JPH09311119A - Oxygen concentration detector for psa type gas concentrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen concentration detector which can be used even for a medical oxygen concentrator at home, and which is small and inexpensive, requiring little sample gas, and long in life. SOLUTION: A small room 6 that is also called as a chamber for housing a new zirconia type oxygen concentration sensor is provided with an inflow port 7 and an outflow port 8, and the diameter of small holes 11, 12 is properly selected and the position of the inflow port 7 is selected in such a way that the gas to be measured is not directly blown against the sensor, so that the detector is constituted in such a way that the accurate measurement of oxygen concentration can be enabled even in a small quantity of sample gas, and that it can be used even as a medical oxygen densitometer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentration detector for a PSA type (pressure fluctuation adsorption type) gas concentrator and a PSA type gas concentrator equipped with the oxygen concentration detector.

[0002]

2. Description of the Related Art The main gas component of air is approximately nitrogen 78.
%, Oxygen 20.8%, and argon 0.9%. We use oxygen gas, nitrogen gas, and argon gas after concentrating them by the technique of separating these gases from the air.
Among them, oxygen gas and nitrogen gas are used in large amounts, and many of them are used. The concentration of the concentrated oxygen gas or nitrogen gas is important, and a concentration detector is used to measure the concentration. Various types of oxygen concentration detectors have been commercialized, but there is no nitrogen gas concentration detector, and nitrogen gas is often used industrially as inert gas. It is common to detect the residual oxygen gas concentration contained therein and subtract it from 100% to obtain the nitrogen gas concentration.

As for the technique of gas concentration, membrane type or PSA type devices which are operated at room temperature have come into widespread use. Among them, health insurance has been applied to home oxygen therapy since March 1985, and a small medical device that concentrates oxygen gas in the air and blows it to a patient for inhalation just by turning on the electricity. Gas concentrators have become widely used. This gas concentrator has a method of concentrating with an oxygen permeable membrane and PSA (Pressure Swing Adsorpt) using an adsorbent.
ion) method, in which the former is concentrated as a gas containing water at an oxygen concentration of about 40% and the latter is obtained as a very dry concentrated gas at about 90%. At present, the concentration device by the PSA method is more often used.

Since these gas concentrators used for medical purposes supply concentrated oxygen gas as a medicine to a patient, the concentration thereof is very important. On the other hand, since the oxygen concentrator is a device composed of various parts, the failure cannot be eliminated. When the adsorbent is deteriorated or some of the parts are broken down, there is a failure that concentrated oxygen gas cannot be obtained even if the appearance is completely normal.

Therefore, it is necessary to monitor the concentration of concentrated oxygen gas so that the patient can be notified and requested for repair or the like when the concentration is reduced. Taking a PSA gas concentrator for medical use that is commonly used as an example, this is explained. Under pressure, more nitrogen gas is adsorbed than oxygen gas, and when the pressure is lowered, the adsorbed nitrogen gas is released (desorption). The adsorbent (in many cases, zeolite) having the property to fill is packed in a pressure vessel called an adsorption cylinder, two of these are prepared, and the air is sucked in by the air compressor, compressed, and switched by the valve means to switch to the adsorption cylinder. When the compressed air is sent to, the oxygen gas that is adsorbed by the adsorbent in the adsorption column and is concentrated is taken out from the other end and stored in the storage tank.

Before the adsorbent in the adsorption column is filled with the adsorbed nitrogen gas, the compressed air is switched to another adsorption column, and the adsorption column on this side concentrates the same as before. During that time, the adsorption cylinder that has adsorbed nitrogen is depressurized to the atmospheric pressure by the switching valve. Then, the nitrogen gas adsorbed on the adsorbent in the adsorption column is desorbed and released into the atmosphere. At this time, a loud sound is emitted, so a silencer is attached to eliminate the sound. Since the pressure of the concentrated oxygen gas stored in the storage tank fluctuates due to the switching, the pressure is made constant through the pressure reducing valve, and then the patient inhales the oxygen gas in accordance with the oxygen flow rate prescribed by the doctor by the flow setting device.

However, when the adsorbent removes nitrogen gas by adsorption, water (water vapor) contained in the air is also removed, so that it is concentrated as very dry oxygen gas, so that the nasal cavity and bronchi become dry during inhalation. Therefore, since the oxygen gas is humidified by the humidifier, it is inhaled after being humidified by, for example, a humidifier for passing water through bubbles. The concentrated oxygen gas taken out from the oxygen concentrator is often guided to the patient's bed or the patient's place by a hose and inhaled by the inhaler, that is, the cannula, and the length of the hose changes depending on the living condition of the patient. There are cases where the length is from 2 m to 18 m or more. The inhaled oxygen amount prescribed by the doctor by the patient is less than 5 L / min in most cases, and particularly 2 L / min or less in most cases. Therefore, the oxygen concentrator has a small capacity of 5 L / min or 2 L / min. This is because a device with a large capacity has a large size and requires a large amount of electricity, so that the device is made as small as possible.

Therefore, the amount of sample gas consumed for detection by the oxygen concentration detector is preferably as small as about 50 mL / min, and at most 200 mL / min is the upper limit. That is, if the patient is prescribed an inhalation rate of 2 L / min by the doctor with a device having an oxygen concentrator capacity of 2 L / min,
If the total of 0.2 L / min of the sample gas flows to the concentrator at 2.2 L / min, the oxygen concentration was 90% at 2 L / min, but it decreased to 85% to 75% at 2.2 L / min. Sometimes. Therefore, it is preferable that the sample gas is small.

A gas concentrator for concentrating oxygen (hereinafter,
Since an oxygen concentrator (also referred to as an oxygen concentrator) is small and inexpensive, the oxygen concentration detector for detecting the oxygen concentration is necessarily required to be small and inexpensive. On the other hand, since the patient has continuously used this oxygen concentrating device for 24 hours continuously, high reliability is required for the device. Even if the device is normal, it is not necessary for the oxygen concentration detector to fail or give an alarm by mistake, so that the oxygen concentration detector is also required to have high reliability. And the maintenance service of such medical equipment is supposed to be handled by a professional engineer, and the number of visits to the patient's home is 5 according to the guidance of the Ministry of Health and Welfare.
000 hours or 6 months, whichever comes first. For this reason, the oxygen concentrator is designed to operate stably without maintenance during that time. However, if it is necessary to replace the sensor unit or perform the concentration calibration work in a short period of time to detect the oxygen concentration, both the patient and the trader will be in trouble.

On the other hand, four types of oxygen concentration detectors are known as shown in the following table. (Reference: Magazine "Instrumentation" 1987. Vol. 30, No. 9, P48)

[Table 1]

The magnetic sensor system described in this table is
Although the sensor has a long life and does not require calibration for a long period of time, it is not suitable for the technical field of the present invention because of its large size and complicated mechanism. The galvanic battery type is small and lightweight, but must be calibrated at the time of use, and the sensor part is a consumable item and must be replaced in a relatively short time. The light and shade type zirconia method flows a reference gas (or air) and a gas to be measured on both sides of a high-temperature zirconia wall, and measures a voltage (current) generated therebetween, so that the structure is large and the power consumption is large. Not suitable as well.

In the limiting current method, a gas-permeable platinum electrode (cathode) is laminated on one surface of a porous alumina substrate, then a zirconia solid electrolyte, and then a platinum electrode (anode) is laminated again by using a high frequency sputtering device. A platinum heater for heating is formed on the other surface of the alumina substrate, and the oxygen concentration can be measured by pulling out the leads from each electrode and placing it as a detection chip in the gas to be measured, so it can be the smallest and cheapest. It turned out that there is a nature.

The heater is energized to a high temperature (400-700
° C), and when a voltage is applied to the cathode and the anode, a constant current flows irrespective of the applied voltage depending on the oxygen concentration, and the value utilizes a characteristic proportional to the oxygen concentration.

That is, as shown in FIG. 1 (C), when a current is applied to the zirconia (ZrO ₂ ) solid electrolyte,

[Number 1] _{^{O 2 + 4e - → 2O 2-}} ···· [Formula 1]

Injection of oxygen into the electrolyte is caused by the electrochemical reaction of. On the other hand, at the anode

[Number 2] _{^{2O 2- → O 2 + 4e -}} ···· [Equation 2]

The reaction of causes the release of oxygen. This is called the oxygen pumping action of the solid electrolyte. Therefore, if oxygen passes through the porous alumina layer that restricts oxygen transport in the process of being transported from the atmosphere to the place where the reaction of Formula 1 occurs, the current value remains constant even when the voltage applied to the electrolyte is increased. A maintained saturation current characteristic appears. This saturation current is called a limit current, and its magnitude is proportional to the oxygen concentration in the atmosphere. The oxygen concentration in the atmosphere is detected from the current obtained by applying a constant voltage (voltage in the region where the limiting current is obtained) to this electrolyte.

The oxygen concentration detection chip formed on the porous alumina substrate can be formed in a square of several millimeters. Since the size of the sensor is reduced, the temperature of the oxygen concentration detection chip, which is kept at a constant temperature by the heater, changes when the gas to be measured is directly contacted with it. However, since the sensor is small, it has been known that if the gas to be measured is directly blown to the wire mesh portion of the oxygen concentration detecting portion, the temperature of the tip portion is affected and an error occurs. The tip portion of this sensor is referred to as an oxygen concentration detecting portion when the lead lead-out pin and the portion of the wire netting are attached. This oxygen concentration detector is placed in the atmosphere to be measured, a voltage is applied between the electrodes, and the oxygen concentration is detected by the value of the current flowing in this circuit.

[0018]

Normally, an oxygen concentration detector has its own pressure setting device such as a pressure reducing valve, a throttle valve, and a flow meter in order to keep the pressure introduced into the detector constant and the flow rate constant. Since the structure is provided, the structure is complicated and the device is large-scale. This provides a small-sized oxygen concentration detector for a PSA gas concentrator with a small amount of sample gas and a long life.

[0019]

The present invention is configured as follows to solve the above problems. A transparent platinum electrode (cathode) is formed on one surface of a porous alumina substrate, and a zirconia solid electrolyte and a platinum electrode (anode) are laminated again, and a platinum heater for heating is formed on the other surface of the alumina substrate. Lead wire is drawn out from each electrode of the chip part formed with, and the chip part is wrapped with a wire mesh guard (cover), and this is used as an oxygen concentration detector. It is a small chamber with an inlet and an outlet, and the inflow amount of the measured gas is determined by the pores provided at the inlet, and the direction of the inflow is such that it does not blow directly to the oxygen concentration detection unit. Is open to the atmosphere and the flow velocity of the gas flowing out of the pores provided at the outflow port causes the atmospheric gas to flow back toward the small chamber due to the gas diffusion action at the operating temperature, which substantially affects the internal gas concentration. No outflow rate Constituting the oxygen concentration detector of PSA type gas concentration apparatus constituted by chamber having a cheat pore size.

Further, in order to facilitate the manufacture of the small chamber containing the oxygen concentration detecting portion and to easily obtain the dimensional accuracy of the necessary portion, the small chamber is divided into three blocks. That is, a small chamber block having an oxygen concentration detector inside,
The small chamber block is composed of an inlet / outlet block having an inlet for introducing the gas to be measured and an outlet for letting out the gas to be measured, and there is a thin plate hermetically sandwiched between these two blocks. The small chambers of the inlet and outlet of the block have pores that determine the passage resistance of the inlet and outlet, and the position of the inlet is such that the measured gas flowing from the inlet has an oxygen concentration. An oxygen concentration detector of a PSA type gas concentrator having a small chamber at a position where it is not blown directly to a detector is constructed.

The pore size of the inflow port is 0.0 in order to keep the inflowing gas amount per minute to 200 mL / min or less.
It is preferably in the range of 5 to 0.5 mm, the volume of the small chamber is preferably 100 mL (100 cc) or less, and more preferably about 10 cc in terms of response time.

The oxygen concentration detector has a structure in which the oxygen gas as the gas to be measured is continuously released into the atmosphere, and the gas may accumulate in the apparatus. Further, it has been known that an error in the measured concentration occurs when the pressure of the gas to be measured in which the oxygen concentration detector is placed fluctuates. Therefore, the pore size of the inlet that flows into the small chamber is small,
The pore size of the outlet is made large to be almost the same as the atmospheric pressure, and the outflow rate is set to have a flow rate higher than the backflow rate due to the gas diffusion action, but if the pressure of the supply gas applied to the inlet changes, the amount of inflow gas will change. The temperature of the chip changes and the temperature of the chip is kept constant by affecting the amount of heat radiated at the temperature, which causes an error due to temperature fluctuations. is there. Further, the oxygen concentration detector based on the limiting current method causes an error because the moisture contained in the gas to be measured is decomposed by the high temperature on the sensor surface and oxygen molecules increase.

On the other hand, it has been found that the PSA type medical oxygen concentrator using the same has the following problems. That is,
The concentrated oxygen gas obtained by the pressure fluctuation basically has a pressure fluctuation, and the gas is dry, but a step of humidifying the gas by the time the patient inhales is involved. Further, the oxygen concentrator has a space for housing electric parts and electric circuits for control, and there is a possibility of fire if an atmospheric environment with a high oxygen concentration in the space occurs. Here, in order to avoid these dangers and to make a safe and simple structure, by combining the mutual characteristics of these oxygen concentrators and oxygen concentration detectors, it is possible to obtain a more preferable structure by the following means without increasing the number of parts. To build. That is, a gas concentrator basically composed of an air compressor, valve means for switching the flow of compressed air, piping means, at least one adsorption cylinder filled with an adsorbent, a product tank for storing concentrated gas, and the like. A pressure reducing valve is attached downstream of the product tank, and the flow rate setter for setting the flow rate of the concentrated gas is attached after the pressure of the concentrated gas is made substantially constant, and , A fan for accommodating these components in a housing and cooling an air compressor or the like that generates heat, an air inlet, an air outlet, etc. provided in the housing, and further provided in the housing In the PSA gas concentrator having a cooling air passage connecting the air intake port and the air exhaust port, the concentrated gas is provided at a position downstream of the pressure reducing valve and upstream of the flow rate setting device. Oxygen concentration detection The oxygen concentration detector is characterized in that the concentrated gas is supplied to a small chamber having therein, and the measured gas flowing out from the small chamber is diffused into the passage of the cooling air. The PSA gas concentrator described above is configured.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows a sectional view of a small chamber according to a preferred embodiment. FIG. 1B shows another embodiment of the small chamber. Corresponding departments in both figures are given the same reference numerals. FIG.
The small chamber block 1 of (A) is a small chamber into which the gas to be measured is introduced, and has an oxygen concentration detection unit 13 inside. This is because the tip portion 14 for detecting the oxygen concentration is supported by the lead pins 3 and 3'which also function as posts supporting the tip portion 14 while penetrating the stem 2 while maintaining airtightness. The tip portion is covered with a wire mesh cover 5. The lead pins 3 and 3 ′ extending from the stem 2 are bonded and connected to the elements formed on the front and back surfaces of the alumina substrate. That is, two lead pins for energizing the platinum heater for heating configured on the back surface of the chip part and two for applying voltage to the platinum electrodes of the gas permeable anode and cathode on both surfaces of the zirconia solid electrolyte There are lead pins 3, 3 '. The oxygen concentration detecting portion 13 having such a structure is fixed to the small chamber block 1 by the fixing tool 15 so as to be airtight to the outside by the O-ring 4 for sealing. The internal volume of the small chamber in this case is about 9 mL (9 cc).

This small chamber block 1 and an inlet / outlet block 9 constituting an inlet / outlet of the gas to be measured into / from this small chamber are fixed by sandwiching a thin plate 10, and the small chamber block 1 of the inflow hole 7 of the inlet / outlet block 9 is fixed to the thin plate 10. There is a pore at a position corresponding to, and the pressure of the measurement gas introduced here is consumed to determine the flow rate of the inflow gas. In the case of the present embodiment, the pressure of the gas to be measured is introduced at 0.03 MPa and the flow rate is 50 mL / min (50 cc / min). The diameter of the pores is about 0.07
mm.

Similarly, there is a pore 11 at a position corresponding to the small chamber block 1 of the outflow hole 8, and the atmospheric velocity of the outside flows back into the small chamber due to the diffusing action of the gas flow rate to substantially affect the concentration of the gas to be measured. The pore size has an outflow rate that does not give

FIG. 1B shows another embodiment of the small chamber. In FIGS. 1 (A) and 1 (B), it is the pores that require high dimensional accuracy in fabrication, and because the pore diameters are small, the pores have a very small diameter in the wall of the small chamber. Since it is very expensive to punch it with a hole or the like, it is easy to manufacture the other parts by making two pores by combining the pores into one thin plate, and it is also easy and cheap to manufacture the pores. I did it. The inlet hole is provided at a position where the gas to be measured does not directly blow on the tip portion 14 and the wire netting cover 5 covering the tip portion 14 to stabilize the temperature of the tip portion 14 at a high temperature (about 700 ° C.).

In order to stabilize the temperature of the chip part, the platinum heater on the back surface of the chip part is also used as a temperature detecting sensor.
This heater and a circuit supplying current to this heater form a bridge to detect changes in the electric resistance of the heater due to temperature changes, amplify this with an amplifier and control the heater current to stabilize the temperature. I am trying. In addition, a constant DC voltage of about 0.8 to 2.5 V is applied between the anode and cathode on both sides of the zirconia solid electrolyte, and the limiting current flowing depending on the oxygen gas concentration is detected to detect the gas concentration. There is a circuit to detect. This is included in the control unit 35 shown in FIG. 2 as a part for controlling another PSA type gas concentrator.

FIG. 2 shows a flow sheet of the present invention applied to an oxygen gas concentrating device for medical use. The air compressor 21 removes dust in the air from the atmosphere by the air compressor 21 to the two adsorption columns 25 and 26 which are pressure vessels filled with an adsorbent that adsorbs more nitrogen gas than oxygen gas, for example, zeolite. Cooling coil 2 receives heat generated by adiabatic compression of air taken in and compressed.
After the temperature is lowered at 3 and dust is removed by the filter 24, compressed air is sent to either the adsorption cylinder 25 or 26 by the valve means 27 (in the case of the present invention, a five-way solenoid valve). Nitrogen gas is adsorbed and removed by the adsorbent, and concentrated oxygen gas is obtained from the other end and stored in the product tank 29 through the pipes 22 and 22 '. After a certain period of time before the nitrogen gas adsorbed by the adsorbent in the adsorption cylinder becomes full, the valve means 27 is switched to switch the blowing of compressed air to the other adsorption cylinder, and this adsorption cylinder is used to Similarly, oxygen gas is concentrated. At this time, the adsorption cylinder used previously is opened to the atmosphere by the valve means 27. At this time, the adsorbed nitrogen gas is discharged by detaching the nitrogen gas by reducing the pressure to atmospheric pressure. A silencer 28 is attached because a loud noise is heard at that time. The pressure of the product gas (concentrated oxygen gas) stored in the product tank 29 changes every time the adsorption cylinder is switched. This pressure fluctuation is caused by the flow rate setting device 32.
Therefore, when the flow rate is set to a value prescribed by a doctor or the like, the flow rate fluctuates, so that the pressure reducing valve 31 reduces the pressure to a constant pressure to a stable value.

A gas concentrator by the PSA method for concentrating the gas in the air while varying the pressure using this adsorbent adsorbs and removes the moisture in the air as well as the nitrogen gas, so that the product gas to be concentrated is It will be very dry, so if you inhale it as it is, your trachea and thirst will be sore.
The patient inhales after humidification by.

The oxygen concentration detector 34 has a characteristic that the limiting current value changes when there is water in the gas to be measured, but in the case of the PSA gas concentrator, since the concentrated gas does not contain water, it is located upstream of the humidifier. If the gas to be measured is taken in, no error will occur due to this. It should be noted that if the pressure in the small chamber in which the oxygen concentration detecting unit fluctuates, an error will occur in the concentration, so that it is downstream of the pressure reducing valve 31 where the pressure is stable, and the pressure set to a constant pressure by the flow rate setting unit 32 is consumed. A stable pressure can be supplied to the oxygen concentration detector 34 by branching out in a range upstream of the flow rate setting device.

Incidentally, the pressure becomes low downstream of the flow rate setting device 32, and the length of the pipe connected to the oxygen gas outlet 38 may change within the range of 2 m to 18 m depending on the patient's convenience, so that pressure fluctuation occurs. Further, since the humidifier 33 further contains water in the gas to be measured, an error will occur in the measured value. For this reason, this configuration is the best method utilizing the mutual characteristics of the product in which the PSA gas concentrator and the oxygen concentration detector are combined.

The electric signal of the oxygen concentration detected by the oxygen concentration detector 34 is detected by the circuit in the control unit 35 through the signal line 36, and the result is displayed on the display 39.
The display of the result may display the concentration by a percentage value, or may display it by a lamp. For example, 85% or more is green, 85-75% is yellow, 7
There is an example in which 5% or less is red. When the numerical value is displayed, the concentration is easy to understand, but there are cases where the patient becomes too nervous about the change in the concentration, which is not good. Therefore, the display method is selected according to the purpose. In addition, when it becomes a certain value or less as necessary, for example, 75% or less, a red lamp may be displayed and the control unit may stop the operation of the apparatus.

The control section includes an electric circuit for controlling the entire PSA device, and details of signals to each section are omitted.
When the gas concentrator concentrates oxygen gas, the oxygen concentration detector continuously releases the sample gas containing high concentration of oxygen. A high concentration oxygen atmosphere will be created locally. It is extremely dangerous that the place including the electric circuit of the device is placed in such an environment that a fire or an explosion may occur. Since this device includes electronic circuits and parts having a heat generating part such as an electric motor and an air compressor, an air intake window is provided in the housing by an air cooling fan 37 to take in external air, and heat is exchanged from the exhaust window. The structure in which the warm air is discharged, and the structure in which the sample gas of the oxygen concentration detector 34 is discharged onto the ventilation passage of the cooling air is such that there is no local high point of the oxygen gas concentration that is discharged to the outside. Is.

The above is an example of an oxygen concentrator for medical use. The activated carbon MSC (morecurar Sive Carbon), which is a molecular sieve that adsorbs oxygen gas more quickly than nitrogen gas, is used as an adsorbent and PSA method is used. Oxygen gas can be adsorbed and removed from the air to concentrate nitrogen gas. In this case as well, since the MSC adsorbs and removes water like oxygen gas, very dry nitrogen can be obtained, so that the present oxygen concentration detector can be used as in the case of oxygen. Further, in the case of the nitrogen gas concentrating device using MSC, since the pressure reducing valve is provided after the product tank, the measured gas is branched from the upstream of the flow rate setting device downstream and is supplied to the oxygen concentration detector 34. The method is the same.

[0036]

By implementing the present invention, the following excellent effects can be expected. When the present invention is applied to the configuration of a small chamber (also referred to as a chamber) that accommodates an oxygen concentration detection unit (oxygen sensor) that measures a limiting current due to the diffusion of oxygen gas, it is always high regardless of changes in the surrounding environmental atmosphere. Stable oxygen concentration can be detected with high accuracy. When the oxygen concentration detector according to the present invention is used as an oxygen sensor for measuring the oxygen concentration of a PSA-type oxygen concentrator or a nitrogen concentrator, it is configured as described in "claim 4" of the invention. By doing so, an accurate and stable measurement result can be obtained, and high-concentration oxygen gas does not stay in the oxygen concentrator, and there is a risk of fire or explosion from the oxygen concentrator. It will never happen.

[Brief description of drawings]

FIG. 1A is a cross-sectional view of a small chamber according to an embodiment. FIG. 1B is a sectional view of a small chamber of another embodiment. FIG. 1C is an explanatory diagram of the operating principle of the zirconia solid electrolyte (oxygen concentration detection unit).

FIG. 2 is a flow sheet when the present invention is applied to a medical oxygen gas concentrator.

[Explanation of symbols]

 1 Small Chamber Block 2 Stem 3,3 'Lead Pin 4 O-ring 5 Wire Mesh Cover 6 Small Chamber 7 Inlet 8 Outlet 9 Inlet / Outlet Block 10 Thin Plate 11, 12 Pore 13 Oxygen Concentration Detector 14 Tip 15 Fixture 20 Filter 21 Air Compression Device 22, 22 'Piping 23 Cooling coil 24 Filter 25, 26 Adsorption cylinder 27 Valve means 29 Product tank 30, 30' Orifice 31 Pressure reducing valve 32 Flow rate setter 33 Humidifier 34 Oxygen concentration detector 35 Controller 36 Signal line 37 Fan 38 Oxygen gas outlet 30 Indicator

Claims (4)

[Claims] 1. A small chamber having an oxygen concentration detector inside and having an inflow port and an outflow port for the gas to be measured, the inflow port being provided with pores for determining the inflow amount of the gas to be measured. ,And,
The inflow direction of the measured gas flowing into the small chamber is such that the measured gas does not directly blow to the oxygen concentration detection unit, and the measured gas flowing out from the outlet toward the atmosphere is A small hole with a diameter is provided so that the flow velocity of the atmospheric gas flows backward toward the small chamber due to the gas diffusion action at the operating temperature and the concentration of the measured gas in the small chamber is not substantially affected. An oxygen concentration detector for a PSA type gas concentrator having a small chamber. 2. A small chamber block having an oxygen concentration detecting section therein, and an inlet / outlet block having an inlet for introducing a gas to be measured into the small chamber block and an outlet for letting out the gas to be measured. Attach a thin plate between the blocks,
The thin plate at the position corresponding to each of the inlet and outlet of the inlet / outlet block has pores that determine the passage resistance of each of the inlet and the outlet, and the position of the inlet is An oxygen concentration detection device for a PSA gas concentrator, comprising a small chamber arranged so that a gas to be measured flowing into the small chamber from the inlet does not directly blow to the oxygen concentration detection unit. vessel. 3. The small chamber according to claim 1, further comprising a small chamber having a diameter of 0.05 mm to 0.5 mm attached to an inlet of the small chamber. Oxygen concentration detector of PSA gas concentrator. 4. A gas concentrator comprising an air compressor, valve means for switching the flow of compressed air, piping means, at least one adsorption cylinder filled with an adsorbent, a product tank for storing condensed gas, and the like. In the device, a pressure reducing valve is attached downstream of the product tank, and after the pressure of the concentrated gas is substantially constant, a flow rate setting device for setting the flow rate of the concentrated gas is attached. In addition, a fan for housing these components in a housing and cooling an air compressor or the like that generates heat, an air intake port, and an air exhaust port are provided in the housing, and further provided in the housing. In the PSA gas concentrator having a cooling air passage connecting the air intake port and the air exhaust port, the concentrated gas is provided at a position downstream of the pressure reducing valve and upstream of the flow rate setting device. The oxygen concentration is detected by branching it out through piping means. 2. The concentrated gas is supplied to a small chamber having therein, and the measured gas flowing out from the small chamber is diffused into the passage of the cooling air. 3. A PSA type gas concentrating device comprising the oxygen concentration detector of the PSA type gas concentrating device according to claim 2.