DE102016215597A1 - Method for determining a safety-relevant coupling state of a separating clutch of a hybrid drive train - Google Patents

Abstract

The invention relates to a method for ascertaining 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 by means of an electrically operated clutch actuator along an actuation path (s). In order to recognize and react to safety-relevant states of the separating clutch, the method is carried out according to the combination of the following features: a clutch characteristic curve (2, 3) is determined and continuously adapted on the basis of a coefficient of friction and a touch point, the clutch characteristic curve (2, 3) is in 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 (intermediate (1), intermediate (x)) of the separating clutch, - a safety-relevant classification into one of the three states (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed ( x)) takes place by means of a depending on operating conditions of the motor vehicle determined and continuously adapted Tastpunkts the separating clutch.

Description

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

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 security concept is usually used. Here, in a first, designed as a functional level level, the function of the separating clutch according to quality management measures, for example, accordingly ISO 26262 displayed. In a second and third, formed as a level of security level monitoring of the separating clutch are shown, which are formed, for example, 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, operating variables such as coefficient of friction and touch point of the separating clutch are continuously determined, for example, and the clutch characteristic is adapted by means of these operating variables. For example, is from the WO 2015/192847 A2 an adaptation of the Tastpunkts for a pressure-based clutch actuator for actuating a friction clutch known. From the DE 10 2008 030 473 A1 is a Tastpunktadaption a friction clutch in a hybrid powertrain known. The not pre-published, 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 not pre-published German Patent Application No. 10 2015 221 031.6 shows a further possibility for determining the tactile point and the coefficient of friction of a separating clutch in a hybrid drive train with a hydrostatically operated clutch actuator, which depending on Schnüffelphasen the clutch actuator touch point and coefficient of friction from torque differences of the moment of the internal combustion engine and a determined from a clutch torque torque can be determined. The not pre-published German Patent Application No. 10 2014 224 850.7 discloses a method for detecting safety-critical actuations of a separating clutch in a hybrid drive train by the speeds of the internal combustion engine and / or the electric machine are evaluated.

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.

• – eine Kupplungskennlinie wird ermittelt und laufend anhand eines Reibwerts und eines Tastpunkts adaptiert,
• – die Kupplungskennlinie wird über den Betätigungsweg in drei Bereiche eines offenen Zustands, eines geschlossenen Zustands und eines zwischen diesen liegenden schlupfenden Zustands der Trennkupplung eingeteilt,
• – eine sicherheitsrelevante Klassifizierung in einen der drei Zustände erfolgt mittels eines abhängig von Betriebszuständen des Kraftfahrzeugs ermittelten und laufend adaptierten Tastpunkts der Trennkupplung.

The method has at least the following features:

• A clutch characteristic is determined and continuously adapted on the basis of a coefficient of friction and a touch point,
• The clutch characteristic is divided over the actuation travel 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 in one of the three states is carried out by means of a depending on operating conditions of the motor vehicle determined and continuously adapted Tastpunkts the separating clutch.

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 Auskuppelpunkt can use the in the not pre-published German Patent Application No. 10 2016 208 035.0 disclosed method can be determined.

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. For example, when requesting an open disconnect clutch, the variance of the touchpoint is interpreted as meaning that the limit beyond which the state of an open disconnect clutch is outputted as present is evaluated without the variance. 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 parent, standing in communication with the communication device control unit while the determined state is compared with the desired status of the clutch and released in accordance with actuation of the 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, in a safety-related malfunction of the friction clutch on the basis of the determined state of the separating clutch of the determined state can be set forcibly. This means, for example, that a disconnect clutch recognized as closed is forcibly opened in a desired state of an open disconnect clutch, and in a desired state of a closed disconnect clutch and in the detected state of an opened or slipping disconnect clutch, the disconnect clutch is forcibly closed.

• – Die Varianz des Tastpunkts zwischen zwei Adaptionen wird abhängig von Einflüssen wie beispielsweise Temperatur, Verschleiß der Reibbeläge der Trennkupplung, einer gegebenenfalls stattfindenden Verschleißnachstellung einer Nachstelleinrichtung der Trennkupplung und/oder dergleichen ermittelt. Eine entsprechende Varianz des Tastpunkts wird dem ermittelten Tastpunkt zugeschlagen.
• – Es werden vom Tastpunkt abhängige Bereiche der Kupplungskennlinie in Zustände „closed“ der geschossenen Trennkupplung, „intermediate“ der schlupfenden oder mit undefiniert klassifiziertem Zustand der Trennkupplung und „open“ der geöffneten Trennkupplung unterschieden. Diese Betrachtung erfolgt aus sicherheitstechnischen Gründen bevorzugt auf Basis einer „worst-case“-Kennlinie. Hierzu werden zusätzlich Randbedingungen, beispielsweise der für die Steigung der Kupplungskennlinie verantwortliche Reibwert der Trennkupplung berücksichtigt.

In other words, a so-called safety-relevant "clutch engagement status" is used to evaluate the clutch condition based on a determination of the clutch condition predetermined safety requirements fulfilling touch point such as Auskuppelpunkts is determined. For the determination of the touch point, the following aspects are advantageously proposed for determining the touch point:

• 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.
• - It is distinguished from the touch point dependent areas of the clutch characteristic in states "closed" of the closed disconnect clutch, "intermediate" of the slipping or undefined classified state of the disconnect clutch and "open" of the opened disconnect clutch. For safety reasons, this consideration is preferably based on a "worst-case" characteristic curve. 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 embodiment shown in the single figure. This shows the diagram 1 of transmitted via a clutch coupling torque M via the actuating travel s for actuating this. The separating clutch is determined by the between the clutch characteristic 2 when new and the clutch characteristic 3 in the state of wear 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 setting of the position of the characteristic curves is carried out by determining the Tastpunkts, here the Auskuppelpunkts AKP (1), for example, in the new state and Auskuppelpunkts 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 the coupling characteristic curves becomes 2 . 3 Depending on the determined tactile point as here Auskuppelpunkt AKP (1), AKP (x) divided into three states, namely a state closed (1), closed (x), in which the separating clutch is securely closed. The second state intermediate (1), intermediate (x) indicates a slipping or unpredictable disconnect 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, for example, the slope of the clutch characteristics 2 . 3 the disengagement 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

 Clutch characteristic

ACP (1)

 disengagement point

ACP (x)

 disengagement point

closed (1)

 Status

closed (x)

 Status

intermediate (1)

 Status

Intermediate (x)

 Status

M

 clutch torque

open (1)

 Status

open (x)

 Status

s

 actuating

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2015/192847 A2 [0004]
• DE 102008030473 A1 [0004]
• DE 102016208035 [0004, 0009]
• DE 102015221031 [0004]
• DE 102014224850 [0004]

Cited non-patent literature

• ISO 26262 [0003]

Claims (10)

Method for determining 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 operated by means of an electrically operated clutch actuator along an actuation path (s), characterized by the combination of the following features: a clutch characteristic ( 2 . 3 ) is determined and adapted on the basis of a coefficient of friction and a touch point, - the clutch characteristic ( 2 . 3 ) is in 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 ( intermediate (1), intermediate (x)) of the disconnect clutch, - a safety-relevant classification into one of the three states (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) by means of a depending on operating conditions of the motor vehicle determined and continuously adapted Tastpunkts the separating clutch. A method according to claim 1, characterized in that the touch point is determined as Auskuppelpunkt (AKP (1), AKP (x)) or Einkuppelpunkt the disconnect clutch. A 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 for determining the safety-relevant state (open (1), open (x), intermediate (1 ), intermediate (x), closed (1), closed (x)). Method according to one of claims 1 to 3, characterized in that between two adaptations of the touch point determines a variance of the touch point and the determination of the state is provided taking into account the variance. A 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 the clutch temperature. Method according to claim 4 or 5, characterized in that for each of the states (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) depending on the variance of the Tastpunkts a clutch characteristic ( 2 . 3 ) with the narrowest limits for each safety-relevant state (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)). Method according to one of claims 1 to 6, characterized in that prior to the release of an actuation of the separating clutch, the plausibility of the actuation based on the states (open (1), open (x), intermediate (1), intermediate (x), closed ( 1), closed (x)) is checked and the operation is released when the corresponding state (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) was determined. Method according to one of Claims 1 to 7, characterized in that the determined state (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) of a communication device of the Motor vehicle is provided. Method according to one of claims 1 to 8, characterized in that in a safety-related malfunction of the friction clutch based on the determined state (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) the determined condition (open (1), open (x), intermediate (1), intermediate (x), closed (1), closed (x)) is set forcibly. A method according to claim 9, characterized in that in a desired state of a closed disconnect clutch and in the determined state (open (1), open (x), intermediate (1), intermediate (x)) of an open or slipping disconnect clutch, the disconnect clutch is forcibly closed ,

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