Control method for carrying out a gear shift in a transmission provided with a clutch gearbox
Control method to carry out a gear shift in a manual automatic transmission provided with a gearbox having at least one clutch and in a road vehicle having an internal combustion engine and at least one reversible electric machine. The control method involves the steps of: receiving a gear shift command; opening and closing the clutch to allow the drive gear to be changed from the current gear to the following gear; determining a torque objective to be generated by the electric machine; controlling the electric machine to pursue the torque objective; and adding, only and exclusively during the gear shift, to the torque objective an additional torque profile which is impulsive and temporary and temporarily modifies the development of the torque objective.
1. A control method to carry out a gear shift in a transmission ( 6 ) provided with a dual-clutch gearbox ( 7 ) and in a road vehicle ( 1 ) comprising an internal combustion engine ( 4 ) and at least one reversible electric machine ( 11 ); the dual-clutch gearbox ( 7 ) has two primary shafts ( 12 ), at least one secondary shaft ( 14 ) connected to drive wheels ( 3 ), and two clutches ( 13 ), each of which is interposed between a drive shaft ( 5 ) of the engine ( 4 ) and a corresponding primary shaft ( 12 ); the control method comprises the steps of:
receiving a gear-shift command from a current gear (A) to a following gear (B);
opening a first clutch ( 13 A) associated with the current gear (A) and simultaneously closing a second clutch ( 13 B) associated with the following gear (B);
controlling, only and exclusively during the gear shift, the electric machine ( 11 ) to generate an additional torque profile (T add ) which is impulsive and comprises a start segment (W) having a first sign and an end segment (X), which immediately follows the start segment (W) and has a second sign, which is contrary to the first sign;
wherein if the gear shift is up the start segment (W) entails for an always positive torque and the final segment (X) entails an always negative torque, and if the gear shift is down the start segment (W) entails an always negative torque and the end segment (X) entails an always positive torque.
2. The control method according to claim 1 , wherein each segment (W, X) entails a torque increase, in absolute value, from zero to a maximum value (T addMAX , T addmin ) and a following torque decrease from the maximum value (T addMAX , T addmin ) to zero.
3. The control method according to claim 1 , wherein each segment (W, X) comprises at least one linear variation over time and at least one exponential variation over time.
4. The control method according to claim 1 , wherein if the gear shift is up:
the start segment (W) entails an exponential torque increase from zero to a maximum positive value (T addMAX ) immediately followed by a linear torque decrease from the maximum positive value (T addMAX ) to zero; and
the end segment (X) entails a linear torque decrease from zero to a minimum negative value (T addmin ) immediately followed by an exponential increase from the minimum negative value (T addmin ) to zero.
5. The control method according to claim 4 , wherein the linear torque decreases from zero to the minimum negative value (T addmin ) entails a greater start slope followed by a smaller end slope.
6. The control method according to claim 4 , wherein the maximum value (T addMAX ) is, in absolute value, greater than the minimum value (T addmin ).
7. The control method according to claim 1 , wherein if the gear shift is down:
the start segment (W) entails an exponential torque decrease from zero to a minimum negative value (T addmin ) immediately followed by a linear torque increase from the minimum negative value (T addmin ) to zero; and
the end segment (X) entails a torque increase from zero to a maximum positive value (T addMAX ) immediately followed by an exponential decrease from the maximum positive value (T addMAX ) to zero.
8. The control method according to claim 7 , wherein the linear torque increase from zero to the maximum positive value (T addMAX ) entails a linear increase immediately followed by an exponential increase.
9. The control method according to claim 7 , wherein the maximum value (T addMAX ) is, in absolute value, smaller than the minimum value (T addmin ).
10. The control method according to claim 1 , wherein the torque objective (T M ) is positive, when an accelerator pedal ( 7 ) is at least partially pressed, and is negative, when the accelerator pedal ( 7 ) is released.
11. The control method according to claim 1 and comprising the steps of:
opening the first clutch ( 13 A) associated with the current gear (A) and closing the second clutch ( 13 B) associated with the following gear (B) in a same first instant (t 1 ); and
completing the opening of the first clutch ( 13 A) associated with the current gear (A) and completing the closing of the second clutch ( 13 B) associated with the following gear (B) in a same second instant (t 2 ) following the first instant (t 1 ).
12. The control method according to claim 11 and comprising the steps of:
generating a gear-shift command at a third instant (t 0 ) prior to the first instant (t 1 ); and
starting the additional torque profile (T add ) at the third instant (t 0 ).
13. The control method according to claim 12 , wherein a maximum, in absolute value, of the additional torque profile (T add ) during the start segment (W) is reached between the third instant (t 0 ) and the first instant (t 1 ).
14. The control method according to claim 11 , and comprising the steps of:
keeping the rotation speed (ω E ) of the drive shaft ( 5 ) constant and equal to a start value (ω A ) set by the gear ratio of the current gear (A) until the second instant (T 2 ), wherein the opening of the first clutch ( 13 A) is completed;
varying progressively after the second instant (t 2 ) the rotation speed (ω E ) of the engine shaft ( 5 ) from the initial value (ω A ) imposed by the gear ratio of the current gear (A) to a final value (ω B ) imposed by the gear ratio of the following gear (B) until a fourth instant (t 3 ) following the second instant (t 2 ) at which the synchronisation of the speed (ω E ) of rotation of the engine shaft ( 5 ) is completed; and
terminating the additional torque profile (T add ) at the fourth instant (t 3 ).
15. The control method according to claim 11 , wherein the start segment (W) ends, and then the end segment (X) starts between the first instant (t 1 ) and the second instant (t 2 ).
16. The control method according to claim 11 , wherein a maximum, in absolute value, of the additional torque profile (T add ) during the end segment (X) is reached at the second instant (t 2 ).
17. The control method according to claim 1 and comprising the steps of:
determining a torque objective (T M ) to be generated by the electric machine ( 11 ) irrespective of the gear shift;
controlling the electric machine ( 11 ) so as to pursue the torque objective (T M ); and
adding, only and exclusively during the gear shift, to the torque objective (T M ), the additional torque profile (T add ), which is impulsive and temporarily changes the development of the torque objective (T M ).