JP2013076482A - Combustion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion apparatus in which, even if a CO sensor goes out of order in performance due to a long term disuse in a non-energization state and causes a drift phenomenon where a sensor output decreases by a large range, the phenomenon is solved promptly and a CO concentration can be properly measured.SOLUTION: The combustion apparatus A includes: the CO sensor Sa operable to provide a sensor output corresponding to a CO concentration of an exhaust gas; and a control means 2 that controls the CO sensor Sa to intermittently execute a heat-up operation for heat-cleaning the sensor during energization to the CO sensor Sa. The control means 2 shortens the execution cycle of the heat-up operation of the CO sensor Sa during a predetermined period at the beginning of the energization start of the CO sensor Sa so as to be shorter than that during an ordinary period after the lapse of the predetermined period.

Description

  The present invention relates to a combustion apparatus such as a gas hot water supply apparatus provided with a CO sensor.

  For example, in a gas hot water supply apparatus installed indoors, a CO sensor is usually provided in an exhaust gas path or the like so that a combustion failure such as incomplete combustion of fuel can be detected. A CO sensor has a configuration in which, for example, a platinum coil is coated with a catalyst such as aluminum oxide and then dried and fired. In such a CO sensor, if contaminants adhere to the surface, the sensor output is output. Cause an error. Therefore, as a means for solving such a fear, a CO sensor is heated up at a substantially constant cycle for heat cleaning, and after this heat cleaning, a means for correcting the zero point of the sensor output from the CO sensor is adopted. (For example, see Patent Documents 1 and 2).

  However, in the past, there was room for improvement as described below.

  When the above-described CO sensor is left in a high-temperature and high-humidity environment without being energized, the performance of the CO sensor is modulated, and the sensor output level is considerably higher than the original output level. There is a tendency to shift higher. Such a phenomenon is seen at the beginning of energization of the CO sensor, and the sensor output level decreases as the CO sensor heat cleaning is repeated, and the heat up is repeated about 10 times, for example. Return to the output level. During the period when this phenomenon occurs, the sensor output drift amount is quite large, so even if the sensor output zero point correction processing is performed immediately after heat cleaning, the actual CO concentration can be detected accurately. The measured value of the CO concentration is lower than the actual CO concentration.

  FIG. 5 shows an example in which heat cleaning and zero point correction are performed immediately after energization of the CO sensor is started. When the CO sensor has been modulated as described above, the performance of the CO sensor is gradually recovered (demodulated) by energization, so that the sensor output level gradually decreases as indicated by the arrow N1. . In such a situation, when the burner combustion drive is started at time t11 and the CO concentration subsequently increases, the CO concentration at time t12 is measured as a numerical value corresponding to the sensor output h1. However, the actual CO concentration at time t12 is a numerical value corresponding to the sensor output (h1 + h2) (h2 is the drift amount of the sensor output). As can be understood from this example, conventionally, if the performance of the CO sensor has been modulated and has not been recovered, the measured value of the CO concentration may be considerably lower than the actual CO concentration. there were. Such a fear is not so preferable for early detection when the CO concentration becomes abnormally high.

  From the viewpoint of extending the service life of the CO sensor, it is desirable to reduce the number of heat-up repetitions as much as possible. For this reason, in the past, the period for performing the heat-up is, for example, about 24 hours. However, if the heat-up is performed in such a period, until the CO sensor recovers to its original performance. The trouble which requires considerable time will arise.

Japanese Patent No. 3711024 Japanese Patent No. 3706247

  The present invention has been conceived under the circumstances as described above, and is caused by being left in a high-temperature and high-humidity environment for a long time in a non-energized state. Providing a combustion device that can eliminate this phenomenon at an early stage and perform an appropriate CO concentration measurement even if the performance is modulated and a drift phenomenon occurs in which the sensor output drops with a large range The challenge is to do.

  In order to solve the above problems, the present invention takes the following technical means.

  A combustion apparatus provided by the first aspect of the present invention includes a CO sensor capable of sensor output corresponding to the CO concentration of exhaust gas, and a heat for heat cleaning the CO sensor when the CO sensor is energized. And a control means for intermittently executing up, wherein the control means is a normal unit after the elapse of the predetermined period in a predetermined period at the beginning of energization of the CO sensor. Compared with the period, the CO sensor is configured to shorten the period during which the heat-up of the CO sensor is performed.

  According to such a configuration, the heat-up of the CO sensor is repeated at a short cycle in a predetermined period at the beginning of energization of the CO sensor. Therefore, even if the CO sensor is left unpowered for a long time under high temperature and high humidity conditions, or even if its performance has been modulated due to other reasons, the performance of this CO sensor Can be recovered early. As a result, the use of the CO sensor for a long period without the performance of the CO sensor being recovered is eliminated, and the state where the CO concentration is measured to be lower than the actual concentration can be terminated early. On the other hand, the heat-up execution frequency can be reduced in the normal period after the predetermined period has elapsed. For this reason, the effect which can suppress as much as possible that the service life of CO sensor becomes short due to heat-up is also acquired.

  In the present invention, preferably, the control means can count the number of times of heat-up executed after the start of energization of the CO sensor, and the period during which the count number is less than the predetermined number is the predetermined period. is there.

  According to such a configuration, the heat-up is performed in a short cycle until the number of heat-ups for the CO sensor reaches a predetermined number, and thereafter, the heat is performed in a long cycle. Therefore, only during the period when the modulated CO sensor is considered necessary to restore its original performance, the heat-up execution frequency is efficiently increased, and the heat-up is wasted after the CO sensor performance is restored. It can be prevented from being executed frequently.

  In the present invention, preferably, each time the heat-up is completed, the control means includes a new sensor output value from the CO sensor detected after each of the most recent one or more heat-ups. , A process of comparing the old sensor output value from the CO sensor detected after each end of one or more heat-ups performed before that, the new sensor output value and the old sensor output value can be executed. The predetermined period is a period in which the difference between sensor output values is equal to or greater than a predetermined value, or a period in which the new sensor output value is equal to or less than the old sensor output value.

According to such a configuration, the following effects can be obtained.
That is, if the performance of the CO sensor that has been modulated has not yet recovered sufficiently, and the amount of drift in sensor output is large, the new sensor output value detected after the latest heat-up is completed. And the difference with the old sensor output value detected after the end of the heat-up performed before that becomes large. Further, the new sensor output value does not become higher than the old sensor output value. During the period of such a state, in other words, during the period when the performance of the CO sensor is not sufficiently recovered, the heat-up is executed with a high frequency. On the other hand, after the performance of the CO sensor is sufficiently recovered, it is also appropriately avoided that the heat-up is frequently performed wastefully. Unlike the above configuration, if it is determined whether the CO sensor has recovered based on the number of heat-ups, the performance is still fully recovered even if the number of heat-ups reaches a predetermined number. In some cases, the performance of the CO sensor may be sufficiently recovered before the number of heat-ups reaches a predetermined number. On the other hand, according to the above configuration, this is not the case.

  In the present invention, preferably, the control means can execute a zero point correction process for the CO sensor after the heat-up is performed, and when the zero point correction process is performed in the predetermined period, The correction process for increasing the points is not executed.

  According to such a configuration, the zero point correction process is executed during the predetermined period, and in the zero point correction process, the measured value of the CO concentration is further lowered than the actual CO concentration. Based on the fact that the process is not executed, it is possible to improve the accuracy of the CO concentration measurement value during the predetermined period.

  A combustion apparatus provided by the second aspect of the present invention includes a CO sensor capable of outputting a sensor corresponding to the CO concentration of exhaust gas, and a heat for heat cleaning the CO sensor when the CO sensor is energized. And a control means for intermittently executing up, wherein the control means is a normal unit after the elapse of the predetermined period in a predetermined period at the beginning of energization of the CO sensor. Compared with the period, the CO sensor is configured to increase the heat-up time per one time.

  According to such a configuration, the heat-up time per CO sensor is lengthened in a predetermined period at the beginning of energization of the CO sensor. Therefore, even if the CO sensor has been left in a non-energized state for a long time under high-temperature and high-humidity conditions, even if the performance has been modulated, Due to the effect of increasing the length of the CO sensor, the performance of the CO sensor can be recovered early. Therefore, similarly to the combustion apparatus provided by the first aspect of the present invention, it is possible to eliminate the use of the CO sensor for a long period of time without recovering the performance of the CO sensor. In addition, since the heat-up time is shortened in the normal period after the predetermined period has elapsed, the problem that the service life of the CO sensor is shortened due to the prolonged heat-up is prevented as much as possible.

  In the present invention, preferably, the combustion drive operation is prohibited until the predetermined period elapses.

  According to such a configuration, the combustion apparatus is appropriately prevented from performing combustion driving during a period in which the performance of the CO sensor is not recovered. Therefore, it is more preferable for improving safety. Further, even if the combustion drive operation of the combustion device is prohibited during the predetermined period, the predetermined period is the beginning of energization of the CO sensor and is a very limited time, and this predetermined period is compared. Therefore, there is almost no inconvenience for the user.

  Other features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.

It is a schematic explanatory drawing which shows an example of the combustion apparatus which concerns on this invention. It is a flowchart which shows an example of the operation processing procedure of the control part shown in FIG. It is a flowchart which shows the other example of the operation processing procedure of the control part shown in FIG. It is a flowchart which shows the other example of the operation processing procedure of the control part shown in FIG. It is explanatory drawing which shows an example of a prior art.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  The combustion apparatus A shown in FIG. 1 is configured as a gas hot water supply apparatus, and the basic hardware configuration itself is the same as that conventionally known. That is, the combustion apparatus A includes a burner 10 that burns fuel gas, a fan 11 that supplies combustion air to the burner 10, and a heat exchanger that recovers heat from the combustion gas generated by the burner 10 to heat hot water. 12, CO sensor Sa, and control unit 2 are provided.

  The CO sensor Sa is for detecting the CO concentration of the combustion gas (exhaust gas) after the heat recovery by the heat exchanger 12 and is provided in the exhaust path of the combustion gas. As this CO sensor Sa, a conventionally known one can be used. For example, a platinum wire coil is coated with a catalyst such as aluminum oxide, dried and fired. If CO is present in the exhaust gas, the CO concentration can be detected based on the principle that the resistance value of the platinum wire coil increases due to the reaction heat with CO. If contaminants adhere to the surface of the CO sensor Sa, an error occurs in the sensor output value. The heat cleaning of the CO sensor Sa is a process of removing the contaminants by causing the CO sensor Sa to heat up by flowing a larger current than usual, and is executed under the control of the control unit 2.

  The control unit 2 is configured using a microcomputer or the like, and performs operation control of each unit of the combustion apparatus A. Moreover, it corresponds to an example of the control means in the present invention. The control unit 2 is in charge of control to intermittently execute the heat-up process for performing the heat cleaning of the CO sensor Sa. However, as will be described later, in a predetermined period at the beginning of energization of the CO sensor Sa, a process for performing heat-up at a cycle shorter than the normal cycle is executed.

  Next, the operation of the above-described combustion apparatus A will be described. An example of the operation processing procedure of the control unit 2 will be described with reference to the flowchart of FIG.

  First, when the combustion apparatus A is powered on, the CO sensor Sa is immediately energized (S1: YES). When energization of the CO sensor Sa is started, the control unit 2 sets the number of heat cleanings (count number) n of the CO sensor Sa to n = 0, and then performs heat-up (S2, S3). ). The time required for this heat-up is, for example, about 25 seconds. When this process is completed, the number n of heat-ups is increased by “1” (S4). This number n of heat-ups is used to determine a heat-up cycle and the like. Next, the control unit 2 determines whether or not the number n of heat-ups is equal to or greater than the predetermined number N (S5), and executes different control depending on whether n ≧ N or not. Here, N is, for example, “10”.

The period in which the number n of heat-ups is less than 10 corresponds to an example of the predetermined time at the beginning of energization of the CO sensor in the present invention. In this period, the sensor output from the CO sensor Sa is corrected for zero point after heat-up, and the heat-up cycle is set to a predetermined cycle C1 (S5: NO, S9, S10). In the zero point correction process, a process for increasing the zero point (a process for changing the zero point to a higher sensor output) is prohibited. According to such a configuration, it is possible to bring the sensor output value close to an appropriate value while suppressing the measured CO concentration value from being lower than the actual CO concentration. The predetermined period C1 is shorter than a period C2 of a normal period to be described later, and is, for example, a period of 3 seconds. When this period C1 is set and this time is up, the heat-up is executed again, but the heat-up is repeatedly executed at intervals of 3 seconds until the number reaches 10 (S10, S8). : YES, S3).

  When the process of repeating the heat-up in the cycle C1 shorter than the cycle C2 of the normal period is performed, the CO sensor Sa has been left in a high-temperature and high-humidity environment for a long time, for example, in a non-energized state before starting energization. As a result, when the performance has been modulated, an effect of restoring the performance can be expected. Therefore, after the above-described processing, the drift phenomenon in which the sensor output of the CO sensor Sa greatly decreases is eliminated or alleviated, and the CO concentration can be measured with high accuracy.

  The period after the number n of heat-ups reaches 10 corresponds to an example of a normal period in the present invention. In this normal period, after the sensor output zero point correction process is performed, the heat-up cycle is set to a predetermined cycle C2 (S5: YES, S6, S7). Unlike the previous step S9, the zero point correction process in step S6 is allowed to increase the zero point. After the number n of heat-ups reaches 10 times, as described above, the drift phenomenon with respect to the sensor output is suppressed. However, it is preferable to set the zero point to an appropriate position and make the measured value of the CO concentration accurate.

  The heat-up cycle C2 is, for example, 24 hours, and heat-up is executed once a day. Therefore, it is possible to prevent the heat-up execution frequency from becoming excessive in a period in which the number n of heat-ups reaches 10 and the performance of the CO sensor Sa is considered to have recovered. This is preferable for suppressing a reduction in the service life of the CO sensor due to heat-up, and also preferable for reducing power consumption.

  When the burner 10 is in combustion drive at the time point when the cycle C2 is up, heat-up is started immediately after the combustion drive is stopped. This also applies to the case where the heat-up is executed with the period C1. As understood from this, the period in the present invention means that the time interval at which the heat-up is performed does not have to be strictly constant, and the operation of each part of the combustion apparatus A and other matters. Depending on the influence, the time interval may change slightly. Although not shown in FIG. 2, in the CO concentration measurement process using the CO sensor Sa, when the CO concentration exceeds a predetermined value, a notification operation to that effect is performed under the control of the control unit 2, and the burner Ten combustion drive forced stop measures are taken.

  In the operation process shown in FIG. 2, the zero point correction process is always performed after the heat up. For example, in the zero point correction process in step S <b> 9, the zero point correction after the second to the ninth heat up is performed. Changes such as omitting the processing can be added. The specific value of the predetermined number N in the operation process is not limited to “10”. Furthermore, the specific length of the periods C1 and C2 is not limited. If the period C1 is shorter than the period C2, the performance of the CO sensor Sa that has been modulated can be recovered early.

The control unit 2 may be configured to execute operation control as shown in FIG. 3 or FIG. 4 instead of the above-described operation control.

  In the operation control shown in FIG. 3, whether to set the heat-up cycle to C1 or C2, in other words, whether or not the performance of the CO sensor Sa has been restored is determined based on the change in the sensor output. Has been. Further, during the period when it is determined that the performance of the CO sensor Sa has not recovered, the combustion drive of the burner 10 is prohibited.

  More specifically, when energization of the CO sensor Sa is started, the control unit 2 causes the first heat-up to be performed in a state in which the combustion drive of the burner 10 is prohibited (S21: YES, S22, S23). ). Next, the control unit 2 stores the value of the sensor output from the CO sensor Sa after the heat up (S24). When the previous heat-up is the first time, the heat-up cycle is set to the cycle C1 (for example, every 3 seconds), and when this cycle C1 is timed up thereafter, the second heat-up is executed ( S25: YES, S26, S27: YES, S23). The sensor output after this heat-up is also stored (S24).

  In the case of the second or subsequent heat-up, the control unit 2 calculates the new sensor output value from the CO sensor Sa detected after the current heat-up and the old sensor output value detected after the previous heat-up. Compare (S28). As a result of the comparison, if the difference between the new sensor output value and the old sensor output value is large and this difference is greater than or equal to a predetermined value, the heat-up cycle is set to C1 (S29: NO, S26). On the other hand, when the difference is less than the predetermined value, the heat-up cycle is set to C2 (for example, 24 hours), and the drive prohibited state of the burner 10 is released (S29: YES, S30, S31). . The period during which NO in step S29 is maintained corresponds to a specific example of a predetermined period at the beginning of energization of the CO sensor referred to in the present invention. It corresponds to an example.

  According to the control described above, the performance of the CO sensor Sa is not sufficiently recovered, and the difference between the new sensor output value and the old sensor output value is increased due to the large amount of drift in the sensor output. Then, the heat-up is repeatedly executed with a short cycle C1. Therefore, the CO sensor Sa can be recovered early. On the other hand, when the performance of the CO sensor Sa is sufficiently recovered, the cycle C2 having a long heat-up cycle is set. Therefore, after the performance of the CO sensor Sa is recovered, it is possible to eliminate the possibility that the heat-up is executed with a high frequency. In the control described above, it is determined whether or not the CO sensor Sa has recovered by comparing the new sensor output value and the old sensor output value. In this way, the determination method based on the sensor output value is used. Therefore, it is possible to make the determination result accurate. During the period when the performance of the CO sensor is not recovered, the combustion drive of the burner 10 is prohibited, which is more preferable for improving safety.

  In the operation procedure described above, based on the difference between the new sensor output value and the old sensor output value, it is determined which of the cycle C1 and C2 the heat-up cycle is in addition to or instead of this. For example, the following method can also be employed. That is, if the new sensor output value is less than or equal to the old sensor output value, the heat-up cycle is set as cycle C1, and if not, the heat-up cycle is set as cycle C2. Even with such a configuration, as described above, it is possible to increase the frequency of heat-up during a period in which the performance of the CO sensor Sa is not sufficiently recovered. If the sensor output drifts in the downward direction, the new sensor output value will not exceed the old sensor output value.If the new sensor output value exceeds the old sensor output value, the drift will be This is because it can be considered that it no longer occurs.

The above-described new sensor output value and old sensor output value do not necessarily have to be sensor output values detected after the current and previous heat-ups. For example, an average value of sensor output values detected after a plurality of heat-ups performed before and before the previous time may be used as the old sensor output value. Similarly, the average value of the sensor output values detected after the latest plural heat-ups can be used as the new sensor output value. In this way, the reliability of the new sensor output value and the old sensor output value is increased, and it is possible to more accurately determine whether or not the performance of the CO sensor Sa has been recovered.

  In the operation control shown in FIG. 4, instead of changing the heat-up cycle of the CO sensor Sa, the heat-up time per time for the CO sensor is changed.

  Specifically, when energization of the CO sensor Sa is started, the control unit 2 thereafter executes the first heat-up, and the heat-up time at that time is a predetermined first time T1. (S41: YES, S42: YES, S43). This first time T1 is, for example, about 200 seconds to 250 seconds, and is the length of 10 times of the normal heat-up time or a length close thereto. On the other hand, the second and subsequent heat-up times are set to a predetermined second time T2 (S42: NO, S46). The second time T2 is, for example, about 25 seconds, similarly to the time required for normal heat-up. After each heat-up, the sensor output zero point correction is performed, and then the heat-up is repeated every time the heat-up cycle times up (S44, S45: YES, S42: NO, S46). The heat up period is, for example, 24 hours.

  According to the above-described operation control, the first time T1, which is the time required for the first heat-up, is considerably long, and the performance of the CO sensor Sa can be recovered only by this first heat-up. is there. Therefore, the performance of the CO sensor Sa can be recovered earlier than when the performance of the CO sensor Sa is recovered by intermittently performing multiple heat-ups. In the operation control described above, the period during which the first heat-up is performed corresponds to a specific example of the predetermined period at the beginning of energization of the CO sensor in the present invention. In addition, since a large current flows through the CO sensor Sa at the time of heat-up, if the heat-up time is lengthened, damage to the CO sensor Sa may increase. In such a case, damage should be reduced. What is necessary is just to control the electric current for heat-up suitably. The first heat-up in the operation control is intended to recover the performance of the CO sensor Sa rather than the cleaning of the CO sensor Sa. Therefore, the heat-up temperature of the CO sensor Sa is set to the heat generation temperature for normal heat cleaning. The temperature may be lower than that. Although not shown in the drawing, preferably, the combustion drive of the burner 10 is prohibited until the first heat-up and the subsequent zero point correction process are completed.

  In the above-described operation control, the performance of the CO sensor Sa is recovered only by the first heat-up, but unlike this, for example, the heat-up time per one time is set to around 100 seconds, for a total of two times. The performance of the CO sensor Sa may be recovered by a plurality of heat-ups, for example, the performance of the CO sensor Sa is recovered by heat-up. In this case, it is preferable to set the heat-up cycle shorter than the normal period until the performance of the CO sensor Sa is recovered. In any case, the performance of the CO sensor Sa can be recovered early if the heat-up time per time is longer than the heat-up time in the normal period.

  The present invention is not limited to the contents of the above-described embodiment. The specific configuration of each part of the combustion apparatus according to the present invention can be modified in various ways within the intended scope of the present invention.

The CO sensor is not particularly limited as long as it can output a sensor corresponding to the CO concentration. As the burner, for example, an oil burner can be used instead of the gas burner. The combustion apparatus according to the present invention does not necessarily have to be configured as a hot water supply apparatus, and may be configured as a combustion apparatus for heating, for example.

A Combustion device Sa CO sensor 2 Control unit (control means)
10 Burner

Claims (6)

A CO sensor capable of sensor output corresponding to the CO concentration of the exhaust gas;
Control means for intermittently executing heat-up for heat-cleaning the CO sensor at the time of energization of the CO sensor;
A combustion device comprising:
The control means shortens the period during which the CO sensor is heated up in a predetermined period at the beginning of energization of the CO sensor, compared to a normal period after the predetermined period has elapsed. Combustion device characterized by being constituted. The combustion device according to claim 1,
The said control means can count the frequency | count of the heat-up performed after the energization start about the said CO sensor, and the period when this count number is less than predetermined times is the said predetermined period. The combustion device according to claim 1,
Each time the heat-up is completed, the control means is performed before the new sensor output value from the CO sensor detected after each of the most recently performed one or more heat-ups. A process of comparing the old sensor output value from the CO sensor detected after each end of one or more heat-ups can be executed,
The combustion apparatus, wherein a period in which a difference between the new sensor output value and the old sensor output value is a predetermined value or a period in which the new sensor output value is equal to or less than the old sensor output value is the predetermined period. A combustion apparatus according to any one of claims 1 to 3,
The control means can execute a zero point correction process for the CO sensor after the heat-up is performed,
A combustion apparatus configured such that when the zero point correction process is performed during the predetermined period, the correction process for increasing the zero point is not executed. A CO sensor capable of sensor output corresponding to the CO concentration of the exhaust gas;
Control means for intermittently executing heat-up for heat-cleaning the CO sensor at the time of energization of the CO sensor;
A combustion device comprising:
The control means increases the heat-up time per one time for the CO sensor in a predetermined period at the beginning of energization of the CO sensor, compared to a normal period after the predetermined period has elapsed. It is comprised in the combustion apparatus characterized by the above-mentioned. A combustion apparatus according to any one of claims 1 to 3 and 5,
A combustion apparatus configured to prohibit a combustion drive operation until the predetermined period elapses.

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