GB2105878A

GB2105878A - Load regulation of an internal combustion engine supercharged with an exhaust gas turbocharger

Info

Publication number: GB2105878A
Application number: GB08225543A
Authority: GB
Inventors: Norbert Stelter; Heinz Dorsch
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 1981-09-09
Filing date: 1982-09-08
Publication date: 1983-03-30
Also published as: IT1190953B; IT8222818A0; FR2512497A1; DE3135691A1; FR2512497B1

Abstract

The throttle valve and the bypass valve are controlled additionally by the engine rotational speed 6 (signal n1) as well as the pressure 13 (signal P2) and temperature 15 (signal nu ) of the charging air. A turbo-charged engine is controlled at low loads by means of a normal throttle valve and subsequently at higher loads by closing a bypass valve for the turbocharger thereby the mass of air supplied is progressively increased over the load range. The function generators 3, 9 provide the control signals to the throttle motor 7 and bypass valve motor 11 in dependence on the accelerator pedal position. <IMAGE>

Description

SPECIFICATION Load regulation of an internal combustion engine supercharged with an exhaust gas turbocharger The present invention relates to the load regulation of an internal combustion engine supercharged by means of an exhaust gas turbocharger.

In engines with exhaust gas turbochargers, the negative alternating charge work is increased in the throttled condition (partial load) in that the exhaust gas turbine built into the exhaust gas line dams up the exhaust gas pressure. The energy transmitted from the exhaust gases by way of the turbine and the compressor to the charging air in the form of pressure is not needed and is therefore again reduced by means of the throttle valve. The alternating charge work increased by the dammed-up exhaust gas pressure reduces the efficiency of the engine and therewith increases the fuel consumption.

The object of the present invention is to provide overall the load regulation or output control of the engine by an appropriate cooperation of the adjusting drives for the throttle valve and the by-pass valve of the turbocharger-turbine in order to perfect the driving behaviour and, above all, to lower the fuel consumption.

As a solution to the underlying problem, a control circuit is proposed according to the present invention in which in the lower partial load range of the combustion engine, the bypass valve assumes a constant nearly fully open position, as a result of which the turbine and the compressor of the turbocharger operate at lower constant rotational speed, and in that for the load control the throttle valve is opened from 0% to 1 00%, whereas in the upper partial load range, the throttle valve is completely opened, and the load control takes place by closing of the by-pass valve and correspondingly high loading of the turbocharger-turbine.

The present invention makes it possible to load the turbocharger-turbine also at a lower partial load with so much of the exhaust gases that it and the compressor synchronous therewith operate at lower base rotational speed.

The engine reacts more rapidly to the accelerator pedal actuation because the turbocharger with a spontaneous output requirement produces more rapidly the required rated rotational speed, respectively, the required charging pressure. At the same time, a smooth transition to the turbo operation is achieved and a jump-like driving behaviour of the vehicle is avoided.

With the use of the electronic control of the throttle valve and of the by-pass valve in accordance with the present invention, the load regulation can be matched accurately to the respectively existing values of the characteristic magnitudes determining the mixture formation and combustion: engine rotational speed as well as pressure and temperature of the charging air, whereby these characteristic magnitudes are linked with the electronically sensed drive pedal position. According to a further feature of the present invention, these characteristic mangitudes do not themselves act on the adjusting drive of the output regulating devices; that is, of the throttle valve and of the by-pass valve, but instead control magnitudes corresponding thereto which are obtained as output signals of nonlinear function converters are used for that purpose.By an appropriate selection of the functional interrelationship between measured input magnitude and output magnitude used for the control, the load regulation of the engine can be matched in an optimum manner to the operating conditions thereof. Furthermore, a signal can be obtained from the speed of the accerator pedal movement which brings about a closing of the by-pass valve by way of the adjusting drive and therewith brings the turbocharger to full rotational speed as soon as or shortly before the throttle valve is completely opened. If the turbocharger has reached the rated speed, respectively, the full charging pressure, then it is throttled again by the opening of the by-pass valve. A desired maximum vehicle acceleration can be achieved in this manner.

In the accompanying drawings: Figure 1 is a block diagram of the loadregulating system in accordance with the present invention; and Figures 2, 3, and 4 are schematic circuit diagrams of the function converters used in the load-regulating system in accordance with the present invention.

Referring now to the drawings and more particularly to Fig. 1, the signal of an electric pickup 1 for the accelerator pedal position 9 which is obtained by way of a potentiometer pickup, is fed in a first line 2 to an anglefunction converter 3 which coordinates according to a predetermined function to the angle of rotation 9 of the accelerator pedal an angle of rotation a2 of the throttle valve in such a manner that beginning with the angle position 0 the throttle valve angle increases with the accelerator pedal angle according to a root function until, at an approximately halfdepressed accelerator pedal position, the throttle valve is completely opened in the angular position a2 max.The angle a2 corresponding to this function variation is fed to a computer circuit 4 together with a control signal n2 obtained from the rotational speed of the engine. The rotational speed control signal n2 is the output signal of a rotational speed function converter 5 which transforms the engine rotational speed n1 detected by way of a rotational speed pickup 6 into a rotational speed signal n2 according to a mathematical function increasing with a reversing point. The output signal of the computer circuit 4 is fed to an electric adjusting motor 7 for the throttle valve which adjusts same by the angle a.

In a further line 8 parallel to the first line 2, the accelerator pedal position * is stored in a function converter 9 which supplies, according to a predetermined function, a control signal P2 for the adjustment of the bypass valve of the exaust gas turbocharger as output magnitude thereof. With the accelerator pedal angle # = O, p2 = p2 max., and the bypass valve is completely opened, so that the exhaust gas turbocharger is not in operation.

Beginning with an approximately half-depressed accelerator pedal, the control signal ss2 decreases with increasing accelerator pedal angle 9 according to a hyperbola or exponential e-function, i.e., beginning at that point the turbocharger-turbine is increasingly loaded.

The actual positions p of the bypass valve additionally depend on the control signals P2 and 82 for the pressure, respectively, and the temperature of the charging air, which are fed together with the control signal p2 to a computer circuit 10 that links with each other all input signals additively or multiplicatively. An electric adjusting drive 11 of the bypass valve is controlled by means of the output signal of the computer circuit 10, which adjusts the bypass valve by the adjusting displacement p.

The pressure control signal P2 is produced in a function converter 1 2 whose input signal p stems from a pressure transducer 1 3 connected to the charging air line. The pressure control signal P2 decreases after a contiuously decreasing function with increasing p" that is, with increasing pressure of the charging air, the closing movement of the bypass valve and therewith the charging increase of the combustion engine is reduced. In contrast thereto, the temperature of the charging air influences the adjusting movement of the by-pass valve according to an entirely different function.The temperature control signal 52 which is obtained in the function converter 1 4 is at first approximately constant with an increasing temperature Si of the charging air which is measured by means of a temperature sensor or pickup 1 5. With an increasing temperature 8" the signal 62 increases jump-like and causes a rapidly accelerated closing movement of the bypass valve. With a further increasing charging air temperature Si, the output signal 62 again remains at a constant magnitude.

By an oppropriate selection of the functional inter relationship obtained in the function converters between measured engine characteristic magnitudes and the control magnitudes coordinated thereto, the load regulation of the internal combustion engine can be optimized in an extremely accurate manner.

The circuits of the function converters which are known from the book, Halbleiter Schaltungstechnik, Third Edition, page 274, are illustrated in Figs. 2, 3, and 4, whereby in the present application, the operational amplifiers for negative input voltages are dispensed with. A circuit is used for each of the function converters 3, 9, 5, 12 and 14, consisting of the partial circuits according to Figs. 2, 3 and 4, whereby depending on the characteristic curve,. several partial circuits according to Fig.

2 are used and the partial circuit according to Fig. 3 is required only for the function converters 9, 1 2 and 14. The output current at the terminal 1 7 of the partial circuit according to Fig. 2 is dependent from the input voltage at the terminal 1 6 and from the adjustment of the potentiometers 18 and 19. A minimum value for the input voltage is predetermined by means of the potentiometer 18, up to which the current flow at terminal 1 7 is equal to zero. With a higher input voltage, the current flow becomes proportional to the input voltage, whereby the proportonality factor is adjustable at the potentiometer 1 9.

According to the partial circuit according to Fig. 3, a constant current flow independent of the input voltage is produced which is adjustable by the potentiometer 20. The output currents of the partial circuits according to Figs. 2 and 3 are fed to the terminal 21 in the circuit of Fig. 4; they are added and are converted into a proportional output voltage at the terminal 22. Characteristic curves of any desired shape can be formed by means of these function converters which can be composed of a constant component and of several components with variable increase or decrease.

Claims

1. A load regulation for an internal combustion engine supercharged by an exhaust gas turbocharger including a throttle valve and a bypass valve through which exhaust gases are operable to flow directly into an exhaust gas line in bypassing relationship to the turbocharger-turbine, characterized by control means for controlling the engine load including first means for causing the bypass valve means to assume a substantially constant, nearly fully open position in a lower partial load range of the internal combustion engine, as a result of which the turbine and compressor of the turbocharger means operate at lower substantially constant rotational speed, and for opening the throttle valve means from about 0% to about 100% for the load regulation in said partial load range by closing the bypass valve and by a correspondingly high loading of the turbine of the turbocharger.

2. A load regulation according to claim 1, characterized by electric adjusting drive means for the throttle valve and bypass valve means.

3. A load regulation according to claim 1, characterized in that the lower partial load range of the internal combustion engine is up to about 50% of the full load.

4. A load regulation according to claim 1 or 2, characterized in that the throttle valve is controllable by the position of an accelerator pedal and the rotational speed of the engine, and in that the bypass valve is controlled by the accelerator pedal position as well as the pressure and temperature of the charging air while the respectively cooperating control magnitudes are linked with each other.

5. A load regulation according to claim 4, characterized in that the control magnitudes are additively linked.

6. A load regulation according to claim 4, characterized in that the control magnitudes are multiplicatively linked.

7. A load regulation according to claim 4, characterized in that the control magnitudes are obtained as output signals from nonlinear function converter means of the measured engine characteristic magnitudes including rotational speed of the engine as well as pressure and temperature of charging air.

8. An electronic load control for an internal combustion engine supercharged by an exhaust gas turbocharger having a turbine and a compressor driven by the turbine, said engine being provided with a throttle valve and a bypass valve through which exhaust gases are able to flow directly into an exhaust gas line in bypassing relationship to the turbocharger-turbine, and electric actuating means for said throttle valve and bypass valve, comprising electronic circuit means operatively connected with said electric actuating means for causing the bypass valve means to assume a substantially constant, at least nearly fully opened position in a lower partial load range of the internal combustion engine so that the turbine and the compressor of the turbocharger means operate at a lower constant rotational speed and for opening the throttle valve from substantially 0% to substantially 100% for the control of the engine in said lower partial load range whereas in the upper partial load range the throttle valve is at least merely completely opened and the engine control takes place by closing of the bypass valve and correspondingly high loading of the turbocharger-turbine.

9. A load control according to claim 8, characterized in that the electronic circuit means are operable to link respectively cooperating control magnitudes representing accelerator pedal position, rotational speed of the engine as well as pressure and temperature of the charging air, the throttle valve being controllable by said electronic circuit means as a function of accelerator pedal position and engine rotational speed while the bypass valve is controllable as a function of accelerator pedal position as well as pressure and temperature of the charging air.

1 0. A load control according to claim 9, characterized in that the electronic circuit means includes nonlinear function converter means operable to produce control magnitudes as output signals thereof from measured engine characteristic magnitudes including engine rotational speed as well as pressure and temperature of the charging air.

11. A load regulation for a turbo-charged internal combustion engine substantially as described with reference to, and as illustrated in, the accompanying drawings.