JP4791238B2 - Gas alarm and alarm method - Google Patents

Description

The present invention relates to a gas detector and the alarm how, in particular, a gas sensor for detecting the concentration of carbon monoxide, gas detector and equipped with an alarm generating means for carbon monoxide to generate a warning to the effect that leaks those related to the alarm how.

  It is known that carbon monoxide (hereinafter referred to as CO) is generated even when the combustion appliance is used in a normal state. In particular, when boiling hot water using a cooking utensil such as a pan or a kettle, CO is generated until the cold cooking utensil warms up. Therefore, the conventional gas alarm does not generate an alarm immediately even if the CO concentration exceeds the set point, and the alarm is issued when the condition exceeding the set point continues even after a predetermined delay time elapses. To generate.

  In the conventional gas alarm device for home use, (1) the alarm is issued within 15 minutes after the CO concentration reaches the low concentration set point 200 ppm, and (2) the CO concentration reaches the high concentration set point 550 ppm. An alarm is issued within 5 minutes after the arrival.

  If the alarm is issued according to the above (1) and (2), the combustion appliance is burned in a room with a small ventilation frequency, the combustion appliance burns incompletely due to lack of oxygen, and the CO concentration continues to rise. An alarm can be given before the concentration of carbon monoxide hemoglobin (hereinafter referred to as COHb) in human blood reaches 25%.

By the way, the low concentration / high concentration set point and the delay time shown in (1) and (2) described above are determined as follows according to the guidelines (demand-required-0113-84) at the time of establishment of the test regulations. It is a thing.
(I) The CO concentration at which COHb is 25% is 230 ppm when the CO concentration increase rate is slow or when it is leaked for infinite time.
(II) When the CO concentration increase rate is fast, the ventilation frequency: 1 time, the room size: 4.5 tatami mats, and when the small water heater at the time of opening is incompletely burned, the following three patterns are verified and the concentration and time Is determined.
i) When the combustion appliance is in a good combustion state and incomplete combustion occurs due to lack of oxygen ii) When the combustion appliance deteriorates over time, and the ventilation fin 1/4 equivalent is blocked iii) The deterioration of the combustion appliance progresses more than ii) If

  As an example, a graph showing the relationship between COHb (%), CO concentration (ppm), and time (min) in ii) is shown in FIG. In the figure, L11 indicates the relationship between COHb and time, and L12 indicates the relationship between CO concentration and time. As shown in the figure, after the start of combustion, the CO concentration continues to increase, and COHb becomes 25% 17 minutes after reaching 230 ppm and 5 minutes after reaching 550 ppm.

  FIG. 20 shows the time from when the CO concentration reaches 230 ppm and 550 ppm to when COHb reaches 25% in the cases (I) and (II) -i) to iii) described above. In the figure, COHb reaches 25% in 2 minutes after reaching 550 ppm in (II) -i), but 15 minutes after reaching 230 ppm before that, COHb = 25% An alarm with less than is possible.

  In the figure, also in (II) -iii), COHb reaches 25% in 10.3 minutes after reaching 230 ppm, but 5 minutes have passed since reaching 550 ppm before that. , COHb = less than 25% can be alarmed. Actually, the low concentration set point is set to 200 ppm lower than 230 ppm for safety.

  However, in the conventional gas alarm device, an alarm is generated before COHb reaches 25% when it is within the limited conditions as shown in (I), (II) -i) to iii). Low density, high density set point and delay time are defined. For this reason, if the generation of CO does not meet the above conditions, an alarm cannot be generated before COHb reaches 25%, or an alarm is generated even though COHb is not at a dangerous level. , Danger and excessive safety are mixed.

  Especially in commercial kitchens, even if there is no ventilation fan operation, the ventilation rate is 5 times / h, which is much larger than that for home use, so the CO does not rise very much even if the combustion equipment burns incompletely There are many cases where the above conditions are not met, such as when the concentration reaches a high level at a rate higher than the CO concentration increase rate assumed for home use, compared to the case for home use.

  FIG. 21 shows the relationship between the CO concentration and COHb when a constant CO concentration flows continuously for the delay time of the current gas alarm device. In the figure, the delay time is 15 minutes for 200 ppm to 550 ppm, the delay time is 5 minutes for 550 ppm or more, and the delay time is infinite for 200 ppm or less. As shown in the figure, an alarm is generated within COHb = 15% at a CO concentration of 200 to 550 ppm. On the other hand, when 1500 ppm or more or slightly lower than 200 ppm, an alarm is generated after COHb = 25% is exceeded. As can be seen from this figure, there is a problem that a danger and excessive safety are mixed, and the gas alarm according to the influence state of CO on the human body cannot be performed accurately.

  Therefore, in order to solve such a problem, a gas alarm device has been proposed in which the delay time is set using a coefficient K corresponding to COHb in consideration of the influence of CO on the human body (Patent Document 1). This gas alarm is the CO concentration reported in “Danger of Combustion in Houses with Low Ventilation Rates for Household Gas Appliances (Oxygen Deficient Combustion)” (Safety Engineering Vol.19 No.4, 1980 report). In this method, a COHb value is obtained from a regression equation including oxygen concentration and leakage time, a coefficient K is determined, and a delay time is determined. The delay time set in this way is a time corresponding to COHb in the blood of the human body, and a gas alarm corresponding to the influence state of CO on the human body can be performed.

  However, in the gas alarm device described above, in order to obtain the coefficient K, it is necessary to obtain COHb. COHb is obtained by substituting the oxygen concentration in the air, the CO concentration in the air, and the leakage time into the relational expression. For this reason, it was necessary to measure the oxygen concentration in addition to the CO concentration. Further, the above relational expression is a very complicated high-order regression equation and requires a high-speed CPU.

Further, in the gas alarm device described above, the delay time when the set point is exceeded is adjusted as in the conventional case. For this reason, there has been a problem that an alarm cannot be issued if CO is unstable for a long time at a level not exceeding the set point.
JP 2002-39980 A

The present invention focuses on the above-mentioned problems, simply and accurately, to provide a gas detector and gas alarm how that can perform the gas alarm in response to the impact status for human body CO Is an issue.

In order to solve the above-mentioned problem, the invention according to claim 1 is a gas alarm device comprising a gas sensor for detecting the concentration of carbon monoxide and an alarm generating means for generating an alarm that carbon monoxide has leaked. A storage means in which an exponential function expression or a logarithmic function expression showing a relationship between a carbon monoxide concentration in a predetermined oxygen concentration and an arrival time until the carbon monoxide hemoglobin concentration in blood reaches a predetermined value is stored in advance. An arrival time calculation means for calculating the arrival time by substituting the carbon monoxide concentration detected by the gas sensor into an exponential function expression or a logarithmic function expression stored in the storage means, and the arrival time calculation means calculating obtains the time product of the reciprocal of the arrival time which is a difference obtained by subtracting the time product of the inverse number 1, and the calculated delay time period obtained by multiplying the arrival time, and to the delay time is 0 And determining means for determining that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined value, wherein the alarm generating means determines whether the carbon monoxide hemoglobin concentration in the blood is determined by the determining means. In the gas alarm device, the alarm is generated when it is determined that the value has been reached.

According to the first aspect of the present invention, the storage means has an exponential function expression indicating the relationship between the carbon monoxide concentration in the predetermined oxygen concentration and the arrival time until the carbon monoxide hemoglobin concentration in the blood reaches a predetermined value. Alternatively, a logarithmic function formula is stored in advance. The arrival time calculating means calculates the arrival time by substituting the carbon monoxide concentration detected by the gas sensor into the exponential function expression or logarithmic function expression stored in the storage means. The judging means obtains the time product of the reciprocal of the arrival time calculated by the arrival time calculating means , and multiplies the difference obtained by subtracting the reciprocal time product from 1 and the arrival time corresponding to the carbon monoxide concentration detected by the gas sensor. When the delay time reaches zero, it is determined that the carbon monoxide hemoglobin concentration in the blood has reached a predetermined value. The alarm generation means generates an alarm when the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached a predetermined value.

  Therefore, the reciprocal / time product of arrival time corresponds to the current carbon monoxide hemoglobin concentration with respect to a predetermined value, and whether or not the carbon monoxide hemoglobin concentration has reached a predetermined value based on the reciprocal / time product of this arrival time Therefore, an alarm can be generated when the carbon monoxide hemoglobin concentration reaches a predetermined value without directly calculating the carbon monoxide hemoglobin concentration using a complicated high-order regression equation. Moreover, the time obtained by multiplying the difference obtained by subtracting the time product of the reciprocal of the arrival time from 1 and the arrival time corresponding to the carbon monoxide concentration corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value. Since the remaining time is set as the delay time, the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value can be clearly obtained.

  The invention according to claim 2 is the gas alarm device according to claim 1, wherein the determination means changes the arrival time corresponding to the carbon monoxide concentration every time the carbon monoxide concentration detected by the gas sensor changes. A setting means for setting a time obtained by multiplying a difference obtained by subtracting the reciprocal time product from 1 and an arrival time corresponding to the carbon monoxide concentration after the change as a delay time, The gas alarm device has a count-down means for counting down a set delay time, and determines that the predetermined value is exceeded when the delay time becomes zero.

  According to the second aspect of the invention, the determination means obtains the time product of the reciprocal of the arrival time corresponding to the carbon monoxide concentration every time the carbon monoxide concentration detected by the gas sensor changes. A time obtained by multiplying the difference obtained by subtracting the reciprocal time product and the arrival time corresponding to the changed carbon monoxide concentration is set as the delay time. Countdown means counts down the set delay time. When the delay time becomes 0 as a result of the count down by the determination means, it is determined that the predetermined value has been exceeded. Therefore, since the countdown means counts down the delay time while the carbon monoxide concentration is not changing, the time product of the reciprocal of the arrival time may be obtained every time the carbon monoxide concentration changes, and it is necessary to obtain it sequentially. Absent.

The invention according to claim 3 is a gas alarm method for generating an alarm that carbon monoxide has leaked until the carbon monoxide concentration at a predetermined oxygen concentration and the carbon monoxide hemoglobin concentration in the blood reach a predetermined value. By substituting the carbon monoxide concentration detected by the gas sensor into the exponential function or logarithmic function equation indicating the relationship with the arrival time, the arrival time corresponding to the carbon monoxide concentration is calculated, and the reciprocal of the calculated arrival time The time obtained by subtracting the reciprocal time product from 1 and the arrival time corresponding to the carbon monoxide concentration detected by the gas sensor is set as a delay time, and the delay time reaches zero. Then, it is determined that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined value, and the alarm is generated.

According to the third aspect of the present invention , the gas sensor has an exponential function expression or a logarithmic function expression indicating the relationship between the carbon monoxide concentration at a predetermined oxygen concentration and the arrival time until the carbon monoxide hemoglobin concentration in the blood reaches a predetermined value. Substituting the carbon monoxide concentration detected by the above, the arrival time corresponding to the carbon monoxide concentration is calculated, the time product of the reciprocal of the calculated arrival time is obtained, and the difference obtained by subtracting the time product of the reciprocal from 1 The time obtained by multiplying the arrival time corresponding to the carbon monoxide concentration is set as the delay time. When this delay time becomes zero, it is determined that the concentration of carbon monoxide hemoglobin in the blood exceeds the predetermined value, Generate an alarm that carbon has leaked.

  Therefore, the time product of the reciprocal of the arrival time corresponds to the current carbon monoxide hemoglobin concentration with respect to the predetermined value. Therefore, an alarm can be generated when the carbon monoxide hemoglobin concentration reaches a predetermined value without directly calculating the carbon monoxide hemoglobin concentration using a complicated high-order regression equation. Moreover, the time obtained by multiplying the difference obtained by subtracting the time product of the reciprocal of the arrival time from 1 and the arrival time corresponding to the carbon monoxide concentration corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value. Since the remaining time is set as the delay time, the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value can be clearly obtained.

  As described above, according to the first and third aspects of the invention, the reciprocal time product of the arrival time corresponds to the current carbon monoxide hemoglobin concentration with respect to the predetermined value, and is based on the reciprocal time product of the arrival time. In order to determine whether or not the carbon monoxide hemoglobin concentration has reached a predetermined value, the carbon monoxide hemoglobin concentration does not have to be directly calculated using a complicated high-order regression equation. Since the alarm can be generated when the value is reached, the gas alarm corresponding to the influence state of carbon monoxide on the human body can be easily and accurately performed. Moreover, the time obtained by multiplying the difference obtained by subtracting the time product of the reciprocal of the arrival time from 1 and the arrival time corresponding to the carbon monoxide concentration corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value. Since the remaining time is set as the delay time, the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined value can be clearly obtained.

  According to the second aspect of the present invention, since the countdown means counts down the delay time while the carbon monoxide concentration is not changing, the time product of the reciprocal of the arrival time is calculated every time the carbon monoxide concentration changes. Since it is only necessary to obtain it and it is not necessary to obtain it sequentially, an alarm can be generated with a simpler and simpler configuration.

First Embodiment Hereinafter, a first embodiment of a gas alarm device and a gas alarm method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a gas alarm device in which the gas alarm method of the present invention is implemented. As shown in the figure, the gas alarm device includes a gas sensor 10. As the gas sensor 10, for example, an electrochemical sensor in which a current corresponding to the CO concentration flows through an oxidation reaction of carbon monoxide (hereinafter referred to as CO) is used. The current corresponding to the CO concentration is converted into a voltage and output to the microcomputer (μCOM) 12.

  The μCOM 12 is used in various processing steps in a central processing unit (hereinafter referred to as CPU) 12a that performs various processes according to a processing program, a ROM 12b that is a read-only memory that stores a program for processing performed by the CPU 12a, and the like. It has a RAM 12c, which is a readable / writable memory having a work area, a data storage area for storing various data, and the like, and these are connected by a bus line.

  CPU12a mentioned above takes in the output of the gas sensor 10 mentioned above, and detects CO density | concentration. Further, the gas alarm device includes a speaker 13 that outputs a CO leakage alarm and a sound alarm output circuit 14 that drives the speaker 13. The voice alarm output circuit 14 is controlled by the CPU 12a.

  Next, the alarm principle of the gas alarm device described above will be described below with reference to FIGS. FIG. 2 shows the relationship between the CO concentration in an oxygen concentration of 21% and the arrival time until the carbon monoxide hemoglobin concentration (hereinafter referred to as COHb) in the blood reaches 3, 5, 10, 15, 20, and 25%, respectively. It is a log-log graph shown. FIG. 3 is a table showing the relationship between the CO concentration in an oxygen concentration of 21% and the arrival time until COHb reaches 3, 5, 10, 15, 20, and 25%, respectively. FIG. 4 is a log-log graph showing the relationship between the CO concentration in 18% oxygen and the time required for COHb to reach 5, 10, 15, 20, and 25%, respectively. FIG. 5 is a table showing the relationship between the CO concentration in 18% oxygen and the arrival time until COHb reaches 5, 10, 15, 20, and 25%, respectively.

  As shown in FIG. 3, for example, when the oxygen concentration is 21%, if 300 ppm of CO continues to leak, COHb = 10% after 18.13 minutes, and 400 ppm of CO continues to leak. After 13.01 minutes, COHb = 10%. Further, as shown in FIG. 5, for example, when the oxygen concentration is 18%, if 300 ppm of CO continues to leak, COHb = 10% after 14.54 minutes, and 400 ppm of CO leaks. If it continues, it will become COHb = 10% after 10.07 minutes.

As is apparent from the log-log graphs of FIGS. 2 and 4, the arrival time decreases exponentially as the CO concentration increases. That is, the relationship between the CO concentration X and the arrival time T until COHb reaches 5, 10, 15, 20, 25% is expressed by an exponential function or a logarithmic function as shown in (1) and (2) below. Can be represented.
T = a1 · ^Xb1 (a1 and b1 are constants) (1)
LogT = b1 ・ LogX + Loga1
= B1 · logX + c (∵Loga1 = c) (2)
As is clear from comparison between FIG. 2 and FIG. 4, when the oxygen concentration is low, the arrival time until COHb becomes 5, 10, 15, 20, and 25% is shortened.

  In the present embodiment, a case where a CO leakage alarm is generated when the oxygen concentration is assumed to be 18% and COHb = 10% will be described. In this case, as shown in the above (1) and (2), the relationship between the CO concentration in the oxygen concentration of 18% and the arrival time until COHb becomes 10% as shown in FIGS. An exponential function expression or logarithmic function expression (straight line L in the figure) is stored in advance in, for example, the ROM 12b (= storage means). Next, the relationship between the reciprocal of the arrival time and the time product corresponding to the CO concentration detected by the gas sensor 10 and the CO concentration will be described. First, when 300 (ppm) leakage occurs, the arrival time corresponding to this CO concentration is 14.54 minutes, as shown in FIGS. Therefore, the reciprocal becomes 1 / 14.54, and the reciprocal / time product increases with a slope of 1 / 14.54 as shown in FIG. If 300 (ppm) leakage continues for 10 minutes, the reciprocal / time product is 10 / 14.54.

  Thereafter, when the CO concentration changes to 200 (ppm), the arrival time corresponding to the CO concentration is 24.48 minutes as shown in FIG. Therefore, the reciprocal is 1 / 24.48, and the reciprocal / time product increases with a slope of 1 / 24.48 which is smaller than the slope 1 / 14.54 at the time of leakage of 300 (ppm) as shown in FIG. To do. If leakage of 200 (ppm) continues for 3 minutes, the reciprocal / time product is (10 / 14.54 + 3 / 24.48). Further, when the CO concentration changes to 400 (ppm), the arrival time corresponding to this CO concentration is 10.07 minutes as shown in FIGS. Accordingly, the reciprocal is 1 / 10.07, and the reciprocal / time product is 1 greater than the slope 1 / 24.48 and 1 / 14.54 at the time of leakage of 200 and 300 (ppm) as shown in FIG. Increases with a slope of /10.07.

  As is clear from this, the reciprocal / time product described above increases more rapidly as the CO concentration is higher, and gradually increases as the CO concentration is lower. That is, the current reciprocal number / time product corresponds to the current COHb with respect to COHb 10%. Therefore, the time obtained by multiplying the difference obtained by subtracting the current reciprocal / time product from 1 and the arrival time corresponding to the current CO concentration corresponds to the remaining time until reaching COHb 10%.

The relationship between the current reciprocal / time product and COHb will be described in more detail. FIG. 7 is a log-log graph showing the relationship between the leakage time T and COHb for each of the CO concentrations of 200, 300, 400, 500, 600, 700, 800, 1000, 1200, and 1400 ppm when the oxygen concentration is 18%. The relationship between the leakage time T and the COHb concentration Y for each CO concentration is almost linear in the logarithmic graph, and is expressed by an exponential function expression or a logarithmic function expression as shown in the following equations (3) and (4). be able to.
Y = a · T ^b (a and b are constants) (3)
LogY = b · LogT + Loga (4)

Further, since the equations (3) and (4) for each CO concentration can be said to be substantially parallel straight lines, the coefficient b in the above (3) and (4) is constant and the coefficient a is a coefficient determined for each CO concentration. The following exponential function formula (5) and logarithmic function formula (6) can be expressed.
Y = ax · T ^b (ax is a constant corresponding to each CO concentration) (5)
LogY = b · LogT + Logax (6)

Therefore, if the current CO concentration and the leakage time T at that concentration are known, the current COHb can be easily calculated. When COHb to be set as an alarm value is Ys% and CO leakage at CO concentration X continues, the arrival time until COHb reaches Ys% as Ts is substituted into the above equation (6). Equation (7) is obtained.
LogYs = b · LogTs + Logax (7)

Further, when an arbitrary leakage time at a predetermined CO concentration is T1, and COHb at this time is Y1, the following expression (8) is obtained. As shown in FIG. 8, the arbitrary leakage time T1 is an arbitrary time until COHb = Ys%, and is shorter than the arrival time Ts.
LogY1 = b · LogT1 + Logax (8)

From equation (7) -equation (8):
LogY1−LogYs = (b · LogT1 + Logax) − (b · LogTs + Logax)
Log (Y1 / Ys) = b (LogT1-LogTs)
= BLog (T1 / Ts)

From the above formula, Y1 / Ys = (T1 / Ts) ^b . Accordingly, the product of the reciprocal 1 / Ts of the arrival time Ts until COHb = Ys when the leakage of the predetermined CO concentration X continues and the arbitrary leakage time T1 is the arbitrary leakage time with respect to COHb = Ys to be set. The ratio of COHb = Y1 at time T1 (Y1 / Ys) is obtained. It can be said that the reciprocal / time product of the arrival time Ts corresponds to the COHb concentration.

Next, a description will be given of how to obtain the remaining time until COHb = Ys when the CO concentration changes midway. As described above, the relationship between the leakage time T and COHbY at different CO concentrations can be expressed by Expression (6) with the same slope b and different intercept Loga.
LogY = b · LogT + Logax (ax is a value corresponding to each CO concentration) (6)

Now, when COHb to be set as an alarm value is Ys%, and CO leakage at a CO concentration X1 having an intercept of Log (a1) continues, the arrival time is T1 until COHb reaches Y2%. ), The following equation (9) is obtained.
LogY2 = bLogT1 + Loga1 (9)

Further, when CO leakage at a CO concentration X2 having an intercept of Csb of Log (a2) is Ys% and COHb to be set as an alarm value is continued, T2 is set as the arrival time until COHb reaches Y2%, and the above equation (6) ), The following equation (10) is obtained.
LogY2 = bLogT2 + Loga2 (10)

As shown in FIG. 9, let us consider a case where leakage at the CO concentration X1 first continues for the leakage time T3, and thereafter leakage at the CO concentration X2 continues. At this time, the relationship between COHb (Y1) at the leakage time T3 when the CO concentration switches from X1 to X2 and the arrival time T4 until the CO concentration X2 continues to leak from the beginning until reaching COHb (Y1) is It can be expressed by the following formula. First, COHb (Y1) and leakage time T3 are substituted into equation (6) to obtain equation (11).
LogY1 = bLogT3 + Loga1 (11)
Next, COHb (Y1) and arrival time T4 are substituted into equation (6) to obtain equation (12).
LogY1 = bLogT4 + Loga2 (12)

From the above formulas (9) and (10), Loga1-Loga2 = bLogT2-bLogT1
From the equations (11) and (12),
LogT4 = (Loga1-Loga2 + bLogT3) / b
= (BLogT2-bLogT1 + bLogT3) / b
= LogT2-LogT1 + LogT3
= Log (T2 / T3 / T1)

  Therefore, T4 = T2 / T3 / T1. The remaining time (T2-T4) after the concentration is switched is T2-T4 = T2- (T2 / T3 / T1) = T2 (1- (T3 / T1)). Therefore, it can be said that “the value obtained by multiplying the difference obtained by subtracting the current reciprocal product / time product (T3 / T1) from 1 and the arrival time (T2) corresponding to the current CO concentration” is the remaining time.

The sum of the reciprocal and time product at this time can be expressed by the following equation (12).
Σ (a / T) = (T3 / T1) + ((T2−T4) / T2)
= (T3 / T1) + (T2 (1- (T3 / T1)) / T2
= 1
Thus, even if the density is switched halfway, if the slope b is the same, it can be said that the sum of the reciprocal and the time product does not change.

  Therefore, the CPU 12a uses a time obtained by multiplying the difference obtained by subtracting the current reciprocal / time product from 1 corresponding to the remaining time until COHb reaches 10% and the arrival time corresponding to the current CO concentration as a delay time, and this delay time. When the value reaches 0, it is determined that the COHb concentration has reached 10%, and an alarm is generated. Thus, an alarm can be generated when COHb reaches 10% (= predetermined value) without directly calculating COHb using a complicated high-order regression equation as in the prior art.

  Specifically, the CPU 12a operates as follows. First, when 300 (ppm) leakage occurs, the arrival time corresponding to this CO concentration is 14.54 minutes as shown in FIG. As shown in FIG. 6, the CPU 12a sets the arrival time 14.54 minutes as a delay time, and counts down the set delay time 14.54 while 300 (ppm) leakage continues. If 300 (ppm) leakage continues for 10 minutes, the delay time is 4.54 (= 14.54-10) as a result of counting down.

  Thereafter, when the CO concentration changes to 200 (ppm), the CPU 12a obtains the reciprocal / time product of the arrival time corresponding to the CO concentration up to the present time. As described above, since 300 (ppm) of CO leakage continues for 10 minutes at the present time, the reciprocal / time product is 10 / 14.54. The CPU 12a then obtains a difference (1-10 / 14.54) obtained by subtracting the reciprocal / time product 10 / 14.54 obtained from 1 and an arrival time 24.48 corresponding to the changed CO concentration 200 (ppm). The time multiplied by minutes was set to 7.64 minutes (= 24.48 · (1-10 / 14.54)) as the delay time, and this setting was made while 200 (ppm) leakage continued. Count down the delay time 7.64 minutes. It should be noted that the delay time of 7.64 minutes reaches the COHb 10% straight line L shown in FIG. 4 corresponding to 200 (ppm) on the straight line L ′ that has been translated to pass 300 (ppm) and 4.54 minutes. It's time.

  If leakage of 200 (ppm) continues for 3 minutes, the delay time is 4.64 minutes (= 7.64-3) as a result of counting down. Further, when the CO concentration changes to 400 (ppm), the CPU 12a obtains the reciprocal / time product α of the arrival time T corresponding to the current CO concentration. As described above, 300 (ppm) of CO leakage continues for 10 minutes and 200 (ppm) of CO leakage continues for 3 minutes, so the reciprocal / time product is (10 / 14.5 + 3 / 24.48). ) Then, the CPU 12a obtains the difference (1− (10 / 14.5 + 3 / 24.48)) obtained by subtracting the reciprocal time product obtained from 1 and the arrival time 10.07 corresponding to the changed CO concentration 400 (ppm). The time 1.91 minutes multiplied by the minute is set again as a new delay time, and the set delay time 1.91 minutes is counted down while 400 (ppm) leakage continues. When the delay time becomes zero, the CPU 12a determines that the COHb concentration has become 10% and generates an alarm.

  The detailed operation of the gas alarm device described above will be described below with reference to the flowchart showing the processing procedure of the CPU 12a in FIG. For example, the CPU 12a starts alarm processing when the CO concentration output from the gas sensor exceeds a predetermined concentration, and obtains the reciprocal / time product. First, the CPU 12a detects the CO concentration (step S1). Next, the CPU 12a performs stepping into, for example, an exponential function expression or a logarithmic function expression representing the relationship between the CO concentration in the oxygen concentration 18% stored in advance in the RAM 12c and the arrival time until the COHb reaches 10%. The arrival time T is obtained by substituting the CO concentration detected in S1 (step S2), and the obtained arrival time T is set as the delay time dl (step S3).

  Next, again, the CPU 12a detects the CO concentration (step S4). If the difference between the CO concentration detected in step S4 and the previously detected CO concentration is equal to or smaller than a predetermined value, it is determined that there is no change in the CO concentration (N in step S5). (Step S6), the process proceeds to step S8.

  In contrast, if the difference between the CO concentration detected in step S5 and the previously detected CO concentration is greater than a predetermined value, it is determined that there is a change in the CO concentration (Y in step S5), and functions as a setting means. The reciprocal / time product α up to the present after the CO concentration exceeds a predetermined concentration is obtained, and the difference time (1−α) obtained by subtracting the reciprocal / time product α obtained from 1 is the arrival time for the changed CO concentration. After the value multiplied by T is newly set as the delay time Tdl (step S7), the process proceeds to step S8.

  As a method for obtaining the reciprocal / time product α from when the CO concentration exceeds a predetermined concentration to the present, for example, it is reset every time it is determined that the CO concentration has changed in step S5, and the CO concentration changes. There is provided a duration counter that is counted up each time it is determined that there is no. This duration counter can count the duration for which the CO concentration remains constant. Each time it is determined that there is a change in the CO concentration in step S5, a value obtained by multiplying the reciprocal of the arrival time corresponding to the CO concentration before the change and the duration counted by the duration counter is integrated. It can ask for.

  In step S8, the CPU 12a functions as a determination unit and determines whether or not the delay time Tdl has become 0 or less. If it is 0 or less (Y in step S8), the CPU 12a determines that COHb has reached 10%. It functions as an alarm generating means and outputs a CO alarm signal to the audio alarm output circuit 14 (step S9). In response to this, the audio alarm output circuit 14 controls the speaker 13 to generate an alarm indicating CO leakage. On the other hand, if the delay time Tdl is greater than 0 (N in step S8), the CPU 12a returns to step S4 again. When the CO concentration becomes equal to or lower than the predetermined concentration again, the CPU 12a terminates the alarm process and resets the reciprocal / time product.

  As described above, the reciprocal / time product α of the arrival time corresponds to the current COHb with respect to COHb = 10%, and it is determined whether or not COHb has reached 10% based on the reciprocal / time product α of the arrival time. Therefore, even if COHb is not directly calculated using a complicated high-order regression equation, an alarm can be generated when COHb reaches 10%. Moreover, the time T · (1−α) obtained by multiplying the difference (1−α) obtained by subtracting the reciprocal of the arrival time / time product α from 1 and the arrival time T corresponding to the CO concentration is 10% COHb. Since this corresponds to the remaining time until reaching the delay time Tdl, the remaining time until COHb reaches 10% can be clearly obtained. Thereby, for example, if the delay time is notified, the user can take an appropriate measure when carbon monoxide leaks.

  Further, according to the gas alarm device described above, every time the CO concentration detected by the gas sensor 10 changes, the reciprocal / time product α of the arrival time corresponding to the CO concentration is obtained, and the reciprocal / time product α is subtracted from 1. A time T · (1−α) obtained by multiplying the difference (1−α) and the arrival time T corresponding to the changed carbon monoxide concentration is set as a delay time Tdl, and the set delay time Tdl is counted down. ing. Further, when the delay time becomes 0 as a result of counting down the delay time Tdl, it is determined that COHb = 10% has been exceeded. Therefore, since the delay time Tdl is counted down while the CO concentration is not changing, the reciprocal of the arrival time and the time product α need only be obtained every time the CO concentration changes, and need not be obtained sequentially. For this reason, the processing capacity of the CPU 12a can be reduced, and an alarm can be generated with a simpler and simpler configuration.

  Further, according to the gas alarm device described above, the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value is represented by an exponential function equation or a logarithmic function equation as shown in the above equations (1) and (2). I was remembered as. Here, a case where the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value is approximated by a linear function will be considered with reference to FIG. In FIG. 11, L21 and L22 are graphs showing an actual relationship between COHb and arrival time when 300 ppm and 500 ppm of CO continue to leak. On the other hand, L31 and L32 approximate the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value by a linear function, and when 300 ppm and 500 ppm of CO obtained from this approximated linear function continue to leak. It is a graph which shows the relationship between COHb and arrival time.

  As shown in the figure, in practice, when 300 ppm continues for 33.15 minutes, COHb = 15%, but when approximated by a linear function, COHb = 15% is reached after 66.9 minutes. . However, the actual COHb after 66.9 minutes has increased to 20.7%. In other words, the linear function cannot accurately approximate the relationship between the actual CO concentration and the arrival time until COHb reaches a predetermined value, and accurately gives a gas alarm according to the influence state of CO on the human body. I can't say that.

  Next, a case where the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value is approximated by an exponential function or a logarithmic function will be considered with reference to FIG. In FIG. 12, L41 and L42 are graphs showing the actual relationship between the COHb logarithmic value and the arrival time logarithmic value when 300 ppm and 500 ppm of CO continue to leak, respectively. on the other hand. Each of L51 and L52 approximates the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value by an exponential function or a logarithmic function, and 300 ppm and 500 ppm of CO calculated from the approximated exponential function and logarithmic function leak. It is a graph which shows the relationship between the COHb logarithm value when continuing, and an arrival time logarithm value. As can be seen from a comparison of FIGS. 11 and 12, it can be seen that the approximation with the exponential function or the logarithmic function can be approximated more accurately than the approximation with the linear function.

  FIG. 13 is a graph showing the relationship between the reciprocal of the arrival time / time product and time when a constant CO concentration continues to leak. In the figure, L61 is an actual measurement value. L62 approximates the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value by an exponential function or a logarithmic function, and the reciprocal / time product of the arrival time obtained from the approximated exponential function or logarithmic function and the elapsed time, The relationship is shown. L63 approximates the relationship between the CO concentration and the arrival time until COHb reaches a predetermined value by a linear function, and shows the relationship between the reciprocal of the arrival time / time product obtained from this approximated linear function and the elapsed time. Also from this graph, the approximation by the logarithmic function or the exponential function can be approximated more accurately than the approximation by the linear function, and the gas alarm according to the influence state of CO on the human body can be performed more accurately.

  In the above-described embodiment, when the CO concentration changes, the reciprocal / time product α of the arrival time corresponding to the CO concentration is obtained, and the difference (1−α) obtained by subtracting the reciprocal / time product α from 1 and after the change A time T · (1−α) obtained by multiplying the arrival time T corresponding to the CO concentration of the gas was set as the delay time Tdl, and the set delay time Tdl was counted down while the CO concentration did not change.

  However, the setting of the delay time of the present invention is not limited to the above-described embodiment. For example, every time the CO concentration is detected in step S4, the reciprocal of the arrival time corresponding to the CO concentration and the time product α are obtained each time. A time T · (1−α) obtained by multiplying the difference (1−α) obtained by subtracting the reciprocal / time product α from 1 and the arrival time T corresponding to the current CO concentration may be set as the delay time Tdl. It is done. As a specific method for obtaining the reciprocal / time product α, for example, when the CO concentration is detected every ΔT, a value Δt / a value obtained by multiplying the previously obtained reciprocal / time product α by 1 / T and Δt. Calculate by adding T.

  In this case, it is not necessary to count down the delay time Tdl. However, every time the CO concentration is detected, it is necessary to obtain the reciprocal / time product α and the arrival time T corresponding to the current CO concentration. Therefore, it is desirable to count down while the CO concentration is not changing as described above.

  In the above-described embodiment, the remaining time until COHb set as the delay time Tdl reaches a predetermined value is expressed as a difference (1-α) obtained by subtracting the reciprocal time product α from 1 and the CO concentration after the change. It was obtained by multiplying the corresponding arrival time T. However, the present invention is not limited to this, and for example, the time T · α obtained by multiplying the arrival time T by the inverse time product α may be subtracted from the arrival time T corresponding to the changed CO concentration.

First Reference Example Next, a first reference example will be described. Since the configuration of the gas alarm device incorporating the C OHb detection device in the first reference example is the same as that of the first embodiment described above with reference to FIG. 1, detailed description thereof is omitted here. The difference from the first embodiment is the contents of the relational expressions stored in the ROM 12b. In the first embodiment described above, as shown in the above (1) and (2), which represents the relationship between the CO concentration in a predetermined oxygen concentration (for example, oxygen concentration 18%) and the arrival time until COHb reaches 10%. An exponential function or logarithmic function is stored in the ROM 12b in advance.

On the other hand, in the first reference example , as shown in FIG. 7, the leakage time T for each of the CO concentrations 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400 ppm at an oxygen concentration of 18%. Exponential function formulas or logarithmic function formulas as shown in the above-described formulas (5) and (6) representing the relationship between COHb and COHb (Y) are stored in advance in the ROM 12b.
Y = ax · T ^b (ax is a constant corresponding to each CO concentration) (5)
LogY = b · LogT + Logax (6)

The operation of the CPU 12a will be described below with reference to the time chart shown in FIG. Also in the first reference example , an example in which an alarm is generated when COHb becomes 10% as in the first embodiment will be described. In the first reference example , the CPU 12a detects COHb at the time of change every time the CO concentration changes. That is, in the first reference example , the time point at which COHb is desired is the time point when the CO concentration has changed as indicated by time points O, A, and B in FIG.

  Further, every time the CO concentration changes, the CPU 12a obtains an arrival time Ta that is a leakage time until COHb reaches 10%. CPU12a calculates | requires the leak time Tb until it reaches COHb of a change time, when the leak of CO density | concentration after a change continues. The CPU 12a sets the time obtained by subtracting the leakage time Tb obtained from the arrival time Ta as the delay time Tdl. When the delay time Tdl reaches 0, the CPU 12a determines that COHb has reached 10% and generates an alarm.

  Now, as shown in FIG. 6, it is assumed that the CO concentration detected by the gas sensor 10 changes from 0 to 300 (ppm) exceeding a predetermined concentration, and CO leakage starts. In response to this change, the CPU 12a first detects COHb at the change time O. Since the CO concentration before changing to 300 (ppm) is 0 (ppm), naturally, COHb at the change time O is 0%. Therefore, the CPU 12a stores 0% as COHb at the change time O.

Further, the CPU 12a obtains an arrival time Ta that is a leakage time for COHb to reach 10% when the leakage of the changed CO concentration of 300 (ppm) continues. Specifically, the CPU 12a first extracts an exponential function expression or a logarithmic function expression as shown in Expressions (13) and (14) corresponding to the CO concentration of 300 (ppm) from the ROM 12b.
^{_{Y = a 300 · T b (}} a 300 constant corresponds to the CO concentration 300ppm) ... (13)
LogY = b · logT + Loga ₃₀₀ (14)

  Next, the CPU 12a sets the leakage time T obtained by substituting Y = 10% into the above equations (13) and (14) as the arrival time Ta. As a result, the arrival time Ta is 14.54 minutes. That is, if the leakage of the CO concentration of 300 (ppm) continues, COHb reaches 10% after 14.54 minutes. Next, the CPU 12a obtains the leakage time Tb until reaching the COHb at the change point O when the leakage of the changed CO concentration 300 (ppm) continues, and the time obtained by subtracting the obtained leakage time Tb from the arrival time Ta Is the delay time Tdl. As described above, COHb at the change time O is 0%. Therefore, it is understood that the leakage time Tb until reaching COHb = 0% at the change time point O is 0 minutes without substituting Y = 0% into the equations (13) and (14).

  By substituting Y = 0% into the equations (13) and (14), the leakage time Tb until COHb = 0% at the change time O is obtained, and the time obtained by subtracting the obtained leakage time Tb from the arrival time Ta is obtained. Although the delay time Tdl may be used, in this embodiment, in order to simplify the calculation, the CPU 12a directly sets the arrival time Ta as the delay time Tdl when COHb = 0% at the change time O.

  As shown in FIG. 6, the CPU 12a sets this delay time Tdl = arrival time Ta = 14.54 minutes, and this set delay time 14.54 minutes while 300 (ppm) leakage continues. Count down. If 300 (ppm) leakage continues for 10 minutes, the delay time is 4.54 (= 14.54-10) as a result of counting down.

  Thereafter, when the CO concentration changes to 200 (ppm), the CPU 12a obtains COHb at the change point A according to this change. That is, time A is the time when COHb is desired. (The time when the CO concentration changes immediately before time A is time O when the CO concentration changes from 0 to 300 (ppm). COHb at time O is naturally 0%. The CPU 12a determines the CO concentration after the change at the change time O. When 300 (ppm) leakage continued, the leakage time until COHb = 0% at the change time O was obtained, and the obtained leakage time and the leak time 10 minutes from the change time O to the time A were added. (The leakage time until the above-mentioned COHb = 0% is naturally 0 minutes without substituting Y = 0% into the equations (13) and (14).)

  Substituting Y = 0% into Equations (13) and (14), the leakage time until reaching COHb = 0% is obtained, and the obtained leakage time and the leakage time from change time O to time A are 10 minutes. Although the addition leak time may be obtained by adding, in the present embodiment, in order to simplify the calculation, the CPU 12a starts the leak detection (time O) while the CO concentration does not change after the start of the CO leak detection. ) To the point of time A to be obtained is defined as the additional leakage time. That is, the CPU 12a sets the leakage time 10 minutes from the change time O to the time A as the addition leakage time. Next, the CPU 12a obtains COHb when the CO concentration 300 (ppm) after the change at the change point O continuously leaks for the addition leak time of 10 minutes, and sets it as COHb at the time point A. That is, the CPU 12a substitutes T = addition leakage time 10 minutes into the equations (13) and (14) to obtain COHb at the time point A. As a result, COHb is 7.27% as is apparent from FIG.

Next, the CPU 12a obtains the leakage time Tb until COHb = 7.27% at the change time A when the leakage of the changed CO concentration of 200 (ppm) continues. Specifically, the CPU 12a extracts an exponential function expression or a logarithmic function expression as shown in Expressions (15) and (16) corresponding to the CO concentration of 200 (ppm) from the ROM 12b.
Y = a ₂₀₀ · T ^b (a ₂₀₀ is a constant corresponding to a CO concentration of 200 ppm) (15)
LogY = b · logT + Loga ₂₀₀ (16)

  Then, the CPU 12a obtains the leakage time Tb by substituting Y = 7.27% into the equations (15) and (16). The leakage time Tb is calculated to be 16.84 minutes. That is, if the leakage of the changed CO concentration of 200 (ppm) continues, COHb becomes 7.27% after 16.84 minutes. Further, the CPU 12a obtains the arrival time Ta until COHb = 10% when the leakage of the changed CO concentration 200 (ppm) continues. That is, the arrival time Ta is obtained by substituting Y = 10% into the above equations (15) and (16). The arrival time Ta is calculated to be 24.48 minutes. After that, the CPU 12a sets a time of 7.64 minutes obtained by subtracting the leakage time Tb = 16.84 minutes from the arrival time Ta = 2.48 minutes as a delay time, and while the leakage of 200 (ppm) continues, Count down the set delay time of 7.64 minutes. If leakage of 200 (ppm) continues for 3 minutes, the delay time is 4.64 minutes (= 7.64-3) as a result of counting down.

  Thereafter, when the CO concentration changes to 400 (ppm), the CPU 12a obtains COHb at the change point B when the CO concentration changes to 400 (ppm). That is, time point B is the time point at which COHb is desired. The time point when the CO concentration changes immediately before time point B is time point A when it changes from 300 (ppm) to 200 (ppm). The COHb% at time A is calculated to be 7.27%. CPU12a calculates | requires leak time Tb until it reaches COHb = 7.27% in change time A when the leak of CO concentration 200 (ppm) after change in change time A continues. When setting the delay time, the leakage time Tb is calculated to be 16.84 minutes, so the CPU 12a diverts it.

  Next, the obtained leakage time Tb = 16.84 minutes and the leakage time 3 minutes from the change time point A to the time point B are obtained as the addition leakage time 19.84 minutes. Further, the CPU 12a detects COHb at the time point B as COHb at the time point B when the CO concentration 200 (ppm) after the change has leaked continuously for 19.84 minutes. Specifically, the addition leakage time 19.84 minutes is substituted for T in the above equations (15) and (16). As a result, COHb at time B is calculated to be 8.19%.

Next, the CPU 12a obtains the leakage time Tb until it reaches 8.19%, which is COHb at the change point B when the leakage of the CO concentration of 400 (ppm) continues. Specifically, the CPU 12a extracts an exponential function expression or a logarithmic function expression as shown in Expressions (17) and (18) corresponding to the CO concentration of 400 (ppm) from the ROM 12b.
Y = a ₄₀₀ · T ^b (a ₄₀₀ is a constant corresponding to a CO concentration of 400 ppm) (17)
LogY = b · logT + Loga ₄₀₀ (18)

  Then, the CPU 12a obtains the leakage time Tb by substituting Y = 8.19% into the equations (17) and (18). The leakage time Tb is calculated to be 8.17 minutes. In addition, the CPU 12a obtains an arrival time Ta until COHb = 10% when leakage of the changed CO concentration 400 (ppm) continues. That is, the arrival time Ta is obtained by substituting Y = 10% into the equations (17) and (18). The arrival time Ta is calculated to be 10.08 minutes. Thereafter, the CPU 12a sets 1.91 minutes as a delay time obtained by subtracting the leakage time Tb = 8.17 minutes from the arrival time Ta = 10.08 minutes, and while the leakage of 400 (ppm) continues, Count down the set delay time of 1.91 minutes. If 400 (ppm) leakage continues for 1.91 minutes, the delay time is 0 minutes as a result of the countdown.

  The detailed operation of the gas alarm device described above will be described below with reference to the flowchart showing the processing procedure of the CPU 12a in FIG. For example, the CPU 12a starts alarm processing when the CO concentration output from the gas sensor 10 exceeds a predetermined concentration. First, the CPU 12a detects the CO concentration (step S20).

  Next, the CPU 12a extracts a function expression corresponding to the CO concentration closest to the CO concentration obtained in step S20 from the function expressions (5) and (6) stored in the ROM 12b. For example, when the detected CO concentration is 210 ppm, a functional expression representing the relationship between the leakage time of 200 ppm and COHb is extracted. The CPU 12a obtains an arrival time Ta until COHb reaches 10% when the leakage of the CO concentration obtained in step S20 continues from the extracted function equation (step S21). Then, the obtained arrival time Ta is set to the delay time dl (step S22).

  Next, the CPU 12a again detects the CO concentration (step S23). If the difference between the CO concentration detected in step S23 and the previously detected CO concentration is equal to or smaller than a predetermined value, it is determined that there is no change in the CO concentration (N in step S24), and the delay time Tdl is counted down. After that (step S25), the process proceeds to step S26.

  On the other hand, if the difference between the CO concentration detected in step S23 and the previously detected CO concentration is larger than the threshold value, it is determined that the CO concentration has changed (Y in step S24), and it acts as a detection means. COHb from the time when the CO concentration exceeds a predetermined value to the time of change is obtained (step S28). Furthermore, when the CO concentration leakage after the change continues, the leakage time Tb until reaching the COHb determined in step S26 is determined (step S29). Further, when the leakage of the CO concentration after the change continues, an arrival time Ta until COHb becomes 10% is obtained (step S30). Next, after setting the time obtained by subtracting the leakage time Tb from the arrival time Ta as the delay time dl (step S31), the CPU 12a proceeds to step S26.

  In step S26, the CPU 12a functions as a determination unit and determines whether or not the delay time Tdl has become 0 or less. If it is 0 or less (Y in step S26), the CPU 12a determines that COHb has reached 10%. It functions as an alarm generating means and outputs a CO alarm signal to the audio alarm output circuit 14 (step S27). In response to this, the audio alarm output circuit 14 controls the speaker 13 to generate an alarm indicating CO leakage. On the other hand, if the delay time Tdl is greater than 0 (N in step S26), the CPU 12a returns to step S23 again. When the CO concentration becomes equal to or lower than the predetermined concentration again, the CPU 12a finishes the alarm process and resets COHb.

  In the above-described embodiment, COHb is obtained every time the CO concentration changes. However, for example, COHb may be obtained periodically and displayed every time it is obtained.

In the first implementation described above, assuming the oxygen concentration 18%, when a COHb10% been described for generating a CO leak alarm. However, the oxygen concentration is determined by, for example, the degree of sealing in the installation room or the condition of the ventilation device, and is not limited to 18%. Also, COHb is not limited to 10%.

Second Reference Example Next, a COHb detection apparatus that periodically detects and displays COHb will be described. Since the configuration of the COHb detection device of the present invention in the second reference example is the same as that of the first embodiment described above with reference to FIG. 1, detailed description thereof is omitted here. The COHb detection apparatus of the second reference example further includes display means such as a liquid crystal display for displaying the detected COHb value.

As in the first reference example , the ROM 12b has a CO concentration of 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, and 1400 ppm at an oxygen concentration of 18%, as shown in FIG. An exponential function expression or a logarithmic function expression as shown in the above-described expressions (5) and (6) representing the relationship between the leakage time T and COHb (Y) is stored.
Y = an · T ^b (an is a constant corresponding to each CO concentration)

  An example of the operation of the COHb detection apparatus having the above-described configuration will be described below with reference to the time chart of FIG. First, as shown in FIG. 16, when the CO concentration detected by the gas sensor 10 exceeds a predetermined concentration, the CO concentration is 300 (ppm) for 4 minutes, and then the CO concentration is changed to 400 (ppm) for 2 minutes. think about. The COHb detection interval Tα is 2 minutes.

When the leakage of the CO concentration detected at the time when COHb is desired to be obtained from the equations (5) and (6) stored in the ROM 12b continues, the CPU 12a The leak time until reaching COHb is obtained, and the added leak time obtained by adding the obtained leak time and the leak time from the time of change to the desired time is obtained, and the equations (5) and (6) stored in the ROM 12b are obtained. ) CO concentration adds leak time at the time to be determined from seeking COHb when leaked continuously, is detected as COHb time to be determined. In the second reference example , the time point to be obtained is every time when a detection interval of 2 minutes elapses as indicated by time points O, C, D, and E in FIG.

Assume that the CO concentration detected by the gas sensor 10 changes from 0 to over 300 (ppm) and leaks. The CPU 12a obtains COHb at time C after 2 minutes have elapsed from time O. That is, time C is the time when COHb is desired to be obtained. Similarly to the first reference example described above, the CPU 12a obtains the leakage time from the CO leakage start time O to the time to be obtained as the additional leakage time while the CO concentration does not change after the start of CO leakage. Therefore, when the time point to be obtained by the CPU 12a is the time point C, the addition leakage time is 2 minutes. Then, the CPU 12a obtains COHb when the CO concentration 300 (ppm) after the change at the change point O continuously leaks for the addition leakage time of 2 minutes, and sets it as COHb at time C.

That is, the CPU 12a extracts an exponential function expression or a logarithmic function expression as shown in Expression (19) corresponding to the CO concentration of 300 (ppm) from the ROM 12b.
LogY = 0.74 · LogT + Log (1.32) (1.32 is a constant corresponding to a CO concentration of 300 ppm) (19)

  The CPU 12a sets COHb (Y) obtained by substituting the leakage time T = 2 minutes into the above equation (19) as COHb at time C. As a result, COHb at time point C is 2.20%, which is displayed on the display means. Next, the CPU 12a obtains COHb at a time point D when two minutes have passed. That is, time point D is the time point at which COHb is desired. Time D is included while the CO concentration has not changed after the start of CO leakage.

  Therefore, the CPU 12a sets the leakage time of 4 minutes from the start of CO leakage to the time point C to be obtained as the addition leakage time. Then, the CPU 12a obtains COHb when the CO concentration 300 (ppm) after the change at the change point O continuously leaks for the addition leakage time of 4 minutes, and sets it as COHb at time C. The CPU 12a sets COHb (Y) obtained by substituting the leakage time T = addition leakage time 4 minutes into the above equation (19) as COHb at time point D. As a result, COHb at time point D is 3.68%, which is displayed on the display means.

Next, the CPU 12a obtains COHb at a point E when two minutes have passed. That is, the time point E is the time point at which COHb is desired. The time point when the CO concentration changes immediately before time point E is time point D when the CO concentration changes from 300 (ppm) to 400 (ppm). The COHb% at time point E is already determined to be 3.68%. CPU12a calculates | requires the leak time Tb until it reaches COHb = 3.68% in the change time D when the leak of CO concentration 400 (ppm) after the change in the change time D continues. That is, the CPU 12a extracts an exponential function expression or a logarithmic function expression as shown in the expression (20) corresponding to the CO concentration of 400 (ppm) from the ROM 12b.
LogY = 0.74 · LogT + Log (1.73) (1.73 is a constant corresponding to a CO concentration of 400 ppm) (20)

  The CPU 12a obtains the leakage time Tb by substituting COHb (Y) = 3.68% into the above equation (20). As a result, the leakage time Tb is 2.78 minutes. The CPU 12a adds the leakage time 2 minutes from the time point D to the time point E to the leakage time Tb = 2.78 minutes to obtain the added leakage time 4.78 minutes. Next, the CPU 12a obtains COHb when the CO concentration 400 (ppm) after the change at the change point D continuously leaks for 4.78 minutes, and sets it as COHb at time point E. The CPU 12a sets COHb (Y) obtained by substituting the added leakage time 4.78 minutes for the leakage time T in the above equation (20) as COHb at time point E. As a result, COHb at the time point E is 5.50%, which is displayed on the display means.

  Next, detailed operation of the above-described gas alarm device will be described with reference to a flowchart showing a processing procedure of the CPU 12a in FIG. For example, when the CO concentration output from the gas sensor 10 exceeds a predetermined concentration, the CPU 12a determines that CO leakage has started and starts alarm processing. First, the CPU 12a detects the CO concentration (step S40). Next, the CPU 12a relates to the CO concentration X closest to the CO concentration detected in step S40 among the above-described CO concentrations 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, and 1400. The expression LogY = 0.74LogT + Logax is extracted (step S41). Thereafter, it is determined whether or not the detection interval Tα (= 2 minutes) has been exceeded since the CO concentration was detected in step S40 (step S42).

  When the detection interval Tα is exceeded, the CPU 12a sets the addition leakage time Tt as the detection interval Tα (step S43), and then substitutes T = Tt into the relational expression extracted in step S41 to obtain the current COHb (Y). (Step S44) The obtained current COHb is displayed on the display means (Step S45).

  Thereafter, the CPU 12a detects the CO concentration again (step S46). Next, the CPU 12a determines that there is no change in the CO concentration if the difference between the CO concentration detected in step S46 and the previously detected CO concentration is less than a predetermined value (N in step S47), and the next step S48. Proceed to

  In the next step S48, it is determined whether or not the detection interval Tα has elapsed since the CO concentration was detected in step S46. When the detection interval Tα elapses (Y in step S48), the CPU 12a sets the time Tt + Tα obtained by adding the detection interval Tα to the previous addition leakage time Tt as the addition leakage time Tt (step S49), and is now extracted. The current COHb (Y) is obtained by substituting T = Tt into the relational expression (step S50), and the obtained COHb is displayed on the display means (step S51). Thereafter, when the CPU 12a detects, for example, a CO concentration exceeding a predetermined concentration and determines that COHb detection needs to be continued (Y in step S52), the CPU 12a returns to step S46. On the other hand, if the CO concentration lower than the predetermined concentration is detected and it is determined that there is no need to continue the detection of COHb (N in step S52), the alarm process is terminated.

  On the other hand, in step S47, the CPU 12a determines that there is a change in the CO concentration if the difference between the CO concentration detected in step S46 and the previously detected CO concentration is greater than or equal to a predetermined value (Y in step S47). ), And proceeds to the next Step S53.

  In the next step S53, a functional expression corresponding to the CO concentration X closest to the CO concentration detected in step S46 among the CO concentrations 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400. LogY = 0.74 LogT + Logax is extracted again. Next, the leak time Tt is obtained by substituting Y = current COHb into the function expression re-extracted in step S53 (step S54). Thereafter, the CPU 12a determines whether or not the detection interval Tα has elapsed since the CO concentration was detected in step S46 (step S55). When the detection interval Tα elapses (Y in step S55), the CPU 12a sets the time obtained by adding the leakage time Tt obtained in step S54 and the detection interval Tα as the addition leakage time Tt (step S56).

  Thereafter, TOH = Tt is substituted into the relational expression re-extracted in step S53 to obtain COHb (Y). After the obtained COHb (Y) is set as the current COHb (step S57), the current COHb is displayed. After being displayed on the means (step S58), the process proceeds to step S52.

In the first embodiment described above, an electrochemical sensor is used as the gas sensor. However, the gas sensor used in the present invention is not limited to the electrochemical type, and may be, for example, a semiconductor type or a catalytic combustion type as long as it detects CO.

In the first embodiment described above, the detection interval for detecting the CO concentration is not particularly described. For example, the detection may be performed at regular intervals, or as the CO concentration increases as described below, the detection is performed. The interval may be shortened.
0 to 500 ppm: Every 30 seconds 500 to 1000 ppm: Every 15 seconds 2000 ppm or more: Every 5 seconds

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

It is a circuit diagram which shows one Embodiment of the gas alarm device which implemented the gas alarm method of this invention. 6 is a log-log graph showing the relationship between the CO concentration in 21% oxygen and the arrival time until COHb reaches 3, 5, 10, 15, 20, and 25%, respectively. It is a table | surface which shows the relationship between CO concentration in 21% of oxygen, and the arrival time until COHb becomes 3, 5, 10, 15, 20, and 25%, respectively. 6 is a log-log graph showing the relationship between the CO concentration in 18% oxygen and the time required for COHb to reach 5, 10, 15, 20, and 25%, respectively. It is a table | surface which shows the relationship between CO concentration in 18% of oxygen, and the arrival time until COHb becomes 5, 10, 15, 20, and 25%, respectively. It is a time chart which shows the relationship between CO density | concentration, a reciprocal number / time product, and delay time. 7 is a log-log graph showing the relationship between leakage time T and COHb for each of CO concentrations of 200, 300, 400, 500, 600, 700, 800, 1000, 1200, and 1400 ppm when the oxygen concentration is 18%. It is a graph which shows the relationship between COHbYs, Y1, arrival time Ts, and leak time T1. It is a graph which shows the relationship between COHbY1, Y2, and leak time T1, T2. It is a flowchart which shows the process sequence of CPU12a in 1st Embodiment. It is a graph which shows the relationship between COHb and arrival time. It is a graph which shows the relationship between COHb and arrival time. It is a graph which shows the relationship between the reciprocal of arrival time, time product, and time. 6 is a log-log graph showing the relationship between leakage time T and COHb for each of CO concentrations of 200, 300, and 400 ppm when the oxygen concentration is 18%. It is a flowchart which shows the process sequence of CPU12a in a 1st reference example . It is a graph which shows the relationship between CO density | concentration and leak time. It is a flowchart which shows the process sequence of CPU12a in a 2nd reference example . It is a table | surface which shows the relationship between the leakage time T and COHb for every CO concentration 200,300,400,500,600,700,800,1000,1200,1400ppm in oxygen concentration 18%. It is a graph which shows the relationship between COHb (%), CO density | concentration (ppm), and time (minutes) in ii). In the case of (I) and (II) -i) -iii), it is a table | surface which shows time until COHb becomes 25% after CO density | concentration reaches | attains 230 ppmm and 550 ppm. It is a graph which shows the relationship between CO density | concentration and COHb when constant CO density | concentration flows continuously for the delay time of the present gas alarm device.

Explanation of symbols

10 Gas sensor 12a CPU (determination means, alarm generation means, setting means, countdown means, detection means)
12b ROM (storage means)

Claims (3)

A gas alarm device comprising a gas sensor for detecting a carbon monoxide concentration and an alarm generating means for generating an alarm that carbon monoxide has leaked,
A storage means in which an exponential function expression or a logarithmic function expression indicating a relationship between a carbon monoxide concentration in a predetermined oxygen concentration and an arrival time until the carbon monoxide hemoglobin concentration in the blood reaches a predetermined value;
Arrival time calculation means for calculating the arrival time by substituting the carbon monoxide concentration detected by the gas sensor into an exponential function expression or logarithmic function expression stored in the storage means ;
A time product of the reciprocal of the arrival time calculated by the arrival time calculating means is obtained, and a time obtained by multiplying the difference obtained by subtracting the time product of the reciprocal from 1 and the calculated arrival time is set as a delay time, and the delay time A determination means for determining that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined value when reaching 0;
The gas alarm device, wherein the alarm generation unit generates the alarm when the determination unit determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined value. The gas alarm device according to claim 1,
The determination means obtains a time product of the reciprocal of the arrival time corresponding to the carbon monoxide concentration every time the carbon monoxide concentration detected by the gas sensor changes, and a difference obtained by subtracting the time product of the reciprocal from 1 A setting means for setting a time obtained by multiplying the arrival time corresponding to the carbon monoxide concentration after the change as a delay time, and a countdown means for counting down the set delay time, wherein the delay time is zero. When it becomes, it is judged that the said predetermined value was exceeded, The gas alarm device characterized by the above-mentioned. A gas alarm method for generating an alarm that carbon monoxide has leaked,
Substituting the carbon monoxide concentration detected by the gas sensor into an exponential function or logarithmic function that indicates the relationship between the carbon monoxide concentration at a given oxygen concentration and the time required for the carbon monoxide hemoglobin concentration in the blood to reach a prescribed value Then, the arrival time corresponding to the carbon monoxide concentration is calculated, the time product of the reciprocal of the calculated arrival time is obtained, the difference obtained by subtracting the time product of the reciprocal from 1 and the carbon monoxide detected by the gas sensor The time multiplied by the arrival time corresponding to the concentration is the delay time,
When the delay time reaches 0, it is determined that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined value, and the alarm is generated.

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