JP2006226398A - Bearing device and manufacturing method of bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device allowing a wedge-like space to be formed between an inside surface of an oil-retaining bearing and a rotary shaft even when a small bearing device used for a fan motor or the like is manufactured and capable of improving motor performance, and to provide a manufacturing method of the bearing device. <P>SOLUTION: This bearing device 1 includes the oil-retaining bearing 3 rotatably supporting the rotary shaft 4 and having a bearing hole formed therein. The bearing device is characterized by that the cross-sectional shape of the bearing hole comprises circular arcs 3a each being a part of a perfect circle and chords 3b formed by linearly cutting other parts of the perfect circle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing device that rotatably supports a rotating shaft (shaft) inserted in an oil-impregnated bearing and a method for manufacturing the bearing device, and in particular, to improve the performance of a motor in which the bearing device is installed. The present invention relates to a bearing device and a method for manufacturing the bearing device.

  Conventionally, there is a hydrodynamic bearing device for rotatingly supporting a polygon mirror, an optical disk or the like. In this hydrodynamic bearing device, the hydrodynamic surface of the rotating shaft and the hydrodynamic bearing surface of the oil-impregnated bearing are provided so as to face each other annularly through a radial gap. The lubricating fluid such as oil injected into the gap is pressurized by a pumping action by dynamic pressure generating means provided on either or both of the rotating shaft and the oil-impregnated bearing when the rotating shaft rotates. As a result, the rotating shaft is supported rotatably relative to the oil-impregnated bearing based on the dynamic pressure of the lubricating fluid.

  Among such dynamic pressure bearing devices, there is one in which a groove for generating dynamic pressure such as a herringbone shape or a spiral shape is provided as means for generating dynamic pressure. Further, a step hydrodynamic bearing device (Rayleigh step hydrodynamic bearing device) in which a groove (concave portion) having a cross-sectional area larger than a groove for generating dynamic pressure such as a herringbone shape or a spiral shape is provided on the inner peripheral surface of the bearing. Yes (see, for example, Patent Document 1).

  FIG. 7 is a cross-sectional view showing a mechanical structure of a conventional step hydrodynamic bearing device 100.

  In FIG. 7, a conventional step hydrodynamic bearing device 100 includes, for example, a convex surface projecting in a step shape in the radial direction on the inner peripheral surface of an oil-impregnated bearing 102 surrounding the rotary shaft 101 in a circumferential shape. The convex portions 102a are provided intermittently at three locations. In addition, the recesses 102b are intermittently provided at three locations so as to be adjacent to the end surface portion of the protrusion 102a and to form a step-like groove (depth is substantially uniform) in the radial direction. Yes. In a narrow space formed between the convex portions 102a and the concave portions 102b and the outer peripheral surface of the rotating shaft 101, the lubricating fluid 103 such as oil (flowing clockwise in FIG. 7) is projected from the concave portion 102b to the convex portion 102a. When entering, the desired dynamic pressure is obtained on the inlet side of the convex portion 102a by being pressurized so as to be squeezed.

  The recess 102b is formed by transferring a molded core or sizing core having the same shape to the inner surface of the oil-impregnated bearing 102 with a groove depth of an inner diameter of about several μm to 0.1 mm. The convex portion 102a finely reduces the porosity (porous), but the concave portion 102b increases the porosity coarsely. Note that the hydrodynamic bearing device 100 described with reference to FIG. 7 is suitable for a spindle motor without a lateral pressure load, particularly an FDD spindle motor.

  By the way, as described above, the concave portion 102 b is formed by transferring a molded core or sizing core having the same shape onto the inner surface of the oil-impregnated bearing 102. The formation of the recess 102b using a molded core is suitable for providing a relatively deep groove (several tens of μm or more). In addition, the groove | channel formed in the shaping | molding process using a shaping | molding core may be crushed in the subsequent sizing process, and may not be crushed. On the other hand, when forming the recessed part 102b using a sizing core, it is suitable when providing a comparatively shallow groove | channel (less than tens of micrometers).

  Moreover, in order to form the recessed part 102b using a shaping | molding core or a sizing core, even if it employ | adopts any method, it is necessary to form the groove | channel (recession) of an axial direction in the outer peripheral surface of a shaping | molding core or a sizing core. is there. There are roughly two types of methods for forming axial grooves (recesses) on the outer peripheral surface of the molded core or sizing core. One is an etching method in which a plate having a predetermined shape is wound around the outer periphery of the core and is etched (dry or wet), and the other is a machining method such as electric discharge machining or grinding.

JP-A-3-107612 (FIG. 1)

  However, in the etching method and the machining method described above, the axial groove may not be accurately formed on the outer peripheral surface of the molded core or the sizing core.

  That is, for example, when manufacturing a small bearing device used for a fan motor or the like used in OA equipment, for example, an oil-impregnated bearing 102 (see FIG. 7) having an inner diameter of 1.5 mm or less is required. When manufacturing the oil-impregnated bearing 102 having an inner diameter of 1.5 mm or less, a molded core or sizing core having an outer diameter of 1.5 mm or less is required. However, if the outer diameter of the molded core or sizing core is smaller than about 1.5 mm, it becomes difficult to wind the plate by the etching method, and bending due to processing occurs in the machining method. An axial groove cannot be formed with high accuracy on the outer peripheral surface of the core.

  The present invention has been made in view of these points, and the object thereof is to form the outer periphery of a molded core or sizing core even when a small bearing device used for a fan motor or the like is manufactured. It is an object of the present invention to provide a bearing device and a method of manufacturing the bearing device that can form an axial groove with high accuracy, and that can improve motor performance.

  In order to solve the above problems, the present invention provides the following.

  (1) In a bearing device having an oil-impregnated bearing in which a bearing hole that rotatably supports a rotating shaft is formed, a cross-sectional shape of the bearing hole is an arc that is a part of a perfect circle and another one of the perfect circles. A bearing device comprising: a string formed by cutting a portion into a straight line.

  According to the present invention, in a bearing device having an oil-impregnated bearing, the cross-sectional shape of the bearing hole formed in the oil-impregnated bearing is such that an arc that is a part of a perfect circle and another part of the perfect circle are linear. Since it is composed of a string formed by cutting, for example, even when manufacturing a small bearing device used for a fan motor or the like, an axial groove is formed on the outer peripheral surface of the molded core or the sizing core. Can be formed with high accuracy, and as a result, motor performance can be improved.

  That is, in order to form a groove on the inner peripheral surface of an oil-impregnated bearing having a small inner diameter, it is necessary to accurately form an axial groove on the outer peripheral surface of a molded core or sizing core having a small inner diameter. In the method and the machining method, it is difficult to form the groove because the processing accuracy is lowered by securing the space for winding the plate and bending due to the processing. In addition, when abandoning the formation of a groove on the inner peripheral surface of an oil-impregnated bearing with a small inner diameter, it was difficult to form an oil film on the inner peripheral surface of the oil-impregnated bearing, which was a cause of motor performance deterioration such as noise and vibration. . However, according to the bearing device according to the present invention, a core obtained by grinding a part of a molded core or sizing core having a perfect cross-sectional shape linearly and axially once or a plurality of times is used. Since the bearing hole of the oil-impregnated bearing is formed, a wedge-shaped gap can be accurately formed between the rotary shaft (shaft) whose cross-sectional shape is a perfect circle, and an oil film is formed on the inner peripheral surface of the oil-impregnated bearing. As a result, the motor performance can be improved, such as noise reduction and vibration prevention.

  In addition, by accurately forming a wedge-shaped gap between the inner peripheral surface of the oil-impregnated bearing having a small inner diameter and the rotating shaft, it is possible to reduce the whirling of the rotating shaft and improve the stability of motor rotation. You can also Furthermore, according to the present invention, since it can be regarded that there is a groove on the inner peripheral surface of the oil-impregnated bearing, the average clearance between the rotary shaft and the oil-impregnated bearing can be increased, and the motor current value can also be reduced. Furthermore, according to the present invention, it can be regarded that there is a convex part on the inner peripheral surface of the oil-impregnated bearing, so the clearance between the rotating shaft and the oil-impregnated bearing can be reduced, and the swing of the rotating shaft can be reduced. You can also

  Here, in the bearing device according to the present invention, a method for forming the “bearing hole” of the oil-impregnated bearing will be described in detail. First, in a molded core or sizing core having a perfect cross-sectional shape, a part of the perfect circle is obtained. A plane extending in the axial direction is formed by cutting linearly and in the axial direction. And if this process is repeated several times, the cross-sectional shape is a molded core composed of an arc that is a part of a perfect circle and a string that is formed by cutting another part of the perfect circle into a straight line. Or a sizing core is completed. After that, when an oil-impregnated bearing is molded or sized using a molded core or sizing core having such a cross-sectional shape, the cross-sectional shape is a circular arc that is a part of a perfect circle and the other part of the perfect circle is linearly cut. Thus, an oil-impregnated bearing having a bearing hole formed of the string formed in this manner is completed.

  The distance between the center of the “bearing hole” and the “string formed by cutting another part of the perfect circle in a straight line” is the radius of the “bearing hole” (“part of the perfect circle”). The radius is smaller than the radius of the “arc”.

  (2) The bearing device according to (1), wherein an inner diameter of the oil-impregnated bearing is 1.5 mm or less.

  According to the present invention, since the inner diameter of the oil-impregnated bearing described above is 1.5 mm or less, it is possible to improve the motor performance and motor rotation stability of the motor in which the bearing device having the oil-impregnated bearing is used. it can.

  As described above, when an oil-impregnated bearing having an inner diameter of 1.5 mm or less is to be manufactured, the conventional etching method or machining method can accurately form an axial groove on the outer peripheral surface of the molded core or sizing core. However, according to the present invention, the groove is formed only through a simple and fine-tuning process in which a part of the molding core or sizing core is linearly and axially ground one or more times. Can be formed with high accuracy.

  (3) The cross-sectional shape of the bearing hole includes at least three or more of the strings, and the distance between the center point of the string and the center point of the subarc formed based on the string is several μm to several The bearing device according to (1) or (2), wherein the bearing device is 10 μm.

  According to the present invention, the above-described cross-sectional shape of the bearing hole includes at least three or more of the above-described strings, and the distance between the center point of the string and the center point of the subarc formed based on the string is Since it is several μm to several tens of μm, dynamic pressure can be generated by a wedge-shaped gap formed between the inner peripheral surface of the oil-impregnated bearing and the rotating shaft.

  (4) The inner diameter of the oil-impregnated bearing is 1.0 mm or less, and the cross-sectional shape of the bearing hole includes at least six strings, and is formed based on the center point of the strings and the strings. The bearing device according to any one of (1) to (3), wherein the distance from the center point of the inferior arc is 5 to 20 μm.

  According to the present invention, the above-described oil-impregnated bearing has an inner diameter of 1.0 mm or less, and the cross-sectional shape of the bearing hole includes at least six strings, and is formed based on the center point of the string and the string. Since the distance from the center point of the inferior arc is 5 to 20 μm, the motor performance and the motor rotation stability of the motor in which the bearing device having the oil-impregnated bearing smaller than the oil-impregnated bearing described above is used. Can be improved.

  (5) Of the inner peripheral surface of the oil-impregnated bearing, the surface including the chord is formed such that the porosity is less than 10% by area ratio, and the surface including the arc of the inner peripheral surface of the oil-impregnated bearing. Is formed so that the porosity is 10 to 20% by area ratio, The bearing device according to any one of (1) to (4),

  Of the inner peripheral surface of the oil-impregnated bearing described above, the surface including the string is formed such that the porosity is less than 10% in terms of area ratio, and among the inner peripheral surfaces of the oil-impregnated bearing described above, the surface including the arc is porous. Therefore, dynamic pressure is likely to be generated on the inner peripheral surface (surface including the string) of the oil-impregnated bearing, and as a result, the motor performance and the motor rotation are stabilized. Can be improved.

  (6) The bearing device according to any one of (1) to (5), wherein a groove is formed in an axial direction near the center of the string on the inner peripheral surface of the oil-impregnated bearing.

  In the inner peripheral surface of the oil-impregnated bearing described above, a groove is formed in the axial direction in the vicinity of the center of the string. Therefore, depending on the depth and width of the groove, the inner peripheral surface of the oil-impregnated bearing rotates. The contact area with the shaft can be increased, and as a result, the wear resistance can be improved.

  Here, various “grooves” such as a groove whose cross-sectional shape is an arc shape and a groove whose cross-sectional shape is a step shape can be considered. Further, by forming this “groove”, it is possible to obtain the same effect as when a general step groove is formed.

  (7) In the method of manufacturing a bearing device including a sizing process for sizing the inner peripheral surface of the oil-impregnated bearing, the sizing process includes an arc whose cross-sectional shape is a part of a perfect circle and another part of the perfect circle. A method of manufacturing a bearing device, wherein a sizing core comprising a string formed by roughly cutting a string is used.

  According to the present invention, in the method for manufacturing a bearing device including a sizing process for sizing the inner peripheral surface of the oil-impregnated bearing, the sizing process includes an arc whose cross-sectional shape is a part of a perfect circle, Since a sizing core comprising a string formed by roughly cutting a part of the sizing core is used, a string (plane) formed by rough cutting of the sizing core is used to generate a portion of the inner peripheral surface of the oil-impregnated bearing. The plane (surface including the chord) part can be crushed. As a result, dynamic pressure is likely to be generated on the inner peripheral surface (surface including the strings) of the oil-impregnated bearing, and as a result, motor performance and motor rotation stability can be improved.

  (8) The method for manufacturing a bearing device according to (7), wherein the sizing core is made of a carbide tool material G2 made of cobalt and tungsten carbide.

  According to the present invention, since the sizing core is made of the G2 material made of cobalt and tungsten carbide, it becomes easy to grind a part of the sizing core linearly and axially once or a plurality of times. The motor performance and motor rotation stability can be improved easily.

  As described above, the bearing device and the manufacturing method of the bearing device according to the present invention grind a part of a formed core or sizing core having a perfect cross-sectional shape linearly and axially once or a plurality of times. Since the bearing hole of the oil-impregnated bearing is formed using the core obtained by the above, a wedge-shaped gap can be accurately formed between the rotary shaft (shaft) whose cross-sectional shape is a perfect circle, As a result, motor performance such as noise reduction and vibration prevention can be improved. In addition, it is possible to improve the stability of the motor rotation by reducing the swing of the rotating shaft, or to increase the average clearance between the rotating shaft and the oil-impregnated bearing to reduce the motor current value.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Mechanical structure of bearing device]
FIG. 1 is a cross-sectional view showing a mechanical structure of a bearing device 1 according to an embodiment of the present invention. 1A is a longitudinal sectional view of the bearing device 1 seen from the side, and FIG. 1B is a transverse sectional view of the bearing device 1 seen from above.

  In FIG. 1A, a bearing device 1 according to an embodiment of the present invention is a cylinder in which a bearing hole is formed that is fitted and held in an inner hole of a bearing holder 2 by press-fitting and rotatably supports a rotating shaft 4. The oil-impregnated bearing 3 has a shape and a thrust bearing 5 that supports the lower end surface 4 a of the rotary shaft 4.

  The oil-impregnated bearing 3 has an arc 3 a and a string 3 b that are opposed to the outer peripheral surface of the rotating shaft 4 through a bearing gap 10. That is, the cross-sectional shape of the bearing hole of the oil-impregnated bearing 3 includes an arc 3a that is a part of a perfect circle and a string 3b that is formed by cutting another part of the perfect circle in a straight line. . If it explains in full detail using FIG.1 (b), the circular arc 3a which is a part of a perfect circle will be intermittently formed in the internal peripheral surface of the oil-impregnated bearing 3 over three places. Moreover, the string 3b formed by cutting another part of the perfect circle in a straight line is intermittently formed at three places so as to be adjacent to the end of the arc 3a. The distance d (see FIG. 1B) between the center point of the string 3b and the center point of the subarc formed based on the string can be several μm to several tens μm, for example. Thereby, dynamic pressure can be generated.

  The bearing holder 2 has an opening on the upper end side and is configured to have a bottomed bag shape. A thrust bearing 5 is fixed to the inner bottom surface of the recess of the bearing holder 2. The thrust bearing 5 includes a thrust bearing surface 5 a that supports the lower end surface 4 a of the rotating shaft 4. Further, the lower end surface 4a of the rotating shaft 4 is finished into a spherical surface in order to reduce the contact resistance with the thrust bearing surface 5a when the rotating shaft 4 rotates.

  FIG. 2 is an explanatory diagram for explaining the sizing core 20 used when manufacturing the bearing device 1 according to the embodiment of the present invention. 2A is an external view of the sizing core 20 viewed from the side, and FIG. 2B is a cross-sectional view of the sizing core 20 shown in FIG. 2A viewed from the right in the drawing. is there.

  In FIG. 2A, the sizing core 20 used when manufacturing the bearing device 1 has an effective portion 21, and the sectional shape of at least the effective portion 21 is a circular arc 20a that is a part of a perfect circle. And a chord 20b formed by cutting another part of the perfect circle in a straight line. Therefore, when sizing is performed on the inner peripheral surface of the oil-impregnated bearing 3 using the sizing core 20, the cross-sectional shape of the inner peripheral surface is an arc 3a which is a part of a perfect circle, and other shapes of the perfect circle. The string 3b is formed by cutting a part in a straight line.

  FIG. 3 is a cross-sectional view showing a mechanical structure of the bearing device 1 according to the embodiment of the present invention. In particular, FIG. 3 (a) shows that the arc 3a, which is a part of a perfect circle, is intermittently formed over eight locations on the inner peripheral surface of the oil-impregnated bearing 3, and the other part of the perfect circle is linear. It is a cross-sectional view which shows a mode that the string 3b formed by cut | disconnecting is formed intermittently over eight places. FIG. 3B and FIG. 3C are an external view and a cross-sectional view of the sizing core 20 used for forming the inner peripheral surface of the oil-impregnated bearing 3 shown in FIG.

  As shown in FIGS. 3A to 3C, the bearing device 1 having a small oil-impregnated bearing 3 having an inner diameter of 1.0 mm or less by setting the number of the strings 3b to 8 (6 or more). Even so, motor performance and motor rotation stability can be improved. In addition, it is preferable that the distance d mentioned above is 5-20 micrometers at this time.

[Production method]
FIG. 4 is a flowchart for explaining a method of manufacturing the oil-impregnated bearing 3 of the bearing device 1 according to the embodiment of the present invention. FIG. 4B shows an outline of the method for manufacturing the sizing core used in step S4 in the flowchart of FIG.

  In FIG. 4A, first, raw materials are mixed (step S1). For example, a solid lubricant is mixed in a raw material powder such as iron, copper, tin, chromium, and nickel at a ratio of 0 to 2 wt%. Also, copper-plated iron powder may be used as the iron raw material powder.

  Next, molding is performed (step S2). More specifically, vertical grooves are provided on the outer peripheral surface of the oil-impregnated bearing 3 (the vertical grooves need not be provided), and the inner peripheral surface of the oil-impregnated bearing 3 is formed into a perfect circle. At this time, the density is, for example, 70% to 90% with respect to the true density. Note that several air escape grooves may be provided on the outer peripheral surface of the oil-impregnated bearing 3. Thereby, it is possible to prevent the lubricating oil from blowing out on the inner peripheral surface of the oil-impregnated bearing 3 due to heat generation.

  Next, sintering is performed at a predetermined temperature (step S3). Sintering does not require heating to a temperature until melting, and does not require strong processing, so that a degree of freedom of deformation can be ensured.

  Next, sizing is performed (step S4). More specifically, the outer diameter of the oil-impregnated bearing 3 is a perfect circle, and the inner diameter of the oil-impregnated bearing 3 is a multi-string shape (a shape composed of a plurality of arcs and a plurality of strings). Here, in order to perform sizing with a multi-string shape, a sizing core 20 having a multi-string cross-sectional shape is used. More specifically, as shown in FIG. 4 (b), in the sizing core 20 having a perfect circle shape at first, a part of the true circle is linearly and axially ground (here, three times). Thus, a rough plane (including the chord 20b) extending in the axial direction is formed. Then, at the same time, an arc 20a that is a part of a perfect circle is formed. Of the inner peripheral surface of the oil-impregnated bearing 3, the portion of the sizing core 20 that is in contact with the rough flat surface (including the chord 20b) during sizing is crushed and becomes porous (preferably less than 10%). ) The portion of the sizing core 20 that contacts the curved surface (including the arc 20a) during sizing becomes rough (preferably 10 to 20%). The sizing core 20 is preferably made of a G2 material (superhard material) made of cobalt and tungsten carbide.

  Finally, washing and oil impregnation are performed (step S5). In this way, the oil-impregnated bearing 3 of the bearing device 1 is manufactured. Then, the oil-impregnated bearing 3 is press-fitted into the inner hole of the bearing holder 2, and the rotating shaft 4 is inserted into the bearing hole of the oil-impregnated bearing 3, whereby the bearing device 1 is completed. According to the bearing device 1 thus completed, a wedge-shaped gap is formed between the inner peripheral surface of the oil-impregnated bearing 3 and the rotary shaft 4 (shaft). An oil film is easily formed on the surface, and as a result, motor performance such as noise reduction and vibration prevention can be improved.

[Modification]
FIG. 5 is a cross-sectional view showing the mechanical structure of the oil-impregnated bearing 3 included in the bearing device 1 according to another embodiment of the present invention.

  In FIG. 5, the oil-impregnated bearing 3 included in the bearing device 1 according to another embodiment of the present invention has an arc 3a and a string 3b formed on the inner peripheral surface thereof, and in the vicinity of the center of the string 3b, A groove 3c is formed in the axial direction. Thus, by forming, for example, an arc-shaped and axial groove 3c near the center of the string 3b, the contact area between the inner peripheral surface of the oil-impregnated bearing 3 and the rotary shaft 4 can be increased, and thus wear resistance is increased. Can be improved.

  Here, when manufacturing the oil-impregnated bearing 3 shown in FIG. 5, the sizing process of step S4 should just be divided into two steps in the flowchart of FIG. That is, in the first sizing process, sizing as described above is performed (see step S4). In the second sizing step, sizing is performed with a perfect circular sizing core having a diameter slightly smaller than the arc 3a and slightly larger than a circle inscribed in the chord 3b. In this way, the oil-impregnated bearing 3 having the groove 3c shown in FIG. 5 is manufactured. In the second sizing, 100% plastic deformation does not occur, and a slight spring back occurs. More specifically, the spring back is large near the center of the string 3b, and the spring back is small near both ends. Therefore, the shape after the second sizing is not a concentric circle, and a groove 3c having a large R is formed.

  In the oil-impregnated bearing 3 shown in FIG. 5, the sizing process is divided into two stages for the purpose of improving the wear resistance. A multi-string bearing can also be adopted. The inner diameter of the perfect circle part of this partially perfected multi-string bearing is the same diameter as the inscribed circle of the multi-string bearing (oil-impregnated bearing 3), and the length of the perfect circle part is about 10 to 20% of the total length.

  FIG. 6 is a perspective sectional view for explaining the mechanical structure of the bearing device 1 according to the embodiment of the present invention. In addition, FIG. 6 shows an application, for example, for a fan motor.

  In FIG. 6, the bearing device 1 according to the embodiment of the present invention has a total of eight strings 3b on the inner peripheral surface of the oil-impregnated bearing 3, and the center point of each string and the inferiority formed based on the string. The distance (= d) from the center point of the arc is 0.01 mm.

On the other hand, the inner diameter dimension (= x ₁ ) of the oil-impregnated bearing 3 is 0.8 mm, its outer dimension (= x ₂ ) is 1.7 mm, and its length (= x ₃ ) is 1.9 mm. The radial clearance between the rotating shaft 4 and the oil-impregnated bearing 3 is 1 to 2 μm. The surface including the arc 3a has a porous area ratio of 10 to 20%, and the surface including the chord 3b has a porous area ratio of less than 2 to 10%. The material of the oil-impregnated bearing 3 is iron-copper-tin type (Fe 48%, Cu-Sn 52%, 40% copper-plated iron powder 80% used). The bearing gap 10 is filled with a synthetic hydrocarbon oil having a viscosity of VG32 as a lubricating fluid. Furthermore, the oil content is 18-23%.

  According to the bearing device 1 shown in FIG. 6, it is possible to manufacture a suitable small bearing device 1 used for a fan motor or the like, and in particular, between the inner peripheral surface of the oil-impregnated bearing 3 and the rotary shaft 4. Since the wedge-shaped gap can be formed with high accuracy, an oil film is easily formed on the inner peripheral surface of the oil-impregnated bearing 3, and motor performance such as noise reduction and vibration prevention can be improved. In addition, the swing of the rotating shaft 4 is reduced, and the stability of motor rotation can be improved. Furthermore, the average clearance between the rotating shaft 4 and the oil-impregnated bearing 3 was increased to reduce the motor current value, and the clearance was decreased to reduce the swing of the rotating shaft 4.

  INDUSTRIAL APPLICABILITY The bearing device and the method for manufacturing the bearing device according to the present invention are useful as those capable of improving motor performance by creating a wedge-shaped gap between the inner peripheral surface of the oil-impregnated bearing and the rotating shaft. .

It is sectional drawing which shows the mechanical structure of the bearing apparatus which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the sizing core used when manufacturing the bearing apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the mechanical structure of the bearing apparatus which concerns on embodiment of this invention. It is a flowchart for demonstrating the manufacturing method of the oil-impregnated bearing of the bearing apparatus which concerns on embodiment of this invention. It is a cross-sectional view which shows the mechanical structure of the oil-impregnated bearing 3 which the bearing apparatus which concerns on other embodiment of this invention has. It is a perspective sectional view for explaining the mechanical structure of the bearing device concerning the example of the present invention. It is a cross-sectional view which shows the mechanical structure of the conventional step dynamic pressure bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing apparatus 2 Bearing holder 3 Oil impregnated bearing 3a Circular arc 3b String 3c Groove 4 Rotating shaft 4a Lower end surface 5 Thrust bearing 5a Thrust bearing surface 10 Bearing clearance 20 Sizing core

Claims (8)

In a bearing device having an oil-impregnated bearing in which a bearing hole for rotatably supporting a rotating shaft is formed,
The bearing device is characterized in that a cross-sectional shape of the bearing hole includes an arc that is a part of a perfect circle and a string that is formed by cutting another part of the perfect circle in a straight line.   The bearing device according to claim 1, wherein an inner diameter of the oil-impregnated bearing is 1.5 mm or less. The cross-sectional shape of the bearing hole includes at least three strings.
The bearing device according to claim 1, wherein a distance between a center point of the string and a center point of a subarc formed based on the string is several μm to several tens μm. The oil-impregnated bearing has an inner diameter of 1.0 mm or less, and a cross-sectional shape of the bearing hole includes at least six strings.
The bearing device according to any one of claims 1 to 3, wherein a distance between a center point of the string and a center point of a subarc formed based on the string is 5 to 20 µm. Of the inner peripheral surface of the oil-impregnated bearing, the surface including the string is formed such that the porosity is less than 10% by area ratio,
The bearing according to any one of claims 1 to 4, wherein the surface including the circular arc among the inner peripheral surfaces of the oil-impregnated bearing is formed so that the porosity is 10 to 20% in terms of area ratio. apparatus.   6. The bearing device according to claim 1, wherein a groove is formed in the axial direction near the center of the string on the inner peripheral surface of the oil-impregnated bearing. In a manufacturing method of a bearing device including a sizing step of sizing the inner peripheral surface of an oil-impregnated bearing
The bearing is characterized in that the sizing step uses a sizing core whose cross-sectional shape is composed of an arc that is a part of a perfect circle and a string that is formed by roughly cutting another part of the perfect circle. Device manufacturing method. 8. The method for manufacturing a bearing device according to claim 7, wherein the sizing core is made of a G2 material made of cobalt and tungsten carbide.

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