JPH07324733A - Combustion equipment - Google Patents

Abstract

PURPOSE:To improve a durability and reliability of a limited current type oxygen sensor and to enable a measurement of concentration of oxygen to be carried out for a long period of time in a stable manner. CONSTITUTION:This combustion equipment is constructed such that a limit current type oxygen sensor 5 and a heater 6 arranged integrally with the sensor 5 are installed in a discharged gas flow passage 4 for use in discharging combustion discharged gas. Either a fuel supplying part 1 for supplying fuel or an air supplying part 2 for supplying air is controlled in response to an oxygen concentration signal obtained from the limit current type oxygen sensor 5. A discharged gas temperature sensing means 13 is installed in the discharged gas flow passage 4 and this is operated to control such that if the discharged gas temperature is high, a generated voltage value of a heating DC power supply 10 for use in operating the heater 6 is made low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device using a limiting current type oxygen sensor (hereinafter referred to as an oxygen sensor) arranged in an exhaust gas passage to detect an oxygen concentration.

[0002]

2. Description of the Related Art A conventional combustion device is disclosed in Japanese Patent Application Laid-Open No. H5-26464.
As shown in Japanese Patent Publication No. 42-42, the ratio of the air supply amount and the fuel supply amount (hereinafter referred to as the air-fuel ratio) is calculated in advance so that complete combustion can be obtained, and the air supply amount or the fuel supply amount based on the calculation It was meant to burn. However, when the combustion equipment is used in various environments, the air-fuel ratio fluctuates from the initially calculated value due to fluctuations in the outside air temperature, fluctuations in atmospheric pressure, and fluctuations in the durability of the fuel supply means and the air supply means.
For example, the air-fuel ratio is greatly different in a high-altitude environment with an oxygen-lean environment of 2000 meters above sea level, and incomplete combustion will occur if the initial calculated value obtained on a flat surface is used.

As a means to solve this, paying attention to the fact that the air-fuel ratio correlates with the oxygen concentration in the combustion exhaust gas passage,
It has been attempted to develop an oxygen sensor that measures the oxygen concentration, and arrange this oxygen sensor in a combustion exhaust gas flow path to develop an optimum combustion device that controls the air-fuel ratio.

FIG. 7 shows an example of conventional combustion equipment. In this combustion apparatus, the fuel is supplied from the fuel supply unit 1, the fuel is burned in the combustion unit 3 while the air is supplied from the air supply unit 2, and the combustion exhaust gas is exhausted through the exhaust gas passage 4 in which the oxygen sensor 5 is arranged. It is a composition. The oxygen sensor 5 is an element driving DC power supply 7 for applying a constant voltage to an electrode film (not shown).
And a device current detection means 8 for detecting the generated current are connected in series to form a closed circuit. The control unit 9 processes the generated current obtained by the element current detection unit 8 as an oxygen concentration signal and controls the fuel supply unit 1 or the air supply unit 2 to control the optimum air-fuel ratio. On the other hand, the oxygen sensor is provided with a heating body 6, and the heating body 6 is connected to a heating DC power supply 10 for applying a constant voltage or a constant power for heating.

[0005]

However, the oxygen sensor 5
In a combustion device that performs air-fuel ratio control by using, the heating body 6 is heated using a heating DC power supply 10 that generates a constant voltage or a constant power, so the operating temperature of the oxygen sensor 5 is There has been a problem that the temperature of exhaust gas is greatly affected by changes in the air supply amount.

FIG. 8 shows the results of measuring the exhaust gas temperature and the oxygen concentration in the exhaust gas when the combustion amount (actually, the fuel supply amount) is changed while the air supply amount is kept constant. The exhaust gas temperature changes depending on the combustion amount (fuel supply amount), and the same combustion amount (fuel supply amount) of 3500 kcal / h.
However, it can be seen that the exhaust gas temperature is different when the oxygen concentration in the exhaust gas is different (actually, the air supply amount is different).

FIG. 9 shows the operating temperature of the oxygen sensor 5 when the voltage generated by the heating DC power source 10 and the power generated thereby are changed. It can be seen that even if the generated voltage (generated power) of the heating DC power supply 10 is the same, the operating temperature of the oxygen sensor 5 rises as the exhaust gas temperature rises.

FIG. 10 shows a voltage-current characteristic of the oxygen sensor 5 when the exhaust gas temperature is changed while the oxygen concentration in the exhaust gas is 5% and the generated voltage of the heating DC power supply 10 is constant. It can be seen that the current increases as the exhaust gas temperature increases. This is because the operating temperature of the oxygen sensor 5 increases as the exhaust gas temperature increases.

From the viewpoint of ensuring the durability and reliability of the oxygen sensor 5, it is desirable that the operating temperature of the oxygen sensor 5 is low. On the contrary, from the viewpoint of ensuring the limiting current characteristics required for the oxygen sensor 5, Higher operating temperature is desirable. However, in the exhaust gas, the operating temperature of the oxygen sensor 5 is greatly affected by the exhaust gas temperature due to changes in the fuel supply amount and the air supply amount, and it is not desirable that the operating temperature becomes excessively high from the viewpoint of ensuring durability reliability.

The present invention solves the above problems of the prior art by making the oxygen sensor less likely to be affected by the fuel supply amount, the air supply amount, and the exhaust gas temperature, and always operating the oxygen sensor at the same operating temperature. The purpose is to ensure sex.

[0011]

In order to achieve the above-mentioned object, the combustion apparatus of the present invention, the exhaust gas temperature detected by the exhaust gas temperature detecting means arranged in the exhaust gas flow path is compared with a set value in the exhaust gas temperature comparison unit, As the exhaust gas temperature increases,
The generated voltage value of the heating DC power supply for operating the heating element arranged in the exhaust gas flow path adjacent to the oxygen sensor is reduced by the heating voltage changing means.

Further, in the combustion device of the present invention, the fuel supply amount supplied from the fuel supply unit is compared with the set value in the fuel supply amount comparison unit, and as the fuel supply amount increases, the oxygen sensor is provided along with the exhaust gas flow. The generated voltage value of the heating DC power supply for operating the heating element arranged in the path is reduced by the heating voltage changing means.

Further, in the combustion device of the present invention, the air supply amount supplied from the air supply unit is compared with the set value in the air supply amount comparison unit in correspondence with the fuel supply amount from the fuel supply unit, and the air supply amount is As the number increases, the heating voltage changing means reduces the generated voltage value of the heating DC power supply for operating the heating element arranged in the exhaust gas flow path along with the oxygen sensor.

[0014]

According to the present invention, in the above structure, the oxygen sensor transfers a large amount of heat from the exhaust gas when the exhaust gas temperature is high, the amount of fuel supplied from the fuel supply unit is large, or the corresponding amount of air supplied is large. The operating temperature of the oxygen sensor naturally rises. Therefore, if the generated voltage value of the heating DC power supply is reduced corresponding to these, the oxygen sensor has an appropriate operating temperature that is not excessively high, and the durability reliability of the oxygen sensor can be secured.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. The same numbers are used for the same components as those described in the conventional example. FIG. 1 is a block diagram of a combustion device according to an embodiment of the present invention. As shown in FIG. 1, in the combustion apparatus, the fuel is supplied from the fuel supply unit 1, and the air is supplied from the air supply unit 2 while the fuel is burned in the combustion unit 3.
The combustion exhaust gas is exhausted through the exhaust gas passage 4. In the exhaust gas passage 4, an oxygen sensor 5 and a heating body 6 that is attached to and integrated with the oxygen sensor 5 are arranged.

The oxygen sensor 5 has its electrode films 1a and 1b.
A device driving DC power supply 7 for applying a constant voltage (not shown in both) and a device current detecting means 8 for detecting a current generated from the oxygen sensor 5 are connected in series to form a closed circuit. There is. The control unit 9 processes the generated current obtained by the device current detection unit 8 as an oxygen concentration signal and controls the fuel supply unit 1 or the air supply unit 2.

A heating DC power supply 10 for applying a voltage for heating is connected to the heating body 6, and the heating DC power supply 10 further includes a heating DC power supply 10 for changing the voltage generated by the heating DC power supply 10. The voltage changing means 11 is provided side by side.

The heating voltage changing means 11 is connected to the exhaust gas temperature comparing section 12. The exhaust gas temperature comparison unit 12 is connected to the exhaust gas temperature detection means 13 arranged in the exhaust gas flow path 4, and when the detected exhaust gas temperature is high, the generated voltage value of the heating DC power supply 10 becomes small. The voltage changing means 11 is controlled.

Further, the heating voltage changing means 11 is connected to the fuel supply amount comparing section 14. Fuel supply amount comparison unit 14
Is connected to the fuel supply unit 1, and controls the heating voltage changing unit 11 so that the generated voltage value of the heating DC power supply 10 becomes smaller when the supplied fuel increases.

Further, the heating voltage changing means 11 is connected to the air supply amount comparing section 15. Air supply amount comparison unit 15
Is connected to the air supply unit 2, and controls the heating voltage changing means 11 so that the generated voltage value of the heating DC power supply 10 becomes smaller when the fuel supplied increases and the air supplied accordingly increases. To do.

FIG. 2 is a diagram showing the operation of the combustion equipment which is an embodiment of the present invention. The exhaust gas temperature comparison unit 12, the fuel supply amount comparison unit 14, or the air supply amount comparison unit 15 determines whether any one of the detected values such as the exhaust gas temperature T, the fuel supply amount F, or the air supply amount Q exceeds a set value. To judge. If the detected value exceeds the set value, the generated voltage value of the heating DC power supply 10 is not changed and the current voltage value V ₀ is maintained as it is within a predetermined time A from the time of the determination, and the oxygen sensor is maintained. The fuel supply unit 1 or the air supply unit 2 is controlled based on the oxygen concentration signal from 5. When the predetermined time A has elapsed, the voltage value generated by the heating DC power supply 10 is changed to a new voltage value V _1, and the control of the fuel supply unit 1 or the air supply unit 2 based on the oxygen concentration signal from the oxygen sensor 5 is released. It The control release of the fuel supply unit 1 or the air supply unit 2 ends after a predetermined time B, and thereafter, the control of the fuel supply unit 1 or the air supply unit 2 based on the oxygen concentration signal from the oxygen sensor 5 is executed again. .

FIG. 3 is a partially cutaway perspective view of the oxygen sensor 5 used in the combustion device according to one embodiment of the present invention. The cathode electrode film 16a and the anode electrode film 16b (not shown) are formed on both surfaces of the oxygen ion conductive solid electrolyte body 17. A spiral spacer 18 is disposed on one side of the solid electrolyte body 17 so as to surround the cathode-side electrode film 16a, and the start end and the end of the solid spacer 17 are spaced apart from each other. A seal plate 19 is arranged. The oxygen diffusion passage 20 is
Partition walls of the spiral spacer 18 facing each other and the solid electrolyte body 1
7 and the seal plate 19 are formed in a spiral space.

The heating element 6 is arranged above the seal plate 19 and is integrated with the oxygen sensor 5.

Next, a description will be given based on a concrete experimental example. The oxygen sensor 5 of FIG. 3 was made of the following materials. The solid electrolyte body 17 is zirconia (ZrO ₂ with 8 mol% of Y ₂ O ₃ added). The electrode films 16a and 16b contain platinum as a main component, and contain a small amount (for example, 5%) of a binder made of copper oxide and bismuth oxide. The spiral spacer 18 is made of glass (coefficient of thermal expansion is substantially the same as that of zirconia, and contains a small amount of heat resistant particles having a predetermined particle size). The seal plate 19 is forsterite, and the heating element 6 is a platinum heater.

The manufacturing method will be described. Electrode film 16a ・ 16b
On top of the solid electrolyte body 17, and further on the spiral spacer 18
Was formed on the solid electrolyte body 17 using a thick film printing technique and a firing technique. The heating element 6 above the sealing plate 19,
It was formed using a thick film printing technique and a firing technique. next,
Helical spacer 18 on solid electrolyte body 17 and seal plate 1
Oxygen diffusion passage 20 was formed by laminating and heating and melting.

The firing is performed at 820 ° C. except for the heating body 6. The firing conditions were determined from the viewpoint of securing the melting point (about 850 ° C.) of the binder made of copper oxide and bismuth oxide added to the platinum electrode in a small amount and the current required to obtain the characteristics.

Finally, a lead wire (not shown) was attached to complete the process. The oxygen sensor 5 and the heating body 6 were used as a packaged body in which a heat insulating material was wrapped, and the heat insulating material was wrapped in a stainless steel wire mesh. .

The effects of the present invention will be described below based on experiments. The oxygen sensor 5 integrated with the heating element 6 shown in FIG. 3 is arranged in the exhaust gas flow path 4, and the air supply unit 2 receives the oxygen concentration signal from the oxygen sensor 5 so that the oxygen concentration in the exhaust gas becomes 10%. We made a prototype of a combustion device that controls the combustion.

This combustion device is a heating combustion device using kerosene as a fuel, and the fuel supply amount, the air supply amount, and the exhaust gas temperature are changed by changing the combustion amount. The fuel supply unit 1 is an electromagnetic pump, and detects the fuel supply amount from the pulse signal of the electromagnetic pump. The air supply unit 2 is a blower fan, and detects the air supply amount from the rotation speed of the blower fan. The exhaust gas temperature is detected by the exhaust gas temperature detecting means 13 including a temperature sensor arranged in the exhaust gas passage 4. The operating temperature of the oxygen sensor 5 is detected by attaching the temperature sensor 13 to the oxygen sensor 5.

Table 1 shows the generated voltage value of the heating DC power supply 10 and the operating temperature of the oxygen sensor 5 under each condition.

[0031]

[Table 1]

The generated voltage value of the heating DC power supply 10 was changed according to the following set values. The set value of the fuel supply amount is F
max is 400 g / h and Fmin is 250 g / h.
When the detected value F is 485 g / h, 400 g / h of Fmax
Since it is larger, the generated voltage value of the heating DC power supply 10 is V
It was set to 9.0V of min. When the detected value F is 340g / h, it is smaller than 400g / h of Fmax and 250g of Fmin.
Since it is larger than / h, the generated voltage value of the heating DC power supply 10 is set to 9.4 V of Vave. On the other hand, the detected value F is 19
In the case of 5 g / h, since it is smaller than Fmin of 250 g / h, the generated voltage value of the heating DC power supply 10 is Vmax of 9.8.
Set to V.

As for the set value of the air supply amount, Qmax is 1.90.
Nm ³ / is h Qmin is 1.20Nm ³ / h. When the detected value Q is 2.33 Nm ³ / h, 1.90 N of Qmax
Since it is larger than m ³ / h, the generated voltage value of the heating DC power supply 10 was set to 9.0 V which is Vmin. Detection value F is 1.6
In the case of ³ Nm ³ / h, it is smaller than 1.90 Nm ³ / h of Qmax and larger than 1.20 Nm ³ / h of Qmin, so that the generated voltage value of the heating DC power supply 10 is set to 9.4 V of Vave. On the other hand, when the detected value Q is 0.93 Nm ³ / h, Qmin
Since it is smaller than 1.20 Nm ³ / h, the generated voltage value of the heating DC power supply 10 is set to 9.8 V which is Vmax.

The set value of the exhaust gas temperature is Tmax of 200 ° C.
And Tmin is 150 ° C. When the detected value T is 250 ° C., it is higher than Tmax of 200 ° C. Therefore, the generated voltage value of the heating DC power supply 10 is set to Vmin of 9.0V. When the detected value T is 190 ° C, it is smaller than Tmax of 200 ° C and larger than Tmin of 150 ° C.
The generated voltage value of Vave was set to 9.4 V of Vave. On the other hand, when the detected value T is 130 ° C., it is smaller than Tmin of 150 ° C., so that the generated voltage value of the heating DC power supply 10 is Vmax of 9.
It was set to 8V.

By changing the generated voltage value of the heating DC power source 10 according to the fuel supply amount, the air supply amount and the exhaust gas temperature, the operating temperature of the oxygen sensor 5 could be maintained at about 500.degree. Therefore, the oxygen sensor 5 was able to secure sufficient durability reliability even when used for a long period of time.

On the other hand, if the generated voltage value of the heating DC power supply 10 is kept constant irrespective of the fuel supply amount, the air supply amount and the exhaust gas temperature as in the conventional case, for example, the operation of the oxygen sensor 5 in the case of high combustion. The temperature becomes excessively high at 550 ° C., and the durability reliability is reduced in a short time. For example, in the case of low combustion, the operating temperature of the oxygen sensor 5 becomes extremely low at 450 ° C., which is necessary for obtaining the characteristics. Problems such as difficulty in obtaining a limiting current have occurred.

Next, the timing of changing the generated voltage value of the heating DC power supply 10 will be described. When any one of the detected values of the exhaust gas temperature T, the fuel supply amount F, or the air supply amount Q is determined to exceed the above-mentioned set value, the generated voltage value of the heating DC power supply 10 is changed for 2 minutes thereafter. The current voltage value was maintained without change. And this 2
The air supply unit 2 was controlled based on the oxygen concentration signal from the oxygen sensor 5 for each minute to adjust the oxygen concentration in the exhaust gas to 10%. This means that these detected values exceeding the set values mean that the fuel supply amount or the air supply amount has changed significantly, and at this time, the air supply unit is based on the oxygen concentration signal from the oxygen sensor 5. This is because the control of No. 2 is performed with the highest priority and the oxygen concentration in the exhaust gas is adjusted to 10%.
In the case of a combustion device with two or more detection values, it is assumed that the determination of the remaining one or more detection values is not performed when it is determined that any one exceeds the set value.

Immediately after 2 minutes of the predetermined time A, the generated voltage value of the heating DC power source 10 is changed to a new voltage value, and the subsequent 0.5 minutes is based on the oxygen concentration signal from the oxygen sensor 5. The control of the air supply unit 2 was released. This is because if the generated voltage value of the heating DC power supply 10 is changed, the oxygen sensor 5 will be erroneously measured and the oxygen concentration cannot be measured accurately. Then, when the predetermined time B is 0.
After 5 minutes, the control of the air supply unit 2 based on the oxygen concentration signal from the oxygen sensor 5 was executed again. As a result, changes in the oxygen concentration signal from the oxygen sensor 5 due to changes in the voltage value generated by the heating DC power supply 10 can be handled smoothly,
The combustion equipment burned normally without producing incomplete combustion.

On the other hand, if the generated voltage value of the heating DC power supply 10 is instantly changed without providing the predetermined time A and the predetermined time B, and the control is always performed by the oxygen concentration signal from the oxygen sensor 5. As the generated voltage value of the heating DC power supply 10 was changed, the oxygen sensor 5 erroneously measured and the accurate oxygen concentration could not be measured, and the combustion equipment caused incomplete combustion.

The experiment was carried out with a combustion device which receives the oxygen concentration signal from the oxygen sensor 5 and controls the air supply unit 2 so that the oxygen concentration in the exhaust gas becomes 10%. Needless to say, a similar effect was obtained with a combustion device in which the oxygen concentration in the exhaust gas was set to 5%, for example. Further, the experiment was carried out on an electrode film containing a small amount (for example, 5%) of a binder containing platinum as a main component and copper oxide and bismuth oxide. In the case of this electrode, the melting point of copper oxide and bismuth oxide used as the binder is about 850 ° C.,
It is not preferable to raise the operating temperature of the oxygen sensor 5 excessively from the viewpoint of ensuring the durability of the electrodes. Therefore, the present invention was particularly effective. Needless to say, the same effect can be obtained with a platinum electrode film using an oxygen sensor having another structure or another bonding material.

In the experiment, a platinum heater was used as the heating element 6. The platinum heater has a small temperature coefficient and also serves as a temperature sensor. Therefore, there is an advantage that the integrated heating body 6 is less likely to be subjected to slight combustion conditions such as exhaust gas temperature and the operating temperature of the oxygen sensor 5 is kept substantially constant.

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a flow chart of the control flow of the combustion equipment according to the first embodiment of the present invention. When you start
In step 1, the RAM in the exhaust gas temperature comparison unit 12 is cleared. Next, in step 2, the exhaust gas temperature comparison unit 12 reads the exhaust gas temperature T, in step 3 the set values Tmax and Tmin are called, and in step 4, the exhaust gas temperature T and the set values Tmax and Tmin are compared. If it is determined in step 5 that the exhaust gas temperature T is higher than or equal to the set value Tmax, the heating voltage changing means 11 is determined in step 6.
Is activated to set the generated voltage value of the heating DC power source 10 to Vmin. On the other hand, when it is determined in step 7 that the exhaust gas temperature T is smaller than the set value Tmax and larger than the set value Tmin, the generated voltage value of the heating DC power supply 10 is set to Vave in step 8. When it is determined in step 9 that the exhaust gas temperature T is less than or equal to the set value Tmin, the generated voltage value of the heating DC power supply 11 is set to Vmax in step 10.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a flow chart of the control flow of the combustion equipment according to the second embodiment of the present invention. When starting, in step 11, RA in the fuel supply amount comparison unit 14
M is cleared. Next, in step 12, the fuel supply amount comparison unit 14 reads the fuel supply amount F, and in step 13, calls the set values Fmax and Fmin.
In step 4, the fuel supply amount F is compared with the set values Fmax and Fmin. If it is determined in step 15 that the fuel supply amount F is greater than or equal to the set value Fmax, the heating voltage changing means 11 operates in step 16 to set the generated voltage value of the heating DC power supply 10 to Vmin. On the other hand, the fuel supply amount F is the set value Fm.
If it is judged in step 17 that it is smaller than ax and larger than the set value Fmin, in step 18, the heating DC power supply 10
The generated voltage value of is set to Vave. Also, the fuel supply amount F
When it is determined in step 19 that is smaller than or equal to the set value Fmin, the generated voltage value of the heating DC power supply 10 is set to Vmax in step 20.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a flow chart of the control flow of the combustion equipment according to the third embodiment of the present invention. When you start
In step 21, the RAM in the air supply amount comparison unit 15 is cleared. Next, in step 22, the air supply amount comparison unit 15 reads the air supply amount Q, and in step 2
The set values Qmax and Qmin are called in 3 and the air supply amount Q is compared with the set Qmax and Qmin in step 24. If,
When it is judged in step 25 that the air supply amount Q is greater than or equal to the set value Qmax, the heating voltage changing means 11 is activated in step 26 to change the generated voltage value of the heating DC power supply 10 to V.
Set to min. On the other hand, when it is judged in step 27 that the air supply amount Q is smaller than the set value Qmax and larger than the set value Qmin, the generated voltage value of the heating DC power supply 10 is set to Vave in step 28. When it is determined in step 29 that the air supply amount Q is smaller than or equal to the set value Qmin, the generated voltage value of the heating DC power supply 10 is set to Vmax in step 30.

[0048]

【The invention's effect】

(1) Since the present invention operates the heating element when the exhaust gas temperature becomes high, the fuel supplied from the fuel supply unit increases, or the air supply amount increases corresponding to the supplied fuel amount. The generated voltage value of the DC power supply for heating becomes small. When the exhaust gas temperature is high, or when the fuel supply unit supplies a large amount of fuel or when the corresponding air supply amount is large, the oxygen sensor exchanges a large amount of heat from the exhaust gas, so the operating temperature of the oxygen sensor naturally rises. To do. Therefore, if the generated voltage value of the heating DC power supply is reduced correspondingly, the oxygen sensor has an appropriate operating temperature that is not excessively high, and durability reliability is improved.

(2) In the present invention, set values are set for the exhaust gas temperature, the fuel supply amount, and the air supply amount, and the detected value is judged to be larger or smaller than the set value. Therefore, whether the generated voltage value of the heating DC power supply is to be large or small is accurately determined, the oxygen sensor has an appropriate operating temperature that is not excessively high, and durability reliability is further improved.

(3) In the present invention, set values are set for the exhaust gas temperature, the fuel supply amount, and the air supply amount, and it is determined whether or not the detected values exceed the set values. When the detected value exceeds the set value, the generated voltage value of the heating DC power supply is maintained as it is and the oxygen voltage from the oxygen sensor The fuel supply unit or the air supply unit is controlled based on the concentration signal. Then, when the predetermined time A has elapsed, the generated voltage value of the heating DC power supply is changed to a new voltage value, and the control of the fuel supply section or the air supply section based on the oxygen concentration signal from the oxygen sensor is released. The control release of the fuel supply section or the air supply section ends after a predetermined time B, and thereafter, the control of the fuel supply section or the air supply section based on the oxygen concentration signal from the oxygen sensor is executed again. Therefore, the change in the oxygen concentration signal from the oxygen sensor due to the change in the generated voltage value of the heating DC power supply can be dealt with smoothly, and the combustion equipment burned normally without causing incomplete combustion.

(4) In the oxygen sensor used in the present invention, the cathode electrode film and the anode electrode film are formed on both surfaces of the oxygen ion conductive solid electrolyte body, and the cathode side electrode film is surrounded on one side of the solid electrolyte body. Moreover, the spiral spacers are arranged such that the starting end and the terminating end are spaced from each other, and the seal plate is arranged on the upper part of the spiral spacer. Since the oxygen diffusion passage is formed in the spiral space surrounded by the partition walls of the spiral spacer facing each other, the solid electrolyte body, and the seal plate, the oxygen sensor can be manufactured using thick film printing. Moreover, since the heating element is arranged on the upper part of the seal plate and is integrated with the oxygen sensor, the structure is simplified, and the oxygen sensor is manufactured together with the oxygen sensor manufacturing using the thick film printing described above. Can be manufactured at low cost. Further, since the oxygen sensor and the heating body are integrated, there is an advantage that the integrated heating body is less likely to be subjected to slight combustion conditions such as exhaust gas temperature.

(5) In the cathode electrode film and the anode electrode film of the oxygen sensor used in the present invention, a small amount (for example, 5%) of a binder composed mainly of platinum and made of copper oxide and bismuth oxide.
%) Contained. The melting point of copper oxide and bismuth oxide used as the binder of the electrode is about 850 ° C, and it is not preferable to raise the operating temperature of the oxygen sensor excessively from the viewpoint of ensuring the durability of the electrode, but when the exhaust gas temperature becomes high. Since the generated voltage value of the heating DC power supply for operating the heating body is reduced in response to such combustion conditions, the oxygen sensor has an appropriate operating temperature that is not excessively high, and durability reliability is improved.

(6) A platinum heater was used as the heating element.
The platinum heater has a small temperature coefficient and also serves as a temperature sensor. Therefore, there is an advantage that the integrated heating body hardly receives a slight combustion condition such as exhaust gas temperature and the operating temperature of the oxygen sensor is kept substantially constant.

[Brief description of drawings]

FIG. 1 is a block diagram of a combustion device according to an embodiment of the present invention.

[Fig. 2] The same operation diagram of the combustion equipment

FIG. 3 is a partially cutaway perspective view of the oxygen sensor and the heating body.

FIG. 4 is a flowchart of a control flow of the combustion device according to the first embodiment of the present invention.

FIG. 5 is a flow chart of a control flow of the combustion device according to the second embodiment of the present invention.

FIG. 6 is a flow chart of a control flow of a combustion device according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a conventional combustion device.

FIG. 8 is a characteristic diagram showing the exhaust gas temperature and the oxygen concentration in the exhaust gas when the combustion amount is changed while the air supply amount is constant.

FIG. 9 is a characteristic diagram showing the operating temperature of the oxygen sensor when the power generated by the heating DC power supply is changed.

FIG. 10 is a voltage-current characteristic diagram of the oxygen sensor when the exhaust gas temperature is changed.

[Explanation of symbols]

 1 Fuel Supply Section 2 Air Supply Section 4 Exhaust Gas Flow Path 5 Oxygen Sensor 6 Heating Body 9 Control Section 10 DC Power Supply for Heating 11 Heating Voltage Change Means 12 Exhaust Gas Temperature Comparison Section 13 Exhaust Gas Temperature Detection Means (Temperature Sensor) 14 Fuel Supply Quantity Comparison Part 15 Air supply amount comparison part 16a Cathode electrode film 16b Anode electrode film 17 Solid electrolyte body 18 Spiral spacer 19 Seal plate 20 Oxygen diffusion passage

Claims (8)

[Claims] 1. A combustion apparatus in which a control unit controls a fuel supply unit for supplying fuel or an air supply unit for supplying air based on an oxygen concentration signal from a limiting current type oxygen sensor arranged in an exhaust gas flow path, The exhaust gas temperature detected by the exhaust gas temperature detecting means arranged in the exhaust gas flow passage is compared with a set value in the exhaust gas temperature comparison unit, and as the exhaust gas temperature becomes higher, it is placed in the exhaust gas flow passage along with the limiting current type oxygen sensor. Combustion equipment in which the voltage value generated by the heating DC power supply for operating the heating element is reduced by the heating voltage changing means. 2. A combustion device in which a control unit controls a fuel supply unit for supplying fuel or an air supply unit for supplying air based on an oxygen concentration signal from a limiting current type oxygen sensor arranged in an exhaust gas flow path, The fuel supply amount supplied from the fuel supply unit is compared with a set value in the fuel supply amount comparison unit, and as the fuel supply amount increases, a heating element arranged in the exhaust gas flow path along with the limiting current type oxygen sensor is provided. Combustion equipment in which the voltage value generated by the heating DC power supply for operation is reduced by the heating voltage changing means. 3. A combustion device in which a control unit controls a combustion supply unit for supplying fuel or an air supply unit for supplying air based on an oxygen concentration signal from a limiting current type oxygen sensor arranged in an exhaust gas flow path, The air supply amount supplied from the air supply unit corresponding to the fuel supply amount from the fuel supply unit is compared with a set value in an air supply amount comparison unit, and as the air supply amount increases, the limiting current type oxygen sensor Combustion equipment in which the heating voltage changing means reduces the generated voltage value of the heating DC power supply for operating the heating element arranged in the exhaust gas flow path. 4. The heating is performed by setting a set value for each of the exhaust gas temperature in claim 1, the fuel supply amount in claim 2, and the air supply amount in claim 3, and determining whether the detected value is larger or smaller than the set value. Combustion equipment designed to control the generated voltage value of the DC power supply for power supply. 5. A set value is set for each of the exhaust gas temperature in claim 1, the fuel supply amount in claim 2, and the air supply amount in claim 3, and from the time when it is determined that the detected value exceeds the set value. Within the predetermined time A, the generated voltage value of the heating DC power supply is not changed, and the fuel supply unit or the air supply unit is controlled based on the oxygen concentration signal from the limiting current type oxygen sensor. Within time B, the combustion device is configured to release the control of the fuel supply unit or the air supply unit based on the oxygen concentration signal from the limiting current type oxygen sensor and change the generated voltage value of the heating DC power supply. 6. A limiting current type oxygen sensor, an oxygen ion conductive solid electrolyte body, and a pair of cathode electrode film and anode electrode film formed on both surfaces of the solid electrolyte body,
A spiral spacer disposed on one side of the solid electrolyte body so as to surround the cathode electrode film so that the starting end and the terminating end are spaced apart from each other, and a sealing body arranged on the upper part of the spiral spacer. 6. The oxygen diffusion passage is formed in a spiral type space surrounded by the partition walls of the solid electrolyte body, the spiral type spacer facing each other, and the seal body, and the heating body is formed in the seal body. Combustion equipment described in. 7. The combustion device according to claim 6, wherein the cathode electrode film and the anode electrode film of the limiting current type oxygen sensor are mainly composed of platinum and contain a small amount of a binder made of copper oxide and bismuth oxide. . 8. The combustion device according to claim 6, wherein the heating element is a platinum heater.