Supercharged internal combustion engine

Abstract

An internal combustion engine is described. The internal combustion engine comprises a valve control which is configured to close inlet valves of the internal combustion engine at Miller or Atkinson closing times. An electrified exhaust-gas turbocharger of the internal combustion engine comprises an electric machine which is operable selectively as a motor or generator. A control unit operates the electric machine of the electrified exhaust-gas turbocharger as a motor in a first load range of the internal combustion engine and as a generator in a second load range which corresponds to greater loads of the internal combustion engine than the first load range.

Claims

1. An internal combustion engine comprising: a valve controller which is configured to close inlet valves of the internal combustion engine at Miller or Atkinson closing times, wherein the closing times of the valve controller are invariable; an electrified exhaust-gas turbocharger having an electric machine which is operable selectively as a motor or generator; and a control unit which is configured to operate the electric machine of the electrified exhaust-gas turbocharger as a motor in a first load range of the internal combustion engine and to operate same as a generator in a second load range which corresponds to greater loads of the internal combustion engine than the first load range.

2. The internal combustion engine according to claim 1, wherein the control unit is configured to not operate the electric machine of the electrified exhaust-gas turbocharger as a generator in the first load range and/or to operate the electric machine of the electrified exhaust-gas turbocharger as a generator only in the second load range.

3. The internal combustion engine according to claim 1, wherein the exhaust-gas turbocharger comprises a compressor and a turbine driving the compressor, which are designed to generate a charge pressure that compensates a charging volume, reduced with respect to the displacement on account of the closing times, in the first load range of the internal combustion engine.

4. The internal combustion engine according to claim 3, wherein a turbine cross section of the turbine is dimensioned or a turbine geometry of the turbine is shaped such that the exhaust-gas turbocharger compensates the charging volume, reduced by the closing times, by the charge pressure in the first load range.

5. The internal combustion engine according to claim 3, wherein the turbine cross section and/or the turbine geometry is invariable.

6. The internal combustion engine according to claim 4, wherein the control unit is configured to convert a mechanical power of the turbine, which goes beyond the power required by the compressor for compensation, by means of the electric machine operated as a generator, in the second load range.

7. The internal combustion engine according to claim 3, wherein the electric machine of the exhaust-gas turbocharger is rigidly coupled to the turbine of the exhaust-gas turbocharger.

8. The internal combustion engine according to claim 1, wherein the valve controller comprises a camshaft driven by a crankshaft of the internal combustion engine, said camshaft determining the closing times.

9. The internal combustion engine according to claim 1, wherein the internal combustion engine also comprises a rechargeable energy store which is connected or connectable to the electric machine of electrified exhaust-gas turbocharger in order to store the electrical energy output during operation as a generator.

10. The internal combustion engine according to claim 1, wherein the internal combustion engine also comprises a second electric machine, which is configured as a power machine in order to convert electrical energy output by the electrified exhaust-gas turbocharger in the second power range.

11. The internal combustion engine according to claim 10, wherein the second electric machine is connected or connectable to the electrical energy store for power supply.

12. The internal combustion engine according to claim 10, wherein the control unit is also configured to connect the second electric machine to the electric machine, operated as a generator, of the electrified exhaust-gas turbocharger for power supply by said electric machine.

13. The internal combustion engine according to claim 1, wherein a wastegate is arranged in the exhaust-gas flow of the internal combustion engine, and the control unit is also configured to open the wastegate in a part of the second load range which corresponds to high loads within the second load range.

14. A motor vehicle, comprising: an internal combustion engine; a valve controller which is configured to close inlet valves of the internal combustion engine at Miller or Atkinson closing times, wherein the closing times of the valve controller are invariable; an electrified exhaust-gas turbocharger having an electric machine which is operable selectively as a motor or generator; and a control unit which is configured to operate the electric machine of the electrified exhaust-gas turbocharger as a motor in a first load range of the internal combustion engine and to operate same as a generator in a second load range which corresponds to greater loads of the internal combustion engine than the first load range.

15. The motor vehicle of claim 14, wherein the motor vehicle is a commercial vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the disclosure are described in the following text with reference to the appended drawings, in which:

(2) FIG. 1 shows a schematic block diagram of one exemplary embodiment of the internal combustion engine;

(3) FIG. 2 shows a schematic diagram of the valve closing times according to different exemplary embodiments; and

(4) FIG. 3 shows a schematic diagram with different power ranges of the internal combustion engine according to an implementation that is combinable with each exemplary embodiment.

DETAILED DESCRIPTION

(5) FIG. 1 shows a schematic block diagram of one exemplary embodiment of an internal combustion engine that is denoted overall by the reference sign 100. The internal combustion engine 100 comprises a valve controller 102, which closes at least inlet valves 104 of the internal combustion engine 100 away from BDC, in particular at Miller or Atkinson closing times. Furthermore, the internal combustion engine 100 comprises an electrified exhaust-gas turbocharger 106 with a turbine 108, a compressor 110 and an electric machine 112. The electric machine 112 of the electrified exhaust-gas turbocharger 106 is operable selectively as a motor or as a generator, for which reason it can also be referred to as an electric motor-generator unit. Furthermore, the internal combustion engine 100 comprises a control unit 114 for controlling the operation of the electric machine 112 of the electrified exhaust-gas turbocharger 106.

(6) According to the control unit 114, in a first load range of the internal combustion engine 100, the electric machine 112 is operated at least at times as a motor. For example, the electric machine 112 can be operated with a variable motor power in the first load range. If electromotive support for the drive of the compressor 110 by the turbine 108 is not necessary, the electric machine 112 can be mechanically and/or electrically decoupled. In a second load range, which comprises greater loads of the internal combustion engine 100 than the first load range, the electric machine 112 is operated at least at times as a generator.

(7) The closing times set by the valve controller 102, for example a camshaft 116 with fixed cams 118, are invariable over the load ranges. The valve controller 102 and the inlet valves are also referred to as an inlet system. The cross section of the exhaust-gas turbine 108 is dimensioned such that sufficient air supply to the internal combustion engine 100 is ensured in the first load range (for example at low to average levels of power of the internal combustion engine 100) without electrical support by the electric machine 112. In the second load range, the exhaust-gas pressure would rise greatly before the inlet into the turbines 108 (for example at higher levels of power) on account of the narrow cross section (for example relative to the exhaust-gas flow of the internal combustion engine 100) of the exhaust-gas turbine 108. This is counteracted by the electric machine 112 of the electrified exhaust-gas turbocharger 106 being operated as a generator. In particular, excess mechanical energy of the exhaust-gas turbine 108 is converted into electrical energy by the electric machine 112 during operation as a generator.

(8) To this end, the internal combustion engine 100 can comprise an electrical energy store 124 and/or a second electric machine 122. The second electric machine 122 is connected on the output side to the internal combustion engine 100, for example to a crankshaft 120 of the internal combustion engine 100. The excess energy of the exhaust-gas turbine 108 is fed to the electrical energy store 124 and/or output via the second electric machine 122 in a parallel hybrid drive together with a mechanical output power of the internal combustion engine 100.

(9) When the internal combustion engine 100 is used in a vehicle, the excess energy of the exhaust-gas turbine 108 can be output to a drive train of the vehicle. The internal combustion engine 100 in the narrower sense, i.e. the combustion motor without the contribution of the second electric machine 122, is for example the main drive of the vehicle.

(10) In the first power range, the electric machine 112 is at most operated as a motor. Preferably, in the first power range, the control unit 114 effects supercharging, independent of the existing exhaust-gas pressure, by controlling the operation of the electric machine 112 as a motor.

(11) In the second power range, the electric machine 112 is operated at least at times as a generator. The control of the operation of the electric machine 112 can differentiate in the second power range of the internal combustion engine 100 between a first subrange and a second subrange, which corresponds to lower levels of power of the internal combustion engine 100. In the first subrange, the electric power converted by the generator increases with increasing power of the internal combustion engine 100. In the second subrange, the generator power of the electric machine 112 is limited to a maximum power during operation as a generator. A further increase in the exhaust-gas pressure is prevented by a wastegate 136 or optionally by opening a turbine adjustment geometry of the exhaust-gas turbine 108.

(12) FIG. 2 shows a schematic diagram 200 of Miller and Atkinson closing times according to different embodiment variants 202 and 204 of the valve controller 102. An angular position of the crankshaft 120 is plotted on the horizontal axis. A valve lift effected by the cam 118 is plotted on the vertical axis.

(13) The inlet system of the internal combustion engine 100 has fixed control timing for closing (closing time for short) of the inlet valves 104 in the intake stroke, i.e. invariable closing times. The diagram 200 also shows the comparative example 203 of a conventional filling-optimized design of the closing time. Compared with the filling-optimized comparative example 203, the closing time appears as an earlier closing point of an inlet stroke curve with Miller closing times in the embodiment variant 202 or as a later closing point of an inlet stroke curve with Atkinson closing times in the embodiment variant 204.

(14) The exhaust-gas turbocharger 106 comprises the exhaust-gas turbine 108 and the compressor 110 and is coupled to the electric machine 112. The compressed charge air passes via a charge-air cooler 126 to the inlet system. The control unit 114 processes (inter alia) the signal from a pressure sensor 128 in the outlet manifold 130 upstream of the turbine 108 and/or from a pressure sensor 132 in the charge-air pipe 134 (preferably downstream of the charge-air cooler 126). Alternatively or additionally to the pressure sensor 128, sensors for determining the combustion air ratio can be arranged in the exhaust-gas manifold 130 (or at some other location), the signals from said sensors being picked up by the control unit 114.

(15) If the measured pressure, the measured combustion air ratio or a value derived from the signals exceeds a predefined maximum value or setpoint value (predefined for example via a characteristic map with respect to the operating state of the internal combustion engine 100), the control unit 114 sends a signal for operation as a generator to the electric machine 112, which, as a generator, brakes the rotor of the exhaust-gas turbocharger 106 until the measured or derived value drops below the maximum value or assumes the setpoint value.

(16) The current generated in this way is fed to the electrical energy store 124 or directly supplies the electric motor 122 connected to the drive train.

(17) FIG. 3 shows a schematic diagram 300 of different operating modes in different load ranges. The load ranges are plotted on the horizontal axis of the diagram 300, for example as torque of the internal combustion engine 100. In order to keep the number of parameters for distinguishing the load ranges clear, the curve in FIG. 3 can represent the basic behaviour of the control unit 114 at a (for example typical or average) engine speed. In this regard, for the sake of clarity of illustration, and without limiting the technical teaching, the terms load, torque and power will no longer be differentiated here. A person skilled in the art can readily differentiate further between different operating modes by means of a higher-dimensional characteristic map (for example as a function of torque and engine speed). The specific values of such a characteristic map can change for different engine speeds.

(18) In the first load range 302, the characteristic-map setpoint values for the pressure and/or the combustion air ratio are not yet reached, and therefore no braking by generator takes place. This does not take place until the second load range, wherein, in the lower subrange 304 of the second load range, the electrical power 306 increases with increasing torque up to a predetermined maximum value. Once this has been reached, the wastegate 136 (the opening cross section 308 of which is shown schematically in the diagram 300) or an adjustable turbine geometry opens in the upper subrange 304-2 of the second load range, in order not to allow the generated electrical power 306 to increase above the maximum value before the maximum torque is reached.

(19) For a person skilled in the art, advantages of the internal combustion engine are apparent, in particular on the basis of the present exemplary embodiment. Thus, without complex variable valve controllers, the advantages of the Miller or Atkinson closing times are realizable, in particular as regards the reduced pressure load at very high specific levels of power. The described technology allows these closing times without a complicated cam adjustment system, as is otherwise required on account of the more unfavourable behaviour in partial-load operation and the lower dynamics.

(20) A further advantage of the Miller or Atkinson closing times that are achievable by means of the technology is a reduction in nitrogen oxide emissions. This effect is comparable with moderately implemented exhaust-gas recirculation (EGR), which can be dispensed with in this case. The omission of a variable valve drive and the EGR section results in much less structural complexity of the internal combustion engine.

(21) Furthermore, as a result of the omission of the EGR, the temperatures downstream of the turbine, or upstream of the inlet into an exhaust-gas aftertreatment (EGA), can increase. Thus, it is possible for the action of the EGA to be improved in particular at low mean pressures. Alternatively or in combination therewith, it is possible to achieve a reduction in the specific fuel consumption in parts of the operating range, for example given good efficiencies of the electrical and supercharging components. The improved action of the EGA can also contribute towards this via higher untreated nitrogen oxide emissions, for example since the improved action of the EGA allows higher untreated nitrogen oxide emissions. These occur for example when the start of injection is shifted to earlier times, this being associated normally with an improved efficiency of the high-pressure process. The technology can thus resolve a trade-off that usually exists (either less untreated nitrogen oxide emissions or lower fuel consumption).

(22) Although the disclosure has been described with reference to exemplary embodiments, it is obvious to a person skilled in the art that various changes can be made and equivalents can be used as a replacement. Furthermore, many modifications can be made in order to adapt a particular application of the internal combustion engine or a particular material to the teaching of the disclosure. Therefore, the disclosure is not limited to the disclosed exemplary embodiments.

LIST OF REFERENCE SIGNS

(23) 100 Internal combustion engine 102 Valve controller of the internal combustion engine 104 Inlet valves of the internal combustion engine 106 Exhaust-gas turbocharger of the internal combustion engine 108 Turbine of the electrified exhaust-gas turbocharger 110 Compressor of the electrified exhaust-gas turbocharger 112 Electric machine of the electrified exhaust-gas turbocharger 114 Control unit 116 Camshaft 118 Cam 120 Crankshaft of the internal combustion engine 122 Electric machine at the crankshaft 124 Electrical energy store 126 Charge-air cooler 128 Exhaust-gas pressure sensor 130 Exhaust-gas manifold 132 Charge-air pressure sensor 134 Charge-air pipe 136 Wastegate 200 Closing-times diagram 202 Miller closing times 203 Comparative example 204 Atkinson closing times 300 Operatin-modes diagram 302 First load range 304-1 Lower subrange of the second load range 304-2 Upper subrange of the second load range 306 Output power of the exhaust-gas turbocharger 308 Opening cross section of the wastegate