DE102008043984A1 - Method and device for operating a vehicle with a hybrid drive - Google Patents

Abstract

The invention relates to a method for operating a vehicle with a hybrid drive, in which a first drive unit (1) provides a contribution to driving the vehicle, wherein a second drive unit (2) by coupling to the first drive unit (1) is started. In order to react as quickly as possible to the closing of the separating clutch (4), a torque build-up (TELM) on the first drive unit (1) takes place in the event of unintentional coupling of the second drive unit (2).

Description

State of the art

The The invention relates to a method for operating a vehicle with a hybrid drive, in which a first drive unit makes a contribution to the drive of the vehicle, with a second Drive unit through a coupling to the second drive unit is started and a device for carrying out the method.

vehicles with a hybrid drive structure have an internal combustion engine and as the second drive unit usually an electric motor. So can drive torque during the driving operation of the hybrid vehicle of both drive units be applied.

at The so-called parallel hybrids is an electrical Drive on the shaft of an internal combustion engine. Electric drive and the internal combustion engine are connected to each other via a separating clutch connected when both contribute to the propulsion of the vehicle. Is the disconnect clutch open, the electric drive drives the vehicle alone.

at such vehicles, the internal combustion engine is running while electric Drive by closing the separating clutch started. So this subsystem takes over the function a starter in a conventional system. In driving conditions, in which is electrically driven or regeneratively braked is the Disconnect clutch opened, to the drag torque of the engine from the rest of the vehicle powertrain decouple, creating a higher Drive train efficiency is achieved.

in the In the event of a fault, the disconnect clutch may be uncontrolled closes. As a result, the internal combustion engine from standstill within short Time accelerates to the speed of the electric drive. The Inertia of the Internal combustion engine delayed while the speed of the electric drive. When inserted Gang leads this to a delay the wheels and so that the vehicle.

Disclosure of the invention

The inventive method for operating a vehicle with a hybrid drive with the features of claim 1 has the advantage that unstable driving conditions, such as she at a sudden delay the wheels may occur, safely prevented. In case of unintentional coupling the second drive unit is immediately a torque build-up at the first drive unit, whereby the unstable driving situations, as they can occur especially on wet roads, prevented become.

Usually In these driving situations, a vehicle dynamics control becomes active via targeted brake interventions at the individual wheels and return the engine torque is trying to get the vehicle back up stabilize. Upon intervention of such an electronic stabilization program (ESP) and thus a further delay of all wheels can be waived.

advantageously, compensates the torque build-up of the first drive unit in the coupling of the second drive unit caused by this Torque loss. The sudden Loss of drive torque caused by the sudden start of the second Drive unit occurs, is compensated because the first drive unit additionally generates as much torque as the loss torque of the second drive unit is large.

In In one embodiment, the torque build-up takes place on the first drive unit immediately after the occurrence of the loss torque of the second drive unit. Since an unstable state is a very time-critical one Act acts, there is a very fast intervention of the first drive unit.

In In a further development, the torque build-up takes place on the first drive unit whenever it is detected that the second drive unit was docked. This will cause an immediate reaction the unintentional start of the second drive unit possible. Consequently will be a delay all wheels reliable prevents, whereby the unstable driving condition is avoided.

advantageously, is the coupling of the second drive unit by monitoring the speed of the second drive unit detected particularly quickly. Since the speed when the second drive unit is zero is, a deviation of zero immediately as the start of the second drive unit detected and appropriate countermeasures can be initiated.

alternative is the coupling of the second drive unit based on a activity a clutch actuator detected. This is especially true for hydraulic Coupling systems possible, where the clutch actuator is opened gets to the hydraulic fluid for operation the separating clutch in circulation.

Both the speed monitoring of the second drive unit and the Kupplungsaktu Ator monitoring is not only very convenient but also very cost-effective solutions, since no additional components for monitoring are necessary, but the components used in the vehicle itself are used.

Around the torque which is additionally built up on the first drive unit is to be able to determine exactly, is a time course the loss moment of an acceleration process on a wheel of the vehicle. Here are the inertia the powertrain components considered for the temporal Behavior of the loss torque of the second drive unit responsible are.

In a particularly simple embodiment of the time course the loss torque stored in at least one map. Consequently can with the help of the parameters stored in the map on the first Drive unit to be built torque to be determined exactly.

In a development is the map speed and / or gang dependent designed. Thus, for every imaginable driving situation the loss moment of the second Drive unit read accurately and the torque of the first Drive units are determined exactly.

In another embodiment of the invention provides in a device for operating a vehicle with a hybrid drive a first Drive unit contributes to the drive of the vehicle, wherein a second drive unit by coupling to the first Drive unit is started. To slow down the wheels to prevent an uncontrolled start of the second drive unit, There are means available in case of unintentional coupling the second drive unit, a torque build-up on the first drive unit initiate. This has the advantage that unstable driving situations in a sudden delay the wheels of the motor vehicle by building up the torque at the first Drive unit can be prevented.

In In one embodiment, the first drive unit and the second Drive unit via a Disconnect coupled together, the first drive unit after closing the separating clutch starts the second drive unit. The sudden and uncontrolled closing the disconnect clutch causes a relief of the rear axle of the Vehicle, wherein the front axle of the vehicle loaded to the same extent becomes. The loss of rear axle load reduces the traction potential at the rear wheels, what by the torque increase is corrected on the first drive unit.

advantageously, elevated a control unit of the first drive unit after detecting the unintentional closure the clutch the torque of the first drive unit. The so suddenly occurring by starting the second drive unit loss torque is compensated by the torque increase of the first drive unit.

In a particularly comfortable design, the controller increases the torque of the first drive unit so far to one in the coupling of the second drive unit caused by this loss torque is compensated. This means that the torque of the first drive unit by exactly the value increases, as the loss moment of the second drive unit decreases. Because this compensates for the traction potential at the rear wheels will be dangerous Driving situations. The driver thus does not take the braking of the wheels true.

Of the Invention leaves numerous embodiments to. One of them should be based on the figures shown in the drawing be explained in more detail.

It shows:

1 : An embodiment of a drive train of a parallel hybrid vehicle

2 : Effects of Failure to Close the Disconnect Coupling of the Prior Art

3 : schematic flow diagram of an embodiment of the method according to the invention

4 : Effects of a faulty closing of the separating clutch with simultaneous compensation by the electric motor.

Same Features are identified by the same reference numerals.

1 shows a drive train of a motor vehicle with a parallel hybrid, in which an electric motor 1 on the drive shaft 3 an internal combustion engine 2 is arranged. Between the electric motor 1 and the internal combustion engine 2 is a disconnect clutch 4 arranged, which in the open state the internal combustion engine 2 from the electric motor 1 decoupled, so that a purely electric driving is possible. To the electric motor 1 closes a converter 5 which, in turn, with an automatic transmission 6 connected is. The automatic transmission 6 leads to an axis 7 that of the internal combustion engine 2 and / or the electric motor 1 applied torque on a wheel 8th above wearing.

The electric motor 1 is from a control unit 9 controlled, which with a speed sensor 10 connected to the drive shaft 3 of the internal combustion engine 2 opposite to rotations of the drive shaft 3 by the internal combustion engine 2 caused to be detected. In addition, the control unit 9 with the gearbox 6 connected to detect which gear is engaged. One at the vehicle axle 7 not shown speed sensor provides the controller 9 Information about the vehicle _speed v _Fzg .

The separating clutch 4 is arranged in a hydraulic system, by which it is hydraulically opened and closed. In the depressurized state is the separating clutch 4 closed. In driving states in which purely electric driving is, the separating clutch 4 open. In the event of a fault, for example in the case of a sudden pressure loss in the hydraulic clutch system, it may happen that the separating clutch 4 closed uncontrollably. This results in the internal combustion engine 2 from standstill in the shortest possible time to the speed of the electric motor 1 accelerated. The inertia of the internal combustion engine 2 delays the speed of the electric motor 1 , This pulls in a gear engaged a delay of the wheels 8th What, similar to a sudden emergency stop, also affects the vehicle. In this case, driving situations may occur, in particular in the case of a wet roadway, in which the sudden loss of driving torque leads to an unstable driving state.

By the delay of the vehicle, the rear axle HA of the vehicle is relieved, on the other hand, the front axle VA is loaded to the same extent. By the loss rear axle load reduces the traction potential to the Rear wheels, so that in case of a fault, as it occurs by ruts, crosswinds or the like, the rear wheels no longer enough Can muster side managers.

The effects, which occur thereby, are to be determined on the basis of 2 be explained in more detail. In the 2 Diagrams shown show the vehicle reactions to a faulty closing of the clutch 4 at a vehicle _speed V _Fzg of about 50 km / h according to the prior art. That when closing the separating clutch 4 occurring clutch torque T _Ko is in 2a shown. As based on the vehicle speed in 2c can be seen, the vehicle is in the so-called push operation, ie rolling out. At the time t = 23.5 s the disconnect clutch closes 4 suddenly, causing violent reactions of the wheels 8th (Coefficient of friction in 2 B ) and the vehicle ( 2d ) leads. This is also due to the in 2d _indicated acceleration a _Fzg occupied. An acceleration a _Fzg varying periodically between positive (0.1) and negative (-0.2) values occurs on the vehicle when the disconnect clutch 4 closes unexpectedly.

In particular, the wheels of the rear axle HA require in this driving situation a necessary coefficient of friction μ _HA of about 0.3. On a dry non-slip road surface there is usually a maximum coefficient of friction of 1.0 to 1.1, so that on such a surface, the vehicle despite the disturbance caused by the faulty closing of the clutch 4 remains stable on the track. As soon as the coefficient of friction of the roadway is reduced by rain, water in ruts or the like, there is a danger of slingshot even at low vehicle speeds.

An embodiment of the method according to the invention will now be described with reference to 3 be explained in more detail. In the block 101 is the disconnect clutch 4 opened and the vehicle is powered by the electric motor 1 driven purely electrically.

In the block 102 monitors the controller 9 with the help of the speed sensor 10 the movement of the drive shaft 3 of the internal combustion engine 2 , During purely electrical operation of the vehicle is the drive shaft 3 of the internal combustion engine 2 , Detects the controller 9 but a movement of the drive shaft 3 of the internal combustion engine 2 , it is concluded that the separating clutch 4 suddenly closed.

The control unit 9 accesses a map stored in a memory in which the mass inertia of the drive train components (such as internal combustion engine 2 , Primary side coupling 4 ) depending on the unregulated closing behavior of the separating clutch 4 are stored. Furthermore, the mass inertias are also stored depending on speed and / or gear. Since the current driving situation, the engaged gear and the vehicle speed are known, is in the block 103 that from the acceleration of the internal combustion engine 2 resulting loss moment determined.

In the block 104 becomes from the thus determined loss moment that for the electric motor 1 necessary torque T _ELM determines which the electric motor 1 is additionally supplied to the loss torque of the internal combustion engine 2 to compensate. The electric motor 1 will be in the block 105 through the control unit 9 so _{pre-controlled} that the additional torque T _{ELM of} the electric motor 1 exactly the same amount as that of the combustion engine 2 has lost momentum. Both moments have opposite signs.

4 shows the vehicle conditions at a faulty closing of the clutch 4 with a simultaneous compensation of the by the internal combustion engine 2 caused loss torque by the electric motor 1 , The vehicle speed here is about 50 km / h. The scale of 4 was opposite the 2 enlarged in order to be able to represent the occurring effects.

As in the previous case, also in this example, the disconnect clutch 4 closed at 23.5 s ( 4a ). The vehicle _speed V _Fzg suffers a brief burglary ( 4c ). The time course of the signals for the vehicle _acceleration a _Fzg and the necessary coefficients of friction μ _HA , μ _vA on the front axle VA and the rear axle HA shows a significantly improved vehicle behavior. This reduces the necessary coefficient of friction μ _HA , μ _vA in comparison to the previous example ( 2 ) by about 50%. This means a significantly improved driving stability even on wet roads.

In 4e is the torque required for compensation T _{ELM of} the electric motor 1 shown. This torque T _ELM is immediately after closing the clutch 4 generated for less than 1 s. This is sufficient for the improvement of the vehicle condition after the sudden closure of the disconnect clutch 4 ,

Claims (13)

Method for operating a vehicle with a hybrid drive, in which a first drive unit ( 1 ) provides a contribution to the drive of the vehicle, wherein a second drive unit ( 2 ) by a coupling to the first drive unit ( 1 ) is started, characterized in that in an unintentional coupling of the second drive unit ( 2 ) a torque build-up (T _ELM ) on the first drive unit ( 1 ) he follows. A method according to claim 1, characterized in that the torque build-up (T _ELM ) of the first drive unit ( 1 ) in the coupling of the second drive unit ( 2 ) compensated by this caused loss moment. A method according to claim 2, characterized in that the torque build-up (T _ELM ) on the first drive unit ( 1 ) immediately after the loss moment of the second drive unit ( 2 ) he follows. A method according to claim 3, characterized in that the torque build-up (T _ELM ) on the first drive unit ( 1 ), if it has been detected that the second drive unit ( 2 ) was docked. A method according to claim 4, characterized in that the coupling of the second drive unit ( 2 ) by monitoring the rotational speed of the second drive unit ( 2 ) is recognized. A method according to claim 4, characterized in that the coupling of the second drive unit ( 2 ) is detected by actuation of a clutch actuator. Method according to one of claims 2 or 3, characterized in that a time profile of the loss torque in an acceleration process on a wheel ( 8th ) of the vehicle is assessed. Method according to claim 7, characterized that the time course of the loss moment in at least one Map is filed. Method according to claim 8, characterized that the map designed speed and / or gear-dependent is. Device for operating a vehicle with a hybrid drive, in which a first drive unit ( 1 ) provides a contribution to the drive of the vehicle, wherein a second drive unit ( 2 ) by a coupling to the first drive unit ( 1 ), characterized in that means ( 9 . 10 ) are present, in an unintentional coupling of the second drive unit ( 2 ) a torque build-up (T _ELM ) on the first drive unit ( 1 ). Apparatus according to claim 10, characterized in that the first drive unit ( 1 ) and the second drive unit ( 2 ) via a separating clutch ( 4 ), wherein the first drive unit ( 1 ) after closing the separating clutch ( 4 ) the second drive unit ( 2 ) starts. Apparatus according to claim 11, characterized in that a control device ( 9 ) of the first drive unit ( 1 ) after detecting the unintentional closure of the separating clutch ( 4 ) the torque (T _ELM ) of the first drive unit ( 1 ) elevated. Apparatus according to claim 12, characterized in that the control device ( 9 ) the torque (T _ELM ) of the first drive unit ( 1 ) so far increased until a at the coupling of the second drive unit ( 2 ) is compensated by this caused loss moment.