JPH07295658A - Hot water supplier - Google Patents

Abstract

PURPOSE:To obtain the easy-to-use hot water supplier which avoids unexpected fire extinction of its burner and suppresses overshooting in a short time even if the amount of water fed to the hot water supplier varies as to a by-pass mixing type hot water supplier. CONSTITUTION:A target upper-limit varying means 40, an operation upper-limit varying means 52, a target restricting means 42, and an manipulated value restricting means 54 are provided; when the amount QT of water supplied to the hot water supplier decreases, the target upper-limit varying means 40 and manipulation upper-limit varying means 52 correct the upper-limit value rhoO-MAX of the target rhoO of control and the upper-limit value rhoM-LIM of an actual operation value rhoM so that they decrease according to the decrease rate of the total flow rate QT. Then if overshooting is caused by the decrease in the total flow rate QT, the target restricting means 42 and operation value restricting means 54 imposes restrictions so that the target value rhoO and manipulated value rhoM do not exceed the upper-limit value rhoO-MAX and upper-limit value rhoM-LIM.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot water supply system of a bypass mixing system, and more particularly to a hot water supply temperature control technique.

[0002]

2. Description of the Related Art A conventional bypass mixing type water heater has a structure shown in FIG.

In this water heater, a water inlet 10 connected to a water pipe or the like is connected to the heat exchanger 6 on one side, and a hot water outlet 12 connected to a currant or a shower is connected to the other side. , The heat exchanger 6 between the inlet 10 and the outlet 12
Are short-circuited by a bypass path 14 for bypassing the.

The heat exchanger 6 is provided with a gas burner 8 for heating the heat exchanger 6. The gas burner 8 is provided with a gas proportional valve 20 for adjusting the gas combustion amount, and the water inlet channel. In the middle of 10, the amount of water passing through the heat exchanger 6 (hereinafter,
A can body flow rate sensor 18 for detecting Q _K is provided. Further, in the middle of the bypass path 14, the amount of water flowing through the bypass path 14 (hereinafter referred to as bypass flow rate) Q
A bypass valve 28 is provided for adjusting _B and changing the distribution ratio ρ (= Q _B / Q _K ) of hot and cold water mixture determined with the above-mentioned can body flow rate Q _K.

Reference numeral 16 is a water temperature sensor for detecting a water temperature T _C , and 22 is a hot water temperature after being heated by the heat exchanger 6.
(Hereinafter referred to as “can body hot water temperature”) T _H detecting can body hot water temperature sensor, 24 denotes a hot water temperature after mixing hot and cold water (hereinafter referred to as hot water supply temperature) T _M , and 26 denotes a can body flow rate. Q _K
Is an overflow servo valve that limits the discharge amount of hot water when the maximum heating capacity of the gas burner 8 is exceeded, and 30 ′ is a controller that controls the hot water supply temperature.

The bypass mixing type water heater having the above-mentioned structure not only controls the gas combustion amount by operating the gas proportional valve 20, but also bypass valve 2 provided in bypass passage 14.
Since the temperature control is performed by operating 8 to change the distribution ratio ρ of the hot water, the responsiveness of the temperature control is faster and the hot water supply is faster than the case of controlling the hot water temperature by changing only the gas combustion amount. It has the advantage that the temperature can be controlled over a relatively wide range.

In such a bypass mixing type water heater, conventionally, the determination of whether the gas burner 8 is ignited or extinguished is made as follows.

First, it is necessary to know the total flow rate Q _T when judging whether the water heater is used or not.

The distribution ratio ρ of the hot and cold water mixture is, as described above, ρ = Q _B / Q _K (1). Therefore, the total flow rate Q _T supplied to the water heater via the water inlet 10 is If the body flow rate Q _K and the distribution ratio ρ are known, it is given by the following equation.

Q _T = Q _K + Q _B = Q _K · (1 + ρ) (2) Then, for the total flow rate Q _T obtained by the equation (2), a threshold value for extinguishing the fire (hereinafter referred to as the total required flow rate) _Set Q _T-MOQ and a threshold value for ignition, Q _T-MOQ + Δ _T (Δ _T is an increment).

For example, Q _T-MOQ = 2.0 liter / min, Q
_{T-MOQ + Δ T = 2.0} + 0.5 = 2.5 liters / minute.

Further, in order to determine whether or not there is a possibility that the hot water will boil in the heat exchanger 6, a threshold value for extinguishing the fire is set for the can body flow rate Q _K detected by the can body flow rate sensor 18. (Hereinafter referred to as can body required flow rate) Q _K-MOQ and threshold value Q at ignition
_{Set K-MOQ} + Δ _K (Δ _K is an increment).

For example, Q _K-MOQ = 1.25 _liters / minute,
Q _K-MOQ + Δ _K = 1.25 + 0.35 = 1.6 _liters / minute.

[0014] The threshold value at the time of ignition, the threshold Q _T-MOQ during fire fighting, Q respectively from the _K-MOQ Δ _T (0.5 liters / minute in the above example), delta _K (the In the example, 0.35 liter /
The reason why it is set to be larger by (min) is to stabilize ignition continuation.

Under this condition, the controller 30 'determines that the total flow rate Q _T is larger than Q _T-MOQ + Δ _T (2.5 _liters / minute) and the can body flow rate Q _K is Q _K-MOQ + Δ _K. (1.6 liter /
If it is larger than (minutes), the water heater is in use,
Moreover, it is judged that there is no possibility of boiling water in the heat exchanger 6, and the gas proportional valve 20 is opened to ignite the gas burner 8.

On the other hand, the controller 30 'controls the total flow rate Q _T
Is less than the total required flow rate Q _T-MOQ (2.0 _liters / minute), or the can body flow rate Q _K is the required body flow rate Q
When it becomes less than _K-MOQ (1.25 liter / min), it is judged that the use of the water heater has stopped, or the water may boil in the heat exchanger 6, and the gas proportional Valve 20
And close the gas burner 8 to extinguish the fire.

Thus, the ignition of the gas burner 8 is Q
The AND condition of both the determination results of the _T-MOQ + _{Δ T} and Q _K-MOQ + _{Δ K,} extinguishing gas burner 8, the OR condition of both the determination results of the Q _T-MOQ and Q _K-MOQ, are controlled respectively .

From the relationship between the equations (1) and (2), the distribution ratio ρ can be described as an equation including the total flow rate Q _T as follows.

Ρ = (Q _T −Q _K ) / Q _K (3) Conventionally, the total required flow rate Q _T-MOQ and the can required flow rate Q _K-MOQ that are used to _{judge the extinction of the gas burner 8} are both Is also a constant value, and from the perspective of the distribution ratio, the above (3)
From the formula, ρ _MOQ = (Q _T-MOQ −Q _K-MOQ ) / Q _K-MOQ (3) ′, and the distribution ratio ρ _MOQ (hereinafter _{referred to} as the necessary distribution ratio) is also constant.

For example, in the above example, Q _T-MOQ = 2.0, Q
_{When K-MOQ} = 1.25, ρ _MOQ = (2.0-1.25) /1.25=6/10.

[0021]

In the water heater of the invention Problems to be Solved conventional bypass mixing method, when the hot water supply control is in a steady state, as the bypass flow rate Q _B is somewhat larger than the can flow Q _K, that is, the The distribution ratio ρ given by the equation (1) is set to be 1 or more.

In the steady state of combustion control, if the bypass flow rate Q _B is set to be larger than the can body flow rate Q _K , even if the hot water having the same hot water supply set temperature T _S is obtained, the overall hot water supply temperature T _S can be obtained. It is easy to secure the amount of hot water, and the heat exchanger 6
The reason is that it is possible to avoid the temperature of the hot water discharged from the bath becoming extremely low.

As described above, the distribution amount ρ is set so that the bypass flow rate Q _B is somewhat higher than the can body flow rate Q _K , and the amount of hot water is throttled on the curran side while the combustion control is being executed. If the water pressure on the side of the water inlet 10 decreases, the total flow rate Q _T is _greater than or _{equal to the} total required flow rate Q _T-MOQ (Q _T >
Q _T-MOQ ), the can body flow rate Q _K may be smaller than the can body required flow rate Q _K-MOQ (Q _K ≦ Q _K-MOQ ). At this time, the controller 30 'determines that the hot water may boil in the heat exchanger 6, and extinguishes the gas burner 8.

For example, as in the above example, the total required flow rate Q _T-MOQ = 2.0 _liters / minute, the required flow rate of the can body Q _K-MOQ =
When the distribution ratio ρ in the steady state is fixed at ρ = 12/10, the total flow rate Q _T decreases and Q _T = 2.5 liter / min. When it becomes minutes, Q _T (= 2.5)> Q _T-MOQ (= 2.0), but Q _K is Q _K = 2.5 / (1 + 12) from the relation of the equation (2). /
10) ≈ 1.14 liters / minute. That is, Q _K (=
Since 1.14) <Q _K-MOQ (= 1.25), the _{gas burner} 8 is extinguished suddenly.

Further, as described above, the distribution ratio ρ in the steady state is
When the total flow rate Q _T is decreased while keeping the constant value, both the bypass flow rate Q _B and the can body flow rate Q _K are correspondingly decreased, and hot water is discharged from the heat exchanger 6 by the decrease of the can body flow rate Q _K. Since the can body water temperature T _H becomes high, the hot water supply temperature T _M
Causes a so-called overshoot.

In order to eliminate this overshoot, the controller 30 'controls so that the distribution ratio ρ becomes large (that is, the bypass flow rate Q _B from the relationship of the equation (1)).
Is controlled to increase the can body flow rate Q _K ). As a result, the decreasing tendency of the can body flow rate Q _K is further accelerated and rapidly _falls below the can body required flow rate Q _K-MOQ, and the _{gas burner} 8
Will be extinguished.

As described above, the controller 30 'controls the extinguishing of the _{gas burner} 8 according to the OR condition of the judgment results of both the total required flow rate Q _T-MOQ and the required can body flow rate Q _K-MOQ . 6 is effective in avoiding boiling of the hot water, but while using the water heater, the total flow rate Q _T
When fluctuates, ignition and extinguishment of the gas burner 8 are frequently repeated in response to this, which causes a phenomenon in which hot water and cold water alternate and the usability deteriorates.

Therefore, in order to solve the above-mentioned problem, the inventors of the present invention, when the total flow rate Q _T is decreased to a certain threshold value Q _T-CRI or less as shown in FIG. Is a constant can body flow rate Q _K that does not fall below the required can body flow rate Q _K-MOQ.
While the opening degree of the bypass valve 28 is adjusted so that the hot water flows through the heat exchanger 6, the temperature control for obtaining the hot water of the desired hot water supply set temperature T _S is handled by adjusting the gas combustion amount exclusively. The water heater was provided (Japanese Patent Application No. 4-134343).
(See No. 7).

For example, as shown in FIG. 7B, the can body required flow rate Q _K-MOQ is 1.25 liter / min, and the threshold value Q _T-CRI.
Is 4 liters / minute, the total flow rate Q _T is 4 liters / minute
If it becomes less than or equal to the minute, the can body flow rate Q _K will always be 1.5 liters / minute, so that the distribution ratio ρ is continuously changed according to the decrease in the total flow rate Q _T , as shown in FIG. Make it smaller.

By doing so, even if the total flow rate Q _T is decreased, the can body flow rate Q _K is below the can body flow rate Q _K-MOQ as long as the total required flow rate Q _T-MOQ or more is flowing. Therefore, the gas burner 8 is not extinguished unexpectedly.

However, such an adjustment of the opening of the bypass valve 28 is simply to prevent the can body flow rate Q _K from falling below the can body required flow rate Q _K-MOQ, and therefore the total flow rate Q _{K.
When T} is between the threshold value Q _T-CRI and the total required flow rate Q _T-MOQ , it is impossible to change the can body flow rate Q _K to some extent to prevent overshoot.

The temperature control for obtaining the hot water having the desired hot water supply set temperature T _S is carried out by adjusting the gas combustion amount exclusively. In this case, the heat capacity of the heat exchanger 6 and the like are related. As compared with the case where the temperature control is performed by changing the distribution ratio ρ of hot water, the responsiveness is poor, and it becomes insufficient to suppress overshoot in a short time. In other words, the advantages of the bypass mixing method cannot be fully utilized, leaving dissatisfaction with the hot water discharge characteristics.

The present invention has been made to solve the above-mentioned problems, and not only prevents boiling of hot water in the heat exchanger, but also changes the total flow rate supplied to the water heater. In this case, the gas burner that heats the heat exchanger is prevented from being repeatedly turned on and off, and overshoot can be suppressed within a short period of time, making it possible to use the advantages of the bypass mixing method. The challenge is to obtain a good water heater.

[0034]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a bypass path for short-circuiting a water inlet path and a hot water outlet path that communicate with each other before and after a heat exchanger. In the middle of, the distribution ratio of the bypass flow rate Q _B flowing through this bypass passage and the can body flow rate Q _K flowing through the heat exchanger.
While a bypass valve for changing (= Q _B / Q _K ) is provided, a target value ρ _O that is a control target of the distribution ratio is calculated based on the incoming water temperature T _S , the desired hot water supply set temperature T _{S, and the} like. At the same time, an operation value ρ _M, which is the operation amount of the actual distribution ratio, is determined based on the target value ρ _O and the measured hot water supply temperature T _M , and the opening degree of the bypass valve is adjusted by the operation value ρ _M. The bypass mixing type water heater having a controller for controlling the hot water temperature by using the following configuration.

That is, in the water heater according to the present invention,
The controller determines that at least one of the total flow rate Q _T (= Q _K + Q _B ), which is the sum of the can body flow rate Q _K and the bypass flow rate Q _B , or the can body flow rate Q _K , is a preset required flow rate Q _T-MOQ. ，
When it is below Q _K-MOQ (Q _T ≤ Q _T-MOQ or Q _K ≤ Q
_In the case of _K-MOQ ), a boiling prevention means for stopping heating of the heat exchanger is provided, and the total flow rate Q _T is set to a preset threshold value Q _T-CRI1 (where Q _T-CRI1 > Q _T compared to _-MOQ), if the entire flow rate Q _T falls below the threshold Q _T-CRI1 is a target upper limit value [rho _O-MAX that determines the upper limit of the settable range of the target value [rho _O, overall flow rate and the target upper limit value varying means for modifying so as to decrease according to the decrease rate of the Q _T, the threshold is set the overall flow rate Q _T advance Q _T-CRI2 (However, Q
_T-CRI2 > Q _T-MOQ ), the total flow rate Q _T is the threshold value Q
If it falls below the _T-Cri2 is the operation limit [rho _M-LIM to determine the upper limit of the controllable range of the operation value [rho _M, total flow rate Q _T
And the target upper limit value ρ _O are corrected so as not to exceed the target upper limit value ρ _O-MAX determined by the target upper limit value changing unit. A target value regulation unit and a manipulation value regulation unit that regulates the manipulation value ρ _M so as not to exceed the manipulation upper limit value ρ _M-LIM determined by the manipulation upper limit value varying unit.

[0036]

In the above configuration, the controller calculates the target value ρ _O which is the control target (feedforward amount) of the distribution ratio based on the incoming water temperature T _S , the desired hot water supply set temperature T _S, etc. ρ _O and measured hot water temperature T _M
The operating value ρ _M , which is the actual operating amount of the distribution ratio (the total amount of feed-forward amount and feedback amount), is determined based on the above, and the opening of the bypass valve is adjusted by this operating value ρ _M to control the hot water temperature. I do.

At this time, if the total flow rate Q _T supplied to the water heater falls below a preset threshold value Q _{T-CRI1 due} to the amount of hot water being reduced on the curran side, the target upper limit value can be changed. means a target upper limit value [rho _O-MAX that determines the upper limit of the settable range of the target value [rho _O, modified to become smaller in accordance with the reduction rate of the total flow rate Q _T.

Further, when the total flow rate Q _T falls below a _preset threshold value Q _T-CRI2 , the operation upper limit value changing means determines the operation upper limit value for determining the upper limit of the controllable range of the operation value ρ _M. ρ _{M -LIM} is corrected so as to become smaller according to the rate of decrease of the total flow rate Q _T.

As the total flow rate Q _T decreases, the target upper limit value changing means decreases the target upper limit value. As a result, the target value ρ _O is relatively higher than the target upper limit value ρ _O-MAX. When the value is large, the target value regulation means regulates the target value ρ _O so as not to exceed the target upper limit value ρ _O-MAX .

Further, the controller increases the operation value ρ _M in order to eliminate the overshoot.
That is, the can flow rate Q _K is reduced and the bypass flow rate Q _B is increased. However, the operation value than the operation upper limit value ρ _M-LIM ρ _M
Is relatively large, the operation value regulation means regulates the operation value ρ _M so as not to exceed the operation upper limit value ρ _M-LIM .

Therefore, even if an overshoot occurs, the can body flow rate Q _K is limited so as not to become equal to or less than the can body required flow rate Q _K-MOQ , so that boiling of hot water in the heat exchanger is avoided and The gas burner will not be extinguished suddenly.

Moreover, since the operating value ρ _M of the distribution ratio can be varied within the range up to the operating upper limit value ρ _M-LIM even if the operating value ρ _M exceeds the target upper limit value ρ _O-MAX , overshoot can be achieved only by the gas combustion amount. As compared with the conventional case that solves the above problem, the responsiveness is high and the overshoot can be suppressed within a short time.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of a bypass mixing type water heater according to an embodiment of the present invention.

In the water heater of this embodiment, the heat exchanger 6 is provided with an inlet 10 communicating with a water pipe or the like on one side thereof.
On the other side, hot water outlets 12 communicating with a curran, a shower, etc. are respectively connected, and a water inlet passage 10 and a hot water outlet 12 are short-circuited by a bypass passage 14 for bypassing the heat exchanger 6.

A gas burner 8 for heating the heat exchanger 6 is arranged in the heat exchanger 6, and a gas proportional valve 20 is provided in the gas burner 8.

An inlet water temperature sensor 16 for detecting the inlet water temperature T _C is provided upstream of the connection point with the bypass passage 14 in the middle of the inlet passage 10, and the bypass passage 14 is also provided.
Can body flow rate Q _K to the heat exchanger 6 downstream from the connection point with
A can body flow rate sensor 18 for detecting

Meanwhile, in the middle of the pouring channel 12, upstream of the connection point between the bypass passage 14, can body water temperature sensor for detecting the can body water temperature T _H after being heated by the heat exchanger 6 22
Is provided, and the hot water supply temperature sensor 24 for detecting the hot water supply temperature T _M after mixing the hot water and the can flow rate Q _{K determine} the maximum heating capacity of the gas burner 8 on the downstream side of the connection point with the bypass passage 14. An overflow servo valve 26 is provided to limit the amount of hot water discharged when it exceeds the limit.

Further, in the middle of the bypass passage 14, a bypass valve 28 for adjusting the bypass flow rate Q _B flowing through the bypass passage 14 to change the distribution ratio (= Q _B / Q _K ) with the can body flow rate Q _K. Is provided.

The bypass valve 28 has a structure in which the valve opening is adjusted by a stepping motor (not shown).

Further, this water heater 1 is provided with a controller 30 for controlling the hot water temperature.

The controller 30 comprises a gas combustion control section 32 and a hot water distribution control section 34.

The gas combustion control section 32 adjusts the opening of the gas proportional valve 20 to perform feedforward and feedback control of the heating amount of the heat exchanger 8 by the gas burner 8, and the target value calculating means 36, Total flow rate calculating means 38, target upper limit value varying means 40, target value regulating means 42,
It comprises a boiling prevention means 44, a gas combustion amount calculation means 46, and a valve drive means 48.

The target value calculating means 36 takes in a desired hot water supply set temperature T _{S which} is predetermined by a command from an operating section (not shown) and the water inlet temperature T _C detected by the water inlet temperature sensor 16, and uses these values as these values. Based on this, the target value ρ _O that is the control target (feedforward amount) of the distribution ratio is calculated by the following equation.

Ρ _O = Q _B / Q _K = β / (T _S −T _C ) (where β is a constant) (4) The total flow rate calculating means 38 is a can body flow rate detected by the can body flow rate sensor 18. Q _K and the target value ρ _{O of the} distribution ratio calculated by the target value calculating means 36 are taken in, and based on these values, the total flow rate Q _T supplied from the water inlet 10 to the water heater 1 by the following equation. Is calculated.

Q _T = Q _K · (1 + ρ _O ) (5) The target upper limit value changing means 40 is given a threshold value Q to be compared with the total flow rate Q _{T in} advance by a command from an operation unit (not shown) or the like. Target upper limit value Q _O-MAX for determining the upper limit of the settable range of _T-CRI1 and target value ρ _O is set respectively.

Then, the target upper limit value changing means 40 takes in these values and sets the total flow rate Q _T calculated by the total flow rate calculating means 38 to the threshold value Q _T-CRI1 (where Q _T-CRI1 > Q).
_T-MOQ ), the total flow rate Q _T is more than the threshold value Q _T-CRI1
In the case of (Q _T ≧ Q _T-CRI1 ), the target upper limit value Q _O-MAX is not changed at all, but the total flow rate Q _T is below the threshold value Q _T-CRI1 (Q _T <Q _T-CRI1 In this case, the target upper limit value ρ _O-MAX is corrected so as to become smaller according to the decreasing rate of the total flow rate Q _T.

That is, the target upper limit value changing means 40 uses the Q
_{When T} <Q _T-CRI1 , the target upper limit value ρ _O-MAX is corrected by the correction coefficient k _O
The value obtained by multiplying is the new target upper limit value ρ after modification.
It is designed to output as _O-MAX .

Here, the above correction coefficient k _O is given by the following equation.

K _O = [{ρ _O-MAX − (ρ _MOQ −α)} / {Q _T-CRI1 −Q _T-MOQ }] · Q _T − [{ρ _O-MAX · Q _T-MOQ − ( ρ _MOQ −α) · Q _T-CRI1 } / {Q _T-CRI1 −Q _T-MOQ }] (where α is a constant) (6) The target value regulation means 42 is calculated by the target value calculation means 36. When the target value ρ _O is regulated so as not to exceed the target upper limit value ρ _O-MAX determined by the target upper limit value changing means 40, and the target value ρ _O exceeds the target upper limit value ρ _O-MAX. In (ρ _O > ρ _{O-MA X} ), the target upper limit value ρ _O-MAX is replaced with the target value ρ _O (ρ _O-MAX → ρ _O ).

The boiling prevention means 44 is the total flow rate calculation means 3
Captures the value of the total flow rate Q _T and the can body can body flow detected by the flow sensor 18 Q _K calculated at 8, the required flow rate to at least one of the total flow rate Q _T and the can flow Q _K has been set in advance When it is below Q _T-MOQ and Q _K-MOQ (when Q _{T ≤Q T-MOQ} or Q _{K ≤Q K-MOQ} ), the valve drive means 48 is controlled to fully close the gas proportional valve 20. The heating of the heat exchanger 6 by the gas burner 8 is stopped.

In the gas combustion amount calculating means 46, the incoming water temperature T _C detected by the incoming water temperature sensor 16, the can body flow rate Q _K detected by the water amount sensor 18, and the actual can body hot water temperature sensor 22 are detected. The can body hot water temperature T _H , a preset desired hot water supply set temperature T _S , and the regulated target value ρ _O output from the target value regulating means 42 are input respectively.

Then, the gas combustion amount calculating means 46 is adapted to obtain the gas combustion amount G by the following equation based on these input values, every predetermined period Δts (for example, 0.1 second). .

G = G _FF + G _FB (7) where G _FF is the feedforward control amount and G _FB is the feedback control amount, which are given by the following equations, respectively.

[0064] _{G FF = N FF · (T} HS -T C) · Q K (8) G FB = N FB · (T HS -T H) (9) However, N _FF, N _FB are both constant, T _HS is a can body set temperature as a control target for obtaining a desired can body water temperature T _H in the heat exchanger 6, this can body set temperature T _HS is given by the following equation.

When ρ _MOQ ≤ ρ ₀ ≤ ρ _O-MAX , T _HS = T _S + β (where β is a constant) (10) When ρ _O <ρ _MOQ or ρ _O > ρ _O-MAX , T _HS = ρ _O · (T _S −T _C ) + T _S However, ρ _O = ρ _MOQ (ρ _O <ρ _MOQ ), ρ _O = ρ _O-MOQ (ρ _O ＞ ρ _O-MOQ ) (11) Valve drive The means 48 drives the gas proportional valve 20 to have an opening corresponding to the gas combustion amount G so that the gas burner 8 is burned under the gas combustion amount G calculated by the gas combustion amount calculation means 46. To do.

On the other hand, the hot and cold water distribution control unit 34 adjusts the opening degree of the bypass valve 28 to adjust the can flow rate Q _K and the bypass flow rate Q _B.
For controlling the feed forward and feedback so that the distribution ratio of the
0, an operation upper limit value changing means 52, an operation value regulating means 54, and a step number converting means 56.

Then, the operation value calculating means 50 has the target value ρ _O regulated by the target value regulating means 42 and the incoming water temperature sensor 1
Incoming water temperature T _C detected by the 6, can body water temperature T _H is detected by the can body water temperature sensor 22 and the hot water temperature sensor 24,
The hot water supply temperatures T _M detected at are input respectively.

Based on these values, the operation value calculation means 50 operates the distribution ratio, which is the operation amount for actually driving the bypass valve 28, every predetermined period Δts (for example, 0.1 second). The value ρ _M is calculated by the following equation.

Ρ _M = ρ _FF + (200 + ρ _FB ) / 200 (12) where ρ _FF is a feedforward control amount, ρ _FB is a feedback control amount, and both ρ _FF and ρ _FB are expressed by the following equations. Given.

[0070] _{ρ FF = ρ O (13)} ρ FB = M P · (ρ FF -ρ A) + M I · Σ (ρ FF -ρ A) (14) However, M _P is a proportionality coefficient, M _I is the integral The coefficient, ρ _A, is the actual distribution rate of the can body flow rate Q _K and the bypass flow rate Q _B , and is given by the following equation.

Ρ _A = (T _H −T _M ) / (T _M −T _C ) (15) The operation upper limit value changing means 52 is provided with the total flow rate Q _{T in} advance by a command from an operation unit not shown. A threshold value Q _T-CRI2 for comparison and an operation upper limit value Q _M-LIM for determining the upper limit of the controllable range of the operation value ρ _M are input.

Then, the operation upper limit value varying means 52 fetches these values respectively and sets the total flow rate Q _T to the threshold value Q _{T.
Compared with T-CRI2} (however, Q _T-CRI2 > Q _T-MOQ ), if the total flow rate Q _T is greater than or _equal to the threshold value Q _T-CRI2 (Q _T ≧ Q _T-CRI2 ), the operation upper limit Although the value Q _M-LIM is not changed at all, when the total flow rate Q _T is below the threshold value Q _T-CRI2 (Q _T <Q _T-CRI2 ), the operation upper limit value ρ _M-LIM becomes the total flow rate. The correction is made so that it becomes smaller according to the decreasing rate of Q _T.

That is, the operation upper limit value changing means 52 uses the Q
_{When T} <Q _T-CRI2 , the correction coefficient k _M is _{added to} the operation upper limit value ρ _M-LIM.
The value obtained by multiplying the
It is designed to output as _M-LIM .

Here, the above correction coefficient k _M is given by the following equation.

K _M = [{ρ _{M-LIM −ρ MOQ} )} / {Q _T-CRI2 −Q _T-MOQ }] · Q _T − [{ρ _M-LIM · Q _{T-MOQ −ρ MOQ} · Q _T-CRI2 } / {QT _{-CRI2-QT -MOQ} }] (16) In the operation value regulation means 54, the operation value ρ _M calculated by the operation value calculation means 50 is determined by the operation upper limit value changing means 52. a restricts so as not to exceed the operation limit [rho _M-LIM is, when the operation value [rho _M exceeds the operating limit ρ _M-LIM (ρ _M
> Ρ _M-LIM ), the operation upper limit value ρ _M-LIM is replaced as the operation value ρ _M (ρ _M-LIM → ρ _M ).

The step number conversion means 56 is data for determining the relationship between the step number of the stepping motor that determines the valve opening degree of the bypass valve 28 and the corresponding operation value ρ _M of the distribution ratio according to the model of the water heater. Pre-stored memory
Includes a (not shown), the operation value [rho _M given from the operation value regulating means 54 in terms of the number of steps S _M, the valve opening by driving the stepping motor of the step number S _M amount corresponding bypass valve 28 It is designed to adjust the degree.

Next, the control operation of the hot water supply temperature in the water heater 1 having the above structure will be described with reference to the flow chart shown in FIG. 2 and the explanatory view shown in FIG.

In this example, the target upper limit value changing means 40
Threshold value Q with which the total flow rate Q _T is compared at
Total flow rate Q in _T-CRI1 and operation upper limit value changing means 52
It is _assumed that the threshold value Q _T-CRI2 with which _T is compared is set to the same value. Therefore, here, Q
_{T-CRI1 =} Q _T-CRI2 = Q _T-CRI (4 liters / minute in this example).

First, the controller 30 determines whether or not the desired hot water supply set temperature T _S set by the operation unit (not shown) is 60 ° C. or higher (step 1).

When the hot water supply set temperature T _S is 60 ° C. or higher, the hot water is discharged, so the step number conversion means 56
The operation value ρ _M of the distribution ratio is set to “0” and the number of steps is forcibly set to the minimum value (step 2). As a result, the bypass valve 28 is driven to the fully closed position (step 3). As a result, the water from the water inlet 10 is
All is supplied to the heat exchanger 6 without flowing through 4.

Further, the gas combustion amount calculating means 46 forcibly sets the set temperature T _{HS of the} can body to the set temperature T _S of hot water (step 4). That is, (8), (9) and T _HS = T _S in the equation to calculate the gas combustion quantity G (Step 5).

Then, the valve drive means 48 drives the gas proportional valve 20 so that the opening degree corresponds to the gas combustion amount G (step 6).

As a result, the hot water having the desired hot water supply set temperature T _S is discharged from the heat exchanger 6 and is supplied to the unillustrated curran or the like via the hot water discharge passage 12.

On the other hand, in step 1, when the hot water supply set temperature T _S is lower than 60 ° C., the target value calculation means 36 determines the desired hot water supply set temperature T _S and the water temperature T _C detected by the water temperature sensor 16. Based on the above equation (4),
A target value ρ _O that is a control target (feedforward amount) of the distribution ratio is calculated (step 10).

Subsequently, the total flow rate calculating means 38 calculates the can body flow rate Q _K detected by the can body flow rate sensor 18 and the target value ρ _O of the distribution ratio calculated by the target value calculating means 36.
The total flow rate Q _T supplied from the water inlet 10 to the water heater 1 is calculated by the equation (5) (step 11).

Then, the value of the total flow rate Q _T is sent to the target upper limit value changing means 40 and the operation upper limit value changing means 52, respectively.

The target upper limit value varying means 40 compares the total flow rate Q _T calculated by the total flow rate calculating means 38 with a preset threshold value Q _T-CRI (step 12).

When the total flow rate Q _T is equal to or larger than the threshold value Q _T-CRI (Q _T ≧ Q _T-CRI ), the target upper limit value ρ _O- which determines the upper limit of the settable range of the target value ρ _{O. MAX} (12/1 in this example)
0) is not changed at all (step 13).

Similarly, the operation upper limit value changing means 52 compares the total flow rate Q _T calculated by the total flow rate calculating means 38 with a preset threshold value Q _T-CRI (step 1).
2).

When the total flow rate Q _T is equal to or larger than the threshold value Q _T-CRI (Q _T ≧ Q _T-CRI ), the operation upper limit value ρ _M- which determines the upper limit of the controllable range of the operation value ρ _{M. LIM} (15/1 in this example)
0) is not changed at all (step 14).

On the other hand, the target upper limit value changing means 40
, The total flow rate Q _T fell below the threshold value Q _T-CRI (Q _T <Q
_T-CRI ), the target upper limit value ρ _O-MAX is multiplied by the correction coefficient k _O given by the equation (6), and the value obtained by this
(= K _O · ρ _O-MAX ) is output to the target value regulating means 42 as a new target upper limit value ρ _O-MAX after correction (step 18).

Since the above correction coefficient k _O is a function proportional to the total flow rate Q _T , as shown in the section sandwiched between Q _T-MOQ and Q _T-CRI in FIG. The target upper limit value ρ _O-MAX becomes smaller according to the decreasing rate of the flow rate Q _T. The total flow rate Q _T is _equal to the total required flow rate Q _T-MOQ (2.0 in this example).
When reduced to liters / min), the influence of the correction coefficient k _O, from the target upper limit value [rho _O-MAX is required distribution ratio [rho _MOQ (6/10 in this embodiment) alpha (although, alpha (6 ) Constant in expression)
It will be a small value.

Similarly, when the total flow rate Q _T is below the threshold value Q _T-CRI (Q _T <Q _T-CRI ), the operation upper limit value varying means 52 sets the operation upper limit value ρ _M-LIM . The correction coefficient k _M given by the above equation (16) is multiplied, and the value obtained by this is used as a new operation upper limit value ρ _M-LIM after correction, and the operation value regulating means 54
(Step 20).

Since the above-mentioned correction coefficient k _M is a function proportional to the total flow rate Q _T , as shown in the section sandwiched between Q _T-MOQ and Q _T-CRI in FIG. The operation upper limit value ρ _M-LIM becomes smaller according to the decreasing rate of the flow rate Q _T. When the total flow rate Q _T drops to the total required flow rate Q _T-MOQ , the operation upper limit value ρ _M-LIM matches the required distribution ratio ρ _MOQ due to the influence of the correction coefficient k _M.

The target value regulating means 42 is the target value calculating means 3
The target value [rho _O calculated in 6 by the aforementioned formula (4), the target upper limit value determined by the target upper limit value varying means 40 [rho
_A comparison is made with _O-MAX and the required distribution ratio ρ _MOQ preset based on the above equation (3) '(step 24).

[0096] As described above, the target upper limit value [rho _O-MAX given from the target upper limit value varying means 40, the entire flow rate Q _T is the threshold Q _T-CRI above a certain threshold Q _T-CRI The target upper limit value ρ _O-MAX decreases as the total flow rate Q _T decreases, but there is a target value ρ _O between the target upper limit value ρ _O-MAX and the required distribution ratio ρ _MOQ. When (ρ _MOQ ≤ ρ _O ≤
ρ _O-MAX ), that is, when the position determined by the relationship between the total flow rate Q _T and the target value ρ _O in FIG. 3 (a) is within the area indicated by A ₁ in FIG. 3 (a), the target value The restriction means 42 outputs the target value ρ _O as it is without any change.

For example, if the total flow rate Q _T is the code c _{1 in} FIG.
When the flow rate Q _T1 corresponding to the position indicated by is greater than or equal to the flow rate Q _T1 , the target value ρ _O remains unchanged.

On the other hand, the total flow rate Q _T is the threshold value Q
_When it becomes equal to or lower than _T-CRI , the target upper limit value changing means 40 reduces the target upper limit value ρ _O-MAX , and as a result, the target value ρ _O relatively exceeds the target upper limit value ρ _O-MAX (ρ _O > Ρ
_O-MAX ).

When it is determined that ρ _O > ρ _O-MAX (step 28), the target value regulating means 42 outputs the target upper limit value ρ _O-MAX as a new target value ρ _O. That is, the target value calculated by the target value calculation means 36 is discarded, and instead, the target upper limit value ρ _O-MAX is replaced with the target value ρ _O (ρ _O-MAX → ρ _O ).
Output (step 29).

For example, if the total flow rate Q _T is the code c _{1 in} FIG.
When the flow rate is less than Q _T1 corresponding to the position indicated by,
The target value ρ _O is the target upper limit value ρ _O-MAX .

Further, the target value regulating means 42 determines that the target value ρ _O calculated by the target value calculating means 36 is the required distribution ratio ρ _MOQ.
Less than (ρ _O <ρ _MOQ ) (Step 30)
_{Replace the} required distribution ratio ρ _MOQ with the target value ρ _O.
(ρ _MOQ → ρ _O ) is output (step 31).

In this way, the target value ρ _O regulated by the target value regulating means 42 is sent to the gas combustion amount calculating means 46 and the operation value calculating means 50, respectively.

The gas combustion amount calculation means 46 has a predetermined cycle Δts.
Every time (for example, 0.1 second), the gas combustion amount G is calculated by the above equations (7) to (11) (step 35).

That is, the gas combustion amount calculating means 46 determines that the target value ρ _O given from the target value regulating means 42 is between the required distribution ratio ρ _MOQ and the target upper limit value ρ _O-MAX (ρ _MOQ
≦ the ρ _O ≦ ρ _O-MAX) based on the equation (10), and when the target value [rho _O is not between the two _{ρ MOQ, ρ O-MAX (} ρ O <ρ MOQ
Alternatively, for ρ _O > ρ _O-MAX , the gas combustion amount G is calculated by the equations (7) to (9) after determining the can set temperature _THS based on the equation (11).

Since the value of the gas combustion amount G is given to the valve drive means 48, the valve drive means 48 drives the gas proportional valve 20 to have an opening corresponding to the gas combustion quantity G ( Step 36), whereby the gas combustion amount is controlled.

On the other hand, the operation value calculation means 50 has the target value ρ _O regulated by the target value regulation means 42 and the incoming water temperature sensor 16
In the incoming water temperature T _C detected, based on the values of the hot water supply temperature T _M detected by the can body water temperature T _H and the hot water temperature sensor 24, is detected by the can body water temperature sensor 22, a predetermined period Δt
The operation value ρ _M of the distribution ratio, which is the operation amount for actually driving the bypass valve 28, is calculated every s (for example, 0.1 second) based on the above equations (12) to (15) ( Step 3
7).

Then, this operation value ρ _M is sent to the operation value regulating means 54 in the next stage.

The operation value regulating means 54 is the operation value calculating means 5
The operation value ρ _M calculated by 0 is used as the operation upper limit value changing means 52.
It is compared with the operation upper limit value ρ _M-LIM determined by (step 38).

Now, when the total flow rate Q _T is reduced due to the amount of hot water being reduced on the calan side, the can body hot water temperature T _H becomes high, and as a result, the hot water supply temperature T _M also becomes high and overshoot occurs. .

In order to eliminate this overshoot, the operation value ρ _M calculated by the operation value calculating means 50 increases. This is, in other words, the control for reducing the can body flow Q _K increases the bypass flow rate Q _B.

In order to suppress the overshoot, even if the operation value ρ _M increases and exceeds the target upper limit value ρ _O-MAX , if it is less than or equal to the operation upper limit value ρ _M-LIM (ρ _M ≤ρ _M-LIM ), Since the can body flow rate Q _K does not drop below the can body required flow rate Q _K-MO , the operation value regulating means 54 outputs the operation value ρ _M as it is without any change.

Explaining this with reference to FIG. 3, as long as the manipulated value ρ _M is increased and exceeds the area indicated by A ₁ in FIG. 10A, it remains within the area indicated by A ₂ . Since the can body flow rate Q _K is within the area shown by B ₂ even if it exceeds the area shown by B ₁ in the same figure (b), it is kept above the can body required flow rate Q _K-MOQ .

Therefore, in the area of A ₁ + A _{2 in} FIG. 3A, the manipulated value ρ _M can be changed as a countermeasure against overshoot.

On the other hand, the operation value ρ _O output from the operation value calculation means 50 in order to suppress the overshoot.
Is increased to exceed the operation upper limit value ρ _O-MAX (ρ _O ＞
ρ _O-MAX ), the can body flow rate Q _K is the can body required flow rate Q _K-MO
The operation value regulating means 54 may be lowered below.
Is the operation upper limit value ρ determined by the operation upper limit value changing means 52.
_{The M-LIM} is reset as the operation value ρ _M (ρ _M-LIM → ρ _M ) and output (step 39).

Similarly, referring to FIG. 3,
If the manipulated value ρ _M is increased and is left to exceed the area indicated by A ₂ in FIG. 10A, the can body flow rate Q _K will change to B in FIG.
It becomes smaller than the area shown by ₂ . And the flow rate of the can body Q _K
When the flow rate of the gas decreases to the required flow rate Q _K-MOQ or less, the boiling prevention means 44 controls the valve drive means 48 to control the gas proportional valve 20.
Is completely closed, and heating of the heat exchanger 6 by the gas burner 8 is stopped.

In order to prevent such a situation from occurring, when the total flow rate Q _T is _{equal to} or more than the total required flow rate Q _T-MOQ , the operation value regulating means 54 changes the operation value ρ _M as shown in FIG. )
When the total flow rate Q _T decreases, the total flow rate Q _T is reduced so that it remains within the A ₁ + A ₂ region of (that is, the can flow rate Q _K does not fall below the B ₂ region of FIG. 3B). , Boiling prevention means 44
This prevents the gas burner 8 from being extinguished suddenly.

In this way, the operation value ρ _M regulated by the manipulation value regulating means 54 is sent to the step number converting means 56.

The step number converting means 56 converts the operation value ρ _M given from the operation value regulating means 54 into the step number S _M (step 40), and operates the stepping motor of the bypass valve 28 by the step number S _M. It is driven to adjust the valve opening (step 41).

The total flow rate Q _T is the required flow rate Q _{T-MOQ for the} can.
_Below (Q _T ≤ Q _T-MOQ ) or when the can body flow rate Q _K is below the can body required flow rate Q _{K-MOQ due} to clogging of the heat exchanger 6 (Q _K ≤ Q _K-MOQ In the case), the boiling prevention means 60
Controls the valve drive means 48 to fully close the gas proportional valve 20, and stops heating of the heat exchanger 6 by the gas burner 8.
This ensures that boiling in the heat exchanger 6 is avoided.

In the above embodiment, when the target value of the distribution ratio calculated by the target value calculating means 36 is ρ _O , the flow rate is equal to or less than the flow rate Q _T1 corresponding to the position indicated by the symbol c ₁ in FIG. 3 (a). Only when the target value ρ _O is reached, the target value ρ _O is regulated so as not to exceed the target upper limit value ρ _O-MAX .

However, as shown in FIG. 4, when the target value ρ _O calculated by the target value calculating means 36 is between the target upper limit value ρ _M-LIM and the required distribution ratio ρ _MOQ , the total flow rate Q _T Is decreased and becomes smaller than the threshold value Q _T-CRI (when the position exceeds the position indicated by the symbol c ₂ in FIG. 4), the target value regulating means 4
In 2, the target value ρ _O may be immediately corrected so as to become smaller according to the decreasing rate of the total flow rate Q _T.

FIG. 5 shows a flow chart for performing such control.

In FIG. 5, step 50 to step 5
Up to 4, the target value ρ _O calculated by the target value calculation means 36
Is to determine whether the target upper limit value ρ _O-MAX and the required distribution ratio ρ _MOQ are within a range of a value smaller by a constant value α, and regulate the target value ρ _O so as not to exceed the range. Processing.

The target value regulating means 42 determines whether or not the total flow rate Q _T has become less than or equal to the threshold value Q _T-CRI (step 5
5) When the total flow rate Q _T is larger than the threshold value Q _T-CRI
(See FIG. 4), without changing the target value ρ _O
It is output as it is (step 56). On the other hand, when the total flow rate Q _T becomes smaller than the threshold value Q _T-CRI , the target value ρ _O is multiplied by the correction coefficient k _L, and the value obtained by this is changed to a new target value ρ after correction. _Set to _O (Step 5
7).

Further, as in the conventional case, the target upper limit value ρ _O-MAX
When the total flow rate Q _T becomes smaller than the threshold value Q _T-CRI , the total flow rate Q _T is decreased according to the decrease (step 58).

The other control operations are the same as in the case of the flowchart shown in FIG.

In step 57, the target value ρ _O
The modification factor k _L used to modify the is given by:

K _L = [{ρ _O − (ρ _MOQ −α)} / {Q _T-CRI1 −Q _T-MOQ }] · Q _T − [{ρ _O · Q _T-MOQ − (ρ _MOQ −α ) ・ Q _T-CRI1 } / {Q _T-CRI1 −Q _T-MOQ }] (where α is a constant) (17) In this way, the total flow rate Q _T decreases and the threshold Q
_{When the} distribution ratio is changed to suppress overshoot when it is less than _T-CRI, the margin (margin) of the control range from the target value ρ _O to the operation upper limit value ρ _M-LIM
Is relatively large, which is convenient for suppressing overshoot.

In the above example, for simplification of description, the respective threshold values set in the target upper limit value changing means 40 and the operation upper limit value changing means 52 are set to Q _T-CRI1 = Q _T-CRI2.
= Q _T-CRI , but the threshold values Q _T-CRI1 and Q _T-CRI2 are different values (however, Q _T-CRI1 > Q _T-CRI2 > Q
It is also possible to set it to _T-MOQ ).

[0130]

According to the present invention, not only can boiling water be prevented from boiling in the heat exchanger, but a gas burner that heats the heat exchanger even when the total flow rate supplied to the water heater fluctuates. Frequent on / off repetitions are avoided, and overshoot can be suppressed within a short period of time, making it possible to obtain a water heater with good usability that takes advantage of the bypass mixing method. Become.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a bypass mixing type water heater according to an embodiment of the present invention.

FIG. 2 is a flowchart of a hot water supply temperature control operation of the water heater of FIG.

3 is an explanatory diagram of a hot water supply temperature control operation of the water heater of FIG. 1, FIG. 3 (a) is a characteristic diagram showing a relationship between a total flow rate and a distribution ratio, and FIG. 3 (b) is a total flow rate and a can body flow rate. It is a characteristic view showing the relationship of.

FIG. 4 is an explanatory diagram when a part of the temperature control operation is changed in the water heater of FIG.

5 is a flowchart in the case of partially changing the temperature control operation in the water heater of FIG.

FIG. 6 is a schematic configuration diagram of a conventional bypass mixing type water heater.

7 is an explanatory diagram of a hot water supply temperature control operation of a conventional water heater, FIG. 7 (a) is a characteristic diagram showing the relationship between the total flow rate and distribution ratio, and FIG. 7 (b) is the total flow rate and can body flow rate. It is a characteristic view which shows a relationship.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water heater, 6 ... Heat exchanger, 10 ... Inlet, 12 ... Outlet, 14 ... Bypass, 22 ... Heating water temperature sensor, 24
... hot water supply temperature sensor, 28 ... bypass valve, 30 ... controller, 32 ... gas combustion control unit, 34 ... hot water distribution control unit,
36 ... Target value calculating means, 40 ... Target upper limit value varying means, 4
2 ... Target value regulating means, 44 ... Boiling preventing means, 46 ... Gas combustion amount calculating means, 48 ... Valve driving means, 50 ... Manipulating value calculating means, 52 ... Manipulating upper limit value varying means, 54 ... Manipulating value regulating means.

Claims (1)

[Claims] 1. A bypass passage short-circuits a water inlet passage and a hot water passage communicated with the front and rear of the heat exchanger, and a heat exchange with a bypass flow rate Q _B flowing through the bypass passage in the middle of the bypass passage. Distribution ratio of the can body flow rate Q _K flowing through the vessel (=
While a bypass valve for changing Q _B / Q _K ) is provided, a target value ρ _O that is a control target of the distribution ratio is calculated based on the incoming water temperature T _S , the desired hot water supply set temperature T _{S, and the} like. Based on the target value ρ _O and the measured hot water supply temperature T _M, etc., the operation value ρ _M that is the operation amount of the actual distribution ratio is determined,
In a bypass mixing type water heater having a controller that controls the hot water supply temperature by adjusting the opening of the bypass valve according to this operation value ρ _M , the controller sums the can body flow rate Q _K and the bypass flow rate Q _B. When at least one of the total flow rate Q _T (= Q _K + Q _B ) or the can body flow rate Q _K is below the preset required flow rates Q _T-MOQ and Q _K-MOQ (Q _T ≤ Q _T-MOQ In the case of Q _K ≦ Q _K-MOQ ), a boiling prevention means for stopping heating of the heat exchanger is provided, and the total flow rate Q _T is set to a preset threshold value Q _T-CRI1 (however, Q Q _T-CRI1> compared to Q _T-MOQ), if the entire flow rate Q _T falls below the threshold Q _T-CRI1 the target upper limit value that determines the upper limit of the settable range of the target value [rho _O [rho _O target upper limit variable hand to fix _-MAX, so as to reduce in accordance with the reduction ratio of the total flow rate Q _T When the entire flow Q _T a preset threshold value Q _{T-CRI2 (However, Q T-CRI2> Q T} -MOQ) compared with, below the entire flow Q _T is the threshold Q _T-Cri2 If the includes operation upper limit value varying means for the operation limit [rho _M-LIM to determine the upper limit of the controllable range of the operation value [rho _M, modified to become smaller in accordance with the reduction rate of the total flow rate Q _T, the target value [rho _O is a target value regulating means for regulating so as not to exceed the target upper limit value [rho _O-MAX is determined by the target upper limit value varying means, said operating value [rho _M is, the operation upper limit value varying means A water heater characterized by comprising: an operation value regulation means for regulating the operation upper limit value ρ _M-LIM determined by the above so as not to exceed.