JP2003314537A - Bearing unit, motor therewith, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing unit, a motor with the same, and an electronic device in which a manufacturing cost is reduced by obtaining a shaft at a low cost. <P>SOLUTION: The bearing unit is provided with a circular supporting portion 130 in section, and a step portion 134 which is integrally mounted on the supporting portion 130, having a circular shape in section and the diameter larger than the diameter of the supporting portion 130. The bearing unit comprises a shaft 60 having a T-shape in section to an axial direction, a radial fluid dynamic bearing 114 rotatably supporting the supporting portion 130 of the shaft 60 to a radial direction, a thrust fluid dynamic bearing 124 rotatably supporting the step portion of the shaft 60 to a thrust direction, and a housing 116 housing and retaining the shaft 60, the radial fluid dynamic bearing 114, and the thrust fluid dynamic bearing 124. The step portion 134 is made of resin. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a bearing unit,
The present invention relates to a motor having a bearing unit and an electronic device.

[0002]

2. Description of the Related Art As an example of electronic equipment using a motor,
There is an information recording / reproducing apparatus, and of these, for example, a hard disk drive has expanded its use, and in addition to a large-sized recording apparatus and a recording apparatus for a personal computer of a desktop type, for example, a notebook type personal computer and a smaller device. It has come to be used for electronic devices such as portable terminal devices of a size. Recently, PC (P
P that has the size of an IC (Integrated Circuit) memory card called a personal computer (card) size or a card-type modem
A C card type hard disk drive is used for this PC
The card-type hard disk device is used by a user by inserting and removing the card-type hard disk device into and from a PC card slot of a notebook personal computer or a portable terminal.

FIG. 12 shows a sectional structure of a hydrodynamic bearing unit for a motor used in a conventional hard disk drive device. The hydrodynamic bearing unit 1060 has a T-shaped step-shaped shaft 1061, a bearing 1062, and a thrust receiver 1063. The bearing 1062 has a pair of herringbones 1062a and 1062a for rotatably supporting the support portion 1068 of the shaft 1061 in the radial direction, and a herringbone for rotatably supporting the step portion 1069 of the shaft 1061 in the thrust direction. 1062b is provided. The thrust receiver 1063 has a step portion 1069 of the shaft 1061.
A herringbone 1063a for supporting the rotatably in the thrust direction is provided.

A metal annular housing 1064 accommodates a bearing 1062 and a shaft 1061 therein, and a thrust receiver 1063 is fitted in an end portion of the housing 1064. The support portion 1068 and the step portion 1069 of the shaft 1061 are integrally formed of a metal such as stainless steel, and have a T-shaped cross section when viewed in the axial direction.

[0005]

The conventional hydrodynamic bearing unit 1060 described above has the following problems.
This dynamic pressure fluid bearing unit 1060 has a bearing 1062 and a thrust bearing 1063 in order to obtain high rotation accuracy.
It is necessary to control the amount of void between the shaft 1061 and the shaft 1061 to be several μm. In the conventional hydrodynamic bearing unit 1060, the shaft 1061 is made by polishing stainless steel as described above in order to obtain accuracy and surface roughness as described above. Usually, the shaft has a straight shape with an I-shaped cross section, and normally, the shaft can be subjected to centerless polishing, so that the shaft can be manufactured at low cost. However, since the conventional shaft 1061 shown in FIG. 12 has a T-shaped cross section, centerless polishing cannot be performed. Therefore, the accuracy and surface roughness of the shaft 1061 must be ensured by normal polishing. The processing cost becomes expensive. As a result, the conventional hydrodynamic bearing unit 1060 has the drawback of being expensive. Further, since the shaft 1061 is made of metal such as stainless steel, it is difficult to provide a dynamic pressure generating groove such as a herringbone groove on the shaft side, and the dynamic pressure generating groove in the thrust direction is the rotating shaft. It is provided not on the side, but on the bearing 1062 side and the thrust receiver 1063 side which are made of sintered metal, resin, or brass having the lowest hardness among metals.
As a result, the bearing 1062 and the thrust receiver 1063 are also expensive. It is therefore an object of the present invention to solve the above problems and provide a bearing unit, a motor having the bearing unit, and an electronic device that can be made inexpensive by obtaining an inexpensive shaft.

[0006]

According to a first aspect of the present invention, there is provided a support portion having a circular cross section, and a circular cross section which is integrally attached to the support portion and has a circular cross section. A shaft having a step portion having a large outer diameter dimension and having a T-shape when viewed in a cross section in the axial direction; a radial dynamic pressure fluid bearing for rotatably supporting the supporting portion of the shaft in the radial direction; A thrust direction dynamic pressure fluid bearing that rotatably supports the step portion of the shaft in the thrust direction; a housing that houses and holds the shaft, the radial direction dynamic pressure fluid bearing, and the thrust direction dynamic pressure fluid bearing. The step portion is a bearing unit made of resin.

According to the first aspect of the present invention, the shaft having a T-shape when viewed in cross section in the axial direction has a support portion and a step portion. The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. The step portion of this shaft is made of resin. Therefore, the supporting portion of the shaft and the step portion can be formed as separate members, and the supporting portion of the shaft can be formed by the centerless polishing process, and the step portion can be easily and easily formed by outsert molding resin on the supporting portion. A shaft having a T-shaped cross section (also referred to as a rotary shaft) can be obtained at low cost.
Therefore, the bearing unit can be manufactured at low cost.

According to a second aspect of the present invention, in the bearing unit according to the first aspect, the step portion has a dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing.

According to the second aspect of the present invention, the dynamic pressure generating groove can be easily formed in the step portion made of resin, as compared with the metallic one, which is inexpensive.

According to a third aspect of the present invention, in the bearing unit according to the first aspect, the step portion has a first dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing, and A second dynamic pressure generating groove is provided on the second surface opposite to the first surface.

According to a third aspect of the present invention, when the first dynamic pressure generating groove is formed on the first surface of the step portion made of resin and the second dynamic pressure generating groove is formed on the second surface of the step portion, as described above. In addition, since the step portion is made of resin as compared with the metal one, the first dynamic pressure generating groove and the second dynamic pressure generating groove can be formed easily and inexpensively.

According to a fourth aspect of the present invention, in the bearing unit according to the third aspect, the groove width of the first dynamic pressure generating groove is different from the groove width of the second dynamic pressure generating groove.

According to a fifth aspect of the present invention, in the bearing unit according to the third aspect, the number of the first dynamic pressure generating grooves is different from the number of the second dynamic pressure generating grooves.

According to a sixth aspect of the present invention, in the bearing unit according to the first aspect, the resin is a liquid crystal polymer.

According to a seventh aspect of the present invention, a support portion having a circular cross section and a circular cross section which is integrally attached to the support portion and has an outer diameter dimension larger than an outer diameter dimension of the support portion. A shaft having a step portion and having a T-shape when viewed in a cross section in the axial direction; a radial dynamic fluid bearing for rotatably supporting the supporting portion of the shaft in a radial direction; and the step portion of the shaft. A thrust direction dynamic pressure fluid bearing that is rotatably supported in the thrust direction; a housing that houses and holds the shaft, the radial direction dynamic pressure fluid bearing, and the thrust direction dynamic pressure fluid bearing;
And the step portion is made of a sintered metal.

According to a seventh aspect, the shaft having a T-shape when viewed in a cross section in the axial direction has a support portion and a step portion. The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. This step portion is made of sintered metal. As a result, the shaft supporting portion and the step portion can be formed as separate members, and the shaft supporting portion can be processed by centerless polishing, and the step portion of the sintered metal is provided on the support portion by, for example, outsert molding. be able to.
As a result, a shaft having a T-shaped cross section can be easily manufactured at low cost. This makes the bearing unit cheaper.

According to an eighth aspect of the present invention, in the bearing unit according to the seventh aspect, the step portion has a dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing.

In the eighth aspect, the dynamic pressure generating groove can be formed easily and inexpensively in the step portion made of sintered metal.

According to a ninth aspect of the present invention, in the bearing unit according to the seventh aspect, the step portion has a first dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing, and The second surface on the side opposite to the first surface has a second dynamic pressure generating groove.

In the ninth aspect, the first dynamic pressure generating groove is formed on the first surface of the step portion made of sintered metal, and the second dynamic pressure generating groove is formed on the second surface of the step portion. But the first
The dynamic pressure generating groove and the second dynamic pressure generating groove can be formed easily and inexpensively.

According to a tenth aspect of the invention, in the bearing unit according to the ninth aspect, the groove width of the first dynamic pressure generating groove is
It is different from the groove width of the second dynamic pressure generating groove.

According to an eleventh aspect of the present invention, in the bearing unit according to the ninth aspect, the number of the first dynamic pressure generating grooves is different from the number of the second dynamic pressure generating grooves.

According to a twelfth aspect of the present invention, there is provided a motor having a bearing unit for rotatably supporting the rotor with respect to the stator, wherein the bearing unit is integrally attached to the supporting portion having a circular cross section and the supporting portion. And a step portion having a circular cross section and having an outer diameter dimension larger than the outer diameter dimension of the support portion, and when viewed in a cross section in the axial direction, T
A shaft having a V-shape, a radial dynamic pressure fluid bearing for rotatably supporting the supporting portion of the shaft in the radial direction, and a thrust dynamic fluid for rotatably supporting the step portion of the shaft in the thrust direction Bearings,
A motor having a bearing unit, comprising: the shaft, the radial direction dynamic pressure fluid bearing, and a housing for accommodating and holding the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of resin. .

According to a twelfth aspect, the shaft having a T-shape when viewed in a cross section in the axial direction has a support portion and a step portion.
The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. The step portion of this shaft is made of resin. Therefore, the supporting portion of the shaft and the step portion can be formed as separate members, the supporting portion of the shaft can be formed by centerless polishing, and the step portion can be formed by, for example, outsert molding a resin on the supporting portion. A shaft having a T-shaped cross section (also referred to as a rotary shaft) can be obtained easily and inexpensively. Therefore, the motor having the bearing unit can be manufactured at low cost.

According to a thirteenth aspect of the present invention, there is provided an electronic device including a motor having a bearing unit for rotatably supporting the rotor with respect to the stator, wherein the bearing unit has a support portion having a circular cross section and the support portion. A shaft that is integrally attached and has a circular cross section, has a step portion that has an outer diameter dimension larger than the outer diameter dimension of the support portion, and that has a T-shape when viewed in a cross section in the axial direction; A radial direction hydrodynamic fluid bearing that rotatably supports the supporting portion of the shaft in a radial direction, a thrust direction hydrodynamic fluid bearing that rotatably supports the step portion of the shaft in a thrust direction, the shaft and the radial direction A dynamic pressure fluid bearing and a housing for accommodating and holding the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of resin. It is an electronic device that.

In the thirteenth aspect, the shaft having a T-shape when viewed in a cross section in the axial direction has a support portion and a step portion.
The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. The step portion of this shaft is made of resin. Therefore, the supporting portion of the shaft can be formed by centerless polishing, and the step portion can be easily and inexpensively formed by outsert molding a resin on the supporting portion, which is a T-shaped section (also referred to as a rotary shaft). ) Can be obtained. Therefore, it is possible to inexpensively manufacture an electronic device including a motor having a bearing unit.

According to a fourteenth aspect of the present invention, there is provided a motor having a bearing unit for rotatably supporting the rotor with respect to the stator, wherein the bearing unit is integrally attached to the support portion having a circular cross section and the support portion. And a step portion having a circular cross section and having an outer diameter dimension larger than the outer diameter dimension of the support portion, and when viewed in a cross section in the axial direction, T
A shaft having a V-shape, a radial dynamic pressure fluid bearing for rotatably supporting the supporting portion of the shaft in the radial direction, and a thrust dynamic fluid for rotatably supporting the step portion of the shaft in the thrust direction Bearings,
A motor having a bearing unit, comprising: the shaft; the radial direction dynamic pressure fluid bearing; and a housing for accommodating and holding the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of sintered metal. Is.

In the fourteenth aspect, the shaft having a T-shape when viewed in a cross section in the axial direction has a supporting portion and a step portion.
The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. This step portion is made of sintered metal. As a result, the shaft supporting portion and the step portion can be formed as separate members, and the shaft supporting portion can be processed by centerless polishing, and the step portion of the sintered metal is provided on the support portion by, for example, outsert molding. be able to.
As a result, a shaft having a T-shaped cross section can be easily manufactured at low cost. For this reason, the motor having the bearing unit becomes inexpensive.

According to a fifteenth aspect of the present invention, there is provided an electronic apparatus including a motor having a bearing unit for rotatably supporting the rotor with respect to the stator, wherein the bearing unit has a support portion having a circular cross section and the support portion. A shaft that is integrally attached and has a circular cross section, has a step portion that has an outer diameter dimension larger than the outer diameter dimension of the support portion, and that has a T-shape when viewed in a cross section in the axial direction; A radial direction hydrodynamic fluid bearing that rotatably supports the supporting portion of the shaft in a radial direction, a thrust direction hydrodynamic fluid bearing that rotatably supports the step portion of the shaft in a thrust direction, the shaft and the radial direction A dynamic pressure fluid bearing and a housing for accommodating and holding the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of sintered metal. Is an electronic device to be butterflies.

According to a fifteenth aspect, the shaft having a T-shape when viewed in a cross section in the axial direction has a support portion and a step portion.
The support portion has a circular cross section. The step portion is integrally attached to the support portion, has a circular cross section, and has an outer diameter dimension larger than the outer diameter dimension of the support portion. The radial hydrodynamic bearing supports a support portion of the shaft so as to be rotatable in the radial direction. The thrust direction dynamic pressure fluid bearing rotatably supports the step portion of the shaft in the thrust direction. The housing accommodates and holds a shaft, a radial dynamic fluid bearing and a thrust dynamic fluid bearing. This step portion is made of sintered metal. As a result, the shaft supporting portion and the step portion can be formed as separate members, and the shaft supporting portion can be processed by centerless polishing, and the step portion of the sintered metal is provided on the support portion by, for example, outsert molding. be able to.
As a result, a shaft having a T-shaped cross section can be easily manufactured at low cost. This makes the electronic device cheaper.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiment described below is a preferred specific example of the present invention,
Although various technically preferable limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the description below.

FIG. 1 is a plan view showing an information recording / reproducing apparatus equipped with a motor having a bearing unit of the present invention.
This information recording / reproducing apparatus is a kind of equipment, and is mounted in electronic equipment such as a computer. 2 and 3 are exploded perspective views of the information recording / reproducing apparatus of FIG. FIG. 4 is an example of a sectional structure of the spindle motor of FIG. 1 to 4
The information recording / reproducing apparatus shown in is a hard disk drive apparatus as an example. The hard disk drive device 1 has a function of magnetically recording information on the disk-shaped recording medium D or magnetically reproducing information already recorded on the disk-shaped recording medium D.
The hard disk drive device 1 is used by being mounted in a PC card slot of a so-called notebook personal computer which is an example of an electronic device,
It is a very small and thin device.

As shown in FIGS. 2 and 3, the hard disk drive device 1 includes a housing (also called an outer housing) 2,
It has a disk-shaped recording medium D, a spindle motor 3, a rotary actuator 4, and the like. The housing 2 has a first member (also called an upper housing) 10 and a second member (also called a lower housing) 12. The space 11 between the first member 10 and the second member 12 accommodates the spindle motor 3, the disk-shaped recording medium D, the rotary actuator 4, and the like. The disc-shaped recording medium D is fixed to the rotor R side of the spindle motor 3 as shown in FIG.
Causes the disc-shaped recording medium D to rotate continuously.

As shown in FIG. 3, the two rotary actuators 4 include a suspension 20, a voice coil 22,
It has two magnetic heads 24 and the like. An electromagnetic force generated between the voice coil 22 shown in FIG. 3 and the magnets 29 and 30 shown in FIG. 3 allows the magnetic head 24 of the rotary actuator 4 to swing in the F direction shown in FIGS. 1 and 2. Information signals can be recorded or already recorded information can be reproduced by positioning the magnetic heads 24, 24 with respect to an arbitrary track of the rotating disk-shaped recording medium D. As the magnetic head 24, for example, GMR (Giant Magnetoresistive Effect Element) or the like can be adopted.

The hard disk device 1 shown in FIG. 1 shows a state in which the first member 10 of the housing 2 shown in FIG. 4 is removed from the second member 12, and the internal disk-shaped recording medium D and the rotary type. The actuator 4 and the like are exposed. A connection terminal 35 for electrically connecting to a computer or the like is provided at the end of the second member 12. The circuit board 37 includes a system LSI (Large Scale Integrated Circuit) 39 and I
General electronic parts such as C (integrated circuit) are arranged.

Next, the structure of the motor 3 shown in FIG. 4 will be described. The motor 3 is a spindle motor and has a rotor R and a stator S. First, the structure of the rotor R of the motor 3 will be described. The rotor R is roughly composed of a turntable 50, a chuck 52, a driving magnet 58 and a shaft (also called a rotor shaft) 60.
have. The shaft 60 has a T-shaped cross section in the axial direction. The turntable 50 is also called a rotor housing and is made of, for example, iron. A hole 51 is formed in the center of the rotor housing,
The mounting portion 61 of the support portion 61 of the shaft 60 is fixed to the hole 51 by press fitting.

The turntable 50 is integrally attached to the shaft 60 as described above, and is a disk-shaped recording medium D (also referred to as a hard disk) which is an object to be rotated.
Are held by using the chuck 52. That is, the inner peripheral portion 63 of the disc-shaped recording medium D is the turntable 50.
On the flange portion 53, and the chuck 52 fixes the inner peripheral portion 63 to the flange portion 53 side. The chuck 52 is a ring-shaped member made of, for example, stainless steel.

The magnet 58 shown in FIG. 4 is a ring-shaped magnet having S and N poles alternately magnetized. For this magnet 58, for example, a neodymium sintered body can be used. The magnet 58 is fixed to the inner peripheral surface of the turntable 50.

With the disc-shaped recording medium D of FIG. 4 mounted on the rotor R, the rotary actuator 4 of FIG. 1 swings to cause the magnetic heads 24, 24 of the suspensions 20, 20 to perform disc-shaped recording. It is possible to record information or reproduce information without contacting one surface and the other surface of the medium D. However, not limited to this,
The magnetic head 24 may be of a type in which information is recorded or reproduced while contacting one surface and the other surface of the disk-shaped recording medium D, respectively.

Next, the structure of the stator S shown in FIG. 4 will be described. The stator S is roughly composed of a housing 80, a bearing unit 110, a driving coil 88, an iron core 89,
It has a flexible printed circuit board (not shown). Housing (also called stator housing) 80
Is made of, for example, stainless steel, and the flexible printed circuit board is fixed to the housing 80 by adhesion. Flexible printed circuit board is coil 8
8 is electrically connected. The U-phase terminal, the V-phase terminal, the W-phase terminal, and the common terminal of the coil 88 are drawn out of the housing 80 via the flexible printed circuit board, and the flexible printed circuit board is supplied with electricity through the connector. Electrically connected to.

The coils 88 are wound around the iron core 89. The coil 88 and the iron core 89 have, for example, 9 poles. On the other hand, in the magnet 58, S poles and N poles are alternately formed along the circumferential direction of, for example, 12 poles. When the coil 88 is energized by the energization control unit 100 in a predetermined energization pattern, the rotor R rotates with respect to the stator S about the shaft 60 due to the interaction between the magnetic field generated by the coil 88 and the magnetic field generated by the magnet 58. It is capable of continuous rotation. The housing 80 has a cylindrical portion 121. The outer peripheral surface of the housing 116 of the bearing unit 110 is fixed to the inner peripheral surface of the cylindrical portion 121 by, for example, press fitting. FIG. 5 shows this bearing unit 110.
It is sectional drawing which shows only.

As shown in FIGS. 4 and 5, the bearing unit 110 has a shaft 60, a bearing 114, a resin housing 116, and a thrust receiver 124. First, the shape of the shaft 60 will be described. The shaft 60 has a supporting portion 1
It has 30 and a step part 134. This axis 60
It has a T-shape when viewed in cross section or in appearance in the axial direction.

The support portion 130 of the shaft 60 is a so-called straight columnar portion. The support portion 130 has a mounting portion 61 at one tip and an inner end portion 131 at the other tip. The inner end portion 131 has a mounting groove 132 having a V-shaped cross section for securely mounting the step portion 134. This straight-shaped support portion 130 is also called a straight-shaped shaft portion, and this support portion 130 is
Made of metal or resin. Since the straight support portion 130 has a straight shape,
By the conventional centerless polishing process, whether it is made of metal or resin, it can be easily processed to ensure sufficient accuracy and surface roughness.

The outer diameter of the step portion 134 is set to be considerably larger than the outer diameter of the support portion 130. As described above, the support portion 130 can be formed easily and inexpensively by, for example, so-called centerless polishing, while the step portion 134 has the inner end portion 13 of the support portion 130.
1, a resin, a sintered metal, or a metal is integrally formed by outsert molding. As a result, the support portion 130 and the step portion 134 are rotating shafts having a T-shaped cross section when viewed in the axial direction, and such a shaft 60 having a T-shaped cross section can be easily and inexpensively manufactured.

That is, conventionally, such a shaft having a T-shaped cross section is made of, for example, stainless steel and cannot be manufactured by the centerless polishing process, resulting in an increase in cost. However, in the shaft 60 according to the embodiment of the present invention, the straight support portion 130 and the disc-shaped step portion 13 are provided.
4 is formed as a separate member, and the step portion 134 is formed on the inner end portion 131 of the formed support portion 130 by, for example, outsert molding, using resin, metal, or sintered metal. Can be lowered. In addition, when the step portion 134 is outsert-molded with respect to the inner end portion 131, a part of the step portion 134 bites into the mounting groove of the inner end portion 131 and is molded. The inner end 131 can be integrally attached so as not to come off reliably.

When the step portion 134 is made of resin,
Nylon or liquid crystal polymer can be used as the material of this resin, but it is a resin that has high accuracy, good environmental resistance, no outgas generation, and no chemical attack with lubricating oil. If so, various resins can be used. Since the kind of resin having such characteristics is used, the bearing unit 110 has high reliability. Also, the step portion 134
As shown in FIG. 5, the outer diameter dimension of the
The step portion 134 also serves as a slip-out prevention portion for preventing the shaft 60 from slipping out in the G direction, because the step portion 134 is set to have a larger outer diameter.

Next, a hydrodynamic bearing structure for rotatably supporting the shaft 60 will be described. The bearing 114 shown in FIGS. 4 and 5 is a radial dynamic pressure fluid bearing that rotatably supports the support portion 130 of the shaft 60 in the radial direction. Thrust receiver 1 shown in FIGS. 4 and 5.
Reference numeral 24 is a thrust direction dynamic pressure fluid bearing that rotatably supports the step portion 134 in the thrust direction. First, the bearing 114, which is a radial dynamic fluid bearing, will be described. The bearing 114 is a cylindrical bearing.
On the inner peripheral surface of the bearing 114, a pair of dynamic pressure generating grooves 117,
117 is formed. The dynamic pressure generating grooves 117, 11
For 7, a herringbone groove can be adopted, for example. A slight gap is formed between the inner peripheral surface of the bearing 114 and the outer peripheral surface of the supporting portion. As the support portion 130 of the shaft 60 rotates, the dynamic pressure generating groove 117, between the outer peripheral surface of the support portion 130 and the inner peripheral surface of the bearing 114,
117 can generate a dynamic pressure by the lubricating oil, whereby the support portion 130 is supported by the bearing 114 so as to be rotatable in the radial direction. This dynamic pressure generating groove 117,
Reference numeral 117 is also referred to as a third dynamic pressure generating groove. The bearing 114 is made of metal, sintered metal, or resin, and the dynamic pressure generating grooves 117, 117 on the inner peripheral surface of the bearing 114 may be formed by rolling, pressing or the like. The outer peripheral surface of the bearing 114 is securely held by the inner peripheral surface 116A of the housing 116.

Next, the thrust bearing 124, which serves as a hydrodynamic bearing in the thrust direction, is mounted on the inner peripheral surface 1 of the housing 116.
It is securely fixed by 16B. The thrust receiver 124 is, for example, a disk-shaped member, and is made of metal, sintered metal,
Or it is made of resin. Thrust receiver 124
The outer diameter dimension of is set to be slightly larger than the outer diameter dimension of the step portion 134. The step portion 134 is rotatable in the accommodation space 116C of the housing 116. The thrust receiver 124 supports the first surface 134A side of the step portion 134 so as to be rotatable in the thrust direction.

FIG. 6 shows an example of the shape of the shaft 60 shown in FIG. The first surface 134A of the step portion 134 of the shaft 60 shown in FIGS. 6B and 6C is in close contact with the upper surface of the thrust receiver 124 as shown in FIG. Figure 6
Second surface 1 of step portion 134 shown in FIGS. 6A and 6B.
34B faces the inner end surface 114E of the bearing 114 as shown in FIG. As shown in FIG. 6C, a plurality of points, for example, six V-shaped herringbone grooves 139 are formed in the first surface 134A along the circumferential direction. Similarly, as shown in FIG. 6A, the second surface 134B
Also, a plurality of points, for example, six V-shaped herringbone grooves 141 are formed.

As the shaft 60 shown in FIG. 5 continuously rotates around the central axis CL, the herringbone groove 139 of FIG. 6C generates dynamic pressure of the lubricating oil against the thrust receiver 124 and the step portion. 134 is rotatably supported in the thrust direction. Similarly, the herringbone groove 141 of FIG. 6 (A) generates dynamic pressure against the inner end surface 114E of the bearing 114 shown in FIG. 5, and also supports the step portion 134 rotatably in the thrust direction.

Since the step portion 134 shown in FIG. 6 is formed by outsert molding using, for example, resin or sintered metal as described above, the first surface 134A and the second surface 134 are formed.
Dynamic pressure generating grooves 139 and 141 such as herringbone grooves can be easily formed in B, respectively, and the shaft 60 can be manufactured at a significantly lower cost than in the conventional case.

The housing 116 shown in FIGS. 4 and 5 is made of resin. As the material of the housing, for example, polyimide, polyamide, polyacetal, fluororesin, liquid crystal polymer or the like can be used. In this way, the entire housing 116 is made of resin, and the housing 116 in FIG. 5 is provided with only the hole 137. The hole 137 is formed in the support portion 130 of the shaft 60.
It is a gap between and. Lubricating oil is filled in a gap between the bearing 114, the support portion 130 of the shaft 60, the step portion 134, and the thrust receiver 124 in the housing 116.

Since the housing 116 is entirely made of resin, it is possible to increase the contact angle with respect to the lubricating oil filled inside, and it is not necessary to apply a surfactant to the sealing member as in the conventional case. However, it is possible to prevent the lubricating oil from leaking to the outside through the gap or scattering, and unlike the conventional case, it is not necessary to separately provide a seal member, so that the fastening portion can be eliminated and the number of parts can be reduced and the cost can be reduced. Such a housing 116 can be molded so as to cover the bearing 114, the shaft 60, and the thrust receiver 124 by, for example, outsert molding. The housing 116 has, for example, a basket shape, and by outsert-molding the housing 116 in this way, an assembly process is not necessary and the cost is low. As in the conventional case, there is no fastening portion for the parts, and the housing has a seamless structure. Therefore, the lubricating oil does not leak or scatter to the outside and has excellent reliability.

Next, another embodiment of the bearing unit 110 of the present invention will be described with reference to FIGS. 7 and 8.
The bearing unit 110 shown in FIG. 7 and FIG.
7 is substantially similar to the bearing unit 110 shown in FIG. 7 except that the bearing unit 110 of FIGS. 7 and 8 is different.
The thrust receiver 124 as shown in FIG.
6 is not built in. Instead, see FIG.
As shown in FIG. 8, a part of the housing 116 functions as the thrust receiver 224. Thrust receiver 22
Reference numeral 4 denotes a part of the housing 116, and the accommodation space 11
It is a part forming 6C. Thrust receiver 224
Is a thrust direction hydrodynamic bearing, and the thrust receiver 224 faces the first surface 134A of the step portion 134. The second surface 134B of the step portion 134 faces the inner surface 116D of the housing 116.

The bearing 114 is surrounded by a housing 116, and the bearing 114 is positioned and fixed along the central axis CL so as to be surrounded by the housing 116. Therefore, the bearing 114 and the step portion 134 are partitioned by the intermediate partition portion 116F of the housing 116. As described above, by omitting the member of the thrust receiver 124 as shown in FIG. 5 and allowing a part of the housing 116 to play the role of the thrust receiver, the number of parts of the bearing unit 110 is reduced and the price of the bearing unit is reduced. Can be lowered.

The parts of the bearing unit 110 shown in FIGS. 7 and 8 which are the same as the corresponding parts of the bearing unit 110 shown in FIGS. 4 and 5 are designated by the same reference numerals and their description is omitted. I am using. In the bearing unit 110 of each embodiment shown in FIGS. 4 and 5 and FIGS. 7 and 8, the step portion 134 is made of resin, sintered metal, or metal, and the first surface 134A of the step portion 134 is formed. Herringbone grooves as dynamic pressure generating grooves are formed on the second surface 134B and the second surface 134B, respectively. Therefore, it is not necessary to provide a dynamic pressure generating groove for generating a dynamic pressure in the thrust direction, for example, on the inner end surface 114E of the bearing 114 shown in FIG. 5 or on the upper surface of the thrust receiver 124. The first and second dynamic pressure generating grooves provided in the step portion 134 form the step portion 134 with respect to the inner end portion 131 of the support portion 130 of the shaft 60 at the same time as outsert molding.
It can be easily formed on the first surface 134A and the second surface 134B of the step portion 134. From the above,
The price of the bearing unit having the dynamic pressure generating groove in the thrust direction can be remarkably reduced.

The depth of the dynamic pressure generating groove of the step portion 134 is
For example, since it is usually about 2 to 5 μm and several μm, even in the bearing unit 110 as a hydrodynamic bearing, the viscosity of the resin is low at the time of molding and a complicated shape can be formed. As a material, it is particularly preferable to use a liquid crystal polymer. Further, in the bearing unit 110 of FIG. 5, it is not necessary to provide a dynamic pressure generating groove on the inner end surface 114E of the bearing 114. In the bearing unit 110 of FIG. 8, it is not necessary to provide the dynamic pressure generating groove on the inner surface 116D of the housing 116. As a result, in FIG. 8, the outer diameter of the bearing 114 can be reduced, which is advantageous in that the material cost can be reduced, and the degree of freedom in the shape of the bearing 114 can be increased.

FIG. 9 shows the bearing unit 110 of FIG. 8 as an example. In FIG. 9, the weight applied to the shaft 60 of the bearing unit 110 is shown. The weight R of the rotor R and the disk-shaped recording medium in FIG. 7 is applied to the shaft 60 along the central axis CL as shown by the arrow. On the other hand, the first dynamic pressure generating groove 139 of the first surface 134A of the step portion 134 generates a dynamic pressure when rotating with respect to the thrust receiver 224, so that the dynamic pressure D1 is generated in the same direction as the weight W direction. To do. At the same time, the second surface 13 of the step portion 134
The second dynamic pressure generating groove 141 of 4B generates a dynamic pressure D2 when rotating with respect to the inner surface 116D of the housing 116. The direction of the dynamic pressure D2 is opposite to the direction of the dynamic pressure D1 and the weight W.

FIG. 10 shows another embodiment of the bearing unit 110 of the embodiment shown in FIGS. 4 and 5 and the shaft 60 applicable to the bearing unit 110 of FIGS. 7 and 8. FIG. 11 similarly shows the bearing unit 110 of FIGS. 4 and 5 and the bearing unit 1 of FIGS. 7 and 8.
10 shows yet another embodiment of a shaft 60 applicable to 10. First, the step portion 134 of the shaft 60 of FIG. 10 has a first dynamic pressure generating groove 139 such as a fishbone groove on the first surface 134A. As shown in FIG. 10A, the second surface 134B of the step portion 134 has a second dynamic pressure generating groove 149 such as a fishbone groove having another shape.

The width of the dynamic pressure generating groove 139 shown in FIG. 10C is set larger than the width of the dynamic pressure generating groove 149 shown in FIG. 10A. By changing the groove width in this way, for example, the dynamic pressure on the first surface 134A side can be adjusted to the second surface 134A.
By making the generated amount slightly larger than the dynamic pressure on the B side, it is possible to control the amount of voids in the thrust direction of the shaft 60, and it is possible to obtain good rotation and lubrication of the shaft 60. Instead of changing the groove width of the dynamic pressure generating groove in this way, the depth of the dynamic pressure generating groove may be changed. That is, the groove depth of the dynamic pressure generating groove 139 is set to the dynamic pressure generating portion 1 of FIG.
The groove is formed deeper than the groove 49.

The dynamic pressure generating groove 139 shown in FIG.
For example, six are formed on the surface 134A. On the other hand, the dynamic pressure generating grooves 149 of FIG. 11A are formed in the second surface 134B, for example, five, which are smaller in number than the grooves.
Thus, the number of dynamic pressure generating grooves on the first surface 134A is equal to that on the second surface 1.
By increasing the number of dynamic pressure generating grooves in 34B, the amount of dynamic pressure generated in the first surface 134A can be increased.
It is possible to control the amount of air gap in the thrust direction of the shaft 60 by making it slightly larger than the amount of dynamic pressure generated in 4B.

The concept of differentiating the shapes of the dynamic pressure generating grooves on the first surface 134A and the second surface 134B as shown in FIGS. 10 and 11 is also applied to the bearing unit 110 of the embodiment shown in FIGS. 4 and 5. Bearing unit 11 of FIGS. 7 and 8
It can be applied to 0 or any of them.
Further, in the above-described embodiment, the dynamic pressure generating groove is formed on both the first surface 134A and the second surface 134B of the step portion 134, but the present invention is not limited to this, and one surface, for example, the first surface.
Although the dynamic pressure generating groove is formed on the surface 134A, the second surface 134B is formed.
Of course, it does not matter even if the dynamic pressure generating groove is not formed in.

Since the dynamic pressure fluid bearing unit of the present invention is molded so that the circumference of the bearing unit is surrounded by the resin housing, there is no leakage of lubricating oil to the outside and the dynamic pressure is excellent in reliability. It became a fluid bearing unit. As the housing is covered with resin around it, outsert molding etc. is possible, the assembly process is not necessary and it is inexpensive, and since there is no fastening part of the parts like the conventional technology (because it is seamless), the lubricating oil to the outside It became a dynamic pressure fluid bearing unit with excellent reliability without leakage or scattering.

The present invention is not limited to the above embodiment. In the above-described embodiment, the motor having the bearing unit is mounted on the hard disk drive device as the information recording / reproducing device. However, not limited to this, the information recording / reproducing apparatus of the present invention may be an optical disk recording / reproducing apparatus, a magneto-optical disk recording / reproducing apparatus, or an optical disk reproducing apparatus.

The hydrodynamic bearing unit according to the embodiment of the present invention can be applied as a bearing unit of a spindle motor for a hard disk drive device as described above. However, the bearing unit of the present invention
It can also be applied as a bearing unit for a fan motor. This fan motor has a fan attached to the shaft,
By rotating this fan, for example, the heat generated by the heating element in the electronic device is released to the outside of the housing of the electronic device. Spindle motors for hard disk drive devices use NRRO (Non-Repetit)
This is a motor that has good rotary machine accuracy such as ive Run-Out), is quiet, is inexpensive, and has high reliability.

The motor equipped with the bearing unit of the present invention can be installed in an information recording / reproducing apparatus such as a hard disk drive. Such an information recording / reproducing apparatus is built in a computer or externally attached. Is like doing. The electronic device in the present invention is
Not only a computer but also a personal digital assistant, a mobile phone, a general electric appliance, and the like are included.

In the hydrodynamic bearing unit according to the present invention, the step portion of the rotary shaft having a T-shaped cross section is formed of metal, sintered metal, resin or the like as a member different from the straight support portion. Compared with the technology, the rotary shaft was much cheaper, and as a result, the hydrodynamic bearing unit was also cheaper. Also, since the resin, etc. is outserted to form the step portion, and at the same time the step portion itself is provided with the dynamic pressure generating groove in the thrust direction, the dynamic pressure generating groove is provided on the end face of the bearing or the dynamic pressure generating groove is formed on the thrust receiver. Since it is not necessary to provide, a dynamic pressure fluid bearing unit has become more inexpensive. By using a resin such as liquid crystal polymer, which has excellent mechanical precision, environmental resistance performance, outgassing performance, and chemical attack, as the resin of the step part, a hard disk drive device (HDD) that is inexpensive and highly reliable, C
It is also possible to provide a fan motor for cooling a heating element such as a PU (Central Processing Unit) or a driver IC.

[0068]

As described above, according to the present invention,
By obtaining an inexpensive shaft, an inexpensive bearing unit, motor and electronic device can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing a hard disk drive device as an information recording / reproducing device to which a motor having a bearing unit of the present invention is applied.

FIG. 2 is an exploded perspective view of the hard disk drive device of FIG.

FIG. 3 is a perspective view of the hard disk drive device of FIG. 1 further disassembled.

FIG. 4 is a cross-sectional view showing a motor for rotating a disk-shaped recording medium of a hard disk drive device.

5 is a sectional view showing a bearing unit used in the motor of FIG.

FIG. 6 is a diagram showing a structural example of a shaft of a bearing unit.

FIG. 7 is a sectional view showing another embodiment of a motor having a bearing unit of the present invention.

8 is a sectional view showing the bearing unit of FIG.

9 is a diagram showing dynamic pressure and the like in the bearing unit of FIG.

FIG. 10 is a view showing another embodiment of the shaft of the present invention.

FIG. 11 is a view showing still another embodiment of the shaft of the present invention.

FIG. 12 is a cross-sectional view showing a conventional bearing unit.

[Explanation of symbols]

3 ... Motor, 60 ... Shaft, 110 ... Bearing unit, 114 ... Bearing (Radial direction dynamic pressure fluid bearing), 124 ... Thrust receiver (Thrust direction dynamic pressure fluid bearing), 130 ... ..Shaft support portions, 134 ..
.Axial step portion, 134A ... first step portion
Surface, 134B ... second surface of step portion, 139, 14
1 ... Dynamic pressure generation groove

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) H02K 7/08 H02K 7/08 AF terms (reference) 3J011 AA20 BA04 CA02 DA01 DA02 JA02 KA02 KA03 MA12 SB02 SB19 SC03 SC04 SC05 SC13 SC14 5D109 BA14 BA16 BA17 BB12 BB18 BB21 BB22 BB34 5H605 AA04 AA07 BB05 BB19 CC04 DD05 DD09 EB03 EB06 EB17 5H607 AA04 BB01 BB14 BB17 CC01 DD02 DD03 DD16 GG03 GG09 GG12 GG15

Claims (15)

[Claims] 1. A support portion having a circular cross section, and a step portion integrally attached to the support portion and having a circular cross section and having an outer diameter dimension larger than an outer diameter dimension of the support portion. A shaft having a T-shape when viewed in a cross section in the axial direction, a radial dynamic fluid bearing for rotatably supporting the supporting portion of the shaft in the radial direction, and the step portion of the shaft being rotatable in the thrust direction A thrust direction dynamic pressure fluid bearing for supporting the thrust direction dynamic pressure fluid bearing, a housing for accommodating and holding the shaft, the radial direction dynamic pressure fluid bearing, and the thrust direction dynamic pressure fluid bearing, and the step portion is made of resin. Bearing unit characterized by. 2. The bearing unit according to claim 1, wherein the step portion has a dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing. 3. The step portion has a first dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing, and a second dynamic pressure on a second surface opposite to the first surface. The bearing unit according to claim 1, which has a generating groove. 4. The groove width of the first dynamic pressure generating groove is the second width.
The bearing unit according to claim 3, wherein the bearing width is different from the groove width of the dynamic pressure generating groove. 5. The bearing unit according to claim 3, wherein the number of the first dynamic pressure generating grooves is different from the number of the second dynamic pressure generating grooves. 6. The bearing unit according to claim 1, wherein the resin is a liquid crystal polymer. 7. A support portion having a circular cross section, and a step portion integrally attached to the support portion and having a circular cross section and having an outer diameter dimension larger than an outer diameter dimension of the support portion. A shaft having a T-shape when viewed in a cross section in the axial direction, a radial dynamic fluid bearing for rotatably supporting the supporting portion of the shaft in the radial direction, and the step portion of the shaft being rotatable in the thrust direction A thrust direction dynamic pressure fluid bearing for supporting the thrust direction dynamic pressure fluid bearing, and a housing for accommodating and holding the shaft, the radial direction dynamic pressure fluid bearing, and the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of a sintered metal. Bearing unit characterized in that 8. The bearing unit according to claim 7, wherein the step portion has a dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing. 9. The step portion has a first dynamic pressure generating groove on a first surface facing the thrust direction dynamic pressure fluid bearing, and a second dynamic pressure groove on a second surface opposite to the first surface. The bearing unit according to claim 7, further comprising a generating groove. 10. The bearing unit according to claim 9, wherein the groove width of the first dynamic pressure generating groove is different from the groove width of the second dynamic pressure generating groove. 11. The number of the first dynamic pressure generating grooves is equal to that of the second dynamic pressure generating grooves.
The bearing unit according to claim 9, wherein the number of the dynamic pressure generating grooves is different. 12. A motor having a bearing unit that rotatably supports a rotor with respect to a stator, wherein the bearing unit has a circular cross-section support portion, and the support portion is integrally attached to the support portion to provide a circular cross-section. A shaft having a step portion having an outer diameter dimension larger than that of the support portion and having a T-shape when viewed in a cross section in the axial direction; and rotating the support portion of the shaft in a radial direction. Rotatably supporting radial dynamic pressure fluid bearing, thrust direction dynamic pressure fluid bearing rotatably supporting the step portion of the shaft in the thrust direction, the shaft, the radial dynamic pressure fluid bearing and the thrust direction motion. A housing for accommodating and holding a pressure fluid bearing, wherein the step portion is made of resin. Data. 13. An electronic device comprising a motor having a bearing unit for rotatably supporting a rotor with respect to a stator, wherein the bearing unit is integrally attached to the support portion having a circular cross section and the support portion. A shaft having a circular cross section and an outer diameter dimension larger than the outer diameter dimension of the support portion, and having a T-shape when viewed in a cross section in the axial direction, and the support portion of the shaft. A radial dynamic fluid bearing that rotatably supports the radial direction; a thrust dynamic fluid bearing that rotatably supports the step portion of the shaft in the thrust direction; and the shaft and the radial dynamic fluid bearing. A housing for accommodating and holding the thrust direction dynamic pressure fluid bearing, wherein the step portion is made of resin. . 14. A motor having a bearing unit for rotatably supporting a rotor with respect to a stator, wherein the bearing unit has a circular support section, and a support section integrally attached to the support section. A shaft having a step portion having an outer diameter dimension larger than that of the support portion and having a T-shape when viewed in a cross section in the axial direction; and rotating the support portion of the shaft in a radial direction. Rotatably supporting radial dynamic pressure fluid bearing, thrust direction dynamic pressure fluid bearing rotatably supporting the step portion of the shaft in the thrust direction, the shaft, the radial dynamic pressure fluid bearing and the thrust direction motion. A housing for accommodating and holding a pressure fluid bearing, wherein the step portion is made of a sintered metal. Motor. 15. An electronic device including a motor having a bearing unit that rotatably supports a rotor with respect to a stator, wherein the bearing unit is integrally attached to the support portion having a circular cross section and the support portion. A shaft having a circular cross section and an outer diameter dimension larger than the outer diameter dimension of the support portion, and having a T-shape when viewed in a cross section in the axial direction, and the support portion of the shaft. A radial dynamic fluid bearing that rotatably supports the radial direction; a thrust dynamic fluid bearing that rotatably supports the step portion of the shaft in the thrust direction; and the shaft and the radial dynamic fluid bearing. A housing for accommodating and holding the thrust direction hydrodynamic bearing, wherein the step part is made of sintered metal. machine.