JPH08189635A - Hot water delivery temperature control method for hot water supplying apparatus - Google Patents

Abstract

PURPOSE: To achieve a delivery of hot water at a comfortable temperature by controlling an absolute value of a correction number calculated based on a difference between a set temperature and the hot water delivery temperature not to exceed a specified maximum correction limit value. CONSTITUTION: A necessary number (necessary combustion value) is calculated based on a set delivery temperature of hot water set by a temperature setting device 11, a temperature of water supplied detected by a water supply temperature sensor 5 and a quantity of passing water detected by a flow rate sensor 6 while a correction number (feedback control value) is calculated based on a difference between the set temperature set by the temperature setting device 11 and a hot water delivery temperature detected by a hot water delivery temperature sensor 8. The correction number is added to the necessary number to determine a control number. In this case, the controller 12 controls an absolute value of the correction number not to exceed the maximum correction limit value predetermined thereby enabling the delivering of hot water at a comfortable temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot water outlet temperature control method for a water heater, which is performed by combining feed forward control and feedback control.

[0002]

2. Description of the Related Art Generally, in a water heater, the hot water temperature is controlled by adjusting the amount of water passing through the heat exchanger and the amount of combustion, and feedforward control and feedback control are used together as a control method. Many things are done. Feedforward control is performed at the set temperature Ts
(° C.), the input water temperature Tc (° C.), and the water flow rate Q (number), the necessary combustion number G _FF , which is the required combustion amount, is changed to G _FF = (T
s -Tc) / 25 calculated in, based on the calculated required scale number G _FF controls the gas proportional control valve controls the gas amount. However, with feedforward control alone,
If the calorific value of the gas is different from the expected value, by controlling the fuel gas flow rate based on the required scale number G _FF, it is impossible to obtain a quantity of heat corresponding to the required scale number G _FF, the hot water temperature There is a problem that hot water cannot be discharged with Th (° C) equal to the set temperature Ts. That is, when the calorific value is smaller than the planned value, the hot water outlet temperature Th becomes lower than the set temperature Ts, and when the calorific value is larger than the planned value, the hot water outlet temperature Th is set.
Becomes higher than the set temperature Ts.

For example, when city gas is used, 12A gas and 13A gas having different calorific values are treated as the same gas group, and the same water heater is used for both gases without changing the gas nozzle diameter. Therefore, when 12A gas having a small calorific value is used in the water heater adjusted to the 13A gas having a large calorific value, the calorific value is insufficient and the hot water outlet temperature Th becomes lower than the set temperature Ts. In order to solve the above-mentioned problem, so-called feedback control using PI (integral + proportional) control, PID (integral + proportional + derivative) control, etc. is used in combination to detect the deviation between the hot water temperature Th and the set temperature Ts. The amount is being controlled.

[0004]

However, in the above-mentioned conventional hot water outlet temperature control of the water heater using both feedforward control and feedback control, the amount of feedback control is not particularly limited. Or an abnormality occurred in the hot water temperature detection circuit,
If the reading value of the hot water outlet temperature Th is fixed, the amount of gas is extremely increased or decreased, and there is a problem that the hot water outlet temperature Th largely changes. That is, the hot water temperature Th
If the read value of is fixed higher than the set temperature Ts, the amount of gas is throttled by the feedback control to the minimum flow rate or the shutoff state, and the actual hot water temperature is significantly lowered, which causes the user discomfort. there were. On the contrary, if the reading value of the hot water temperature Th is fixed lower than the set temperature Ts, the amount of gas is increased to the maximum flow rate by the feedback control, and the hot water is discharged at an abnormally high hot water temperature Th, which may cause boiling. There was a problem.

An object of the present invention is to solve the above problems and to provide a hot water outlet temperature control method for a water heater capable of performing hot water discharge at a comfortable hot water temperature by limiting the feedback control amount.

[0006]

In order to achieve the above object, a method of controlling hot water discharge temperature of a water heater according to the present invention comprises a water temperature detecting means provided in each of the heat exchanger inlet side water passage and outlet side water passage. In a water heater provided with hot water temperature detection means and water flow amount detection means, and hot water temperature setting means for setting hot water temperature, a set temperature set by the hot water temperature setting means,
The required number is calculated based on the incoming water temperature detected by the incoming water temperature detecting means and the water flow rate detected by the water flow rate detecting means, and the difference between the set temperature and the hot water temperature detected by the hot water temperature detecting means is calculated. A hot water temperature control method for calculating a correction scale number based on the above, and adding the correction scale number to a required scale number to obtain a control scale number, wherein the absolute value of the correction scale number is a predetermined maximum correction. By not exceeding the limit value, there is no fear that the correction number (feedback control amount) will become excessive, and especially in the vicinity of the minimum number, the output number will be controlled sufficiently. Safe control can be performed with a simple structure without requiring a complicated structure. In addition, the ratio between the absolute value of the above-mentioned correction number and the required number is
By not exceeding the predetermined maximum correction limit ratio, it is possible to eliminate the risk of the correction number (feedback control amount) becoming excessive and to make the correction number near the maximum number sufficient. Therefore, it is possible to discharge hot water at the set temperature with a margin. Further, since the maximum correction limit ratio is set to a constant value in the range from the minimum number to the maximum number, the controller can have a simple configuration. Furthermore, the absolute value of the correction number does not exceed the sum of the predetermined equality correction limit value and the equality correction limit value set by the product of the required number and the predetermined correction limit ratio. This eliminates the risk of the correction number (feedback control amount) becoming too large, and makes it possible to set the correction number to a sufficient value over the entire range from the minimum number to the maximum number, with a margin. It is possible to discharge hot water at the set temperature. Further, since the geometric correction limit ratio is set to a constant value in the range from the minimum number to the maximum number, the controller can be configured simply.

[0007]

Embodiments of the present invention will be described with reference to the drawings. In FIG. 5, the schematic configuration of the water heater to which the present invention is applied includes a heat exchanger 1, a burner 2 for heating the heat exchanger 1, an inlet 3 connected to the inlet side of the heat exchanger 1 and an outlet side. Flow rate control valve 7 having a hot water supply channel 4 connected to the water supply channel, a water temperature sensor (water temperature detecting means) 5 and a flow rate sensor (water flow rate detecting means) 6 provided in the water channel 3 and driving means such as a servomotor. A hot water outlet temperature sensor (hot water temperature detecting means) 8 provided in the hot water discharge passage 4 and a gas supply passage 9 communicating with the burner 2.
The proportional control valve 10 provided on the
It has 12 and.

The controller 12 is equipped with a microcomputer, and the incoming water temperature Tc detected by the incoming water temperature sensor 5, the water flow amount Q detected by the flow rate sensor 6, the outgoing hot water temperature Th detected by the outgoing hot water temperature sensor 8, and the temperature The set temperature Ts from the setter 11 is input, and the control signals calculated based on the respective inputs are output to the water flow rate adjusting valve 7 and the proportional control valve 10, respectively.

In the controller 12, the required number (required combustion amount) is calculated based on the incoming water temperature Tc, the water flow rate Q and the set temperature Ts.
G _FF is calculated by the following formula (feedforward control). G _FF = (Ts −Tc) · Q / 25 At the start of the hot water discharge operation, the feed forward control is performed at the required number G _FF , but thereafter the set temperature Ts
And the hot water temperature Th, and in the present embodiment, the water flow rate Q
The correction number G _K is calculated based on the following equation (feedback control). G _K = K _P (Ts −Th) Q + (1 / K _I ) ∫ (Ts −
Th) Qdt, and the hot water output control is performed by the output power number G (G = G _FF + G _K ), which is the control amount obtained by adding the correction size G _K to the required size G _FF , and the set temperature Ts is the hot water temperature Th. If it is larger, the corrected scale number G _K is positive (G _K > 0), the output scale number G becomes larger than the required scale number G _FF , and the set temperature Ts is equal to the tapping temperature Th.
If it is smaller, the correction number G _K is negative (G _K <0), the output number G is smaller than the required number G _FF , and the set temperature Ts is equal to the hot water temperature Th (ΔG = 0). In this case, the corrected number G _K is zero (G _K = 0) and the output number G is the required number G.
_Is equal to _FF .

In the first embodiment of the present invention, the absolute value G _KI of the correction scale number G _K does not exceed the maximum correction limit value G _Kmax (for example, G _Kmax = 2) which is a predetermined constant value. The output number G is maintained such that the upper limit is equal to or less than the sum of the required number G _FF and the maximum correction limit value G _Kmax , and the lower limit is equal to or more than the difference obtained by subtracting the maximum correction limit value G _Kmax from the required number G _FF. (G _FF
-G _Kmax ≤ G ≤ G _FF + G _Kmax ). FIG. 1 shows a correlation diagram showing the relationship between the required number G _FF and the output number G, and the ideal line Lo is the case where the required number G _FF and the actual hot water number G _FB are equal (ΔG = 0), The upper limit line Lu ₁ shows the sum of the required number of outputs G _FF and the maximum correction limit value G _Kmax (G = G _FF + G _Kmax ), and the lower limit line Ld ₁ shows the required number G _FF and the maximum correction limit. Value G _Kmax
The difference (G = G _FF −G _Kmax ) is shown. Required number G
_{The FF and the} output number G are the minimum number G set in advance.
_MIN. (Eg 2.5) and maximum number G _MAX. (Eg 16)
Output number G is between the minimum number G _MIN. (No. 2.5) and the maximum number G _MAX. (No. 16), the upper limit line Lu ₁ and the lower limit line It is controlled to a value between Ld ₁ .

According to this configuration, the correction scale number G _K (feedback control amount) calculated based on the difference ΔG (ΔG = G _FF −G _FB ) between the required scale number G _FF and the actual hot water scale number G _FB. There is no fear of becoming too large, and especially in the vicinity of the minimum number G _MIN. (2.5), a sufficient output number G is controlled, and the controller 12 does not require a complicated configuration and has a simple configuration. With this, safe control can be performed.

In the second embodiment, the above-mentioned correction number G _K
The ratio (G _KI / G _FF ) between the absolute value of G _KI and the required number G _FF is
The maximum correction limit ratio Amax. (For example, 0.35) set in advance is not exceeded, and the absolute value G of the correction number G _{K
Since KI} is kept below the product G _FF · A max. Of the required number G _FF and the maximum correction limit ratio A max. (0.35), the output number G is the minimum corrected output number (1-A max. ) ・ G _FF and maximum corrected output number (1 + Amax.) ・ G _FF , that is, (1
-Amax.) · G _FF ≦ G ≦ (1 + Amax.) · G _FF . Fig. 2 shows the correlation diagram of the required number G _FF and the output number G. The ideal line Lo is the case where the required number G _FF and the actual hot water number G _FB are equal, and the upper limit line Lu ₂ is the maximum corrected output number. Number {G
= (1 + Amax.) · G _FF }, and the lower limit line Ld ₂ indicates the minimum corrected output number {G = (1-Amax.) · G _FF }. The required number G _{FF and the} output number G are limited between the predetermined minimum number G _MIN. (No. 2.5) and the maximum number G _MAX. (No. 16), respectively _. G is the minimum number G
It is controlled to a value between the upper limit line Lu ₂ and the lower limit line Ld ₂ between _MIN. (2.5) and maximum number G _MAX. (16).

According to this configuration, the fear that the correction number G _K (feedback control amount) becomes excessive is eliminated, and
The correction number G _K near the maximum number G _MAX. (16) can be set to a sufficient value, and the set temperature Ts can be tapped with a margin. Also, the maximum correction limit ratio Amax.
(0.35) from the minimum number G _MIN. (2.5) to the maximum number G
_{Since the maximum} value ( _MAX. 16) is kept constant, the controller 12 can have a simple structure.

In the third embodiment, the above correction number G _K
The absolute value G _KI of the product of the predetermined equality correction limit value G _KO (eg, G _KO = 1), the required number G _FF and the predetermined correction limit ratio A (eg, A = 0.30) Does not exceed the sum of the geometric correction limit value G _FF · A set by (G _KI ≤ G _KO + G _FF ·
A), the output scale number G is the minimum corrected output scale number {(1-A) · G _FF −G _KO } and the maximum corrected output scale number {(1 + A) · G _FF + G _KO }. Between, that is, {(1-
A) ・ G _FF −G _KO } ≦ G ≦ {(1 + A) · G _FF + G _KO }
Controlled by the range of. Required number G _FF and output number G in Figure 3
The ideal line Lo is the case where the required number G _FF and the actual hot water number G _FB are equal, and the upper limit line Lu ₃ is the maximum corrected output number {(1 + A) · G _FF + G _KO } The lower limit line Ld ₃ indicates the minimum corrected output number {(1-A) · G _FF −G _KO }. Required number G _{FF and} output number G are predetermined minimum number G _MIN. (No. 2.5) and maximum number G _MAX. (16
From being restricted between No.), the output scale number G, the minimum scale number G _MIN. And between the maximum scale number G _MAX. (16 No.) (2.5 No.), the upper limit line Lu ₃ and the lower limit line It is controlled to a value between Ld ₃ .

With this configuration, the shortage of the first and second embodiments is compensated, the fear that the correction number G _K (feedback control amount) becomes excessive, and the minimum number G _MIN. (2.5 No.) to the maximum number G _MAX. (No. 16), the correction number G _K can be set to a sufficient value, and the set temperature Ts can be tapped with a margin. In addition, set the geometric correction limit ratio A (0.30) to the minimum number G
_{Since the} constant value is set from _MIN. (2.5) to maximum number G _MAX. (16), the controller 12 can have a simple structure.

More specifically, the limit value of the correction number G _K is fixed from the minimum number G _MIN. (No. 2.5) to the maximum number G _MAX. (No. 16) to a constant maximum correction limit value G _Kmax (G _Kmax = In the case of 2) (see the first embodiment), in the vicinity of the maximum number G _MAX. (No. 16), a range smaller than the error of the feedforward control amount in the normal state, that is, the allowable error (for example, 30%). Since it is controlled by (2/16 = 0.125), the limit of the correction number G _K , which is the feedback control amount, becomes small, and the correction number G _K is irrespective of whether the hot water temperature is normally read. There is a risk that it will be difficult to tap the hot water at the set temperature. In order to avoid this problem, the maximum correction limit value G _Kmax
If the value is increased, the limit of the correction number G _K becomes too large in the vicinity of the minimum number G _MIN. (No. 2.5), and the tapping temperature may become high.

Further, the absolute value of the G _KI, minimum scale number G _MIN. Maximum number No. from (2.5 No.) G _MAX. Constant maximum correction limit required scale number G _FF up (No. 16) of the correction scale number G _K The product of the ratio Amax. (0.35) and G _FF · Amax. Is maintained below (see the second embodiment).
In the vicinity of the minimum number G _MIN. (No. 2.5), the feed-forward control amount error in the normal state, that is, the control is performed within a range smaller than the permissible error, and the outlet temperature reading is normally performed. Regardless, the correction number G _K may be too small and it may be difficult to discharge the set temperature.
That is, the maximum secondary pressure Pmax. (For example, 100 mmAq) of the proportional control valve 10 corresponding to the maximum number G _MAX.
Minimum secondary pressure P of proportional control valve 10 corresponding to _MIN. (No. 2.5)
min. (for example, 20 mmAq), if there is an error (for example, 1 mmAq) at the time of adjustment, the minimum secondary pressure Pmin. adjustment has a larger error than the maximum secondary pressure Pmax. % But 5% on the minimum side), the allowable error on the minimum number G _MIN. Side is larger than that on the maximum number G _MAX. Side, so if only a fixed maximum correction limit ratio Amax. There is a problem that the number G _K is too small.

In the third embodiment, the absolute value G _KI of the correction number G _K is set to the difference correction limit value G _KO (1) and the ratio correction limit value G _FF · A (0.30 · G _FF ). _Does not exceed the sum (G _KI ≤ G
_KO + G _FF · A), so the minimum number G _MIN. (2.5
No.) near the difference correction limit value G _KO (1), a sufficient control range can be secured (1 / 2.5 = 0.40), an appropriate correction number G _K can be obtained, and hot water can be discharged at the set temperature. . Also, near the maximum number G _MAX. (No. 16), a sufficient correction range can be secured by the geometric correction limit G _FF · A (0.30 · G _FF ) to obtain an appropriate correction number G _K. The hot water can be discharged at the set temperature.

Referring to FIG. 4, the control ranges of the respective embodiments will be described. The control range of the first embodiment is graphic I, the control range of the second embodiment is graphic II, and the control range of the third embodiment is graphic II.
I, and the inside of each figure is the control area. The straight line A is the maximum number G _MAX. (No. 16), which is the sum of the necessary number G _FF and the correction number G _K (G _FF + G _K = G _MAX. = 16),
The straight line B is the minimum number G of the sum of the required number G _FF and the correction number G _K.
MIN. (No. 2.5) (G _FF + G _K = G _MIN. = 2.5),
The control area is below the straight line A and above the straight line B. FIG.
As is clear from the above, the minimum number G is the one of the first embodiment.
There is a margin in the vicinity of _MIN. (No. 2.5), that in the second embodiment has a margin in the maximum number G _MAX. (No. 16), and that in the third embodiment is the minimum number G _MIN. (2.5) _. No.) to the maximum number G _MAX.
There is a margin in the control range over the entire range up to (No. 16).

[0020]

Since the present invention is constructed as described above, it has the following effects. Calculate the required number based on the set temperature, incoming water temperature, and water flow rate, calculate the correction number based on the difference between the set temperature and the hot water temperature, and add the corrected number to the required number to control In the outlet hot water temperature control method for obtaining the number of corrections, since the absolute value of the correction number is set so as not to exceed the predetermined maximum correction limit value, the correction number (feedback control amount) may become excessive. In particular, a control of a sufficient output number is performed especially near the minimum number of numbers, and a complicated configuration is not required for the controller, and safe control can be performed with a simple configuration. In addition, the ratio between the absolute value of the correction number and the required number does not exceed the predetermined maximum correction limit ratio, thereby eliminating the risk of the correction number (feedback control amount) becoming excessive. The correction number near the maximum number can be set to a sufficient value, and the hot water at the set temperature can be discharged with a margin. Further, since the maximum correction limit ratio is set to a constant value in the range from the minimum number to the maximum number, the controller can have a simple configuration. Furthermore, the absolute value of the correction number does not exceed the sum of the predetermined equality correction limit value and the equality correction limit value set by the product of the required number and the predetermined correction limit ratio. This eliminates the risk of the correction number (feedback control amount) becoming too large, and makes it possible to set the correction number to a sufficient value over the entire range from the minimum number to the maximum number, with a margin. It is possible to discharge hot water at the set temperature. Further, since the geometric correction limit ratio is set to a constant value in the range from the minimum number to the maximum number, the controller can be configured simply.

[Brief description of drawings]

FIG. 1 is a correlation diagram showing a control range of a first embodiment of the present invention.

FIG. 2 is a correlation diagram showing a control range of the second embodiment of the present invention.

FIG. 3 is a correlation diagram showing a control range of a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a control range of each embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a water heater to which the present invention is applied.

[Explanation of symbols]

1 Heat Exchanger, 2 Burner, 3 Inlet Channel, 4 Outlet Channel 5 Inlet Temperature Sensor (Inlet Temperature Detection Means) 6 Flow Rate Sensor (Inlet Volume Detection Unit), 7 Inlet Volume Control Valve 8 Outlet Temperature Sensor (Outlet Temperature Detector) , 9 gas supply path 10 proportional control valve, 11 temperature setting device, 12 controller

Claims (3)

[Claims] 1. A water inlet temperature detecting means, a hot water outlet temperature detecting means, a water flow amount detecting means, and a hot water temperature setting means for setting the hot water temperature, which are provided in the inlet side water passage and the outlet side water passage, respectively. In the water heater, the necessary number is calculated based on the set temperature set by the hot water temperature setting means, the water temperature detected by the water temperature detection means, and the water flow rate detected by the water flow rate detection means. In the hot water temperature control method, a correction scale is calculated based on the difference between the set temperature and the hot water temperature detected by the hot water temperature detecting means, and the correction scale is added to the required scale to obtain a control scale. There is provided a hot water outlet temperature control method for a water heater, wherein the absolute value of the correction number does not exceed a predetermined maximum correction limit value. 2. An inlet water temperature detecting means, an outgoing hot water temperature detecting means and a passing water quantity detecting means respectively provided in the heat exchanger inlet side water passage and the outlet side water passage, and a hot water temperature setting means for setting a hot water temperature. In the water heater, the necessary number is calculated based on the set temperature set by the hot water temperature setting means, the water temperature detected by the water temperature detection means, and the water flow rate detected by the water flow rate detection means. In the hot water temperature control method, a correction scale is calculated based on the difference between the set temperature and the hot water temperature detected by the hot water temperature detecting means, and the correction scale is added to the required scale to obtain a control scale. A hot water outlet temperature control method for a water heater, wherein the ratio between the absolute value of the correction number and the required number does not exceed a predetermined maximum correction limit ratio. 3. An inlet water temperature detecting means, an outlet hot water temperature detecting means and a passing water amount detecting means respectively provided in the heat exchanger inlet side water passage and outlet side water passage, and a hot water temperature setting means for setting the outlet water temperature. In the water heater, the necessary number is calculated based on the set temperature set by the hot water temperature setting means, the water temperature detected by the water temperature detection means, and the water flow rate detected by the water flow rate detection means. In the hot water temperature control method, a correction scale is calculated based on the difference between the set temperature and the hot water temperature detected by the hot water temperature detecting means, and the correction scale is added to the required scale to obtain a control scale. Therefore, the absolute value of the correction number does not exceed the sum of the predetermined equality correction limit value and the equality correction limit value set by the product of the required number and the predetermined correction limit ratio. A hot water dispenser characterized by Hot water temperature control method.