JPH01200118A - Combustion air amount control device for burner - Google Patents

Abstract

PURPOSE:To feed a proper amount of combustion air and to maintain combustion in an excellent state, by a method wherein the number of revolutions of a DC motor for running a fan is rapidly restored to a target value. CONSTITUTION:By means of a control power output means 5, the number of revolutions of a DC motor 1 detected by a number of revolutions detecting means 3 is compared with the target number of revolutions decided from a combustion amount by a number of revolutions deciding means 4. When the number of revolutions of the DC motor 1 is below a target value, a first control voltage signal is outputted, and reversely, when the number of revolutions of the DC motor 1 exceeds a target value, a second control voltage signal is outputted. In a drive circuit 2, while the first control voltage signal is inputted, a DC voltage by means of which the DC motor 1 is run is continuously increased. Reversely, while the second control voltage signal is inputted, the DC voltage is continuously decreased. While the control voltage signal is not inputted, the DC voltage is maintained at a specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a combustor that forcibly supplies combustion air for combustion, and particularly relates to a device for controlling the amount of combustion air supplied.

(Prior Art) Combustors whose combustion amount can be varied are widely known, and the oil combustor that was previously filed by the applicant is one of them.

The configuration of this type of combustor applied to, for example, an oil water heater will be described with reference to FIG. 4. 51 is a DC motor that rotates a fan 53 attached to a frame 52, 54 is a mixing pipe;
56 is a burner that is connected to the mixing tube 54 and has an elongated burner port 56; 57 is an air jetting plate that is inclined on both sides of the long side of the elongated burner port 56 and has a large number of air jetting ports 58; , 59 is a combustion chamber formed by removably placing a heat exchanger 60 in the upper opening of the frame 52, and 61 is a vaporization pipe connected to a nozzle pipe 63 having a nozzle port 62 for heating and vaporizing fuel oil. , 64 are electromagnetic bodies that operate the opening and closing of the nozzle opening 62.

In the above configuration, when a combustion command is issued by detecting the inflow of water into the heat exchanger 60 by an appropriate detection means (not shown), the DC motor 51 is driven and combustion air is supplied by the fan 53. , a part of which flows into the mixing tube 53 as primary air. At the same time, the electromagnetic body 64 opens the nozzle port 62, and the fuel sent to the vaporizing pipe 61 is heated and vaporized to become vaporized gas, which is ejected from the nozzle port 62 into the mixing pipe 64 and mixed to form a premixture. Na.

Then, it flows out into the combustion chamber 59 from the elongated flame port 56 of the burner 55. The premixture is ignited by an appropriate ignition means (not shown) to form a flame F, and the remaining combustion air excluding the secondary air is sent to the air blowing plate 57 as secondary air to the flame F. The combustion reaction is promoted by ejecting air from a large number of air ejection ports 58 provided in the air. The heat exchanger 60 is heated by the combustion heat of the flame F, and the inflow water is converted into hot water and hot water is discharged.

In many combustors, not just the oil combustor described above, the amount of combustion is successively changed based on various data in order to achieve, for example, the hot water temperature, heating temperature, etc. desired by the user.

Furthermore, especially in combustors that forcefully supply combustion air for combustion, if the amount of combustion changes, the amount of combustion air must also be changed at the same time.In other words, if the amount of combustion air is in excess of the amount of combustion If there is such a problem, the flame F may become unstable, lifting combustion may occur, and heat loss to objects to be heated such as the heat exchanger 60 will increase, resulting in a decrease in heat exchange efficiency. This is because when the amount of air is insufficient, incomplete combustion such as red flames may occur, producing soot and carbon monoxide, which is harmful to the human body.

In order to change the amount of combustion air, it is sufficient to change the rotation speed of the fan 53, that is, the voltage applied to the DC motor 51 in stages.
For this purpose, a circuit as shown in FIG. 5 is often used.

In FIG. 5, 65 is a digital signal output means for outputting a digital signal, 66 is a D/A converter, 67 is a comparator,
68 is a feedback system, 69 is a transistor, 70 is a signal line, and A and B are connection terminals to the DC motor 51.

In the circuit configured as described above, the D/A converter 66 outputs the reference voltage V ref converted based on the digital signal output by the digital signal output means 65 to the comparator 67 . The comparator 67 connects the reference voltage V ref and the feedback system 6
In order to adjust the output voltage by comparing the feedback voltage Vfb input from the DC motor 8, a voltage corresponding to the reference voltage Vref is applied to the DC motor 51 via the transistor 69. That is, if the digital signal changes simultaneously with the change in combustion amount, it is possible to supply approximately the appropriate amount of combustion air for each of the various combustion amounts.

(Problems to be Solved by the Invention) In the conventional technology described above, even if the voltage applied to the DC motor δ1 is stable, the load changes due to blockage of the supply and exhaust ports, wind pressure, etc. The rotational speed fluctuates, the amount of combustion air becomes excessive or insufficient, and various abnormal combustions as described above occur, and this state tends to continue for a relatively long time.

In addition, in order to supply an appropriate amount of combustion air for each of the determined various combustion amounts, the number of digital signals input to the D/A converter 66, that is, the number of digital signal output means 65 and the D/A
The number of signal lines 70 between the converters 66 is increased, and the reference voltage V re
The configuration must be such that f can be output in various ways.

However, in this case, the reference voltage V ref has to be a discrete value, and therefore the voltage applied to the DC motor 51 also changes in stages. had the problem of being difficult to adopt.

The present invention aims to solve such conventional problems.

(Means for Solving the Problems) In order to achieve the above-described object, the combustion air amount control device for a combustor of the present invention rotates a fan by driving it with a DC voltage, and outputs a rotation speed proportional signal. a DC motor, a rotation speed detection means for detecting the rotation speed of the DC motor from the rotation speed proportional signal, and a rotation speed determination means for determining a target rotation speed of the DC motor based on the determined combustion amount; The rotation speed is compared with the target rotation speed, and when the target rotation speed is not reached, the first control voltage signal is output from one side, and on the other hand, when the target rotation speed is exceeded, the second control voltage signal is output from the other side. control voltage output means for outputting a voltage signal, and continuously increases the DC voltage while the first control voltage signal is input, and conversely increases the DC voltage while the second control voltage signal is input; a drive circuit that continuously decreases the voltage and functions as a sample-and-hold circuit while the respective control voltage signals are not input, and maintains the DC voltage constant;
It is composed of

(Function) With the above-described configuration, the present invention compares the rotation speed of the DC motor with the target rotation speed determined based on the combustion amount,
When these differ, the voltage applied to the DC motor is continuously controlled by the first control voltage signal or the second control voltage signal, and when the rotation speed recovers to the target rotation speed by this control, each of the above-mentioned controls is applied. The output of the voltage signal is stopped, and the target rotation speed can be maintained thereafter.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, 1 is a DC motor, which is driven by a DC voltage from a drive circuit 2 and outputs a rotation speed proportional signal. 3 is a rotation speed detection means for detecting the rotation speed of the DC motor 1 from the rotation speed proportional signal; 4 is a rotation speed determination means for determining the target rotation speed of the DC motor based on the determined combustion amount; and 5 is the rotation speed determination means described above. The control voltage output means compares the rotation speed and the target rotation speed and outputs a first control voltage signal from one or a second control voltage signal from the other to the drive circuit 2 when they are different. The drive circuit 2 increases or decreases the voltage applied to the DC motor 1 while the first control voltage signal or the second control voltage signal is input, and when the respective control voltage signals are not input, it becomes a sample-and-hold circuit and maintains a constant voltage. It has a configuration that can apply the same to the DC motor l.

FIG. 2 is a circuit diagram of the embodiment of FIG. 1. In FIG. 2, numeral 6 denotes a microcomputer having a baud)p for outputting a first control voltage signal, a baud q for outputting a second control voltage signal, and a baud)r for inputting a rotational speed proportional signal, and is capable of executing various control programs. and a memory 7 that stores control data, etc., and a CPU that reads programs in the memory 7 and executes processing.
8, an input/output circuit 9 for outputting various control signals, and these constitute the rotation speed detection means 3, the rotation speed determination means 4, and the control voltage output means 5 described in FIG. lO connects the emitter to zero potential Vss and connects the port p
11 is a transistor whose emitter is connected to the circuit power supply +Vcc and is turned on when transistor 10 is turned on; 12 and 13 are resistors Ra and Rh for determining time constants, respectively;
, 14 is a transistor whose emitter is connected to the zero potential Vss and is turned on by the output of the second control voltage signal from the port q. 16 is a sample-and-hold circuit, and the capacitance is the same as the charging voltage of the electrolytic capacitor 16 whose capacitance is C. The configuration is such that a potential reference voltage V ref is input to the voltage follower 17 . 1st is a transistor whose collector is connected to the unregulated power source +Vc for power use, and pace is a transistor whose collector is connected to the output of the voltage follower 17. The DC motor 1 is connected to connection terminals A and H provided in the drive circuit 2, and
The rotation speed proportional signal is input to the boat r via a connection terminal M. Note that 19, 20, 21 and 22 are current limiting resistors, and 23 is a noise absorbing resistor.

The operation in the above configuration will be explained below.

During combustion, the DC motor 1 is rotating, and a rotation speed proportional signal consisting of, for example, a pulse signal is input to the microcomputer 6 via a baud)r. The rotational speed detection means 3 measures the number of rotational speed proportional signals input within a preset time to determine the rotational speed, and outputs a signal based on the measurement result to the control voltage output means 5. On the other hand, the rotation speed determining means 4 determines a target rotation speed of the DC motor l so as to supply an appropriate amount of combustion air based on the determined combustion amount stored in the memory 7, and also based on this target rotation speed. The output signal is output to the control voltage output means 5. In order to determine the target rotation speed, the relationship between various combustion amounts and the amount of combustion air that provides good combustion efficiency or heat exchange efficiency for each combustion amount is determined in advance through experiments, and the relationship between It is sufficient to use a method such as storing the information in the memory 7 and sequentially reading it for determination.

The control voltage output means 5 does not output the first control voltage signal and the second control voltage signal while comparing the signals from the rotation speed detection means 3 and the rotation speed determination means 4 and determining that there is no difference. That is, since the transistor 10 is off, the transistor 11 is also off, and the transistor 14 is also off, and a stable voltage is supplied to the DC motor l from a sample-and-hold circuit 15 consisting of an electrolytic capacitor 16 and a voltage follower 17 via the transistor 18. A voltage is applied. Therefore, unless the load, combustion amount, etc. change, the rotational speed will match the target rotational speed as shown in section A of FIG. In FIG. 3, the rotational speed fluctuation, the voltage applied to the DC motor 1, and the combustion amount change are in the same time series, and in the time series diagram of the rotational speed fluctuation, the dotted line indicates the target rotational speed.

Next, when the rotation speed decreases due to a change in the load applied to the DC motor 1 and becomes different from the target rotation speed, the control signal output means 5 outputs a first control voltage signal from the boat p. At this time, the transistor 11 is turned on at the same time as the transistor 10 is turned on, and charge is accumulated in the electrolytic capacitor 16, so that the reference voltage Vref input to the voltage follower 17 is as follows: Vref=Vcc [1-exp(-Ta/C11R
a)] (however, Ta increases according to the first control voltage signal output time), so the voltage applied to the DC motor l, that is, the rotation speed increases and recovers to the target rotation speed.At the same time as this recovery, the first control Since the output of the voltage signal is stopped, the target rotation speed is maintained thereafter. The above aspect is shown in the opening section of Figure 3.

On the contrary, when the rotational speed increases relative to the target rotational speed, the control signal output means 5 outputs the second control voltage signal from the boat q. At the same time, transistor 14
turns on, the charge in the electrolytic capacitor 16 is discharged and the reference voltage V ref input to the voltage follower 17
is V ref = V c [exp(-T b /
C·Rb)] (where Tb is the first control voltage signal output time and Vc is the voltage of the electrolytic capacitor 16 immediately before the transistor 14 is turned on). In this case, after the rotational speed of the DC motor 1 decreases and quickly recovers to the target rotational speed, the output of the second control voltage signal is stopped. This aspect is as shown in the sections in FIG.

Also, if the combustion amount changes, the target rotation speed is determined anew at the same time, and although it will be different from the rotation speed, the first control voltage signal or the second control voltage signal will be output in the same way as above. As a result, the rotational speed increases or decreases and recovers to the target rotational speed, and this state is maintained thereafter.

As described above, while the control voltage output means 5 outputs the first control voltage signal or the second control voltage signal, the reference voltage ref input to the voltage follower 16 changes continuously, so that the voltage is applied to the DC motor l. The applied voltage can be changed continuously to quickly restore the target rotation speed.
As a result, an appropriate amount of combustion air can be supplied.

(Effects of the Invention) Hereinafter, the combustion air amount control device for a combustor of the present invention compares the rotation speed of the DC motor and the target rotation speed determined based on the combustion amount, and when they differ, the control device starts from one side. By outputting one control voltage signal or a second control voltage signal from the other, it is possible to continuously control the voltage applied to the DC motor to quickly recover the target rotation speed, and at the same time, to control the rotation speed. It has the effect of being able to maintain a constant combustion rate, and it is also able to supply the appropriate amount of combustion air for various combustion volumes, maintaining good combustion, making it extremely useful for combustors where the combustion volume can be varied. It can be a device, etc.
It has many industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of the combustion air amount control device of the present invention, Fig. 2 is a circuit diagram of the same device, Fig. 3 is a time series diagram of rotation speed fluctuation, applied voltage change, and combustion amount change, and Fig. 4 5 is a configuration diagram illustrating a combustor, and FIG. 5 is a circuit diagram of a conventional combustion air amount control device. l--DC motor, 2--drive circuit, 3---
Rotation speed detection means, 4--Rotation speed determination means, 5-
Control voltage output means. Patent applicant Representative of Dainichi Industries Co., Ltd.
Fumio Sasaki 11th 21m Ml-) 1st 51st

Claims (1)

[Claims] a DC motor driven by a DC voltage to rotate the fan and output a rotation speed proportional signal; a rotation speed detection means for detecting the rotation speed of the DC motor from the rotation speed proportional signal; a rotation speed determining means for determining a target rotation speed of the DC motor based on the rotation speed; On the contrary, control voltage output means outputs a second control voltage signal from the other side when the target rotation speed is exceeded, and continuously increases the DC voltage while the first control voltage signal is input, On the contrary, while the second control voltage signal is input, the DC voltage is continuously decreased, and while each control voltage signal is not input, it becomes a sample-and-hold circuit and maintains the DC voltage constant. A combustion air amount control device for a combustor, comprising: a drive circuit;