DE102016209939B4 - Method for avoiding a critical driving situation in a vehicle with a hybrid drive - Google Patents

Abstract

A method for avoiding a critical driving situation in a vehicle having a hybrid drive, in which a hybrid disconnect clutch (4) separates or connects an internal combustion engine (2) and an electric motor (3), wherein a combustion engine (2) and / or the electric motor (3 ) is transmitted to the drive wheels (10) of the vehicle and the hybrid disconnect clutch (4) by a hydraulic clutch actuator (12) is actuated, wherein an engine speed and an electric motor speed are measured and evaluated, depending on the evaluation of the hybrid drive in a state is offset, by means of which the critical driving situation is prevented by a faulty entrainment of the internal combustion engine (2) or the electric motor (3), wherein the evaluation of the engine speed and the electric motor speed are compared with each other and depending on the comparison, a start of the internal combustion engine (2) erla ubt or is suppressed, wherein a difference between the measured engine speed and the measured electric motor speed is determined, which is compared with a threshold, which falls below the threshold value by the difference, the start of the internal combustion engine (2) is prevented, characterized in that the Determining the difference and the comparison with the threshold value are performed when the electric motor speed has exceeded an idle speed.

Description

The invention relates to a method for avoiding a critical driving situation in a vehicle with a hybrid drive having the features according to the preamble of claim 1.

The DE 10 2010 042 916 A1 discloses a method for detecting an unauthorized connection of the clutch arranged between the electric machine and the internal combustion engine in a parallel hybrid drive train of a motor vehicle.

From the DE 10 2008 030 480 A1 For example, a method for controlling a starting clutch in a hybrid vehicle is known. In hybrid vehicles, which allow different combinations of types of drive, such as electric motor, elektrozeratorisch, internal combustion engine in push or pull operation, internal combustion engine or electric motor ON, a mechanical decoupling of the moments of the internal combustion engine and electric motor is known. This decoupling of the internal combustion engine and electric motor is carried out by a hybrid disconnect clutch, which is hydraulically actuated.

An automatic actuation of the hybrid disconnect clutch via a clutch actuator, consisting of a control unit with a corresponding software for controlling the hybrid disconnect clutch and an electro-hydraulic actuator for actuating the hybrid disconnect clutch. In such a clutch actuator, a functional level of software provides the clutch status to a parent vehicle strategy. This functional level of software distinguishes between an open clutch, a closed clutch or an unknown clutch. The unknown clutch is a clutch in which a fault has been diagnosed.

The hydraulic system used may leak over a longer period of operation. Usually, such a leak is detected by a diagnostic function by a pressure sensor signal is evaluated. Due to the system dimensioning in the region of slight leakage, the detection of such a leak can not be carried out safely in all coupling systems. Thus, it may happen that the hybrid disconnect clutch is already partially closed without the leakage being detected. In this case, the functional level software will report the hybrid disconnect clutch as open, although it may be transmitting momentarily. The superimposed security strategy at the vehicle level has to intercept this case. So far, it is checked on the vehicle level with security software, whether the signals delivered by the software at the functional level are correct. Since the safety function always has an effect on the diagnosis, this leads to the activation of a control lamp and to a disturbance of the driver. Due to the sensitivity of the safety software on the vehicle level, this error detection is very common.

The invention has for its object to provide a method for avoiding critical driving situations in a vehicle with a hybrid drive, in which by detecting the problem already at the functional level of the software, a reaction of the safety function with effect on the diagnosis is prevented.

This object is achieved by a method having the features according to claim 1. Further preferred embodiments and advantageous embodiments of the invention will become apparent from the dependent claims.

According to the invention, the object is thus achieved in that an engine speed and an electric motor speed are measured and evaluated, being offset depending on the evaluation of the hybrid drive in a state by which the critical driving situation is prevented by a faulty entrainment of the engine or the electric motor. Examining existing potential errors at the functional level of the software significantly reduces the likelihood of misdiagnosis and thus prevents activation of the control lamp. Thus, an activation of the security software is prevented at the vehicle level.

Advantageously, these are compared with each other for the evaluation of the engine speed and the electric motor speed and it is a start of the engine allowed or prevented depending on the comparison. Since it can be determined on the basis of the comparison between engine speed and electric motor speed, whether the internal combustion engine via a hybrid disconnect clutch, which was reported as open, is still entrained, because this is already closed or partially closed due to leakage in the hydraulic clutch system, the engine start by the software reliable be prevented, which is particularly relevant when Ankriechen or electric driving in the lower speed range of the vehicle.

In one embodiment, a difference between the measured engine speed and the measured electric motor speed is determined, which is compared with a threshold value, wherein falls below the threshold value by the difference of the start of the Internal combustion engine is prevented. By determining the difference between engine speed and electric motor speed, which is also referred to as slip, it is easy to prevent the start of the engine to prevent a possible significant acceleration of the vehicle by the suddenly existing engine torque.

In a variant, the formation of the difference and the comparison with the threshold value are carried out when the electric motor speed has exceeded an idling speed. Thus, the slip condition applies only when the idle speed is reached, otherwise the vehicle would be accelerated at an engine start.

In one embodiment, a start of the internal combustion engine after a predetermined first period is allowed, in which it is checked whether a faulty entrainment of the internal combustion engine takes place. In this predetermined first period, the engine speed and the electric motor speed are continuously measured and evaluated. The period of time is determined so that a reliable conclusion is possible as to whether the clutch signal output by the software at the functional level corresponds to the correct state of the hybrid disconnect clutch.

In a further development, the starting process is carried out after initiation of a starting process of the internal combustion engine and subsequent undershooting of the threshold value by the difference between the engine speed and the electric motor speed. The boot process is thus not stopped, although the difference is smaller than the threshold.

In an alternative, the starting process is continued while the internal combustion engine is running.

In one embodiment, the evaluation of engine speed and electric motor speed is performed before initiating a startup process of the internal combustion engine.

In this case, especially critical driving situations which occur when the vehicle is crawling or in the lower speed range in purely electric driving are prevented.

Advantageously, an opening of the drive train of the hybrid vehicle is initiated when the internal combustion engine is running. This has the advantage that when the internal combustion engine no torque can be transmitted to the drive wheels, so that in case of malfunctions of the hybrid disconnect clutch no uncontrolled driving situation of the vehicle can occur.

In one embodiment, when the starting process of the internal combustion engine is initiated, the drive train is not closed for a predetermined second period in which a faulty entrainment of the electric motor is checked. The second time period is selected so that a reliable conclusion can be drawn as to whether the signal output by the software at the functional level can be correctly evaluated by the closed state of the hybrid disconnect clutch. Due to this fact, a critical driving situation can be excluded without the aid of the safety software of the superordinate vehicle level.

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

Show it:

1 a schematic diagram of a hybrid drive,

2 an embodiment for an electric driving with a start of the internal combustion engine,

3 an embodiment for an electrical Ankriechen the hybrid vehicle with open hybrid disconnect clutch and the engine off,

4 an embodiment of an error case when electrical Ankriechen the hybrid vehicle,

5 an embodiment of the method according to the invention.

In 1 is a schematic diagram of a drive train of a hybrid vehicle shown. This powertrain 1 includes an internal combustion engine 2 and an electric motor 3 , Between the combustion engine 2 and the electric motor 3 is right behind the combustion engine 2 a hybrid disconnect clutch 4 arranged. internal combustion engine 2 and hybrid disconnect coupling 4 are over a crankshaft 5 connected with each other. The electric motor 3 has a rotatable rotor 6 and a fixed stator 7 on. The output shaft 8th the hybrid disconnect clutch 4 is with a gearbox 9 connected, which contains a coupling element, not shown, for example, a second clutch or a torque converter, between the electric motor 3 and the transmission 9 are arranged and the drive train 9 . 10 off or on. The gear 9 transmits that from the internal combustion engine 2 and / or the electric motor 3 generated torque on the drive wheels 10 of the hybrid vehicle. The electric motor 3 and the gearbox 9 form a gear system 11 which is powered by a hydraulic clutch actuator 12 is controlled. The internal combustion engine 2 is with a hybrid starter generator 13 connected.

When driving the hybrid vehicle, two cases are to be distinguished in which it can lead to critical driving situations in a misjudgment of the coupling state.

In the first case, an electric driving of the hybrid vehicle without an internal combustion engine 2 occur. This case is in 2 shown. The hybrid vehicle drives purely-electrically with the electric motor 3 with a closed drive train 9 . 10 , meaning that the gearbox clutch is closed and the hybrid disconnect clutch 4 is open. The internal combustion engine 2 is off. Will now the internal combustion engine 2 via the hybrid starter generator 13 started, the engine speed is that of the electric motor 3 adjusted and the hybrid disconnect coupling 4 will be closed.

In the second case, there is a creeping of the hybrid vehicle with activated electric motor 3 without switched on internal combustion engine 2 , At the in 3 As shown, the hybrid vehicle travels purely electrically with the electric motor 3 with closed drive train 9 . 10 , The hybrid separation clutch 4 is open and the internal combustion engine 2 out.

It can come in principle to two sources of error. Is the internal combustion engine 2 turned off and is dragged along because the hybrid disconnect clutch 4 Although reported as open, but actually closed or partially closed, this leads to a critical driving situation, which is particularly relevant when Ankriechen and electric driving in the lower speed range.

In the second fault, the electric motor 3 switched off and is dragged along. because also the hybrid separation clutch 4 although reported as open, actually closed or partially closed. This case is always relevant when the internal combustion engine 2 is started to over the hybrid starter generator 13 to charge a not shown battery.

Such an error case is in 4 shown in more detail, where the hybrid disconnect coupling 4 is open and the vehicle creeps electrically. At the same time the internal combustion engine becomes 2 entrained, with the engine speed and the electric motor speed are approximately equal. Due to the reported open condition of the hybrid disconnect clutch 4 but the engine speed would have to be zero.

In order to avoid these error cases, in a given period of time, the software of a functional level of the hybrid disconnect clutch is used 4 output signal is checked whether it is the actual state of the hybrid disconnect clutch 4 equivalent. The actual state of the hybrid disconnect clutch 4 is documented by an additional flag in the functional level software.

To determine the condition of the hybrid disconnect clutch 4 An internal combustion engine speed and an electric motor speed are measured and determined from these the slip. The slip is a difference between the engine speed and the motor speed. If the amount of the difference is less than a threshold, e.g. B. 50 U / min, then the additional flag "Allow engine start" is output by the software, which is set to FALSE. This prevents the start of the internal combustion engine 2 he follows.

If the engine start has already been initiated and the flag "Allow engine start" changes from TRUE to FALSE only then, since the slip is smaller than the threshold, the starting process of the internal combustion engine 2 not stopped. The same is true even when the internal combustion engine is running 2 , in which the flag "Allow engine start" has no influence.

By preventing engine startup, a potential significant acceleration of the vehicle by the sudden existing engine torque with closed or partially closed hybrid disconnect clutch 4 prevented. However, the slip condition is only applied when the idling speed is reached, otherwise the vehicle accelerates at an engine start.

In the event that the electric motor 3 The internal combustion engine is allowed to be towed 2 be started, but care must be taken that the powertrain 9 . 10 is open, ie the clutch arranged in the transmission is not closed. No gear must be engaged in the gearbox or a (double) clutch must be open in the gearbox. As an alternative to the "allow engine start" flag, in this case, a "close drive train" flag can be used.

The process according to the invention should be carried out with the aid of the in 5 shown embodiment, where the speed over time and the speed of the engine 2 dashed near zero, while the speed of the electric motor 3 increases. In diagram A, it is first determined that the slip is greater than the threshold value after a certain jump. In addition, it is considered in Chart B whether the idling speed has been reached by the electric motor speed. Since these two signals are "ORDERED", in diagram C the engine start will only be allowed if the idle speed is reached and the slip is greater than the threshold.

In the diagram D below it is assumed that initially the powertrain 9 . 10 is open and then closed. When the powertrain 9 . 10 is closed, the flag "engine start allowed" in diagram D changes from TRUE to FALSE. That is, the starting process in the case of the entrained electric motor 3 may only be initiated when the powertrain 9 . 10 not closed. The flag "engine start allowed" is now logically ORed from diagram C and diagram E to the final acting flag in diagram F.

In the alternative situation for signal "engine start allowed" is ensured when Ankriechen that permission to start the engine 2 is issued only if a possible incorrect entrainment of the internal combustion engine 2 was detected. Accelerates the electric motor 3 So very fast beyond the idle speed, so the flag "engine allowed" could be set to true, although the error has not been detected. Alternatively, a "close drive train allowed" flag may be used to control the condition of the powertrain.

LIST OF REFERENCE NUMBERS

1

Hybrid powertrain

2

internal combustion engine

3

electric motor

4

Hybrid clutch

5

crankshaft

6

rotor

7

stator

8th

output shaft

9

transmission

10

drive wheels

11

transmission system

12

Hydraulic clutch actuator

13

Hybrid Starter Generator

Claims (5)

A method for avoiding a critical driving situation in a vehicle with a hybrid drive, in which a hybrid disconnect clutch ( 4 ) an internal combustion engine ( 2 ) and an electric motor ( 3 ) separates or connects, whereby one by the internal combustion engine ( 2 ) and / or the electric motor ( 3 ) output moment of drive wheels ( 10 ) of the vehicle and the hybrid disconnect coupling ( 4 ) by a hydraulic clutch actuator ( 12 ) is actuated, wherein an engine speed and an electric motor speed are measured and evaluated, being offset depending on the evaluation of the hybrid drive in a state by means of which the critical driving situation by a faulty entrainment of the internal combustion engine ( 2 ) or the electric motor ( 3 ) is suppressed, wherein for the evaluation of the engine speed and the electric motor speed these are compared with each other and depending on the comparison, a start of the internal combustion engine ( 2 ) is determined or inhibited, wherein a difference between the measured engine speed and the measured electric motor speed is determined, which is compared with a threshold value, wherein when falling below the threshold value by the difference, the start of the internal combustion engine ( 2 ) is inhibited, characterized in that the determination of the difference and the comparison with the threshold value are performed when the electric motor speed has exceeded an idle speed. A method according to claim 1, characterized in that a start of the internal combustion engine ( 2 ) is allowed after a predetermined first period, in which it is checked whether a faulty entrainment of the internal combustion engine ( 2 ) he follows. Method according to at least one of the preceding claims, characterized in that after initiation of a starting process of the internal combustion engine ( 2 ) and subsequent undershooting of the threshold value by the difference between the engine speed and the electric motor speed of the starting process is carried out further. Method according to at least one of the preceding claims, characterized in that the evaluation of engine speed and electric motor speed before initiating a starting process of the internal combustion engine ( 2 ) he follows. Method according to at least one of the preceding claims, characterized in that when starting the internal combustion engine ( 2 ) one in a transmission ( 9 ) of the drive train ( 9 . 10 ) arranged clutch is not closed a predetermined second period, in which a faulty entrainment of the electric motor ( 3 ) is checked.

Images