JP7037040B2 - Low oxygen concentration air supply device - Google Patents

Description

The present disclosure relates to a device for supplying low oxygen concentration air.

In Patent Document 1 below, in order to control the atmosphere in the storage where fruits, vegetables, etc. are stored in a nitrogen-rich state, the air in the storage is guided to the adsorption tower to adsorb nitrogen and to adsorb difficult-to-adsorb oxygen. A technique is disclosed in which nitrogen is released to the outside of the system, and the adsorbed nitrogen is recovered under reduced pressure conditions and returned to the storage. The air in the storage is supplied to the adsorption tower by being compressed by a blower, and the adsorbed nitrogen is recovered by reducing the pressure in the adsorption tower with a vacuum pump and returned to the storage.

Japanese Unexamined Patent Publication No. 7-313502

The technique described in Patent Document 1 requires a blower and a vacuum pump to adsorb and desorb nitrogen to the adsorption tower. Of these, the blower generates a large amount of heat in order to adiabatically compress the air, needs to be cooled by itself, and the heated air is supplied to the adsorption tower, which causes deterioration of the adsorption efficiency.

The present disclosure proposes a supply device capable of supplying low oxygen concentration air by adsorbing and desorbing nitrogen to an adsorbed portion by a negative pressure generator without compressing air by an air compressor such as a blower. do.

(1) The low oxygen concentration air supply device of the present disclosure is
Two adsorbents that selectively adsorb nitrogen over oxygen,
A negative pressure generator that sucks air from the suction part,
A decompression mechanism that sequentially switches between the two adsorption units by the negative pressure generator to reduce the pressure in the region below atmospheric pressure, and
A supply / discharge mechanism having a supply path and a discharge path for low oxygen concentration air and allowing air sucked from the adsorption section to flow to the supply path or the discharge path while the suction portion is being depressurized.
It is provided with an adsorption mechanism for opening the adsorption portion after depressurization to atmospheric pressure to increase the pressure and allowing outside air to flow through the adsorption portion by the negative pressure generator to adsorb nitrogen.

The low oxygen concentration air supply device having the above configuration supplies low oxygen concentration air by adsorbing and desorbing nitrogen to the adsorption part by a negative pressure generator without compressing the air by an air compressor. be able to. It should be noted that the supply device of the present disclosure may include two suction portions, and does not prevent the supply device from including three or more suction portions.

(2) Preferably, the first switching unit in which the supply / discharge mechanism switches the path through which the air flows to either the supply path or the discharge path according to the oxygen concentration of the air sucked from the adsorption portion. It is equipped with.
With such a configuration, the air sucked from the adsorption portion can be switched between the supply path and the discharge path to flow.

(3) Preferably, the decompression mechanism includes a second switching unit that switches between the two suction units and connects to the negative pressure generator.
With such a configuration, the pressure of each of the two adsorption portions can be reduced.

(4) Preferably, the adsorption mechanism includes a third switching unit that switches between the two adsorption units and connects them to the atmosphere.
With such a configuration, the two adsorption portions can be sequentially opened to the atmospheric pressure.

(5) Preferably, the suction mechanism further includes a suction operation unit that connects the suction unit to the negative pressure generator by a route different from that of the decompression mechanism.
With such a configuration, nitrogen can be adsorbed by allowing outside air to flow through the adsorption portion using a negative pressure generator.

(6) Preferably, the first switching section switches the path through which the air flows to either the supply path or the discharge path based on the suction time of the air from the adsorption section.
With such a configuration, oxygen of a predetermined concentration can be flowed through the supply path without directly measuring the oxygen concentration.

(7) Preferably, the supply / discharge mechanism includes a sensor for detecting the oxygen concentration of the air sucked from the adsorption unit, and the first switching unit causes the air to flow based on the detection signal of the sensor. The route is switched to either the supply route or the discharge route.
With such a configuration, the oxygen concentration can be measured and oxygen of a predetermined concentration can be flowed to the supply path as accurately as possible.

It is explanatory drawing which shows the container to which the supply device of the low oxygen concentration air which concerns on 1st Embodiment is applied. It is a schematic block diagram which shows the supply device of low oxygen concentration air. It is a flowchart which shows the operation procedure of a supply device. It is a figure which shows the opening / closing timing of the on-off valve of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a schematic diagram which shows the air flow of a supply device. It is a graph which shows the fluctuation of the pressure in the suction cylinder of a feeding device. It is a graph which shows the relationship between the pressure of the adsorption cylinder, and the amount of nitrogen adsorption. It is a schematic block diagram which shows the supply apparatus of the low oxygen concentration air which concerns on 2nd Embodiment. It is a schematic block diagram which shows the supply apparatus of the low oxygen concentration air which concerns on 3rd Embodiment.

Hereinafter, the low oxygen concentration air supply device according to the embodiment will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is an explanatory diagram showing a container to which the low oxygen concentration air supply device according to the first embodiment is applied.
The supply device 10 of the present embodiment is applied to, for example, a container 1 used for marine transportation and the like, which stores plants such as fruits and vegetables for a long period of time while maintaining freshness. Specifically, the supply device 10 takes in outside air (atmosphere) and has a predetermined oxygen concentration (for example, 10% or less) lower than the oxygen concentration (about 21%: volume content) of the outside air, that is, low oxygen concentration air. To generate. Then, the supply device 10 supplies the generated low oxygen concentration air into the container 1 which is the supply destination to reduce the oxygen concentration in the container 1, and the storage A housed in the container 1, for example, a boxed plant. Maintains plant freshness by reducing the amount of breathing. Further, the supply device 10 exhausts the air having a high oxygen concentration generated in the process of generating the air having a low oxygen concentration to the outside.

FIG. 2 is a schematic configuration diagram showing a low oxygen concentration air supply device 10.
The supply device 10 of the present embodiment includes suction units 21 and 22, a negative pressure generator 12, a decompression mechanism 13, a suction mechanism 14, and a supply / discharge mechanism 15. In addition, in FIG. 2, the direction of the air flow in the supply device 10 is indicated by an arrow.

The adsorption portions 21 and 22 are cylindrical members that are filled with an adsorbent and are installed in an upright posture. Therefore, in the following, the suction portion is also referred to as a “suction tube”. The supply device 10 of the present embodiment includes a first suction cylinder 21 and a second suction cylinder 22. The first and second suction cylinders 21 and 22 have inflow ports 21a and 22a for allowing air to flow in from the outside, and first and second suction cylinders 21 and 22 for allowing air to flow out from the inside of the first and second suction cylinders 21 and 22, respectively. It is provided with a first outlet 21b, 22b and a second outlet 21c, 22c.

The adsorbent filled inside the first and second adsorption cylinders 21 and 22 is, for example, smaller than the molecular diameter of the nitrogen molecule (3.0 angstroms) and smaller than the molecular diameter of the oxygen molecule (2.8 angstroms). Is also composed of a porous zeolite having pores with a large pore diameter. By using this zeolite, the first and second adsorption cylinders 21 and 22 can selectively adsorb nitrogen rather than oxygen.

FIG. 14 is a graph showing the characteristics of the suction cylinders 21 and 22. As is clear from FIG. 14, the adsorption cylinders 21 and 22 have the property of adsorbing more nitrogen than oxygen. Further, in the adsorption cylinders 21 and 22, the amount of nitrogen adsorbed increases as the pressure increases, and the amount of nitrogen adsorbed decreases as the pressure decreases. Therefore, nitrogen can be adsorbed on the adsorbent by increasing the pressure in the adsorption cylinders 21 and 22, and nitrogen is desorbed (desorbed) from the adsorbent by decreasing the pressure in the adsorption cylinders 21 and 22. Can be done. As an example, the supply device 10 of the present embodiment changes the pressure in the adsorption cylinders 21 and 22 in the range of 0 to -60 (kPa) to adsorb and desorb nitrogen. Therefore, the amount of nitrogen adsorbed on each of the adsorption cylinders 21 and 22 in this case is about 1.3 to 2.3 (L / 100 g).

As shown in FIG. 2, the negative pressure generator 12 is composed of one vacuum pump that generates a vacuum state lower than the atmospheric pressure. The vacuum pump 12 includes a suction port 12a and a discharge port 12b, sucks air from the suction port 12a by driving a motor, increases the pressure of the air, and discharges the air from the discharge port 12b.

The depressurizing mechanism 13 is provided between the outlets 21b and 22b of the first and second suction cylinders 21 and 22 and the suction port 12a of the vacuum pump 12. Then, the depressurizing mechanism 13 alternately switches the first and second suction cylinders 21 and 22 by the vacuum pump 12 to reduce the pressure in the region below the atmospheric pressure.

More specifically, the depressurizing mechanism 13 has suction paths 24a and 24b and a second switching unit 32. The suction paths 24a and 24b are composed of pipes through which air flows, and are a first suction path 24a connecting the first outlet 21b of the first suction cylinder 21 and the suction port 12a of the vacuum pump 12, and a second suction cylinder. It has a second suction path 24b that connects the first outlet 22b of 22 and the suction port 12a of the vacuum pump 12. The first suction path 24a and the second suction path 24b are connected to the vacuum pump 12 in a state of being merged on the downstream side in the air flow direction.

The second switching unit 32 has a second on-off valve e2 provided in the first suction path 24a and a fourth on-off valve e4 provided in the second suction path 24b. By alternately opening the second on-off valve e2 and the fourth on-off valve e4, the first suction cylinder 21 and the second suction cylinder 22 are alternately connected to the vacuum pump 12. The first and second suction cylinders 21 and 22 connected to the vacuum pump 12 are depressurized by sucking the air inside, and become a negative pressure.

The suction mechanism 14 opens the first and second suction cylinders 21 and 22 that have been depressurized by the above-mentioned decompression mechanism 13 to atmospheric pressure to increase the pressure, and the first or second suction cylinder 21 and the vacuum pump 12 increase the pressure. The outside air is circulated through 22 to adsorb nitrogen.

Specifically, the adsorption mechanism 14 has an atmosphere opening unit 26 and an adsorption operation unit 27.
The atmosphere opening portion 26 is provided between the outside of the supply device 10 and the inflow ports 21a and 22a of the first and second suction cylinders 21 and 22, and the first and second suction cylinders 21 and 22 are large, respectively. It is open to atmospheric pressure.

The atmosphere opening unit 26 has inflow paths 28a and 28b and a third switching unit 33. The inflow paths 28a and 28b are composed of pipes through which air flows, and one end thereof is connected to the inflow port 21a of the first suction cylinder 21 and one end thereof is connected to the inflow port 22a of the second suction cylinder 22. It has a connected second inflow path 28b. The other end of the first inflow path 28a and the other end of the second inflow path 28b merge with each other and are connected to the outside (outside air) of the supply device 10. However, the other end of the first inflow path 28a and the other end of the second inflow path 28b may not be merged with each other, and each may be connected to the outside.

The third switching unit 33 has a first on-off valve e1 provided in the first inflow path 28a and a third on-off valve e3 provided in the second inflow path 28b. The first on-off valve e1 and the third on-off valve e3 are alternately opened to connect the first suction cylinder 21 and the second suction cylinder 22 to the outside air alternately. Then, the atmosphere opening unit 26 opens the inside to the atmospheric pressure by connecting the first and second adsorption cylinders 21 and 22, respectively, to the outside air.

The suction operation unit 27 is provided between the outlets 21c and 22c of the first and second suction cylinders 21 and 22 and the suction port 12a of the vacuum pump 12, and is provided in the first and second suction cylinders 21 and 22. Nitrogen is adsorbed on the adsorbent by circulating air. The suction operation unit 27 has suction paths 29a and 29b, a fifth on-off valve e5, and a check valve 30a and 30b.

The suction paths 29a and 29b are composed of pipes through which air flows, and are a third suction path 29a connecting the second outlet 21c of the first suction cylinder 21 and the suction port 12a of the negative pressure generator 12, and a second suction path 29a. It has a fourth suction path 29b that connects the second outlet 22c of the suction cylinder 22 and the suction port 12a of the vacuum pump 12. The third suction path 29a and the fourth suction path 29b are connected to the vacuum pump 12 in a state of being merged on the downstream side in the air flow direction.

Check valves 30a and 30b are provided in the third suction path 29a and the fourth suction path 29b, respectively. The check valves 30a and 30b prevent the backflow of air from the third and fourth suction paths 29a and 29b to the second outlets 21c and 22c.
The fifth on-off valve e5 is provided in the piping portion after the merging of the third suction path 29a and the fourth suction path 29b. By opening the fifth on-off valve e5, both the first and second suction cylinders 21 and 22 are connected to the vacuum pump 12, and the air inside is sucked by the vacuum pump 12.

The supply / discharge mechanism 15 blows out the air sucked from the first and second suction cylinders 21 and 22 to a predetermined path.
The supply / discharge mechanism 15 is provided between the discharge port 12b of the vacuum pump 12 and the outside of the supply device 10. The supply / discharge mechanism 15 has blowout paths 35a and 35b and a first switching unit 31. The outlet paths 35a and 35b are supply paths 35a connecting the discharge port 12b of the vacuum pump 12 and the storage chamber in the container 1, and discharge paths 35b connecting the discharge port 12b of the vacuum pump 12 and the outside of the supply device 10. It consists of. The supply path 35a and the discharge path 35b are connected to the discharge port 12b in a state of being merged on the upstream side in the air flow direction. The supply path 35a is a path for flowing low oxygen concentration air reduced to a predetermined oxygen concentration to the container 1. On the other hand, the discharge path 35b is a path for discharging air having an oxygen concentration higher than a predetermined oxygen concentration to the outside.

The first switching unit 31 has a seventh on-off valve e7 provided in the supply path 35a and a sixth on-off valve e6 provided in the discharge path 35b. The seventh on-off valve e7 and the sixth on-off valve e6 connect the vacuum pump 12 to the inside or the outside of the container 1 by alternately opening, and the first and second suction cylinders 21 and 22 sucked by the vacuum pump 12 The air inside is selectively blown into either the inside or the outside of the container 1.

The operations of the vacuum pump 12 and the mechanisms 13, 14, and 15 (1st to 7th on-off valves e1 to e7) described above are controlled by a control device (not shown). Specifically, the vacuum pump 12 is controlled to always operate during the operation of the supply device 10. The first to seventh on-off valves e1 to e7 repeatedly adsorb and desorb nitrogen to the first and second adsorption cylinders 21 and 22, and supply low oxygen concentration air to the container 1 at a predetermined timing. Opening and closing is controlled.

FIG. 3 is a flowchart showing the operation procedure of the supply device 10. The supply device 10 has steps 1 to 8 shown in FIG. 3 as one cycle, and by repeating this cycle, nitrogen is adsorbed and desorbed from the adsorbents in the first and second adsorption cylinders 21 and 22. A low oxygen concentration air having a predetermined oxygen concentration is supplied into the container 1.

FIG. 4 is a diagram showing opening / closing timing of each on-off valve e1 to e7 of the supply device 10. The first to seventh on-off valves e1 to e7 are opened in the step marked with a thick line in FIG. 4 during steps 1 to 8, and are closed in the other steps. Steps 1 to 8 proceed with the passage of time. 5 to 12 are explanatory views showing the air flow in the supply device 10. Further, FIG. 13 is a graph showing fluctuations in pressure in the suction cylinders 21 and 22 of the supply device 10.

Hereinafter, the operation of the supply device 10 will be described in detail with reference to FIGS. 3 to 13.
(Step 1)
As shown in FIG. 3, first, the first adsorption cylinder 21 is in a state where the pressure is reduced to below atmospheric pressure and nitrogen is desorbed in the previous step of step 1 (step 8 of the previous cycle), and the second is The adsorption cylinder 22 is in a state where nitrogen is adsorbed by being increased in pressure in the range of atmospheric pressure or less in the previous step of step 1 (step 8 of the previous cycle).

As step 1, the supply device 10 performs a suction step (pressure increase) on the first suction cylinder 21.
Specifically, as shown in FIGS. 4 and 5, the supply device 10 opens the first on-off valve e1, the fifth on-off valve e5, and the sixth on-off valve e6, and closes the other on-off valves. The first suction cylinder 21 is opened to atmospheric pressure by being connected to the outside. As a result, the outside air flows into the first adsorption cylinder 21, the pressure in the first adsorption cylinder 21 increases to the atmospheric pressure, and the nitrogen contained in the inflowing air is adsorbed by the adsorbent.

Further, by the operation of the vacuum pump 12, the air flows into the first suction cylinder 21 and the air after nitrogen is adsorbed by the adsorbent is discharged to the outside through the fifth on-off valve e5 and the sixth on-off valve e6. To.
As shown in FIG. 13, immediately after the start of step 1, the pressure of the second suction cylinder 22 is increased in the range of atmospheric pressure or less in the previous step of step 1 (step 8 of the previous cycle), and the first suction cylinder 21 is increased. Although the pressure is reduced in the previous step of step 1, the pressure of the first suction cylinder 21 is increased in a very short time by opening the first on-off valve e1, and the pressure becomes higher than that of the second suction cylinder 22. Further, by opening the first and fifth on-off valves e1 and e5, the resistance of the air flowing through the first suction cylinder 21 is reduced. Therefore, in this step 1, air is sucked exclusively from the first suction cylinder 21 rather than the second suction cylinder 22. Therefore, in step 1, the second suction cylinder 22 substantially performs a standby step continuously from the previous step (step 8 of the previous cycle).

(Step 2)
As shown in FIG. 3, the supply device 10 performs a preliminary decompression step on the first adsorption cylinder 21 and a decompression step (discharge) on the second adsorption cylinder 22 as step 2.
Specifically, as shown in FIGS. 4 and 6, the supply device 10 opens the fourth on-off valve e4, the fifth on-off valve e5, and the sixth on-off valve e6, and closes the other valves.

The first suction cylinder 21 is shut off from the outside by opening the first on-off valve e1, and is continuously connected to the vacuum pump 12 by opening the fifth on-off valve e5. Therefore, the air inside the first suction cylinder 21 is sucked and the pressure is slightly reduced (see FIG. 13). The depressurization of the first adsorption cylinder 21 is a preliminary depressurization performed in advance before the substantial decompression step in steps 6 to 8 described later, and the low oxygen concentration air is applied in steps 6 to 8. This is done to generate it earlier.

The second suction cylinder 22 is sucked into the vacuum pump 12 by opening the fourth on-off valve e4. Further, by opening the fifth on-off valve e5, the vacuum pump 12 is also sucked from the second outlet 22c. As a result, the pressure of the second suction cylinder 22 is also reduced (see FIG. 13).

Further, by opening the sixth on-off valve e6, the air in the first and second suction cylinders 21 and 22 is discharged to the outside. At this time, the oxygen concentration of the air flowing out from the first outlet 22b of the second adsorption cylinder 22 gradually decreases, but the air flowing out from the first adsorption cylinder 21 and the second adsorption cylinder 22 As for the air flowing out from the second outlet 22c of the above, since nitrogen is adsorbed by the adsorbent and the oxygen concentration is high, the oxygen concentration as a whole is not lowered to the oxygen concentration to be supplied to the container 1. Therefore, the air sucked from the first and second suction cylinders 21 and 22 is discharged to the outside through the sixth on-off valve e6.

(Step 3)
As shown in FIG. 3, as step 3, the supply device 10 performs a standby step for the first suction cylinder 21 and subsequently performs a depressurization step (discharge) for the second suction cylinder 22.
Specifically, as shown in FIGS. 4 and 7, the supply device 10 opens the fourth on-off valve e4 and the sixth on-off valve e6, and closes the other on-off valves.

By closing the first and fifth on-off valves e5, the first suction cylinder 21 stops the flow of air and goes into a standby state.
The second suction cylinder 22 is sucked into the vacuum pump 12 by opening the fourth on-off valve e4. In step 3, since the fifth on-off valve e5 opened in step 2 is closed, the pressure in the second suction cylinder 22 is further reduced (see FIG. 13). In this step 3, since the air sucked from the second suction cylinder 22 is still in a state higher than the oxygen concentration to be supplied to the container 1, it is discharged to the outside through the sixth on-off valve e6.

(Step 4)
As shown in FIG. 3, the supply device 10 continuously performs a standby step for the first suction cylinder 21 and a decompression step (supply) for the second suction cylinder 22 as step 4.
Specifically, as shown in FIGS. 4 and 8, the supply device 10 opens the fourth on-off valve e4 and the seventh on-off valve e7, and closes the other on-off valves.

By closing the first and fifth on-off valves e5, the air flow of the first suction cylinder 21 is stopped, and the standby state is continued.
The second suction cylinder 22 is sucked into the vacuum pump 12 by opening the fourth on-off valve e4, and the sucked air is supplied to the container 1 by further opening the seventh on-off valve e7. The second suction cylinder 22 is continuously depressurized from step 2 to step 3, and the internal pressure is further lowered. Therefore, as shown in FIG. 14, nitrogen adsorbed by the adsorbent is more easily desorbed, and air having a high nitrogen concentration, in other words, air having a low oxygen concentration, flows out from the second adsorption cylinder 22.

That is, the oxygen concentration of the air sucked from the second adsorption cylinder 22 becomes a predetermined value or less (for example, 10% or less) by depressurizing the second adsorption cylinder 22 only for the time when steps 2 to 3 elapse. Become. As a result, low oxygen concentration air having a predetermined oxygen concentration or less is generated and supplied into the container 1 via the seventh on-off valve e7.

In the next steps 5 to 8, the steps performed for the first suction cylinder 21 in steps 1 to 4 are performed for the second suction cylinder 22, and conversely, for the second suction cylinder 22. The performed step is performed on the first suction cylinder 21.

(Step 5)
As shown in FIG. 3, as step 5, the supply device 10 continuously performs a standby step for the first suction cylinder 21 and a suction step (pressure increase) for the second suction cylinder 22.
Specifically, as shown in FIGS. 4 and 9, the supply device 10 opens the third on-off valve e3, the fifth on-off valve e5, and the sixth on-off valve e6, and closes the other valves. Since the second suction cylinder 22 is in a decompressed state in step 4, the second suction cylinder 22 is opened to the atmospheric pressure by opening the third on-off valve e3 and connecting to the outside. As a result, the outside air flows into the second adsorption cylinder 22, the pressure in the second adsorption cylinder 22 increases to atmospheric pressure (see FIG. 13), and the nitrogen in the inflowing air is adsorbed by the adsorbent.

Further, by the operation of the vacuum pump 12, the air flows into the second suction cylinder 22 and the air after nitrogen is adsorbed by the adsorbent is discharged to the outside through the fifth on-off valve 5 and the sixth on-off valve e6. To.
As shown in FIG. 13, immediately after the start of step 5, the pressure of the first suction cylinder 21 is increased in the range of atmospheric pressure or less in the step of step 4, and the pressure of the second suction cylinder 22 is reduced in the step of step 4. However, by opening the third on-off valve e3, the pressure of the second suction cylinder 22 is increased in a very short time, and the pressure becomes higher than that of the first suction cylinder 21. Further, by opening the third and fifth on-off valves e3 and e5, the resistance of the air flowing through the second suction cylinder 22 becomes smaller. Therefore, in this step 5, air is sucked exclusively from the second suction cylinder 22 rather than the first suction cylinder 21. Therefore, in step 5, the first suction cylinder 21 substantially continues the standby step from the step of step 4.

(Step 6)
As shown in FIG. 3, as step 6, the supply device 10 performs a decompression step (discharge) on the first adsorption cylinder 21 and a preliminary decompression step on the second adsorption cylinder 22.
Specifically, as shown in FIGS. 4 and 10, the supply device 10 opens the second on-off valve e2, the fifth on-off valve e5, and the sixth on-off valve e6, and closes the other valves.

The second suction cylinder 22 is shut off from the outside by opening the third on-off valve e3, and is continuously connected to the vacuum pump 12 by opening the fifth on-off valve e5. Therefore, the air inside the second suction cylinder 22 is sucked and the pressure is slightly reduced (see FIG. 13). The depressurization of the second adsorption cylinder 22 is a preliminary depressurization performed in advance before the substantial decompression step in steps 2 to 4 described above, and the low oxygen concentration air is applied in steps 2 to 4. This is done to generate it earlier.

The first suction cylinder 21 is sucked into the vacuum pump 12 by opening the second on-off valve e2. Further, by opening the fifth on-off valve e5, the vacuum pump 12 is also sucked from the second outlet 21c. As a result, the pressure of the first suction cylinder 21 is also reduced (see FIG. 13).

Further, by opening the sixth on-off valve e6, the air in the first and second suction cylinders 21 and 22 is discharged to the outside. At this time, the oxygen concentration of the air flowing out from the first outlet 21b of the first adsorption cylinder 21 gradually decreases, but the air flowing out from the second adsorption cylinder 22 and the first adsorption cylinder 21 In the air flowing out from the second outlet 21c, nitrogen is adsorbed by the adsorbent and the oxygen concentration is high, so that the oxygen concentration as a whole is not lowered to a predetermined oxygen concentration to be supplied to the container 1. Therefore, the air sucked from the first and second suction cylinders 21 and 22 is discharged to the outside through the sixth on-off valve e6.

(Step 7)
As shown in FIG. 3, as step 7, the supply device 10 continuously performs a decompression step (discharge) on the first suction cylinder 21 and a standby step on the second suction cylinder 22.
Specifically, as shown in FIGS. 4 and 11, the supply device 10 opens the second on-off valve e2 and the sixth on-off valve e6, and closes the other on-off valves.

The first suction cylinder 21 is sucked into the vacuum pump 12 by opening the second on-off valve e2. Since the fifth on-off valve e5 opened in step 6 is closed, the pressure in the first suction cylinder 21 is further reduced (see FIG. 13). In step 7, since the air sucked from the first suction cylinder 21 is still in a state higher than the oxygen concentration to be supplied to the container 1, it is discharged to the outside through the sixth on-off valve e6.
The second suction cylinder 22 is put into a standby state by closing the third and fifth on-off valves e3 and e5 to stop the air flow.

(Step 8)
As shown in FIG. 3, as step 8, the supply device 10 performs a decompression step (supply) on the first suction cylinder 21 and subsequently performs a standby step on the second suction cylinder 22.
Specifically, as shown in FIGS. 4 and 12, the supply device 10 opens the second on-off valve e2 and the seventh on-off valve e7, and closes the other on-off valves.

The first suction cylinder 21 is sucked into the vacuum pump 12 by opening the second on-off valve e2, and the sucked air is supplied to the container 1 by opening the seventh on-off valve e7. The first suction cylinder 21 is continuously depressurized from step 6 to step 7, and the internal pressure is further lowered. Therefore, as shown in FIG. 14, the nitrogen adsorbed by the adsorbent is more easily desorbed, and the air having a high nitrogen concentration, that is, the air having a low oxygen concentration flows out from the first adsorption cylinder 21. As a result, low oxygen concentration air having a predetermined oxygen concentration or less is generated and supplied into the container 1 via the seventh on-off valve e7.

By closing the third and fifth on-off valves e3 and e5, the air flow of the second suction cylinder 22 is stopped and the standby state is continued.
After that, by repeating this cycle with the above steps 1 to 8 as one cycle, the nitrogen adsorption operation and the desorption operation for the first and second adsorption cylinders 21 and 22 are performed, and the first and second adsorption cylinders are performed. The low oxygen concentration air sucked from the adsorption cylinders 21 and 22 of the above is supplied to the container 1. Therefore, the oxygen concentration in the container 1 is kept low, and the respiration of the plants in the container 1 is suppressed, so that the fresh state is maintained for a long period of time.

According to steps 1 to 8 described above, the pressure inside the first suction cylinder 21 and the second suction cylinder 22 fluctuates as shown in FIG. Specifically, the pressure in each of the suction cylinders 21 and 22 fluctuates in the range of atmospheric pressure or less, and in steps 2 to 4, the second suction cylinder 22 is depressurized by the vacuum pump 12, and steps 6 to 8 are performed. In, the first suction cylinder 21 is depressurized by the vacuum pump 12. That is, the first and second suction cylinders 21 and 22 are alternately depressurized by the depressurizing mechanism 13. The first and second adsorption cylinders 21 and 22, respectively, are increased in pressure by being released to atmospheric pressure after the decompression is completed, and air is circulated inside to adsorb nitrogen. (Step 1 and Step 5).

[Second Embodiment]
FIG. 15 is a schematic configuration diagram showing a low oxygen concentration air supply device 10 according to the second embodiment.
In this embodiment, the first switching unit 31 in the supply / discharge mechanism 15 is configured by the switching valve e10. Further, the second switching unit 32 in the pressure reducing mechanism 13 is configured by the switching valve e9. Further, the third switching unit 33 in the suction mechanism 14 is configured by the switching valve e8. Each switching valve e8 to e10 has a function of switching to one of the two paths to allow air to flow. Further, the switching valves e8 and e9 also have a function of blocking the air flow in both of the two paths. Then, by switching the air flow path by the switching valves e10, e9, and e8 at the same timing as the opening / closing timing of the on-off valves e1 to e7 shown in FIG. 3, the same operation as that of the first embodiment is performed. Can be done.

[Third Embodiment]
FIG. 16 is a schematic configuration diagram showing a low oxygen concentration air supply device 10 according to a third embodiment.
In this embodiment, the supply / discharge mechanism 15 includes an oxygen concentration sensor 37 that detects the oxygen concentration at the discharge port 12b of the vacuum pump 12. Then, the opening / closing of the sixth on-off valve e6 and the seventh on-off valve e7 in the first switching unit 31 is switched based on the detection signal of the oxygen concentration sensor 37. Specifically, when the oxygen concentration detected by the oxygen concentration sensor 37 is higher than the predetermined oxygen concentration to be supplied to the container 1, the sixth on-off valve e6 is opened and the seventh on-off valve e7 is closed. , Exhaust air to the outside. On the contrary, when the oxygen concentration detected by the oxygen concentration sensor 37 is equal to or lower than the predetermined oxygen concentration to be supplied to the container 1, the sixth on-off valve e6 is closed and the seventh on-off valve e7 is opened to open the container 1. Supply low oxygen concentration air to. That is, the transition from step 3 to step 4 in FIGS. 3 and 4 and the transition from step 7 to step 8 are performed based on the detection signal of the oxygen concentration sensor 37.

[Effects of the present disclosure]
The low oxygen concentration air supply device 10 shown in each of the above embodiments has two suction cylinders 21 and 22 that selectively adsorb nitrogen rather than oxygen, and a vacuum pump 12 that sucks air from the suction cylinders 21 and 22. It has a decompression mechanism 13 that sequentially (alternately) switches between the two suction cylinders 21 and 22 by the vacuum pump 12 to reduce the pressure in the region below the atmospheric pressure, and a supply path 35a and a discharge path 35b for low oxygen concentration air. In addition, the supply / discharge mechanism 15 that causes the air sucked from the suction cylinders 21 and 22 to flow to the supply path 35a or the discharge path 35b while the suction cylinders 21 and 22 are being depressurized, and the suction cylinder 21 that has finished depressurization. 22 is provided with a suction mechanism 14 for opening the pressure to atmospheric pressure to increase the pressure and allowing outside air to flow through the suction cylinders 21 and 22 by a vacuum pump 12 to adsorb nitrogen.

In the above supply device 10, a vacuum pump 12 is used as a device for generating an air flow, and an air compressor such as a blower for generating compressed air is not used. Then, the supply device 10 decompresses each of the adsorption cylinders 21 and 22 in the region below the atmospheric pressure by the vacuum pump 12, desorbs the nitrogen adsorbed on each of the adsorption cylinders 21 and 22, and supplies low oxygen concentration air to the supply path 35a. To discharge. On the other hand, the adsorption cylinders 21 and 22 that have been decompressed are increased in pressure by opening to atmospheric pressure, and nitrogen is adsorbed again by circulating outside air by the vacuum pump 12. Therefore, it is possible to supply low oxygen concentration air into the container 1 by using the vacuum pump 12 without using an air compressor. Therefore, the number of parts can be reduced, the structure of the supply device 10 can be simplified, and the manufacturing cost can be reduced. Further, when an air compressor is used, the efficiency of nitrogen adsorption with respect to the adsorption cylinders 21 and 22 may deteriorate due to the temperature rise of the compressed air. However, since the air compressor is not used in this embodiment, the air compressor is not used. Deterioration of adsorption efficiency can be suppressed. Further, since it is not equipped with an air compressor that requires a large amount of electric power for driving, it is possible to efficiently supply low oxygen concentration air with a small amount of energy.

The supply / discharge mechanism 15 of each of the above embodiments is the first to switch the air flow path to either the supply path 35a or the discharge path 35b according to the oxygen concentration of the air sucked from the suction cylinders 21 and 22. A switching unit 31 (sixth on-off valve e6 and seventh on-off valve e7 (see FIG. 2) or switching valve e10 (see FIG. 15)) is provided. Therefore, among the air sucked from each of the suction cylinders 21 and 22, air having a predetermined oxygen concentration (low oxygen concentration air) can be supplied to the container 1, and the other air can be discharged to the outside.

In the supply device 10 of the first and second embodiments, the switching of the air flow between the discharge path 35b and the supply path 35a by the first switching unit 31 is performed in steps 2 to 3 and steps 6 to 7. It is done according to the progress. In other words, the supply device 10 has passed a predetermined time in the step of sucking air from each of the suction cylinders 21 and 22 to reduce the pressure, and the oxygen concentration of the air sucked from each of the suction cylinders 21 and 22 becomes equal to or less than the predetermined time. It is determined that the air flow path is switched from the discharge path 35b to the supply path 35a. With such a configuration, low oxygen concentration air can be supplied to the container 1 without using an oxygen concentration sensor or the like.

On the other hand, in the supply device 10 of the third embodiment, the supply / discharge mechanism 15 includes an oxygen concentration sensor 37 (see FIG. 16), and the supply path 35a provides a path through which air flows based on the detection signal of the oxygen concentration sensor 37. And the discharge path 35b. Therefore, it is possible to supply the container 1 with low oxygen concentration air having a predetermined oxygen concentration more accurately than in the first and second embodiments.

In each of the above embodiments, the depressurizing mechanism 13 includes a second switching unit 32 that switches between the two suction cylinders 21 and 22 and connects them to the vacuum pump 12. Therefore, each of the adsorption cylinders 21 and 22 can be sequentially (alternately) connected to the vacuum pump 12 to suck air and reduce the pressure, and the nitrogen adsorbed by the adsorbent of each of the adsorption cylinders 21 and 22 can be desorbed. Low oxygen concentration air can be generated.

In each of the above embodiments, the suction mechanism 14 includes a third switching unit 33 that switches between the two suction cylinders 21 and 22 and connects them to the outside (atmosphere). Therefore, the suction cylinders 21 and 22 can be sequentially (alternately) opened to atmospheric pressure to increase the pressure. That is, although the supply device 10 of each of the above embodiments is not provided with an air compressor such as a blower as in the prior art, it is easy to open the suction cylinders 21 and 22 from the negative pressure state to the atmospheric pressure. The pressure can be increased.

In each of the above embodiments, the suction mechanism 14 further includes a suction operation unit 27 for connecting the suction cylinders 21 and 22 to the vacuum pump 12 by a route different from that of the decompression mechanism 13. Therefore, using the negative pressure generator 12 used to depressurize each of the adsorption cylinders 21 and 22, while depressurizing one of the adsorption cylinders, the outside air is circulated to the other adsorption cylinder by another route to generate nitrogen. Can be adsorbed.

Although the embodiments have been described above, it will be understood that various modifications of the embodiments and details are possible without departing from the spirit and scope of the claims.
For example, the implementation time of each step 1 to 8, that is, the opening / closing timing of the on-off valves e1 to e7 in the first to third switching units 31 to 33 of each of the above embodiments, or the switching timing of the switching valves e8 to e10. , It is possible to change as appropriate according to the installation environment of the supply device 10, the supply conditions of low oxygen concentration, and the like.

In each of the above embodiments, the on-off valve e5 in the suction operation unit 27 of the suction mechanism 14 may be provided in each of the third suction path 29a and the fourth suction path 29b. In this case, both on-off valves e5 may be opened at the same time during the suction step (steps 1 and 5 in FIG. 3), or the suction paths 29a and 29b corresponding to the suction portions 21 and 22 for performing the suction step. Only the on-off valve e5 may be opened. In the latter case, the check valves 30a and 30b in the suction paths 29a and 29b can be omitted. However, by providing only one on-off valve e5 for the third and fourth suction paths 29a and 29b as in each of the above embodiments, the number of on-off valves can be reduced and the cost can be reduced.

In each of the above embodiments, the third and fourth suction paths 29a and 29b and the on-off valve e5 in the suction operation unit 27 of the suction mechanism 14 can be omitted, and the suction step (steps 1 and 5 in FIG. 3) can be performed. It can also be performed by using the first and second suction paths 24a and 24b by opening the on-off valves e2 and e4 in the second switching unit 32. That is, the decompression mechanism 13 can be used as a part of the adsorption mechanism 14.

The supply device 10 of the present disclosure may include two suction portions for sequentially switching the depressurization step and the like. That is, the supply device 10 may include three or more suction portions, and at least two of them may function as the first and second suction portions 21 and 22 of each of the above embodiments.
For example, the supply device 10 can include two or more sets of first and second suction cylinders 21 and 22. In this case, the decompression mechanism 13, the suction mechanism 14, and the supply / discharge mechanism 15 are configured so that the first suction cylinders 21 of each set or the second suction cylinders 22 of each set perform the same process. Can be done.

Further, for example, the supply device 10 may include three or more suction portions for sequentially switching the decompression step and the like. For example, when the supply device 10 includes three suction parts, each suction part sequentially performs a decompression step every 1/3 cycle of one cycle, and each suction part performs a suction step in 2/3 cycle after decompression. , The decompression mechanism 13, the adsorption mechanism 14, and the supply / discharge mechanism 15 can be configured so as to perform the preliminary depressurization step and the standby step. The same configuration can be made when there are four or more suction portions.

In each of the above embodiments, the preliminary decompression step can be omitted. Further, the depressurizing step can be performed on the second suction cylinder 22 between steps 1 and 4, and can be performed on the first suction cylinder 21 between steps 5 and 8.
The supply devices 10 of each of the above embodiments can be combined with each other in some configurations or can be replaced with some configurations.

10: Supply device 12: Vacuum pump (negative pressure generator)
13: Decompression mechanism 14: Adsorption mechanism 15: Supply / discharge mechanism 21: First adsorption cylinder (adsorption part)
22: Second adsorption cylinder (adsorption part)
27: Adsorption operation unit 31: 1st switching unit 32: 2nd switching unit 33: 3rd switching unit 35a: Supply path 35b: Discharge path 37: Oxygen concentration sensor

Claims (7)

Two adsorbents (21, 22) that selectively adsorb nitrogen over oxygen,
One negative pressure generator (12) that sucks air from the suction part (21, 22), and
A decompression mechanism (13) that sequentially switches between the two adsorption portions (21, 22) by the negative pressure generator (12) to reduce the pressure in the region below the atmospheric pressure.
It has a supply path (35a) and a discharge path (35b) for low oxygen concentration air, and was sucked from the adsorption section (21,22) while the adsorption section (21,22) was depressurized. A supply / discharge mechanism (15) for flowing air through the supply path (35a) or the discharge path (35b),
The adsorption part (21,22) which has finished decompression is opened to atmospheric pressure to increase the pressure, and the negative pressure generator (12) circulates outside air to the adsorption part (21,22) to adsorb nitrogen. With a mechanism (14) ,
The decompression mechanism (13) has a suction path (24a, 24b) for connecting the suction portion (21, 22) to the suction port (12a) of the negative pressure generator (12).
The suction path (14) is different from the suction path (24a, 24b) of the decompression mechanism (13), and connects the suction portion (21,22) to the suction port (12a). A low oxygen concentration air supply device having (29a, 29b) . The supply / discharge mechanism (15) has a path for flowing the air according to the oxygen concentration of the air sucked from the adsorption portion (21, 22) between the supply path (35a) and the discharge path (35b). The low oxygen concentration air supply device according to claim 1, further comprising a first switching unit (31) for switching to either one. The first or second aspect of the present invention, wherein the decompression mechanism (13) includes a second switching unit (32) that switches between the two suction units (21, 22) and connects to the negative pressure generator (12). Low oxygen concentration air supply device. The hypoxia according to any one of claims 1 to 3, wherein the adsorption mechanism (14) includes a third switching unit (33) that switches between the two adsorption units (21, 22) and connects to the atmosphere. Concentrated air supply device. The suction mechanism (14) includes a suction operation unit (27) having a suction path (29a, 29b) and an on-off valve (e5) for opening and closing the suction path (29a, 9b). The device for supplying low oxygen concentration air according to any one of 1 to 4. Based on the suction time of air from the adsorption unit (21, 22), the first switching unit (31) has a path through which the air flows, whichever is the supply path (35a) or the discharge path (35b). The low oxygen concentration air supply device according to claim 2, which switches to a crab. The supply / discharge mechanism (15) includes a sensor (37) for detecting the oxygen concentration of air sucked from the suction unit (21, 22), and the first switching unit (31) is the sensor (37). The low oxygen concentration air supply device according to claim 2, wherein the air flow path is switched to either the supply path (35a) or the discharge path (35b) based on the detection signal of the above.

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