BELLOWS PUMP DEVICE

Abstract

A bellows pump device includes: a first electropneumatic regulator 51 that adjusts a first air pressure of pressurized air in a first discharge-side air chamber 21A of a first air cylinder unit 27; a second electropneumatic regulator 52 that adjusts a second air pressure of pressurized air in a second discharge-side air chamber 21B of a second air cylinder unit 28; and a control unit 6 that controls the first electropneumatic regulator 51 such that the first air pressure is continuously decreased during a period from a time when a second bellows 14 starts contracting until a first bellows 13 comes into a most contracted state, and controls the second electropneumatic regulator 52 such that the second air pressure is continuously decreased during a period from a time when the first bellows 13 starts contracting until the second bellows 14 comes into a most contracted state.

Description

TECHNICAL FIELD

The present invention relates to a bellows pump device.

BACKGROUND ART

As a bellows pump used for feeding a transport fluid such as a chemical solution or a solvent in semiconductor production, chemical industries, or the like, a bellows pump which includes: a pair of bellows configured to suck a transport fluid thereinto and discharge the transport fluid therefrom by expanding/contracting independently of each other; and air cylinders configured to cause the respective bellows to expand/contract, by supplying/discharging compressed air (see, for example, PATENT LITERATURE 1), has been known. The bellows pump disclosed in PATENT LITERATURE 1 controls drive of each air cylinder such that, before one bellows comes into a most contracted state (end of discharge), the other bellows is caused to contract from a most expanded state to discharge a transport fluid.

By controlling drive of each air cylinder as described above, at a time of switching from contraction of one bellows to expansion thereof (from discharge of the transport fluid to suction thereof), the other bellows has already contracted to discharge the transport fluid. Accordingly, great fall of the discharge pressure of the transport fluid at the time of switching can be reduced. As a result, pulsation at the discharge side of the bellows pump can be reduced.

CITATION LIST

Patent Literature

PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No. 2004-293502

SUMMARY OF INVENTION

Technical Problem

The above bellows pump includes a check valve that prevents backflow of the transport fluid in a discharge process of discharging the transport fluid by contraction of each bellows. When one bellows is switched from a discharge process to a suction process, the check valve that has opened in the discharge process to permit discharge of the transport fluid is pressed to close by the transport fluid discharged from the other bellows.

However, there is the following problem. Specifically, when one bellows is switched from a discharge process to a suction process, the other bellows has already contracted to discharge high-pressure transport fluid as described above, and thus the check valve is pressed to rapidly close by the high-pressure transport fluid. Therefore, the impact generated when the check valve rapidly closes is transmitted to the interior of a transport fluid discharge pipe connected to the bellows pump, whereby, as shown in FIG. 10, surge pressure (a portion surrounded by a broken line in the drawing) is generated within the discharge pipe.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bellows pump device that can reduce pulsation and inhibit generation of surge pressure at the discharge side when switching is made from discharge of a transport fluid to suction thereof.

Solution to Problem

(1) A bellows pump device according to the present invention is a bellows pump device including: a pump head having a suction passage and a discharge passage for a transport fluid; a first bellows and a second bellows mounted on the pump head so as to be expandable/contractible independently of each other and configured to suck the transport fluid from the suction passage thereinto by expansion thereof and discharge the transport fluid therefrom to the discharge passage by contraction thereof; a check valve configured to permit flow of the transport fluid in one direction in the suction passage and the discharge passage and block flow of the transport fluid in another direction in the suction passage and the discharge passage; a first driving unit having a first suction-side fluid chamber and a first discharge-side fluid chamber and configured to supply a pressurized fluid to the first suction-side fluid chamber thereby causing the first bellows to expand to a most expanded state, and supply the pressurized fluid to the first discharge-side fluid chamber thereby causing the first bellows to contract to a most contracted state; and a second driving unit having a second suction-side fluid chamber and a second discharge-side fluid chamber and configured to supply a pressurized fluid to the second suction-side fluid chamber thereby causing the second bellows to expand to a most expanded state, and supply the pressurized fluid to the second discharge-side fluid chamber thereby causing the second bellows to contract to a most contracted state, wherein the second bellows contracts from the most expanded state before the first bellows comes into the most contracted state, and the first bellows contracts from the most expanded state before the second bellows comes into the most contracted state, the bellows pump device further including a first fluid pressure adjustment unit configured to adjust a first fluid pressure of the pressurized fluid in the first discharge-side fluid chamber of the first driving unit, a second fluid pressure adjustment unit configured to adjust a second fluid pressure of the pressurized fluid in the second discharge-side fluid chamber of the second driving unit, and a control unit configured to control the first fluid pressure adjustment unit such that the first fluid pressure is decreased stepwise or continuously during a period from a time at which the second bellows starts contracting to a time at which the first bellows comes into the most contracted state, and control the second fluid pressure adjustment unit such that the second fluid pressure is decreased stepwise or continuously during a period from a time at which the first bellows starts contracting to a time at which the second bellows comes into the most contracted state.

According to the present invention, before one bellows of the first bellows and the second bellows comes into the most contracted state, the other bellows contracts from the most expanded state. Accordingly, at a time of switching from contraction of the one bellows to expansion thereof (from discharge of the transport fluid to suction thereof), the other bellows has already contracted to discharge the fluid, and thus fall of the discharge pressure at the time of switching can be reduced. As a result, pulsation at the discharge side of the bellows pump device can be reduced.

Moreover, the control unit controls the fluid pressure adjustment unit corresponding to the discharge-side fluid chamber corresponding to the other bellows such that the fluid pressure in the discharge-side fluid chamber is decreased stepwise or continuously during a period from a time at which the one bellows starts contracting to a time at which the other bellows comes into the most contracted state. Owing to this control, before the other bellows comes into the most contracted state, the check valve that permits flow of the transport fluid from the other bellows to the discharge passage gradually moves in a valve closing direction from a valve-open state. Accordingly, when the other bellows is switched from the most contracted state to expansion, impact due to rapid closing of the check valve can be alleviated. As a result, surge pressure can be inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

(2) Preferably, the control unit controls the first fluid pressure adjustment unit such that the first fluid pressure reaches zero before or when the first bellows comes into the most contracted state, and controls the second fluid pressure adjustment unit such that the second fluid pressure reaches zero before or when the second bellows comes into the most contracted state.

In this case, before or when the other bellows comes into the most contracted state after the one bellows starts contracting, the fluid pressure in the discharge-side fluid chamber corresponding to the other bellows is stepwise or continuously decreased and reaches zero. Since the fluid pressure in the discharge-side fluid chamber is decreased as described above, the check valve corresponding to the other bellows closes before or when the other bellows comes into the most contracted state. Accordingly, the check valve can be prevented from rapidly closing when the other bellows is switched from the most contracted state to expansion. As a result, surge pressure can be further inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

(3) Preferably, the control unit controls the first fluid pressure adjustment unit such that the first fluid pressure reaches zero at the time at which the first bellows comes into the most contracted state, and controls the second fluid pressure adjustment unit such that the second fluid pressure reaches zero at the time at which the second bellows comes into the most contracted state.

In this case, during the period from the time at which the one bellows starts contracting to the time at which the other bellows comes into the most contracted state, the fluid pressure in the discharge-side fluid chamber corresponding to the other bellows is stepwise or continuously decreased, and reaches zero at the time at which the other bellows comes into the most contracted state. Accordingly, the check valve corresponding to the other bellows slowly closes as compared to the case where the fluid pressure reaches zero before the other bellows comes into the most contracted state. As a result, surge pressure can be further inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

Advantageous Effects of Invention

According to the present invention, when switching is made from discharge of the transport fluid to suction of the transport fluid, pulsation can be reduced and generation of surge pressure can be inhibited at the discharge side.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a bellows pump device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a bellows pump.

FIG. 3 is an explanatory diagram showing operation of the bellows pump.

FIG. 4 is an explanatory diagram showing operation of the bellows pump.

FIG. 5 is a time chart showing an example of control of electropneumatic regulators by a control unit.

FIG. 6 is a graph showing the discharge pressure of a transport fluid discharged from a discharge passage of the bellows pump.

FIG. 7 is a time chart showing first to third modifications for control of the electropneumatic regulator by the control unit.

FIG. 8 is a time chart showing fourth and fifth modifications for control of the electropneumatic regulator by the control unit.

FIG. 9 is a time chart showing a sixth modification for control of the electropneumatic regulator by the control unit.

FIG. 10 is a graph showing the pressure within a discharge pipe to a conventional bellows pump.

DESCRIPTION OF EMBODIMENTS

Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[Entire Configuration of Bellows Pump Device]

FIG. 1 is a schematic configuration diagram of a bellows pump device according to an embodiment of the present invention. The bellows pump device of the present embodiment is used, for example, in a semiconductor production apparatus when an object to be transported (transport fluid) such as a chemical solution or a solvent is supplied in a certain amount. The bellows pump device includes: a bellows pump 1; an air supply device 2 such as an air compressor that supplies pressurized air (pressurized fluid) to the bellows pump 1; a mechanical regulator 3, a first electropneumatic regulator (first fluid pressure adjustment unit) 51, and a second electropneumatic regulator (second fluid pressure adjustment unit) 52 that adjust the air pressure of the pressurized air; a first solenoid valve 4; a second solenoid valve 5; and a control unit 6.

FIG. 2 is a cross-sectional view of the bellows pump 1 according to the present embodiment. The bellows pump 1 of the present embodiment includes: a pump head 11 that is disposed at a center portion; a pair of pump cases 12 that are mounted at both sides of the pump head 11 in a right-left direction (horizontal direction); a first bellows 13 and a second bellows 14 that are mounted on side surfaces of the pump head 11 in the right-left direction and within the respective pump cases 12; and a total of four check valves 15 and 16 that are mounted on the side surfaces of the pump head 11 in the right-left direction and within the respective first and second bellows 13 and 14.

[Configurations of Bellows]

The first bellows 13 and the second bellows 14 are each formed in a bottomed cylindrical shape from a fluorine resin such as polytetrafluoroethylene (PTFE) or a tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer (PFA). A flange portion 13a and a flange portion 14a are integrally formed at open end portions of the first and second bellows 13 and 14 and are hermetically pressed and fixed to the side surfaces of the pump head 11. Peripheral walls of the first and second bellows 13 and 14 are each formed in an accordion shape, and are configured to be expandable/contractible independently of each other in the horizontal direction.

Specifically, each of the first and second bellows 13 and 14 is configured to expand/contract between a most expanded state where an outer surface of a working plate 19 described later is in contact with an inner side surface of a bottom wall portion 121 of the pump case 12 and a most contracted state where an inner side surface of a piston body 23 described later is in contact with an outer side surface of the bottom wall portion 121 of the pump case 12. The working plate 19, together with one end portion of a connection member 20, is fixed to each of outer surfaces of bottom portions of the first and second bellows 13 and 14 by bolts 17 and nuts 18.

[Configurations of Pump Cases]

An opening peripheral portion of the pump case 12 (hereinafter, also referred to as “first pump case 12A”), which is formed in a bottomed cylindrical shape, is hermetically pressed and fixed to the flange portion 13a of the first bellows 13. Accordingly, a first discharge-side air chamber (first discharge-side fluid chamber) 21A is formed within the first pump case 12A such that a hermetic state thereof is maintained.

A first suction/discharge port 22A is provided in the first pump case 12A and connected to the air supply device 2 via the first solenoid valve 4, the first electropneumatic regulator 51, and the mechanical regulator 3 (see FIG. 1). Accordingly, the first bellows 13 contracts to the most contracted state by continuously supplying the pressurized air from the air supply device 2 via the mechanical regulator 3, the first electropneumatic regulator 51, the first solenoid valve 4, and the first suction/discharge port 22A into the first discharge-side air chamber 21A.

An opening peripheral portion of the pump case 12 (hereinafter, also referred to as “second pump case 12B”), which is formed in a bottomed cylindrical shape, is hermetically pressed and fixed to the flange portion 14a of the second bellows 14. Accordingly, a second discharge-side air chamber (second discharge-side fluid chamber) 21B is formed within the second pump case 12B such that a hermetic state thereof is maintained.

A second suction/discharge port 22B is provided in the second pump case 12B and connected to the air supply device 2 via the second solenoid valve 5, the second electropneumatic regulator 52, and the mechanical regulator 3 (see FIG. 1). Accordingly, the second bellows 14 contracts to the most contracted state by continuously supplying the pressurized air from the air supply device 2 via the mechanical regulator 3, the second electropneumatic regulator 52, the second solenoid valve 5, and the second suction/discharge port 22B into the second discharge-side air chamber 21B.

The connection member 20 is supported by the bottom wall portion 121 of each pump case 12A, 12B so as to be slidable in the horizontal direction, and the piston body 23 is fixed to another end portion of the connection member 20 by a nut 24. The piston body 23 is supported so as to be slidable in the horizontal direction relative to an inner circumferential surface of a cylindrical cylinder body 25, which is integrally provided on the outer side surface of the bottom wall portion 121, with a hermetic state maintained.

Accordingly, at the first pump case 12A side, a space surrounded by the bottom wall portion 121, the cylinder body 25, and the piston body 23 is formed as a first suction-side air chamber (first suction-side fluid chamber) 26A of which a hermetic state is maintained. In addition, at the second pump case 12B side, a space surrounded by the bottom wall portion 121, the cylinder body 25, and the piston body 23 is formed as a second suction-side air chamber (second suction-side fluid chamber) 26B of which a hermetic state is maintained.

In the cylinder body 25 at the first pump case 12A side, a suction/discharge port 251 is formed so as to communicate with the first suction-side air chamber 26A. The suction/discharge port 251 is connected to the air supply device 2 via the first solenoid valve 4, the first electropneumatic regulator 51, and the mechanical regulator 3 (see FIG. 1). Accordingly, the first bellows 13 expands to the most expanded state by continuously supplying the pressurized air from the air supply device 2 via the mechanical regulator 3, the first electropneumatic regulator 51, the first solenoid valve 4, and the suction/discharge port 251 into the first suction-side air chamber 26A.

In the cylinder body 25 at the second pump case 12B side, a suction/discharge port 252 is formed so as to communicate with the second suction-side air chamber 26B. The suction/discharge port 252 is connected to the air supply device 2 via the second solenoid valve 5, the second electropneumatic regulator 52, and the mechanical regulator 3 (see FIG. 1). Accordingly, the second bellows 14 expands to the most expanded state by continuously supplying the pressurized air from the air supply device 2 via the mechanical regulator 3, the second electropneumatic regulator 52, the second solenoid valve 5, and the suction/discharge port 252 into the second suction-side air chamber 26B.

Because of the above configuration, the first pump case 12A, in which the first discharge-side air chamber 21A is formed, and the piston body 23 and the cylinder body 25 that form the first suction-side air chamber 26A, form a first air cylinder unit (first driving unit) 27 that causes the first bellows 13 to perform expansion/contraction operation continuously between the most expanded state and the most contracted state.

In addition, the second pump case 12B, in which the second discharge-side air chamber 21B is formed, and the piston body 23 and the cylinder body 25 that form the second suction-side air chamber 26B, form a second air cylinder unit (second driving unit) 28 that causes the second bellows 14 to perform expansion/contraction operation continuously between the most expanded state and the most contracted state.

[Configurations of Detection Units]

A pair of proximity sensors 29A and 29B are mounted on the cylinder body 25 of the first air cylinder unit 27. A detection plate 30 to be detected by each of the proximity sensors 29A and 29B is mounted on the piston body 23 of the first air cylinder unit 27. The detection plate 30 reciprocates together with the piston body 23, so that the detection plate 30 alternately comes close to the proximity sensors 29A and 29B, whereby the detection plate 30 is detected by the proximity sensors 29A and 29B.

The proximity sensor 29A is disposed at such a position that the proximity sensor 29A detects the detection plate 30 when the first bellows 13 is in the most contracted state. The proximity sensor 29B is disposed at such a position that the proximity sensor 29B detects the detection plate 30 when the first bellows 13 is in the most expanded state. Detection signals of the respective proximity sensors 29A and 29B are transmitted to the control unit 6. In the present embodiment, the pair of proximity sensors 29A and 29B form a first detection unit 29 that detects an expanded/contracted state of the first bellows 13.

Similarly, a pair of proximity sensors 31A and 31B are mounted on the cylinder body 25 of the second air cylinder unit 28. A detection plate 32 to be detected by each of the proximity sensors 31A and 31B is mounted on the piston body 23 of the second air cylinder unit 28. The detection plate 32 reciprocates together with the piston body 23, so that the detection plate 32 alternately comes close to the proximity sensors 31A and 31B, whereby the detection plate 32 is detected by the proximity sensors 31A and 31B.

The proximity sensor 31A is disposed at such a position that the proximity sensor 31A detects the detection plate 32 when the second bellows 14 is in the most contracted state. The proximity sensor 31B is disposed at such a position that the proximity sensor 31B detects the detection plate 32 when the second bellows 14 is in the most expanded state. Detection signals of the respective proximity sensors 31A and 31B are transmitted to the control unit 6. In the present embodiment, the pair of proximity sensors 31A and 31B form a second detection unit 31 that detects an expanded/contracted state of the second bellows 14.

The pressurized air generated by the air supply device 2 is alternately supplied to the first suction-side air chamber 26A and the first discharge-side air chamber 21A of the first air cylinder unit 27 by the pair of proximity sensors 29A and 29B of the first detection unit 29 alternately detecting the detection plate 30. Accordingly, the first bellows 13 continuously performs expansion/contraction operation.

In addition, the pressurized air generated by the air supply device 2 is alternately supplied to the second suction-side air chamber 26B and the second discharge-side air chamber 21B of the second air cylinder unit 28 by the pair of proximity sensors 31A and 31B of the second detection unit 31 alternately detecting the detection plate 32. Accordingly, the second bellows 14 continuously performs expansion/contraction operation. At this time, expansion operation of the second bellows 14 is performed during contraction operation of the first bellows 13, and contraction operation of the second bellows 14 is performed mainly during expansion operation of the first bellows 13. By the first bellows 13 and the second bellows 14 alternately repeating expansion/contraction operation as described above, suction and discharge of the transport fluid to and from the interiors of the respective bellows 13 and 14 are alternately performed, whereby the transport fluid is transported.

The first and second detection units 29 and 31 are composed of proximity sensors, but may be composed of other detection means such as limit switches. In addition, the first and second detection units 29 and 31 detect the most expanded states and the most contracted states of the first and second bellows 13 and 14, but may be configured to detect states in the middle of expansion/contraction of the first and second bellows 13 and 14.

[Configuration of Pump Head]

The pump head 11 is formed from a fluorine resin such as PTFE or PFA. A suction passage 34 and a discharge passage 35 for the transport fluid are formed within the pump head 11. The suction passage 34 and the discharge passage 35 are opened in an outer peripheral surface of the pump head 11 and respectively connected to a suction port and a discharge port (both are not shown) provided at the outer peripheral surface.

The suction port is connected to a storage tank for the transport fluid or the like, and the discharge port is connected to a transport destination for the transport fluid. In addition, the suction passage 34 and the discharge passage 35 each branch toward both right and left side surfaces of the pump head 11, and have suction openings 36 and discharge openings 37 that are opened in both right and left side surfaces of the pump head 11. Each suction opening 36 and each discharge opening 37 communicate with the interior of the bellows 13 or 14 via the check valves 15 and 16, respectively.

[Configurations of Check Valves]

The check valves 15 and 16 are provided at each suction opening 36 and each discharge opening 37.

The check valve 15 (hereinafter, also referred to as “suction check valve”) mounted at each suction opening 36 includes: a valve case 15a; a valve body 15b that is housed in the valve case 15a; and a compression coil spring 15c that biases the valve body 15b in a valve closing direction.

The valve case 15a is formed in a bottomed cylindrical shape. A through hole 15d is formed in a bottom wall of the valve case 15a so as to communicate with the interior of the bellows 13 or 14. The valve body 15b closes the suction opening 36 (performs valve closing) by the biasing force of the compression coil spring 15c, and opens the suction opening 36 (performs valve opening) when a back pressure generated by flow of the transport fluid occurring with expansion/contraction of the bellows 13 or 14 acts thereon.

Accordingly, the suction check valve 15 opens, when the bellows 13 or 14 at which the suction check valve 15 is disposed expands, to permit suction of the transport fluid in a direction from the suction passage 34 toward the interior of the bellows 13 or 14 (in one direction). In addition, the suction check valve 15 closes, when the bellows 13 or 14 at which the suction check valve 15 is disposed contracts, to block backflow of the transport fluid in a direction from the interior of the bellows 13 or 14 toward the suction passage 34 (in another direction).

The check valve 16 (hereinafter, also referred to as “discharge check valve”) mounted at each discharge opening 37 includes: a valve case 16a; a valve body 16b that is housed in the valve case 16a; and a compression coil spring 16c that biases the valve body 16b in a valve closing direction.

The valve case 16a is formed in a bottomed cylindrical shape. A through hole 16d is formed in a bottom wall of the valve case 16a so as to communicate with the interior of the bellows 13 or 14. The valve body 16b closes the through hole 16d of the valve case 16a (performs valve closing) by the biasing force of the compression coil spring 16c, and opens the through hole 16d of the valve case 16a (performs valve opening) when a back pressure generated by flow of the transport fluid occurring with expansion/contraction of the bellows 13 or 14 acts thereon.

Accordingly, the discharge check valve 16 opens, when the bellows 13 or 14 at which the discharge check valve 16 is disposed contracts, to permit outflow of the transport fluid in a direction from the interior of the bellows 13 or 14 toward the discharge passage 35 (in one direction). In addition, the discharge check valve 16 closes, when the bellows 13 or 14 at which the discharge check valve 16 is disposed expands, to block backflow of the transport fluid in a direction from the discharge passage 35 toward the interior of the bellows 13 or 14 (in another direction).

[Operation of Bellows Pump]

Next, operation of the bellows pump 1 of the present embodiment will be described with reference to FIG. 3 and FIG. 4. In FIG. 3 and FIG. 4, the configurations of the first and second bellows 13 and 14 are shown in a simplified manner

As shown in FIG. 3, when the first bellows 13 contracts and the second bellows 14 expands, the respective valve bodies 15b and 16b of the suction check valve 15 and the discharge check valve 16 that are mounted at the left side of the pump head 11 in the drawing receive pressure from the transport fluid within the first bellows 13 and move to the right sides of the respective valve cases 15a and 16a in the drawing. Accordingly, the suction check valve 15 closes, and the discharge check valve 16 opens, so that the transport fluid within the first bellows 13 is discharged through the discharge passage 35 to the outside of the pump.

Meanwhile, the valve body 15b of the suction check valve 15 mounted at the right side of the pump head 11 in the drawing moves to the right side of the valve case 15a in the drawing due to a suction effect by the second bellows 14. In addition, the valve body 16b of the discharge check valve 16 mounted at the right side of the pump head 11 in the drawing moves to the right side of the valve case 16a in the drawing due to a suction effect by the second bellows 14 and a pressing effect by the transport fluid discharged from the first bellows 13 to the discharge passage 35. Accordingly, the suction check valve 15 opens, and the discharge check valve 16 closes, so that the transport fluid is sucked from the suction passage 34 into the second bellows 14.

Next, as shown in FIG. 4, when the first bellows 13 expands and the second bellows 14 contracts, the respective valve bodies 15b and 16b of the suction check valve 15 and the discharge check valve 16 that are mounted at the right side of the pump head 11 in the drawing receive pressure from the transport fluid within the second bellows 14 and move to the left sides of the respective valve cases 15a and 16a in the drawing. Accordingly, the suction check valve 15 closes, and the discharge check valve 16 opens, so that the transport fluid within the second bellows 14 is discharged through the discharge passage 35 to the outside of the pump.

Meanwhile, the valve body 15b of the suction check valve 15 mounted at the left side of the pump head 11 in the drawing moves to the left side of the valve case 15a in the drawing due to a suction effect by the first bellows 13. In addition, the valve body 16b of the discharge check valve 16 mounted at the left side of the pump head 11 in the drawing moves to the left side of the valve case 16a in the drawing due to a suction effect by the first bellows 13 and a pressing effect by the transport fluid discharged from the first bellows 13 to the discharge passage 35. Accordingly, the suction check valve 15 opens, and the discharge check valve 16 closes, so that the transport fluid is sucked from the suction passage 34 into the first bellows 13.

By repeatedly performing the above operation, the left and right bellows 13 and 14 can alternately suck and discharge the transport fluid.

[Configurations of Solenoid Valves]

In FIG. 1, the first solenoid valve 4 switches between: supply/discharge of the pressurized air to/from one air chamber of the first discharge-side air chamber 21A and the first suction-side air chamber 26A of the first air cylinder unit 27; and supply/discharge of the pressurized air to/from the other air chamber. The first solenoid valve 4 is composed of, for example, a three-position solenoid switching valve including a pair of solenoids 4a and 4b. Each of the solenoids 4a and 4b is magnetized on the basis of a command signal received from the control unit 6.

The second solenoid valve 5 switches between: supply/discharge of the pressurized air to/from one air chamber of the second discharge-side air chamber 21B and the second suction-side air chamber 26B of the second air cylinder unit 28; and supply/discharge of the pressurized air to/from the other air chamber. The second solenoid valve 5 is composed of, for example, a three-position solenoid switching valve including a pair of solenoids 5a and 5b. Each of the solenoids 5a and 5b is magnetized upon reception of a command signal from the control unit 6.

Although each of the first and second solenoid valves 4 and 5 of the present embodiment is composed of the three-position solenoid switching valve, each of the first and second solenoid valves 4 and 5 may be a two-position solenoid switching valve which does not have a neutral position.

In FIG. 1, a first quick discharge valve 61 is disposed between the first discharge-side air chamber 21A (first suction/discharge port 22A) of the first air cylinder unit 27 and the first solenoid valve 4 and adjacently to the first discharge-side air chamber 21A. The first quick discharge valve 61 has a discharge port 61a through which the pressurized air is discharged, and is configured to permit flow of the pressurized air from the first solenoid valve 4 to the first discharge-side air chamber 21A and to discharge the pressurized air flowing out from the first discharge-side air chamber 21A, through the discharge port 61a. Thus, the pressurized air within the first discharge-side air chamber 21A can be quickly discharged through the first quick discharge valve 61, not via the first solenoid valve 4.

Similarly, a second quick discharge valve 62 is disposed between the second discharge-side air chamber 21B (second suction/discharge port 22B) of the second air cylinder unit 28 and the second solenoid valve 5 and adjacently to the second discharge-side air chamber 21B. The second quick discharge valve 62 has a discharge port 62a through which the pressurized air is discharged, and is configured to permit flow of the pressurized air from the second solenoid valve 5 to the second discharge-side air chamber 21B and to discharge the pressurized air flowing out from the second discharge-side air chamber 21B, through the discharge port 62a. Thus, the pressurized air within the second discharge-side air chamber 21B can be quickly discharged through the second quick discharge valve 62, not via the second solenoid valve 5.

[Configuration of Control Unit]

The control unit 6 controls drive of each of the first air cylinder unit 27 and the second air cylinder unit 28 of the bellows pump 1 by switching the respective solenoid valves 4 and 5 on the basis of detection results of the first detection unit 29 and the second detection unit 31 (see FIG. 2).

Specifically, on the basis of the detection results of the first detection unit 29 and the second detection unit 31, the control unit 6 controls drive of the first and second air cylinder units 27 and 28 such that: the second bellows 14 is caused to contract from the most expanded state before the first bellows 13 comes into the most contracted state; and the first bellows 13 is caused to contract from the most expanded state before the second bellows 14 comes into the most contracted state.

Here, the term “before” the first bellows 13 comes into the most contracted state means that a contraction progress position of the first bellows 13 is closer to a contraction end position (most contracted position) than to a contraction start position (most expanded position), and more specifically means that a state where the first bellows 13 has contracted up to 60% to 90% (preferably 60% to 70%, more preferably 66%) of a contraction period T12 (see FIG. 5) from a time point of start of contraction of the first bellows 13 to a time point at which the first bellows 13 comes into the most contracted state. Similarly, the term “before” the second bellows 14 comes into the most contracted state means that a contraction progress position of the second bellows 14 is closer to a contraction end position (most contracted position) than to a contraction start position (most expanded position), and more specifically means that a state where the second bellows 14 has contracted up to 60% to 90% (preferably 60% to 70%, more preferably 66%) of a contraction period T22 (see FIG. 5) from a time point of start of contraction of the second bellows 14 to a time point at which the second bellows 14 comes into the most contracted state.

Accordingly, at a time of switching from contraction of one bellows to expansion thereof (from discharge of the transport fluid to suction thereof), the other bellows has already contracted to discharge the transport fluid. Thus, great fall of the discharge pressure of the transport fluid at the time of switching can be reduced. As a result, pulsation at the discharge side of the bellows pump 1 can be reduced.

[Configurations of Electropneumatic Regulators]

In FIG. 1 and FIG. 2, the first electropneumatic regulator 51 is disposed between the mechanical regulator 3 and the first solenoid valve 4. The first electropneumatic regulator 51 adjusts the air pressure of the pressurized air in the first suction-side air chamber 26A of the first air cylinder unit 27, and the air pressure (first fluid pressure) of the pressurized air in the first discharge-side air chamber 21A of the first air cylinder unit 27.

Similarly, the second electropneumatic regulator 52 is disposed between the mechanical regulator 3 and the second solenoid valve 5. The second electropneumatic regulator 52 adjusts the air pressure of the pressurized air in the second suction-side air chamber 26B of the second air cylinder unit 28, and the air pressure (second fluid pressure) of the pressurized air in the second discharge-side air chamber 21B of the second air cylinder unit 28.

The electropneumatic regulators 51 and 52 are disposed at the upstream sides of the solenoid valves 4 and 5, but may be disposed at the downstream sides of the solenoid valves 4 and 5. However, in this case, impact pressures generated when the solenoid valves 4 and 5 are switched act at the primary sides of the electropneumatic regulators 51 and 52. Thus, from the standpoint of preventing breakdown of the electropneumatic regulators 51 and 52, the electropneumatic regulators 51 and 52 are preferably disposed at the upstream sides of the solenoid valves 4 and 5.

The electropneumatic regulators 51 and 52 only have to adjust at least the air pressure of the pressurized air in the discharge-side air chambers 21A and 21B. In addition, in the present embodiment, the electropneumatic regulators 51 and 52, which directly adjust the air pressure, are used as fluid pressure adjustment units, but the air pressure may be adjusted indirectly using an air flow rate adjusting valve which adjusts an air flow rate, or a device that adjusts the pressure or flow rate of a gas other than air (for example, nitrogen), a liquid, or the like may be used.

[Examples of Control of Electropneumatic Regulators]

FIG. 5 is a time chart showing an example of control of the electropneumatic regulator 51 (52) by the control unit 6 of the present embodiment. In FIG. 5, the control unit 6 controls the first electropneumatic regulator 51 such that the air pressure in the first suction-side air chamber 26A of the first air cylinder unit 27 is a constant value P during an expansion period T11 in which the first bellows 13 expands.

In addition, the control unit 6 controls the first electropneumatic regulator 51 such that the air pressure in the first discharge-side air chamber 21A of the first air cylinder unit 27 is the constant value P during a first contraction time T121 from a contraction start time point t1 of the first bellows 13 to a contraction start time point t2 of the second bellows 14 in the contraction period T12 in which the first bellows 13 contracts.

Subsequently, the control unit 6 controls the first electropneumatic regulator 51 such that, in the contraction period T12, during a second contraction time T122 from the contraction start time point t2 of the second bellows 14 to a contraction end time point t3 at which the first bellows 13 comes into the most contracted state, the air pressure in the first discharge-side air chamber 21A is continuously decreased from P, and reaches zero before or when the first bellows 13 comes into the most contracted state. For example, the control unit 6 of the present embodiment controls the first electropneumatic regulator 51 such that the air pressure in the first discharge-side air chamber 21A is linearly and continuously decreased from P, and reaches zero at the contraction end time point t3 at which the first bellows 13 comes into the most contracted state.

Meanwhile, the control unit 6 controls the second electropneumatic regulator 52 such that the air pressure in the second suction-side air chamber 26B of the second air cylinder unit 28 is the constant value P during an expansion period T21 in which the second bellows 14 expands.

In addition, the control unit 6 controls the second electropneumatic regulator 52 such that the air pressure in the second discharge-side air chamber 21B of the second air cylinder unit 28 is the constant value P during a first contraction time T221 from the contraction start time point t2 of the second bellows 14 to a contraction start time point t1 of the first bellows 13 in the contraction period T22 in which the second bellows 14 contracts.

Subsequently, the control unit 6 controls the second electropneumatic regulator 52 such that, in the contraction period T22, during a second contraction time T222 from the contraction start time point t1 of the first bellows 13 to a contraction end time point t4 at which the second bellows 14 comes into the most contracted state, the air pressure of the second discharge-side air chamber 21B is continuously decreased from P, and reaches zero before or when the second bellows 14 comes into the most contracted state. For example, the control unit 6 of the present embodiment controls the second electropneumatic regulator 52 such that the air pressure in the second discharge-side air chamber 21B is linearly and continuously decreased from P, and reaches zero at the contraction end time point t4 at which the second bellows 14 comes into the most contracted state.

FIG. 6 is a graph showing the discharge pressure of the transport fluid discharged from the discharge passage 35 of the bellows pump 1 of the present embodiment. As shown in FIG. 6, it is found that, by the control unit 6 controlling the first and second electropneumatic regulators 51 and 52 as described above, great fall of the discharge pressure at a time of switching from contraction of one bellows to expansion thereof (from discharge of the transport fluid to suction thereof) (portions surrounded by broken lines in the drawing) can be reduced. In addition, when the graph shown in FIG. 6 of the present embodiment is compared with the graph shown in FIG. 10 of the conventional art, it is found that occurrence of surge pressure can also be inhibited at the time of switching.

Advantageous Effects of Present Embodiment

As described above, in the bellows pump device of the present embodiment, before the one bellows 13 (14) comes into the most contracted state, the other bellows 14 (13) contracts from the most expanded state. Accordingly, at a time of switching from contraction of the one bellows 13 (14) to expansion thereof (from discharge of the transport fluid to suction thereof), the other bellows 14 (13) has already contracted to discharge the fluid, and thus fall of the discharge pressure at the time of switching can be reduced. As a result, pulsation at the discharge side of the bellows pump device can be reduced.

The control unit 6 controls the electropneumatic regulator 52 (51) corresponding to the discharge-side air chamber 21A (21B) corresponding to the other bellows 14 (13) such that, during a period from a time at which the one bellows 13 (14) starts contracting to a time at which the bellows 14 (13) comes into the most contracted state, the air pressure in the discharge-side air chamber 21B (21A) is continuously decreased. Owing to this control, before the other bellows 14 (13) comes into the most contracted state, the discharge check valve 16 corresponding to the other bellows 14 (13) gradually moves in the valve closing direction from a valve-opened state. Accordingly, when the other bellows 14 (13) is switched from the most contracted state to expansion, impact due to rapid closing of the discharge check valve 16 can be alleviated. As a result, surge pressure can be inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

Before or when the other bellows 14 (13) comes into the most contracted state after the one bellows 13 (14) starts contracting, the air pressure in the discharge-side air chamber 21B (21A) corresponding to the other bellows 14 (13) is continuously decreased and reaches zero. Since the air pressure in the discharge-side air chamber 21B (21A) is decreased as described above, the discharge check valve 16 corresponding to the other bellows 14 (13) closes before or when the other bellows 14 (13) comes into the most contracted state. Accordingly, the discharge check valve 16 can be prevented from rapidly closing when the other bellows 14 (13) is switched from the most contracted state to expansion. As a result, surge pressure can be further inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

During the period from the time at which the one bellows 13 (14) starts contracting to the time at which the bellows 14 (13) comes into the most contracted state, the air pressure in the discharge-side air chamber 21B (21A) corresponding to the other bellows 14 (13) is continuously decreased, and reaches zero at the time at which the other bellows 14 (13) comes into the most contracted state. Accordingly, the discharge check valve 16 corresponding to the other bellows 14 (13) slowly closes as compared to the case where the air pressure reaches zero before the other bellows 14 (13) comes into the most contracted state (see FIG. 8). As a result, surge pressure can be further inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

[Modifications of Control of Electropneumatic Regulators]

FIG. 7 is a time chart showing a first modification, a second modification, and a third modification for control of the electropneumatic regulator 51 (52) by the control unit 6.

In the first modification shown by a solid line in FIG. 7, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the second contraction time T122 (T222) from the contraction start time point t2 (t1) of the one bellows 14 (13) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) is decreased stepwise from P, and reaches zero at the contraction end time point t3 (t4). In the first modification, the air pressure is decreased in two steps, but may be decreased in three or more steps.

In the second modification shown by an alternate long and short dash line in FIG. 7, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the second contraction time T122 (T222) from the contraction start time point t2 (t1) of the one bellows 14 (13) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) corresponding to the other bellows 13 (14) is continuously decreased in a concave curve from P, and reaches zero at the contraction end time point t3 (t4).

In the third modification shown by an alternate long and two short dashes line in FIG. 7, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the second contraction time T122 (T222) from the contraction start time point t2 (t1) of the one bellows 14 (13) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) corresponding to the other bellows 13 (14) is continuously decreased in a convex curve from P, and reaches zero at the contraction end time point t3 (t4).

Thus, in the first to third modifications in FIG. 7 as well, the same advantageous effects as those of the above embodiment are achieved. In the first modification, the control unit 6 controls the electropneumatic regulator 51 (52) such that the air pressure in the discharge-side air chamber 21A (21B) is linearly decreased in each step, but may control the electropneumatic regulator 51 (52) such that the air pressure is decreased in a curve in each step, as in the second modification or the third modification.

FIG. 8 is a time chart showing a fourth modification and a fifth modification for control of the electropneumatic regulator 51 (52) by the control unit 6.

In the fourth modification shown by a solid line in FIG. 8, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during a period from the contraction start time point t2 (t1) of the one bellows 14 (13) to a contraction halfway time point t5 (t6) before the other bellows 13 (14) comes into the most contracted state, the air pressure in the discharge-side air chamber 21A (21B) is continuously decreased from P, and reaches zero at the contraction halfway time point t5 (t6). Then, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during a period from the contraction halfway time point t5 (t6) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) is maintained at zero.

In the fifth modification shown by an alternate long and short dash line in FIG. 8, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the period from the contraction start time point t2 (t1) of the one bellows 14 (13) to the contraction halfway time point t5 (t6) before the other bellows 13 (14) comes into the most contracted state, the air pressure in the discharge-side air chamber 21A (21B) is continuously decreased from P, and reaches P′ (0<P′<P) at the contraction halfway time point t5 (t6). Then, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the period from the contraction halfway time point t5 (t6) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) is zero.

Thus, in the fourth and fifth modifications as well, similar to the above embodiment, during the period from the time at which the one bellows 14 (13) starts contracting to the time at which the other bellows 13 (14) comes into the most contracted state, the air pressure in the discharge-side air chamber 21A (21B) corresponding to the other bellows 13 (14) is continuously decreased. Accordingly, when switching is made from discharge of the transport fluid to suction of the transport fluid, pulsation can be reduced and generation of surge pressure can be inhibited at the discharge side.

Moreover, before the other bellows 13 (14) comes into the most contracted state after the one bellows 14 (13) starts contracting, the air pressure in the discharge-side air chamber 21A (21B) corresponding to the other bellows 13 (14) is continuously decreased and reaches zero. Since the air pressure in the discharge-side air chamber 21A (21B) is decreased as described above, the discharge check valve 16 corresponding to the other bellows 13 (14) closes before the other bellows 13 (14) comes into the most contracted state. Accordingly, the discharge check valve 16 can be prevented from rapidly closing when the other bellows 13 (14) is switched from the most contracted state to expansion. As a result, surge pressure can be further inhibited from being generated at the discharge side of the bellows pump device when switching is made from discharge of the transport fluid to suction of the transport fluid.

FIG. 9 is a time chart showing a sixth modification for control of the electropneumatic regulator 51 (52) by the control unit 6. In this modification, the control unit 6 controls the electropneumatic regulator 51 (52) such that, during the second contraction time T122 (T222) from the contraction start time point t2 (t1) of the one bellows 14 (13) to the contraction end time point t3 (t4) of the other bellows 13 (14), the air pressure in the discharge-side air chamber 21A (21B) is continuously decreased from P, and reaches P″ (0<P″<P) at the contraction end time point t3 (t4) at which the other bellows 13 (14) comes into the most contracted state. At the contraction end time point t3 (t4), if the corresponding solenoid valve 4 (5) is switched, the pressurized air within the discharge-side air chamber 21A (21B) is released to the atmosphere, and the air pressure in the discharge-side air chamber 21A (21B) becomes zero from P″.

Thus, in the sixth modification as well, similar to the above embodiment, during the period from the time at which the one bellows 14 (13) starts contracting to the time at which the other bellows 13 (14) comes into the most contracted state, the air pressure in the discharge-side air chamber 21A (21B) corresponding to the other bellows 13 (14) is continuously decreased. Accordingly, when switching is made from discharge of the transport fluid to suction of the transport fluid, pulsation can be reduced and generation of surge pressure can be inhibited at the discharge side.

In each of the modifications in FIG. 8 and FIG. 9, the control unit 6 linearly and continuously decreases the air pressure in the discharge-side air chamber 21A (21B) when controlling the electropneumatic regulator 51 (52), but may decrease the air pressure stepwise as in the first modification in FIG. 7, or may continuously decrease the air pressure in a curve as in the second or third modification in FIG. 7.

The embodiment disclosed herein is merely illustrative and not restrictive in all aspects. The scope of the present disclosure is defined by the scope of the claims rather than the meaning described above, and is intended to include meaning equivalent to the scope of the claims and all modifications within the scope.

REFERENCE SIGNS LIST

6 control unit

11 pump head

13 first bellows

14 second bellows

15 suction check valve (check valve)

16 discharge check valve (check valve)

21A first discharge-side air chamber (first discharge-side fluid chamber)

21B second discharge-side air chamber (second discharge-side fluid chamber)

26A first suction-side air chamber (first suction-side fluid chamber)

26B second suction-side air chamber (second suction-side fluid chamber)

27 first air cylinder unit (first driving unit)

28 second air cylinder unit (second driving unit)

34 suction passage

35 discharge passage

51 first electropneumatic regulator (first fluid pressure adjustment unit)

52 second electropneumatic regulator (second fluid pressure adjustment unit)

Claims

1. A bellows pump device comprising:

a pump head having a suction passage and a discharge passage for a transport fluid;

a first bellows and a second bellows mounted on the pump head so as to be expandable/contractible independently of each other and configured to suck the transport fluid from the suction passage thereinto by expansion thereof and discharge the transport fluid therefrom to the discharge passage by contraction thereof;

a check valve configured to permit flow of the transport fluid in one direction in the suction passage and the discharge passage and block flow of the transport fluid in another direction in the suction passage and the discharge passage;

a first driving unit having a first suction-side fluid chamber and a first discharge-side fluid chamber and configured to supply a pressurized fluid to the first suction-side fluid chamber thereby causing the first bellows to expand to a most expanded state, and supply the pressurized fluid to the first discharge-side fluid chamber thereby causing the first bellows to contract to a most contracted state; and

a second driving unit having a second suction-side fluid chamber and a second discharge-side fluid chamber and configured to supply a pressurized fluid to the second suction-side fluid chamber thereby causing the second bellows to expand to a most expanded state, and supply the pressurized fluid to the second discharge-side fluid chamber thereby causing the second bellows to contract to a most contracted state, wherein

the second bellows contracts from the most expanded state before the first bellows comes into the most contracted state, and the first bellows contracts from the most expanded state before the second bellows comes into the most contracted state, the bellows pump device further comprising

a first fluid pressure adjustment unit configured to adjust a first fluid pressure of the pressurized fluid in the first discharge-side fluid chamber of the first driving unit,

a second fluid pressure adjustment unit configured to adjust a second fluid pressure of the pressurized fluid in the second discharge-side fluid chamber of the second driving unit, and

a control unit configured to control the first fluid pressure adjustment unit such that the first fluid pressure is decreased stepwise or continuously during a period from a time at which the second bellows starts contracting to a time at which the first bellows comes into the most contracted state, and control the second fluid pressure adjustment unit such that the second fluid pressure is decreased stepwise or continuously during a period from a time at which the first bellows starts contracting to a time at which the second bellows comes into the most contracted state.

2. The bellows pump device according to claim 1, wherein the control unit controls the first fluid pressure adjustment unit such that the first fluid pressure reaches zero before or when the first bellows comes into the most contracted state, and controls the second fluid pressure adjustment unit such that the second fluid pressure reaches zero before or when the second bellows comes into the most contracted state.

3. The bellows pump device according to claim 2, wherein the control unit controls the first fluid pressure adjustment unit such that the first fluid pressure reaches zero at the time at which the first bellows comes into the most contracted state, and controls the second fluid pressure adjustment unit such that the second fluid pressure reaches zero at the time at which the second bellows comes into the most contracted state.