DE102016208662A1 - A method of operating a powertrain component or powertrain for a hybrid vehicle - Google Patents

Abstract

Method for operating a drive train component or a drive train of a hybrid vehicle, wherein the drive train component or the drive train has at least one drive shaft (21), an output shaft (22), an electric machine (1) operatively connected to the drive shaft (21), and a starting element (3) in the power flow between the electric machine (1) and the output shaft (22), wherein the electric machine (1) is adapted to drive the output shaft (22) for driving the hybrid vehicle, and one with the electric machine (1) via a clutch (10) connectable internal combustion engine (9), wherein during a drive of the output shaft (22) solely by means of the electric machine (1) the torque (1t) of the electric machine (1) to a value (1t- e) is limited, which is below a maximum torque (1t-max) of the electric machine (1), so that upon reaching or exceeding this Value (1t-e) by a desired drive torque (ts1, ts2) is a sufficient torque reserve of the electric machine (1) is available to the internal combustion engine (10) while canceling the torque limit by means of the electric machine (1) to start, wherein the value (1t-e) for limiting the torque (1t) of the electric machine (1) with increasing differential speed (3n) of the starting element (3) is raised, and powertrain component or drive train for a hybrid vehicle.

Description

The invention relates to a method for operating a drive train component or a drive train for a hybrid vehicle. The invention further relates to a drive train component or a drive train for a hybrid vehicle.

In the prior art, it is known to use the electric machine set up for driving a hybrid vehicle also for starting the internal combustion engine of the hybrid vehicle. The patent application DE 10 2011 005 468 A1 In this connection, the Applicant teaches, when the reciprocating internal combustion engine is switched off, to determine a starting torque for starting the reciprocating internal combustion engine which is available from the electric machine as a function of a current operating state of the reciprocating internal combustion engine, and a torque available from the electric machine for further functions that can be represented by the electric machine from the difference of the maximum torque currently generated by the electric machine and the starting torque to determine.

The patent application DE 10 2007 061 730 A1 describes a similar method, wherein the starting torque for starting the internal combustion engine is determined while driving. The aim of such a determination of the engine starting torque is to reduce the frequency of starting operations of the internal combustion engine.

It is an object of the invention to further reduce the frequency of starting operations of the internal combustion engine.

The object is achieved by the method according to claim 1. Advantageous embodiments will become apparent from the dependent claims, the description and from the figures. In claim 7, a drive train component or a drive train for a hybrid vehicle is also claimed with a control unit for controlling the specified in claim 1 method for solving the problem.

A method of operating a powertrain component or powertrain of a hybrid vehicle is disclosed. The drive train component can be formed for example by a hybrid module, which is arranged between the internal combustion engine and a transmission gear of the drive train. The powertrain component may also be formed by the transmission gearbox itself. In any case, the drive train component or the drive train comprises a drive shaft and an output shaft, an electric machine operatively connected to the drive shaft, and a starting element in the force flow between the electric machine and the output shaft.

A starting element allows the formation of a differential speed between two halves of the starting element, which are in operative connection with the drive shaft and the output shaft. Examples of such a starting element are hydrodynamic torque converters or friction clutches. By the starting element, the rotational speed of the electric machine can be higher than the rotational speed of the output shaft, even taking into account a transmission ratio between the electric machine and the output shaft.

The electric machine is both adapted to drive the output shaft for driving the hybrid vehicle, as well as to start a connectable to the electric machine via a clutch internal combustion engine. The starting of the internal combustion engine can take place in the state of the hybrid vehicle or during a driven by the electric machine driving operation of the hybrid vehicle.

During a drive of the output shaft alone by means of the electric machine, the torque of the electric machine is limited to a value which is below a maximum possible torque of the electric machine. As a result, a torque reserve of the electric machine is formed, so that upon reaching or exceeding this value by a desired drive torque sufficient torque is available to start the internal combustion engine by means of the electric machine. If the engine is started, the limitation of the electric machine torque is canceled.

According to the invention, the value for limiting the electric machine torque is increased with increasing differential speed of the starting element. In other words, the torque reserve for starting the internal combustion engine is reduced with increasing differential speed of the starting element. Because in the presence of a differential speed of the starting element additional rotational energy is stored in the electric machine, which can also be used in the presence of a start request of the engine for starting the internal combustion engine. Thus, more torque is available for driving the hybrid vehicle solely by means of the electric machine. The purely electric drive of the hybrid vehicle can thus cover a larger driving range, whereby the frequency of starting operations of the internal combustion engine can be reduced.

Preferably, the value for limiting the electric machine torque is raised only after reaching or exceeding a minimum speed of the electric machine. Because at low speed of the electric machine whose additional rotational energy is low, so that a consideration of the reserve torque can be neglected. The minimum speed can be, for example, 700 revolutions per minute.

According to a preferred embodiment, the raising of the value for limiting the electric machine torque is ramped. The ramp gradient used may depend on the slope of the differential speed curve. As a result, the dynamics of the components involved, for example when starting the hybrid vehicle can be considered.

Preferably, the value for limiting the electric machine torque is raised only up to a maximum value, which is less than the maximum torque that can be set by the electric machine. As a result, an additional torque reserve is created, which can be used in case of need by auxiliary consumers, for example by a hydraulic pump. If this need arises, the limitation of the electric machine torque can be canceled, and the torque capacity of the electric machine is fully utilized.

Preferably, after a successful increase in the value for limiting the electric machine torque, this value is reduced again as soon as the differential speed reaches or falls below a minimum value. Such a case may occur, for example, after a starting operation with slipping start-up element, when the starting element approaches the synchronous state again. This allows the dynamics of the components involved to be taken into account. Preferably, the reduction is ramped.

In addition to the method according to the invention, a drive train component or a drive train for a hybrid vehicle is specified which comprises a drive shaft, an output shaft, an electric machine operatively connected to the drive shaft, a starting element in the force flow between the electric machine and the output shaft and a control unit , The control unit is set up to control the method described above.

Embodiments of the invention are described in detail below with reference to the accompanying figures. The same and comparable components are provided with the same reference numerals. Show it:

1 a parallel hybrid powertrain with a hydrodynamic torque converter as a starting element;

2 a parallel hybrid powertrain with a start-up element integrated in the transmission;

3 temporal courses of different sizes of the drive train.

1 schematically shows a trained as a parallel hybrid powertrain powertrain of a motor vehicle. The powertrain has an internal combustion engine 9 and an electric machine 1 , being between the internal combustion engine 9 and the electric machine 1 a separating clutch 10 is switched. Furthermore, the drive train includes the 1 a gearbox 2 with a drive shaft 21 and an output shaft 22 , as well as a starting element 3 , wherein the starting element 3 between the electric machine 1 and the drive shaft 21 is switched. At the starting element 3 it is a hydrodynamic torque converter, which of a parallel-connected lock-up clutch 3B can be bridged. The output shaft 22 is in drive connection with drive wheels of the motor vehicle.

Should one with the drive train of the 1 equipped motor vehicle alone with the help of the electric machine 1 approach, this can be done with slipping converter or via the closed lock-up clutch 3B bridged converter done. During a starting process with slipping converter, the electric machine 1 have any speed while the output shaft 22 stands still, for example by actuation of a service brake of the motor vehicle. For a start-up procedure with closed lock-up clutch 3B are the speeds of electrical machine 1 and output shaft 22 through that in the transmission 2 Coupled selected gear ratio.

2 schematically shows a trained as a parallel hybrid powertrain powertrain of a motor vehicle, wherein the starting element 3 now in the transmission 2 is integrated. The starting element 3 For example, it may be one of the switching elements used to form the transmission ratio of the transmission 2 contributes. The electric machine 1 is with the drive shaft 21 firmly connected. The output shaft 22 is in drive connection with drive wheels of the motor vehicle.

Should one with the drive train of the 2 equipped motor vehicle alone with the help of electric machine 1 approach, this can be done with slipping start-up element 3 or with closed starting element 3 respectively. In a starting process with slipping start-up element 3 can the electric machine 1 have any speed while the output shaft 22 stands still, for example by actuation of a service brake of the motor vehicle. In a starting process with closed starting element 3 are the speeds of electrical machine 1 and output shaft 22 through that in the transmission 2 Coupled selected gear ratio.

Then, if with the powertrain according to 1 or 2 is purely electric, is the internal combustion engine 9 typically shut down and between the internal combustion engine 9 and the electric machine 1 switched disconnect clutch 10 fully open. In hybrid operation, however, in which both the internal combustion engine 9 as well as the electric machine 1 Running and providing torque is between the internal combustion engine 9 and the electric machine 1 switched disconnect clutch 10 closed.

The operation of the internal combustion engine 9 is powered by a motor control and the operation of the transmission 2 controlled by a transmission control. For controlling and / or regulating the operation of the electrical machine 1 typically there is a hybrid control. The starting element 3 , or the lock-up clutch 3B is controlled by a starting element control.

Typically, the starting element control and the transmission control are implemented in a common control device, namely in a transmission control device. The hybrid control may also be part of the transmission control device. The engine control is typically part of a separate control device, namely a motor control device. Engine control device and transmission control device exchange data with each other.

In accordance with 1 built-up powertrain can be the electric machine 1 and the starting element 3 to be summarized structurally to a so-called hybrid module, which in the drive train between the engine 9 and the transmission 2 is arranged. This hybrid module can thus form a drive train component. In accordance with 2 Built-up powertrain can be the transmission 2 together with the integrated starting element 3 and the electric machine 1 to be summarized structurally to a hybrid transmission. The electric machine 1 and the gearbox 2 are arranged in a common housing. Such a hybrid transmission can thus form a drive train component.

3 shows time courses of different sizes of the drive train according to 1 in a purely electrically driven starting, including a speed 1n the electric machine 1 , a speed 21n the drive shaft 21 , a value 1t-e for limiting the torque 1t the electric machine 1 , a reserve torque 1t-res the electric machine 1 , and two different desired drive torques ts1, ts2. The lockup clutch 3B is open, so that a differential speed 3n of the starting element 3 between the electric machine 1 and the drive shaft 21 can train.

At the beginning of the process is the electric machine 1 accelerated in response to the target drive torque ts1, ts2, so that their speed 1n increases. At the turbine wheel of the torque converter 3 Now builds up a torque, so that the speed 21n the drive shaft also rises. In the transmission 2 a gear is engaged, so that the vehicle starts from a standstill. The speed 1n the electric machine 1 increases faster than the speed 21n the drive shaft 21 so that the differential speed 3n between impeller and turbine of the torque converter 3 elevated. The value 1t-e for limiting the electric machine torque 1t remains constant. Thus, a constant reserve torque 1t-res held in order, if necessary, the internal combustion engine 9 by means of the electric machine 1 to be able to start. The static, not increased value 1t-e , and inversely the static, unreduced reserve torque 1t-res can depend on several factors, for example, a temperature of the internal combustion engine 9 ,

At time T1, the speed reaches 1n the electric machine 1 a minimum value 1n-min in which the electric machine 1 turns significantly faster than the drive shaft 21 , From time T1, the value becomes 1t-e for limiting the electric machine torque 1t ramped up until it reaches a maximum value which is less than the maximum by the electric machine 1 producible torque 1t-max , By increasing the value 1t-e can the target drive torque ts1, ts2 at time T2 by means of the electric machine 1 continue to be presented, so the internal combustion engine 9 does not have to be started. Without the increase in value 1t-e would have the internal combustion engine 9 be started at time T2 to ensure the implementation of the desired drive torque ts1, ts2.

At time T3 reaches the differential speed 3n a minimum value 3n-min , causing the value 1t-e for limiting the electric machine torque 1t is again reduced ramped. The ramp slope of the reduction of the value 1t-e is less than the ramp slope to increase the value 1t-e , The target drive torque ts2 exceeds the value at time T4 1t-e so that the implementation of the target drive torque ts2 is no longer by the electric machine 1 is guaranteed. Then the internal combustion engine would have to 9 to be started. The course of the desired drive torque designated as ts1 drops sufficiently, so that the electric machine 1 can implement the desired drive torque ts1. A start of the internal combustion engine 9 can therefore be omitted. At time T5 the value reaches 1t-e for limiting the electric machine torque 1t again its static value.

In the 3 shown temporal courses are also on a drive train according to 2 applicable. As the electric machine 1 in such a drive train fixed to the drive shaft 21 is connected, the speed is 21n in 3 through the output side speed of the in the transmission 2 integrated starting element 3 to replace.

LIST OF REFERENCE NUMBERS

1

Electric machine

1n

Speed of the electric machine

1n-min

Minimum speed of the electric machine

1t

Torque of the electric machine

1t-max

Maximum torque of the electric machine

1t-e

Value for limiting the torque of the electric machine

1t-res

Reserve torque of the electric machine

2

transmission

21

drive shaft

22

output shaft

ts1, ts2

Target drive torque

3

starting element

3n

Differential speed at the starting element

3n-min

Minimum value of the differential speed at the starting element

3B

lock-up clutch

9

internal combustion engine

10

clutch

T1

time

T2

time

T3

time

T4

time

T5

time

t

Time

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 102011005468 A1 [0002]
• DE 102007061730 A1 [0003]

Claims (7)

Method for operating a drive train component or a drive train of a hybrid vehicle, - wherein the drive train component or the drive train has at least one drive shaft ( 21 ), an output shaft ( 22 ), one with the drive shaft ( 21 ) electrically connected electrical machine ( 1 ), as well as a starting element ( 3 ) in the power flow between the electric machine ( 1 ) and the output shaft ( 22 ), wherein the electric machine ( 1 ) is arranged to the output shaft ( 22 ) to drive the hybrid vehicle, and one with the electric machine ( 1 ) via a coupling ( 10 ) connectable internal combustion engine ( 9 ), wherein during a drive of the output shaft ( 22 ) solely by means of the electric machine ( 1 ) the torque ( 1t ) of the electric machine ( 1 ) to a value ( 1t-e ), which is below a maximum torque (1tmax) of the electric machine ( 1 ), so that when this value is reached or exceeded ( 1t-e ) by a desired drive torque (ts1, ts2) a sufficient torque reserve of the electric machine ( 1 ) is available to the internal combustion engine ( 10 ) while canceling the torque limit by means of the electric machine ( 1 ), characterized in that the value ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) with increasing differential speed ( 3n ) of the starting element ( 3 ) is raised. Method according to claim 1, characterized in that the value ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) only after reaching or exceeding a minimum speed ( 1n-min ) of the electric machine ( 1 ) is raised. Method according to claim 1 or claim 2, characterized in that the raising of the value ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) takes place like a ramp. Method according to one of claims 1 to 3, characterized in that the value ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) is raised to a maximum value that is less than the maximum torque ( 1t-max ) of the electric machine ( 1 ). Method according to one of Claims 1 to 4, characterized in that, after a value has been increased ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) this value ( 1t-e ) is reduced again as soon as the differential speed ( 3n ) a minimum value ( 3n-min ) reaches or falls below. Method according to claim 5, characterized in that the reduction of the value ( 1t-e ) for limiting the torque ( 1t ) of the electric machine ( 1 ) takes place like a ramp. Drive train component or drive train for a hybrid vehicle, comprising at least one drive shaft ( 21 ), an output shaft ( 22 ), one with the drive shaft ( 21 ) electrically connected electrical machine ( 1 ), a starting element ( 3 ) in the power flow between the electric machine ( 1 ) and the output shaft ( 22 ) and a control unit, characterized in that the control unit is arranged to control the method according to one of claims 1 to 6.

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