JPH04180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention automatically adjusts the amount of gas by calculating the required amount of heat based on the amount of water, set temperature, and water supply temperature. This invention relates to a gas instantaneous water heater to which so-called feedforward control is applied.

Prior Art Conventional technologies for this type of gas instantaneous water heater include, for example, Japanese Patent Application No. 150227/1982 and Japanese Patent Application No. 075156/1983. In the conventional example, a feed forward control component includes a temperature setting device that sets the hot water temperature, a water supply temperature sensor, and a water flow sensor.

(Set temperature - Water supply temperature) x Water volume (Formula 1) The required amount of heat is calculated and the gas proportional control valve is driven, and the hot water temperature is set using feedback control based on the deviation between the set temperature and the hot water temperature. It is configured to control the temperature equally.

In this case, two temperature sensors are required to detect the water supply temperature and the hot water outlet temperature, respectively, which not only increases the cost of the equipment, but also causes errors in the two temperature sensors to affect the target temperature of each of the feed forward calculation and the feedback calculation. This method has the disadvantage that a large difference occurs, the temperature of the hot water changes stepwise, and it takes a long time to settle the temperature of the hot water.

Problems to be Solved by the Invention The present invention attempts to solve the problems in the prior art, and aims to reduce errors in mutual control targets when using feedforward control and feedback control in combination, thereby improving hot water temperature stability. In addition to improving
The aim is to reduce costs and provide an inexpensive water heater.

Means for Solving the Problems In order to achieve this object, the present invention provides a method for controlling the amount of gas according to the deviation between the hot water temperature detected by a temperature sensor installed at the outlet of a heat exchanger and the set temperature of a temperature setting device. and a control constant calculator that calculates and stores a functional formula or proportionality constant for the amount of heat required for the amount of water and set temperature from the control output of the feedback calculator when the hot water temperature is stable. A feedback calculator is provided to calculate the required amount of heat by inputting signals from the water flow sensor and temperature setting device using a proportional constant, and the gas proportional control valve is driven by signals from both the feedback calculator and the feedback calculator. It is composed of

Effect In the above configuration, during the first hot water supply after the device is powered on, only the feedback calculator operates, and the feedback calculation unit operates based on the deviation between the set temperature and the hot water temperature.
PID control is performed, and eventually the hot water temperature becomes stable and matches the set temperature. At this time, the control output of the feedback calculator is the required amount of heat according to the set temperature and water amount, and the control constant calculator calculates the water amount signal of the water flow sensor, the set temperature signal of the temperature setting device, and the control output of the feedback calculator. Accordingly, the calculation constant K can be calculated backward from the relational expression: Required heat amount = Control output = α x (Set temperature - K) x Water amount (Formula 2). Here, α indicates the thermal efficiency of the heat exchanger and is determined in advance. In other words, the K calculated here
corresponds to the inlet water temperature.

Thereafter, when the set temperature or water volume is changed, the required amount of heat is immediately calculated by the feedforward calculator based on the constant K, and the gas volume is immediately adjusted to stabilize the water temperature, which is a characteristic of feedforward control. Demonstrates flexibility and quick response.

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a heat exchanger 2 heated by a burner 1, a temperature sensor 3 provided at the outlet of the heat exchanger, a water flow sensor 4 provided in a water supply channel, and a gas supply to the burner 1 are shown. A gas proportional control valve 5 and a temperature setting device 6 provided in the path, a feedback calculation device 7 which receives the deviation between the temperature sensor 3 and the temperature setting device 6 and performs feedback calculation, and a temperature sensor 3 and a temperature setting device 6. The stability detector 8 receives the deviation of the water temperature and detects the stability of the water temperature, and the stability detector 8
a control constant calculator 9 that calculates and stores a proportional constant by inputting each control output signal of the water amount sensor 4, temperature setting device 6, and feedback calculator 7;
and a feed forward calculator 10 which calculates the required amount of heat by inputting each signal of the output of the proportional constant calculator 9.
The output of the feedback calculator 7 and the output of the feedback calculator 10 via the switch 11 controlled by the stability detector 8 are added to drive the gas proportional control valve 5.

In the above configuration, when water supply is started after the equipment is powered on (t1 in Fig. 2), the feedback calculator 7 is activated and the gas amount is PID-controlled based on the deviation between the outlet hot water temperature and the set temperature. matches the set temperature and stabilizes. Since the deviation is zero at this time, only the integral term I of the PID is output. The stability detector 8 detects stability of the outlet hot water temperature when the deviation is zero or below a certain value for a certain period of time. (Fig. 2 t2) The control constant calculator 9 is operated at the detection timing of the stability detector 8, and the above-mentioned formula 2
Find the constant K. When the constant K is determined, the required amount of heat is calculated in the feedback calculator 10, and at the same time as the switch 11 is turned on, the integral term of the feedback calculator is reset, and the control output to the gas proportional control valve is fed back from the feedback calculator. The baton is passed to the yield forward calculator. Since the feedback calculation output at this time is obtained from the feedback control output, both signals have the same value and switching is performed smoothly. After that, when the water amount is changed at t3, the feed forward calculator 10 immediately calculates the required amount of heat and adjusts the gas amount. Thereafter, the feedback calculator 7 functions to correct slight errors in the feedback calculator 10. The feedforward calculation constant (corresponding to the inlet water temperature) is calculated backwards based on the actual gas amount when the hot water temperature is stable, so it is not affected by variations in the inlet water temperature sensor as in the conventional case. , the amount of correction due to feedback can be made much smaller than in the conventional example. As a result, there are fewer fluctuations in the temperature of the hot water, and the stabilization time is also shortened.

Generally, the water supply temperature fluctuates depending on the season.
It does not change during use. Therefore, as in this embodiment, if the above operation is repeated every time the device is powered on, fluctuations in the water supply temperature can be absorbed.

Effects of the Invention As described above, according to the gas instantaneous water heater of the present invention, a feedback computing unit, a control constant computing unit, and a feed forward computing unit are provided, and the feedback computing unit allows the water temperature to be stabilized at a set temperature. The control constant calculator calculates and stores the function or calculation constant of the required amount of heat for the amount of water and set temperature based on the control output signal of the feedback calculator, and thereafter the feedback calculator calculates the required amount of heat based on the control output signal of the feedback calculator. As a result, the following effects can be expected.

(1) Unlike the conventional technology, which uses separate temperature sensors to detect the outlet water temperature and the inlet water temperature, the calculation constants for the feedback calculation are determined based on the results of the feedback control. There is no error in the target temperature with the feedback calculation, and the settling time for the tapping temperature can be shortened.

(2) Since the feedback calculator calculates the calculation constant when the hot water temperature is stabilized at the set temperature, it is not affected by time delays due to the heat capacity of the heat exchanger or changes in the efficiency of the heat exchanger due to differences in hot water temperature. Since accurate constants can be calculated and feed forward calculations are highly accurate, fluctuations in the outlet temperature when the water amount changes can be reduced and settling time can be shortened.

(3) Since an expensive temperature sensor can be configured with one,
We can provide high quality water heaters at low prices.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a gas instantaneous water heater according to an embodiment of the present invention, and FIG. 2 is an operational explanatory diagram showing temporal changes in the hot water temperature, gas amount, etc. DESCRIPTION OF SYMBOLS 1...Burner, 2...Heat exchanger, 3...Temperature sensor, 4...Water flow sensor, 5...Gas proportional control valve, 6...Temperature error device, 7...Feedback calculator, 9... Control constant calculator, 11...Feed forward calculator.

Claims (1)

[Claims] 1 A burner, a heat exchanger, a temperature sensor for a heated body provided at the outlet of the heat exchanger, a temperature setting device for setting the hot water temperature, and a water amount for detecting the amount of water supplied to the heat exchanger. a sensor, a gas proportional control valve provided in the gas supply path to the burner, and a feedback calculator that performs PID feedback control of the gas amount based on the deviation between the hot water temperature measured by the temperature sensor and the temperature set by the temperature setting device. and,
Calculate a functional formula or calculation constant for the required amount of heat for the water amount and set temperature using the control output signal of the feedback calculator when the hot water temperature is stable, the water amount signal of the water amount sensor, and the set temperature of the temperature setting device.
a control constant calculator to store, and a feed forward calculation that calculates the required amount of heat by inputting the signal of the water amount sensor and the set temperature of the temperature setting device based on the function or calculation constant obtained by the control constant calculator. a gas instantaneous water heater, the gas proportional control valve being driven by signals from both the feedback computing unit and the feedback computing unit.