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1. WO2020115259 - MODULE DE PROPULSION HYBRIDE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

A HYBRID DRIVE MODULE

Technical Field

The present invention relates to a hybrid drive module, to an engine assembly comprising a hybrid drive module, to a hybrid vehicle and to a method for controlling a hybrid drive module.

Background

Hybrid powertrains for passenger cars are gaining interest and various solutions for such applications have been proposed during the recent years.

Especially it has been suggested to provide the hybrid functionality as a separate module which is added to the existing powertrain. One example of an existing hybrid drive module includes a first sprocket which is intended to be connected to the crankshaft of the internal combustion engine indirectly via a disconnect clutch arranged in series with a dual mass flywheel, and an electrical motor, preferably a 48V electrical motor, being drivingly connected to a second sprocket. The sprockets are connected by means of a belt, thus forming a belt drive, in order to allow for various driving modes such as pure electrical driving, recuperation, traction mode, and boost. In this prior art system the electrical motor, the flywheel, the clutch, and the belt drive are formed as a standalone module which can be added to an existing powertrain.

The hybrid drive module should be designed to fit with existing drivelines, and to provide desired performance to the vehicle. Bump start is one critical driving condition, i.e. when it is desired to get power from the non running internal combustion engine and when torque from the electrical motor is used to start the internal combustion engine. Due to the relative high inertia of the internal combustion engine the time required for performing a bump start may be relatively long, and it would be desirable to provide a hybrid drive module which allows for faster bump starts. It is also desired to provide a way of starting the internal combustion engine without significantly affecting the available power of the vehicle.

Summary

It is thus an object of the teachings herein to provide an improved hybrid drive module overcoming the disadvantages of prior art solutions.

According to a first aspect, a hybrid drive module is provided for connection to a powertrain of a vehicle, the hybrid drive module comprising an electrical motor connected with an upstream crankshaft of an associated internal combustion engine via at least one clutch and via at least one flywheel. The electrical motor being further connected with a downstream transmission via at least a

transmission clutch. At least one flywheel is arranged on a rotational shaft of the powertrain, the rotational shaft being connected to the powertrain by the transmission clutch and/or by the at least one clutch. The rotational energy of the rotational shaft is configured to be used to start the internal combustion engine. By allowing the rotational energy of the rotational shaft, which comprises at least one flywheel, to be used for starting the associated internal combustion engine can such an engine start be achieved without adversely affecting the propulsion of the vehicle.

The rotational shaft may at an upstream end be delimited by a first clutch and at a downstream end by the transmission clutch.

Furthermore, the electric motor may connect to the rotational shaft, allowing the electric motor to control the rotational velocity, and hence the rotational energy thereof in relation to the remaining powertrain.

The first clutch may further be a disc clutch, a conical clutch or a dog clutch.

The first clutch may comprise an actuating member controlling the connection state of the first clutch, the member being moveable from a connected first position having a conical clutch interface, to an intermediate disconnected position, and to a second connected position having a disc-shaped clutch interface. A conical clutch interface provides less noise-vibrations-harshness (NVH) related issues than a corresponding disc-clutch and excellent torque transfer ability. A disc-clutch may in some applications however be easier to control. The above configuration of the first clutch allows control of actuation thereof to apply the conical clutch and the disc clutch respectively when suitable. For instance, when slip is required in the first clutch is the disc clutch used, and when high torque transfer for a given axial load on the actuating member is preferred, the conical clutch interface is used.

In another embodiment, the first clutch may comprise an actuating member controlling the connection state of the first clutch, the member being moveable from a connected first position having a dog clutch interface, to an intermediate disconnected position, and to a second connected position having a disc-shaped clutch interface. The dog clutch interface is beneficial at times when no slip is required in the first clutch, and when high torque transfer is to be transferred.

The actuating member may further be spring biased into the first position, allowing the first position to be maintained and attained without active actuation by means of for instance hydraulic or electromechanical actuators.

The rotational shaft may at an upstream end be delimited by a first clutch and at a downstream end by a second clutch.

The electric motor may connect to an intermediate shaft delimited at a downstream end by the transmission clutch and at an upstream end by the second clutch.

The at least one flywheel arranged on the rotational shaft may further be a dual mass flywheel, providing reduction of vibrations as well as an increase in rotational inertia to the rotational shaft.

The hybrid drive may further comprise two flywheels, wherein a first flywheel being arranged on the rotational shaft.

Further still, a dual mass flywheel may be arranged on the intermediate shaft providing increased rotational inertia as well as a NVH-reduction to the powertrain.

A dual mass flywheel may further be arranged on the crankshaft.

The second clutch may be a disc clutch, a conical clutch or a dog clutch.

Furthermore, the electric motor may connect to the powertrain via a chain drive or the electric motor may be coaxially arranged on a shaft of the hybrid drive module.

The hybrid drive module may further comprise a housing at least enclosing the chain drive, at least one clutch and at least one flywheel.

In one embodiment, the transmission clutch forms a part of the hybrid drive module.

In a second aspect is an engine assembly provided, comprising an internal combustion engine and a hybrid drive module of the first aspect. A housing is at least partly formed by an end section of an engine block of said internal combustion engine.

In a third aspect is a hybrid vehicle provided, comprising an engine assembly according to the second aspect.

In a fourth aspect is a method provided for controlling a hybrid drive module according to the first aspect in order to start an internal combustion engine of an associated hybrid vehicle. The method comprises providing rotational velocity to the rotational shaft by the electric motor, and transferring rotational energy from the rotational shaft to the crankshaft of the internal combustion engine by at least partially engaging the first clutch. The internal combustion engine can thereby be started rapidly on demand without negatively effecting the propulsion of the vehicle.

In one embodiment, wherein the rotational shaft is at an upstream end delimited by a first clutch, and at a downstream end by a second clutch, the second clutch normally being disengaged during electric propulsion mode, the method comprises: when the vehicle is moving, providing rotational velocity to the rotational shaft by dragging forces through the second clutch, or by at least partially engaging the second clutch when the rotational shaft has a rotational velocity below a predetermined value. When the vehicle is at a standstill, providing rotational velocity to the rotational shaft by at least partially engaging the second clutch and by subsequently providing torque by the electric motor. Transferring rotational energy of the rotational shaft to the crankshaft of the internal combustion engine by at least partially engaging the first clutch, completely engaging the first clutch, and completely the second clutch completely.

In one embodiment, the providing of rotational velocity to the rotational shaft when the vehicle is moving and when the rotational shaft has a rotational velocity below a predetermined value further comprises providing additional torque by the electric motor when the second clutch is at least partially engaged, increasing the reliability of the engine start procedure during all driving conditions.

Brief Description of the Drawings

Embodiments of the teachings herein will be described in further detail in the following with reference to the accompanying drawings which illustrate non-limiting examples on how the embodiments can be reduced into practice and in which:

Fig. 1 shows a schematic outline of a hybrid drive module according to prior art;

Fig. 2 shows two diagrams representing speed and torque of the hybrid drive module shown in Fig. 1 during a cold start;

Fig. 3 shows two diagrams representing speed and torque of the hybrid drive module shown in Fig. 1 during a slip start;

Fig. 4 shows a schematic outline of a hybrid drive module according to an embodiment;

Fig. 5 is a cross-sectional view of parts of the hybrid drive module shown in Fig. 4;

Fig. 6 shows two diagrams representing speed and torque of the hybrid drive module shown in Fig. 4 during a cold start;

Fig. 7 shows two diagrams representing speed and torque of the hybrid drive module shown in Fig. 4 during a slip start;

Fig. 8 shows a schematic outline of a hybrid drive module according to an embodiment;

Fig. 9 shows a schematic outline of a hybrid drive module according to an embodiment;

Fig. 10 shows a schematic outline of a hybrid drive module according to an embodiment;

Figs 11 to 13 show cross-sectional views of parts of the hybrid drive module according one embodiment;

Fig. 14 shows a diagram of the torque transfer over the first clutch according to the embodiment shown in Fig 11 to 13;

Figs. 15 to 17 show cross-sectional views of parts of the hybrid drive module;

Fig. 18 shows a diagram of the torque transfer over the first clutch according to the embodiment shown in Figs. 15 to 17;

Fig. 19 shows a schematic flowchart of a method for controlling a hybrid drive module to start an associated internal combustion engine; and

Fig. 20 shows a diagram of a hybrid drive module starting sequence of an associated internal combustion engine.

Detailed Description

Starting in Fig. 1 a schematic layout of a prior art engine assembly 10 of a vehicle is shown. The vehicle is typically a passenger car, and the engine assembly comprises an internal combustion engine 20 and a hybrid drive module 100 according to an embodiment. As will be explained in the following the hybrid drive module 100 is mechanically connected to a crankshaft 22 of the internal combustion engine 20 in order to provide additional drive torque to a transmission 300 arranged in series with the hybrid drive module 100. Hence, the transmission is also connected to the crankshaft 22 as is evident from Fig. 1.

The hybrid drive module 100 comprises an electrical motor 110 and a chain drive 120 connecting the electrical motor 110 with the crankshaft 22. The electrical motor 110 is for this purpose driving a first sprocket 122 of the chain drive 120, whereby upon activation of the electrical motor 110 rotational

movement of the first sprocket 122 is transmitted to a second sprocket 124 of the chain drive 120 via a chain 126.

The second sprocket 124 is drivingly connected to the crankshaft 22 via a coupling. In the embodiment shown in Fig. 1, the second sprocket 124 is connected to the output of a disconnect clutch 130 receiving driving torque from a dual mass flywheel 140. For parallel two-clutch systems, commonly denoted hybrid P2 systems, the disconnect clutch 130 is often referred to as the CO clutch. The dual mass flywheel 140 receives input torque directly from the crankshaft 22

Also illustrated in Fig. 1 is a further optional clutch 150, here

representing a launch clutch, or a transmission clutch. Again referring to P2 systems, the transmission clutch is often referred to as the Cl clutch. The transmission clutch 150 is arranged downstream, i.e. on the output side of the hybrid drive module 100 upstream the transmission. It should be realized that the transmission clutch 150 could be replaced by a torque converter or similar.

The electrical motor 110 is preferably a 48V motor / alternator which thus can be used to provide hybrid functionality to the existing powertrain of the vehicle.

Operation of the prior art hybrid drive module will now be described with reference to Figs. 2 and 3.

In Fig. 2 a cold/bump start is illustrated by the diagrams. At time t=0.2 s the electrical motor 110 is activated by applying a torque of approximately 120 Nm whereby the rotational speed of the electrical motor 110, and hence the rotational shaft DFM2-secondary (see Fig. 1) is increased up to approximately 2900 rpm. Slightly after t=0.8 s the clutch 130 is engaged whereby the rotational speed of DMF2-secondary decreases rapidly as the clutch 130 transfers rotational motion to the dual mass flywheel 140, and hence the rotational shaft DMF2-primary (see Fig. 1). The output of the dual mass flywheel 140, i.e. the rotational shaft DMF1 (see Fig. 1) will also start to rotate by increasing the rotational speed until the clutch 130 provides no rotational speed difference between DMF2-secondary and DMF2-primary approximately at t=l s, at which time the internal combustion engine 20 is started. At this point the electrical motor 110 is deactivated, and the variations of the speed of DMF 1 are caused by the crank shaft 22 being driven by the internal combustion engine 20. According to this particular embodiment approximately 1 second will consequently be required to accelerate the crankshaft 22 and to start the internal combustion engine 20.

In Fig. 3 a slip start is illustrated by the diagrams. At t=15 s the torque request from the driver is increased. Following this the electrical motor 110 is activated thus accelerating the rotational shaft DMF2-secondary up to

approximately 2000 rpm at t= 15.2 s. At this point the clutch 130 is engaged whereby DMF2-primary accelerates to reach the speed of DMF2-secondary. Also at this point the internal combustion engine 20 delivers a certain torque to the driveline until the rotational speed of DMF2-secondary reaches the speed of the gearbox input shaft, i.e. on the output side of clutch 150. At this point the torque of clutch 130 is reduced while the torque from the internal combustion engine 20 is slightly increased. Slightly after t= 15.4 s, when the rotational speeds of DMF 1, DMF2-primary, and DMF2-secondary are substantially the same, the electrical motor 110 is deactivated and the clutches 130, 150 are engaged further until the torque from the internal combustion engine 20 reaches the torque request from the driver.

Now turning to Fig. 4 an embodiment of a hybrid drive module 200 is shown. Compared to the hybrid drive module 100 described with reference to Fig. 1 the first clutch 230 of the hybrid drive module 200 is positioned between the internal combustion engine 20 and the dual mass flywheel 240. A rotational shaft 280 is thus formed, which is delimited upstream by the first clutch 230 and downstream by the transmission clutch 250. The transmission clutch 250 connects the transmission input shaft 310 with the rotational shaft 280. The transmission clutch 250 may be controlled by an actuator, by an electronic clutch system, and/or by means of operator input via a clutch pedal.

A primary inertial mass 242 of the dual mass flywheel 240 is connected to a rotational shaft 280, to which the second sprocket 224 carrying the chain 226 is also connected. The primary inertia mass 242 is connected to a secondary inertial mass 244 also forming part of the dual mass flywheel 240. The secondary inertial mass 244 is in turn coupled to one side of the first clutch 230. The other side of the clutch 230 is connected to the crankshaft 22.

Preferably, one or more springs may be provided connecting the internal masses 242, 244 to each other such that the secondary inertial mass 244 may rotate relative the primary inertial mass 242 whereby the springs may deform causing a reduction of torsional vibrations being transmitted from the internal combustion engine 20.

The dual mass flywheel 240 and the clutch 230 are arranged

concentrically with the crankshaft 22, thereby reducing the axial length of the hybrid drive module 200.

A cross-sectional view of the hybrid drive module 200 is shown in Fig. 5. Here it is evident that the clutch 230 and the dual mass flywheel 240 are stacked in a radial direction in a concentric manner, which provides for a very compact unit having a reduced axial length. As is shown in Fig. 5 the clutch 230 is a disc clutch; however the clutch 230 may in some embodiments be realized as a cone clutch, especially for applications where it is desired to reduce rattle noise. Such solution will also allow for no axial force on the crankshaft 22 when the clutch 230 is disconnected. The various embodiments of the first clutch 230 will be discussed further in relation Figs 11-18.

In Fig. 6 a cold/bump start is illustrated by the diagrams, performed using the hybrid drive module 200 shown in Figs. 4 and 5. The cold start is used when the associated vehicle is essentially at a standstill. At time t=0.2 s the electrical motor 210 is activated by applying a torque of approximately 120 Nm whereby the rotational speed of the electrical motor 210, and hence the rotational shaft 280 (see Figs. 4-5) is increased up to approximately 1900 rpm. Due to the arrangement of the hybrid drive module 200, the entire dual mass flywheel 240 will rotate and the rotational shaft 280 will consequently attain a considerable rotational energy. Slightly after t=0.7 s the clutch 230 is at least partially engaged whereby the rotational speed of the rotational shaft 280 (i.e. the rotational speed of the dual mass flywheel 240) decreases rapidly as the clutch 230 transfers rotational energy to the crankshaft 22. Upon this the internal combustion engine 20 is rapidly started, as the rotational inertia of the rotational shaft 280 together with the flywheel 240 is significant in relation to the inertia of the crankshaft 22 and the components connected thereto. Immediately after that the engine 20 is started the electrical motor 210 is deactivated. The clutch 230 is further controlled to provide for a minimum slip across the clutch 230, as is shown in the diagram. According to this particular embodiment approximately 0,8 s will consequently be required to accelerate the crankshaft 22 and to start the internal combustion engine 20; compared to the embodiment described with reference to Figs. 1-3 a reduction of almost 20% is obtained.

In Fig. 7 a slip start is illustrated by the diagrams, performed using the hybrid drive module 200 shown in Figs. 4 and 5. The slip start is used when the vehicle is moving. At t= 15 s the torque request from the driver is increased.

Following this the electrical motor 210 is activated thus accelerating the rotational shaft 280 up to approximately 1600 rpm at approximately t= 15.15 s. A certain slip is allowed temporarily over the transmission clutch 250 to allow the rotational shaft 280 to increase its velocity over that of the transmission input shaft 310, as shown in Fig. 7. At this point the clutch 230 is engaged whereby the built up rotational energy in the rotational shaft 280 is transferred to the crankshaft 22. The turning of the crankshaft 22 induces an engine start and the crankshaft 22 eventually accelerates to reach the speed of the transmission input shaft 310. The internal combustion engine 20, once started, delivers a certain torque to the driveline facilitating that the rotational speed of the crankshaft 22 reaches the speed of the transmission input shaft 310, i.e. on the output side of clutch 250. Slightly after t= 15.25 s, when the rotational speeds of the rotational shaft 280 and the crankshaft 22 are substantially the same, the electrical motor 210 is deactivated and the clutches 230, 250 are engaged further until the torque from the internal combustion engine 20 reaches the torque request from the driver. Also this start sequence is substantially faster than the slip start described with reference to Fig. 3.

The hybrid drive module 200, having the dual mass flywheel 240 arranged on the rotational shaft 280 delimited by the transmission clutch 250 and the clutch 230, and to which the electric motor 210 connects, will provide a number of advantages. For example, it is possible to provide a more compact assembly with improved torque accuracy. Additionally, it is possible to reduce the risk for transmitting oscillations to the driveline. It will also be possible to provide a disconnect functionality with built-in speed reduction, thereby decreasing the axial force acting on the crankshaft 22. It is to be realized that while the electric motor 210 in all embodiments is shown as being connected to the powertrain via a chain drive 220, it may just as well be arranged directly on the powertrain in a coaxial manner. This may be achieved for instance by attaching the rotor of the electric motor 210 to the rotational shaft 280.

Turning now to Fig. 8, another embodiment of a hybrid drive module 200 is shown. The embodiment shown in Fig. 8 shares many features with the embodiment shown in Fig. 4, whereby the following description will focus mainly on the differing features. The general idea of the hybrid drive module 200 of Fig. 8 corresponds to that of Fig. 4, i.e. using the rotational energy of a rotational shaft 280 to facilitate starting of the internal combustion engine 20. However, in the embodiment shown in Fig. 8, an additional clutch 260 is provided. The first clutch 230 and the second clutch 260 delimit the rotational shaft 280, and a flywheel 240 is attached to the rotational shaft 280 between the first clutch 230 and the second clutch 260. The electric motor 210 may connect directly (coaxially) or via a chain drive 220 (as is the case for all embodiments shown in Figs. 8 to 10) to an intermediate shaft 281, the intermediate shaft being downstream of the rotational shaft 280 and delimited by the second clutch 260 and the transmission clutch 250.

The two operating scenarios, i.e. bump/cold start and slip start, for starting the internal combustion engine 20 will now be described separately.

For a cold start scenario, i.e. when the associated vehicle is at a standstill, firstly the second clutch 260 will engage. When the second clutch 260 is engaged, intermediate shaft 281 is rotationally connected to the rotational shaft 280. After this, the electric motor 210 will provide a rotational velocity to the intermediate shaft 281 and thus also to the rotational shaft 280, which builds up rotational energy rapidly. When a certain RPM threshold is reached, the first clutch 230 will be partially engaged allowing a smooth transfer of the built up rotational energy in the intermediate shaft 281 and the rotational shaft 280 to the crankshaft 22. The crankshaft 22 will then begin to rotate, thus starting the internal combustion engine 20. Once the rotational shaft 280 and the crankshaft 22 are synchronized, the first clutch 230 may be engaged fully. The electric motor 210 may be shut down once the RPM threshold mentioned above is reached or when the internal combustion engine 20 is determined to be started, for instance by measuring the crankshaft RPM or the torque output therefrom depending on the application. With the internal combustion engine 20 started, it will, when the transmission clutch 250 is engaged, provide propulsive force to the wheels of the vehicle.

Since the electric motor 210 only has to achieve a rotational velocity of the intermediate shaft 281 and the rotational shaft 280, and not the entire crankshaft 22 and all rotating/reciprocating components of the engine 20, it is able to more quickly achieve the required RPM threshold and the load on the electric motor 210 can be reduced. The RPM threshold is adjustable by altering the mass of the flywheel 240. In addition, the configuration depends on the associated internal combustion engine 20 in relation to the mass of the flywheel 240. For instance, a large displacement engine with many cylinders may require a heavier flywheel 240 and/or a higher threshold RPM. It is also possible to use the electric motor 210 directly for starting the engine 20 by also engaging the first clutch 230, as this will directly connect the rotation of the electric motor to that of the internal combustion engine 20.

Turning now to the slip start scenario, i.e. when the vehicle is in electric mode and the electric motor 210 alone provides the propulsive force to the vehicle when a demand for a start of the internal combustion engine 20 arises.

The transmission clutch 250 is engaged to allow the electric motor 210 to drive the wheels of the vehicle, and the intermediate shaft 281 rotates with the rotational velocity of the input shaft to the transmission 300. It is desired to be able to start the internal combustion engine 20 without affecting the available power from the electric motor 210 that is usable for propulsion. This should preferably be achieved for essentially any driving condition, i.e. both for high RPMs as well as high torque outputs. The embodiments shown in Fig. 8 solves this problem by configuring the second clutch 260 such that dragging forces in the clutch 260, which is normally not engaged during electric drive mode, will cause the rotational shaft 280 to essentially rotate with the intermediate shaft 281, albeit with a slight delay during rapid accelerations/decelerations. The dragging forces also provide a slight dampening of vibrations during electric mode.

When it is requested that the internal combustion engine 20 is to be started, the rotational shaft 20 already rotates with a RPM higher than the threshold RPM due to the dragging forces. The mass of the flywheel 240 is adapted such that the rotational energy of the rotational shaft 280 is sufficient for starting the engine 20 over essentially the entire spectrum in which the vehicle operates. However, if it is detected that the rotational energy for some reason is insufficient for starting the engine 20, the electric motor 210 may assist to provide additional power to the crankshaft 22. This may be achieved by engaging the second clutch 260 at least partially and/or for instance by allowing a certain slip in the transmission clutch 250 as described in relation to the first

embodiment, whereby the rotational energy of the intermediate shaft 281 and the rotational shaft 280 can be increased by the electric motor 210 to a sufficient level for starting the engine 20.

During normal slip starts, the rotational energy of the rotational shaft 280 generated by the dragging forces over the second clutch 260 is transferred to the crankshaft 22 by engaging the first clutch 230, preferably partially such that a smooth transfer occurs. The first clutch 230 may be held in partial engagement until the rotational shaft 280 and the crankshaft 22 are synchronized or in some embodiments until the crankshaft 22 and the transmission input shaft 310 are synchronized, after which the first clutch 230 is completely engaged. The second clutch 260 is engaged once the crankshaft 22 is synchronized with the

transmission 300 input shaft.

The first clutch 230 and the second clutch 260 may be actuated by the same actuator, wherein a spring provides a biasing force that holds the second clutch 260 in a disengaged state. When the actuator presses on the clutches 230, 260, the first clutch 230 will engage first and when the force of the spring is overcome, the second clutch 260 will start to engage. Preferably is the force of the spring selected such that approximately 70 Nm of torque is transferable by the first clutch 230 when the second clutch 260 starts to engage.

The second clutch 260 may further be realized as a disc clutch, a cone clutch or as a dog clutch, the disc clutch naturally provides adjustability and does not require complete synchronization when being engaged. However, a disc clutch is susceptible to wear and may limit torque output, and in these aspects is a dog clutch is superior.

Different embodiments of the first clutch 230 will be further discussed in relation to Figs 11-17.

Turning now to Fig. 9, another embodiment of the hybrid drive module 200 is shown. The principle of operation for a cold start and a slip start for hybrid drive module of the embodiments shown in Figs. 9 and 10 is essentially the same as for the embodiment shown in Fig. 8, whereby the above description is applicable also these embodiments.

The hybrid drive module 200 shown in Fig. 9 comprises an intermediate shaft 281 to which the dual mass flywheel 240 is attached. Downstream of the flywheel 240 is the electric motor 210 connected to the intermediate shaft 281, although as mentioned the electric motor 210 may be arranged coaxially on the intermediate shaft 281 as well. The intermediate shaft 281 is in the downstream direction delimited by the transmission clutch 250 and in the upstream direction by the second clutch 260. The rotational shaft 280 comprises a second flywheel 270, which may be a dual mass flywheel or another type of flywheel as well. The rotational shaft 280 connects to the intermediate shaft 281 via the second clutch 260 and to the crankshaft 22 of the engine 20 via the first clutch 230. The flywheel 240 arranged on the intermediate shaft 281 turns with the intermediate shaft 281 during electric mode as well as during internal combustion engine mode and thus efficiently reduces vibrations and evens out the power delivery during each mode. The flywheel 270 arranged on the rotational shaft 280 provides the rotational energy that is required for starting the engine 20, as discussed in relation to Fig. 8.

Turning now to Fig. 10, where one further embodiment of the hybrid drive module 20 is shown. The intermediate shaft 281, as in the embodiment of Fig. 8, does not comprise a flywheel. The electric motor 210 however, as for all the embodiments in Figs. 8-10, connects to the intermediate shaft 281. The intermediate shaft 281 is in the downstream direction delimited by the

transmission clutch 250 and in the upstream direction by the second clutch 260. The rotational shaft 280 connects to the intermediate shaft 281 via the second clutch 260 and to the crankshaft 22 of the engine 20 via the first clutch 230. A flywheel 270 is arranged on the rotational shaft 280, the flywheel may be a dual mass flywheel 270 or another type of flywheel as well. Another flywheel 240 is arranged on the crankshaft 22 of the engine 20. The mass of the flywheel 270 arranged on the rotational shaft 280 may be higher than that of the flywheel 240 arranged on the crankshaft 22, and thus allowing the rotational energy stored in the rotational shaft 280 to translate into a sufficient rotational velocity of the crankshaft 22 to start the engine 20.

Turning now to Figs 11 to 13, an embodiment of the first clutch 230 is shown. The clutch 230 connects the crankshaft 22 with a flywheel 240, 270, shown here in the shape of a dual mass flywheel 240. The first clutch 230 comprises an actuating member 231 that is axially moveable between two axial end positions. Shown in Fig. 11, the actuating member 231 is in an engaged position where the clutch interface is conical. The actuating member 231 is biased into this position by a spring, such that the clutch 230 is kept engaged by the force of the spring. The cone shaped clutch interface provides a larger possible torque transfer and is less susceptible to noise, vibrations and harshness (NVH) problems than its disc counterpart is. However, the engagement and slippage is more difficult to control. This equates to that the conical clutch interface is well suited for use when the internal combustion engine 20 provides the propulsive power to the vehicle, as slippage is not desired and a high torque tolerance is required.

In Fig. 12, the actuating member 231 is shown in a disconnected or non-engaged position between the two axial end positions. The actuating member 231 is kept in this position when the electric motor 210 provides the propulsive power to the vehicle, as the internal combustion engine 20 thus is disconnected from the powertrain.

In Fig. 13, the actuating member 231 is shown in a position providing a disc clutch interface between the crankshaft 22 and the flywheel 240. This is the position that the actuating member 231 attains during a start sequence of the internal combustion engine 20. As it is important to be able to control the slip and torque transfer over the clutch 230 during the engine start sequence, the disc clutch provides this ability to the hybrid drive module 20. The disc clutch interface may comprise one or several clutch discs. Once the engine 20 is started and the synchronization as described above is achieved, the actuating member may be moved into the position shown in Fig. 11.

Fig. 14 shows the torque transfer over the clutch 230 when the actuating member 231 moves from one axial end position to the other, with the torque transfer changing gradually in both directions.

In Figs. 15 to 17 another embodiment of the first clutch 230 is shown. As for the embodiment shown in Figs. 11 to 13, the clutch 230 comprises an axially moveable actuating member 231. In Fig. 15, the actuating member 231 is shown in a position used when the internal combustion engine 20 provides the propulsive power to the vehicle. The interface between the actuating member 231 and the flywheel 240 is in the shape of a dog clutch. The dog clutch interface is beneficial as it not as susceptible to wear as a disc clutch configuration is and as it may cope with a higher torque output than a friction clutch. The dog clutch interface however requires a relatively high accuracy of the synchronization between the crankshaft 22 and the flywheel 240 for allowing acceptable connection/engagement. The actuating member 231 may be spring biased as the embodiment shown in Figs 11 to 13.

In Fig. 16, the actuating member 231 is shown in a disconnected or disengaged position. The actuating member 231 is kept in this position when the electric motor 210 provides the propulsive power to the vehicle, as the internal combustion engine 20 thus is disconnected from the powertrain.

Fig. 17 shows the actuating member 231 in a position providing a disc clutch interface between the crankshaft 22 and the flywheel 240, which is used during the engine start sequence as is described in relation to Fig. 13.

Fig. 18 shows the torque transfer over the clutch 230 when the actuating member 231 moves from one axial end position to the other. The dog clutch off-course provides an on-off characteristic to the clutch 230, and the disc clutch on the other hand allows for a variable torque transfer through the clutch 230.

Fig. 19 shows a schematic outline of a method for controlling the hybrid drive module for starting the internal combustion engine 20. The method comprises the steps of providing 1001 rotational velocity to the rotational shaft 280 by the electric motor 210. Subsequently is at least a part of the rotational energy attained by the rotational shaft 280 transferred 1002 from the rotational shaft 280 to the crankshaft 22 of the internal combustion engine 20 by at least partially engaging the first clutch 230, whereby the engine 20 is started.

The starting sequence is different depending on whether the associated vehicle is at a standstill or is moving. The method comprises providing 1001

rotational velocity to the rotational shaft 280 by the electric motor 210. When the vehicle is moving, this may be achieved, as is earlier mentioned, preferably by the dragging forces through the disengaged/disconnected second clutch 260. As an alternative when it is determined that the rotational shaft 280 has a rotational velocity below a predetermined value, it may be achieved by at least partly engaging the second clutch 260. Hence it is ensured that sufficient rotational energy for starting the engine 20 is present in the rotational shaft 280. The latter scenario typically occurs at very slow speeds. In order for the vehicle to avoid losing momentum and/or to avoid that the operator of the vehicle notices a drop in power, the electric motor 210 may provide additional torque to the powertrain when the second clutch 260 is engaged.

When the vehicle is at a standstill, the rotational velocity is provided 1001b to the rotational shaft 280 by engaging the second clutch 260 and by subsequently providing torque from the electric motor 210. This causes the rotational shaft 280 to accelerate to a sufficiently high rotational velocity.

In either of the two scenarios, i.e. both when the vehicle is moving and when the vehicle is at a standstill, the rotational energy is subsequently transferred 1002 from the rotational shaft 280 to the crankshaft 22 of the internal combustion engine 20 by at least partly engaging the first clutch 230. The first clutch 230 is subsequently fully engaged 1002a, either when the crankshaft 22 reaches the RPM of the transmission 300 input shaft 310, or when the crankshaft 22 reaches the RPM of the rotational shaft 280. The second clutch 260 is also subsequently fully engaged 1002b. This preferably occurs when the crankshaft 22 and the transmission input shaft 310 is synchronized in cases where the vehicle is moving.

This is further illustrated in Fig. 20, where the actuation of the first clutch 230 and the second clutch 260 is shown during a start sequence when the associated vehicle is moving.

The upper line shows how the transmission input shaft 310 is rotating with an essentially constant RPM. The dotted line representing the RPM of the rotational shaft 280 is shown initially following that of the transmission input shaft 310. The crankshaft 22 is shown being zero. Neither of the first 230 and the second clutch 260 is engaged. This is essentially the state of the hybrid drive module 200 during electric mode, when the electric motor 210 alone provides propulsive power to the associated vehicle.

At, or slightly before, time Ti, a request for a start of the internal combustion engine 20 is determined. This entails that the first clutch 230 is

partially applied, causing a transfer of rotational energy from the rotational shaft 280 to the crankshaft 22. The rotational shaft 280 RPM thus decreases, while the crankshaft 22 RPM increases until synchronization between the two occurs. This process should preferably be smooth, which is achieved by the actuation of the first clutch 230. At this point, the crankshaft 22 has attained sufficient RPM for the engine 20 to on its own continue the starting sequence and increase the RPM until, at T2, synchronization is achieved between the crankshaft 22 and the transmission input shaft 310. At T2, the first clutch 230 is completely engaged, as is the second clutch 260. However, the first clutch 230 may also be completely engaged once synchronization between the crankshaft 22 and the rotational shaft 280 is achieved, or at any time-point therefrom until T2.

For other embodiments, also possible within the scope of this

application, high voltage hybrid electrical motors may be utilized. More specifically, the provision of the chain drive 220 or the coaxial arrangement of the electric motor 210 allows for modularity with high voltage hybrid electrical motors in comparison to if a belt drive would be used. A belt drive could never accommodate the much higher loads provided by a more powerful high voltage hybrid electrical motor.

It should be mentioned that the improved concept is by no means limited to the embodiments described herein, and several modifications are feasible without departing from the scope of the appended claims.