SE1650358A1

SE1650358A1 - A control system for charge control of a combustion engine and a method for carrying out such a control

Info

Publication number: SE1650358A1
Application number: SE1650358A
Authority: SE
Inventors: Johansson Pontus; Gunnarsson Niclas; Wetterstrand Anton
Original assignee: Scania Cv Ab
Priority date: 2016-03-17
Filing date: 2016-03-17
Publication date: 2017-09-18
Also published as: WO2017160207A1; SE541433C2; DE112017000934T5

Abstract

A control system for charge control of a combustion engine (1) comprises a waste gate valve (10) installed in the exhaust pipe (7) from the engine to form a bypass of exhaust gas with respect to a turbine (6) driving a compressor (4). A control unit (18) controls a control valve (11) and by that the waste gate valve (10). The control unit (18) is configured to control the control valve (10) to deliver air of a determined pressure determining the open degree of the waste gate valve by a first use of compressed-air from a compressor-air tank (13) and by a second use of compressed-air from an outlet of the compressor (4) and make a relation of the second use to the first use higher for high loads of the engine than for low engine loads.(Fig 1).

Description

A CONTROL SYSTEM FOR CHARGE CONTROL OF ACOMBUSTION ENGINE AND A METHOD FOR CARRYING OUTSUCH A CONTROL TECHNICAL FIELD OF THE INVENTION The present invention relates to a control system for chargecontrol of a combustion engine, comprising: a turbo charger with a compressor in an intake pipe to the engineand a turbine in an exhaust pipe from the engine, a waste gate valve installed in the exhaust pipe to form a bypassof exhaust gas with respect to the turbine in the exhaust pipe, a control valve configured to control the waste gate valve bydelivering air of a pressure determining the open degree of thewaste gate valve, a compressed-air tank connected to the control valve to delivercompressed-air to the control valve, and a control unit configured to control the control valve and by thatthe waste gate valve, as well as a method for carrying out a charge control of an engineaccording to the preamble of the appended independent method claim.

The invention is not restricted to any particular type of combustionengine or fuel, and only by means of examples may fuels in theform of diesel, ethanol, biogas and petrol be mentioned.Furthermore, the invention relates to charge control of combustionengines intended for all types of use, such as in industrialapplications, in crushing machines and in all types of motoralthough the invention vehicles, is particularly applicable to wheeled motor vehicles, especially utility vehicles, such as trucksand buses, and it will for that sake mainly be discussed for thisuse so as to illuminate the invention but not in any way restrict itthereto.

Accurate control of a waste gate valve in a turbo chargedcombustion engine is of great importance for obtaining properoperation of such an engine in all types of situations, not only forobtaining an optimum performance of the engine but also for addressing emission regulations being more and more strict.

When driving a vehicle with a low engine load the waste gate valvehas mostly to be controlled to open to a high degree for makingthe exhaust gases from the engine to bypass the turbine, whereasfor high engine loads the waste gate valve shall be open to a lowerdegree for making the turbine to drive the compressor of the turbocharger powerfully. lt is of great importance that the control of thewaste gate valve follows the change of loads and conditions forthe engine quickly for instantaneously obtaining the behavior ofthe engine desired for obtaining an optimum with respect to performance and emissions and also avoiding turbo overspeeding.

BACKGROUND ART A control system according to the introduction is already knownthrough for example US 2009/0301084 A1 system having a PWM (Pulse Width Modulation) valve as control in which a control valve for controlling a waste gate valve by use of compressed-airfrom a compressed-air tank is described. However, a disadvantage of controlling the waste gate valve by compressed-air from a compressed-air tank is that the feedback of this control to changesin the operation conditions of the engine is rather slow resulting indeviations in the form of considerable “over reactions” when tryingto follow operation conditions changing rapidly by regulating thenumber of revolutions of the turbine. Thus, the charge pressureand turbine speed may in some cases not be regulated as accurate as desired.

EP 2 848 790 A1 discloses a control system for charge control ofa combustion engine combining an electrical control of the wastegate valve with use of compressed-air from an outlet of thecompressor to control a waste gate valve. The main control iscarried out by an electrical motor, but by utilizing compressed-airfrom the compressor outlet under some conditions the size of the electrical motor may be reduced.

SUMMARY OF THE INVENTION The object of the present invention is to provide a control systemand a method of the type defined in the introduction beingimproved in at least some aspect with respect to such systems and methods already known.

This object is with respect to the control system obtained byproviding such a control system with the features listed in the characterizing part of appended claim 1.

By having a control unit configured to control the control valve todeliver air of a determined pressure by a first use of compressed- air from the compressed-air tank and by a second use of compressed-air from the Compressor outlet and make a relation ofthe second use to the first use higher for high loads of the enginethan for low engine loads an improved accuracy of a charge controlof the combustion engine may be obtained in a cost efficient andreliable way. At low engine loads mostly calling for a high opendegree of the waste gate valve compressed-air from thecompressed-air tank may be used by the control valve to controlthe waste gate valve, but when the engine load rises the pressureof the compressed-air from the compressor outlet will also risemaking it increasingly able to be used for control of the opendegree of the waste gate valve, which will then mostly have to beopened less, although a control of the open degree to achieve anoptimum of result with respect to performance, emissions etc. iscarried out at each level of the load. The feedback of the controlusing compressed-air from the compressor outlet with respect toregulation of charge pressure and turbine speed will be excellentand result in a self-regulating control system making it possible toobtain an optimum result with respect to engine performance andThus, controlled over the entire operation range of the combustion creation of emissions. the waste gate valve may beengine and by a high accuracy at least for loads where this is ofgreatest importance. lt is stretched that the present invention doesnot exclude that said relation may be 0:1 or 1:0 during someoperation conditions of the combustion engine, so that then onlycompressed-air from the compressor air tank or only compressed-air from the compressor outlet will be used by the control valve forcontrolling the waste gate valve. “Higher for high loads of saidengine than for low engine loads” is in this disclosure to beinterpreted broadly and does not mean that the relation has to increase as soon as the load increases, but that the relation is under normal operation conditions of the engine higher for highloads, which are loads of at least 70% of the maximum load, thanfor low loads, which are loads of less than 30% of the maximumload. But this does not exclude that for e.g. an engine operationpoint with an engine load of 60% of the maximum load said relationis higher than for another engine operation point with an engine load of 65% of the maximum load.

According to an embodiment of the invention the control unit isconfigured to control the control valve to deliver air of a determinedpressure by only using compressed-air from the compressor outletas of a predetermined level of the load of said engine, and saidpredetermined level is at least 60%, preferably at least 70%, morepreferably at least 80%, most preferably at least 90% of themaximum load of said engine. Thus, said relation is 1:0 for loadsbeing so high that the pressure of the compressed-air from thecompressor outlet is high enough for open the waste gate valve asmuch as it may then be required to be open, so that the benefit ofthe excellent feedback of this control to regulation of chargepressure and turbine speed may then be fully utilized. Which ofthese different levels is applicable will depend upon the intendeduse of the combustion engine and other design parameters thereof.

According to another embodiment of the invention the control unitis configured to control the control valve to make said relation ofthe second use to the first use increasing with increasing loads ofsaid engine. This means that the participation of compressed-air from the compressor outlet in the control of the waste gate valve will increase with the possibility to use it, so that it may increasingly benefit from the advantages thereof.

According to another embodiment of the invention the control unitis configured to control the control valve to have said first use ofcompressed-air from the compressed-air tank exceeding thesecond use of compressed-air from the compressor outlet for loadsof said engine at least up to 30% of the maximum load of saidengine. For low engine loads for which the pressure ofcompressed-air from the compressor outlet is low a reliable controlof the waste gate valve to open comparatively much when askedfor may be reliably ensured by the use of compressed-air from the compressor air tank.

According to another embodiment of the invention the control unitis configured to control the control valve to alternatively switch incompressed-air from the compressed-air tank and compressed-airfrom the compressor outlet to pass the control valve to create airof a pressure determining the open degree of the waste gate valve.This constitutes an advantageous way of “mixing” the two uses for a control system operating according to the present invention.

According to another embodiment of the invention constituting afurther development of the embodiment last mentioned the controlunit is configured to control said relation by controlling the relationof time intervals of switching in compressed-air from thecompressor air tank with respect to compressed-air from thecompressor outlet. Said relation may by this type of control easilyand accurately be modified to change rapidly for adapting to changing operation conditions of the engine.

According to another embodiment of the invention the controlsystem comprises a further valve arranged in the air flow from thecompressed-air tank to the control valve and configured to reducethe pressure of the compressed-air arriving to the control valvefrom said tank with respect to the pressure of the compressed-airin said tank. A compressed-air tank used by a control system forcharge control of a combustion engine has often the task toprovide compressed-air to other equipment, especially in a motorvehicle, which require a comparatively high pressure, so that thepressure of the compressed-air in the compressed-air tank is on alevel not suitable for a sensitive control of a waste gate valve.Thus, a reduction of the pressure of the compressed-air arriving tothe control valve from the tank will result in a more accurate controlof the waste gate valve by less expensive parts involved.

According to another embodiment of the invention thecompressed-air tank is configured to deliver compressed-air toarrive to the control valve for said first use with a pressure of 2-10bar, 2-5 bar or 2-4 bar. These are suitable levels of the pressureof compressed-air from the compressed-air tank to be used forproper control of the waste gate valve and will enable to open it fully when needed.

According to another embodiment of the invention the controlsystem comprises a cut-off valve arranged in the air flow from thecompressor-air tank to the control valve, and the control unit isconfigured to control the cut-off valve to be open to provide thecontrol valve with compressed-air from the compressed-air tank or to be closed for preventing compressed-air from the compressed- air tank to reach the control valve. The arrangement of such a cut-off valve constitutes an option to enable restriction of the controlvalve to said second use, i.e. use of compressed-air from the compressor outlet, when this is desired.

According to another embodiment of the invention the control valvehas a controllable open degree, and the control unit is configuredto control the control valve to modify the pressure determining theopen degree of the waste gate valve by modifying the open degreeof the control valve. A possibility is then to use a PWM (PulseWidth l\/lodulation) valve as control valve and configuring thecontrol unit to control the open degree of the control valve by switching the control valve according to a PWM-pattern.

The object of the present invention is with respect to the methodobtained by providing a method according to the appendedindependent method claim. The advantages of such a method andembodiments thereof defined in dependent claims appear clearlyfrom the above discussion of embodiments of the control system according to the invention.

The invention also relates to a computer program, a computerprogram product, an electronic control unit and a motor vehicledefined in the corresponding appended claims.

Further advantageous features as well as advantages of the present invention appear from the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a specific description of an embodiment of the invention cited as an example.ln the drawings: Fig 1 is a schematic view illustrating a control system forcharge control of a combustion engine according to anembodiment of the invention, Fig 2 is a schematic view illustrating the way of operation ofthe control valve of the control system shown in Fig 1, Fig 3 is a flow chart illustrating the steps carried out in amethod according to an embodiment of the invention,and Fig 4 is a schematic view illustrating an electronic control unit for implementing a method according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THEINVENTION Fig 1 illustrates schematically the general structure of a controlsystem for charge control of a combustion engine 1 of a motorvehicle 2 according to an embodiment of the invention comprisinga turbo charger 3 with a compressor 4 arranged in an intake pipe5 to the engine and a turbine 6 in the exhaust pipe 7 from the engine, which is connected to the compressor 4 by a shaft 8 for driving the Compressor by the flow of exhaust gases hitting theturbine blades. A charge air cooler 9 is arranged downstream the COmpfeSSOf.

The control system further comprises a waste gate valve 10installed in the exhaust pipe to form a bypass B of exhaust gaswith respect to the turbine 6 in the exhaust pipe. Thus, the opendegree of the waste gate valve will decide the influence of theexhaust gas flow in the exhaust pipe upon the turbine and by thatupon the operation of the compressor 4. A control valve 11 isconfigured to control the waste gate valve 10 by delivering air of apressure determining the open degree of the waste gate valve byinfluencing an actuator member 12, the position of which will bedependent upon the air pressure delivered thereto and deciding the open degree of the waste gate valve 10.

A compressed-air tank 13, which typically will contain compressed-air of a pressure of 7-10 bar and used to deliver compressed-airto different pieces of equipment, such as brakes, of the motorvehicle, is connected to the control valve 11 through a further valve14 configured to reduce the pressure of the compressed-airarriving to the control valve from the tank 13, for instance to be inthe order of 3 bar.

The control system also comprises a member 15 divertingcompressed-air from an outlet of the compressor 4 to the controlvalve. Thus, the control valve 11 has two inlets as shown more indetail in Fig 2, one 16 receiving air from the air tank 13 and one17 receiving air from the member diverting compressed-air from the compressor outlet. A control unit in the form of an electronic 11 control unit 18 is configured to control the control valve, and thiscontrol unit may be the same as the electronic control unitcontrolling other equipment of the motor vehicle. This control unitis configured to control the control valve to alternatively switch incompressed-air from the compressed-air tank 13 and compressed-air from the compressor outlet from the member 15 to pass thecontrol valve to create air of a pressure determining the opendegree of the waste gate valve by being applied to the actuatormember 12. The control unit will do this by considering operationconditions of the combustion engine, such as the level of the loadthereof, when determining the relation of air to be taken from thetwo sources, the compressed-air tank 13 and the outlet of thecompressor. The control unit 18 will then preferably control thecontrol valve 11 to use compressed-air from the compressor outletas much as possible for obtaining the open degree of the wastegate valve 10 required for obtaining the performance and emission level asked for.

Fig 3 illustrates a flow chart of a method according to anembodiment of the present invention carried out for a controlsystem for charge control of the type shown in Fig 1. The methodis started with the step S1 of measuring parameters of the existingoperation point of the engine, whereupon in a step S2 the engineoperation point measured is compared with a table of relations ofuse of compressed-air from compressed-air tank and compressoroutlet for engine operation points. lt is then in a step S3 decidedwhich relation is to be used, whereupon in a step S4 the controlvalve is controlled to switch in compressed-air from the two sources according to this relation. 12 Computer program code for implementing a method according tothe invention is with advantage included in a computer programwhich can be read into the internal memory of a computer, e.g. theinternal memory of an electronic control unit of a motor vehicle.Such a computer program is with advantage provided via acomputer program product comprising a data storage mediumwhich can be read by a computer and which has the computerprogram stored on it. Said data storage medium is for example anoptical data storage medium in the form of a CD ROM disc, a DVDdisc etc., a magnetic data storage medium in the form of a harddisc etc., or a flash memory or a memory of the ROM, PROM,EPROM or EEPROM type. Fig. 4 illustrates very schematically anelectronic control unit 18 comprising an execution means 19, e.g.a central processor unit (CPU), for execution of computersoftware. The execution means 19 communicates with a memory20, e.g. of the RAM type, via a data bus 21. The control unit 18comprises also a non-transitory data storage medium 22, e.g. inthe form of a flash memory or a memory of the ROM, PROM,EPROM or EEPROM type. The execution means 19 communicateswith the data storage medium 22 via the data bus 21. A computerprogram comprising computer program code for implementing amethod according to the invention, e.g. in accordance with theembodiment illustrated in Fig. 3, is stored on the data storage medium 22.

The invention is of course in no way restricted to the embodimentsdescribed above, since many possibilities for modifications thereofare likely to be obvious to one skilled in the art without having todeviate from the scope of invention defined in the appended claims. 13 The control valve may be a PWM-valve and the control unit willthen control it accordingly to be fully open with O % PWM controland closed with 100 % PWM control. Such a PWM-valve may alsobe arranged downstream the control valve of the type present inthe embodiment disclosed above, so that these two valvestogether form a control valve in a control system according to the invenüon.

The control unit will receive information about the engine load inany conceivable way, directly or indirectly, and it is not necessary that a member measuring this load is present.

The further valve arranged between the compressed-air tank andthe control valve may be combined with or replaced by a cut-off valve or both these valves may be omitted.

Claims

1. 4 Claims A control system for charge control of a combustion engine, comprising: o a turbo charger (3) with a compressor (4) in an intake pipe(5) to the engine (1) and a turbine (6) in an exhaust pipe (7)from the engine, o a waste gate valve (10) installed in the exhaust pipe to forma bypass (B) of exhaust gas with respect to the turbine (7)in the exhaust pipe, ø a control valve (11) configured to control the waste gatevalve (10) by delivering air of a pressure determining theopen degree of the waste gate valve, ø a compressed-air tank (13) connected to the control valve(11) to deliver compressed-air to the control valve, and v a control unit (18) configured to control the control valve(11) and by that the waste gate valve (10), characterized in that the system further comprises v a member (15) diverting compressed-air from an outlet ofthe compressor (4) to the control valve (11), and that the control unit (18) is configured to control the control valve (11) to deliver air of a determined pressure by a first use of compressed-air from the compressed-air tank (13) and by a second use of compressed-air from the compressor outlet and make a relation of the second use to the first usehigher for high loads of said engine (1) than for low engine loads. A control system according to claim 1, characterized in that the control unit (18) is configured to control the control valve (11) to deliver air of a determined pressure by only using com-pressed-air from the Compressor outlet as of a predeterminedlevel of the load of said engine, and that said predeterminedlevel is at least 60%, preferably at least 70%, more preferablyat least 80%, most preferably at least 90% of the maximum load of said engine. A control system according to claim 1 or 2, characterized inthat the control unit (18) is configured to control the controlvalve (11) to make said relation of the second use to the first use increasing with increasing loads of said engine. A control system according to any of the preceding claims,characterized in that the control unit (18) is configured tocontrol the control valve (11) to have said first use ofcompressed-air from the compressed-air tank (13) exceedingthe second use of compressed-air from the compressor (4)outlet for loads of said engine at least up to 30% of the maximum load of said engine. A control system according to any of the preceding claims,characterized in that the control unit (18) is configured tocontrol the control valve (11) to alternatively switch incompressed-air from the compressed-air tank (13) andcompressed-air from the compressor (4) outlet to pass thecontrol valve to create air of a pressure determining the open degree of the waste gate valve (10). A control system according to claim 5, characterized in that the control unit (18) is configured to control said relation by 10. 16 controlling the relation of time intervals of switching in com-pressed-air from the compressed-air tank (13) with respect to compressed-air from the Compressor (4) outlet. A control system according to any of the preceding claims,characterized in that it comprises a further valve (14)arranged in the air flow from the compressed-air tank (13) tothe control valve (11) and configured to reduce the pressureof the compressed-air arriving to the control valve from saidtank with respect to the pressure of the compressed-air in said tank. A control system according to any of the preceding claims,characterized in that the compressed-air tank (13) isconfigured to deliver compressed-air to arrive to the controlvalve (11) for said first use with a pressure of 2-10 bar, preferably 2-5 bar, more preferably 2-4 bar. A control system according to any of the preceding claims,characterized in that it comprises a cut-off valve arranged inthe air flow from the compressed-air tank (13) to the controlvalve (11), and that the control unit (18) is configured tocontrol the cut-off valve to be open to provide the control valvewith compressed-air from the compressed-air tank (13) or tobe closed for from the preventing compressed-air compressed-air tank to reach the control valve. A control system according to any of claims 1-4 and 7-9 notdependent on claims 5 or 6, characterized in that the control valve (11) has a controllable open degree, and that the control 11. 12. 17 unit (18) is configured to control the control valve to modifythe pressure determining the open degree of the waste gate valve (10) by modifying the open degree of the control valve. A control system according to claim 10, characterized in thatthe control valve is a PWM (Pulse Width Modulation) valveand the control unit (18) is configured to control the opendegree of the control valve by switching the control valve according to a PWl\/I-pattern. A method for carrying out a charge control of a combustionengine (1) having a charge control system comprising: a turbo charger (3) with a compressor (4) in an intake pipe (5)to the engine and a turbine (6) in an exhaust pipe (7) from theengine, a waste gate valve (10) installed in the exhaust pipe to form abypass (B) of exhaust gas with respect to the turbine (6) inthe exhaust pipe, a control valve (11) configured to control the waste gate valve(10) by delivering air of a pressure determining the opendegree of the waste gate valve, and a compressed-air tank (13) connected to the control valve (11)to deliver compressed-air to the control valve, in which the method comprises the step of o controlling the control valve (11) and by that the waste gate valve (10),characterized byo diverting compressed-air from an outlet of the compressor(4) to the control valve (11), and 13. 14. 15. 18 o carrying out said controlling of the control valve (11) bycontrolling it to deliver air of a determined pressure by afirst use of compressed-air from the compressed-air tank(13) and by a second use of compressed-air from thecompressor (4) outlet while making a relation of the seconduse to the first use higher for high |oads of said engine than for low engine |oads. A method according to claim 12, characterized by carryingout said controlling of the control valve (11) by controlling itto deliver air of a determined pressure by only usingcompressed-air from the compressor (4) outlet as of apredetermined level of the load of said engine, in which saidpredetermined level is at least 60%, preferably at least 70%,more preferably at least 80%, most preferably at least 90% of the maximum load of said engine. A method according to claim 12 or 13, characterized bycarrying out said controlling of the control valve (11) bycontrolling it to alternatively switch in compressed-air from thecompressed-air tank (13) and compressed-air from thecompressor (4) outlet to pass the control valve to create air ofa pressure determining the open degree of the waste gate valve (10). Computer program comprising a computer program code forcausing a computer to implement a method according to anyof claims 12-14 when the computer program is executed in the computer. 16. 17. 18. 19 A computer program product comprising a data storagemedium which can be read by a computer and on which theprogram code of a computer program according to c|aim 15 is stored. An electronic control unit comprising an execution means(19), a memory (20) connected to the execution means and adata storage medium (22) which is connected to the executionmeans and on which the computer program code of a computer program according to c|aim 15 is stored. A motor vehicle, especially a wheeled motor vehicle, in par-ticular a heavy wheeled motor vehicle (2), such as a truck ora lorry or a bus, characterized in that it is provided with acontrol system for charge control of an engine (1) of the motor vehicle according to any of claims 1-11.