JPH0745931B2 - Burner air-fuel ratio controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to control of an air-fuel ratio in a combustion device that uses gas, petroleum, or the like as a fuel.

2. Description of the Related Art In recent years, when burning gas or oil as fuel, the mixture ratio of fuel and air, that is, the air-fuel ratio is optimally controlled to prevent incomplete combustion, and the generation of nitrogen oxides (NOx) is reduced. The demand for clean combustion is increasing.

This air-fuel ratio control is best detected by detecting the combustion state of the burner and controlling the combustion air amount or the fuel supply amount so as to keep it constant, and various types have been proposed in the past. There is.

For example, as disclosed in JP-A-51-31533, as shown in FIG. 4, a flame rod which detects a flame ion current by an electrode rod inserted in a flame is used as a combustion state detection sensor. It is a means for controlling the air-fuel ratio in accordance with.

In FIG. 4, kerosene is used as fuel, which is vaporized in the vaporization chamber 1 and mixed with air from the blower 3 in the mixing chamber 2 to form a flame 5 in the combustion chamber 4 for combustion. The control circuit 6 drives and controls the fuel pump 7 that supplies fuel oil and the blower 3. At the same time, it is inserted into the flame 5, the flame rod 9 is arranged so as to be insulated by the combustion chamber 4 and the insulator 8, the flame current If flowing between the flame chamber 9 and the combustion chamber 4 is measured by the control circuit 6, and this flame current is measured.
The drive amount of the fuel pump 7 is controlled according to If.

The flame current If has a certain correlation with the air-fuel ratio, and generally the air-fuel ratio m
A convex carp with a peak near = 1 is shown. Therefore, the air-fuel ratio can be controlled by controlling the fuel supply amount or the air amount so that the flame current If becomes a constant value. Here, the air-fuel ratio m = 1 means a state in which a theoretical air amount necessary for complete combustion of fuel is supplied, and m>
When 1 is in excess of air, when m <1 is in excess of fuel. The value of the air-fuel ratio m for obtaining the best combustion state is determined according to the burner.

Problems to be Solved by the Invention Here, when the amount of supplied fuel changes due to variations in the fuel pump and the fuel passage, as factors of variation in the air-fuel ratio m,
Alternatively, variations in the blower for supplying the combustion air or external factors such as the outside air temperature and the oxygen concentration may be considered.

In the configuration shown in FIG. 4, since the feedback control of the air-fuel ratio is performed by the flame current If, all of these variations are corrected and the air-fuel ratio is kept constant.

Here, it has been stated that the flame current If has a correlation with the air-fuel ratio m, but this is the case when the combustion is stable, and the flame stabilizes before the combustion stabilizes, for example immediately after the burner is ignited. It takes several minutes until the flame current If becomes unstable and the air-fuel ratio cannot be controlled. The control circuit outputs so as to maintain the designed air-fuel ratio, but if there are the above-mentioned variation factors during this period, the air-fuel ratio will vary as it is, resulting in transient incomplete combustion, or in the worst case, misfire or flashback. Can occur.

Means for Solving the Problems In order to solve the above problems, the present invention provides a burner for burning fuel, a fuel control means for controlling the amount of fuel supplied to the burner, and an air supply for supplying the combustion means. Means, a combustion sensor for detecting the combustion state of the burner, and a controller for driving and controlling the fuel control means and the air supply means.This controller has predetermined combustion such as ignition control during burner ignition and extinction control during extinction. A sequence control unit that controls operation according to a sequence, an air-fuel ratio control unit that corrects and controls the air supply unit or the combustion control unit according to a signal from the combustion sensor while the burner is burning, and a correction control amount by this air-fuel ratio control unit. The air-fuel ratio of the burner is controlled by the memory means for storing and the signal from the memory value of the memory means after the start of combustion of the burner until the output of the combustion sensor stabilizes. And an initial control circuit.

With the above configuration, before the combustion sensor outputs a normal output due to stable combustion immediately after the burner is ignited, the fuel control means according to the output of the storage unit that stores the correction control amount by the air-fuel ratio control at the previous combustion. , Or to output to the air supply means,
Once burned, it has the effect of learning the optimal conditions based on the variation of each functional part and the environmental condition of the combustor, and based on this, prevents the air-fuel ratio from largely deviating during the initial stage of ignition when the combustion condition is unstable. .

Embodiment An embodiment of the burner air-fuel ratio control device of the present invention will be described below with reference to the drawings. In the embodiment, a petroleum fin heater that burns kerosene as fuel to heat the interior will be described as an example.

In FIG. 1, fuel kerosene is led from a fuel tank 10 to a vaporized mixture 12 by a fuel pump 11. The vaporized mixture 12 is preheated by an electric heater (not shown) or the like in advance, so that the kerosene is vaporized. Further, it is mixed with the combustion air supplied from the blower 13 and burned in the burner 14. Combustion exhaust gas burned by the burner 14 is mixed with indoor air by a convection fan 15 and discharged into the room to perform an indoor air-shutdown. Reference numeral 16 is a flame rod inserted into the combustion flame of the burner.
The combustion state of 14 is detected by the flame current detection unit 18 of the controller 17.

The sequence control unit 19 controls the ON / OFF of the carburetor, the drive timing of the convection fan 15 and the igniter (not shown) when the burner 14 is ignited, or the fuel pump when the fire is extinguished.
11 is a pump drive unit 20 that drives and controls the fuel pump 11 to control the combustion of the burner 14 according to a predetermined combustion sequence such as the on / off timing of the blower 13 and the blower.
A signal is output to a motor drive unit 21 that drives and controls the motor 13.

Now, the flame current If detected by the flame rod 16 when the burner 14 is burning at a constant combustion amount by the output of the pump drive section 20 has the characteristics shown in FIG. FIG. 2 shows the combustion air amount Q _{A on} the horizontal axis, the flame current If on the vertical axis, and the combustion amount Q _F as a parameter. In the figure, the state of the air amount Q _A0 when the combustion amount is Q _F2 is the state of the air-fuel ratio m = 1, and in this example, the state of Q _A2 is the best combustion state. That is, air-fuel ratio m> 1
It is assumed that the fuel is burnt at, for example, m = 1.5.

When the combustion amount is Q _F2 and the air amount is Q _A4 which is smaller than Q _A2, m <1.5 and flame current If becomes I _{f1 and} target value I
_It is larger than _f0 . Therefore, the air amount QA is increased until If = If0 and returned to m = 1.5. The air-fuel ratio control unit 22 performs the above control, and in the present embodiment, the variation amount ΔQA of the air amount QA for returning to m = 1.5 is output as the correction control amount. On the contrary, when the amount of air is large and Q _A5 , m> 1.5 and I _f = I _f2 , and the amount of air is reduced to I _f0 . Further, when the amount of combustion was greater Q _F1 than Q _F2 air amount Q _F2 in m <1.5 next flame current becomes I _f3. Therefore, the air amount is corrected up to the air amount Q _A1 where I _f = I _f0 and m = 1.5. On the contrary, when the combustion amount is Q _F3 , the flame current becomes I _f4 , and when the air amount is reduced to Q _A3 , the flame current I _f = I _f0 . The above control is performed by the air-fuel ratio control unit 22 of FIG. 1, and the required air flow rate Q _A is controlled by the motor drive unit 21.
Is used to control the blower 13 by converting it into the rotation speed of the blower 13 to maintain the air-fuel ratio m = 1.5. Other than this method, the air-fuel ratio control may be a method of controlling the fuel supply amount so that the flame current _If becomes constant. Further, the flame current setting value I _f0 may be varied according to the amount of combustion Q _F supplied by the pump drive unit 20. Further, the detection of the combustion state can be obtained by using a signal other than the signal of the flame current _If , for example, a temperature signal of the burner 14 or a signal of a chemical combustion sensor for detecting the combustion state.

Here, the example will be described using the air-fuel ratio control described with reference to FIG. It is now assumed that the target combustion amount Q _{F2 is} Q _F1 due to variations in the fuel pump 11. Therefore, the air volume is the standard value Q
More Q _A1 than _A2 is required. This ΔQ _A = Q _A1 −Q
_A2 becomes the correction amount of the air-fuel ratio and is stored in the storage unit 23.

The value of the correction amount ΔQ _A stored in the storage unit 23 continues to be stored even after the combustion is stopped, and the sequence control is performed when the initial flame is unstable and the air-fuel ratio control unit 22 does not operate when the combustion is next started. The unit 19 switches the initial control circuit 24 to the storage unit 23 side,
Combustion is performed with an air amount Q _A1 according to ΔQ _A stored in the storage unit 23. The air amount Q _A1 is the air-fuel ratio control unit when it was previously burned.
Since it is the value obtained in step 22, the air-fuel ratio m does not fall significantly from 1.5 this time. After the flame is stabilized, the sequence control unit 19 switches the signal from the initial control circuit 24 to the air-fuel ratio control unit 22, and burns the burner 14 with a QA value according to normal air-fuel ratio control. Therefore, the initial control circuit 24 is a sequence control unit.
The signal of 19 determines the air-fuel ratio by the signal of the storage unit 23 for a certain time after the start of burner combustion, and thereafter functions as a switch for switching to normal air-fuel ratio control according to the combustion state (block in FIG. 1). See figure). At this time, a new correction value ΔQ _A is learned and stored in the storage unit 23.

Here, when the burner 14 burns for the first time, that is, when the previous stored value ΔQ _A does not exist in the storage unit 23, the storage unit 23 stores the preset air amount, that is, the standard combustion amount Q _{F2 in} FIG. It is set to burn by the air amount Q _A2 . At this time, the air-fuel ratio at the initial stage of ignition deviates from the design value, but once burned, it is learned and stored in the storage unit 23, so that the air-fuel ratio is controlled to be normal from the next time.

The correction amount ΔQ _A changes due to variations in the pump 11 and the blower 13 and external factors such as room temperature and oxygen concentration in the room. If the value stored in the storage unit 23 is an abnormal value such as an oxygen deficient state in the room, a problem will occur the next time combustion is performed under normal conditions. Therefore, in FIG.
The correction amount ΔQ _A after a lapse of a predetermined time until the burner 14 starts combustion and the combustion state stabilizes is stored, and the change in ΔQ _A thereafter is not stored. This is because immediately after the start of combustion, there is no oxygen deficiency and the external conditions are most stable. With this configuration, the stored value stored in the storage unit 23 can store a value that corrects only variations due to initial conditions such as variations in pumps and motors.

FIG. 3 shows a flow chart when the controller 17 which performs the above operation is realized by a microcomputer. The same symbols are given to the blocks that perform the operation corresponding to FIG. still,
The correction of the stored value may not be performed every time immediately after the operation, but when the stored value is once stored, the same stored value may be used until the stored data disappears due to power loss of the microcomputer. In this case, if the storage unit is configured to use a non-volatile memory, the user can always maintain the optimum air-fuel ratio by storing the stored value at the time of factory shipment.

In the present embodiment, the oil fan heater has been described as an example, but in the case of gas fuel, the same effect can be obtained by using the gas amount control valve instead of the pump 11. Further, it can be widely applied to combustors other than the fan heater.

Effects of the Invention As described above, the burner air-fuel ratio control device of the present invention has the following effects.

(1) When the combustion immediately after the combustion of the burner is unstable and the air-fuel ratio is not controlled, the pump or the pump is used to control the fuel or air amount based on the air-fuel ratio correction amount learned and stored at the previous combustion. The air-fuel ratio is maintained at the set value even if there are variations in the blower, preventing abnormal combustion and generation of harmful exhaust gas.

(2) Since there is a configuration in which the equipment automatically learns by once burning and finds the optimum point, it is possible to save man-hours for managing the initial variation of parts.

(3) Similarly, since the stored value is corrected at every combustion, even if the characteristics of parts such as the deterioration of the pump and the dust in the air passage, that is, the characteristics of the parts change over time, the optimum value is always tracked in accordance with the optimum value. The air-fuel ratio is maintained.

[Brief description of drawings]

FIG. 1 is a block diagram of an air-fuel ratio control device for a burner showing an embodiment of the present invention, FIG. 2 is a characteristic diagram for explaining the control operation of the device, and FIG. 3 is a microcomputer showing the configuration of FIG. A flow chart to be expressed, FIG. 4 is a configuration diagram for explaining a conventional example. 11 ... Fuel pump (fuel control means), 13 ... Blower (air supply means), 14 ... Burner, 16 ... Frame rod, 17 ...
... controller, 19 ... sequence control section, 22 ... air-fuel ratio control section, 23 ... storage section (storage means), 24 ... initial control circuit, 25 ... timer circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Kokawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yasushi Hirata 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A burner for burning fuel, fuel control means for controlling the amount of fuel supplied to the burner, air supply means for supplying combustion air, and a combustion sensor for detecting the combustion state of the burner, It is composed of a controller for driving the fuel control means and the air supply means, the controller is a sequence control section for controlling the operation according to a predetermined combustion sequence such as ignition control and extinguishing control, and a signal from a combustion sensor in which the burner is burning. Accordingly, an air-fuel ratio control unit for correcting and controlling the air supply unit or the fuel control unit, a storage unit for storing a correction control amount by the air-fuel ratio control unit, and until the output of the combustion sensor stabilizes after the start of combustion of the burner. A burner air-fuel ratio control device comprising an initial control circuit for controlling the air-fuel ratio of the burner in accordance with a signal from the stored value of the storage means. 2. The burner according to claim 1, wherein the storage means has a timer circuit for storing a correction control amount from the air-fuel ratio control unit after a predetermined time has elapsed after starting the combustion of the burner. Air-fuel ratio control device.