DE102017116238A1 - Method for determining oil damage in friction clutches - Google Patents

Abstract

Method for determining an oil damage of a friction clutch for dual-clutch transmissions (1) by means of a control unit, wherein the dual-clutch transmission (1) comprises a first clutch (2) and a second clutch (3), wherein the determination of oil damage in a defined driving condition by means of monitored pressure-controlled and / or pressure-controlled cross-fading from the first clutch (2) to the second clutch (3).

Description

Field of the invention

The present invention relates to a method for determining an oil damage of a friction clutch for dual-clutch transmission by means of a control unit, wherein the dual-clutch transmission comprises a first clutch and a second clutch.

State of the art

From the DE102006027436A1 For example, a method and a device for controlling or regulating an automatic or automated transmission in a motor vehicle are known. Sensors measure at least one oil parameter which is evaluated in a control unit. Based on this evaluation, at least one transmission parameter is controlled or regulated.

Summary of the invention

It is an object of the invention to determine the oil quality in a simple manner in order to determine the end of the service life of the transmission oil in advance and thus to ensure a safe and economical operation of the coupling system.

The object is achieved by a method having the features of claim 1.

According to the invention a method for determining an oil damage of a friction clutch is provided for dual-clutch transmission, by means of a control unit, wherein the dual-clutch transmission comprises a first clutch and a second clutch, wherein the determination of the oil damage in a defined driving condition by means of monitored pressure-controlled and / or pressure-controlled transition of the first clutch after the second clutch takes place.

By cross-fading is meant that the torque is transmitted from a first clutch to a second clutch, wherein the transmission of the torque is effected by opening the first clutch and preferably simultaneously closing the second clutch. The opening or closing of the first clutch and the second clutch takes place pressure-controlled and / or pressure-controlled. The crossfade may also be sequential, that is, the second clutch does not begin to close until the first clutch is fully or nearly fully open.

The determination that the transmission of the torque from the first clutch to the second clutch takes place is to be understood so that, conversely, the transmission of the torque from the second clutch to the first clutch can take place. The method can thus be carried out by cross-fading in both directions.

In the control unit are measured as "monitoring" preferably measured by sensors parameters and compared with setpoints. If these measured parameters deviate from the specified setpoint values or setpoint curves, a warning can be output.

The coefficient of friction as a quotient of normal and circumferential forces in the clutch system is essentially dependent on the speed difference. This dependency has in the new condition of the gear oil on the speed difference increasing course. Aging of the oil changes the coefficient of friction and can lead to a deterioration of the driving characteristics. The inventive method provides by performing a cross-fade, a direct measurement of the coefficient of friction for different differential speeds and thus allows a good characterization of oil damage.

• - Druckgesteuert
• - Druckgeregelt

It is preferred to distinguish between two measurement variants:

• - pressure controlled
• - Pressure controlled

Pressure-controlled or speed-controlled means that the rotational speeds of the transmission input shafts during the transition should follow a predetermined time course. For this purpose, a regulation of the coupling pressures is required. Depending on the damage to the oil, the necessary action with regard to the coupling pressure is pronounced to varying degrees and can be used to assess the damage to the oil.

Under pressure control is understood that the coupling pressures during the transition should follow a predetermined time course. As a reaction to this pressure curve, depending on the oil damage, a chronologically different course of the transmission input rotational speeds occurs, so that the assessment of the present oil damage can take place herewith.

The clutches can be actuated hydraulically or by an electromechanical actuation, in which the respective clutch is closed or opened by means of an electric actuator, for example a servomotor or a solenoid. Both aforementioned method variants can also be transferred to an electromechanical actuation and thus a method according to the invention can also be carried out with an electromechanically actuated coupling.

A reliable determination of the oil damage is preferably carried out when both clutches can be blended in a no-load condition, so that no influences from "outside" can influence or distort the measurement result. The defined driving state is therefore present in particular when the dual-clutch transmission is decoupled from the drive train, in particular from an output shaft of the dual-clutch transmission.

In a preferred embodiment, the defined driving state is present when the vehicle is stationary.

However, it is also possible for the determination according to the invention of the oil damage to be carried out in another defined driving state, for example during the so-called "sailing", that is to say during the drive train, in particular the drive wheels are decoupled from the vehicle drive while driving.

According to one embodiment of the invention, the first clutch for frictionally connecting a first input shaft to a motor output shaft and the second clutch for frictionally connecting a second input shaft to the motor output shaft are formed.

In dual-clutch transmissions usually two friction clutches can be coupled, each with an input shaft, wherein the input shafts, each with an output shaft forming a partial transmission. By means provided with synchronizing switching elements different gears are switchable, wherein the gears are graded such that between the gear ratios of a sub-gear each have a gear ratio of the other sub-transmission.

The friction clutches are preferably designed as multi-plate clutches.

In a preferred embodiment, all odd gears are rotatably connected to the first input shaft. With the second input shaft, all straight gears are non-rotatably switchable. Preferably, the gears are arranged as fixed gears on the input shafts. At the transmission output shafts, the gears are arranged as idler gears.

Preferably, a bridge circuit is designed for the positive connection of the first input shaft to the second input shaft.

The bridge circuit is preferably realized in that idler gears of both partial transmissions, which are mounted on the same transmission output shaft, are connected to each other by means of a synchronizer. As a result, the first input shaft and the second input shaft can be connected to one another in such a way that they rotate with one another and thus form, for example, a first gear.

During the bridge circuit, the drive train, in particular the drive wheels, can be decoupled from the drive. During this driving state, the oil damage can be determined, since here the cross-fading from the first clutch to the second clutch without action on a vehicle movement is feasible.

• - Druckgesteuertes Überblenden des Druckes der ersten Kupplung nach der zweiten Kupplung,
• - Messen der Drehzahl an der Eingangswelle der ersten Kupplung und/oder der Eingangswelle der zweiten Kupplung,
• - Vergleichen des/der Messwerte mit einem vorgegebenen Grenzwert oder Verlauf innerhalb einer vorgegebenen Zeitspanne,
• - Feststellen der Ölschädigung in Abhängigkeit vom Vergleichsergebnis.

The measurement is preferably carried out with decoupled, in particular shut down, powertrain by the following steps:

• Pressure-controlled cross-fading of the pressure of the first clutch after the second clutch,
• Measuring the rotational speed at the input shaft of the first clutch and / or the input shaft of the second clutch,
• Comparing the measured value (s) with a predetermined limit value or course within a predetermined period of time,
• - Determination of oil damage depending on the comparison result.

After measuring the rotational speed at the first input shaft and the rotational speed at the second input shaft, the rotational speed difference is preferably determined by determining the rotational speed difference between the first input shaft and the second input shaft by the control unit. This speed difference can be compared with a predetermined limit or a predetermined course.

• - Druckgeregeltes Überblenden der ersten Kupplung nach der zweiten Kupplung,
• - Erfassen des Druckregeleingriffs der ersten Kupplung und/oder zweiten Kupplung während der Überblendung,
• - Vergleichen des/der Messwerte mit einem vorgegebenen Grenzwert oder Verlauf innerhalb einer vorgegebenen Zeitspanne,
• - Feststellen der Ölschädigung in Abhängigkeit vom Vergleichsergebnis.

Alternatively, the measurement can be carried out with decoupled, in particular shut down, powertrain by the following steps:

• Pressure-controlled cross-fading of the first clutch after the second clutch,
• Detecting the pressure control intervention of the first clutch and / or second clutch during the transition,
• Comparing the measured value (s) with a predetermined limit value or course within a predetermined period of time,
• - Determination of oil damage depending on the comparison result.

The duration of such a measurement and thus the "predetermined time period" is relatively short, preferably between 0.5 and 3 sec., In particular about 1 sec.

In addition, further oil parameters for the determination of the oil damage can be taken into account, as an oil parameter, for example, the Oil level, the oil temperature or the oil pressure are measured by means of sensors. Advantageously, a combination of these parameters is evaluated in the control unit and serves to check the plausibility of the oil damage.

The oil has properties, such as surface-active behavior, viscosity and flow behavior, etc., which can be reinforced by the addition of additives that deteriorate continuously during the operating time in the transmission. Even if one of these properties is outside the desired parameters, the oil has reached its useful life and an oil change is required.

The control unit for measuring at least one parameter of the oil can be arranged either in the transmission or outside the transmission.

The oil loses its viscosity over time, which also changes the coefficient of friction on the clutch. This thereby changing coefficient of friction is compensated by changing the pressurization of the hydraulic cylinder to the corresponding clutch. If the pressure measured on the hydraulic cylinder reaches a critical value, the end of the service life of the oil can be displayed. To obtain a more meaningful value, for example, the oil temperature is taken into account. Also, the degree of contamination of the oil has a negative effect on the coefficient of friction.

Due to the increasing pressure on the hydraulic cylinder required to compensate for the reduced coefficient of friction with the age of the oil and the resulting oil damage, the life of the oil can be estimated and continuously displayed to the driver in a display. This display can be displayed, for example, in km or in months / years.

The determination of the oil damage can be carried out as often as desired and the measuring interval is usually specified by the vehicle manufacturer. For example, the determination or measurement can be carried out at each start. Alternatively, the measurement can take place at intervals, for example at regular time intervals or as a function of the kilometers traveled.

In a further embodiment of the invention, a warning is issued during or before reaching the predetermined limit value or given course over an impending oil change.

The warning may preferably be made optically, by display on a display or by a warning light. But it can also, alternatively or additionally, acoustically, for example, by announcement or a beep done.

According to the invention, a transmission device is provided, comprising a first clutch, a second clutch, and a control unit, the control unit being designed to carry out a method as described above.

list of figures

• 1 ist eine schematische Darstellung einer Brückenschaltung.
• 2 ist ein Diagramm zur Darstellung unterschiedlicher Charakteristiken der Ölschädigung.
• 3 ist eine Darstellung der Überblendung von der ersten Kupplung zur zweiten Kupplung bei Drucksteuerung.
• 4 ist ein Diagramm zur Darstellung des resultierenden Drehmomentenverlaufs der Kupplung bei unterschiedlicher Charakteristik der Ölschädigung, bei Drucksteuerung.
• 5 ist ein Diagramm zur Darstellung des Drehzahlverlaufs der Kupplung in Abhängigkeit der Ölschädigung, bei Drucksteuerung.
• 6 ist ein Diagramm zur Darstellung der Drehbeschleunigung an der Kupplung in Abhängigkeit der Ölschädigung, bei Drucksteuerung.
• 7 zeigt den Kupplungsdruckverlauf bei einer druckgeregelten sequentiellen Überblendung.
• 8 ist ein Diagramm zur Darstellung des Drehmomentenverlaufs bei einer druckgeregelten sequentiellen Überblendung.
• 9 ist ein Diagramm zur Darstellung des Drehzahlverlaufs bei einer druckgeregelten sequentiellen Überblendung.

The invention will now be described by way of example with reference to the drawings.

• 1 is a schematic representation of a bridge circuit.
• 2 is a diagram illustrating different characteristics of oil damage.
• 3 is a representation of the transition from the first clutch to the second clutch in pressure control.
• 4 is a diagram illustrating the resulting torque curve of the clutch with different characteristics of the oil damage, in pressure control.
• 5 is a diagram showing the speed curve of the clutch as a function of oil damage, in pressure control.
• 6 is a graph showing the rotational acceleration of the clutch as a function of oil damage, in pressure control.
• 7 shows the clutch pressure curve in a pressure-controlled sequential blending.
• 8th is a diagram illustrating the torque curve in a pressure-controlled sequential blending.
• 9 is a diagram showing the speed curve in a pressure-controlled sequential blending.

Detailed description of the invention

In 1 is a schematic representation of a bridge circuit in a dual-clutch transmission 1 shown. The first clutch 2 is with the first input shaft 4 connected. The second clutch 3 is with the second input shaft 5 connected.

When bridge circuit, or activation of the bridge circuit, the first clutch 2 connected to the first input shaft 4 is connected by coupling a gear, for example, the fifth gear 6 , with another gear, for example the sixth gear 7 , and thus by coupling the two input shafts 4 and 5 , with the second clutch 3 connected.

On the input shafts 4 . 5 the fixed wheels are for gear five and six.

The fifth gear 6 and the sixth gear 7 are coupled to the same output shaft by means of a synchronizer.

The idler gears of gears five and six can be connected to the output shaft. However, this does not occur during the process according to the invention, so that the drive train - in the direction of the wheels of the vehicle - is decoupled from the dual-clutch transmission.

By fading from the first clutch 2 after the second clutch 3 can be easily determined the oil quality and thus the service life of the oil and the expected remaining service life of the oil. As described, the motor vehicle can be decoupled from the drive train in the bridge circuit and thus assume a defined driving state, for example vehicle standstill.

2 shows different characteristics of oil damage. On the abscissa, the speed difference ν (at the first input shaft 4 and at the second input shaft 5 measured) and shown on the ordinate of the friction coefficient μ of the friction lining of the friction clutch. O1 shows the course of the oil characteristic when the ratio change of the friction coefficient Δμ to change the speed difference Δν> 0, the oil is then or little damaged. O2 shows the course of the oil characteristic when the ratio change of the friction coefficient Δμ to change of the rotational speed difference Δν = 0, the oil is then slightly damaged or aged. O3 shows the course of the oil characteristic when the ratio change of the friction coefficient Δμ to change the speed difference Δν <0, the oil is then significantly damaged and must be replaced or replaced.

In the 3 - 6 becomes a crossfade from the first clutch 2 to the second clutch 3 shown at pressure control.

In 3 becomes the crossfade from the first clutch 2 to the second clutch 3 at constantly increasing clutch pressure p shown. On the ordinate is the clutch pressure p , on the abscissa the passage of time t shown. The first clutch 2 is through the course V1.1 shown and indicates a defined clutch pressure before the transition begins p on. The second clutch 3 gets through the course V2.2 shown and has no clutch pressure at the beginning of the crossfade p on. During crossfading, the first clutch 2 opened while the second clutch 3 is closed. By opening the first clutch 2 the clutch pressure drops p while on the second clutch 3 the clutch pressure p increases. At full crossfade, the pressure is p at the first clutch dropped to 0, while the second clutch 3 a defined clutch pressure p having.

4 shows the resulting clutch torque M in the case of a transition according to 3 at different oil damages. For aged oil ( MO3.1 ) the clutch needs a longer period of time t In order to reach the maximum torque of the clutch, with aged oil a smaller maximum clutch torque is achieved than with newer oil ( MO1.1 ).

The resulting clutch torque M is preferably determined only on a clutch, for example on the second clutch 3 ,

The history MO1.1 shows the resulting clutch torque at Δμ / Δν> 0 that is not damaged oil. The max. Clutch torque is reached quickly and drops slightly at the end of the measurement period. The history MO2.1 shows the resulting clutch torque at Δμ / Δν = 0, the same max. Clutch torque can no longer be achieved, but the clutch torque is held approximately constant until the end.

At course MO3.1 is the resulting clutch torque at Δμ / Δv <0, that is damaged oil. The resulting clutch torque M is even lower and climbs towards the end, before dropping again briefly. Due, for example, to this increase in clutch torque M or the rotational acceleration of the clutch at the same clutch pressure p can be concluded on an oil damage.

In 5 is the time course of the rotational speed N of, by means of cross-fading according to 3 coupled, input shaft ( 5 ), until the engine speed is reached, depending on the oil damage. The more damaged the gear oil ( NO3.1 ), the longer it takes for the input shaft 5 is aligned with the engine speed. The history NO1.1 is the shortest at Δμ / Δv> 0 to reach the engine speed at the input shaft. The history NO2.1 is slightly longer at Δμ / Δv = 0, until the engine speed is reached. course NO3.1 is given at Δμ / Δv <0 and takes even longer to reach the engine speed. Measuring this longer time required for aged oil until the speed compensation has occurred can also be used to detect oil damage.

In 6 becomes the spin A at the coupling depending on the oil damage ( AO1.1 . AO2.1 . AO3.1 ) - similar to the clutch torque of 4 , The highest spin AO1.1 is achieved with new oil in a shorter time than with an existing oil damage. The course essentially corresponds to the resulting clutch torques M in 4 ,

Due to the measured values, which are in the in 4 to 6 shown diagrams, the oil damage can be determined in the control unit and determines the time for a required oil change or displayed.

In the 7 - 9 becomes a sequential crossfade from the first clutch 2 to the second clutch 3 , with pressure control, shown.

7 shows a sequential fade from the first clutch 2 to the second clutch 3 with pressure control, while the required clutch pressure p over time t applied, for the second clutch ( V2 ) or first clutch ( V1 ). This is the second clutch 3 closed when the first clutch 2 fully or almost completely open. The history V2.2O1 the increase in pressure is lowest for uninjured oil, Δμ / Δv> 0. The history V2.2O2 the pressure increase at Δμ / Δv = 0 is faster or higher than the curve Δμ / Δv> 0. The course V2.2O3 the pressure increase of the clutch at Δμ / Δv <0, so aged oil, is even faster or the maximum applied pressure even higher. In this course V2.2O3 an oil change is required or soon to be carried out.

8th shows that the clutch torque curve M for Δμ / Δv> 0, Δμ / Δv = 0 and Δμ / Δv <0 ( MO1.2 . MO2.2 . MO3.2 ) is the same because to achieve this characteristic of the clutch pressure p with damaged oil - accordingly 7 - is raised until the desired characteristic is reached. If the max. clutch pressure p would be achieved and the characteristic for M according to 8th could not be achieved, an oil change would be required in any case. Analogous to this characteristic for M also sees the characteristic for the spin A in the pressure-controlled case.

9 shows that the course of the speed N at the input shaft at pressure control also equal for different oil damages ( NO1.2 . NO2.2 and NO3.2 ). If the characteristic could no longer be reached in a predetermined / predetermined time, an oil change would be required.

LIST OF REFERENCE NUMBERS

1

Transmission, dual-clutch transmission

2

first clutch

3

second clutch

4

first input shaft

5

second input shaft

6

fifth gear

7

sixth gear

8th

Motor output shaft

O1

Oil characteristic friction coefficient> 0

O2

Oil characteristic friction coefficient = 0

O3

Oil characteristic friction coefficient <0

V1.1

History of clutch pressure first clutch

V2.1

Course clutch pressure second clutch

MO1.1

Course resulting clutch torque Δμ / Δν> 0

MO2.1

Course resulting clutch torque Δμ / Δν = 0

MO3.1

Course resulting clutch torque Δμ / Δν <0

NO1.1

Course max. Speed Δμ / Δν> 0

NO2.1

Course max. Speed Δμ / Δν = 0

NO3.1

Course max. Speed Δμ / Δν <0

AO1.1

Course of spin Δμ / Δν> 0

AO2.1

Course of spin Δμ / Δν = 0

AO3.1

Course of spin Δμ / Δν <0

V1.2

History of clutch pressure first clutch

V2.201

Course clutch pressure second clutch Δμ / Δν> 0

V2.202

Course clutch pressure second clutch Δμ / Δν = 0

V2.203

Course clutch pressure second clutch Δμ / Δν <0

MO1.2

Course resulting clutch torque Δμ / Δν> 0

MO2.2

Course resulting clutch torque Δμ / Δν = 0

MO3.2

Course resulting clutch torque Δμ / Δν <0

NO 1.2

Course max. Speed Δμ / Δν> 0

NO2.2

Course max. Speed Δμ / Δν = 0

NO3.2

Course max. Speed Δμ / Δν <0

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006027436 A1 [0002]

Claims (9)

Method for determining an oil damage of a friction clutch for dual-clutch transmissions (1) by means of a control unit, wherein the dual-clutch transmission (1) comprises a first clutch (2) and a second clutch (3), characterized in that the determination of oil damage in a defined driving state means monitored pressure-controlled and / or pressure-controlled cross-fading from the first clutch (2) to the second clutch (3). Method for determining an oil damage of a friction clutch after Claim 1 , characterized in that the defined driving condition is present when the dual-clutch transmission is free of load, in particular when the vehicle is stationary. Method for determining an oil damage of a friction clutch according to at least one of the preceding claims, characterized in that the first clutch (2) for frictionally connecting a first input shaft (4) with an engine output shaft (8) and the second clutch (3) for frictionally connecting a second input shaft (5) are formed with the motor output shaft (8). Method for determining an oil damage of a friction clutch after Claim 3 , characterized in that a bridge circuit for the positive connection of the first input shaft (4) with the second input shaft (5) is formed, wherein the pressure-controlled and / or pressure-controlled cross-fading is preferably carried out with the bridge circuit activated. Method for determining an oil damage of a friction clutch after Claim 3 or 4 , characterized in that the determination of the oil damage by means of pressure-controlled cross-fading from the first clutch (2) after the second clutch (3), wherein during and / or shortly after the cross-fade, the speed (N) and / or the torque (M) and / or the rotational acceleration (A) at the first and / or second input shaft (2, 3) is measured or that the determination of the oil damage by means of pressure-controlled cross-fading from the first clutch (2) to the second clutch (3), wherein during and / or shortly after the cross-fading the clutch pressure (p) on the first and / or second input shaft (2, 3) is measured. Method for determining an oil damage of a friction clutch according to at least one of the preceding claims, characterized in that the determination in decoupled, in particular shutdown, powertrain by the following steps: - Pressure-controlled cross-fading of the pressure of the first clutch (2) after the second clutch (3) Measuring the rotational speed (N) at the first input shaft (4) of the first clutch (2) and / or the second input shaft (5) of the second clutch (3), comparing the measured value (s) with a predetermined limit value or course within a predetermined period of time, - determining the oil damage as a function of the comparison result. Method for determining an oil damage of a friction clutch according to at least one of the preceding Claims 1 to 5 , characterized in that the determination in decoupled, especially decommissioned powertrain by the following steps: - Pressure-controlled cross-fading of the first clutch (2) after the second clutch (3), - detecting the pressure control intervention of the first clutch (2) and / or second clutch (3) during the crossfade, - comparing the measured value (s) with a predetermined limit or course within a predetermined period of time, - determining the oil damage as a function of the result of the comparison. Method for determining an oil damage of a friction clutch according to at least one of the preceding claims, characterized in that a warning about a necessary oil change is issued at or before reaching the predetermined limit value or course. Transmission device comprising a first clutch (2), a second clutch (3), and a control unit, characterized in that the control unit is adapted to a method according to one of Claims 1 to 8th perform.

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