JPH0373774B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to various combustion devices such as water heaters and fan heaters, and more specifically, to a sensor that detects the concentration of combustible gas components in combustion gas from a burner. , and a heater for heating the sensor, as well as a determination means for determining incomplete combustion based on the detection information of the sensor, so that incomplete combustion can be detected early, and the sensor temperature can be managed by the heater. The present invention relates to a combustion device that maintains the concentration detection function of a sensor at a high level regardless of changes in combustion exhaust gas temperature caused by various disturbances and can accurately detect incomplete combustion.

[Conventional technology]

Conventionally, in the above-mentioned combustion apparatus, from the viewpoint of maintaining the sensor temperature as stably as possible at the optimum temperature (the temperature at which the concentration detection sensitivity of the sensor is the best) regardless of changes in the combustion exhaust gas temperature caused by various disturbances, The sensor temperature is detected and the heater is feedback-controlled so as to maintain the detected temperature at a predetermined optimum temperature (for example, see Japanese Patent Laid-Open No. 89624/1983).

[Problem that the invention seeks to solve]

However, the control configuration for the heater becomes complicated in order to perform feedback control, such as a temperature detection means for detecting the sensor temperature and a means for comparing the detected sensor temperature with a predetermined optimum temperature, which reduces manufacturing and equipment costs. There was a cost disadvantage.

Additionally, due to control errors in the feedback control mentioned above, the sensor temperature was erroneously adjusted and maintained at a temperature that deviated from the optimum temperature, which led to a decrease in the accuracy of incomplete combustion detection. .

An object of the present invention is to solve the above problem by providing a rational incomplete combustion determination configuration that effectively utilizes the specific characteristics of a sensor that detects the concentration of combustible gas components.

[Means for solving problems]

The characteristic configuration of the combustion apparatus according to the present invention is that it is provided with a sensor that detects the concentration of combustible gas components in the combustion gas from the burner, and a heater that heats the sensor, and prevents incomplete combustion based on the information detected by the sensor. In the configuration provided with a determination means for making a determination, the output value of the sensor changes with changes in the concentration of combustible gas components, and changes quadratically with changes in temperature, and shows an extreme value at a predetermined temperature. and a heater control means for automatically operating the heater by timer control so as to change the temperature of the sensor up and down over a temperature range including the predetermined temperature in the center of the range, and the determination means The structure is such that incomplete combustion is determined when the sensor output value exceeds a set value in the process of the sensor temperature changing up and down, and its functions and effects are as follows.

[Effect]

In other words, in a sensor with the above characteristics, as shown in FIG. 3, the predetermined temperature (Tx) at which the sensor output value (sensor resistance value R in the example of FIG. In the example shown in the figure, this corresponds to the optimum temperature that maximizes the sensitivity (sensitivity to CO concentration), so in a sensor with this characteristic, the temperature range (ΔT) of an appropriate width that includes the predetermined temperature (Tx) in the center of the range. By automatically operating the heater under timer control to change the sensor temperature (T) up and down, the range of change in the sensor temperature (T) due to changes in the combustion gas temperature caused by various disturbances is shown in the broken line and in Figure 4. Even if the sensor temperature (T) changes slightly, as shown by the dashed line, there is always a point where the sensor temperature (T) becomes the optimum temperature (Tx), that is, a point where the sensor sensitivity is the best. It can be done.

The sensor sensitivity is maximized by determining incomplete combustion when the sensor output value R exceeds the set value during the upward and downward change process of the sensor temperature (T) in such a temperature range (ΔT). When incomplete combustion occurs such that the sensor output value R exceeds the above set value at the optimum temperature (Tx), at any point in the sensor temperature change process,
In other words, at some point in the sensor output value change process as the sensor temperature (T) changes up and down, a point can be obtained where the sensor output value R exceeds the above set value, thereby eliminating the above-mentioned failure. The occurrence of complete combustion can be accurately detected.

In other words, although the sensor temperature (T) is changed, incomplete combustion can be detected in various ways with substantially the same detection accuracy as maintaining the sensor temperature (T) accurately at the optimum temperature (Tx) at all times. It can always be accurately detected regardless of changes in combustion gas temperature caused by external disturbances.

〔Effect of the invention〕

As a result, compared to conventional devices that perform feedback control of the heater to maintain the sensor temperature at the optimum temperature based on sensor temperature detection, there is no need for a means for detecting the sensor temperature or a means for comparing the detected sensor temperature with the optimum temperature. This allows for a simple heater control configuration in which the heater is simply controlled by a timer, thereby making it possible to improve the productivity of the device and reduce the cost of the device.

In addition, it is possible to avoid the situation where the sensor temperature is erroneously investigated and maintained at a temperature that deviates from the optimum temperature due to a control error in feedback control, and the detection accuracy of incomplete combustion is deteriorated. The accuracy of detecting incomplete combustion has also been improved.

〔Example〕

Next, an example will be described.

FIG. 1 shows a schematic configuration of a gas water heater, which includes a casing 1, a water tube type water heating heat exchanger 2, and
A heating gas burner 3 is installed therein, and a hot water supply pipe 5 from a heat exchanger 2 is connected to a tap 4 for hot water.

A water flow switch 7 is installed in the water supply pipe 6 to the heat exchanger 2, a flame rod 8 for detecting combustion flame is installed near the burner 3, and a combustion gas exhaust path 9 in the casing 1 is connected to a water flow switch 7 for detecting combustible gas in the exhaust combustion gas. A sensor 10 for detecting the concentration of the component (in this example, the concentration of carbon monoxide) is provided, and
Gas valve 1 for intermittent fuel supply to burner 2
1, as well as the control device 13 that automatically operates each of the burner spark plugs 12, the following circuits (a) to (c): of
Based on the ON operation, the gas valve 11 is opened and the ignition plug 12 is activated to ignite the burner 3. Based on the OFF operation of the water flow switch 7 in conjunction with the closing operation of the tap 4, the gas valve 11 is closed. Ignition extinguishing circuit 13 that extinguishes burner 3
A. (B) After the ignition operation, the gas valve 11 is kept open only when the combustion flame is detected based on the combustion flame detection by the flame rod 8, and thereby the raw gas caused by the extinguishment is kept open. raw gas release prevention circuit 13B that prevents the release of raw gas; an incomplete combustion determination circuit 13 that closes the gas valve 11 to prevent continuation of incomplete combustion;
C. is provided.

As shown in FIG. 3, the concentration detection sensor 10 has a resistance value R as its output value in response to an increase in the concentration of combustible gas components in the exhaust combustion gas (increase in CO concentration).
The sensor structure is shown in Figure 2 as a specific sensor structure. As shown in _FIG .
A protective frame 14 formed of stainless steel wire mesh
In addition, electrode wires 17 are provided at both ends of the membrane-like sintered body 16 in the longitudinal direction of the cylindrical body 15.
Further, an electric heater 18 for adjusting the sensor temperature is inserted through the ceramic cylindrical body 15.

As a control circuit for the electric heater 18, the sensor temperature (T) is periodically changed up and down over an appropriately wide temperature range (ΔT) including the above-mentioned predetermined temperature (Tx) in the center of the range. A heater control circuit 13D that alternately repeats energization for one minute and non-energization for two minutes for the electric heater 18,
In addition to being additionally equipped to the control device 13, the incomplete combustion determination circuit 13C is controlled by the sensor resistance value R in the process in which the sensor temperature (T) periodically changes up and down by the timer control of the electric heater 18 by the heater control circuit 13D. The configuration is such that incomplete combustion is determined when the concentration exceeds the set lower limit value corresponding to the set upper limit concentration.

In other words, by determining incomplete combustion in this manner, the temperature of the exhaust combustion gas changes due to disturbance requirements such as changes in outside temperature and water supply amount, and this causes the sensor temperature (T) to change. Even if the range of change is slightly displaced as shown by the broken lines and dashed-dotted lines in Fig. 4, the above-mentioned predetermined temperature (Tx) at which the sensor resistance value R has a minimum value, that is, the optimum temperature (Tx) at which the sensor sensitivity is the best. When incomplete combustion occurs such that the sensor resistance value R exceeds the set lower limit value corresponding to the set upper limit concentration, the sensor temperature (T) The occurrence of incomplete combustion can be accurately detected when the sensor resistance value R exceeds the lower limit value at any point in the process of changing the sensor resistance value R as the sensor resistance value R changes upward and downward. be.

[Another example]

Next, another example will be described.

The specific control structure for operating the heater 18 by timer control can be modified in various ways.

The specific timer control program for periodically changing the sensor temperature (T) up and down and the width of the sensor temperature up and down change range (ΔT) may be set as appropriate.

Further, the present invention can be applied to various combustion devices such as water heaters and fan heaters.

[Brief explanation of drawings]

FIG. 1 is a schematic device configuration diagram of a water heater, FIG. 2 is a partially cutaway enlarged view of a sensor, FIG. 3 is a graph showing sensor characteristics, and FIG. 4 is a graph showing a sensor temperature control mode. 3... Burner, 10... Sensor, 18... Heater, 13C... Judgment means, 13D... Heater control means.

Claims (1)

[Claims] 1. A sensor 10 for detecting the concentration of combustible gas components in the combustion gas from the burner 3 and a heater 18 for heating the sensor 10 are provided, A combustion apparatus is provided with a determination means 13C for determining combustion, and the sensor 10 is configured such that its output value R changes with changes in the concentration of combustible gas components and changes quadratically with changes in temperature. The temperature (T) of the sensor 10 is changed vertically over a temperature range (ΔT) that includes the predetermined temperature (Tx) in the center of the range. A heater control means 13D is provided to automatically operate the heater 18 by timer control, and the determination means 13C is determined to be incomplete when the sensor output value R exceeds the set value during the up and down change process of the sensor temperature (T). A combustion device configured to determine combustion.