SE527460C2 - Method of operating an internal combustion engine - Google Patents

Abstract

The method involves storing fuel in an inlet line (5) of an internal combustion engine (1). Overlapping of valve strokes between an inlet valve (10) and an exhaust valve (20) of a cylinder (15) is controlled so that, during an intake stroke, the inlet and exhaust valves are open and the stored fuel arrives in an exhaust gas pipe (25) of the engine for being burnt with the mass of scavenging air arriving in the pipe (25).

Description

527 460 2 between the intake pipe and the exhaust part before the exhaust turbocharger turbine, the possibility is obtained of an air mass not participating in the internal combustion process, i.e. in the combustion process in a cylinder of the internal combustion engine, a so-called purge air mass, which together with the fuel until the exhaust part is lit by means of the igniter in the exhaust part. In this way, the exhaust enthalpy and thus the efficiency of the exhaust turbocharger increases. In addition, it is possible in this way to heat up a catalyst arranged in the exhaust part, if any.

Advantages of the invention The method according to the invention for driving an internal combustion engine with the characteristic features according to the main claim, on the other hand, has the advantage that a valve overlap between an outlet valve and an inlet valve of at least one cylinder is set in such a way that in an intake stroke by opening the inlet valve of the at least one cylinder of the internal combustion engine, the outlet valve of the cylinder is also opened, so that the stored fuel reaches an exhaust part of the internal combustion engine and there ignites together with a purge air mass which has also reached the exhaust part. In this way, it is possible to realize the combustion of an oxygen / fuel mixture required for an increase in exhaust enthalpy in the exhaust part of the internal combustion engine, even in the case of an internal combustion engine with intake pipe injection.

Through the measures specified in the dependent claims, advantageous further developments and improvements are possible of the procedure specified in the main requirement.

It is particularly advantageous then, depending on a predetermined first air / fuel mixture ratio for the lu fi / fuel mixture to be burned in the exhaust section, a setpoint is formed for a quantity of fuel to be stored. In this way, it is also possible for the combustion of the air / fuel mixture in the exhaust section to observe a predetermined lu fi / fuel mixture ratio or set a desired air / fuel mixture ratio.

In this case, the purge air mass that has reached the exhaust section can be determined in a simple manner depending on the operating state of the dry combustion engine, in particular on operating variables such as valve overlap, engine speed and engine load and depending on the determined purge air mass and the predetermined first air flow. the ratio, the setpoint for the amount of fuel to be stored can be formed.

A further advantage is obtained when the main fuel for the combustion in the at least one cylinder of the dry combustion engine is injected at the earliest when the outlet valve of the at least one cylinder is closed at the intake stroke. In this way it is possible to divide the injection of fuel in the intake pipe to the internal combustion engine into a first quantity of fuel intended for the combustion in the exhaust part, and a second or main quantity of fuel intended for the combustion in the dry combustion engine at least one cylinder.

For this division, a time distance can then be selected between the injection of the main fuel and the injection of the dry-stored fuel, so that the first amount of fuel and the second amount of fuel are injected independently of each other.

However, it can also be advantageously arranged in such a way that the main fuel and the stored fuel are injected in succession immediately one after the other. In this case, only a single injection is required for the main fuel and the stored fuel.

A further advantage is obtained when the total amount of fuel to be injected into the at least one cylinder is determined depending on a predetermined second air / fuel mixture ratio for the lu fl / fuel mixture to be burned both in the exhaust part and in the at least one cylinder. In this way, despite 527 460 4 two different injections during a suction rate, it is possible to regulate a common predetermined luñ / fuel mixing ratio.

A further advantage is obtained when air / fuel ice mixture in the exhaust part is ignited by means of an igniter. In this way, it is ensured that the air / fuel mixture that has reached the exhaust part is actually burned and the exhaust enthalpy can thereby increase.

Drawing An exemplary embodiment of the invention is shown in the drawing and is explained in more detail in the following description. Fig. 1 shows a schematic view of an internal combustion engine and fi g. 2 is a flow chart for a process as an example of the method according to the invention.

Description of the working example I fi g. 1, the numeral 1 characterizes an internal combustion engine, which may, for example, be designed as an Otto engine or as a diesel engine and may drive a vehicle. The combustion engine 1 comprises at least one cylinder 15, the combustion chamber of which can be fed via an air supply 35 with an ficlub fi. In the usual way but not absolutely necessary, an air flow meter 40 is arranged in the air supply 35, for example a hot air mass meter, which measures the fresh air mass flow to the at least one cylinder 15 and leads the measurement result on to a motor controller 85. the fresh air in the air supply 35 is in fi g. 1 characterized by an arrow. In the flow direction of the fresh air following the purge gauge 40, a compressor 45 is arranged in the air supply 35, which compresses the fresh hatch removed to the at least one cylinder 15 and for this purpose is driven by a turbine 75 of an exhaust gas turbine charger in the shaft 90. in turn of an exhaust mass fl fate in an exhaust part 25 of the internal combustion engine 1. The compressor 45 in the flow direction for the fresh air subsequently is in the air supply 35, especially in the case where the internal combustion engine 1 year is designed as an Otto engine, a rotary damper 50 arranged. The degree of opening of the throttle 527 460 is set by the motor controller 85 in a manner known to a person skilled in the art, for example to convert a torque desired by the driver. In addition, it can be arranged so that at the damper position it is registered by means of an i fi g. 1, for example in the form of a potentiometer, and the rotary damper position thus registered is returned to the motor controller 85 as a signal for the motor load.

The portion of the lu supply 35 between the rotary damper 50 and an inlet valve 10 to the at least one cylinder 15 is referred to as the suction pipe and is in fi g. 1 is characterized by the reference numeral 5. In the intake pipe 5, fuel can be injected via an injection valve 55. The injection valve 55 is also controlled by the motor control 85, for example in such a way that a predetermined air / fuel mixture flow ratio for combustion is set. Via the inlet valve 10, the ice valve and the fuel from the intake pipe 5 reach the combustion chamber of the cylinder 15 when the inlet valve 10 is in the open state. 1 a spark plug 60 is provided, which ignites the air-1 fuel mixture present in the combustion tube of the at least one cylinder 15. The spark plug 60 is also controlled by the motor controller 85 in a manner known to those skilled in the art for setting a suitable ignition timing. The exhaust gases formed during the combustion of the lu / fuel mixture in the combustion chamber of the at least one cylinder 15 are expelled from the combustion chamber to the exhaust part 25 via an outlet valve 20. In the portion with the at least one cylinder 15 a speed sensor 65 is arranged, which the engine speed in a manner known to the skilled person and leads the measured value on to the engine controller 85. In the exhaust part 25 can also be an option, which in fi g. 1 is shown in broken lines, an igniter 30, for example in the form of a glow path fi, is arranged to ignite a lu fi / fuel mixture which reaches fi am to the exhaust portion 25 and thereby raise the exhaust enthalpy. The igniter 30 is then also controlled by the motor controller 85, in order to complete the appropriate ignition temperature at the appropriate time. The scattering direction of the exhaust gases is in fi g. 1 likewise characterized by an arrow. Following the igniter 30 in the exhaust gas flow direction direction is in the exhaust portion 25 according to the example in fi g. 1 a lambda probe 70 is provided. This measures the oxygen content of the exhaust gases in a manner known to those skilled in the art and passes this value on to the engine controller 85, which determines a real value for the total air / fuel mixture ratio. The lambda probe 70 subsequently in the direction of flow of the exhaust gases in the exhaust part 25, a turbine 75 is arranged. The order between the lambda probe 70 and the turbine 75 in the exhaust section 25 may also be reversed. On the turbine 75 in the flow direction of the exhaust gases following in the exhaust part 25 is, where applicable, i.e. as an option, a catalyst 80 is provided.

According to the example in fi g. 1, the valve control times for the inlet valve 10 and the outlet valve 20 of the motor controller 85 are also determined. This can be done, for example, according to a completely variable valve control in a manner known to those skilled in the art. Alternatively, the opening and closing times of the inlet valve 10 and the outlet valve 20 can be set in a manner known to those skilled in the art in a corresponding setting of an inlet camshaft and / or an outlet camshaft. In this case, a variable camshaft adjustment can be provided. In the following, it is assumed as an example that there is an fi independently variable valve control.

According to the invention, it is now arranged that via the injection valve 55 fuel is stored in the injection pipe 5 when the inlet valve 10 is closed. the at least one cylinder 15 with opening of the inlet valve 10, the outlet valve 20 is still open, so that the stored fuel reaches the exhaust part 25 and ignites there together with a purge air mass which has also reached the exhaust part 25.

In this case, for example, for the lu fi / fuel mixture in the exhaust part 25 to be ignited, a first air / fuel mixture ratio can be determined. Furthermore, the purge mass which has reached the exhaust part 25 can be determined depending on the operating condition of the internal combustion engine 1. In particular, the purge mass can be determined in a manner known to those skilled in the art from the combustion engine l sizes such as valve overlap, engine speed and engine load. The valve overlap is known in the motor controller 85 due to the control of the inlet valve 10 and the outlet valve 20 according to the fully variable valve control and characterizes the time or angle at which both the inlet valve 10 and the outlet valve 20 are open at the intake rate. In the case of using the inlet core shaft and / or outlet camshaft, the valve overlap is known due to the known setting of the inlet camshaft relative to the outlet camshaft. The engine speed is made available by the speed sensor 65. The engine load can be determined based on the throttle position in a manner known to those skilled in the art. From the known operating quantities, the purge air mass can be modeled in a manner known to those skilled in the art. Alternatively, the purge mass can be determined via one or more of the characteristic icon directions as a function of the known operating variables valve overlap, engine speed and power. The characteristic icon tips can then be suitably applied in a test bench in a manner known to the person skilled in the art. Depending on the purge air purge thus determined and the predetermined first lu fl / fuel mixture ratio, it is then possible to determine a setpoint for the amount of fuel to be stored. For this purpose, for example, by means of a further characteristic range depending on the purge air mass and the predetermined first air / fuel mixing ratio, the required storage angle or the required storage time can be determined for the injection of fuel into the intake pipe 5. This additional characteristic area can be method is suitably applied in a test bench. The required storage angle or the required storage time produces each angle or period of time for which the respective fuel must be injected into the intake pipe 5 when the inlet valve 10 is closed. due to the valve overlap, the outlet valve 20 is still open. As a result, in the case of a positive pressure drop between the intake pipe 5 and the exhaust part 10, the combustion tube of the at least one cylinder 15 and the outlet valve 20 to the exhaust part 25 and the outlet valve 20 flow to the exhaust part 25 and the outlet valve 20 to the exhaust part the positive pressure drop between the intake pipe 5 and the exhaust part 25 is realized, for example, in a manner known to those skilled in the art by a suitable configuration of the geometry of the exhaust part and the geometry of the turbine 75. For setting the positive pressure drop between the intake pipe 5 and the exhaust part It is further advantageous when a suitable number of cylinders for the internal combustion engine 1 is selected, in particular when a few cylinders in a cylinder block are used, for example in the case of a three-cylinder engine or a six-cylinder engine, which exhaust-wise comprises two cylinder blocks and thus two exhaust manifolds, each of which is designed according to igt the exhaust part 25 in fi g. The positive pressure drop is present between the intake pipe 5 and the exhaust section 25 in the exhaust direction flow of the turbine 75. By combustion of the lu fi / fuel mixture in the exhaust section in the exhaust direction of the exhaust before the turbine 75, the exhaust enthalpy is increased and thus the efficiency of the exhaust turbocharger is improved. This leads to a higher range of torque in the lower speed range for the internal combustion engine, so that, for example, a so-called turbo lag can be compensated at start-up. In addition, the increase in the exhaust enthalpy enables a faster heating of the catalyst 80, in particular during a cold start of the internal combustion engine 1.

The purge air mass fl is any air mass flow which, during the valve overlap, i.e. during the state of simultaneous opening of the inlet valve 10 and the outlet valve 20, which due to the positive pressure drop between the intake pipe 5 and the exhaust part 25, from the air supply 35 at least one cylinder 15 reached the exhaust part 25 or as residual gas is forced out of the dry combustion chamber of the at least one cylinder 15 by the purge air mass in the exhaust part 25. The setpoint for the amount of fuel to be stored is converted by corresponding control of the injection valve 55 under the influence of engine control 85. The fuel thus stored is referred to as purge fuel and is also purged due to the positive pressure drop between the intake pipe 5 and the exhaust section 25 after opening the inlet valve 10 during the valve overlap, from the intake pipe 5 via the combustion chamber of the at least one cylinder 15 to the exhaust gas 25 and ignites there together with the purge air mass. The setpoint for the amount of fuel to be stored can then be selected in such a way that, based on the purge air mass determined on 527 460 9, a desired air / fuel mixing ratio is set, which is referred to as the first determined lu fi / fuel mixing ratio. This desirable air / fuel mixing ratio may initially be less specified and thus rich for optimizing the ignition process in the exhaust part 25. Then and in an ideal way, the setpoint for the fuel mass to be stored can then be selected in such a way that a stoichiometric air / fuel mixture ratio is set in the exhaust section 25.

Furthermore, it is arranged that the fuel for the combustion in the cylinder 15, which is referred to as the main fuel, is injected via the injection valve 55 into the intake pipe 5 at the earliest when the outlet valve 20 of the cylinder 15 is closed at an intake stroke. The inlet valve 10 is then still open. In this way, the fuel mass required for the actual combustion in the cylinder 15 is injected at an open inlet valve 10 and a closed outlet valve 20 in the form of the main fuel. In this case, the injection of the main fuel by means of a time distance can take place separately from the injection of the stored fuel. In this way, the injection of fuel for the intake stroke of the cylinder 15 is divided into two separate injections. Alternatively, it may also be arranged that injection of fuel for the intake stroke of the cylinder 15 is carried out continuously, i.e. that the main fuel and the stored fuel are injected in immediate succession. In this way, only a single injection of fuel is required for the intake stroke of the cylinder. With the closing of the outlet valve 20, the fuel then injected is combusted only in the combustion chamber of the cylinder 15 and thus constitutes the main fuel. The fuel injected for closing the outlet valve 20 is then the pre-stored fuel, unless it is combusted in the exhaust part 25 and thus constitutes the pre-stored fuel. The determined storage angle or the established storage time must in this case be set on the basis of an angle or time at which an injection of fuel via the injection valve 55 into the intake pipe 5 no longer results in an implementation of this fuel to the exhaust part and thus a combustion of this fuel in the exhaust section 25. This angle or time can, for example, be applied separately in a test bench and thereby, depending on the operating modes of the internal combustion engine, as the engine speed and load, be saved in a characteristic range. In this case, the injection of the main fuel can still absolutely be started at a time at which the outlet valve 20 is still open. In both cases mentioned, the inlet valve 10 should be open at least as long as both the pre-stored fuel and also the main fuel have at least completely reached the combustion chamber of the cylinder 15.

Finally, it can be arranged that the total amount of fuel to be injected into the cylinder 15 for the intake stroke is determined depending on a predetermined second air / fuel mixing ratio for both the fuel to be burned in the exhaust section 25 and in the combustion chamber of the cylinder 15. This can be realized, for example, by means of a so-called lambda control in a manner known to those skilled in the art.

For this purpose, the oxygen content determined by the lambda probe 70 in the exhaust gases of the engine controller 85 is converted to an actual value of the air / fuel mixing ratio for both the air / fuel mixture burned in the exhaust portion 25 and the combustion tube of the cylinder 15 compared to the determined other air mixture. / fuel mixture ratio and depending on the comparison, the injection valve 55 is controlled by the engine controller 85 in such a way that the amount of main fuel to be injected to approximate the determined actual value is adapted to the determined second air / fuel mixture ratio. The amount of fuel to be stored has already been determined in the manner described above through the first determined lu fi / fuel mixing ratio. The second determined air / fuel mixing ratio can also be selected, for example, as a stoichiometric lu fi / fuel mixing ratio.

I fi g. 2 is a flow chart prepared as an example of a process for the method according to the invention. After starting the program, the motor controller 85 in a program point 100 determines the purge air mass in a described manner depending on the operating quantities of the internal combustion engine 1. Then a transition is made to a program point 105. 527 460 ll In the program point 105 the motor controller 85 calculates the dry storage angle of the pre-stored fuel starting from the opening time of the inlet valve 10 at the intake rate of the cylinder 15. There is then a transition to a program point 110.

In program item 110, the actual value of the air / fuel mixture ratio is determined by means of the measurement signal fi from the lambda probe 70 of the motor controller 85 in the manner described.

Then there is a transition to a program item 1 15.

At program item 115, the engine controller 85 determines, by means of the alarm control as described, by comparing the actual value with the determined second lu fi / fuel mixture ratio the amount of fuel to be injected. Then there is a transition to a program item 120.

At program point 120, the engine controller 85 starts injecting the pre-stored fuel from the set storage time. Then there is a transition to a program item 125.

In program item 125, the engine controller 85 tests, by comparing the amount of fuel already stored, with the amount of fuel to be stored, if the amount of fuel to be stored had already been reached. If this is the case, a transition is made to a program item 130, otherwise a return is made to the program item 120 and fuel is stored again.

At the program point 130, the motor controller 85 tests if the outlet valve 20 should already be closed. If this is the case, a transition is made to a program item 135, otherwise to a program item 140.

At program point 135, the engine controller 85 begins to inject the main fuel.

Then the program ends. 527 460 12 In program item 140, the motor controller 85 traverses a waiting loop of, for example, fl your milliseconds. Then return to program item 130.

If the driver of the vehicle signals a starting process by corresponding maneuvering of the accelerator pedal, in the area close to fi ill load and at relatively low engine speeds, for example up to a maximum of 2200 rpm, in the sense of achieving a so-called volume utilization or in order to achieve a sufficiently high spontaneous torque. the inlet camshaft is set to its earliest possible position or the inlet valve 10 is adjusted for as early a closure as possible by the motor controller 85.

Due to the early closing of the inlet valve 10, the cylinder filling of the cylinder 15 is significantly improved at the known low engine speeds, since a return of already sucked-in lumen is prevented. In addition, in the case of a large valve overlap present at the same time, a sufficiently large purge mass flow is obtained, which purges the residual gases from the cylinder 15 to the exhaust part 25.

By the method according to the invention it is possible to increase the exhaust enthalpy upstream of the exhaust turbocharger's turbine 75 also when using an internal combustion engine with intake manifold injection. As a result of this increased exhaust enthalpy, the turbine 75 of the exhaust turbocharger may provide more mechanical power for the compression of the charge hatch. The vehicle's starting condition can thus be significantly improved due to the increased charging pressure.

The process according to the invention is realizable even without the use of a catalyst and / or without the use of an igniter. The temperatures reached in the exhaust section 25 upstream of the turbine 75 may be sufficient to ignite the air-to-fuel mixture in the exhaust section 25.

Claims (10)

10 15 20 25 30 527 460 13 Patent claims A method of driving an internal combustion engine (1), wherein fuel is dry stored in an intake pipe (5) of the internal combustion engine (1) when the inlet valve (10) is closed, characterized in that a valve overlap between an outlet valve (20) and a inlet valve (10) of at least one cylinder (15) is set in such a way that in an intake stroke with opening of the inlet valve (10) of the at least one cylinder (15) of the internal combustion engine (1) is the outlet valve (20) of the cylinder (15) still open, so that the stored fuel reaches an exhaust part (25) of the internal combustion engine (1) and ignites there together with a purge fi mass which has also reached the exhaust part (25). Method according to Claim 1, characterized in that a required valve overlap is set via a corresponding bay axis setting. Method according to Claim 1, characterized in that a required valve overlap is set by a corresponding, in particular fully variable, control of the inlet valve (10) and the outlet valve (20). Method according to one of the preceding claims, characterized in that, depending on an established first air / fuel mixing ratio for the air / fuel mixture to be combusted in the exhaust section (25), a setpoint is formed for a quantity of fuel to be stored dry. Method according to Claim 4, characterized in that the purge mass reaching the exhaust section (25) is determined depending on the operating state of the internal combustion engine (1), in particular on operating variables such as valve overlap, engine speed and engine load and, depending on the determined purge mass and the determined first air / fuel mixture ratio is set, the setpoint for the amount of fuel to be stored dry. 10 15 20 527 460 14 Method according to one of the preceding claims, characterized in that the main fuel for the combustion in at least one cylinder (15) is injected by the internal combustion engine (1) at the earliest when the outlet valve (20) of the at least one cylinder (15) is closed at the intake stroke. Method according to claim 6, characterized in that the main fuel and the stored fuel are injected separately by means of a time interval. Method according to claim 6, characterized in that the main fuel and the stored fuel are injected immediately in succession. Method according to one of Claims 6 to 8, characterized in that the total amount of fuel to be injected into the at least one cylinder (15) is determined in dependence on a determined second lu fi / fuel mixing ratio for the lu fi / fuel mixture. to be burned both in the exhaust section (25) and in the at least one cylinder (1 5). Method according to one of the preceding claims, characterized in that the lu fi fuel mixture in the exhaust part (25) is ignited by means of an igniter (30).