WO2010057728A1 - Method and device for operating a motor vehicle with a hybrid drive - Google Patents

Abstract

The invention relates to a method for operating a motor vehicle with a hybrid drive, wherein a first drive unit (1) contributes to driving the motor vehicle, and wherein a second drive unit (2) is started by being coupled to the first drive unit (1). In order to be able to respond quickly to the closing of the separation coupling (4), a torque build-up (T_ELM) takes place on the first drive unit (1) if the second drive unit (2) is accidentally coupled.

Description

 description

title

Method and device for operating a vehicle with a hybrid drive

State of the art

The invention relates to a method for operating a vehicle with a hybrid drive, in which a first drive unit provides a contribution to the drive of the vehicle, wherein a second drive unit is started by a coupling to the second drive unit and an apparatus for performing the method ,

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

In the so-called parallel hybrids is an electric 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, if both contribute to the propulsion of the vehicle. If the disconnect clutch is open, the electric drive drives the vehicle alone.

In such vehicles, the internal combustion engine is started while the electric drive is running by closing the separating clutch. This subsystem thus assumes the function of a starter in a conventional system. In driving states in which the vehicle is driven electrically or regeneratively braked, the disconnect clutch is opened in order to decouple the drag torque of the internal combustion engine from the rest of the vehicle driveline, thereby achieving a higher driveline efficiency. In the event of a fault, it may happen that the separating clutch closes uncontrollably. As a result, the internal combustion engine is accelerated from standstill within a very short time to the speed of the electric drive. The inertia of the internal combustion engine delays the speed of the electric drive. With an engaged gear this leads to a deceleration of the wheels and thus of 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, as they can occur in a sudden deceleration of the wheels are reliably prevented. If the second drive unit is unintentionally coupled, a torque build-up takes place immediately on the first drive unit, as a result of which the unstable driving situations, which can occur in particular on wet roads, are prevented.

Usually, in these driving situations, a driving dynamics control becomes active, which attempts to stabilize the vehicle by means of targeted braking interventions on the individual wheels and the return of the engine torque.

An intervention of such an electronic stabilization program (ESP) and thus a further deceleration of all wheels can be dispensed with.

Advantageously, the torque build-up of the first drive unit compensates for a torque loss caused by the coupling of the second drive unit. The sudden loss of drive torque, which occurs due to the sudden start of the second drive unit is compensated because the first drive unit additionally generates as much torque as the loss torque of the second drive unit is large.

In one embodiment, the torque build-up on the first drive unit takes place immediately after the occurrence of the loss torque of the second drive unit. Since an unstable state is a very time-critical process, the first drive unit intervenes very quickly. In a development, the torque build-up on the first drive unit always takes place when it is detected that the second drive unit has been coupled. As a result, an immediate response to the unintentional start of the second drive unit is possible. Thus, a delay of all wheels is reliably prevented, whereby the unstable driving state is avoided.

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

Alternatively, the coupling of the second drive unit is detected by means of actuation of a clutch actuator. This becomes particularly possible in hydraulic clutch systems where the clutch actuator is opened to circulate the hydraulic fluid to actuate the disconnect clutch.

Both the speed monitoring of the second drive unit and the

Clutch actuator 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.

In order to be able to precisely determine the torque which is to be additionally built up on the first drive unit, a time profile of the torque loss on an acceleration procedure on a wheel of the vehicle is evaluated. The mass inertia of the drive train components, which are responsible for the temporal behavior of the torque loss of the second drive unit, is taken into account.

In a particularly simple embodiment, the time profile of the loss torque is stored in at least one map. Thus, with the help of the parameters stored in the map, the torque to be built up on the first drive unit can be determined exactly. In a development, the map is designed speed and / or gear-dependent. Thus, for each imaginable driving situation, the torque loss of the second drive unit can be read accurately and the torque of the first drive unit can be accurately determined.

In another development of the invention, in a device for operating a vehicle with a hybrid drive, a first drive unit contributes to driving the vehicle, wherein a second drive unit is started by a coupling to the first drive unit. In order to prevent a braking of the wheels in an uncontrolled start of the second drive unit, means are provided which initiate a torque build-up on the first drive unit in case of unintentional coupling of the second drive unit. This has the advantage that unstable driving situations are prevented by a sudden deceleration of the wheels of the motor vehicle by the construction of the torque at the first drive unit.

In one embodiment, the first drive unit and the second drive unit are connected to one another via a separating clutch, wherein the first drive unit starts the second drive unit after closing the separating clutch. The sudden and uncontrolled closing of the separating clutch causes a relief of the rear axle of the vehicle, wherein the front axle of the vehicle is loaded to the same extent. The loss of rear axle load reduces the traction potential at the rear wheels, which is corrected by the torque increase on the first drive unit.

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

In a particularly convenient embodiment, the control unit increases the torque of the first drive unit until a torque loss caused by the coupling of the second drive unit is compensated for by this. This means that the torque of the first drive unit increases by exactly the same value as the torque loss of the second drive unit. decreases power unit. Since this compensates for the traction potential at the rear wheels, dangerous driving situations are avoided. The driver thus does not perceive the braking of the wheels.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

It shows:

Figure 1: an embodiment of a drive train of a parallel hybrid vehicle

Figure 2: Effects of a faulty closing of the separating clutch according to the prior art

FIG. 3 shows a schematic flow diagram of an exemplary embodiment of the method according to the invention

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

Identical features are identified by the same reference numerals.

FIG. 1 shows a drive train of a motor vehicle with a parallel hybrid, in which an electric motor 1 is arranged on the drive shaft 3 of an internal combustion engine 2. Between the electric motor 1 and the internal combustion engine 2, a separating clutch 4 is arranged, which decouples the internal combustion engine 2 of the electric motor 1 in the open state, so that a purely electric driving is possible. To the electric motor 1, a converter 5 connects, which in turn is connected to an automatic transmission 6. The automatic transmission 6 leads to an axle 7, which transmits the torque applied by the internal combustion engine 2 and / or the electric motor 1 to a wheel 8.

The electric motor 1 is controlled by a control unit 9 which is connected to a speed sensor 10, which is opposite to the drive shaft 3 of the internal combustion engine 2, to rotations of the drive shaft 3, through the Combustion engine 2 are caused to detect. In addition, the controller 9 is connected to the transmission 6 to detect which gear is engaged. A not shown on the vehicle _axle 7 speed sensor provides the controller 9 information about the vehicle speed v _Fz g.

The separating clutch 4 is arranged in a hydraulic system, by which it is hydraulically opened and closed. In the depressurized state, the separating clutch 4 is closed. In driving states in which purely electric driving is, the separating clutch 4 is opened. 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 closes uncontrollably. As a result, the internal combustion engine 2 is accelerated from standstill in a very short time to the rotational speed of the electric motor 1. The inertia of the internal combustion engine 2 delays the rotational speed of the electric motor 1. This causes a delay of the wheels 8 with an engaged gear, which also has a similar effect on a sudden emergency braking on 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.

Due to the deceleration of the vehicle, the rear axle HA of the vehicle is relieved, the front axle VA, however, charged to the same extent. The loss of Hinterachslast reduces the traction potential on the rear wheels, so that in a disturbance, as occurs by ruts, crosswinds or the like, the rear wheels can not muster enough cornering forces.

The effects which occur are to be explained in more detail with reference to FIG. The diagrams shown in Figure 2 show the vehicle _reactions in a faulty closing of the _separating clutch 4 at a vehicle _speed V _Fzg of about 50 km / h according to the prior art. The clutch torque T _Ko occurring when the clutch 4 closes is shown in FIG. 2 a. As can be seen from the vehicle speed in FIG. 2 c, the vehicle is in the so-called coasting mode, that is, coasting out. at the time t = 23.5 s closes the clutch 4 suddenly, which leads to violent reactions of the wheels 8 (coefficient of friction in Figure 2b) and the vehicle (Figure 2d). This is also confirmed by the acceleration a _Fzg shown in FIG. 2d. An acceleration a _Fzg which fluctuates periodically between positive (0.1) and negative (-0.2) _values occurs when the _separating 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. As a rule, a maximum coefficient of friction of 1. 0 to 1. 1 prevails on a dry grip track surface, so that the vehicle remains track-stable on such an underground despite the fault caused by the faulty closing of the separating clutch 4. As soon as the coefficient of friction of the road surface is reduced by rain, water in ruts or the like, there is the danger of skidding even at low vehicle speeds.

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

In block 102, the control unit 9 monitors the movement of the drive shaft 3 of the internal combustion engine 2 with the aid of the rotational speed sensor 10. In purely electrical operation of the vehicle, the drive shaft 3 of the internal combustion engine 2 is detected. However, the control unit 9 detects a movement of the drive shaft 3 of the internal combustion engine 2. it is concluded that the separating clutch 4 has suddenly closed.

The control unit 9 accesses a stored in a memory map in which the inertia of the powertrain components (such as combustion engine 2, primary side clutch 4) in response to the unregulated

Closed behavior of the separating clutch 4 are stored. Furthermore, the mass inertias are also stored depending on speed and / or gear. Since the engaged gear and the vehicle speed are known from the current driving situation, the torque loss resulting from the acceleration of the internal combustion engine 2 is determined in block 103. In block 104, the torque T _ELM necessary for the electric motor 1 is determined from the loss torque determined in this way, which torque is additionally supplied to the electric motor 1 in order to compensate for the loss torque of the internal combustion engine 2. The electric motor 1 is piloted in block 105 by the control unit 9 in such a way that the additional torque T _{ELM of} the electric motor 1 has exactly the same amount as the loss torque caused by the internal combustion engine 2. Both moments have opposite signs.

FIG. 4 shows the vehicle conditions during a faulty closing of the vehicle

Disconnect 4 with a simultaneous compensation caused by the internal combustion engine 2 loss torque by the electric motor 1. The vehicle speed is here about 50 km / h. The scale of Figure 4 has been increased compared to Figure 2 in order to still be able to represent the effects occurring.

As in the previous case, the separating clutch 4 is closed at 23.5 s in this example (Figure 4a). The vehicle _speed V _Fzg suffers a brief break-in (FIG. 4c). The time course of the signals for the vehicle acceleration acceleration _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. Thus, the required coefficient of friction μ _HA , U _{VA is} reduced by approximately 50% compared to the previous example (FIG. 2). This means a significantly improved driving stability even on wet roads.

FIG. 4e shows the torque T _{ELM of} the electric motor 1 necessary for compensation. This torque T _ELM is generated immediately after the closing of the separating clutch 4 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

claims 1. A 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 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). 2. The method according to claim 1, characterized in that the torque build-up (T _ELM ) of the first drive unit (1) compensates for a loss moment caused by the coupling of the second drive unit (2). 3. The method according to claim 2, characterized in that the torque build-up (T _ELM ) on the first drive unit (1) immediately after the occurrence of the loss torque of the second drive unit (2). 4. The method according to claim 3, characterized in that the torque build-up (T _ELM ) on the first drive unit (1) takes place when it has been detected that the second drive unit (2) has been coupled. 5. The 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 detected. 6. The method according to claim 4, characterized in that the coupling of the second drive unit (2) is detected by means of an actuation of a Kupplungsaktuators. 7. The method according to any one of claims 2 or 3, characterized in that a time profile of the loss torque is evaluated on an acceleration process on a wheel (8) of the vehicle. 8. The method according to claim 7, characterized in that the time profile of the loss torque is stored in at least one map. 9. The method according to claim 8, characterized in that the characteristic field is designed speed and / or gear-dependent. 10. A 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) is started, characterized characterized in that means (9, 10) are provided which, in the event of an unintentional coupling of the second drive unit (2), establish a torque build-up (T _ELM ) on the first drive unit (1). 1 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) are interconnected, wherein the first drive unit (1) after closing the separating clutch (4) the second Drive unit (2) starts. 12. The device according to claim 1 1 characterized in that a control unit (9) of the first drive unit (1) after detecting the unintentional closure of the separating clutch (4) increases the torque (T _ELM ) of the first drive unit (1). 13. The apparatus according to claim 12, characterized in that the control unit (9) the torque (T _ELM ) of the first drive unit (1) so far increased until a in the coupling of the second drive unit (2) caused by this loss moment is compensated.