JP2833223B2 - Combustor fan motor control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fan motor of a combustor.

[0002]

2. Description of the Related Art Conventionally, in a combustor such as a gas water heater, feedforward control for determining an operation amount based on a relationship between a target rotation speed and a plurality of constants, and feedback for changing the operation amount based on the actual rotation speed. In combination with the control, the rotation speed of the fan, that is, the rotation speed of the DC fan motor is controlled. In this control method, constants are obtained by experiment for each model and stored as fixed data in the control device of each combustor, and the constants are not changed.

[0003]

However, in the conventional fan motor control method, the feed forward is controlled by the variation of the fan motor itself, the DC power supply of the fan motor, the exhaust resistance, or the secular change for each combustor. In some cases, control constants deviated significantly from appropriate values. In this case, the target rotation speed is finally controlled by the feedback control.However, it takes time for the fan rotation speed to reach the specified rotation speed at the time of pre-purge, and ignition is delayed, or in the worst case, a fan abnormality is detected. There was a problem of entering safe operation.

An object of the present invention is to provide a method of controlling a fan motor of a combustor which can change a constant of feed forward control to an optimum value.

[0005]

According to the present invention, there are provided feedforward control for determining an operation amount based on a relationship between a target rotation speed and a plurality of constants, and feedback control for changing the operation amount based on an actual rotation speed. In a fan motor control method of a combustor that controls the number of rotations of a fan in combination,
At the time of prepurge, the fan is sequentially rotated at a plurality of different rotation speeds, an optimum value of the constant is calculated based on the operation amount at each rotation speed, and the calculated constant is used as a new constant. And

[0006]

In the pre-purge, the fan is sequentially rotated at a plurality of different rotational speeds at different times. Then, the optimum value of the constant is calculated from the operation amount required to control the fan at each rotation speed, and the constant obtained by the calculation is used as a new constant. Therefore, the constant of the feedforward control can be changed to an optimum value.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram of a control device adopting a method of controlling a fan motor of a combustor according to one embodiment of the present invention.
It is connected to an input terminal of a conversion circuit 2 for converting an input pulse into a DC voltage corresponding to the pulse width. This conversion circuit 2
Is composed of an inverting amplifier 2a having hysteresis characteristics, resistors 2b and 2c, capacitors 2d and 2e, and an operational amplifier 2f. The output terminal of the conversion circuit 2 is connected to the control voltage input terminal of the power supply circuit 3, and the output terminal of the power supply circuit 3 is connected to the power supply input terminal of a fan motor 4 that drives a fan (not shown). Microcomputer 1
The output terminal of a rotation speed sensor 5 that detects the rotation speed of the fan driven by the fan motor 4 and outputs a pulse signal corresponding thereto is connected to the rotation speed signal input terminal 1b.

Next, the operation will be described. A pulse signal as shown in FIG. 2 is output from the control signal output terminal 1a of the microcomputer 1. This pulse signal has a constant period T and a pulse width WPLS that changes according to the target rotation speed and the actual rotation speed of the fan, which will be described later. The pulse signal output from the control signal output terminal 1a of the microcomputer 1 is converted by the conversion circuit 2 into a DC voltage of 0 to 5 volts according to the pulse width WPLS,
It is supplied to the control voltage input terminal of the power supply circuit 3. As a result, the power supply circuit 3 has 0 to 0 corresponding to the input voltage from the conversion circuit 2.
A DC voltage of 40 volts is supplied to the fan motor 4. Then, the fan motor 4 rotates at a rotation speed according to the voltage and the load supplied by the power supply circuit 3 to drive the fan. The rotation speed of the fan is detected by the rotation speed sensor 5 and supplied to the rotation speed signal input terminal 1b of the microcomputer 1 as a pulse signal.

The pulse width WPLS of the pulse signal output from the control signal output terminal 1a of the microcomputer 1 is
It is calculated by the following equation 1.

[0010]

(Equation 1)

WI: Integral term for correcting pulse width WPLS WS: Target rotation speed FFA: Constant FFB: Constant FFC: Constant

That is, in the equation (1), the term determined by the target rotational speed WS and the constants FFA, FFB, and FFC is a part by the feedforward control, and the constants FFA, FF
For B and FFC, values experimentally obtained for each model are stored in a memory built in the microcomputer 1. The gist of the present invention is to appropriately change the constants FFA, FFB, and FFC to optimal values, which will be described later. The integral term WI is a part based on feedback control. When a difference occurs between the target rotational speed WS and the actual rotational speed NW detected by the rotational speed sensor 5, the microcomputer 1 time-divides the difference and integrates the integral term. The control is performed so that the actual rotation speed NW matches the target rotation speed WS.
Therefore, if the constants FFA, FFB, and FFC deviate significantly from the appropriate values, the integral term WI increases, and it takes too much time for the actual rotational speed NW to coincide with the target rotational speed WS, causing the above-described inconvenience.

Next, the constants FFA and FF which are the gist of the present invention.
The operation of the microcomputer 1 when changing B and FFC will be described with reference to FIG. When the power is turned on, it is first determined in step 1 whether there is a learning request, that is, a request to change the constants FFA, FFB, and FFC. This learning request is obtained, for example, by turning on a learning request flag when the integral term WI exceeds a predetermined value and storing it in a RAM or the like with a backup power supply built in the microcomputer 1. can get. If there is a learning request in step 1, the process proceeds to step 2 to determine whether there is a combustion request, that is, whether the operation switch has been operated. If there is no combustion request in step 2, the process proceeds to step 3, where the target rotational speed WS
Is set to the pre-purge rotation speed, and the fan motor 4 is driven. At this time, no feedback control is performed, and the integral term W
I is always set to 0, and the pulse width of the pulse signal output from the control signal output terminal 1a of the microcomputer 1 according to the difference between the actual rotation speed NW detected by the rotation speed sensor 5 and the target rotation speed WS. Modify WPLS appropriately. This is because if feedback control is performed, if the constant FF
If A, FFB, and FFC deviate significantly from the appropriate values, it takes too much time for the actual rotational speed NW to match the target rotational speed WS, which causes the above-described inconvenience. The initial pulse width WPLS at this time is determined using the constants FFA, FFB, and FFC changed during the previous learning. If this is the first learning, the initial value set before leaving the warehouse is used. Next, the routine proceeds to step 4, where it is determined whether or not the actual rotational speed NW matches the target rotational speed WS and is stabilized. If the actual rotational speed NW is stable, the routine proceeds to step 5, where the current target rotational speed WS1 and the pulse width are determined. The WPLS 1 is stored in a memory built in the microcomputer 1. Next, the routine proceeds to step 6, where the target rotational speed WS is set near the maximum rotational speed, and the fan motor 4 is driven. At this time, as in step 3, the feedback control is not performed, the integral term WI is always set to 0, and the microcomputer is controlled according to the difference between the actual rotation speed NW detected by the rotation speed sensor 5 and the target rotation speed WS. The pulse width WPLS of the pulse signal output from the control signal output terminal 1a is appropriately changed. The reason is the same as in step 3. The initial pulse width WPLS at this time is the constant FF changed during the previous learning.
A, FFB, and FFC are used to determine. If this is the first learning, the initial value set before leaving the warehouse is used. Next, the routine proceeds to step 7, where it is determined whether or not the actual rotational speed NW matches the target rotational speed WS and is stabilized. If the actual rotational speed NW is stable, the routine proceeds to step 8, where the current target rotational speed WS2 and the pulse width are determined. The WPLS 2 is stored in a memory built in the microcomputer 1. Next, the routine proceeds to step 9, where the constants FFA and FF are obtained from the target rotational speeds WS1 and WS2 and the pulse widths WPLS1 and WPLS2 stored in steps 5 and 8.
Calculate the optimal values of B and FFC, and
And stored in the memory built in. That is, the target rotation speed WS and the pulse width WPLS have a relationship as shown in FIG.
When the constant FFB is fixed at 100, the relationship of the following Expressions 2 and 3 is obtained from the above Expression 1, and from this, the constant FFA is obtained as shown in Expression 4 below, and the constant FFC is obtained as shown in Expression 5 below.

[0014]

(Equation 2)

[0015]

(Equation 3)

[0016]

(Equation 4)

[0017]

(Equation 5)

The execution of step 9 terminates the learning routine and returns to the normal routine. If there is no learning request in step 1, this learning routine is terminated and the routine returns to the normal routine. If there is a combustion request in step 2, this learning routine is ended and a combustion control routine is executed. At this time, control is performed using the constants FFA, FFB, and FFC changed during the previous learning. If this is the first learning, the initial value set before leaving the warehouse is used. If it is determined in step 4 that the actual rotation speed NW matches the target rotation speed WS and is not stable, the process returns to step 4. If it is determined in step 7 that the actual rotation speed NW matches the target rotation speed WS and is not stable, the process returns to step 7.

Thus, the constants FFA, FFB, FFC
Is appropriately changed to an optimal value, so that it takes time for the fan speed to reach the specified speed at the time of pre-purge, and ignition is delayed, or in the worst case, the fan operates in a safe operation with a fan abnormality. The problem is solved. If feedback control is not performed when the constants FFA, FFB, and FFC are changed as in the present embodiment, the constant F
Even if FA, FFB, and FFC deviate greatly from the appropriate values, it does not cause such a problem that it takes too much time to enter the safe operation of the fan abnormality and interrupt the learning operation.

In the above embodiment, the constants FFA, FFB, and FFC are changed only when there is a learning request. However, the constants FFA, FFB, and FFC may be changed every time a prepurge is performed. Further, the learning request may be input manually. Further, in the above embodiment, the learning was performed by setting the target rotation speed WS at the pre-purge rotation speed and near the maximum rotation speed. This is because the optimum values of the constants FFA, FFB, and FFC are obtained more accurately. It is not necessary to do so. In addition, the present invention can of course be applied to a combustor that performs control based on a calculation formula other than the above formula (1).

[0021]

According to the present invention, there is provided the above construction.
According to the method described in the above, feed-forward control that determines the operation amount according to the relationship between the target rotation speed and a plurality of constants,
In a fan motor control method for a combustor that controls the number of rotations of a fan by combining feedback control that changes the operation amount based on the actual number of rotations,
The fan is sequentially rotated at a plurality of rotation speeds different from each other, the optimum value of the constant is calculated based on the operation amount at each rotation speed, and the constant obtained by the calculation is used as a new constant. It takes time for the number to reach the specified number of revolutions, and problems such as delaying ignition or, in the worst case, starting a safe operation with a fan abnormality are eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a control device employing a method of controlling a fan motor of a combustor according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a pulse signal output from a control signal output terminal of the microcomputer.

FIG. 3 is a flowchart illustrating the operation of the microcomputer during learning.

FIG. 4 is an explanatory diagram showing a relationship between a target rotation speed WS of a fan and a pulse width WPLS of a pulse signal output from a control signal output terminal of the microcomputer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microcomputer 2 Conversion circuit 3 Power supply circuit 4 Fan motor 5 Speed sensor

Claims (1)

(57) [Claims] The control of a fan speed by combining feedforward control for determining an operation amount based on a relationship between a target rotation speed and a plurality of constants, and feedback control for changing the operation amount based on an actual rotation speed. In the method of controlling the fan motor of the combustor, the fan is sequentially rotated at a plurality of rotation speeds different from each other at the time of prepurge, and the optimum value of the constant is calculated based on the operation amount at each rotation speed. A method for controlling a fan motor of a combustor, wherein a constant is used as a new constant.