JP2884220B2 - Combustion control 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 combustion control apparatus for controlling a combustion apparatus such as a gas water heater, and more particularly, to a combustion control apparatus for forcibly supplying a combustion section with an optimal amount of air according to the amount of combustion at each time. It relates to improvement for proper control.

[0002]

2. Description of the Related Art In recent years, control of combustion equipment as described above is often performed using a microcomputer (hereinafter simply abbreviated as "microcomputer") as a main combustion control circuit. In order to forcibly supply the optimum amount of air corresponding to the amount, the driving speed supplied to the fan motor is exclusively monitored and feedback control is performed, and the number of revolutions of the fan is determined in advance as appropriate for the combustion amount at each time. Is controlled to maintain the set rotation speed.

[0003] This point will be further described with reference to a typical example of the conventional combustion control device shown in Fig. 2. In the case shown in the figure, the combustion equipment to be controlled is a gas water heater, and the user is shown in the figure. When water is generated by opening an unillustrated faucet or the like, it is detected by an unillustrated water flow sensor or the like, and the burner 23 is ignited by an unillustrated ignition device. Of course, gas as fuel is supplied to the burner 23, which is a combustion section, via a gas proportional valve 24, but after the start of combustion, it is necessary at each time according to required data such as a hot water supply temperature set by a user. The combustion control circuit 11 controls the valve opening of the gas proportional valve 24 so that the supply gas amount matches the combustion amount to be supplied, thereby supplying the gas from the water supply through the heat exchanger 26 that is appropriately heated. The water is heated and brought to the temperature desired by the user and supplied. Actually, feedback control is also employed for this hot water supply temperature control, but since this is not a subject of improvement by the present invention, illustration and detailed description are omitted.

However, during combustion by the burner 23, the combustion control circuit 11 operates a fan (the fan itself is not shown) in order to stably supply an appropriate amount of air to the burner 23 at that time. A magnitude corresponding to (generally proportional to) the drive voltage is supplied to the driven fan motor 25 in order to supply a drive voltage at which a predetermined number of revolutions will be obtained according to the combustion amount at that time. Is supplied to the fan motor voltage drive circuit 31. When the fan motor voltage drive circuit 31 receives the fan motor drive voltage command signal Sv, the fan motor drive power supply Vb
The switching transistor 12 connected to is turned on. Then, the capacitor in the smoothing circuit 13 connected to the output of the switching transistor 12 starts to be charged and its potential starts to rise, but this smoothing circuit output potential is divided by the resistors 32 and 33 and the fan motor voltage driving circuit 31
The feedback voltage value (that is, the drive voltage value information actually applied to the fan motor 25) is indicated by the respective drive voltage value command signal Sv applied from the combustion control circuit 11. When the drive voltage value becomes equal to the set drive voltage value, the fan motor voltage drive circuit 31 turns off the switching transistor 12 there. Thereby, the smoothing circuit 13
The inside capacitor potential starts to decrease, and when it decreases to a predetermined value, the fan motor voltage drive circuit 31 turns on the switching transistor 12 again. By repeating such an operation, the fan motor voltage drive circuit 31 performs feedback control so as to keep the set drive voltage value specified by the combustion control circuit 11 on average.

On the other hand, the actual fan motor rotation speed at that time is detected by a rotation speed sensor 35, and the rotation speed detection circuit 34 can recognize an electric quantity that can be understood by the combustion control circuit 11, for example, an actual rotation speed signal at a voltage value. It is converted to Sa and sent to the combustion control circuit 11, and the combustion control circuit 11 compares the set rotation speed at that time with this actual rotation speed, and when a difference between the values exceeds a predetermined magnitude occurs. To correct this, the magnitude of the drive voltage command signal Sv to be sent to the fan motor voltage drive circuit 31 is changed. As a result, the rotation speed of the fan motor 25 is also feedback-controlled, and is controlled so as to always maintain the set rotation speed.

[0006]

However, in this kind of combustion equipment, main components such as a combustion part are housed in an appropriate housing, and an opening position and an opening area are fixed to a machine wall 22 of the housing. In order to be able to flexibly cope with each situation of a house where a water heater is installed or a fixed exhaust port 21 is provided, the exhaust is allowed up to a predetermined length range in a predetermined cross-sectional area range. Pipe (irregular exhaust port 2
1 ') is connected. However, even when the combustion equipment was installed correctly at the beginning, due to aging and changes in the surrounding environment, the fixed exhaust port 21 attached to the equipment and the irregular exhaust port 21 'connected to the exhaust pipe tended to block. May be. In such a case, the above-described feedback control acting to always maintain the fan motor rotation speed at a preset rotation speed set in advance according to the amount of combustion at each time may be adversely affected.

For example, regardless of whether the exhaust port 21 is the fixed exhaust port 21 or the irregular exhaust port 21 ′, if the exhaust system including the exhaust port becomes clogged due to clogging or the like, the amount of air to be driven by the fan decreases. The load on the fan motor is rather light, and the number of revolutions of the fan motor tends to increase with the same driving power as compared with the case where the exhaust system is normal. In such a case, the above-described conventional feedback control functions to suppress this within a predetermined rotation speed fluctuation range, and substantially reduces the rotation speed of the fan motor. However, when the exhaust system tends to be blocked, the fan motor must actually rotate at a higher rotation speed in order to compensate for the shortage of supply air. As is apparent from these facts, the conventional feedback control that always keeps the fan motor rotation speed at the set rotation speed clearly acts in an undesirable direction when the exhaust system tends to be clogged, and is substantially effective. Means that the amount of air supplied to the combustion section is insufficient. Insufficient air supply, of course, can lead to improper combustion and, in some cases, serious danger.

Conversely, for example, when the exhaust pipe is opened due to breakage or rust, the amount of air to be driven by the fan may increase (the load on the fan increases). However, also in this case, the conventional feedback control causes a problem. In other words, although the fan motor has a heavy load, its rotation speed tends to decrease,
Conventional feedback control gives a higher drive voltage to the fan motor in order to increase the fan motor rotation speed, which tends to decrease, thereby resulting in a fan motor drive current that is otherwise increased. As it works to make it even larger, it generates wasteful power consumption. Of course, if the overload state in which both the voltage and the current are large continues for a long time, the fan motor may be burned out.

However, it does not mean that the fan motor is completely free. Some kind of feedback control of the fan motor is indispensable for achieving optimal combustion in the normal operation mode, and cannot be omitted.

The present invention has been made in view of such circumstances.
Even if the exhaust system tends to be closed or open, and in any case, a situation that deviates from the normal state in the design specifications, supply an appropriate amount of air to the combustion section as much as possible. It is an object of the present invention to provide a combustion control device capable of continuing combustion safely.

Further, another object of the present invention is to forcibly combust combustion when the closed state or the open state of the exhaust system has reached such a level that it is no longer appropriate to correct the fan motor speed. A combustion control device that shuts down and preferably issues an alarm may be provided.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a fan for driving a fan by forcibly supplying an appropriate amount of air for the respective amount of combustion required in a combustion section. A combustion control device for controlling a motor, comprising: (a) a combustion control circuit for issuing a drive current value command signal indicating a fan motor drive current value set as appropriate for the current combustion amount for each current combustion amount. And (b) supplying a drive current of a corresponding magnitude to the fan motor based on the command of the drive current value command signal, and generating an actual current value signal indicating the magnitude of the current actually flowing through the fan motor. A constant current drive circuit that controls the value of the current that is actually flowing after the feedback to be equal to the drive current value set by the combustion control circuit; and (c) the combustion control circuit Whether the value of the current actually flowing to the motor has an error exceeding a predetermined allowable range with respect to the drive current value set as appropriate for the current combustion amount, or an error below the predetermined allowable range, And stopping combustion in the combustion section.

Further, in a specific embodiment of the present invention,
As described above, a combustion control device that activates an alarm device when the combustion control circuit stops combustion in the combustion section occurs. Note that the combustion control circuit can be realized by a microcomputer in recent technical circumstances.

[0014]

FIG. 1 shows a schematic configuration of a combustion apparatus equipped with a combustion control device according to an embodiment of the present invention. The device of this embodiment described here is already shown in FIG. As in the conventional example described above, a combustion control device for a gas water heater in which air is forcibly sent to a combustion unit by a fan is assumed. Therefore, components denoted by the same reference numerals as those in FIG. 2 may be the same as or similar to those in the conventional device shown in FIG.
The description of each of them is referred to the above description. It should be noted, however, that the present invention can be applied to any combustion control device that is a type of combustion device that forcibly supplies an amount of air according to the amount of combustion to a combustion unit. The fuel type and the like are arbitrary, and are not limited to the gas shown in the figure.

In the present embodiment, the combustion control circuit 11 is constituted by the microcomputer 11;
When combustion occurs in the combustion control circuit 11, the combustion control circuit 11 determines the corresponding rotation speed (for the fan motor) based on the fan rotation speed data stored in advance in memory means (not shown) according to the combustion amount at that time. A drive current value command signal Si for supplying a drive current If necessary for obtaining the set rotation speed) is transmitted to the fan motor constant current drive circuit 15. This signal Si
In the case of this embodiment, is actually a voltage pulse signal with a variable duty ratio, which is set to a predetermined duty ratio for each set rotational speed according to the amount of combustion at that time.

The constant current drive circuit 15 receiving the fan motor drive current value command signal Si turns on and off the switching transistor 12 in accordance with the duty ratio of the signal Si, whereby the current from the fan motor drive power supply Vb is reduced. Since the current flows into the capacitor in the smoothing circuit 13 when the switching transistor 12 is on and flows out when the switching transistor 12 is off, the driving current supplied to the fan motor 25 in terms of the average current value on the time axis The value of the current If is substantially constant with a magnitude corresponding to the duty ratio of the fan motor drive current value command signal Si. Therefore, in other words, when the combustion control circuit 11 changes the duty ratio of the drive current value command signal Si in order to change the fan motor setting rotation speed that is appropriate at each time, the fan motor 25 is supplied to the fan motor 25 accordingly. The value of the driving current If also changes to the corresponding magnitude.

On the other hand, the magnitude of the current If actually flowing in the fan motor 25 at each time is detected by the current detection circuit 14 and is returned to the fan motor constant current drive circuit 15 as an actual current value signal Sb. You. This current detection circuit 14 can be actually configured with a simple circuit configuration, for example, by a single low resistance inserted in series with the drive current line of the fan motor 25, and the voltage across the resistance is defined as the actual current value signal Sb. It is fed back to the current drive circuit 15. When the magnitude of the actual current If flowing through the fan motor 25, represented by the actual current value signal Sb, is different from the magnitude of the drive current value commanded by the combustion control circuit 11. The constant current drive circuit 15 compensates for this, and the drive current If actually flowing through the fan motor 25
The duty ratio related to ON / OFF of the switching transistor 12 is variably controlled so that the magnitude of the duty ratio becomes a magnitude instructed by the combustion control circuit 11.

As described above, according to the present invention, the current If supplied to the fan motor 25 is not controlled by feedback control so as to always keep the fan motor rotation speed constant in consideration of the fan motor drive voltage as in the conventional example. The feedback control is performed so as to maintain the current value set at each time instructed by the combustion control circuit 11, so that an air supply system that is resistant to blockage and opening of the exhaust system can be configured. That is, the standard exhaust port
If the clogging or the like occurs in the irregular exhaust port 21 or the irregular exhaust port 21 ′ and becomes a tendency to block, the load of the fan becomes rather light as described above, so that the rotation speed of the fan motor 25 increases, The magnitude of the flowing current If is going to be reduced,
In such a case, as a result of the conventional feedback control to reduce the rotation speed to the set rotation speed only by focusing on the rotation speed (naturally, the magnitude of the driving current If acts in a direction to lower the rotation speed), the air supply amount is insufficient. While it happened,
Since the present invention focuses on the drive current flowing through the fan motor 25, in such a case, on the contrary, in order to perform feedback control so as to push up the magnitude of the fan motor drive current that tends to decrease to the set current value, The fan speed actually increases rather. Therefore, when the exhaust system becomes clogged, it is necessary to increase the rotation speed of the fan in accordance with the tendency, so that a sufficient amount of air can be supplied to the combustion section.

Conversely, when the exhaust opening area becomes large due to damage to the exhaust port and the load on the fan becomes heavy,
Under the conventional rotation speed constant control, the value of the drive current If supplied to the fan motor in order to forcibly increase the rotation speed of the fan that tends to decrease tends to be considerably increased as a result. In such a situation, the magnitude of the drive current If supplied to the fan motor 25 is
It functions to decrease toward the set current value represented by the drive current value command signal Si transmitted from the combustion control circuit 11. Therefore, problems such as overheating of the fan motor 25 are unlikely to occur, and a necessary and sufficient amount of air can be supplied to the combustion section.

However, there is an allowable range for any correction. It is also conceivable that the closed state or open state of the exhaust system becomes unacceptable. Therefore, in the present invention,
The actual current value signal Sb representing the magnitude of the current actually flowing to the fan motor 25 is also applied to the combustion control circuit 11,
In the combustion control circuit 11, this value deviates from a predetermined allowable range (for example, this range can be a range that can be corrected by the constant current drive circuit 15) as compared with the current set current value. In the case, that is, since there is a lower limit and an upper limit from the "predetermined allowable range", even if the upper limit is exceeded, or even if the value falls below the lower limit,
It acts on the fuel system such as the gas proportional valve 24 to stop the fuel supply to the combustion part 23 and to forcibly stop the combustion, and more desirably emits an alarm signal and activates the alarm device 16 for use. To let the person know that something went wrong.

As the alarm device 16, an audible sound generating device such as a buzzer is generally used.
In many cases, a remote control unit (not shown) connected to the combustion control circuit 11 is also connected, and this is also usually provided with various information display units. Such an information display unit can be used in combination as the alarm device 16 that performs the operation, and the information display unit can be configured to provide a character display or a pictorial display indicating that a service person is called because an abnormality has occurred, for example. it can.

[0022]

According to the present invention, in a combustion device of a forced air supply type to a combustion part, the rotation speed of a fan motor is changed flexibly to achieve safe combustion as much as possible even if some abnormality occurs in the exhaust system. Variable control can be performed, and the disadvantages of the feedback control that always tries to keep the set rotation speed can be eliminated or mitigated. In addition, if the error of the actual current value flowing through the fan motor with respect to the current set current value exceeds the set current value by a predetermined value or more, conversely, the error drops by a predetermined value or more. In this case as well, the combustion can be stopped quickly, so that it is possible to cope with a situation where it is difficult to know what kind of aging of the exhaust system will occur at the actual installation location, and to achieve a high level of safety.

In the present invention, since the feedback control is performed with respect to the fan motor drive current, the current actually flowing to the fan motor may be detected in order to capture the correction amount. Only needs to be done. As in the past, a rotation speed sensor that detects the fan motor rotation speed for feedback control to keep the fan motor rotation speed at a constant rotation speed, and a conversion circuit for converting the detection signal into an electric signal that can be understood by a microcomputer, For example, since a conversion circuit or the like including a Hall element becomes unnecessary, the structure of the fan motor and peripheral circuits are simplified, and as a result, the entire combustion equipment is reduced in cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a combustion control device configured according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a fan motor control circuit in a conventional combustion control device.

[Explanation of symbols]

 11 Combustion control circuit or microcomputer, 12 switching transistor, 13 smoothing circuit, 14 current detection circuit, 15 fan motor constant current drive circuit, 16 alarm device, 21, 21 'exhaust port, 23 burner, 24 gas proportional valve, 25 fan motor , 26 heat exchanger, If current flowing to fan motor, drive current command signal to Si fan motor, actual speed signal of Sb fan motor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F23N 5/24 104 F23N 3/08 F23N 5/26 101 H02P 5/00 H02P 5/168

Claims (3)

(57) [Claims] 1. A forced air supply by a fan for an amount of air required for a specific combustion amount required in a combustion unit.
A combustion control device for controlling a fan motor for driving the fan, wherein a drive current value command signal representing a fan motor drive current value set as appropriate for the current combustion amount is provided for each of the current combustion amounts. A combustion control circuit for generating; a driving current of a magnitude corresponding to the command of the driving current value command signal to the fan motor, and an actual current indicating the magnitude of the current actually flowing to the fan motor; A constant current drive circuit that receives the feedback of the value signal and controls the value of the actually flowing current to be equal to the drive current value set by the combustion control circuit; If the value of the current actually flowing to the fan motor has an error exceeding a predetermined allowable range with respect to the drive current value set as appropriate for the above-described current combustion amount, an error lower than the predetermined allowable range will be obtained. Even when produced, stopping the combustion in the combustion section; combustion control apparatus according to claim. 2. The combustion control device according to claim 1, wherein the combustion control circuit activates an alarm device when stopping combustion in the combustion section. 3. The combustion control device according to claim 1, wherein the combustion control circuit is constituted by a microcomputer.