JPH0440608B2 - - 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, is increasingly being adopted in response to the deviation between the set temperature and the detected temperature.

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, and by the time the control is stabilized, hot water will be dispensed at a temperature that is significantly different from the set temperature.This transient response should be prevented. I needed a means.

As a means to prevent this kind of transient response, for example, Japanese Patent Application No. 55-105710 (Japanese Unexamined Patent Publication No. 57-31722)
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. 7, a PID control circuit 1 including an integrator AI' calculates the deviation between the reference voltage Va' obtained by dividing the power supply voltage VCC by resistance and the output voltage Vb' of the thermistor RT' as a temperature detection means. ′,
The output V' is configured to control the drive current of a constant current drive circuit 3' that determines the opening degree of the proportional valve 2' that adjusts the fuel supply amount, and the Voltage set to low value
An overshoot detection circuit 4' is provided which compares Vc', that is, the overshoot reference voltage, with the detection voltage Vb' to determine the occurrence of overshoot due to temperature change. Therefore, by shifting the input level of the integrator AI' and forcibly lowering the output V' of the PID control circuit 1', the proportional valve 2' is returned to the minimum opening that maintains combustion. It is configured to do so.

However, the overshoot detection circuit 4' shifts the integrator AI' to a state where its output saturates to the lower limit value and makes it inactive, and also prevents the proportional valve 2' from opening at the lowest limit. degree is 2
PID control circuit 1' by two resistors R2' and R3'.
Because the setting is independent of the operation of the
There was a problem in that the return of the PID control circuit 1' to the active state was delayed and a large undershoot occurred.

In other words, if the amount of hot water that comes out suddenly changes, the hot water temperature fluctuates up and down relative to the set temperature, and it takes time to stabilize.

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.

The combustion apparatus of the present invention includes a control means including at least an integrating means for proportionally controlling the amount of fuel supplied based on a comparison result between the set temperature and the detected temperature in order to maintain the hot water temperature at the set temperature, and A combustion control device comprising a transient response detection means that operates to amplify the output of the pre-control means in a direction to reduce the difference when the difference between the detected temperature and the set temperature exceeds a predetermined value, and its characteristics The structure is that saturation prevention means is provided for maintaining the output of the integrating means at a set value so that the output of the integrating means does not saturate while the transient response detecting means executes the operation.

With the above characteristic configuration, the combustion apparatus of the present invention operates as follows.

That is, when the difference between the detected temperature and the set temperature exceeds a predetermined value, the transient response detection means is activated to amplify the output of the control means in the direction of reducing the difference. However, at the same time, the saturation prevention means works, so that the output of the integrating means included in the control means is maintained at a predetermined level that does not reach the saturation level.

Therefore, as the difference between the detected temperature and the set temperature becomes smaller, the transient response detection means is deactivated and when steady control is restored, the integration means quickly returns to the steady operation region. In other words, the control delay caused by the time required for the integrating means to return to the normal operating region is reduced.

A detailed explanation of the operation will be added based on FIGS. 1 and 2. If the detected temperature t becomes higher than the set temperature _t0 due to a decrease in the amount of hot water dispensed, the control means 1:
The output voltage V is lowered to lower the detected temperature t. However, due to a control delay in the entire system including the fuel control device, the detected temperature t does not drop immediately and an overshoot occurs.

The transient response detection means 4 detects this and operates to amplify the output of the control means in the direction of lowering the detected temperature t. Specifically, as shown in FIG. 2, for example, the output of the comparator A4 of the transient response detection means 4 becomes H level, and the input level of the operational amplifier A2 of the integrating means AI is forcibly raised.

However, if the output voltage V tries to fall below the set voltage Vα determined by the resistors R7 and R8, the output of the converter A3 of the saturation prevention means 5 is inverted to L level, working to lower the input level of the operational amplifier A2. Therefore, the saturation prevention means 5 maintains the output voltage V at the set voltage Vα by the negative feedback effect of the comparator A3, which is an operational amplifier with an infinite amplification factor.

In other words, the output of the integrating means AI is maintained at a predetermined level Vα that does not reach the saturation level (the negative power supply voltage of the operational amplifier A2). In addition, the set voltage Vα
is the voltage corresponding to the minimum fuel supply amount, that is, the resistance R
It is sufficient to set the voltage to be slightly lower than the voltage determined by 9 and R10.

Therefore, when the output of the comparator A4 of the transient response detecting means 4 returns to the L level as the detected temperature t decreases, the integrating means AI quickly returns to the steady operating region. In other words, the voltage of the capacitor C quickly returns to the normal operating region.

The above effect is the same even when the temperature suddenly drops to the detected temperature t due to a sudden increase in the amount of hot water dispensed. However, the specific circuit configuration will be different from that shown in FIG.

Due to the above-mentioned effects, the following excellent effects can be obtained.

That is, as described above, the return to the normal operating range is faster, and as a result, transient fluctuations in the hot water temperature can be suppressed as much as possible. As in the above-mentioned specific example, if overshoot is detected, it is possible to reduce the undershoot when the hot water temperature t returns to the set temperature _t0 , as shown in Figure 3. Ta. Incidentally, if the saturation prevention means 5 is not provided, there will be large transient fluctuations in undershoot as shown by the broken line.

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
A detection voltage Va obtained from a connection point A between R1 and R2 is inputted to a PID control circuit 1 having a configuration described later through a buffer A0, and is also inputted to a comparator A4 as a transient response detection means 4. on the other hand,
The reference voltage Vb obtained from the connection point B on the power supply side of the three resistors R3, R4, and R5 is input to the PID control circuit 1 as a comparison standard for the detection voltage Va, and the reference voltage obtained from the connection point C on the ground side is inputted to the PID control circuit 1. Vc is inputted to a comparator A4 constituting the transient response detection means 14 as a comparison standard for overshoot detection.

The configuration is configured to output a voltage V corresponding to the deviation between the reference voltage Vb and the detected voltage Va to a constant current 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
exceeds a predetermined amount α1 with respect to the set temperature t ₀ and becomes higher than the overshoot reference temperature t ₀ ', the output voltage V of the PID control circuit 1 is forcibly lowered by the output D of the converter A4, The proportional valve 2 is controlled in the closing direction to prevent overshoot from occurring.

The PID control circuit 1 includes a first operational amplifier A1
and a second operational amplifier A.
It has an integrator AI consisting of 2nd grade. Further, the output D of the comparator A4 of the transient response detection means 4 is connected to the operational amplifier A2 via the diode D1 and the resistor R6.
When an overshoot is detected, the resistor R is connected to the input of the operational amplifier A2.
By adding a predetermined voltage corresponding to 6,
The level of the output of the PID control circuit 1, that is, the output V of the integrator AI, is forcibly lowered.

A saturation prevention means 5 is provided to prevent the operation of the integrator AI from becoming saturated due to the operation of the comparator A4. The output voltage V of the integrator AI is the lower limit voltage VL determined by the resistors R7 and R8.
If the voltage is to drop further, the output of comparator A3 of saturation prevention means 5 is inverted to L level, and the output of operational amplifier A is
It works in the direction of lowering the input level of 2. Therefore, the saturation prevention means 5 maintains the output voltage V at the lower limit voltage VL by the negative feedback effect described above.

In other words, the output of the integrating means AI is maintained at a predetermined level VL that does not reach the saturation level (the negative power supply voltage of the operational amplifier A2). In other words, the charging voltage of the capacitor C can be suppressed to a low level.

Further, although the resistors R9 and R10 are used to set the lower limit value of the output current of the constant current drive circuit 3 regardless of the output V of the RID control circuit 1, they may be omitted.

Moreover, FIG. 3 shows that in the embodiment shown in FIG.
This drawing shows a transient response of temperature when the flow rate changes, and the response shown by the broken line in the drawing shows the response when there is no saturation prevention means 5 as in the conventional example.

Another embodiment will be described below with reference to the drawings.

As shown in FIG. 4, the configuration is basically the same as that of the embodiment shown in FIG. By adding a predetermined voltage corresponding to the resistor R6 to the input, the second
It is configured to perform the same operation as the embodiment shown in the figure. 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, the input of the operational amplifier A1 and the operational amplifier A2
Since the polarity of the signal is inverted at the input of the comparator A4, the polarity of the diode D1 is inverted and connected to invert the active polarity of the output D of the comparator 4, and the reference voltage VC, which is the input signal of the comparator A4, is detected. The voltage Va inputs are switched and connected.

Next, FIG. 5 shows another embodiment in which both overshoot and undershoot are detected, and the saturation prevention means 5 is configured to regulate both the upper and lower limits of the active range of the integrator AI. I will explain based on.

That is, a comparator A4 for detecting overshoot and a comparator A4' for detecting undershoot are provided, and resistors R3 and R
3', R4, R5 to compare the reference voltages Vc, VC' for determining the transient response with the detection voltage Va, and the integrator set by the resistors R7', R7, R8. Comparator A3' that gives negative feedback to the upper limit value VH of the active range of AI and the lower limit value
A comparator A3 that provides negative feedback to VL is provided, and when an overshoot occurs, the output V of the integrator AI is maintained at the lower limit value VL by the comparator A3, and when an undershoot occurs, the output V of the integrator AI is maintained by the comparator A3'. Therefore, the configuration is such that the output V of the integrator AI is maintained at the upper limit value VH.

In addition, in order to automatically adjust the gain of the PID control circuit 1 according to the flow rate, as shown in FIG. 6, a resistor RG is installed to determine the gain of the buffer circuit A0.
may be configured as a flow rate sensor whose resistance value changes in accordance with the flow rate.

Further, the PID control circuit 1 may be configured as a proportional control circuit using only the integrator AI, omitting the differentiator A1.

Furthermore, the control circuit 1 or the entire fuel 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.
3 is an explanatory diagram of its operation, FIGS. 4 to 6 are circuit block diagrams of another embodiment, and FIG. 1 is a block diagram showing the configuration of a conventional example. 1... Control means, 4... Transient response detection means, 5
...Saturation prevention means, AI...integration means.

Claims (1)

[Claims] 1. In order to maintain the hot water temperature at the set temperature t0, the control means 1 includes at least an integrating means AI that proportionally controls the fuel supply amount based on the comparison result between the set temperature t0 and the detected temperature t, and When the difference between the temperature t and the set temperature t0 exceeds a predetermined value,
The combustion control device includes a transient response detection means 4 that performs an operation to amplify the output of the control means 1 in a direction to reduce the difference, wherein while the transient response detection means 4 is performing the operation, the integration means A combustion control device that is provided with a saturation prevention means 5 that maintains the output of AI at a set value so that the output of AI does not become saturated.