Approach to integrating a starter-generator with an automatic transmission

[0002] This application claims the benefit of U.S. Provisional Application No. 60/267,679 filed Feb. 9, 2001.

[0003] The present invention relates to a power train for a motor vehicle. More particularly, the invention relates to a power train that allows a starter/generator to drive a transmission pump and to selectively engage an internal combustion engine.

[0004] Vehicle transmissions include an internal combustion engine, a starter/generator, and a transmission input. Incorporating a starter/generator into a transmission presents several issues. For example, crankshaft-mounted starter/generators add a large mass, i.e., the mass of the rotor, to the crankshaft. This adds load to the crankshaft bearings, and can exacerbate crankshaft deformation and stress due to dynamic loading. Ultimately, deformation of the crankshaft can make it difficult to maintain the small, uniform air gap desirable for the starter/generator.

[0005] The present invention provides a power train having a starter/generator that is not mounted on the crankshaft. Furthermore, the starter/generator is able to directly drive a transmission pump, and can selectively engage a torque converter and/or an internal combustion engine.

[0006] Briefly, a power train in accordance with the present invention comprises an internal combustion engine, a starter/generator that has a rotor, a torque converter, a transmission pump directly connected to the rotor, a selectively engageable clutch disposed between the starter/generator and internal combustion engine, and a transmission input directly connected to the output turbine of the torque converter.

[0007] FIG. 1 is a schematic representation of a power train in accordance with a first preferred embodiment of the present invention, while FIGS. 1aand 1bare schematic representations of variations of the power train shown in FIG. 1; and

[0008] FIG. 2 is a schematic representation of a power train in accordance with a second preferred embodiment of the present invention.

[0009] The following description of the preferred embodiments of the invention provides examples of the present invention. The embodiments discussed herein are merely exemplary in nature, and are not intended to limit the scope of the invention in any manner. Rather, the description of these preferred embodiments serves to enable a person of ordinary skill in the relevant art to make and use the present invention.

[0010] FIGS. 1 illustrates a schematic representation of a first preferred embodiment of the present invention. In this embodiment, a power train 10 includes an internal combustion engine 20, a torque converter 30, a starter/generator 40, a transmission input 50, and a transmission pump 60. A clutch 70 is disposed between the engine and the starter/generator. The engine is well known in the art, and will not be described in detail herein.

[0011] The torque converter 30 includes an input impeller 32, an output turbine 34, and a stator 36. The torque converter 30 includes a first clutch 38. In a first preferred embodiment, illustrated in FIG. 1, the input impeller 32 is drivingly or directly connected to the engine 20. In this embodiment, there is no clutch disposed between the engine and the impeller. A selectively engageable second clutch 70 is disposed between a rotor 42 of the starter/generator and the impeller 32.

[0012] The transmission input 50 preferably comprises a multi-speed transmission, but any suitable vehicle transmission can be utilized. The transmission pump 60 preferably comprises a hydraulic pump.

[0013] Thus, the arrangement of the first preferred embodiment allows the engine 20 to drive the impeller 32 of the torque converter 30 directly. The rotor 42 of the starter/generator 40 and the transmission pump 60, however, are driven through the second clutch 70. This arrangement allows for an inertia start, and places the starter/generator 40 on the transmission side of the torque converter 30. This allows the rotor 42 to run on bearings 80 (FIG. 1a) on the transmission pump cover or the shaft 37 (FIG. 1b) of the stator 36, which eliminates the need to place the rotor 42 on a crankshaft. Preferably, the housing of the pump 60 is integrally made with the housing of the starter/generator 40, as shown by the integrated housing 90 of FIG. 1a. Alternatively, the pump housing can be made integral with the torque converter housing, as shown by the integrated housing of FIG. 1b.

[0014] In this embodiment, the starter/generator 40 can directly drive the transmission pump 60 without having to also supply torque to the impeller 32 or engine 20. This is accomplished by disengaging the second clutch 70. This allows the engine 20 to be turned off when the vehicle is stopped while the starter/generator continues to power the transmission pump. The engine can be quickly restarted upon torque demand, using energy stored in the rotating starter/generator 40 to supply a portion of the engine cranking torque.

[0015] FIG. 2 illustrates a second preferred embodiment of the power train of the present invention. Like references in FIG. 2 refer to similar components and/or features illustrated in FIG. 1. In this embodiment, the engine 120 is not directly connected to the input impeller 132 of the torque converter 130. Rather, the engine 120 is connected to the rotor 142 of the starter/generator 140. The selectively engageable clutch 170 is disposed between the engine 120 and the rotor 142. Preferably, the rotor 142 is directly connected to the transmission pump 160 and the impeller 132.

[0016] This arrangement allows the engine 120 to be advantageously disconnected from the transmission input 150 during periods of regenerative braking. Clutch 138 can be engaged during regenerative braking to provide a direct connection from the transmission input 150 to the starter/generator 140 for improved energy capture. When the engine 120 is disconnected and the vehicle stopped, the starter/generator 140 can drive the transmission pump 160 as in FIG. 1. In this embodiment, however, this occurs at a lower efficiency than in the first preferred embodiment because the starter/generator 140 also must drive the impeller 132.

[0017] The foregoing disclosure includes the best mode devised by the inventors for practicing the invention. It is apparent, however, that several variations in accordance with the present invention may be conceivable to one of ordinary skill in the relevant art. Inasmuch as the foregoing disclosure is intended to enable such person to practice the instant invention, it should not be construed to be limited thereby, but should be construed to include such aforementioned variations. As such, the present invention should be limited only by the spirit and scope of the following claims.