JPH03206396A - Pump - Google Patents

Abstract

PURPOSE:To feed highly pure liquid by forming at least main part of the outer surface of a liquid contact section in a pump, from a material having a surface subjected to mirror-surface finish by an electrolytic composite polishing so as to reduce fine particles and the elusion of metal. CONSTITUTION:In a pump, for example, a vortex flow pump, a plurality of blades 18 are formed at the peripheral edge of a disc. An impeller 12 fitted on a rotary shaft 16 is journalled to a bearing 17 through the intermediary of a seal box 14. Further, the casing 13 and the impeller 12 define therebetween a fluid passage 20 which is communicated with a fluid inlet port 19. With this arrangement, at least a main part of the outer surface of a liquid contact part in the pump is formed from a material having a surface subjected to mirror- surface finish by electrolytic composite polishing. Further, the surface roughness of the mirror surface is set to a value less than 0.1mumRmax. Thereby, it is possible to feed liquid having a high purity near to a theoretical purity.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a pump.

[Prior Art] With the remarkable development of the semiconductor industry in recent years, large amounts of high-purity water containing little impurities such as particles are being used.

Furthermore, as LSIs become more highly integrated and performant, and ultra-LSIs with minimum pattern dimensions on the order of submicrons are being manufactured, even the presence of even the slightest impurity can cause pattern defects in LSIs. (Resistivity 18.25
High purity water with a level close to MΩ・cmat (25° C.) has come to be required.

In order to achieve high purity water at a level close to theoretically pure water, the particle size must be at least 0.
Particles of 2 μm or more are 10 pieces/m A or less, particles with a particle size of 0.1 to 0.2 μm are 100 pieces/m
100 particles with a particle size of 0.1 μm or less
m II. Must be as follows.

However, even if high-purity water is used as the source water before being supplied to the water supply system, fine particles may get mixed in from the water supply system, such as pumps, piping, and their components.
Metals etc. eluted from these inner surfaces are mixed in, resulting in a significant decrease in purity.

For pipes, various types of pipes, regulators, and other piping and their components, smooth the surfaces in contact with liquid, and
Structural improvements have also been made, such as cleaning out water accumulation in the piping system from the main line, and progress is being made in the direction of solving the above problems.

However, appropriate cleaning technology has not yet been developed for pumps, which are most susceptible to contamination and have the greatest impact on determining whether or not to supply high-purity water. Without any effort,
Currently, it is used for semiconductor high-purity water.

In other words, conventional pumps generally use SCS as the material.
13 are used, and the pump is manufactured by the following process.

(Casting into a specified shape) = (Heat treatment) = (Pickling) = (Cutting) = (Burr removal) = (Alcohol cleaning) - (Cleaning) =
(Assembly) = (Performance test) However, the inner surface of a pump manufactured by such a process has a cast metal surface, and the surface is extremely uneven. Furthermore, even if the casting surface is removed by cutting, cracks, pores, folds, blowholes, etc. still exist. Furthermore, the surface has become porous due to heat treatment, and corrosion has progressed at grain boundaries due to pickling.

Therefore, the surface contains particles and non-metallic inclusions, and is prone to chemical contamination, which causes deterioration in the quality of high-purity water.

Moreover, in terms of structure, it has a complicated shape that lacks consideration for high-purity water, has a large surface area in contact with liquid, and has many dead spaces.

In addition, pump particles are caused by friction on the pump shaft seal,
It also occurs due to vibrations, etc., and metal powder etc. get mixed into the pump.
There are also structural problems such as the generation of particles.

Note that it is also conceivable to provide a filter to remove particles. However, in the case of particles larger than 0.1 μm, it is possible to remove such particles to some extent by installing a filter downstream of the pump, but
It is difficult to remove fine particles with a filter of less than m.

In order to solve these problems, mechanical polishing (puff polishing) has been attempted as a treatment for the inside of the pump, but abrasives and brighteners are mixed into the surface, increasing the amount of TOC (total organic carbon). These may actually deteriorate the quality of the water, and may also cause a number of other disadvantages. Therefore, these technologies cannot be called complete technologies.

In addition to these methods, there is also a general immersion electrolytic polishing method, but it does not improve surface roughness, etc., and cannot be said to be a technology that can be used for pumps for high-purity water.

[The problem to be solved by the invention] The present invention provides a pump for supplying high-purity liquid that is capable of suppressing the generation of particles and transporting high-purity liquid close to theoretical purity while maintaining a high specific resistance value. The purpose is to provide.

[Means for Solving the Problems] The pump of the present invention is characterized in that at least the main surface of the liquid-contacting part inside the pump is made of a material whose surface is mirror-finished by electrolytic composite polishing.

[Function] The inventors of the present invention have made extensive efforts to obtain a pump capable of suppressing the generation of particles and pumping out liquid such as water while maintaining a high specific resistance value. It has been found that the objective can be achieved by using rolled material or forged material for the surface and mirror-finishing it by electrolytic composite polishing.

The present invention was made based on the above findings,
The electrolytic composite polishing method creates an extremely smooth inner surface of the pump with no pores, making it difficult for minute particles to be generated, and the amount of metal elution is small, making it possible to transfer high-purity liquid close to theoretically pure water. Possible pumps can be provided.

In the present invention, in order to maintain high purity, the contact surface with water (
By performing electrolytic composite polishing on at least the main area of the inner surface (inner surface in contact with liquid), the inner surface is mirror-finished, significantly reducing the generation of particles, reducing chemical contamination that is adsorbed and desorbed on the inner surface, and improving the specific resistance value. Altitude can be maintained.

[Implementation example code] Examples of embodiments of the present invention will be described below.

The pump to which the present invention is applied is a pump that is generally sold under the name of an ultrapure water pump, and its type is not particularly limited.
a)), a centrifugal pump (FIG. 2(a)) is preferred.

The vortex pump shown in FIG. 1(a) typically has the following configuration. That is, a plurality of blades 18 are formed on the periphery of the disk (FIG. 1(b)). Rotating axis 1
An impeller 12 integrally attached to the casing 13 is supported by a bearing 17 via a seal box 14 within the casing 13, and the space formed by the casing 13 and the impeller 12 serves as a housing passage 20. ing. Fluid passage 20 is in communication with fluid volume 19. In a pump having such a structure, when the rotary shaft 16 is driven by a drive means (not shown) to rotate the impeller 12, the fluid within the blades 18 of the impeller 12 flows out from the outer periphery of the blades 18 due to centrifugal force. From the fluid passage 20 through the side of the blade 18 to the blade 1
A flow flows into the impeller 12, and the fluid receives energy due to the centrifugal force of the rotation of the impeller 12, which is converted into velocity energy and pressure energy within the fluid passage 2o, and this action is repeated within the impeller 12. The pressure of the fluid is increased and the fluid is discharged through the discharge port. A pump with this structure has less dead space, and since the only sliding part is the shaft seal, it is suitable for the present invention as a pump that generates fewer particles.

The centrifugal pump shown in FIG. 2(a) has a plurality of vanes 18 extending from the periphery of a disk in a direction slightly deviated from the radial direction (FIG. 2(b)), which is also integral with the rotating shaft 16. An impeller 12 is mounted on a bearing 17 within the cover 11 via a seal box 14.The impeller 12 is covered with a casing 13, and the head of the casing 13 is The port 19 is opened.Also in a pump having such a structure, when the rotary shaft 16 is driven by a driving means (not shown) to rotate the impeller 12, the fluid flowing from the fluid inlet flows through the impeller 12. Energy is received by the impeller 18 and discharged in the circumferential direction of the impeller 12.The pump having this structure also has little dead space and has few sliding parts, so it is suitable as a pump that generates few particles.

Note that the pump may be made of materials such as steel, aluminum alloy, titanium alloy, etc., and is not limited to these materials as long as it is a metal pump.

Moreover, in the present invention, a plastically worked material is used. As the plastically processed material, for example, a material obtained by plastic processing such as rolling, forging, extrusion, etc. may be used. Materials other than plastically processed materials (
For example, if a cast material is used, a surface that can suppress the generation of particles cannot be obtained even if electrolytic composite polishing, which will be described later, is performed.

The pump of the present invention may be manufactured, for example, by the following steps.

(Forging into specified shape) = (Heat treatment) = (Pickling) - (Shape cutting) = (Burr removal) = (Cleaning) = (Electrolytic composite polishing)
→ (Cleaning) = (Assembling) In the present invention, the surface roughness of the mirror surface is preferably 0.1 μm Ra+ax or less.

The electrolytic composite polishing method applied in the present invention involves electrolytically eluting the anodic metal to be polished, and also polishing the passivated oxide film formed on the surface of the metal to a mirror-like finish by the abrasive action of abrasive grains. This is a method of processing. At the same time, an anodic reaction of elution and oxidation is applied to the polished surface through a passivated electrolyte at an electrolytic current rate of several A/cm2 or less, while applying a speed above a certain level to the polishing abrasive grains to scrape the polished surface. (Japanese Patent Publication No. 57-4775.9, Japanese Patent Publication No. 58-19409).

This will be explained in more detail based on FIG.

FIG. 3 shows an example of a tool used in the mirror finishing method of the present invention, in which 1 is a tool connected to a drive shaft and rotated by a drive device, and 2 is a copper plate formed at the bottom of tool 1. A disk-shaped cathode, 3 is an exposed surface formed in a cross shape on the lower surface of the cathode 2, 4 is an outlet for the electrolytic solution 5 provided through the center of the cathode 2, and 6 is an exposed surface 3 on the lower surface of the cathode 2 7 is a thin film of electrically insulating paint, etc., which prevents useless leakage current from flowing out from the circumferential surface of the cathode 2 and the circumferential surface of the tool 1. Prevention and electrolysis Wi. 5 is transferred from the electrolyte supply device via the drive shaft of the tool 1, and is transferred from the outlet 4 to the exposed surface 3 and the metal to be polished (not shown).
is supplied to the gap between the tool and the tool and is discharged outside the tool. Then, the cathode side and the anode side of a direct current or pulsed voltage are connected to the cathode 2 of the tool 1 and the metal to be polished, respectively.

During the polishing process, a voltage is applied between the cathode 2 of the tool 1 and the metal to be polished as described above, and an electrolytic solution 5 is supplied between them, and the cathode 2 is rotated while being pressed against the metal to be polished. The anodic melting of the metal to be polished is performed, and the convex portions of the passivated oxide film generated on the uneven portions of the surface of the metal to be polished are removed by abrasion using the abrasive grains 6. The parts are preferentially electrolytically eluted and finished to a mirror surface.

To give an example of polishing, #120 to #1 500 S
Initial surface roughness with iC abrasive grains is 20-50μmRmax
When scratching the inner surface of SUS3 1 6L, if you use a 20% NaNO3 aqueous solution as the passivation type electrolyte and change the electrolytic current density in the range of 0 to 6 A/cm', the roughness can be reduced to 0. An inner surface with a surface roughness of 1 μm Rtnax or less can be obtained.

Furthermore, aluminum alloys and the like can also be polished using the same method.

It goes without saying that the pump according to the present invention can be used not only in the semiconductor field but also in fields such as biotechnology, pharmaceuticals, foods, and the chemical industry.

Further, if a corrosion-resistant material such as stainless steel, aluminum, or titanium is used as the material, it is possible to transfer corrosive materials without causing chemical contamination.

[Example] Embodiments of the present invention will be described below based on the drawings.

(Example 1) Example 1 will be described using the vortex pump shown in FIG. 1(a) as an example.

In the wooden example, the cover 11, casing 13, impeller 12, etc. are die-forged from SUS3 1 6L material into a predetermined shape, and after forging, heat treatment and pickling to remove scale are sequentially performed, followed by drilling and drilling. Surface grinding was performed, and then electrolytic composite polishing was performed. The composite electrolytic polishing was performed using the polishing apparatus shown in FIG.

In addition, in FIG. 1(a), the inner surface indicated by A is 0.
The surface was mirror-finished to a surface roughness of 1 μmRmax or less.

The quality of the water supplied to this pump was measured using the system shown in FIG.

The details of measurement 7 will be explained with reference to FIG.

A pump, an ion exchanger, an RO membrane (reverse osmosis @), a heat exchanger, and a heater cooler were connected in series through stainless steel pipes, and the high purity water shown in Table 1 (source water, 0.07~0.0. 1
80 μm particles/m It ) were supplied from the pump port in the clean room, and the pump was operated to transfer source water. As the stainless steel pipe, a pipe having an inner surface with a passive oxide film formed after electrolytic polishing was used.

A sample was taken at the sampling point at the pump outlet, and the particles in the sample were measured.

On the other hand, for comparison, a similar measurement was carried out on a canned pump designed to minimize dead space for ultrapure water, but a large amount of both particles of 0.1 μm or less and particles of 0.1 μm or more were generated.

Next, a specific resistance value start-up test was conducted using the measurement system shown in FIG. In the start-up test, the specific resistance value at the outlet of the cooler was measured over time, and the specific resistance value was 18.2MΩ. The point at which the temperature reached cm was defined as the point at which the rise started. The measurement results are shown in Table 2 and FIG. As shown in Table 2 and FIG. 5, the pump according to this example had a quick start-up, maintained a high specific resistance value of 18.2 MΩ after 30 minutes, and no decrease was observed.

On the other hand, in the case of the canned pump of the comparative example, 18.
It took six months to achieve 15MΩ・Cm.

The above-mentioned measurement of the specific resistance value was performed using a specific resistance meter.

In addition, when the TOC and viable bacteria were investigated for the sample, the TOC was 50 μg c/fl. Below, live bacteria are 1
pieces/100 m ft. In addition, the measurement of viable bacteria was carried out using a membrane soil test.

(Example 2) When the same measurements as in Example 1 were performed on the centrifugal pump shown in FIG. 2(a), the same values as in Example 1 were obtained for the particle generation suppressing effect.

Also, the same results as in Example 1 were obtained in the start-up test.

[Effects of the Invention] According to the present invention, generation of particles is extremely small;
It is possible to transfer liquid without reducing purity, and therefore it is also possible to transfer high-purity water.

Table 1 particle results (pcs/mIL) table 2 Resistivity results

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of a pump according to Example 1 of the present invention, and FIG. 1(b) is a perspective view of an impeller of the pump. FIG. 2(a) is a sectional view of a pump according to a second embodiment of the present invention, and FIG. 2(b) is a plan view of an impeller of the pump. FIG. 3 is a plan view and a sectional view of an apparatus used for electrolytic composite polishing. FIG. 4 is a system layout diagram for measuring the quality of feed water. FIG. 5 is a graph showing the start-up time of the supply water. (Explanation of symbols) 1...A tool connected to a drive shaft and rotated by a drive device, 2...A disc-shaped cathode made of a copper plate formed at the bottom of the tool I, 3...A cathode 2 Exposed surface formed in a cross shape on the lower surface, 4... Outlet of an electrolytic chamber provided through the center of the cathode 2, 5... Electrolyte outlet, 6... Exposed surface of the lower surface of the cathode 2 3 and abrasive grains attached to the entire surface except for the outlet 4, 7...a thin film of electrically insulating paint, etc.]
2... Impeller, 13... Casing, 1 4... Seal box, 1 6... Rotating shaft, 1 7... Bearing, 1 8... Vane, 1 9... Fluid inlet , 20...Fluid passage. Figure (0) 19 Old 20 Figure I (b) Figure 2 (b) Figure 3 Figure 3 (b)

Claims (4)

[Claims] (1) At least the main surface of the liquid-contacted parts inside the pump is
A pump characterized in that it is made of a material whose surface has been made mirror-finished by electrolytic composite polishing. (2) The pump according to claim 1, wherein the mirror surface has a surface roughness of 0.1 μmRmax or less. (3) The pump according to claim 1 or 2, wherein the pump is a vortex pump. (4) The pump according to claim 1 or 2, wherein the pump is a centrifugal pump.