Method for carrying out gear shifting in a twin-clutch gearbox
View Patent ↗The invention relates to a method for carrying out gear shifting in a twin-clutch gearbox comprising at least two gearbox input shafts which are respectively coupled to the engine by means of a clutch. According to the invention, after recognizing a desire to change gear, the clutch associated with the active torque transmitting gearbox input shaft is opened until the slip limit is reached and the engine torque is controlled according to the type of shifting in order to achieve the vehicle acceleration desired by the driver.
1. A method for carrying out gear shifting in a twin-clutch transmission having at least two transmission input shafts, each of which is coupled via a respective clutch to an engine, wherein after recognition of a desire to shift, a first clutch from said respective clutches, assigned to the transmission input shaft that is transmitting the torque, is disengaged up to a slip limit and an engine torque(T eng ) is driven as a function of a type of shifting in order to achieve a vehicle acceleration desired by a driver, wherein a torque (T emotor ) of an electric motor is used as an additional torque.
2. The method as described in claim 1 , wherein an additional torque is used to achieve the vehicle acceleration desired by the driver.
3. The method as described in claim 2 , wherein, in the driving of the torque (T emotor ) of the electric motor, the required vehicle acceleration is determined as a function of specific vehicle and/or transmission variables, so that a target torque of the electric motor is calculated and the calculated target torque of the electric motor is used if the target torque is within predetermined minimum and maximum limit values.
4. The method as described in claim 2 , wherein said respective clutches further comprise a second clutch and wherein, when the torque (T emotor ) of the electric motor is insufficient, the clutch torque of one of said first or second clutches is used to control the vehicle acceleration.
5. The method as described in claim 1 , wherein the type of shifting is determined shortly before the beginning of the shift.
6. The method as described in claim 5 , wherein, when said first clutch is disengaged and when said second clutch is brought into the slipping state by a decrease of the clutch torque of said first clutch, it being decided at the beginning of the slip phase of said second clutch whether the drive train is under pulling load or pushing load in which a check is made of when the slip is positive or negative on said second clutch.
7. The method as described in claim 6 , wherein when there is positive slip on said first clutch that is transmitting torque, if an engine speed (ω eng ) is somewhat larger than a speed of the active transmission input shaft (ω inpshaft ), a pulling load is present, and when there is negative slip, if the engine speed (ω eng ) is somewhat smaller than the speed of the active transmission input shaft (ω inpshaft ), a pushing load is present.
8. The method as described in claim 5 , wherein when the clutch is gripping a check is made of whether the entered engine torque (T eng ) is larger than the dynamic engine torque ({dot over (ω)} eng ·J eng ).
9. The method as described in claim 8 , wherein if the entered engine torque (T eng ) is larger than the dynamic engine torque ({dot over (ω)} eng ·J eng ) the twin-clutch transmission is in pulling mode, the engine being accelerated if the engaged clutch is disengaged, and if the entered engine torque (T eng ) is less than the dynamic engine torque ({dot over (ω)} eng ·J eng ), the twin-clutch transmission is in pushing mode.
10. The method as described in claim 5 , wherein the state is considered in which none of the clutches is in the gripping state.
11. The method as described in claim 10 , wherein the transmitted clutch torque
(
T
clA
/
B
transferred
)
is determined from the minimum value of the particular clutch torque T clA/B that is set and the slip limit of the particular clutch
(
T
clA
/
B
slip
)
.
12. The method as described in claim 10 , wherein in pulling mode the following formula applies:
sign
(
ω
eng
-
i
A
·
ω
vehicle
)
·
i
A
·
T
clA
transferred
+
sign
(
ω
eng
-
i
B
·
ω
vehicle
)
·
i
B
·
T
clB
transferred
≥
0
and in pushing mode the following formula applies:
sign
(
ω
eng
-
i
A
·
ω
vehicle
)
·
i
A
·
T
clA
transferred
+
sign
(
ω
eng
-
i
B
·
ω
vehicle
)
·
i
B
·
T
clB
transferred
<
0
whereby,
ω vehicle =vehicle speed,
i A =overall ratio of the gear of the first input shaft,
i B =overall ratio of the gear of the second input shaft,
T
clA
transferred
=
transmitted
clutch
torque
of
the
first
clutch
and
T
clB
transferred
=
transmitted
clutch
torque
of
the
second
clutch
.
13. The method as described in claim 1 , wherein the slip limit (T clA slip ) of said first or second clutch is determined according to the following formula:
T
clA
slip
=
T
eng
-
J
eng
T
eng
+
T
vehicle
i
A
-
i
B
i
A
-
1
·
T
clB
J
eng
+
J
vehicle
i
A
2
-
sign
(
1
-
i
B
i
A
)
·
T
clB
.
14. The method as described in claim 13 , wherein an external vehicle torque (T vehicle ) of the vehicle is determined for determination of the slip limit
(
T
clA
slip
)
.
15. The method as described in claim 14 , wherein the external vehicle torque (T vehicle ) of the vehicle is determined when said first or second clutch is gripping and slipping according to the following formula:
T
vehicle
=
i
A
·
[
ω
.
eng
(
J
eng
+
J
vehicle
i
A
2
)
-
T
eng
+
i
B
i
A
-
1
·
T
clB
]
.
16. The method as described in claim 14 , wherein the external vehicle torque (T vehicle ) of the vehicle when said first clutch is just starting to slip and when said first clutch is disengaged is determined according to the following formula:
T
vehicle
=
1
i
A
·
J
eng
·
(
J
vehicle
·
T
eng
-
sign
{
ω
eng
-
i
A
·
ω
vehicle
}
·
{
i
A
2
·
J
eng
+
J
vehicle
}
·
T
clA
)
.
17. The method as described in claim 14 , wherein, if neither of said first and second clutches is gripping, the external vehicle torque (T vehicle ) of the vehicle is determined according to the following formula:
T vehicle ={dot over (ω)} vehicle ·J vehicle −sign(ω eng −i A ·ω vehicle )· i A ·T clA −sign(ω eng −i B ·ω vehicle )· i B ·T clB .
18. The method as described in claim 1 , wherein, in an upshift in pulling mode or a pulling upshift, the engine torque (T eng ) is increased in order to develop a slip reserve and keep the motor speed above the speed of the old transmission input shaft that is assigned to the starting gear, said first clutch that is assigned to the starting gear is then disengaged with a constant ramp function and said second clutch assigned to the target gear is engaged with the same ramp function, the engine torque (T eng ) is reduced to a minimum in order to synchronize the engine speed with the speed of the new transmission input shaft that is assigned to the target gear, and the torque (T emotor ) of the electric motor is driven in such a manner that the vehicle acceleration desired by the driver is achieved.
19. The method as described in claim 1 , wherein, in an upshift in pushing mode or a pushing upshift, the engine torque (T eng ) is reduced to a minimum in order to synchronize the engine speed with the speed of the new transmission input shaft, the vehicle acceleration is driven with said first clutch, said first clutch is disengaged with a constant ramp function if the engine speed drops below the speed of the new shaft, said first clutch is disengaged with a constant ramp function if the engine speed drops below the speed of the new shaft, said first clutch is disengaged with a constant ramp function and said second clutch is engaged and the torque (T emotor ) of the electric motor is driven in such a manner that the vehicle acceleration desired by the driver is achieved.
20. The method as described in claim 1 , wherein, in a downshift in pulling mode or a pulling downshift, the engine torque (T eng ) is increased in order to synchronize the engine speed with the speed of the new transmission input shaft, the vehicle acceleration is driven with said first clutch, said first clutch is disengaged with a constant ramp function if the engine speed climbs above the speed of the new shaft, said first clutch is disengaged with constant ramp function and the second clutch is engaged if the engine speed climbs above the speed of the new shaft, and the torque (T emotor ) of the electric motor is driven in such a manner that the vehicle acceleration desired by the driver is achieved.
21. The method as described in claim 1 , wherein, in a downshift in pushing mode or a pushing downshift, the engine torque (T eng ) is reduced to a minimum in order to develop a slip reserve and keep the engine speed under the speed of the old transmission input shaft, said first clutch is disengaged with a constant ramp function and said second clutch is engaged with the same ramp function, the engine torque (T eng ) is increased in order to synchronize the engine speed with the speed of the new transmission input shaft, and the torque (T emotor ) of the electric motor is driven in such a manner that the vehicle acceleration desired by the driver is achieved.