JP2009221938A - Pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump having an extended life. <P>SOLUTION: A main shaft 16 is rotatably supported in a casing 13 by ball bearings 14, 15, and the casing 13 has a suction opening 11 and a discharge opening 12. An impeller 17 is connected to a shaft end part of the main shaft 16, and the impeller 17 is structured to be driven and rotated by a canned motor 18 via the main shaft 16. A front shroud 44 is provided to the axial front side of the impeller 17 and a rear shroud 45 is provided to the axial rear side. An axially confronting predetermined axial gap 47 is formed between the casing 13 and the front shroud 44. Radially confronting seal parts 48, 49 are arranged between the casing 13 and the front shroud 44. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a pump for conveying, for example, a supercritical CO ₂ fluid or liquid CO ₂ .

For example, as a pump for conveying a supercritical CO ₂ fluid or liquid CO ₂ , there is a semiconductor cleaning circulation pump. With the recent high integration of semiconductor devices, the processing line width of wafers is also required to be miniaturized, and is expected to be 0.10 μm or less in the future, compared with the current mainstream of 0.18 μm. However, in the conventional semiconductor cleaning method using a liquid such as ultrapure water, the resist formed on the wafer collapses due to the capillary force caused by the interfacial tension between the gas and the liquid (resist collapse). ) May occur.

  In order to eliminate such inconvenience, a semiconductor cleaning apparatus using a supercritical fluid has been developed instead of a conventional liquid such as ultrapure water. A supercritical fluid has a very high permeability compared to a liquid and penetrates into any fine structure. In addition, since there is no interface between gas and liquid, there is a feature that capillary force does not work during drying.

Carbon dioxide (CO ₂ ) is mainly used as the supercritical fluid. Carbon dioxide has a critical density of 468 kg / m ³ under relatively mild conditions, that is, a critical temperature of 31.2 ° C. and a critical pressure of 7.38 MPa, as compared with other liquid solvents. In addition, since it is a gas at normal temperature and normal pressure, it can be gasified by returning to normal temperature and normal pressure, so that it is easy to separate the object to be cleaned and contaminants. This makes it possible to simplify the cleaning process and reduce costs.

In such a semiconductor cleaning apparatus using a supercritical CO ₂ fluid, the supercritical CO ₂ fluid is usually pressurized to about 20 MPa. Therefore, as a circulation pump for cleaning the wafer by circulating the supercritical CO ₂ fluid, Because of the pressure resistance, a so-called sealless canned motor pump type is used. Further, a ball bearing is used as the bearing, and this is used in a pumped liquid (supercritical CO ₂ fluid) as a semiconductor cleaning agent.

  The ball bearing receives a radial load and a thrust load acting on the rotor. In addition, a preload load is controlled by a bearing preload spring installed on the shaft end side bearing on the side opposite to the impeller side, thereby preventing so-called revolving slip (side slip) of the ball bearing. Also, the radial rigidity (spring constant) of the ball bearing is controlled by the bearing preload, and the natural frequency of the rotor is adjusted.

  An example of such a pump is described in Patent Document 1 below.

JP 2007-231958 A

However, in the conventional pump described above, since the ball bearing is used in a supercritical CO ₂ fluid (or liquid CO ₂ ) having a low viscosity, lubrication by pumping cannot be expected. Therefore, wear occurs in the ball bearing, and the main shaft and the impeller move along the direction of the rotation axis. The impeller boosts the fluid sucked from the suction port by its rotation and discharges it from the discharge port. The direction gap is set very narrow. However, when the main shaft and the impeller move along the direction of the rotation axis due to wear on the ball bearing, there is a problem that interference occurs between the impeller and the casing, and the pump life is reduced.

  The present invention solves the above-described problems, and an object thereof is to provide a pump capable of extending the life.

  In order to achieve the above object, a pump according to a first aspect of the present invention includes a casing having a suction port and a discharge port, a main shaft rotatably supported by ball bearings in the casing, and a shaft end portion of the main shaft. An impeller to be coupled; and a cand motor capable of driving and rotating the impeller via the main shaft, and boosts the fluid sucked from the suction port by the rotation of the impeller and discharges the fluid from the discharge port. In the pump, a front shroud is provided on the front side in the axial direction of the impeller, and a rear shroud is provided on the rear side in the axial direction of the impeller, and is axially provided between the casing and the front shroud. A predetermined gap which opposes is provided, and a seal part which opposes in the diameter direction is provided between the casing and the front shroud.

  In the pump according to a second aspect of the present invention, a plurality of the seal portions are provided side by side in the axial direction of the impeller.

  The pump of the invention of claim 3 is characterized in that, in the casing, a fluid outlet from the impeller is communicated with the discharge port via a diffuser and a volute chamber, and a throttle portion is provided in the diffuser. .

  In the pump of the invention of claim 4, the shape of the throttle portion is set according to a fluid outflow angle at the outlet of the diffuser and a passage area ratio between the outlet of the diffuser and the volute chamber. Yes.

  The pump of the invention of claim 5 is characterized in that a preload spring for applying a preload to the ball bearing is provided, and the preload spring is formed by laminating a plurality of ring-shaped corrugated plate materials.

The pump of the invention of claim 6 is characterized in that the impeller is capable of conveying a supercritical CO ₂ fluid or liquid CO ₂ by being rotationally driven, and is used as a semiconductor cleaning circulation pump.

  According to the pump of the first aspect of the invention, the main shaft is rotatably supported by the ball bearing in the casing having the suction port and the discharge port, the impeller is connected to the shaft end portion of the main shaft, and the main shaft is supported by the canned motor. The impeller is configured to be capable of driving and rotating, and a front shroud is provided on the front side in the axial direction of the impeller, a rear shroud is provided on the rear side in the axial direction, and an axial direction is provided between the casing and the front shroud. While providing the predetermined gap which opposes, the seal part which opposes in a radial direction is provided between the casing and the front shroud. Therefore, the backflow of the fluid from the discharge port to the suction port can be prevented by the seal portion, and even if the main shaft and the impeller move in the rotational axis direction due to wear of the ball bearing, the impeller and the casing Since the predetermined gap is provided between them, they do not interfere with each other, and the pump life can be extended.

  According to the pump of the invention of claim 2, since the plurality of seal portions are provided side by side in the axial direction of the impeller, fluid leakage between the impeller and the casing is reduced by the plurality of seal portions, and the discharge port The backflow of the fluid to the suction port can be appropriately prevented.

  According to the pump of the invention of claim 3, the fluid outlet from the impeller is communicated with the discharge port via the diffuser and the volute chamber, and the restrictor is provided in the diffuser, so that the fluid outflow angle at the outlet of the diffuser is increased. Thus, the loss from the diffuser outlet to the volute chamber inlet can be reduced, and the impeller can be allowed to move to prevent interference.

  According to the pump of the invention of claim 4, the shape of the throttle portion is set according to the fluid outflow angle at the outlet of the diffuser and the passage area ratio between the outlet of the diffuser and the volute chamber. And the total velocity of the radial velocity and the circumferential velocity in the fluid flowing out from the diffuser outlet to the volute chamber is reduced to reduce the diffuser effect, that is, from the fluid velocity energy (dynamic pressure) to the pressure energy. Conversion to (static pressure) can be sufficiently ensured, and pump efficiency can be improved.

  According to the pump of the fifth aspect of the invention, the preload spring for applying preload to the ball bearing is provided, and a plurality of ring-shaped corrugated plate materials are laminated to constitute the preload spring. Therefore, the preload is applied to the ball bearing by the preload spring. As a result, revolving slip of the ball bearing can be suppressed and a long life can be achieved, and a plurality of corrugated plate materials are laminated to constitute a preload spring, so that the load with respect to the change amount of the spring crushing allowance can be achieved. The amount of change can be reduced and an appropriate preload can be applied.

According to the pump of the sixth aspect of the invention, the supercritical CO ₂ fluid or liquid CO ₂ can be transported by rotating the impeller and used as a semiconductor cleaning circulation pump. Can be eliminated, and the cleaning process can be simplified and the cost can be reduced.

  Exemplary embodiments of a pump according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a sectional view showing a semiconductor cleaning device circulation pump as a pump according to an embodiment of the present invention, and FIG. 2 is an enlarged view showing a main part of the semiconductor cleaning device circulation pump of this embodiment.

  As shown in FIGS. 1 and 2, the semiconductor cleaning device circulation pump of the present embodiment is rotatably supported by a casing 13 having a suction port 11 and a discharge port 12 and ball bearings 14 and 15 in the casing 13. A main shaft 16, an impeller 17 connected to the shaft end of the main shaft 16, and a canned motor 18 that can drive and rotate the impeller 17 via the main shaft 16. The fluid sucked from 11 is pressurized and discharged from the discharge port 12.

  The casing 13 includes a ring-shaped discharge / suction side casing 21 and a purge-side casing 22 that are arranged with a cylindrical outer cylinder 23 sandwiched between them, and are connected by connecting bolts 24. The manifold 25 is fixed to and connected by connecting bolts 26. In the manifold 25, a pumped liquid suction port 11 is formed on an extension axis of the axis of the main shaft 16, and a discharge port 12 is formed on the outer peripheral side of the suction port 11.

  The ball bearings 14 and 15 are angular ball bearings, which are mounted on the discharge / suction side casing 21 and the purge side casing 22 and rotatably support the main shaft 16. An impeller 17 is fitted to the shaft end portion of the main shaft 16 and fixed by a connecting bolt 27.

In this embodiment, the ball bearings 14 and 15 are made of ceramic materials (for example, silicon nitride Si ₃ N ₄₎ on the inner and outer rings and balls in order to improve wear resistance and corrosion resistance and reduce centrifugal load during high-speed rotation. , Alumina Al ₂ O ₃ , silicon carbide SiC, etc.). Thus, the wear resistance with respect to the particle brought in from the outside improves by making a bearing material into a total ceramic. In addition, the cage is designed so that drag loss (rotational resistance) is reduced. Thereby, revolution slip prevention and preload load (thrust bearing load) can be reduced, and the life of the ball bearings 14 and 15 can be extended. As a material for the cage, PEEK material (polyether / ether / ketone) is used from the viewpoint of corrosion resistance to the cleaning agent, wear resistance, and securing strength against high-speed rotation. In place of the PEEK material, stainless steel or fiber composite may be used.

  The canned motor 18 includes a stator 28 fixed to the inner periphery of the outer cylinder 23 and a rotor 29 provided on the outer periphery of the main shaft 16 so as to face the stator 28.

  On the other hand, the purge side casing 22 is formed with a purge port 30 for discharging a part of the sucked liquid on the extension axis of the axis of the main shaft 16. Further, a preload spring 31 is sandwiched between the purge side casing 22 and the angular ball bearing 15. The preload spring 31 is formed by laminating a plurality of ring-shaped corrugated springs positioned around the other end of the main shaft 16, and applies an axial preload to the ball bearing 15 as a constant pressure spring system.

  Therefore, when the canned motor 18 is energized, the rotor 29 rotates with respect to the stator 28, the main shaft 16 rotates with the rotor 29, and the impeller 17 rotates in conjunction with the rotation. Then, the pumped liquid is sucked from the suction port 11, boosted by the centrifugal force of the impeller 17, guided to the discharge port 12 side, and discharged to the outside. Further, a part of the pumped liquid sucked from the suction port 11 passes through the ball bearings 14 and 15 and the canned motor 18, cools them, and then is discharged from the purge port 30 as a purge flow.

  In the present embodiment, the circulation pump configured as described above is configured such that the impeller 17 is a closed type, and the main shaft 16 and the impeller 17 are supported by the casing 13 so as to be movable by a predetermined amount in the axial direction. At the same time, a seal is formed in the radial direction between the casing 13 and the impeller 17.

  That is, the suction / discharge casing 21 constituting the casing 13 is formed with a housing hole 41 communicating with the suction port 11 at the center thereof, and the outer ring 42 and the outer ring 43 are fixed to the inner circumferential surface of the housing hole 41. Has been. On the other hand, the impeller 17 includes a plurality of blades 46 between a front shroud 44 having a ring shape provided on the front side in the axial direction and a rear shroud 45 having a disk shape provided on the rear side in the axial direction. They are provided at equal intervals in the circumferential direction.

  In this case, the front shroud 44 includes a disk portion 44a that is horizontal in the radial direction of the impeller 17 and a cylindrical portion 44b that is horizontal in the axial direction. A predetermined gap 47 facing in the axial direction is provided between one end portion of the outer ring 43 (casing 13) and the surface portion of the disk portion 44 a in the front shroud 44. Further, between the inner peripheral portion of the outer peripheral ring 43 (casing 13) and the outer peripheral portion of the cylindrical portion 44b in the front shroud 44, radially opposed seal portions 48 and 49 are provided. The seal portions 48 and 49 are displaced in the radial direction of the impeller 17 and are provided side by side in the axial direction of the impeller 17. In addition, it is desirable to provide a plurality of seal portions 48 and 49, not limited to two, and may be provided three or more.

  In the casing 13, the fluid outlet 17 a from the impeller 17 is communicated with the discharge port 12 through the diffuser 51, the volute chamber 52, and the communication passage 53. That is, a fluid outlet 17a from the impeller 17 is formed at the joint between the suction / discharge casing 21 and the manifold 25, and a diffuser 51 is formed in communication with the fluid outlet 17a. The diffuser 51 converts fluid velocity energy (dynamic pressure) into pressure energy (static pressure). The volute chamber 52 is formed in a spiral shape at the joint between the suction / discharge casing 21 and the manifold 25, with one end communicating with the diffuser 51 and the other end communicating with the communication passage 53.

The diffuser 51 is provided with a throttle portion. That is, the diffuser 51, to the channel width W ₁ of the inlet portion of the fluid outlet 17a side from the impeller 17 _(flow channel area), channel width W _{2 (the} passage in the outlet portion of the volute chamber 52 side By forming the (area) to be narrow (small), the diaphragm portion is configured. That is, by enlarging the inlet portion of the diffuser 51 with respect to the outlet portion, the movement of the impeller 17 in the axial direction by the predetermined gap 47 is allowed, and the pressure fluid can be appropriately introduced into the diffuser 51.

  The shape of the throttle portion in the diffuser 51, that is, the inclination angle depends on the fluid outflow angle α from the outlet portion of the diffuser 51 and the area ratio Y between the passage area of the outlet portion of the diffuser 51 and the area of the volute chamber 52. Is set. The fluid flowing from the diffuser 51 to the volute chamber 52 has a fluid outflow angle α with respect to the tangent line of the diffuser 51, and the velocity V is divided into a circumferential velocity Vθ and a radial velocity Vm. The area ratio Y of the volute chamber 52 is a ratio (Y = Ad / Av) between the passage area Ad at the outlet of the diffuser 51 and the area Av of the volute chamber 52.

  In general, in view of the friction loss from the outlet portion of the diffuser 51 to the inlet portion of the volute chamber 52 and the loss caused by the speed difference between the discharge speed of the diffuser 51 and the inflow velocity of the volute chamber 52, the fluid outflow angle α is By setting the angle to about 15 °, the maximum pump efficiency can be ensured. Further, loss at the tongue end of the volute chamber 52 occurs when the difference between the attachment angle of the tongue end of the volute chamber 52 and the fluid outflow angle is too large. This is because, since the tongue end of the volute chamber 52 is thick, it is difficult to set the attachment angle of the tongue end of the volute chamber 52 to several degrees (small angle).

  As a result, in this embodiment, by providing the throttle portion in the diffuser 51, the loss is reduced by increasing the fluid outflow angle α at the outlet portion of the diffuser 51. Moreover, the movement of the impeller 17 in the axial direction is allowed by increasing the width of the inlet portion of the diffuser 51. In this case, when the diffuser 51 is squeezed, the radial velocity Vm increases, but the circumferential velocity Vθ is decelerated (free vortex flow) by storing the angular momentum. Accordingly, the aperture shape is set to such an extent that the total speed of the radial speed Vm and the circumferential speed Vθ is reduced.

  Accordingly, when the impeller 17 rotates, the pumped liquid is sucked from the suction port 11 and is boosted by the centrifugal force of the impeller 17. The pressure-lifted liquid passes through the diffuser 51 from the fluid outlet 17a, whereby the fluid velocity energy is converted into pressure energy, flows into the volute chamber 52, and is discharged from the discharge port 12 to the outside through the communication passage 53. Is done. At this time, since the casing 13 and the impeller 17 are sealed in the radial direction by the seal portions 48 and 49, the pumped liquid boosted by the impeller 17 does not leak to the suction port 11, and the fluid outlet 17 a To the diffuser 51 properly.

  Further, even if the main shaft 16 and the impeller 17 are moved in the axial direction by the predetermined gap 47, the positional relationship between the outer ring 43 and the front shroud 44 is not displaced by the seal portions 48 and 49. 11 properly flows into the diffuser 51 without leaking.

  As described above, in the pump of this embodiment, the main shaft 16 is rotatably supported by the ball bearings 14 and 15 in the casing 13 having the suction port 11 and the discharge port 12, and the blade is attached to the shaft end portion of the main shaft 16. The wheel 17 is connected, and the impeller 17 can be driven and rotated by the canned motor 18 via the main shaft 16. The front shroud 44 is provided on the front side in the axial direction of the impeller 17, and the rear side in the axial direction on the rear side. A shroud 45 is provided, a predetermined gap 47 is provided between the casing 13 and the front shroud 44 in the axial direction, and seal portions 48 and 49 are provided between the casing 13 and the front shroud 44 in the radial direction. Provided.

  Therefore, the backflow of the fluid from the discharge port 12 to the suction port 11 can be prevented by the seal portions 48 and 49, and the main shaft 16 and the impeller 17 are moved in the direction of the rotation axis due to wear of the ball bearings 14 and 15 and the like. Even if it moves, the predetermined gap 47 is provided between the impeller 17 and the casing 13, so that they do not interfere with each other and the pump life can be extended.

  Further, in the pump of this embodiment, a plurality of seal portions 48 and 49 are provided side by side in the axial direction of the impeller 17. Accordingly, fluid leakage between the impeller 17 and the casing 13 is reduced by the plurality of seal portions 48 and 49, and the backflow of fluid from the discharge port 12 to the suction port 11 can be appropriately prevented.

  In the pump of this embodiment, the fluid outlet 17 a from the impeller 17 is communicated with the discharge port 12 via the diffuser 51 and the volute chamber 52, and the restrictor is provided in the diffuser 51. Accordingly, the total velocity of the circumferential velocity and the radial velocity in the fluid flowing out from the fluid outlet 17a of the impeller 17 to the diffuser 51 is decelerated, whereby the fluid velocity energy (dynamic pressure) is reduced by the diffuser 51. It can be appropriately converted into energy (static pressure).

  At this time, the restrictor is provided in the diffuser 51, and the loss can be reduced by increasing the fluid outflow angle α at the outlet of the diffuser 51. Further, by increasing the width of the inlet portion in the diffuser 51, it is possible to reduce the loss at the diffuser inlet at the impeller exit due to the axial movement of the impeller 17.

  Further, the shape of the throttle portion in the diffuser 51 is set according to the fluid outflow angle from the outlet portion of the diffuser 51 and the passage area ratio between the outlet portion of the diffuser 51 and the inlet portion of the volute chamber 52. Therefore, by setting the throttle portion to an appropriate shape, the radial speed of the diffuser 51 increases, but the circumferential speed decreases and the total speed decreases. As a result, the diffuser 51 decelerates. Thus, the fluid velocity energy can be properly converted into pressure energy, and the pump efficiency can be improved by making the fluid velocity in the volute chamber 52 appropriate.

  Further, in the pump of this embodiment, a preload spring 31 for applying a preload to the ball bearings 14 and 15 is provided, and a plurality of ring-shaped corrugated plate materials are laminated to constitute the preload spring 31. Therefore, by applying preload to the ball bearings 14 and 15 by the preload spring 31, it is possible to extend the life by suppressing the revolving slip of the ball bearings 14 and 15, and a plurality of corrugated plate materials are laminated. By configuring the preload spring 31, it is possible to reduce the load change amount with respect to the change amount of the spring crushing allowance and apply an appropriate preload.

Further, in the pump of this embodiment, the impeller 17 is driven to rotate so that a supercritical CO ₂ fluid or liquid CO ₂ can be transported and used as a semiconductor cleaning circulation pump, whereby the object to be cleaned after cleaning is dried. Can be eliminated, and the cleaning process can be simplified and the cost can be reduced.

  In the above-described embodiment, the pump of the present invention has been described as a circulation pump for a semiconductor cleaning device, but may be applied to a normal centrifugal pump.

  The pump according to the present invention provides a predetermined gap facing the axial direction between the casing and the front shroud, and a seal portion facing the radial direction between the casing and the front shroud. It is possible to extend the life by suppressing leakage and wear of components, and can be applied to any pump.

It is sectional drawing showing the circulation pump for semiconductor cleaning apparatuses as a pump which concerns on one Example of this invention. It is an enlarged view showing the principal part of the circulation pump for semiconductor cleaning apparatuses of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Suction port 12 Discharge port 13 Casing 14,15 Ball bearing 16 Main shaft 17 Impeller 18 Canned motor 31 Preload spring 44 Front shroud 45 Rear shroud 46 Blade 47 Predetermined clearance 48, 49 Seal part 51 Diffuser 52 Volute chamber

Claims (6)

A casing having a suction port and a discharge port;
A main shaft rotatably supported by ball bearings in the casing;
An impeller coupled to the shaft end of the main shaft;
A canned motor capable of driving and rotating the impeller via the main shaft;
A pump that boosts the fluid sucked from the suction port by the rotation of the impeller and discharges the fluid from the discharge port.
A front shroud is provided on the front side in the axial direction of the impeller, and a rear shroud is provided on the rear side in the axial direction of the impeller,
A predetermined gap facing in the axial direction is provided between the casing and the front shroud, and a seal portion facing in the radial direction is provided between the casing and the front shroud.
A pump characterized by that.   The pump according to claim 1, wherein a plurality of the seal portions are provided side by side in the axial direction of the impeller.   3. The pump according to claim 1, wherein a fluid outlet from the impeller is communicated with the discharge port through a diffuser and a volute chamber in the casing, and the throttle is provided in the diffuser. .   The pump according to claim 3, wherein the shape of the throttle portion is set according to a fluid outflow angle at the outlet of the diffuser and a passage area ratio between the outlet of the diffuser and the volute chamber.   5. The preload spring for applying preload to the ball bearing is provided, and the preload spring is configured by laminating a plurality of ring-shaped corrugated plate materials. 6. Pump. The impeller is capable of transferring the supercritical CO ₂ fluid or liquid CO ₂ by driving the rotation, according to claims 1, characterized by being used as a semiconductor cleaning circulation pump in any of 5 Pump.

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