DE10321281A1 - Automatic gearbox gear change method for either changing up or down in which torque transfer to the new gear change element commences before synchronized rotation speeds are achieved - Google Patents

Abstract

Automatic gear change control method in which the gear change element that is to be disconnected is free from a control pressure or torque before a synchronized rotation speed is reached, while the gear change element that is to be connected takes up a part of the torque before the synchronized rotation speed is reached. When the synchronized rotation speed is reached it transmits the whole torque.

Description

The Invention relates to a control method for improving the Shift speed and shift comfort of an automatic transmission according to the generic term of claim 1.

It it is generally known that in automatic transmissions such as load-shifting automated manual transmissions or automatic shifting step change gearboxes special emphasis is placed on that translation change operations for one Vehicle occupants if possible can be carried out quickly and smoothly. To meet these requirements to become special control procedures are necessary with which Help the for the implementation of translation change processes necessary fluid-operated switching elements of the transmission, such as piston-cylinder arrangements on clutches or brakes, specifically with the control pressure to be supplied for the respective switching process is optimal. With known control methods there have been advances in switching speed and the switching comfort made, however, these are especially for fast Upshifts or downshifts, at those in the sense of double switching from one translation stage to the next but one translation stage is still in need of improvement.

So is through DE 100 35 479 A1 A control method has become known in which it is provided that for each gear shift the switching element to be switched on or off required for the next gear shift in the same switching direction is prepared during the shift for the upcoming switching operation in such a way that it is already filled with a control pressure medium or the pressure thereof Control pressure medium in the switching element concerned is lowered to a certain switching pressure. In addition, according to this prior art, it can be provided that when shifting into gear while driving, all shift elements are prepared for possible sequential shifts, which can be controlled on the basis of the transmission gear currently shifted when shifting into gear, i.e. both the shift elements of the next higher and the next lower gear.

To This publication is based on the described postponement of the preparatory phase for a gear shift time saved in the previous gear shift sequence, so that compared to other technical solutions in a comparable one Period a higher one Number of circuits possible is. This is advantageous in itself since it is used, for example, in motor vehicles with automatic powershift transmissions at high positive or negative Vehicle accelerations can be very meaningful, closely behind one another two successive transmission gears in the sense of a fast To shift sequential or alternatively a gear to skip.

The one from the DE 100 35 479 A1 Known fast sequential connection is associated with the disadvantage that two speed synchronizations of the gear components involved in the switching process are necessary in a short time, which can lead to loss of comfort if vibrations occur on these components. Such vibrations always occur when the dynamic torque transmitted by the transmission does not correspond to the torque generated by the drive motor of the motor vehicle. In addition, after the synchronization, a new load transfer must be carried out, in which the output torque is reduced at least to the level which corresponds to the current engine torque multiplied by the gear ratio of the new gear.

A Double circuit with the method known in the prior art also has the disadvantage that the engine speed by a substantial higher Amount changed than with a sequential connection, which is why the initial Differential speed at the gear change operation involved gear components when skipping a gear ratio nearly is twice as big. This then has the consequence that the friction work on the switching Coupling with the same to be transmitted Torque is about twice as high. If you want the same transmission output torque generate, so is an increase in the load upshift Clutch torque necessary so that the friction and friction work on the clutch plates continues to rise. Automated from such a way running double circuit has usually been out design reasons waived.

Against this background, it is the object of the invention to present a control method for a sequential or double shift, in which the mechanical load on a transmission switching process of an automatic powershift transmission involved switching elements of two gears is kept almost as low as in an ordinary shift from one translation stage to the next immediately following transmission stage, and in which a strong synchronization surge is avoided.

The solution this task results from the features of the main claim, while advantageous developments and refinements of the invention subordinate claims are removable.

Accordingly, a control method is proposed in which the shift element A to be disengaged is made tax-free or torque-free before reaching the synchronous speed N _SYN AB at time t ₁₁ of the gear of the first ongoing upshift or downshift gear (n + 1; gear n - 1), in which the shifting element D to be engaged for the subsequent upshift or downshift (gear n + 2; gear n - 2) regardless of the time progress of the first upshift or downshift in a time period t prior to reaching the synchronous speed N _{S YN} AB ₈ -t ₁₀ , t ₈ -t ₁₁ already takes over part of the torque to be transmitted by the automatic transmission, and in which the shifting element D to be engaged after this time t ₁₀ ; t ₁₁ transmits the entire torque.

In one embodiment of the invention, the transmission can be controlled in such a way that the first shift element B for the first upshift or downshift operation (gear n + 1; gear n - 1) in the period t ₈ -t ₁₀ from one slipping in one non-slipping operation is transferred.

moreover can by the inventive method ensured be that before reaching the synchronous speed of the first running Upshift or downshift (Gear n + 1; gear n - 1) the subsequent upshift or downshift (Gear n + 2; gear n - 2) is possible with the help of the second switching element D.

This Control procedures can be used to carry out both sequential circuits (Gear n + 1; gear n - 1) as well as double shifts (gear n + 2; gear n - 2) of all related Circuit types can be used.

To According to a further aspect of the invention, a gear change process can also be carried out as a double circuit (Gear n + 2; gear n - 2) be started by the control process but based on a control unit or Driver signal canceled and as a follow-up circuit (gear n + 1; gear n - 1) to be continued.

Furthermore are the starting times for the preparation of those to be switched on or off Switching elements as well as the time of transition from the preparatory to the switching phase through circuit-specific application parameters influenced.

Finally, it can be provided that the control method runs with each upshift or downshift operation and is only used to carry out a sequential or double shift if, until the synchronous speed N _SYN AB of the first nine gear (gear n + 1; gear n - 1) a sequential or double switching request is determined at time t ₁₁ .

The control method according to the invention presented here works in a double circuit control technology similar to a typical sequential circuit. The shift from the nth gear into the n + 1th gear is initiated with the aid of a first shift element. In this control sequence, a switching element is brought from a non-actuation situation into an actuation position in a rapid filling phase t ₁ -t ₃ , an application phase t ₃ -t ₄ , a load transfer phase t ₄ -t ₆ and a slip phase t ₆ -t ₁₀ . In the rapid filling phase, the switching element is filled with a pressure medium, while in the application phase, the actuating piston of the switching element is applied to the movable switching element components with a low load. In the load takeover phase, an increasing torque is transmitted by the switching element, while in the slipping phase the switching element is operated by slipping.

In the meantime (as far as this has not yet happened) the shift element of the next higher gear stage for the n + 2nd gear gear with regard to the quick filling phase, application phase, load transfer phase and slip phase is already being prepared t ₈ –t ₁₀ , so that if necessary, one of this shift element is activated immediately without a great delay Torque can be transmitted.

If the double shift is canceled by the transmission control unit or the driver, the preparation of this shifting element remains unused. The point in time at which the preparation of the second-mentioned switching element D begins depends on the synchronization speed and other system restrictions, which include, for example, the pressure medium delivery rate per unit of time.

The innovation according to the invention is now that the second-mentioned shift element D already takes over torque in a time period t ₈ -t ₁₀ which is before the time t ₁₀ in which the first-mentioned shift element B transmits torque without slippage. Furthermore, it is ensured that the shift element A to be disconnected from the previous gear before the synchronous speed N _Syn AB is reached is free of pressure or torque at time t ₁₁ .

at The control method according to the prior art is opposed first the synchronization of the switching element to be switched on awaited, before the next higher switching element in the gear sequence the torque takes over.

at a load transfer of the second switching element before the synchronization of the first switching element the torque acting direction of the switching elements A, B and D is the same, since they also have the same differential speed direction (more synchronous Slip). By controlling the load transfer of the switching elements none of the switching elements mentioned has a braking effect. So there is Fortunately, no gear tension with torque drop and sync shock in Drivetrain, but a torque take-over, in which the dynamic Torque, which reduces the angular momentum of the drive motor and corresponds to the gearbox input masses, is maintained.

The control behavior according to the invention can be explained with the aid of a drawing attached to the description. This drawing shows 1 the control pressure curve P of the switching elements involved in a double shift from third gear to fifth gear during time t, whereas 2 the course of transmission speeds that are important in this context and 3 the course of the transmission output torque and the proportion of the dynamic torque in the total output torque of the transmission for the same time period t as in 1 and 2 represents. The variables mentioned are shown by way of example for an automatic powershift transmission in which at least two transmission shifting elements are involved in the transmission of torque from the transmission input to the transmission output for each transmission gear engaged. In this example, the switching elements mentioned are activated for the following gear ratios:

In again 1 shows the control pressure curve shown for a double gear change from third to fifth gear, the shift elements A and D are acted upon at time t ₀ with a comparatively high shift pressure P_SED and P_SEA, which characterizes the engaged third gear.

At time t ₁ , after a shift request from the vehicle driver or from a transmission control device, the upshift from third gear to fifth gear is initiated in that the control pressure P_SEB of shift element B is raised in a rapid filling phase starting at time t ₁ . Shortly thereafter, the switching pressure P_SED on the switching element D is reduced by a predetermined amount at the time t ₂ and is maintained during the application phase of the switching element B over the period t ₃ to t ₄ .

How 2 clarifies, during this period t ₀ to t ₄ the turbine speed n_T of a torque converter upstream of the transmission or the transmission input shaft speed increases continuously. At time t ₄ , when changing gear from third to fourth gear, an increase in the control pressure P_SEB on the switching element B results in a load transfer, while at the same time the torque transmitted by the switching element D is reduced by a further reduction in the control pressure P_SED.

A comparison of 1 With 3 shows that at time t ₅ when the two control pressure curves P_SED and P_SEB are cut, a small dip M _SYN 1 in the output torque M _{AB can be} determined, which is generated by the torque transfer from the switching element D to the switching element B and is barely perceptible by vehicle occupants. At time t ₆ , the connected switching element B already takes over the full torque and the speed n_T drops, while the switching element D with a minimal overspeed shot pressure remains in position.

During the period t ₆ to t ₇ , therefore, only the two switching elements A and B are involved in the torque transmission, the switching element B still being operated in slip. Starting at time t ₇ , the change from fourth gear to fifth gear is initiated, at which the switching pressure P_SEA on switching element A is reduced until it has dropped far below said control pressure value M _ST at time t ₁₀ .

Shortly after the start of the switching element A being switched off, the complete connection of the switching element B, which is completed by the time t ₁₀ , is initiated with a further increase in the control pressure P_SEB at the time t ₈ . A further slip operation of the switching element B is avoided. Also at time t ₈ , an increase in control pressure P_SED begins at switching element D, which was in the ready position in this double circuit up to time t ₈ .

Like a comparison of 1 and 2 shows, there is an overlap of the control pressure curve P_SED of the shift element D to be engaged with the control pressure curve P_SEA of the shift element A to be disengaged at a time t ₉ , which is still significantly ahead of the time (t ₁₁ ) at which the transmission input shaft speed or the turbine speed n_T of the torque converter the synchronous speed N _SYN AB of the switching elements A, B has reached.

In the subsequent time period t ₁₀ to t ₁₂ , the shift element B is completely and no longer slidably coupled into the torque transmission in fifth gear (shift pressure P_SEB), while the shift element D only slips torque.

From the aforementioned point in time t ₁₂ , when the synchronous speed N _SYN BD is approached or reached, the shift pressure P_SED in the shift element D can be increased further, while other shift elements (not shown here) for the sixth and seventh gear can be controlled with respect to their control pressure as previously described. As a result, in the course of the output torque M _AB a renewed gear change-related synchronization shock M _SYN 3 can be recorded, which, like the torque drop M _SYN 1, is hardly noticeable by the vehicle occupant.

How 3 shows, the described control of the switching elements of the powershift transmission is associated with the essential advantage that the comparatively strong synchronization surge and load transfer drop M _SYN 2 occurring in control methods according to the prior art in sequential or double shifts does not occur in the control ancestor according to the invention, and in the period t ₁₀ to t _{12 there is} a smooth output torque curve.

wheelset and depending on the starting gear (Gear n) are the shifting elements A and D of the transmission considered here identical (see also gear shift element table), so that the shift element A is switched off again after successful double switching in the fifth.

This Control procedure is of course in addition to the one described Subsequent upshifting under engine load (gears n, n + 1, n + 2, ...) also for sequential downshifts with engine thrust, engine braking and / or retarder braking (gears n, n - 1, n - 2, ...) usable with advantage.

It is therefore part of the invention that the control method mentioned is also used for transmission control if a first upshift or downshift by the driver and / or by one stored in a transmission control unit Driving strategy has not yet been explicitly signaled that a Sequence or double shift (n +/- 2 gears) is desired.

Indeed it will it in everyday Operation of such a transmission, especially in passenger cars be such that after registering the shift request, the transmission shift sequence quite a bit has advanced before the driver repeats it, for example Actuate of the gear selector lever the transmission control unit signals that it is actually a double or sequential circuit wishes and / or one in a transmission control unit stored driving strategy gives such a shift instruction.

There the process steps according to the invention are carried out with every switching operation anyway, they are through advantages achievable by this procedure can be used in each of the switching processes, in which a second upshift or downshift signal until shortly before the synchronization point of the first in this regard Upshift or downshift is registered.

Furthermore heard it to the scope of the invention that the control method according to the invention can be used with all conceivable switching types in automatic transmissions. An example here is only on translation change processes under Indicated with the help of a retarder or an engine braking effect.

n_T

rotational speed the transmission input shaft / turbi

nendrehzahl a torque converter

N _{SYN_} SA

Synchronous speed the switching elements A, B

N _{SYN_} SB

Synchronous speed the switching elements B, D

M _ST

Static torque, zero line (M _ST = 0)

MS _YN 1

Last takeover burglary

M _SYN 2

Synchronization shock; Last takeover burglary

M _SYN 3

synchronization shock

M _dyn

dynamic torque component

P

control pressure on the switching element

P_SEA

switching pressure of switching element A

P_SEB

switching pressure of switching element B

P_SED

switching pressure of switching element C

t

time

Claims (8)

Control method for improving the shifting speed and the shifting comfort of successive upshifts or downshifts of an automatic transmission, wherein when executing a high following a first upshift or downshift (gear n + 1; gear n - 1) with the aid of a first shift element (B) - or downshift (gear n + 2; gear n - 2) at least a second switching element (D) is switched on or off, with each first upshift or downshift (gear n + 1; gear n - 1) that for the subsequent second upshift or downshift (gear n + 2; gear n - 2) required shifting element (D) during the first upshift or downshift (gear n + 1; gear n - 1) with regard to the shift pressure (P) is prepared or remains prepared, characterized in that the switching element (A) to be disconnected before reaching the synchronous speed (N _SYN AB) at the time (t ₁₁ ) of the gear of the first current upshift or downshift (gear n + 1; Gear n - 1) is free of control pressure or torque that the shifting element (D) to be engaged for the subsequent upshift or downshift (gear n + 2; Gear n - 2), regardless of the time progress of the first upshift or downshift, in a period prior to reaching the synchronous speed N _SYN AB (t ₈ -t ₁₀ , t ₈ -t ₁₁ ), part of the transmission to be transmitted by the automatic transmission Torque takes over and that the switching element (D) to be switched on transmits the entire torque after this time (t ₁₀ , t ₁₁ ). Control method according to claim 1, characterized in that the first switching element (B) for the first upshift or downshift operation (gear n + 1; gear n - 1) in the period (t ₈ -t ₁₀ ) from a slipping to a non-slipping operation is transferred. Control method according to claim 1 or claim 2, characterized in that before reaching the synchronous speed (N _SYN AB) of the first ongoing upshift or downshift (gear n + 1; gear n - 1) at time (t ₁₀ ) the subsequent up - or downshift (gear n + 2; gear n - 2) with the help of the second switching element (D) begins. Control method according to at least one of the previous ones Expectations, characterized in that with this control method Sequence (gear n + 1; gear n - 1) or a double gear (gear n + 2; Gear n - 2) of all circuit types becomes. Control method according to at least one of the previous ones Expectations, characterized in that the double shift (gear n + 2; Gear n - 2) control process started by a control unit or Driver signal aborted and as a follow-up circuit (gear n + 1; gear n - 1) continued becomes. Control method according to at least one of the previous ones Expectations, characterized in that the start times for preparation the switching elements to be switched on or off via circuit-specific application parameters can be influenced. Control method according to at least one of the previous ones Expectations, characterized in that the time of transition from the preparatory to the switching phase circuit-specific application parameters can be influenced. Control method according to at least one of the preceding claims, characterized in that this runs with each upshift or downshift operation and is only used to carry out a sequential or double shift if the synchronous speed (N _SYN AB) of the first nine gear () is reached. Gear n + 1; gear n - 1) at the time (t ₁₁ ) a sequential or double shift request is determined.