JPH0361101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas instantaneous water heater that automatically adjusts the amount of combustion depending on the amount of water and obtains a constant hot water temperature.

Configuration of conventional example and its problems In a gas instantaneous water heater, means are known to detect the amount of water entering the heat exchanger, calculate the required amount of heat from the set temperature, water temperature, and amount of water, and adjust the amount of combustion. In FIG. 1, it has a burner 1, a heat exchanger 2, a water amount detector 3, an incoming water temperature detector 4, a temperature setting device 5, a proportional control valve 6 for a gas passage, and a calorific value calculation circuit 7. A temperature rise value is determined from the set temperature and the water inlet temperature, and the value is multiplied by the water amount signal from the water amount detector 3 to determine the required amount of heat and the proportional control valve 6 is adjusted. The purpose of this method is to reduce transient fluctuations in hot water temperature when the load changes suddenly, such as sudden changes in water volume. This is important in order to suppress The water amount detector 3 is generally of a type that detects the rotational speed of a movable blade, which changes depending on the amount of water. In order to obtain a water volume signal from a frequency proportional to the rotation speed, frequency-voltage conversion or pulse number detection per unit time is performed, but this causes a delay in water volume detection and is a factor that increases transient temperature fluctuations. Ta.

Purpose of the Invention The present invention aims to solve the above-mentioned problems of the conventional method, and provides a gas instantaneous water heater that suppresses transient temperature fluctuations, eliminates malfunctions due to noise and defective water flow sensor pulses, and provides a stable hot water temperature. It is something to do.

Structure of the Invention In order to achieve this object, the present invention provides a water amount signal calculator that measures the period of a frequency signal of a water amount detector and obtains a water amount signal by reciprocal calculation, and detects the amount of change in the water amount signal per unit time. and a differential corrector that stores the differential signal of the differentiator for each unit time and passes the differential signal only when the differential signal of the same polarity occurs two or more times in a row, The proportional control valve is configured to be driven by a signal that is the sum of the output and the output of the differential corrector.

With the above configuration, when the amount of water changes suddenly, the differentiator continuously outputs differential signals of the same polarity because the direction of change in the amount of water in the differentiator is constant. Therefore, the differential corrector does not allow the second and subsequent differential signals to pass through. Since it is added to the output of the calorific value calculator, the combustion amount changes rapidly, suppressing transient fluctuations in the hot water temperature. Furthermore, changes in the water level signal due to external noise entering the water level detector or missing pulses are sporadic, so the differential signal is reversed (positive and negative) and is removed by the differential signal corrector, resulting in no output signal. It acts so as not to affect the

DESCRIPTION OF EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 2, the frequency signal of the water amount detector 3 is guided to a water amount calculator 8, where the period (time interval) of the frequency pulse is determined and reciprocally calculated to obtain a water amount signal proportional to the amount of water. More specifically, the water amount calculator is composed of a microcomputer, which measures the period of the frequency pulse of the water amount detector connected to the input port or interrupt input using an internal timer, and obtains the water amount signal by a program using reciprocal calculation. . The water amount signal is input to the calorific value calculator 7, and the output of the differentiator 9 is input to the differential corrector 10.
is input to. The output of the differential corrector 10 is added to the output of the calorific value calculator 7 to drive the proportional control valve 6.

If the water volume suddenly changes in the above configuration, Figure 3a
The water amount signal changes as shown below. The differentiator 9 outputs a differential signal (b) in FIG. 3 by determining the difference between the water amount signals at sampling times n and n-1. Since the amount of water is changing monotonically, the differential signal has the same polarity continuously. The differential corrector 10 stores the differential signal at each sampling time and compares it with the previous stored value. If the polarities are the same, the differential signal at that time is passed as an output signal, and if the polarities are different, the differential signal is not passed. At sampling time n in Figure 3, the differential signal becomes negative polarity twice in a row, so the figure c
Pass the differential signal as shown below. Therefore, the combustion amount is the output of the calorific value calculator 7 proportional to the water amount signal a until time n, as shown in d in the same figure, but after time n, the output c of the differential corrector 10 is added, and the amount becomes d in the same figure.
Only the shaded area is smaller than the calorific value. Therefore, the transient fluctuation f of the tapped water temperature can be suppressed to be smaller than g in the case of using only the calorific value calculation signal.

On the other hand, if noise enters the water amount detector or if a pulse from the water amount detector is missing, the water amount signal becomes a single pulse signal as shown in Fig. 3h. Therefore, the differential signal i is a series of signals with different polarities. The differential corrector 10 stores a negative signal at time m-1, but becomes a positive signal at time m, and since the polarity is different, it does not allow the differential signal i to pass through, so its output signal becomes j. Therefore, the combustion amount k is not affected by changes in the water amount signal h and is stable, so that fluctuations in the tapped water temperature do not occur.

Effects of the Invention As described above, according to the present invention, there is provided a water amount calculator that calculates the water amount based on the period of the frequency signal of the water amount detector, a differentiator that detects the amount of change in the water amount signal per unit time, and the differentiator. It has a differential compensator which stores the differential signal of the same polarity and passes the differential signal only when the differential signal of the same polarity occurs two or more times in a row. By configuring the control valve to be driven, (1) When the water volume suddenly changes, a larger change is given than the change in combustion volume in response to the change in water volume, so overshoot and undershoot values can be kept smaller. .

(2) Since the output of the differential corrector does not occur due to noise or missing water flow detector pulses, stable operation is achieved without malfunctions.

There is an effect.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional gas instantaneous water heater, Fig. 2 is a block diagram of a gas instantaneous water heater according to an embodiment of the present invention, and Fig. 3 is a diagram showing the signals of various parts showing the operation of the same water heater. This is a graph against axis time. 1...Burner, 2...Heat exchanger, 3...Water amount detector, 4...Incoming water temperature detector, 5...Temperature setting device,
6...Proportional control valve, 7...Calorie amount calculator, 8...Water amount calculator, 9...Differentiator, 10...Differential corrector.

Claims (1)

[Claims] 1 A burner, a heat exchanger, a water amount detector that generates a frequency signal according to the amount of water supplied to the heat exchanger, an incoming water temperature detector that detects the temperature of water, and an incoming water temperature detector that detects the temperature of hot water coming out of the heat exchanger. a temperature setting device to set, a proportional control valve to continuously adjust the combustion amount of the burner, a water amount signal calculator that detects the period of the frequency signal of the water amount detector and obtains a water amount signal by reciprocal calculation, and the water amount a calorie calculator that calculates a required calorie signal from the signal, an inlet water temperature signal of the inlet water temperature detector, and a set temperature signal of the temperature setting device; a differentiator that detects the amount of change in the water amount signal per unit time; a differential corrector that stores the differential signal of the differentiator for each unit time and passes the differential signal only when the differential signal of the same polarity occurs two or more times in a row;
A gas instantaneous water heater configured to drive the proportional control valve by a signal that is the sum of the output of the calorific value calculator and the output of the differential corrector.