JPH06137997A - Method for evaluating dynamic pressure gas bearing, its cleaning method, and dynamic pressure gas bearing - Google Patents

Abstract

PURPOSE:To provide a method for evaluating dynamic gas bearing for improving reliability regarding the performance and durability of dynamic pressure gas bearing, a method for cleaning the dynamic gas bearing, and the dynamic pressure gas bearing. CONSTITUTION:A vent hole 4 for communicating the surrounding of the lower part of a fixed shaft 2 with each static pressure generation part 3 generating static pressure around the fixed shaft 2, is formed in the fixed shaft 2 where a hollow rotator 1 is extermaly engaged with a small space, a pressure sensor 5 is connected to each vent hole 4, and the static pressure of the static pressure generation part 3 when the rotator 1 rotates, is measured by the pressure sensor 5 for evaluation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the performance of a dynamic pressure gas bearing, a method for cleaning a dynamic pressure gas bearing, and a dynamic pressure gas bearing.

[0002]

2. Description of the Related Art In a high speed scanner motor used in a laser printer, as shown in a sectional view of FIG. 5, a rotary body 1 is externally fitted to a fixed shaft 2 with a minute space of, for example, about 30 .mu.m. A gas bearing is used.

An edge cut groove 2a is provided over the entire circumference at an intermediate height portion of the peripheral surface of the fixed shaft 2 of the dynamic pressure gas bearing, and a pair is formed on each of the upper and lower peripheral surfaces of the edge cut groove 2a. Herringbone grooves 2b-2e are formed. The herringbone grooves 2b to 2e forming the upper and lower pairs have a depth of about 5 to 12 μm,
They are inclined in opposite directions with a predetermined interval. When the rotating body 1 is rotated, the air in the minute space is drawn between the upper and lower herringbone grooves 2b to 2e, and the static pressure generating portion 3 around the upper part of the fixed shaft 2 and the static pressure around the lower part. Positive static pressure is generated in the generator 3, and this pressure causes the rotor 1 to rotate.
Are supported by the fixed shaft 2 in a non-contact manner. In addition, the edge cutting groove 2a
Negative static pressure is generated in the static pressure generating portion 3 around.

[0004]

By the way, this dynamic pressure gas bearing is manufactured with dimensional accuracy of micron order according to the theoretically determined design value, and its performance is merely required as the design value. No, the actual performance, that is, the bearing pressure has not been evaluated.

Further, problems such as seizure that occurs in the initial stage of use due to minute machining scraps, corrosion of the inner peripheral surface of the rotating body and the outer peripheral surface of the fixed shaft, abnormal contact due to external force during rotation, seizure, and fluctuation in rotation may occur. However, the product is merely aged for about 120 hours (run-in operation) to determine whether or not these problems occur.

Therefore, the reliability of the performance and durability of the dynamic pressure gas bearing is low, and a fundamental solution for increasing this reliability has not yet been found. The present invention has been made in view of the above circumstances, and is a method for evaluating a dynamic pressure gas bearing, which is capable of enhancing reliability of performance and durability of the dynamic pressure gas bearing, a method for cleaning the dynamic pressure gas bearing, and An object is to provide a dynamic pressure gas bearing.

[0007]

In order to achieve the above-mentioned object, the method for evaluating a dynamic pressure gas bearing according to the present invention has a hollow rotating body 1 with a small space outside as shown in FIG. 1, for example. In the fixed shaft 2 to be fitted, an inverted L-shaped ventilation hole 4 is formed, which connects the respective static pressure generating portions 3 that generate static pressure around the fixed shaft 2 to the periphery of the lower portion of the fixed shaft 2. It is characterized in that a pressure sensor 5 is connected to each vent hole 4 and the static pressure of the static pressure generating portion 3 during rotation of the rotating body 1 is measured and evaluated by the pressure sensor 5.

In order to achieve the above-mentioned object, the method for cleaning a dynamic pressure gas bearing according to the present invention has a hollow rotary member 1 with a small space on a fixed shaft 2 as shown in FIG. In the fixed shaft 2 of the dynamic pressure gas bearing to be fitted, the respective ventilation holes 4 for communicating the respective static pressure generating portions 3 in which static pressure is generated around the fixed shaft 2 with the periphery of the lower portion of the fixed shaft 2 are formed, and the dry clean gas is supplied. Each vent 4
It is characterized in that it is blown out from the lower end to the periphery of the fixed shaft 1.

Further, the dynamic pressure gas bearing of the present invention has a hollow rotation as shown in FIG. 3, for example, in order to be able to carry out the above-described dynamic pressure gas bearing evaluation method and dynamic pressure gas bearing cleaning method. In a dynamic pressure gas bearing including a body 1 and a fixed shaft 2 on which the rotating body 1 is fitted with a small space, each of the static shafts in which static pressure is generated around the fixed shaft 2. An inverted L-shaped ventilation hole 4 that communicates with the lower end surface of the fixed shaft 2 from the peripheral surface of the pressure generating portion 3 through the inside of the fixed shaft 2, and is attached to and detached from the lower end portion of each ventilation hole 4. And a plug 11 for sealing

[0010]

[Operation] According to the dynamic pressure gas bearing of the present invention, when the plug 11 is removed, the pressure sensor 5 is connected to the lower end portion of the vent hole 4,
A dry clean gas can be introduced into the ventilation hole 4. Further, if the vent hole 4 is sealed with the plug 11, the static pressure capacity of each static pressure generating portion 3 is increased by the vent hole 4, and the external force during rotation and the centripetal force during low speed rotation are increased.

According to the method for evaluating a dynamic pressure gas bearing of the present invention, the performance of the dynamic pressure gas bearing can be evaluated by measuring the static pressure of each static pressure generating portion 3 through the ventilation hole 4, and at the development stage. ,
The optimum design value can be obtained based on the evaluation value,
At the production stage, it is possible to inspect whether or not the product satisfies the required performance.

Further, according to the method for cleaning a dynamic pressure gas bearing of the present invention, the dry cleaning gas is blown out into a minute space between the rotating body 1 and the fixed shaft 2 through each ventilation hole 4, whereby the rotating body is rotated. It is possible to dry the surfaces of the fixed shaft 1 and the fixed shaft 2 to prevent them from corroding, and it is possible to discharge minute processing chips from the minute space between the rotating body 1 and the fixed shaft 2.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for evaluating a dynamic pressure gas bearing, a method for cleaning a dynamic pressure gas, and a dynamic pressure gas bearing according to an embodiment of the present invention will be specifically described below with reference to the drawings.

The dynamic pressure gas bearing on which the present invention is based is shown in FIG.
As shown in the cross-sectional view of FIG. 1, a hollow rotating body 1 and a fixed shaft 2 to which the rotating body 1 is externally fitted with a minute space of, for example, about 30 μm placed. The rotating body 1 is a rotor of a high-speed scanner motor used in a laser printer, for example, and rotates at a high speed of about 18,500 to 27,500 rpm. The rotating body 1 and the fixed shaft 2 are made of iron, carbon steel,
Made of magnetic material such as stainless steel.

An edge cutting groove 2a is formed at an intermediate height of the peripheral surface of the fixed shaft 2.
Are recessed over the entire circumference, and herringbone grooves 2b to 2e are formed on the upper side and the lower side, respectively.
The herringbone grooves 2b to 2e forming the upper and lower pairs have a depth of 5 to 5, respectively.
They are about 12 μm and are inclined in opposite directions with a predetermined interval.

When the rotating body 1 is rotated, the air in the minute space is entrained and the upper and lower herringbone grooves 2b-2 are paired.
Guided by e, as shown in FIG. 4, air is gathered between the pair of herringbone grooves 2b and 2c on the upper side and between the pair of herringbone grooves 2b and 2c on the lower side, so that the air flows forward. Static pressure is generated, and this pressure supports the rotating body 1 on the fixed shaft 2 in a non-contact manner. Further, a negative static pressure is generated around the edge cut groove 2b.

As shown in FIG. 1, inside the fixed shaft 2 of this dynamic pressure gas bearing, each static pressure generating portion 3 in which static pressure is generated around the fixed shaft 2 is communicated with the periphery of the lower portion of the fixed shaft 2. The book vent 4 is formed. The shape of each vent hole 4 is not particularly limited, but here, from the peripheral surface of the fixed shaft 2 facing the static pressure generating portion 3 of the fixed shaft 2 so that the vent hole 4 can be easily formed by drilling. It is formed in an inverted L shape reaching the lower surface.

It is also possible to form the ventilation hole 4 in a U-shape so that the lower end of the ventilation hole 4 opens to the peripheral surface of the fixed shaft 2. As shown in FIG. 2, a compressor 9 is connected to the lower end of the vent hole 4 via a filter 6, a flow rate control valve 7 and a cooler 8, and is pressurized by the compressor 9 and dehumidified by the cooler 8 and the filter 6 The dry clean air dedusted in (1) is blown out to each static pressure generating portion 3 through each ventilation hole 4, and water and dust are discharged from the ventilation hole 4 and the minute space between the rotating body 1 and the fixed shaft 2.

As a result, it is possible to prevent the surfaces of the rotating body 1 and the fixed shaft 2 from being dried and causing corrosion for a long period of time. Further, by discharging the dust from the ventilation hole 4 and the minute space between the rotary body 1 and the fixed shaft 2, it is possible to prevent the rotary wear from being induced by the dust at the initial stage of rotation,
It is possible to prevent seizure due to rotating abrasion powder generated at the initial stage of rotation. Further, since such seizure can be prevented, the rotation stop frequency of the rotating body 1 can be increased during age running,
The age running time can be shortened to, for example, about 1 hour, and the reliability of the durability of the product can be improved.

After the dynamic pressure gas bearing is cleaned by the above procedure, as shown in FIG. 1, the pressure sensors 5 are screwed into the respective vent holes 4, and these pressure sensors 5 are attached to the pressure indicator 10. The pressure of each static pressure generating part 3 is measured (for example, samples No. 1 to No. 6 in FIG. 4), and the performance of the dynamic pressure gas bearing is evaluated.

At the development stage, the optimum design value can be obtained based on this evaluation, and the optimum dimension value and the optimum dimension accuracy can be obtained by additional machining. At the production stage, the required performance is based on this evaluation. It is possible to check whether or not is satisfied. In addition, by frequently stopping the rotation of the rotating body 1 for about one hour while performing this inspection, sufficient age running can be completed.

As described above, the optimum design value, the optimum dimensional value, the optimum dimensional accuracy, etc. for actually satisfying the required performance are obtained, and after confirming that the actual product satisfies the required performance, the product is put on the market. The reliability of the product performance can be significantly increased.

After removing the pressure sensor 5 from each of the vent holes 4 of the fixed shaft 2 which has been subjected to these performance evaluations, each vent hole 4 is sealed with a plug 11 as shown in FIG. Since each vent hole 4 sealed by the plug 11 communicates with each static pressure generating portion 3,
Each vent hole 4 increases the static pressure capacity of each static pressure generating portion 3, thereby increasing the external force during rotation and the centripetal force during low speed rotation. As a result, abnormal contact, seizure, and rotation speed fluctuation during rotation are less likely to occur, and durability can be improved.

In this embodiment, the plug 11 is extended to the vicinity of the bent portion of each vent hole 4, and the magnet 12 is supported at its tip end so as not to contact the peripheral surface of the vent hole 4. Magnet 12
The diameter may be about 0.5 to 1 mm, and the gap between the magnet 12 and the peripheral surface of each vent hole 4 may be about 0.5 mm or more.

The magnet 12 sucks and captures wear particles generated by the contact between the rotating body 1 and the fixed shaft 2 which are rotating, into the air holes 4, and captures them. Delays the progress of wear on the outer peripheral surface. As a result, seizure, rotation abnormality, and rotation speed fluctuation are less likely to occur over a long period of time, and durability is further enhanced.

[0026]

As described above, according to the dynamic pressure gas bearing of the present invention, the cleaning method of the dynamic pressure gas bearing of the present invention can be carried out by removing the plug and feeding the dry clean gas into the ventilation hole. . Further, the method for evaluating a dynamic pressure gas bearing of the present invention can be implemented by removing the plug and connecting the pressure sensor to the ventilation hole.

Moreover, according to the dynamic pressure gas bearing of the present invention,
Closing the vent with a plug increases the static pressure capacity by the vent, increasing external force during rotation and centripetal force during low-speed rotation, which causes abnormal contact during rotation, seizure, and fluctuations in rotational speed. It becomes difficult and durability can be improved.

According to the method for cleaning a dynamic pressure gas bearing of the present invention, water can be removed from the ventilation hole, the inner peripheral surface of the rotating body, and the peripheral surface of the fixed shaft. Corrosion of the outer peripheral surface of the fixed shaft can be prevented, and durability can be improved. Further, since dust in the ventilation hole and between the rotating body and the fixed shaft can be removed, contact wear powder is less likely to be generated in the initial stage of rotation, and seizure, abnormal wear, etc. can be prevented. Further, since it is possible to prevent the occurrence of seizure and abnormal wear in the initial stage of rotation, it is possible to increase the frequency of rotation stop of the rotating body and shorten the age running time.

According to the dynamic pressure gas bearing evaluation method of the present invention, the performance can be evaluated by measuring the actual static pressure of the product with the pressure sensor. Therefore, at the development stage, the optimum design value,
It is possible to obtain the optimum dimensional value, the optimum dimensional accuracy, etc., and at the production stage, it is possible to inspect whether the required performance is satisfied, and it is possible to remarkably improve the durability of the shipped product and the reliability of the performance. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a dynamic pressure gas bearing and an evaluation method thereof according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a dynamic pressure gas bearing and a cleaning method thereof according to an embodiment of the present invention.

FIG. 3 is a sectional view of a dynamic pressure gas bearing according to an embodiment of the present invention.

FIG. 4 is a pressure distribution diagram showing a pressure distribution around a fixed shaft of the present invention.

FIG. 5 is a cross-sectional view of a conventional dynamic pressure gas bearing.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 Rotating body 2 Fixed shaft 3 Static pressure generating part 4 Vent hole 5 Pressure sensor 11 Plug 12 Magnet

Claims (5)

[Claims] 1. A static pressure generating part (1) in which a static pressure is generated around a fixed shaft (2) into which a hollow rotating body (1) is fitted with a minute space. 3) Form a vent hole (4) that connects the lower part of the fixed shaft (2) to the periphery of the fixed shaft (2), connect a pressure sensor (5) to each vent hole (4), and rotate the rotating body (1) Static pressure generation part
A method for evaluating a dynamic pressure gas bearing, characterized in that the static pressure of (3) is measured and evaluated by a pressure sensor (5). 2. A hydrostatic gas bearing fixed shaft (2) in which a hollow rotating body (1) is fitted onto a fixed shaft (2) with a small space therebetween. Attach the pressure generator (3) to the fixed shaft (2)
Inverted L-shaped ventilation holes (4) communicating with the lower part of the ventilation hole (4) are formed, and dry clean gas is fed from the lower end of each ventilation hole (4) to the fixed shaft (2).
A method for cleaning a dynamic pressure gas bearing, characterized in that it is blown out to the surroundings. 3. A dynamic pressure gas bearing comprising a hollow rotating body (1) and a fixed shaft (2) to which the rotating body (1) is externally fitted with a small space, the fixed shaft (2) Is a reverse pressure that communicates from the peripheral surface of the static pressure generating part (3) where static pressure is generated around the fixed shaft (2) through the inside of the fixed shaft (2) to the lower end surface of the fixed shaft (2). L-shaped ventilation holes (4)
And a plug (11) which is attached to and detached from the lower end of each vent hole (4) and seals each vent hole (4). 4. The dynamic pressure gas bearing according to claim 3, wherein a magnet (12) is arranged at a bent portion of each vent hole (4). 5. The dynamic pressure gas bearing according to claim 4, wherein a magnet (12) is supported by the plug (11).