JPH0783428A - Oxygen sensor controller - Google Patents

Abstract

PURPOSE:To provide controller that shortens the heat-up time of an oxygen sensor and reduces changes with time in characteristic of the oxygen sensor and a sensor heater. CONSTITUTION:This oxygen sensor controller comprises a heater controller 4 for holding a temperature of an oxygen sensor 1 at a predetermined value. The heater controller intermittently supplies a rated voltage to the sensor 1 to intermittently measure oxygen concentration. During the idle period, the heater controller keeps a sensor heater 3 in a range of temperature that does not adversely affect the life of the heater itself. Accordingly, a total measuring time of the sensor is shortened, and heat-up time of the sensor is also shortened. Further, since repetition of a heat cycle and a temperature difference of high and low temperature are reduced, its life can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor control device for detecting the oxygen concentration in air or exhaust gas.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a limiting current type oxygen sensor (hereinafter referred to as an oxygen sensor) is provided with electrodes 21 and 22 on both surfaces of a zirconia solid electrolyte 20, and a voltage 23 is applied to both ends thereof. Then, when an electric current is applied, an electrochemical reaction of injecting and releasing oxygen generated in the cathode 21 and the anode 22 occurs. By limiting the supply of oxygen in the process of injecting and releasing oxygen, a saturation current characteristic appears in the voltage-current characteristic as shown in FIG. 5, and its magnitude is almost proportional to the oxygen concentration in the atmosphere. The oxygen sensor utilizes this characteristic to supply oxygen to the cathode through the gas diffusion port 24, and at this stage the rate of diffusion is controlled to obtain a limiting current proportional to the oxygen concentration supplied.

This oxygen sensor is excellent in stability and has a long life, but has a drawback that it has to be operated by being heated to a high temperature because of its large internal resistance. For this reason,
In this type of oxygen sensor, a sensor heating heater 25 is attached in the vicinity of the oxygen sensor section, and a predetermined voltage 26 is applied to
Use after self-heating.

Further, since the oxygen sensor itself obtains a limiting current proportional to the oxygen concentration supplied by limiting the oxygen diffusion rate, the oxygen sensor itself has a very precise and small shape. In addition, since the sensor heating heater 25 is also arranged in close contact therewith, it is configured to heat in a very small area.

The oxygen sensor is used to measure the oxygen concentration in the room air for indoor environment measurement so as to output the measured value, or is attached to the exhaust path of the combustor to correct the exhaust gas. Detects the oxygen concentration in the air, compares it with a target value of the air-fuel ratio so that it becomes a preset value, and controls at least one of the combustion air amount and fuel amount to stabilize combustion in the burner section. Use to let.

[0006]

However, the above-mentioned conventional oxygen sensor has a temperature dependence that the limiting current increases as the ambient temperature increases and decreases as the ambient temperature decreases, as shown in FIG. However, the predetermined output of the oxygen sensor cannot be obtained until the predetermined high temperature is reached.

Therefore, when it is used for measuring the indoor environment, the sensor heater 25 is energized and held in a heated state, but the sensor heater 25 is always energized and remains at a high temperature. From
Damage to the zirconia electrolyte 20, which is the substrate, and electrodes 21, 2
There is a problem that the life of the oxygen sensor and the sensor heater 25 itself is shortened due to the occurrence of peeling of 2 and the like.

Therefore, if the measurement is performed intermittently,
Repeated ON / OFF of heating by the sensor heating heater 25, that is, heating from room temperature to high temperature at the same time, and extreme heat cycle between room temperature and high temperature, damage of the zirconia electrolyte 20 which is the substrate, peeling of the electrodes 21, 22 and the like occur. As a result, the life of the oxygen sensor and the sensor heater 25 itself could not be lengthened.

When used for combustion correction of a combustor, if the electrodes 21, 22 of the oxygen sensor and the sensor heating heater 25 are energized in accordance with ignition / extinction of combustion, the zirconia electrolyte 20 of the oxygen sensor will be used. When the energization is started at a low temperature, the output of the oxygen sensor cannot be used during the heat-up time of the oxygen sensor by the sensor heater 25.

Therefore, if the output of the oxygen sensor is not used for the heat-up time, it is almost impossible to correct the combustion of the burner portion based on the output of the oxygen sensor when the ignition and the extinction of combustion are repeated in a short time. There was a problem. When the ignition and extinguishing of combustion are repeated, the sensor heater 25 turns on / off the heating.
Repeatedly, that is, heating from room temperature to a high temperature, and an extreme heat cycle between room temperature and high temperature, the zirconia electrolyte 20 that is the substrate is damaged, the electrodes 21 and 22 are peeled off, etc. Also, there has been a problem that the life of the sensor heater 25 itself is shortened.

Further, if the combustion is left with the combustion stopped, the oxygen sensor is kept at a low temperature,
Water and dust in the atmosphere, and other components adhere to the electrodes 21 and 22 of the oxygen sensor and the sensor heater 25, and the surface of the zirconia electrolyte 20 and the electrodes 21 and 2 which are the substrates thereof.
2 The surface may be covered or oxidized to impair its properties.

Therefore, in order to reduce the number of times of heat-up, if the sensor heating heater 25 is energized and held in a heated state even when the burner is not burning, the sensor heating heater 25 is always in a high temperature state. Therefore, the life of the oxygen sensor and the heater for heating the sensor itself is shortened by the damage of the zirconia electrolyte 20 which is the substrate and the peeling of the electrodes 21, 22 as described above.

Therefore, conventionally, the electric power of the sensor heating heater 25 has been devised by devising a mounting structure which is not greatly affected by the moisture and dust of the exhaust gas, selecting and adjusting the resistance of the sensor heating heater 25, and adjusting the applied voltage. Of the sensor heater 25 is suppressed to an extremely small value, and the deterioration of the service life due to the temperature variation of the sensor heater 25 is suppressed.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to shorten the heat-up time and reduce the secular change of the oxygen sensor and the sensor heating heater to extend the service life.

[0015]

In order to achieve the above-mentioned object, the present invention uses an oxygen sensor for detecting the oxygen concentration and an oxygen sensor for controlling the oxygen sensor when used for measuring the indoor environment. A sensor control unit that outputs a value according to the oxygen concentration, a sensor heating heater that is arranged in close contact with the oxygen sensor and that keeps the temperature of the oxygen sensor at a high temperature, and a heater that can arbitrarily set the temperature of the sensor heating heater. The sensor control unit intermittently supplies a rated voltage to the oxygen sensor so that the oxygen concentration is intermittently measured, and the heater control unit intermittently supplies the rated voltage to the sensor heating heater. In addition, the temperature of the sensor heating heater is high at a level that does not shorten the life of the sensor heating heater itself during non-measurement. Configured to control the heater so as to maintain, and unmeasured o'clock has a configuration in which a sensor holding part for holding an output value corresponding to the oxygen concentration of the previous oxygen sensor has detected.

When used for the combustion correction of the combustor, an oxygen sensor provided in the exhaust path of the burner for detecting the oxygen concentration and the output from the oxygen sensor are used as the air-fuel ratio target value of the air-fuel ratio target setting section. A combustion control unit that controls at least one of the amount of combustion air and the amount of fuel in comparison with, and a sensor control unit that controls the oxygen sensor and outputs a value according to the oxygen concentration detected by the oxygen sensor,
A sensor heating heater which is disposed in close proximity to the oxygen sensor and holds the temperature of the oxygen sensor at a high temperature, and a heater control unit which can arbitrarily set the temperature of the sensor heating heater are provided, and the heater control unit is a burner unit. The heater is controlled so that the temperature of the sensor heater is maintained at a high level within the range where the life of the sensor heater itself is not shortened during non-combustion.

[0017]

When the present invention is used for measuring the indoor environment, the oxygen sensor intermittently measures the oxygen concentration, so that the total measuring time of the oxygen sensor is shortened and the oxygen sensor and the sensor are reduced. The heating heater is kept at a high temperature for a short time, and the temperature of the sensor heating heater is kept high at a level that does not shorten the life of the sensor heating heater itself during non-measurement. Can be shortened,
Further, since the heat cycle by the sensor heater is repeated and the temperature difference between high and low is reduced, the life can be further extended. In addition, even during non-measurement, moisture and dust in the atmosphere, other components adhere to the oxygen sensor and the sensor heating heater to cover or oxidize the zirconia electrolyte surface or electrode surface, which is its substrate,
It also eliminates the possibility of impairing its characteristics.

Further, when used for correcting the combustor, the oxygen sensor does not measure the oxygen concentration during non-combustion as described above, so that the total measuring time of the oxygen sensor is shortened and the oxygen sensor and sensor heating are reduced. The time the heater is kept at high temperature is shortened, and the temperature of the sensor heating heater is kept high at a level that does not shorten the life of the sensor heating heater itself during non-measurement, so the heat up time of the oxygen sensor is shortened. In addition, since the heat cycle by the sensor heater and the temperature difference between high and low are reduced, the life can be further extended. Even during non-measurement, moisture, dust, and other components in the atmosphere adhere to the oxygen sensor and sensor heater to cover or oxidize the zirconia electrolyte surface or electrode surface, which is the substrate, and its characteristics. It also eliminates the possibility of damage.

Therefore, the life is long, the heat-up time is short, the response is good, and the influence of the surrounding environment can be suppressed, and the mounting structure can be made easy to use.

[0020]

Embodiments of the present invention will be described below with reference to FIGS. First, the case of using for indoor environment measurement will be described with reference to FIG. Reference numeral 1 is an oxygen sensor that detects the oxygen concentration, and 2 is a sensor control unit that controls the oxygen sensor 1 and outputs a value according to the oxygen concentration detected by the oxygen sensor 1. Reference numeral 3 is a sensor heating heater which is arranged in close contact with the oxygen sensor 1 and maintains the temperature of the oxygen sensor 1 at a high temperature.
The temperature can be set arbitrarily. Reference numeral 5 is a timer control unit that sends a signal to the sensor control unit 2 and the heater control unit 4 so as to intermittently measure the oxygen concentration. 6
Is a sensor measurement value holding unit that holds an output value corresponding to the oxygen concentration output from the sensor control unit 2 until the next oxygen concentration measurement, and outputs the held oxygen concentration to the display control unit 7, The sensor display unit 8 is configured to display.

In the above configuration, the timer control section 4
Until the time elapses, the sensor heating heater 3 is constantly applied by the heater control unit 4 with a temperature level within a range that does not impair the heat resistant life of the oxygen sensor 1 and the sensor heating heater 3, for example, 80% of the rated voltage. Therefore, the temperatures of the oxygen sensor 1 and the sensor heater 3 are kept at high temperatures. Further, when the timer control unit 5 times up and a signal for starting the oxygen concentration measurement is output from the timer control unit 5 to the sensor control unit 2 and the heater control unit 4, the oxygen is measured by the sensor control unit 2 and the heater control unit 4. The rated voltage is applied to the sensor 1 and the sensor heater 3. Then, when the output of the oxygen sensor 1 becomes stable, a value corresponding to the oxygen concentration measured by the sensor control unit 2 is output to the sensor measurement holding unit 6 and at the same time a measurement end signal is sent to the timer control unit 5. Is output. Then, the timer control unit 5 outputs a signal of the oxygen concentration measurement end to the sensor control unit 2 and the heater control unit 4, and at the same time, restarts the timer count. In addition, the sensor heater 3 has a heater controller 4
As a result, the voltage of 80% of the rated voltage is applied again. After that, the same operation is repeated and the measurement of oxygen concentration is repeated.

Here, since the oxygen sensor 1 measures the oxygen concentration intermittently for a very short time by the timer control unit 5, the time period during which the oxygen sensor 1 and the sensor heater 3 are kept at high temperature is shortened. During normal non-measurement, the temperature of the sensor heating heater 3 is maintained at a high temperature within a range that does not shorten the life of the sensor heating heater 3 itself, so that the heat-up time of the oxygen sensor 1 can be shortened, and the sensor heating heater can also be shortened. Since the heat cycle by 3 and the temperature difference between high and low are reduced, the life can be further extended. Further, even during non-measurement, moisture and dust in the atmosphere, other components adhere to the oxygen sensor 1 and the sensor heating heater 3 to cover or oxidize the substrate surface of the zirconia electrolyte or the electrode, It also eliminates the possibility of impairing its characteristics.

Next, the case of use for correcting the combustor will be described with reference to FIGS. In FIG. 2, 9 is a burner for burning fuel, which is supplied with fuel from a pump 10 and is supplied with combustion air from a burner blower 11, and the pump 10 and burner blower 11 are controlled by a controller 12. Reference numeral 13 denotes an oxygen sensor unit that is provided in the exhaust passage 9A of the burner 10 and detects the oxygen concentration of the burner unit 9, and has an oxygen sensor 14 and a sensor heater 15.

FIG. 3 shows the control unit 12, and 16 is a sensor control unit for controlling the oxygen sensor 14 and outputting a value corresponding to the oxygen concentration detected by the oxygen sensor 14.
Reference numeral 17 is a heater control unit for controlling the sensor heating heater 16, and 18 is the sensor control unit 15 and the heater control unit 17
A timer control unit that sends a signal to measure the oxygen concentration, 19 is an air-fuel ratio target setting unit, 20 is an air-fuel ratio target value of the air-fuel ratio target setting unit 19 and the output from the sensor control unit 15 is compared, and The combustion control unit controls at least one of the combustion air amount and the combustion amount so as to reduce the difference.

In the above structure, the non-combustion sensor heating heater 16 is constantly controlled by the heater control unit 17 to a temperature level within a range that does not impair the heat resistant life of the oxygen sensor 15 and the sensor heating heater 17, for example, a rated voltage of 80.
% Voltage is applied, and the temperatures of the oxygen sensor 1 and the sensor heater 3 are kept high. When a combustion start command is issued by a signal from the operation button or the like, the timer control unit 18 sends an oxygen concentration measurement start signal to the sensor control unit 15 and the heater control unit 17.
Is output to the sensor control unit 15 and the heater control unit 1.
Oxygen sensor 14 and sensor heater 16 from 7
The rated voltage is applied to. At the same time, the pump 10 and the burner blower are energized to start combustion based on a predetermined sequence. Then, when the output of the oxygen sensor 14 becomes stable, the sensor control unit 15
The value according to the oxygen concentration measured more is output to the combustion control unit 20. The combustion control unit 20 includes an air-fuel ratio target setting unit 19
Pump 1 to reduce the difference by comparing with the air-fuel ratio target value of
0 and the burner blower 11 to change the control amount of the pump 10 and the burner blower 11 to change the ratio of the combustion air amount and the combustion amount.

In this way, the control amounts of the pump 10 and the burner blower 11 are changed so that the air-fuel ratio target value is in accordance with the oxygen concentration measured by the oxygen sensor 14, and the ratio between the combustion air amount and the combustion amount is changed. Repeat changing feedback.

Here, since the oxygen sensor 14 measures the oxygen concentration by the sensor control output unit 15 only during combustion, as in the previous embodiment, the time during which the oxygen sensor 14 and the sensor heating heater 16 are kept at a high temperature. Becomes shorter and the sensor heater 1
Since the temperature of 6 is kept at a high temperature within a range that does not shorten the life of the sensor heating heater 16 itself, the heat-up time of the oxygen sensor 14 can be shortened and the heat cycle of the sensor heating heater 16 can be repeated repeatedly. Since the temperature difference is also reduced, the life can be further extended. The temperature is 1 degree Celsius even during non-measurement.
If it is set to be 00 degrees or more, moisture and dust in the atmosphere, and other components adhere to the oxygen sensor 14 and the sensor heater 16 to cover the surface of the zirconia electrolyte or the electrode surface, which is the substrate, or to be oxidized. Or let me
It also eliminates the possibility of impairing its characteristics.

[0028]

As described above, the oxygen sensor control device of the present invention can shorten the heat-up time at the start of oxygen sensor measurement, reduce the secular change of the oxygen sensor and the sensor heating heater, and extend the service life. , The oxygen sensor can be used easily and with high reliability.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a combustion device using an oxygen sensor control device according to another embodiment of the present invention.

FIG. 3 is a block diagram of an oxygen sensor control device of the combustion device.

FIG. 4 is a diagram showing the operating principle of the oxygen sensor used in the present invention.

[Figure 5] Typical characteristics of the sensor

[Figure 6] Temperature characteristic diagram of the same sensor

[Explanation of symbols]

 1, 14 Oxygen sensor 2, 16 Sensor control unit 3, 15 Sensor heating heater 4, 17 Heater control unit 5, 18 Timer control unit 9 Burner 19 Air-fuel ratio target setting unit 20 Combustion control unit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuhisa Morikami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An oxygen sensor for detecting an oxygen concentration, a sensor control unit for controlling the oxygen sensor to output a value according to the oxygen concentration detected by the oxygen sensor, and an oxygen sensor provided in close proximity to the oxygen sensor. A sensor heating heater that holds the temperature of the sensor at a high temperature and a heater control unit that can arbitrarily set the temperature of the sensor heating heater are provided, and the sensor control unit ratings the oxygen sensor to intermittently measure the oxygen concentration. The voltage is supplied intermittently, and the heater control unit also supplies the rated voltage to the sensor heating heater intermittently, and the temperature of the sensor heating unit shortens the life of the sensor heating unit itself when not measuring. An oxygen sensor control device configured to control the heater so as to keep the temperature at a high level within a range that does not. 2. The oxygen sensor control device according to claim 1, further comprising a sensor holding unit that holds an output value corresponding to the oxygen concentration detected by the previous oxygen sensor during the non-measurement time. 3. An oxygen sensor for detecting the oxygen concentration provided in the exhaust passage of the burner, and an output from the oxygen sensor is compared with an air-fuel ratio target value of an air-fuel ratio target setting section to determine the combustion air amount or the fuel amount. A combustion control unit that controls at least one of them, a sensor control unit that controls the oxygen sensor and outputs a value according to the oxygen concentration detected by the oxygen sensor, and an oxygen sensor that is disposed in close proximity to the oxygen sensor. A sensor heating heater that holds the temperature at a high temperature and a heater control unit that can arbitrarily set the temperature of the sensor heating heater are provided, and the heater control unit controls the temperature of the sensor heating heater when the burner unit is not burning. Oxygen sensor control device configured to control the heater so as to maintain the high temperature at a level that does not shorten the service life of the.