Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2001-12-14
2003-06-24
Richter, Sheldon J. (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S600000, C060S601000, C060S603000, C123S564000
Reexamination Certificate
active
06581382
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German Patent Document 100 62 350.6, filed Dec. 14, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for controlling a supercharging device for an internal combustion engine, especially in a motor vehicle.
A known system for controlling the boost pressure of an internal combustion engine with an exhaust turbocharger is described in German patent specification DE 39 43 010 C2. To regulate boost pressure, a blow-off valve is opened or closed according to a duty cycle of a trigger signal. In stable driving conditions, a duty cycle is taken from a table in which duty cycle values are listed in relation to the actual intake line pressure and engine speed. In this manner, the boost pressure can be kept at a maximum permissible pressure limit. If the permissible pressure limit is exceeded during partial-load operation, the base duty cycle is corrected with the aid of a proportional and integral (PI) controller in order to return the intake line pressure to a value below the pressure limit. During full load operation, the base duty cycle is also corrected with the aid of the PI controller, in order to keep the intake line pressure close to the pressure limit. During full load operation, this type of PI controller operation only takes place when, on the one hand, the intake line pressure falls within a range surrounding the pressure limit and, on the other hand, a local maximum intake line pressure was exceeded and the intake line pressure gradient is therefore less than zero. Accordingly, strong surges in supercharging pressure during the acceleration of a vehicle is avoided because an integral (I) controller is only activated after a local intake line pressure maximum is exceeded and when the intake line pressure is already approaching the pressure limit.
German disclosure document DE 198 01 395 A1 discloses a device for controlling boost pressure in an exhaust gas turbocharger with a variably adjustable turbine geometry. In this device, the air mass flow in the suction pipe, in an initial low load and/or RPM range, is used as a control variable for the exhaust gas re-circulation control device. In a second, higher load and/or RPM range, the boost pressure in the suction pipe is used as the control variable. The control device may be provided with a single controller in which the control variable is switched between the air mass flow and the boost pressure.
The invention relates to a method and apparatus for controlling a supercharging device with which an improved dynamic and an improved quality of control are achieved for all types of exhaust gas turbochargers.
To this end, a method is provided, according to the present invention, for controlling a supercharging device for an internal combustion engine, especially an exhaust gas turbocharger for a diesel engine of a motor vehicle, in which a range of control is divided into at least four sub-ranges, each having different control characteristics, depending on a gradient of the variable being controlled and a difference between the variable being controlled and a control variable. As a result of these measures, an improved dynamic and improved quality of control can be attained by adjusting the control characteristic to conform to a given condition of operation. If the control difference is constant but the gradients are variable, various control segments can be set and a variable control characteristic can be achieved. The control variable or the set value can be derived from a characteristic field, such as a set value plotted against load and engine speed for boost pressure, or an air mass flow plotted against the desired injection volume and the engine speed. An exhaust gas turbocharger with variable turbine geometry, the settings of which are adjusted, can be provided as a supercharging device.
In a further embodiment of the invention, it is provided that the sub-ranges are subdivided according to a positive or negative difference between the variable being controlled and the control variable, and according to a positive or negative gradient of the variable being controlled. As a result of these measures, the range of control is divided into four sub-ranges or four quadrants, with a subdivision of this nature being especially suitable for controlling a supercharging device of an internal combustion engine. Thus, aggressive control parameters are preferably used with positive gradients of the variable being controlled, so that a high dynamic is achieved with increases in the variable being controlled, such as the boost pressure. On the other hand, defensive control parameters are used with negative gradients of the variable being controlled, so that, for example, undershooting at decreasing boost pressure can be avoided and a high quality of control can be attained. In contrast to conventional controllers, this not only makes allowances for the difference between the variable being controlled and the control input or the set value, but also for the dynamic behavior of the variable being controlled. In this manner, the variable being controlled can be adjusted more quickly to a predetermined set value without running the risk of significant overshoot or undershoot. If, for example, a PI controller is provided, two characteristic fields can be provided for each quadrant, in which fields the P component and/or the I component is stored as a factor of the gradient of the variable being controlled and the control difference.
In a further embodiment of the invention, the control characteristic is determined by proportionally acting and integrating controller components and, in the case of negative gradients of the variable being controlled, a stronger emphasis is placed on the controller components with integrating action. As a result of these measures, undershooting at negative gradients of the variable being controlled is avoided and/or the variable being controlled is gradually brought closer to the reference variable.
In a further embodiment of the invention, it is provided that the control characteristic is determined by proportionally acting and integrating controller components and, in the case of positive gradients of the variable being controlled, that a stronger emphasis is placed on the proportionally acting controller components. As a result of these measures, a high dynamic can be achieved at boost pressure below the set value and minor overshooting at boost pressure above the set value when the gradients of the variable being controlled are positive, such as in the case of increasing boost pressure, by quickly returning the boost pressure to the set value.
In a further embodiment of the invention, it is provided that controller components with integrating action are only activated to the control characteristic once the variable being controlled has almost reached the control variable, falling within a predetermined range around the control variable. As a result of these measures, a high dynamic and rapid approaching of the control variable is achieved, as controller components with integrating action are only activated when the variable being controlled has almost reached the control variable. On the other hand, a high quality of control is achieved, especially within a predetermined range around the control variable, as the controller components with integrating action then provide for precise adjustment of the set value.
In a further embodiment of the invention, a default value of the supercharging device and a correction of the default value, which are subject to the actual fuel injection volume, are provided. Such a correction of the default value is especially advantageous in a diesel engine. To limit exhaust smoke during full load acceleration from low engine speeds, the fuel injection volume must be restricted, thus preventing the available fuel injection volume from providing the necessary exhaust gas energy. As a result of the dynamic correction of the default
Weber Siegfried
Wiltschka Joachim
Daimler-Chrysler AG
Richter Sheldon J.
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