JP2002071615A - Gas concentration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a detector as a whole by preventing large variations in zero-point output values of a gas concentration sensor due to dew condensation, etc., and the deterioration of the gas concentration sensor. SOLUTION: In this gas concentration detector, a control means H causes the gas concentration sensor S to be powered intermittently and repetitively so as to switch it to a powered state when the concentration of a specific gas component is detected and to switch it to a non-powered state when the concentration of the specific gas component is not detected. The control means H memorizes, as a reference output value, the zero-point output value of the sensor S in a situation allowing a prediction that the specific component is zero when the sensor S is in a powered state. When zero-point deviation of the zero-point output value in the powered state of this time from the reference output value in the powered state of the last time is larger than a proper zero-point value, the sensor S is kept in a powered state, even if, thereafter, the concentration of the specific gas component is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration detection sensor for detecting a gas concentration of a specific component in a gas to be detected in an energized state, and switching to an energized state when detecting the gas concentration of the specific component. In addition, the present invention relates to a gas concentration detection device provided with control means for repetitively interrupting and energizing the gas concentration detection sensor so as to switch to a non-energized state when the gas concentration of the specific component is not detected.

[0002]

2. Description of the Related Art A gas concentration detecting device as described above is used to prevent the life of a gas concentration detecting sensor from being shortened or to reduce the running cost by energizing the gas concentration detecting sensor. In order to switch to the energized state when detecting the concentration and to switch to the non-energized state when not detecting the gas concentration of the specific component, the energization to the gas concentration detection sensor is repeatedly intermittently energized.

[0003]

In the above-mentioned conventional gas concentration detecting device, the power supply to the gas concentration detection sensor is stopped because the power supply to the gas concentration detection sensor is repeated and intermittently supplied. At times, the temperature of the gas concentration detection sensor becomes low, and the gas concentration detection sensor is in a state where dew condensation easily occurs. When dew condensation occurs on the gas concentration detection sensor, the zero point output value of the gas concentration detection sensor in a state where the specific component is predicted to be zero fluctuates greatly. Therefore, if the state in which dew condensation occurs on the gas concentration detection sensor continues or is frequently repeated, the amount of decrease in the zero point output value of the gas concentration detection sensor is accumulated, and the zero point output value is reduced. There is a possibility that the temperature of the gas concentration detection sensor may be lowered unrecoverably or that the sensitivity of the gas concentration detection sensor may be deteriorated earlier.

[0004] Incidentally, the zero point output value of the gas concentration detection sensor in a state where the specific component is predicted to be zero is a reference value when detecting the gas concentration of the specific component in the gas to be detected. If the output value of the zero point decreases so as to be unrecoverable, the device itself may become inoperable.

The present invention has been made in view of such a point, and an object of the present invention is to prevent a large fluctuation of a zero point output value of a gas concentration detecting sensor due to dew condensation or the like and a deterioration of the gas concentration detecting sensor. It is an object of the present invention to provide a gas concentration detecting device capable of preventing deterioration as a whole.

[0006]

According to the first aspect of the present invention, there is provided a gas concentration detecting sensor for detecting a gas concentration of a specific component in a gas to be detected in an energized state. When the gas concentration of the specific component is detected, the state is switched to an energized state, and when the gas concentration of the specific component is not detected, the state is switched to a non-energized state. In the gas concentration detection device provided with control means for energizing, when the energization to the gas concentration detection sensor is in an energized state, the control means may be in a state in which the specific component is predicted to be zero. The zero point output value of the gas concentration detection sensor is stored as a reference output value, and the reference output value stored in the previous energization state and the current energization state are stored. Based on the zero point output value of the gas concentration detection sensor, if the zero point deviation between the reference output value and the zero point output value is larger than the proper zero point value, the subsequent gas concentration of the specific component is not detected. At this time, the power supply to the gas concentration detection sensor is maintained in the power supply state.

That is, when the power supply to the gas concentration detection sensor is in the energized state, the control means determines the reference output value stored in the previous energized state and the zero point output value of the gas concentration detection sensor in the current energized state. If the zero point deviation is larger than the proper zero point value, the power supply to the gas concentration detection sensor is maintained in an energized state even when the gas concentration of the specific component is not detected thereafter. When the zero point output value of the detection sensor fluctuates from the zero point output value in the previous energized state and the zero point deviation becomes larger than the proper zero point value, normally, the energization to the gas concentration detection sensor is switched to the non-energized state. Even when the gas concentration of the specific component is not detected, keep the gas concentration detection sensor energized and keep the temperature of the gas concentration detection sensor high. It can become.

Accordingly, if dew condensation occurs in the gas concentration detection sensor, the temperature of the gas concentration detection sensor can be maintained high even when the gas concentration of the specific component is not detected, and the gas concentration detection sensor due to dew condensation or the like can be maintained. Thus, it is possible to provide a gas concentration detection device that can prevent a large fluctuation of the zero point output value and deterioration of the gas concentration detection sensor and can prevent deterioration of the entire device.

According to the second aspect of the present invention, the control means periodically supplies power to the gas concentration detection sensor when the gas concentration of the specific component is not detected when the gas concentration is not detected. Specifically, a zero point output value for the return determination of the gas concentration detection sensor in a state where the specific component is predicted to be zero is detected, and the zero point output value for the return determination is the preceding zero point output value. From the zero point output value of the gas concentration detection sensor when detecting the gas concentration of the specific component, if the zero point deviation at that time has fluctuated more than the return determination value to a side smaller than the zero point proper value, It is configured to release the current supply to the gas concentration detection sensor from being maintained in the current supply state.

That is, the control means determines that the zero point deviation is larger than the proper zero point value.
When energization to the gas concentration detection sensor is maintained when the gas concentration of the specific component is not detected thereafter, energization to the gas concentration detection sensor is performed when the gas concentration of the specific component is not detected. The zero point output value of the gas concentration detection sensor, which fluctuates greatly due to condensation, etc., is maintained on the side where the zero point deviation is smaller than the proper zero point value, that is, the side where the zero point output value becomes an appropriate value. It is periodically determined whether or not the gas concentration detection sensor has returned to a value equal to or greater than the return determination value. The maintenance is released, and the power supply to the gas concentration detection sensor is switched to the non-power supply state.

Therefore, if the control means can determine that the zero point output value of the gas concentration detection sensor has been restored by maintaining the power supply to the gas concentration detection sensor in an energized state, the gas concentration detection sensor Since the power supply to the sensor is stopped, the control unit determines that the zero point deviation is larger than the proper zero point value, and simply transmits the gas concentration to the gas concentration detection sensor during the period when the gas concentration of the specific component is not subsequently detected. Compared to the case where the power is kept in the energized state, the power to the gas concentration detection sensor can be shortened for a shorter time, and the deterioration of the gas concentration detection sensor itself due to the power supply can be prevented.

According to the third aspect of the present invention, the control means stores an initial reference value of the gas concentration detection sensor in a state where the specific component is predicted to be zero.
The control means, when energization of the gas concentration detection sensor is in an energized state, the zero point output value of the gas concentration detection sensor and the initial reference value in a state where the specific component is predicted to be zero. When the deviation between the zero point output value and the initial reference value is equal to or greater than the sensor abnormality determination value, it is determined that the gas concentration detection sensor is abnormal.

In other words, when the power supply to the gas concentration detection sensor is in the power supply state, the control means determines that the deviation between the zero point output value of the gas concentration detection sensor and the stored initial reference value is equal to or greater than the sensor abnormality determination value. If there is, it is determined that the gas concentration detection sensor is abnormal, so that it is possible to detect the abnormality of the gas concentration detection sensor such that the zero point output value of the gas concentration detection sensor fluctuates too much from the initial reference value. However, when the abnormality is detected, the user is prompted to replace the gas concentration detection sensor, or by suppressing the operation of the device thereafter, a new operation is performed by using the gas concentration detection sensor with the abnormality. It is possible to prevent an abnormality from occurring.

According to the fourth aspect of the present invention, the gas concentration detection sensor uses a combustion exhaust gas burned by a burner that burns fuel and combustion air supplied by the ventilation means as a detection target gas, It is configured to detect the gas concentration of a specific component in the combustion exhaust gas, the control means,
During the burning of the burner and during the post-purging by the ventilation means after the burning of the burner is stopped, the gas concentration of the specific component is detected, and after the post-purging until the next combustion of the burner is started. Is set when the gas concentration of the specific component is not detected.

That is, the gas concentration detection sensor detects the flue gas which may cause dew condensation or the like as a gas to be detected and detects the gas concentration of a specific component in the flue gas. By effectively utilizing the fact that even if dew condensation occurs in the gas to be detected due to the action of the device, it is possible to accurately detect the gas concentration of a specific component in the combustion exhaust gas while effectively utilizing the fact that deterioration of the entire device can be prevented. This makes it possible to appropriately adapt the gas concentration detection sensor. Further, the control means may detect the gas concentration of the specific component during the burning of the burner and during the post-purging by the ventilation means after the burning of the burner is stopped, and from the post-purging to the next start of the burning of the burner. Since the gas concentration of the specific component is not detected during the interval, the gas concentration detection sensor can be energized in accordance with the combustion of the burner, and the gas concentration of the specific component in the combustion exhaust gas can be accurately detected. Become.

According to the fifth aspect of the present invention, the gas concentration detection sensor is configured to detect a concentration of carbon monoxide gas in the combustion exhaust gas. That is, the gas concentration detection sensor detects the concentration of carbon monoxide gas in the flue gas burned by the burner by the cooperation with the fourth aspect, and condensing occurs in the flue gas. In addition, it is possible to detect the concentration of carbon monoxide gas in the combustion exhaust gas while preventing deterioration of the entire apparatus. Therefore, generation of carbon monoxide gas due to incomplete combustion of the burner can be accurately detected, and occurrence of abnormality due to incomplete combustion of the burner can be prevented.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which a gas concentration detecting device according to the present invention is applied to a water heater as a configuration in which a gas concentration detecting sensor detects gas concentration in combustion exhaust gas burned by a burner will be described with reference to the drawings. It will be described based on the following. The hot water supply apparatus includes a hot water supply section Y for heating water supplied from a water supply path 8 and supplying hot water to the hot water supply path 7, a control section H as control means for controlling the operation of the hot water supply section Y, and a control section H thereof. And a remote control device for instructing a control operation.

The hot water supply unit Y comprises a combustion chamber 1, a burner 2 provided inside the combustion chamber 1, a heat exchanger 3 for heating water, and the like.
An exhaust passage 5 for discharging the combustion gas outside the room and a fan 4 as ventilation means for ventilating the combustion air through the burner 2 and discharging the combustion gas from the burner 2 to the outside through the exhaust passage 5 are also provided. . A water supply path 6 for supplying water for heating and a water supply path 7 for supplying hot water heated in the heat exchanger 3 to a hot water tap (not shown) are connected to the heat exchanger 3. Supply path 8 for supplying fuel gas through
Is provided.

The water supply passage 6 is provided with a water supply amount sensor 9 for detecting a water supply amount Qi to the heat exchanger 3, and a hot water supply passage 7 is provided with a hot water supply temperature sensor 10 for detecting a hot water supply temperature Tx for a hot water tap. Provided. The fuel supply path 8 is connected to a general household gas supply pipe.
Electromagnetic proportional valve 11 for adjusting fuel supply amount Ip to burner 2
And an on-off valve 12 for interrupting the supply of fuel. An igniter 18 for igniting the burner 2 and a frame rod 19 for detecting ignition are provided near the burner 2.
Is provided.

The remote control device R is connected to the control unit H by wire or wirelessly, and has an operation switch 13 for instructing operation and stop of the hot water supply device, and a set target hot water supply temperature Tp.
And a display lamp 15, 16, 17 for displaying various information. In addition, the display lamp 15 is configured to display whether or not the hot water supply device is operating, and the display lamps 16 and 17 are configured to display an abnormal state as described later.

In the exhaust passage 5, a contact combustion type CO sensor S as a gas concentration detection sensor is provided in contact with the combustion gas of the burner 2, and this CO sensor S is used for combustion generated by the burner. It is configured to output an output value corresponding to the concentration D of carbon monoxide (CO) gas contained in the exhaust gas. That is, the CO sensor S is connected to the heat exchanger 3
The combustion exhaust gas burned by the burner 2 after the heat exchange is used as a detection target gas, and the concentration D of the carbon monoxide gas in the combustion exhaust gas is detected.

The CO sensor S will be specifically described. As shown in FIG. 2, the CO sensor S has a sensor element 23, a temperature compensation reference element 24, and a temperature compensation reference element 24 on a pedestal 22 inside a protective frame 21 made of stainless steel. , CO sensor S
Temperature sensor 25 for detecting the ambient temperature Ta. The sensor element 23 and the temperature-compensating reference element 24 are each composed of a platinum wire carrying a catalyst.
Further, the sensor element 23 and the temperature-compensating reference element 2
4, and the resistance elements 26 and 27 are connected in a bridge circuit state as shown in FIG.

The sensor element 23 and the temperature-compensating reference element 24 are heated to a set temperature for detection of about 250 ° C. by the flow of an electric current, and the unburned components that come into contact with their surfaces are burned by the catalytic action. At this time, since the catalyst carried on the sensor element 23 has selectivity for CO, a difference occurs between the element temperatures of the sensor element 23 and the temperature compensation reference element 24. Further, since the resistance value of the platinum wire changes depending on the temperature, the C
As the O concentration increases, the difference between the resistance values of the sensor element 23 and the temperature compensation reference element 24 increases.

Therefore, the output value Vs corresponding to the CO concentration in the combustion gas is determined by the sensor element 2 in the bridge circuit.
3 from the connection between the temperature-compensating reference element 24 and the connection between the resistance elements 26 and 27 (unit:
(Volts). Note that reference numeral 28 in FIG. 2 denotes a connector portion to a lead wire connected to the control unit H.

The output value Vs of the CO sensor S has a temperature characteristic that it changes according to the ambient temperature Ta even if the CO concentration is the same, and the relationship is shown in FIG. That is, FIG. 4 shows the temperature characteristics of the output value Vs of the CO sensor S when the CO concentration D is predicted to be zero. The solid line L1 in FIG. This graph shows the temperature characteristics of the zero point output value of the CO sensor S when the CO concentration D is predicted to be zero when the device is not shipped (for example, at the time of shipment or until the first burner burns).

In FIG. 4, as the CO concentration D increases, the output value Vs of the CO sensor S increases in a state where the solid line L1 is translated in a direction in which the output value increases. In addition,
In FIG. 4, the range where the ambient temperature Ta is 70 to 200 ° C. generally corresponds to a region where the burner 2 is burning.
The range below ° C generally corresponds to a region where the combustion of the burner 2 is stopped.

When the ambient temperature Ta is fixed at a predetermined temperature, there is a correlation between the CO concentration D and the output value Vs represented by Vs = α × D + β. Incidentally, α is the sensitivity of the CO sensor S, and β is the zero point output value when the CO concentration D is predicted to be zero when the ambient temperature Ta is a predetermined temperature. FIG. 5 shows a correlation between the CO concentration D and the output value Vs. A solid line M1 in FIG. 5 indicates that the CO sensor S has not deteriorated (for example, during shipment or until the first burner burns. At the beginning).

Output value Vs accompanying use of the CO sensor S
The relationship between and the CO concentration D will be described. As shown by a broken line L2 in FIG. 4, when the zero point output value decreases when the CO concentration D is predicted to be zero, the correlation between the CO concentration D and the output value Vs is as shown in FIG. When the CO output D is predicted to be zero, the zero point output value decreases, as shown by a broken line L2 in FIG.
The correlation between the CO concentration D and the output value Vs is as shown by a broken line M3 in FIG.

In FIG. 4, as indicated by broken lines L2 and L3, as the CO sensor S is used, the CO concentration D increases.
The zero point output value when is predicted to be zero tends to decrease when the solid line L1 is translated in a direction in which the output value decreases. Therefore, as shown in FIG.
Assuming that the deviation of the zero point output value when the concentration D is predicted to be zero is ΔV, the deviation ΔV tends to increase as the CO sensor S is used. In addition, CO sensor S
Is used, the sensitivity α of the CO sensor S also changes. Between the sensitivity α and the deviation ΔV, α = αC × (1−K1 × ΔV) (By the way, αC is an initial value) It has been determined by experiment that there is a correlation shown.

That is, the CO concentration D
Is predicted to be zero, the output value at the zero point decreases, and the sensitivity α also decreases (slope is gentle). Incidentally, K1 is a predetermined constant. Therefore, the correlation between the CO concentration D of the CO sensor S during use and the output value Vs is expressed as follows: Vs = α × D + β = αC × (1−K1 × ΔV) × D + β.

The control section H is provided with a microcomputer, and as shown in FIG. 1, a combustion control means 101 for controlling the combustion operation of the burner 2 and the operation of the fan 4.
An incomplete combustion determining means 102 for determining an incomplete combustion state based on the output value of the CO sensor S, and switching to an energized state when the CO concentration D is detected, and a non-conductive state when the CO concentration D is not detected. In order to switch to the energized state, the CO sensor S is constituted by a CO sensor control unit 103 for repeatedly intermittently energizing the CO sensor S for energizing, and a storage unit 104 for storing various control information.

The CO sensor control means 103 detects the CO concentration D during the combustion of the burner 2 and during the post-purge by the fan 4 after the combustion of the burner 2 is stopped.
When the CO concentration D is detected, the energization of the CO sensor S is set to the energized state, and the period from after the post-purge to the start of combustion of the next burner 2 is defined as when the CO concentration D is not detected. In order to keep the energization of the CO sensor S in a non-energized state when is not detected, the energization of the CO sensor S is repeatedly interrupted and energized.

Also, the CO sensor control means 103 outputs the CO
When energization of the sensor S is in the energized state, the zero point output value of the CO sensor S in a state where the CO concentration D is predicted to be zero is stored in the storage unit 104 as the reference output value Vm, Based on the reference output value Vm stored in the storage means 104 in the energized state and the zero point output value of the CO sensor S in the current energized state, the zero point deviation P1 between the reference output value and the zero point output value and zero A zero-point check process for comparing with the point appropriate value Pt is executed, and a zero-point deviation P
When 1 is larger than the proper zero point value Pt, the power supply to the CO sensor S is maintained in the conductive state even when the subsequent CO concentration D is not detected.

That is, the CO sensor control means 103
Each time the CO sensor S is energized when detecting the CO concentration D, the zero point output value of the CO sensor S is stored in the storage unit 104 as a reference output value. Is compared with the zero point output value of the CO sensor S when the current CO sensor S is energized, and if the zero point deviation P1 is larger than a proper zero point value (for example, 100 volts). , Usually CO
Even when the CO concentration D is not detected after the energization of the sensor S is stopped, the energization of the CO sensor S is continued. Incidentally, the proper zero point value is set in consideration of the amount of decrease in the zero point output value when dew condensation occurs in the CO sensor S.
When the dew condensation occurs, the zero point deviation P1 is set to be larger than the proper zero point value.

As described above, the CO sensor control means 10
3 means that the energization to the CO sensor S is maintained in the energized state even when the CO concentration D is not detected. In the state in which the energized state is maintained, the CO concentration D is periodically measured.
A zero point output value for the return determination of the CO sensor S in a state where it is predicted to be zero, and a CO sensor for detecting the zero point output value for the return determination and the CO concentration D before it. S is compared with the zero point output value of S, and the zero point output value for return determination is calculated from the zero point output value of the CO sensor S when the previous CO concentration D is detected. A zero point recovery determination process is performed to determine whether or not the zero point has recovered by fluctuating more than the return determination value to a value smaller than the proper zero point value Pt. The power supply to S is released from being maintained in the power supply state.

That is, when the CO concentration D is detected, the zero point deviation P1 becomes larger than the proper zero point value, and the energization of the CO sensor S is continued even when the subsequent CO concentration D is not detected. In the above, the zero point output value for the return determination of the CO sensor S is detected, and the zero point output value for the return determination is the zero point deviation P1 from the zero point output value when the CO concentration D is detected. When the return determination value (for example, 20 volts) is changed to a value smaller than the value Pt, the power supply to the CO sensor S is stopped.

By the way, the side where the zero point deviation P1 is smaller than the proper zero point value Pt means that when the zero point output value when detecting the CO concentration D is larger than the reference output value, the CO concentration D is detected. When the zero point output value when detecting the CO concentration D is smaller than the reference output value, the CO concentration D
5 shows the side that rises from the zero point output value when detecting the.
When the zero point output value of the CO sensor S fluctuates greatly due to condensation, the zero point output value when detecting the CO concentration D becomes smaller than the reference output value. In the state where the power supply to the CO sensor S is continued even when D is not detected, the side where the zero point deviation P1 is smaller than the proper zero point value Pt is defined as the zero point when the CO concentration D is detected. When the return determination value (for example, 20 volts) has risen from the output value, the power supply to the CO sensor S is stopped.

Further, the CO sensor control means 103 outputs the CO
When energization of the sensor S is in the energized state, the initial reference value Vo of the CO sensor S and the zero output value of the CO sensor S in a state where the CO concentration D stored in the storage unit 104 is predicted to be zero. If the deviation between the zero output value and the initial reference value Vo is equal to or greater than the sensor abnormality determination value Pa (for example, 1000 volts), it is determined that the CO sensor S is abnormal.

The control section H includes a remote controller R, a fan 4, a water supply amount sensor 9, a hot water supply temperature sensor 10, an electromagnetic proportional valve 11, an intermittent valve 12, an igniter 18, a frame rod 19, a CO sensor S, a temperature sensor 25 are connected.

As described above, when the zero point output value of the CO sensor S fluctuates from the zero point output value in the previous energized state due to dew condensation or the like, and the zero point deviation becomes larger than the zero point proper value, the CO signal is usually output. Even when the CO concentration D that switches the energization to the sensor S to the non-energization state is not detected, the energization to the CO sensor S is maintained in the energization state, and the temperature of the CO sensor S is maintained high. And C
When dew condensation occurs on the O sensor S, even when the CO concentration D is not detected, the temperature of the CO sensor S is maintained high, and a large change in the zero point output value of the CO sensor S due to dew condensation or C
It is possible to prevent the deterioration of the O sensor S and prevent the deterioration of the entire device.

Assuming that the zero point deviation is larger than the proper zero point value, when the subsequent CO concentration D is not detected, C
By maintaining the energization of the CO sensor S in the energized state while the energization of the O sensor S is maintained in the energized state, the zero point output value of the CO sensor S greatly fluctuated due to condensation or the like is reduced to zero. On the side where the deviation is smaller than the proper zero point value, that is, on the side where the zero point output value becomes an appropriate value, it is periodically determined whether or not the return is greater than or equal to the return determination value. If the output value has returned equal to or greater than the return determination value, the power supply to the CO sensor S is released from maintaining the power supply state, the power supply to the CO sensor S is made as short as possible, It is configured to prevent deterioration.

The combustion control means 101 controls a water supply amount Qi which is adjusted by a hot water tap and detected by a water supply amount sensor 9.
Is equal to the set water amount, the ignition control of the burner 2 is executed, the fuel supply amount Ip of the burner 2 is adjusted so that the hot water supply temperature Tx becomes the set target hot water supply temperature Tp, and the rotation speed of the fan 4 is changed to the fuel supply amount Ip A combustion control process for controlling the rotation speed of the fan 4 so as to reach a preset target rotation speed, and when the water supply amount Qi becomes smaller than the set water amount, the combustion of the burner 2 is stopped. Have been.

The storage means 104 is, for example, an EEPRO
M (electrically writable and erasable non-volatile memory), etc., and the CO sensor S in a state where the CO concentration D is expected to be zero when the CO sensor S is not deteriorated (for example, at the time of shipment). Initial reference value Vo and CO
The zero point output value of the CO sensor S in a state where the CO concentration D is predicted to be zero during use of the sensor S is stored as a reference output value Vm. As described above, since the CO sensor S has a temperature characteristic that changes in accordance with the ambient temperature Ta even if the CO concentration D is the same, the storage unit 104 stores the initial reference value Vo in the ambient temperature Ta. In the state of being associated, that is, the solid line L1 in FIG.
Is stored in the form of map data.

The reference output value Vm is a value obtained by correcting the zero point output value of the CO sensor S in a state where the CO concentration D is predicted to be zero in accordance with the set temperature (for example, 25 ° C.). Is stored.

The incomplete combustion determination means 102 basically calculates the CO concentration D based on the output value Vs of the CO sensor S by the following equation: Vs = α × D + β. That is, based on the deviation ΔV between the initial reference value Vo and the reference output value Vm corresponding to the set temperature, α is set to α = αC × (1−K1 × Δ
V) and β is changed to the ambient temperature Ta.
And a function F (Ta, ΔV) of the above ΔV,
It is configured to calculate the O concentration D. Note that αC
(Initial value) is stored in advance.

Further, if the state where the calculated concentration becomes equal to or higher than the set concentration (for example, 1000 ppm) continues for a set time (for example, 20 seconds), the incomplete combustion judgment means 102 judges that the incomplete combustion state has occurred. , Display lamp 17
The fact that the combustion is incomplete is notified by turning on.

Immediately after the start of combustion of the burner 2, a transient incomplete combustion state occurs in the combustion of the burner 2, and the CO concentration D
Becomes extremely high temporarily, so that the incomplete combustion determination operation is performed during a set time (for example, 60 seconds) after the start of combustion so as not to determine a transient incomplete combustion state immediately after the start of combustion. Not configured.

Hereinafter, the control operation in the control unit H will be described with reference to FIG.
This will be described based on the flowchart shown in FIG. Water supply amount Q detected by water supply amount sensor 9 when hot water supply is started
When i exceeds the set water amount and the start of combustion is commanded (step 1), the power supply of the CO sensor S is turned on to set the element temperature to the set temperature for detection (about 250 ° C.) (step 2). Subsequently, an ignition control process for the burner 2 is executed (step 3). That is, the electromagnetic proportional valve 11 and the on-off valve 12 are opened to supply the fuel gas to the burner 2 and the igniter 18 ignites.

By the way, normally, when the start of combustion is commanded, a pre-purge operation for ventilating only the fan 4 is performed before the burner 2 is ignited, but the power supply of the CO sensor S is turned on at the same time as the pre-purge operation is performed. Alternatively, the ignition may be performed by the igniter 18 after the play purge.

When ignition is confirmed by the frame rod 19 (step 4), a combustion control process, an incomplete combustion determination control process described later, and a determination as to whether or not incomplete combustion is performed (steps 5 to 7). . When ignition is not confirmed in the above-described ignition control process or when incomplete combustion is determined in the incomplete combustion determination control process (step 7), the solenoid valve 11 and the on-off valve 12 are closed and the burner is closed. A combustion stop process for stopping the combustion of No. 2 is executed, the display lamp 17 is turned on to display an abnormality, and
Turn off the power of the CO sensor S, and turn on the burner 2 until there is a reset operation such as turning off / on the device power switch.
Is prohibited (steps 8 to 11).

In the determination of incomplete combustion, if the incomplete combustion is not determined, the hot water tap is closed and the combustion based on the fact that the water supply amount Qi detected by the water supply amount sensor 9 falls below the set water amount. Until a stop command is issued (step 12), the combustion control process and the incomplete combustion determination control process are repeated. When the combustion stop command is issued, the combustion stop process is executed. Then, even after the burner 2 stops the combustion, the ventilation (post-purge) by the fan 4 is performed for the post-purge set time (5 minutes). Execute (Step 1
3, 14).

When ventilation is performed by the fan 4 for the post-purge set time (5 minutes) after the combustion is stopped, the burner 2 is not burning, and the CO concentration D is expected to be zero. Output value V of the CO sensor S
s is read as a zero-point output value, the zero-point output value is corrected in accordance with the set temperature, the temperature-corrected zero-point output value is stored as a reference output value Vm, and the zero-point output value and The zero point check processing is executed by comparing the reference output value Vm stored in the previous energization state with the reference output value Vm (step 15).

By the way, in this embodiment, the zero-point check processing is executed after the fan 4 has been ventilated for a set time (5 minutes) for post-purging after stopping the combustion, and
The time of the zero point check process is also included in the post purge,
During the post-purge and during the combustion of the burner 2, the time when the CO concentration D is detected is determined. Note that the zero point check process can be executed during the ventilation operation of the fan 4 for a set time for post-purge (5 minutes) after the combustion is stopped.

If the deviation P2 between the zero point output value of the CO sensor S after the above temperature correction and the initial reference value Vo corresponding to the set temperature is equal to or greater than the sensor abnormality determination value Pa, it is determined that the CO sensor S is abnormal. Then, the display lamp 16 is turned on to notify that maintenance is required, the power supply of the CO sensor S is turned off, and an interlock for inhibiting the subsequent operation of the apparatus is applied (steps 16 to 19).

When the deviation P2 between the zero-point output value of the CO sensor S after the temperature correction and the initial reference value Vo corresponding to the set temperature is smaller than the sensor abnormality determination value Pa, the zero-point deviation P1 becomes zero. If it is larger than the point appropriate value Pt (step 20), the power supply to the CO sensor S is continued and the burner 2
A set time for recovery determination after combustion of
Every 30 minutes), a zero point recovery determination process is executed (steps 21 and 22).

That is, every time a set time for recovery determination has elapsed since the combustion of the burner 2 was stopped, a zero point output value for return determination of the CO sensor S is detected, and the zero point output value for return determination is detected. Is changed from the zero point output value at the time of detecting the CO concentration D to the side where the zero point deviation P1 is made smaller than the proper zero point value Pt by a return discriminating value (for example, 20 volts). The point recovery determination process is repeated (step 23). By the way, as described above, when the zero point recovery determination processing is periodically repeated, the hot water supply is started and the water supply amount Q detected by the water supply amount sensor 9 is determined.
When the start of combustion is instructed because i exceeds the set water amount, the process proceeds to step 2 (step 24).

If the zero point deviation P1 is equal to or smaller than the proper zero point value Pt (step 20), each time the integrated combustion time of the burner 2 exceeds the heat cleaning set time, or the number of combustions of the burner 2 is equal to or more than the set number of times. When the heat cleaning timing is reached, the power supply of the CO sensor S is turned off (steps 25 and 27). If the integrated combustion time of the burner 2 has reached the heat cleaning timing due to elapse of the heat cleaning set time or the like, the temperature of the CO sensor S is stored in the storage unit 1 at the time of shipment or the like.
A heat cleaning control process for controlling the energization of the CO sensor S so as to reach the cleaning reference temperature stored in the CPU 04 (step 26).

Incidentally, after the heat cleaning control is executed, the reference output value Vm stored in the storage means 104 is stored again to the same value as the initial reference value Vo at the time of shipment. Note that the heat cleaning control is performed to prevent the sensitivity of the CO sensor S from deteriorating and extend the life of the detection element by flying off the attached matter such as the detection element of the CO sensor S.

Next, the determination as to whether or not the combustion is incomplete will be described with reference to the flowchart shown in FIG.
The flowchart shown in FIG. 8 shows the incomplete combustion determination control process surrounded by the dotted line in FIG. 6 and the determination of the incomplete combustion. First, the output value Vs of the CO sensor S is read (step 31), and β is changed to β = F (T
a, ΔV), and α is α = αC ×
(1−K1 × ΔV), Vs = α ×
D + β, that is, [Vs = αC × (1−K1 × ΔV) × D
+ F (Ta, ΔV)] (steps 32 and 33). Subsequently, when the CO concentration D is higher than the set concentration (for example, 1000 ppm), the counter is started, and when the state where the CO concentration D is higher than the set concentration continues for more than the set time (for example, 20 seconds) (step). 34 to 36), it is determined that the combustion state is incomplete, and the process proceeds to step 8.

If the CO concentration D is smaller than the set concentration, the timer for counting the time is reset and the process proceeds to step 12 (step 37), and the state where the CO concentration D is larger than the set concentration is longer than the set time. If not, the process proceeds to step 12 (step 36).

[Another Embodiment] (1) In the above embodiment, the CO sensor control means 103
However, even when the CO concentration D is not detected, the energization to the CO sensor S is maintained in the energized state. In the state in which the energized state is maintained, the zero point recovery determination process is periodically executed. When the zero point has recovered, CO
Although it is configured to release the current supply to the sensor S in the current supply state, the CO sensor control unit 103
, While the CO concentration D is not detected, the CO sensor S
It is also possible to carry out the configuration by maintaining the power supply to the power supply state. That is, when the CO concentration D that maintains the energization of the CO sensor S in the energized state is not detected, the above-described zero point recovery determination process is not performed, and simply
The energization of the CO sensor S is maintained in the energized state.

(2) In the above embodiment, the initial reference value of the CO sensor S and the zero-point output value of the CO sensor S in the energized state are stored in the storage means 104 for storing various control information as the reference output value Vm. The CO sensor control means 103 is provided with a memory, and the memory is stored in the memory.
Initial reference value of the sensor S and CO in the energized state
It is also possible to store the zero-point output value of the sensor S as the reference output value Vm, and to operate by using only the CO sensor control means 103 as the control means.

(3) In the above embodiment, in the zero point check processing, the zero point output value of the CO sensor S after the temperature correction is compared with the initial reference value Vo corresponding to the set temperature. It is also possible to simply execute the comparison by comparing the zero point output value of the CO sensor S with the initial reference value Vo. In this case as well, the proper zero point value is determined when dew condensation occurs on the CO sensor S. The setting is made in consideration of the amount of decrease in the zero point output value.

(4) In the above embodiment, the gas concentration detection sensor detects the exhaust gas burned by the burner 2 as the gas to be detected, and detects the CO concentration D as the gas concentration of a specific component in the exhaust gas. However, the gas concentration of the specific components in the combustion exhaust gas is not limited to the CO concentration, but a sensor that detects the gas concentration of various other specific components such as the oxygen gas concentration and the hydrogen gas concentration is applied. It is possible to do.

The gas concentration detection sensor uses the combustion exhaust gas burned by the burner 2 as the detection target gas.
The detection target gas is not limited to the combustion exhaust gas, and various gases can be applied such as indoor air as the detection target gas.

(5) In the above embodiment, an example is shown in which the gas concentration detecting device according to the present invention is applied to a hot water supply device.
It can be applied to various other devices such as a combustion device such as a fan heater.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a water heater.

FIG. 2 is a sectional view of a CO sensor.

FIG. 3 is a circuit configuration diagram of a CO sensor.

FIG. 4 is an output value of a CO sensor when the CO concentration D is expected to be zero.

FIG. 5 is a diagram showing an output value of a CO sensor with respect to a CO concentration D;

FIG. 6 is a flowchart showing a control operation of a control unit.

FIG. 7 is a flowchart showing a control operation of a control unit.

FIG. 8 is a flowchart showing a control operation of a control unit.

[Explanation of symbols]

 2 Burner 4 Ventilation means H Control means S Gas concentration detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G060 AA03 AB08 AE19 AF09 AG03 BA03 BB07 BB18 BD02 HC02 HC07 HC09 HC15 HC22 HD01 HE10 KA03 3K003 EA02 FA05 GA03

Claims (5)

[Claims] A gas concentration detection sensor for detecting a gas concentration of a specific component in a gas to be detected in an energized state, switching to an energized state when detecting the gas concentration of the specific component, and detecting the gas concentration of the specific component. Control means for switching between non-energized states when the gas concentration is not detected, and a control means for intermittently energizing and energizing the gas concentration detection sensor, wherein the control means includes: When energization of the gas concentration detection sensor is in an energized state, the zero point output value of the gas concentration detection sensor in a state where the specific component is predicted to be zero is stored as a reference output value, and Based on the reference output value stored in the energized state and the zero point output value of the gas concentration detection sensor in the current energized state. When the zero point deviation from the point output value is larger than the proper zero point value, the power supply to the gas concentration detection sensor is maintained in a conductive state even when the gas concentration of the specific component is not detected thereafter. Gas concentration detector. 2. The method according to claim 1, wherein the control unit periodically supplies the gas concentration detection sensor with a current of zero when the gas concentration of the specific component is not detected. Detecting a zero point output value for return determination of the gas concentration detection sensor in a state predicted as a state,
The zero point output value for the return determination is a zero point deviation from the zero point output value of the gas concentration detection sensor when the gas concentration of the specific component is detected earlier than the zero point appropriate value. 2. The gas concentration detecting device according to claim 1, wherein the gas concentration detecting device is configured to release the current supply to the gas concentration detection sensor from being maintained in an energized state when the gas concentration detection value fluctuates to a value smaller than a return determination value. 3. The control means stores an initial reference value of the gas concentration detection sensor in a state where the specific component is predicted to be zero. When energization is in an energized state, based on the zero point output value of the gas concentration detection sensor and the initial reference value in a state where the specific component is predicted to be zero, the zero point output value and the initial The specific component concentration detection device according to claim 1, wherein the device is configured to determine that the gas concentration detection sensor is abnormal when a deviation from a reference value is equal to or greater than a sensor abnormality determination value. 4. The gas concentration detection sensor detects, as a detection target gas, a combustion exhaust gas burned by a burner that burns fuel and combustion air supplied by a ventilation unit, and a gas of a specific component in the combustion exhaust gas. The control means is configured to detect the gas concentration of the specific component during the burning of the burner and during the post-purge by the ventilation means after the burning of the burner is stopped, and The gas concentration detection device according to any one of claims 1 to 3, wherein the gas concentration of the specific component is not detected during a period from after the post-purge until the next start of combustion of the burner. . 5. The gas concentration detection device according to claim 4, wherein the gas concentration detection sensor is configured to detect a concentration of carbon monoxide gas in the combustion exhaust gas.