JP2008275019A - Fluid bearing manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device manufacturing method for easily forming a lubricating fluid reservoir part which has high dimensional accuracy without depending on a complicated die assembly or additional lathe machining. <P>SOLUTION: A groove rolling tool 10 is fed to a sleeve 1 in the axial direction while being rotated to form the lubricating fluid reservoir part 3 having a machining pitch smaller than the axial groove width of a first radial hydrodynamic pressure generating groove 2a. Thus, the lubricating fluid reservoir part can be accurately machined without using lathe machining or pressing work with a complicated die assembly. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to sleeve processing of a hydrodynamic bearing device, and more particularly, to a method for forming a highly accurate lubricating fluid reservoir between radial bearings arranged vertically.

  The hard disk drive (hereinafter referred to as HDD) market continues to expand, and along with this, the number of hydrodynamic bearing spindle motors that use fluids such as oil, low-viscosity grease, and ionic liquid as the lubricating fluid may increase year by year. is needed. In order to meet such demands, it is essential to supply bearing parts with a low productivity and high productivity. Among bearing components, a sleeve member having a dynamic pressure generating groove requires a particularly high processing accuracy and requires many processing steps. Conventionally, it has been required to use a sintered material that has been widely used in optical disc drives or the like as a sleeve with high productivity, and a method for forming a dynamic pressure generating groove has been proposed.

  As an example, dynamic pressure is generated by inserting a core rod with a radial dynamic pressure generating groove forming part with a height of several μm on the outer periphery into a sleeve blank and applying pressure from the upper and lower surfaces and outer periphery using a die and punch. There is a method of forming a groove (for example, Patent Document 1).

As another method of forming the radial dynamic pressure generating groove, a shaft is formed by rotating a groove rolling tool having a plurality of rolling balls having a maximum outer diameter slightly larger than the inner diameter on the inner peripheral surface of the sleeve blank. There is a method in which a dynamic pressure generating groove is plastically processed by inserting in a direction (for example, Patent Document 2).
Japanese Patent Laid-Open No. 11-37156 JP-A-10-281144

  However, in the grooving method described in the above-mentioned Patent Document 1, a lubricating fluid pool is formed between the upper and lower radial bearings. The shape is not directly formed directly by the core rod etc., but there are many factors such as the die and punch, the relative shape of the core rod, and the density variation of the sleeve blank itself. In order to be affected in a complicated manner, the shape variation becomes large. Moreover, the radial width of the lubricant reservoir cannot be increased. The lubricating fluid reservoir is provided in order to secure the bearing rigidity in the radial dynamic pressure portion by separating and storing bubbles generated in the bearing from the radial dynamic pressure generating groove. If the volume of the lubricating fluid reservoir is not sufficient, bubbles will flow back into the radial dynamic pressure generating groove and NRRO (Non Repetitive Run Out) will increase to deteriorate the rotational accuracy, or the lubricating fluid reservoir As a result, the friction torque increases. However, with the groove processing method described in Patent Document 1, it is impossible to ensure the dimensions / accuracy required for the lubricating fluid reservoir.

  On the other hand, in Patent Document 2, although the radial dynamic pressure generating groove can be processed, the groove of the lubricating fluid reservoir cannot be formed on the inner periphery of the sleeve, so it is necessary to form it on the shaft side or the sleeve side by cutting with a lathe. is there. For this reason, the number of processing steps increases, which significantly impedes productivity improvement.

  The present invention solves the above-described conventional problems, and provides a method of manufacturing a hydrodynamic bearing device capable of easily forming a lubricating fluid reservoir with high dimensional accuracy without resorting to complicated molds or additional lathe processing. The purpose is to do.

In order to solve the above-described conventional problems, the method of manufacturing a hydrodynamic bearing device according to the present invention includes inserting a groove rolling tool having a plurality of balls projecting on the outer periphery thereof coaxially into the inner peripheral cylindrical surface of the sleeve, The groove rolling tool performs a relative rotation and an axial relative feed with respect to the sleeve, so that a plurality of grooves having a substantially arc shape in the axial cross section are provided on the inner peripheral surface of the sleeve by plastic working. A hydrodynamic bearing manufacturing method comprising: a first step of inserting the groove rolling tool into the inner circumferential cylindrical surface in a direction from one end side to the other end side of the sleeve; and the groove rolling tool. A second step of forming a first radial dynamic pressure generating groove by rotating relative to the sleeve and relatively moving in a direction from the one end side toward the other end side; and the groove rolling tool While rotating relative to the sleeve A third step of forming a lubricating fluid reservoir having a machining pitch smaller than the axial groove width of the first radial dynamic pressure generating groove, which is relatively fed in a direction from the one end side toward the other end side; The fourth step of forming the second radial dynamic pressure generating groove by relatively feeding the groove rolling tool relative to the sleeve while relatively rotating in the direction from the one end to the other end. And a fifth step of extracting the groove rolling tool in a direction from the other end side toward the one end side while rotating relative to the sleeve.

  As a result, it is possible to process the lubricating fluid reservoir with high accuracy without using lathe processing or press processing using a complicated mold, and productivity can be greatly increased.

  Further, in the method for manufacturing a hydrodynamic bearing device according to the present invention, a groove rolling tool having a plurality of balls protruding from the outer periphery is coaxially inserted into the inner peripheral cylindrical surface of the sleeve, and the groove rolling tool is A method of manufacturing a hydrodynamic bearing in which a plurality of grooves having a substantially arc-shaped axial cross-sectional shape are formed by plastic working on an inner peripheral surface of a sleeve by performing relative rotation and relative axial feed on the sleeve. A first step of inserting the groove rolling tool into the inner peripheral cylindrical surface in a direction from one end side to the other end side of the sleeve, and in a state where the ball protrudes by a first value, A second step of forming a first radial dynamic pressure generating groove by relatively feeding the groove rolling tool relative to the sleeve while relatively rotating in the direction from the one end to the other end; A second greater than the first value of the ball; The groove rolling tool is relatively rotated with respect to the sleeve in a state of projecting only by the value of the first radial dynamic pressure while being relatively rotated in the direction from the one end side toward the other end side. A third step of forming a lubricating fluid reservoir having a machining pitch smaller than the axial groove width of the generated groove, and the groove protruding in a third value smaller than the second value. A fourth step of forming a second radial dynamic pressure generating groove by relatively rotating a rolling tool with respect to the sleeve while relatively feeding in a direction from the one end side toward the other end side; And a fifth step of extracting the groove rolling tool from the sleeve in the direction from the other end side toward the one end side.

  As a result, it is possible to accurately process the lubricating fluid reservoir having a deep groove depth without using lathe processing or pressing using a complicated mold.

  According to the method of manufacturing a hydrodynamic bearing device of the present invention, it is possible to greatly improve the shape accuracy of the lubricating fluid reservoir disposed between the radial dynamic pressure generating grooves, and simultaneously processing the radial dynamic pressure generating grooves. Since the reservoir can also be formed, extremely high productivity can be obtained.

  Embodiments of a method for manufacturing a hydrodynamic bearing device of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a sleeve in each step of forming a radial dynamic pressure generating groove 2a, 2b and a lubricating fluid reservoir 3 by a groove rolling method on the sleeve 1 of the hydrodynamic bearing in the first embodiment. In FIG. 1 (a), immediately before the groove rolling, the sleeve 1 made of an iron-based or copper-based sintered body has an inner peripheral cylindrical surface 1a having an inner diameter dimension Di. Here, the groove rolling tool 10 is provided with a plurality of hard rolling balls 12 such as ceramic on the outer periphery. The outer dimension Do of the rolled ball 12 is set to be approximately 10 μm larger than the inner diameter Di of the inner peripheral cylindrical surface 1a of the sleeve 1. Here, when this groove rolling tool 10 is given relative feed and relative rotation in the axial direction to the sleeve 1, as shown in FIG. 1 (b), the rolling groove 4 tilted with respect to the axial direction. Is formed, and the first radial dynamic pressure generating groove 2a is formed.

  Further, as shown in FIG. 1 (c), when the groove rolling tool 10 advances to the back of the sleeve 1 (the lower side in the figure), the shaft is more effective than when the first radial dynamic pressure generating groove 2a is processed. Reduce relative direction feed and increase relative rotation. As a result, the machining pitch is reduced and the lubricating fluid reservoir 3 is formed.

  Then, when the machining process further proceeds and the groove rolling tool 10 advances to the lower end side of the sleeve 1 as shown in FIG. 1 (d), it is the same level as when machining the first radial dynamic pressure generating groove 2a again. Give axial relative feed and relative rotation. As a result, the second radial dynamic pressure generating groove 2b is formed. Finally, the groove rolling tool 10 is exposed from the sleeve 1 opposite to the above process.

  The above process is organized as shown in FIG. That is, it is as follows.

(1) Insert the groove rolling tool 10 into the inner circumferential cylindrical surface 1a in the direction from the one end side to the other end side of the sleeve 1,
(2) The first radial dynamic pressure generating groove having the first machining pitch by relatively feeding the groove rolling tool 10 in the direction from the one end side to the other end side while rotating relative to the sleeve 1. 2a,
(3) The groove rolling tool 10 is relatively rotated with respect to the sleeve 1 and is relatively fed in the direction from the one end side to the other end side. From the axial groove width of the first radial dynamic pressure generating groove 2a Forming a lubricating fluid reservoir having a small second machining pitch;
(4) A second radial dynamic pressure generating groove having a third processing pitch by relatively rotating the groove rolling tool 10 relative to the sleeve 1 while relatively rotating in the direction from the one end to the other end. 2b,
(5) While rolling the groove rolling tool 10 relative to the sleeve 1, the groove rolling tool 10 is extracted in the direction from the other end side toward the one end side. A relational diagram of the relative feed Z in the axial direction between the machining tool 10 and the relative rotation amount θ is shown.

  As shown in FIG. 1A, the end of the groove rolling tool 10 is inserted into the inner peripheral cylindrical portion 1a of the sleeve 1, and the outer periphery of the rolled ball 12 is still in contact with the inner peripheral cylindrical surface 1a of the sleeve 1. The stage that is not performed is set to Z = 0. From this stage, the groove rolling tool 10 starts relative rotation and axial relative feed with respect to the sleeve 1. At this time, relative feed and relative rotation are set so that the lead angle (groove angle) of the upper half of the first radial dynamic pressure generating groove 2a is θ11. In the figure, Z1s indicates the time when the rolled ball 12 is positioned at the upper end of the sleeve 1.

  When the processing further proceeds and reaches Z = Z1c, the rotational direction of the groove rolling tool 10 is reversed so that the radial dynamic pressure generating groove has a herringbone shape. Then, the relative feed and the relative rotation are set so that the groove angle of the lower half of the first radial dynamic pressure generating groove 2a is θ12. In general, in the hydrodynamic bearing device, θ11 and θ12 are set to 5 to 20 °.

  Here, when the processing of the first radial dynamic pressure generating groove 2a is finished and the rolling ball reaches Z = Z1e, the axial relative feed is temporarily stopped and only the relative rotation is performed. As a result, the boundary between the radial dynamic pressure generating groove 2a and the lubricating fluid reservoir 3 (the lubricating fluid reservoir boundary 20a) is clarified. Then, a smaller relative feed and a larger relative rotation are given than when the radial dynamic pressure generating groove 2a is processed, so that the processing pitch Pr becomes smaller than the processing pitch Pg1 of the radial dynamic pressure generating groove 2a. Further, when the processing of the lubricating fluid reservoir 3 is completed and the rolling ball reaches Z = Z2s, the axial relative feed is temporarily stopped and only the relative rotation in the reverse direction is performed. As a result, the boundary between the radial dynamic pressure generating groove 2b and the lubricating fluid reservoir 3 (the lubricating fluid reservoir boundary 20b) is clarified. As a result, the lubricating fluid reservoir 3 having a sufficient volume is formed.

  Next, relative feed and relative rotation are set so that the groove angle of the upper half of the second radial dynamic pressure generating groove 2b is θ21. When the processing further proceeds and reaches Z = Z2c, the rotation direction of the groove rolling tool 10 is reversed so that the radial dynamic pressure generating groove has a herringbone shape. Then, relative feed and relative rotation are set so that the groove angle of the lower half of the second radial dynamic pressure generating groove 2b is θ22. In general, in the hydrodynamic bearing device, θ21 and θ22 are set to 5 to 20 °.

  Finally, in order to extract the groove rolling tool 10 from the sleeve 1, the reverse rotation and feed are applied. In this way, the radial dynamic pressure generating groove 2a and the lubricating fluid reservoir 3 can be formed.

  Here, the relationship between the rolling ball 12 and the rolling groove 4 in the groove rolling will be described with reference to FIG. FIG. 4 is an enlarged view of only two rolling balls 12 arranged on the outer periphery of the groove rolling tool 10. The rolling ball 12 disposed on the outer periphery of the groove rolling tool 10 is set such that its outer diameter Do is larger than the inner diameter Di of the inner peripheral cylindrical surface 1a of the sleeve 1 by δ. Further, when the rolling groove 4 is formed, axial feed and relative rotation of the groove rolling processing tool 10 are set so that the groove angle becomes θ.

  Here, since the rolling ball 12 has a radius Rb and is larger than the inner peripheral cylindrical surface 1a of the sleeve 1 by δ, the rolling ball 12 is hit when it is assumed that the groove rolling tool 10 is stopped with respect to the sleeve 1. The trace shape is approximated to a circle with a radius Y in the figure (more precisely, it becomes an ellipse with a longer circumferential direction, but if Rb is small with respect to Di, there is no significant effect even if it is regarded as a circle). Here, Y is approximated by equation (2).

Further, the relationship between the axial width W and the radius Y of the formed rolling groove 4 is expressed by Expression (3).

That is, the axial width W increases as the groove angle θ increases. Incidentally, since θ is 5 to 20 °, the axial width W is only 0.4 to 6% larger than that in the case of the groove angle θ = 0 °. Therefore, it can be considered that there is no significant influence on W even if θ changes somewhat in practical use. Thus, the radial dynamic pressure generating groove portions 2a and 2b have a depth δ and an axial groove width W, and the cross-sectional shape is substantially an arc shape.

  Next, the processing state of the lubricating fluid reservoir 3 will be described. In the processing of the lubricating fluid reservoir 3, as described above, the axial feed is made smaller than the radial dynamic pressure generating grooves 2a and 2b, and the relative rotation amount is made larger. Therefore, the groove angle θ at the time of forming the lubricating fluid pool portion 3 becomes smaller. The groove angle θ at this time is around 5 °, which is substantially equal to twice the radius Y. Here, as shown in FIG. 5, the processing pitch Pr of the lubricating fluid reservoir 3 is smaller than the axial width W of the first radial dynamic pressure generating groove 2a. Here, as shown in FIG. 5, the shape of the lubricating fluid reservoir 3 in the cross section substantially matches the arc of the value Rg represented by the equation (4), as shown in FIG. 5.

Here, Zr in FIG. 5 is expressed by equation (5).

By reducing this Zr, the inner peripheral surface of the lubricating fluid reservoir 3 is further smoothed. Here, by making Zr smaller than δ / 2, the average depth δave of the lubricating fluid reservoir 3 becomes 84% with respect to δ, and the lubricating fluid reservoir 3 can secure a sufficient volume.

  By the way, the condition for making Zr smaller than δ / 2 is expressed by the equation (1).

By determining Pr in this manner, even if bubbles are generated inside the bearing, the bubbles can be reliably retained in the lubricating fluid reservoir 3 and the rotational accuracy can be maintained.

(Embodiment 2)
FIG. 6 is a cross-sectional view of the sleeve 1 formed by the fluid dynamic bearing manufacturing method according to the second embodiment. In the present embodiment, the groove bottom diameter Do2 of the lubricating fluid reservoir 3 is set to be larger than the groove bottom diameters Do1 and Do3 in the first and second radial dynamic pressure generating grooves 2a and 2b. In this way, in order to increase the groove bottom diameter Do2 of the lubricating fluid reservoir 3, the groove rolling tool 30 in the second embodiment is configured as shown in FIGS. FIG. 7A is a front view of the groove rolling tool 30. FIG. 7B is a bottom plan view of the groove rolling tool 30.

  As shown in FIG. 7A, an upper regulating ring 35 is fixed above the rolling shank 31, a lower regulating ring 33 near the center, and a plurality of parts fixed to the rolling ball holder 36 at the lower part. A number (four in the figure) of rolling balls 32 are arranged.

  Here, FIG. 8 shows a cross section XOY in FIG. The rolling shank 31 has a tapered portion 34 whose lower end is divided into four crotch portions. A rolling ball holder 36 is disposed coaxially with the rolling shank 31. The rolling ball holder 36 also has a lower tip divided into four forks. Here, the rolling ball 32 is fixed to a rolling ball holder 36. Note that the position of the rolling ball holder 36 is restricted with respect to the rolling shank 31 by a rotation prevention pin 41. Here, a slider ring 38 is disposed on the lower crotch portion of the rolling shank 31 and the rolling ball holder 36.

  As shown in FIG. 9, the slider ring 38 has four shank relief openings, and a cylindrical slider shank 39 is fixed below the slider ring 38. Further, a spherical slider ball portion 37 is formed below the slider shank 39.

  The slider ring 38 is attached to the rolling shank 31 by means of an upper restriction ring 35 and a lower restriction ring 33 via two thrust roller bearings 40. The upper restriction ring 35 and the lower restriction ring 33 are locked by a non-rotating pin (not shown) so as not to loosen. An inner circumferential lead screw 35 a is formed on the upper inner circumferential portion of the upper regulating ring 35. The inner lead screw 35 a is engaged with an upper lead screw 31 a provided on the upper outer periphery of the rolling shank 31. The slider ball portion 37 is fixed so as to contact the tapered portion 34 disposed below the rolling shank 31. A gear portion 35 b is formed on the upper outer periphery of the upper restriction ring 35.

  Here, when the first and second radial dynamic pressure generating grooves 2a and 2b are formed, the slider ball portion 37 hits in the vicinity of the center of the tapered portion 34 of the rolling shank 31, as shown in FIG. It is configured as such.

  On the other hand, when forming the lubricating fluid pool part 3, it carries out as follows. First, rotational torque is applied to the gear portion 35 b disposed on the upper outer periphery of the upper restriction ring 35, and the upper restriction ring 35 and the lower restriction ring 33 are rotated integrally with the rolling shank 31. Then, as shown in FIG. 11B, the slider ring 38 is pulled upward so that the slider ball portion 37 abuts above the taper portion 34. As a result, the taper portion 34 opens outward by the interaction with the slider ball portion 37, and the outer diameter of the rolling ball 32 becomes Do2.

  A method of processing the sleeve 1 using the groove rolling tool 30 configured as described above will be described. FIG. 10 is an overall external view of the groove rolling apparatus 60. In this groove rolling apparatus 60, a base ring 58 for mounting and holding the sleeve 1 is fixed on the base plate 57. In addition, on the base plate 57, an axial feed screw 55 is rotatably supported by bearing means (not shown), and a guide pole 56 is fixed. Here, an axial feed motor 52 is attached to the guide pole 56 to rotate the axial feed screw 55. Further, a motor holder 54 is attached to the guide pole 56 via a linear guide bearing 59. When the axial feed motor 52 rotates, the motor holder 54 moves up and down parallel to the guide pole 56. A phase feed motor 51 and a slider motor 50 are fixed to the motor holder 54.

  Here, the phase feed motor 51 is connected to the rolling shank 31 of the groove rolling tool 30 and applies a rotational feed to the groove rolling tool 30. A slider gear 53 is connected to the slider motor 50, and the slider gear 53 is engaged with a gear portion 35 b formed on the upper side of the upper regulating ring of the groove rolling tool 30. Here, when the phase feed motor 51 is rotated to rotate the gear portion 35b with respect to the main body of the groove rolling tool 30, as shown in FIGS. 11A and 11B, the slider ring 38 and the slider ball portion 37 moves up and down. And the taper part 34 of the rolling shank 31 lower end side opens and closes, and the outer diameter of the rolling ball 32 can change between Do1, Do3, and Do2.

  In order to rotate the phase feed motor 51 without changing the outer diameter of the rolling ball 32 during the processing of the sleeve 1, the upper regulating ring 35 and the lower regulating ring 33 rotate relative to the rolling shank 31. Therefore, the slider motor 50 is also rotated at the same time.

  If the lubricating fluid pool part 3 is formed using the groove rolling processing device 60 configured as described above, the groove bottom diameters Do1 and Do3 in the first and second radial dynamic pressure generating grooves 2a and 2b are as follows. The groove bottom diameter Do2 of the lubricating fluid reservoir 3 can be increased. This makes it possible to easily form the large-capacity lubricating fluid reservoir 3 with high accuracy and high productivity.

  In the present embodiment, since the protruding amount of the rolling ball 32 can be changed, when the groove rolling tool 30 is extracted from the sleeve 1, the state shown in FIG. The protruding amount of the rolling ball 32 may be reduced by moving the slider ball portion 37 further downward, and the rolling shank 31 may be pulled out as it is without rotating in that state.

  In order to ensure this operation, the tapered portion 34 can be kept in contact with the slider ball portion 37 at all times (that is, the crotch portion of the rolling shank 31 and the rolling ball holder is connected to the slider ball portion 37. It is preferable that the tip of the crotch portion is slightly squeezed and deformed in the initial state so that the contact force always works between them.

  (A) In the above description, the sleeve 1 has dealt with a simple cylindrical sintered body, but it is clear that the present invention is not limited to this. For example, it is obvious that the sleeve 1 may be provided with a dynamic pressure generating groove for a thrust bearing, a step portion for attaching a thrust plate, and other configurations.

  (B) In the above description, the groove rolling is described as being performed only in the forward direction, but the phase is shifted when the groove rolling tool is extracted, and the rolling process is performed when returning to the backward direction, Radial dynamic pressure generating grooves may be formed twice as many as the number of rolling balls provided on the outer periphery of the groove rolling processing tool. Further, the lubricating fluid reservoir may be shifted in phase with the forward direction to further reduce the processing pitch and obtain a wider lubricating fluid reservoir.

  (C) Although the slider ball portion for opening the rolling shank in the second embodiment is spherical, the present invention is not limited to this. Needless to say, for example, it may be formed of a single or a plurality of tapered surfaces.

  (D) In the above description, the case where the sleeve material is a sintered material has been described. However, the present invention is not limited to this, and it goes without saying that any material that can be plastically processed, such as brass or stainless steel, can be applied. Yes.

  The fluid dynamic bearing manufacturing method according to the present invention can easily form a lubricating fluid reservoir with high dimensional accuracy without resorting to complicated molds and additional lathes, and achieves both high accuracy and high productivity. be able to. The spindle motor using the fluid bearing processed in this way is useful as a spindle motor for HDDs, optical disk devices, laser scanners, video tape recorders, data streamers, and the like.

(A) Cross-sectional view showing the relationship between the sleeve at the start of rolling of the fluid dynamic bearing in Embodiment 1 of the present invention and the groove rolling tool for rolling, (b) No. 1 in Embodiment 1 of the present invention. 1 is a cross-sectional view of a sleeve during the formation of a radial dynamic pressure generating groove, (c) a cross-sectional view of the sleeve during formation of a lubricating fluid reservoir in Embodiment 1 of the present invention, and (d) Embodiment 1 of the present invention. Sectional view of the sleeve during formation of the second radial dynamic pressure generating groove in FIG. The flowchart of the manufacturing method of the fluid bearing in Embodiment 1 of this invention FIG. 5 is a relationship diagram of relative feed and relative rotation of the hydrodynamic bearing sleeve and groove rolling tool in Embodiment 1 of the present invention. Relationship explanatory drawing which shows the relationship between the radial dynamic pressure generating groove and rolling ball in Embodiment 1 of this invention Relationship explanatory drawing which shows the relationship between the processing pitch and groove width at the time of formation of the lubricating fluid pool part in Embodiment 1 of this invention Cross-sectional view of a sleeve of a fluid dynamic bearing in Embodiment 2 of the present invention (A) Front view of groove rolling tool in Embodiment 2 of the present invention, (b) Lower plan view of groove rolling tool in Embodiment 2 of the present invention Cross-sectional view of groove rolling tool in Embodiment 2 of the present invention (A) Slider plan view of groove rolling tool in Embodiment 2 of the present invention, (b) Slider cross-sectional view of groove rolling tool in Embodiment 2 of the present invention Overall appearance view of groove rolling apparatus in Embodiment 2 of the present invention (A) Cross-sectional view at the time of radial dynamic pressure generating groove formation of the groove rolling tool in Embodiment 2 of the present invention, (b) Lubricating fluid pool part of the groove rolling tool in Embodiment 2 of the present invention Cross section during formation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sleeve 1a Inner peripheral cylindrical surface 2a 1st radial dynamic pressure generation groove part 2b 2nd radial dynamic pressure generation groove part 3 Lubricating fluid pool part 4 Rolling groove 10, 30 Groove rolling tool 12, 32 Rolling ball 20a, 20b Lubricating fluid reservoir boundary 31 Rolling shank 31a Upper lead screw 33 Lower restriction ring 34 Tapered part 35 Upper restriction ring 35a Inner circumferential lead screw 35b Gear part 36 Rolling ball holder 37 Slider ball part 38 Slider ring 38a Shank escape part 39 Slider shank 40 Thrust roller bearing 41 Non-rotating pin 50 Slider motor 51 Phase feed motor 52 Axial feed motor 53 Slider gear 54 Motor holder 55 Axial feed screw 56 Guide pole 57 Base plate 58 Base Grayed 59 linear guide bearing 60 groove rolling device

Claims (3)

A groove rolling tool in which a plurality of balls protrude from the outer periphery is inserted coaxially into the inner peripheral cylindrical surface of the sleeve, and the groove rolling tool is rotated relative to the sleeve and is relatively fed in the axial direction. A fluid bearing manufacturing method in which a plurality of grooves whose axial cross-sectional shape forms a substantially arc shape on the inner peripheral surface of the sleeve by plastic working,
A first step of inserting the groove rolling tool into the inner peripheral cylindrical surface in a direction from one end side to the other end side of the sleeve;
A second step of forming the first radial dynamic pressure generating groove by relatively feeding the groove rolling tool relative to the sleeve while relatively rotating in the direction from the one end to the other end; ,
While relatively rotating with respect to the sleeve, the groove rolling tool is relatively fed in the direction from the one end side toward the other end side, and is smaller than the axial groove width of the first radial dynamic pressure generating groove. A third step of forming a lubricating fluid reservoir having a machining pitch;
A fourth step of forming a second radial dynamic pressure generating groove by relatively feeding the groove rolling tool relative to the sleeve while relatively rotating in the direction from the one end to the other end; ,
A fifth step of extracting the groove rolling tool from the other end side toward the one end side while rotating relative to the sleeve;
A method for manufacturing a hydrodynamic bearing, comprising: A groove rolling tool in which a plurality of balls protrude from the outer periphery is inserted coaxially into the inner peripheral cylindrical surface of the sleeve, and the groove rolling tool is rotated relative to the sleeve and is relatively fed in the axial direction. A fluid bearing manufacturing method in which a plurality of grooves whose axial cross-sectional shape forms a substantially arc shape on the inner peripheral surface of the sleeve by plastic working,
A first step of inserting the groove rolling tool into the inner peripheral cylindrical surface in a direction from one end side to the other end side of the sleeve;
With the ball protruding by a first value, the groove rolling tool is relatively rotated with respect to the sleeve, and is relatively fed in the direction from the one end side toward the other end side, A second step of forming a radial dynamic pressure generating groove of
A direction from the one end side toward the other end side while rotating the groove rolling tool relative to the sleeve in a state where the ball is protruded by a second value larger than the first value. A third step of forming a lubricating fluid reservoir having a machining pitch smaller than the axial groove width of the first radial dynamic pressure generating groove;
A direction from the one end side toward the other end side while rotating the groove rolling tool relative to the sleeve in a state where the ball is protruded by a third value smaller than the second value. A fourth step of forming a second radial dynamic pressure generating groove,
A fifth step of extracting the groove rolling tool from the sleeve in the direction from the other end to the one end;
A method for manufacturing a hydrodynamic bearing, comprising: The second machining pitch Pr is expressed with respect to the groove depth δ of the first or second radial dynamic pressure generating groove and the axial groove width W of the first or second radial dynamic pressure generating groove. (1) is satisfied, The manufacturing method of the hydrodynamic bearing of Claim 1 or Claim 2 characterized by the above-mentioned.