Support structure for combined ball bearings

Abstract

To provide a support structure of a combined ball bearing capable of remarkably reducing a burden to a worker by reducing the number of processes necessary for a process to apply pretension to a shaft.SOLUTION: With respect to a constitution of a support structure 100 of a combined ball bearing 110 in the support structure of the combined ball bearing for supporting an end portion of a shaft 106 by a combined bearing, a male screw portion 106b is formed on the end portion of the shaft 106, a male screw portion 102a is formed on an outer periphery of an outer ring 102 of the combined bearing, the support structure of the combined ball bearing includes: a first nut 120 attached to the male screw portion 106b of the end portion of the shaft 106 to hold an inner ring 104; and a second nut 130 attached to the male screw portion 102a of the outer ring 102, and pretension is applied to the shaft by pulling the outer ring 102 to a frame 109 of a device main body by the second nut 130.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a support structure for a duplex ball bearing in which an end of a shaft is supported by a duplex bearing. [Background technology]

[0002] Duplex ball bearings, which combine multiple angular contact ball bearings, have been known as bearings used in machine tools, etc. For example, Patent Document 1 discloses a back-to-back (DB) bearing, but there are also various other types of bearing combinations, such as face-to-face (DF) and parallel (DT) bearings. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-169804 A Summary of the Invention [Problem to be solved by the invention]

[0004] In ball bearings, it is necessary to form a gap between the balls and the outer and inner rings so that the balls, which are rolling elements, can rotate. However, if the gap is too wide, the range of movement of the balls becomes large, so a preload is sometimes applied to the ball bearings. And when supporting a shaft that requires high positional accuracy, such as a precision ball screw that is a feed device, in addition to the preload of the support bearings, a pretension is sometimes applied to the shaft itself.

[0005] FIG. 6 is a diagram for explaining the support structure of a conventional duplex ball bearing. For example, FIG. 6 illustrates a case where one side of a shaft 12 is supported by a back-to-back type (DB) bearing 10 and a pretension is applied to the shaft 12. A ball 15 is disposed between an inner ring 14 and an outer ring 16. The bearing 10 is preloaded by being fastened between a shaft nut 26 and a shoulder 12a of the shaft. In the case of such a back-to-back type (DB), a pretension is applied to the shaft 12 by pushing it against a frame 22 with a bolt 18 for the purpose of a pretension load. After that, the shaft nut 26 is removed, the frame 22 and the bearing 10 are removed, and a shim 20 is fitted between a housing 24 of the device body and a flange of the frame 22, and then the frame 22 is fastened to the housing 24 again. The reason why such disassembly and reassembly are necessary is that in order to determine the thickness of the shim 20, a target pretension load state must be created at the time of measuring the clearance between the housing 24 and the flange of the frame 22.

[0006] In view of these problems, the present invention aims to provide a support structure for a combination ball bearing that can significantly reduce the burden on workers by reducing the number of steps required for the process of applying pretension to the shaft. [Means for solving the problem]

[0007] In order to solve the above problems, a representative configuration of a support structure for a combined ball bearing according to the present invention, in which the end of a shaft is supported by a combined bearing, includes a male threaded portion formed on the end of the shaft, a male threaded portion formed on the outer periphery of the outer ring of the combined bearing, a first nut attached to the male threaded portion of the end of the shaft to hold the inner ring, and a second nut attached to the male threaded portion of the outer ring, and is characterized in that pretension is applied to the shaft by pulling the outer ring against the frame of the device body with the second nut.

[0008] According to the above configuration, the inner ring of the bearing is fixed to the shaft by the first nut. Then, the outer ring is pulled against the frame of the device body by the second nut, thereby applying pretension to the shaft. In this case, it is not necessary to fit a spacer such as a shim or a collar after applying pretension. Therefore, it is not necessary to dismantle the bearing and frame after adjusting the pretension and then reassemble them. This reduces the number of steps required for applying pretension to the shaft, and significantly reduces the burden on the worker.

[0009] The support structure of the combination ball bearing preferably includes a concave surface formed on the outer periphery of the outer ring and a collar that fixes the rotation of the second nut, and the inner periphery of the collar preferably has a convex portion that corresponds to the concave surface on the outer periphery of the outer ring. By providing the collar in this configuration, it is possible to prevent the outer ring from rotating when applying pretension to the shaft. This makes it possible to effectively prevent the outer ring and collar from rotating relative to the frame of the device body. Effect of the Invention

[0010] The rolling bearing of the present invention can provide a support structure for a duplex ball bearing that can significantly reduce the burden on workers by reducing the number of steps required to apply pretension to the shaft. [Brief description of the drawings]

[0011] [Figure 1] 2A to 2C are diagrams illustrating a support structure of the duplex ball bearing according to the present embodiment. [Diagram 2] FIG. [Diagram 3] 1A to 1C are diagrams illustrating an assembly process of the support structure. [Figure 4] 1A to 1C are diagrams illustrating an assembly process of the support structure. [Diagram 5] 11A to 11C are diagrams illustrating other configurations of a duplex ball bearing to which the support structure of the present embodiment can be applied. [Figure 6] FIG. 1 is a diagram illustrating a conventional duplex ball bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown or described.

[0013] Fig. 1 is a diagram illustrating a support structure for a duplex ball bearing according to this embodiment (hereinafter simply referred to as a support structure 100). Fig. 2 is an exploded perspective view of the support structure 100. Figs. 3 and 4 are diagrams illustrating an assembly process for the support structure 100.

[0014] As shown in Fig. 1, in a duplex ball bearing 110 supported by 100 of this embodiment, a plurality of balls 108, which are rolling elements, are arranged between an outer ring 102 and an inner ring 104. In this embodiment, duplex ball bearing 110 is a back-to-back (DB) angular contact ball bearing. Two rows of outer ring 102 are integrally molded, and two rows of inner ring 104 are separate.

[0015] In this embodiment, the shaft 106 is a shaft that requires high positional accuracy in the axial direction, such as a ball screw. A small diameter portion 106a is formed at the end of the shaft 106, and the inner ring 104 of the duplex ball bearing 110 is fitted into this small diameter portion 106a. As shown in Figure 2, a male thread portion 106b and a shaft groove 106c are formed at the end of the shaft 106.

[0016] As shown in FIG. 3(a), a washer 140 for holding the inner ring 104 and a first nut 120 (so-called shaft nut) are attached to the male threaded portion 106b at the end of the shaft 106.

[0017] The star washer 140 has one pawl 142 formed on its inner periphery and a number of teeth 144 formed on its outer periphery. The pawl 142 is inserted into the shaft groove 106c of the shaft 106. This makes it possible to prevent the star washer 140 from rotating relative to the shaft 106.

[0018] By screwing the first nut 120 into the male threaded portion 106b, the two inner rings 104 are sandwiched and fixed between the shaft shoulder 106d and the first nut 120, and a preload is applied. When a predetermined preload is reached, the teeth 144 of the star washer are bent and inserted into the nut groove 122 on the outer periphery of the first nut 120, as shown in FIG. 3(b). This prevents the first nut 120 from rotating relative to the star washer 140, and therefore prevents the first nut 120 from rotating relative to the shaft 106.

[0019] On the other hand, a male thread portion 102a is formed on the outer periphery of the outer ring 102 of the duplex ball bearing 110. Then, as shown in Fig. 4(a), a collar 150 is attached to the frame 109, and a second nut 130 (a large-diameter nut with a structure similar to that of the shaft nut) is attached from above to the male thread portion 102a.

[0020] The collar 150 is fastened to the frame 109 by inserting a bolt 160 through a bolt hole 154. This fixes the rotation of the second nut 130. A plurality of teeth 152 (two in this embodiment) are provided on the outer periphery of the collar 150.

[0021] When the second nut 130 is fastened to the male thread portion 106b formed on the outer periphery of the outer ring 102, the outer ring 102 is pulled against the frame 109 via the collar. When the outer ring 102 is pulled, a pretension is applied to the shaft 106 via the duplex ball bearing 110. When a predetermined pretension is reached, the teeth 152 of the collar 150 are bent and inserted into the nut groove 132 on the outer periphery of the second nut 130, as shown in FIG. 4(b). This stops the second nut 130 from rotating and maintains the pretension.

[0022] According to the above configuration, there is no need to fit a spacer such as a shim or collar after applying pretension to the shaft 106. Therefore, there is no need to disassemble and reassemble the duplex ball bearing 110 after adjusting the pretension. This reduces the number of steps required to apply pretension to the shaft 106, and significantly reduces the burden on the worker.

[0023] As another configuration, for example, a concave surface may be formed on the outer periphery of the outer ring 102, and a corresponding convex portion may be formed on the inner periphery of the collar 150. According to this configuration, the rotation of the outer ring 102 can be stopped by the collar 150, so that the rotation of the outer ring 102 can be prevented when the second nut 130 is tightened.

[0024] 5 is a diagram illustrating another configuration of a duplex ball bearing to which the support structure 100 of this embodiment can be applied. The support structure 100 of this embodiment can also be applied to a three-row duplex ball bearing 210, for example, as shown in FIG. 5(a). Also, the support structure 100 of this embodiment can be applied to up to a four-row duplex ball bearing 310, for example, as shown in FIG. 5(b). Increasing the number of bearing rows in this way can improve the load-bearing capacity and rigidity of the bearing.

[0025] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Industrial Applicability]

[0026] The present invention can be utilized as a support structure for a duplex ball bearing in which an end of a shaft is supported by a duplex bearing. [Explanation of symbols]

[0027] 10...bearing, 12...shaft, 12a...shaft shoulder, 14...inner ring, 15...ball, 16...outer ring, 18...bolt, 20...shim, 22...frame, 24...housing, 26...shaft nut, 30...bearing, 100...support structure, 102...outer ring, 102a...male thread portion, 104...inner ring, 106...shaft, 106a...thin diameter portion, 106b...male thread portion, 106c...shaft groove, 108...ball, 109...frame, 110...combined ball bearing, 120...first nut, 122...nut groove, 130...second nut, 132...nut groove, 140...star washer, 142...claw, 144...tooth, 150...collar, 152...tooth, 154...bolt hole, 210...combined ball bearing, 310...combined ball bearing

Claims

[Claim 1] In a support structure for a duplex ball bearing in which the end of a shaft is supported by a duplex bearing, A male thread portion formed on an end portion of the shaft; A male thread portion formed on an outer periphery of an outer ring of the combined bearing; A first nut that is attached to the male threaded portion of the end of the shaft and holds an inner ring; A second nut attached to the male thread portion of the outer ring; Including, 13. A support structure for a duplex ball bearing, comprising: a second nut that pulls the outer ring against a frame of a main body of the device, thereby applying a pretension to the shaft.

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