DE102019212409A1 - Method for determining an actual filling volume of a hydraulic adjusting element of a gear shift element - Google Patents

Abstract

Method for determining an actual filling volume of a hydraulic adjusting element of a frictional shifting element during rapid filling and / or rapid emptying. Storage of an empirically determined pressure-volume characteristic curve (10) for the actuating element, which is determined by a sensitivity point (11) at which the switching element actuatable by the actuating element begins to transmit torque, and through a contact point (12) in which there is a stiffness and so that a pressure sequence behavior of the switching element actuatable by the actuating element changes, is subdivided into characteristic curve areas, a first characteristic curve region defining an air gap region (13) between a completely emptied and an adjusting element filled up to the sensitivity point, a second characteristic curve region defining an elasticity region (14) between a An actuator filled up to the sensitivity point and an actuator filled up to the contact point are defined, and characteristic volume flows (VS13SB, VS13SE, VS14SB, VS14SE) are defined for the air clearance area and the elasticity area for both quick filling and quick emptying. Determining the actual filling volume depending on whether rapid filling and / or rapid emptying has been carried out, the actual filling volume being determined by integrating the characteristic volume flow defined for the rapid filling and / or for the rapid emptying for the respective range of characteristics.

Description

The invention relates to a method for determining an actual filling volume of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle. The invention also relates to a method for controlling a frictional shifting element of a transmission of a motor vehicle and a control device for carrying out the respective method.

A transmission of a motor vehicle has shift elements. To carry out a gear change or a shift in a transmission, at least one previously opened shift element must be closed and at least one previously closed shift element must be opened.

The shifting elements of a transmission can be frictional shifting elements, such as clutches or brakes, and positive shifting elements, such as claws.

To open and close a switching element, the respective switching element is actuated via a hydraulic actuating element, in particular via a hydraulic actuating piston that interacts with a valve. The actuation of a frictional switching element via a hydraulic actuator is subdivided into several phases, with sudden, discontinuous changes in the fill level of the hydraulic actuator being carried out in a so-called discrete phase, whereas in a continuous phase only non-sudden and therefore constant changes in the fill level of the actuator are permitted are.

When closing a frictional shifting element, the discrete phase of the hydraulic adjusting element is also referred to as discrete quick fill, whereas when opening a frictional shifting element, the discrete phase of the hydraulic adjusting element is also referred to as discrete quick emptying.

Up to now, it has been difficult to reliably determine the actual position of the control element in the case of a discrete quick fill and a discrete quick emptying of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle. The actual position of the actuating element determines the degree of opening or degree of closing of the switching element and thus the transmission capability of the same. If the actual position of the hydraulic actuating element cannot be determined easily and reliably, difficulties arise in regulating the actual position of the hydraulic actuating element to a desired target position in order to precisely control the torque transmitted by the switching element actuated via the hydraulic actuating element adjust.

There is accordingly a need to simply and reliably determine the actual position of the hydraulic adjusting element in the event of a discrete rapid filling and discrete rapid emptying of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle.

Proceeding from this, the invention is based on the object of creating a novel method for determining an actual filling volume of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle, a method for controlling a frictional shifting element of a transmission of a motor vehicle and a control unit for performing the respective method .

This object is achieved by a method for determining an actual filling volume of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle according to patent claim 1.

The method according to the invention comprises at least the storage of an empirically determined pressure-volume characteristic curve for the hydraulic adjusting element and the determination of the actual filling volume of the hydraulic adjusting element on the basis of the stored pressure-volume characteristic curve, depending on whether a discrete rapid filling and / or a discrete Quick emptying of the same is made.

The stored pressure-volume characteristic is determined by a sensitivity point at which the frictional shifting element actuated by the hydraulic adjusting element is just beginning to transmit torque, and by a contact point at which there is a rigidity and thus a pressure sequence behavior of the frictional shifting element actuated by the hydraulic adjusting element changes, subdivided into several characteristic areas.

A first characteristic curve area defines an air clearance area of the adjusting element between a completely emptied adjusting element and an adjusting element filled up to the sensitivity point. A second characteristic curve range defines an elasticity range between an actuating element filled up to the sensitivity point and an actuating element filled up to the contact point. For the air clearance area and the elasticity area, characteristic volume flows are defined for both a discrete quick filling and a discrete quick emptying.

The actual filling volume of the actuating element is determined by integrating the characteristic volume flow defined for the rapid filling and / or for the rapid emptying for the respective range of the characteristic curve.

With the method according to the invention, the absolute actual filling volume of the hydraulic adjusting element is determined in order to determine the actual position of the hydraulic adjusting element. The absolute actual filling volume correlates directly with the actual position of the hydraulic control element. According to the invention, the empirically determined pressure-volume characteristic curve of the respective hydraulic adjusting element, which is stored on the control side, is used to determine the actual filling volume, this pressure-volume characteristic curve being subdivided into at least the air clearance area and the elasticity area by the sensitivity point and the contact point. The characteristic volume flows are defined for these two areas for both quick filling and quick emptying, on the basis of which the absolute actual filling volume and thus ultimately the actual position of the hydraulic control element can be determined with the aid of integration. This enables the actual filling volume and thus the actual position of a hydraulic adjusting element to be determined easily and reliably.

The sensitivity point is preferably defined by a sensitivity pressure, a sensitivity volume, a sensitivity period for the rapid filling and a sensitivity period for the rapid emptying. The contact point is preferably defined by a contact pressure, a contact volume, a contact time for the rapid filling and a contact time for the quick emptying. For the air gap area, the characteristic volume flow for the discrete quick filling is preferably defined by the ratio of the sensitivity volume and the sensitivity period for the quick filling, with the characteristic volume flow for the discrete quick emptying for the air gap area being defined by the ratio of the sensitivity volume and the sensitivity period for the quick emptying is defined. The characteristic volume flow for the discrete quick filling is preferably defined for the elasticity range by the ratio of the difference between the contact volume and the sensitivity volume and the difference between the contact time for the quick filling and the sensitivity time for the quick filling, with the characteristic volume flow for the discrete for the elasticity range Rapid emptying is defined by the ratio of the difference between the contact volume and the sensitivity volume and the difference between the contact duration for the rapid emptying and the sensitivity duration for the rapid emptying. This enables an advantageous, simple and precise determination of the actual filling volume of a hydraulic actuating element of a frictional actuating element of a transmission of a motor vehicle.

According to an advantageous development of the invention, the stored, empirically determined pressure-volume characteristic curve is adapted during operation, with offset values for the sensitivity pressure and the sensitivity volume being determined during the adaptation for the sensitivity point, depending on which the sensitivity point and the contact point are adapted. The offset value for the sensitivity pressure is determined by measurement in the case of a quick fill. the offset value for the sensitivity volume is computationally determined as a function of an offset time determined by measurement during rapid filling and as a function of the characteristic volume flow of the air gap area for discrete rapid filling. This makes it possible to compensate for manufacturing tolerances and wear via the adaptation.

A method for actuating a frictional shifting element of a transmission of a motor vehicle using the method for determining the actual filling volume of the hydraulic actuating element of the frictional shifting element is defined in claim 11.

The control device according to the invention is defined in claim 12.

• 1 eine exemplarisch, empirisch ermittelte Druck-Volumen-Kennlinie für ein hydraulisches Stellelement eines reibschlüssigen Schaltelements eines Getriebes eines Kraftfahrzeugs;
• 2 die Druck-Volumen-Kennlinie der 1 zusammen mit einer Druck-Drehmoment-Kennlinie des reibschlüssigen Schaltelements;
• 3 die Druck-Volumen-Kennlinie der 1 bei einer Adaption;
• 4 Zustände eines hydraulischen Stellelements bei der Befüllung und Entleerung desselben.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. It shows:

• 1 an exemplary, empirically determined pressure-volume characteristic curve for a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle;
• 2 the pressure-volume characteristic of the 1 together with a pressure-torque characteristic of the frictional shifting element;
• 3 the pressure-volume characteristic of the 1 at an adaptation;
• 4th States of a hydraulic control element when it is filled and emptied.

The invention relates to a method for determining an actual fill volume of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle in the case of a discrete quick filling or in the case of a discrete quick emptying of the hydraulic adjusting element. The determined actual filling volume is an absolute actual filling volume, which correlates with an actual position of the hydraulic control element.

The frictional shifting element, which is actuated by a hydraulic actuating element, can be a clutch or a brake of an automatic transmission, a converter lockup clutch of a converter of the transmission or a disconnecting clutch of the transmission.

To determine the actual filling volume of the hydraulic adjusting element, an empirically determined pressure-volume characteristic curve for the hydraulic adjusting element is stored on the control side in a control unit of the transmission. This pressure-volume characteristic curve for the hydraulic actuator is subdivided into several characteristic curve ranges by a sensitivity point and a contact point.

The sensitivity point of the pressure-volume characteristic curve is that point on the pressure-volume characteristic curve at which the frictional shifting element that can be actuated by the hydraulic adjusting element is just beginning to transmit torque. When the hydraulic actuating element is accordingly filled up to the sensitivity point, the frictional shifting element actuatable by the hydraulic actuating element can be felt in the drive train of the motor vehicle.

The contact point of the pressure-volume characteristic curve is that point of the pressure-volume characteristic curve at which a rigidity and thus a pressure sequence behavior of the frictional shifting element that can be actuated by the hydraulic adjusting element change. If the hydraulic control element is filled to a point that is between the sensitivity point and the contact point, this causes a relatively elastic behavior. If the adjusting element is filled beyond the contact point, this results in a relatively stiff behavior.

As already stated, the sensitivity point and the contact point subdivide the pressure-volume characteristic curve into several characteristic curve areas, namely in a first characteristic curve area between the completely emptied control element and the sensitivity point, this first characteristic line area defining an air gap area of the control element. A second characteristic curve area extends between the sensitivity point and the contact point. This second characteristic curve range is also referred to as the elasticity range. If the actuating element is filled further or more than the contact point, it is operated in a so-called stiffness range. This stiffness range extends between the contact point and a point of maximum filling of the hydraulic adjusting element.

In 1 is an exemplary, empirically determined pressure-volume characteristic curve stored on the control side 10 a hydraulic adjusting element of a frictional shifting element of a transmission is shown, wherein in 1 the pressure-volume curve 10 shows a relationship between a control pressure p and an absolute filling volume V of the hydraulic control element. 1 continues to show the sensitivity point 11 as well as the contact point 12 the pressure-volume curve 10 . As already mentioned, it is the sensitivity point 11 around that point on the pressure-volume curve 10 in which that from that to the sensitivity point 11 filled hydraulic control element actuated frictional shifting element is just beginning to transmit torque. This sensitivity point 11 is through a sensitivity pressure p11 and by a sensitivity volume V11 Are defined. The point of contact 12 the pressure-volume curve 10 is that point of the same at which the elasticity or rigidity and thus a pressure sequence behavior of the switching element that can be actuated by the hydraulic adjusting element changes. So shows 1 that is in the contact point 12 the slope of the pressure-volume characteristic changes. This corresponds to a change in the rigidity and the pressure follow-up behavior of the switching element to be actuated by the actuating element. The point of contact 12 is by a contact pressure p12 and by a contact volume V12 Are defined.

Sensitivity point 11 and contact point 12 subdivide the pressure-volume curve 10 into several characteristic curve areas, namely in the first characteristic curve area 13 , which is also used as an air play area 13 is designated, the second range of characteristics 14th , which is also called the elastic range 14th is referred to, as well as in a third range of characteristics 15th , which is also called the stiffness area 15th referred to as. In the air play area 13 the switching element activated by the actuating element cannot transmit any torque. Only when the control element is above the sensitivity point 11 is also filled, the switching element actuated by the actuating element can transmit torque. As already stated, changes in the contact point 12 the so-called pressure sequence behavior of the actuating element and thus switching element. While in the area of elasticity 14th a defined pressure change causes only a relatively small change in the absolute filling volume, in the stiffness range 15th a change in pressure of the same amount a relatively large change in the absolute filling volume.

As already mentioned, it is the pressure-volume characteristic stored on the control side 10 to one about trials empirically determined pressure-volume characteristic. So shows 1 an empirically determined measurement signal curve 16 , from which the pressure-volume characteristic curve is linearized 10 is derived.

As already stated, this is the point of sensitivity 11 through the sensitivity pressure p11 and the sensitivity volume V11 Are defined. The point of contact 12 is through the contact point p12 and the contact volume V12 Are defined.

In addition, these are indicators 11 and 12 defined or characterized by time periods, namely the sensitivity point 11 by a sensitivity period t11SB for quick fill and a sensitivity period t11SE for quick emptying. These two sensitivity periods as well t11SB and t11SE are determined empirically. In the sensitivity period t11SB for rapid emptying, this is the time span that is required to reach the completely emptied control element up to the sensitivity point 11 to fill. In the sensitivity period t11SE for the quick emptying, however, it is the time span that is required for the adjusting element, starting from the sensitivity point 11 to empty completely. Also the point of contact 12 is defined by corresponding contact times, namely by a contact time t12SB for quick fill and a contact time t12SE for quick emptying. At the contact time t12SB for quick filling, this is the period of time that is required for the fully emptied control element to reach the contact point 12 to fill. At the contact time t12SE for quick emptying, however, it is the time span that is required for the actuating element, starting from the contact point 12 to empty completely.

Depending on the above sizes, which is the contact point 12 and the sensitivity point 11 define are for the air play area 13 and the elastic range 12 Characteristic volume flows are defined for both discrete rapid filling and discrete rapid emptying.

So will for the air play area 13 a first characteristic volume flow VS13SB for discrete quick filling through the ratio of the sensitivity volume V11 and the sensitivity period t11SB defined for quick fill. The following applies: $$\text{VS13SB = V11 / t11SB}\text{.}$$

For the air play area 13 continues to be a corresponding characteristic volume flow VS13SE for the discrete quick emptying through the ratio of the sensitivity volume V11 and the sensitivity period t11SE defined for the discrete quick emptying, so that the following applies: $$\text{VS13SE = V11 / t11SE}\text{.}$$

The same applies to the elasticity range 14th corresponding characteristic volume flows are defined for discrete quick filling and discrete quick emptying. For the area of elasticity 14th becomes the characteristic volume flow VS14SB for the discrete quick filling by the ratio of the difference between the contact volume V12 and the sensitivity volume V11 and the difference between the contact time t12SB and the sensitivity period t11SB each defined for quick fill. For the characteristic volume flow of the elasticity area 14th for the discrete quick filling the following applies: $$\text{VS14SB =}\left(\text{V12- V11}\right)/\left(\text{t12SB- t11SB}\right).$$

The same applies to the elastic range 14th the characteristic volume flow rate V14SE for the discrete quick emptying by the ratio of the difference between the contact volume V12 and the sensitivity volume V11 and the difference between the contact time t12SE and the sensitivity period t11SE each defined for quick emptying so that the following applies to this characteristic volume flow: $$\text{VS14SE =}\left(\text{V12- V11}\right)/\left(\text{t12SE- t11SE}\right).$$

With all of the above-described parameters of the pressure-volume characteristic 10 , namely with sensitivity pressure p11 , with contact printing p12 , at the sensitivity volume V11 , at the contact volume V12 , for the sensitivity periods t11SE , t11SB , for the contact times t12SB , t12SE and with the characteristic volume flows VS13SB , VS13SE , VS14SB , VS14SE these are parameters of the empirically determined pressure-volume characteristic 10 that are stored on the control side.

If the actual filling volume of the hydraulic control element is to be determined in the case of a discrete quick fill and / or a discrete quick emptying of the respective hydraulic control element, this is done depending on whether a discrete quick fill and / or a discrete quick emptying of the same is carried out on the basis of the corresponding characteristic Volume flows, with the actual filling volume and thus ultimately an actual position of the respective hydraulic adjusting element by integrating the for quick filling and / or for quick emptying for the respective characteristic range 13 , 14th defined, characteristic volume flow is determined.

4th visualizes different states of a hydraulic control element when it is filled and emptied. So visualized 4th a first state 17th which corresponds to an initialization of the filling process or emptying process and in which the filling volume does not yet change. Also in one of the initialization 17th subsequent hibernation 18th there is no change in volume in the actuator. A condition 19th corresponds to a discrete quick fill and a state 20th a discrete quick emptying, which is in the characteristic curve ranges described above 13 , 14th and 15th subdivide. Also shows 4th a state 21st continuous filling and / or emptying of the adjusting element. A block 22nd merges the states in order to determine the absolute filling volume of the actuating element. The invention is used in the states 19th and 20th to determine the actual filling volume of the hydraulic control element with the discrete quick filling and discrete quick emptying. In the states 17th , 18th and 21st the invention is not used.

In 2 is the pressure-volume curve 10 of the 1 together with a pressure-torque characteristic 23 shown. In the pressure-torque curve 23 shows a relationship between a torque M, which can or should be transmitted by a shifting element of the transmission to be operated, and the control pressure p of the actuating element.

Based on the pressure-torque characteristic 23 For a setpoint torque MSOLL to be transmitted by the frictionally engaged shifting element to be controlled, a setpoint control pressure pSOLL can then be used using the pressure-volume characteristic 10 Depending on the target control pressure PSOLL, a target filling volume VSOLL can be determined for the hydraulic control element with which the same is to be filled in order to be able to transmit the desired target torque MSOLL on the respective switching element.

The switching element is closed and the switching element is opened using a discrete rapid filling of the hydraulic actuating element when closing the respective frictional switching element or a discrete rapid emptying of the hydraulic actuating element when opening the respective frictional switching element.

If the frictional switching element is subsequently closed or opened, namely when closing using a discrete quick fill and when opening using a discrete quick emptying of the hydraulic control element actuating the frictional switching element, the control element is controlled with the target control pressure pset over time, with then which, as a result of the actuation of the actuating element with the target actuation pressure pSoll, is determined as described above, namely by integrating the characteristic volume flows that have been described in detail above. Then, when the determined actual filling volume VIST corresponds to the target filling volume VSOLL, the filling or emptying of the hydraulic control element is ended.

The sensitivity periods t11SB and t11SE as well as the contact times t12SB and t12SE are dependent both on the temperature of the transmission and on a speed of the actuating element or half of the switching element to be actuated, with which the hydraulic actuating element is coupled. If the frictional shifting element to be actuated is a brake, the hydraulic actuating element is typically coupled to a stationary, stator-side half of the frictional shifting element, so that the sensitivity periods then last t11SB and t11SE as well as the contact times t12SB and t12SE are not dependent on the speed. The level of pressure control also has an influence on the sensitivity periods and contact periods. For different transmission temperatures and / or speeds of the shifting element and different control pressure levels, appropriate sensitivity periods and contact periods are preferably stored on the control side, between which interpolation can be made if necessary.

According to an advantageous development of the invention, it is provided that the empirically determined pressure-volume characteristic curve stored on the control side 10 is adapted during operation in order to compensate for tolerance effects and wear effects.

For adapting the sensitivity point 11 as well as the contact point 12 offset values are determined depending on which the sensitivity point is 11 and contact point 12 be adapted. The empirically determined pressure-volume characteristic curve stored on the control side 10 accordingly provides a reference characteristic curve which is adapted and adjusted using the offset values determined during operation. this shows 3 , where in 3 on the one hand, the empirically determined pressure-volume characteristic curve stored on the control side 10 and on the other hand an adaptive pressure-volume characteristic 10 ' is shown.

This is how when adapting the pressure-volume characteristic 10 a pressure offset value OFp and a volume offset value OFV determined, depending on which the sensitivity point 11 and the point of contact 12 be adapted, namely the sensitivity point 11 to the adapted sensitivity point 11 ' and the point of contact 12 to the adapted contact point 12 ' .

This corresponds to a parallel shift of the empirically determined pressure-volume characteristic curve stored on the control side 10 in two directions, namely in the pressure direction and volume direction around the offset values described above.

For the adapted sensitivity pressure 11 ' and adapted contact pressure p12 ', the following applies: $$\begin{array}{c}\text{p11 '= p11 + OFp}\\ \text{p12 '= p12 + OFp}\end{array}$$

The following applies to the adapted sensitivity volume V11 'and the adapted contact volume V12': $$\begin{array}{c}\text{V11 '= V11 + OFV}\\ \text{V12 '= V12 + OFV}\end{array}$$

The offset value OFp for sensitivity printing p11 and the offset value OFV for the sensitivity volume V11 with a quick fill up to the sensitivity point 11 determined.

So can the offset value OFp for sensitivity printing p11 with a quick fill up to the sensitivity point 11 can be determined by measurement.

The offset value OFV for the sensitivity volume V11 becomes dependent on one for the quick fill up to the sensitivity point 11 determined offset time tOF, which is determined by measurement and dependent on the characteristic volume flow VS13SB of the air play area 13 determined by calculation for discrete quick filling. The following applies: $$\text{OFV = tOF × VS13SB}\text{.}$$

In the case of a quick fill, the offset value OFp for sensitivity printing p11 and the offset value OFV for the sensitivity volume V11 be determined.

The offset value OFP for the sensitivity pressure p11 is metrologically and the offset value OFV for the sensitivity volume V11 calculated based on the metrologically determined time offset tOF. This with the quick filling up to the sensitivity point 11 determined offset values OFp and OFV are used to adapt the sensitivity point 11 as well as for adapting the contact point 12 used.

List of reference symbols

10

Pressure-volume characteristic

10 '

adapted pressure-volume characteristic

11

Sensitivity point

11 '

adapted sensitivity point

p11

Sensitivity point

V11

Sensitivity volume

t11SB

Sensitivity period

t11SE

Sensitivity period

12

Contact point

12 '

adapted contact point

p12

Contact pressure

V12

Contact volume

t12SB

Contact time

t12SE

Contact time

13

Air play area

VS13SB

Volume flow

VS13SE

Volume flow

14th

Elastic range

VS14SB

Volume flow

VS14SE

Volume flow

15th

Stiffness range

16

Measurement signal curve

17th

Status

18th

Status

19th

Status

20th

Status

21st

Status

22nd

block

23

Pressure-torque characteristic

OFp

Pressure offset value

OFV

Volume offset value

Claims (12)

Method for determining an actual filling volume of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle with a discrete quick filling and / or with a discrete quick emptying of the hydraulic adjusting element, storing an empirically determined pressure-volume characteristic curve (10) for the hydraulic adjusting element, wherein the pressure-volume characteristic curve (10) through a sensitivity point (11), in which the frictional switching element actuatable by the hydraulic adjusting element begins to transmit torque, and through a contact point (12), in which a rigidity and thus a pressure sequence behavior of the frictional shifting element that can be actuated by the hydraulic adjusting element changes, is subdivided into several characteristic curve areas (13, 14, 15), a first characteristic curve area defining an air gap area (13) between a completely emptied adjusting element and an adjusting element filled up to the sensitivity point, with a second characteristic curve area defining a The elasticity range (14) is defined between an actuating element filled up to the sensitivity point and an actuating element filled up to the contact point, whereby for the air clearance area (13) and the elasticity area (14) both for a discrete quick filling and for a discrete quick emptying respectively As characteristic volume flows (VS13SB, VS13SE, VS14SB, VS14SE) are defined, the actual filling volume of the hydraulic control element is determined depending on whether a discrete quick filling and / or a discrete quick emptying of the same has been carried out, the actual filling volume being integrated by integrating the quick filling and / or for the quick emptying for the respective characteristic curve area (13, 14) defined, characteristic volume flow (VS13SB, VS13SE, VS14SB, VS14SE) is determined. Procedure according to Claim 1 , characterized in that the sensitivity point (11) is defined by a sensitivity pressure (p11), a sensitivity volume (V11) and a sensitivity period (t11 SB, t11SE). Procedure according to Claim 2 , characterized in that the sensitivity point (11) is defined by a sensitivity period (t11SB) for the rapid filling and a sensitivity period (t11SE) for the rapid emptying, the sensitivity period (t11SB) for the rapid filling being that period of time that is required by a to fill the fully emptied control element up to the sensitivity point (11), the sensitivity period (t11SE) for rapid emptying being the time required to completely empty the control element starting from the sensitivity point (11). Procedure according to Claim 3 , characterized in that for the air play area (13) the characteristic volume flow (VS13SB) for the discrete quick filling is defined by the ratio of the sensitivity volume (V11) and the sensitivity time period (t11SB) for the quick filling, for the air play area (13) the characteristic Volume flow (VS13SE) for the discrete quick emptying is defined by the ratio of the sensitivity volume (11) and the sensitivity period (t11SE) for the quick emptying. Method according to one of the Claims 1 to 4th , characterized in that the contact point (12) is defined by a contact pressure (p12), a contact volume (V12) and a contact duration (t12SB, t12SE). Procedure according to Claim 5 , characterized in that the contact point (12) is defined by a contact time period (t12SB) for rapid filling and a contact period (t12SE) for rapid emptying, the contact period (t12SB) for rapid filling being the period of time that is required to reach a to fill the completely emptied control element up to the contact point (12), the contact time (t12SE) for the rapid emptying being the time required to completely empty the control element starting from the contact point (12). Procedure according to Claim 6 , characterized in that for the elasticity range (14) the characteristic volume flow (VS14SB) for the discrete quick filling is given by the ratio of the difference between the contact volume (V12) and the sensitivity volume (V11) and the difference between the contact time (t12SB) and the sensitivity time ( t11SB) is defined for the quick filling, for the elasticity range (14) the characteristic volume flow (VS14SE) for the discrete quick emptying by the ratio of the difference between the contact volume (V12) and the sensitivity volume (V11) and the difference between the contact time (t12SE) and the sensitivity period (t11SE) is defined for the rapid emptying. Method according to one of the Claims 1 to 7th , characterized in that the stored, empirically determined pressure-volume characteristic curve (10) is adapted during operation. Procedure according to Claim 8 , characterized in that during the adaptation for the sensitivity point (11) offset values (OFp, OFV) for the sensitivity pressure (p11) and the sensitivity volume (V11) are determined, depending on which the sensitivity point (11) and the contact point (12) are adapted become. Procedure according to Claim 9 , characterized in that the offset value (OFp) for the sensitivity pressure (p11) is determined by measurement during rapid filling, the offset value (OFV) for the sensitivity volume (V11) is dependent on an offset time determined by measurement during rapid filling and dependent on the characteristic volume flow (VS13SB) of the air clearance area (13 ) is calculated for the discrete quick filling. Method for controlling a frictional shifting element of a transmission of a motor vehicle, namely for closing the same with a discrete quick filling or for opening the same with a discrete quick emptying of a hydraulic actuating element which actuates the frictional shifting element, with the following steps: Determining a nominal filling volume (VSOLL) for the hydraulic Actuating element depending on one of the nominal torque (MSOLL) to be transmitted via the frictional shifting element, filling the hydraulic adjusting element with a discrete quick filling or emptying the hydraulic adjusting element with a discrete quick emptying, determining an actual filling volume (VIST) for the hydraulic adjusting element according to the method according to one of the Claims 1 to 10 Completion of the filling or emptying of the hydraulic adjusting element when the actual filling volume (VIST) corresponds to the target filling volume (VSOLL). Control unit of a motor vehicle, in particular transmission control unit of a transmission of the motor vehicle, characterized in that it is set up, the method according to one of the Claims 1 to 11 to be carried out on the control side.

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