DE102017200948A1 - Method for operating a turbocharged internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating a turbocharged internal combustion engine (4) with at least two parallel turbochargers (6a, 6b), wherein at least a first of the two turbochargers (6a, 6b) is an electrically charged turbocharger (6a), wherein a detected boost pressure request (L) due to a change in an accelerator pedal position by a motor vehicle driver, at least the rotational speed of the electrically charged turbocharger (6a) is adjusted. Furthermore, the invention relates to an engine assembly (2) with such a turbocharged internal combustion engine (4) and a motor vehicle, in particular passenger car, with such an engine assembly (2).

Description

The invention relates to a method for operating a turbocharged internal combustion engine having at least two parallel turbochargers, wherein at least a first of the two turbochargers is an electrically charged turbocharger. Furthermore, the invention relates to an engine assembly with such a turbocharged internal combustion engine and a motor vehicle, in particular passenger car, with such an engine assembly.

It is known that by a turbocharger, including turbo, a performance or efficiency increase of internal combustion engines, such as. B. of gasoline or diesel engines for driving motor vehicles, can be achieved.

Exhaust gas turbochargers have an exhaust gas turbine and a compressor. The exhaust gas turbine drives the compressor and increases the air flow or reduces the suction work of the piston. The exhaust gas turbine draws its drive energy from the residual pressure of the exhaust gas of the internal combustion engine.

Furthermore, electric turbochargers are known which have an electric motor as drive instead of an exhaust gas turbine. The advantage here is that an electric motor has a lower inertia than an exhaust gas turbine. Thus, an electric turbocharger has a shorter response time to load changes than an exhaust gas turbocharger. The so-called turbo lag is correspondingly lower.

From the DE 20 2014 105 279 U1 a turbocharged internal combustion engine having at least two parallel turbochargers is known, wherein at least a first of the two turbochargers is an electrically charged turbocharger. Such an arrangement of two turbochargers is referred to as a twin-turbo, or TwinTurbo in English. If both turbochargers are driven by an exhaust gas turbine, only the first turbine of the first turbocharger is constantly driven in the exhaust stream, while the second turbine of the second turbocharger is switched on only with a corresponding power requirement, which then drives the second compressor. Then both turbochargers work in parallel on the principle of the "classic" twin turbocharger. The advantages of the larger flow rate of two turbochargers can be used in the upper speed range, while in the lower speed ranges with only one turbine used, this can build up a boost pressure more quickly.

Problems with the use of sequential twin turbochargers are the control of torque fluctuations in the connection or disconnection of the second turbocharger and corresponding power fluctuations.

There is therefore a need to show at least one way in which the boost pressure can be kept constant in order to avoid perceptible power fluctuations for the motor vehicle driver, in particular in the event of a change of operating mode in which one of the two turbochargers is switched on and / or off.

The object of the invention is achieved by a method for operating a turbocharged internal combustion engine with at least two parallel turbochargers, wherein at least a first of the two turbochargers is an electrically charged turbocharger, wherein responsive to a detected boost pressure request due to a change in accelerator pedal position by a motor vehicle driver out at least the speed the electrically charged turbocharger is adjusted. As a result, the shorter response time of an electrically driven turbocharger is made use of, the time until the run-up of the slower, z. B. by an exhaust turbine driven turbocharger, bridged and so provides a substantially constant boost pressure in the intake manifold of the internal combustion engine. Under a substantially constant boost pressure while a supercharger pressure is understood that does not lead to noticeable for a motor vehicle driver power loss. Thus, a homogenization of the boost pressure can be achieved.

According to one embodiment, a TSO valve (turbine shut-off valve) is triggered in response to the detected boost pressure request. The TSO valve can be an electromechanical valve that can be controlled with an electrical control voltage. The TSO valve is disposed between an exhaust port of the engine and an input of an exhaust turbine that drives the second turbocharger. In other words, with the TSO valve, the second turbocharger can be switched on by switching on a partial exhaust gas flow.

According to a further embodiment, a CSO valve (compressor shut-off valve) is activated in response to the detected charge pressure requirement. The CSO valve is disposed between an output of a compressor of the second turbocharger and an input of a charge air cooler and an intake manifold of the internal combustion engine. In other words, it can be unlocked with the CSO valve of the compressor of the second turbocharger.

According to a further embodiment, the boost pressure request is detected in response to a planned operating mode change. Here, an operating mode change is understood as meaning a change from an operation with an active turbocharger to an operation with two active turbochargers and / or vice versa. Such a Operating mode change entails particularly large fluctuations in the boost pressure, resulting in a corresponding boost pressure request. Thus, a homogenization of the boost pressure can be achieved at particularly critical operating mode changes.

According to a further embodiment, the electrically charged turbocharger is coupled or coupleable to an exhaust gas turbine. Thus, a combination operation is possible, in which an electric machine is used only supportive to compensate for insufficient exhaust pressure for driving the exhaust gas turbine.

According to a further embodiment, an electric machine driving the electrically charged turbocharger is operable in a generator mode. Thus, stored kinetic energy can be converted into electrical energy and fed into the electrical system of the motor vehicle.

According to a further embodiment, at least a second of the two turbochargers is an electrically charged turbocharger, wherein at least the rotational speed of the second electrically charged turbocharger is adjusted in response to a detected boost pressure requirement. Thus, the response of the turbocharger can be further improved, d. H. the internal combustion engine responds even faster to performance requirements of a motor vehicle driver.

According to a further embodiment, the second electrically charged turbocharger is coupled or coupleable to an exhaust gas turbine. Thus, in the second turbocharger a combination operation is possible in which an electric machine is used only supportive to compensate for an insufficient exhaust gas pressure for driving the exhaust gas turbine.

According to a further embodiment, an electric machine driving the second electrically charged turbocharger is operable in a generator mode. Thus, this stored kinetic energy can be converted into electrical energy and fed into the electrical system of the motor vehicle.

Furthermore, the invention relates to an engine assembly and a motor vehicle, in particular a car, with such an engine assembly.

The invention will now be explained with reference to a drawing. It shows:

1 an engine assembly with an internal combustion engine and with at least one electric turbocharger for carrying out an embodiment of the method according to the invention.

The 1 shows an engine assembly 2 with a turbocharged internal combustion engine 4 for driving a motor vehicle, such as. B. a car. The internal combustion engine 4 is formed in the present embodiment as a gasoline engine. Alternatively, the internal combustion engine 4 also be designed as a diesel engine.

For turbocharging the internal combustion engine 4 are in the present embodiment, a first turbocharger 6a and a second turbocharger 6b intended. The motor assembly 2 in the present embodiment, in addition to a TSO valve 8th and a CSO valve 10 also a charge air cooler 16 , an intake manifold 18 and a controller 20 on.

In the present embodiment, the first turbocharger 6a and the second turbocharger 6b identical construction. The first and second turbochargers 6a . 6b each have a first and second exhaust gas turbine 12a . 12b , a first and second electric machine 14a . 14b and a first and second compressor, respectively 22a . 22b on.

The first turbocharger 6a and the second turbocharger 6b form in the present embodiment, a so-called parallel sequential biturbo. In a parallel sequential biturbo are not both exhaust gas turbines 12a . 12b constantly driven by a respective partial exhaust gas flow, but the second exhaust gas turbine 12b is only switched on with the corresponding power requirement and then drives the second compressor 22b at. Once that's done, both turbochargers work 6a . 6b parallel. The aim of this technique is a better usability of the speed range. In the upper speed range, one has the advantage of the larger flow rate of two turbochargers 6a . 6b , while in the low speed ranges, the low inertia of only one of the exhaust gas turbines 6a . 6b a fast and early build up of the boost pressure and thus causes a good response.

By a corresponding coupling (not shown), the first and second electric machine 14a . 14b with the respective first and second compressor 22a . 22b get connected. Thus, with the first and second electric machine 14a . 14b the respective first and second compressor 22a . 22b driven alone, or the first and second electric machine 14a . 14b drive together with the respective first and second exhaust gas turbine 12a . 12b the respective first and second compressor 22a . 22b on, so that the first and second electric machine 14a . 14b the respective first and second exhaust gas turbine 12a . 12b can assist in the presence of a low exhaust pressure.

The first or second electric machine 14a . 14b are designed in the present embodiment to be operated both in the engine and generator mode. Thus, kinetic energy of the respective partial exhaust gas streams can be converted into electrical energy and fed into the electrical system of the motor vehicle. Furthermore, the corresponding clutches can be designed to be the first or second electric machine 14a . 14b from the respective first and second compressor 22a . 22b decouple, so that the respective first and second compressor 22a . 22b not driven unnecessarily with.

The TSO valve (turbine shut-off valve) 8th is in the present embodiment, a controllable with an electrical control voltage electromechanical valve. The TSO valve 8th is between an exhaust port of the internal combustion engine 4 and an input of the second exhaust gas turbine 12b arranged the second compressor 22b Turbocharger drives. By opening the TSO valve 8th can on the second exhaust gas turbine 12b a partial exhaust gas flow are switched, then the second compressor 22b drives.

The CSO valve (compressor shut-off valve) 10 is in the present embodiment also a controllable with an electrical control voltage electromechanical valve. The CSO valve 10 is between an output of a second compressor 22b and an input of the intercooler 16 arranged. By opening the CSO valve 10 can compressed air from the second compressor 22b to the entrance of the intercooler 16 be routed to the first compressor 22a to support.

The control unit 20 is via control lines, which are not shown for reasons of clarity, with the TSO valve 8th , the CSO valve 10 , the electric machine 14a and the second electric machine 14b Control signals S transmitted connected.

In operation z. B. at a low boost pressure request L, the first compressor 22a driven by the partial exhaust gas flow passing through the first exhaust gas turbine 12a flows while the TSO valve 8th and the CSO valve 10 each are closed. In other words, the second turbocharger 6b is deactivated.

An increase in the boost pressure requirement L due to a change in an accelerator pedal position by a motor vehicle driver results in an operating mode change from an operating mode with only one active turbocharger 6a to an operating mode with two active turbochargers 6a . 6b , This is done by the control unit 20 Control signals S to the TSO valve 8th and the CSO valve 10 Transfer to open them. Further, a control signal S to the second electric machine 14b in order to operate these in engine operation at a speed in the in particular during the operating mode change a constant boost pressure in the intake manifold 18 causes so that there is no perceptible for the motor vehicle driver performance drop. When a sufficient boost pressure is provided by a corresponding partial exhaust gas flow through the second exhaust gas turbine 12b flows, the controller can 20 the second electric machine 14b deactivate again.

On a particularly abrupt boost pressure request L can from the controller 20 another control signal S to the first electric machine 14a in order to operate these in addition during engine operation with a speed, the constant boost pressure in the intake manifold 18 causes.

On a now following reduction of the boost pressure request L, the controller 20 to the second electric machine 14b or both electrical machines 14a . 14b Control signals S transmitted to operate in generator mode. Thus, stored kinetic energy, eg. B. rotational energy of the first exhaust gas turbine 12a and / or the first compressor 22a and / or the second exhaust gas turbine 12b and / or the second compressor 22b converted into electrical energy and fed into the electrical system of the motor vehicle.

Thus, the boost pressure can be homogenized in particular in a mode change, in which one of the two turbochargers and / or switched off, to avoid noticeable power fluctuations for the motor vehicle driver, and it also increases energy efficiency.

LIST OF REFERENCE NUMBERS

2

 motor assembly

4

 Internal combustion engine

6a

 first electric turbocharger

6b

 second electric turbocharger

8th

 TSO valve

10

 CSO valve

12a

 first exhaust gas turbine

12b

 second exhaust gas turbine

14a

 first electric machine

14b

 second electric machine

16

 Intercooler

18

 intake manifold

20

 control unit

22a

 first compressor

22b

 second compressor

L

 Boost pressure requirement

S

 control signal

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202014105279 U1 [0005]

Claims (14)

Method for operating a turbocharged internal combustion engine ( 4 ) with at least two parallel turbochargers ( 6a . 6b ), wherein at least a first of the two turbochargers ( 6a . 6b ) an electrically charged turbocharger ( 6a ), wherein a detected boost pressure request (L) due to a change in an accelerator pedal position by a motor vehicle driver at least the speed of the electrically charged turbocharger ( 6a ) is adjusted. The method of claim 1, wherein the monitored boost pressure request is a TSO valve ( 8th ) is driven. Method according to claim 1 or 2, wherein, based on the detected charge pressure requirement, a CSO valve ( 10 ) is driven. Method according to one of the preceding claims, wherein the charge pressure request (L) is detected in response to a planned operating mode change. Method according to one of the preceding claims, wherein the electrically charged turbocharger ( 6a ) with an exhaust gas turbine ( 12a ) is coupled or can be coupled. Method according to one of the preceding claims, wherein one of the electrically charged turbocharger ( 6a ) driving electric machine ( 14a ) is operable in a generator mode. Method according to one of the preceding claims, wherein at least a second of the two turbochargers ( 6b ) an electrically charged turbocharger ( 6b ), wherein, in response to a detected boost pressure request (L), at least the rotational speed of the second electrically charged turbocharger ( 6b ) is adjusted. Method according to claim 6, wherein the second electrically charged turbocharger ( 6b ) with an exhaust gas turbine ( 12b ) is coupled or can be coupled. Method according to one of the preceding claims, wherein a second electrically charged turbocharger ( 6b ) driving electric machine ( 14b ) is operable in a generator mode. Motor assembly ( 2 ), with a turbocharged internal combustion engine ( 4 ) with at least two parallel turbochargers ( 6a . 6b ), wherein at least a first of the two turbochargers ( 6a . 6b ) an electrically charged turbocharger ( 6a ), the engine assembly ( 2 ) is adapted to a detected boost pressure request (L) due to a change in an accelerator pedal position by a motor vehicle driver at least the rotational speed of the electrically charged turbocharger ( 6a ). Motor assembly ( 2 ) according to claim 10, in which at least a second of the two turbochargers ( 6b ) an electrically charged turbocharger ( 6b ). Motor assembly ( 2 ) according to claim 10 or claim 11, in which first electrically charged turbochargers ( 6a ) and / or the second electrically charged turbocharger ( 6b ) with an exhaust gas turbine ( 12a . 12b ) is coupled or can be coupled. Motor assembly ( 2 ) according to one of claims 10 to 12, in which a first electrically charged turbocharger ( 6a ) driving electric machine ( 14b ) and / or a second electrically charged turbocharger ( 6b ) driving electric machine ( 14b ) is operable in a generator mode or are. Motor vehicle, in particular passenger car, with an engine assembly ( 2 ) according to one of claims 10 to 13.

Images