DE102015215357A1 - Determining a coupling status of a coupling - Google Patents

Abstract

Described is a method for determining a coupling status of a clutch (5), the input side with a crankshaft (13) of a drive train of an internal combustion engine (3) and the output side with a transmission input shaft (15) of a transmission (7) of the drive train is coupled in the coupling status or solved, the method comprising: determining an actual rotational speed (n, 21) of the internal combustion engine (3); for each possible gear ratio of the transmission (7): calculating an expected speed (n model, i.Gang) of the internal combustion engine associated with the coupling status based at least on a speed signal (45) and the respective gear ratio; Calculating a difference (95, nDif, i.Gang) associated with the respective gear ratio from the actual speed and the expected speed; the method further comprising: determining a speed difference threshold (99) in response to a time gradient of a torque of the drive train (97, MMK, mKM); Detecting a coupling status if a minimum of the calculated differences is less than the speed difference threshold (99), the speed difference threshold being continuously updated.

Description

The present invention relates to a method for determining a coupling status of a clutch and a motor control unit, which is designed to carry out the method.

In motor vehicles, clutches are used to establish or release the coupling between the drive motor and the transmission. In a vehicle, e.g. a four-wheeled or two-wheeled vehicle, the coupling between the transmission and the engine is made by a frictional connection of a clutch. A coupling may e.g. a clutch disc which may be clamped between two attached to the engine crankshaft discs. In this case, one disk may be the flywheel rigidly connected to the crankshaft and the other may be the co-rotating so-called pot / pressure disk, which is pressed against the flywheel with a diaphragm spring. In this case, the clutch disc may be connected in a torsionally rigid manner by means of a toothed coupling with the transmission shaft. To release the clutch, the diaphragm spring, which presses with its outer edge on the cup wheel on the clutch disc can be lifted by being axially braced at its inner edge.

Modern motor vehicles are equipped with electronic control units that make it possible to perform or represent complex engine and vehicle functions. The control units or engine control units are supplied with signals on physical quantities, whereupon they calculate control signals for various components of the vehicle and output to them. A physical quantity represents the adhesion (referred to here as coupling status) of the vehicle clutch, which is conventionally only technically difficult to meter and expensive to mediate. For this reason, this variable is conventionally not detected by sensors, but modeled approximately by evaluating two switches along the clutch pedal travel and a processed signal of the neutral gear sensor. Conventionally, two switches - the clutch switch and the interlock switch - as well as the neutral gear detection are evaluated in a vehicle with manual transmission. With unactuated clutch, both switches are inactive, with halbgetretener clutch only the clutch switch and fully trimmed switch both are operated simultaneously. The switches are conventionally not selectively activated, but indicate that a certain threshold has been exceeded by the Kupplungspedalweg. Conventionally, adhesion, i. Coupling connected, closed when both the Interlockschalter and the clutch switch are made, the neutral gear detection is, however, unactuated. However, the evaluation of only these two hardware switches can lead to misstatements regarding the coupling status of the clutch.

For controlling an engine of the motor vehicle or other components of the motor vehicle, it may be advantageous to determine the coupling status of the clutch, i. connected (i.e., existing traction) or dissolved (i.e., no existing traction) to know. Conventionally, so-called hardware switches are evaluated for this purpose. However, these only allow evidence of traction (i.e., coupled or released to coupling status) when the clutch is fully opened or completely closed or in a coupled state. According to the state of the art, at intermediate positions of the coupling between the coupling status and the coupling status, no indication of the coupling status, i. Presence or absence of the frictional connection are made. From the prior art, a detection of the coupling status via hardware switches is also known, wherein a neutral gear detection is included, which is however relatively slow and inaccurate.

The patent DE 10207940 B4 discloses a method and apparatus for traction detection in vehicles with manual transmission, wherein a formed from engine speed and wheel speed quotient with the fixed gear ratios of the individual gears of the vehicle transmission is compared and detected at compliance to adhesion, wherein a speed-monitoring function is provided such that the adhesion detection is only allowed for the speed matching a gear.

The published European patent application EP 1950461 A2 discloses a determination arrangement for determining an engagement state of a clutch, wherein it is determined that the clutch is in an engaged state when it remains determined for a reference time that a ratio between an actual engine speed and an actual rotational speed of a drive system is substantially equivalent to a pre-calculated one Ratio of one of the gears is.

The European patent EP 2331848 B1 discloses a method for determining the state of a transmission, wherein during a predetermined period of time the change in gear ratio of a vehicle and the inertia, which is accelerated, are observed to determine a state of the vehicle transmission.

The US patent US 7,517,301 B2 discloses a method for determining a gear ratio of a manual transmission, wherein a current transmission output speed is determined based on the vehicle speed in response to a torque request signal, further determining an effective gear ratio based on the engine speed and the transmission output speed, and wherein the effective transmission gear Ratio is compared with each of the predetermined transmission gear ratios.

A detection of the coupling state of a clutch via a speed gradient can only detect a frictional connection when a gear is firmly engaged, and the clutch no longer slips.

An object of the present invention is to provide a method and an engine control unit for determining a coupling status of a clutch, wherein the coupling status can be reliably and easily determined without much additional hardware, in particular start-up operations can already be detected in slipping clutch. Furthermore, the coupling status should be determined faster and more accurately and be determinable in a variety of driving situations.

The object is achieved by the subject matters of the independent claims, which are directed to a method for determining a coupling status of a clutch or to an engine control unit. Further advantageous embodiments of the invention will become apparent from the subclaims and the following description of preferred embodiments of the present invention.

According to a first aspect of the present invention, there is provided a method of determining a coupling status of a clutch input coupled to a crankshaft of a powertrain of an internal combustion engine and output side to a transmission shaft of a transmission of the powertrain coupled or released in the coupling state, the method comprising :
Determining an actual rotational speed of the internal combustion engine;
for every possible gear ratio of the gearbox:
Calculating an expected speed of the internal combustion engine associated with the coupling status based at least on a speed signal and the respective gear ratio;
Calculating a difference between the actual speed and the expected speed associated with the respective gear ratio;
the method further comprising:
Determining a speed difference threshold as a function of a time gradient of a torque of the drive train;
Detecting a coupling status if a minimum of the calculated differences is less than the speed difference threshold,
wherein the speed difference threshold is continuously updated.

Information about the detected coupling status may be used for a variety of functions within a vehicle, in particular to increase driving safety and ride comfort.

Embodiments may be implemented in engine control units of manual cars or motorcycles.

Up-and-down moving pistons within cylinders of the internal combustion engine can drive the crankshaft during operation. The transmission may include a manual transmission with four, five, six or more gears and a reverse gear. The clutch may be disposed between the crankshaft and the transmission shaft to couple and connect both shafts in the coupling state connected by frictional engagement and released in the coupling state from each other.

The determination of the actual speed of the internal combustion engine may be e.g. by means of an encoder or other sensor, e.g. can output an angular velocity or a number of revolutions per unit time. The respective gear ratio of the transmission may be determined as a ratio of a rotational speed of an input shaft of the transmission and a rotational speed of an output shaft of the transmission when a certain gear is engaged. The output shaft of the transmission may be coupled to drive wheels of the vehicle in which the internal combustion engine and the clutch are arranged.

Coupled in the coupling state, the crankshaft is connected to the transmission output shaft via the clutch, the transmission input shaft and the transmission, so that at a known engaged gear, ie known ratio, can be closed by the rotational speed of the crankshaft to the rotational speed of the transmission output shaft. Since initially the engaged gear, and thus the gear ratio, can be unknown, expected speeds for all possible gears engaged, ie all possible gear ratios are calculated. The speed signal may include, for example, a rotational speed of the transmission output shaft, a rotational speed of a drive wheel or a driving speed of the vehicle.

Differences are then calculated, each time from the actual speed and the speed associated with the associated gear ratio. The speed difference threshold need not be constant in time, but may change with time, in the case in which a torque of the drive train (strong) changes, so that its time gradient is large. In this case, the torque of the drive train, e.g. torque supplied by the crankshaft (also referred to as clutch-side engine torque) and / or torque applied to the transmission input shaft (also referred to as modeled clutch torque).

The temporal gradient can represent as a time derivative (Differenziation) of the torque of the drive train. The dependence of the speed difference threshold may e.g. as a function of the absolute value of the temporal gradient of the torque of the drive train. With a comparatively large torque gradient of the drive train, driveline oscillations may occur which would distort the determination of the coupling status unless the speed difference threshold were adjusted. A large temporal gradient of the torque of the drive train may indicate a load change, in particular a large change in a requested torque.

It is further noted that the clutch is in the coupled state when the smallest calculated difference (ie, the minimum of calculated differences) is less than the speed difference threshold, which is continuous (eg, at time intervals) as a function of the time gradient of the powertrain torque one-hundredth of a second, one-tenth of a second, 0.5 second or 1 second, or at intervals between 0.1 second and 10 seconds).

In this case, it is thus recognized on a positive connection of the clutch via a correct gear ratio of the transmission. The detection of the minimum of the speed differences may be combined with other detection methods for detecting the coupling status of the clutch. This can reliably, quickly and without a large amount of hardware, the adhesion or the coupling status of the clutch are detected in a variety of driving situations. The information about the coupling status can be used advantageously in other functions in order to achieve a comfort gain.

The speed difference threshold may be raised (i.e., increased) for an increasing (i.e., increasing) absolute amount (a value that is always greater than or equal to zero) of the torque gradient of the powertrain. The temporal gradient may e.g. be positive or negative, but the absolute value of the temporal gradient is always positive. If the torque of the drivetrain changes, this can lead to driveline vibrations, which can lead to inaccuracies in the determination of the speed difference. In order to reduce or avoid false statements about the coupling state of the clutch due to the drive train vibrations, the speed difference threshold is raised with large changes in the torque of the drive train, in particular increased suddenly, if an amount of the temporal gradient of the torque of the drive train exceeds a gradient threshold. A sudden increase may require not filtering the gradient of the torque of the drive train and also the amount of the temporal gradient of the torque of the drive train, e.g. Filter bandpass, thus avoiding a signal delay. The speed difference threshold can thus be increased immediately if the amount of the temporal gradient of the torque exceeds the gradient threshold in an unfiltered manner. Thus, a reliable detection can be achieved on the coupling state.

For a period of time (eg, between 0.1 s and 5 s), the determination of the coupling status may be suspended based on the calculated differences and the speed difference threshold, and instead the coupling status may be determined as the previously determined coupling status. For example, a temporal Entprellung be performed, in particular a temporary suspension of the detection function the coupling status, during which the (previously) determined coupling state remains unchanged ("frozen").

The differences in rotational speeds may be debounced before the determination of the minimum, and the speed difference threshold may be low-pass filtered or reduced in size as the amount of the temporal gradient falls below the gradient threshold. The low-pass filtering of the differences can reduce noise and thus reduce misidentification of the coupling status. The speed difference threshold can thus be reduced more slowly than it is increased, if initially the time gradient of the torque of the drive train exceeds the gradient threshold and then (at a later time) the time gradient of the torque falls below the gradient threshold. The reduction of the speed difference threshold may in particular be effected in accordance with an attenuation of the drive train vibrations, which are damped due to friction. Thus, an adaptation of the speed difference threshold to amplitudes of disturbing drive train vibrations can be achieved, whereby a detection of the coupling status of the clutch can be improved.

The speed signal used to calculate the expected speed may be indicative of a vehicle speed of a vehicle including the clutch, wherein calculating the expected speed of the internal combustion engine associated with the coupling status may further be based on a wheel dimension of a drive wheel of the vehicle. Due to the vehicle speed and the wheel dimensions (e.g., diameter, radius) of the drive wheel, it is possible to deduce the rotational speed of the drive wheel and thus the rotational speed of the transmission output shaft. The vehicle speed signal and also the wheel dimension of the drive wheel are conventionally available physical quantities. Thus, additional sensors for performing the method need not be necessary.

The torque of the drive train may include a drive-related (drive by the internal combustion engine), torque applied to the clutch on the input side (for example, a torque of the crankshaft immediately on the input side of the clutch). In this case, determining the drive-related torque applied to the clutch on the input side can comprise at least one determination of an amount of fuel which is supplied to the internal combustion engine. The drive-related, the input side applied to the clutch torque can also be referred to as a motor torque at the clutch level. This can be conventionally determined by known methods. For this, e.g. a combustion process in a combustion chamber of the internal combustion engine are modeled to determine an indicated torque generated directly by the internal combustion engine. Furthermore, taking into account friction losses, a torque transmitted to the crankshaft can be determined, and finally the engine torque at the clutch level (drive-related torque applied to the clutch on the input side).

The speed difference threshold can be determined in embodiments of the present invention, depending on (only) a time gradient of the drive-related, on the input side torque applied to the clutch. In other embodiments, further e.g. Torques are consulted, depending on which the speed difference threshold can be determined or changed.

The method may further comprise determining a torque applied on the output side (also referred to as a modeled clutch torque) based on an inertia-related torque applied on the input side of the clutch and the input torque on the input side of the clutch, the torque of the drive train also being the torque may include certain output on the clutch torque applied.

The inertial, on the input side applied to the clutch torque can e.g. be determined by a product of an inertial moment and a temporal change in a rotational speed of the internal combustion engine. From the engine torque at the clutch level (input torque applied to the clutch on the input side), the product of moment of inertia and speed acceleration can be subtracted to determine the modeled clutch torque (the torque applied to the clutch on the output side). If the coupling state of the clutch is determined to be released, then the drive-related torque applied to the clutch on the input side can be substantially the inertia-related torque applied to the clutch on the input side, so that a torque applied to the clutch on the output side is essentially determined to be zero ,

The speed difference threshold can thus be changed as a function of, for example, the maximum (or another function) from the absolute values of the time change of the drive-related torque applied to the clutch on the input side and the torque applied to the clutch on the output side. Thus, the determination of the coupling state of the clutch can be further improved.

Further, coupled to a coupling status (even then) may be inferred if a minimum of the calculated unbalanced differences is less than the speed difference threshold and the particular torque applied to the clutch is greater than a torque threshold. Thus, the coupling state can be determined even more reliable and accurate.

The method may further comprise determining a time change in an amount of the particular output torque applied to the clutch, and solving a coupling status determination if the time change of the magnitude of the particular torque applied to the clutch is less than a further gradient threshold is less than zero. In this case, it can be determined that the torque applied to the output side of the clutch drops, which can take place when the coupling status changes to released. However, due to filtering of the signals, the detection of the drop in the torque applied to the output side of the clutch can be relatively slow, although the drop is in fact erratic. By means of a comparison of the change over time of the amount of the specific torque applied to the clutch on the output side against the further gradient threshold, a decoupling between the crankshaft and the transmission input shaft can be reliably concluded.

According to another aspect of the present invention, there is provided an engine control apparatus configured to execute or control a method of determining a coupling status of a clutch according to any one of the preceding embodiments. The engine control unit may e.g. comprise a processor and a memory in which a software program product is loaded, which receives instructions which, when executed by the processor, perform a method for determining a coupling status of a clutch, as explained in the embodiments described above.

Embodiments of the present invention will now be explained with reference to the attached drawings. The invention is not limited to the illustrated or described embodiments.

1 schematically illustrates a part of a vehicle having a clutch and an engine control unit according to an embodiment of the present invention, which is configured to carry out a method for determining a coupling status of a clutch according to an embodiment of the present invention;

2 schematically illustrates a method for determining a coupling status of a clutch according to an embodiment of the present invention;

3 Figure 10 illustrates graphs in a graph illustrating powertrain vibrations taken into account in accordance with embodiments of the present invention;

4 illustrates quantities calculated in embodiments of the present invention;

5 Figure 10 illustrates graphs in a graph that are calculated in a method for determining a coupling status according to embodiments of the present invention;

6 FIG. 10 illustrates curves illustrating a modeled coupling moment calculation as employed in embodiments in accordance with the present invention; FIG.

7 illustrates a scheme for determining a force flow or coupling status according to an embodiment of the present invention;

8th schematically illustrates a method of detecting a coupling status based on a speed difference according to an embodiment of the present invention; and

9 illustrates a possible implementation for detecting a coupling status of a clutch according to an embodiment of the present invention.

The in 1 illustrated part 1 of a vehicle comprises an internal combustion engine 3 , a clutch 5 , a gearbox 7 , at least one drive wheel 9 , as well as an engine control unit 11 , which is designed and configured for controlling vehicle functions, a method for determining a coupling status of a clutch, in particular the clutch 5 perform. The coupling 5 is on the input side with the crankshaft 13 a drive train of the internal combustion engine 3 coupled and is the output side with a transmission shaft, more precisely, a transmission input shaft 15 , the transmission 7 coupled to the drive train.

About schematically in 1 illustrated piston rods 17 , which are connected to pistons, which within cylinders of the internal combustion engine 3 are driven back and forth, drives the internal combustion engine 3 the crankshaft 13 at. For determining a rotational speed of the internal combustion engine 3 is a sensor 19 provided, which is a measurement signal 21 to the control unit 11 transmitted, wherein the measurement signal 21 the actual speed of the internal combustion engine 3 displays.

The gearbox allows a coupling of the gearbox input shaft 15 with a gearbox output shaft 23 over a plurality of gear ratios, including the transmission 7 Has associated with different gears associated gears, as is known in the art.

The coupling 5 has an engine flywheel 25 on which rigid with the crankshaft 13 connected is. A clutch disc 27 is between the engine flywheel 25 and a pressure washer 29 the clutch 5 arranged which thrust washer 29 with the clutch disc 27 and the engine flywheel 25 can be moved into a traction (coupled state) by a clutch lever 31 is released or released, so that a diaphragm spring 33 goes into a non-prestressed state. In 1 is the coupling state solved the clutch 5 illustrated. Connected in a coupling state, there is a frictional connection both between the engine flywheel 25 and the clutch disc 27 as well as between the clutch disc 27 and the pressure disc 29 ,

The engine control unit 11 is configured to perform a method for determining a coupling status of a clutch according to an embodiment of the present invention, which is schematically illustrated in FIG 2 as a procedure 35 is illustrated. In the process step 37 is an actual speed (eg by the signal 21 ) of the internal combustion engine 3 certainly. Then, a loop for every possible transmission ratio of the transmission 7 carried out. This is done in a query step 39 queried whether already for all gears of the transmission 7 in the process steps 41 and 43 specified calculations have been performed. If this is not the case, then it becomes the procedural step 41 branches, in which one, connected in coupling status, expected speed of the internal combustion engine 3 at least based on a speed signal, eg signal 45 , which corresponds to the driving speed of the vehicle, and the respective transmission ratio is calculated. Further, in the process step 43 calculates a difference between the actual speed and the expected speed assigned to the respective gear ratio. Then the process branches again to the query 39 that loop in a loop to the process steps 41 and 43 returns, as there are other gear ratios of the transmission 7 for which the required values have not yet been calculated.

When all the differences associated with the respective gear ratio have been calculated from the actual speed and the expected speed associated with that gear ratio, the step becomes 47 in which a speed difference threshold is determined as a function of a time gradient of a torque of the drive train. In the process step 49 Finally, a coupling status is detected connected if a minimum of the calculated differences is less than the speed difference threshold, wherein the speed difference threshold is updated continuously.

The engine control unit 11 then gives the detected coupling status, eg as a signal 51 to one or more vehicle components and / or uses the detected coupling status of the clutch 5 in further internal calculations to determine or determine various control signals.

That in the process 35 used torque of the drive train may include, for example, a motor torque at the clutch level or be (also as drive-related, input side of the clutch 5 applied torque), which thus at the end of the crankshaft or on the engine flywheel 25 is applied. Alternatively or additionally, the torque of the drive train may include or be a modeled clutch torque (also as an output side, on the clutch 5 applied torque), thus indicating the transmission input shaft 15 if there is an adhesion between Flywheel 25 and thrust washer 29 consists, which is connected in the coupling state rotatably connected to the transmission input shaft.

The engine torque at the clutch level is abbreviated to MMK and the modeled clutch torque is abbreviated as mKM. The clutch-level engine torque is conventionally available. This value indicates how much torque is available at the clutch. In one approach of the present invention, the moment that attaches to the clutch to the transmission 7 is transmitted, modeled and is then referred to as a modeled clutch torque. According to embodiments of the invention, a positive connection is made (ie connected to the coupling state) as soon as this modeled clutch torque exceeds a certain threshold. According to one embodiment of the present invention, the modeled clutch torque mKM is calculated from the engine torque at the clutch level (MMK) and an inertia-related torque applied to the clutch on the input side according to the following equation: -MKM = MMK-J * d / dt (n) * 2 * π / 60 (Eq. 1)

Here, J denotes the moment of inertia of the internal combustion engine 3 including all mitrotierten masses up to the engine flywheel 25 and n denotes the rotational speed of the internal combustion engine 3 , If the modeled clutch torque mKM now exceeds a certain threshold, then the clutch is connected to a traction, that is to say to a coupling state 5 closed. The modeled clutch torque corresponds to that via the clutch 5 on the gearbox 7 transmitted moment. Without traction, no moment can be transmitted, so zero would be calculated on the left side of the above equation. This means that as soon as a modeled clutch torque> 0 Nm is calculated from the above formula, it is possible to start from an at least partially closed drive train.

The torque threshold can be used with a warm engine, e.g. between 20 and 40 Nm, with a cold engine e.g. between 50 and 70 Nm. Other values are possible.

The engine torque at clutch level (MMK) may indicate an error if the loss (torque) e is not known exactly. In addition, the signal has to be filtered relatively strongly, since the engine speed gradient (d / dt (n)) represents a reaction to the engine torque, which must first be measured and thus available later. Since the engine speed gradient signal, which eg from the speed signal 21 can be calculated by time derivative, is available with delay, it is ground as well as the engine torque at the clutch level by a low-pass filtering. Different filter time constants (eg between 100 ms and 500 ms, other values are possible) can be used. This heavy filtering can reduce noise and increase accuracy, but at the cost of timing inaccuracies. With the driveline opening, the modeled clutch torque must be filtered only below the detection threshold, which delays the detection of the open drivetrain. For this purpose, a blanking is provided, which becomes active as soon as the gradient of the amount of the modeled clutch torque falls below a certain threshold.

In 3 curves are represented in a graph in which the abscissa 53 the time and the ordinate 55 displays the values of different physical quantities. The curve 57 indicates the engine speed, the curve 59 indicates the engine speed gradient, the curve 61 indicates the engine torque at clutch level (MMK) and the curve 63 indicates the modeled clutch torque (mKM) calculated according to the above equation. At the time 65 a shift from push to pull under traction (ie, coupled state connected) was performed at the time 67 became the clutch 5 opened under load, ie offset open in the coupling state. As can be seen, the modeled clutch signal (on curve 63 ) due to the filtering time slow from, although the transmission input shaft 15 already completely off the crankshaft 13 is decoupled. However, if the gradient of the amount of the modeled clutch torque is evaluated, whether it has fallen below a certain threshold, it can be reliably concluded that a coupling state has been achieved.

In the process, the model can detect clutch operations and a sliding clutch at high speed deviations as an existing traction.

The inertia of the signal can delay detection mainly at very small modeled clutch torques (eg below 40 Nm, other values are possible). In particular, in the event that very little torque is transmitted and a gear is engaged positively, this can Detection method with the detection or using the speed differences (described below) are combined, since the model can not make any statement about the drive train state in this situation.

According to an embodiment of the present invention, the coupling state is detected based on calculated speed differences. Manual transmissions typically have fixed gear ratios which are dependent upon the gear engaged. This results in a typical ratio of engine speed and vehicle speed (the so-called n-v ratio). If the current ratio does not coincide with any of the gears specified by the geometry of the transmission, it is to be assumed that no gear stage is engaged in a force-fitting manner and the drive train is thus opened, ie. the coupling is released in the coupling state.

According to embodiments of the present invention, for each possible gear of the transmission 7 calculated a model speed, with which the engine 3 would rotate at a given speed of the vehicle, if full adhesion would be made, ie if the coupling state would be connected. Their distance from the actual engine speed can provide information about whether there is a full-force transmission ratio.

The transmission output speed is determined from the vehicle speed according to the following equation:

From the transmission output speed can be calculated using the gear ratios r _{i, gear} from the gearbox data equivalent model speeds according to the following formula: n _{model i.Gang} = r · n _{i.Gang transmission output} (Eq. 3)

From the difference between the engine speed and the model speeds, differential speeds result as follows: n _{Dif, i.Gang} = n _Motor - n _{Model, i.Gang} ( _Figure 4)

The smaller the differential speed, the more likely it is that a gear is engaged and traction is present, i. the coupling state is connected.

3 illustrated in a coordinate system with an abscissa 69 , which indicates the time, and an ordinate 71 indicating different physical quantities, a curve 73 , which indicates the engine speed, and a curve 75 , which illustrates the engine torque at the clutch level. With strong gradients of the clutch torque to be transmitted, there are powertrain vibrations, which are reflected in a speed deviation. If the adhesion detection takes place via a comparison of the rotational speed difference with a threshold value, the threshold value can be undershot, which could be incorrectly interpreted as a coupling state. Out 4 It can be seen that inaccuracies in the engine speed, especially at high gradients of the engine torque at the coupling level, eg at the times 68 and 70 respectively. For this reason, an expansion (ie increase) of the speed difference threshold is provided at high gradients in the clutch torque or in the engine torque at the clutch level.

This expansion (magnification) is then returned to the original value, but not jumped but slower than the threshold was increased.

Coincidentally, however, it may also happen that a correct transmission ratio is established, even though the drive train is open. In this case, a false positive would be detected if the vehicle, for example. With open drive train rolls out, as in 4 illustrated in a graph, the abscissa 77 indicating the time, and the ordinate 79 indicates different physical quantities. The curve 81 indicates the engine speed, the curve 83 the differential speed, the curve 85 a constant differential speed threshold and the 87 the vehicle speed. The vehicle rolls out with the clutch depressed, but the speed difference drops anyway 83 occasionally randomly below the threshold 85 , As a remedy, the speed differences are debounced, so that random short-term undershooting of the threshold are suppressed. One Accidental recognition of a correct gear ratio can be effectively prevented by debouncing, but this makes the detection of open, unlocked powertrains sluggish.

The differential speed method for determining the coupling status can be functionally implemented as follows:
First, for each possible gear, the model speeds are calculated according to Eq. 3 calculated. They are subtracted from the actual engine speed to produce differential speeds in accordance with Eq. 4, of which the smallest amount is compared with a threshold to be applied. If this value is undershot, it may be assumed that a suitable gear ratio exists, so that it is concluded that a coupling state is connected. Due to the faulty determinations during load changes, the threshold value is immediately widened during load changes and then reduced again. The goal is that the driveline oscillations within this expanded boundary can calm down without exceeding the threshold. The differential speed is thereby framed uninterrupted by the recognition window. The expansion depends on the maximum value of the gradient of the engine torque at the clutch level and the gradient of the modeled clutch torque. The engine torque allows a fast response of the function with the driveline closed, while the modeled clutch torque provides indications of driveline vibration that were not triggered by the moment of the engine.

6 illustrated in a graph with abscissa 89 , which indicates the time, and ordinate 91 indicating different physical quantities, a curve 93 , which indicates the engine speed, a curve 95 , which indicates the differential speed, a curve 97 , which indicates the engine torque at the clutch level and a curve 99 , which indicates the differential speed threshold, which is selected as a function of the gradient of the engine torque at the clutch level and is accordingly updated continuously.

As from the curve 99 can be seen, is at large changes in the engine torque at the clutch level (curve 97 ), eg at times 88 and 90 , the differential speed threshold 99 suddenly increased and then slowly reduced again.

It is useful for the detection of the coupling status based on the consideration of the speed differences to combine this method with another method, e.g. with the method described above, which is based on the modeled clutch torque.

7 FIG. 12 illustrates a scheme for determining a force flow or coupling status in accordance with an embodiment of the present invention. FIG. In the block 101 is the modeled clutch torque according to the above Eq. 1 calculated. In the block 103 the comparison is made with a torque threshold, wherein when a first torque threshold is exceeded 105 is closed connected to coupling state and falls below a second torque threshold 107 (which is smaller than the first torque threshold 105 is closed) is released on coupling state. In short, the adhesion status is thus recognized by the amount of the modeled clutch torque with a hysteresis. For strongly negative gradients of the amount of modeled clutch torque becomes a skip function 109 active. If this skip function is active, then the connection state is closed. The coupling state or adhesion status becomes element 111 output.

8th schematically illustrates a method for detecting a coupling status based on a speed difference. Based on the vehicle speed, the wheel diameter D (s. 1 ) and the gear ratios of the transmission 7 A modeled speed (eg, according to equation 3) is calculated via the respective current vehicle speed with which the engine would have to rotate if the respective gear had been engaged and a coupling state would have been present. From these model speeds, in each case the difference of the actual engine speed is formed so that modeled differential speeds (eg according to equation 4) are calculated. The gear with the smallest differential speed can be determined as the next most plausible gear. The differential speed is continuously recalculated and compared with thresholds. If the differential speed is less than the threshold, the gear is considered to be engaged. Only after debouncing the gear is recognized as recognized plausibility. However, this debouncing can also be ended prematurely, if it is confirmed from another source of information that moment is transmitted and that the gear ratio is not just randomly correct. Then the gear is output directly as recognized.

The differential speeds are in the block 113 and the thresholding is calculated in the block 115 educated. The speed difference threshold is dependent on the torque gradient at the clutch level of the engine. The gradient of the modeled clutch torque (see eg Block 101 in 7 ). The lower the gradient in magnitude, the narrower the range, that is, the lower the differential speed threshold within which the gear is considered potentially engaged, and within which it is closed when coupled. The background here is that with drive train vibrations caused by load changes, the transmission ratio does not oscillate for a short time. The enlargement or reduction of the differential speed threshold as a function of the gradient of the engine torque at the clutch level can "envelop" the drive train vibration, ie be formed according to an amplitude of a drive train vibration. The expansion of the oscillation can take place directly and unfiltered, while the constriction can run low-pass filtered. The debounce is in the block 117 performed and the comparison of the differential speeds with the differential speed threshold is in block 119 carried out.

The traction status 121 can eg the traction status 111 out 7 correspond. If this traction status is determined to be closed or connected and at the same time the speed difference is less than the speed difference threshold, the result block is displayed 123 detected connected to coupling status and issued that gear as engaged, which leads to the lowest speed difference.

9 illustrates a possible implementation for detecting a coupling status of a clutch combining both proposed methods.

The variable a is calculated true if, based on the method based on the modeled clutch torque, a coupling status is determined to be connected. Otherwise the variable will be set as wrong.

The variable b is set to true if the method for determining the coupling statuses determines a coupling status as being connected based on the speed differences. Otherwise, the variable b is set to false.

The variable o has the meaning that the coupling state is validly determined to be open, the variable vo has the meaning that the coupling state is provisionally determined to be open.

The variable vg has the meaning that the coupling status is provisionally determined to be closed, the variable g has the meaning that the coupling state is found valid closed.

The variable vg is set if the variable a is true, otherwise the variable o is set. The variable g is set if the variable b is true, otherwise the variable vo is set. If the variable vg is set and additionally the variable b, the variable g is set. If the variable vo is set and in addition the variable a is not set, the variable o is set. Furthermore, if variable o is set, variable g is set if variable b is set. Other implementations are possible.

LIST OF REFERENCE NUMBERS

1

Part of a vehicle

3

Internal combustion engine

5

clutch

7

transmission

9

drive wheel

11

Engine control unit

13

crankshaft

15

Transmission input shaft

17

piston rods

19

sensor

21

measuring signal

23

Transmission output shaft

25

Flywheel

27

clutch disc

29

thrust washer

31

clutch lever

33

diaphragm spring

35

method

37, 41, 43 47, 49

 steps

39

query

45

speed signal

51

output

53, 69, 77, 89

abscissa

55, 71, 79, 81

 ordinate

57, 61, 73, 75

 curves

81, 83, 85, 87

 curves

93, 95, 97, 99

 curves

57, 59, 61, 63

 curves

65, 67, 68, 70, 88, 90

 timings

101, 103, 109, 111

 blocks

105, 107

 threshold

113, 115, 117, 119, 121, 123

 scheme blocks

a, b, o, vo, vg, g

 Variables of the engine control unit

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

• DE 10207940 B4 [0005]
• EP 1950461 A2 [0006]
• EP 2331848 B1 [0007]
• US 7517301 B2 [0008]

Claims (10)

Method for determining a coupling status of a coupling ( 5 ), the input side with a crankshaft ( 13 ) of a drive train of an internal combustion engine ( 3 ) and the output side with a transmission input shaft ( 15 ) of a transmission ( 7 ) of the powertrain is connected or released in the coupling state, the method comprising: determining an actual rotational speed (n, 21 ) of the internal combustion engine ( 3 ); Performing, for each possible gear ratio of the transmission ( 7 ) The steps of: calculating an expected coupled at coupling status speed (n _{model i.Gang)} of the internal combustion engine at least based (on a speed signal 45 ) and the respective gear ratio; Calculating a difference associated with the respective gear ratio ( 95 , n _{Dif, i.Gang} ) from the actual speed and the expected speed; the method further comprising: determining a speed difference threshold ( 99 ) as a function of a time gradient of a torque of the drive train ( 97 , MMK, mKM); Detecting a coupling status if a minimum of the calculated differences is less than the speed difference threshold ( 99 ), wherein the speed difference threshold is continuously updated. Method according to claim 1, wherein the speed difference threshold ( 99 ) for an increasing absolute value of the temporal gradient of the torque ( 97 , MMK, mKM) of the drive train is raised. Method according to claim 1 or 2, wherein the speed difference threshold ( 99 ) is increased abruptly if an amount of the temporal gradient of the torque ( 97 , MMK, mKM) of the drive train exceeds a gradient threshold and / or wherein, for a period of time, the determination of the coupling status based on the calculated differences and the speed difference threshold ( 99 ), and instead the coupling status is determined as the previously determined coupling status. Method according to one of the preceding claims, wherein the differences ( 95 , n _{Dif, i.Gang} ) are _debounced before the minimum is determined and the speed difference threshold is low-pass filtered or reduced with respect to increasing the lesser amount of a time change as the amount of the time gradient falls below the gradient threshold , Method according to one of the preceding claims, wherein the speed signal ( 45 ) is indicative of a vehicle speed of a vehicle including the clutch, and wherein calculating the expected speed of the internal combustion engine associated with coupling statuses further based on a wheel dimension (D) of a wheel ( 9 ) of the vehicle takes place. Method according to one of the preceding claims, wherein the torque of the drive train comprises a drive-dependent, on the input side of the clutch applied torque (MMK), wherein the determining of the drive-related, on the input side of the clutch torque (MMK) comprises at least one determination of an amount of fuel, which Internal combustion engine ( 3 ) is supplied.  The method of any one of the preceding claims, further comprising: Determining a torque applied on the output side to the clutch based on an inertia-related torque applied on the input side to the clutch and the drive-related torque applied to the clutch on the input side (MMK), wherein the torque of the drive train further comprises the specific output side of the clutch torque applied (mKM).  A method according to any one of the preceding claims, wherein closing occurs associated with a coupling status if a minimum of the calculated unbalanced differences is less than the speed difference threshold and the particular torque applied to the clutch side is greater than a torque threshold. The method of claim 7 or 8, wherein the method further comprises: determining a change over time of an amount of the particular output torque applied to the clutch (mKM); and determining a coupling status, if the change with time of the amount of the specific torque applied to the clutch on the output side (mKM) is less than a further gradient threshold which is less than zero. Engine control unit ( 11 ) configured to execute or control a method according to any one of the preceding claims.

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