DE4042563C2 - Emission control system for use in an internal combustion engine - Google Patents

Description

The invention relates to an exhaust gas purification system for Use in an internal combustion engine with a filter, in the particles contained in the exhaust gas separated and collected with the particles collected in the filter always then be burned if the filter needs to be regenerated is.

With such an exhaust gas cleaning system known from EP 0 220 484-A2 system will raise the temperature in the filter Flow control valve operated according to data that the State the operating state of the internal combustion engine, such as speed and torque on the filter and the fuel injection quantity. The targeted regeneration is always initiated when the Ab back pressure exceeds a predetermined value.

From DE-PS 37 29 857 is a method for the regeneration of a Soot separator in a diesel engine, in which the jewei current speed and respective power of the diesel engine detected to distinguish two areas of the engine map. In one area there is insufficient regeneration and in the other area there is sufficient automatic regeneration tion of the soot separator by oxidation instead. A first loading operating time counter adds up all operating states in the first loading map of the map during a second operating time All operating states in the second area of the map added up. When a predetermined total value is reached in the Most counter is by targeted internal performance increase or by adding fuel to the exhaust gas, an operating point in the second Range of the engine map adjusted and the second counter activated. When a predetermined total value is reached in second counter, both counters are set to zero and the Lei Increase in performance or the addition of fuel to the exhaust gas taken.  

DE-OS 37 23 470 describes a method for regeneration known a soot filter, in which at all loads and Speeds of the internal combustion engine a measure of the covering thickness of the soot filter is obtained, so that an effective and Control requirements appropriate regeneration of the soot filter to be able to. The value of the exhaust gas back pressure and the Speed is a measure of the thickness of the soot filter and the value thus calculated with a predetermined maximum value compared to the covering thickness. If the maximum value is exceeded the regeneration of the soot filter is initiated.

The object of the invention is to provide an exhaust gas cleaning system create where the need to regenerate the fil ters can be determined even more reliably.

In an exhaust gas cleaning system, this task is performed by the Claim 1 specified teaching solved.

The invention is characterized in that the amount of part chen, which are each collected in the filter, by the following Measures can be determined very precisely:

• (1) There are respective amounts (ΔPCT1) of collected part Chen added per unit of time and respective amounts (ΔPCT2) of subtracted burned particles per unit of time.
• (2) Any amount (ΔPCT1) of collected particles per time unit is calculated from a first map in which the quantity of collected particles according to the machine load and the Machine speed is determined. Any amount (ΔPCT2) of burned particles per unit of time becomes a second Map calculated according to the amount of particles burned Specification of the machine load and the machine speed is determined.

The main advantages obtained by these features ( 1 ) and ( 2 ) will now be explained:
By using the first and second cards according to feature ( 2 ), the amount (ΔPCT1) of the particles collected per unit of time and the amount (ΔPCT2) of the particles burned per unit of time correspond very precisely to the prevailing operating conditions of the internal combustion engine. In addition, the use of the cards facilitates the determination of these amounts (ΔPCT1) and (ΔPCT2), especially when using a microprocessor that is already used in a motor vehicle. As a result, the particles that are collected on the one hand and burned on the other hand are determined very precisely in accordance with the respective operating states of the internal combustion engine, as a result of which a very precise decision can be made as to whether the time that requires regeneration of the filter has come or not. This prevents excessive fuel consumption due to early regeneration by increasing the exhaust gas temperature of the filter, while at the same time preventing damage to the filter due to excessive heating due to late regeneration, in which a large amount of collected particles is instantaneously burned would.

According to the characteristic (1), the very precisely determined Quantity (ΔPCT1) added per unit of time and the be very precise agreed amount (ΔPCT2) per unit of time subtracted to the resul exact amount of particles collected in the filter to determine. It should be emphasized that a continuous Adding and subtracting per time unit only makes sense is when the respectively determined quantities (ΔPCT1) and (ΔPCT2) after Provided the machine load and the machine speed very are exactly certain values. Would these amounts be (ΔPCT1) and (ΔPCT2) relatively inaccurate values and would make them continuous added or subtracted per unit of time, there could be errors gradually increase, which then again determines the determination of the Ent time of a necessary regeneration of the filter ent could become inaccurately speaking.  

An embodiment of the invention is based on the drawing explained in detail. In detail show:

Fig. 1, an internal combustion engine generating means with a filter and Re, in which the invention is Applic bar,

Fig. 2 is a block diagram showing the essential details of an embodiment of the invention,

Fig. 3A and 3B are flow charts for illustrating the working example, which is performed in the control according to the embodiment,

Fig. 4 to 8 data tables that are used in connection with the embodiment.

Fig. 1 shows an internal combustion engine in which a Grundzu standing open intake throttle valve 6 is arranged in the intake main line 5 and with a vacuum servomotor 8 is Betriebsverver connected.

The vacuum chamber of the vacuum servo motor is connected to a vacuum pump via a three-way solenoid valve 19 . When the valve 19 is turned on, a negative pressure of a predetermined size is applied to the vacuum chamber of the servo instead of the atmospheric pressure.

An exhaust gas throttle valve 21 of the flap type which is open in the basic state is arranged in the exhaust gas line 2 at a point upstream of a filter 3 . The valve is operationally connected to a vacuum servo motor 22 . A three-way solenoid valve 23 is designed such that the application of the vacuum from the pump to the vacuum chamber of the servo motor is controlled.

A bypass channel 24 bridges the filter 3 . A closed bypass control valve 25 of the flap type is arranged in the bypass channel 24 and operatively connected to a vacuum servo motor 26 be in the basic state. A solenoid valve 27 is designed such that the application of the vacuum to the vacuum chamber of this Vorrich device is controlled.

A heating device 29 is arranged immediately upstream of the filter 3 and is designed such that the filter is warmed up by a control unit 41 when an excitation signal is supplied.

The heater 24 and the bypass control valve 25 are provided in combination with each other to form a filter temperature control arrangement.

A semiconductor type pressure sensor 31 is arranged to detect the pressure difference ΔP that results at the filter, while thermocouple type temperature sensors 32 , 33 are arranged to determine the inlet and outlet temperatures at the upstream and downstream ends of the Filters prevail, and to emit TIN and TOUT signals, respectively.

A crank angle sensor 43 is arranged to detect the revolving speed Ne of the engine 1 , while an engine load sensor 35 is arranged to output a signal Q which represents the accelerator pedal depression travel. An engine coolant temperature sensor 36 is arranged to output a TW signal to the control unit.

The control unit 41 contains a microprocessor, which responds to the outputs of the above-mentioned sensors and, in a suitable manner, outputs drive signals to the three-way solenoid valves 19 , 23 and 27 .

Fig. 2 shows the essential details of an embodiment, which is characterized in that a quantity of collecting particles per unit time ΔPCT1 or a quantity of erosion particles per unit time ΔPCT2 is determined. Because ΔPCT1 and ΔPCT2 are dependent on engine operating conditions and parameters, they change with them. The accumulated particulate amount SUM obtained by adding ΔPCT1 and subtracting ΔPCT2 also consequently changes with the engine operating conditions.

It is therefore possible to determine the exact amount of particles that have been collected, and therefore it can be determined if a Regeneration is required.

The output of the sensor that detects the exhaust gas temperature on the downstream side of filter 3 (TOUT) is not used.

Fig. 3A and 3B show a flow chart showing the operation which is carried out at a programmed control sequence. In step 2S1 the outputs of the sensors are scanned and the instantaneous values of Ne, Q, TW and TIN are read.

In this flowchart, steps 2S1, 2 S13 and 2 S14 are selected such that the timing for initiating the regeneration is controlled thereby. In step 2S2, the status of a flag F for a required regeneration is checked. If it is not time to regenerate the filter, then it is found that the flag F is cleared (F = 0). If F = 0, then the control flow goes to step 2S3. In this step, it is determined when it is time to integrate an ΔPCT value. When the time for integration is reached, the control flow goes to step 2S4. It should also be mentioned that the interval Δt between the integrations can be set to 2-3 second intervals, for example.

In step 2S4 it is determined in which operating range the internal combustion engine is operating. In this preferred embodiment, listed data are used for this purpose, which are shown, for example, in FIG. 4. As can be seen from this figure, the engine operation is divided into two engine speed (Ne) / load (O) ranges. The first is an area in which the combustible particles combusted burn off spontaneously, and the other is an area in which the particles collect in the filter 3 .

In particular, step 2S4 is one in which is determined when the current engine speed and Bela Indicate that the exhaust gases are sufficiently hot (400 ° C or larger) to initiate regeneration or not. If then the engine is working in the "collection" zone total particle volume should be increased by adding ΔPCT1 will. On the other hand, if the engine is in the "Self-burning" zone is located, then the total particle amount can be reduced by deducting the value ΔPCT2 is pulled.

If in step S4 it results that the collection of the particles is to be expected, then the control process with the step 2S5 continued while proceeding to step 2S6 when there is a burn.

In steps 2S5 and 2S6, the particle quantity ΔPCT1 collected per unit of time and the particle quantity ΔPCT2 burned off per unit of time are derived by looking up the data tables of the type shown in FIGS. 5 and 6.

In steps 2S7 and 2S8, the data listed in FIGS . 7 and 8 are used to derive correction factors KTW1 and KTW2 relating to the coolant temperature, which are used to correct the values of ΔPCT1 and ΔPCT2, as in the equations (12) and (13).

ΔPCT1 ← ΔPCT1 × KTW1 (12)
ΔPCT2 ← ΔPCT2 × KTW2 (13)

As can be seen from Fig. 7, at low coolant temperatures, the value of PCT1 is increased by providing a relatively large correction factor. The reason for this can be seen in the fact that under these conditions the amount of particles given off by the internal combustion engine is greater than in the case of a completely warmed up internal combustion engine. For similar reasons, the value of ΔPCT decreases as the engine coolant temperature rises. Namely, when the engine cooling medium temperature rises, this results in that the engine is warmed up, and the amount of particles emitted by the engine then tends to become smaller.

In step 2S9, the current value of TIN is passed with a agreed T1 (T1 = 400 ° = TREG) compared.

If TIN <T1, then the control flow is with the Step 2S11 continues while if the result in Step 2S4 is such that the control flow with the step 2S6 is continued, the control sequence becomes when TIN <T1 proceeding from step 2S10 to step 2S12. In steps 2S11 and 2S12, the values of ΔPCT1 and ΔPCT2 integrated, i.e. H.:

SUM ← SUM + ΔPCT1 (14)
SUM ← SUM - ΔPCT2 (15)

If it is found that TIN is T1 in step 2S9, then step 2S11 is bypassed. The reason for this is that even if the engine operation falls within the Sam melzone because TIN <T1, it indicates that the engine has immediately undergone a change from the high speed / high load mode (i.e., it is operating in a transient mode) ), so that he can wait that the filter 3 is sufficiently warm to initiate the combustion of the particles that occur at this time. Therefore, the amount of particles collected per unit of time should not be added up under these circumstances.

Similarly, if it is found that TIN <T1 in Step 2S10 is expected to decrease the internal combustion engine Machine operating state from a low speed / low rig loading mode has changed and that at that time sufficient heat is not available to protect the ver initiate combustion. Therefore, step 2S12 of the control bypassed.  

In step 2S13, the SUM value is predetermined Reference value (for example 10 square meters) compared. If SUM Is the reference value, this indicates that sufficient Collected particles to ensure regeneration, and the control flow goes to step 2S14, in which the above-mentioned flag F for a required Regeneration is set (F = 1).

Setting the flag F causes the control continue from step 2S2 to steps 2S16 to 2S20 is set in which suitable control commands are generated, that control the opening and closing of the throttle valves. In particular In particular, the current TIN value is verified with T1 in step 2S16 like. If TIN T1 ≠, the filter can rain spontaneously and the control flow goes to step 2S18 continued.

If, however, TIN <T1, the control flow continues with step 2S17, in which the coolant temperature TW is compared with a predetermined value (for example 50 ° C.). If TW is greater than the given value, the control flow goes to step 2S19. In this step, commands are issued which activate the heating device 29 and initiate the throttling of the intake and exhaust system. As stated above, this increases the exhaust gas temperature to a value at which the combustion of the accumulated particles can be initiated.

On the other hand, if the coolant temperature is lower than the preset value, the control flow proceeds from step 2S17 to step 2S20, in which commands are issued with which all throttle valves 6 , 21 and 25 are opened. As already stated in the description, it is concluded from these circumstances that there is no possibility of raising the temperature of the exhaust gases to the value of TREG.

In step 2S21 the regeneration time is measured and with compared to a predetermined time value in step 2S22. This Time can be set in the order of 10 seconds or the like will. The regeneration to be determined runs for one agreed time period. The control process then progresses  step 2S23, in which the in the already completed Data used for regeneration operations are deleted, and the Flag F is reset for a necessary regeneration (F = 0).

In summary, an operating mode is used in which a given number of parameters is monitored and the accumulation of such sufficient particles is predicted that regeneration is guaranteed. In this case, the regeneration is maintained for a predetermined time in order to burn off the particles collected in the filter 3 .

Claims (2)

1. Exhaust gas cleaning system for use in an internal combustion engine with:
a filter ( 3 ) in which particles from an exhaust gas from the internal combustion engine ( 1 ) are separated and collected, the particles being combustible when heated;
means ( 6 , 21 , 25 , 29 ) for raising the temperature in the filter ( 3 ) for burning the particles when they are actuated;
means ( 41 ) for dividing the operating states of the internal combustion engine into a first zone in which the particles are separated off and collected in the filter ( 3 ) and a second zone in which the particles are burned in the filter ( 3 );
a device ( 35 , 34 ) for detecting a machine load (Q) and an engine speed (Ne) to determine an operating state of the internal combustion engine;
means ( 41 ) for determining whether the detected operating condition of the internal combustion engine falls into the first or second zone in accordance with the engine load (Q) and the engine speed (Ne);
means ( 41 ) for calculating the amount of particles which are collected in the filter ( 3 ) per unit time in the first zone and the amount of particles which are burned in the filter ( 3 ) per unit time in the second zone , in accordance with the determination result of the determination device ( 41 );
means ( 41 ) for determining the amount of particles collected in the filter ( 3 ) by adding respective amounts of collected particles per unit time and subtracting respective amounts of burned particles per unit time;
means ( 41 ) for determining that a time to regenerate the filter ( 3 ) has come in accordance with the amount of the accumulated particles, and
means ( 19 , 23 , 27 ) for actuating the means ( 6 , 21 , 25 , 29 ) for raising the temperature in response to the determination that the time requiring regeneration has come,
wherein the calculating means ( 41 ) means for calculating the amount of the collected particles from a first map in which the amount of collected particles in the filter ( 3 ) is determined in accordance with the engine load (Q) and the engine speed (Ne) , and means for calculating the amount of burned parts from a second card ent, in which the amount of burned in the filter ( 3 ) Chen chen is determined in accordance with the machine load (Q) and the engine speed (Ne). 2. The exhaust gas purification system according to claim 1, further comprising means ( 41 ) for correcting the amount of the collected particles and the amount of the burned particles in accordance with the coolant temperature (Tw) of the internal combustion engine.