JPH0732410A - Production of dynamic pressure bearing - Google Patents

Abstract

PURPOSE:To minimize an effect of a shrinkage of a resin on an inner peripheral side to prevent the deformation of the inner periphery to produce a dynamic pressure bearing having a good bearing performance. CONSTITUTION:An insert member 2 made of a small-diameter shaft part 2a having a pattern 11 for forming dynamic pressure grooves on the outer periphery thereof and a large-diameter shaft part 2b is fitted into a hole made of a small- diameter cylindrical part 1a and a large-diameter cylindrical part 1b in a mold 1. A sleeve 3 is tightly fitted into between the small-diameter cylindrical part 1a of the mold 1 and the small-diameter shaft part 2a of the insert member 2 so that the end face of the sleeve 3 is positioned beyond a stepped part 1c of the mold 1 toward the large-diameter shaft part 2b of the insert member 2. A gate member 4 is tightly fitted into between the inner periphery of the large-diameter cylindrical part 1b of the mold 1 and the outer periphery of the large-diameter shaft part 2b of the insert member 2 so that the end face thereof is positioned outside a stepped part 2c of the insert member 2. A resin melted by heating is injected into a space 10 formed by the mold 1, the insert member 2, the sleeve 3, and the gate member 4 through a path provided in the gate member 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing manufacturing method for manufacturing a dynamic pressure bearing made of resin by insert molding.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a sleeve-shaped dynamic bearing having a dynamic pressure groove on the inner circumference thereof, there is one as shown in FIG. This dynamic pressure bearing manufacturing method uses a small-diameter cylindrical portion 21.
a mold 21 having a hole composed of a and a large-diameter cylindrical portion 21b
And a pattern 25 for forming a dynamic pressure groove on the outer periphery, and this pattern 25 is the large diameter cylindrical portion 21 of the mold 21.
A cylindrical insert member 22 fitted and inserted so as to be positioned inside b, and an opening portion between the inner circumference of the large-diameter cylindrical portion 21b of the mold 21 and the outer circumference of the insert member 22 are closely fitted. And a gate member 23, and the mold 21, the insert member 22, and the gate member 23 form a space 24 into which the resin is to be supplied. Then, the mold 21 is heated to a high temperature, and a resin (heated and melted) is injected and filled into the space 24 from a passage (not shown) provided in the gate member 23. After the elapse of a predetermined cooling period, the mold 2
Remove the insert member 22 and the gate member 23 from 1,
The cured resin dynamic pressure bearing is taken out of the mold 21.

[0003]

By the way, in the method of manufacturing the dynamic pressure bearing, the heat of the resin in the space 24 is absorbed by the low temperature insert member 22 during the cooling period, and both sides of the insert member 22 in the axial direction are absorbed. Since heat is conducted to the center, the central portion of the dynamic pressure bearing formed in the space 24 cools faster than both ends. Therefore, curing starts from the inner peripheral side of the central portion of the dynamic pressure bearing, and both end portions having high heat are pulled by contraction of the central portion, and as shown in FIG. The inner diameter of the central portion is enlarged and the outer diameter is reduced, the inner peripheral surface 26a is not the same cylindrical surface due to this deformation, and the error in the inner diameter dimension becomes large, so that there is a problem that the bearing performance cannot be obtained. is there.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method of manufacturing a dynamic pressure bearing which can minimize the influence of shrinkage of the resin on the inner circumference side and prevent the inner circumference from being deformed and which has good bearing performance. .

[0005]

In order to achieve the above object, a method of manufacturing a dynamic pressure bearing according to a first aspect of the present invention is a method of manufacturing a dynamic pressure bearing in which a resin dynamic pressure bearing is insert-molded.
It is characterized in that expanded diameter step portions are formed on the inner peripheral side of both ends of the dynamic pressure bearing.

A method of manufacturing a dynamic pressure bearing according to claim 2 is
The method of manufacturing a dynamic pressure bearing according to claim 1, wherein a mold having a hole having a small diameter cylindrical portion and a large diameter cylindrical portion, a small diameter shaft portion having a pattern for forming a dynamic pressure groove on the outer periphery, and a large diameter A small diameter shaft portion, the small diameter shaft portion being located inside the small diameter cylindrical portion of the mold, and the small diameter shaft portion having the pattern being located inside the large diameter cylindrical portion. Insert member, and the small-diameter cylindrical portion of the mold and the small-diameter shaft portion of the insert member is closely fitted, the end surface of the small-diameter cylindrical portion and the large-diameter cylindrical portion of the mold A sleeve located closer to the large-diameter shaft portion side of the insert member than the step portion, and closely between the inner circumference of the large-diameter cylindrical portion of the mold and the outer circumference of the large-diameter shaft portion of the insert member. The small diameter shaft portion and the large diameter shaft portion of the insert member that are fitted together have an end surface. A gate member located outside the step portion is used to form a space to which the resin is to be supplied, and the heated and melted resin is injected into the space from a passage provided in the gate member to form both ends. The present invention is characterized in that a dynamic pressure bearing having an enlarged diameter step portion is formed on the inner peripheral side.

[0007]

According to the method of manufacturing a dynamic pressure bearing of claim 1,
A dynamic pressure bearing made of resin is insert-molded to form an enlarged diameter step portion on the inner peripheral side of both ends of the dynamic pressure bearing. At the time of this insert molding, the temperature of the member in contact with the inner diameter of the dynamic pressure bearing and the expanded diameter step can be made low, and the heat of the resin can be absorbed by the member, so the inner diameter side portion of the dynamic pressure bearing can be cooled evenly and contracted due to contraction. Since the deformation is suppressed and the inner peripheral surface is the same cylindrical surface having a predetermined inner diameter, a dynamic pressure bearing having good bearing characteristics can be manufactured.

Further, according to the method of manufacturing a dynamic pressure bearing of the second aspect, an insert member including a small diameter shaft portion and a large diameter shaft portion having a pattern for forming the dynamic pressure groove on the outer periphery is provided in the mold. It is inserted into the hole formed by the small diameter cylindrical portion and the large diameter cylindrical portion. At this time, the small-diameter shaft portion of the insert member is located inside the small-diameter cylindrical portion of the mold, and the small-diameter shaft portion having the pattern is located inside the large-diameter cylindrical portion of the mold. Then, the sleeve is tightly fitted between the small-diameter cylindrical portion of the mold and the small-diameter shaft portion of the insert member. The end surface of this sleeve is positioned closer to the large-diameter shaft portion side of the insert member than the stepped portion between the small-diameter cylindrical portion and the large-diameter cylindrical portion of the mold. On the other hand, the gate member is tightly fitted between the inner circumference of the large-diameter cylindrical portion of the mold and the outer circumference of the large-diameter shaft portion of the insert member. The end surface of the gate member is positioned outside the stepped portion between the small diameter shaft portion and the large diameter shaft portion of the insert member. Thus, the mold, the insert member, the sleeve, and the gate member are used to form a space into which the resin is to be supplied, and the heated and melted resin is injected from the passage provided in the gate member into this space. The heat-melted resin is filled in the space, and the heat of the resin is absorbed by the insert member via the outer circumference of the small-diameter shaft portion of the insert member facing the space. Further, the resin, which becomes the dynamic pressure bearing filled in the space, is applied to the insert member and the sleeve through the outer circumference of the large-diameter shaft portion of the insert member facing the space and the step thereof, and the outer circumference of the sleeve and the end surface thereof. Since the heat is absorbed, the heat absorbing area is widened, and the heat of the central portion and the heat of both ends escape substantially.

Therefore, since the insert member and the sleeve can be cooled to a low temperature to absorb the heat of the resin, the inner peripheral portion of the dynamic pressure bearing can be uniformly cooled to suppress the contraction of the resin and the inner peripheral surface. Since the two are made to have the same cylindrical surface with a predetermined inner diameter, a dynamic pressure bearing having good bearing characteristics can be manufactured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a dynamic pressure bearing of the present invention will be described in detail below with reference to an embodiment.

FIG. 1 is a sectional view of a mold for insert-molding a dynamic pressure bearing according to an embodiment of the present invention.
Is a mold having a hole composed of a small-diameter cylindrical portion 1a and a large-diameter cylindrical portion 1b, and 2 is a pattern 1 for forming a dynamic pressure groove on the outer circumference.
1 has a small-diameter shaft portion 2a and a large-diameter shaft portion 2b, the small-diameter shaft portion 2a is located inside the small-diameter cylindrical portion 1a of the mold 1, and a portion having the pattern 11 of the small-diameter shaft portion 2a is formed. The insert member 3 fitted and inserted so as to be located inside the large diameter cylindrical portion 1b of the mold 1 is closely fitted between the small diameter cylindrical portion 1a of the mold 1 and the small diameter shaft portion 2a of the insert member 2. The sleeve 4 which is inserted and whose end surface 3a is located closer to the large-diameter shaft portion 2b of the insert member 2 than the step portion 1c of the small-diameter cylindrical portion 1a and the large-diameter cylindrical portion 1b of the mold 1 is Inner circumference of large diameter cylindrical portion 1b and large diameter shaft portion 2b of insert member 2
Is closely fitted to the outer periphery of the insert member 2
The gate member is located outside the step 2c of the small diameter shaft portion 2a and the large diameter shaft portion 2b. The mold 1, the insert member 2, the sleeve 3, and the gate member 4 are used to form a space 10 for insert-molding the dynamic pressure bearing. The gate member 4 is provided with a passage (not shown) and a gate (not shown) for injecting the heated and melted resin into the space 10. The outer diameter of the sleeve 3 is substantially the same as the large-diameter shaft portion 2b of the insert member 2. Further, the end surface 3a of the sleeve 3 and the stepped portion 2c of the insert member 2 are located at substantially the same size from both ends of the space 10 toward the center in the axial direction.

In the above structure, the heated and melted resin is injected from the gate of the gate member 4 into the space 10. The heat of the resin filled in the space 10 is absorbed via the outer circumference of the small-diameter shaft portion 2a of the insert member 2 facing the space 10, and the heat of the large-diameter shaft portion 2b of the insert member 2 facing the space 10 is absorbed. It is absorbed by the insert member 2 and the sleeve 3 through the outer periphery and the step portion 2c and the outer periphery of the sleeve 3 and the end surface 3a. For this reason, since the heat radiation area of the inner peripheral side portion of the resin which becomes the dynamic pressure bearing in the space 10 becomes large and the heat of both end portions is easily absorbed, the inner peripheral side portion is cooled uniformly and the inner peripheral side portion is cooled. The influence of the contraction of the side part can be reduced. Therefore, as shown in FIG. 3 (b), the inner peripheral surface 12a of the dynamic pressure bearing 12 is made the same cylindrical surface without deformation. After the elapse of a predetermined cooling period, the insert member 2, the sleeve 3 and the gate member 4 are removed from the mold 1 and the molded dynamic pressure bearing is taken out. In this way, the large-diameter shaft portion 2 of the insert member 2 is provided on the inner peripheral side of both ends of the insert-molded dynamic pressure bearing.
An enlarged diameter step portion is formed by b and the sleeve 3.
Further, the pattern 11 of the insert member 2 is transferred to the inner circumference of the dynamic pressure bearing to form a dynamic pressure generating groove on the inner circumference of the dynamic pressure bearing.

In this way, the influence of the resin shrinkage on the inner peripheral side portion of the dynamic pressure bearing can be minimized and the inner peripheral deformation can be prevented. Therefore, the inner peripheral surface can be the same cylindrical surface, and the inner diameter can be made to have a predetermined accuracy.
A dynamic pressure bearing having good bearing performance can be manufactured.

In the above embodiment, the stepped portion 2c of the insert member 2 and the end surface 3a of the sleeve 3 are planes perpendicular to the axis, but may be tapered.

Further, in the above embodiment, the diameter-increasing stepped portions having substantially the same diameter and the same axial length are formed on the inner peripheral sides of both ends of the dynamic pressure bearing. The length in the axial direction may be an appropriate size.

[0016]

As is apparent from the above, the method for manufacturing a dynamic pressure bearing according to the invention of claim 1 is such that when resin dynamic pressure bearings are insert-molded, the inner circumferential sides of both ends of the dynamic pressure bearings are formed. The diameter-increasing step portion is formed on the.

Therefore, according to the method of manufacturing a dynamic pressure bearing of the first aspect of the present invention, the temperature of the member contacting the inner circumference of the dynamic pressure bearing and the enlarged diameter step portion is lowered at the time of the insert molding, and the heat of the resin is applied to the member. Therefore, the inner peripheral surface of the dynamic pressure bearing is evenly cooled, deformation due to contraction is suppressed, and the inner peripheral surface is made the same cylindrical surface with a predetermined inner diameter dimension. It can be manufactured.

A method of manufacturing a dynamic pressure bearing according to a second aspect of the present invention is the method of manufacturing a dynamic pressure bearing according to the first aspect,
Inserting an insert member consisting of a small diameter shaft portion and a large diameter shaft portion having a pattern for forming a dynamic pressure groove on the outer periphery into a hole formed by a small diameter cylindrical portion and a large diameter cylindrical portion of a mold, The small-diameter shaft portion is located inside the small-diameter cylindrical portion of the mold, and the small-diameter shaft portion having the above pattern is located inside the large-diameter cylindrical portion of the mold. The sleeve is tightly inserted between the small-diameter shaft portion of the insert member and the end surface of the sleeve is positioned closer to the large-diameter shaft portion of the insert member than the step between the small-diameter cylindrical portion and the large-diameter cylindrical portion of the mold. On the other hand, the gate member is tightly fitted between the inner circumference of the large-diameter cylindrical portion of the mold and the outer circumference of the large-diameter shaft portion of the insert member, and the end surface of this gate member is used as the small-diameter shaft portion of the insert member. Be positioned outside the step with the large diameter shaft, and With concerts member and the sleeve and the gate member to form a space to the resin is supplied,
The resin which is heated and melted is injected from the passage provided in the gate member into this space to form the dynamic pressure bearing having the radially expanded stepped portions on the inner peripheral sides of both ends.

Therefore, according to the method of manufacturing the dynamic pressure bearing of the second aspect of the present invention, the heated and melted resin is filled in the space, and the heat of the resin is applied to the small-diameter shaft portion of the insert member facing the space. Is absorbed by the insert member through the outer periphery of the insert member, and is also absorbed by the insert member and the sleeve through the outer periphery of the large-diameter shaft portion of the insert member facing the space and its step, and the outer periphery of the sleeve and its end face. Therefore, the heat absorbing area of the resin is widened and the heat of both end portions of the dynamic pressure bearing is easily absorbed. Therefore, by lowering the temperature of the insert member and the sleeve,
Since the heat of the resin can be efficiently absorbed by these, the inner peripheral side portion of the dynamic pressure bearing made of this resin can be cooled uniformly. Therefore, in the inner peripheral side portion of the dynamic pressure bearing, the influence of the shrinkage of the resin is reduced, the inner peripheral surface can be the same cylindrical surface, and the inner diameter dimension of a predetermined accuracy can be obtained.
It is possible to manufacture a dynamic pressure bearing having good bearing characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of a mold showing a method of manufacturing a dynamic pressure bearing according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a mold showing a conventional method for manufacturing a dynamic pressure bearing.

FIG. 3 (a) is a sectional view of a dynamic pressure bearing formed by a conventional dynamic pressure bearing manufacturing method, and FIG. 3 (b) is a dynamic pressure bearing formed by the conventional dynamic pressure bearing manufacturing method. It is a sectional view of a bearing.

[Explanation of symbols]

1 ... Mold, 1a ... Small diameter cylindrical portion, 1b ... Large diameter cylindrical portion, 2 ...
Insert member, 2a ... Small diameter shaft portion, 2b ... Large diameter shaft portion, 3
... Sleeve member, 4 ... Gate member, 10 ... Space, 11 ...
pattern.

Claims (2)

[Claims] 1. A method of manufacturing a dynamic pressure bearing in which a resin dynamic pressure bearing is insert-molded, characterized in that expanded diameter step portions are formed on the inner peripheral sides of both ends of the dynamic pressure bearing. Manufacturing method. 2. The method for manufacturing a dynamic pressure bearing according to claim 1, wherein a die having a hole composed of a small-diameter cylindrical portion and a large-diameter cylindrical portion and a pattern for forming a dynamic pressure groove are provided on the outer periphery. It consists of a small diameter shaft portion and a large diameter shaft portion, the small diameter shaft portion is located inside the small diameter cylindrical portion of the mold, and the small diameter shaft portion having the pattern is located inside the large diameter cylindrical portion. The insert member fitted so as to be tightly fitted between the small diameter cylindrical portion of the mold and the small diameter shaft portion of the insert member, and the end surface of the small diameter cylindrical portion of the mold and the A sleeve positioned on the large-diameter shaft portion side of the insert member with respect to the stepped portion with the large-diameter cylindrical portion, an inner circumference of the large-diameter cylindrical portion of the mold, and an outer circumference of the large-diameter shaft portion of the insert member. Is tightly fitted between the insert member and the end surface of the insert member above the small-diameter shaft portion. The large-diameter shaft portion and a gate member located outside the stepped portion are used to form a space into which the resin is to be supplied, and the resin is heated and melted into the space through a passage provided in the gate member. Is injected to mold a dynamic pressure bearing having an enlarged diameter stepped portion on the inner peripheral side of both ends, and a method for manufacturing a dynamic pressure bearing.