Engine control unit for vehicles equipped with a turbocharger

Abstract

Engine control system for controlling an internal combustion engine in a motor vehicle equipped with a turbocharger, comprising at least one control element for influencing the air mass flow flowing into at least one cylinder of the internal combustion engine, wherein the internal combustion engine has, in addition to the throttle valve, a variable-stroke intake valve as a control element, and the load control of the internal combustion engine is primarily achieved by controlling the stroke of the variable-stroke intake valve to influence the air mass flow flowing into at least one cylinder of the internal combustion engine, and wherein, in order to reduce the overpressure that occurs before the intake valve when the intake valve closes, the intake valve is closed with a time delay when the intake valve is requested to close, while the throttle valve remains open.

Description

[0001] The invention relates to an engine control system for motor vehicles equipped with a turbocharger for reducing an overpressure that occurs in front of the control element when a control element influencing the air mass flow is closed.

[0002] Currently, in motor vehicles with turbochargers, an electrically or mechanically controlled diverter valve is used to reduce the overpressure that builds up before the throttle valve when the throttle valve closes. This valve reduces the overpressure that builds up before the throttle valve due to the turbocharger's continued operation by opening a connection to the ambient pressure. Such a diverter valve is known, for example, from DE 10 2006 013 291 A1.

[0003] From DE 101 56 409 A1 a method for improving the smooth running of multi-cylinder internal combustion engines is known.

[0004] From EP 1 336 737 A2 and EP 1 008 739 A1, engine control systems for internal combustion engines with turbochargers are already known, in which, in order to reduce the overpressure that occurs before the throttle valve when the throttle valve is closed, the throttle valve is closed with a time delay when the throttle valve is requested to close.

[0005] A disadvantage of such solutions is that the use of a bypass valve increases the manufacturing costs of the internal combustion engine.

[0006] The object of the invention is to provide an alternative solution for reducing the overpressure that occurs before the throttle valve when the throttle valve closes with a turbocharger still running, with lower manufacturing costs.

[0007] This problem is solved by a motor control unit according to claim 1. Advantageous further developments result from the dependent claims.

[0008] The basic idea of ​​the invention is that, in order to reduce the overpressure that occurs in front of the control element when the air mass flow control element closes, no bypass valve is used, but rather the pressure is reduced by a time-delayed closing of the control element.

[0009] If the internal combustion engine is designed such that the throttle valve is used as the air mass control device (this is the case, for example, when the engine's load control is primarily achieved by controlling the throttle valve's opening degree), then the overpressure that builds up before the throttle valve when it closes, especially with the turbocharger still running, can be reduced by delaying or pre-closing the throttle valve. In other words, the engine control unit is designed so that the throttle valve closes with a time delay when a closing action is requested. The throttle valve closes with such a time delay that the pressure, or rather the excess air mass, is absorbed by the engine by allowing the air mass to flow into at least one cylinder.

[0010] If the engine, in addition to the throttle valve, also has a variable-stroke intake or exhaust valve (TVDI), then, by appropriately controlling the stroke when the throttle valve is further open, the effect described above can be achieved in conjunction with the measures described above, thus eliminating the need for a diverter valve. Accordingly, in vehicles where the load control of the internal combustion engine is primarily achieved by controlling the stroke of a variable-stroke intake valve to influence the air mass flow into at least one cylinder of the engine, the overpressure that occurs when the intake valve closes can be reduced by delaying the closing of the intake valve when it is requested to close. The intake valve is closed with such a time delay that the pressure...The excess air mass is absorbed by the engine by allowing it to flow into at least one cylinder. The resulting engine torque can then be advantageously reduced (in both variants) by at least one of the following measures.

[0011] If the requested driver torque is zero and the throttle valve is open, one alternative approach is to reduce the engine torque by preventing fuel injection into at least one cylinder – in other words, by cutting off fuel injection to individual cylinders. Alternatively or additionally (with a requested driver torque of zero and a slightly open throttle valve), the ignition of at least one cylinder can be prevented by ignition cut-off.

[0012] As an alternative to ignition cut-out, the ignition timing of at least one cylinder can also be retarded to a very late rate to reduce the applied engine torque, whereby in an advantageous embodiment of this alternative, the setting of the very late ignition timing can also be combined with a division of the fuel injection quantity into a multiple injection.

[0013] The engine control system according to the invention eliminates the need for a bypass valve, resulting in significant cost savings. Implementing the engine control system entails only a relatively small additional effort.

Claims

[1] Engine control system for controlling an internal combustion engine in a motor vehicle equipped with a turbocharger, comprising at least one control element for influencing the mass airflow flowing into at least one cylinder of the internal combustion engine, wherein the internal combustion engine has, in addition to the throttle valve, a variable-stroke intake valve as a control element, and the load control of the internal combustion engine is primarily achieved by controlling the stroke of the variable-stroke intake valve to influence the mass airflow flowing into at least one cylinder of the internal combustion engine, and wherein, in order to reduce the overpressure that occurs before the intake valve when the intake valve is closed, the intake valve is closed with a time delay when the intake valve is requested to close, while the throttle valve remains open. [2] Motor control according to claim 1, characterized by, that the intake valve is closed with such a time delay that the excess air mass can flow out into at least one cylinder. [3] Motor control according to any of the preceding claims, characterized by , that the remaining engine torque is reduced by preventing fuel injection into at least one cylinder, provided that the driver's requested torque is zero and the throttle valve is still slightly open. [4] Motor control according to any of the preceding claims, characterized by , that the remaining engine torque is reduced by preventing ignition in at least one cylinder, provided that the driver's desired torque is zero and the throttle valve is still slightly open. [5] Motor control according to any of the preceding claims, characterized by, that the remaining engine torque is reduced by retarding the ignition timing in at least one cylinder, assuming the driver's desired torque is zero and the throttle valve is still slightly open. [6] Motor control according to claim 5, characterized by , that in addition, the fuel is injected into the cylinder by means of multiple injections.