TECHNICAL FIELD

The invention relates to a damper assembly for a vehicle powertrain.

BACKGROUND

Conventional vehicle powertrains having only a combustion engine as a power source typically have a flywheel mounted to the engine crankshaft. In an automatic transmission, a flexplate is connected to the flywheel and forms a starter ring gear. The flexplate connects to a torque converter that contains an internal damper assembly that is submerged in oil. Hybrid powertrains may not need a starter ring gear because a hybrid powertrain may have one or more motor/generators that may be used to start the engine. A flexplate with a ring gear may still be included in order to allow the engine to be started for compliance testing during production. In a manual transmission, torque converters are not used, and a flywheel that has starter ring gear teeth is typically used in place of a flexplate.

SUMMARY

A powertrain with a damper assembly is provided that has neither a flywheel nor a flexplate, thus reducing the axial packaging size of the damper assembly, allowing the overall axial length of the powertrain to be decreased. The powertrain includes an engine having a crankshaft, and a transmission having a transmission input member. The powertrain may be a hybrid powertrain, having another source of power, such as one or more motor/generators, in addition to the engine. A damper assembly is included that has an engine-side cover plate facing the engine, a transmission-side cover plate facing the transmission, and a retaining member between the cover plates. Resilient members are positioned between the engine-side cover plate and the transmission-side cover plate and supported by the retaining member. The engine-side cover plate is directly connected to the crankshaft for common rotation therewith. At least one generally-annular weighted member may be connected to the engine-side cover plate. The generally-annular weighted member has teeth at an outer perimeter to form a ring gear that may be used for starting the engine. Because the weighted member forms the ring gear, the gear teeth are thicker in an axial direction than if formed by a flexplate or by the engine-side cover plate.

The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic fragmentary cross-sectional illustration of a powertrain having a damper assembly connected between an engine and a transmission, taken at lines 1-1 in FIG. 2;

FIG. 2 is a perspective illustration of the damper assembly of FIG. 1, viewing the side of the damper assembly that faces the transmission; and

FIG. 3 is a perspective illustration of the damper assembly of FIGS. 1 and 2, viewing the side of the damper assembly that faces the engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, FIG. 1 shows a powertrain 10. The powertrain 10 includes an engine 12 indicated in general by the area represented by phantom lines and in fragmentary view by the engine crankshaft 14. The powertrain 10 also includes a transmission 16 indicated in general by the area represented by phantom lines, and in fragmentary view by the transmission input member 17. A portion of a transmission end cover 18 and a transmission casing 20 are also shown. One or more motor/generators, intermeshing gears, and selectively engagable torque-transmitting mechanisms may also be enclosed by the transmission casing 20, such that the transmission 16 is a hybrid transmission.

The engine 12 provides power to the transmission 16, and is connected to the transmission 16 though a damper assembly 22, as further described below. The damper assembly 22 reduces torsional vibrations caused by torque transferred from the engine 12 to the transmission 16. The damper assembly 22 is a â€œdryâ€ damper assembly, without the presence of oil or fluid as in conventional torque converters with internal damper assemblies, that uses spring isolation between relevant components to dampen oscillations.

The damper assembly 22 includes a retaining member 24, also referred to as a flange. The retaining member 24 has a plurality of spring pockets 26 spaced at various radial distances around the retaining member 24. Resilient members 28, which in this damper assembly 22 are coil springs, are positioned in the spring pockets 26.

The damper assembly 22 has an engine-side cover plate 30 that faces the engine 12. The engine-side cover plate 30 may be stamped steel, or any other suitable component, and has a central opening 31 that fits over a portion of the crankshaft 14. A series of apertures 32 in the engine-side cover plate 30 align with apertures 33 (one shown) in a flange portion 34 of the crankshaft 14. A series of bolts 36, one shown, extend through the apertures 32 and apertures 33 to directly connect the engine-side cover plate 30 for common rotation with the crankshaft 14. The engine-side cover plate 30 extends slightly axially to form a hub portion 38 in order to be appropriately positioned for connection to the crankshaft 14. The damper assembly 22 has no flexplate, which is a component typically connected for resisting thrust load in a torque converter and used for starting the engine with its ring gear and a 12-Volt starter application. Because a flexplate is not used, the axial space occupied by the damper assembly 22 between the engine 12 and the transmission 16 is reduced.

The damper assembly 22 further includes a transmission-side cover plate 40 directly connected for common rotation with the engine-side cover plate 30 by rivets 42 or other types of fasteners. The transmission-side cover plate 40 has an inner annular opening 44 that clears the transmission end cover 18. Thus, the engine-side cover plate 30 and the transmission-side cover plate 40 rotate together commonly with the crankshaft 14.

The retaining member 24 is splined or otherwise secured for rotation with a hub portion, also referred to as a mounting shaft 50. The mounting shaft 50 has external splines 52 so that it can fit within and be secured to the internal splines 54 of the transmission input member 17. Sealing components 56 are positioned between the transmission cover plate 18 and the transmission input member 17.

The transmission-side cover plate 40 defines a plurality of spring pockets 58 through which the sides of the springs 28 partially extend, as shown in FIG. 2. The engine-side cover plate 30 also has spring pockets 60, as shown in FIG. 3, through which the springs 28 may partially extend when compressed. Referring again to FIG. 1, when torsional vibrations occur due to differences in rotational speed of the crankshaft 14 and the transmission input member 17, the engine-side cover plate 30 and the transmission-side cover plate 40 will rotate slightly relative to the retaining member 24. This places pressure on the springs 28 as the sides of the spring pockets 26 and 58 move closer together and compress the springs 28, causing the springs 28 to elastically deform. Thus, the springs 28 dampen vibrations between the engine 12 and the transmission 16. The springs 28 may be of varying sizes to provide multiple spring rates.

Referring to FIG. 2, arcuate slots 64 spaced circumferentially about the transmission-side face plate 40 receive tabs 66 extending from the retaining member 24. The tabs 66 move within the slots 64 when the springs 28 are compressing. The ends 68, 69 of the slots 64 limit movement of the tabs 66 to prevent inelastic deformation of the springs 28, i.e., deformation beyond their designed limitations.

Referring again to FIG. 1, a first generally-annular weighted member 70, also referred to as an inertia plate, is connected for common rotation with the engine-side cover plate 30 near an outer extremity of the engine-side cover plate 30 with the same rivets 42 used to also connect the engine-side cover plate 30 with the transmission-side cover plate 40. The first annular weighted-member 70 has teeth 73 at an outer periphery 74 that form a ring gear, as best shown in FIG. 3. The teeth 73 are engaged with a starter motor assembly (not shown) to allow the starter motor to crank the crankshaft 14 to start the engine 12.

A second weighted annular member 75 is riveted to the first generally-annular weighted member 70 using a series of rivets 76. The inertia of both weighted members 70, 75 acts on the engine-side cover plate 30. Because the ring gear is formed by teeth 73 on the first generally-annular weighted member 70, the teeth 73 may be as wide in the axial direction as the width of the first generally-annular weighted member 70. In other embodiments, the teeth may be formed by both the first generally-annular weighted member 70 and the second generally-annular weighted member 75, and thus may be even wider, or may be formed by only the second weighted member 75. Using the first generally-annular weighted member 70 and/or the second generally-annular weighted member 75 to form the teeth results in wider teeth, able to handle heavier torque loading, than if the teeth were formed by the relatively thin engine-side cover plate 30.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.