JPH0446336B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a temperature control device such as a gas instantaneous water heater that employs a proportional control method, and in particular, the present invention relates to a temperature control device such as a gas instantaneous hot water heater that employs a proportional control method. This invention relates to an improvement for suppressing the overshoot phenomenon in which the actual hot water supply temperature rises transiently.

<Conventional technology> Conventionally, in the case of water heaters etc. as mentioned above,
In order to keep the hot water temperature as close to the set temperature as possible,
Based on the deviation between the hot water supply temperature and the set temperature, there is a PID type proportional control circuit that performs proportional, integral, and differential calculations of the required amount of heat at each time, and measures so that the required amount of heat can be generated by the burner. It is used as a temperature control device.

One of the problems that must be taken into consideration in such a temperature control device, especially in terms of safety measures, is the overshoot phenomenon of hot water supply temperature.

In other words, when there is a sudden change in the load such as a fluctuation or change in the hot water supply temperature, there is a risk that the hot water supply temperature will greatly exceed the set temperature, even temporarily or transiently, and no measures should be taken to prevent this. If not, there is a risk of burns to the user.

Therefore, from the past, regarding this point,
The results were taken into consideration, and the result appeared as a device configuration as shown in FIG.

The deviation between the preset temperature and the actual hot water temperature detected by the hot water temperature sensor 5 is determined in the proportional control circuit 1, and based on this deviation, the proportional control circuit 1 also calculates the following: Proportional (P), integral (I), and differential (D) calculations are performed and the results are output to the proportional solenoid valve drive element 2.

The proportional solenoid valve driving element 2 variably controls the amount of current flowing through the proportional solenoid valve 3 based on the above output from the proportional control circuit 1, so that the proportional solenoid valve 3 drives an amount of fuel corresponding to the amount of current. The gas stream is fed to a combustion section or burner (not shown).

In addition to this main proportional control system, there is an overshoot detection system that compares the hot water temperature obtained from the hot water temperature sensor 5 with an overshoot detection temperature that is set in advance to be a certain value higher than the set temperature. A circuit 6 is provided, and when the hot water temperature exceeds the overshoot detection temperature, the overshoot detection circuit 6 inverts its output from logic "L" to logic "H", and the power supply 4 The switching element (generally a power switching transistor) 7 arranged in series in the line supplying current to the proportional solenoid valve 3 is turned off, and the proportional solenoid valve 3 is closed or the gas is at a minimum. Set the quantity supply state.

<Problems to be Solved by the Invention> Even in the conventional temperature control device as described above, the response after successfully suppressing overshoot and returning to normal operation is good. This is because the proportional control circuit 1 continues to operate even when the overshoot suppression operation is being performed.

However, in proportional control operations, especially when the differential time is set short and the integral time is long, if the proportional gain is small, the output signal of the proportional control circuit 1 will not change much when overshoot is detected. After the overshoot was suppressed, too much gas was released, which sometimes led to overshoot and hunting in the hot water supply temperature.

The present invention has been made to solve these drawbacks of conventional devices.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a temperature control circuit specified by the following configuration.

a A sensor that detects the hot water supply temperature; b A proportional control circuit that performs proportional, differential, and integral calculations based on the deviation between the hot water supply temperature obtained from the sensor and a preset temperature; c The above calculations of the proportional control circuit. a proportional solenoid valve that adjusts the amount of fuel to the combustion section with its output; d) increases the proportional gain of the proportional control circuit when the hot water temperature obtained from the sensor exceeds an overshoot detection temperature that is higher than the set temperature; A temperature control device comprising: a switching circuit that performs a switching circuit;

<Operation> According to the configuration of the present invention, when the hot water temperature sensor detects a hot water temperature higher than the overshoot detection temperature, that is, when overshoot is occurring, the proportional gain of the proportional control circuit is be made larger.

Therefore, the amount of fuel flowing through the proportional solenoid valve can be sufficiently suppressed and, if necessary, even reduced to a minimum level.

Therefore, after the overshoot is suppressed or canceled, the control is resumed from the lowest level, so in principle there is no chance of hunting of the hot water supply temperature or another overshoot.

<Embodiment> FIG. 1 shows a schematic configuration of a preferred embodiment of a temperature control device according to the present invention.

The same reference numerals are used in FIG. 1 to designate components that may be the same or the same as those in the conventional device shown in FIG. 2 described above.

That is, the proportional control circuit 1 receives the current hot water temperature signal from the hot water temperature sensor 5, and drives the proportional solenoid valve 2 via the proportional solenoid valve driving element 3.
The circuit portion to be controlled may be completely the same as in the prior art. Therefore, although it is simply referred to as the proportional control circuit 1, in reality, as mentioned above, the proportional control circuit 1
is not only proportional (P) control, but also includes integral (I) and differential (D) control, so-called
This is a circuit that performs PID control. However, in the embodiment of the present invention, the switching element 7, which was disposed in the line from the power source 4 to the proportional solenoid valve 3 in FIG. 2 showing the conventional circuit, is omitted because it becomes unnecessary.

What is provided instead is a gain switching circuit 8 for increasing the proportional gain of the proportional control circuit 1 when an overshoot occurs.

The gain switching circuit 8 detects when the overshoot detection circuit 6 detects the overshoot, that is, when the hot water temperature obtained from the hot water temperature sensor 5 is a certain value higher than the preset water level. When the overshoot detection circuit 6 detects that a predetermined overshoot detection temperature is exceeded, the proportional gain in the proportional control circuit is set to a larger value than before,
Preferably, the value is set to a sufficiently large value, and the proportional control circuit 1
Desirably, the output is reduced to near the lowest level.

In response to this, the proportional solenoid valve drive element 2 is set to a conductivity state near the lowest level, and the proportional solenoid valve 3 is also sufficiently throttled, so that the amount of fuel supplied to the combustion section is reduced to close to the lowest level. As a result, the amount of heat of combustion is reduced to almost the minimum amount.

As a result, when the overshoot state of the hot water supply temperature is eventually resolved and the overshoot state is detected by the overshoot detection circuit 6, the gain switching circuit 8 switches the proportional gain back to the original relatively small value, and The normal proportional control operation thereby resumes from the above-mentioned lowest level combustion state.

<Effects of the Invention> As described above, according to the present invention, when an overshoot occurs in the hot water supply temperature, the amount of combustion can be quickly suppressed, and the transient rise in the hot water supply temperature can be suppressed to the minimum level. In addition, normal proportional control operation after overshoot is resolved is as follows.
Since the combustion will be restarted from the lowest level of combustion,
The hot water supply temperature does not overshoot again or hunting occurs again, and the hot water supply temperature can be controlled in an overall stable manner.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of a temperature control device of the present invention, and FIG. 2 is a schematic configuration diagram of an example of a conventional temperature control device. In the figure, 1 is a proportional control circuit, 2 is a proportional solenoid valve drive element, 3 is a proportional solenoid valve, 4 is a power supply, 5 is a hot water temperature sensor, 6 is an overshoot detection circuit, 7 is a switching element, and 8 is a proportional gain switching circuit,
It is.

Claims (1)

[Claims] 1 a. A sensor that detects the hot water supply temperature; b. A proportional control circuit that performs proportional, integral, and differential calculations based on the deviation between the hot water supply temperature obtained from the sensor and a preset temperature; c a proportional solenoid valve that adjusts the amount of combustion to the combustion section using the calculated output of the proportional control circuit; d when the hot water temperature obtained from the sensor exceeds an overshoot detection temperature that is higher than the set temperature; a proportional gain switching circuit that switches the proportional gain of the proportional control circuit to a larger value, and returns the proportional gain of the proportional control circuit to the value before switching after the overshoot is eliminated; Temperature control device.