JPH0317296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen concentration detection device that detects a decrease in oxygen concentration in air supplied to a burner of a combustion equipment by a change in flame current.

Combustion equipment that burns gas, oil, etc. for heating, hot water, etc. consumes oxygen in the indoor air and releases carbon dioxide gas when used in a closed room. As the combustion continues, the burner causes incomplete combustion as the oxygen concentration in the combustion air decreases, and as a result, the amount of carbon monoxide generated increases, leading to an extremely dangerous situation. Therefore, when using combustion equipment indoors, it is necessary to occasionally open windows to provide ventilation and restore the oxygen concentration in the air, but human senses cannot detect when the oxygen concentration has decreased. Therefore, a device that detects a drop in oxygen concentration and issues an alarm or activates a safety device is considered to be very useful.

Conventionally, there has been a device suitable for such a purpose that detects a change in the combustion state in the flame caused by a decrease in the oxygen concentration of the combustion air as a change in flame current. In other words, a needle electrode whose tip protrudes into the combustion flame is installed insulated from the burner.
The electrodes have a positive voltage with respect to the burner (e.g.
30V) is applied. The flame current is constantly detected by taking advantage of the phenomenon that the flame current flowing from the needle electrode toward the burner decreases in approximately proportion to the decrease in the oxygen concentration of the combustion air supplied to the burner. This device has the function of determining that the oxygen concentration has decreased and stopping combustion when the value is lower than a certain set limit.

Although such a device is useful, it has a drawback in that it cannot distinguish and judge fluctuation factors other than oxygen concentration. In other words, the flame current increases not only when the oxygen concentration of the combustion air changes, but also when the combustion conditions change due to changes in the amount of fuel supplied to the burner or the ratio of air to fuel. Therefore, when trying to adjust the firepower according to the load, for example, a decrease in flame current at low firepower may be misjudged as a decrease in oxygen concentration, or because the flame current value is large at high firepower. ,
This causes the inconvenience that a decrease in oxygen concentration cannot be detected. In order to deal with such inconveniences, in the case of combustion equipment that allows switching of firepower, the limit of flame current can be set by adding a fixed correction current set according to each firepower to the flame current when switching. It is now possible to detect a decrease in oxygen concentration without changing the value.

However, with such improvement means, it is not easy to continuously change the corrected current value in accordance with the thermal power for combustion equipment that can continuously adjust the thermal power from large thermal power to small thermal power. There were many errors and the result was not necessarily satisfactory.

The present invention attempts to improve the detection accuracy of oxygen concentration by changing the flame current limit set value in accordance with the adjustment of the thermal power.
In other words, by automatically changing the fuel supply amount in response to changes in the fuel supply amount, the possibility of the device malfunctioning due to fluctuation factors other than oxygen concentration is eliminated, and a decrease in the oxygen concentration of the combustion air is always detected with high accuracy. This is what makes it possible.

The objects of the present invention are as follows: (a) A combustion amount control output circuit that outputs a control output proportional to the amount of fuel supplied based on a signal for driving a fuel supply means that supplies fuel to a burner; ) The correspondence relationship between the fuel supply amount and the reference flame current when burning at a specified oxygen concentration lower than 19% is incorporated in advance, and when the control output is input, the corresponding reference flame current is determined and , a determination reference signal conversion circuit that converts the reference flame current into a determination reference output signal and outputs the same; (c) a flame current detection electrode that is insulated from the burner and provided to protrude into the combustion flame; d) a flame current detection circuit that detects a flame current generated when a positive voltage is applied to the flame current detection electrode and outputs a flame current detection signal; (e) a flame current detection circuit that receives the flame current detection signal and outputs a flame current detection signal; (f) a flame current output circuit that compares the judgment reference output signal and the flame current output signal and outputs an alarm signal when the flame current output signal<the judgment reference output signal; A current signal comparison circuit; and (g) an alarm output circuit that inputs the alarm signal and generates an output for driving a caution alarm or a combustion stop cutoff switch. This is achieved by providing

A combustion device equipped with the device of the present invention can accurately measure oxygen concentration even when the combustion amount can be adjusted arbitrarily, that is, when conventional devices cannot prevent oxygen concentration detection accuracy from decreasing. decline can be detected. In addition, it is possible to always maintain optimal detection accuracy over a wide combustion range from full-capacity large firepower to very weak small firepower, so even if the oxygen concentration is low, alarms and safety devices may be delayed and cause damage. It has excellent performance and can be used with peace of mind even by those who are inexperienced in operating combustion equipment, without the inconvenience of causing a fire or having to activate a safety device to extinguish the fire even though the oxygen concentration has not decreased. be.

An embodiment of the present invention will be described with reference to FIG. This figure shows an oxygen concentration detection device that is installed in combination with a liquid fuel combustor that pumps petroleum to a burner and burns it using a fuel pump as a fuel supply means. The fuel pump 1 is adapted to be operated by a signal issued from a control circuit which maintains the temperature of the object heated by the burner 2 constant, for example. Then, it is possible to select an appropriate value from the voltage value, current value, current pulse width, frequency value, etc. of the drive signal to the fuel pump 1 to make the control output proportional to the fuel supply amount, but the combustion amount control output The circuit 4 here generates a control output based on a signal from a temperature detector 10 or the like. Reference numeral 5 denotes a judgment reference signal converting circuit which converts the control output and outputs a judgment reference output signal obtained when the control output is input, and the conversion is performed as follows.

That is, the determination reference signal conversion circuit 5 has a correspondence relationship between the fuel supply amount and the reference flame current when the burner 2 burns at various oxygen concentrations, as shown in FIG. 2, built in in advance based on experiments. Ori,
When a control output is input, a corresponding reference flame current is determined based on the fact that this and the fuel supply amount are in a proportional relationship with each other, and the reference flame current is further converted into a judgment reference output signal. .

On the other hand, fuel sent from a fuel pump 1 is burned in a grounded burner 2. A positive voltage is applied from a flame current detection circuit 6 to the flame current detection electrode 3 provided so as to protrude into the flame, so that flame current can be extracted. The flame current detection circuit 6 detects the flame current and outputs a flame current detection signal, and the flame current output circuit 7 inputs the flame current detection signal and converts it into a stable flame current output signal. Further, the flame current signal comparison circuit 8 compares the flame current output signal and the determination reference output signal,
An alarm signal is generated when the flame current output signal is smaller than the judgment reference output signal. Reference numeral 9 denotes an alarm output circuit which, when an alarm signal is input, outputs a signal to drive an alarm buzzer 11 as a warning alarm to notify abnormal combustion or a cutoff switch 12 to stop combustion for safety. .

When a combustion device with this configuration is in normal combustion operation, the flame current will decrease as the amount of fuel supplied decreases when the oxygen concentration in the air is 21% of normal. . This is mentioned above in the second
To explain using a diagram, when the fuel supply amount is F and combustion is taking place in fresh air,
The flame current is equivalent to FA, and as the oxygen concentration decreases to 19%, 18%, etc., the flame current decreases to FB, FC, etc., respectively. Similarly, when the fuel supply amount is F', the flame current has an oxygen concentration of 21%, 19%, 18%...
Correspondingly, they change as F′A′, F′B′, F′C′, etc., respectively.

By the way, when the combustion equipment is performing normal combustion at an oxygen concentration of 21%, a flame current as defined by the curve AA' flows between the flame current detection electrode 3 and the burner 2. Therefore, the flame current output signal input to the flame current signal comparison circuit 8 through the flame current detection circuit 6 and the flame current output circuit 7 in this order is used as a reference for determining the oxygen deficiency state by the determination reference signal conversion circuit 8.
is the specified oxygen concentration, for example 18% (the curve
It always maintains a larger value than the judgment reference output signal output based on CC'). Therefore, in such a state, the flame current signal comparison circuit 8 does not output an alarm signal. However, as the oxygen concentration decreases, the flame current output signal gradually approaches the determination reference output signal, and when the oxygen concentration falls below 18%, the flame current output signal finally becomes smaller than the determination reference output signal. Only at this point does the flame current signal comparison circuit 8 output an alarm signal, which activates the alarm output circuit 9 and activates the alarm lamp, alarm buzzer 11, etc., or activates the emergency cutoff valve or cutoff switch for fuel. Combustion interruption operations such as turning off the 12 etc. are automatically executed sequentially or simultaneously.

As described above, the oxygen concentration detection device of the present invention changes the standard for determining oxygen deficiency based on the specified oxygen concentration depending on the combustion amount, and when it is determined that the flame current has become smaller than the standard. Since an alarm is generated, a decrease in the oxygen concentration in the air can be detected with high accuracy from large to small thermal power, and excellent practical effects can be obtained, such as improving the safety of use of combustion equipment.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the oxygen concentration detection device of the present invention,
FIG. 2 is a graph illustrating the correspondence between the fuel supply amount and the reference flame current at various oxygen concentrations. DESCRIPTION OF SYMBOLS 1... Fuel pump, 2... Burner, 3... Flame current detection electrode, 4... Combustion amount control output circuit, 5...
...Judgment reference signal conversion circuit, 6...Flame current detection circuit, 7...Flame current output circuit, 8...Flame current signal comparison circuit, 9...Alarm output circuit, 10...Temperature detector, 11...Alarm Buzzer, 12... cutoff switch.

Claims (1)

[Claims] 1. A device for detecting the oxygen concentration of combustion air, which is installed in a combustion device that can continuously adjust the amount of combustion, comprising: (a) a fuel supply for supplying fuel to a burner; a combustion amount control output circuit that outputs a control output proportional to the amount of fuel supplied based on a signal for driving the means; and (b) a standard when burning at a specified oxygen concentration lower than the amount of fuel supplied and 19%. The correspondence relationship with the flame current is incorporated in advance, and when the control output is input, a reference flame current corresponding to this is determined, and the reference flame current is converted into a judgment reference output signal and outputted as a judgment reference signal conversion. (c) a flame current detection electrode insulated from the burner and provided to protrude into the combustion flame; and (d) a flame current detection electrode that detects the flame current generated when a positive voltage is applied to the flame current detection electrode. a flame current detection circuit that detects and outputs a flame current detection signal; (e) a flame current output circuit that inputs the flame current detection signal and converts it into a flame current output signal; (f) the judgment reference output signal; a flame current signal comparison circuit that compares the flame current output signal with the flame current output signal and outputs an alarm signal when the flame current output signal<judgment reference output signal; An oxygen concentration detection device comprising: an alarm output circuit that generates an output for driving a combustion stop cutoff switch.