Field of the Invention This invention relates to a vehicle drivetrain and, more particularly but not exclusively, to a drivetrain for a hybrid motor vehicle.

Background of the Invention The applicant has determined that it would be desirable to provide an alternative vehicle drivetrain, particularly an alternative vehicle drivetrain for a hybrid motor vehicle with two forward speeds.

Examples of the invention seek to provide a useful alternative drivetrain for hybrid motor vehicles.

Summary of the Invention

In accordance with one aspect of the present invention, there is provided a vehicle drivetrain, including an output shaft for connecting to a drive of the vehicle, a first electric motor arranged to drive the output shaft in a first speed range, and a second electric motor arranged to drive the output shaft in a second speed range.

Preferably, the first speed range is a first drive ratio of the output shaft relative to a rotor of the first electric motor, and the second speed range is a second drive ratio of the output shaft relative to a rotor of the second electric motor.

Preferably, the second electric motor is in direct driving connection to the output shaft. In a preferred form the first and second electric motors are housed within a common transmission housing.

Preferably, the drivetrain includes an internal combustion engine having an output shaft in driving connection with the rotor of the first electric motor. More preferably, the output shaft of the internal combustion engine is in driving connection with the rotor of the first electric motor via a first friction clutch. Even more preferably, the output shaft of the internal combustion engine is in constant driving connection with the rotor of the first electric motor via a one way clutch arranged such that the internal combustion engine is able to drive the rotor of the first electric motor.

Preferably, the first electric motor drives the output shaft via a lay shaft. More preferably, the first electric motor drives the lay shaft via a second friction clutch. In one form, the first electric motor is arranged to operate as a starting motor to start the internal combustion engine.

Preferably, the first and/or second electric motor is arranged to operate as a generator when the vehicle is driven by the internal combustion engine and/or when the vehicle is coasting.

In a preferred form, all three of the first electric motor, the second electric motor and the internal combustion engine are arranged to launch the vehicle from a standstill, either individually or in combination.

Preferably, when driving in the second speed range the second electric motor is arranged to drive the first electric motor as a generator by way of the engaged second friction clutch. In one form, drive units of the drivetrain consist of only the first electric motor and the second electric motor. Preferably, both the first electric motor and the second electric motor are in constant direct driving connection with the output shaft. Preferably, the second electric motor is able to operate in reverse so as to drive the output shaft in a reverse speed range.

In a preferred form, the first friction clutch is adapted to be slipped for launching the vehicle from standstill when the internal combustion engine is in operation.

Preferably, in the absence of hydraulic pressure the output shaft is able to be driven by the second electric motor.

In one form, the first and second electric motors are operated in combination with the internal combustion engine to provide a high torque launch of the vehicle.

Preferably, the drivetrain includes a parking mechanism which is operable to selectively lock the output shaft against rotation relative to a housing of the transmission. Preferably, the first electric motor is mounted in a transverse orientation relative to the vehicle and is coupled to the output shaft by a first gear, and wherein the second electric motor is mounted in line with the first electric motor and is coupled to the output shaft by a second gear. More preferably, the second electric motor is in direct engagement with the output shaft, and the first electric motor is coupled to said first gear via a friction clutch. Even more preferably, the output shaft is arranged in direct engagement with a housing of a differential by a third gear.

Brief Description of the Drawings The invention is described, by way of non-limiting example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic cross-sectional view of a vehicle drivetrain in accordance with one example of the present invention; Figure 2 is a diagrammatic cross-sectional view of a vehicle drivetrain in accordance with a second example of the present invention;

Figure 3 is a diagrammatic cross-sectional view of a vehicle drivetrain in accordance with a third example of the present invention; and

Figure 4 is a diagrammatic cross-sectional view of a vehicle drivetrain in accordance with a fourth example of the present invention.

Detailed Description

With reference to Figure 1 , there is shown a vehicle drivetrain 10 which uses an internal combustion engine as well as two electric motors to provide two forward speeds. More specifically, the vehicle drivetrain 10 includes an output shaft 12 for connecting to a drive of the vehicle, a first electric motor 14 arranged to drive the output shaft 12 in a first speed range, and a second electric motor 16 arranged to drive the output shaft 12 in a second speed range.

The first speed range is a first drive ratio of the output shaft 12 relative to a rotor 18 of the first electric motor 14, and the second speed range is a second drive ratio of the output shaft 12 relative to a rotor 20 of the second electric motor 16. In the example shown in Figure 1, the second electric motor 16 drives the output shaft 12 via a short lay shaft 22, by which the second electric motor 16 is in direct driving connection to the output shaft 12. The first electric motor 14 is in driving connection with the output shaft 12 by way of a long lay shaft 24, and a friction clutch which is operable to selectively couple/decouple the first electric motor 14 and the long lay shaft 24. The first electric motor 14 and the second electric motor 16 are housed within a common transmission housing 26. The drivetrain 10 includes an internal combustion engine 28 having an output shaft

30 in driving connection with the rotor 18 of the first electric motor 14. The output shaft 30 of the internal combustion engine 28 is in driving connection with the rotor 18 of the first electric motor 14 via a first friction clutch 32. The output shaft 30 of the internal combustion engine 28 is also in constant driving connection with the rotor 18 of the first electric motor 14 via a one way clutch 34 arranged such that the internal combustion engine 28 is able to drive the rotor 18 of the first electric motor 14 in one direction (ie. in the direction of operation of the internal combustion engine 28).

A second friction clutch 36 is provided between the rotor 18 and the long lay shaft 24 such that the first electric motor 14 is able to be selectively engaged/disengaged from the long lay shaft 24. Advantageously, by virtue of the provision of the first friction clutch 32, the first electric motor 14 is arranged to operate as a starting motor to start the internal combustion engine 28. Also, the first electric motor 14 and/or the second electric motor 16 is/are arranged to operate as a generator when the vehicle is driven by the internal combustion engine 28 and/or when the vehicle is coasting. As such, the first electric motor 14 and/or the second electric motor 16 is/are able to be used to charge an energy storage system of the vehicle in this way, and may incorporate a regenerative braking system.

In one form, all three of the first electric motor 14, the second electric motor 16 and the internal combustion engine 28 are arranged to launch the vehicle from a standstill, either individually or in combination.

The second friction clutch 36 may be used to drive the first electric motor 14 as a generator when driving in the second speed range under power of the second electric motor Figure 2 differs from Figure 1 in that the second electric motor 16 drives the output shaft 12 in a direct 1 :1 ratio, through the absence of the short lay shaft 22 which is present in Figure 1. In the examples shown in Figures 1 and 2, the first friction clutch 32 is adapted to be slipped for launching the vehicle from standstill when the internal combustion engine 28 is in operation. Advantageously, the examples shown in Figures 1 and 2 of the drawings are able to provide drive of the output shaft 12 by way of the second electric motor 16 in the absence of hydraulic pressure which may be required to operate the friction clutches. The first and second electric motors 14, 16 may be operated in combination with the internal combustion engine 28 to provide a high torque launch of the vehicle.

In the example shown in Figure 3, drive units of the drive train 10 consist of only the first electric motor 14 and the second electric motor 16, as the internal combustion engine is omitted. In this form, the second electric motor 16 provides a direct drive of the output shaft 12 in a 1 :1 drive ratio, with the first electric motor 14 also being in constant direct driving connection with the output shaft 12 via the long lay shaft 24 to provide a second speed range. The second electric motor 16 may be able to operate in reverse so as to drive the output shaft 12 in a reverse speed range.

Each of the examples shown include a parking mechanism 38 which is able to selectively lock the output shaft 12 against rotation relative to the housing 26 of the transmission. Figure 4 shows an alternative example wherein the first electric motor 14 is mounted in a transverse orientation relative to the vehicle and is coupled to the output shaft 12 by a first gear 40. The second electric motor 16 is mounted in line with the first electric motor 14 and is coupled to the output shaft 12 by a second gear 42 in a different drive ratio. The drivetrain 10 shown in Figure 4 may be used in a front wheel drive configuration, or a transverse rear drive configuration. The second electric motor 16 is in direct engagement with the output shaft 12, and the first electric motor 14 is coupled to the first gear 40 via a friction clutch 44. In other examples, the friction clutch 44 may be omitted such that the first electric motor 14 is in direct driving engagement with the output shaft 12. The output shaft 12 is arranged in direct engagement with a housing of a differential 46 by a third gear 48.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

The short lay shaft 22 and the long lay shaft 24 may have helical/spur gears, and a hydraulic pump may be driven by the output shaft 12, an input shaft, either electric motor 14, 16, or may be accessory driven.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.