DE102016009015A1 - Method for providing a derating function based on a temperature difference - Google Patents

Abstract

The temperature-related wear of components of a drive train (10) of a motor vehicle is to be reduced. The invention relates to a method for operating a drive train (10) which comprises a plurality of components, for example an electrical energy store (12), an inverter (14) and an electrical machine (30). In this case, a detection device (44) determines a temperature difference (40) within the plurality of components. By adjusting means (64), the operating state of one or more components is subsequently adjusted so that a predetermined difference limit value (42) for the temperature difference is not exceeded.

Description

The invention relates to a method for operating a drive train for a motor vehicle, wherein the drive train comprises a plurality of components by determining an operating parameter within the plurality of components and adjusting the operating state of one or more of the components when the operating parameter exceeds a predetermined threshold. In addition, the invention relates to a control device for a drive train of a motor vehicle, wherein the drive train comprises a plurality of components, with a detection device for determining an operating parameter within the plurality of components and an adjusting device for adjusting an operating state of one or more of the components, if the operating parameter has a predetermined limit exceeds.

An electric drive train of a motor vehicle, for example an electric vehicle or hybrid vehicle, comprises a plurality of components, for example but not limited to an electrical energy store, an inverter or inverter and an electrical machine. The electrical energy storage device can be constructed from one or more battery cells and designed as a high-voltage storage, with a voltage of over 60 V or as low-voltage storage with a voltage of less than 60 V. The electrical energy storage device supplies the electrical machine with electrical energy via the inverter. The inverter, often referred to as inverter, comprises a circuit arrangement of electronic components, in particular power modules, such as IGBTs, MOSFETs and diodes. The electric machine may be, for example, a permanent-magnet synchronous machine. The electrical energy storage device supplies the electrical machine with electrical energy via the inverter.

Depending on the amount of voltage provided by the electrical energy storage and the performance of the electric motor according to specifications, the individual components and electronic components of the drive train are dimensioned and developed. The aim is to ensure the longest possible service life and the lowest possible wear of components and individual electronic components. On the other hand, oversizing for cost and weight reasons should be avoided.

Each component and each electronic component has operating parameters by means of which the expected service life of a component and / or an electronic component can be predicted. Therefore, limit values are defined for the operating parameters, under the observance of which, for example, according to experience or determined by simulation, a sufficient life for an application results.

For example, is from the DE 10 2014 007 311 A1 a method for operating a drive train and a motor vehicle with a drive train known, wherein an evaluation determines at least one operating parameter of each of the components of the drive train. From these operating parameters, an actual state value, in particular an actual wear value, and a deviation from a predefined target value, in particular a desired wear value, are calculated for each of the three components. If there is a deviation between the two values, a setpoint for the operating parameter is predefined which at best compensates for the deviation between the actual wear value and the setpoint wear value.

From the US 2013/0076327 For example, there is known an electrical energy recovery system and method for operating an electrical energy recovery system wherein an electronic controller limits a temperature of a circuit to a threshold by providing a derating function. This can be done by limiting the power provided by the system.

A cooling system can be used to counteract high temperatures. Such a cooling system can cool one component or several components, for example by means of a cooling medium, in particular water or air. In this case, a heat transfer from the component to the cooling medium take place.

If an electric vehicle or a hybrid vehicle is accelerated, a high engine torque is requested via the electric machine. As a result of the engine torque, the electric current in the power electronics, in particular the inverter, increases very strongly and reaches a maximum value in a short time. As a result, the temperature in the semiconductor of an electronic component, for example a power module, can rise very rapidly. Since a direct measurement of the temperature of the semiconductor is only possible with difficulty, the temperature is measured at a circuit arrangement, in particular a direct copper board (DCB), to which the power module is assigned. For example, at a temperature at the circuit of 80 ° C, a reduction of the electrical energy stored by the electrical energy storage and / or power is initiated, there is a so-called derating. In fact, the temperature in the power module could be at 140 ° C, for example.

The derating model of power modules, in particular IGBTs, MOSFETs or diodes, is often based on a temperature model which takes into account only the absolute temperatures of the power modules. The calculation model for the temperature often includes the temperature measured at the circuit arrangement, also called setup and connection technology, of the power modules. The circuit arrangement can be realized for example by means of a direct copper board or direct bonded copper. The temperature of the circuit arrangement is only an estimate from which, based on a temperature model, the actual temperature in the semiconductor of the power module is concluded.

The prior art has the disadvantage that the components and individual electronic components, although protected from exceeding limit values, for example exceeding a temperature limit, but not protected against the occurrence of high temperature spreads, for example within the circuit arrangement or the direct copper board ,

It is an object of the present invention to reduce the wear of the components of a drive train of a motor vehicle and to extend their life.

This object is achieved by a method and by a drive train according to the respective independent claims.

Advantageous embodiments of the invention are the subject of the dependent claims and the figure.

An inventive method is used to operate a drive train for a motor vehicle. The drive train has a plurality of components, for example but not limited to an electrical energy storage, an inverter or inverter and an electric machine. The electrical energy storage device supplies the electrical machine with electrical energy via the inverter. An operating parameter is determined within the multiple components of the drive train. The operating state of one or more of the components is adjusted when the operating parameter exceeds a predetermined limit.

In order to reduce the wear on the plurality of components and to increase the service life, it is provided according to the invention that a temperature difference is determined as an operating parameter within the plurality of components. If this temperature difference exceeds the predetermined limit value or difference limit value, the operating state of one or more of the plurality of components is adjusted. The one component, within which or the components between which the temperature difference is measured, but may not be the component or the components whose operating state is adjusted. In other words, by adjusting the operating state of one or more components, it prevents the occurrence of harmful temperature differences within one component or between multiple components. As a result, thermal stresses can be limited within one or more components and thus the wear can be reduced.

In one embodiment of the method according to the invention, a temperature spread within a component can be determined. Rigid connections between individual components of different or even opposing heating rates, for example within the circuit arrangement of the inverter, are particularly sensitive to thermal stresses. Thus, the limitation of temperature differences is particularly advantageous here.

In a further embodiment, it is provided that the drive train comprises a cooling system which cools at least one further of the plurality of components. Here, the cooling of hot components can result in particularly high temperature gradients. Therefore, it is provided that a temperature difference between the cooling system and a further of the plurality of components, in particular the component to be cooled, is determined. This can be done, for example, by determining the temperature difference between the further component to be cooled and a heat exchanger or between the additional component to be cooled and a cooling medium.

In a particularly advantageous manner, the method according to the invention, for determining and limiting a temperature difference within or between a plurality of components, may be combined with a method which determines the absolute temperature of at least one of the plurality of components.

In this case, the absolute temperature of the components can also be assigned a predetermined absolute limit value. Again, then, the operating state of one or more of the plurality of components can be adjusted such that this absolute limit is not exceeded. In other words, both the occurrence of a harmful absolute temperature and the occurrence of a harmful temperature difference is then avoided. This means that as soon as one of the two temperature values, the absolute temperature or the temperature difference, exceeds its assigned absolute limit value or difference limit value, the operating state of one or more of the several components is adjusted. The two events "Exceeding the absolute limit value" and "Exceeding the differential limit value" can be logically linked via an OR, for example. In this particularly advantageous embodiment of the invention, the drive train is therefore protected against increased wear due to excessive temperature differences and resulting thermal stresses as well as increased wear due to excessive absolute temperatures.

In addition, the object is achieved by a control device for a drive train of a motor vehicle, wherein the drive train comprises a plurality of components, with a detection device for determining an operating parameter within the plurality of components and a fitting device for adjusting an operating state of one or more of the components, if the operating parameter exceeds predetermined limit, wherein the operating parameter represents a temperature difference within the plurality of components.

The preferred embodiments and their advantages presented with reference to the method according to the invention also apply correspondingly to the control device according to the invention.

The single FIGURE shows a schematic representation of an embodiment of the method according to the invention with a drive train according to the invention.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiment, however, the described components of the embodiment each represent individual, independent features of the invention to be considered, which further develop the invention independently of each other and thus individually or in a different than the combination shown as part of the invention. Furthermore, the described embodiment can also be supplemented by further features of the invention already described.

The figure shows a drive train 10 , with an electrical energy storage 12 , an inverter 14 and an electric machine 30 , The electrical energy storage device can be constructed from one or more battery cells and designed as a high-voltage storage, with a voltage of over 60 V, or as a low-voltage storage, with a voltage of less than 60 V. The electric machine may be, for example, a permanent-magnet synchronous machine.

The inverter 14 includes a circuit arrangement 16 with at least one power module 18 For example, a MosFET or an IGBT. A detection device 44 detects a temperature difference 40 between the circuit arrangement 16 and the power module 18 and compare the temperature difference 40 with a predetermined difference limit 42 , In the event that the difference limit 42 is not exceeded, it repeats this periodically 46 , Once the difference limit 42 is exceeded, it outputs a corresponding signal 48 , Another detection device 54 detects an absolute temperature 50 of the power module 18 and compares this absolute temperature 50 with a predetermined absolute limit 52 , In the event that the absolute limit 52 is not exceeded, it repeats this periodically 56 , Once the absolute limit 52 is exceeded, it outputs a corresponding signal 58 ,

The two signals 48 and 58 become a logical OR gate 60 directed. Once one of the two signals 48 . 58 indicates a respective overrun, gives the logical OR gate 60 a corresponding signal 62 to the adjustment device 64 out, which on the further signal 62 reacts by checking the operating status of one or more components 12 . 14 . 30 of the electric motor 10 adapts. This happens here, for example, by a current limit in the inverter 14 , This current limit can be used to further heat up the power module 18 be avoided. In this case, different characteristics for the current limit in question. In this exemplary embodiment, for example, when a limit value is exceeded, the available current is limited to a fixed value. In another embodiment, however, it is also possible to dynamically regulate the current limitation as a function of the level of the exceeding of the respective limit value. For this purpose, it would be advantageous not only to indicate the exceeding of the respective limit value, but also to use a deviation from the respective limit value.

To the thermal protection of the drive train 10 , in particular of the at least one power module 18 , and the construction and connection technology, here by a circuit arrangement 16 In order to ensure, both temperature mapping based on the absolute temperature is required 50 as determined by the registration unit 54 is provided as well as a temperature derating based on the temperature difference 40 as determined by the registration unit 44 provided. There is also an adjustment device 64 necessary to adjust the operating state accordingly.

In a further exemplary embodiment, for example, a motor vehicle, in particular an electric vehicle or a hybrid vehicle, with a drive train 10 , comprising an electrical energy store 12 , an inverter 14 , an electric machine 30 and a cooling system 32 , put into operation. If the motor vehicle in very cold condition, for example -20 ° C, put into operation and immediately high torque from the electric machine 30 requested, it results in a high current load for the at least one power module 18 and the temperature of the power module 18 rises very fast. Would in the context of temperature derating only the absolute temperature 50 monitored, the absolute temperature would be 50 the power module very fast z. B. reach 140 ° C and there is a temperature spread of 160 K within the chosen construction and connection technology. For example, only 80 K.

This temperature spread can in the embodiment by the detection device 44 for the temperature difference 40 and / or by a further evaluation unit for a further temperature difference in each case together with the adjusting device 64 be limited to a predetermined limit, for example 70 K. This derating model works primarily at low ambient temperatures. The two detection units 44 . 54 for the temperature difference 40 and for the absolute temperature 50 are linked via an OR gate. In other words, either a derating model A uses the absolute temperature 50 or a derating model B with respect to the temperature difference 40 , The derating model A is mainly used in high ambient temperatures when the cooling circuit 32 is warm and the monitored component, especially the power module 18 , can no longer be cooled optimally and the permissible absolute temperature 52 reached. The derating model B is especially important in cold environments or when the cooling circuit 32 is cold and high electrical power through the electric machine 30 is requested. The targeted adjustment of the operating state, in particular the reduction of the available power, the wear can be reduced and the life can be increased.

In a preferred embodiment, the control device is for the drive train 10 a motor vehicle, in particular a hybrid vehicle, an electric vehicle or a fuel cell vehicle assigned.

LIST OF REFERENCE NUMBERS

10

powertrain

12

electrical energy storage

14

inverter

16

circuitry

18

power module

30

electric machine

32

cooling system

40

temperature difference

42

Difference threshold

44

Detecting device for temperature difference

46

periodic recording

48

Signal of the difference limit value violation

50

absolute temperature

52

Absolute limit

54

Absolute temperature detection device

56

periodic recording

58

Signal of absolute limit value violation

60

OR gate

62

Signal for adjustment device

64

matching device

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 102014007311 A1 [0005]
• US 2013/0076327 [0006]

Claims (6)

Method for operating a drive train ( 10 ) for a motor vehicle, wherein the drive train ( 10 ) comprises a plurality of components, by - determining an operating parameter within the plurality of components and - adjusting an operating state of one or more of the components when the operating parameter exceeds a predetermined threshold, characterized in that - the operating parameter is a temperature difference ( 40 ) within the multiple components. A method according to claim 1, characterized in that as the temperature difference ( 40 ) a temperature spread within one of the components is determined. A method according to claim 1, characterized in that the plurality of components of the drive train ( 10 ) a cooling system ( 32 ) and an electrical component ( 18 ), and the temperature difference ( 40 ) between the cooling system ( 32 ) and the electrical component ( 18 ) is determined. Method according to one of the preceding claims, characterized in that for the adaptation additionally an absolute temperature ( 50 ) at least one of the several components is taken into account. A method according to claim 4, characterized in that the adjustment of the operating state is initiated if the absolute temperature ( 50 ) a predetermined absolute limit ( 52 ) exceeds. Control device for a drive train of a motor vehicle, wherein the drive train comprises a plurality of components, with - a detection device ( 44 ) for determining an operating parameter within the plurality of components and - an adjustment device ( 64 ) for adjusting an operating state of one or more of the components when the operating parameter exceeds a predetermined limit, characterized in that - the operating parameter is a temperature difference ( 40 ) within the multiple components.

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