EP3672821A1

EP3672821A1 - Impulse start in a hybrid drivetrain

Info

Publication number: EP3672821A1
Application number: EP18765573.3A
Authority: EP
Inventors: Bernhard Hoess; Thomas Jung; Sebastian Kobler
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2017-08-23
Filing date: 2018-08-23
Publication date: 2020-07-01
Also published as: MX2019011722A; US11359593B2; ZA201906627B; US20200208600A1; CN110382274A; DE102017214787A1; CN110382274B; WO2019038394A1

Abstract

Method for operating a hybrid drive device of a motor vehicle, a hybrid drive device and a motor vehicle. The hybrid drive device comprises an internal combustion engine, an electric machine and an impulse start module which comprises two clutches (KS, KO) and a flywheel mass. The method comprises the following steps: opening the first clutch of the impulse start module, detecting an activation request for the internal combustion engine, closing the first clutch when the second clutch is opened or closed in order to start the internal combustion engine.

Description

Impulse start in a hybrid powertrain

description

The invention relates to a method for operating a hybrid drive device of a motor vehicle, a hybrid drive device and a motor vehicle.

Hybrid drives for motor vehicles, in which an electric machine between the engine and the transmission is arranged, are known. For example, these are hybrid drives in which the electric machine is coupled directly to the engine (mild hybrid) or between the engine and electric machine, a clutch is present (parallel hybrid drive). It is an object of the present invention to provide an improved method for the operation of a hybrid powertrain.

The achievement of the object of the invention is achieved by the features of the independent claims. Advantageous developments of the invention will become apparent from the

Dependent claims.

The invention is based on the following knowledge. In a motor vehicle with a mild hybrid powertrain, is usually, the electric machine between the

Combustion engine and the transmission arranged, wherein the electric machine can be decoupled via a clutch from the engine. However, such a hybrid drive is not designed for a pulse start of the internal combustion engine.

For such a hybrid drive of a motor vehicle, the electric starting operation is possible as a bridged start: The electric machine accelerates the motor vehicle, starting at a speed zero of the electric machine, all necessary for the power flow clutches are closed in the transmission. Another possibility is the approach via an internal gear starting element: The electric machine on

Transmission input rotates at a certain speed, a gear-internal starting element (for example, a clutch) is in the slip. At the end of the starting process, this clutch is then completely closed.

In a powertrain as shown in Fig. 1, the start of the internal combustion engine VM via the moment of inertia of the rotating electric machine EM and a flywheel S. When requesting a start of the engine VM, for example, when a power limit of the electric machine EM is reached or the available Capacity of the battery (SOC) is low, there is first a speed increase of the electric machine EM, wherein the transmission input clutch GEK from the transmission G is in slip and transmits the torque required for the propulsion to the output A. If the rotational speed at the electric machine EM is then sufficiently high, the clutch K is closed to the internal combustion engine VM. The synchronous speed for the internal combustion engine VM is above the speed of the transmission input clutch GEK. Subsequently, the slip in the transmission input clutch GEK is reduced. The object of the invention is achieved by a method for operating a hybrid drive device of a motor vehicle, wherein the hybrid drive device comprises an internal combustion engine, an electric machine and a pulse start module. The pulse start module includes two clutches and one flywheel. The method comprises the following steps: opening the first clutch of the pulse start module, determining a request for the internal combustion engine, closing the first clutch when the second clutch is open or closed to start the internal combustion engine. The

Zustartanforderung can be done via a control unit of the hybrid drive device or the vehicle. The flywheel includes a rotational inaccuracy reducing element or a flywheel.

In the method according to the invention, the focus is on the processes during the transition from electric driving to hybrid driving and vice versa.

In a further development it is provided that the start of the internal combustion engine takes place via a mutual actuation of the first and second clutch of the pulse start module. For this purpose, in some embodiments, the second clutch is opened, while the first clutch is closed at the same time. In other words, the closing or opening of the first and second clutch is parallel or simultaneous.

In a further development, it is provided that the start of the internal combustion engine is executed as an initial start. Initial start includes the start of the internal combustion engine when the vehicle is stationary. An initial start of the internal combustion engine can after a

Zustartanforderung occur, according to which a battery of the vehicle electrical energy for electrical consumers, eg. Air conditioning, seat heating, etc., must provide, and the state of charge of the battery would fall below a minimum limit.

In a further development, it is provided that the pulse start module the

The internal combustion engine starts when the electric starts and the inertia of the

Impulse start module by means of the closed second clutch with the electric

Machine is coupled. In some embodiments, this flywheel includes the rotational inaccuracy reducing element of the internal combustion engine. The A rotational inaccuracy reducing element is in particular connected to the electric machine during electric driving, wherein the second clutch is closed.

In a further development, it is provided that the pulse start module the

Internal combustion engine during engine off-sailing starts.

In a further development, it is provided that the pulse start module the

Internal combustion engine starts during electric driving. In a further development, it is provided that a rotational speed of the flywheel mass is selected such that, when the internal combustion engine is started up, its rotational speed, after switching on the flywheel mass, is above an idling rotational speed.

In a further development, it is provided that the electric machine is switched at least one gear higher after opening the second clutch, before switching on the internal combustion engine.

In other words, it is a switching strategy for the electric machine, especially in electric driving, selected so that the flywheel sendrehzahl comes to rest so that the engine has a speed above the idle speed of the engine when you start immediately after switching on the flywheel. In some embodiments, the speed is well above the idle speed of

Combustion engine. In some embodiments, the speed of the

Internal combustion engine after switching on the flywheel close to a target speed for the subsequent hybrid operation. The electric machine is switched at least one gear higher after opening the clutch before the internal combustion engine is taken into the power flow.

In a further development, it is provided that a speed of the electric machine is selected before the start of the engine so that the speed of the

Internal combustion engine, after switching on the flywheel, between a natural frequency speed of the engine and the idle speed, wherein in at least a portion of the on switch the flywheel closed the second clutch again or kept closed. The electric machine supports the acceleration of the internal combustion engine by its inertia and / or torque side.

Furthermore, a hybrid drive device according to the invention of a motor vehicle is specified. The hybrid drive apparatus includes an internal combustion engine, an electric machine, and a pulse start module disposed between the internal combustion engine and the electric machine and including a first clutch and a second clutch. To start the internal combustion engine, the first clutch is closed when the second clutch of the pulse start module is open or closed.

In a further development, it is provided that the pulse start module

Torsion-reduction element comprises.

Furthermore, a motor vehicle according to the invention, in particular

Passenger car specified for applying the method, wherein the motor vehicle has a hybrid drive device comprising an internal combustion engine and an electric machine.

Other developments of the invention will become apparent from the dependent claims.

Specific embodiments of the invention will now be described with reference to the accompanying drawings. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully disclose the scope of the invention to a person skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like characters refer to like elements.

Further details of the invention can be found in the exemplary embodiments, which will be described below with reference to the figures. Show it: Figure 2: a hybrid powertrain;

Figure 3: a first variant of an electrical starting based on speed and

Clutch status;

Figure 4: a second variant of an electrical starting based on speed and

Clutch status;

Figure 5: an engine off sailing based on speed and clutch status;

FIG. 6 shows a condition of the internal combustion engine from an electric driving on the basis of speed and clutch status;

FIG. 7A shows a first variant of an initial start of the internal combustion engine when the vehicle is stationary on the basis of speed and torque;

FIG. 7B shows a second variant of an initial start of the internal combustion engine on the basis of FIG

Speed and torque; FIG. 7C shows a third variant of an initial start of the internal combustion engine on the basis of rotational speed and torque;

In Figure 2, a hybrid powertrain is shown schematically. The hybrid drive device HA includes an engine VM, an electric machine EM, and a

Pulse start module IM, which is arranged between the engine VM and the electric machine EM and comprises a first clutch KS and a second clutch K0. Between the clutches KS and K0 a Schwaldenheitheitsreduzierungs- element DU is arranged. Instead of the rotation inaccuracy reducing element DU, a flywheel is used in some embodiments. The start of the internal combustion engine VM via a mutual actuation of the first KS and second K0 coupling of the pulse start module IM.

The figures described below each relate to an operating strategy for the method for operating a hybrid propulsion device HA of a P2-Mild Hybrid powertrain vehicle, as shown in FIG. The first clutch KS separates this

Acceleration Reducing Element DU (Dual Mass Flywheel,

Torsionsschwingungsdämpfer, Drehzahladaptiver Tilger, ...), hereinafter also called DU element, from the internal combustion engine VM.

The lower axis in each figure indicates the change in clutch or the speeds over time. The transitions from one state to another or from one speed to another are in the milliseconds (ms) range. The states in which the vehicle is represented electrically or hybridically (that is to say with connection of the internal combustion engine) comprise a range of seconds. The speed indicated with LL corresponds to one

Idling speed of the internal combustion engine and is between 600 - 900 revolutions / minute.

FIG. 3 shows a first variant of an electrical approach based on speed and clutch status, also called electrical creep. In this first variant, the vehicle is at the beginning, the speed of VM and EM is zero. During or shortly before starting, the electric machine EM is brought to a certain speed. The second

Coupling K0 is closed, so that the DU element is mitbeschleunigt.

The moment of the electric machine EM accelerates the vehicle. The starting element is here in the transmission iAE. If you do not crawl with an accelerator pedal and with a constant speed, the electric machine EM rotates so that a pulse start of the internal combustion engine is possible at any time. The iAE is in slippage. In this variant of the start, the first clutch KS is first closed at start request. The internal combustion engine VM is started and accelerated to a self-adjusting synchronous speed, which is above the speed at the iAE. There is thus no change of investment at the iAE, which would be noticeable at the downforce.

Subsequently, the slip is reduced in the iAE and the engine VM takes over the propulsion.

This condition can be implemented as long as the closing of the first

Clutch KS adjusting speed on the engine VM above the speed at the transmission iAE lies. The speed at the transmission iAE is considered to be directly proportional to the speed (in a fixed gear).

Figure 4: a second variant of an electrical starting based on speed and

Clutch status. In the event that the limit speed for the first start variant, in Fig. 3, is exceeded in creep, the Zustart takes place analogous to Fig. 4. In Zustart here the flywheel of the DU element is first decoupled, by opening the second clutch K0 , The electric machine EM can provide the complete available power for propulsion of the vehicle. Subsequently, the internal combustion engine VM is started by closing the first clutch KS. The still missing speed range up to the connection speed of the internal combustion engine VM leads by combustion of fuel. Upon reaching the transmission input speed, a speed control begins to control the engine VM to the target speed and the second clutch K0 can be closed. Afterwards, the internal combustion engine VM takes over the propulsion and the electric machine EM reduces its torque.

Figure 5 shows engine off sailing based on speed and clutch status. Engine-off sailing means that the engine VM is disconnected from the powertrain and the first clutch KS is open. The driver does not operate an accelerator pedal and the electric machine EM therefore does not provide a positive moment. The vehicle can thus roll more or less freely. All internal transmission clutches are closed, the gears are tracked according to the speed. The second clutch K0 is closed. The inertia of the DU element DU thus always has the same speed as the

Transmission input.

The free rolling is represented by the decrease of the speed of nJ. At start request, the second clutch K0 is opened quickly. The flywheel can rotate freely. By closing the first clutch KS of the engine VM is started and dragged to a synchronous speed. Subsequently, the engine VM builds up speed by burning fuel. Upon reaching the transmission input speed, a speed control begins to control the engine VM to the target speed and the second clutch K0 can be closed. Afterwards, the internal combustion engine VM takes over the propulsion and the electric machine EM reduces its torque. The support from the engine off recuperation is identical. With the difference that the speed in the recuperation due to the negative moment at the

electric machine EM decreases more strongly.

FIG. 6 shows a status of the internal combustion engine from an electric drive on the basis of speed and clutch status. The charge from the electric driving runs like the start from the motor-off sailing (see Fig. 5). During the landing, the electric machine EM can provide the complete power for propulsion of the vehicle. A first vehicle reaction can thus be displayed.

During electric driving, the second clutch K0 is closed, the

Flywheel DU thus rotates with transmission input speed. Through an adapted transmission shift strategy, this speed can always be kept in a suitable for the pulse start speed band.

Due to some boundary conditions (low outside temperature, low battery charge, etc.), it may happen that a start of the internal combustion engine is initiated at the start of the journey. Since an additional starting device is dispensed with, an impulse start of the internal combustion engine also takes place here. For this purpose, three start variants are conceivable, in the

Figures 7A-7C are shown. The names of the curves are:

niAE: speed of the internal clutch iAE,

nVM: rotational speed of the internal combustion engine VM,

nJ: rotational speed of the flywheel J,

nEM: rotational speed of the electric machine EM,

MEM: moment of the electric machine EM and

KS, K0 or iAE: Status of the corresponding coupling.

FIG. 7A shows a first variant of a cold start of the internal combustion engine on the basis of rotational speed and torque. The first clutch KS and the second clutch K0 are closed at the beginning. The internal combustion engine VM is started over the moment of the electric machine. FIG. 7B shows a second variant of a cold start of the internal combustion engine on the basis of rotational speed and torque. The flywheel DU is brought to a certain starting speed by the moment of the electric machine. Subsequently, the

Internal combustion engine VM started by closing the first clutch KS. Here, the inertia of the DU element and the electric machine acts on the crankshaft to cause the

Start combustion engine VM.

FIG. 7C shows a third variant of a cold start of the internal combustion engine based on rotational speed and torque and can be seen as a combination of the first and second variants (FIGS. 7A, 7B): the electric machine and the flywheel DU turn up at the beginning. Once a certain speed is reached, the first clutch KS is closed. Under the effect of torque of the electric machine EM and the inertia of flywheel and electric machine EM, the engine VM is started.

It should be understood that the methods, devices and systems described herein may be used alone as well as in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the methods, apparatus, and systems described herein may be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

Claims

1. A method for operating a hybrid drive device (HA) of a motor vehicle, wherein the hybrid drive device comprises an internal combustion engine (VM), an electric machine (EM) and a pulse start module (IM), wherein the pulse start module two clutches (KS, K0) and a flywheel comprising, the method comprising the steps of:

a) opening the first clutch (KS) of the pulse start module,

b) determining a booster request for the internal combustion engine,

c) Closing the first clutch (KS) with the second open or closed

Clutch (K0) to start the internal combustion engine.

2. The method of claim 1, wherein the start of the internal combustion engine via a

mutual actuation of the first and second clutch of the pulse start module takes place.

3. The method according to claim 1 or 2, wherein the start of the internal combustion engine as

Initial start is executed.

4. The method of claim 1 or 2, wherein the pulse start module starts the engine during electric starting and the flywheel of the pulse start module is coupled by means of the closed second clutch to the electric machine.

5. The method of claim 1 or 2, wherein the pulse start module starts the engine during engine off-sailing or during electric driving.

6. The method according to any one of the preceding claims, wherein a speed of

Flywheel is chosen so that when the internal combustion engine whose speed, after switching on the flywheel, above an idle speed of the engine is.

7. The method of claim 6, wherein the electric machine after opening the second clutch (K0), before the switching on of the internal combustion engine, at least one gear is switched higher.

8. Hybrid drive device of a motor vehicle, comprising

an internal combustion engine (VM),

- an electric machine (EM), and

a pulse start module, which is arranged between the internal combustion engine and the electric machine and comprises a first clutch KS and a second clutch K0, as well as a flywheel mass between the clutches,

wherein at the start of the internal combustion engine, the first clutch (KS) is closed when the second clutch (K0) is open or closed.

9. Hybrid drive device of a motor vehicle, wherein the flywheel of

Pulse start module comprises a rotation inequality reduction (DU) element.

10. Motor vehicle, in particular passenger car, for applying a method according to one of claims 1 to 7 wherein the motor vehicle a

Hybrid drive device according to one of claims 8 to 9.