Bearing assembly

Abstract

A bearing assembly (1) is disclosed that includes a first raceway element (2) and a second raceway element (4), and a ball (6) is disposed between the raceway elements (2, 4). The ball (6) rolls on a raceway (8) disposed on the raceway elements (2, 4). In cross section, the bearing assembly (1) conceptually has a rotation axis (A) of the ball (6). R ) and the rotation axis (A R ) perpendicular to the axis (A S ) into four quadrants (I, II, III, IV) arranged clockwise, and the ball (6) has four contact points (PI, P-II, P-III, P-IV) with the raceway (8), each of which is located in one of the four quadrants (I, II, III, IV). The raceway (8) of the second raceway element (4) is located in the first quadrant (I) and the second quadrant (II), and the raceway (8) of the first raceway element (2) is located in the third quadrant (III) and the fourth quadrant (I). The center point (MI) of the radius of curvature (RI) of the orbit (8-I) in the first quadrant (I) is in the third quadrant (III), the center point (M-II) of the radius of curvature (R-II) of the orbit (8-II) in the second quadrant (II) is in the fourth quadrant (IV), the center point (M-III) of the radius of curvature (R-III) of the orbit (8-III) in the third quadrant (III) is in the first quadrant (I), and the center point (M-IV) of the radius of curvature (R-IV) of the orbit (8-IV) in the fourth quadrant (IV) is in the second quadrant (II).

Description

[Technical Field]

[0001] The present invention relates to a bearing assembly comprising a first raceway element and a second raceway element as described in claim 1. [Background technology]

[0002] In high-precision transmissions, particularly in robot joints or wind turbine blade bearings, the bearings used must often perform rotational motion of less than 360° at low speeds. Simultaneously, complex load conditions can arise due to both radial and axial forces, inclination moment loads, and load combinations. For this purpose, cross-roller bearings, which can be used as a single bearing, are commonly employed, whereas other bearing types would require two bearings. Cross-roller bearings offer high rigidity, high running precision, and small clearances. They utilize cylindrical rollers that are alternately and continuously inserted between bearing rings inclined at 45°. Such cross-roller bearings are known for both rotational and linear motion applications.

[0003] However, in cylindrical rollers, sliding, or so-called slippage, occurs more frequently between the roller and the raceway surface and between the roller side and the opposing raceway, which can lead to increased wear. Sliding also occurs between the rollers themselves, which favors spacers, and consequently increases the complexity of the bearing and adds to the cost of assembly. Sliding also leads to significant energy loss in such bearings. Furthermore, in cross-roller bearings, edge stresses can occur, especially under high loads. While these edge stresses can be mitigated by special raceway contours, these contours are always provided only for individual load cases, resulting in insufficient load distribution in other load cases. The closer the load direction is to the roller's axis of rotation, the smaller the load supported by the roller. As a result, under certain load conditions, a situation arises where only 50% of the usable rollers support the load. Moreover, in some cases, because the rollers are arranged alternately, half of the rollers may support more load than the other half, creating unevenly distributed load zones. Additionally, arranging rollers alternately requires special mechanisms for positioning the rollers, adding extra effort to the assembly of the bearing.

[0004] Other possible solutions for supporting a load when axial force is dominant are axial ball bearings or four-point contact ball bearings, for example, when additional bending moment support is required. However, these bearings also have some drawbacks. Axial ball bearings have minimal radial load stiffness, and radial loads can lead to eccentricity between the bearing rings. Centrifugal force causes the balls in axial ball bearings to exhibit increased sliding. This can lead to high contact pressure, as there are only two contact points between the ball and the raceway. The two contact points between the ball and the raceway change with the load direction, which causes a dynamic change in the axis of rotation of the ball, resulting in high non-constant sliding and therefore large energy loss. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the object of the present invention is to provide a bearing assembly that has low energy loss, is stable against radial and axial loads, is cost-effective, and is easy to manufacture. [Means for solving the problem]

[0006] This objective is achieved by the bearing assembly described in claim 1.

[0007] The bearing assembly includes a first raceway element and a second raceway element, with balls positioned between the raceway elements. Each ball rolls on a raceway positioned on the raceway element.

[0008] The bearing assembly can be a ball bearing in the form of a radial bearing, an axial bearing, or a linear bearing. In the case of a radial bearing, the first and second raceway elements correspond to the inner and outer rings. In the case of an axial bearing, the inner and outer rings (i.e., the first and second raceway elements) are called the housing disk and shaft disk. In the case of a linear bearing, the first and second raceway elements correspond to the rail and carriage.

[0009] To enable low sliding and friction losses, as well as high bending stiffness and low maximum contact pressure with the raceway, each ball has four contact points with the raceway. This means that each ball has a total of four contact points, i.e., two contact points for each raceway element. At each contact point, the raceway and the ball share the same tangent, and the radius of curvature, i.e., the distance between the center of the circle of curvature of the raceway's curvature and the contact point, is perpendicular to this tangent. These four contact points divide the contact pressure, in contrast to other bearings, thereby reducing contact stress and consequently wear, friction, and other surface damage.

[0010] Conventional four-point contact ball bearings, which can be used as axial bearings, also have four contact points, but these contact points exist only in theory. During operation, only two of the four theoretical contact points are active, which therefore leads to high contact pressure at these two active contact points. In contrast, in the bearing assembly proposed here, all four contact points are always active, and the contact pressure is better distributed. Conventional four-point contact ball bearings further suffer from reduced contact stiffness in both the axial and radial directions because the normal direction of the contact points is not aligned with the axial or radial axis. Moreover, such bearings require a high axial preload to be able to support radial loads.

[0011] To achieve this, the bearing assembly is conceptually divided in cross-section into four quadrants arranged clockwise by the axis of rotation of the balls and an axis perpendicular to the axis of rotation of the balls. Here, the axis of rotation of the balls is considered the conceptual axis of rotation when stationary. During operation, the axis of rotation of the balls is not fixed and can move.

[0012] The trajectories of the second orbital element are in the first and second quadrants, and the trajectories of the first orbital element are in the third and fourth quadrants. The center of the radius of curvature of the trajectory in the first quadrant is in the third quadrant, the center of the radius of curvature of the trajectory in the second quadrant is in the fourth quadrant, the center of the radius of curvature of the trajectory in the third quadrant is in the first quadrant, and the center of the radius of curvature of the trajectory in the fourth quadrant is in the second quadrant. Here, each of the four contact points of the ball is in one of the four quadrants. This special arrangement ensures that each ball always has four contact points with its trajectory, and that these contact points are maintained even under load. In conventional four-point contact ball bearings, the load is applied to only two or at most three contact points during operation under load. Axial ball bearings function with only two contact points, and cross roller bearings also function with only two contact lines. The four contact points thus generate lower contact pressure for each contact point with the ball, which can reduce wear on the bearing assembly, for example, and at the same time, the arrangement of the contact points allows for support of radial and axial loads.

[0013] The use of balls simplifies the assembly of bearing assemblies because, compared to rollers, the balls can be installed without a specific orientation. The use of balls is even more advantageous because they are perfectly symmetrical elements, not requiring the alternating orientation of rolling elements as seen in cross-roller bearings. This allows all rolling elements to support the load between all tracks, even when operating under special conditions, rather than relying on only half of the elements as in the case of cross-roller bearings. Furthermore, the balls can rotate freely around their center and therefore transmit the load at any point on their surface. This maximizes the utilization of the ball's surface, distributing contact across the entire ball surface and thus wear across the entire ball surface. In contrast, in cross-roller bearings, for example, only certain areas of the rolling element surface wear.

[0014] The bearing assembly described here can be implemented as a total rolling bearing without the additional wear occurring at the same point every time, as is the case with roller bearings. Because the balls make point contact with each other, there is virtually no wear on the balls. However, the contact point "moves" across the surface of the balls, and therefore the load is not always applied to the same point, which leads to a lower total load on the balls. This is because, in contrast to roller bearings, the orientation of the balls changes relative to the axis of rotation. Alternatively, a cage can be used, and spacers can be used instead of a full cage. This bearing assembly provides sufficient space in the area along the axis of rotation of the balls to accommodate both spacers and cages.

[0015] According to one embodiment, the intersection of the two radii of curvature of the raceway of the first raceway element lies on an axis perpendicular to the rotation axis of the ball, and the intersection of the two radii of curvature of the raceway of the second raceway element also lies on an axis perpendicular to the rotation axis of the ball. These axes may be a common axis, in particular an axis perpendicular to the rotation axis and passing through the center point of the ball. The intersections may also lie on the rotation axis. Each raceway thus has two radii of curvature whose center points do not coincide, each raceway is composed of two segments, and there is a transition portion between these segments. The transition portion between the two raceways or the contact line of the two raceways lies on a plane that passes through the center point of the ball and is perpendicular to the virtual rotation axis of the ball. These two radii of curvature and their special arrangement can ensure that the ball always has four contact points with the raceways. The two radii of curvature may be different or identical.

[0016] According to a further embodiment, these radii of curvature are identical. This leads to symmetrical separation of the radii of curvature and their center points on the four quadrants. With this symmetrical arrangement, the load is evenly distributed over the four contact points between the balls and the raceways.

[0017] According to a further embodiment, the contact points are arranged offset relative to the rotation axis of the ball perpendicularly thereto. This means that the contact points are preferably arranged on the rotation axis of the ball and on an axis perpendicular to the rotation axis of the ball. In this way, it can be prevented that the bearing assembly behaves as an axial or radial ball bearing having only two contact points, which would result in reduced radial or axial stiffness. Furthermore, in contrast to radial or axial ball bearings which have one contact point on each of the raceway elements, this bearing assembly can support radial or axial loads in a directly defined manner from the start of loading. Similarly, in contrast to ball bearings which have only one contact point on one of the shafts, it can support axial or radial loads in a directly defined manner from the start of loading.

[0018] According to a further embodiment, the contact points are arranged in a region of ±20°, preferably ±10°, about an axis perpendicular to the rotation axis of the ball. The contact points between the ball and the raceway may vary within this region depending on the application. This arrangement results in special kinematics of the ball provided by the four contact points, since the rotation axis of the ball always remains perpendicular to the axis about which the contact points are arranged, even during loading.

[0019] According to one embodiment, the radius of curvature is a variable radius. This means that the respective raceway may be arcuate, elliptical or substantially ovate.

[0020] The first race element and / or the second race element may be configured as split race elements, and a preloading mechanism is provided for controlling the contact points between the balls and the raceway. By preloading the respective race elements, the preload at the contact points can be adjusted by adjusting the gap between the portions of the split race element.

[0021] The bearing assembly can be embodied as an axial bearing, a radial bearing or a linear bearing. Depending on the respective design of the bearing assembly, the rotation axis of the balls can be perpendicular to the rotation axis of the bearing (in the case of axial bearings), parallel to the rotation axis of the bearing (in the case of radial bearings), and perpendicular to the direction of movement (in the case of linear bearings).

[0022] Many different bearing configurations exhibiting the advantages of the bearing assemblies as respectively described above are therefore possible with the bearing assembly described herein. In particular, the bearing assembly described herein provides good radial load stiffness and low wear behavior due to low sliding behavior.

[0023] In a further embodiment, a transmission, particularly a high-precision transmission, is provided, comprising the bearing assembly described above. Such a high-precision transmission can be used, for example, in a robot where very precise control of the movement sequence and therefore the joints in which the bearings are used is required. The bearing assembly can be used, for example, as a bearing in a robotic application to connect a continuous arm or arm section.

[0024] Further advantages and favorable embodiments are described in the description, drawings, and claims. In particular, the combinations of features described in the description and drawings are purely illustrative, and these features may exist individually or in other combinations.

[0025] The present invention will be described in more detail below using exemplary embodiments shown in the drawings. The exemplary embodiments and combinations shown herein are purely illustrative and are not intended to define the scope of the invention. This scope is defined solely by the pending claims. [Brief explanation of the drawing]

[0026] [Figure 1] A schematic cross-sectional view of the bearing assembly is shown. [Figure 2] Figure 1 shows a schematic cross-sectional view of a bearing assembly as a single-row axial bearing. [Figure 3] Figure 1 shows a schematic cross-sectional view of a bearing assembly as a single-row radial bearing. [Figure 4] Figure 1 shows a schematic cross-sectional view of a bearing assembly as a double-row axial bearing. [Figure 5] Figure 1 shows a schematic cross-sectional view of a bearing assembly as a double-row radial bearing. [Figure 6] Figure 1 shows a schematic cross-sectional view of a bearing assembly as a linear bearing with segmented orbital elements. [Modes for carrying out the invention]

[0027] In the following, identical or functionally equivalent elements are indicated by the same reference number.

[0028] Figure 1 shows a bearing assembly 1 comprising a first raceway element 2 and a second raceway element 4. Balls 6 are positioned between the raceway elements 2 and 4 as rolling elements. The balls 6 roll on raceways 8, which are positioned on the raceway elements 2 and 4.

[0029] The bearing assembly 1 can be configured as a ball bearing, particularly as a radial or axial bearing, or as a linear bearing. In the case of a radial bearing, the first raceway element 2 and the second raceway element 4 correspond to the inner and outer rings. In the case of an axial bearing, the first raceway element 2 and the second raceway element 4 correspond to the shaft disk and the housing disk. In the case of a linear bearing, the first raceway element 2 and the second raceway element 4 correspond to the rail and the carriage.

[0030] In the bearing assembly 1 shown in Figure 1, the track 8 can be conceptually divided into four quadrants I, II, III, and IV. The division into the four quadrants I, II, III, and IV corresponds to the axis of rotation of the ball A R and rotation axis A R Axis A is perpendicular to it. S This is brought about by the fact that the orbit of the second orbital element 4 is formed by two segments 8-I and 8-II and lies in the first quadrant I and the second quadrant II, and the orbit of the first orbital element 2 is formed by two orbital segments 8-III and 8-IV and lies in the third quadrant III and the fourth quadrant IV.

[0031] The ball 6 is in contact with the raceways 8-I and 8-II at two contact points P-I and P-II located in the two contact zones 10-I and 10-II, and is in contact with the raceways 8-III and 8-IV at two contact points P-III and P-IV located in the contact zones 10-III and 10-IV. The raceway 8 has a special design to ensure that the ball 6 reliably contacts the raceway 8 at the contact points P-I, P-II, P-III and P-IV. The center point M-I of the curvature radius R-I of the raceway segment 8-I is located in the third quadrant III, the center point M-II of the curvature radius R-II of the raceway segment 8-II is located in the fourth quadrant IV, the center point M-III of the curvature radius R-III of the raceway segment 8-III is located in the first quadrant I, and the center point M-IV of the curvature radius R-IV of the raceway segment 8-IV is located in the second quadrant II.

[0032] In the embodiment shown in Figure 1, the intersection of the curvature radii R-I and R-II of the first quadrant I and the second quadrant II is on the axis A S , and the intersection of the curvature radii R-III and R-IV of the third quadrant III and the fourth quadrant IV is also on the axis A S . However, the intersection does not have to be located on the axis A S . Here, the radius of curvature R is understood to mean the radius that defines the curvature, that is, the distance between the raceway 8 and the center point M. In particular, as shown in Figure 1, a straight line passing through M-I and M-III intersects a straight line passing through M-II and M-IV at an intersection point S. In the case shown herein, the intersection point S is simultaneously located at the intersection of the rotation axis A R and the axis A S , but this is not absolutely necessary. This specific design of the curvature radius R of the raceway 8 ensures that the ball 6 contacts the raceway 8 at the contact points P-I, P-II, P-III and P-IV. The contact points P-I, P-II, P-III and P-IV are located in the contact zone 10 in a region of ±20°, particularly ±10°, around the axis A S .

[0033] In order to ensure that the ball bearing 1 is not only capable of supporting axial or radial loads, the contact points P-I, P-II, P-III, P-IV are arranged along the axis A SIt is always offset relative to the ball. In this way, the ball 6 always has four contact points PI, P-II, P-III, and P-IV with the raceway 8 located in contact zones 10-I, 10-II, 10-III, and 10-IV, respectively, achieving good radial load stiffness, good load and pressure distribution, and consequently low wear behavior.

[0034] The bearing assembly 1 can be used in different configurations, as shown in Figures 2 to 6.

[0035] As shown in Figure 2, the bearing assembly can be used as a single-row axial ball bearing, in which case the rotation axis A R is the bearing rotation shaft A L It is perpendicular to axis A. Here, contact zones 10-I, 10-II, 10-III, and 10-IV are located around axis A. S The bearing's rotation axis A L It is parallel to it.

[0036] Alternatively, as shown in Figure 3, bearing assembly 1 can also be used as a single-row radial bearing. In this case, rotation axis A R The rotation axis A of bearing 1 L It is parallel to axis A, around which contact zones 10-I, 10-II, 10-III, and 10-IV are located. S In this case, bearing rotation axis A L It is perpendicular to it.

[0037] The bearing assembly 1 can be used as a double-row axial ball bearing (Figure 4) or as a double-row radial ball bearing (Figure 5). In the case of a double-row axial ball bearing, the rotation axis A R The bearing's rotation axis A L It is perpendicular to the axis of rotation, and in the case of a double-row radial ball bearing, axis A R The bearing shaft A L It is parallel to it.

[0038] In the case of such double-row axial or radial ball bearings, the inner ring 2 or outer ring 4 can be configured as segmented rings (not shown). In this case, a preloading mechanism, such as a screw connection, can be used to control the contact points PI, P-II, P-III, P-IV, or contact zone 10 between the balls 6 and the raceway 8. The preloads of the respective rings 2 and 4 allow the preloads of contact points PI, P-II, P-III, and P-IV to be adjusted by adjusting the gaps between the segments of the segmented rings 2 and 4. Single-row axial or radial ball bearings can also be realized with segmented rings 2 and 4 and a preloading mechanism.

[0039] The bearing assembly 1 can also be used as a linear bearing, as shown in Figure 6. In this case, the first raceway element 2 is formed by the rail, and the second raceway element is formed by the carriage 12, from which element 4' is separated. In this case, the second raceway element 4' can have its preload or gap adjusted by the preload element 14 to adjust the contact points PI, P-II, P-III, P-IV or contact zones 10-I, 10-II, 10-III, 10-IV. In the case of the linear bearing 1 in Figure 6, the ball rotation axis A R It is perpendicular to the direction of movement of the bearing 1 in the carriage 12.

[0040] The ball bearings described herein can achieve good radial and axial load rigidity as well as low wear behavior due to lower friction. [Explanation of Symbols]

[0041] 1. Bearing Assembly 2. First orbital element 4. Second orbital element 6 balls 8 orbits 10 Contact Zones 12 Carriage 14 Preload mechanism Quadrant I, II, III, IV A L bearing rotation shaft A R Ball rotation axis A S Ball rotation axis A R A perpendicular axis M is the center point of the radius of curvature. P contact point R radius of curvature S intersection

Claims

1. A bearing assembly (1) comprising a first raceway element (2) and a second raceway element (4), wherein a ball (6) is positioned between the first raceway element (2) and the second raceway element (4), and the ball (6) rolls on a raceway (8) positioned on the first raceway element (2) and the second raceway element (4), wherein in cross-section, the bearing assembly (1) is conceptually arranged clockwise by the axis of rotation (AR) of the ball (6) and the axis (AS) perpendicular to the axis of rotation (AR) of the ball (6). The system is divided into four quadrants (I, II, III, IV), the ball (6) has four contact points (P-I, P-II, P-III, P-IV) with the trajectory (8), each contact point (P-I, P-II, P-III, P-IV) is located in one of the four quadrants (I, II, III, IV), the trajectory (8) of the second trajectory element (4) is in the first quadrant (I) and the second quadrant (II), the trajectory (8) of the first trajectory element (2) is in the third quadrant (III) and the fourth quadrant (IV), and the center of the radius of curvature (R-I) of the trajectory (8-I) in the first quadrant (I) Point (M-I) is in the third quadrant (III), the center point (M-II) of the radius of curvature (R-II) of the trajectory (8-II) in the second quadrant (II) is in the fourth quadrant (IV), the center point (M-III) of the radius of curvature (R-III) of the trajectory (8-III) in the third quadrant (III) is in the first quadrant (I), the center point (M-IV) of the radius of curvature (R-IV) of the trajectory (8-IV) in the fourth quadrant (IV) is in the second quadrant (II), and the contact points (P-I, P-II, P-III, P-IV) are perpendicular to the axis of rotation (AR) of the ball (6). The ball (6) is positioned offset from the axis (AS), and the intersection of the radii of curvature (R-I, R-II) of the trajectories (8-I, 8-II) in the first quadrant (I) and the second quadrant (II), and / or the intersection of the radii of curvature (R-III, R-IV) of the trajectories (8-III, 8-IV) in the third quadrant (III) and the fourth quadrant (IV), is not on the axis (AS), and the contact points (P-I, P-II, P-III, P-IV) of the ball (6) with the trajectory (8) are around the axis (AS) which is perpendicular to the axis of rotation (AR) of the ball (6).A bearing assembly characterized by being positioned within a range of ±10°.

2. The bearing assembly according to claim 1, wherein the radius of curvature (R-I, R-II, R-III, R-IV) of the raceway (8) is a variable radius.

3. The bearing assembly according to claim 1 or 2, wherein the first raceway element (2) and / or the second raceway element (4) are configured as segmented raceway elements, and a preloading mechanism is provided to control the contact points (P-I, P-II, P-III, P-IV) between the ball (6) and the raceway (8).

4. The bearing assembly according to any one of claims 1 to 3, wherein the bearing assembly (1) is a ball bearing, the first raceway element (2) is an inner ring or a shaft disk, and the second raceway element (4) is an outer ring or a housing disk.

5. The rotation axis (AR) of the ball (6) is the rotation axis (A) of the ball bearing (1). Ｌ The bearing assembly according to claim 4, which is perpendicular or parallel to ).

6. The bearing assembly according to any one of claims 1 to 3, wherein the bearing assembly (1) is a linear bearing, the first track element (2) is a rail, and the second track elements (4, 12) are a carriage.

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