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 each being provided with an inner raceway, and balls running in two rows on the outer raceway and the inner raceway. [Background technology]

[0002] Such double-row angular contact ball bearings are used in a variety of fields where a bearing is required to support both radial and axial loads. One example of an application is as a rotary table bearing for such a double-row angular contact ball bearing, which can be used to support a rotary table of a machine tool that rotates at high speed. The angular contact ball bearing allows the rotary table to rotate at high speed, particularly at a speed that cannot be achieved with axial / radial bearings that are normally used for 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 provided on the table side, and the inner ring is placed on the outside of 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 rotational position of the rotary table with high precision relative to the fixed machine frame, i.e. to measure the exact angular position. For this purpose, it is necessary to additionally install a measuring device for measuring the angle. This measuring device is preferably arranged in the plane of the angular contact ball bearing, through which the pipe of the rotary table passes, as described above, and for this purpose, a corresponding mounting must be provided on the frame so that the measuring device can be positioned in the bearing plane. This is because, while in the bearing plane the tilt in the bearing is minimal, if the measuring device is arranged, for example, at the lower end of the above-mentioned pipe, significantly larger tilt angles can occur, which is why the measurements in this area become too imprecise. Regardless of this, such an integration of a measuring device is disadvantageous on the one hand in that there are corresponding difficulties in mounting and positioning the measuring device inside the pipe in the bearing plane, and also in that this naturally occupies the inside of the pipe, blocking the center of the axis, making it impossible, for example, to route cables or wiring through the pipe or to integrate an oil distributor, etc. 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 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 invention comprises an integrated angle measuring device. This means that the angle measuring device is part of the angular contact ball bearing and is therefore mounted 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 designed. The ring element has a ring section that protrudes axially beyond the outer ring, which allows a measuring body to be arranged on the outer cylindrical side surface of the ring section. The measuring body is an angle reference that can be detected by the measuring device, which allows a very accurate angle measurement with a very high resolution. The measuring device is arranged on the outer ring and has 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 has many advantages. On the one hand, as mentioned above, it allows the rotary table to be rotated at very high speeds, which is not possible with axial / radial bearings. In addition, the integration of the angle measuring system allows the angular ball bearing to be pre-set in the factory after both the measuring body and the measuring device are mounted on the ring section of the inner ring and on 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 adjustments during assembly, which often require multiple trial and error procedures, can be avoided. Needless to say, the installation of the angle measuring system can also be avoided, since it is integrated in the bearing itself.

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

[0009] The measuring device itself is arranged on the axial ring surface of the outer ring, i.e., since it 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, the measuring device can be configured in a quasi-standardized manner and installed on angular contact ball bearings of different dimensions, since differences in the axial position of the measuring device relative to the measuring body can be compensated for with the corresponding bearing-specific adapter. The measuring device or its housing therefore has a uniform size, and the 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 comprises a housing which 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 comprises 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 different types or may be configured for different measuring methods. They may be inductive, optical or magnetoresistive, all of which allow highly accurate position detection. The measuring signals output by the measuring means are transmitted via suitable signal lines to a corresponding control device, which in particular controls the rotational movement of the rotary table. These signal lines may be an integrated part of the measuring device. However, it may also be envisaged that the measuring device is provided with suitable interfaces, such as plug contacts, which allow a corresponding signal transmission in analogue or serial manner.

[0013] As mentioned above, the measuring body is provided on the cylindrical outer surface of the axially projecting ring section. Preferably, this measuring body is or comprises a ring shrunk onto the metal surface and provided with an angular scale. The angular scale may be applied, for example, by etching the metal ring. This ring is shrunk onto the ring section, and for this purpose the ring is slightly heated and expanded or the ring section is cooled and the diameter of the ring section is slightly reduced, in which case both heating and cooling may also be performed. Once the ring has been put on and the temperature has been 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 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 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 further relates to 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 of the type mentioned 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 description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of an angular contact ball bearing according to the present invention, partially in perspective; [Diagram 2] FIG. 2 is a partial perspective view of the angular contact ball bearing of FIG. 1, not cut; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] FIG. 1 shows a perspective cross-sectional partial view of an angular contact ball bearing 1 according to the invention. The angular contact ball bearing 1 comprises an outer ring 2 and an inner ring 3, the inner ring 3 consisting 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 in 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, which are formed in the two ring elements 4, 5. The balls 12 of the first ball row run on the raceways 8 and 10, and the balls 13 of the second ball row run on the raceways 9 and 11. The 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, so that the lubricant is kept in the actual rolling area.

[0019] As shown in Fig. 1, the ring element 5 is wider in the axial direction than the ring element 4. The ring element 5 projects in the axial direction from the outer ring by a ring portion 17, which is configured as a ring flange projecting radially outwards. A measuring body 19 is arranged on the outer side 18 of the ring portion 17. This measuring body is a shrunk-on metal ring with etched angular references, optionally covered by a protective ring. This measuring body 19 is fixed in position and connected immovably to the ring portion 17 and therefore to the inner ring 3.

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

[0021] The measuring means 21 are 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 fixing, the measuring device 20 or the housing 22 has a number of holes 25, likewise the adapter 23 has corresponding holes that align with the holes 25, through which fixing screws are guided and tightened in corresponding holes 26 of the outer ring 2, as shown in FIG.

[0022] The measuring device 20 or the housing 22 is preferably constructed 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 close to the measuring body 19 is adjusted by a specifically constructed adapter, which is wider or narrower depending on the required position. The measuring device 20 is connected to the adapter 23, so that the measuring gap 27 between the measuring means 21 and the measuring body 19 is simultaneously determined and fixed. Since 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, when the bearing is assembled, this angle measuring system can already be pre-installed in the factory, so that no assembly work of the angle measuring system on site is required. In addition, the exact positioning of the measuring means 21 with respect to the measuring body 19 as well as the width of the measuring gap 27 can be set and checked in the factory, so that only the completed angular contact ball bearing 1 has to be installed.

[0023] As shown in figures 1 and 2, despite the integration of the angle measuring system, the angular contact ball bearing 1 is a very small unit, with a negligible increase in radial size and only a slight axial length due to the axial projection of the ring parts 17 and the axial arrangement of the measuring device 20. Therefore, integration into a machine frame is easily feasible. The figures also clearly show that there is no space radially inside the inner ring 3 that is occupied by the angle measuring system. This allows third-party objects such as cables, wiring, hoses or other items to be easily placed or installed 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 workpieces by cutting material, with its outer ring 2 directly or indirectly connected in a fixed position to a machine frame or the like and its inner ring 3 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 Cage 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. A double-row angular contact ball bearing comprising 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), and balls (12, 13) running in two rows on the outer and inner raceways (8, 9, 10, 11), the ring elements (4, 5) having a ring portion (17) being:

1. A double-row angular contact ball bearing, comprising: a ring part (17) which projects axially beyond the outer ring (2); a measuring body (19) is provided on an outer cylindrical side surface (18) of the ring part (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).

2. 2. Angular contact ball bearing according to claim 1, characterized in that the measuring device (20) is arranged on an axial ring surface (24) of the outer ring (2).

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

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

5. 5. 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).

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

7. 7. The angular contact ball bearing according to claim 1, wherein the measuring body (19) is or includes a ring which is press-fitted onto the side surface (18) and is provided with an angle scale.

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

9. 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 an angular contact ball bearing (1) according to any one of claims 1 to 8.

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