DE102018207005A1 - System for operating an electric machine - Google Patents

Abstract

The invention relates to a system (2) for operating an electric machine (10), which is designed to drive a vehicle, the vehicle comprising the following components: a drive train, which is driven by the electric machine (10), at least one wheel (13) as a first mechanical load, which can be coupled to the drive train via a first clutch (21), and at least one second mechanical load, which can be coupled to the drive train via a respective second clutch and controlled via a respective actuator, wherein the system (2) configured to transmit torque to the at least one second mechanical load from the electric machine (10) upon closure of the respective second clutch (23), wherein the respective actuator is configured to control a value of the transmitted torque.

Description

The invention relates to a system and a method for operating an electric machine.

In a current drive concept for an electric vehicle or electric car, an electric drive motor is used only for propulsion of the electric vehicle. For air conditioning of an interior of the electric vehicle, a separate electric air conditioning compressor is used, which is powered directly via a high-voltage battery of the electric vehicle. Thus, it is possible to operate the electric drive motor and the electric air compressor as components of the electric vehicle maximum independently of each other. However, in each case a power electronics must be installed and operated for each component, whereby higher losses than necessary are generated.

The publication AT 512 443 B1 describes a drive train for a vehicle with an internal combustion engine with at least one first electric machine whose motor shaft is drive-connected to a drive shaft of the internal combustion engine via a mechanical transmission.

A method for operating an air conditioning compressor of an air conditioner is in the document DE 10 2005 022 210 B4 described. In this case, an electric motor is connected to an electric energy storage and integrated in a guided from an internal combustion engine to a transmission drive train.

An arrangement for connecting an accessory drive to a drive train of a vehicle is from the document DE 10 2014 212 874 A1 known. In this case, the accessory drive is connected to a crankshaft of an internal combustion engine.

Against this background, it was an object to improve an operation of an electric machine of a vehicle.

This object is achieved by a system and a method having the features of the independent patent claims. Embodiments of the system and method are evident from the dependent claims.

The system according to the invention is intended for operating an electric machine, which is designed to drive a vehicle. The system includes as components a powertrain driven by the electric machine, at least one wheel for propelling the vehicle as a first mechanical load to be coupled to the powertrain via a first clutch, and at least one second, Further mechanical load, which can be coupled via a respective second, further coupling to the drive train and via an example. In the at least one second mechanical load provided respective, for example, designed as a swash plate, actuator is controlled on. The system is designed to transmit torque to the at least one second mechanical load when the respective second, further clutch is closed by the electric machine. The respective actuator, for example, the swash plate, is designed as a translator of the torque to control a value of the transmitted torque.

The respective actuator, for example, is designed as a swash plate, is arranged in a possible embodiment of the system according to the invention in the second load and / or formed as part of the second load.

In an embodiment, the electric machine to be operated is also a component of the system according to the invention.

By adjusting or adjusting the respective actuator (swash plate) with the system, a compression capacity of the at least one second mechanical load to regulate or regulated, with the compaction performance in an embodiment, an additional mechanical load of the electric machine is set, and or whereby the on the at least one second, further mechanical load transmitted torque to regulate or is regulated or regulated.

The system has in design a control unit in which a map for efficiency of the electric machine is stored, wherein the control device is adapted to a particular current, for example. Original operating point of the electric machine on the map with an efficiency optimal operating point, eg. A local or global peak or a local or global maximum of the map to compare and move the current operating point by opening the respective second clutch, or by closing the respective second clutch and by setting the respective actuator to the efficiency optimal operating point. The map describes in a 3D representation of a functional relationship or dependence between speed, torque and efficiency of the electric machine. In general, the electric machine is at a given, ie fixed or, for example, operated by a driver, set speed, so that a two-dimensional dependence between torque and efficiency is to be considered, to optimum efficiency, as a rule maximum efficiency, set the electric machine at a given speed.

The at least one second mechanical load is as a compressor, in particular air conditioning compressor or air compressor, or pump and thus, for example. As a working machine, in particular for treating, d. H. Conveying, displacing and / or compressing or compressing a liquid or gaseous medium formed and usually has the swash plate as an actuator. By adjusting the actuator, the compression power of the second mechanical load is varied, whereby a translation of the torque from the electric machine to the at least one second mechanical load is adjusted.

The swash plate as an actuator of the second mechanical load and thus of the compressor is positioned at a variably adjustable angle α relative to a piston, in particular a compressor piston, of the compressor. By adjusting or adjusting this angle α, a stroke of the compressor piston and thus a compression capacity of the compressor is set. The delivery rate is independent of the speed. Furthermore, the torque to be translated or transmitted is regulated as a function of the angle α. A power for conveying the medium through the compressor and the stroke of the compressor are greater, the greater the angle α. If α = 0 °, the power to convey the medium is 0. In this case, the second clutch can be opened to decouple any drag losses.

The method according to the invention is provided for operating an electric machine which is designed to drive a vehicle. The vehicle has as components the electric machine, a drive train, which is driven by the electric machine, at least one wheel as the first mechanical load, which is coupled or coupled to the drive train via a first clutch, and at least one second, additional mechanical load, which can be coupled or coupled to the drive train via a respective second, further clutch and can be actuated or actuated via a respective actuator. In the method, a current operating point of the electric machine and an efficiency-optimal operating point for the electric machine is determined. Depending on a relative position of the current operating point to the optimum operating point, the respective second clutch is closed or opened, wherein at or by closing the respective second clutch of the electric machine in addition to torque, which is transmitted to the first mechanical load to the at least one second mechanical load in addition torque is transmitted. When the respective second clutch is closed, a value of the torque to be transmitted from the electric machine to the at least one second mechanical load is regulated and / or adjusted, and the torque from the electric machine to the at least one second load corresponding to the set and / or transferred regulated value.

The example designed as a swash plate actuator is usually arranged in the second mechanical load.

As described above, in the method in the embodiment, a map is used to describe a dependency of an efficiency of the electric machine on the torque and a rotational speed of the electric machine. The electric machine is operated in the current, for example, original operating point with a current, for example, original value of the rotational speed and a current, for example, original value of the torque. From the map, a characteristic curve is determined for this current value of the rotational speed, with the operating point that is optimal in terms of efficiency usually being determined as a high point or as the maximum of this characteristic curve, ie. H. is determined as the point on the characteristic curve at which the efficiency assumes a maximum value. The value of the torque on the characteristic curve associated with this maximum value of the efficiency is referred to below as the efficiency-optimal value of the torque. In addition, the operating point, in particular load point, the electric machine is determined on the characteristic curve, which is dependent on the current value of the torque. Taking into account a position of the current operating point relative to the optimum operating point of operation, the current value of the torque is shifted in the direction of the optimum efficiency value or to the optimum value of the torque, or whereby the current operating point on the characteristic in the direction of or to efficiency optimal operating point / s is shifted.

During a drive of the vehicle, a first portion of the torque of the electric machine is transmitted via the drive train of the vehicle to the at least one wheel of the vehicle. Via the respective actuator, a second portion of the torque of the electric machine is transmitted to the at least one second mechanical load, wherein said second portion of the torque has a value greater than or equal to zero. Here, the second portion of the torque, which is transmitted from the electric machine to the at least one second mechanical load, depending on how the current operating point is moved, changed or determined or controlled or adjusted.

In an embodiment of the method, the current value of the torque is compared with the efficiency-optimal value of the torque for the electric machine. In a first case, when the current value is less than the optimum efficiency value, the current value is increased toward the optimum efficiency value and the at least one second mechanical load is increased by closing the respective second clutch and / or adjusting the respective actuator provided in the original current operating point. In a second case, if the current value of the torque is greater than the torque efficiency value, the current value is reduced to the optimum efficiency value and the at least one second mechanical load is less torque by adjusting the respective actuator than at the original operating point and / or no torque is provided by opening the respective second clutch.

In a current, for example, original operating situation of the electric machine, it is therefore first checked whether the respective second clutch is closed or opened in the current, for example, the original operating situation. When initially closed respective second clutch, the second portion of the transmitted torque is greater than or equal to zero, wherein the respective second clutch remains closed in the first case and via the actuator, for example. The swash plate is controlled to be provided for the at least one second load torque , In the second case, the torque to be provided for the at least one second load is first at least reduced in the direction of efficiency-optimal torque by controlling or adjusting the actuator, for example the swash plate, and possibly opening the respective second clutch. When the respective second clutch is initially opened, the second component of the transmitted torque is equal to zero, the respective second clutch being closed in the first case and remaining open in the second case.

The second load is, for example, designed as a compressor or compressor, in particular as a swash plate compressor. It is possible that the second load is regulated by adjusting the actuator either internally or externally. If the second load, for example, the compressor, is controlled internally, the swash plate is controlled as an actuator based on a pressure gradient of the medium before and after the compressor. If the compressor is externally controlled as a second load, the swash plate is also externally controlled as an actuator. In an externally controlled compressor, it is possible to arbitrarily set a gradient of the torque, so that a connection of the second load by closing the second clutch is smoothly possible. The connection or a connection operation of an internally controlled compressor is carried out similarly, but with a higher gradient for the torque is provided, which can not always be smoothed out by the driving electric machine smoothly.

With an embodiment of the system, when carrying out an embodiment of the method, it is possible to improve the efficiency of the electric machine and thus of the vehicle by shifting the operating point of the electric machine to be designated as the load point, which electric energy is provided by a battery as the energy store of the vehicle , Here, the second mechanical load, in particular the air conditioning compressor, connected to the drive train of the vehicle or coupled via a respective second clutch. Thus arises analogously, as in the case of an internal combustion engine, the possibility to move the load point of the electric machine as a prime mover by the second mechanical load. Primarily, the electric machine is used to propel the vehicle. If necessary, the second mechanical load is connected directly to the electric machine by means of the respective second clutch and by means of the actuator as a translation. With the second mechanical load, which is designed in one embodiment as a swash plate compressor, it is possible to determine the compression capacity of the second mechanical load by adjusting the swash plate as an actuator. The compaction performance corresponds to an additional mechanical load applied by the electric machine in one embodiment of the method when the electric machine provides torque to the at least one second mechanical load.

Depending on the operating point at which the electric machine is operated as a drive machine, the additional load which acts on the electric machine by the at least one second mechanical load shifts and thus influences the operating point of the electric machine, thereby achieving a better efficiency for the electric machine or can be achieved. It is further contemplated that a demand for power applied to the electric machine and transmitted thereto for driving the at least one wheel is usually dictated by a desire of a driver of the vehicle. Thus, it is possible that, for example, at a maximum possible acceleration of the vehicle, the electric machine is operated as a prime mover in an operating point in which a large first portion of the torque from the electric machine to the at least one wheel, usually four wheels in the case a car, is transmitted. In this Case, a mechanical load of the electric machine by the at least one second mechanical load by the actuator, for example. The swash plate, reduced and / or set by opening the respective second clutch to zero, whereby the efficiency of the electric machine is improved.

Within the scope of the method, an operating strategy is carried out for the electric machine, which regulates the current operating point to an operating point that is optimal in terms of efficiency. This operating strategy can be adjusted depending on the respective current operating point and the characteristic diagram for the efficiency of the electric machine. The current operating point of the electric machine is changed by load change, i. H. depending on the relative position of the current operating point to the optimal operating point by load increase or increase the mechanical load or by load shedding or reducing the mechanical load of the electric machine by the at least one second mechanical load, positively influenced or shifted to the efficiency optimum operating point, whereby the Efficiency of the electric machine is increased. As a result, an increase in the range of the electric machine can be achieved.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or alone, without departing from the scope of the present invention.

• 1 zeigt in schematischer Darstellung eine aus dem Stand der Technik bekannte Anordnung.
• 2 zeigt in schematischer Darstellung eine Ausführungsform des erfindungsgemäßen Systems bei Durchführung einer Ausführungsform des erfindungsgemäßen Verfahrens.
• 3 zeigt Diagramme, die bei Durchführung der Ausführungsform des Verfahrens gemäß 2 berücksichtigt werden.

The invention is schematically illustrated by means of embodiments in the drawings and will be described schematically and in detail with reference to the drawings.

• 1 shows a schematic representation of an arrangement known from the prior art.
• 2 shows a schematic representation of an embodiment of the system according to the invention when carrying out an embodiment of the method according to the invention.
• 3 shows diagrams that in carrying out the embodiment of the method according to 2 be taken into account.

The figures are described coherently and comprehensively. Same components are assigned the same reference numerals.

In the 1 schematically illustrated and known from the prior art arrangement is provided for a vehicle and has as components a control unit 100 , a high-voltage battery 102 , a power electronics 104 , an electric machine 106 , a gearbox 108 for at least one wheel of the vehicle and an electric air conditioning compressor 110 (eKK). To drive the vehicle is via a first branch electrical energy from the high-voltage battery 102 via the power electronics 104 to the electric machine 106 transferred and converted by this into mechanical energy, which continues through the transmission 108 is transmitted to the at least one wheel to its drive. In addition, via a second branch, starting from the high-voltage battery 102 the electric air conditioning compressor 110 provided electrical power for its operation.

In the 2 schematically illustrated embodiment of the system according to the invention 2 is for a vehicle, eg. Motor vehicle, especially car, provided. In this case, the vehicle has as components a high-voltage battery as electrical energy storage 4 , a power electronics 6 , a control unit 8th (ECU), an electric machine 10 as a drive machine of the vehicle, which is designed here as an asynchronous motor and having an inverter, a transmission 12 that with at least one sketchy wheel 13 As the first mechanical load of the vehicle is connected, and a second mechanical load, here as a compressor 14 is trained on. Further shows 2 a first and a second electrical connection 16 . 18 , A first mechanical connection or connection 20 , a second mechanical connection or connection 22 and the gearbox 12 are formed here as components of a drive train of the vehicle.

To drive or move the vehicle is electrical energy from the electrical energy storage 4 over the first electrical connection 16 , the power electronics 6 and the second electrical connection 18 to the electric machine 10 transfer. This electrical energy is supplied by the electric machine 10 converted into mechanical energy and via the first mechanical connection 20 to the transmission 12 and thus also to the at least one wheel 13 transmitted as the first mechanical load, with the electric machine 10 to the at least one wheel 13 a first portion of its torque is transmitted, whereby the vehicle is driven.

The embodiment of the system according to the invention 2 comprises at least one component of the vehicle, in particular the control unit 8th , this is an arithmetic unit 24 having, wherein in a memory of the control device 8th a map 26 for an efficiency of the electric machine 10 stored or stored. In addition, the embodiment of the system includes 2 a first clutch 21 about which the at least one wheel 13 over the transmission 12 to the first mechanical connection 20 the drive train and thus to the electric machine 10 can be coupled. The system 2 further comprises a second clutch 23 about which the compressor 14 and thus the at least one second mechanical load on the second mechanical connection 22 the drive train and thus to the electric machine 10 at least temporarily can be coupled. This second clutch 23 Here is the compressor 14 assigned and via a pulley to the compressor 14 connected. The second, here magnetic coupling 23 is from the controller 8th via a line symbolized by an arrow 32 electrically controlled and / or operated.

The here mechanical air compressor 14 is via the second clutch 23 and the second mechanical connection 22 directly to the electric machine 10 flanged. During operation of the electric machine 10 , here at a drive of the vehicle, when the electric machine 10 the at least one wheel 13 drives are from the electric machine 10 as operating parameters current values of a torque and a rotational speed as feedback signals via a first line 28 to the control unit 8th transmitted. It is with the map 26 for the efficiency from the current value of the speed and the current value of the at the electric machine 10 applied torque from the controller 8th the current operating point, in particular load point, the electric machine 10 determined. With this current operating point is based on the map 26 at a given speed of the controller 8th determines whether an operation of the electric machine 10 with or without a second mechanical load leads to an improvement in the efficiency. In addition, an efficiency-optimal value of the torque for the electric machine 10 from the controller 8th over a second line 30 the power electronics 6 given that, taking into account this value for the torque, a value of electrical energy from the electrical energy storage 4 to the electric machine 10 is to be transmitted is set.

Depending on the current operating point of the electric machine 10 is taking into account the map 26 For the efficiency decided whether the efficiency can be improved if by the electric machine 10 in addition the compressor 14 is driven as a second mechanical load. If such an improvement of the efficiency can be achieved, the compressor becomes 14 over the second mechanical clutch 23 and the second mechanical connection 22 with the electric machine 10 connected. Thus, in addition, a second portion of the torque of the electric machine 10 over the second connection 22 of the drive train to the compressor 14 be transmitted. Furthermore, it is provided that the compressor 14 a swash plate as an actuator, whose operation of the control unit 8th is controlled, wherein formed as a swash plate actuator in the compressor 14 arranged and configured to give a value of the to the compressor 14 from the electric machine 10 to set the torque to be transmitted.

The diagram 3a has an abscissa 34 on, along the values for the torque M of the electric machine 10 are plotted in Newton meters (Nm). Along an ordinate 36 of this diagram are values for the speed n of the electric machine 10 applied in revolutions / minute. Along an applicate 38 of the diagram are values of the efficiency η of the electric machine 10 Plotted in percent.

In the diagram 3a is the three-dimensional map 26 for the efficiency of the electric machine 10 located.

For a mechanical power of the electric machine 10 applies: $${\text{P}}_{\text{mech}}=\text{M * n * 2}\mathrm{\pi }$$

For the electric power of the electric machine 10 applies: $${\text{P}}_{\text{DC}}=\text{U * I}$$

Here, Pmech is the mechanical power on a rotor shaft of the electric machine 10 and is expressed in watts (W). P _DC as electric power of the electric machine 10 is set by setting the voltage U in volts and the current I in amperes, wherein the electric power P _DC and the voltage U and the current I of the electric machine 10 starting from the energy store 4 over the electrical connections 16 . 18 and the power electronics 6 is provided, wherein the electrical connections 16 . 18 are formed as parts of a power network formed, for example, as an AC network (DC bus).

For the efficiency of the electric machine 10 in motor operation applies: $$\mathrm{\eta \; =}{\text{P}}_{\text{mech}}/{\text{P}}_{\text{DC}}$$

For the efficiency of the electric machine 10 in regenerative operation: $$\mathrm{\eta \; =}{\text{P}}_{\text{DC}}/{\text{P}}_{\text{mech}}$$

The efficiency can be in the range of 0 to 100%.

When driving the vehicle is the motor-driven electric machine 10 starting from the energy store 4 the electric power P _DC provided by the electric machine 10 the mechanical power Pmech is converted. Depending on a speed of the vehicle, this results in a current value of the rotational speed of the electric machine 10 , This current value is in the diagram 3b that's out of the diagram 3a shows through a plane 40 indicated the map 26 cuts and parallel to the abscissa 34 for the torque and perpendicular to the ordinate 36 is arranged for the speed. This is from the three-dimensional map 26 a two-dimensional characteristic 42 determined for the efficiency, which is dependent on the here constant value of the speed and the torque and in the diagram 3c is shown. This characteristic corresponds to this 42 an intersection of the map 26 and the plane 40 for the current, here constant value of the speed. The characteristic 42 thus shows a dependence of the efficiency, along the Applikaten 38 is plotted, of the torque, here along the abscissa 34 is applied, at a constant speed.

In the operation of the electric machine 10 Two possible cases arise in the diagrams from the others 3d . 3e and 3f are described. In both cases, each becomes a current operating point 44 ( 3d ), 46 ( 3e) or a current load point of the electric machine 10 determined, which results in each case at a current value of the torque. In addition, each one efficiency-optimal operating point 48 ( 3d ), 50 ( 3e) the electric machine 10 on the characteristic 42 determined.

In a first scenario or case ( 3d ) is the vehicle during a trip from the electric machine 10 powered without them from the compressor 14 as the second mechanical load is additionally loaded. It follows that the current operating point 44 at the current value for the torque that is less than an efficiency-optimal value of the torque at which the efficiency-optimal operating point 48 results. In this first case, the second clutch 23 closed, if it should not be initially closed, and by adjusting the operating parameter for the swash plate as the actuator of the compressor 14 the compression capacity of the compressor 14 increases, thereby increasing the torque for the electric machine 10 shifted from the current value in the direction of the optimal efficiency value and the efficiency is improved (curved arrow 52 ).

In the second case ( 3e) drives the electric machine 10 the vehicle and is additionally by the second mechanical load (compressor 14 ) charged. The current value of the torque at which the current operating point 46 the electric machine 10 on the characteristic 42 is greater than the efficiency-optimal value for the torque for which the optimum operating point 50 results. In this second case, the compression capacity of the compressor 14 is reduced by adjusting the operating parameter of the swash plate as an actuator and thus also the torque that is from the electric machine 10 to the compressor 14 is reduced, with the current operating point 46 on the characteristic 42 towards the optimal operating point 50 shifted and the efficiency is improved (curved arrow 54 ). Should that of the electric machine 10 to the compressor 14 To be transmitted torque to be reduced to zero, so will the second clutch 23 opened, causing the compressor 14 from the drive train or the electric machine 10 is decoupled.

In summary, look at the diagram 3f in which is indicated by a dashed line of the optimum efficiency value of the torque for the optimal operating point 48 . 50 the electric machine 10 on the characteristic 42 is indicated. In the first case ( 3d ) a mechanical load on the electric machine 10 through the compressor 14 increased, whereby the efficiency is improved by load increase (straight arrow 52 ). In the second case ( 3e) becomes a mechanical load on the electric machine 10 through the compressor 14 reduced and performed to improve the efficiency of a load reduction (straight arrow 54 ).

The method is performed by the controller 8th a value of an operating parameter of the actuator designed as a swash plate and / or set, wherein a signal required for this purpose from the control unit 8th via a third line 32 to the compressor 14 is transmitted. In this case, by adjusting the swash plate and thus the actuator of the compressor 14 the compression capacity and thus a stroke of the compressor 14 controlled, whereby a value of the torque, starting from the electric machine 10 to the compressor 14 is transmitted. In this case, the originally current value of the rotational speed of the electric machine remains 10 constant. The torque and thus a corresponding additional mechanical load on the electric machine 10 is by changing the compression capacity of the compressor 14 changed with the swash plate as an actuator, wherein a respective operating point 44 . 46 or load point on the characteristic curve 42 is moved. No torque at all to the compressor 14 be delivered, so becomes the second clutch 23 opened or so can the second clutch 23 be opened.

The swash plate is here in a housing of the compressor 14 arranged. This includes the compressor 14 a drive shaft that protrudes partially out of the housing of the compressor. Here is the drive shaft with the second clutch 23 connected. The second clutch 23 is here from the controller 8th magnetically opened and thus switched off or magnetically closed and thus switched on. It is provided here that the magnetic second clutch 23 is designed for two positions, namely an open position and a closed position. An example. Semi-open position or intermediate position in which, for example, when starting a conventional car with a manual switch, slippage is possible, is not provided here.

The in the housing of the compressor 14 arranged swash plate faces a piston of the compressor 14 and / or to its drive shaft at an angle α, which is adjusted in carrying out the embodiment of the method according to the invention. By adjusting this angle α becomes a stroke of the compressor 14 and thus increases its compression capacity for conveying a medium, wherein the compression power is greater, the greater the angle α as operating parameters of the compressor 14 is. A value of the torque when the second clutch is closed 23 from the electric machine 10 to the compressor 14 is transmitted from the compression capacity of the compressor 14 and thus dependent on the angle α, wherein the torque is greater, the greater the angle α is set.

LIST OF REFERENCE NUMBERS

2

system

4

energy storage

6

power electronics

8th

control unit

10

electric machine

12

transmission

13

wheel

14

compressor

16, 18

electrical connection

20, 22

mechanical connection

21

first clutch

23

second clutch

24

computer unit

26

map

28, 30, 32

management

34

abscissa

36

ordinate

38

applicate

40

level

42

curve

44, 46, 48, 50

operating point

52, 54

arrow

56

line

58, 60

arrow

100

control unit

102

High-voltage battery

104

power electronics

106

electric machine

108

transmission

110

air compressor

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

• AT 512443 B1 [0003]
• DE 102005022210 B4 [0004]
• DE 102014212874 A1 [0005]

Claims (9)

A system for operating an electric machine (10), which is designed for driving a vehicle, the vehicle comprising the following components: a drive train, which is driven by the electric machine (10), at least one wheel (13) as a first mechanical load, the a first clutch (21) can be coupled to the drive train, and at least one second mechanical load, which can be coupled via a respective second clutch to the drive train and controlled via a respective actuator, wherein the system (2) is designed to close when closing the respective second clutch (23) from the electric machine (10) to transmit torque to the at least one second mechanical load, wherein the respective actuator is adapted to control a value of the transmitted torque. System after Claim 1 in which the respective actuator is designed as a swash plate. System after Claim 1 or 2 in which, by adjusting the respective actuator, a compression capacity of the at least one second mechanical load can be regulated or regulated, wherein the torque transmitted to the at least one second mechanical load can be regulated. System according to one of the preceding claims, which has a control unit (8) in which a characteristic diagram (26) for an efficiency of the electric machine (10) is stored, wherein the control unit (8) is adapted to a current operating point (44, 46 ) of the electric machine (10) on the characteristic map (26) with an efficiency-optimal operating point (48, 50) and compare the current operating point (44, 46) by opening the respective second clutch (23), or by closing the respective second clutch ( 23) and by adjusting the respective actuator to the efficiency optimum operating point (48, 50) to move. System according to one of the preceding claims, wherein the at least one second mechanical load as a compressor (14), in particular air conditioning compressor, or as a pump is formed. A method of operating an electric machine (10) adapted to drive a vehicle, the vehicle comprising the electric machine (10), a driveline powered by the electric machine (10), at least one wheel (13) as the first mechanical load, which can be coupled to the drive train via a first clutch (21), and at least one second, further mechanical load, which can be coupled to the drive train via a respective second clutch (23) and can be actuated via a respective actuator, wherein; Method a current operating point (44, 46) and an efficiency optimal operating point (48, 50) for the electric machine (10) are determined and in dependence of a relative position of the current operating point (44, 46) to the efficiency optimum operating point (48, 50) respective second clutch (23) is closed or opened, wherein with closed respective second clutch (23) with the respective actuator a W ert one of the electric machine (10) to the at least one second mechanical load to be transmitted torque is set, and the torque is transmitted from the electric machine (10) to the at least one second load corresponding to the set value. Method according to Claim 6 in which a characteristic diagram (26) is used with which a dependency of an efficiency of the electric machine (10) on the torque and a rotational speed of the electric machine (10) is described, wherein the electric machine (10) at the current operating point (44, 46 ) is operated with a current value of the speed and a current value of the torque, wherein from the map (26) for this current value of the speed, a characteristic (42) is determined, wherein the efficiency optimum operating point (48, 50) as a maximum of this characteristic (42) is assigned, which is assigned an efficiency-optimal value of the torque, wherein the current value of the torque by opening the respective second clutch (23), or by closing the respective second clutch (23) and setting the respective actuator in the direction of optimal efficiency Value of the torque is shifted, wherein the current operating point (44, 46) on the characteristic (42) in the direction of the efficiency optimal operating point (48, 50) is shifted. Method according to Claim 6 or 7 in which, during a drive of the vehicle, a first portion of the torque of the electric machine (10) is transmitted via the drive train of the vehicle to at least one wheel of the vehicle, wherein via the respective actuator, a second portion of the torque of the electric machine (10) to the at least a second mechanical load is transmitted, said second portion of the torque having a value greater than or equal to zero, wherein the second portion of the torque transmitted from the electric machine (10) to the at least one second mechanical load depends on how current operating point (44, 46) is to be moved, is changed. Method according to one of Claims 7 or 8th in which, for the electric machine (10), the current value of the torque is compared with the efficiency-optimal value of the torque, wherein for a first case, if the current value the torque is less than the optimum torque value, the current value is increased toward the optimum efficiency value, and more torque is provided to the at least one second mechanical load via closing the respective second clutch (23) and / or adjusting the respective actuator for a second case, when the current value of the torque is greater than the torque efficiency value, reducing the current value to the optimum efficiency value and the at least one second mechanical load via adjusting the respective actuator and / or opening the respective second clutch ( 23) less torque is provided.

Images