JPS6222384B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to temperature control of water heaters that use gas, oil, electricity, etc. as heat sources, and solves the conventional problem of not being able to obtain the set water temperature when the water supply is overloaded with a large amount of water. In addition to installing a water supply flow rate controller,
The purpose is to provide a new control device that starts with a small flow rate in order to supply hot water at a set temperature as soon as possible after the start of use.

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

FIG. 6 is a block diagram of a conventional gas water heater, in which combustion heat from a gas burner 1 serving as a heat source and water are exchanged with a heat exchanger 2 to provide hot water. The temperature control device 3 receives the signal TWO from the hot water temperature detector 4 and the signal TWR from the hot water temperature setting device 5, determines a predetermined combustion amount from the deviation between them (TER=TWR-TWO), and controls the amount of heat supplied. The water temperature is controlled by controlling the vessel 6. 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. 5 is a diagram showing the relationship between the water supply amount W (horizontal axis) of the gas water heater and the temperature rise ΔT (vertical axis). 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 and the temperature rise ΔT,
The water supply amount W, which is a load, is expressed as η·Qg _MAX =WΔT (1), where η is the combustion efficiency, and further written as ΔT=η·Qg _MAX /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 larger than W ₁ , that is, in a flow rate range of W>W ₁ , control becomes impossible, and the outlet temperature TWO 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. 6 are devices having the same functions. In the control device 7, the hot water temperature detector 4
The signal TWO of the water supply temperature sensor 8 and the signal TWi of the water supply 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 Sometimes, 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.

However, in the present invention, in order to speed up the start-up of hot water temperature control, the following control method is adopted.

In FIG. 2, the horizontal axis represents elapsed time and the vertical axis represents hot water temperature, and shows the transient response characteristics after the start of use. A is the response when the load is smaller than B, and if the respective water supply amounts are W I and W B, then W I < W
There is a relationship between As is clear from the figure, it takes a considerable amount of time to reach the target value TUP in case B, while it quickly settles in case B with a slight overshoot. As described above, the dead time and delay time of the system differ due to the difference in flow rate, that is, the difference in the process to be controlled, which causes a difference in the same calculation method. By the way, even if you adjust the calculation parameters to achieve the optimal response for each flow rate, if the TUP is close to the process gain of the system (temperature rise value according to the water heater's capacity curve), the result will be as shown in Figure 2 (b). The response characteristics are very sharp, and it takes a long time to settle.
In other words, as described above, the water supply amount controller can always reach the set temperature in a steady state, but it may take a long time from the start of use until the temperature is stabilized.

Figure 3 shows the relationship between water supply amount and settling time.
The characteristics of A, B, and C are that the temperature rise is TUP _A , respectively.
This is the case for TUP _B and TUP _C. Furthermore, it can be seen that there is a relationship of TUP _A > TUP _B > TUP _C , and the higher the temperature rise value for the same flow rate, the longer the settling time is required. From the actual specifications of the equipment, it is desirable to shorten the settling time as much as possible to obtain hot water at the set temperature as quickly as possible. For example, if the settling time is t ₁ , and the set temperature rise value is TUP _A , then WW _A 〓 may result in a response that satisfies the specifications, but if W > W _A 〓, the settling time will be longer than t ₁ . I end up.

Therefore, as shown in Fig. 4, from the value of TUP _A known at the start of use and the characteristic diagram shown in Fig. 3, the first predetermined water supply amount within the range that satisfies the settling time t ₁ , for example, up to W _A 〓 In order to limit the water supply amount, the water supply amount controller is controlled to start combustion and control the hot water temperature, so that the second predetermined water supply amount W _A is reached when the aforementioned deviation TER converges within a predetermined value. By controlling the water supply amount controller accordingly, not only can the start-up be made faster, but also the set temperature can be achieved. Here, when changing from the first predetermined water supply amount to the second predetermined water supply amount, if the change is made over a predetermined time taking into account the process delay time, it is possible to control the hot water temperature to follow the flow rate change. There is a change in W _A 〓 → W _A without significantly deviating from the target value. This can also be applied when changing the target value, that is, when increasing TUP.

As is clear from the above explanation, according to the water heater control device of the present invention, the water supply amount is always limited to a controllable range, so the desired hot water temperature can be obtained at any time, and the water supply amount is throttled to a predetermined value. Since the temperature is started from a cold state, the set temperature can be reached in a short period of time, giving the user a great advantage.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a gas water heater showing an embodiment of the present invention, Fig. 2 is a hot water temperature characteristic diagram of the same water heater, Fig. 3 is a settling time characteristic diagram using temperature rise as a parameter, and Fig. 4 is a diagram of settling time characteristics using temperature rise as a parameter. The figure is a water supply amount control diagram by the control device of the present invention, FIG. 5 is a capacity characteristic diagram of a water heater, and FIG. 6 is a configuration diagram of a conventional gas water heater. 1... Heat source, 2... Heat exchanger, 4... Water supply temperature detector, 5... Hot water temperature setting device, 6... Supply heat amount controller, 7... Control device, 8... Water supply temperature detector, 9
...Water supply controller.

Claims (1)

[Claims] 1 A heat source, a heat exchanger, a water supply temperature detector, a hot water temperature detector, a hot water temperature setting device, a supply heat quantity controller, and a supply water quantity controller, and the signal of the hot water temperature setting device and the hot water supply temperature detector are provided. Temperature detector signal deviation (TER)
The supplied heat amount controller is controlled depending on the temperature of the water supply, and the water supply amount controller is controlled depending on the difference (TUP) between the signal of the hot water temperature setting device and the signal of the water supply temperature detector, and the water heater is used. At the time of starting or when the difference (TUP) of the above-mentioned signals changes, the supply water amount controller is set to the first predetermined water supply amount, and after the control is started, when the above-mentioned deviation (TER) reaches within a predetermined value, the above-mentioned A water heater control device comprising: a control device that sets the water supply amount controller to a second predetermined water supply amount that is larger than the first predetermined water supply amount.