JPH07167424A - Method and device for controlling fan for forced blower type combustion apparatus - Google Patents

Abstract

PURPOSE:To enable a combustion to be always kept at the most suitable mixing ratio by a method wherein a driving current attained when the number of revolution of a fan motor is coincided with a predetermined number of revolution is defined as a reference current value of the fan motor and subsequently the fan motor is controlled in such a way that this reference current value may be maintained. CONSTITUTION:A fuel control part 15 feeds a voltage setting signal giving a reference current to a voltage comparing part 12, wherein this voltage setting signal is compared with a DC voltage outputted from a current converting part 11 and then its error signal is sent to a pulse width control part 10. The pulse width controlling part 10 controls a pulse width of a pulse waveform signal outputted in response to the error signal sent from the voltage comparing part 12, causes a DC voltage outputted from the DC converting part 11 to be variable, thereby a feed-back control is carried out in such a way that the driving current for the fan motor 7 may coincide with the reference current. As a result, the driving current for the fan motor 7 is kept at the reference current corresponding to the set number of revolution giving the most suitable air feeding amount and then combustion can be always carried out under the most suitable mixing ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan control method and apparatus for a forced air combustion system in which combustion air is forcibly supplied by a fan and mixed with fuel such as gas or oil for combustion.

[0002]

2. Description of the Related Art For gas and oil burning equipment such as a water heater, a so-called forced air type combustion device is widely used in which air is forcibly blown by a fan to burn and exhaust gas is exhausted to the outside. Has been. In this forced air blowing type combustion device, if the air supply and exhaust are blocked by the back wind that enters from the exhaust port, there are problems such as incomplete combustion, and in the worst case, the back wind blows out the combustion flame. It happened.

In the conventional forced air blowing type combustion device, in order to solve these problems, when the driving current is kept constant, if the load of the fan motor is reduced by the back wind, the rotation speed of the fan depends on the characteristics of the motor. The fan motor drive current is controlled to a predetermined constant value that corresponds to the gas supply amount, and the fan motor speed is automatically increased during backwind to keep the supply air amount constant. The method of controlling so that it is adopted. With this control method, the rotation speed of the fan motor automatically rises when headwind occurs, so the amount of air supply and exhaust is kept constant,
Stable combustion can be secured.

[0004]

However, when the drive current of the fan motor is controlled so as to be maintained at a predetermined constant value corresponding to the gas supply amount as in the conventional case, even if the drive current is the same, the difference in ambient temperature is different. Therefore, there is a problem that the rotation speed of the fan motor is different. For example, comparing 5 ° C. and 40 ° C., the number of revolutions at 40 ° C. is higher by 15 to 20% than at 5 ° C. Further, even if the ambient temperature is the same, there is a problem that the characteristics differ for each fan motor and the rotation speed for the same drive current differs for each fan motor.

Therefore, even if the drive current of the fan motor is preset to a predetermined value corresponding to the gas supply amount, the rotation of the fan motor with respect to the same drive current may change due to changes in ambient temperature and differences in characteristics of individual fan motors. Since the numbers are different, the amount of supplied air becomes excessive and deficient, and there is a problem that combustion is not performed at the optimum mixing ratio.

The present invention has been made to solve the above problems, and its object is to prevent headwinds even if the ambient temperature changes, the characteristics of individual fan motors differ. Even so, it is an object of the present invention to provide a fan control method for a forced air combustion device that can maintain combustion at an optimum mixing ratio.

[0007]

In order to solve the above problems, a fan control method of the present invention sets a rotation speed of a fan motor corresponding to an amount of supplied gas, and the rotation speed of the fan motor is set to the set rotation speed. Is detected and stored as a reference current value for optimum combustion air supply, and thereafter, the fan motor drive current is controlled so as to match the reference current value. Further, the set rotation speed of the fan motor is updated each time the supply gas amount is changed.

Further, when the supply gas amount is updated, an error between the reference rotation speed corresponding to the supply gas amount before the change and the actual detected rotation speed before the change is obtained, and the changed supply gas is calculated based on the error. It is characterized in that the reference rotation speed corresponding to the amount is corrected, and the corrected rotation speed is set as a new set rotation speed for the changed supply gas amount.

Further, according to the first fan control device of the present invention, the drive current control means for controlling the drive current of the fan motor, the rotation speed detection means for detecting the rotation speed of the fan motor, and the drive current flowing through the fan motor. Based on the rotation speed detection signal of the rotation speed detection means and the detection drive current signal of the drive current detection means, the rotation speed of the fan motor becomes a set rotation speed corresponding to the supply gas amount. The drive current at the time of coincidence is detected and stored as a reference current value of the drive current corresponding to the supply gas amount at that time, and a combustion control means for sending a voltage setting signal giving the reference current value to the drive current control means, The drive current control means compares the voltage setting signal given from the combustion control means with the drive voltage applied to the fan motor to determine the drive voltage of the fan motor. And controls to match the serial voltage setting signal.

The second fan control device of the present invention is
Drive current control means for controlling the drive current of the fan motor, rotation speed detection means for detecting the rotation speed of the fan motor, drive current detection means for detecting the drive current flowing through the fan motor, and rotation of the rotation speed detection means. A current setting signal to the drive current control means when the number of rotations of the fan motor matches the setting number of rotations corresponding to the supply gas amount is stored based on the number detection signal, and the stored current setting signal is used to drive the stored current setting signal. Combustion control means for sending to the current setting means, wherein the drive current control means compares the current setting signal given from the combustion control means with the detected drive current signal detected by the drive current detection means. The driving current of the motor is controlled so as to match the current setting signal.

[0011]

According to the fan control method of the present invention, the drive current of the fan motor when the fan motor coincides with the set rotational speed corresponding to the supply gas amount is set as the subsequent reference current value. Therefore, even if the ambient temperature changes, even if the characteristics of individual fan motors differ, or even if headwind occurs, it is possible to send the optimum combustion air corresponding to the amount of supply gas at that time, Combustion can always be performed with an optimum mixing ratio. Further, when the supply gas amount is changed, the set rotational speed is updated each time, so that even if the supply gas amount changes, optimum combustion can always be maintained.

Further, when the supply gas amount is changed, correction is added based on an error between the reference rotation speed corresponding to the supply gas amount before the change and the actual detected rotation speed before the change, so that the supply after the change is performed. Set a new set speed for the gas amount. Therefore, even if the amount of supply gas is changed, it is possible to perform combustion at an optimum mixing ratio according to the actual rotation condition. Further, in the case where the drive current of the fan motor is controlled to the constant reference current value as in the present invention, when the back wind occurs, the influence thereof appears as a change in the rotation speed of the fan motor 7. Therefore, when the backwind is acting, the correction is performed using the actual rotation speed changed by the backwind, so that the optimum amount of combustion air can be supplied even if the backwind is acting.

Further, in the case of the first fan control device of the present invention, the drive voltage of the fan motor is calculated by comparing the voltage setting signal given from the combustion control means with the drive voltage of the fan motor applied to the fan motor. By controlling and matching the drive current of the fan motor with the reference current value, optimum combustion can be automatically realized.

Further, according to the second fan control device of the present invention, the drive current of the fan motor is compared by comparing the current setting signal given from the combustion control means with the detected drive current signal detected by the drive current detection means. Is controlled to match the drive current of the fan motor with the reference current value, the structure of the combustion control means can be further simplified.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention. In the figure, 1 is a gas burner, 2 is a heat exchanger, and a gas proportional valve 3 for controlling the flow rate of gas is connected to the gas burner 1. On the other hand, a water inlet temperature sensor 4 and a water flow sensor 5 are connected to the water inlet side of the heat exchanger 2, and a hot water temperature sensor 6 is connected to the hot water outlet side.

Reference numeral 7 is a fan motor for sending combustion air to the gas burner 1, 8 is a rotation sensor for detecting the rotation speed of the fan motor, 9 is an AC / DC comparator for converting AC power supply voltage to DC power supply voltage, and 10 is AC / DC comparator 9
A pulse width control unit for variably controlling and outputting a DC power supply voltage sent from a pulse waveform signal having a predetermined pulse width, 11 converts the pulse waveform signal output from the pulse width control unit 10 into a DC voltage, It is a DC converter that supplies a drive voltage to the fan motor 7.

Reference numeral 12 is a voltage comparison unit that compares the output voltage of the DC conversion unit 11 with the voltage setting signal given from the combustion control unit 15, detects the error signal thereof, and sends it to the pulse width control unit 10. The circuit composed of these reference numerals 10 to 12 constitutes the drive current control unit 13 of the fan motor 7.

Reference numeral 14 is a drive current detecting portion for detecting a drive current flowing through the fan motor 7, 15 is a combustion control portion composed of a microcomputer for controlling the operation of the entire apparatus, and 16 is various operation keys and indicators. It is an operation unit composed of. The internal ROM 17 of the combustion control unit 15
Stores the reference rotation speed of the fan motor 7 that gives the optimum supply air amount corresponding to each gas supply amount. The reference rotation speed stored in the built-in ROM 17 gives the set rotation speed of the fan motor when there is no wind.

Next, the operation of the above embodiment will be described with reference to the flow chart of FIG. First, after operating the keys and switches of the operation unit 16 to set the hot water temperature and the like (step S
1, S2), when the hot water supply tap (not shown) is opened, the combustion control unit 15 supplies the amount of supply gas for obtaining the set hot water temperature based on the water temperature signal from the water temperature sensor 4 and the water flow signal from the water flow sensor 5. Is calculated, and the optimum supply gas amount for giving the set hot water temperature at that time is determined (step S3). This supply gas amount is calculated by a calculating device such as a microcomputer, and is supplied gas amount = (set hot water temperature−inlet temperature) × (inlet amount)
It is obtained by calculating x (efficiency).

The combustion control unit 15 controls the opening of the gas proportional valve 3 so that the supply gas amount is determined as described above, ignites the gas burner 1, and at the same time the built-in ROM 17 changes the supply gas amount to the determined supply gas amount. The reference rotation speed of the corresponding fan motor 7 is read, and the read reference rotation speed is determined as the set rotation speed (step S4).
Is started to reach the set rotational speed.

When the drive of the fan motor 7 is started as described above, the combustion control unit 15 confirms that the supply gas amount has not changed (step S5), and then the current operating state is controlled to the constant rotation speed. It is determined whether it is the mode or the constant drive current control mode (step S6). If the fan motor 7 has just started to be driven, the fan motor 7 has not yet reached the set rotation speed, and therefore the process proceeds to rotation speed control (step S7). Further, when the steady operation by the constant drive current control described later is started, the process proceeds to step S14.

When the processing shifts to the step S7 side by the determination in the above step S6, the combustion control section 15 monitors the rotation speed of the fan motor 7 from the rotation pulse signal output from the rotation sensor 8 (step S8), Fan motor 7
It is determined whether or not the number of rotations of No. 1 matches the set number of rotations determined above.

When the rotation speed of the fan motor 7 rises and coincides with the determined set rotation speed, the combustion control unit 15 responds the detected current signal sent from the drive current detection unit 14 at that time to the set rotation speed. It is detected as a reference current value of the drive current to be stored and stored in an internal RAM (not shown) (step S9).

When the reference current value is detected and stored as described above, the processing shifts to the constant drive current / current control mode (step S10) to maintain the drive current of the fan motor 7 at the reference current value. Feedback control is performed (step S11).

That is, the combustion control unit 15 sends a voltage setting signal giving the reference current value of the detected and stored drive current to the voltage comparison unit 12, and the voltage comparison unit 12 outputs the voltage setting signal and the DC conversion unit 11 from the voltage setting signal. The output DC voltage is compared and the error signal is sent to the pulse width control unit 10.
The pulse width control unit 10 controls the pulse width of the pulse waveform signal output based on the error signal sent from the voltage comparison unit 12, and changes the DC voltage output from the DC conversion unit 11, Feedback control is performed so that the drive current of the fan motor 7 matches the reference current value.

As a result, the drive current of the fan motor 7 is maintained at the reference current value corresponding to the set rotational speed that gives the optimum supply air amount, so that the characteristics of the individual fan motors and the ambient temperature of the operating environment differ. Also, combustion can be performed at an optimum mixing ratio. The temperature of the hot water discharged from the heat exchanger 2 is detected by the hot water temperature sensor 6, and is fed back to the combustion control unit 15 to control the opening of the gas proportional valve 3 so that the hot water temperature is always set. To be done.

Further, even if the load of the fan motor 7 is reduced by the back wind and the amount of blown air is reduced accordingly, and the amount of air supplied to the gas burner 1 is about to be reduced, the drive current of the fan motor is constant at the reference current value. To be maintained at
The rotation speed of the fan motor 7 is automatically increased by the amount of reduction of the load due to the back wind, the decrease in the amount of air supplied to the gas burner 1 is prevented, and stable combustion is maintained even during the back wind.

In step S8, it is extremely difficult in practice to completely match the rotation speed of the fan motor 7 with the set rotation speed. Therefore, when actually configuring the device, a value when the rotation speed of the fan motor 7 falls within a predetermined allowable range with respect to the set rotation speed, for example, ± 0.5.
The value when it falls within the range of ± 2% may be regarded as the reference current value of the drive current and stored. This permissible range is determined depending on the magnitude of the set rotation speed. For example, when the set rotation speed is 1000 rpm, ± 2% and 4000 r
In the case of pm, it is set to ± 0.5% or the like.

When the supply gas amount is changed during the steady operation in the constant drive current control mode, it is detected in step S5, and the process proceeds to step S12, and the changed supply is performed. A process of setting a new set speed corresponding to the gas amount is performed.

That is, when the supply gas amount is changed, the combustion control unit 15 reads out a new reference rotational speed of the fan motor 7 corresponding to the changed supply gas amount from the built-in ROM 17, and at the same time, supplies the supply gas before the change. An error between the reference rotation speed with respect to the gas amount and the actual rotation speed of the fan motor 7 before the change is calculated, and the correction rate α = (old detection rotation speed−old reference rotation speed) based on the obtained error. / (Old reference rotation speed) is calculated, and the rotation speed is corrected by multiplying the correction rate α by the reference rotation speed for the new supply gas amount read from the built-in ROM 17, and the corrected reference rotation speed is calculated. It is determined as a new set rotational speed corresponding to the changed supply gas amount (step S12).

After the new set rotational speed is determined, the rotational speed control mode for detecting a new reference current value is entered again (steps S13, S6, S7), and in the same manner as described above. The reference current value of the drive current corresponding to the new set rotation speed is detected and stored (steps S8 to S).
9).

In this way, even when the supply gas amount is changed, the optimum air amount corresponding to the changed supply gas amount is quickly supplied, and stable combustion can be achieved within a very short time. You can The amount of gas supplied to the gas burner 1 always changes depending on the amount of water flow and the temperature of the water,
As described above, since the set rotation speed of the fan motor 7 changes rapidly with respect to the change in the supply gas amount, it is possible to always maintain optimum combustion even if the supply gas amount changes.

Further, when the supply gas amount is changed at the time of headwind, if the reference speed read from the built-in ROM 17 is determined as the new set speed of the fan motor 7 as it is, the amount of air supply corresponding to the headwind is supplied. Will run out. However, in the present invention, such a problem can be solved by the correction processing in step S12.

That is, in the case of the present invention, the fan motor 7
Since the drive current is controlled to a constant reference current value, the number of rotations of the fan motor 7 changes when a back wind occurs. Therefore, it is possible to detect the occurrence of backwind by the change in the rotation speed of the fan motor 7. And the fan motor 7
The amount of change in the number of revolutions indicates the strength of the headwind. Since the correction rate α in step S12 is calculated using the actual rotation speed of the fan motor 7 that has changed due to this backwind, the new set rotation speed obtained by multiplying the correction rate α is the strength of the backwind at that time. The set number of revolutions is set by inserting, and as a result, the optimum amount of combustion air can be supplied even when headwind occurs.

Further, during the steady operation by the constant drive current control, the actual rotation speed of the fan motor 7 may be lower than the reference rotation speed, or the drive current may be decreased due to a calculation error due to the correction process (step S12). Even if the rotation speed of the fan motor 7 is increased in response to headwinds while keeping the reference current value constant, the detected rotation speed may fall below the reference rotation speed for some reason as the rotation speed changes. Something may happen. Therefore, in such a case, by detecting this in step S15, returning the processing to the steps S7 and S8 side once, and resetting the reference current value of the drive current again, the rotation speed is always higher than the reference rotation speed. It is controlled so that it can be maintained.

FIG. 3 is a block diagram of the second embodiment of the present invention. The second embodiment is different from the first embodiment in that the current comparing section 12 'is used in place of the voltage comparing section 12 in the driving current control section 13, and the detected current sent from the driving current detecting section 14 is used. The point is that the signal is directly sent to the current comparison unit 12. The same or corresponding parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The operation of the above-mentioned different parts will be briefly described. The combustion controller 15 monitors the rotation speed of the fan motor 7 by the rotation pulse signal from the rotation sensor 8,
The current setting signal to the current comparison unit 12 'is gradually changed. Then, when the rotation speed of the fan motor 7 matches the set rotation speed corresponding to the supply gas amount at that time, the current setting signal given from the combustion control unit 15 to the current comparison unit 12 'at that time is fixed and maintained. The current comparison unit 12 'is supplied with this fixed and maintained current setting signal reference current value.

The current comparison unit 12 ′ compares the current setting signal given from the combustion control unit 15 with the detected current signal sent from the drive current detection unit 14 and sends the error signal to the pulse width control unit 10. send.

The pulse width controller 10 comprises a current comparator 12 '.
The pulse width of the pulse waveform signal output based on the error signal sent from the fan motor 7 is controlled by varying the DC voltage output from the DC converter 11.
The feedback control is performed so that the drive current of (1) matches the reference current value.

In the case of the second embodiment, since it is not necessary to send the drive current of the fan motor 7 detected by the drive current detector 14 to the combustion controller 15 one by one, the structure of the combustion controller 15 is simplified. In addition, the control program built in the combustion control unit 15 can be simplified.

In each of the above-mentioned embodiments, the drive current of the fan motor is controlled to the constant reference current value by the feedback control, but it goes without saying that the feedforward control may be used. Further, the present invention is not limited to the above embodiment, and various modifications can be made in line with the spirit of the invention.

[0042]

As described above, according to the present invention, even if the characteristics of the individual fan motors or the ambient atmospheric temperature changes, the air quantity that always provides the optimum mixing ratio is supplied to the combustion section. It is possible to achieve optimum combustion.

Further, since the drive current is kept constant at the reference current value, even if the rotation speed of the fan motor is reduced by the back wind, the rotation speed of the fan motor is automatically increased, and combustion is performed against the back wind. Since it acts to feed air, stable combustion can be maintained even when headwind occurs.

Furthermore, it is possible to quickly react to a change in the supply gas amount, and when determining a new set rotational speed for the changed supply gas amount, a reference corresponding to the supply gas amount before the change. Since the correction is made based on the error between the number of revolutions and the actual detected number of revolutions before the change, the optimum amount of combustion air can be supplied and stable even if headwind is acting. It is possible to maintain combustion.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a flowchart of the operation of the first embodiment.

FIG. 3 is a block diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Gas Burner 2 Heat Exchanger 3 Gas Proportional Valve 7 Fan Motor 8 Rotation Sensor 10 Pulse Width Control Section 11 DC Converter 12 Voltage Comparison Section 12 'Current Comparison Section 13 Drive Current Control Section 14 Drive Current Detection Section 15 Combustion Control Section 16 Operation part 17 Built-in ROM

Claims (5)

[Claims] 1. A fan control method for a forced air combustor, which controls the rotation speed of a fan motor so that the combustion air quantity corresponds to the supply gas quantity, and sets the rotation speed of the fan motor corresponding to the supply gas quantity. Then
The drive current of the fan motor when the rotation speed of the fan motor matches the set rotation speed is detected and stored as a reference current value for optimal combustion air supply, and thereafter the drive current of the fan motor matches the reference current value. A method for controlling a fan of a forced air blowing type combustion device, which is characterized in that: 2. The fan control method according to claim 1, wherein the set rotation speed of the fan motor is updated each time the supply gas amount is changed. Fan control method. 3. The fan control method according to claim 2, wherein an error between the reference rotation speed corresponding to the supply gas amount before the change and the actual detected rotation speed before the change is obtained, and the error after the change is calculated based on the error. A fan control method for a forced air combustion device, wherein a reference rotation speed corresponding to a supply gas amount is corrected, and the corrected rotation speed is set as a new set rotation speed for the changed supply gas amount. 4. A fan control device for a forced air combustion device, which controls the rotation speed of a fan motor so that the amount of combustion air corresponds to the amount of supply gas, and drive current control means for controlling the drive current of the fan motor. A rotation speed detection means for detecting the rotation speed of the fan motor, a drive current detection means for detecting a drive current flowing in the fan motor, a rotation speed detection signal of the rotation speed detection means, and a detection drive current of the drive current detection means Based on the signal, the drive current when the rotation speed of the fan motor matches the set rotation speed corresponding to the supply gas amount is detected and stored as the reference current value of the drive current corresponding to the supply gas amount at that time, and the reference current is stored. Combustion control means for sending a voltage setting signal giving a value to the drive current control means, wherein the drive current control means is a voltage setting signal given from the combustion control means. Fan control unit and controls so that the driving voltage of the fan motor is equal to the voltage setting signal by comparing the drive voltage applied to the fan motor. 5. A drive current control means for controlling a drive current of a fan motor in a fan control device of a forced air type combustion device for controlling a rotation speed of a fan motor so as to obtain a combustion air amount corresponding to a supply gas amount. The number of rotations of the fan motor is detected based on the number of rotations detection means for detecting the number of rotations of the fan motor, the driving current detection means for detecting the driving current flowing through the fan motor, and the number of rotations detection signal of the number of rotations detection means. A combustion control means for storing a current setting signal to the drive current control means when the set rotation speed corresponding to the supply gas amount matches, and sending the stored current setting signal to the drive current setting means, The drive current control means compares the current setting signal supplied from the combustion control means with the detected drive current signal detected by the drive current detection means to determine the fan mode. Fan control unit motor drive current and controls to match the current setting signal.