WO2004076225A1

WO2004076225A1 - Method for adapting the characteristic curve of a clutch

Info

Publication number: WO2004076225A1
Application number: PCT/EP2004/001485
Authority: WO
Inventors: Jörg Fähland; Bernd Cappelmann
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2003-02-26
Filing date: 2004-02-17
Publication date: 2004-09-10
Also published as: JP2006519343A; DE10308517A1; DE10308517B4; JP4500800B2

Abstract

The invention relates to a method for adapting the characteristic curve of a clutch of an automatic twin-clutch transmission, particularly in a motor vehicle, during operation of the engine. Said method comprises the following steps: a) a manipulated coupling variable having a defined value is generated on a clutch (K1; K2) associated with a free transmission input shaft (W1; W2); b) waiting until the rotational speed (nfW) of the free transmission input shaft (W1; W2) is identical to the engine speed (nMot); c) a synchronizing device (S1-S4) associated with a gear (G1-G6) of the free transmission input shaft (W1; W2) is actuated, a value of a manipulated synchronization variable increasing in accordance with an increasing synchronizing force; d) the value of the manipulated synchronization variable, at which the rotational speed (nfW) of the free transmission input shaft (W1; W2) diverges from the engine speed (nMot), is determined; e) the determined value of the manipulated synchronization variable is assigned to the defined value of the manipulated coupling variable. A clutch torque corresponding to a synchronizing torque that corresponds to the determined value of the manipulated synchronization variable is assigned to the defined value of the manipulated coupling variable.

Description

Clutch characteristic curve adaptation method

The invention relates to a method for adapting the clutch characteristic of an automated double clutch transmission, in particular a motor vehicle.

A dual clutch transmission typically has a first transmission input shaft associated with a first clutch and gear wheels of one or more odd-numbered gears and a second transmission input shaft associated with a second clutch and gear wheels of one or more even-numbered gears. In a dual clutch transmission designed in this way there is a shifting process, i. H. a change from an active active gear to the next higher or lower gear, the so-called target gear, first in an engagement of the target gear, which z. B. can take place via an associated shift sleeve and a synchronizing device connected to this, and in a subsequent simultaneous disconnection of the clutch assigned to the transmission input shaft of the active gear and closing of the clutch assigned to the transmission input shaft of the target gear. The power transmission takes place alternately via the first or the second transmission input shaft.

In the automated control of such a switching process, relatively precise knowledge of the coefficients of friction of the two clutches is required in order to avoid an interruption of the tractive force and a shift jerk by controlling corresponding clutch partial forces, i. H. to achieve the most comfortable possible transition from the active gear to the target gear.

The friction values of the clutches can change due to wear, temperature changes, contamination and other influences, so that an adaptation of the clutch control to the current friction conditions is desirable, as is known, for example, from DE 197 51 455 A1 in the form of a characteristic curve adaptation. The adaptation of the characteristic curve adapts the relationship between a transmitted torque of the respective clutch and a clutch actuating force assigned to this torque or a control variable linked to the clutch actuating force Friction conditions. With larger torques, it is possible to determine the respectively transmitted torque and thus the coefficient of friction of the clutch in question via operating parameters and characteristic maps of an assigned drive motor. With smaller torques <20 Nm, however, this is not possible or would be associated with greater inaccuracies. However, the area of smaller transmitted torques is particularly important for controlling comfortable starting and shifting processes.

DE 199 31 160 A1 describes a method for adapting the clutch characteristic of an automated double clutch transmission, which is particularly suitable for smaller transmitted torques, first of all generating a defined clutch actuating force for closing a clutch assigned to a free transmission input shaft, then actuating a synchronizing device assigned to a gear of the free transmission input shaft the actuation of the relevant synchronizing device is released at a later point in time, then a speed gradient of the free transmission input shaft is determined, a transmitted torque of the clutch assigned to the free transmission input shaft is determined, and finally the clutch characteristic curve of the clutch assigned to the free transmission input shaft using the values of Clutch actuating force and the associated transmitted torque is adapted. This method requires synchronization, i.e. that the transmitted clutch torque on the free transmission shaft is smaller than the torque transmitted by the synchronizing device. Otherwise the procedure will not work correctly.

The invention is therefore based on the object of designing and developing the known method in such a way that an alternative method for adapting the clutch characteristic of an automated double clutch transmission is implemented, in which in particular the control effort is reduced.

This object, which has been shown above, is now achieved by a method according to the features of patent claim 1. Further advantages and details of the invention emerge from the subclaims.

There are now a number of options for designing and developing the method according to the invention. For this purpose, reference may first be made below to the claims following claim 1. In the following the procedure for coupling lungskaplinie adaption of an automated double clutch transmission explained in more detail using a process variant with the help of the following drawing. In the drawing shows

1 shows the process flow according to the invention in the form of a flow chart,

Fig. 2 temporal profiles of speeds and torques of the free transmission input shaft according to the inventive method in the form of a diagram, and

Fig. 3 shows the structure of a double clutch transmission according to the prior art as a schematic diagram.

A known double clutch transmission G, in which the method according to the invention can be used, is shown schematically in FIG. 3. The dual clutch transmission G has six forward gears G1 to G6 assigned gear pairs and gears of a reverse gear R. On the output side, the respective gear wheels can be rotated and are mounted or connected to a transmission output shaft W3 via switching and synchronizing devices S1 to S4. The switching and synchronizing devices S1, S3 and S4 are designed to be effective on both sides, while the synchronizing device S2 is only effective on one side. On the input side, the respective gear wheels are each permanently connected to one of two transmission input shafts W1 and W2. The odd-numbered gears G1, G3 and G5 and the reverse gear R are assigned to the first transmission input shaft W1, the even-numbered gears G2, G4 and G6 to the second transmission input shaft W2. The two transmission input shafts W1 and W2 are each connected to a separate clutch K1 or K2, via which they can be connected to or separated from the drive motor M. During normal driving operation, one of the gears G1-G6 is shifted and the clutch K1 or K2 connected to the corresponding transmission input shaft W 1 or W2 to which the gear is assigned is closed.

In a shift operation, the target gear that is assigned to the other, open clutch K1 or K2 is shifted. A transition from the active gear to the target gear then takes place by simultaneously opening the clutch of the active gear and closing the clutch of the target gear. The power flow of the transmission runs alternately either via the first clutch K1, the first transmission input shaft W1 and a gear pair assigned to it, or via the second clutch K2, the second transmission input shaft W2 and a gear pair assigned to the transmission output shaft W3. For the method according to the invention, the currently not used free clutch K1 or K2, the corresponding free transmission input shaft W1 or W2 and a synchronizing device S1-S4 are used, which is assigned to a gear G1-G6 of the relevant transmission input shaft W1 or W2.

The variant of the method according to the invention for clutch characteristic curve adaptation of an automated double clutch transmission G shown in FIG. 1 is intended for use in a motor vehicle. The method for coupling characteristic curve adaptation takes place on the free, i.e. H. Coupling K1 or K2 of one of two transmission input shafts W1 or W2 currently not integrated into a power transmission takes place. Before the method is carried out, it is first checked whether the motor vehicle is in a quasi-stationary operating state, i. H. whether there is no acceleration or deceleration phase. If this test turns out to be negative, the program branches to the end of the program without executing program steps, from where, for example, a branch can be branched back to a higher-level control program. If a quasi-stationary operating state is present, a clutch manipulated variable with a defined value is first generated on a clutch (K1; K2) assigned to a free transmission input shaft (W1; W2). The clutch manipulated variable can be, for example, a hydraulic or electrical variable for setting a clutch actuating force FK. This depends on the hydraulically and / or electrically actuated actuators used in each case. The clutch torque MK corresponding to the defined value of the clutch manipulated variable is advantageously in the range from 5 Nm to 20 numbers. The correspondence between the defined value of the clutch manipulated variable and the clutch torque MK is derived from the characteristic curve used so far, which is adapted. The clutch torque MK of the free clutch K1 or K2 has the result that the associated free transmission input shaft W1 or W2 is accelerated to the engine speed nMot of the drive motor M.

Then it is waited until the speed nfW of the free transmission input shaft W1; W2 is equal to the engine speed nMot. In the case of a dry clutch, the clutch torque MK should be selected so that the clutch is at least slightly closed so that the free transmission input shaft W1 or W2 is brought to an engine speed nMot of the drive engine M. In the case of a wet clutch, the drag torques, even with the clutch open, are such that the free transmission input shaft W1 or W2 is driven to the engine speed nMot of the drive engine M. Should there still be a slip, then waits until the speed nfW of the free transmission input shaft W1; W2 is sufficiently constant.

A gear G1-G6 of a synchronizing device S1-S4 to be actuated is determined. The corresponding respective gear can always be the same for each of the two transmission input shafts W1 or W2. However, the next higher or the next lower gear or the synchronization device associated with this gear can also be determined depending on an active gear currently engaged. Now this gear G1-G6 of the free transmission input shaft W1 is actuated; Synchronization device S1-S4 assigned to W2 with an increasing value of a synchronization control variable corresponding to an increasing synchronization force. It is synchronized, so to speak. A shifting of the gear in question, ie engaging this gear, is avoided. With increasing closing of the synchronizing device, an increasing synchronizing torque MSync is also transmitted. As soon as the synchronizing torque MSync exceeds the clutch torque, the speed nfW of the free transmission input shaft W1 is released; W2 depends on the engine speed nMot. The value of the synchronization manipulated variable at which this detachment takes place is determined.

The synchronizing manipulated variable can be, for example, a hydraulic or electrical variable for setting a synchronizing force FSync. A known stored characteristic curve applies to the assignment between the synchronizing manipulated variable or the synchronizing force FSync and a synchronizing torque MSync caused thereby. The synchronization mechanism and therefore this characteristic curve change only very little with time and are therefore suitable for adapting the clutch characteristic curve.

In the next process step, the defined value of the synchronizing manipulated variable is assigned to the defined value of the clutch manipulated variable. This updates a point on the characteristic curve and thus adapts the characteristic curve.

A clutch torque that corresponds to a synchronization torque corresponding to the determined value of the synchronization control variable is preferably assigned to the defined value of the clutch control variable. It goes without saying that a friction or drag torque of the free transmission input shaft and associated co-rotating components can be taken into account in the assignment. The points on the characteristic curve at which an adaptation takes place can be predetermined constantly or can be varied within a predetermined range. This range is advantageously limited by the clutch torque MKo of the open clutch and by a maximum clutch torque MKmax, which should not be exceeded to protect the synchronizer rings.

The method according to the invention is particularly advantageously suitable for determining drag moments of a wet clutch and taking them into account when determining the clutch engagement point. The drag torques are dependent on current operating parameters, such as the viscosity of the gear oil, which in turn depends on the oil temperature. Here, the method according to the invention can be used in such a way that first the drag torque of the open clutch MKo is determined in a first step and then an adaptation takes place in a second step with the clutch slightly closed, which takes the determined drag torque into account. In the second step, a clutch torque MK is set after the previously stored characteristic curve, which is larger by a predetermined differential torque deltaM than the drag torque of the open clutch MKo determined in the first step. The predetermined differential torque deltaM is vzw. only a few Nm, for example 1-3 Nm with a clutch capacity of 400 numbers. With this clutch torque set, the method according to the invention is repeated and the set characteristic point at MK is adapted. In this way, the clutch engagement point of a wet clutch can be monitored depending on the operating state. The first and second process steps run vzw. in quick succession.

With the clutch torque MKo, drag torques, in particular of a wet clutch, can be determined and taken into account. The method according to the invention can be used in such a way that first the drag torque MKo of a wet clutch, ie when the clutch is fully open, is determined and then an adaptation takes place at one or more points of the characteristic curve, which takes the determined drag torque into account.

The method according to the invention is advantageously repeated at a regular time interval or an irregular time interval, for example after a predetermined driving performance of the vehicle. After determining a synchronization torque lying outside an expected synchronization torque range, an adaptation of a clutch engagement point is preferably carried out. For this purpose, the method according to the invention is repeated at other points on the clutch characteristic.

In order to clarify the previously described method, the time profiles of speeds n and torques M over time t are shown in a simplified linearized form in FIG. 2. The continuous horizontal line 10 indicates the course of the engine speed nMot. The broken line 20 indicates the course of the rotational speed nfW of the free transmission input shaft of the automated double clutch transmission G. The dash-dotted line 14 indicates the course of the synchronizing torque Msync generated by the synchronizing device S1-S4 used and the uninterrupted line 16 indicates the course of the synchronous torque generated by the free clutch K1 or K2 transmitted torque MK again.

Since quasi-steady-state operation of the motor vehicle in question is assumed here, the engine speed nMot is constant over time t. The speed nfW of the free transmission input shaft is initially also constant and in this example is at a speed that is between standstill and the engine speed nMot. At time t1, the free clutch K1 or K2 of the automated double clutch transmission G is closed under the action of the clutch actuating force FK in accordance with the defined value of the clutch actuating variable, so that the clutch torque MK on the free transmission input shaft W1 or W2 in the free clutch K1 or K2 is transmitted, which leads to an acceleration of the free transmission input shaft W1 or W2 from the output speed to the engine speed nMot, which is reached at time t2. At time t3, the synchronizing device S1-S4 of a higher gear compared to the engaged active gear is actuated, which leads to the generation of the synchronizing torque MSync acting on the free transmission input shaft W1 or W2. This synchronous torque MSync is ramped up between t3 and t5. At t4, the synchronous torque MSync exceeds the clutch torque MK, and the speed nfW of the free transmission input shaft W1; W2 separates from the engine speed nMot. The value of the synchronization manipulated variable at which this detachment takes place is determined.

As a result, the free clutch K1 or K2 slips and the associated free transmission input shaft W1 or W2 is braked until time t5, at which the actuation of the synchronizing device is released again, and thus a shift of the gear concerned is avoided. Thereupon, the free transmission input shaft W1 or W2 is accelerated again essentially under the effect of the clutch torque MK to the engine speed nMot, which is reached at time t6. At time t7, the free clutch K1 or K2 is separated again and the associated free transmission input shaft W1 or W2 is delayed again under the effect of predominant frictional torques.

The inventive method is vzw. realized with the help of a corresponding control device, not shown here. The corresponding control unit, in particular a corresponding transmission control unit, has the corresponding electrical and / or electronic units here and is connected to the actuators of the synchronizing device and to the motor or the actuator of the clutch via corresponding signal lines. The transmission control unit therefore controls the shift sequences in the double clutch transmission G and the phase of the synchronization of the corresponding gear, the current speeds of the motor shaft or the transmission input being reported to the control unit in turn via signal lines via corresponding provided speed sensors, not shown here. Vzw. the transmission control unit has a microprocessor for processing the data and storing the corresponding, in particular adapted characteristic curve.

As a result, with the method according to the invention, a quick and comfortable adaptation of the clutch characteristic is possible, specifically with components already present in the control system, as a result of which the method is very inexpensive.

B EZ U GSZE I C H E N L I ST E

dn / dt speed gradient

FK clutch actuating force

FSync synchronizing power

G dual clutch transmission

G1 first forward gear

G2 second forward gear,

G3 third forward gear

G4 fourth forward gear

G5 fifth forward gear

G6 sixth forward gear

K1 first clutch

K2 second clutch

M drive motor

M torque

MK (transmitted) clutch torque

MSync synchronous torque n speed nfW speed of the free transmission input welie nMot speed of the drive motor

R reverse gear

51 first synchronization device

52 second synchronization device

53 third synchronizer

54 fourth synchronizing device t time, point in time t1 start of the free clutch t2 first reaching the engine speed of the free transmission input shaft t3 start of actuation of the synchronizing device t4 beginning of tearing off the speed of the free transmission input shaft from the engine speed t5 end of actuation of the synchronizing device t6 second reaching of the motor speed of the free transmission input shaft t7 closing end of the free clutch

W1 first transmission input welie W2 second transmission input and W3 transmission output shaft

Claims

PAT EN TA NSPRÜ CHE

1. Method for adapting the clutch characteristics of an automated double clutch transmission, in particular a motor vehicle, with the engine running, with the method steps:

(a) generating a clutch manipulated variable with a defined value on a clutch (K1; K2) assigned to a free transmission input shaft (W1; W2),

(b) wait until the speed (nfW) of the free transmission input shaft (W1; W2) is equal to the motor speed (nMot),

(c) actuating a synchronizing device (S1-S4) assigned to a gear (G1-G6) of the free transmission input shaft (W1; W2) with an increasing value of a synchronizing manipulated variable corresponding to an increasing synchronizing force,

(d) Determine the value of the synchronization manipulated variable at which the speed (nfW) of the free transmission input shaft (W1; W2) is different from the motor speed! (nMot) takes over,

(e) Assigning the determined value of the synchronization control variable to the defined value of the clutch control variable.

2. The method for clutch characteristic curve adaptation according to claim 1, characterized in that the defined value of the clutch manipulated variable is assigned a clutch torque which corresponds to a synchronized torque corresponding to the determined value of the synchronizing manipulated variable.

3. The method for clutch characteristic adaptation according to claim 1 or 2, characterized in that a first value of the synchronizing manipulated variable is determined for the clutch manipulated variable with a first defined value corresponding to an open clutch, in particular a wet clutch, which is assigned a drag torque of the open clutch.

4. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that a second value of the synchronizing manipulated variable is determined for the clutch manipulated variable with a second defined value corresponding to a slightly closed clutch, which is assigned to the clutch torque of the slightly closed clutch.

5. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that the synchronizing manipulated variable is a control variable for actuating a synchronizing ring.

6. The method for clutch characteristic adaptation according to claim 3, characterized in that the synchronizing manipulated variable is a hydraulic pressure for actuating a synchronizer ring.

7. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that the clutch manipulated variable is a hydraulic pressure for actuating the clutch.

8. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that the clutch characteristic adaptation is carried out in the presence of a quasi-stationary mode of operation of the motor vehicle.

9. The method for coupling characteristic adaptation according to one of the preceding claims, characterized in that the coupling characteristic adaptation is repeated at a regular or irregular time interval.

10. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that the defined value of the clutch manipulated variable is varied when the clutch characteristic curve adaptation is repeated.

11. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that in each case the synchronizing device (S1-S4) assigned to a specific gear (G1-G6) of the free transmission input shaft (W1; W2) is actuated.

12. A method for clutch characteristic adaptation according to one of the preceding claims, characterized in that, based on the currently engaged gear, the synchronizing device (S1-S4) assigned to the next higher or next lower gear of the free transmission input shaft (W1; W2) is actuated.

13. The method for clutch characteristic adaptation according to one of the preceding claims, characterized in that the actuation of the synchronizing device is carried out with a defined synchronizing force (Fsync) which is dimensioned such that a shifting of the gear concerned is avoided.

14. A method for clutch characteristic curve adaptation according to one of the preceding claims, characterized in that an expected clutch torque range ([Me1, Me2]) is defined, which corresponds to an expected synchronization torque range.

T5. Method for clutch characteristic curve adaptation according to claim 14, characterized in that after a synchronization torque lying outside the expected synchronization torque range has been determined, an adaptation of a clutch engagement point is carried out.

16. A method for Kuppiungskennlinienadaption a wet clutch according to any one of the preceding claims, characterized in that in a first process step the process steps (a) to (e) are performed at the clutch open, wherein a first value of the Synchronisierstellgröße is determined ^'that a drag torque of the is assigned to the open clutch, and in a second process step, process steps (a) to (e) are carried out with the clutch closed in a defined manner, a clutch torque being set close to but greater than the determined drag torque of the open clutch.