DE102007019729A1 - Method for operating a drive train - Google Patents

Abstract

The invention relates to a method for operating a drive train comprising at least one automatic transmission and a drive unit of a motor vehicle, wherein a starting gear and a starting speed are determined for starting the motor vehicle and wherein a starting operation by closing a starting element, in particular with the particular starting gear and with the determined starting speed a startup clutch is triggered. According to the invention, the method comprises at least the following steps: a) vehicle-side forces or moments are determined which must be overcome when starting as driving resistances; b) motor-side forces or moments are determined which reduce a motor torque provided by the drive unit, which provides the same for starting; c) an acceleration is determined for starting; d) Depending on the particular vehicle-side forces or moments, depending on the specific engine-side forces or moments, depending on the specific acceleration and depending on a translation of the determined starting gear a required engine torque for the starting process is calculated formula; e) on the basis of the calculated engine torque, an engine speed is determined, which is used as the starting speed.

Description

The The invention relates to a method for operating at least one Automatic transmission and a drive unit comprehensive powertrain of a motor vehicle.

The Main components of a drive train of a motor vehicle are a drive unit and a transmission. A gearbox converts torques and speeds and thus sets the traction power supply of the drive unit around. The present invention relates to a method of operation a drive train, the at least one drive unit and a Automatic transmission includes. For the purposes of the present invention are intended under the term automatic transmissions all transmissions with an automated Gear change or an automatic gear change are understood. Between the drive unit and the automatic transmission of a drive train is a preferably designed as a starting clutch starting element switched, whereby to trigger a startup of the Motor vehicle, the starting element under consideration a predetermined starting gear and a previously determined Starting speed is automated or automatically closed.

From the DE 198 39 837 A1 as well as from the DE 198 39 838 A1 methods are known by means of which a starting gear can be determined for a starting process with the aid of an electronic control device.

From the DE 102 02 520 A1 a method is known with the aid of which a starting speed for a starting operation can be determined, namely such that a setpoint based on characteristic setpoint starting speed during the startup on the basis of a parameter that reflects the actual acceleration behavior of the motor vehicle is modified.

Of these, Based on the present invention, the problem underlying a novel method for operating an at least one automatic transmission and to provide a powertrain comprehensive drive train.

This Problem is solved by a method according to claim 1 solved. According to the invention, the method comprises at least the following steps: a) there are forces on the vehicle or determined moments that overcome when starting as driving resistances Need to become; b) there are engine-side forces or moments, which provided by the drive unit Reduce engine torque, which provides the same for starting; c) an acceleration is determined for starting; d) dependent from the determined vehicle-side forces or moments, depending on the specific engine-side forces or Moments, depending on the specific acceleration as well depending on a translation of the determined Starting gear is a required engine torque for calculated the starting process formulaically; e) on Based on the calculated engine torque, an engine speed is determined which is used as the starting speed.

With The present invention is the first time a method for Operating a powertrain proposed in which for a starting process a required for the starting process Engine torque is calculated formulaically, namely based on pre-determined vehicle forces or moments, depending on predetermined engine-side Forces or moments, depending on one in advance certain acceleration as well as depending on a translation a determined starting gear. For this calculated, for The starting torque required motor torque is the starting speed intended for the starting process. This will be an optimal Starting behavior of a motor vehicle while minimized Guaranteed loading of the starting element.

With Help of the method according to the invention can dynamic influences, such. B. a temperature-dependent Reduction of engine power, as well as influences of different Vehicle configurations, such. B. axle translations and Tire radii, when determining the starting speed for be considered the startup process.

preferred Further developments of the invention will become apparent from the dependent claims and the description below. embodiments of the invention are, but are not limited to, explained in detail with reference to the drawing. Showing:

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

The present invention relates to a method for operating a drive train of a motor vehicle, wherein such a drive train comprises at least one drive unit and an automatic transmission. The inventive method relates to the start of the motor vehicle, wherein the inventive method is described below with reference to 1 will be described in detail.

1 illustrates the inventive method for operating a powertrain comprising a drive unit and an automatic transmission with the aid of a signal flow diagram, wherein the inventive method according to 1 divided into a total of five steps or blocks.

In a first block or step 1 In the method according to the invention, forces or moments on the motor vehicle are determined which must be overcome when starting as driving resistances.

at the forces on the vehicle side or moments during the Starting as driving resistances are overcome must be at least an on-board Rolling resistance force and a vehicle-side gradient resistance force. An air resistance force can be neglected when starting become.

In a second block or step 2 In the method according to the invention, engine-side forces or moments are determined which reduce an engine torque provided by the drive unit, which provides the same for starting up. This is at least a friction torque on the motor side and a loss moment on the engine-side ancillary units or on the motor-side auxiliary consumable.

On Basis of the vehicle-side rolling resistance, the vehicle-side Gradient resistance force, the motor-side friction torque and the Loss torque motor-side ancillaries can be calculated Engine torque are determined, which is sufficient to a motor vehicle to hold at a standstill, which, however, still allows no access.

In a third block or step 3 The method according to the invention additionally determines an acceleration for starting the motor vehicle. This is the desired or desired acceleration for the starting process.

After a first variant can be in block 3 the acceleration for starting directly depending on an accelerator pedal operation, a vehicle mass, a driving resistance and a drive train ratio are given, the drive train ratio of a wheel radius, a translation of the driven axle and the translation of the particular starting gear is dependent.

wobei α_KFZ die Beschleunigung zum Anfahren ist, wobei i_GES die Antriebsstrangübersetzung ist, wobei r_RAD der Radradius ist, wobei n_MOT die Motordrehzahl ist, und wobei t_ANFAHR die Schließzeit der Anfahrkupplung bis zur schlupffreien Übertagung ist.Alternatively, it is possible in block 3 to calculate the acceleration for starting assuming a uniformly accelerated movement of the motor vehicle based on a closing time of the starting clutch to the slip-free transmission. The calculation of the acceleration for starting on the basis of the closing time of the starting clutch to the slip-free transmission takes place with the following formula:

where α _{KFZ is} the acceleration to start, where i _GES is the driveline ratio, where r _{RAD is} the wheel radius, where n _{MOT is} the engine speed, and t _{ANFAHR is} the closing time of the _launch clutch to slip-free transmission.

In a subsequent block or step 4 The process of the invention is carried out depending on the block 1 certain vehicle-side forces or moments, depending on the in block 2 certain engine-side forces or moments, depending on the block 3 certain acceleration and depending on a translation of the starting gear a formulaic calculation of the engine torque required for the starting process.

wobei M_MOT das benötigte Motormoment ist, wobei M_REIB das motorseitiges Reibmoment ist, wobei M_MOT,PTO das Verlustmoment motorseitiger Nebenaggregate ist, wobei F_ROLL die fahrzeugseitige Rollwiderstandskraft ist, wobei F_STEIG die fahrzeugseitige Steigungswiderstandskraft ist, wobei α_KFZ die Beschleunigung zum Anfahren ist, wobei i_GES die Antriebsstrangübersetzung ist, wobei r_RAD Radradius ist, wobei η_GES der Antriebsstrangwirkungsgrad ist, wobei m_KFZ die Masse des Kraftfahrzeugs ist, und wobei e eine antriebsstrangübersetzungsabhängige Größe ist. Für die antriebsstrangübersetzungsabhängige Größe e gilt der folgende formelmäßige Zusammenhang:

wobei J_RAD das Massenträgheitsmoment des Rads ist, wobei i_ACHSE die Achsübersetzung ist, wobei J_ABTRIEB das Massenträgheitsmoment des Abtriebs ist, wobei i_GES die Antriebsstrangübersetzung ist, wobei J_MOT das Massenträgheitsmoment des Motors ist, wobei m_KFZ die Masse des Kraftfahrzeugs ist, und wobei r_RAD der Radradius ist.The motor torque required for the starting process is calculated using the following formula:

where M _{MOT is} the required engine torque, where M _{REIB is} the engine side friction torque, where M _{MOT, PTO} is the engine torque Loss torque of engine side auxiliaries, where F _{ROLL is} the vehicle side rolling resistance force, where F _{STEIG is} the vehicle side _grade resistance force, where α _{KFZ is} the acceleration to start, where i _{GES is} the driveline ratio, where r _{RAD is the wheel} radius, where η _{GES is} the driveline efficiency, where m is the _{vehicle body} mass, and where e is a drive train ratio dependent quantity. For the drive train ratio dependent variable e the following formulaic relationship applies:

wherein J _RAD is the moment of inertia of the wheel, where i _axis is the axle ratio, wherein J _OUTPUT is the moment of inertia of the output, where i _GES is the drive train ratio, where J _MOT is the moment of inertia of the engine, wherein m _car is the mass of the motor vehicle, and where r _{RAD is} the wheel radius.

In block 4 the formula-calculated engine torque for the starting process can be limited by a maximum permissible engine torque, which is predetermined by an accelerator pedal actuation.

Following the formula-based calculation of the engine torque required for the start-up procedure, a block or step is performed 5 the method according to the invention on the basis of the calculated engine torque, the determination of an engine speed, which is used as the starting speed for the starting process.

in this connection is proceeded so that from the calculated engine torque means a motor characteristic or a motor map the smallest possible Engine speed is determined at the calculated engine torque is available. The starting speed is as low as possible chosen to be a burden and thus a wear of the Starting clutch to be kept as low as possible.

The Map or the characteristic of the engine or drive unit can be stored statically. However, the motor characteristic is preferred or the engine map on the basis of which determines the starting speed is continuously provided by the drive unit. Provided in the map or in the characteristic of the engine or drive unit dynamic effects, such. B. temperature influences or Turbocharger pressures, not yet considered, can the same directly or by others transmitted from a motor control Sizes are taken into account.

The in block 5 determined engine speed is used as the starting speed. The control of the engine speed can be done via a transmission internal controller or an internal motor controller. Then, when the engine speed control via an internal-transmission controller, a motor intervention can be done via a torque setting. Then, however, when the engine speed control is done via an engine-internal controller, a speed is specified as the engine intervention, namely in step 5 determined engine speed.

As already mentioned, there is preferably a limitation of the block 4 Calculated engine torque through the maximum permissible engine torque, which is determined by the accelerator pedal operation. This may be the case that the predetermined by the accelerator pedal engine torque is not sufficient to accelerate the motor vehicle.

In this case, then the starting clutch remains open for a long period of time, whereby the same, however, in particular on slopes of a higher load and thus a higher wear is exposed. This can be counteracted by during the startup depending on a predetermined minimum acceleration or a maximum slip time of the starting clutch, a minimum torque or an offset for in block 4 Calculated engine torque is taken into account. Alternatively, it is also possible to specify via the accelerator pedal actuation no maximum permissible engine torque, but rather an acceleration or a clutch slip time.

As already stated, in block 5 from the block 4 calculated engine torque by means of an engine map or an engine characteristic curve determines the lowest engine speed at which the calculated engine torque is available. This engine speed is used as the starting speed. For reasons of comfort, z. B. due to a deteriorating engine run-round or a deteriorating acoustics, it is possible that this minimum engine speed can not be used as the starting speed. In this case is then selected as the starting speed, a higher engine speed.

Furthermore, it can be provided that in block 5 the starting speed is limited to a maximum permissible value, namely a maximum starting speed. This may be necessary because the engine torque calculation in block 4 and the engine speed determination in block 5 used sizes can be faulty.

The method according to the invention can be used both in pure starting operations and in maneuvering operations. It is in the nature of shunting that for shunting operations in block 3 certain acceleration is less than with pure starting operations.

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QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19839837 A1 [0003]
• - DE 19839838 A1 [0003]
• - DE 10202520 A1 [0004]

Claims (8)

Method for operating an at least one automatic transmission and a power plant comprising a powertrain of a motor vehicle, wherein for starting the motor vehicle, a starting gear and a starting speed be determined, and where with the particular starting gear and with the certain starting speed a start-up by closing a starting element, in particular a starting clutch triggered will, with at least the following steps: a) it will be on-board Forces or moments determined that overcome when starting as driving resistances Need to become; b) there are engine-side forces or moments determines a motor torque provided by the drive unit, which provides the same for starting, reduce; c) an acceleration is determined for starting; d) dependent from the determined vehicle-side forces or moments, depending on the specific engine-side forces or moments, depending on the specific acceleration as well as depending on a translation of the determined Starting gear is a required engine torque for calculated the starting process formulaically; e) On the basis of the calculated engine torque is an engine speed determined, which is used as the starting speed. Method according to claim 1, characterized in that that in step a) at least one vehicle-side rolling resistance force and an on-vehicle grade resistance force can be determined. Method according to claim 1 or 2, characterized that in step b) at least one motor-side friction torque and a Loss of torque motor-side ancillaries are determined. Method according to one of claims 1 to 3, characterized in that in step c) the acceleration for starting on the basis of an accelerator pedal operation, a Motor vehicle mass, a driving resistance and a drive train ratio is determined. Method according to one of claims 1 to 3, characterized in that in step c) the acceleration for starting on the basis of a closing time of the starting clutch until slip-free transmission formulaically is calculated. Method according to one of claims 1 to 5, characterized in that in step d) the motor torque required for the starting process with the formula

where M _MOT is the engine-side friction torque, where M _{MOT, PTO is} the torque loss of engine-side accessories, where F _{ROLL is} the on-board rolling resistance force, where F _{STEIG is} the vehicle side _grade resistance force, where α is the _{vehicle speed} Acceleration for startup is where i _GES is the driveline ratio, where r _{RAD is} the wheel radius, where η _GES is driveline efficiency, where m is the _{vehicle body} mass, and e is a driveline ratio dependent quantity. Method according to Claim 6, characterized that the calculated engine torque by a maximum permissible Engine torque, which is determined by an accelerator pedal operation will be limited. Method according to one of claims 1 to 7, characterized in that in step e) on the basis of the calculated Engine torque via a motor map or a motor characteristic the engine speed used as the starting speed is determined.