DE102015219299B4 - Method, computer program, storage medium and control unit for operating an internal combustion engine with an additional compressor - Google Patents

Abstract

Method for operating an internal combustion engine (100) with a main charger (200) and with an additional compressor (510) that can be driven electrically by a motor generator (520), the motor generator (520) being driven by the additional compressor (510) in selected operating states of the internal combustion engine (100) is driven and operated in a generator expansion operation and provides electrical power, and with a flap (700) arranged in a bypass (600) of the additional compressor (510), which is controlled depending on the operating state of the internal combustion engine (100) to form a definable opening cross section, characterized in that in a static recuperation operating point, the flap (700) arranged in the bypass (600) is controlled in such a way that a maximum possible air flow is routed via the electric additional compressor (510) and that a minimum possible air flow via the bypass ( 600) is guided.

Description

The invention relates to a method for operating an internal combustion engine with a main charger system and with an additional compressor that can be driven electrically by a motor generator, wherein the motor generator can be operated in selected operating states of the internal combustion engine, driven by the additional compressor, in a regenerative expansion mode and provides electrical power.

The invention also relates to a computer program that is set up to carry out each step of the method and a machine-readable storage medium on which the computer program is stored and an electronic control unit for such a combustion engine that is set up to carry out each step of the method.

State of the art

Electric compressors or additional compressors are known to support the functioning of a main charger, usually an exhaust gas turbocharger, in internal combustion engines of vehicles, which preferably work in the lower engine speed range. These compressors are operated, for example, in the form of directly driven radial compressors, so-called turbomachines, at a relatively high speed in the range of 50,000 rpm.

As an alternative to this, such compressors can also be designed as so-called positive-displacement machines, which are implemented, for example, as charging units in single-stage or two-stage arrangements, electrically or mechanically driven. It is known that positive-displacement machines are much better suited for what is known as expansion operation, in which the functioning of the compressor is reversed.

A compressor usually works when the internal combustion engine is subjected to high load requirements, for example when electrical energy is supplied in a first operating mode, the electric motor compressor mode or charging mode. The internal combustion engine can be either an Otto engine or a diesel engine.

In overrun phases of the vehicle, in which there are no load requirements on the internal combustion engine, the compressor is operated in a second operating mode, generator expansion mode. The energy released during these overrun phases is converted into electrical energy and stored in a battery, for example. This process of recovering energy is also referred to as recuperation and the energy generated in this way is referred to as recuperation energy. The generated electrical energy is stored, for example, in a battery in the vehicle and is available for upcoming acceleration processes or can be used to feed electrical consumers and in this way relieve the internal combustion engine when driving the generator.

The recuperation takes place in static recuperation operating points.

From the DE 60 2004 001 149 T2 , the EP 1 355 052 A1 and the WO 2015/066060 A1 Methods for operating internal combustion engines with additional compressors are already known.

Disclosure of Invention

Advantages of the Invention

In contrast, the method according to the invention for operating an internal combustion engine enables the expansion operation of the electric auxiliary compressor not only in static operation with constant conditions and speeds, but in particular also in transient operation. This is made possible and implemented by a flap which is arranged in a bypass of the electric auxiliary compressor and which can be controlled to form a predeterminable, desired opening cross section. It is provided that, in a static recuperation operating point, the controllable flap in the bypass is controlled in such a way that a maximum possible air flow is routed via the electric auxiliary compressor and a minimum possible air flow is routed via the bypass. Such a recuperation operating point is, for example, a moving vehicle at a constant speed of, for example, 80 km/h with a low load. In the event of small load changes, the changes in the air flow can be quickly regulated simply by the controllable flap in the bypass.

According to one embodiment, it is provided that, starting from the static recuperation operating point, a slight load jump towards a lower load is generated with the help of a larger regenerative braking torque and thus higher power generation during recuperation. In the event of a large jump in load to a lower load, which cannot be compensated for quickly enough by the electric auxiliary compressor, the throttle valve of the combustion engine closes quickly.

If a high (motor) load is suddenly requested during recuperation in the static recuperation operating point (regenerative). the adjustable flap is controlled in such a way that the bypass is fully open. In this case, the electric auxiliary compressor is "run up" very quickly. As a result, the naturally aspirated full load is reached quickly or abruptly and the turbocharger is flowed through with a high air flow on the fresh air side, which leads to a desired slight increase in speed of the turbocharger rotor despite poorer efficiency. In this way, the use of the electric auxiliary compressor achieves the purpose of accelerating the sluggish turbocharger to nominal speeds as quickly as possible, so that the turbocharger alone can fill the combustion engine with as much air as possible and thus generate high engine torque and high performance can. As soon as the electric additional compressor has reached a minimum speed during the speed increase, which conveys more air than is needed in the suction full load and can therefore build up pressure itself, the controllable flap in the bypass is controlled in such a way that the bypass is closed very quickly and the electric auxiliary compressor can build up boost pressure.

The electric additional compressor and the bypass with the controllable flap arranged in it can be arranged upstream of the main charger.

In another embodiment, it is provided that the electric auxiliary compressor together with the bypass and the flap arranged in it are arranged downstream of the main charger.

The method according to the invention for operating an internal combustion engine provides that the flap arranged in the bypass of the additional compressor is controlled depending on the operating state of the internal combustion engine in order to form a definable opening cross section. The controllable and thus actively controllable flap in the bypass enables a broad use of the additional electric compressor in the torque map. The flap can be constructed in the same way as or similar to a throttle flap known per se. According to the invention, it is therefore provided that, in addition to the throttle valve of the internal combustion engine, the further controllable valve is arranged in the bypass.

According to an advantageous embodiment of the method according to the invention, it is provided that the throttle valve of the internal combustion engine arranged downstream of the controllable flap is controlled depending on the operating state of the internal combustion engine and the open position of the controllable flap. The control of the controllable flap in the bypass and the control of the throttle valve of the internal combustion engine are thus coordinated with one another.

It is particularly advantageously provided that a direct change from motor compressor operation to generator expansion operation of the additional compressor and vice versa is carried out depending on the operating state of the internal combustion engine. This is possible because no reversal of the direction of rotation of the electric auxiliary compressor is required. It can thus be switched from a motor compressor operation to a certain extent directly into a generator expansion operation for recuperation and vice versa. The advantage here is that the internal combustion engine and the charger are already rotating and do not have to be braked down to a standstill and then accelerated again. This saves run-up time and energy. This also results in the primary function of the electric auxiliary compressor, the advantage of the fastest possible speed ramp-up, which requires less time and less energy as a result.

According to one embodiment of the method, the kinetic energy of the additional compressor is very advantageously used for recuperation when switching from motorized compressor operation at high speeds to generator-driven expansion operation at lower speeds.

Such a switchover can take place, for example, if, after accelerating a vehicle, full load and high load are still required, which are essentially provided using the main charger, the electric auxiliary compressor is run down and switched off.

According to an advantageous embodiment of the method according to the invention, it is also provided that the static recuperation operating point is shifted to higher loads when there is a high electrical energy requirement.

The present method can be implemented, for example, using a computer program that contains a corresponding program code for this purpose.

It is advantageous to set up an electronic control unit such as an engine controller for an internal combustion engine in question in such a way that it can implement the steps of the method.

Furthermore, it is advantageously provided that the computer program on a machine-readable ren storage medium to save. This makes it easier to retrofit existing control units.

character list

Exemplary embodiments of the invention are explained in more detail in the following description.

• 1 eine erste Ausführungsform eines erfindungsgemäß betriebenen Verbrennungsmotors;
• 2 eine zweite Ausführungsform eines erfindungsgemäß betriebenen Verbrennungsmotors;
• 3 schematisch das Drehmoment über der Drehzahl zur Darstellung eines Mehrquadrantenbetriebs eines elektrischen Zusatzverdichters und
• 4 das Drehmoment über der Drehzahl zur Darstellung des erweiterten Einsatzbereichs des elektrischen Zusatzverdichters.

Show it:

• 1 a first embodiment of an internal combustion engine operated according to the invention;
• 2 a second embodiment of an internal combustion engine operated according to the invention;
• 3 schematically the torque over the speed to represent a multi-quadrant operation of an electric auxiliary compressor and
• 4 the torque over the speed to show the extended range of application of the electric auxiliary compressor.

Description of exemplary embodiments

a in 1 Internal combustion engine 100 shown has an intake duct 110 and an exhaust gas duct 120 . A main charger 200, for example a turbocharger, which has an impeller 210 in the intake duct and a turbine wheel 220 in the exhaust duct, the turbine wheel 220 in the exhaust duct being driven by the exhaust gas and driving the impeller 210 in the intake duct 110 in a manner known per se to increase the air throughput to increase in the intake port 110 can be controlled by a control unit 300 via a control line 230 shown in dashed lines. A throttle valve 400, known per se, is arranged in intake duct 110 immediately before (that is, upstream of) the intake area of engine 100, which can also be controlled by control unit 300 via a control line 430 (shown in dashed lines). An electric auxiliary compressor 510 , which can be driven by a motor generator 520 , is arranged in the intake passage 110 downstream of the main charger 210 and upstream of the throttle valve 400 . Motor generator 520 can be controlled via a control line 530 . A controllable and controllable flap 700 is arranged in a bypass 600 of the electric auxiliary compressor 510 and is controlled by the control unit 300 via a control line 730 . This flap 700 can correspond to the throttle flap 400 in terms of its design. It should be emphasized at this point that all control lines 230, 430, 530, 730 are bidirectional lines, ie data is transferred from control unit 300 to the corresponding units and vice versa, signals are transmitted from the corresponding units to control unit 300.

In 2 Another embodiment of the internal combustion engine operated according to the invention is shown, which differs from that in 1 illustrated differs only in that the electric auxiliary compressor 510, which is driven by the motor generator 520, and the bypass 600, in which the controllable flap 700 is arranged, is arranged upstream of the main charger 200, whereas these components are arranged in the in 1 internal combustion engine shown are arranged downstream of the main charger 200.

The basic idea of the method according to the invention is the use of the actively controllable flap 200 in the bypass 600 for the widest possible use in the torque map. In contrast to the internal combustion engines known from the prior art, the internal combustion engine according to the invention thus has two control flaps in the air path. A direct change from motorized compressor operation of electric auxiliary compressor 510, in which auxiliary compressor 510 is driven by motor generator 520, to recuperation in regenerative expansion operation, in which auxiliary electric compressor 510 drives motor generator 520 and this acts as a generator, is possible and also a reverse change from generator expansion operation to motor compressor operation. The motor generator 520 and the supercharger 510 are already rotating and do not have to be specially braked down to zero and accelerated again. This saves run-up time and energy. This enables the electric additional compressor to ramp up its speed very quickly and thus optimal support for the main charger 200. This support is the primary function of the electric additional compressor. If there is a switch from motor operation at high or maximum speed of electric additional compressor 510 to generator operation at a lower speed level, the stored kinetic energy of electric additional compressor 510 can also be used for recuperation, just like a static recuperation operating point , in which the vehicle moves, for example, at a speed of 80 km/h with a low load. This recuperation operating point is reached, for example, when the main charger 200 has taken over the function of charging the engine 100 and to this extent the electric auxiliary compressor 510 can be “run down”. If slight changes in load have to be made in this state and the electric auxiliary compressor 510 cannot compensate for these slight changes in load, provision is made to use as large a part of the air flow as possible to guide the electric additional compressor 510 in order to enable optimal recuperation and at the same time to guide a minimum amount of air via the active, controllable flap 400. In the case of small changes in load, the controllable flap 400, also referred to below as the control flap for short, can quickly correct the changes in the air flow. A slight jump in load to a lower load can be realized with a larger regenerative braking torque and thus higher power generation and increased recuperation.

A large jump in load towards a lower load, which the additional electric compressor 510 cannot compensate for quickly enough, is implemented by rapidly closing the throttle flap 400 of the internal combustion engine 100 .

If a high engine load is suddenly requested during recuperation at this static recuperation operating point, bypass 600 can quickly be fully opened by appropriately activating control flap 700, and electric auxiliary compressor 510 can be ramped up as quickly as possible. As a result, the suction full load is reached quickly or suddenly and the main charger 200 is flowed through with a high air flow on the fresh air side, which leads to a desired slight increase in the rotational speed of the turbocharger rotor 210 . In this respect, the primary purpose of the electric auxiliary compressor 510 is fulfilled, namely to accelerate the sluggish exhaust gas turbocharger 200 to the rated speed as quickly as possible, so that the turbocharger 200 alone can generate the largest possible air charge of the internal combustion engine 100 and thus a high engine torque and high performance can be generated. If the electric additional compressor 510 has reached a minimum speed during this speed ramp-up, which conveys more air than is needed in the suction full load and can therefore build up pressure, the bypass 600 is quickly closed by appropriate activation of the control valve 700 and the electric additional compressor In this case, the 510 can really build up charging pressure. Failure to close the bypass 600 would result in undesired backflow through the open bypass 600 .

The advantageous recuperation described above can be implemented at appropriate recuperation operating points. The operating range of recuperation can be shifted to higher loads by shifting the load point, for example if there is a very high electrical energy requirement. Because the vehicle electrical system is supported by the additional recuperation energy, alternators can be used in the corresponding vehicle that are designed for lower performance and downtimes, which means that cost savings are possible.

In 3 the multi-quadrant operation described is shown, ie the operation of the electric additional compressor both as a motor-driven compressor and in generator expansion operation. The torque M is plotted against the speed n and at a point 3 is a motor load point with compressor operation and at a point 4 the generator operation for recuperation in the expansion operation is shown. Motor operation usually has a higher speed n than generator operation.

In 4 shows the extended range of application in which recuperation is possible. Line 401 represents the static maximum torque characteristic of a turbocharged Otto engine. Recuperation as described above can be carried out in a large sub-area 402 . In contrast, in a region 405 there is too little vacuum in the intake manifold for the expansion operation, and in a region 406 there is too little air volume. The figure shows that there is a minimum speed n at which the charger must rotate in order to overcome static friction.

Claims (9)

Method for operating an internal combustion engine (100) with a main charger (200) and with an additional compressor (510) that can be driven electrically by a motor generator (520), the motor generator (520) being driven by the additional compressor (510) in selected operating states of the internal combustion engine (100) is driven and operated in a generator expansion operation and provides electrical power, and with a flap (700) arranged in a bypass (600) of the additional compressor (510), which is controlled depending on the operating state of the internal combustion engine (100) to form a definable opening cross section, characterized in that in a static recuperation operating point, the flap (700) arranged in the bypass (600) is controlled in such a way that a maximum possible air flow is guided via the electric additional compressor (510) and that a minimum possible air flow via the bypass ( 600) is guided. procedure after claim 1 , characterized in that starting from the static recuperation operating point a load jump to a smaller load depending on the size of the load jump by a larger regenerative braking torque and / or by a fast Closing the throttle valve (400) of the internal combustion engine (100) is realized. procedure after claim 1 , characterized in that starting from the static recuperation operating point in the event of a load jump to a high load, the flap (700) arranged in the bypass (600) is controlled in such a way that the bypass (600) opens quickly and that at the same time the electrical Additional compressor (510) is switched to maximum motorized compressor operation. Method according to one of the preceding claims, characterized in that a throttle flap (400) of the internal combustion engine (100) arranged downstream of the bypass (600) is controlled depending on the operating state of the internal combustion engine (100) and the open position of the controllable flap (700). Method according to one of the preceding claims, characterized in that a direct change from motor compressor operation to generator expansion operation of the additional compressor (510) and vice versa is carried out depending on the operating state of the internal combustion engine (100). Method according to one of the preceding claims, characterized in that the kinetic energy of the additional compressor (510) is used for recuperation when changing from motor-driven compressor operation at high speeds to generator-driven expansion operation at lower speeds. Computer program which is set up to carry out each step of the method according to one of the preceding claims. Machine-readable storage medium on which a computer program claim 7 is saved. Electronic control unit for an internal combustion engine (100) which is set up, each step of the method according to one of Claims 1 until 6 to perform.

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