JPH11326266A - Control device for oxygen sensor with heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a control device by which the concentration of oxygen can be detected with high responsivity by a method wherein the heating value of a heater is increased and a poisoning substance such as silicon or the like is burned and blown from the surface of a detecting element. SOLUTION: An oxygen sensor 2 which is installed at the exhaust pipe 1 of an engine and which is equipped with a heater is provided with a zirconia tube 6 which protrudes toward the inside of the exhaust pipe 1, and a heater 7 which is molded to be a small-diameter rod shape by a silicon nitride material is provided at the inside of the zirconia tube 6. When a poisoning substance such as silicon or the like which is contained in an exhaust gas is stuck to the surface of the zirconia tube 6, the responsivity of the sensor 2 is lowered. Then, a control device is constituted in such a way that, while the heater 7 is heated at a high capacity of 70 W or higher, the zirconia tube 6 is heated up to a temperature of, e.g. about 900 deg.C so as to burn and blow the poisoning substance from its surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an oxygen sensor with a heater which is suitably used for detecting, for example, the oxygen concentration in exhaust gas, and more particularly to a burn-off control for a poisoning substance or the like on a detection element. The present invention relates to a control device for an oxygen sensor with a heater as described above.

[0002]

2. Description of the Related Art In general, in an automobile engine equipped with a supercharger such as a turbocharger, an oxygen sensor with a heater is provided on the exhaust pipe side, and the oxygen sensor detects the oxygen concentration in the exhaust gas. The air-fuel ratio control of the engine is performed according to the detection signal.

[0003] In this case, in the case of an engine with a supercharger, the engine is often operated with an air-fuel ratio tending to be rich.
The temperature drops to about 0 ° C. On the other hand, the oxygen concentration detecting element provided in the oxygen sensor is activated at a temperature of, for example, about 350 ° C. and operates normally. For this reason, engines such as supercharged engines use oxygen sensors with heaters,
The oxygen concentration detecting element is heated by a heater.

In this type of oxygen sensor with a heater according to the prior art, an oxygen concentration detecting element made of a zirconia tube is provided at the tip end of a sensor casing, and a rod-shaped heater made of a ceramic material is provided in the detecting element. Is inserted, and the detection element is heated from the inside by the heater.

[0005]

By the way, in the above-mentioned prior art, an oxygen sensor is mounted in the middle of the exhaust pipe of the engine, and the oxygen concentration detecting element is protruded into the exhaust pipe. Impurities contained therein adhere to the outer surface of the detection element, and for example, the protective layer of the detection element is clogged by these impurities (hereinafter, referred to as poisoning substances), and the response for detecting the oxygen concentration is reduced. There is a problem of doing.

On the other hand, Japanese Unexamined Utility Model Publication No. Hei 6-86067 discloses a double-cylinder protector provided at the distal end of a sensor casing to protect a protruding end of a detecting element. An oxygen sensor (hereinafter, referred to as another conventional technology) is described in which a poisonous substance such as lead attached to the outer surface of a detection element is burned off by providing heat from the heater by providing a ceramic heater.

However, the other conventional oxygen sensor merely has a configuration in which a cylindrical ceramic heater is provided in a protector surrounding the detection element from the outside, and the amount of heat (capacity) of the heater is variably controlled. There is no disclosure of a configuration of a control device or the like that performs the control.

[0008] Further, in the other prior art, only lead or the like is cited as an example of the poisoning substance in the exhaust gas, and to what temperature the detecting element is heated by the heater is specifically disclosed. It has not been.

On the other hand, the inventor of the present invention has investigated in detail, among impurities contained in exhaust gas, a poisoning substance which adversely affects the response of the oxygen sensor.
It was confirmed that the responsiveness was reduced by the poisoning substance such as i attached to the surface (outer surface) of the detection element.

Then, in order to remove poisonous substances such as silicon from the surface of the detection element by burning off, the detection element is heated to a temperature of, for example, 800 ° C. or more, preferably about 900 to 930 ° C. We have learned that it is necessary.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention can burn off poisonous substances such as silicon from the surface of a detection element by increasing the calorific value of a heater, and reduce the oxygen concentration. It is an object of the present invention to provide a control device for a heater-equipped oxygen sensor capable of detecting a high-speed response with high responsiveness, stably outputting the detection signal over a long period of time, and improving reliability.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a detection element for detecting an oxygen concentration and an oxygen sensor with a heater having a heater for heating the detection element. The present invention is applied to a control device for an oxygen sensor with a heater, comprising: a power supply control means for controlling power supply to the heater for generating heat in the heater of the oxygen sensor.

[0013] A feature of the configuration adopted by the invention of claim 1 is that the power supply control means includes a low-capacity state corresponding to a heat generation amount for activating the detection element and a heat generation higher than the low-capacity state. The capacity of the heater is variably controlled in at least two stages of a high capacity state having an amount, and the heater heats the detection element to a temperature of 800 ° C. or more in the high capacity state.

With this configuration, when the capacity of the heater is set to the low capacity state, the heater can generate heat at a low capacity, and the heater is heated to a temperature suitable for activating the oxygen concentration detecting element. Thus, for example, even when the temperature of the exhaust gas is low, the oxygen concentration in the exhaust gas can be favorably detected by the detecting element. On the other hand, when the capacity of the heater is set to the high capacity state, 800
The detection element can be heated to a temperature equal to or higher than ° C., and poisons attached to the surface of the detection element and the like can be burned off by heat from the heater.

According to the second aspect of the present invention, in order to prevent the detection element from being deteriorated by heat from the heater, the power supply control means sets the heater to a high capacity state within a predetermined time period. The heater is switched to a low-capacity state when a predetermined time is exceeded.

Thus, for example, the heater can be controlled to the high-capacity state only once within a predetermined time until the engine is started and stopped, and the detecting element is excessively heated by the heat from the heater. Thermal degradation can be prevented.

According to the third aspect of the present invention, an oxygen sensor with a heater is provided in the middle of the exhaust pipe of the engine, and the power supply control means lowers the heater at least based on the temperature of the exhaust gas flowing in the exhaust pipe of the engine. The switching control between the capacity state and the high capacity state is performed.

Accordingly, when the temperature of the exhaust gas is low, the amount of poisoning substances contained in the exhaust gas is small, so that the heater capacity is set to a low capacity until the reference temperature is reached to activate the detection element. Can be. When the temperature of the exhaust gas rises to the reference temperature or higher and the amount of the poisoning substance increases with the increase in the amount of the exhaust gas, the heater capacity is switched to a high capacity state, for example, to a temperature of 800 ° C. or more. The detection element can be heated, and burnout control of the poisoning substance can be performed within a predetermined time range.

Further, in the invention according to claim 4, the energization control means controls the heater to the high capacity state for a predetermined time when the temperature of the exhaust gas reaches the reference temperature, and otherwise sets the heater to the low capacity state. The configuration is such that the calorific value of the state is suppressed below.

Thus, the heater can be controlled to the high capacity state within a predetermined time period, for example, only once before the engine is started and stopped.
Exposure to a high temperature state of about ° C. for a long time (for example, for 10 minutes or more) can be avoided, and thermal deterioration of the detection element can be prevented.

According to a fifth aspect of the present invention, there is provided an oxygen sensor with a heater provided in the middle of an exhaust pipe of an engine for detecting an oxygen concentration in exhaust gas and a heater for heating the detection element. Exhaust temperature detecting means for detecting the temperature of exhaust gas discharged from the engine into the exhaust pipe, and controlling the energization of the heater in accordance with a signal from the exhaust temperature detecting means to activate the detecting element And a power supply control means for switching the capacity of the heater in at least two stages of a low capacity state corresponding to the heat generation amount and a high capacity state having a heat generation amount higher than the low capacity state.

With this configuration, the heater capacity can be variably controlled according to the temperature state of the exhaust gas, and the detection element can be activated when the heater capacity is switched to a low capacity. When the temperature of the exhaust gas rises, the heater capacity is switched to a high capacity state, for example, by heating the detecting element to a temperature of 800 ° C. or more, so that the poisoning substances attached to the surface of the detecting element are removed by the high heat from the heater. Can be burned out.

According to the present invention, the exhaust temperature detecting means has an exhaust temperature detecting map for detecting the temperature of the exhaust gas in accordance with the engine speed and the load condition. The heater is controlled to a high-capacity state within a predetermined time range in order to control the energization of the heater according to the detection result by the detection map and to prevent the detection element from being deteriorated by heat from the heater. When the predetermined time is exceeded, the heater is switched to the low capacity state.

In this case, the temperature state of the exhaust gas can be monitored (monitored) using the exhaust temperature detection map by sequentially detecting the engine speed and the load state, and the heater capacity can be reduced according to the detection result. At least 2 with high capacity
It can be variably controlled in stages. By controlling the heater to the high-capacity state only within a predetermined time period before starting and stopping the engine, it is possible to prevent the detection element from being thermally degraded due to the influence of heat from the heater.

According to the seventh aspect of the present invention, the exhaust temperature detection map is a characteristic map previously divided into a plurality of temperature regions corresponding to the engine speed and the load state. The amount of heat generated by the heater is changed by switching control of the amount of power supplied to the heater for each temperature region.

With this, the amount of electricity supplied to the heater can be variably switched and controlled in each temperature range of the exhaust gas derived from the engine speed and the load state, and the amount of heat generated by the heater corresponds to the temperature state of the exhaust gas. Can be changed.

Further, in the invention of claim 8, the exhaust temperature detecting means comprises a temperature sensor provided in the exhaust pipe, and the energization control means determines the temperature of the exhaust gas detected by the temperature sensor as a predetermined reference value. When the temperature is reached, the heater is controlled to the high capacity state for a predetermined time, and at other times, the heater is suppressed to the heat generation amount in the low capacity state or less.

Thus, the temperature of the exhaust gas can be monitored using the temperature sensor. When the temperature of the exhaust gas reaches the reference temperature after the engine is started, by controlling the heater to the high-capacity state for a predetermined time, for example, the detection element is exposed to a high temperature state of about 900 to 1000 ° C. for a long time. Can be avoided, and thermal degradation of the detection element can be prevented.

Further, according to the ninth aspect of the present invention, the heater is formed by using a silicon nitride material. As a result, high heat resistance can be imparted to the heater, and when the heater is switched to the high capacity state, power exceeding, for example, 50 W (watt) can be supplied to the heater.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for an oxygen sensor with a heater according to an embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 to FIG. 7 show a first embodiment of the present invention. In the drawing, reference numeral 1 denotes an exhaust pipe, which exhaust gas discharged from an exhaust port (not shown) of the engine body is directed in the direction of arrow A. A screw hole 1 </ b> A for attaching a heater-equipped oxygen sensor 2, which will be described later, is formed in the middle of the exhaust pipe 1 in the radial direction.

The exhaust pipe 1 is provided with a catalytic device (not shown) made of a three-way catalyst or the like located downstream of the screw hole 1A. Has a function of reducing the amount of harmful components discharged into the atmosphere by causing a catalytic reaction.

Reference numeral 2 denotes an oxygen sensor with a heater provided in the middle of the exhaust pipe 1. Reference numeral 3 denotes a sensor casing of the oxygen sensor 2. The sensor casing 3 includes a stepped cylindrical holder 4. On the outer periphery of one end of the shape holder 4, a male screw portion 4A is formed as a mounting portion. The oxygen sensor 2 is attached to the exhaust pipe 1 by screwing the external thread 4A of the cylindrical holder 4 into the screw hole 1A of the exhaust pipe 1 via a washer 5 or the like. The tube 6 is configured to protrude into the exhaust pipe 1.

Reference numeral 6 denotes a zirconia tube which constitutes an oxygen concentration detecting element. The zirconia tube 6 is formed of a ceramic material such as zirconium oxide and has a bottomed cylindrical shape. (Not shown). The zirconia tube 6 generates an electromotive force between the inner electrode and the outer electrode when a difference occurs in the oxygen concentration between the outer exhaust gas and the inner air, and uses the electromotive force as a detection signal to be described later. Is output to the contact plate 11 side.

Reference numeral 7 denotes a heater for heating the zirconia tube 6 from the inside. The heater 7 is formed into a small-diameter rod shape from a ceramic material such as silicon nitride having high heat resistance and the like. The heater pattern (not shown) made of the above material is formed.
The heater 7 is inserted into the zirconia tube 6 from the insulating cylinder 8 side, and heats the zirconia tube 6 from the inside.

Reference numeral 9 denotes a pair of terminal pins (only one is shown) provided in the sensor casing 3 for supplying power to the heater 7.
Each of the terminal pins 9 is an elongated metal bar having a spring property.
As shown in FIG. 1, one end side formed by bending and bent in a substantially U-shape is connected to the protruding end side of the heater 7 by means such as brazing. The other end of each terminal pin 9 protrudes from the inside of the insulating cover 10 to the cap 12 described later, and supplies power to the heater 7 through each external lead wire 14.

Reference numeral 11 denotes a contact plate for leading out a detection signal of the oxygen concentration output from the zirconia tube 6 to the outside. The contact plate 11 is inserted into the insulating cylinder 8 and attached to the sensor casing 3. One end side is sandwiched between the insulating cylinder 8 and the open end of the zirconia tube 6 to be connected to the inner electrode. The other end of the contact plate 11 protrudes outside through the insulating cover 10, and the protruding end is connected to a lead wire 15 described later.

Reference numeral 12 denotes a stepped cylindrical cap fixed to the other end of the sensor casing 3 by means such as caulking.
Reference numeral 3 denotes an insulating sealing member provided in the cap 12, and the sealing member 13 is formed of, for example, a heat-resistant fluorine-based resin material.
5 is sealed in the cap 12 in a liquid-tight manner.

Reference numerals 14 and 14 denote power supply leads for supplying power to the heater 7 from the outside.
Each terminal pin 9 is connected to each terminal pin 3 using, for example, a crimp terminal.

Numeral 15 denotes a signal output lead wire for guiding a detection signal from the zirconia tube 6 to the outside. The lead wire 15 is connected to the other end of the contact plate 11 in the seal body 13 using a crimp terminal or the like. Have been.

Reference numeral 16 denotes a cylindrical protector provided at one end of the cylindrical holder 4. The protector 16 projects together with the zirconia tube 6 into the exhaust pipe 1, and protects the zirconia tube 6 from the outside in the exhaust pipe 1. Things.

Next, 17 is an engine start switch.
The start switch 17 is connected to a control unit 26 described later as shown in FIG. Reference numeral 18 denotes a crank angle sensor.
And outputs a detection signal to the control unit 26.

Reference numeral 19 denotes a flow meter as an air flow meter. The flow meter 19 detects an intake air amount Q of the engine.
The detection signal is output to the control unit 26.

Numeral 20 denotes a heater control switch which constitutes means for controlling power supply to the heater 7 together with the control unit 26. The heater control switch 20 is provided between the power supply 21 and the heater 7 as shown in FIG. The contact 20A is configured to be selectively connected to any of the fixed contacts 20B, 20C, 20D, 20E, and 20F.

Here, in the heater control switch 20, a resistor 22 is provided between the fixed contact 20C and the heater 7, and a resistor 23 is provided between the fixed contact 20D and the heater 7. Further, a resistor 24 is provided between the fixed contact 20E and the heater 7, and a resistor 25 is provided between the fixed contact 20F and the heater 7.

When the movable contact 20A of the heater control switch 20 is connected to the fixed contact 20C, the heater 7 is supplied with power from the power supply 21 through the resistor 22 to be in a low capacity state of the capacity W0 (for example, about 13 watts). At this time, the heating value of the heater 7 is set to a temperature suitable for activating the zirconia tube 6.

When the movable contact 20A of the heater control switch 20 is switched from the fixed contact 20C to the fixed contact 20D, the heater 7 is supplied with power from the power supply 21 through the resistor 23, thereby providing a capacity W1 (for example, about 50 watts). At this time, the zirconia tube 6 is heated from the inside with a higher calorific value than the low capacity state of the capacity W0.

When the movable contact 20A is connected to the fixed contact 20E, the heater 7 is supplied with power from the power source 21 through the resistor 24, so that the heater 7 is controlled to a high capacity state of a capacity W2 (for example, about 60 watts). The heater 7 heats the zirconia tube 6 from the inside with a higher heating value than the state of the capacity W1. Further, when the movable contact 20A is connected to the fixed contact 20F, the heater 7 is supplied with power from the power supply 21 through the resistor 25, so that the heater 7 is controlled to a high capacity state of a capacity W3 (for example, about 70 watts). Heats the zirconia tube 6 from the inside with a higher heating value than the state of the capacity W2.

In this case, while the heater 7 is in the low capacity state when the capacity is W0, it is switched in three stages in the high capacity state, and the respective capacities W1, W2 and W3 are, for example, 50 watts and 70 watts. Between,

[0050]

## EQU1 ## The relationship is set as follows: 50 ≦ W1 <W2 <W3 ≦ 70

On the other hand, when the movable contact 20A of the heater control switch 20 is switched to the fixed contact 20B, the heater 7
Is shut off from the power supply 21 and is kept in an operation stop state, and the heating of the zirconia tube 6 by the heater 7 is stopped.

A control unit 26 is constituted by a microcomputer or the like. The input side of the control unit 26 is connected to the start switch 17, the crank angle sensor 18, the flow meter 19 and the like, and the output side is the heater control switch 20 and the like. It is connected to the. And
The control unit 26 constitutes a power supply control means together with the heater control switch 20, and controls the heater 7 in accordance with the programs shown in FIGS.

Further, the control unit 26 is
M, a RAM, and the like.
6A, the exhaust temperature detection map, the burnout control flag F, the timer T, the set time Tk1 (for example, about 10 minutes), and the like shown in FIG. 4 are stored together with the programs shown in FIGS. The burn-off control flag F is set to 0 at step 1 described later when the engine is started. When the burn-off control described later is executed after the engine is started, F = 1.
Is switched to Further, the set time Tk1 is previously obtained as a fixed time based on experimental data or the like in order to avoid thermal deterioration of the heater 7.

On the other hand, the exhaust temperature detection map shown in FIG. 4 is created as a characteristic map divided in advance into five temperature ranges I, II, III, IV and V according to the engine speed N and the basic injection amount Tp. This is the temperature of the exhaust gas of the engine (hereinafter referred to as exhaust temperature), the engine speed N, and the basic injection amount Tp.
Is determined based on experimental data and the like.
The region I shown in FIG. 4 is, for example, an exhaust temperature region of 600 ° C. or less, where the engine speed N is equal to the speed N1 (eg, about 3000 rpm) and the engine speed N2 (eg, 4000 rpm).
(about pm) represents, for example, a heat-dissipation region at 600 ° C. or higher and 700 ° C. or lower.

Further, when the engine speed N is between the engine speed N2 and the engine speed N3 (for example, about 4500 rpm).
III represents, for example, an exhaust temperature region of 700 ° C. or more and 800 ° C. or less.
(about pm), for example, represents an exhaust temperature region of 800 ° C. or more and 900 ° C. or less, and a region V exceeding the rotation speed N4 represents an exhaust temperature region of, for example, 900 ° C. or more. .

Further, the control unit 26 determines the basic injection amount Tp based on the engine speed N from the crank angle sensor 18 and the intake air amount Q from the flow meter 19.
To

[0057]

## EQU2 ## Tp = K.times.Q / N where K: has a function of calculating as a constant. The basic injection amount Tp is always calculated during the operation of the engine in order to increase or decrease the fuel injection amount according to the load state of the engine.

The control device of the oxygen sensor with heater 2 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

First, when controlling the air-fuel ratio of an automobile engine or the like, the sensor casing 3 is screwed to the exhaust pipe 1 of the vehicle via the external thread 4A of the cylindrical holder 4 as shown in FIG. 6 is fixed in a state where the front end side thereof protrudes into the exhaust pipe 1. When the exhaust gas flowing in the exhaust pipe 1 in the direction of arrow A is introduced around the zirconia tube 6 by the operation of the engine, the zirconia tube 6 has an oxygen concentration between the outer exhaust gas and the inner atmosphere. Causes a large density difference.

As a result, an electromotive force is generated in the zirconia tube 6 between the inner electrode and the outer electrode, and this electromotive force is used as a detection signal of the oxygen concentration in the contact plate 11,
An external control unit 26 via the lead wire 15
And so on. And the control unit 26
On the side, the fuel injection amount is corrected and calculated according to the detection signal, and the air-fuel ratio of the engine is feedback-controlled.

The heater 7 is supplied with power from each lead wire 14 side through each terminal pin 9. For example, by causing the heater 7 to generate heat in a low capacity state of a capacity W0, the heater pattern becomes a heat source and the zirconia is generated. The tube 6 is heated from the inside, and the zirconia tube 6 is activated at an early stage even when the engine is started at a low temperature, and the detection signal of the oxygen concentration is output in a stable state.

The heater control process of the control unit 26, which is a feature of the present embodiment, will be described with reference to FIGS.

First, when the engine is started by the start switch 17 and the processing operation is started, the burn-off control flag F is set to F = 0 in step 1 and the engine speed N and the basic injection amount are set in the next step 2. Read Tp. In step 3, the exhaust temperature detection map shown in FIG. 4 is read, and it is determined whether or not the exhaust temperature region corresponding to the engine speed N and the basic injection amount Tp at this time is the region I.

If "YES" is determined in step 3, since the exhaust temperature can be detected (estimated) as the region I where the exhaust temperature is 600 ° C. or less, the process proceeds to step 4 to operate the heater 7 with the capacity W0. As shown in FIG. 3, the movable contact 20A of the heater control switch 20 is
C, and power is supplied from the power supply 21 to the heater 7 through the resistor 22. During this time, the timer T is kept stopped.

Next, in step 5, it is determined whether or not an engine stop operation has been performed, and if "YES" is determined, the processing operation is terminated. In step 5, "N
While determining "O", the process returns to step 2, and the subsequent processes are repeated.

On the other hand, if "NO" is determined in the step 3, the routine proceeds to the next step 6, where the exhaust temperature region is set as shown in FIG.
It is determined whether or not the area V is in the middle. When it is determined "YES" in step 6, the zirconia tube 6 may be thermally degraded, for example, in a high temperature state in which the exhaust temperature exceeds 900 ° C.
To move the movable contact 20A of the heater control switch 20 shown in FIG.
The direction is switched to the direction B, and the heater 7 is shut off from the power supply 21. During this time, the timer T is kept stopped.

If "NO" is determined in the step S6, the process proceeds to a step S8, wherein the burning control flag F is set to F
= 1 has been determined, and when it is determined to be "YES", the zirconia tube 6 is not thermally degraded because the after-mentioned burn-off control has already been performed after the engine is started. Further, further burn-off control is prohibited, and thereafter, only the control processing in steps 2 to 7 is repeated until the engine is stopped.

Next, when "NO" is determined in step 8, the burn-off control flag F becomes F = 0, and the burn-off control is not yet executed after the engine is started. In step 9, the timer T is operated (started). Then, in step 10, it is determined whether or not the exhaust temperature region is the region II.
If the determination is "S", for example, it can be detected that the exhaust temperature is at 600 ° C. or more and 700 ° C. or less. Therefore, the process proceeds to step 11 to operate the heater 7 with the capacity W3. 20 movable contacts 20
A is turned to the fixed contact 20F in the direction of arrow C to switch.
Power is supplied from the power supply 21 to the heater 7 through the resistor 25.

As a result, when the exhaust temperature rises to 600 ° C. or more and the amount of poisonous substances such as silicon Si contained in the exhaust gas increases with the increase in the amount of exhaust gas, a high capacity W3 of, for example, about 70 watts is obtained. The heater 7 can generate heat, and the zirconia tube 6 can be heated to a temperature of, for example, 800 ° C. or more, preferably about 900 to 930 ° C., by the inner heater 7 and the outer exhaust temperature.

When the poisoning substance has adhered to the surface of the zirconia tube 6, the zirconia tube 6 is heated from inside and outside to perform burn-off control to burn off the poisoning substance from the surface side. be able to. As a result, as shown by the characteristic line in FIG. 5, the zirconia tube 6 can be subjected to the burn-off control for temporarily increasing the element temperature of the zirconia tube 6 to, for example, 800 ° C. or more (preferably about 900 to 930 ° C.). Tube 6
The response at the time of detecting the oxygen concentration is, for example, 1.5 Hz
The frequency can be improved to a frequency f1 of (hertz) or more, preferably to a frequency f2 of about 2 Hz.

In step 12, it is determined whether or not the timer T has exceeded a set time Tk1 of, for example, about 10 minutes.

[0072]

## EQU3 ## If it is determined that T.gtoreq.Tk1, and if "YES", if the above-mentioned burn-off control is continued for a longer time, the zirconia tube 6 may be thermally degraded.
At step 13, the burn-off control flag F is switched to F = 1, thereby prohibiting the subsequent burn-off control as described above. In step 13, the timer T is set to T =
It is preferable to stop at 0 and reset.

While the determination in step 12 is "NO", the processing from step 5 shown in FIG. 6 is repeated. If "NO" is determined in step 10, the process proceeds to step 14 to determine whether or not the exhaust temperature region is the region III. If "YES" is determined, for example, the exhaust temperature is 700 ° C or more. Then, since it can be detected that the temperature is 800 ° C. or less, the process proceeds to step 15 and the movable contact 20A of the heater control switch 20 shown in FIG. Power is supplied from the heater 21 to the heater 7 through the resistor 24.

Thus, the heater 7 can be heated with a high capacity W2 of, for example, about 60 watts in a state where the exhaust temperature is as high as 700 ° C. or more, and the zirconia tube 6 is connected to the inner heater 7 and the outer exhaust Depending on the temperature, for example, a temperature of 800 ° C. or higher, preferably 900 to 930 ° C.
It can be heated to about the temperature. In this case, since the exhaust temperature has risen to, for example, 700 ° C. or more, the poisoning burn-off control in step 15 is executed with the capacity of the heater 7 switched to the capacity W2 of about 60 watts. After that, the processing after step 12 is repeated.

If "NO" is determined in the step 14, the exhaust temperature region becomes the region IV. For example, it can be detected that the exhaust temperature is 800 ° C. or more and 900 ° C. or less. In order to operate the heater 7 at the capacity W1, the movable contact 20A of the heater control switch 20 shown in FIG.
To the heater 7 through the resistor 23.

Thus, the heater 7 can be heated with a large capacity W1 of, for example, about 50 watts in a state where the exhaust temperature is as high as 800 ° C. or more, and the zirconia tube 6 is connected to the inner heater 7 and the outer exhaust pipe. Depending on the temperature, for example, a temperature of 800 ° C. or higher, preferably 900 to 930 ° C.
It can be heated to about the temperature. In this case, since the exhaust temperature has risen to, for example, 800 ° C. or more, the poisoning burn-off control in step 16 is executed with the capacity of the heater 7 switched to the capacity W1 of about 50 watts. After that, the processing after step 12 is repeated.

Thus, according to the present embodiment, after the engine is started, the exhaust temperature is, for example, 600 ° C. or more and 9 ° C.
In the engine operating region (regions II, III, and IV shown in FIG. 4) in which the temperature is not higher than 00 ° C., the heater 7 has a high capacity W3,
By causing the heat to be generated by either W2 or W1, burn-out control of the poisoning substance can be executed. For example, the poisoning substance such as silicon Si contained in the exhaust gas adheres to the surface side of the zirconia tube 6 and the response is reduced. And the like can be solved by the burn-off control.

In this case, as shown by the characteristic line in FIG. 5, the element temperature of the zirconia tube 6 is temporarily reduced to, for example, 80 degrees.
Since the burn-off control for raising the temperature to 0 ° C. or more (preferably about 900 to 930 ° C.) can be performed, the responsiveness of the zirconia tube 6 when detecting the oxygen concentration is, for example, 1.
Frequency f1 of about 5 Hz (Hertz) or more, preferably 2
The frequency can be improved to the frequency f2 level of about Hz.

Since the above-mentioned burn-off control is performed only once after the engine is started, for example, within a set time Tk1 of about 10 minutes, the zirconia tube 6 is deteriorated by heat from the heater 7. Such a situation can be avoided, and the durability and life of the zirconia tube 6 can be extended.

Further, when the heater 7 is set to a high capacity, the heater capacity is changed to the capacity W3, W2, W
Since it is configured to selectively switch to either
This can also prevent the zirconia tube 6 from thermally deteriorating.

Therefore, according to the present embodiment, the amount of heat generated by the heater 7 during the running of the vehicle or the like is determined by the capacity W1 in relation to the exhaust temperature.
, W2, W3, the poisoning substances such as silicon Si can be burned off from the surface side of the zirconia tube 6, and the performance of detecting the oxygen concentration by the oxygen sensor 2 can be improved. The responsiveness can be improved.

Further, it becomes possible to stably output the detection signal of the oxygen concentration from the oxygen sensor 2 for a long period of time, so that the feedback control of the air-fuel ratio can be performed with high reliability, and the operating performance of the engine can be ensured. Can be improved.

Further, by detecting the temperature state of the exhaust gas using the exhaust temperature detection map shown in FIG. 4, the current engine control equipment (for example, the crank angle sensor 18, the flow meter 1) can be used.
Using 9), the exhaust temperature can be monitored (monitored) with high accuracy from the engine speed N and the basic injection amount Tp. For example, there is no need to provide a dedicated temperature sensor or the like in the exhaust pipe 1. This has the effect of reducing the number of parts and improving the assemblability.

Next, FIGS. 8 to 10 show a second embodiment of the present invention. The feature of this embodiment is that the temperature of exhaust gas is detected by a temperature sensor and poisoning substances are detected in accordance with the detection result. That is, the burn-off control is performed. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 31 denotes a temperature sensor as exhaust temperature detecting means. The temperature sensor 31 is constituted by, for example, a semiconductor-type temperature sensor or a thermocouple, and is provided at an intermediate portion of the exhaust pipe 1 shown in FIG. Things. The temperature sensor 31 detects the temperature t of the exhaust gas discharged from the engine body into the exhaust pipe 1 and outputs a detection signal to a control unit 33 described later. In this case, the temperature sensor 31 may also be used as a temperature sensor built in a catalyst device or the like usually provided on the downstream side of the exhaust pipe 1.

Reference numeral 32 denotes a heater control switch, which together with the control unit 33 constitutes a means for controlling the energization of the heater 7, which is provided between the power supply 21 and the heater 7 as shown in FIG. The contact 32A is selectively connected to any of the fixed contacts 32B, 32C, and 32D. A resistor 22 is provided between the fixed contact 32C of the heater control switch 32 and the heater 7, and a resistor 2 is provided between the fixed contact 32D and the heater 7.
3 are provided.

When the movable contact 32A of the heater control switch 32 is connected to the fixed contact 32C, the heater 7 is supplied with power from the power supply 21 through the resistor 22 to be in a low capacity state of the capacity W0 (for example, about 13 watts). Controlled. When the movable contact 32A of the heater control switch 32 is switched from the fixed contact 32C to the fixed contact 32D, the heater 7 is supplied with power from the power supply 21 through the resistor 23, thereby providing a high capacity state of the capacity W1 (for example, about 50 watts). Is controlled.

On the other hand, when the movable contact 32A of the heater control switch 32 is switched to the fixed contact 32B, the heater 7
Are shut off from the power supply 21 and are kept in an operation stop state, and the heating of the zirconia tube 6 by the heater 7 is stopped.

Reference numeral 33 denotes a control unit which constitutes a power supply control means together with the heater control switch 32.
The control unit 33 has substantially the same configuration as the control unit 26 described in the first embodiment. The input side of the control unit 33 is connected to the start switch 17, the crank angle sensor 18, the temperature sensor 31, and the like, and the output side is connected to the output side. Is connected to the heater control switch 32 and the like. And
The control unit 33 stores programs and the like shown in FIG. 10 in a storage unit 33A composed of a ROM, a RAM, and the like, and performs control processing of the heater 7.

In the storage unit 33A of the control unit 33, for example, a reference temperature t0 of about 600 ° C. and a judgment value Nk of the engine speed N (for example, Nk = 3600r)
pm), a burn-off control flag F, a timer T, a set time Tk2 (for example, a time of about 10 minutes), and the like. Note that the set time Tk2 is determined in advance as a fixed time based on experimental data or the like in order to avoid thermal deterioration of the heater 7.

Next, the heater control process of the control unit 33 according to the present embodiment will be described with reference to FIG.

First, when the engine is started by the start switch 17 and the processing operation is started, the burn-off control flag F is set to F = 0 in a step 21, and in the next step 22, the heater 7 is operated with the capacity W0. Therefore, FIG.
The movable contact 32A of the heater control switch 32 as shown in FIG.
Is connected to the fixed contact 32C, and power is supplied from the power supply 21 to the heater 7 through the resistor 22.

Next, at step 23, it is determined whether or not an engine stop operation has been performed, and if "YES", the processing operation is terminated. Further, while the determination at step 23 is “NO”, the process proceeds to step 24 to read the temperature t of the exhaust gas from the temperature sensor 31. Then, in step 25, it is determined whether or not the temperature t is equal to or higher than a reference temperature t0 of, for example, about 600 ° C.

[0094]

## EQU4 ## If it is determined that t.gtoreq.t0, and if "NO" is determined, step 22 is executed.
Then, the heater 7 is operated with the capacity W0, and the zirconia tube 6 is activated by the heat from the heater.

If "YES" is determined in the step 25, the process proceeds to a step 26, in which the burn-off control flag F
Determines whether or not F = 1 has been switched. When it is determined "NO" in step 26, the burn-off control flag F becomes F = 0, and since the burn-off control has not been executed yet after the engine is started, the process proceeds to step 27 and the timer proceeds to step 27. Activate (start) T,
In the next step 28, in order to operate the heater 7 with the capacity W1, the movable contact 32A of the heater control switch 32 shown in FIG. Power is supplied to the heater 7.

As a result, when the exhaust temperature rises to 600 ° C. or more and the amount of poisoning substances such as silicon Si contained in the exhaust gas increases as the amount of exhaust gas increases, the capacity W1 of, for example, about 50 watts is increased. The heater 7 can generate heat, and the zirconia tube 6 can be heated to a temperature of, for example, 800 ° C. or more, preferably about 900 to 930 ° C., by the inner heater 7 and the outer exhaust temperature.

When the poisoning substance has adhered to the surface of the zirconia tube 6, the zirconia tube 6 is heated from inside and outside to perform burn-off control so as to burn off the poisoning substance from the surface side. be able to.

Next, at step 29, it is determined whether or not the timer T has exceeded a predetermined time Tk2 of, for example, about 10 minutes.

[0099]

It is determined that T ≧ Tk2, and while the determination is “NO”, the burn-off control is continued in step.

If "YES" is determined in the step 29, the zirconia tube 6 may be thermally deteriorated if the burn-out control is continued for a longer time. Timer T is set to T
= 0 and stopped in a reset state. Then, at step 31, the burn-off control flag F is switched to F = 1 to prohibit the burn-off control thereafter.

Next, if "YES" is determined in the step 26, since the further burn-off control is prohibited by the processing in the step 31, the step 3 is executed.
2 and the engine speed N from the crank angle sensor 18
Read. Then, in the next step 33, it is determined whether or not the engine speed N is equal to or greater than a determination value Nk of, for example, about 3600 rpm.

[0102]

## EQU6 ## It is determined that N ≧ Nk.

When the determination in step 33 is "YES", the temperature of the exhaust gas rises as the engine speed N increases, and the zirconia tube 6
Is sufficiently activated, and the zirconia tube 6 is heated by the heater 7.
Zirconia tube 6 may be thermally degraded by heat from the exhaust gas. Therefore, in step 34, the energization of the heater 7 is stopped, so that the movable contact 32 of the heater control switch 32 shown in FIG.
A is switched in the direction of arrow B to the fixed contact 32B,
To the power supply 21.

On the other hand, if "NO" is determined in the step 33, the process returns to the step 22, and thereafter, the steps 22 to 26 and the steps 32 to 26 are performed until the engine is stopped.
Only the control processing over 34 is repeated.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. Can directly detect the temperature t of
Burnout control of the poisoning substance can be executed according to the detection result, and thermal deterioration of the zirconia tube 6 can be prevented.

In the second embodiment, FIG.
In the above description, it is described that the energization / stop of the heater 7 is determined based on the engine speed N by the processing of steps 32 to 34 shown in FIG. It is also possible to adopt a configuration for determining whether to energize or stop the power supply 7.

Next, FIG. 11 shows a third embodiment of the present invention. In this embodiment, the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof will be omitted. It shall be. However, a feature of the present embodiment is that the activation time of the zirconia tube 6 at the time of a low-temperature start of the engine or the like is reduced by controlling the heater 7 to a high capacity state immediately after the start of the engine.

Here, in the present embodiment, the program shown in FIG. 11 is stored in the storage unit 33A of the control unit 33 shown in FIG. Is performed.

That is, in the heater control processing shown in FIG.
After the engine is started by the start switch 17 and the processing operation is started, it is determined in a step 41 whether or not an engine stop operation has been performed. The movable contact 32A of the heater control switch 32 illustrated in FIG. 9 is switched to the fixed contact 32D, and power is supplied from the power source 21 to the heater 7 through the resistor 23 in order to operate the heater 7 in the high capacity state of the capacity W1.

Thus, immediately after the start of the engine, the heating of the heater 7 is increased at a high capacity of, for example, about 50 watts. Even when the temperature of the exhaust gas is low, the zirconia tube 6 is heated by the heater 7 to a temperature of, for example, 350 ° C. or more. The zirconia tube 6 can be quickly heated to a temperature, and the activation time of the zirconia tube 6 at the time of starting the engine at a low temperature can be greatly reduced.

Next, at step 43, the temperature t of the exhaust gas is read from the temperature sensor 31, and at step 44, it is determined whether the temperature t is equal to or higher than the reference temperature t0 of, for example, about 600 ° C. The determination is made as in the expression, and while the determination is "NO", the process returns to step 41 and the subsequent processing is repeated.

Then, if "YES" is determined in the step 44, the process shifts to the next step 45 to operate (start) the timer T. Then, the next step 46
Then, it is determined whether or not the timer T has exceeded a set time Tk3 of, for example, about 10 minutes.

[0113]

## EQU7 ## It is determined that T≥Tk3, and while the determination is "NO", the process returns to step 41, and the burning control of the poisoning substance is continued in step 42 again. The predetermined time Tk3 is a time previously determined based on experimental data and the like.

As a result, when the exhaust gas temperature rises to 600 ° C. or more and the amount of poisonous substances such as silicon Si contained in the exhaust gas increases with the increase in the amount of exhaust gas, for example, 5
The heater 7 can generate heat with a high capacity W1 of about 0 watts, and the zirconia tube 6 can be heated up to a temperature of, for example, 800 ° C. or more, preferably about 900 to 930 ° C. by the inner heater 7 and the outside exhaust temperature. Can be heated.

When the poisoning substance adheres to the surface of the zirconia tube 6, the zirconia tube 6 is heated from inside and outside, so that the burning control is performed so as to burn off the poisoning substance from the surface side. be able to.

Next, if "YES" is determined in step 46, if the burn-out control is continued for a longer time, the zirconia tube 6 may be thermally deteriorated. Timer T, T =
It is stopped in the state reset to 0. After executing the burn-off control in step 42 immediately after the start of the engine, only the processing in steps 48 to 52 described later is performed, and the burn-off control thereafter is prohibited.

Next, at step 48, the heater 7 is set to the capacity W
To operate at 0, the movable contact 32A of the heater control switch 32 is connected to the fixed contact 32C as illustrated in FIG. 9, and power is supplied from the power supply 21 to the heater 7 through the resistor 22. Then, in step 48, the heater 7 is set to, for example, 1
By operating with a capacity W0 of about 3 watts, the zirconia tube 6 is activated by the heat from the heater.

Next, at step 49, it is determined whether or not an engine stop operation has been performed. If "YES" is determined, the processing operation is terminated. In addition, while the determination at step 49 is “NO”, the process proceeds to step 50 to read the engine speed N. At the next step 51, it is determined whether or not the engine speed N is equal to or greater than a determination value Nk of, for example, about 3600 rpm. Is determined in accordance with the equation (6).

When the determination at step 51 is "YES", the temperature of the exhaust gas rises as the engine speed N increases, and the zirconia tube 6
Is sufficiently activated, and the zirconia tube 6 is heated by the heater 7.
Zirconia tube 6 may be thermally degraded by heat from the exhaust gas. Therefore, in step 52, in order to stop the energization of the heater 7, the movable contact 32A of the heater control switch 32 illustrated in FIG.
Shut off against 1.

On the other hand, if "NO" is determined in the step 51, the process returns to the step 48, and thereafter, only the control processes in the steps 48 to 52 are repeated until the engine is stopped.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. However, in the present embodiment, in particular, in the present embodiment, the heater is started immediately after the engine is started. By operating the zirconia tube 7 at a high capacity of, for example, about 50 watts, the zirconia tube 6 can be quickly heated by the heater 7 even when the temperature of the exhaust gas is low. Can be greatly reduced,
Thermal deterioration of the zirconia tube 6 can also be prevented.

In the second and third embodiments,
When the heater 7 is in a high capacity state, the capacity W is, for example, about 50 watts.
Although described as being set to 1, the present invention is not limited to this. For example, the heater capacity may be switched to the capacity W2 of about 60 watts described in the first embodiment,
In short, it is sufficient that the heater 7 has such a capacity that the burnout control of the poisoning substance can be executed when the heater 7 is switched to the high capacity state.

In the second and third embodiments,
Although it has been described that the temperature t of the exhaust gas is detected by using the temperature sensor 31, the exhaust gas detection map shown in FIG. 4 may be used instead, for example, similarly to the first embodiment. A configuration may be adopted in which the temperature of the target is detected.

On the other hand, in the first embodiment, the exhaust gas temperature is detected by using the exhaust temperature detection map shown in FIG. 4, but instead, for example, the second embodiment is used. Using the same temperature sensor 31 as described in
A configuration may be adopted in which the exhaust temperature regions I, II, III, IV, V, etc. are detected and the capacity of the heater is controlled based on the detected regions.

In the first embodiment, the movable contact 20A of the heater control switch 20 is replaced with the fixed contacts 20B to 20B.
By selectively switching connection to any of the 20F
Although the power supply to the heater 7 is stopped or the heater capacity is switched to one of the capacities W0, W1, W2 and W3, the present invention is not limited to this. A power supply control means including a power transistor and the like for power control may be provided between them so that the heater capacity can be continuously changed.

In the second and third embodiments, instead of the heater control switch 32 and the like, a configuration may be adopted in which energization control means including a power transistor and the like for power control is provided.

[0127]

As described above in detail, according to the first aspect of the present invention, the capacity of the heater is controlled by the power supply control means so as to correspond to the low capacity state corresponding to the amount of heat generated for activating the detecting element. Since the detection element is heated to a temperature of 800 ° C. or more when the heater is set to the high capacity state, the detection element is variably controlled in at least two stages of a high capacity state having a heat generation value higher than the capacity state. The burnout control of poisoning substances can be executed by increasing the heat generation amount of the heater during traveling or the like,
Poisoning substances such as silicon can be burned off from the surface side of the detection element, and the performance of detecting the oxygen concentration by the oxygen sensor with a heater can be improved, and the responsiveness can be improved. Therefore, it is possible to stably output the detection signal of the oxygen concentration from the oxygen sensor for a long period of time, and it is possible to perform feedback control of the air-fuel ratio or the like with high reliability, and to surely improve the operation performance of the engine.

According to the second aspect of the present invention, the heater is controlled to the high capacity state within the predetermined time range by the power supply control means, and the heater is switched to the low capacity state when the predetermined time is exceeded. For example, it is possible to execute burnout control of a poisoning substance that sets the heater to a high-capacity state within a predetermined time period until the engine is started and stopped, and the detection element is excessively heated by the influence of heat from the heater, and It is possible to prevent deterioration.

According to the third aspect of the present invention, the heater is switched between at least the low-capacity state and the high-capacity state based on the temperature of the exhaust gas flowing through the exhaust pipe of the engine. When the temperature rises above the reference temperature and the amount of poisoning substances contained in the exhaust gas increases, by switching the heater capacity to a high capacity state, for example, the detection element is heated to a temperature of 800 ° C. or more. The burn-off control of the poison can be effectively executed, and the response of the detection element can be reliably improved.

Further, according to the present invention, when the temperature of the exhaust gas reaches the reference temperature, the heater is controlled to the high-capacity state for a predetermined period of time. Since the engine is controlled to be less than the amount, the engine is started and stopped, for example, 1
The burnout control of the poisoning substance can be executed within a predetermined time only once, to prevent the detecting element from being exposed to a high temperature of about 900 to 1000 ° C. for a long time, and to prevent thermal deterioration of the detecting element. Can be.

On the other hand, in the invention according to claim 5, energization of the heater is controlled in accordance with a signal from the exhaust temperature detecting means, and the capacity of the heater is set to at least two of the low capacity state and the high capacity state.
Since the switching is performed in stages, the heater capacity can be variably controlled according to the exhaust gas temperature state, and the detection element can be activated when the heater capacity is switched to the low capacity. By switching the heater capacity to a high capacity state when the temperature of the exhaust gas rises, poisoning substances adhering to the surface of the detection element can be burned off by high heat from the heater, and the oxygen sensor by the oxygen sensor with a heater can be used. The concentration detection performance can be improved, and the response can be improved. Therefore, the detection signal of the oxygen concentration can be stably output from the oxygen sensor for a long time, and the feedback control of the air-fuel ratio and the like can be performed with high reliability.

Further, in the invention according to claim 6, an exhaust temperature detection map for detecting the temperature of the exhaust gas in accordance with the engine speed and the load state is used, and the heater is energized according to the detection result by the exhaust temperature detection map. , It is possible to monitor (monitor) the temperature state of the exhaust gas by detecting the number of revolutions and the load state of the engine, and to adjust the heater capacity in at least two stages of the low capacity and the high capacity according to the detection result. It can be variably controlled. By controlling the heater to the high-capacity state only for a predetermined time period before the engine is started and stopped, it is possible to prevent the detection element from being deteriorated by the influence of heat from the heater.

Further, according to the present invention, the exhaust temperature detection map is constituted by a characteristic map previously divided into a plurality of temperature regions corresponding to the engine speed and the load state, and the power supply control means. Since the amount of power supply to the heater is switched and controlled for each temperature region, the amount of heat generated by the heater is changed for each temperature region of the exhaust gas based on the exhaust temperature detection map, and the burnout control of poisoning substances and the like are improved. In addition to being able to be performed with reliability, thermal deterioration of the detection element can be prevented, and durability and life can be improved.

In this case, since the temperature state of the exhaust gas is detected using the exhaust temperature detection map, the current engine control equipment (for example, a crank angle sensor, a flow meter, etc.) is used to determine the engine speed. By detecting the load state, the temperature of the exhaust gas can be known, and there is no need to provide a dedicated temperature sensor or the like in the middle of the exhaust pipe, so that the number of parts can be reduced and the assemblability can be improved.

Further, in the invention according to claim 8, the exhaust temperature detecting means is a temperature sensor provided in the exhaust pipe, and when the temperature of the exhaust gas detected by the temperature sensor reaches the reference temperature, the power supply controlling means The heater is controlled to the high-capacity state for a predetermined period of time, and at other times, the heater is suppressed to the heating value or less in the low-capacity state. Therefore, the temperature of the exhaust gas is detected using the temperature sensor, and after the engine starts, When the temperature of the exhaust gas reaches the reference temperature, by controlling the heater to the high-capacity state for a predetermined period of time, it is possible to prevent the detection element from being exposed to a high temperature state of about 900 to 1000 ° C. for a long time. Can be prevented from being thermally degraded.

Further, in the invention according to the ninth aspect, since the heater is formed by using a silicon nitride material, high heat resistance can be given to the heater, and when the heater is switched to the high capacity state. In addition, the detection element can be heated to a high temperature to stably perform the burn-off control of the poisoning substance.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state where an oxygen sensor with a heater according to a first embodiment of the present invention is attached to an exhaust pipe.

FIG. 2 is a control block diagram illustrating a control device of the oxygen sensor with a heater according to the first embodiment.

FIG. 3 is an electric circuit diagram specifically illustrating a heater control switch and the like in FIG. 2;

FIG. 4 is a characteristic diagram showing an exhaust temperature detection map stored in a storage unit of the control unit.

FIG. 5 is a characteristic diagram showing a relationship between element temperature and response in a state in which burnout control of a poisoning substance is performed.

FIG. 6 is a flowchart showing a heater control process by a control unit.

FIG. 7 is a flowchart following FIG. 6;

FIG. 8 is a control block diagram illustrating a control device of an oxygen sensor with a heater according to a second embodiment.

FIG. 9 is an electric circuit diagram specifically illustrating a heater control switch and the like in FIG. 8;

FIG. 10 is a flowchart showing a heater control process according to the second embodiment.

FIG. 11 is a flowchart showing a heater control process according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust pipe 2 Oxygen sensor with heater 3 Sensor casing 6 Zirconia tube (detection element) 7 Heater 17 Start switch 18 Crank angle sensor 19 Flow meter 20, 32 Heater control switch (Electrification control means) 21 Power supply 26, 33 Control unit 31 Temperature Sensor

Claims (9)

[Claims] An oxygen sensor equipped with a detecting element for detecting an oxygen concentration, a heater for heating the detecting element, and a power supply for controlling power supply to the heater to generate heat in the heater of the oxygen sensor. In a control device for an oxygen sensor with a heater, comprising: a control unit; and a power supply control unit, wherein a low-capacity state corresponding to a calorific value for activating the detection element and a high-capacity having a higher calorific value than the low-capacity state The oxygen with a heater, wherein the capacity of the heater is variably controlled in at least two stages of a capacity state, and the heater heats the detection element to a temperature of 800 ° C. or more when the heater is in a high capacity state. Sensor control device. 2. The power supply control means controls the heater to a high-capacity state within a predetermined time period in order to prevent the detection element from being deteriorated by heat from the heater. The control device for a heater-equipped oxygen sensor according to claim 1, wherein the heater is switched to a low-capacity state when the pressure exceeds a predetermined value. 3. The heater-equipped oxygen sensor is provided in the middle of an exhaust pipe of the engine, and the energization control means sets the heater in at least a low capacity state and a high capacity based on the temperature of exhaust gas flowing in the exhaust pipe of the engine. The control device for an oxygen sensor with a heater according to claim 1 or 2, wherein the control device is configured to perform switching control to a state. 4. The power supply control means controls the heater to a high-capacity state for a predetermined time when the temperature of the exhaust gas reaches a reference temperature. 4. The control device for an oxygen sensor with a heater according to claim 3, wherein the control device is configured to suppress the temperature of the oxygen sensor. 5. An oxygen sensor with a heater provided in the middle of an exhaust pipe of an engine and detecting a concentration of oxygen in exhaust gas and a heater for heating the detection element. Exhaust temperature detecting means for detecting the temperature of the exhaust gas discharged toward the heater; and controlling the power supply to the heater in accordance with a signal from the exhaust temperature detecting means to correspond to a heat value for activating the detecting element. A control device for an oxygen sensor with a heater, comprising: an energization control means for switching the capacity of the heater in at least two stages of a low capacity state and a high capacity state having a higher calorific value than the low capacity state. 6. The exhaust temperature detecting means has an exhaust temperature detecting map for detecting the temperature of the exhaust gas in accordance with the engine speed and the load state, and the energization controlling means uses the exhaust temperature detecting map. Control the energization to the heater according to the detection result, and, in order to avoid the detection element is deteriorated by heat from the heater, control the heater to a high capacity state within a predetermined time range, The control device for an oxygen sensor with a heater according to claim 5, wherein the heater is switched to a low-capacity state when a predetermined time is exceeded. 7. The exhaust temperature detection map comprises a characteristic map previously divided into a plurality of temperature regions corresponding to the number of revolutions of the engine and the load state, 7. The control device for an oxygen sensor with a heater according to claim 6, wherein the amount of heat generated by the heater is changed by switching and controlling the amount of electricity supplied to the heater. 8. The exhaust temperature detecting means includes a temperature sensor provided in the exhaust pipe, and the energization control means determines that the temperature of the exhaust gas detected by the temperature sensor has reached a predetermined reference temperature. 6. The system according to claim 5, wherein the heater is controlled to be in a high-capacity state for a predetermined time, and otherwise, the heater is suppressed to a heat generation amount in a low-capacity state.
3. The control device for an oxygen sensor with a heater according to claim 1. 9. The control device for an oxygen sensor with a heater according to claim 1, wherein the heater is formed using a silicon nitride material.