WO2009077323A2

WO2009077323A2 - Method and device for the operation of a hybrid drive of a vehicle

Info

Publication number: WO2009077323A2
Application number: PCT/EP2008/066601
Authority: WO
Inventors: Stefan Wallner
Original assignee: Zf Friedrichshafen Ag
Priority date: 2007-12-17
Filing date: 2008-12-02
Publication date: 2009-06-25
Also published as: DE102007055831A1; WO2009077323A3

Abstract

The invention relates to a method and a device for operating a hybrid drive (1) of a vehicle comprising a drive train (2) that essentially has a combustion engine (3), at least one triggerable clutch (4), at least one electric machine (5), and an automatic transmission (7). The combustion engine (3) can be non-positively connected to the electric machine (5) by means of the at least one clutch (4) and can be started using the electric machine (5). A start of the combustion engine (3) can be coordinated with a gear-shifting process of the transmission (7). In order to obtain a shifting process that is as short and comfortable as possible when the combustion engine (3) is started, a torque on the transmission input (6) is lowered and a dragging moment is applied to the combustion engine (3) once a request for a start has been detected and a request for shifting gears has been simultaneously made by triggering the clutch (4), such that an engaged gear is disengaged and the combustion engine (3) can be started already before a break in the shifting process has been reached.

Description

Method and device for operating a hybrid drive of a vehicle

The invention relates to a method and a device for operating a hybrid drive of a vehicle according to the preamble of patent claim 1 and of patent claim 7, respectively.

Hybrid powertrains are becoming increasingly important in vehicle construction due to their potential for reducing pollutant emissions and energy consumption. Such vehicles have various sources of power, in particular combinations of combustion and electric motors are advantageous because they on the one hand the range and performance advantages of internal combustion engines and on the other hand, the flexible uses of electric machines as a sole or Hilfsanthebsquelle or as a starter generator and generator for power generation and recuperation to be able to use.

Hybrid powertrains are demanded by the market, which can be implemented in vehicles as far as possible without additional space requirements, with the least possible complexity and with low cost and design effort. In principle, a distinction is made between two hybrid topologies, the series hybrid and the parallel hybrid. Such arrangements are already known and are constantly being developed.

In the series hybrid, the drive machines are arranged behind one another in terms of drive technology. In this case, the internal combustion engine, for example a diesel engine, serves as drive for a generator which feeds an electric machine. The vehicle is driven exclusively by the electric motor. The internal combustion engine is decoupled from the drive wheels and can therefore constantly in an operating point, ie at a certain torque and constant speed can be operated. This drive concept is suitable, for example, for buses in urban short-distance traffic, wherein preferably an operating point in which the efficiency of the internal combustion engine is as high as possible and at the same time pollutant emissions, fuel consumption and noise are in a favorable range is set. On the other hand, it is unfavorable for the series hybrid that the efficiency of the drive is limited due to the mechanical-electrical multiple conversion.

In contrast, Parallelhybrid-Anthebstränge by parallel with respect to the power flow arrangement of the drive train aggregates in addition to the superposition of drive torques offer the possibility of driving with purely internal combustion engine drive or purely electric motor drive. In principle, in the case of the parallel hybrid, the internal combustion engine can be largely operated at optimum torque by respectively loading or supporting by means of one or more electrical machines, so that the maximum efficiency of the internal combustion engine can be effectively utilized. The support of the internal combustion engine reduces fuel consumption on average.

Since at short-term increased power requirements in the so-called boost mode, such as overtaking, a summation of the drive power is possible, the engine can be designed almost without sacrificing performance and ride comfort of the vehicle comparatively small, and weight and space-saving, which also reduces emissions and low cost , The electric machine can also act as an integrated starter generator (ISG) to start the engine via a clutch. Furthermore, the electric machine is used in generator mode for charging an electrical energy storage and can be used for recuperation. As a transmission for Ation of the translation of the drive of the driven axles are basically all forms of vehicle transmissions into consideration.

In a common construction of a parallel hybrid drive, as shown for example in US 2005/0221947 A1, the internal combustion engine via a first clutch with an electric machine can be coupled. The electric machine can be connected to a transmission via a second clutch. It is also possible that, as shown in DE 10 2004 043 589 A1, a second electric machine is arranged between the second clutch and the transmission.

Instead of a direct arrangement between the engine and transmission or a direct non-positive connection via a clutch, the electric machine can also be coupled via a planetary gear. As a result, the electric machine can act as an electrodynamic starting element (EDA), which in turn eliminates the need for a conventional starting clutch. Such a hybrid system with EDA is known for example in connection with the automated AS Tronic transmission from the applicant's production program and particularly suitable for commercial vehicles in urban distribution traffic with frequent startup, braking and maneuvering.

The aim of numerous developments in hybrid technology are operating strategies that use the existing hybrid components as effectively and energy-efficiently as possible, depending on the driving situation, with the greatest possible consideration of driver wishes and high driving comfort. For this purpose, a selection of developments is described below.

DE 10 2004 043 589 A1 discloses such an operating strategy in a parallel hybrid sub-train, for example in conjunction with the 6-speed automatic trolley 6HP26 known from the Applicant's production program, in which a nominal state of charge of a rather sporty or rather economical driving style is dependent electrical energy storage is determined. The drive power is distributed according to a current drive request of the driver to the hybrid units so that this target state of charge is maintained. A particularly sporty driving requires to keep the energy storage always at full capacity, in order to provide the summed power of the drive units when boosting. On the other hand, a more economical driving style requires that the energy store be frequently emptied in order to effectively utilize the already occurring recuperation energy for filling up the store.

WO 2006 1 1 434 A1 discloses a method in which an electric machine and an internal combustion engine jointly generate a requested desired torque, wherein a momentary torque reserve of the electric machine is taken into account in order to minimize a respective torque reserve of the internal combustion engine.

From WO 2007 020 130 A1 a method for recuperation in a hybrid vehicle is known, wherein the proportion of the electric machine is coordinated in the deceleration with a brake pressure exerted by the driver.

From US Pat. No. 7,174,980 B2, a method for controlling a hybrid drive is known in which, with the aid of an electric machine, a sudden drag torque behavior of the internal combustion engine is prevented and, depending on the requirement, a drag torque characteristic of the entire hybrid drive is influenced.

DE 10 2005 044 828 A1 describes a method for determining an optimum operating point of a hybrid drive, whereby a drive torque requested by the driver on the one hand and a dynamic behavior of the existing vehicle units, eg a so-called turbo lag, on the other hand are taken into account. For this purpose, an optimization algorithm is proposed. in the previously determined maps and current constraints, such as the current accelerator pedal position and the vehicle speed, enter, which are then applied to variables such as the torque distribution between the drive units and the transmission ratio.

DE 10 2005 044 268 A1 discloses a method in which, in order to increase the efficiency of a hybrid drive, a charge state of an energy store or an energy flow (output energy / electrical energy) in the vehicle is regulated as a function of a cost function for energy consumption or pollutant emission.

In DE 699 32 487 T2 a method for controlling and monitoring the state of charge of an electrical energy storage in a hybrid vehicle is described, even with insufficient recuperation in certain driving situations, for example, repeated short successive accelerations and decelerations or in a gradient, the no immediate Following downhill follows, a sufficient state of charge of the memory is adjusted.

Finally, DE 10 2005 049 458 A1 proposes a forward-looking strategy in which, with the aid of digital road maps, locating devices and distance-related velocity distributions stored in temporal-spatial traffic patterns, an activation or deactivation of a hybrid aggregate is decided in the respective route section.

Of particular importance in a hybrid vehicle is the flawless change between the drive forms while driving. In particular, the frequently occurring starts of the internal combustion engine from a purely electromotive drive, for example in urban transport or in convoy traffic, should be reliable and comfortable. This can be a Switching strategy and a hybrid operating strategy be correlated such that relatively often a switching request coincides with an engine start request.

In a hybrid-Abhebsstrang with an automated transmission with a traction interruption during gear changes usually the engine start is initiated from the time from which the transmission is switched to neutral. First of all, the torque applied to the transmission input must be lowered in order to be able to interpret the currently engaged gear. When driving electrically, the drive torque of the electric machine is usually reduced. Thereafter, a clutch for power transmission between the internal combustion engine and the electric machine is engaged and the drive torque of the electric machine raised again to start the engine in the traction interruption break. Subsequently, the transmission can be synchronized in the usual way to the connection speed of the target gear and the target gear can be engaged.

A disadvantage of this conventional engine starting method is that the switching time can be significantly extended by the start of the internal combustion engine in the switching pause. Furthermore occurs by the construction and dismantling of the torque on the electric machine on an additional load change in the drive train, which can adversely affect the gear comfort and longevity of the powertrain components.

From DE 199 04 129 C1, a method is known, with which the switching operation can be shortened in an automated transmission. In this case, as soon as a gear change is signaled, for example, by the fact that the driver taps the shift lever, the engine torque of the drive unit, regardless of a current accelerator operation, lowered by a corresponding control to reduce the powertrain torque, as from the powertrain torque a the gear disengagement counteracting force results. At the same time, a shifting force, for example a hydraulic pressure, is built up on an actuator of the gear to be disengaged, with the consequence that, as soon as the applied shifting force exceeds the degrading counteracting moment, the gear can be designed. As this is done regardless of whether the clutch is still engaged or already disengaged, the shift can be shortened in time as a result. In order to limit the load of the drive train in such switching operations, the switching force of the respective actuator is preferably set so that the torque at the transmission input is in the range of zero when the disengagement of the gear takes place.

Although this document mentions that the method can also be carried out in an electric motor as a drive unit or generally in a hybrid drive. However, the person skilled in the art does not find any indication of a starting sequence of the internal combustion engine from electric travel during a switching operation.

Against this background, the invention has for its object to provide a method and an apparatus for operating a hybrid drive with an internal combustion engine, an electric machine and an automated manual transmission, which at the same time a start of the engine via the electric machine in a switching operation with a high operating comfort short time switching sequence allow.

The solution to this problem arises from the features of the independent claims, while advantageous embodiments and modifications of the invention are the dependent claims.

The invention is based on the finding that the shift sequence in the event of a gear change interrupted in an automated transmission in a hybrid drive by a coincident with the gear change Engine start request for the start of the internal combustion engine is not extended beyond the usual internal gear shift time out when the engine start is already initiated before the traction-interrupted switching phase, so that the internal combustion engine as possible already in the switching pause. This is made possible by initiating the lowering of the gear to be lowered during gear change at the transmission input torque in the crankshaft of the initially still stationary internal combustion engine.

Accordingly, the invention is based on a method for operating a hybrid drive of a vehicle, wherein the vehicle has a drive train, which essentially comprises an internal combustion engine, at least one controllable clutch, at least one electric machine and an automated manual transmission, in which the internal combustion engine via the at least a clutch to the electric machine frictionally connected and can be started by means of the electric machine, wherein a start of the internal combustion engine with a gear change of the gearbox is coordinated.

Under an automated transmission, a transmission is understood with traction interrupted switching operations, with corresponding actuators for engaging and disengaging the gear ratios are automatically controlled and actuated.

A gear change is understood to mean a traction-interrupted gear shift in which an original gear step is designed and a target gear step is engaged. Basically, this also includes the special case that an original gear stage (engaged gear) and a target gear stage (gear to be engaged) are the same, ie that although a circuit, but no translation change occurs. To achieve the object, the invention provides the following method steps:

a) detecting a switching request for gear change of the gearbox between an inserted gear stage and a einzulegenden target gear and a start request for starting the engine from electric drive with the clutch open, taking into account a minimum start speed of the electric machine as a start condition, b) lowering a torque at one with the D) exerting a drag torque on the internal combustion engine via a drive torque of the electric machine overlapping with the two previous steps b) and c. D) exerting a drag torque on the internal combustion engine over a drive torque of the electric machine overlapping with the two previous steps b) and c ) until the start of the engine, e) complete closing of the clutch and setting a superimposed drive torque of the electric machine and the Verbrennungsmo in coordination with a predetermined switching sequence for inserting a target gear.

Through this process is advantageously achieved that circuits with simultaneous start of the engine in such a hybrid powertrain equally fast or at least approximately as fast as in pure circuits without starting the engine. In this case, the drive torque remains largely constant on the electric machine, in contrast to conventional methods with alternating torque reduction gear layout and torque build-up for starting the engine. As a result, additional load changes in the drive train are avoided, which driving comfort of the hybrid drive is increased and the drive train components are protected mechanically.

Furthermore, the object is achieved by a device for carrying out the method. For this purpose, the invention is based on a device for operating a hybrid drive of a vehicle, comprising a drive train, essentially comprising an internal combustion engine, an electric machine, a controllable clutch for non-positive connection of the internal combustion engine with the electric machine, an automated transmission and a control unit for controlling the clutch. In addition, it is provided that by means of an appropriately designed control unit, the clutch, starting from a purely electromotive drive with open clutch, is controllable such that at substantially constant electric drive torque of the electric machine, a torque acting on the transmission gear on a transmission input shaft passes zero, while a drag torque is transmitted to the internal combustion engine, so that an engaged gear is interpretable with torque-free transmission and the internal combustion engine during the transmission of the drag torque can be started.

In principle, the method according to the invention can be used in all types of land, water and air vehicles with such parallel hybrid drive trains.

The starting sequence of the internal combustion engine is preferably carried out in three phases:

A first phase is based on an operating situation in which the vehicle drives with a purely electromotive drive, ie with the clutch open and with the internal combustion engine switched off. A hybrid operating strategy in the form of control programs issues the command that the Internal combustion engine is started. This command is coordinated in time with a gear change initiated by a shift strategy. This may be the case, for example, when a monitored state of charge of an electric drive energy storage device falls below a threshold value, ie in particular when the drive energy battery is empty or almost empty or if an available drive torque reserve of the electric machine is insufficient to fulfill a current or very soon to be expected drive torque request, ie at too low electrical drive torque.

In principle, however, the start request for starting the internal combustion engine can also be carried out directly by the driver if he considers this to be appropriate or desirable from the driving situation he perceives and signals this via a suitable actuating member and a sensor. As a starting condition, a minimum starting speed of the electric machine is specified. This may preferably be an idle speed of the internal combustion engine. This ensures that the electric machine is able to carry out a tow start of the internal combustion engine until it reaches its idling speed.

In a second phase, the torque applied to the transmission input is lowered, so that the engaged gear can be designed with a torque-free transmission. For this purpose, preferably designed as a friction clutch coupling between the engine and the electric machine is driven in the closing direction, ie partially engaged that the stationary crankshaft of the engine receives the torque and the torque drops at the transmission input. Towards the end of this phase, the gear is designed when the torque at the transmission input through the closing operation of the clutch passes through a zero crossing, so briefly assumes the value zero or no torque applied to the transmission input. The start of the internal combustion engine is assigned to a third phase. This is due to the crankshaft to a towing the engine sufficiently large torque, so that can be started with the towing of the engine or the crankshaft of the engine is already rotated by the electric machine. In case of (stand-alone) fuel injection, the engine starts. Subsequently, the previously partially engaged clutch is fully closed, so that - if the engine operation of the electric machine is not switched off - a summed drive torque of both drive units is available on the drive train.

The shift sequence can then be continued in a conventional manner with a synchronization of the interacting gear elements and completed with the engagement of the desired target gear, wherein the drive torque or total torque of the drive units is set according to a conventional shift sequence.

To clarify the invention, the description is accompanied by a drawing of an embodiment. In this shows

1 is a schematic representation of a hybrid drive for performing a method according to the invention,

Fig. 2 shows a speed curve of an internal combustion engine and an electric machine in carrying out the method, and

Fig. 3 shows a torque curve of the electric machine and a clutch in the implementation of the method.

Accordingly, FIG. 1 shows a diagram of a vehicle hybrid drive 1 with a parallel hybrid drive train 2, as may be provided, for example, for a commercial vehicle (truck, bus, special vehicle). The structure of such a drive train 2 is known per se to the person skilled in the art. Of the Drive train 2 has an internal combustion engine 3, for example a diesel engine, which can be connected to an electric machine 5 via a clutch 4, which is advantageously designed as a friction clutch. Essential to the invention is an inventive control of this drive train 2, in particular the coupling. 4

The electric machine 5 is arranged downstream of an automated transmission 7 drive technology. The electric machine 5 is connected in a manner not shown and explained manner via a second clutch or via internal gear shift elements with the transmission for driving torque transmission. In Fig. 1, only a transmission input shaft 6 is indicated for simplicity as a connecting element for torque transmission between the electric machine 5 and the transmission 7.

The manual transmission 7, an unspecified power take-off (PTO: Power Take-Off) 8 be arranged downstream. About the transmission gear 7 and a differential 9, a respective applied output torque of the hybrid drive 1 can be forwarded in a conventional manner to a drive axle 10 and via this to the drive wheels 1 1.

Depending on the operating situation, the electric machine 5 can be operated as an electric drive unit or as a generator. For this purpose, it is connected to a converter 12, which can be controlled by a converter control unit 13. About the inverter 12, the electric machine 5 with an electric drive energy storage 14, for example, a 340V high-voltage battery (and supercaps are possible) connected. In motor operation, the electric machine 5 is powered by the energy storage 14 with electrical energy. In regenerative operation, that is to say when driving via the internal combustion engine 3 and / or in the recuperation mode, the energy store 14 is charged via the electric machine 5. Furthermore, the electric machine 5 functions as an integrated starter generator (ISG) for starting the internal combustion engine 3. The high-voltage circuit of the energy accumulator 14 and the control units connected thereto are connected via a bidirectional DC-DC converter (DC / DC) 15 to a vehicle electrical system (24V or 12V) 16. The energy store 14 can be monitored and regulated via a battery management system (BMS) 17 with respect to its state of charge (SOC). The DC-DC converter 15 can be controlled via a DC-DC converter control unit 18. In addition, a control unit 19 for unspecified brake control functions, in particular an anti-lock braking system (ABS) or an electronic brake system (EBS) and a further control unit 20 for an electronic diesel injection control (EDC) of the example designed as a diesel engine combustion engine 3 is provided. The individual control units mentioned can also be combined, at least in part, in a control unit.

Furthermore, an integrated control device 21 is arranged, in which a transmission control unit (TCU: Transmission Control Unit), a hybrid control unit (HCU: Hybrid Control Unit) and various operating functions are combined. The control device 21 is associated with a control unit 25 for controlling the clutch 4, which may also be integrated into the control device 21.

A respective drive energy distribution and function control of the individual components of the hybrid drive can be controlled via a central strategy unit 22 which, advantageously via a data bus (eg CAN) 23, with the control device 21 and the control unit 25 and the relevant control devices 13, 17, 18, 19 is connected by signal technology.

In the following, a method according to the invention is described, which can be carried out with the hybrid drive 1. The process is carried out in three phases I, II and III. To illustrate these three phases I, II, III are in Fig. 2 temporal courses Π _EM , Π _{VM of} the rotational speeds of the electric machine 5 and the internal combustion engine 3 and in Fig. 3 temporal courses M _EM , M _{K of} the torques of the electric machine 5 and the clutch 4 shown.

Phase I: During electric driving, in which the internal combustion engine 3 is stationary and the clutch 4 is open, the internal combustion engine 3 is to be started, for example because the electrical energy of the drive battery 14 will soon be exhausted. At the same time a gear change is provided by the operating strategy 22 or signaled by the driver. The electric machine 5 runs at a constant speed Π _EM above an intended idle speed of the engine 3 and with a constant drive torque M _EM .

Phase II. Via the control unit 25, the clutch 4 is driven in the closing direction, so that contact their friction partners, whereby an increasing clutch torque M _{κ is} generated (Fig. 3). The partial closure of the clutch 4 causes the transmission input 6 a torque drop. If the torque at the transmission input 6 is zero, the currently engaged gear is designed via the control device 21.

Phase III. At the same time, the unchanged drive torque M _{EM of} the electric machine 5 acts on the crankshaft 24 of the internal combustion engine 3, so that it is entrained and starts according to the ignition timing in the fuel injection, whereupon the engine speed Π _VM increases. The clutch 4 is then completely closed, whereby the transmitted clutch torque M _{κ is} constant (FIG. 3) and the speed curves ΓI _VM , n _EM of the internal combustion engine 3 and the electric machine 5 align (FIG. 2). Combustion engine 3 and electric machine 5 now run in the block. A resulting total torque of the drive units 3 and 5 is adjusted so that it corresponds to a conventional shift sequence. In the traction-interrupted phase of the synchronization of the transmission 7 until engagement of the target gear, the internal combustion engine 3 thus already runs and stands, without lengthening the shift sequence, directly available as a drive source.

LIST OF REFERENCES

1 hybrid drive

2 powertrain

3 internal combustion engine

4 clutch

5 electric machine

6 transmission input shaft

7 Automated manual transmission

8 power take-off

9 differential

10 drive axle

1 1 vehicle wheel

12 inverters

13 Inverter control unit

14 Electric drive energy storage

15 DC-DC converter

16 electrical system

17 battery management system

18 Voltage transformer control unit

19 Electronic brake control

20 Electronic diesel injection control

21 control device

22 operating strategy unit

23 data bus

24 crankshaft

25 clutch control unit n speed

Π _EM speed of the electric machine

Π _VM speed of the internal combustion engine M drive torque

M _EM torque of the electric machine

M _K torque at the clutch t time

Claims

Patent claims

1. A method for operating a hybrid drive (1) of a vehicle, wherein the vehicle has a drive train (2), essentially an internal combustion engine (3), at least one controllable clutch (4), at least one electric machine (5) and an automated Gearbox (7), in which the internal combustion engine (3) via the at least one clutch (4) to the electric machine (5) non-positively connectable and by means of the electric machine (5) is startable, wherein a start of the internal combustion engine (3) a gear change of the gearbox (7) is coordinated, characterized in that the following steps are provided: f) detecting a shift request for gear change of the gearbox (7) between an inserted original gear stage and a einzulegenden target gear and a start request for starting the engine (3) electric drive with the clutch (4) open, taking into account a minimum start speed hl the electric machine (5) as a start condition, g) lowering a torque at one with the clutch (4) operatively connected transmission input shaft (6) of the gearbox (7) by driving the clutch (4) in the closing direction, h) designing the original gear stage Reaching a zero crossing of the torque at the transmission input shaft (6), i) exerting a drag torque on the internal combustion engine (3) via a drive torque of the electric machine (5) overlapping with the two previous steps b) and c) until starting the internal combustion engine (3) , j) Completely closing the clutch (4) and setting a superimposed drive torque of the electric machine (5) and the internal combustion engine (3) in coordination with a predetermined shift sequence for engaging a target gear.

2. Method according to claim 1, characterized in that the minimum starting rotational speed specified as start condition is an idling rotational speed or a rotational speed lying above the idling rotational speed of the internal combustion engine (3).

3. The method according to claim 1 or 2, characterized in that a start request for starting the internal combustion engine (3) takes place via a hybrid operating strategy.

4. The method according to claim 3, characterized in that a start of the internal combustion engine (3) is initiated when a monitored state of charge of an electric drive energy storage device (14) falls below a threshold value.

5. The method according to claim 3 or 4, characterized in that a start of the internal combustion engine (3) is initiated when an available drive torque reserve of the electric machine (5) to fulfill a current or very soon expected drive torque request is too low.

6. The method according to any one of claims 1 to 5, characterized g e - k e n n e c i n e that a start request for starting the internal combustion engine (3) via a driver request.

7. An apparatus for operating a hybrid drive (1) of a vehicle, comprising a drive train (2), essentially comprising an internal combustion engine (3), an electric machine (5), a controllable clutch (4) for non-positive connection of the internal combustion engine (3) with the electric machine (5), an automated manual transmission (7) and a control unit (25) for actuating the clutch (4), characterized net, that the control unit (25) is designed such that starting from a purely electromotive driving with the clutch (4), the clutch (4) is controllable such that at largely constant electric drive torque of the electric machine (5) on the manual transmission (7) effective torque at a transmission input shaft (6) passes through the value zero, while a drag torque is transmitted to the internal combustion engine (3), so that an engaged gear with torque-free transmission (7) is interpretable and the internal combustion engine (3) during the transmission the drag torque is bootable.