Patent Application
20240131290
The present invention relates to an oxygen concentrator that separates and concentrates oxygen in the air and supplies it to a user. More specifically, with respect to an oxygen concentrator in which a pilot type solenoid valve is used in at least either of the supply flow path opening/closing unit or the exhaust flow path opening/closing unit, the present invention relates to an oxygen concentrator, a control method, and a control program capable of controlling the pressures in a plurality of adsorption cylinders so as to prevent a drop of the pilot pressure (the discharge pressure of the pressurized air supply unit, the internal pressure of the concentrated oxygen gas tank, or the internal pressure of the adsorption cylinder).
Conventionally, as one of the therapies for patients with respiratory diseases such as asthma and chronic obstructive pulmonary disease, there has been performed an oxygen therapy, in which a patient inhales oxygen gas or oxygen-enriched gas. In recent years, in order to improve a patient's quality of life (QOL), home oxygen therapy (HOT) of performing oxygen therapy at the patient's home has become mainstream. In home oxygen therapy, as an oxygen supply source for supplying oxygen gas to a patient, used is an oxygen concentrator that concentrates oxygen contained in air to produce oxygen gas and supplies the produced oxygen gas.
As oxygen concentrators, pressure swing adsorption (PSA) oxygen concentrators and vacuum pressure swing adsorption (VPSA) or vacuum swing adsorption (VSA) oxygen concentrators are widely used.
An oxygen concentrator has a plurality of adsorption cylinders filled with an adsorbent that selectively adsorbs nitrogen gas, and each of the plurality of adsorption cylinders repeats an adsorption step and a desorption step to produce concentrated oxygen gas, which is stored in a concentrated oxygen gas tank. The adsorption step is a step of producing oxygen gas from pressurized air by taking the pressurized air into the adsorption cylinder and adsorbing nitrogen gas on the adsorbent, and storing the produced concentrated oxygen gas in a concentrated oxygen gas tank. The desorption step is a step of depressurizing the adsorption cylinder by exposure to the atmosphere, and exhausting to the atmosphere the nitrogen gas adsorbed on the adsorbent in the adsorption step. The oxygen concentrator can continuously produce concentrated oxygen gas by repeating a rotation of adsorption step and desorption step among a plurality of adsorption cylinders.
There has been made the following proposals concerning the oxygen concentrator: in order to improve the efficiency of desorption in the desorption step, the concentrated oxygen gas produced in the adsorption cylinder during the adsorption step is flowed back from the end of the concentrated oxygen outlet side through the purge valve as purge gas to the adsorption cylinder in the desorption step, subsequently, in order to efficiently produce highly concentrated oxygen gas, the adsorption cylinder is depressurized to exhaust nitrogen and then is made communicate with the adsorption cylinder in the pressurization step via a pressure equalizing valve and the pressure is equalized (PTLs 1 and 2).
On the other hand, in order to suppress the power consumption of the oxygen concentrator, a method of controlling the compressor rotation speed to adjust the amount of air supplied (PTL 2) and a method of using a pilot type solenoid valve have been proposed (PTL 3). Since a pilot type solenoid valve operates a large main valve with a pilot pressure and thus switches the valve, the power consumption required for valve switching can be reduced even for a large effective flow passage cross section compared to a conventional direct-acting solenoid valve. In addition, since the flow rate loss can thus be reduced, which allows reduction of the discharge flow rate of the compressor, there can be reduced the power consumption required to drive the compressor, which is the mainly power-consuming device in the oxygen concentrator, supposedly resulting in power saving in the concentrator.
A pilot type solenoid valve requires supply of a pilot pressure for the switching operation, and, for example, when the pilot pressure is supplied by discharge pressure of the pressurized air supply unit, the discharge pressure of the pressurized air supply unit must be equal to or higher than the minimum operating pressure of the pilot type solenoid valve. The pilot pressure can be supplied by the internal pressure of the concentrated oxygen gas tank, the internal pressure of the adsorption cylinder, or the like, as well as the discharge pressure of the pressurized air supply unit. Therefore, the pilot pressure (the discharge pressure of the pressurized air supply unit, the internal pressure of the concentrated oxygen gas tank, or the internal pressure of the adsorption cylinder) must be equal to or higher than the minimum operating pressure of the pilot type solenoid valve.
However, in the case of pressure equalization by making the depressurized adsorption cylinder and the adsorption cylinder in the pressurization step communicate via the pressure equalizing valve, the cylinder pressure drops to the pressure under which the pressure is equalized between both adsorption cylinders, resulting also in drops of the discharge pressure of the pressurized air supply unit and the pressure in the concentrated oxygen gas tank. More specifically, since there is only a supply valve between the pressurized air supply unit and the adsorption cylinder, when the supply valve is open, the pressurized air supply unit and the adsorption cylinder communicate with each other, and the discharge pressure of the pressurized air supply unit will drop to the internal pressure of the adsorption cylinder.
In addition, in the running oxygen concentrator, the concentrated oxygen gas is always extracted from the concentrated oxygen gas tank at a predetermined flow rate; when the internal pressure of the adsorption cylinder is higher than the internal pressure of the concentrated oxygen gas tank, the gas automatically flows from the adsorption cylinder to the concentrated oxygen gas tank through the check valve provided between the adsorption cylinder and the concentrated oxygen gas tank, resulting in keeping the internal pressure at the same level between the adsorption cylinder and the concentrated oxygen gas tank; when the pressure equalization causes the internal pressure of the adsorption cylinder to drop below the pressure in the concentrated oxygen gas tank, the gas flow from the adsorption cylinder to the concentrated oxygen gas tank stops, and thus the pressure in the concentrated oxygen gas tank drops due to the continuous extraction of the concentrated oxygen gas at the predetermined flow rate, and further drops to the dropped internal pressure of the adsorption cylinder.
In addition, this problem appears prominently in the case of low flow rate operation and causes a bad effect: for example, although a low flow rate operation allows suppression of power consumption by lowering the rotation speed of the pressurized air supply unit and reducing the amount of supplied air in accordance with the oxygen extraction flow rate, the rotation speed of the pressurized air supply unit cannot be lowered below the level that satisfies the condition under which the minimum operating pressure or more of the pilot type solenoid valve is maintained. In addition, since the rotation speed of the pressurized air supply unit cannot be lowered further, air is supplied excessively with respect to the oxygen extraction flow rate, causing oxygen overadsorption resulting in another bad effect of oxygen concentration reduction.
As the present invention has been made in view of such circumstances, an object of the present invention is to solve the problem: during the pressure equalization step, by preventing a pilot pressure drop (the discharge pressure of the pressurized air supply unit, the internal pressure of the concentrated oxygen gas tank, or the internal pressure of the adsorption cylinder), to maintain the pilot pressure equal to or higher than the minimum operating pressure of the pilot type solenoid valve. Accordingly, an oxygen concentrator, a control method, and a control program are provided that enable control of the pressurized air supply unit rotation speed to suppress power consumption or to prevent the reduction in the oxygen concentration due to overadsorption of oxygen.
Accordingly, the present invention is an oxygen concentrator capable of preventing pressure drops in both cylinders in the pressure equalization step and, as a result, preventing a drop in pilot pressure supplied to a pilot type solenoid valve used in at least either of the supply flow path opening/closing unit or the exhaust flow path opening/closing unit, as well as a pressure drop in the adsorption cylinder, by starting pressurization in advance in the already depressurized adsorption cylinder before the pressure equalization step, thereby equalizing the pressure from the condition under which the cylinder pressure of the already depressurized adsorption cylinder is increased, and includes the following embodiments.
An oxygen concentrator according to one aspect of an embodiment of the present invention includes:
In the oxygen concentrator according to one aspect of an embodiment, the flow path opening/closing control unit, during (d) pre-pressurization step, preferably controls the exhaust flow path opening/closing unit from an adsorption cylinder during pre-pressurization to a closed state.
In the oxygen concentrator according to one aspect of an embodiment, the flow path opening/closing control unit, during (b) and (e) pressure equalization steps, preferably controls all of the supply flow path opening/closing units for the plurality of adsorption cylinders to an open state.
In the oxygen concentrator according to one aspect of an embodiment, the flow path opening/closing control unit, in the second half of (c) depressurized desorption step, preferably controls a part of concentrated oxygen gas produced in an adsorption cylinder during pressurized adsorption to be purged to an adsorption cylinder during depressurized desorption.
In the oxygen concentrator according to one aspect of an embodiment, the flow path opening/closing control unit, during (c) depressurized desorption step, preferably controls the communication flow path opening/closing unit to a closed state.
In the oxygen concentrator according to one aspect of an embodiment, the flow path opening/closing control unit, during (b) and (e) pressure equalization steps, may control the communication flow path opening/closing unit to a closed state.
A control method of an oxygen concentrator according to one aspect of an embodiment is
A control program of an oxygen concentrator according to one aspect of an embodiment is
In accordance with the present embodiment, during the pressure equalization step, prevention of a drop in pilot pressure (the discharge pressure of the pressurized air supply unit, the internal pressure of the concentrated oxygen gas tank, or the internal pressure of the adsorption cylinder) facilitates, even in the case of low flow rate operation, maintaining easily the pilot pressure equal to or higher than the minimum operating pressure of the pilot type solenoid valve, enabling control of the pressurized air supply unit rotation speed, and thus suppression of the power consumption.
In addition, decrease in the rotation speed of the pressurized air supply unit can reduce the amount of supplied air, which brings the effect of suppressing overadsorption of oxygen that occurs when the extraction flow rate is low with respect to the amount of supplied air.
The objects and advantages of the present invention may be recognized and obtained by means of the elements and combinations particularly pointed out in the CLAIMS. Both the general description above and the detailed description below are exemplary and explanatory, and are not for limiting the present invention as claimed.
Hereinafter, an oxygen concentrator, a control method, and a control program according to one aspect of the present disclosure will be described with reference to the drawings. However, it should be noted that the technical scope of the present disclosure is not limited to those embodiments, but extends to the invention described in the CLAIMS and equivalents thereof. In the following description and drawings, components having the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.
The oxygen concentrator includes a plurality of adsorption cylinders (4A and 4B) filled with an adsorbent that preferentially adsorbs nitrogen over oxygen, a pressurized air supply unit (1) supplying pressurized air to the adsorption cylinders, a pair of supply flow path opening/closing units (2A, 2B) that connects the pressurized air supply unit and the adsorption cylinders and opens/closes the gas flow paths of the pressurized air, a pair of exhaust flow path opening/closing units (3A, 3B) that opens/closes gas flow paths for atmospheric releasing and exhausting the adsorption cylinders, a concentrated oxygen gas tank (7) that stores concentrated oxygen gas produced by the plurality of adsorption cylinders, a communication flow path opening/closing unit (pressure equalizing/purging) (5) that connects the ends of each adsorption cylinder on the concentrated oxygen gas outlet side and passes therethrough a part of the produced concentrated oxygen gas, and a flow path opening/closing control unit that controls opening/closing of the supply flow path opening/closing units (2A, 2B), the exhaust flow path opening/closing units (3A, 3B), and the communication flow path opening/closing unit (pressure equalizing/purging) (5). Although here is shown a communication flow path opening/closing unit having one flow path, there may be employed a configuration having flow paths for pressure equalizing and purging independent of each other.
Opening and closing is controlled by the flow path opening/closing control unit for the supply flow path opening/closing units (2A, 2B), the exhaust flow path opening/closing units (3A, 3B), and the communication flow path opening/closing unit (pressure equalizing/purging) (5). The supply flow path opening/closing units (2A, 2B), the exhaust flow path opening/closing units (3A, 3B), and the communication flow path opening/closing units (pressure equalizing/purging) (5) are, for example, electromagnetic valves and control valves (solenoid valves, piezo valves), etc., and are controlled in accordance with a signal input from the flow path opening/closing control unit. The flow path opening/closing control unit has one or more processors and their peripheral circuits. The flow path opening/closing control unit controls integrally the operation of the oxygen concentrator, and is a processor such as a Micro Control Unit (MCU), for example.
The oxygen concentrator performs an oxygen gas production process of producing concentrated oxygen gas from raw material air and delivering the produced concentrated oxygen gas to the nostrils of a user, a patient using the oxygen concentrator.
Although
First, raw material air is taken in from the outside through an air intake opening provided with an external air intake filter or the like for removing foreign matter such as dust. The pressurized air supply unit (1) compresses the air taken in through the external air intake filter to produce pressurized air, and the produced pressurized air is passed through the supply flow path opening/closing unit (2A, 2B) and supplied to either of the pair of adsorption cylinders (4A and 4B). The pressurized air supply unit (1) is also called a compressor, and examples thereof include an oscillating air compressor and a rotary air compressor such as a screw type, a rotary type, and a scroll type.
A pair of adsorption cylinders (4A and 4B) is filled with an adsorbent of zeolite that selectively adsorbs nitrogen gas over oxygen gas in pressurized air. Zeolite selectively adsorbs nitrogen gas contained by about 77% in the pressurized air supplied from the pressurized air supply unit (1).
A pair of adsorption cylinders (4A and 4B) adsorbs nitrogen gas and produces oxygen gas in the pressurized air supplied from the pressurized air supply unit (1) through the supply flow path opening/closing units (2A, 2B). While the adsorption cylinder (4A) produces oxygen gas, the adsorption cylinder (4B) exhausts the adsorbed nitrogen gas to the outside of the oxygen concentrator through the exhaust flow path opening/closing unit (3B). While the nitrogen gas adsorbed by the adsorption cylinder (4A) is exhausted to the outside of the oxygen concentrator through the exhaust flow path opening/closing unit (3A), the adsorption cylinder (4B) produces oxygen gas. Oxygen gas is produced alternately between a pair of adsorption cylinders (4A and 4B), enabling the oxygen concentrator to produce oxygen gas continuously. Although the oxygen concentrator is described using a pair of adsorption cylinders (4A and 4B) as an example, the oxygen concentrator according to an embodiment may have three or more adsorption cylinders. When three or more adsorption cylinders are provided, the operation is performed in such a way that the adsorption step and the desorption step can be repeated in turn among the plurality of adsorption cylinders. For example, in the case of a three-cylinder type with three adsorption cylinders (4A, 4B and 4C), the control is performed by switching the cylinders sequentially as follows: when the adsorption cylinder (4A) is in the adsorption step, a group of adsorption cylinders (4B and 4C) is in the desorption step; when the adsorption cylinder (4B) is in the adsorption step, a group of adsorption cylinders (4C and 4A) is in the desorption step; when the adsorption cylinder (4C) is in the adsorption step, a group of adsorption cylinders (4A and 4B) is in the desorption step.
The supply flow path opening/closing unit and/or the exhaust flow path opening/closing unit are pilot type solenoid valves. A pilot type solenoid valve switches the operation of a large main valve with a pilot pressure (air pressure). A supply source of the pilot pressure can be a discharge pressure of the pressurized air supply unit, an internal pressure of the concentrated oxygen gas tank, or an internal pressure of the adsorption cylinder, in which particularly the discharge pressure of the pressurized air supply unit, which is the supply source of air, is most utilized. The pilot pressure varies depending on the characteristics of the pilot type solenoid valve used, but the present specification shows an example where 40 kPa or more is required. The pilot pressure is permitted to temporarily drop below the minimum operating pressure of the pilot type solenoid valve as long as the pressure does not hinder the opening and closing of the pilot type solenoid valve. Although an oxygen concentrator is more efficient if both the supply flow path opening/closing unit and the exhaust flow path opening/closing unit are pilot type solenoid valves, also included in the problem to be solved in the present invention is a case in which either one is a pilot type solenoid valve.
A pair of check valves (6A and 6B) is provided between each of the pair of adsorption cylinders (4A and 4B) and the concentrated oxygen gas tank (7). Providing check valves (6A, 6B) between the adsorption cylinders (4A and 4B) and the concentrated oxygen gas tank (7) can prevent the concentrated oxygen gas from flowing back to the adsorption cylinder side when the internal pressure of the concentrated oxygen gas tank becomes higher than the internal pressure of the adsorption cylinder. The check valve (6A) is in an open state while the adsorption cylinder (4A) produces oxygen gas, allowing the concentrated oxygen gas produced by the adsorption cylinder (4A) to flow into the concentrated oxygen gas tank (7). In addition, the check valve (6B) is in a closed state while the nitrogen gas adsorbed by the adsorption cylinder (4B) is exhausted to the outside of the oxygen concentrator through the exhaust flow path opening/closing unit (3B), which prevents the concentrated oxygen gas stored in the concentrated oxygen gas tank (7) from being exhausted to the outside of the oxygen concentrator through the adsorption cylinder (4B).
The concentrated oxygen gas tank (7), also called a product tank, stores the oxygen gas produced by each of the pair of adsorption cylinders (4A and 4B). The internal pressure of the concentrated oxygen gas tank (7) fluctuates depending on the internal pressure change associated with the production of concentrated oxygen gas in each of the adsorption cylinders (4A and 4B). In order to keep, at a predetermined level, the pressure of the concentrated oxygen gas delivered from the concentrated oxygen gas tank (7) having internal pressure fluctuation associated with the production of concentrated oxygen gas, there is provided a pressure regulating valve, such as a pressure reducing valve.
The concentrated oxygen gas extracted from the concentrated oxygen gas tank (7) is controlled to flow at a predetermined flow rate by adjusting the opening of a solenoid valve of the flow rate control unit in accordance with the flow rate output signal input from the control unit.
The concentrated oxygen gas adjusted to the predetermined flow rate, from which foreign matter such as dust produced in the process of producing concentrated oxygen gas is removed by an air filter, is moderately moistened by a humidifier to prevent from nostrils to respiratory tract of the user from drying and supplied to the user from the end of the flow path such as a cannula.
The concentration and flow rate of the concentrated oxygen gas can be measured by connecting a concentration sensor and a flow rate sensor in the flow path of the concentrated oxygen gas between the air filter of the outlet filter and the humidifier.
In the oxygen concentrator according to an embodiment, the pressure in the adsorption cylinder is controlled so as to prevent a drop in pilot pressure supplied to a pilot type solenoid valve used in at least either of the supply flow path opening/closing unit or the exhaust flow path opening/closing unit, and for this purpose, there is provided a flow path opening/closing control unit that performs opening/closing control of the supply flow path opening/closing units (2A, 2B), the exhaust flow path opening/closing units (3A, 3B), and the communication flow path opening/closing unit (5). The control of the pressure in the adsorption cylinder will be explained with reference to
As described above, the oxygen concentrator can continuously produce concentrated oxygen gas by repeating a rotation of adsorption step and desorption step among a plurality of adsorption cylinders. First, along
In T1, T4 of the example of
In the present specification, low flow rate operation is defined as performed with oxygen gas in the flow rate range of 0.1 LPM or more and less than 2.00 LPM.
T2/T5, as shown in
T3-1/T6-1, as shown in
Note that, although
T3-2/T6-2, as shown in
Through steps T1 to T6-2, one cycle of adsorption and desorption is completed in one adsorption cylinder, and by repeating this cycle, concentrated oxygen gas can be continuously produced. The cycle time does not matter as long as the concentration of produced oxygen reaches a specified value. As shown in
The present technology can be applied to any oxygen concentrator as long as being continuous-flow type, regardless of a stationary type or portable type.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-032686 | Mar 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/008494 | 3/1/2022 | WO |
