TECHNICAL FIELD

The invention relates to a method for controlling the powertrain of a vehicle according to th preamble of claim 1. The invention relates to a system for controlling the powertrain of a vehicle according to the preamble of claim 7. The invention also relates to a motor vehicle. The invention also relates to a computer program and a computer program product.

BACKGROUND ART Mechanically driven superposition transmissions are mechanically complicated and demand a relatively huge development effort. Electrically driven superposition transmissions are mechanically simpler in their construction, but for the dominating product using this type of gear box, military tracked vehicles, the power demands are big over the whole range of rotational speed. This entails that cost-efficient induction electric engines by that cannot be used due to the drastically reduced output power of induction electric engines at increasing rotational speed.

OBJECT OF THE INVENTION

One object of the present invention is to accomplish a method for controlling the powertrain of a vehicle which facilitates efficient operation and utilization of a cost-efficient powertrain.

Another object of the present invention is to accomplish a system for controlling the powertrain of a vehicle which facilitates efficient operation and utilization of a cost-efficient powertrain.

SUMMARY OF THE INVENTION These and other objects, which will be apparent from the following description, are achieved by means of a method, a system, a vehicle, as well as a computer program and a computer program product of the kind given by way of introduction and which further shows the distinctive features stated in the characterising parts of the enclosed independent claims. Preferred embodiments of the method, the system and the vehicle are defined in the attached dependent claims.

According to the invention the objects are achieved by a method for controlling the powertrain of a vehicle, which powertrain comprises a combustion engine unit for mechanical driving of said powertrain, an electric motor unit arranged to be supplied with electrical energy for electrical driving of said powertrain as well as a generator unit driven by means of said combustion engine unit for generation of electrical energy, and means for controlling the powertrain of the vehicle, wherein the method comprises controlling the driving torque which is provided to the powertrain in such a way that the powertrain is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed; and the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. Hereby utilisation of a more cost-efficient electric motor unit in the form of an induction motor is facilitated since efficient propulsion of the vehicle is facilitated also when the induction motor cannot provide for the power demand of the vehicle.

Hereby high efficiency is achieved at high speeds through utilisation of direct mechanical driving at higher power demand. Further hereby acceleration with maximum torque utilisation is facilitated already for vehicles that stand still through driving by means of the electric motor unit at said lower power demand.

According to an embodiment of the method the driving of the powertrain to a common drive shaft is done both at said lower power demand and at said higher power demand. Hereby the powertrain is utilised efficiently. According to an embodiment of the method said higher power demand corresponds to a power demand of the vehicle which the electric motor unit cannot provide for completely. As a consequence the powertrain is driven mechanically by means of the combustion engine unit when the electric motor unit cannot completely provide for the power demand, whereupon the powertrain is utilised efficiently for efficient propulsion of the vehicle.

According to an embodiment of the method said lower power demand changes to said higher power demand at a propulsion speed exceeding half the maximum available speed of the vehicle.

According to an embodiment of the method an electrical power path for driving of the powertrain with electrical energy by means of said electric motor unit is connected in parallel to a mechanical power path for mechanical driving of the powertrain by means of said combustion engine unit. This results in achieving great flexibility since changes in one power path do not influence what is happening in the other power path.

According to an embodiment the method comprises the step of controlling the driving torque provided to the powertrain in such a way that the powertrain is partially driven by means of said electric motor unit and said combustion engine unit in a power demand range between said lower and said higher power demand for optimising the efficiency. Hereby optimising of the efficiency for efficient propulsion of the vehicle is facilitated.

According to an embodiment of the method said power demand range between said lower and said higher power demand is chosen in such a way that both purely mechanical and purely electric propulsion is possible in this power demand range for optimising the efficiency. This facilitates great flexibility for optimising the efficiency.

According to an embodiment of the invention an electrical power path for driving of the powertrain with electrical energy by means of said electric motor unit is connected in parallel to a mechanical power path for mechanical driving of the powertrain by means of said combustion motor unit; and wherein driving in said power demand range between said lower and said higher power demand can be done both via the electrical power path and via the mechanical power path. This facilitates great flexibility for optimising the efficiency. Further, controlling of the powertrain is enabled where no energy storage arrangement is needed. According to an embodiment of the method said electric motor unit is constituted by an induction motor. Hereby a cost-efficient powertrain is achieved since an induction motor is relatively cheaper than other types of motor units such as permanent magnetic motor or similar. According to an embodiment the objects are achieved by a system for controlling a powertrain of a vehicle, which powertrain comprises a combustion engine unit for mechanical driving of said powertrain, an electric motor unit arranged to be supplied with electrical energy for electrical driving of said powertrain, as well as a generator unit driven by means of said combustion engine unit for generation of electrical energy, and means for controlling the powertrain of the vehicle, comprising means for controlling the driving torque which is provided to the powertrain in such a way that the powertrain is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed and that the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. Hereby efficient driving with utilisation of cost-efficient powertrain is facilitated since utilisation of an induction motor with corresponding driving torque output as with using of a relatively more expansive permanent magnetic motor is facilitated. Hereby utilisation of a more cost-efficient electric motor unit in the form of an induction motor is facilitated since efficient propulsion of the vehicle is facilitated even when the induction motor cannot provide for the power demand of the vehicle. Hereby high efficiency is achieved at high speeds through utilisation of direct mechanical driving at higher power demand. Further, acceleration with maximum torque utilisation is hereby already facilitated for vehicles that stand still through driving by means of the electric motor unit at said lower power demand.

According to an embodiment of the system driving of the powertrain is arranged to be done to a common drive shaft both at said lower power demand and at said higher power demand. Hereby the powertrain is utilised efficiently. According to an embodiment of the system said higher power demand corresponds to a power demand at the vehicle which the electric motor unit cannot provide for completely. As a consequence the powertrain is driven mechanically by means of the combustion engine unit when the electric motor unit cannot completely provide for the power demand, whereupon the powertrain is utilised efficiently for efficient propulsion of the vehicle.

According to an embodiment of the system said lower power demand changes to said higher power demand at a propulsion speed exceeding half the maximum available speed of the vehicle.

According to an embodiment of the system, the system is arranged in such a way that an electrical power path for driving of the powertrain with electrical energy by means of said electric motor unit is connected in parallel to a mechanical power path for mechanical driving of the powertrain by means of said combustion engine unit. Hereby a flexible system is achieved where both power paths can bet optimised basically independent from each other.

According to an embodiment the system comprises means for controlling the driving torque provided to the powertrain in such a way that the powertrain is partially driven by means of said electric motor unit and said combustion engine unit in a power demand range between said lower and said higher power demand for optimising the efficiency. Hereby optimising of the efficiency for efficient propulsion of the vehicle is achieved.

According to an embodiment of the system, the system is arranged in such a way that both purely mechanical and purely electric propulsion is possible in said power demand range between said lower and said higher power demand for optimising the efficiency. This results in a system with great flexibility for optimising the efficiency.

According to an embodiment of the system, the system is arranged in such a way that an electrical power path for driving of the powertrain with electrical energy by means of said electric motor unit is connected in parallel to a mechanical power path for mechanical driving of the powertrain by means of said combustion motor unit; and wherein driving in said power demand range between said lower and said higher power demand can be done both via the electrical power path and via the mechanical power path. This results in a system with great flexibility for optimising the efficiency. Further, a system is enabled where no energy storing arrangement is needed, which can lower costs.

According to an embodiment of the system said electric motor unit is constituted by an induction motor. Hereby a cost-efficient powertrain is achieved since an induction motor is relatively cheaper than other types of motor units such as permanent magnetic motor or similar.

According to an embodiment of the system said means for controlling the powertrain of the vehicle comprise means for synchronising rotational speed at the transition from driving by means of said electric motor unit to driving by means of said combustion engine unit. According to an embodiment of the system, driving of said drive shaft comprises clutch members for engagement and disengagement of said mechanical driving. Hereby efficient utilisation of the powertrain is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood better with reference to the following detailed description read together with the enclosed figures, where the same reference signs relate to the same parts throughout the many views, and in which:

Fig.l schematically illustrates a motor vehicle according to an embodiment of the present invention; Fig. 2 schematically illustrates a block diagram of a system for controlling the powertrain of a vehicle;

Fig. 3 schematically illustrates driving torque output as a function of speed;

Fig. 4 schematically illustrates power output as a function of speed in relation to the power demand of the vehicle; Fig. 5 schematically illustrates speed as a function of rotational speed of the combustion engine unit; Fig. 6 schematically illustrates a block diagram of a method for controlling the powertrain of a vehicle; and

Fig. 7 schematically illustrates a computer according to an embodiment of the present invention.

DETAILED DESCRIPTION

Herein the term "link" relates to a communication link which can be a physical wire, such as an opto-electrical communication wire, or a non-physical wire, such as a wireless connection, for example a radio or a microwave link. Herein the term "power electronic unit" relates to a unit configured to achieve electricity supply of an electric motor unit/electric motor. The power electronic unit is thus configured to supply the electric motor with electrical energy. According to a variant, such a power electronic unit is configured to convert alternating voltage/alternating current into direct- current voltage/direct current and direct-current voltage/direct current into alternating voltage/alternating current. According to a variant, such a power electronic unit is configured to step up or to step down voltage. According to a variant, such a power electronic unit is configured to enable connection to an energy storage arrangement such as a battery, a capacitor or similar. According to a variant such a power electronic unit is configured to control the rotational speed of electric motors. Herein the term "propulsion rotational speed" relates to the rotational speed which the ground contacting members of the vehicle have, i.e. the rotational speed which the driving wheels of the vehicle have.

Herein the term "power demand" relates to the power demand of the vehicle for propulsion.

Fig. 1 illustrates schematically a motor vehicle 1 according to an embodiment of the present invention. The exemplified vehicle 1 is constituted by a heavy vehicle in the form of a military tracked vehicle. The vehicle comprises a system for controlling the powertrain of a vehicle according to embodiments of the present invention. Fig. 2 schematically illustrates a block diagram of a system I for controlling the powertrain of a vehicle according to an embodiment of the present invention.

The system I comprises a powertrain 10 for propulsion of a motor vehicle, for example the vehicle 1 illustrated in Fig. 1. The powertrain 10 comprises a drive shaft 12. The drive shaft 12 is connected with ground contacting members 14a, 14b comprising driving wheels which according to an embodiment are arranged to drive driving tracks of the vehicle. The ground contacting members are thus according to a variant constituted by driving tracks for a track-driven vehicle. According to a variant the ground contacting members are constituted by tyre equipped driving wheels for a wheel-driven vehicle.

The drive shaft 12 comprises a left drive shaft section 12a and a right drive shaft section 12b. Said driving wheels comprise a left drive wheel 14a connected to the left drive haft section 12a and an opposite right driving wheel 14b connected to the right drive shaft section 12b.

The powertrain 10 comprises further a transmission configuration 34. The transmission configuration 34 comprises according to this variant a left transmission unit 34a and a right transmission unit 34b. Respective transmission unit comprises according to an embodiment a reduction gearing.

The transmission configuration 34 comprises a differential arrangement which can be constituted by any suitable differential for achieving a differential functioning. Respective drive shaft section 12a, 12b is connected to respective driving wheel 14a, 14b via respective transmission unit 34a, 34b.

The left transmission unit 34a is connected with a left wheel axle 13a connected to the left driving wheel 14a. The right transmission unit 34b is connected to a right wheel axle 13b connected to the right driving wheel 14b. The powertrain 10 comprises a combustion engine unit 42 for mechanical driving of said powertrain. The combustion engine unit 42 is according to a variant constituted by a diesel engine. Hereby the power train 10 is constituted by a diesel-electrical powertrain. The powertrain 10 comprises further a generator unit 44 connected to said combustion engine unit 42. Said combustion engine unit 42 is arranged to drive said generator unit 44 for generation of electrical energy.

The powertrain comprises a power electronic unit 46. The power electronic unit 46 comprises an AC/DC-conversion unit which is connected with the generator unit 44 and configured for converting the alternating voltage from the generator unit 44 into direct-current voltage.

The power electronic unit 46 further comprises a DC/AC-conversion unit 46b which is connected to the AC/DC-conversion unit 46a and configured to convert direct-current voltage into controllable alternating voltage. Said powertrain 10 comprises an electric motor unit 49 for propulsion of a vehicle. Said electric motor unit 49 is arranged to be supplied with said electrical energy. The electric motor unit 49 is constituted by an induction motor. The electric motor unit 49 is connected with the drive shaft 12 and arranged to drive it.

Speed and driving torque of said electric motor unit 49 is controlled by means of the alternating voltage which is converted by the DC/AC-converting unit 46b from direct-current voltage into controlled alternating voltage.

The powertrain 10 comprises according to an embodiment an energy storage arrangement 48. Said energy storage arrangement 48 comprises according to an embodiment one or several supercapacitors. According to an alternative embodiment, said energy storage arrangement 48 comprises one or several battery units. According to an embodiment, said energy storage arrangement comprises both supercapacitor and battery unit. Said direct current intermediate link 46 is according to a variant directly connected with said energy storage arrangement 48. Said energy storage arrangement 48 is arranged to store said generated electrical energy from the generator unit and at breaking converted kinetic energy, as well as charging at charging station or corresponding. The energy storage unit comprises according to an alternative embodiment a fuel cell unit.

The powertrain 10 comprises further a clutch member 50 for engagement and disengagement of mechanical driving of said drive shaft 12. The clutch member 50 is connected with the drive shaft 12 via a transmission arrangement 60. The clutch member 50 is hereby connected to the right drive shaft section 12b.

The powertrain 10 is arranged to be driven by means of said electric motor unit 49 and hereby by electrical energy generated by means of said generator unit 44 at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. The arrow Al shows the electrical power path. The clutch member 50 is thus disengaged at driving by means of the electric motor unit 49.

The powertrain 10 is further arranged to be driven mechanically by means of said combustion engine unit 42 at a certain higher power demand which is required to provide for a certain driving torque demand coupled to a certain propulsion rotational speed. The arrow A2 shows the mechanical power path. The clutch member 50 is thus engaged to the drive shaft 12 at driving by means of the combustion engine unit 42. The clutch member 50 comprises according to a variant detection members for detecting whether the clutch member 50 is engaged or disengaged. In the powertrain 10 the electrical power path Al is connected in parallel to the mechanical power path A2. In the shown example the power transmission components in the mechanical power path A2 between the generator unit 44 and the drive shaft 12 are separated from the power transmission components in the electrical power path Al between the generator unit 44 and the drive shaft 12. The power transmission components in the mechanical power path A2 between the generator unit 44 and the drive shaft 12 are for example the clutch member 50 and the transmission arrangement 60. The power transmission components in the electrical power path Al between the generator unit 44 and the drive shaft 12 are for example the power electronic unit 46 and the electric motor 49. Also the wires and/or other means for current transmission are included in the power transmission components in the electrical power path Al.

The expression connected in parallel means in this context what usually is meant with parallel connection in electronics. In one example this means that the electrical power path Al and the mechanical power path A2 have power transmission components according to the above which are not used in the respective other power transmission path. With the expression connected in parallel it is not meant that the components should be physically placed in parallel to each other.

Accordingly driving of the powertrain is arranged to be done to a common drive shaft in the form of the drive shaft 12 at both said lower power demand and at said higher power demand.

At the transition from driving by means of said electric motor unit 49 to driving by means of said combustion engine unit 42 the synchronisation of the rotational speed is arranged to happen at engagement of the clutch member, wherein the rotational speed of the combustion engine unit 42 at said transition is arranged to be lowered so that the synchronisation of the rotational speed is facilitated. The rotational speed of the combustion engine unit 42 is then increased at increasing speed.

According to an embodiment the driving torque which is provided to the powertrain 10 is arranged to be controlled in such a way that the powertrain 10 is partly driven by means of said electrical motor unit 49 and said combustion engine unit 42 in a power demand range between said lower and higher power demand for optimising the efficiency. This is described in more detail with reference to figure 6.

The system I further comprises a manoeuvring member 90 for power request, where the manoeuvring member according to a variant comprises a throttle unit 90, such as a throttle pedal. The power request is generated based on a performed action which corresponds to a request to deliver power to the vehicle for propulsion of the same. According to a variant, said power request is performed by the operator of the vehicle, according to a variant by the driver of the vehicle. The power request could even be done automatically, be pre-programmed, or the like, such as for a driverless vehicle/autonomous vehicle. The power request of the manoeuvring member in the form of the throttle unit 90 corresponds to a requested driving torque.

When power transmission to the ground contacting members 14a, 14b is requested in system I, power is in one embodiment always transferred from the combustion engine unit 42 to the ground contacting members 14a, 14b, either directly via the mechanical power path A2, or indirectly via the electrical power path Al. In such an embodiment there is thus no energy storage unit 10 needed, which can result in cost savings.

The system I further comprises means for controlling the powertrain 10. Said means comprise at least one electronic control unit 100 for controlling the powertrain 10. The electronic control unit 100 is arranged to control at driving the driving torque which is provided to the powertrain 10 in such a way that the powertrain 10 is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing a certain driving torque demand coupled to a certain propulsion rotational speed; and that the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed.

The electronic control unit is signal-connected to said combustion engine unit 42 via a link. The electronic control unit is arranged to receive a signal from said combustion engine unit 42 representing drive data for determination of the power which the combustion engine can provide.

The electronic control unit 100 is signal-connected to said throttle unit 90 via a link. The electronic control unit 100 is arranged to receive a signal from said throttle unit 90

representing throttle data for requested performance such as torque/power, where said throttle data comprises performance data such as torque data and/or power data.

The electronic control unit 100 is signal-connected to said combustion engine unit 42 via a link. The electronic control unit 100 is arranged to send a signal to said combustion engine unit 42 representing performance data such as torque data and/or power data for the requested torque from throttle unit 90. The electronic control unit 100 is signal-connected to said combustion engine unit 42 via a link. The electronic control unit 100 is arranged to receive a signal from said combustion engine unit 42 representing rotational speed data and torque data at the combustion engine unit 42. The electronic control unit 100 is signal-connected to said power electronic unit 46 via a link. The electronic control unit 100 is arranged to send a signal to said power electronic unit 46 representing rotational speed data and torque data for requested rotational speed and torque. The electronic control unit 100 is signal-connected to said clutch member 50 via a link. The electronic control unit 100 is arranged to receive a signal from the clutch member 50 representing data for clutch status of the clutch member, that is whether the clutch member is engaged or disengaged.

The electronic control unit 100 is signal-connected to said clutch member 50 via a link. The electronic control unit 100 is arranged to send a signal to the clutch member 50 representing clutch activation data for engaging or disengaging of the clutch member 50.

The electronic control unit 100 comprises data which relates to the specific performance of the electric motor unit 49 comprising power which the electric motor unit 49 can provide at different rotational speeds. The electronic control unit 100 comprises data which relates to the specific performance of the combustion engine unit comprising the power of the combustion engine unit 42 as a function of the rotational speed. The electronic control unit 100 comprises data which relates to the power demand of the vehicle, related to the propulsion rotational speed/speed.

The electronic control unit 100 is arranged to process said rotational speed data, torque data and said data for performance of the electrical motor unit 49, combustion engine unit 42 and data for the power demand of the vehicle at the actual propulsion rotational speed/speed of the vehicle for thus determining whether the power demand of the electric motor unit is provided for.

The electronic control unit 100 is arranged to control the driving torque which is provided to the powertrain 10 in such a way that the powertrain 10 is driven mechanically by the combustion engine unit 42 at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed.

If the power demand for propulsion is not provided for by the electric motor unit 49, which is constituted by an induction motor, the electric control unit 100 is arranged to send a signal to the clutch member 50 to activate the engagement of the clutch member 50 such that the powertrain 10 is driven mechanically by means of the combustion engine unit 42 when the power demand of the electric motor unit 49 cannot be provided for, alternatively keeps engagement of the combustion engine unit 42 if the clutch member is already engaged.

According to a variant, the electronic control unit 100 is arranged to send a signal to the clutch member 50 to activate engaging of the clutch member 50 so that the powertrain 10 is driven mechanically by means of the combustion engine unit 42 at the propulsion rotational speed where the power at the electric motor unit 49 starts declining, that is where the electric motor unit 49 cannot provide the installed power of the combustion engine unit 42. The electronic control unit 100 is arranged to control the driving torque which is provided to the powertrain 10 in such a way that the powertrain 10 is driven by means of said electric motor unit 49 and hereby with electrical energy generated by means of said generator unit 44 at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. If the power demand at the electric motor unit 49 is provided for, the electronic control unit 100 is arranged to send a signal to the clutch member 50 to activate disengagement of the clutch member such that the powertrain 10 is driven by means of said electric motor unit 49 and hereby with electrical energy generated by means of said generator unit 44, alternatively keep disengagement of the combustion engine unit 42. The electric control unit 100 is arranged to at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed.

According to an embodiment the electronic control unit 100 is arranged to control the driving torque which is provided to the powertrain 10 in such a way that the powertrain is partially driven by means of said electrical motor unit 49 and said combustion engine unit 42 in a power demand range between said lower and said higher power demand for optimising the efficiency.

Fig. 3 illustrates schematically the driving torque output as a function of the speed of the vehicle. The continuous line illustrates the characteristic for the driving torque of an induction motor as a function of the speed which essentially corresponds to the propulsion rotational speed of the vehicle. The induction motor has a dependence which essentially is proportional to the quotient of the rotational speed squared. The dashed line illustrates the characteristic for the driving torque of a permanent magnetic motor (PM-motor) as a function of the speed which essentially corresponds to the propulsion rotational speed of the vehicle. The permanent magnetic motor has a dependence which essentially is proportional to the quotient of the rotational speed.

The dotted line illustrates the characteristic for the driving torque of a combustion engine unit, here a diesel engine.

Initially the driving torque is constant. Above a certain speed vO said rotational speed dependence arises at the induction motor and the PM-motor.

Above a certain speed vl corresponding to a certain rotational speed the induction motor does not manage to provide the power of the diesel engine, whereupon the power of the induction motor is declining as is evident from Fig. 4. Hereby the diesel engine is engaged at speed vl so that the vehicle is driven mechanically by means of the diesel engine up to maximum speed v2 of the vehicle, whereby efficiently driving is enabled despite the restrictions of the cost-efficient induction motor.

Fig. 4 illustrates schematically the power output as a function of the speed in relation to the power demand of the vehicle in accordance to the conditions illustrated in the curve in Fig. 3.

The continuous line illustrates the characteristic for power output at the induction motor as a function of the speed which essentially is proportional to the propulsion rotational speed of the vehicle.

The dashed line illustrates the characteristic for power output of the PM-motor as a function of the speed which essentially corresponds to the propulsion rotational speed of the vehicle. The permanent magnetic motor has a dependence which basically is proportional to the quotient of the rotational speed.

The dotted line illustrates the characteristic for power output of the diesel engine. The dot-dashed line illustrates the power demand of the vehicle as a function of the speed.

Hereby it is evident that the power of the induction motor and the PM-motor increases up to the speed vO. For the PM-motor the power is then constant up to the speed v2 constituting the maximum speed of the vehicle. For the induction motor the power is constant up to the speed vl and starts then decreasing until the maximum speed v2 of the vehicle.

The power demand of the vehicle increases basically linearly with an increased speed until the maximum speed v2 of the vehicle. At the point P the power of the induction motor is going to fall below the power demand of the vehicle, whereupon the induction motor cannot provide for the power demand of the vehicle.

Above a certain speed vl corresponding to a certain rotational speed the induction motor thus does not manage to provide the power of the diesel engine, whereupon the power of the induction motor is decreasing as mentioned. Hereby the diesel engine is engaged at the speed vl such that the vehicle is driven mechanically by means of the diesel engine up to the maximum speed v2 of the vehicle, whereby efficient driving is enabled despite the restrictions of the cost-efficient induction motor.

According to a variant, the vehicle is constituted by a tracked vehicle. According to a variant the speed vO is of the order of 10-20 km/h, the speed vl of the order of 45-50 km/h and v2 of the order of 70-80 km/h. At driving of the vehicle from standing still the vehicle is propelled through driving by means of the electric motor unit 49 by supplying it with electrical energy from the generator unit 44, whereupon the vehicle accelerates up to a propulsion speed exceeding half of the maximum provided speed of the vehicle, according to this variant around 2/3 of the maximum provided speed of the vehicle, that is as long as maximum power can be kept of the electric motor unit in the form of said induction motor. Hereby the combustion engine unit 42, here the diesel engine, operates on maximum power with a maximum rotational speed of 2100 rpm, for example, whereupon the clutch member 50 is disengaged.

When the electric motor unit 49 starts losing in power, a transition to mechanical driving occurs through the clutch member 50 being brought into engagement, under which phase the rotational speed of the combustion engine unit 42 is lowered to a lower rotational speed of for instance 1100 rpm. While the clutch member 50 is closing, transmission of electrical energy is occuring. The vehicle accelerates then synchronously with the rotational speed of the combustion engine 42. Hereby a good efficiency is achieved at start and with high driving torques since the electrical transmission here is better than torque conversion transmission. Further a better efficiency is achieved at higher speeds since the mechanical transmission there is better than the electrical transmission.

According to a variant the power of the diesel engine is in the order of 600 kW.

Hereby utilisation of a more cost-efficient electric motor unit in the form of an induction motor is enabled instead of a considerably more expensive PM-motor since efficient propulsion of the vehicle is enabled even when the induction motor cannot provide for the power demand of the vehicle by thus engaging direct mechanical driving. Hereby high efficiency is enabled at high speeds through utilisation of direct mechanical driving at higher power demand, since mechanical driving by means of the combustion engine unit, here the diesel engine, at higher speeds and higher propulsion rotational speeds results in a higher efficiency than an electric motor unit such as a PM-motor at corresponding high

speed/propulsion rotational speed. Further, acceleration with maximum utilisation of the torque is hereby enabled already for vehicles standing still through driving by means of the electric motor unit at said lower power demand. Fig. 5 illustrates schematically speed as a function of rotational speed of the combustion engine unit, for instance diesel engine.

Mechanical driving through engaging to the drive shaft for driving of drive wheels by means of the combustion engine unit is not possible below a certain rotational speed nO and a certain speed vO of the combustion engine unit. This is illustrated with range A in Fig. 5. In this range the powertrain has thus to be driven by means of the electric motor unit 49 and hereby with electrical energy generated by the generator unit 44. For a certain combustion engine unit in the form of a diesel engine the lowest allowed rotational speed nO can for instance be in the order of 600 rpm and the speed vO in the order of 25 km/h. The range A illustrates the range where the rotational speed of the combustion engine unit is even at idle running too high for driving the vehicle and therefore the electric motor unit has to be used. Above a certain rotational speed nl and a certain speed vl of the combustion engine unit electrical driving by means of the electric motor unit 49 in the form of an induction motor is not possible since the induction motor at this rotational speed of the electrical motor unit and this speed no longer can provide for the power demand of the vehicle. The electric motor unit 49 loses hereby power and the combustion engine unit 42 has higher output power than the electric motor unit 49 can perform. This is illustrated with range B in Fig. 5. In this range the powertrain has thus to be driven mechanically by means of the combustion engine unit 42.

In all ranges between range A where only electrical driving by means of the electric motor unit 49 is possible and the range B where only mechanical driving by means of the combustion engine unit 42 is possible, electrical driving by means of the electrical motor unit and/or mechanical driving by means of the combustion engine unit is possible. The electrical driving is hereby performed via the electrical power path Al. The mechanical driving is hereby performed via the mechanical power path A2. Hereby, it is enabled between range A and range B to drive the powertrain electrically and/or mechanically and thus optimising the efficiency. For example, the rotational speed of the combustion engine unit can be set to another rotational speed when the clutch member is disengaged which facilitates optimising of the efficiency.

Thus the electric motor unit and/or the combustion engine unit can be used between nO and nl. At driving with the electrical motor unit it is hereby possible to accelerate at maximum power by means of the electric motor unit, whereas at driving with the combustion engine unit the power is depending on the torque characteristic of the engine. Simplified one can say that at completely "flat" torque curve M, that is the power increases linearly with increasing rotational speed, the output power of the combustion engine unit increases linearly with the rotational speed, that is at nO = (nl)/2 the power at nO is also equal to half of the power at nl. With the electric motor unit the power at nO can be equal to the power at nl (or even at n2), and therefore a faster acceleration can be achieved.

Hence, according to an embodiment, the driving torque provided to the powertrain is controlled in such a way that the powertrain is driven partially by means of said electric motor unit and said combustion engine unit in a power demand range between a lower power demand and a higher power demand for optimisation of the efficiency. Both the driving of the electric motor unit and the combustion engine are mechanically coupled to the speed of the vehicle when they are engaged.

The electric motor unit has a maximum torque from zero and can then drive with constant power, when the speed exceeds the level where maximum torque times speed is higher than available power, up to a certain speed which according to a variant is approximately half or 2/3 of the maximum power depending on the configuration, after which the power decreases.

The combustion engine unit has an idle rotational speed which corresponds to a speed of the vehicle, i.e. it is not possible to drive slower. It has simplified "flat" torque curve, i.e. the power increases linearly with increasing rotational speed. When the electric motor unit is engaged and the combustion engine unit is disengaged, the rotational speed of the combustion engine unit is disconnected and can be put on a point for maximum power. Thereafter the combustion engine unit is synchronised with the electric motor unit which is approximately done at rotational speed nl, and thereafter the combustion engine unit is mechanically engaged and/or mechanically disengaged. Fig. 6 illustrates schematically a block diagram of a method for controlling the powertrain of a vehicle according to an embodiment of the present invention. The powertrain comprises a combustion engine unit for mechanical driving of said powertrain, an electric motor unit arranged to be supplied with electrical energy for electrical driving of said powertrain as well as a generator unit driven by means of said combustion engine unit for generation of electrical energy, and means for controlling the powertrain of the vehicle.

According to an embodiment the method for controlling the powertrain of a vehicle comprises controlling SI the driving torque which is provided to the powertrain in such a way that the powertrain is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed; and that the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. With reference to Fig. 7 a diagram is shown of an embodiment of an arrangement 500. The control unit 100 which is described in relation to Fig. 2 can in one embodiment comprise the arrangement 500. The arrangement 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write-memory 550. The non-volatile memory 520 has a first memory part 530, wherein a computer program, such as an operative system, is stored for controlling functions of the arrangement 500. Further, the arrangement 500 comprises a bus- controller, a serial communication port, l/0-member(s), an A/D-converter, a time- and date input- and transmission unit, an event counter and a interruption controller (not shown). The non-volatile memory 520 has also a second memory part 540. A computer program P is provided which comprises controlling of the powertrain of a vehicle according to the inventive method.

The program P comprises routines for controlling the driving torque which is provided to the powertrain in such a way that the powertrain is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed; and that the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed. The program P can be stored in an executable way or in a compressed way in a memory 560 and/or in a read/write memory 550.

When it is written that the data processing unit 510 performs a certain function it should be understood that the data processing unit 510 performs a certain part of the program which is stored in the memory 560, or a certain part of the program which is stored in the read/write memory 550.

The data processing unit 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 is arranged to communicate with the data processing unit 510 via a data bus 514. To the data port 599, for instance links connected with the controlling unit 100 can be connected.

When data are received at the data port 599, it is temporarily stored in the second memory part 540. When the received input data temporarily have been stored, the data processing unit 510 is put in order to perform execution of code in a way described above.

The received signals on the data port 599 can be used of the arrangement 500 to control the driving torque which is provided to the powertrain in such a way that the powertrain is driven by means of said electric motor unit and hereby with electrical energy generated by means of said generator unit at a certain lower power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed; and that the powertrain is driven mechanically by means of said combustion engine unit at a certain higher power demand which is required for providing for a certain driving torque demand coupled to a certain propulsion rotational speed.

Parts of the methods described herein can be performed of the arrangement 500 with the help of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the arrangement 500 runs the program, the herein described methods are executed.

The description above of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing. It is not intended to be exhaustive or to limit the invention to the described variants. Obviously, many modifications and variations will be apparent for a person skilled in the art. The embodiments have been chosen and described for best explaining the principles of the invention and its practical applications, and thereby enable a person skilled in the art to understand the invention for different embodiments and with the different modifications which are useful for the intended use.