JPS6222385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to hot water temperature control for water heaters that use gas, oil, electricity, etc. as a heat source, and solves the conventional problem of not being able to obtain the set hot water temperature when the water supply is overloaded with a large amount of water. In order to solve the problem, we installed a supply water flow controller and
To provide a new control device that effectively supplies hot water at a temperature set as soon as possible after the start of use, near the maximum hot water supply function.

Hereinafter, a gas water heater that uses gas as fuel will be described as an example.

FIG. 4 is a block diagram of a conventional gas water heater, in which combustion heat from a burner 1 serving as a heat source and water are exchanged with a heat exchanger 2 to provide hot water. In the temperature control device 3,
The signal (TW) from the hot water temperature detector 4 and the signal (TWR) from the hot water temperature setting device 5 are taken in, a predetermined combustion amount is determined from the deviation between them (TER = TWR - TW), and the supply heat amount controller 6 is controlled. The temperature of the hot water is controlled. Generally, a thermistor is often used as the hot water temperature detector 4, and a PiD method is often used as the hot water temperature control algorithm.

FIG. 3 is a diagram showing the relationship between the water supply amount W (horizontal axis) and the temperature rise ΔT (vertical axis) of the gas water heater. The thick solid line in the figure represents the temperature rise characteristic at the maximum combustion amount Qg _MAX , that is, the capacity curve of the water heater. In other words, the maximum combustion amount Qg _MAX , the temperature rise ΔT, and the water supply amount W, which is the load, are as follows, where η is the combustion efficiency, η・Qg _MAX = W・ΔT (1), and ΔT=η・Qg _MAX / It is written as W (2). Therefore, at each water supply amount W, there is no temperature rise greater than the solid line shown in the figure. For example, when the maximum combustion amount Qg _MAX , the amount of hot water released is
If W ₁ , the temperature rise will be ΔT ₁ as shown. The above-mentioned temperature control device 3 receives the set temperature signal TWR from the hot water temperature setting device 5 and the water supply temperature.
When the difference from TWi, that is, the value ΔT at which the temperature should be increased, is ΔT ₁ , it acts effectively in the flow rate range of water supply amount WW ₁ . However, in a load greater than W ₁ , that is, in a flow rate range of W>W ₁ , control becomes impossible, and the outlet temperature TW will never reach the set temperature TWR no matter how long it takes.

In this way, the maximum combustion amount Qg _MAX limits the amount W of hot water that can be heated and whose hot water temperature can be controlled. It is an object of the present invention to provide a control device that eliminates such drawbacks of conventional water heaters, allows a desired hot water temperature to be obtained at all times, and reaches a set temperature in a short period of time after the start of use.

FIG. 1 is a block diagram of a gas water heater of the present invention. Devices with the same numbers as in FIG. 4 are devices having the same functions. In the control device 7, the hot water temperature detector 4
signal TW and signal TWi of feed water temperature sensor 8
, the signal TWR of the hot water temperature setting device 5 is taken in, and the TWR
The predetermined combustion amount is determined from the deviation TER _between In some cases, the water supply amount controller 9 is used to limit the amount of water supplied ( _W1 is the maximum water supply amount that can be controlled). With this method, you will always get hot water at the set temperature.

In addition, in order to absorb fluctuations in the amount of water supplied which is a load due to water pressure fluctuations or variations in the characteristics of the water supply amount controller 9, the water supply amount controller 9 is controlled in accordance with the temperature deviation TER described above. This means that if the deviation TER remains above a predetermined value in a steady state after a predetermined period of time has elapsed, mainly taking into account the process response delay of the heat exchanger, after the water amount change operation according to the TUP described above, the amount of water supplied will be increased. operate in the direction of reducing. This operation allows you to absorb variations in load and obtain the desired water temperature.

By the way, it will be explained below that the water heater can be used efficiently by changing the predetermined time until the steady state is reached after the aforementioned operation of changing the amount of water supplied, depending on TUP.

FIG. 2A shows a case where the change in TUP, that is, the target value, is small. From the top, hot water temperature TW
, the amount of water supplied W, and the amount of gas supplied Qg over time. Combustion starts at t=t ₀ , and at that point the water supply amount is throttled down to W ₁ depending on TUP ₁ . After the start of combustion, the hot water temperature TW rises, and when the predetermined time _t1 has elapsed, the deviation TER is within the predetermined value ΔT, and continues as it is.
Hot water temperature control continues with the water supply amount of W ₁ . ΔQg
is the margin of gas supply amount with respect to the maximum supply amount during steady state, and when water supply amount control is implemented, ΔQg
The smaller the water heater is, the more the water heater is being used to its maximum capacity, and this can be said to be an effective method in terms of water supply restrictions.

Figure 2B is an example of a case where the target value change is large.
This is an example in which the predetermined time after the water supply amount variation operation is _t1 , which is the same as in A. As in A from above, the time characteristics of the hot water temperature TW, supply water volume W, and supply gas volume Qg are t = t ₀
Combustion has started. At t=t ₀ , W is TUP ₂
W is limited to ₂ depending on. In this example B, since the target value change is large, the deviation TER of the outlet hot water temperature TW does not converge within the predetermined value ΔT even after the predetermined time _t1 has elapsed. For this reason, the set water temperature is obtained by further reducing the supplied water amount by ΔW. Originally,
Water supply amount control using TER should be performed when the system reaches a steady state, and especially when the change in target value is large, it is necessary to set a large predetermined time. By the way, setting a large predetermined time for all target value changes will result in a delay in the next control operation (for example, water supply amount control using TER), and will also result in unnecessarily prolonging the water temperature settling time. obtain.

Therefore, as shown in FIG. 2C, when the target value change is large, the water heater can be used effectively by setting the predetermined time to a large value t ₂ (>t ₁ ). It is the gas supply margin Δ in the steady state shown in Figure 2B.
This can be seen from the fact that Qg is larger than ΔQg in FIG. 2C. In other words, in the control method shown in FIG. 2B, as a result of controlling the amount of water supplied to obtain the set temperature, there is still room in the capacity of the water heater, and the amount of water supplied can be increased. In contrast, in C, the set hot water temperature is obtained using the water supply control value W ₂ according to TUP ₂ .

As explained above, according to the water heater control device of the present invention, the amount of water supplied is always limited to a range where the temperature can be controlled, so in addition to the excellent effect that hot water of the desired temperature is always obtained, the amount of change in the target value is By changing the predetermined time it takes for the system to reach a steady state after the water supply control operation according to the amount of water supplied, unnecessary restrictions on the amount of water supplied are eliminated, and the water heater can be used effectively in terms of water supply. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a gas water heater according to an embodiment of the present invention, and FIG. 2A is a time characteristic diagram of hot water temperature, water supply amount, and gas supply amount when the change in target value is small.
B is a characteristic diagram when the change in target value is large; C is a characteristic diagram when the predetermined time is long and the change in target value is large; Figure 3 is a characteristic diagram showing the relationship between water supply amount and temperature rise of a gas water heater; FIG. 4 is a configuration diagram of a conventional gas water heater. 4... Hot water temperature detector, 5... Temperature setting device, 6
... Supply heat amount controller, 7 ... Control device, 8 ... Incoming water temperature detector, 9 ... Supply water amount controller.

Claims (1)

[Claims] 1 comprises an inlet water temperature detector, an outlet water temperature detector, a temperature setting device, a supply heat amount controller, and a supply water amount controller, and the deviation (TER) between the signal of the temperature setting device and the signal of the outlet hot water temperature detector is provided. ), and the difference between the signal of the temperature setting device and the signal of the water inlet temperature sensor (TUP).
When the deviation (TER) does not converge within a predetermined value even after a predetermined time period corresponding to the signal difference (TUP) has elapsed after controlling the water supply amount controller depending on A water heater control device that includes a control device that drives a water heater.