JP2800394B2 - Combustion control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device that detects an abnormality in a combustion state of a combustion device using gas, petroleum, or the like and stops the combustion device.

2. Description of the Related Art Generally, when gas or oil is burned as fuel, stable combustion can be maintained by optimizing the ratio of fuel to air and supplying the fuel. The ratio between the fuel and the air amount is called an air-fuel ratio. If the air-fuel ratio is inappropriate, there is a risk that flashback, misfire, or incomplete combustion may occur.

Conventionally, a combustion control device that detects an abnormality in a combustion state and stops the operation has detected an abnormality in the air-fuel ratio and stops the combustion. For example, according to Japanese Unexamined Utility Model Publication No. 61-89649, a flame rod 2 is provided near a burner 1 as shown in FIG. Circuit 3
If the flame current value of the flame current supply circuit 3 does not reach the predetermined level 4 after a lapse of a predetermined time from the start of the ignition operation, the judging means 5 judges that an abnormal combustion state has occurred and performs a digestion operation or the like.

Problems to be Solved by the Invention In such a conventional combustion control device, the flame current and the air-fuel ratio have characteristics shown by a solid line in FIG. The horizontal axis represents the primary air ratio μ. Here, if the air-fuel ratio is described as the primary air ratio μ, the flame current If has a distribution having a peak at μ = μ ₀ (μ ₀ is approximately 0.8 to 0.9). Burner 1 differs Stable primary air ratio can be maintained by constituting the optimum combustion state, for example, with the configuration to maintain optimum combustion state in the vicinity of mu = mu _a, as shown in dashed line in FIG. 5 CO In some cases, it is a characteristic of occurrence. In this case, to prevent CO generation, μ = μ ₂ ~
detecting an abnormal combustion outside the scope of mu _1, although want to do digestion operation, the decision means 5 in the configuration as described above
The level to have only one, mu = flammable range and set the level the If ₁ corresponding to mu ₁ are those performs narrow frequently digestion operation, the level corresponding to μ = μ ₂ If ₂
With the setting can not detect abnormal combustion condition in μ> μ _1,
There was a problem that it was not possible to correctly distinguish normal combustion from abnormal combustion.

An object of the present invention is to solve such a conventional problem, and it is an object of the present invention to correctly determine normal combustion and abnormal combustion regardless of the burner configuration and to ensure safety.

Means for Solving the Problems To achieve the above object, the present invention provides a burner that burns fuel, a fuel supply unit that supplies fuel to the burner, a frame rod inserted into a combustion flame, and the flame rod. A safety circuit section for detecting abnormal combustion and stopping the fuel supply means, wherein the safety circuit section changes a supply amount of the fuel supply means by a predetermined amount and detects a flame current detected by the flame rod at that time. A state determining unit for determining a combustion state based on a change; and an air excess setting value for determining a predetermined excess air abnormality and an excess fuel setting value for determining an abnormality due to excess fuel. A comparison unit that employs any one of them as a set value by a signal and compares whether the flame current detected by the frame rod is equal to or less than a set value, and a signal from the comparison unit. It is an object of the present invention to provide a stopping means for stopping the fuel supply means when the flame current is equal to or less than a set value.

According to the present invention, according to the problem solving means described above, the state determination unit changes the supply amount of the fuel supply means, and determines whether it is in the air excess state or the fuel excess state by the flame current detected by the frame rod at that time, According to the judgment of the state judging unit, the comparing unit compares either the excess air set value or the excessive fuel set value with the flame current as a set value, and if the flame current is equal to or less than the set value, the stop unit stops the fuel supply means. Burner digestion can be performed.

Embodiment An embodiment of the present invention will be described below with reference to FIG. This embodiment is an oil combustor using kerosene as fuel and has the characteristics shown in FIG.

As shown in the figure, a pump (fuel supply means) supplies fuel oil to a carburetor 8 preheated by a heater 7. The burner fan 9 supplies air to the carburetor 8, mixes the air with fuel oil, and burns on the surface of the burner 1. The safety circuit unit 10 stops the pump 6 when the combustion becomes abnormal, and extinguishes the flame.
Detects the flame current If flowing through the circuit. The state determination unit 12 is the pump 6
Is changed by a predetermined amount, and the combustion state is determined based on the change in the flame current If at that time. The comparison unit 13 sets If ₁ to an excess air set value 14 for determining an abnormality due to a predetermined excess air.
Excess fuel set value for determining abnormalities due to excess fuel
15 has If ₂ , one of which is adopted as a set value according to a signal of the state determination unit 12, and this set value is compared with the output of the flame current detection circuit 11. When the flame current is equal to or less than the set value according to the signal from the comparing unit 13, the stopping unit 16
The pump 6 is stopped.

The operation will be described with reference to FIG. 2 in the above configuration. When a predetermined time has elapsed after the start of combustion, the detection starts when the combustion is stabilized. A flame current If flowing from the flame rod 2 to the burner 1 is detected by a flame current detection circuit 11. Here, with the rotation speed of the burner fan 9 fixed, that is, with the supply air amount kept constant, the state determination unit 12 slightly increases the oscillation frequency of the pump 6. The pump 6 has an oscillation frequency substantially proportional to the fuel supply amount. When the oscillation frequency is slightly increased, the fuel supply amount increases, and the primary air ratio μ decreases.
Here, if increasing the flame current If mu> mu ₀ and is determined, it is determined that the mu <mu ₀ A decrease If is. The above determination is made by the state determination unit 12 and a signal is transmitted to the comparison unit 13. The comparison unit 13 adopts If ₁ as the set value If _s if μ <μ ₀ is determined by the state determination unit 12 and sets If _s = If ₁ , and if μ> μ ₀ , sets If ₂ as the set value If _s adopted and If _s = If _2. Since then
If the flame current If becomes If <If _s has stops 16 as abnormal combustion stops digesting pump 6.

As described above, in the embodiment described above, the state determination unit 12 initially sets μ <
was performed mu ₀ or mu> mu ₀ judgment, but may be periodically determined every predetermined time. In this case, a change in state during combustion can be detected, and the accuracy of the determination can be improved.

Next, another embodiment of the present invention will be described with reference to the flowchart shown in FIG. In this case, the comparison unit 13
The case of the If> the If ₁ is normal, and in the case of the If <the If ₂ stop unit 16 stops the pump 6 as an abnormal. If ₂ <If <If ₁
In this case, the state determination unit 12 slightly increases the oscillation frequency of the pump 6. Performs similarly mu <mu ₀ or mu> mu ₀ of determination in the above embodiment than the change in the flame current If at this time, when it becomes mu> mu ₀ to stop the pump 6 is determined to be abnormal. μ
<The case where a mu ₀ the If> normally as long as the If _2, after a re _{If> If 1, If 2 <} If < condition determining section 12 if the the If ₁ is μ <μ _0, μ > carry out the μ ₀ of the judgment. In this embodiment, the operation frequency of the state determination unit 12 is reduced, so that it is possible to accurately determine whether the state is normal or abnormal.

In the above embodiment, the state determination unit 12 slightly increases the oscillation frequency of the pump 6 to determine μ <μ ₀ , μ> μ ₀ ,
Judgment is possible even if the oscillation frequency of the pump 6 is slightly reduced.
In this case, if the logic is reversed and If increases, μ <
If μ ₀ and If decrease, μ> μ ₀ .

In this embodiment, an oil combustor has been described as an example, but gas fuel can be easily realized by using gas proportional valve control instead of a pump.

Effect of the Invention As is apparent from the above embodiment, according to the present invention, there are two levels of a predetermined excess air setting value and a predetermined excess fuel setting value, and one of the two levels is set by a signal from the fuel control unit. Since the fuel supply means is stopped when the flame current is equal to or less than the set value, it is possible to determine whether the air is excessive or the fuel is excessive, and detect abnormal combustion at different set values. It is possible to provide a safe combustor that can accurately determine whether the combustion is normal or abnormal.

[Brief description of the drawings]

FIG. 1 is a block diagram of a combustion control device according to one embodiment of the present invention, FIG. 2 is a flowchart of the combustion control device, FIG. 3 is a flowchart of a combustion control device of another embodiment of the present invention, FIG. Is a block diagram of a conventional combustion control device, and FIG. 5 is a characteristic diagram of a combustor. DESCRIPTION OF SYMBOLS 1 ... Burner, 2 ... Frame rod, 6 ... Pump (fuel supply means), 10 ... Safety circuit part, 12 ... State determination part, 13 ... Comparison part, 14 ... Air excess set value, 15 ... Excess fuel set value, 16 ... Stop part.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Takiguchi 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-159030 (JP, A) JP-A-62- 9118 (JP, A) Hikaru 1-123055 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23N 5/12

Claims (1)

(57) [Claims] 1. A burner for burning fuel, fuel supply means for supplying fuel to the burner, a frame rod inserted in a combustion flame, and abnormal combustion detected by the flame rod to stop the fuel supply means. A safety circuit unit, wherein the safety circuit unit changes a supply amount of the fuel supply unit by a predetermined amount, and determines a combustion state based on a change in a flame current at that time; and a predetermined abnormality caused by excess air. The flame current detected by the flame rod detected by the flame rod has two levels of an excess air set value for determining the excess air and an excess fuel set value for determining an abnormality due to the excess fuel. And a stop unit for stopping the fuel supply means when the flame current is equal to or less than a set value according to a signal from the comparison unit. The control device.