JP3147632B2 - Catalyst deterioration detection device for catalytic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst deterioration detecting device for a catalytic converter for purifying exhaust gas of an engine.

[0002]

2. Description of the Related Art In recent years, a high level of reduction of harmful exhaust gas to an engine has been demanded, and a catalytic converter is known as a device for purifying the exhaust gas. The purification function will gradually decrease.

[0003] For this reason, a catalyst deterioration detecting device has been proposed, in which a temperature sensor is mounted at two places, such as an inlet of a catalytic converter and inside a catalyst, and a temperature difference between the two points is not deteriorated. It is determined whether or not there is any deterioration as compared with the state described above. When there is deterioration, a warning light or the like is lit to notify the driver (Japanese Patent Laid-Open No. 2-27109, etc.). reference).

[0004]

However, in this case, if the temperature sensor is installed at a different location, the environment exposed to the exhaust gas or the oxidizing atmosphere is different, so that the deterioration state of the temperature sensor during long-term use is different. Come. this is,
Influences catalyst deterioration judgment.

On the other hand, when temperature sensors are mounted at two locations inside the catalyst, when the length of the catalyst is relatively short, it is difficult to arrange the temperature sensors upstream and downstream with respect to the gas flow.

An object of the present invention is to provide a catalyst deterioration detecting device which can solve such problems.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for detecting deterioration of a catalyst of a catalytic converter for purifying exhaust gas of an engine as shown in FIG. a temperature sensor 1 of the first temperature cell
A second temperature sensor 2, which is disposed on the same cross section of the catalyst with respect to the sensor 1 and detects the temperature around the catalyst, is compared with the detection values of the two temperature sensors 1, 2 to determine the temperature difference at a certain point in time. And determining means 3 for determining deterioration when the value is equal to or more than a predetermined value.

According to a second aspect of the present invention, the certain point in time is a point in time when a predetermined time has elapsed after the start of the engine.

In a third aspect of the present invention, the certain time point is a time of a steady operation.

[0010] In a fourth aspect, the first and second temperature sensors are provided.
The sensors are integrated into one support .

[0011]

The temperature of the catalyst is high in the center due to the reaction heat of the inflowing exhaust gas at the catalyst, and the rise of the temperature in the peripheral portion is delayed in the initial stage of the inflow of the exhaust gas. The temperature rises slowly, and the temperature difference between the peripheral part and the central part increases.

Therefore, in the first invention, the deterioration of the catalyst is accurately determined based on the difference between the temperature of the central portion of the catalyst detected by the first temperature sensor and the temperature of the peripheral portion of the catalyst detected by the second temperature sensor. Further, variation in deterioration of the temperature sensor can be suppressed.

In the second invention, the temperature difference between the central portion of the catalyst and the peripheral portion of the catalyst when a predetermined time has elapsed after the start of the engine is compared. Deterioration determination can be performed accurately.

In the third aspect of the invention, the deterioration of the catalyst can be accurately determined in a stable state by comparing the temperature difference between the central portion of the catalyst and the peripheral portion of the catalyst during steady operation.

According to the fourth aspect of the invention, the structure is simplified and the mounting becomes easy.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the catalytic converter 10 accommodates a catalyst (three-way catalyst) 11 therein and is installed in an exhaust pipe (not shown) for guiding exhaust gas of the engine. The exhaust gas flows in the direction of the arrow in the figure.

As the catalyst 11, a monolith catalyst is used, and for example, a honeycomb type of alumina is employed. An insulator 12 is mounted around the catalyst 11.

The catalyst 11 has first and second temperature sensors 13 and 14 for detecting the temperature inside the catalyst 11.

As shown in FIG. 3, the temperature sensors 13 and 14 are heat sensing units 15 and 1 made of a metal resistor or a thermistor.
6 are integrally incorporated into a sensor support 17 made of ceramic, and the catalyst 1 is inserted through a mounting hole of the converter housing 18.
It is inserted into 1 and fixed.

The heat sensing portion 15 of the first temperature sensor 13
The heat sensing unit 16 of the second temperature sensor 14 is mounted on the front end side of the sensor support 17 so as to detect the temperature of the central portion of the catalyst 11. Assembled in the middle of body 17.

The sensor support 17 is provided with the temperature sensor 1
3 and 14 are mounted so as to be arranged on the same cross section downstream from the gas inlet end of the catalyst 11 by a predetermined value or more.

FIG. 4 shows a heat sensing unit 2 using a thermocouple.
An example in which 0 and 21 are incorporated in the sensor support 22 is shown.

The first and second temperature sensors 13 and 14
Are sent to the determination circuit 25 through the amplifiers 23 and 24, respectively.

The determination circuit 25 receives various operating condition signals such as engine load, rotation speed, cooling water temperature, and the like, and a signal from an ignition switch 26.

Based on these signals, the temperature is detected by the first and second temperature sensors 13 and 14 at a predetermined time by the determination circuit 25 at a predetermined time, and the catalyst 1 is detected based on these detected values.
1 is determined. When it is determined that the battery is deteriorated, a lighting signal is output to a warning lamp 27 provided in a driver's seat or the like.

This will be described with reference to the flowchart of FIG.

First, in step 1, when the ignition switch 26 of the engine is turned on and it is detected that the engine has been started, the timer is started in step 2.

After the start, when a specified time (for example, several tens of seconds) TM elapses in step 3, the detection signals of the first and second temperature sensors 13 and 14 are read in step 4, and the internal (catalyst center) temperature is read. b and outside (periphery of catalyst)
The temperature a is measured.

Next, in step 5, the difference ΔT between the inside temperature b and the outside temperature a is calculated, and in step 6, the difference ΔT is compared with a deterioration determination specified value (for example, 40 to 50 ° C.).

If the difference ΔT is larger than the specified value for determining deterioration, it is determined that the catalyst 11 has deteriorated, and the warning lamp 27 is turned on in step 7.

Here, when the temperature state of the cross section of the catalyst 11 immediately after the start of the engine is shown, when the catalyst 11 is new,
As shown in FIGS. 6 and 7, the reaction temperature of the inflowing exhaust gas causes the inner temperature b, which is surrounded by the peripheral portion, to rise quickly and the outer temperature a to rise somewhat later. 8 and FIG. 9, the rise of the outer temperature a is delayed, and the difference ΔT between the outer temperature a and the inner temperature b is increased.

When the catalyst 11 deteriorates, the difference ΔT between the outside temperature “a” and the inside temperature “b” during the steady operation increases.

That is, by comparing the difference ΔT between the inside temperature b and the outside temperature a of the catalyst 11 at the time when the predetermined time TM has elapsed after the start of the engine with the predetermined deterioration determination specified value, the deterioration of the catalyst 11 is accurately determined. Can be determined. When the catalyst 11 is deteriorated, the warning lamp 27 is turned on to notify the driver that the catalyst replacement time has come.

Further, since the temperature sensors 13 and 14 are integrated into the sensor support 17 and are arranged on the cross section of the catalyst 11, the temperature sensors 13 and 14 can be easily mounted.
Since the structure is simplified and the temperature sensors 13 and 14 are arranged inside the catalyst 11, the environment to which the temperature sensors 13 and 14 are exposed is substantially the same. , 14 deteriorate, there is little variation in the deterioration.

Therefore, the variation in the output between the two temperature sensors 13 and 14 is suppressed, and the reliability of the temperature sensors 13 and 14 and the reliability of the deterioration judgment of the catalyst 11 are improved.
Accurate replacement time of the catalyst 11 can be detected by the deterioration determination.

FIG. 10 shows another embodiment of the present invention, in which the temperature of the catalyst 11 is judged by detecting the temperature by the first and second temperature sensors 13 and 14 during the steady operation of the engine. is there.

In this case, in step 11, based on the respective operating condition signals such as the load of the engine, the number of revolutions, and the cooling water temperature,
It is determined whether or not the engine is in a predetermined steady running state (the load and the number of revolutions of the engine are within a certain range).

If the vehicle is in a predetermined steady running state, step 1
In step 2, detection signals from the first and second temperature sensors 13 and 14 are read, and an internal (catalyst center) temperature b and an external (catalyst peripheral) temperature a are measured.

Next, at step 13, the difference ΔT between the inside temperature b and the outside temperature a is calculated, and at step 14, the difference ΔT
Is compared with a specified value for deterioration determination (takes a value smaller than the specified value for deterioration determination in the above embodiment).

If the difference ΔT is larger than the specified value for determining deterioration, it is determined that the catalyst 11 has deteriorated, and the warning lamp 27 is turned on in step 15.

That is, when the catalyst 11 deteriorates, the difference ΔT between the inside temperature b and the outside temperature a of the catalyst 11 increases even during the steady operation due to the delay in the reaction, thereby increasing the inside temperature b during the steady operation. By comparing the difference ΔT between the temperature and the outside temperature a with a predetermined deterioration determination specified value, the deterioration of the catalyst 11 can be accurately determined. During steady operation, the change in the difference ΔT between the inside temperature b and the outside temperature a is small, so that deterioration of the catalyst 11 can be determined in a stable state, and the determination can be easily performed.

[0043]

[0044]

[0045]

As described above, the first invention is a device for detecting deterioration of a catalyst of a catalytic converter for purifying exhaust gas of an engine, comprising: a first temperature sensor for detecting a temperature of a central portion of the catalyst; The same temperature of the catalyst
A second temperature sensor that is disposed on one cross section and detects the temperature around the catalyst, and compares the detection values of the two temperature sensors with each other to determine that the temperature has deteriorated when a temperature difference at a certain point in time is equal to or greater than a predetermined value. With the provision of the means, it is possible to suppress the variation in the deterioration of both temperature sensors, accurately determine the deterioration of the catalyst, and improve the reliability.

According to the second aspect of the present invention, it is possible to accurately determine the deterioration of the catalyst based on the temperature rising state of the central portion and the peripheral portion of the catalyst at the initial stage of the inflow of the exhaust gas.

According to the third aspect of the present invention, it is possible to accurately determine the deterioration of the catalyst in a stable state at the time of steady operation.

According to the fourth invention, the assemblability of the temperature sensor is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a configuration sectional view of an embodiment.

FIG. 3 is a configuration diagram in which a temperature sensor is incorporated in a sensor support.

FIG. 4 is a configuration diagram showing another example using a thermocouple for a temperature sensor.

FIG. 5 is a flowchart of catalyst deterioration determination.

FIG. 6 is an explanatory diagram showing a rising state of the temperature of the catalyst when the catalyst is new.

FIG. 7 is a graph showing a temperature rise characteristic of a catalyst when the catalyst is new.

FIG. 8 is an explanatory diagram showing a rising state of the temperature of the catalyst when the catalyst is deteriorated.

FIG. 9 is a graph showing a rising characteristic of the temperature of the catalyst when the catalyst is deteriorated.

FIG. 10 is a flowchart of catalyst deterioration determination according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Catalytic converter 11 Catalyst 13 1st temperature sensor 14 2nd temperature sensor 15, 16 Heat sensing part 17 Sensor support 25 Judgment circuit 26 Ignition switch 27 Warning lamp 30, 31 Sensor support

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Claims (4)

(57) [Claims] An apparatus for detecting deterioration of a catalyst of a catalytic converter for purifying exhaust gas of an engine, comprising: a first temperature sensor for detecting a temperature of a central portion of the catalyst;
A second temperature sensor that is disposed on the same cross section of the catalyst with respect to the temperature sensor and detects the temperature around the catalyst; A catalyst deterioration detecting device for a catalytic converter, comprising a judgment means for judging deterioration in the case of (1). 2. The catalyst deterioration device for a catalytic converter according to claim 1, wherein a certain time point is a time point when a predetermined time has elapsed after the start of the engine. 3. The catalyst deterioration device for a catalytic converter according to claim 1, wherein a certain time point is a time of a steady operation. 4. The apparatus according to claim 1, wherein said first and second temperature sensors are connected to one support.
The catalyst deterioration device for a catalytic converter according to claim 1, wherein the catalyst deterioration device is integrated with the holding body .