JP2012228415A - Oxygen concentrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen concentrator capable of guaranteeing a flow rate as prescribed, while securing the oxygen concentration of oxygen-enriched gas regardless of the environmental condition.SOLUTION: The oxygen concentrator includes a mass flow controller 22 including a mass flowmeter and a flow control valve, and a CPU 32 that corrects the flow rate set in the mass flow controller 22 to an accurate flow rate value at the air pressure of the usage environment based on the air pressure of the usage environment detected by an air pressure sensor 37, whereby the flow rate set in the mass flow controller 22 is corrected to a flow rate value that is based on the volume of a gas at the air pressure of the usage environment. Thus, oxygen-enriched gas can be supplied at the accurate flow rate matching the air pressure of the usage environment. Thus, an oxygen inhalation treatment as prescribed by the doctor can be achieved regardless of the altitude and temperature of a usage location. The oxygen concentration will not be lowered even in an environment at a high altitude or high temperatures, and the oxygen inhalation treatment with a stably maintained oxygen concentration can be carried out.

Description

The present invention relates to an oxygen concentrator equipped with a flow rate control device and for supplying oxygen-concentrated gas mainly inhaled for medical purposes.

  Oxygen inhalation therapy is given to patients whose respiratory system function has been reduced due to diseases such as lung cancer, emphysema, chronic bronchitis, and pneumonia. As an oxygen gas supply source in such oxygen inhalation therapy, an oxygen gas cylinder, a liquid oxygen storage tank, a pressure fluctuation adsorption (PSA) oxygen concentrator, or the like is used. In recent years, pressure fluctuation adsorption type oxygen concentrators have become mainstream as a source of oxygen gas used for home oxygen therapy.

  The main components of the pressure fluctuation adsorption type oxygen concentrator are a compressor that feeds the raw air, an electromagnetic valve that switches the destination of the raw air, and two adsorption cylinders that selectively take out oxygen. After the foreign material is removed by the filter, the raw air is compressed by the compressor and sent to the adsorption cylinder.

  The flow path of the raw material air is usually switched by a solenoid valve. The adsorption cylinder is filled with zeolite having a higher affinity for nitrogen than for oxygen. Nitrogen stays in the adsorption cylinder to which the raw material air is fed from the raw material air port, and the oxygen-enriched gas enriched with oxygen flows out from the product port first. In this way, while one adsorption cylinder is producing oxygen, a part of the produced oxygen is fed into the other adsorption cylinder and the nitrogen adsorbed in the previous step is purged (washed out) with oxygen. The oxygen-enriched gas is fed into the oxygen buffer tank, the oxygen gas supply pressure is controlled by the pressure-reducing valve, passes through the flow rate controller (flow rate setting device), the oxygen concentration meter, and the humidifier, and finally reaches the user through the cannula. Supplied.

  Two types of flow rate controllers are mainly used. One is an orifice, and the other is a flow meter and a proportional solenoid valve or a so-called mass flow controller in which they are integrated.

  Those using an orifice are based on the principle that when the pressure difference (differential pressure) between the primary side and the secondary side of the orifice is constant, the flow rate is proportional to the area of the orifice opening. Actually, an orifice opening having a hole diameter corresponding to a desired flow rate is formed on a circular arc of a metal disk from a small hole diameter to a large hole diameter, and the corresponding orifice is selected by rotating the disk in the form of a rotary switch.

  On the other hand, the mass flow controller includes a mass flow meter (flow meter) and a proportional solenoid valve. The mass flow meter is a micro flow sensor in which a heating element and a temperature sensor are arranged on a small silicon chip. The flow of gas is measured by the temperature change of the temperature sensor, and the measured flow rate matches the set flow rate. The degree of opening of the proportional solenoid valve is adjusted so that

  The following patent documents 1 to 4 are disclosed as prior art documents relating to such an oxygen concentrator.

JP 2001-259039 A JP 2003-144550 A JP 2002-45424 A JP 2007-89684 A

◆ Patent Document 1
Patent Document 1 discloses an oxygen concentrator equipped with a thermal mass flow controller (mass flow controller). This oxygen concentrator uses a thermal mass flow meter as a flow meter for oxygen gas, a solenoid valve or a piezo valve as a flow control valve, and supplies oxygen gas at a set flow rate value even when a load is applied to the oxygen gas supply side. It is what you want to supply.

◆ Patent Document 2
Patent Document 2 discloses an oxygen concentrator that controls the opening degree of a flow rate adjustment valve based on a flow rate measurement result on the secondary side.

◆ Patent Document 3
Patent Document 3 discloses an oxygen concentration system that switches the orifice to increase the flow rate of oxygen gas to the user when the altitude is high based on the altitude detected by the altitude sensor.

◆ Patent Document 4
Patent Document 4 relates to a PSA type oxygen concentrator. In the PSA system, since the oxygen concentration is lowered in an environment where the atmospheric pressure is low, it is disclosed that the supply amount of the raw air is increased by increasing the rotation speed of the compressor when the atmospheric pressure sensor detects the atmospheric pressure.

  The inhalation amount of the oxygen-enriched gas in the oxygen inhalation therapy is indicated by a flow rate per unit time, for example, “5.0 [L / min]” in a doctor's prescription.

  In order to control the flow rate of the oxygen-enriched gas in accordance with a prescription, control by an orifice and control by a mass flow controller are generally employed.

  In the orifice method, the flow rate is controlled by passing an orifice, which is a small opening, when the gas on the primary side flows to the secondary side. Therefore, in the orifice method, the flow rate is determined by the differential pressure between the primary side and the secondary side of the orifice. In the oxygen concentrator, the primary side pressure is controlled to be substantially constant by the pressure reducing valve, while the secondary side pressure is constant.

  However, on the secondary side, there are a humidifier that humidifies oxygen gas, a cannula for a user to inhale oxygen gas from the nose, and a thin plastic tube that connects the cannula and the oxygen concentrator. In the bubbling humidifier, the bubble-like oxygen-enriched gas is released into the water from a tube having a porous body at the end, so that the secondary pressure varies depending on the water level in the humidifier. Pressure loss may occur due to the blockage of the porous body. In addition, the user may extend the tube when inhaling the oxygen-enriched gas at a location away from the apparatus, and the tube itself may be bent. Even with these factors, the pressure load on the secondary side fluctuates and the pressure on the secondary side does not become constant.

  As described above, when the pressure on the secondary side varies, the differential pressure before and after the orifice also varies. Therefore, basically, in the orifice method, the actual situation is that the oxygen inhalation treatment according to the prescription may not be realized due to various secondary factors.

  A mass flow controller (mass flow meter) detects the mass of a gas passing therethrough and controls the flow rate by controlling the mass of the gas. For this reason, when the flow rate of the oxygen-enriched gas is controlled by the mass flow controller, the flow rate is not affected by the pressure fluctuation on the secondary side, and supply of the oxygen-enriched gas at a constant flow rate can be realized.

  Since the mass flow controller controls the flow rate based on the mass, it must express the flow rate by converting the measured mass into a volume. Usually, it is displayed in terms of the volume of one standard state (for example, 20 [° C.], 1013 [hPa]). When the usage environment deviates from the standard state, the flow rate as a volume may not match the prescription.

  It is assumed that the oxygen concentrator whose flow rate is controlled by the mass flow controller is set to a flow rate of 5.0 [L / min]. The mass flow controller controls the mass of the flowing gas so as to be 5.0 [L / min] in the standard state. If the environment in which the oxygen concentrator is used is at an altitude of 1000 [m] and an atmospheric pressure of 900 [hPa], the actual volumetric flow rate in that environment will be 5.6 [L / min], and more oxygen than in the prescription instructions. Will be inhaled.

  Further, the volume flow rate of the oxygen-enriched gas varies depending on the environmental temperature. For example, if the setting is 5.0 [L / min], the mass flow controller controls the mass of the flowing gas so as to be 5.0 [L / min] in the standard state (20 [° C.]). If the environment is 5 [° C.], the actual volume flow rate is 5 × 278/293 = 4.74 [L / min]. Conversely, if the environment is 35 [° C.], the actual volume flow rate is 5 × 308/293 = 5.26 [L / min].

  Although these are physically unavoidable, the actual situation is that the flow rate according to the prescription cannot be achieved depending on the use environment.

  As described above, when a patient inhales an oxygen-enriched gas for treatment, a doctor prescribes a flow rate of oxygen gas. Usually, it is prescribed in units of [L (liter) / min], but the flow rate may be reduced by the resistance of the flow path on the user side, and its volume depends on temperature and atmospheric pressure. It is desirable to overcome these variable factors to realize an oxygen inhalation treatment with an accurate flow rate according to a prescription in any use environment and any use form.

  Among the prior arts, Patent Documents 1 and 2 described above merely correct flow rate changes caused by load fluctuations on the oxygen enriched gas user side, and cannot correct volume fluctuations due to environmental factors. In Patent Document 3, the orifice is switched when the altitude of the environment is high. Although the flow rate of oxygen gas to the user increases, the concentration may decrease as the flow rate increases, and it is not possible to realize oxygen inhalation treatment as prescribed. Patent Document 4 aims to suppress a decrease in the concentration of the oxygen-enriched gas. There is no mention of volumetric flow fluctuations due to atmospheric pressure drop due to environmental factors.

The present invention has been made in view of such circumstances, and provides an oxygen concentrator capable of guaranteeing a supply flow rate as prescribed in a prescription while ensuring the oxygen concentration of the oxygen-enriched gas under any circumstances. For the purpose.

In order to achieve the above object, a first oxygen concentrator of the present invention includes a mass flow meter and a flow control valve, and a flow rate control means for controlling the flow rate of the oxygen concentrated gas,
The gist of the invention is that it includes a correction unit that detects the atmospheric pressure of the usage environment by the atmospheric pressure sensor and corrects the set flow rate in the flow rate control unit to a flow rate value based on the volume of gas at the atmospheric pressure of the usage environment.

To achieve the above object, a second oxygen concentrator of the present invention includes a mass flow meter and a flow rate control valve, and a flow rate control means for controlling the flow rate of the oxygen enriched gas,
The gist of the invention is that it includes a correction unit that detects the temperature of the use environment with a temperature sensor and corrects the set flow rate in the flow rate control unit to a flow rate value based on the volume of gas at the temperature of the use environment.

In order to achieve the above object, a third oxygen concentrator of the present invention includes a mass flow meter and a flow control valve, and a flow rate control means for controlling the flow rate of the oxygen concentrated gas,
A pressure sensor and a temperature sensor for detecting the atmospheric pressure and temperature of the usage environment, and a correction means for correcting the set flow rate in the flow control means to a flow rate value based on the gas volume at the atmospheric pressure and temperature of the usage environment. The gist.

  The first oxygen concentrator of the present invention corrects the set flow rate in the flow rate control means to a flow rate value based on the volume of gas at the atmospheric pressure of the use environment. For this reason, the oxygen-enriched gas can be supplied at an accurate flow rate corresponding to the atmospheric pressure of the altitude using the apparatus. Therefore, the oxygen inhalation treatment according to the doctor's prescription can be realized regardless of the altitude of the place of use. In addition, even in an environment with a high altitude, the oxygen concentration does not decrease, and oxygen inhalation therapy can be performed while maintaining the oxygen concentration stably.

In the first oxygen concentrator of the present invention, when the barometric sensor is a capacitance type microchip microsensor barometer,
The barometric sensor can be incorporated into, for example, a control board, can be easily incorporated into equipment, and the apparatus itself is not complicated or enlarged.

In the first oxygen concentrator of the present invention, when the atmospheric pressure sensor is mounted on the operation control board of the oxygen concentrator,
It can be easily incorporated into equipment, and the device itself is not complicated or enlarged.

  The second oxygen concentrator of the present invention corrects the set flow rate in the flow rate control means to a flow rate value based on the volume of gas at the temperature of the usage environment. For this reason, oxygen concentration gas can be supplied with the exact flow volume according to the environmental temperature which uses an apparatus. Therefore, the oxygen inhalation treatment according to the doctor's prescription can be realized regardless of the temperature of the place of use. Further, even in an environment where the temperature is high, the oxygen concentration does not decrease, and an oxygen inhalation treatment can be performed in which the oxygen concentration is stably maintained.

In the second oxygen concentrator of the present invention, when the temperature sensor is mounted on the operation control board of the oxygen concentrator,
It can be easily incorporated into equipment, and the device itself does not become complicated and large.

  The third oxygen concentrator of the present invention corrects the set flow rate in the flow rate control means to a flow rate value based on the gas volume at the atmospheric pressure and temperature of the use environment. For this reason, oxygen concentration gas can be supplied with the exact flow volume according to the atmospheric pressure and temperature of use environment. Accordingly, it is possible to realize oxygen inhalation treatment according to the doctor's prescription regardless of the altitude and temperature of the place of use. In addition, even in an environment where the altitude and temperature are high, the oxygen concentration does not decrease, and oxygen inhalation therapy can be performed while maintaining the oxygen concentration stably.

In the third oxygen concentrator of the present invention, when the atmospheric pressure sensor and the temperature sensor are mounted on the operation control board of the oxygen concentrator,
It can be easily incorporated into equipment, and the device itself does not become complicated and large.

It is a lineblock diagram showing an example of an oxygen concentrator to which the present invention is applied. It is a functional block diagram which shows a control means. It is a figure which shows an example of a microflow sensor.

  Next, the best mode for carrying out the present invention will be described.

  FIG. 1 is a flow sheet of a medical oxygen concentrator according to an embodiment of the present invention. In this example, an oxygen concentrator using a two-cylinder pressure fluctuation adsorption method used in home oxygen therapy is shown.

  This oxygen concentrator functions as a compressor 3 as a compressor for supplying raw material air and an adsorbing section for adsorbing nitrogen in the raw material air supplied from the compressor and concentrating oxygen 2. The suction cylinders 12 and 13 are provided. In addition, electromagnetic valves 8 and 9 for switching the adsorption cylinders 12 and 13 for supplying the raw air from the compressor 3 are provided. Then, the raw material air is fed into the adsorption cylinders 12 and 13 to adsorb nitrogen, and the oxygen-enriched gas enriched with oxygen is supplied to the user using the supply tube and the cannula 26 connected to the oxygen outlet 25. It has become.

  In this oxygen concentrator, the raw material air is removed by a dustproof filter 1 attached to the housing 28 and an intake filter 2 provided at the inlet of the air flow path, and pressurized by the compressor 3 to be adsorbed by the compressor 3. 12 and 13. The compressor 3 generates heat due to motor electric power, adiabatic compression heat of air, or the like, and thus is cooled by blowing air from the blower 4. Foreign matter generated in the compressor 3 is removed by the in-line filter 5.

  The adsorption cylinders 12 and 13 are filled with an adsorbent (zeolite) having a strong affinity with nitrogen. For example, when raw material air is fed into the raw material ports of the adsorption cylinders 12 and 13, Oxygen with low affinity with zeolite comes out first. This is stored in the oxygen buffer tank 19 as an oxygen-enriched gas. This process is referred to as “oxygen concentration process (pressurization process)”.

  Before the nitrogen gas comes out from the product port of the adsorption cylinder 12 at the end of the oxygen concentration process, the source air destination is switched from one adsorption cylinder 12 to the other adsorption cylinder 13. The adsorption cylinders 12 and 13 are provided with electromagnetic valves 8 and 9 corresponding to the adsorption cylinders 12 and 13, respectively.

  When the raw material air is sent to the adsorption cylinder 12, switching control is performed so that the electromagnetic valve 8 corresponding to the adsorption cylinder 12 is “open” and the electromagnetic valve 9 corresponding to the adsorption cylinder 13 is “closed”. When the raw material air is sent to the adsorption cylinder 13, switching control is performed so that the electromagnetic valve 9 corresponding to the adsorption cylinder 13 is “open” and the electromagnetic valve 8 corresponding to the adsorption cylinder 12 is “closed”.

  While the oxygen concentration process (pressurization process) is performed in one adsorption cylinder (in this description, it is 12), the other adsorption cylinder (in this description, 13 and the previous oxygen concentration process (pressurization process)) is completed. In this case, nitrogen is adsorbed on the zeolite. Therefore, the pressure in the adsorption cylinder 13 is released and nitrogen is discharged to the atmosphere. Subsequently, part of the oxygen-enriched gas generated in the adsorption cylinder 12 performing the oxygen concentration process (pressurization process) is introduced from the product port of the adsorption cylinder 13 through the purge valve 14, and the inside of the adsorption cylinder 13 is oxygenated. Replace. This series of steps is called “nitrogen desorption step (purge step)”.

  Opening valves 10 and 11 are provided in the respective adsorption cylinders 12 and 13 so as to correspond to the respective adsorption cylinders 12 and 13 and control the nitrogen desorption process (purge process). That is, while the adsorption cylinder 12 is performing the oxygen concentration process (pressurization process), the release valve 10 is “closed” to maintain the pressurized state in the adsorption cylinder 12. When performing the nitrogen desorption process (purge process) with the adsorption cylinder 12, the release valve 10 is set to "open", and the adsorbed nitrogen is released to the atmosphere. Similarly, while the adsorption cylinder 13 is performing the oxygen concentration process (pressurization process), the open valve 11 is “closed” to maintain the pressurized state in the adsorption cylinder 13. When performing the nitrogen desorption process (purge process) with the adsorption cylinder 13, the open valve 11 is opened, and the adsorbed nitrogen is released to the atmosphere. Noise when the adsorption cylinders 12 and 13 are opened to the atmosphere is silenced by the silencer 27 provided at the exhaust outlet.

  The oxygen-enriched gas used in the purge process is taken from the product port of one adsorption cylinder 12 (or 13) performing the oxygen enrichment process (pressurization process) and the other adsorption performing the nitrogen desorption process (purge process). It is supplied to the product port of the cylinder 13 (or 12) through the purge line. The purge line is provided with a direct-acting purge valve 14 and orifices 15 and 16. The purge valve 14 is installed to accurately control the purge time, and the orifices 15 and 16 are installed to control the flow rate of the oxygen-enriched gas passing therethrough.

  The produced oxygen-enriched gas is stored in the oxygen buffer tank 19, the supply pressure is adjusted by the pressure reducing valve 20, the flow rate is controlled by the mass flow controller 22, and the oxygen concentration meter 23 measures the oxygen concentration. A bacteria filter 21 is provided to protect the mass flow controller 22 and the oxygen concentration meter 23 from foreign substances.

  In addition, noise-generating devices and parts are housed in a metal soundproof box. It is the compressor 3 and the exhaust opening that generate particularly loud noise. The operation sound of the blower 4 and the intake sound to the compressor 3 are then loud. Since the blower 4 cools the outside air against the compressor 3, it cannot coexist with the compressor 3. The intake filter 2 cannot coexist with the exhaust opening portion with less oxygen. Accordingly, the soundproof box is divided into two rooms, the compressor 3 and the exhaust opening are accommodated in the first soundproof box 29, and the blower 4 and the intake filter 2 are accommodated in the second soundproof box 30. In this example, the electromagnetic valves 8 and 9 are accommodated in the second soundproof box 30 from the relationship between temperature and space. The entire device is housed in a housing 28 constructed from wood and plastic.

  Since the produced oxygen-enriched gas is in an absolutely dry state, the humidifier 24 provides humidity and the cannula 26 is used. In this example, the humidifier 24 is a bubbling humidifier 24, and the oxygen enriched gas whose oxygen concentration is measured by the oxygen concentration meter 23 is ejected from the porous member into a container filled with purified water. To humidify.

  The mass flow controller 22 includes a mass flow meter and a flow rate control valve, and functions as a flow rate control means of the present invention that controls the flow rate of the oxygen-enriched gas. The target flow rate in the mass flow controller 22 is corrected by the control means 31.

  FIG. 2 is a functional block diagram showing the control means 31.

  The control means 31 includes a CPU 32 that controls the mass flow controller 22 based on a set flow rate in a flow rate setting device 34 (not shown in FIG. 1). The flow rate setter 34 inputs the flow rate indicated by the prescription as the set flow rate value.

  The control means 31 includes an atmospheric pressure sensor 37 and a temperature sensor 38. The atmospheric pressure sensor 37 detects the atmospheric pressure of the usage environment, and the temperature sensor 38 detects the temperature of the usage environment. The CPU 32 corrects the target flow rate value in the mass flow controller 22 to a flow rate value based on the gas volume at the atmospheric pressure and temperature of the use environment, and functions as the correction means of the present invention.

  In this description, the apparatus is provided with both the atmospheric pressure sensor and the temperature sensor, and the flow rate value is corrected based on both the atmospheric pressure and the temperature of the usage environment. However, only the atmospheric pressure of the usage environment is provided with only the atmospheric pressure sensor. The flow rate value may be corrected based on the above, or only the temperature sensor may be provided and the flow rate value may be corrected based only on the temperature of the use environment.

The first pressure gauge 35 measures the discharge pressure of the compressor 3, and the CPU 32 uses an alarm means (not shown) when the discharge pressure of the compressor 3 detected by the first pressure gauge 35 exceeds a preset pressure threshold. Alarm of abnormal pressure.
The second pressure gauge 36 measures the pressure of the humidifier upstream 39, and the CPU 32 gives alarm means (not shown) when the pressure of the humidifier upstream 39 detected by the second pressure gauge 36 is out of the preset pressure range. Thus, an abnormality such as leakage / detachment of the humidifier 24 or bending of the cannula 26 is warned.
The CPU 32 refers to the timer 33 and turns on / off the electromagnetic valves 8 and 9 according to a predetermined time cycle.
The timer 33 is referred to when the CPU 32 calculates the average value of the concentration, flow rate, pressure, etc. of the oxygen-enriched gas over a certain period of time. Furthermore, the timer 33 is also referred to when the CPU 32 accumulates the operation time of the apparatus, and is referred to in various scenes of operation control.
In addition, when the oxygen concentration detected by the oxygen concentration meter 23 falls below a specified value for a certain time, the CPU 32 warns the abnormality by an alarm means (not shown).

  Hereinafter, the operation of the CPU 32 as the correction unit will be described in detail.

  The mass flow controller 22 controls the flow rate by measuring the mass of the flowing gas in principle, and normally expresses the volume flow rate in terms of 20 [° C.] and 1013 [hPa]. For example, when 5.0 [L / min] is set, the mass flow controller flows oxygen gas corresponding to 5.0 [L / min] at 20 [° C.] and 1013 [hPa]. If [hPa], the actual volumetric flow rate in the environment is 5.0 × 900/1013 = 5.63 [L / min]. If the volumetric flow rate is to be accurately set to 5.0 [L / min] in an environment of 900 [hPa], the set flow rate of the mass flow controller is set to 5.0 × 900/1013 = 4.44 [L / min]. That's fine.

  The barometric sensor 37 is not particularly limited as long as it can extract an electrical signal, and various types can be applied. For example, a capacitance type microchip sensor (Akizuki Dentsu Co., Ltd., MPL115A1, MPL115A2) that can be incorporated into the control board can be suitably used. Moreover, what integrated the atmospheric | air pressure sensor and the temperature sensor (Akizuki electronic trading company, SPC1000-D01) can be used suitably.

  A microsensor barometer is a chip type manufactured by applying integrated circuit technology. It has extremely high processing accuracy, is excellent in accuracy and stability, and can be easily incorporated into equipment. Therefore, it can be suitably applied to the present invention. Among them, a capacitance type micro sensor is a chamber made of silicon or the like that forms a capacitor. A change in the distance between electrodes due to atmospheric pressure is detected as a change in capacitance and output as a digital signal. Therefore, it can be suitably applied to the present invention.

  The flow rate of oxygen gas can be controlled by a combination of a mass flow meter and a proportional solenoid valve, but can also be suitably controlled by a mass flow controller 22 in which both are integrated. Here, a case where the mass flow controller 22 is applied will be described.

  The measurement principle of the mass flow controller 22 is as follows.

  FIG. 3 is a conceptual diagram of a microflow sensor incorporated in the mass flow controller 22.

  In the microflow sensor, a heater (Rh), an upstream temperature sensor (Ru), a downstream temperature sensor, and an ambient temperature sensor (Rr) are formed of a platinum thin film on the surface of a silicon chip base.

  The resistance value of the platinum thin film changes depending on the temperature and functions as a resistance temperature detector. The heater (Rh) is located at the center of the base. The upstream side temperature sensor (Ru) and downstream side temperature sensor (Rd) of the gas flow are located on both sides of the heater. The ambient temperature sensor (Rr) is located at the periphery of the base. Has been placed.

  When there is no gas flow, the temperature distribution on both sides of the heater (Rh) is symmetric as shown by the dotted line in FIG. 3, and the temperatures of the upstream temperature sensor (Ru) and the downstream temperature sensor (Rd) are equal.

  When a gas flow occurs here, the temperature of the upstream temperature sensor (Ru) decreases and the temperature of the downstream temperature sensor (Rd) increases as shown by the solid line in FIG. By detecting this temperature difference (resistance difference) with a bridge circuit, an electrical output corresponding to the flow can be obtained. Thus, since the microflow sensor uses the measurement principle using heat, the output is related to the thermal conductivity of the gas, and the mass flow rate can be measured.

  When controlling the gas flow rate, the opening of the proportional solenoid valve is adjusted so that the measured mass flow rate matches the set flow rate. In this way, the mass flow controller 22 can supply a much more accurate flow rate than the orifice type flow rate control.

  Since the mass flow sensor measures the mass of oxygen gas, it must be expressed in terms of volume. Normally, it is displayed in terms of the standard state of gas, but the actual situation is that various standard states are defined by the technical field.

  For example, in conventional school education, the standard state of gas is 0 [° C.] (273.15 [K]) and 1 atm (101.325 [kPa]), which is referred to as a normal condition. It was. In addition, the standard of 25 [° C.] and 100.000 [kPa] called SATP (standard ambient temperature and pressure) is sometimes used.

  In this application, 20 [° C.] (293.15 [K]) and 1 [atmospheric pressure] (101.325 [kPa]) closest to the human living environment will be described as a standard state.

  Here, generally, the mass flow controller 22 mounted on the oxygen concentrator performs calibration using oxygen gas in a standard state in advance, and when the oxygen gas flow rate 5.0 [L / min] is selected, The flow rate is controlled to be 5.0 [L / min] under the conditions of 20 [° C.] and 1 [atmospheric pressure]. The mass flow controller 22 is designed so that it can be converted into the volume of another standard state, so that it is set to output a volume flow rate at 0 [° C.] and 1 [atmospheric pressure] as necessary. It is also possible.

  If the oxygen concentrator is used in the same environment as the standard condition, that is, 20 [° C.], 1 [atm], the oxygen-concentrated gas at the flow rate as prescribed can be accurately flowed, and inhalation treatment according to the prescription It can be performed. However, when used in an environment away from this standard state, the flow rate of the oxygen-enriched gas deviates from the prescription.

  For example, consider how the oxygen concentrator works in Karuizawa, Denver in the US, Kunming in China, and the Dead Sea in Jordan. When the mass flow controller 22 flows oxygen gas in a standard state at 5.0 [L / min], in Karuizawa at an altitude of 1000 [m] and an atmospheric pressure of 900 [hPa], the gas expands by the lower atmospheric pressure, so the flow rate is 5 .63 [L / min]. In Denver at an altitude of 1600 [m] and an atmospheric pressure of 835 [hPa], 6.07 [L / min] flows, and in Kunming at an altitude of 1900 [m] and an atmospheric pressure of 805 [hPa], 6.29 [L / min] flows. On the other hand, the flow rate is 4.78 [L / min] in the dead sea at sea level minus 400 [m] and atmospheric pressure 1060 [hPa].

  As described above, the actual flow rate varies depending on the environment in which the apparatus is used. Therefore, in order to provide a correct flow rate in any altitude environment, the following may be performed.

  First, the oxygen concentrator is equipped with a pressure sensor 37 and more preferably a temperature sensor 38.

  When the oxygen flow rate of 5.0 [L / min] is selected according to the prescription in the flow rate setting device 34 and used in Karuizawa at an altitude of 1000 [m], the barometric pressure measured by the barometer, here 900 [hPa] ] Is used to correct the set flow rate, and 5.0 [L / min] × 900/1013 = 4.44 [L / min] is instructed to the mass flow meter. The mass flow meter accurately flows 4.44 [L / min] oxygen under standard conditions. Of course, this is 4.44 [L / min] × 1013/900 = 5.00 [L] in an environment of atmospheric pressure 900 [hPa].

  Similarly, the flow rate of oxygen gas varies depending on the temperature of the environment.

If the ambient temperature is 35 [° C.], the flow rate is 5.0 [L / min] × 308/293 = 5.26 [L / min] in the standard state, 20 [° C.] and 5.0 [L / min]. Min].
In order to correct the case where the environmental temperature is 35 ° C., the indication value to the mass flow meter may be set to 5.0 [L / min] × 293/308 = 4.765 [L / min].

If the procedure described above is generalized including correction of atmospheric pressure and air temperature, an instruction value to the mass flow controller 22 is expressed by the following equation.
Indicated value = V × Pa × Ts / (Ps × Ta) [L / min]
V: oxygen flow rate setting value [L / min]
Ps: Standard atmospheric pressure [hPa] = 1013.25 [hPa]
Ts: Standard temperature [K] = 293.15 [K]
Pa: atmospheric pressure [hPa]
Ta: Environmental temperature [K]

  In the above description, the control mechanism of the mass flow controller 22 is taken as an example and a method for supplying an accurate oxygen flow rate has been described. However, the present invention can be similarly applied to a combination of a mass flow meter and a proportional solenoid valve.

  In addition to controlling the flow rate of oxygen gas produced by a pressure fluctuation adsorption type oxygen concentrator, if a mass flow meter is used for flow rate control even when oxygen gas is supplied from a cylinder or liquid oxygen container, The present invention is equally applicable.

  As described above, according to the present embodiment, the set flow rate in the mass flow controller 22 is corrected to a flow rate value based on the gas volume at the atmospheric pressure and temperature of the use environment. Thereby, oxygen concentration gas can be supplied with the exact flow volume according to the atmospheric pressure and temperature of use environment. Accordingly, it is possible to realize oxygen inhalation treatment according to the doctor's prescription regardless of the altitude and temperature of the place of use. In addition, even in an environment where the altitude and temperature are high, the oxygen concentration does not decrease, and oxygen inhalation therapy can be performed while maintaining the oxygen concentration stably.

  Further, when the atmospheric pressure sensor 37 and the temperature sensor 38 are mounted on the operation control board of the oxygen concentrator, it is easily incorporated into the device, and the apparatus itself is not complicated or enlarged. .

Further, when the atmospheric pressure sensor 37 is a capacitance type microchip type microsensor barometer, the atmospheric pressure sensor 37 can be incorporated into a substrate, for example, and can be easily incorporated into equipment, and the apparatus itself is complicated and large. It does not become.

DESCRIPTION OF SYMBOLS 1 Dust-proof filter 2 Intake filter 3 Compressor 4 Blower 5 In-line filter 8 Solenoid valve 9 Solenoid valve 10 Release valve 11 Release valve 12 Adsorption cylinder 13 Adsorption cylinder 14 Purge valve 15 Orifice 16 Orifice 19 Oxygen buffer tank 20 Pressure reducing valve 21 Bacteria filter 22 Mass flow Controller 23 Oxygen concentration meter 24 Humidifier 25 Oxygen outlet 26 Cannula 27 Silencer 28 Case 29 First soundproof box 30 Second soundproof box 31 Control means 32 CPU
33 Timer 34 Flow rate setting device 35 First pressure gauge 36 Second pressure gauge 37 Air pressure sensor 38 Temperature sensor 39 Humidifier upstream

Claims (7)

A flow rate control means for controlling the flow rate of the oxygen-enriched gas, including a mass flow meter and a flow rate control valve;
An oxygen concentrator comprising: correction means for detecting the atmospheric pressure of a use environment by an atmospheric pressure sensor and correcting a set flow rate in the flow control means to a flow rate value based on a gas volume in the atmospheric pressure of the use environment.   The oxygen concentrator according to claim 1, wherein the barometric sensor is a capacitance type microchip microsensor barometer.   The oxygen concentrator according to claim 1 or 2, wherein the atmospheric pressure sensor is mounted on an operation control board of the oxygen concentrator. A flow rate control means for controlling the flow rate of the oxygen-enriched gas, including a mass flow meter and a flow rate control valve;
An oxygen concentrator comprising: a correction unit that detects a temperature of a use environment by a temperature sensor and corrects a set flow rate in the flow control unit to a flow rate value based on a gas volume at the temperature of the use environment.   The oxygen concentrator according to claim 4, wherein the temperature sensor is mounted on an operation control board of the oxygen concentrator. A flow rate control means for controlling the flow rate of the oxygen-enriched gas, including a mass flow meter and a flow rate control valve;
A pressure sensor and a temperature sensor for detecting the atmospheric pressure and temperature of the usage environment, and a correction means for correcting the set flow rate in the flow control means to a flow rate value based on the gas volume at the atmospheric pressure and temperature of the usage environment. A featured oxygen concentrator.   The oxygen concentrator according to claim 6, wherein the atmospheric pressure sensor and the temperature sensor are mounted on an operation control board of the oxygen concentrator.

Images