WO2007085359A1

WO2007085359A1 - Method for controlling a motor vehicle drive train

Info

Publication number: WO2007085359A1
Application number: PCT/EP2007/000310
Authority: WO
Inventors: Stefan Wallner; Notker Amann
Original assignee: Zf Friedrichshafen Ag
Priority date: 2006-01-26
Filing date: 2007-01-16
Publication date: 2007-08-02
Also published as: DE102006003724A1

Abstract

The invention relates to a method for controlling a motor vehicle drive train comprising an internal combustion engine (2), an electric motor/generator (3) and a gearbox transmission (4), which are intercoupled by means of a summarising gear (5) that has two input elements (6, 7) and one output element and by means of a lock-up clutch (12) that is configured as a friction clutch, the first input element being rotatably fixed to the crankshaft (9) of the internal combustion engine (2), the second input element being rotatably fixed to the rotor (10) of the electric motor/generator (3) and the output element being rotatably fixed to the input shaft (11) of the gearbox transmission (4). According to said method, the lock-up clutch (12) is situated between two elements of the summarising gear (5) and a speed differential (DELTAn) between the input shaft (11) of the gearbox transmission (4) and the internal combustion engine (2), which occurs when the lock-up clutch (12) is disengaged, is synchronised and the lock-up clutch (12) is subsequently engaged. The aim of the invention is to permit a rapid, low-wear synchronisation of the speed differential DELTAn. To achieve this, said speed differential DELTAn = n_GE - n_VM is synchronised with the aid of the electric motor/generator (3), whereby a positive torque M_EM > 0 that acts in the rotational direction of the crankshaft (9) of the internal combustion engine (2) and the input shaft (11) of the gearbox transmission (4) is generated by the electric motor/generator (3) if the speed differential is negative (DELTAn < 0), or a negative torque M_EM < 0 that acts against the rotational direction of the crankshaft (9) of the internal combustion engine (2) and the input shaft (11) of the gearbox transmission (4) is generated if the speed differential is positive (DELTAn > 0).

Description

Method for controlling a motor vehicle drive train

The invention relates to a method for controlling a motor vehicle drive train, which comprises an internal combustion engine, an electric machine and a transmission, which are coupled to each other via a summation with two input elements and an output element and a frictional clutch designed as a friction clutch by the first input element with the Crankshaft of the internal combustion engine, the second input element to the rotor of the electric machine, and the output member to the input shaft of the transmission is rotatably connected, and wherein the lock-up clutch between two elements of the summation gear is arranged, wherein a lock-up difference occurs with the clutch open between the input shaft of the transmission and the internal combustion engine is synchronized and then the lock-up clutch is closed.

A drive train of a motor vehicle of the type described above is known per se from DE 199 34 696 A1 and DE 101 52 471 A1. In this drive train, the summation gear is in each case designed as a simple planetary gear with a sun gear, a planet carrier with several planetary gears and a ring gear. The ring gear forms the first input element and is non-rotatably connected to the crankshaft of the internal combustion engine. The sun gear forms the second input element and is non-rotatably coupled to the rotor of the electric machine. The planet carrier forms the output element and is non-rotatably connected to the input shaft of the gearbox. The lockup clutch is arranged in terms of drive technology between the sun gear and the planet carrier of the planetary gear.

In the drive train according to DE 199 34 696 A1, the lockup clutch in contrast to the presently assumed training as Claw clutch formed so that the lock-up clutch can be closed only during synchronous operation of the engine and the input shaft of the gearbox, and thus can only be used to a limited extent. In order to enable a drive of the motor vehicle alone with the electric machine, a directional freewheel between the crankshaft and a housing part is arranged, whereby the crankshaft secured against reverse rotation and thus the drive torque of the electric machine is supported against the housing. In order to enable starting of the internal combustion engine with the electric motor when the vehicle is stationary, a further directional freewheel between the input shaft of the gearbox and a housing part is arranged, whereby the input shaft secured against reverse rotation and thus the drive torque of the electric machine is supported against the housing.

In the drive train according to DE 101 52 471 A1, the lockup clutch, as assumed for the present invention, is designed as a friction clutch, so that the lockup clutch is also used for a rotational speed difference between the input shaft of the shift transmission and the internal combustion engine for transmitting a torque in slip operation can be. In order to enable a pulse start of the internal combustion engine by means of the electric machine with the motor vehicle and in neutral gear, a further friction clutch between the input shaft of the gearbox and a housing part is arranged, whereby the input shaft can be braked after reaching a starting speed of the electric machine to start the engine.

Below, in the description of the invention without limiting the scope of an example of a largely identical structure of the drive train is assumed, the lock-up clutch is assumed as a friction clutch, in particular as a wet multi-plate clutch, but alternatively can also be designed as a dry clutch. alternative to the known arrangement, the lockup clutch can also be arranged between the ring gear and the sun gear, that is, between the crankshaft of the internal combustion engine and the rotor of the electric machine.

During normal driving, the lock-up clutch is fully closed, so that the planetary gear is blocked and rigidly rotates. In this operating state, the rotational speeds and the directions of rotation of the internal combustion engine, the electric machine and the input shaft of the gearbox are identical. The electric machine is operated in this state mainly as a generator for supplying the electrical system, but can be operated in certain operating situations, especially in acceleration phases of the motor vehicle, temporarily as a motor.

For gear change within the gearbox, the torque of the engine is almost simultaneously reduced, switched off the electric machine and fully open the lock-up clutch. As a result, the input shaft of the gearbox is decoupled from the engine, so that the loaded load gear designed load-free and the target gear to be engaged can be synchronized and loaded load-free. The switching operation inevitably results in a speed difference between the input shaft of the gearbox and the internal combustion engine, which is positive in a downshift and negative in a upshift. This speed difference is usually compensated after the switching process, that the lock-up clutch is coordinated with the torque build-up of the engine closed controlled. However, this requires a certain period of time and is disadvantageously associated with a relatively high wear on the friction elements of the lockup clutch and with an undesirable heating of the lockup clutch and adjacent components and possibly also the transmission oil. Against this background, the present invention has the object to provide a method by which in a drive train of the type mentioned a synchronization of the speed difference faster and less wear than previously feasible. Such a method should also be usable in drive trains containing comparable components, but in other propulsion combination combination.

The solution of this object is based on the features of the preamble of claim 1 of a method for controlling a motor vehicle powertrain, which includes an internal combustion engine, an electric machine and a transmission, via a summation with two input elements and an output element as well as a friction clutch trained bypass clutch are coupled together by the first input member to the crankshaft of the internal combustion engine, the second input member to the rotor of the electric machine and the output member to the input shaft of the transmission is rotatably connected, and by the lock-up clutch between two elements of the summation gear is arranged, wherein a synchronized with the lock-up clutch open speed difference .DELTA.n between the input shaft of the transmission and the engine and then the lock-up clutch is closed.

In this context, it should be noted that the term "gear" to understand all types of gear that have a true neutral position with an output speed "zero", so do not generate an output speed with the value "zero" by an internal gear speed summation The term "gearbox" therefore includes, for example, manual transmissions, automated manual transmissions, planetary automatic transmissions and continuously variable transmissions. Furthermore, according to the invention, it is provided according to the method that this speed difference Δn = n_GE-n_VM is synchronized by means of the electric machine by a positive torque M_EM> effective in the direction of rotation of the crankshaft of the internal combustion engine and the input shaft of the transmission by the electric machine with a positive speed difference Δn> 0 0 and negative rotational speed difference .DELTA.n <0 a counter to the rotational direction of the crankshaft of the engine and the input shaft of the transmission effective negative torque M_EM <0 is generated.

An effective in the direction of rotation of the crankshaft of the engine and the input shaft of the transmission torque M_EM the electric machine acts, each amplified by the effective gear ratio between the electric machine and the respective shaft, braking, so drehzahlabsenkend on the crankshaft of the engine and driving, so speed increasing the input shaft of the transmission. Such a positive torque M_EM> 0 of the electric machine therefore acts synchronizing to a negative speed difference (Δn <0), which typically occurs in an upshift.

Conversely, an effective against the direction of rotation of the crankshaft of the engine and the input shaft of the transmission torque M_EM the electric machine, each amplified by the effective translation between the electric machine and the respective shaft, driving, so speed increasing on the crankshaft of the engine and braking, so drehzahlabsenkend on the input shaft of the transmission. Such a negative torque M_EM <0 of the electric machine therefore acts synchronizing to a positive speed difference (Δn> 0), which typically occurs during a downshift.

Because the input element of the summation gear connected to the electric machine, in the preferred embodiment, the sun gear of the planetary gear, depending on the size of the circuit-dependent speed difference .DELTA.n temporarily reverse, so contrary to the direction of rotation of the two shafts, rotate, in this case, a positive torque M_EM> 0 by generating a drag torque in generator mode and a negative torque M_EM <0 generated by the generation of a drive torque during engine operation of the electric machine.

By using the electric machine to synchronize a speed difference .DELTA.n between the input shaft of the transmission and the crankshaft of the internal combustion engine, the lock-up clutch remain open during synchronization, and closed slip and wear-free upon reaching the synchronous operation of the input shaft and the internal combustion engine. As a result, unnecessary wear on the friction elements of the lockup clutch and heating of the lockup clutch and adjacent components are avoided.

Advantageous embodiments and further developments of the method according to the invention are the subject of the dependent claims 2 to 7.

Since the internal combustion engine is only relatively difficult to control due to a high moment of inertia and a time-delayed influence on the combustion process, the torque M_VM of the internal combustion engine is suitably controlled during the synchronization of the rotational speed difference Δn as a function of vehicle and operation-dependent operating parameters and the speed n_VM of the internal combustion engine Presetting a dependent of the speed difference Δn target speed n_VM_soll regulated, the target speed n_VM_soll is set substantially via the torque M_EM the electric machine. The internal combustion engine thus remains in its operating state at the beginning of the switching operation until the synchronization of the rotational speed difference Δn has ended by means of the electric machine and the lockup clutch is closed. Thereafter, the internal combustion engine is controlled depending on the usual operating parameters and the driver's power demand.

During the synchronization of the rotational speed difference Δn, the electric motor also has to support the momentary torque of the internal combustion engine (tractive torque or drag torque) and the torque applied to the input shaft of the transmission (driving resistance torque) against each other. The total required torque M_EM_erf of the electric machine can therefore optionally from the torque required for the current drive torque and for the synchronization of the speed difference Δn M_GE_soll at the input shaft of the transmission by retroactive calculation with the translation i_EM / GE between the electric machine and the input shaft of the transmission, or off the required for the current drive torque and for the synchronization of the speed difference Δn torque M_VM_soll at the crankshaft of the internal combustion engine by recalculation with the translation i_EM / VM between the electric machine and the internal combustion engine are determined.

In this case, the determined torque M_EM_soll may exceed the maximum torque M_EM_max that can be generated by the electric machine, in particular in the case of a weaker dimensioned electric machine, which would result in at least a delay of the synchronization. It is therefore expedient to check in principle whether the required torque M_EM_soll exceeds the maximum torque M_EM_max of the electric machine, in which case the required residual torque ΔM_EM_R = M_EM_soll - M_EM_max is applied by partially closing the lockup clutch as clutch torque M_K_soll.

The torque M_K, which can be generated by the lockup clutch, always has the correct meaning, ie speed compensating, independently of its arrangement, since in each case the faster rotating component is braked and the slower-moving component is slowed down. mer rotating component is accelerated. In this approach, although a certain amount of wear on the friction elements of the lock-up clutch is accepted. However, this wear is significantly lower than in a complete synchronization of the speed difference Δn via the lock-up clutch.

Regardless of whether the torque M_EM_max of the electric machine is sufficient or not, the synchronization of the speed difference Δn by the electric machine can be assisted and accelerated by partially closing the lock-up clutch during synchronization.

Likewise, the synchronization of the rotational speed difference Δn by the electric machine by means of the internal combustion engine can be assisted by increasing the torque M_VM_soll to be set and / or the predetermined target rotational speed n_VM_soll during synchronization with positive rotational speed difference Δn> 0 and decreasing it with negative rotational speed difference Δn <0.

To clarify the invention, the description is accompanied by a drawing with exemplary embodiments. In this shows

1 is a functional diagram of the method for synchronizing a speed difference between an input shaft of a transmission and an internal combustion engine in a drive train,

2 shows a part of the functional diagram according to FIG. 1 for determining the torques of an electric machine and a lock-up clutch,

3 is a first application example for synchronizing a speed difference in the form of a speed diagram over time,

4 shows a second application example for synchronizing a speed difference in the form of a speed diagram over time, Fig. 5 shows the general structure of the underlying powertrain in a simplified schematic representation, and

Fig. 6 shows a preferred practical embodiment of the drive train according to FIG. 5 in a schematic representation.

A drive train 1 according to FIG. 5 comprises an internal combustion engine 2, an electric machine 3 and a transmission 4, which are coupled to one another via a summation transmission 5 with two input elements 6, 7 and one output element 8. The first input element 6 is rotatably connected to the crankshaft 9 of the internal combustion engine 2, the second input element 7 with the rotor 10 of the electric machine 3, and the output member 8 with the input shaft 11 of the transmission 4 respectively. A bypass clutch 12 designed as a friction clutch is arranged between two elements of the summation gear 5, in the present case between the two input elements 6, 7. The internal combustion engine 2, the electric machine 2 and the lock-up clutch 12 are connected via sensor and control lines 13 to a control unit 14, via which the components of the drive train 1 can be controlled in a coordinated manner.

A preferred practical embodiment of the drive train 1 is shown in FIG. 6. In this drive train 1, the summation gear 5 is formed as a simple planetary gear 15 with a sun gear 16, a planet carrier 17 with a plurality of planetary gears 18 and a ring gear 19. The ring gear 19 forms the first input element 6 and is connected via a flywheel 20 and a torsional vibration damper 21 with the crankshaft 9 of the engine 2 in connection. The sun gear 16 forms the second input element 7 and is directly rotationally coupled to the rotor 10 of the electric machine 3. The planet carrier 17 forms the output element 8 and is directly connected to the input shaft 11 of the here formed as an automated transmission transmission 4 in combination. An arranged between the input shaft 11 and a housing part 22 directional freewheel 23 serves to support the input shaft 11 at a start of the engine 2 by the electric machine 3. The transmission 4 is executed in countershaft design and has a total of six forward gears and one reverse gear, each via one Claw clutch are selectively switchable. The lock-up clutch 12 is disposed between the rotor 10 of the electric machine 3 and a connecting shaft 24 through which the engine 2 is in communication with the ring gear 19.

In such a drive train 1, when the lock-up clutch 12 is open, a speed difference between the input shaft 11 of the gearbox 4 and the engine 2 or the crankshaft 9, which is compensated according to the invention by means of the electric machine 3, occurs during a shift within the gearbox 4 and during a starting operation. before the lock-up clutch 12 is fully closed.

For this purpose, it is provided according to the functional diagram of FIG. 1 that the torque M_VM or M_VM_soll of the internal combustion engine 2 essentially as a function of vehicle and operation-dependent operating parameters, such as the vehicle speed v, the engaged gear G, and the accelerator pedal position x_Fp, from a setpoint generator 14.1 is controlled or predetermined, whereas the speed n_VM of the engine 2 by regulating a dependent of the speed difference .DELTA.n = n_GE - n_VM between the input shaft 11 of the gearbox 4 and the crankshaft 9 of the engine 2 target speed n_VM_soll is controlled by a controller 14.2. In this case, the setpoint speed n_VM_soll is set essentially via the torque M_EM generated by the electric machine 3 and thus the speed difference Δn is synchronized. As shown in more detail in Hg. 2, this is determined by the controller 14.2 of the control unit 14 on the input shaft 11 of the transmission 4 required torque M_GE_soll and specified, which is to be applied by the electric machine 3, the current driving maneuver and additionally to enable the synchronization of the speed difference .DELTA.n. The required torque M_EM_soll of the electric machine results from the required torque M_GE_soll at the input shaft 11 by recalculation with the translation i_EM / GE between the electric machine 3 and the input shaft eleventh

In the preferred embodiment of the drive train 1 according to FIG. 6, M_EM_soll = M_GE_soll / (1-io), with stand translation i ₀ , therefore applies. With a typical stand translation of i ₀ = -3, this means that M_EM_soll is a quarter of M_GE_soll.

The required torque M_EM_soll is set by means of an associated inverter 25 on the electric machine 3, provided that this does not exceed the maximum possible torque M_EM_max of the electric machine 3. By recalculating the actual torque M_EM_act to the input shaft 11 and forming the difference with the predefined setpoint torque M_GE_soll, a possible residual torque ΔM_GE_R is determined, which is to be applied by partially closing the lockup clutch 12 as a clutch torque M_K_soll.

In Fig. 3 such a synchronization for a push downshift is shown. At time tθ the target gear is engaged, whereby a positive speed difference Δn = n_GE - n_VM> 0 between the input shaft 11 of the transmission 4 and the internal combustion engine 2 is present. By the subsequent generation of a counter to the direction of rotation of the input shaft 11 and the crankshaft 9 of the engine 2 effective torque M_EM the input shaft 11 is delayed and the relevant motor vehicle with it slowed down and simultaneously relieves the internal combustion engine 2 and thus accelerates the crankshaft 9 until at time t1 synchronism between the two shafts 9, 11 and thus also at the lock-up clutch 12 is reached. Therefore, the lock-up clutch 12 can be closed slip-free and wear-free at time t1. Subsequently, the further overrun with completely closed lock-up clutch 12 via the control of the internal combustion engine. 2

In Fig. 4 is shown in a similar form a synchronization for a pull upshift. At time tθ, the target gear is engaged, causing a negative speed difference Δn = n_GEn_VM <0 between the input shaft 11 of the transmission 4 and the engine 2. By the subsequent generation of an effective in the direction of rotation of the input shaft 11 and the crankshaft 9 of the engine 2 torque M_EM the input shaft 11 and thus the respective motor vehicle is accelerated, and at the same time the engine 2 loaded and thus the crankshaft 9 braked.

Due to the simultaneously increasing torque M_VM of the internal combustion engine 2, the speed n_VM of the internal combustion engine 2 nevertheless rises slightly, but at the time t1, it is overtaken by the higher rising speed n_GE of the input shaft 9 of the transmission 4, so that due to the achieved synchronism between the two shafts 9 , 11 the lock-up clutch 12 can be closed without slippage and wear. Subsequently, the further acceleration of the motor vehicle takes place when the lock-up clutch 12 is completely closed via the control of the internal combustion engine 2. Regardless of the embodiments shown in Figures 5 and 6, the invention also covers drive trains with all other possible and different drive couplings between the engine 2, the electric machine 3, the summation 5, the clutch 12 and the transmission 4, which, however, not shown separately is.

Bezuαszeichen

1 powertrain

2 internal combustion engine

3 electric machine

4 gearbox, manual transmission, automated manual transmission

5 summation terms

6 (first) input element

7 (second) input element

8 output element

9 crankshaft

10 rotor

11 input shaft

12 lockup clutch

13 sensor and control line

14 control unit

14.1 Setpoint generator

14.2 Controller

15 planetary gear

16 sun wheel

17 planet carriers

18 planetary gear

19 ring gear

20 flywheel

21 torsional vibration damper

22 housing part

23 directional freewheel

24 connecting shaft

25 inverters G Gear i Gear ratio io Gear ratio of the planetary gear i_EM / GE Gear ratio between 3 and 11 i_EM / VM Gear ratio between 3 and 2

M torque

M_EM torque of 3

M_EM_is actual moment of 3

M_EM_max maximum torque of 3

M_EM_soll nominal torque of 3

M_GE torque of 11

M_GE_setpoint nominal torque of 11

M_K torque of 12

M_K_soll Target torque of 12

M_VM torque of 2

M VM should nominal torque of 2 n speed n_GE speed of 11 n_VM speed of 2 n_VM_act actual speed of 2 n_VM_setpoint speed of 2 t time to time t1 time

V Driving speed x_Fp accelerator pedal position

ΔM_EM_R residual torque of 3

ΔM_GE_R residual torque of 11

Δn speed difference between 11 and 2

Claims

claims

1. A method for controlling a motor vehicle drive train, comprising an internal combustion engine (2), an electric machine (3) and a transmission (4) via a summation gear (5) with two input elements (6, 7) and an output element (8 ) and via a lockup clutch (12) designed as a friction clutch, in which the first input element with the crankshaft (9) of the internal combustion engine (2), the second input element with the rotor (10) of the electric machine (3) and the output element ( 8) with the input shaft (11) of the transmission (4) is rotatably connected, and in which the lock-up clutch (12) is arranged between two elements of the summation (5), wherein a gap opened when the lock-up clutch (12) occurred speed difference (Δn) between the input shaft (11) of the transmission (4) and the internal combustion engine (2) synchronized and then the lock-up clutch (12) is closed, thereby geken nzeichnet that this speed difference Δn = n_GE - n_VM is synchronized by means of the electric machine (3) by the electric machine (3) at a negative speed difference (Δn <0) in the direction of rotation of the crankshaft (9) of the internal combustion engine (2) and the input shaft (11) of the transmission (4) effective positive torque M_EM> 0 or positive rotational speed difference (Δn> 0) against the direction of rotation of the crankshaft (9) of the internal combustion engine (2) and the input shaft (11) of the transmission (4) effective negative Torque M_EM <0 is generated.

2. The method according to claim 1, characterized in that the torque (M_VM) of the internal combustion engine (2) is controlled substantially as a function of vehicle and operation-dependent operating parameters, and that the speed (n_VM) of the internal combustion engine (2) by specifying a rotational speed dependent on the speed difference (Δn) number (n_VM_soll) is controlled, wherein the target speed (n_VM_soll) is set substantially via the torque (M_EM) of the electric machine (3).

3. The method according to claim 1 or 2, characterized in that the required torque (M_EM_soll) of the electric machine (3) from the torque required for the current drive torque and for the synchronization of the rotational speed difference (Δn) (M_GE_soll) on the input shaft (11) of the transmission (4) by recalculation with the ratio (i_EM / GE) between the electric machine (3) and the input shaft (11) of the transmission (4) is determined.

4. The method according to claim 1 or 2, characterized in that the required torque (M_EM_soll) of the electric machine (3) from the torque required for the current drive torque and for the synchronization of the speed difference (Δn) (M_VM_soll) on the crankshaft (9) of the internal combustion engine (2) by recalculation with the translation (i_EM / VM) between the electric machine (3) and the internal combustion engine (2) is determined.

5. The method of claim 3 or 4, characterized in that it is checked whether the required torque (M_EM_soll) exceeds the maximum torque (M_EM_max) of the electric machine (3), and that, if the result is positive, the required residual torque (ΔM_EM_R = M_EM_soll - M_EM_max ) is generated by a partial closing of the lock-up clutch (12) as a clutch torque (M_K_soll).

6. The method according to at least one of claims 1 to 5, characterized in that the synchronization of the speed difference (Δn) with the electric machine (3) by means of the lock-up clutch (12) is supported by the lock-up clutch (12) is partially closed during synchronization ,

7. The method according to at least one of claims 1 to 6, characterized in that the synchronization of the speed difference (Δn) with the electric machine (3) by means of the internal combustion engine (2) is supported by the torque to be set (M_VM_soll) and / or the predetermined Setpoint speed (n_VM_soll) during synchronization increased with positive speed difference (Δn> 0) and lowered with negative speed difference (Δn <0).