DE102017219221A1 - Method and control device for operating an automatic transmission of a motor vehicle - Google Patents

Abstract

Method for operating an automatic transmission (3) of a motor vehicle, wherein, when an actual speed is less than a set speed with active cruise control function, for reducing a difference between the set speed and the actual speed of a drive unit (1) Load requested and depending on at least one shift map by the automatic transmission (3) at least one downshift is requested. Depending on the actual speed and depending on the difference between the target speed and the actual speed, a target acceleration for the motor vehicle is determined. For gears that are available for a downshift, a gear-dependent maximum acceleration is determined. Depending on a comparison between the desired acceleration and the gear-dependent maximum accelerations, a limiting gear is determined. Then, when the target gear of a downshift determined depending on the or each shift map is smaller than the limiting gear, a downshift is limited to the limiting gear, whereas when the target gear of a downshift determined depending on the or each shift map is greater than that Limitation gear is or corresponds to the same, a downshift in the determined depending on the or each shift map destination gear is allowed.

Description

The invention relates to a method and a control device for operating an automatic transmission of a motor vehicle.

Automatic transmissions of motor vehicles are connected between a drive unit and an output of the motor vehicle. An automatic transmission executes shifts or gear changes automatically or automatically, converts depending on the engaged gear speeds and torques and thus provides the traction of the drive unit on the output.

From practice, automatic transmission with a plurality of switching elements are known, wherein in each non-positive gear of the automatic transmission, a first defined number of switching elements closed or switched on and a second defined number of switching elements is opened or switched off. In this case, automatic transmissions are known which comprise at least one positive switching element and at least one frictional switching element. A positive switching element can be designed as a claw. A frictional switching element may be designed as a clutch or brake. In the execution of a gear change of a non-positive actual gear in a non-positive target gear at least one switching element of the automatic transmission is opened or switched off and at least one other switching element of the automatic transmission closed or switched.

From the prior art it is known that a motor vehicle with an automatic transmission can use a speed control function. A cruise control function is also referred to as cruise control. A cruise control function controls the speed of the motor vehicle such that an actual speed of the motor vehicle corresponds to a desired setpoint speed. When using an adaptive cruise control function, which is known as ACC (Adaptive Cruise Control), the motor vehicle can be decelerated automatically to a speed that is below the desired target speed, namely, when a distance to a preceding object is exceeded ,

From the DE 100 21 770 A1 a method for controlling an automatic transmission for a motor vehicle with cruise control function is known. From this prior art, it is known that when an adaptive cruise control function falls below the distance to a preceding vehicle, the vehicle is decelerated to a speed that is below the target speed, wherein, if again a sufficient distance between the preceding object and the motor vehicle, the motor vehicle subsequently automatically accelerates again to the setpoint speed. The DE 100 21 770 A1 proposes also, depending on external influences on the motor vehicle, in particular depending on a roadway inclination to choose a driving program.

From the DE 197 16 088 A1 For example, a vehicle control system for a motor vehicle having an automatic transmission and a cruise control function is known. The vehicle control system disclosed therein has an obstacle detection device for detecting obstacles that hinder the driving of the motor vehicle. When an obstacle is detected, the control of the automatic transmission is influenced.

Then, when the actual cruise control function, the actual speed of the motor vehicle is less than the target speed of the motor vehicle, and the difference between the target speed and the actual speed to be reduced, is required by a drive unit of the motor vehicle load and dependent on At least one shift map required at least one downshift and then optionally at least one upshift of the automatic transmission. Under certain circumstances, several downshifts can be requested in a row, which then can form high accelerations in powerful vehicles with powerful drive unit, which are perceived as uncomfortable. This is a disadvantage.

On this basis, the invention is based on the object to provide a novel method and a control device for operating an automatic transmission of a motor vehicle.

This object is achieved by a method according to claim 1.

According to the invention, a target acceleration for the motor vehicle is determined as a function of the actual speed and the difference between the set speed and the actual speed. For gears that are available for a downshift, a gear-dependent maximum acceleration is determined. Depending on a comparison between the desired acceleration and the gear-dependent maximum accelerations, a limiting gear is determined. Then, when the target gear of a downshift determined depending on the or each shift map is smaller than the limiting gear, a downshift is limited to the limiting gear. Then, when the determined depending on the or each switching map destination gear a Downshift is greater than or equal to the limiting gear, a downshift in the determined depending on the or each shift map target gear is allowed.

With the present invention, it is possible to restrict the number of downshifts requested and executed upon reduction of a difference between the target speed of the cruise control function and the actual speed of the motor vehicle. For this purpose, a limitation course is determined, namely depending on the comparison between the desired acceleration of the motor vehicle and gear-dependent or gear-specific maximum accelerations. Consequently, the limiting gear can ultimately also be used as an uncomfortable, excessive acceleration of the motor vehicle.

According to an advantageous development, the target acceleration for the motor vehicle is additionally dependent on a gradient or gradient, in or in which the motor vehicle is operated, and / or depending on an active driving mode and / or depending on a road condition and / or dependent determined by weather conditions and / or dependent on navigation data. This allows a particularly advantageous determination of the desired acceleration for the motor vehicle.

According to an advantageous development of the gear-dependent maximum acceleration is determined depending on a gear-dependent maximum possible force, depending on a driving resistance and depending on a mass of the motor vehicle. The gear-dependent, maximum possible force is determined such that a drive unit speed is determined for each gear depending on the actual speed of the motor vehicle, that depending on the drive unit speed and a full load characteristic curve a maximum possible drive unit torque is determined, and that depends on the maximum possible Drive unit torque the gear-dependent, maximum possible force is determined. This makes a particularly advantageous determination of the gear-dependent or gear-specific maximum acceleration possible.

According to an advantageous development, the transition-dependent maximum acceleration of the same is compared with the desired acceleration and then, if the maximum acceleration of the current gear is less than the desired acceleration, the current gear to order the limiting gear starting from a current gear a gear is reduced and the gear-dependent maximum acceleration of the same again compared with the target acceleration, this being repeated until the maximum acceleration of the gear is greater than the target acceleration or the same, then this gear as a limiting gear is used. This makes a particularly advantageous determination of the limitation course possible.

The control unit is defined in claim 9.

• 1 ein exemplarisches Antriebstrangschema eines Antriebsstrangs eines Kraftfahrzeugs;
• 2 ein Signalflussdiagramm zur Verdeutlichung der Erfindung; und
• 3 ein weiteres Signalflussdiagramm zur Verdeutlichung der Erfindung.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

• 1 an exemplary powertrain diagram of a drive train of a motor vehicle;
• 2 a signal flow diagram to illustrate the invention; and
• 3 another signal flow diagram to illustrate the invention.

The invention relates to a method and a control device for operating an automatic transmission of a motor vehicle with cruise control function.

1 shows a highly schematic block diagram of a motor vehicle with a drive unit 1 and one between the drive unit 1 and a downforce 2 switched automatic transmission 3 , In the automatic transmission 3 You can automatically set gears. Depending on the automatic transmission 3 engaged gear converts the same speeds and torques and thus provides the traction power supply of the drive unit 1 at the output 2 ready.

The operation of the drive unit 1 is from an engine control unit 4 and the operation of the automatic transmission 3 from a transmission control unit 5 controlled and / or regulated. The engine control unit exchanges this 4 with the drive unit 1 and the transmission control unit 5 with the automatic transmission 3 Data from. Furthermore, change the engine control unit 4 and the transmission control unit 5 with each other data.

Then, when a cruise control function of the motor vehicle is active, it tries to control the actual speed of the motor vehicle to a predetermined target speed of the motor vehicle. However, it is possible, for example, that the driver side is exited from the cruise control function, which then can reduce the actual speed, for example when rolling or sailing the motor vehicle. If, in the following, the driver regains access to the cruise control function, returning to the previously valid setpoint speed, the difference between the actual speed and the target speed are reduced.

A similar situation can occur with an adaptive cruise control function, especially when a distance to a preceding vehicle decreases with the cruise control function active. In this case, then the adaptive cruise control function automatically reduces the actual speed of the motor vehicle below the target speed. If, in the following, the distance to the preceding object increases again or if the object in front disappears, the actual speed should then be increased again to the setpoint speed.

The present invention now relates to such details, by means of which, when the active speed control function, the actual speed of the motor vehicle is smaller than the target speed of the motor vehicle and the difference between the target speed and the actual speed to be reduced, the Dismantling comfortable, especially without too high accelerations, can be performed.

Then, when the difference between the setpoint speed and the actual speed is to be reduced when the speed control function is active, the drive unit will output 1 of the motor vehicle load requested. Further, depending on at least one shift map, typically in the transmission control unit 5 is deposited, initially at least one downshift in the automatic transmission 3 and then possibly at least one upshift in the automatic transmission 3 requested.

According to the invention, a target acceleration for the motor vehicle is determined as a function of the actual speed and the difference between the set speed and the actual speed. Furthermore, for gears that are available for a downshift, a gear-dependent maximum acceleration is determined. Depending on a comparison between the desired acceleration and the gear-dependent maximum accelerations becomes a limit gear for the automatic transmission 3 determined. Then, when the target gear of a downshift determined depending on the or each shift map is smaller than the limiting gear, the downshift is limited to the limiting gear. Then, on the other hand, when the target gear of a downshift determined according to the or each shift map is greater than or equal to the limiting gear, the downshifts in the target gear determined depending on the or each shift map are allowed and executed. The number of downshifts is therefore limited via the limitation procedure. Excessive accelerations in the reduction of the difference between the target speed and the actual speed can be avoided, which increases ride comfort and driving safety.

Further details of the invention are described below with reference to the signal flow diagrams of 2 and 3 described.

The blocks 6 and 7 of the signal flow diagram of 2 exemplify in the transmission control unit 5 stored shift maps. This is how the block visualizes 6 slope-based, comfort-oriented shift maps and the block 7 Visualizes slope-based, performance-oriented shift maps.

In a block 8th depends on the switching characteristics of the 6 and 7 Determines what circuit / s in the automatic transmission 3 to perform for the reduction of the difference between the target speed and the actual speed is / are. This can then be in the block 8th at least one downshift and then optionally at least one upshift be determined.

Depending on the difference between the desired speed of a cruise control function and the actual speed of the motor vehicle, either one of the shift maps of the blocks may initially be 6 and 7 be selected, or by interpolation between switching maps of the 6 and 7 an interpolated switching characteristic field can be determined on the basis of which then the determination of at least one downshift and optionally at least one upshift in block 8th he follows.

A switching map is the input value of the actual speed of the vehicle and the load request to the drive unit 1 provided, in which case the shift map depending on the actual speed of the motor vehicle and the load request to the drive unit 1 Circuits determined on the control side, so for example, at least one downshift and subsequently optionally at least one upshift.

The block 9 of the signal flow diagram of 2 visualizes a check whether the target speed of the motor vehicle with active cruise control function is greater than the actual speed of the motor vehicle and whether a difference between the target speed and the actual speed should be reduced.

If this is the case, starting from block 9 on block 10 branched, being in block 10 the already mentioned limitation course is determined. Otherwise it will be on block 11 branches and no limitation course determined.

The determination of the limitation course in block 10 is based on a comparison between the determined target acceleration of the motor vehicle and the determined gear-dependent or gear-specific maximum accelerations available for a downshift gears of the automatic transmission 3 , The block 10 the 2 includes the blocks 12 to 15 the 3 ,

In block 12 is first dependent on the actual speed of the motor vehicle for the respective available for a downshift gear of the automatic transmission 1 determines a gear-dependent or gear-specific drive unit speed.

In the block 13 Then, depending on the gear-specific or gear-dependent drive unit speed, a determination is made of a gear-dependent or gear-specific maximum possible drive unit torque of the drive unit 1 , Which is determined depending on the determined gear-specific drive unit speed and dependent on a full-load characteristic curve for the respective gear. Preferably, the full-load characteristic curve is dependent on a prevailing air pressure and / or a prevailing intake air temperature. The determination of the gear-dependent or gear-specific, maximum possible drive unit torque thus preferably takes place as a function of the air pressure and as a function of the intake air temperature.

This maximum possible drive unit torque is in block 13 determined and the block 14 provided, wherein in the block 14 depending on the gear-specific or gear-dependent, maximum possible drive unit torque a gear-dependent, maximum possible force on the wheels of the output 2 of the motor vehicle is determined.

The determination of the gear-dependent or gear-specific, maximum possible force on the wheels of the output 2 takes place depending on a gear ratio of the automatic transmission 3 and / or depending on an efficiency of the automatic transmission 3 and / or depending on an axle ratio of the motor vehicle and / or depending on a diameter of the wheels of the output 2 , Preferably, the determination of the gear-dependent or gear-specific, maximum possible force takes place at least as a function of the gear ratio and the axle ratio. Preferably, in this case additionally the efficiency of the transmission and / or the diameter of the wheels of the output 2 considered.

This in block 14 certain, gear-dependent or gear-specific maximum possible force is then the block 15 provided in block 15 Depending on the dependent or gear-specific, maximum possible force, the respective gear-dependent or gear-specific maximum acceleration is determined.

The respective gear-specific maximum acceleration is dependent on the respective maximum possible force, a driving resistance and a mass of the motor vehicle, wherein the difference between the gear-dependent maximum possible force and the driving resistance is set in relation to the vehicle mass to the gear-specific maximum acceleration to investigate.

The driving resistance is composed of a speed-dependent component and a gradient-dependent component. The vehicle mass of the motor vehicle is known control side.

It will be in block 10 not only the gear-dependent or gear-specific maximum accelerations for the gears, which are available for a downshift, determined, but also the target acceleration for the motor vehicle.

The target acceleration for the motor vehicle, which is gear-independent, depending on the current actual speed of the motor vehicle, depending on the difference between the target speed and the actual speed, preferably depending on a slope and preferably depending on a driver selected Driving mode is determined.

The target acceleration for the motor vehicle is preferably additionally determined depending on a road surface condition and / or depending on weather conditions and / or dependent on navigation data.

As already stated, in block 10 the limiting gear is determined, depending on a comparison between the desired acceleration and the gear-dependent or fully specific maximum accelerations.

Based on the current gear, the respective maximum acceleration of the same is compared with the desired acceleration. If the current gear provides a lower maximum acceleration than required by the target acceleration, the gear is preferably reduced by one gear. If the next lower gear also has a lower maximum acceleration than required, the gear is again reduced by preferably one gear. This is repeated until a gear is found whose maximum acceleration is greater than the target acceleration. This gait is then used as a limitation walk.

The one in block 10 determined limitation course as well as in block 8th gear determined according to at least one shift map become the block 16 the 2 provided in block 16 It checks if the block is in 8th depending on at least one shift map determined gear is smaller than the limitation gear.

If this is the case, so is the block 8th depending on at least one shift map determined gear less than the limitation course of the block 10 , so starting from block 16 on block 17 branched, in which case in block 17 Downshifts are limited to the limiting gear.

On the other hand, it depends on the or each switching characteristic in block 8th determined gear greater than the limitation course of the block 10 or corresponds to it, starting from block 16 on block 18 branched, in which case in block 18 Downshifts should not be limited to the limiting gear.

As already stated, the determination of the target acceleration takes place in block 10 depending on the actual speed of the motor vehicle and the difference between the target speed and the actual speed. Furthermore, the determination of the desired acceleration preferably takes place as a function of the gradient or the gradient of the motor vehicle, and / or depending on the driving mode selected by the driver.

Furthermore, a road condition, a road type, weather conditions, times of day and / or seasons, navigation data or GPS data and the like can be taken into account when determining the desired acceleration.

The limitation of downshifts to the limitation course in block 17 remains active until, based on the or each switching characteristic in block 8th a gear is requested which is greater than or equal to the limitation gear. In this case, the limitation to the limiting gear is then canceled and allows gear changes without consideration of the limiting gear.

The invention is used when with active cruise control function, the actual speed of the motor vehicle is smaller than the target speed and the difference between the target speed and the actual speed to be reduced.

This may be the case in a cruise control or in a non-adaptive cruise control function, if initially the cruise control has been deactivated manually, the vehicle has slowed down and then manually following the cruise control again by actuating a resume or resume element such as a button or switch old target speed is activated.

Furthermore, in the case of an adaptive cruise control function, this can be the case when the distance to a preceding vehicle decreases when the cruise control function is active, therefore the actual speed of the motor vehicle is adjusted below the setpoint speed and subsequently the distance to the preceding vehicle increases again Actual speed should be increased to the target speed.

Further, in a non-adaptive cruise control function and in an adaptive cruise control function, this may be the case when the desired speed is increased.

Further, this may be the case for a non-adaptive cruise control function and an adaptive cruise control function, e.g. a speed limit and thus the target speed is increased, especially when leaving a locality.

The invention further relates to a control device for operating the automatic transmission 3 , The control unit according to the invention is preferably the transmission control unit 5 , The control unit then requests, when active cruise control function, an actual speed of the motor vehicle is less than a target speed of the motor vehicle, for reducing a difference between the target speed and the actual speed of the drive unit 1 of the motor vehicle load and depending on at least one shift map of the automatic transmission 3 first at least one downshift and then optionally at least one upshift.

Depending on the actual speed and the difference between the setpoint speed and the actual speed, the control unit determines the setpoint acceleration for the motor vehicle. The setpoint acceleration determined as a function of the actual speed and the difference between the setpoint speed and the actual speed can also be provided and read in by another control unit, for example by an engine control unit.

The control unit determines a gear-dependent maximum acceleration for gears that are available for a downshift. Depending on a comparison between the desired acceleration and the gear-dependent maximum accelerations, the control unit determines a limiting gear. If the target gear of a downshift, determined as a function of the or each shift map, is less than the limiting gear, the control unit limits a downshift to the limiting gear.

Then, when the target gear of a downshift determined according to the or each shift map is greater than or equal to the limiting gear, the controller allows a downshift to the target gear determined depending on the or each shift map.

The control unit according to the invention is preferably the transmission control unit 5 , It has hardware and software to perform the procedure. The hardware includes data interfaces for data exchange with participating modules of the motor vehicle, a processor for data processing and a memory for data storage. The software includes program blocks for carrying out the method.

LIST OF REFERENCE NUMBERS

1

power unit

2

output

3

automatic transmission

4

Engine control unit

5

Transmission Control Module

6

block

7

block

8th

block

9

block

10

block

11

block

12

block

13

block

14

block

15

block

16

block

17

block

18

block

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10021770 A1 [0005]
• DE 19716088 A1 [0006]

Claims (11)

Method for operating an automatic transmission (3) of a motor vehicle, wherein when active speed control function, an actual speed of the motor vehicle is less than a target speed of the motor vehicle, for reducing a difference between the target speed and the actual speed of a Drive unit (1) of the motor vehicle load requested and depending on at least one switching map of the automatic transmission (3) first at least one downshift and then possibly at least one upshift is requested, characterized in that dependent on the actual speed and depending on the difference between the target -Speed and the actual speed is determined a target acceleration for the motor vehicle, for gears that are available for a downshift, a gear-dependent maximum acceleration is determined, depending on a comparison between the target acceleration If, depending on the or each shift map determined target gear of a downshift is smaller than the limiting gear, a downshift is limited to the limiting gear, whereas, if the dependent on the or each shift map determined target gear downshift is greater than the limiting gear or the same, a downshift in the determined depending on the or each shift map target gear is allowed. Method according to Claim 1 , characterized in that the target acceleration for the motor vehicle is additionally determined depending on a slope or a gradient in or in which the motor vehicle is operated, and / or depending on an active driving mode. Method according to Claim 1 or 2 , characterized in that the target acceleration for the motor vehicle is additionally determined depending on a road condition and / or depending on weather conditions and / or dependent on navigation data. Method according to one of Claims 1 to 3 , characterized in that the respective gear-dependent maximum acceleration is determined depending on a gear-dependent maximum possible force, depending on a driving resistance and depending on a mass of the motor vehicle. Method according to Claim 4 , characterized in that the gear-dependent, maximum possible force is determined such that a drive unit speed is determined depending on the actual speed of the motor vehicle depending on the drive unit speed and a full load characteristic curve a maximum possible drive unit torque is determined, depending on the maximum possible drive unit torque the gear-dependent, maximum possible force is determined. Method according to Claim 5 , characterized in that the gear-dependent, maximum possible force is further determined depending on a gear ratio of the automatic transmission (3) and / or dependent on an axle ratio and / or depending on a wheel diameter and / or depending on an efficiency of the automatic transmission (3) , Method according to Claim 5 or 6 , characterized in that the full load characteristic curve is dependent on a prevailing air pressure and / or a prevailing intake air temperature. Method according to one of Claims 1 to 7 , characterized in that for determining the limiting gear starting from a current gear, the gear-dependent maximum acceleration of the same compared with the target acceleration and when the maximum acceleration of the current gear is less than the target acceleration, the current gear is preferably is reduced by a gear and the gear-dependent maximum acceleration of the same again compared with the target acceleration, this being repeated until the maximum acceleration of the gear is greater than the target acceleration or the same, then this gear as Limitation course is used. Method according to one of Claims 1 to 8th , characterized in that after the limitation of downshifts to the limiting gear, the limitation remains active until a determined depending on the or each shift map target gear is greater than the limitation or corresponds to the same. Control unit for operating an automatic transmission (3), wherein the control unit, when an actual speed of the motor vehicle is less than a desired speed of the motor vehicle when the cruise control function is active, for reducing a difference between the target speed and the actual speed of a Drive unit (1) of the motor vehicle load requests and depends of at least one switching map of the automatic transmission (3) first at least one downshift and then possibly at least one upshift requests, characterized in that the controller depending on the actual speed and the difference between the target speed and the actual speed a target acceleration determined for the motor vehicle, the control unit for gears that are available for a downshift, determines a gear-dependent maximum acceleration, the controller determines depending on a comparison between the desired acceleration and the gear-dependent maximum accelerations a limiting gear, the controller then if the target gear of a downshift determined as a function of the or each shift map is less than the limiting gear, limits a downshift to the limiting gear, whereas if the ECU determines it depends on the or each shift map elte target gear of a downshift is greater than or equal to the limiting gear, allows a downshift in the determined depending on the or each shift map target gear. Control unit after Claim 10 , characterized in that the same the method according to one of Claims 1 to 9 on the control side.

Images