JPH0330776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device for proportionally controlling the combustion of combustion equipment, and more specifically, to maintain the temperature of hot water at a set temperature based on a comparison result between the set temperature and the detected temperature. The present invention relates to a combustion control device including a control means including at least an integrating means for proportionally controlling the amount of fuel supplied.

Conventionally, in this type of combustion control device,
From the viewpoint of energy saving, proportional control means that can automatically adjust the amount of fuel supply, that is, the amount of heat supplied, in response to the deviation between the set temperature and the detected temperature is increasingly being adopted.

The above-mentioned proportional control means can freely adjust the hot water temperature and can perform stable temperature control without supplying unnecessary fuel, but it does not prevent transient load fluctuations, such as sudden changes in the amount of hot water coming out. If this occurs, a transient response such as overshoot or undershoot will occur in the control, resulting in hot water being dispensed with a temperature that fluctuates greatly relative to the set temperature, and a means to prevent this transient response is required. It was hot.

As a means to prevent this kind of transient response, for example, Japanese Patent Application Laid-Open No. 57-31722 (Japanese Patent Application No. 105710-1982)
Although there is a combustion control device disclosed in the publication, this means is not sufficient and has the following disadvantages.

That is, as shown in FIG. 6, the deviation between the reference voltage Vb' obtained by dividing the power supply voltage VCC by resistance and the output voltage Va' of the thermistor RT' as a temperature detection means is calculated by the PID control circuit 1 including the integrator AI'. ′,
The output V' is configured to control the drive current of the proportional valve drive circuit 3' that determines the opening degree of the proportional valve 2' that adjusts the fuel supply amount, and also controls the drive current of the proportional valve drive circuit 3' to a predetermined value with respect to the reference voltage Vb'. An overshoot detection circuit 4' is provided, which compares a voltage set to a low value, that is, an overshoot discrimination voltage Vc', with the detection voltage Va' to determine the occurrence of an overshoot due to a temperature change. 4', the input level of the integrator AI' is shifted to forcefully lower the output V' of the PID control circuit 1', thereby controlling the proportional valve 2' to maintain combustion. It is configured to return to the opening position.

However, the overshoot detection circuit 4' is configured to detect the occurrence of an overshoot based only on the amount of temperature change, that is, the deviation of the detection voltage Va' with respect to the reference voltage Vc'. Since it operates to temporarily lower the output V' of the PID control circuit 1' by shifting the input of AI', it has the following drawbacks.

In other words, since temperature control is temporarily stopped regardless of the rate of temperature change, the return of the integrator to the active state after an overshoot occurs is delayed, and a new undershoot of the same degree as the overshoot occurs. There was an inconvenience that it took a long time for the temperature to stabilize after it occurred.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a combustion control device equipped with a control means that exhibits less transient response to sudden load changes.

In order to achieve the above object, a combustion control device according to the present invention includes at least an integrating means for comparatively controlling the fuel supply amount based on the comparison result between the set temperature and the detected temperature in order to maintain the hot water temperature at the set temperature. In the configuration including a control means, determining that a transient response has occurred in the temperature control when the deviation of the detected temperature from the set temperature is equal to or greater than a predetermined value, and the rate of change of the detected temperature is equal to or greater than a predetermined value, The present invention is characterized in that it is provided with a transient response detection means that outputs a signal for performing predetermined combustion control to prevent a transient response.

The above configuration will be explained below based on the block diagram shown in FIG.

Figure 1 is a block diagram of a combustion control device for adjusting the hot water temperature by proportionally controlling the amount of gas burned, such as in a gas water heater. Temperature setting means VR for adjusting the temperature t detected by the means RT and the water temperature
Based on the deviation Δt from the set temperature t0, the integrator
The PID control means 1 equipped with AI is configured to proportionally control the opening degree of a proportional valve 2 serving as a means for adjusting the amount of fuel supplied.

Furthermore, the detected temperature t and the set temperature t0 are compared, and the detected temperature t is at least a predetermined ratio with respect to the set temperature t0, that is, the deviation Δt is at least a preset predetermined value α1, and the detected temperature t If the rate of change ΔG of
A transient response detection means 4 is provided which outputs a signal D for temporarily stopping the operation of the control means 1 and performing predetermined fuel control to prevent a transient response.

In configuring the transient response detection means 4, the deviation Δt between the detected temperature t and the set temperature t0 is equal to the predetermined value α.
1 Overshoot determination temperature t set high
temperature deviation detection means 5 for detecting whether the detected temperature is greater than or equal to 0', and change rate detection means 6 for determining whether the differential value ΔG of the detected temperature, which is the rate of change of the detected temperature t, is greater than or equal to the predetermined value α2. , and a means 7 for calculating the AND of the respective means 5 and 6, and is configured to output a transient response detection signal D corresponding to the temperature deviation Δt and its rate of change ΔG.

Further, when the operation of the PID control means 1 is temporarily stopped by the output of the integrator AI, which is the output V of the PID control means 1, and the output D of the transient response detection means 4, the opening of the proportional valve 2 is determined. When the output V falls below the reference voltage VL, the output V of the integrator AI is adjusted to the input voltage. Regardless, the output V is fed back to the input side of the integrator AI in order to maintain the reference voltage VL.
A saturation prevention means 8 is provided to control the operation of the AI so that it does not become saturated.

Then, by controlling the operation stoppage of the PID control means 1 in accordance with the deviation Δt and the rate of change ΔG of the detected temperature t, the operation of the PID control means 1 is prevented from stopping more than necessary, and overshoot is prevented. It is controlled to reduce the occurrence of transient responses such as undershoot and undershoot.

Due to the above structure, the following excellent effects have been achieved.

In other words, even if a transient response to load fluctuations such as overshoot occurs due to sudden fluctuations in the amount of hot water dispensed, the transient response prevention control time is controlled in accordance with the amount and speed of the fluctuation, and normal operation is maintained. This reduces the delay in operation when returning to a normal PID control state, making it possible to minimize transient fluctuations in actual temperature changes.

Hereinafter, specific embodiments of the present invention will be described based on the drawings.

As shown in Fig. 2, two resistors R1 and R2, a thermistor RT as a temperature detection means, and a variable resistor VR as a temperature setting means are connected in series between the power supply Vcc and the ground point.
and the ground point, there are three resistors R3, R4, R5.
The two resistors R of the bridge circuit connected in series
The detection voltage Va obtained from the connection point A of 1 and R2 is input to the PID control circuit 1 having the configuration described later through the buffer circuit A0, and also to the overshoot detection circuit 4 as a transient response detection means having the configuration later. has also been entered. On the other hand, the three resistors R
The reference voltage Vb obtained from the connection point B on the power supply side of 3, R4, and R5 is input to the PJD control circuit 1 as a comparison standard for the detected voltage Va, and the reference voltage Vc obtained from the connection point C on the ground side is inputted to the It is input to the shoot detection circuit 4 as a comparison standard for overshoot detection.

The voltage V corresponding to the deviation between the reference voltage Vb and the detected voltage Va is configured to be outputted to the proportional valve drive circuit 3 that determines the opening degree of the proportional valve 2 that adjusts the fuel supply amount, and The detection voltage Va becomes lower than the voltage Vc, that is, the detection temperature t
When the deviation Δt between the set temperature t0 and the set temperature t0 becomes higher than the reference temperature t0′, which is set higher than the predetermined value α1, and the rate of change, that is, the differential value ΔG of the detected temperature t, exceeds the predetermined value α2, the overflow occurs. The output voltage V of the PID control circuit 1 is forcibly reduced by the output D of the shoot detection circuit 4, and the proportional valve 2 is controlled in the direction of closing, thereby preventing the occurrence of overshoot.

The PID control circuit 1 includes a first
, a second operational amplifier A2 constituting an integrator AI, and a third operational amplifier A3 as a saturation prevention means 8 configured as described later. Connect the output D of the integrator A2 to the input of the integrator A2 via the diode D1 and the resistor R6, and when an overshoot is detected, add a predetermined voltage corresponding to the resistor R6 to the input of the integrator A2. Accordingly, the level of the output of the PID control circuit 1, that is, the output V of the integrator A2 is forcibly lowered.

Then, in order to prevent the operation of the integrator A2 from being saturated due to the operation of the overshoot detection circuit 4, the power supply Vcc is connected to the resistor R7 by the amplifier A3.
A diode D2 amplifies the deviation between the voltage VL corresponding to the minimum fuel supply amount divided by R8 and the output V of the integrator A2 and connects it to the input side of the integrator A2.
By providing negative feedback through the integrator A2, the output V of the integrator A2 is prevented from falling below the voltage VL regardless of the input level. Note that the diode D2 operates to prevent feedback to the input side when the output V of the integrator A2 is larger than the voltage VL.

Further, although the resistors 9R and R10 are used to set the lower limit value of the output current of the proportional valve drive circuit 3 regardless of the output V of the PID control circuit 1, they may be omitted.

The overshoot detection circuit 4 includes a comparator A4 as a temperature deviation detection means whose output E becomes "H" level when the detection voltage Va becomes lower than the reference voltage Vc, and a differential value ΔG of the detection voltage Va. When the differentiator 9 consisting of operational amplifiers A5 and A6 and the differential value ΔG exceed the speed reference voltage α2, which is the reference value of the speed of change, the output F
A differential value discriminating circuit 6 is provided as a means for detecting the rate of change, which is composed of a comparator A7 whose output becomes "H" level, and an AND circuit 7 is provided as a means for calculating the logical product of the outputs E and F of the comparators A4 and A7. .

Then, the overshoot detection circuit 4
When it is detected that the temperature deviation Δt is greater than a predetermined value α1 and the rate of change ΔG is greater than a predetermined value α2, the output D of the AND circuit 7 causes the input of the integrator A2 to correspond to the resistor R6. By adding a predetermined voltage, the output V of the PID control circuit 1 is lowered, and the amount of fuel supplied is reduced.

Incidentally, FIG. 3A is a time chart showing the transient response of temperature when the flow rate changes in the embodiment shown in FIG. In addition, as shown in Figure B, even when the set temperature t0 is increased by operating the temperature setting variable resistor VR, if the overshoot temperature change is very gradual, the differential value Discrimination circuit 6 does not operate, therefore overshoot detection circuit 4 does not operate unnecessarily, and no transient response occurs. Furthermore, the response shown by the broken line in the figure shows the temperature change when the PID control means does not include the transient response detection means as in the conventional example.

Another embodiment will be described below.

In this embodiment, as shown in FIG.
The configuration is basically the same as that of the embodiment shown in the figure, and the output D of the overshoot detection circuit 4 is applied to the input of the differentiator A1 constituting the PID control circuit 1 to provide a voltage corresponding to the resistor R6. By adding , the configuration is such that the same operation as the embodiment shown in FIG. 2 is performed.

In the figure, the same reference numerals and numbers as in FIG. 2 indicate the same structure or function as the embodiment shown in FIG. 2.

That is, since the polarity of the signal is reversed at the input of the differentiator A1 and the input of the integrator A2, the polarity of the diode D1 is reversed and connected in order to reverse the active polarity of the output D of the overshoot detection circuit 4. At the same time, the output D of the AND circuit 7 is inverted.

In addition, in order to automatically vary the gain of the PID control circuit 1 according to the flow rate, as shown in FIG. 5, a resistor RG is installed to determine the gain of the buffer circuit A0.
may be configured as a flow rate sensor.

Further, the PID control circuit 1 may be configured as a proportional control circuit using only the integrator A2, omitting the integrator A1, and similarly, the saturation prevention means 8 may include an operational amplifier, a resistor, a Zener diode, etc. Any device may be used as long as it can operate as a limiter for the amount of feedback.

Further, the saturation prevention means 8 may be configured to regulate the upper limit value of the output V of the PID control circuit 1.

Furthermore, the control circuit 1 or the entire combustion control device may be configured by a microcomputer, and the configuration can be modified in various ways.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a circuit diagram showing the specific configuration of the combustion control device according to the present invention, and FIGS. 3A and 3B are explanatory diagrams of its operation.
4 and 5 are circuit diagrams of another embodiment, and FIG. 6 is a block diagram showing the configuration of a conventional example. 1... Proportional control means, 4... Transient response detection means, V... Fuel supply amount, AI, A2... Integrating means,
t0: Set temperature, t: Detected temperature, Δt: Deviation, ΔG: Rate of change, α1, α2: Predetermined value.

Claims (1)

[Claims] 1. A combustion control device comprising a control means 1 including at least an integrating means AI for comparatively controlling the fuel supply amount V based on the comparison result between the set temperature t0 and the detected temperature t in order to maintain the hot water temperature at the set temperature t0. and the deviation Δt of the detected temperature t from the set temperature t0 is greater than or equal to the predetermined value α1, and the rate of change of the detected temperature t is ΔG
A transient response detection means 4 is provided which determines that a transient response has occurred in the temperature control when is equal to or greater than a predetermined value α2, and outputs a signal D to perform a predetermined fuel control to prevent the transient response. A combustion control device characterized by: