Thin section bearing and computer tomograph having a thin section bearing of this type

Abstract

The invention relates to a thin section bearing (1, 1'), in particular for a computer tomograph, comprising at least one inner ring (2, 2a, 2b), at least one outer ring (3, 3a, 3b) and a plurality of spherical rolling elements (4), wherein: the at least one inner ring (2, 2a, 2b) has an inside diameter (Di) of greater than 700 mm; the at least one outer ring (3, 3a, 3b) and the at least one inner ring (2, 2a, 2b) are made of an unhardened metal base material (6) having a hardness of less than 58 HRC; the at least one outer ring (3, 3a, 3b) and the at least one inner ring (2, 2a, 2b) each form at least one raceway region (7a, 7b, 7c, 7d) in contact with the rolling elements (4); and the base material (6) is laser-hardened in the at least one raceway region (7a, 7b, 7c, 7d), and the raceway region (7a, 7b, 7c, 7d) has a hardness of at least 58 HRC.

Description

[0001] Thin rinqlaqer and computer tomography with such a thin rinqlaqer

[0002] The invention relates to a thin-ring bearing comprising at least one outer ring, at least one inner ring and a plurality of spherical rolling elements, wherein the at least one inner ring is designed with an inner diameter of greater than 700 mm, in particular for use in a computer tomography scanner.

[0003] DE10 2009 056038 A1 describes a thin-section bearing and a method for producing a bearing ring from wire-shaped material for a thin-section bearing. The wire is rolled, bent, and the free ends are welded together. The resulting solid ring is then annealed and finally cold-rolled and optionally hardened.

[0004] Thin-section bearings are rolling bearings that have a large inner diameter Di of the inner ring relative to the distance A between the inner diameter and outer diameter of the bearing (seen in cross-section). In particular, the ratio A / Di is between 1:30 and 1:150.

[0005] DE 10 2007 049 071 A1 describes a wire race bearing with two concentrically arranged support rings, each with running wires in facing recesses, between which rolling elements roll on corresponding raceways. The wire race bearing is designed as a four-point contact ball bearing and is used as a slewing ring in computed tomography.

[0006] DE 10 2004 062 116 B3 discloses a bearing assembly for a medical device such as a computer tomography scanner. The bearing assembly has a one-piece inner ring and a one-piece outer ring, each with a hollow cylindrical base contour.

[0007] DE 10 2017 222 208 B3 describes a computed tomography device and a method for arranging a bearing ring of a rolling bearing. It is stated there that computed tomography devices typically have a stationary part and a rotating part, with the rotating part having a radiation source for X-rays and an X-ray detector that interacts with the radiation source. The rotating part can, for example, have a mass of approximately 600 to 900 kg and rotate at a rotational speed of approximately 60 to 240 revolutions per minute. A very precise, smooth, and silent rotation of the rotary movement is essential. The rotary movement of the rotating part can be driven by means of a direct drive or by means of a drive belt that interacts with a pulley of the rotating part.A rolling bearing can be used to support the rotating part relative to the stationary part. A rolling bearing has a plurality of rolling elements and several raceways for rolling the rolling elements.

[0008] High running accuracy, extremely smooth running, zero backlash, and high tilting rigidity are essential for producing high-quality images. Bearing rings made of high-purity and therefore expensive steel grades, which are usually completely hardened, have been used for this purpose. This often leads to stress and distortion of the bearing rings during the hardening process.

[0009] It is therefore an object of the invention to provide a suitable thin-ring bearing which brings about cost savings with regard to its production and a reduction in thermal distortion in the hardening process.

[0010] The object is achieved by a thin-section bearing comprising at least one inner ring, at least one outer ring and a plurality of spherical rolling elements, wherein the at least one inner ring is formed with an inner diameter Di of greater than 700 mm, wherein the at least one outer ring and the at least one inner ring are formed from an unhardened metallic base material with a hardness of less than 58 HRC, wherein the at least one outer ring and the at least one inner ring each form at least one raceway region in contact with the rolling elements, and wherein the base material is laser-hardened in the at least one raceway region and the raceway region has a hardness of at least 58 HRC. Due to only local laser hardening of the at least one inner ring and the at least one outer ring, distortion of the bearing rings is minimized.The cost-effective, unhardened metallic base material is hardened only in the area that comes into contact with the rolling elements and forms a raceway for the rolling elements. This leads to significant cost savings in the production of a thin-section bearing.

[0011] However, to improve the microstructure, it has proven effective to temper the metallic base material to a hardness of 250 +100HV before laser hardening.

[0012] It is preferred if the metallic base material is made of steel with a proportion of

[0013] 0.38 to 0.56 wt% C,

[0014] 0.3 to 1.2 wt% Mn,

[0015] 0.9 to 1.2 wt% Cr,

[0016] 0.15 - 0.30 wt% Mo,

[0017] Rest iron and unavoidable impurities or other elements, such as Si, Al,

[0018] P, S, Pb, with a proportion of less than 0.5 wt.%. This is cost-effective, laser-hardenable, and suitable for the thin-section bearing according to the invention. Steels of type 1.7228 (50CrMo4) or 1.7225 (42CrMo4) have proven particularly suitable.

[0019] It is preferred to have an outer ring and an inner ring, each having two separate, annular raceway areas running parallel to each other. The two raceway areas are preferably separated by an annular groove. The groove serves as a lubricant reservoir and prevents the heat-affected zones of two raceway areas from overlapping.

[0020] Alternatively, it has proven effective to have two outer rings and / or two inner rings, each with an annular raceway area. The two outer rings and / or the two inner rings can have local recesses in an area where their raceways adjoin each other.

[0021] A free surface of the at least one raceway region, which forms a raceway for the rolling elements, can be machined and / or burnished. The free surface of the at least one raceway region, which forms a raceway for the rolling elements, is in particular honed.

[0022] The at least one raceway region is preferably configured with different thicknesses, viewed across a cross-section through the at least one outer ring or the at least one inner ring. Preferably, the penetration depth of the laser hardening in the base material is at its maximum in the region of a contact angle profile.

[0023] A computer tomograph comprising at least one thin-ring bearing according to the invention has proven itself with regard to achievable high running accuracy, extreme running smoothness, freedom from play and high tilting stiffness of the thin-ring bearing.

[0024] Figures 1 to 4 illustrate examples of thin-section bearings according to the invention.

[0025] Figure 1 shows a section through a first thin-ring bearing with an outer ring and an inner ring;

[0026] Figure 2 shows an enlarged section of the first thin-ring bearing according to Figure 1 in the area of ​​the cut surfaces;

[0027] Figure 3 shows a section through a second thin-section bearing with two outer rings and two inner rings; and

[0028] Figure 4 shows an enlarged section of the second thin-section bearing according to Figure 3 in the area of ​​the cut surfaces. Figure 1 shows a section through a first thin-section bearing 1 with an outer ring 3 and an inner ring 2. Furthermore, a plurality of spherical rolling elements 4 are present. The inner ring 2 is designed with an inner diameter Di of greater than 1 m. The outer ring 3 and the inner ring 2 are made of an unhardened metallic base material 6 with a hardness of less than 58 HRC (see Figure 2). The outer ring 3 and the inner ring 2 each form at least one raceway region 7a, 7b, 7c, 7d in contact with the rolling elements 4. The base material e is laser-hardened in the raceway regions 7a, 7b, 7c, 7d and the raceway regions 7a, 7b, 7c, 7d have a hardness of at least 58 HRC.A ratio A / Di lies in the range of 1:30 to 1:150, whereby the distance A between the inner diameter Di and an outer diameter of the thin-section bearing 1 (seen in cross-section) is recorded. The outer ring 3 and the inner ring 2 each have two separately arranged, annular and parallel raceway areas 7a, 7b; 7c, 7d, which are separated from each other by an annular groove 9a, 9b.

[0029] Figure 2 shows an enlarged section of the first thin-section bearing 1 according to Figure 1 in the region of the intersection surfaces (see the area circled by a dashed line in Figure 1). The contact angles 5 are indicated by dashed lines in Figure 2. In the areas of the raceway regions 7a, 7b, 7c, 7d that intersect the contact angles 5, the hardening depth in the base material 6 is at its maximum. A free surface 8 of the raceway regions 7a, 7b, 7c, 7d each forms a raceway for the rolling elements 4.

[0030] Figure 3 shows a section through a second thin-section bearing 1' with two outer rings 3a, 3b and two inner rings 2a, 2b. Furthermore, a plurality of spherical rolling elements 4 are present. The inner rings 2a, 2b have an inner diameter Di of greater than 700 mm. The outer rings 3a, 3b and the inner rings 2a, 2b are made of an unhardened metallic base material e with a hardness of less than 58 HRC (see Figure 4). The outer rings 3a, 3b and the inner rings 2a, 2b each form a raceway region 7a, 7b, 7c, 7d in contact with the rolling elements 4. The base material 6 is laser-hardened in the raceway areas 7a, 7b, 7c, and 7d, and the raceway areas 7a, 7b, 7c, and 7d have a hardness of at least 58 HRC. The ratio A / Di is in the range of 1:30 to 1:150, whereby the distance A between the inner diameter Di and an outer diameter of the thin-section bearing 1' (seen in cross-section) is measured.The outer rings 3a, 3b and the inner rings 2a, 2b each have an annular raceway area 7a, 7b; 7c, 7d.

[0031] Figure 4 shows an enlarged section of the second thin-section bearing 1' according to Figure 3 in the area of ​​the intersection surfaces (see the area circled by a dashed line in Figure 3). The contact angles 5 are indicated by dashed lines in Figure 4. In the areas of the raceway regions 7a, 7b, 7c, 7d that intersect the contact angles 5, the hardening depth in the base material 6 is at its maximum. A free surface 8 of the raceway regions 7a, 7b, 7c, 7d each forms a raceway for the rolling elements 4.

[0032] List of reference symbols

[0033] 1 , r thin section bearing

[0034] 2, 2a, 2b inner ring

[0035] 3, 3a, 3b outer ring

[0036] 4 rolling elements

[0037] 5 pressure angles

[0038] 6 Base material

[0039] 7a, 7b, 7c, 7d career area

[0040] 8 free surface of the running track area or track

[0041] 9a, 9b annular groove

[0042] A distance

[0043] The inner diameter

Claims

Patent claims 1 . Thin-ring bearing (1, 1') comprising at least one inner ring (2, 2a, 2b), at least one outer ring (3, 3a, 3b) and a plurality of spherical rolling elements (4), wherein the at least one inner ring (2, 2a, 2b) is formed with an inner diameter (Di) of greater than 700 mm, wherein the at least one outer ring (3, 3a, 3b) and the at least one inner ring (2, 2a, 2b) are formed from an unhardened metallic base material (6) with a hardness of less than 58 HRC, wherein the at least one outer ring (3, 3a, 3b) and the at least one inner ring (2, 2a, 2b) each form at least one raceway region (7a, 7b, 7c, 7d) in contact with the rolling elements (4), and wherein the base material (6) in the at least one raceway region (7a, 7b, 7c, 7d) is laser hardened and the raceway area (7a, 7b, 7c, 7d) has a hardness of at least 58 HRC.

2. Thin-ring bearing (1, 1') according to claim 1, wherein the metallic base material (6) consists of steel with a proportion of 0.38 to 0.56 wt% C, 0.3 to 1.2 wt% Mn, 0.9 to 1.2 wt% Cr, 0.15 - 0.30 wt% Mo, Rest iron and unavoidable impurities or other elements, such as Si, Al, P, S, Pb, with a proportion of less than 0.5 wt.%.

3. Thin-ring bearing (1) according to one of claims 1 or 2, wherein an outer ring (3) and an inner ring (2) are present, each having two raceway regions (7a, 7b; 7c, 7d) arranged separately from one another and extending parallel to one another in an annular manner.

4. Thin-ring bearing (1) according to claim 3, wherein the two raceway regions (7a, 7b; 7c, 7d) are separated from one another by an annular groove (9a, 9b).

5. Thin-ring bearing (1') according to one of claims 1 or 2, wherein two outer rings (3a, 3b) and / or two inner rings (2a, 2b) are present, each having an annular raceway region (7a, 7b, 7c, 7d) 6. Thin-ring bearing (1, 1') according to one of claims 1 to 5, wherein a free surface (8) of the at least one raceway region (7a, 7b, 7c, 7d), which forms a raceway for the rolling elements (4), is machined and / or rolled.

7. Thin-ring bearing (1, 1') according to claim 6, wherein the free surface (8) of the at least one raceway region (7a, 7b, 7c, 7d), which forms a raceway for the rolling elements (4), is honed.

8. Thin-ring bearing (1, 1') according to one of claims 1 to 7, wherein the at least one raceway region (7a, 7b, 7c, 7d) is of different thicknesses as seen over a cross section through the at least one outer ring (3, 3a, 3b) or the at least one inner ring (2, 2a, 2b).

9. Computer tomograph, comprising at least one thin-ring bearing (1, 1') according to one of claims 1 to 8.

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