Thin-walled ring bearing and computed tomography apparatus having such thin-walled ring bearing

Abstract

The present invention relates to a thin-walled ring bearing (1) particularly for a computed tomography apparatus, comprising at least one outer ring (2a, 2b), at least one inner ring (3a, 3b), and a plurality of spherical rolling elements (4), wherein at least one inner ring (3a, 3b) has an inner diameter (D i ) formed to be larger than 700 mm, at least one inner ring (3a, 3b) and at least one outer ring (2a, 2b) are formed from an uncured metal base material (6) having a hardness of less than 60 HRC, at least one inner ring (3a, 3b) and at least one outer ring (2a, 2b) each form a raceway surface (5), and the base material (6) is at least partially covered in the region of the raceway surface (5) by a functional layer (7) having a functional layer thickness in the range of 0.5 to 3 mm, and the functional layer (7) is formed from a metal functional layer material having a hardness of at least 60 HRC. The present invention relates to a thin-walled ring bearing (1).

Description

Technical Field

[0001] The present 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 at least one inner ring is formed with an inner diameter greater than 700 mm, particularly for use in a computed tomography apparatus.

Background Art

[0002] German Patent Application Publication No. 102009056038 describes a thin-ring bearing and a method for manufacturing a bearing ring from a wire-shaped material for a thin-ring bearing.

[0003] A thin-ring bearing is a rolling bearing having a large inner diameter D of the inner ring with respect to the distance A between the inner diameter and the outer diameter of the bearing (as seen in cross section). In particular, the ratio of A / D i is 1:30 to 1:150. i

[0004] German Patent Invention No. 102017222208 discloses a computed tomography apparatus and a method for arranging bearing rings of a rolling bearing. The rolling bearing is configured as a three-point ball bearing and has a bearing ring with a groove profile, a first wire ring, and a second wire ring. Such a computed tomography apparatus typically has a fixed part and a rotating part, and the rotating part has a radiation source for X-ray radiation and a detector for X-ray radiation that operates in combination with the radiation source. The rotating part has a mass of about 600 to 900 kg and can rotate at a speed of about 60 to 240 revolutions per minute. A rolling bearing can be used for the rotary bearing of the rotating part with respect to the fixed part.

[0005] In this regard, in order to generate high-quality images, high running accuracy, extremely smooth running, no backlash, and high tilting rigidity are essential. So far, for this purpose, bearing rings made of high-purity, and thus expensive, steel grades have been used.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, an object of the present invention is to provide a suitable thin-ring bearing that enables significant cost reduction in manufacturing.

Means for Solving the Problems

[0007] This object is achieved for a thin-ring bearing comprising at least one outer ring, at least one inner ring, and a plurality of spherical rolling elements, wherein at least one inner ring is formed with an inner diameter greater than 700 mm, at least one inner ring and at least one outer ring are formed from an uncured metal substrate having a hardness of less than 60 HRC, at least one inner ring and at least one outer ring each form a raceway surface, and the substrate is at least partially covered in the region of the raceway surface with a functional layer having a functional layer thickness in the range of 0.5 to 3 mm, the functional layer being formed from a metal functional layer material having a hardness of at least 60 HRC.

[0008] This means that only the functional layer can be formed of a high-quality, very pure, over-rolling-resistant, high-hardness functional layer material. Since the functional layer material can be applied separately and with a thin functional layer thickness, the material-related manufacturing costs of the bearing rings are significantly reduced. In this regard, the functional layer thickness of the functional layer is selected according to the minimum case depth required on each ring to create a functional and durable component. The substrate to which the functional layer is applied no longer needs to meet high purity requirements. Stress and distortion can also be minimized without the need to subject the entire bearing ring to heat treatment.

[0009] The metal substrate is preferably formed from steel. The metal substrate is particularly selected from bearing steel, quenched and tempered steel, or skin-pass steel. For example, weldable quenched and tempered steel having a carbon content of less than 0.3% by weight is used. Alternatively, aluminum can also be used as the metal substrate.

[0010] The metal functional layer material preferably comprises the following components: 0 to 10% by mass of Mo, 0 to 19% by weight of W, 0 to 5% by weight of V, 3.5 to 5% by weight of Cr, 0 to 11% by weight of Co, 0.75 to 1.2% by weight of C, and the balance is steel composed of iron and unavoidable impurities or other elements such as Mn, Si, Cu, Ni, P, S in a proportion of less than 0.5% by weight.

[0011] In particular, steel of type 1.3344 (X 130 WMoCrV 6-5-4-3) is used. Powder metallurgy high-speed steel having high hardness is preferred.

[0012] Alternatively, the metal functional layer material is preferably a hard metal based on tungsten carbide in a nickel-bonded matrix, also known in the market as "Cermadur".

[0013] A combination of a metal substrate in the form of quenched and tempered steel having a carbon content of less than 0.3% by weight and a functional layer material made of steel of type 1.3344 is particularly preferred here.

[0014] The functional layer is applied to the base material, in particular by laser beam welding. This results in a wavy structure in the transition region between the base material and the functional layer, which is recognizable in the microscopic image and can be influenced by the process parameters during laser beam welding. The resulting heat-affected zone extends into the base material, and the waviness extends over a region corresponding to the measured distance Z between the mean value of the wave crests and the mean value of the wave troughs, this distance Z being at least 50 μm. This ensures a particularly tight and gap-free bond between the base material and the functional layer. The waviness and expansion of the heat-affected zone depend on the application parameters such as power, application speed and application width.

[0015] The free surface of the functional layer that forms the track for the rolling element is preferably reworked by machining and / or roller burnished. In this way, the free surface of the functional layer, and thus the flatness and surface roughness of the track, comply with the requirements for the application of rolling bearing components. In particular, the free surface of the functional layer is ground and polished.

[0016] In order to optimize the tension on the ring and also increase the hardness of the functional layer material, at least one outer ring and / or at least one inner ring can also be heat treated. In particular, the heat treatment is carried out over a period of 1 to 2 hours in a temperature range of 400 °C to less than 600 °C. The at least one outer ring and / or the at least one inner ring are then cooled to room temperature. In the case of a particularly preferred combination of a metallic base material in the form of a quenched and tempered steel with a carbon content of less than 0.3 wt% and a functional layer material made of steel of type 1.3344, this heat treatment is preferably carried out in a temperature range of 500 °C to less than 600 °C.

[0017] The track bearing surface is preferably covered only by the functional layer in the contact area with the rolling element. This saves functional layer material and further reduces the cost of the bearing ring.

[0018] The functional layer thickness can also be formed in different ways when viewed in cross-section of the track bearing surface, which further reduces costs.

[0019] It is preferable that two outer rings and / or two inner rings are provided. This makes it considerably easier to mount the thin-ring bearing at the place of use.

[0020] The thin-ring bearing is configured to have a square or mainly square cross-section. The thin-ring bearing is preferably configured as a deep groove ball bearing, a four-point bearing, or an angular ball bearing.

[0021] A computed tomography apparatus comprising at least one thin-ring bearing according to the present invention has proven to have good results. For possible designs of the computed tomography apparatus, reference may be made to the German Patent Invention No. 102017222208 mentioned at the beginning.

[0022] Figures 1 to 3 are intended to illustrate, by way of example, the thin-ring bearing according to the present invention.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0024] Figure 1 shows a cross-section of a thin-ring bearing 1 having split outer rings 2a, 2b, split inner rings 3a, 3b, and rolling elements 4. The inner diameter D of the split inner rings 3a, 3b i is configured to be greater than 1 m. The distance A between the inner diameter D i and the outer diameter of the split outer rings 2a, 2b is only 30 mm, resulting in a ratio of A / D of at least 1:34. The cross-section of the thin-ring bearing 1 (see the region indicated by the dotted line) is shown enlarged in Figure 2. i

[0025] Figure 2 shows the enlarged details of Figure 1. The same reference numerals as in Figure 1 denote the same components. Split outer rings 2a, 2b made of a base material 6 and having a raceway receiving surface 5 can be seen. Split inner rings 3a, 3b made of a base material 6 and having a raceway receiving surface 5 can also be seen. A functional layer 7 made of a functional layer material is applied to the raceway receiving surface 5 in each case. In this regard, the functional layer 7 is applied with different functional layer thicknesses when viewed from the cross-section of the raceway receiving surface 5. In addition, the functional layer 7 does not completely cover each raceway receiving surface 5. Thereby, the functional layer material is saved and the cost of the thin-ring bearing 1 is reduced.

[0026] Figure 3 shows a microscopic image of a cross-section passing through the functional layer 7 of the inner ring 3a and the adjacent base material 6. The functional layer 7 is formed on the base material 6 by laser vapor deposition welding. A wavy structure exists in the transition region 12, in which the base material 6 is fused with the functional layer 7. The distance Z (see the dashed line) between the average value of the wave crests and the average value of the wave troughs is at least 50 μm. The free surface 8 of the functional layer 7 on the side opposite to the base material 6 is reprocessed here by grinding and polishing. The free surface 8 of the functional layer 7 is shown as flat here for simplicity, but in the thin-ring bearing 1, it has a curvature for receiving the rolling elements 4 in the form of balls.

Explanation of Reference Numerals

[0027] 1 Thin-ring bearing 2a, 2b Outer ring 3a, 3b Inner ring 4 Rolling element 5 Raceway receiving surface 6 Base material 7 Functional layer 8 Free surface of the functional layer 12 Transition region A Distance D i Inner diameter

Claims

1. A thin-ring bearing (1), comprising at least one outer ring (2a, 2b), at least one inner ring (3a, 3b), and a plurality of spherical rolling elements (4), wherein the at least one inner ring (3a, 3b) is formed with an inner diameter (Di) greater than 700 mm, the at least one inner ring (3a, 3b) and the at least one outer ring (2a, 2b) are formed from an uncured metal substrate (6) having a hardness of less than 60 HRC, the at least one inner ring (3a, 3b) and the at least one outer ring (2a, 2b) each form a raceway surface (5), and the substrate (6) is at least partially covered in the region of the raceway surface (5) by a functional layer (7) having a functional layer thickness in the range of 0.5 to 3 mm, the functional layer being formed from a metal functional layer material having a hardness of at least 60 HRC.

2. The thin-ring bearing (1) according to claim 1, wherein the metal substrate (6) is formed from steel.

3. The thin-ring bearing (1) according to claim 1 or 2, wherein the metal functional layer material is formed from steel of type 1.3344 (X 130 WMoCrV 6-5-4-3) or from a hard metal based on tungsten carbide in a nickel-bonded matrix.

4. The thin-ring bearing (1) according to any one of claims 1 to 3, wherein the functional layer (7) is applied to the substrate (6) by laser beam welding, thereby forming a wavy transition region between the substrate (6) and the functional layer (7) when viewed in cross section.

5. The thin-ring bearing (1) according to any one of claims 1 to 4, wherein the free surface (8) of the functional layer (7) forming the raceway for the rolling elements (4) is reworked by machining and / or roller burnishing.

6. The thin-ring bearing (1) according to any one of claims 1 to 5, wherein the at least one outer ring (2a, 2b) and / or the at least one inner ring (3a, 3b) is heat treated.

7. The thin-ring bearing (1) according to any one of claims 1 to 6, wherein the raceway surface (5) is covered by the functional layer (7) only in the contact region with the rolling elements (4).

8. The thin-ring bearing (1) according to any one of claims 1 to 7, wherein two outer rings (2a, 2b) and / or two inner rings (3a, 3b) are provided.

9. The thin-ring bearing (1) according to any one of claims 1 to 8, wherein the functional layer thickness is formed in different manners when viewed from the cross section of the raceway bearing surface (5).

10. A computed tomography apparatus comprising at least one thin-ring bearing (1) according to any one of claims 1 to 9.

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