BEARING ARRANGEMENT

Abstract

The invention relates to a bearing arrangement designed as a fixed/floating bearing for a rotor of a fan, having a bearing tube, a compression spring, a shaft arranged coaxially with respect to the bearing tube, and two identically formed ball bearings arranged between the bearing tube and the shaft, each ball bearing having an inner ring and an outer ring, wherein multiple different fit zones are formed axially along the bearing tube, wherein, in a first axial fit zone, one of the ball bearings as a fixed bearing is attached by its inner ring on the shaft and its outer ring is fixed with a press fit on a continuous, shoulder-free portion of the bearing tube and, in a second axial fit zone, another of the ball bearings as a floating bearing is attached by its inner ring to the shaft and its outer ring is axially displaceably arranged with a clearance fit on a continuous, shoulder-free portion of the bearing tube, wherein the compression spring is arranged in a third axial fit zone and, exerting a preload against the outer rings of the ball bearings, is positioned axially between the ball bearings and is designed to eliminate bearing play of the floating bearing.

Description

FIELD

The disclosure relates to a bearing arrangement designed as a fixed/floating bearing for a rotor fan.

SUMMARY

In prior art uses, bearing tubes have fixed/floating bearing arrangements with floatingly projecting shaft loads. As a rule, a bearing tube with an inner shoulder or a geometrical shoulder, for adjoining a bearing, is provided for bracing the bearings in an O-arrangement. The first bearing is inserted into the bearing tube from one axial side. A spring and the second bearing are inserted from the other axial side. Both inner rings of the bearings are fixedly connected to be mounted to the shaft. The bearing assembly is self-supporting up to the amount of the preload. If the outer ring of the first bearing is for example fixed by caulking, gluing, or a retaining ring, the mounting is defined in all directions.

The bearings are machined and inserted from two sides in such bearing tubes. In addition, a geometrical bearing shoulder must be provided, which is not always desired. Furthermore, the coaxiality of the bearing seats is not optimal with two-sided machining.

It is an underlying problem of the disclosure to provide a bearing arrangement for a rotor fan that features improved coaxiality of the bearing seats and a simplified assembly option from a single axial side.

This problem is solved by the combination of features including a bearing arrangement designed as a fixed/floating bearing for a fan rotor comprising a bearing tube, a compression spring, a shaft arranged coaxially with respective to the bearing tube, and two identically formed ball bearings arranged between the bearing tube and the shaft. Each ball bearing has an inner ring and an outer ring. Multiple different fit zones are formed axially along the bearing tube. A fixed bearing, is attached by its inner ring on the shaft and its outer ring is fixed with a press fit on a continuous shoulder-free portion of the bearing tube. In a second axial fit zone, another of the ball bearings as a floating bearing, is attached by its inner ring to the shaft and its outer ring is axially displaceably arranged with a clearance fit on a continuous, shoulder-free portion of the bearing tube. The compression spring is arranged in a third axial fit zone. The compression spring is positioned axially between the ball bearings exerting a preload against the outer rings of the ball bearings to eliminate bearing play of the floating bearing.

According to the disclosure, a bearing arrangement, designed as a fixed/floating bearing for a rotor fan, is proposed with a bearing tube, a compression spring, a shaft arranged coaxially with respect to the bearing tube and two identically formed ball bearings arranged between the bearing tube and the shaft. Each ball bearing has an inner ring and an outer ring. Multiple different fit zones are formed axially along the bearing tube. In a first axial fit zone, one of the ball bearings, as a fixed bearing, is attached by its inner ring on the shaft. Its outer ring is fixed with a press fit on a continuous shoulder-free portion of the bearing tube. In a second axial fit zone, another of the ball bearings, as a floating bearing, is attached by its inner ring to the shaft. Its outer ring is axially displaceably arranged with a clearance fit on a continuous shoulder-free portion of the bearing tube. The compression spring is arranged in a third axial fit zone. It exerts a preload against the outer rings of the ball bearings. The spring is positioned axially between the ball bearings and is designed to eliminate bearing play of the floating bearing. To this end, the compression spring is selected such that it has a sufficient spring force for the respective bearings.

The solution according to the disclosure does without geometrical shoulders or bearing shoulders on the bearing tube for the bearings. The present disclosure provides different fit zones for the two bearings, one as a press fit and one as a clearance fit. This enables completely one-sided machining and assembly of the bearings. Furthermore, the coaxiality of the two bearing seats is optimized.

Assembly is simplified because the fixed bearing, the compression spring, and the floating bearing can be inserted from the same side and only pressing processes that can easily be monitored can be used. Also, no additional parts, such as retaining rings, or additional materials, such as adhesive, are required.

The different fit zones are preferably determined by different tolerance zones of the inner diameter of the bearing tube. The regions of the compression spring and the floating bearing feature a clearance fit with the outer ring. The region of the fixed bearing features a press fit with the outer ring of the bearing. The bearing arrangement uses an O-arrangement braced on the outer ring.

In one embodiment of the bearing arrangement, the third axial fit zone corresponds to the second axial fit zone in the region of the compression spring. Thus, only two different fit zones are provided. The clearance fit in the region of the spring can have a greater tolerance than the one of the floating bearing.

Furthermore, in an advantageous embodiment of the bearing arrangement, an axial fit length L1 of the first fit zone of the fixed bearing is defined as 0.35∩L1≤D≤0.5⋅L1. Here D is an inner bearing tube diameter of the bearing tube. In addition, an axial fit length L2 of the second fit zone of the floating bearing is defined as 0.35⋅L2≤D≤0.5⋅L2. This short axial length of the fit zones reduces required machining to small axial sections. The third fit zone of the compression spring is always located axially between the two fit zones of the press fit and clearance fit of the two ball bearings.

In a further development of the bearing arrangement, the first and the second fit zones each adjoin axial edge sections of the bearing tube. Their position is thus unique and easily determined.

The entire axial holding force must be borne by the press fit of the outer ring of the fixed bearing with the bearing tube. To ensure this over a wide temperature range, a material is selected for the bearing tube that has an expansion coefficient very similar to the material of the outer rings of the ball bearings. In a preferred embodiment, the material of the outer rings of the ball bearings is even identical to a material of the bearing tube, for example, steel.

In a favorable solution, the outer rings of the ball bearings and the bearing tube are formed of soft magnetic steel. This is due to the fact that non-magnetic, austenitic steels have a too high expansion coefficient.

The expansion coefficient is of subordinate importance for the shaft to be mounted and may deviate from that of the bearing tube. But it is defined such that it is similar to the expansion coefficient of the inner ball bearing rings and that the press fit is not impaired and there is no impermissible radial change of air of the ball bearing.

For use in a fan, an embodiment of the bearing arrangement is advantageous where a projection is formed on an axial end section of the bearing tube and integral with the bearing tube. The projection comprises a receiving space for inserting a fan wheel. Thus the bearing tube, in addition to its bearing function, can define a receptacle for the fan wheel and contribute to a compact design requiring little installation space and a small number of parts. The disclosure therefore also related to a fan having the bearing arrangement described above.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

Other advantageous further developments of the disclosure are presented in the dependent claims or are explained in more detail below with reference to the figures and together with a preferred embodiment of the disclosure.

FIG. 1 is a perspective cross-sectional view of a bearing arrangement of a rotor of a fan;

FIG. 2 is a perspective cross-sectional view of a bearing arrangement of a rotor of a fan; and

FIG. 3 is a cross-sectional view of a fan with a bearing arrangement.

DETAILED DESCRIPTION

FIGS. 1 and 2 show two exemplary embodiments of bearing arrangements 1 designed as fixed/floating bearings for a fan rotor 11.

Referring now to FIG. 1, it shows a perspective sectional view of the bearing arrangement 1 with the bearing tube 2, a shaft 28 of a drive motor arranged coaxially with the bearing tube 2, of which motor only the rotor 11 is shown.

Two identically configured ball bearing 3, 6, each with an inner ring 4, 7 and an outer ring 5, 8, are arranged between the bearing tube 2 and the shaft 28. One of the bearings is used as a fixed bearing and the other one as a floating bearing. The compression spring 9, which exerts a spring force to eliminate the bearing clearance against the two outer rings 5, 8, is located axially between the two ball bearings 3, 6.

Different fit zones are formed due to different tolerance zones on the inner wall surface of the bearing tube 2 in the region of the two ball bearings 3, 6.

In a preferred exemplary embodiment, the fit of the two bearings due to different tolerance zones of the diameters are implemented as follows:

Diameter of the shaft=4.002-4.005 mm

Diameters of the inner rings 4, 7=3.995-4.000 mm

Diameters of the outer rings 5, 8=10.995-11.000 mm

Diameter of the bearing tube for ball bearing 6 (fixed bearing)=10.983-10.993 mm

Diameter of the bearing tube for ball bearing 3 (floating bearing)=11.000-11.011 mm

Diameter of the bearing tube in the region of the compression spring 9=11.000- 11.04 mm

The geometrical dimensions are adjusted accordingly for greater or smaller embodiments.

The ball bearing 6 is configured as a fixed bearing, the ball bearing 3 as a floating bearing, but this arrangement may also be reversed. The inner ring 7 is fastened to the shaft 28. The outer ring 8 is fixed to a continuous shoulder-free section of the bearing tube 2 by means of a press fit. No bearing shoulder or any other geometrical shoulder is provided on the inner wall surface of the bearing tube 2. The bearing tube 2 extends continuously without a step in the axial direction. Thus, all components can be mounted from a single axial side. The second, identically configured ball bearing 3 is a floating bearing and likewise fastened with its inner ring 4 to the shaft 28. The outer ring 5 is also arranged in an axially movable manner and, with a clearance fit, on a continuous shoulder-free shoulder of the bearing tube 2. The third fit zone is provided in the axial region of the compression spring 9 between the two ball bearings 3, 6. In the exemplary embodiment shown, this zone corresponds to the fit zone of the ball bearing 3 defining the floating bearing, such that only two different fit zones are provided. The third fit zone in the region of the compression spring 9 can be variably adjusted and may differ from the two fit zones of the ball bearings 3, 6.

In the exemplary embodiment shown, the axial fit length L1 of the first fit zone of the ball bearing 6, defining the fixed bearing, and the second fit zone of the ball bearing 3, defining the floating bearing, is further defined as 0.4 of the inner bearing tube diameter of the bearing tube 2. Both fit zones each directly adjoin the axial edge sections of the bearing tube 2.

In the exemplary embodiment according to FIG. 1, a collar 25 formed integrally with the bearing tube 2 is configured on the upper axial end section of the bearing tube 2, which collar defines the receiving space 87 for inserting the fan wheel 17.

The exemplary embodiment according to FIG. 2 has the same features as the one from FIG. 1. However, it differs in that the collar 25 is not provided on the bearing tube 2 but as a separate component. In the embodiment shown, the collar 25 is formed by a flow divider that is described in more detail with reference to FIG. 3.

FIG. 3 shows a sectional view of a radial fan 100 with the bearing arrangement 1 from FIG. 1. The radial fan 100 includes an electric motor 92 configured as an encapsulated motor with a rotor 11 and a stator 32. The magnets of the rotor 11 are attached to the shaft 28 that extends axially along the axis of rotation through the radial fan 100. The fan wheel 17 configured as a radial fan wheel is fastened to the shaft 28 The fan wheel 17 when in operation, takes in air by means of its impeller vanes axially through the inlet 69 and blows out air via the discharge nozzle 33 at the outlet 44. The radial fan 100 further includes the fan housing, which is formed by the outer part 40, the inner part 50, and the housing cover 19, where the motor 52 is accommodated. The circuit board 110 with electronics components fixed thereon for regulating the radial fan 100, is attached axially between the inner part 50 and the motor 52 and to the housing cover 19. The inner part 50, on the one hand forms a free space for the electronics components on a side facing the motor 52. On the other hand, the inner part 50 defines, together with the outer part, the helical pressure space D on the opposite axial side of the radial fan 100 facing the outer part 40. The inner part 50 extends radially outwards between the outer part 40 and the housing cover 19 and is fixed by the outer part 40 and the housing cover 19. Seals 25 are provided to seal off the two axial regions separated by the inner part 50. The electronics components are arranged in the free space adjacent to the pressure space D. Thus, the electronic components face the flow, whereby heat is dissipated to the inner part 50 and cooling takes place.

The annular flow divider 18 enclosing the fan wheel 17, and also forming the bearing tube 2, is arranged radially adjacent to the fan wheel 17. The flow divider 18 and the outer part 40 form a diffuser into the pressure space D.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways.

Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1.-11. (canceled)

12. A bearing arrangement designed as a fixed/floating bearing for a fan rotor, comprising: a bearing tube, a compression spring, a shaft arranged coaxially with respect to the bearing tube, and two identically formed ball bearings arranged between the bearing tube and the shaft, each ball bearing has an inner ring and an outer ring;multiple different fit zones are formed axially along the bearing tube, in a first axial fit zone, one of the ball bearings as a fixed bearing is attached by its inner ring on the shaft and its outer ring is fixed with a press fit on a continuous, shoulder-free portion of the bearing tube, in a second axial fit zone, another of the ball bearings as a floating bearing is attached by its inner ring to the shaft and its outer ring is axially displaceably arranged with a clearance fit on a continuous, shoulder-free portion of the bearing tube;the compression spring is arranged in a third axial fit zone, positioned axially between the ball bearings, the compression spring exerting a preload against the outer rings of the ball bearings to eliminate bearing play of the floating bearing.

13. The bearing arrangement according to claim 12, wherein the different fit zones are formed by tolerance zones of an inner diameter of the bearing tube.

14. The bearing arrangement according to claim 12 wherein the third axial fit zone corresponds to the second axial fit zone.

15. The bearing arrangement according to claim 12, wherein an axial fit length L1 of the first fit zone of the fixed bearing is defined as 0.35⋅L1≤D≤0.5⋅L1, wherein D is an inner bearing tube diameter of the bearing tube.

16. The bearing arrangement according to claim 12, wherein an axial fit length L2 of the second fit zone of the floating bearing is defined as 0.35⋅L2≤D≤0.5⋅L2, wherein D is an inner bearing tube diameter of the bearing tube.

17. The bearing arrangement according to claim 12, wherein the first and/or the second fit zone each adjoin axial edge sections of the bearing tube.

18. The bearing arrangement according to claim 12, wherein a base material of the outer rings of the ball bearings is the same as a material of the bearing tube.

19. The bearing arrangement according to claim 12, wherein the outer rings of the ball bearings (3, 6) and the bearing tube are formed of soft magnetic steel.

20. The bearing arrangement according to claim 12, wherein a collar is formed on an axial end section of the bearing tube and integral with the bearing tube, which collar comprises a receiving space for inserting a fan wheel.

21. The bearing arrangement according to claim 12, wherein a separate collar is arranged on an axial end section of the bearing tube, which collar comprises a receiving space for inserting a fan wheel.

22. A fan having a bearing arrangement according to claim 12.