JP2004263638A - Pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump, restraining the occurrence of water hammering and cavitation. <P>SOLUTION: A pair of check valves 1, 2 are provided in an inflow passage 3e and an outflow passage 3d in a pump body 3, thereby lowering the flow velocity per one check valve. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pump for transferring a fluid, and more particularly to a pump used for circulating and transferring a chemical solution in a semiconductor manufacturing apparatus.
[0002]
[Prior art]
Conventionally, as a pump for circulating or transferring a chemical solution in a semiconductor manufacturing apparatus, a bellows constituting a diaphragm of a pump working chamber is reciprocated by an air cylinder to generate a pump action, and the pump is sucked into a pump working chamber from a suction port. There is known a configuration in which a chemical solution is discharged from a discharge port (for example, see Patent Literature 1 and Patent Literature 2). Check valves are arranged in the flow path from the suction port to the pump action chamber and in the flow path from the pump action chamber to the discharge port, respectively, so that a chemical solution flows in one direction.
[0003]
[Patent Document 1]
JP-A-2002-174180 (pages 4 to 5, FIG. 2)
[Patent Document 2]
JP-A-11-324924 (pages 4 to 6, FIG. 1)
[0004]
[Problems to be solved by the invention]
In the conventional pump as described above, when the check valve on the flow path changes from open to closed at the end of the suction stroke, the flow rate of the chemical solution in the suction system from the external suction pipe to the pump instantaneously increases. It becomes 0. As a result, a rapid pressure rise and pressure drop, that is, a water hammer, occurs in the suction system. As a result, large vibrations occur in the pump and the piping connected to the pump. Also, the bellows in the pump vibrate greatly. When such vibrations are repeated, the sealing performance of the pipe joint is reduced, the bellows is broken, and the like, and the chemical liquid leaks. Also, the water hammer is a damped vibration, but the amplitude at the initial stage of the vibration is large, so that the check valve chatters until the amplitude is sufficiently reduced. The pump disclosed in Patent Document 2 is provided with a relief pipe or a relief valve outside the pump as a measure against the water hammer. However, this does not provide a means for eliminating the water hammer by the pump itself, and a system outside the pump. Becomes complicated.
Further, in the conventional pump, bubbles are easily generated in the chemical solution passing through the check valve during the suction stroke and the discharge stroke, and the inside of the check valve is damaged by cavitation. Therefore, the life of the check valve is short.
[0005]
In view of the above-mentioned conventional problems, an object of the present invention is to provide a pump that reduces water hammer and suppresses cavitation.
[0006]
[Means for Solving the Problems]
The pump of the present invention is a pump body having an inflow path and an outflow path of a fluid, a pump cylinder provided at one end of the pump body, and is capable of extending and contracting along the center axis direction inside the pump cylinder, A bellows that forms a pump working chamber together with the pump body and the pump cylinder, an air cylinder portion that expands and contracts the bellows, and wraps the pump cylinder, the bellows, and the air cylinder portion. An outer cover that is screwed to the pump body and fastened to each other in the direction of the central axis while being sandwiched between the pump body and a plurality of check valves provided in parallel with an inflow passage of the pump body. It is something.
In the pump configured as described above, the fluid is divided into the plurality of check valves in the inflow path of the pump body, and the flow rate of the fluid passing through one check valve is reduced. Therefore, the water flow hammer can be reduced by reducing the flow velocity drop when the flow velocity instantaneously becomes zero. Further, the fluid passing through the check valve does not become lower than the saturated vapor pressure due to the decrease in the flow velocity, and the generation of bubbles can be prevented. Therefore, occurrence of cavitation can be suppressed.
[0007]
Further, the pump may include a plurality of check valves provided in parallel with the outflow passage of the pump body.
In this case, the fluid is diverted to the plurality of check valves in the inflow path and the outflow path of the pump body, and the flow velocity of the fluid passing through one check valve decreases. Therefore, the water flow hammer can be reduced by reducing the flow velocity drop when the flow velocity instantaneously becomes zero. In addition, the fluid that passes through the check valve does not become lower than the saturated vapor pressure due to the decrease in the flow velocity, and the generation of bubbles can be prevented. Therefore, occurrence of cavitation can be suppressed.
[0008]
In the above-mentioned pump, the central axis may be horizontal in the installed state, and the check valve for discharging may be arranged above and the check valve for sucking may be arranged below.
In this case, the gas staying in the pump action chamber is easily released naturally via the check valve for discharge. Therefore, a decrease in pump capacity can be prevented.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view of a pump according to a first embodiment of the present invention, which is used for circulating or transferring a chemical solution (for example, including fluorine or the like) in a semiconductor manufacturing apparatus in a clean room. The pump is of a horizontal type and is usually installed in the state shown in the figure (the upper part in the figure is the top and the lower part is the ground). The pump is constituted by a plurality of members coaxially arranged on a common center axis A, and the outer or inner peripheral shape of each member is basically circular. Specifically, the pump includes a pump body 3 having a pair of two check valves 1 and 2 (details will be described later) arranged sideways, a cylindrical pump cylinder 4, and a double cylindrical form. A bellows 5 whose outer cylindrical portion 5a can be extended and contracted in a bellows shape in the direction of the central axis A; a spacer 6 screwed (fitted at the left end) inside the inner cylindrical portion 5b of the bellows 5; A round rod-shaped shaft 7 to be screwed (the left end is fitted), a ring-shaped piston case 8 through which the shaft 7 is inserted, and the shaft 7 to be screwed (the right end is fitted) and The main elements are a piston 9 inserted and slidable in the direction of the central axis A, a piston cover 10 covering the end surfaces of the piston case 8 and the piston 9, and a cylindrical outer cover 11 enclosing all or a part of the above-mentioned parts. It is configured as The pump cylinder 4 may be formed integrally with the pump body 3 (by cutting or the like).
[0010]
The spacer 6, the shaft 7, the piston case 8, the piston 9 and the piston cover 10, which are located on the right side of the bellows 5 as a partition wall, constitute an air cylinder portion. By configuring the air cylinder portion in this manner, it is not necessary to externally attach the air cylinder, and the whole pump becomes compact. It is preferable that the pump is compact because the installation area in the clean room is reduced. Also, even if a small amount of abrasion powder is generated from the air cylinder portion due to long-term use, the abrasion powder hardly scatters outside the pump, so that the clean room is not contaminated.
[0011]
In the above configuration, the bellows 5 has the outer peripheral surface 5a1 on the base side of the outer cylindrical portion 5a fitted inside the pump cylinder 4. The spacer 6 and the piston case 8 are in a mutually engaged (including a screwed) relationship via the shaft 7, and the spacer 6 is fitted in the inner cylindrical portion 5 b of the bellows 5. The left end of the piston case 8 forms a cylindrical projection 8c. The outer diameter of the projection 8c is substantially the same as the inner diameter of the outer cylindrical portion 5a of the bellows 5, so that the bellows 5 is formed. Can be fitted to the piston case 8. Further, the piston 9 is fitted to the piston case 8 and the shaft 7. The piston cover 10 and the piston case 8 have a relationship equivalent to each other via a plurality of positioning pins 12 (only one is shown). Therefore, the pump cylinder 4, the bellows 5, the spacer 6, the shaft 7, the piston case 8, the piston 9, and the piston cover 10 use fastening members such as rods and bolts, including other sealing members (such as O-rings). The structure is such that they are fitted to each other and positioned.
[0012]
On the other hand, an annular stopper portion 11a is formed from the right end of the outer cover 11 to the inner peripheral side. Further, the outer peripheral surface of the pump body 3 is externally threaded, and the inner peripheral surface of the outer cover 11 is internally threaded, and both are screwed together. By such screwing, members inside the outer cover 11 can be uniformly tightened. In particular, with a single screw having a relatively large diameter, the degree of tightening by screwing becomes uniform as a whole. Further, a central axis A acting on a contact surface between the pump body 3 and the pump cylinder 4, a contact surface between the pump cylinder 4 and the outer cylinder portion 5a of the bellows 5, and a contact surface between the outer cylinder portion 5a and the piston case 8 Pressure can be substantially uniform. As described above, the “pump action chamber” formed by partitioning the liquid space 13 by the bellows 5, the pump cylinder 4, and the pump body 3 which receive a substantially uniform pressure on the contact surface is deformed due to torsion of members, etc. Since there is no uneven fastening load, leakage of the chemical solution due to these factors can be prevented.
[0013]
A first air chamber C1 is formed inside the bellows 5 to advance the piston 9 to the left. The first air chamber C1 communicates with the port P1 through a hole 8a passing through the piston case 8. are doing. A second air chamber C2 for retreating the piston 9 is formed between the left end surface of the piston 9 and the piston case 8. The second air chamber C2 communicates with the port P2 via a hole 8b formed in the piston case 8.
[0014]
The third air chamber C3 formed between the right end face of the piston 9 and the piston cover 10 is opened through a hole 10b provided in the piston cover 10. A hole 9a having a slightly smaller diameter than the hole 10a penetrating the piston cover 10 is formed on the right end surface of the piston 9 at a position coaxial with the hole 10a penetrating the piston cover 10. A pin (not shown) is implanted in the hole 9a to form the hole 9a. By loosely inserting, the rotation of the piston 9, that is, the torsion of the bellows 5 can be prevented.
[0015]
FIG. 2A is a view of the pump body 3 as viewed leftward from the liquid space 13 side in FIG. (B) is the side view which looked at the pump body 3 from the same direction as FIG. (C) is a view of the pump body 3 viewed from the opposite side to (a). FIGS. 3A and 3B are a sectional view taken along line AA and a sectional view taken along line BB in FIG. 2A, respectively. As shown in FIG. 2A, a total of four check valves 1 and 2 are provided and fitted to the pump body 3. The upper pair of check valves 1 is for discharging, has a valve body 1a urged rightward by a spring 1b (made of resin) in FIG. 1, and allows the chemical to flow only in the direction of the arrow. The pair of check valves 1 are provided in parallel with each other on the flow path, and the liquid medicine in the liquid space 13 is discharged from the side discharge port 3 a and the upper discharge port 3 d through an outflow path 3 d formed in the pump body 3. The water is discharged from the outlet 3c to the outside of the pump (see FIG. 2C). The lower pair of check valves 2 is for suction, has a valve body 2a urged leftward by a spring 2b (made of resin) in FIG. 1, and allows the chemical to flow only in the direction of the arrow. The pair of check valves 2 are provided in parallel with each other on the flow path, and the chemical solution flows from an inlet 3b provided on the side surface through an inflow passage 3e formed in the pump body 3 ((c in FIG. 2). ) Is taken into the liquid space 13.
[0016]
The pump has an external liquid type pump structure in which check valves 1 and 2 are fitted inside a pump body 3 and a liquid space 13 is formed inside a pump cylinder 4. Thus, the liquid space 13 can be made the minimum necessary space, which can contribute to shortening the span of the pump in the direction of the central axis A. Further, as shown in FIG. 1, the check valves 1 and 2 do not project from the inner end face of the pump body 3 facing the liquid space 13. This is more preferable for shortening the span.
[0017]
Regarding the material of each part, the contact parts of the pump body 3, the pump cylinder 4, the bellows 5, etc. are made of a fluororesin such as PTFE (polytetrafluoroethylene) or PFA (polytetrafluoroethylene-perfluoroalkylvinyl ether copolymer). Is preferred. Non-contact portions such as the spacer 6, the shaft 7, the piston case 8, the piston 9, the piston cover 10, and the outer cover 11 are preferably made of PP (polypropylene), PPS (polyphenylene sulfide), POM (polyoxymethylene), or the like. The check valves 1 and 2 are preferably made of PFA or PTFE, including the internal springs 1b and 2b. In addition, the sealing member and the O-ring are also made of resin. That is, all members constituting the pump are made of resin. Therefore, there is no risk of metal ions entering a work such as a semiconductor wafer, which contributes to the stability of semiconductor quality.
Although the bellows 5 and the shaft 7 are connected via the spacer 6 in FIG. 1, the connection strength via the spacer 6 improves the fastening strength, which tends to be insufficient in the resin material. be able to.
[0018]
FIG. 3 is a sectional view showing an assembled state of the pump. In the figure, the pump cylinder 4, the bellows 5, the spacer 6, the shaft 7, the piston case 8, the piston 9, and the piston cover 10 are in a mutually fitted relationship as described above, and are positioned by the fitting. Are "centered out" on a common central axis A. Therefore, centering can be easily performed between the air cylinder portions (6 to 10) and the bellows 5, which are not easily centered. The fitting body thus configured is tightly inserted into the outer cover 11 (substantially equivalent to fitting, for example, a gap of about 0.2 mm). By the insertion, the peripheral edge portion 10c of the piston cover 10 comes into contact with the stopper portion 11a of the outer cover 11, whereby the inserted fitting body is restricted at the right end thereof. Further, when the male screw of the pump body 3 is screwed into the female screw of the outer cover 11 and tightened, the left end of the fitting body is regulated by the pump body 3 so as to be pulled out and sandwiched between the stopper part 11a as shown in FIG. Fixed to state.
[0019]
Further, the outer cover 11 restricts radial displacement of the pump cylinder 4, the bellows 5, the piston case 8, and the piston cover 10 substantially inscribing the inner peripheral surface thereof. Hold. As a result, radial displacement of other members that are fitted to these members is also restricted. That is, the outer cover 11 positions each member housed therein in the radial direction, and stably maintains the positioning state. For this reason, even after assembly, each member is held by the outer cover 11 and there is substantially no deviation in the radial direction.
[0020]
As described above, each part constituting the structure of the pump is regulated from the outside by the outer cover 11, is arranged on the center axis A inside, and is fixed in a state of being accurately positioned with respect to each other. Since the pump assembled in this manner is not fastened using a rod, a bolt, or the like as in the related art, the members are not twisted or deformed for a long time. Also, the axial center deviation of the air cylinder portions (6 to 10) does not become a problem, and abnormal wear of each member of the air cylinder portion due to the axial center misalignment may cause a malfunction and a deterioration of the pump function. Absent.
In addition, since the pump cylinder 4, the bellows 5, and the air cylinder part are fitted at least partially alternately into a fitting body, it is possible to shorten the span in the central axis direction only in the overlapping part (for example, air). The shaft 7 of the cylinder part can also be arranged in the bellows 5), and the pump can be made compact. This is preferable because the installation area occupied in the clean room is reduced as described above.
[0021]
In the above description related to FIG. 3, the respective members of the pump cylinder 4, the bellows 5, the spacer 6, the shaft 7, the piston case 8, the piston 9, and the piston cover 10 are fitted to each other, and the outer cover is referred to as a "fitting body". Although it is described that the members are tightly inserted into the outer cover 11, the members may be individually or sequentially inserted into the outer cover 11 in a state where the members are fitted to some extent, and a “fitting body” may be assembled in the outer cover 11. .
[0022]
In the pump configured as described above, the compressed air is supplied to the port P1, and the port P2 is evacuated or depressurized, whereby the piston 9 advances with the shaft 7 and the spacer 6, and the bellows 5 extends to the left. I do. As a result, the check valve 1 on the discharge side is opened, and the liquid medicine is discharged from the discharge ports 3a and 3c. Conversely, by supplying compressed air to the port P2 and exhausting or reducing the pressure of the port P1, the piston 9 retreats together with the shaft 7 and the spacer 6, and the bellows 5 contracts to the illustrated state. As a result, the check valve 2 on the suction side is opened, and the liquid medicine is sucked from the suction port 3b. The repetition of such reciprocating motion causes a pump action to transfer the chemical solution.
[0023]
By providing the pair of check valves 2 on the suction side in parallel as described above, the chemical solution is diverted to the two check valves 2 during the suction stroke. Therefore, the flow rate of the chemical solution passing through each check valve 2 is reduced as compared with the case where only one check valve 2 is provided. Due to this decrease in flow velocity, the flow velocity drop when the flow velocity instantaneously becomes 0 at the end of the suction stroke is reduced, and the water hammer is reduced. Specifically, assuming that the fluid pressure for pushing the valve body 2a of the check valve 2 that has been turned from open to closed in the opening direction is P1, and the fluid pressure on the liquid space 13 side is P2, P1 is determined by the water hammer when the valve is closed. Vibration is attenuated, but the amplitude of the vibration at this time is substantially halved compared to the case where the check valve 2 is single. Therefore, the time during which P1> P2 may be transiently satisfied after the valve is closed is negligible, and chattering of the check valve 2 is greatly reduced. Further, due to the decrease in the flow velocity, the fluid pressure does not drop below the saturated vapor pressure in the vicinity of the check valve 2 during the passage of the chemical solution, and almost no bubbles are generated in the chemical solution. Therefore, occurrence of cavitation can be suppressed.
[0024]
On the other hand, by providing a pair of check valves 1 on the discharge side in parallel, the chemical solution is diverted to the two check valves 1 in the discharge stroke. Accordingly, as in the case of the end of the suction stroke, the water hammer generated at the end of the discharge stroke is also reduced, and the chattering of the check valve 1 is greatly reduced. Further, the occurrence of cavitation can be suppressed by the decrease in the flow velocity.
In this manner, the water hammer can be reduced in both the suction and discharge strokes, and the occurrence of vibrations that threaten the sealing performance can be suppressed. In addition, the life of the check valves 1 and 2 can be prolonged due to a significant reduction in chattering and suppression of cavitation.
The interval between the check valves arranged in parallel is preferably within three times the flow path diameter r of the check valve. If it exceeds three times, a large deviation may occur in the opening / closing operation of the check valve, or the pressure loss may increase before reaching the check valve having a longer flow path.
[0025]
In addition, the pump is placed sideways so that the central axis is directed sideways, and the check valve 1 for discharge is located above, so that the gas staying in the liquid space 13 (pump action chamber) (from the mixed air or the chemical solution). There is an advantage that gas (evolved gas) easily escapes naturally from the outlets 3a and 3c via the check valve 1. Therefore, a situation in which a large amount of gas stays in the liquid space 13 to be filled with the chemical liquid and the pump capacity is reduced is unlikely to occur. That is, it is possible to prevent a decrease in pump capacity. In addition, in the initial stage of starting the pump, it is unavoidable that air has entered the pump. Therefore, it is necessary to perform an air bleeding operation and wait for the pump capacity to stabilize. However, according to the configuration in which the gas is easily released as described above, the air is quickly released at the initial stage of starting, and the pump capacity is stabilized in a short time.
In addition, since the check valves 1 and 2 are arranged sideways, the springs 1b and 2b have less fatigue and last longer.
[0026]
Although the pump of the above embodiment is for transferring a chemical solution containing fluorine or the like, it is needless to say that a pump for transferring other various fluids may be used.
Although two check valves 1 and 2 are provided, three or more check valves may be provided if necessary.
Further, even with a pump using a diaphragm instead of a bellows, the same action and effect can be obtained by the above-described configuration of the check valves 1 and 2.
In addition, even if the parallel check valve is provided only in the inflow passage 3e, there is a certain effect.
[0027]
【The invention's effect】
In the present invention configured as described above, by providing a plurality of check valves in parallel, the fluid is diverted to the plurality of check valves, and the flow rate of the fluid passing through one check valve decreases. The water flow hammer can be reduced by reducing the flow velocity drop when the flow velocity instantaneously becomes zero. In addition, since the fluid passing through the check valve does not fall below the saturated vapor pressure due to the decrease in the flow velocity, the generation of bubbles can be prevented, and thus the occurrence of cavitation can be suppressed.
[Brief description of the drawings]
FIG. 1 is a sectional view of a pump according to a first embodiment of the present invention.
FIG. 2 is a view showing an appearance of a pump body in the pump.
FIG. 3 is a sectional view of the pump body.
FIG. 4 is a sectional view showing an assembled state of the pump.
[Explanation of symbols]
1, 2 Check valve 3 Pump body 3d Outflow path 3e Inflow path 4 Pump cylinder 5 Bellows 6 Spacer 7 Shaft 8 Piston case 9 Piston 10 Piston cover 6-10 Air cylinder section 11 Outer cover

Claims (3)

A pump body having an inflow path and an outflow path for fluid,
A pump cylinder provided at one end of the pump body,
A bellows extendable and contractable in the pump cylinder along a central axis direction, and form a pump working chamber together with the pump body and the pump cylinder;
An air cylinder section for expanding and contracting the bellows,
While enclosing the pump cylinder, the bellows, and the air cylinder portion, and sandwiching them between the pump body in the center axis direction, the pump cylinder, the bellows, and the air cylinder portion are screwed with the pump body and mutually fastened in the center axis direction. Cover and
A plurality of check valves provided in parallel with an inflow passage of the pump body. 2. The pump according to claim 1, further comprising a plurality of check valves provided in parallel with an outflow passage of the pump body. 3. The pump according to claim 2, wherein, in the installed state, the central axis is horizontal, the check valve for discharging is arranged above, and the check valve for sucking is arranged below.

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