JPH0361102B2 - - 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 for detecting the amount of water entering the heat exchanger, calculating the required amount of heat from the set temperature, water temperature, and amount of water, and adjusting the amount of combustion. In FIG. 1, it has a burner 1, a heat exchanger 2, a water amount detector 3, an inlet 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 obtained 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 obtain the required amount of heat and the proportional control valve 6 is adjusted. The purpose of this system 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 rotational 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 problems of the conventional example described above, and provides a gas instantaneous water heater that suppresses transient temperature fluctuations, eliminates malfunctions due to noise, defective water flow sensor pulses, etc., and has a stable hot water temperature. It is something.

Structure of the Invention In order to achieve this object, the present invention provides a water amount 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. a differentiator, a differential corrector that stores the differential signal of the differentiator for each unit time and passes the differential signal only when a differential signal of the same polarity occurs two or more times in a row, and a differential corrector that corrects the output signal of the differential corrector. and a signal switching device that compares the combustion amount with a negative threshold and switches the combustion amount to the maximum value when it is larger than the positive threshold, and to the minimum value when it is smaller than the negative threshold.

With the above configuration, when the amount of water changes suddenly, the differentiator's direction of change in water amount is constant, so the differentiator continuously outputs differential signals of the same polarity, and the differential corrector passes the second and subsequent differential signals. . When the output signal of the differential corrector exceeds a positive or negative threshold, the signal switching device temporarily switches the combustion amount to the maximum or minimum, giving priority to the signal from the calorific value calculator, thereby suppressing transient fluctuations in the hot water temperature. Furthermore, changes in the water level signal due to external noise or missing pulses entering the water level detector are sporadic, and the differential signal is reversed (positive and negative), so it is removed by the differential corrector and does not affect the output signal in any way. It acts so as not to give

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 from 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 signal of the water amount detector connected to the input port or interrupt input using an internal timer, and obtains the water amount signal using an inverse calculation program. . 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. The signal switch 11 is a differential corrector 10
The signal to be sent to the proportional control valve 6 is selectively switched to either the output of the calorific value calculator 7, the maximum combustion amount signal, or the minimum combustion amount signal, depending on the output.

The timer 12 is activated by the signal switch 11 and is configured to control switching of the signal switch 11 only for a set time according to the output signal of the calorific value calculator 7.

If the water volume suddenly changes in the above configuration, Figure 3a
The water volume 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 is passed as an output signal at that time, 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. Differential corrector 10
Since the output signal c becomes smaller than the negative threshold value at time n, the signal switch 11 switches the combustion amount to the minimum value and starts the timer 12. Therefore, the combustion amount is the output of the calorific value calculator 7 that is proportional to the water amount signal a until time n, as shown in d in the figure, but after time n, it is switched to the minimum value for the set time τ of the timer 12, and the value is changed to the diagonal line in the figure. The output e of the calorific value calculator 7 is smaller than the output e of the calorific value calculator 7 in only a portion thereof. 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.

The timer 12 changes the set time τ according to the ratio between the output signal e of the calorific value calculator 7 and the minimum value at that time. In other words, when the ratio between e and the minimum value is large, the set value τ is shortened, and when the ratio between e and the minimum value is small, the set time τ is lengthened so that the area of the shaded area in the figure remains almost constant. This prevents the combustion amount from being overcorrected.

The above action occurs when the amount of water suddenly decreases, but when the amount of water suddenly increases, a continuous positive differential signal is generated and the signal switch 11 switches the combustion amount to the maximum value. The set time of the timer 12 at this time is set long when the output of the calorific value calculator 7 is large, and conversely set short when the output is small. In this way, transient fluctuations in the hot water temperature can be suppressed to a small level, similar to when the amount of water suddenly decreases.

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. a differential compensator that stores the differential signal for each unit time and passes the differential signal only when the differential signal of the same polarity continues two or more times; and the output signal of the differential corrector is set as positive and negative thresholds. By using a signal switch that switches the combustion amount to the maximum value when the comparison is greater than the positive threshold, and to the minimum value when it is smaller than the negative threshold, (1) When the water amount suddenly changes, the Since a larger change is given than the change in combustion amount according to the change, the values of overshoot and undershoot can be suppressed to a smaller value.

(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...Calorific value calculator, 8...Water amount calculator, 9...Differentiator, 10...Differential corrector,
11...signal switch, 12...timer.

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 inlet water temperature detector that detects the temperature of water, and a A temperature setting device that sets the outlet temperature of the exchanger, a proportional control valve that continuously adjusts the combustion amount of the burner, and a water amount calculation that detects the period of the frequency signal of the water amount detector and obtains a water amount signal by reciprocal calculation. a calorie calculator that calculates a required calorie signal from the water amount signal, the inlet water temperature signal of the inlet water temperature detector, and the set temperature signal of the temperature setting device to drive the proportional control valve; and a unit of the water amount signal. a differentiator that detects the amount of change per 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; The output signal of the differential corrector is compared with positive and negative thresholds, and when it is larger than the positive threshold, the combustion amount is set to the maximum value by giving priority to the output of the calorific value calculator, and the combustion amount is set to the maximum value than the negative threshold. A gas instantaneous water heater consisting of a signal switch that also switches the combustion amount to the minimum value when it is small. 2. The signal switching device changes the length of time for switching the combustion amount to the maximum value or the minimum value according to the ratio between the output signal of the calorific value calculator and the maximum value or minimum value of the combustion amount. The gas instantaneous water heater described in item 1.