DE102017116238B4 - Method for determining oil damage in friction clutches and transmission devices - Google Patents

Abstract

A method for determining oil damage to a friction clutch for double clutch transmissions (1) by means of a control unit, the double clutch transmission (1) comprising a first clutch (2) and a second clutch (3), the oil damage being determined 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), the first clutch (2) for frictional connection of a first input shaft (4) with an engine output shaft (8) and the second clutch (3) for non-positive connection of a second input shaft (5) to the motor output shaft (8), characterized in that a bridge circuit is designed for the positive connection of the first input shaft (4) to the second input shaft (5), the pressure-controlled and / or pressure-controlled fading is carried out when the bridge circuit is activated.

Description

Field of invention

The present invention relates to a method for determining oil damage to a friction clutch for dual clutch transmissions by means of a control unit, the dual clutch transmission comprising a first clutch and a second clutch. The invention also relates to a transmission device comprising a first clutch, a second clutch, and a control unit.

State of the art

From the DE 10 2006 027 436 A1 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. At least one transmission parameter is controlled or regulated based on this evaluation.

The EP 0 191 458 A1 discloses an oil destruction warning system for a motor vehicle, comprising first means for detecting respective values of deterioration factors of oil, the deterioration factors being closely related to the operating history of the motor vehicle; second means for adding the detected values using a predetermined calculation formula and integrating the added values over time; third means for outputting a warning signal when the integrated value exceeds a predetermined limit; and a fourth means which, when refilling oil, postpones the output of the warning signal by a period of time which corresponds to the ratio of the refilled oil to the total amount of oil.

From the DE 10 2004 035 262 A1 A method for controlling an automatic transmission that is operatively connected to a motor vehicle is known in which at least one clutch can be engaged by means of an actuator or can be switched open with a clearance and has an adjustable clearance, the clearance of the at least one clutch being set so that a The optimum between the minimization of the shift reaction time of the clutch and the minimization of the drag loss of the clutch is achieved, as well as the weighting between the minimization of the shift reaction time and the minimization of the drag loss of the at least one clutch depending on the operating parameters of the clutch and / or the operating state of the motor vehicle and / or environmental conditions of the motor vehicle is selected automatically.

The DE 10 2006 008 755 A1 discloses a method for controlling a friction clutch of a power-shiftable automatic transmission of a motor vehicle, by means of which, when shifting from an original gear to a target gear, a speed adjustment of a shaft of the transmission assigned to the target gear is carried out, with a clutch torque being set so that a through - a Friction power characteristic value of the friction clutch and - a friction work characteristic characterizing friction work of the friction clutch specified operating point does not leave a definable, permissible operating range.

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 safe and economical operation of the clutch system.

The object is achieved by a method with the features of claim 1, as well as by a transmission device with the features of claim 7.

According to the invention, a method for determining oil damage to a friction clutch is provided, for dual clutch transmissions, by means of a control unit, wherein the dual clutch transmission comprises a first clutch and a second clutch, the determination of the oil damage in a defined driving state by means of monitored pressure-controlled and / or pressure-controlled fading of the first clutch takes place after the second clutch, the first clutch being designed for the frictional connection of a first input shaft to an engine output shaft and the second clutch for frictional connection of a second input shaft to the engine output shaft, a bridge circuit for the positive connection of the first input shaft to the second input shaft is formed, wherein the pressure-controlled and / or pressure-regulated cross-fading is carried out with the bridge circuit activated.

According to the invention, a bridge circuit is designed for positively locking connection of the first input shaft to the second input shaft.

The bridge circuit is preferably implemented in that idler gears of both sub-transmissions, which are mounted on the same transmission output shaft, are connected to one another by means of a synchronizing device. Thereby, the first input shaft and the second input shaft are such connectable with each other so that they rotate with each other and thus form a first gear, for example.

During the bridge circuit, the drive train, in particular the drive wheels, can be decoupled from the drive. The oil damage can be determined during this driving state, since here the fading from the first clutch to the second clutch can be carried out without affecting vehicle movement.

Cross-fading is understood to mean that the torque is transmitted from a first clutch to a second clutch, the torque being transmitted by opening the first clutch and preferably simultaneously closing the second clutch. The opening and closing of the first clutch and the second clutch are pressure-controlled and / or pressure-regulated. The cross-fading can also take place sequentially, i.e. the second clutch only begins to close when the first clutch is fully or almost fully open.

The determination that the torque is transmitted from the first clutch to the second clutch is to be understood in such a way that, conversely, the torque can also be transmitted from the second clutch to the first clutch. The method can therefore be carried out by fading in both directions.

As “monitoring”, parameters measured by sensors are read into the control unit and compared with setpoints. If these measured parameters deviate from the specified setpoints or setpoint curves, a warning can be issued.

The coefficient of friction as the quotient of normal and peripheral forces in the clutch system is essentially dependent on the speed difference. When the gear oil is new, this dependency has a curve that increases over the speed difference. Aging of the oil changes the coefficient of friction and can lead to a deterioration in driving characteristics. The method according to the invention offers a direct measurement of the coefficient of friction for different rotational speeds by carrying out a cross-fading and thus allows a good characterization of oil damage.

• - Druckgesteuert
• - Druckgeregelt

A distinction is preferably made between two measurement variants:

• - Pressure controlled
• - Pressure regulated

Pressure-regulated or speed-controlled means that the speeds of the transmission input shafts should follow a predetermined time sequence during the cross-fading. To do this, it is necessary to regulate the clutch pressures. Depending on the damage to the oil, the necessary action with regard to the clutch pressure is different and can be used to assess the existing oil damage.

Pressure-controlled is understood to mean that the clutch pressures should follow a predetermined time curve during the fade. As a reaction to this pressure curve, depending on the oil damage, the transmission input speeds vary over time, so that the existing oil damage can be assessed.

The clutches can be actuated hydraulically or by electromechanical actuation in which the respective clutch is closed or opened by means of an electrical actuator, for example a servomotor or a lifting magnet. Both of the 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 electro-mechanically actuated clutch.

A reliable determination of the oil damage is preferably done if both clutches can be faded in a load-free state so that no “outside” influences 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 when the vehicle is stationary.

However, it is also possible that the determination of the oil damage according to the invention is carried out in a different defined driving state, for example during what is known as “sailing”, that is to say while the drive train, in particular the drive wheels are decoupled from the vehicle drive while driving.

According to the invention, the first clutch is designed for the frictional connection of a first input shaft to an engine output shaft and the second clutch for frictional connection of a second input shaft to the engine output shaft.

In double clutch transmissions, two friction clutches can generally be coupled with one input shaft each, the input shafts each being a partial transmission with one output shaft form. Different gears can be shifted by means of shift elements provided with synchronizing devices, the gears being stepped in such a way that a gear step of the other sub-transmission lies between the gear steps of a sub-transmission.

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

In a preferred embodiment, all uneven gears can be shifted non-rotatably with the first input shaft. With the second input shaft, all even gears can be shifted in a torque-proof manner. The gears are preferably arranged as fixed gears on the input shafts. The gears are arranged as idler gears on the transmission output shafts.

• - 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 the drive train decoupled, in particular shut down, by the following steps:

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

After measuring the speed on the first input shaft and the speed on the second input shaft, the speed difference is preferably determined by determining the 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 value 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, when the drive train is decoupled, in particular when it is shut down, the measurement can be carried out using the following steps:

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

The duration of such a measurement and thus the “specified time span” is relatively short, preferably between 0.5 and 3 seconds, in particular approx. 1 second.

In addition, further oil parameters can be taken into account for the determination of the oil damage, whereby the oil level, the oil temperature or the oil pressure can be measured by means of sensors as oil parameters. A combination of these parameters is advantageously 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 intensified differently by adding additives, which continuously deteriorate during the operating time in the transmission. Even if any of these properties are 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 changing coefficient of friction is compensated by changing the pressure applied to the hydraulic cylinder on the corresponding clutch. If the pressure measured at the hydraulic cylinder reaches a critical value, the end of the service life of the oil can be displayed. In order to obtain a more meaningful value, the oil temperature is also taken into account, for example. The degree of contamination of the oil also has a negative effect on the coefficient of friction.

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

The determination of the oil damage can be carried out as often as required and the measurement 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 according to the invention, a warning is issued when or before the predetermined limit value or predetermined profile is reached about an imminent oil change.

The warning can preferably take place optically, by indication on a display or by a control lamp. It can also, alternatively or additionally, take place acoustically, for example by means of an announcement or a beep.

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.

Figure list

• 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 is described below by way of example with reference to the drawings.

• 1 Figure 3 is a schematic representation of a bridge circuit.
• 2 Fig. 13 is a diagram showing various characteristics of oil deterioration.
• 3 is a representation of the fading from the first clutch to the second clutch in pressure control.
• 4th is a diagram to show the resulting torque curve of the clutch with different characteristics of the oil damage, with pressure control.
• 5 is a diagram to show the speed curve of the clutch as a function of the oil damage, with pressure control.
• 6th is a diagram to show the rotational acceleration at the clutch as a function of the oil damage, with pressure control.
• 7th shows the clutch pressure curve with a pressure-controlled sequential fade.
• 8th is a diagram to show the torque curve in a pressure-controlled sequential fade.
• 9 is a diagram to show the speed curve in a pressure-controlled sequential fade.

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 4th connected. The second clutch 3 is with the second input shaft 5 connected.

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

On the input shafts 4th , 5 are the fixed gears for gear five and six.

The fifth gear 6th and the sixth gear 7th can be coupled to the same output shaft by means of a synchronizing device.

The idler gears of gears five and six can be connected to the output shaft. However, this does not take place during the method 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 the oil quality and thus the useful life of the oil and the expected remaining useful life of the oil can be determined in a simple way. The motor vehicle can be decoupled from the drive train in the bridge circuit, as described, and can thus assume a defined driving state, for example vehicle standstill.

2 shows different characteristics of oil deterioration. The speed difference v (on the first input shaft 4th and on the second input shaft 5 measured) and the friction coefficient µ of the friction lining of the friction clutch is shown on the ordinate. O1 shows the course of the oil characteristic when the ratio of the change in the coefficient of friction Δµ to the change in the speed difference Δν> 0, the oil is then not or only slightly damaged. O2 shows the course of the oil characteristic when the ratio of the change in the coefficient of friction Δµ to the change in the speed difference Δν = 0, the oil is then somewhat damaged or aged. O3 shows the course of the oil characteristic when the ratio of the change in the coefficient of friction Δµ to the change in the speed difference Δν <0, the oil is then clearly damaged and must be replaced or exchanged.

In the 3 - 6th becomes a dissolve from the first clutch 2 to the second clutch 3 shown with pressure control.

In 3 becomes the fade from the first clutch 2 to the second clutch 3 shown with constantly increasing clutch pressure p. On the ordinate is the clutch pressure p, on the The abscissa shows the time course t. The first clutch 2 is through the course V1.1 shown and has a defined clutch pressure p before the transition begins. The second clutch 3 is represented by curve V2.2 and has no clutch pressure p at the beginning of the fade. During the fade, the first clutch will be 2 opened during the second clutch 3 is closed. By opening the first clutch 2 the clutch pressure p falls while on the second clutch 3 the clutch pressure p increases. With complete fading, the pressure p on the first clutch has fallen to 0, while the second clutch 3 has a defined clutch pressure p.

4th shows the resulting clutch torque M with a fade according to 3 with different oil damage. For aged oil ( MO3.1 ) the clutch needs a longer period of time t to reach the maximum torque of the clutch, whereby a smaller maximum clutch torque is achieved with older oil than with newer oil ( MO1.1 ).

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

The history MO1.1 shows the resulting clutch torque at Δµ / Δν> 0, i.e. with undamaged oil. The max. The clutch torque is reached quickly and drops slightly towards the end of the measurement period. The history MO2.1 shows the resulting clutch torque at Δµ / Δν = 0, the same max. The clutch torque can no longer be achieved, but the clutch torque is kept almost constant until the end. With course MO3.1 is the resulting clutch torque at Δµ / Δν <0, i.e. with damaged oil. The resulting clutch torque M is even lower and increases towards the end before it drops again briefly. Because of this increase in clutch torque M or the rotational acceleration of the clutch with the clutch pressure p remaining the same, it can be concluded that the oil has been damaged.

In 5 the time course of the speed N is, by means of fading according to 3 coupled, input shaft ( 5 ), shown 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 / Δν> 0 to reach the engine speed on the input shaft. The history NO2.1 is a little longer at Δµ / Δν = 0 until the engine speed is reached. course NO3.1 is given at Δµ / Δν <0 and takes even longer to reach the engine speed. The measurement of this time, which is longer with aged oil, until the speed compensation is achieved, can also be used to detect oil damage.

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

Based on the measured values, which are included in the in 4th to 6th can be seen in the diagrams, the oil damage can be determined in the control unit and the time for a required oil change can be determined or displayed.

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

7th shows a sequential fade from the first clutch 2 to the second clutch 3 with pressure control, where the required clutch pressure p is plotted against time t, for the second clutch (V2) or first clutch (VI). The second clutch 3 closed when the first clutch 2 is fully or almost fully open. The history V2.2O1 The increase in pressure is lowest with undamaged oil, Δµ / Δν> 0. The history V2.2O2 of the pressure increase at Δµ / Δν = 0 is faster or higher than the curve Δµ / Δν> 0. The curve V2.2O3 the pressure increase of the clutch at Δµ / Δν <0, i.e. with aged oil, is even faster or the maximum pressure applied is even higher. With this course V2.2O3 an oil change is necessary or to be carried out soon.

8th shows that the clutch torque curve M for Δμ / Δν> 0, Δμ / Δν = 0 and Δμ / Δν <0 ( MO1.2 , MO2.2 , MO3.2 ) is the same, since the clutch pressure p with damaged oil is required to achieve this characteristic 7th - is increased until the desired characteristic is reached. If the max. Clutch pressure p would be reached and the characteristic curve for M according to 8th could no longer be achieved, an oil change would in any case be required. The characteristic curve for the rotational acceleration A in the pressure-regulated case also looks analogous to this characteristic curve for M.

9 shows that the course of the speed N on the input shaft with pressure control is also the same for various types of oil damage ( NO1.2 , NO2.2 and NO3.2 ) is. If the characteristic curve could no longer be reached within a predetermined / specified time, an oil change would be necessary.

List of reference symbols

1

Transmission, dual clutch transmission

2

first clutch

3

second clutch

4th

first input shaft

5

second input shaft

6th

fifth gear

7th

sixth gear

8th

Engine output shaft

O1

Oil characteristics Friction coefficient> 0

O2

Oil characteristic coefficient of friction = 0

O3

Oil characteristics Friction coefficient <0

V1.1

Clutch pressure curve for the first clutch

V2.1

Clutch pressure curve for the second clutch

MO1.1

Course of the resulting clutch torque Δµ / Δν> 0

MO2.1

Course of the resulting clutch torque Δµ / Δν = 0

MO3.1

Course of the 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

Rotational acceleration curve Δµ / Δν> 0

AO2.1

Rotational acceleration curve Δµ / Δν = 0

AO3.1

Rotational acceleration curve Δµ / Δν <0

V1.2

Clutch pressure curve for the first clutch

V2.2O1

Clutch pressure curve for second clutch Δµ / Δν> 0

V2.2O2

Clutch pressure curve for second clutch Δµ / Δν = 0

V2.2O3

Clutch pressure curve for the second clutch Δµ / Δν <0

MO1.2

Course of the resulting clutch torque Δµ / Δν> 0

MO2.2

Course of the resulting clutch torque Δµ / Δν = 0

MO3.2

Course of the resulting clutch torque Δµ / Δν <0

NO1.2

Course max. Speed Δµ / Δν> 0

NO2.2

Course max. Speed Δµ / Δν = 0

NO3.2

Course max. Speed Δµ / Δν <0

Claims (7)

A method for determining oil damage to a friction clutch for double clutch transmissions (1) by means of a control unit, the double clutch transmission (1) comprising a first clutch (2) and a second clutch (3), the oil damage being determined 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), the first clutch (2) for frictional connection of a first input shaft (4) with an engine output shaft (8) and the second clutch (3) for non-positive connection of a second input shaft (5) to the motor output shaft (8), characterized in that a bridge circuit is designed for the positive connection of the first input shaft (4) to the second input shaft (5), the pressure-controlled and / or pressure-controlled fading is carried out when the bridge circuit is activated. Method for determining oil damage to a friction clutch according to Claim 1 , characterized in that the defined driving state is present when the dual clutch transmission is load-free, namely when the vehicle is stationary. Method for determining oil damage to a friction clutch according to Claim 1 , characterized in that the oil damage is determined by means of pressure-controlled fading from the first clutch (2) to the second clutch (3), the speed (N) and / or the torque (M) during and / or shortly after the fading and / or the rotational acceleration (A) is measured on the first and / or second input shaft (2, 3) or that the oil damage is determined by means of pressure-controlled fading from the first clutch (2) to the second clutch (3), with during and / or shortly after the transition, the clutch pressure (p) is measured at the first and / or second input shaft (2, 3). Method for determining oil damage to a friction clutch according to at least one of the preceding claims, characterized in that the determination is carried out with the drive train decoupled, shut down, by the following steps: Pressure-controlled superimposing of the pressure of the first clutch (2) to the second clutch (3), - Measuring the speed (N) on 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 curve within a predetermined one Time span, - Determination of the oil damage depending on the comparison result. Method for determining oil damage to a friction clutch according to at least one of the preceding Claims 1 to 3 , characterized in that when the drive train is decoupled and shut down, the determination is made by the following steps: - Pressure-controlled crossover of the first clutch (2) after the second clutch (3), - Detection of the pressure control intervention of the first clutch (2) and / or second clutch ( 3) during the cross-fading, - comparison of the measured value (s) with a specified limit value or course within a specified time span, - determination of the oil damage depending on the comparison result. Method for determining oil damage to a friction clutch according to at least one of the preceding claims, characterized in that a warning is issued about a necessary oil change when or before the predetermined limit value or profile is reached. Transmission device comprising a first clutch (2), a second clutch (3) and a control unit, characterized in that the control unit is designed to implement a method according to one of the Claims 1 to 6th execute.

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