FR2870887A1 - Internal combustion engine e.g. gasoline engine, controlling method for motor vehicle, involves controlling overlapping of valve strokes so that inlet and exhaust valves are open and fuel arrives in exhaust gas pipe for being burnt with air - 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

Field of the invention

  The present invention relates to a method of managing an internal combustion engine in which fuel is stored in an intake pipe of the internal combustion engine, having a closed intake valve.

  STATE OF THE ART Methods for managing an internal combustion engine are already known, according to which fuel is stored upstream in the intake duct of the internal combustion engine when the intake valve is closed.

  It is furthermore known that engines with turbocharging by an exhaust gas turbocharger, in particular those whose turbine of the exhaust gas turbocharger is of variable geometry, have low starting torques. The relatively low mass flow rate of the exhaust gases of the internal combustion engine at the starting speed results in very poor yields of both the turbine and the compressor of the turbocharger. The consequence is a relatively low boost pressure rise with a relatively low torque potential in the low range range of the internal combustion engine. If the internal combustion engine drives a motor vehicle, in extreme situations such as in a very steep climb, high altitude, the start can be hindered by the operation of accessories.

  DE 101 40 120 A1 discloses a method of managing an internal combustion engine comprising an exhaust gas turbocharger producing in addition to a primary injection, also a post-injection into one or more cylinders. of the engine and the post-injection generates a fuel / air fuel mixture which is ignited by the control of an ignition means installed in the exhaust line of the internal combustion engine. The post-injection is carried out if the opening angle of the exhaust valve and the intake valve of the corresponding cylinder intersect. Due to a suitably large overlap of the valve races such as corresponding adjustment of the intake camshaft and the exhaust camshaft and when a pressure drop occurs sufficient positive pressure between the intake pipe and the exhaust pipe upstream of the exhaust gas turbocharger turbine it is possible to have a mass of air that does not participate in the internal combustion process in the exhaust gas turbocharger. cylinder of the internal combustion engine, in other words a mass of rinsing air (scavenging air) which will be ignited in the exhaust pipe using the ignition means with the fuel of the post injection arriving in the exhaust pipe. This increases the enthalpy of the exhaust gas and thus the efficiency of the exhaust gas turbocharger. In addition, it will warm up more quickly any catalyst of the exhaust pipe.

  DESCRIPTION AND ADVANTAGES OF THE INVENTION The present invention relates to a method for managing an internal combustion engine of the type defined above, characterized in that the overlap of the valve races is set between the intake valve and a pressure relief valve. exhausting at least one cylinder so that during the admission time, with the opening of the intake valve of the cylinder of the internal combustion engine, the exhaust valve of the cylinder is still open and for the fuel stored in an engine exhaust pipe to be ignited with the mass of rinsing air also entering the exhaust pipe.

  The method according to the invention has the advantage of adjusting the overlap of the valve races between the exhaust valve and the admission valve of at least one cylinder during the admission time, and to achieve the combustion necessary for increasing the enthalpy of the exhaust gases of the air / fuel mixture in the exhaust gas duct of the internal combustion engine, even in the case of injection into the intake duct.

  It is particularly advantageous if, as a function of a first air / fuel mixture ratio, predefined for the air / fuel mixture to be burned in the exhaust gas duct, a set value is set for the quantity or dose of fuel to be used. store upstream. This makes it possible to regulate the combustion of the air / fuel mixture in the exhaust gas duct on a predefined ratio of air / fuel mixture or to respect this ratio.

  It is thus possible to determine in a simple manner the mass of rinsing air that has arrived in the exhaust gas duct according to the operating state of the internal combustion engine, in particular according to operating parameters such as the overlap of the valve races. , the engine speed and the engine load, then according to the mass of rinsing air obtained and the first predefined air / fuel mixture ratio, the set value of the quantity of fuel to be stored upstream is formed.

  It is also advantageous that the main fuel for the combustion is injected at least at least in a cylinder of the internal combustion engine when the exhaust valve of at least one cylinder is closed in the admission time. Thus, the injection of fuel into the intake pipe of the internal combustion engine splits into a first quantity of fuel intended for combustion in the exhaust pipe and a second main quantity or quantity of fuel provided for the combustion engine. combustion in at least one cylinder of the internal combustion engine.

  For this separation it is possible to choose the interval between the injection of the main fuel and the injection of the fuel to be stored upstream so as to inject the first quantity of fuel and the second quantity of fuel independently.

  It is also advantageously provided to inject the main fuel and the fuel to be stored upstream, directly in succession. In this case, a single injection is required for the main fuel and the fuel to be stored upstream.

  It is also advantageous that all the quantity of fuel injected into at least one cylinder is predefined, starting from a predefined second air / fuel mixture ratio for both the exhaust gas pipe and the air / fuel mixture. to burn in a cylinder. Despite two different injections during an admission time, it allows to regulate the entire predefined air / fuel mixture ratio.

  It is also advantageous for the air / fuel mixture in the exhaust gas line to be ignited by ignition means. This ensures that the air / fuel mixture in the exhaust pipe is effectively burned and that the enthalpy of the exhaust gas is thus increased.

  Drawings The present invention will now be described in greater detail with the aid of the accompanying drawings in which: - Figure 1 is a schematic representation of an internal combustion engine, - Figure 2 shows a flowchart of a example of execution of the process of the invention.

Description of the embodiment

  According to FIG. 1, reference numeral 1 denotes an internal combustion engine, for example a gasoline engine or a diesel engine, driving a vehicle. The internal combustion engine 1 comprises at least one cylinder 15 whose combustion chamber is supplied with fresh air by a fresh air supply pipe 35. Usually, but this is not essential, the air supply line 35 comprises an air mass flow meter 40, for example a hot-air mass air flow meter which measures the mass flow rate of fresh air supplying at least one cylinder 15 and transmitting the result of the measurement to a motor control 85. flow direction of the fresh air in the fresh air supply duct 35 is indicated by an arrow in FIG.

  Downstream of the air mass flowmeter 40, in the direction of flow of the fresh air, the air supply line 35 comprises a compressor 45 which compresses the fresh air intended for at least one cylinder 15 and for this purpose the turbine 75 of an exhaust gas turbocharger is driven via a shaft 90.

  The turbine 75 is itself driven by the mass flow rate of the exhaust gas of the exhaust gas conduit 25 of the internal combustion engine 1. Downstream of the compressor 45 in the direction of flow of the fresh air, the air supply line 35 comprises a throttle flap 50 especially in the case of an internal combustion engine 1 consisting of a gasoline engine. The degree of opening of the throttle flap 50 is set in a known manner by the motor control 85 for example to convert a torque demand of the driver. Provision can further be made to enter the position of the throttle flap by a throttle valve sensor not shown in FIG. 1, for example in the form of a potentiometer, and to transmit as a return signal the position thus grasped by the flap. throttling to the motor control 85 as a signal representing the load of the motor. The segment of the air supply line 35 between the throttle flap 50 and an intake valve 10 of a cylinder 15 is also referred to as the intake duct; it bears the reference 5 in Figure 1. Fuel is injected into the intake pipe 5 by the injector 55.

  The injector 55 is also controlled by the motor control 85, for example to adjust a certain air / fuel mixture ratio for combustion. Fresh air and fuel flow from the intake pipe 5 into the combustion chamber of the cylinder 15 through the inlet valve 10 when it is open. If the internal combustion engine 1 is a gasoline engine as shown in broken lines in FIG. 1, there is a spark plug 60 which ignites the air / fuel mixture of the combustion chamber of the cylinder 15. The spark plug 60 is also controlled by the engine control 85 to set the appropriate ignition timing. The exhaust gases resulting from combustion of the air / fuel mixture in the combustion chamber of the cylinder 15 are expelled through the exhaust valve 20 of the combustion chamber of the cylinder 15 into the exhaust gas conduit 25. A rotational speed sensor 65 is provided at the cylinder 15 to enter the rotational speed of the motor and transmit the measurement information to the motor control 85. Optionally, as shown by a broken line in FIG. the exhaust gas duct 25 may be equipped with ignition means 30, for example a spark plug, for igniting the air / fuel mixture arriving in the exhaust gas duct 25 and thereby increasing the exhaust gas enthalpy.

  The ignition means 30 is also controlled by the engine control 85 to provide an appropriate ignition temperature at the proper time. The direction of flow of the exhaust gas is also shown in Figure 1 by an arrow. Downstream of the ignition means 30, in the flow direction of the exhaust gas, the exhaust gas duct 25 comprises a lambda probe 70 as indicated in the example of FIG. the oxygen content of the exhaust gas and transmits the information to the engine control 85 which from there determines the overall actual value of the air / fuel mixture. The lambda probe 70 is followed in the flow direction of the exhaust gases in the exhaust gas duct 25 by the turbine 75. It is also possible to reverse the order of succession of the lambda probe 70 and the turbine 75 in the exhaust gas duct 25. The turbine 75 can be followed in the direction of the flow of the exhaust gas in the exhaust gas pipe 25, where appropriate, that is to say optional catalyst 80.

  According to the example of FIG. 1, the control times of the intake valve 10 and of the exhaust valve 20 are also predefined by the motor control 85. This can be done, for example, according to a totally variable control of the valves. . Alternatively, the opening and closing times of the intake valve 10 and the exhaust valve 20 can be adjusted by appropriate adjustment of the inlet camshaft and / or the exhaust camshaft. In this case, a variable adjustment of the camshafts can be provided. In the following and by way of example, it will be assumed a totally variable control of the valves.

  According to the invention, the injector 55 stores or stores fuel in the intake pipe 5 when the intake valve 10 is closed. It is furthermore provided a valve stroke overlap between the opening time of the exhaust valve 20 and the opening time of the intake valve 10 so that in the intake port of a cylinder 15, the opening of the intake valve 10 finds the exhaust valve 20 still open so that the fuel stored or stored passes into the exhaust pipe 25 to be lit with the air mass flushing also arriving in the exhaust pipe 25.

  Thus, it is possible for example to provide a first air / fuel mixture ratio for the air / fuel mixture ignited in the exhaust gas duct 25. In addition, the mass of rinsing air that arrives in the gas duct. The exhaust 25 can be determined according to the operating state of the internal combustion engine 1. In particular, the mass of rinsing air can be determined from the operating parameters of the internal combustion engine 1 such as the overlap of the strokes. valve, engine speed and engine load. The overlap of the valve races is known to the motor controller 85 due to the control of the intake valve 10 and the exhaust valve 20 according to the fully variable valve control; this characterizes the time or the angle for the-

  both the intake valve 10 and the exhaust valve 20 are open during the admission time. In the case of the use of an intake camshaft and / or an exhaust camshaft, the overlap of the valve races is known due to the known camshaft setting of intake with respect to the exhaust camshaft. The engine speed is provided by the rotational speed sensor 65. The engine load can be determined from the position of the throttle flap. Starting from the known operating parameters, the mass of rinsing air can be modeled. Alternatively, the rinsing air mass can also be obtained by one or more fields of characteristics depending on the operating parameters mentioned, namely the overlap of the valve strokes, the engine speed and the engine load. Fields of characteristics can be obtained for example by application, that is to say by measurements made on a test bench. Depending on the mass of rinsing air thus obtained and the first predefined air / fuel mixing ratio, a set value of the quantity of fuel to be stored upstream is determined. For this purpose it is possible, for example, to use a characteristic field to determine, as a function of the mass of rinsing air and of the first predefined air / fuel mixing ratio, the required advance angle, or the advance time. required for the injection of fuel into the suction line 5. This other field of characteristics can also be obtained by application on a test bench.

  The required feed angle or feed time respectively corresponds to the angle or time during which fuel is to be injected into the intake line 5 while the intake valve 10 is closed. . If then the intake valve 10 is opened during the admission time of the cylinder 15, because of the overlap of the races, the exhaust valve 20 is still open. Thus, the fuel stored while the intake valve 10 was closed, as well as the mass of rinsing air in the case of a positive pressure drop between the intake pipe 5 and the exhaust pipe 25, can pass through the inlet valve 10 open, the combustion chamber of at least one cylinder 15 and the exhaust valve 20 to arrive in the exhaust pipe 25 and be lit there by the means d The positive pressure drop between the intake pipe 5 and the exhaust gas pipe 25 is achieved by a suitable configuration of the geometry of the exhaust gas pipe 25 and the geometry of the turbine. 75. To adjust the positive pressure drop between the intake pipe 5 and the exhaust pipe 15, it is advantageous to choose a number of cylinders suitable for the internal combustion engine 1, and to use a number less cylinders of a cyl bench indres, for example in the case of a three-cylinder engine or a six-cylinder engine, comprising for the exhaust gas, two banks of cylinders and thus three exhaust pipes made as the gas pipe Figure 1. The positive pressure drop exists between the intake pipe 5 and the exhaust pipe 25 in the direction of passage of the exhaust gas, upstream of the turbine 75. combustion of the air / fuel mixture in the exhaust gas conduit 25 in the direction of passage of the exhaust gas, upstream of the turbine 75, increases the enthalpy of the exhaust gas and thus improves the efficiency of the turbocharger exhaust gas. This results in a larger available torque in the low speed range of the internal combustion engine so that for example we can compensate the hole of the turbocharger at startup. By increasing the enthalpy of the exhaust gas, it is furthermore possible to heat the catalyst 80 more rapidly, in particular at the cold start of the internal combustion engine 1.

  The rinse air mass flow rate is the mass flow rate of air that occurs during valve stroke overlap, i.e., during the opening of the inlet valve 10 simultaneously with the opening of the exhaust valve 20, due to the positive pressure drop between the inlet pipe 5 and the exhaust pipe 25 to pass from the air supply 35 or inlet pipe 5 through the combustion chamber of at least one cylinder in the exhaust gas duct 25 or corresponding to the return of the residual gas from the combustion chamber of at least one cylinder 15 driven by the rinse air mass in the The set point of the amount of fuel to be stored upstream is converted by the engine control 85 into an appropriate control of the injector 55. This fuel reserve is also referred to as a rinsing fuel. because of the pressure drop in sitive between the intake pipe 5 and the exhaust pipe 25, after the opening of the inlet valve 10, during the overlap of the valve races for the intake pipe 5, this mass of air passes through the combustion chamber of the cylinder 15 to pass into the exhaust pipe 25 to be ignited with the rinse air mass. The set value of the quantity of fuel to be stored in this way has been chosen as described so that, starting from the mass of rinsing air obtained, a desired air / fuel mixture ratio is set called the first air mixing ratio. / fuel, pre-defined. This desired air / fuel mixing ratio may also be less than unity at start-up.

  thus optimally match the ignition operation in the exhaust gas conduit 25. Then, ideally, the target value of the fuel mass to be stored upstream will be selected to have a ratio air / fuel mixture, stoichiometric in the exhaust pipe 25.

  It is furthermore provided that the fuel for combustion in at least one cylinder 15, also referred to as the main fuel, is injected into the intake pipe 5 or rather via the injector 55 if the exhaust valve 20 The cylinder 15 is closed during the admission time of this cylinder 15. The admission valve 10 is then always open. Thus, the fuel mass required for the actual combustion in at least one cylinder 15 is injected when the intake valve 10 is open and the exhaust valve 20, closed, in the form of the main fuel. The injection of the main fuel can be done according to a time interval distinct from the fuel injection previously stored. In this way the injection of the fuel for the admission time of the cylinder 15 is divided into two distinct injections. Alternatively, it is also possible to perform continuous fuel injection during the admission time of at least one cylinder 15, that is to say that the main fuel and the fuel stored beforehand will be injected directly one after the other.

  In this case, it suffices for a single injection of fuel during the admission time of at least one cylinder 15. The closing of the intake valve 20 ensures the combustion of the fuel which is then injected only into the combustion chamber of the cylinder 15 and thus represents the main fuel. The fuel injected before the closing of the exhaust valve 20 is then the pre-stored fuel since it is burned in the exhaust gas pipe 25 and thus represents the fuel supplied. The predetermined feed means or the predetermined feed time must be set in this case from the angle or time at which injection of the fuel through the injector 55 into the suction line 5 does not occur. leads more to the crossing of the fuel in the exhaust pipe 25 and thus to the combustion of this fuel in the exhaust gas pipe 25. This angle or this instant can be obtained appropriately by application on a bench of This is why they will not take into account operating variables of the internal combustion engine such as the engine rotation speed and the engine load recorded in a characteristic field. In this case, the main fuel injection can begin at a time when the exhaust valve 20 is still open. In either case, the inlet valve 10 must remain open at least until both the pre-stored fuel and the main fuel have been injected completely into at least the combustion chamber of minus one cylinder 15.

  Finally, it is possible to pre-define the total quantity of fuel injected into a cylinder during the admission time according to a predefined second air / fuel mixture ratio for both the air / fuel mixture to be burned in the gas line. 25 and in the combustion chamber of a cylinder 15. This can be done for example using a lambda control. The oxygen content determined by the lambda probe 70 in the exhaust gas is converted by the engine control 85 into a real value of the air / fuel mixture ratio of both the air / fuel mixture burned in the gas line. 25 and in the combustion chamber of a cylinder 15 to be compared to the second preset air / fuel mixing ratio and control the injector 55 by the motor control 85 according to the comparison so that the main amount of fuel to be injected is adapted to bring the actual value obtained to the second preset air / fuel mixture ratio. The amount of fuel to be stored upstream is already defined as described above by the first air / fuel mixture ratio. The second predefined air / fuel mixing ratio may for example be chosen as a stoichiometric air / fuel mixture ratio.

  FIG. 2 shows a flow chart of an exemplary execution of the method according to the invention. After starting the program, the motor control 85 determines at program point 100 the mass of rinsing air as has already been described in relation to the operating parameters of the internal combustion engine 1. go to program point 105.

  At program point 105, the motor controller 85 calculates as described the feed angle or feed time for injecting the fuel quantity to be stored, starting from the opening time of the intake valve. 10 in the intake duct of at least one cylinder 15. Then one goes to the program point 110.

  At program point 110 the actual value of the air / fuel mixture ratio is determined by the measurement signal of the lambda probe 70 by the motor control 85. Then, program point 115 is passed.

  At program point 115, the engine control 85 determines by lambda control, as described, by comparing the actual value and the second air / fuel mixing ratio, the amount of main fuel to be injected. . Then we go to program point 120.

  At program point 120, the motor control 85 requests injection of the stored fuel from the pre-defined advance time. Then we go to program point 125.

  At program point 125, the engine control 85 compares the amount of fuel already stored with the amount of fuel to be stored, to determine if the amount of fuel to be stored is already reached. If yes, go to program point 130; otherwise, return to program point 120 and continue to store fuel.

  At program point 130, the motor control 85 checks whether the exhaust valve 20 has already been closed. If this is the case, go to program point 135; if not, go to program point 140.

  At program point 135, the motor control 85 requests injection of the main fuel. Then we leave the program.

  At program point 140, the motor controller 85 traverses a waiting loop, for example several milliseconds. Then return to program point 130. If the driver of the vehicle signals a start operation corresponding to the operation of the accelerator pedal, then in the range close to the maximum load and for a relatively low engine speed for example at most up to 2200 rpm, to optimize the degree of supply mentioned or to reach a sufficiently high spontaneous torque, the intake camshaft is set to its most advanced position possible or the motor control 85 controls the inlet valve 10 to close as soon as possible. The advanced closure of the intake valve 10 considerably improves the filling of the cylinder 15 for low engine speeds evoked because it avoids a discharge of the air mass sucked.

  For a large valve stroke overlap existing at the same time, there will also be a mass flow of sufficiently large flushing air which discharges the residual gas from the cylinder to the exhaust gas pipe 25.

  The method according to the invention makes it possible to increase the enthalpy of the exhaust gases upstream of the turbine 75 of the exhaust gas turbocharger even if a combustion engine with injection is used in the intake duct. Due to this increase in exhaust gas enthalpy, the exhaust gas turbocharger turbine 75 will be able to provide greater mechanical power to compress the charge air. This significantly improves the starting behavior of the vehicle by increasing the supply pressure.

  The process according to the invention can be carried out without using a catalyst and / or without using an ignition means. The temperatures obtained in the exhaust gas line upstream of the turbine 75 may be sufficient to ignite the air / fuel mixture in the exhaust gas pipe 25.

Claims (1)

  11 A method of managing an internal combustion engine (1) in which fuel is stored in an intake pipe (5) of the internal combustion engine (1), having a closed intake valve (10), characterized in that the overlap of the valve races between the intake valve (10) and an exhaust valve (20) of at least one cylinder (15) is adjusted so that during the admission time with the opening of the intake valve (10) of the cylinder (15) of the internal combustion engine (1), the exhaust valve (20) of the cylinder (15) is still green and for the fuel stored in an exhaust pipe (25) of the engine (1) to be ignited with the mass of rinsing air also arriving in the exhaust gas pipe (25).   2) Method according to claim 1, characterized in that one adjusts the required overlap of the valves by appropriate adjustment of the camshafts.   3) Process according to claim 1, characterized in that one adjusts the necessary overlap of the valves by a suitable control, in particular completely variable of the intake valve (10) and the exhaust valve (20).   4) Process according to claim 1, characterized in that according to a first air / fuel mixture ratio, pre-defined for the air / fuel mixture to be burned in the exhaust gas duct (25) is formed a set value of a quantity of fuel to be stored upstream.   5) Process according to claim 4, characterized in that the mass of rinsing air arriving in the exhaust gas duct (25) is determined according to the operating state of the internal combustion engine (1) in particular according to the operating parameters such as the overlap of the valve races, the engine speed and the engine load and according to the mass of rinsing air thus obtained and the first predefined air / fuel mixing ratio, the va their setpoint of the amount of fuel to be stored upstream.   Process according to Claim 1, characterized in that the main fuel for combustion is injected into a cylinder (15) of the internal combustion engine (1) at the earliest when the cylinder exhaust valve (20) ( 15) is closed in the admission time.   7) A method according to claim 6, characterized in that the main fuel and the fuel to be stored upstream are injected separately, by injections separated by a time interval.   8) Process according to claim 6, characterized in that the main fuel and the fuel to be stored separately are injected separately upstream directly one after the other.   9) Method according to one of claims 6 to 8,   characterized in that the entire amount of fuel injected into a cylinder (15) is predefined according to a predefined second air / fuel mixture ratio in the exhaust gas line (25). ) and in at least one cylinder (15) for the air / fuel mixture to be burned.   The method according to claim 1, characterized in that the air / fuel mixture is ignited in the exhaust gas duct (25) by means of an ignition means (30).