DE102007057224A1 - Drive system i.e. hybrid drive system, for motor vehicle, has sub-systems including fuel cell-system and supplied with compressed air by common supply device, where supply device includes compressors driven by electric motor - Google Patents

Abstract

The system has a sub-system (10) including a fuel cell-system (12), and another sub-system that is different from the former sub-system. The sub-systems are supplied with compressed air by a common supply device (24), where the supply device includes compressors (30, 34), which are driven by an electric motor (36). The sub-systems have an internal combustion engine (20) for delivering exhaust gas to a turbine (28), where the exhaust gas drives the turbine. The turbine is coupled with the compressors.

Description

The The invention relates to a drive system for a motor vehicle according to the preamble of claim 1, d. H. with a first Subsystem comprising a fuel cell system and a second, subsystem different from the first subsystem, both Subsystems via a common feeder with compressed air are supplied.

Fuel cell systems In the long term, conventional internal combustion engines are to be used in drive systems replace. To a wide use of fuel cell systems prepare, it makes sense in a transitional period To use hybrid systems, d. H. Drive systems, both a Fuel cell system as a first subsystem as well as a conventional Subsystem to include drive. The classic example of This further subsystem is a conventional internal combustion engine. The hybrid system, however, can be next to the fuel station system as well include a gas turbine plant.

By using two subsystems in the drive system such a drive system is very complex and takes up a lot of space. The use of synergy effects is therefore welcome. This can happen, for example, in the air supply. Both fuel cells and conventional internal combustion engines need to be supplied with compressed air. In a motor vehicle with a hybrid drive system, space and costs can be saved if the subsystems are assigned a common supply device which provides the compressed air. So is in the DE 103 03 867 A1 described that in a system of internal combustion engine and fuel cell for compressing the charge air for the internal combustion engine and for supplying air to the fuel cell system, the same compressor is used. Accordingly, the DE 103 03 867 A1 a drive system for a motor vehicle according to the preamble of claim 1 ready.

In the DE 103 22 296 A1 It is described that an internal combustion engine is connected on the exhaust side to a turbine that drives an air compressor that compresses air for a fuel cell system.

Of the Use of hybrid systems from fuel cell systems and internal combustion engine is particularly useful if, depending on the performance requirements a drive system focuses on the fuel cell system, Focusing on the internal combustion engine or both be used to the same extent. Previous hybrid systems have the disadvantage that the respective fuel cell system rather less can be used than the internal combustion engine. The control of internal combustion engines can be easily changed in their operation to meet different performance requirements becomes. In particular, when the power requirements change quickly are, for. B. in an acceleration of the motor vehicle with the relevant Drive system by the driver, so far almost exclusively the internal combustion engine used.

It The object of the invention, in a drive system consisting of two subsystems, of which a subsystem comprises a fuel cell system, the fuel cell system more frequent and intense, d. H. with larger Use proportion. The task is accomplished by a drive system for a motor vehicle according to claim 1 solved.

According to the invention the common feeder (over both subsystems be supplied with compressed air) a compressor, by means of an electric motor is driven (and actually in operation is driven).

The Invention is based on the recognition that the focus Use of the internal combustion engine promoted in a hybrid system thereby is that the exhaust gas from the internal combustion engine an exhaust gas turbocharger is fed, d. H. a turbine, which is a compressor drives. Will now be according to the invention, a compressor operated by an electric motor, one is from the exhaust gas of the Internal combustion engine independent, and the compressor can light and short-term air also for the fuel cell system provide.

The Knowledge according to the invention does not mean that not also the exhaust gas of the internal combustion engine can be used. Rather, preference is still given to the exhaust gas of an internal combustion engine supplied to a turbine to drive these. This turbine must be coupled with a compressor that is for compressed Air in the common feeder ensures.

The Invention allows two alternatives: the one with the turbine, which is driven by the exhaust gas of the internal combustion engine, coupled Compressor may be another compressor, that of the one of the Electric motor drivable compressor is different, or it can to be the same compressor.

When two compressors are used, it is facilitated to provide an embodiment in which exhaust gas discharged from the fuel cell system is directed to a turbine for the purpose of driving it, which is coupled to the compressor drivable by the electric motor. Through the turbine, the electric motor can be relieved become. So obtained electric energy can be stored in the battery of the fuel cell system. The embodiment is facilitated in two different compressors because the exhaust gases from the engine on the one hand and the fuel cell system on the other hand then do not have to be merged.

If two compressors are provided, it makes sense to at least one of the compressors and preferably at both a bypass for To provide air. In the case of the internal combustion engine less should be used and the focus of the power delivery the fuel cell system is located, air can be passed to the compressor which is driven by the exhaust gas of the internal combustion engine. Then the electric motor does the job of providing a charge air pressure which is suitable for the fuel cell system. Is a Operating state produced in which the internal combustion engine produces strong exhaust gas flow, makes the of the exhaust gases of the internal combustion engine Powered compressors work a lot and it can work on the the electric motor driven compressor are dispensed with, so that then the bypass to this compressor will be opened can.

It has already been mentioned above that also an embodiment it is possible at which the exhaust gas from the internal combustion engine the drivable by the electric motor compressor in addition to the electric motor to its discharge drives. As the electric motor as already explained above, a charge air pressure to provide sufficiently good operation of the fuel cell system, It makes sense, even from the fuel cell system discharged exhaust gas to drive the single compressor. Thus, the exhaust gas discharged from the fuel cell system becomes the same turbine as the exhaust gas of the internal combustion engine passed. In the mentioned embodiment, there is the problem that the exhaust gas from the internal combustion engine quite different properties as the exhaust gas of the fuel cell system has. The exhaust gas of the internal combustion engine usually has a very high temperature and is subject to strong pressure fluctuations (pulsations). The mean pressure fluctuates for example, up to 50%. The exhaust gas of the fuel cell system is relatively cold (reaches approximately only approx 100 ° C) and is not subject to strong pressure fluctuations. It is preferable to avoid that the pressure fluctuations which the Internal combustion engine generates the operation of the fuel cell system affect. First, you can be the simplest Measure a check valve between fuel cell system and turbine in front of the inlet for the output from the internal combustion engine Provide exhaust.

Especially It is efficient when the exhaust gas from the internal combustion engine to a first inlet of a container and the exhaust gas from fuel cell system is directed to a second inlet of the container, wherein the tank leads to the turbine on the outlet side. Such a container can buffer the pressure fluctuations. For this he should be bigger in his volume its than the other piping in the system. The desirable ones Properties of the container can be expressed in such a way that this is to be designed so that when pressure fluctuations occur with a certain fluctuation amplitude at the first inlet on the second Inlet pressure fluctuations occur with a fluctuation amplitude which is smaller than the fluctuation amplitude at the first inlet. Already with a relatively simple trained large-volume container, where the two inlets are sufficiently far from each other are spaced, one obtains the effect that pressure fluctuations be buffered by 50% around an average at the first inlet so far that at the second inlet only pressure fluctuations of 10% around an average occur. Together with the container can also the above mentioned check valve can be used.

The Invention allows, as shown above, a more extensive Use of the fuel cell system in a hybrid fuel cell system and further system, in particular internal combustion engine. A refinement the system is made by using such, by an electric motor driven compressor, which is mechanically adjustable (a "variable Geometry "has) such that it at the same speed different Charges generated. So that the mechanical adjustment in the short term It should be done by one of an electronic control unit delivered control command be effected. One becomes the one electronic Control unit also provide the operation of the two subsystems controls. Depending on whether the focus of the internal combustion engine works, mainly the fuel cell works or the fuel cell in addition to the internal combustion engine works and, in particular, at short notice between these operating modes should be changed, the compressor can be set accordingly become. Due to the changed charge pressure at the same speed a different air mass is moved. It does not have to be in the short term the speed can be changed when the air supply is fast to change. This can be especially true for accelerations of the motor vehicle be useful if z. B. in addition to the fuel cell amplified the internal combustion engine work should.

following preferred embodiments of the invention below Referring to the drawings, wherein:

1 schematically the structure of an driving system for a motor vehicle according to a first embodiment of the invention,

2 schematically shows the structure of a drive system for a motor vehicle according to a second embodiment of the invention,

3 schematically shows the structure of a drive system for a motor vehicle according to a third embodiment of the invention and

4 schematically shows the structure of a drive system for a motor vehicle according to a fourth embodiment of the invention.

A drive system for a motor vehicle, which is designed as a hybrid drive system, comprises as the first subsystem 10 a fuel cell system with a fuel cell stack 12 which generates electric current, that of a battery 14 is supplied, which is an electric motor 16 feeds a drive torque to a shaft 18 emits.

As a second subsystem, the drive system includes an internal combustion engine 20 (Internal combustion engine), which is a shaft 22 drives, where by a suitable circuit or a suitable transmission, the waves 18 and 22 be coupled so that one and the same drive axle through the shafts 18 and 22 is driven.

The fuel cell stack 12 requires compressed air and the combustion engine too. It makes sense to compressed air via a common supply device 24 provide. Via a controllable air dosing element 26 It determines how much air to the fuel cell stack 12 and how much air to the internal combustion engine 20 arrives. In a manner known per se, the supply device comprises 24 out

1 an exhaust gas turbocharger 27 ie one via a turbine 28 driven compressor 30 , The turbine 28 is about exhaust pipes 32 the exhaust gas of the internal combustion engine 20 fed. According to the invention is now a second compressor 34 provided by an electric motor 36 is driven. The compressor 30 fulfilled additionally or alternatively to the compressor 34 the task of compressing the charge air. Reason for driving the compressor 34 with the electric motor 36 is that with increased demand of compressor air through the fuel cell stack 12 through the internal combustion engine 20 little or no exhaust gas is generated, leaving the compressor 30 is not driven sufficiently. By providing the electric motor 36 , which in the execution according to 1 the compressor 34 as an additional compressor next to the compressor 30 drives, so can the fuel cell system 10 be used to a greater extent than in conventional drive systems in hybrid form. A corresponding, not shown in the figure electronic control can that of the electric motor 36 control delivered power, simultaneously with the Luftdosierelement 26 and the internal control members of the fuel cell stack 12 or the electric motor 16 on the one hand and the internal combustion engine 20 on the other hand. By the control can also be provided that on the performance of one of the compressors 30 and 34 is completely dispensed with. To the compressor 30 is a bypass line 38 with an electrically controllable valve 40 provided, and to the compressor 34 a bypass line 42 with an electrically controllable valve 44 , The electronic controller responsible for the operation of fuel cell stacks 12 and internal combustion engine 20 is responsible, can control the respectively supplied air relatively well.

In the embodiment of 1 the exhaust gas is removed from the fuel cell stack 12 over a line 46 and a so-called controllable back pressure flap 48 directed. Through the back pressure flap 48 ensures that in the fuel cell stack 12 the right pressure prevails.

A second embodiment of the invention is described with reference to 2 shown. The second embodiment of the invention differs in its feeding device 24 ' from the feeder 24 , in that the compressor 34 not only by the electric motor 36 is rotatable but with a turbine 50 is coupled, which via an exhaust pipe 46 ' the exhaust gas of the fuel cell stack is supplied. In this embodiment, thus also the exhaust gas from the fuel cell stack 12 used for power delivery. The electric motor 36 must therefore give less power overall than in the embodiment according to 1 , The embodiment of 2 has the advantage that the exhaust gas from the fuel cell stack 12 separately from the exhaust gas of the internal combustion engine 20 is treated. This happens at the cost of providing the second compressor 30 , as well as in the embodiment according to 1 the case is.

The invention can now also be used with a feed device 24 '' be realized for compressed air, which is only the single compressor 34 includes. In this case, the exhaust gas from the fuel cell stack with the exhaust gas from the internal combustion engine 20 merged. The exhaust gas from the fuel cell stack 12 is cold exhaust gas and has low pressure fluctuations. The exhaust gas from the internal combustion engine 20 however, it is extremely hot and has strong pressure fluctuations. It is to be avoided that the exhaust gas from the internal combustion engine in the fuel cell stack 12 passes or the temperatures of the exhaust gas from the engine 20 and its pressure fluctuations the fuel cell stack 12 to reach. Because of this, an exhaust pipe leads 32 ' of the internal combustion engine 20 via a check valve 52 to a first inlet of a container 54 a container 56 , The exhaust gas from the fuel cell stack system 12 leads through an exhaust pipe 46 ' and a check valve 58 to a second inlet 60 same container 56 , The outlet 62 the container goes into an exhaust pipe 64 over, in which the exhaust fumes from fuel cell stack 12 and internal combustion engine 20 equally to the turbine 50 be transported. Already the check valves 52 and 58 prevent an exchange of the exhaust gases. Through the check valves 52 and 58 is not yet guaranteed that pressure fluctuations are compensated. The first inlet 54 but is in the container 56 from the second inlet 60 so far away, and the container 56 possibly internally also designed to be suitable that pressure fluctuations of 50% around an average at the inlet 54 not until the inlet 60 but that can arrive at the inlet 60 at most fluctuations of 10% occur around a mean value.

The exhaust pipe 46 '' includes in an additional branch 66 again a controllable back pressure flap 68 , through which optimal operation of the fuel cell stack 12 can be adjusted.

A fourth embodiment, as in 4 is shown differs in their supply device 24 '' from the embodiment 3 , And in the present case is a specially designed compressor 34 ' used. This compressor should have a variable geometry, and be mechanically adjustable such that at the same speed different boost pressures can be generated, so that the compressed air mass is independent of the speed and therefore can be changed at short notice. The mechanical adjustment is electrically controlled preferably via the same, not shown in the figures, the control unit, the operation of the fuel cell stack 12 or the electric motor 16 on the one hand and the internal combustion engine 20 on the other hand controls and z. B. also for the control of Luftdosierelements 26 responsible for. Such a mechanically adjustable compressor is for example in the DE 102 52 767 A1 described. The compressor described there 34 ' includes funds 70 for adjusting the inlet angle to the compressor wheel ("Mitdralleinrichtung"), and by this inflow angle, the power consumption of the compressor is influenced 34 ' with the element 70 , allows to quickly influence the transported compressed air mass, without changing the speed of the compressor 34 ' would have to change. This is especially the case if you want to switch between operating modes of the drive system at short notice, eg. B. when the fuel cell stack 12 should be added or short term, the power consumption of the engine 20 should be increased.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10303867 A1 [0003, 0003]
• - DE 10322296 A1 [0004]
• - DE 10252767 A1 [0029]

Claims (11)

Drive system for a motor vehicle, with a first subsystem ( 10 ), which is a fuel cell system ( 12 ), and with a second, from the first subsystem ( 10 ) different subsystem ( 20 ), whereby both subsystems are connected via a common supply device ( 24 . 24 ' . 24 '' . 24 ' ) are supplied with compressed air, characterized in that the common supply device ( 24 . 24 ' . 24 '' . 24 ' ) a compressor ( 34 . 34 ' ), which by means of an electric motor ( 36 ) is drivable. Drive system according to claim 1, characterized in that the second subsystem comprises an internal combustion engine ( 20 ), which gives off exhaust gas which is a turbine ( 28 . 50 ) is passed for the purpose of their drive, with a compressor ( 30 ; 34 . 34 ' ) is coupled. Drive system according to claim 2, characterized in that the turbine ( 28 ) coupled compressors ( 30 ) another compressor ( 30 ), that of the electric motor ( 36 ) drivable compressor ( 34 ) is different. Drive system according to claim 3, characterized in that of the fuel cell system ( 12 ) discharged exhaust gas to a turbine ( 50 ) for the purpose of their drive, which is connected to the compressor ( 34 ) coupled by the electric motor ( 36 ) is drivable. Drive system according to claim 3 or 4, characterized in that on at least one of the compressors a bypass ( 38 . 42 ) is provided for air that can be opened and closed. Drive system according to claim 2, characterized in that the turbine ( 50 ) coupled compressors ( 34 ) of the electric motor ( 36 ) drivable compressors ( 34 ). Drive system according to claim 6, characterized in that the fuel cell system ( 12 ) discharged exhaust gas to the same turbine ( 50 ) like the exhaust gas of the internal combustion engine ( 20 ). Drive system according to claim 7, characterized in that the exhaust gas from the internal combustion engine ( 20 ) to a first inlet ( 54 ) of a container ( 56 ) and the exhaust gas from the fuel cell system ( 12 ) to a second inlet ( 60 ) of the container ( 56 ), the outlet ( 62 ) of the container ( 56 ) to the turbine ( 50 ) leads. Drive system according to claim 8, characterized in that the container ( 56 ) is designed so that when pressure fluctuations occur with a certain fluctuation amplitude at the first inlet ( 54 ) at the second inlet ( 60 ) Pressure fluctuations occur with a fluctuation amplitude which is smaller than the fluctuation amplitude at the first inlet ( 54 ). Drive system according to claim 8 or 9, characterized by a check valve ( 58 ) between fuel cell system ( 12 ) and second inlet ( 60 ). Drive system according to one of claims 6 to 9, characterized in that the compressor ( 34 ' ) is mechanically adjustable to produce different boost pressures at the same speed, wherein a mechanical adjustment is effected by a control command issued by an electronic control unit, wherein the electronic control unit also the operation of the two subsystems ( 10 . 20 ) controls.