Oxygen concentration device

1. A pressure swing adsorption-type oxygen concentration device comprising:

a plurality of adsorption cylinders packed with an adsorbent that selectively adsorbs nitrogen rather than oxygen; a compressor that supplies compressed air to the adsorption cylinders;

a flow path switching means that repeats, by sequentially switching a flow path between the compressor and each adsorption cylinder, at a prescribed timing, an adsorption step where pressurized air is supplied to each adsorption cylinder and an oxygen-concentrated gas is taken out, a desorption step where each adsorption cylinder is decompressed and the adsorbent is regenerated, and a purge step where the oxygen-concentrated gas from an adsorption cylinder at an adsorption step side is introduced to an adsorption cylinder at a desorption step side;

a flow rate setting means that supplies the oxygen-concentrated gas by adjusting a flow rate to a desired value; and

a control means that controls operation of an oxygen concentration sensor to measure a concentration of the oxygen-concentrated gas, a pressure sensor to detect a pressure of the adsorption cylinder, the compressor and the flow path switching means,

wherein the control means controls a speed of revolution of the compressor based on a detected value of the oxygen concentration sensor, judges deterioration of the adsorbent due to moisture absorption based on the detected value of the oxygen concentration sensor, a detected value of the pressure sensor, and an operating time of the adsorption cylinder, wherein the operating time is an accumulated number of hours of usage of the adsorption cylinder, and when criteria for judgment of deterioration due to moisture absorption are satisfied, controls a switching time of the flow path switching means so that a time for the purge step becomes shorter than an initially set value.

2. The oxygen concentration device according to claim 1 , wherein the criteria for judgment of the deterioration due to moisture absorption are to satisfy all three conditions: that the detected value of the oxygen concentration sensor is not more than a prescribed concentration value; that the speed of revolution of the compressor is an upper limit value of control and the detected value of the pressure sensor is not less than a pressure value at an initial stage of use of the device when the compressor is revolving at the upper limit value of control; and that the operating time of the adsorption cylinder is not less than a prescribed time.

3. The oxygen concentration device according to claim 1 , wherein the criteria for judgment of the deterioration due to moisture absorption are to satisfy all three conditions: that the detected value of the oxygen concentration sensor is not more than a prescribed concentration value; that the speed of revolution of the compressor is the speed of revolution of the compressor at a maximum flow rate set value and the detected value of the pressure sensor is not less than a pressure value at an initial stage of use of the device when the compressor is revolving at the maximum flow rate set value; and that the operating time of the adsorption cylinder is not less than a prescribed time.

4. The oxygen concentration device according to claim 2 , wherein when, after controlling the switching time of the flow path switching means so that the time of the purge step becomes shorter than an initially set time, the criteria for judgment of the deterioration due to moisture absorption are satisfied again, the switching time of the flow path switching means is controlled so that the time of the purge step becomes shorter than the set time of the previous control.

5. The oxygen concentration device according to claim 2 , wherein the prescribed value of the oxygen concentration sensor is 90% or less and the prescribed operating time of the adsorption cylinder is 2000 hours or more.