermally induced axial relative displacements between two components, which compensates for a very small axial space requirement by simple means comparatively large thermally induced relative changes in length between two components.

This object is achieved by a device with the features of claim 1.

Accordingly, in the device according to the invention, at least one compensation part is provided with a drive element which has a higher coefficient of thermal expansion than the compensation part. The drive element acts as a kind of reinforcing element and amplifies the radial movement - that is, the expansion or contraction of the compensating part in the radial direction - the compensating part beyond the movement of the compensating part, which is in any case due to the thermal and temperature-coefficient behavior. If, for example, the compensation part is designed as a steel or aluminum ring, the mechanical coupling with the drive element causes an additional Radialbewegungs- component with temperature change, which is based solely on the elongation / contraction of the drive element and causes an elastic radial springing of the compensating part and thus its active surface. A first advantage of the invention is that with very simple and few additional components compared to the state of the art significantly less expensive compensation even comparatively large relative changes in length between components is realized. Another advantage of the invention is that these properties are ensured long-term stability even at high operating loads, because the mechanically loaded parts (balancing parts) in their material selection can be optimized independently of the responsible for the compensation movement drive element. The mechanically highly loaded compensating parts can thus consist of inexpensive and robust materials such as steel, while the drive element is made of a material with a much higher temperature coefficient.

In order to allow an even greater material expansion or contraction substantially in the radial direction of the compensating part, a preferred embodiment of the invention provides that the compensating part has at its periphery a separation point which has an increased radial mechanical Auffederungsbzw. Contractility causes. Thus, the compensating part can experience orders of magnitude larger radial expansions than the compensating part known from the initially mentioned DE 41 18 933 A1 in the form of a metal disc.

Preferably, the separation point can be formed by telescoping ends of the compensation part. Thus, irrespective of the expansion or contraction state, it is ensured with particularly simple means that the compensation part always has an outwardly closed shape.

With regard to the production costs and production technology preferred is an embodiment of the invention, according to which the separation point is formed by a slot. In the simplest case, an axial material recess may be provided, so that the compensation part can expand mechanically resiliently radially under enlargement of the slot and vice versa while reducing the slot is radially compressible. This embodiment has an off elastic material existing compensating part the further advantage that this with radial bias - can be mounted - for example in a housing bore.

A particularly simple embodiment of the drive element provides that this is designed annular. The drive element can be accommodated in particular in likewise annularly shaped compensation parts of this. In this respect, a particularly advantageous variant of the invention provides that the compensation part is hollow and filled with a material forming the drive element. Particularly preferably, the advantageously hollow ring-shaped compensating part can be produced by corresponding folding, for example a steel strip, and filled with the material of the drive element. In terms of manufacturing technology, the drive element can also be formed only by solidification or connection, for example polymerization, of the material introduced into the cavity of the compensating part.

According to a mechanically particularly advantageous embodiment of the invention, it is provided that the drive element is axially slotted and is supported with its slot boundary surfaces on a counterpart. The counterpart may preferably be formed as an integral part of a holding element on which the drive element is applied. According to a further advantageous embodiment of the invention, the holding element holds the balancing parts together to form a structural unit.

The counterpart may be according to a preferred variant of the invention, a piston which is mounted in the compensating part.

With regard to the above-mentioned decoupled possibility of optimization of the materials for the compensation parts on the one hand and the drive element on the other hand provides an advantageous embodiment of the inventions that the drive element made of plastic, eg VITON® consists. Further advantages and aspects of the invention will become apparent or supplementary from the following description of the invention with reference to the drawings.

Show:

1 shows a first embodiment of the invention in longitudinal section,

FIG. 2 is an exploded view of essential elements of the device according to the invention, and the arrangement of the elements in the region of a separation point is greatly enlarged;

Figure 3 shows a second embodiment of a device according to the invention in longitudinal section and

Figure 4 in an exploded view of essential elements of the device of Figure 3 and greatly enlarged representation of these elements in the region of a separation point.

The devices shown in the figures are used for example to ensure or maintain a set bearing clearance or a bearing preload for a tapered roller bearing, in particular in a differential or a transmission of a motor vehicle.

As Figure 1 shows, the device acts on a so-called X-arrangement tapered roller bearing 1 on the outer ring 2 a. The outer ring 2 is received in a bore 3 of an aluminum die-cast housing 4. A bearing cage 5 holds spaced a plurality of tapered rollers 6. The tapered rollers roll on the tread 7 of the outer ring 2 and on the running surface 8 of the bearing inner ring 9 from. The inner ring 9 is pressed onto one end 10 of a gear shaft 11. With the aid of the device according to the invention relative position changes in the axial direction A between the housing 4 on the one hand and the shaft 11 on the other hand compensated insofar that, if necessary, on the outer ring 2 a corresponding, the bias voltage ensuring axial force F is exercised. The thermally induced relative displacements are explained in detail as explained in the beginning on their different temperature coefficients and their design dependent on their amount.

The device comprises a first compensating part 12 with a conical bore 14. The cone forms a first active surface or sliding surface 15. The compensating part 12 is made of steel and is therefore mechanically highly loadable and inexpensive to produce. The device comprises a second compensating part 18, which in this embodiment is configured as a compensating ring and made of a multiply bent steel disc. Of course, however, other cross sections for the compensation part 18 can be selected. The compensation part 18 has a circumferential cavity 19, which is filled with a plastic material 20 - for example an elastomer. The plastic can already be prefabricated in a corresponding ring shape or first filled into the cavity 19 and then by suitable manufacturing methods - for example, a heat treatment - obtained in the balancing part of its solid form.

The material 20 forms a ring 21 (drive ring) whose temperature coefficient is material-related by a multiple greater than the temperature coefficient of the compensation part 18. The ring 21 thereby forms a drive element 22. Under drive element is in the context of the present invention, a component to understand the Reinforcement of the radial expansion or radial contraction of the compensating part 18 is used. As can be seen from FIG. 1 and subsequently also from FIG. 2, the compensation part 18 completely surrounds the drive element 22, so that there is a close mechanical coupling here. When the temperature rises, the drive element 22 expands significantly more than the compensation part 18, with the result that it imparts its radial extent to the compensation part 18. This would basically be complete circumferential compensating part 18 possible. Particularly preferably, the compensation part 18 has an axially extending slot or a recess 24. As a result, the compensation part 18 can spring up mechanically much more strongly - driven by the drive element - than it would allow the material elasticity of the compensation part 18 alone.

The slot 24 forms a defined separation point 25 in the compensation part 18. In the region of the separation point 25, a steel piece is received in the form of a circular segment, which forms a piston 26. In its outer contour, the piston 26 is matched to the inner contour 28 of the cavity 19 and thus displaceably mounted in the compensation part 18 along the circumference.

Details of this arrangement are shown more clearly in FIG. 2, in which the compensation element 18, also referred to as inner ring, with the separation point 25 (slot 24) is shown. Alternatively, the open ends 30, 31 of the split-off compensation part 18 can also engage in one another in the manner of a telescope and thus form a closed shape in the circumferential direction U.

In the exploded view of FIG. 2, shown outside the compensation part 18, there is the drive ring 21, which acts as a drive element 22 in the previously described manner. Furthermore, the first compensating part 12 can be seen, which forms an outer ring insofar. The plastic ring 21 also has at its periphery a recess or a slot 32 into which the piston 26 is inserted. As shown in particular in the lower part of Figure 2 greatly enlarged partially illustrated region of the separation point 25, the slot 32 of the drive member 22 is filled by the piston 26. The drive element is supported with its slot boundary surfaces 35, 36 on the corresponding end faces 37, 38 of the piston 26. This construction has the advantage that a significantly increased radial mobility of the compensating part 18 is realized by the slot 24, without the drive element 22 being exposed to unwanted external influences due to the slit 24, which changes its width according to its operation. With an expansion of the drive element 22 due to temperature increase or a contraction due to temperature reduction, the compensation part 18 is forcibly imposed on the radial expansion or contraction of the drive member 22, ie, the compensation member 18 is moved radially accordingly. It slides with the formed on its outside, the first drive element 12 facing active surface 40 having a corresponding cone angle δ, on the corresponding active surface 15 of the first equalizer 12. This results in a significant increase in length ΔH the device length H.

For clarification, the essential design parameters are shown in FIG. The change in length ΔH is calculated according to the formula AT

Where:

H: initial length of the device

D _m0 : effective diameter of the compensating part 18 or of the drive element 22 α: temperature coefficient of the material 20

ΔT: temperature difference between the initial state and the compensation state δ: half angle of the conical cone of the active surface 15 or 40

The axial displacement .DELTA.H which can be compensated in this way is measured using typical bearing geometries and a drive element made of VITON®

D _m o = 55 mm δ = 45 ° 0 ( _V i _TON = 15 ° 10 ^"5" K ^"1

ΔT = 100 ° C too ΔH = 1, 24 mm.

It can thus be seen that extremely small relative axial displacements can be compensated for with an extremely small axial space requirement with the device according to the invention. In this case, a significant advantage is that the drive element is made of a material optimized with regard to the temperature coefficient, which has 30 to 45 times higher thermal expansion compared to steel. By contrast, the compensating parts which are mechanically stressed during operation are produced from a material (for example steel) optimized in terms of manufacturing technology and material strength.

With regard to the sliding angle δ or the conical cone angle, care must be taken that no self-locking occurs. Assuming a coefficient of friction of μ = 0.1, the condition tan δ> μ results in a limit value δ> 4, 17 °.

This also shows that a very space-saving temperature compensation is possible with the device according to the invention.

Figures 3 and 4 show a further device according to the invention, wherein already described in the figure 1, functionally identical components are provided with the same reference numerals. The exemplary embodiment according to FIGS. 3 and 4 differs from the exemplary embodiment according to FIGS. 1 and 2 essentially in that the second compensation part 48 (inner part) is designed as a partially open steel molded part which has an approximately V-shaped cross-section. The first compensating part 65 (outer part) is designed substantially like that shown in FIG. In the opening 49 formed by the V, a drive element 52 is inserted in the form of an elastomeric ring. On its outer side 53, the compensation part 48 is matched with an effective surface 54 on the cone angle or the orientation of the active surface 15 of the compensating part 65. The active surfaces or sliding surfaces 15, 54 act as before described together so that the drive element 52 acts as a drive device which causes an axial displacement when the temperature increases.

The compensation part 48 has a slot or a recess 55 through which, as already described, the radial deformability of the compensation part 48 is extended far beyond its thermal or material-elastic limits. In addition, a holding element 58 is provided, which has a piston 59 as an integral part. The piston 59 penetrates into a slot 60 of the drive element 52 in such a way that the slot boundary surfaces 62, 63 are supported on the piston 59 (FIG. 4). The first compensating part 65 covers the drive element 52 from the other side. The compensating part 48, which is also referred to as an inner ring, is designed as a steel part and has the advantage, due to the radial spring property imparted by the slot 55, under bias into the bore 3 of the housing 4 (FIG. Figure 3) can be used.

The steel piston 59 also prevents here that the material of the drive element 52 evades due to thermal expansion. When the device heats or cools, the space occupied by the plastic of the drive element 52 changes considerably in the radial direction, which leads to the desired greater expansion or, on cooling, contraction of the compensation part 48. Particularly advantageously, holding element 58 can additionally hold together the compensating parts and drive element 52 as structural unit 72 via an engagement 70 in lateral surface 71 of compensating part 65. This is easier to handle and mount; In addition, so the material of the drive member 52 in either radial direction in the region of the slot (filled by the piston 59) dodge. Bezugszeicheniiste

1 tapered roller bearing

2 outer ring

3 hole

4 die-cast aluminum housing

5 bearing cage

Roll 6 cones

7 Tread of the outer ring

8 Tread of the inner ring

9 bearing inner ring

10 End of the gear shaft

11 gear shaft

12 first compensation part

14 conical bore

15 effective area

18 second compensation part

19 circumferential cavity

20 plastic material

21 ring

22 drive element

24 recess

25 separation point

26 pistons

28 inner contour of the compensating part 18

30, 31 open ends of the compensating part 18

32 recess / slot

35, 36 slot interfaces

37, 38 end faces of the piston 26th

40 effective area

48 compensation part

49 opening 52 drive element

53, 54 outside

55 slot, recess

58 compensation part

59 pistons

60 slot

62, 63 slit interfaces

65 compensation part

70 intervention

71 lateral surface

72 unit

F axial force

A axial direction

U circumferential direction

Claims

claims

1. A device for the compensation of thermally induced relative axial displacements between two components with two balancing parts (12, 18), the cooperating active surfaces (15, 40) a thermally induced relative radial movement of the active surfaces (15, 40) in an axial temperature-compensating movement at least implement a compensating part (18), characterized in that a compensating part (18) with a drive element (22) having a higher coefficient of thermal expansion than the compensating part (18) is coupled in such a way that the drive element (22) its thermally induced changes in geometry Balancing part under reinforcement of its radial movement.

2. Device according to claim 1, characterized in that the compensation part (18) on the circumference of a separation point (25) which causes an increased radial Auffederungs- or contractility of the compensating part (18).

3. A device according to claim 2, characterized in that the separating point (25) is formed by telescoping ends of the compensating part.

4. Apparatus according to claim 2, characterized in that the separation point (25) is formed by a slot (24).

5. Apparatus according to claim 1, 2 or 3, characterized in that the drive element (22) is annular.

6. Device according to one of the preceding claims, characterized in that the Anthebselement (22) is received by the compensating part (18).

7. Apparatus according to claim 6, characterized in that the compensation part (18) is hollow and filled with a drive element (22) forming material (20).

8. Device according to one of the preceding claims, character- ized in that the drive element (22) is axially slotted and with its slot boundary surfaces (35, 36) on a counterpart (26) is supported.

9. Device according to claim 8, characterized in that the counterpart (59) is an integral part of a holding element (58) on which the drive element (48) rests.

10. The device according to claim 9, characterized in that the holding element (58) the compensating parts (65, 48) together to form a construction unit (72) holds together.

11. The device according to claim 8, characterized in that the counterpart is a piston (26) which is mounted in the compensating part.

12. Device according to one of the preceding claims, characterized in that the drive element (22) consists of plastic.