JP2518487B2 - How to control the water heater - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bypass mixing type instantaneous water heater provided with a bypass passage for bypassing a heat exchanger, and the minimum water flow rate (MOQ) when the flow rate suddenly decreases.
) Relating to the method of controlling the water heater.

[0002]

2. Description of the Related Art Conventionally, in a momentary water heater (hereinafter referred to as "water heater"), in order to prevent low temperature corrosion of the heat exchanger, a bypass passage bypassing the heat exchanger is provided, and a heat exchanger outlet part is provided. The hot water outlet temperature is kept high, and in a bypass mixing type water heater equipped with such a bypass passage, if the hot water discharge amount (total water flow amount) Q _T fluctuates, the can body water flow rate Q _H There fluctuates, the can body the hot water temperature T _H by a change of the can body through water Q _H is changed, by opening and closing a bypass valve provided in the bypass passage to adjust the hot water temperature T _O increase or decrease the bypass water Q _B Something, for example,
When the can body hot water discharge temperature T _H rises when the can body water flow rate Q _H decreases, the bypass valve is opened to increase the bypass water quantity Q _B to adjust the final hot water temperature.

[0003]

However, in the above conventional water heater control, the flow rate ratio (distribution ratio) between the can body water flow rate Q _H and the bypass water flow rate Q _B is constant (Q _H : Q _B = co
nst.) (for example, Q _H : Q _B = 10: 1)
2) When the hot water discharge amount Q _T is drastically reduced to near the operation minimum total water flow amount MOQ _T, which is the minimum total flow rate required for hot water discharge operation, the hot water discharge amount Q _T exceeds MOQ _T. But
M can body through water Q _H is decreased to require a minimum of a can body flow operation below the minimum can body through water MOQ _H to perform combustion operation
There was a problem that it became OQ _H OFF and combustion stopped. An example will be described with specific numerical values. The flow rate ratio between the can body water flow rate Q _H and the bypass water flow rate Q _B can be calculated as Q _H : Q _B.
= 10:12, operating minimum total water flow MOQ _T OFF value 1.8 l / mi
n., in a water heater that sets the operation minimum can body through water MOQ _H OFF value to 1.3 l / min., the tapping amount Q _T from 10 l / min. 2.
When the tapping operation is performed at 2 l / min. (Q _T > MOQ _T OFF value), Q _H : Q _B = 10:12, so Q _H = 1.0 l / mi
n., Q _B = 1.2 l / min., the can body water flow rate Q _H becomes less than the operating minimum can body water flow rate MOQ _H (Q _H <MOQ _H OFF value), and MOQ _H OFF, and combustion It will be stopped. Further, since the can body the hot water temperature T _H by the can body through water Q _H sharply decreases from overshooting, the set flow rate Q _H: Q _B = 10: further can body passing than 12 water Q _H To increase the proportion of the bypass water amount Q _B to

An object of the present invention is to provide a stable hot water discharge operation without sharply reducing the hot water discharge amount Q _T and performing a hot water discharge operation so that the can body water flow rate Q _H does not fall below the operating minimum can body water flow rate MOQ _H. It is to provide a method for controlling a water heater capable of performing the above.

[0005]

In order to achieve the above object, a method of controlling a water heater according to the present invention comprises a heat exchanger, a bypass passage for bypassing the heat exchanger, and a bypass for adjusting at least the bypass water amount Q _B. and the valve, to adjust the can body through water Q _H
In a water heater provided with a can body water flow valve, a can body water flow rate sensor for detecting the can body water flow rate Q _H flowing through the heat exchanger is provided, and when the can body water flow rate Q _H suddenly decreases. , Can body
Drive the water valve in the opening direction at the maximum speed to increase the water flow rate in the can body.
Causes, by reducing the bypass water Q _B the bypass valve at maximum speed to drive in the closing direction to ensure the can body through water Q _H, can body through water Q _H operating minimum can body through water MOQ _HK By maintaining the above, the stable hot water discharge operation can be performed without the can body water flow rate Q _H falling below the operating minimum can body water flow rate MOQ _H. In addition, the can body through water _{Q H}
By providing a can body water flow sensor to detect,
Water _{Q H} is equal to or greater than the operating minimum can body through water _{MOQ HK}
This can be reliably detected.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a water inlet passage 2 is connected to the inlet side of the heat exchanger 1, and a hot water outlet passage 3 is connected to the outlet side thereof, and a bypass passage 4 that bypasses the heat exchanger 1 and connects the water inlet passage 2 with the hot water outlet passage 3 is formed. Hot and cold water mixing provided with a can body water passage valve that is provided at the confluence of the bypass passage 4 and the hot water passage 3 and that regulates the can body water flow rate Q _H, and a bypass valve that regulates the bypass water flow rate Q _B. Valve 5
And an overflow prevention servo valve 6 provided in the hot water outlet passage 3 on the downstream side of the merging portion, and a water inlet temperature T _C provided on the upstream side of the bypass passage 4 branch portion of the water inlet passage 2. On the outlet side of the heat exchanger 1, a temperature sensor 7, a can body water flow rate sensor 8 for detecting a can body water flow rate Q _H provided between the branch portion of the bypass 4 and the inlet side of the heat exchanger 1. a can body the hot water temperature sensor 9 for detecting the can body tapping temperature T _H which is provided upstream of the tapping path 3 than the hot and cold water mixing valve 5, the over-spill prevention servo valve 6
A hot water outlet temperature sensor 10 is provided downstream of the hot water from the heat exchanger 1 and cold water from the bypass passage 4 to detect the hot water outlet temperature T _O. Incoming water temperature T _C detected by the sensor, can body hot water temperature T _H, the hot water temperature T _O, the can body through water Q _H and a preset temperature entered into the controller 12, the hot and cold water mixing according to the result The operation signal of the valve 5 and the overflow servo valve 6 is the controller 12
Output from In addition, 11 is a burner.

Explaining the hot water temperature control, the set temperature T _SK , the incoming water temperature T _C , the set temperature T _S , the can body water flow rate (can body hot water discharge amount) Q _H, and the bypass water amount Q _B are explained. The following equation holds in between. Q _H · T _SK + Q _B · T _C = (Q _H + Q _B ) · T _S T _SK = {(Q _H + Q _B ) T _S −Q _B · T _C } / Q _H For example, T _SK = 2.2 · T _S −1.2 ・ When set to T _C ,
The mixing ratio of hot and cold water in the hot and cold water mixing valve 5 is Q _H : Q _B = 1
It will be 0:12. With the set temperature T _S set as the target,
Can bodies through water Q _H and a bypass water Q _B and the mixing ratio adjusted to the leaving water temperature T _O obtained in advance the hot water temperature control operation amount of the hot and cold water mixing valve 5 for tapping temperature control for controlling the Q-theta It is calculated based on the characteristic function.

Next, the drive control operation of the hot and cold water mixing valve 5 when the flow rate suddenly decreases will be described with reference to the flow chart of FIG. The can body water flow rate Q _H detected by the can body water flow rate sensor 8 at a predetermined time interval (measured by the number of pulses at several msec., For example) is less than or equal to a preset water flow rate Q _S (for example, 3 l / min.). It is confirmed whether or not the water flow rate Q _{H in the} can body is further decreasing when the water flow rate is decreased. After a predetermined period of time, this time the newly detected can body water flow rate Q _H1 is compared with the previously detected previous can body water flow _rate Q _H0, and the current can body water flow rate Q _H1 is lower than the previous can body water flow _rate Q _H0. If it is confirmed that it is obviously small, that is, if Q _H1 ≤Q _H0 / α (α is a constant and α> 1), then the can body water flow rate Q _H
Together but determines that the decline is driven in the direction of the closed position at maximum speed bypass valve for adjusting the bypass water Q _B of the hot and cold water mixing valve 5 (full closing or minimum valve opening position), can body through The can water passage valve for adjusting the amount of water Q _H is driven at the maximum speed in the direction of the fully open position to move the hot and cold water mixing valve 5 to a predetermined standby position (in this embodiment, the bypass valve is closed and the can water passage valve is opened. Keeping the can body water flow rate Q _{H above the} operating minimum can body water flow rate MOQ _H (for example, operating minimum can body water flow rate MOQ _H OFF value is 1.3 l / min.) , M
It does not become OQ _H OFF (at this time, the hot water temperature T _O decreases).

As a means for confirming whether or not the can body water flow rate Q _H is decreasing, a differential value dQ _H / dt of the can body water flow rate Q _H with respect to time may be obtained. _{When H} / dt is zero and can body water flow rate Q _H is constant, when it is a positive value, can body water flow rate Q
_{When H} has a tendency to increase and the negative value has a tendency for the water flow rate Q _{H in the} can to decrease, a predetermined value β (β ≧ 0) or more (dQ _H / dt ≧ β)
In that case, the can body water flow rate Q _H does not tend to decrease at least, and it is not necessary to control the hot water mixing valve 5 to reduce the bypass water amount Q _B and increase the can body water flow rate Q _H. On the contrary, if it is less than the predetermined value β (dQ _H / dt <β), the can body water flow rate Q _H
Because There is decreasing, to drive the closed position the bypass valve of the hot and cold water mixing valve 5 at maximum speed, by driving the fully open position the can body through the water valve at maximum speed, the can body through water Q _H
To keep the operating minimum can body water flow rate over MOQ _H.

After fixing the hot and cold water mixing valve 5 to the standby position (ensuring the minimum operating can water flow MOQ _H ), the normal drive control of the hot and cold water mixing valve 5 is restored if a predetermined restoration condition is satisfied. . As the return condition, for example, can body water flow rate Q
_H is increased to a predetermined set value Q _S1 (for example, Q _S1 ≧ Q _S )
The above may occur (Q _H ≧ Q _S1 ).

Further, in the above embodiment, the bypass valve of the hot and cold water mixing valve 5 and the can body water passage valve are driven simultaneously, but only the bypass valve may be driven in the closing direction. Further, even if the return condition is satisfied, the drive control of the hot and cold water mixing valve 5 is not returned to the normal state, and the feedback control by the set temperature T _S and the hot water discharge temperature T _{O is performed} with the hot and cold water mixing valve 5 fixed at the standby position. The hot water mixing valve 5 drive control may be returned to the normal state after performing the above process to adjust the amount of combustion and adjusting the hot water discharge temperature T _O.

[0012]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, when the amount of tapping water is throttled and the total flow rate is drastically reduced, at least the amount of mixed water is reduced to reduce the water flow rate in the can body. Since the amount of water flowing through the can is reduced to less than the minimum amount of water flowing through the minimum can, the combustion is stopped because the amount of water flowing through the can is reduced to a predetermined amount or more. Also, a can body that detects the can body water flow rate Q _H.
By providing the through water sensor, can body through water Q _H luck
Make sure that the minimum flow rate of water in the can is over MOQ _HK.
Can be detected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a water heater to which the present invention is applied.

FIG. 2 is a flowchart showing a control operation when the flow rate is reduced according to the present invention.

[Explanation of symbols]

1 heat exchanger, 2 water inlet passage, 3 hot water outlet passage, 4 bypass passage 5 can body inlet solenoid valve, 6 overflow prevention servo valve, 7 inlet water temperature sensor 8 inlet water amount sensor, 9 can body outlet temperature sensor, 10 outlet temperature sensor 11 burners, 12 controllers

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadahiko Oshio 32 Akashi-cho, Chuo-ku, Kobe City, Hyogo Prefecture Noritsu Co., Ltd. 56) References JP-A-1-247950 (JP, A) JP-A-1-174829 (JP, A) JP-A-64-3435 (JP, A)

Claims (1)

(57) [Claims] 1. A water heater comprising a heat exchanger, a bypass path for bypassing the heat exchanger, a bypass valve for adjusting at least the amount of bypass water, and a can water flow valve for adjusting the water flow rate of the can body . , the can body through water sensor for detecting the can body through water provided, when the can body through water is rapidly decreased, the can body
Drive the water flow valve in the opening direction at maximum speed to increase the water flow rate in the can body
At the same time, the bypass valve is driven at the maximum speed in the closing direction to reduce the amount of bypass water.