JPH0222849B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a combustion control device, and particularly to a combustion control device that detects fluctuations in power supply voltage and controls the amount of combustion air.

(Prior Art) Generally, in a combustor, it is necessary to supply an appropriate amount of combustion air in accordance with the amount of gas to be supplied.
This will be explained using the conventional method shown in FIG. 1st
As shown in the figure, when a blower fan 1 is rotated by a motor 2 to supply combustion air, a disk 4 is provided on the shaft 3, and the rotation speed is detected by a magnetic sensor or a photoelectric sensor 5. , further via the amplifier 6 to the microcomputer (hereinafter referred to as
After feeding back to MPU 7 and performing arithmetic processing there, a phase angle control device 8 is activated to control the rotational speed of the motor 2 (air volume by the fan).

(Problems to be Solved by the Invention) Since the above-mentioned conventional method is a feedback method, it requires a means for detecting the rotational speed of the motor, a means for feedback, etc., and therefore has many problems in terms of reliability and economy. was.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly reliable combustion control device without using a feedback method.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a combustion control device for a forced combustion appliance that supplies an appropriate amount of air for the amount of gas supplied. an integrating circuit that detects the peak value of the positive half-wave of the power supply voltage applied to the motor, a switching element that discharges the integral circuit with the negative half-wave, and a converter that converts the peak value of the power supply voltage into a digital quantity. an analog-to-digital converter to perform the calculation, a timing synchronization unit to input the digital amount into the microcomputer, a phase control unit to which the output from the calculation unit of the microcomputer is introduced, and a combustion air supply motor. The unit is characterized in that it has a correction calculation function according to fluctuations in the power supply voltage.

(Function) In the present invention, when controlling the rotation speed of the blower motor, we focus on the fact that the main cause of error is fluctuations in the power supply voltage as shown in Figure 2, and detect the peak value of the power supply voltage applied to the motor. The present invention attempts to perform phase control of the motor by performing correction calculations in accordance with the fluctuations.

(Example) An example will be described below with reference to the drawings. FIG. 3 is a configuration diagram of an embodiment of a combustion control device according to the present invention. In FIG. 3, A is a peak value detection section which detects the peak value of the positive half wave of the power supply voltage, and a peak value reset section B performs a reset using the next negative half wave. That is, the peak value is thresholded with a positive half wave and reset with the next negative half wave, which are alternately performed. The peak value detected every positive half wave by the peak value detection section described above is introduced into the A/D conversion section C and converted into a digital quantity, which is input to the MPU 7.
The timing signal at that time is provided by the timing synchronization section D. by these means
The MPU 7 performs a correction calculation according to the input peak value, and outputs a duty output P to the gate of the phase control circuit.

The details of the specific device will be explained below. Reference numeral 9 denotes a power transformer, the primary winding 10 of which is connected to an AC power source 11, and the secondary winding 12 connected to a voltage dividing resistor 14 and 1 through a diode 13 having positive polarity.
5 is connected. Diode 1 is connected from the voltage dividing point.
An integrating circuit consisting of a resistor 17 and a capacitor 18 is connected through the integrator 6, and its output is further connected to the positive terminal of a comparator 20 through an operational amplifier 19. Further, the negative terminal of the comparator 20 is connected to the MPU 7 via the ladder circuit 21, and the output of the comparator 20 is input to the _P1 terminal of the MPU 7. The diode 22 is provided with a polarity opposite to the secondary winding 12 of the power transformer 9, and is connected to a voltage dividing resistor 23.
and 24 is the same as in the case of the diode 13 described above. The voltage dividing point is connected via a Zener diode 25 to the base of a transistor 26 as a discharging switching element, and the transistor 26 is connected between one end of the integrating circuit and ground.

On the other hand, the plus side terminal of the comparator 27 is connected to a voltage dividing point of positive polarity to input a positive half wave, and the minus side terminal is connected to the power supply via the variable resistor 28.

Next, the operation will be explained. The positive half wave of the power supply 11 is voltage-divided by resistors 14 and 15 via a diode 13, and this divided voltage appears in an integrating circuit consisting of a resistor 17 and a capacitor 18. At this time, as shown in FIG. 4, the reference starting voltage V _t is determined for the positive half wave of the voltage, and the peak value V _p
Since the input impedance _of the operational amplifier 19 is considered to be almost infinite, the transistor 26 is connected at time t ₁ to reset it in consideration of leakage current. The negative half-wave of the power supply voltage turns on the transistor 26 via the Zener diode. The peak value of the power supply voltage is then introduced to the positive terminal of the comparator 20 via the operational amplifier 19.

Here, a negative terminal (reference terminal) of the comparator 20 is connected to a ladder circuit 21, and individual reference voltages determined by the number of ladders (number of bits) constituting the ladder circuit are sequentially output. Therefore, at the point where each reference voltage from the ladder circuit 21 matches the peak value of the power supply voltage input to the comparator 20, the output of the comparator 20 is digitized and input to the _P1 terminal.

In the MPU 7, each ladder constituting the ladder circuit 21 is sequentially scanned to generate an output step by step, and each time, a point that coincides with the peak value of the voltage is determined and digitized. In short, A/D conversion is performed by a combination of a ladder circuit and an MPU.

On the other hand, the timing synchronization section determines at what point the digital signal is taken in with respect to the positive half wave of the input power supply voltage, and the reference voltage applied to the negative terminal of the comparator 27 and the rising position of the half-wave of the input power supply voltage, when this becomes equal to or higher than the reference voltage, the output is set to the "H" level and is introduced to the _P2 terminal. That is, only when the _P2 terminal is at "H" level, the peak value detection level at that time is introduced into the _P1 terminal.

FIG. 5 is a flowchart for explaining the operation. That is, in step 51 after the start, the terminal
It is determined whether or not the "H" level has been set at _P2 , and if it is "H" level (Y), the process moves to step 52, waits for time t, and moves to step 53, where the peak value of the voltage is set to A/ D-convert and input. Next, the process moves to step 54, where a correction amount according to the power supply voltage value is calculated, and the process moves to step 55, where the correction amount is added to the basic amount, and is outputted to the phase angle control device via step 56. Note that if the "H" level does not rise to the _P2 terminal in step 51 (N), the process returns to the original state and repeats these operations.

[Effects of the Invention] As explained above, according to the present invention, the peak value is detected every positive half wave of the power supply voltage of the blower motor,
By combining this with a ladder circuit and MPU, A/
Since the phase control circuit is controlled by performing D conversion and calculating the correction amount according to the power supply voltage, reliability is improved by reducing the number of parts, and combustion control that allows efficient control is achieved. equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a conventional combustion control device, Fig. 2 is a diagram showing variations in motor rotation speed due to variations in power supply voltage, Fig. 3 is a configuration diagram of an embodiment of a combustion control device according to the present invention, and Fig. 4 5 is a diagram for explaining the detection of a peak value from a half-wave of the power supply voltage, and FIG. 5 is a flowchart for explaining the operation. A...Peak value detection section, B...Peak value reset section, C...A/D conversion section, D...Timing synchronization section, 1...Fan, 2...Motor, 3...Shaft, 4... Disc, 5... rotation speed detection means,
6...Amplifier, 7...MPU, 8...Phase angle control device, 9...Power transformer, 10...Primary winding,
11...Power supply, 12...Secondary winding, 13, 16,
22...Diode, 14, 15, 17, 23,
24... Resistor, 18... Capacitor, 19... Operational amplifier, 20, 27... Comparator, 21... Ladder circuit, 25... Zener diode, 28...
Variable resistance.

Claims (1)

[Claims] 1. In a combustion control device for a forced combustion appliance that supplies an appropriate amount of air for the amount of gas supplied, an integrating circuit that detects the peak value of a positive half-wave of a power supply voltage applied to a combustion air supply motor; a switching element that discharges the integrating circuit by a negative half wave;
an analog-to-digital conversion section that converts the peak value of the power supply voltage into a digital quantity; a timing synchronization section that takes the digital quantity into the microcomputer; a phase control section into which the output from the calculation section of the microcomputer is introduced; 1. A combustion control device comprising: an air supply motor; and wherein the calculation section has a correction calculation function according to fluctuations in power supply voltage.