HYBRID DRIVELINE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a method for shifting in vehicles with a hybrid power- train according to the preamble of claim 1 . The invention also relates to a hybrid powertrain according to the preamble of claim 7 and a vehicle according to the pre- amble of claim 8, comprising such a hybrid powertrain.

A hybrid-driven vehicle is operated by a combustion engine and an electric machine, which interact to deliver the desired output and to, among others, achieve a good fuel economy in the vehicle. The electric machine may also be used to brake the vehicle, wherein the electric machine functions as a generator and thus returns energy to an electric accumulator in the vehicle. The vehicle is also equipped with a gearbox to distribute power from the combustion engine and the electric machine, and to achieve a suitable gear ratio for the vehicle's driving wheels. In automated manual transmissions (AMT) with a single input shaft, shifting is carried out by disconnecting the combustion engine from the input shaft and bringing the gearbox into a substantially zero torque state, disengaging the current gear, synchronising the input shaft and a lay shaft to the next gear, engaging the next gear and subsequently adding a torque on the input shaft by connecting and accelerating the combustion engine and/or accelerating the electric machine. Such a transmission may also comprise a split gear unit between the input shaft and the lay shaft.

When an automated manual transmission is comprised in a hybrid powertrain, the split gear unit is shifted first, synchronising the lay shaft's speed with the input shaft's speed via the split gear unit, so that it corresponds to the next gear ratio, and subsequently, with the help of the electric machine, synchronising the input shaft's and the lay shaft's speed with the speed corresponding to the next gear of a main shaft. Doing this sequentially entails an undesirably long time to complete the shifting, which entails that the vehicle's speed may be reduced unwittingly, which thus requires more energy and an increased fuel consumption to accelerate the vehicle to a desired speed.

Document DE10201 1080849 shows how the shifting time may be shortened by si- multaneously shifting a main gearbox and a range gearbox.

Document DE102009000710 shows a transmission equipped with a braking device and an electric motor to control the shifting. SUMMARY OF THE INVENTION

Despite prior art solutions, there is a need to develop a transmission which is equipped with a split gear unit and main gear unit, which transmission has a brief shifting time.

The objective of the present invention is thus to provide a transmission, which is equipped with a split gear unit and a main gear unit, which transmission has a brief shifting time. This objective is achieved with a method for shifting in a vehicle with a hybrid power- train of the type specified above, which is characterised by the features specified in claim 1 .

By shifting the split gear unit and simultaneously synchronising the input shaft's speed with the speed of the lay shaft and the main shaft, a brief shifting time may be achieved. As an example, the time for shifting between certain gear steps may be shortened by a period of around 0.25 seconds, which corresponds to a reduction in time by approximately 50%. According to one embodiment of the invention, the synchronisation of the lay shaft's speed with, on the one hand, the speed of the input shaft, and, on the other hand, the speed of the main shaft, is initiated at a joint first point in time, with a synchronisation means arranged at the split gear unit. This entails a brief shifting time, since the synchronisation means arranged at the split gear unit may be used to simultaneously impact the synchronisation of the lay shaft's speed with, on the one hand, the speed of the input shaft, and, on the other hand, the speed of the main shaft.

The above objectives are also achieved with a hybrid powertrain of the type specified above, which is characterised by the features specified in claim 7, and by a vehicle of the type specified above, which is characterised by the features specified in claim 8.

Other advantages of the invention are set out in the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which: Fig. 1 shows a schematic side view of a vehicle with a powertrain according to the present invention,

Fig. 2 shows a schematic side view of a powertrain according to the present invention,

Fig. 3 shows a cross section through a schematically displayed gearbox, which is comprised in the powertrain according to the present invention,

Fig. 4 shows a diagram of a sequential shifting in a vehicle with a hybrid powertrain according to the present invention,

Fig. 5 shows a diagram of a shifting in a vehicle with a hybrid powertrain according to the present invention, and Fig. 6 shows a flow chart of a shifting in a vehicle with a hybrid powertrain according to the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 shows a schematic side view of a vehicle 1 , comprising a hybrid powertrain 2 with a combustion engine 3 and an electric machine 4, which are connected to a gearbox 6. The gearbox 6 is also connected to the driving wheels 8 of the vehicle 1 via a propeller shaft 7.

Fig. 2 shows a schematic view of a hybrid powertrain 2, comprising a combustion engine 3 and an electric machine 4, which are connected to an input shaft 10 of the gearbox 6. The combustion engine 3 may be connected to and disconnected from the input shaft 10 via a coupling device 12, which may be manually and/or automatically manoeuvrable. The gearbox 6 is an automated manual transmission (AMT) of a split type and comprises a split gear unit 13 and a main gear unit 15. The split gear unit 13 connects an input shaft 10 with a lay shaft 16. The main gear unit 15 connects the lay shaft 16 with a main shaft 14. On the input shaft 10, the lay shaft 16 and the main shaft 14, one or several transmission elements 20 in the form of cogwheels 21 , 23, 25, 27, 29 and gears 32, 34, 36, 38, 40 are arranged, connecting the respective shafts 10, 16, 14. A first speed sensor 42 is arranged at the input shaft 10 to de- tect the speed of the input shaft 10, a second speed sensor 44 is arranged at the lay shaft 16 to detect the speed of the lay shaft 16 and a third speed sensor 46 is arranged at the main shaft 14 to detect the speed of the main shaft 14. Between the main shaft 14 and an output shaft 18, a retarder 22 is arranged. The output shaft 18 is connected to a final gear 24, which in turn is connected to the driving wheels 8 of the vehicle 1 via a driving shaft 48. An electronic control device 26 is connected to the combustion engine 3, the coupling device 12, the electric machine 4, the gearbox 6 and the speed sensor via electrical conductors 28. Instead of transmitting signals through the electrical conductors 28, signals between the electronic control device 26 and the combustion engine 3, the coupling device 12, the electric machine 4, the gearbox 6, and the speed sensors may be transmitted wirelessly. The electronic control device 26 may comprise a memory M and a computer program P. It is also possible to connect a computer 30 to the control device 26. Fig. 3 shows schematically a gearbox 6, which is comprised in the hybrid powertrain 2 according to the present invention. The gearbox 6 is, as mentioned above, an automated manual transmission of a split type and comprises a split gear unit 13 and a main gear unit 15. The split gear unit 13 comprises cogwheels 21 , 23 which are mounted on the input shaft 10 and gears 32, 34 which are attached on the lay shaft lay shaft 16, which cogwheels 21 , 23 and gears 32, 34 engage with each other and form two gear sets 50, 52 with different gear ratios. These gear ratios are usually referred to as high split and low split. The connection of the cogwheels 21 , 23 on the input shaft 10 is carried out with one or several axially shiftable sleeves 54, 56, which are shifted axially with non-displayed manoeuvring forks. The split gear unit 13 may be designed with or without a neutral state. In the event it is designed without a neutral state, one of the cogwheels 21 , 23 is connected with the input shaft 10 at the same time as the second cogwheel 21 , 23 is disconnected from the input shaft 10. The main gear unit 15 comprises, according to the embodiment displayed, three gear sets 58, 60, 62 which connect the lay shaft 16 with the main shaft 14. Each gear set 58-62 comprises cogwheels 25, 27, 29 which are mounted on the main shaft 14 and gears 36, 38, 40 which are attached on the lay shaft 16, which cogwheels 25-29 and gears 36-40 engage with each other in the respective gear sets 58-62. The gear sets 58-62 have different gear ratios. The connection of the cogwheels 25-29 on the input shaft 10 is carried out with one or several axially shiftable sleeves 64, 66, and 68, which are shifted axially with non-displayed manoeuvring forks. It is possible to set the main gear unit 15 in a neutral state by bringing the shiftable sleeves 64-68 out of engagement with the respective cogwheels 25-29 on the main shaft 14.

The speed sensors 42-46 are, as mentioned above, arranged at the input shaft 10, the lay shaft 16 and the main shaft 14, in order to detect the speed of the respective shafts 10, 16, 14. Between the main shaft 14 and the output shaft 18, a retarder 22 is arranged. However, the retarder 22 may be excluded, so that the main shaft 14 is connected directly with the output shaft 18. It is also possible to connect a range gearbox (not displayed) to the output shaft 18, with the objective of achieving a greater number of gear ratio possibilities in the vehicle 1 . A shifting that involves a change of gears in the gearbox 6 will be described, below, with reference to Figures 2 and 3. The main shaft 14 and the output shaft 18 are in rigid engagement with one another during the shifting operation, which means that the main shaft 14 has a rotation speed determined by the rotation speed of the output shaft 18, and thus by the driving shaft 48 operated by the vehicle 1 (Fig. 2) and the propeller shaft 7 (Fig. 1 ), and the synchronous speed to be achieved to complete the shifting operation is that of the lay shaft 16. First, the main gear unit 15 is brought into a neutral state, the split gear unit 13 is shifted to a new gear, and the electric machine 4 is controlled so that it achieves the speed of the input shaft 10, which has been calculated for the new gear to be selected, whereupon the synchronisation means 70 of the split gear unit 13 is controlled to start the connection of the input shaft with the lay shaft, by initiating the engagement of the newly selected cogwheel 21 or 23 with the input shaft 10. This will result in a deceleration or acceleration of the lay shaft 16, depending on which cogwheel, 21 or 23, is connected. When the speed of the input shaft 10 and the lay shaft 16 have been synchronised with each other, and are connected via the selected gear set 50 or 52, the electric machine 4 is controlled to achieve a synchronous speed between the lay shaft 16 and the main shaft 14, in order to be able to impact the selected sleeve 64-68 in question in the main gear device 15, to initiate the engagement of the respective cogwheels 25-29 with the main shaft 14. When the lay shaft 16 and the main shaft 14 have achieved a synchronous speed, and a substantially zero torque state has arisen between the lay shaft 16 and the main shaft 14, the selected sleeve 64-68 is connected, for connection of the selected cogwheel 64-68 with the main shaft 14. The lay shaft 16 is thus connected with both the main shaft 14 and the input shaft 10, which entails that a torque may be added to the powertrain 2 via the electric machine 4 and/or the combustion engine 3, by way of connection of the combustion engine 3 through the coupling device 12. The synchronisation means 70 of the split gear device 13 may consist of conventional synchronisation rings (not displayed). The above described shifting process thus takes place sequentially, and may also be described with the diagram in Fig. 4. The top graph in Fig. 4 shows how an up-shift occurs from high split to low split in the split gear unit 13 and how, subsequently, a down-shift is carried out in the main shift device 15 in a sequence. At the point in time t1 , the synchronisation of the speed of the lay shaft 16 with the speed of the input shaft 10 is initiated. The speed of the lay shaft 16 is represented by the solid curve CJOS in the top graph in Fig. 4. The lay shaft 16 will, with the help of the synchronisation means 70 at the input shaft 10, be braked to a speed corresponding to that of the input shaft 10, having regard to the gear ratio via the split gear device 13. In the event the gear ratio through the split gear device 13 should be 1 :1 , the lay shaft 16 would achieve the same speed as the speed of the input shaft 10. Since there is a gear ratio in the split gear device 13, the lay shaft 6 will be braked to the speed of the input shaft 10, converted to the gear ratio through the gear set 50, 52, which is connected to the split gear device 13. Thus, the meaning of the expression synchronisa- tion of the speed of the shafts 10, 14, 16 with each other will always comprise a conversion to the gear ratio between them. This converted engine speed is represented by the line ω in the top graph, and represents the speed of the input shaft 10 converted into the speed of the lay shaft 16 with the gear ratio in the split gear device 13, regarding the gear that is to be engaged in the split gear unit 13. The dashed line represents the speed of the input shaft 10, converted into the gear ratio which existed before the change of gears in the split gear unit 13. At the point in time t2, the lay shaft 16 has achieved a synchronous speed with the speed of the input shaft 10 ωίη, so that the synchronisation of the speed of the lay shaft 16 is carried out during the time period T1 . Subsequently, the synchronisation of the speed ooS of the lay shaft 16 in relation to the speed of the main shaft 14 is initiated, having regard to the gear ratio through the main gear device 15. Such speed is represented by the dashed line ωΗ in the top graph. The speed ooS of the lay shaft 16 is accelerated with the electric machine 4 and reaches the main shaft's 14 converted speed ωΗ at the point in time t3, so that the cogwheel 25-29 for the selected gear is connected with the main shaft 14 via a coupling sleeve 64-68. Thus, the synchronisation of the speed of the lay shaft 16 with the converted speed of the main shaft 14 has been completed during the time period T2. The total time for the shifting process thus becomes the total time T1 and T2. Similar shifting processes may be described for a reverse shifting in the gearbox 6 via the bottom diagram in Fig. 4.

Preferably, a shifting operation is carried out according to the inventive method, when both the input shaft 10 and the lay shaft 16 will be accelerated simultaneously or de- celerated simultaneously during the synchronisation process. Thus, the total time T1 and T2 may be considerably reduced, since the synchronisation of the speed of the lay shaft 16 with the speed of the input shaft 10 is initiated at the same time as the speed of the lay shaft 10 is synchronised with the speed of the main shaft 14. Such a shifting operation is displayed in Fig. 5.

At the point in time t1 , the synchronisation of the speed of the lay shaft 16 with the speed of the input shaft 10 is initiated. The speed of the lay shaft 16 is represented by the solid curve ooS in the top graph in Fig. 5. The lay shaft 16 will, with the help of the synchronisation means 70 at the input shaft 10, be accelerated to a speed corresponding to that of the of the input shaft 10, having regard to the gear ratio via the split gear device 13. Since there is a gear ratio in the split gear device 13, the lay shaft 16 will be accelerated to the speed of the input shaft 10, converted to the gear ratio through the gear set 50, 52, which is connected to the split gear device 13. This converted engine speed is represented by the line ω in the top graph, and represents the speed of the input shaft 10 converted into the speed of the lay shaft 16, with the gear ratio in the split gear device 13 for the gear that is to be engaged in the split gear unit 13. The dashed line represents the speed of the input shaft 10 converted into the gear ratio which existed before the change of gears in the split gear unit 13. At the point in time t2, the lay shaft 16 has achieved a synchronous speed with the speed ωίη of the input shaft 10, so that the synchronisation of the speed of the lay shaft 16 is carried out during the time period T1 . At the point in time t1 , the synchronisation of the speed ooS of the lay shaft 16 in relation to the speed of the main shaft 16 is initiated, having regard to the gear ratio through the main gear device 15. Such speed is represented by the dashed line ωΗ in the top graph. The speed ooS of the lay shaft 16 is thus accelerated with the synchronisation device 70 for the split gear unit 13, also to initiate the synchronisation of the speed of the lay shaft 16 with the converted speed of the main shaft 14. At the point in time t2, the input shaft 10 and the lay shaft 16 operate synchronously, entailing that the input shaft 10 and the lay shaft 16 are connected via one of the gear sets 50, 52 on the input shaft 10 and the lay shaft 16 at the point in time t2. Thus the lay shaft 16 is accelerated with the electric machine 4 via the input shaft 10, so that the lay shaft 16 achieves a synchronous speed ooS with the converted speed ωΗ of the main shaft 14 at the point in time t3, whereupon the cogwheel 25-29 for the selected gear is connected with the main shaft 14 via a coupling sleeve 64-68. Thus, the synchronisation of the speed ooS of the lay shaft 16 with the converted speed ωίη of the input shaft 10 and the converted speed ωΗ of the main shaft 14 has been completed during the time period T2. The total time for the shifting process thus becomes the time T2.

Similar shifting processes may be described for an up-shift in the gearbox 6 with the bottom diagram in Fig. 5.

In the context, it should be mentioned that if a shifting operation will be carried out and if the lay shaft 16 will be accelerated or decelerated in the opposite direction in relation to the acceleration or deceleration of the input shaft 10, the shifting process described in connection with Fig. 5 will not be possible, since the synchronisation device 70 in the split gear unit 13 will not be able to handle such a synchronisation without a risk of defective synchronisation, with a resulting scraping sound. Instead, this requires the sequential shifting process described in connection with Fig. 4.

Fig. 6 shows a flow chart of the method for shifting in a vehicle 1 with a hybrid power- train 2 according to the present invention. The method comprises the following steps: a) to bring the main gear unit 15 into a substantially zero torque state;

b) in the event the input shaft 10 and the lay shaft 16 must both be accelerated or decelerated: to initiate synchronisation of the speed of the lay shaft 16 with, on the one hand, the speed of the input shaft 10, and, on the other hand, the speed of the main shaft 14, at a joint point in time t1 ;

c) to engage the gear in the split gear unit 13 when the speed of the lay shaft 16 speed has been synchronised with the speed of the input shaft 10 at a second point in time t2, and

d) to engage the gear in the main gear unit 15 when the speed of the lay shaft 16 has been synchronised with the speed of the main shaft 14 at a third point in time t3. Preferably, the speed of the respective shafts 10, 14, 16 is detected with a first speed sensor 42 arranged at the input shaft 10, a second speed sensor 44 arranged at the lay shaft 16 and/or a third speed sensor 46 arranged at the main shaft 14. Since the gear ratio depending on the gear engaged is known, it is possible to calculate the speed of one of the shafts 10, 14, 16, based on knowledge of the speed of two of the shafts 10, 14, 16. Thus, it would be possible to equip only two of the shafts 10, 14, 16 with speed sensors.

Preferably, the synchronisation in step b) is carried out with a synchronisation means 70 arranged at the split gear unit 13.

Preferably, the speed of the lay shaft 16 and the speed of the main shaft 14 are syn- chronised between the steps c) and d), by accelerating or decelerating the electric machine 4 between the second point in time t2 and the third point in time t3.

The method also comprises the additional step, before step a):

e) of disconnecting the combustion engine 3 from the input shaft 10 via a coupling device 12.

Preferably, the synchronisation and the shifting are controlled via an electronic control device 26.

According to the invention, a computer program P is provided, which may comprise procedures for shifting in a vehicle 1 with a hybrid powertrain 2 according to the present invention. The computer program P may comprise procedures for shifting in a vehicle 1 with a hybrid powertrain 2 according to the method steps specified above.

The program P may be stored in an executable manner, or in a compressed manner, in a memory M and/or a read/write memory R.

The invention also relates to a computer program product, comprising program code stored in a medium readable by a computer 30, to perform the method steps specified above, when said program code is executed in the electronic control device 26, or another computer 30 connected to the control device 26. The components and features specified above may, within the framework of the invention, be combined between different embodiments specified.