JP2004324674A - Method for forming dynamic pressure generating groove - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a dynamic pressure generating groove capable of simplifying aligning work for a bearing sleeve to a tool, and achieving a low defective generation ratio. <P>SOLUTION: As a rolling work tool 1 for forming the dynamic pressure generating groove, a work tool 1 having a small diameter shaft part 12 of smaller outer diameter than a support shaft part 11 and a work shaft part 13 is used between the support shaft part 11 and the work shaft part 13. In this constitution, tolerable quantity of deflection between the inner diameter center of a workpiece (sleeve) and the rotation center of the tool 1 is increased. Concentricity of a radial dynamic pressure generating groove formed by rolling work to the sleeve inner diameter is improved. Aligning work between the sleeve and the work tool 1 can thus be simplified. High-precision dynamic pressure bearing parts can be provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a processing method for forming a groove by plastic working on an inner peripheral surface of a hollow cylindrical workpiece, and more specifically, to form a radial dynamic pressure generating groove on an inner peripheral surface of a bearing sleeve of a dynamic pressure bearing. A processing method suitable for
[0002]
[Prior art]
The dynamic pressure bearing device injects a working fluid between two members arranged to face each other with a slight gap therebetween, and forms a dynamic pressure generating groove in one of the opposing surfaces of these two members. These members are supported in a non-contact manner by dynamic pressure generated by relative rotation of the members.
[0003]
Among the dynamic pressure bearings, a dynamic pressure generating groove of a radial dynamic pressure bearing that supports rotation around an axis employs a V pattern or a herringbone pattern or the like in the circumferential direction, and is arranged to face each other with a small gap therebetween. Either the outer peripheral surface of the rotating shaft (shaft) or the inner peripheral surface of the cylindrical body (sleeve) is formed by plastic working. As a method for processing the radial dynamic pressure generating groove having such a shape with high precision, ball rolling in which plastic processing is performed using a hard ball is suitably used (for example, Patent Document 1 or Patent Document 2 or the like). See.).
[0004]
FIG. 2 is an explanatory view schematically showing a method of forming a radial dynamic pressure generating groove by ball rolling. This figure shows an example in which two radial dynamic pressure generating grooves 3v, 3v which are spaced apart in the axial direction are formed on an inner peripheral surface 3y of a cylindrical workpiece (sleeve 3). In the drawing, reference numeral 2 denotes a processing jig, 3 denotes a sleeve on which a dynamic pressure generating groove is to be formed, and 4 denotes a chuck of a lathe or the like (not shown).
[0005]
FIG. 3 is a cross-sectional view showing the structure of the processing jig 2 used for ball rolling of the dynamic pressure generating groove, and FIG. 4 is a cross-sectional view taken along line AA of FIG. The processing jig 2 includes a support shaft 21 for fixing to a lathe or the like (not shown), a columnar processing shaft 22 formed integrally with the support shaft 21, and a processing shaft 22. And a plurality of balls 10 formed of a hard material.
[0006]
A plurality (six in this example) of guide holes 22h penetrating through the mounting holes 22a are provided at equal intervals in the circumferential direction on the outer peripheral surface 22x near the tip of the processing shaft portion 22. The balls 10 are fitted into the guide holes 22h from the mounting holes 22a side, respectively, and are supported by pins 23 fitted in the mounting holes 22a.
[0007]
As shown in FIG. 4, the outer diameter D1 of the processing shaft portion 22 is formed smaller than the inner diameter of the sleeve 3 to be processed. The diameter D2 of a circumscribed circle connecting the radially outer ends of the balls 10 protruding from the processing shaft portion 22 is set to be several μm to several tens μm larger than the inner diameter of the sleeve 3. As a material forming the ball 10, a hard metal (such as a cemented carbide) or ceramics is preferably used.
[0008]
FIG. 5 is a schematic cross-sectional view illustrating a procedure for forming the radial dynamic pressure generating groove 3v by rolling. In the rolling process of the dynamic pressure generating groove, first, while rotating the processing jig 2 in one direction (positive direction), the processing shaft portion 22 of the processing jig 2 is relatively moved in the axial direction, and the workpiece is processed. Push it into the inner circumference of the object (sleeve 3). After the ball 10 arranged on the processing shaft portion 22 reaches the axial middle point M of the section where the dynamic pressure generating groove is to be formed, the processing jig 2 is rotated in the opposite direction while the processing shaft 2 is rotated. The portion 22 is further advanced to form half of the dynamic pressure generating grooves 3v. Thereafter, the same operation is performed while pulling out the processing jig 2 in the reverse direction, thereby forming the remaining half of the dynamic pressure generating grooves 3v. According to this method, twice the number of radial dynamic pressure generating grooves 3v as the number of balls disposed on the processing shaft portion 22 are formed by one reciprocation of the processing jig 2.
[0009]
As a method of forming a protruding portion (convex portion) on the outer peripheral surface of the processing jig which contributes to the rolling of the groove shape, in addition to the method of mounting the above-mentioned hard ball on the outer peripheral surface of the processing shaft portion, There has been proposed a method of mounting a ring or the like having a shape protruding from the outer peripheral surface to a part of the surface, or a method of integrally forming convex portions of various shapes on the outer peripheral surface of the processing shaft portion (see Patent Document 3 and the like). reference).
[0010]
[Patent Document 1] JP-A-61-6426 [Patent Document 2] JP-A-11-333541 [Patent Document 3] JP-A-8-24367
[Problems to be solved by the invention]
By the way, in order to generate uniform dynamic pressure in the circumferential direction, the radial dynamic pressure generating grooves as described above have a large number of grooves of the same shape, and the bottom surfaces of these grooves are in relation to the inner diameter of the workpiece (sleeve). It is necessary to work to be coaxial. Therefore, the center position of the jig and the sleeve used for this processing must be accurately matched by moving the sleeve or the jig in the horizontal direction. Specifically, the centering adjustment is performed so that the relative positional shift between the center of the inner diameter of the sleeve and the rotation center of the jig is 2 to 3 μm or less.
[0012]
However, while the sleeve is fixed at the outer diameter, the center of the inner diameter has a slight error for each individual sleeve, and it is not always possible to set the center of the inner diameter at the same position every time. Therefore, the centering operation of the jig must be performed for each sleeve to be processed, and it is necessary to perform the operation precisely, which is a very labor-intensive and man-hour operation for the manufacturing process.
[0013]
If the dynamic pressure generating groove is not formed concentrically with the inner diameter of the sleeve, it cannot be used as a component of the dynamic pressure bearing.
[0014]
The present invention has been made in order to address the above-described problem, and provides a method of processing a dynamic pressure generating groove which can simplify the centering operation of a bearing sleeve and a jig and has a low failure rate. It is intended to be.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 comprises a support shaft portion at one end and a processing shaft portion at the other end, the processing shaft having an outer diameter smaller than the inner diameter of a cylindrical workpiece. By inserting a rod-shaped jig in which a plurality of convex portions are formed on the outer periphery of the portion while giving relative rotation to the inner diameter of the workpiece, the inner peripheral surface of the workpiece has In the method of processing a dynamic pressure generating groove for forming a fine groove having a pattern corresponding to a trajectory, the jig is provided between the support shaft and the processing shaft as the jig. The present invention is characterized in that a jig provided with a misalignment adjusting means for absorbing a deviation of the center of the inner diameter of the workpiece is used.
[0016]
The present invention uses a processing jig provided with a misalignment adjusting means capable of autonomously absorbing a relative positional shift between the center of the inner diameter of the workpiece and the rotation center of the jig, thereby achieving an intended purpose. It is to achieve the purpose.
[0017]
That is, according to the processing method of the first aspect, the jig itself is provided with the function of adjusting the misalignment, so that the centering is adjusted to be usually 2 to 3 μm or less. The tolerance of the deviation between the center of the inner diameter and the rotation center of the jig can be increased. Therefore, the centering operation, which is a very labor-intensive and man-hour-consuming operation, can be simplified, and the processing speed can be increased.
[0018]
Further, the misalignment adjusting means can improve the concentricity of the radial dynamic pressure generating groove formed by the rolling process with respect to the inner diameter of the sleeve, as compared with the conventional processing method. Therefore, according to the processing method of the present invention, the processing accuracy of the rolling processing of the dynamic pressure generation groove is improved, and it is possible to reduce the defective rate of the product.
[0019]
Here, as a specific example of the jig provided with the misalignment absorbing means, a configuration in which a small-diameter shaft portion having an outer diameter smaller than the processing shaft portion is formed between the support shaft portion and the processing shaft portion of the jig. Can be suitably adopted. (Claim 2)
[0020]
According to the invention of claim 2, by forming a part of the rod-shaped jig closer to the support shaft portion than the processing shaft portion as a small-diameter shaft portion having a smaller diameter than the processing shaft portion, the rigidity of this portion is reduced to other portions. Can be set lower than. Therefore, when there is a deviation between the center of the inner diameter of the sleeve and the rotation center of the processing shaft, the deviation is reduced by causing the deformation (displacement) of the small diameter shaft. The small diameter shaft portion is desirably formed as close as possible to the support shaft portion in order to increase the allowable amount of the displacement as much as possible.
[0021]
Further, the method of providing the misalignment adjusting means in the present invention is not limited to this small diameter shaft portion. For example, a slit or a hole may be provided between the support shaft portion and the processing shaft portion of the jig to reduce rigidity, or the degree of heat treatment (quenching or the like) of the material may be partially changed. . In addition, another member having lower rigidity than the material of the processing shaft portion may be interposed and arranged at this portion. However, the method of providing the small-diameter shaft portion is rational because the processing is easy and the deformation (displacement) has no directionality.
[0022]
According to a third aspect of the present invention, the position where the processing jig is chucked on a lathe or the like is taken into consideration, and one end of the jig is provided around the support shaft portion around the misalignment adjusting means. And a fixing member whose other end extends toward the processing shaft portion is disposed.
[0023]
According to this invention, by fixing the jig using the outer periphery of the fixing member, it becomes possible to mount the jig on a lathe or the like at a position close to the processing shaft portion located at the tip of the jig. Therefore, the rotation reference position of the jig approaches the workpiece, and the misalignment can be easily adjusted.
[0024]
Furthermore, the invention according to claim 4 shows a preferred configuration example of the convex portion provided on the outer peripheral surface of the processing shaft portion of the jig, wherein the convex portion is formed of the processing shaft portion. It is constituted by a ball fitted into a guide hole provided on the outer peripheral surface.
[0025]
In addition, this convex part has a shape protruding to the outer peripheral surface at a part of the processing shaft part, or a ring or the like is attached, or various shapes of convex parts are integrally formed on the outer peripheral surface of the processing shaft part. You may comprise.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a structure of a jig used for processing a dynamic pressure generating groove according to an embodiment of the present invention. In the case of this embodiment, as in the conventional example, two radial dynamic pressure generating grooves 3v, 3v spaced apart in the axial direction are formed on the inner peripheral surface 3y of the cylindrical workpiece (sleeve 3). (See FIG. 2).
[0027]
The processing jig 1 used in this embodiment includes a support shaft 11, a processing shaft 13 integrally formed with the support 11, and a space between the support shaft 11 and the processing shaft 13. The small-diameter shaft portion 12 formed, the pin 14 fitted on the inner periphery of the processing shaft portion 13, and the plurality of balls 10 are mainly constituted. The structure of the machining shaft 13 is substantially the same as the example shown in FIG. 3, and a mounting hole 13 a concentric with the support shaft 11 is provided near the tip of the machining shaft 13. Further, a plurality of guide holes 13h (six in this example) are provided on the outer peripheral surface 13x at equal intervals in the circumferential direction. The balls 10 are fitted into these guide holes 13h from the side of the mounting holes 13a, respectively, and are supported by pins 14 fitted into the mounting holes 13a.
[0028]
The rolling of the dynamic pressure generating groove using the processing jig 1 is also performed in the same manner as in the example described with reference to FIG. 5, and the plurality of balls 10 are held on the outer peripheral surface of the processing shaft 13. By moving the processing jig 1 in the axial direction relative to the workpiece (sleeve 3) while rotating the processing jig 1 forward and backward (left and right), the dynamic pressure generating grooves 3v, 3v will be formed.
[0029]
The feature of the working method of the dynamic pressure generating groove in the present embodiment is that a jig for the rolling process is provided between the support shaft 11 and the work shaft 13 between the support shaft 11 and the work shaft 13. The point is that the processing jig 1 in which the small diameter shaft portion 12 having a small diameter is formed is used. Around the small diameter shaft portion 12, a cylindrical fixing member 15 having one end fixed to the outer periphery 11 x of the support shaft portion 11 and the other end extending toward the processing shaft portion 13 is slightly different from the processing shaft portion 13. It is arranged with a gap.
[0030]
The small-diameter shaft portion 12 is provided to reduce the rigidity of the portion. With this structure, the processing shaft portion 13 can be made movable in the radial direction. That is, even when there is a relative displacement between the center of the inner diameter of the sleeve 3 and the rotation center of the machining shaft 13 during the rolling process, the machining shaft 13 can absorb the misalignment.
[0031]
The fixing member 15 aims at bringing the position where the processing jig 1 is attached to a lathe or the like (not shown) as close to the axial processing shaft portion 13 as possible. By fixing the jig 1 at a position (downward in the drawing) near the processing shaft portion 13 on the outer peripheral surface 15x of the member 15, it is easy to adjust the displacement between the center of the inner diameter of the sleeve 3 and the rotation center of the processing shaft portion 13. Become. In addition, a gap is provided between the inner peripheral surface 15y of the fixing member 15 and the outer peripheral surface 13x of the machining shaft portion 13 so as not to hinder the function of adjusting the misalignment of the machining shaft portion 13.
[0032]
By using the jig 1 having the above-described configuration, in the processing of the dynamic pressure generating groove in the present embodiment, the allowable amount of the relative displacement between the center of the inner diameter of the sleeve 3 and the rotation center of the jig 1 is increased. At the same time, the concentricity of the radial dynamic pressure generating groove 3v formed by the rolling with respect to the inner diameter of the sleeve 3 is improved.
[0033]
The centering operation between the center of the inner diameter of the sleeve and the rotation center of the jig, which has conventionally been performed with a limit of 2 to 3 μm, has an error of several tens μm by adopting the processing method in the present embodiment. With high degree of centering work, high-precision rolling can be performed, and the efficiency of the manufacturing process can be improved.
[0034]
In the above-described embodiment, an example in which the large-diameter fixing member 15 is arranged around the support shaft 11 has been described. However, instead of arranging the fixing member 15, the support shaft 11 is different from the conventional example. They may be formed to have the same diameter.
[0035]
In addition, the size, number, arrangement, and the like of the balls 10 forming the convex portion of the processing shaft portion outer peripheral surface 13x are not particularly limited, and the material of the workpiece on which the dynamic pressure generating groove is to be formed and the desired It may be changed as appropriate depending on the shape and pattern of the dynamic pressure generating groove to be formed.
[0036]
【The invention's effect】
As described in detail above, according to the dynamic pressure generating groove processing method of the present invention, the allowable amount of relative displacement between the center of the inner diameter of the sleeve to be processed and the rotation center of the processing jig is increased, The centering operation between these sleeves and the processing jig can be simplified. Further, the concentricity of the dynamic pressure generating groove with respect to the sleeve inner diameter is improved, and a highly accurate dynamic pressure bearing component can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a structure of a jig used for processing a dynamic pressure generating groove according to an embodiment of the present invention.
FIG. 2 is an explanatory view schematically showing a method of forming a radial dynamic pressure generating groove by ball rolling.
FIG. 3 is a sectional view showing the structure of a conventional processing jig used for ball rolling of a dynamic pressure generating groove.
FIG. 4 is a sectional view taken along line AA of FIG. 3;
FIG. 5 is a schematic cross-sectional view illustrating a procedure for forming a dynamic pressure generating groove using a processing jig.
[Explanation of symbols]
1, 2 Processing jig 3 Sleeve 3v Dynamic pressure generating groove 3y Inner peripheral surface 4 Chuck 10 Ball (convex portion)
11 Support shaft portion 11x Outer peripheral surface 12 Small diameter shaft portion 13 Machining shaft portion 13a Mounting hole 13h Guide hole 13x Outer peripheral surface 14 Pin 15 Fixing member 15x Outer peripheral surface 15y Inner peripheral surface 21 Support shaft portion 22 Processing shaft portion 22a Mounting hole 22h Guide hole 22x outer peripheral surface 23 pin

Claims (4)

A rod-shaped jig comprising a support shaft portion at one end and a processing shaft portion at the other end, and a plurality of protrusions formed on the outer periphery of the processing shaft portion having an outer diameter smaller than the inner diameter of the cylindrical workpiece, A dynamic pressure generating groove for forming a fine groove in a pattern corresponding to the trajectory of each convex portion on the inner peripheral surface of the workpiece by inserting the inner diameter of the workpiece while giving relative rotation. In the method,
As the jig, a jig provided with a misalignment adjusting means between the support shaft portion and the processing shaft portion for absorbing a deviation between a rotation center of the processing shaft portion and an inner diameter center of the workpiece is used. A method for processing a dynamic pressure generating groove, characterized in that: The moving shaft according to claim 1, wherein a small-diameter shaft portion having an outer diameter smaller than that of the processing shaft portion is formed between the support shaft portion and the processing shaft portion as the misalignment adjusting means. Processing method of pressure generating groove. 2. A fixing member having one end fitted to the outer periphery of the support shaft portion and the other end extending toward the processing shaft portion is arranged around the misalignment adjusting means. 3. The method for processing a dynamic pressure generating groove according to item 2. The machining of the dynamic pressure generating groove according to claim 1, 2, or 3, wherein the convex portion is formed by a ball fitted into a guide hole provided on an outer peripheral surface of the machining shaft portion. Method.

Images