DE102018009574A1 - Method for operating a drive train for a hybrid vehicle - Google Patents

Abstract

The invention relates to a method for operating a drive train for a hybrid vehicle, in which the drive train is an internal combustion engine (12), a transmission via which wheels of the hybrid vehicle can be driven by means of the internal combustion engine, a high-temperature cooling circuit (18) through which a high-temperature coolant can flow. in which at least one cylinder housing (14) of the internal combustion engine (12) is arranged, and a low-temperature cooling medium through which can flow through a low-temperature cooling circuit (20), in which the transmission is arranged, wherein at least one fluidically from the high-temperature cooling circuit ( 18) separate branch (46) of the low-temperature cooling circuit (20) through the cylinder housing (14), wherein during an electric drive, during which the wheels are driven via the transmission by means of an electric machine of the drive train and the internal combustion engine (12) is decoupled from the transmission and the transmission is cooled by means of the low-temperature cooling medium, at least a portion of the low-temperature cooling medium through the branch (46) is passed, whereby at least the cylinder housing (14) by means of the branch (46) flowing through Partly heated or kept warm.

Description

The invention relates to a method for operating a drive train for a hybrid vehicle according to the preamble of patent claim 1.

Such methods for operating powertrains for hybrid vehicles, in particular for so-called P2 hybrid vehicles, are already well known from the general state of the art. In the method, the drive train formed for example as a P2 drive train has an internal combustion engine and a transmission drivable by the internal combustion engine, via which wheels of the hybrid vehicle and thus the hybrid vehicle as a whole can be driven by means of the internal combustion engine. The drive train furthermore has a high-temperature cooling circuit, through which a high-temperature cooling medium can flow, in which at least one cylinder housing of the internal combustion engine is arranged. As a result, at least the cylinder housing can be cooled by means of the high-temperature cooling medium flowing through the high-temperature cooling circuit. In addition, a low-temperature circuit through which a low-temperature cooling medium can flow is provided, in which the transmission is arranged. As a result, the transmission can be cooled by means of the low-temperature cooling medium flowing through the low-temperature circuit.

Furthermore, the DE 10 2007 016 205 B4 an apparatus for heating a crankcase breather and for cooling power electronics in a hybrid vehicle, comprising an internal combustion engine and an electric motor.

In addition, the DE 103 00 294 A1 to take a power transmission thermal management system for a hybrid vehicle as known.

Object of the present invention is to develop a method of the type mentioned in such a way that a particularly advantageous operation of the hybrid vehicle can be realized.

This object is achieved by a method having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

In order to develop a method specified in the preamble of claim 1 type such that a particularly advantageous operation of the drive train and thus the hybrid vehicle can be implemented in total, it is inventively provided that at least one fluidly separated from the high-temperature cooling circuit branch of the low-temperature cooling circuit passes through the cylinder housing. The cylinder housing forms at least one or more cylinders of the example designed as a reciprocating engine internal combustion engine. In this case, the cylinder housing may be formed as a crankcase or as a cylinder crankcase, on which a preferably constructed as a crankshaft output shaft of the internal combustion engine is rotatably mounted. Thus, at least in an internal combustion engine operation of the drive train, at least the crankcase can be cooled by means of the high-temperature cooling medium. This is done in particular such that the high-temperature cooling medium flows through the high-temperature cooling circuit and thus through the crankcase.

According to the invention, it is now provided that at least the aforementioned branch of the low-temperature cooling circuit also passes through the cylinder housing or through the crankcase, wherein during an electric drive, during which the wheels are driven via the transmission by means of at least one electric machine of the drive train and the Internal combustion engine is decoupled from the transmission and from the wheels and the transmission is cooled by means of the low-temperature cooling circuit flowing through low-temperature cooling medium, at least a portion of the low-temperature cooling medium through the branch and thus through the cylinder housing (crankcase) is passed, whereby at least the Cylinder housing is heated or kept warm by means of the branch flowing through the part. Since the branch, in particular the low-temperature cooling circuit as a whole, is fluidically separated from the high-temperature cooling circuit at least during the said electric drive, a mixing of the high-temperature cooling medium with the low-temperature cooling medium or vice versa is omitted.
In other words, there is no replacement of the low-temperature cooling medium and the high-temperature cooling medium. In other words, at least the part of the low-temperature cooling medium is passed through the branch and thus through the cylinder housing during the electric drive, without any mixing or replacement of the low-temperature cooling medium and the high-temperature cooling medium. The part of the low-temperature cooling medium is also referred to as low-temperature coolant flow, which is passed through the cylinder housing (crankcase) during the electric drive. Since the low-temperature cooling medium is used during the electric drive in order to cool the transmission, for example via a transmission oil heat exchanger, wherein at least the low-temperature coolant Coolant flow is used to cool the transmission, in particular via the transmission oil heat exchanger, there is an at least indirect, in particular direct, heat transfer from the transmission, in particular from a transmission oil for cooling and lubricating the transmission, to which the low-temperature cooling circuit flowing through low-temperature Cooling medium and thus a previously described low-temperature coolant flow. As a result, the transmission or the transmission oil is cooled, and the low-temperature cooling medium and thus the low-temperature coolant flow described above are heated.

Following this, at least the low-temperature coolant flow flows through the branch. As a result, at least the previously heated low-temperature coolant flow can be used to heat or to keep the cylinder housing warm. For this purpose, an at least indirect, in particular direct, heat transfer from the low-temperature coolant flow flowing through the branch to the cylinder housing (crankcase) takes place. As a result, for example, the low-temperature coolant stream is cooled again, and the cylinder housing is heated or kept warm. Since the low-temperature cooling circuit and the high-temperature cooling circuit are fluidly separated from each other at least during said electrical drive, the low-temperature cooling medium does not mix with the high-temperature cooling medium, so that an undesirable mutual influence of the low-temperature cooling circuit and the high-temperature cooling circuit is omitted.

The branch has, for example, at least one channel through which the low-temperature coolant flow can pass, and which is for example either cast into the cylinder housing or subsequently joined into the cylinder housing, for example by a pipe designed in particular as a water pipe. Thus, it can be provided in an advantageous embodiment of the invention that the branch is formed integrally with the cylinder housing.

It has been found to be advantageous if the branch is formed by casting the cylinder housing and / or poured into the cylinder housing.

A further embodiment provides that the branch has at least one pipe element formed separately from the cylinder housing and joined to the cylinder housing, which can be flowed through by the part.

In a further embodiment of the invention, it is provided that during an internal combustion engine drive, during which the wheels are driven via the transmission of the internal combustion engine, the low-temperature cooling medium flows through the low-temperature cooling circuit, while a flow of the low-temperature cooling medium through the branch is omitted. Thus, during the combustion engine drive, the branch for the low-temperature cooling medium is blocked. In this way, an undesirable, excessive heating of the low-temperature cooling medium can be avoided by the cylinder housing.

The branch extending in or through the cylinder housing is, for example, an exchange section, which is arranged in the cylinder housing (crankcase). For example, the high-temperature cooling circuit or the high-temperature cooling medium can be heated via the exchange path, in particular by a heat transfer from the low-temperature coolant flow flowing through the branch to the high-temperature cooling circuit or to the high-temperature cooling medium.

The low-temperature cooling circuit and the high-temperature cooling circuit are collectively referred to as cooling circuits, wherein the high-temperature cooling medium and the low-temperature cooling medium are collectively referred to as a cooling medium. The respective cooling medium is preferably a fluid, in particular a liquid, wherein the respective cooling medium may comprise at least or exclusively water. The cooling circuits and thus the cooling media differ in particular in that the low-temperature cooling medium flows through the low-temperature cooling circuit at a maximum first temperature, the high-temperature cooling medium having a second maximum temperature higher than the first maximum temperature by the high-temperature cooling circuit flows. For example, the first maximum temperature is 60 degrees Celsius, with the second maximum temperature being in a range of, for example, 90 degrees Celsius to 120 degrees Celsius inclusive. Thus, for example, during at least one operating state of the powertrain, the cooling media flows at different temperature levels through the cooling circuits, the temperature level of the high-temperature cooling medium being higher than the temperature level of the low-temperature cooling medium.

If, for example, the electric drive switches over to the internal combustion engine drive so that, for example, the internal combustion engine, which is also referred to as an internal combustion engine, is switched on, for example, the low-temperature coolant is diverted by means of a valve, so that a flow of the Low-temperature cooling medium through the branch is omitted. In this way it can be avoided that the low-temperature cooling medium reaches the high temperature level of the high-temperature cooling medium. Under internal combustion engine ride is to be understood that the wheels are driven at least by means of or exclusively by means of the internal combustion engine, so that, for example, during the combustion engine driving caused by the electric machine driving the wheels is omitted, or during the internal combustion engine driving the wheels both by means of the internal combustion engine also powered by the electric machine.

The powertrain is a hybrid powertrain because it includes both the internal combustion engine and the electric machine. In this case, the drive train is preferably a P2 hybrid powertrain, so that the wheels can be driven by the electric machine via the transmission, while the internal combustion engine is decoupled from the transmission and from the wheels, for example via a clutch. The invention is based on the following findings: For example, in a purely electric driving operation of a P2 hybrid powertrain, the transmission and thus the transmission oil are heated because the transmission is driven by the electric machine. The transmission or the transmission oil is heated by friction in the transmission. However, the cylinder housing, which is designed, for example, as a crankcase or cylinder crankcase, is usually not heated and is not kept warm, since the internal combustion engine is deactivated during purely electric driving and is not driven. In other words, during the electric driving operation, no movement and no combustion take place in the cylinder housing, since the internal combustion engine is in its uncontrolled operation during the purely electric driving operation. Usually, this can cause the internal combustion engine to cool down or cool down considerably. If the internal combustion engine, which is also referred to as a combustor, is then switched on or activated in order, for example, to achieve high system outputs, respective cylinder walls bounding the cylinder only have very low temperatures. As a result, there may be high fuel inputs in an engine oil for lubricating the internal combustion engine. This can lead to an oil overfilling of the internal combustion engine and viscosity changes of the engine oil and thus to increased wear. The aforementioned problems and disadvantages can now be avoided by the method according to the invention.

Since the gear is driven by the electric machine and thus heated during the electric drive, waste heat of the electric machine or the transmission is used to heat or warm the cylinder housing via the low-temperature cooling medium and the branch by means of the waste heat. In this case, a space-saving guidance of the low-temperature cooling medium is provided by the branch and thus by the cylinder housing, in particular in comparison to circulation heat exchangers, via which the cooling media can exchange heat. Since the low-temperature cooling circuit per se is integrated into the crankcase via the branch, the high-temperature cooling circuit and thus a high-temperature pump provided for conveying the high-temperature cooling medium through the high-temperature circuit can remain deactivated during the purely electrical drive described above. During the electric drive, for example, the low-temperature cooling medium is conveyed through the low-temperature cooling circuit and thus through the branch by means of a low-temperature pump, while the high-temperature pump is deactivated. By the method according to the invention, excessive dilution of the engine oil can be avoided. In addition, a particularly low-wear operation can be realized, so that excessive wear of the internal combustion engine can be avoided. In addition, since at a transition from the electric drive to the internal combustion engine driving the cylinder housing has a sufficiently high temperature, since it was previously heated or kept warm, the fuel consumption of the internal combustion engine can be kept very low.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

The drawing shows in the single FIGURE is a schematic representation of a cooling device for cooling a hybrid powertrain formed powertrain for a hybrid vehicle.

The single FIGURE shows a schematic representation of a cooling device 10 for cooling a drive train designed as a hybrid drive train for a hybrid vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car. By means of the drive train, at least two wheels of the Hybrid vehicle and thus the hybrid vehicle to be driven in total. The following is a method for operating the drive train and thus the cooling device with reference to FIG .. 10 described.

The drive train has an internal combustion engine 12 on, by means of which the wheels can be driven by combustion engine. This includes the internal combustion engine 12 a cylinder housing 14 and one separately from the cylinder housing 14 trained and with the cylinder housing 14 connected cylinder head 16 , The cylinder housing 14 is, for example, a crankcase referred to as a crankcase, since the cylinder housing 14 Cylinder of the internal combustion engine 12 forms and there on the cylinder housing 14 designed as a crankshaft output shaft of the internal combustion engine 12 is rotatably mounted. In addition, the drive train comprises a transmission which can not be identified in the figure and can be driven by the internal combustion engine, via which the wheels of the hybrid vehicle by means of the internal combustion engine 12 can be driven. The cooling device 10 and thus the powertrain include a high-temperature refrigeration cycle, also referred to as HT-cycle 18 , which can be flowed through by a high-temperature cooling medium, also referred to as HT medium. Here are the cylinder housing 14 and the cylinder head 16 in the high temperature refrigeration cycle 18 arranged and thus flowed through by the high-temperature cooling medium. To the internal combustion engine 12 By means of the high-temperature cooling medium to cool, the high-temperature cooling medium through the high-temperature cooling circuit 18 directed. As a result, a heat transfer from the cylinder housing 14 and from the cylinder head 16 to the high temperature cooling medium. As a result, the cylinder housing 14 and the cylinder head 16 cooled, and the high-temperature cooling medium is heated.

The cooling device 10 and thus the powertrain moreover comprise a low-temperature cooling circuit, also referred to as an NT circuit 20 , which can be flowed through by a low-temperature cooling medium, also referred to as NT medium. While the cylinder housing 14 and the cylinder head 16 at the high temperature cooling circuit 18 are arranged is in the low-temperature circuit 20 arranged in the figure unrecognizable transmission. As a result, the transmission can be cooled by means of the low-temperature cooling medium. This cooling of the transmission is preferably via a transmission oil heat exchanger 22 which is in the low-temperature refrigeration cycle 20 is arranged. The transmission oil heat exchanger 22 is flowed through by transmission oil for cooling and lubricating the transmission and the low-temperature cooling medium. In this case, a heat transfer from the transmission to the transmission oil, whereby the transmission is cooled. In addition, a heat transfer from the transmission oil via the transmission oil heat exchanger 22 done to the low-temperature cooling medium, whereby the transmission oil is cooled and the low-temperature cooling medium is heated. The high-temperature cooling medium and the low-temperature cooling medium are collectively also referred to as cooling media or media, wherein the respective cooling medium is preferably a liquid and at least or exclusively comprises water. In addition, the high-temperature cooling circuit 18 and the low-temperature cooling circuit 20 collectively referred to as cooling circuits or circuits.

In the high-temperature refrigeration cycle 18 are also a cooler 24 , a thermostat 26 , Also referred to as a water pump and preferably designed as an electrically operable pump pump 28 , an engine oil heat exchanger 30 , an exhaust gas turbocharger 32 , a heating heat exchanger 34 and a surge tank 36 arranged. By means of the thermostat 26 For example, the high-temperature cooling medium can be divided into several partial flows and into respective partial branches of the high-temperature cooling circuit 18 be split. The pump 28 is preferably an electrically operable pump, by means of which the high-temperature cooling medium through the high-temperature cooling circuit 18 can be promoted.
The engine oil heat exchanger 30 For example, the high-temperature cooling medium and / or another, for example formed as a liquid coolant can flow through, wherein the engine oil heat exchanger and engine oil for lubricating the internal combustion engine 12 can be flowed through. About the engine oil heat exchanger 30 For example, a heat transfer from the engine oil to the coolant or to the high-temperature coolant, whereby the engine oil is cooled and the coolant or the high-temperature coolant is heated. About the heating heat exchanger 34 a heat transfer from the high temperature cooling medium to air can take place, which is the heating heat exchanger 34 flows around. This will be the heat exchanger 34 heated air around. The heated air is supplied, for example, the interior of the hybrid vehicle, whereby the interior can be heated. The cooler 24 For example, air, in particular ambient air, can flow around it. About the radiator 24 may be a heat transfer from the high-temperature cooling medium to the radiator 24 flow around the air, whereby the high-temperature cooling medium is cooled.

In the low-temperature cooling circuit 20 are a cooler 37 , not in the figure indicated integrated starter generator, a charge air cooler 38 , the transmission oil heat exchanger 22 and a pump designed, for example, as an electrically operable pump 40 arranged. By means of the exhaust gas turbocharger 32 can air, which is the cylinders of the internal combustion engine 12 is fed, compressed. By compressing the air, it is heated. About the intercooler 38 , which is designed as a water-air heat exchanger, the compressed air can be cooled by a transition from the compressed air through the intercooler 38 to the intercooler 38 flowing through low-temperature cooling medium. The heated low-temperature cooling medium can by means of the cooler 37 be cooled by a heat transfer from the low-temperature cooling medium through the radiator 37 in air, which is the cooler 37 flows around. By means of the pump 40 can the low-temperature cooling medium through the low-temperature cooling circuit 20 be encouraged. In addition, in the low temperature refrigeration cycle 20 an example designed as a rotary valve valve element 42 arranged, by means of which, for example, the low-temperature cooling medium in partial streams and thereby in respective sub-branches of the low-temperature cooling circuit 20 can be split. In addition, a presently designed as a 3/2-way valve valve element 44 provided, by means of which, for example, at least one flow of the low-temperature cooling medium can be adjusted as needed.
The trained as a hybrid powertrain powertrain also includes at least one electric machine, by means of which the wheels can be electrically driven via the transmission.

In order to have a particularly advantageous operation of the internal combustion engine which is particularly low in wear and fuel consumption 12 and thus to be able to realize the drive train and the hybrid vehicle as a whole, at least one runs fluidly from the high-temperature cooling circuit 18 separate branch 46 the low-temperature cooling circuit through the cylinder housing 14 ,

During an electric drive during which the wheels are electrically driven via the transmission by means of the electric machine and the internal combustion engine 12 is decoupled from the transmission and from the wheels and the transmission by means of the low-temperature cooling circuit 20 is cooled by flowing low-temperature cooling medium, at least part of the low-temperature cooling medium through the branch 46 passed, whereby at least the cylinder housing 14 by means of the branch 46 flowing through part of the low-temperature cooling medium is heated or kept warm. In other words, during the said electric drive, the wheels are driven by the electric machine via the transmission, so that the transmission is driven by the electric machine. As a result, the transmission and thus the transmission oil are heated. During the electric drive, the low-temperature cooling medium flows through the low-temperature cooling circuit 20 so that the transmission oil through the transmission oil heat exchanger 22 cooled by means of the low-temperature cooling medium and the low-temperature cooling medium via the transmission oil heat exchanger 22 is heated by the transmission oil and thus by the transmission.

During the electric drive, for example, a clutch is opened, whereby the internal combustion engine is decoupled from the transmission and from the wheels. This puts the internal combustion engine 12 silent during electrical operation. In other words, the internal combustion engine 12 not driven during the electric drive. In particular, the internal combustion engine 12 deactivated during the electric drive, so that the internal combustion engine 12 during the electric drive is in its unfired mode. During the electric drive, at least the aforementioned part of the low-temperature cooling medium is passed through the branch 46 directed. As a result, a heat transfer from the previously heated low-temperature cooling medium to the cylinder housing 14 done, whereby the cylinder housing 14 is heated or kept warm. To the example of the transmission oil heat exchanger 22 coming low-temperature cooling medium through the branch 46 to guide, the valve element 44 switched to a first switching position, not shown in the figure.

For example, the internal combustion engine 12 activated and thus switched on, the valve element 44 for example, switched to a second switching position shown in the figure. In the episode becomes the branch 46 bypassed by the low temperature cooling medium. In other words, the branch becomes 46 blocked for the low-temperature cooling medium, so then, for example, during an internal combustion engine drive a flow of the low-temperature cooling medium through the branch 46 omitted.

At least the branch 46 at least during the electrical drive from the high temperature refrigeration cycle 18 is fluidically isolated, during the electric ride at least the part of the low-temperature cooling medium through the branch 46 and thus through the cylinder housing 14 passed through, without causing a mixing of the cooling media. As a result, undesirable impairments of the cooling circuits can be avoided. As in the combustion engine drive the branch 46 can be fluidly blocked to avoid that the low-temperature cooling medium is excessively heated by the high-temperature cooling medium, whereby an advantageous operation can be ensured.

Because the cylinder housing 14 heated or kept warm during the electric drive, has the cylinder housing 14 At the beginning of the internal combustion engine ride a beneficial high temperature, so that excessive dilution of fuel to operate the internal combustion engine 12 avoided by the engine oil and wear of the internal combustion engine 12 can be kept very low. In addition, the fuel consumption of the internal combustion engine 12 be kept particularly low.

LIST OF REFERENCE NUMBERS

10

cooling device

12

Internal combustion engine

14

cylinder housing

16

cylinder head

18

High-temperature cooling circuit

20

Low-temperature cooling circuit

22

Transmission oil heat exchanger

24

cooler

26

thermostat

28

pump

30

Engine oil heat exchanger

32

turbocharger

34

Heater core

36

surge tank

37

cooler

38

Intercooler

40

pump

42

valve element

44

valve element

46

branch

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 102007016205 B4 [0003]
• DE 10300294 A1 [0004]

Claims (5)

Method for operating a drive train for a hybrid vehicle, in which the drive train an internal combustion engine (12), a drivable by the internal combustion engine (12) transmission over which wheels of the hybrid vehicle can be driven by means of the internal combustion engine, a high-temperature cooling medium can flow through a high-temperature cooling circuit (18), in which at least one cylinder housing (14) of the internal combustion engine (12) is arranged, and a low-temperature cooling medium can flow through low-temperature cooling circuit (20), in which the transmission is arranged, characterized in that at least one fluidically from the high-temperature refrigeration cycle (18) separate branch (46) of the low-temperature cooling circuit (20) through the cylinder housing (14), wherein during an electric drive during which the wheels via the transmission by means of at least one electric machine of the drive stranded and the internal combustion engine (12) is decoupled from the transmission and the wheels and the transmission is cooled by means of the low-temperature cooling circuit (20) flowing through low-temperature cooling medium, at least a portion of the low-temperature cooling medium through the branch (46) whereby at least the cylinder housing (14) is heated or kept warm by means of the part flowing through the branch (46). Method according to Claim 1 the armature (46) is formed integrally with the cylinder housing (14). Method according to Claim 1 or 2 , characterized in that the branch (46) formed by casting the cylinder housing (14) and / or is poured into the cylinder housing (14). Method according to one of the preceding claims, characterized in that the branch (46) at least one separately from the cylinder housing (14) formed and with the cylinder housing (14) joined tubular element, which is flowed through by the part. Method according to one of the preceding claims, characterized in that during a combustion engine drive, during which the wheels are driven via the transmission of the internal combustion engine (12), the low-temperature cooling medium flows through the low-temperature cooling circuit (20), while a flow of low temperature Cooling medium through the branch (46) is omitted.

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