JPS61202011A - Combustion apparatus of forced feed and discharge type - Google Patents

Abstract

PURPOSE:To prevent abnormal combustion on a burner when the pressure in a room where an apparatus is installed is lowered in case that the number of revolution of a fan is lowered in the state that the combustion rate of a burner is at the minimum or nearly the lowest, by providing a controlling circuit to control a fan in accordance with the combustion rate of a burner, and a lowest limit circuit to set the lowest number of revolution for the fan, and by connecting the output of a room pressure sensor which detects the pressure in a room to said lowest limit circuit. CONSTITUTION:In a lowest limit circuit 49, a room pressure sensor 43 detects the room pressure in a room where an apparatus 1 is installed. The output of a sensor 43 is amplified by operational amplifiers 44, 45, 46, 47, and then it is fed into the positive input of an operational amplifier 38 in a PID circuit 20 through a diode 48. When the difference between the temperature in tap hot water and a set temperature is very small, a proportional control valve 6 is throttled, the output of an operational amplifier 37 is made lower than that of the lowest limit circuit 49, and a fan 9 is controlled to the revolved at the lowest number of revolution based on the output of an amplifier 37, the room pressure sensor 43 detects the pressure in a room if it is lowered down to the negative pressure. The positive input voltage of an operational amplifier 38 in the PID circuit 20 is varied based on the detected negative pressure and the lowest number of revolution of a fan 9 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a forced air supply and exhaust type combustor which is installed indoors and which takes in combustion air and discharges combustion exhaust outdoors.

(b) Conventional technology: Combustion air for the burner is forcibly supplied by a fan. In particular, as shown in Japanese Patent Application Laid-open No. 59-129324, the combustion air is supplied to the burner according to the load to be heated by the burner. In devices that increase or decrease the amount of combustion in the burner, the number of revolutions of the fan is controlled in accordance with the amount of combustion in the burner to improve combustion efficiency.

On the other hand, with a combustor that is installed indoors and exhausts the combustion exhaust from the burner outside, and also takes in combustion air from the outside, when the amount of burner combustion is small and the fan speed is low, the appliance is placed in the kitchen, for example. 115111fflHg in the kitchen using ventilation, range hood, etc.
If the pressure reaches a certain level of negative pressure, the air inside the appliance may leak to the outside, causing incomplete combustion and causing the burner to misfire.

(C) Problems to be Solved by the Invention This invention solves the problem of abnormal combustion of the burner when the pressure in the room where the appliance is installed decreases when the burner combustion amount is at or close to the minimum and the fan rotation speed is low. The purpose is to stop fat.

(d) Means for solving the problem The present invention provides a lower limit circuit for setting the minimum rotation speed of the fan, and connects the output of a room pressure sensor that detects the pressure inside the equipment installation room to this lower limit circuit, The fan's minimum rotation speed is adjusted according to the indoor pressure.

(E) The pressure inside the room where the effect device is installed is detected by a room pressure sensor, and when the room pressure decreases, the minimum rotation speed of the fan is increased accordingly.

(f) Example An example of the present invention will first be explained based on FIG.
) is the main body of the forced air/exhaust water heater, and the exterior case (2
) is equipped with a heat exchanger (3) and a gas burner (4) that heats it.
), a governor (5) that controls the fuel supply to this gas burner
), a proportional control valve (6), an electromagnetic on-off valve (7), (8), a fan (9) for forcibly discharging combustion exhaust from the gas burner (4) to the outside and supplying combustion air; It mainly houses a control circuit (10) that controls a proportional control valve (6), electromagnetic on-off valves (7), (8), etc. The exterior case (2) has a sealed structure, and has an intake duct (11) connected to the outside, and one end connected to the discharge hole (12) of the fan (9).
) and is connected to an exhaust duct (13) whose other end communicates with the outside.

Here, a part of the control circuit (10) will be explained based on FIG. 2. (14) is a commercial power supply connected to a power switch (14).
Step-down transformer (16) and fan (9) via 15)
In addition, a DC constant voltage circuit (17) is connected to the secondary winding of the step-down transformer (16).

(18) is a photo ink converter for detecting the rotation speed of the fan (9), which is connected to the F-V conversion circuit (19) that converts the output pulses generated from this into room pressure;
The output of the V conversion circuit is connected to a PID circuit (20) that performs proportional, integral, and differential control, and the output of this PID circuit is connected to the positive input (21') of the operational amplifier (21). Connect the pace to the negative input (21") via a diode (24) to the transistor (23) connected to the bridge (22) of the DC constant voltage circuit (17) to generate a synchronous pulse that is synchronized with the wave number on the power supply side. Circuit (25)
The output of the operational amplifier (21) is connected to a drive circuit (26) that controls the rotation of the fan (9).
It is connected to a transistor (29) that drives a phototriac (27) and a pair of LEDs (28>), and these mainly control the fan (9).

On the other hand, (30) is a thermistor that detects the hot water temperature of the heat exchanger (3), which is a load, and is connected to a variable resistance for setting (31) that sets the hot water temperature, and these outputs are connected to an operational amplifier (
32) is connected to the negative input (32'') of the operational amplifier, and the output of this operational amplifier is connected to a transistor (33) that drives the proportional control valve (6) to form a proportional control circuit (34). (32) operates so that the negative input (32") and positive input (32') voltages are the same, and the proportional control valve (6) converts the current flowing through the resistor (35) into room pressure. Op amp (32) through resistor (36)
It is controlled by feeding back to the negative input (32'') of.

Further, the terminal voltage of the resistor (35) is amplified by the operational amplifier (37), and the output of this operational amplifier is
Connected to the positive input of the operational amplifier (38) that constitutes the ID circuit (20), the fan (
9).

(39) reads the negative input of the operational amplifier (40) directly to the output of the operational amplifier (37), and passes the output through the diode (41) in the opposite direction to the positive input of the operational amplifier (38) of the PI'D circuit (20). In the upper limit circuit connected to the input, when the output of the operational amplifier (37) is higher than the voltage set by the resistors (42a) (42b) connected to the positive input (40'), the output is inverted and the output of the operational amplifier (38) is The positive input is fixed to the output of the operational amplifier (40), thereby setting the maximum rotation speed of the fan (9).

(43) is a pneumatic sensor that detects the indoor pressure in a kitchen or the like where the appliance body (1,) consisting of a well-known pressure sensor is attached to the appropriate position of the exterior case (2), and this output is sent to an operational amplifier (44). After amplifying in (45), (46), and (47), the output is connected to the positive input of the operational amplifier (38) of the above PID circuit (20) via the diode (48), and these are used to set the lower limit and 7 points. It constitutes a circuit (49).

Therefore, since there is almost no difference between the hot water temperature and the set temperature, the proportional control valve (6) is throttled down, and the output of the operational amplifier (37) is smaller than the output of the lower limit circuit (49), and at this output, the fan (9) is turned to the lowest limit. When the pressure in the room where the appliance body (1) is installed falls to negative pressure during rotation control with the number of times, the room pressure sensor (43) detects this and the P
The positive input voltage of the operational amplifier (38) of the ID circuit (20) is changed to increase the minimum rotation speed of the fan (9).

(G) Effects of the Invention Due to the uninvented configuration, even if the pressure in the room where the device is installed drops to negative pressure when the forced air supply/exhaust fan rotates at the minimum rotation speed, abnormal combustion of the burner and exhaust gas will not occur in the room. It is possible to prevent leakage.

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[Brief explanation of drawings]

FIG. 1 is a front vertical sectional view of the present invention, and FIG. 2 is an electric circuit diagram. (4)...Gas burner, (9)...Fan, (10
)...control circuit, (43)...room pressure sensor, (4
9)...lower limit circuit.

Claims (1)

[Claims] (1) In a device that is installed indoors and has a fan installed on the downstream side of the burner, the fan sucks combustion air from the burner from outside and discharges combustion exhaust from the burner to the outside. In addition to providing a control circuit that controls the amount according to the amount of rotation, a lower limit circuit that sets the minimum rotation speed of the fan is provided, and the output of the room pressure sensor that detects the pressure in the room is connected to this lower limit circuit. A forced air supply and exhaust type combustor.