DE102010025371B4 - bearing arrangement - Google Patents

Abstract

Bearing arrangement comprising a housing, in which a shaft extends, wherein the housing has a greater coefficient of thermal expansion than the shaft, and a shaft bearing first bearing, which is rotatably connected via its outer ring to the housing and its inner ring with the shaft, and an axially spaced, the shaft bearing second rolling bearing, the second rolling bearing (7) via its inner ring (11) with a higher thermal expansion coefficient than the inner ring (11) having the component is connected, so that during operation of the bearing assembly (1 ) due to the thermal expansion of the component results in a radial expansion of the inner ring (11) of the second rolling bearing (7), characterized in that the component is a rotationally fixed to the housing (2) connected to the axial pin (8) and that the second rolling bearing ( 7) via its outer ring (9) with the shaft (3) and via its inner ring (11) with the A xialzapfen (8) is connected, wherein the axial pin (8) is formed of a light metal.

Description

Field of the invention

The invention relates to a bearing assembly comprising a housing, in which a shaft extends, wherein the housing has a larger coefficient of thermal expansion than the shaft, and a shaft bearing first bearing, the non-rotatably via its outer ring with the housing and its inner ring with the Shaft is connected, and an axially spaced, the shaft bearing second rolling bearing, the second roller bearing is connected via its inner ring with a higher thermal expansion coefficient than the inner ring having component, so that in operation of the bearing assembly due to the thermal expansion of the device a radial extension of the inner ring of the second rolling bearing results ..

Background of the invention

It is known in the storage of waves, in particular in a so-called O- or X-arrangement of skew bearings, such as angular contact ball bearings or tapered roller bearings, as part of the assembly to set a specific game respectively a bias, which in operation about as a Temperature increase or a decrease in temperature relative to the installed state is variable, so that there may be a change in the employment of the bearing assembly relative to the mounting state. In particular, in bearing arrangements with components of different, differing in their thermal expansions materials this effect is enhanced. Due to the different thermal expansion coefficients of individual components of the bearing assembly can lead to strong influences on the life. In particular, in preloaded bearing arrangements occurs due to the different thermal expansion coefficients of the materials used an axial expansion, which causes a change in bias, which has a negative effect on the bearing properties, especially their running properties, so possibly bearing assemblies must be used with an increased load capacity. In addition, for example, in the tooth contact of the gears on the shaft increased noise.

From the prior art, different solutions are known to reduce the resulting bearing play in bearing arrangements with a light metal housing and a steel shaft passing through this.

DE 34 17 699 A1 relates to a synchronous transmission with a light metal housing, in which the existing steel transmission shafts are mounted near their ends by means of rolling bearings. In this case, at least one of the transmission shafts is mounted by means of adjusted tapered roller bearings and formed as a telescopic shaft with two telescopically axially mutually displaceable parts, between which an axially expandable rod-shaped expansion compensation member of the same material as the housing is arranged.

DE 602 05 198 T2 relates to a bearing device with a gear shaft mounted on tapered rollers in a housing, wherein the gear shaft has a smaller thermal expansion coefficient than the housing. The bearing device is designed so that the contact angle of the tapered rollers with respect to the outer rings of the tapered roller bearings is between 8 ° and 13.5 °.

Out DE 31 50 330 A1 is a transmission with a light metal housing and at least one steel shaft known, which is mounted without clearance between two transverse walls of the housing in thrust bearings. Furthermore, at least one transverse wall is provided, which compensates for the different thermal expansions between the housing and the shaft. Here, at or in at least one transverse wall control members are arranged with a different coefficient of expansion compared to the light metal, which deform the transverse wall with temperature changes by generating a bimetallic effect in the region of the thrust bearings.

EP 1 013 971 A2 relates to a transmission with a divided into two segments gear housing, which consist of materials with different thermal expansions. In this case, the geometric dimensions of the two gear segments, in particular in the axial direction, are matched to one another in such a way that, during operation of the bearing, they expand thermally for exactly the same extent as two shafts received within the bearing.

In the with JP H 03-4026 A disclosed arrangement with a ceramic bearing should be compensated by high operating temperatures resulting stresses in the inner ring of the ceramic bearing. An axially supported on the shaft compensating ring is provided at the end with conical surfaces. The ceramic bearing sits on a radial spacer sleeve, which is the front side via a conical surface with the conical surface of the balancing ring in contact. At normal temperature, the radial clearance in the inner ring and the spacer sleeve is zero. The material of the shaft has a higher thermal expansion coefficient than the spacer sleeve. The thermal expansion coefficient of the material of the balancing ring is higher than that of the material of the shaft. From the thermal expansion of the Wave resulting voltages are compensated via the compensation ring.

In US 3,311,431 A a bearing arrangement of a shaft by means of two rolling bearings is described in a housing. The materials of the shaft and the housing are optionally the same or different and accordingly have either the same or differing thermal expansion coefficients. Specifically, it is assumed that the shaft and the housing made of a light metal and the bearing are made of a steel material. The different thermal expansions of the steel of the bearings and the shaft and the housing are compensated by cone rings, with conical outer or. Inner surfaces of the bearing rings correspond. The coefficients of thermal expansion of the conical rings correspond to those of the materials of the shaft or of the housing.

In DE 101 56 890 C1 a differential gear of a motor vehicle is disclosed. The differential housing of the differential is mounted on a bearing via two roller bearings in the housing of the differential gear. The bearings are in X-arrangement against each other employed angular contact and sit with their inner rings on a bearing bush. One of the angular contact bearings sits with the outer ring in the housing of the differential gear and the other with its outer ring in the differential housing. The bearing bush is seated on the shaft of a drive shaft, which in turn is mounted on the bearing point. With such an arrangement a variety of material and combination of materials for the housing, the shaft and the bearings should be made possible for the purpose of lightweight construction, the combinations of steel and light metal for the housing, the shaft and the bearing bush are provided in a suitable mutual assignment. It is provided, for example, that the materials of the inner rings have a lower coefficient of thermal expansion than the material of the bearing bush on which they sit.

However, the known from the prior art solutions are on the one hand in terms of their effect, that is, in particular to compensate for the resulting change in operation of the bearing preload, often insufficient, on the other hand, known from the prior art bearing shaft designs are elaborate and include a variety on items, which is disadvantageous, especially for cost reasons.

Summary of the invention

The invention is therefore based on the problem of specifying a simply constructed bearing assembly with a reduced change of its bearing preload during operation.

The problem is inventively achieved by a bearing assembly according to claim 1. The component of the invention is a non-rotatably connected to the housing axial pin. In this case, the second rolling bearing is connected via its outer ring with the shaft and via its inner ring with the axial pin. Accordingly, in this bearing arrangement, a bearing of the first roller bearing is provided via the outer ring with the non-rotating housing and the inner ring with the rotatable shaft and a bearing of the second roller bearing on the outer ring with the rotatable shaft and the inner ring with the non-rotating axial pin. The axial pin is preferably non-rotatably connected to the housing, wherein a one-piece design of the axial pin with the housing is conceivable. Likewise, the axial pin can be used as a separate component in a corresponding recess of the housing and there fixedly connected to this. The axial pin may be formed as a solid component or as an at least partially hollow cylindrical component, provided that a radial expansion or expansion of the inner ring of the second rolling bearing by the axial pin enabling sufficiently high radial thermal expansion is possible.

The axial pin is made of a light metal such as aluminum or magnesium or corresponding alloys and thus has a larger coefficient of thermal expansion than the inner ring of the second rolling bearing, which is usually made of a bearing steel, such as 100Cr6, manufactured. The axial pin may consist of the same material as the housing of the bearing assembly. In addition to the above, of course, an embodiment of the axial pin in other materials is conceivable, as long as this has a greater coefficient of thermal expansion than the material forming the shaft.

The invention is based on the idea to design the bearing assembly by a suitable dimensioning of the distances, fits, angles and materials used in particular with respect to the rolling bearing and the housing such that the operational change of the bearing clearance or the bias voltage by the different thermal expansion coefficients between the housing and shaft is compensated, so that there is no negative influence on the bearing settings or a change in the preload of the bearing assembly by temperature gradients or - changes. According to the invention, the different coefficients of thermal expansion of the bearing components are utilized, wherein during operation of the bearing assembly In addition to the known axial expansion or widening of the bearing assembly, a specific radial expansion or widening of the inner ring of the second rolling bearing is generated by the thermal expansion of the component, essentially due to the larger thermal expansion coefficient of the housing relative to the shaft. In this case, the radial expansion, in contrast to the axial expansion of the bearing assembly does not lead to an increase, but to a reduction of the axial bearing clearance. Basically, the bearing assembly according to the invention by the clearance compensation during operation on a life span increase over a wide temperature range and a correspondingly reduced noise. The bearing assembly according to the invention is versatile and can be installed, for example, in vehicle transmissions.

Preferably, the bearings are angular contact ball bearings or tapered roller bearings. The entire bearing assembly is in this case an angular contact bearing arrangement. Angular contact ball bearings, in particular, single-row designs are used, self-holding units with massive outer and inner rings and ball and cage assemblies. The raceways of the inner and outer rings are offset in the direction of the bearing axis against each other, so that both radial and axial forces can be absorbed. Tapered roller bearings are also axially and radially resilient and consist of solid outer and inner rings with tapered raceways and tapered rollers with cages. It should be noted with reference to the second embodiment of the device according to the invention in the form of the sleeve, that the rolling bearings are mounted in this case in a so-called X-arrangement on the shaft.

In a further development of the invention, the housing is made of light metal, in particular of aluminum or an aluminum alloy, and the shaft of steel, in particular of a hardened tempering steel, such as Cf53 (material no. 1.1213). In principle, other material combinations are conceivable as long as the mechanical requirements of the bearing assembly expectant stability is given.

list of figures

• 1 eine Prinzipdarstellung einer erfindungsgemäßen Lageranordnung einer ersten Ausführungsform in einer Schnittansicht,
• 2 eine Prinzipdarstellung der in 1 mit III gekennzeichneten Einzelheit
• 3 eine vergrößerte Prinzipdarstellung der 2.

An embodiment of the invention is illustrated in the drawing and will be described in more detail below. Show it:

• 1 a schematic representation of a bearing assembly according to the invention of a first embodiment in a sectional view,
• 2 a schematic representation of in 1 with III marked detail
• 3 an enlarged schematic representation of 2 ,

Detailed description of the drawing

1 shows a schematic diagram of a bearing arrangement according to the invention 1 in a first embodiment in a sectional view. The bearing arrangement 1 includes an aluminum housing 2 into which a steel shaft formed of a corrugated steel such as Cf53 3 extends so that the housing 2 an approximately two times larger thermal expansion coefficient than the shaft 3 having. The bearing arrangement 1 is set with a certain preload. On the wave 3 are unspecified pinion. A the wave 3 bearing first rolling bearing in the form of tapered roller bearing 4 is about his outer ring 5 rotatably with the housing 2 and about his inner ring 6 with the wave 3 connected. In addition to the wave 3 axially spaced is a second, the shaft 3 bearing tapered roller bearing 7 , The tapered roller bearings 4 . 7 are made of a typical bearing steel. Furthermore, a component in the form of an axial pin 8th made of aluminum, the second tapered roller bearing 7 over its outer ring 9 with the wave 3 via one of these associated flange-like section 10 and about his inner ring 11 with the axial pin 8th connected is. The axial pin 8th is with the case 2 rotatably connected. The connection takes place via fastening means, not shown, nevertheless, the axial pin 8th with the housing 2 also be made in one piece. Instead of tapered roller bearings 4 . 7 would also be the use of Schrägkegellagern conceivable.

In operation of the bearing assembly 1 it comes through the different thermal expansion coefficients between housing 2 and wave 3 to an axial expansion of the bearing assembly 1 , as described by the double arrow marked with Δx ₁ , and thus to a change in the preload or the bearing clearance in the tapered roller bearings 4 . 7 , as related to the first tapered roller bearing 4 the outer ring 5 to the left and related to the tapered roller bearing 7 the inner ring 11 moved to the right. In operation of the bearing assembly 1 it comes due to the compared to the wave 3 as well as to the inner ring 11 higher thermal expansion coefficient of the axial pin 8th in addition to a radial expansion or widening of the axial pin 8th and thereby to a radial expansion of the inner ring 11 the second tapered roller bearing 7 as indicated by the double arrow marked Δy shown. The radial expansion of the inner ring 11 originates from that of the axial pin 8th outgoing heat input. This changes the diameter of the inner ring 11 compared to the diameter of the outer ring 9 tapered roller bearing 7 so that their distance from each other decreases, resulting in a normal force on the tapered roller bearing 7 results. In this way, taking into account the distances, angles and thermal expansion coefficients of the materials used during operation of the bearing assembly 1 resulting bearing clearance are largely compensated to fully, it is so far no influence on the employment, that is, no change in the set bias of the bearing assembly 1 due to temperature fluctuations. The exact operating principle of the clearance compensation of the bearing assembly 1 will be explained below on the basis of 3 and 4 explained in more detail.

Based on 2 and 3 the principle of the present invention will be explained in more detail.

wobei α sich durch Subtraktion der unterschiedlichen Wärmeausdehnungskoeffizienten der Welle 3 und des Axialzapfens 8 ergibt (α = α_Al - α_St), L die axiale Ausgangslänge, das heißt der Abstand zwischen den Kegelrollenlagern 4, 7, und ΔT die Temperaturänderung im Betrieb der Lageranordnung 1 darstellt. Dabei ist die oben mit Δx₁ eingeführte axiale Aufweitung der Lageranordnung 1 der Längendehnung ΔL gleichzusetzen, sodass sich insgesamt ergibt $$\Delta {\text{x}}_1=\Delta \text{L}={\mathrm{\alpha }}_{\text{Al}}-{\mathrm{\alpha }}_{\text{St}}\times \text{L}\times \Delta \text{T}.$$

It is doing with reference to the embodiment according to 1 assumed that the case 2 , as well as the axial pin 8th made of aluminum (thermal coefficient of linear expansion α _Al approximately 24 × 10 ^-6 K ^-1 ) and the shaft 3 made of steel (thermal coefficient of linear expansion α _St approximately 12 × 10 ^-6 K ^-1 ). The axial expansion or expansion of the bearing assembly 1 is calculated according to the general formula for elongation $$\Delta \text{L}=\mathrm{\alpha }\times \text{L}\times \Delta \text{T}.$$

where α is obtained by subtracting the different thermal expansion coefficients of the shaft 3 and the axial pin 8th gives (α = α _Al - α _St ), L the axial initial length, that is the distance between the tapered roller bearings 4 . 7 , and ΔT the temperature change during operation of the bearing assembly 1 represents. Here, the above with .DELTA.x ₁ introduced axial expansion of the bearing assembly 1 equate to the elongation ΔL so that the overall result $$\Delta {\text{x}}_1=\Delta \text{L}={\mathrm{\alpha }}_{\text{al}}-{\mathrm{\alpha }}_{\text{St}}\times \text{L}\times \Delta \text{T},$$

In the present example, an initial length of L = 100 mm and a temperature change ΔT of 100 K is assumed. Accordingly, Δx _{1 is} calculated by substituting the values to 0.12 mm. The bearing arrangement 1 accordingly widens in operation by about 0.12 mm in the axial direction.

The calculation of Δy results analogously, wherein instead of the initial length L now the diameter D of the axial pin 8th must be used. This is in the example 50 mm. Accordingly, Δy is calculated to be 0.06 mm. This is evident $$\Delta \text{y}=\Delta \text{D}={\mathrm{\alpha }}_{\text{al}}-{\mathrm{\alpha }}_{\text{St}}\times \text{D}\times \Delta \text{T},$$

The axial pin 8th accordingly expands in operation by 0.06 mm in the radial direction and conditions such a radial expansion of the inner ring 11 the second tapered roller bearing 7 ,

In 2 is the calculated radial expansion Δy of the second tapered roller bearing 7 in vector representation in the region between the tapered roller 13 and the inner ring 11 tapered roller bearing 7 shown. The axial extent of the tapered roller bearing 7 is denoted by Δx ₂ , where Δx _{2 is} smaller than Δx ₁ .

How out 3 which fragmentary the inner ring 11 tapered roller bearing 7 shows, it is apparent, between the angle of attack β, the axial extent .DELTA.x ₂ and the radial extent .DELTA.y the following geometric relationship $$\text{tan}\mathrm{\beta \; =}\Delta \text{y /}\Delta {\text{x}}_2,$$

This can be changed and you get Δx ₂ = Δy / tanβ.

The entire Axialspielveränderung Δx _ges the bearing assembly 1 results from the difference between Δx ₁ and Δx ₂ , so that: $$\Delta {\text{x}}_{\text{ges}}=\Delta {\text{x}}_1-\Delta {\text{x}}_2,$$

It follows that by a suitable choice of the distances L, D, fits and the angle β compensation of the different elongations between housing 2 and wave 3 the bearing arrangement 1 is possible, so it can lead to a clearance compensation respectively a set bias of the bearing assembly 1 remains essentially unchanged.

Based on the above example, Δx ₁ = 0.12 mm and Δy = 0.06 mm. At an exemplary angle of attack of β = 11 °, Δx _{2 is} calculated to be 0.31 mm via the angle β or tan β. After subtracting Δx ₂ from Δx ₁ , Δx _ges = -0.19 mm, which results in a contraction or preload of the bearing arrangement 1 at a temperature increase by 100 K means.

If one changes the angle β, for example, 25.6 °, Ax ₂ calculated to be 0.12 mm, that is, Ax ₂ corresponds exactly Ax _1, from which it follows that the entire Axialspielveränderung Ax is _ges 0 mm. In this case, the operational temperature increase of 100 K has no effect on the play of the bearing assembly 1 or its bias.

LIST OF REFERENCE NUMBERS

1

bearing arrangement

2

casing

3

wave

4

Tapered roller bearings

5

outer ring

6

inner ring

7

Tapered roller bearings

8th

axial pin

9

outer ring

10

flange-like section

11

inner ring

Claims (3)

Bearing arrangement comprising a housing, in which a shaft extends, wherein the housing has a greater coefficient of thermal expansion than the shaft, and a shaft bearing first bearing, which is rotatably connected via its outer ring to the housing and its inner ring with the shaft, and an axially spaced, the shaft bearing second rolling bearing, the second rolling bearing (7) via its inner ring (11) with a higher thermal expansion coefficient than the inner ring (11) having the component is connected, so that during operation of the bearing assembly (1 ) due to the thermal expansion of the component results in a radial expansion of the inner ring (11) of the second rolling bearing (7), characterized in that the component is a rotationally fixed to the housing (2) connected to the axial pin (8) and that the second rolling bearing ( 7) via its outer ring (9) with the shaft (3) and via its inner ring (11) with the Axial pin (8) is connected, wherein the axial pin (8) is formed of a light metal. Bearing arrangement after Claim 1 , characterized in that the rolling bearings are angular contact ball bearings or tapered roller bearings (4, 7). Bearing arrangement after Claim 1 or 2 , characterized in that the housing (2) made of light metal and the shaft (3) is formed of steel.

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