A powertrain for a vehicle

Abstract

A powertrain for a vehicle has four power units, comprising two engines and two power sinks (one of which is a drivetrain) At least three clutches are provided in couplings between pairs of the power units, and they are independently controllable to engage or disengage the couplings. This provides a flexible coupling of power sources (such as the engines) to the power sinks (such as the drivetrain).

Description

A POWERTRAIN FOR A VEHICLEFIELD

[0001] Embodiments of the present disclosure relate generally to the driving of vehicles, such as agricultural vehicles. In particular, it relates to a powertrain for a vehicle which includes multiple power sources (engines) and multiple power consuming units, such as the main drivetrain of the vehicle and other powered accessories.BACKGROUND

[0002] Agricultural vehicles place particular demands on the powertrain used to supply power to the units to be powered. A primary power unit is the drivetrain, for delivering motive force to move the vehicle, but there are secondary power units such as a hydraulic system and a power take off (PTO) shaft. The drivetrain also has different requirements for different uses, such as different speed and torque requirements for road driving or during agricultural / off-road uses.

[0003] There is therefore a need for a powertrain that can deliver power in a flexible and adaptable manner.

[0004] There is also a desire to replace internal combustion engines with electric motors. One known approach is to provide multiple electric motors, whereby separate motors can perform power delivery to loads separately, or else power can be combined from the separate motors. For example, EP3927571 discloses a powertrain in which two electric motors are used to drive an output shaft. They can drive the shaft separately or jointly by means of an arrangement of clutches. However, the flexibility to drive additional loads is limited.

[0005] There is a need for a powertrain design with increased flexibility and versatility.BRIEF SUMMARY

[0006] The scope of this disclosure is defined by the claims.

[0007] According to examples in accordance with this disclosure, there is provided a powertrain for a vehicle, the powertrain comprising:

[0008] first to fourth power units, wherein the first power unit comprises a first engine, the second power unit comprises a first power sink in the form of a vehicle drivetrain, the third power unit comprises a second engine and the fourth power unit comprises a second power sink;

[0009] a first clutch providing a first coupling between the first and second power units;

[0010] a second clutch providing a second coupling between the second and third power units;

[0011] a third clutch providing a third coupling between the fourth and first power units; and

[0012] a fourth coupling between the third and fourth power units,

[0013] wherein the first to third clutches are independently controllable to engage or disengage the first to third couplings.

[0014] This powertrain arrangement provides flexibility in coupling power between two power sources and two power sinks. Each clutch provides a coupling between one power unit e.g. a power source and another power unit e.g. a power sink. However, the arrangement of three clutches for example enables the same power source and power sink to be connected by the other two clutches. The independent clutch control enables two power source - power sink pairs to be connected independently, or else it enables two power sources to be connected together to deliver power to one or both of the power sinks. This is of particular interest when the powertrain is for delivering power to power sinks having very different loads, such as a drivetrain at low speeds, a drivetrain at high speeds, a hydraulic load, a PTO etc. Power sinks may also be referred to herein as consumers or loads.

[0015] The layout is especially useful in the case if one power sink (e.g. the drivetrain) uses a wide speed range (e.g. 0-6000 rpm) and another power sink (e.g. an auxiliary consumer such as a hydraulic pump) has a narrower speed range in which it can be operated (e.g. 500-3000 rpm), and if the other power sink has to be run all the time when the vehicle is in motion (e.g. hydraulic pump providing hydraulic flow / power to a hydraulic steering system).

[0016] Additionally, auxiliary consumers such as a hydraulic pump can be run in their most favorable speed range regarding efficiency. In the case of an electric tractor, it can increase the operating time of the tractor.

[0017] Each clutch is part of a selectively engageable torque transmission path. A clutch is any device that enables the transfer of torque to be selectively engaged and disengaged. The drivetrain is connected to at least one axle of the vehicle. The independent control of the clutches means that each of the associated torque transmission paths is selectively engageable in combination with any one or more of the other torque transmission paths.

[0018] It is noted that there may be other components in addition to the clutch, in particular gearing, in the couplings between a pair of power units. For example, the first coupling between the first power unit (engine) and the second power unit (drivetrain) may include a gear train. Similarly, the fourth coupling between the third power unit (e.g. a second engine) and the fourth power unit (e.g. auxiliary drive shaft) may also include gearing.

[0019] The third power unit and the fourth power unit may be couplable by the fourth coupling independently of the first to third couplings. Accordingly, the third and fourth power unit may be coupled to each other by the fourth coupling and power may be transmitted between the third and fourth power unit while the first to third couplings are disengaged. No power may be transmitted between the power units by the disengaged first to third couplings.

[0020] The independent coupling of the power units through the first to fourth couplings may provide a high level of flexibility and adaptability for the powertrain to deliver power.

[0021] There are two power engines (which may be internal combustion engines or electric motors or a combination) and two consumer loads. Of course, an engine may also function as a load, for example if an electric motor is being used in regenerative mode.

[0022] The flexibility of the powertrain arrangement enables the two engines to perform alternative functions, or to combine their power outputs to drive one or both of the power sinks.

[0023] A gear ratio and / or function of torque versus speed between the first engine and the vehicle drivetrain when the first clutch is engaged is preferably different to that between the second engine and the vehicle drivetrain when the second clutch is engaged.

[0024] Thus, the powertrain can be used to implement different gearing by selecting which engine is coupled to the drivetrain.

[0025] The powertrain is for example selectively configurable for operation in operative states in which:

[0026] a. the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the second and third clutches and the fourth coupling; and

[0027] b. the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the first and third clutches and the fourth coupling.

[0028] These two operating modes enable both loads to be driven by both engines, but different gear ratios may be achieved.

[0029] The powertrain is for example selectively configurable for operation in an operative state in which:

[0030] c. the first engine is coupled only to the vehicle drivetrain via the first clutch, and / or the second engine is coupled only to the second power sink via the fourth coupling.

[0031] Thus, each engine may be used to drive only one load.

[0032] The powertrain is for example selectively configurable for operation in operative states in which:

[0033] d. the first engine is coupled simultaneously to both of the vehicle drivetrain and the second power sink via the first and third clutches respectively; and

[0034] e. the second engine is coupled simultaneously to both of the vehicle drivetrain and the second power sink via the second clutch and fourth coupling respectively.

[0035] Thus, each engine may be used to drive both loads (if the fourth coupling is a permanent coupling, the second engine will always be connected to the second power sink).

[0036] The powertrain of may be selectively configurable for operation in an operative state in which:

[0037] f. the first and second engines are both coupled simultaneously only to the second power sink via the third clutch and fourth coupling respectively.

[0038] In one implementation, the fourth coupling comprises a permanent coupling.Thus, there are three clutches, and a permanent coupling between the second engine and the second power sink. A three-clutch design can achieve the operating states explained above.

[0039] In another implementation, the powertrain further comprises:

[0040] a fourth clutch providing the fourth coupling between the third and fourth power units,

[0041] wherein the first to fourth clutches are independently controllable to engage or disengage the first to fourth couplings.

[0042] This provides further flexibility in coupling power between the two engines and the two power sinks. In particular, it enables the couplings to the two engines to be independent.

[0043] With four clutches, the powertrain arrangement may comprise a first engine, a second engine, a primary driven output shaft operatively connected to at least one axle of the vehicle, an auxiliary driven output shaft operatively connected to at least one consumer, and an arrangement for selectively transmitting motive power from the engines to the driven output shafts. The arrangement defines a first selectively engageable torque transmission path between the first engine and the primary driven shaft, a second selectively engageable torque transmission path between the second engine and the primary driven shaft, a third selectively engageable torque transmission path between the first engine and the auxiliary driven shaft and a fourth selectively engageable torque transmission path between the second engine and the auxiliary driven shaft.

[0044] Each of the first, second, third, and fourth selectively engageable torque transmission paths in this arrangement comprises a respective clutch selectively engageable to enable torque transmission along the respective torque transmission path. The arrangement is configured such that each of the first, second, third, and fourth torque transmission paths is selectively engageable independently of the other torque transmission paths. Each of the first, second, third, and fourth torque transmission paths is selectively engageable in combination with any one or more of the other of the first, second, third, and fourth torque transmission paths.

[0045] For a four-clutch arrangement, the powertrain is for example selectively configurable for operation in a further operative state in which:

[0046] g. the first engine is coupled only to the second power sink via the third clutch, and the second engine is coupled only to the vehicle drivetrain via the second clutch.

[0047] The powertrain is for example selectively configurable for operation in an operative state in which:

[0048] h. the first and second engines are both coupled simultaneously only to the vehicle drivetrain via the first and second clutches respectively.

[0049] Thus, by enabling the fourth coupling to be selectable, additional modes of operation are enabled.

[0050] The first engine is for example directly connected to an input of a first ratio unit, the second engine is connected to an input of a second ratio unit through the fourth clutch, the first clutch is between an output of the first ratio unit and the vehicle drivetrain, the second clutch is between the second engine and the drivetrain, and the third clutch is between the input of the first ratio unit and the output of the second ratio unit.

[0051] This provides a particular implementation with two ratio units. The ratio units are for example gear trains, although other torque transfer systems may be used, such as chains or belts. It enables different ratios to be implemented. The first ratio unit may have a selectable gear ratio between the input and output, for example selectable between two values.

[0052] The first and third power units for example each comprise an electric motor.

[0053] Thus, the arrangement enables implementation of an electric vehicle such as an electric tractor with a flexible use of the electric power from two electric motors.

[0054] The fourth power unit for example comprises an auxiliary output shaft. The auxiliary output shaft is for example for driving a PTO and / or a hydraulic pump. When the auxiliary output shaft is for driving a hydraulic pump, a fifth clutch may be provided between the auxiliary output shaft and a PTO.

[0055] At least two of the first coupling, the second coupling, the third coupling, and the fourth coupling may be drivingly interconnectable. The first and third couplings may be drivingly interconnectable. The third and fourth couplings may be drivingly interconnectable. The second and fourth couplings may be drivingly interconnectable. The first and second couplings may be drivingly interconnectable. The first coupling, the second coupling, the third coupling,and the fourth coupling may all be drivingly interconnectable in a series such that drive from each power source can be selectively transmitted to each power sink through either one of at least two different torque transmission pathways.

[0056] The examples above make use of two engines, such as two electric motors.However, the powertrain may be used in a hybrid machine, in which case there may be an internal combustion engine additional to two electric motors. An output shaft of the internal combustion engine is for example operatively coupled via a further clutch to the second or fourth power unit.

[0057] This disclosure also provides an agricultural machine comprising the powertrain as defined above.BRIEF DESCRIPTION OF THE DRAWINGS

[0058] One or more embodiments of this disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0059] Fig. 1 shows in conceptual form two possible layouts of a powertrain;

[0060] Fig. 2 shows one particular configuration in which the fourth power unit comprises a hydraulic pump as well as a PTO shaft;

[0061] Fig. 3 shows a modification in which an internal combustion engine ICE is added;

[0062] Fig 4 shows a schematic implementation of the arrangement shown conceptually in Fig. 2;

[0063] Fig. 5 shows first and second operative states of the circuit;

[0064] Fig. 6 shows third and fourth operative states of the circuit;

[0065] Fig. 7 shows fifth and sixth operative states of the circuit;

[0066] Fig. 8 shows seventh and eighth operative states of the circuit;

[0067] Fig. 9 shows a ninth operative state of the circuit;

[0068] Fig. 10 shows in detail the connections for the operating mode of the left image in Fig. 8;

[0069] Fig. 11 shows in detail the connections for the operating mode of the right image in Fig. 8; and

[0070] Fig. 12 shows in detail the connections for the operating mode of Fig. 9.

[0071] DETAILED DESCRIPTION

[0072] The subject matter of this disclosure will be described with reference to theFigures.

[0073] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0074] This disclosure provides a powertrain for a vehicle that has four power units, comprising two engines and two power sinks (one of which is a drivetrain). At least three clutches are provided in couplings between pairs of the power units, and they are independently controllable to engage or disengage the couplings. This provides a flexible coupling of power sources (such as the engines) to the power sinks (such as the drivetrain).

[0075] Figs, la and lb show in conceptual form two possible layouts of the powertrain.It shows power units and clutches between the power units. There will be other components at various locations in the powertrain such as gearing, but these are omitted in Figs, la and lb so that only the connections that can be made by the clutches can be easily understood.

[0076] A basic implementation is shown in Fig. la.

[0077] The powertrain comprises first to fourth power units Pl to P4, each comprising a power source or a power sink. The first power unit Pl comprises a power source in the form of an engine El and the second power unit P2 comprises a first (main) power sink SI in the form of a vehicle drivetrain that is connected to at least one axle of the vehicle. For example, the engine El is for providing motive power to the drivetrain SI, but the engine El may be used for poweringone or more other power sinks. The third power unit P3 comprises a second engine E2 and the fourth power unit P4 comprises a second (auxiliary) power sink S2.

[0078] A first clutch Cl provides a first coupling between the first and second power units P1,P2, a second clutch C2 provides a second coupling between the second and third power units P2,P3, and a third clutch C3 provides a third coupling between the first and fourth power units P4,P1.

[0079] There is a direct (fourth) coupling between the third power unit P3 (second engine E2) and the fourth power unit P4 (second power sink S2). The arrangement is shown schematically as a square configuration with three clutches at three of the corners and one fixed connection in the other corner. This is simply to make the difference with the second implementation of Fig. lb clearer. Each clutch enables or disables the interconnection of the adjacent pair of power units. The first to third clutches are independently controllable to engage or disengage the first to third couplings.

[0080] This powertrain arrangement provides flexibility in coupling power between power sources and power sinks. The arrangement of three clutches (and a fixed connection) enables the adjacent power source and power sink to be connected either by the clutch between them, or by the other two clutches and fixed connection.

[0081] Fig. lb shows a second implementation, in which a fourth clutch C4 provides the fourth coupling between the third and fourth power units P3,P4. The first to fourth clutches are then independently controllable to engage or disengage the first to fourth couplings.

[0082] This powertrain arrangement provides additional flexibility in coupling power between power sources and power sinks.

[0083] In both cases, the independent clutch control enables two power source - power sink pairs to be connected independently (El to SI and E2 to S2), or else it enables the two power sources to be connected together to deliver power to one of the two power sinks, or indeed to both of the power sinks.

[0084] This is of particular interest when the powertrain is for delivering power to very different loads, such as a drivetrain at low speeds, a drivetrain at high speeds, a hydraulic load, a PTO etc.

[0085] Fig. 2 shows one particular configuration for the arrangement of Fig. lb, in which the fourth power unit P4 comprises a hydraulic pump "HYD" as well as a PTO drive shaft. To enable the PTO shaft to be enabled and disabled, a further fifth clutch C5 is provided.

[0086] This arrangement of the fourth power unit may of course be applied to the three clutch arrangement of Fig. la, in which case the further clutch forming part of the fourth power unit would become the fourth clutch of the overall configuration.

[0087] Each clutch forms a selectively engageable torque transmission path. A clutch is to be understood as any device that enables the transfer of torque to be selectively engaged and disengaged.

[0088] The two engines El and E2 are for example electric motors. Thus, in Fig. 2, power unit Pl comprises first electric motor EMI and power unit P3 comprises second electric motor EM2. However, the same connection scheme may be applied where the first and second engines are internal combustion engines or electric motors or a combination.

[0089] Each of the two engines may be considered to be primarily associated with a respective load. Thus, the first engine EMI may be considered to be primarily associated with the drivetrain and the second engine may be considered to be primarily associated with the second power sink, such as an auxiliary drive shaft. The flexibility of the powertrain arrangement however enables the two engines to perform alternative functions, or to combine their power outputs to drive one or both of the power sinks.

[0090] Fig. 3 shows a modification in which an internal combustion engine ICE is added.It connects between the third and fourth clutch C3, C4 via a clutch C6. The internal combustion engine connects to a front PTO fPTO and to a rear PTO, rPTO as well as being able to connect to the other power sinks (P2 and P4). The ICE can also be connected to one of the electric motors, which could then work in generator mode and provide electric power to the other electric motor driving the drivetrain. This would be a serial hybrid mode. The output shaft of the internal combustion engine is thus coupled to the auxiliary line between clutches C3 and C4.

[0091] This arrangement of the ICE may of course be applied to the three clutch arrangement of Fig. la, in which case the ICE may be connected between the third clutch C3 and the third power unit P3 via the additional clutch.

[0092] Figure 4 shows a schematic representation of an implementation of the arrangement shown in Fig. 2.

[0093] The first engine El (e.g. first electric motor) is directly connected to an input 40 of a first ratio unit RU1 (e.g. first gear train). The second engine E2 (e.g. second electric motor) is connectable to an input 50 of a second ratio unit RU2 (e.g. second gear train) through the fourth clutch C4. The ratio units provide a drive ratio between an input and output, for example implemented as a gear train, belt or chain.

[0094] The first clutch Cl is between an output 42 of the first ratio unit and the first sink SI, i.e., the vehicle drivetrain. The first ratio unit implements a first gear ratio between its input and output 40, 42 and the second ratio unit implements a second gear ratio between its input and output 50, 52.

[0095] The second clutch C2 is between the second engine E2 and the drivetrain SI. The third clutch C3 is between the input 40 of the first ratio unit RU1 and the output 52 of the second ratio unit RU2. The second sink S2, i.e. the auxiliary sink, is connected to an intermediate output 54 of the second ratio unit RU2.

[0096] The first engine El can drive the drivetrain using the first ratio unit RU1 (via clutch Cl) or it can drive the drivetrain using the second ratio unit RU2 (via clutches C3, C4 and C2). The second engine can drive the drivetrain directly (via clutch C2) or it can provide drive assistance to the first engine El via the second ratio unit RU2 (via clutches C4 and C3).

[0097] Thus, for an implementation using electric motors and gear trains, the first electric motor El can drive the drivetrain using the first gear train (via clutch Cl) or it can drive the drivetrain using the second gear train (via clutches C3, C4 and C2). The second electric motor can drive the drivetrain directly (via clutch C2) or it can provide drive assistance to the first electric motor via the second gear train (via clutches C4, and C3, with clutch C2 open).

[0098] The second power sink S2, for example a hydraulic pump, is connected to the intermediate output 54 from the second gear train. In one example, a PTO drive shaft can also connect to the intermediate output 54 through a further clutch as shown in Fig. 2.

[0099] For a default drive speed of the first engine El and a default drive speed of the second engine E2, the gear ratio between the input 50 and the intermediate output 54, and thegear ratio between the output 52 and the intermediate output 54, result in a same drive speed at the intermediate output 54. In this way, the two engines can be combined (at their default drive speeds) to drive the hydraulic circuit.

[0100] This provides a particular implementation with two ratio units, such as gear trains. It enables different gear ratios to be implemented.

[0101] It will be appreciated that the designations "input" and "output" as used in relation to the first and second ratio units RU1, RU2 are not necessarily intended to be limiting in terms of the direction in which drive is transmitted through the ratio units. For example, when the first engine El is driving the first power sink SI through the second ratio unit RU2 with the clutches C3, C4 and C2 closed and clutch Cl open, the "output" 52 becomes the input and the "input" 50 becomes the output. The terms input and output are merely intended to designate respective ends of the ratio units over which a drive ratio is obtained.

[0102] The drivetrain is shown as a differential gear arrangement 60. The wheels 70 are driven by the differential gear arrangement 60 using conventional gear stages (not shown). As illustrated in FIG. 4 gearing may be provided between the outputs of clutches Cl and C2 and a drive shaft to the drive train 60. This may be provided to enable the drive shaft to be off set in an appropriate position and / or to provide a further drive ratio.

[0103] In a modification to Fig. 4, the ratio unit RU1 may have a selectable gear ratio between the input 40 and output 42, for example selectable between two values. For this purpose, a gear train may be used with two branches, and the first clutch Cl becomes a clutch arrangement which enables the output from the first electric motor EMI to connect to either branch or to be disconnected. The two branches provide different gearing between the input 40 and the output 42.

[0104] The different connections that can be made using the circuit of Fig. 4 will now be shown, using the schematic representation of Fig. lb, and in which the drivetrain is represented as D and the PTO and hydraulic circuit are represented simply as auxiliary output "Aux".

[0105] In Figs. 5 to 9, clutches that are engaged to provide a torque coupling are shown as bold circles and clutches that are disengaged, to provide isolation, are shown as empty circles.The bold parts of the square path around the four clutches represent torque transfer paths. The power sources are represented as electric motors EMI and EM2 and the ratio units RU1, RU2 are represented as gear trains GT1 and GT2.

[0106] Fig. 5 shows on the left an operative state in which the first engine EMI is coupled only to the vehicle drivetrain via the first clutch Cl and the second engine EM2 is coupled only to the second auxiliary output S2 via the fourth clutch C4. The coupling to the drivetrain uses the first gear train GT1 and the coupling to the auxiliary output uses (half of) the second gear train GT2.

[0107] The two couplings shown may also be used individually (by not operating one motor and / or opening the associated clutch).

[0108] Fig. 5 shows on the right an operative state in which the first engine EMI is coupled only to the auxiliary output Aux (S2) via the third clutch C3 and the second engine EM2 is coupled only to the drivetrain via the second clutch C2. The coupling to the drivetrain is direct (no gearing) and the coupling to the auxiliary output uses (the other half of) the second gear train GT2.

[0109] Again, the two couplings shown may also be used individually (by not operating one motor and / or opening the associated clutch).

[0110] Thus, each engine can be used to drive either of the power sinks. This may be the only drive connection, or it may be at the same time that the other engine of the pair is driving the other of the power sinks of the pair. It means the drivetrain and the auxiliary output can be driven at independent speeds.

[0111] Fig. 6 shows on the left an operating state in which the first engine EMI is coupled simultaneously to both of the vehicle drivetrain and the auxiliary power sink via the first and third clutches respectively, independently of the second engine.

[0112] Fig. 6 shows on the right an operating state in which the second engine EM2 is coupled simultaneously to both of the vehicle drivetrain and the auxiliary power sink via the second and fourth clutches respectively, independently of the first engine.

[0113] Thus, each engine may be used alone to drive both of the power sinks.

[0114] Fig. 7 shows on the left an operating state in which the first and second enginesEMI, EM2 are both coupled simultaneously only to the vehicle drivetrain via the first and second clutches respectively with the third and fourth clutches open.

[0115] Fig. 7 shows on the right an operating state in which the first and second enginesEMI, EM2 are both coupled simultaneously only to the second power sink via the third and fourth clutches respectively with the first and second clutches open.

[0116] Thus, the two engines may be connected together to drive a selected one of the two power sinks.

[0117] When both motors connect to the same load as in Fig. 7, if different gear ratios are used, the motors need to be driven at different speeds. The clutches are for example dog clutches. These have benefits over friction clutches, requiring a smaller space for a similar torque carrying capacity, and no need to lubricate (vs. wet multi-plate clutches). There is also less energy consumption when not engaged (vs. wet multi-plate clutches, etc.).

[0118] When a speed difference is needed between the different motors, before they can be coupled together via dog clutch(es), the motors are synchronized by speed control (and / or torque control).

[0119] Of course, in the case of friction clutches, in addition to motor-based synchronization, when engaging the clutch(es), the clutches may be allowed to slip as part of the synchronization process.

[0120] After the clutches have been engaged, the motors can be controlled via torque control so that the motors remain synchronized. Typically, electric motors have a speed (rpm) control mode and a torque (Nm) control mode. A controller can tell the inverter (which drives the electric motor) to drive the motor at certain speed and it can also request a certain torque from the electric motor. When electric motors are coupled together, the most likely control mode is torque control. In this way, the two electric motors do not fight against each other, which might happen if both motors were in speed control mode.

[0121] Fig. 8 shows on the left an operating state in which the first and second enginesEMI, EM2 are both coupled simultaneously to both the vehicle drivetrain and the auxiliary power sink via the first, third and fourth clutches.

[0122] Fig. 8 shows on the right an operating state in which the first and second enginesEMI, EM2 are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the second to fourth clutches.

[0123] These two operating modes enable both loads to be driven by both engines, but different gear ratios to the drivetrain are achieved.

[0124] If electric motors EMI and EM2 have a similar design (in terms of power, size, torque response, and speed range), having the different gear ratios realizes two different gears. This may enable use of low cost and small electric motors.

[0125] It is also possible to have the same gear ratio between the first electric motor and the drivetrain as between the second electric motor and the drivetrain, but to have different performance (e.g. EMI provides high torque at low vehicle speeds e.g. for doing field work, whereas EM2 provides high power at high vehicle speeds e.g. for driving) by changing the parameters of the second motor.

[0126] Thus, a gear ratio and / or function of torque versus speed between the first engine and the vehicle drivetrain when the first clutch is engaged may be designed to be different to that between the second engine and the vehicle drivetrain when the second clutch is engaged.

[0127] Fig. 9 shows an operating state in which the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the first to fourth clutches, thereby coup ling the input 40 to the first geartrain to the output 52 of the second gear train and connecting the output 42 of the first gear train to the input 50 of the second gear train.

[0128] In the preferred arrangement, there are different gear ratios (i) between the first engine El and the drivetrain via clutch Cl and (ii) between the first engine El and the drivetrain via clutches C3, C4 and C2. around the system. In this case, the configuration of Figure 9 may be used deliberately as a locking state, and no torque transfer arrows are shown. This may be used as parking brake.

[0129] However, it is also possible to have the same gear ratios. This would enable the four clutches to be engaged without locking the system. It would then enable power from both engines to be delivered to both sinks. However, if this configuration is enabled, the gear ratiobetween the first engine EMI and the drivetrain will need to be the same in both directions around the loop (i.e., the same for Fig. 8 right image as for Fig. 5 left image). However, a change in power or torque performance of the motors may be achieved instead of a gear ratio change as mentioned above.

[0130] Figs. 10 to 12 show how some of the interconnections explained with reference to Figs. 5 to 9 are implemented in the more detailed circuit. The drivetrain is represented simply as sink SI. The clutches that are closed have bold circles around them and the torque transfer paths are shown in bold.

[0131] Fig. 10 shows the connections for the operating mode of the left image in Fig. 8, in which the first and second engines EMI, EM2 are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the first, third and fourth clutches Cl, C3, C4.

[0132] The first and second engines are driven with a speed differential corresponding to the gear ratio of the second gear train GT2. Thus, their powers are combined. They together drive the auxiliary output Aux. The gear ratio between the first engine EMI and the drivetrain corresponds to the gear ratio of the first gear train GT1, and the gear ratio between the second engine EM2 and the drivetrain corresponds to the product of the gear ratios of the two gear trains.

[0133] Fig. 11 shows the connections for the operating mode of the right image in Fig.8, in which the first and second engines EMI, EM2 are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the second to fourth clutches C2, C3, C4.

[0134] The first and second engines are again driven with a speed differential corresponding to the gear ratio of the second gear train GT2. Thus, their powers are combined and they together drive the auxiliary supply S2 in the same way as in Fig. 10. However, the gear ratio between the first engine EMI and the drivetrain now corresponds to the gear ratio of the second gear train GT2 (the second ratio unit RU2), and the gear ratio between the second engine EM2 and the drivetrain may be a 1:1 ratio.

[0135] Thus, Figs. 10 and 11 provide different gear ratios between the first engine EMI and the drivetrain, in both cases also using the second engine to supplement the power delivery.

[0136] Fig. 12 shows the connections for the operating mode of Fig. 9, in which the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the first to fourth clutches, for example to operate as a brake.

[0137] This couples the input 40 to the first gear train to the output 52 of the second gear train, and couples the output 42 of the first gear train to the input 50 of the second gear train.

[0138] The first coupling Cl, second coupling C2, third coupling C3, and fourth couplingC4 each represent a torque transmission path which can be used independently of the others and, where a clutch is present, is engageable or disengageable independently of the others. However, the couplings are drivingly interconnectable in a circuit so that drive can be selectively transmitted between various of the couplings by appropriate control of the clutches. This enables torque from either engine El, E2 to be selectively transmitted to at least the first power sink SI through two or more of the couplings in at least one operating state. In this regard, the first and second couplings Cl, C2 are drivingly interconnectable, the first and third couplings Cl, C3 are drivingly interconnectable, the second and fourth couplings C2, C4 are drivingly interconnectable, and the third and fourth couplings C3, C4 are drivingly interconnectable.

[0139] The detailed examples above relate to the four-clutch design of Fig. lb. However, many of the interconnections are possible with the three-clutch design of Fig. la. In particular, all connections which do not require isolation between the third and fourth power units can be implemented. Thus, for the three-clutch implementation, the second engine is always driving the auxiliary power sink, either alone, or in combination with the first engine.

[0140] Within the scope of this application, it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.

[0141] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the subject matter of this disclosure, from a study of thedrawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0142] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0143] Any reference signs in the claims should not be construed as limiting the scope.

[0144] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

Claims

CLAIMSWhat is claimed is:

1. A powertrain for a vehicle, the powertrain comprising: first to fourth power units (P1-P4), wherein the first power unit (Pl) comprises a first engine (El), the second power unit (P2) comprises a first power sink (SI) in the form of a vehicle drivetrain, the third power unit (P3) comprises a second engine (E2) and the fourth power unit comprises a second power sink (S2); a first clutch (Cl) providing a first coupling between the first and second power units (P1,P2); a second clutch (C2) providing a second coupling between the second and third power units (P2,P3); a third clutch (C3) providing a third coupling between the first and fourth power units (P4,P1); and a fourth coupling between the third and fourth power units (P3,P4), wherein the first to third clutches are independently controllable to engage or disengage the first to third couplings.

2. The powertrain of claim 1, wherein the third power unit (P3) and the fourth power unit (P4) are couplable by the fourth coupling independently of the first to third couplings.

3. The powertrain of claim 1 or 2, wherein a gear ratio and / or function of torque versus speed between the first engine (El) and the vehicle drivetrain when the first clutch is engaged is different to that between the second engine (E2) and the vehicle drivetrain when the second clutch is engaged.

4. The powertrain of any one of claims 1 to 3 , which is selectively configurable for operation in operative states in which:a. the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the second and third clutches and the fourth coupling; and b. the first and second engines are both coupled simultaneously to both the vehicle drivetrain and the second power sink via the first and third clutches and the fourth coupling.

5. The powertrain of any one of claims 1 to 4, which is selectively configurable for operation in operative states in which: c. the first engine is coupled only to the vehicle drivetrain via the first clutch, and / or the second engine is coupled only to the second power sink via the fourth coupling.

6. The powertrain of any one of claims 1 to 5, which is selectively configurable for operation in operative states in which: d. the first engine is coupled simultaneously to both of the vehicle drivetrain and the second power sink via the first and third clutches respectively; and e. the second engine is coupled simultaneously to both of the vehicle drivetrain and the second power sink via the second clutch and fourth coupling respectively.

7. The powertrain of any one of claims 1 to 6, which is selectively configurable for operation in operative states in which: f. the first and second engines are both coupled simultaneously only to the second power sink via the third clutch and fourth coupling respectively.

8. The powertrain of any one of claims 1 to 7, wherein the fourth coupling comprises a permanent coupling.

9. The powertrain of any one of claims 1 to 8, further comprising: a fourth clutch (C4) in the fourth coupling between the third and fourth power units (P3,P4),wherein the first to fourth clutches are independently controllable to engage or disengage the first to fourth couplings.

10. The powertrain of claim 9, which is selectively configurable for operation in a plurality of different operative states including at least an operative state in which: g. the first engine is coupled only to the second power sink via the third clutch, and the second engine is coupled only to the vehicle drivetrain via the second clutch.

11. The powertrain of claim 9 or 10, which is selectively configurable for operation in an operative state in which: h. the first and second engines are both coupled simultaneously only to the vehicle drivetrain via the first and second clutches respectively.

12. The powertrain of any one of claims 1 to 11, wherein the first engine (El) is directly connected to an input of a first ratio unit (RU1), the second engine (E2) is connected to an input of a second ratio unit (RU2) through the fourth coupling, the first clutch (Cl) is between an output of the first ratio unit (RU1) and the vehicle drivetrain, the second clutch (C2) is between the second engine (El) and the drivetrain, and the third clutch (C3) is between the input of the first ratio unit (RU1) and the output of the second ratio unit (RU2).

13. The powertrain of any one of claims 1 to 12, wherein the first and third power units (Pl, P3) each comprise an electric motor (EMI, EM2).

14. The powertrain of any one of claims 1 to 13, wherein the fourth power unit (P4) comprises an auxiliary output shaft for driving a PTO and / or a hydraulic pump.

15. The powertrain of claim 14, wherein the auxiliary output shaft is for driving a hydraulic pump and a fifth clutch (C5) is provided between the auxiliary output shaft and a PTO.

16. An agricultural machine comprising the powertrain of any one of claims 1 to 15.

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