JPH09189628A - Gas residual meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas residual meter easy to handle in which the residual time capable of using a gas cylinder can be precisely and quickly grasped. SOLUTION: In the measurement of the pressure of a gas within a gas cylinder every prescribed time by a pressure sensor 17 to calculate the residual time of the gas, this gas residual meter has a memory means 32 for storing the measured pressure value, a main arithmetic part 31 for determining the pressure descending quantity per unit time from the pressure value stored in the memory means 32 and the latest pressure value, and calculating the residual time from the pressure descending quantity the latest pressure value, and a liquid crystal display 11 for displaying the residual time calculated by the main arithmetic part 31. The precise residual time can be calculated and displayed from the pressure descending quantity (dP) per unit time, so that the residual time can be precisely and quickly grasped, and the handling is facilitated since no changing operation such as arithmetic parameter is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas fuel gauge for displaying a remaining time in which a gas cylinder filled with gas can continue supplying gas.

[0002]

BACKGROUND ART Conventionally, as a device for knowing the remaining amount of gas filled in a gas cylinder, a weight type gas remaining amount detecting device for detecting the remaining amount of gas from the weight of the gas cylinder measured by a load cell. (JP-A-3-94125), or a gas pressure type gas residual amount meter (Japanese Patent Laid-Open No. 61-19304) for detecting the residual amount of gas from the pressure of the gas in the gas cylinder.
No. 1) is known. The weight type gas remaining amount detection device has a structure in which a load cell is provided at a position where it comes into contact with a corner portion of an inclined cylinder stand, and the weight of the gas cylinder is added to the load cell with the gas cylinder placed on the cylinder stand. ing. Then, the remaining amount of gas in the gas cylinder is detected from the weight detected by the load cell. Since such a weight-type gas residual amount detection device detects the weight of the gas cylinder with the load cell, it detects the residual gas amount in a relatively large cylinder that does not need to be moved once it is placed and empty. Is used for. The gas pressure type gas fuel gauge has a Bourdon tube or the like for converting the pressure in the gas cylinder into a mechanical displacement, and is configured to display the pressure with a pointer on a dial. The remaining gas amount can be grasped by replacing the indicated gas pressure value. Since such a gas pressure type gas fuel gauge detects the gas fuel level with a pressure gauge, it is easy to obtain a small and lightweight gas level meter. It is often used to detect the total amount of remaining gas. On the other hand, in recent years, in order to treat diseases such as chronic respiratory failure at home, medical gas,
In particular, portable cylinders filled with oxygen are becoming popular. If a patient is equipped with various devices such as a medical gas cylinder, a regulator, and a suction device at home, he / she can inhale a predetermined amount of medical gas instructed by a doctor at home, so that he / she can perform treatment while at home. it can. Here, the portable medical gas cylinder is equipped with the above-described gas pressure type gas fuel gauge, and the gas pressure gas fuel gauge measures the amount of remaining gas.

[0003]

However, in the conventional gas pressure type gas fuel level gauge, the pressure value of the indicated gas must be read as the gas fuel level, and it becomes necessary to get used to grasping the gas gas level. However, there is a possibility that the remaining time when the gas cylinder can be used may be mistaken and the usability may be poor. In particular, when detecting the remaining amount of gas in a gas cylinder filled with medical gas, the usage conditions of the cylinder may change due to a change in the inhalation flow rate or a change in the capacity of the cylinder according to a doctor's instruction. When the usage conditions change, the relationship between the pressure value of the gas in the cylinder and the remaining time that gas can be supplied changes, so when the patient who is the user himself reads the pressure, it changes depending on the conditions at that time. Since it is necessary to use such a ratio, there is a high possibility that the remaining time is mistakenly recognized, and if the remaining time is mistakenly recognized, the medical gas treatment is interrupted and proper treatment cannot be performed.

Such a problem also occurs when a conventional weight type gas residual amount detecting device, which needs to read the remaining time from the weight of the cylinder, is adopted. Moreover, since the weight type gas level detector has a structure that measures the weight of the cylinder fixed on the cylinder base, it can be applied to large cylinders that do not move frequently, but it is designed for medical use. However, there is a problem that it cannot be applied to a relatively small portable cylinder.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas fuel gauge which can accurately and quickly grasp the remaining time that the gas cylinder can be used and is easy to handle.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a gas fuel gauge for displaying the remaining time in which a gas cylinder can continue supplying gas, and is a pressure measurement for measuring the pressure of the gas in the gas cylinder every predetermined time. Means, a storage means for storing the pressure value measured by the pressure measuring means, a pressure drop amount per unit time is obtained from the pressure value stored in the storage means and the latest pressure value, and this pressure drop amount and The present invention is characterized by further comprising a calculating means for calculating the remaining time from the latest pressure value and a display means for displaying the remaining time calculated by the calculating means. In the above, in the case where the power source for driving the gas fuel gauge is a battery, if the state in which the amount of pressure drop per unit time obtained by the calculating means is below a predetermined value continues for a predetermined time or more, Power operation means for cutting off the connection with the power source, or power operation means for switching the operation mode of the arithmetic means to a sleep mode for stopping the function of the arithmetic means while maintaining the connection with the power source. Is desirable. Further, when the power source for driving the gas fuel gauge is a battery, the power saving means is provided for switching the operation mode of the operation means to the low power consumption mode when the operation means does not perform the operation. Is preferred. At this time, as the power saving means,
When switching to the low power consumption mode, it is also possible to employ one that shuts off the power to the pressure measuring means. Further, the display means displays the latest pressure value obtained by the pressure measurement means from the start of new measurement until the calculation means can calculate the remaining time. Is desirable. Further, the storage means stores a fixed value that is input in advance as a pressure drop amount per unit time, and the calculating means determines that the pressure drop amount per unit time obtained by calculation is equal to or less than a predetermined value. When the above state continues after a predetermined time has elapsed, it is preferable that the remaining time is calculated based on the fixed value stored in the storage means.

In the present invention as described above, the pressure of the gas in the gas cylinder is measured every predetermined time, and the measured pressure value is stored in the storage means. Therefore, the latest measurement from the previous measurement value stored in the storage means is performed. By subtracting the value, pressure drop Δ
If P is found and this pressure drop ΔP is divided by the measurement period ΔT, which is the time between each measurement, as shown in FIG. 1, the slope of the pressure fluctuation with respect to time, that is, the amount of pressure drop per unit time dP is obtained. Since the pressure value P, which is the latest measured value, decreases by the pressure drop amount dP per unit time, the remaining time T can be obtained by the following equation. T = P / dP = P / (ΔP / ΔT) = ΔT * P / ΔP If this calculation is performed by the calculation means and the result is displayed on the display means, the remaining time in which the gas cylinder can be used can be accurately and quickly set by the user. Can be grasped by Moreover, when using the gas fuel gauge, even if the gas flow rate is changed, there is no need to change the calculation parameters and the like due to the change in flow rate, so the user simply operates the power switch, etc. And you can read the exact time remaining,
It is easy to handle, and the above-mentioned object is achieved thereby.

It should be noted that, even if the gas is not used because the power switch is forgotten to be turned off, the gas fuel gauge is operating, or the arithmetic means merely waiting is operating. In some cases, useless power is consumed, such as when the same power is consumed as it is. In such a case, if the pressure drop amount dP calculated by the calculation means is less than or equal to a predetermined value,
If a power operating means for disconnecting the connection with the power source, or a power operating means for switching the operation mode of the computing means to a sleep mode for stopping the function of the computing means while maintaining the connection with the power source is provided, Even if you forget to turn off the power switch, useless battery consumption can be suppressed. When the computing means is composed of a computer such as a microprocessor, the transition to the sleep mode is achieved by completely stopping the clock of the built-in CPU. On the other hand, when the computing means that is merely waiting consumes the same power as when the computing means is operating, a power saving means is provided to switch the operation mode of the computing means from the normal mode to the low power consumption mode. In this case, the operation mode is switched according to the state of the calculation means, and even if the gas fuel gauge is operated by the battery, the battery is not wasted unnecessarily, and there is no inconvenience that the replacement time is accelerated. Here, the low power consumption mode refers to an operation mode in which the power consumption is suppressed by, for example, reducing the calculation speed of the calculation means. And, as the power saving means,
If a device that cuts off the power to the pressure measuring means when switching to the low power consumption mode is adopted, the power consumption is further suppressed, and the waste of the battery can be minimized. Also, if the pressure is measured periodically, at least the next measurement must be completed after a new measurement is started,
The remaining time cannot be calculated. For this reason, if a device that displays the latest pressure value obtained by the pressure measuring device is used as the display device from the time when a new measurement is started until the calculation device can calculate the remaining time, By input,
Since the pressure value is displayed, it is convenient to check the pressure inside the cylinder without using the cylinder. Further, when the state where the pressure drop amount per unit time obtained by the calculation is equal to or less than the predetermined value continues after the predetermined time elapses, for example, when the state where the pressure drop amount becomes zero continues for a long time, The calculation means cannot calculate the remaining time. In such a case, as the storage unit, a unit in which a fixed value input as a pressure drop amount per unit time is stored in advance is adopted, and as the calculation unit, the pressure drop amount per unit time obtained by calculation. If the state of being equal to or less than a predetermined value continues even after a predetermined time has elapsed, a method of calculating the remaining time based on the fixed value stored in the storage means is adopted, and an appropriate value is set as the above-mentioned fixed value. This makes it possible to calculate an appropriate remaining time from the measured value obtained by the latest pressure measurement.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a portable oxygen inhaler 1 for home medical care according to this embodiment. This oxygen inhaler 1 includes an oxygen cylinder 2 filled with oxygen, a regulator 3 that adjusts the flow rate of oxygen supplied, and a gas fuel gauge 10 for displaying the remaining amount of oxygen in the oxygen cylinder 2. It is equipped with and. The regulator 3 includes an opening / closing valve 4 for opening / closing a flow passage provided inside.
A flow rate setting dial 5 for setting the flow rate of oxygen supplied to the outside, and a connection port 6 for connecting an oxygen mask or the like are provided.

As shown in FIG. 3, the gas fuel gauge 10 includes a liquid crystal display 11 as a display means for displaying the remaining time during which the oxygen cylinder 2 can supply oxygen, and a start switch 12. It is provided on the front part of the case 13. The liquid crystal display 11 has two time display sections 11A and 11B for displaying time and minute display sections 11C and 11D for displaying minute. Hour display 11B and minute display 11C
Between them is provided a colon display section 11E indicating that the remaining time is being displayed. Also, the liquid crystal display 11
Can also display the pressure inside the oxygen cylinder 2, as shown in FIG. In order to display the pressure, the liquid crystal display 11 has a decimal point display section 11F for displaying a decimal point and "MP" which is a unit of pressure.
By displaying "a", a unit display portion 11G indicating that the liquid crystal display 11 is displaying pressure is provided. When the liquid crystal display 11 is displaying the pressure, the time display portions 11A and 11B represent digits after the decimal point, the minute display portion 11C represents the first digit of the decimal point, and the minute display portion 11
D is now obsolete.

As shown in FIG. 5, the case 13 has a front portion (upper side in the drawing) opened. At the front opening of the case 13, a lid part 14 incorporating the liquid crystal display 11 is provided.
Is fitted. On the back surface of the case 13, a joint portion 15 for connecting to the upstream side of the on-off valve 4 of the regulator 3,
A communication hole (16) for making the inside of the case (13) atmospheric pressure is provided. The joint portion 15 is made of a pipe-shaped member, and
A pressure guiding path 15A is formed which communicates with the inside of the oxygen cylinder 2 and guides the pressure inside the oxygen cylinder 2. Inside the case 13, a pressure sensor 17 for detecting the pressure inside the oxygen cylinder 2,
A substrate 18 on which an electric circuit for calculating the remaining time of oxygen in the oxygen cylinder 2 is formed from the pressure value measured by the pressure sensor 17, and a button type battery 19 for supplying electric power to the electric circuit of the substrate 18. Is provided. The pressure sensor 17
Detects the gauge pressure, which is the pressure difference between the pressure inside the oxygen cylinder 2 and the atmospheric pressure.
Is fixed so as to face the inside of the pressure guiding path 15A, and is electrically connected to the substrate 18 by a conductive wire (not shown).

FIG. 6 shows an electric circuit 20 formed on the aforementioned substrate 18. The electric circuit 20 is mainly composed of a CPU 30 composed of a microprocessor. In the electric circuit 20, in addition to the CPU 30, an amplifier 21 that amplifies an analog electric signal from the pressure sensor 17, an A / D converter 22 that converts the analog electric signal amplified by the amplifier 21 into a digital electric signal, Battery 19 to pressure sensor 17 and C
A power supply circuit 23 for controlling the power supplied to the PU 30 and the like, and a CP
An oscillator circuit 24 for transmitting a main clock and a sub clock which are clock signals to U30 is provided. Here, the sub clock is the CPU 30 during arithmetic processing.
The clock signal is slower (longer cycle) than the main clock sent to. On the other hand, inside the CPU 30,
Main calculation unit that calculates the remaining time T of the oxygen cylinder 2 based on the pressure value detected by the pressure sensor 17 by hardware
31, a storage unit 32 for storing the pressure value and the like detected by the pressure sensor 17, and a display calculation unit 33 that is an interface for displaying the remaining time and the like calculated by the main calculation unit 31 on the liquid crystal display 11 are provided. ing. Further, inside the CPU 30, a timer 34 for managing the time in the CPU 30 by counting the clocks transmitted by the transmitting circuit 24 by software, and an electric power operation means for cutting off the power supply of the gas fuel gauge 10. 35 and a power saving means 36 for switching the operation mode of the gas fuel gauge 10 from the normal mode to the low power consumption mode.

The timer 34 sends a measurement timing signal to the A / D converter 22 and the main arithmetic unit 31 at every predetermined time T ₁ . Each time the A / D converter 22 receives a measurement timing signal from the timer 34, the A / D converter 22 converts a measurement value indicating the pressure detected by the pressure sensor 17 into a digital signal and sends the digital signal to the main arithmetic unit 31. . Here, the pressure sensor 17, the amplifier 21, the A / D converter 22, and the timer
Including 34, the pressure of oxygen in the oxygen cylinder 2 is kept for a predetermined time T
A pressure measuring means for measuring each _one is configured. Here, in the pressure measurement performed at every predetermined time T ₁ , a plurality of (for example, four) pressure values measured at minute time intervals are sent to the main calculation unit 31, and the main calculation unit 31 makes a plurality of pressure values. The sum of the pressure values is used as the pressure value for the pressure measurement, and the remaining time is calculated by multiplying the sum of the plurality of pressure values by a predetermined coefficient. As a result, multiple measurement data are averaged, and even if abnormal data occurs during measurement,
The influence is minimized, and a plurality of processes such as an arithmetic process for calculating an average value from the sum of a plurality of pressure values and a storage process for storing the average value are omitted, and the consumption of the battery 19 is suppressed. It is like this.

The remaining time T in the main computing unit 31 is stored in the storage means 32.
In order to determine whether to turn off the power supply to the first storage unit 32A that stores the pressure value obtained by the measurement and the gas fuel gauge 10, a plurality of pressures measured in a predetermined period are calculated. A second storage unit 32B for storing a value and a third storage unit 32C for storing a fixed value previously input as the pressure drop amount dP are provided. The storage unit 32 and the A / D converter 22 are connected to the main arithmetic unit 31, and each time the measurement timing signal is received,
The pressure value stored in the storage means 32 and the latest pressure value from the A / D converter 22 are input. As a result, the main calculation unit 31 obtains the pressure drop amount dP per unit time at the same timing as the measurement timing, and determines the remaining time T from the pressure drop amount dP and the latest pressure value P.
Is a calculation means for calculating. Here, since the pressure drop amount dP cannot be obtained unless the pressure is measured twice or more after the power is turned on, the main calculation unit 31 cannot calculate the remaining time T. Therefore, from the start of new measurement until the main calculation unit 31 becomes able to calculate the remaining time T, the latest pressure value obtained from the pressure sensor 17 is displayed on the liquid crystal display 11 by the main calculation unit 31. And the latest pressure value is displayed on the liquid crystal display 11. Further, the pressure drop amount obtained by the main calculation unit 31 is less than or equal to a predetermined value, here,
When the resolution is less than the resolution of the / D converter 22, the accuracy of the obtained pressure drop amount is poor and cannot be used as data for calculating the accurate remaining time T in the main calculation unit 31. Therefore, if the state in which the pressure drop amount is equal to or less than the predetermined value continues after the lapse of a predetermined time T ₂ after the power is turned on, the storage means
The fixed value stored in the third storage unit 32C of 32 is input to the main calculation unit 31, and the main calculation unit 31 calculates the remaining time T based on this fixed value.

When the state in which the amount of pressure drop calculated by the main arithmetic unit 31 is below the predetermined value continues for a predetermined time T ₃ or more after the power is turned on, the electric power operating means 35 supplies oxygen. A determination process is performed to determine that the cylinder 2 is not used, and the gas fuel gauge 10 is turned off. However, the predetermined time T ₃ is longer than the predetermined time T ₂ . More specifically, the second of the storage means 32 will be described.
The storage unit 32B, within a predetermined time period up to the present from the predetermined time T ₃ before the time point, the pressure value obtained in the measurement performed a plurality of times are stored in plural numbers. The power operating means 35 is a storage means.
When the measured value before the predetermined time T ₃ and the latest measured value are sent from 32 via the main calculation unit 31, the pressure drop amount at the predetermined time T ₃ is obtained based on these measured values, and this pressure drop amount is The power is cut off when the value is below a predetermined value. At this time, the electric power operating means 35 obtains the pressure drop amount based on the pressure value measured with the predetermined time T ₃ interposed therebetween, thereby obtaining the pressure drop amount in a span longer than the predetermined time T ₁ which is the measurement cycle. It is designed to be used. As a result, it is possible to detect a state where the oxygen cylinder 2 is used even though the flow rate is minute, which cannot be discriminated by the pressure drop amount in a short span, and to make a distinction from the state where the oxygen cylinder 2 is not used. ing. It should be noted that the determination process of the electric power operation means 35 is not performed every time the pressure is measured, but is performed in accordance with one pressure measurement performed a plurality of times. As a result, in the determination process of the electric power operating means 35, the pressure value stored in the second storage section 32B is thinned out,
The size of the second storage unit 32B can be reduced. For example, when the predetermined time T ₁ which is the measurement cycle is 1 minute and the predetermined time T ₃ which is the span for obtaining the pressure drop amount used in the determination process is 30 minutes, the determination process is performed for each measurement. , It is necessary to store 30 measured values, but it is sufficient to store 15 measured values if the determination process is performed once in two measurements.

The power saving means 36 switches the operation mode of the main arithmetic unit 31 from the normal mode to the low power consumption mode, and also the pressure sensor 17, the amplifier 21, and the A / D converter 22.
By shutting off the power to the battery 19, the battery 19 is prevented from being consumed. Specifically, the power saving means 36 includes
A busy signal that is output only while the main calculation unit 31 is performing calculation is input. When the input of the busy signal is stopped, the power saving means 36 sends a main clock stop signal to the oscillation circuit 24 to activate the sub clock of the oscillation circuit 24. When the oscillator circuit 24 receives the main clock stop signal, it only sends out to the CPU 30 a sub clock that is slower than the main clock. The CPU 30 that has received the sub clock operates at a low speed based on this sub clock, and the power consumption thereof is suppressed. On the other hand, when the busy signal is input again to the power saving means 36, the power saving means 36 again outputs the C signal.
PU30 is designed to operate at high speed with the main clock.

In this embodiment, the above-mentioned predetermined time T
₁ , T ₂ , T ₃ are set so that T ₁ <T ₂ <T ₃ . For example, the predetermined time T ₁ is a value of about 1 minute, the predetermined time T ₂ is a value of about 5 minutes, and the predetermined time T ₃ is 30.
It can be set to a value on the order of minutes.

Next, the operation of the gas fuel gauge 10 of this embodiment will be described with reference to the flowchart. As shown in FIG. 7, the gas fuel gauge 10 includes a rising process starting from step S100, a measuring process starting from step S200, a calculation / judging process starting from step S300, and a measurement returning process starting from step S400. The power cutoff process of step S500 is performed. In the series of operations, among these processes, the rising process is performed only once immediately after the gas fuel gauge 10 is powered on, and the measurement process, the calculation / judgment process,
And each process of the measurement return process is repeated many times until the use of the oxygen cylinder 2 is completed. Then, the power cutoff process is performed only once when the operation of the gas fuel gauge 10 is completed.

The start-up process starts when the start switch 12 is operated, and as shown in FIG.
In S100, after performing an ON process for bringing the connection between the CPU 30 and others and the battery 19 into a conductive state, the process proceeds to step S101.
In step S101, the pressure value detected by the pressure sensor 17 is set to A
It is read via the D / D converter 22, multiplied by a coefficient for averaging in step S102, and the latest pressure value obtained as a result is digitally displayed in step S103, and at the same time, step S104.
Then, it is stored in the first storage section 32A of the storage means 32. When the display and storage of the latest pressure value is completed, the main calculation unit 31 does not need to operate at high speed until a predetermined time elapses, and thus the low power consumption mode (hereinafter, referred to as “low power mode”) in step S105. ) Is switched to. In this low power mode, the pressure sensor 17, the amplifier 21, and the A / D converter 22
Power to is cut off. Step S106 is repeated until the predetermined time elapses and the measurement process is started, and the timing for returning to the normal mode is waited for. After the lapse of a predetermined time, the process returns to the normal mode in step S107, the rising process is completed, and the process proceeds to the next measurement process.

In the measuring process, as shown in FIG. 9, first, in step S200, the pressure value detected by the pressure sensor 17 is read through the A / D converter 22, and then in step S201.
The latest pressure value is calculated by multiplying by the coefficient for averaging.
In step S202, the old pressure value stored in the first storage section 32A of the storage means 32 in step S104 is read out, and then the process proceeds to step S203. In step S203, the pressure drop amount ΔP is calculated based on the old pressure value read in step S202 and the latest pressure value obtained in step S201. This pressure drop Δ
Since P is used in the next calculation / judgment process, it is held in a register or the like as a storage means in the main calculation unit 31. After calculating the pressure drop amount ΔP in step S203, in step S204, the latest pressure value obtained in step S201 is stored in the first storage section 32A of the storage means 32, whereby the measurement process is completed, Move to the next calculation / judgment process.

In the calculation / judgment process, as shown in FIG. 10, according to the pressure drop amount ΔP obtained in step S203,
Calculation processing of the remaining time T performed in steps S301 to S302,
Also, one of the determination processes performed in steps S303 to S331 for determining whether or not to turn off the power is selectively executed. That is, in step S300, it is determined whether the pressure drop amount ΔP obtained in step S203 is equal to or greater than a predetermined value. Here, when the pressure drop amount ΔP is larger than the predetermined value, the process proceeds to step S301, and the remaining time T is calculated. In the calculation processing of the remaining time T in step S301, regarding the pressure value obtained by the measurement performed up to a predetermined number of times (n-th) after the power is turned on, and the pressure value obtained by the subsequent measurement Are handled differently. For the pressure values measured up to the n-th time, the pressure drop amount dP is calculated based on the pressure value obtained in the first measurement, and the remaining time T is calculated. Then, for the pressure value measured after the n-th time, the pressure drop amount dP is calculated from the difference from the past pressure value by the time n times the predetermined time T ₁ which is the measurement cycle, and the remaining time T is calculated. To do.

For example, the predetermined time T ₁ is 1 minute, and the third
The case where the handling of the pressure value measured after the first time is different will be described. When the pressure values P _{T1 to} P _T6 are obtained by the first to sixth measurements after the power is turned on, the pressure drop amount dP calculated during the second to sixth measurements
_{2 to} dP ₆ are represented by the following equations, respectively. dP ₂ = (P _T2 −P _T1 ) / 1 (minute) dP ₃ = (P _T3 −P _T1 ) / 2 (minute) dP ₄ = (P _T4 −P _T1 ) / 3 (minute) dP ₅ = (P) _T5 −P _T2 ) / 3 (minutes) dP ₆ = (P _T6 −P _T3 ) / 3 (minutes) The pressure drop amount dP _k for the k th time before the n th time is expressed by the following equation. dP _k = (P _Tk −P _T1 ) / (T ₁ * (k−1)) Further, the pressure drop amount dP _m at the m-th time after the n-th time is expressed by the following equation. dP _m = (P _Tm −P _{T (mn)} ) / (T ₁ * n) Thus, the pressure drop amount dP is obtained, and after the remaining time T is calculated, the remaining time T is displayed in step S302. Then, the calculation process is completed, and the process proceeds to the next measurement restoration process.

On the other hand, if the pressure drop amount ΔP is smaller than the predetermined value in step S300, the process proceeds to step S303, and in step S303 and the subsequent steps, a judgment about power-off is made. Steps
In S303, one of the pressure value display process, the remaining time calculation process, and the power shutoff determination process is selectively executed based on the time that has elapsed after the power was turned on. Specifically, the elapsed time after the power is turned on is the predetermined time T ₂
If it is shorter than that, proceed to step S310,
The latest pressure value is displayed on the liquid crystal display 11, and the process returns to the next measurement return process. In addition, the elapsed time after the power is turned on,
The time is longer than the predetermined time T ₂ and the predetermined time T ₃
If the time is shorter than that, the process proceeds to step S320, and in steps S320 and S321, the remaining time T is determined based on the fixed value stored in the third storage unit 32C of the storage means 32 and the latest pressure value. The calculated remaining time T is displayed on the liquid crystal display 11, and the process returns to the next measurement return process.

Further, if the elapsed time after the power is turned on is longer than the predetermined time T ₃ , step S330.
Proceed to. In step S330, it is determined whether or not the pressure measurement this time was accompanied by a determination process regarding power-off. For example, if the determination process regarding the power shutoff is performed once for every two pressure measurement processes, one of the two pressure measurement processes becomes the measurement period for performing the determination process, and it is determined which measurement period. It will be. Here, if the current pressure measurement process is the measurement cycle for performing the determination process, the process proceeds to step S331, and the determination process of whether to turn off the power is performed. On the other hand, if the current pressure measurement process is a measurement cycle in which the determination process is not performed, the remaining time calculation process after step S320 is performed. In step S331, the second storage unit 32 of the storage unit 32
The pressure drop amount is obtained from the pressure value stored in B at a time T ₃ before the current time point and the latest pressure value. Then, when the pressure drop amount is larger than the predetermined value, the process proceeds to the next measurement return process, while when the pressure drop amount is smaller than the predetermined value, the process proceeds to the next power shutoff process, and step S500.
Turn off the gas fuel gauge 10 to stop the gas fuel gauge 10.

When the state where the calculated pressure drop amount becomes equal to or less than the predetermined value occurs after the power is turned on by such processing, the supply of oxygen is started before the predetermined time T ₂ has elapsed. Assumed, the latest pressure value is displayed. Then, after the measurement return processing, the measurement processing is performed again. In addition, when the above-mentioned state continues even after the predetermined time T ₂ has passed from the power-on,
Before the elapse of the predetermined time T ₃ , it is considered that the supply amount from the oxygen cylinder 2 is small, and the accurate remaining time T cannot be calculated by the measurement at every predetermined time T ₁ , and the fixed value of the storage means 32 is lowered. The remaining time T is calculated and displayed by using it as the amount, and then the measurement return processing is performed and the measurement processing is performed again. On the other hand, if the above-mentioned state continues even after the lapse of the predetermined time T ₃ , it is considered that the memory has been forgotten to be erased, the power is cut off, and the gas fuel gauge 10 is stopped.

As shown in FIG. 11, in the measurement return process, in step S400, it is determined whether or not the current pressure measurement is accompanied by a determination process regarding power-off, as in step S330 described above. If accompanied by,
When the determination process is not involved, the process proceeds to step S401, skips step S401, and proceeds to step S402.
In step S401, the latest pressure value is input to the second storage section 32B of the storage means 32, and the latest pressure value is set for the predetermined time T ₃
Advance and stored in the second storage section 32B as the old pressure value (a pressure value measured at a predetermined time before T ₃ at the time of judgment processing) used in the determination process after. In step S402, step
Similar to S105, the main calculation unit 31 is switched to the low power mode, a predetermined time has elapsed, until the transition to the measurement process,
By repeating step S403, the low power mode is maintained, and the timing for returning to the normal mode is waited for. After the lapse of a predetermined time, the process returns to the normal mode in step S404, the measurement return process is completed, and the process returns to the measurement process again. By repeating the above-described processing while the oxygen cylinder 2 is used, the accurate remaining time T is displayed on the liquid crystal display 11, and when the use of the oxygen cylinder 2 is finished, the pressure drop amount exceeds the predetermined value. When it becomes smaller, the power supply of the gas fuel gauge 10 is automatically cut off.

According to this embodiment as described above, the following effects can be obtained. That is, since the pressure of oxygen in the oxygen cylinder 2 is measured every predetermined time T ₁ and the measured pressure value is stored in the storage means 32, the latest pressure value from the pressure value stored in the storage means 32 is stored. To obtain the pressure drop ΔP, and by dividing this pressure drop ΔP by the time between each measurement, the pressure drop amount dP per unit time is obtained,
An accurate remaining time T can be obtained from this pressure drop amount dP. Since the calculated remaining time T is digitally displayed on the liquid crystal display 11, the user can easily grasp the remaining time T at which the oxygen cylinder 2 can be used just by looking at the liquid crystal display 11. Therefore, it is not necessary to read the remaining time T from the pressure value as in the conventional case, and the remaining time T can be grasped more accurately and quickly than in the conventional case.

Moreover, the pressure drop amount dP per unit time
Since the remaining time T is calculated from the above, even if the oxygen flow rate is changed, the setting operation of the calculation parameters and the like is not necessary at all due to the change of the flow rate, and the user simply operates the start switch.
Only by operating 12, it is possible to read the accurate remaining time and facilitate its handling. Moreover, since the reading of the pressure value to the remaining time T and the setting operation of the calculation parameter etc. are not necessary at all, even a user who is using the gas fuel gauge 10 for the first time can easily handle it and is unfamiliar. It is possible to prevent erroneous recognition of the remaining time T due to misunderstanding or the like.

Furthermore, after the power is turned on, if the pressure drop amount dP calculated by the main computing unit 31 is less than or equal to the predetermined value even after the predetermined time T ₃ has elapsed, the power operation means 35 for disconnecting the connection with the power supply 35. Even if you forget to turn off the power, it is detected that oxygen is not used, the power is automatically cut off, the battery 19 is not wastefully consumed, and the replacement time of the battery 19 can be extended. As a result, energy saving can be achieved.

Further, the power saving means 36 for switching the operation mode from the normal mode to the low power mode is provided, and when the main arithmetic unit 31 is not operating, the main arithmetic unit 31 is operated at a low speed, and the pressure sensor 17 and the amplifier are also operated. 21, and A /
Since the power supply to the D converter 22 is cut off, the battery 19 is not wasted, the replacement time of the battery 19 can be extended, and energy saving can be achieved.

Further, since the latest pressure value is displayed after the power is turned on, the latest pressure value is displayed immediately after the power is turned on, and although the cylinder is not used, it is convenient for checking the pressure in the cylinder. Can be achieved.

Further, when a fixed value inputted as a pressure drop amount per unit time in advance is stored in the storage means 32 and the state where the calculated pressure drop amount per unit time is below a predetermined value continues for a long time, Since the remaining time T is calculated using the fixed value stored in the storage means 32, the amount of pressure drop based on the pressure value measured at every predetermined time T ₁ such as when supplying oxygen at a minute flow rate. Therefore, even when the appropriate remaining time T cannot be calculated, the appropriate remaining time can be calculated from the measurement value obtained by the latest pressure measurement.

Further, based on the pressure value measured with the predetermined time T ₃ interposed, the pressure drop amount in a wide time interval is obtained,
Since the electric power operation means 35 for judging based on this pressure drop amount is provided, it is possible to reliably distinguish between the state where the oxygen cylinder 2 is used and the state where the oxygen cylinder 2 is not used, even though the flow rate is small, and the power supply You can make an accurate decision to shut down.

Further, the judgment processing by the power operating means 35 is
Since the pressure measurement is not performed each time the pressure measurement is performed, but is performed with one pressure measurement performed a plurality of times, the second storage unit
The pressure values stored in 32B are thinned out, the number of pressure values stored in the second storage section 32B is reduced, and the storage area of the second storage section 32B can be reduced.

Further, with respect to the pressure value obtained by the measurement up to the n-th time which is defined in advance, the remaining time T is calculated from the pressure drop amount dP obtained with the pressure value obtained by the first measurement as a reference. On the other hand, for the pressure value after the n-th time, the pressure drop amount dP is obtained from the difference from the past pressure value by the time n times the predetermined time T ₁ which is the measurement cycle, and the remaining time T is calculated. Therefore, after the power is turned on, the remaining time T can be quickly calculated after the second measurement is completed, and the measurement cycle is n times the predetermined time T _{1 in} the nth and subsequent measurements. Therefore, even if the pressure pulsates, the averaged pressure drop amount dP is calculated, and the more accurate remaining time T can be calculated.

Further, in the pressure measurement performed at every predetermined time T ₁ , a plurality of pressure values measured at a minute time interval are sent to the main calculation section 31, and the sum of the plurality of pressure values is calculated as the pressure of the pressure measurement. Since it is adopted as a value, even if multiple measurement data are averaged and abnormal data occurs during measurement, the effect can be minimized and the arithmetic processing that calculates the average value from the sum of multiple pressure values Alternatively, a plurality of processes such as a storage process for storing the average value thereof are omitted, and from this point as well, the consumption of the battery 19 can be suppressed.

Although the present invention has been described above with reference to the preferred embodiment, the present invention is not limited to this embodiment, and various improvements and design changes can be made without departing from the gist of the present invention. It is possible. For example, the display means is not limited to a liquid crystal display, but an analog pointer type meter driven by a digital servo mechanism or the like, or a plurality of LEDs arranged in an arc shape or a linear shape, and the number of LEDs corresponding to the remaining time T. It may be a level meter type display that lights up, or the display is not limited to the one that is integrated with the gas cylinder, and may be displayed on a television receiver in the home or a CRT of a personal computer, and an audio display is also performed. May be.

Further, in the above embodiment, when the pressure drop amount per unit time obtained by the computing means is equal to or less than the predetermined value for a predetermined time or more, the power operating means for disconnecting the connection with the power source is provided. By providing the power supply, it is possible to cope with forgetting to turn off the power supply. Power operation means for switching the operation mode of 1 to the sleep mode in which the function of the calculation means is stopped while maintaining the connection with the power supply may be provided. More specifically, the power operating means includes a main clock and a sub clock of the transmission circuit 24 when the pressure drop amount per unit time is below a predetermined value for a predetermined time or more.・
LCD display with stopping both clock
11, pressure sensor 17, amplifier 21, and A / D converter 22
The one that cuts off the power supply to can be adopted. In this way, the current flowing through the electric circuit of the gas fuel gauge is suppressed to a leak current level, resulting in a remarkably low power consumption, which can suppress battery consumption to the same extent as when the power is cut off, and is incorporated in the CPU. The memory stored in the volatile memory such as the RAM can be retained, and when the sleep mode is returned to the normal mode, the inconvenience due to the disappearance of the data in the volatile memory can be prevented. Further, the power source is not limited to a disposable button type battery, but may be an ordinary commercial power source or a rechargeable secondary battery. If a secondary battery is used, it can be charged when not in use, so that it can maintain safety because it has a low voltage when in use, and it does not require battery replacement, thus saving resources.

The CPU is not limited to one having an A / D converter and storage means built therein, but may be an external storage means or A
It may be connected to the / D converter. Further, the gas cylinder is not limited to a medical oxygen cylinder, but may be a gas cylinder filled with another kind of medical gas, and is not limited to a medical gas cylinder, and is filled with a fuel gas or a semiconductor manufacturing gas. A gas cylinder may be used, and the present invention is particularly preferably applied to a gas cylinder containing a gas that maintains a gas state even when it is filled inside.

[0040]

As described above, according to the present invention, the remaining time when the gas cylinder can be used can be grasped accurately and quickly, and the handling can be facilitated.

[Brief description of the drawings]

FIG. 1 is a graph for explaining the principle of the present invention.

FIG. 2 is a side view showing an oxygen inhaler according to an embodiment of the present invention.

FIG. 3 is a front view showing the gas fuel gauge of the embodiment.

FIG. 4 is a front view showing a different state of the gas fuel gauge according to the embodiment.

FIG. 5 is a sectional view taken along line VV of FIG. 3;

FIG. 6 is a block diagram showing an electric circuit of the gas fuel gauge of the embodiment.

FIG. 7 is a flow chart for explaining the operation of the gas fuel gauge of the embodiment.

FIG. 8 is a flowchart illustrating details of a rising process in FIG.

9 is a flowchart illustrating details of the measurement process in FIG.

FIG. 10 is a flowchart illustrating details of calculation / determination processing in FIG.

11 is a flowchart illustrating the details of the measurement return process in FIG.

[Explanation of symbols]

 2 Oxygen cylinder as gas cylinder 10 Gas fuel gauge 11 Liquid crystal display as display means 17 Pressure sensor constituting pressure measuring means 19 Battery 21 Amplifier constituting pressure measuring means 22 A / D converter constituting pressure measuring means 31 Main calculation unit as calculation means 32 Storage means 34 Timer constituting pressure measurement means 35 Electric power operation means 36 Electric power saving means

Claims (7)

[Claims] 1. A gas fuel gauge for displaying the remaining time during which the gas cylinder can continue to supply gas, the pressure measuring means for measuring the pressure of the gas in the gas cylinder every predetermined time, and the pressure measuring means. A storage unit that stores the measured pressure value, and a pressure drop amount per unit time is obtained from the pressure value stored in this storage unit and the latest pressure value,
A gas fuel gauge, comprising: a calculating unit that calculates the remaining time from the pressure drop amount and the latest pressure value; and a display unit that displays the remaining time calculated by the calculating unit. 2. The gas fuel gauge according to claim 1, wherein the power source for driving the gas fuel gauge is a battery, and
When the state in which the amount of pressure drop per unit time obtained by the calculating means is equal to or less than a predetermined value continues for a predetermined time or more,
A gas fuel gauge comprising an electric power operating means for cutting off the connection with the power source. 3. The gas fuel gauge according to claim 1, wherein the power source for driving the gas fuel gauge is a battery, and
When the state in which the amount of pressure drop per unit time obtained by the calculating means is equal to or less than a predetermined value continues for a predetermined time or more,
A gas fuel gauge, comprising: power operation means for switching the operation mode of the arithmetic means to a sleep mode for stopping the function of the arithmetic means while maintaining the connection with the power source. 4. The gas fuel gauge according to any one of claims 1 to 3, wherein the power source for driving the gas fuel gauge is a battery, and when the computing means does not perform computation, A gas fuel gauge, comprising a power saving means for switching the operation mode of the calculation means to a low power consumption mode. 5. The gas fuel gauge according to claim 4, wherein the power saving means switches to a low power consumption mode.
A gas fuel gauge, characterized in that power to the pressure measuring means is cut off. 6. The gas fuel gauge according to any one of claims 1 to 5, wherein the display means is capable of calculating the remaining time after the measurement is newly started. Up to, the latest gas pressure value obtained by the pressure measuring means is displayed. 7. The gas fuel gauge according to any one of claims 1 to 6, wherein the storage means stores a fixed value input in advance as a pressure drop amount per unit time. When the state in which the amount of pressure drop per unit time obtained by the calculation is less than or equal to a predetermined value continues even after a predetermined time has elapsed, the calculation means calculates the remaining time based on the fixed value stored in the storage means. A gas fuel gauge characterized by being calculated.