Double-row angular contact ball bearing

Abstract

The invention relates to a double-row angular contact ball bearing comprising an outer ring (2) and an inner ring (3) consisting of two axially interconnected ring elements (4, 5). The outer ring (2) is provided with two outer raceways (8, 9), the ring elements (4, 5) are provided with inner raceways (10, 11), on which balls (12, 13) run in two rows, the ring parts (17) of the ring elements (4, 5) projecting axially beyond the outer ring (2) and the ring parts (17) are provided with measuring bodies (19) on their outer cylindrical side surfaces (18). The outer ring (2) is provided with a measuring device (20) having measuring means (21) for detecting the measuring bodies (19), which are located radially close to the measuring bodies (19) and at a slight distance therefrom across a measuring gap (27).

Description

[Technical Field]

[0001] The present invention relates to a double-row angular contact ball bearing comprising an outer ring and an inner ring consisting of two ring elements connected in the axial direction, the outer ring being provided with two outer raceways, the ring elements being each provided with an inner raceway, and balls running in two rows on the outer raceways and the inner raceways. [Background technology]

[0002] Such double-row angular contact ball bearings are used in a variety of fields where bearings are required to support both radial and axial loads. One example of an application is as a rotary table bearing, which can be used to support the high-speed rotating table of a machine tool. Angular contact ball bearings enable rotary tables to rotate at high speeds, particularly at speeds that cannot be achieved with the axial / radial bearings typically used in rotary table bearings. The outer ring of the angular contact ball bearing is connected to a fixed machine frame or the like, and the inner ring is connected to the rotary table via, for example, a pipe installed on the table side. The inner ring is located outside the inner ring, through which the angular contact ball bearing passes.

[0003] In such applications as rotary table bearings, it is often necessary to measure the rotary table's rotational position relative to the fixed machine frame with high precision, i.e., to measure its exact angular position. For this purpose, an additional measuring device for measuring the angle must be installed. This measuring device is preferably located in the plane of the angular contact ball bearing, through which the rotary table's pipe passes, as described above. For this purpose, the frame must be provided with a corresponding mounting that allows the measuring device to be positioned in the bearing plane. This is because, while tilt within the bearing is minimal in the bearing plane, if the measuring device were located, for example, at the lower end of the pipe, a significantly larger tilt angle could occur, resulting in inaccurate measurements in this area. Regardless of this, integrating a measuring device in this way has the disadvantages of considerable difficulty in mounting and positioning the measuring device inside the pipe within the bearing plane, as well as the fact that this naturally occupies space inside the pipe and blocks the center of the axis, making it impossible, for example, to route cables or wiring through the pipe or to integrate an oil distributor. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention is based on the problem of identifying a relatively improved angular contact ball bearing. [Means for solving the problem]

[0005] In order to solve this problem, the present invention provides an angular contact ball bearing of the initially mentioned type, characterized in that a ring element having a ring portion protrudes in the axial direction beyond an outer ring, a measuring body is provided on the outer cylindrical side surface of the ring portion, and the outer ring is provided with a measuring device having measuring means for detecting the measuring body, the measuring means being positioned radially close to the measuring body and slightly spaced from it across a measuring gap.

[0006] The double-row angular contact ball bearing according to the present invention has an integrated angle measuring device. This means that the angle measuring device is part of the angular contact ball bearing, and therefore the angle measuring device is attached and positioned at the same time as the angular contact ball bearing is installed. To make this possible, at least one of the ring elements of the two-part inner ring is specially configured. The ring element has a ring portion that protrudes axially beyond the outer ring, allowing a measuring body to be placed on the outer cylindrical side surface of the ring portion. This measuring body is an angular reference that can be detected by the measuring device, thereby enabling very high-resolution and very accurate angle measurements. The measuring device is arranged on the outer ring and includes a measuring means. The measuring means is arranged close to the measuring body with a very narrow radial gap so that the measuring means can detect the measuring body.

[0007] This angular contact ball bearing offers many advantages. On the one hand, as mentioned above, this angular contact ball bearing allows the rotary table to rotate at extremely high speeds, which would be impossible with axial / radial bearings. In addition, the integrated angle measuring system allows the angular contact ball bearing to be pre-set in the factory after both the measuring body and the measuring device have been mounted on the ring section of the inner ring and the outer ring, respectively, so that the measuring gap between the measuring means and the measuring body can be set very precisely in the factory. This means that very complex and repetitive setting and adjustment during assembly, which often requires multiple trial and error procedures, can be avoided. Needless to say, the angular contact ball bearing does not even need to be installed, since it is integrated into the bearing itself.

[0008] Finally, since the angle measurement system is integrated into the angular contact ball bearing itself, the angle measurement system is ultimately positioned along the axial extension of the angular contact ball bearing, not positioned radially inside the angular contact ball bearing, so the center of the shaft is not blocked. As a result, the center of the shaft is not blocked and can be used for passing other components through or integrating them.

[0009] The measuring device itself is arranged on the axial ring surface of the outer ring. That is, since the measuring device is axially fixed on the outer ring, it is inherently very close to the outer surface of the ring part on which the measuring body is provided. According to a first variant of the invention, an adapter may be provided, via which the measuring device is arranged on the outer ring. By using this adapter, differences in the axial positioning of the measuring device relative to the measuring body can be compensated for by using an adapter specific to the corresponding bearing, so that the measuring device can be configured in a quasi-standardized manner and installed on angular contact ball bearings of different sizes. The measuring device or its housing therefore has a uniform size, and its actual axial position close to the measuring body is set by the specific adapter.

[0010] Of course, instead of using such an adapter, it is also conceivable to arrange the measuring device directly on the outer ring, in which case different dimensions of measuring device or measuring device housing would have to be provided for different bearing sizes.

[0011] The measuring device itself suitably has a housing that accommodates the measuring means and at the same time forms the interface to the adapter or directly to the outer ring, depending on the chosen configuration. The housing has one or more corresponding holes for receiving fixing screws or the like. For example, the housing is a plastic housing, which is easy to manufacture.

[0012] The measuring means themselves may be of various types or may be configured for various measuring methods. They may be inductive, optical or magnetoresistive, all of which allow for highly accurate position detection. The measurement signals output by the measuring means are transmitted via suitable signal lines to a corresponding control device, which specifically controls the rotational movement of the rotary table. These signal lines may be integrated parts of the measuring device. However, it is also conceivable that the measuring device is provided with suitable interfaces, such as plug contacts, which allow for the transmission of corresponding signals in analog or serial manner.

[0013] As mentioned above, the measuring body is provided on the cylindrical outer surface of the axially protruding ring section. Preferably, this measuring body is or includes a ring that is shrink-fitted onto a metal surface and provided with an angular scale. The angular scale may be applied, for example, by etching the metal ring. This ring is shrink-fitted onto the ring section; for this purpose, the ring is slightly heated to expand it or the ring section is cooled to slightly reduce its diameter, in which case both heating and cooling may be performed. After the ring is placed and the temperature is equalized, the metal ring is finally fixed immovably on the ring section, and the ring may then be covered with a protective coating.

[0014] As mentioned above, the angular contact ball bearing is preferably implemented or configured as a rotary table bearing or configured to be used as such a rotary table bearing. However, the application of the angular contact ball bearing is not limited thereto. Other applications may be envisaged in which highly accurate angle detection of two components that can rotate relative to each other is required.

[0015] Besides the axial angular contact ball bearing itself, the invention also relates to a machine tool for machining workpieces by cutting material, comprising a machine frame and a table for supporting the workpiece, the table being mounted on the machine frame so as to rotate about its axis of rotation by means of an angular contact ball bearing of the type described above.

[0016] The invention will be explained below on the basis of exemplary embodiments with reference to the drawings, in which: The drawings are schematic diagrams. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a partial perspective view showing a cross section of an angular contact ball bearing according to the present invention. [Figure 2] FIG. 2 is a partial perspective view of the angular contact ball bearing of FIG. 1, uncut; DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 shows a perspective, cross-sectional, partial view of an angular contact ball bearing 1 according to the present invention. The angular contact ball bearing 1 comprises an outer ring 2 and an inner ring 3. The inner ring 3 consists of two axially interconnected ring elements 4, 5. The two ring elements 4, 5 are axially connected to one another by suitable connecting screws, which are fastened into corresponding receiving holes 6, 7 of the ring elements. Two outer raceways 8, 9 are formed in the outer ring, to which corresponding raceways 10, 11 are assigned, formed in the two ring elements 4, 5. Balls 12 of the first ball row run on raceways 8 and 10, and balls 13 of the second ball row run on raceways 9 and 11. Balls 12, 13 are guided and held in a common cage 14. In the axial direction, the angular contact ball bearing 1 is closed by two sealing elements 15, 16, ensuring that the lubricant is kept within the actual rolling area.

[0019] As shown in Figure 1, ring element 5 is wider in the axial direction than ring element 4. Ring element 5 protrudes in the axial direction from the outer ring by a ring portion 17, which is configured as a ring flange protruding radially outward. A measuring body 19 is arranged on the outer surface 18 of ring portion 17. This measuring body is a shrunk-on metal ring with an etched angular reference, optionally covered by a protective ring. This measuring body 19 is fixed in position and is connected immovably to ring portion 17 and therefore to the inner ring 3.

[0020] Furthermore, a measuring device 20 is provided which includes measuring means 21, shown here only in dashed lines, which are able to interact with the measuring body 19, i.e. to measure the angular scale, and which, by means of an associated control device, are able to measure with high precision the actual rotational position of the inner ring 3 relative to the fixed outer ring 2. The measuring means 21 are suitable measuring sensors arranged for inductive, optical or magnetoresistive measurements.

[0021] The measuring means 21 is accommodated in a suitable housing 22, which is preferably a plastic component. To fix the measuring device 20 in place, an adapter 23 is provided, which is fixed axially on an axial ring surface 24 of the outer ring 2, and the measuring device 20 is fixed axially to the adapter 23. For fixation, the measuring device 20 or the housing 22 has a number of holes 25, and the adapter 23 likewise has corresponding holes that align with the holes 25, through which fixing screws are guided and tightened into corresponding holes 26 in the outer ring 2, as shown in Figure 2.

[0022] The measuring device 20 or the housing 22 is preferably configured as a standardized component so that the measuring device 20 can be positioned in the same way for angular contact ball bearings of different sizes. The axial position adjacent to the measuring body 19 is adjusted by a specifically configured adapter, which is wider or narrower depending on the required position. When the measuring device 20 is connected to the adapter 23, the measuring gap 27 between the measuring means 21 and the measuring body 19 is simultaneously determined and fixed. Because the entire angle measuring system consisting of the measuring body 19 and the measuring device 20 is integrated into the angular contact ball bearing 1 itself, the angle measuring system can be pre-installed in the factory when the bearing is assembled, eliminating the need for on-site assembly of the angle measuring system. In addition, the exact positioning of the measuring means 21 relative to the measuring body 19 and the width of the measuring gap 27 can be set and checked in the factory, so that the completed angular contact ball bearing 1 only needs to be installed.

[0023] As shown in Figures 1 and 2, despite the integration of the angle measurement system, the angular contact ball bearing 1 is a very compact unit, and the axial protrusion of the ring section 17 and the axial arrangement of the measuring device 20 result in a negligible increase in radial size and only a slight axial lengthening. Therefore, integration into a machine frame is easily feasible. The drawings also clearly show that there is no space radially inside the inner ring 3 that would be occupied by the angle measurement system. This allows for the easy placement or installation of third-party objects such as cables, wiring, hoses, or other items in this area during assembly.

[0024] The angular contact ball bearing 1 is preferably a rotary table bearing, for example, installed in a machine tool for machining a workpiece by cutting material. Its outer ring 2 is directly or indirectly connected in a fixed position to a machine frame or the like, and its inner ring 3 is directly or indirectly connected to a table, which is mounted rotatably about an axis of rotation for holding a workpiece. [Explanation of symbols]

[0025] 1 Axial angular contact ball bearing 2 outer ring 3 inner ring 4 Ring Elements 5 Ring Elements 6 Receiving hole 7 Receiving hole 8 orbits 9 orbit 10 orbits 11 orbit 12 balls 13 balls 14 cages 15 Sealing Elements 16 Sealing Elements 17 Ring section 18 External surface 19 Dimensional measure 20 Measuring Devices 21 Measurement means 22 Housing 23 Adapter 24 ring surface 25 holes 26 holes 27 Measuring gap

Claims

1. The invention comprises an outer ring (2) and an inner ring (3) consisting of two ring elements (4, 5) connected to each other in the axial direction, the outer ring (2) being provided with two outer raceways (8, 9), the ring elements (4, 5) being provided with inner raceways (10, 11), respectively, and balls (12, 13) running in two rows on the outer raceways and the inner raceways (8, 9, 10, 11); 1. A double-row angular contact ball bearing comprising: a ring element (4, 5) having a ring portion (17) protruding in the axial direction beyond the outer ring (2); a measuring body (19) is provided on an outer cylindrical side surface (18) of the ring portion (17); the outer ring (2) is provided with a measuring device (20) having a measuring means (21) for detecting the measuring body (19), the measuring means being positioned radially adjacent to the measuring body (19) and slightly spaced from the measuring body (19) across a measuring gap (27); and the measuring device (20) is arranged in a space in a corner formed by an axial ring surface (24) of the outer ring (2) and a surface facing radially outward.

2. 2. Angular contact ball bearing according to claim 1, characterized in that an adapter (23) is provided, and the measuring device (20) is arranged on the outer ring (2) via the adapter (23).

3. Angular contact ball bearing according to claim 1, characterized in that the measuring device (20) is arranged directly on the outer ring (2).

4. 2. Angular contact ball bearing according to claim 1, characterized in that the measuring device (20) has a housing (22) and the measuring means (21) are accommodated in the housing (22).

5. 2. Angular contact ball bearing according to claim 1, characterized in that the measuring means (21) are inductive, optical or magnetoresistive measuring means (21).

6. 2. An angular contact ball bearing according to claim 1, characterized in that the measuring body (19) is a ring that is tightly fitted onto the side surface (18) and is provided with an angle scale.

7. 2. The angular contact ball bearing according to claim 1, which is a rotary table bearing.

8. 10. A machine tool for machining a workpiece by cutting material, comprising: a machine frame; and a table for supporting the workpiece, the table being mounted on the machine frame so as to rotate about an axis of rotation by means of an angular contact ball bearing (1) according to claim 1.

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