JP2002018543A - Machining jig of groove for generating dynamic pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining jig capable of machining a highly precise groove for generating dynamic pressure and being manufactured at high mass productivity. SOLUTION: This machining jig 9 comprises an outer cylinder 3 having a plurality of holes 10, a core pin 4 inserted in the outer cylinder 3 via a space in the radial direction, and balls 2 arranged in the holes 10. The holes 10 are provided continuously in the circumferential direction of the outer cylinder 3 piercing the outer cylinder in the radial direction, and a circumferential groove 5 having a recessed surface 5a of the radius R of curvature larger than the radius of the balls 2 is provided in a part in contact with the balls 2 of the outer circumferential surface of the core pin 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for processing a dynamic pressure generating groove of a dynamic bearing.

[0002]

2. Description of the Related Art As a conventional processing jig for a groove for generating a dynamic pressure, there is, for example, one described in JP-A-11-93954. First, the structure of the jig for processing the dynamic pressure generating groove will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view of a conventional processing jig for a groove for generating dynamic pressure, and FIG.
It is CC sectional view taken on the line of FIG.

[0003] A sleeve 6 is fixed to a main shaft (not shown) of the lathe, and the main shaft can rotate forward and reverse. On the other hand, a machining jig 9 is attached to a turning table (not shown) of the lathe that can move in the axial direction of the spindle, and the processing jig 9 can move in the axial direction by moving the cutting table. It has become. The processing jig 9 includes a core pin 4 that is movable in the axial direction and the radial direction with respect to the support portion 1 for fixing to the cutting tool, an outer cylinder 3 fitted to the core pin 4 through a radial gap, and an outer cylinder. And three balls 2 respectively disposed at three radial holes 10 (see FIG. 6) provided at equal intervals in the circumferential direction at the main shaft side tip portion. A flange 15 is provided at an end of the core pin 4 on the support portion 1 side to prevent the core pin 4 from coming off. The outer cylinder 3 is fixed to the support 1. The radial hole 10 is a hole that penetrates the outer cylinder 3 in the radial direction. Also, the ball 2 is harder than the sleeve 6,
The core pin 4 has the same hardness as the ball 2.

[0004] The sum of the diameter of the core pin 4, the diameter of one ball 2 and the diameter of the other ball 2, ie,
The diameter of a circle connecting the radially outer ends of the plurality of balls 2 in contact with the core pin 4 and centering on the axis of the core pin 4 is made larger than the inner diameter of the sleeve 6 to be grooved by a predetermined dimension. Next, a method of forming a groove in the sleeve 6 by using the above-described jig for processing a groove for generating a dynamic pressure will be described.

After the main shaft is rotated forward, the processing jig 9 is moved in the axial direction toward the main shaft, and the outer cylinder 3 of the processing jig 9 is inserted into the sleeve 6. Inner surface 7 of sleeve 6
The ball 2 is pressed into contact with the outer cylinder 3
Continue to move in the axial direction. Then, since the outer cylinder 3 and the ball 2 make a spiral movement relatively to the sleeve 6, a spiral groove 8a is formed in the inner diameter surface 7 by plastic working by ball rolling.

Next, when the main spindle is reversed and the processing jig 9 is moved in the axial direction toward the main spindle, the outer cylinder 3 is moved.
The ball 2 makes a spiral motion relative to the sleeve 6 in a direction opposite to the above. As a result, a spiral groove 8b in a direction opposite to the above is formed by plastic working by ball rolling. By such an operation, the dynamic pressure generating grooves 8 are plastically worked at two locations on the inner diameter surface 7 of the sleeve 6 at intervals in the axial direction.

[0007]

However, in the above-mentioned conventional jig for processing a groove for generating a dynamic pressure, the core pin 4 has a cylindrical shape, and the outer peripheral surface thereof has a cylindrical surface. Therefore, the ball 2 and the core pin 4 are in contact with each other on the convex surfaces (the spherical surface and the cylindrical surface), and the contact portion is substantially in point contact. In the case of point contact, the surface pressure of the contact portion increases, so that the ball 2 is deformed during the groove processing and the ball 2 does not rotate smoothly, or the dynamic pressure generating groove is processed in a meandering state. Problem may occur.
In the worst case, a problem such as breaking of the ball 2 may occur, and it is necessary to replace the processing jig 9 during the processing, which causes a problem in mass productivity.

Therefore, the present invention solves the above-mentioned problems of the conventional jig for processing a dynamic pressure generating groove, and can process a highly accurate groove for generating a dynamic pressure, and can mass-produce the groove. It is an object of the present invention to provide a processing jig for a groove for generating a dynamic pressure having a high value.

[0009]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, the dynamic pressure generating groove processing jig of the present invention includes an outer cylinder having a plurality of holes, a core pin inserted into the outer cylinder via a radial gap, and a ball disposed in the hole. And the hole penetrates the outer cylinder in the radial direction and is provided side by side in the circumferential direction of the outer cylinder. Further, a portion of the outer peripheral surface of the core pin where the ball is in contact is provided with the hole of the ball. A peripheral groove having a concave surface with a radius of curvature larger than the radius is provided.

As described above, since the peripheral groove having a concave surface is provided in a portion of the outer peripheral surface of the core pin where the ball contacts, the convex surface (spherical surface) of the ball and the concave surface of the peripheral groove come into contact with each other. That is, the ball and the core pin are in surface contact, not point contact. Therefore, the surface pressure of the contact portion is significantly smaller than that in the case where the convex surfaces are in contact with each other.

As a result, since the ball hardly undergoes plastic deformation during the groove machining, there is a possibility that the ball will not rotate smoothly, and the dynamic pressure generating groove will be machined in a meandering state. Absent. Further, since there is almost no problem such as the ball being broken during the processing, there is no need to change the processing jig of the groove for generating the dynamic pressure during the processing, and the mass productivity is very high.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a working jig for a groove for generating dynamic pressure according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. FIG. 1 is a longitudinal sectional view of a jig 9 for processing a groove for generating dynamic pressure according to the present embodiment, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 4 is an enlarged view of a part of the portion, in which a ball 2 and a core pin 4 are enlarged (an outer cylinder 3 is omitted). In addition, FIG.
In FIG. 3, the same or corresponding parts as in FIG.
The same reference numerals are given as.

First, the structure of the dynamic pressure generating groove processing jig 9 of the present embodiment will be described. A sleeve 6 is fixed to a main shaft (not shown) of the lathe. The main shaft can rotate forward and reverse. On the other hand, a tool post (not shown) of the lathe movable in the axial direction of the main spindle has a processing jig 9 for forming a groove for generating dynamic pressure.
Is attached, and the processing jig 9 of the groove for generating dynamic pressure can be moved in the axial direction by the movement of the tool rest.

The jig 9 for processing a groove for generating dynamic pressure includes a plurality of holes 1.
0, a thin and long core pin 4 inserted into the outer cylinder 3 through a radial gap, a ball 2 disposed in a hole 10, and a support portion to which the outer cylinder 3 is fixed. And 1. As described above, the outer peripheral surface of the core pin 4 and the outer cylinder 3
A radial clearance is interposed between the inner diameter surface and the inner diameter surface. From this, the thin and long core pin 4 can freely move in the radial direction by the radial clearance, so that the axial center between the inner diameter of the sleeve 6 and the outer diameter surface of the outer cylinder 3 does not match. However, the radial position of the ball 2 is automatically aligned, and the depth of the dynamic pressure generating groove 8 processed by the ball 2 becomes uniform. In order to facilitate alignment of the axis of the core pin 4 with the sleeve 6, the radial clearance is preferably 0.01 mm or more.

The end of the core pin 4 on the support portion 1 side has a flange 15 having a larger diameter than other portions.
Are opposed to the outer cylinder 3 and the end face of the support portion 1 via a slight axial clearance. Further, the outer peripheral surface of the flange 15 is opposed to the inner peripheral surface of the support portion 1 via a radial gap. The core pin 4 is movable in the axial direction with respect to the outer cylinder 3 by the clearance in the axial direction, and is movable in the radial direction by the clearance in the radial direction. Note that the structure of the flange 15 is not limited to the present embodiment, since the core pin 4 moves freely in the radial direction and does not have to come off the outer cylinder 3.

The hole 10 penetrates the outer cylinder 3 in the radial direction.
The outer cylinder 3 is provided at an end of the outer cylinder 3 on the main shaft side (opposite to the support 1). Also, three holes 2 are provided, and are arranged at equal intervals in a line in the circumferential direction of the outer cylinder 3 (see FIG. 2). The ball 2 is disposed in the hole 10 through a gap, and the ball 2 can freely rotate in the hole 10.

The number of the balls 2 may be two or more, but is preferably three when the inner diameter of the sleeve 6 is 10 mm or less. When the number of the balls 2 is three, the core pins 4 are guided by the three balls 2, so that the alignment of the core pins 4 is improved. Even if there are only balls of limited dimensions, if there are three balls 2,
By changing the dimensions of one or two of the three balls 2, a dynamic pressure generating groove 8 having a desired depth can be provided.

The ball 2 on the outer peripheral surface of the core pin 4
Is provided with a peripheral groove 5 having a concave surface 5a having a radius of curvature R larger than the radius of the ball 2, and the ball 2 and the core pin 4 are in surface contact with the concave surface 5a of the peripheral groove 5. Thereby, the surface pressure at the contact portion between the ball 2 and the core pin 4 when the dynamic pressure generating groove 8 is processed can be reduced.

FIG. 4 shows the result of calculation of the contact pressure of the contact portion between the ball 2 and the core pin 4. The vertical axis in the graph of FIG. 4 is the surface pressure of the contact portion between the ball 2 and the core pin 4, and the horizontal axis is the ratio R / D (radius of curvature ratio) between the diameter D of the ball 2 and the radius of curvature R of the concave surface 5a. ). The surface pressure is indicated by a relative value with the surface pressure being 1.0 when the curvature radius ratio is 0.5.

As can be seen from the graph, the surface pressure decreases as the curvature radius ratio approaches 0.5. When the curvature radius ratio exceeds 3, the surface pressure does not greatly differ from the surface pressure when the core pin 4 does not have the circumferential groove 5 (for example, the conventional example), and the effect of providing the circumferential groove 5 becomes poor. Is preferably 3 or less, more preferably 1 or less. And
The sum of the diameter of the core pin 4, the diameter of one ball 2, and the diameter of the other ball 2, that is, connecting the radially outer ends of the plurality of balls 2 in contact with the core pin 4 and centering on the axis of the core pin 4 The diameter of the circle is larger than the inner diameter of the sleeve 6 to be grooved by a predetermined dimension. When the sum is increased, the depth of the dynamic pressure generating groove 8 can be increased.

Next, a method of forming a groove in the sleeve 6 using the processing jig 9 for forming a groove for generating dynamic pressure as described above will be described. First, after rotating the main shaft forward, the processing jig 9 for the groove for generating dynamic pressure is moved in the axial direction toward the main shaft, and the outer cylinder 3 of the processing jig 9 for forming the groove for dynamic pressure is moved. Insert into sleeve 6. Although the ball 2 is pressed against the inner diameter surface 7 of the sleeve 6, the outer cylinder 3 continues to move in the axial direction as it is. Then, since the outer cylinder 3 and the ball 2 make a spiral movement relatively to the sleeve 6, a spiral groove 8a is formed in the inner diameter surface 7 by plastic working by ball rolling.

When the spiral groove 8a is formed, the rotation of the main shaft and the axial movement of the working jig 9 of the dynamic pressure generating groove are temporarily stopped. Next, after the main shaft is reversed, the processing jig 9 for the groove for generating dynamic pressure is moved in the axial direction toward the main shaft, and the outer cylinder 3 and the ball 2 are moved in the opposite direction to the sleeve 6 in the opposite direction. Will perform a spiral motion relative to the body.
As a result, a spiral groove 8b in a direction opposite to the above is formed by plastic working by ball rolling.

By such an operation, the dynamic pressure generating grooves 8 are plastically worked on the inner diameter surface 7 of the sleeve 6 at two locations spaced apart in the axial direction. The number of the dynamic pressure generating grooves 8 provided on the inner diameter surface 7 of the sleeve 6 can be measured by a two-point contact method using a stylus in a process inspection. Even numbers of 6, 12, and 18 are preferable so that a mountain portion is arranged.

The forward and reverse rotation of the main spindle of the lathe and the axial movement of the slide on which the processing jig 9 for the dynamic pressure generating groove is mounted on the tool rest are performed while being controlled by an NC device or the like. Or manually. Also, the dynamic pressure generating groove 8
May be performed on a lathe as described above, or may be performed by a dedicated grooving machine after turning is completed. When the groove 8 for generating dynamic pressure is machined in this manner, the contact pressure between the ball 2 and the core pin 4 is small, and the ball 2 hardly undergoes plastic deformation during machining of the groove. It is less likely that problems such as no longer rotating or the dynamic pressure generating groove 8 is processed in a meandering state will occur, and it is possible to process the dynamic pressure generating groove with high accuracy.

Further, since there is almost no problem such as the ball 2 being broken during processing, there is no need to replace the processing jig 9 for the groove for generating dynamic pressure during processing.
Very high mass productivity. In the present embodiment, the core pin 4 is made of SUJ2, hardened steel such as high-speed steel, or carbide, and the ball 2 is made of SUJ2, carbide, silicon nitride, zirconia, or the like.

When the ball 2 is made of a hard material having a large crushing load, such as silicon nitride or zirconia, the core pin 4 is preferably made of a superhard material having a high hardness. Also,
When the carbide core pin 4 is used, the core pin 4 of hardened steel is used.
, The core pin 4 hardly undergoes plastic deformation. As a result, the depth of the dynamic pressure generating groove 8 to be processed does not change, so that the dynamic pressure generating groove 8 having a constant depth can be provided for a long time.

However, if both the core pin 4 and the ball 2 are made of carbide, the hardness of the core pin 4 and that of the ball 2 are equal, and the ball 2 may be broken. Therefore, it is desirable that the hardness of the ball 2 be higher than the hardness of the core pin 4. That is, when the core pin 4 is made of hardened steel, it is desirable to use carbide, silicon nitride, zirconia, or the like as the material of the ball 2. When the core pin 4 is made of a super hard material, it is desirable that the ball 2 is made of a material such as silicon nitride or zirconia which is harder than the super hard and has a large crushing load.

As described above, the hardness of the ball 2 is
If the ball 2 is harder, the ball 2 will not be broken and the ball 2 will hardly be plastically deformed. Therefore, the ball 2 will not rotate smoothly or the groove 8 for generating dynamic pressure will meander. Almost no. Further, since the ball 2 does not break, there is no need to replace the processing jig 9 of the groove for generating dynamic pressure during processing, and mass productivity is very high.

The dynamic pressure generating groove processing jig 9 of this embodiment has the core pin 4 having the peripheral groove 5, but the core pin 4 is made of hardened steel, and the ball 2 is made of carbide or nitride. In the case where the core pin 4 is made of silicon, the peripheral groove 5 may not be provided in the core pin 4 from the beginning. That is, by performing an operation of forming a groove in a dummy sleeve having a slightly larger inner diameter in advance, the core pin 4 having low hardness is plastically deformed, and a circumferential groove (concave surface) is formed in the core pin 4. Thereafter, by performing an operation of performing groove processing while gradually approaching the inner diameter of the sleeve to a regular one, a necessary peripheral groove can be formed in the core pin 4. After the circumferential groove is formed in the core pin 4, the sleeve 6 on which the dynamic pressure generating groove 8 is to be formed
If a groove is formed on the inner diameter surface 7 (of a regular inner diameter), the same effect as described above can be obtained.

However, in this case, since the peripheral groove is formed by plastic deformation in the core pin 4 by forming a groove in the dummy sleeve, the core pin 4 or the ball 2 has a large dimension by the amount of the peripheral groove. You need to use something. Further, the workpiece on which the dynamic pressure generating groove 8 is provided may be a single sleeve as in the present embodiment or a unit in which the sleeve and the housing are integrated.
The material of the sleeve 6 is not particularly limited, and examples thereof include a copper alloy, stainless steel, a sintered metal, a sintered oil-impregnated metal, and the like.

[0031]

As described above, in the processing jig of the groove for generating dynamic pressure according to the present invention, since the peripheral groove having the concave surface is provided in the portion of the outer peripheral surface of the core pin where the ball contacts, the groove between the core pin and the ball is formed. The contact pressure of the contact portion is much smaller than the case where the convex surfaces contact each other. As a result, the ball hardly undergoes plastic deformation during groove processing.Therefore, there is little possibility that the ball will not rotate smoothly or the groove for dynamic pressure generation will be processed in a meandering state, and the accuracy will be low. It is possible to process a dynamic pressure generating groove having a high level.

Further, since there is almost no problem that the ball is broken during the processing, there is no need to change the processing jig of the groove for generating the dynamic pressure during the processing, and the mass productivity is very high.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a working jig for a groove for generating dynamic pressure of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a partially enlarged view of a portion B in FIG. 1;

FIG. 4 is a graph showing a correlation between a radius ratio and a surface pressure.

FIG. 5 is a longitudinal sectional view showing a structure of a conventional processing jig for a groove for generating dynamic pressure.

FIG. 6 is a sectional view taken along line CC of FIG. 5;

[Explanation of symbols]

 2 Ball 3 Outer cylinder 4 Core pin 5 Circumferential groove 5a Concave surface 8 Groove for generating dynamic pressure 9 Jig for processing groove for generating dynamic pressure 10 Hole D Ball diameter R Curvature radius of concave surface

Claims (1)

[Claims] An outer cylinder having a plurality of holes, a core pin inserted into the outer cylinder through a radial gap, and a ball disposed in the hole; A radially penetrating cylinder is provided side by side in the circumferential direction of the outer cylinder, and a portion of the outer peripheral surface of the core pin where the ball is in contact has a concave surface having a radius of curvature larger than the radius of the ball. A processing jig for a groove for generating dynamic pressure, wherein a groove is provided.