Vacuum generation device and vacuum generation method

Abstract

To improve the energy efficiency of operation of a vacuum generation device.SOLUTION: A vacuum generation device 1 comprises: a gas flow passage 13 connecting a first tank 11 and a second tank 12 so that gas 8 flows, and provided with a first valve 14; a first liquid flow passage 15 connecting the first tank 11 and the second tank 12 so that liquid 9 flows, and provided with a liquid pump 16; and a second liquid flow passage 18 connecting the first tank 11 and the second tank 12 so that the liquid 9 flows, and provided with a second valve 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vacuum generating device and a vacuum generating method. [Background technology]

[0002] The vacuum generating devices disclosed in Patent Documents 1 and 2 generate negative pressure by moving liquid between a pair of tanks containing the liquid. More specifically, a liquid pump moves liquid from one tank to the other, and the pressure in one tank is reduced by this liquid movement. Next, the liquid pump moves liquid from the other tank, where the amount of liquid has increased, to the one tank, thereby reducing the pressure in the other tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 3-182700 [Patent Document 2] Japanese Patent Publication No. 50-145911 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vacuum generators of Patent Documents 1 and 2, liquid cannot be moved between tanks unless the liquid pump is driven. In other words, the driving force for moving liquid between tanks cannot be obtained without power. In this respect, the vacuum generators of Patent Documents 1 and 2 have room for improvement in terms of energy efficiency during operation.

[0005] The present invention aims to improve the energy efficiency of vacuum generating equipment operation. [Means for solving the problem]

[0006] a first valve provided in the first gas flow path, capable of switching between connecting and blocking the first gas flow path; a first liquid flow path connecting the first tank and the second tank so that the liquid flows; a liquid pump provided in the first liquid flow path, for delivering the liquid; a second liquid flow path connecting the first tank and the second tank so that the liquid flows, the second liquid flow path not provided with a liquid pump, and different from the first liquid flow path; a second valve provided in the second liquid flow path, capable of switching between connecting and blocking the second liquid flow path; an atmosphere release flow path connecting the second tank and the atmosphere so that the gas flows; and a third valve provided in the atmosphere release flow path, for maintaining the pressure of the gas in the second tank at or below atmospheric pressure.

[0007] The first valve is closed to block the first gas flow path, and the second valve is closed to block the second liquid flow path. With the first and second valves in this state, the liquid pump pumps the liquid from the first tank to the second tank. This pumping reduces the liquid in the first tank, decompresses the gas in the first tank, and increases the degree of vacuum. In other words, a vacuum can be generated.

[0008] When a vacuum is generated, the liquid in the first tank decreases and the liquid in the second tank increases as the liquid is pumped out. The second valve is then opened, connecting the second liquid flow path, which does not have a liquid pump. By opening the second valve, the pressure difference between the gas in the first and second tanks allows liquid to move from the second tank to the first tank via the second liquid flow path. In other words, liquid can be returned from the second tank to the first tank without driving the liquid pump. In this way, by utilizing the pressure difference between the gas in the first and second tanks to move liquid from the second tank to the first tank, improved energy efficiency (energy savings) can be achieved during operation.

[0009] When returning liquid from the second tank to the first tank, by opening the first valve to communicate the first gas flow path after or simultaneously with opening the second valve, the gas in the first tank and the gas in the second tank communicate and the pressures are equalized, allowing liquid to move from the second tank to the first tank via the second liquid flow path. In this way, moving liquid from the second tank to the first tank by utilizing the pressure equalization between the first and second tanks also achieves improved energy efficiency during operation.

[0010] The third valve may be a check valve that allows flow from the second tank to the atmosphere.

[0011] If the third valve is an atmosphere release valve such as an on-off valve or a solenoid valve, it is necessary to provide a sensor that measures the pressure of the gas in the second tank and to control the opening and closing of the atmosphere release valve based on the detection result of this sensor.In contrast, if the third valve is a check valve, it is not necessary to provide a sensor that measures the pressure of the gas in the second tank or a control device, which simplifies the configuration of the vacuum generator and thereby reduces costs.

[0012] The liquid pump may be a one-way pump that can pump the liquid only from the second tank to the first tank.

[0013] The liquid moves from the second tank to the first tank via the second liquid flow path. Therefore, the liquid pump that pumps the liquid from the first tank to the second tank via the first liquid flow path only needs to be a one-way pump, and does not need to be a two-way pump. By using a one-way pump as the liquid pump, the configuration of the vacuum generator can be simplified, thereby reducing costs.

[0014] The device may further include a vacuum tank, a second gas flow path connecting the vacuum tank to the first tank so that the gas can flow, and a check valve provided in the second gas flow path to allow the gas to flow from the vacuum tank to the first tank.

[0015] With this configuration, a vacuum can be generated in the vacuum tank by generating a vacuum in the first tank. The first tank can be in a vacuum state or in a non-vacuum state due to the movement of liquid from the second tank. However, by providing a check valve in the second gas flow path, a vacuum can be continuously generated in the vacuum tank.

[0016] The liquid pump may further include a liquid level sensor that detects when the level of the liquid in the first tank has dropped to a predetermined lower limit level, and a control device that controls operation of the first valve, the second valve, and the liquid pump based on at least an input from the liquid level sensor, wherein the control device closes the first valve and the second valve and drives the liquid pump to move liquid from the first tank to the second tank via the first liquid flow path, thereby reducing the pressure in the first tank and generating a vacuum, and when the liquid level sensor detects that the level of the liquid in the first tank has dropped to the lower limit level while the liquid pump is being driven, the control device stops driving the liquid pump, and after stopping driving of the liquid pump, the control device switches the second valve from closed to open, thereby allowing liquid to flow from the second tank to the first tank via the second liquid flow path.

[0017] The control device may further include a first pressure sensor that detects the pressure of the gas in the first tank and a second pressure sensor that detects the pressure of the gas in the second tank, and the control device controls the operation of the first valve and the second valve further based on the first pressure sensor and an input from the first pressure sensor, and the control device may switch the first valve from closed to open after switching the second valve from closed to open or simultaneously with switching the second valve from closed to open, thereby equalizing the pressures of the gas in the first tank and the second tank, causing liquid to flow from the second tank to the first tank via the second liquid flow path, and when the control device detects, after switching the first valve from closed to open, that the pressure of the gas in the first tank and the pressure of the gas in the second tank have become the same based on the input from the first pressure sensor and the second pressure sensor, it may switch the first valve and the second valve from open to closed, respectively.

[0018] A second aspect of the present invention includes a first tank and a second tank capable of storing a gas and a liquid, respectively; a first gas flow path connecting the first tank and an upper part of the second tank so that the gas flows; a first valve provided in the first gas flow path and capable of switching between communication and blocking of the first gas flow path; a first liquid flow path connecting a lower part of the first tank and a lower part of the second tank so that the liquid flows; a liquid pump provided in the first liquid flow path and feeding the liquid; a second liquid flow path connecting the lower part of the first tank and the lower part of the second tank so that the liquid flows, not provided with a liquid pump and different from the first liquid flow path; a second valve provided in the second liquid flow path and capable of switching between communication and blocking of the second liquid flow path; a step of preparing a vacuum generating device including an atmosphere-opening flow path connected so that the gas can flow therethrough, and a third valve provided in the atmosphere-opening flow path for controlling the opening of the second tank to the atmosphere via the atmosphere-opening flow path; a step of using the liquid pump to move the liquid from the first tank to the second tank via the first liquid flow path, thereby generating a vacuum in the first tank; and a step of opening the second valve to communicate the second liquid flow path, and after or simultaneously with opening the second valve, opening the first valve to communicate the gas in the first tank and the second tank via the first gas flow path, thereby moving the liquid from the second tank to the first tank via the second liquid flow path.

[0019] The liquid pump may be a one-way pump capable of pumping the liquid only from the first tank to the second tank, and after the first valve and the second valve are opened, when the liquid levels in the first tank and the second tank become the same, the process may proceed to a step in which the liquid pump moves the liquid from the first tank to the second tank via the first liquid flow path. [Effects of the Invention]

[0020] The vacuum generating device and method according to the present invention can improve the energy efficiency of operation. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a diagram showing the configuration of a vacuum generating device according to an embodiment of the present invention (first step). [Figure 2] FIG. 2 is a diagram showing the configuration of a vacuum generating device according to an embodiment of the present invention (first step). [Figure 3] FIG. 2 is a diagram showing the configuration of a vacuum generating device according to an embodiment of the present invention (first step). [Figure 4] FIG. 2 is a diagram showing the configuration of a vacuum generating device according to an embodiment of the present invention (first step). [Figure 5] FIG. 3 is a configuration diagram of a vacuum generating device according to an embodiment of the present invention (second step). [Figure 6] FIG. 3 is a configuration diagram of a vacuum generating device according to an embodiment of the present invention (second step). [Figure 7] FIG. 10 is a configuration diagram of a vacuum generating device according to a first modified example of the embodiment of the present invention. [Figure 8] FIG. 10 is a configuration diagram of a vacuum generating device according to a second modified example of the embodiment of the present invention. [Figure 9] FIG. 10 is a configuration diagram of a vacuum generating device according to a third modified example of the embodiment of the present invention. [Figure 10] FIG. 10 is a configuration diagram of a vacuum generating device according to a fourth modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the present invention will be described with reference to the accompanying drawings.

[0023] Referring to FIG. 1, a vacuum generating device 1 according to an embodiment of the present invention includes a vacuum pump 2 and a vacuum tank 3.

[0024] The vacuum pump 2 and the vacuum tank 3 are connected by a gas flow path (second gas flow path) 4. When the vacuum pump 2 is operating, the vacuum tank 3 is evacuated to a vacuum by the vacuum pump 3. The gas flow path 4 is provided with a check valve 5 that allows gas to flow from the vacuum tank 3 to the vacuum pump 2 but prevents gas from flowing from the vacuum pump 2 to the vacuum tank 3.

[0025] The vacuum tank 3 is fluidly connected to a target (not shown) to be vacuumed via a vacuum supply flow path 7 provided with a vacuum supply switching valve 6, which is comprised of an on-off valve or a solenoid valve. The target to be vacuumed is not particularly limited, and examples include a vacuum suction pad and a vacuum freeze dryer. When the vacuum supply switching valve 6 is open, a vacuum is supplied to the target to be vacuumed via the vacuum supply flow path 7. In FIG. 1, the vacuum supply switching valve 6 is shown filled in black to indicate that it is closed, and when the vacuum supply switching valve 6 is open, it is shown as an outline. This also applies to each valve described below.

[0026] The vacuum pump 2 includes a first tank 11 and a second tank 12 capable of storing a gas (air in this embodiment) 8 and a liquid (water in this embodiment) 9, respectively.

[0027] The vacuum pump 2 is provided with a gas flow path (first gas flow path) 13 that connects the upper part of the first tank 11 and the upper part of the second tank 12 so that the gas 8 flows. The gas flow path 13 is provided with a first valve 14 that is made up of an on-off valve or a solenoid valve and that can switch between connecting and blocking the first gas flow path 13.

[0028] The vacuum pump 2 includes a first liquid flow path 15 that connects the lower part of the first tank 11 and the lower part of the second tank 12 so that the liquid 9 flows therethrough. The first liquid flow path 15 is provided with a liquid pump 16 that delivers the liquid 9. In this embodiment, the liquid pump 16 is a one-way pump that can deliver the liquid 9 only from the first tank 11 to the second tank 12. By using a one-way pump as the liquid pump 16 instead of a two-way pump, the configuration of the vacuum pump 2 can be simplified, resulting in cost reduction.

[0029] In this embodiment, first liquid flow path 15 is provided with a shutoff valve 17 in addition to liquid pump 16. Shutoff valve 17 in this embodiment is made up of an on-off valve or a solenoid valve, and is capable of switching between communication and shutoff of first liquid flow path 15. In this embodiment, shutoff valve 17 is provided between first tank 11 and liquid pump 16. Shutoff valve 17 may also be provided between second tank 12 and liquid pump 16.

[0030] The vacuum pump 2 is provided with a second liquid flow path 18 separate from the first liquid flow path 15, which connects the lower part of the first tank 11 with the lower part of the second tank 12 so that the liquid 9 flows. The second liquid flow path 18 is not provided with a liquid pump like the liquid pump 16 provided in the first liquid flow path 15. The second liquid flow path 18 is provided with a second valve 19 made of an on-off valve or a solenoid valve, which can switch between connecting and blocking the second liquid flow path 18.

[0031] The vacuum pump 2 is provided with an atmosphere-opening passage 21 that connects the upper part of the second tank 12 to the atmosphere. The gas 8 in the second tank 12 flows to the atmosphere through the atmosphere-opening passage 21. A third valve 22 is provided in the atmosphere-opening passage 21. In this embodiment, the third valve 22 is made up of an on-off valve or a solenoid valve, and is capable of switching between connecting and blocking the atmosphere-opening passage 21.

[0032] The vacuum pump 2 is equipped with a level switch (liquid level sensor) LS that detects when the liquid level of the liquid 9 in the first tank 11 drops to a preset lower limit level. The vacuum pump 2 also is equipped with a first pressure sensor PS1 that detects the pressure of the gas 8 in the first tank 11 and a second pressure sensor PS2 that detects the pressure of the gas 8 in the second tank 12.

[0033] The vacuum pump 2 is equipped with a control device 23. The control device 23 controls the operation of the vacuum supply switching valve 6, first valve 14, liquid pump 16, shutoff valve 17, second valve 19, and third valve 22 in accordance with a stored program based on inputs from the level switch LS, first pressure sensor PS1, and second pressure sensor PS2. The control device 23 receives a detection signal from the level switch LS that the level of the liquid 9 in the first tank 11 has dropped to a lower limit. The control device 23 also receives a detection value of the pressure of the gas 8 in the first tank 11 from the first pressure sensor PS1 and a detection value of the pressure of the gas 8 in the second tank 12 from the second pressure sensor PS2. The control device 23 can be constructed using a computer equipped with storage devices such as ROM and RAM, input / output devices, an arithmetic unit such as an MPU, and other devices, and software implemented thereon.

[0034] The operation of the vacuum pump 2, that is, the control of the vacuum pump 2 executed by the control device 23, will now be described.

[0035] The operation of the vacuum pump 2 is generally composed of two steps, namely, a first step and a second step, and the first step and the second step are repeated.

[0036] In the first step, the liquid 9 is moved from the first tank 11 to the second tank 12 by the liquid pump 16, thereby reducing the pressure of the gas 8 in the first tank 11 and generating a vacuum. As described above, the vacuum tank 3 is connected to the first tank 11 via the gas flow path 4, so when a vacuum is generated in the first tank 11, the vacuum tank 3 is also evacuated and reduced in pressure. As will be described later, the first tank 11 can be in either a vacuum state or a non-vacuum state due to the movement of the liquid 9 from the second tank 12. However, by providing a check valve 5 in the gas flow path 4, a vacuum can be continuously generated in the vacuum tank 3.

[0037] In the second step, the liquid 9 is transferred from the second tank 12 to the first tank 11. Unlike the first step, the transfer of the liquid from the second tank 12 to the first tank 11 in the second step is achieved by the difference in pressure between the gas 8 in the first tank 11 and the second tank 12, and the liquid pump 16 is not used.

[0038] The first and second steps will be explained in more detail below.

[0039] First, the first step will be described with reference to FIGS.

[0040] 1, at the start of the first step, the liquid level of the liquid 9 in the first tank 11 is the same as the liquid level of the liquid 9 in the second tank (liquid level LH). Also, at the start of the first step, the first valve 14 is closed, the shut-off valve 17 is open, the second valve 19 is closed, and the third valve 22 is closed. With each valve in this open / closed state, the liquid pump 16 is driven to pump out the liquid 9. The liquid pump 16 moves the liquid from the first tank 11 to the second tank 12 via the first liquid flow path 15.

[0041] Referring to FIG. 2, as the liquid 9 is moved by the liquid pump 16, the amount of the liquid 9 in the first tank 11 decreases, and the liquid level drops. As described above, the first valve 14 is closed, and the gas flow path 13 connecting the gas 8 in the first tank 11 and the gas 8 in the second tank 12 is blocked. In other words, the gas 8 in the first tank 11 is sealed. Therefore, as the liquid level of the liquid 9 in the first tank 11 drops, the gas 8 in the first tank 11 is depressurized, generating a vacuum. Meanwhile, in the second tank 12, as the liquid is moved by the liquid pump 16, the amount of the liquid 9 increases, and the liquid level rises. As described above, the first valve 14 is closed, and the gas flow path 13 connecting the gas 8 in the first tank 11 and the gas 8 in the second tank 12 is blocked. Also, as described above, at the start of the first step, the third valve 22 is closed, and the atmosphere-opening flow path 21 is blocked. Therefore, as the liquid level of the liquid 9 in the second tank 12 rises, the pressure of the gas 8 in the second tank 12 rises. When the second pressure sensor PS2 detects that the pressure of the gas 8 in the second tank 12 has risen to atmospheric pressure, the third valve 22 is switched from closed to open, the atmosphere release flow path 21 becomes connected, and the second tank 12 is opened to the atmosphere.

[0042] 3, the operation of the liquid pump 16 continues until the level switch LS detects that the level of the liquid 9 in the first tank 11 has dropped to the lower limit level. Referring to Fig. 4, when the level switch LS detects this, the liquid pump 16 is stopped and the shutoff valve 17 is switched from open to closed.

[0043] Next, the second step will be described with reference to FIGS.

[0044] 4, at the start of the second step, the level of the liquid 9 in the first tank 11 is at the lower limit level. Also, at the start of the second step, the first valve 14 is closed, the shutoff valve 17 is closed, the second valve 19 is closed, and the third valve 22 is open. Also, the liquid pump 16 remains stopped.

[0045] Referring to FIG. 5, the second valve 19 is switched from a closed state to an open state, and the third valve 22 is switched from an open state to a closed state. When the second valve 19 is opened, the second liquid flow path 18 is opened. That is, the liquid 9 in the first tank 11 and the liquid 9 in the second tank 12 are connected to each other. When the second valve 19 is opened, the gas 8 in the first tank 11 is at negative pressure, while the gas 8 in the second tank 12 is at atmospheric pressure. Therefore, due to the pressure difference between the gas 8 in the first tank 11 and the gas 8 in the second tank 12, the liquid 9 moves from the second tank 12 to the first tank 11 via the second liquid flow path 18. That is, the liquid 9 can be returned from the second tank 12 to the first tank 11 without driving the liquid pump 16. In this way, by utilizing the pressure difference between the gas 8 in the first tank 11 and the second tank 12 to move the liquid 9 from the second tank 12 to the first tank 11, it is possible to improve the energy efficiency (energy saving) of the operation of the vacuum pump 2. The state in Figure 5 continues for, for example, a predetermined fixed time.

[0046] Next, referring to FIG. 6 , the first valve 14 is switched from closed to open, and the gas flow path 13 is opened. That is, the gas 8 in the first tank 11 and the gas 8 in the second tank 12 are connected to each other. When the first valve 14 is open, the pressure of the gas 8 in the first tank 11 is lower than the pressure of the gas 8 in the second tank 12. Therefore, the gas 8 in the first tank 11 and the gas 8 in the second tank 12 are connected to each other via the gas flow path 13, and the pressures of the gas 8 in the first tank 11 and the gas 8 in the second tank 12 are equalized. Then, the liquid 9 moves from the second tank 12 to the first tank 11 via the second liquid flow path 18. In this way, the movement of the liquid 9 from the second tank 12 to the first tank 11, utilizing the equalization of the pressures of the first tank 11 and the second tank 12, can also improve the energy efficiency of the operation of the vacuum pump 12.

[0047] 6, when the pressure of the gas 8 in the first tank 11 detected by the pressure sensor PS1 and the pressure of the gas 8 in the second tank 12 detected by the second pressure sensor PS2 become the same, that is, when the liquid level of the liquid 9 in the first tank 11 and the liquid level of the liquid 9 in the second tank 12 become the same (liquid level LH), the first valve 14 is switched from open to closed to block the gas flow path 13, and the second valve 19 is switched from open to closed to block the second liquid flow path 18, thereby completing the second step. Thereafter, the first step described with reference to FIGS. 1 to 4 is executed again.

[0048] In the second step of this embodiment, after the liquid 9 is moved from the second tank 12 to the first tank 11 via the second liquid flow path 18 by utilizing the pressure difference between the gas 8 in the first tank 11 and the second tank 12 by opening the second valve 19 as shown in Figure 5, the first valve 14 is opened to move the liquid 9 from the second tank 12 to the first tank 11 by utilizing the equalization of the pressure of the gas 8 in the first tank 11 and the second tank 12. However, the first valve 14 may be opened simultaneously with the opening of the second valve 19. In other words, the state shown in Figure 4 may be transitioned to the state shown in Figure 6 without passing through the state shown in Figure 5.

[0049] Figures 7 to 10 show modified examples of this embodiment. Points not specifically mentioned in these modified examples are the same as those in the embodiment described with reference to Figures 1 to 6. In Figures 7 to 9, elements that are the same as or similar to those in the embodiment are denoted by the same reference numerals.

[0050] 7, a check valve is used as the third valve 22, which allows the flow of gas 8 released from the second tank 12 to the atmosphere but prevents the flow in the opposite direction. If the third valve 22 is an atmosphere release valve such as an on-off valve or a solenoid valve, the control device 23 needs to control the opening and closing of the third valve 22 based on the detection result of the second pressure sensor PS2. In contrast, if the third valve 22 is a check valve, control by the second pressure sensor PS2 and the control device 23 is not required, which simplifies the configuration of the vacuum pump 2 and thereby reduces costs.

[0051] In a second modified example shown in Figure 8, when liquid pump 16 is stopped, it is possible to prevent the flow of liquid 9 from second tank 12 to first tank 11 via first liquid flow path 15. In such a case, there is no need to provide shutoff valve 17 (see Figure 1, for example) in first liquid flow path 15. By eliminating shutoff valve 17, it is possible to simplify the configuration of vacuum pump 2 and thereby reduce costs.

[0052] 9, a check valve is used as the shutoff valve 17 provided in the first liquid flow path 15. The check valve allows the liquid 9 to flow from the first tank 11 to the second tank 12, but prevents the liquid 9 from flowing in the reverse direction, that is, from the second tank 12 to the first tank 11. By using a check valve as the shutoff valve 17, the opening and closing control by the control device 23, which is required when an opening and closing valve or a solenoid valve is used, is not required. In this respect, the configuration of the vacuum pump 2 can be simplified, and costs can be reduced accordingly.

[0053] 10, the interior of a container 50 is divided into two spaces by a partition wall 51, thereby constituting a first tank 11 and a second tank 12. The partition wall 51 extends vertically, and the first tank 11 and the second tank 12 are disposed side by side adjacent to each other with the partition wall 51 interposed therebetween.

[0054] While specific embodiments of the present invention and their modifications have been described above, the present invention is not limited to the above-described embodiments and can be implemented with various modifications within the scope of the present invention. For example, an appropriate combination of the contents of the individual embodiments may be considered as one embodiment of the present invention.

[0055] For example, the vacuum tank 3 is directly connected to the first tank 11 via the gas flow path 4, but one end of the gas flow path 4 may be connected to the vacuum tank 3 and the other end of the gas flow path 4 may be connected to the gas flow path 13 on the side closer to the first tank 11 than the first valve 14. Furthermore, the second liquid flow path 18 connects the lower part of the first tank 11 and the lower part of the second tank 12 so that the liquid 9 flows therethrough, but the second liquid flow path 18 may be configured by branching off from the first liquid flow path 15. [Explanation of symbols]

[0056] 1. Vacuum generator 2. Vacuum pump 3. Vacuum Tank 4. Gas flow path (second gas flow path) 5. Check valve 6 Vacuum supply switching valve 7 Vacuum supply channel 8 Gases 9 liquid 11 First Tank 12 Second Tank 13 Gas flow path (first gas flow path) 14 First valve 15 First liquid flow path 16 Liquid Pump 17 Shut-off valve 18 Second liquid flow path 19 Second valve 21 Atmospheric release flow path 22 Third valve 23 Control device 50 containers 51 Bulkhead LS Level Switch (Liquid Level Sensor) PS1 First pressure sensor PS2 Second pressure sensor

Claims

1. a first tank and a second tank capable of storing a gas and a liquid, respectively; a first gas flow path connecting the first tank and the second tank so that the gas flows; a first valve provided in the first gas flow path and capable of switching between communication and blocking of the first gas flow path; a first liquid flow path connecting the first tank and the second tank so that the liquid flows; a liquid pump provided in the first liquid flow path and configured to pump the liquid; a second liquid flow path that connects the first tank and the second tank so that the liquid flows therethrough, that is not provided with a liquid pump, and that is different from the first liquid flow path; a second valve provided in the second liquid flow path and capable of switching between communication and blocking of the second liquid flow path; an atmosphere open flow path that connects the second tank and the atmosphere so that the gas can flow; a third valve provided in the atmosphere release passage for maintaining the pressure of the gas in the second tank at or below atmospheric pressure; A vacuum generating device comprising:

2. 2. The vacuum generating apparatus of claim 1, wherein said third valve is a check valve that allows flow from said second tank to atmosphere.

3. 2. The vacuum generating device according to claim 1, wherein the liquid pump is a one-way pump capable of pumping the liquid only from the first tank to the second tank.

4. A vacuum tank and a second gas flow path connecting the vacuum tank to the first tank so that the gas flows therethrough; a check valve provided in the second gas flow path to allow gas to flow from the vacuum tank to the first tank; The vacuum generating device of claim 1 further comprising:

5. a liquid level sensor that detects when the liquid level in the first tank drops to a preset lower limit liquid level; a control device that controls operations of the first valve, the second valve, and the liquid pump based on an input from at least the liquid level sensor; Furthermore, the control device closes the first valve and the second valve, and drives the liquid pump to move the liquid from the first tank to the second tank via the first liquid flow path, thereby reducing the pressure in the first tank and generating a vacuum; the control device stops driving the liquid pump when the liquid level sensor detects that the liquid level of the liquid in the first tank has dropped to the lower limit liquid level while the liquid pump is being driven; the control device switches the second valve from closed to open after the driving of the liquid pump is stopped, thereby causing liquid to flow from the second tank to the first tank via the second liquid flow path; The vacuum generating device according to claim 1 .

6. a first pressure sensor that detects the pressure of the gas in the first tank; a second pressure sensor that detects the pressure of the gas in the second tank; Furthermore, the control device controls operation of the first valve and the second valve further based on the first pressure sensor and an input from the second pressure sensor; the control device switches the first valve from closed to open after the second valve is switched from closed to open, or simultaneously with the second valve being switched from closed to open, and thereafter, liquid flows from the second tank to the first tank via the second liquid flow path; 6. The vacuum generating device according to claim 5, wherein after switching the first valve from closed to open, when the control device detects, based on inputs from the first pressure sensor and the second pressure sensor, that the pressure of the gas in the first tank and the pressure of the gas in the second tank have become the same, the control device switches the first valve and the second valve from open to closed, respectively.

7. a first tank and a second tank capable of storing a gas and a liquid, respectively; a first gas flow path connecting the first tank and an upper portion of the second tank so that the gas can flow; a first valve provided in the first gas flow path and capable of switching between communication and blocking of the first gas flow path; a first liquid flow path connecting a lower portion of the first tank and a lower portion of the second tank so that the liquid flows; a liquid pump provided in the first liquid flow path and configured to pump the liquid; a second liquid flow path that connects the lower portion of the first tank and the lower portion of the second tank so that the liquid flows, that is not provided with a liquid pump, and that is different from the first liquid flow path; a second valve provided in the second liquid flow path and capable of switching between communication and blocking of the second liquid flow path; an atmosphere open flow path that connects the upper portion of the second tank to the atmosphere so that the gas can flow; a third valve provided in the atmosphere release passage for controlling the release of the second tank to the atmosphere via the atmosphere release passage; providing a vacuum generating device comprising: moving the liquid from the first tank to the second tank through the first liquid flow path with the liquid pump, thereby creating a vacuum in the first tank; opening the second valve to communicate the second liquid flow path, and after or simultaneously with the opening of the second valve, opening the first valve to communicate the gas in the first tank with the gas in the second tank via the first gas flow path, thereby moving liquid from the second tank to the first tank via the second liquid flow path; A vacuum generation method comprising:

8. the liquid pump is a one-way pump capable of pumping the liquid only from the first tank to the second tank, 8. The vacuum generating method according to claim 7, wherein, when the liquid levels in the first tank and the second tank become the same after the first valve and the second valve are opened, the method proceeds to a step of moving the liquid from the first tank to the second tank via the first liquid flow path using the liquid pump.

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