Determining the coupling status of a coupling

Abstract

Method for determining the coupling status of a clutch (5) that is coupled on the input side to a crankshaft (13) of a drive train of an internal combustion engine (3) and on the output side to a transmission input shaft (15) of a transmission (7) of the drive train, in the coupled state or disengaged, wherein the method comprises: determining an actual rotational speed (n, 21) of the internal combustion engine (3); performing, for each possible transmission ratio of the transmission (7), the steps of: calculating an expected rotational speed (nModel,i.Gear) of the internal combustion engine when coupled, at least based on a speed signal (45) and the respective transmission ratio; calculating a difference (95, nDif,i.) associated with the respective transmission ratio.gear) from the actual speed and the expected speed; wherein the method further comprises: determining a speed difference threshold (99) as a function of a time gradient of a drive train torque (97, MMK, mKM); determining a coupled state if a minimum of the calculated differences is less than the speed difference threshold (99), wherein the speed difference threshold is continuously updated by repeating the determination of the speed difference threshold (99) as a function of the gradient of the drive train torque (97, MMK, mKM).

Description

[0001] The present invention relates to a method for determining the coupling status of a clutch and to an engine control unit configured to execute the method.

[0002] Clutches are used in motor vehicles to connect and disconnect the engine and transmission. In a vehicle, such as a four-wheeled or two-wheeled vehicle, the connection between the transmission and engine is established by the frictional engagement of a clutch. A clutch can, for example, consist of a clutch disc, which may be clamped between two discs attached to the engine crankshaft. One disc can be the flywheel, rigidly connected to the crankshaft, and the other can be the rotating clutch disc, also known as the pot or pressure disc, which is pressed against the flywheel by a diaphragm spring. The clutch disc can also be rigidly connected to the transmission shaft via a gear coupling. To disengage the clutch, the diaphragm spring, which presses against the clutch disc via the pot disc with its outer edge, can be released by axially compressing its inner edge.

[0003] Modern motor vehicles are equipped with electronic control units (ECUs) that enable the execution and representation of complex engine and vehicle functions. These ECUs, or engine control units, receive signals about physical quantities, which they then use to calculate and output control signals for various vehicle components. One such physical quantity is the frictional engagement (referred to here as the "engaged" state) of the vehicle's clutch, which is conventionally difficult and expensive to measure. Therefore, this quantity is not typically measured directly by sensors, but rather approximated by evaluating two switches along the clutch pedal travel and a processed signal from the neutral gear sensor.In a vehicle with a manual transmission, two switches – the clutch switch and the interlock switch – as well as the neutral gear detection are conventionally evaluated. With the clutch disengaged, both switches are inactive; with the clutch half-engaged, only the clutch switch is active; and with the clutch fully engaged, both are activated simultaneously. The switches are not typically activated at a specific point, but rather indicate that a certain threshold of clutch pedal travel has been exceeded. Conventionally, a positive clutch engagement (i.e., a connected clutch state) is assumed when both the interlock and clutch switches are activated, but the neutral gear detection is inactive. However, evaluating only these two hardware switches can lead to inaccurate conclusions regarding the clutch's engagement status.

[0004] To control a motor vehicle's engine or other vehicle components, it can be advantageous to know the clutch's engagement status, i.e., engaged (meaning there is a force transmission) or disengaged (meaning there is no force transmission). Traditionally, this is done using hardware switches. However, these switches only provide information about the force transmission (i.e., the engagement status – engaged or disengaged) when the clutch is fully open or disengaged, or fully closed or engaged. According to the current state of the art, in intermediate clutch positions between the engaged and disengaged states, no information can be provided about the engagement status, i.e., the presence or absence of a force transmission.Furthermore, detection of the coupling status via hardware switches is known from the prior art, which includes neutral position detection, but this is relatively slow and inaccurate.

[0005] Patent DE 10207940 B4 discloses a method and a device for detecting friction in vehicles with manual transmissions, wherein a quotient formed from engine speed and wheel speed is compared with the fixed gear ratios of the individual gears of the vehicle transmission and, if there is a match, friction is detected, wherein a speed monitoring function is provided such that the friction detection is only permitted for the speed appropriate to a gear.

[0006] The disclosed 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 engagement state if, for a reference time, it remains determined that a ratio between an actual machine speed and an actual rotational speed of a drive system is essentially equivalent to a pre-calculated ratio of one of the gears.

[0007] European patent EP 2331848 B1 discloses a method for determining the state of a transmission, wherein the change in the transmission ratio of a vehicle and the mass inertia, which is accelerated, are observed during a predetermined period of time in order to determine a state of the vehicle transmission.

[0008] US patent US 7,517,301 B2 discloses a method for determining a selection of a gear ratio of a manual transmission, wherein an instantaneous transmission output speed is determined based on the vehicle speed in response to a torque request signal, wherein furthermore an effective transmission gear ratio is determined based on the machine speed and the transmission output speed, and wherein the effective transmission gear ratio is compared with each of the predetermined transmission gear ratios.

[0009] Detecting the coupling state of a clutch via a speed gradient can only detect a power transmission when a gear is firmly engaged and the clutch is no longer slipping.

[0010] An object of the present invention is to provide a method and an engine control unit for determining the coupling status of a clutch, wherein the coupling status can be determined reliably and simply without significant additional hardware effort, and wherein, in particular, starting processes can be detected even when the clutch is slipping. Furthermore, the coupling status should be determined more quickly and accurately and be determinable in a multitude of driving situations.

[0011] The problem is solved by the subject matter of the independent claims, which relate to a method for determining the coupling status of a clutch or to an engine control unit. Further advantageous embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments of the present invention.

[0012] According to a first aspect of the present invention, a method for determining the coupling status of a coupling which is coupled on the input side to a crankshaft of a drive train of an internal combustion engine and on the output side to a transmission shaft of a transmission of the drive train, whether it is engaged or disengaged, is provided, wherein the method comprises: Determining the actual rotational speed of the internal combustion engine; for every possible gear ratio of the transmission: Calculating the expected rotational speed of the internal combustion engine when coupled, at least based on a speed signal and the respective gear ratio; Calculating the difference between the actual rotational speed and the expected rotational speed, corresponding to the respective gear ratio; the procedure further features: Determining a speed difference threshold as a function of a time gradient of a drive train torque; Determining a coupling status (connected) if a minimum of the calculated differences is less than the speed difference threshold, where the speed difference threshold is continuously updated.

[0013] Information about the detected coupling status can be used for a variety of functions within a vehicle, in particular to increase driving safety and driving comfort.

[0014] These designs can be implemented in engine control units of manually operated automobiles or motorcycles.

[0015] Pistons moving up and down within the cylinders of an internal combustion engine can drive the crankshaft during operation. The transmission can be a manual gearbox with four, five, six, or more gears, as well as a reverse gear. The clutch can be located between the crankshaft and the transmission shaft to couple the two shafts by friction in the engaged state and to disengage them in the disengaged state.

[0016] The actual rotational speed of the internal combustion engine can be determined, for example, using an encoder or other sensor that can output, for instance, an angular velocity or a number of revolutions per unit of time. The respective gear ratio of the transmission can be defined as the ratio of the rotational speed of an input shaft to the rotational speed of an output shaft when a specific gear is engaged. The transmission's output shaft can be coupled to the drive wheels of the vehicle in which the internal combustion engine and the clutch are located.

[0017] In the engaged state, the crankshaft is connected to the transmission output shaft via the clutch, the transmission input shaft, and the transmission itself. Therefore, if the selected gear (i.e., the gear ratio) is known, the rotational speed of the transmission output shaft can be inferred from the crankshaft's rotational speed. Since the selected gear, and thus the gear ratio, may initially be unknown, expected rotational speeds are calculated for all possible selected gears (i.e., all possible gear ratios). The speed signal can include, for example, the rotational speed of the transmission output shaft, the rotational speed of a drive wheel, or the vehicle's speed.

[0018] Differences are then calculated, each based on the actual rotational speed and the rotational speed assigned to the corresponding gear ratio. The speed difference threshold does not have to remain constant over time, but can change over time, particularly if the drivetrain torque also changes (significantly), resulting in a large temporal gradient. This drivetrain torque can include, for example, torque supplied by the crankshaft (also referred to as engine torque at the clutch level) and / or torque applied to the transmission input shaft (also referred to as modeled clutch torque).

[0019] The time gradient can be represented as a time derivative (differentiation) of the drivetrain torque. The dependence of the speed difference threshold can, for example, be a dependence on the absolute value of the time gradient of the drivetrain torque. With a comparatively large time gradient of the drivetrain torque, drivetrain vibrations can occur that would distort the determination of the coupling status if the speed difference threshold were not adjusted. A large time gradient of the drivetrain torque can indicate a load change, especially a large change in the requested torque.

[0020] It is further determined that the clutch is in the engaged state if the smallest calculated difference (i.e., the minimum of the calculated differences) is smaller than the speed difference threshold, which is continuously updated depending on the time gradient of the drive train torque (e.g., at intervals of one hundredth of a second, one tenth of a second, 0.5 seconds or 1 second, or at intervals in a range between 0.1 seconds and 10 seconds).

[0021] This method detects clutch engagement via a correct transmission ratio. Detection based on the minimum speed difference can be combined with other methods for determining the clutch engagement status. This allows for reliable, rapid detection of clutch engagement or engagement status in a wide range of driving situations, requiring minimal hardware. The information about the engagement status can then be used to enhance comfort in other functions.

[0022] The speed difference threshold can be raised (i.e., increased) for an increasing absolute value (a value always greater than or equal to zero) of the time gradient of the drivetrain torque. The time gradient can be positive or negative, but its absolute value is always positive. Changes in drivetrain torque can cause drivetrain vibrations, which can lead to inaccuracies in determining the speed difference. To reduce or even eliminate erroneous conclusions about the coupling state due to drivetrain vibrations, the speed difference threshold is raised for large changes in drivetrain torque, particularly if the time gradient exceeds a certain gradient threshold.A sudden increase may require not filtering the torque gradient of the drivetrain, nor the magnitude of the time gradient of the drivetrain torque (e.g., using a bandpass filter), in order to avoid signal delay. The speed difference threshold can therefore be increased immediately if the magnitude of the time gradient of the torque exceeds the gradient threshold in its unfiltered state. This allows for reliable detection of the coupling state.

[0023] For a period of time (e.g., between 0.1 s and 5 s), the determination of the coupling status based on the calculated differences and the speed difference threshold can be suspended, and instead, the coupling status can be determined as the previously determined coupling status. For example, temporal debouncing can be performed, specifically a temporary suspension of the coupling status detection function, during which the (previously) determined coupling state remains unchanged ("frozen").

[0024] The speed differences can be debounced or low-pass filtered before determining the minimum, and the speed difference threshold can be low-pass filtered or reduced with a smaller rate of change over time compared to increasing it, if the magnitude of the time gradient falls below the gradient threshold. Low-pass filtering of the differences can reduce noise and thus minimize false detection of the coupling status. The speed difference threshold can therefore be reduced more slowly than it is increased if the time gradient of the drivetrain torque initially exceeds the gradient threshold and subsequently (at a later time) the time gradient of the torque falls below the gradient threshold. Reducing the speed difference threshold can be achieved, in particular, by damping the drivetrain vibrations, which are damped due to friction.This allows the speed difference threshold to be adjusted to the amplitude of disruptive drivetrain vibrations, thereby improving the detection of the clutch's engagement status.

[0025] The speed signal used to calculate the expected rotational speed can be indicative of the vehicle speed of the vehicle encompassing the clutch. Furthermore, the calculation of the expected rotational speed of the internal combustion engine when the clutch is engaged can be based on the wheel dimensions of one of the vehicle's drive wheels. Based on the vehicle speed and the wheel dimensions (e.g., diameter, radius) of the drive wheel, the rotational speed of the drive wheel, and thus the rotational speed of the transmission output shaft, can be determined. Both the vehicle speed signal and the wheel dimensions of the drive wheel are readily available physical quantities. Therefore, no additional sensors are required to implement this method.

[0026] The torque of the drivetrain can include a drive-related torque (drive by the internal combustion engine) applied at the clutch input (e.g., a crankshaft torque directly at the clutch input). Determining this drive-related input torque at the clutch can at least involve determining the amount of fuel supplied to the internal combustion engine. This drive-related input torque at the clutch can also be referred to as engine torque at the clutch level. It can be determined conventionally using known methods. For example, a combustion process in a combustion chamber of the internal combustion engine can be modeled to determine an indicated torque directly generated by the engine.Furthermore, taking friction losses into account, a torque transmitted to the crankshaft can be determined, and finally, from this, the engine torque at the clutch level (drive-related input torque applied to the clutch) can be calculated.

[0027] In embodiments of the present invention, the speed difference threshold can be determined as a function (exclusively) of a time gradient of the drive-induced torque applied to the input side of the clutch. In other embodiments, further torques, e.g., can be included, as a function of which the speed difference threshold can be determined or changed.

[0028] The method can further include determining an output torque applied to the clutch (also referred to as modeled clutch torque) based on an inertia-induced input torque applied to the clutch and the drive-induced input torque applied to the clutch, wherein the drive train torque can further include the determined output torque applied to the clutch.

[0029] The inertial torque applied to the clutch input can be determined, for example, by the product of a moment of inertia and the rate of change of the internal combustion engine's rotational speed. The product of the moment of inertia and the rotational acceleration can be subtracted from the engine torque at the clutch level (the input torque applied to the clutch) to determine the modeled clutch torque (the output torque applied to the clutch). If the clutch is determined to be disengaged, the magnitude of the input torque applied to the clutch due to inertia can be essentially the same as the input torque applied to the clutch due to inertia, so that the output torque applied to the clutch is essentially zero.

[0030] The speed difference threshold can thus be changed depending on, for example, the maximum (or another function) derived from the absolute values ​​of the time-dependent changes in the input torque and output torque applied to the clutch, driven by the drive. This further improves the determination of the clutch's engagement state.

[0031] Furthermore, a connected coupling state can be inferred (even if) a minimum of the calculated unbounced differences is smaller than the speed difference threshold and the determined output torque at the coupling is greater than a torque threshold. This allows the coupling state to be determined even more reliably and accurately.

[0032] The method can further include determining the time-dependent change in the magnitude of a specific output torque applied to the coupling and detecting a disengaged coupling state if the time-dependent change in the magnitude of the specific output torque applied to the coupling is less than a further gradient threshold, which is less than zero. It can be determined that the output torque applied to the coupling decreases, which can occur when the coupling state changes to disengaged. However, due to signal filtering, the detection of the decrease in the output torque applied to the coupling can be relatively slow, even though the decrease actually occurs abruptly.By comparing the change over time of the magnitude of the specific output torque applied to the clutch against the further gradient threshold, a reliable conclusion can be drawn about a decoupling between the crankshaft and the transmission input shaft.

[0033] According to a further aspect of the present invention, an engine control unit is provided which is configured to execute or control a method for determining the coupling status of a clutch according to one of the preceding embodiments. The engine control unit can, for example, comprise a processor and a memory in which a software program is loaded, which receives instructions which, when executed by the processor, perform a method for determining the coupling status of a clutch, as explained in the embodiments described above.

[0034] 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.

[0035] Fig. Figure 1 schematically illustrates a part of a vehicle with a clutch and an engine control unit according to an embodiment of the present invention, which is configured to perform a method for determining a coupling status of a clutch according to an embodiment of the present invention;

[0036] Fig. Figure 2 schematically illustrates a method for determining the coupling status of a coupling according to an embodiment of the present invention;

[0037] Fig. Figure 3 illustrates curves in a graph to illustrate powertrain vibrations taken into account according to embodiments of the present invention;

[0038] Fig. Figure 4 illustrates quantities which are calculated in embodiments of the present invention;

[0039] Fig. Figure 5 illustrates curves in a graph which are calculated in a method for determining a coupling status according to embodiments of the present invention;

[0040] Fig. Figure 6 illustrates curves to illustrate a calculation of a modeled coupling torque as used in embodiments according to the present invention;

[0041] Fig. Figure 7 illustrates a scheme for determining a force flow or coupling status according to an embodiment of the present invention;

[0042] Fig. Figure 8 schematically illustrates a method for detecting a coupling status based on a speed difference according to an embodiment of the present invention; and

[0043] Fig. Figure 9 illustrates a possible implementation for detecting the coupling status of a coupling according to an embodiment of the present invention.

[0044] The in Fig. 1 illustrated part 1 A vehicle includes 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 equipped to control vehicle functions, a method for determining a coupling status of a coupling, in particular the coupling 5 to execute. The clutch 5 is connected to the crankshaft on the input side. 13 of a powertrain of the internal combustion engine 3 coupled and is connected on the output side to a transmission shaft, more precisely a transmission input shaft. 15 , of the gearbox 7 coupled to the drivetrain.

[0045] About schematically in Fig. 1 illustrated piston rod 17 , which are connected to pistons located inside cylinders of the internal combustion engine 3 The internal combustion engine is driven by the movement back and forth. 3 the crankshaft 13 to determine the rotational speed of an internal combustion engine. 3 is a sensor 19 provided which a measurement signal 21 to the control unit 11 transmitted, whereby the measurement signal 21 the actual rotational speed of the internal combustion engine 3 displays.

[0046] The gearbox allows coupling of the gearbox input shaft. 15 with a gearbox output shaft 23 via a plurality of gear ratios, for which the gearbox 7 has gears assigned to different gear sets, as is known from the prior art.

[0047] The clutch 5has an engine flywheel 25 on, which is rigidly connected to the crankshaft 13 is connected. A clutch disc 27 is between the engine flywheel 25 and a pressure plate 29 the clutch 5 arranged which pressure plate 29 with the clutch disc 27 and the engine flywheel 25 can be moved into a force-fit connection (connected coupling state) by using a clutch lever 31 is released or loosened, so that a diaphragm spring 33 transitions to a non-prestressed state. In Fig. 1 is the coupling state released by the coupling 5 illustrated. In a coupled state, a force transmission exists between both the engine flywheel and the engine flywheel. 25 and the clutch disc 27 as well as between the clutch disc 27 and the pressure plate 29 .

[0048] The engine control unit11 is equipped to carry out a method for determining a coupling status of a coupling according to an embodiment of the present invention, which is schematically described in Fig. 2 as a procedure 35 is illustrated. In the process step 37 Is an actual rotational speed (e.g., determined by the signal) 21 ) the internal combustion engine 3 determined. Then a loop is created for each possible gear ratio of the transmission. 7 This is done in a query step. 39 Queryed whether all gears of the transmission were already set up. 7 the procedural steps 41 and 43 The specified calculations have been performed. If this is not the case, the process continues to the next step. 41 branched, in which, when connected in coupling state, an expected rotational speed of the internal combustion engine 3at least based on a speed signal, e.g. signal 45 , which corresponds to the vehicle's speed, and the respective gear ratio is calculated. Furthermore, in the process step 43 The process calculates a difference between the actual and expected rotational speed, corresponding to the respective gear ratio. The procedure then branches back to the query. 39 , which are in a loop for so long, going through the process steps 41 and 43 returns, as it has further gear ratios of the transmission. 7 There are some for which the required values ​​have not yet been calculated.

[0049] Once all differences associated with the respective gear ratio have been calculated between the actual rotational speed and the expected rotational speed associated with that gear ratio, the process step 47The process involves determining a speed difference threshold as a function of a time gradient of the drivetrain torque. In this process step... 49 A coupling status is finally determined to be connected if a minimum of the calculated differences is smaller than the speed difference threshold, with the speed difference threshold being continuously updated.

[0050] The engine control unit 11 It then outputs the detected coupling status, e.g. as a signal. 51 , to one or more vehicle components and / or uses the detected coupling status of the coupling 5 in further internal calculations to determine or ascertain various control signals.

[0051] The procedure 35The torque used by the drivetrain can, for example, include or be an engine torque at the clutch level (also known as drive-related, input-side torque at the clutch). 5 applied torque), which is thus at the end of the crankshaft or at the engine flywheel. 25 is present. Alternatively or additionally, the drivetrain torque can include or be a modeled clutch torque (also known as output-side, at the clutch). 5 applied torque), which is thus at the gearbox input shaft 15 is present, provided there is a force transmission between the engine flywheel 25 and pressure plate 29 consists of a component which, in the coupled state, is connected to the gearbox input shaft in a rotationally fixed manner.

[0052] The engine torque at the clutch level is abbreviated as MMK, and the modeled clutch torque is abbreviated as mKM. The engine torque at the clutch level is conventionally available. This value indicates how much torque is available at the clutch. In one approach of the present invention, the torque that is transmitted to the transmission at the clutch is 7 The transmitted torque is modeled and then referred to as the modeled clutch torque. According to embodiments of the invention, a force transmission is inferred (i.e., the coupling state is connected) 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 inertial torque applied to the clutch input side according to the following equation: –mKM = MMK – J d / dt(n) 2 π / 60 (Eq. 1)

[0053] Here, J denotes the moment of inertia of the internal combustion engine. 3 including all rotating 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 exceeds a certain threshold, a frictional connection, i.e., a coupling state, is established. 5 Closed. The modeled clutch torque corresponds to that transmitted via the clutch. 5 on the gearbox 7 Transmitted torque. Without a frictional connection, no torque can be transmitted, so zero would be calculated on the left side of the equation above. This means that as soon as a modeled coupling torque > 0 Nm is calculated from the formula above, it can be assumed that the drivetrain is at least partially closed.

[0054] The torque threshold can be, for example, between 20 and 40 Nm when the engine is warm, and between 50 and 70 Nm when the engine is cold. Other values ​​are possible.

[0055] The engine torque at the clutch level (MMK) can exhibit an error if the loss torques are not precisely known. Furthermore, the signal must be filtered relatively heavily because the engine speed gradient (d / dt(n)) represents a response to the engine torque that must first be measured and is therefore only available later. Since the engine speed gradient signal, which is derived, for example, from the speed signal 21Since the torque, which can be calculated by time derivative, is available with a delay, it is smoothed out by low-pass filtering, just like the engine torque at the clutch level. Various filter time constants can be used (e.g., between 100 ms and 500 ms; other values ​​are possible). While this strong filtering can reduce noise and increase accuracy, it comes at the cost of temporal inaccuracies. When the drivetrain opens, the modeled clutch torque must first be filtered below the detection threshold, which delays the detection of the open drivetrain. A suppression mechanism is implemented for this purpose, which becomes active as soon as the gradient of the magnitude of the modeled clutch torque falls below a certain threshold.

[0056] In Fig. 3 are curves represented in a graph in which the abscissa 53 time and the ordinate 55The curve displays the values ​​of various physical quantities. 57 displays the engine speed, the curve 59 displays the engine speed gradient, the curve 61 displays the engine torque at clutch level (MMK) and the curve 63 displays the modeled clutch torque (mKM), which is calculated according to the equation above. At time 65 A change from thrust to tension was carried out under force transmission (i.e., coupled state connected), at which time 67 Was the clutch 5 Opened under load, i.e., switched to the open coupling state. As can be seen, the modeled coupling signal (on curve) 63 ) due to the filtering, only decreases slowly over time, even though the gearbox input shaft 15 already completely removed from the crankshaft 13It is decoupled. However, if the gradient of the magnitude of the modeled coupling torque is evaluated to determine whether it has fallen below a certain threshold, a reliable conclusion can be drawn about a coupling state.

[0057] The model can detect engagement processes and a slipping clutch at high speed deviations as existing frictional engagement.

[0058] The signal's inertia can delay detection, especially at very low modeled clutch torques (e.g., below 40 Nm; other values ​​are possible). Particularly when very little torque is transmitted and a gear is engaged, this detection method can be combined with the detection of, or use of, speed differences (described below), as the model cannot provide information about the drivetrain state in this situation.

[0059] According to one embodiment of the present invention, the engagement state is detected or determined based on calculated speed differences. Manual transmissions typically have fixed gear ratios that depend on the selected gear. This results in a typical ratio between engine speed and vehicle speed (the so-called nv ratio). If the current ratio does not correspond to any of the gears determined by the transmission geometry, it can be assumed that no gear is engaged and the drivetrain is therefore open, i.e., the clutch is disengaged.

[0060] According to embodiments of the present invention, for each possible gear of the transmission 7 a model speed is calculated at which the motor 3The difference between this speed and the actual engine speed can indicate whether a gear ratio with full traction is present at a given vehicle speed.

[0061] The gearbox output speed is determined from the vehicle speed according to the following equation:

[0062] The gearbox output speed can be used to calculate the gear ratios r. i,Gang Equivalent model speeds are calculated from the gearbox data using the following formula: n Modell,i.Gang = r i.Gang ·n Getriebe,Ausgang (Eq. 3)

[0063] The difference between the motor speed and the model speeds results in the following differential speeds: n Dif,i.Gang = n Motor – n Modell,i.Gang (Eq. 4)

[0064] The smaller the difference in rotational speed, the more likely it is that a gear is engaged and there is a power transmission, i.e., the coupling state is connected.

[0065] Fig. 3 illustrated in a coordinate system with an abscissa 69 , which displays the time, and an ordinate 71 , which displays various physical quantities, a curve 73 , which displays the engine speed, as well as a curve 75 , which illustrates the engine torque at the clutch level. With strong gradients of the clutch torque to be transmitted, drivetrain vibrations occur, which are reflected in a speed deviation. If the power transmission detection is based on a comparison of the speed difference with a threshold value, the threshold value may be undershot, which could be incorrectly interpreted as a engaged state. From Fig. 4 shows that inaccuracies in the engine speed are particularly noticeable with strong gradients of engine torque at the clutch level, e.g. at the times 68 and 70 This occurs. For this reason, in the case of high gradients in clutch torque or engine torque at the clutch level, a widening (i.e., increasing) of the speed difference threshold is provided.

[0066] This expansion (enlargement) is then reduced back to the original value, but not abruptly, rather more slowly than the threshold was increased.

[0067] However, it can also happen by chance that a correct gear ratio is established even though the drivetrain is open. In this case, a positive connection would be incorrectly detected if the vehicle, for example, coasts with the drivetrain open, as in Fig. 4 illustrated in a graph, where the abscissa 77 which indicates the time, and the ordinate 79The curve displays various physical quantities. 81 displays 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 coasts with the clutch engaged, yet the speed difference decreases. 83 occasionally randomly below the threshold 85 As a remedy, the speed differences are debounced, thus suppressing random, brief drops below the threshold. Debouncing effectively prevents the accidental detection of a correct gear ratio, but this makes the detection of open, unlocked drive trains slower.

[0068] The method using a differential rotational speed to determine the coupling status can be implemented functionally as follows: First, the model speeds are calculated for each possible gear according to Eq. 3. These are subtracted from the actual engine speed to generate differential speeds according to Eq. 4, the smallest of which is compared to an applied threshold value. If this value is undershot, it is assumed that a suitable gear ratio is present, thus indicating a coupled state. Due to the erroneous determinations during load changes, the threshold value is immediately widened during load changes and then subsequently reduced again. The aim is to allow the drivetrain vibrations to settle within this widened limit without exceeding the threshold. The differential speed is thus continuously framed within the detection window. The widening depends on the maximum value of the gradients of the engine torque at the clutch level and the gradient of the modeled clutch torque.With the drivetrain engaged, the engine torque enables a rapid response from the function, while the modeled clutch torque provides indications of drivetrain vibrations not caused by the engine torque.

[0069] Fig. 6 illustrated in a graph with abscissa 89 , which indicates the time, and ordinate 91 , which displays various physical quantities, a curve 93 , which displays the engine speed, a curve 95 , which indicates the difference in rotational speed, a curve 97 , which displays the engine torque at the clutch level and a curve 99 , which specifies the differential speed threshold that is chosen depending on the gradient of the engine torque at the clutch level and is therefore continuously updated.

[0070] As if coming out of the curve 99As can be seen, with strong changes in engine torque at the clutch level (curve) 97 ), e.g. at certain times 88 and 90 , the differential speed threshold 99 increased abruptly and then slowly decreased again.

[0071] To detect the coupling status based on the consideration of the speed differences, it is useful to combine this method with another method, e.g. with the method described above, which is based on the modeled coupling torque.

[0072] Fig. Figure 7 illustrates a scheme for determining a force flow or coupling status according to an embodiment of the present invention. In the block 101 The modeled coupling torque is calculated according to Eq. 1 above. In the block 103 The comparison is made with a torque threshold, whereby when a first torque threshold is exceeded, 105The coupling state is linked and a second torque threshold is undershot. 107 (which are smaller than the first torque threshold) 105 The coupling state is determined based on the magnitude of the modeled coupling torque and its hysteresis. In short, the frictional state is identified using this equation. For strongly negative gradients of the modeled coupling torque magnitude, a suppression function is used. 109 Active. When this hiding function is active, the coupling state is closed. The coupling state or force-fit status is displayed in element 111 issued.

[0073] Fig. Figure 8 schematically illustrates a method for detecting a coupling status based on a speed difference. Using the vehicle speed and the wheel diameter D (see Figure 8), the method is used to determine the coupling status. Fig. 1) and the gear ratios of the transmission 7A modeled rotational speed (e.g., according to Eq. 3) is calculated based on the current vehicle speed. This is the speed at which the engine would have to rotate if the respective gear were engaged and a coupling state were present. The difference between these modeled rotational speeds and the actual engine speed is calculated, resulting in modeled differential rotational speeds (e.g., according to Eq. 4). The gear with the smallest differential rotational speed can be determined as the next most plausible gear. The differential rotational speed is continuously recalculated and compared to threshold values. If the differential rotational speed is less than the threshold, the gear is considered possibly engaged. Only after debouncing is the gear recognized as plausible. However, this debouncing can also be terminated prematurely if it is confirmed from another source of information that torque is being transmitted and that the gear ratio is not merely coincidentally correct.The gear selection is then immediately flagged as recognized.

[0074] The differential speeds are measured in the block 113 The calculation and thresholding are performed in the block 115 The speed difference threshold depends on the torque gradient at the clutch level of the engine. The gradient of the modeled clutch torque (e.g., block) can also be used. 101 in Fig. 7) must be taken into account. The smaller the gradient in magnitude, the narrower the range, i.e., the lower the differential speed threshold within which the gear is considered possibly engaged and within which a connected state is inferred. The rationale here is that with drivetrain vibrations caused by load changes, the gear ratio does not oscillate momentarily. The increase or decrease of the differential speed threshold as a function of the gradient of the engine torque at the clutch level can "envelop" the drivetrain vibration, i.e., be formed according to the amplitude of a drivetrain vibration. The expansion of the vibration can occur directly and unfiltered, while the narrowing can be low-pass filtered. The debouncing is implemented in the block 117 The comparison of the differential speeds with the differential speed threshold is carried out in block [number]. 119 carried out.

[0075] The power transmission status 121 can, for example, the power transmission status 111 out of Fig. 7 corresponds. If this force transmission status is determined to be closed or connected and at the same time the speed difference is smaller than the speed difference threshold, the result block will show... 123 The system detects the connected coupling status and indicates that the gear with the smallest speed difference is engaged.

[0076] Fig. Figure 9 illustrates a possible implementation for detecting the coupling status of a coupling, which combines both proposed methods.

[0077] The variable 'a' is calculated as true if, based on the procedure and starting from the modeled coupling torque, a coupling status of 'connected' is determined. Otherwise, the variable is set to false.

[0078] The variable b is set to true if the procedure for determining the coupling status based on the rotational speed differences identifies a coupling status as connected. Otherwise, the variable b is set to false.

[0079] The variable o means that the coupling state is validly determined to be open, the variable vo means that the coupling state is provisionally determined to be open.

[0080] The variable vg means that the coupling status is provisionally determined to be closed, the variable g means that the coupling state is validly determined to be closed.

[0081] 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 the variable `b` is also true, then the variable `g` is set. If the variable `vo` is set and the variable `a` is not set, then the variable `o` is set. Furthermore, if the variable `o` is set, then the variable `g` is set. Other implementations are possible. Reference symbol list 1 part of a vehicle 3 Internal combustion engine 5 Clutch 7 gearboxes 9 drive wheel 11 Engine control unit 13 Crankshaft 15 Gearbox input shaft 17 piston rods 19 Sensor 21 Measurement signal 23 Gearbox output shaft 25 Engine flywheel 27 Clutch disc 29 Pressure plate 31 Clutch levers 33 Membrane spring 35 procedures 37, 41, 43, 47, 49 Procedural steps 39 Query 45 speed signal 51 Output signal 53, 69, 77, 89 Abscissa 55, 71, 79, 81 Ordinates 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 points in time Blocks 101, 103, 109, 111 105, 107 threshold 113, 115, 117, 119, 121, 123 Schema blocks a, b, o, vo, vg, g Variables of the engine control unit QUOTES INCLUDED IN THE DESCRIPTION

[0082] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0083] DE 10207940 B4

[0005] EP 1950461 A2

[0006] EP 2331848 B1

[0007] US 7517301 B2

[0008]

Claims

[1] Method for determining the coupling status of a coupling ( 5 ), which is connected on the input side with a crankshaft ( 13 ) of a powertrain of an internal combustion engine ( 3 ) and on the output side with a transmission input shaft ( 15 ) of a gearbox ( 7 ) of the powertrain is coupled, connected or disconnected in the coupling state, wherein the method has: Determining an actual rotational speed (n, 21 ) the internal combustion engine ( 3 ); Perform for every possible gear ratio of the transmission ( 7 ) of the steps: Calculating an expected rotational speed (n) when connected in a coupled state Modell,i.Gang ) the internal combustion engine at least based on a speed signal ( 45 ) and the respective translation ratio; Calculating a difference assigned to the respective translation ratio ( 95 , nDif,i.Gang ) from the actual rotational speed and the expected rotational speed; the procedure further features: Determining a speed difference threshold ( 99 ) as a function of a time gradient of a drivetrain torque ( 97 , MMK, mKM); Determining a coupling status (connected) if a minimum of the calculated differences is less than the speed difference threshold ( 99 ), where the speed difference threshold is continuously updated. [2] Method according to claim 1, wherein the speed difference threshold ( 99 ) for an increasing absolute value of the time gradient of the torque ( 97 , MMK, mKM) of the powertrain is raised. [3] Method according to claim 1 or 2, wherein the speed difference threshold ( 99 ) is increased abruptly if a certain amount of the time gradient of the torque ( 97, MMK, mKM) of the drive train exceeds a gradient threshold and / or where, for a period of time, the determination of the coupling status is based on the calculated differences and the speed difference threshold ( 99 ) is suspended and instead the coupling status is determined to be the previously determined coupling status. [4] Method according to one of the preceding claims, wherein the differences ( 95 , n Dif,i.Gang ) before determining the minimum, the speed difference threshold is debounced or low-pass filtered, and the speed difference threshold is low-pass filtered or reduced with a smaller amount of temporal change compared to the increase when the magnitude of the temporal gradient falls below the gradient threshold. [5] Method according to one of the preceding claims, wherein the speed signal ( 45) is indicative of a vehicle speed of a vehicle encompassing the clutch and wherein the calculation of the rotational speed of the internal combustion engine expected when the coupling is engaged is further based on a wheel dimension (D) of a wheel ( 9 ) of the vehicle. [6] Method according to one of the preceding claims, wherein the torque of the drive train comprises a drive-related input torque (MMK) applied to the clutch, wherein determining the drive-related input torque (MMK) applied to the clutch comprises at least determining a quantity of fuel which is supplied to the internal combustion engine ( 3 ) is supplied. [7] Method according to any one of the preceding claims, further comprising: Determining an output torque (mKM) at the clutch based on an inertia-induced input torque at the clutch and the drive-induced input torque (MMK), wherein the torque of the drive train further includes the specific output torque (mKM) applied at the clutch. [8] Method according to the preceding claim, wherein a conclusion to a coupling status is made if a minimum of the calculated unbounced differences is smaller than the speed difference threshold and the determined output torque applied to the coupling is greater than a torque threshold. [9] Method according to claim 7 or 8, wherein the method further comprises: Determining a change over time of the amount of the specified output torque (mKM) applied to the clutch; and determining a coupling status is solved if the time change of the magnitude of the determined output torque (mKM) applied to the coupling is less than a further gradient threshold, which is less than zero. [10] Engine control unit ( 11 ), which is trained to execute or control a process according to any of the preceding claims.