JPH07180537A - Catalyst deterioration detecting device for catalytic converter - Google Patents

Abstract

PURPOSE:To accurately judge deterioration of a catalyst by a method wherein the detecting values of first and second temperature sensors are compared with each other and when a temperature difference at some point of time exceeds a given value, it is decided that deterioration occurs. CONSTITUTION:The heat sensing part 15 of a first temperature sensor 13 is incorporated in the tip part of a sensor support body 17 so that the temperature of the central part of a catalyst 11 is detected. The heat sensing part 16 of a second temperature sensor 14 is incorporated in the middle of a sensor support body 17 so that the temperature of the peripheral part of the catalyst 11 is detected. Detecting signals from the first and second sensors 13 and 14 are inputted to a decision circuit 25 through amplifiers 23 and 24. Based on a signal outputted to the deciding circuit 25, the first and second temperature sensors 13 and 14 are compared with each other. When a temperature difference at some point of time exceeds a given value, it is decided that deterioration occurs and a warming lamp 27 is lighted ON. This constitution performs proper decision of deterioration of the catalyst 11, suppresses the occurrence of unevenness in deterioration of the two temperature sensors, and improves reliability.

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 engine exhaust gas.

[0002]

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

For this reason, a catalyst deterioration detecting device has been proposed, which is one in which temperature sensors are attached at two places such as the inlet of a catalytic converter and the inside of a catalyst, and the temperature difference between the two points is not deteriorated. In comparison with the above state, it is determined whether or not there is deterioration, and when there is deterioration, a warning light or the like is turned on to inform the driver (Japanese Patent Laid-Open No. 27109/1990, etc.). reference).

[0004]

However, in this case, if the mounting position of the temperature sensor is different, the environment exposed to the exhaust gas and the oxidizing atmosphere is different, so that the deterioration state of the temperature sensor is different during long-term use. Come on. this is,
Affects the judgment of catalyst deterioration.

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

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

[0007]

A first aspect of the present invention is a device for detecting deterioration of a catalyst of a catalytic converter for purifying engine exhaust gas as shown in FIG. Temperature sensor 1, a second temperature sensor 2 for detecting the temperature around the catalyst, and both temperature sensors 1, 2.
There is provided a judging means 3 for comparing the detected values of No. 3 and judging when the temperature difference at a certain time point is a predetermined value or more as deterioration.

In a second aspect of the invention, the certain time point is a time point when a predetermined time has elapsed after the engine was started.

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

According to a fourth aspect of the invention, the first and second temperature sensors are integrally incorporated in one support, and are arranged on the same cross section of the catalyst.

[0011]

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

Therefore, according to the first aspect of the invention, the deterioration of the catalyst can be accurately determined by the difference between the temperature of the catalyst center portion by the first temperature sensor and the temperature of the catalyst peripheral portion by the second temperature sensor. Further, variation in deterioration of the temperature sensor can be suppressed.

In the second aspect of the present invention, the temperature difference between the catalyst central portion and the catalyst peripheral portion at the time when a predetermined time has elapsed after the engine is started is compared, so that the catalyst temperature is increased based on the temperature rising state of the catalyst peripheral portion. Deterioration can be accurately judged.

According to the third aspect of the present 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.

In the fourth aspect of the invention, the structure is simplified and the mounting is 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 has a catalyst (three-way catalyst) 11 housed therein and is installed in the middle of an exhaust pipe (not shown) for guiding engine exhaust gas. 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 shape of alumina is adopted. An insulator 12 is mounted around the catalyst 11.

The catalyst 11 is provided with 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 portions 15 and 1 which are metal resistors or thermistors.
6 is integrally incorporated in the sensor support 17 made of ceramic, and the catalyst 1 is inserted through the mounting hole of the converter housing 18.
It is inserted in 1 and fixed.

The heat sensing portion 15 of the first temperature sensor 13 is
The heat sensing portion 16 of the second temperature sensor 14 is incorporated in the tip side of the sensor support 17 so as to detect the temperature of the central portion of the catalyst 11, and the heat sensing portion 16 of the second temperature sensor 14 supports the sensor so as to detect the temperature of the peripheral portion of the catalyst 11. It is incorporated in the middle of the body 17.

This sensor support 17 is used for the temperature sensor 1
3, 14 are attached so that they are arranged on the same cross section downstream from the gas inlet end of the catalyst 11 by a predetermined value or more.

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

These first and second temperature sensors 13 and 14
The detection signal of 1 is sent to the determination circuit 25 through the amplifiers 23 and 24, respectively.

The judgment circuit 25 receives the operating condition signals such as engine load, rotation speed, cooling water temperature, etc., and the signal from the ignition switch 26.

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

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

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

After the start, when the specified time TM (for example, several tens of seconds) 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)
Measure the temperature a.

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

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

Here, showing the temperature condition of the cross section of the catalyst 11 immediately after the engine is started, when the catalyst 11 is new,
As shown in FIG. 6 and FIG. 7, the reaction temperature of the inflowing exhaust gas causes the inner temperature b surrounded by the peripheral portion to rise faster and the outer temperature a to rise somewhat, but when the catalyst 11 deteriorates, it deteriorates. As shown in FIG. 8 and FIG. 9, the outside temperature a rises slowly, and the difference ΔT between the outside temperature a and the inside temperature b increases.

As the catalyst 11 deteriorates, the difference ΔT between the outside temperature a and the inside temperature b during steady operation also increases.

That is, by comparing the difference ΔT between the inner temperature b and the outer temperature a of the catalyst 11 at the time when a predetermined time TM has elapsed after the engine is started, the deterioration of the catalyst 11 is accurately determined by comparing it with a predetermined deterioration determination prescribed value. Can be determined. When the catalyst 11 deteriorates, 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 arranged on the cross section of the catalyst 11, the temperature sensors 13 and 14 can be easily attached.
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 becomes substantially the same, and therefore the temperature sensor 13 is used during long-term use. , 14 is deteriorated, the variation in the deterioration is small.

Therefore, variations in the output between the temperature sensors 13 and 14 are suppressed, and the reliability of the temperature sensors 13 and 14 and the reliability of the deterioration determination of the catalyst 11 are improved,
An accurate replacement timing of the catalyst 11 can be detected by the deterioration determination.

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

In this case, at step 11, based on the operating condition signals such as engine load, rotation speed, cooling water temperature,
It is determined whether the engine is in a predetermined steady running state (engine load and rotation speed are within a certain range).

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

Next, in step 13, the difference ΔT between the inner temperature b and the outer temperature a is calculated, and in step 14, the difference ΔT.
Is compared with the deterioration determination prescribed value (takes a value smaller than the deterioration determination prescribed value of the above-mentioned embodiment).

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

That is, when the catalyst 11 deteriorates, the reaction delays, so that the difference ΔT between the inside temperature b and the outside temperature a of the catalyst 11 widens even during steady operation, whereby the inner temperature b during steady operation is increased. By comparing the difference ΔT between the outside temperature a and the predetermined deterioration determination prescribed value, the deterioration of the catalyst 11 can be accurately determined. During steady operation, since the change in the difference ΔT between the inner temperature b and the outer temperature a is small, the deterioration of the catalyst 11 can be determined in a stable state, and the determination can be easily performed.

FIG. 11 shows another embodiment of the present invention, in which the first and second temperature sensors 13 and 14 are connected to separate sensor support members 30 and 30, respectively.
The first temperature sensor 13 that is incorporated in the sensor 31 and detects the temperature of the central portion of the catalyst 11 is located downstream of the second temperature sensor 11 that detects the temperature of the peripheral portion of the catalyst 11 with respect to the exhaust flow direction. It was placed in.

As the catalyst 11 deteriorates, the difference between the outside (catalyst peripheral portion) temperature and the inside (catalyst center portion) temperature widens as described above, but the deterioration of the catalyst 11 progresses from the upstream side. Therefore, the temperature sensor 1 for detecting the outside temperature is
By disposing 4 on the upstream side, the temperature difference due to deterioration becomes more prominent, and it becomes easier to determine the deterioration of the catalyst 11.

[0045]

As described above, according to the first aspect of the present invention, in the device for detecting the deterioration of the catalyst of the catalytic converter for purifying the exhaust gas of the engine, the first temperature sensor for detecting the temperature of the central portion of the catalyst and the catalyst Since the second temperature sensor that detects the temperature of the peripheral portion and the determination means that compares the detection values of both temperature sensors and determines that the temperature difference at a certain point of time is equal to or more than a predetermined value as deterioration, both temperature sensors are provided. Suppress variations in sensor deterioration,
The deterioration of the catalyst can be accurately determined, and the reliability is improved.

According to the second aspect of the invention, the deterioration of the catalyst can be accurately judged based on the rising state of the temperature of the central portion and the peripheral portion of the catalyst at the initial stage of inflow of exhaust gas.

According to the third aspect of the invention, the deterioration of the catalyst can be accurately judged in a stable state during steady operation.

In the fourth aspect, the assembling property of the temperature sensor is improved.

[Brief description of drawings]

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

FIG. 2 is a configuration cross-sectional view of an example.

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

FIG. 4 is a configuration diagram showing another example in which a thermocouple is used as 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 temperature rise characteristic diagram of the 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 characteristic diagram of temperature rise of the catalyst when the catalyst deteriorates.

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

FIG. 11 is a sectional view showing the configuration of another embodiment.

[Explanation of symbols]

 10 Catalytic Converter 11 Catalyst 13 First Temperature Sensor 14 Second Temperature Sensor 15,16 Heat Sensing Part 17 Sensor Support 25 Judgment Circuit 26 Ignition Switch 27 Warning Lamp 30,31 Sensor Support

Claims (4)

[Claims] 1. A device for detecting deterioration of a catalyst of a catalytic converter for purifying engine exhaust gas, comprising: a first temperature sensor for detecting a temperature of a central portion of the catalyst; and a second temperature sensor for detecting a temperature of a peripheral portion of the catalyst. A catalyst deterioration detecting device for a catalytic converter, comprising: a temperature sensor; and a judgment means for comparing the detection values of the temperature sensors and judging that the temperature difference at a certain time point is a predetermined value or more. 2. The catalyst deterioration detecting device for a catalytic converter according to claim 1, wherein a certain point of time is a point of time when a predetermined time has elapsed after the engine was started. 3. The catalyst deterioration detecting device for a catalytic converter according to claim 1, wherein a certain point of time is a steady operation. 4. The catalyst deterioration of the catalytic converter according to claim 1, wherein the first and second temperature sensors are integrally incorporated in one support and arranged on the same cross section of the catalyst. Detection device.