DE102016219793B3 - Method for monitoring a dual-clutch transmission - Google Patents

Abstract

The invention relates to a method for monitoring a dual-clutch transmission, via which a torque of a drive unit is transferable to an output, wherein in each of the two clutches of the dual clutch transmission a respective clutch torque (K _S , K _O ) is monitored, and wherein, if one for the Clutch torque (K _S ), which has the smaller amount of both clutch torques (K _S , K _O ), characteristic value exceeds a variable, predefinable clutch torque threshold (S _K ), an error reaction (F) is initiated, wherein a gradient (G _n ) a speed (n) of the drive unit (110) is monitored, and wherein, when the gradient (G _n ) of the rotational speed of the drive unit falls below a predeterminable gradient threshold value (G _S ), the clutch torque threshold value (S _K ) is reduced to a minimum value (S _M ) becomes.

Description

The present invention relates to a method for monitoring a dual clutch transmission, via which a torque of a drive unit can be transmitted to an output, as well as a computing unit and a computer program for its implementation.

State of the art

In addition to manual transmissions automatic transmissions can be used in motor vehicles for torque conversion. Not only so-called converter transmissions but also so-called double-clutch transmissions can be counted for this purpose. In a dual-clutch transmission two (automated) couplings are present, each associated with a transmission shaft.

During a gear shaft usually the odd gears (or gears) are assigned, the other gear shaft are assigned to the even gears. For a gear or speed step change then an initially open clutch can be closed while, possibly with a short time delay, the initially closed clutch is opened. In this way, a fully automated gear change without interruption of traction is possible.

In the WO 2007/124710 A1 For example, such a dual-clutch transmission will be described. In addition, there is also mentioned that when changing gear problems may occur such as a slump or an unpredictable increase in a clutch torque of the two clutches.

From the DE 10 2009 032 220 A1 a method for monitoring an automatic drivetrain is known. In this case, it is provided to detect a speed parameter, to check whether the speed parameter is greater than a threshold value for a predetermined period of time and to initiate a measure for lowering the speed parameter if the speed parameter for the time span is greater than the threshold value.

Disclosure of the invention

According to the invention, a method for monitoring a dual-clutch transmission as well as a computing unit and a computer program for carrying it out with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

An inventive method is used to monitor a dual-clutch transmission, via which a torque of a drive unit (this may in particular be an internal combustion engine, which then serves as a drive) is transferable to an output. About the output, the torque can then be transferred to wheels of a corresponding motor vehicle. It is now monitored at each of two clutches of the dual clutch transmission a respective clutch torque. The clutch torque describes the torque transmission between the drive unit and the internal combustion engine and the transmission shaft associated with the respective clutch (in a dual-clutch transmission, as mentioned, two separate transmission shafts present). In a closing clutch (ie, the clutch is initially open and then closed) increases the clutch torque and in an opening clutch (ie the clutch, which is initially closed and then opened), the clutch torque is reduced.

If a characteristic value for the clutch torque having the smaller amount of both clutch torques now exceeds a variable, predefinable clutch torque threshold, an error reaction is initiated. An error usually occurs when both clutches close at the same time. The clutch torque, which has the small amount, is usually a closing clutch. As for the clutch torque, which has the smaller amount of both clutch torque, characteristic value is in particular the corresponding clutch torque itself in question, but also conceivable is a (temporal) integral on this clutch torque. It is understood that the Kupplungsmomentenschwellwert is respectively determined accordingly, so for example, directly indicates a certain clutch torque or a corresponding integral.

As such an error reaction, a reduction of the clutch torque, which has the smaller amount of both clutch torques, ie in particular the closing clutch or a complete opening of the closing clutch or an opening, in particular a simultaneous opening, of both clutches can be provided in particular. In this way it can be prevented that blocks the dual-clutch transmission or that an unwanted delay occurs. In general, such an error case of two simultaneously closed clutches leads to an unstable or safety-critical driving situation. This would be the case, for example, when the clutch torque of the closing clutch rises too fast, so that a high adhesion of both transmission shafts, respectively connected to the output via a selected gear, would be made with the drive. With regard to a suitable choice, in particular a dynamic change of the Kupplungsmomentenschwellwerts reference is made to the following explanations.

Furthermore, now a gradient of a rotational speed of the drive unit is monitored and if this gradient of the rotational speed of the drive unit falls below a predefinable gradient threshold, d. H. If, for example, there is an unexpectedly strong fall in the rotational speed, the clutch torque threshold value is reduced to a minimum value. This minimum value can be chosen so that even a safe switching, d. H. a change of gear without delay, is possible. As such, blockage can already be prevented by monitoring the clutch torque of the closing clutch (or the one with the smaller amount) and initiating the fault reaction when the clutch torque threshold is exceeded. However, since this Kupplungsmomentenschwellwert is usually specified as a function of an actual torque of the drive unit and in particular changed dynamically, a safe signal for the actual torque of the drive unit is necessary for reliable detection of a corresponding error or a safe initiation of the error reaction, otherwise the adjustment of the torque limit torque and thus the initiation of the fault reaction could not be done with appropriate security.

An incorrectly oversampled or calculated signal for the actual rotational torque due to an unsolicited or non-existent safety integrity level of the actual rotational torque could lead to a clutch torque threshold that was calculated too high. A malfunction in the dual-clutch transmission could thus not be discovered or too late.

For the sake of completeness, it should be noted at this point that a safe signal can be understood as a signal having a certain safety integrity level or ASIL ("Automotive Safety Integrity Level"). Such a reliable signal for the actual torque can be provided, for example, by a control unit of the drive unit, that is to say an engine control unit.

However, depending on the (required) safety classification of the fault in the dual-clutch transmission, it may happen that the signal provided by the engine control unit for the actual torque does not have the required level of security. With the proposed method, in which additionally monitors the gradient of the speed (or a speed gradient) of the drive unit and based on it, if necessary, the Kupplungsmomentenschwellwert - in particular independent of the actual torque of the drive unit - is set to a minimum value, which thus immediately an error response another level of surveillance will be added, which will increase the overall security level.

This means that even if the safety integrity level of a signal of the actual torque of the drive unit is not sufficiently high, a required, higher safety integrity level for initiating an error reaction can still be provided. Apart from that, however, even in cases where, for example, no signal for actual torque with a safety integrity level, for example, only a signal with so-called. QM level ("Quality Management") is present, yet a (higher) safety integrity level for Initiate an error reaction can be achieved.

Preferably, the Kupplungsmomentenschwellwert, in particular dynamically, depending on the clutch torque of an opening clutch and / or an actual torque of the drive unit and / or a currently selected gear on a gear shaft of the opening clutch and / or a currently selected gear on a transmission shaft of the closing Clutch specified. The variables mentioned are those variables which have an influence on the torque or power transmission from the drive unit to the transmission shafts in the dual-clutch transmission. By suitable consideration of one or more of these variables, the clutch torque threshold value can thus be dynamically adjusted in a shift operation such that, on the one hand, there is no loss of traction (clutch torque threshold as high as possible) but, on the other hand, no unwanted deceleration or stalling occurs (clutch torque threshold as low as possible).

Advantageously, the speed of the drive unit is detected using a speed sensor and / or read as a signal that is present on a communication medium. Such a speed sensor can for example be supplied with power directly from an executing computing unit, for example a transmission control unit, and read in. It is also conceivable that the speed is not detected directly on the internal combustion engine (or a crankshaft), but at the entrance of the dual clutch transmission. The communication medium may be, for example, a bus (for example a so-called CAN bus) which is used in a vehicle for the purpose of Signal transmission or for communication between different control devices is used with each other. This is usually a signal to the speed of the drive unit, which is often read and used by other control devices. This signal can be provided for example by a control unit for the drive unit or the internal combustion engine, ie an engine control unit. Both variants mentioned represent simple ways to obtain the speed of the drive unit for further processing.

It is particularly expedient to increase a safety integrity level for the rotational speed using the rotational speed sensor and using the read-in signal with respect to the safety integrity level of the rotational speed sensor and / or the safety integrity level of the signal. This makes it possible to increase the overall achieved safety integrity level for initiating an error response. Again, no highly secure signal for the actual torque of the drive unit is necessary.

An arithmetic unit according to the invention, for. As a control device, in particular a transmission control unit, a motor vehicle is, in particular programmatically, adapted to perform an inventive method.

Also, the implementation of the method in the form of a computer program is advantageous because this causes very low costs, especially if an executive controller is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memory, such. As hard drives, flash memory, EEPROMs, DVDs u. a. m. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below with reference to the drawing.

Brief description of the drawings

1 schematically shows a dual-clutch transmission, which connects an internal combustion engine with an output.

2 showed schematically gradients of clutch torque and speed of the internal combustion engine.

3 schematically shows a sequence of a method according to the invention in a preferred embodiment.

Embodiment (s) of the invention

In 1 is schematically a powertrain 100 , which may be part of a motor vehicle, with a dual-clutch transmission 120 shown that an internal combustion engine 110 as a drive unit with an output or an output shaft 130 connects and in which a method according to the invention can be carried out.

The internal combustion engine 110 is via a drive shaft 111 with the dual-clutch transmission 120 connected. In the dual-clutch transmission itself are two clutches 121 and 126 with a respective transmission shaft 122 respectively. 127 provided, both via the respective coupling with the drive shaft 111 are connectable to the transmission of torque.

On the two transmission shafts 122 and 127 are each partial transmission 123 respectively. 128 provided in each of which different gears are provided for the selection of speed levels or gears. Both transmission shafts 122 . 127 or both partial transmissions 123 . 128 are each by means of a suitable gear to the output shaft 130 connected, which in turn has a differential 140 with wheels 141 . 142 connected is.

About a designed as a transmission control unit arithmetic unit 190 can the dual-clutch transmission 120 operate. This means in particular that each of the two clutches 121 . 126 and also each of the two partial transmissions 123 . 128 each can be operated separately and automated. About a speed sensor 160 can the transmission control unit 190 the speed of the internal combustion engine 110 determine.

An engine control unit 180 serves the operation of the internal combustion engine 110 , In particular, the engine control unit 180 an actual torque of the internal combustion engine 110 and determine or calculate a speed of the internal combustion engine.

Furthermore, a trained as a bus communication medium 170 shown via the engine control unit 180 and the transmission control unit 190 connected to each other. In this case, the engine control unit, for example, a signal for the speed of the internal combustion engine on the bus 170 which is the gearbox control unit 190 can read.

In 2 are shown schematically gradients of clutch torque and the speed of the internal combustion engine. These are in two Diagrams each applied a clutch torque K and a speed n over time t.

In the upper diagram, a curve of a clutch torque K _{O of} an initially closed and then opening clutch and a clutch torque K _{S of} an initially open and then closing clutch are shown for a regular shift of a dual clutch transmission. The speed of the internal combustion engine or its course is designated by n.

Based on the course of the speed n, it can be seen that the dual-clutch transmission is properly controlled and works, ie. H. that it is not blocked in particular. In this way, no loss of traction occurs, but the frictional connection and the torque transmission are transferred from one to the other clutch.

The lower diagram now shows a gradient for a non-standard switching process. On the course of the speed n, a relatively strong fall in speed can be seen. In the context of the present invention, however, this speed reduction can now be detected, so that an error reaction can be initiated by reducing the clutch limit value to the minimum value.

In the context of this error reaction, the closing or both clutches can be controlled accordingly to prevent blocking of the double gear. Such blocking is indicated on the basis of the speed curve n '. The activation of the clutches may include, for example, a short-term opening or a reduction of the clutch torque of the closing clutch

In 3 schematically a flow of a method according to the invention is shown in a preferred embodiment. The clutch torque K _{O of} the opening clutch, the speed range F _O on the transmission shaft of the closing clutch, the speed range F _S on the transmission shaft of the opening clutch and the actual torque M _{B of} the internal combustion engine can be detected or determined by the transmission control unit.

From these variables, the clutch torque threshold value S _K can then be calculated dynamically during a shift operation of the dual-clutch transmission. The clutch torque threshold value S _K is preferably a function of the respective current clutch torque K _{O of} the opening clutch, the currently selected gear stage F _S on the transmission shaft of the closing clutch, the currently selected gear stage F _O on the gear shaft of the opening clutch and the actual torque M. _{B of} the internal combustion engine 110 specified.

Furthermore, the clutch torque K _{S of} the closing clutch is detected or determined. For the clutch torque threshold S _K then results - for the case that the clutch torque of the closing clutch has the smaller amount - the quotient of the actual torque M _B with the absolute amount of the difference between the speed levels F _S and F _O , ie for the monitoring applies : Min (K _S , K _O ) ≥ M _B / | F _O - F _S |

The minimum of the clutch torques is relevant because only the slipping clutch (this has a smaller clutch torque) contributes to the deceleration. In the case of the clutch which has already been closed, a further increase in the clutch torque has no influence on the deceleration, since the condition, ie. H. closed clutch, this does not change.

Furthermore, the difference in gear ratios can play an important role. The Kupplungsmomentenschwellwert is minimal if z. B. on the one gear shaft of the first and on the other gear shaft of the reverse gear are engaged. By contrast, the clutch torque threshold is maximum when the gears or their translations differ only slightly, such as. B. between the sixth and seventh gear. In the extreme case of identical gear ratios (which, however, will not occur in practice), the clutch torque threshold would diverge, thus both clutches could be closed without causing a delay.

The clutch torque K _{S of} the closing clutch can now be compared during the shift continuously with the clutch torque threshold S _K. As soon as the clutch torque K _{S of} the closing clutch exceeds the clutch _torque threshold value S _K , an error reaction F, for example an opening of the clutches, can be effected.

Furthermore, a gradient G _{n of} the rotational speed of the internal combustion engine can be detected or determined and compared with a predefinable gradient threshold value G _S. As soon as the gradient G _{n of} the speed falls below the gradient threshold value G _S , which can be suitably selected, it can be assumed that there has been a sharp fall in speed, which indicates an error in the shifting process in the dual-clutch transmission.

Thereupon, the clutch torque threshold value S _{K can be set} to a minimum value S _M , which accordingly influences the initiation of the error reaction, causing it in particular earlier. In this way, the safety integrity level can be increased to detect an error during the shift in the dual-clutch transmission or to initiate a corresponding error response, especially without the presence of a secure signal to the actual torque of the internal combustion engine.

Claims (10)

Method for monitoring a dual-clutch transmission ( 120 ), via which a torque of a drive unit ( 110 ) on an output ( 130 ) is transferable, with each of the two couplings ( 121 . 126 ) of the dual-clutch transmission ( 120 ) a respective clutch torque (K _S , K _O ) is monitored, and wherein, if one for the clutch torque (K _S ), of the two clutch torque (K _S , K _O ) has the smaller amount, characteristic value of a variable, predetermined clutch torque threshold (S _K ), an error reaction (F) is initiated, characterized in that a gradient (G _n ) of a rotational speed (n) of the drive unit ( 110 ), wherein, when the gradient (G _n ) of the rotational speed of the drive unit falls below a predefinable gradient threshold value (G _S ), the clutch torque threshold value (S _K ) is reduced to a minimum value (S _M ). Method according to Claim 1, the clutch torque threshold value (S _K ) being dependent on the clutch torque (K _O ) of an opening clutch and / or an actual torque (M _B ) of the internal combustion engine ( 110 ) and / or a currently selected gear (F _O ) on a gear shaft of the opening clutch and / or a currently selected gear (F _S ) is set on a gear shaft of the closing clutch. A method according to claim 1 or 2, wherein the minimum value (S _M ) is predetermined independently of an actual torque (M _B ) of the drive unit. Method according to one of the preceding claims, wherein the speed (n) of the drive unit using a speed sensor ( 160 ) and / or as a signal transmitted on a communication medium ( 170 ), is read. Method according to claim 4, wherein the signal transmitted on the communication medium ( 170 ) than by a control unit ( 180 ) for the internal combustion engine ( 110 ) provided signal on the communication medium ( 170 ) is present. A method according to claim 4 or 5, wherein a safety integrity level for the speed (n) using the speed sensor ( 160 ) and using the read-in signal to the safety integrity level of the speed sensor ( 160 ) and / or the safety integrity level of the signal is increased. Method according to one of the preceding claims, wherein the error reaction (F) a reduction of the clutch torque (K _S ), the smaller amount of both clutch torque (K _S , K _O ), or opening the closing clutch or opening of both clutches ( 121 . 126 ) of the dual-clutch transmission ( 120 ). Arithmetic unit ( 190 ), which is adapted to perform a method according to any one of the preceding claims. Computer program comprising a computing unit ( 190 ) to perform a method according to any one of claims 1 to 7, when it on the computing unit ( 190 ) is performed. Machine-readable storage medium with a computer program stored thereon according to claim 9.

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