Method for Departing from a Recuperation Phase in a Parallel Hybrid Vehicle

Abstract

A method for exiting from a recuperation phase in a parallel hybrid vehicle includes, in a first step, the vehicle is in a recuperation phase, started by means of a trigger, with a predefined recuperation driving demand, and, in a second step, the electric machine is brought to an increased rotational speed during the recuperation phase. In a third step, a phase for departing from the recuperation phase is started by means of a trigger, wherein, in this phase, the internal combustion engine is made available for coupling to the electric machine, such that a target rotational speed determined between the internal combustion engine to be connected and the electric machine for the connection to the transmission input is set, and in parallel, by means of an upshift, a highest possible gear ratio for the connection to the drivetrain is set, in order to satisfy a present driving demand. In a fourth step, the departure from the recuperation phase is completed.

Claims

1. A method for exiting a recuperation phase in a parallel hybrid vehicle, comprising an internal combustion engine and an electric machine which can be coupled thereto via a clutch with interaction with a device for shock isolation, comprising at least one flywheel mass and one second clutch, which electric machine can be connected to a transmission which is connected to a drive train, wherein the internal combustion engine can be completely decoupled from the electric machine using the clutch, wherein the method comprises: in a first step the vehicle is in a recuperation phase, started by a trigger, with a predefined recuperation driving request, in a second step, the electric machine is brought to an increased rotational speed during the recuperation phase, in a third step, a phase for exiting the recuperation phase is started by a trigger, wherein in the phase for exiting the recuperation phase, the internal combustion engine is made available for coupling to the electric machine in that the second clutch is opened, and when the latter is open, the clutch is closed, with the result that the start of the internal combustion engine is carried out as a pulse start in such a way that a target rotational speed which is determined between an internal combustion engine which is to be connected and a flywheel mass for connecting to the transmission input is set, and in parallel a maximum possible gearspeed for connecting to the drive train is set by means of a gearspeed upshift, in order to satisfy a present driving request, and in a fourth step, the second clutch is closed in a controlled fashion, with the result that the exit from the recuperation phase is completed.

2. A method for exiting a recuperation phase in a parallel hybrid vehicle comprising an internal combustion engine and an electric machine which can be coupled thereto via a clutch and which can be connected to a transmission which is connected to a drive train, wherein the internal combustion engine can be completely decoupled from the electric machine using the clutch, wherein the method comprises: in a first step, the vehicle is in a recuperation phase, started by a trigger, with a predefined recuperation driving request, in a second step, the electric machine is brought to an increased rotational speed during the recuperation phase, in a third step a phase for exiting the recuperation phase is started by a trigger, wherein in the phase for existing the recuperation phase, the internal combustion engine is made available for coupling to the electric machine, controlled closing of the clutch and application of positive torque in the electric machine takes place, with the result that the start of the internal combustion engine is carried out as a supported pulse start in such a way that a target rotational speed which is determined between the internal combustion engine to be connected and the electric machine is set for connecting to the transmission input, and in parallel a maximum possible gearspeed for connecting to the drive train is set by means of a gearspeed upshift, in order to satisfy a driving request, and in a fourth step, the clutch is closed completely, with the result that the exit from the recuperation phase is completed.

3. The method as claimed in claim 2, wherein in the third step, in the phase for exiting the recuperation phase, the controlled closing of the clutch is carried out by placing the clutch in a slipping state.

4. The method as claimed in claim 2, wherein in the fourth step, in the case of the driving request of an overrun upshift, the method comprises closing the clutch with a coupling rotational speed between the internal combustion engine and the electric machine below the target rotational speed of the new gearspeed, and in the case of the driving request of a traction request with a coupling rotational speed between the internal combustion engine and electric machine above the target rotational speed of the new gearspeed said clutch is closed.

5. The method as claimed in claim 3, wherein in the fourth step, in the case of the driving request of an overrun upshift, the method comprises closing the clutch with a coupling rotational speed between the internal combustion engine and the electric machine below the target rotational speed of the new gearspeed, and in the case of the driving request of a traction request with a coupling rotational speed between the internal combustion engine and electric machine above the target rotational speed of the new gearspeed said clutch is closed.

6. The method as claimed in claim 2, wherein in the third step, for the assisted pulse start the kinetic energy from the pulse of the electric machine in conjunction with involved transmission components and the available torque of the electric machine are used.

7. The method as claimed in claim 3, wherein in the third step, for the assisted pulse start the kinetic energy from the pulse of the electric machine in conjunction with involved transmission components and the available torque of the electric machine are used.

8. The method as claimed in claim 4, wherein in the third step, for the assisted pulse start the kinetic energy from the pulse of the electric machine in conjunction with involved transmission components and the available torque of the electric machine are used.

9. The method as claimed in claim 1, wherein at the entry into the recuperation phase, the method comprises adjusting the gearspeed by one or more gearspeed downshifts to a gearspeed below the gearspeed which was at least intended for the re coupling of the internal combustion engine.

10. The method as claimed in claim 2, wherein at the entry into the recuperation phase, the method comprises adjusting the gearspeed by one or more gearspeed downshifts to a gearspeed below the gearspeed which was at least intended for the re coupling of the internal combustion engine.

11. The method as claimed in claim 3, wherein at the entry into the recuperation phase, the method comprises adjusting the gearspeed by one or more gearspeed downshifts to a gearspeed below the gearspeed which was at least intended for the re coupling of the internal combustion engine.

12. The method as claimed in claim 1, wherein the trigger for entering the recuperation phase is activation of the brake pedal, and in order to exit the recuperation phase the trigger is a reduction in or termination of the activation of the brake pedal, activation of accelerator pedal or an undershooting of a speed threshold.

13. The method as claimed in claim 2, wherein the trigger for entering the recuperation phase is activation of the brake pedal, and in order to exit the recuperation phase the trigger is a reduction in or termination of the activation of the brake pedal, activation of accelerator pedal or an undershooting of a speed threshold.

14. The method as claimed in claim 3, wherein the trigger for entering the recuperation phase is activation of the brake pedal, and in order to exit the recuperation phase the trigger is a reduction in or termination of the activation of the brake pedal, activation of accelerator pedal or an undershooting of a speed threshold.

15. The method as claimed in claim 1, wherein during the recuperation phase, the method comprises adjusting the gearspeed such that the at least necessary kinetic energy of the electric machine is kept available in order to implement the pulse start request.

16. The method as claimed in claim 2, wherein during the recuperation phase, the method comprises adjusting the gearspeed such that the at least necessary kinetic energy of the electric machine is kept available in order to implement the pulse start request.

17. The method as claimed in claim 3, wherein during the recuperation phase, the method comprises adjusting the gearspeed such that the at least necessary kinetic energy of the electric machine is kept available in order to implement the pulse start request.

18. A parallel hybrid vehicle comprising: an internal combustion engine and an electric machine which can be coupled thereto via a clutch and which is connected to a transmission which is connected to a drive train, wherein the internal combustion engine can be completely decoupled from the electric machine using the clutch, at least one sensing device, control device and execution device respectively configured to sense a trigger for entering and exiting a recuperation phase, and transmitting, receiving and processing signals, wherein the vehicle is configured such that: in a first step, the vehicle is in a recuperation phase, started by a trigger, with a predefined recuperation driving request, in a second step, the electric machine is brought to an increased rotational speed during the recuperation phase, in a third step a phase for exiting the recuperation phase is started by a trigger, wherein in the phase for existing the recuperation phase, the internal combustion engine is made available for coupling to the electric machine, controlled closing of the clutch and application of positive torque in the electric machine takes place, with the result that the start of the internal combustion engine is carried out as a supported pulse start in such a way that a target rotational speed which is determined between the internal combustion engine to be connected and the electric machine is set for connecting to the transmission input, and in parallel a maximum possible gearspeed for connecting to the drive train is set by means of a gearspeed upshift, in order to satisfy a driving request, and in a fourth step, the clutch is closed completely, with the result that the exit from the recuperation phase is completed.

19. A parallel hybrid vehicle comprising an internal combustion engine and an electric machine which can be coupled thereto via a clutch with interaction with a device for shock isolation, comprising at least one flywheel mass and one second clutch, which electric machine is connected to a transmission which is connected to a drive train, wherein the internal combustion engine can be completely decoupled from the electric machine using the clutch with interaction with the device for shock isolation, at least one sensing device, control device and execution device respectively configured to sense a trigger for entering and exiting a recuperation phase, and transmitting, receiving and processing signals, wherein the vehicle is configured such that: in a first step the vehicle is in a recuperation phase, started by the sensed trigger, with a predefined recuperation driving request, in a second step, the electric machine is brought to an increased rotational speed during the recuperation phase, in a third step, a phase for exiting the recuperation phase is started by a trigger, wherein in the phase for exiting the recuperation phase, the internal combustion engine is made available for coupling to the electric machine in that the second clutch is opened, and when the latter is open, the clutch is closed, with the result that the start of the internal combustion engine is carried out as a pulse start in such a way that a target rotational speed which is determined between an internal combustion engine which is to be connected and a flywheel mass for connecting to the transmission input is set, and in parallel a maximum possible gearspeed for connecting to the drive train is set by means of a gearspeed upshift, in order to satisfy a present driving request, and in a fourth step, the second clutch is closed in a controlled fashion, with the result that the exit from the recuperation phase is completed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a typical topology of a parallel hybrid arrangement according to the prior art.

[0026] FIG. 2 shows a further typical topology of a parallel hybrid arrangement according to the prior art.

[0027] FIG. 3 shows a flow diagram of the method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028] FIGS. 1 and 2 show a typical topology of a parallel hybrid arrangement according to the prior art. The illustration comprises a typical topology of a transmission 3, which can be shifted in a automated fashion in a plurality of gearspeeds, in a motor vehicle, preferably of a hybrid vehicle, having a conventional internal combustion engine (VM) 1 in combination with an electric machine (EM) 2 in a P2 arrangement (FIG. 1) and/or with a momentum start module (FIG. 2), that is to say a parallel hybrid arrangement. The electric machine EM2 can be coupled to the internal combustion engine VM1 or decoupled therefrom by means of the clutch K0 on the basis of a predefined operating strategy. The electric machine EM2 is connected to the transmission 3 which can be shifted in an automated fashion in a plurality of gearspeeds and which can be a planetary gear mechanism, double clutch transmission a CVT (continuously variable transmission) or some other type of transmission which can be shifted in an automated fashion in a plurality of gearspeeds. The transmission 3 is in turn connected to the drive train 4 for driving one or more wheels 5 of the hybrid vehicle.

[0029] As described above, in known methods the exiting from a recuperation phase is normally triggered by means of the accelerator pedal, i.e. the internal combustion engine VM1 is first switched on when the accelerator pedal is operated, i.e. there is an active running up of the internal combustion engine VM1. This gives rise to a delay in the availability of the engine torque and therefore in the response to the driver's request. Furthermore, this method is not optimal for low-voltage on-board power systems, e.g. on-board power systems based on e.g. 48V, since a very large amount of electrical energy is required for coupling the internal combustion engine VM1. This does not constitute a problem in high voltage systems, since they have sufficient power to implement the driver's request acceleration. However, it is disadvantageous that high voltage systems take up a very large amount of space and are heavy. Therefore, a different strategy has to be found for future applications in the low voltage range.

[0030] As is shown in FIG. 1, it is possible to provide just one clutch K0 for decoupling and coupling the internal combustion engine VM1 to the electric machine EM2, which can be referred to as a P2 hybrid. In FIG. 2, an extension of the P2 system to form a momentum start apparatus, i.e. a system with flywheel storage apparatus and flywheel mass is shown. This system has, in addition to the clutch K0 which always has to be directly arranged on the internal combustion engine VM1 since this clutch K0 serves for coupling or decoupling the internal combustion engine VM1, a device for shock isolation K1 and 6 which is formed as a momentum start apparatus. This device for shock isolation has at least one flywheel mass 6 and a second clutch K1, wherein the flywheel mass is arranged between the clutch K0 and the second clutch K1. The second clutch K1 serves to couple the electric machine EM2 to the internal combustion engine VM1 via the flywheel mass 6 with virtually complete shock decoupling. It is therefore an intermediate step for coupling the electric machine EM2 to the internal combustion engine VM1 in comparison with the P2 system which ensures an improvement of the coupling, to be more precise a reduction in the shock during coupling. Therefore, the coupling becomes even more comfortable for the driver, since the jolt during coupling is eliminated.

[0031] FIG. 3 shows a flow diagram of the method according to both embodiments of the present invention. The objective of the proposed method is to shorten significantly the time period without sufficient implementation of the load request of the driver and without high consumption of electrical energy, as described above, and therefore to permit or improve the use of a P2 system or of a momentum start apparatus, that is to say of a parallel hybrid system, on a low voltage basis, that is to say e.g. on a 48 V basis. By means of the proposed method it is possible to comply with the driver's wish more quickly, and the consumption of electrical energy for propelling the vehicle can be limited.

[0032] In order to implement the method, in a first step S1 the trigger for deactivating or shutting down and starting the internal combustion engine VM1 is made a pedal position, e.g. the position of the brake pedal or else of the accelerator pedal or a speed threshold (for the exiting from the recuperation phase) which is undershot. The entry into the recuperation phase is initiated e.g. by depressing the brake pedal. In this context, the clutch K0 between the internal combustion engine VM1 and the electric machine EM2 is opened, and the internal combustion engine VM1 is shut down, i.e. switched off.

[0033] At the same time, in a second step S2, a plurality of gearspeed downshifts are carried out in the transmission 3. The gearspeed downshifts are carried out in such a way that the electric machine EM2 which is connected to the transmission input shaft is brought to a high rotational speed and therefore placed in the state of high kinetic energy. For this purpose, shifting back is preferably carried out by more gearspeeds than would be necessary for the braking operation. As a result, improved recuperation can be achieved, i.e. more energy is available at the end of the recuperation phase, in order e.g. to couple the internal combustion engine VM1. In a further step, the rotational speed difference from which at any time an engine start of the internal combustion engine VM1 can take place according to the known pulse start method by closing the clutch K0 will now be considered. During the recuperation phase, adjustment of the gearspeeds in the transmission 3, adapted to the deceleration of the vehicle, takes place in order to maintain the state of high kinetic energy in electric machine EM2. That is to say e.g. shifting down of the gearspeeds takes place in order to optimize the recuperation further.

[0034] The exiting from the recuperation phase is triggered in a third step S3 by releasing the brake pedal or undershooting a speed threshold or activating the accelerator pedal, also simultaneously with the brake pedal. This can be detected e.g. by a correspondingly present sensor system and be passed on for processing to e.g. a control unit. After the sensing of the start of the recuperation phase, the internal combustion engine VM1 is coupled to the electric machine EM2 again depending on which parallel hybrid system is used, that is to say P2 or momentum start apparatus. In the case of the P2 system shown in FIG. 1, i.e. the clutch is placed in the slipping state by controlled closing of the clutch K0, and the start of the internal combustion engine VM1 is carried out as a supported pulse start by applying positive torque in the electric machine EM2. The objective here is to carry out the pulse start in such a way that the rotational speed which is set between the connected internal combustion engine VM1 and the electric machine EM2 is set above the rotational speed for connecting to the output. The objective is therefore that a target rotational speed which is determined between the internal combustion engine VM1 to be connected and the electric machine EM2 for connecting to the transmission input is set, and in parallel a maximum possible gearspeed for connecting to the drive train 4 is set by means of a gearspeed upshift, in order to satisfy a driving request which is present.

[0035] In the case of the momentum start apparatus which is shown in FIG. 2, the second clutch K1 is opened, with the result that in an intermediate step the electric machine EM 2 is disconnected from the flywheel mass 6, but it is still decoupled from the internal combustion engine VM1 by means of the clutch K0. If the second clutch K1 is open, controlled closing of the clutch K0 takes place, with the result that the start of the internal combustion engine is carried out as a pulse start, a target rotational speed which is determined between the internal combustion engine VM1 to be connected and the flywheel mass 6 for connecting to the transmission input is set, and in parallel a maximum possible gearspeed for connecting to the drive train 4 is set by means of a gearspeed upshift, in order to satisfy a driving request which is present.

[0036] In parallel with the supported pulse start, the transmission 3 therefore carries out in both cases shifting up of the gearspeeds, preferably to a gearspeed above the gearspeed which is required to couple the internal combustion engine VM1. Therefore, at least the proportional implementation of the driver's wish is achieved by means of the friction shifting torques, wherein the objective is that the maximum possible gearspeed for connecting to the driver train 4 is reached above the idling rotational speed, i.e. the transmission input rotational speed is kept as low as possible.

[0037] Subsequently, in a fourth step S4, the complete frictional engagement between the internal combustion engine VM1, the electric machine EM2 and the output by closing the drive train, i.e. the clutch K0 in the P2 system or the second clutch K1 in the momentum start apparatus, is represented, and the recuperation phase is therefore ended.

[0038] In one example, the entering and the exiting of the recuperation phase are triggered by activating the brake pedal. As a result, the internal combustion engine VM1 is decoupled from the electric machine EM2 and therefore from the transmission 3, that is to say switched off, i.e. it does not supply any torque, by opening the clutch K0.

[0039] The kinetic energy of the electric machine EM2 is already raised at the start of the recuperation phase by shifting down the gearspeeds below the required gearspeed for the requested target rotational speed for recoupling the internal combustion engine VM1. During the recuperation phase, further adjustment takes place, that is to say e.g. shifting down, of the gearspeeds, where necessary, in order to keep the kinetic energy in the electrical machine EM2 as high as possible.

[0040] The exiting of the recuperation phase takes place in turn by means of a trigger, in this example by releasing the brake pedal. During the release of the brake pedal, in the P2 system the clutch K0 is placed in a slipping state in a controlled fashion and/or the second clutch K1 is first opened in the momentum start apparatus, and the clutch K0 is then closed, with the result that the internal combustion engine VM1 and electric machine EM2 are disconnected from one another. Then, a target rotational speed or connection rotational speed or coupling rotational speed is determined on the basis of the sensed driving request, and shifting up of the gearspeeds takes place to a gearspeed which is higher than the gearspeed which is required for the coupling, i.e. for the requested rotational speed, in order to correspond to the driver's wish. The determination of the requested rotational speed is carried out by means of known methods.

[0041] Driving requests, which can occur when the exiting of the recuperation phase is triggered, can be an overrun upshift or a traction upshift. In an overrun upshift, that is to say when the brake pedal is released without a request that acceleration is to take place, that is to say, e.g. by non-activation of the accelerator pedal, in the P2 system the clutch K0 is closed with a coupling rotational speed below the target rotational speed of the new gearspeed. In the case of a traction upshift, that is to say in the case of an acceleration request, e.g. as a result of activation of the accelerator pedal, in the P2 system the clutch K0 is closed with a coupling rotational speed above the target rotational speed of the new gearspeed. In the case of the momentum start apparatus, the controlled closing of the clutch, here of the second clutch K1, has to take place first in the fourth step S4, since the clutch K0 has already been completely closed in the third step S3.

[0042] For the supported pulse start in order to exit the recuperation phase in the P2 system, the mechanical energy and the kinetic energy (corresponding to the rotational speed difference before and after the shifting up of the gearspeeds) from the pulse of the electric machine EM2 in conjunction with the corresponding transmission component such as the transmission input shaft and the rotating wheelsets etc. and the available torque of the electric machine EM2 are used to start the internal combustion engine VM1. The internal combustion engine VM1 supplies here a negative torque by revving up or tow starting by means of the clutch K0 which closes in a controlled fashion. Therefore, a supported pulse start takes place during an upshift into a gearspeed which is the highest one possible, in order to permit at least largely jolt-free coupling.

[0043] The momentum start apparatus can be used to permit completely jolt-free coupling. In this case, the flywheel mass 6 acts as it were as a buffer system between the internal combustion engine VM1 and the electric machine EM2. The coupling therefore does not take place directly via the clutch K0 and the internal combustion engine VM1 but rather via the intermediate step that the internal combustion engine VM1 is connected to the flywheel mass 6 via the clutch K0, and only then does the coupling to the electric machine EM2 take place, with the result that the vibrations of the internal combustion engine VM1 are already damped. For this purpose, a known irregular rotation system, that is to say an irregular rotation damper or a torque superimposition apparatus can be used as the flywheel mass 6. By using a flywheel mass 6, the pulse at the start of the internal combustion engine VM1 can be taken from the system, with the result that jolt-free coupling can take place. In addition, other systems, even systems which are not completely mechanical, can also be used as the flywheel mass.

[0044] By means of the proposed method it is possible to achieve more rapid connection of the internal combustion engine VM1 to the output for rapid implementation of driver's wishes at the accelerator pedal, since the internal combustion engine VM1 is already made available when the brake pedal is released, and not only when a request for acceleration is made. At the same time, it is possible to raise the recuperation potentials which arise when the drag torque of the coupled internal combustion engine VM1 does not have to be overcome in braking recuperation phases.

[0045] An additional advantage is that even in the P2 system less torque disruption occurs at the transmission output as a result of the slipping transmission in the case of the clutch K0 which closes in parallel with the upshift, with the result that the starting of the internal combustion engine VM1 takes place in a significantly more comfortable way for the driver and less loading acts on the mechanical components. In the case of the momentum start apparatus, the jolt is completely eliminated, and this therefore constitutes an improvement with respect to the P2 system.

[0046] Although the method is designed for starting the internal combustion engine VM1 during a braking phase, i.e. when the vehicle is traveling, it can also be used for starting from a stationary state. This applies analogously to the sequence described above.

[0047] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.