EP3662183A1

EP3662183A1 - Method for operating a drive train of a motor vehicle, in particular a car

Info

Publication number: EP3662183A1
Application number: EP18752115.8A
Authority: EP
Inventors: Sven ROLAND
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2017-08-04
Filing date: 2018-08-01
Publication date: 2020-06-10
Also published as: WO2019025489A1; CN110945270A; DE102017213611A1; CN110945270B; US11345352B2; US20200164883A1; DE102017213611B4

Abstract

The invention relates to a method for operating a drive train of a motor vehicle, which drive train has at least one drive engine, a transmission device and at least one wheel which can be driven by the drive engine via the transmission device, in which method respective actuations are brought about by respective shifting elements of the transmission device, in order, as a result, to influence a transmission of a torque which is provided by the drive engine from the drive engine via the transmission device to the wheel, wherein - the torque which is provided by the drive engine is set as a function of a transmission function (20) which specifies a factor, by which the torque is to be multiplied, in order to calculate a wheel torque which results from the torque and the transmission and acts on the wheel; - respective parameters (10a-10e) are determined which characterize respective states of the respective shifting elements, which respective states result from the effect of the actuations; and - the transmission function (20) is monitored in a manner which is dependent on the determined parameters (10a-10e).

Description

Method for operating a drive train of a motor vehicle, in particular of a motor vehicle

DESCRIPTION:

The invention relates to a method for operating a drive train of a motor vehicle, in particular a motor vehicle, according to the preamble of patent claim 1. Such methods for operating drive trains for motor vehicles, in particular motor vehicles, are already well known from the general state of the art and in particular from series vehicle construction. In this case, the respective drive train comprises a drive motor designed, for example, as an internal combustion engine, in particular as a reciprocating internal combustion engine, and at least one wheel. The drive train usually comprises a plurality of wheels. The drive train further comprises a transmission device, via which the wheel or the wheels can be driven by the drive motor or are. In the respective method for operating such a drive train, for example, respective actuations of respective shift elements of the transmission device are effected in order to influence a transmission of a torque provided by the drive motor from the drive motor via the transmission device to the wheel. By the respective effecting the respective actuation of the respective switching element, for example, a gear change of the transmission device can be effected, whereby the transmission of the torque is influenced by the drive motor to the wheel. In the context of such a gear change, for example, a change is made from a first gear to a second gear of the transmission device, the gears differing in their respective gear ratios.

Furthermore, DE 195 04 847 A1 discloses a method for controlling a torque transmission system with or without power split, in particular for motor vehicles. From DE 10 201 1 079 888 A1 a method for determining an operating state of a device is known, via which stroke volumes of a first hydraulic machine and a second hydraulic machine are variable.

In addition, DE 100 27 332 A1 discloses a method for detecting at least one predetermined gear shift position of a transmission device as known. Object of the present invention is to develop a method of the type mentioned in such a way that a particularly comfortable and at the same time a particularly safe operation of the drive train can be realized. This object is achieved by a method having the features of claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims. In the method according to the invention, a drive train of a motor vehicle, in particular of a motor vehicle and preferably a passenger car, operated, the drive train having at least one drive motor, a transmission device and at least one via the transmission device of the drive motor driven wheel. The drive motor is designed, for example, as an internal combustion engine, in particular as a reciprocating internal combustion engine. In particular, it is conceivable that the drive train has a plurality of wheels. The wheels or the wheel can or can be driven by the drive motor, whereby, for example, the motor vehicle as a whole is driven by the drive motor.

In the method, respective actuations of respective switching elements of the transmission device are effected to thereby influence a transmission of a torque provided by the drive motor and also referred to as drive torque, engine torque or engine torque from the drive motor via the transmission device to the wheel or to the wheels. In order to be able to realize a particularly comfortable and particularly safe operation of the drive train and thus of the motor vehicle as a whole, it is provided according to the invention that the torque provided by the drive motor is set as a function of a transmission function which indicates a factor with which multiplying the torque (engine torque) to calculate a wheel torque, in particular sum wheel torque, resulting from the torque and from the transmission of the torque from the drive motor to the wheel and acting on the wheel.

Furthermore, it is provided in the method according to the invention that respective parameters are determined which characterize respective states of the respective switching elements resulting from the actuation of the actuations. In addition, it is provided according to the invention that the transmission function or the factor is monitored as a function of the parameters determined.

The drive motor has, for example, an output shaft designed in particular as a crankshaft, via which the drive motor can provide or provide the torque, which is also referred to as drive engine torque. For example, multiply the prime mover torque by the factor to calculate the sum wheel torque. The factor is thus, for example, a physical factor which can be calculated, for example, by dividing a transmission output torque by a transmission input torque, in particular including a so-called converter factor. The transmission input torque corresponds, for example, to the engine torque (torque provided by the drive motor), since, for example, the engine torque is transmitted to the transmission device and introduced into the transmission device, so that the transmission input torque is introduced into the transmission device. The transmission output torque corresponds for example to the wheel torque and results in particular from the transmission of the engine torque from the drive motor via the transmission device to the wheel. As part of the transmission, for example, the engine torque (transmission input torque) is converted by means of the transmission device in the wheel torque or transmission output torque, in particular such that the Engine torque or the transmission input torque and the wheel torque or the transmission output torque have different torque values from each other.

For example, in a gear change, which is performed in the transmission device, in particular in a transmission of the transmission device, for example, the factor, in particular at least substantially continuously changes from an actual transmission ratio to a desired or target transmission ratio. In this case, the gear change is effected or carried out, for example, by the actuation of the switching elements. Preferably, the gear change is performed with an overlap so that, for example, a first one of the first clutch of the switching elements is opened, while a second clutch formed as a second of the switching elements is closed. Such a gear change with overlap is already well known and is, for example, in a converter automatic transmission, performed to perform, for example, the gear change comfortable and thus jerk-free or low-jerk.

Usually, the factor and the described change from the actual transmission ratio to the target transmission ratio can not or only qualitatively be calculated, since the drive train is usually not equipped with a sufficient number of sensors, which, however, kept the weight and the cost of the powertrain low can be. Therefore, according to the invention recourse is made to the said parameters in order to monitor the transfer function or the factor. In particular, the invention is based on the finding that the transfer function or a transmission behavior resulting from the transfer function, which characterizes the transmission of the torque from the drive motor to the wheel via the transmission device, can not be formed or checked or monitored or can only be monitored or monitored on the basis of speed ratios. since the transmission behavior of a torque calculation is used and thus used for adjusting the torque provided by the drive motor.

The engine torque is set, for example, based on a request or a request of the driver of the motor vehicle, this requirement or this request of the driver is also referred to as driver's request. The driver's specification of the rotary torque is usually determined on the machine level and thereby on the basis of an accelerator pedal value and on the basis of the rotational speed of the drive motor, in particular the output shaft. The accelerator pedal value thereby characterizes a position of an accelerator pedal by means of which the driver can set the torque to be provided by the drive engine.

By means of the method according to the invention, the driver's intention determination can now be made on the wheel plane, so that an at least almost radome-neutral gearshift, that is to say an at least almost wheel torque-neutral and thus low-jerk or jerk-free shifting, can be realized. To set, for example, the torque to be provided by the drive motor to or according to the driver's request, the driver's request is considered as acting on the wheel, desired wheel torque and shared, for example, by the transfer function to thereby realize a particularly comfortable operation, in particular a particularly comfortable gear change , This concept can also be used, for example, in the context of an electronic stability program (ESP), in particular when requesting a Bremsrekuperationsmoments an electric machine, as well as a request for a Schubrekulu- tionmoment on the electric machine.

As a possible disadvantage of the previously described, at least almost radomomentenneutral switching has been identified that the transfer function is basically tuned to a switching behavior. This means that, for example, in a gear change excessive jerk avoided or deliberately provoked or caused to be. In this case, however, it can not be detected whether, for example, a signal transmitted via a data bus, in particular electrical, for carrying out the at least almost radome-neutral switching has an excessive deviation from a transmission ratio that is physically present in the transmission device. It can be disadvantageous in this case, in particular, if an excessively low transmission ratio is determined or adjusted, even though a relatively larger transmission ratio has been physically set in the transmission device. As a result, the engine torque, also referred to as engine torque, can be set to a disadvantageous torque value, which can lead to undesirable effects. An example of this may be that the transmission ratio for an eighth gear of the transmission device is transmitted, although physically in the transmission device, a second gear is engaged.

This above-described, fundamentally possible disadvantage can now be avoided or compensated for by the method according to the invention, since the transfer function or its setting is monitored as a function of the parameters mentioned. In this way it is possible to make the transfer function plausible. If, for example, an error of the transfer function, in particular an unfavorable value of the transfer function, is detected, then the transfer function can, for example, be transferred or capped, that is to say limited, if the error is present continuously for a predefinable period of time. In this way, a particularly safe operation of the drive train can be realized because unwanted effects such as accelerations can be avoided. Since the monitoring of the transfer function is based on the parameters and on these on the states of the switching elements, a particularly robust monitoring and design can be realized. In particular, requirements for maximum delays in a case of recuperation of the drive train can be met.

It has proven to be particularly advantageous if, during the monitoring of the transfer function, its value is influenced as a function of the parameters determined, in particular set or restricted to a desired value. As a result, unfavorable, undesired effects causing values of the transfer function can be avoided, whereby a particularly safe operation can be realized.

A further embodiment is characterized in that, depending on the parameters, at least one check value is determined with which an actual value of the transfer function is compared. The actual value of the transfer function or of the factor is to be understood in particular as meaning a value which the transfer function or the factor initially has and which can be changed, for example, so that it is possible, for example, to change the actual value to the desired value.

It has proven to be particularly advantageous if the value of the transfer function is influenced when a difference between the actual Value and the validation value exceeds a predefined threshold. The background of this embodiment is to tolerate slight deviations of the transfer function or of the factor, in particular of the actual value, from the check value since such slight deviations do not lead to undesirable driving conditions. However, if the actual value deviates excessively from the check value, the transfer function or the factor is influenced, in particular such that the transfer function or its value is set to the desired value or that the transfer function or the factor is limited or capped. By setting the transfer function or the value of the transfer function to the desired value, it is to be understood in particular that the actual value set, for example, initially set to the desired value or changed. In this way, a safe condition of the drive train can be set specifically.

By tolerating slight deviations of the actual value from the check value, unnecessary and, in particular, unnecessarily frequent influencing of the transfer function or of the factor can be avoided, so that comfortable operation can be realized in the predominant operating ranges of the drive train.

In order to realize a particularly safe and comfortable operation, it is provided in a further embodiment of the invention that the value of the transfer function or of the factor is affected if a period of time, also referred to as fault tolerance time, during which the difference continuously exceeds the threshold value, is a predefinable time limit exceeds. If, for example, the excessive deviation of the actual value from the check value only occurs for a very short time, this may be, for example, a short-term overshoot and / or an error detection. In order to avoid resulting from such short-term overshoots or false detections and thus undesirable influences on the transfer function or the factor, and to influence the transfer function and then only if the excessive deviation of the actual value of the check value is actually present, it is now planned to influence the transfer function as a function of the fault tolerance time. Preferably, the fault tolerance time is at least 100 milliseconds, more preferably at least 200 milliseconds, and preferably at least 300 milliseconds. It has proven particularly advantageous if the error tolerance time is 300 milliseconds. Preferably, the fault tolerance time is less than 500 milliseconds, especially less than 400 milliseconds.

For example, the threshold value is 30 percent of the validation value, so that, for example, the transfer function is affected if the actual value is greater than 1.3 times or less than 0.7 times the validation value.

A further embodiment is characterized in that, depending on the parameters, at least one transmission ratio of the transmission device resulting from a gear engaged in the transmission device, in particular in the transmission, is determined. On the basis of the parameters, it can be detected, for example, whether and, if so, which of the switching elements are open or closed. In particular, it can be determined on the basis of the parameters whether the actuation was successful, that is to say whether the actuation has led to a desired desired state of the respective switching element. The actuation is effected, for example, by appropriate activation, in particular control or regulation, of the switching elements, in particular of valve elements of the switching elements. The effecting of the actuations leads, for example, to the respective desired desired state of the respective switching element when the drive train is functional and thus has no malfunction.

However, if, for example, an error occurs, for example, despite the actuation, that is, despite the activation, if necessary, at least one of the switching elements not to the desired desired state of the one switching element, so that, for example, at least one switching element open remains even though it should be closed, or so that, for example, at least one switching element remains closed even though it is to be opened. In other words, it is possible on the basis of the parameters to detect reactions of the valve elements on the actuation of the actuations, so that it can be recognized whether the respective, characterized by the respective parameter state of the respective switching element the desired desired state or one of the desired desired State corresponds to different error state of the respective switching element. By determining the state can be determined whether, and if so, which gear of the transmission device or the transmission is engaged, so that in the sequence, the gear ratio of the engaged gear or a resulting from the gear ratio of the transmission device can be determined. The transmission ratio is stored, for example, in a memory device, in particular in a map stored in the memory device.

It has proved to be particularly advantageous if the transmission ratio is used as the check value. In this way, for example, a particularly safe operation can be ensured for the following reasons: First, for example, the gear ratio or the factor assuming that the drive train is error-free, set or predetermined, so that the gear ratio or the factor, for example, has a first value. The use of this first value leads, if the drive train is error-free, to a desired shift behavior, so that, for example, then comes to a low-jerk or jerkless gear change. This is the case, for example, because in the case of a faultless drive train, the actuation of the actuations leads or has led to the respective desired states of the switching elements, whereby, for example, a desired setpoint gear is actually engaged in the transmission device or in the transmission. Then, the first value of the transmission behavior advantageously corresponds to the actually engaged gear, and an advantageous gear change can be performed.

For example, due to an error, as described above, it may happen that the actuation of at least one of the switching elements does not lead to the desired desired state, so that, for example, not the desired target gear, but one of the target Gear different different gear is engaged respectively. If now the engine torque to be adjusted based on the first value of the transfer function, while not the desired target gear, but the other gear is engaged, it could lead to an unfavorable gear change or unfavorable effects. However, based on the parameters, it can now be recognized that at least one of the switching elements is not in the desired desired state. In particular, it can be recognized that not the desired desired gear, but the other gear different from the desired gear is inserted. As a result, for example, the transfer function is influenced in such a way that the initially set first value of the transfer function is set to a different second value. By setting the second value, for example, unwanted effects, which would occur while maintaining the first value, can be avoided, so that despite the fact that not the desired target gear, but the other, different gear, is inserted, unfavorable effects can be avoided. This embodiment is based in particular on the knowledge that in particular the gear actually engaged in the transmission or its transmission ratio greatly influences the transmission of the torque from the drive motor to the wheel and thus the wheel torque acting on the wheel.

In a particularly advantageous embodiment of the invention, monitoring of the transmission function is omitted if the transmission device is unable to transmit a predeterminable torque of, for example, 50 Newton meters or more. In other words, if, for example, a torque that can be transmitted at most by the transmission device from the drive motor to the wheel falls below a limit torque, the monitoring of the transmission function is omitted since, for example, a torque or force lock in the transmission device is interrupted or opened. For this purpose, it can happen, for example, that at least one clutch of the transmission device is open, so that lower torques can be transmitted via the transmission device only in relation to the predefinable torque. In other words, for example, the transfer function is then and only monitored when the transmission device is able to transmit the predetermined torque and torque over the predetermined torque, since then, for example, in the transmission device, a sufficient adhesion exists or is closed. In this embodiment, a monitoring blanking is thus provided. Under this monitoring suppression is to be understood that the monitoring of the transfer function is omitted if the transmission device is unable to transmit the predetermined torque. A further embodiment is characterized in that the respective parameter comprises an electric current resulting from the respective effecting of the respective actuation and flowing through the respective switching element. In other words, for example, results from the effect of the respective operation, that is, for example, from the aforementioned driving the respective switching element, an electric current flowing through the respective switching element. If it is detected, for example, that the electric current is within a normal range and thus, for example, falls below an upper limit and exceeds a lower limit, then it can be deduced that the respective switching element has the desired desired state or has come into the desired desired state is. However, if, for example, it is determined, in particular detected, that the electric current exceeds the upper limit or falls below the lower limit, then it can be deduced that the drive train has an error and, in particular, that the actuation of the respective actuation has not led to the desired result, and that respective switching element, for example, does not assume the desired desired state or has not come in the desired desired state. In other words, in this embodiment, a current-based detection of the respective state of the respective switching element is provided. In combination with the above-described determination of the transmission ratio or the engaged gear thus, for example, a current-based gear determination is provided, by means of which the transfer function or the factor is monitored and in particular influenced.

Finally, it has proven to be particularly advantageous if the respective switching element has at least one valve whose actuation is effected, for example. The valve is, for example, a solenoid valve or an electrically operable valve, so that, for example, when the switching element or the valve is faultless, results from the respective effecting the respective actuation of a different current from zero, which by the valve, in particular by its Coil, flows.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description and the following in the Description of figures mentioned and / or shown alone in the figures features and combinations of features can be used not only in the specified combination, but also in other combinations or alone, without departing from the scope of the invention.

The drawing shows in:

1 shows a diagram for illustrating a method according to the invention for operating a drive train of a motor vehicle;

Fig. 2 is another diagram for illustrating the method; and

Fig. 3 is another diagram for illustrating the method. In the figures, the same or functionally identical elements are provided with the same reference numerals.

In the following, a method for operating a drive train of a motor vehicle, in particular of a motor vehicle such as a passenger car, is explained with reference to FIG. The drive train comprises at least one drive motor, a transmission device and at least one wheel drivable by the drive motor via the transmission device. The drive motor is, for example, an internal combustion engine, in particular a reciprocating internal combustion engine, wherein the drive motor has, for example, an output shaft designed in particular as a crankshaft. Via the output shaft, the drive motor can also provide torques which are designated as machine torques or engine torques and which can be transmitted to the wheel via the transmission device. For this purpose, for example, the respective, provided by the drive motor via the output shaft torque, in particular via a transmission input shaft, in the transmission device, in particular in a transmission of the transmission device, initiated so that, for example, the torque provided by the drive motor corresponds to a transmission input torque. The transmission device provides, for example, a transmission output torque resulting from the torque provided by the drive motor which, for example, corresponds to a wheel torque acting on the wheel and thus on the wheel plane. The transmission in this case has a plurality of switching elements, wherein in the context of said method for operating the drive train, respective actuations of the respective switching elements are effected. As part of the respective effecting the respective actuation, for example, the respective switching element is controlled, in particular controlled or regulated. The respective switching element, for example, as a brake or clutch, in particular frictional or positive clutch, be formed, wherein the respective switching element, for example, has at least one valve. By means of the respective valve, for example, a flow of a fluid, in particular a liquid, can be influenced or adjusted, wherein the flow of the fluid is influenced by the activation of the switching element via the respective valve. The respective valve is, for example, an electrically operable valve, which is also referred to as an electric valve. If, for example, the respective switching element is free from errors, an electric current results, for example, from the activation, which flows through the valve, in particular through a coil of the valve, and lies, for example, within a normal range. As a result, for example, results from the respective effecting the respective actuation, that is, from the driving, at least temporarily, a desired desired state of the valve and thus of the switching element as a whole.

If the respective switching element or the respective valve has an error, for example, no current flow through the valve results from the respective activation or the electrical current flowing through the valve is outside the normal range. As a result, for example, the respective valve and thus the respective switching element come or remain in a different state from the desired desired state. The respective desired state and the respective error state are collectively referred to as states.

The respective actuations of the respective switching elements are effected to thereby influence a transmission of the respective, provided by the drive motor torque from the drive motor via the transmission device to the wheel. By driving the switching elements, for example, a gear change can be performed. In this case, for example, the transmission device has at least one transmission which has a plurality of switchable or insertable gears with respective ratios or gear ratios. For example, the gears differ in their transmission ratio. nissen. Under a gear change, which is also referred to as switching, for example, to understand that a first engaged first gear of the transmission designed and thus deactivated and a first designed or deactivated second gear of the transmission is engaged and thus activated. For this purpose, for example, a first clutch is opened and a second clutch is closed, wherein, for example, the first clutch is a first of the shifting elements and the second clutch is a second of the shifting elements. Preferably, such a gear change takes place with overlap, so that, for example, the first clutch is opened, while the second clutch is closed or vice versa. As a result, a comfortable gear change can be performed.

The transmission is designed, for example, as an automatic transmission and may have a hydrodynamic torque converter, which is also referred to simply as a converter. Thus, the transmission is formed, for example, as a converter automatic transmission, which is also referred to as a converter-automatic or converter-automaton. Furthermore, it is conceivable that the transmission device has a differential gear, also referred to as an axle drive, via which, for example, the respective torque is transmitted or distributed to wheels of the drive train spaced from each other in the vehicle transverse direction.

Under an upshift of the transmission is to be understood, for example, that the first gear designed and the opposite of the first gear greater, second gear is engaged. For example, a downshift is understood to mean that the second gear is designed and the first or second gear that is lower or lower than the second gear is engaged. In this case, for example, the transmission ratio of the second gear is less than the transmission ratio of the first gear, so that, for example, in the course of an upshift, the transmission ratio of the transmission is reduced, wherein in the course of a downshift, the transmission ratio is increased. In this case, for example, the transmission has eight shiftable gears or gears. Fig. 1 shows a diagram in which curves 10a-e are entered. The curves 10a-e are respective current curves which illustrate the respective, previously described, resulting from the effects of the actuations and flowing through the switching elements electrical currents, so that, for example, at least five switching elements are provided. Furthermore, so-called current thresholds 12, 14 and 16 are entered in the diagram shown in FIG. 1, which are respective threshold values or limits for the respective electrical currents. In order to realize a particularly safe and comfortable operation of the drive train, it is provided in the process that the provided by the drive motor torque (engine torque) is set in response to a transfer function indicating a factor with which of the drive motor To multiply the torque provided via the output shaft to calculate the above-described, resulting from the torque and from the transmission of the torque from the drive motor via the transmission device to the wheel and acting on the wheel wheel torque. In particular, the engine torque is set in the previously described gear change with overlap in the manner described, so that in the process not about a speed-based circuit is performed, but in comparison to conventional methods is a change from a speed-based circuit to an at least almost radmomentenneutrales Switch provided, which is also referred to as master shift. In the course of the gear torque neutral switching of the drive motor fits according to the transmission function also called transmission function be called clutch torque engine torque, for example, especially during the gear change or during the circuit, the wheel torque, which is also referred to simply as wheel torque, at least in Maintain constant. As a result, an at least almost smooth shifting can be realized, since, for example, excessive torque increases or an excessive torque drop at the wheel can be avoided.

The transfer function or the factor, in particular its value, is adapted to the respective gear change, for example, and is predefined in particular as a function of that of the gears into which the shift is made or to which the shift is made. If the drive train is now error-free, then the respective activation causes the respective desired state of the respective switching element, so that the respective switching element comes into its respective desired state or is in its respective desired state. Subsequently, the system switches to a desired nominal gear, whereby a sol- circuit in combination with the transfer function leads to an advantageous circuit. However, if there is now an error in the drive train, so that despite the activation of the switching elements of one or more of the switching elements or all switching elements not come in the desired target state, but in an error state or remain in an error state, so For example, it is not switched to the desired target gear, but it is switched, for example, in a different gear from the target gear or the transmission remains in a different gear from the target gear. In such a fault of the drive train now adapted to the target gear transfer function would lead to undesirable effects, which can now be avoided by the method.

For this purpose, it is provided that respective parameters are determined which characterize respective states of the respective switching elements resulting from the actuation or the actuation of the actuation, and the transfer function is monitored and in particular influenced as a function of the determined parameters. The respective parameter comprises the electric current described above, so that the transfer function is monitored on the basis of the respective electrical currents. In particular, the gear currently engaged in the transmission or a gear ratio resulting from the engaged gear ratio of the transmission device can be determined on the basis of the electrical currents. If, for example, the determined gear deviates from the desired gear, the transfer function can be changed, for example, from an initially set actual value to an advantageous target value, or the transfer function is capped or limited, so that, for example, from the previously described error of the drive train resulting undesirable effects can be avoided.

An error in the transfer function can consequently lead to an unfavorable wheel torque, as a result, for example, can lead to undesirable effects such as jerky movements. In particular, the following error cases are to be considered:

In a first of the error cases, the transmission function erroneously changes the engine torque, for example, by transmitting the wrong gear to an engine control unit. Here, for example, instead the second gear transmits the fourth gear, whereby the wheel torque is too high.

In the second error case, the gear ratio changes erroneously, and the transmitted transmission function remains unchanged. This occurs, for example, when the transmission is incorrectly changed from the third gear to the second gear and the transfer function continues to transmit the third gear or emanating from the third gear. This also immediately results in too high a wheel torque.

Unfavorable values of the wheel torque can lead to unwanted accelerations, resulting in, for example, an uncomfortable, jerky ride. For example, in a recuperation or overrun operation can lead to undesirable delays of the motor vehicle. However, now that the transfer function is monitored in the manner described, excessively erroneous wheel torques and thus excessively high accelerations and excessive delays can be avoided. Furthermore, in the diagram shown in FIG. 1, for example, a monitoring area 18 is entered, which extends, for example, continuously from the current threshold 14 to the current threshold 16 or vice versa. In addition, a history 20 entered in the diagram shown in FIG. 1 illustrates the transfer function or its value, whereby a monitoring area 22 for monitoring the transfer function is also shown. From theoretical analysis considerations, the maximum permissible deviation during the shift of a gear jump of +/- 30 percent has proven to be an advantageous limit value for a wrong transfer function. This maximum permissible deviation of the transfer function from, for example, a check value is based on underlying transmission characteristics such as the gear ratio and vehicle characteristics such as vehicle curb weight, driving resistance, etc., for example, the maximum allowable deviation +/- 30 percent of the bridging value. The underlying maximum tolerance threshold is to be checked and worked out, for example, with every gearbox new development or with each new vehicle. Overall, it can be seen that the transfer function is monitored for a maximum permissible deviation during the shift and, for example, in a fixed gear. In particular, a monitoring of the transfer function is provided when driving in a fixed gear without circuit. Such driving in a fixed gear without a circuit is realized, for example, by energizing exactly three of the switching elements, which can be recognized, for example, by means of the courses 10a-c. Thus, for example, in FIG. 1, driving in fixed gear is illustrated. Fig. 2 illustrates, for example, a circuit, in particular a sequential circuit, so that exactly one gear jump is provided. Further, for example, Fig. 3 illustrates multiple circuits, so that the gear jump is greater than 1.

In particular, for example, the following assumptions are based on: Driving in the fixed gear without a circuit is realized by an energization of exactly three of the switching elements. During a circuit, more than three switching elements may be involved for a short time. During a circuit, for example, two out of four switching elements remain maximally energized. It should be possible to define a lower actual current threshold of the respective valve per switching element, which certainly does not generate a power circuit break. This lower actual current threshold is also referred to as the first current limit and is, for example, the current threshold 12. It should be possible to define a second actual current threshold of the valve per switching element, which guarantees transmission of a maximum uncritical torque of, for example, a maximum of 50 Newton meters. It should be possible to define a third actual current threshold per switching element, in which the respective switching element is not in slippage and proportionately the total torque of Drive motor can transmit. This third actual current threshold is, for example, also referred to as the third current limit and is, for example, the current threshold 16. In this case, for example, sufficient supply of the respective switching element with the aforementioned fluid, in particular with oil, is assumed. The respective current limit should be so robust that it can attenuate voltage fluctuations, in particular at a control unit. For reasons of robustness, the monitoring of the transfer function is not realized on the basis of speed differences, but on the basis of the electrical currents of the switching elements, also referred to as valve flow. The background to this is that, in contrast to speed-based monitoring, unwanted slippage in the clutch does not necessarily lead to fault detection and consequently to limitation. The transfer function should be on an impermissibly high deviation from a gear jump compared to the actual physical actual value can be monitored. The calculation of the transfer function is done, for example, on the product of converter ratio, gear ratio and axle ratio, the converter ratio is the translation of the hydrodynamic torque converter, the transmission shaft, the transmission ratio and the axle ratio is the translation of the Differenzialget ebes. The monitoring of the transfer function should take into account all quantities of the defined overall transmission ratio.

When driving in fixed gear, for example, only exactly three switching elements above the current threshold 16 may be controlled. It should be determined based on the Bestromungsmusters an allowable gear combination. In other words, it is possible, depending on the parameters and thereby, for example, depending on the courses 10a-e to determine whether and if so which of the gears is engaged. This is done as part of a gear determination. Thus, for example, based on the parameters of the currently engaged gear and in particular its gear ratio is used, for example, the gear ratio is used as the aforementioned check value. Preferably, the transfer function should not deviate more than a predefinable threshold from the transmitted gear ratio of the engaged gear, the threshold being, for example, 30 percent. If, for example, a deviation of the transfer function from the transmission ratio of the currently engaged gear is more than the threshold value, an error, in particular the transfer function, is deduced. If this error is present, for example, continuously during a period of time of, for example, 300 milliseconds, also referred to as the error tolerance time (FTZ), then the transfer function, in particular its value, is set to a desired value or capped or limited. In Fig. 1, for example, an upper gear ratio 24 and a lower gear ratio 26 are registered, which are respective limits within which the transfer function should be, so that no error of the transfer function is determined. For example, if the error is continuous throughout the fault tolerance time, then, for example, the transfer function is capped to the upper gear ratio 24 (upper limit) or lower gear ratio 26 (lower limit), particularly depending thereon. whether the transfer function or its deviation has cut or cut the upper or lower limit.

In addition, the monitoring of the transfer function should only be enabled when at least three current thresholds of the valves greater than the current threshold 14 have been detected. Thus, a critical disturbance torque on the drive or output is physically possible. If, for example, no excessive deviation of the transfer function from the check value, in particular from the value of the determined smallest gear, so that the transfer function is between the upper and lower limits, or, for example, less than four current thresholds are detected below the current threshold 14, the error tolerance time is filtered back , Furthermore, for example, the transfer function is monitored in circuits or adaptations, which are illustrated in FIGS. 2 and 3. In this case, the fault tolerance time is entered in FIG. 2 and designated by 28. Furthermore, in FIG. 2, the mentioned overlap, also referred to as moment overlap, is entered and designated by U. In circuits or adaptations exactly two gears and thus gear ratios should be determined as upper and lower limits (gear ratios 24 and 26) for the switching operation. For the gear ratio without converter influence, for example, the corresponding value is used due to the gear determination. The determined fixed gear ratios form the physical upper and lower limits and consequently the limits of the monitoring. Again, for example, the transfer function should deviate at most 30 percent from the determined transmission ratio of the smallest gear. If the deviation exceeds 30 percent of the check value or the determined transmission ratio of the smallest gear, then there is an error. If this error is present, for example, continuously during the error tolerance time, the transfer function or its value is capped to the upper or lower limit (gear ratios 24 and 26) after the error tolerance time has elapsed, depending on whether the deviation or the transfer function is the upper or lower limit has cut lower limit. The monitoring should only be enabled when at least three current thresholds of the valves were greater than the current threshold 14 detected. This is only a critical disturbance torque on the drive or output physically possible. If the deviation exceeds the threshold value and thus, for example, 30 percent of the transmission ratio of the determined lowest gear or if less than four current thresholds are detected below the current threshold 14, then the fault tolerance time is filtered back. The respective fault tolerance time defines, for example, a monitoring area in which the transfer function is monitored. In particular, it is provided that monitoring also takes place during the torque overlap, and preferably independently of the fault tolerance time.

Further, for example, the transfer function in a so-called reversing, that is, in a reverse drive or when engaging a reverse gear of the transmission monitored. If, for example, a gear formed as a forward gear or a forward gear is shifted into a reverse gear or a reverse gear by means of which a reverse drive of the motor vehicle can be effected, then the electric currents and thus the energization pattern of the switching elements or the valves are likewise determined. In this case, a shift or a gear change is not possible because there is only one reverse gear or only one reverse gear. The monitoring of the transfer function is performed, for example, as in the case of driving in fixed gear.

Another state is, for example, a so-called traction, which is provided, for example, in passages or driving steps designated N or P. In these driving steps no frictional connection is allowed, whereby even in designated with D or R stages of traction can be interrupted, such as in a start-stop operation, a freewheel and / or a stand decoupling. In this case, for example, less than three switching elements are energized above the current source 14. If this state of traction is detected, no more than the uncritical torque of, for example, 50 Newton meters can be transmitted. As a result, the monitoring of the transfer function is to be hidden and the fault tolerance time is filtered back. Another condition is for example a mistake or a special treatment. The hydrodynamic torque converter has, for example, a turbine wheel or a turbine and a pump wheel or a pump, wherein the turbine can be driven by the pump, for example hydrodynamically. The turbine is associated, for example, a turbine speed sensor, by means of which a rotational speed of the turbine is detected. In case of failure of the turbine speed sensor, a fixed gear should be engaged and a further switching can be prevented. In this state, the gear ratio should be used without converter influence. For the influence of the transformer overshoot, the maximum value should be assumed in order to realize a safe operation. For example, if an output speed sensor fails, a fixed gear should be engaged. In this case, the gear ratio should be used without converter influence. For the influence of the converter overshoot, a calculated value from a converter slip should continue to be used. If the engine speed fails, a fixed gear should be engaged. In this condition, the gear ratio should be used under transducer influence. For the influence of the transducer movement, the maximum value should be assumed.

If, in a valve failure to control or actuation of the switching elements no frictional connection is possible, so that, for example, less than three valves of the switching elements are energized, then the monitoring is hidden, for example. In this case, for example, a qualitative value may still be sent out of the most likely reconnection path. If more than three valves of the switching elements are energized longer than the permissible fault tolerance time above the current source 14, this leads to a restriction of the degree of freedom of the transmission.

Claims

CLAIMS:

A method for operating a drive train of a motor vehicle having at least one drive motor, a transmission device and at least one wheel drivable by the drive motor, in which respective actuations are effected by respective shift elements of the transmission device, thereby transmitting a torque provided by the drive motor from the drive Drive motor via the transmission device to affect the wheel

characterized in that:

the torque provided by the drive motor is adjusted in response to a transfer function indicating a factor with which the torque is to be multiplied to calculate a wheel torque resulting from the torque and transmission and acting on the wheel;

respective parameters are determined which characterize respective states of the respective switching elements resulting from the actuation of the actuations; and

- The transfer function is monitored in dependence on the determined parameters.

Method according to claim 1,

characterized in that

when monitoring the transfer function whose value is influenced as a function of the determined parameters, in particular set or limited to a desired value.

Method according to claim 1 or 2,

characterized in that

depending on the parameters at least one check value is determined with which an actual value of the transfer function is compared.

Process according to claims 2 and 3,

characterized in that

the value of the transfer function is influenced if a difference between the actual value and the check value exceeds a predefinable threshold value. Method according to claim 4,

characterized in that

the value of the transfer function is affected when a period of time during which the difference consistently exceeds the threshold exceeds a predeterminable time limit.

Method according to one of the preceding claims,

characterized in that

depending on the parameters at least one of a gear engaged in the gear mechanism resulting gear ratio of the transmission device is determined.

Method according to claim 6, in which reference is made to one of claims 3 to 5,

characterized in that

as the check value, the gear ratio is used.

Method according to one of the preceding claims,

characterized in that

the monitoring of the transfer function is omitted when the transmission device is unable to transmit a predetermined torque.

Method according to one of the preceding claims,

characterized in that

the respective parameter comprises an electric current resulting from the respective effecting of the respective actuation and flowing through the respective switching element.

Method according to claim 9,

characterized in that

the respective switching element has at least one valve.