JP6653079B2 - Water heater - Google Patents

Description

  The present invention relates to a hot water supply apparatus that performs control by combining feedforward control and feedback control to maintain a hot water supply temperature at a set temperature.

  2. Description of the Related Art Conventionally, in a hot water supply apparatus, in addition to feedback control (FB control) based on a deviation of a tapping temperature from a set temperature, feedforward control based on a difference temperature between a set temperature and an incoming water temperature so that hot water at a set temperature is supplied. Hot water temperature control combined with (FF control) is performed.

  For example, in Patent Literature 1, an output heat amount is calculated from a difference temperature between an inlet water temperature and a tap water temperature and a flow rate, and an operation coefficient is learned based on a ratio of an output heat amount to a heat amount required for tapping hot water at a set temperature. A hot water supply apparatus that performs hot water temperature control that adjusts the output of a heating unit by combining FF control and FB control based on this calculation coefficient is described.

JP 2014-137206 A

  However, when the incoming water temperature fluctuates sharply, the variation of the incoming water temperature in the operation coefficient is delayed, and the temperature of the hot water discharged from the hot water supply device fluctuates, and there is a possibility that the hot water at the set temperature cannot be discharged. For example, when the incoming water temperature suddenly drops from high temperature to low temperature, the output of the heating means is increased to heat the hot water even though the hot water remains in the water heater, so that the hot water is excessively heated. And the tapping temperature rises. Then, since the heating means is stopped by the safe operation of the hot water supply device, low-temperature hot water is discharged following high-temperature hot water, and the hot water temperature is not stable, which is not preferable.

  On the other hand, if the incoming water temperature rises sharply from low to high temperatures, the output of the heating means is reduced and heating is performed despite the low-temperature hot water remaining in the hot-water supply device. Insufficient and the tapping temperature becomes low. Then, since the output of the heating means is increased and the heating is performed to compensate for the drop in the hot water temperature, the incoming high-temperature hot water is excessively heated, and the high-temperature hot water remaining in the hot water supply device is followed by the high-temperature hot water. Hot water is to be discharged, and the hot water temperature is not stable, which is not preferable.

  An object of the present invention is to provide a hot water supply device capable of stabilizing a tap water temperature even when the incoming water temperature fluctuates rapidly.

A hot water supply apparatus according to a first aspect of the present invention includes a heat exchanger for heating hot water flowing inside by a combustion gas generated in a combustion section, and an input water temperature detecting means for detecting an input water temperature introduced into the heat exchanger. Hot water temperature detecting means for detecting the temperature of hot water discharged from the heat exchanger; flow rate detecting means for detecting the flow rate of hot water passing through the heat exchanger; and Control means for controlling the required amount of heat generated in the combustion unit at predetermined intervals based on the incoming water temperature, the hot water temperature, the flow rate and the hot water set temperature, and the control means includes a difference between the incoming water temperature and the hot water temperature. Learning means for calculating an output heat quantity from the temperature and the flow rate, and learning an operation coefficient based on a ratio of the output heat quantity to the required generated heat quantity, a difference temperature between the hot water supply set temperature and the incoming water temperature, and the flow rate Feedforward control means for calculating a first required heat quantity based on the calculation coefficient; and a second necessary generation based on the difference between the hot water supply set temperature and the tapping temperature, the flow rate, and the calculation coefficient. a feedback control means for calculating the amount of heat, and the first required heat generation amount and the second required amount of heat generated and adding means for setting the required amount of heat generated by adding the learning means, the predetermined When the rate of change of the incoming water temperature in a cycle is out of a predetermined range, the operation coefficient is returned to an initial value.

  A hot water supply apparatus according to a second invention is characterized in that in the first invention, the hot water supply apparatus is configured to be able to operate immediately.

According to the hot water supply apparatus of the first invention, when the rate of change of the incoming water temperature in a predetermined cycle is out of the predetermined range due to a rapid change of the incoming water temperature, it is necessary to return the operation coefficient that is sequentially updated to the initial value. By performing hot water temperature control for controlling the amount of generated heat, fluctuations in the hot water temperature can be suppressed, and hot and cold water can be discharged at a stable temperature.

According to the hot water supply apparatus of the second invention, since the hot water supply apparatus is configured to be capable of quick hot water operation, when hot water is supplied from a hot water tap or the like during the hot water operation and low-temperature water flows into the hot water supply apparatus, Although variations in the incoming water temperature when the hot water in which the start of the hot water operation is heated from a low temperature of hot water heated to a high temperature is drowned again water heater is increased, the rate of change of the incoming water temperature in a given period if out of the predetermined range Since the hot water temperature control is performed by returning the operation coefficient to the initial value, it is possible to control the fluctuation of the hot water temperature and to supply hot and cold water at a stable temperature.

It is a schematic structure figure of an instant hot water circulation system which has a hot water supply device of the present invention. It is a functional block diagram for explaining hot water temperature control in the hot water supply device of the present invention. It is a figure which shows roughly the relationship between the weight parameter of an operation coefficient, and a flow volume. It is a flowchart which shows the processing procedure of hot water temperature control. It is a figure showing an example of hot water temperature control of the hot water supply device concerning this example. It is a flowchart which shows the temperature rise control of hot water at the time of the start of a hot water operation.

  Hereinafter, embodiments for carrying out the present invention will be described based on examples.

  As shown in FIG. 1, the hot water circulation system 1 includes a hot water supply device 2, a water supply passage 3 for supplying hot water to the hot water supply device 2, a hot water supply passage 4 from which the hot water heated by the hot water supply device 2 is supplied, A circulation pump 5 that sends hot water flowing through the passage 4 to the hot water supply device 2 via the water inlet passage 3; and a circulation passage 6 that allows hot water discharged from the hot water supply device 2 to re-enter the hot water supply device 2 is formed. .

  The water inlet passage 3 is connected to a water supply passage 7 for supplying tap water to the hot water supply device 2 through the water inlet passage 3 and an expansion tank 8 for absorbing thermal expansion of the circulating hot water. An air separator 9 to be separated and a check valve 10 for preventing backflow are provided. The water supply passage 7 is provided with a check valve 11 for preventing hot water flowing through the water inlet passage 3 from flowing back to the water supply passage 7. A hot water tap F is provided in the hot water passage 4. One or a plurality of hot water taps F may be provided.

  Hot water supply device 2 includes a heating passage 12, a burner 13, a heat exchanger 14, a gas proportional valve 15, a tap water flow control valve 16, and a control unit 17 (corresponding to control means).

  The heating passage 12 has an upstream end connected to the inlet passage 3, a downstream end connected to the outlet passage 4, and supplies hot water supplied from the inlet passage 3 and heated in the heat exchanger 14 to the outlet passage 4. The tapping flow rate adjusting valve 16 can control the tapping flow rate by adjusting the opening degree by the control unit 17.

  The burner 13 generates a high-temperature combustion gas by burning a mixture of fuel gas supplied from a gas pipe (not shown) and air supplied from a combustion fan (not shown) in a combustion section. The amount of fuel gas supplied to the burner 13 is controlled by adjusting the opening of the gas proportional valve 15 by the control unit 17. The amount of air supplied from the combustion fan is controlled so that the air-fuel ratio in combustion in the burner 13 is constant.

  The heat exchanger 14 heats hot water by exchanging heat between high-temperature combustion gas generated by combustion in the burner 13 and hot water flowing through the heating passage 12.

  The heating passage 12 is provided with a flow rate sensor 18 (corresponding to flow rate detecting means), an incoming water temperature sensor 19 (corresponding to incoming water temperature detecting means), and a tapping temperature sensor 20 (corresponding to tapping temperature detecting means). ing. The flow rate Q of the heating passage 12 is detected by the flow rate sensor 18. The incoming water temperature sensor 19 is provided upstream of the heat exchanger 14 and detects the incoming water temperature Tc. Hot water temperature sensor 20 is provided downstream of heat exchanger 14, and detects hot water temperature Th. The detected flow rate Q, incoming water temperature Tc, and outgoing water temperature Th are transmitted to the control unit 17.

  The control unit 17 executes hot water temperature control for controlling the hot water temperature Th according to the set temperature Tr set by operating the operation remote controller 21 or the like. More specifically, the control unit 17 calculates the required amount of heat generated by the burner 13 for controlling the hot water temperature, and adjusts the opening of the gas proportional valve 15 according to the required amount of generated heat. When the amount of heat generated in the burner 13 changes due to the adjustment of the opening of the gas proportional valve 15, the amount of heat contributing to an increase in water temperature via the heat exchanger 14 changes, so that the tapping temperature Th changes.

  As shown in FIG. 2, the control unit 17 includes a learning unit 22 for learning the operation coefficient R, a feedforward control unit 23 (FF control unit 23), a feedback control unit 24 (FB control unit 24), and an addition unit. The required heat quantity Utl is set by calculation of each means. Generally, in a hot water supply device, the required generated heat amount Utl is calculated in units of the number of units. The number 1 corresponds to the amount of heat required to raise the hot water temperature by 25 ° C. under the flow rate of Q = 1 (L / min). Therefore, the required amount of generated heat may be hereinafter referred to as the input number.

  The control unit 17 sets the input number Utl so as to control the tapping temperature Th according to the set temperature Tr. In accordance with the set input number Utl, the amount of fuel gas supplied to the burner 13 of the water heater 2 is controlled, and the amount of heat generated by the burner 13 is controlled.

  The learning means 22 is based on the flow rate Q detected by the flow rate sensor 18, the incoming water temperature Tc detected by the incoming water temperature sensor 19, the tap water temperature Th detected by the tap water temperature sensor 20, and the input number Utl. , The operation coefficient R is learned.

  The calculation coefficient R corresponds to a ratio of the output heat amount (the output heat amount actual ratio) Kr to the required generated heat amount Utl, which is represented by the product of the temperature of the heated hot water (Th-Tc) and the flow rate Q. Kr is defined by the following equation (1).

  The actual output heat amount ratio Kr is ideally 25 from the definition of the number described above. However, the output calorific value actual ratio Kr fluctuates from 25 in accordance with the adjustment deviation in the gas proportional valve 15, the state of the incoming water temperature, and the like. For example, when the incoming water temperature is high, the heat exchange efficiency in the heat exchanger 14 is lower than the expected heat exchange efficiency, and the actual output heat amount ratio Kr is smaller than 25.

  The learning means 22 learns the operation coefficient R in accordance with the following equation (2) at every fixed control period Δt, for example, at every 100 ms. In equation (2), R (n) is a learning value calculated based on the learning result in the n-th control cycle, and R (n-1) is the (n-1) -th cycle previous. ) Is the learning value calculated in the control cycle. The parameter L is a parameter that weights the operation coefficient R (n−1) one cycle before and the current output calorie actual ratio Kr calculated from the flow rate Q (n) detected this time and the like.

  As shown in FIG. 3, the parameter L is set to a large value when the flow rate is small, and is set to be a small value as the flow rate Q increases. When the flow rate Q is large, the behavior of the output heat amount is stable, so that the current output heat amount actual ratio is reflected in the operation coefficient R (n) rather than the operation coefficient R (n-1) one cycle before. Weighted by the parameter L. When the flow rate Q is small, the output calorie tends to fluctuate. Therefore, the parameter L (n-1) is calculated so that the computation coefficient R (n-1) one cycle earlier than the current actual output calorie ratio is reflected in the computation coefficient R (n). Weighted by As the parameter L, the characteristics shown in FIG. 3 can be set in advance by actual machine experiments or simulations. According to the characteristics shown in FIG. 3, a function formula or a table for obtaining the parameter L from the flow rate Q may be created in advance.

  The FF control unit 23 determines the FF based on the difference between the set temperature Tr (n) and the incoming water temperature Tc (n), the flow rate Q (n), and the learning value R (n) calculated by the learning unit 22. The number of inputs Uff (n) (corresponding to the first necessary heat generation) by the control is calculated. The input number Uff (n) by the FF control is the number required to change the water input amount (flow rate Q (n)) of the hot water supply device 2 from the input water temperature Tc (n) to the set hot water temperature Tr (n). Represents

  The FB control means 24 calculates the difference between the set temperature Tr (n) and the tapping temperature Th (n), the flow rate Q (n), and the learning value R (n) calculated by the learning means 22 according to the following equation (4). ), The input number Ufb (n) (corresponding to the second necessary heat generation) by the FB control is calculated. The input number Ufb (n) by the FB control is the number required to change the water input amount (flow rate Q (n)) of the hot water supply device 2 by the difference temperature (Tr (n) -Th (n)). Represent. Kp is a proportional gain set for each water heater.

The adding means 25 calculates the input number Uff (n) of the FF control calculated by the FF control means 23 and the input number Ufb (n) of the FB control calculated by the FB control means 24 according to the following equation (5). Are added to set the input number Utl (n) of the hot water supply apparatus 2.
Utl (n) = Uff (n) + Ufb (n) (5)

  In the hot water temperature control by the control unit 17, the input number Utl is set every predetermined control period Δt, for example, every Δt = 100 ms. As shown in FIG. 4, in the process in the n-th control cycle, the number of input signals Utl (n) is set. Sm (m = 1, 2,...) Represents each step.

  First, in S1, the flow rate Q (n), the incoming water temperature Tc (n), and the outgoing water temperature Th (n) in the current (n-th) control cycle detected by the flow rate sensor 18, the incoming water temperature sensor 19, and the outgoing water temperature sensor 20 are described. ), Necessary data such as the set hot water temperature Tr (n) is acquired.

Next, in S2, it is determined whether or not the rate of change of the incoming water temperature Tc (n) is within a predetermined range. For example, it is determined whether or not the difference between the current incoming water temperature Tc (n) and the previous incoming water temperature Tc (n-1) is within a predetermined range. Since the control cycle is predetermined, the temperature difference can be regarded as the rate of change here. When the determination is Yes, the process proceeds to S3, and when the determination is No, the process proceeds to S4. The predetermined range is, for example, a range represented by the following equation (6). The range represented by the expression (6) is appropriately set according to the control cycle Δt, the specifications of the hot water supply device 2, and the like.
−10 ° C. ≦ (Tc (n) −Tc (n−1)) ≦ 10 ° C. (6)

  Next, in S3, the current operation coefficient R (n) is calculated by the learning means 22 according to the above equation (2), and the flow proceeds to S5. The initial value of the operation coefficient R (n) can be set to R (0) = 25 according to the definition of the number.

  On the other hand, if the determination in S2 is No, in S4, the operation coefficient R (n) is set to the initial value 25, and the process proceeds to S5.

  Next, in S5, FF control reflecting the operation coefficient R (n) set in S3 or S4 is executed in accordance with the above equation (3), and the number of input signals Uff (n) by FF control is calculated. Proceed to.

  Next, in S6, FB control reflecting the operation coefficient R (n) set in S3 or S4 is executed according to the above equation (4), and the number of input signals Ufb (n) by FB control is calculated. Proceed to.

  Next, in S7, the input number Utl (n) of the water heater 2 in the current (n-th) control cycle is set according to the above equation (5).

Next, the operation and effect of the hot water supply device 2 of the present invention will be described.
As shown in FIG. 5, in the instant hot water circulation system 1 in which the hot water operation is executed at the circulation flow rate Q = 8 L / min so that hot water at the set temperature Tr = 75 ° C. can be supplied, for example, the elapsed time t = 110 s Is stable at the inlet water temperature Tc = about 72 ° C. and the tap water temperature Th = about 83 ° C., and the calculation coefficient R (n) = about 20. Note that a solid line represents a value obtained by the hot water supply device 2 of the present invention, and a broken line and a dashed line represent values obtained by the conventional hot water supply device described in Patent Document 1. The conventional hot water supply device has the same configuration as the hot water supply device of the present invention except for the above-described hot water temperature control.

  When hot water of about 15 ° C. is supplied from the hot-water tap F or the like to the hot water supply device 2 around the elapsed time t = 127 s, the incoming water temperature Tc decreases. When the rate of change of the incoming water temperature Tc is out of the predetermined range, for example, when the incoming water temperature Tc drops sharply from −10 ° C./100 ms, the operation coefficient R (n) is returned to the initial value. Here, the change rate of the incoming water temperature Tc is about −11 ° C./100 ms, which is out of the predetermined range, so that the calculation coefficient R (n) is set to 25.

  Since the input number Utl (n) is set based on the above equations (2) to (5), the input reflecting the desired heat exchange efficiency by returning the operation coefficient R (n) to the initial value. The number Utl (n) is set. Therefore, even if the incoming water temperature drops rapidly, the input signal number Utl (n) by the hot water temperature control does not become unnecessarily large, so that the outgoing water temperature Th becomes high after the elapsed time t = 127 s and the safe operation is performed. As a result, the burner 13 is not stopped, and an excessive temperature drop of the tapping temperature Th does not occur. That is, according to the hot water supply device 2 of the present invention, hot water can be discharged at a stable temperature.

  On the other hand, in the conventional hot water supply apparatus, a sudden decrease in the incoming water temperature Tc is not immediately reflected in the calculation coefficient R (n), but rises rapidly to around the elapsed time t = 140 s. Since the reduced heat exchange efficiency is reflected in the calculation coefficient R (n), if the input number Utl (n) for heating the low-temperature hot and cold water is set based on the calculation coefficient R (n). The input number Utl (n) becomes larger than necessary. Therefore, the tapping temperature Th rises excessively around the elapsed time t = 140 s, and the combustion of the burner 13 is stopped by the safe operation. After the elapsed time t = 145 s, the tapping temperature Th is excessively decreased due to the stop of the combustion. I have.

  Next, a case will be described in which the hot water operation is started in a state where the circulation passage 6 of the hot water supply system 1 is filled with low-temperature hot water.

  As shown in FIG. 6, the instant hot water operation is started, and in S11, it is determined whether or not it is the initial combustion period. Although not described in detail because it is described in Patent Document 1, it is determined whether or not the difference between the set temperature Tr and the tapping temperature Th is equal to or lower than a predetermined temperature α ° C. (eg, α = 3). When the determination is Yes, the process proceeds to S13, and the initial temperature increase control based on the flow rate Q is performed to perform the temperature increase quickly. When the determination is No, the process proceeds to S12 to perform the above-described hot water temperature control.

  Immediately after the start of the hot water operation, the hot water temperature Th approaches the set temperature Tr, and if it is determined in the above S11 that it is not the initial combustion period (No), the heated hot water passes through the circulation passage 6 and returns to the hot water supply device 2 again. Until water is supplied, low-temperature hot water is supplied. At this time, the operation coefficient R (n) may become larger than 25 due to learning.

  When the heated hot water enters the hot water supply device 2 again, an increase in the incoming water temperature Tc is detected. When the rate of change of the incoming water temperature is outside the predetermined range, for example, when the incoming water temperature rises sharply from 10 ° C./100 ms, the operation coefficient R (n) is returned to the initial value.

  Since the input signal number Uff (n) is calculated by reflecting the initial value of the operation coefficient R (n) according to the above equations (2) to (5), even if the incoming water temperature Tc rises sharply, the hot water temperature control is performed. The number of input numbers Utl (n) cannot be reduced unnecessarily. Therefore, the hot water temperature Th from the hot water supply device 2 does not excessively decrease. That is, according to the hot water supply apparatus 2 of the present invention, hot water can be stably discharged.

  As described above, hot water supply apparatus 2 of the present invention sets operation coefficient R (n) to an initial value in hot water temperature control if the rate of change of incoming water temperature is outside a predetermined range, and this initial value is FF. This is reflected in both control and FB control. Therefore, the update of the operation coefficient R (n) by learning is stopped and returned to the initial value in response to the rapid change of the incoming water temperature, so that the update of the operation coefficient R (n) does not delay, and the abrupt increase of the incoming water temperature Tc occurs. It is possible to improve the accuracy of hot water temperature control of hot water supply device 2 by performing FF control and FB control corresponding to various changes.

  If the change rate of the incoming water temperature is within a predetermined range, the operation coefficient R (n) is learned, and this learned value is reflected in both the FF control and the FB control. Since the actual operation coefficient R (n) is learned and reflected in the FF control and the FB control, the accuracy of the hot water temperature control of the hot water supply device 2 can be improved.

  In the hot water supply apparatus 2 of the present embodiment, an example has been described in which the calorie for heating hot water is generated by the burner 13 that burns the fuel gas. However, the amount of generated heat is controlled in accordance with the required generated heat quantity set by the control unit 17. Any heat source device, such as a petroleum burner that burns petroleum, can be used as long as it is configured as possible.

  In addition, those skilled in the art can implement various modifications to the above-described embodiment without departing from the spirit of the present invention, and the present invention includes such modifications.

DESCRIPTION OF SYMBOLS 1 Hot water circulation system 2 Hot water supply apparatus 6 Circulation passage 12 Heating passage 13 Burner 14 Heat exchanger 15 Gas proportional valve 16 Hot water flow control valve 17 Control unit (control means)
18 Flow rate sensor (flow rate detection means)
19 Incoming water temperature sensor (incoming water temperature detecting means)
20 Hot water temperature sensor (hot water temperature detecting means)
22 learning means 23 feed forward control means (FF control means)
24 Feedback control means (FB control means)
25 Addition means

Claims (2)

A heat exchanger for heating the hot water flowing inside by the combustion gas generated in the combustion section,
Incoming water temperature detecting means for detecting the incoming water temperature introduced into the heat exchanger,
Tapping temperature detection means for detecting tapping temperature of tapping water from the heat exchanger,
Flow rate detection means for detecting the flow rate of hot and cold water passing through the heat exchanger,
Control means for controlling the required amount of heat generated in the combustion section at predetermined intervals based on the incoming water temperature, the outlet water temperature, the flow rate and the hot water supply set temperature detected by these detection means,
The control means includes:
Learning means for calculating an output heat amount from the difference between the inlet water temperature and the tap water temperature and the flow rate, and learning an operation coefficient based on a ratio of the output heat amount to the required generated heat amount,
Feedforward control means for calculating a first necessary generated heat amount based on the difference between the hot water supply set temperature and the incoming water temperature, the flow rate, and the calculation coefficient;
Feedback control means for calculating a second required generated heat amount based on the difference between the hot water supply set temperature and the tapping temperature, the flow rate, and the calculation coefficient;
Adding means for adding the first necessary heat quantity and the second necessary heat quantity to set the required heat quantity,
The water heater, wherein the learning means returns the operation coefficient to an initial value when a change rate of the incoming water temperature in the predetermined cycle is out of a predetermined range.   The hot water supply device according to claim 1, wherein the hot water supply device is configured to be able to operate immediately.