DE102007048862B4 - Method and device for limiting the speed of an engine - Google Patents

Abstract

Method for limiting the maximum speed of a motor (2) by specifying a setpoint torque; the setpoint torque (M) of the motor (2) can be determined as a function of the maximum speed and a predicted speed, which depends on the current speed and a speed gradient (s) , so that the speed (n) of the motor (2) is limited; characterized in that the target torque (M) of the motor (2) is determined as a function of the predicted speed (npr), which depends on a speed gradient (n), which is weighted according to the state of the adhesion with a weighting factor.

Description

Technical field

The invention relates to a method and a device for limiting the speed of an engine, in particular an internal combustion engine, in the event of rapid changes in load torque.

State of the art

In today's internal combustion engines, the maximum speed is limited by limiting the internal engine torque. This is done with the help of a suitable regulation. In addition to the current speed, a prediction of the speed curve is used as the control variable so that the intervention of the actual control can be started before the maximum speed is exceeded. Based on the current speed gradient, a speed is estimated that would occur after a certain time (prediction time). As a result, a speed limit can intervene before the current engine speed is at or above the maximum speed. Taking the speed gradient into account ensures that the actual engine speed is reliably adjusted to its maximum value and that the maximum value is not exceeded or is exceeded only for a short time.

The DE 10 2005 027 361 A1 describes a method for operating an internal combustion engine. The speed is compared with a maximum permissible speed. The speed value used for the comparison is predicted on the basis of the current speed, the speed gradient and the current gear ratio.

The DE 199 13 272 A1 describes a method for controlling an internal combustion engine. The speed is limited to a specified value.

Also from the DE 195 06 082 A1 a method for speed limitation is known.

During switching operations in a motor vehicle, in particular under full load, there is no closed drive train for a short time, i.e. there is no frictional connection between the engine and the wheels of the vehicle driven by the engine. As a result, the engine speed can increase very rapidly during downshifts and very steep speed gradients are achieved. However, these speed gradients in the case of a brief open force connection are not meaningful in an implausible form for the behavior of the speed when the force connection is closed, since a much lower speed gradient would occur if the force connection was closed.

However, since the state of the open frictional connection is only present for a very short time, namely for the time of the switching process, the speed prediction, which takes the speed gradient into account, may lead to an intervention without the actual risk of the speed of the motor exceeds the specified maximum speed. Especially in a switching process in which e.g. If a driver overtakes the accelerator pedal (kickdown), the intervention of the speed limitation due to a high predicted speed gradient is a hindrance, since in this case the torque is reduced during the shifting process. The driver therefore has only a reduced torque available during (and possibly immediately after) the shifting process.

It is therefore an object of the present invention to provide a method and a device for limiting the speed of an engine, in which the speed limitation takes into account the speed gradient in a plausible manner or takes a plausible (modeled) speed gradient into account.

Disclosure of the invention

The above object is achieved by the method according to claim 1 and by the device according to the independent claim.

Further advantageous embodiments of the invention are specified in the dependent claims.

According to a first aspect, a method for limiting the maximum speed of an engine by specifying a target torque is provided. The setpoint torque of the motor is dependent on the maximum speed and a predicted speed, which depends on the current speed and a speed gradient, so that the speed of the motor is limited. The speed gradient is taken into account as a function of a state of the frictional connection to the motor when determining the target torque. The setpoint torque of the motor is determined as a function of the predicted speed, which depends on a speed gradient that is weighted with a weighting factor in accordance with the state of the frictional connection.

The above method makes it possible to plausibility check the influence of the speed gradient when limiting the internal engine torque to limit the maximum speed of the engine and to take it into account for the speed limitation in accordance with an event that leads to a change in the load torque on the drive train. Thus, for example at a switching operation in which the drive train is opened briefly, the resulting high speed gradient is not taken into account or is taken into account to a lesser extent in order not to trigger any intervention in the limitation of the internal torque.

Furthermore, depending on a first state of the frictional connection, in particular when the frictional connection is closed, the speed gradient can be taken into account and, depending on a second state of the frictional connection, in particular when the frictional connection is open, the speed gradient cannot be taken into account.

Furthermore, the state of the frictional connection can be determined by a coupling state of a clutch.

The state of the adhesion to the motor can be indicated by an event signal. The speed gradient can then be adjusted as a function of a first state of the event signal, which indicates an opening of the frictional connection, the adaptation being delayed by a first time period from the onset of the first state of the event signal, and / or during a second time period while which the speed gradient is weighted with decreasing weighting.

As an alternative or in addition, the speed gradient can be adapted as a function of a second state of the event signal, which indicates a closing of the force fit, the adaptation being delayed by a third time period from the onset of the second state of the event signal, and / or during a fourth time period , during which the speed gradient is weighted with increasing weighting.

According to a further aspect, a device is provided for limiting the maximum speed of an engine by specifying a target torque. The device comprises an engine control in order to determine the target torque of the engine as a function of the maximum engine speed and a predicted engine speed, which depends on the current engine speed and a speed gradient, so that the engine speed is limited. The engine control is further developed to take the speed gradient into account depending on a state of the force connection to the engine for the determination of the target torque.

According to a further aspect, a computer program is provided which contains a program code which, when executed on a data processing unit, carries out the above method.

Figure list

• 1 eine schematische Darstellung eines Motorsystems mit einer Drehzahlbegrenzung gemäß einer Ausführungsform der vorliegenden Erfindung;
• 2 ein Blockdiagramm zur Darstellung der Funktion der Drehzahlbeschränkung gemäß einer ersten Ausführungsform der Erfindung;
• 3 ein Blockdiagramm zur Darstellung der Funktion der Drehzahlbeschränkung gemäß einer zweiten Ausführungsform der Erfindung; und
• 4 ein Diagramm zur Darstellung der zeitlichen Verläufe der Drehzahl, der prädizierten Drehzahl sowohl ohne als auch mit Anwendung des erfindungsgemäßen Verfahrens bei einem Schaltvorgang eines automatischen Getriebes.

Preferred embodiments of the present invention are explained in more detail with reference to the accompanying drawings. Show it:

• 1 is a schematic representation of an engine system with a speed limitation according to an embodiment of the present invention;
• 2nd a block diagram illustrating the function of the speed restriction according to a first embodiment of the invention;
• 3rd a block diagram illustrating the function of the speed restriction according to a second embodiment of the invention; and
• 4th a diagram showing the temporal profiles of the speed, the predicted speed both without and with the use of the inventive method in a switching process of an automatic transmission.

Description of the embodiments

In 1 is a schematic representation of an engine system 1 shown in which a speed limitation can be realized according to the present invention. The engine system 1 includes an internal combustion engine 2nd , in particular an internal combustion engine, which has a drive train 3rd and via a clutch 5 with a gear 4th can be coupled. To control the clutch 5 and the transmission 4th is a transmission control 6 provided that takes over, for example, the functions of an automatic transmission in a motor vehicle. To control the engine 2nd , which can be an internal combustion engine, for example, is an engine control 7 provided to control the internal combustion engine 2nd a speed information about a speed n either directly from the internal combustion engine 2nd or via a speed sensor 8th that on the powertrain 3rd is arranged, receives.

Especially when using such an engine system 1 the corresponding internal combustion engine is in a motor vehicle 2nd limited in its maximum speed, for example to damage the engine 2nd to avoid by too high speed. The speed n of the internal combustion engine 2nd is limited by the target torque of the internal combustion engine, which is an input variable for the torque control of the internal combustion engine 2nd is reduced accordingly. The speed limitation is in the motor control 7 among other functions for controlling the internal combustion engine 2nd executed. When limiting the speed, the speed gradient, ie the time course of the speed, is also taken into account. For this purpose, a speed prediction is made using the speed gradient carried out. The speed prediction is usually carried out in such a way that a future speed is estimated, which occurs after a certain prediction time, assuming a constant speed gradient during the prediction time. An estimated future speed of the internal combustion engine can thus be used for the speed limitation 2nd can be determined after a predetermined prediction time t _pr . This makes it the engine control 7 possible, a limitation of the target torque of the internal combustion engine 2nd even before the maximum speed of the internal combustion engine is actually reached 2nd to reduce so as to overshoot the speed of the internal combustion engine 2nd Avoid as far as possible via the maximum speed. The prediction time t _pr can essentially be freely determined and is usually between 50 ms and one second, preferably between 70 ms and 500 ms, particularly preferably between 90 ms and 300 ms, and in particular at 200 ms, for internal combustion engines for use in motor vehicles.

In 2nd Fig. 3 is a block diagram showing preferably in the engine controller 7 executed function for speed limitation according to a first embodiment of the invention. The engine control 7 detects the current speed n in a suitable manner and determines it in a differentiation stage 11 the current speed gradient n _degrees . In a low pass filter stage 12th the speed gradient n _{degrees is} low-pass filtered in order to filter out noise that occurs, for example, due to the discretization of the speed signal from the signal for the speed gradient n _degrees . The filtered speed gradient becomes a multiplier 13 supplied, in which the speed gradient n _{grad is} multiplied by the predetermined prediction time t _pr . A speed change Δn can thus be determined after the prediction time t _pr , provided that the determined speed gradient does not essentially change during the prediction time. The speed change Δn determined in this way becomes common with the speed n of a summation stage 14 fed to a predicted speed npr to investigate.

In normal operation of the engine system 1 this predicted speed npr a target torque specification level 16 supplied to determine the target torque M _{mot_soll} with which the internal combustion engine 2nd in a corresponding manner by the engine control 7 is controlled. The target torque specification level 16 comprises a characteristic diagram, a functional relationship or a suitable regulation in order to determine the target torque M _{mot_soll} . In the simplest case, the maximum speed is regulated via a speed-dependent (or dependent on the predicted speed) limiting torque from a characteristic curve. Furthermore, regulation can be provided, the controlled variable of which is the speed difference between the maximum speed and the predicted speed.

An event occurs in which, for example, the drive train 3rd due to the clutch opening 5 is interrupted and thus the frictional connection is opened, this can cause a high speed gradient, which under certain circumstances, ie at a high speed n, which is close to a maximum speed, leads to a reduction in the target torque of the internal combustion engine M _{mot_soll} by the target torque setting stage 16 can lead. In the case of a gear change, in which it is already known in advance that it will be completed after a certain (short) period of time, intervention in the speed limitation due to a high speed gradient is not necessary and under certain circumstances, namely when changing down due to an overtaking maneuver that is starting Motor vehicle, a hindrance, since this can extend the switching time and possibly reduce the drive torque provided immediately after the switching intervention. Therefore, a switchover stage is provided with the aid of an event signal E. 15 to be controlled in such a way that, in the case of an event which is known to lead to an increase in the speed gradient only for a limited period of time, as is the case, for example, with a switching operation, with an ESP intervention and the like, instead of the predicted one Speed signal n _pr only the speed signal n of the target torque setting level 16 is supplied to the target torque M _{mot_soll of} the internal combustion engine 2nd to determine. In the exemplary embodiment shown, the event signal E is generated by the transmission control 6 provided that also clutch 5 and the transmission 4th is triggered and thus can generate the event signal E in such a way that it indicates in a suitable manner the time at which the force connection opens and the time at which the force connection closes.

A downshift of the switching stage 15 so the predicted speed n _pr in the target torque specification level 16 is taken into account again, takes place as soon as the frictional connection is closed again, which is indicated by the event signal E.

In 3rd is another embodiment for the method for limiting the speed n of the internal combustion engine 2nd shown. In contrast to the embodiment of the 2nd is in the embodiment of 3rd no switching stage 15 provided, based on an event signal E between the current speed n and the predicted speed n _pr switches. Instead, in the embodiment, the 3rd provided that the speed n in a differentiating stage 21 is derived to get n _degrees . The speed gradient n _degrees is in a low pass filter stage 22 low pass filtered and a multiplier 23 supplied to multiply the filtered speed gradient n _degrees by a predetermined prediction time t _pr . This corresponds essentially to the corresponding sub-functions of the embodiment of FIG 2nd . The result is a speed change Δn, which indicates the estimated speed change after the predetermined prediction time t _pr .

Instead of adding the speed change Δn and the current speed n to the predicted speed npr is a further multiplication level 24th provided that the speed change Δn with a weighting value EG applied, whereby the influence of the rotational speed gradient n _degree for the determination of the setpoint torque M of the engine _{mot_soll} 2nd can be set. In the illustrated example, the rotational speed gradient is not taken into account when a weight value of 0 and a weight value of 1 of the rotational speed gradient is N _degrees in full measure taken into account, as for example. Is desired for normal operation. The weighted speed change Δn x EG becomes a summation level 26 supplied in which the weighted speed change is added to the speed n and as a predicted speed n _pr a corresponding target torque specification level 27 or a corresponding torque control for the internal combustion engine is supplied by the target torque M _{mot_soll of} the internal combustion engine 2nd to obtain. The embodiment of the 3rd has the advantage that the speed gradient n _degree relevant for the implementation of the method can be modeled, which is particularly advantageous if the information about the frictional connection before and after the gearshifts is insufficiently accurate, for example by the transmission control 6 can be determined.

The weighting factor EG For example, depending on the coupling state of the clutch 5 be determined. Furthermore, the weighting factor EG when the coupling is opened, ie when the frictional connection is opened, after a certain first time period t _{1 has been changed} linearly, parabolically or via another (preferably monotonous) function during a second time period t ₂ from 0 to 1. The weighting factor can be adjusted to the same extent when the frictional connection is closed EG after a third period of time t ₃ , either with a sudden jump from 1 to 0 or correspondingly linear, parabolic or via another (preferably monotonous) function during a fourth period of time t ₄ from 1 to 0. By the sudden change in the weighting factors 0 and 1, the same function can be realized as with the changeover stage 15 the embodiment of the 2nd .

In 4th Diagrams are shown which show the time course of the engine speed n, the predicted engine speed npr , the gear engaged, and the engine speed n ' map without using the method according to the invention. 4th shows a shift operation when shifting from a second gear to a first gear by the transmission control for the automatic transmission. It can be seen that in a conventional method the actual speed n of the motor overshoots or undershoots compared to the motor speed that results when the method according to the invention is applied.

The present invention has the advantage that with a torque limitation that takes the speed gradient into account, there is no unnecessarily premature limitation of the target torque M _{mot_soll of} the internal combustion engine 2nd due to an incorrectly expected exceeding of the maximum speed n _MAX he follows. Furthermore, the method according to the invention ensures that the engine output is not limited by the torque control in the event of a brief interruption of the frictional connection, such as, for example, in downshifts to a lower gear to initiate an overtaking maneuver. The engine mechanics protection is ensured. The switching time is not due to an incorrectly expected exceeding of the maximum speed n _MAX extended (optimal short switching time is achieved).

The provision of the weighting factors EG for weighting the speed change Δn is compared to a hard switchover, as in the embodiment of FIG 2nd shown, makes sense if there is no reliable information available as to whether a gearshift actually takes place without a frictional engagement or if a compromise between engine protection and maximum power output is to be found during the gearshifting operation or if the frictional engagement is not fully open, but only partially open, ie the clutch is grinding, for example.

After the switching process has been completed, there should be a positive connection again. However, since the actual positive frictional engagement occurs only after a delay, the speed prediction is reactivated using a time profile of a factor. This ensures that the activation of the speed limitation always uses a value of the speed / speed gradient that is as plausible as possible.

Claims (8)

Method for limiting the maximum speed of an engine (2) by specifying a target torque; the setpoint torque (M _{mot_soll} ) of the motor (2) depending on the maximum speed and a predicted speed which depends on the current speed and a speed gradient (n _degrees ), can be determined so that the speed (s) of the motor (2) is limited; characterized in that the target torque (M _{mot_soll} ) of the motor (2) is determined as a function of the predicted speed (npr), which depends on a speed gradient (n _degree ) that is weighted with a weighting factor in accordance with the state of the adhesion. Procedure according to Claim 1 , the speed gradient (n _degrees ) being taken into account as a function of a first state of the force fit, in particular when the force fit is closed, and wherein the speed gradient (n _degrees ) is not taken into account as a function of a second state of the force fit, especially when the force fit is open. Procedure according to one of the Claims 1 to 2nd , wherein the state of the frictional connection is determined by a coupling state of a clutch. Procedure according to Claim 1 to 3rd , the state of the adhesion to the motor (2) being indicated by an event signal. Procedure according to Claim 4 , wherein the speed gradient is adjusted as a function of a first state of the event signal, which indicates an opening of the frictional engagement, the adaptation being delayed by a first time period from the onset of the first state of the event signal; and / or - takes place during a second period during which the speed gradient (n _degrees ) is weighted with decreasing weighting. Procedure according to Claim 4 or 5 , wherein the speed gradient (n _grad ) is adjusted as a function of a second state of the event signal, which indicates a closing of the force fit, the adaptation being delayed by a third time period from the onset of the second state of the event signal; and / or - takes place during a fourth period during which the speed gradient (n _degrees ) is weighted with increasing weighting. Device for limiting the maximum speed of an engine (2) by specifying a target torque; with a motor controller (7) to determine the target torque (M _{mot_soll} ) of the motor (2) depending on the maximum speed and a predicted speed, which depends on the current speed (n) and a speed gradient (n _degrees ), so that the speed (s) of the motor (2) is limited; characterized in that the motor controller (7) is designed to determine the target torque (M _{mot_soll} ) of the motor (2) as a function of the predicted speed (npr), which depends on a speed gradient (n _degree ), which according to the state of the Adhesion is weighted with a weighting factor. Computer program, which contains a program code which, when executed on a data processing unit, a method according to one of the Claims 1 to 6 executes.

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