Hybrid automated manual transmission

[0002] The present invention relates generally to hybrid vehicles and more particularly to an automated manual transmission for overcoming traditional and hybrid vehicle deficiencies.

[0003] Automobile manufacturers continuously strive to improve the fuel efficiency of the vehicles they design. Fuel efficiency can be achieved through improvements in practically any feature of an automobile. Component weight, engine and transmission configuration and aerodynamics are just a few examples of the almost limitless areas increased efficiency can be achieved.

[0004] More recently, automobile manufacturers have ventured into the area of hybrid vehicles. A hybrid vehicle has both a traditional combustion engine and an electric motor/generator for driving the vehicle. A hybrid vehicle offers significantly increased fuel efficiency due to the assistance of the electric motor/generator. Although hybrid vehicles offer improved efficiency, the overall powertrain implemented with such a vehicle is still oversized for its application.

[0005] The powertrains of conventional and even hybrid vehicles are inefficient as they are designed to provide more power than required for the vehicle at cruising speeds. Specifically, the combustion engine of such powertrains is larger than required to provide power for acceleration and hill climbs. This extra power is not required for a vehicle once it is up to cruising speed. As a result, conventional vehicles are less efficient than desired.

[0006] Therefore, it is desirable in the industry to have an improved vehicle powertrain for implementation in a vehicle, such as a hybrid vehicle, which overcomes the inefficiencies inherent in a conventional powertrain.

[0007] In achieving the above identified objectives, the present invention provides an improved powertrain configuration comprising a split path transmission operable by a combustion engine and an electric motor/generator. The combustion engine drives the split path transmission while the electric motor/generator assists in such driving. In turn, the split path transmission communicates rotational motion to a rear differential for driving a pair of rear wheels. The split path transmission is operably attached to both an engine output and a first electric motor/generator by way of a planetary splitter and a lock-up clutch. A second electric motor/generator is implemented for driving a front differential. The split path transmission comprises three conventional plate clutches and three drive gear pairs for achieving six forward drive ratios. A reverse gear ratio is achieved using the first electric motor/generator. The first electric motor/generator initially generates power for powering the second electric motor/generator, for driving the vehicle at low speeds. It is also foreseen that the split path transmission may drive the front differential and the second electric motor/generator may drive the rear differential.

[0008] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.

[0009] FIG. 1 is a schematic view of a split path transmission according to the principles of the present invention; and

[0010] FIG. 2 is a schematic view of a hybrid vehicle implementing the split path transmission of the present invention.

[0011] At the outset, it is important to note that the herein described embodiment is a preferred embodiment and merely exemplary in nature. Being exemplary, the preferred embodiment is in no way intended to limit the invention or its application.

[0012] With reference to FIG. 1, a schematic view of a split path transmission 10 is shown. Split path transmission 10 includes a vibration damper connection 13 having a flywheel and dampening device, a lock-up clutch 14, a planetary splitter 16, a first electric motor/generator 20, a first multi-plate clutch 34, a second multi-plate clutch 36, a third multi-plate clutch 38, and a geartrain 39. Geartrain 39 includes a drive gear 40 fixed to an intermediate shaft 44, a driven gear 46 fixed to a layshaft 48 and meshed with drive gear 40, a first constant-mesh gearset 50 and a second constant-mesh gearset 52. First gearset 50 includes a first transfer gear 54 on layshaft 48 which is meshed with a first speed gear 56 rotatably supported on an output shaft 58. Likewise, second gearset 52 includes a second transfer gear 60 on layshaft 48 which is meshed with a second speed gear 62 rotatably supported on output shaft 58. A parking pawl 64 is fixed to output shaft 58.

[0013] An input shaft 66 is attached to a sun gear 28 of planetary splitter 16. Input shaft 66 is connected to an internal combustion engine 12 (see FIG. 2) via conventional vibration damper 13, such that sun gear 28 always runs at engine speed. A planet carrier 30 of planetary splitter 16 is attached to split path transmission 10 via intermediate shaft 44. A ring gear 32 of planetary splitter 16 is in operable communication with first electric motor/generator 20. A plurality of planet gears 33 are supported by planet carrier 30 in meshing engagement with sun gear 28 and ring gear 32. Ring gear 32 is selectively connectable to input shaft 66 via lock-up clutch 14.

[0014] Split path transmission 10 uses three conventional multi-plate clutches 34, 36, 38 to engage three different drive ratios. First multi-plate clutch 34 is provided between intermediate shaft 44 and output shaft 58 for providing a first drive ratio (1:1 direct ratio) when first multi-plate clutch 34 is engaged. Second multi-plate clutch 36 is operable to selectively couple first speed gear 56 to output shaft 58 for establishing a second drive ratio. Likewise, third multi-plate clutch 38 is operable to selectively couple second speed gear 62 to output shaft 58 for establishing a third drive ratio.

[0015] Because planetary splitter 16 comes before geartrain 39 in the power transfer path, clutches 14, 34, 36 and 38 can be selectively engaged to achieve a six speed transmission with reverse. As noted, transfer gears 54 and 60 are in constant mesh with speed gears 56 and 62 which are selectively engageable to output shaft 58. Each gear couple is capable of producing a forward drive ratio while engagement of clutch 34 provides a direct drive ratio of 1:1. In operation, first through third gears are achieved with planetary splitter 16 operating in a ‘low’ setting. The ‘low’ setting is defined with lock-up clutch 14 being in a disengaged state wherein ring gear 32 is permitted to rotate relative to sun gear 28. In contrast, fourth through sixth gears are achieved with planetary splitter 16 operating in a ‘high’ setting. The ‘high’ setting is defined when lock-up clutch 14 is in an engaged state. It is foreseen that lock-up clutch 14 could be controlled by a transmission controller (not shown) or other mechanism. By selectively engaging one of conventional multi-plate clutches 34, 36, 38, a gear ratio and drive path are produced.

[0016] In order to achieve reverse operation, first electric motor/generator 20 drives ring gear 32 in a reverse direction, faster than that of the output of the combustion engine 12 (see FIG. 2). The preferred embodiment achieves a 3.4:1 reverse ratio by driving ring gear 32 in a reverse direction at 750 rpm as compared to an opposite rotating output of 480 rpm of input shaft 66.

[0017] With reference to FIG. 2, a hybrid vehicle powertrain 1 is shown which utilizes split path transmission 10 of the present invention. Hybrid vehicle powertrain 1 includes combustion engine 12, a first differential 22 operably connected to output shaft 58 and a first pair of wheels 24, and a second differential 23 operably connected to a second pair of wheels 25. Second differential 23 is operably attached to a second electric motor/generator 21 via a planetary gearset 17. Planetary gearset 17 includes a sun gear 70 operably driven by second electric motor/generator 21. A plurality of planet gears 72 are supported on a carrier 74 and in meshing engagement with sun gear 70 and a fixed ring gear 76. Carrier 74 is in driving engagement with second differential 23. As such, second electric motor/generator 21 is operable to drive second differential 23. A battery 26 powers both first and second electric motor/generators 20, 21, as well as stores energy created by either generator 20 or generator 21 in a re-generation mode. A controller 27 is also provided for managing the operation of first and second electric motor/generators 20, 21 and possibly actuation of clutches 14, 34, 36 and 38.

[0018] When the vehicle is stationary, ring gear 32 rotates in an opposite direction to the engine output generating electric power. The generated electric power is fed to battery 26 and/or second electric motor/generator 21. If a small amount of electric power develops at first motor/generator 20 due to rotation of ring gear 32 then the reaction torque drives hybrid vehicle powertrain 1 at low speeds, simulating creep in an automatic transmission. The amount of electrical power required to achieve this is a function of various vehicle parameters, including but not limited to, weight. An increase in power of first electrical motor/generator 20 slows the rotation of ring gear 32 and causes the vehicle to accelerate. As the rotation of ring gear 32 approaches zero, a first planetary ratio is established. The first planetary ratio of the preferred embodiment is 2.9:1. In order to achieve a 1:1 ratio, lock-up clutch 14 is applied, providing a direct power transfer path between the output of engine 12 and ring gear 32. Once a 1:1 ratio is achieved, the assistance of electric power is no longer utilized and hybrid vehicle powertrain 1 achieves cruising speed.

[0019] It is also anticipated that the vehicle configuration will not be limited to split path transmission 10 only driving rear differential 22 and second electric motor/generator 21 driving front differential 23. In contrast, hybrid vehicle powertrain 1 can be configured such that split path transmission 10 drives front differential 23 and second electric motor/generator 21 drives rear differential 22.

[0020] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention. Such variations or modifications, as would be obvious to one skilled in the art, are intended to be included within the scope of the following claims.