METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE, DEVICE, AND INTERNAL COMBUSTION ENGINE

Abstract

A method for operating an internal combustion engine, device, and an internal combustion engine including a motor which has a crankshaft. A charge air flow is supplied to the motor that is compressed by means of a compressor via a second rotational movement, and a power turbine for producing a first rotational movement is acted on by an exhaust gas flow discharged from the motor. The following steps are provided: in a first operating mode, operating the internal combustion engine in four-stroke operation, and in a second operating mode, operating the internal combustion engine in two-stroke operation. The crankshaft can be driven by the power turbine via the first rotational movement, and the compressor can be driven by the crankshaft via the second rotational movement, wherein the second rotational movement for the compressor can be set differently from the first rotational movement of the power turbine.

Claims

1. A method for operating an internal combustion engine, the internal combustion engine including a motor having a crankshaft, the method comprising the steps of: compressing a charge air flow with a compressor and supplying the charge air flow to the motor, the compressing of the charge air flow taking place via a second rotational movement and a power turbine for producing a first rotational movement acted on by an exhaust gas flow discharged from the motor; operating the internal combustion engine in a first operating mode, the first operating mode being a four-stroke operation of the motor; operating the internal combustion engine in a second operating mode, the second operating mode being a two-stroke operation of the motor; driving the crankshaft by the power turbine by way of the first rotational movement; and driving the compressor by the crankshaft by way of the second rotational movement, the second rotational movement for the compressor being settable differently from the first rotational movement of the power turbine.

2. The method as claimed in claim 1, further comprising the step of switching from the four-stroke operation of the first operating mode to the two-stroke operation of the second operating mode.

3. The method as claimed in claim 1, further comprising the step of switching from the two-stroke operation of the second operating mode to the four-stroke operation of the first operating mode.

4. The method as claimed in claim 1, wherein the power turbine is couplable by way of a turbine coupling to the crankshaft of the motor.

5. The method as claimed in claim 4, wherein the turbine coupling is a hydrodynamic coupling, in particular a fill-controlled hydrodynamic coupling.

6. The method as claimed in claim 1, wherein the compressor is coupled by way of a compressor coupling to the crankshaft of the motor.

7. The method as claimed in claim 6, wherein the compressor coupling is a hydrodynamic coupling, in particular a fill-controlled hydrodynamic coupling.

8. The method as claimed in claim 1, wherein the power turbine is coupled to the crankshaft via a power turbine transmission arranged between the turbine coupling and the crankshaft.

9. The method as claimed in claim 1, wherein the compressor is coupled to the crankshaft via a compressor transmission arranged between the compressor coupling and the crankshaft.

10. The method as claimed in claim 1, wherein during operation of the internal combustion engine in two-stroke operation the cylinders are scavenged by head loop scavenging.

11. A device for operating an internal combustion engine having a motor with a crankshaft, the device comprising: a charger arrangement including: at least one compressor that supplies a charge air flow to the motor, the compressor compressing the charge air; and at least one power turbine that is acted on by an exhaust gas flow discharged from the motor, the charger arrangement carrying out a method including the steps of: compressing a charge air flow with the at least one compressor and supplying the charge air flow to the motor, the compressing of the charge air flow taking place via a second rotational movement and the power turbine for producing a first rotational movement acted on by an exhaust gas flow discharged from the motor; operating the internal combustion engine in a first operating mode, the first operating mode being a four-stroke operation of the motor; operating the internal combustion engine in a second operating mode, the second operating mode being a two-stroke operation of the motor; driving the crankshaft by the power turbine by way of the first rotational movement; and driving the compressor by the crankshaft by way of the second rotational movement, the second rotational movement for the compressor is set differently from the first rotational movement of the power turbine.

12. An internal combustion engine, comprising: a motor with a crankshaft; and a charger arrangement including: at least one compressor that supplies a charge air flow to the motor, the compressor compressing the charge air; and at least one power turbine that is acted on by an exhaust gas flow discharged from the motor, the charger arrangement carrying out a method including the steps of: compressing a charge air flow with the at least one compressor and supplying the charge air flow to the motor, the compressing of the charge air flow taking place via a second rotational movement and the power turbine producing a first rotational movement is acted on by an exhaust gas flow discharged from the motor; operating the internal combustion engine in a first operating mode, the first operating mode being a four-stroke operation of the motor; operating the internal combustion engine in a second operating mode, the second operating mode being a two-stroke operation of the motor; driving the crankshaft by the power turbine by way of the first rotational movement; and driving the compressor by the crankshaft by way of the second rotational movement, the second rotational movement for the compressor is set differently from the first rotational movement of the power turbine.

13. The internal combustion engine as claimed in claim 12, wherein the driving steps are carried out by a coupling arrangement that is of electromechanical design, wherein the first rotational movement is converted into a generator current or the generator current is converted into the second rotational movement.

14. The internal combustion engine as claimed in claim 12, wherein the power turbine drives a generator.

15. The internal combustion engine as claimed in claim 12, wherein the crankshaft of the motor drives a generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0055] FIG. 1A shows a schematic illustration of one sequence of a two-stroke combustion process;

[0056] FIG. 1B is a schematic illustration of another sequence of the two-stroke combustion process;

[0057] FIG. 2A shows a schematic illustration of one sequence of a four-stroke combustion process that is sequentially shown in FIGS. 2A-2D;

[0058] FIG. 2B shows a schematic illustration of one sequence of the four-stroke combustion process that is sequentially shown in FIGS. 2A-2D;

[0059] FIG. 2C shows a schematic illustration of one sequence of the four-stroke combustion process that is sequentially shown in FIGS. 2A-2D;

[0060] FIG. 2D shows a schematic illustration of one sequence of the four-stroke combustion process that is sequentially shown in FIGS. 2A-2D;

[0061] FIG. 3 shows a schematic illustration of a development of a charger arrangement according to an embodiment of the present invention;

[0062] FIG. 4 shows a schematic illustration of an alternative implementation according to another embodiment of the present invention;

[0063] FIG. 5 shows a schematic illustration of scavenging of a cylinder in two-stroke operation according to the concept of the invention; and

[0064] FIG. 6 shows a motor characteristic map applicable to the motor components of the present invention illustrated in FIGS. 1-5.

[0065] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0066] Now referring to the drawings, and more particularly to FIG. 1A and FIG. 1B that show a schematic illustration of the sequence of a two-stroke combustion process. FIG. 1A illustrates a cylinder 420 in which there is arranged a piston 424, which is movable translationally in the direction of the cylinder axis of cylinder 420. In the illustration, piston 424 is situated in the vicinity of bottom dead center BDC. According to the principle of head loop scavenging, gas, in particular a two-stroke charge air flow L2T, flows into a combustion chamber 432 formed substantially from a cylinder wall 422 of cylinder 420 and piston 424. For this purpose, charge air L2T is conveyed through at least one inlet valve 426E into combustion chamber 432.

[0067] Two-stroke charge air flow L2T is for this purpose previously compressed to a sufficiently high pressure for the two-stroke operation by a compressor 300 which is driven according to the concept of the invention. At the same time, exhaust gas situated in combustion chamber 432 is displaced as charge air flow L2T flows in. This exhaust gas leaves combustion chamber 432 in the form of a two-stroke exhaust gas flow A2T through at least one outlet valve 426A which in the present case is arranged on the upper side of cylinder 420 in the vicinity of top dead center TDC.

[0068] The operation illustrated in FIG. 1A thus comprises a charging of combustion chamber 432 with charge air L2T and virtually at the same time an ejection of exhaust gas A2T.

[0069] In FIG. 2B, piston 424 is situated in the vicinity of top dead center TDC, that is to say combustion chamber 432 has nearly reached its minimum volume. This means that charge air L2T which previously flowed into combustion chamber 432 has been compressed by the upward movement of piston 424 and thus by the reduction of combustion chamber 432. Here, inlet valve 426E and outlet valve 426A, 426 are closed to prevent charge air L2T from exiting. The state illustrated represents virtually the end of the compression operation.

[0070] An ignition IGN of the compressed gas in combustion chamber 432 then causes piston 426 to be moved downward in the direction of bottom dead center BDC by the expanding gas in the phase which is also referred to as working phase. Virtually upon bottom dead center BDC being reached by piston 424, the cycle begins anew by the charging or ejecting operation illustrated in FIG. 1A.

[0071] Now, additionally referring to FIGS. 2A to 2D, there is shown a schematic illustration of the sequence of a four-stroke combustion process. FIG. 2A illustrates the operation of charging in a cylinder 420. By virtue of the position of a piston 424 close to bottom dead center TBC, combustion chamber 432 has virtually its largest possible volume. Particularly by previous pressurization by a compressor 300 (not shown here in more detail) and/or by a negative pressure produced by the downward movement of piston 424, a four-stroke charge air flow L4T flows through opened inlet valve 426E into combustion chamber 432. By contrast to the two-stroke operation illustrated in FIG. 1A, outlet valve 426A is closed in the present case.

[0072] In FIG. 2B, piston 424 is situated close to top dead center TDC. Inlet valve 426E and outlet valve 426A are closed; the gas which flowed in in the previous step illustrated in FIG. 2A is thus already compressed at the presently illustrated time point. The state illustrated in FIG. 2B represents virtually the end of the compression. There occurs an ignition IGN.

[0073] In FIG. 2C, piston 424 is again situated at bottom dead center BDC. This state has been preceded by an expansion by ignition IGN of the compressed gas, which in turn has occurred subsequent to the end state of compression illustrated in FIG. 2B. The state illustrated in FIG. 2C thus represents virtually the end of the work or the working phase in which in particular a drive movement of a motor 1200 is produced.

[0074] In FIG. 2D, there finally occurs the ejection of an exhaust gas which has arisen during the preceding expansion or ignition. For this purpose, outlet valve 426A is opened such that, during an upward movement of piston 424 or with a reduction of combustion chamber 432, the exhaust gas leaves combustion chamber 432 in the form of a four-stroke exhaust gas flow A4T.

[0075] FIG. 3 shows a schematic illustration of a development of a charger arrangement 100 according to the concept of the invention. Here, charger arrangement 100 comprises in particular a power turbine 200 and a compressor 300. An exhaust gas flow A discharged from a motor 1200 is in particular guided completely through power turbine 200 in which the energy of the exhaust gas is converted into movement energy, in particular into a first rotational movement RT. Charger arrangement 100 further comprises a coupling arrangement 150. In the present case, the rotational movement produced by the power turbine is transmitted via a turbine output shaft 202 to a turbine coupling 250, which is preferably designed as a hydrodynamic coupling.

[0076] The hydrodynamic coupling makes it possible in particular for rotational speed jumps to be adapted in a jerk-free manner or jerk-reducing manner and for torsional vibrations to be advantageously damped. The rotational movement is further transmitted from turbine coupling 250 via a power turbine transmission drive shaft 204 to a power turbine transmission 280 which serves particularly for rotational speed adaptation of the rotational movement produced by power turbine 200. The rotational speed adaptation occurs in particular to reduce or step down the generally relatively high rotational speed of power turbine 200 to a rotational speed suitable for coupling into a crankshaft 400 of motor 1200. Typical step-up or step-down ratios here are between 25 and 30.

[0077] The stepped-down rotational movement is transmitted from power turbine transmission 280 to crankshaft 400 of motor 1200. In this way, the energy obtained from exhaust gas flow A is returned in mechanical form to motor 1200. With particular preference, power turbine transmission 280 further comprises a freewheel in order to prevent the power flow in the case that the rotational speed of power turbine transmission drive shaft 204 is less than the rotational speed of crankshaft 400.

[0078] Furthermore, according to the concept of the invention, a compressor transmission 380 is driven by crankshaft 400 of motor 1200. Compressor transmission 380 changes the rotational speed of the rotational movement emanating from crankshaft 400 in such a way that it is suitable, in particular sufficiently high, to drive compressor 300.

[0079] The correspondingly stepped-up rotational movement is then transmitted via a compressor transmission output shaft 304 from compressor transmission 380 to a compressor coupling 350, which in turn provides a second rotational movement RV for compressor 300 which is transmitted via a compressor drive shaft thereto. Analogously to turbine coupling 250, compressor coupling 350 has the advantage that rotational speed jumps are adjusted in particular in a jerk-free manner and torsional vibrations are damped by the mode of operation of a hydrodynamic coupling. In particular, a fill-controlled hydrodynamic coupling ensures that the transmission power of the compressor coupling can be controlled or regulated by adapting the filling level of a coupling fluid within a coupling space 258. In particular, it is possible in this way for a rotational speed of compressor 300 that is optimum in each case for an instantaneous operating state of motor 1200 to be set in a regulating manner.

[0080] Compressor 300, which in the present case is designed as a flow compressor, is mechanically driven in this manner by the rotational movement of crankshaft 400. Consequently, compressor 300 can advantageously compress a charge air flow L supplied to motor 1200.

[0081] Also schematically illustrated is a device 900 for operating internal combustion engine 1000, which in the present case comprises a regulating and processor means 910. As illustrated in the present case by dashed lines, this regulating and processor means 910 is connected in a signal-conducting manner to turbine coupling 250, power turbine transmission 280, compressor coupling 350 and compressor transmission 380. In this way, the concept of the invention can be implemented for example in the sense of an automatic system or control circuit illustrated in this preferred embodiment. In particular, the rotational movements, that is to say here the rotational movements RT and RV, can be set according to this embodiment. These rotational movements RT and RV can be stepped up or stepped down by actuating power turbine transmission 280 and/or compressor transmission 380.

[0082] Additionally or alternatively, the transmission of the rotational movement can be interrupted or used by actuating turbine coupling 250 and/or compressor coupling 350.

[0083] Furthermore, the regulating and processor means 910 is in signal-conducting connection with an, in particular superordinate, controller of internal combustion engine 1000, said controller being only indicated here, but not shown in further detail. Additionally or alternatively, it can also be part thereof in order to implement the method according to the concept of the invention, in particular the switching of motor 1200 from two-stroke operation to four-stroke operation or from four-stroke operation to two-stroke operation.

[0084] FIG. 4 shows a schematic illustration of an alternative implementation according to the concept of the invention. There is shown an internal combustion engine 1000 having a charger arrangement 100 which comprises a power turbine 200 and a compressor 300. Power turbine 200 is acted on by an exhaust gas flow A originating from a motor 1200.

[0085] The thus produced movement energy or rotational movement RT is transmitted via a generator drive shaft 212 to a turbine-side generator 220. This turbine-side generator 220 converts the movement energy into electrical energy which is transmitted via a turbine-side generator line 221 particularly in the form of a turbine-side generator current 242 to a turbine regulator 240.

[0086] In turbine regulator 240, turbine-side generator current 242 is regulated according to setpoint values 241 which originate in particular from a superordinate controller, in particular motor electronics. A turbine-side generator current 243 regulated in this way is then transmitted via a turbine-side motor line 222 to a turbine-side motor 230. The latter is connected in a torque-transmitting manner to a crankshaft 400 of motor 1200, with the result that a rotational movement RM produced by turbine-side motor 230 can be used to drive crankshaft 400, in particular to support the rotational movement RK of crankshaft 400.

[0087] By contrast with the development shown in FIG. 3, there thus does not take place in the present case a complete mechanical recovery of the exhaust gas energy. Instead, a conversion into electrical energy, a regulation and a subsequent back-conversion into mechanical energy result in an electromechanical recovery of the exhaust gas energy.

[0088] Furthermore, according to the concept of the invention, crankshaft 400 in this development is connected in a torque-transmitting manner to a compressor-side generator 224.

[0089] This compressor-sign generator 224 converts the movement energy transmitted by crankshaft 400 in the form of a rotational movement into electrical energy which is transmitted in particular in the form of a compressor-side generator current 246 via a compressor-side generator line 225 to a compressor regulator 244. In this compressor regulator 244, compressor-side generator current 246 is regulated according to setpoint values 245 for compressor regulator 244. Analogously to turbine regulator 240, setpoint values 245 likewise originate in particular from a superordinate controller, in particular motor electronics.

[0090] A regulated compressor-side generator current 247 is then channeled via a compressor-side motor line 226 to a compressor-side motor 234. This compressor-side motor 234 is connected in a torque-transmitting manner to compressor 300 via a compressor drive shaft 312. The driving of compressor 300 by compressor-side motor 234 therefore compresses a charge air flow L which is supplied to motor 1200.

[0091] By contrast to the development shown in FIG. 3, in the present case a rotational movement is electromechanically transmitted from crankshaft 400 to compressor 300, that is to say not completely mechanically, but by a conversion of movement energy into electrical energy, a regulation and a back-conversion of electrical energy into movement energy. What is concerned in the present case is thus an electromechanical coupling arrangement 150.

[0092] Such a development particularly advantageously makes it possible, both on the turbine side and compressor side, for a rotational speed conversion to occur through the conversion of movement energy into electrical energy, and vice versa. Furthermore, it is also possible that the movement energy converted into electrical energy can be stored by suitable energy stores, in particular batteries, and can be converted back at a later time point into movement energy again.

[0093] FIG. 5 further shows the principle of the scavenging of a cylinder 420 particularly in two-stroke operation. For this purpose, the cylinder is illustrated in a state analogous to the state shown in FIG. 1A. Here, combustion chamber 432 is pronounced virtually as far as possible, that is to say piston 424 is situated virtually at bottom dead center BDC. A charge air flow L2T flows through at least one inlet valve 426E into combustion chamber 432. According to the concept of the invention, a charge air flow L is compressed by a compressor 300 and channeled into at least one supply duct 434 via a charge air cooler 440 and a distributor (not shown in more detail here). Here, according to the concept of the invention, compressor 300 is not directly mechanically connected to power turbine 200, as would be the case in the transferred sense in an exhaust gas turbocharger. In the present case, a torque-transmitting connection between power turbine 200 and compressor 300 is substantially produced via a coupling arrangement 150 (not shown here) and a crankshaft 400. In this way, there is in particular the possibility of closing or opening the torque-transmitting connection or of only partially producing it in particular by a fill-controlled hydrodynamic coupling, in particular to influence the rotational speed of the transmitted rotational movement. Furthermore, there is the possibility of stepping up or stepping down the rotational movement by means of transmissions (not shown further here).

[0094] Furthermore, the flow of charge air flow L2T into combustion chamber 432 according to the concept of a two-stroke motor is accompanied by the simultaneous ejection of an exhaust gas flow A2T via at least one opened outlet valve 426A and furthermore an exhaust gas manifold 430. Exhaust gas flow A is furthermore channeled to power turbine 200 in which the remaining energy contained in exhaust gas flow A is further converted into a mechanical rotational movement. However, this energy is lower by comparison with an exhaust gas flow A4T discharged in four-stroke operation.

[0095] FIG. 6 schematically shows the characteristic map of a motor. Here, the effective average pressure p.sub.mc, is plotted on the ordinate and is for its part proportional to torque M.sub.d of the motor via the following relationship:

[00001]$p_{\mathrm{me}}=\frac{M_d*2.Math..Math.}{V_H*i}$

[0096] Here, furthermore, V.sub.H is the total swept volume of the motor and i is the number of working cycles per revolution (0.5 for four-stroke operation, 1 for two-stroke operation).

[0097] The motor rotational speed n.sub.Mot is plotted on the abscissa. Furthermore, isolines B1-B7 each denote operating points of equal effective motor power P.sub.e. Operating point B1 corresponds in the present case to a motor power of 10%, operating point B2 to a motor power of 20%, operating point B3 to a motor power of 30%, operating point B4 to a motor power of 50%, and operating point B5 to a motor power of 70%. According to the concept of the invention, switching to 2-stroke operation is possible or expedient at any time in these operating points B1-B5, in particular to increase the motor power in the short term and to achieve an operating point in an upper region further to the right in the diagram illustrated here. Isolines B6 and B7 illustrated as solid lines show certain operating points of the motor. Here, isoline B6 corresponds to a motor power of 80%, and isoline B7 corresponds to a motor power of 100%. Such operating points are approached particularly in standby-state operation, where an operation in two-stroke operation is not advantageous. A two-stroke operation is therefore expedient whenever, particularly in the transient range, quick power jumps are intended to be achieved. The area K furthermore denotes the total power range of the motor, which is delimited by limit G enclosing power range K.

[0098] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SIGNS

[0099] 100, 100 Charger arrangement [0100] 150, 150 Coupling arrangement [0101] 200, 200 Power turbine [0102] 202 Turbine output shaft [0103] 204 Power turbine transmission drive shaft [0104] 212 Generator drive shaft [0105] 220 Turbine-side generator [0106] 221 Turbine-side generator line [0107] 222 Turbine-side motor line [0108] 224 Compressor-side generator [0109] 225 Compressor-side generator line [0110] 226 Compressor-side motor line [0111] 230 Turbine-side motor [0112] 234 Compressor-side motor [0113] 240 Turbine regulator [0114] 241 Setpoint values for the turbine regulator [0115] 242 Turbine-side generator current [0116] 243 Regulated turbine-side generator current [0117] 244 Compressor regulator [0118] 245 Setpoint values for the compressor regulator [0119] 246 Compressor-side generator current [0120] 247 Regulated compressor-side generator current [0121] 250 Turbine coupling [0122] 258 Coupling space [0123] 280 Power turbine transmission [0124] 300, 300 Compressor [0125] 302 Compressor drive shaft [0126] 304 Compressor transmission output shaft [0127] 312 Compressor drive shaft [0128] 350 Compressor coupling [0129] 380 Compressor transmission [0130] 400, 400 Crankshaft [0131] 420 Cylinder [0132] 422 Cylinder wall [0133] 424 Piston [0134] 426 Valve [0135] 426A Outlet valve [0136] 426E Inlet valve [0137] 430 Exhaust gas manifold [0138] 432 Combustion chamber [0139] 434 Supply duct [0140] 440 Charge air cooler [0141] 900 Device for operating an internal combustion engine [0142] 910 Regulating and processor means [0143] 1000, 1000 Internal combustion engine [0144] 1200, 1200 Motor [0145] A, A Exhaust gas flow [0146] A2T Cylinder exhaust gas flow in 2-stroke operation [0147] A4T Cylinder exhaust gas flow in 4-stroke operation [0148] B1-B7 Isolines with operating points each of equal effective motor power [0149] G Limit of the power range [0150] K Power range [0151] L, L Charge air flow [0152] L2T Cylinder charge air flow in 2-stroke operation [0153] L4T Cylinder charge air flow in 4-stroke operation [0154] TDC Top dead center [0155] RK Rotational movement of the crankshaft [0156] RM Rotational movement of the turbine-side motor [0157] RT Rotational movement of the power turbine, first rotational movement [0158] RV Rotational movement for the compressor, second rotational movement [0159] BDC Bottom dead center [0160] IGN Ignition