MXPA99005190A

MXPA99005190A - Method for controlling a direct-injection internal combustion engine

Info

Publication number: MXPA99005190A
Application number: MXPA/A/1999/005190A
Authority: MX
Inventors: Achleitner Erwin
Original assignee: Siemens Ag 80333 Muenchen De; Siemens Automotive Sa Toulouse Fr
Priority date: 1996-12-05
Filing date: 1999-06-04
Publication date: 2000-01-01

Abstract

The internal combustion engine can be selectably driven either with a homogenous mixture or a stratified charge. The use of one of these operational modes is determined by the load and torque as well as by the temperature of the coolant of the internal combustion engine.

Description

PROCEDURE TO CONTROL AN INTERNAL COMBUSTION ENGINE OF DIRECT INJECTION FIELD OF THE INVENTION The invention relates to a method for controlling an internal combustion engine with direct injection, ignition from the outside, which can be operated both with a homogeneous mixture as well as with high excess air forming a stratified load.

BACKGROUND OF THE INVENTION Internal combustion engines with direct injection constitute a great potential for the reduction of fuel consumption with a low emission of pollutants. Unlike injecting in an Otto internal combustion engine, where the fuel is injected into the intake pipe, it can be mixed there with the aspirated air and flows to the cylinders as an essentially homogeneous air / fuel mixture. In the direct injection, fuel with high injection pressure is injected directly into the combustion chamber. The fuel must be fed into the combustion chamber of the cylinder in the form of the smallest possible droplets and, by means of load stratification, the mixture is enriched in such a way in the area of the spark plug that a safe ignition is guaranteed, but the Combustion takes place on average with a strongly impoverished mixture (air indices? > l, depending on the mode of operation of the internal combustion engine). German Patent DE 43 32 171 A1 discloses a method and a device for operating a four-stroke internal combustion engine with external ignition and internal injection, where, in order to reduce fuel consumption and maintain optimum emission values of Exhaust gases, the internal combustion engine is operated in five different characteristic modes according to various criteria. In a first mode, with a completely open suction cross section, avoiding an exhaust gas feedback, the fuel is injected during the suction time in the combustion chamber. In a second mode, also avoiding the feedback of the exhaust gas, the suction cross-section is further modified. In a third mode, with a regulated supply of exhaust gas, the suction cross section is reduced to a certain small value, also being injected into the suction time. In a fourth mode, with a constant partial opening and amount of controlled exhaust gas feedback, the injection moves with decreasing load until the compression time before starting the ignition. In a fifth mode with a partially open suction cross section and avoiding exhaust gas feedback, the injection is also carried out at the compression time before the start of ignition. The predetermination of the injection quantity and the control of the modes is carried out by adjusting a vehicle accelerator pedal operated with the internal combustion engine.

OBJECTIVES AND ADVANTAGES OF THE INVENTION The invention is based on the objective of providing a method for controlling an internal combustion engine ignited from the outside, which works with direct injection, of the type mentioned at the beginning, which makes it possible to better adjust to the conditions of Current operation of the internal combustion engine switching between the various combustion modes. This objective is achieved by the features of claim 1. Advantageous embodiments and embodiments are subject of the sub-claims. According to the method according to the invention, the internal combustion engine, depending on the temperature of the cooling agent, is operated either with a homogeneous mixture or with a layered charge. In this way, a faster heating of both the catalyst and the internal combustion engine itself can be carried out.

For all the mode of operation of the internal combustion engine, two characteristic fields are provided with characteristic modes comparable with respect to the load and revolutions of the internal combustion engine and, depending on the temperature of the cooling agent, either one of the characteristic modes is used, valid for a cold internal combustion engine, or the other, valid for a hot internal combustion engine. If the internal combustion engine is operated in heating with maximum possible exhaust gas flow rate *, losses due to throttling and thus fuel consumption can be reduced and the exhaust gas temperature can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing shows an embodiment of the invention and is illustrated in more detail in the following description. They show: Figure 1, a schematic reproduction of an internal combustion engine operating according to the method according to the invention. And Figure 2, diagrams of operating modes of the internal combustion engine, depending on the load and the revolutions, at various temperatures of the internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows as non-detailed schematic reproduction, an internal combustion engine with injection of high pressure tank (Common Rail), which, depending on the operating parameters, can work with both a homogeneous mixture and also with stratified load, and presents a device for the feedback of the exhaust gas. For reasons of clarity, only those parts indispensable for understanding the invention are shown. In particular, only one cylinder of a multi-cylinder internal combustion engine is shown. With reference 10 a piston is shown, which delimits in a cylinder 11 a combustion chamber 12. In it, a suction channel 13 opens out, through which the combustion air flows into the cylinder 11, controlled by a control valve. inlet 14. Controlled by an outlet valve 15, an exhaust gas channel 16 branches out of the combustion chamber 12, in the other path of which an oxygen sensor in the form of a wide-band (linear) lambda probe 17 is arranged. and a NOx reservoir catalyst 18. This serves, in areas of operation with poor combustion, to be able to maintain the required exhaust gas limit values. Thanks to its coating, it absorbs the NOx compounds in the exhaust gas produced with poor combustion. To reduce the NOx emissions of the internal combustion engine, which are especially produced in internal combustion engines with direct injection and stratified loading operation, an exhaust gas feedback is provided. By means of the mixture of already burned exhaust gas with the fresh air sucked in, the peak combustion temperature is reduced, thereby reducing the emission of nitrogen oxide depending on the temperature. This mechanism is also valid for a homogeneous mixture of the internal combustion engine. For this purpose, in order to supply a defined partial flow of the exhaust gas, from the exhaust gas channel 16, an exhaust gas feedback line 19, branching off in the direction of the flow of the exhaust gas, before the catalytic converter 18, branches off. which, downstream of a throttle valve 20, opens into the suction channel 13. The quantity of the refluxed exhaust gas is adjusted by a valve 22, usually referred to as an exhaust gas check valve, controllable by means of an electronic control device (STG) 21. Alternatively to the above, the exhaust gas feedback valve can also be controlled pneumatically, for example, with the aid of a pressure capsule. The fresh air necessary for combustion in the cylinder 11 flows through an air filter not shown and an air flow meter 23 into the suction pipe 13 towards the throttle valve 20. This is a throttle member operated by a electric motor (gas E), whose opening cross-section, in addition to the drive by the driver (desire of the driver), depending on the mode of operation of the internal combustion engine, can be adjusted by signals from the electronic control device 21. this way, for example, disturbing load change reactions of the vehicle can be reduced when accelerating and decelerating, as well as the torque jumps from the operation with homogeneous mixture to the operation with stratified load and air path not strangled. Also, to monitor and review, a signal for adjusting the throttle valve is supplied to the control device 21. A spark plug 24 and an injection valve 25 arrive at the combustion chamber 12, through which fuel can be injected into the combustion chamber 12 against the compression pressure. The movement and preparation of the fuel for this injection valve 25 is effected by a common Common Rail system for direct fuel injection. The fuel is moved under reduced pressure (usually 1 bar) from a fuel tank 26, by means of a fuel pump 27, usually arranged in the tank, which has a pre-filter, and is then passed through a filter. fuel 28 towards a high-pressure fuel pump 29. This is operated either mechanically by a coupling with the crankshaft of the internal combustion engine or electrically. It increases the fuel pressure to a value normally of 100 bar in a high-pressure tank 30 (common rail), to which the supply lines of all the injection valves are connected and which, thus, supplies them with fuel. The pressure in the high-pressure tank 30 is registered with a pressure sensor 31 in the control device 21. Depending on this pressure signal, the pressure in the tank 30 is adjusted by a pressure regulator 32 to a value constant or variable. The excessive fuel is not fed back to the fuel reserve tank 26, but to the inlet line of the high-pressure pump 29. A temperature sensor 33 records a signal corresponding to the temperature of the internal combustion engine, for example, through a temperature measurement of the cooling agent TKW. The number of revolutions N of the internal combustion engine is recorded with the aid of a sensor 34 which detects the marks of the crankshaft or of a transmission wheel connected to it. Both signals are fed to the control device 21 for processing, in particular to control the internal combustion engine with respect to the control strategy to be selected, homogenous mixture or stratified mixture. Other control parameters that are required for the operation of the internal combustion engine, such as throttle position, suction air temperature, throttle valve position, knock sensor signals, battery voltage, dynamics requirements of movement, etc., are also fed to the control device 21 and in the figure are identified in general with the reference 35. Through the parameters already mentioned, in the control device 21, when carrying out stored control routines, recognizes, among other things, the state of charge of the internal combustion engine. Likewise, the parameters are prepared and processed in such a way that, in certain operating states of the internal combustion engine, it is possible to carry out, inter alia, a switching of the operation with homogeneous mixture to the operation with stratified load and vice versa and / or a feedback of the exhaust gas. The switching between homogenous operation and stratified operation and vice versa is carried out, on the one hand, by influencing the opening cross-section (throttling) of the suction channel, by means of an electric throttle valve, and on the other, modifying the injection moment. To obtain a homogeneous mixture in the combustion chamber, in the strangulated operation, the injection takes place early in the suction time, while to obtain a stratified mixture, either in the partially choked operation or in the completely strangled operation, the injection takes place late in the compression time. Since the temperature of the catalyst has a decisive influence on the exhaust gas emissions, it constitutes an important parameter for the control of the internal combustion engine and the selection of the combustion mode. On the one hand, it must be guaranteed that, after a cold start, the internal combustion engine reaches its operating temperature as soon as possible, and on the other, during the normal operation of the internal combustion engine, the temperature of the exhaust gas must be keep at a sufficient value, to operate the catalyst in its optimal mode of operation. Internal combustion direct injection engines that operate with extremely impoverished and stratified mixtures have very low values for exhaust gas temperatures, which, especially in low load operating modes, can be located below the exhaust temperature. catalyst start. One possibility to raise the temperature of the exhaust gas is the feedback of the same. In the operation with stratified loading of the internal combustion engine, the exhaust gas feedback also serves to reduce the NOx emission. An effective measure to raise the temperature of the catalyst is the strangulation of the internal combustion engine also in the layered operation. In this way the time during which the catalyst does not work due to too low a temperature can be shortened. This strategy, however, leads to a certain impact on the fuel consumption advantages. Figure 2 shows the distribution of the different modes of operation of the internal combustion engine (homogeneous, stratified, with and without exhaust gas feedback) within an operating mode of the internal combustion engine established between the load and the revolutions. Two different characteristic fields KF1, KF2 are shown in the form of diagrams, the characteristic field according to Figure 2A being the _ of a cold internal combustion engine, and the characteristic field according to Figure 2B, that of a hot internal combustion engine . In both characteristic fields, the number of revolutions N is located on the abscissa and a load dimension on the ordinate. As such, it is possible to use, for example, the torque of the internal combustion engine, the average pressure or the air flow determined in the suction channel with the help of the air flow meter. Both characteristic fields are divided into overlapping areas. The temperature of the internal combustion engine is determined with the evaluation of the temperature sensor signal 33 and compared with a first threshold value. If the temperature TK of the internal combustion engine is below said threshold value or if the time after starting is less than a predetermined value, a cold internal combustion engine is assumed and the control mode for it is selected with base in the characteristic field shown in Figure 2A, depending on the momentary load and revolutions. After a cold start and the next hot operation of the internal combustion engine, ie when the temperature TKW is still below the threshold value, with a low load, or in the lower partial load range and a low number of revolutions N, the internal combustion engine operates with a homogeneous mixture, slightly poor. Typical air indices for this are in the range? = 1.05 - 1.10. This characteristic field interval is indicated in the figure with the. A typical value for running revolutions without load is indicated on the abscissa with NLL = 800 l / min. This slight impoverishment of the homogeneous mixture, together with a displacement of the ignition in the direction of later, although it reduces the degree of action of the internal combustion engine, has the advantage that the catalyst reaches its starting temperature more quickly and, thus, , is able to more quickly transform harmful components of the exhaust gas into harmless compounds. If after this control measure, the temperature of the internal combustion engine is still below the threshold value, but in the meantime the load increased, the internal combustion engine is still operated with a slightly impoverished mixture and active gas feedback of escape (characteristic field zone 2a) .. The characteristic field zone 2a is bounded in the direction of greatest load by the full load line 3a. To obtain a maximum torque during operation with full load of the internal combustion engine, the internal combustion engine is operated with a homogeneous, rich mixture? < 1 without exhaust gas feedback. The passage of the characteristic field according to FIG. 2A to the characteristic field according to FIG. 2B is already carried out depending on the temperature of the internal combustion engine or on a dimension derived therefrom, in particular the temperature of the cooling agent TKW. The foregoing can be carried out, for example, by comparing the current temperature with the aforementioned threshold value, or it is checked if the temperature, since the start of the internal combustion engine, was increased by a predetermined value. Alternatively to the above, the step between both characteristic fields can also be established by time. If a query results in that a certain time has elapsed since the start of the internal combustion engine, a hot internal combustion engine is assumed and the control of it passes to a mode as established in the characteristic field according to Figure 2b. The switching values (temperature, time) are determined experimentally on the test bench for each type of internal combustion engine and used catalyst and stored in a memory of the electronic control device. According to the characteristic field of Figure 2b, in the case of a warm, or hot, internal combustion engine with low loads and a range of revolutions of up to half, with strangled operation, it is operated with stratified load and active gas feedback. of escape AGR (characteristic field area Ib). In the partial load range from low to high speed values, the internal combustion engine is operated with stratified load and active exhaust gas feedback (characteristic field zone 2b). The foregoing can be done either with partial throttling or without throttling. Above the characteristic field zone 2b, there is the characteristic field area 3b. This includes the upper partial load range with low to medium speed and the low load range up to higher partial load with very high numbers of revolutions. In this characteristic field zone, the internal combustion engine is operated with a homogenous, poor mixture and active exhaust gas feedback. In the case of even higher loads up to the complete load line VL, is the internal combustion engine operated independently of the number of revolutions, with a homogeneous, stoichiometric mixture? = 1 and active feedback of exhaust gas (characteristic field zone 4b). In the case of full load VL of the internal combustion engine, the exhaust gas feedback is not allowed and a homogeneous rich mixture is adjusted.

Claims

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A method for controlling an internal combustion engine with direct injection, ignition from the outside, which is operated optionally strangled or not throttled with homogeneous mixture or with excess air, forming a stratified load in the cylinder, - in certain modes of operation of the engine of

• Internal combustion, a part of the exhaust gas is mixed with the combustion air with the help of an exhaust gas feedback, - the start of the injection for the fuel is controlled in such a way that - to obtain a homogeneous mixture in the cylinder fuel is injected into the suction pipe between the top dead center and the bottom dead center of the respective cylinder piston, - to obtain a stratified load in the cylinder fuel is injected into the cylinders shortly before top dead center before of the ignition in the compression time, and - the operating area of the internal combustion engine, depending on the load and the number of revolutions, is divided into several characteristic field zones and these determine whether the internal combustion engine is operated with homogenous mixture or with a stratified load, characterized in that in the switching of the operation with homogeneous mixture to the operation with load to stratified and vice versa, the temperature of the cooling agent (TKW) of the internal combustion engine is taken into account. 2. A method according to claim 1, characterized in that for the entire operating zone of the internal combustion engine there are two characteristic fields (KFl, KF2) with characteristic field zones (la, Ib; 2a, 2b). , 3b) comparable with respect to the load and the number of revolutions of the internal combustion engine and, depending on the temperature of the cooling agent (TKW) of the internal combustion engine, one or the other of the characteristic fields (KFl, KF2) is used. to control the internal combustion engine.

3. A method according to claim 1, characterized in that the first characteristic field (KFl) contains characteristic field zones (la, 2a) that are used for control of the internal combustion engine after starting and with that cold, and the second characteristic field (KF2) includes characteristic field zones (Ib, 2b, 3b, 4b) that are used for the control of the warm or internal combustion engine.

4. A method according to claim 2 or 3, characterized in that the switching of the first characteristic field (KFl) to the second characteristic field (KF2) is effected when the temperature of the cooling agent (TKW) exceeds a predetermined threshold value. .

5. A method according to claim 2 or 3, characterized in that the switching of the first characteristic field (KF1) to the second characteristic field (KF2) takes place when a predetermined time passes.

6. A method according to claim 4 and 5, characterized in that the switching values are determined experimentally in the test bench for each type of internal combustion engine and catalyst used and stored in a memory of a device control (21) assigned to the internal combustion engine.

7. A method according to claim 1, characterized in that with the internal combustion engine cold and low load, low number of revolutions, that is operated with a slightly poor homogenous mixture (characteristic field zone la).

8. A method according to claim 1, characterized in that with the internal combustion engine cold and high load until full load, that is operated with a slightly poor homogenous mixture and active exhaust gas feedback (characteristic field zone 2a).

9. A method according to claim 1, characterized in that the internal combustion engine is operated with a maximum rate of exhaust gas feedback during the heating operation.

10. A method according to claim 1, characterized in that the internal combustion engine is warm, or hot, with low loads and a range of revolutions lower than half, in the strangulated operation is operated with stratified load. and active feedback of exhaust gas (characteristic field zone Ib).

11. A method according to claim 1, characterized in that during the regeneration phase of the deposit catalyst (18), the internal combustion engine is operated with a rich homogeneous mixture.

12. A method according to claim 1, characterized in that in the case of low external temperatures, the operation of the internal combustion engine with homogeneous mixture is prolonged, to accelerate the heating of the internal space of a vehicle driven by the Internal combustion engine.