JP2004301253A - Processing method of dynamic pressure generating groove - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method for continuously forming a highly accurate dynamic pressure generating groove even when using a member composed of aluminum or an aluminum alloy as a workpiece. <P>SOLUTION: Rolling processing of the dynamic pressure generating groove 2v is performed on a bearing sleeve 2 by using a processing tool 1 for forming a diamond-like carbon (DLC) coating film 12 on a surface (a surface of a ball 10) of a projecting part projecting from a columnar processing part 1b. Friction between the projecting part and the workpiece can be reduced by adopting this tool. Even when performing the rolling processing on the workpiece using a metallic material rich in ductility such as the aluminum and the aluminum alloy, agglutination of this metallic material to the tool can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a processing method for forming a dynamic pressure generating groove in a member of a dynamic pressure bearing using plastic deformation caused by a convex portion protruding from a jig.
[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, a herringbone pattern, or the like, and a rotating shaft ( Either the outer peripheral surface of the shaft) or the inner peripheral surface of the tubular body (sleeve) is formed by plastic working. As a method for processing the radial dynamic pressure generating groove having such a shape with high accuracy, ball rolling in which plastic processing is performed using a hard ball is suitably used (for example, see Patent Document 1 and the like). .
[0004]
FIG. 3 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 2v, 2v spaced apart in the axial direction are formed on an inner peripheral surface 2x of a cylindrical workpiece (sleeve). A processing jig 1 for holding a plurality of balls 20 on an outer peripheral surface near a tip while fixing a sleeve 2 on which a dynamic pressure generating groove is to be formed to a chuck 3 of a lathe or the like (not shown). By moving the sleeve 2 in the axial direction relative to the sleeve 2 while rotating forward and backward (left and right), a dynamic pressure generating groove 2v of a V pattern or a herringbone pattern is formed in the circumferential direction.
[0005]
FIG. 4 is a partial cross-sectional view showing the structure of a conventional processing jig used for ball rolling of a dynamic pressure generating groove, and FIG. 5 is an end view taken along the arrow B in FIG. The processing jig 1 includes a support portion 1a for fixing to a lathe or the like (not shown), a small-diameter cylindrical processing portion 1b formed integrally with the support portion 1a, and an inner periphery of the processing portion 1b. And a plurality of balls 20 formed of a hard material. The vicinity of the front end of the processed portion 1b is formed in a hollow cylindrical shape concentric with the support portion 1a, and a guide hole 1h having an opening diameter substantially equal to the diameter of the ball 20 is formed in this hollow portion. Are provided at equal intervals in the circumferential direction (six in this example). The balls 20 are fitted into the guide holes 1h from the inner peripheral side of the processed portion 1b, respectively, and are supported by support pins 1c fitted to the inner periphery of the processed portion 1b. As shown in FIG. 5, the diameter D of a circumscribed circle connecting the radially outer ends of the balls 20 protruding from the outer peripheral surface of the processed portion 1b is several μm to a dozen or more than the inner diameter of the sleeve 2 to be processed. It is set to be about μm larger. In addition, as a material forming the ball 20, a hard metal (such as a hard metal) or ceramics is preferably used.
[0006]
FIG. 6 is a schematic cross-sectional view illustrating a procedure for forming the dynamic pressure generating groove 2v by rolling. In this rolling, first, while rotating the processing jig 1 in one direction (positive direction), the processing portion 1b of the processing jig 1 is relatively moved in the axial direction, and the workpiece (sleeve 2) is rotated. Into the inner circumference of. After the ball 20 disposed in the processing portion 1b reaches the axial middle point M of the section where the dynamic pressure generating groove is to be formed, the processing portion 1b is rotated while rotating the processing jig 1 in the reverse direction. Is further advanced to form half of the dynamic pressure generating grooves 2v. Thereafter, the same operation is performed while pulling out the processing jig 1 in the reverse direction, whereby the remaining half of the dynamic pressure generating grooves 2v are formed. According to this method, a single reciprocation of the processing jig 1 forms twice as many dynamic pressure generating grooves as the number of balls disposed in the processing portion 1b.
[0007]
In addition, 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-described hard ball on the outer peripheral surface of the processing portion, one method of forming the protruding portion is described. A method has been proposed in which a pin or ring having a shape protruding from the outer peripheral surface is attached to the portion, or a method of integrally forming convex portions having various shapes on the outer peripheral surface of the processed portion (see Patent Document 2, etc.). ).
[0008]
The plastic working by rolling is also used when a similar dynamic pressure generating groove is formed on the outer peripheral surface of a shaft of a dynamic pressure bearing. In this case, contrary to the above-described conventional example, a processing jig having a pipe-shaped processing portion in which a plurality of balls made of a hard material are arranged on the inner peripheral surface is used (see Patent Document 3 and the like).
[0009]
[Patent Document 1] JP-A-61-6426 [Patent Document 2] JP-A-8-243675 [Patent Document 3] JP-A-61-111714
[Problems to be solved by the invention]
By the way, in the above-mentioned method of processing a dynamic pressure generating groove, when processing a workpiece (work) made of aluminum or an aluminum alloy, there is a problem that the jig becomes unusable after several processings. there were.
[0011]
This problem is caused by the extremely high ductility of aluminum and aluminum alloys. Aluminum is used on the surface of metal (steel, cemented carbide, etc.) or ceramics conventionally used for the convex part of this jig. Adhesion causes problems such as an increase in friction due to processing and a variation in the shape of the dynamic pressure generating groove. For this reason, although aluminum and aluminum alloys are usually advantageous for reducing the weight of parts, it is difficult to form a radial dynamic pressure generating groove by rolling, and it has not been suitable for mass production of dynamic pressure bearing parts.
[0012]
The present invention has been made to address the above-described problem, and even when a member made of aluminum or an aluminum alloy is used as a workpiece, it is possible to continuously form high-precision dynamic pressure generating grooves. The purpose is to provide a possible processing method.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a plurality of protrusions projecting at equal intervals in a circumferential direction from an outer peripheral surface of a cylindrical member having an outer diameter smaller than the inner diameter of a cylindrical workpiece. By inserting a jig provided with relative rotation to the inner periphery of the workpiece, a movement for forming a fine groove having a pattern corresponding to the locus of the convex portion on the inner peripheral surface of the workpiece. In the method for processing a pressure generating groove, a jig in which a diamond-like carbon coating is formed on at least a surface of the projection that comes into contact with a workpiece is used as the jig.
[0014]
Here, when the convex portion is formed by a ball fitted into a guide hole provided on the outer peripheral surface of the processed portion, a diamond-like carbon coating may be formed on the surface of the ball. (Claim 2)
[0015]
Further, the invention according to claim 3 includes a jig provided with a plurality of convex portions projecting at equal intervals in a circumferential direction from an inner peripheral surface of a cylindrical member having an inner diameter larger than an outer diameter of a cylindrical workpiece. In the method of processing a dynamic pressure generating groove for forming a fine groove of a pattern corresponding to the trajectory of the convex portion on the outer peripheral surface of the workpiece by inserting while giving relative rotation to the outer circumference of the workpiece, As the jig, a jig in which a diamond-like carbon coating is formed on at least the surface of the projection that comes into contact with the workpiece is used.
[0016]
Furthermore, similarly to claim 2, when the convex portion is formed by a ball fitted into a guide hole provided on the inner peripheral surface of the processed portion, a diamond-like carbon coating is formed on the surface of the ball. It may be formed. (Claim 4)
[0017]
The present invention provides a method of processing a dynamic pressure generating groove by rolling, wherein a diamond-like carbon coating (hereinafter, DLC coating) having smoothness, low wear, and low affinity for metals is provided on a contact surface with a workpiece. The intention is to achieve the intended purpose by intervening.
[0018]
That is, according to the present invention, the DLC film is provided on the surface of the convex portion (the surface of the ball used in the case of ball rolling), which is the contact surface with the workpiece, in the rolling process of the dynamic pressure generating groove. By using the processing jig, the friction between the projection and the workpiece can be reduced. In addition, the DLC film is strong and has poor affinity with metals as workpieces, so that the DLC film can also have an effect of preventing adhesion of cutting powder and the like generated by rolling. Therefore, according to the dynamic pressure generating groove processing method of the present invention, the life of the processing jig is improved as compared with the conventional processing jig.
[0019]
Also, particularly when this jig is used, even when rolling is performed on a workpiece using a highly ductile metal material such as aluminum and an aluminum alloy, adhesion of the metal material to the protrusions is prevented. Is prevented. Therefore, according to the processing method of the present invention, a highly accurate dynamic pressure generating groove can be continuously processed even with a workpiece using such a highly ductile metal material.
[0020]
The present invention provides a method using a processing jig in which a pin or a ring having a shape protruding on the inner and outer peripheral surfaces is attached to a part of the processed portion, and various shapes of convexes are formed on the inner and outer peripheral surfaces of the processed portion. Using a processing jig in which the part is integrally formed, or forming a dynamic pressure generating groove on the outer peripheral surface of the shaft of the dynamic pressure bearing using a pipe-shaped processing jig with multiple balls arranged on the inner peripheral surface, etc. Including the general formation of dynamic pressure generating grooves by rolling, but especially in the case of ball rolling, which is frequently used in this field, by previously applying a DLC film to a ball to be used, it has been conventionally used. There is also an advantage that the present invention can be easily implemented with a minimum cost increase by diverting an existing jig.
[0021]
Further, the DLC film only needs to be formed at least on the surface of the convex portion of the processing jig, and may be applied to the entire processing portion of the processing jig or the entire processing jig.
[0022]
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 side view showing the appearance of a jig used for processing a dynamic pressure generating groove according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. Components having the same functions as those of the conventional example are denoted by the same reference numerals. Also, in the case of this embodiment, similarly to the conventional example, two radial dynamic pressure generating grooves 2v, 2 at an axial distance from each other are formed on the inner peripheral surface 2x of the cylindrical workpiece (sleeve 2). 2v is formed.
[0023]
The basic structure of the processing jig 1 according to this embodiment is the same as that of the conventional example shown in FIG. 4, and includes a support portion 1a and a small-diameter processing portion 1b formed integrally with the support portion 1a. A support pin 1c fitted on the inner periphery of the processed portion 1b and a plurality of balls 10 are provided. The vicinity of the tip of the processing portion 1b is formed in a hollow cylindrical shape concentric with the support portion 1a, and a guide hole 1h having an opening diameter substantially equal to the diameter of the ball 10 is formed in this hollow portion. Are provided at equal intervals in the circumferential direction (six in this example). The balls 10 are fitted into the guide holes 1h from the inner peripheral side of the processed portion 1b, respectively, and are supported by support pins 1c fitted to the inner periphery of the processed portion 1b.
[0024]
Rolling of the dynamic pressure generating groove using the processing jig 1 is also performed in the same manner as in the conventional example described with reference to FIGS. 3 and 6, and a plurality of balls 10 are formed on the outer peripheral surface of the processed portion 1b. By rotating the processing jig 1 holding the workpiece forward and backward (left and right) in the axial direction relative to the workpiece (sleeve 2), the dynamic pressure of the V pattern or herringbone pattern is generated in the circumferential direction. The grooves 2v are formed.
[0025]
The feature of the method of processing the dynamic pressure generating groove in the present embodiment is that a diamond-like carbon (DLC) film 12 is formed on the surface of each ball 10 arranged in the processed portion 1b as shown in the cross-sectional view of FIG. The point is that rolling is performed using the processing jig 1.
[0026]
By using this processing jig, the method of processing the dynamic pressure generating groove in the present embodiment reduces friction with the workpiece during rolling. The DLC film also has an effect of preventing the attachment of cutting powder and the like generated by the rolling process. Therefore, according to the method of processing a dynamic pressure generating groove of the present invention, the life of the processing jig 1 is improved as compared with the conventional processing jig.
[0027]
Also, in particular, even when rolling is performed on a workpiece made of aluminum or an aluminum alloy, by using the processing jig 1 having a DLC film, the material of the workpiece is applied to the surface of each ball 10. Adhesion is prevented. Therefore, according to the dynamic pressure generating groove processing method of the present invention, the rolling process can be continuously performed even on a workpiece made of aluminum or an aluminum alloy.
[0028]
Although the material of the base 11 of the ball 10 in the above embodiment is not particularly limited, for example, a hard metal material such as a cemented carbide, a ceramic, or the like can be used. The size, number, arrangement, etc., of the balls are not particularly limited, and may be appropriately determined depending on the material of the workpiece on which the dynamic pressure generating groove is to be formed, the desired shape and pattern of the dynamic pressure generating groove, and the like. Just change it.
[0029]
【The invention's effect】
As described in detail above, according to the method for processing a dynamic pressure generating groove of the present invention, by using a processing jig having a DLC film on the surface of a projection protruding from a processing portion, The service life can be improved.
[0030]
Further, even when rolling is performed on a workpiece using a highly ductile metal material such as aluminum and an aluminum alloy, adhesion of the metal material to the projections is prevented, and the rolling process is continuously performed. Can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an appearance of a jig used for processing a dynamic pressure generating groove according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, showing the structure of the processing jig according to the embodiment of the present invention.
FIG. 3 is an explanatory view schematically showing a method of forming a radial dynamic pressure generating groove by ball rolling.
FIG. 4 is a partial cross-sectional view showing the structure of a conventional processing jig used for ball rolling of a dynamic pressure generating groove.
FIG. 5 is an end view seen from arrow B in FIG. 4;
FIG. 6 is a schematic cross-sectional view illustrating a procedure for forming a dynamic pressure generating groove using a processing jig.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing jig 1a Support part 1b Processing part 1c Support pin 1h Guide hole 2 Sleeve 2v Dynamic pressure generating groove 2x Inner peripheral surface 3 Chuck 10 Ball 11 Base 12 Diamond-like carbon coating 20 Ball

Claims (4)

A jig provided with a plurality of projections projecting at equal intervals in the circumferential direction from an outer peripheral surface of a cylindrical member having an outer diameter smaller than the inner diameter of a cylindrical workpiece while applying relative rotation to an inner circumference of the workpiece. By inserting, on the inner peripheral surface of the workpiece, in the method of processing a dynamic pressure generating groove for forming a fine groove of a pattern corresponding to the locus of the convex portion,
A method for processing a dynamic pressure generating groove, comprising using a jig having a diamond-like carbon film formed on at least a surface of the projection in contact with a workpiece. 2. The dynamic pressure generating groove according to claim 1, wherein the convex portion is formed by a ball having a diamond-like carbon coating fitted into a guide hole provided on an outer peripheral surface of the cylindrical member. 3. Processing method. A jig provided with a plurality of convex portions projecting at equal intervals in the circumferential direction from the inner peripheral surface of a cylindrical member having an inner diameter larger than the outer diameter of the columnar workpiece while applying relative rotation to the outer periphery of the workpiece. By inserting, on the outer peripheral surface of the workpiece, in the method of processing a dynamic pressure generating groove for forming a fine groove of a pattern corresponding to the locus of the convex portion,
A method for processing a dynamic pressure generating groove, comprising using a jig having a diamond-like carbon film formed on at least a surface of the projection in contact with a workpiece. The dynamic pressure generating groove according to claim 3, wherein the convex portion is formed by a ball having a diamond-like carbon coating fitted into a guide hole provided on an inner peripheral surface of the cylindrical member. Processing method.

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