JPS6034010B2 - gas water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas water heater, and particularly provides a gas water boiler that proportionally controls the gas flow rate using an electromagnetic proportional valve to control the combustion amount and control the hot water temperature. It is something.

Generally, a gas boiler using an electromagnetic proportional valve, as shown in Figure 1, has a main body 1 with a gas burner 2, an electromagnetic proportional valve 3 that controls the gas flow rate, and heat-exchanges the water W to make it into hot water. It has a heat exchanger 4, a first temperature detector 5a that detects the hot water temperature, a second temperature detector 5b that detects the water temperature during heat exchange, and an electromagnetic sensor according to the output from each temperature detector 5a, 5b. It consists of a controller 6 for controlling the coil current of the proportional proportional valve 3 to control the valve function.

The controller 6 has a configuration as shown in FIG. That is, the outputs of the first temperature detector 5a and the second temperature detector 5b are input to the temperature voltage converter 61, and the output of the converter 61 is input to the intensifier 6.
2, and the output of the minimum value guarantee circuit 67 for maintaining the minimum valve opening of the proportional valve 3 is compared with the output of the large 4 discriminator 63,
The larger one is output and applied to the proportional valve coil 31. Here, the minimum valve function is determined by the TDR of the burner 2, and corresponds to the minimum combustion amount of the burner 2. In other words, when the output of the multiplier 62 is small, an attempt is made to make the valve opening of the proportional valve 3 less than or equal to the maximum 4. Since the output of the minimum value guarantee circuit 67 is selected at 63 and applied to the coil 31, the minimum valve opening of the proportional valve 3 is maintained and the minimum combustion amount is guaranteed. The conventional example described above has a so-called cascade control system, in which the first temperature detector 5a controls the outlet water temperature, and the second temperature detector 5b is used to improve response speed and reduce residual deviation.

A temperature sensor is usually used as a temperature sensor, but in order to detect the water temperature, it requires a high degree of moisture-proofing treatment, and the response speed of the detector itself needs to be fast, which makes the detector expensive. I'm making it into something. In addition, processing is required to install a temperature sensor on the piping, and an appropriate disturbance plate must be inserted upstream of the sensor installation location to detect the average water temperature. This increases the number of processing steps and makes the water circuit system expensive. The present invention aims to solve the above-mentioned drawbacks, and aims to use only the first temperature detector 5a as a temperature detector, improve the steady-state characteristics of the conventional example, and obtain an equivalent overheating response. It is.

An embodiment of the present invention is shown in FIGS. 3 and 4 below.

In FIG. 3, the output of the temperature detector 5a is converted into a voltage by a temperature conversion circuit 64 and input to a proportional differentiation circuit 65. The output of the proportional differential circuit 65 is input to the proportional integral circuit 66, and the larger one is selected and outputted by the magnitude discriminator 63 between the output of the proportional integral circuit 66 and the output of the minimum value guarantee circuit 67. is applied to the coil 31 of. The output of the proportional differentiation circuit 65 is further inputted to a response compensation circuit 60'.
The response compensation circuit 60 generates a signal that turns off the switch 69 when the magnitude of the output of the proportional differentiation circuit 65 is larger than a predetermined value.
outputs. In normal steady-state conditions, this proportional valve controller operates as a so-called PjD controller, with the distant action and low residual deviation characteristic of PiD controllers. However, due to the minimum value guarantee circuit 67, the valve opening of the proportional valve never becomes less than the minimum valve opening, so that good combustion can be maintained. Also, if the flow rate suddenly changes from large to small,
When the amount of combustion becomes excessive and the hot water temperature attempts to rise, this rise is detected by the temperature detector 5a, and the proportional/differential circuit 6
The output of No. 5 becomes large, operating the response compensation circuit 60 and turning off the switch 69, and the combustion amount becomes zero, so the temperature of the hot water drops. Therefore, overshoot when changing the flow rate can be kept small. If there is no such response compensation circuit, that is, if only PiD control is used, the combustion amount will only decrease to the combustion amount equivalent to the minimum valve opening given by the minimum value guarantee circuit 67, so the overshoot will be very large. turn into. FIG. 4 is a specific circuit example of the proportional valve controller shown in FIG. 3.

5a' is a temperature detector, which has a resistance of 64A.
~64D forms a bridge circuit and converts temperature into voltage.

Bridge output is resistor 65B, 65C, capacitor 65
A, the signal is input to a proportional differentiation circuit consisting of an OBE amplifier 65D. The transfer function of the proportional differential circuit is given by -KP (10 STo). That is, the output of the proportional differentiation circuit is the sum of the bridge output proportionally multiplied and the bridge output divided. The output of the proportional differentiation circuit is the resistance 66A, 66
B, a capacitor 66C, and an obeamp 66D. The proportional volume thoracic transfer function is −Ki(
10 points). The minimum value guarantee circuit 67 generates a voltage Vmin obtained by dividing the DC power supply Vcc by resistors 67A and 678.
Output. The outputs VP and Vmin of the proportional-integral circuit are input to a size discriminator consisting of diodes 63A and 63B, respectively. Transistor 31A, resistor 31
B is input to the voltage-current conversion circuit consisting of proportional valve coil 3.
The current is 1. On the other hand, the DC component of the output of the proportional differentiation circuit is cut off by a capacitor 600E and resistors 600F and 600G, and becomes a positive input to the comparator 600. The negative input of the comparator 600 is given a voltage obtained by dividing V by resistors 600A and 600B via a resistor 600C. In the steady state, the output of the proportional differential circuit is stable, so the positive input to the comparator 600 is approximately zero, and therefore the output of the comparator 600 is zero J. When a disturbance such as flow rate fluctuation occurs, the hot water temperature rises and falls, but its differential value appears in the output of the proportional differential circuit, and due to the differential value, the 600 days positive input to the comparator becomes larger than its load input,
The output of the comparator 600 days is /・, and the monostable multi which triggers the monostable multi which will be described later is resistor 601A, 6
018, 601C, 601D, comparator 601E,
It consists of an obeamp 601F and a diode 601G, and is triggered when the output of the comparator 600 becomes high, and the output of the obeamp 601F becomes no for a predetermined period of time, and the switching transistor 69 is connected through a resistor 69A.
Turn on 8. When transistor 698 is turned on, the base input of transistor 31B becomes zero, so the current in coil 31 becomes zero, the valve coefficient of the proportional valve becomes zero, and combustion becomes zero. The monostable multi output remains high for a predetermined period of time, but during this time, the capacitor 600D installed at the negative input of the comparator 600 days is charged via the diode 600J, and the comparator is prohibited from operating again for a certain period of time after the monostable multi operation. . This is because the monostable multi is activated and the combustion amount becomes zero, causing the outlet temperature to drop rapidly.After the monostable multi operation ends, combustion restarts and the temperature rises rapidly again.This sudden rise causes the comparator to There is a possibility that it will operate for 600 days, and if this is repeated, it is obvious that the hot water temperature will not be stable. This is to prevent this. While the transistor 69B is on, the proportional differential circuit output of the integral capacitor 66C decreases due to a decrease in the tap water temperature, so normally the proportional integral circuit output increases and attempts to charge the integral capacitor 66C. However, transistor 69B is turned on, so it is not charged. Therefore, immediately after the transistor 69B is turned off, the proportional-integral circuit output is equal to the proportional-differential circuit output and is small, so
The current in the proportional valve coil 31 becomes small, so there is no so-called full-open ignition, and there is no explosive ignition. That is, due to the above-mentioned reset operation of the capacitor 66C, the current in the proportional valve coil 31 gradually increases after the transistor 69B is turned off, and the valve opening gradually increases, resulting in so-called slow ignition, which is similar to that seen in full-open ignition. There is no problem with sound ignition mistakes. As detailed above, according to the present invention, it is possible to prevent an excessive transient response when changing the flow rate with a single temperature detector such as a thermistor, and furthermore, it is possible to prevent the proportional valve from turning on and off in a short period of time, and the ignition is also a trailing ignition. .

This eliminates the need for the second temperature sensor and the processing required to attach it, making it possible to reduce costs and facilitate manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional water heater, FIG. 2 is a diagram of the controller shown in FIG. 1, FIG. 3 is a diagram of a controller according to an embodiment of the present invention, and FIG. 3 is a specific circuit diagram of FIG. 5a... Temperature detector, 31... Coil of electromagnetic proportional valve, 60... Response compensation circuit, 67... Minimum temperature guarantee circuit. Figure 1 Figure 2 Figure 3 - Figure 4

Claims (1)

[Claims] 1 A gas burner, a heat exchanger, an electromagnetic proportional valve that controls the combustion amount of the gas burner, a temperature detector that detects the temperature of hot water, and a valve opening of the electromagnetic proportional valve according to the output of the temperature detector. a temperature control circuit that controls the temperature of the electromagnetic proportional valve; a minimum value guarantee circuit that maintains the minimum valve opening of the electromagnetic proportional valve; and a minimum value guarantee circuit that maintains the minimum valve opening of the electromagnetic proportional valve; 1. A gas water heater comprising a proportional valve controller comprising a control circuit and a response compensation circuit that sets the output to zero regardless of the output of the minimum value guarantee circuit.