Method for determination of at least a drag torque effective on the input side of an automatic motor vehicle transmission

Abstract

A method of determining at least one drag torque acting on the input side of an automatic transmission, such that prior to the determination a separator clutch located between the transmission and an engine is disengaged. To be able to carry out the determination regardless of the type of transmission concerned, also prior to the determination, the transmission is shifted to neutral and subsequently the drag torque is calculated when the engine is deactivated. For this, a first gradient of a transmission input rotational speed is determined, before an engine rotational speed of the engine falls below the transmission input rotational speed, and a second gradient of the transmission input rotational speed is determined, after the engine rotational speed falls below the transmission input rotational speed. The method is stored as a computer program stored on data carrier of a drive-train control unit of a motor vehicle.

Claims

1. A method of determining at least one drag torque (M.sub.Getr, M.sub.Kup 1) acting on an input side of an automatic motor vehicle transmission (3) of a motor vehicle such that, prior the determination, a separator clutch (2) located between the motor vehicle transmission (3) and a drive engine (1) is disengaged (S4), the method comprising the steps of: shifting the motor vehicle transmission (3) into neutral (S2) once the motor vehicle is stopped, initiating deactivation of the drive engine and disengaging the separator clutch after the drive engine (1) is deactivated, calculating, via a processor of a transmission control unit, the at least one drag torque (M.sub.Getr, M.sub.Kup 1) determining (S5), via the processor of the transmission control unit, a first gradient ({dot over (n)}.sub.Getr, I) of a transmission input rotational speed (n.sub.Getr), before an engine rotational speed (n.sub.Mot) of the drive engine (1) falls below the transmission input rotational speed, determining (S7), via the processor of the transmission control unit, a second gradient ({dot over (n)}.sub.Getr, II) of the transmission input rotational speed (n.sub.Getr), after the engine rotational speed (n.sub.Mot) falls below the transmission input rotational speed (n.sub.Getr), determining (S9), as the drag torque, at least one of a drag torque (M.sub.Kup 1) of the separator clutch (2) and a drag torque (M.sub.Getr) of a drive input side part of the motor vehicle transmission (3) shifted to neutral, and recording the drag torque (M.sub.Kup 1), determined for the separator clutch (2), as a function of a current road inclination ().

2. The method according to claim 1, further comprising the step of recording the drag torque (M.sub.Getr), determined for the drive input side part of the motor vehicle transmission (3) shifted to neutral, as a function of a current transmission temperature (T.sub.Getr).

3. The method according to claim 1, further comprising the step of carrying out the determination while the motor vehicle is parked.

4. The method according to claim 3, further comprising the step of storing the determined at least one drag torque (M.sub.Getr, M.sub.Kup 1) in a memory.

5. A method of determining at least one drag torque (M.sub.Getr, M.sub.Kup 1) acting on an input side of an automatic motor vehicle transmission (3) of a motor vehicle such that, prior the determination, a separator clutch (2) located between the motor vehicle transmission (3) and a drive engine (1) is disengaged (S4), the method comprising the steps of: shifting the motor vehicle transmission (3) into neutral (S2) once the motor vehicle is stopped; initiating deactivation of the drive engine and disengaging the separator clutch after the drive engine (1) is deactivated; calculating, via a processor of a transmission control unit, the at least one drag torque (M.sub.Getr, M.sub.Kup 1); determining (S5), via the processor of the transmission control unit, a first gradient ({dot over (n)}.sub.Getr, I) of a transmission input rotational speed (n.sub.Getr), before an engine rotational speed (n.sub.Mot) of the drive engine (1) falls below the transmission input rotational speed; determining (S7), via the processor of the transmission control unit, a second gradient ({dot over (n)}.sub.Getr, II) of the transmission input rotational speed (n.sub.Getr), after the engine rotational speed (n.sub.Mot) falls below the transmission input rotational speed (n.sub.Getr); initiating the method with a routine of a computer program stored in a memory of a control unit of the motor vehicle only once the motor vehicle completely stops; ensuring that deactivation of the drive engine is initialed; monitoring the engine rotational speed and the transmission input rotational speed after disengagement of the separator clutch; calculating at least one of a drag torque of the separator clutch and a drag torque of a drive input side part of the motor vehicle transmission shifted to neutral during deactivation of the drive engine; calculating, with the control unit, at least one of the drag torque of the separator clutch and the drag torque of the drive input side part of the motor vehicle transmission shifted to neutral, during deactivation of the drive engine, based on a mass moment of inertia of the drive input side part of the motor vehicle transmission shifted to neutral, which is stored in the control unit; and recording, in a memory of the control unit, the drag torque of the separator clutch as a function of a current road inclination.

6. The method according to claim 5, further comprising the step of recording, in a memory of the control unit, the drag torque of the drive input side part of the motor vehicle transmission shifted to neutral as a function of a current transmission temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An advantageous embodiment of the invention, which will be explained below, is represented in the figures, which show:

(2) FIG. 1: A schematic representation of a drive-train of a motor vehicle;

(3) FIG. 2: An operating sequence diagram of a method according to the invention that corresponds to a preferred embodiment of the invention; and

(4) FIG. 3: A diagram in which rotational speed variations as a function of time during the course of the method are plotted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIG. 1 shows a schematic representation of a drive-train of a motor vehicle, the motor vehicle being a commercial vehicle such as a truck. Within the drive-train a drive engine 1 in the form of an internal combustion engine can be connected on its drive output side, by way of an interposed separator clutch 2, to a downstream motor vehicle transmission 3. In this case the motor vehicle transmission 3 is designed in the form of an automated group transmission in whichnot represented in any greater detail herea splitter group is connected upstream or downstream from a main group and/or a range group is connected downstream from the main group. Gear steps in the main group of the motor vehicle transmission 3 can be engaged individually by means of unsynchronized interlocking shifting elements in the form of claw clutches, and for that purpose a rotational speed equalization has to be carried out in the area of the shifting element concerned in each case, between the clutch halves to be coupled with one another with interlock.

(6) During the corresponding shifting operations in the main group the rotational speed equalization is regulated by a transmission control unit 4, which before a shift to a respective next gear carries out the necessary equalization by braking or accelerating the drive input side part of the motor vehicle transmission 3 shifted to neutral. For such braking, the transmission control unit 4 can use a transmission brakealso not shown in this casewhereas an acceleration is carried out by means of the drive engine 1 in combination with the separator clutch 2. For that purpose, during the shifting processes the transmission control unit 4 can issue control commands to an engine control unit 5 of the drive engine 1 and can also regulate the opening and closing of the separator clutch 2.

(7) However, to be able to adjust the corresponding synchronous rotational speeds with precision, in the transmission control unit 4 drag torques M.sub.Getr and M.sub.Kup1 that act on the transmission input side are stored, which have to be taken into account appropriately when regulating the rotational speed concerned by means of a transmission brake or by the drive engine 1. These drag torques M.sub.Getr and M.sub.Kup1, of which the drag torque M.sub.Getr is that of the input side of the motor vehicle transmission 3 in neutral whereas the drag torque M.sub.Kup1 is a residual transmission torque of the separator clutch 2, will have been determined in advance while the motor vehicle having this drive-train was being stopped in the context of a procedure according to the invention, which will now be described in more detail in the flowchart of FIG. 3 with reference to the chart in FIG. 2.

(8) The method according to the invention is initiated in a step S1 when it is recognized that the commercial vehicle has stopped, for example because the vehicle is at rest and the driver has performed corresponding actions from which that process can be inferred. In a step S2 which, however, can also be part of the recognition that the vehicle has stopped, the motor vehicle transmission is shifted to neutral in that in the unsynchronized main group, the claw clutch which until then was still engaging an associated gear step, is opened. At this point in time, since the separator clutch 2 is still closed an engine rotational speed n.sub.Mot and a transmission input rotational speed n.sub.Getr are equal, as can be seen in the initial portion of FIG. 3.

(9) In a subsequent step S3 it is then checked whether the drive engine 1 is being deactivated, and for the recognition of that process the transmission control unit 4 checks an ignition signal from the engine control unit 5. If this is not the case the system springs back to before step S3 and a new check is started, whereas if it is indeed the case, in step S4 the separator clutch 2 is opened. Since the transmission input has now been separated from the drive engine 1, the drag torques M.sub.Getr and M.sub.Kup1 acting on the drive input side part of the motor vehicle transmission 3 bring about a fall of the transmission input rotational speed n.sub.Getr.

(10) As can be seen in FIG. 3 by following the time variations of the transmission input rotational speed n.sub.Getr and of the engine rotational speed within a zone I the transmission input rotational speed n.sub.Getr is lower than the engine rotational speed n.sub.Mot. The result of this is that the drag torques M.sub.Getr and M.sub.Kup1 act in opposition to one another, since the drag torque M.sub.Getr of the transmission input side part of the motor vehicle transmission 3 acts to reduce the rotational speed, whereas in contrast the drag torque M.sub.Kup1 of the clutch 2, originating in aerodynamic effects and wobbling movements and which is therefore the result of a latent connection of the transmission input to the drive engine 1, is trying to increase the rotational speed of the transmission input. This interplay of the two drag torques M.sub.Getr and M.sub.Kup1 brings about a certain reduction of the transmission input rotational speed n.sub.Getr, which is determined in step S5 with reference to a measurement of the gradient {dot over (n)}.sub.Getr, I.

(11) In a subsequent step S6 the transmission control unit 4 checks whether the engine rotational speed n.sub.Mot is still higher than the transmission input rotational speed n.sub.Getr, i.e. whether the condition corresponding to zone I in FIG. 3 still prevails. If so, the system springs back to before step S6 and a new check is started. On the other hand, if it is recognized that the engine rotational speed n.sub.Mot has already fallen below the transmission input rotational speed n.sub.Getr, a situation represented in FIG. 3 by the zone II, then the system advances to step S7.

(12) In zone II, compared with zone I the conditions have changed to the effect that owing to the now lower rotational speed of the drive engine 1, a drag torque M.sub.Kup2 of the separator clutch 2 also acts to slow down the transmission input. In step S7 a gradient {dot over (n)}.sub.Getr, II of the transmission input rotational speed n.sub.Getr is now also determined for zone II, which is different from the first gradient {dot over (n)}.sub.Get, I on account of the changed interplay of the drag torque M.sub.Getr of the motor vehicle transmission 3 and the drag torque M.sub.Kup2 of the separator clutch 2.

(13) After step S7, in the following steps S8 and S9 the relevant drag torques M.sub.Kup1 and M.sub.Getr are determined by writing the equations:
M.sub.Getr+M.sub.Kup1=J.sub.Getr.Math.2.Math.{dot over (n)}.sub.Getr,I
M.sub.Getr+M.sub.Kup2=J.sub.Getr.Math.2.Math.{dot over (n)}.sub.Getr,II
in which the measured gradients {dot over (n)}.sub.Getr, I and {dot over (n)}.sub.Getr, II are used. In addition a mass moment of inertia J.sub.Getr of the drive input side part of the motor vehicle transmission 3 shifted to neutral, which is stored in the transmission control unit 4, is also included. To be able to solve the equations, in step S8 the assumption is also made that:
M.sub.Kup1=M.sub.Kup2,
so that in step S9, finally, for the determination of the drag torques M.sub.Kup1 and .sub.Mgetr the equations:
M.sub.Getr=J.sub.Getr.Math..Math.(n.sub.Getr,I+n.sub.Getr,II)
M.sub.Getr=J.sub.Getr.Math..Math.({dot over (n)}.sub.Getr,I{dot over (n)}.sub.Getr,II)
can be formulated.

(14) In a subsequent step S10 the two drag torques M.sub.Kup1 and M.sub.Getr are then stored in a non-volatile memory of the transmission control unit 4, wherein the drag torque M.sub.Kup1 of the separator clutch 2 is stored as a function of a current road inclination , whereas the drag torque of the drive input side part of the motor vehicle transmission 3 shifted to neutral is stored as a function of a current transmission temperature T.sub.Getr, i.e. the transmission oil temperature. For the subsequent operation of the motor vehicle, the parameters stored in that manner can be retrieved to enable appropriate regulation of the motor vehicle transmission 3.

(15) Accordingly, by virtue of the method according to the invention drag torques acting on the input side can be determined regardless of the type of transmission concerned.

INDEXES

(16) 1 Drive engine 2 Separator clutch 3 Motor vehicle transmission 4 Transmission control unit 5 Engine control unit M.sub.Getr Drag torque of the drive input side part of the transmission in neutral M.sub.Kup1 Drag torque of the clutch M.sub.Kup2 Drag torque of the clutch n.sub.Mot Engine rotational speed n.sub.Getr Transmission input rotational speed {dot over (n)}.sub.Getr, I Gradient of the transmission input rotational speed {dot over (n)}.sub.Getr, II Gradient of the transmission input rotational speed Road inclination T.sub.Getr Transmission temperature