JP2005066072A - Medical oxygen concentrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure swing adsorption oxygen concentrator used for a home oxygen therapy, which is quiet, and has a low power consumption. <P>SOLUTION: This pressure swing type oxygen concentrator is equipped with at least one adsorption cylinder which is filled with an adsorbent selectively adsorbing nitrogen more than oxygen, an air compressor for pressure pump and/or vacuum pump of air to/from the adsorption cylinder, and a switching valve which switches adsorption/desorption channels. In the pressure swing type oxygen concentrator, a motor which drives the air compressor is a brushless motor which is equipped with an inverter and is driven by a DC power source. Also, a buffer tank of which the tank capacity (V) to a discharging amount q(L/min) per unit time which is converted into 25°C-1atm of the air compressor satisfies V≥q/600(L) is provided between the air compressor and the switching valve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an oxygen concentrator for separating and concentrating oxygen from the air, and more particularly to a pressure fluctuation adsorption type oxygen concentrator used for oxygen inhalation therapy performed at home for medical use.

  A medical oxygen concentrator used for home oxygen therapy uses air as a raw material and concentrates about 21% oxygen contained therein to about 40% or 90%. The method uses a membrane-type oxygen concentrator that uses an oxygen-enriched membrane that selectively permeates oxygen, and an adsorbent that selectively adsorbs nitrogen, such as zeolite, and a raw material in an adsorption cylinder filled with this. There is a pressure fluctuation adsorption type oxygen concentrator that adsorbs and separates nitrogen by adding air. The concentration of oxygen concentrated by the former oxygen concentrator is about 40% and the latter is about 90%. At present, the latter is mainstream, and the present invention relates to the latter.

Such a pressure fluctuation adsorption type oxygen concentrator is a 5A type zeolite, a 13X type zeolite, or an X type zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 2.0 to 3.0, and at least 88% of the AlO ₄ tetrahedral unit is more than 88%. High-performance Li zeolite associated with Li cations is packed in one, two, or many adsorption cylinders, and the atmosphere is pressurized with a compressor to adsorb nitrogen and separate oxygen. At the same time, there are various PSA systems that change the flow path and reduce the pressure up to atmospheric pressure to desorb the adsorbed nitrogen, or VPSA systems that increase the desorption regeneration efficiency by reducing the adsorption cylinder to a vacuum state. Has been supplied to.

JP 2000-176019 A JP-A-63-242901 JP-A-60-200804 JP 59-274654 A

  The basic performance required for an oxygen concentrator used for home oxygen therapy includes quietness, energy saving, and the like as requirements required for home medical use in addition to the oxygen concentration performance. This is due to the following reason.

  Oxygen concentrators used in home oxygen therapy are mostly covered by health insurance and less burdened by the patient, but the operating expenses are burdened by the patient, and the patient operates continuously for 24 hours a day. The electricity bill is a heavy burden, and a device with low power consumption is an essential requirement. In addition, oxygen concentrators used in home oxygen therapy are often used 24 hours a day, and at night, it is required that the operation sound of the device be a quiet device that does not disturb the sleep of patients including family members.

Next, regarding the two requirements required for these oxygen concentrators, the prior art has the following aspects.
(1) About low power consumption Since the main power consumption part in an oxygen concentrator is an air compressor, since the efficiency improvement of this part implement | achieves low power consumption, there exists a great effect. In particular, as a device configuration for realizing high efficiency, instead of the reciprocating piston type that has been generally used, a highly efficient rotary scroll type or helical type air compressor is used for driving. For this purpose, it is becoming common to use a DC motor having higher efficiency than an AC induction motor. As in Japanese Patent Application Laid-Open No. 2000-176019, a device configuration using a scroll compressor and a DC brushless motor is a known technique.

(2) Quietness Conventionally, when the equipment configuration using an AC induction motor has been the mainstream, the operating noise and pressure of the air compressor that takes in the air as raw material and compresses it is the source of the operating noise in the equipment. Exhaust noise generated by pressure switching and exhaust of the adsorption cylinder of the variable adsorption type oxygen concentrator was the main one.

  Exhaust noise can be silenced relatively well by installing a high-performance silencer. However, the operation sound of the air compressor contains a lot of low-frequency sound accompanied by vibrations and is not easily lowered. Currently, there are piston type, vane type and scroll type air compressors used for oxygen enrichment for medical use. In the vane type, the carbon used is worn out, black carbon comes out on the secondary side, and a filter is required to remove it. In addition, this filter must be replaced frequently. In addition, the wear life of the carbon vane is 2000 to 4000H, and maintenance frequently occurs, so that the piston type is mainly used.

  The noise level of a piston type air compressor is usually in the range of 80 to 60 dBA in the class of air compressor of the class used for the above-mentioned type of oxygen concentrator, and this is caused by the operation of the piston. This is due to the low-frequency operating noise associated with vibrations in the air compressor and torque fluctuations in the motor. As means for preventing the propagation of vibrations to the other, a means for floating by a spring or an anti-vibration rubber as shown in JP-A-63-242901, and JP-A-60-200804 and JP-A-59. As shown in Japanese Patent Publication No. 274654 / etc., Sound is contained by a double soundproof box. However, it cannot be completely sealed, and it is necessary to cool the heat generated by the drive motor and air compression, and a fan is attached. However, since noise leaks to the outside through the intake and discharge ports for cooling air, a bent passage is provided to prevent this. Since various soundproofing measures are taken in this way, the apparatus is large and heavy, weighing 40-60 kg, and it is difficult for one maintenance person to carry it up and down the stairs of the building.

  The rotary scroll type and helical type air compressors have a valveless structure, have no valve opening / closing noise, and are advantageous in terms of noise, and thus have recently been increasingly applied to medical oxygen concentrators.

  However, in recent years, brushless electric motors for direct current have been used as energy-saving technologies, and noise generated from motors has become a new issue. Originally, the PSA and VPSA type oxygen concentrators based on the basic principle of adsorbing and desorbing nitrogen components using pressure fluctuations in the adsorption cylinder are essentially processes with periodic load fluctuations. An electric motor for driving an air compressor is required to perform work in accordance with the load fluctuation. When comparing a conventional AC induction motor and a DC brushless motor, the fluctuation in the rotational speed when the required torque changes due to the difference in the rotational speed-torque characteristics of the direct current brushless motor. large. Since the cycle of the rotational speed coincides with the period of the roaring sound, and the rotational speed fluctuation range of the rotational speed fluctuation is proportional to the size of the roaring sound, the rotational speed fluctuation is a big problem.

  As a specific example, when a piston type air compressor is combined with a two-cylinder oxygen concentrator operated at an adsorption process pressure of 150 kPa ± 20 kPa and a required flow rate of 70 L / min, The rotational speed fluctuation is 1680 ± 20 rpm, whereas in the direct current brushless motor, the rotational speed fluctuation is 1680 ± 200 rpm. As a countermeasure against fluctuations in the rotational speed of the brushless motor for direct current, it is effective to increase the control speed of feedback control and increase the precision of rotational speed control with a drive inverter. In this case, however, the load on the CPU is increased. There is a drawback that the power consumption is accompanied and the control time constant needs to be set individually for each load condition.

  The present invention provides a pressure fluctuation adsorption type oxygen concentrator that is quiet and has low power consumption used for home oxygen therapy as described above. Therefore, as a result of intensive studies on the problem, the present inventor has found the following oxygen concentrator.

  That is, the present invention has at least one adsorption cylinder filled with an adsorbent capable of selectively adsorbing nitrogen rather than oxygen, and an air compressor for pressurizing and / or evacuating air to the adsorption cylinder. In the pressure fluctuation type oxygen concentrator, the electric motor that drives the air compressor is a brushless electric motor that is driven by a DC power source, and includes an inverter, and holds compressed air between the air compressor and the adsorption cylinder. The buffer tank capacity V (L) is V> = with respect to the discharge amount q (L / min) per unit time converted to 25 ° C.-1 atm of the air compressor. The oxygen concentrator is characterized by being q / 600 (L).

  By installing a buffer tank between the air compressor driven by the DC brushless motor and the switching valve, it is possible to provide a quiet and low power consumption pressure fluctuation adsorption type oxygen concentrator.

  A schematic diagram of the medical oxygen concentrator of the present invention is shown in FIG. Such an oxygen concentrator supplies pressurized air to an adsorption cylinder filled with 5A-type zeolite as an adsorbent that selectively adsorbs nitrogen rather than oxygen, takes out an oxygen-concentrated gas having an oxygen concentration of 90%, and a humidifier This is a two-cylinder pressure fluctuation adsorption type oxygen concentrator that supplies a respiratory disease patient, who is a user, via, for example, at a flow rate of 3 L / min.

  The air compressor is a helical blade type air compressor having a compression ratio in a range of 1.5 to 3.0 and an excluded volume in a range of 50 cc / rev or less. The electric motor that drives the air compressor is a brushless DC electric motor that has the capability of being operated at 5000 rpm or less, and the rotational speed can be arbitrarily changed by controlling the electric motor with an inverter.

  Between the air compressor and the switching valve, the capacity V (L) is V ≧ q / 600 with respect to the discharge amount q (L / min) converted to 25 ° C.-1 atm per unit time of the air compressor. A buffer tank having a size of (L) is inserted. As a result of intensive investigations on the capacity of the buffer tank, when the displacement volume of the air compressor is D (L) and the compression ratio is r, the effect is manifested when V ≧ 200 D / r × 0.1 (L). I found out. However, since the values of D (L) and r, which are design specifications of the air compressor, are often undisclosed values, as a result of studying an air compressor applicable as a medical oxygen concentrator, V It was found that ≧ q / 600 (L).

  Although the upper limit is not specified, it is clear that the larger the performance, the smaller the pressure fluctuation range. However, since the requirement required from the apparatus specification is to make it as small as possible while maintaining the performance of the buffer tank, the upper limit is the level that can be installed in the concentrator housing.

  In the present invention, a configuration in which such a buffer tank is installed between the air compressor and the switching valve is employed in the oxygen concentrator. In the configuration in which the air compressor driven by the DC brushless motor and the switching valve are directly connected by piping as in the conventional configuration, the pressure fluctuation on the outlet side of the air compressor due to valve switching is large, and the load fluctuation Since the rotation speed of the electric motor fluctuates in accordance with the cycle, a periodic beat sound is generated. However, in the configuration of the present invention, the buffer tank installed between the air compressor and the switching valve acts as an accumulator for absorbing pressure fluctuations, and the load fluctuations are greatly reduced. It was found that the fluctuation was suppressed and the beat sound was eliminated. Also, by mitigating load fluctuations, the efficiency of the motor itself can be increased, resulting in a reduction in power consumption. At the same time, it is possible to extend the motor life and provide a highly reliable oxygen concentrator. It becomes.

  Hereinafter, examples and comparative examples of an oxygen concentrator realizing a flow rate of 5 L / min with an oxygen concentration of 91% will be described.

[Example 1]
A diameter of 60 mm is provided between two helical cylinders filled with a density of 0.8 in an adsorption cylinder having a diameter of 70 mm and a length of 400 mm, and a helical compressor capable of obtaining a flow rate of 70 L / min and a switching valve. A cylindrical buffer tank having a length of 400 mm is connected and operated as in the flow sheet of FIG. The helical compressor is operated at a constant rotational speed command by an inverter with a brushless motor for direct current, and the actual rotational speed is measured by a tachometer.

[Comparative Example 1]
Two helical cylinders with a density of 0.8 packed in an adsorption cylinder with a diameter of 70mm and a length of 400mm, and a helical compressor with a performance of 70L / min. Connect to the valve and operate. Other conditions are the same as those in the first embodiment.

  Table 1 shows the results of the above examples and comparative examples. The fluctuation range of the rotational speed was ± 20 rpm, which was 1/10 of that of the comparative example, and the noise fluctuation level was also converged to Δ0.9 dBA, which was 29% of the comparative example. The power consumption was reduced by 5 W without affecting the oxygen concentration and yield. Thus, the performance difference between Example 1 and Comparative Example 1 is very large. By installing a buffer tank between the air compressor driven by the DC brushless motor and the switching valve, periodic beat noise is generated. It turns out that the rotation speed fluctuation | variation of the motor which becomes a cause is improved significantly. It can also be seen that power consumption is improved.

The schematic block diagram of the 2 cylinder type oxygen concentrator of this invention.

Claims (1)

  At least one adsorption cylinder filled with an adsorbent capable of selectively adsorbing nitrogen rather than oxygen, an air compressor for pressurizing and / or evacuating air to the adsorption cylinder, and an adsorption / desorption flow path In the pressure fluctuation type oxygen concentrator provided with a switching valve for switching, the electric motor that drives the air compressor is a brushless electric motor that is driven by a DC power source that includes an inverter, and the air compressor and the air compressor Between the switching valves, a buffer whose tank capacity (V) is V ≧ q / 600 (L) with respect to the discharge amount q (L / min) per unit time converted to 25 ° C.-1 atm of the air compressor An oxygen concentrator comprising a tank.

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