JP2551290B2 - Combustion device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forced ventilation type combustion device having a combustion fan for supplying combustion air.

[0002]

2. Description of the Related Art Conventionally, a combustion fan in a forced ventilation type combustion device is subject to variations in product accuracy during mass production.
Since the relationship between the control voltage and the number of revolutions is not constant, in a combustion fan in which the number of revolutions for the control voltage is within the prescribed standard range, the upper limit performance to obtain the prescribed number of revolutions with the lowest control voltage within the allowable range. Process of product design of a combustion device using an upper limit fan with a lower limit fan with a lower limit performance to obtain a predetermined rotation speed at the highest control voltage within an allowable range, and a standard fan with a standard performance The operation was confirmed by experiments, and the relational expression of the feedforward control of the rotation speed with respect to the control voltage (calculating the FF control amount V _FF ) and the relational expression of the feedback control based on the detected rotation speed (FB
The PI constant of (calculating the control amount V _FB ) is determined, and a constant relational expression and PI constant are applied to all the combustion fans.

For example, the equation for obtaining the control voltage V of the combustion fan in the usage range when it is used in a combustion device is expressed as follows. V = V _FF + V _FB = a · Rs + b + Kp (Rs −R) + (1 / K _I ) Σ {Kp (Rs −R)} where V _FF = a · Rs + b V _FB = Kp (Rs −R ) + (1 / K _I ) Σ {K p (Rs −R)} a, b: constants of the relational expression of feedforward control, K _I : I (integral) constant, Kp: P (proportional) constant, Rs: combustion Rotation speed of the combustion fan, R: detected rotation speed of the combustion fan.

[0004]

However, in the conventional control of the combustion fan, the constant relational expression and PI constant are applied to all the combustion fans.
The number of revolutions corresponding to the control voltage V of the combustion fan, which is calculated and supplied by the above formula, that is, the amount of air blown per unit time differs depending on the individual fan, and during the pre-purge operation performed immediately before ignition of the combustion device. In order to secure the air flow required for reliable pre-purge, the operating time is set in consideration of the fan with the lowest rotation speed corresponding to the control voltage V, that is, the fan with the lowest air flow per unit time. As a result, the pre-purge operation will stabilize from the start of the pre-purge operation to the target rotation speed at which the ignition operation can be performed, and the pre-purge operation time until the completion of the pre-purge will be set to be long in consideration of safety. There is a problem that the ignition operation is delayed because the time is long.

An object of the present invention is to correct the ignition amount by correcting the feedforward control amount based on the time from the start of the pre-purge operation to the stabilization of the target rotation speed for each combustion fan and the control voltage at that time. An object of the present invention is to provide a combustion device capable of smoothly controlling a combustion fan without causing a delay.

[0006]

In order to achieve the above object, the combustion apparatus of the present invention comprises a combustion fan for adjusting the rotation speed by controlling the supply voltage, and a controller composed of a microcomputer or the like. in the combustion apparatus, the time T ₁ of the and the combustion fan reaches the target speed from the time of pre-purge startup is the maximum time allowed for pre-purge operation predetermined value Tmax. When it exceeds, the measured voltage value V ₂ supplied to the combustion fan and the initial voltage value V ₁ which is calculated corresponding to the target rotation speed Rs and is the feedforward control amount V _FF supplied at the beginning are set. Compare and the difference Δ
v, the feedforward control amount V _{FF after that}
(For example, V _FF = A · Rs + B) is changed (for example, V _FF = A · Rs + B is changed to V _FF = A · Rs +).
Change to C. However, C = B + Δv), the initial voltage value V ₁₁ which is the feedforward control amount V _FF corresponding to the target rotation speed required for the combustion fan at the time of the next operation start is calculated by the above-mentioned arithmetic expression and supplied, When the combustion fan reaches the target rotation speed smoothly for a predetermined time Tmax. It is possible to perform the pre-purge operation in the inside and perform the voltage control corresponding to the variation in the characteristics of the individual fans at the time of mass production.
On the other hand, the combustion fan has been
Predetermined time T ₁ to reach the number of turns is the maximum allowable time
The value Tmax. When it is less than,
The word control amount V _FF is not changed.

[0007]

Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a hot water supply device will be described as an example of the combustion device. The hot water supply device 1 includes a heat exchanger 2 arranged above, a combustor 3 arranged below the heat exchanger 2, and a lower part of the combustor 3. The combustion fan 4 disposed in the intake passage is provided in a casing 5 having an exhaust port 51 in the upper part, and an ignition plug 6 and a flame rod 7 are provided in the vicinity of the combustor 3.

An inlet 21 and an outlet 22 are connected to the heat exchanger 2, and the inlet temperature sensor 8 and the water amount sensor 9 are connected to the inlet 21.
The hot water outlet temperature sensor 10 is provided in the hot water outlet passage 22, and the detection signals from the hot water temperature sensor 8, the water amount sensor 9, and the hot water temperature sensor 10 are input to a controller 11 such as a microcomputer. Based on the detection signal, the controller 11 outputs a control signal to the capacity switching valve 31 and the proportional control valve (not shown) provided in the gas supply passage 30 connected to the combustor 3.

Further, the combustion fan 4 is provided with a rotation speed detection sensor 41, and the detection rotation speed R from the rotation speed detection sensor 41 is input to the controller 11 and required for combustion in the combustor 3. The target rotation speed Rs corresponding to the air flow rate is obtained, the FF control amount V _FF by feedforward control is calculated based on the target rotation speed Rs, and the deviation (Rs-R) between the target rotation speed Rs and the detected rotation speed R is calculated. FB control amount V _FB by feedback control is calculated based on
V _FF + V _FB is output to the combustion fan 4, and the combustion fan 4
Control the rotation speed of.

The control voltage V of the combustion fan 4 is calculated by the following equation. V = V _FF + V _FB where V _{FF is a} feed forward (FF) control amount, V _{FB is a} feedback (FB) control amount,

Next, the control operation will be described. The relationship between the ideal standard fan control voltage V conforming to the standard and the target rotation speed Rs is represented by the FF control amount V _FF = A · Rs + B in the usage range, as shown in FIG. ,
At the start of the first operation after the water heater 1 is installed, the FF control amount V _FF = A · Rs + B (A, B) which is the characteristic of the standard fan.
Is a constant), and the FF control amount V _FF = V corresponding to the target prepurge rotation speed R _S1 (equal to the ignition rotation speed R ₁ ).
₁ (initial voltage value) is supplied to the combustion fan 4 to start it.

When mass-producing combustion fans, the characteristics of the individual combustion fans produced vary, so the FF control amount V _FF based on the characteristics of the standard fan (FIG. 2), that is, the initial voltage value V ₁ Is supplied to the combustion fan 4, the rotation speed R increases with the characteristics shown in FIGS. 3 and 4,
When the rotation speed R exceeds the target prepurge rotation speed R _S1 , the control voltage V is lowered from the initial voltage value V _1, and the control voltage V is adjusted until the target prepurge rotation speed R _S1 is obtained, and the time T ₁
The measured voltage value V ₂ (V ₂ = V ₁ + Δv, where Δv is the difference between the first initial voltage value V ₁ and the measured voltage value V ₂ ) at which the control voltage V is different from the initial voltage value V ₁ after the lapse of time is the rotation speed R. Stabilizes at the target prepurge rotation speed R _S1 (ignition rotation speed R ₁ ) (for example, in FIG. 4, the voltage difference Δv = V ₂ −V ₁ is negative).

Here, the time T ₁ during which the rotation speed R stabilizes at the target prepurge rotation speed R _S1 is compared with the maximum allowable prepurge operation time Tmax. If T ₁ > Tmax. the difference between V ₁ and the actual measurement voltage value V ₂ Δv (Δv = V ₂
(-V ₁ = V-V _FF = V _FB , that is, the amount corrected by feedback) is stored, and the target pre-purge rotation speed R _S1 is equal to the ignition rotation speed R ₁ as described above, so that the combustion fan 4 has an ignition rotation speed. The number R ₁ is reached, the ignition operation is performed as it is, and after the ignition is detected, the arithmetic expression of the FF control amount V _FF is changed to V _FF = A · Rs + C (however, C = B + Δv),
Shift to steady-state combustion operation, and FF when starting operation from the next time
The voltage calculated by the control amount V _FF = A · Rs + C is supplied.

On the other hand, when T ₁ ≤Tmax., The value of the difference Δv between the FF control amount V _FF = V ₁ and the control voltage V ₂ is small, and the target prepurge rotation speed R _S1 is quickly stabilized. Therefore, it is not necessary to correct the arithmetic expression of the FF control amount V _FF , and the prepurge operation is performed for the minimum required prepurge operation time Tmin.

FIG. 6 is a flow chart of the above-mentioned operation control operation, and shows the control operation when the target prepurge rotation speed R _S1 is equal to the ignition rotation speed R ₁ , namely, the target prepurge rotation speed R _S1 and the ignition rotation speed R ₁ . Is different, the rotation speed of the combustion fan is changed to the ignition rotation speed R ₁ after the prepurge operation is completed, and then the ignition operation is started.

Although the present invention has been described with reference to the embodiments applied to the water heater, the present invention is not limited to the water heater, and is applied to heating devices, boilers, furnaces and other general combustion devices. Of course, you can do that.

[0017]

Since the present invention is configured as described above, the feedforward is performed based on the time from the start of the pre-purge operation to the stabilization of the target rotation speed for each combustion fan and the control voltage at that time. By correcting and supplying the control amount, the combustion fan smoothly reaches the target rotation speed and performs pre-purge operation within a predetermined time, and voltage control corresponding to the variation in the characteristics of each fan during mass production Therefore, the combustion fan can be smoothly controlled without causing ignition delay.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a hot water supply device to which a combustion device according to the present invention is applied.

FIG. 2 is a characteristic diagram showing a relationship between a target rotation speed of a standard fan and a control voltage.

FIG. 3 is an example of a change over time in the number of revolutions of the combustion fan from the start-up.

FIG. 4 is an example of a change with time of a control voltage from the time of rising of a combustion fan.

FIG. 5 is a characteristic diagram showing a relationship between a target rotational speed of a combustion fan after correction and a control voltage.

FIG. 6 is a flowchart of control operation.

[Explanation of symbols]

 1 Water heater 2 Heat exchanger 3 Combustor 4 Combustion fan 5 Casing 11 Controller

Claims (1)

(57) [Claims] 1. In a combustion device having a combustion fan, when the time from the startup of the pre-purge to the target rotation speed of the combustion fan exceeds a predetermined value which is a maximum allowable time , the combustion fan is supplied to the combustion fan. a control voltage that is one compares the initial voltage value and a feedforward control amount supplied to the beginning corresponding to the target rotation speed, by the difference, to change the subsequent feed-forward control amount arithmetic expression
On the other hand, the combustion fan has set the target rotation from the start of prepurge.
If the time to reach the number is less than the specified value,
A combustion device characterized in that the feedforward control amount afterward is not changed .