FR2895444A1 - Internal combustion engine exhaust gas treatment control comprises monitoring of exhaust system temperature and components and adjusting as necessary - Google Patents

Abstract

A downstream exhaust gas treatment system for an internal combustion engine (10) and an exhaust gas system (20) with at least one catalyzer (40) and a particle filter (50) comprises monitoring the temperature of the exhaust system and of at least one of its components, and applying measures at various levels if the set temperature is exceeded. For example, at a first level in normal conditions the temperature is regulated within the engine by reducing the throttling of intake air and/or post-injection, or by closing the exhaust gas recycling shutter (111). At other levels the particle filter heating is reduced, and the post-injection dose is reduced or delayed.

Description

Field of the Invention The present invention relates to a method of

  control of an exhaust gas after-treatment system of an internal combustion engine comprising an engine block and at least one exhaust system (20) equipped with at least one catalyst and one filter with downstream particles. The invention also relates to a device for controlling a downstream exhaust gas treatment system of an internal combustion engine comprising an engine block equipped with a control unit cooperating with a regulating installation, and at least one an exhaust gas evacuation system comprising at least one catalyst followed by a particulate filter, the temperature of which is predicted to be measured by at least one temperature measurement system.

  STATE OF THE ART Internal combustion engines, and in particular diesel-type internal combustion engines, are often equipped with an exhaust gas after-treatment system comprising a soot particle filter or diesel particulate filter (DPF). . This is in particular necessary because of the reinforcement of the regulation concerning the limit values imposed on the exhaust gases according to the EU VI regulation. The use of particulate filters is an effective way to reduce particle emissions and this solution is already planned in series by different manufacturers. The soot stored in the filter, however, must be burned discontinuously to ensure the desired filtering effect. To regenerate the particulate filter it is necessary to apply temperatures higher than the usual temperature of the exhaust gases. Without this measurement, the particles oxidize at about 550-600 C. By combining the soot particle filter with an oxidation catalyst (OXI-KAT catalyst) or by applying a catalytic coating to the filter and / or by addition of an additive, it is possible to reduce the lower temperature threshold for oxidation below 500 C. However, the purpose of the developments is to eliminate the systems using additives.

  In some operating states of the internal combustion engine it can happen that the regeneration proceeds in an uncontrolled way too fast or too slow. In particular, in the case of an uncontrolled rapid combustion, because of the highly exothermic oxidation of the particles, there is an annoying heat release which combines with a steep temperature front, mobile in the filter with temperatures very high. Such situations must be avoided safely and if they occur they must be controlled and dominated by appropriate means. If the regeneration proceeds too slowly, the regeneration measures must be implemented too long, resulting in an increase in fuel consumption. In addition, there is a risk that the motor will stop or go into an operating mode that forces the stopping of the regeneration phase.

  It is known from DE-OS 10333441 A, EP 1384868 A2 to avoid such situations by applying a method with a control device of a downstream exhaust gas treatment system, in particular a particles of an internal combustion engine. According to these documents, a set value (LAS) of the lambda signal (L) or a variation of the lambda signal (L) is predefined. We enter the actual value of the lambda signal (L) or the variation of the lambda signal (L). Starting from the comparison between the actual value and the set-point value (LAS), a control signal for a setting or actuating element for controlling the reaction in the exhaust aftertreatment system and which slaves the actual value on the set point (LAS). With the aid of such adjustment or actuation elements, it is possible to influence the quantity of oxygen contained in the exhaust gases. The adjusting elements may be an exhaust gas recirculation valve, a throttle flap, actuating elements acting on an exhaust gas turbo-compressor and / or a fuel metering system ensuring the post injection of fuel into the internal combustion engine. The document EP 1364110 B1 describes another method and a corresponding device according to which the regeneration operation determining a characteristic quantity is controlled as a function of at least one operating parameter of the internal combustion engine and of at least one parameter of operation of the particulate filter characterizing the future intensity of a reaction of a particulate filter. If a threshold is exceeded by the characteristic quantity, at least one measurement decreasing the oxygen concentration in the exhaust gas of the internal combustion engine to prevent the characteristic quantity from reaching the threshold. If the soot particle filter reaches a certain level of charge and the regeneration of the filter is not ensured due to the state of operation of the engine, the state of the art foresees increasing the temperature of the exhaust gases. exhaust to quickly burn the particles. For this purpose, the hydrocarbon concentration of the exhaust gases is increased to transform them into the oxidation catalyst and to cause a rise in temperature. Increasing the concentration in the exhaust line is usually done by post-injection into the fuel system of the engine block or by direct dosing of diesel in the exhaust system; the metered quantity is normally preset according to the operating point of the motor. In this context, it is known to increase the concentration of hydrocarbons by a throat of the sucked air or a reduction of the pressure of the injection manifold. In addition, methods can also be applied which delay the main injection or use an offset post-injection. In particular, in particulate filters located below the level and at a distance from the engine, the maximum permitted temperature is limited by the exhaust manifolds, the turbine and the pre-catalyst, which limit the energy supplied by the gases. exhaust. To allow heating as efficient as possible it is necessary that the actions internal to the engine on the constriction of the air sucked, the offset in the direction of the delay of the main injection, the modification of the pre-injection and / or post-injection are not applied as closely as possible to the permitted temperatures.

  To avoid field or environmental influences and standard manufacturing tolerances, a safety strip must be adhered to, which at least increases the heating time required and continues to increase fuel consumption. OBJECT OF THE INVENTION The object of the present invention is to develop a method of controlling the exhaust gas downstream treatment system which makes it possible to provide guaranteed and economical heating in internal combustion to the engine in order to regenerate the particulate filter. The invention also aims to develop a device for carrying out the method. DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose, the invention relates to a process of the type defined above, characterized in that using at least one measuring installation the temperature of the gas system is monitored. Exhaust and temperature of at least one of its components and in case of temperature rise a concept of multilevel measurements is applied. The method according to the invention makes it possible in particular in the case of extreme environmental influences, such as extreme ambient temperatures or extreme altitudes, to apply the heating strategy to the regeneration of the particulate filter with a reduced security interval. This allows for particularly safe and fuel-efficient heating, internally to the engine.

  According to a preferred embodiment, according to a first level, under normal conditions, a regulation of the temperature is carried out using control variables internal to the motor, in a control loop. The application is near the temperature of the components. This allows a particularly efficient heating of the particulate filter. The time required for regeneration is shortened significantly, which has an advantageous effect on fuel consumption. As a regulating variable internal to the engine, it is possible to reduce the throttling of the air intake, and / or post-injection when the throttle flap of the exhaust gas recirculation system is closed or substantially closed. This avoids additional installations that would be necessary to provide heating.

  In the event of a corrected overrun in time of the maximum allowed temperature of the components, in a second level the limit value acting on the throttle flap of the exhaust gas recirculation system is regulated and opens in stages or opens it completely. It is advantageous to allow a direct decrease in the critical temperature of the components such as the collector and, if appropriate, the turbo-compressor, without having to reduce the heating of the particulate filter already. However, the condition is that the exhaust gas recirculation be completely closed or only open at a minimum level during the heating mode, which is obligatory for many engine adaptations because of the risk of an increase in the black smoke development or combustion variations. According to a preferred embodiment, it inter-comes on the maximum mass recycled according to the operating point by an action on the regulation of the limit value, which reduces the risk of a development of black fumes and which more is advantageous because we have a sufficient reserve of torque. If, in the event of a subsequent, corrected overflow for the maximum permissible component temperature, another limit value control is carried out in a subsequent level, which acts on the heating control variables of the particulate filter, it is possible to take Protective measures that produce a direct decrease in temperature in the exhaust gas recirculation system. According to a preferred variant of the process, in the context of the limit value regulation in the event of exceeding the temperature, it is possible to reduce the post-injection dose and / or to resume the delay of the post-injection and / or to reduce the throttling of the sucked air and / or advance the main injection. These measures allow a significant reduction in component temperatures in the exhaust gas recirculation system. As a backup reaction, in the event of other corrected overruns in the time of the maximum permissible component temperature, in a final level all internal measurements of the motor for the heating of the particulate filter are stopped. This safety shutdown avoids a destructive overrun of the maximum temperature of the components if the previously executed control process has no effect to reduce the temperature. For the return adjustment there is provided a variant of pro-ceded according to which in case of exceeding the maximum temperature of the components downwards, the measures taken are neutralized as a function of the levels of escalation of the measurement concept by proceeding level by level. According to a preferred embodiment variant, the component critical temperature is over-monitored by a temperature measurement or by modeling. By modeling, we can also take into account the complex relationships that depend on a large number of influence coefficients. From the actual rise in temperature, taking into account an additional tolerance and a comparison of this value with the temperature increase calculated in a model, it is possible to detect brief temperature variations or deviations of tolerances for sensors. temperature, which contributes to a temperature control less sensitive to incidents. Particularly accurate temperature control is achieved if the maximum allowable temperatures of the components of the exhaust gas recirculation system are predefined as a function of the characteristic field. This makes it possible, for example, to take into account the different operating states of the internal combustion engine and thus to control an optimum regeneration temperature of the particulate filter, also taking into account other parameters of the engine. The invention also relates to a device of the type defined above, characterized in that cascaded control circuits are implemented in the control unit by means of which countermeasures are launched in case exceeding a maximum permissible component temperature. This ensures the safety of the particle filter heater and reduces the risk of heating shutdown. It is generally necessary to avoid such a heating shutdown because it would only indefinite combustion and incomplete soot, so that it would significantly complicate the clear detection of the soot charge to ensure the launch of regeneration. According to a preferred embodiment, in a first level, the control unit comprises a control circuit for heating the particle filter internally to the motor, in a second level a limit value regulation is provided for recycling. exhaust gas and in a third level there is provided a further limit value control of particle control heating quantities of the particle filter These levels of escalation per-mate an exact regulation of the temperature in the vicinity of the permissible maximum temperature of the components of the exhaust system. If the control unit is connected by at least one signal transmission line to at least one temperature sensor and the control unit is connected for the regulation of the post-injection dose by a transmission line. signals to a fuel-saving system of the engine block, then as an internal measurement engine can in particular regulate the post-injected dose in a first level and reduce it if the temperature is close to the maximum temperature of component. According to an equally preferred variant, the control unit is connected by at least one signal transmission line to at least one temperature sensor and the post-injection dose control unit 30 is connected by a line signals to a fuel metering system of the engine block. This allows, on the one hand, the regulation of the amount of exhaust gas recirculation and, on the other hand, the taking of other internal measures to the engine to regulate the amount of air sucked.

  In turbocharged internal combustion engines, the exhaust gas system includes an exhaust gas turbocharger upstream of the catalyst, which significantly increases the power output of the internal combustion engine.

  To protect the exhaust gas turbocharger against overheating, the control unit is connected by a signal transmission line to another temperature sensor installed in the exhaust gas system upstream of the gas turbocharger. exhaust. This solution is important in the case of fuel combustion in the elbow of the engine block collector because it could have in this case extreme temperatures in the exhaust gas turbocharger. As a device promoting post-injection, the exhaust system comprises at least one fuel metering system connected by a signal transmission line to the control unit. This allows additional fuel to be metered into the exhaust system for rapid heating of the needed rich mixture. The fuel metering unit can thus be additionally integrated as another adjustment variable in the cascade temperature control. If the control unit has at least one characteristic field unit for presetting the maximum temperature of the parts or components, in this preferred embodiment, complex operating parameters can also be taken into account.

  In particular, in different cases of loads or operating phases of the internal combustion engine it may be advantageous to predefinitely vary the maximum temperature of the parts or components. According to a preferred embodiment, the functions of the control circuit and the limit value controls can be executed in the control unit in the form of programs and / or circuits and be at least partially part of a control. main engine, a function registered as a control program that can be integrated in a particularly simple manner as a routine in the engine management control program. This allows economic updates of the programs. Drawings The present invention will be described below in more detail with the aid of an exemplary embodiment shown in the accompanying drawings in which: - Figure 1 shows schematically an internal combustion engine equipped with a system of downstream treatment of exhaust gas, and - Figure 2 shows a control flowchart of the aftertreatment system of exhaust gas. DESCRIPTION OF EMBODIMENTS FIG. 1 schematically shows an internal combustion engine 1 equipped with an exhaust gas after-treatment system comprising, as main components, an engine block 10, a control unit 130 cooperating with a control installation and an exhaust gas system 20. The exhaust system of the exemplary embodiment shown comprises a catalyst 40 and a particulate filter 50 installed downstream. In addition, in the example shown, the exhaust system 20 includes an exhaust gas turbocharger 30 for increasing power. The temperature of the parts is monitored by temperature sensors 70, 80, 90, 100 installed in different places. The first temperature sensor 70 in the direction of flow is upstream of the exhaust gas turbocharger 30 and is used primarily to monitor the temperature of the exhaust gas turbocharger 30 and the exhaust gas manifold temperature. engine block 10 upstream of the exhaust gas turbocharger 30. The temperature sensors 80, 90 can detect the temperatures upstream and downstream of the catalyst 40 or upstream of the particulate filter 50. The last temperature sensor 100 installed in the direction of flow of exhaust gas is used to monitor the temperature of the exhaust gas. All the temperature sensors 70, 80, 90, 100 are connected by corresponding signal transmission lines 71, 81, 91, 101 to the control unit 130. The control unit 130 is connected by a transmission line signal 12 to a fuel metering system 11 of the engine block 10. The fuel metering system 11 is usually controlled by a main engine control, not shown here. The internal combustion engine 1 also comprises an external exhaust gas recycling system 110 whose active components consist of an adjustable throttle flap 111 connected by a signal transmission line 112 to the control unit 130. On the supply side, the internal combustion engine 1 comprises an adjustable throttling element 120 of the sucked air connected by another signal transmission line 121 also to the control unit 130. a fuel metering unit 60 in the exhaust gas system (in the example shown, the installation is provided behind the exhaust gas turbocharger 30) and this unit is connected by a signal transmission line 61 to the control unit 130. According to the invention, in the control unit 130 there are cascade control circuits with which, in case of exceeding a maximum permitted temperature of coins we launch countermeasures. In a first level there is a control circuit 131 of the internal heating of the motor of the particulate filter. In a second level, there is a limit value regulation 133 for the recycling of the exhaust gas 110 and in a third level there is another limit value regulation 134 for the heating quantities of the particulate filter. According to a preferred embodiment, the functions of the control circuit 131 and the limit value controls 132, 133 are implemented in the form of programs and / or circuits in the control unit 130 and are at least partially part of a main engine control. The controller 130 includes at least one feature field unit for presetting the maximum component temperature and containing the maximum component temperature recorded according to the operating points. Figure 2 depicts the method using a flow chart.

  In the control unit 130, using at least one measuring installation, the temperature in the exhaust gas system 20 and the temperature in at least one of its components are monitored; if the temperature is exceeded, a multilevel measurement concept is applied.

  In a first level, under normal conditions for the control circuit 131, the temperature is regulated by means of adjustment variables internal to the motor. As engine internal control variables there is firstly the reduction of the sucked air restriction (ALD) or a post-injection (NE), the throttle valve 111 being closed or practically closed for recycling exhaust gases 110. The temperature of the pieces (TB) is compared by an interrogation 135 to the maximum permitted temperature of the pieces (Tmax). If the temperature of the pieces (TB) exceeds this for a given minimum duration, in the second level the regulation of the limit value 132 acting on the throttle flap 111 of the exhaust gas recirculation system 110 is carried out. For this purpose, the throttle flap 111 of the exhaust gas recirculation system 110 is opened. This allows a direct lowering of the critical component temperature, namely the exhaust gas manifold and the gas turbocharger. Exhaust 30. The condition is however that the exhaust gas recirculation system 110 is closed or is only opened in the minimum position during the normal heating mode of the particulate filter 30, otherwise there is the risk of increased soot formation and combustion variations. The setting action on the limit value control 132 is thus limited to a maximum recycling mass depending on the operating point. In a new interrogation 135 the comparison between the component temperature (TB) and the maximum allowed component temperature (Tmax) is repeated. In the event of further time-corrected overflows for the maximum permissible component temperature, the next limit control 133 acting directly on the heating control variables of the particulate filter 50 is then carried out to a next level. For this purpose, in the event of a temperature rise, the post-injection dose (NE) is reduced and / or the delay in the post-injection delay direction (phi NE) is reduced and / or the aspirated air (ALD) and / or shifted in the direction of advance a main injection (phi HE). In a last level, in the event of a new overshoot with time correction of the maximum permitted component temperature, which is determined by a new request 135, all the measurements internal to the motor and used to heat the particle filter. This is done by a shutdown program 134.

  If the maximum component temperature is exceeded, it is possible to go back step by step again to neutralize the escalation levels of the measurement concept. For a rebound correction, it is furthermore advantageous if the critical temperature of the part is monitored by a monitoring measurement or by modeling. The brief temperature variations can be perceived as disturbances without reacting with the measures described above. In practice, this cascade control method makes that, for example, for a heating mode in application, with oxygen strangulation (ALD), a post-injection (NE) produces a variation for the gas recirculation. exhaust (AGR) followed, in addition to a known decrease in the NOx nitrogen oxides content in the exhaust gas, by a continuous decrease in temperature after the exhaust gas turbocharger 30, which is particularly linked to the increase in the external recycling of exhaust gases. All other temperature changes as well as the torque curve are not influenced at first. The method and the device as described and presented allow a temperature monitoring and a regulation on the one hand safely avoiding overheating components

  13 in the exhaust gas control 20 and on the other hand allow a heating internal to the engine and optimized from the point of view of con-summation, the particulate filter 50 for its regeneration.

Claims (10)

  1) A method of controlling a downstream exhaust gas treatment system of an internal combustion engine (1) comprising an engine block (10) and at least one exhaust gas system (20) equipped with at least one catalyst (40) and a downstream particulate filter (50), characterized in that at least one measuring device monitors the temperature of the exhaust gas system and the temperature of at least one of its components and in case of temperature rise a concept of multilevel measurements is applied. 2) Method according to claim 1, characterized in that in a first level, under normal conditions, a temperature control is carried out using internal control variables in the motor, in a control loop (131). 3) Process according to claim 2, characterized in that as control variables internal to the engine is carried out a reduction of the constriction of the air sucked, and / or a post-injection, the throttle flap (111) d an exhaust gas recirculation (110) being closed or substantially closed. 4) Process according to Claim 1, characterized in that, in the event of a time-corrected overflow from the maximum allowed temperature of the component, a second level of regulation is carried out to regulate the limit value (132) which acts on the throttle flap (111) of the exhaust gas recirculation system (110). 5) Method according to claim 4, characterized in that limits a setting action on the limit value control (132) to a maximum recycling mass depending on the operating point-ment. 6) Method according to claim 1, characterized in that for another overflow corrected in time beat of the maximum permitted component temperature, at the next level is performed another limit value regulation (133) which acts on the quantities of heating control of the particulate filter (50). 7) Method according to claim 6, characterized in that during the limit value regulation (133), in case of exceeding the temperature, the post-injection dose is reduced and / or post-injection and / or delayed. the throttling of the sucked air is reduced and / or the advance of the main injection is neutralized. 8) A method according to claim 1, characterized in that in case of other overruns corrected in time beat of the maximum permitted component temperature, at the last level, all means internal to the engine are stopped for heating the filter. with particles. 9) A method according to claim 1, characterized in that in case of downward operation of the maximum component temperature is again neutralized, level by level, the measures corresponding to the level of escalation of the measurement concept taken. 10) Process according to Claim 1, characterized in that the critical component temperature is monitored by temperature measurement or modeling. 11) Process according to Claim 1, characterized in that the maximum permissible temperature is predefined. of component in the exhaust gas system (20) according to the field of characteristics. 12) A control device for a downstream exhaust gas treatment system of an internal combustion engine (1) comprising a motor unit (10) equipped with a control unit (130) cooperating with an installation of regulator, and at least one exhaust gas exhaust system (20) comprising at least one catalyst (40) followed by a particulate filter (50), the temperature of which is expected to be captured by at least one temperature measurement, characterized in that cascaded control circuits are implemented in the control unit (130) by means of which countermeasures are initiated when exceeding a maximum permitted component temperature. 13) Device according to claim 12, characterized in that in a first level, the control unit (130) comprises a control circuit (131) for heating the particle filter internally to the engine, in a second level there is a limit value control (133) for the recirculation of the exhaust gases (110) and in a third level there is provided another limit value control (134) of the heating control variables of the particulate filter. cles. Device according to Claim 12, characterized in that the control unit (130) is connected by at least one signal line (81, 91, 101) to at least one temperature sensor (80, 90, 100) and the control unit (130) for regulating the post-injection dose is connected by a signal line (12) to a fuel metering system (11) of the engine block (10). Device according to Claim 12, characterized in that the control unit (130) is connected by at least one signal transmission line (112) to at least one throttle flap (111) of the exhaust gas recirculation system. exhaust (110) and / or at least one other signal line (121) to an air suction throttle (120). 16) Device according to claim 12, characterized by an exhaust gas turbocharger (30) installed in the exhaust gas recirculation system (20) upstream of the catalyst (40). 17) Device according to claim 12, characterized in that the control unit (130) is connected by a signal transmission line (71) to another temperature sensor (70) of the exhaust gas recirculation system. (20) upstream of the exhaust gas turbocharger (30). Device according to claim 12, characterized in that the exhaust gas recirculation system (20) comprises at least one fuel metering device (60) connected by a signal transmission line (61) to the control unit (130). 19) Device according to claim 12, characterized in that the control unit (130) comprises at least one characteristic field unit to predefine the maximum temperature of the components. Device according to Claim 12, characterized in that the functions of the control circuit (131) and the limit value controls (132, 133) are implemented in the control unit (130) in the form of programs and / or or circuits and are at least partially part of a main engine control. 10