WO2012152490A1

WO2012152490A1 - Method for controlling a hybrid drive train of a motor vehicle

Info

Publication number: WO2012152490A1
Application number: PCT/EP2012/054852
Authority: WO
Inventors: Manuel RISS
Original assignee: Zf Friedrichshafen Ag
Priority date: 2011-05-09
Filing date: 2012-03-20
Publication date: 2012-11-15
Also published as: EP2707237A1; DE102011075512A1

Abstract

The invention relates to a method for controlling a hybrid drive train of a motor vehicle. The drive train has an internal combustion engine (VM) with a driveshaft (2), a semi-automatic geared transmission (G) with at least one input shaft (GE), and an electric machine (EM) which can be operated as a motor and as a generator and which comprises a rotor (3), said rotor being connectable to the driveshaft (2) of the internal combustion engine (VM) via an automated separating clutch (K1) and being connected to the input shaft (GE) of the geared transmission (G). The internal combustion engine (VM) is activated close in time to an imminent gear shift of the geared transmission (G) after a transition into the internal combustion or hybrid drive operation is requested during an electric drive operation. The aim of the invention is to take into account the general time conditions during the activation of the internal combustion engine. According to the invention this is achieved in that the activation duration of the internal combustion engine (Δt_{VM_ZS}), the period of time until the beginning (Δt_{S_0}) of the gear shift, and the possible maximal duration of an ongoing electric drive operation (Δt_{EF_max}) are determined, and a decision is carried out dependent on said time durations (Δt_{VM_ZS}, Δt_{S_0}, Δt_{EF_max}) as to whether the internal combustion engine (VM) is activated before, during, or after the intended gear shift.

Description

Method for controlling a hybrid drive train of a motor vehicle

The invention relates to a method for controlling a hybrid powertrain of a motor vehicle having an internal combustion engine with a drive shaft, an automated multi-step transmission with at least one input shaft, and an operable as a motor and as a generator electric machine with a rotor via an automated disconnect clutch with the drive shaft of Combustion engine is connected and is in communication with the input shaft of the stepped transmission, wherein the internal combustion engine is switched during an electric driving after a request for the transition to the combustion or hybrid driving time close to an upcoming circuit of the stepped transmission.

A parallel hybrid powertrain of the type described above is well known. Such a hybrid powertrain has the advantage that the motor vehicle in question can be driven either in pure electric driving with parked or idling internal combustion engine in pure combustion driving with powerless electric machine or in hybrid driving with combined drive through the engine and the electric machine. In the combustion driving mode, the electric machine can be operated as a generator as needed and the power generated thereby can be used to supply an electrical system and / or to charge an electrical energy store. In general, the electric machine can also be operated as a generator during deceleration of the motor vehicle and the kinetic energy recovered in the process can be stored in an electrical energy store.

The multi-step transmission can be designed as an automated transmission, which has a single input shaft and is switchable with traction interruption. The input shaft of the gearbox can be connected or connectable directly or via an automated clutch with the rotor of the electric machine. However, the multi-step transmission may also be formed as a powershift transmission in the design of a planetary automatic transmission with a single input shaft or in the design of a dual-clutch transmission with two input shafts. The input shaft of a planetary automatic transmission can directly or via a hydrodynamic torque converter with the rotor of the electric machine in communication. In contrast, the two input shafts of a dual-clutch transmission via an associated clutch with the rotor of the electric machine can be connected.

In such a hybrid powertrain, during an electric vehicle operation, when an increased power demand, which can not be met by the electric machine alone, or when the state of charge of the associated electrical energy storage device has reached or fallen below a critical limit value while the power requirement is unchanged, must be acted upon. In this case, the internal combustion engine is switched on, i. started as needed, accelerated to the speed of the input shaft of the stepped transmission, and coupled by closing the clutch to the hybrid powertrain. As a result, the motor vehicle can subsequently be driven jointly by the internal combustion engine or the electric machine in the combustion driving mode alone by the internal combustion engine or in hybrid driving mode. In accelerator pedal operation, increased output of the powertrains may be requested with greater driver depression of the accelerator pedal, e.g. to accelerate the motor vehicle for performing an overtaking operation. During operation of a cruise control system, an increased power output of the drive units can be requested, for example, when driving into a gradient through the cruise control system in order to maintain the predetermined setpoint speed.

If the request to switch on the internal combustion engine, as provided herein, is timely close to an upcoming shift of the stepped transmission, wherein the circuit can be both an upshift and a downshift, it must be decided whether the internal combustion engine before , during or after the execution of the circuit is to be switched on.

In a method known from EP 1 762 417 A1 for controlling a corresponding hybrid drive train with a planetary automatic transmission Stepped transmission formed is provided that the internal combustion engine immediately before a proposed circuit of the stepped transmission in a

Towing started and then coupled, if it is a downshift. If it is an upshift, the internal combustion engine is started immediately after a proposed circuit of the stepped transmission in a tow start and then coupled. As a result, the speed difference to be bridged at the tow start of the internal combustion engine to the disconnect clutch is minimized, whereby the thermal load and the mechanical wear of the disconnect clutch to be reduced. In addition, thereby the speed of the input shaft of the stepped transmission, to which the internal combustion engine must be accelerated before coupling, kept low, whereby the noise and the fuel consumption of the internal combustion engine are reduced.

In DE 10 2007 045 366 A1 a method for controlling a corresponding hybrid powertrain is described with a multi-step transmission, the input shaft is connected directly via a clutch, or via a hydrodynamic torque converter with the rotor of the electric machine or connectable. In this known method it is provided that the internal combustion engine is started immediately after or at the end of a circuit of the stepped transmission during the load build-up of the circuit in a towing start by closing the clutch by means of the electric machine. In this case, the separating clutch is fully opened again before reaching the synchronous speed between the engine and the electric machine and the internal combustion engine by the complete closing of the clutch only coupled when this after switching on the ignition and / or the injection of fuel in about the speed the electric machine or the input shaft of the stepped transmission has been accelerated.

In the known control methods, however, it is not considered how long the process of starting and coupling of the internal combustion engine lasts, when the intended switching operation begins, and how long a continuation of the electric driving operation is still possible. As a result, these control methods are only applicable under certain conditions or only with certain restrictions.

The present invention is therefore based on the object to present a method for controlling a hybrid powertrain of a motor vehicle of the type mentioned, in which the said time frame conditions are considered in the connection of the internal combustion engine.

This object is achieved in conjunction with the features of the preamble of claim 1, characterized in that the connection period of the internal combustion engine, the time period until the start of the circuit, and the possible maximum duration of a continued electric driving operation are determined, and that is decided in dependence on these periods, whether the Connection of the internal combustion engine before, during or after the scheduled circuit.

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

The invention is therefore based on a known per se hybrid powertrain of a motor vehicle having an internal combustion engine with a drive shaft, an automated multi-step transmission with at least one input shaft and an operable as a motor and a generator electric machine with a rotor. The rotor of the electric machine can be connected via an automated separating clutch with the drive shaft of the internal combustion engine and is directly or via a clutch with the input shaft of the stepped transmission in combination.

If during an electric drive mode with the engine turned off or idle, and thus the disconnect clutch opened, in time proximity to an upcoming shift transmission circuit, a request to transition to combustion or hybrid drive occurs, it must be decided whether the engine is before, during, or after the scheduled shift is switched on. According to the invention, this decision is dependent on the connection duration of the internal combustion engine, the Period up to the start of the shift and the possible maximum duration of a continued electric driving operation made previously determined.

In contrast to the known control method, the connection of the internal combustion engine thus takes place not only as a function of the type of circuit (upshift or downshift) but also as a function of the relevant time sequences and their relation to each other.

To achieve the most comfortable possible connection of the internal combustion engine is provided in the case of an upcoming upshift that this takes place before the circuit, provided that the activation period of the internal combustion engine AtvM_zs and the possible maximum duration of a continued electric driving AtEF max each is smaller than the period until the start of the circuit Ats_o (AtvM_zs <Ats_o; AtEF max <Ats_o), and that the connection of the internal combustion ^¬ engine takes place during or after the circuit, if the connection duration of the internal combustion engine AtvM_zs or the possible maximum duration of a continued electric driving AtEF max greater than or equal to the period until the start of the circuit Ats_o is (AtvM_zs ^ Ats_o; AtEF_max ^ Ats_o). The connection of the combus ^¬ tion motor is thus preferably during the zugkraftfreien or zugkraftabgesenkten phase or during the load building phase of the upshift, which is also associated with a low input shaft speed to which the engine must be accelerated. Only if this is not possible, for example due to a deeply discharged electrical energy store, and this is possible without delaying the upshift, the internal combustion engine is switched on before the upshift.

In the case of an imminent downshift, however, it is provided that the connection of the internal combustion engine takes place before the shift, if the connection period of the internal combustion engine AtvM_zs or the possible maximum duration of a continued electric driving AtEF_max is less than the time period until the circuit Ats_o start (AtvM_zs <Ats_o or AtEF_max <Ats_o ), and that the on ^¬ circuit of the internal combustion engine during or after the circuit takes place when the connection period of the internal combustion engine AtvM_zs and the possible maximum duration of a continued electric drive operation AtEF max is greater than or equal to the time until the start of the shift Ats_o (A M_ZS ^ Ats_o and AtEF max ^ Ats_ ₀ ) - ^{| n} this case, the advantage of a lower input shaft speed at a connection of the internal combustion engine before the downshift is compared to the advantage of a ruck freer flow at a connection of the internal combustion engine during or immediately after the downshift.

When the internal combustion engine is turned off when the disconnection request is open (nvM = 0), the connection period of the internal combustion engine AtvM_zs becomes the sum of the start time of the internal combustion engine AtvM_st, which includes cranking the internal combustion engine to a minimum start speed nvM_st and the internal combustion engine start of the internal combustion engine , and the Ankoppeldauer the internal combustion engine AM _. AK, which includes the acceleration of the internal combustion engine to the input shaft speed n _G E of the stepped transmission and the closing of the clutch, determined (AtvM_zs

= AtvM_St + AtvM_AK) -

If, however, the internal combustion engine is already idling at the time of the connection request with the disconnect clutch open (nvM = nidie), the turn-on duration of the internal combustion engine A M_ZS is determined as the engagement time of the internal combustion engine A M_AK (A M_ZS = A M_AK), which determines the acceleration of the engine Combustion engine to the input shaft speed UQE of the stepped transmission and the closing of the separating clutch comprises.

The time until the start of the shift Ats_o can be calculated from the current input shaft speed n _G E_o of the stepped transmission, the shift speed n _G E_s of the stepped transmission, and the current speed gradient (noE ct) o of the transmission input shaft according to the equation Ats_o = (nGE_s - I ^ GE O) / (c noE / d) o are determined.

The shift speed n _G E_s the stepped transmission is preferably determined based on a valid for the combustion or hybrid driving switching characteristic, since a valid for the electric driving mode switching characteristic to one for the Internal combustion engine can cause unfavorable circuit. Due to different torque-speed characteristics of an electric machine and an internal combustion engine, different shift characteristics are usually used for an electric driving operation and for a combustion operation.

The possible maximum duration of a continued electric vehicle operation AtEF max is preferably determined from the state of charge of an electrical energy store assigned to the electric machine, the driver's current power requirement or a speed control system and the expected thermal load of the electric machine by the continued electric vehicle operation.

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

1 a), torque curves of an electric machine and of the internal combustion engine (FIG. 1 b) as well as state curves of a separating clutch and a clutch (FIG. 1 c) of a parallel-acting hybrid powertrain according to FIG. 3 during a first control sequence according to the invention for switching on the internal combustion engine,

2 a), torque curves of the electric machine and of the internal combustion engine (FIG. 2 b) as well as state curves of the separating clutch and the clutch (FIG. 2 c) of the parallel-active hybrid drive train according to FIG. 3 during a second control sequence according to the invention for switching on the internal combustion engine, and

3 shows a schematic view of a parallel-acting hybrid drive train for carrying out the control method according to the invention according to FIG. 1 and FIG. 2. In Fig. 3 is a schematic representation of a parallel-effective hybrid powertrain 1, in which the control method according to the invention is applicable by way of example, which will be described below. The hybrid powertrain 1 comprises an internal combustion engine VM with a drive shaft 2, an electric machine EM operable as a motor and as a generator with a rotor 3 and a rotor shaft 4, and a stepped transmission G with an input shaft GE. In the present case, the stepped gearbox G is designed, for example, as an automated manual transmission that can be switched with traction interruption. The rotor 3 of the electric machine EM is the input side via an automated clutch K1 with the drive shaft 2 of the engine VM connectable and separable from this, so that the engine VM if necessary, started by the electric machine EM, coupled to this and can be decoupled from this. On the output side, the rotor 3 or the rotor shaft 4 of the electric machine EM is connected to the input shaft GE of the stepped transmission G via an automated clutch K2. On the output side, the stepped gearbox G has an output shaft 5, which is in drive connection via an axle differential 6 with the drive wheels 7a, 7b of a drive axle of the relevant motor vehicle.

Is a motor vehicle with such a hybrid powertrain 1 in pure electric driving, i. with the internal combustion engine VM switched off and the disconnect clutch K1 open, it may be necessary to switch on the internal combustion engine VM due to an increased demand of the driver or a cruise control system or due to a low state of charge of the associated electrical energy store. to start and to couple by closing the clutch K1 to the drive train. However, if this request to switch on the internal combustion engine VM occurs in time proximity to an impending shift of the shift G, it must be decided whether the engine VM before, during or after the proposed circuit drive-coupled to the drive train.

Hereinafter, with reference to the speed curves n _G E (t) of the input shaft GE of the stepping gear G and n _V ivi (t) of the internal combustion engine VM shown in FIG. 1 a, the torque curves Μ _Ε Μ (Ϊ) shown in FIG. M _V M (t) the Electric machine EM and the internal combustion engine VM, as well as the illustrated in Fig. 1 c, the respective degree of closure reproducing state curves x << i (t), x «2 (t) of the clutch K1 and the clutch K2 explained how starting from an electric driving the internal combustion engine VM due to a first decision in temporal proximity to an upshift of the stepped transmission G in one

Towing started and subsequently coupled.

After the occurrence of the request for switching on the internal combustion engine VM at the time tO first the connection duration of the internal combustion engine AtvM_zs, the period up to the circuit start Ats_o the intended upshift, and the possible maximum duration of a continued electric driving operation AtEF max determined. Since the possible maximum duration of a continued electric driving operation AtEF max is greater than the time until the start of shift Ats_ ₀ (AtEF max> Ats_ ₀ ) _> it is decided that the connection of the internal combustion engine VM takes place during the load build-up phase, ie at the end of the upshift.

Accordingly, from the time the switching speed n _G E_s is reached, the upshift takes place at the time t1, whereby the no load of the input shaft GE is achieved by reducing the torque MEM delivered by the electric machine EM to zero. The clutch K2 can therefore remain closed during the upshift. During the load building phase, ie after the actual upshift from the time t2, the internal combustion engine VM is accelerated by the partial closing of the clutch K1 and the simultaneous increase of the output from the electric machine EM torque MEM initially up to the minimum start speed n _V M_st and then about to Time t3 started combustion engine. Thereafter, the internal combustion engine VM is accelerated by increasing its output torque MVM to the input shaft rotational speed noE and coupled to the driveline through simultaneous closing of the disconnect clutch K1, which is completed at time t4. In the meantime, the torque MEM delivered by the electric machine EM is reduced to zero, ie the electric machine EM is turned off. The connection of the internal combustion engine VM (AtvM_zs, t2-14) thus consists of starting the internal combustion engine (AtvM_st, t2-13) and coupling the internal combustion engine (AtvM_AK, t3 - 14) together. Due to the connection of the internal combustion engine VM at the end of the upshift, this is particularly low-jerk and at low input shaft speed no and thus very comfortable.

With reference to the illustrated in Fig. 2a speed curves n _G E (t), n _V ivi (t) of the input shaft GE of the stepped transmission G and the internal combustion engine VM, the torque curves ΜΕΜ (Ϊ) shown in Fig. 2b, Mvivi (t) of the electric machine EM and the internal combustion engine VM, as well as the illustrated in Fig. 2c, the respective degree of closure reproducing state curves χκι (ΐ), XK2 (t) of the clutch K1 and the clutch K2 will be explained below, as starting from an electric driving the internal combustion engine VM due to a second Decision timed close to an upshift of the stepped transmission G started in a tow start and subsequently coupled.

After the occurrence of the request for switching on the internal combustion engine VM at the time tO, the connection period of the

AtvM_zs, the period until the start of the shift Ats_o the intended upshift, and determines the maximum possible duration of a continued electric driving operation AtEF max. Since the possible maximum duration of a continued electric vehicle operation AtEF max and also the activation period of the internal combustion engine AtvM_zs are now smaller than the time until the start of the shift Ats_o (AtvM_zs <Ats_o; AtEF max <Ats_o), it is decided that the ^ignition circuit of the internal combustion engine VM is executed before the upshift.

Consequently, the internal combustion engine VM is accelerated immediately, ie, from the time t0, by the partial closing of the separating clutch K1 by the electric machine EM up to the minimum starting rotational speed nvM_st and then started at approximately the time t1 'combustion engine. Thereafter, the internal combustion engine VM is accelerated by increasing its output torque M _V M to the input shaft speed noE and coupled by the simultaneous completion of the disconnect clutch K1 to the drive train, which is completed at time t2 '. Meanwhile, the output from the electric machine EM torque M _E M is reduced to zero and the electric machine EM thus turned off. The connection of the internal combustion engine VM (AtvM_zs, t0 - 12 ') is composed again of the starting of the internal combustion engine (AtvM_st, t0 - 11') and the coupling of the internal combustion engine (AtvM_AK, t1 '- 12'). Thereafter, the drive is continued briefly in the combustion driving mode before the switching speed nGE_s is reached at time t3 '. Then, the intended upshift is performed between the times t3 'to t4'. The load freedom of the input shaft GE during the upshift is achieved in the present case by reducing the output from the engine VM torque M _V M and through the opening of the clutch K2. Alternatively, this can also be achieved by receiving a correspondingly high regenerative torque by the electric machine EM with the clutch K2 closed. Due to the connection of the internal combustion engine VM before the upshift, this is not necessarily low-jerk and at relatively high input shaft speed UQE, which is relatively uncomfortable, but unavoidable due to the existing short maximum duration of a continued electric vehicle operation AtEF max.

REFERENCE CHARACTERS

1 hybrid powertrain

2 drive shaft of the internal combustion engine

3 rotor of the electric machine

4 rotor shaft of the electric machine

5 output shaft of the stepped gearbox

6 axle differential

7a, 7b drive wheels

EM electric machine

G stepped gearbox

GE Input shaft of the stepped gearbox

K1 separating clutch

K2 clutch

M torque

M _E M torque of the electric machine

MVM torque of the internal combustion engine

n speed

n _G E Speed of the stepped gearbox, input shaft speed riGE_s Switching speed

nvM engine speed, engine speed

nvM_st Minimum start speed of the internal combustion engine

t time

tO Current time

t1 - t4 times

t1 '- t4' times

VM internal combustion engine

XK degree of closure of a clutch

XKI Closing degree of the separating clutch K1

XK2 Closing degree of the separating coupling K2

At period, duration

AtEF max Maximum possible electric travel time

Ats o period until the start of the shift ΔΐνΜ_Ακ docking duration

AtvM_st Starting time of the internal combustion engine

AtvM_zs activation period

Claims

claims

1 . A method of controlling a hybrid powertrain of a motor vehicle comprising an internal combustion engine (VM) with a drive shaft (2), an automated step transmission (G) having at least one input shaft (GE), and an electric machine (EM) operable as a motor and generator with a rotor (3), which is connectable via an automated disconnect clutch (K1) with the drive shaft (2) of the internal combustion engine (VM) and with the input shaft (GE) of the stepped transmission (G) is in communication, wherein the internal combustion engine (VM) during a Electric vehicle operation after a request to transition to the

Combustion operation or hybrid driving operation is timed close to an upcoming circuit of the stepped transmission (G), characterized in that the connection duration of the internal combustion engine (AtvM_zs), the period until the start of the circuit (Ats_ ₀ ) and the possible maximum duration of a continued electric driving operation (AtEF max) determined and that depending on these periods (AtvM_zs, Ats_o, AtEF max) a decision is made as to whether the connection of the

Internal combustion engine (VM) before, during or after the intended circuit takes place.

2. The method according to claim 1, characterized in that the connection of the internal combustion engine (VM) in the case of an imminent upshift takes place before the circuit, if the connection duration of the internal combustion engine (AtvM_zs) and the possible maximum duration of a continued electric driving operation (AtEF max) each less than the period until the start of the shift (Ats_o) is (AtvM_zs <Ats_o and AtEF_max <Ats_o), and occurs during or after the shift, if the connection duration of the internal combustion engine (A M_ZS) or the possible maximum duration of a continued electric driving operation (AtEF_max) is greater than or equal to Period until the start of the shift (Ats o) is (A M_ZS ^ Ats o or AtEF_max ^ Ats o) -

3. The method according to claim 1 or 2, characterized in that the connection of the internal combustion engine (VM) in the case of an imminent downshift occurs before the circuit when the connection period of the combustion engine gate (AtvM_zs) or the possible maximum duration of a continued electric vehicle operation (AtEF max) is less than the period until the start of the shift (Ats_ ₀ )

(AtvM_zs <Ats_o or AtEF_max <Ats_o), and occurs during or after the shift, if the activation period of the internal combustion engine (AtvM_zs) and the possible maximum duration of a continued electric driving operation (AtEF max) is respectively greater than or equal to the time period until the start of the shift (Ats_o) (AtvM_zs ^ Ats_o and

AtEFjnax ^ Ats_o) -

4. The method according to any one of claims 1 to 3, characterized in that the connection period of the internal combustion engine (AtvM_zs) as the sum of the starting time of the internal combustion engine (AtvM_st), which the towing of

Internal combustion engine (VM) to a minimum starting speed (n _V M_st) and the internal combustion engine start of the internal combustion engine (VM) comprises, and the Ankoppeldauer of the internal combustion engine (A M_AK), which the acceleration of the internal combustion engine (VM) to the input shaft speed (ηοε) of the stepped transmission ( G) and the closing of the separating clutch (K1), is determined (A M_ZS = AtvM_st + A M_AK), if the internal combustion engine (VM) at the time of the connection request (t = tO) with the disconnect clutch (K1 = 0) off is

(n _V M = 0).

5. The method according to any one of claims 1 to 4, characterized in that the connection duration of the internal combustion engine (A M_ZS) is determined as the Ankoppeldauer the internal combustion engine (A M_AK) (AtvM_zs = Δΐνκ / ι_Ακ), which accelerates the internal combustion engine (VM) to the input shaft speed (ηοε) of the stepped transmission (G) and the closing of the clutch (K1), if the internal combustion engine (VM) at the time of the connection request (t = tO) with idle clutch (K1 = 0) is operated at idle

(nvM = nidie) -

6. The method according to any one of claims 1 to 5, characterized in that the period until the start of the shift (Ats_ ₀ ) from the current input shaft speed (noE_o) of the stepped transmission (G), the switching speed (noE_s) of the Stage gear (G) and the current speed gradient (/ n _G E / c / t) o the transmission input shaft (GE) according to the equation Ats_o = (nGE_s - I ^ GE O) / (noE ct) o be ^¬ true.

7. The method according to claim 6, characterized in that the switching speed (noE_s) of the stepped shift transmission (G) is determined by means of a valid for combustion or hybrid driving switching characteristic.

8. The method according to any one of claims 1 to 7, characterized in that the maximum possible duration of a continued electric driving (AtEF max) from the state of charge of the electric machine (EM) associated electrical energy storage, the current power requirement of the driver or a cruise control system, and the expected thermal load of the electric machine (EM) is determined by the continued electric driving operation.