Method for manufacturing ball bearing

Abstract

To provide a manufacturing method that is applicable to a ball bearing in which a radial inner gap is 0.SOLUTION: A method for manufacturing a ball bearing in which a radial inner gap is 0, includes: a first step of inserting a plurality of balls between an inner ring raceway groove and an outer ring raceway groove in a radial direction; a second step of supporting a bearing outer diameter face of an outer ring at two positions apart from each other in a circumferential direction at an inferior angle of less than 180 degrees about a center axis of the outer ring; a third step of forming a range in the circumferential direction in which an inscribed circle that is in contact with the inner ring raceway groove and the outer ring raceway groove in a cross-section including a center axis of the inner ring exceeds a diameter of the ball in a range of a superior angle exceeding 180 degrees about a center axis of the outer ring by relatively moving the inner ring in a radial direction toward an inner circumferential face of the outer ring positioned between the two positions and by elastically deforming the outer ring via the ball positioned between the two positions; a fourth step of moving the ball into the range; and a fifth step of forming an interval between the ball positioned in the range and the adjacent ball.SELECTED DRAWING: Figure 6E

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a ball bearing.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a ball bearing, particularly a method for arranging balls between an inner ring and an outer ring. In this arrangement method, after placing a plurality of balls in the ring-shaped space between the inner ring and the outer ring, one of the inner ring and the outer ring is rotated with respect to the other in an eccentric state, so that the plurality of balls are dispersed and moved along the circumferential direction in the space, and air is blown between the dispersed and moved balls to arrange the plurality of balls at equal intervals.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The arrangement method of Patent Document 1 is a method in which the inner ring and the outer ring are eccentric within the range of the radial internal clearance of the ball bearing to widen the radial interval between the inner and outer rings at a part in the circumferential direction, and the dispersed movement of the balls is enabled in this interval. Therefore, it is necessary for the ball bearing to have a positive radial internal clearance (hereinafter, also referred to as "positive clearance"), and it is difficult to apply the arrangement method of Patent Document 1 to a ball bearing with a radial internal clearance of 0 (hereinafter, also referred to as "negative clearance"). The negative clearance is a state of a ball bearing in which all the balls of the ball bearing are in contact with all the contact parts between the balls and the outer ring raceway groove, and all the contact parts between the balls and the inner ring raceway groove, and elastic deformation occurs in the balls, the inner ring raceway groove, and the outer ring raceway groove at all the contact parts, and internal preload is generated.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a manufacturing method applicable also to a ball bearing having a radial internal clearance of 0.

Means for Solving the Problems

[0006] The manufacturing method of the ball bearing of the present disclosure is comprising an inner ring having an inner ring raceway groove, an outer ring having an outer ring raceway groove, and a plurality of balls disposed in a radial gap between the inner ring raceway groove and the outer ring raceway groove, and being a manufacturing method of a ball bearing having a radial internal clearance of 0, the plurality of balls include a first ball, a second ball, and a third ball, a first step of inserting a plurality of balls between the inner ring raceway groove and the outer ring raceway groove in the radial direction; a second step of supporting the bearing outer diameter surface of the outer ring at two positions circumferentially spaced apart by a first interval at a minor angle of less than 180 degrees about the central axis of the outer ring; a third step of relatively moving the inner ring radially toward the inner circumferential surface of the outer ring located at the first interval at the two positions, and elastically deforming the outer ring through the inner ring raceway groove, the first ball, and the outer ring raceway groove located at the first interval at the two positions, so as to form a first circumferential range in which an inscribed circle in contact with the inner ring raceway groove and the outer ring raceway groove in a cross section including the central axis of the inner ring is larger than the diameter of the second ball in a range of a major angle exceeding 180 degrees about the central axis of the outer ring; a fourth step of relatively rotating the inner ring and the outer ring to move the second ball to the first range; and a fifth step of forming a gap between the second ball disposed in the first range and the third ball adjacent to the second ball.

Effects of the Invention

[0007] The manufacturing method of the present disclosure can also be applied to a ball bearing having a radial internal clearance of 0.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 6D

Figure 6E

Figure 6F

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 9C

Figure 9D

Figure 10

Embodiments for Carrying Out the Invention

[0009] <Outline of Embodiments of the Present Disclosure> The outline of the embodiments of the present disclosure will be listed and described below. (1) The method for manufacturing a ball bearing according to an embodiment of the present disclosure is a method for manufacturing a ball bearing including an inner ring having an inner ring raceway groove, an outer ring having an outer ring raceway groove, and a plurality of balls disposed in a radial gap between the inner ring raceway groove and the outer ring raceway groove, and having a radial internal clearance of 0, the plurality of balls include a first ball, a second ball, and a third ball, a first step of inserting a plurality of balls between the inner ring raceway groove and the outer ring raceway groove in the radial direction, a second step of supporting the bearing outer diameter surface of the outer ring at two positions circumferentially spaced apart by a first interval at a minor angle of less than 180 degrees about the central axis of the outer ring, a third step of relatively moving the inner ring radially toward the inner circumferential surface of the outer ring located at the first interval at the two positions, and elastically deforming the outer ring through the inner ring raceway groove, the first ball, and the outer ring raceway groove located at the first interval at the two positions, so as to form a first circumferential range in which an inscribed circle in a cross section including the central axis of the inner ring and contacting the inner ring raceway groove and the outer ring raceway groove is larger than the diameter of the second ball in a range of a major angle exceeding 180 degrees about the central axis of the outer ring, a fourth step of relatively rotating the inner ring and the outer ring to move the second ball to the first range, and a fifth step of forming a gap between the second ball disposed in the first range and the third ball adjacent to the second ball.

[0010] According to this manufacturing method, even for a ball bearing having a radial internal clearance of 0 (negative clearance), by forcibly elastically deforming the outer ring, a first circumferential range can be formed in which an inscribed circle in a cross section including the central axis of the inner ring and contacting the inner ring raceway groove and the outer ring raceway groove is larger than the diameter of the second ball. In this first circumferential range, the second ball can move circumferentially without strongly rubbing against the inner ring raceway groove and the outer ring raceway groove, so that a gap can be easily formed between the second ball and the third ball.

[0011] Note that the first to fifth steps do not necessarily have to be performed in this order. Among the first to fifth steps, any plurality of steps may be performed at overlapping timings.

[0012] (2) In the manufacturing method of (1) above, the first range in the third step includes a portion having a height difference such that the rear side is higher in the vertical direction than the front side with respect to the moving direction of the second ball in the fourth step. Thereby, a vertical height difference occurs in the first range in the circumferential direction where the inscribed circle is larger than the diameter of the second ball, and the second ball can be moved by its own weight due to this vertical height difference.

[0013] (3) In the manufacturing method of (2) above, the central axis of the ball bearing is arranged horizontally. Thereby, a vertical height difference can be easily formed in the first range in the third step.

[0014] (4) In the manufacturing method according to any one of (1) to (3) above, in the fifth step, a spacing holding member is inserted between the second ball arranged in the first range and a third ball adjacent thereto. Thereby, the spacing between the adjacent second ball and third ball can be reliably held.

[0015] Note that in this specification, ball bearings with a radial internal clearance of 0 include those exemplified in FIGS. 9A to 9D. The ball bearings 35, 635 shown in Fig. 9A are two-point contact ball bearings (deep groove ball bearings). The two-point contact ball bearings 35, 635 include an inner ring 835 having a first inner ring raceway groove 8351a and an outer ring 834 having a first outer ring raceway groove 8341a. The first inner ring raceway groove 8351a has a cross-section in the shape of an arc with a single radius. The first outer ring raceway groove 8341a has a cross-section in the shape of an arc with a single radius. The first inner ring raceway groove 8351a and the first outer ring raceway groove 8341a each contact the ball 836 at one point P1, P2. With the central axes of the inner and outer rings 835, 834 aligned with each other, the first distance L1 between the point P1 on the first inner ring raceway groove 8351a that contacts the ball 836 and the point P2 on the first outer ring raceway groove 8341a is equal to or less than the diameter of the ball 836 (the diameter of the ball 836 in the unloaded state, hereinafter the same). The inscribed circle that contacts the first inner ring raceway groove 8351a and the first outer ring raceway groove 8341a in the cross-section including the central axis of the inner ring 835 is smaller than the diameter of the ball 836.

[0016] The ball bearings 35, 635 shown in FIG. 9B are four-point contact ball bearings. The four-point contact ball bearings 35, 635 include an inner ring 835 having a second inner ring raceway groove 8352a and an outer ring 834 having a second outer ring raceway groove 8342a. The second inner ring raceway groove 8352a further has a first inner ring raceway groove portion 8352a1 disposed on the first axial side (the right side in FIG. 9B) and a second inner ring raceway groove portion 8352a2 disposed on the second axial side (the left side in FIG. 9B). The first inner ring raceway groove portion 8352a1 and the second inner ring raceway groove portion 8352a2 have arc-shaped cross-sections with different center positions of the arcs. The second outer ring raceway groove 8342a further has a first outer ring raceway groove portion 8342a1 disposed on the first axial side and a second outer ring raceway groove portion 8342a2 disposed on the second axial side. The first outer ring raceway groove portion 8342a1 and the second outer ring raceway groove portion 8342a2 have arc-shaped cross-sections with different center positions of the arcs. The first inner ring raceway groove portion 8352a1 and the second inner ring raceway groove portion 8352a2 each contact the ball 836 at one point P11, P12, and the first outer ring raceway groove portion 8342a1 and the second outer ring raceway groove portion 8342a2 each contact the ball 836 at one point P21, P22. With the central axes of the inner and outer rings 835, 834 aligned with each other, the distance from the point P11 on the first inner ring raceway groove portion 8352a1 that contacts the ball 836 to the center O of the ball 836 is defined as the second distance L2, the distance from the point P22 on the second outer ring raceway groove portion 8342a2 that contacts the ball 836 to the center O of the ball 836 is defined as the fifth distance L5, the distance from the point P12 on the second inner ring raceway groove portion 8352a2 that contacts the ball 836 to the center O of the ball 836 is defined as the third distance L3, and the distance from the point P21 on the first outer ring raceway groove portion 8342a1 that contacts the ball 836 to the center O of the ball 836 is defined as the fourth distance L4. In this case, each of the second distance L2, the third distance L3, the fourth distance L4, and the fifth distance is equal to or less than 1 / 2 (radius) of the diameter of the ball 836. The inscribed circles in contact with the first inner ring raceway groove portion 8352a1, the second inner ring raceway groove portion 8352a2, the first outer ring raceway groove portion 8342a1, and the second outer ring raceway groove portion 8342a2 in the cross-section including the central axis of the inner ring 835 are smaller than the diameter of the ball 836.

[0017] The ball bearings 35, 635 shown in Fig. 9C are three-point contact ball bearings. The three-point contact ball bearings 35, 635 include an inner ring 835 having the first inner ring raceway groove 8351a and an outer ring 834 having the second outer ring raceway groove 8342a. The first inner ring raceway groove 8351a, the first outer ring raceway groove portion 8342a1, and the second outer ring raceway groove portion 8342a2 each contact the ball 836 at one point P1, P21, P22. When the distance from the point P1 on the first inner ring raceway groove 8351a contacting the ball 836 to the center O of the ball 836 is defined as the sixth distance L6, the distance from the point P21 on the first outer ring raceway groove portion 8342a1 contacting the ball 836 to the center O of the ball 836 is defined as the seventh distance L7, and the distance from the point P22 on the second outer ring raceway groove portion 8342a2 contacting the ball 836 to the center O of the ball 836 is defined as the eighth distance L8, each of the sixth distance L6, the seventh distance L7, and the eighth distance L8 is equal to or less than 1 / 2 (radius) of the diameter of the ball 836. The inscribed circle in contact with the first inner ring raceway groove 8351a, the first outer ring raceway groove portion 8342a1, and the second outer ring raceway groove portion 8342a2 in the cross-section including the central axis of the inner ring 835 is smaller than the diameter of the ball 836.

[0018] The ball bearings 35, 635 shown in Fig. 9D are also three-point contact ball bearings. The three-point contact ball bearings 35, 635 include an inner ring 835 having the second inner ring raceway groove 8352a and an outer ring 834 having the first outer ring raceway groove 8341a. The first inner ring raceway groove portion 8352a1, the second inner ring raceway groove portion 8352a2, and the first outer ring raceway groove 8341a each contact the ball 836 at one point P11, P12, P2. When the distance from the point P11 on the first inner ring raceway groove portion 8352a1 contacting the ball 836 to the center O of the ball 836 is defined as the ninth distance L9, the distance from the point P2 on the first outer ring raceway groove 8341a contacting the ball 836 to the center O of the ball 836 is defined as the tenth distance L10, and the distance from the point P12 on the second inner ring raceway groove portion 8352a2 contacting the ball 836 to the center O of the ball 836 is defined as the eleventh distance L11, each of the ninth distance L9, the tenth distance L10, and the eleventh distance L11 is equal to or less than 1 / 2 (radius) of the diameter of the ball 836. The inscribed circle in contact with the first inner ring raceway groove 8352a, the second inner ring raceway groove portion 8352a2, and the first outer ring raceway groove 8341a in the cross-section including the central axis of the inner ring 835 is smaller than the diameter of the ball 836.

[0019] In addition, the "radial internal clearance" in this specification means the radial internal clearance (theoretical internal clearance) of the ball bearing itself, which is defined as the radial internal clearance in JIS B 0104-1991 Terms for Rolling Bearings 05.08.01 Radial Internal Clearance. However, when there is a negative clearance, the radial internal clearance is defined as 0. It does not mean the radial internal clearance (residual clearance) after the shaft is assembled to the inner ring or the outer ring is assembled to the housing. However, as will be described later, when other elements (such as the shaft) are "formed integrally" with the inner ring and the outer ring, those elements are also included in the ball bearing.

[0020] First, an embodiment of a steering gear device in which a ball bearing manufactured by the manufacturing method of the ball bearing of the present disclosure is used will be described, and then an embodiment of the manufacturing method of the ball bearing of the present disclosure will be described. The ball bearing of the present disclosure is used, for example, in a dual pinion type electric power steering device, a column type electric power steering device, etc.

[0021] (Dual Pinion Type Electric Power Steering Device) FIG. 1 is a configuration diagram schematically showing an example of a dual pinion type electric power steering device 1 including a steering gear device 3. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1 showing a part of the steering gear device 3. In FIG. 2, the lower side of the drawing corresponds to the lower side in the vertical direction when mounted on a vehicle. FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1 showing a part of the steering gear device 3. In FIG. 3, the lower side of the drawing corresponds to the lower side in the vertical direction when mounted on a vehicle.

[0022] The dual pinion type electric power steering apparatus 1 includes a steering wheel 10, a steering shaft 2, a first pinion shaft 32, a rack shaft 31, a housing 33, two rack bushes 30, 34, two bearings 35, 36, a first rack guide mechanism 39, and a steering assist device 5. The steering assist device 5 includes a controller 50, a torque sensor 51, an electric motor 52, a speed reduction mechanism 53, a second pinion shaft 54, two bearings 55, 56, a worm housing 57, and a second rack guide mechanism 59. The speed reduction mechanism 53 includes a worm 531 and a worm wheel 532. The bearing 35 is a ball bearing manufactured by the manufacturing method of the ball bearing of the present disclosure.

[0023] A driver who drives an automobile equipped with this dual pinion type electric power steering apparatus 1 performs a steering operation by rotating the steering wheel 10. The steering shaft 2 includes a column shaft 21, a first universal joint 23, an intermediate shaft 22, and a second universal joint 24. The first universal joint 23 includes a first yoke (not shown), a plurality of first rolling elements (not shown), a first cross shaft (not shown), a plurality of second rolling elements (not shown), and a second yoke (not shown). The second universal joint 24 includes a third yoke (not shown), a plurality of third rolling elements (not shown), a second cross shaft (not shown), a plurality of fourth rolling elements (not shown), and a fourth yoke (not shown).

[0024] The column shaft 21 fixes the steering wheel 10 at one end in the extending direction. The column shaft 21 fixes the first yoke of the first universal joint 23 at the other end in the extending direction. The column shaft 21 is rotatable about the central axis in the extending direction. The first yoke is swingably fitted to a first pair of trunnions on the same central axis of the first cross shaft via a plurality of first rolling elements. The second yoke is swingably fitted to a second pair of trunnions on the same central axis of the first cross shaft via a plurality of second rolling elements. The central axis of the first pair of trunnions and the central axis of the second pair of trunnions intersect at an angle of 90 degrees.

[0025] The second yoke of the first universal joint 23 fixes one end of the intermediate shaft 22 in the extending direction. The intermediate shaft 22 fixes the third yoke of the second universal joint 24 to the other end in the extending direction. The third yoke is swingably fitted to a third pair of trunnions on the same central axis of the second cross shaft via a plurality of third rolling elements. The fourth yoke is swingably fitted to a fourth pair of trunnions on the same central axis of the second cross shaft via a plurality of fourth rolling elements. The central axis of the third pair of trunnions and the central axis of the fourth pair of trunnions intersect at an angle of 90 degrees. The fourth yoke of the second universal joint 24 fixes one end of the first pinion shaft 32 in the extending direction. Thus, when the driver rotates the steering wheel 10, the column shaft 21 rotates about the central axis in its extending direction, the intermediate shaft 22 also rotates about the central axis in its extending direction, and the first pinion shaft 32 also rotates about the central axis in its extending direction.

[0026] Inside the dual pinion type electric power steering apparatus 1, the first pinion shaft 32, the rack shaft 31, the housing 33, the two rack bushes 30, 34, the first bearing 35, the second bearing 36, the first rack guide mechanism 39, the electric motor 52, the speed reduction mechanism 53, the second pinion shaft 54, the third bearing 55, the fourth bearing 56, the worm housing 57, and the second rack guide mechanism 59 constitute a steering gear apparatus 3 as a rack and pinion type steering device. In FIG. 1, the housing 33 is represented by a virtual line (two-dot chain line), and its interior is shown.

[0027] The first pinion shaft 32 extends from the upper side to the lower side in the vertical direction of the vehicle. The first pinion shaft 32 has, along the extending direction, from one end side to the other end, a serration portion 324, a first shaft portion 322, a first pinion tooth portion 320, and a first boss portion 323. Serrations are formed on the serration portion 324. The serrations of the serration portion 324 are fixed to the fourth yoke of the second universal joint 24. The first shaft portion 322 has a cylindrical shape. The first pinion tooth portion 320 has first pinion teeth 321 formed on the entire circumferential surface. The extending direction of the first pinion teeth 321 has an angle other than 90 degrees with respect to the extending direction of the central axis of the first pinion shaft 32. The first boss portion 323 has a cylindrical shape.

[0028] The housing 33 has a first opening 332 on the steering wheel 10 side, and the side opposite to the first opening 332 is sealed. The first pinion shaft 32 is housed inside the housing 33. The first pinion shaft 32 is rotatably supported by two bearings 35 and 36 with respect to the housing 33. The first bearing 35 is a ball bearing of the present disclosure. The first bearing 35 includes an inner ring, an outer ring, balls, and a cage. The inner ring is fixed to the first shaft portion 322, the outer ring is fixed to the housing 33, and the balls roll between the inner ring and the outer ring. The second bearing 36 is a roller bearing. The second bearing 36 includes rollers and an outer ring. The outer ring is fixed to the housing 33, and the rollers roll between the outer peripheral surface of the first boss portion 323 and the outer ring.

[0029] In a state where the first pinion shaft 32, the first bearing 35, and the second bearing 36 are inserted into the housing 33, a lid 37 through which the first pinion shaft 32 passes is fixed to the first opening 332 of the housing. A seal is fixed to the lid 37, and the seal is slidable on the outer peripheral surface 322b of the first shaft portion 322 of the first pinion shaft 32. A cover member 38 is further fixed to the housing 33. The cover member 38 covers a part of the first shaft portion 322 of the first pinion shaft 32 from the radially outer side.

[0030] The rack shaft 31 includes, from one end to the other end in the extending direction, a first cylindrical portion 316, a first rack tooth portion 310, a second cylindrical portion 317, a second rack tooth portion 314, and a third cylindrical portion 318. The first rack tooth portion 310 has first rack teeth 311 formed in a part of the circumferential direction, and the other part of the circumferential direction is a cylindrical surface 312 centered on the extending direction of the rack shaft 31. The second rack tooth portion 314 has second rack teeth 315 formed in a part of the circumferential direction, and the other part of the circumferential direction is a cylindrical surface 313 centered on the extending direction of the rack shaft 31. The outer peripheral surfaces of the first cylindrical portion 316, the second cylindrical portion 317, and the third cylindrical portion 318 are each a cylindrical surface centered on the extending direction of the rack shaft 31. The extending direction of the first rack teeth 311 has an angle other than 90 degrees with respect to the extending direction of the rack shaft. The extending direction of the second rack teeth 315 has an angle other than 90 degrees with respect to the extending direction of the rack shaft 31. If the angle of the first rack teeth 311 with respect to the extending direction of the rack shaft 31 is X, the angle of the second rack teeth 315 with respect to the extending direction of the rack shaft 31 is π - X.

[0031] The housing 33 extends in a direction different from the first opening 332 on the steering wheel 10 side, and has a second opening 333 at one end in the extending direction and a third opening 334 at the other end. The rack shaft 31 is housed inside the housing 33 along the extending direction of the housing 33. The first cylindrical portion 316 at one end in the extending direction of the rack shaft 31 protrudes from the second opening 333 at one end in the extending direction of the housing 33. The third cylindrical portion 318 at the other end in the extending direction of the rack shaft 31 protrudes from the third opening 334 at the other end in the extending direction of the housing 33. The housing 33 has a fourth opening 335. The fourth opening 335 is on the other end side in the extending direction of the housing than the first opening 332. The housing 33 further has a fifth opening 336 and a sixth opening 337. The fifth opening 336 is in the radial direction centered on the extending direction of the housing 33 at substantially the same position in the extending direction of the housing 33 as the first opening 332 and in a direction perpendicular to the first opening 332. The sixth opening 337 is in the radial direction centered on the extending direction of the housing 33 at substantially the same position in the extending direction of the housing 33 as the fourth opening 335 and in a direction perpendicular to the fourth opening 335.

[0032] The first rack bush 30 is fixed to one end of the housing 33 in the extending direction thereof. The first rack bush 30 is fixed to the housing 33 adjacent to the second opening 333. The first rack bush 30 is slidable on the outer peripheral surface of the first cylindrical portion 316 of the rack shaft 31. The second rack bush 34 is fixed to the other end of the housing 33 in the extending direction thereof. The second rack bush 34 is fixed to the housing 33 adjacent to the third opening 334. The second rack bush 34 is slidable on the outer peripheral surface of the third cylindrical portion 318 of the rack shaft 31.

[0033] The first pinion teeth 321 formed on the first pinion tooth portion 320 of the first pinion shaft 32 and the first rack teeth 311 formed on the first rack tooth portion 310 of the rack shaft 31 are in rolling and sliding contact with each other via the grease composition G. The first pinion teeth 321 and the first rack teeth 311 are meshed with each other via the grease composition G. When the first pinion shaft 32 rotates with respect to the housing 33 about the central axis in its extending direction, the rack shaft 31 moves linearly in the extending direction of the housing 33 with respect to the housing 33.

[0034] The first rack guide mechanism 39 is fixed to the housing 33. The first rack guide mechanism 39 is fixed to the fifth opening 336. The fifth opening 336 is on the side of the cylindrical surface 312, which is the other part in the circumferential direction of the first rack tooth portion 310 of the rack shaft 31, at the position where the first pinion shaft 32 meshes with the rack shaft 31 in the extending direction of the housing 33.

[0035] The first rack guide mechanism 39 has a first support yoke 391, a first sheet member 392, a first coil spring 393, and a first plug 394. The first sheet member 392 is sandwiched between a cylindrical surface 312, which is the other part in the circumferential direction of the first rack tooth portion 310 of the rack shaft 31, and the cylindrical surface of the first support yoke 391. The first sheet member 392 is fixed to the first support yoke 391. The first sheet member 392 and the cylindrical surface 312, which is the other part in the circumferential direction of the first rack tooth portion 310 of the rack shaft 31, are in slidable contact via a grease composition G. The first sheet member 392 includes a metal layer such as bronze, for example, and a resin layer such as PTFE, for example, and the resin layer contacts the cylindrical surface 312 via the grease composition G. The first plug 394 is fixed to the fifth opening 336 of the housing 33. The first plug 394 contacts one end of the first coil spring 393. The first support yoke 391 contacts the other end of the first coil spring 393. The first coil spring 393 is shorter than its free length in a state where the first plug 394 is fixed to the fifth opening 336. Thus, the first sheet member 392 is pressed against the rack shaft 31 with respect to the housing 33.

[0036] The second pinion shaft 54 extends from the upper side to the lower side in the vertical direction of the vehicle. The second pinion shaft 54 has, along the extending direction, from one end side to the other end, a fitting portion 544, a second shaft portion 542, a second pinion tooth portion 540, and a second boss portion 543. The fitting portion 544 has a cylindrical shape. The second shaft portion 542 has a cylindrical shape. The second pinion tooth portion 540 has second pinion teeth 541 formed on the entire circumferential surface. The extending direction of the second pinion teeth 541 has an angle other than 90 degrees with respect to the extending direction of the central axis of the second pinion shaft 54. The second boss portion 543 has a cylindrical shape.

[0037] The worm wheel 532 is fitted into the fitting portion 544. The worm 531 is fixed to the output shaft 521 of the electric motor 52. The electric motor 52 is fixed to the worm housing 57. The worm housing 57 has a seventh opening 571. The output shaft 521 of the electric motor 52 is disposed in the internal space of the worm housing 57 through the seventh opening 571. The electric motor 52 is fixed to the worm housing 57 so as to close the seventh opening 571 of the worm housing 57.

[0038] The worm 531 is disposed in the internal space of the worm housing 57. The worm wheel 532 is disposed in the internal space of the worm housing 57. The worm housing 57 has an eighth opening 572 vertically upward, and the assembly of the second pinion shaft 54 and the worm wheel 532 is inserted into the internal space of the worm housing 57 from the eighth opening 572. The eighth opening is closed by a lid 58. The worm housing 57 has a ninth opening 573 on the opposite side of the eighth opening 572. A part of the second shaft portion 542 of the second pinion shaft 54, the second pinion tooth portion 540, and the second boss portion 543 protrude from the ninth opening 573 of the worm housing 57.

[0039] The worm housing 57 is fixed to the housing 33. The ninth opening 573 of the worm housing 57 communicates with the fourth opening 335 of the housing 33 to seal the internal space from the external space.

[0040] The third bearing 55 is a ball bearing. The bearing 55 includes an inner ring, an outer ring, and balls. The inner ring is fixed to the second shaft portion 542, the outer ring is fixed to the worm housing 57, and the balls roll between the inner ring and the outer ring. The bearing 56 is a roller bearing. The bearing 56 includes rollers and an outer ring. The outer ring is fixed to the housing 33, and the rollers roll between the outer peripheral surface of the second boss portion 543 and the outer ring.

[0041] The second pinion teeth 541 formed on the second pinion tooth portion 540 of the second pinion shaft 54 and the second rack teeth 315 formed on the second rack tooth portion 314 of the rack shaft 31 are in rolling and sliding contact via the grease composition G. The second pinion teeth 541 and the second rack teeth 315 are meshed via the grease composition G. When the second pinion shaft 54 rotates with respect to the housing 33 about the central axis in its extending direction, the rack shaft 31 moves linearly in the extending direction of the housing 33 with respect to the housing 33.

[0042] The housing 33 has the second rack guide mechanism 59 fixed thereto. The second rack guide mechanism 59 is fixed to the sixth opening 337. The sixth opening 337 is on the cylindrical surface 313 side, which is the other part in the circumferential direction of the second rack tooth portion 314 of the rack shaft 31 at the position where the second pinion shaft 54 meshes with the rack shaft 31 in the extending direction of the housing 33.

[0043] The second rack guide mechanism 59 includes a second support yoke 591, a second seat member 592, a second coil spring 593, and a second plug 594. The second seat member 592 is sandwiched between the cylindrical surface 313, which is the other part in the circumferential direction of the second rack tooth portion 314 of the rack shaft 31, and the cylindrical surface of the second support yoke 591. The second seat member 592 is fixed to the second support yoke 591. The second seat member 592 and the cylindrical surface 313, which is the other part in the circumferential direction of the second rack tooth portion 314 of the rack shaft 31, are in slidable contact via the grease composition G. The second seat member 592 includes a metal layer such as bronze and a resin layer such as PTFE, and the resin layer contacts the cylindrical surface 313 via the grease composition G. The second plug 594 is fixed to the sixth opening 337 of the housing 33. The second plug 594 contacts one end of the second coil spring 593. The second support yoke 591 contacts the other end of the second coil spring 593. The second coil spring 593 is shorter than its free length in a state where the second plug 594 is fixed to the sixth opening 337. Thus, the second seat member 592 is pressed against the rack shaft 31 with respect to the housing 33.

[0044] The torque sensor 51 detects the steering torque applied by the driver to the steering wheel 10 via the column shaft 21. The reduction mechanism 53 is an assembly in which a worm 531 that rotates integrally with the output shaft 521 of the electric motor 52 meshes with a worm wheel 532 that rotates integrally with the second pinion shaft 54. A motor current is supplied from the controller 50 to the electric motor 52. The controller 50 controls the electric motor 52 based on the steering torque detected by the torque sensor 51, the vehicle speed, etc., and transmits the rotational force of the output shaft 521 of the electric motor 52 decelerated by the reduction mechanism 53 to the second pinion shaft 54. The rotational force of the second pinion shaft 54 is applied as steering assist force from the second pinion teeth 541 to the second rack teeth 315.

[0045] The housing 33 is fixed to an automobile (not shown) with the extending direction of the housing 33 aligned with the vehicle width direction. Ball joint sockets 11, 11 are fixed to one end and the other end of the rack shaft 31, respectively, and tie rods 12, 12 connected to these ball joint sockets 11, 11 are connected to the raceways of the rolling bearings that rotatably support a pair of left and right front wheels 14, 14 via knuckle arms 13, 13. When the rack shaft 31 moves linearly in the extending direction of the housing 33, the left and right front wheels 14, 14, which are the steered wheels, are steered.

[0046] A grease composition G is encapsulated within a housing 33. The grease composition G is interposed between the rolling and sliding surfaces of a first pinion tooth 321 and a first rack tooth 311 that come into contact with each other by meshing therewith, thereby lubricating the space between both rolling and sliding surfaces. The grease composition G is interposed between the sliding surface of a first seat member 392 and the sliding surface of a cylindrical surface 312, which is the other part in the circumferential direction of a first rack tooth portion 310 of a rack shaft 31, that come into contact with each other by pressing against each other, thereby lubricating the space between both sliding surfaces. The grease composition G is interposed between the rolling and sliding surfaces of a second pinion tooth 541 and a second rack tooth 315 that come into contact with each other by meshing therewith, thereby lubricating the space between both rolling and sliding surfaces. The grease composition G is interposed between the sliding surface of a second seat member 592 and the sliding surface of a cylindrical surface 313, which is the other part in the circumferential direction of a second rack tooth portion 314 of a rack shaft 31, that come into contact with each other by pressing against each other, thereby lubricating the space between both sliding surfaces.

[0047] In the thus configured steering gear device 3, a ball bearing manufactured by the method for manufacturing a ball bearing of the present disclosure is used as a bearing 35. Since the ball bearing manufactured by the method for manufacturing a ball bearing of the present disclosure can have a radial internal clearance of 0, when the radial internal clearance is 0, it is possible to suppress the occurrence of play in the meshing portion between the first pinion tooth 321 and the first rack tooth 311.

[0048] (Column type electric power steering device) FIG. 4 is a configuration diagram schematically showing an example of a column type electric power steering device 601 including a steering gear device 603. FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4 showing a part of the steering gear device 603. In FIG. 5, the lower side of the drawing corresponds to the lower side in the vertical direction when mounted on a vehicle.

[0049] The column-type electric power steering apparatus 601 includes a steering wheel 610, a steering shaft 602, a pinion shaft 632, a rack shaft 631, a housing 633, two rack bushes 630, 634, two bearings 635, 636, a rack guide mechanism 639, and a steering assist device 4. A driver who drives an automobile equipped with this column-type electric power steering apparatus 601 performs a steering operation by rotating the steering wheel 610. The steering shaft 602 includes a column shaft 621, a first universal joint 623, an intermediate shaft 622, and a second universal joint 624. The first universal joint 623 includes a first yoke (not shown), a plurality of first rolling elements (not shown), a first cross shaft (not shown), a plurality of second rolling elements (not shown), and a second yoke (not shown). The second universal joint 624 includes a third yoke (not shown), a plurality of third rolling elements (not shown), a second cross shaft (not shown), a plurality of fourth rolling elements (not shown), and a fourth yoke (not shown). The bearing 635 is a ball bearing manufactured by the method for manufacturing a ball bearing of the present disclosure.

[0050] The column shaft 621 fixes the steering wheel 610 at one end in the extending direction. The column shaft 621 fixes the first yoke of the first universal joint 623 at the other end in the extending direction. The column shaft 621 is rotatable about the central axis in the extending direction. The first yoke is swingably fitted to a first pair of trunnions on the same central axis of the first cross shaft via a plurality of first rolling elements. The second yoke is swingably fitted to a second pair of trunnions on the same central axis of the first cross shaft via a plurality of second rolling elements. The central axis of the first pair of trunnions and the central axis of the second pair of trunnions intersect at an angle of 90 degrees.

[0051] The second yoke of the first universal joint 623 fixes one end of the intermediate shaft 622 in the extending direction. The intermediate shaft 622 fixes the third yoke of the second universal joint 624 at the other end in the extending direction. The third yoke is swingably fitted onto a third pair of trunnions on the same central axis of the second cross shaft via a plurality of third rolling elements. The fourth yoke is swingably fitted onto a fourth pair of trunnions on the same central axis of the second cross shaft via a plurality of fourth rolling elements. The central axis of the third pair of trunnions intersects the central axis of the fourth pair of trunnions at an angle of 90 degrees. The fourth yoke of the second universal joint 624 fixes one end of the pinion shaft 632 in the extending direction. Thus, when the driver rotates the steering wheel 610, the column shaft 621 rotates about its central axis in the extending direction, the intermediate shaft 622 also rotates about its central axis in the extending direction, and the pinion shaft 632 also rotates about its central axis in the extending direction.

[0052] Inside the column type electric power steering apparatus 601, the pinion shaft 632, the rack shaft 631, the housing 633, the two rack bushes 630, 634, the two bearings 635, 636, and the rack guide mechanism 639 constitute a steering gear apparatus 603 as a rack and pinion type steering device. In FIG. 4, the housing 633 is represented by a virtual line (two-dot chain line), and its interior is shown.

[0053] The pinion shaft 632 extends from the upper side to the lower side in the vertical direction of the automobile. The pinion shaft 632 has, from one end side to the other end along the extending direction, a serration portion 724, a shaft portion 722, a pinion tooth portion 720, and a boss portion 723. Serrations are formed on the serration portion 724. The serrations of the serration portion 724 are fixed to the fourth yoke of the second universal joint 624. The shaft portion 722 has a cylindrical shape. The pinion tooth portion 720 has pinion teeth 721 formed on the entire circumferential surface. The extending direction of the pinion teeth 721 has an angle that is not 90 degrees with respect to the extending direction of the central axis of the pinion shaft 632. The boss portion 723 has a cylindrical shape.

[0054] The housing 633 has a first opening 732 on the steering wheel 610 side, and the side opposite to the first opening 732 is sealed. The pinion shaft 632 is housed inside the housing 633. The pinion shaft 632 is rotatably supported by two bearings 635, 636 with respect to the housing 633. The bearing 635 is a ball bearing of the present disclosure. The bearing 635 includes an inner ring, an outer ring, balls, and a cage. The inner ring is fixed to the shaft portion 722, the outer ring is fixed to the housing 633, and the balls roll between the inner ring and the outer ring. The bearing 636 is a roller bearing. The bearing 636 includes rollers and an outer ring. The outer ring is fixed to the housing 633, and the rollers roll between the outer peripheral surface of the boss portion 723 and the outer ring.

[0055] With the pinion shaft 632 and the two bearings 635, 636 inserted into the housing 633, a cover 637 through which the pinion shaft 632 passes is fixed to the first opening 732 of the housing. A seal is fixed to the cover 637, and the seal is slidable on the outer peripheral surface 722b of the shaft portion 722 of the pinion shaft 632. A cover member 638 is further fixed to the housing 633. The cover member 638 covers a part of the shaft portion 722 of the pinion shaft 632 from the radially outer side.

[0056] The rack shaft 631 includes a first cylindrical portion 716, a rack tooth portion 710, and a second cylindrical portion 717 from one end to the other end in the extending direction. The rack tooth portion 710 has rack teeth 711 formed in a part of the circumferential direction, and the other part of the circumferential direction is a cylindrical surface 712 centered on the extending direction of the rack shaft 631. The outer peripheral surfaces of the first cylindrical portion 716 and the second cylindrical portion 717 are each a cylindrical surface centered on the extending direction of the rack shaft 631. The extending direction of the rack teeth 711 has an angle other than 90 degrees with respect to the extending direction of the rack shaft 631.

[0057] The housing 633 extends in a direction different from that of the first opening 732 on the steering wheel 610 side, and has a second opening 733 at one end and a third opening 734 at the other end in the extending direction. The rack shaft 631 is housed inside the housing 633 along the extending direction of the housing 633. One end of the rack shaft 631 in the extending direction protrudes from the second opening 733 at one end of the housing 633 in the extending direction. The other end of the rack shaft 631 in the extending direction protrudes from the third opening 734 at the other end of the housing 633 in the extending direction.

[0058] The first rack bush 630 is fixed to one end of the housing 633 in the extending direction. The first rack bush 630 is fixed to the housing 633 adjacent to the second opening 733. The first rack bush 630 is slidable on the outer peripheral surface of the first cylindrical portion 716 of the rack shaft 631. The second rack bush 634 is fixed to the other end of the housing 633 in the extending direction. The second rack bush 634 is fixed to the housing 633 adjacent to the third opening 734. The second rack bush 634 is slidable on the outer peripheral surface of the second cylindrical portion 717 of the rack shaft 631.

[0059] The pinion teeth 721 formed on the pinion tooth portion 720 of the pinion shaft 632 and the rack teeth 711 formed on the rack tooth portion 710 of the rack shaft 631 are in rolling and sliding contact via the grease composition G. The rack teeth 711 and the pinion teeth 721 are meshed via the grease composition G. When the pinion shaft 632 rotates with respect to the housing 633 about the central axis in its extending direction, the rack shaft 631 moves linearly in the extending direction of the housing 633 with respect to the housing 633.

[0060] The housing 633 is fixed to an automobile (not shown) such that the extending direction of the housing 633 coincides with the vehicle width direction. Ball joint sockets 11, 11 are fixed to one end and the other end of the rack shaft 631 respectively, and tie rods 12, 12 connected to these ball joint sockets 11, 11 are connected to the raceway rings of the rolling bearings that rotatably support a pair of left and right front wheels 14, 14 via knuckle arms 13, 13. When the rack shaft 631 moves linearly in the extending direction of the housing 633, the left and right front wheels 14, 14, which are steering wheels, are steered.

[0061] A rack guide mechanism 639 is fixed to the housing 633. The housing 633 has a fourth opening 736 on the cylindrical surface 712 side, which is the other part in the circumferential direction of the rack tooth portion 710 of the rack shaft 631 at the position where the pinion shaft 632 meshes with the rack shaft 631 in the extending direction.

[0062] The rack guide mechanism 639 includes a support yoke 791, a seat member 792, a coil spring 793, and a plug 794. The seat member 792 is sandwiched between the cylindrical surface 712, which is the other part in the circumferential direction of the rack tooth portion 710 of the rack shaft 631, and the cylindrical surface of the support yoke 791. The seat member 792 is fixed to the support yoke 791. The seat member 792 and the cylindrical surface 712, which is the other part in the circumferential direction of the rack tooth portion 710 of the rack shaft 631, are in slidable contact via a grease composition G. The seat member 792 includes a metal layer such as bronze and a resin layer such as PTFE, and the resin layer contacts the cylindrical surface 712 via the grease composition G. The plug 794 is fixed to the fourth opening 736 of the housing 633. The plug 794 contacts one end of the coil spring 793. The support yoke 791 contacts the other end of the coil spring 793. The coil spring 793 is shorter than its free length in a state where the plug 794 is fixed to the fourth opening 736. Therefore, the seat member 792 is pressed against the rack shaft 631 with respect to the housing 633.

[0063] The steering assist device 4 includes a controller 40, a torque sensor 41 that detects the steering torque applied by the driver to the steering wheel 610, an electric motor 42, and a speed reduction mechanism 43 that reduces the rotational force of the output shaft 421 of the electric motor 42 and transmits it to the column shaft 621. The speed reduction mechanism 43 is an assembly in which a worm 431 that rotates integrally with the output shaft 421 of the electric motor 42 and a worm wheel 432 that rotates integrally with the column shaft 621 are engaged with each other. A motor current is supplied to the electric motor 42 from the controller 40. The controller 40 controls the electric motor 42 based on the steering torque detected by the torque sensor 41, the vehicle speed, etc., and the rotational force of the output shaft 421 of the electric motor 42 reduced by the speed reduction mechanism 43 is applied to the column shaft 621 as steering assist force.

[0064] A grease composition G is enclosed in the housing 633. The grease composition G is interposed between the rolling and sliding surfaces of the pinion teeth 721 and the rolling and sliding surfaces of the rack teeth 711 that come into contact with each other when the pinion teeth 721 and the rack teeth 711 mesh with each other, thereby lubricating between the two rolling and sliding surfaces. The grease composition G is interposed between the sliding surface of the seat member 792 and the sliding surface of the cylindrical surface 712, which is the other part in the circumferential direction of the rack tooth portion 710 of the rack shaft 631, that come into contact with each other when the seat member 792 and the rack shaft 631 are pressed against each other, thereby lubricating between the two sliding surfaces.

[0065] In the steering gear device 603 configured as described above, a ball bearing manufactured by the manufacturing method of the ball bearing of the present disclosure is used as the bearing 635. Since the ball bearing manufactured by the manufacturing method of the ball bearing of the present disclosure can make the radial internal clearance zero, when the radial internal clearance is zero, it is possible to suppress the occurrence of play in the meshing portion between the pinion teeth 721 and the first rack teeth 711.

[0066] The ball bearing manufactured by the manufacturing method of the ball bearing of the present disclosure can be used in the above-described dual pinion type electric power steering device, column type electric power steering device, etc.

[0067] [Manufacturing Method of Ball Bearing] Hereinafter, the manufacturing method of the ball bearings 35 and 635 will be described. In particular, the method of arranging the balls 836 between the inner ring 835 and the outer ring 834 will be described. FIGS. 6A to 6F are diagrams for explaining the procedure of the manufacturing method of the ball bearing. The ball bearings 35 and 635 are assembled by incorporating a plurality of balls 836 between the inner ring 835 and the outer ring 834, and inserting the claws 837b of the cage 837 between adjacent balls 836. The ball bearings 35 and 635 are four-point contact ball bearings shown in FIG. 9B. The ball bearings 35 and 635 may be two-point contact ball bearings (deep groove ball bearings) shown in FIG. 9A, three-point contact ball bearings shown in FIG. 9C, or three-point contact ball bearings shown in FIG. 9D instead of the four-point contact ball bearings. The intervals between the plurality of balls 836 are kept constant by the cage 837. The operation of incorporating a plurality of balls 836 between the inner ring 835 and the outer ring 834 (the first step of the manufacturing method) is performed by eccentrically moving the inner ring 835 in the radial direction with respect to the outer ring 834 (see arrow a) as shown in FIG. 6A, thereby forming a widened portion WS of the interval between the outer ring 834 and the inner ring 835 in a part of the circumferential direction, and sequentially inserting the plurality of balls 836 into the portion WS.

[0068] The ball bearings 35 and 635 of the present embodiment have a radial internal clearance of 0. That is, the inner ring 835, the outer ring 834, and the balls 836 are always in contact. Therefore, even if a plurality of balls 836 are incorporated between the inner ring 835 and the outer ring 834, they cannot be freely moved in the circumferential direction. At the stage of assembling the ball bearings 35 and 635, it is extremely difficult to insert the claws 837b of the cage 837 between the adjacent balls 836 with a circumferential interval therebetween. If the balls 836 are forcibly moved in the circumferential direction, there is a high possibility that the inner ring 835, the outer ring 834, or the balls 836 will be damaged. In particular, when the radial internal clearance of the ball bearings 35 and 635 is a negative clearance, it is difficult to move the balls 836 in the circumferential direction.

[0069] Also, the inner rings 835 of the ball bearings 35 and 635 in the present embodiment are formed separately from the first pinion shaft 32 of the steering gear device 3 or the pinion shaft 632 of the steering gear device 603.

[0070] The manufacturing method of the present embodiment is suitable for the ball bearings 35 and 635 with a radial internal clearance of 0, and is executed using the manufacturing apparatus 850 shown in FIGS. 6B and 8. This manufacturing apparatus 850 includes a support device 851 that supports the outer peripheral surface of the outer ring 834 and a drive device 852 that moves and rotates the inner ring 835. The support device 851 of the present embodiment includes two support members 853. Each support member 853 is in contact with the bearing outer diameter surface of the outer ring 834. The support device 851 supports the bearing outer diameter surface 834h of the outer ring 834 with the central axis C horizontal.

[0071] The first support member 853 and the second support member 853 of the support device 851 are arranged at intervals in the circumferential direction of the outer ring 834 so as to contact the bearing outer diameter surface 834h of the outer ring 834 at a minor angle within a range where the central angle θ of the ball bearings 35 and 635 is less than 180 degrees. The central angle θ is preferably 120 degrees or less, and more preferably 90 degrees or 90 degrees or less. In the illustrated example, the support member 853 is formed in a columnar shape. However, the support member 853 may be in a plate shape or the like. The support member 853 may be in point contact (line contact) or surface contact with the outer peripheral surface of the outer ring 834.

[0072] The drive device 852 includes a first drive body 856 and a second drive body 857. The first drive body 856 includes, for example, an electric motor. The first drive body 856 is connected to the inner ring 835 of the ball bearings 35 and 635 and rotates the inner ring 835 around the central axis C of the inner ring 835. Therefore, the first drive body 856 rotates the inner ring 835. The first drive body 856 is connected to the inner ring 835 with the central axis C oriented in the horizontal direction.

[0073] The second driver 857 includes, for example, an actuator such as a fluid pressure cylinder or a motor and a ball screw type cylinder. The second driver 857 moves the inner ring 835 in a direction orthogonal to the central axis C of the inner ring 835. Therefore, the second driver 857 moves the inner ring 835 in the radial direction. The second driver 857 of the present embodiment moves the first driver 856 or a member (shaft 824) that rotates integrally with the inner ring 835 in a horizontal direction orthogonal to the central axis C via a bearing (not shown).

[0074] The manufacturing apparatus 850 further includes a spacing member 860. As illustrated in FIG. 7, the spacing member 860 has a cylindrical shape. Specifically, the spacing member 860 includes a cylindrical base portion 861 and a plurality of comb portions 862 protruding from the base portion 861 toward the first side in the axial direction. The plurality of comb portions 862 are strip-shaped and curved in an arc shape centered on the central axis C1 of the base portion 861. The number of the comb portions 862 is the same as the number of balls 836 of the ball bearings 35 and 635. All of the plurality of comb portions 862 protrude in the same direction in the axial direction from the base portion 861. The plurality of comb portions 862 have different protruding lengths from the base portion 861. The plurality of comb portions 862 are arranged side by side in the circumferential direction of the base portion 861 in the order of the axial lengths. The tips of some of the comb portions 862 are inclined with respect to the circumferential direction of the base portion 861.

[0075] The spacing member 860 is arranged with its central axis C1 coinciding with the central axis C of the inner ring 835. The spacing member 860 is configured to be movable in the direction along the central axis C1. For example, the spacing member 860 is configured to be movable in the direction along the central axis C1 by an actuator such as a fluid pressure cylinder or a screw type cylinder. Therefore, the spacing member 860 approaches or separates from the ball bearings 35 and 635 along the central axis C of the ball bearings 35 and 635. Further, the spacing member 860 is driven and rotated by a motor around the central axis C1. The spacing member 860 is, for example, driven and rotated by the first driver 856. The spacing member 860 may be driven and rotated by another driver (motor). The spacing member 860 may be driven to rotate passively by a ball in the direction along the central axis C1.

[0076] As shown in FIG. 6B, immediately after incorporating a plurality of balls 836, the ball bearings 35, 635 have a state in which the plurality of balls 836 are arranged with a bias in a part of the circumferential direction. A method of setting the ball bearings 35, 635 in the manufacturing apparatus 850 includes connecting the inner ring 835 to a rotating body (usually a rotating shaft, but may be a rotating housing if the shaft is fixed) of the first driving body 856 of the driving device 852, and contacting the two support members 853 with the bearing outer diameter surface 834h of the outer ring 834 within the circumferential range where the plurality of balls 836 are arranged with a bias (second step of the manufacturing method). The circumferential interval between the position where the first support member 853 contacts the bearing outer diameter surface 834h and the position where the second support member 853 contacts the bearing outer diameter surface 834h is the first interval. In the present embodiment, the two support members 853 are arranged at an interval in the vertical direction. Therefore, the two support members 853 are brought into contact with the bearing outer diameter surface 834h of the outer ring 834 above and below the central axis C of the ball bearings 35, 635.

[0077] The first ball 836a, the second ball 836b, and the third ball 836c described below are distinguished by the forces and positions acting during manufacturing, and are all balls 836 manufactured to the same standard. After setting the ball bearings 35 and 635 in the manufacturing apparatus 850, the manufacturing apparatus 850 moves the inner ring 835 radially in the direction of arrow b in FIG. 6B by the second driver 857 (the third step of the manufacturing method). Specifically, the second driver 857 moves the inner ring 835 radially toward the inner peripheral surface of the outer ring 834 located between the two support members 853. In the example shown in FIG. 6B, the second driver 857 moves the inner ring 835 in the left direction with the inferior angle θ. As a result, the outer ring 834 receives a force (arrow c) directed to the right in FIG. 6B from the two support members 853 and a force (arrow d) directed to the left from the inner ring 835 via the first ball 836a. The first ball 836a is a ball located within the first interval among the plurality of balls 836. Therefore, the inner peripheral surface of the outer ring 834 is deformed into a substantially elliptical shape as exaggerated by the two-dot chain line L in FIG. 6B. Thereby, a first circumferential range R1 with an increased radial interval between the inner ring 835 and the outer ring 834 is formed within the superior angle (2π - θ) that is not the inferior angle θ of the ball bearings 35 and 635. In this first range R1, the radial clearance between the inner ring 835, the outer ring 834, and the balls 836 can be set to a "positive clearance" greater than 0. In a cross-section including the central axis C1 of the inner ring 835 in the first range R1, the inscribed circle in contact with the inner ring raceway groove 835a and the outer ring raceway groove 834a is larger than the diameter of the balls 836. This first range R1 is formed on the radially opposite side that is shifted in phase by approximately 180 degrees with respect to the first interval. Hereinafter, this first range R1 is also referred to as the "positive clearance range R1". At this stage, the plurality of balls 836 are all arranged in a circumferential range outside the positive clearance range R1.

[0078] Next, as shown in FIG. 6C, the manufacturing apparatus 850 rotates the inner ring 835 in the direction of arrow e (the fourth step of the manufacturing method). Each ball 836 moves (revolves) in the same direction f as the rotational direction e of the inner ring 835 while rotating (spinning) due to the contact between the inner ring 835 and the outer ring 834. Due to this movement, each ball 836 sequentially moves into the positive clearance range R1. The ball 8361 that enters the first clearance range R1 (positive clearance range R1) is the second ball 836b. The second ball 836b is a ball 836 that is located within the first range R1 among the plurality of balls 836. The spacing maintaining member 860 rotates around the central axis C1 at the same speed in the same direction f as the movement of the plurality of balls 836.

[0079] The ball 8361 located on the most downstream side in the movement direction f that enters the upper end (starting end) of the positive clearance range R1, which is the second ball 836b, has its restraint by the inner ring 835 and the outer ring 834 released and drops under its own weight, and moves to the lower end (ending end) of the positive clearance range R1 as shown in FIG. 6D. As a result, a gap is formed between the ball 8361 and the second ball 8362 from the downstream side in the movement direction f (the fifth step of the manufacturing method). At this time, the ball 8362 is the third ball 836c. The third ball 836c is a ball 836 that is adjacent to the second ball among the plurality of balls 836. At this timing, the spacing maintaining member 860 moves axially and approaches the ball bearings 35, 635, and the longest comb portion 862 is inserted between the two balls 8361, 8362, in other words, between the second ball 836b and the third ball 836c (the fifth step of the manufacturing method).

[0080] Subsequently, when the inner ring 835 is rotated continuously, the second ball 8362 from the downstream side in the movement direction f moves to the upper end of the positive clearance range R1 and becomes the second ball 836b, and moves to the lower end of the positive clearance range R1 as shown in FIG. 6E. Then, a gap is formed between this ball 8362 and the third ball 8363 from the downstream side in the movement direction f. The ball 8363 becomes the third ball 836c. At this timing, the spacing maintaining member 860 moves further axially while rotating with the inner ring 835 and approaches the ball bearings 35, 635, and the second longest comb portion 62 is inserted between the two balls 8362, 8363, in other words, between the second ball 836b and the third ball 836c.

[0081] Thereafter, the manufacturing apparatus 850 repeats the same operation as described above. As shown in FIG. 6F, all the comb portions 862 of the spacing holding member 860 are inserted between a plurality of balls 836, in other words, between the second ball 836b and the third ball 836c. Thereafter, the ball bearings 35 and 635 are removed from the manufacturing apparatus 850 together with the spacing holding member 860, and one 837b of the cages 837 is inserted between the respective balls 836 in such a manner as to replace the spacing holding member 860, and the ball bearings 35 and 635 are assembled.

[0082] In the manufacturing method described above, the inner ring 835 of the ball bearings 35 and 635 is moved toward the first circumferential interval between the first support member 853 and the second support member 853, and the outer ring 834 is forcibly deformed via the inner ring raceway groove 835a, the first ball, and the outer ring raceway groove 834a, thereby forming the first clearance range R1 (positive clearance range R1). The second ball 836b is moved within the positive clearance range R1. Therefore, the inner ring 835, the outer ring 834, and the balls 836 are not strongly rubbed against each other due to the movement of the balls 836, and it is possible to suppress damage to these components. Further, the positive clearance range R1 is arranged such that the upstream side in the moving direction f of the second ball 836b is higher than the downstream side. Therefore, the second ball 836b that has moved into the positive clearance range R1 can be dropped by its own weight within the positive clearance range R1. Thereby, a gap is surely formed between the second ball 836b and the third ball 836c, and the comb portion 862 of the spacing holding member 860 can be inserted into the gap.

[0083] The manufacturing apparatus 850 manufactures the ball bearings 35 and 635 with the central axis C being horizontal. Therefore, it is possible to easily form a height difference in the positive clearance range R1. In the above embodiment, the height difference is formed such that one end of the positive clearance range R1 is the highest and the other end is the lowest. Therefore, the distance that the ball 836 (the second ball 836b) falls by its own weight can be made longer, and a gap can be more surely formed between the balls 836.

[0084] [Other Embodiments] In the embodiments described above, the ball bearings 35 and 635 are applied to the steering gear device 3 and the steering gear device 603. However, the ball bearings 35 and 635 can be applied not only to the steering gear device 3 and the steering gear device 603 but also to any device. Further, in the above embodiments, the inner rings 835 of the ball bearings 35 and 635 are separate from the first pinion shaft 32 and the pinion shaft 632. However, the inner ring 835 may be integral with the first pinion shaft 32 and the pinion shaft 632, may be integral with another type of shaft, or may be configured separately from another type of shaft.

[0085] In the above embodiments, the manufacturing apparatus 850 manufactures the ball bearing 35 (arranges the balls 836) with the central axis C horizontal. However, the manufacturing apparatus 850 may manufacture the ball bearings 35 and 635 with the central axis C directed in a direction other than horizontal. For example, it may manufacture the ball bearings 35 and 635 with the central axis C inclined with respect to the horizontal direction and the vertical direction. In this case, it is preferable that a portion having a height difference is formed in at least a part of the positive clearance range R1. Further, the manufacturing apparatus 850 may manufacture the ball bearings 35 and 635 with the central axis C directed in the vertical direction. In this case, since the positive clearance range R1 is arranged horizontally, the second ball 836b that has entered the positive clearance range R1 does not fall due to its own weight. However, since the second ball 836b within the positive clearance range R1 does not strongly contact the inner ring 835 and the outer ring 834, it is easy to move in the circumferential direction. Therefore, an interval can be easily formed between the two balls 836 by forcibly inserting, for example, the comb portion 862 of the interval holding member 860 between the second ball 836b within the positive clearance range R1 and the third ball 836c adjacent thereto.

[0086] In the above-described embodiment, the distance between the second ball 836b and the third ball 836c was maintained by inserting the comb portion 862 of the spacing maintaining member 860 between the second ball 836b and the third ball 836c, but it is not limited thereto. For example, similar to Patent Document 1, the distance may be maintained by blowing air between the second ball 836b and the third ball 836c. Alternatively, a spacing maintaining member having a number of comb portions less than the number of balls 836 may be provided, and a comb portion may be inserted between the second ball 836b and the third ball 836c within the positive clearance range R1 to set a certain distance. Then, after both balls 836 deviate from the positive clearance range R1, the comb portion may be removed and inserted between another second ball 836b and third ball 836c. Outside the positive clearance range R1, since the balls 836 cannot freely move in the circumferential direction, there may be cases where the distance once set by the comb portion can be maintained without the comb portion.

[0087] In the above-described embodiment, the manufacturing apparatus 850 fixed the circumferential position of the outer ring 834 and rotated the inner ring 835 (shaft 824), but it is not limited thereto. The manufacturing apparatus 850 only needs to be able to relatively rotate the inner ring 835 and the outer ring 834. For example, the manufacturing apparatus 850 may fix the circumferential position of the inner ring 835 and rotate the outer ring 834. In this case, for example, it is preferable to form the support member 853 of the support device 851 in a roller shape and rotate the support member 853 as the outer ring 834 rotates. Further, the outer ring 834 may be rotated by rotationally driving the roller-shaped support member 853.

[0088] In the above-described embodiment, the manufacturing apparatus 850 fixed the radial position of the outer ring 834 and moved the inner ring 835 in the radial direction (arrow b direction), but it is not limited thereto. The manufacturing apparatus 850 only needs to be able to relatively move the inner ring 835 and the outer ring 834 in the radial direction. For example, as shown in FIG. 10, the manufacturing apparatus 850 may fix the radial position of the inner ring 835 and move the first support member 853 and the second support member 853 in the radial direction of the outer ring 834 (in the direction opposite to arrow b).

[0089] The embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the rights of the present invention is shown not by the above-described embodiments but by the claims, and includes the meaning equivalent to the claims and all modifications within the scope thereof.

Explanation of Signs

[0090] 35, 635: Ball bearing 834: Outer ring 835: Inner ring 836: Ball 850: Manufacturing apparatus 860: Spacer member C: Central axis R1: First clearance range (positive clearance range)

Claims

1. A method for manufacturing a ball bearing having a clearance of 0 in the radial direction, comprising an inner ring having an inner raceway groove, an outer ring having an outer raceway groove, and a plurality of balls disposed in the radial direction between the inner raceway groove and the outer raceway groove, The plurality of balls includes a first ball, a second ball, and a third ball, A first step of inserting a plurality of balls between the inner raceway groove and the outer raceway groove in the radial direction, A second step of supporting the bearing outer diameter surface of the outer ring at two positions circumferentially spaced apart by a first interval less than 180 degrees about the central axis of the outer ring, A third step of relatively moving the inner ring in the radial direction toward the inner peripheral surface of the outer ring located at the first interval at the two positions, and elastically deforming the outer ring through the inner raceway groove, the first ball, and the outer raceway groove located at the first interval at the two positions, so as to form a first circumferential range in which the inscribed circle in the cross section including the central axis of the inner ring and contacting the inner raceway groove and the outer raceway groove is larger than the diameter of the second ball in a range of a major angle exceeding 180 degrees about the central axis of the outer ring, A fourth step of relatively rotating the inner ring and the outer ring to move the second ball to the first range, A fifth step of forming a gap between the second ball disposed in the first range and the third ball adjacent to the second ball. A method for manufacturing a ball bearing, comprising:

2. The method for manufacturing a ball bearing according to claim 1, wherein the first range in the third step includes a portion having a height difference such that the rear side is higher than the front side in the vertical direction with respect to the moving direction of the second ball in the fourth step.

3. The method for manufacturing a ball bearing according to claim 2, wherein the central axis of the ball bearing is horizontally disposed.

4. The method for manufacturing a ball bearing according to any one of claims 1 to 3, wherein in the fifth step, a gap holding member is inserted between the second ball disposed in the first range and the third ball adjacent thereto.

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