FI ELD OF THE I NVENTION AND P RIOR ART

The present invention relates to a method for the control of a ve ^¬ hicle according to the preamble to claim 1 .

The invention is particularly, but not exclusively, focused on the performance of such a method in motor vehicles in the form of wheeled commercial vehicles, especially heavy goods vehicles, such as trucks and buses.

The invention thus relates to a method carried out in a hybrid ve- hide, which, generally, is a vehicle that may be powered by a primary engine, e.g. a combustion engine , and a secondary engine, such as at least one electrical machine. The vehicle is suitably, but for the purposes of the present invention not necessari ly, equipped with means for storage of electric energy, such as a battery or a capacitor for storage of electric energy, and control equipment to control the flow of electric energy between the means and the electrical machine. The electrical machine(s) may in such a case alternately operate as an engine or as a generator, depending on the vehicle's operating mode. When the ve- hide decelerates, the electrical machine generates energy that may be stored, and the stored electric energy is used later for e.g. operation of the vehicle .

Using a conventional clutch mechanism , which disconnects the gearbox's input shaft from the combustion engine during a shift- ing process in the gearbox, entails disadvantages, such as heating of the clutch mechanism's discs, which results in an increased fuel consumption and wear of the clutch discs. There are also large losses as a result, in particular when the vehicle is started. A conventional clutch mechanism is also relatively heavy and costly. It also occupies a relatively large space in the vehicle. Friction losses also arise at the use of a hydraulic converter/torque converter commonly used in automatic transmission . By ensuring that the vehicle has a drive system in which the output shaft of the combustion engine, the rotor of the electrical machine and the input shaft of the gearbox are connected with a planetary gear, the conventional clutch mechanism and the disadvantages associated therewith may be avoided. A vehicle with a drive system of this type constitutes prior art, as set out in E P 1 31 9 546 and SE 536 329.

Certainly, a range of advantageous methods to control a vehicle with a drive system of the type described in SE 538 329 constitute prior art, however there is naturally a constant endeavour to improve the manner of controlling such vehicles, especially in certain specific operating situations.

SUMMARY OF TH E I NVENTION The objective of the present invention is to show a method of the type defined above, which is in line with the above-mentioned endeavour. This objective is achieved according to the invention by providing a method according to the enclosed clai m 1 . Having a drive system in a vehicle with a second electrical machine opens up a possibility for an i mproved behaviour in a range of operational situations, compared to prior art drive systems lacking such a design of the drive system. Such an operational situation includes driving the vehicle purely electrically, i .e. with the combustion engine turned off, and when there is a desire to start the combustion engine in order to use it for the vehicle's propulsion. In such case, first, the first locking means is set in the release position , and subsequently, throughout the progress of the method , the first electrical machine is controlled to achieve the requested torque for transmission to the output shaft of the planetary gear. The second electrical machine is controlled towards and until a standstill , and when this has been achieved , the second locking means are moved to the locked position , whereupon the rotational speed of the second electrical machine is controlled towards the combustion engine's idling speed, and fuel is then injected into the combustion engine which therefore starts. Accordingly, the combustion engine may be started, without the powertrain downstream of the planetary gear's output shaft having to be interrupted, i .e. in case of there being a gearbox the gear must be disengaged, while maintaining forward momentum. Such an approach entails that the driver of the vehicle, a cruise control or other torque controlling function of the vehicle, during the performance of the method , is free to deter- mine and change the torque transmitted to the vehicle's power- train , via the planetary gear's output shaft.

According to one embodiment of the invention , the method comprises a step g) , carried out after step f) , of control of electric power to/from said electric energy storage means, and/or electri- cal auxiliary aggregates in the vehicle and/or loads through control of the second electrical machine. Such electric auxiliary aggregates and loads, such as a servo control device, may accordingly both consume and produce electric power.

According to another embodiment of the invention, said control of electric output occurs in step g) , in such a way that power balance is achieved, wherein free selection, within the limitations generally specified for the drive system , of charge current to or discharge current from said electric energy storage means and/or electric auxiliary aggregates and/or loads occurs in accordance with prevailing operational situation in the vehicle. The term power balance means that it is possible, within the general li mitations specified for the drive system, to freely select the charge current to, or the discharge current from the energy storage means and/or the electric auxiliary unit and/or loads in the vehicle at existing operating modes, which is naturally very advantageous at the control of the requested torque out from the planetary gear, since this may be selected in the manner being most advantageous in each specific case.

According to another embodi ment of the invention, where needed, the maintenance of power balance is temporarily waived while step g) is implemented . This may be because the combus- tion engine is not able to build up torque quickly enough to meet the output requirement, or because the latter is greater than what the combustion engine is able to provide. The abandonment of the objective of maintaining power balance entails that the electric energy storage means must deliver a current to the first elec- trical machine, and/or the electric auxiliary unit, and/or loads in the vehicle, which is usually possible, if not desirable.

According to another embodiment of the invention, the method is implemented in a vehicle with a said drive system, wherein the planetary gear's sun wheel is said first component, and the ring gear is said third component. By connecting the first electrical machine's rotor with the ring gear and the combustion engine's output shaft with the sun wheel , a compact construction is achieved, which is easy to fit into already existing spaces for powertrains (drive systems) with clutch mechanisms instead of planetary gears.

According to another embodiment of the invention, the method is implemented in a vehicle with a gearbox having an input shaft, which is connected with said second output shaft in the planetary gear. Via the inventive method , the combustion engine may be started without any torque interruption, and with a potential for the driver of the vehicle to maintain or change the torque trans- mitted to the vehicle's powertrain.

The invention also relates to a computer program with the features listed in claim 7, a computer program product with the features listed in claim 8, and an electronic control device with the features listed in claim 9.

Other advantageous features and advantages with the invention are set out in the description below. BRI E F DESCRI PTION OF TH E DRAWI NGS Below are descriptions of an example embodiment of the invention with reference to the enclosed drawings, in which : Fig. 1 is a very simplified view of a powertrain in a vehicle that may be equipped with a drive system for the performance of a method according to the invention,

Fig. 2 is a more detailed, but still simplified view of

said drive system,

Fig . 3 is a si mplified view, illustrating the general structure of a drive system in a vehicle, for which a method according to one embodiment of the invention is carried out,

Fig. 4 is a flow chart showing a method according to one embodiment of the invention, and

Fig. 5 is a fundamental diagram of an electronic control device for implementation of one or several methods according to the invention.

DETAI LED DESC RI PTION OF AN EMBODI M ENT ACCORDI NG TO TH E I NVENTION

Fig. 1 shows a powertrain for a heavy goods vehicle 1 . The powertrain comprises a combustion engine 2, a power transmission 3 in the form of for example a speed gearbox, a continuously variable transmission (CVT) , or a direct transmission, a number of driving shafts 4 and driving wheels 5. Between the combustion engine 2 and the gearbox 3 the power-train comprises an intermediate section 6, Fig. 2 shows a part of the components in the intermediate section 8 in more detail , more specifically those which also occur in prior art drive systems, such as the one ac~ cording to SE 536 329. The combustion engine 2 is equipped with an output shaft 2a and the gearbox 3 with an input shaft 3a in the intermediate section 6. The output shaft 2a of the combustion engine is coaxially arranged in relation to the input shaft 3a of the gearbox. The combustion engine's output shaft 2a and the input shaft 3a of the gearbox are rotatably arranged around a common rotational axis 7. The intermediate section 6 comprises a house 8, enclosing a first electrical machine 9 and a planetary gear. The electrical machine 9 comprises, in a customary manner, a stator 9a and a rotor 9b. The stator 9a comprises a stator- core, which is fixed in a suitable manner on the inside of the house 8. The stator core comprises the stato s windings. The first electrical machine 9 is adapted, under certain operating circumstances, to use stored electrical energy to supply driving force to the input shaft 3a of the gearbox, and, under other oper- ating conditions, to use the kinetic energy of the input shaft 3 of the gearbox to extract and store electric energy.

The planetary gear is arranged substantially radially inside of the electrical machine's stator 9a and rotor 9b. The planetary gear comprises, in a customary manner, a sun wheel 1 0, a ring gear

1 1 and a planetary wheel carrier 1 2. The planetary wheel carrier

1 2 supports a nu mber of cogwheels 1 3, which are rotatably arranged in a radial space between the teeth of the sun wheel 1 0 and the ring gear 1 1 . The sun wheel 1 0 is fixed on a peripheral surface of the combustion engine's output shaft 2a. The sun wheel 1 0 and the combustion engine's output shaft 2a rotate as one unit with a first rotational speed The planetary wheel carrier 1 2 comprises an attachment section 1 2a, which is attached on a peripheral surface of the input shaft 3a of the gearbox with the help of a splines-joint 1 4, With the help of this joint, the planetary wheel carrier 1 2 and the gearbox's input shaft 3a may rotate as one unit with a second rotational speed n ₂ . The ring gear 1 1 comprises an external peripheral surface on which the rotor 9b is fixedly mounted . The rotor 9b and the ring gear 1 1 constitute one rotatable unit which rotates at a third rotational speed n ₃ .

The drive system comprises a first locking means, since the combustion engine's output shaft 2a is equipped with a shiftable clutch element 1 5. The clutch element 1 5 is mounted on the combustion engine's output shaft 2a with the help of a splines- joint 1 6. The clutch element 1 5 is in this case arranged in a twist- fast manner on the combustion engine's output shaft 2a, and is shiftably arranged in an axial direction on the combustion en- gine's output shaft 2a. The clutch element 1 5 comprises a clutch section 1 5a, which is connective with a clutch section 1 2b in the planetary wheel carrier 1 2. A schematically displayed shifting element 1 7 is adapted to shift the clutch element 1 5 between a first position where the clutch sections 1 5a, 1 2b are not in en- gagement with each other, corresponding to a release position in the first locking means, and a second position where the clutch sections 1 5a, 1 2b are in engagement with each other, corresponding to a locked position of the first locking means. In such locked position the combustion engine's output shaft 2a and the gearbox's input shaft 3a will be locked together, and accordingly these and the electrical machine's rotor will rotate at the same speed. This state may be referred to as a locked planet. The locking mechanism may also advantageously have the design described in the Swedish patent application SE 536 559, and comprise a sleeve equipped with first splines, which, in the release position, engage with second splines on a first component of the planetary gear, and which in the locked position engage with third splines on a second component of the planetary gear. In this case the first component is preferably the planetary wheel carrier, and the second component is the sun wheel . The locking mechanism may then be adapted like an annular sleeve, enclosing the planetary wheel carrier substantially concentrically. The locking means may also be made of a suitable type of friction clutch.

An electronic control device 1 8 is adapted to control the shifting element 1 7. The control device 1 8 is also adapted to determine the occasions on which the electrical machine should operate as an engine, and the occasions on which it should operate as a generator. In order to so determine, the control device 1 8 may receive up to date information relating to suitable operating parameters. The control device 1 8 may be a computer with software for this purpose. The control device 1 8 controls a schematically displayed control equipment 1 9, which controls the flow of eiec- trie energy between a hybrid battery 20 and the stator windings 9a of the electrical machine. On occasions where the electrical machine 9 operates as an engine, stored electric energy is supplied from the hybrid battery 20 to the stator 9a. On occasions where the electrical machine operates as a generator electric energy is supplied from the stator 9a to the hybrid battery 20. The hybrid battery 20 delivers and stores electric energy with a voltage in the range of 300-900 Volt. Since the intermediate section 6 between the combustion engine 2 and the gearbox 3 in the vehicle is limited , the electrical machine 9 and the planetary gear must constitute a compact unit. The planetary gear's components 1 0, 1 1 , 1 2 are arranged substantially radially inside the electrical machine's stator 9a. The rotor 9b of the electrical machine, the ring gear 1 1 of the planetary gear, the combustion engine's output shaft 2a and the input shaft 3a of the gearbox are here ro- tatably arranged around a common rotation axis 5. With such an embodiment the electrical machine 9 and the planetary gear occupy a relatively small area. The vehicle 1 is equipped with an engine control function 21 , with which the engine speed n t and/or torque of the combustion engine 2 may be controlled. The control device 1 8 accordingly has the possibility of activating the engine control function 21 and of creating a substantially zero torque state in the gearbox 3 at engagement and disengagement of gears in the gearbox 3. Naturally, the drive system may, instead of being controlled by one single control device 1 8, be controlled by several different control devices.

The part of a drive system of a vehicle, thus far described , and displayed in Fig. 2, and on which a method according to the invention may be implemented is extant in the drive system accord- ing to SE 536 329. Below, a part of the drive system, which may be added to this part for the implementation of the invention, will be described with reference to Fig. 3.

The drive system, specifically the intermediate section 6, also has a second electrical machine 30 with a stator 31 , with stator windings and a rotor 32 which is connected with the combustion engine's output shaft 2a. A second locking means 33, which may have a similar design as the first locking means 34, illustrated in more detail in Fig. 2, is adapted to separate, in a release posi- tion , a first part 35 of the combustion engine's output shaft, arranged nearest the combustion engine, from a second part 38 thereof, connected with the sun wheel 1 0 of the planetary gear, so that the second electrical machine's rotor 32 and the sun wheel 1 0 are allowed to rotate independently of the first section 35 of the combustion engine's output shaft. The second locking means may be moved to a locked position in which both the parts 35, 38 of the combustion engine's output shaft are locked together, and accordingly the first part 35 is locked together with the second electrical machine's rotor. The control device 1 8 is adapted to control fuel supply to the combustion engine 2 and to control exchange of electric energy between the first electrical machine 9 and the second electrical machine 30 on the one hand, and, on the other hand, electric energy storage means, such as batteries, and electric auxiliary aggregates and loads in the vehicle, such as servo control units, pu mps, cooling aggregates and similar.

A range of positive features are achieved in the drive system through the added arrangement of the electrical machine 30 and the second locking means 33. If the vehicle is driven with the first locking means 34 in a locked position , and for example the second locking means 33 in a locked position , and a request arises for shifting the first locking means 34 into a release position, the power unit configuration is controlled towards a torque balance between the components that are locked together, i .e. the plane- tary wheel carrier 1 2 and the sun wheel 1 0, via the first locking means 34. This may be achieved by controlling the first electrical machine 9, and at least one of the second electrical machine 30 and the combustion engine 2, since the second locking means 33 is in a locked position, towards said torque balance, so that there is also a possibility for energy storage in the hybrid battery 30 if desired. Here, torque balance is achieved when the following relation between the torques applied is met for the example configuration displayed in Fig. 3 :

su n wheel ⁼⁼ ~Z~ ' ri ng gear

where

Su n wheel and T _{ri n g g e a} r represent the torque applied to the sun wheel and the ring gear, respectively, where T _{s u n w h eej} = T _{i ce} + Tem2 and T _{ri n g} gear = T _em i where

Tjce is torque applied to the combustion engine's output shaft

T _{e rn2} is torque applied via the second electrical machine's stator to its rotor

T _{e m} i is torque applied via the first electrical machine's stator to its rotor,

Z _s is the number of teeth on the sun wheel ,

Z _r is the number of teeth on the ring gear. Accordingly, torque balance relates to the state where a torque acts on a ring gear arranged in the planetary gear, representing the product of the torque acting on the planetary wheel carrier of the planetary gear and the gear ratio of the planetary gear, while simultaneously a torque acts on the planetary gear's sun wheel , representing the product of the torque acting on the planetary wheel carrier and (1 minus the planetary gear's gear ratio) . At such torque balance said first locking means 34 does not transfer any torque between the components of the planetary gear. Once torque balance has been achieved , the first locking means 34 may easily be moved to the release position, so that the planetary gear's components are no longer locked together. The inventive method facilitates start of the combustion engine, while the vehicle is driven without any torque interruption in the vehicle's powertrain, and with freedom for the vehicle's driver, cruise control or other torque controlling function in the vehicle to determine and change the powertrain torque during the method . However, this comes with a small reservation, since in some operational situations, due to sizing constraints, it may become neces- sary to achieve a quick start of the combustion engine to reduce the torque in the powertrain somewhat, since the second electrical machine's torque is consumed in order to cancel the reaction torque from the first electrical machine on the one hand , and , on the other hand , in order to crank the combustion engine. There- fore, the first electrical machine may in this case be controlled to transmit to the planetary gear's output shaft a requested torque, which is somewhat lower than the torque transmitted to such shaft when the method is started . A great advantage of a drive system according to Fig. 3, with or without the second locking means, is the potential for continuous electric power supply by the electric units in all operating modes, with the combustion engine connected in a steady state. This is normally not achieved with hybrid solutions having only one elec- trical machine. When the first locking means is in a locked posi- tion , said electric unit is supplied by substantially distributing the requested electrical power to the electric auxiliary aggregates and the electric loads of the vehicle between the electrical machines. In this way, the losses in the electrical machines are minimised , since the torque per electrical machine is halved compared to if an electrical machine had supplied all the electrical output. Since the loss effects of the electrical machines substantially scale against the torque applied squared , this entails substantially a halving of the losses of the electrical machines. However, such a distribution (50/50) is potentially not optimal in case the two electrical machines have dimensions which differ considerably from each other, but efforts are still made to select said proportions with this optimal distribution in mind. When the first locking means is open , the first electrical machine will determine the torque in the power-train. The engine speed of the combustion engine is controlled to an operational point, which is selected by minimising the losses of the combustion engine together with losses of the electrical machine and the in- verier. The second electrical machine is then used to balance the output for potential energy storage means, electrical aggregates and the first electrical machine. It is a great strength that the power supply of the electrical aggregates may also take place, even if the vehicle is not equipped with an electrical energy stor- age system . The supply may also take place continuously during all types of up- and down-shifts, during crawling, start-off and braking. All driving modes, except electrical driving and brake regeneration, may be implemented without any electrical storage means or with a defective energy storage means. In operating modes, with or without a defective electrical energy storage means, the voltage of the second electrical machine normally will be controlled to maintain the correct voltage level on the DC-link (supply voltage to the two inverters connected to the stators of the electrical machines) . It is also conceivable that the voltage of the first electrical machine may be controlled in some cases. Voltage control is a "mode" of the inverter, where a voltage is requested from the inverter. The inverter then controls the electrical machine's torque in such a way that the requested voltage is maintained on the inverter's supply side.

Fig. 4 illustrates a flow chart of a method according to one embodi ment of the present invention , i mplemented in a vehicle with a drive system of the type displayed in Fig. 3. The vehicle is driven with the combustion engine turned off and the second locking means in a release position, and if the first locking means is not in a release position, then it is first moved into such position in a step Throughout the progress of the method , a step S ₂ is performed, in the form of control of the first electrical machine to achieve a requested torque on the planetary gear's out- put shaft. In a step S ₃ , the second electrical machine is controlled to a standstill , whereupon in step S ₄ the second locking means are moved to a locked position. Subsequently, in step S ₅ , the second electrical machine is controlled toward the combustion engine's idling speed, whereupon the latter is started by way of fuel injection in a step S ₆ .

Computer program code for implementation of a method according to the invention is suitably included in a computer program, which is loadable into the internal memory of a computer, such as the internal memory of an electronic control device of a vehi- cle. Such a computer program is suitably provided via a computer program product, comprising a data storage medium readable by an electronic control device, which data storage medium has the computer program stored thereon. Said data storage medium is e.g. an optical data storage mediu m in the form of a CD-ROM , a DVD , etc. , a magnetic data storage medium in the form of a hard disk drive, a diskette, a cassette, etc. , or a Flash memory or a ROM , PROM , EPROM or EEPROM type memory. Fig. 5 very schematically illustrates an electronic control device 1 8, comprising execution means 37, such as a central processor unit (CP U) , for the execution of computer software. The execution means 37 communicates with a memory 38, e.g. a RAM memory, via a data bus 39. The control device 1 8 also comprises a durable data storage medium 40, e.g. in the form of a Flash memory or a ROM , P ROM , EPROM or E EPROM type memory. The execution means 37 communicates with the data storage means 40 via the data bus 39. A computer program comprising computer program code for the implementation of a method ac- cording to the invention is stored on the data storage medium 40.

The invention is obviously not limited in any way to the embodiments described above, but numerous possible modifications thereof should be obvious to a person skilled in the area, without such person departing from the spirit of the invention as defined by the appended claims.

The inventive method could be carried out in a vehicle with a drive system, which has the planetary gear's ring gear as said first component and the sun wheel as said third component, which means that the first electrical machine's rotor would be connected with the planetary sun wheel and the second electrical machine's rotor and the combustion engine would be connected with the planetary gear's ring gear instead of with the sun wheel . Advantageously, however, the planetary gear's output shaft for transmission of torque for the vehicle's propulsion is connected with the planetary wheel carrier.

Nor is it necessary for the output shaft from the planetary gear to be an input shaft in a gearbox, instead the vehicle could have no gearbox.

"Electrical energy storage means" as used in this docu ment means an energy storage means with an electrical interface in relation to the first and second electrical machine of the drive system, but storage of energy does not have to be electrical . This entails that in addition to an electrical battery and capacitor, for example flywheels, other mechanical means and means for building up pressure, e.g . pneumatic or hydraulic means, may be considered .