JPS60232425A - Combustion control unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a combustion control device used, for example, in a gas instantaneous water heater, which automatically adjusts the combustion amount according to the flow rate of a heated object to obtain a constant outlet temperature. It is something.

Conventional configuration and its problems In gas instantaneous water heaters, there is a known means for detecting the amount of water entering the heat exchanger, calculating the required amount of heat based on the set temperature and water temperature, and adjusting the amount of combustion.

In Fig. 1, a burner 1, a heat exchanger 2, a water amount detector 3, an inlet water temperature detector 4 at the inlet of the heat exchanger, an outlet temperature detector S at the outlet of the heat exchanger, a proportional control valve 6 in the gas passage, and a temperature setting. A temperature rise calculation circuit 8 determines the necessary temperature rise using the temperature setting device 7 and the incoming water temperature detector 4, and a water amount detection circuit 9
Multiply by the amount of heat calculation circuit 10 to find the required amount of heat,
On the other hand, the temperature error detection circuit 11 detects the temperature error of the hot water discharged by the hot water temperature detector 5 and the temperature setting device 7, and the output is added to the output of the heat amount calculation circuit 10 via the feedback calculation circuit 12. 6. In this configuration, the required amount of heat is determined by the amount of heat calculation circuit 10, and the proportional control valve 6 is adjusted to give the required amount of heat to the heated object, thereby obtaining hot water at the set temperature. Since errors in the hot water temperature detector 4, the proportional control valve 6, etc., errors in the output water temperature, variations in circuit settings, etc., may cause errors in the hot water temperature, the signal from the hot water temperature detector 5 is fed as a feed bank via the feedback calculation circuit 12, and in particular, its integral element. This acts to eliminate steady errors in the hot water temperature.

This method aims to suppress transient fluctuations in the tapped water temperature when changing the amount of water or changing the set temperature, but it has the following drawbacks due to the use of a feed bank calculation circuit.

Fig. 2 a shows the water supply amount, b shows the combustion amount, and C shows the change in the hot water temperature. When the amount of water supplied suddenly decreases at time t1, the amount of combustion is throttled down to point d by the calorific value calculator 10. The hot water temperature is determined by the heat capacity of heat exchanger 2, the delay τ of the water flow sensor, etc.
temporarily rises as in The feedback calculation circuit 12 performs PID calculation on the temperature error e to reduce the combustion amount as shown in the figure f. Due to this decrease in the amount of combustion, the temperature at the exit island decreases as shown in g in the figure due to a delay in the control system, and then the amount of combustion increases due to the integral element of the feed bank calculation circuit 12, and the temperature at the outlet becomes stable at the same point. Since the feedback calculation circuit is used in this way, the hot water temperature causes an unnecessary under sheet g, and it takes a long time for the hot water temperature to stabilize.

OBJECTS OF THE INVENTION The present invention aims to solve the problems of the conventional example described above, and aims to suppress fluctuations in the hot water temperature during transient periods and shorten the settling time.

Structure of the Invention In order to achieve this object, the present invention includes a heat amount change detector for detecting a sudden change in the required heat amount, and a timer started by the heat amount change detector, and the timer detects a sudden change in the required heat amount. The configuration is such that the output of the feedback calculator is zero for a certain period of time.

With this configuration, when the required amount of heat suddenly changes due to a change in the amount of water or a change in the setting, the heat amount change detector detects this, starts the timer, stops the operation of the feedback calculator for a certain period of time, and only outputs the heat amount calculator. It acts to drive the proportional control valve.

Description of examples Next, one embodiment of the present invention will be described using the drawings.

In FIG. 3, the signals from the water amount detector 3, incoming water temperature detector 4, and temperature setting device 7 are processed by a water amount detection circuit 9 and a temperature rise calculation circuit 8, and a required amount of heat is calculated by a heat amount calculation circuit 10. A temperature error detector 11 detects the difference between the signals from the hot water temperature detector 5 and the temperature setting device 7, and a feed bank calculation circuit 12 performs a PID calculation. The output of the calorific value calculation circuit 10 and the output of the feedback calculation circuit 12 are added together to drive the proportional control valve 6 via the proportional valve drive circuit 13.

On the other hand, the output of the heat amount calculation circuit 1o is the heat amount change detection circuit 1"3
and its output starts a timer 15.

The output of the timer 15 is guided to the feedback calculation circuit 12, which resets the integral element and further sets the output signal to zero. In FIG. 3, the same members as in FIG. 1 are given the same numbers.

The operation will be explained using the above configuration. Figure 4 a shows the amount of water supplied;
h indicates the output of the heat amount change detection circuit 14, l indicates the output of the timer 15, 1 indicates the combustion amount, and k indicates the respective changes in the hot water temperature. When the water supply amount suddenly decreases at time t1, the water amount detector 3
After a delay, the amount of combustion is increased to one point by the heat amount calculation circuit 10.

At this time, the heat amount change detection circuit 14 differentiates the output signal of the heat amount calculation circuit 10, and when a change greater than or equal to - is detected, it generates an output pulse of the same type.The timer 15 generates an output i for τ1 after inputting h. . While the output signal of the timer 15 is being output, the output of the feedback calculation circuit 12 is zero, so the combustion amount maintains a value of 1 determined only by the output of the heat amount calculation circuit 10.

During this period, the hot water temperature rises once and reaches point m due to the heat capacity of the heat exchanger 2 and the delay of the water flow rate detector 3, but it decreases again and reaches point n at time t2 when one hour τ1 of the timer has elapsed. The timer one hour τ1 is set to be slightly longer than the sum of the time constant of the heat exchanger and the delay due to the length of the piping to the hot water temperature detector 5. Therefore, the hot water temperature at point n deviates by the error of the output of the calorific value calculator 10, and the temperature error ε
The temperature has deviated from the set temperature. From time t2, the output of the feedback arithmetic circuit 12 becomes effective, and the amount of furnace firing is corrected by its integral element, reaching stability at time t3. During this time, the feedback calculation circuit corrects only the slight temperature error ε, so that stability can be reached in a short time and unnecessary undershoots do not occur.

Effects of the Invention To summarize, according to the present invention, the present invention has a configuration including a heat amount change detector for detecting a sudden change in the required heat amount, and a timer that is activated by the heat amount change detector and makes the output of the feedback calculation circuit zero for a certain period of time. , the operation of the feedback calculation circuit is stopped for temperature changes that cannot be corrected due to the heat capacity of the heat exchanger, the delay of the water flow rate detector, etc., and only the correction operation is performed for the error in the output of the heat amount calculation unit. In order to
It suppresses the occurrence of uncontrolled overshoot or undershoot during transient periods, reduces changes in outlet temperature, and shortens the settling time to reach stability, making it an easy-to-use and safe device that can be applied to instantaneous water heaters, etc. It is possible to provide

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional combustion control device, FIG. 2 is an explanatory diagram of the operation of the conventional example, FIG. 3 is a configuration diagram of a combustion control device according to an embodiment of the present invention, and FIG. 4 is a configuration diagram of a combustion control device according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of the operation of one embodiment of the present invention. 1... burner, 2... heat exchanger, 3 water amount detector, 4 inlet water temperature detector, 5... hot water temperature detector,
6. Proportional control valve, 7... Temperature setting device, 10...
... Calorific value calculation circuit, 12... Feedback calculation circuit, 14 ... Heat amount change detection circuit, 15-timer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) A burner, a heat exchanger, a flow rate detector that detects the flow rate of the heated body, an inlet temperature detector that detects the inlet temperature of the heated body, an outlet temperature detector that detects the outlet temperature, and the burner. A proportional control valve that continuously adjusts the amount of combustion of Activated by a calculator, a feedback calculator that calculates the difference between the signals of the outlet temperature detector and the temperature setting device including an integral element, a heat amount change detector that detects a sudden change in the required heat amount, and a supplementary heat amount change detector. and a timer configured to drive the proportional control valve with the sum of the signals from the heat amount calculator and the feedback calculator, and to make the output of the feedback calculator zero for a certain period of time after a sudden change in the required heat amount by the timer. combustion control device. (2) The combustion control device according to claim 1, wherein the heat amount change detector is configured to perform detection using a differential value of the output signal of the heat amount calculator.