JP7251096B2 - water heater - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water heater, and more particularly to hot water temperature control in the water heater.

Hot water supply temperature control in a hot water supply apparatus is required to quickly stabilize the outlet hot water temperature to the set hot water supply temperature. For example, Japanese Patent No. 6064613 (Patent Document 1) discloses a feedforward control proportional to the product of the temperature difference between the hot water supply temperature and the inlet water temperature and the flow rate, and a feedback control proportional to the temperature difference between the hot water supply temperature and the outlet hot water temperature. Hot water supply temperature control that controls the amount of heat generated in combination with control (so-called proportional compensation control) is described. Patent Literature 1 describes that the ratio (conversion factor) of the actual output heat amount to the input number (heat amount) is learned and reflected in the calculation of the feedforward term to improve the control accuracy.

Japanese Patent No. 6064613

A hot water supply apparatus is required to quickly raise the outlet hot water temperature, especially at the start of hot water supply. However, in feedback control, if the gain is increased, overshoot occurs due to the effect of wasted time from the change in the input heat quantity to the change in the detected value of the hot water supply temperature due to the distance between the heat exchanger and the hot water supply temperature sensor. Or, there is concern about the occurrence of undershoot.

On the other hand, in the feedforward control of Patent Document 1, the control amount is constant when the temperature difference between the hot water supply set temperature and the incoming water temperature is constant, so it effectively meets the need for a rapid temperature rise at the start of hot water supply. is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object of the present invention is to quickly stabilize the hot water supply temperature with respect to the hot water supply set temperature when the hot water supply is started and when the hot water supply set temperature is changed. is to provide feedforward control that

In one aspect of the present invention, a water heater includes a heating mechanism configured to heat fluid passing therethrough, first and second temperature detectors, a flow rate detector, and a control device. The first temperature detector is arranged upstream of the heating mechanism and detects the temperature of water entering the water heater. The second temperature detector is arranged downstream of the heating mechanism and detects the temperature of hot water discharged from the hot water supply device. The flow detector detects the flow rate of fluid passing through the water heater. The control device controls the amount of heat input to the heating mechanism based on the detected values of the incoming water temperature, the outgoing hot water temperature, and the flow rate, so that the outgoing hot water temperature is stabilized at the hot water supply set temperature. According to the addition value of the first feedforward term proportional to the target heat quantity according to the product of the detected value of the incoming water temperature and the temperature difference between the hot water supply set temperature and the detected value of the flow rate, and the second feedforward term Control the amount of heat input. The second feedforward term has a polarity such that the change width of the input heat quantity becomes larger than the change width of the first feedforward term when the target heat quantity changes, and the absolute value decreases with time. calculated to

Advantageous Effects of Invention According to the present invention, it is possible to realize feedforward control in which the hot water supply temperature is quickly stabilized with respect to the hot water supply set temperature when hot water supply is started and when the hot water supply set temperature is changed.

1 is a schematic configuration diagram of a water heater according to an embodiment of the present invention; FIG. FIG. 2 is a block diagram illustrating an input/output relationship in hot water supply temperature control of the hot water supply apparatus shown in FIG. 1; FIG. 10 is a conceptual waveform diagram for explaining an example of the response of the output scale to the input scale; 4 is a flowchart for explaining control processing of hot water supply temperature control in the hot water supply apparatus; FIG. 4 is a conceptual waveform diagram for explaining an operation example of feedforward control; 9 is a flowchart for explaining control processing at the start of combustion operation according to the first modification; FIG. 11 is a flow chart for explaining a control process for limiting the maximum issue number according to the second modification; FIG. FIG. 11 is a conceptual waveform diagram for explaining an operation example of feedforward control according to a second modified example; FIG. 11 is a conceptual waveform diagram for explaining an operation example of feedforward control according to a third modified example; FIG. 11 is a flowchart for explaining control processing related to updating of learning coefficients according to a third modification; FIG. FIG. 4 is a schematic diagram illustrating a modification of the configuration of the hot water supply apparatus according to the embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

FIG. 1 is a schematic configuration diagram of a water heater according to an embodiment of the present invention.
1, hot water supply apparatus 100 according to the present embodiment includes hot water supply pipe 110, bypass pipe 120, gas burner 130, heat exchanger 140, gas proportional valve 150, flow control valve 160, and a control device 200 .

Hot water supply pipe 110 is configured to connect from the water inlet to the hot water supply port. Flow control valve 160 is inserted and connected to hot water supply pipe 110 . By adjusting the degree of opening of the flow control valve 160 using the control device 200, the amount of hot water to be discharged can be controlled.

Gas burner 130 generates heat by combusting a mixture of gas supplied from a gas pipe (not shown) and air supplied from a combustion fan (not shown). The gas pressure supplied to gas burner 130 (that is, the amount of gas supplied per unit time) is controlled according to the opening of gas proportional valve 150 . The amount of air supplied from the combustion fan is controlled so as to keep the air-fuel ratio in combustion in the gas burner 130 constant.

The amount of heat generated by combustion in gas burner 130 is used to raise the temperature of the fluid (water) passing through hot water supply pipe 110 via heat exchanger 140 . That is, the gas burner 130 and the heat exchanger 140 can constitute a "heating mechanism" for heating water, which is a typical example of "fluid." Furthermore, in the hot water supply apparatus 100 illustrated in FIG. 1, a bypass pipe 120 is provided that connects the output of the heat exchanger 140 and the upstream side and downstream side of the heat exchanger 140 so as not to pass through the heat exchanger 140. It is configured to mix the output (low temperature water) of the bypass pipe 120 and the output (high temperature water) of the heat exchanger 140 and supply hot water. Furthermore, a bypass flow valve 125 is further provided for controlling the flow ratio of the bypass pipe 120 to the total flow (bypass flow ratio). Note that the arrangement of the bypass pipe 120 and the bypass flow valve 125 may be omitted.

The control device 200 includes a CPU (Central Processing Unit) 201 , a memory 202 , an input/output (I/O) circuit 203 and an electronic circuit 204 . The CPU 201 , memory 202 and I/O circuit 203 can exchange signals with each other via the bus 205 . The electronic circuit 204 is configured to execute predetermined arithmetic processing using dedicated hardware. The electronic circuit 204 can exchange signals with the CPU 201 and the I/O circuit 203 .

Hot water supply pipe 110 is provided with a flow rate sensor 210 and temperature sensors 220 and 230 . A flow rate Q of hot water supply pipe 110 is detected by flow rate sensor 210 . The temperature sensor 220 is provided upstream of the heat exchanger 140 and detects the incoming water temperature Tc. Temperature sensor 230 is provided on the downstream side of heat exchanger 140 and detects outlet heated water temperature Th. The detected flow rate Q, inlet water temperature Tc, and outlet hot water temperature Th are input to the controller 200 . That is, flow sensor 210 corresponds to an example of a "flow detector," temperature sensor 220 corresponds to an example of a "first temperature detector," and temperature sensor 230 corresponds to an example of a "second temperature detector." , corresponding to an embodiment.

In addition, in a configuration in which the bypass pipe 120 and the bypass flow valve 125 are arranged, the flow sensor 210 may be arranged so as to detect the flow rate passing through the heat exchanger 140 . In this case, the flow rate Q of the hot water supply pipe 110 (that is, the flow rate through the hot water supply device 100) is obtained using the flow rate detected by the flow rate sensor 210 and the bypass flow ratio obtained from the opening of the bypass flow valve 125. be able to.

Control device 200 receives output signals (detected values) from each sensor and user commands through I/O circuit 203, and generates control commands to each device in order to control the overall operation of water heater 100. . The user command includes an ON/OFF command for the operation switch of hot water supply apparatus 100 and a hot water supply set temperature (Tr*) command.

Water heater 100 is in the ON state of the operation switch, and when flow rate Q detected in response to opening of a hot water tap (not shown) becomes equal to or greater than a predetermined minimum operating flow rate (MOQ), gas burner 130 Combustion is started, and the hot water supply operation is started. Conversely, when the flow rate Q detected in response to plugging falls below the minimum operating flow rate (MOQ) during the hot water supply operation, combustion in the gas burner 130 is stopped and the hot water supply operation is stopped. Also, even if the operation switch is turned off while Q≥MOQ during the hot water supply operation, the combustion in the gas burner 130 is stopped and the hot water supply operation is stopped.

FIG. 2 shows a block diagram for explaining the input/output relationship in hot water supply temperature control of hot water supply apparatus 100. As shown in FIG.

Referring to FIG. 2, in hot water supply apparatus 100, heat exchanger 140 adjusts the heating amount of the fluid in accordance with the input heat amount corresponding to the heat amount generated by gas burner 130 in FIG. The amount of temperature increase to temperature Th is controlled. In hot water supply apparatus 100 of FIG. 1, the amount of input heat can be controlled by controlling the degree of opening of gas proportional valve 150 .

The output heat quantity QO reflecting the outlet heated water temperature Th changes according to the change in the input heat quantity. Generally, in a hot water supply apparatus, the amount of heat is calculated in units of scale. 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). Hereinafter, the output heat quantity QO and the input heat quantity QI are also referred to as the output scale QO and the input scale QI. The output scale number QO is represented by the following formula (1).

QO = (Th-Tc) Q/25 (1)
As shown in FIG. 3, the response of the output scale to the input scale, that is, the change in the discharged hot water temperature Th, consists of a first-order lag (time constant T) in temperature rise accompanying heating and a temperature rise from heating by the heat exchanger 140 to It is given as a combination with the dead time L until detection by the sensor 230 .

That is, the transfer function G(s)=QO(s)/QI(s) between the input number QI(s) and the output number QO(s) in the frequency domain is given by the following equation (2). be

G(s)={k/(T·s+1)}·exp(−L·s) (2)
In equation (2), s is the Laplace operator, and k is a constant specific to hot water supply apparatus 100 . It is understood that the dead time L and the time constant T change with the flow rate Q.

Next, hot water supply temperature control in hot water supply apparatus 100 will be described.
FIG. 4 is a flowchart for explaining control processing for hot water supply temperature control. The control process shown in FIG. 4 can be executed by the control device 200, for example, each time a certain control cycle Ts elapses. In the following description, the value in the current control cycle is denoted by the symbol [n], and the value in the previous control cycle is denoted by the symbol [n-1].

Referring to FIG. 4, control device 200 calculates target number Ur[n] according to the following equation (3) at step (hereinafter simply referred to as "S") 110. As shown in FIG. The target scale number Ur indicates a scale number required to raise the temperature from the inlet water temperature Tc to the hot water supply set temperature Tr*.

Ur[n]=(Tr*−Tc)·Q/25 (3)
The control device 200 calculates the learning coefficient k[n] in the current control cycle in S120. The learning coefficient k corresponds to the constant k in equation (2), and is indicated by the actual ratio (QO/QI) of the input number and the output number in the steady state. Theoretically, k=1.0 in a steady state controlled to Tr*=Th, but it is assumed that k≠1 due to the effects of heat loss and the like in the actual machine. By learning the ratio of the actual values of the input scale and the output scale, it is possible to increase the accuracy of setting the input scale that matches the target scale.

In S130, the control device 200 uses the target number Ur[n] (S110) and the learning coefficient k[n] (S120) to generate a first feedforward term (hereinafter also referred to as a "first FF term" ) is calculated according to equation (4).

FF1[n]=Ur[n]/k[n] (4)
FF1 is calculated in proportion to the target number Ur using (1/k[n]) as a proportional coefficient. That is, by introducing the learning coefficient k in S120, the proportionality coefficient is also updated according to the actual ratio of the input scale number and the output scale number. When the target number Ur is constant, by setting QI=FF1[n], it is possible to control Th=Tr* after a certain period of time has elapsed. That is, FF1 corresponds to the control amount for setting Th=Tr* in the steady state.

On the other hand, when the hot water supply operation is started, the target scale Ur changes stepwise from 0 to the value calculated by the formula (3). Similarly, when at least one of the flow rate Q, inlet water temperature Tc, and hot water supply set temperature Tr* changes during the hot water supply operation, the target scale Ur also changes. Therefore, in the present embodiment, a second FF term is introduced to improve the response of the outlet heated water temperature Th in the transient state accompanying changes in the target scale Ur.

In S140, control device 200 sets FF2[n], which is a second feedforward term (hereinafter also referred to as a "second FF term"), according to Equations (5) and (6) below.

FF2[n]=α/k[n]·ΔUr+β·FF2[n−1] (5)
ΔUr=U[n]−Ur[n−1] (6)
α in equation (5) is the adjustment gain, and β is the attenuation coefficient (0<β<1) of the second FF term. It is understood that the first term of FF2[n] is proportional to the amount of change ΔUr from the previous control cycle of the target number Ur.

Also, the damping coefficient β of the second term of FF[2] can be set according to the following equation (7) using the time constant T of the first-order lag and the control cycle Ts.

β=γ・exp(−Ts/T) (7)
γ in Equation (7) is an adjustment gain. The time constant T changes according to the flow rate Q. For example, in S140, the decrement coefficient β can be set by referring to a previously created formula or table for setting the time constant T from the detected value of the flow rate Q. By using the equation (7), the attenuation of FF2 by the multiplication of the attenuation coefficient β can be made faster than the attenuation by the time constant T.

In S150, the control device 200 sets a control amount (hereinafter also referred to as "FF control amount") FF[n] by feedforward control by adding the first FF term and the second FF term (FF[n ]=FF1[n]+FF2[n]). For example, it is possible to set the input heat quantity QI[n]=FF[n] in the current control cycle only by feedforward control.

FIG. 5 is a conceptual waveform diagram for explaining an operation example of feedforward control.
Referring to FIG. 5, at time t0, the target scale Ur increases from 0 to U1 as the hot water supply operation is started. Furthermore, at time t2, the target scale Ur is lowered from U2 to U1 by changing the set hot water supply temperature Tr*. It is assumed that the incoming water temperature Tc and the flow rate Q are constant.

The first FF term (FF1) is set to a value corresponding to U1 in response to the start of hot water supply operation at time t0. Until time t2, FF1 is maintained at a constant value under the condition that the target number Ur does not change.

At time t0, the second FF term (FF2) is set to FF2>0 because ΔUr>0 in equation (5) as the target number Ur increases from 0 to U1. . Therefore, the polarity of FF2 is set such that the amount of change in the FF control amount (FF1+FF2) is greater than the amount of change in FF1.

After time t0, the absolute value of FF2 attenuates according to the multiplication of attenuation coefficient β, and FF2 attenuates to 0 at time t1. By setting the damping coefficient β based on the time constant T according to the above equation (7), the length of time between times t0 and t1 is set equal to or shorter than the time constant T.

At time t2, the first FF term (FF1) is set to a value corresponding to U2 as the target number Ur decreases from U1 to U2. As a result, FF1 decreases at time t2. Further, at time t2, ΔUr<0 in equation (5), so the second FF term (FF2) is set to FF2<0. Also in this case, the polarity of FF2 is set such that the amount of change in the FF control amount (FF1+FF2) is larger than the amount of change in FF1.

After time t2, the absolute value of FF2 is attenuated according to the multiplication of attenuation coefficient β, and FF2 is attenuated to 0 at time t3. The time length between times t2 and t3 can be set equal to or shorter than the time constant T, like the time length between times t0 and t1.

Thus, according to the hot water supply temperature control of the hot water supply apparatus according to the present embodiment, in addition to the first FF term (FF1) for setting Th=Tr* in the steady state, FF1 By adding a second FF term (FF2) having the same polarity as the changing direction of FF1, the transient response can be improved so that the outlet heated water temperature Th quickly settles to the set hot water supply temperature Tr*.

Furthermore, since the second FF term (FF2) is set to attenuate according to the time constant T, the feedforward control amount is increased or decreased by a constant amount in a certain period immediately after the hot water supply operation is started or immediately after the hot water supply set temperature is changed. Overshoot or undershoot of the outlet heated water temperature Th can be suppressed as compared with simple control that causes the temperature Th to rise.

In addition, in contrast to the feedforward control according to the present embodiment, in order to compensate for the temperature error in the steady state, the feedback control using the detection value of the temperature sensor 230, for example, the control deviation (Tr*-Th) of the outlet heated water temperature It is also possible to further combine the proportional compensation control in which the gain value is multiplied by the gain value.

In addition, the outlet heated water temperature Th can be supplementarily controlled by feedback control of the degree of opening of the bypass flow valve 125 using the detected value of the temperature sensor 230, that is, the ratio of the flow rate of the bypass pipe 120 to the total flow rate (bypass flow rate ratio). can be done. Specifically, the opening degree of the bypass flow valve 125 is controlled so that the bypass flow rate is decreased when Th<Tr*, and the bypass flow rate is increased when Th>Tr*. can do. However, the feedback control based on the detected value of the temperature sensor 230 is less effective than the above-described feedforward control in improving the transient response immediately after the hot water supply operation is started or immediately after the hot water supply set temperature is changed. Even in a configuration in which the bypass pipe 120 and the bypass flow valve 125 are omitted, it is possible to improve the transient response of the outlet hot water temperature by similarly applying the hot water supply temperature control by controlling the input heat amount according to the present embodiment. It is possible.

(First modification)
At the start of the hot water supply operation (time t0 in FIG. 5), the target scale Ur greatly increases from 0, so the absolute value of the second FF term (FF2) also becomes relatively large. On the other hand, there are cases where the hot water supply temperature Th is close to the hot water supply set temperature Tr* at the start of the hot water supply operation, such as when the hot water supply operation is restarted in a short time after the hot water supply operation was stopped last time. In such a case, there is concern that the addition of the number by the second FF term (FF2) will be excessive and the control accuracy of the outlet heated water temperature Th will decrease.

Therefore, as a first modified example, it is possible to further add the processing at the start of the combustion operation shown in the flowchart of FIG.

Referring to FIG. 6, when the hot water supply operation is started (when the determination is YES in S100), in S105, the control device 200 replaces the incoming water temperature Tc in the equation (3) with the current (that is, the time when the hot water supply operation is started). The initial value Ur[0] of the target number Ur is calculated using the detected value of outlet heated water temperature Th. That is, Ur[0] is set according to Equation (8) below.

Ur[0]=(Tr*−Th)·Q/25 (8)
In the first control cycle (n=1) after the start of hot water supply operation, control device 200 advances the process to S110 in FIG. 4 after setting Ur[0] in S105. As a result, after Ur[1] is set in S110, in S140, using Ur[0] obtained in S105 and Ur[1] obtained in S110, ΔUr=Ur[1]−Ur FF2[1] can be calculated assuming [0] and FF2[0]=0.

On the other hand, after the first control cycle (n≧2), the control device 200 skips S105 and advances the process to S110 in FIG. 4 due to a NO determination in S100. In this case, FF2[n] can be calculated by S140 using Ur[n−1] and FF2[n−1] in the previous control cycle.

As a result, according to the first modification, when the outlet hot water temperature Th at the start of the hot water supply temperature is near the hot water supply set temperature Tr*, the control amount of the feedforward control (second FF term) becomes excessive. can be prevented. As a result, it is possible to prevent the control accuracy of the outlet heated water temperature Th from deteriorating due to the outlet heated water temperature Th at the start of the hot water supply operation.

(Second modification)
In actual hot water supply temperature control, it is common to limit the input scale QI by setting an upper limit value (hereinafter referred to as maximum scale Fmax). As a result, even if the FF control amount is set according to FF1+FF2 in order to improve the transient response, the input heat amount is insufficient for the control value during the period of FF1+FF2>Fmax, and the control accuracy of the outlet heated water temperature Th decreases. There is concern that

FIG. 7 is a flow chart showing a control process for limiting the maximum issue number according to the second modification.
Referring to FIG. 7, control device 200 executes the maximum number limit processing in S160 after the processing in S150 of FIG. S160 has S162 to S167. 7, the hot water supply temperature control is performed only by the feedforward control described in FIG. 4, and the input heat quantity QI is assumed to be equal to the FF control amount FF[n] calculated in S150.

In S160, the control device 200 calculates the integrated value E[n] of the amount exceeding the maximum number Fmax. Specifically, the excess amount (FF[n]-Fmax ), the integrated value E[n] in the current control cycle is calculated. The maximum number Fmax corresponds to an example of [maximum input heat quantity].

When E[n]>0 (when determined as YES in S163), the controller 200, on the condition that FF[2]<ε calculated in S140 is not satisfied (when determined as NO in S164), performs Modify FF[n]=Fmax. On the other hand, when E[n]≤0 (NO determination in S163) or FF[2]<ε (NO determination in S164), E[n] is cleared to 0 by S165. At the same time, in S166, the input heat quantity QI is set without correcting the FF control amount FF[n] from the calculated value in S150.

The determination value ε in S164 can be set to, for example, about 5% of FF1[n]. Even if the flow rate Q and the incoming water temperature Tc continue to change slightly, the determination value ε is such that S164 makes a NO determination during the period from time t1 to t2 in FIG. 5 and the period after time t3. It is set in advance so that

FIG. 8 shows a conceptual waveform diagram for explaining an operation example of feedforward control to which the maximum number limit shown in FIG. 7 is applied.

8, the first FF term (FF1) and the second FF term (FF2) are calculated in the same manner as in FIG. 5 from time t0 to t1. In the period from time t0 to ta, (FF1+FF2)>Fmax, and an amount exceeding the maximum number Fmax occurs.

Therefore, in the period from time t0 to ta, the FF control amount FF is corrected to the upper limit of Fmax, and the integrated value E is increased. After time ta, since FF<Fmax, the integrated value E begins to decrease, but is corrected to FF control amount FF=Fmax until time tb when E decreases to 0, that is, in the period from time ta to tb. be. After time tb when the integrated value E=0, the FF control amount is not corrected and is set to FF=FF1+FF2.

Therefore, in FIG. 8, the integrated value of (FF1+FF2-Fmax) in the period from time t0 to ta is equivalent to the integrated value of (Fmax-FF1-FF2) in the period from time ta to tb. In other words, the amount of heat corresponding to the integrated value of the excess amount (FF-Fmax) in the upper limit limit period from time t0 to ta is calculated in the period after time ta when FF<Fmax (time ta to time tb). is added to the FF control amount.

As a result, it is possible to realize the maximum number limit and to secure the total value of the input heat quantity according to the control value (FF1+FF2) before the limit. Therefore, for example, even when the maximum number limit is applied due to a large flow rate Q, the total heat amount can be input according to the FF control for improving the transient response, so the control accuracy of the outlet heated water temperature Th is reduced. can be prevented.

In addition, by adding the processing of S164, the period in which the input heat amount (FF control value) is increased from the original control value to the maximum number Fmax is limited to the period of FF[2]>ε, so that the input heat amount can be prevented from becoming excessive.

(Third modification)
In the third modified example, update processing of learning coefficients during feedforward control will be described. As described in Patent Document 1, the learning coefficient k reflects the performance of the ratio of the input number and the output number (QO / QI), so that the setting accuracy of the input number suitable for the target number introduced to increase The learning coefficient k[n] in the n-th control cycle is set so that the actual ratio of the input scale number QI[n-1] in the previous control cycle and the output scale number QO[n] in the current control cycle is learned. , for example, can be obtained according to the following equation (9).

k[n]=r·k[n−1]+(1−r)·QO[n]/QI[n−1] (9)
In equation (9), r is a parameter for adjusting the learning speed and is set within the range of 0≦r≦1. When r=1, k[n]=k[n-1], and updating of the learning coefficient can be prohibited.

The learning coefficient k is preferably calculated in a steady state in which the input scale QI and the output scale QO do not change significantly. Therefore, if the learning coefficient k is updated during the period in which the second FF term by the feedforward control according to the present embodiment is influencing, there is a concern that the control accuracy will be lowered.

FIG. 9 is a conceptual waveform diagram for explaining an operation example of feedforward control according to the third modification. Also in FIG. 9, the first FF term (FF1) and the second FF term (FF2) are calculated in the same manner as in FIG.

In the third modified example, a learning prohibition flag is newly introduced. The learning prohibition flag is set to "1" during the period of |FF2|>ε (the period of time t0 to t1 and the period of time t2 to t3). Further, the learning prohibition flag is set to is also set to "1". The above ε can be set to be the same as in S164 of FIG.

On the other hand, the learning prohibition flag is set to "0" after the dead time has elapsed, that is, during the period from time tx to t2 and during the period after time ty. The elapse of the dead time L can be detected by measuring time with a timer (not shown) built in the control device 200 or by counting the number of cycles of the internal clock used in the control device 200 .

In the example of FIG. 9, the period from time t0 to t1 and the period from time t2 to t3 correspond to an example of the "first period", the period from time t1 to tx and the period from time t3 to ty. The period corresponds to one embodiment of the "second period".

As described above, the dead time L is the time required for the temperature sensor 230 to detect the temperature rise caused by the heat exchanger 140, that is, the time when the fluid (high-temperature water) output from the heat exchanger 140 reaches the temperature sensor 230. It changes according to the flow rate Q because it corresponds to the time required to reach it. For this reason, the dead time L can also be set using the detected value of the flow rate Q at time t1 or t3 by previously creating a formula or table for setting the dead time L from the detected value of the flow rate Q. can.

In this manner, the learning prohibition flag is set to "1" until the temperature sensor 230 detects the outlet heated water temperature Th based on the input heat amount reflecting the second FF term. On the other hand, in the period after |FF2|=0, the temperature sensor 230 detects the outlet heated water temperature Th based on the input heat amount reflecting the feedforward control only by the first FF term (FF1), the learning prohibition flag is set. ="0".

FIG. 10 is a flowchart for explaining control processing related to update of learning coefficients according to the third modification.

Referring to FIG. 10, control device 200 executes the processes of S121 to S123 shown in FIG. 10 at S120 of FIG.

When the value of the learning prohibition flag is "1" (YES determination in S121), control device 200 sets r=1 in equation (9) in S122 and maintains the learning coefficient without updating it. A learning coefficient k[n] in the control cycle is calculated (k[n]=k[n−1]). As a result, the calculation of the FF control amount in S130 to S150 is executed using the learning coefficient k[n] whose updating is prohibited. Note that the learning coefficient k is maintained even during non-execution of the hot water supply operation including the OFF period of the operation switch. Therefore, the value at the end of the previous hot water supply operation is used as the initial value of the learning coefficient at the start of the hot water supply operation.

On the other hand, when the value of the learning prohibition flag is "0" (when the determination is NO in S121), the control device 200 sets 0<r<1 in the equation (9) in S123 to perform learning in the control cycle. Calculate the coefficient k[n]. The learning parameter r is variably set according to the flow rate Q so that the learning speed increases as the flow rate increases, that is, r decreases. By previously creating a formula or table for setting the learning parameter r from the detected value of the flow rate Q, in S123, the detected value of the flow rate Q in the control cycle can be used to set the learning parameter r.

Thus, in the steady state with the learning prohibition flag=“0”, the calculation of the FF control amount in S130 to S150 is executed using the learning coefficient k[n] updated according to the actual results. On the other hand, in the transient state where the outlet heated water temperature Th influenced by the second FF term is detected, feedforward control is executed using the learning coefficient k[n] whose update is prohibited.

As described above, according to the third modification, in the steady state, by appropriately setting the learning coefficient k[n] based on the actual performance, the control accuracy of the outlet heated water temperature Th is increased, and the second FF term In the transient state in which the response speed is increased, it is possible to prevent the control accuracy from deteriorating due to the deviation of the learning timing of the learning coefficient k[n].

Some or all of the first to third modifications described above can be combined and applied to hot water supply temperature control (FIG. 4) in the hot water supply apparatus according to the present embodiment. .

In the configuration in which the bypass pipe 120 and the bypass flow valve 125 are arranged as shown in FIG. In addition, it is also possible to control the amount of input heat.

In this case, as shown in FIG. 11, on the downstream side of the heat exchanger 140 (heating mechanism), on the upstream side of the connection point between the bypass pipe 120 and the hot water supply pipe 110, to detect the high temperature water temperature Thh. of temperature sensors 240 are additionally arranged. The hot water temperature Thh corresponds to the output temperature of the heating mechanism. The flow sensor 210 is also preferably arranged to detect the flow rate through the heat exchanger 140 . In the configuration of FIG. 11, the bypass flow valve 125 corresponds to one embodiment of the "flow regulating mechanism" and the temperature sensor 240 corresponds to one embodiment of the "third temperature detector".

In this case, for the target scale number Ur [n] for setting the high-temperature water temperature Thh on the outlet side of the heating mechanism to the target temperature Thh*, it is assumed that the flow rate of the heating mechanism is (1−r) Q Considering this, it can be obtained by the following formula (10). That is, in S110 of FIG. 4, it is possible to calculate the target number Ur[n] according to the equation (10) and execute the feedforward control according to the present embodiment.

Ur[n]=(Thh*−Tc)・(1−r)・Q/25 (10)
On the other hand, in the case of controlling to Thh=Thh*, in order to set the outlet heated water temperature Th=Tr*, the following equation (11) is calculated using the flow rate ratio (bypass flow rate ratio) r of the bypass pipe 120 to the total flow rate. must be established.

(Thh*-Tr*) Q (1-r) = (Tr*-Tc) Qr (11)
By solving the equation (11) for r, the following equation (12) is obtained for the bypass flow ratio r.

r=(Thh*−Tr*)/(Thh*−Tc) (12)
By substituting (1−r)=(Tr*−Tc)/(Thh*−Tc) obtained from equation (12) into equation (10), the following equation (13) is obtained.

Ur[n]=(Thh*−Tc)・(Tr*−Tc)/(Thh*−Tc)・Q/25
= (Tr*-Tc) Q/25 (13)
Since the equations (13) and (3) are the same, the target number Ur [n] is calculated according to the target temperature Thh* of the high-temperature water temperature Thh by the equation (10), and the feed according to the present embodiment It is understood that even when the forward control is executed, the same control operation as when the target number Ur[n] is calculated by the formula (3) based on the set hot water supply temperature Tr* and the total flow rate Q is realized. be done. In other words, the target amount of heat is set according to the product of the temperature difference between the inlet water temperature Tw and the set hot water supply temperature Tr* and the flow rate Q of the entire hot water supply apparatus 100 also according to equation (10).

Even when the feedforward control according to the present embodiment is executed using the target number Ur[n] calculated by the equation (10), part or all of the above-described first to third modifications can be performed. A combination is possible. However, the equation (8) in the first modification can be transformed into the following equation (14) considering that the flow rate of the heat exchanger 140 is (1−r) Q. be. Alternatively, only Ur[0] can be calculated by applying equation (8).

Ur[0]=(Thh*-Thh)*(1-r)*Q/25 (14)
In addition, in the hot water supply apparatus according to the present embodiment, the gas burner 130 is exemplified as the "heat source mechanism" that generates the amount of heat for heating the water in the hot water supply pipe 110, but application of the present invention is limited to such a configuration. It should be clearly stated that it is not a thing. That is, any "heat source mechanism" can be employed as long as it is configured to be able to control the amount of heat generated according to the required amount of heat generated (input scale) set by the control device 200 . For example, instead of a gas burner, any heat source such as a petroleum burner or a heat pump mechanism can be applied.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

100 hot water supply device 110 hot water supply pipe 120 bypass pipe 125 bypass flow valve 130 gas burner 140 heat exchanger 150 gas proportional valve 160 flow control valve 200 control device 201 CPU 202 memory 203 I/O circuit , 204 electronic circuit, 205 bus, 210 flow sensor, 220, 230, 240 temperature sensor, Fmax maximum number, L dead time, Q flow rate, QI input heat amount (input number), QO output heat amount (output number), T: time constant (primary lag), Tc: incoming water temperature, Th: outgoing hot water temperature, Thh: hot water temperature, Thh*: target temperature (high temperature water temperature), Tr*: set hot water supply temperature, Ts: control cycle, Ur: target number, k: learning coefficient, r learning parameter.

Claims (4)

A water heater,
a heating mechanism configured to heat a fluid passing through;
a first temperature detector disposed on the upstream side of the heating mechanism and detecting the temperature of water entering the water heater;
a second temperature detector disposed on the downstream side of the heating mechanism and detecting the temperature of discharged hot water from the hot water supply device;
a flow rate detector that detects the flow rate of the fluid passing through the water heater;
a control device for controlling the amount of heat input to the heating mechanism so that the outlet hot water temperature stabilizes at a set hot water supply temperature based on the detected values of the inlet water temperature, the outlet hot water temperature, and the flow rate;
The control device is
According to the sum of the first feedforward term proportional to the target heat quantity according to the product of the detected value of the incoming water temperature and the temperature difference between the hot water supply set temperature and the detected value of the flow rate, and the second feedforward term controlling the amount of heat input;
The second feedforward term has a polarity such that the change width of the input heat quantity becomes larger than the change width of the first feedforward term when the target heat quantity changes, and the absolute value changes with time calculated to decrease to
The first feedforward term and the second feedforward term are periodically calculated from the start of the hot water supply operation,
The second feedforward term is a first term proportional to the amount of change in the target heat quantity from the previous control cycle, and the second feedforward term in the previous control cycle greater than 0 and less than 1 calculated by addition with the second term multiplied by the damping factor,
When calculating the initial value of the second feedforward term at the start of the hot water supply operation, the target heat amount in the previous control cycle is the inlet water temperature at the start of the hot water supply operation or the A water heater calculated according to a product of a temperature difference between an outlet hot water temperature and the hot water supply set temperature, and the flow rate . The damping coefficient is determined according to the time constant with which the output heat quantity changes according to the product of the temperature difference between the outlet hot water temperature and the incoming water temperature and the flow rate with respect to the change in the input heat quantity, according to the detected value of the flow rate. 2. The water heater according to claim 1 , wherein the absolute value is set to attenuate. When the calculated value of the input heat quantity is higher than a predetermined maximum input heat quantity, the control device limits the actual input heat quantity to the maximum input heat quantity, and reduces the maximum input heat quantity from the calculated value. Calculate the integrated value of the subtracted excess amount, and in the period after the restriction, when the calculated value is lower than the maximum input heat amount, the heat amount corresponding to the integrated value during the restriction is added to the calculated value. 3. The water heater according to claim 1 , wherein a period for setting the amount of heat is provided. The control device adjusts the proportional coefficient between the first feedforward term and the target heat quantity in calculating the first feedforward term to the current temperature difference between the outlet hot water temperature and the current inlet water temperature and the flow rate. update according to the actual ratio between the output heat quantity according to the product of and the input heat quantity,
The updating of the proportionality coefficient is performed during a first period in which the second feedforward term is greater than a predetermined minimum value, and in the first period until a predetermined time elapses from the end of the first period. prohibited for a period of 2,
The length of the second period is set to be equal to the time required for the heated fluid output from the heating mechanism to reach the second temperature detector according to the detected value of the flow rate. The hot water supply apparatus according to claim 1 or 2 , which is set.

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