JPH0742214Y2 - Fluid bearing motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a fluid dynamic bearing motor.

[Prior Art] A fluid dynamic bearing motor is typically used for rotating a polygon mirror of a laser printer of an information processing device, and has a high rotation speed (5000 rpm or more) and durability (several thousands of hours or more). Since it is required, a normal ball bearing cannot satisfy the specifications, and a fluid bearing is exclusively used for rotation support of a rotor provided with a polygon mirror.

FIG. 6 is a central sectional view of a fluid dynamic bearing motor proposed by the applicant of the present invention, out of the types of conventional fluid dynamic bearing motors using a fluid dynamic bearing. In the figure, all the constituent elements of the fluid dynamic bearing motor are housed in the housing 100 as shown in the figure, and are kept airtight against the outside air so that outside air including dust does not flow into the inside. A shaft body 9 having a large number of fluid grooves 9a on its outer peripheral surface is vertically provided from the center position of the bottom surface of the housing 100. The sleeve 2 constituting the rotor is inserted and supported as shown in the figure. is doing. The inner diameter of the sleeve 2 is slightly larger than the outer diameter of the shaft body 9, while a sintered body 2a having an appropriate fluid permeability is fixed to the upper end opening of the sleeve 2.

A flange portion 3 is formed on the upper portion of the sleeve 2, and the polygon mirror 4 is positioned and fixed by this flange portion. Further, a rotating magnet 6 which is magnetized in multiple poles in the radial direction is fixed to the outer peripheral surface of the lower portion of the sleeve 2.

On the other hand, a stator 8 for generating a rotating magnetic field is fixed to the inner peripheral surface of the housing 100 at a position surrounding the outer peripheral surface of the magnet 6.

The rotating magnetic field generated by the stator 8 acts on the magnet 6 of the sleeve 2 supported in this way, and
In the state of rotating around the shaft at a high speed, the fluid (air) is moved between the outer peripheral surface of the shaft body 9 and the inner peripheral surface of the sleeve 2 by the action of a large number of fluid grooves 9a provided on the outer peripheral surface of the shaft body 9. The shaft 9 and the sleeve 2 are brought into non-contact with each other by actively introducing the fluid film between them, and the rotor is floated in the thrust direction by the attraction force between the rotating magnet and the stator in the bearing. The thrust vibration of the rotor is prevented by appropriately discharging the fluid upward through the sintered body 2a. In addition to this, a thrust fluid bearing having a dynamic pressure groove in the thrust direction may be mounted.

[Problems to be Solved by the Invention] FIG. 7 is a diagram showing a fluid flow direction and a fluid pressure distribution of the fluid dynamic bearing motor of FIG. 6, respectively. FIG. 7 (a) is a fluid of the fluid dynamic bearing motor. 7 (b) shows the pressure distribution in the Y-Y 'cross section of FIG. 7 (a), and FIG. 7 (c) shows the flow of X in FIG. 7 (a). -X '
It is a figure which has shown each pressure distribution in a cross section.

First, in FIG. 7 (a), the sleeve 2 is attached to the stator 8
As a result of the magnet 6 being attracted and driven by the rotating magnetic field generated in the housing 2 to rotate the sleeve 2 at a high speed, the fluid in the housing 100 flows in the direction shown by the arrow to form convection and form the sleeve 2
Generates a pressure distribution on the outer peripheral surface of the. That is, the seventh
In FIG. 3B, the pressure of the fluid is positive (+) on the outer peripheral surface of the polygon mirror 4 fixed on the sleeve 2, but negative (-) at other portions.
In particular, the pressure near the sintered body 2a for exhausting the fluid becomes a large negative pressure.

Next, in FIG. 7 (c), the pressure distribution gradually increases with the center of rotation as the apex, and a positive pressure is obtained at a corresponding position on the outer peripheral surface of the polygon mirror 4, and as a result, the polygon mirror 4 and the sleeve 2 are Depending on the shape, the pressure near the sintered body 2a cooperates with a large negative pressure to generate buoyancy in the direction of arrow F in the figure, which makes it impossible to form a fluid film, or causes the rotor to float excessively. is there.

Next, FIG. 8 shows a central cross-sectional view of a conventional hydrodynamic bearing motor having a different structure. The hydrodynamic bearing motor shown in FIG. 8 has basically the same structure as that of the hydrodynamic bearing motor shown in FIG.
Is provided below the outer peripheral surface of the sleeve 2, and the distance between the Z surface of the housing and the mirror surface is about 10 mm or less.

FIG. 9 shows the flow direction of the fluid and the pressure distribution of the fluid generated when the fluid bearing motor of FIG. 8 rotates at high speed. FIG. 9 (a) shows the fluid flow of the fluid bearing motor by arrows. On the other hand, FIG. 9 (b) shows Y- of FIG. 7 (a).
It is a figure showing pressure distribution in a Y'section.

First, in FIG. 9 (a), the sleeve 2 is attached to the stator 8
As a result of the rotation of the magnet 6 generated by the rotation of the magnet 6 and the rotation of the sleeve 2 at a high speed, the fluid in the housing 100 flows in the direction shown by the arrow to form convection, and the pressure distribution on the outer peripheral surface of the sleeve 2 is reduced. Occur. That is, in FIG. 9 (b), the pressure of the fluid becomes positive at the upper part of the sleeve 2 with the outer peripheral surface of the polygon mirror 4 fixed on the sleeve 2 as a boundary, while negative pressure at the upper part of the sleeve 2. Becomes

As a result, depending on the shapes of the polygon mirror 4 and the sleeve 2, a sinking force is generated in the direction indicated by the arrow F, which is greater than the thrust holding force of the bearing or exerts a sufficient influence, so that the bearing can be formed. It may be lost or its life may be shortened.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the first invention is to form a fluid groove on the outer peripheral surface and to fix the shaft in a hermetically sealed housing. Rotatably supported by a fluid bearing consisting of a body and a sleeve provided at the opening end with a sintered body that holds the sintered body rotatably while receiving a thrust load generated between the shaft bodies and allows fluid pressure to appropriately pass therethrough, and By making the unevenness of the pressure distribution in the outer surface portion generated when the rotor rotates so as to obtain the rotational driving force from the driving means, it is possible to prevent the buoyancy of the rotor from occurring regardless of the overall shape of the rotor, and to maintain a normal condition. A fluid bearing motor in which a fluid film is formed in the fluid bearing to ensure the function of the fluid bearing.

A second object of the present invention is to prevent the occurrence of sinking of the rotor by making the pressure distribution of the outer peripheral surface portion evenly generated when the rotor rotates regardless of the overall shape of the rotor. A fluid bearing motor in which a normal fluid film is formed in the fluid bearing to ensure the function of the fluid bearing.

[Means for Solving Problems] In order to solve the above problems and achieve the object, the fluid dynamic bearing motor of the present invention has the following configuration. That is, a shaft body having a fluid groove formed on the outer peripheral surface thereof and fixed in a hermetically sealed housing, and a sinter that holds the shaft rotatably while receiving a thrust load generated between the shaft bodies and allows a fluid pressure to appropriately pass therethrough. A fluid bearing motor rotatably supported by a fluid bearing composed of a sleeve provided at an opening end and having a rotor adapted to obtain a rotational driving force from a driving means, which is generated when the rotor is rotated. In order to make the pressure distribution of the outer surface portion of the rotor uniform, the fluid passage having one end opened near the sintered body and the other end opened on the inner peripheral surface of the housing is formed. And

Further, preferably, a fluid groove is formed on the outer peripheral surface and a shaft body fixed in a hermetically sealed housing and rotatably held while receiving a thrust load generated between the shaft bodies, and a fluid pressure appropriately passes therethrough. A hydrodynamic bearing motor comprising a rotor rotatably supported by a hydrodynamic bearing formed of a sleeve provided at an opening end of the sintered body, and a rotor adapted to obtain a rotational driving force from a driving means. In order to make the pressure distribution of the outer peripheral surface portion of the rotor uneven, which is sometimes generated, one end is opened in the vicinity of the opening portion for inserting the sleeve into the shaft body and the other is formed on the inner peripheral surface of the housing. It is characterized by forming a fluid passage having an open end.

[Operation] With the above configuration, the pressure distribution in the outer peripheral surface portion of the rotor, which is generated when the rotor is rotated, is made uniform by the fluid passages provided by opening both ends on the inner surface of the housing.

[Embodiment] A preferred embodiment of a fluid dynamic bearing motor according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a central sectional view of the fluid dynamic bearing motor of the first embodiment.

In the figure, all the constituent elements of the fluid dynamic bearing motor are housed in a totally hermetically-sealed housing 100 as shown in the figure, and are kept airtight with respect to the outside air so that the outside air including dust is contained in the housing 100. It has a structure that does not flow inside.

And from the center position of the bottom surface of this housing 100,
A shaft body 9 provided with a large number of fluid grooves 9a is vertically provided on the outer peripheral surface, and the sleeve 2 is inserted and supported as shown in the drawing. The inner diameter of the sleeve 2 is slightly larger than the outer diameter of the shaft body 9, while a sintered body 2a having an appropriate fluid permeability is fixed to the upper end opening of the sleeve 2.

A flange portion is formed on an upper portion of the sleeve 2, and the polygon mirror 4 is positioned and fixed by the flange portion, and a magnet 6 which is magnetized in a radial direction in multiple directions is fixed on an outer peripheral surface of the lower portion of the sleeve 2. Has been done. on the other hand,
A stator 8 for generating a rotating magnetic field is fixed to the inner peripheral surface of the housing 100 at a position surrounding the outer peripheral surface of the magnet 6.

The rotating magnetic field generated by the stator 8 acts on the magnet 6 of the sleeve 2 supported in this way, and
In the state of rotating around the shaft at a high speed, the fluid (air) is moved between the outer peripheral surface of the shaft body 9 and the inner peripheral surface of the sleeve 2 by the action of the numerous fluid grooves 9a provided on the outer peripheral surface of the shaft body 9. The shaft 9 and the sleeve 2 are brought into a non-contact state by positively introducing the fluid film between the shaft body 9 and the sleeve 2, and the rotor is levitated in the thrust direction by the attraction force of the rotating magnet and the stator. The thrust vibration of the rotor is prevented by appropriately discharging the fluid through the sintered body 2a upward. Also,
In addition to the sintered member, a thrust fluid bearing having a dynamic pressure groove in the thrust direction may be mounted.

Next, in the upper wall portion of the housing 100, the fluid passage 1 is provided with openings 1a and 1b having both ends open toward the inside of the housing 100.

When the hydrodynamic bearing motor described above is started, the positive pressure of the fluid generated on the outer peripheral surface of the polygon mirror 4 fixed on the sleeve 2 explained with reference to FIG. The positive pressure and the negative pressure cancel each other out by acting on the sintered body 2a which is to be in a negative pressure state when there is no fluid passage 1 as a result of the passage of the positive pressure and the negative pressure. Unbalanced pressure distribution will be eliminated or reduced.

FIG. 2 shows a diagram of a specific example of a fluid dynamic bearing motor having a structure based on FIG. 1. FIG. 2 (a) is a central sectional view, and FIG. 2 (b) is FIG. 2 (a). ) Is a sectional view taken along the line ZZ ′ of FIG.

In both figures of FIG. 2, the basic structure is substantially the same as that of FIG. 1, so the same reference numerals are given and the description is omitted and only the different parts will be described.
The lower housing 7 and the lower housing 7 are connected by respective flange portions. Further, the shaft body 9 is hung from above the base portion 10, while the base portion 10 and the lower housing 7 are integrally fixed.

On the other hand, in the upper wall portion of the upper housing 5, a total of eight fluid passages 1 are machined and formed as grooves at intervals of 45 degrees, but the discs 3 are provided by being adhered onto these grooves. As a result, A common opening 1a and eight openings 1b are arranged. Here, since the eight openings 1b are located on the outer peripheral surface of the polygon mirror 4, positive pressure can be efficiently applied to the sleeve 2.

As described above, in the prototype model of the specific example described above, it was confirmed that a fluid film having a substantially constant thickness is always formed between the sleeve 2 and the shaft body regardless of the rotation speed.

Next, FIG. 3 is a central cross-sectional view of the fluid dynamic bearing motor of the second embodiment, and shows a state in which the fluid passage 1 is provided in the conventional fluid dynamic bearing motor shown in FIG. It was confirmed that also in the fluid dynamic bearing motor shown in FIG. 3, a fluid film having a substantially constant thickness is always formed between the sleeve 2 and the shaft body regardless of the rotation speed.

Further, FIG. 4 is a central sectional view of the fluid dynamic bearing motor of the third embodiment, and shows how the fluid passage 1 is provided in the conventional fluid dynamic bearing motor shown in FIG. In the fluid dynamic bearing motor shown in FIG. 4, it is effective in removing the pressure difference between the portions open in the opening 1a and the opening 1b, and the gap between the sleeve 2 and the shaft body is substantially constant. It was confirmed that a thick fluid film was always formed regardless of the rotation speed.

Further, FIG. 5 is a central sectional view of the fluid dynamic bearing motor of the fourth embodiment, and shows a state in which the fluid passage 1 is provided in the conventional fluid dynamic bearing motor shown in FIG. It has been confirmed that also in the fluid dynamic bearing motor shown in FIG. 5, a fluid film having a substantially constant thickness is always formed between the sleeve 2 and the shaft body regardless of the rotation speed.

Here, it is preferable that each of the fluid passages 1 described above has a large number of components as described in the concrete example of FIG. Also,
The fluid passages 1 shown in FIGS. 2, 4, and 5 may be provided in an appropriate combination.

As described above, in the hydrodynamic bearing motor according to the embodiment of the present invention, the pressure distribution of the fluid outside the rotor is made uniform by eliminating the bias, and the normal hydrodynamic bearing function is not impaired. Will be provided.

In the embodiments described above, only the hydrodynamic bearing motor for high speed rotation of the polygon mirror has been described, but the present invention is not limited to this, and a motor using a hydrodynamic bearing for rotating shaft support of a rotor is not limited to the fluid of the present invention. All bearing motors are applicable.

[Effects of the Invention] As described above, according to the first invention, the fluid groove is formed on the outer peripheral surface and the shaft body fixed in the closed housing and the thrust load generated between the shaft bodies are provided. A rotor rotatably supported while being rotatably supported by a fluid bearing composed of a sleeve having an opening end provided with a sintered body that allows fluid pressure to pass therethrough as appropriate, and a rotational driving force is obtained from a driving means. By making the uneven pressure distribution in the external surface portion generated during rotation of the rotor, buoyancy of the rotor is prevented regardless of the overall shape of the rotor, and a normal fluid film is formed in the fluid bearing. It is possible to provide a fluid dynamic bearing motor having a secured function.

Further, according to the second aspect of the present invention, regardless of the overall shape of the rotor, the pressure distribution in the outer surface portion generated when the rotor rotates is made uniform, thereby preventing the occurrence of sedimentation of the rotor and ensuring normal fluid flow. It is possible to provide a fluid dynamic bearing motor in which the film is formed in the fluid dynamic bearing to ensure the function of the fluid dynamic bearing.

[Brief description of drawings]

FIG. 1 is a central sectional view of a fluid dynamic bearing motor of the first embodiment, and FIGS. 2A and 2B are central sectional views of a specific example of a fluid dynamic bearing motor having a structure based on FIG. 1 and ZZ ′. Fig. 3 is a central sectional view of the fluid dynamic bearing motor of the second embodiment, Fig. 4 is a central sectional view of the fluid dynamic bearing motor of the third embodiment, and Fig. 5 is a fluid dynamic bearing motor of the fourth embodiment. FIG. 6 is a central cross-sectional view of a fluid dynamic bearing motor proposed by the applicant of the present invention in a conventional fluid dynamic bearing motor type using a fluid dynamic bearing, and FIG. 7A is a fluid dynamic bearing motor. Showing the flow of the fluid by arrows, FIG. 7 (b) is a pressure distribution diagram in a cross section taken along the line YY ′ of FIG. 7 (a), and FIG. 7 (c) is a diagram of FIG. 7 (a). FIG. 8 is a pressure distribution diagram in a cross section taken along the line XX ′, FIG. 8 is a central cross-sectional view of a conventional hydrodynamic bearing motor having another structure, and FIG. The flow of the fluid is shown by arrows, and FIG. 9 (b) is a pressure distribution diagram in a cross section taken along the line YY 'of FIG. 9 (a). In the figure, 1 ... fluid passage, 1a, 1b ... opening, 2 ... sleeve, 3 ... disk, 4 ... polygon mirror, 5 ... upper housing, 6 ... magnet, 7 ... lower housing, 8 ...
... stator, 9 ... shaft, 100 ... housing.

Claims (2)

[Scope of utility model registration request] 1. A shaft body having a fluid groove formed on the outer peripheral surface thereof and fixed in a hermetically sealed housing, and rotatably held while receiving a thrust load generated between the shaft bodies and appropriately passing a fluid pressure. A hydrodynamic bearing motor comprising a rotor rotatably supported by a hydrodynamic bearing formed of a sleeve provided at an opening end and having a rotor configured to obtain a rotational driving force from a driving means. In order to make the pressure distribution of the outer peripheral surface portion of the rotor sometimes uneven, a fluid passage having one end opened near the sintered body and the other end opened at the inner peripheral surface of the housing is formed. A fluid dynamic bearing motor characterized by the above. 2. A shaft body having a fluid groove formed on the outer peripheral surface thereof and fixed in a hermetically sealed housing, and rotatably held while receiving a thrust load generated between the shaft bodies and appropriately passing a fluid pressure. A hydrodynamic bearing motor comprising a rotor rotatably supported by a hydrodynamic bearing formed of a sleeve provided at an opening end and having a rotor configured to obtain a rotational driving force from a driving means. In order to make the pressure distribution of the outer peripheral surface portion of the rotor uneven, which is sometimes generated, one end is opened in the vicinity of the opening portion for inserting the sleeve into the shaft body and the other is formed on the inner peripheral surface of the housing. A fluid dynamic bearing motor, wherein a fluid passage having an open end is formed.