DE19801391A1 - Process to control the gear selection process in an automotive automatic gear box - Google Patents

Abstract

A process controls the change from one gear to another using an automatic automotive gearbox. When a change in gear is not underway, the motor target torque value is essentially determined by the position of the accelerator pedal. During the gear change process, the motor target torque value is regulated both before and after the gear selection process by an electrical control, in proportion to the respective gear.

Description

The invention relates to a method for smooth shifting of an automatic transmission motor-driven motor vehicle, the target engine torque outside of Gear changes are essentially specified by an accelerator pedal and during gear changes the engine target torque by an electrical control device depending on the respective gear is specified before and after the switching process.

In automatic transmissions in motor vehicles occurs during a shift process by the Gear ratio change a jerk in the drive train. Assuming that the driver does that If the accelerator pedal remains constant during the shifting process, the driving becomes when there is a fixed connection pedal engine torque the gear ratio change cause a jump in the output torque.

In known methods, the accelerator pedal deflection does not give the engine torque, but that Output torque on the rear axle. The output torque is calculated as the product of the Engine torque and the overall gear ratio (gear ratio and other possible gear ratio tongues). With the relationship between accelerator pedal and engine torque, the output torque changes in Ratio of the respective gear ratio. There is a more or less large jerk in the Powertrain. The output torque remains in the context of the accelerator pedal output torque constant before and after switching. In the known methods, an attempt is made to reverse the Solving only output-driven problems, but problems often arise here.

An object of the present invention is therefore to change the switching pressure at the end of a Minimize the switching process even more in order to achieve a pull-neutral switching (CNS).

This object is achieved in that the previously existing engine torque (M _motist ) to a value during the switching process

M _motn = M _motist × i _is / i _goal

is changed, where i _is the gear ratio before the gearshift and i _{goal is} the gear ratio after the gearshift, which at the end of the gearshift the modified engine torque M _{motn is} maintained for a predeterminable period of time t _SR , and that thereafter with the pedal value remaining the same ( PW) of the accelerator pedal, the changed engine torque M _{motn is} returned to the original level M _motist present before the switching operation.

In the method according to the invention, an engine torque-oriented adaptation is first carried out during the change of the gear ratio, ie the engine torque is converted to a corresponding value calculated from the change in the gear ratio. The calculated engine torque is then maintained for the time t _SR for the time during which the switching pressure would otherwise occur, as a result of which it is achieved that the shift is carried out at this point in time in an output-oriented manner. Overall, this enables shift-neutral shifting, that is, shifting that is almost jerk-free, in particular even if the driver maintains the pedal value before the shifting operation. In addition, it is achieved that the speed is maintained after shifting without the driver having to correct the pedal value.

The measures listed in the subclaims are advantageous developments and Improvements of the method specified in claim 1 are possible.

The motor nominal torque is expediently performed outside of switching operations by a function

M _{mot set} = f (PW, n)

or a corresponding map is specified.

The transition from the engine torque M _motist to the value M _motn during the switching process takes place according to a transition function which is particularly adapted to the changing gear ratio so that no accelerations or decelerations occur.

Correspondingly, the transition from the changed value of the engine torque M _motn to the original engine torque value M _motist present before the switching operation takes _place according to a transition function which is designed such that the vehicle does not experience any unwanted acceleration.

PT functions have proven to be particularly suitable as transition functions, in particular PT1 functions.

The predeterminable time period t _SR is determined by measurement technology and specified in the form of stored values, in particular as map values. This leads to a further minimization of the switching pressure.

An embodiment of the invention is shown in the drawing and in the following Description explained in more detail. Show it:

Fig. 1 is a block diagram for explaining the inventive method and

Fig. 2 shows a corresponding signal diagram.

Referring to FIG. 1, the engine torque M _motsoll outside of switching operations is preset as a function of accelerator pedal position of an accelerator pedal 10. The pedal value PW acts on a driving behavior map 11 from which the target engine torque M _{mot target is formed} as a function of the engine speed n. This target engine torque M _{mot target} is _fed directly to the output of the setpoint formation device shown in FIG. 1 and acts on an engine control device (not shown) or engine control device to form a corresponding actual engine torque.

In an output torque calculating stage 12 the output torque M is constant _from in each case depending on the present transmission gear ratio ness i _is calculated as the product of M and _{is motsoll} i. In the numerical example according to FIG. 2, there is initially a target _engine torque M _{mot target} or engine torque _Mot of 100 Nm, which leads to an output torque M _from 1,000 Nm at a ratio of 10 of the first gear.

If there is now a shift command for the automatic transmission, the engine torque M _{motn is} calculated in an engine torque calculation stage based on the new gear ratio i _target that should _initially be present after the shifting process over a period of time t _R to avoid the shift pressure.

This engine torque is calculated as the quotient of the output torque M _from before the gearshift and the desired target gear i _target . During the shifting process, the engine torque changes from 100 Nm to 200 Nm according to a transition function from M _motist to the calculated value M _motn , that is to say in the numerical example according to FIG. 2, since the second gear provided as the target gear has the gear ratio 5 . This transition function is designed so that when the gear ratio changes during the switching process, the output torque remains essentially constant, although a certain fluctuation range is of course possible. The transition function during the switching is defined in the first transition function calculation stage 14 , a PT or PT1 behavior having proven particularly suitable. Other control functions or modifications of the PT behavior are of course also possible in principle.

At the end of the switching process, where a switching pressure usually occurs, the determined changed engine torque M _motn is now _maintained for a period of time t _SR by means of a time stage 15 , as a result of which the switching pressure is avoided or substantially reduced. This time period t _SR is determined by measurement technology, the determined values being stored, for example, in a map.

After the time period t _SR , the switching process is completed. If the engine torque M _{motn were} now maintained, the vehicle would accelerate unintentionally and the driver would have to make a corresponding correction by changing the accelerator pedal position. To avoid this, the changed engine torque M _motn is now in a second transition calculation stage 16 by means of a transition function back to the original level M _motsoll , which is designed so that an unwanted acceleration of the vehicle is just prevented. This transition function can also have PT or PT1 behavior. The engine torque is now controlled or regulated again via the driving behavior map 11 .

The stages shown in Fig. 1 can of course be realized, for example, by a microcomputer, the maps being stored in a memory of the microcomputer.

Claims (6)

1. A method for jerk-free switching of an automatic transmission of a motor vehicle driven by a motor, wherein the desired engine torque outside of switching operations is essentially specified by an accelerator pedal and during switching operations, the desired engine torque is specified by an electronic control device depending on the respective transmission gear before and after the switching operation is characterized in that during the switching operation the previously existing engine torque M _motist to a value
M _motn = M _motist × i _is / iziel
is changed, where i _is the gear ratio before the gearshift and i _goal after the gearshift is that at the end of the gearshift the changed engine torque M _{motn is} maintained for a predeterminable period of time t _SR , and that thereafter with the pedal value (PW) remaining the same Accelerator pedal ( 10 ), the changed engine torque M _{motn is} returned to the original level M _motist present before the switching operation. 2. The method according to claim 1, characterized in that the engine target torque outside of switching operations by a function
M _{mot set} = f (PW, n)
or a corresponding map is specified. 3. The method according to claim 1 or 2, characterized in that the transition from the engine _torque M _motist to the changed value M _motn during the switching process takes place according to a transition function. 4. The method according to any one of the preceding claims, characterized in that the transition from the changed value of the engine torque M _motn to the original engine torque value M _motist present before the switching operation takes place according to a transition function which is designed so that the motor vehicle does not experience any unwanted acceleration . 5. The method according to claim 3 or 4, characterized in that the transition function PT function is, in particular a PT1 function. 6. The method according to any one of the preceding claims, characterized in that the predeterminable time period t _{SR is} determined by measurement and is specified in the form of stored values, in particular as map values.