Pressing Structure of Ball Bearing and Method for Manufacturing Rotating Shaft

Abstract

To facilitate the application of pressurization to a steel ball of a bearing that supports a shaft.SOLUTION: A pressurization structure of a ball bearing has: an inner race 2 fixed to a rotational shaft 1; an outer race 6 that is arranged in a mounting hole 4 provided in a housing 3, and holds a steel ball 5 between itself and the inner race 2; and a first ring nut 7 that has a male screw 7a to be screwed into a female screw 4a on the inner periphery of the mounting hole 4, and is tightened so as to apply a predetermined pressure to the steel ball 5 between the inner race 2 and the outer race 6 by rotation of the male screw 7a.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pressure application structure of a ball bearing and a method for manufacturing a rotating shaft.

Background Art

[0002] Conventionally, there are two types of preloading methods for bearings: fixed-position preloading and constant-pressure preloading, and fixed-position preloading is often used. In the support of the shaft constituting the gimbal mechanism used for supporting precision equipment, etc., in order to eliminate the play between the inner ring ~ steel ball ~ outer ring of the bearing, the thickness and number of shims sandwiched between the housing and the outer ring are adjusted to position the outer ring in the axial direction, and the adjustment of the preload amount applied to the steel balls has been carried out.

[0003] Further, in Cited Document 1, as a bearing structure related to the present invention, a structure is disclosed in which a double-row bearing that supports the steering shaft of an automobile is fixed to the steering shaft and locked by a so-called double nut.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the adjustment method using the shim has the problem that the work is complicated and delicate, so it has to rely on the touch of a skilled worker. In addition, the bearing support structure described in Patent Document 1 relates to the adjustment of one bearing used for supporting the steering shaft of an automobile, so it cannot be directly applied to the adjustment of the bearing that supports the shaft of the gimbal that is mainly supported at both ends. Further, the technology for eliminating the play between the double-row bearings cannot be directly applied to the structure for eliminating the play between the inner ring and the outer ring of the bearing.

[0006] The object of this invention is to apply an appropriate pressure between the inner race, outer race and steel balls of a bearing.

Means for Solving the Problem

[0007] To solve the above problems, this invention proposes the following means. The pressure application structure of a ball bearing according to the first aspect of the present invention includes an inner race fixed to a rotating shaft, an outer race disposed in a mounting hole provided in a housing and holding steel balls between the inner race, and a first ring nut having a male thread that engages with a female thread on the inner circumference of the mounting hole and is tightened so as to apply a predetermined pressure to the steel balls between the inner race and the outer race by rotation of the male thread.

[0008] A method for manufacturing a rotating shaft according to the second aspect of the present invention is a method for manufacturing a rotating shaft in which an inner race is fixed to the rotating shaft, and an outer race that holds steel balls between the inner race is disposed in a mounting hole provided in a housing, the method including a step of fixing the inner race to the rotating shaft, a step of disposing the outer race in the mounting hole, a step of moving the outer race in a direction along the rotating shaft by screwing and rotating a male thread on the outer circumference of a first ring nut with a female thread on the inner circumference of the mounting hole, and a step of applying a pressure in the direction of the rotating shaft to the steel balls between the inner race and the outer race by tightening the first ring nut with a predetermined torque.

Advantages of the Invention

[0009] According to the present invention, an appropriate pressure can be applied between the outer race, inner race and steel balls of a ball bearing.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] The minimum configuration example of the present invention will be described with reference to FIG. 1. The pressure application structure of this ball bearing includes an inner race 2 fixed to a rotating shaft 1, an outer race 6 disposed in a mounting hole 4 provided in a housing 3 and holding steel balls 5 between the inner race 2, and a male screw 7a that engages with a female screw 4a on the inner periphery of the mounting hole 4. The first ring nut 7 is tightened so that a predetermined pressure is applied to the steel balls 5 between the inner race 2 and the outer race 6 by the rotation of the male screw 7a.

[0012] According to the above configuration, by rotating the first ring nut 7 with a predetermined torque, the outer race 6 can be moved along the rotating shaft 1, and the steel balls 5 between the outer race 6 and the inner race 2 can be held in a state where a pressure is applied in the direction of the rotating shaft 1 according to the torque applied to the first ring nut 7.

[0013] Moreover, the minimum configuration example of the manufacturing method of the rotating shaft according to the present invention is a manufacturing method of a rotating shaft in which the inner race 2 is fixed to the rotating shaft 1, and an outer race 6 that holds steel balls 5 between the inner race 2 is disposed in a mounting hole 4 provided in the housing 3, the method including: a step of fixing the inner race 2 to the rotating shaft 1; a step of disposing the outer race 6 in the mounting hole 4; a step of moving the outer race 6 in a direction along the rotating shaft 1 by screwing and rotating a male screw 7a on the outer periphery of a first ring nut 7 with a female screw 4a on the inner periphery of the mounting hole 4; and a step of applying a pressure in the direction of the rotating shaft 1 to the steel balls 5 between the inner race 2 and the outer race 6 by tightening the first ring nut 7 with a predetermined torque.

[0014] According to the above configuration, by rotating the first ring nut 7 with a predetermined torque, the outer race 6 can be moved along the rotating shaft 1, and a pressure in the direction of the rotating shaft 1 can be applied to the steel balls 5 between the outer race 6 and the inner race 2 according to the torque applied to the first ring nut 7.

[0015] A configuration according to a first embodiment of the present invention, which embodies FIG. 1, will be described with reference to FIGS. 2 to 8. In the drawings, the same reference numerals are given to the configurations common to FIG. 1 to simplify the description. As shown in FIGS. 2 and 3, the housing 3 has a cylindrical appearance and has bearings 10 at its left and right ends. In one embodiment, the entire bearing composed of the inner race 2, the outer race 6, and the steel balls 5 is referred to as the bearing 10. Thus, the shaft 1 is supported between the bearings 10 provided at one end and the other end.

[0016] The inner race 2 of the bearing 10 is attached to the shaft 1 by a shaft fixing nut 11. Specifically, male threads 12 are formed at both ends of the shaft 1, and by screwing the female threads 13 on the inner circumference of the shaft fixing nut 11 into the male threads 12, the inner race 2 is sandwiched between the large-diameter portion 14 at the center of the shaft 1 and the shaft fixing nut 11, and the shaft 1 and the inner race 2 are integrally connected.

[0017] A part of the outer race 6 of the bearing 10 is a large-diameter flange portion 61, and it is axially positioned by the flange portion 61 and a first ring nut 7 into which a male thread 7a is screwed into the female thread 4a of the mounting hole 4 at the end of the housing 3. Further, the first ring nut 7 is fixed in a non-rotating state by applying an outward force along the rotating shaft 1 by screwing the male thread 15a on the outer circumference of a second ring nut 15 screwed into the female thread 4a on the inner side of the first ring nut 7 into the female thread 4a. Note that the preload adjustment and management of the bearing 10 are carried out by tightening the first ring nut 7, and after adjustment, the second ring nut 15 is tightened to be fixed in a predetermined pressurized state.

[0018] The process of attaching the bearing 10 to the shaft 1 and applying pressure to the steel balls 5 of the bearing 10 to manufacture a rotating shaft will be described. Screw the first ring nut 7 and the second ring nut 15 into the mounting holes 4 at both ends of the housing 3, and arrange them inward so as not to interfere with the side surface of the outer race 6 of the bearing 10 to be arranged in a later process.

[0019] Place the shaft 1 into the housing 3, insert its end into the inner race 2, and screw in the shaft fixing nut 11 to fix the inner race 2 to the shaft 1. As shown in Fig. 4, before tightening the first ring nut 7, the steel balls 5 are arranged at a position approximately in the center between the outer race 6 and the inner race 2, and there are gaps δo and δi between the outer race 6 and the inner race 2 and the steel balls 5.

[0020] When the first ring nut 7 is tightened and moved in the axial end direction (to the left in Fig. 4), as shown in Fig. 5, it approaches the side surface of the outer race 6. In this state, there is a gap l between the side surface of the outer race 6 and the side surface of the first ring nut 7. From this state, when the first ring nut 7 is further tightened, the gaps δo and δi become smaller, and as shown in Fig. 6, the outer race 6 (specifically, the side surface of the groove on its inner circumference), the inner race 2 (specifically, the side surface of the groove on its outer circumference), and the steel balls 5 come into contact.

[0021] When the first ring nut 7 is further tightened from the state of Fig. 6, due to the thrust force corresponding to the tightening torque, the outer race 6, the inner race 2, and the steel balls 5 are slightly elastically deformed, preload is applied, and the applied pressure increases according to the tightening. As shown in Fig. 7, the bearing 10 is positioned on the shaft 1 in a state where the contact point between the inner race 2 and the steel balls 5 and the contact point between the outer race 6 and the steel balls 5 are arranged on the chain line C.

[0022] It should be noted that it is desirable to alternately tighten the first ring nut 7 little by little on one end side and the other end side of the shaft 1 to evenly apply a predetermined applied pressure to the bearings 10 at both ends of the shaft 1.

[0023] In this way, after adjusting the tightening torque of the first ring nut 7 at both ends of the shaft 1, as shown in FIG. 7, the second ring nut 15 is tightened so as to be further moved in the axial end direction from the position in contact with the side surface of the first ring nut 7. By tightening the second ring nut 15, the contact pressure between the male threads 7a, 15a on the outer circumferences of the first ring nut 7 and the second ring nut 15 and the female thread 4a on the inner circumference of the mounting hole 4 is maintained due to the elastic deformation of the female thread 4a, and the first ring nut 7 can be fixed at a position where a predetermined applied pressure is generated. By applying a predetermined applied pressure through the above steps, a rotating shaft including the shaft 1 supported by the bearings 10 at both ends in the housing 3 can be manufactured.

[0024] Note that the tightening of the first ring nut 7 is performed, for example, as shown in FIGS. 8 and 9, by providing through holes 7b (two are shown in FIG. 8, but as shown in FIG. 9, a plurality are provided in the circumferential direction) penetrating the first ring nut 7 in the thickness direction, and rotating a pair of pins 20 inserted into these through holes 7b using a tool provided at diagonal positions at the tip of the arm 21. Further, the arm 21 inserts the tip of the shaft 22 at the center (formed in a hexagonal bolt shape, for example) into a torque wrench 23 having a hexagonal nut-shaped hole (a tool having a mechanism for displaying the generated torque or limiting the torque to a set torque), and is performed by operating the handle 25 at the tip of the arm 24. Instead of the torque wrench 23, it may be rotated using a tool capable of driving the shaft with a predetermined torque such as a torque driver (not shown). Furthermore, as shown in FIG. 9, arc-shaped slits 7c are provided at a plurality of locations in the circumferential direction in the first ring nut 7 (so as to avoid the through hole 7b), and the second ring nut 15 is also provided with a through hole 7b similar to the through hole 7b of the first ring nut 7. A pin 20 of a tool as shown in FIG. 8 is passed through the slit 7c of the first ring nut 7 to reach the position of the second ring nut 15 and inserted into the through hole 7b, and the tool can be rotated in the same manner as the first ring nut 7. It can also be performed by operating the second ring nut 15 with a tool inserted through an opening (indicated by reference numeral 3a in FIG. 2) provided in a part of the cylindrical housing 3.

[0025] According to the structure for applying pressure using the ring nut described in one embodiment, the preload amount of the bearing 10 can be adjusted and managed by the torque for tightening the first ring nut 7. The thrust generated in the first ring nut 7 can be calculated from the tightening torque and the nominal diameter by the following formula (1). F = T / (K·d) (Formula (1)) F: Thrust T: Tightening torque d: Nominal diameter K: Torque coefficient

[0026] By using the thrust obtained by the above formula (1) and referring to the characteristic curve showing the relationship between the axial load and axial displacement of the bearing, the preload amount can be estimated. As described above, the preload of the bearing, which has been adjusted and managed by the operator's touch, can be quantified with a tool that can adjust the axial torque, such as a precision torque driver, to a predetermined value, and can be easily adjusted and managed. The above characteristic curve shows the displacement amount of the bearing that increases as the load increases due to the phenomenon of elastic deformation occurring at the contact portion between the raceway ring and the rolling elements when a load is applied to the bearing. The characteristic curve is also called Axial Load - Axial Displacement.

[0027] In the above-described embodiment, two types of ring nuts, i.e., the first and the second, are used. However, a male thread may be provided on the outer periphery of the outer race and screwed into the female thread on the inner periphery of the housing. In this case, since the outer peripheral portion of the outer race also serves as the first ring nut, it is sufficient if there is one type of ring nut (corresponding to the second ring nut in one embodiment) for preventing the outer race from rotating.

[0028] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

Industrial Applicability

[0029] The present invention can be used for the pressure application structure of a bearing and the manufacturing method of a rotating shaft.

Explanation of Reference Numerals

[0030] 1 Rotating shaft (shaft) 2 Inner race 3 Housing 3a Opening 4 Mounting hole 4a Female thread 5 Ball 6 Outer race 7 (First) ring nut 7a Male thread 7b Through hole 7c Slit 10 Bearing 11 Shaft fixing nut 12 Male thread 13 Female thread 14 Large diameter portion 15 Second ring nut 61 Flange portion

Claims

1. An inner race fixed to a rotating shaft, An outer race disposed in a mounting hole provided at an axial end of a cylindrical housing that houses the rotating shaft and holding steel balls between the outer race and the inner race, A first ring nut having a male thread that engages with a female thread on the inner periphery of the mounting hole and being tightened so as to apply a predetermined pressure to the steel balls between the inner race and the outer race by rotation of the male thread, having, An annular support member having a diameter larger than the inner diameter of the first ring nut and smaller than the inner diameter of the mounting hole is integrally provided at an axially outer end of the outer race, The inner race is provided at one end and the other end of the rotating shaft, The outer race is provided on the outer periphery of each of the inner races at the one end and the other end, One of the first ring nuts contacts at least a part of the support member of the outer race at the one end and applies a pressure in one direction along the rotating shaft, The other of the first ring nuts contacts at least a part of the support member of the outer race at the other end and applies a pressure in the other direction along the rotating shaft, A pressure application structure of a ball bearing.

2. having a second ring nut that engages with the female thread on the inner periphery of the mounting hole and applies a force in the direction along the rotating shaft between the second ring nut and the first ring nut, The pressure application structure of the ball bearing according to claim 1.

3. A method for manufacturing a rotating shaft, wherein inner races are fixed to one end and the other end of the rotating shaft, and outer races that hold steel balls between the inner races at the one end and the other end are disposed in mounting holes provided at axial ends of a cylindrical housing, a step of fixing the inner race to the rotating shaft, a step of disposing the outer race in the mounting hole, A step of moving the outer race in a direction along the rotation axis by screwing and rotating a male screw on the outer periphery of a first ring nut with a female screw on the inner periphery of the mounting hole; A step of applying a pressure in a direction along the rotation axis to the steel balls between the inner race and the outer race by tightening the first ring nut with a predetermined torque; having A step of applying a pressure in a direction along the rotation axis to the steel balls between the inner race and the outer race at one end of the rotation axis by tightening the first ring nut at one end of the rotation axis with a predetermined torque; A step of applying a pressure in a direction along the rotation axis to the steel balls between the inner race and the outer race by tightening the first ring nut at the other end of the rotation axis with a predetermined torque; By alternately executing A step of applying a predetermined pressure to the steel balls at one end of the rotation axis and the steel balls at the other end of the rotation axis; having An annular support member having a diameter larger than the inner diameter of the first ring nut and smaller than the inner diameter of the mounting hole is integrally provided at an axially outer end of the outer race, and a pressure is applied to the support member from the first ring nut. A method for manufacturing a rotating shaft.

4. Further having a step of applying a force in the axial direction of the rotation axis between the first ring nut by screwing a second ring nut with a female screw on the inner periphery of the mounting hole; The method for manufacturing a rotating shaft according to claim 3.

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