JP2005273908A - Method and device for filling lubricant into dynamic pressure bearing device and method of filling liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant filling method capable of accurately filling a proper amount of lubricant when the lubricant is filled in the clearances of the bearings of a dynamic pressure bearing device by using a nozzle and preventing the surface of the bearing unit from being contaminated by splashing. <P>SOLUTION: The concentration of gases mixed in the lubricant is lowered by an deaerating treatment, and the proper amount of the lubricant is filled in the clearances of the bearings put in a reduced pressure atmosphere. In this case, the lubricant is filled at a pressure higher than a pressure in the deaerating treatment. After filling the lubricant, the pressure is recovered to push the lubricant to the bottoms of the clearances of the bearings. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid injection method for pouring a predetermined amount of liquid into a specific part such as a mechanical device under a reduced pressure environment. In particular, the present invention relates to a method for filling a fluid dynamic bearing device used in a signal recording / reproducing apparatus such as a hard disk drive with a lubricating liquid. Furthermore, it is related with the filling apparatus used for this filling operation | work.

(1) Structure of dynamic pressure bearing device Various types of fluid dynamic pressure bearings have been conventionally used for spindle motors used in signal recording / reproducing devices such as hard disk drive devices. A fluid dynamic pressure bearing is a bearing in which a lubricating fluid such as a lubricating liquid is interposed between a shaft and a sleeve, and the fluid pressure generated in the lubricating fluid has a supporting force.

  An example of a spindle motor using such a hydrodynamic bearing device is shown in FIGS. 10A and 10B.

  In the hydrodynamic bearing device 5 mounted on the spindle motor of FIG. 10A, the taper seal portion 53 of the lubricating liquid is formed only at one place. The shaft 51 has a sleeve 52 inserted therein, and a radial load is supported by the radial dynamic pressure bearings 55 and 55. A thrust plate 56 is attached to the tip of the shaft 51, and axial loads are supported by thrust dynamic pressure bearings 58, 58 formed there. The bottom of the sleeve 52 is closed by a thrust bush 57, and the bearing gap from the lubricating liquid interface 53 to the tip of the shaft is filled without being interrupted by the lubricating liquid. The open part where the bearing gap is connected to the outside air is only on the upper side, and the tapered seal part 53 is formed there.

  In such a structure, the area where the lubricating liquid comes into contact with the outside air is small, bubbles are not easily mixed in the lubricating liquid, and the lubricating liquid is not easily vaporized, and the reliability is high. However, in order to inject the lubricating liquid, it is necessary to exhaust the air in the bearing gap in advance, and equipment for that is required.

  The hydrodynamic bearing device 5 ′ mounted on the spindle motor of FIG. 10B has two opening portions of the bearing gap in the vertical direction, and two tapered seal portions 53 and 53 in the vertical direction. Such a structure is useful because the central fixed shaft can be used as, for example, a support for supporting the housing of the hard disk, although the evaporation of the lubricating liquid is slightly accelerated.

  When injecting the lubricating liquid, for example, if the lubricating liquid is injected into the upper taper seal portion, the bearing gap gradually expands downward due to capillary action, and the air is discharged from the lower side. However, the shape of the bearing gap is complicated, and a slight difference in the gap causes a difference in the penetration of the lubricating liquid, resulting in unevenness. For this reason, even in this structure, it is necessary to discharge the air in the bearing gap in advance.

  As a result, unless the structure is such that the air inside the gap is easily discharged, the hydrodynamic bearing device needs to exhaust the bearing gap when filling the lubricating liquid.

(2) Known filling method and its problems As a method of injecting lubricating liquid after exhausting air that fills the bearing gap to the hydrodynamic bearing device such as 5 or 5 'described above, for example, There are various methods.

(2-1) First method One is to place a bearing device and a container filled with a lubricating liquid in a vacuum container, and evacuate the inside of the container, so that the open part of the bearing gap is immersed in the lubricating liquid. Alternatively, after being submerged in the lubricating liquid, air is introduced into the vacuum vessel to restore the pressure. This method is disclosed in Patent Document 1, for example. Due to the atmospheric pressure applied by the return pressure, the lubricating liquid is surely pushed into the back of the bearing gap.

  This method can be realized with relatively simple equipment, but the lubricating liquid adheres to the outside of the bearing device. In particular, when it is mounted on a hard disk drive, if the lubricating liquid adheres to the outside of the bearing device, it causes contamination of the disk. For this reason, a process of carefully wiping off the adhering lubricant is required, which greatly impairs productivity. When the shaft head has a screw hole for fixing the disc clamper, the lubricant enters the screw hole and the screw groove. It is extremely difficult to remove the lubricating liquid that has entered such a narrow portion.

(2-2) Second method As another method, in a state where the bearing device is evacuated in a vacuum vessel, a lubricating liquid is used in a bearing gap opening portion or a taper seal portion by using a cylindrical thin tube such as a thin injection needle. This is a method of dropping and then restoring the pressure. This method is disclosed by Fig. 1 of Patent Document 2 and the description of the relevant part of the text.

  If this method is used, it is expected that the step of wiping off the lubricant adhering to the outside of the bearing device can be omitted, but in reality, it does not always work well. This is because when the lubricating liquid is discharged from the needle tip, the lubricating liquid often foams and bursts at the needle tip, and the outside of the bearing device is contaminated by the splash.

  In order to eliminate foaming, it seems that the air previously dissolved in the lubricating liquid should be sufficiently removed. However, in practice, even if the deaeration treatment is performed, foaming occurs, and it is difficult to eliminate contamination outside the bearing device.

(3) About use of a dispenser In order to inject a predetermined amount into a place where a small amount of liquid is aimed, a dispenser has been used conventionally. The dispenser is most simply composed of a nozzle having a small inner diameter and a mechanism for feeding liquid into the nozzle. An industrially used dispenser is composed of a nozzle part, a mechanism for applying a delivery pressure to liquid, a valve mechanism for controlling the outflow of liquid, a mechanism for electrically controlling a series of operations, and the like. ing. An example of such a dispenser is disclosed in Patent Document 3.

  However, it is not always easy to accurately pour a predetermined amount of liquid onto a part placed under vacuum or a mechanical device using such a dispenser. This is because, unlike when working under atmospheric pressure, in a reduced pressure environment, even if an attempt is made to stop the injection by closing the valve, it does not stop immediately. Under atmospheric pressure, if the valve is closed, it is held down by atmospheric pressure, and no more liquid flows out, whereas in a reduced pressure environment, the force is weakened and the liquid continues to flow out due to inertia. Also, under reduced pressure, the outflow speed of the liquid also increases, and as a result of hitting the target to be injected vigorously, it will be splashed and splashed, the amount of liquid injection is insufficient, or even the part where the liquid does not want to adhere Troubles such as sticking occur.

  In order to eliminate such troubles, it is necessary to inject the lubricant sufficiently slowly. This requirement increases the time required for a single injection and impairs productivity.

  Thus, conventionally, there has been no known injection method that can accurately inject a predetermined amount of liquid, does not contaminate the surroundings, and has high productivity.

Japanese Patent Laid-Open No. 2002-213453 US Pat. No. 5,778,948 JP 2001-165153 A

  An object of the present invention is to provide a liquid injection method for pouring a predetermined amount of liquid into a specific part such as a mechanical device in a reduced pressure environment. In particular, the object is to provide a method of filling a lubricating fluid into a hydrodynamic bearing device used in a signal recording / reproducing apparatus such as a hard disk drive. Furthermore, it is providing the filling apparatus used for this filling operation | work.

  In order to solve the problem of the preceding paragraph, the invention of claim 1 of the present application includes a rotating portion, a fixed portion that supports the rotating portion so as to be relatively rotatable, and a bearing held between the rotating portion and the fixed portion. By feeding the lubricating liquid toward the open portion using a nozzle to a hydrodynamic bearing device having a gap and at least one open portion that is formed at one end of the bearing gap and surrounds the rotating portion and faces the outside air, A method of filling a bearing gap with a lubricating liquid, wherein the concentration of a gas dissolved in the lubricating liquid is reduced to a first concentration that is a concentration approximately equilibrated with a gas atmosphere at a predetermined first pressure. Deaeration process, pressure adjustment process in which the atmosphere of the open part is a second pressure that is higher than the first pressure and lower than the atmospheric pressure, and is opened using a nozzle in the atmosphere realized by the pressure adjustment process And a lubrication process for pouring the lubricating liquid after the deaeration process Providing lubricating liquid filling method for the apparatus.

  In order to solve the problem of the preceding paragraph, the invention of claim 2 of the present application includes a rotating portion, a fixed portion that rotatably supports the rotating portion, and a bearing held between the rotating portion and the fixed portion. By feeding the lubricating liquid toward the open portion using a nozzle to a hydrodynamic bearing device having a gap and at least one open portion that is formed at one end of the bearing gap and surrounds the rotating portion and faces the outside air, A method of filling a bearing gap with a lubricating liquid, in which the atmosphere in the open part is dissolved in the open part using a nozzle in a pressure adjusting process in which the second pressure is used and the atmosphere realized by the pressure adjusting process. There is provided a method of filling a fluid dynamic bearing device with a lubricating liquid, which comprises a step of pouring a lubricating liquid having a first concentration that is lower than a concentration at which a gas concentration is balanced with a second pressure.

  In order to solve the problem of the preceding paragraph, the invention according to claim 3 of the present application provides a method of filling the fluid dynamic bearing device with the lubricating liquid, wherein the deaeration step is a step of exposing the lubricating liquid to an atmosphere of the first pressure. To do.

  In order to solve the problem of the preceding paragraph, the invention of claim 4 of the present application includes a rotating portion, a fixed portion that rotatably supports the rotating portion, and a bearing held between the rotating portion and the fixed portion. By feeding the lubricating liquid toward the open portion using a nozzle to a hydrodynamic bearing device having a gap and at least one open portion that is formed at one end of the bearing gap and surrounds the rotating portion and faces the outside air, A method for filling a bearing gap with a lubricating liquid, and storing a lubricating liquid having a volume smaller than the capacity of the internal space in an internal space of the lubricating liquid tank having an internal space that is airtight to the outside. And evacuating the cavity remaining inside the lubricating liquid tank to the first pressure, exposing the lubricating liquid to the first pressure atmosphere, and the atmosphere of the open portion, and the atmosphere of the open portion more than the first pressure. By the pressure adjustment process that makes the second pressure higher than the atmospheric pressure, and the pressure adjustment process Under the expressed atmosphere, the cavity portion is increased to a pressure higher than the second pressure to apply a delivery pressure to the lubricating liquid, and through a nozzle communicating with the region where the lubricating liquid inside the lubricating liquid tank is stored, There is provided a method of filling a fluid dynamic bearing device with a lubricating liquid, which comprises an oiling step of pouring a lubricating liquid into an open portion.

  In order to solve the above-mentioned problem, in the invention of claim 5 of the present application, the hydrodynamic bearing device has only one open portion, and the bearing gap communicates with the outside air only through the open portion. Provided is a method of filling a lubricating liquid into

  In order to solve the problem of the preceding paragraph, in the invention of claim 6 of the present application, the lubrication step is executed once or a plurality of times with a predetermined interval, and once or a plurality of times The total amount of the lubricating liquid poured from the nozzle in the oiling process is approximately equal to an appropriate amount to be retained by the bearing device.

  In order to solve the problem of the preceding paragraph, in the invention of claim 7 of the present application, after performing the oiling step at least once, the atmosphere in the open portion is restored to a third pressure higher than the second pressure. There is provided a method for filling a fluid dynamic bearing device with a lubricating liquid, which includes a pressure step.

  In order to solve the problem of the preceding paragraph, in the invention of claim 8 of the present application, with respect to the hydrodynamic bearing device filled with the lubricating liquid, the atmosphere of the bearing gap opening portion is placed in a pressure environment larger than the atmospheric pressure in the lower stratosphere, In that state, the position of the filled lubricating liquid interface is measured to make it the first interface height, and then the atmosphere of the open portion is equal to or lower than the atmospheric pressure of the lower stratosphere, and the second In this state, the position of the filled lubricating liquid interface is measured and this is set as the second interface height, and the second interface height and the first pressure are adjusted to be the fourth pressure. The dynamic pressure bearing device inspection method is to eliminate the hydrodynamic bearing device as a defective product when the difference in interface height between the two becomes a predetermined value or more, and to make it non-defective when it is less than the predetermined value. I will provide a.

  In order to solve the above-mentioned problem, the invention of claim 9 of the present application is directed to a lubricating liquid, one or more evacuation devices, one or more gas introduction sources, and an outside. A lubricating liquid tank having an internal space that keeps hermeticity, storing a volume of lubricating liquid smaller than the capacity of the internal space, and connecting the vacuum exhaust device and the gas introduction source to a hollow portion not filled with the lubricating liquid; , Connected to one end side of the internal space filled with the lubricating fluid, piping, connected to the other end of the piping, connected to the valve mechanism on one end side, and the other end side pointed A lubricating liquid comprising: a nozzle; and a vacuum vessel capable of accommodating at least a nozzle tip portion and at least a bearing gap opening portion of the hydrodynamic bearing device, and connected to a vacuum exhaust device and a gas introduction source. A filling device is provided.

  In order to solve the problem of the preceding paragraph, the invention of claim 10 of the present application is directed to a lubricating liquid introducing mechanism capable of introducing a lubricating liquid dropwise from the outside of the lubricating liquid tank to the inside under a condition where the cavity is decompressed. A lubricating liquid filling device is provided.

  In order to solve the above-mentioned problem, the invention according to claim 11 of the present application is that the lubricating liquid tank includes a stirring mechanism for stirring the lubricating liquid, and the stirring mechanism is in a state where the space portion in the lubricating liquid tank is decompressed. Thus, a lubricating liquid filling device capable of stirring the lubricating liquid inside the lubricating liquid tank is provided.

  In order to solve the above-mentioned problem, the invention according to claim 12 of the present application is that the valve mechanism closes at least one of the flow paths of the lubricating liquid from one end of the pipe to the tip of the nozzle, The closed portion that does not allow distribution is formed, and by forming and eliminating the closed portion, an open state that allows the passage of the lubricating liquid and a closed state that blocks the passage of the lubricating liquid. One state is created, and can be controlled to be shut off after being opened for a predetermined time. The time required for the shut-off operation is sufficiently larger than the open time required for one lubricant feeding operation. A short and substantially negligible lubricating fluid filling device is provided.

  In order to solve the above-mentioned problem, the invention according to claim 13 of the present application is characterized in that the valve mechanism is formed in the valve base and the valve base, extends in one direction, and opens at the end on one side. And a cover rod, which is inserted in the supply hole so as to be movable in one direction and in the opposite direction, and has a gap through which the liquid can flow in the axial direction between the supply hole and the supply hole opening. The cap is fixed to the valve base, and the gap between the peripheral edge of the supply hole opening and the reverse direction surface is kept airtight, and the cap is open to the reverse direction surface of the cap part. The obstruction hole and the obstruction rod are driven in the longitudinal direction of the obstruction rod, and the end of the obstruction rod in one direction is obstructed, at the position where the obstruction is formed by sealing the periphery by the end portion by displacing in the direction side Extruding towards the hole, pressing the end of the blocking rod against the periphery of the blocking hole to create a closed state, And a blocking rod drive mechanism that can be driven in the opposite direction to create an open state of the blocking hole, and the nozzle is attached in a form protruding from one direction surface of the cap portion, and the proximal end side of the nozzle Is fixed in an embedded manner in a unidirectional surface of the cap portion, and the cavity inside the nozzle provides a lubricating liquid filling device in which the base portion is continuous with the closing hole.

  In order to solve the problem of the preceding paragraph, the invention according to claim 14 of the present application provides a lubricating liquid filling method in which the volume of the flow path from the closed portion to the tip of the nozzle is substantially equal to the volume inside the nozzle.

  In order to solve the problem of the preceding paragraph, a fifteenth aspect of the present invention provides a valve base, a supply hole formed on the valve base, extending in one direction, and opening at an end on one side, and a supply hole It is housed inside the supply hole so that it can move in one direction and in the opposite direction, and has a gap through which the liquid can flow, and is fixed to the valve base covering the supply hole opening. The cap hole, which is fixed between the opening of the supply hole and the periphery of the opening, faces the valve base of the cap part, the nozzle attached to protrude from the cap part to one side, and the cap part. Opening at the site, displacing the one end of the closing rod in one direction, the periphery is sealed by the end to form the closing portion, and the blocking is continuous to the proximal end side of the nozzle Drive the hole and the closing rod in one direction and the opposite direction to move at least two positions In one position, the end on one side of the closing rod is pressed against the periphery of the closing hole to close the closing hole, and in one position, the end on one side of the closing rod is There is provided an injection device comprising: a closing rod driving mechanism which allows a liquid to flow while being separated from the periphery of the closing hole.

  In order to solve the problem of the preceding paragraph, the invention of claim 16 of the present application is a liquid injection method in which a predetermined amount of liquid is poured into a target member in a reduced pressure environment using a cylindrical capillary tube nozzle. A pressure adjusting step of placing the target member and the tip of the cylindrical thin tube under a reduced pressure environment, and supplying the lubricating liquid with a pressure higher than the pressure under the reduced pressure environment by a delivery pressure to the cylindrical thin tube, There is provided a liquid injection method comprising a liquid injection step of flowing out from a tip of a thin tube toward a target member for a predetermined time and satisfying Formula 1.

  In order to solve the problem of the preceding paragraph, the invention of claim 17 of the present application provides a liquid injection method in which the liquid injection method further satisfies Formula 2.

  In order to solve the problem of the preceding paragraph, in the invention of claim 18 of the present application, the cylindrical thin tube is supplied with liquid from the liquid supply mechanism, and a valve mechanism is provided between the lubricating liquid supply mechanism and the cylindrical thin tube. The valve mechanism has an occlusion portion adjacent to the base portion of the cylindrical thin tube, and the occlusion portion provides a liquid injection method capable of blocking and opening the flow path.

  In order to solve the problem of the preceding paragraph, the invention of claim 19 of the present application provides a liquid injection method using atmospheric pressure as a pressure source for applying a delivery pressure.

  In order to solve the problem of the preceding paragraph, the twentieth invention of the present application is that the valve mechanism is within the time necessary for switching the flow path from closed to open, or within the time required to switch from open to closed. The amount of liquid flowing out from the cylindrical tube is negligibly small compared to the target supply amount, and a liquid injection method is provided to control the supply amount by adjusting the length of the opening time of the valve mechanism. To do.

  In order to solve the problem of the preceding paragraph, in the twenty-first invention of the present application, the target member includes a rotating part, a fixing part that supports the rotating part relatively rotatably, and a gap between the rotating part and the fixing part. A hydrodynamic bearing device having a retained bearing gap and at least one open portion that is formed at one end of the bearing gap and surrounds the rotating portion and faces the outside air. A liquid injection method is provided which is a lubricating liquid retained by the liquid.

(1) Regarding Invention Regarding Filling Method of Lubricating Fluid According to the filling method of the present invention, when lubricating fluid is lubricated to the open portion of the gap end portion of the hydrodynamic bearing under reduced pressure, the pressure near the nozzle tip is slightly It is characterized by enhancing. The pressure should just be higher than the pressure at the time of degassing the lubricating liquid.

  In the conventional injection method, the inside of the vacuum vessel in which the lubricating liquid is injected is evacuated as much as possible to reduce the pressure. This seems to be a natural action, but it is not indispensable for lubrication. The first reason for exhausting the bearing gap is that the air in the gap refuses to enter the lubricating liquid. However, when the pressure in the bearing gap is less than about 1000 Pa, the surface tension of the lubricating liquid is calculated to overcome the pressure of the remaining gas and penetrate into the bearing gap. Therefore, if the lubricating liquid is simply filled, there is little need to reduce the pressure below this level.

  Actually, it is difficult to evacuate the narrow bearing gap, and the pressure is less likely to decrease than the open portion of the gap. Therefore, it is necessary to further reduce the pressure in the vacuum vessel. Further, since the less air remaining in the bearing gap, the better, the working conditions for reducing the pressure as much as possible were selected.

  However, for example, below 100 Pa, the volume of remaining air is reduced to 1/1000 when the pressure is returned to normal pressure. Even if it exhausts more than this, the effect of reducing a residual gas is few. On the other hand, at such a low pressure, when the lubricating liquid is injected, an undesired phenomenon occurs that the supplied lubricating liquid foams and scatters at the tip of the cylindrical thin tube.

  According to the study by the present inventors, such a foaming phenomenon occurs when the pressure in the vacuum vessel for performing the oiling operation is lower than the pressure inside the lubricating liquid tank when the lubricating liquid is deaerated. Therefore, in the present invention, the pressure in the vacuum vessel is slightly higher than the pressure during the deaeration process. In this way, foaming can be suppressed. As described above, if the pressure is about 1000 Pa or less, it is possible to fill the hydrodynamic bearing device with the lubricating liquid even if the pressure in the vacuum vessel is increased.

  The lubricant can be degassed by exposure to a reduced pressure environment, but it is not essential to always expose to a reduced pressure environment. In short, it is sufficient that when the lubricating liquid flows out from the nozzle tip, the dissolved gas concentration of the lubricating liquid is sufficiently lowered as compared with the pressure in the vacuum vessel so that foaming does not occur. Therefore, after deaeration by exposure to a reduced pressure environment, the pressure of the container used for deaeration may be temporarily increased to apply an extrusion pressure to the lubricating liquid. This is because even if the pressure in the lubricating liquid tank is increased, the concentration of the gas dissolved in the lubricating liquid does not increase immediately. Further, the deaeration method is not limited to stirring in a reduced pressure environment.

  As a method of applying pressure to the lubricating liquid, a method of applying pressure due to a difference in height at a high position in the lubricating liquid tank may be considered. However, a higher pressure delivery pressure can be stably applied by increasing the pressure in the lubricating liquid tank.

  According to the filling method of the present invention, it is possible to fill the hydrodynamic bearing device as shown in FIG. 10A with only one opening portion of the bearing gap.

  In the filling method of the present invention, since the lubricating liquid can be injected in a plurality of times, the required amount of lubricating liquid can be filled even when the required amount of lubricating liquid cannot be injected into the bearing gap opening portion at once.

  In the filling method of the present invention, the lubricating liquid is injected into the bearing gap opening, and then the inside of the vacuum vessel is increased to the third pressure, so that the lubricating liquid can be surely pushed into the back of the bearing device. In addition to performing the lubrication process a plurality of times, the pressure increasing process can be performed a plurality of times. The third pressure in this case must be a pressure that can overcome the surface tension of the lubricating liquid. As described above, the standard is 1000 Pa.

  The inspection method of the present invention confirms that problems such as overflow of the lubricating liquid do not occur in the atmospheric pressure environment in the lower stratosphere of the hydrodynamic bearing filled with the lubricating liquid by the method belonging to the present invention. For this reason, it can be assured that no trouble occurs in the bearing device even when transported by an international aircraft flying in the lower stratosphere region.

(2) About the invention related to the lubricating liquid filling apparatus The manufacturing apparatus of the present invention used for filling the fluid dynamic pressure bearing device with the lubricating liquid includes a lubricating liquid tank filled with the lubricating liquid up to the middle of the inside, It consists of a vacuum vessel for placing the hydrodynamic bearing device in a reduced pressure environment, a nozzle for pouring the lubricating liquid into the bearing device, and a vacuum exhaust system for exhausting and returning the pressure inside the lubricating liquid tank and vacuum vessel. ing.

  In this filling device, the air dissolved in the lubricating liquid can be removed by reducing the pressure in the cavity of the lubricating liquid tank. On the other hand, by pressurizing the hollow portion, pressure can be applied to the lubricating liquid to push it out from the nozzle tip. That is, the function of both the deaeration tank for performing the deaeration process of the lubricating liquid and the pressure container for pressurizing and extruding the lubricating liquid is realized by one vacuum container. Furthermore, since the internal pressure of the vacuum container that fills the lubricating liquid can be freely controlled, foaming of the lubricating liquid during lubrication can be suppressed.

  In addition, this filling device can introduce the lubricating liquid dropwise into the lubricating liquid tank. Since the degassing from the lubricating liquid is promoted by the impact and droplet formation at the time of dropping, the dissolved gas concentration in the lubricating liquid can be efficiently reduced.

  This filling device includes a lubricating liquid stirring mechanism in the lubricating liquid tank, and can efficiently reduce the concentration of dissolved gas in the lubricating liquid.

  In this filling device, the valve mechanism for controlling the lubrication has only two states of closing and opening, and switching is quick. Since there are only two states of the valve mechanism, the control is simple, and the delivery amount can be controlled only by the length of the opening time.

  In this filling apparatus, since the valve closing portion is located adjacent to the base portion of the nozzle, the capacity from the closing position to the nozzle tip is minimized. For this reason, there is substantially no place where bubbles accumulate between the closed portion and the tip of the nozzle. When repeatedly depressurizing and restoring the vacuum vessel, if there is a part where air bubbles are first formed from the closed part, the lubricating liquid remaining in the nozzle part will blow out, contaminating the device and the hydrodynamic bearing device. It may end up. However, if this valve mechanism is used, such troubles can be reduced.

(3) Invention relating to nozzle In the liquid injection method of the present invention, a cylindrical capillary having a constant inner diameter is used as the nozzle, and various sizes and delivery pressures are selected according to the following equations 1 and 2.

数式２：

円筒細管から流出する液体には、先端部で表面張力によって制動を受ける。表面張力による制動が、液体が持つ運動量を上回る条件を、数式１は表している。数式１が満足される場合、円筒細管先端から流れ出る液体は、この条件下では円筒細管先端で速度を失い、狙った場所を越えて飛び散ったりすることがない。また、円筒細管への液体の供給を止めると同時に、液体の流出が止まるため、液体の流出量の制御が容易かつ高精度となる。数式１が満足されない場合は、液体の供給を止めても、細管内部に残る液体が慣性のために流れ出続けるため、流出量の制御は困難になる。 Formula 1:

Formula 2:

The liquid flowing out from the cylindrical thin tube is braked by the surface tension at the tip. Formula 1 expresses the condition that the braking by the surface tension exceeds the momentum of the liquid. When Equation 1 is satisfied, the liquid flowing out from the tip of the cylindrical thin tube loses speed at the tip of the cylindrical thin tube under this condition, and does not scatter over the target location. Further, since the supply of the liquid to the cylindrical thin tube is stopped and the outflow of the liquid is stopped, the control of the outflow amount of the liquid becomes easy and highly accurate. If Equation 1 is not satisfied, even if the supply of the liquid is stopped, the liquid remaining inside the narrow tube continues to flow out due to inertia, so that it is difficult to control the outflow amount.

  In the present invention, it is assumed that the tip of the cylindrical thin tube and the liquid injection target are in a reduced pressure environment, but the pressure is not zero. When injecting a liquid such as a lubricating liquid, the injecting operation is performed at a pressure of about 100 Pa or less. Therefore, if the speed at which the lubricating liquid flows out is sufficiently slow with respect to this pressure, the outflow is stopped only by that pressure. However, such a condition is a situation where the injection rate is excessively low and the productivity is low.

  Formula 2 gives a lower limit to the right side of Formula 1 from this viewpoint. Make this greater than zero. That is, a condition for supplying the liquid at a high speed is given to such an extent that the outflow of the liquid cannot be stopped without braking by the surface tension.

  In the liquid injection method of the present invention, a valve mechanism can be used to allow the liquid to flow out for a predetermined time. In the valve mechanism, since the closed portion of the flow path is adjacent to the cylindrical thin tube base, there is no useless space between the closed portion and the tip of the cylindrical thin tube. For this reason, the start and stop of the outflow of the liquid respond more reliably to the on / off switching of the liquid injection operation by the valve mechanism. Further, since there is no useless space, there is no part where bubbles accumulate in the middle of the path from the valve mechanism to the tip of the cylindrical thin tube. This also ensures control of the liquid injection operation.

  In the liquid injection method of the present invention, the liquid injection process may be performed by applying atmospheric pressure to the liquid. Since atmospheric pressure is a pressure source that is inexpensive and can obtain a relatively stable pressure, it is possible to perform highly accurate liquid injection work while suppressing equipment costs.

  The liquid injection method of the present invention may use a valve mechanism that responds sufficiently quickly to the liquid injection speed. It is possible to further reduce the error in the amount of liquid that is introduced and stopped.

  In the liquid injection method of the present invention, a lubricating liquid is injected into the hydrodynamic bearing device. Since the lubrication operation can be performed with high accuracy under a reduced pressure environment, the lubricating liquid can be efficiently injected into the hydrodynamic bearing device.

(1) Lubricating liquid filling apparatus (1-1) Overall apparatus FIG. 1 shows a lubricating liquid filling apparatus 1 for carrying out a lubricating liquid filling method according to the present invention. The lubricating liquid filling apparatus 1 includes a vacuum vessel 2, an injection apparatus 3, a lubricating liquid tank 4, and a vacuum exhaust apparatus, a gas introduction mechanism R, and a pipe connecting them for depressurizing the inside thereof. Yes.

  Here, a general rotary pump P is used as the vacuum exhaust device. The gas introduction mechanism R includes a flow rate adjusting valve W and a filter for preventing dust from entering, and introduces air around the apparatus. By adjusting the flow rate adjustment valve W so that the inflow speed of the gas does not become excessively large, the intrusion of dust can be prevented more reliably. GB1 and GB2 are Penning vacuum gauges, and can monitor the pressure inside the vacuum vessel 2 and the lubricating liquid tank 4.

  The injection device 3 includes a valve mechanism 30 for controlling the outflow of the lubricating liquid and a cylindrical thin tube 32 attached to the tip of the valve mechanism. The injection device 3 is connected to the bottom of the lubricating liquid tank 4 through a pipe. The hydrodynamic bearing device 5 is placed inside the vacuum vessel 2 and injected with a lubricating liquid supplied from the tip of the cylindrical thin tube 32.

  The vacuum vessel 2 has a glass covered cylindrical shape with an opening on the lower side, and the internal state can be observed from the outside. In FIG. 1, the lower opening is closed by a base 21. The closed portion is kept airtight by a rubber O-ring (not shown). The vacuum vessel 2 is connected to the rotary pump P and the gas introduction mechanism R through the ventilation valves V and W.

  FIG. 2 shows the lubricating liquid tank 4 and the injection device 3. In FIG. 2A, a space 45 is left in the upper part of the lubricating liquid tank 4, and the concentration of the gas dissolved in the lubricating liquid can be lowered by reducing the pressure of this part. In addition, a pipe 42b is connected to this part, and the space portion is decompressed and pressurized through this part. At the time of decompression, the stirring mechanism is operated to promote the reduction of the gas concentration dissolved in the lubricating liquid. The stirring mechanism includes a rod 44 provided with a magnet and a stirring bar 43 also provided with a magnet. By rotating the rod 44, the stirring bar 43 inside the lubricating liquid tank is rotated. The inside of the lubricating liquid tank 4 is connected to the injection device 3 through a pipe 42 and further connected to the outside through a cylindrical thin tube 32 attached to the tip thereof.

  In order to lubricate the hydrodynamic bearing device with the lubricating liquid, the lubricating liquid fed to the injection device 3 needs to be accompanied by a sufficiently large and stable extrusion pressure. Otherwise, the amount of lubrication varies from operation to operation, and the product uniformity cannot be ensured especially in mass production.

  For this reason, in FIG. 2A, the extrusion pressure is applied by introducing atmospheric pressure air into the space portion 45. As another method, in FIG. 2B, the lubricating liquid is stored in the cylinder 46 and the weight 48 is placed on the piston 47 to apply the extrusion pressure. The method (B) is excellent in that an extrusion pressure can be applied without exposing the lubricating liquid to air. However, once the lubricating oil is put into the lubricating liquid tank, degassing treatment cannot be performed on the spot, so it is necessary to adjust the lubricating liquid in advance to sufficiently reduce the dissolved gas concentration. is there. The operator should decide which method to choose in consideration of other conditions.

  Lubricating operation can also be performed by placing a plurality of hydrodynamic bearing devices in the vacuum vessel 2. By moving the hydrodynamic bearing device sequentially and lubricating it, lubricating fluid can be lubricated to a plurality of hydrodynamic bearing devices with one exhaust. However, in order to perform this operation, it is necessary to attach a jig capable of mounting a plurality of hydrodynamic bearing devices and a mechanism for moving the jig in the vacuum vessel 2. As an example of such a jig and mechanism, a jig capable of mounting a plurality of hydrodynamic bearing devices arranged in the circumferential direction, and this jig can be rotated and sequentially moved directly under a cylindrical tube. The rotation mechanism can be raised.

(1-2) Valve mechanism As will be described later, the lubricating liquid filling apparatus 1 exposes the tip of the cylindrical thin tube 32 to the atmospheric pressure in a state where the inside of the lubricating liquid tank 4 is depressurized for degassing of the lubricating liquid. There is. In that case, the outside air tends to enter the lubricating liquid tank. Conversely, when injecting the lubricating liquid, the tip of the cylindrical thin tube 32 is under reduced pressure, while the space 45 is at atmospheric pressure to apply the lubricating liquid injection pressure. In this case, the lubricating liquid tends to flow outward. In either case, the flow must be stopped by a valve mechanism. For this reason, the valve mechanism of the injection device 3 is required not to cause leakage not only in a state where the internal pressure is high but also in a state where the external pressure is high. As such a valve, the valve mechanism 30 having the structure shown in FIG. 3 can be used.

  FIG. 3 is a cross-sectional view showing a main part of the injection device 3. A cylindrical thin tube 32 is attached to the tip of the injection device 3 and lubricates the hydrodynamic bearing device from the end. The inflow port 34 is connected to the lubricating liquid tank 4 through a pipe 42 and is supplied with a lubricating liquid to which a delivery pressure is applied. The closing rod 33 is accommodated in a supply hole 35 formed in the valve base 31 and is moved in the front-rear direction by a drive mechanism 38. When the closing rod 33 is pushed downward in the figure by the drive mechanism 38, the closing hole 37 is closed to form a blocking portion (FIG. 3A). Conversely, when pulled upward in the figure, the blocking hole 37 is in an open state, allowing the passage of the lubricating liquid (FIG. 3B). The drive mechanism 38 has a simple function of simply moving the closing bar 33 in the front-rear direction, and can be constituted by, for example, a spring and an electromagnet. The closing rod 33 can be driven at high speed only by electrical on / off switching.

  In the valve mechanism 30 configured in this way, the closing portion formed by the distal end of the closing rod 33 and the closing hole 37 is located very close to the proximal end portion of the cylindrical thin tube 32 (nozzle), and further from the closing portion. Does not have extra cavities to collect bubbles. The flow path of the lubricating liquid from the closing portion of the injection device 3 is substantially constituted only by a cavity inside the cylindrical thin tube 32.

(2) Filling Work (2-1) Filling Work First, as shown in FIG. 4 (A), the vacuum vessel 2 is lifted and opened, and the hydrodynamic bearing device 5 is installed at a predetermined position on the table 21. To do. At this time, in order to increase the positioning accuracy, a dedicated jig or a stage capable of precise movement may be used.

  In this state, the inside of the vacuum vessel 2 is at atmospheric pressure, but the space portion 45 of the lubricating liquid tank 4 is continuously evacuated and reduced to a pressure of 10 Pa (first pressure). Further, when the rod 44 provided with the magnet rotates, the stirrer 43 in the lubricating liquid tank 4 rotates, and the lubricating liquid is stirred. The airtightness between the lubricating liquid tank 4 and the vacuum vessel 2 is maintained by the injection device 3. The lubricating liquid is continuously exhausted and agitated while being exposed to an atmosphere having a pressure of 10 Pa. In such a situation, it can be determined that the concentration of the gas dissolved in the lubricating liquid is in a substantially equilibrium concentration with an atmosphere of 10 Pa pressure.

  Next, the vacuum vessel 2 is lowered, the opening side is closed with the base 21, the inside is evacuated, and the pressure is reduced. The injection device 3 and the lubricating liquid tank 4 are lowered together with the vacuum vessel 2 and moved to a lower position. As a result, the tip of the cylindrical thin tube 32 is located at the seal portion 53 of the fluid dynamic bearing device. The seal portion 53 (FIG. 5) is formed in the opening portion of the bearing gap. As a result of the downward movement of the lubricating liquid tank 4, the relative position with the rod 44 changes and the magnetic force does not work, so the stirrer 43 stops rotating and the stirring stops.

  Next, the degree of exhaust of the vacuum vessel 2 is adjusted so that the pressure inside the vacuum vessel 2 is slightly higher than the first pressure (second pressure) (pressure adjustment step).

  Next, in order to apply a delivery pressure to the lubricating liquid, ambient air is introduced into the space portion 45 to raise it to atmospheric pressure. Ambient air is useful as the easiest and constant pressure source. However, it is not always necessary to set the pressure to atmospheric pressure, and it may be freely selected using an appropriate apparatus, whether it is lower than atmospheric pressure or higher.

  Next, the valve mechanism 30 is opened for a predetermined time, and an appropriate amount of lubricating liquid to be held by the fluid dynamic bearing device 5 is sent out. At this time, the lubricating liquid inside the lubricating liquid tank 4 is exposed to air at atmospheric pressure. However, since the stirring is stopped, the lubricating liquid drawn from the lower part of the lubricating liquid tank 4 is almost equal to the first pressure. A balanced state is maintained.

  The extruded lubricating liquid flows out from the tip of the cylindrical thin tube 32. The pressure inside the vacuum vessel 2 is 30 Pa (second pressure) in the previous pressure adjusting step, and is larger than the first pressure. Therefore, the lubricating liquid flowing out from the tip of the cylindrical thin tube 32 is foamed on the spot. There is nothing. For this reason, the operation of wiping off the lubricating liquid scattered by foaming and adhering to the hydrodynamic bearing device can be omitted. In addition, since there is no loss due to foaming, variations in the injection amount are reduced and accuracy is improved.

  If necessary, the inside of the vacuum vessel 2 may be once depressurized to a pressure (fifth pressure) lower than the second pressure. For example, the pressure may be reduced to 10 Pa, which is about the same as the first pressure. By doing so, the exhaust of the bearing gap becomes more complete. However, prior to lubrication, it is necessary to return to a pressure higher than the first pressure (second pressure) to prevent foaming of the lubricating liquid.

(2-2) Situation of Seal Part FIG. 5 shows an enlarged view of the vicinity of the seal part 53 of the fluid dynamic bearing device 5 immediately after lubrication.

  A bearing gap 54 is formed between the shaft 51 and the sleeve 52, and a seal portion 53 is formed at an open end thereof. The tip of the cylindrical thin tube 32 is approaching just before coming into contact with the wall surface of the seal portion 53, and in this state, the lubricating liquid was injected. The shaft 51 constitutes a rotating part, and the sleeve 52 constitutes a fixed part. The seal portion 53 is formed in an opening portion of the bearing gap and surrounds the rotating shaft.

  The lubricated lubricating oil spreads over the entire circumference of the seal portion due to affinity with the wall surface of the seal portion, but does not reach the back of the bearing gap 54. At this time, the lubricating liquid 6 does not need to fill the entire seal portion, but it must block the entire gap around the seal portion. In addition, since the surroundings have been reduced to 30 Pa in advance, the bearing gap is also reduced to a pressure close to that, and due to the affinity with the wall surface, the lubricating liquid can easily enter the interior of the bearing gap. . The right side of FIG. 5 schematically shows the state immediately after lubrication. Immediately after lubrication, the lubricating liquid 6 remains in the open part, but immediately shifts to the state depicted on the left side due to the affinity with the wall surface. On the left side, a part of the lubricating liquid penetrates into the back of the bearing gap 54, and the level of the lubricating liquid at the seal portion 53 is lowered accordingly.

  Depending on the shape of the seal portion 53 and the amount of lubricating liquid to be retained by the bearing, the required amount of lubricating liquid may not be lubricated in a single operation. In that case, you may lubricate in 2 steps or more. After the first lubrication, the second and subsequent lubrication operations can be performed by estimating the time until the lubricating liquid spreads around the entire circumference of the seal portion 53 and the liquid level is sufficiently lowered.

  After the lubrication operation is completed, the inside of the vacuum vessel 2 is restored (third pressure). By restoring the pressure, a pressure difference is generated between the inside and outside of the lubricating liquid 6 in FIG. 5, and the lubricating liquid 6 is pushed into the bearing gap 54 to complete the injection of the lubricating liquid. It is easiest to return to atmospheric pressure, but even if it is returned to a pressure lower than atmospheric pressure, if the pressure is sufficient to push the lubricant into the back of the bearing gap, it will hinder the injection operation. Does not occur. Alternatively, the lubricating liquid may be pushed in to secure a sufficient space in the seal portion 53, and then exhausted and lubricated.

  FIG. 6 is an enlarged view of the seal portion of the hydrodynamic bearing device 5 ′ having the slope portion 60 on the upper end surface of the sleeve as in FIG. 5. An oil repellent film is formed on the slope portion and the shaft surface. When the hydrodynamic bearing device has such a structure, the lubricated lubricating liquid fills the slope (the right half of the figure) and then penetrates into the back of the bearing gap by capillary action (the left half of the figure). . Since there is a slope, not only can a large amount of lubricating liquid be injected at once, but the lubricating liquid is not left on the upper end surface of the sleeve.

(2-3) Air Clogging Check Work The hydrodynamic bearing device 5 that has finished the injection work is subjected to a work for checking whether air is caught. Although the filling method of the present invention is very reliable, it may still cause poor injection. Inspection is performed to eliminate such defective products.

  FIG. 7 is a diagram for explaining this operation. The hydrodynamic bearing device 5 that has been injected is placed under atmospheric pressure. In this case, the pressure environment can be inspected in principle if the pressure is higher than the fourth pressure, which will be described later, but atmospheric pressure may be easily realized.

  The hydrodynamic bearing device 5 is installed inside a vacuum box 91 provided with an exhaust mechanism, and is fixed using an appropriate jig (not shown). In this state, the liquid level position of the lubricating liquid in the open portion when atmospheric pressure is applied is measured. The measurement is performed using a laser displacement meter 93 and passing through the glass lid 92.

  Next, the vacuum pump P and the ventilation valve are operated to lower the pressure inside the vacuum box 91 to a fourth pressure of 1000 Pa. In this state, the liquid level position is measured again and compared with the liquid level position before decompression. At this time, if the amount of increase in the liquid level exceeds a predetermined value, it is rejected as a defective product, and a non-defective product is regarded as a good product.

  When the hydrodynamic bearing device is transported by air freight, the aircraft flies in the lower stratosphere region at the highest altitude near 14 km above the sky. The atmospheric pressure at this altitude is about 140 hPa, which is sufficiently larger than 1000 Pa (10 hPa). For this reason, if it passes the pressure reduction test of 1000 Pa, even if it is transported in a cargo compartment that is not pre-loaded at all, the hydrodynamic bearing device is judged to be extremely unlikely to cause oil leakage due to aircraft transportation. it can.

(2-4) Prior Degassing of Lubricating Liquid and Filling into Filling Device When the lubricating liquid charged into the lubricating liquid filling device 1 is separately degassed in advance, it is degassed in the lubricating liquid tank 4. Processing time can be shortened. In the filling method of the present invention, since the inside of the lubricating liquid tank 4 is repeatedly exposed to the atmosphere, the lubricating liquid that has not been sufficiently degassed should first be degassed in a separate vacuum container. I can degas.

FIG. 8 shows the configuration of a deaeration device used for such a purpose. The vacuum box 9 is mounted on a magnetic stirring bar drive mechanism 8, and the lubricating liquid 6 is contained in the lubricating liquid storage container 7 inside the vacuum box 9.

  The inside of the vacuum box 9 is depressurized to a pressure lower than the first pressure by the vacuum pump P. The target is to reduce the pressure to 10 Pa or less and continue exhausting. In this state, stirring is continued for a long time, and the dissolved gas is reduced to such an extent that it is in equilibrium with the pressure atmosphere.

  In addition to the preliminary deaeration process, when introducing into the lubricating liquid tank 4, a deaeration effect may be obtained. FIG. 9 shows a method of dropping into the lubricating liquid tank 4.

  That is, the lubricating liquid is poured into the funnel 100 and dropped into the lubricating liquid tank 4 via the micro flow rate valve 101 in the form of drops. The inside of the lubricating liquid tank 4 is depressurized to about 10 Pa. Droplets have a large surface area per volume and degassing proceeds rapidly. Further, the deaeration further proceeds when the droplet hits the inner surface or the liquid surface of the lubricating liquid tank and receives an impact.

  A heater (not shown) is attached to the vacuum box 9 and the lubricating liquid tank 4 used for preliminary deaeration. As a result, the lubricating liquid is heated up to 60 degrees and deaerated. In general, gas is degassed rapidly because its solubility in liquid decreases as the temperature increases.

(3) Selection of Optimal Injection Conditions (3-1) Derivation of Equations 1 and 2 Equation 1 is derived as a condition in which the surface tension exceeds the momentum of the lubricating liquid at the tip of the cylindrical thin tube. Hereinafter, the derivation process will be described.

The inner radius of the cylindrical capillary is a (m), the length of the cylindrical capillary is L (m), the pressure P (Pa) between both ends of the cylindrical capillary, the viscosity η (Pa · s) of the lubricant, and the density of the lubricant Let ρ (kg / m ³ ), the surface tension σ (N / m) of the lubricating liquid, and the atmospheric pressure at the tip of the cylindrical capillary tube be P _m (Pa). Then, as shown in FIG. 11, the moment when the lubricating liquid is about to flow out from the opening end is considered.

  At this time, surface tension acts between the opening end of the cylindrical thin tube and the lubricating liquid that has come out of the opening as shown by the arrows in the figure. Under the condition that all the momentum of the lubricating liquid is taken away by this surface tension, the lubricating liquid does not fly off from the opening end but is captured by the cylindrical capillary opening. In order to realize a precise lubrication operation, it is necessary for the lubricating liquid to lose its momentum at the opening end of the cylindrical thin tube and be gently supplied to the open portion. Such a condition can be obtained by calculating the impulse due to the surface tension acting on the unit volume of the lubricating liquid flowing out and searching for a condition where the momentum does not exceed the impulse.

  As is apparent from FIG. 11, at the moment when the lubricating liquid starts to flow out from the opening end, the surface of the lubricating liquid extends substantially parallel to the axis of the cylindrical capillary and is connected to the opening end edge. Therefore, the braking force for the lubricant flowing out is a value obtained by applying surface tension to the circumference of the opening end. Therefore, the required condition is calculated as follows.

微少時間Δｔの間に潤滑液に作用する力積；

微少時間Δｔの間に流出する潤滑液が有する運動量；

（ただし、ｕは円筒細管中を流れる潤滑液の速さ）
表面張力と雰囲気の圧力による力積が運動量を上回っていなければならない；

これを整理すると数式１が得られる。なお、数式２は、表面張力σがゼロであっても、数式１が満足される条件であり、数式１から直接に得られる。 Surface tension acting from the opening of the cylindrical capillary tube;

Impulse acting on the lubricating liquid for a minute time Δt;

The momentum of the lubricating liquid flowing out during the minute time Δt;

(However, u is the speed of the lubricating fluid flowing in the cylindrical thin tube)
Impulse from surface tension and atmospheric pressure must exceed momentum;

If this is rearranged, Formula 1 is obtained. Note that Formula 2 is a condition that satisfies Formula 1 even when the surface tension σ is zero, and is obtained directly from Formula 1.

が得られる。後述する表１の様に、円筒細管の適切な長さの下限定める際には、この数式７を用いると便利である。同様に、上限は、

なお、数式１は、液体の境界面に作用する慣性力と界面張力の比である、Weber数を用いて表現する事ができる；

ただしここで、

である。 Solving Equation 6 for L;

Is obtained. As shown in Table 1 to be described later, it is convenient to use Equation 7 when determining the lower limit of the appropriate length of the cylindrical thin tube. Similarly, the upper limit is

Equation 1 can be expressed using the Weber number, which is the ratio of the inertial force acting on the liquid interface and the interfacial tension;

Where

It is.

(3-2) Results of Filling Work Lubricating work was performed by changing the surface tension and viscosity of cylindrical capillaries of various sizes. Table 1 shows the working conditions. The cylindrical thin tube used is a product manufactured by EFD Inc. (USA) and is made of stainless steel. In the table, 27G, 30G, and 32G in the size column are standards related to the diameter of the needle used in the company's products. Because each dimension has a dimensional tolerance, and the inner radius varies from product to product, the inner radius values in the table are the upper and lower limits obtained from the company.

表２には、ＡからＪの各条件について、数式１左辺、数式２左辺（これは、数式１の右辺に等しい）、及び、数式７、数式８から求めた、細管長さの上下限、更に、実際の注油作業の良否を示している。注油作業良否の欄において、不良とは、潤滑液を安定して注油できなかったことを意味する。条件Ｊについて、一部不良とあるのは、一部の製造ロットの円筒細管において、注油量にバラツキが生ずるなどして、安定して注油できなかったことを意味する。 The lubricant used was a polyol ester type, and was tested at 20 ° C. from A to G and at 40 ° C. from H to J. Since the viscosity and the surface tension are strongly influenced by temperature, the values change. Moreover, in H to J, the internal pressure of the vacuum vessel at the time of lubrication is 30 Pa. In each of the conditions from A to J, experiments were performed on cylindrical capillaries of five different production lots.

Table 2 shows the upper and lower limits of the capillary length obtained from Equation 1 left side, Equation 2 left side (this is equal to the right side of Equation 1), Equation 7 and Equation 8 for each condition from A to J. Furthermore, it shows the quality of the actual lubrication work. In the column of the lubrication work quality, the failure means that the lubricating liquid could not be lubricated stably. With respect to the condition J, “partially defective” means that the cylindrical capillaries of some production lots could not be lubricated stably due to variations in the amount of lubrication.

  The values on the left side of Equation 1 and the left side of Equation 2 are displayed with a width corresponding to the width of the inner radius of the cylindrical thin tube. When the range of values on the left side of Formula 2 is completely below the range of values on the left side of Formula 1, the lubrication work result is good. On the other hand, when a part overlaps, a part is unnecessary or it is defective.

  In the upper limit column, the minimum value when variation is taken into account is shown, and in the lower limit column, the maximum value when variation is also taken into account is shown. When the actual length of the cylindrical tube exceeded the lower limit, the result of the lubrication work was good. However, regarding the condition H, the length of the cylindrical thin tube is larger than the upper limit value. This means that an excessively long cylindrical capillary is selected. Lubrication is possible even under these conditions, but a shorter length is better to increase productivity.

  In Table 2, with respect to A, C, D, E, F, G, and I that gave good results, the outflow of the lubricating liquid stopped as the valve was shut off. There was a variation in the timing when the outflow ceased for the defective ones.

  In addition, the above is based on the assumption that the tip of the cylindrical tubule has a circular cross section (perpendicular to the extending direction of the tubule). The length of the cylindrical tubule L, the pressure P between both ends of the cylindrical tubule, the viscosity η of the lubricating liquid, the viscosity η, the density ρ of the lubricating liquid, and the surface tension σ of the lubricating liquid dominate the phenomenon. However, in addition to these, the long axis of the ellipse or the inclination θ of the cross section of the tip of the cylindrical thin tube with respect to the extending direction also affects.

  When θ is a small value, it can be considered that the same relationship as in Equation 1 holds. As θ increases, it becomes difficult to obtain a relational expression similar to Equation 1 by primary calculation. Further, since the direction of the surface tension is greatly inclined with respect to the direction of movement of the lubricating liquid, the movement of the lubricating liquid at the tip of the cylindrical thin tube is also complicated. However, even in such a case, the relationship between the momentum of the lubricating liquid and the impulse due to the surface tension determines the phenomenon that occurs with respect to the lubricating liquid, and the relational expression of Equation 1 is an effective judgment criterion.

  The best mode for carrying out the present invention described above is not limited to the contents described here. For example, the rotary shaft bearing type is shown as the dynamic pressure bearing device for injecting the lubricating liquid, but the effect of the present invention is not changed even if this is a fixed shaft type dynamic pressure bearing device. As the lubricating liquid to be used, one having a higher viscosity, one having a large surface tension, or one having a small surface tension may be used. In addition, the effect of the present invention can be obtained as long as the liquid is not limited to the lubricating liquid and can be used for the liquid injection operation in a reduced pressure environment.

Schematic diagram of a lubricating liquid filling apparatus according to the present invention Schematic diagram of injection device and lubricating liquid tank Enlarged view of the main part of the injection device 3 Operation explanatory diagram of lubricating liquid filling device Enlarged view of the hydrodynamic bearing device seal Enlarged view of the hydrodynamic bearing device seal Air entrapment confirmation work explanatory diagram Lubrication liquid degassing work illustration Explanatory drawing of the operation of dropping the lubricating liquid into the lubricating liquid tank Spindle motor with fluid dynamic bearing Cylindrical capillary end enlarged view

Explanation of symbols

1 Lubricating liquid filling device 2 Vacuum container 21 units 3 Lubricating liquid delivery mechanism (needle valve)
32 Cylindrical narrow tube 33 Needle valve closing rod 34 Lubricating fluid supply port 35 Small chamber 36 Opening portion 37 Cylindrical thin tube starting end 38 Closing rod driving mechanism 4 Lubricating fluid tank 42 Piping 43 Magnetic stirrer 44 Rod 45 with magnet 45 Lubricating fluid tank Space portion 46 Cylinder 47 Piston 48 Weight 5 Hydrodynamic bearing device 51 Shaft 52 Sleeve 53 Sealing portion 54 Bearing gap 55 Radial bearing portion 56 Thrust plate 57 Thrust bushing 58 Thrust bearing portion 59 Opening wall surface 6 Lubricating liquid 7 Lubricating liquid storage container 8 Magnetic stirrer drive mechanism 9 Vacuum box 91 Vacuum box 92 Glass lid 93 Laser displacement meter F Filter G1, GB1, GB2, G3, G4 Pirani type vacuum gauge P Rotary pump R Gas introduction mechanism V Ventilation valve W Flow rate adjustment valve

Claims (21)

A rotating portion; a fixed portion that rotatably supports the rotating portion; a bearing gap held between the rotating portion and the fixed portion; and the rotating portion formed at one end of the bearing gap. This is a method of filling the bearing gap with a lubricating liquid by sending a lubricating liquid toward the opening using a nozzle to a hydrodynamic bearing device having at least one opening facing the outside air. And
A degassing step of reducing the concentration of the gas dissolved in the lubricating liquid to a first concentration, which is a concentration that is substantially equilibrated with respect to a gas atmosphere at a predetermined first pressure;
A pressure adjusting step in which the atmosphere of the open portion is a second pressure higher than the first pressure and lower than atmospheric pressure;
In an atmosphere realized by a pressure adjusting step, an oiling step of pouring the lubricating liquid that has passed through the degassing step into the open portion using the nozzle;
A method for filling a fluid dynamic bearing device with a lubricating liquid. A rotating portion; a fixed portion that rotatably supports the rotating portion; a bearing gap held between the rotating portion and the fixed portion; and the rotating portion formed at one end of the bearing gap. This is a method of filling the bearing gap with a lubricating liquid by sending a lubricating liquid toward the opening using a nozzle to a hydrodynamic bearing device having at least one opening facing the outside air. And
A pressure adjusting step in which the atmosphere of the open portion is a second pressure;
In the atmosphere realized by the pressure adjusting process, the first concentration of lubricating liquid, which is lower than the concentration at which the dissolved gas concentration is in equilibrium with the second pressure, is poured into the opening using the nozzle. Lubrication process;
A method for filling a fluid dynamic bearing device with a lubricating liquid. The degassing step is a step of exposing the lubricating liquid to an atmosphere of a first pressure.
The method for filling a fluid dynamic bearing device with a lubricating liquid according to claim 1. A rotating portion; a fixed portion that rotatably supports the rotating portion; a bearing gap held between the rotating portion and the fixed portion; and the rotating portion formed at one end of the bearing gap. This is a method of filling the bearing gap with a lubricating liquid by sending a lubricating liquid toward the opening using a nozzle to a hydrodynamic bearing device having at least one opening facing the outside air. And
Storing a lubricating liquid having a volume smaller than the capacity of the internal space in the internal space of the lubricating liquid tank having an internal space that keeps airtightness with respect to the outside; and
A degassing step of evacuating the cavity left inside the lubricating liquid tank to a first pressure and exposing the lubricating liquid to the first pressure atmosphere;
A pressure adjusting step in which the atmosphere of the open portion is a second pressure higher than the first pressure and lower than atmospheric pressure;
Under an atmosphere realized by the pressure adjusting step, the cavity portion is increased to a pressure higher than a second pressure to apply a delivery pressure to the lubricating liquid, and the lubricating liquid inside the lubricating liquid tank is stored. An oiling step of pouring the lubricating liquid into the open portion through a nozzle communicating with a region where
A method for filling a fluid dynamic bearing device with a lubricating liquid. The hydrodynamic bearing device has only one open part, and the bearing gap communicates with the outside air only through the open part.
The method for filling a fluid dynamic bearing device according to any one of claims 1 to 4, characterized in that: The lubrication step is executed once or a plurality of times at predetermined intervals,
The total amount of the lubricating liquid poured from the nozzle by the one or a plurality of lubrication steps is approximately equal to an appropriate amount that the bearing device should hold.
The method for filling a fluid dynamic bearing device according to any one of claims 1 to 5, characterized in that: The method for filling the fluid dynamic bearing device according to any one of claims 1 to 6, further comprising:
After performing the oiling step at least once, the atmosphere of the open part is increased to a third pressure higher than the second pressure, and a re-pressure step is included.
A method of filling a fluid dynamic bearing device with a lubricating liquid, characterized by the above. About the hydrodynamic bearing device filled with the lubricating liquid by the lubricating liquid filling method according to claim 7,
The atmosphere of the bearing gap opening is placed in a pressure environment greater than atmospheric pressure in the lower stratosphere,
In that state, the position of the filled lubricating liquid interface is measured and this is the first interface height,
Next, the atmosphere of the open portion is adjusted to be a fourth pressure that is equal to or lower than the atmospheric pressure of the lower stratosphere and is larger than the second pressure,
In that state, the position of the filled lubricating liquid interface is measured and this is the second interface height,
When the difference between the second interface height and the first interface height exceeds a predetermined value, the dynamic pressure bearing device is excluded as a defective product. ,
Inspection method of hydrodynamic bearing device. A lubricant,
One or more evacuation devices and one or more gas introduction sources;
A cavity that has an internal space that is airtight with respect to the outside, stores the lubricating liquid having a volume smaller than the capacity of the internal space, and the vacuum exhaust device and the gas introduction source are not filled with the lubricating liquid A lubricating liquid tank connected to the part,
A pipe connected at one end to the portion filled with the lubricating liquid in the internal space; and
A valve mechanism connected to the other end of the pipe;
A nozzle connected to the valve mechanism on one end side and having a pointed shape on the other end side;
A vacuum vessel capable of accommodating at least the nozzle tip and at least the bearing gap opening of the hydrodynamic bearing device, and connected to the vacuum exhaust device and the gas introduction source;
A lubricating liquid filling apparatus comprising: Having a lubricating liquid introduction mechanism capable of dropping the lubricating liquid into the lubricating liquid tank from the inside to the inside under a condition where the cavity is decompressed;
The lubricating liquid filling device according to claim 9, characterized in that: The lubricating liquid tank includes a stirring mechanism for stirring the lubricating liquid,
In a state where the space portion in the lubricating liquid tank is decompressed, the lubricating liquid inside the lubricating liquid tank can be stirred by the stirring mechanism.
The lubricating liquid filling device according to claim 9 or 10, characterized in that: The valve mechanism is
Blocking at least one of the flow paths of the lubricating liquid from one end of the pipe to the tip of the nozzle can be a closed portion that does not allow the flow of the lubricating liquid,
By forming and eliminating the blocking portion, at least two states of an open state that allows passage of the lubricating liquid and a closed state that blocks passage of the lubricating liquid are created,
It can be controlled to shut off after opening for a predetermined time,
The time required for the shut-off operation is sufficiently shorter than the opening time required for one lubricating liquid delivery operation, and can be substantially ignored.
The lubricating liquid filling apparatus according to claim 9, wherein the lubricating liquid filling apparatus is characterized in that: The valve mechanism is
A valve base;
A supply hole formed in the valve base, extending in one direction and opening at an end on one side;
A closing rod, which is inserted in the supply hole so as to be movable in one direction and in the opposite direction, and has a gap through which the liquid can flow in the axial direction between the supply hole and the inner peripheral surface;
A cap portion that covers the supply hole opening and is fixed to the valve base, and is fixed between the periphery of the supply hole opening and the opposite surface in an airtight manner;
An opening in the reverse direction surface of the cap part, and a closing hole in a position where the periphery is sealed by the end part by displacing the one-direction end part of the closing bar to the one side,
Driving the closing rod in the longitudinal direction, pushing the end of the closing rod in one direction toward the closing hole, and pressing the closing rod tip against the periphery of the closing hole to create a closing state, Furthermore, a closing rod drive mechanism that can be driven in the reverse direction to create an open state of the blocking hole;
Consists of
The nozzle is attached so as to protrude from a unidirectional surface of the cap part,
The base end side of the nozzle is fixed in a state of being embedded in a unidirectional surface of the cap portion, and the cavity inside the nozzle is continuous with the blocking hole at the base portion.
The lubricating liquid filling apparatus according to claim 9, wherein the lubricating liquid filling apparatus is characterized in that: The volume of the flow path from the closed portion to the tip of the nozzle is substantially equal to the volume inside the nozzle.
The lubricating liquid filling method according to claim 12 or 13, characterized in that: A valve base;
A supply hole formed in the valve base, extending in one direction and opening at an end on one side;
A closing rod that is accommodated in the supply hole so as to be movable in one direction and in the opposite direction, and has a gap through which the liquid can flow between the supply hole inner peripheral surface,
A cap portion that covers the supply hole opening and is fixed to the valve base, and is fixed airtight between the supply hole opening peripheral edge; and
A nozzle attached in a form protruding from the cap portion toward one side;
The cap portion is opened at a portion facing the valve base portion, and the closing rod one-direction end portion is displaced in one direction side so that a peripheral edge is sealed by the end portion to constitute a closing portion, And a blocking hole continuous to the base end side of the nozzle;
The closing rod can be driven in one direction and the opposite direction to take at least two positions. In one position, the end of the closing rod in one direction is pressed against the periphery of the closing hole. A closing rod drive mechanism that closes the hole and allows the liquid to flow by separating the end of the closing rod in one direction from the periphery of the closing hole at the other position;
An infusion device consisting of A liquid injection method for pouring a predetermined amount of liquid onto a target member under a reduced pressure environment using a cylindrical capillary tube nozzle,
A pressure adjusting step of placing the target member and the tip of the cylindrical thin tube in a reduced pressure environment;
Supplying a lubricating liquid having a pressure higher than the pressure in a reduced pressure environment by a delivery pressure to the cylindrical thin tube, and causing the lubricating liquid to flow out from the tip of the cylindrical thin tube toward the target member for a predetermined time. Liquid process;
Consists of
In SI unit system
The inner radius of the cylindrical capillary is a, the length is L,
The viscosity of the lubricating liquid is η, the surface tension is σ, the density is ρ,
The delivery pressure is P,
The pressure under the reduced pressure environment is Pa
When satisfying the following formula 1,

An injection method characterized by things. The liquid injection method according to claim 16, wherein
Furthermore, the following formula 2 is satisfied:

An injection method characterized by things. The cylindrical thin tube is supplied with the liquid from a liquid supply mechanism,
A valve mechanism is interposed between the lubricating liquid supply mechanism and the cylindrical thin tube,
The valve mechanism has a closed portion adjacent to the base of the cylindrical capillary tube,
The blocking portion is capable of blocking and opening the flow path.
The liquid injection method according to claim 16 or 17, wherein the liquid injection method is characterized. As a pressure source for applying the delivery pressure, atmospheric pressure is used.
The liquid injection method according to claim 16, wherein the liquid injection method is characterized. The amount of the liquid flowing out of the cylindrical thin tube within the time required for the valve mechanism to switch the flow path from closed to open or the time required to switch from open to closed is the target and Is negligibly small compared to the supply volume
The supply amount is controlled by adjusting the length of the opening time of the valve mechanism.
The liquid injection method according to claim 18 or 19, characterized in that: 21. The liquid injection method according to claim 16, wherein:
The target member includes a rotating portion, a fixed portion that relatively rotatably supports the rotating portion, a bearing gap held between the rotating portion and the fixed portion, and one end of the bearing gap. An open part in a hydrodynamic bearing device having at least one open part formed and surrounding the rotating part and facing the outside air,
The liquid is a lubricating liquid held by the hydrodynamic bearing device.
An injection method characterized by things.

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