Control of supercharged internal combustion engines

Details Control of supercharged internal combustion engines Control of supercharged internal combustion engines

1990-01-08

1992-06-16

Bertsch, Richard A.

Power plants

Fluid motor means driven by waste heat or by exhaust energy...

With supercharging means for engine

F02D 2300

Patent

active

051216043

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a method of controlling the charging pressure of a supercharged internal combustion engine. The invention also relates to devices for controlling the charging pressure of a supercharged internal combustion engine.


BACKGROUND OF THE INVENTION

A method and device of the kind referred to above are described in European Patent 0 084 037. In the known method and device, the characteristic field determines the desired charging pressure taking into account the output power, the composition of the exhaust gas, soot content of the exhaust, etc. As a result, supercharged diesel engines employing such method and device are supplied with too much air for combustion during most of the time of operation, for example when travelling at a comfortable cruising speed. The excess air is simply compressed and then expelled. The result is poor efficiency and high fuel consumption.


SUMMARY OF THE INVENTION

With the method and device of the invention, the charging pressure is reduced in the part load range, which is the range in which most vehicles are operated for most of the time.
It is convenient for the characteristic field to be a three-dimensional field comprising a range of curves to give a desired charging pressure for different engine speeds and different desired outputs (different injected fuel quantities per stroke in the case of a diesel engine or different air quantities in the case of a petrol engine) but for a given charging air temperature, e.g. 50.degree. C. However, charging air temperature is an inportant operating parameter and it can be taken into account in accordance with other embodiments of the invention. Still other embodiments of the invention ensure that the engine is not mechanically overstressed.
Improved servo-control can be obtained with other embodiments of the invention and a provision for over-boost is obtained with still further embodiments of the invention.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a block schematic diagram of a turbo-charged diesel engine fitted with a control device in accordance with the invention;
FIG. 2 is a block circuit diagram of the control device;
FIG. 3 represents in graphical form a characteristic field stored in a memory zone of the control device;
FIG. 4 represents a control characteristic field stored in another memory zone of the control device;
FIG. 5 is a block circuit diagram of a simplified control device;
FIG. 6 is a more detailed block circuit diagram of part of the control device of FIG. 2; and
FIG. 7 shows graphs to illustrate over-boost.


DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a diesel engine 10 fitted with a turbocharger 12 which comprises a compressor 14 in the induction passage 16 leading to the engine 10 and a turbine 18 in the exhaust gas passage 20 leading from the engine. The turbine 18 directly drives the compressor 14 at a speed n.sub.L. The power output of the turbine 18 can be adjusted by means of a by-pass valve 22 (a so-called "wastegate") in a by-pass passage 24 by-passing the turbine 18. A pneumatic actuator 26 operates the by-pass valve 22. Instead of providing the by-pass valve and passage, the turbine could be of the variable geometry type, whereby the pneumatic actuator adjusts the turbine output by adjusting the turbine geometry. The pneumatic actuator is controlled by an electro-pneumatic converter 28. In the illustrated embodiment, the actuator 26 comprises a diaphragm 30 which is biassed in the closing direction of the by-pass valve 22 by a spring 32 which can open the by-pass valve 22 by application of vacuum to a chamber 34. The converter 28 controllably applies vacuum from a source P.sub.u to the chamber 34 via a conduit 36 in response to an electrical control variable TV received at an input 38. The vacuum source P.sub.u can be a vacuum pump driven by the engine 10.
The control variable TV is supplied by an electronic regula

REFERENCES:
patent: 4459809 (1984-07-01), Tadokoro et al.
patent: 4556038 (1985-12-01), Okamoto et al.
patent: 4646522 (1987-03-01), Mamiya et al.
patent: 4686830 (1987-10-01), Buck et al.
patent: 4807147 (1989-02-01), Halbert et al.

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