Propagation measurement method, gas flow rate measurement method, propagation measurement program, gas flow rate measurement program, gas flow rate measurement device, and oxygen concentrator

Abstract

To provide a propagation measurement method which allows for accurately measuring propagation time of an ultrasonic wave by accurately grasping the propagation state of the ultrasonic wave.SOLUTION: A propagation measurement method provided herein comprises: alternately transmitting an ultrasonic pulse group comprising multiple pulses to propagate the same in a measurement flow path; setting an initial measurement waiting time value (S21); detecting a reference pulse reception time; and deriving the propagation time of the pulses in the measurement flow path from the sum of the initial measurement waiting time value and the reference pulse reception time (S22).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a propagation measurement method for measuring the propagation state of ultrasonic waves emitted from an ultrasonic sensor, and a gas flow velocity measurement method including the propagation measurement method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an ultrasonic gas concentration flow rate measuring device that measures the flow rate and concentration of a gas by arranging ultrasonic transmitters and receivers opposite each other in a measurement flow path in a measurement pipe through which a gas flows (see, for example, Patent Document 1).

[0003] Such gas concentration flow rate measuring devices are also used in oxygen concentrators. As shown in Patent Document 2, an oxygen concentrator is a device that, for example, compresses air, removes nitrogen from the air, and generates highly concentrated oxygen. Note that an oxygen concentrator is a device used to supply oxygen to patients who must receive oxygen at home due to, for example, respiratory failure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6305209 [Patent Document 2] Patent No. 5499265 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, in an ultrasonic gas concentration flow rate measuring device, the flow rate of the gas is calculated based on the difference between the speed at which the ultrasonic wave emitted from the ultrasonic sensor on the upstream side of the gas flow in the measurement flow path propagates and the speed at which the ultrasonic wave emitted from the ultrasonic sensor on the downstream side propagates, and the flow rate and concentration of the gas are calculated and measured based on this flow rate. Therefore, in order to measure the flow rate and concentration of the gas more accurately, it is necessary to correctly grasp the propagation state of the ultrasonic wave in the measurement flow path.

[0006] Therefore, the present invention provides a propagation measurement method and the like that can accurately measure the propagation time of ultrasonic waves by accurately grasping the propagation state of the ultrasonic waves.

[0007] A propagation measurement method according to one aspect of the present invention is a propagation measurement method for measuring the propagation status in a measurement flow path of ultrasonic waves emitted from a pair of ultrasonic sensors arranged respectively on the upstream and downstream sides of a measurement flow path through which gas can flow, and includes the steps of alternately emitting a pulse group of ultrasonic waves including a plurality of pulses in a forward direction from the upstream ultrasonic sensor toward the downstream ultrasonic sensor and in a reverse direction from the downstream ultrasonic sensor toward the upstream ultrasonic sensor to propagate the ultrasonic waves through the measurement flow path, setting an initial measurement waiting time value which is the time from when a reference pulse of the pulse group is emitted from one of the ultrasonic sensors to when a leading pulse of the pulse group that is further forward in the propagation direction than the reference pulse is estimated to be received by the other ultrasonic sensor, detecting a reference pulse reception time from when it is estimated that the leading pulse will be received by the other ultrasonic sensor to when the reference pulse is received by the other ultrasonic sensor, and calculating the propagation time of the pulse in the measurement flow path from the sum of the initial measurement waiting time value and the reference pulse reception time.

[0008] The above-mentioned propagation measurement method further includes a step of calculating an updated measurement waiting time by subtracting a predetermined adjustment value for waiting time calculation from the propagation time, and a step of replacing the measurement waiting time initial value with the updated measurement waiting time, and a step of detecting the reference pulse reception time using the updated measurement waiting time, and a step of calculating the propagation time are executed again.

[0009] The above propagation measurement method may further include a step of determining whether the post-update measurement waiting time is within a predetermined range after calculating the post-update measurement waiting time, and a step of correcting the post-update measurement waiting time by adding a predetermined waiting time correction value to the post-update measurement waiting time only if the post-update measurement waiting time is outside the predetermined range.

[0010] The above propagation measurement method includes a step of calculating the propagation time until the post-update measurement waiting time becomes a value within a predetermined range, a step of calculating the post-update measurement waiting time, and measurement The step of correcting the latency may be repeated.

[0011] In the above propagation measurement method, in the step of determining whether the post-update measurement waiting time is a value within a predetermined range, the determination may be made based on a molecular weight of the gas calculated based on the sound speed in the measurement flow path obtained from the propagation time of the pulse in the forward direction and the propagation time of the pulse in the reverse direction.

[0012] In the above propagation measurement method, measurement In the step of correcting the waiting time, a waiting time correction value may be added to the post-update measurement waiting time such that the post-update measurement waiting time becomes longer in each of the forward direction and the reverse direction when the molecular weight of the gas becomes smaller than a predetermined minimum threshold, or a waiting time correction value may be added to the post-update measurement waiting time such that the post-update measurement waiting time becomes shorter in each of the forward direction and the reverse direction when the molecular weight of the gas becomes larger than a predetermined maximum threshold.

[0013] In the above propagation measurement method, in the step of determining whether the post-update measurement waiting time is a value within a predetermined range, the determination may be made based on whether a difference between the propagation time of the pulse in the forward direction and the propagation time in the reverse direction is greater than a predetermined maximum value.

[0014] In the above propagation measurement method, measurement In the step of correcting the latency, the post-update measurement latency for the pulse in the reverse direction may be made to match the post-update measurement latency for the pulse in the forward direction, or a latency correction value may be added to the post-update measurement latency for the pulse in the forward direction so as to match the post-update measurement latency for the pulse in the reverse direction.

[0015] In the above-mentioned propagation measurement method, in the step of determining whether the updated measurement waiting time is a value within a predetermined range, the determination may be made based on whether an amount of change in the propagation time becomes greater than a predetermined maximum amount of change after the step of calculating the propagation time is executed again.

[0016] In the above propagation measurement method, the waiting time calculation adjustment value is t inv_ost When the reference pulse is the N1th pulse in the group of pulses, the preceding pulse is the N2th pulse in the group of pulses, and the period of the pulse is X, the waiting time calculation adjustment value may satisfy the following formula (1): <t inv_ost <(N1 - N2) × X (1)

[0017] In the above propagation measurement method, the step of detecting the reference pulse reception time and the step of calculating the propagation time are executed multiple times using the same measurement waiting time initial value and the same updated measurement waiting time, and when a group of multiple values ​​obtained by executing the step of calculating the propagation time multiple times using the same measurement waiting time initial value and the same updated measurement waiting time is defined as a group of sample values ​​under the same conditions, each for the same measurement waiting time initial value and the same updated measurement waiting time, the step of calculating the propagation time may use an average value obtained by excluding at least a portion of the group of sample values ​​under the same conditions other than the median of the group of sample values ​​under the same conditions from the group of sample values ​​under the same conditions as the propagation time.

[0018] A gas flow rate measuring method according to one aspect of the present invention includes the steps of: blocking the inflow of gas into the measurement flow path; executing the above-mentioned propagation measuring method while the inflow of gas into the measurement flow path is blocked; flowing gas into the measurement flow path after execution of the propagation measuring method; measuring a gas inflow propagation time, which is the time it takes for the pulse to propagate in the measurement flow path while gas is flowing into the measurement flow path; and a flow rate calculating step of calculating a flow rate of gas in the measurement flow path based on the gas inflow propagation time in the forward direction and the gas inflow propagation time in the reverse direction. The step of measuring the gas inflow propagation time includes detecting the preceding pulse with the other ultrasonic sensor. The method includes the steps of: detecting a gas inflow reference pulse reception time from the time it is estimated that the reference pulse will be received to the time the reference pulse is received by the other ultrasonic sensor; calculating a gas inflow propagation time of the pulse in the measurement flow path from the sum of the post-update measurement waiting time and the gas inflow reference pulse reception time; calculating a gas inflow post-update measurement waiting time by subtracting the waiting time calculation adjustment value from the gas inflow propagation time; and replacing the post-update measurement waiting time with the gas inflow post-update measurement waiting time, and re-executing the step of detecting the gas inflow reference pulse reception time using the gas inflow post-update measurement waiting time and the step of calculating the gas inflow propagation time.

[0019] In the above-mentioned gas flow velocity measurement method, the step of setting the measurement waiting time initial value may include calculating the speed of sound in the measurement flow path from the gas temperature and the molecular weight of the gas, and dividing the length of the measurement flow path in the propagation direction by the speed of sound to calculate the measurement waiting time initial value.

[0020] A propagation measurement program according to one aspect of the present invention is for measuring the propagation status of ultrasonic waves emitted from a pair of ultrasonic sensors arranged respectively on the upstream and downstream sides of a measurement flow path through which gas can flow. The program causes a computer to function as: a sensor operation means for alternately emitting a group of ultrasonic pulses including a plurality of pulses in a forward direction from the upstream ultrasonic sensor to the downstream ultrasonic sensor and in a reverse direction from the downstream ultrasonic sensor to the upstream ultrasonic sensor, thereby propagating the group of ultrasonic pulses through the measurement flow path; a latency initial value setting means for setting a measurement latency initial value which is the time from when a reference pulse of the group of pulses is emitted from one of the ultrasonic sensors to when a leading pulse that is further forward in the propagation direction than the reference pulse of the group of pulses is estimated to be received by the other ultrasonic sensor; a pulse detection means for detecting a reference pulse reception time from when it is estimated that the leading pulse will be received by the other ultrasonic sensor to when the reference pulse is received by the other ultrasonic sensor; and a propagation time calculation means for calculating the propagation time of the pulse in the measurement flow path from the sum of the measurement latency initial value and the reference pulse reception time.

[0021] In the above propagation measurement program, the computer may further function as an updated waiting time calculation means for calculating an updated measurement waiting time by subtracting a predetermined waiting time calculation adjustment value from the propagation time, and a waiting time update means for replacing the measurement waiting time initial value with the updated measurement waiting time, and the computer may again function as the pulse detection means and the propagation time calculation means using the updated measurement waiting time.

[0022] A gas flow velocity measurement program according to one aspect of the present invention causes the computer to function as: a gas blocking means for blocking the inflow of gas into the measurement flow path; a gas blocking time propagation measurement means for executing the above-mentioned propagation measurement program while the inflow of gas into the measurement flow path is blocked; a gas inflow means for causing gas to flow into the measurement flow path after the propagation measurement program is executed; a gas inflow time propagation measurement means for measuring a gas inflow time propagation time which is the time it takes for the pulse to propagate in the measurement flow path while gas is flowing into the measurement flow path; and a flow velocity calculation means for calculating a gas flow velocity in the measurement flow path based on the gas inflow time propagation time in the forward direction and the gas inflow time propagation time in the reverse direction, the gas inflow propagation time calculation means calculating a gas inflow propagation time of the pulse in the measurement flow path from the post-update measurement waiting time to the time the reference pulse is received by the other ultrasonic sensor; post-gas inflow update waiting time calculation means calculating a gas inflow post-update measurement waiting time by subtracting the waiting time calculation adjustment value from the gas inflow propagation time; and waiting time replacement means replacing the post-update measurement waiting time with the gas inflow post-update measurement waiting time, and the computer is caused to function again as the gas inflow pulse detection means and the gas inflow propagation time calculation means using the gas inflow post-update measurement waiting time.

[0023] A gas flow velocity measuring device according to one aspect of the present invention includes a measurement unit that forms a measurement flow path through which gas flows, a valve that adjusts the inflow of gas into the measurement flow path, a pair of ultrasonic sensors that are arranged on the upstream and downstream sides of the measurement flow path, a temperature sensor that measures the temperature of the gas, and a calculation device that calculates a flow velocity of gas based on the time it takes for an ultrasonic wave emitted from one of the ultrasonic sensors to propagate through the measurement flow path and the time it takes for an ultrasonic wave emitted from the other ultrasonic sensor to propagate through the measurement flow path, the calculation device including an opening / closing operation unit that adjusts the opening of the valve, and a sensor operation unit that, in a closed state in which the valve blocks the inflow of gas into the measurement flow path, alternately transmits a pulse group of the ultrasonic wave, including a plurality of pulses, in a forward direction from the upstream ultrasonic sensor to the downstream ultrasonic sensor and in a reverse direction from the downstream ultrasonic sensor to the upstream ultrasonic sensor, thereby propagating the ultrasonic wave through the measurement flow path, and a calculation device that estimates that, in the closed state, after a reference pulse of the pulse group is transmitted from one of the ultrasonic sensors, a leading pulse of the pulse group that is forward in the propagation direction of the reference pulse is received by the other ultrasonic sensor. a pulse detection unit that detects a reference pulse reception time from when the preceding pulse is estimated to be received by the other ultrasonic sensor to when the reference pulse is received by the other ultrasonic sensor in the closed state; a propagation time calculation unit that calculates a propagation time of the pulse in the measurement flow path from the sum of the measurement propagation time initial value and the reference pulse reception time in the closed state; and an updated measurement propagation time calculation unit that calculates a propagation time of the pulse in the measurement flow path by subtracting a predetermined waiting time calculation adjustment value from the propagation time in the closed state. and a wait time update unit that, in the closed state, replaces the measurement wait time initial value with the updated measurement wait time, wherein the pulse detection unit detects the reference pulse reception time again using the updated measurement wait time, and the propagation time calculation unit recalculates the propagation time using the updated measurement wait time, and the arithmetic device, in an open state in which the valve is allowing gas to flow into the measurement flow path, calculates a time from when it is estimated that the preceding pulse transmitted from one of the ultrasonic sensors has been received by the other ultrasonic sensor,a gas inflow pulse detection unit that detects a gas inflow reference pulse reception time from when the reference pulse transmitted from one of the ultrasonic sensors is received by the other ultrasonic sensor; a gas inflow propagation time calculation unit that calculates a gas inflow propagation time, which is the time it takes for the pulse to propagate in the measurement flow path, from the sum of the post-update measurement waiting time and the gas inflow reference pulse reception time in the open state; and a gas inflow post-update waiting time calculation unit that calculates a gas inflow post-update measurement waiting time by subtracting the waiting time calculation adjustment value from the gas inflow propagation time in the open state. and a gas inflow waiting time updating unit that replaces the updated measurement waiting time with the gas inflow updated measurement waiting time, the gas inflow pulse detection unit detects the gas inflow reference pulse reception time again using the gas inflow updated measurement waiting time, and the gas inflow propagation time calculation unit calculates the gas inflow propagation time again using the gas inflow updated measurement waiting time, and the arithmetic device further includes a flow velocity calculation unit that calculates a flow velocity of the gas in the measurement flow path based on the gas inflow propagation time in the forward direction and the gas inflow propagation time in the reverse direction.

[0024] An oxygen concentrator according to one embodiment of the present invention comprises the above-mentioned gas flow rate measuring device that calculates the flow rate of an oxygen-containing gas, and a concentrator main body provided with the gas flow rate measuring device, and the calculation device further has a flow rate concentration calculation unit that calculates the flow rate of the oxygen-containing gas and the oxygen concentration in the oxygen-containing gas based on the flow rate of the oxygen-containing gas. Effect of the Invention

[0025] According to the above-mentioned propagation measurement method, it is possible to accurately grasp the propagation state of ultrasonic waves and accurately measure the propagation time of ultrasonic waves. [Brief description of the drawings]

[0026] [Figure 1] 1 is an overall view of an oxygen concentrator according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram showing a configuration of the oxygen concentrator. [Diagram 3] FIG. 2 is a block diagram of a gas flow rate measuring device in the oxygen concentrator. [Figure 4] 3A and 3B are diagrams showing ultrasonic waves emitted from an ultrasonic sensor of the gas flow velocity measuring device. [Diagram 5] FIG. 2 is a functional block diagram of a calculation unit of the gas flow velocity measuring device. [Figure 6] 11 is a flowchart of a flow velocity measurement program executed in the computing device, showing the state while the inflow of gas into the measurement flow path is blocked. FIG. [Figure 7] 11 is a flowchart of a flow velocity measurement program executed in the arithmetic device, illustrating the state during which gas flows into the measurement flow path. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. (Overall composition) 1 and 2, the oxygen concentrator 1 of this embodiment is a device that supplies oxygen to a patient, concentrating air GA taken in from the outside to generate a high-concentration (for example, about 90%) oxygen-containing gas G. Specifically, the oxygen concentrator 1 includes a concentrator main body 100 having an intake filter 11, a compressor 12, a nitrogen adsorption mechanism 13, a tank 14, and a housing 120 (see FIG. 1), and a gas flow rate measuring device 15 incorporated in the concentrator main body 100.

[0028] In the oxygen concentrator 1, air GA taken in from the outside through an intake filter 11 provided on the back of a housing 120 is compressed by a compressor 12, and nitrogen contained in the compressed air GA is adsorbed by a catalyst (not shown) by a nitrogen adsorption mechanism 13 to generate an oxygen-containing gas (gas containing oxygen and nitrogen) G containing a high concentration of oxygen, which can be supplied to a patient. Hereinafter, the oxygen-containing gas G will be simply referred to as "gas G".

[0029] Here, as shown in FIG. 2, the nitrogen adsorption mechanism 13 includes a pair of adsorption towers 13a and 13b. A catalyst such as zeolite is filled in the pair of adsorption towers 13a and 13b. One of the adsorption towers 13a and 13b is pressurized to adsorb nitrogen to the catalyst, and the other is depressurized to release the nitrogen adsorbed to the catalyst and prepare for the next pressurization. In this way, in the nitrogen adsorption mechanism 13, the pair of adsorption towers 13a and 13b are alternately pressurized and depressurized to generate high-concentration oxygen. The high-concentration oxygen generated by the nitrogen adsorption mechanism 13 is stored in the tank 14. The oxygen stored in the tank 14 is supplied to the patient as gas G after passing through a gas flow rate measuring device 15. That is, the oxygen concentrator 1 of this embodiment employs a PSA (Pressure Swing Adsorption) method.

[0030] stomach Here, each component part of the oxygen concentrator 1 is centrally controlled by a control unit (not shown). The control unit is composed of a CPU, RAM, ROM, etc., and executes various controls. The CPU is a so-called central processing unit, and executes various programs to realize various functions. The RAM is used as a working area for the CPU. The ROM stores programs executed by the CPU (for example, a propagation measurement program and a gas flow velocity measurement program, which will be described later).

[0031] 1, the housing 120 has a substantially rectangular parallelepiped shape. The housing 120 is provided with an operation button 121, a display 122, and a discharge tube (such as a rubber tube) 123 that is connected to the gas flow velocity measuring device 15 and discharges the gas G.

[0032] (Gas flow rate measuring device) Next, the gas flow rate measuring device 15 will be described in detail. The gas flow rate measuring device 15 is incorporated in a housing 120. As shown in Fig. 2, the gas flow rate measuring device 15 is provided downstream of the tank 14 to measure the flow rate of the gas G, and is capable of calculating (measuring) the concentration and flow rate of oxygen in the gas G based on this flow rate. More specifically, as shown in Fig. 3, the gas flow rate measuring device 15 is an ultrasonic measuring device, and includes a measuring unit 20, a temperature sensor 30, a computing device 40, an ultrasonic sensor 60, a pressure sensor 70, and a proportional valve 80.

[0033] (Temperature Sensor) The temperature sensor 30 is provided on the surface of the device substrate 50. The temperature sensor 30 is capable of measuring the temperature of a gas G flowing through a measurement flow path F, which will be described later, for example, on the downstream side of the measurement flow path F.

[0034] (Pressure Sensor) The pressure sensor 70 is provided on the surface of the device substrate 50, similar to the temperature sensor 30. The pressure sensor 70 is capable of measuring the pressure of gas G flowing through a measurement flow path F, which will be described later, for example, on the upstream side of the measurement flow path F. The pressure of gas G measured by the pressure sensor 70 is used, for example, in calculations in the calculation device 40, which will be described later, when determining a constant that may vary depending on the pressure.

[0035] (Measurement part) The measurement unit 20 is provided on the surface of the device substrate 50, similar to the temperature sensor 30 and the pressure sensor 70. The measurement unit 20 is cylindrical and has a measurement flow path F formed therein through which gas G flows from the tank 14 (see FIG. 3). In addition, an inlet flow path 24 for introducing gas G into the measurement flow path F is formed at the upstream end of the measurement flow path F in the measurement unit 20, and an outlet flow path 25 for guiding gas G from the measurement flow path F is formed at the downstream end of the measurement flow path F. The inlet flow path 24 and the outlet flow path 25 extend along the surface of the device substrate 50 in a direction perpendicular to the direction in which the measurement flow path F extends. The measurement unit 20 is formed of a resin material, such as ABS resin.

[0036] (Proportional valve) The proportional valve 80 is disposed on the surface of the device substrate 50 and is provided further upstream of the inlet flow path 24. The proportional valve 80 controls the flow rate of the gas G flowing through the measurement flow path F by being opened and closed based on a numerical value designated by an operation button 121 (see FIG. 1 ) of the concentrating device main body 100.

[0037] (Ultrasonic Sensor) A pair of ultrasonic sensors 60 are provided, one on the upstream side and one on the downstream side of the measurement flow path F. The ultrasonic sensors 60 are arranged facing each other in the direction in which the measurement flow path F extends. Each ultrasonic sensor 60 has an ultrasonic element (not shown) that is a transmitter / receiver capable of transmitting and receiving ultrasonic waves. The ultrasonic wave transmitted from the ultrasonic sensor 60A on the upstream side of the measurement flow path F can be received by the ultrasonic sensor 60B on the downstream side of the measurement flow path F. On the other hand, the ultrasonic wave transmitted from the ultrasonic sensor 60B on the downstream side of the measurement flow path F can be received by the ultrasonic sensor 60A on the upstream side of the measurement flow path F. A comparator circuit (not shown) is connected to each ultrasonic sensor 60, and the received ultrasonic wave is converted into a square wave.

[0038] As shown in Fig. 4, the ultrasonic sensor 60 transmits a pulse group PG of ultrasonic waves including a plurality of pulses PU. The pulse group PG is transmitted alternately from the upstream ultrasonic sensor 60A and the downstream ultrasonic sensor 60B. In this embodiment, the pulse group PG includes, for example, five or more pulses PU.

[0039] Hereinafter, the propagation direction of the pulse group PG emitted from the upstream ultrasonic sensor 60A toward the downstream side is referred to as the forward direction, and the propagation direction of the pulse group PG emitted from the downstream ultrasonic sensor 60B toward the upstream side is referred to as the reverse direction. The propagation direction of the pulse group PG coincides with the direction in which the measurement flow path F extends, i.e., the longitudinal direction of the measurement unit 20. Note that the propagation direction of the pulse group PG may intersect with the longitudinal direction of the measurement unit 20, as long as the pulse group PG has at least a component that travels from the upstream side (downstream side) to the downstream side (upstream side) of the measurement flow path F.

[0040] In addition, the N1-th pulse PU in the pulse group PG is called a reference pulse PU1, and the N2-th pulse PU, which is a pulse PU ahead of the reference pulse PU1 in the propagation direction, is called a leading pulse PU2. In this embodiment, a case where N1=5 and N2=4 will be described as an example. That is, the reference pulse PU1 indicates the fifth pulse PU in the pulse group PG, and the leading pulse PU2 indicates the fourth pulse PU in the pulse group PG.

[0041] (computing device) The arithmetic device 40 is a computer and is composed of a CPU, RAM, ROM, etc. The CPU is a so-called central processing unit, which executes various programs to realize various functions. The RAM is used as a working area for the CPU. The ROM stores the programs executed by the CPU. The arithmetic device 40 is electrically connected, for example, to the back surface of the device substrate 50, which is opposite to the front surface (see FIG. 3).

[0042] As shown in FIG. 5, the calculation device 40 has an opening / closing operation unit 200, a sensor operation unit 201, a waiting time initial value setting unit 202, an initial pulse detection unit 203, an initial propagation time calculation unit 204, an initial updated waiting time calculation unit 205, an initial waiting time judgment unit 206, an initial waiting time correction unit 207, an initial waiting time update unit 208, a gas inflow pulse detection unit 220, a gas inflow propagation time calculation unit 221, a gas inflow updated waiting time calculation unit 222, a gas inflow waiting time judgment unit 223, a gas inflow waiting time correction unit 224, a gas inflow waiting time update unit 225, a flow velocity calculation unit 226, and a flow rate concentration calculation unit 227.

[0043] The opening / closing operation unit 200 adjusts the opening of the proportional valve 80 to change the amount of gas G flowing into the measurement flow path F. The initial sensor operation unit 201 operates the ultrasonic sensor 60 to transmit the pulse groups PG alternately in the forward and reverse directions as described above, and propagate them within the measurement flow path F.

[0044] <Initial operation> The waiting time initial value setting unit 202 sets a measurement waiting time initial value t 1inv Set the measurement wait time initial value t 1inv are set for both the forward and reverse pulse groups PG, respectively.

[0045] In this embodiment, the measurement waiting time initial value t 1inv [μs] is the temperature of the gas G measured by the temperature sensor 30. gas [°C], the molecular weight of gas G is M [g / mol], the specific heat ratio of gas G is k, the gas constant is R, the absolute zero is T0 [°C], the sound speed in the measurement flow path F is c [m / s], and the length in the propagation direction of the ultrasonic wave in the measurement flow path F is L [m], which is calculated and set by the following formulas (1) and (2). Note that constants such as the molecular weight M, the specific heat ratio k, the gas constant R, the absolute zero is T0, and the length L of the measurement flow path F are stored in advance in the calculation device 40.

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[0046] When it is estimated that the other ultrasonic sensor 60 receives the leading pulse PU2 in the closed state, the initial pulse detection unit 203 detects the measurement waiting time initial value t 1invThe reference pulse reception time t2 [μs] from the time when the leading pulse PU2 has elapsed until the reference pulse PU1 is received by the other ultrasonic sensor 60 is detected by an external interrupt. The external interrupt starts when it is estimated that the leading pulse PU2 will be received by the other ultrasonic sensor 60, that is, while the amplitude of the leading pulse PU2 is at its maximum. After the external interrupt starts, the reference pulse PU1 is detected at the timing when the amplitude of the reference pulse PU1 changes from its minimum to its maximum (reference pulse PU1 detection timing). The reference pulse reception time t2 from the start of the external interrupt to the reference pulse PU1 detection timing is detected for both the forward and reverse pulse groups PG. In this embodiment, the initial pulse detection unit 203 detects a reference pulse PU1 for each of a plurality of (for example, 10) pulse groups PG. 1inv The detection of the reference pulse PU1 is performed multiple times using

[0047] In the closed state, the initial propagation time calculation unit 204 calculates the measurement waiting time initial value t 1inv The propagation time t3 [μs] of the pulse PU in the measurement flow path F is calculated from the sum of the reference pulse reception time t2 and the forward pulse group PG. The propagation time t3 is calculated for both the forward and reverse pulse groups PG. Hereinafter, the propagation time of the forward pulse PU is referred to as t 3(f) The propagation time of the reverse pulse PU is t 3(b) Let us assume that.

[0048] In this embodiment, the initial propagation time calculation unit 204 calculates a measurement wait time initial value t 1inv and the reference pulse reception time t2. That is, the same measurement waiting time initial value t 1inv Using this, the measurement waiting time initial value t 1inv and the reference pulse reception time t2. 3msr The calculation of is performed multiple times.

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[0049] In the closed state, the initial post-update waiting time calculation unit 205 calculates a waiting time calculation adjustment value t from the propagation time t3 by the following equation (4): inv_ost [μs] is subtracted to calculate the post-update measurement waiting time t1. The post-update measurement waiting time t1 is calculated for both the forward and reverse pulse groups PG.

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[0050] Here, as described above, in the case where the reference pulse PU1 is the N1th pulse PU of the pulse group PG, and the leading pulse PU2 is the N2th pulse of the pulse group PG, when the period of the pulse PU is X, the waiting time calculation adjustment value t inv_ost is calculated by the following formula (5).

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[0051]

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[0052] The initial waiting time determination unit 206 determines whether the post-update measurement waiting time t1 is within a predetermined range in the above-mentioned closed state, because the post-update measurement waiting time t1 should be within a predetermined range to some extent in a situation where there is no flow of the gas G.

[0053] In the closed state, only when the updated measurement waiting time t1 is outside a predetermined range, the initial waiting time correction unit 207 sets the updated measurement waiting time t1 to a predetermined waiting time correction value t c_ost The updated measurement waiting time t1 is corrected by adding the waiting time correction value t c_ost exists for both positive and negative values.

[0054] First, the initial latency correction unit 207 calculates the propagation time t 3(f) and the propagation time of the pulse PU in the opposite direction t 3(b) If the difference between the pulse width and the pulse width is greater than a predetermined maximum value, the post-update measurement waiting time t 1(b) The measurement waiting time t after updating the forward pulse PU 1(f) or the post-update measurement waiting time t 1(f) The waiting time after updating the measurement in the reverse direction pulse PU is t 1(b) The latency correction value t c_ost is added to the updated measurement waiting time t1. Here, the forward pulse PU propagation time t 3(f) and the propagation time of the pulse PU in the opposite direction t 3(b) The maximum difference from is a value determined based on the specifications of the oxygen concentrator 1, and is a value determined by the maximum flow rate of the gas G flowing through the measurement flow path F, the length L of the measurement flow path F, and the like.

[0055] Next, the initial waiting time correction unit 207 corrects the propagation time t of the forward pulse PU calculated by the initial propagation time calculation unit 204 using the updated measurement waiting time t1. 3(f) and the propagation time of the pulse PU in the opposite direction t 3(b) The sound speed c1 in the measurement flow path F obtained from the above is calculated by the following formula (7), and the molecular weight M1 of the gas G is calculated by the following formula (8).

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[0056] In the closed state, the initial waiting time update unit 208 updates the measurement waiting time initial value t 1inv is replaced with the measurement waiting time t1 after updating.

[0057] <Initial operation> The gas inflow pulse detection unit 220 is configured to detect a gas inflow reference pulse reception time t from the time when the leading pulse PU2 is estimated to be received by the other ultrasonic sensor 60 to the time when the reference pulse PU1 is received by the other ultrasonic sensor 60 in a state where the proportional valve 80 is allowing gas G to flow into the measurement flow path F (hereinafter referred to as an open state). 2X is detected by an external interrupt. The external interrupt starts when it is estimated that the leading pulse PU2 is received by the other ultrasonic sensor 60, that is, while the amplitude of the leading pulse PU2 is at its maximum. The reference pulse PU1 is detected at the timing when the amplitude of the reference pulse PU1 changes from its minimum to its maximum. The gas inflow reference pulse reception time t 2X are detected for both the forward and reverse pulse groups PG, respectively. In this embodiment, the gas inflow pulse detection unit 220 detects the reference pulse PU1 for each of a plurality of (for example, 10) pulse groups PG. That is, detection of the reference pulse PU1 is executed a plurality of times using the same post-update measurement waiting time t1.

[0058] In the above-mentioned open state, the gas inflow propagation time calculation unit 221 calculates the updated measurement waiting time t1 and the gas inflow reference pulse reception time t 2X From the sum of these, the gas inflow propagation time t 3X Calculate the gas inflow propagation time t 3X is calculated for both the forward and reverse pulse groups PG. In the following, the propagation time of the forward pulse PU at the gas inflow time is defined as t 3X(f) The propagation time of the reverse pulse PU at the time of gas inflow is t 3X(b) Let us assume that.

[0059] In this embodiment, the gas inflow propagation time calculation unit 221 calculates the updated measurement waiting time t1 and the gas inflow reference pulse reception time t 2X That is, by using the same updated measurement waiting time t1, the following equation (10) is used to calculate the sum of the updated measurement waiting time t1 and the reference pulse reception time t 2X The value t 3Xmsr The calculation of is performed multiple times.

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[0060] In the above-mentioned open state, the gas inflow post-update waiting time calculation unit 222 calculates the gas inflow propagation time t 3X From the above waiting time calculation adjustment value t inv_ost Subtract t from the measurement waiting time after updating when gas flows in. 1X Calculate the measurement waiting time after updating at gas inflow t 1X are calculated for both the forward and reverse pulse groups PG, respectively.

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[0061] In the open state, the gas inflow waiting time determination unit 223 determines the post-update measurement waiting time t 1X It is determined whether or not the value is within a predetermined range.

[0062] The gas inflow waiting time correction unit 224 corrects the gas inflow updated measurement waiting time t 1X Only when the value is outside the predetermined range, the measurement waiting time t after updating at the time of gas inflow is 1X The above latency correction value t c_ost By adding 1X Correct the following. Similarly to the initial latency correction unit 207, the gas inflow latency correction unit 224 first calculates the gas inflow propagation time t 3X(f) The propagation time of the pulse PU in the opposite direction at the time of gas inflow is t 3X(b) When the difference between the pulse width and the measured value is greater than a predetermined maximum value, the measurement waiting time t after updating the gas inflow in the reverse direction pulse PU is 1X(b) The measurement waiting time t after updating the gas inflow at the forward pulse PU 1X(f) or the post-update measurement waiting time t 1X(f) The waiting time after updating the measurement in the reverse direction pulse PU is t 1X(b) The latency correction value t c_ost After updating the measurement waiting time t 1X Add to.

[0063] Next, the gas inflow waiting time correction unit 224 calculates the gas inflow propagation time updated measurement waiting time t 1X The forward pulse PU gas inflow propagation time t 3X(f) The propagation time of the pulse PU in the opposite direction at the time of gas inflow is t 3X(b) The sound velocity c in the measurement flow path F is calculated from 1X is calculated by the following formula (12), and the molecular weight M of the gas G is calculated by the following formula (13). 1X Calculate.

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[0064] In the open state, the gas inflow waiting time update unit 225 updates the post-update measurement waiting time t1 to the post-update measurement waiting time t 1X Replace with.

[0065] The flow velocity calculation unit 226 calculates the forward gas inflow propagation time t 3X(f) and the propagation time t 3X(b) Based on this, the flow velocity v [m / s] of the gas in the measurement flow path F is calculated.

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[0066] The flow rate concentration calculation unit 227 calculates the flow rate Q [m 3 / s] is calculated. The cross-sectional area of ​​the measurement flow path F is A [m 2 The proportional valve 80 is controlled by the control unit so that the calculated flow rate Q becomes a preset flow rate.

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[0067] In addition, the flow rate concentration calculation unit 227 calculates the molecular weight M 1X Based on this, the oxygen concentration P in gas G is calculated using the following equation (16): O2 Calculate [%]. Note that M O2 [g / mol] is the molecular weight of oxygen, M N2 [g / mol] is the molecular weight of nitrogen. M O2 =32, M N2 = 28. The oxygen and nitrogen adsorption mechanism 13 is controlled by the control unit so that the calculated oxygen concentration becomes a preset value.

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[0068] Next, a procedure for executing the gas flow velocity measurement program (gas flow velocity measurement method) will be described with reference to FIGS. 6, first, the inflow of gas G into the measurement flow path F is blocked. That is, the proportional valve 80 is closed by the opening / closing operation unit (gas blocking means) 200 (step S1). Next, a propagation measurement program (propagation measurement method) is executed in a state where the inflow of gas G into the measurement flow path F is blocked (step S2).

[0069] In step S2, the waiting time initial value setting unit 202 first sets the measurement waiting time initial value t 1inv(Step S21). Then, after a predetermined time has elapsed since execution of step S1, the ultrasonic sensor 60 is operated by the sensor operation unit to transmit pulse groups PG alternately in the forward and reverse directions, the initial pulse detection unit 203 detects the reference pulse reception time t2, and the initial propagation time calculation unit 204 calculates the propagation time t3 of the pulse PU in the measurement flow path F (Step S22).

[0070] Furthermore, in step S2, the initial post-update waiting time calculation unit 205 calculates the post-update measurement waiting time t1, and the initial waiting time determination unit 206 determines whether the post-update measurement waiting time t1 is within a predetermined range. If the post-update measurement waiting time t1 is outside the predetermined range, the initial waiting time correction unit 207 corrects the post-update measurement waiting time t1.

[0071] Specifically, the post-update measurement waiting time t1 is determined by first measuring the propagation time t 3(f) and the propagation time of the pulse PU in the opposite direction t 3(b) It is then determined whether the difference between the propagation time t 3(f) and propagation time t 3(b) If it is determined that the difference between the propagation time t 3(f) and propagation time t 3(b) If it is determined that the difference between the measured molecular weight M1 and the measured molecular weight M2 is equal to or smaller than the predetermined maximum value, it is determined whether the molecular weight M1 is greater than the predetermined maximum molecular weight and whether the molecular weight M1 is smaller than the predetermined minimum molecular weight (step S25). If the molecular weight M1 is greater than the predetermined maximum molecular weight or is smaller than the predetermined minimum molecular weight, the post-update measurement waiting time t1 is corrected (step S26). After correcting the post-update measurement waiting time t1 in steps S24 and S26, the process returns to step S22 to calculate the propagation time t3 and again determine whether the post-update measurement waiting time t1 needs to be corrected. Steps S22 to S26 are repeated until the post-update measurement waiting time t1 becomes a value within the predetermined range.

[0072] Furthermore, in step S2, if the updated measurement waiting time t1 is within a predetermined range, the initial waiting time update unit 208 updates the measurement waiting time initial value t 1inv is replaced with the updated measurement waiting time t1 (step S27). After step S27, the propagation time t3 is calculated again (step S28), and the propagation measurement program (step S2) is terminated.

[0073] After the propagation measurement program (step S2) is executed, gas G is caused to flow into the measurement flow path F as shown in Fig. 7. That is, the proportional valve 80 is opened by the opening / closing operation unit (gas shutoff means) 200 (step S3). At this time, the proportional valve 80 is held at a predetermined opening degree, and gas G is allowed to flow into the measurement flow path F at a predetermined flow rate.

[0074] Next, the ultrasonic sensor 60 is operated by the sensor operation unit 201 to transmit a pulse group PG alternately in the forward and reverse directions, and the gas inflow time pulse detection unit 220 detects the gas inflow time reference pulse reception time t 2X The gas inflow propagation time calculation unit 221 calculates the gas inflow propagation time t 3X is calculated (step S4).

[0075] Thereafter, the gas inflow post-update waiting time calculation unit 222 calculates the gas inflow post-update measurement waiting time t 1X The gas inflow waiting time determination unit 223 calculates the post-update measurement waiting time t 1X It is judged whether the value is within a predetermined range. 1X is outside the predetermined range, the gas inflow waiting time correction unit 224 corrects the gas inflow updated measurement waiting time t X Correct the following.

[0076] Specifically, the measurement waiting time after updating at the time of gas inflow t 1X In the judgment, first, the forward pulse PU's gas inflow propagation time t 3X(f) The propagation time of the pulse PU in the opposite direction at the time of gas inflow is t3X(b) In step S5, it is determined whether the difference between the gas inflow propagation time t 3(f) and gas inflow propagation time t 3(b) When it is determined that the difference between the 1X On the other hand, in step S6, the gas inflow propagation time t 3(f) and gas inflow propagation time t 3(b) When it is determined that the difference between the molecular weight M 1X is greater than a predetermined maximum molecular weight, and the molecular weight M 1X It is then determined whether the molecular weight M is smaller than a predetermined minimum molecular weight (step S7). 1X is greater than a predetermined maximum molecular weight, or the molecular weight M 1X If the molecular weight is smaller than the predetermined minimum molecular weight, the measurement waiting time t 1X (Step S8). In Step S6 and Step S8, the measurement waiting time after updating at the time of gas inflow t 1X After correcting, return to step S4 and correct the gas inflow propagation time t 3X Calculate the measurement waiting time t 1X Steps S4 to S8 are performed to determine whether or not the measurement waiting time t 1X This is repeated until the value falls within a predetermined range.

[0077] Furthermore, the measurement waiting time after updating at the time of gas inflow t 1X is within a predetermined range, the gas inflow waiting time update unit 225 updates the post-update measurement waiting time t1 to the post-update measurement waiting time t 1X After step S9, the flow velocity calculation unit 226 calculates the forward gas inflow propagation time t 3X(f) The gas inflow propagation time in the opposite direction is t 3X(b)Based on this, the flow velocity of the gas G in the measurement flow path F is calculated (step S10), and the flow rate concentration calculation unit 227 calculates the flow rate of the gas G and the oxygen concentration in the gas G (step S11). Note that steps S10 and S11 may be performed before step S9.

[0078] After step S11, return to step S4 and measure the gas inflow propagation time t 3X The calculation of is continuously repeated. The gas flow rate measurement program can be executed while changing the opening of the proportional valve 80. The opening and closing control of the proportional valve 80 is executed while avoiding abrupt changes in the flow rate of the gas G within a range where no error occurs in the gas flow rate measurement program (within an applicable range).

[0079] In the oxygen concentrator 1 of the present embodiment described above, the measurement waiting time initial value t 1inv After setting, the measurement wait time initial value t 1inv Based on the propagation time t3 calculated from the sum of the reference pulse reception time t2 and the measurement wait time initial value t 1inv The propagation time t3 and the gas inflow propagation time t are calculated by replacing the propagation time t3 with the post-update measurement waiting time t1. 3X Therefore, it is possible to calculate the propagation time t3 and the gas inflow propagation time t4 more accurately in accordance with the actual propagation state of the pulse PU. 3X Therefore, the propagation time t3 and the gas inflow propagation time t 3X Therefore, the propagation state of the ultrasonic waves can be accurately grasped, and the propagation time of the ultrasonic waves can be accurately measured. As a result, the measurement accuracy of the flow velocity, flow rate, and concentration of the gas G can be improved.

[0080] Furthermore, the initial measurement waiting time t 1inv , the post-update measurement waiting time t1, and the post-update measurement waiting time t 1X These values ​​are corrected until they fall within a predetermined range, and then the propagation time t3 and the gas inflow propagation time t 3X In order to calculate again, the propagation time t3 and the gas inflow propagation time t3X In this embodiment, the measurement accuracy can be improved by further increasing the post-update measurement waiting time t1 and the post-update measurement waiting time t 1X These corrections are repeated until the propagation time t3 and the gas inflow propagation time t 3X It is possible to improve the measurement accuracy.

[0081] The measurement waiting time initial value t 1inv , the post-update measurement waiting time t1, and the post-update measurement waiting time t 1X The presence or absence of correction is determined by the propagation time t3 of the forward and reverse pulse PU (propagation time t 3X ) and the molecular weights M1, M2, and M3 of the gas G are determined based on the difference 1X Therefore, the determination is made in two stages based on the post-update measurement waiting time t1 and the post-update measurement waiting time t 1X This can improve the accuracy of determining whether or not correction is required.

[0082] For example, immediately after the operation of the oxygen concentrator 1 is stopped, the oxygen concentration of the gas G in the tank 14 is high. As time passes after the operation of the oxygen concentrator 1 is stopped, the oxygen concentration of the gas G in the measurement flow path F decreases and becomes the same as that of the atmosphere. When the operation of the oxygen concentrator 1 is started in this state, the gas G with a high oxygen concentration in the tank 14 flows into the measurement flow path F all at once. Then, the measured propagation time t3 becomes shorter than the actual value, and the molecular weight M1 calculated from this propagation time t3 may be smaller than the minimum molecular weight. Therefore, the post-update measurement waiting time t1 needs to be corrected as described above.

[0083] In addition, for example, when high temperature, high humidity, and low pressure air is present in the measurement flow path F after the operation of the oxygen concentrator 1 is stopped, the molecular weight of the gas G in the measurement flow path F becomes smaller than the average molecular weight of air, 28.9. Therefore, the measurement waiting time initial value t 1invThe actual initial value of the measurement wait time is smaller than the actual value. Then, the measured propagation time t3 becomes longer than the actual value, and the molecular weight M1 calculated from this propagation time t3 may be larger than the maximum molecular weight mentioned above. Therefore, it is necessary to correct the measurement wait time t1 after updating as described above.

[0084] Therefore, the initial measurement waiting time t 1inv , the post-update measurement waiting time t1, and the post-update measurement waiting time t 1X By making a judgment to correct the initial measurement waiting time t 1inv , the post-update measurement waiting time t1, and the post-update measurement waiting time t 1X After correcting the propagation time t3 to a more accurate value (gas inflow propagation time t 3X ) can be calculated and measured.

[0085] The waiting time calculation adjustment value t inv_ost is calculated by the above formula (5). In other words, in this embodiment, the waiting time calculation adjustment value is t inv_ost is 1 / 2 the period of the pulse PU (12.5 μs). Therefore, the time when the amplitude of the preceding pulse PU2 is at its maximum is the post-update measurement waiting time t1, and the post-update measurement waiting time t 1X Therefore, the post-update measurement waiting time t1 and the post-update measurement waiting time t 1X can be set accurately.

[0086] In addition, the propagation time t3 and the gas inflow propagation time t 3X is set to the average value obtained by removing at least a part of the values ​​other than the median value from the group of values ​​sampled under the same conditions as described above. Therefore, the propagation time t3 and the gas inflow propagation time t 3X Since noise can be eliminated when calculating the propagation time t3 and the gas inflow propagation time t 3X The accuracy can be further improved.

[0087] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention. For example, there is no particular limitation as to which of the pulse group G the reference pulse PU1 and the leading pulse PU2 are set to. For example, the reference pulse PU1 may be the fifth pulse PU, and the leading pulse PU2 may be the third pulse PU. Also, if the intensity of the first or second pulse PU of the pulse group PG is sufficient, the first or second pulse PU may be the leading pulse PU2 or the reference pulse PU1.

[0088] Furthermore, the post-update measurement waiting time t1 (post-update measurement waiting time t 1X In the step of determining whether the propagation time t3 (gas inflow propagation time t) in the forward direction and the reverse direction is within a predetermined range, 3X ) or only the molecular weight may be determined. Alternatively, the molecular weight may be determined first and then the propagation time t3 (gas inflow propagation time t 3X ) may be used. In addition, even when the determination is based on the molecular weight, the forward post-update measurement waiting time t 1(f) (Measurement waiting time after updating at gas inflow t 1X(f) ) and the post-update measurement waiting time t 1(b) (Measurement waiting time after updating at gas inflow t 1X(b) ) may be made to match.

[0089] In addition, the measurement waiting time after updating t1 (the measurement waiting time after updating at the time of gas inflow t 1X In the step of determining whether the propagation time t3 (gas inflow propagation time t 3X ) is calculated again, and then the propagation time t3 (gas inflow propagation time t 3X ) is greater than a predetermined maximum change amount. In other words, it may be determined whether the change amount of the propagation time t3 (gas inflow propagation time t 3X When the change in the waiting time correction value t c_ostAfter updating the measurement waiting time t1 (after updating the measurement waiting time t 1X ) is added to the propagation time t3 (gas inflow propagation time t 3X The maximum amount of change in the period X of the pulse PU is 1 / 2, that is, 12.5 μs in the above embodiment.

[0090] In addition, the above propagation measurement program is executed before calculating the updated measurement waiting time t1, that is, before calculating the waiting time initial value t 1inv It is also possible to carry out the steps up to the step of calculating the propagation time t3 using the above-mentioned method.

[0091] Moreover, the gas flow rate measuring device 15 can be used in devices other than the oxygen concentrator 1. Moreover, the oxygen concentrator 1 is not limited to a PSA type device, and may be a device using other methods such as a membrane separation type. [Industrial Applicability]

[0092] According to the propagation measurement method of the present invention, the propagation state of the ultrasonic wave can be accurately grasped, and therefore the propagation time of the ultrasonic wave can be accurately measured. [Explanation of symbols]

[0093] 1. Oxygen concentrator 15 Gas flow rate measuring device 20 Measuring part 30 Temperature Sensor 40 Arithmetic unit 60(60A, 60B) Ultrasonic sensor 70 Pressure Sensor 80 Proportional Valve 100 Concentration device body 200 Opening and closing operation section 201 Sensor operating part 202 Waiting time initial value setting section 203 Initial Pulse Detection Unit 204 Initial propagation time calculation unit 205 Initial update waiting time calculation unit 206 Initial waiting time judgement unit 207 Initial Latency Correction Unit 208 Initial Waiting Time Update Unit 220 Gas inflow pulse detector 221 Gas inflow propagation time calculation section 222 Gas inflow update waiting time calculation unit 223 Gas inflow waiting time judgment unit 224 Gas inflow waiting time correction unit 225 Gas inflow waiting time update unit 226 Flow velocity calculation section 227 Flow rate concentration calculation section F Measurement flow path G Oxygen-containing gas PG Pulse Group PU Pulse PU1 Reference Pulse PU2 Leading Pulse

Claims

1. A propagation measurement method for measuring a propagation state in a measurement flow path through which a gas can flow, the propagation state being measured by a pair of ultrasonic sensors respectively disposed on an upstream side and a downstream side of the measurement flow path, the method comprising: a step of alternately transmitting a group of ultrasonic pulses including a plurality of pulses in a forward direction from the ultrasonic sensor on the upstream side toward the ultrasonic sensor on the downstream side and in a reverse direction from the ultrasonic sensor on the downstream side toward the ultrasonic sensor on the upstream side, and propagating the group of ultrasonic pulses through the measurement flow path; setting an initial value of a measurement waiting time, which is a time from when a reference pulse of the pulse group is transmitted from one of the ultrasonic sensors until when a leading pulse of the pulse group that is forward in a propagation direction of the reference pulse is estimated to be received by the other ultrasonic sensor; detecting a reference pulse reception time from a time when the leading pulse is estimated to be received by the other ultrasonic sensor to a time when the reference pulse is received by the other ultrasonic sensor; calculating a propagation time of the pulse in the measurement flow path from a sum of the measurement wait time initial value and the reference pulse reception time; A propagation measurement method comprising:

2. calculating an updated measured latency time by subtracting a predetermined latency time calculation adjustment value from the propagation time; replacing the measurement wait time initial value with the updated measurement wait time; Further comprising:

2. The propagation measurement method according to claim 1, further comprising the steps of: detecting the reference pulse reception time using the updated measurement waiting time; and calculating the propagation time.

3. determining whether the post-update measurement waiting time is within a predetermined range after calculating the post-update measurement waiting time; correcting the updated measurement waiting time by adding a predetermined waiting time correction value to the updated measurement waiting time only when the updated measurement waiting time is outside a predetermined range; The propagation measurement method of claim 2 further comprising:

4. 4. The propagation measurement method according to claim 3, further comprising repeating the steps of calculating the propagation time, calculating the post-update measurement waiting time, and correcting the post-update measurement waiting time until the post-update measurement waiting time becomes a value within a predetermined range.

5. In the step of determining whether the post-update measurement waiting time is within a predetermined range, The propagation measurement method according to claim 3 or 4, wherein the judgment is based on the molecular weight of the gas calculated based on the sound speed in the measurement flow path obtained from the propagation time of the pulse in the forward direction and the propagation time of the pulse in the reverse direction.

6. In the step of correcting the updated measurement waiting time, The molecular weight of the gas is adding the latency correction value to the updated measurement latency in each of the forward direction and the reverse direction such that the updated measurement latency is longer when the latency correction value is smaller than a predetermined minimum threshold; or 6. The propagation measurement method according to claim 5, further comprising adding a latency correction value to the updated measurement latency in each of the forward direction and the reverse direction such that the updated measurement latency becomes shorter when the latency correction value exceeds a predetermined maximum threshold.

7. In the step of determining whether the post-update measurement waiting time is within a predetermined range, 7. The propagation measurement method according to claim 3, wherein the determination is made based on whether or not a difference between the propagation time of the pulse in the forward direction and the propagation time of the pulse in the reverse direction is greater than a predetermined maximum value.

8. In the step of correcting the updated measurement waiting time, 8. The propagation measurement method according to claim 3, further comprising: adding the latency correction value to the post-update measurement latency such that the post-update measurement latency for the pulse in the reverse direction coincides with the post-update measurement latency for the pulse in the forward direction, or the post-update measurement latency for the pulse in the forward direction coincides with the post-update measurement latency for the pulse in the reverse direction.

9. In the step of determining whether the post-update measurement waiting time is within a predetermined range, 9. The propagation measurement method according to claim 3, further comprising the step of: calculating the propagation time again, and then making a determination based on whether or not a change in the propagation time is greater than a predetermined maximum change.

10. The waiting time calculation adjustment value is t ｉｎｖ_ｏｓｔ The reference pulse is N of the group of pulses. １ the preceding pulse is the Nth pulse of the group of pulses ２ 10. The propagation measurement method according to claim 2, wherein when a pulse is an .sup.th pulse and a period of the pulse is X, the waiting time calculation adjustment value satisfies the following formula (1). 0<t ｉｎｖ_ｏｓｔ <(N １ -N ２ )×X・・・(1)

11. the step of detecting the reference pulse reception time and the step of calculating the propagation time are performed a plurality of times using the same measurement wait time initial value and using the same updated measurement wait time; When a group of a plurality of values ​​obtained by performing the step of calculating the propagation time using the same measurement waiting time initial value and the same updated measurement waiting time a plurality of times is defined as a group of sample values ​​under the same conditions for the same measurement waiting time initial value and the same updated measurement waiting time, 11. The propagation measurement method according to claim 2, wherein in the step of calculating the propagation time, the propagation time is determined to be an average value obtained by excluding at least a portion of the group of sample values ​​under the same conditions other than the median value of the group of sample values ​​under the same conditions from the group of sample values ​​under the same conditions.

12. A step of blocking the flow of gas into the measurement flow path; 12. The propagation measurement method according to claim 2, wherein the propagation measurement method is performed in a state where an inflow of gas into the measurement flow path is blocked; flowing a gas into the measurement flow path after performing the propagation measurement method; measuring a gas inflow propagation time, which is a time it takes for the pulse to propagate through the measurement flow path while gas is flowing into the measurement flow path; a flow velocity calculation step of calculating a flow velocity of the gas in the measurement flow path based on the forward gas inflow propagation time and the reverse gas inflow propagation time; Including, The step of measuring the gas inflow propagation time includes: detecting a gas inflow reference pulse reception time from a time when the preceding pulse is estimated to be received by the other ultrasonic sensor to a time when the reference pulse is received by the other ultrasonic sensor; calculating a gas inflow-time propagation time of the pulse in the measurement flow path from a sum of the updated measurement waiting time and the gas inflow-time reference pulse reception time; calculating a post-gas inflow updated measurement latency by subtracting the latency calculation adjustment value from the gas inflow propagation time; replacing the post-update measurement waiting time with the post-update measurement waiting time at the time of gas inflow; Including, The gas flow velocity measuring method further comprises the steps of: detecting the gas inflow reference pulse reception time using the post-gas inflow update measurement waiting time; and calculating the gas inflow propagation time.

13. 13. The gas flow velocity measurement method according to claim 12, wherein in the step of setting the measurement waiting time initial value, a sound speed in the measurement flow path is calculated from a gas temperature and a molecular weight of the gas, and the measurement waiting time initial value is calculated by dividing the length in the propagation direction in the measurement flow path by the sound speed.

14. A computer is provided to measure a propagation state of ultrasonic waves in a measurement flow path through which a gas can flow, the ultrasonic waves being transmitted from a pair of ultrasonic sensors disposed on the upstream side and the downstream side of the measurement flow path, respectively. a sensor operation means for alternately transmitting a group of ultrasonic pulses including a plurality of pulses in a forward direction from the ultrasonic sensor on the upstream side to the ultrasonic sensor on the downstream side and in a reverse direction from the ultrasonic sensor on the downstream side to the ultrasonic sensor on the upstream side, thereby propagating the group of ultrasonic pulses through the measurement flow path; a waiting time initial value setting means for setting an initial value of a measurement waiting time, which is a time from when a reference pulse of the pulse group is transmitted from one of the ultrasonic sensors until when a leading pulse of the pulse group that is located forward in a propagation direction of the reference pulse is estimated to be received by the other ultrasonic sensor; a pulse detection means for detecting a reference pulse reception time from a time when the preceding pulse is estimated to be received by the other ultrasonic sensor to a time when the reference pulse is received by the other ultrasonic sensor; and a propagation time calculation means for calculating a propagation time of the pulse in the measurement flow path from the sum of the measurement wait time initial value and the reference pulse reception time; Propagation measurement program to function as.

15. The computer, an updated waiting time calculation means for calculating an updated measurement waiting time by subtracting a predetermined waiting time calculation adjustment value from the propagation time; and a wait time update means for replacing the measurement wait time initial value with the updated measurement wait time; It also functions as 15. The propagation measurement program according to claim 14, for causing the computer to function again as the pulse detection means and the propagation time calculation means by using the updated measurement waiting time.

16. The computer, a gas blocking means for blocking the inflow of gas into the measurement flow path; a gas interruption time propagation measurement means for executing the propagation measurement program according to claim 15 in a state where the inflow of gas into the measurement flow path is interrupted; a gas inflow means for injecting a gas into the measurement flow path after execution of the propagation measurement program; a gas inflow propagation measuring means for measuring a gas inflow propagation time, which is a time taken for the pulse to propagate through the measurement flow path while the gas is flowing into the measurement flow path; and a flow velocity calculation means for calculating a flow velocity of the gas in the measurement flow path based on the forward gas inflow propagation time and the reverse gas inflow propagation time; Functioning as a The gas inflow propagation measurement means includes: a gas inflow time pulse detection means for detecting a gas inflow time reference pulse reception time from a time when the preceding pulse is estimated to be received by the other ultrasonic sensor to a time when the reference pulse is received by the other ultrasonic sensor; a gas inflow propagation time calculation means for calculating a gas inflow propagation time of the pulse in the measurement flow path from the sum of the updated measurement waiting time and the gas inflow reference pulse reception time; a gas inflow time post-update waiting time calculation means for calculating a gas inflow time post-update measurement waiting time by subtracting the waiting time calculation adjustment value from the gas inflow time propagation time; a waiting time replacement means for replacing the post-update measurement waiting time with the post-update measurement waiting time at the time of gas inflow; Including, a gas flow velocity measurement program for causing the computer to function again as the gas flow-time pulse detection means and the gas flow-time propagation time calculation means by using the gas flow-time updated measurement waiting time;

17. a measurement section that forms a measurement flow path through which a gas flows; a valve for adjusting the inflow of gas into the measurement flow path; a pair of ultrasonic sensors disposed on the upstream side and the downstream side of the measurement flow path, respectively; a temperature sensor for measuring the temperature of the gas; a calculation device that calculates a flow velocity of the gas based on a time taken for an ultrasonic wave emitted from one of the ultrasonic sensors to propagate through the measurement flow path and a time taken for an ultrasonic wave emitted from the other ultrasonic sensor to propagate through the measurement flow path; Equipped with The computing device includes: an opening / closing operation unit for adjusting the opening degree of the valve; a sensor operation unit that, when the valve is in a closed state in which gas is prevented from flowing into the measurement flow path, alternately transmits a group of ultrasonic pulses including a plurality of pulses in a forward direction from the upstream ultrasonic sensor to the downstream ultrasonic sensor and in a reverse direction from the downstream ultrasonic sensor to the upstream ultrasonic sensor, thereby propagating the group of ultrasonic pulses through the measurement flow path; a waiting time initial value setting unit that sets a measurement waiting time initial value, which is a time from when a reference pulse of the pulse group is transmitted from one of the ultrasonic sensors until when a leading pulse of the pulse group that is forward in a propagation direction of the reference pulse is estimated to be received by the other ultrasonic sensor in the closed state; a pulse detection unit that detects a reference pulse reception time from a time when the leading pulse is estimated to be received by the other ultrasonic sensor to a time when the reference pulse is received by the other ultrasonic sensor in the closed state; a propagation time calculation unit that calculates a propagation time of the pulse in the measurement flow path from a sum of the measurement wait time initial value and the reference pulse reception time in the closed state; an updated waiting time calculation unit that calculates an updated measurement waiting time by subtracting a predetermined waiting time calculation adjustment value from the propagation time in the closed state; a wait time update unit that replaces the measurement wait time initial value with the updated measurement wait time in the closed state; having the pulse detection unit detects the reference pulse reception time again using the updated measurement waiting time, and the propagation time calculation unit calculates the propagation time again using the updated measurement waiting time; The computing device includes: a gas inflow pulse detection unit that detects a gas inflow reference pulse reception time from a time when the leading pulse transmitted from one of the ultrasonic sensors is estimated to be received by the other of the ultrasonic sensors to a time when the reference pulse transmitted from one of the ultrasonic sensors is received by the other of the ultrasonic sensors in an open state in which the valve is allowing gas to flow into the measurement flow path; a gas inflow propagation time calculation unit that calculates a gas inflow propagation time, which is the time it takes for the pulse to propagate through the measurement flow path, from the sum of the updated measurement waiting time and the gas inflow reference pulse reception time in the open state; a gas inflow post-update waiting time calculation unit that calculates a gas inflow post-update measurement waiting time by subtracting the waiting time calculation adjustment value from the gas inflow propagation time in the open state; a gas inflow waiting time update unit that replaces the post-update measurement waiting time with the gas inflow post-update measurement waiting time in the open state; and the gas inflow pulse detection unit detects the gas inflow reference pulse reception time again using the gas inflow update measurement waiting time, and the gas inflow propagation time calculation unit calculates the gas inflow propagation time again using the gas inflow update measurement waiting time, The gas flow velocity measuring device, wherein the calculation device further includes a flow velocity calculation unit that calculates the flow velocity of gas in the measurement flow path based on the gas inflow propagation time in the forward direction and the gas inflow propagation time in the reverse direction.

18. The gas flow rate measuring device according to claim 17, which calculates a flow rate of an oxygen-containing gas; A concentrator body provided with the gas flow rate measuring device; Equipped with The computing device further includes a flow rate concentration calculation unit that calculates a flow rate of the oxygen-containing gas and an oxygen concentration in the oxygen-containing gas based on a flow velocity of the oxygen-containing gas.

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