SE537013C2 - Exhaust gas return by facilitating the opening of at least one cylinder exhaust valves - Google Patents

Description

537 013 In the event that a fixed geometry (FGT) turbocharger was used instead, the latter problem would not arise. In addition, such a turbocharger is available at a lower cost and is less complicated than a VGT-type turbocharger. With an FGT-type turbocharger, the engine's fuel consumption will be low, as the pressure in the exhaust gas collectors will then be at the same level as the pressure in the first line, but then you can not drive a sufficient amount of exhaust gas to the inlet side because the differential pressure is missing.

This means that it is the exhaust pulses that occur when the exhaust valves of the cylinders are opened that can be used to pulsate the recirculation of the exhaust gases. It is desirable to increase the proportion of exhaust gases which in such an arrangement can be returned to the air supply to the engine in order to reduce the content of harmful nitrogen oxides in the exhaust gases.

U.S. Pat. No. 4,131,095 discloses an arrangement in which it drives the EGR by returning exhaust gases from a cylinder of the engine at low power take-off therefrom and no EGR at all at higher take-offs from the engine. However, this type of drive of EGR leaves much to be desired in terms of the possibility of achieving low levels of NOXi GVQGSGFFIG.

SUMMARY OF THE INVENTION The object of the present invention is to provide an arrangement of initially defined kind, which is improved in at least some respect relative to previously known such arrangements.

This object is achieved according to the invention by providing such an arrangement as stated in claim 1. 537 013 By opening at least one exhaust valve earlier in at least one cylinder than in at least one other cylinder, the exhaust pulses from said first cylinder will be stronger than if the previously opened the exhaust valve of this cylinder is opened in the combustion cycle of this cylinder at the same place as the at least one exhaust valve of said second cylinder. This means that the first cylinder's exhaust pulse will drive a larger proportion of exhaust gases for recirculation to the air supply than would otherwise have been the case. An earlier opening of the exhaust valve will mean that part of the pressure created during combustion cannot be converted into mechanical energy, and thus the efficiency of the engine deteriorates. Thus, a maintenance of the engine's emitted power can not take place without a slightly increased fuel consumption of the cylinder in question. However, as such an earlier opening is not made in all cylinders, fuel consumption can be kept at a desired low level. In this case, the first cylinder can have several exhaust valves and only one or more or all of them, i.e. an arbitrary number of them, can be opened earlier in the combustion cycle of the cylinder than at least one exhaust valve in the combustion cycle of said second cylinder.

According to an embodiment of the invention, said exhaust valve of said first cylinder is arranged to open 5-60 degrees, 5-30 degrees or 10-20 degrees earlier than at least one exhaust valve of at least one other said second cylinder. This constitutes possible intervals for a previous opening of an exhaust valve of a said first cylinder without the fuel consumption of the cylinder becoming unacceptably high. How large an earlier opening of the exhaust valve in question is chosen may depend on the intended use of the internal combustion engine.

According to another embodiment of the invention, at least one said second second cylinder has its exhaust outlet connected to the second line. By using several cylinders in this way to drive the EGR but only one or some to do so by extra strong exhaust pulse, the desired proportion of exhaust gases can be returned to the air supply and at the same time the engine's fuel consumption is kept low.

According to another embodiment of the invention, all cylinders of the engine have their exhaust outlets connected to said second line.

By using exhaust pulses from all cylinders for recirculating exhaust gases to the air supply, this exhaust flow becomes substantially even at the same time as a previous opening of at least one exhaust valve of one or more said first cylinders has a increasing effect on this flow.

According to another embodiment of the invention, said second line comprises at least one inlet opening for receiving exhaust gases arranged close to, such as the center of, particularly aligned with, the exhaust outlet of said first cylinder. By such a location of the inlet opening to the second line, the stronger exhaust pulse from the cylinder in question can be used maximally for driving the EGR, so that the desired proportion of recycled exhaust gases can be achieved with minimal extra fuel consumption of the engine.

According to another embodiment, the invention comprises a control unit configured to control said at least one exhaust valve of said first cylinder to open at least 5 degrees of crankshaft earlier in that combustion cycle of that cylinder than at least one exhaust valve of at least one second said cylinder. This makes the control of the exhaust gas recirculation simple and reliable. An advantage of utilizing such a control unit is that it allows the exhaust valve to be switched to open earlier only in cases where exhaust gas recirculation is required. In some operating cases no exhaust gas recirculation is required and the current exhaust valve can in these operating cases be set to open at the same time as 537 013 other exhaust valves. During these operating cases, the engine will operate in a conventional manner and without the influence of the invention. An advantage of this is that the fuel consumption can be improved and the operating cases with reduced fuel consumption due to utilization of the invention can be limited.

According to another embodiment of the invention, the arrangement comprises an exhaust manifold designed to receive exhaust gases from several said cylinders and connected to an exhaust outlet line for discharging exhaust gases from the arrangement, and the second conduit has at least one opening opening in the exhaust manifold for receiving exhaust gas. end of the exhaust manifold in the region of its connection to the exhaust outlet line. It is advantageous to provide an opening of the second line at this point in the exhaust manifold to prevent exhaust gases from one cylinder flowing in the opposite direction to exhaust gases from another cylinder.

According to another embodiment of the invention, the arrangement comprises a turbocharger connected to the first line for compressing air supplied to the engine by means of exhaust gases from the engine. In this case, the said turbocharger is advantageously of the type which has a fixed geometry (FGT). By opening at least one exhaust valve of at least one cylinder connected to said second line earlier so that a stronger exhaust pulse for driving EGR gases is generated, the exhaust gas recirculation can be driven at a desired high level in an internal combustion engine equipped with a fixed geometry turbo.

At the same time, a low fuel consumption of the engine is obtained, which leads to lower costs and a more robust construction than when using a turbocharger of type VGT in the arrangement. According to another embodiment of the invention, the engine has at least two said first cylinders, and a control unit of the arrangement is designed to initiate combustion in the engine cylinders in an order so that said first cylinders are substantially evenly distributed or evenly distributed therein. By distributing the cylinders with stronger exhaust pulses evenly or substantially evenly in the engine's sequence of ignition, the flow of exhaust gases recirculated to the air supply becomes substantially even and thus the amount of NOX resulting in combustion in the engine is minimal.

According to another embodiment of the invention, a control unit of the arrangement is designed to control said at least one exhaust valve of said one first cylinder to have a cranked fixed opening distance to said at least one exhaust valve of said at least one second cylinder. This makes the control of EGR simple and reliable. This means that the control unit does not really control the at least one exhaust valve of said first cylinder to open earlier, but when it opens it is not controllable at all. The distance in crank degrees between the opening of the exhaust valves of the various cylinders of the engine is fixed in this embodiment, i.e. always the same.

According to another embodiment of the invention, the internal combustion engine has six cylinders, and two of the cylinders are first cylinders, both of which have their exhaust outlet connected to said second line and which have at least one exhaust valve which a control unit of the arrangement is designed to control to open at least crank degrees earlier in the combustion cycle than at least one exhaust valve of the other four other cylinders. By using two of the six cylinders to provide an amplified exhaust pulse to drive EGR gases, the NOX content formed during engine combustion can be kept low and yet the earlier opening of the exhaust valves of these two cylinders 537 013 will only have an insignificant effect on the engine. fuel consumption.

It is particularly advantageous in this case if also the four second cylinders are connected to said second line and the two first cylinders are evenly distributed in the ignition sequence of the engine, i.e. with two second cylinders lit between the two first cylinders.

According to another embodiment of the invention, the internal combustion engine has eight cylinders, and two, three or four of the cylinders are first cylinders, both of which have their exhaust outlet connected to said second line and which have at least one exhaust valve which a control unit of the arrangement is designed to control. to open at least 5 crank degrees earlier in the combustion cycle than at least one exhaust valve of the other said second cylinders. The reasoning above regarding the embodiment with an internal combustion engine with six cylinders is also applicable here.

The invention also relates to a method for controlling air supply to an internal combustion engine with at least three cylinders according to the appended independent method patent claims. The result of carrying out such a method and the advantages thereof appear with all the desired clarity from the above description of the arrangement according to the invention.

The invention also relates to a computer program, a computer program product, an electronic control unit and an internal combustion engine.

Other advantageous features and advantages of the invention will become apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS 537,013 Hereinafter, exemplary embodiments of the invention are described with reference to the accompanying drawings, in which: Fig. 1 is a simplified view of an arrangement of an internal combustion engine of the type according to the invention, Fig. 2 is a relative more detailed view of a part of a said arrangement according to an embodiment of the invention, Fig. 3 shows a diagram illustrating the exhaust pressure over crank degrees of the three cylinders illustrated at the top of Fig. 2 and how this changes upon a previous opening of the exhaust valve of the third of the cylinders , and Fig. 4 is a schematic diagram of an electronic control unit for implementing a method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION An arrangement of an internal combustion engine is schematically illustrated in Fig. 1. The arrangement has an internal combustion engine 7 provided with six cylinders 1-6 in the form of a straight, six-cylinder engine, and may be for an industrial or marlnt use.

The arrangement has an air intake 8 for fresh air to the engine, from which the air is led via a first line 9 to the engine cylinders for combustion of fuel mixed therein in the cylinders. A supercharger in the form of a solid geometry (FGT) turbocharger 10 is provided to compress the air to be supplied to the cylinders. The turbocharger conventionally comprises a compressor 11 and a turbine 12. The air which has been overpressured via the compressor 11 is cooled in a charge air cooler 16 and then proceeds to an air inlet pipe 17 included in the first line 537 013 which leads the air to cylinders 1-6. The engine comprises two exhaust gas collectors 27, 31 (see Fig. 2) to which the exhaust gases are led from the cylinders, where cylinders 1-3 lead the exhaust gases to one exhaust gas collector 27 and where exhaust gases from cylinders 4-6 are led to the other exhaust gas collector 31. From the respective the exhaust gas collectors 27, 32, the exhaust gases are led further via exhaust outlet lines 13, 14 to the turbine 12. The turbine 12 is thus provided with a double inlet, ie a so-called Twin Scroll Turbine. The exhaust gases that drive the turbine 12 exit into the environment via an exhaust pipe 15.

The arrangement also has an EGR system for recirculating a part of the exhaust gases resulting from the combustion in the engine to the part of the first line 9 which extends downstream of the charge air cooler 16 for mixing with fresh air in the air supply to the engine. It is schematically illustrated how for that purpose a second line 18 extends with two line portions 19, 20 from the exhaust outlet lines 13, 14 and then further via a non-return valve 21 and an EGR cooler 22 to the first line 9.

The arrangement further comprises in an advantageous embodiment a control unit 23 designed to control at least the opening of exhaust valves of the cylinders, i.e. when in the combustion cycle the combustion chamber of the respective cylinders is to be connected to the cylinder's exhaust outlet for emitting exhaust gases. This can be the same control unit that is designed to initiate combustion in the engine cylinders and also control other components of the arrangement. The control of the opening time of the valves can suitably be done indirectly by controlling an arrangement arranged for this purpose for controlling variable valve times, for example one where the camshaft of the motor is brought to rest against alternative cam cams. Alternatives where the valves can be controlled directly with the help of electromagnets are also possible. 537 013 Here, each cylinder has two exhaust valves 41,42 controlled by the control unit and two inlet valves 43, 44. However, each cylinder could have a different number of exhaust valves and inlet valves. For example, one, three or four exhaust valves.

Reference is now also made to Fig. 2. In the embodiment shown, the exhaust outlets 24-26 of three of the cylinders 1-3 are connected to one exhaust collector 27, while the exhaust outlets 28-30 of the other cylinders 4-6 are connected to the other exhaust collector 31. The pressure in the exhaust manifolds 27, 31 will be approximately the same as in the air inlet pipe 17, so that there is no differential pressure which drives the recirculation of exhaust gases through the second line 18, but such a drive will instead be provided by the exhaust pulses resulting when the exhaust valves of the cylinders are opened, so that a pulsed EGR flow is obtained. The non-return valve 21 prevents the respective exhaust pulse from returning when the pressure in the exhaust manifolds 27,31 drops.

The control unit 23 controls at least one, but preferably both exhaust valves 41, 42 of a first cylinder 3, 4 connected to the respective exhaust collector 27, 31 to open at least 5 degrees of cranking and at most 60 degrees of cranking and here about 20 degrees of cranking earlier in that cylinder's combustion cycle. an exhaust valve of the two other cylinders 1, 2, and 5, 6, respectively, connected to the exhaust gas collector in question, in the operating cases where exhaust gas recirculation is to take place. This means that the first cylinders have exhaust valves which open when the piston of the cylinder has not reached as far in the stroke, which means that the fuel consumption of that cylinder increases slightly, but at the same time the exhaust pulse from said first cylinder will be clearly stronger (see further down the discussion of Fig. 3) than for said second cylinders and thus have a more driving effect on the reflux of exhaust gases in the second line 18. The respective line portions 19, 20 of the 537,013 second line are arranged with their inlet opening 32, 33 for receiving exhaust gases in front of and directed in the extension of the exhaust outlet 26, 28 of said first cylinder 3, 4 at the same time as the cylinders having their exhaust outlets opening into the exhaust manifold at one end thereof in the region of its connection to the exhaust outlet line 13, 14, i.e. at the so-called turbo foot, are those selected to be said first cylinders. All in all, this means that the exhaust pulse generated by the previous opening of an exhaust valve is used to the maximum to drive the EGR. Advantageously, all, here two, exhaust valves of the cylinders 3, 4 arranged in the middle of the inlet openings 32, 33 are opened earlier in order to obtain an EGR strong driving exhaust pulse. Fig. 2 also shows schematically how a small bucket 34, 35 can be arranged to help also utilize a part of the exhaust pulses from the two other cylinders 1, 2 and 5, 6, respectively, to drive EGR.

The control unit 23 is adjustable and can be set to open the current exhaust valve (exhaust valves) at the same time as the other exhaust valves of the engine in the operating cases when exhaust gas recirculation is not required.

This means that the work generated during combustion can be utilized optimally.

A control unit for controlling the initiation of combustion in the cylinders of the engine is designed to do this in an order so that the first two cylinders are evenly distributed in that order, and for this purpose the ignition sequence 1 5 3 6 2 4 is selected here, where 3 and 4 are the cylinders with exhaust valves that are opened earlier. This provides a substantially uniform flow of exhaust gases in the second line for mixing with the air in the first line and the proportion of recycled exhaust gases is kept at the desired high level to achieve a low content of NOX out of the engine and still maintains a favorable low fuel consumption of the engine. The stronger exhaust pulses from cylinders 3 and 4 do not disturb the other cylinders 11 537 013 thanks to the twin scroll turbine, turbine wheels with double inlet, and even distribution in the ignition sequence.

The diagram in Fig. 3 shows how the pressure P at the inlet opening 32 for the EGR outlet from cylinders 1-3 develops over the number of crank degrees CP of the cylinders. The three peaks 2, 1 and 3 are attributable to the opening of exhaust valves of corresponding cylinders, and curve A illustrates the cylinder pressure in cylinder 3, while curve B illustrates the lifting of the exhaust valves in cylinder 3 in unexposed length units (mm). It can be seen that the exhaust pressure is highest after the exhaust valves on cylinder 3 have opened, which is due to the exhaust outlet of this cylinder being aligned with the inlet opening 32. Dashed line B.1 shows that the exhaust valves of cylinder 3 are opened 20 degrees earlier, and the dashed line line 3.1 shows what then happens to the exhaust pressure and that this then increases considerably, since the cylinder pressure will then (curve A) be higher (AA) when the opening takes place.

In an alternative embodiment of the invention, the arrangement instead comprises an internal combustion engine in the form of a V8 engine with eight cylinders, which then advantageously have an ignition sequence 1 5 4 2 6 3 7 8 and a shown Twin Scroll Turbo placed at one end of the internal combustion engine near cylinders 4 and 8. Then the exhaust valves from cylinders 4 and 8, and possibly also from cylinder 3, can advantageously be opened earlier to obtain an even distribution in the ignition sequence.

Computer program code for implementing a method according to the invention is suitably included in a computer program which can be read into the internal memory of a computer, such as the internal memory of an electronic control unit of a said arrangement, for example of a motor vehicle. Such a computer program is suitably provided via a computer program product comprising a data storage medium readable by an electronic control unit, which data storage medium has the computer program stored thereon. Said data storage medium is, for example, an optical data storage medium in the form of a CD-ROM, a DVD disc, etc., a magnetic data storage medium in the form of a hard disk, a floppy disk, a cassette tape, etc., or a flash memory or a memory of the type ROM, PROM, EPROM or EEPROM.

Fig. 4 very schematically illustrates an electronic control unit 36 comprising an execution means 37, such as a central processing unit (CPU), for executing computer software. The execution means 37 communicates with a memory 38, for example of the RAM type, via a data bus 39. The control unit 36 also comprises data storage medium 40, for example in the form of a Flash memory or a memory of the type ROM, PROM, EPROM or EEPROM.

The execution means 37 communicates with the data storage medium 40 via the data bus 39. A computer program comprising computer program code for implementing a method according to the invention is stored on the data storage medium 40.

The invention is of course not in any way limited to the embodiments described above, but a number of possibilities for modifications are possible. For example, the arrangement could lack turbochargers. Another alternative is that, for example, in an internal combustion engine of the type shown in Fig. 2, only the cylinders of one exhaust manifold, such as cylinders 1-3, are connected to the other line for EGR, and then, for example, the control unit may be designed to control the exhaust valves of cylinders 2 and 3 to open earlier in their combustion cycle than other cylinders. In that case, a single inlet opening to the second line could then be arranged in the middle of cylinder 3 or even a further such opening in the middle of cylinder 2.

It is pointed out once again that the definition of the control unit is to interpret as also including the case that controllability of the distance in crank degrees between the opening of the exhaust valves of the internal combustion engine cylinders is missing and this distance is set to be unchanged over time. 14

Claims (9)

1. 0 15 20 25 30 537 013 2. Claims Arrangement of an internal combustion engine (7) with at least three cylinders (1-6) comprising a first line (9) for supplying air to the internal combustion engine in the cylinders, a second line (18) for conducting a part of the internal combustion exhaust gases resulting in the engine back to said first conduit for mixing with fresh air in the air supply to the engine, an outlet (24-26, 28-30) for exhaust gases from at least one of the cylinders being connected to said second conduit (18) , characterized in that all the exhaust valves of at least one first said cylinder (3, 4), which have their exhaust outlet (26, 28) connected to said second line (18), are arranged to open at least 5 crank degrees earlier in the combustion cycle of that cylinder. than all the exhaust valves of at least one other second mentioned cylinder (1, 2, 5, 6). Arrangement according to claim 1, characterized in that said exhaust valves of said first cylinder (3, 4) are arranged to open 5. -60 degrees of cranking, 5-30 degrees of cranking or 10-20 degrees of cranking earlier than the exhaust valves of the at least one other mentioned cylinder (1, 2, 5, 6). Arrangement according to claim 1 or 2, characterized in that at least one said second cylinder (22) has its exhaust outlet (24, 25, 29, 30) connected to said second line (18). . Arrangement according to claim 3, characterized in that all cylinders (1- 6.) of the engine has its exhaust outlets (24-26, 28-30) connected to said second line (18). Arrangement according to any one of the preceding claims, characterized in that said second line (18) comprises at least one inlet opening (32, 33) for receiving exhaust gases arranged close to, as in the middle of, specially aligned with , the exhaust outlet (26, 28) of said first cylinder (3, 4). Arrangement according to claim 1, characterized by a control unit (23) which is designed to control said exhaust valves of at least a first said cylinder (3, 4) to open at least 5 degrees of cranking earlier in that combustion cycle of that cylinder than all exhaust valves of at least another second said cylinder. (1, 2, 5, 6). Arrangement according to claim 6, characterized in that the control unit (23) is designed to control the exhaust valves of said at least one first cylinder (3, 4) to open 5-60 crank degrees, 5-30 crank degrees or 10-20 crank degrees earlier than all exhaust valves of at least one other second mentioned cylinder (1, 2, 5,6). Arrangement according to any one of the preceding claims, characterized in that it comprises an exhaust gas collector (27, 31) designed to receive exhaust gases from several said cylinders (1-6) and connected to an exhaust outlet line (13, 14) for discharging exhaust gases, and that the second conduit (18) has at least one opening (32, 33) opening in the exhaust manifold for receiving exhaust gases arranged at one end of the exhaust manifold in the region of its connection to the exhaust outlet conduit. . Arrangement according to any one of the preceding claims, characterized in that it comprises turbochargers (10) connected to the first line (9) for compressing air supplied to the engine by means of exhaust gases from the engine, and said turbocharger (10) is a turbocharger. unit with fixed geometry. Arrangement according to claims 8 and 9, characterized in that the turboag 11 12. 13. 13. 14. assembly on the exhaust side of the engine is connected to the exhaust outlet line (13, 14) downstream of the exhaust manifold opening ( 32, 33). Arrangement according to one of the preceding claims, characterized in that the engine (7) has at least two said first cylinders (3, 4), and in that a control unit (23) of the arrangement is designed to initiate combustion in the engine cylinders (1-6) in an order so that said first cylinders are substantially evenly distributed or evenly distributed therein. Arrangement according to any one of the preceding claims, characterized in that a control unit (23) of the arrangement is designed to control said exhaust valves of said at least one first cylinder (3, 4) to have a fixed opening distance in crank degrees to all exhaust valves of at least another second said cylinder (1, 2, 5, 6). Arrangement according to one of the preceding claims, characterized in that the internal combustion engine (7) has six cylinders (1-6), and in that two (3, 4) of the cylinders are first cylinders which both have their exhaust outlet (26, 28). connected to said second line (18) and which have exhaust valves as a control unit (23) of the arrangement is designed to control to open at least 5 crank degrees earlier in the combustion cycle than the exhaust valves of the other four other cylinders (1, 2, 5, 6). Arrangement according to any one of claims 1-12, characterized in that the internal combustion engine has eight cylinders, and that two, three or four of the cylinders are first cylinders which both have their exhaust outlet connected to said second line and which have exhaust valves. 2D 25 30 15. 16. 537 013 as a control unit of the arrangement is designed to control to open at least 5 crank degrees earlier in the combustion cycle than the exhaust valves of the other mentioned second cylinders. Method for controlling air supply to an internal combustion engine (7) with at least three cylinders (1-6), in which a part of the exhaust gases resulting from the combustion in the engine is returned and mixed into fresh air for supply together therewith to the engine, characterized in that all exhaust valves of at least one first said cylinder (3, 4), which have their exhaust outlet (26, 28) connected to a line (18) for conducting exhaust gases to be mixed into the fresh air for supplying air to the engine, are opened at least 5 degrees of cranking earlier in the combustion cycle of that cylinder than all the exhaust valves of at least one other second mentioned cylinder (1, 2, 5, 6). Computer program which is chargeable directly into the internal memory of a computer, which computer program comprises computer program code for bringing the computer, for an arrangement at an internal combustion engine (7) with at least three cylinders (1-6), a first line (9) for air supply to the engine for combustion in the cylinders and a second line (18) for conducting a part of the exhaust gases resulting from the combustion in the engine back to said first line for mixing with fresh air for the air supply to the engine: - to control exhaust valves of said cylinders (1-6) and - in controlling the exhaust valves controlling all the exhaust valves of at least one first said cylinder (3, 4) having their exhaust outlet (26, 28) connected to said second conduit (18), to be opened at least 5 degrees of cranking earlier in the combustion cycle of that cylinder than all the exhaust valves of at least one other second mentioned cylinder (1, 2, 5, 6). 18 10 1 7. 1 8. 1 A computer program product comprising a computer storage medium readable by a computer, the computer program code of a computer program according to claim 16 being stored on the data storage medium. Electronic control unit of an arrangement at an internal combustion engine comprising an execution means (37), a memory (38) connected to the execution means and a data storage medium (40) connected to the execution means, the computer program code of a computer program according to claim 16 being stored on said data storage medium. Internal combustion engine, characterized in that it is provided with an arrangement according to any one of claims 1-14. 19