JP2007162687A - Internal combustion engine operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge an available load region for the self-ignition of an otto engine. <P>SOLUTION: This method for operating an internal combustion engine, particularly, the otto engine with controlled self-ignition comprises introducing fuel-air mixture into a combustion chamber, and compressing it in a compression stroke V. Spark ignition generates flame sheets in the fuel-air mixture at one or more positions during the compression stroke V for compressing and/or heating the remaining fuel-air mixture to release the self-ignition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for operating an internal combustion engine, in particular an Otto engine, with controlled auto-ignition, in which a fuel-air mixture is introduced into a combustion chamber and compressed in a compression stroke.

  The invention further relates to an internal combustion engine operating in such a way.

  In a direct-injection gasoline internal combustion engine known based on the known prior art, gasoline is directly injected into a combustion chamber provided in a cylinder of the internal combustion engine. The gasoline-air mixture compressed in the combustion chamber is subsequently ignited by ignition sparks in the combustion chamber. The volume of the ignited gasoline-air mixture expands explosively and moves a piston that can reciprocate within the cylinder. The reciprocating motion of the piston is transmitted to the crankshaft of the internal combustion engine.

  A direct injection internal combustion engine can be operated in various operating modes. As the first operation mode, “stratified combustion operation” is known. This stratified combustion operation is used particularly at relatively small loads. As the second operation mode, “homogeneous combustion operation” is known. This homogeneous combustion operation is used when the load applied to the internal combustion engine is relatively large. The various operating modes differ from one another particularly in terms of injection timing and injection time and ignition timing.

  In stratified combustion operation, during the compression phase of the internal combustion engine, gasoline is injected into the combustion chamber so that there is a fuel cloud in the immediate vicinity of the spark plug at the ignition timing. This injection can be done in a wide variety of ways. That is, it is conceivable that the injected fuel cloud already exists in the vicinity of the spark plug during or immediately after the injection, and is ignited by this spark plug. Similarly, it is conceivable that the injected fuel cloud is guided to the spark plug by the air supply movement and then ignited only after that. In both combustion methods, uniform fuel distribution is not performed in the combustion chamber, and stratified charge is performed.

  The advantage of stratified combustion operation is that an extremely small amount of fuel can be used to implement the relatively small load applied to the internal combustion engine. However, larger loads cannot be satisfied by stratified combustion operation.

  In homogeneous combustion operation, which is used for larger loads, gasoline is injected during the intake phase of the internal combustion engine, so that vortex formation of the gasoline in the combustion chamber takes place before ignition takes place, and consequently Distribution can take place. To this extent, the homogeneous combustion operation substantially corresponds to the operation mode of the internal combustion engine when fuel is injected into the intake pipe in a conventional manner. If necessary, homogeneous combustion operation can be used for smaller loads.

  An HCCI mode (Homogenous Charge Compression Ignition) of an internal combustion engine is known. This HCCI mode is sometimes called CAI (Controlled Auto Ignition), ATAC (Active Thermo Atmosphere Combustion) or TS (Toyota Soken). When the internal combustion engine is operated in this HCCI mode, the ignition of the air-fuel mixture is not performed by spark ignition but by controlled self-ignition. The HCCI combustion process can occur, for example, with a high content of hot residual gas and / or high compression and / or high inflow air temperature. The prerequisite for self-ignition is a sufficiently high energy level in the cylinder. Internal combustion engines which can be operated in HCCI mode are known, for example, on the basis of US Pat. No. 6,260,520, US Pat. No. 6,39,0054, German Patent No. .

  HCCI combustion has the advantages of reduced fuel consumption and reduced toxic emissions compared to conventional spark ignition combustion. However, the control of the combustion process and especially the self-ignition of the mixture is complex. That is, the operation amount that affects the combustion process, for example, the operation amount for fuel injection (injection amount or injection timing and injection time), internal or external exhaust gas recirculation, intake valve and exhaust valve (variable valve control), It is necessary to control the exhaust gas back pressure (exhaust gas flap), and in some cases, the ignition ratio, the air inflow temperature, the fuel quality, and the compression ratio in an internal combustion engine having a variable compression ratio.

Currently, controlled auto-ignition can only be used in a narrow load range. This is because self-ignition is currently driven only by its reaction kinetics (Reaktionskinetik).
US Pat. No. 6,260,520 US Pat. No. 6,39,0054 German Patent No. 19927479 WO 98/10179 pamphlet

  It is therefore an object of the present invention to provide a method which can improve the method of the type mentioned at the outset and expand the load area available for self-ignition of the Otto engine.

  A further object of the present invention is to provide an internal combustion engine suitable for carrying out such a method.

  In order to solve this problem, the method of the present invention is a method for operating an internal combustion engine, particularly an Otto engine, with controlled self-ignition, wherein a fuel-air mixture is introduced into a combustion chamber and a compression stroke is performed. In the method of the type of compression, the fuel-air mixture is compressed and / or heated at one or more points during the compression stroke by means of spark ignition and thereby self-ignited. A flame front to release is now generated.

  In order to solve the above problems, the internal combustion engine of the present invention is an internal combustion engine having a controlled self-ignition operation mode, in which a fuel-air mixture is introduced into a combustion chamber and compressed in a compression stroke. In a type of internal combustion engine, the fuel-air mixture is compressed and / or heated by spark ignition at one or more points and thereby self-ignited. A flame surface that can be released is now generated.

  The present invention uses stratified injection in combination with spark ignition to allow self-ignition at different load points to be controlled in an open loop or closed loop manner. By igniting a defined amount of stratified injection, flame propagation promotes the self-ignition of the remaining mixture, thereby controlling this combined combustion (flame propagation + self-ignition) in an open loop or closed loop manner It becomes possible to do. With stratified injection, unlike conventional auto-ignition, where combustion is only defined by reaction kinetic characteristics after closing the gas exchange valve on the intake side, and later in the compression stroke or near ignition-top dead center Can affect combustion. Different gas exchange valve strategies and injection strategies are required at different load points. Furthermore, supercharging can be used to expand the characteristic map area, for example towards higher loads. With an open loop or closed loop control of stratified injection in the vicinity of ignition-top dead center, a stratified hot flame surface can be initiated. This flame front can quickly ignite the rest. Such layered injection can be used as a controlled variable for open loop control or closed loop control. In this case, it is advantageous if the flame front is formed by one or more spark plugs and / or lasers.

  It is advantageous if the internal combustion engine is operated in a stratified combustion operation. In this case, the fuel is brought into the combustion chamber during the compression stroke.

  It is advantageous if the fuel-air mixture additionally contains exhaust gas to form a fuel-air-exhaust gas mixture. In this case, it is advantageous if the exhaust gas remains in the combustion chamber due to negative valve overlap (residual gas retention) in the charging alternation stroke. In the case of a negative valve overlap, the gas exchange valve on the exhaust side is closed before reaching top dead center, so some of the combusted gas remains in the cylinder.

  In the following, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows one cylinder of an internal combustion engine and components of a fuel supply system belonging to the internal combustion engine. In the drawing, a direct injection type internal combustion engine (gasoline direct injection type Otto engine BDE) is exemplarily shown. The internal combustion engine includes a fuel tank 11, and an electric fuel pump (EKP) 12, a fuel filter 13, and a low-pressure regulator (DR) 14 are disposed in the fuel tank 11. A fuel line 15 extends from the fuel tank 11, and this fuel line 15 communicates with a high pressure pump (HDP) 16. The high pressure pump 16 is followed by a pressure accumulation chamber (Rail) 17. A plurality of injection valves 18 are arranged in the pressure accumulating chamber 17, and these injection valves 18 are preferably arranged directly corresponding to the combustion chamber 26 of the internal combustion engine. In a direct injection internal combustion engine, at least one injection valve 18 corresponds to each combustion chamber 26. However, in this case, a plurality of injection valves 18 may be provided for each combustion chamber 26. The fuel is pumped from the fuel tank 11 to the high-pressure pump 16 through the fuel filter 13 and the fuel line 15 by the electric fuel pump 12. The fuel filter 13 serves to remove foreign particles from the fuel. Using the low pressure regulator 14, the fuel is controlled to a defined value, usually on the order of about 4-5 bar, in the low pressure range of the fuel supply system. A high-pressure pump 16 which is preferably driven directly by the internal combustion engine compresses the fuel and pumps this fuel into the pressure accumulator chamber 17. The fuel pressure then reaches a maximum value of about 150 bar. FIG. 1 exemplarily shows one combustion chamber 26 of a direct injection type internal combustion engine. Generally, an internal combustion engine has a plurality of cylinders, and each of these cylinders has one combustion chamber 26. have. In the combustion chamber 26, at least one injection valve 18, at least one spark plug 24, at least one intake valve 27, and at least one exhaust valve 28 are arranged. The combustion chamber 26 is partitioned by a piston 29 that can slide up and down in the cylinder. New air is sucked into the combustion chamber 26 from the intake passage 36 via the intake valve 27. Using the injection valve 18, the fuel is directly injected into the combustion chamber 26 of the internal combustion engine. The fuel is ignited using the spark plug 24. The piston 29 is driven by the expansion of the ignited fuel. The movement of the piston 29 is transmitted to the crankshaft 35 via the connecting rod 37. A segment disk 34 is disposed on the crankshaft 35, and the segment disk 34 is probed by the rotation speed sensor 30. The rotational speed sensor 30 generates a signal that characterizes the rotational movement of the crankshaft 35.

  Exhaust gas generated during combustion flows from the combustion chamber 26 into the exhaust gas pipe 33 via the exhaust valve 28. The exhaust gas pipe 33 is provided with a temperature sensor 31 and an oxygen sensor 32. The temperature sensor 31 is used to detect the temperature of the exhaust gas, and the oxygen sensor 32 is used to detect the oxygen content of the exhaust gas.

  A pressure sensor (DS) 21 and a pressure control valve (DSV) 19 are connected to the pressure accumulation chamber 17. The inlet side of the pressure control valve 19 is connected to the pressure accumulation chamber 17. A return flow line 20 is led out from the outlet side of the pressure control valve 19, and the return flow line 20 communicates with the fuel line 15.

  Instead of the pressure control valve 19, a quantity control valve provided in the fuel supply system 10 may be used. The actual value of the fuel pressure in the pressure accumulating chamber 17 is detected using the pressure sensor 21, and this actual value is transmitted to the control device (SG) 25. The control device 25 generates a control signal based on the detected actual value of the fuel pressure. The pressure control valve 19 is controlled by this control signal. The injection valve 18 is controlled via an electrical final stage (not shown). This final stage may be arranged inside or outside the control device 25. Various actuators and sensors are connected to the control device 25 via the control signal line 22. The control device 25 incorporates various functions that work to control the internal combustion engine. In modern controllers, these functions are programmed with a computer and subsequently filed in the memory of the controller 25. Functions filed in memory are activated in connection with demands placed on the internal combustion engine. In this case, strict requirements are imposed particularly on the real-time capability of the control device 25. In principle, pure hardware implementation of control of the internal combustion engine is possible as an alternative to implementation of control software for the internal combustion engine.

  A throttle valve 38 is disposed in the intake passage 36. The turning position of the throttle valve 38 can be adjusted by the control device 25 via the signal line 39 and an associated electric actuator (not shown).

  Another ignition device 40 may be disposed in the combustion chamber. This other ignition device 40 may be another ignition plug in addition to the ignition plug 24 or may be, for example, a laser. Using another ignition device 40 or spark plug 24, a spark ignition, described below, for releasing self-ignition is released. Another ignition device 40 is controlled by the control device 25. For this purpose, this other ignition device 40 is electrically connected to the control device 25.

  In the first operating mode, i.e. the homogeneous combustion mode of the internal combustion engine, the throttle valve 38 is partially opened or closed in relation to the desired air mass to be supplied. The fuel is injected into the combustion chamber 26 by the injection valve 18 during the intake stroke generated by the piston 29. At the same time, the sucked air gives the injected fuel a swirl or other vortex, which distributes the fuel into the combustion chamber 26 substantially uniformly / homogeneously. Thereafter, the fuel-air mixture is compressed during the compression stroke in which the volume of the combustion chamber 26 is reduced by the piston 29, and then generally ignited by the spark plug 24 just before the piston 29 reaches top dead center.

  In the second operation mode, that is, the stratified combustion operation mode of the internal combustion engine, the throttle valve 38 is largely opened. The fuel is injected into the combustion chamber 26 by the injection valve 18 during the compression stroke produced by the piston 29. Next, since the fuel is first ignited using the spark plug 24, the piston 29 is driven by the expansion of the ignited fuel in the work stage to be performed next. Another mode of operation that is possible is the homogeneous lean combustion mode of operation. In this homogeneous lean combustion operation mode, fuel is injected into the combustion chamber 26 during the intake phase, as in the homogeneous combustion operation mode.

  FIG. 2 is a diagram showing the relationship between the combustion chamber pressure p (bar) in the combustion chamber 26 of the internal combustion engine and the crankshaft angle ° KW. The horizontal axis represents a crankshaft angle of −180 ° to 540 °, and the vertical axis represents the combustion chamber pressure (bar). In this case, the top dead center L-OT in the charging police box is arbitrarily set. The charging alternation, as is well known, exhausts the combusted exhaust gas (this is done at a crankshaft angle of -180 ° to 0 °) and sucks in the surrounding fresh air or fuel-air mixture (this Is done in the crankshaft angle range of 0 ° to 180 °). When the crankshaft makes one more turn, that is, at a crankshaft angle of 360 °, the ignition-top dead center (Z-OT) is reached. The compression stroke is performed between the crankshaft angle 180 ° and the crankshaft angle 360 ° shown in FIG. 2, and the combustion gas is expanded between the crankshaft angle 360 ° and the crankshaft angle 540 °. Is called. The individual strokes in FIG. 2 are -180 ° to 0 ° discharge AU, 0 ° to 180 ° suction AN, 180 ° to 360 ° compression stroke V, and 360 ° to 540 ° expansion (combustion). It is represented by E. In the compression stroke, air or fuel-air mixture or fuel-air-exhaust gas mixture is compressed and heated at this time. The mixture is generally ignited just before reaching ignition-top dead center Z-OT. This can be done by spark ignition, as is normally done in an Otto engine, or by controlled auto-ignition in the operating mode according to the invention. Ignition of the mixture results in a pressure increase, as is well known, which is converted to mechanical energy in the subsequent work process.

  In the controlled self-ignition operation mode, injection is performed in the compression stroke in the stratified combustion operation, and self-ignition (see FIG. 2) is performed immediately before reaching the ignition-top dead center Z-OT. For this purpose, it is necessary that the gas-air-fuel-exhaust gas mixture has a sufficient ignition temperature. This is not guaranteed in all operating conditions. Therefore, according to the present invention, self-ignition is promoted by spark ignition. This is done in the combustion chamber 26 by, for example, a spark plug or other ignition means, such as a laser. Spark ignition generates a flame surface that travels only slowly, based on fuel concentration and pressure characteristics. This flame front continues to compress the remaining fuel-air-exhaust gas mixture, raising its temperature. This creates a pressure and temperature that is sufficient for self-ignition in the fuel-air-exhaust gas mixture not ignited by the flame front. That is, the self-ignition is generated by an increase in pressure and temperature in the combustion chamber generated by using spark ignition.

  FIG. 3 shows a flowchart of the method according to the invention. The method starts at step 101 with fuel injection. This is done in the intake stroke or compression stroke (depending on the Otto engine operating mode "stratified combustion operation", "homogeneous combustion operation", "homogeneous lean combustion operation", etc.). Subsequently, in step 102, the fuel-air-exhaust gas mixture is compressed. Thereafter, in step 103, a portion of the fuel-air-exhaust gas mixture is ignited by spark ignition. This produces a slowly progressing flame surface that, in step 104, brings the remaining mixture to controlled self-ignition.

It is a figure showing roughly one cylinder of an internal-combustion engine provided with a fuel supply system. It is a diagram which shows the relationship between a combustion chamber pressure (p) and a crankshaft angle (° KW). 4 is a flowchart for carrying out the method according to the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel supply system 11 Fuel tank 12 Electric fuel pump 13 Fuel filter 14 Low pressure regulator 15 Fuel line 16 High pressure pump 17 Accumulation chamber 18 Injection valve 19 Pressure control valve 20 Return flow line 21 Pressure sensor 22 Control signal line 24 Spark plug 25 Control device 26 Combustion chamber 27 Intake valve 28 Exhaust valve 29 Piston 30 Rotational speed sensor 31 Temperature sensor 32 Oxygen sensor 33 Exhaust gas pipe 34 Segment disk 35 Crankshaft 36 Air supply path 37 Connecting rod 38 Throttle valve 39 Signal line 40 Ignition device 101 Step 102 steps 103 steps 104 steps

Claims (7)

  Method for operating an internal combustion engine, in particular an Otto engine, with controlled self-ignition, wherein the fuel-air mixture is introduced into the combustion chamber (26) and compressed in the compression stroke (V) In the fuel-air mixture, the remaining fuel-air mixture is compressed and / or heated and thereby releases self-ignition at one or more points during the compression stroke (V) by spark ignition. A method for operating an internal combustion engine characterized by generating a flame front.   The method of claim 1, wherein the flame front is generated by one or more spark plugs (24, 40).   The method according to claim 1 or 2, wherein the flame front is generated by a laser (40).   4. The method according to claim 1, wherein the fuel is introduced into the combustion chamber in a compression stroke (V).   5. A process as claimed in claim 1, wherein the fuel-air mixture additionally contains exhaust gas, forming a fuel-air-exhaust gas mixture.   6. The method according to claim 1, wherein the exhaust gas remains in the combustion chamber due to a negative valve overlap in the charging alternating stroke.   An internal combustion engine having a controlled self-ignition mode of operation, wherein a fuel-air mixture is introduced into the combustion chamber (26) and compressed in the compression stroke (V) In the fuel-air mixture, a spark surface is generated at one or more locations by means of spark ignition which can compress and / or heat the remaining fuel-air mixture and thereby release self-ignition. An internal combustion engine having a controlled self-ignition mode of operation, characterized in that

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