Detailed Description
The preferred embodiments of the present invention are described below.
First, referring to fig. 1, the oxygen concentrator 150 of the present invention includes two adsorption cylinders 152a and 152b filled with high-performance Li-X zeolite as an adsorbent, a compressor 156 connected to the adsorption cylinders 152a and 152b via a switching valve 154 and supplying pressurized air to the adsorption cylinders 152a and 152b, and an ultrasonic oxygen concentration measuring unit 170 disposed downstream of the adsorption cylinders 152a and 152 b.
Either one of the adsorption cylinders 152a and 152b is selected by the switching valve 154 to communicate with the compressor 156. The air sucked into the compressor 156 through the filter 158 is compressed by the compressor 156, and the pressurized air is supplied to the adsorption cylinders 152a and 152b selected by the switching valve 154. The adsorption cylinders 152a and 152b blocked by the switching valve 154 and the compressor 156 are opened to the atmosphere, and the adsorbed nitrogen gas is released to regenerate the adsorbent.
In the adsorption cylinder 152a or 152b, the concentrated oxygen gas from which the nitrogen gas has been removed is supplied to the product tank 162 via the check valves 160a and 160 b. The concentrated oxygen gas is supplied from the product tank 162 to the ultrasonic oxygen concentration measuring means 170 via the pressure regulating valve 164, the flow rate setter 166, and the flow rate measuring device 168. The concentrated oxygen gas whose oxygen concentration is measured by the ultrasonic oxygen concentration measuring means 170 is supplied to a user or a patient after removing solid particles from the concentrated oxygen gas through the product filter 172.
Next, a preferred embodiment of the ultrasonic oxygen concentration measuring device constituting the ultrasonic oxygen concentration measuring means 170 will be described with reference to fig. 2.
The ultrasonic oxygen concentration measurement device 100 includes a pipe line 102 through which concentrated oxygen or calibration gas flows, and the pipe line 102 includes a straight portion 108 and vertical portions 104 and 106 connected to both ends of the straight portion. An ultrasonic transducer 118 is fixed as an ultrasonic transmitter/receiver to one end inside the straight portion 108, and a reflecting plate 122 is fixed to the other end inside the straight portion 108 so as to face the ultrasonic transducer 118. In the present embodiment, the distance between the ultrasonic transducer 118 and the reflecting plate 122 is defined as an inspection distance.
A transmission/reception switch 124 is connected to the ultrasonic transducer 118, and the transmission/reception switch 124 switches the operation mode of the ultrasonic transducer 118 between a transmission mode in which the ultrasonic transducer 118 transmits ultrasonic waves and a reception mode in which the ultrasonic transducer 118 receives ultrasonic waves. The transmission/reception switch 124 is connected to the microcomputer 126, and the microcomputer 126 controls the switching operation of the transmission/reception switch 124.
The vertical portion 104 on the upstream side in the flow direction of the gas flowing through the pipeline 10 has an inlet port 104a, and a concentrated oxygen source 112 and a calibration gas source 114 are connected to the inlet port 104a via a supply pipeline 110. The concentrated oxygen source 112 may be formed by the compressor 156, the adsorption canisters 152a, 152b, etc. of fig. 1.
The calibration gas source 114 may include a container (not shown) for storing a calibration gas whose composition and composition ratio are accurately known in advance, for example, a mixed gas containing 20% oxygen and 80% nitrogen, a pressure reducing valve (not shown) provided between the container and the supply line 110, and the like. The calibration gas source 114 may further include a temperature adjustment device 113 for adjusting the temperature of the calibration gas supplied to the pipeline 102 as a means for changing the temperature of the apparatus 100, particularly the pipeline 102. In the example of fig. 1, the temperature adjustment device 113 includes a heating wire 113a and a power supply device 113b that supplies power to the heating wire 113 a.
The vertical portion 106 on the downstream side in the flow direction of the gas flowing through the piping 102 has an outlet port 106a to which the product filter 172 is attached in the embodiment of fig. 1. The correction gas for correction is directly discharged to the outside from the product filter 172 or from the outlet port 106 a.
Temperature sensors 116, 120 for measuring the temperature of the enriched oxygen or calibration gas flowing in the conduit 102 are preferably arranged in the vertical portions 104, 106 so as not to disturb the flow in the straight portion 108. The temperature sensors 116 and 120 are connected to a microcomputer 126. When the temperature of the concentrated oxygen gas does not change much, either one of the temperature sensors 116 and 120 may be used.
Further, a driver 128 for driving the ultrasonic transducer 118, a receiver 130 for a/D converting a signal from the ultrasonic transducer 118, a display device 134 for displaying an operation state or a measurement result of the apparatus 100, and a memory 132 composed of a memory device or a storage disk device for storing an operating system of the microcomputer 126 and various parameters are connected to the microcomputer 126.
Next, the operation of the ultrasonic oxygen concentration measurement device 100 will be described.
First, before starting a normal measurement procedure for measuring the concentration of a specific gas in concentrated oxygen, the inspection distance between the ultrasonic transmitter/receiver 118 and the reflecting plate 122 is corrected by the procedure described below to obtain the reference distance L in advance0。
The line 102 is supplied with, for example, a mixture ratio of oxygen to nitrogen of P: (1-P) (0. ltoreq. P. ltoreq.1) as a calibration gas having a known composition and composition ratio. At this time, the average value of the temperatures of the calibration gas measured by the two temperature sensors 116 and 120 is used as the reference temperature T0(K) Is stored in the memory 132. If the reference temperature T is0(K) The degree (K) may be any degree without departing from the range of the temperature in which the device is used.
While the calibration gas is being supplied, a pulse for generating an ultrasonic wave is transmitted from the microcomputer 126 to the driver 128, and a pulse voltage is applied from the driver 128 to the ultrasonic transducer 118 via the transmission/reception switch 124. The ultrasonic transducer 118 transmits an ultrasonic wave corresponding to this pulse voltage. The ultrasonic waves transmitted from the ultrasonic transducer 118 propagate through the concentrated oxygen gas flowing through the straight portion 108 of the pipe 102, are reflected by the reflecting plate 122, and are returned to the ultrasonic transducer 118 again. Immediately after the pulse voltage is applied to the ultrasonic transducer 118, the transmission/reception switch 124 switches the operation mode of the ultrasonic transducer 118 from the transmission mode to the reception mode so that the returned ultrasonic wave is received by the ultrasonic transducer 118. The ultrasonic transducer 118 transmits an electric signal corresponding to the received ultrasonic wave to the microcomputer 126 via the transmission/reception switch 124 and the receiver 130. The microcomputer 126 transmits the transmission to the 1 st converter 118 according to the first transmissionThe propagation time t is calculated by the timing of pulse transmission and the timing of subsequent reception of the electrical signal from the ultrasonic transducer 1180(sec)。
Here, the temperature T0(K) The ultrasonic propagation velocity C of the calibration gas0(m/sec) can be expressed by the following formula (3) according to the aforementioned formula (1).
C0＝((κRT0)/(M02P+MN2(1-P)))1/2 ...(3)
On the other hand, because
C0＝2L0/t0 ...(4)
Can therefore obtain
L0＝((κRT0)/(MO2P+MN2(1-P)))1/2×t0/2 ...(5)
In the example of fig. 2, if the ultrasonic propagation velocity in the stationary calibration gas or the concentrated oxygen gas is C (m/sec), and the flow velocity of the concentrated oxygen gas from the ultrasonic transducer 118 toward the reflecting plate 122 is V (m/sec), the ultrasonic propagation velocity from the ultrasonic transducer 118 toward the reflecting plate 122 becomes C + V, and the ultrasonic propagation velocity in the direction of returning the ultrasonic wave reflected by the reflecting plate 122 to the ultrasonic transducer 118 becomes C-V. Since the ultrasonic propagation velocity measured by the apparatus 100 according to embodiment 1 is the average velocity of the back-and-forth ultrasonic waves, the flow velocity V of the concentrated oxygen is cancelled out, and the ultrasonic propagation velocity C in the stationary concentrated oxygen is measured.
These operations are performed by the microcomputer 126. The reference temperature T thus calculated0Lower inspection distance L0(m) is stored in the memory 132 as a reference distance.
According to the above method, calibration gas having known composition and composition ratio is supplied to the apparatus 100, and the measured value is measured from the ultrasonic wavePropagation time t of the ultrasonic wave transmitted by the transducer 1180(sec) whereby the temperature T is corrected0(K) Reference distance L between lower ultrasonic transducer 118 and reflection plate 1220(m) of the reaction mixture. This method can automatically complete the correction process by the microcomputer 126 by a simple operation, for example, by pressing a button (not shown) provided on the apparatus 100 only once during the supply of the correction gas to the apparatus 100. In addition, since the calculation itself is simple, the processing can be completed instantaneously. Even if the positional relationship between the ultrasonic transducer 118 and the reflecting plate 122 changes due to a change over time of the apparatus 100 or the like, and the propagation distance of the ultrasonic wave changes, the apparatus can be easily calibrated to update the reference temperature and the reference distance stored in the memory 132.
As described above, the concentrated oxygen gas output from the oxygen concentrator contains argon gas at a substantial concentration in addition to oxygen gas and nitrogen gas. Further, the concentration of argon gas is not always constant but varies with the flow rate of the concentrated oxygen gas generated by the oxygen concentrator.
Table 1 shows the results of the composition analysis performed on each flow rate of the concentrated oxygen gas outputted from the oxygen concentrator. The gas composition analysis was performed by gas chromatography.
TABLE 1
| Flow (liter/minute) | Oxygen concentration (%) | Argon concentration (%) | Concentration of Nitrogen (%) |
| 1.00 | 93.5 | 6.4 | 0.1 |
| 2.00 | 94.0 | 5.2 | 0.8 |
| 3.00 | 93.5 | 5.4 | 1.1 |
As shown in table 1, the ratio of oxygen to argon was varied depending on the flow rate. Although table 1 shows the results of measuring the concentrated oxygen generated by the oxygen concentrator 150, the oxygen concentration outputted is somewhat different even in the same type of oxygen concentrator, but the ratio of the oxygen/argon concentration is the same. On the other hand, if the type or amount of the adsorbent and the type of the machine base such as the shape of the adsorption cylinder are different, the oxygen/argon ratio is different.
Next, a correction coefficient generating means for generating a correction coefficient for deriving the oxygen concentration of the concentrated oxygen gas composed of oxygen gas, argon gas, and nitrogen gas based on the flow rate of the concentrated oxygen gas will be described.
One method of correcting the change in the argon concentration with the change in the flow rate is a method of directly describing the average molecular weight M in formula (1) with the presence ratio of oxygen to argon according to table 1.
That is, if the molecular weights of oxygen, nitrogen and argon are 32, 28 and 40, respectively, and the oxygen concentration is expressed by 100 × P (%), the average molecular weight M can be expressed by the following formula (6) when the output flow rate from the oxygen concentrator is 1.00 l/min.
M＝32P+40(6.4/93.5)P+28(1-P-(6.4/93.5)P) ...(6)
Further, the specific heat ratio k may be expressed by the following equation, where the specific heat ratio of a mixed gas of oxygen and nitrogen is 1.4 and the specific heat ratio of argon is 1.67.
k＝1.4(1-(6.4/93.5)P)+1.67(6.4/93.5)P ...(7)
Therefore, if the sound velocity and temperature in the concentrated oxygen gas can be measured, the oxygen concentration 100 × P (%) can be obtained from the equations (1), (6), and (7).
In the above example, when the concentrated oxygen concentration is 1.00 liter/min, in the case of other flow rates, the oxygen/argon concentration ratio of (6.4/93.5) in the formulas (6) and (7) may be changed to the oxygen/argon concentration ratio at other flow rates. In this case, the oxygen/argon concentration ratio is a correction coefficient for the argon concentration, and the accurate oxygen concentration can be measured by referring to a table based on the concentrated oxygen flow rate to the argon concentration correction coefficient, or by obtaining the relationship between the oxygen/argon concentration ratio and a previously measured flow rate by an approximate expression and deriving the argon concentration correction coefficient as a function of the flow rate.
For simple calculation, the following method may be considered. First, assuming that the oxygen-enriched gas consists of only oxygen and nitrogen, the oxygen concentration is calculated by equation (2). The oxygen concentration obtained here is a value obtained by neglecting the presence of argon gas, and therefore is a value different from the actual oxygen concentration. However, since the concentration ratio of oxygen to argon at a specific flow rate is known, the oxygen concentration can be approximated by multiplying a specific coefficient by a value of the oxygen concentration calculated in advance, as described later.
For example, when the flow rate of the concentrated oxygen gas is 1.00 l/min, the oxygen concentration is calculated by assuming that the specific heat ratio k is 1.4 and the presence of argon is ignored by using equation (2), the oxygen concentration is calculated as 102.8 (%). However, if the actual oxygen concentration is known to be 93.5 (%) in advance, the concentration can be determined as the concentration correction coefficient at 1.00 l/min (93.5/102.8), and when the concentrated oxygen flow rate is 1.00 l/min, the oxygen concentration can be accurately measured by multiplying the concentration correction coefficient (93.5/102.8) by the oxygen concentration determined by the equation (2).
In the case other than 1.00 l/min, if the same concentration correction coefficient is obtained in advance and the table is referred to from the concentrated oxygen flow rate to the concentration correction coefficient, or the concentration correction coefficient with respect to the flow rate is obtained in advance by an approximate expression, the concentration correction coefficient at each flow rate can be determined and the accurate oxygen concentration can be measured. The correction coefficient generation means can be realized by storing a table or an approximation for such a correction coefficient and the above correction coefficient generation algorithm in the memory 132 and executing them by the microcomputer 126.
Next, embodiment 2 of the present invention will be explained with reference to fig. 3.
Embodiment 2 is basically configured in the same manner as embodiment 1 except that the flow rate measuring instrument 168 in embodiment 1 is replaced with an ultrasonic type oxygen concentration flow rate measuring means 268.
Referring to fig. 3, the oxygen concentrator 250 includes two adsorption cylinders 252a and 252b filled with high-performance Li-X zeolite as an adsorbent, a compressor 256 connected to the adsorption cylinders 252a and 252b via a switching valve 254 and supplying pressurized air to the adsorption cylinders 252a and 252b, and an ultrasonic oxygen concentration flow rate measuring unit 268 disposed downstream of the adsorption cylinders 252a and 252 b.
Either one of the adsorption cylinders 252a and 252b is selected by the switching valve 254 to communicate with the compressor 256. The air sucked into the compressor 256 through the filter 258 is compressed by the compressor 256, and the pressurized air is supplied to the adsorption cartridges 252a and 252b selected by the switching valve 254. The adsorption cylinders 252a and 252b blocked by the switching valve 254 and the compressor 256 are opened to the atmosphere, and the adsorbed nitrogen gas is released to regenerate the adsorbent.
The concentrated oxygen gas from which the nitrogen gas has been removed in the adsorption cylinder 252a or 252b is supplied to the product tank 262 via the check valves 260a and 260 b. The concentrated oxygen is supplied from the product tank 262 to the ultrasonic oxygen concentration flow rate measuring means 268 via the pressure regulating valve 264 and the flow rate setter 266. The concentrated oxygen gas whose oxygen concentration and flow rate are measured by the ultrasonic oxygen concentration flow rate measuring means 268 is supplied to the user or the patient after removing solid particles from the concentrated oxygen gas through the product filter 270.
Next, a preferred embodiment of an ultrasonic oxygen concentration flow rate measurement device constituting the ultrasonic oxygen concentration flow rate measurement means 268 will be described with reference to fig. 4.
The embodiment of fig. 4 is basically the same as the embodiment of fig. 2 except that the reflection plate 122 in the embodiment of fig. 2 is replaced with a 2 nd ultrasonic transducer 222 as a 2 nd ultrasonic transmitter/receiver provided opposite to the 1 st ultrasonic transducer 218 as a 1 st ultrasonic transmitter/receiver.
The ultrasonic oxygen concentration flow rate measurement device 200 according to the embodiment of fig. 4 includes a pipe 202 through which concentrated oxygen or calibration gas flows, and the pipe 202 includes a straight portion 208 and vertical portions 204 and 206 connected to both end portions of the straight portion. In the present embodiment, the straight portion 208 is particularly composed of a pipe member having a circular cross section whose inner diameter does not change in the longitudinal direction, and the 1 st ultrasonic transducer 218 is fixed to the upstream end portion of the inside thereof as the 1 st ultrasonic transmitter/receiver, and the 2 nd ultrasonic transducer 222 as the 2 nd ultrasonic transmitter/receiver is fixed to the 1 st ultrasonic transducer 218 so as to face each other to the downstream end portion of the inside of the straight portion 208. In the present embodiment, the distance between the 1 st ultrasonic transducer 218 and the 2 nd ultrasonic transducer 222 is defined as the inspection distance.
The 1 st and 2 nd ultrasonic transducers 218 and 222 are connected to a transmission/reception switch 224, and the transmission/reception switch 224 independently switches the operation mode of the 1 st and 2 nd ultrasonic transducers 218 and 222 between a transmission mode in which the 1 st and 2 nd ultrasonic transducers 118 and 222 transmit ultrasonic waves and a reception mode in which the 1 st and 2 nd ultrasonic transducers 118 and 222 receive ultrasonic waves. The transmission/reception switch 224 is connected to the microcomputer 226, and the microcomputer 226 controls the switching operation of the transmission/reception switch 224.
The vertical portion 204 on the upstream side of the line 202 has an inlet port 204a, and a concentrated oxygen gas source 212 and a calibration gas source 214 are connected to the inlet port 204a via a supply line 210. The concentrated oxygen source 212 may be formed by the compressor 256 or the adsorption cylinders 252a, 252b, etc. of fig. 3.
The calibration gas source 214 may include a container (not shown) for storing the components and components of the calibration gas, which are known to be correct, a pressure reducing valve (not shown) provided between the container and the supply line 210, and the like. The calibration gas source 214 may further include a temperature adjustment device 213 as a mechanism for changing the temperature of the apparatus 200, particularly the pipe 202. In the example of fig. 1, the temperature adjustment device 213 includes a heating wire 213a and a power supply device 213b that supplies power to the heating wire 213 a.
The vertical portion 206 on the downstream side of the pipe 202 has an outlet gas port 206a, and concentrated oxygen gas or calibration gas for concentration measurement or calibration is exhausted from the outlet gas port 206a to the outside. When it is not preferable to directly discharge these gases to the outside, a gas treatment device (not shown) may be appropriately disposed on the downstream side of the outlet port 206a, as in embodiment 1.
Temperature sensors 216, 220 for measuring the temperature of the enriched oxygen gas or calibration gas flowing through the conduit 202 are preferably disposed on the vertical portions 204, 206 so as not to disturb the flow in the straight portion 208. The temperature sensors 216 and 220 are connected to a microcomputer 226. When the temperature of the concentrated oxygen gas does not change much, either one of the temperature sensors 216 and 220 may be used.
Further, a receiver 230 for driving the driver 228 for the 1 st ultrasonic transducer 218 to a/D convert a signal from the 1 st ultrasonic transducer 218, a display 234 for displaying an operation state or a measurement result of the apparatus 200, and a memory 232 composed of a nonvolatile memory or a memory disk device for storing an operation system of the microcomputer 226 and various parameters are connected to the microcomputer 226.
Next, the operation of the embodiment of fig. 4 will be described.
First, before starting a normal measurement process for measuring the concentration of a specific gas in concentrated oxygen, the inspection distance between the 1 st and 2 nd ultrasonic transducers 218 and 222 and the inner diameter D of the straight portion 208 of the pipe 202 are corrected to obtain a reference distance L in advance0And a reference inner diameter D0。
In the present embodiment, the flow rate adjustment valve of the correction gas source 214 is set to a predetermined flow rate Q0The same calibration gas as in embodiment 1 is supplied from the calibration gas source 214 to the pipe 202. At this time, the average value of the temperatures of the calibration gas measured by the two temperature sensors 216 and 220 is used as the reference temperature T0(K) Is stored in the memory 232.
While the calibration gas is being supplied, a pulse for generating ultrasonic waves is transmitted from the microcomputer 226 to the driver 228, and a pulse voltage is applied to the 1 st ultrasonic transducer 218 via the transmission/reception switch 224. The 1 st ultrasonic transducer 218 transmits ultrasonic waves corresponding to the pulse voltage, and the ultrasonic waves transmitted from the 1 st ultrasonic transducer 218 propagate through the concentrated oxygen gas flowing through the straight portion 208 of the pipe 202 and are converted by the 2 nd ultrasonic wavesReceived by the processor 222. The 2 nd ultrasonic transducer 222 transmits an electric signal corresponding to the received ultrasonic wave to the microcomputer 226 via the transmission/reception switch 224 and the receiver 230. The microcomputer 226 calculates the forward propagation time t based on the time when the transmission pulse is first transmitted to the driver 228 and the time when the electric signal from the 2 nd ultrasonic transducer 222 is received1(sec)。
Immediately after the transmission/reception switch 224 receives the electric signal from the 2 nd ultrasonic transducer 222, the operation mode of the 1 st ultrasonic transducer 218 is switched from the transmission mode to the reception mode, and the operation mode of the 2 nd ultrasonic transducer 222 is switched from the reception mode to the transmission mode. Then, a pulse for generating an ultrasonic wave is transmitted from the microcomputer 226 to the driver 228, and a pulse voltage is applied to the 2 nd ultrasonic transducer 222 via the transmission/reception switch 224. The 2 nd ultrasonic transducer 222 transmits an ultrasonic wave corresponding to the pulse voltage, and the 1 st ultrasonic transducer 218 receives the ultrasonic wave. The 1 st ultrasonic transducer 218 transmits an electric signal corresponding to the received ultrasonic wave to the microcomputer 226 via the transmission/reception switch 224 and the receiver 230. The microcomputer 226 calculates the propagation time t in the reverse direction from the time when the transmission pulse is first transmitted to the 2 nd ultrasonic transducer 222 and the time when the electric signal from the 1 st ultrasonic transducer 218 is received2(sec)。
Here, by finding t1And t2The propagation time t of the ultrasonic wave is defined by the following equation (8) except for the influence of the flow of the calibration gas in the pipe 2020。
t0＝(t1+t2)/2 ...(8)
Furthermore, the temperature T0(K) C of the ultrasonic wave in the gas0(m/sec) can be obtained from the above formula (3).
On the other hand, because
C0＝L0/t0 ...(9)
Can therefore obtain
L0＝((κRT0)/(MO2P+MN2(1-P)))1/2×t0 ...(10)
These calculations are performed in the microcomputer 226. The reference temperature T thus calculated0Lower inspection distance L0(m) is stored in the memory 232 as a reference distance.
Furthermore, the reference distance L is used0A propagation velocity V in the forward direction with respect to the flow of the correction gas01(m/sec) and propagation velocity V in the reverse direction02(m/sec) are each composed of V01＝L0/t1，V02＝L0/t2So that the flow velocity V of the correction gas flowing in the pipe 2020(m/sec) can be obtained from the following formula (11) using the above formula (2).
V0＝(V01-V02)/2 ...(11)
Converting the flow velocity (m/sec) into the flow rate (m)3Sec), the cross-sectional area (m) of the straight portion 208 when the straight portion 208 is cut by a plane perpendicular to the center line of the straight portion 208 of the pipe 2022) Multiplied by the flow velocity V. That is, let the reference temperature T0(K) Lower straight portion 208 has a reference inner diameter D0(m), the following relationship holds.
V0π(D0/2)2＝Q0 ...(12)
That is, the reference temperature T0(K) Lower reference inner diameter D0(m) can be obtained from the following formula (13).
D0＝2(Q0/(D0/2))1/2 ...(13)
The above calculation is performed by the microcomputer 226.The reference inner diameter D obtained here0(m) is stored in memory 232.
By the above method, calibration gas of known composition and concentration is supplied to the apparatus 200, and propagation times t in the forward and reverse directions with respect to the flow of the calibration gas are measured from the 1 st and 2 nd ultrasonic transducers 218 and 2221、t2Thereby correcting the reference distance L between the 1 st and 2 nd ultrasonic transducers 218, 2220(m) of the reaction mixture. In particular, as in the present embodiment, the reference inner diameter D can be corrected at the same time by supplying the correction gas to the apparatus 200 at a predetermined flow rate0(m)。
Although the correction coefficient of the oxygen concentration is generated based on the flow rate of the concentrated oxygen measured by the flow rate measuring instrument 168 in embodiment 1, the correction coefficient of the oxygen concentration is generated based on the flow rate of the concentrated oxygen measured by the ultrasonic type oxygen concentration flow rate measuring device 200 in embodiment 2. The remaining functions are the same as those in embodiment 1.