DE10300555A1 - Determining the degradation of an exhaust gas treatment device for an internal combustion engine by monitoring the time taken for the temperature to drop after a reduction agent is injected - Google Patents

Abstract

The exhaust gas treatment unit (42) can be activated by adding a reduction agent. The time taken between adding the reduction agent and the temperature dropping to a preset temperature after a rise due to the addition of the reduction agent is measured. If the time taken is shorter than the preset time, the unit is degraded. An exhaust gas treatment unit (42) is placed in the exhaust pipe (40) of an internal combustion engine (1). It can be activated by adding a reducing agent. The unit contains means (71) of adding a reducing agent when the internal combustion engine stops after running; means (79) of measuring the temperature of the unit and means (80) of measuring the time taken between adding the reduction agent and the temperature dropping to a preset temperature after a rise due to the addition of the reduction agent. There are also means (80) of determining whether the exhaust gas treatment device is degraded. If the temperature of the unit is less than or equal to an activation temperature for the reducing agent, the agent is not added even when the engine stops. The unit also includes means (78) of measuring the exhaust gas temperature upstream of the unit and if the temperature of the gases leaving the unit is higher than the temperature of the gases entering it, the reducing agent is not added even when the engine stops. The exhaust gas treatment unit also contains means of storing NOx when the inlet gases are rich in oxygen and releasing NOx when the inlet gases have a low oxygen concentration. The amount of NOx stored is estimated and when it is less than or equal to a present amount the reducing agent is not added even when the engine stops. The exhaust gas treatment unit is a catalytic converter with a NOx trap. An Independent claim is also included for the process for using such a device.

Description

The invention relates to a Deterioration detection device and a Deterioration determination procedure for a Internal combustion engine exhaust gas control apparatus.

Of the catalysts for removing nitrogen oxides (NOx) from an exhaust gas, there is a storage reduction type NOx catalyst that absorbs NOx during a state of excessive oxygen concentration (lean state) and releases NOx when a state of low oxygen concentration (fuel-rich state) occurs Adding fuel as a reducing agent is induced in the exhaust gas so that the discharged NOx reacts with the fuel (HC) on an activated catalyst (platinum (Pt) or the like) and reduces it to N ₂ , which is released to the ambient air.

The NOx catalyst has a NOx absorbent, the NOx from is absorbed into the exhaust gas during a lean state of the exhaust gas and releases NOx during a rich state of the exhaust gas, and a noble metal catalyst that is fueled by a Reducing agent is activated to reduce oxidation Simplify reactions between NOx and fuel. The NOx The catalytic converter controls the exhaust gas by a combination of the NOx Memory delivery function and the activation function.

Therefore, factors for deterioration of the NOx Catalyst deterioration in absorption Dispensing function of the NOx absorbent and one Deterioration in the activation function of the Noble metal catalyst. Examples of causes of the Deterioration of the NOx catalyst is a reduction regarding the NOx storage capacity due to a Sulfur poisoning (S poisoning), a reduction in Activation of the precious metal catalyst due to sintering and the same.

Examples of the method for determining the degree of Deterioration of the above catalyst a method as described in Japanese Patent Laid-Open No. 03-232644 where the degree of deterioration is described of a catalyst is determined from the time between the Change the catalyst environment to a rich state to cause NOx to be released from the catalyst, and the completion of the delivery of the NOx is required (if the Delivery level of an air / fuel ratio sensor Levy level corresponding to a rich air / fuel Ratio reached), a process like that in Japanese Laid-Open Publication No. 2000-104536 in which catalyst deterioration based on a signal is detected by a NOx sensor that is downstream of a Catalyst is provided (a timing diagram of the NOx Sensor signal, the gradient of a NOx concentration in the Time chart and the time of a Catalyst regeneration process), a process as described in the Japanese Patent Laid-Open No. 11-229859 is, using a temperature sensor that is on a NOx catalyst is provided and a NOx sensor that is provided downstream of the catalyst, a Deterioration of the catalyst based on the conditions the NOx removal at the time of high temperature of the NOx catalyst and at the time of a low temperature of which according to a time-dependent information from the Temperature sensor as a temperature indication device and the NOx sensor is determined, a method as it is in the Japanese Patent Laid-Open No. 7-208151 in which, using a NOx sensor, the is provided downstream of a NOx catalyst the catalyst has deteriorated when the Time from the completion of the NOx emission from the Catalyst expires until the value determined according to the NOx Concentration is released, which is detected by the NOx sensor becomes, increases to a predetermined value, lower or is equal to a predetermined value, and so on.

In all of the above methods, the concentration of NOx or oxygen (O ₂ ) or the like in the exhaust gas is measured, and deterioration of the catalyst is determined from the value of the concentration. To measure the concentration of the above gas, it is necessary that gas flows around the sensor for measurement. If the gas does not flow, the value obtained by measuring the sensor only indicates the concentration of the exhaust gas around the sensor, but does not necessarily show the concentration of an atmosphere or environment of the catalyst that is provided upstream of the sensor, the concentration of the exhaust gas emitted by the internal combustion engine. Therefore, in order to perform a catalyst deterioration process as mentioned above, it is necessary that the internal combustion engine is in operation and exhaust gas and therefore exhaust gas must flow. While the internal combustion engine is operating, various conditions regarding the exhaust gas such as temperature, concentration, flow rate, flow rate thereof, and so on change depending on the load of the internal combustion engine, its speed, and so on. Since each of the above-mentioned catalyst deterioration methods makes a determination regarding the deterioration of the catalyst during the operation of the internal combustion engine, it is necessary to take into account changes in various conditions that occur depending on the operating state of the internal combustion engine.

With regard to the procedure that the deterioration of a Catalyst determined by using a NOx sensor that detected the NOx concentration, a NOx sensor with the highest accurate measurement for determining the deterioration for a practical use is not provided. So if a such NOx sensor actually to determine the Catalyst degradation is used very much high cost or very low accuracy in discovery of deterioration.

It is an object of the invention to be highly accurate Determination with regard to the deterioration of a NOx Controllability of a catalyst regardless of the Allow accuracy of exhaust gas concentration detection.

A first aspect of the invention is a Deterioration determination procedure for a Exhaust control device for determining deterioration the exhaust control device comprising: adding a Reductant to the exhaust control device to the Exhaust control device to heat when it detects that an internal combustion engine is about to stop while the Internal combustion engine is in operation and the Exhaust control device operating in the exhaust passage of the Internal combustion engine is provided by adding a Reducing agent can be activated; Measuring a time from the addition of the reducing agent takes place until one Temperature of the exhaust control device to a predetermined one Temperature decreased; and determine that the Exhaust control device has not deteriorated if the time that is measured is longer than a predetermined time and determine that the exhaust control device is has deteriorated if the time that is measured is shorter than is a predetermined time.

To perform this deterioration determination process becomes a deterioration determination device for a Exhaust control device used, comprising: an exhaust control device operating in an exhaust passage an internal combustion engine is provided and by adding a reducing agent can be activated; a Reductant addition device for adding the Reducing agent to the exhaust control device under one Condition that the internal combustion engine from an operating state stops; a Exhaust control device temperature measuring device, which in the Exhaust control device for measuring a Exhaust control device temperature is provided; a Temperature reaching time measuring device for measuring a time, from a point in time when the reducing agent through the Reductant addition device is added to a Time expires when the Exhaust control device temperature to a predetermined one Temperature decreased after due to the addition of the Reducing agent has risen; and a Deterioration determination device for determining that the exhaust control device has not deteriorated, if the time passed by the Temperature reaching time measuring device is measured longer than a predetermined time, and for determining that the Exhaust control device has deteriorated when the Time taken by the temperature reaching time measuring device is measured is shorter than a predetermined time.

That means that in the method and in the device the following way is determined whether the catalyst has worsened. Simultaneously with the detection that the Internal combustion engine is about to stop, fuel becomes too added to the exhaust control device associated with the Catalyst is provided. Because of the added Fuel is the catalyst temperature, that is Exhaust control device temperature, raised to the To activate the catalyst. A time that runs out until the Catalyst temperature to a predetermined temperature reduced, at which the activation of the catalyst continues, is being measured. The time from adding the fuel to the predetermined temperature is reached with time compared by adding the fuel to one the deteriorated catalyst works in the same way, until the catalyst temperature reaches a predetermined one Temperature after the rise due to the addition of the Fuel reduced. Based on the Comparative result is determined whether the catalyst has worsened. The above predetermined Temperature is a temperature at which the activation of a fresh or new catalyst of the same type like the catalyst in the exhaust control device is provided due to a drop in temperature, after the temperature has risen to a temperature that the activation of the new catalyst allowed.

Because the catalyst deterioration detection control is carried out after the internal combustion engine has stopped, it becomes possible to determine the deterioration under perform constant conditions without going through different conditions that are affected by the Internal combustion engine are generated. Since there is no further Demand there, the concentration of the exhaust gas for the determination to measure the deterioration of the catalyst is not necessary, an exhaust gas concentration sensor with high accuracy to use.

Although the criterion in the first aspect, that of the To determine the deterioration used, the length of the Time of catalyst temperature rise due to a Oxidation-reduction reaction of the fuel is that to the Catalyst is added, it is possible to Catalyst temperature directly using, for example a thermocouple or the like as a device for determining to measure the time of the catalyst temperature increase. Therefore it is possible to increase the catalyst temperature in one state measure at which the internal combustion engine is stopped and it there is no gas flow. When measuring the catalyst temperature there is a case where the catalyst temperature is not can be measured directly. In this case it is possible to Temperature of the exhaust gas flowing out of the catalytic converter Use the temperature measuring device to measure that on a downstream side of the catalyst is provided, and the measured temperature indirectly as a catalyst temperature use.

A condition for implementing the first point of view is possible. If the exhaust control device temperature lower than or equal to one Reducing agent activation temperature is at which the Activation caused by adding the reducing agent , the addition of the reducing agent to the Exhaust control device despite stopping the Internal combustion engine avoided.

Another condition is also possible. The Exhaust control device further has one Exhaust gas temperature measuring device upstream of the Exhaust control device for measuring a temperature of inflowing exhaust gas is provided, which in the Exhaust control device flows in, and when the Exhaust control device temperature higher than the temperature of the inflowing exhaust gas, the addition of the Reducing agent to the exhaust control device despite the Stopping the internal combustion engine avoided.

In the first embodiment, fuel is considered a Reducing agent is added to the catalyst and becomes a Temperature rise of the catalyst measured. However, if the Catalyst temperature lower than or equal to that Reducing agent activation temperature is at which Temperature rise response by adding fuel caused fuel remains on the Catalyst deposited, so that the catalyst deterioration cannot be done. If the Exhaust control device temperature higher than the temperature of the exhaust gas that is in the exhaust control device inflows, it means that a temperature rise reaction by fuel on the catalyst in the Exhaust control device progresses. Therefore, if during this state is the time of the catalyst temperature rise, the after the addition of the fuel occurs, is measured an accurate measurement of time is impossible because of fuel before Addition of fuel is present. It is therefore possible to Control of the first point of view among the above to avoid the conditions mentioned.

The exhaust gas control device can furthermore include a storage Reduction function for storing nitrogen oxide in the Exhaust gas is present in a main body of the Have exhaust gas control device when the exhaust gas inflow himself in a state of excessive oxygen concentration located, and for dispensing and reducing the in the Main body stored nitric oxide when the Exhaust gas inflow is lower in a state Oxygen concentration, as well as a Memory estimation device for estimating a memory amount of the Nitric Oxide. If with this structure Memory estimator estimates that the amount of memory of the Nitric oxide lower than or equal to a predetermined one Amount is, the addition of the reducing agent to the Exhaust control device despite stopping the Internal combustion engine avoided.

The catalyst has a NOx absorbent, the NOx in Depends on the ambient atmosphere stores and drains. Therefore, a means for a temperature rise due to the Heat is provided by the oxidation-reduction reactions of the added fuel with from the NOx absorbent emitted NOx is generated. However, if at the time of Determination of deterioration after the internal combustion engine stops storing the NOx in the NOx absorbent less than or equal to that for adequate reactions with the Amount of fuel added is required amount the temperature rise capability of the catalyst lowers. As a result, it becomes impossible to determine whether a Temperature drop due to deterioration of the catalyst or due to insufficient oxidation-reduction reactions is caused. Therefore, it is suitable to save the amount of memory To estimate NOx via the NOx storage estimation device and the Adding the reducing agent to the exhaust control device to avoid if the estimated amount of memory is less than or is equal to a predetermined amount.

Therefore, it becomes possible to Determination of catalyst deterioration independent of Fluctuations in the flow rate of the exhaust gas Exhaust gas concentration and so on depending on the Operating state of the internal combustion engine are caused to achieve.

In the second aspect of the invention, the deterioration is determined by a deterioration determination method for an exhaust gas control device, which comprises:
Adding fuel to a catalyst provided within an exhaust control device provided on an exhaust system of an internal combustion engine when a temperature of the catalyst becomes higher than or equal to a temperature at which an oxidation-reduction reaction starts on an undegraded catalyst; Measuring a catalyst temperature and an upstream exhaust gas temperature on an upstream side of the catalyst; and determining a state of deterioration of the exhaust control device based on a temperature difference of the upstream exhaust gas temperature from the catalyst temperature.

To perform the above Deterioration determination procedure has one Deterioration device for a Exhaust control device on: a catalyst, the is provided in an exhaust passage of an internal combustion engine, for controlling exhaust gas emitted from the internal combustion engine becomes a catalyst inflow exhaust temperature measuring device for measuring a temperature of an exhaust gas inflow, which in the Catalyst flows in. A catalyst temperature measuring device for measuring a catalyst temperature of the catalyst; a Reductant addition device for adding respectively Adding a reducing agent to the catalyst; a Differential temperature detection device or one Temperature difference detection device for detecting a Difference of the catalyst temperature from the temperature of the Exhaust gas inflow that occurs when the reducing agent to the Catalyst through the reducing agent addition device will be added; and a Deterioration determination device for determining that the Catalyst has deteriorated if either one Condition that a detected temperature of the exhaust gas inflow, when the occurrence of a temperature difference by the Temperature difference detection device is detected, larger than a predetermined temperature, or a condition that the temperature difference caused by the Temperature difference detection device is detected lower than a predetermined temperature difference is satisfied. Furthermore, the reducing agent addition device can Realize addition of the reduction if the Catalytic converter temperature reaches a reference temperature that a temperature is set at which an oxidation-reduction Reaction on an unscathed catalyst begins.

Exhaust components, such as HC, CO, and NOx, undergo oxidation-reduction reactions on the catalyst and therefore change to H ₂ O, CO ₂ , N _2, and so on, which are released into the ambient air. The temperature (ignition temperature or light-off temperature) at which the catalytic converter is activated so that the oxidation-reduction reactions of HC, CO and NOx on the catalytic converter starts to increase as the catalytic converter deteriorates. A deteriorated catalyst has a reduced ability to store and release NOx. Therefore, the amount of NOx that reacts with the reducing agent on the catalyst per unit time also decreases as the catalyst deteriorates. This means that the amount of the oxidation-reduction reactions decreases. With decreases in the amount of the oxidation-reduction reactions, the amount of the increase in the catalyst temperature caused by reaction heat generated by the oxidation-reduction reactions, that is, the difference between the catalyst temperature and the catalyst exhaust gas inflow temperature, also decreases.

The deterioration determination method uses these Characteristics. That is, the ignition temperature of one undegraded catalyst than a predetermined one Determination temperature is set and a reducing agent a catalyst in question at Deterioration is added when the Detection temperature is reached. Based on the Degree of a temperature rise reaction caused by the addition of the reducing agent is caused, the state of the Catalytic converter deterioration determined.

If at a time of adding fuel to the Exhaust gas passage of the internal combustion engine the catalyst temperature is lower than or equal to an activation temperature at which an oxidation-reduction reaction begins on the catalyst, and therefore a temperature rise reaction is not caused is the exhaust control device with the catalyst only a portion of the exhaust passage. During this state the catalyst temperature and the temperature of the exhaust gas upstream from the catalyst. Therefore, if the Fuel at or below the activation temperature is added, the added fuel is stored on the Catalyst off or is released into the ambient air. If therefore the addition of the fuel is done at a time will when the temperature of the catalyst, the Deterioration assessment is exposed to or about the Temperature rises at which an oxidation-reduction reaction starts on an unimpaired catalyst, the Determination of the deterioration of the catalyst be performed.

In terms of Catalyst exhaust gas inflow temperature measuring device and the Catalyst temperature measuring devices include examples of the Method of measurement a method in which the Exhaust gas temperature and the catalyst temperature directly above one Thermocouple or the like can be measured. Especially in With regard to the catalyst temperature, a measuring method is at which the temperature of the exhaust gas downstream of the Catalyst is measured and the measured temperature as one Catalyst temperature is considered to be an example. With regard to the temperature difference detection device it is possible to use a method in which signals which are on based on the temperatures recorded by the Catalyst exhaust gas inflow temperature measuring device and the Be measured by a catalyst temperature measuring device ECU (electronic control unit) are processed, and an exhaust gas at which a temperature difference (Δt) occurs, is recorded.

The exhaust gas control device furthermore has a storage Reduction function for storing a nitrogen oxide that is in the exhaust gas is contained in a main body of the Exhaust control device when the exhaust gas inflow is in is in a state of excessive oxygen concentration, and to drain and reduce that stored in the main body Nitric oxide when the exhaust gas inflow is in a state low oxygen concentration, and a Memory estimation device for estimating a memory amount of the Nitric Oxide. If with this structure by the Memory estimator is estimated to be the amount of memory of nitrogen oxide is less than or equal to one predetermined amount, the addition of the reducing agent avoided by the reducing agent addition device.

In the NOx catalyst there is a support or one Load the support device with a NOx absorbent NOx stores and depending on the ambient atmosphere drains off, and with a precious metal that reactions between drained NOx and the reducing agent simplified. Therefore is the catalyst by a heat of reaction caused by the Oxidation-reduction reactions between the added Fuel and that of the NOx absorbent on the Noble metal released NOx is heated. Using this temperature increase reaction becomes the determination regarding the deterioration of the NOx catalyst carried out. To perform the deterioration determination of the NOx catalyst by the above method it is necessary that an amount of NOx is used for the Determination of deterioration is necessary in the NOx catalyst is stored, and that the stored NOx is released if there is a reaction between NOx and the reducing agent for the deterioration determination is to be caused. If hence the amount of NOx stored in the NOx catalyst is estimated to be less than or equal to the amount required for the deterioration assessment is needed, it is possible the addition of the reducing agent to the NOx catalyst avoid being inside the exhaust control device is provided, that is, the execution of the Avoid deterioration assessment.

From the above This is what the deterioration assessment procedure needs Catalyst deterioration determination method on the Basis of a difference between the maximum values of Δt largely the amount of NOx storage, that is, the Temperature rise reaction based on an oxidation Reduction reaction between NOx and the reducing agent. Therefore is the amount of NOx storage required for this determination procedure is required when the estimated NOx Amount of memory used, using other investigative techniques can also be carried out. With regard to the Memory estimation device is possible, for example a To use a method in which the NOx storage amount required for the case of a new catalyst is required until a Maximum value of Δt is generated during a load state of the Internal combustion engine, the amount of fuel added in the Combustion chamber, the exhaust gas temperature required for the storage of NOx required time, and so on are known in advance is calculated and is stored in the ECU as a NOx Memory map stored, and with reference to this figure shows a minimal amount of NOx storage that is necessary for one catalyst in question at the Deterioration assessment is necessary, is estimated, and the estimated value is used as the NOx storage amount.

In summary, the concept that the above is based as follows: the Degree of deterioration of an exhaust control device is determined using the fact that the Exhaust control device is activated, in particular the Temperature rises when a reducing agent is added becomes. The characteristic of the temperature response of the Exhaust control device is made using a single recorded parameters examined, the temperature response describes. The parameter can be the time until the Exhaust control device reaches a certain temperature or be the temperature when the exhaust control device reaches the ignition temperature (light-off temperature).

The above task and other features as well Advantages of the invention will be apparent from the following description of preferred embodiments with reference to the attached drawings recognizable, in which similar Reference numerals are used to represent similar elements become.

Fig. 1 is a schematic diagram illustrating a diesel engine system according to a first embodiment of the invention;

Fig. 2 is a conceptual diagram illustrating a configuration in the vicinity of an ECU according to the first embodiment;

Fig. 3 is a conceptual sectional diagram of a catalyst enclosure in the first embodiment;

Fig. 4 is a graph indicating catalyst temperature rise time and the determination references thereof in the first embodiment;

Fig. 5 shows a map A indicating the amount of fuel added in the first embodiment;

Fig. 6 shows a map B showing the expected activation time in the first embodiment;

Fig. 7 is a flowchart showing a Katalysatorverschlechterungsermittelungssteuerung in the first embodiment;

Fig. 8 is a schematic diagram showing a diesel engine system according to a second embodiment of the invention;

Fig. 9 is a conceptual diagram showing a structure in the vicinity of an ECU according to the second embodiment;

Fig. 10 is a graph showing relationships between the ignition temperature and the catalyst temperature of the second embodiment;

Fig. 11 is a graph showing relationships between the temperature difference .DELTA.t and the catalyst deterioration in the second embodiment; and

Fig. 12 is a flowchart showing a Katalysatorverschlechterungsermittelungssteuerung in the second embodiment.

A first embodiment in which the Deterioration detection device and the Deterioration determination procedure for a Engine exhaust control device on Diesel engine systems will be applied below described.

Referring to FIG. 1, an internal combustion engine (hereinafter simply referred to as an "internal combustion engine") 1 is a four-cylinder diesel internal combustion engine system that has a fuel supply system 10 , combustion chambers 20 , an intake system 30 , an exhaust system or an exhaust system 40 and so on as main sections. A structure of the diesel engine system is described below.

The fuel supply system 10 has a supply pump 11 , a pressure manifold (common rail) 12 , fuel injectors 13 , a shutoff valve 14 , a fuel addition nozzle 17 , an engine fuel passage P1, a fuel addition passage P2, and the like.

The supply pump 11 increases the pressure of the fuel pumped up from a fuel tank (not shown) and supplies the pressurized fuel to a common line 12 via the engine fuel passage P1. The common line 12 performs the function of maintaining a predetermined pressure of the high pressure fuel supplied from the supply pump 11 (pressure accumulation function), and distributes the pressurized fuel to the fuel injection valves 13 . Each fuel injection valve 13 is an electromagnetic valve that has an electromagnetic solenoid (not shown). Each fuel injection valve 13 is opened appropriately to inject fuel into a corresponding one of the combustion chambers 20 .

The supply pump 11 leads a part of the fuel pumped up from the fuel tank to the fuel addition nozzle 17 via the fuel addition passage P2. The shutoff valve 14 is provided on the fuel addition passage P2 from the supply pump 11 to the fuel addition nozzle 17 . In an emergency, the shutoff valve 14 shuts off the fuel addition passage P2 so that the supply of the fuel stops. The fuel addition nozzle 17 is an electromagnetic valve similar to the fuel injection valves 13 . The fuel addition nozzle 17 adds fuel as a reducing agent to the exhaust system 40 through an injection.

The intake system 30 forms a passage of the intake air supplied to the combustion chambers 20 (intake passage). On the other hand, the exhaust system 40 forms a passage of exhaust gas that is discharged from the combustion chambers 20 (exhaust gas passage).

The internal combustion engine 1 is further provided with a known charging device (turbocharger) 50 . The turbocharger 50 has a turbine wheel 52 and a compressor 53 , which are connected by a shaft 51 . The compressor 53 is exposed to the intake air in the intake system 30 . The turbine wheel 52 is exposed to the exhaust gas in the exhaust system 40 . The turbocharger 50 thus constructed has an effect of increasing the intake pressure (charging effect) by rotating the compressor 53 by using the exhaust gas flow (exhaust gas pressure) received by the turbine wheel 52 .

In the intake system 30 , an intercooler 31 is provided downstream of the turbocharger 50 and forcibly cools the intake air that is heated due to the charging. A throttle valve 32 , which is provided further downstream from the intercooler 31 , is an electronically controlled opening-closing valve, the opening of which can be adjusted continuously or continuously. The throttle valve 32 performs the function of reducing the passage area (passage area) of the intake passage to adjust (decrease) the supply of the intake air under a predetermined condition.

The internal combustion engine 1 is also provided with an exhaust gas recirculation passage (EGR passage) 60 that bypasses a passage upstream of the combustion chambers 20 (a passage in the intake system 30 ) and a passage downstream of the combustion chambers 20 (a passage in the exhaust system 40 ). In particular, the EGR passage 60 connects a connection between an exhaust manifold 40 a upstream of the turbocharger 50 in the exhaust system 40 and a passage downstream of the throttle valve 32 in the intake system 30 . The EGR passage 60 performs the function of appropriately returning a portion of the exhaust gas to the intake system 30 . The EGR passage 60 is provided with an EGR valve 61 that is continuously opened and closed by electronic regulation or control to freely adjust the flow rate of the exhaust gas through the ERG passage 60 , and an ERG cooler 62 for cooling exhaust gas provided that flows through the EGR passage 60 (returns).

In the exhaust system 40 , the exhaust manifold 40 a, which is connected to the combustion chambers, is coupled to a cylinder head. Along an exhaust path on a downstream side at a location of the turbine wheel 52 , an exhaust passage 40 b, a NOx catalyst case 42 and an exhaust passage 40 c are provided, which are sequentially connected in this order toward a downstream side. The NOx catalyst mount 42 includes an NOx catalyst 42 b of the storage reduction type, the hazardous components, such as NOx and the like from the exhaust gas removed, as is described below.

Different sensors are attached to the internal combustion engine at different locations and emit signals with regard to the ambient conditions of the locations, the operating state of the internal combustion engine 1 and so on.

That is, a line pressure sensor 70 outputs a detection signal corresponding to the fuel pressure collected in the common line 12 . A fuel pressure sensor 71 outputs a detection signal corresponding to the pressure of the fuel (fuel pressure) that is introduced into the fuel addition nozzle 17 from the fuel flowing in the fuel addition passage P2. An air flow meter 72 outputs a detection signal corresponding to the amount of intake air flow (intake air amount) in the intake system 30 upstream of the throttle valve 32 . An air / fuel ratio sensor (A / F sensor) 73 outputs a detection signal that changes continuously according to the concentration of oxygen in the exhaust gas upstream of the NOx catalyst case 42 in the exhaust system 40 . An exhaust gas temperature sensor 74 outputs a detection signal corresponding to the temperature of the exhaust gas downstream of the NOx catalyst case 42 in the exhaust system 40 . A NOx sensor 75 outputs a detection signal that changes continuously according to the concentration of the NOx in the exhaust gas downstream of the NOx catalyst case 42 in the exhaust system 40 . A catalyst exhaust gas inflow temperature sensor 78 outputs a detection signal corresponding to the temperature of the exhaust gas inflow at an inlet of the NOx catalyst enclosure 42 . A catalyst temperature sensor 79 outputs a detection signal corresponding to the temperature of the catalyst in the NOx catalyst case 42 .

Furthermore, an accelerator operation amount sensor 76 is attached to an accelerator pedal (not shown) and outputs a detection signal corresponding to the amount of depression of the pedal. The detection signal from the accelerator operation amount sensor 76 serves as a basis for a work amount required by the engine 1 . A crank angle sensor 77 outputs a detection signal (pulse) at every predetermined rotation angle of an output shaft (crank shaft) of the internal combustion engine 1 . An ignition switch 90 outputs signals that initiate start control and stop control of the engine 1 , and also serves as a main circuit breaker. These sensors 70 to 79 and 90 are electrically connected to an electronic control unit (ECU) 80 .

As indicated in Fig. 2, the ECU 80 has an operation logic circuit which includes a central processing unit (CPU) 81 , a read only memory (ROM) 82 , an access memory (RAM) 83 , an auxiliary RAM 84 , the stored information maintains a time counter 85 and so on even when vehicle operation stops, which are connected and also connected to an input port 86 and an output port 87 via a bidirectional bus 88 . The input port 86 has an A / D converter.

The ECU 80 inputs detection signals from the various sensors via the input port 86 . On the basis of these signals, the CPU 81 performs basic controls on the fuel injection of the engine 1 and the like from the ECU 80, and also performs various controls on the operating state of the engine 1 , such as a fuel addition control for determining an amount of fuel required for the engine Injection of a reducing agent (fuel serving as a reducing agent), addition timing, and so on, and also performs controls related to stopping the engine 1 and so forth from programs stored in the ROM 82 .

The fuel supply system 10 for supplying the fuel to the combustion chambers via the fuel injection valves 13 , the NOx catalyst provided in the exhaust system 40 , the ECU 80 for controlling the functions of the fuel supply system 10 and the NOx catalyst, and so on constitute an exhaust control device for the internal combustion engine 1 according to the embodiment. The above controls, including the fuel addition control and the like, are realized by operations of various elements of the exhaust control device including the ECU 80 , which outputs instruction signals regarding the above controls.

Of the above-mentioned components of the internal combustion engine 1 , the NOx catalyst case 42 provided in the exhaust system 40 is described in detail below in terms of its structure and function.

FIG. 3 is an enlarged sectional view of the NOx catalyst case 42 shown in FIG. 1 along with a portion of the internal structure of the NOx catalyst case 42 . The NOx catalyst mount 42 includes an NOx catalyst 42 b of the storage reduction type.

The NOx catalyst 42 is b, for example using a support composed mainly of alumina (Al ₂ O _3), and by charging the surfaces of the support with a substance that serves as a NOx absorbent such as alkali metals, including Potassium (K), sodium (Na), lithium (Li), cesium (Ce) and so on, and alkaline earth metals including barium (Ba), calcium (Ca) and so on, and rare earths including ythrium (Y) and so on formed in combination with a noble metal serving as an oxidation catalyst (noble metal catalyst) such as platinum (Pt) or the like. In this embodiment, the absorbent is supported on a filter that traps particles contained in the exhaust gas.

The NOx absorbent has a characteristic of storing NOx during a high oxygen concentration state in the exhaust gas and releasing NOx during a low oxygen concentration state in the exhaust gas. If HC, CO or the like is present in the exhaust gas, when NOx is discharged into the exhaust gas, oxidation-reduction reactions occur between the NOx as the oxidation components and the HC and CO as the reduction components due to the noble metal catalyst that causes the oxidation reactions of HC or CO simplified. This means that HC and CO are oxidized to CO ₂ and H ₂ O and NOx is reduced to N ₂ .

The noble metal catalyst of the NOx catalyst 42 b facilitates the oxidation of HC, so that heat from the oxidation reactions of HC raises the catalyst temperature.

If a predetermined limit amount of NOx is stored in the NOx absorbent, the NOx absorbent becomes unable to store more NOx in the exhaust gas despite a state of high oxygen concentrations. With reference to the engine 1, a control for restoring the NOx storing capability of the NOx catalyst 42 b, as described below, is repeated at predetermined intervals. That is, before the storage of the NOx in the NOx catalyst 42 b contained in the NOx catalyst case 42 reaches a limit amount, a reducing agent is added in an exhaust passage upstream of the NOx catalyst case 42 to reduce the NOx To activate catalyst 42 b for the reduction of NOx stored therein.

NOx control is described in detail below.

Usually has a diesel internal combustion engine Fuel air mixture that is used for combustion in a Combustion chamber is provided with a high oxygen concentration most business areas. The oxygen concentration in a mixture intended for combustion directly in the oxygen concentration of the exhaust gas with a Subtraction of the amount of oxygen given for the Combustion is used.

If the oxygen concentration (air-fuel ratio) of the mixture is high, it means that the Oxygen concentration (air-fuel ratio) of the exhaust gas generally becomes correspondingly high.

Since the NOx catalyst 42 b, the characteristic of storing NOX, has when the oxygen concentration of the exhaust gas is high and for reducing the NOx to _NO2 or NO if the oxygen concentration of the exhaust gas is low, as mentioned above, holds the NOx catalyst 42 b continued NOx as long as the concentration of oxygen is high in the exhaust gas. However, the storage of NOx in the NOx catalyst 42 has a boundary b. When the NOx catalyst 42 b a limit amount of NOx stored, the NOx occurs in the exhaust gas simply by the NOx catalyst enclosure 42 without any further storage of NOx in the NOx catalyst 42 b therethrough.

For resuming the NOx storing capability of the NOx catalyst, it is necessary to add a reducing agent into the NO x absorbent, which is b in the NOx catalyst 42 is present. However, due to the engine concentration, the exhaust gas having a low oxygen concentration, that is, the exhaust gas containing a large amount of fuel serving as a reducing agent, is unlikely to be exhausted when normal fuel injection is performed in the internal combustion engine. Therefore, it is a normal practice to adopt a method in which auxiliary fuel injection is performed by injecting fuel as an unburned fuel separately from the main injection that is performed to drive the power conversion in the combustion chambers of an internal combustion engine, a method in which fuel in the exhaust gas is injected from an auxiliary fuel nozzle provided in the exhaust passage and so on. By such a method, fuel is injected into the exhaust gas to increase the amount of a reducing agent component in the exhaust gas, so that the NOx storage ability is restored by the reducing agent component and therefore the catalyst is regenerated (NOx catalyst regeneration control).

The ECU 80 of the engine 1 monitors continuously the concentration of NOx in the exhaust gas downstream of the NOx catalyst 42 b on the basis of the output signal of the NOx sensor 75 miles. The NOx storage capacity (memory efficiency) of the NOx catalyst 42 b decreases when an amount of NOx stored in the NOx catalyst 42 b increases, that is, when the amount of NOx stored in the NOx Catalyst 42 b is stored, the maximum amount (saturation amount) of NOx reached, which can be stored by the NOx catalyst 42 b. That is, when the amount of NOx stored in the NOx catalyst 42 b increases, the concentration of the NOx passing through the NOx catalyst skirt 42 and downstream discharged increases. Thus, there is a correlation between the transition of the storage of the NOx in the NOx catalyst 42 b and the transition from the concentration of the NOx in the exhaust gas that is discharged from the NOx catalyst case 42 . Therefore, the transition from the NOx concentration, the amount of NOx stored in the NOx catalyst 42 b, on the basis of the type to be detected.

Therefore, when the NOx concentration is greater downstream from the NOx catalyst mount 42 than a predetermined concentration in the exhaust gas, the ECU 80 determines that the storage of NOx in the NOx catalyst b 42 reaches a predetermined amount, and performs a fuel addition control by adding of unburned fuel into the exhaust gas by using a fuel adder as follows. That is, fuel is added to the exhaust gas upstream of the NOx catalyst case 42 in the exhaust system 40 to temporarily increase the amount of a reducing agent component in the exhaust gas flowing into the NOx catalyst case 42 , and thereby add the air-fuel - The ratio of the exhaust gas is reduced. As a result, the NOx in the catalyst reacts with the fuel, which is provided as a reducing agent, and is therefore removed.

In an exemplary control method, from an engine operation history or the like stored in the auxiliary RAM 84 , more specifically, from the stored output signals of the accelerator operation amount sensor 76 , the crank angle sensor 77 , the time counter 85 , and so on, the CPU 81 determines whether the Fuel addition is to be performed as a NOx removal method, compared with programs stored in the ROM 82 in advance.

Through the above-described restoration method of the NOx catalyst 42 b, the NOx catalyst 42 b its NOx storage ability to restore. However, if the restoration process of the NOx catalyst 42 is repeated b, the exhaust gas control performance of the catalyst lowers gradually due to a time-dependent degradation or the like.

Examples of problems caused by deteriorated exhaust control performance of the catalyst are an increase in the reducing agent activation temperature at which the catalyst is activated by the addition of a reducing agent, a decrease in the reaction performance of the catalyst, and the like. When the NOx removal control is performed by using a deteriorated NOx catalyst with reference to a predetermined temperature preset at the reductant activation temperature of a NOx catalyst in a new state (fresh catalyst), sufficient NOx removal can be due to the difference the reducing agent activation temperature are not carried out. Therefore, it is necessary to determine the degree of deterioration of the NOx catalyst 42 b and to perform the NOx removal control according to the degree of deterioration.

A NOx catalyst deterioration determination method in the first embodiment of the invention will be described below described.

As described above, a deteriorated catalyst has a higher activation temperature and a lower reaction performance than a non-deteriorated catalyst. Therefore, as indicated in Fig. 4, when fuel is added to a deteriorated catalyst and a fresh catalyst under the same conditions, the catalysts experience a difference in time caused by the temperature rise caused by the addition of the fuel. expires when the catalyst temperature reaches a predetermined temperature at which the catalyst activity disappears. Using this characteristic, deterioration of the catalyst is determined. That is, after fuel is added as a reducing agent to the NOx catalyst 42 b, the catalyst activation time is measured. A reduction in catalyst activation time is used as a factor in catalyst deterioration.

The catalyst activation time can be measured more accurately if the measurement is performed in a state that is free from influences of the internal combustion engine 1 , that is, free of influences such as the flow rate of the exhaust gas, the exhaust gas concentration and so on. Therefore, the measurement of the catalyst activation time is performed in a state in which the atmosphere or the environment of the NOx catalyst 42 b is generally stable, that is, in a state in which the engine 1 is stopped, and in which the catalyst temperature of the NOx Catalyst 42 b is still in a temperature range that allows the NOx catalyst 42 b to be activated by the addition of fuel.

To measure the catalyst activation time after the engine 1 stops, fuel is added simultaneously with the engine 1 stopped. That is, a stop signal is output to the ECU simultaneously with the operation of the ignition switch 90 to a stop side. In response, the ECU 80 performs engine stop control. Simultaneously with the engine stop control, the ECU 80 performs catalyst deterioration determination control. The catalyst deterioration determination control and the engine stop control are described below.

At the time of stopping the engine 1 , a stop signal in response to the rotation of the ignition switch 90 toward the stop side is detected by the ECU 80 . Based on the detection signal, the CPU 81 performs engine stop control stored in the ROM 82 . Master controls associated with engine stop control include stopping the fuel supply system 10 , stopping the supply of oxygen to the combustion chambers by closing the throttle valve 32 , supplying electrical power to devices that also operate after the engine is stopped, such as For example, devices associated with cooling the engine 1 or the like, setting the shutdown time of the electric power, and the like.

Simultaneously with the switching of the ignition key 90 to the stop side, the ECU 80 detects a signal from the catalyst temperature sensor 79 and determines whether the catalyst temperature is higher than or equal to a temperature that allows activation of added fuel. Subsequently, the ECU 80 detects a signal from the catalyst exhaust gas inflow temperature sensor 78 and determines a difference between the temperature based on the catalyst exhaust gas inflow temperature sensor 78 and the temperature based on the catalyst temperature sensor 79 . If the temperature detected by the catalyst temperature sensor 79 is higher than the temperature detected by the catalyst exhaust gas inflow temperature sensor 78 , there is a possibility of a temperature increase reaction occurring in the NOx catalyst 42 b, and therefore the fuel addition becomes 1 after the engine stops not carried out but the normal engine stop control is carried out.

When the temperature detected by the catalyst temperature sensor 79 is substantially equal to or lower than the temperature detected by the catalyst exhaust gas inflow temperature sensor 78 , the period from the previous fuel addition to the current stop of the engine 1 and the period from the start of the engine 1 up to the current stop of the engine 1 with reference to data stored in the RAM 83 and the time counter 85 . If one of the periods is equal to or less than a predetermined time, it can be assumed that the present storage of NOx in the NOx catalyst 42 b is less than a predetermined amount of NOx due to reactions with the added fuel, and therefore the Added fuel after stopping the engine 1 avoided and the normal engine is further controlled.

When the aforementioned measured time is equal to or longer than the predetermined time, fuel is added into the exhaust passage through the fuel addition nozzle 17 . At this time, the CPU 81 determines an amount of added fuel S based on the catalyst temperature at the time of adding fuel with reference to a map A ( FIG. 5) stored in the ROM 82 . Figure A indicates an amount of fuel that must be added to an undegraded fresh catalyst at a predetermined catalyst temperature so that reactions of fuel continue until the catalyst temperature drops to a temperature or below that facilitates activation of the fresh catalyst. Therefore, with reference to Figure A, a predetermined amount of fuel is added to the exhaust gas by controlling the electromagnetic solenoid of the fuel addition nozzle 17 .

In connection with the determination of the ECU 80 to perform the addition of fuel, stop control of the electric power stored in the ROM 82 of the ECU 80 is performed so that the electric power of the ECU 80 is not stopped until the catalyst deterioration determination control ends ,

The time (Tact) from the addition of the fuel until the result of the detection based on the signal from the catalyst temperature sensor 79 reaches a predetermined temperature at which the activation of a fresh catalyst stops is measured by the time counter 85 . Furthermore, the CPU 81 reads from an image B ( FIG. 6) stored in the ROM 82 an expected activation time (Ttrg), that is, a time during which a temperature raising reaction of the fuel leads to an undiminished catalyst at a predetermined catalyst temperature and a predetermined exhaust gas inflow temperature continues before the catalyst temperature reaches a predetermined temperature.

The CPU 81 compares the measured time (Tact) of the time counter 85 from the addition of the fuel until the predetermined temperature is reached with the expected activation time (Ttrg). If Tact is shorter than TTRG, the CPU 81 determines that the NOx catalyst 42 b has deteriorated. If Tact is as TTRG longer, the CPU 81 determines that the NOx catalyst 42 b has not reached a deteriorated state. The CPU 81 then stores these results in the auxiliary RAM 84 and ends the catalyst deterioration determination control. Then, the electric power of the ECU 80 is stopped by the electric power stop control.

A specific operation of the "catalyst deterioration determination control" performed by the ECU 80 of the engine 1 according to the embodiment will be described below with reference to the flowchart of FIG. 7.

First, the ignition switch 90 is switched to the stop side in S701. In response, the ECU 80 executes the engine stop control. Along with this control, the catalyst deterioration determination control is also performed.

It is then determined in S702 whether the catalyst temperature of the NOx catalyst (catalyst temperature) is equal to that Catalyst temperature or greater than this, which allows that the catalyst is activated by a reducing agent (Catalyst activation temperature). If the Catalyst temperature greater than that Catalyst activation temperature or equal to this, the process proceeds to the next step. If the catalyst temperature is lower than that Is the catalyst activation temperature, the process continues S715 further, where the fuel addition, that is the Catalyst deterioration detection control stopped becomes. The following is in S716 Engine stop control performed. This ends the Routine.

In S703, it is determined whether the catalyst temperature is lower than or equal to the temperature of the exhaust gas entering the Catalyst flows. If the catalyst temperature is lower than or is equal to the exhaust gas inflow temperature, the Proceed to the next step. If the Catalyst temperature higher than the exhaust gas inflow temperature the process proceeds to S715 where the Fuel addition is stopped. The following is in S716 Engine stop control performed. This ends the Routine.

In S704, it is determined whether the period between the previous fuel addition, that is, the previous reduction of NOx and the present determination, as well as the period between the start of the engine 1 and the present determination, is not longer than or equal to the periods (predetermined periods of time) are needed b for the storage of NOx in the NOx catalyst 42nd If the periods are equal to or longer than the predetermined periods, the process proceeds to the subsequent step. If the periods are shorter than the predetermined periods, the process proceeds to S715 where the fuel addition is stopped. The engine stop control is then executed in S716. Then the routine ends.

In the above steps S702 to S704 determines whether the Catalyst deterioration determination control executable is. The steps described below determine whether the catalyst has deteriorated.

In S705, an expected activation time Ttrg is calculated from the Catalyst temperature and the exhaust gas inflow temperature below Estimated with reference to Figure B. Below is in S706 started the measurement of the activation time. In S707 the amount of fuel added S. which according to the Catalyst temperature with reference to Figure A is determined, added. The process then proceeds to that next step.

In S708 to S710, the time required for the execution of the Step S707 continues until the catalyst temperature is equal to that or becomes lower than a predetermined value. In S708 determines whether the catalyst temperature is equal to or is lower than the predetermined value. If the Catalyst temperature equal to or lower than that is a predetermined value, the operation proceeds to next step. In S710 the value Tact "1" added. If it is determined in S708 that the Catalyst temperature is higher than the predetermined value, The process proceeds to S709, where "1" to tact will be added. The process then returns to S708. The is repeated until the catalyst temperature is equal to or becomes smaller than the predetermined value.

In S711 the value Tact and the value Ttrg are compared. If the value is lower than the value Tact TTRG, the operation proceeds to S712 proceeds in which it is determined is that the NOx catalyst 42 has deteriorated b. If Tact is greater than or equal TTRG, the operation proceeds to S713 proceeds in which it is determined is that the NOx catalyst 42 is not deteriorated b. The result of S712 or S713 is then stored in the auxiliary RAM 84 and the routine ends.

Although in this routine the process steps associated with the expected activation time, activation time and Fuel additions are linked sequentially in S705 through S707 are executed, the sequence of these process steps is not limited; for example, these steps can be done simultaneously be carried out.

In this embodiment, the periods from the previous fuel addition and the starting of the engine 1 are measured at the time of the present determination, to estimate the amount of NOx stored in the NOx catalyst 42 b for the determination. However, other methods of estimating the storage of NOx in the catalyst can be used. For example, it is suitable upstream provide a further NOx-sensor and a flow meter of the NOx catalyst skirt 42 and the storage of NOx in the NOx catalyst 42 b of the flow rate of the exhaust gas and the difference between the NOx concentration to determine the upstream and downstream of the exhaust control device are detected. Although the catalyst temperature and the exhaust gas temperature are used as factors for determining the expected activation time in the above embodiment, it is also possible to add other factors, such as a catalyst atmosphere temperature, which changes depending on the water temperature, the air temperature and so on , For the factors that determine the amount of fuel added, it is also possible to take the exhaust gas temperature, the catalyst atmosphere temperature and so on as factors other than the catalyst temperature. In the above embodiment, although the determination is made based on a single measurement process, it is further preferable to perform the catalyst deterioration determination control multiple times and to make the determination based on collective results to further improve the accuracy of the determination.

In the above embodiment, although the catalyst temperature sensor 79 is used as an exhaust control device temperature measuring device for directly measuring the catalyst temperature, that is, the temperature of the exhaust control device, the exhaust control device temperature measuring device is not limited to this. For example, it is also possible to detect the temperature of exhaust gas discharged from the NOx catalyst 42 b by using a temperature sensor which is provided downstream of the NOx catalyst 42 b, and the exhaust gas temperature detected as an indirect catalyst temperature to use.

In the above embodiment, the time which expires until the catalyst temperature reaches a predetermined Temperature rises as a criterion used to determine whether the catalyst has deteriorated. If different Determination criteria are provided, it will be possible Degree of deterioration of a fresh catalyst to that Time of execution of the Catalyst deterioration detection control too determine.

The acceptance of the deterioration detection device and the The method according to the first embodiment does it possible regardless of different conditions of the Internal combustion engine to determine whether the catalyst has worsened.

A second embodiment will now be described, in which the deterioration determination device and the Method of an internal combustion engine exhaust control device of the Invention are applied to a diesel engine combustion system. In the second embodiment, constructions that comparable to that of the first embodiment are, by comparable reference numerals in the drawings shown and are not described below.

Fig. 8 shows a diesel engine system, in which a Verschlechterungsermittelungsvorrichtung and a Verschlechterungsermittelungsverfahren are applied according to the second embodiment. The system shown in FIG. 8 is not provided with the NOx sensor 75 , the catalyst temperature sensor 79 and the ignition switch 90 , which are provided in the first embodiment. These components are not essential elements in the second embodiment. The system shown in FIG. 8 can be provided with the NOx sensor 75 , the catalyst temperature sensor 79 and the ignition switch 90 as in the first embodiment.

Fig. 9 shows an electrical construction around an ECU in this embodiment. In comparison with the construction shown in FIG. 2, an ECU 80 in the construction shown in FIG. 9 does not receive signals from a NOx sensor, a catalyst temperature sensor and an ignition switch. The catalyst deterioration determination in this embodiment does not need these signals. However, these signals may be input to the ECU 80 for a purpose other than the catalyst deterioration determination in this embodiment.

Further, in this embodiment, as described above in connection with the first embodiment, the "control with respect to the stopping of the internal combustion engine 1", which is executed by the ECU 80, not essential. When a catalyst regeneration control, as described above in connection with the first embodiment is performed, the amount of added fuel as a reducing agent, the addition timing thereof, and the like, depending on the catalyst temperature (exhaust gas temperature) of the NOx catalyst 42 is b, the to regenerate, vary from the amount of NOx stored in the catalyst, and so on. When determining the amount of added fuel, and the addition timing values are based on the exhaust gas control ability of the NOx catalyst 42 b at the time of installation on the vehicle fixed. However, the exhaust gas control ability of the NOx catalyst 42 b changes due to time-dependent degradation or the like, when the NOx catalyst 42 b is used over a long time. Therefore, it is necessary to determine the degree of deterioration of the NOx catalyst 42 b and to change the control values for use in the NOx catalyst regeneration control according to the degree of deterioration.

The catalyst deterioration determination related to the NOx catalyst 42 b in this embodiment will be described below. Examples of problems caused with a decreased exhaust gas performance of the catalyst include an increase in the temperature (ignition temperature) at which oxidation-reduction reactions start between the reducing agent added to the exhaust gas and the NOx generated by that NOx catalyst is discharged b 42, which reduction ability is caused by a reduction in the oxidation, as shown in Fig. 10 is indicated, as well as other problems such as a reduction in the NOx storage reaction performance including a reduction in the storage of NOx in the NOx catalyst 42 b, a reduction in the emission of the NOx, and so on. If the NOx removal control is performed using a deteriorated catalyst with respect to a predetermined temperature, for example, the ignition temperature or the light-off temperature of a catalyst in a new state (fresh catalyst), sufficient NOx removal can cannot be achieved due to the difference in ignition temperature. That is, when fuel is added to a deteriorated catalyst at about the ignition temperature of a fresh catalyst, the fuel deposits on the deteriorated catalyst or is released into the atmosphere as an unburned gas because oxidation-reduction reactions on the catalyst do not proceed ,

Even if oxidation-reduction reactions on one deteriorated catalyst take place, the point of highest temperature caused by the deteriorated catalyst is achieved due to the temperature raising effect of Oxidation-reduction reactions lower and will Reaction rate of which is also slower. If the Catalyst regeneration control based on a fresh catalyst under the above conditions is carried out, the temperature of the deteriorated Reach the highest temperature for the catalyst deteriorated catalyst due to the oxidation reduction Reactions is possible. However, since the Catalyst regeneration control based on a fresh catalyst is carried out, it is determined that the temperature rise due to an insufficient amount of Fuel does not progress, which responds to the Catalyst is exposed. This determination gives the Possibility of adding a lot of fuel to the catalyst admit that is greater than the amount of fuel required to Removal of NOx is necessary. In this case it is stored Fuel on or off the catalyst emitted into the atmosphere as an unburned gas.

As a means for measuring the ignition temperature, the catalyst exhaust gas inflow temperature sensor 78 and the catalyst exhaust gas outflow temperature sensor 74 are used. If the exhaust gas does not contain a reducing agent or if the temperature of the NOx catalyst 42 b is lower than the activation temperature, although the exhaust gas contains a reducing agent, the oxidation-reduction reaction between fuel and the NOx does not occur on the NOx catalyst 42 b , Therefore, in this state, the exhaust gas temperature Tin on the inlet side of the NOx catalyst 42 b and the exhaust gas temperature Tex on the outlet side of the NOx catalyst 42 b become substantially the same.

However, when the NOx from the NOx catalyst b 42 through the added into the exhaust gas fuel is removed, increase the oxidation-reduction reactions involving the removal of the NOx, the exhaust temperature Tex, so located that Tin is smaller Tex results, and therefore a temperature difference Δt occurs between Tin and Tex. The inlet-side temperature Tin at the time of occurrence of a temperature difference Δt is an ignition temperature.

After the ignition temperature is reached, the Temperature difference Δt between Tin and Tex taken into account. Due to a decrease in NOx drainage capability that is required for the oxidation-reduction reactions are needed, and in particular, a reduction in the NOx release capacity allows deteriorated catalyst a lesser amount of NOx in that Exhaust gas per unit time as a fresh catalyst also in a state in which the catalyst atmosphere is rich or is enriched. Because the exhaust gas is sufficient Amount of fuel that contains the oxidation reduction Reacts with the drained NOx and is subject to the catalyst temperature rises, the amount of Oxidation-reduction reactions per unit of time by the amount of the NOx emitted.

Therefore, due to the difference in the amount of the oxidation Reduction reactions a time difference with respect to the increase in catalyst temperature leading to Time of the oxidation-reduction reactions is caused.

That is, in the case of a deteriorated catalyst with a reduced amount of the oxidation-reduction reactions, the temperature difference Δt between Tin and Tex (Tex-Tin) is not very large, as indicated in FIG. 11. In the case of a fresh catalyst with a relatively large amount of the oxidation-reduction reactions, however, the temperature difference Δt is large.

Furthermore, since a deteriorated catalyst is a has reduced oxidation-reduction ability deteriorated catalyst a lower maximum one Catalyst temperature by oxidation-reduction reactions as the fresh catalyst due to a synergetic effect a reduced release amount of NOx, the oxidation Reduction reactions and the reduced oxidation Reduction ability of the catalyst is subject.

Taking into account the above circumstances based on the catalyst deterioration determination of variations in temperature difference carried out at When the ignition temperature occurs, between one deteriorated catalyst and an unscathed Catalyst. As an investigative process, a Inflammation detection temperature, which as a reference at Determine the catalyst deterioration is used in advance fixed and fuel will be added when the in question standing catalyst the ignition inflammation temperature reached. Based on the presence / absence of one The temperature raising reaction and the degree of the reaction becomes the Determination of the deterioration of the catalyst carried out.

More specifically, an inflammation detection temperature is preset as a reference for determination of the deterioration. Furthermore, using a catalyst whose ignition temperature is equal to the ignition detection temperature, the rise in the temperature of the catalyst caused by the addition of the fuel is measured and is determined as a temperature rise value. Then, the ignition determination temperature and the temperature rise value are stored in the ROM 82 of the ECU 80 in advance. In the process a Verschlechterungsermittelung is caused to exhaust gas in the NOx catalyst 42 b flows and the temperatures Tin, Tex are upstream and downstream of the NOx catalyst 42 b via the Katalysatorabgaseinströmungstemperatursensor 78 and 74 Katalysatorabgasausströmungstemperatursensor measured. At the time when the CPU 81 detects that the temperatures Tin, Tex have reached the ignition detection temperature, the CPU 81 sends a signal to the fuel addition nozzle 17 to add a predetermined amount of fuel into the exhaust gas.

For the fuel adding a predetermined amount of NOx in the NOx catalyst 42 b verified in advance. The predetermined amount may be set as an amount of NOx that is necessary to the oxidation-reduction reactions with the added fuel continue until the catalyst temperature of the NOx catalyst 42 b is raised to a maximum value by the oxidation-reduction reactions is , Therefore, the above-mentioned preset amount of the fuel to be added is also set as an amount needed to achieve the oxidation-reduction reactions with the above-mentioned stored amount of NOx.

As a means for checking the stored amount of NOx, there is an image for calculating an amount of NOx discharged from the engine 1 from the amount of fuel injected into the engine 1 and information obtained from the accelerator operation amount sensor 76 , the air / fuel Ratio sensor 73 and so on is stored in the ROM 82 in advance. On the basis of the map and the period between the previous fuel addition and the current fuel addition, the amount of NOx that has flown into the NOx catalyst 42 b, is calculated. If the calculated value reaches the predetermined amount of storage of NOx, it is believed that the NOx catalyst 42 b, the predetermined amount of NOx stored has.

If the temperature difference Δt after fuel is added does not exist between the temperatures Tin and Tex measured by the catalyst exhaust gas inflow temperature sensor 78 and the catalyst exhaust gas outflow temperature sensor 74 , the CPU 81 determines that the NOx catalyst 42 b has deteriorated. If the temperature difference Δt is equal to or larger than the predetermined value, the CPU 81 determines that the NOx catalyst 42 b has not deteriorated.

Using the method described above the reducing agent added when the Inflammation detection temperature is reached and will determines whether the catalyst has deteriorated. In which Detection process occurs a temperature increase reaction on when the fuel at the Inflammation detection temperature is added. But when the temperature difference Δt is less than a predetermined value there is a possibility of insufficient progress the temperature raising response due to an insufficient Amount of NOx stored, an insufficient amount the reducing agent that is added, and so on. For in this case, the investigation is therefore avoided or Determination of deterioration by performing the test again Investigation procedure achieved.

Regarding the "catalyst deterioration determination control" performed by the ECU 80 of the engine 1 in this embodiment, a specific process will be described below with reference to the flowchart of FIG. 12.

First, in S601 to S603, the catalyst temperature is set to Inflammation detection temperature brought. If in S601 it is determined that the catalyst temperature is higher than that Is inflammation detection temperature, this step repeated until the catalyst temperature is lower than that Inflammation detection temperature becomes. If the Catalyst temperature less than or equal to Inflammation detection temperature, the process continues the next step. S602 determines whether the Catalyst temperature less than or equal to Inflammation detection temperature is. If the investigation at S610 is "NO", the answer at S602 is "YES" because the Determination of "NO" at S601 means that the Catalyst temperature less than or equal to Inflammation detection temperature is. Then he strides Proceed to S603.

S603 determines whether the catalyst temperature is equal to Inflammation detection temperature is. If the Inflammation Detection Temperature Catalyst Temperature is the same, the process proceeds to S604, in which one predetermined amount of fuel is added. If not in S603 it is determined that the catalyst temperature of the Inflammation detection temperature is the same, the process reverses back to S602. The determination steps of S602 and S603 are repeated until the catalyst temperature of the Inflammation detection temperature becomes the same. During this repeated process, the catalyst temperature rises. If the catalyst temperature over the Inflammation detection temperature increases as the Determination steps of S602 and S603 are repeated the answer at S602 is "NO" and the process returns to S601 back.

After the catalyst temperature of the Inflammation detection temperature as a result of the process of S601 to S603 becomes the same, the fuel addition in S604 executed.

After fuel is added in S604, it is determined in S605 whether the temperature difference between the exhaust gas inflow temperature measured by the catalyst exhaust gas inflow temperature sensor 78 and the exhaust gas outflow temperature measured by the catalyst exhaust gas outflow temperature sensor 74 (exhaust gas outflow temperature - exhaust gas inflow temperature) is less than a predetermined value ,

If it is determined that the temperature difference is greater than or is equal to a predetermined value, the process proceeds S609 continues to determine that the catalyst has not worsened. Then the routine ends. If in S605 it is determined that the temperature difference is less than that is a predetermined value, the operation proceeds to next step.

In S606, an determination regarding the Temperature difference carried out. If the temperature difference is less than 1 ° C, the process proceeds to S608, which determines that the catalyst is deteriorating Has. Then the routine ends. If the temperature difference is larger than 1 ° C, the process proceeds to S607 where one clear determination due to insufficient oxidation Reduction reactions are avoided. Then the routine ends or the process returns to S601 to do the same Perform the determination process again.

When determining the catalyst deterioration this Embodiment is added fuel when the Inflammation detection temperature is reached, and the Presence / absence of a temperature increase reaction, caused by the addition of fuel, and the Amount of the temperature raising reaction at the same time determined. However, these factors can be handled separately become. For example, it is possible to accept an operation at which the temperature at which the catalyst is a Temperature rise reaction begins, is sensed, and a Temperature difference Δt determined from the recorded temperature is, and this value with the Inflammation detection temperature is compared to determine if the catalyst has deteriorated. in the Regarding a method of detecting the temperature at which the catalyst starts a temperature raising reaction Fuel added to a catalyst whose Ignition temperature is to be recorded when the temperature of the Catalyst is low, for example at Ignition temperature of a fresh catalyst, so that the Fuel is deposited on the catalytic converter. Then the Catalyst temperature raised and the Ignition temperature of the catalyst detected at which one Difference between Tin and Tex due to the deposited Fuel occurs. After the ignition temperature is detected a value Δtmax is detected in a similar manner. This Investigation makes it possible to get a degree Deterioration of a catalyst in question on the Basis of the degree of increase in the ignition temperature as well as the presence / absence of deterioration to determine the catalyst.

The use of the Catalyst deterioration detection device and Method according to this embodiment makes it possible the deterioration of a NOx removal ability Determine catalyst without using a NOx sensor.

Although the first and second embodiments use the fuel addition nozzle 17 as the reducing agent adding means, which is a fuel injection device provided in the exhaust passage for adding fuel to the exhaust gas, the adding means is not limited to this. For example, it is possible to add fuel to a combustion chamber at a timing that is different from the combustion stroke, so that the added fuel is expelled from the combustion chamber as an unburned fuel that can be used as a reducing agent. That is, the device is not particularly limited as long as a reducing agent can be added to an exhaust control device.

Although in the foregoing description the device and the Method of the invention mainly in connection with a NOx catalyst of the storage reduction type is described, the invention is not only based on a NOx catalyst Storage reduction design limited, but also to others Catalysts applicable, which is a characteristic of warming up in response to adding a reducing agent, such as for example, three-way catalysts for the Exhaust control of gasoline engines and the like is used be, filters, and so on.

In such applications, the invention realizes one Determination of deterioration as in the aforementioned Embodiments.

While the invention has been described with reference to what is currently considered their preferred embodiments considered, it is understood that the invention is not to the disclosed embodiments or constructions is limited. In contrast, it is intended with the invention that they various modifications and equivalent arrangements covers. While in addition the various elements of the disclosed invention in various combinations and Configurations shown that are exemplary are others Combinations and configurations including more, less or just a single embodiment as well within the basic idea and scope of the invention.

With respect to characteristics of a NOx catalyst, which a tendency to decrease catalyst activation ability and a tendency to increase the Reducing agent activation temperature according to the Are deterioration of the catalyst, fuel is considered a Reducing agent to the NOx catalyst by adding Fuel into the exhaust gas via a fuel injector added to the condition under which the internal combustion engine is stopped. Then the time that runs out until the Temperature of the NOx catalyst a predetermined temperature reached after the climb, measured. If the measured time is shorter than an expected catalyst activation time determines that the catalyst has deteriorated.

Claims (11)

1. deterioration determination device for an exhaust gas control device, characterized by :
an exhaust gas control device ( 42 ) which is provided in an exhaust gas passage ( 40 ) of an internal combustion engine ( 1 ) and which can be activated by adding a reducing agent;
reducing agent adding means ( 71 ) for adding the reducing agent to the exhaust control device ( 42 ) under a condition that the internal combustion engine ( 1 ) stops from an operating state;
an exhaust control device temperature measuring device ( 79 ) provided on the exhaust control device ( 43 ) for measuring an exhaust control device temperature;
temperature reaching time measuring means ( 80 ) for measuring a time from a point in time when the reducing agent is added by the reducing agent adding means ( 71 ) to a point in time when the exhaust gas control device temperature decreases to a predetermined temperature after rising due to the addition of the reducing agent, expires and
deterioration determining means ( 80 ) for determining that the exhaust control device ( 42 ) has not deteriorated when the time measured by the temperature reaching time measuring device ( 80 ) is longer than a predetermined time and for determining that the exhaust control device ( 42 ) has deteriorated, when the time measured by the temperature reaching time measuring device is shorter than a predetermined time. 2. The deterioration detection device according to claim 1, characterized in that when the exhaust control device temperature is lower than or equal to a reducing agent activation temperature at which activation is caused by adding the reducing agent, adding the reducing agent to the exhaust control device ( 42 ) despite the stop of the internal combustion engine ( 1 ) is avoided. 3. deterioration detection device according to claim 1 or 2, characterized in that
the exhaust gas control device ( 42 ) further comprises an exhaust gas temperature measuring device ( 78 ), which is provided upstream of the exhaust gas control device ( 42 ), for measuring a temperature of an exhaust gas inflow,
which flows into the exhaust gas control device ( 42 ), and when the exhaust gas control device temperature is higher than the temperature of the exhaust gas inflow, the addition of the reducing agent to the exhaust gas control device ( 42 ) is avoided despite the stop of the internal combustion engine ( 1 ). 4. The deterioration determination device according to one of claims 1 to 3, characterized in that the exhaust gas control device ( 42 ) further comprises a storage reduction function for storing a nitrogen oxide present in the exhaust gas in a main body of the exhaust gas control device ( 42 ) when the exhaust gas inflow is in an excessive oxygen concentration state and has for releasing and reducing the nitrogen oxide stored in the main body when the exhaust gas inflow is in a low oxygen concentration state. 5. deterioration determination device according to claim 4, characterized in that
the exhaust gas control device ( 42 ) has a storage estimation device for estimating a storage amount of the nitrogen oxide, and
if it is estimated by the storage estimator that the storage amount of the nitrogen oxide is less than or equal to a predetermined amount, the addition of the reducing agent to the exhaust gas control device ( 42 ) is avoided despite the engine ( 1 ) stopping. 6. A deterioration determination method for an exhaust gas control device for determining a deterioration of the exhaust gas control device ( 42 ), which is provided in an exhaust passage ( 40 ) of the internal combustion engine ( 1 ), characterized by
Adding a reducing agent to the exhaust gas control apparatus (42) to heat the exhaust gas control apparatus (42) when it is detected that an internal combustion engine (1) is about to stop, while the engine (1) is in operation, and wherein the exhaust gas control apparatus by Adding a reducing agent can be activated:
Measure a time from the addition of the reducing agent until a temperature of the exhaust control device ( 42 ) decreases to a predetermined temperature: and
Determining that the exhaust control device ( 42 ) has not deteriorated if the measured time is longer than a predetermined time, and
Determine that the exhaust control device ( 42 ) has deteriorated if the time is less than a predetermined time. 7. deterioration determination device for an exhaust gas control device, characterized by
a catalytic converter ( 42 b) which is provided in an exhaust gas passage ( 40 ) of an internal combustion engine ( 1 ) for controlling an exhaust gas emitted by the internal combustion engine ( 1 );
a catalyst exhaust gas inflow temperature measuring device ( 78 ) for measuring a temperature of an exhaust gas inflow that flows into the catalyst ( 42 b);
a catalyst temperature measuring device ( 74 ) for measuring a catalyst temperature of the catalyst ( 42 b);
a reducing agent adding means ( 17 ) for adding a reducing agent to the catalyst ( 42 b);
temperature difference detection means ( 80 ) for detecting a difference in the catalyst temperature from the temperature of the exhaust gas inflow that occurs when the reducing agent is added to the catalyst ( 42 b) by the reducing agent adding means ( 17 ); and
deterioration determination means ( 80 ) for determining that the catalyst ( 42 b) has deteriorated when a condition that the detected temperature of the exhaust gas inflow when the occurrence of a temperature difference is detected by the temperature difference detection means ( 80 ) is greater than a predetermined temperature and from a condition that the temperature difference detected by the temperature difference detector ( 80 ) is less than a predetermined temperature difference, a condition is satisfied. 8. The deterioration detection device according to claim 7, characterized in that the reducing agent adding means ( 17 ) realizes the addition of the reducing agent when the catalyst temperature reaches a reference temperature set as a temperature at which an oxidation-reduction reaction starts with an un-deteriorated catalyst. 9. The deterioration detection device according to claim 7 or 8, characterized in that the exhaust gas control device furthermore a storage Reduction function for storing one in the exhaust gas nitrogen oxide present in a main body of the Exhaust control device when the exhaust gas inflow in a state of excessive oxygen concentration located, and for draining and reducing the Has nitrogen oxide in the main body is stored when the exhaust gas inflow is in a State of low oxygen concentration. 10. The deterioration determination device according to claim 9, characterized in that
the exhaust gas control device has a storage estimation device for estimating a storage amount of the nitrogen oxide, and
if it is estimated by the storage estimation device that the storage amount of the nitrogen oxide is less than or equal to a predetermined amount, the addition of the reducing agent by the reducing agent adding device is avoided. 11. The deterioration determination method for an exhaust gas control device, characterized by
Adding a fuel to a catalytic converter ( 42 b) which is provided within an exhaust gas control device which is provided in an exhaust system ( 40 ) of an internal combustion engine ( 1 ) when a temperature of the catalytic converter ( 42 b) becomes equal to or higher than a temperature, in which an oxidation-reduction reaction begins with an unimpaired catalyst;
Measuring a catalyst temperature and an upstream exhaust gas temperature on an upstream side of the catalyst ( 42 b); and
Determining a deterioration state of the exhaust control device based on a temperature difference between the upstream exhaust gas temperature and the catalyst temperature.