JP2003522897A - Control device and control method for NOx regeneration of NOx storage catalyst - Google Patents

Abstract

(57) Abstract: The present invention starts NO _X regeneration if exceeded at least NO _X downstream of the NO _X emission threshold storage catalyst (14) of the load state or _the NO _X storage catalyst (14), to a method and apparatus for controlling of the NO _X regeneration of an automobile engine exhaust gas pipe (10) arranged in (12) was _the NO _X storage catalyst (14). (A) an internal combustion engine (10) detects whether or not it is shifted to idling, raising the (b) any one or any combination, i.e. the threshold of idling load state or NO _X emissions below , starts the first NO _X regeneration after the lapse of a predetermined time interval, and may stop NO _X regeneration ongoing when switching the idling configured to be performed.

Description

Detailed Description of the Invention

The present invention relates to a control device and a control method for NO _X regeneration of a NO _X storage catalyst arranged in an exhaust gas pipe of an internal combustion engine for automobiles, which has the features recited in the superordinate concept of the independent claims.

It is well known to incorporate exhaust gas purification equipment into an exhaust gas pipe for purification of exhaust gas of an internal combustion engine. In that case, the exhaust gas purification facility usually comprises components such as a particle filter or a catalyst. In an attempt to reduce crude emissions from internal combustion engines, this catalyst consists of a reducing catalyst. If the mass flow of reducing harmful substances, such as carbon monoxide CO and incompletely burned hydrocarbons HC, is high enough in the area of the reducing catalyst, NO _X is converted by the reducing agent into nitrogen.

From the viewpoint of minimizing fuel consumption, it has been found to be advantageous to operate the internal combustion engine with a lean excess air ratio. However, operation in the fuel economy optimization region is accompanied by an increase in NO _X emission on the one hand and a decrease in the reducing agent mass flow rate on the other hand. Therefore, in order to avoid high NO _X release, a NO _X storage agent that absorbs NO _X as a nitrate is assigned to the catalyst. N
The O _X storage agent can be combined with the catalyst as a so-called NO _X storage catalyst.

The storage capacity of the NO _X storage catalyst is of course quantitatively limited, so that NO _X regeneration must be carried out at regular intervals in order to avoid NO _X leakage. A switch to theoretical or rich operation is performed during NO _X regeneration. The NO _X, which was previously absorbed in the form of nitrate, is released again. Normally, the NO _X regeneration is performed by loading the NO _X storage catalyst or N
O _X sensing measuring device is activated when the threshold is exceeded for the NO _X release of detecting (leak discharge). The disadvantage here is that the need for regeneration is determined according to the same criteria at all driving stages of the vehicle. However, since the exhaust gas flow rate is much smaller in the idling stage, and therefore the mass flow rate of the reducing agent is small at the start of NO _X regeneration, the desorbed NO _X can be reduced only incompletely by the catalyst component. NO _X not only inconvenient high NO _X released during regeneration, the fuel consumption increases to cause the reproduction of the idling phase is greater than the phase of the high load demand for the internal combustion engine.
Also, NO _x regeneration when idling often has the drawback of being accompanied by unwanted noise generation. Further, the NO _X regeneration during idling takes a long time because the exhaust gas flow rate is small, and therefore the operation that is disadvantageous to fuel consumption must be maintained for a long time.

The object of the present invention is therefore to provide a method and a device with which the above-mentioned drawbacks of the prior art can be overcome. The solution found then has to be easily integrated into a model already proven in control technology.

According to the invention, this problem is solved by a device and a method for the control of NO _X regeneration of a NO _X storage catalyst having the features of the independent claims. By this method (a) the internal combustion engine is detected whether or not it is shifted to idling, (b) any one or any combination of the following, namely, the tooth for the load condition or NO _X released upon (i) the idling By raising the threshold value, (ii) starting NO _X regeneration only after a predetermined period has elapsed, and (iii) stopping the NO _X regeneration that is currently in progress when switching to idling, for example, during idling operation. extending the lean stage to the next always required NO _X regeneration, or predetermined may be controlled according to the time interval.

In that case, the device according to the invention comprises means capable of carrying out the above-mentioned process steps. Such means is preferably a control device which stores in digital form a procedure enabling control of NO _X regeneration during idling. The control unit can be realized as a separate control unit or in most cases integrated into an already existing engine control unit.

When NO _X regeneration is performed together with switching to idling, switching to idling is performed in the thrust cutoff stage, or the rotational speed is higher than a predetermined threshold value, or the vehicle speed is still at a predetermined limit. If the speed is exceeded, it is preferable to end NO _X regeneration. To cancel the NO _X regeneration, it sets a marker to continue the NO _X regeneration in a subsequent acceleration phase. If NO _X regeneration had to be performed already during idling, the marker is of course cancelled.

Further, it is preferable to carry out NO _X regeneration by setting an excess air ratio of 0.85 to 1.0. Also NO _X play in any case must be made leaner than the normal of NO _X regeneration. This was compared to "standard" NO _X regeneration obviously smaller excess air ratio than 0.85, noise generation can be reduced. In another preferred embodiment of the method, NO _X regeneration during idling is initiated whenever a switch to λ = 1 operation is required for any reason. This is the case, for example, when trying to increase the pressure of the braking force amplifier.

As a whole, the number of times of NO _X regeneration during idling operation can be reduced as a whole by comparison with the other driving stages of the vehicle by the above measures, so that fuel consumption, NO _X emission during NO _X regeneration and noise generation are reduced. Will be reduced.

Other embodiments of the invention are apparent in the other features recited in the dependent claims.

[0012]   Next, embodiments of the invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an internal combustion engine 10 in which an NO _X storage catalyst 14 is placed after an exhaust gas pipe 12. In this case, a suitable sensor device is arranged in the exhaust gas pipe 12 for detecting the excess air ratio of the exhaust gas and the proportion of certain harmful substance components. For example, the gas sensor 16 is provided as a lambda sensor, and the gas sensor 18 is provided as an NO _X sensing and measuring device.
The data detected by the sensor device is sent to the engine control device 20 as is well known.
The engine control unit 20 stores in digital form a model that determines the manipulated variables for the components arranged in the internal combustion engine 10. These components can regulate the combustion process with respect to excess air ratio, ignition angle or fuel injection quantity. For example, the operation angle may be the opening angle of the exhaust gas recirculation valve 22 or the position of the throttle valve 24. Devices and methods for controlling the combustion process are well known and will not be described in detail here.

Further, other state parameters such as throttle valve position or accelerator pedal position are read by the engine control unit 20. As is known, this parameter makes it possible to determine whether the vehicle is in the idling phase. This state of the vehicle is then read by the controller 36. In this case, the control device 36 is mounted on the engine control device 20.

If the excess of oxygen is dominated in the combustion process of the air-fuel mixture, the NO _X crude emission of the internal combustion engine 10 will increase, and at the same time, the reducing agent, carbon monoxide CO and CO necessary for the conversion of NO _X will increase. Incomplete combustion hydrocarbon HC is reduced. This operating range has proved to be particularly advantageous for fuel consumption, so that NO _X must be absorbed by the storage components of the NO _X storage catalyst 14 in order to reduce NO _X emissions. When the theoretical or rich operation is switched, the NO _X stored in the form of nitrate rapidly desorbs again immediately at least immediately after the change of the atmospheric conditions of the NO _X storage catalyst 14. If the mass flow rate of the reducing agent is too low, it is not possible to supply the reducing agent to the catalyst components of the NO _X storage catalyst at the required scale, which is undesirable.
O _X release can occur.

The following method (see FIG. 2) keeps the lean operation longer in the idling stage, which is characterized by a particularly low exhaust gas flow rate, and at the same time the number of NO _X regenerations during the idling operation to other operating stages. It is possible to reduce it. Also N
The noise caused by O _X playback can be suppressed.

First, in the first question, it is checked whether the vehicle is in the idling stage (step S1). If this is denied, the NO _X regeneration of the NO _X storage catalyst 14 can be controlled in the usual way. For that purpose, for example, the NO _X storage catalyst 1 is used.
It is possible to monitor the load condition of No. 4 or the NO _X emission downstream of the NO _X storage catalyst 14 (step S2). When the threshold value of this amount is exceeded, NO _X regeneration is started by switching to theoretical or rich operation.

When the idling stage is being performed, first, in the next question (step S3),
It is ascertained whether the switch to idle takes place during the ongoing NO _X regeneration. If yes, in step 4, there is a thrust cut-off phase and / or whether the vehicle still has a speed higher than a predetermined limit speed and / or the number of revolutions exceeds a predetermined threshold value. Can be confirmed. If these peripheral conditions exist, the NO _X regeneration is terminated for the time being (step S5). Otherwise, the NO _X regeneration that is currently in progress is stopped and the marker is set (step S6). The marker ensures that after the end of the idling phase, NO _x regeneration is resumed, for example in the next acceleration phase of the vehicle.

Subsequent to steps S5 and S6, or if the switch to idling does not take place during the ongoing NO _X regeneration (step S3), a new threshold value is determined to determine the need for regeneration. Confirmation is performed (step S7). To that end, the load conditions or NO _x emission thresholds utilized in conventional methods are raised. Of course, the threshold value must be set so that a large amount of NO _X leakage does not occur when idling. However, since the exhaust gas mass flow rate is low, this can be guaranteed even at a threshold value higher than that in other operating stages of the internal combustion engine 10.

As an alternative to the last procedure, a fixed time interval after which NO _X regeneration must be performed can be set in step S7. In addition to the above control procedure for NO _X regeneration during idling, the excess air ratio during NO _X regeneration is set to a range of λ = 0.85 to 1.0 and at least a value that is not richer than conventional NO _X regeneration. This proved to be advantageous as it would generate much less noise.

[Brief description of drawings]

FIG. 1 is a principle diagram of an internal combustion engine in which an NO _X storage catalyst is arranged in an exhaust gas pipe.

FIG. 2 is a block configuration diagram for controlling NO _X regeneration of the NO _X storage catalyst during idling.

[Explanation of symbols]

10 Internal Combustion Engine 12 Exhaust Gas Pipe 14 NO _X Storage Catalyst 16 Gas Sensor 18 Gas Sensor 20 Engine Control Device 22 Exhaust Gas Recirculation Valve 24 Throttle Valve 36 Control Device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/04 305 F02D 41/04 305A 45/00 314 45/00 314Z F term (reference) 3G084 AA00 AA04 BA05 BA09 BA20 CA03 DA10 DA39 EA07 EA11 EB24 FA05 FA10 FA30 FA33 3G091 AA02 AA11 AA12 AA17 AA28 AB06 BA07 BA14 BA33 CB02 CB07 CB08 DA01 DA02 DA08 DB10 EA01 EA03 EA07 EA33 EA34 EA39 FA08 FA12 FB10 FB11 FB12 FC02 HA36 HA37 HB05 3G301 HA13 HA15 JA25 JA37 KA07 LA00 LA03 MA01 NA08 NC08 NE13 NE14 NE15 NE17 NE23 PD09Z PE01Z PF01Z PF03Z

Claims (9)

[Claims] 1. A least _the NO _X storage catalyst (14) of the load state or _the NO _X storage catalyst (14) downstream of the NO _X emission automotive internal combustion engine to start the NO _X regeneration if exceeds the threshold for the ( In the control method of NO _X regeneration of the NO _X storage catalyst (14) arranged in the exhaust gas pipe (12) of 10), (a) detecting whether the internal combustion engine (10) is shifted to idling or not. , (B) any one or any combination of the following, that is, (i) increase the load state or the threshold value of NO _X emission during idling, and (ii) perform NO _X regeneration only after a predetermined period has elapsed. A method for controlling NO _X regeneration, which is characterized by starting (iii) stopping the NO _X regeneration currently in progress when switching to idling. 2. When the thrust cut-off stage is present, or the vehicle speed exceeds a predetermined limit speed or the rotation speed is higher than a predetermined threshold value, the NO _X regeneration currently in progress when switching to idling is performed. The control method for NO _X regeneration according to claim 1, wherein the control is not stopped. Wherein when cancel NO _X regeneration ongoing, of the NO _X regeneration according to claim 2, characterized in that to set a marker to continue the NO _X regeneration in a subsequent acceleration phase of the motor vehicle Control method. 4. The method for controlling NO _X regeneration according to claim 3, wherein when the NO _X regeneration has already been performed during idling operation, the marker is canceled. 5. A range of 0.85 to 1.0 during idling operation, provided that
Anyway normal NO_XNO is set by setting an excess air ratio that is not richer than in the case of regeneration. _X Regeneration is performed, NO of any one of Claim 1 to 4 characterized by the above-mentioned._XAgain
Raw control method. 6. The control of NO _X regeneration according to claim 1, wherein when it is necessary to switch to λ = 1 operation for some reason, NO _X regeneration is started. Method. 7. At least _the NO _X storage catalyst (14) initiates the NO _X regeneration if exceeds the threshold for downstream of the NO _X release of the load state or _the NO _X storage catalyst (14) of the internal combustion engine for an automobile In a control device for NO _X regeneration of a NO _X storage catalyst (14) arranged in an exhaust gas pipe (12) of (10), (a) detecting whether or not the internal combustion engine (10) is shifted to idling Then, (b) any one or any combination of the following, that is, (i) the threshold value for the load condition or NO _X emission at the time of idling is raised, and (ii) NO _X regeneration is performed only after a predetermined period has elapsed. And (iii) means for stopping the NO _X regeneration currently in progress when switching to idling, the control unit for NO _X regeneration. 8. The above-mentioned means is NO when idling._XNO of storage catalyst (14) _X It is characterized by comprising a control device (36) that stores the control procedure for reproduction in digital form.
NO according to claim 7_XPlayback controller. 9. The control device for NO _X regeneration according to claim 8, wherein the control device (36) is incorporated in an engine control device (20).