This U.S. patent application claims priority to German Patent Application DE 10 2010 017 406.8, filed Jun. 17, 2010, which is incorporated by reference herein in its entirety.
The invention relates to a method for operating a drivetrain of a motor vehicle.
A drivetrain of a motor vehicle comprises a drive unit and a transmission. The present invention relates to a method for operating a drivetrain whose drive unit is formed by an internal combustion engine and at least one turbocharger which interacts with the internal combustion engine.
It is already known from practice for a driver demand or a driver demand torque to be determined as a function of a present actuation of an accelerator pedal or throttle pedal by the driver, that is to say as a function of a present accelerator pedal actuation, wherein a drive unit torque which is dependent on the driver demand torque is provided by the drive unit. To avoid abrupt load changes in the drivetrain as a result of a fast change in the accelerator pedal actuation, it is known from practice to provide the drive unit torque as a function of the driver demand torque via a so-called load shock damping facility, wherein in the case of a load shock damping facility, the drive unit torque is built up by the drive unit as a function of the driver demand torque via so-called load filter gradients.
A load filter gradient is to be understood to mean a preferably ramp-shaped torque build-up which, for example in the event of a step-like change in the accelerator pedal actuation or a step-like change of a driver demand torque, is limited by the load shock damping facility to a torque build-up rate adapted to the driver demand, without inciting excessive vibrations or jerks in the drivetrain.
From practice, a load shock damping facility is already known which operates with three load filter gradients for building up the drive unit torque as a function of the driver demand torque, wherein a first load filter gradient is active in the overrun mode of the motor vehicle, a second load filter gradient is active for the transition from the overrun mode into the traction mode of the motor vehicle, and a third load filter gradient is active in the traction mode of the motor vehicle.
When such a load shock damping facility having three load filter gradients is used in a drivetrain whose internal combustion engine interacts with at least one turbocharger, in the event of a step-like accelerator pedal actuation or pedal input PI, the profiles shown in
According to
This is perceived by the driver as being uncomfortable and non-sporty, and there is accordingly a demand for the longitudinal acceleration a to be built up in the drivetrain without turbo lag perceptible to the driver.
An object of the present invention is to provide an improved method for operating a drivetrain of a motor vehicle, which is described hereinafter.
Said object is achieved by means of a method for operating a drivetrain of a motor vehicle, the drivetrain having a drive unit with an internal combustion engine and with at least one turbocharger, a driver demand torque being determined as a function of a present accelerator pedal actuation, and a drive unit torque which is dependent on the driver demand torque being provided by the drive unit via a load shock damping facility in such a way that the drive unit torque is built up as a function of the driver demand torque via load filter gradients of the load shock damping facility, characterized in that, in the case of a relatively high driver demand torque, to ensure a comfortable and dynamic build-up of the drive unit torque using the or each turbocharger, a nominal value for an air-based torque of the drive unit is increased more quickly to a maximum value than a nominal value for an ignition-based torque of the drive unit.
According to aspects of the invention, in the case of a relatively high driver demand torque, to ensure a comfortable and dynamic build-up of the drive unit torque using the or each turbocharger, a nominal value for an air-based torque of the drive unit is increased more quickly to a maximum value than a nominal value for an ignition-based torque of the drive unit.
According to aspects of the invention, in the case of a relatively high driver demand torque, the nominal value for the so-called air-based torque, which is dependent on the charge pressure or the cylinder charge, is increased preferably abruptly to a maximum value. A nominal value of the so-called ignition-based torque, which is dependent on the ignition angle efficiency of the internal combustion engine, is increased preferably gradually to the maximum value. In this way, methods for load shock damping known from the prior art are expanded by a further load filter gradient for high driver demand torques, wherein said load filter gradient is active in particular in an upper part-load range between an, in effect, naturally-aspirated operating mode of the drive unit and a turbocharged operating mode of the drive unit. By means of the invention, a longitudinal acceleration can be built up in the drivetrain without turbo lag perceptible to the driver. Furthermore, the so-called response time can be shortened.
According to a further aspect of the invention, the nominal value for the air-based torque is increased abruptly to the maximum value, in particular the driver demand torque, in one step, whereas the nominal value for the ignition-based torque is increased gradually to the maximum value, in particular the driver demand torque, in a plurality of steps or along a linear guide ramp or along a non-linear guide curve.
Preferred refinements of the invention will emerge from the subclaims and from the following description. Exemplary embodiments of the invention will be explained in more detail on the basis of the drawing, without the invention being restricted to said exemplary embodiments. In the drawing:
The present invention relates to a method for operating a drivetrain of a motor vehicle, wherein the drivetrain has a drive unit and a transmission. The drive unit comprises an internal combustion engine which interacts with at least one turbocharger. The invention now relates to a method for operating such a drivetrain, by means of which method a drive unit torque can be built up by the drive unit in a comfortable and dynamic manner as a function of a present actuation of an accelerator pedal or throttle pedal, wherein for this purpose, a driver demand torque is determined as a function of a present accelerator pedal actuation, and wherein a drive unit torque which is dependent on the driver demand torque is provided or built up by the drive unit via a load shock damping facility. A load shock damping facility comprises a plurality of load filter gradients which take effect as a function of the driver demand torque and via which the drive unit builds up drive unit torque as a function of the driver demand torque. For example, from practice, load shock damping methods are known which provide different or separate load filter gradients for the overrun mode, the traction mode and a transition region between the overrun mode and the traction mode of a drivetrain, in order to build up the drive unit torque for these operating regions as a function of the driver demand torque determined from the present accelerator pedal actuation.
With the present invention, it is now proposed that, in a drive unit with a turbocharger, in the event of a relatively high driver demand torque, to ensure a comfortable and dynamic build-up of the drive unit torque using the or each turbocharger, a further, separate load filter gradient be used, specifically in such a way that a nominal value for an air-based torque of the drive unit is increased more quickly to a maximum value than a nominal value for an ignition-based torque of the drive unit.
A nominal value for the air-based torque of the drive unit or internal combustion engine is preferably increased abruptly to a maximum value, whereas a nominal value for an ignition-based torque of the drive unit or internal combustion engine is increased gradually to a maximum value.
The ignition-based torque is to be understood to mean a drive unit torque which can be provided as a function of the ignition angle, and which is based on the so-called ignition angle efficiency. The air-based torque is to be understood to mean a drive unit torque which can be provided as a function of a cylinder charge, wherein the cylinder charge can be influenced by means of load control elements of the internal combustion engine. The cylinder-charge-based air-based torque of the internal combustion engine is also referred to as base torque or torque of a slow torque path of the internal combustion engine. The ignition-based torque which is dependent on the ignition angle efficiency is also referred to as torque of a fast torque path of the internal combustion engine.
Here, the profile shown in
As already stated, the nominal value for the air-based torque is increased preferably abruptly to the maximum value and the nominal value for the ignition-based torque is increased gradually to the maximum value, wherein said two maximum values are of equal magnitude, that is to say each correspond to the driver demand torque determined as a function of the accelerator pedal actuation.
The nominal value MNOM,2 for the air-based torque is, according to
The present invention proposes a modified load shock damping facility for turbocharged internal combustion engines, which modified load shock damping facility in particular provides a separate load filter gradient for the transition region from the, in effect, naturally-aspirated operating mode of the internal combustion engine to the turbocharged operating mode of the internal combustion engine. In this way, perceptible turbo lag can be eliminated and the response time in the build-up of the longitudinal acceleration can be shortened. This increases both the driving comfort and also the dynamics or sportiness during the operation of the drivetrain.
If the invention is used in an internal combustion engine with a variable valve drive in which for example a valve lift switchover can be realized, the invention offers further advantages. A time is then preferably selected for a valve lift switchover such that the latter takes place in a region marked in
Number | Date | Country | Kind |
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102010017406.8 | Jun 2010 | DE | national |