JPS58106322A - Combustion controller - Google Patents

Abstract

PURPOSE:To improve the combustion efficiency of a combustion controller by controlling a fuel flow rate control valve in response to the deviation between a target temperature and the detected temperature and stepwisely varying the rotating speed of a fan motor in accordance with the magnitude of the deviation. CONSTITUTION:In a hot water supplying device, when a cock is opened to detect the water stream by a flow switch 10, a combustion sequence control circuit 15 is started, thereby rotating a fan motor 12. When wind pressure is then detected by a wind pressure detector 13, a solenoid changeover valve 3 is opened. Simultaneously, the deviation between the outputs of a water temperature sensor 11 and a target temperature setter 17 is obtained by a deviation detecting circuit 18, a flow rate control valve 5 is controlled through a PID arithmetic circuit 19 in accordance with the deviation, and a burner 2 is ignited and burnt. In this state, the output of the circuit 19 is inputted to a fan motor speed control circuit 22, the output of the circuit 19 is discriminated at the level in a plurality of steps, thereby operating a switching element 21 and stepwisely varying the rotating speed of the motor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in combustion control devices for combustion equipment such as water heaters.

In recent years, water heaters have been used to detect the output S temperature from the heat exchanger, perform PID calculation to determine a predetermined control amount from the deviation from the arbitrarily set sums, and supply fuel according to this control amount. By adjusting the valve opening of the flow control valve installed in the passageway, the combustion state in the burner is set to low combustion at low output and dryness.
By controlling the combustion rate to be high at high altitudes,
Some devices have appeared that are equipped with a combustion control device that operates to maintain the s-tub at a target temperature regardless of the temperature of the hot water used or changes in water temperature.

In this way, this type of water heater can detect I! Feedback control is performed so that the water temperature matches the set temperature, so unlike water heaters that have been widely used in the past, where the combustion state can only be changed at a constant level or in stages, the combustion state can be changed regardless of changes in water temperature or temperature. It has the great effect of always being able to obtain the desired temperature, and is oriented towards energy conservation.

However, in conventional combustion control devices, only the amount of fuel supplied to the burner is controlled based on the above deviation, and the supply of combustion air is always a constant amount regardless of the combustion state in the burner. Since combustion air is supplied by a fan motor, there is an excess or deficiency in the amount of combustion air supplied, resulting in poor combustion efficiency, which undermines the significance of introducing PID control with the aim of saving energy.

Therefore, in order to match the air-fuel ratio and improve combustion efficiency, the rotation speed of the fan motor must be controlled by the above-mentioned control amount, that is, PIDl.
It is sufficient to perform control using the output signal of the il calculating circuit, and for this purpose, a switching means for changing the rotational speed of the fan motor stepwise, and a control means for outputting a switching signal to the switching means according to the output level of the PID calculating circuit are required. It is conceivable to provide a

As is well known, in response to the step input of the li difference signal shown in FIG. 1(a), the PrD calculation circuit generates a signal (A) proportional to the deviation and a signal integrated with the deviation, as shown in FIG. 1(b). (B) and a signal (C) obtained by differentiating the speed of change of the deviation are combined to output a signal (D>. Therefore, when adopting such a configuration, the problem is that the output signal of the PID performance circuit is differentiated. In other words, since the control means creates a switching signal according to the level of the output signal of the PID calculation circuit, the switching signal is naturally output in response to this differential signal as well. However, since the motor has inertia, the switching signal responsive to this differential signal simply opens and closes the contact of the switching means, and the switching signal at this time results in wasting the life of the contact. This is expected to have an adverse effect on the lifespan and reliability of the combustion control device itself.

This invention was developed in light of these problems, and its purpose is to make it possible to vary the rotational speed of the fan motor according to the combustion state without adversely affecting the lifespan or reliability of the combustion control device itself. An object of the present invention is to provide a combustion control device.

In order to achieve the above object, the present invention provides a PID algorithm that outputs a control amount for changing the valve opening of a flow rate control valve that adjusts the amount of fuel supplied to a burner in accordance with the deviation between a target temperature signal and a detected temperature signal. A circuit, a switching element for stepwise switching the rotational speed of a fan motor that supplies combustion air to the burner, and a plurality of levels of the output of the PTD sieve circuit, and the switching element is operated by the discriminated output. and a fan motor speed control circuit that changes the rotational speed of the fan motor in steps.
III device, characterized in that the fan motor speed control circuit includes a delay circuit that prevents the fan motor speed control circuit from responding to a high-speed change component of the output of the PID calculation circuit.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the basic configuration of a water heater equipped with a combustion control device according to the present invention.

In the figure, the fuel supply path leading to the burner 2 in the main body 1 of the water heater includes an electromagnetic switching valve 3 that turns on and off the supply of fuel. an igniter 6 that is provided with a governor 4 and a flow control valve 5 that adjusts the fuel flow, and that generates an ignition spark in conjunction with the burner 2;
A flame detector 7 is provided to detect whether the ignition is normally ignited by the ignition operation, and an alarm 8 is provided to issue an alarm in the event of an abnormality such as when normal ignition is not achieved. 5- Then, a flow switch 10 is installed at the water inlet leading to the heat exchanger 9 to detect the water flow passing through the heat exchanger 9, and a humidity sensor such as a thermistor is installed at the outlet side to detect the temperature at the outlet 1m. 11 are provided respectively.

Further, a fan motor 12 is provided at the upper opening of the main body 1, and a wind pressure switch 13 detects that the fan motor 12 has started to rotate.

Further, a combustion control device 114 that controls the output S of the water heater to be constant is composed of a combustion sequence control circuit 15 and an Ii temperature control circuit 16, and the combustion sequence control circuit 15 includes an electromagnetic switching valve. 3° igniter 6. flame detector 7
．． Alarm 8. Flow switch 10 and wind pressure switch 13
Each element is connected. Also, m-control Akebono 17
Flow control valve 5.1 degree sensor 11 and temperature setting device 16
The fan motor 12 is connected to a combustion sequence control circuit 15 and a temperature control circuit 16, respectively.

This hot water temperature control circuit 16 is connected to the temperature signal detected by the temperature sensor 11 41! A deviation detection circuit 18 that generates a deviation signal from the target temperature 6- jet by the rlI setting device 17 and a PID ID frame circuit 19 that outputs a predetermined control amount based on this deviation signal according to the output of this PID calculation circuit 19. a valve drive circuit 20 that adjusts the valve opening degree of the flow control valve 5 to a predetermined opening degree;
and a fan motor speed control circuit 22 that differentiates the output of the PID calculation circuit 19 into multiple levels and operates a switching element 21 that changes the rotation speed of the fan motor 12 to change the rotation speed of the fan motor 12 in stages.
It is made up of.

Next, FIGS. 3 and 4 are diagrams showing specific examples of the fan motor speed control circuit 22 of the m temperature control circuit.

In the figure, the fan motor speed control circuit 22 is PrD
A comparator 3o binarizes the output vo of the arithmetic circuit 19 at the level of the reference voltage V1, and the output v2 of this comparator 30 is integrated with a time constant determined by a resistor R and a capacitor C. The rotation speed of the fan motor 12 is controlled by a relay 21 as a switching element. By doing so, by switching contacts (not shown), it is possible to switch between two stages of low-speed rotation and high-speed rotation.

Next, the operation of the water heater equipped with the combustion control device configured as described above will be explained. Now, when the faucet is opened and water flow is detected by the flow switch 1o, the combustion sequence control circuit 15 is activated and the fan motor 12 starts rotating. When the wind pressure caused by the rotation of the fan motor 12 is detected by the wind pressure switch 13, the combustion sequence control circuit 15 opens the electromagnetic switching valve 3. At the same time, the deviation between the water temperature detected by the temperature sensor 11 and the target concentration determined by the target temperature setter 17 is determined by the deviation detection circuit 17 and output to the PID calculation circuit 19. As a result, the PID calculation circuit 19 outputs a predetermined control amount to the flow rate control valve 5 via the valve drive circuit 20, and the valve opening degree of the flow rate control valve 5 is adjusted to an appropriate opening degree, so that the burner 2 receives a predetermined flow rate. Since fuel is supplied, the combustion sequence control circuit 15 operates the igniter 6 to generate an ignition spark. As a result, the burner 2 is normally ignited, and when combustion starts, this is detected by the flame detector 7, and if there is an ignition error, the alarm 8 is activated.

As burner 2 ignites normally and enters a normal combustion state,
Heat exchange in the heat exchanger 9 progresses, and hot water is dispensed from the faucet. This WaS is detected by the temperature sensor 11, and the deviation from this and the target temperature is again determined by the deviation detection circuit 18. Based on this newly determined deviation, the PID calculation circuit 19 outputs a predetermined amount of 1lJIIl to the flow rate control valve 5 via the valve drive circuit 20 in order to reduce the deviation, and the valve opening degree of the flow rate control valve 5 is adjusted. Ru.

Here, for example, if the S boiler is initially used with a low hot water output and is changed to a high hot water output at time TO, 1iai will first exhibit a temperature drop, and then the target I! The output of the PID calculation circuit 19 in this transient state is as shown in FIG. 4(a).

That is, when the deviation detection circuit 18 detects a temperature immediately below the temporary m temperature, the PID calculation circuit 19 calculates the rate of change in the rate of fall of this 9-Ii, and outputs a differential waveform with a steep rise. , by increasing the combustion state of the burner
It operates so that the deviation between the temperature and the target temperature is rapidly reduced.

When the exhaust temperature increases and the temperature deviation reaches a steady value, the PID calculation circuit 19 performs a proportional-integral operation, so that the output vO follows a gradual upward curve and the burner combustion state becomes a predetermined high combustion state.

When such an output VO is input to the comparator 30, as is well known, the magnitude relationship between vO and Vl is compared, and H
Level and 1. Level 2111 (Figure 4(b)
). At this time, the differential signal output part ab is inverted to the short poem IIL level, and the output part ab shifts to the proportional integral signal part.
Then it becomes H level again, and after 0 points it becomes H level and stable. The delay circuit 32 is connected to the comparator 3.
The rise and fall of the 0 output are delayed by a predetermined time, respectively, and if the time 1Wl (b - a ) of the output waveform of the comparator 30 is less than or equal to the delay time m of the delay circuit 32, the level signal of that ablll is delayed. It does not appear at the output of circuit 32. Therefore, the transistor 33
- As shown in figure <a>, there are mixed states between a and b, and 0
The transistor 33 is turned off at point d after a predetermined delay time (T) after passing through the point. In other words, the relay 21 is not caused to perform the above-mentioned unnecessary switching operation, and is turned on up to point d, causing the fan motor to rotate at low speed, and after point d, it is turned off, and the fan motor switches to speed rotation. , the combustion state after point d is one in which the air-fuel ratio is improved.

The above is an explanation of the case where the combustion state changes from a low combustion state to a high combustion state, but the same applies to the reverse case.Also, if the water heater is used in a certain combustion state and for some reason I2! Even if the differential signal is output from the PID calculation circuit 19 due to a temporary change in the differential signal, the transistor 33 does not operate due to the action of the delay circuit 32, so the rotation speed of the fan motor 21 will not be changed.

As a result, the contacts of the relay 21 are not forced to operate unnecessarily, so that their lifespan is not wasted.

As explained in detail above, according to the present invention (f11-32), the simple configuration of the delay circuit allows the combustion air to match the combustion state without impairing the service life or reliability of the combustion control unit. , it is possible to provide a combustion control device that can significantly improve combustion efficiency.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the deviation signal and PID derivation waveform, Figure 2
The figure is a basic configuration diagram of a water heater equipped with a combustion control device according to the present invention, and FIGS. 3 and 4 are schematic configuration diagrams and operation explanatory diagrams showing specific examples of the combustion control device. 2...Burner 5...Flow control valve 11...Temperature sensor 12...Fan motor 14...Combustion control device 17... ...eyes! Onmaro setting device 19... PID calculation circuit 21... Switching element (relay) 22...
...Fan motor speed control circuit 30...Comparator 12- Patent applicant Tateishi Electric Co., Ltd. 13- Fig. 1 1% J (b Fig. 2 12 Small to 17 3rd drawing 2

Claims (1)

[Claims] (1) A PTD calculation circuit that outputs a control layer that changes the valve opening of a flow control valve that adjusts the fuel supply to the burner according to the deviation between the target temperature signal and the detected m degree signal, and a PTD calculation circuit that outputs a control layer that changes the valve opening of the flow control valve that adjusts the fuel supply to the burner, a switching element that changes the rotational speed of the fan motor in stages, and a switching element that discriminates the output of the PID calculation circuit into multiple levels, and operates the switching element with the discriminated output to gradually change the rotational speed of the fan motor. A combustion control device that controls a fan motor speed control circuit that changes the speed of the fan motor, the fan motor speed control circuit including a delay circuit that prevents the fan motor speed control circuit from responding to the speed change component of the output of the PID calculation circuit. A combustion control device characterized by having: