DE102014200253B4 - Method for starting an internal combustion engine of a hybrid vehicle and hybrid vehicle - Google Patents

Abstract

Method for starting an internal combustion engine of a hybrid vehicle with a drive train (1) comprising an internal combustion engine (2), a main electric machine (3), an auxiliary electric machine (4) and a starting gearbox (5), wherein the main electric machine (3 ) via a separating clutch (7) to the internal combustion engine (2) is coupled and the auxiliary electric machine (4) via a coupling element (8) with the internal combustion engine (2) is coupled and wherein the main electric machine (3) provides a drive torque, characterized by the steps from a first time (t1) operating the auxiliary electric machine (4) such that it exerts a torque on the internal combustion engine (2) via the coupling element (8) and thereby increases the speed of the internal combustion engine (2) until reaching a start criterion, so the internal combustion engine (2) supports a starting process itself from a second point in time (t2); and from a third point in time (t3), at least partially closing the separating clutch (7) and operating the main electric machine (3) in such a way that the main electric machine (3) substantially provides the driving torque via the starting element (6) and at the same time a torque via the separating clutch (7) on the internal combustion engine (2) exercises.

Description

The invention relates to a method for starting an internal combustion engine of a hybrid vehicle with a drive train and a hybrid vehicle with a drive train.

Hybrid vehicles typically have both an internal combustion engine and a main electric machine, both of which can individually or simultaneously provide a drive torque for driving a drive wheel depending on the current mode of operation.

A hybrid vehicle in which the drive torque is simultaneously provided by a main electric machine and an internal combustion engine is also called a parallel hybrid. In a parallel hybrid, both the internal combustion engine and the main electric machine are typically arranged on a transmission input shaft.

A hybrid controller, which is also called hybrid coordinator, controls the respective operating mode, such. B. pure electric driving, pure driving with internal combustion engine or mixed operation.

If the hybrid vehicle is in an operating mode in which it is driving purely electrically, the internal combustion engine is typically switched off. Demands the hybrid control due z. B. a higher power requirement or low battery power to a drive torque from the internal combustion engine, so the internal combustion engine must be restarted.

For the start or restart of an internal combustion engine of a hybrid vehicle various embodiments are known in the art.

From the German patent application DE 10 2009 058 133 A1 For example, a hybrid vehicle is known in which an internal combustion engine is started by an auxiliary electric machine. Thus, the main electric machine can be made smaller and does not have to provide torque for the starting process. Furthermore, a quick start is possible by the auxiliary electric machine with associated transmission parts builds up a corresponding angular momentum, then take advantage of this for the start. Thus, only the auxiliary electric machine for starting the internal combustion engine is used in a complex system. Accordingly, the auxiliary electric machine must provide the power for starting the internal combustion engine alone and be sized accordingly.

From the German patent application DE 10 2007 061 895 A1 For example, a hybrid vehicle is known in which an internal combustion engine is started by a starter. Thus, the main electric machine can be designed with low power, since it does not have to hold torque for the starting process. An overrunning clutch ensures that no further drive energy is exerted by the main electric machine on the engine or starter during normal driving. Thus, only the starter for starting the internal combustion engine is used, which is correspondingly heavily loaded due to the frequent starts and restarts of the internal combustion engine.

From the German patent application DE 198 38 853 A1 For example, a hybrid vehicle is known in which an internal combustion engine is started by a starter. Furthermore, an electric motor supports the starting process. The electric motor is designed with greater power to reduce a Radmomenteinbruch and to assist the starting process of the internal combustion engine.

From the German patent application DE 10 2004 023 673 A1 For example, a hybrid vehicle is known in which a slip operation is attempted by means of a clutch and an automatic transmission to provide a constant torque at the drive wheels.

The German patent application DE 10 2010 037 678 A1 shows a (hybrid) motor vehicle with a motor and an electric machine that can deliver torque to the engine and to the motor vehicle drive wheels. In addition, a starter motor is provided which is operatively connected to the engine. The starter motor may be used to provide torque to start the engine without additional torque from the electric machine.

A hybrid drive device for a motor vehicle is known from the German Offenlegungsschrift DE 10 2005 024 359 A1 known. It has a drive train with an internal combustion engine, with a first electric machine and with a second electric machine, wherein the second electric machine is provided for starting the internal combustion engine. The second electric machine is arranged with its rotor shaft parallel to the drive shaft of the drive train.

Out US 2007/0227790 A1 For example, a controller for a hybrid vehicle is known. The controller controls and limits the transmission of power from an engine to the drive wheels during a startup of the engine. Thereby, a hybrid mode is generated, in which the hybrid vehicle from both Engine as well as by a motor generator of the hybrid vehicle is driven.

US 2008/0200302 A1 For example, a hybrid vehicle and an associated method are known in which power is transmitted from a shaft of an internal combustion engine of the hybrid vehicle to a drive wheel of the hybrid vehicle. There is also provided a power transmission device having an electric machine connected to the engine and a shaft of the drive wheel via a disconnect clutch. Furthermore, a starting system is provided, which is mechanically independent of the electric machine and is connected to the internal combustion engine. The internal combustion engine is started by simultaneously transmitting torque to the shaft of the internal combustion engine via the starting system and the separating clutch.

The object of the invention is to provide a simple, improved quick start option for an internal combustion engine of a hybrid vehicle.

This object is achieved by the inventive method for starting an internal combustion engine of a hybrid vehicle according to claim 1 and a hybrid vehicle according to claim 7.

According to a first aspect, the invention provides a method for starting an internal combustion engine of a hybrid vehicle with a drive train, comprising an internal combustion engine, a main electric machine, an auxiliary electric machine and a transmission with starting element, wherein the main electric machine can be coupled via a separating clutch to the internal combustion engine and the auxiliary electric machine can be coupled via a coupling element with the internal combustion engine and wherein the main electric machine provides a drive torque. The method comprises the steps: starting from a first time, operating the auxiliary electric machine such that it exerts a torque on the internal combustion engine via the coupling element and thereby increases the speed of the internal combustion engine until a starting criterion is reached, so that the internal combustion engine starts at a second time (t2) Startup process supported; and from a third point in time, at least partially closing the separating clutch and operating the main electric machine in such a way that the main electric machine continues to essentially supply the drive torque via the starting element and at the same time exerts a torque via the separating clutch to the internal combustion engine.

According to a second aspect, the invention provides a hybrid vehicle with a drive train comprising an internal combustion engine, a main electric machine, an auxiliary electric machine, a transmission with starting element and a controller, wherein the main electric machine can be coupled via a separating clutch to the internal combustion engine and the auxiliary electric machine via a coupling element is coupled to the internal combustion engine, the main electric machine provides a drive torque and the controller is adapted to carry out the method according to the first aspect.

Further advantageous embodiments of the invention will become apparent from the subclaims and the following description of preferred embodiments of the present invention.

In the following, a method according to the invention for starting an internal combustion engine of a hybrid vehicle will be described.

The hybrid vehicle is on (at least) a drive axis z. B. configured as a parallel hybrid, as described above. The hybrid vehicle includes a powertrain that includes an internal combustion engine, a main electric machine, an auxiliary electric machine, and a start-up transmission.

The main electric machine can be coupled to the internal combustion engine via a (first) separating clutch and the auxiliary electric machine can be coupled to the internal combustion engine via a coupling element. In some embodiments, the coupling element can be a second disconnect clutch, via which the auxiliary electric machine can be mechanically coupled to the internal combustion engine, and the disconnect clutch can mechanically separate the auxiliary electric machine from the internal combustion engine. In other embodiments, the auxiliary electric machine is constantly mechanically coupled to the internal combustion engine and the coupling element comprises, for example, a belt or the like via which the auxiliary electric machine is coupled to the crankshaft of the internal combustion engine.

The first and second separating clutch can, for. B. be designed as a friction clutch.

The transmission can z. B. as a dual-clutch transmission with a double clutch, also referred to as the drive clutch, be designed as a starting element. Alternatively, the transmission can be designed as a stepped automatic with hydrodynamic torque converter / lock-up clutch as starting element. Alternatively, the transmission can also be used as an automated manual transmission with simple, automated clutch designed as a starting element.

The main electric machine provides a drive torque, which via the starting element, for. B. the drive clutch, and the transmission, z. B. a dual-clutch transmission, is transmitted to at least one drive wheel. As a result, the hybrid vehicle is in a running state where it can travel forwards or backwards. The internal combustion engine is typically off at this time and does not provide a drive comment. In some embodiments, the internal combustion engine is still warm, so that it may be a warm start in the starting process of the internal combustion engine. In other embodiments, it may also be a cold start of the internal combustion engine.

From a zero point in time, which can be determined, for example, by a controller of the hybrid vehicle, which is also called hybrid coordinator or hybrid controller, the starting process of the internal combustion engine is initiated. From a first point in time, which in some embodiments may also be at the same time as the zero point in time, a start criterion of the internal combustion engine can be achieved by operating the auxiliary electric machine such that it exerts a torque on the internal combustion engine via the coupling element and thereby increases the speed of the internal combustion engine. so that the internal combustion engine can support the starting process itself from a second point in time. The start criterion can, for. As an injection speed, a crankshaft angle or the like. Consequently, the starting criterion can be defined by specifying a specific injection speed, a specific crankshaft angle or the like.

In some embodiments, starting from the operation of the auxiliary electric machine, the auxiliary electric machine is mechanically coupled to the internal combustion engine via the coupling element, which may comprise a second separating clutch.

For example, the internal combustion engine receives fuel from an injection from the second time point, and thus provides a torque which it uses to increase its own speed. The main electric machine can be coupled via the slipping clutch so with the internal combustion engine that no torque of the internal combustion engine is used as the drive torque. In this phase, the torque generated by the internal combustion engine itself can be used only to increase its own speed.

From a third point in time, which in some embodiments may be after the second time (or even before or at the second time), the method includes at least partially closing the disconnect clutch and operating the main electric machine such that the main electric machine continues to substantially transfer the drive torque provides the driving clutch and at the same time exerts a torque on the separating clutch on the internal combustion engine. The closing of the separating clutch can be "fast" or "slow". The "faster" the disconnect clutch is closed, the higher the angular momentum is transferred from the main electric machine to the internal combustion engine and the "slower" the clutch is closed, the higher the torque component is transmitted from the main electric machine to the internal combustion engine.

Due to the fact that the main electric machine continues to provide the same drive torque for driving the at least one drive wheel, for example, a driver of the hybrid vehicle does not participate in the starting process of the internal combustion engine since there is no or almost no change in the drive torque applied to the at least one drive wheel. Thus, a quick start option for the internal combustion engine is provided in which a noticeable reduction of the drive torque at the drive wheel is at least partially avoided.

In order for the main electric machine to simultaneously provide the drive torque and a torque to assist the starting operation of the internal combustion engine, in some embodiments, the main electric machine is configured to maintain and, if necessary, provide a corresponding starting assistance torque. However, since the starting process is also supported by the auxiliary electric machine, the torque to be kept smaller than in known from the prior art embodiments in which the main electric machine alone provides the torque for the starting operation of the internal combustion engine. In addition, the auxiliary electric machine need not be dimensioned to perform the starting operation of the internal combustion engine alone since the main electric machine also provides torque to the main electric machine. Accordingly, the auxiliary electric machine may be smaller in size than is the case in the prior art embodiments in which the auxiliary electric machine alone performs the starting operation of the internal combustion engine. The fact that the internal combustion engine itself provides a torque from a certain speed, that of the auxiliary electric machine and the Main electric machine for the starting operation of the internal combustion engine to be provided torque further reduced.

The auxiliary electric machine may be configured as a belt starter generator or the like, wherein, as mentioned, unlike the conventional starter, the auxiliary electric machine may have a lower power and need not be designed to start the internal combustion engine alone.

Consequently, in some embodiments, the participation of a conventional electric pinion starter, i. H. a conventional starter that can start the internal combustion engines alone without the support of the main electric machine, not required for the starting process and in some embodiments may even be dispensed with entirely.

In some embodiments, a driven in micro-slip clutch or operated in micro-slip starting element is set from the zeroth time of a micro-slip operation in a macro-slip operation. In the micro-slip mode, only a slight deviation between the rotational speed of the dual-clutch transmission and that of the main electric machine (or of the internal combustion engine) is permitted, whereby the engine torques are determining the wheel torque, whereas in macro-slip operation this difference may be greater (here the clutch torque is determining the wheel torque). This is exploited in some embodiments in order to increase the rotational speed of the main electric machine and thus to be able to provide the drive torque and at the same time the torque assisting the starting process. In micro-slip operation, for example, in gasoline engines and in electrical operation, a speed difference of 6 revolutions per minute for pull and thrust state is common, without the present invention should be limited thereto. In micro-slip, the drive clutch can be operated so that it acts like a rigid shaft to the outside. In macro-slip operation, in some embodiments, there is no restriction on the differential speed and, as mentioned, the drive clutch is the torque-determining member.

In some embodiments, the speed of the main electric machine is increased accordingly already from the zeroth point in time. In these embodiments, as mentioned, the starting element, for. For example, the drive clutch may be set to the macro slip mode from the zeroth point in time to allow the speed of the main electric machine to be increased without increasing the drive torque acting on the at least one drive wheel of the hybrid vehicle. By increasing the rotational speed from this point in time, the excess angular momentum can also be increased in some embodiments, which can be transmitted to the internal combustion engine by rapidly closing the first separating clutch, as already explained above.

In some embodiments, accordingly, the disconnect clutch is closed at the third time such that an angular momentum of the main electric machine is transmitted to the internal combustion engine. The angular momentum arises in some embodiments in that the drive clutch is switched from the above-mentioned micro-slip operation into a macro-slip operation and then the rotational speed of the main electric machine is raised beyond the synchronous rotational speed.

The first disconnect clutch may also be slowly closed in some embodiments, such that there is adequate slippage over an extended period of time, and thus torque is transferred from the main electric machine to the internal combustion engine. Thus, in these embodiments, at / from this third time point, there are four torque sources, namely a first torque provided by the auxiliary electric machine, a second torque provided by the internal combustion engine itself through the initiated starting operation, a third torque derived from the third Main electric machine is provided and a fourth torque, which is provided from the excess angular momentum of the main electric machine.

In some embodiments, as of a fourth point in time, the auxiliary electric machine is disconnected from the internal combustion engine via the coupling element which, as mentioned above, may comprise a second disconnect clutch and / or the auxiliary electric motor is switched off. As already stated above, the auxiliary electric machine can be dimensioned so that it does not carry out the complete starting process of the internal combustion engine alone. As a result, during the starting process, a speed gradient can occur which, under certain circumstances, the auxiliary electric machine itself can no longer follow, which is why the auxiliary electric machine would hinder the starting process.

In order to determine the fourth point in time at which the auxiliary electric machine is disconnected and / or switched off, in some embodiments at least one operating parameter of the auxiliary electric machine can be determined. In some embodiments, the operating parameter z. B. the speed gradient and / or the torque output of the auxiliary electric machine, which is monitored accordingly, so that the auxiliary electric machine of the internal combustion engine is disconnected and / or switched off when the product of the determined speed gradient and moment of inertia of the auxiliary electric machine minus the torque output exceeds a predetermined value, for example zero. Accordingly, the fourth time may also be at or before the third time.

From a fifth point in time, in some embodiments, the separating clutch can be completely closed, so that the internal combustion engine and the main electric machine are completely coupled to each other and thus have a synchronous speed. As a result, the internal combustion engine can also be coupled to the at least one drive wheel. This synchronous speed may still be above the synchronous speed. In order to adapt the rotational speed of the internal combustion engine and the main electric machine to the synchronous rotational speed, the driving clutch can be continuously transferred from a macro-slip operation into a micro-slip operation.

From a sixth point in time, in some embodiments, the drive torque provided by the main electric machine may be reduced and the internal combustion engine increases its torque output so that from a seventh point in time the drive torque may be fully provided by the internal combustion engine. This happens, for example, in that the electric power of the main electric machine is reduced, while the power of the internal combustion engine is increased accordingly. As a result, the internal combustion engine can gradually take on the task of providing the drive torque proportionally and finally completely.

Thus, in some embodiments, the method includes four phases, a first phase in which the hybrid vehicle is driving purely electrically, a second phase in which the speed of the internal combustion engine is raised for (re-) starting, a third phase in which the torque of the main electric machine and that of the internal combustion engine is increased accordingly, also called momentum blending, and a fourth phase in which the hybrid vehicle is traveling hybrid with the assistance of the internal combustion engine.

In the second phase, in which the speed of the internal combustion engine is increased, as described above, in some embodiments, the four above-mentioned torque sources can be utilized.

In some embodiments, start management of the internal combustion engine may be configured accordingly by utilizing the above-mentioned four torque sources according to a desired request as to whether or not, for B. a dynamic, faster start of the internal combustion engine or the most energy-efficient start of the internal combustion engine is desired. For this purpose, as stated above, the various torque sources and method steps must be combined with each other as required at the respective times, wherein, as mentioned, the order of the times can also be reversed.

Some embodiments relate to a hybrid vehicle with a driveline, as stated above. The powertrain includes an internal combustion engine, a main electric machine, an auxiliary electric machine, a transmission with starting element, as explained in detail above, and a controller.

The main electric machine can be coupled to the internal combustion engine via a (first) separating clutch and the auxiliary electric motor can be coupled to the internal combustion engine via a coupling element, in particular a second separating clutch.

The main electric machine provides a drive torque as stated above. The controller is configured to at least partially execute the method described above.

The controller may be a hybrid controller, also called a hybrid coordinator, and / or may include other controllers or controls, such as a hybrid controller. As a control element for the engine control (injection), controls for controlling the clutch, disconnect couplings, the transmission and starting element, etc. Since the control of the individual components of a hybrid vehicle is basically known, a detailed description of the control and its components is not required.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

1 schematically illustrates an embodiment of a hybrid vehicle;

2 schematically shows a controller for a hybrid vehicle;

3 shows a first embodiment of a method for restarting an internal combustion engine;

4 shows a second embodiment of a method for restarting an internal combustion engine;

5a shows a speed curve for a train driving condition;

5b shows a speed curve for a coast-drive state;

5c shows a speed curve for a train upshift driving condition;

5d shows a speed curve for a train-downshift driving condition; and

5e shows a speed curve for a train-wheel slip driving condition.

An embodiment of a hybrid vehicle with a drive train 1 is in 1 illustrated. In the present embodiment, it is a so-called parallel hybrid, in which both a combustion engine on a transmission input shaft 2 as well as a main electric machine 3 are arranged.

The transmission input shaft opens into an automatic dual-clutch transmission 5 with driving clutches 6 that the internal combustion engine 2 and the main electric machine 3 couple to at least one drive wheel, so that one of the internal combustion engine 2 and / or main electric machine 3 generated drive torque corresponding to the at least one drive wheel will project.

The internal combustion engine 2 and the main electric machine 3 are via a (first) separating clutch 7 Coupled with each other.

In addition, as an auxiliary electric machine 4 a belt starter generator using a double belt tensioner 16 with a coupling element 8th that the auxiliary electric machine 4 with the internal combustion engine 2 coupled. The coupling element 8th is designed as a (second) separating clutch.

Further shows 1 an example of an air conditioning compressor unit 9 , also to the drive train 1 belongs.

A high-voltage battery 10 is via a high-voltage electrical system 11 with the main electric machine 3 and the air conditioning compressor unit 9 electrically coupled. There is also a 12V battery 12 via a 12 V electrical system 13 with the auxiliary electric machine 4 coupled. For converting the voltages of the high-voltage network 11 on the voltage of the 12 V electrical system 13 is a DC-DC converter 14 between the 12 V electrical system 13 and the high-voltage electrical system 11 coupled.

In some embodiments, the auxiliary electric machine can also be integrated on a different voltage than 12 V, for example in the high-voltage electrical system. If the voltage level of the auxiliary electric machine is at a different voltage than 12 V and than that of the high-voltage vehicle electrical system, a further DC-DC converter for electrical coupling of the auxiliary electric machine is required.

2 schematically illustrates a controller 15 which are used to control the drive train 1 of the hybrid vehicle and configured to at least partially execute the methods described herein.

The control 15 is with the individual components of the drive train to be controlled 1 connected, namely with the internal combustion engine 2 , the main electric machine 3 , the auxiliary electric machine 4 , the dual-clutch transmission 5 with driving clutches 6 and with the (first) separating clutch 7 and the coupling element 8th , This connection between the controller 15 and the individual components of the drive train to be controlled 1 is to be understood only logically and not as an actual, physical connection.

The same applies to the controller 15 itself, which in the embodiments may include a plurality of controls to implement the individual control tasks and method steps described herein.

3 now illustrates a first embodiment of a method for starting an internal combustion engine of a hybrid vehicle with a drive train as described above 1 ,

3 shows on the abscissa the time and on the ordinate in the bottom third speed curves "EM" for the main electric machine 3 , "VKM" for the internal combustion engine 2 and "wheel" for the least a driven wheel. In the middle third shows 3 Torque curves "EM" for the main electric machine 3 , the torque curve "VKM1" of the internal combustion engine 2 , the starting and Reibmomentverlauf "VKM2" of the internal combustion engine 2 , the torque curve "HEM" of the auxiliary electric machine 4 and the drive torque curve "wheel" on the wheel, which is constant. The top third of the 1 shows coupling capacity curves "K0" for the separating clutch 7 , "K3" for the coupling element 8th and "K12" for the drive clutch 6 ,

In the scenario described here, the hybrid vehicle is initially in an operating state of pure electric driving, which is present until the time t0. In the present case, it is a constant speed, ie wheel speed and wheel torque are constant, as the 3 can be removed. Until the time t0 is the drive clutch 6 in a micro-slip-controlled state and leads slight fluctuations in the driver's desired torque immediately after (see arrow 21 the coupling capacity curve K12). Due to the constant driving speed, the torque and the speed of the main electric machine 4 also constant, as can be seen from the torque curve HEM or the speed curve HEM. The internal combustion engine 2 is switched off until time t0 and thus has a torque and a speed of zero (see speed curve VKM).

Represents the controller 15 fixed that the internal combustion engine 2 is required, it initiates the starting procedure for the internal combustion engine described below 2 ,

The starting procedure starts at the zeroth time t0 with that of the control 15 given start command. The speed of the main electric machine 3 is increased (see speed curve EM) and in parallel from the time t0, the state of the clutch 6 frozen (see coupling capacity curve K12). That is the driving clutch 6 is set by a micro-slip operation with only a few turns differential speed in a macro slip operation with a correspondingly higher differential speed. This makes it possible, without affecting the wheel torque and the wheel speed, the torque of the main electric machine 3 to increase and thereby accelerate it. As a result, it is also possible from the time t0 an angular momentum in the main electric machine 3 build up, as can be seen from the torque curve EM.

After a short time at time t1, the coupling element 8th closed and the control of the auxiliary electric machine 4 provides a torque and thus raises the speed of the internal combustion engine 2 until the time t2, as can be seen from the torque curve HEM and the speed curve VKM. From an injection speed of z. B. 200 U / min, or another start criterion, such. B. a crankshaft angle, the internal combustion engine 2 about the own fuel injection and the associated representation of an inner starting torque, the torque curve VKM2 in 3 is illustrated, accelerate itself. The effective torque of the internal combustion engine 2 at the crankshaft remains zero.

From a time t3, the separating clutch 7 slowly closed, as can be seen in the increase of the coupling capacity curve K0. This torque is from the time t3 on the internal combustion engine 2 transferred to the further acceleration of the internal combustion engine 2 to support. The additional torque of the main electric machine 3 is maintained from the time t3 and also serves to increase the speed of the internal combustion engine 2 , From time t3, the internal combustion engine 2 therefore by the auxiliary electric machine 4 , the internal combustion engine 2 own fuel injection, the transfer of angular momentum from the main electric machine 3 and immediately by the additional torque of the main electric machine 3 accelerated together, as well as from the increasing speed increase in the speed curve VKM the internal combustion engine 2 out 3 results.

By using said four torque sources to accelerate the internal combustion engine 2 can speed gradient of the internal combustion engine 2 occur that are so high that the auxiliary electric machine 4 can not continue to support the starting process, but can even hinder him by braking effect. Accordingly, from a time t4, the coupling element 8th be opened and thus the auxiliary electric machine 4 be decoupled (see also arrow 23 ).

As stated above, in some embodiments, for. B. the speed gradient and / or the torque of the auxiliary electric machine 4 be determined and carried out on the basis of the determined values, the decoupling. The decoupling of the auxiliary electric machine 4 is not set to the time t4 after the time t3 or t2, but of course can also be before the time t2 or t3, that is also in the time intervals between time t1 and t2 or t2 and t3.

From a time t5 are the speed of the internal combustion engine 2 and the main electric machine 3 Synchronized (see superimposed speed curves VKM and EM). The common speed of main electric machine 3 and internal combustion engine 2 is now typically higher than the synchronous speed of the dual-clutch transmission 5 (See arrow 24 , which indicates a dotted line representing the synchronous speed of the dual-clutch transmission 5 shows). For this reason, a coupling-in process closes at the time t6, which is the common rotational speed of the main electric machine 3 and internal combustion engine 2 to the synchronous speed of the dual-clutch transmission 5 as evidenced by the falling speed curve course EM and VKM results (both curves are superimposed).

From the time t5 only the friction losses of the internal combustion engine have to 2 be overcome, but no inertias for further acceleration of the internal combustion engine 2 (see waste in torque curve VKM1 from time t5). As a result, the increase in the torque of the main electric machine 3 be withdrawn. In addition, the fuel injection of the internal combustion engine 2 be reduced. The separating clutch 7 will be closed. Is the disconnect clutch 7 completely closed, is the internal combustion engine 2 coupled with the output.

From a time t6 finds one. Momentum blending takes place, the required driving torque or drive torque from the main electric machine 3 in the internal combustion engine 2 transferred. The internal combustion engine 2 builds an effective torque for driving the hybrid vehicle, as can be seen from the increasing torque curve VKM2.

In the case shown here, the electric drive is through the main electric machine 3 After completion of the torque transition from a time t7 in a generator operation by a corresponding load point increase transferred, so that the high-voltage battery 10 through the main electric machine 3 is reloaded. In addition, the driving clutches 6 put back into the micro-slip mode.

The restart of the internal combustion engine is at time t7 by stopping the momentum blending from the main electric machine 3 on the internal combustion engine 2 completed and the hybrid vehicle is in the operating state "driving with internal combustion engine 2 and main electric machine 3 ' , which is also referred to herein as "hybrid driving".

The order of the times t0 to t7 is not fixed, but may vary depending on the embodiment. So z. B. also the separating clutch 7 be partially closed before the time t3, z. B. before the time t2, from which the internal combustion engine supports the starting process itself.

In 4 is a second embodiment of a method for starting an internal combustion engine of a hybrid vehicle with a drive train as described above 1 shown, the method according to 4 is a so-called pulse-start method.

The 4 essentially corresponds to the 3 and the designations are identical and also the procedure of 4 corresponds essentially to that of 3 , therefore also fully to the description of 3 above.

The main difference of the pulse-starting method to the method 3 is that in the pulse-start method of 4 the steps that take place at the times t1, t3 and t4 take place substantially simultaneously from a common time t1, 3, 4, so that on the internal combustion engine 2 a strong angular momentum acts and thereby the speed and the torque of the internal combustion engine 2 be raised very quickly, ie impulsively.

Even in the scenario described here, the hybrid vehicle is initially in an operating state of pure electric driving that is present until the time t0. In the present case, it is a constant speed, ie wheel speed and wheel torque are constant, as the 4 can be removed. Until the time t0 is the drive clutch 6 in a micro-slip-controlled state and leads slight fluctuations in the driver's desired torque immediately after (see arrow 31 ). Due to the constant driving speed, the torque and the speed of the main electric machine 3 also constant (see torque curve EM and speed curve EM). The internal combustion engine 2 is off until time t0 and thus has a torque and zero speed.

Represents the controller 15 fixed that the internal combustion engine 2 is required, it initiates the pulse-start method for the internal combustion engine described below 2 ,

The starting procedure begins at the first time t0 with the starting command given by the hybrid coordinator. The rotational speed of the main electric machine EM is increased, and angular momentum is built up, and in parallel, from the time t0, the state of the driving clutch becomes 6 frozen. That is the driving clutch 6 is set by a micro-slip operation with only a few turns differential speed in a macro slip operation with a correspondingly higher differential speed, as stated above. Accordingly, from the time t0, the rotational speed of the main electric machine 3 above the synchronous speed of the dual-clutch transmission 5 (See arrow 32 indicating on a dashed line representing the synchronous speed).

At a second time t1, 3, 4, the coupling element 8th closed and the control of the auxiliary electric machine 4 provides a torque and thus raises the speed of the internal combustion engine 2 at. At the same time, the separating clutch 7 closed quickly. This will cause the inertia of the main electric machine 3 stored angular momentum on the internal combustion engine 2 transferred to the further acceleration of the internal combustion engine 2 to support. The additional torque of the main electric machine 3 is maintained and to increase the speed of the internal combustion engine 2 used. In the short interval between the time t1, 3, 4 and the shortly following time t2, 5, the separating clutch 7 completely closed until time t5. In this time interval, the internal combustion engine 2 therefore by the auxiliary electric machine 4 , the internal combustion engine 2 own fuel injection from reaching a start criterion, the transfer of angular momentum from the main electric machine 3 and immediately by the additional torque of the main electric machine 4 accelerated together, as well as from the steeply rising speed of the internal combustion engine 2 from the speed curve VKM 4 results. The auxiliary electric machine 4 is decoupled accordingly shortly after the time t1, 3, 4, which is why the sake of simplicity, the speeds and torques of the auxiliary electric machine 4 as well as the position of the coupling element 8th in 4 not shown.

From a time t5 are the speed of the internal combustion engine 2 and the main electric machine 3 synchronized and the disconnect clutch 7 is completely closed, as it is already in connection with the 3 has been explained for the time t5 and is apparent from the associated speed curves EM and VKM and the associated clutch capacity curve K0. Up to the time t6 closes as above in connection with 3 performed a coupling-on, the common speed of the main electric machine 3 and internal combustion engine 2 to the synchronous speed (see arrow 32 ) of the dual clutch transmission 5 transferred.

From a point in time t6, the above-explained torque superimposition takes place, which is the required driving torque or drive torque from the main electric machine 3 (see torque curve EM) in the internal combustion engine 2 (see torque curve VKM1). In addition, the clutch is 6 put back into micro-slip mode (see arrow 33 ).

Also in the case shown here is the electric drive by the main electric machine 3 After completion of the torque transition from a time t7 in a generator operation by a corresponding load point increase transferred, so that the high-voltage battery 10 through the main electric machine 3 is reloaded. In addition, the driving clutches 6 put back into the micro-slip mode.

The restart of the internal combustion engine is at time t7 by stopping the momentum blending from the main electric machine 3 on the internal combustion engine 2 completed.

Without limiting the general public, the procedures of the 3 and 4 been declared for the so-called train operation of a hybrid vehicle. When "train" the hybrid vehicle from the main electric machine 3 and / or the internal combustion engine 2 driven, in contrast to the thrust, where the hybrid vehicle is the main electric machine 3 and / or the internal combustion engine 2 "Drives" (downhill or the like).

The 5a to 5e illustrate, by way of example, various scenarios in which the methods described herein may find application as a re-start method for the internal combustion engine, wherein the 5a and 5e an example of the pulse start method of 4 Respectively.

The 5a to 5e show each in the ordinate the speed and in the abscissa the time course. The times t0; t1, 3, 4; t5 and t6 correspond to the steps described above and those associated with 4 described steps are analogous to the method according to 4 Therefore, not all steps will be described repeatedly for each time point in the following. The time t6-a denotes the entry into a micro-slip operation, and the time t6-b denotes the beginning of the momentary glare from the main electric machine 3 on the internal combustion engine 2 as described above.

In all cases the 5a to 5e is the hybrid train before the time t0 in a state of pure electric driving. The speed curves, a reference numeral with " 40 "Show the speed curve of the main electric machine, while the reference numerals" 41 "The synchronous speed of the dual-clutch transmission 5 show (are reference numerals " 41 " and " 42 "Present the speed curves show the synchronous speed for two gears, that is" 41 "For a first (low) and" 42 "For another gear (high)).

5a shows a train operating state in which is accelerated, as at the increasing synchronous speed 41a is removable.

The speed 40a the main electric machine 3 shows, however, a course, as he already did in 4 was declared. From the time t0, the speed is increased, in the pulse start interval between t1, 3, 4 to t2, 5, the speed drops and from the time t2, 5, it is synchronous with the speed of the internal combustion engine and the coupling operation begins and the speed 40a approaches the synchronous speed 41 at.

5b shows a thrust mode, at the synchronous speed 41b due to the braking effect of the main electric machine 3 decreases continuously. The speed 40b the main electric machine 3 is lower than the synchronous speed 41b and falls sharply in the pulse start interval between the time t0, 1, 3, 4 and the time t2, 5, since there the internal combustion engine by means of the main electric machine 3 is started and due to the thrust no electrical energy to the main electric machine 3 is supplied. Between the time t2, 5 and the time t6-a, the speed increases through the coupling with the starting internal combustion engine 2 and approaches the synchronous speed 41b , At time t6-a, the clutch becomes 6 put back into micro-slip mode.

5c shows a train operating state in which a gear is upshifted. The synchronous speed 41c for a first low gear and the synchronous speed 42c for a second high gear of the dual clutch transmission 5 both rise. At time t0 and before time t1, 3, 4 the low gear is engaged and the speed 40c is above the synchronous speed 41c , At time t1, 3, 4, the pulse start method is used, as discussed above 4 described for the internal combustion engine 2 started and the speed of the main electric machine drops sharply in the pulse start interval between t1, 3, 4 and t2, 5. This represents the speed transition of the upshift from low to high gear, so that between the time t2, 5 to the time t6-a, at which again the clutch 6 in the micro-slip mode is set, the speed 40c to the synchronous speed 42c of the high passage.

5d shows a train operating state in which a gear is switched back. The synchronous speed 42d for a high gear and the synchronous speed 41d for a low gear each rise. At time t0 and before time t1, 3, 4, the vehicle is driving in the higher gear, and the speed 40d is above the synchronous speed of the higher gear 42d , where the speed 40d the main electric machine between the time t0 and the time t1, 3, 4 increases, as also above in connection with 4 was explained. At time t1, 3, 4, the pulse starting method is as described above 4 described for the internal combustion engine 2 started and the speed of the main electric machine drops sharply in the pulse start interval between t1, 3, 4 and t2, 5, 6-b. At time t6-b, the moment blending described above is performed. At the same time, the speed conversion of the circuit is performed so that between the time t2, 5, 6-b to the time t6-a, at which the torque transfer of the circuit is performed and the driving clutch 6 is put back into the micro-slip mode, the speed 40d to the synchronous speed 41d of the low gear.

5e shows a train operating state in which a wheel slip of a drive wheel occurs during the starting process of the internal combustion engine. In this case, the separating clutch 7 be closed immediately, since the wheel moment determining member is the slipping wheel itself. At time t0, 1, 3, 4, the pulse coupling 7 closed, the closing process is finished at t2, 5, 6-a. At time t6-a, the clutch becomes 6 put back into the micro-slip mode and the speed 40e the main electric machine 3 rises synchronously with the synchronous speed as described above, because here the main electric machine 3 and the internal combustion engine 2 are coupled.

• t0: t0-a Startkommando t0-b Aussetzen des Mikroschlupfbetriebs der Fahrkupplung (des Anfahrelements); oder Öffnen einer Wandlerüberbrückungskupplung; oder: Schlupfaufbau über der Fahrkupplung eines ASG (automatischen Schaltgetriebes) t0-c Eintritt in vorbereitenden Schlupfaufbau t0-d Darstellung Momenteneingriff Hauptelektromaschine, um eine Schlupfreserve für den Start der Verbrennungskraftmaschine bereitzustellen
• t1: t1-a Ankoppeln der Hilfselektromaschine t1-b Momentenaufbau in der Hilfselektromaschine
• t2: Einspritzbeginn der Verbrennungskraftmaschine zur Darstellung Startmoment + Reibmoment
• t3: Momentenaufbau der ersten Trennkupplung (7) durch schnelles oder langsames Schließen
• t4: t4-a Abkoppeln der Hilfselektromaschine t4-b Rücknahme des Moments Hilfselektromaschine
• t5: t5-a Rücknahme des Startmoments in der Verbrennungskraftmaschine t5-b Rücknahme des Momenteneingriffs der Hauptelektromaschine (siehe t0-d) t5–c Eintritt in Aufkopplungsphase, in der die gemeinsame Drehzahl der Hauptelektromaschine und der Verbrennungskraftmaschine an die Synchrondrehzahl angepasst wird
• t5–d vollständiges Schließen der ersten Trennkupplung (7)
• t6: t6-a Eintritt in Mikroschlupfbetrieb Fahrkupplung (6) (des Anfahrelements), oder: Schließen der Wandlerüberbrückung, oder: Schließen der Fahrkupplung beim ASG t6-b Beginn Momentenüberblendung von Hauptelektromaschine auf Verbrennungskraftmaschine
• t7: Ende Momentenüberblendung und Beginn der Betriebsart „Fahren VKM und EM”

In summary, therefore, in some embodiments, the following method steps occur at least partially, wherein in some embodiments the steps are included at the times t0, t2, t3, t5-a, t5-d t6-b t7, while steps at other times are optional in some embodiments are. In addition, in some embodiments, the order of times is interchangeable, e.g. For example, the time t2 may be before the time t3, etc., as already stated above.

• t0: t0-a start command t0-b Suspend the micro-slip operation of the drive clutch (start-up element); or opening a lockup clutch; or: Slip structure over the clutch of an ASG (automatic gearbox) t0-c Entry in preliminary slippage structure t0-d Representation of torque intervention of the main electric machine to provide a slip reserve for the start of the internal combustion engine
• t1: t1-a coupling of the auxiliary electric machine t1-b torque build-up in the auxiliary electric machine
• t2: start of injection of the internal combustion engine to show starting torque + friction torque
• t3: torque build-up of the first disconnect clutch ( 7 ) by fast or slow closing
• t4: t4-a Disconnecting the auxiliary electric machine t4-b Reversing the torque Auxiliary electric machine
• t5: t5-a Take-back of the starting torque in the internal combustion engine t5-b Withdrawal of the momentary engagement of the main electric machine (see t0-d) t5-c Entry in the coupling-up phase in which the common rotational speed of the main electric machine and the internal combustion engine is adapted to the synchronous rotational speed
• t5-d fully closing the first disconnect clutch ( 7 )
• t6: t6-a entry into micro-slip mode drive clutch ( 6 ) (of the starting element), or: Closing the torque converter lockup, or: Closing the drive clutch on the ASG t6-b Start torque superimposition of the main electric machine on the internal combustion engine
• t7: End of moment transition and start of operating mode "Driving VKM and EM"

LIST OF REFERENCE NUMBERS

1

drive train

2

Internal combustion engine

3

Main electrical machine

4

Auxiliary electric motor

5

Double clutch

6

Clutch of 5

7

(first) separating clutch (for main electric machine)

8th

Coupling element, designed as a second separating clutch (for auxiliary electric machine)

9

Air compressor unit

10

High-voltage battery

11

High-voltage electrical system

12

12V starter battery

13

12V electrical system

14

DC converter

15

control

16

Double belt tensioner

21

Arrow micro-slip operation

22

Arrow injection speed

23

Arrow opening separating clutch K3

24

Arrow synchronous speed

31

Arrow micro-slip operation

32

Arrow synchronous speed

33

Arrow micro-slip operation

40a-e

Speed of the main electric machine

41a-e

Synchronous speed (low gear)

42c, d

Synchronous speed (high gear)

K12

Coupling capacity curve of the drive clutch 6

K0

Coupling capacity curve for separating clutch 7 (for main electric machine)

K3

Coupling capacity curve for coupling element 8th (for auxiliary electric machine)

EM

Torque or speed curve of the main electric machine 3

HEM

Torque curve of the auxiliary electric machine 4

VKM

Speed curve of the internal combustion engine 2

VKM1

Driving torque curve of the internal combustion engine 2

VKm2

Reibmomentverlauf the internal combustion engine 2

wheel

Speed or torque curve for at least one driven wheel

Claims (7)

Method for starting an internal combustion engine of a hybrid vehicle with a drive train ( 1 ), which is an internal combustion engine ( 2 ), a main electric machine ( 3 ), an auxiliary electric machine ( 4 ) and a transmission ( 5 ) with starting element ( 6 ), wherein the main electric machine ( 3 ) via a separating clutch ( 7 ) to the internal combustion engine ( 2 ) and the auxiliary electric machine ( 4 ) via a coupling element ( 8th ) with the internal combustion engine ( 2 ) and wherein the main electric machine ( 3 ) provides a drive torque, characterized by the steps: starting from a first time (t1) operating the auxiliary electric machine ( 4 ) such that it has a torque on the internal combustion engine ( 2 ) via the coupling element ( 8th ) and thereby the speed of the internal combustion engine ( 2 ) until reaching a start criterion, so that the internal combustion engine ( 2 ) supports a starting process itself from a second time (t2); and from a third time (t3) at least partially closing the separating clutch ( 7 ) and operating the main electric machine ( 3 ) such that the main electric machine ( 3 ) continue essentially the drive torque via the starting element ( 6 ) and at the same time a torque via the separating clutch ( 7 ) to the internal combustion engine ( 2 ) exercises. Method according to claim 1, wherein the separating coupling ( 7 ) is closed such that an angular momentum of the main electric machine ( 3 ) to the internal combustion engine ( 2 ) is transmitted. Method according to one of the preceding claims, wherein as of a fourth point in time (t4) the auxiliary electric machine ( 3 ) via the coupling element ( 8th ) of the internal combustion engine ( 2 ) is separated. Method according to claim 3, wherein the fourth point in time (t4) depends on at least one operating parameter of the auxiliary electric machine ( 3 ) is determined. Method according to one of the preceding claims, wherein from a fifth point in time (t5) the rotational speeds of the internal combustion engine ( 2 ) and the main electric machine ( 3 ) are synchronous. Method according to one of the preceding claims, wherein at a sixth point in time (t6) that of the main electric machine ( 3 ) is reduced and from a seventh time (t7) by the internal combustion engine ( 2 ) provided. Hybrid vehicle with a drive train ( 1 ), which is an internal combustion engine ( 2 ), a main electric machine ( 3 ), an auxiliary electric machine ( 4 ), a transmission ( 5 ) with starting element ( 6 ) and a controller ( 15 ), wherein the main electric machine ( 3 ) via a separating clutch ( 7 ) to the internal combustion engine ( 2 ) and the auxiliary electric machine ( 4 ) via a coupling element ( 8th ) with the internal combustion engine ( 2 ), the main electric machine ( 3 ) provides a drive torque and the controller is adapted to carry out the method according to one of claims 1 to 6.

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