JPH01232106A - Detector of deterioration of catalyst - Google Patents

Abstract

PURPOSE:To detect deterioration of a catalyst accurately by a method wherein deterioration of a catalyst is identified by comparing reference temperature of the catalyst, which is specified on the basis of engine operating status, with detected catalyst temperature. CONSTITUTION:In a device for setting reference temperature c, reference temperature of a catalyst is specified on the basis of engine operating status. In a device for detecting deterioration of the catalyst d, the reference temperature and catalyst temperature detected by a device for detecting catalyst temperature b are compared with each other so as to detect deterioration of the catalyst. The reference temperature is specified by a prior experiment based on the number of rotations, an aperture of a choke valve, vehicle speed and temperature of cooling water. This permits deterioration of the catalyst to be detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a catalyst deterioration detection device for internal combustion engines such as automobiles, and more particularly to a device that accurately detects deterioration in conversion efficiency of a catalyst.

(Conventional technology) In recent years, the requirements for automobile engines have become more sophisticated, and there is a tendency for contradictory issues such as reduced exhaust gas, high output, and low fuel consumption to be achieved at a high level. be. In addition, engine exhaust gas regulations in particular have become stricter in recent years, and therefore, for example, using catalysts etc.
01 Efforts are being made to reduce harmful exhaust components such as HC and NOx.

As a conventional device for detecting deterioration of a catalytic converter of this kind, there is one described, for example, in Japanese Patent Application Laid-Open No. 56-88919 (High Temperature Alarm).

This device detects an abnormal temperature rise in the heat of oxidation reaction within the catalytic converter and notifies the driver, and is comprised of an exhaust temperature sensor, a switching module, and an exhaust temperature warning light. For example, when the exhaust gas temperature exceeds 850° C., a warning is issued to the driver, indicating that the catalyst in the catalytic converter is exhibiting an abnormal temperature rise.

(Problems to be Solved by the Invention) However, such conventional catalyst deterioration detection'! j
The system was configured to warn of abnormal rises in the catalyst temperature in the catalytic converter based on the output of the exhaust temperature sensor, so although abnormalities in the catalyst temperature could be detected, it was not possible to accurately detect deterioration in the conversion performance of the catalyst. Therefore, it is not possible to accurately determine whether the catalyst has actually deteriorated, and there is a problem that it is not always possible to efficiently reduce harmful exhaust gas components.

(Objective of the Invention) Therefore, the present invention focuses on the fact that there is a correlation between the conditions determined from the operating state of the engine and the catalyst temperature, and provides a catalyst deterioration detection device that can accurately detect catalyst deterioration. It is intended to.

(Means for solving the problem) In order to achieve the above purpose, the catalyst deterioration detection device according to the present invention has the following features:
As the basic conceptual diagram is shown in Fig. 1, the operating state detection means a detects the operating state of the engine, and the catalyst temperature detecting means detects the catalyst temperature of the catalytic converter. The apparatus includes a reference temperature setting means C for setting a reference temperature of the catalyst of the converter, and a deterioration detection means d for detecting deterioration of the catalyst by comparing the catalyst temperature of the catalytic converter with the reference temperature.

(Operation) In the present invention, deterioration of the catalyst is determined from the difference between the catalyst reference temperature determined from the engine operating conditions and the actual catalyst temperature.

Therefore, deterioration of the catalytic converter is accurately detected and
An increase in harmful exhaust components is effectively prevented.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 5 are diagrams showing an embodiment of the catalyst deterioration detection device according to the present invention.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes an engine, intake air is supplied from an air cleaner 2 to each cylinder through an intake pipe 3, and fuel is injected by an injector 4 based on an injection signal Si. The exhaust gas burned in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, and the harmful components (Go, HC, NOx) in the exhaust gas are removed in the catalytic converter.
) is purified by a three-way catalyst and discharged.

The intake air flow 11Qa is detected by an air flow make 7 and controlled by a throttle valve 8 in the intake pipe 3. Throttle valve 8
The opening TVO is detected by the throttle valve opening sensor 9. Further, the rotational speed N of the engine 1 is detected by a crank angle sensor 10, and the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 11. Further, the catalyst temperature Td of the catalytic converter 6 is detected by a catalyst temperature sensor (catalyst temperature detection means) 12. In addition, vehicle speed Vsp
is detected by the vehicle speed sensor 13.

The air flow meter 7, throttle valve opening sensor 9, crank angle sensor 10, water temperature sensor 11 and vehicle speed sensor 13 constitute the driving state detecting means 14, and the outputs from the driving state detecting means 14 and the catalyst temperature sensor 12 are It is input to the control unit 20. The control unit 20 has functions as reference temperature setting means and deterioration detection means, and includes CPU 21, ROM 22, RAM 23, N
VM (non-volatile memory) 24 and I10 boat 25
Consisted of. The CPU 21 reads necessary external data from the I10 boat 25 according to the program written in the ROM 22, and also exchanges data with the RAM 23 and NVM 24.
Processing values for fuel injection control and detecting deterioration of the catalytic converter 6 in the exhaust system are processed, and the processed data is output to the I10 port 25 as necessary. The I10 port 25 is connected to the operating state detection means 14 and the catalyst temperature sensor 1.
2 is input, and the I10 port 25
An injection signal Si and an alarm signal Ar are outputted from.

The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 and NVM 24 store data used in calculations in the form of a map or the like. Further, the alarm signal Ar is input to a light emitting diode 26, which lights up when the catalyst is abnormal to warn the driver of deterioration of the catalytic converter 6.

Next, the effect will be explained.

FIG. 3 is a flowchart showing a program for controlling deterioration determination of the catalytic converter, which is written in the ROM 22, and this program is executed once in synchronization with the engine rotation.

First, the engine speed N is detected at P, and the throttle valve 8 is detected at P2.
Read the opening TVO at P, and read the vehicle speed Vsp at P. Next, read the cooling water temperature TW in P4,
At P, the temperature Tw of the cooling water is compared with a predetermined value Two. '
When pw<Two, it is determined that the engine 1 is not sufficiently warmed up, and the current routine is ended.

On the other hand, when Tw≧Two, it is determined that warming up has been completed and the process proceeds to P6. At P, a reference temperature Tst of the catalyst temperature is calculated based on various parameters representing the operating state, such as the rotational speed N of the engine 1, the opening degree TVO1 of the throttle valve 8, the vehicle speed Vsp, and the temperature Tw of the cooling water. This catalyst reference temperature TS
t is preset based on the operating state of the engine l, and is a temperature at which the catalytic converter 6 does not deteriorate and exhibits normal operation, and is determined, for example, by experiment. The specific data is shown in Figure 4.5.

FIG. 4 shows the case where the vehicle speed Vsp is Okm/h, and FIG. 5 shows the case where the vehicle speed Vsp is 100 km/h.

As is clear from these figures, the temperature of the catalyst in the catalytic converter 6, which should be normal, is low (, It has been shown that the load increases with high loads. Therefore, these data are stored in advance as a map in the ROM 22. Note that Section 4.
Although FIG. 5 shows data at 0 and 100 w/h, intermediate vehicle speeds between 0 and 1100 k/h are obtained by performing interpolation calculations.

Returning to FIG. 3 again, at P, the actual catalyst temperature Tc is read, and at P8, the catalyst temperature Tc and the above-mentioned catalyst base, quasi-temperature '
A difference value Δt from rst is determined, and it is determined whether this difference value Δt exceeds a predetermined value. When the difference value Δt is larger than the predetermined value, it is determined that the catalyst of the catalytic converter 6 is normal, and this routine is ended. On the other hand, when the difference value Δt is smaller than the predetermined value, the catalyst is abnormal. In other words, when the difference value Δt between the two is smaller than the predetermined value, the catalyst temperature T
Since c does not rise sufficiently, it is determined that the catalyst has deteriorated,
At P, an alarm signal Ar is output and the light emitting diode 26 is turned on to warn the driver.

In this way, in this embodiment, the actual catalyst temperature Tc is detected, and this catalyst temperature Tc is compared with the catalyst reference temperature Tst determined by the operating state of the engine l, and when the difference value Δt between the two is smaller than a predetermined value, Since the catalyst temperature Tc has not risen sufficiently and it has been determined that the catalyst has deteriorated,
Deterioration of the catalyst can be accurately determined. When deterioration of the catalyst is determined, the driver is informed by the lighting of the light emitting diode 26 and can immediately take necessary measures, such as maintenance at the factory.

As a result, a vehicle equipped with this catalyst deterioration detection device will no longer be driven for a long period of time without knowing the deterioration state of the catalyst, and as a result, an increase in harmful exhaust components can be effectively prevented. This can contribute to improving emission characteristics.

In this embodiment, the operating state of the engine 1 is detected using the rotational speed N of the engine 1 and the opening degree TVO of the throttle valve 8.
Although parameters such as 1-vehicle speed Vsp are used, it is of course possible to use other parameters in addition to such parameters for more effective determination.

Further, the type of the catalytic converter 6 is not limited to a three-way catalyst, but may also be an oxidation catalyst or the like. In short, the actual catalyst temperature T
This method can be applied to any device that can effectively detect deterioration of the catalyst from the difference between c and the catalyst reference temperature Tst.

(Effects) According to the present invention, the deterioration of the catalyst can be checked by comparing the catalyst reference temperature determined by the engine operating conditions and the actual catalyst temperature.
Since they are separated, deterioration of the catalyst in the catalytic converter can be accurately detected.

As a result, in a vehicle equipped with the catalyst deterioration detection device according to the present invention, an increase in harmful exhaust gas can be effectively prevented.

[Brief explanation of the drawing]

Figure 1 is a basic conceptual diagram of the present invention, Figures 2 to 5 are diagrams showing an embodiment of the catalyst deterioration detection device according to the present invention, Figure 2 is an overall configuration diagram thereof, and Figure 3 is a diagram of the catalyst. FIG. 4.5 is a flowchart showing the deterioration determination program, and is a diagram showing the relationship between the vehicle speed and the reference temperature of the catalyst. l...Engine, 6...Catalytic converter, 12...Catalyst temperature sensor (catalyst temperature detection means)
, 14... Operating state detection means, 20... Control unit (reference temperature detection means, deterioration detection means).

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine; b) Catalyst temperature detection means for detecting the catalyst temperature of the catalytic converter; and c) A catalyst temperature detecting means for detecting the catalyst temperature of the catalytic converter based on the operating state of the engine. d) deterioration detection means for detecting deterioration of the catalyst by comparing the catalyst temperature of the catalytic converter with the reference temperature. .