JPH0650176B2 - Combustion control device for water heater - Google Patents

Description

Detailed Description of the Invention

<Industrial application> The present invention relates to a combustion control device for a water heater, and more specifically, by adjusting a ratio of a combustion on time and a combustion off time to a predetermined ratio and performing a cycle combustion operation, hot water having a predetermined temperature is obtained. The present invention relates to a combustion control device in a water heater that can discharge hot water. <Prior art> In order to obtain a set hot water supply temperature, a water heater that performs on-off cycle combustion operation at the adjusted ratio by adjusting the ratio of the combustion on time and the combustion off time of the burner,
For example, it is proposed in Japanese Utility Model Publication No. 54-127249. In addition, when burning the burner, if the reburn switch is turned on during post-purging in a water heater that performs pre-barge before starting combustion and performs post-purging after combustion is stopped, pre-purging is canceled to improve hot water discharge characteristics. The applicant of the present invention is Japanese Patent Application No. 62-21973 for a water heater that restarts combustion.
Proposed in No. 4. By the way, in the water heater of the above-mentioned on-off cycle combustion operation method, and in the method of canceling the pre-purge when the re-operation command is input during the post-purge after the operation is stopped, there is a problem in the operation of the water heater near the minimum operating flow rate. It was That is, in the operation near the minimum operating flow rate, the flow rate is low, and therefore, the off time of the on / off cycle is generally longer than the on time in many cases. On the other hand, when the flow rate changes near the minimum operating flow rate, the operation is often stopped and restarted frequently. And in that case
When the operation is restarted during the post-purge, the prepurge is canceled, and as a result, the combustion is started after the post-purge time shorter than the off time of the cycle combustion. For example, there is a case where the post-purge time is 3 seconds while the off time of the cycle combustion is 5 seconds. In such a case, if the flow rate changes frequently in the vicinity of the minimum operating flow rate, the result is that the off-time of the cycle combustion is substantially shortened, and there arises a problem that the outlet heated water temperature gradually shifts to a high temperature range. An example of control conditions for starting and stopping the combustion operation in the vicinity of the minimum working flow rate in the conventional water heater will be described with reference to FIG. Two reference flow rates as the minimum working flow rate, eg 2. per minute.
5 Set the flow rate as the first reference flow rate to 2.0 per minute.
The flowing flow rate is used as the second reference flow rate. The flow rate is detected every short time indicated by a black dot. Then, as the condition for performing the combustion operation, a value that once exceeds the first reference flow rate as the flow rate, and then exceeds the second reference flow rate continuously a plurality of times (two times in the case shown in FIG. 4). When is detected, the combustion operation is started at that time (point A, point I). The conditions for stopping the combustion operation are:
If the flow rate lower than the second reference flow rate is detected once, and then the flow rate less than the first reference flow rate is continuously detected a plurality of times (two times in the case shown in FIG. 4), combustion is performed at that time (point F). Is configured to stop. That is, in the case of the flow rate change shown in FIG. 4, the conventional device starts the combustion operation as shown in Table 1,
It becomes a stop situation. As is clear from Table 1, in the conventional device, the on-off cycle combustion operation is started and stopped four times from the time A to the time L. <Problems to be Solved by the Invention> As described above, in the conventional device, the on / off cycle combustion operation is frequently performed when the flow rate becomes unstable near the minimum working flow rate or when the detection nozzle for flow rate detection enters. Therefore, there is a drawback that the on-off cycle combustion OFF time is substantially shortened and the hot water temperature shifts to a high temperature side during operation near the minimum working flow rate. Therefore, the present invention eliminates the above-mentioned drawbacks of the prior art and reduces unnecessary start and stop of operation even if there is instability of the flow rate near the minimum operating flow rate or instability of the detected flow rate due to noise,
An object of the present invention is to provide a combustion control device for a water heater, in which the hot water temperature does not shift to a high temperature side. <Means for Solving the Problems> The combustion control device for a water heater according to the present invention performs an on-off cycle combustion operation to adjust the hot water supply temperature to a predetermined set hot water temperature by the on-off ratio, and also the on-off cycle. When the on-off cycle combustion operation is restarted during the air post purge after the combustion operation is stopped, the on-off cycle combustion control device is a combustion control device in the water heater that cancels the air prepurge prior to the start of combustion. As the minimum working flow rate condition when operating,
A first reference flow rate and a second reference flow rate which is lower than the first reference flow rate and in which the hysteresis region of the on / off cycle combustion operation start / stop is configured are set, and the flow rate detected at a short time interval is continuous for a certain number of times. Then, when the flow rate is equal to or higher than the first reference flow rate, the on-off cycle combustion operation is performed, and when the detected flow rate is continuously lower than or equal to the second reference flow rate for a certain number of times, the on-off cycle It is characterized in that the combustion operation is stopped, and in other cases, the current operation state is maintained. The flow rate detection time interval is determined according to the change characteristic of the flow rate in the vicinity of the minimum operating flow rate of the water heater constituted by the first reference flow rate and the second reference flow rate. Appropriate intervals can be used, ranging from seconds to several seconds. Further, the fixed number of times can be changed to an appropriate number of times which can remove mere fluctuation of the flow rate and detection noise, although it depends of course on the detection time interval of the flow rate. <Operation> When the on-off cycle combustion operation is performed, in order to stop the operation due to the flow rate, the detected flow rate must be equal to or lower than the second reference flow rate for a certain number of times continuously. I won't. That is, if the flow rate exceeding the second reference flow rate is detected even once in a fixed number of consecutive times, the current state is maintained, that is, the on / off cycle combustion operation is continuously performed. Further, when the on-off cycle combustion operation is stopped due to the flow rate, the detected flow rate must be equal to or higher than the first reference flow rate for a certain number of times in order to restart the operation. . That is, if a flow rate lower than the first reference flow rate is detected even once in a fixed number of consecutive times, the current state is maintained, that is, the on / off cycle combustion operation is stopped. <Embodiment> FIG. 1 is an overall configuration diagram of a device of the present invention. Reference numeral 1 is a combustion can body, 2 is a burner, and 3 is a heat exchange coil wound around the combustion can body. The water supplied through the water inlet pipe 4 is instantaneously heated in the heat exchange coil 3 and discharged from the hot water outlet pipe 5. 6 is a controller of the water heater, which has a microcomputer 7 built therein. 8 is a remote control unit, 9 is a flow rate detection sensor, and 10 is a water temperature sensor. The hot water temperature is adjusted as follows. That is, when the hot water outlet temperature is set by the remote control unit 8, the set hot water outlet temperature, the water inlet temperature by the water inlet temperature sensor 10, and the required heat quantity per unit time are calculated in the microcomputer 7 by the flow rate detection sensor 9. Then, the ratio between the combustion on time and the combustion off time for obtaining the set hot water temperature is calculated from the calculated required heat amount and the combustion heat amount of the burner 2. Then, the actual combustion on-time and combustion off-time are determined from this ratio, and this is regarded as one cycle, and the cycle combustion operation is performed. For example, when the ratio of the combustion on to the combustion off is 1: 5, the on / off cycle combustion operation is performed with the actual combustion on time being 1 second, the actual combustion off time being 5 seconds, and the cycle being 6 seconds. You can Now, the hot water supply switch (not shown) of the remote control unit 8 is pressed,
When the hot water discharge run 5a of the hot water discharge pipe 5 is opened, water entry is started, and when the flow rate becomes equal to or higher than the minimum operating flow rate set for the water heater, the on-off cycle combustion operation is started.
Then, air prepurge is performed prior to the start of this operation. On the other hand, when the on / off cycle combustion operation is stopped, the air post purge is performed for several seconds, for example, 3 seconds. When the on / off cycle combustion operation is restarted during the air post purge, the present apparatus cancels the air prepurge and starts the combustion. This cancellation of the prepurge is originally a means for making the response of the apparatus quick by canceling it. For example, while the post-purge time is 3 seconds, the off time of the on-off cycle combustion becomes 5 seconds. In such a case, cancellation of the prepurge may cause re-combustion 3 seconds after the combustion is stopped. This is especially likely to occur when the flow rate is near the minimum operating flow rate. That is, since the flow rate is small in this vicinity, the combustion off time naturally becomes long, and the change in flow rate near the minimum operating flow rate,
This is because the on / off cycle combustion operation is likely to be repeatedly stopped and restarted due to noise in flow rate detection. In the present invention, as a means for reducing unnecessary stop and restart of the on-off cycle combustion operation near the minimum working flow rate,
The microcomputer 7 of the controller 6 has the following control means. This will be described with reference to the flowchart of FIG. 2 and FIG. During the operation of the water heater, the flow rate of the water flowing through the water inlet pipe 4 is detected by the flow rate detection sensor 9 and is read into the microcomputer 7 every 50 μsec, for example (flow (a)). On the other hand, as the minimum working flow rate condition when performing the on-off cycle combustion operation, the first reference flow rate, for example, 2.5 / m
In, and a second reference flow rate, for example, 2.0 / min are set in advance according to the characteristics of the water heater. Two of the first reference flow rate and the second reference flow rate are provided in consideration of the flow rate hysteresis between the start and stop of the on-off cycle combustion operation. First, it is judged whether or not the read flow rate is less than or equal to a second reference flow rate (flow (b)). If it is less than the second reference flow rate, 0 is given as an input data signal (flow (c)), If the flow rate exceeds the reference flow rate of (1), it is further determined whether or not it is the first reference flow rate or more (flow (d)). In this case (when the flow rate is between the first reference flow rate and the second reference flow rate), the previous confirmation data (described later) is given (flow (f)). Then, it is further judged whether or not the input data signal is 1 consecutively n times, for example 3 consecutive times (flow (flow)), and when it is 1 continuously, that is, for example, (111). In this case, [1] is added as the final data (flow (h)), and it is used as an output signal for driving. On the other hand, if the input data does not become 1 for n consecutive times, it is further judged whether the input data is 0 for n consecutive times, for example, 3 consecutive times (flow (i)), and continuously. When it is 0, that is, when it is (000), for example, as finalized data

[0] is added to the output signal to stop the operation (flow (nu)). Furthermore, when the input data does not become zero for n consecutive times (in this case, 0 and 1 are input to consecutive n times of input data).
In case of mixing), the previous fixed data is added as the fixed data, and the fixed data signal is used as the output signal (flow (L)). That is, the previous state is maintained. The above is specifically described for the case of FIG. The black dots indicate the time of detection. At time A, the input data is 1, and the input data is 1 twice before, so the input data becomes 1 three times in a row, and as a result, the confirmed data is [1].
And the on / off combustion operation is started. At the time point B, the last confirmed data [1] is added as the input data.
Similarly, at the time point C, the last confirmed data [1] is added as the input data. At the time of D, the input data becomes 0. However, at this time point D, since the input data is (110) in the past two times in total, the previous finalized data [1] is added as finalized data. Input data is 1 at time E. In the F time, the input data is 1 and the input data of the past two times is (011). Therefore, the previous fixed data [1] is added as the final data. Table 2 below shows the input data and confirmed data at each time point. As is clear from Table 2, in the case of the present invention, the on / off cycle combustion operation is not stopped even if there is a flow rate fluctuation as shown in FIG. This indicates that the start / stop of the operation is not unnecessarily repeated even when the flow rate fluctuates near the minimum operating flow rate, as compared with the case of the conventional example shown in Table 1. As described above, in the present invention, the useless start and stop of the operation is not repeated unless the first reference flow rate is equal to or higher than the first reference flow rate or equal to or lower than the second reference flow rate in the present invention. This is because it is configured to maintain the current operating state. FIG. 3 is a simplified block diagram showing another example. 20 is a control heater, and 21 is a hot water pipe that can be heated by the heater 20. 22 is a fin and may be omitted. The hot water pipe
When the hot water P and the steam bubble Q are mixed in 21, the strength of the heating by the heater 20 is changed to cause the steam bubble Q in the hot water pipe 21 to move, resulting in a stagnant state. It is possible to cause the warm water to flow in a certain direction. <Effect> The present invention is configured as described above, and when the detected flow rate is equal to or higher than the first reference flow rate for a certain number of times continuously, the on-off cycle combustion operation is performed, and the second number of times is continuously performed for a certain number of times. When the flow rate is below the standard flow rate, the on-off cycle combustion operation is stopped, and in other cases, the current operation state is maintained, so the flow rate frequently fluctuates near the minimum operating flow rate, Alternatively, even if the detected flow rate value frequently changes due to the influence of noise, it is possible to prevent unnecessary stop and restart of the operation. Therefore, even if the water heater adopts the on-off cycle combustion operation and the air pre-purge is canceled when the operation is restarted during the air post purge, in the operation near the minimum working flow rate, The drawback that the hot water temperature shifts to a temperature higher than the set hot water temperature is eliminated.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an apparatus for carrying out the present invention, and FIG. 2 is a control flowchart by a microcomputer in the embodiment. FIG. 3 is a diagram showing another example, and FIG. 4 is a diagram showing an example of flow rate change near the minimum operating flow rate. 1: Combustion can 2: Burner 4: Water inlet pipe 5: Hot water outlet pipe 6: Controller 7: Microcomputer 9: Flow rate detection sensor 10: Water inlet temperature sensor

Claims (1)

[Claims] 1. An on / off cycle combustion operation is performed to adjust a predetermined hot water discharge temperature according to the on / off ratio, and an on / off cycle combustion operation is performed during an air post purge after the stop of the on / off cycle combustion operation. A combustion control device in a water heater that cancels air prepurge prior to the start of combustion when restarted, and has a first reference flow rate as a minimum operating flow rate condition when performing the on-off cycle combustion operation. And a second reference flow rate which is lower than that and in which the hysteresis region of the on-off cycle combustion operation start and stop is formed, is set, and the flow rate detected at a short time interval is continuously repeated a fixed number of times for the first reference flow rate. When the flow rate is higher than the reference flow rate of, the on / off cycle combustion operation is performed, and the detected flow rate continues for a certain number of times. If equal to or less than the second reference flow rate, the stop-off cycle combustion operation, water heater combustion control apparatus characterized by being configured to maintain the current operating state otherwise.