WO2010020520A1

WO2010020520A1 - Method for detecting a wear of a motor disconnect clutch

Info

Publication number: WO2010020520A1
Application number: PCT/EP2009/059556
Authority: WO
Inventors: Ralf Schuler; Christof Jach; Werner Urban; Kaspar Schmoll Genannt Eisenwerth
Original assignee: Robert Bosch Gmbh
Priority date: 2008-08-22
Filing date: 2009-07-24
Publication date: 2010-02-25
Also published as: DE102008041446A1; DE102008041446B4

Abstract

The invention relates to a method for detecting a wear of a motor disconnect clutch comprising a clutch actuator and a clutch release mechanism movable by means of the clutch actuator, which comprises moving (401) the clutch actuator along a target value course, detecting (403) an actual value course, and detecting (405) a difference between an actual value of the actual value course and a target value of the target value course to detect the wear of the motor disconnect clutch.

Description

description

title

Method for detecting wear of an engine disconnect clutch

Technical area

The present invention relates to engine disconnect couplings, which in particular in

Hybrid vehicles are used with a hybrid drive.

State of the art

The concept of the hybrid drive is gaining increasing importance in the automotive industry due to its associated optimization of fuel consumption, emission reduction and improvement of the subjective driving sensation. Furthermore, the hybrid drives used in modern hybrid vehicles in addition to an internal combustion engine on at least one other drive source, which does not have to be operated with fossil fuels, which can be used as a further drive source in addition to an internal combustion engine, for example, an electric motor. By a suitable strategy of the operation of the hybrid drive so advantages of the different drive sources can be optimally used and disadvantages avoided.

In modern hybrid drives, a distinction is made between a parallel hybrid, a serial hybrid and a split hybrid. All hybrid drives have in common is the use of two energy storage, namely a battery and a fuel tank. To drive the hybrid vehicle, the internal combustion engine can be decoupled from a drive train for example for purely electric driving via an electrically controllable engine disconnect clutch and restarted at an increased power requirement or low battery state via an engine disconnect clutch with the electric machine. The engine disconnect clutch is controlled to a defined slip torque during the opening and closing operations of the engine disconnect clutch.

Fig. 1 illustrates a structure of a considered engine disconnect clutch, which is controlled by a hydraulic system. In this case, an electric clutch actuator 101 moves a hydraulic master cylinder 103, which is connected via a hydraulic line 105 with a slave cylinder 107, in which a generally hydraulic clutch release 109 is arranged. The clutch release 109 moves under the influence of a hydraulic force in the slave cylinder 107, wherein a value curve of the clutch release 109 is limited by a mechanical restriction 111. The hydraulic force on the clutch release 109 acts on a plate spring 113, which exerts a force on a clutch disc 115 and thereby realizes a corresponding clutch torque.

The clutch friction plate 115 is equipped with a pad spring, via which a frictional force is transmitted. However, proper functioning of the engine disconnect clutch can only be ensured as long as sufficient friction lining is present so that the state of wear of the engine disconnect clutch must be identified or monitored. DE 10 2005 061 080 A1 describes a method for detecting a

Damage to a coupling having at least two components transmitted by frictional engagement torque, in which a single damage value is determined as a function of the friction loss.

Disclosure of the invention

The present invention is based on the recognition that monitoring the wear condition of the engine disconnect clutch may be accomplished by estimating a friction energy contribution upon actuation of the engine disconnect clutch. The friction energy contribution, for example, depending on its size of a friction energy class of a plurality of for example, be assigned in a histogram arranged friction energy classes. By counting the friction energy contributions associated with the respective friction energy class, it is thus possible to record how many times a questionable friction power has been generated, from which a total friction power relative to a friction energy class can be derived. In addition, a sum of the energies accumulated in the friction energy classes provides a total output friction which characterizes the wear condition of the engine disconnect clutch.

The invention is based on the further realization that there is a connection between the clutch actuator travel shown in FIG. 1, which is limited by a mechanical stop, and the clutch torque. Thus can be determined by a suitable method of the clutch actuator whose actual value curve and compared with a desired value curve, from which a statement about the state of wear of the engine disconnect clutch can be obtained by measurement.

The above concepts can be used independently or cooperatively. For example, the measurement of the wear condition may be estimated based on the above-mentioned histogram to avoid unnecessary measurements if the wear condition of the engine disconnect clutch is not critical.

The invention relates to a method for detecting wear of an engine disconnect clutch having a clutch actuator, such as a clutch actuator, and a clutch releaser movable by means of the Kupplungsaktuators with moving the Kupplungsaktuators along a setpoint course, for example, a predetermined characteristic curve, detecting a Istwertverlaufs and detecting a Difference between an actual value of the actual value curve and a desired value of the setpoint curve for detecting the wear of the motor-separating clutch. According to one embodiment, the actual value is compared with a position of a mechanical stop of the clutch release in the wear-free coupling state in which this is not moved further. This can ensure a clear measurement. The position of the mechanical stop, for example, by a

Coupling contact point or be determined by the mechanical limit 111 shown in FIG. 1.

According to an embodiment, the desired value course is determined by a SoII value characteristic curve which defines a position of the clutch actuator as a function of time, wherein the characteristic curve has a first ramp-shaped section with a first slope and a second ramp-shaped section with a second slope the second ramped portion follows the first ramped portion and has a smaller pitch than the first ramped portion. The ramp-shaped configuration of the Verfahrkennlinie allows easy and accurate control of the clutch actuator.

According to one embodiment, the clutch actuator is within a first time interval at a first speed with a first value course, which is shorter than a wear-free coupling state is to be traced to a mechanical stop of the clutch release value course, and within a second time interval, which follows the first time interval with a second speed, which is less than the first speed, up to a mechanical stop of the

Clutch release procedure. Thus, a wear measurement is possible only on the basis of a position of the clutch actuator. According to one embodiment, the clutch actuator is moved back within a third time interval, which follows the second time interval, so that a defined initial state for a further measurement is achieved.

According to one embodiment, a profile of the actual value profile is filtered, in particular low-pass filtered, and compared with the unfiltered actual value profile in order to detect an actual position of the clutch actuator or of the clutch release device. Thus, in particular the position at which the slave cylinder reaches its mechanical stop and thus the actual value course remains in a stationary state can be reliably detected.

According to one embodiment, to monitor the wear of an engine disconnect clutch before or after detecting wear, the following steps are performed: detecting a friction energy contribution generated in a clutch operation, assigning the detected friction energy contribution to a friction energy class from a plurality of friction energy classes which are particularly in one Histogram are arranged, and increasing a count value associated with the friction energy class, which has been assigned the detected friction energy contribution. The wear measurement is therefore only carried out if a measurement requirement has been determined on the basis of the previously performed estimation.

According to one embodiment, the detection of wear is triggered when a sum of the counts or a sum of the counts weighted with the respective friction energy contributions has reached a predetermined threshold. The measurement of wear is thus triggered by a simple criterion.

According to one embodiment, the friction energy contribution E is determined based on the following formula slipping

E = JJMMCClth »nDiff» ώ

I = Sch !upft> € gmn

where MCIth is a clutch torque and nDiff is a speed difference of clutch discs of the engine disconnect clutch. The integral is preferably replaced by a sum, so that the determination of the friction energy contributions with low complexity is possible.

According to one embodiment, after reaching a maximum possible actual value of the wear in the form of a Reibbelagabnahme by extrapolation, in particular by a linear extrapolation, on the basis of a previously detected difference between an actual value and a target value, in particular using the following formula

IDeltaFrcWstg Re f _{^ 1 1 ττr f ^} ζ / • wClthWghTot wClthTot Re f

in the IDeltaFrcWstgRef, a pad wear detected on the basis of the difference between an actual value and a target value, in which a maximum value characteristic of the clutch actuator has been achieved, wCIthTotRef a friction energy contribution achieved when the maximum torque value is reached by the clutch actuator, and wCIthWghTot designate a total friction energy of the engine disconnect clutch. Thus, a monitoring of wear progress is possible even if a wear measurement can no longer be performed.

In one aspect, the method may include a method of monitoring wear of an engine disconnect clutch with sensing a

Frictional energy contribution generated in a coupling process Associating the detected friction energy contribution to a friction energy class from a plurality of friction energy classes and increasing a count associated with the friction energy class to which the sensed friction energy contribution has been assigned.

According to one embodiment, the friction energy contribution is detected based on a clutch torque associated with the clutching operation. Thus, a simple detection of the friction energy contribution is possible.

According to an embodiment, the energy values associated with the plurality of friction energy classes are summed to form a

To get total friction energy, which indicates the state of wear. The advantage here is that the complexity is low.

According to one embodiment, the plurality of friction energy classes are arranged in a histogram. Therefore, a simple and clear presentation and capture is possible.

According to one embodiment, each of the plurality of friction energy classes or the friction energy contribution associated with the respective friction energy class is multiplied by a weighting factor, in particular by an empirically determined weighting factor, to account for the respective friction energy contribution to the wear of the engine disconnect clutch. The weighting factor therefore contributes to an even more accurate detection of the wear.

According to one embodiment, for detecting a wear contribution of the respective friction energy class, it is multiplied by its associated friction energy contribution. According to one embodiment, a wear progress is detected by the following formula

NuherClassHist-l

πax, lifetιme

wherein E _max , _Nf etime the friction energy generated by the engine disconnect clutch within a predetermined period of time, in particular within a lifetime of the engine disconnect clutch, E ₁ of the respective

Friction energy contribution associated with frictional energy class, z, count value associated with each frictional energy class, NumberClassH is the number of energy classes, and wt, a weighting factor. As a result, a simple and accurate monitoring of wear is possible.

According to one embodiment, a metrological detection of the wear is performed when a sum of the counts or a sum of the count values weighted with the respective friction energy contributions has reached a predetermined threshold. Thus, the wear measurement must be performed only if it appears necessary.

The invention further relates to a program-technically configured device which is designed to execute a computer program for carrying out the method according to the invention.

drawings

Further embodiments will be made with reference to the accompanying drawings

Drawings explained in more detail. Show it:

Fig. 1 is an engine disconnect clutch; FIG. 2 is a flowchart of a method of monitoring wear of an engine disconnect clutch; FIG.

3 shows a histogram with friction energy classes arranged therein; and

4 shows a flowchart of a method for metrological detection of a wear of an engine disconnect clutch.

Description of the embodiments

Fig. 2 shows a course of the method for monitoring the wear of the engine disconnect clutch, which, for example, two or more

Clutch discs may have. The method includes the step 201 of detecting a friction energy contribution generated in a clutching operation, such as closing or opening a clutch. The detected friction energy contribution is assigned in step 203 a friction energy class, which consists of a plurality of in a

Histogram arranged friction energy classes is selected. After an allocation of the friction energy contribution to a friction energy class, a count value is increased in step 205, for example by means of a counter, wherein the count value is associated with the friction class to which the detected friction energy contribution has been assigned.

The friction energy contribution can be detected, for example, by a measurement of a temperature that arises, for example, in a closing operation of the clutch due to the friction of the clutch discs. Since a corresponding abrasion on the clutch linings is produced by the friction power applied to the respective clutch disc, the wear of the engine-disconnect clutch can thus be determined.

A typical clutch energy input, or friction energy contribution, during engine restart is about 2.7 kJ. The Motor disconnect clutch is specified so that it can withstand a lifetime at least a total friction energy of, for example, 5.4 ^* 10 ⁹ J, which corresponds to one million clutch actuations. In order to conclude on the worn clutch, therefore, the friction energy contributions, ie the energy inputs, can be summed over the life of the engine disconnect clutch, so that upon reaching the possible total energy input can be concluded on a worn clutch.

In order to take into account the different clutch energy inputs due to specimen spreads or the chosen hybrid strategy as well as the fact that very high energy contributions contribute disproportionately to the wear, according to the invention the respective friction energy entries are determined and recorded in a histogram for each coupling process.

FIG. 3 shows such a histogram with N friction energy classes 301, which are plotted with an energy step width of, for example, 1 kJ. The height of the histogram bar associated with the respective friction energy class is determined by a frequency z, which corresponds to the number of friction energy contributions attributable to the respective friction energy class.

Optionally, the friction energy classes may be weighted with a wear weight factor that takes into account the respective contribution of the respective friction energy class to the wear of the engine disconnect clutch. Because higher friction energies generally result in accelerated clutch wear, the weighting factor may increase linearly or non-linearly with increasing energies of the respective friction energy classes, for example. FIG. 3 shows by way of example a course 303 of such a weighting factor, which can also be interpreted as a wear weight. The friction energy contributions, for example, via a speed difference of the clutch discs nDiff and the example known clutch torque Mcith using the formula

O ScLrhuluuμpjfeeπnudee

E = JMClth »nDiff .dt I = Slip> egmn

be determined.

Preferably, the energy histogram illustrated in FIG. 3 is designed such that the majority of the friction energy contributions, i. the clutch energy inputs, is covered. The width of the individual histogram classes is selected, for example, such that the statistical average results in a suitable distribution of the friction energy entries over the histogram classes.

As mentioned above, high energy inputs contribute disproportionately to the wear of the engine disconnect coupling as low energy contributions. Therefore, according to one embodiment, the individual energy contributions are weighted in the estimation of the wear progress on the basis of the energy histogram as a function of the respective height of the respective histogram bar. The wear progress, for example, on the basis of the formula

NuherClasxHιst-l

i = 0 voaxjifetime

be monitored. Here Ei denotes the frictional energy class i in joules, Zj the singular number of the energy input events for the class i, some one Weighting factor for the respective energy class i and E _max , intimate a clutch load capacity specified for the respective engine disconnect clutch over a specified total life of the engine disconnect clutch. In order to record the energy histogram as well as the determined wear variables over the life of the motor disconnect clutch, these variables can be stored in a non-volatile memory following an estimation cycle, for example, and be read out there again during a control unit initialization.

For metrological detection of the state of wear, a method with the sequence shown in Fig. 4 can be used. This method is particularly suitable for detecting a wear of an engine disconnect clutch, as shown for example in Fig. 1, which has a clutch actuator and a movable by means of the clutch actuator Kupplungsausrücker. In step 401, the clutch actuator is moved along a setpoint course. Since, depending on a current wear of the engine disconnect clutch, the actual value curve of the clutch actuator differs from the desired desired value course, the actual value course is detected in step 403. In step 405, a difference between an actual value of the value history at, for example, a predetermined position of the clutch actuator and a target value at which the clutch actuator is expected to be in a wear-free state is detected to detect wear of the engine-disconnect clutch ,

In Fig. 5, a sequence of wear measurement is again shown by a change over time of a position of the clutch actuator. This is moved along a setpoint course. Furthermore, the position 503 of a mechanical stop in the wear-free state and a detected, current actual position 505 are entered. A difference 507 between these two sizes gives a wear path that is due to the clutch wear. The course of the setpoint course 501 comprises a first ramp-shaped rise 509 with a pitch that is greater than a pitch of a second section 511 immediately following the section 509. The course of the desired value course 501 furthermore comprises a third section 513, which has a negative slope and immediately follows the second section 511. FIG. 5 also shows a profile of the actual value profile 515. This follows the set value curve until the clutch actuator reaches the current stop position 505, ie the actual value. Thus, the wear of the engine disconnect clutch can be detected on the basis of the difference between the actual value 505 and the target value 503.

A wear measurement can be carried out, for example, if the vehicle brake is activated or if, in the case of an automatic transmission, the driving steps N or P are engaged. In order not to interrupt the hybrid drive, the wear measurement can also be carried out during a controller overrun.

For carrying out the method, the clutch actuator is moved, for example, starting from a closed coupling state along the steep opening ramp 509 to a position in which the

Clutch release is shortly before its mechanical stop. The position of the mechanical stop is known for the new state of the coupling system, for example, on the geometric conditions and can therefore be accurately determined and approached. Subsequently, the clutch on the slow opening ramp 511 is opened further, so that a cautious

Procedure of the releaser against the mechanical stop 505 is performed. The stop position is detected when the actual clutch position no longer follows the setpoint position ramp. This is identified by the conditions that, for example, the actual position remains in a stationary state and deviates by more than a certain threshold from a desired value. As a criterion For examining the stationary behavior of the clutch position, for example, a difference between unfiltered and low-pass filtered current actual position can be used. As long as the actual position does not follow the setpoint position ramp, there is a stationary deviation between the unfiltered and the filtered actual position corresponding to a product of a ramp gradient and a filter time constant. In a stationary state, in which the actual position no longer follows the setpoint ramp, this difference is correspondingly smaller. It is therefore closed to the stationary actual position, when the difference between the unfiltered and the filtered actual position is, for example, half of the stationary deviation.

The stop position 503 in the wear-free state is already known, for example. However, this position may be determined during the first wear measurement and stored as a non-volatile reference value for the clutch new state, for example. Subsequently, the locking ramp 513 is moved until a closed coupling state has been reached again.

To eliminate accidental measurement errors, the determined stop positions can be filtered. For this purpose, it is possible, for example, to use a median filter which is composed of the current and, for example, a plurality, which may be predetermined, e.g. four, ignore the largest and smallest values of past measurements and form the arithmetic mean of, for example, three remaining values.

As mentioned above, the first measured stop position value may be used as a reference value for a new clutch state. After each further wear measurement, the respective optionally filtered stop position value is compared with the reference value for the new condition. The resulting difference is a measure of the Reibbelagsverschleiß and can for example via a characteristic in a Reibbelagsabrieb showing the decrease of the friction lining thickness with respect to a Reibbelagsdicke when new characterized, to be converted. This characteristic depends on the geometric lever ratios on the plate spring of the coupling shown in Fig. 1 and can be measured in the laboratory.

The method for detecting the wear measurement based on the method of the clutch actuator may be initiated, for example, by the aforementioned energy histogram method. In this case, for example, a wear measurement can be carried out if the accumulated energy inputs have a significant progress, for example 1% of the specified coupling load capacity. For this purpose, for example, the clutch can be opened so far until the clutch release abuts his mechanical stop. As the course of wear increases with increasing pad wear, the change in this value over the service life is a measure of the actual clutch wear.

In the event that the clutch actuator can no longer drive the slave cylinder to the stop, because, for example due to the advanced lining wear the necessary value course would be greater than the maximum possible value curve, the clutch lining wear by a example linear extrapolation from the last wear measurement and the associated Total coupling energy input using the formula

IDeltaFrcWstg Re f J / • wClthWghTot wClthTot Re f

be determined. Where IDeltaFrcWstgRef is a value detected based on the difference between an actual value and a target value

Coating abrasion, in which a maximum course of the values of the clutch actuator was achieved, wCIthTotRef a friction energy contribution, which results when the maximum value course through the clutch actuator is reached and at a Coupling operation was achieved, and wCIthWghTot a total friction energy of the engine disconnect clutch.

With the determined wear values, for example, a corresponding diagnostic entry can be triggered in a targeted manner in order, for example, to point out in good time a heavily worn coupling. In addition, with increasing wear, the hybrid operating strategy could also be changed accordingly to prevent or at least slow down further wear.

Claims

claims

A method of detecting wear of an engine disconnect clutch having a clutch actuator and a clutch release movable by means of the clutch actuator, comprising:

Method (401) of the clutch actuator along a setpoint course;

Detecting (403) an actual value course; and

Detecting (405) a difference between an actual value of the actual value course and a desired value of the setpoint course for detecting the wear of the motor disconnect clutch.

2. The method of claim 1, wherein the clutch actuator is a Spindelaktuator.

3. The method according to any one of the preceding claims, wherein the actual value is compared with a position of a mechanical stop of the clutch release in the wear-free coupling state.

4. The method according to claim 1, wherein the desired value course is determined by a desired value characteristic curve defining a position of the clutch actuator as a function of time, wherein the value characteristic curve has a first ramp-shaped section with a first gradient and a second ramp-shaped profile Section having a second pitch, wherein the second ramped portion follows the first ramped portion and has a smaller pitch than the first ramped portion.

5. The method according to claim 1, wherein, within a first time interval at a first speed, the clutch actuator has a first value course, which is shorter than a value course to be traveled in the wear-free clutch state up to a mechanical stop of the clutch release, and within a second time interval, which follows the first time interval, at a second speed which is less than the first speed, until a mechanical stop of the clutch release is made, wherein the clutch actuator is moved back within a third time interval which follows the second time interval.

6. The method according to any one of the preceding claims, in which a course of the actual value is filtered, in particular low-pass filtered, and compared with the unfiltered actual value curve to detect a stationary behavior of the actual position of the clutch actuator or the clutch release.

A method according to any one of the preceding claims, wherein to monitor wear of an engine disconnect clutch before or after detecting wear:

Detecting a friction energy contribution generated in a clutching operation; and

Assigning the detected friction energy contributions to a friction energy class from a plurality of friction energy classes, which are arranged in particular in a histogram, and

Incrementing a count associated with the friction energy class associated with the sensed friction energy contribution.

8. The method of claim 6, wherein the detecting of wear is triggered when a sum of the counts or a sum of the counts weighted with the respective friction energy contributions has reached a predetermined threshold.

A method according to any of the preceding claims 6 or 7, wherein the friction energy contribution E is determined on the basis of the following formula

slipping

E = JJMMCClth »nDiff» ώ

I = Sch !upft> € gmn

where MCIth is a clutch torque and nDiff is a speed difference of clutch discs of the engine disconnect clutch.

10. The method according to any one of the preceding claims, in which after reaching a maximum possible actual value of the wear in the form of a Reibbelagabnahme by extrapolation, in particular by a linear extrapolation, on the basis of a previously detected difference between an actual value and a target value Value, in particular using the following formula

wClthTot ref

in the IDeltaFrcWstgRef, a pad abrasion detected on the basis of the difference between an actual value and a target value, in which a maximum value characteristic of the clutch actuator has been reached, wClthTotRef achieves a friction energy contribution which reaches when the maximum value course through the clutch actuator and a clutch operation is reached has been, and wCIthWghTot denote a total friction energy of the engine disconnect clutch.

11. A program-equipped device, which is designed to execute a computer program for carrying out the method according to one of claims 1 to 10.