JPS645214B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a water heater that maintains the load temperature at a preset constant temperature using a gas proportional valve that proportionally controls the combustion amount of a gas burner according to the input amount; This relates to heating devices such as gas hot air blowers.

Conventional heating devices of this type include so-called feedback control, which controls a gas proportional valve based on the temperature of hot water or hot air, and a feedback control, which controls a gas proportional valve based on water volume, water supply temperature, air volume, air temperature, etc. There was a feed forward control.

Figure 1 shows an example of application of feedback control to a water heater, in which 1 is a heat exchanger, 2 is a gas burner, 3 is a gas proportional valve installed in the gas supply path 4 of the gas burner 2, and 5 is a gas proportional valve installed in the gas supply path 4 of the gas burner 2. A hot water temperature detector is provided in a hot water supply path 6 downstream of the heat exchanger 1, 7 is a temperature setting device, and 8 is a proportional control section. Additionally, gas burners generally have a minimum combustion amount that can lead to lifting and extinguishing fires, and there is a range in which they can be throttled. This problem is solved by adopting blinking control that extinguishes the gas burner when the proportional output is less than the proportional output commensurate with the combustion quantity, and ignites the gas burner again when the proportional output exceeds the output commensurate with the minimum combustion quantity. This will be explained based on FIG. As the water temperature rises, the proportional output from the proportional control section 8 decreases, and the gas amount decreases. When the gas amount decreases to the minimum combustion amount A of the gas burner 2, the gas proportional valve 3 is fully closed or a separately provided electromagnetic valve is closed, and the gas burner 2 is extinguished. As the burner is extinguished, the water temperature gradually decreases.
As the output decreases, the output from the proportional control section 8 increases, and when the output corresponds to the minimum combustion amount A, the gas burner 2 is ignited again. By combining flashing control and throttling control in this way, it is possible to control the hot water temperature over a wide range. However, with this feedback control, the insensitivity time (delay time) of the hot water temperature detector to changes in disturbance is long, and transient characteristics with respect to changes become a problem.

As shown in FIG.
0 and a water flow rate detector 11 are provided, and the proportional control unit 8 subtracts the water supply temperature detected by the water supply temperature detector 10 from the set temperature, and then multiplies the water flow rate detected by the water flow rate detector 11. It has been output. In this feedback control, the delay time to a change in disturbance is extremely small, and the responsiveness is significantly better than that in feedback control. However, in feed forward control, if the gas burner is extinguished below a certain output in order to prevent lifting and extinguishing of the gas burner as described above, for example, the gas burner cannot be ignited while the current condition continues (4. (Figure), because flashing control could not be performed, the water temperature continued to drop, and water temperature control could only be performed within a narrow range.

The present invention aims to solve the above-mentioned problems of the conventional method.When the gas burner has a range in which the gas burner can be throttled beyond the minimum combustion amount, throttle control is performed mainly by feedforward control, and the gas burner reaches the minimum combustion amount. It is an object of the present invention to provide a heating device which has good transient characteristics and can perform temperature control over a wide range by switching to feedback control and performing blinking control when the gas proportional valve is throttled and goes out of the throttleable range.

An example in which the present invention is applied to an instantaneous water heater will be described below.

21 is a heat exchanger, 22 is a gas burner, 23 is a gas proportional valve provided in the gas supply path 24 of the gas burner 22, and 25 is a hot water temperature detector provided in the hot water supply path 26 downstream of the heat exchanger 21, which measures the temperature of the fluid to be heated. That is, the water temperature is detected. 27 is a feed water temperature detector installed in the water supply channel 28 upstream of the heat exchanger 21;
This is to detect the temperature of the fluid flowing toward the water supply point 1, that is, the temperature of the water supply. Reference numeral 29 is a water amount detector which detects the fluid flow rate, that is, the amount of water. 30 is a temperature setting device. 31 subtracts the feed water temperature detected by the feed water temperature detector 27 from the set temperature of the temperature setting device 30, multiplies it by the amount of water detected by the water amount detector 29, and determines whether or not it is within the throttling possible range based on the amount of calculation obtained. This is a control section that determines whether or not the switch is on and switches a switch 32, which will be described later. 33 is a gas proportional system which compares the hot water temperature from the hot water temperature detector 25 and the set temperature of the temperature setting device 30 and performs blinking control when the minimum combustion amount of the gas burner 22 is lower than the minimum combustion amount by combining the results with proportional, integral or differential information. valve 2
This is the first control section that controls the third and the like. 34 performs the same calculation as the control unit 31, and also disturbs the water temperature (measurement error, change in gas specific gravity) as shown in this embodiment.
This is a second control section that performs aperture control as a control element for correction. Furthermore, when the control unit 31 switches the switch 32, if the calculated output of the control unit 31 is within the throttleable range that is greater than or equal to the minimum combustion amount of the gas burner 22, the second control unit 34 is switched to a state that is outside the throttleable range that is less than or equal to the minimum combustion amount. In this case, the first control section 33 is connected to the gas proportional valve 23 or the like. Note that the switch 32 is not limited to the mechanical type shown in this embodiment, but may be an electrical type. Further, the first control section 33 does not necessarily have to control only the gas proportional valve 23, but may control it together with a separately provided ON-OFF type solenoid valve (not shown).

The present invention has the above-described configuration. When the hot water tap is opened and water is passed through the heat exchanger 21, first, detection signals of the water supply temperature and water amount are input to the control unit 31, and the control unit 31 outputs (set temperature - water supply temperature) ) x amount of water inflow is calculated. If this calculation output is within the throttleable range equal to or greater than the minimum combustion amount of the gas burner, the second control section 34 is connected to the gas proportional valve 23, and the gas proportional valve 2 is connected to the gas proportional valve 23.
3 is throttled proportionally by the second control unit 34 according to changes in the water supply temperature and water amount, and the hot water temperature is maintained at a set constant temperature. At this time, if the water supply temperature rises and the water amount decreases, the gas proportional valve 23
The input amount gradually decreases to throttle the gas amount, and when the gas amount is throttled down to the minimum combustion amount of the gas burner 22, the control section 31 switches the switch 32, and the first control section 33 switches the gas proportional valve. 23 etc. will be controlled.

This relationship will be explained based on FIG. When the amount of water decreases for some reason, the second control section 34 throttles the amount of gas in proportion to the decrease in the amount of water. Then, consider a condition in which the amount of water decreases below a certain amount of water Wo and the amount of water continues to flow to the heat exchanger 21.
In addition, the above-mentioned constant water amount Wo is then controlled by the second control section 34.
It is assumed that the amount of gas throttled by the gas proportional valve 23 corresponds to the minimum combustion amount Go of the gas burner 22.
Therefore, when the gas amount is reduced to the gas amount Go, the control section 31 switches the switch 32, and the first control section 33 controls the gas proportional valve 23 and the like. Then, the first control unit 33 detects the hot water temperature and controls the gas proportional valve 23 by comparing it with the set temperature.
When the input amount of No. 3 exceeds a set value corresponding to the gas amount Go, the gas burner 22 is ignited, and when it falls below the set value, it is extinguished, and the water temperature is controlled to be approximately constant. That is, as described above, in the present invention, the throttle control is performed by the second control section 34 using feedforward control in the throttleable range of the gas burner 22 exceeding the minimum combustion amount, and the throttle control is performed by the first control section 3 below the set value.
3, the blinking control is performed by feedback control.

Therefore, according to the present invention, the delay time with respect to changes in disturbance is extremely small, the responsiveness and transient characteristics are excellent, and the temperature can be controlled over a wide range, making it possible to provide an extremely useful heating device.

[Brief explanation of drawings]

1 and 3 are block diagrams of a conventional water heater, FIGS. 2 and 4 are explanatory diagrams of the conventional water heater, and FIG. 5 is a block diagram of a water heater in which the present invention is implemented. FIG. 6 is an explanatory diagram of the water heater. 21...Heat exchanger, 22...Gas burner, 23
...Gas proportional valve, 33...First control section, 34...
...Second control unit.

Claims (1)

[Claims] 1 A heat exchanger, a gas burner, a gas proportional valve that proportionally controls the combustion amount of the gas burner according to the input amount, a first control section that controls the gas amount based on the temperature of the heated fluid, and a second control section that throttles and controls the gas proportional valve based on the temperature and flow rate of the fluid heading to the exchanger, and the second control section controls the gas proportional valve within the throttleable range of the gas burner, and the first control section below that range. A heating device characterized in that the amount of gas is controlled by.