DE10016186C2 - Method and device for adjusting an automatic transmission in a vehicle - Google Patents

Abstract

In a method for setting an automatic transmission in a vehicle with a speed control system, taking into account vehicle state variables and vehicle operating variables, control signals are generated for engaging a specific gear stage in order to maintain a target speed specified in the control system. DOLLAR A To improve the transient response when approaching the target speed, a lower gear limit with a minimum gear level is provided, the minimum gear level being set to a level that exceeds a target gear currently to be engaged from the actually engaged gear level by a certain value. The minimum gear is set in the event that the target gear is smaller than the previous minimum gear.

Description

The invention relates to a method for adjustment an automatic transmission in a vehicle according to the preamble of claim 1.

From the publication DE 195 09 492 C2 a speed Control system with limiter function known, over which one maximum speed are automatically maintained can. The control system limits the vehicle speed the permissible maximum speed by setting the Mo tors and the automatic transmission of the vehicle.

The vehicle speed is approaching from a lower one Speed level based on the permissible maximum speed, it becomes more common at low acceleration the greatest possible in the transmission to reduce the speed gear set. If now during the approx accelerated to the top speed is triggered, a transmission downshift is carried out, to get into the range of maximum torque and a to be able to perform higher acceleration. However, if in Time of gear change down the speed gap at the top speed is only low, the Ge exists drive that due to the suddenly increasing torque and the higher acceleration the vehicle speed over the permissible maximum overshoots. This danger can additionally Lich reinforced by the fact that at the moment of the transmission downshift  the converter in the automatic transmission is open, see above that interventions of the speed control system in the engine management to reduce the engine torque no impact on the vehicle speed.

In the publication DE 44 34 022 A1 there is a speed control system described at a maximum speed is specified, which by interventions in the throttle valve position and gearbox influences must be observed. To at for example, a maximum permissible speed of 30 km / h to be observed and an over in the case of strong acceleration will avoid swinging beyond this speed limit proposed to start from a standing position in second gear to Ge to prevent transmission upshifts or the number of highs reduce circuits, the cause of overshoot could be. Furthermore, transmission upshifts can be pre-selected be pulled to switching phases in the immediate vicinity of the Ge avoid speed limit.

Is when approaching the speed limit by means of pressing the accelerator pedal a high driver demand generated, so is also in the control system of DE 44 34 022 A1 Transmission downshift carried out to the required high loading to be able to accelerate. This takes place shortly before Errei Chen the permissible maximum speed, can also with this Overshoot cannot be ruled out.

The invention is based on the problem, the Einschwingver stop in vehicles with automatic transmission when approaching improve a given target speed.

This problem is solved according to the invention with the features of the Proverb 1 solved.  

According to the new method, a lower gear is first limited with a minimum gear level, in particular special a passage window can be selected, which additionally also includes an upper gear limit for lower gear limitation. The lower gear limit with the minimum gear and give if necessary, the upper gear limit is also preferred depending speed of the current vehicle speed and depending on it the maximum or target speed to be set according to ei ner predetermined function determined. The lower gear limit causes a reduction in the number of switching changes because also at high moments triggered by the driver using the accelerator pedal request a transmission downshift is prevented, so that jumps in torque in the drive torque avoided and one in We considerable smooth and jerk-free settling on the Maximum or target speed is enabled.

To further improve the transient response, the Minimum gear step set to a modified value, if additional conditions are met. The driving is stuff in a speed range below the specified NEN maximum or target speed and is towards the Top or target speed accelerates and is above in addition, the target gear to be engaged is smaller than the minimum gear, so this is set to a gear level that the one to be engaged Finish by a certain value, usually one, exceeds. The term "target gear" is used here Gear step denotes which is based on a driver request or a request from the cruise control system depending on the actually selected, current gear step as next gear is to be selected. The finish line is there regularly around the value one above or below the ac actual gear ratio. For example, because of a strong pedal actuation by the driver a downshift is triggered, provided the additional conditions are met  are - the minimum gear step when approaching the Maximum or target speed set to one gear, which expediently the target gear to be engaged by the value one exceeds. The initial value of the minimum gear step is then expediently determined by the speed control system, if the vehicle speed is within one matching speed distance to the maximum or target speed is located.

The result of the method according to the invention is that in particular when approaching the target speed with high loading acceleration a targeted upshift to the newly determined Minimum gear level or at least maintaining the gear level fe is carried out; Downshifts are excluded. This is particularly useful for vehicles with powerful Motors and a correspondingly high acceleration ability Advantages, since in such vehicles a sole reduction engine torque through intervention in the ignition and injection response too slow compared to vehicle acceleration greed to prevent overshoot. In addition, high Driver requests lead to downshifts that over can amplify the vibration process. These effects are caused by the increase in the minimum gear step compensated for now a comparative even at an early stage of acceleration wise high minimum gear step is specified, which from the car mat gearbox is to be inserted. The vehicle is approaching with ver relatively high gear and accordingly reduced on drive torque to the target speed without risk of over swing on.

In expedient further training it is provided that each new one matching the minimum gear to additional conditions is coupled. For example, as an additional condition be given that the engine speed is a predetermined  Threshold exceeds. Another condition, the additional or alternatively to the engine speed, lies in the assessment of vehicle acceleration, with a redefinition of the minimum gear to the one to be engaged Finish is done only in the event that the vehicle acceleration a given acceleration threshold ü exceeds. The additional conditions are designed to ensure that setting the minimum gear to a minimum not done at too low engine speeds to avoid that a sufficient Mo for vehicle acceleration Torque can no longer be applied. It should also be ensured by querying the acceleration, that only in acceleration areas where more common a downshift is to be expected, the specification of a Minimum gear step is carried out.

As a further condition, it is advantageously checked whether the target or maximum speed at a given speed scope to ensure that an invention appropriate lower gear limit is only carried out if that Vehicle moves in a speed range in which chem high accelerations with downshifts can go, can occur.

In a preferred further development it is provided that at the same time with the redefinition of the minimum gear step a holding time is waited, within which it is checked whether the target gear corresponds to the minimum gear step. Since the minimum Gear step is the gear step into which the gearbox in the relevant driving phase can be switched using This review will determine whether a proper one Switching operation has been carried out, or whether due to a Special influence, for example due to a manual guided switching process, a proper raising of the  Gear to the minimum gear is prevented. If if the latter applies, further measures can be taken which expediently ensure that following the stops time no switching operations disturbing the transient process can be carried out. These measures include for example, setting the minimum gear to the target gear; the minimum gear step may be egg reduced a lower gear.

Further measures can be taken to ensure that a renewed procedure is only possible if certain te requirements are met. This includes the Case that previously an upshift in the transmission in a higher Gear stage has been carried out, the upshift ent neither manually or via a control signal from the control system can be carried out. The upshift can trigger send condition for a new process run be drawn.

As an alternative or cumulative condition, the Gearbox condition are considered, the insertion of the Idle position, engaging reverse gear or the Resetting the minimum gear level to the value 1 (e.g. se after restarting the engine) as a trigger terium can be used.

Further advantages and expedient embodiments can be found in the further claims, the description of the figures and FIGS. 1 and 2, which show an associated flow chart with the individual method steps for controlling an automatic transmission of a vehicle for setting a predetermined vehicle target speed.

The flow chart shown in the figures is, for example  in a speed control system, preferably in one Limiter system, a motor vehicle as part of a Re gel and control unit implemented via which the various units gate of the vehicle. In a practical version is the speed control system as a speed Limiter system to limit the vehicle speed a specifiable maximum speed executed, which either which is specified directly by the driver or by a vehicle system taking into account external conditions and influences such as speed limits, vis conditions or traffic density is determined automatically. in the Speed control system become control signals for manipulation tion of vehicle units, especially gearbox Control signals for loading an automatic transmission in the Vehicle. With the speed control system this is up to influence the vehicle's transmissible drive torque influence; both the engine torque of the internal combustion engine machine as well as the transmission path between internal combustion engine Machine and vehicle wheels are manipulated, especially on positions in the automatic transmission.

The flowchart shown represents an advantageous manipulation of an automatic transmission in a motor vehicle in order to maintain a predetermined maximum or target speed v _max . In the following it is assumed that the vehicle speed, while avoiding an overshoot, starting from a lower speed level to the predetermined maximum or maximum speed Target speed v _{max is} to be increased.

According to FIG. 1, the flowchart begins with the start method step 1 , in which the start values required for the method sequence are initialized. The initial values to be initialized are parameters required for the process sequence, which, as variably adjustable variables, depend on vehicle status variables and vehicle parameters. The parameters to be initialized are, in particular, a lower gear limit with a minimum gear level of gear _min and an upper gear limit with a maximum gear level. The specification of this gear window suitably depends on the current vehicle speed.

The queries in accordance with the following method steps 2 and 3 represent basic requirements that must be fulfilled for the method according to the invention to be carried out.

In method step 2 , it is first checked whether a shift operation, in particular into a higher gear stage, is currently being carried out. For this, a query is started, whether the target speed step transition _target actually inserted actual gear Gan _g exceeds. In this case, the method is initially not carried out further; the yes branch is returned to method step 2 in accordance with a renewed, cyclical query regarding the current switching process. There is also a jump back in the event that it is determined in an alternative query in method step 2 that no forward gear is engaged in the transmission. If this is the case, the transmission is in neutral or in reverse gear; a process run is not possible, there is a return to process step 2 .

If the inquiries in method step 2 are not answered in the affirmative, the no-branch is branched according to method step 3 , in which a further query takes place with regard to the minimum gear stage gear _min . If the minimum gear step gear _{min is set} to the value one, the vehicle speed has dropped so far that the minimum gear step gear _{min is} set to the basic value one according to the calculation function responsible for the lower limit. In this case, too, it would not be expedient to continue with the method according to the invention and the yes branch is jumped back to the first query according to method step 2 .

If it is determined in step 3 that the minimum gear step, gear _{min, is} at a value greater than one, then, in accordance with the no-branching of step 3 , the method according to the invention can be continued according to the following method steps.

The following process steps 4 to 8 contain conditions which must be fulfilled so that the process according to the invention can be carried out to stabilize the transient process.

According to method step 4 , a query is made as to whether the predetermined target or maximum speed v _max , which is to be complied with by adjusting the automatic transmission, is within a speed range which is characterized by a lower speed limit v _u and an upper speed limit v _o is. This restriction to a defined speed range is intended to ensure that the process sequence is only carried out in a speed range in which large acceleration values are possible. The lower speed limit v _u and the upper speed limit v _o depend, among _{other things} , on the specific performance data of the internal combustion engine; Useful values are in the range of v _u = 40 km / h and v _o = 80 km / h. If the predetermined target or maximum speed V _max lies outside the defined speed range, the no-branch is returned accordingly to the beginning of the condition block before method step 4 and a new query is started in the next cycle. Otherwise, the yes branch continues accordingly.

In step 5 it is checked whether a forward gear is engaged in the transmission and whether the transmission is currently outside of a shift. The last-mentioned condition, which is checked cumulatively, is carried out by querying whether the target gear gear _{target is} identical to the gear gear currently engaged. The target gear stage gear _target is defined here as the gear stage which, based on the current gear stage gear, _is to be selected next on the basis of a gearbox control signal from the control unit. As far as the target gear gear _target and the actual gear gear gear _is above, the automatic transmission is not in a gearshift operation and the yes branch can be continued in accordance with the following method step 6 . Otherwise, in accordance with the No branch, a return to the condition block before method step 4 is returned.

According to method step 6 , it is checked whether the target gear gear _{target is} smaller than the minimum gear stage gear _min . The _minimum gear stage gear _min , which represents the lower limit of the gear window, is usually set to a value greater than one as a function of the vehicle speed in accordance with a defined function at the beginning of the method sequence. The query according to method step 6 serves the purpose of determining whether the target gear of the transmission is smaller than the lower gear limit gear _min , because only in this case is it appropriate to raise the gear lower limit and the yes branch corresponding to the following method step 7 continued. Otherwise, the No branch is returned accordingly to the beginning of the condition block.

Steps 7 and 8 contain further conditions that must be met in order to raise the lower gear limit. According to method step 7 , a query is made as to whether the actual engine speed n _is a speed threshold value n _limit rises. In method step 8 ( FIG. 2), a corresponding query takes place with regard to the actual acceleration a _{ist of} the vehicle and an acceleration threshold a _limit . If the assigned threshold values are not exceeded, the No branch is returned to step 4 in accordance with the beginning of the condition block. Otherwise, the yes branch is continued accordingly.

After all conditions of the condition block are met, the minimum gear stage gear _{min is set} to a value in process step 9 which exceeds the target gear stage gear _target in the transmission by a value of one. At the same time, a holding time t _{H is} started, during which it is checked whether the target gear gear _target in the transmission has actually reached the gear lower limit gear _min . The fulfillment of this condition is checked in method step 10 , wherein in the positive case - target gear gear _target has reached the lower limit gear _min - the process is ended and the yes branch is continued according to process step 13 , according to which a restart is started or the entire process is cycled again.

If it is determined in the query after method step 10 that the target gear stage gear _target has not yet reached the minimum gear stage gear _min , the No branch is accordingly continued to the following method step 11 , in which a query is carried out as to whether the Holding time t _{H has} expired. If this is not the case, the No branch is returned to method step 10 accordingly. It is checked again whether the target gear stage gear _{target has reached} the minimum gear stage gear _min within the holding time t _H. If this is not achieved in the predetermined holding time t _H , the yes branch of method step 11 continues in accordance with method step 12 , in which the lower gear limit gear _{min is set} to the currently valid target gear stage gear _target . This means that within the holding time t _H the minimum gear step initially set has not been reached and the minimum gear step gear _min is now reduced to the currently valid target gear step gear _target . This takes into account processes that are generated within the holding time t _H, for example by a manually triggered blockage of the transmission by corresponding setting of the gear selector lever, for example by an appropriate position of the selector lever preventing an upshifting of the transmission.

The method ends with method step 13 , according to which the entire method is restarted at cyclical intervals.

Claims (11)

1. A method for setting an automatic transmission in a vehicle with a speed control system, in which, taking into account vehicle state variables and vehicle operating variables, control signals for engaging a specific gear ratio to maintain a target speed (v _max ) specified in the control system are generated are, according to a current driver requirement or a current requirement of the speed control system, a target gear (gear _target ) to be selected by the automatic transmission from the actually engaged gear stage (gear _is ) _is determined, characterized in that

• - that depending on the current vehicle speed and depending on the target speed (v _max ) to be maintained, a lower gear limit with a minimum gear stage (gear _min ) is specified, this gear stage being selected as the new target gear ( _target gear) by the automatic transmission,
• - that the minimum gear stage (gear _min ) is raised in the event of a new _target gear (gear _target ) to be engaged, a higher value that exceeds a certain value, that the vehicle is accelerating towards the specified target speed ( v _max ) be found and that the _target gear (gear _target ) initially determined is smaller than the previous minimum gear step (gear _min ).

2. The method according to claim 1, characterized in that the minimum gear step (gear _min ) is set to a gear step exceeding the target gear ( _target gear) by the value one. 3. The method according to claim 1 or 2, characterized in that the manipulation of the minimum gear stage (gear _min ) is carried out only in the event that the engine speed (n _ist ) exceeds a given speed threshold (n _limit ). 4. The method according to any one of claims 1 to 3, characterized in that the manipulation of the minimum gear stage (gear _min ) is carried out only in the event that the vehicle acceleration (a _ist ) exceeds a given acceleration threshold value (a _limit ) , 5. The method according to any one of claims 1 to 4, characterized in that the manipulation of the minimum gear stage (gear _min ) is carried out only in the event that the target speed to be reached (v _max ) is within a defined speed range. 6. The method according to any one of claims 1 to 5, characterized in that a holding time (t _H ) is started at the same time as the redefinition of the minimum gear stage (gear _min ), during which it is checked whether the target gear (gear _target ) is the Has reached the minimum gear (gear _min ). 7. The method according to claim 6, characterized in that for the case that the target gear (transition _destination) has not reached the minimum gear (Gang _min) within the holding time (t _h), the minimum gear (Gang _min) to a defined value is reduced. 8. The method according to claim 7, characterized in that the minimum gear stage (gear _min ) is set to the target gear (gear _target ). 9. The method according to claim 7 or 8, characterized, that a new process run is only possible in the event is that the transmission upshifts to a higher gear stage is carried out. 10. The method according to any one of claims 7 to 9, characterized, that a new process run is only possible in the event is that the neutral or reverse gear is engaged  becomes. 11. The method according to any one of claims 7 to 10, characterized in that a renewed process run is only possible in the event that the minimum gear stage (gear _min ) is reset to the value one.