JP4943743B2 - Gas alarm and method - Google Patents

Description

  The present invention relates to a gas alarm device and the alarm method, and more particularly to a gas alarm device and an alarm method for generating an alarm that carbon monoxide has leaked.

  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 number of ventilations, 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 among 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. 14 shows the time from when the CO concentration reaches 230 ppm and 550 ppm to when COHb becomes 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. 15 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 occurs uneasy for a long time at a level not exceeding the set point.
JP 2002-39980 A

  Therefore, the present invention provides a gas alarm device and a gas alarm method that can perform a gas alarm according to the influence state of the CO on the human body simply and accurately, paying attention to the above problems. Let it be an issue.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a gas alarm device for generating an alarm that carbon monoxide has leaked, a gas sensor for detecting carbon monoxide concentration, and a predetermined oxygen concentration. Storage means for storing in advance the relationship between the carbon monoxide concentration and the arrival time until the carbon monoxide hemoglobin concentration in the blood reaches a predetermined amount, and subtracting the detection delay time of the gas sensor from the arrival time Correction means for correcting the arrival time, and carbon monoxide detected by the gas sensor from the time when the carbon monoxide concentration detected by the gas sensor exceeds a predetermined concentration from the relationship stored in the storage means Integration means for obtaining a time product of the reciprocal of the corrected arrival time corresponding to the concentration, and a time product of the reciprocal of the arrival time integrated by the integration means. A determination means for determining that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount, and when the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount The gas alarm device is provided with alarm generation means set to generate an alarm.

  According to the first aspect of the present invention, the gas sensor detects the carbon monoxide concentration. The storage means stores in advance 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 amount. The correcting means corrects the arrival time by subtracting the detection delay time of the gas sensor from the arrival time. From the time when the integration means detects the carbon monoxide concentration detected by the gas sensor from the relationship stored in the storage means exceeds the predetermined concentration, the corrected arrival time corresponding to the carbon monoxide concentration detected by the gas sensor from the time point to the present time Find the time product of the inverse of. The determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached a predetermined amount based on the time product of the reciprocal of the arrival time integrated by the integration means. The alarm generation means is set to generate an alarm when the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached a predetermined amount.

  Therefore, the reciprocal / time product of the arrival time corresponds to the current carbon monoxide hemoglobin concentration with respect to the predetermined amount, and whether or not the carbon monoxide hemoglobin concentration has reached the predetermined amount based on the reciprocal / time product of the arrival time. Therefore, even when the carbon monoxide hemoglobin concentration is not directly calculated using a complicated high-order regression equation, an alarm can be generated when the carbon monoxide hemoglobin concentration reaches a predetermined amount. Moreover, the arrival time corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined amount, and the arrival time is corrected by further subtracting the detection delay time of the gas sensor from this arrival time. For this reason, the actual blood hemoglobin concentration reaches the predetermined amount before the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount due to the detection delay time of the gas sensor. Can be prevented.

  The invention according to claim 2 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 amount. The arrival time is corrected by subtracting the detection delay time of the gas sensor from the arrival time of the relationship with the arrival time of the gas, and from the point in time when the carbon monoxide concentration detected by the gas sensor exceeds the predetermined concentration from the relationship To obtain a time product of the reciprocal of the corrected arrival time corresponding to the carbon monoxide concentration detected by the gas sensor until the carbon monoxide in the blood based on the integrated time product of the reciprocal of the arrival time It is determined whether the hemoglobin concentration has reached the predetermined amount, and if it is determined that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount, the warning is performed. It consists in gas alarm method characterized by generating a.

  According to the second aspect of the present invention, the detection delay time of the gas sensor is calculated from the arrival time in 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 amount. Subtract the time to correct the arrival time. From the above relationship, the time product of the reciprocal of the corrected arrival time corresponding to the carbon monoxide concentration detected by the gas sensor from the time point when the carbon monoxide concentration detected by the gas sensor exceeds a predetermined concentration is obtained. Based on the time product of the reciprocal of the integrated arrival time, it is determined whether or not the carbon monoxide hemoglobin concentration in the blood has reached a predetermined amount, and it is determined that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount Then, an alarm is generated.

  Therefore, the reciprocal / time product of the arrival time corresponds to the current carbon monoxide hemoglobin concentration with respect to the predetermined amount, and whether or not the carbon monoxide hemoglobin concentration has reached the predetermined amount based on the reciprocal / time product of the arrival time. Therefore, even when the carbon monoxide hemoglobin concentration is not directly calculated using a complicated high-order regression equation, an alarm can be generated when the carbon monoxide hemoglobin concentration reaches a predetermined amount. Moreover, the arrival time corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined amount, and the arrival time is corrected by further subtracting the detection delay time of the gas sensor from this arrival time. For this reason, the actual blood hemoglobin concentration reaches the predetermined amount before the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount due to the detection delay time of the gas sensor. Can be prevented.

  As described above, according to the first and second 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 amount, 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 amount, the carbon monoxide hemoglobin concentration can be determined without directly calculating the carbon monoxide hemoglobin concentration using a complicated high-order regression equation. Since the alarm can be generated when the fixed amount is reached, the gas alarm according to the influence state of the carbon monoxide on the human body can be easily and accurately performed. Moreover, the arrival time corresponds to the remaining time until the carbon monoxide hemoglobin concentration reaches a predetermined amount, and the arrival time is corrected by further subtracting the detection delay time of the gas sensor from this arrival time. For this reason, the actual blood hemoglobin concentration reaches the predetermined amount before the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount due to the detection delay time of the gas sensor. Since it can prevent, the gas alarm according to the influence state with respect to the human body of carbon monoxide can be performed still more correctly.

  Hereinafter, an embodiment of a gas alarm device and a gas alarm method of the present invention will be described 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 reciprocal / time product of the arrival time corresponding to the CO concentration detected by the gas sensor 10 from the time when the CO concentration detected by the gas sensor 10 exceeds a predetermined concentration of 100 (ppm) to the present time, and the CO concentration The relationship will be described. First, when leakage of 300 (ppm) exceeding 100 (ppm) 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, when the reciprocal / time product reaches 1, it can be determined that COHb is 10%.

  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 the COHb reaches 10%. Therefore, as a method of determining whether or not COHb has reached 10% based on the reciprocal / time product, the difference obtained by subtracting the current reciprocal / time product from 1 is multiplied by the arrival time corresponding to the current CO concentration. It is also conceivable to set the time as the delay time and determine that COHb has become 10% when the delay time becomes zero. Thus, even when COHb is not directly calculated using a complicated high-order regression equation as in the prior art, an alarm can be generated when COHb reaches 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. As is clear from the above, when the reciprocal / time product of the arrival time reaches 1, it can be determined that COHb has reached 10%. Also, 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 is set as a delay time, and when this delay time becomes 0, COHb becomes 10%. Judgment can be made.

  However, in the above method, it is not possible to obtain an accurate reciprocal / time product of the arrival time until COHb reaches 10% due to the detection delay time of the gas sensor 10. The detection delay time of the gas sensor 10 will be described. For example, let us consider a case where 300 (ppm) CO leakage occurs as shown in FIG. As shown in FIG. 10B, the gas sensor 10 does not detect the 300 (ppm) CO leakage immediately after the occurrence of the 300 (ppm) CO leakage, but has a structural structure such as an alarm case structure. Due to delay factors, electrical delay factors due to circuit factors, etc., the detected concentration gradually increases after the occurrence of 300 (ppm) CO leakage, and the detected concentration reaches 300 (ppm) after the detection delay time TL.

  Assume that the detection delay time TL is 1 minute. At time A (FIG. 10 (b)) when the gas sensor 10 detects the occurrence of 300 (ppm) leakage, 300 (ppm) leakage has actually occurred 1 minute before the detection delay time, and COHb There is only 13.54 minutes remaining until 10%. Nevertheless, as described above, in the method of simply calculating the reciprocal / time product of the arrival time, the reciprocal / time product of the arrival time is obtained with the arrival time being 14.54 minutes at time A (FIG. 10 (d )).

  As a result, at time point B (FIG. 10 (c)) when COHb actually reaches 10% and the reciprocal / time product of the arrival time becomes 1, the reciprocal / time product of the arrival time is not 1 (FIG. 10 (d)), an alarm cannot be generated. For this reason, the situation where COHb becomes larger than 10% of assumption at the time of actually generating an alarm will occur.

  Therefore, in this embodiment, the detection delay time TL of the gas sensor 10 is obtained in advance and stored in a storage unit such as the ROM 12b. Then, the arrival time is corrected by subtracting the detection delay time TL of the gas sensor 10 from the arrival time corresponding to the CO concentration detected by the gas sensor 10, and when the reciprocal / time product of the corrected arrival time reaches 1, COHb is 10 It is judged that it became%. The detection delay time changes depending on the structure change such as the case of the gas leak alarm or the circuit change due to the sensor change, and may be obtained experimentally or empirically for each product.

  Next, the reciprocal / time product of the corrected arrival time corresponding to the CO concentration detected by the gas sensor 10 from the time when the CO concentration detected by the gas sensor 10 exceeds a predetermined concentration of 100 (ppm) to the present time. The relationship with the CO concentration will be described. First, when leakage of 300 (ppm) exceeding 100 (ppm) occurs, the arrival time corresponding to this CO concentration is 14.54 minutes, as shown in FIGS. When the arrival time is corrected by setting the time 13.54 minutes obtained by subtracting the detection delay time 1 minute from the arrival time 14.54 minutes as the true arrival time, the reciprocal of the arrival time becomes 1 / 13.54, and the reciprocal / time product is As shown in FIG. 10 (e), it increases with a slope of 1 / 13.54. If 300 (ppm) leakage continues for 10 minutes, the reciprocal / time product is 10 / 13.54.

  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. When the arrival time is corrected with the arrival time 23.48 minutes obtained by subtracting the detection delay time 1 minute from the arrival time 24.48 minutes, the reciprocal of the arrival time becomes 1 / 23.48, and the reciprocal time product is As shown in FIG. 10E, it increases with a slope of 1 / 23.48. If leakage of 200 (ppm) continues for 3 minutes, the reciprocal / time product is (10 / 13.54 + 3 / 23.48).

  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. When the arrival time is corrected with the arrival time of 10.07 minus the detection delay time of 1 minute as the true arrival time, the reciprocal of the arrival time becomes 1 / 9.07, and the reciprocal / time product is As shown in FIG. 10E, it increases with a slope of 1 / 9.07.

  As is clear from comparison of FIGS. 10C and 10E, when the reciprocal / time product of the actual arrival time reaches 1, the reciprocal / time product of the arrival time obtained using the gas sensor 10 is The time when 1 is reached can be made substantially the same. Therefore, it is possible to prevent the actual COHb from reaching 10% before the reciprocal / time product of the arrival time obtained using the gas sensor 10 reaches 1 due to the detection delay time 1 minute of the gas sensor 10. Can do.

  The detailed operation of the above-described gas alarm will be described below with reference to a flowchart showing the processing procedure of the CPU 12a in FIG. When the power to the gas alarm is turned on, the CPU 12a detects the CO concentration x using the gas sensor 10 (step S1). Thereafter, the CPU 12a starts a constant interval timer (step S2). Next, the CPU 12a determines whether or not the current CO concentration x detected in step S1 exceeds 100 (ppm) (= predetermined concentration) (step S3).

  When the current concentration is less than 100 ppm (N in step S3), the CPU 12a waits for the fixed interval t to elapse after the time of the fixed interval t is ended by the fixed interval timer and the previous CO is detected (step S3). Y in S4), the process returns to step S1.

On the other hand, when the current CO concentration is 100 ppm or more (Y in step S3), the CPU 12a determines, for example, the CO concentration in the oxygen concentration 18% stored in advance in the ROM 12b, and the arrival time until COHb reaches 10%. By substituting the current CO concentration x into an exponential function equation or a logarithmic function equation indicating the relationship, an arrival time T _n corresponding to the current CO concentration is obtained (step S5). Then, CPU 12a serves as a correction means, to set a value obtained by subtracting the previously stored detection delay time TL within ROM12b from the arrival time _{T n} obtained in step S5 as the correction arrival time _{T n} ', the arrival time T _n is corrected (step S6).

Then, the CPU 12a functions as an integrating means, and the inverse number / time product Σ (1 / T ′) of the current corrected arrival time T _n ′ is set to a fixed interval t and the inverse number 1 / the corrected arrival time T _n ′ obtained in step S6. T _n 'and the multiplied value t / _{T n'} the reciprocal-time product of the current by adding Σ (1 / T ') to (∵Σ (1 / T') ← Σ (1 / T ') + t / T _n ') (step S7).

  Next, the CPU 12a functions as a determination unit. If the reciprocal / time product Σ (1 / T ′) has reached 1 (Y in step S8), the CPU 12a determines that COHb has reached 10% and generates an alarm. And outputs a CO leakage signal to the voice 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 value stored in the reciprocal / time product Σ (1 / T ′) is less than 1 (N in step S8), the CPU 12a determines that COHb has not reached 10% and is constant. The time measurement is completed by the interval timer, and after a certain interval t has elapsed since the previous detection of the CO concentration (Y in step S10), the CO concentration is detected again using the gas sensor 10 (step S11). Then, the CPU 12a starts a constant interval timer (step S12).

  Next, the CPU 12a determines whether or not the detected CO concentration of 100 ppm or less has continued for 1 hour or longer (step S13). If it has not continued for 1 hour or more (N in step S13), the CPU 12a returns to step S5 again. On the other hand, if it continues for 1 hour or more (N in step S13), it is determined that there is no CO leakage, and the reciprocal of the arrival time / time product Σ (1 / T ′) is reset to 0 (step S14). ), The process returns to step S1.

  According to the above gas alarm device, the reciprocal / time product Σ (1 / T ′) of the corrected arrival time corresponds to the current COHb with respect to COHb = 10%, and the reciprocal / time product Σ (1 / T ′) to determine whether or not COHb has reached 10%, even when COHb has reached 10% without directly calculating COHb using a complicated high-order regression equation. An alarm can be generated.

Further, according to the gas detector, as shown in FIG. 10, a value obtained by subtracting the detection delay time TL from the arrival time T _{n 'as} the corrected arrival time T _n' corrected arrival time T _n inverse-time product of Based on the above, it is determined whether or not COHb has reached 10%. For this reason, it is possible to prevent the actual COHb from reaching 10% before it is determined by the gas alarm that the COHb has reached 10% due to the detection delay time TL of the gas sensor 10. A gas alarm corresponding to the influence state of CO on the human body can be performed more accurately.

  In the above-described embodiment, it is determined that COHb becomes 10% when the reciprocal / time product of the corrected arrival time reaches 1, but the present invention is not limited to this. That is, it is only necessary to make a determination based on the reciprocal / time product of the correction arrival time. For example, a time obtained by multiplying the difference obtained by subtracting the reciprocal / time product of the correction arrival time from 1 and the correction arrival time corresponding to the current CO concentration. May be set as the delay time, and it may be determined that COHb has reached 10% when the delay time becomes zero.

  The detailed operation of the above-described gas alarm will be described below with reference to a flowchart showing the processing procedure of the CPU 12a in FIG. First, the CPU 12a performs the same operation as steps S1 to S6 already described with reference to FIG. Detailed description is omitted here.

Next, the CPU 12a sets the corrected arrival time T _n ′ obtained in step S6 as the delay time Tdl (step S20). Next, the CPU 12a waits for the elapse of the predetermined interval t after the completion of the time measurement by the constant interval timer and the previous detection of the CO concentration (step S21), and detects the CO concentration using the gas sensor 10 (step S22). ).

  Thereafter, the CPU 12a starts the fixed interval timer again (step S23). Next, if the difference between the current CO concentration detected in step S22 and the previous CO concentration is equal to or less than the threshold value, the CPU 12a determines that the CO concentration has not changed (N in step S24), and functions as a countdown unit. Then, after subtracting a predetermined interval t from the delay time Tdl and counting down (step S25), the process proceeds to step S26.

On the other hand, if the difference between the current CO concentration detected in step S22 and the previous CO concentration is greater than the threshold value, it is determined that there is a change in the CO concentration (Y in step S24), and it functions as an integrating means. The reciprocal / time product Σ (1 / T ′) of the corrected arrival time from when the value exceeds 100 (ppm) to the present is obtained (step S27). Then, the correction reached by subtracting the detection delay time TL from the arrival time T _n for a value and CO concentration after the change is a CO concentration of current obtained by subtracting the reciprocal-time from 1 correction arrival time product Σ (1 / T ') time _{T n} 'and time multiplied by (1-Σ (1 / T ')) · T n ' was newly set as the delay time Tdl (steps S28), the process proceeds to step S26.

  As a method for obtaining the reciprocal / time product Σ (1 / T ′) from the time when the CO concentration exceeds 100 (ppm) to the present, for example, every time it is determined in step S24 that there is a change in the CO concentration. A duration counter is provided that is reset and counted up every time it is determined that there is no change in the CO concentration. This duration counter can count the duration for which the CO concentration remains constant. Each time it is determined in step S5 that there is a change in the CO concentration, the reciprocal of the corrected arrival time (1 / Tn ′) corresponding to the CO concentration before the change and the duration counted by the duration counter are calculated. It can be obtained by integrating the multiplied values.

  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 proceeds to step S9 in FIG. On the other hand, if the delay time Tdl is greater than 0 (N in step S26), the CPU 12a determines whether or not the current CO concentration of 100 (ppm) or less continues for 1 hour or more (step S29). ). If it has not continued for 1 hour or more (Y in step S29), the CPU 12a returns to step S21 again. On the other hand, if it continues for 1 hour or more (N in step S30), the process proceeds to step S14 in FIG.

In the above-described embodiment, when the CO concentration changes, the reciprocal / time product Σ (1 / T ′) of the corrected arrival time corresponding to the CO concentration is obtained, and the reciprocal / time product Σ (1 / T ′) is calculated from 1. (1−Σ (1 / T ′)) · T _n ′ multiplied by the difference obtained by subtracting the difference and the corrected arrival time T _n ′ corresponding to the changed CO concentration is set as the delay time Tdl, and the CO concentration While the value did not change, the set delay time Tdl was counted down.

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, the reciprocal of the corrected arrival time corresponding to the CO concentration / time product Σ (1 / T ′ ) And the difference obtained by subtracting the reciprocal time product Σ (1 / T ′) from 1 is multiplied by the corrected arrival time T _n ′ corresponding to the current CO concentration (1− (Σ (1 / T)) · It is also conceivable to set T _n ′ as the delay time Tdl.

In this case, it is not necessary to count down the delay time Tdl, but it is necessary to obtain the reciprocal / time product Σ (1 / T ′) and the corrected arrival time T _n ′ corresponding to the current CO concentration every time the CO concentration is detected. In addition, since high processing capability is required for the CPU 12a, it is desirable to count down while the CO concentration is not changing as described above.

  Further, in the above-described embodiment, an exponential function expression and a logarithmic function expression indicating the relationship between the CO concentration and the arrival time until COHb reaches 10%, for example, are stored. However, when it is difficult to calculate the exponent due to the performance of the CPU 12a, the exponential function equation and the logarithmic function equation described above are approximated by a combination of several linear functions, and the arrival time with respect to the CO concentration is obtained by the approximate equation. Is also possible. It is also conceivable to store a table showing the relationship between the CO concentration and the arrival time until COHb becomes 10%, for example, as shown in FIGS. 3 and 4, and obtaining the arrival time for the CO concentration from this table. It is done.

  In the above-described embodiment, an electrochemical type gas sensor is used. 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.

  Further, in the above-described embodiment, the example in which the CO leakage alarm is generated when the oxygen concentration is assumed to be 18% and COHb becomes 10% has been described. 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%.

  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. (A) to (e) consider the actual CO concentration, the CO concentration detected by the gas sensor, the reciprocal / time product of the actual arrival time, the reciprocal / time product of the arrival time obtained using the gas sensor, and the detection delay time. It is a time chart which shows the relationship between the reciprocal of the arrival time and time product. It is a flowchart which shows the process sequence in the alarm process of CPU which comprises a gas alarm device. It is a flowchart which shows the process sequence in the alarm process of CPU which comprises the gas alarm device in other embodiment. 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 (correction means, integration means, judgment means, alarm generation means)
12b ROM (storage means)

Claims (2)

A gas alarm that generates a warning that carbon monoxide has leaked,
A gas sensor for detecting carbon monoxide concentration;
Storage means for storing in advance the relationship between the carbon monoxide concentration in a predetermined oxygen concentration and the arrival time until the carbon monoxide hemoglobin concentration in the blood reaches a predetermined amount;
Correction means for correcting the arrival time by subtracting the detection delay time of the gas sensor from the arrival time;
The corrected arrival time corresponding to the carbon monoxide concentration detected by the gas sensor from the time point when the carbon monoxide concentration detected by the gas sensor exceeds a predetermined concentration from the relationship stored in the storage means. Integration means for obtaining a time product of the inverse of
Determining means for determining that the concentration of carbon monoxide hemoglobin in the blood has reached the predetermined amount based on a time product of the reciprocal of the arrival time integrated by the integrating means;
A gas alarm device comprising: an alarm generating means set to generate an alarm when the determination means determines that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount . A gas alarm method for generating an alarm that carbon monoxide has leaked,
Of 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 amount, the arrival time is corrected by subtracting the detection delay time of the gas sensor from the arrival time. ,
From the relationship, the time product of the reciprocal of the corrected arrival time corresponding to the carbon monoxide concentration detected by the gas sensor from the time when the carbon monoxide concentration detected by the gas sensor exceeds a predetermined concentration to the present time is obtained. ,
Determining whether the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount based on the time product of the reciprocal of the integrated arrival time;
A gas alarm method, wherein the alarm is generated when it is determined that the carbon monoxide hemoglobin concentration in the blood has reached the predetermined amount.

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