Motor adopting improved mechanism

A motor adopting an improved mechanism is composed of a stator having a shaft and a rotor provided with a sleeve and a hub, wherein the shaft is inserted into the hub and the hub is fixed on an outer circumferential surface of the sleeve. The outer circumferential surface of the sleeve is provided with a first outer circumferential surface, a second outer circumferential surface and a receiving surface that links between the first and second outer circumferential surfaces. The hub is provided with a base section, a through hole and a first protruded section protruding downward from the base section. A tip end portion of the first protruded section is provided with a hitting surface that contacts with the receiving surface of the sleeve and a second protruded section that links to the contacting surface and protrudes downward from the contacting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a motor adopting an improved mechanism, particularly, relates to a motor of which hub is formed from a metal plate through a press working.

2. Description of the Related Art

A motor is commonly installed in a disc driving unit that drives a disc such as a hard disc and an optical disc to rotate.

It has been strongly required for such a disc driving unit to be thinner in thickness and lower in price as a portable disc driving unit such as a portable disc drive and a portable music player has been popularized recently.

As a matter of course, such a requirement has been also directed toward a motor to be installed in such a disc driving unit.

It has been commonly applied for a conventional motor that a rotor hub of the motor was produced from a rod stock of aluminum through a cutting process. In this regard, there has been a limit to thinning in thickness and lowering in price. In this connection, a rotor hub is generically referred to as “hub” in some cases.

Accordingly, in order to contribute to the above-mentioned market demand, various technologies for producing a rotor hub from a thin metal plate through a press working have been proposed. Some examples of such a technology are disclosed in the Japanese publication of unexamined patent applications No. 2003-338102 and No. 2001-245461 that was filed by the same inventor as the present invention.

The motors disclosed in the Japanese publication of unexamined patent applications No. 2003-338102 and No. 2001-245461 are a so-called shaft rotating type motor. In such a shaft rotating type motor, a radial bearing section such as a sleeve that supports a shaft axially is fixed to a stator side.

Further, both the shaft, which is supported by the radial bearing section so as to be rotatable freely, and a rotor hub, which is fixed to an outer circumferential surface of the shaft, rotate as a rotor.

In the meantime, when the rotor hub that is formed by the press working is fixed to the outer circumferential surface of the shaft, it is essential for the rotor hub to be provided with some amounts of engaging length with respect to the shaft along an axis of revolution of the shaft so as to obtain prescribed fixing strength between the rotor hub and the shaft or a prescribed degree of orthogonality with respect to the shaft.

In order to achieve an enough amount of engaging length, a through hole having a protruding section in a cylindrical shape is formed in the center of the rotor hub so as to engage the through hole of the rotor hub with the outer circumferential surface of the shaft.

Further, a bearing or an outer peripheral section of a sleeve is engaged with the through hole of the rotor hub.

More specifically, in the case of the Japanese publication of unexamined patent applications No. 2003-338102, a projected holding part1c(see Abstract, FIG. 3 and paragraph [0019] in column 5) is equivalent to the above-mentioned protruding section of the rotor hub.

FIG. 7is a cross sectional view of a conventional motor according to the prior art or the Japanese publication of unexamined patent applications No. 2001-245461.

Further, in the case of the Japanese publication of unexamined patent applications No. 2001-245461, as shown inFIG. 7, a holding section106in a cylindrical shape, which is formed on a rotor hub105and engages with a shaft102, is equivalent to the above-mentioned protruding section of the rotor hub.

In such a structure of the rotor hub in which the protruding section of the rotor hub engages with the outer circumferential surface of the shaft, increasing an engaging length between the protruding section and the shaft is one method for improving the engaging strength and for obtaining the degree of orthogonality with a high degree of accuracy. However, the structure of the rotor hub creates a problem such that the motor results in increasing in total thickness.

On the contrary, in case of increasing the engaging length between the protruding section and the shaft without increasing total thickness of the motor, an engaging length between a radial bearing and a shaft is obliged to be shortened, and resulting in generating another problem such that the radial bearing fails to exhibit its primary performance and life of the bearing is shortened.

In other words, the other problem deteriorates dynamic characteristics of the motor and results in shortening the life of the motor.

Further, the rotor hub is provided with a flat surface on which a disc is mounted directly or through a member such as a sheet (hereinafter the “flat surface” is referred to as “disc mounting surface”). A location of the disc mounting surface in an axial direction affects a position of a disc surface directly, so that the location of the disc mounting surface must be positioned with a high degree of accuracy.

With respect to the disc mounting surface, in the Japanese publication of unexamined patent applications No. 2003-338102, a disk receiver1bis exhibited as the disc mounting surface. In the case of the Japanese publication of unexamined patent applications No. 2001-245461, a flat surface107is shown as the disc mounting surface inFIG. 7.

However, the protruding section is formed by a burring process during the press working, so that an interval between a top surface of a flat section of the disc mounting surface and a tip of the protruded section is hardly obtained with a high degree of accuracy.

Accordingly, it is difficult to determine the location of the rotor hub in the axial direction in relation to the shaft with a high degree of accuracy.

Generally, in a disc driving unit, it is essential for an optical pickup or a head to be disposed without slanting with respect to a disc mounted thereon as far as possible. In this regard, it is desirable for a height or a location in the axial direction of the hub having the disc mounting surface to be determined with a high degree of accuracy.

SUMMARY OF THE INVENTION

Accordingly, in consideration of the above-mentioned problems of the prior arts, an object of the present invention is to provide a motor adopting an improved mechanism, which enables to be thinned in thickness and lowered in price, and further the motor never diminishes dynamic characteristics or shortens life of the motor.

In order to achieve the above object, the present invention provides, according to an aspect thereof, a motor adopting an improved mechanism comprising: a stator having a shaft; and a rotor provided with a sleeve into which the shaft is inserted and a hub fixed on an outer circumferential surface of the sleeve, wherein the rotor rotates with centering an axis of the shaft, and wherein the outer circumferential surface of the sleeve is provided with a first outer circumferential surface having a first diameter, a second outer circumferential surface having a second diameter that is larger than the first diameter, and a receiving surface that links between the first outer circumferential surface and the second outer circumferential surface and intersects with the shaft at right angles, and wherein the hub is provided with a base section that extends in a direction intersecting with an axis of the shaft at right angles, a through hole that is formed in the center of the base section and engages with the outer circumferential surface of the sleeve, and a first protruded section that protrudes downward from the base section in the through hole side in parallel with the axis of the shaft, and further wherein a tip end portion of the first protruded section is a surface intersecting with the axis of the shaft at right angles and provided with a hitting surface that contacts with the receiving surface of the sleeve and a second protruded section that links to the contacting surface and protrudes downward from the contacting surface in an opposite direction toward the base section.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, a rotor hub is defined as “hub”.

First Embodiment

In reference toFIGS. 1-5, a motor adopting an improved mechanism according to a first embodiment of the present invention is described in detail.

A motor according to the first embodiment of the present invention is a disc driving motor, which is installed in a disc driving unit and drives a hard disc to rotate.

FIG. 1is a cross sectional view of a motor adopting an improved mechanism according to a first embodiment of the present invention.

FIG. 2is an enlarged cross sectional view in part of a major part of the motor shown inFIG. 1.

FIGS. 3a-3care cross sectional drawings for explaining each step of forming a hub through a press working.

FIG. 4is an enlarged cross sectional drawing in part showing a right side of the third step of forming the hub shown inFIG. 3c.

FIG. 5is a cross sectional view of the motor shown inFIG. 1when a disc is loaded thereon.

InFIGS. 1,2and5, a cross section of a motor adopting an improved mechanism is symmetrical to an axis CL of revolution, so that each drawing shows just right half of the motor and is generically referred to as a cross sectional view of the motor.

InFIG. 1, a motor50is composed of a stator50S and a rotor50R.

As shown inFIG. 1, the stator50S is further composed of a motor base1, a shaft2, a coil3, a core4and a thrust ring9. The shaft2is force fitted into a through hole1aprovided on the motor base1. The coil3is wound around the core4. The core4is fixed to an outer circumferential surface of an annular wall section1bformed on the motor base1. The thrust ring9is fixed to one tip end portion of the shaft2opposite to the motor base1side.

Further, the motor base1is formed from aluminum through a diecasting process and the shaft2is produced from a stainless steel material through a cutting process.

Furthermore, the thrust ring9is also produced from a stainless steel material through a cutting process.

On the other hand, the rotor50R is further composed of a sleeve5having a through hole5a, a hub6, a ring magnet7and a counter plate8. The hub6is glued to an outer circumferential surface5bof the sleeve5or glued to the sleeve5after the sleeve5is force fitted in a through hole6kaof the hub6. The ring magnet7is fixed on an inner wall surface of a circumferential wall6aof the hub6, wherein the circumferential wall6aextends downward from an outer circumference of a base section6kof the hub6. The counter plate8is installed on a stepped section5a2having a plurality of steps that is provided on a top end portion of the sleeve5so as to plug an opening hole of the through hole5a.

Further, the sleeve5is produced from a copper based material, a stainless steel material or an aluminum based material through a cutting process. The hub6is produced from a one-millimeter-thick metal plate of a magnetic body such as an iron based material and a magnetic stainless steel material through a press working. The counter plate8is produced from a stainless steel material through a cutting process.

Furthermore, a sheet11made from resin is affixed on a top surface6k1of the base section6kof the hub6. The sheet11is provided for preventing a disc from being scratched by the hub6when the disc is loaded on the motor50. The sheet11can be made from a polyester resin film having a thickness of 0.1 mm, for instance.

More, one pair of radial dynamic pressure grooves RD1and RD2is formed on an outer circumferential surface2aof the shaft2, wherein the dynamic pressure grooves RD1and RD2are disposed so as to be apart from each other in an axial direction of the axis CL of revolution.

Moreover, thrust dynamic pressure grooves SD1and SD2are formed on top and bottom surfaces of the thrust ring9respectively.

The above-mentioned components of the motor50are assembled such that the shaft2is inserted into the through hole5aof the sleeve5.

Further, the thrust ring9is sandwiched between the counter plate8and the sleeve5so as to remain a gap (second gap) between the bottom surface of the thrust ring9and a base surface5a3of the stepped section5a2of the sleeve5and another gap (fourth gap) between a bottom surface8aof the counter plate8and the top surface of the thrust ring9.

Hereupon, lubricant10is filled in a gap route that goes from a taper seal section TS to a gap between a top surface2bof the shaft2and the bottom surface8aof the counter plate8as a remotest section of the gap route through a first gap between the outer circumferential surface2aof the shaft2including the radial dynamic pressure grooves RD1and RD2and an inner circumferential surface of the sleeve5, the second gap between the base surface5a3of the sleeve5and the bottom surface of the thrust ring9including a thrust dynamic pressure groove SD2, a third gap between the sleeve5and an outer circumferential surface of the thrust ring9and the fourth gap between the top surface of the thrust ring9including a thrust dynamic pressure groove SD1and the bottom surface8aof the counter plate8as the remotest section of the gap route.

The taper seal section TS is a sealing section for preventing the lubricant10from leaking out from the gap route by means of physical action such as the capillary phenomenon. In this connection, a fluid level10aof the lubricant10is designated to be positioned in the middle of the taper seal section TS.

Further, radial dynamic pressure bearing sections RB1and RB2are constituted by the radial dynamic pressure grooves RD1and RD2and their confronting surface of the sleeve5, that is, the inner circumferential surface of the through hole5aof the sleeve5and the lubricant10filled in the first gap between them.

Furthermore, a first thrust dynamic pressure bearing section SB1is constituted by the thrust dynamic pressure groove SD1and its confronting surface, that is, the top surface of the thrust ring9formed with the thrust dynamic pressure groove SD1and the bottom surface8aof the counter plate8and the lubricant10filled in the fourth gap between them.

More, a second thrust dynamic pressure bearing section SB2is constituted by the thrust dynamic pressure groove SD2and its confronting surface, that is, the bottom surface of the thrust ring9formed with the thrust dynamic pressure groove SD2and the base surface5a3of the sleeve5and the lubricant10filled in the second gap between them.

In the motor50in which the stator50S and the rotor50R are assembled as mentioned above, the rotor50R starts to rotate when prescribed electricity is supplied to the coil3from outside of the motor50.

In this regard, the rotor50R is supported so as to be rotatable freely with respect to the stator50S while the rotor50R is floated by dynamic pressure generated by each of the thrust and radial dynamic pressure bearing sections RB1, RB2, SB1and SB2as the rotor50R rotates.

In reference toFIG. 2, a structure of fixing the hub6to the sleeve5is described in detail next.

FIG. 2shows partially a major part of the motor50inFIG. 1.

InFIG. 2, “ΦA” denotes a first outer diameter of a first outer circumferential surface5b1of the sleeve5, “ΦB” denotes a second outer diameter of a second outer circumferential surface5b2of the sleeve5, “ΦC” denotes an inner diameter of the through hole5aof the sleeve5and “Lt1” denotes a total length in the axis CL direction of the sleeve5.

Further, as shown inFIG. 2, the outer circumferential surface5bis constituted by the first outer circumferential surface5b1having the first outer diameter ΦA and the second outer circumferential surface5b2having the second outer diameter ΦB, wherein the second outer diameter ΦB is larger than the first outer diameter ΦA by a difference d3.

Furthermore, a location of a boundary section between the first and second outer circumferential surfaces5b1and5b2of the sleeve5is positioned at a distance Lt2from a bottom end surface5tof the sleeve5. The boundary section is a stepped section5chaving a receiving surface5c1, which intersects with the axis CL at right angles.

More, a circumferential groove5dis formed on the top end portion of the sleeve5opposite to the bottom end surface5tconfronting with the motor base1.

More specifically, a length or a width in the axis CL direction of a deepest section of the circumferential groove5dis “L1” and a depth of the circumferential groove5dfrom the first outer circumferential surface5b1is “d1”.

Moreover, a wall surface5d1is provided at an upper edge portion of the circumferential groove5das a slanted surface, wherein the wall surface5d1is inclined so as to increase a width in the axis CL direction of the circumferential groove5din accordance with a distance from the deepest section toward the first outer circumferential surface5b1. An angle of gradient of the wall surface5d1is 45 degrees, for instance, with respect to the axis CL.

Typical values of the above-mentioned dimensions, for instance, are as follows:

On the other hand, as shown inFIG. 2, the hub6is provided with the through hole6kain the center, wherein the through hole6katightly engages with the first outer circumferential surface5b1having the first outer diameter ΦA of the sleeve5.

Further, the hub6is provided with a protruded section6c(hereinafter referred to as “first protruded section6c”), which protrudes downward from the base section6kof the hub6in the through hole6kaside in parallel with the shaft2.

Furthermore, an inner circumferential surface6bof the first protruded section6calso tightly engages with the first outer circumferential surface5b1having the first outer diameter ΦA of the sleeve5.

More, the first protruded section6cis formed by a burring process during a press working. The forming process of the first protruded section6cwill be detailed.

Moreover, a stepped section6dhaving a shape corresponding to the stepped section5cof the sleeve5is formed on a tip end portion of the first protruded section6c.

More specifically, the tip end portion of the first protruded section6c, which is a surface that intersects with the axis CL at right angles, is provided with a hitting surface6d1, which contacts with the receiving surface5c1of the sleeve5, and a thin cladding section6hn(hereinafter referred to as “second protruded section6hn”), which protrudes downward toward the motor base1from the hitting surface6d1.

Further, an inner diameter of an inner circumferential surface of the second protruded section6hnis “ΦB6”.

Furthermore, the inner diameter ΦB6is larger than the second outer diameter ΦB of the second outer circumferential surface5b2of the sleeve5.

Accordingly, the inner circumferential surface of the second protruded section6hnis separated from the second outer circumferential surface5b2of the sleeve5.

Further, the thickness of the second protruded section6hnis thinner than that of the first protruded section6c.

Furthermore, a length in the axis CL direction of the first protruded section6cfrom the hitting surface6d1to the tip end of the second protruded section6hnis “d2”. In other words, the second protruded section6hnprotrudes downward from the hitting surface6d1by the distance “d2”.

More, a length Lk in the axis CL direction of the first protruded section6cis equivalent to a length in the axis CL direction of an area in which the hub6engages with the first outer circumferential surface5b1of the sleeve5, wherein the inner circumferential surface6bof the first protruded section6cmaintains the first outer diameter ΦA within the area. As a matter of fact, the length Lk is an engaging length of the hub6with respect to the sleeve5.

Typical values of the above-mentioned dimensions, for instance, are as follows:

In reference toFIGS. 3a-4, the forming process of the first protruded section6cis described in detail next.

FIGS. 3a-3care cross sectional drawings for explaining each step of forming the first protruded section6cof the hub6through a press working andFIG. 4is an enlarged cross sectional drawing in part showing a right side of the third step of the forming process through the press working shown inFIG. 3c.

Firstly, as shown inFIG. 3a, a prepared hole6M1with centering on an axis CL1is formed on a sheet metal6M through a piercing process, and then the sheet metal6M having the prepared hole6M1is sandwiched between female dies61and62(first step).

Secondly, as shown inFIG. 3b, a burring punch63is force fitted into the prepared hole6M1in an arrow direction along the center axis CL1so as to form a protruded section6M2(hereinafter referred to as “first protruded section6M2”) through a so-called burring process (second step).

Hereupon, the first and second steps are the same processes as the normal burring process.

Thirdly, as shown inFIG. 3c, the sheet metal6M having the first protruded section6M2is sandwiched between a female die64and a male die65.

More specifically, the female and male dies64and65securely fasten the sheet metal6M by sandwiching inner and outer surfaces of the first protruded section6M2along its contour between them.

Then, a stepped section (shown as “6d” inFIG. 2) is formed on a tip end surface at an innermost side of the first protruded section6M2by punching a male die66having an annular punching section66P into the tip end surface in an arrow D66direction (third step). In this connection, a tip of the annular punching section66P is formed in a specific shape that corresponds to the hitting surface6d1of the stepped section6dof the hub6shown inFIG. 2.

The punching process makes the tip of the first protruded section6M2(6c) result in plastic deformation, and the second protruded section6hnis formed thereon.

According to the above-mentioned forming process of the second protruded section6hn, as shown inFIG. 4, the hitting surface6d1is formed by punching the tip end surface of the first protruded section6c(6M2) by means of the male die66while both the inner circumferential surface6bof the first protruded section6c(6M2) and the top surface6k1of the base section6kare securely fastened by the male die65.

Accordingly, the forming process can achieve exceptional effect such that dimensions of the first inner diameter ΦA of the inner circumferential surface6band a distance Lc from the top surface6k1of the base section6kto the hitting surface6d1are formed with a high degree of accuracy.

As a matter of course, since the second protruded section6hnis formed as relief of the plastic deformation, a distance Ld from a tip end surface6hn1of the second protruded section6hnto the top surface6k1results in being formed with a low degree of accuracy. However, there is really very little chance that the second protruded section6hncontributes to functions of the motor50, so that the second protruded section6hnnever affects functions or characteristics of the motor50.

On the contrary, in the case of the Japanese publication of unexamined patent applications No. 2003-338102 and No. 2001-245461 as the prior arts, the projected holding part1cand the holding section106(hereinafter referred to as “protruded section”) were just formed by the burring process as the same process as shown inFIG. 3b, so that the tip end portion of the protruded sections1cand106were not restricted in dimensions.

Accordingly, the length in the axial direction of the protruded sections1cand106that corresponds to the distance Lc inFIG. 4is hardly regulated with a high degree of accuracy, and resulting in failing to achieve the above-mentioned exceptional effect to be realized by the present invention.

In the above-mentioned structure of fixing the hub6to the sleeve5shown inFIG. 2, the hub6is tightly engaged with the sleeve5in the radial direction between the first outer circumferential surface5b1of the sleeve5and the inner circumferential surface6bof the hub6within the range of the distance Lk in the axis CL direction.

Further, the hitting surface6d1of the hub6tightly contacts with the receiving surface5c1of the sleeve5in the thrust direction.

Accordingly, the hub6can be positioned in extremely higher accuracy with respect to the sleeve5in the axis CL direction.

In reference toFIG. 5, a state of loading a disc on the motor50according to the first embodiment of the present invention is described next.

FIG. 5is a cross sectional view of the motor50when a disc is loaded thereon.

InFIG. 5, a disc D is a platter having a center hole Da in the center and placed on the sheet11of the motor50, wherein the motor50is placed such that the motor base1is located at the bottom.

Then the disc D is fixed to the motor50by means of a clamper12.

More specifically, the clamper12is produced from aluminum through a cutting process and formed in a ring shape. The shape of the clamper12is designed for having some degree of elasticity.

Further, a chamfered corner section12ais formed at a lower edge section of an outer circumference of the clamper12. The chamfered corner section12acontacts with a corner edge of the center hole Da of the disc D.

Furthermore, an inner diameter ΦK of a center hole of the clamper12is formed so as to be slightly smaller than the first outer diameter ΦA of the first outer circumferential surface5b1of the sleeve5.

More, the clamper12is force fitted or shrink fitted into the circumferential groove5dof the sleeve5and clamps down the disc D placed on the sheet11by sandwiching the disc D between the clamper12and the sheet11.

When the disc D is clamped down by the clamper12, a top corner edge12bof an inner circumference of the clamper12contacts with the slanted wall surface5d1of the circumferential groove5d, and resulting in automatically centering the clamper12. The disc D is also centered automatically as the clamper12is automatically centered.

When the clamper12is installed on the sleeve5, downward force F1is applied to the hub6through the disc D and the sheet11. However, since the hitting surface6d1of the hub6tightly contacts with the receiving surface5c1of the sleeve5as mentioned above, the hub6never moves downward toward the motor base1side.

In other words, the location of the hub6in the axis CL direction is maintained in position with a high degree of accuracy.

Second Embodiment

In reference toFIG. 5, a motor adopting an improved mechanism according to a second embodiment of the present invention is described next.

FIG. 6is a cross sectional view of a motor50A according to a second embodiment of the present invention showing a disc loaded thereon.

The motor50A according to the second embodiment of the present invention is identical to the motor50according to the first embodiment of the present invention except for the sleeve5, the hub6and a clamping mechanism for a disc. Therefore, the same components as the motor50are denoted by the same reference signs and their descriptions are omitted.

InFIG. 6, a sleeve5A and a hub6A of the motor50A according to the second embodiment of the present invention are different in their shapes from the sleeve5and the hub6of the motor50according to the first embodiment of the present invention.

Further, a shape and a material of a clamper12A for clamping a disc D is also different from the clamper12of the motor50.

More specifically, the sleeve5A of the motor50A is not provided with the circumferential groove5don an outer circumferential surface of the sleeve5A.

Further, the hub6A is provided with a raised section6At, which tightly engages with a center hole Da of the disc D without any rattling.

Furthermore, an outer circumferential surface6At1of the raised section6At of the hub6A tightly engages with the center hole Da of the disc D, and resulting in centering the disc D.

On the other hand, the clamper12A according to the second embodiment of the present invention is produced from a metal thin plate having springiness and provided with a center hole12Ab that engages with the sleeve5A and a recessed section12Aa that is dented circumferentially. One example of a material for the clamper12A is a stainless steel material having a thickness of 0.6 mm.

The clamper12A that engages with the sleeve5A is depressed by a stop ring13so as not to come out from the sleeve5A. The stop ring13is force fitted on an outer circumferential surface5Ab of the sleeve5A and fixed thereto in such a way that the recessed section12Aa of the clamper12A contacts with the disc D and depress the disc D downward.

Further, the position of the recessed section12Aa contacting with the disc D is designated to be a position on the disc D opposite to the sheet11affixed on the hub6A so as not to warp the disc D.

According to the clamping mechanism of the motor50A based on the second embodiment of the present invention, it is not necessary for the sleeve5A to be provided with a circumferential groove, so that the sleeve5A can be manufactured in lower cost.

Further, a length LAK of a first protruded section6Ac of the hub6A that is a range of engaging the first protruded section6Ac with the sleeve5A in the axis CL direction can be enlarged by an amount of protrusion of the raised section6At. In other words, the raised section6At can enlarge an engaging length (LAK).

Accordingly, fixing strength of the hub6A against the sleeve5A can be improved furthermore.

As mentioned above, according to the present invention, a motor can be thinned in thickness and lowered in price.

Further, the motor achieves excellent effects such that dynamic characteristics of the motor never diminished, life of the motor never shortened and a disc loaded on the motor is positioned in the axial direction with a high degree of accuracy.

While the invention has been described above with reference to a specific embodiment thereof, it is apparent that many changes, modifications and variations in configuration, materials and the arrangement of equipment and devices can be made without departing from the invention concept disclosed herein.

For instance, a method of forming the hitting surface6d1in the second protruded section6dof the hub6or6A is not limited to the above-mentioned press working. In the case of the hub6as a representative of the hubs6and6A hereinafter, the hitting surface6d1can be formed through a cutting process in such a way that the outer circumference of the tip of the first protruded section6cis cut off based on the top surface6k1or a bottom surface of the base section6kof the hub6after the first protruded section6cis formed by the burring process. By the cutting process, the location in the axis CL direction of the hitting surface6d1can be positioned with a high degree of accuracy.

Further, the hub6can be produced from a metal block through a cutting process totally. In this case, the location in the axis CL direction of the hub6can be positioned with a high degree of accuracy by contacting the hitting surface6d1of the hub6formed through the cutting process with the receiving surface5c1of the sleeve5.

In any cases, however, there is fear that forming the hub6through the cutting process raises manufacturing cost of the hub5.

Accordingly, it is desirable for the hitting surface6d1of the hub6to be formed through the above-mentioned press working from the viewpoint of suppressing the rise of manufacturing cost.

In addition thereto, it will be apparent to those skilled in the art that various modifications and variations could be made in the bearing device and the motor mounted with the bearing device in the present invention without departing from the scope of the invention.