ACCELERATION METHOD FOR A HYBRID DRIVETRAIN

Abstract

An acceleration method for a hybrid drivetrain includes providing the hybrid drivetrain, setting an initial torque transmission ratio of a belt-drive transmission to a lower transmission ratio, and opening a first disconnect clutch to interrupt torque transmission between an internal combustion engine and an electric machine. The method also includes receiving an acceleration command, shifting the torque transmission ratio with a transmission adjustment gradient from the lower transmission ratio towards an upper transmission ratio, increasing a rotor speed of a rotor shaft of the electric machine with a rotor shaft adjustment gradient, and engaging a first disconnect clutch to rotate an ICE shaft to start the internal combustion engine and increase a rotational speed of the ICE shaft towards a current rotor speed.

Claims

1.-10. (canceled)

11. An acceleration method for a hybrid drivetrain, comprising: providing the hybrid drivetrain comprising: a belt-drive transmission comprising: a transmission input shaft; a transmission output shaft; and a belt for transmitting a torque between the transmission input shaft and the transmission output shaft with a torque transmission ratio that is variable between a lower transmission ratio and an upper transmission ratio, greater than the lower transmission ratio; an internal combustion engine comprising an ICE shaft for outputting an engine torque to the transmission input shaft; an electric machine comprising a rotor shaft for outputting an electric machine torque to the transmission input shaft; and a first disconnect clutch arranged in a first torque path between the electric machine and the internal combustion engine; setting an initial torque transmission ratio of the belt-drive transmission to the lower transmission ratio; opening the first disconnect clutch to interrupt torque transmission between the internal combustion engine and the electric machine; receiving an acceleration command; shifting the torque transmission, ratio with a transmission adjustment gradient from the lower transmission ratio towards the upper transmission ratio; increasing a rotor speed of the rotor shaft with a rotor shaft adjustment gradient; and engaging the first disconnect clutch to rotate the ICE shaft to start the internal combustion engine and increase a rotational speed of the ICE shaft towards a current rotor speed.

12. The acceleration method of claim 11 wherein: the hybrid drivetrain further comprises a second disconnect clutch arranged in a second torque path between the electric machine and the belt-drive transmission; and the method further comprises actuating the second disconnect clutch in accordance with the torque.

13. The acceleration method of claim 11 wherein: the hybrid drivetrain further comprises an adaptive system pressure source; the belt-drive transmission and the first disconnect clutch are hydraulically fed from the adaptive system pressure source; and the method further comprises keeping a hydraulic system power sensed by the hybrid drivetrain as a product of a current system pressure and a current hydraulic volume flow of the adaptive system pressure source below a predetermined maximum power limit value.

14. The acceleration method of claim 13 wherein the step of shifting the lower transmission ratio with an adjustment gradient towards the upper transmission ratio and increasing a rotor speed of the rotor shaft is executed until the hydraulic system power reaches the predetermined maximum power limit value.

15. The acceleration method of claim 13 wherein: the step of shifting the lower transmission ratio with an adjustment gradient towards the upper transmission ratio and increasing a rotor speed of the rotor shaft is executed in two sub-steps; a first sub-step includes adjusting the adjustment gradient for a maximum hydraulic flow; and a second sub-step includes adjusting the adjustment gradient for increased electric machine torque for increasing a system pressure of the adaptive system pressure source.

16. The acceleration method of claim 13 wherein, the step of engaging the first disconnect clutch to rotate the ICE shaft to start the internal combustion engine and increasing the rotational speed of the ICE shaft towards the current rotor speed further comprises: shifting the torque transmission ratio towards the upper transmission ratio; increasing the rotor speed; and reducing the transmission adjustment gradient or the rotor shaft adjustment gradient.

17. The acceleration method of claim 13 wherein: the hybrid drivetrain further comprises: a first pump with an electric drive unit; and a second pump driven by the internal combustion engine; the first pump provides the hydraulic system power during the step of shifting the lower transmission ratio with a transmission adjustment gradient towards the upper transmission ratio and increasing a rotor speed of the rotor shaft with a rotor shaft adjustment gradient; and the first pump and the second pump provide the hydraulic system power during the step of engaging the first disconnect clutch to rotate the ICE shaft to start the internal combustion engine and increasing the rotational speed of the ICE shaft towards the current rotor speed.

18. The acceleration method of claim 11 wherein the acceleration method is immediately aborted if the acceleration command is aborted.

19. The acceleration method of claim 11 wherein the torque transmission ratio is shifted towards the lower transmission ratio if the acceleration command is aborted.

20. The acceleration method of claim 11 wherein the first disconnect clutch is engaged and rotational energy of the ICE shaft is transmitted to the belt-drive transmission if the acceleration command is aborted during the step of engaging the first disconnect clutch to rotate the ICE shaft to start the internal combustion engine and increasing the rotational speed of the ICE shaft towards the current rotor speed.

21. The hybrid drivetrain of claim 11 configured to execute the method of claim 11.

22. The hybrid drivetrain of claim 21 further comprising a second disconnect clutch arranged in a second torque path between the electric machine and the belt-drive transmission.

23. A hybrid vehicle comprising: a drive wheel; and the hybrid drivetrain of claim 21 arranged to transmit the torque to the drive wheel.

24. The hybrid vehicle of claim 23 wherein: the hybrid drivetrain further comprises a second disconnect clutch comprising a first partial clutch and a second partial clutch; the first partial clutch is arranged in a second torque path between the electric machine and the transmission input shaft; and the second partial clutch is arranged in a third torque path directly connecting the electric machine to the drive wheel.

25. The hybrid vehicle of claim 23 further comprising a third disconnect clutch arranged in a fourth torque path between the transmission output shaft and the drive wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present disclosure is explained in detail below based on the technical background with reference to the associated drawings, which show example embodiments. The disclosure is in no way restricted by the purely schematic drawings, and it should be noted that the drawings are not dimensionally accurate and are not suitable for defining proportions. In the figures:

[0067] FIG. 1 shows a speed diagram;

[0068] FIG. 2 shows a torque transmission diagram;

[0069] FIG. 3 shows an adjustment gradient diagram;

[0070] FIG. 4 shows a rotational speed diagram;

[0071] FIG. 5 shows a system pressure diagram;

[0072] FIG. 6 shows a volume flow diagram;

[0073] FIG. 7 shows a hydraulic performance diagram; and

[0074] FIG. 8 shows a hybrid drivetrain of the P2/P3 category in a hybrid vehicle.

DETAILED DESCRIPTION

[0075] FIG. 1 shows a speed diagram with a speed axis 28 as the y axis and a time axis 29 as the x axis, for example of a hybrid vehicle 22 as in FIG. 8, which is referred to here without limitation of generality for the explanation of the participating components of the hybrid drivetrain 1. The letters represent steps a. to c. or sub-steps thereof. This also applies in the following to FIGS. 2 to 7. With the speed profile 30 shown, for example, in the operating state before the acceleration command has been received (in step a.), there is a constant speed, for example approximately 50 km/h. This represents a partial load operation or overrun operation. At a point in time 0, here at the vertical line below the letter a., an acceleration command is output (step a.), for example by means of a tip-in a gas pedal in a hybrid vehicle 22. Thereupon in step b., here (optionally) comprising the sub-steps b0.1 and b0.2, the speed of the rotor shaft 10 (see rotor speed curve 37 in FIG. 4) is increased and the torque transmission ratio is raised from a lower transmission ratio 5 to the upper half (see FIG. 2). This is followed by an acceleration of the hybrid vehicle 22, which is brought about purely by the electric machine 9. This continues in step c., here (optionally) comprising sub-steps c0.1 and c0.2, wherein the internal combustion engine 7 is started in parallel here (see combustion engine speed curve 38 in FIG. 4). It should be noted that the acceleration command from step a. via steps b. and c. is maintained, for example by holding down a gas pedal. This is indicated by the arrow pointing to the right. The acceleration is also continued, for example, according to this acceleration method, wherein the internal combustion engine 7 then takes over or assists the electric machine 9. The acceleration method is aborted, for example, when the acceleration command is canceled, i.e., for example, the gas pedal is no longer depressed or is depressed too little. For example, the entire acceleration method takes 1.3 seconds [thirteen tenths of a second]. Sub-step b0.1 takes, for example, 0.2 seconds, sub-step b0.2 takes, for example, 0.5 seconds, sub-step c0.1 takes, for example, 0.1 seconds, and sub-step c0.2 takes, for example, 0.5 seconds.

[0076] FIG. 2 shows a torque transmission diagram of a belt-drive transmission 2, which relates to the speed diagram in FIG. 1 and the associated description. The y axis is the transmission ratio axis 31 and the x axis is again the time axis 29. Below the time axis 29 the lower half 32 is shown, and above the time axis 29 the upper half 33 of the (e.g., entire) adjustable torque transmission ratio of the belt-drive transmission 2 is shown. In the example shown, the lower transmission ratio 5 set in the initial operating state (before time 0) is the minimum transmission ratio of the belt-drive transmission 2, for example. Regardless of this, in the example shown, the upper transmission ratio 6 set in the final operating state (after step c.) is the maximum transmission ratio, e.g., of the belt-drive transmission 2. In this example, the gear ratio curve 34 runs almost continuously increasing from the start of sub-step b0.1 to the end of sub-step c0.2 from the lower transmission ratio 5 to the upper transmission ratio 6 (and here optionally increased even further after the acceleration method). Between the sub-steps b0.1 and b0.2, (any) one intermediate transmission ratio 19 is identified, which is in the lower half. In the case of a symmetrical belt-drive transmission 2, the lower half 32 is to be referred to as overdrive and the upper half 33 as underdrive, wherein a torque is reduced in overdrive, i.e., the torque transmission ratio is less than 1 and a torque is transmitted in underdrive, i.e., the torque transmission ratio is greater than 1. For example, the minimum transmission ratio 5 is 0.5 [half] and the maximum transmission ratio 6 is 2 [two].

[0077] FIG. 3 shows an adjustment gradient diagram of a torque transmission ratio of a belt-drive transmission 2, which relates to the speed diagram in FIG. 1 and the torque transmission diagram in FIG. 2, as well as the associated description. The speed of the change in the gear ratio of the belt-drive transmission 2 is thus shown. The y axis is accordingly the adjustment gradient axis 35 (speed of the change in the transmission ratio) and the x axis is again the time axis 29, wherein the time axis 29 runs through the adjustment gradient 12 from zero here. After the initial operating state (before time 0), there is no change in the torque transmission ratio of the belt-drive transmission 2 in question and, from time 0, there is an exclusively positive change in the torque transmission ratio. This is particularly advantageous for rapid acceleration (with sufficient electrical torque reserve) but not a requirement for the acceleration method proposed here. First, the torque transmission ratio is quickly increased in a sub-step b0.1 because here the system pressure 16 is still low (see FIG. 5) and thus, despite a high hydraulic volume flow 17 necessary for a rapid change of the torque transmission ratio (see FIG. 6), an acceptable or permissible system power 15 (see FIG. 7) can still be maintained below a predetermined maximum power limit value 18. In sub-step b0.2, the change in the torque transmission ratio is now advanced further (see FIG. 2), but not with an increasing adjustment gradient 12, here, for example, with an adjustment gradient 12 greater than zero, which is constant after a short decrease.

[0078] In sub-step c0.1, the adjustment gradient 12 (based on the marked intermediate transmission ratio 19 achieved, here optionally in the lower half 32) is increased quickly while the first disconnect clutch 11 is engaged (see FIGS. 4 and 6) and the system pressure 16 must be increased further (see FIG. 5). With the system pressure 16 now present after sub-step c0.1, it is advantageous to reduce the change in the displacement gradient 12 again in step c0.2, but, for example, to raise the displacement gradient 12 further for fast acceleration. The system power 15 remains below the maximum power limit value 18 (see FIG. 7). After step c., the upper, e.g., maximum, transmission ratio 6 is reached. According to technical and/or performance-related parameters, the adjustment gradient 12 is then brought back to zero. In one embodiment, the adjustment gradient 12 is briefly below zero, i.e., theoretically the change in the torque transmission ratio is reduced again, but this serves the purpose of a transfer to the upper transmission ratio 6 quickly and then an adaptation of the adjustment to continuous operation in this set transmission ratio 6, for which a lower contact pressure is necessary than to adjust the torque transmission ratio.

[0079] FIG. 4 shows a rotational speed diagram of an electric machine 9 and an internal combustion engine 7, which relates to the preceding diagrams in FIGS. 1 to 3 and the associated description. The y axis is the rotational speed axis 36 and the x axis is again the time axis 29, wherein the time axis 29 runs through the rotational speed of zero here. The initially upper curve represents the rotor speed curve 37, for example at the currently usual 1,600 rpm, and the initially lower curve shows the combustion engine speed curve 38. In step b., the rotor speed is increased in response to step a., and this continues in step c., and for example also thereafter if the acceleration command continues to be present. Only in sub-step c0.1, the first disconnect clutch 11 is engaged and thus the internal combustion engine 7 is started by the electric machine 9 and brought to an operating speed, in this example at the start of step c0.2. After step c0.1, the first disconnect clutch is engaged for full torque transmission. It should be pointed out that the internal combustion engine 7 has already changed from a torque sink to a torque source from the start of sub-step c0.2, i.e., when the operating speed is reached, currently usually 800 rpm. After step c. the hybrid vehicle 22 in question can be additionally or exclusively accelerated by means of the internal combustion engine 7. The sub-step c0.1 is carried out at a point in time of the acceleration method, while the electric machine 9 has such a sufficient torque reserve that the electric machine 9 is able to accelerate the hybrid vehicle 22 in question and to start the internal combustion engine 7 at the same time. An additional (separate) starter is not necessary here.

[0080] FIG. 5 shows a system pressure diagram of a system pressure source 14 of a hybrid drivetrain 1, which relates to the preceding diagrams in FIGS. 1 to 4 and the associated description. The y axis is the system pressure axis 39 and the x axis is again the time axis 29. Initially, the system pressure 16 is at a low level, constant in this example. In steps b. and c., in response to the acceleration command of step a., the system pressure 16 is raised adaptively, i.e., adjusted to the current demand. The aim here is to continuously increase the system pressure 16, taking into account the efficiency and/or the performance.

[0081] FIG. 6 shows a volume flow diagram of a system pressure source 14 of a hybrid drivetrain 1 (see FIG. 8), which relates to the preceding diagrams in FIGS. 1 to 5 and the associated description. The y axis is the volume flow axis 40 and the x axis is again the time axis 29. Initially, the hydraulic volume flow 17 is at a low level, constant in this example. In step b0.1, the acceleration command in step a. towards the hydraulic volume flow 17 is increased (e.g., quickly) until at least approximately the predetermined maximum power limit value 18 (see FIG. 7) is reached at the current system pressure 16 (see FIG. 5). For example, the power falls below the predetermined maximum power limit value 18, taking into account the maximum possible, maximum efficient and/or maximum noise emitting adjustment speed of the torque transmission ratio of the belt-drive transmission 2 in question. Subsequently, in sub-step b0.2, the hydraulic volume flow 17 is reduced so that the predetermined maximum power limit value 18 is not exceeded until the end of sub-step b0.2 despite the increasing system pressure 16 (see FIG. 5). During the transition to sub-step c0.1, the hydraulic volume flow 17 is briefly and greatly reduced because an increased system pressure 16 is briefly necessary here to engage the first disconnect clutch 11 (see increase in FIG. 5). Subsequently, the hydraulic volume flow 17 is increased again and, taking into account further parameters, it is therefore reduced overall when the system pressure 16 rises below the predetermined maximum power limit value 18.

[0082] FIG. 7 shows a hydraulic performance diagram of a system pressure source 14 of a hybrid drivetrain 1 (see FIG. 8), which relates to the preceding diagrams in FIGS. 1 to 6 and the associated description and represents the product of the current system pressure 16 and the current hydraulic volume flow 17. This value is approximately proportional to an electrical power consumption, provided that or as long as the system pressure source 14 is provided solely by an electric pump 20 (from step c., the mechanical pump 21 may be added as a support). Alternatively, the system power 15 shown here is the total system power 15 without taking into account the provision, i.e., also including the power decrease at the ICE shaft 8. The y axis is the power axis 41 and the x axis is again the time axis 29. Initially, the system power 15 is at a low level, in this example constant. In step b0.1, the acceleration command in step a. towards the system power 15 as a result of the increase in the hydraulic volume flow 17 and the system pressure 16 (see FIGS. 5 and 6), at least approximately the predetermined maximum power limit value 18 is reached. For example, such a maximum power limit value 18 corresponds to 400 W [four hundred watts]. Until the end of the acceleration method, and if the acceleration command persists, the system power 15 is kept engaged to the predetermined maximum output limit value 18. On the one hand, the hydraulic volume flow 17 and the system pressure 16 are coordinated with one another for fast acceleration, primarily a change in the torque transmission ratio on the belt-drive transmission 2 in question, and on the other hand, other parameters such as efficiency, noise emissions and acceleration reserve, for example in a conventional manner, are taken into account.

[0083] FIG. 8 shows a hybrid drivetrain 1 of the P2/P3 category in a hybrid vehicle 22 in an (optional) front-cross arrangement for driving by means of the front axle 42, optionally also or solely by means of the rear axle 43, via a left drive wheel 23 and a right drive wheel 24 shown in a schematic view from above. The hybrid drivetrain 1 is in front of the driver's cab 44 and the shafts of the components shown are arranged transversely to the longitudinal axis 45, i.e., parallel to the front axle 42 and rear axle 43. The hybrid drivetrain 1 shown includes as torque sources (e.g., also operable as torque sinks) an internal combustion engine 7 with an ICE shaft 8 and an electric machine 9 with a rotor shaft 10 (here the arrow points to the rotor for clarity). The internal combustion engine 7 and the electric drive machine 9 are connected by means of a belt-drive transmission 2 via a load connection 46 and a differential 47 to transmit torque to the drive wheels 23, 24. The belt-drive transmission 2 has a transmission input shaft 3 with an input-side conical pulley pair 48 and a transmission output shaft 4 with an output-side conical pulley pair 49, wherein the two conical pulley pairs 48,49 are connected to one another in a torque-transmitting manner by means of a belt drive 50.

[0084] Here (optionally) a further partial powertrain 51 is provided in parallel, which is designed as a fixed spur gear and by means of which the internal combustion engine 7 and the electric machine 9 are also connected to the drive wheels 23, 24 via the consumer connection 46 and the differential 47 in a torque-transmitting manner. The connection is separable solely to the internal combustion engine 7 by means of a first disconnect clutch 11 (commonly referred to as a K0 clutch or K1 clutch). Furthermore, the connection to the internal combustion engine 7 and the electric machine 9 is made by means of a second disconnect clutch 13 (generally referred to as K2 clutch) is separable from the drive wheels 23, 24, or can be switched between a transmission by means of the belt-drive transmission 2 or by means of the parallel partial powertrain 51. The machines 7, 9 can be disconnected from the transmission input shaft 3 of the belt-drive transmission 2 by means of a first partial clutch 26 of the second disconnect clutch 13 and disconnected from the parallel partial powertrain 51 by means of a second partial clutch 27 of the second disconnect clutch 13.

[0085] Optionally, a third disconnect clutch 25 is also provided behind the transmission output shaft 4 of the belt-drive transmission 2, which is designed as a claw clutch, for example, so that the transmission output shaft 4 can be disconnected from the consumer connection 46. In a drive state of the hybrid vehicle 22 in which the parallel partial powertrain 51 is used, the belt-drive transmission 2 is not dragged along when the first partial clutch 26 of the second disconnect clutch 13 is disengaged and the third disconnect clutch 25 is disengaged. This increases the efficiency of this drive state. Furthermore, it is shown here that the belt-drive transmission 2 or the conical pulley pairs 48, 49 are supplied by a system pressure source 14, wherein an electric pump 20 and a mechanical pump 21 are (optionally) provided connected in parallel here. The electric pump 20 is in operation at least when the internal combustion engine 7 is switched off and the mechanical pump 21 may be inseparably connected to the ICE shaft 8.

[0086] Optionally, a further electric machine is also provided (not shown), for example on the input side of the belt-drive transmission 2, for example without an interposed disconnect clutch, and/or in a separate drivetrain, for example on the rear axle 43 or on the front axle 42 in engagement with the differential 47 or with the consumer connection 46.

[0087] The acceleration method proposed here allows rapid acceleration of a hybrid drivetrain with the efficient use of the powertrain without high power consumption.

REFERENCE NUMERALS

[0088] 1 Hybrid drivetrain [0089] 2 Belt-drive transmission [0090] 3 Transmission input shaft [0091] 4 Transmission output shaft [0092] 5 Lower transmission ratio [0093] 6 Upper transmission ratio [0094] 7 Internal combustion engine [0095] 8 ICE shaft [0096] 9 Electric machine [0097] 10 Rotor shaft [0098] 11 K0 clutch [0099] 12 Adjustment gradient [0100] 13 K2 clutch [0101] 14 System pressure source [0102] 15 System power [0103] 16 System pressure [0104] 17 Hydraulic volume flow [0105] 18 Maximum power limit value [0106] 19 Intermediate transmission ratio [0107] 20 Electric pump [0108] 21 Mechanical pump [0109] 22 Hybrid vehicle [0110] 23 Left drive wheel [0111] 24 Right drive wheel [0112] 25 Claw clutch [0113] 26 First partial clutch [0114] 27 Second partial clutch [0115] 28 Speed axis [0116] 29 Time axis [0117] 30 Speed curve [0118] 31 Transmission ratio axis [0119] 32 Lower half (overdrive) [0120] 33 Upper half (underdrive) [0121] 34 Transmission ratio curve [0122] 35 Adjustment gradient axis [0123] 36 Rotational speed axis [0124] 37 Rotor speed curve [0125] 38 Combustion engine speed curve [0126] 39 System pressure axis [0127] 40 Volume flow axis [0128] 41 Power axis [0129] 42 Front axle [0130] 43 Rear axle [0131] 44 Driver's cab [0132] 45 Longitudinal axis [0133] 46 Consumer connection [0134] 47 Differential [0135] 48 Input-side cone pulley pair [0136] 49 Output-side cone pulley pair [0137] 50 Belt drive [0138] 51 Partial powertrain