WO2018033181A1

WO2018033181A1 - Method for ascertaining a safety-relevant clutch state of a separating clutch of a hybrid powertrain

Info

Publication number: WO2018033181A1
Application number: PCT/DE2017/100681
Authority: WO
Inventors: Florian Ziefle; Volker Küss; Mark LIBER
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2016-08-19
Filing date: 2017-08-15
Publication date: 2018-02-22
Also published as: DE112017004140A5; DE102016215597A1

Abstract

The invention relates to a method for ascertaining a safety-relevant clutch status of a motor vehicle hybrid powertrain separating clutch which is arranged between an internal combustion engine and an electric machine and which is actuated along an actuation path (s) automatically by means of an electrically driven clutch actuator. In order to detect safety-relevant states of the separating clutch and respond thereto, the method is carried out according to the combination of the following features: a clutch characteristic curve (2, 3) is ascertained and continuously adapted using a friction coefficient and an engagement point, the clutch characteristic curve (2, 3) is divided into three states, namely an open state (open(1), open(x)), a closed state (closed(1), closed(x)), and a slip state (intermediate(l), intermediate(x)) lying between the open state and the closed state of the separating clutch, over the actuation path (s), and a safety-relevant classification into one of the three states (open(1), open(x), intermediate(l), intermediate(x), closed(1), closed(x)) is carried out using a separating clutch engagement point which is ascertained on the basis of operating states of the motor vehicle and is continuously adapted.

Description

Method for determining a safety-relevant coupling state of a

Disconnect coupling of a hybrid powertrain

The invention relates to a method for determining a safety-related coupling status of a between an internal combustion engine and an electric machine arranged automatically actuated by means of an electrically operated clutch actuator along an actuation path separating clutch of a hybrid drivetrain of a motor vehicle.

In many hybrid powertrains an automatically actuated separating clutch is provided between an internal combustion engine and an electric machine, which allows a start of the internal combustion engine by the electric machine and a hybrid operation of the motor vehicle in the closed state. In the opened state of the separating clutch, for example, a sailing operation, a recuperation operation and an electromotive driving operation are possible. In case of failure of the clutch or its control can occur depending on the current operating condition of the motor vehicle, an undesirable and case-dependent behavior of the clutch. For example, a moment may be undesirably transmitted or a moment requested, for example, in overtaking operations and the like may be omitted.

In order to avoid such malfunctions, a 3-level safety concept is usually used. Here, the function of the separating clutch according to quality management measures, for example, according to ISO 26262 mapped in a first, designed as a functional level level. In a second and third level, designed as a level of security, monitoring of the separation clutch, for example, trained according to ASIL (Automotive Safety Integrity Level).

The separating clutch is often controlled by means of a torque interface. This means that a desired torque to be transmitted is adjusted by means of an actuation of the separating clutch along an actuating torque. The relationship between torque and actuating travel is set by means of a so-called clutch characteristic, which is continuously adapted to occurring operating variables such as wear, temperature and / or the like. For this purpose, for example, operating variables such as coefficient of friction and touch point of the separating clutch are continuously determined and the clutch characteristic is adapted by means of these operating variables. For example, WO 2015/192847 A2 discloses an adaptation of the touch point for a pressure-based clutch actuator for actuating a friction clutch. From DE 10 2008 030 473 A1 a Tastpunktadaption a friction clutch in a hybrid powertrain is known. The unpublished German Patent Application No. 10 2016 208 035.0, which is hereby incorporated in full in the present application, discloses the detection and adaptation of a Auskuppelpunkts arranged between an internal combustion engine and an electric motor separating clutch of a hybrid powertrain. The non-prepublished German patent application no. 10 2015 221 031.6 shows another possibility for determining the tactile point and the coefficient of friction of a separating clutch in a hybrid powertrain with a hydrostatically operated clutch actuator, depending on sniffer phases of the clutch actuator touch point and coefficient of friction of torque differences of the Internal combustion engine and a determined from a clutch torque torque can be determined. The non-prepublished German Patent Application No. 10 2014 224 850.7 discloses a method for detection safety-critical actuations of a separating clutch in a hybrid drive train by evaluating the rotational speeds of the internal combustion engine and / or the electric machine.

The object of the invention is to propose a method for determining a safety-relevant coupling status of a separating clutch. In particular, a security-relevant monitoring concept is to be proposed, which is provided on a security level.

The object is achieved by the method of claim 1. The dependent of the claim 1 claims give advantageous embodiments of the subject matter of claim 1 again.

The proposed method serves to determine a safety-relevant coupling status of a separating clutch of a hybrid drive train of a motor vehicle, which is arranged automatically between an internal combustion engine and an electric machine and actuated by an electrically operated clutch actuator along an actuation path.

The method has at least the following features:

a clutch characteristic is determined and adapted on the basis of a coefficient of friction and a touch point,

the clutch characteristic is divided over the actuation path into three regions of an open state, a closed state and a slipping state of the separation clutch lying between them,

A safety-relevant classification into one of the three states takes place by means of a sensing point of the separating clutch which is determined and continuously adapted as a function of operating states of the motor vehicle. According to the proposed method, a safety-critical clutch state is determined separately from the functional level with the control of the disconnect clutch, with function variables of the functional level, such as the touch point, which can be determined as input or decoupling determined. The Auskuppel- point can be determined using the method disclosed in the unpublished German patent application no. 10 2016 208 035.0.

In addition, an absolute value of the actuating travel of the separating clutch can be included as a necessary or optional condition for determining the safety-relevant coupling status. This absolute value can be determined for example by means of a displacement sensor of a linearly displaced actuator of the clutch actuator or rotational characteristics of a rotor of an electric motor of the clutch actuator, taking into account a gear ratio for converting the rotational movement of the rotor into a linear movement of the actuator. For this purpose, corresponding rotation angle sensors or the like may be provided.

To delineate the three states such as clutch states against each other, a variance of the touch point can be determined between two adaptations of the Auskuppelpunkts and thus the position of the clutch characteristic and the determination of the state can be provided taking into account the variance. This means that the limits of the states overlap each other with tolerance ranges. In this case, the narrowest limits of the states are preferably used for the safety-relevant determination. These boundary considerations can be interpreted depending on the desired state of the clutch or the driver's desired torque. If, for example, an open disconnect clutch is requested, the variance of the touch point is interpreted such that the limit beyond which the state of an open disconnect clutch is output as present is devoid of variance Is evaluated. This leads to a narrower range, in which the separating clutch is interpreted as open. Similarly, the ranges in which the disconnect clutch is classified into the other two states are reduced by the corresponding variance of the touchpoint. The variances are thereby preferably added to those states for which the desired state of the separating clutch does not apply.

The variance can be, for example, dependent on measurement tolerances and / or system-related deviations of the touch point, which are determined, for example, by the wear state of the disconnect clutch, the clutch temperature and / or the like. The coupling temperature can be determined by means of a temperature sensor or a temperature model.

On the basis of the proposed method, the plausibility of the operation is advantageously checked prior to the release of an actuation of the separating clutch, ie before or during actuation of the separating clutch in the functional level, that is, the safety-critical coupling status is detected, and the actuation is released, if the corresponding condition has been determined.

The method may be installed and performed within the controller responsible for operating the disconnect clutch. For this purpose, the control unit with corresponding sensors to be evaluated, for example via a communication device such as CAN bus, a wireless connection or the like. About this communication device driver's request moments, desired clutch states and the like can be read. Alternatively, the safety-relevant coupling status can be determined in another, for example, higher-level control device, wherein the determined state of the separating clutch of a communication device of the motor vehicle is provided. In the higher-level, in signal communication with the communication device Henden control unit while the determined state is compared with the desired status of the separating clutch and released in accordance with actuation of the separating clutch. Actuation of the separating clutch is understood to be the opening of the closed or closing of the opened separating clutch independently of the design of the separating clutch as a forcibly closed or forcibly opened separating clutch.

Furthermore, with a safety-related malfunction of the friction clutch on the basis of the determined state of the separating clutch, the determined state can be set forcibly. This means, for example, that a disconnect clutch recognized as closed is forcibly opened in the case of a desired state of an open disconnect clutch and the disconnect clutch is forcibly closed in the case of a desired state of a closed disconnect clutch and in the determined state of an opened or slipping disconnect clutch.

In other words, a so-called safety-relevant "clutch engagement status" is used for evaluating the clutch state, which is determined on the basis of a determination of a tactile point such as a coasting point that meets the given safety requirements Tastpunkt suggested:

The variance of the contact point between two adaptations is determined as a function of influences such as, for example, temperature, wear of the friction linings of the separating clutch, an optionally occurring wear adjustment of an adjusting device of the separating clutch and / or the like. A corresponding variance of the touch point is added to the determined tactile point. A distinction is made between areas of the clutch characteristic that are dependent on the contact point and states "closed" in the closed disconnect clutch, "intermediate" of the slipping or undefined condition of the disconnect clutch and "open" of the disconnect clutch. worst-case "characteristic. For this purpose, additional boundary conditions, for example, the responsible for the slope of the clutch characteristic coefficient of friction of the clutch are taken into account.

As a result of the proposed method, the safety-relevant coupling status in the security level can already be determined parallel to the implementation of the target torque in the functional level and made available to external control devices via the communication device, for example wirelessly or via CAN bus or the like. In this case, a higher-level method, for example in a device for carrying out a vehicle hybrid strategy, can be omitted in the necessary decisions as to whether a safety-related malfunction and thus a resulting safety-oriented actuation command of the disconnect clutch is present or greatly simplified as follows:

If desired state = "closed" & "ClutchEngagementStatus" <> "closed", then "close_command"

The invention will be explained in more detail with reference to the exemplary embodiment illustrated in the single FIGURE. This shows the diagram 1 of transmitted via a clutch coupling torque M via the actuation path s for actuating this. The clutch is based on the located between the clutch characteristic 2 in the new state and the clutch characteristic 3 in the wear state depending on the wear and continuously adapted clutch characteristics to a desired Clutch torque controlled by a corresponding actuation travel s is set by a clutch actuator.

The adjustment of the position of the characteristic curves is carried out by determining the touch point, here the Auskuppelpunkts AKP (1), for example, in the new state and the Auskuppel- point AKP (x) in the wear state. The slope of the clutch characteristics is determined by determining a coefficient of friction.

For the safety-relevant determination of the coupling status, the range of clutch characteristics 2, 3 is divided into three states depending on the determined contact point, such as disengaging point AKP (1), AKP (x), namely a state closed (1), closed (x), in which Disconnect coupling is securely closed. The second state intermediate (1), intermediate (x) indicates a slipping or unpredictable separating clutch. The third state open (1), open (x) indicates a safely opened disconnect clutch. The indices (1) indicate the states determined for the new state of the separating clutch as a function of the disengaging point AKP (1). The indices (x) indicate that for the state of wear of the separating clutch depending on the disengaging point AKP (x). Between the disengaging points AKP (1), AKP (x) are any number of adapted disengaging points and correspondingly many differently adapted states for safety-relevant assessment of the coupling status. Depending on influencing parameters which, for example, influence the slope of the clutch characteristics 2, 3, the disengaging points AKP (1), AKP (x) can be provided with variances, the states minus the variances being determined. LIST OF REFERENCE NUMBERS

1 diagram

2 clutch characteristic

3 Coupling characteristic

AKP (1) disengagement point

AKP (x) disengagement point

closed (1) state

closed (x) state

intermediate (l) state

intermediate (x) state

M clutch torque

open (1) state

open (x) state

s actuation path

Claims

Claims Method for determining a safety-relevant clutch status of a separating clutch of a hybrid drive train of a motor vehicle, which is arranged between an internal combustion engine and an electric machine and is automatically actuated by means of an electrically operated clutch actuator along an actuation path (s), characterized by the combination of the following features: a clutch characteristic curve (2, 3) is determined and continuously adapted based on a coefficient of friction and a touch point, the clutch characteristic curve (2, 3) is divided into three states via the actuation path (s), namely an open state (open(1), open(x)), a closed state ( closed(1 ), closed(x)) and a slipping state between these (intermediate(l), intermediate(x)) of the separating clutch, a safety-relevant classification into one of the three states

(open(1), open(x), intermediate(l), intermediate(x), closed(1), closed(x)) is carried out using a touch point of the separating clutch that is determined and continuously adapted depending on the operating states of the motor vehicle.

Method according to claim 1, characterized in that the touch point is determined as a disengagement point (AKP(1), AKP(x)) or engagement point of the separating clutch.

Method according to claim 1 or 2, characterized in that, in addition to the touch point, an absolute value of the actuation path (s) of the separating clutch and/or a coefficient of friction of the separating clutch is used to determine the safety-relevant state (open(1), open(x), intermediate(l ), intermediate(x), closed(1 ), closed(x)) is used.

Method according to one of claims 1 to 3, characterized in that a variance of the touch point is determined between two adaptations of the touch point. telt and the determination of the state is provided taking the variance into account.

5. The method according to claim 4, characterized in that the variance is determined at least depending on the state of wear of the separating clutch and / or on the clutch temperature.

6. The method according to claim 4 or 5, characterized in that for each of the states (open(1), open(x), intermediate(l), intermediate(x), closed(1), closed(x)) depending on the variance of the touch point creates a clutch characteristic curve (2, 3) with the narrowest limits for each safety-relevant state

(open(1 ), open(x), intermediate(l ), intermediate(x), closed(1 ), closed(x)) is determined.

Method according to one of claims 1 to 6, characterized in that before the release of an actuation of the separating clutch, the plausibility of the actuation is based on the states (open(1), open(x), intermediate(l),

intermediate(x), closed(1 ), closed(x)) is checked and the actuation is released if the corresponding state (open(1 ), open(x), intermediate(l ), intermediate(x), closed(1 ), closed(x)) was determined.

8. Method according to one of claims 1 to 7, characterized in that the determined state (open(1), open(x), intermediate(l), intermediate(x), closed(1), closed(x)) is one Communication device of the motor vehicle is provided.

9. The method according to one of claims 1 to 8, characterized in that in the event of a safety-relevant malfunction of the friction clutch based on the determined state (open(1), open(x), intermediate(l), intermediate(x), closed(1) , closed(x)) of the separating clutch the determined state (open(1 ), open(x), intermediate(l ), intermediate(x), closed(1 ), closed(x)) is forced is set.

Method according to claim 9, characterized in that in the desired state of a closed separating clutch and in the determined state (open(1), open(x), intermediate(l), intermediate(x)) of an open or slipping separating clutch, the separating clutch is forcibly closed .