Patent Application
20090078077
The present invention relates generally to viscous torsional vibration dampers, and more particularly to a self-centering viscous torsional vibration damper.
Viscous vibration dampers for overcoming torsional oscillations or vibrations in rotary masses such as crankshafts are known in the prior art. For example, U.S. Pat. No. 2,514,139 discloses such a torsional vibration damper. As shown, such dampers generally comprise a damper housing that contains an inertial mass or flywheel. Spaces or gaps between the housing and the inertial mass are filled with a viscous medium. The inertial mass rotates relative to the housing to provide damping by viscous sheer of the viscous medium between the housing and the inertial mass.
With parenthetical reference to corresponding parts, portions, or surfaces of the disclosed embodiment, merely for purposes of illustration and not by any way of limitation, the present invention provides an improved viscous torsional vibration damper (15) comprising a housing (16) adapted to be connected to a rotary member to be damped, the housing comprising an annular chamber (19) having an inner cylindrical surface (24) and an outer cylindrical surface (21) oriented about a central axis (x-x), an inertial mass (28) within chamber and having an inner cylindrical surface (32) and an outer cylindrical surface (29) oriented about an axis of rotation (r-r), the inertial mass and the chamber configured such that the inertial mass is rotatable in the chamber relative to the housing, a clearance gap (44) between the housing and the inertial mass, a viscous fluid disposed in the clearance gap, at least one centering element (35) between the opposed inner cylindrical surfaces of the chamber and the inertial mass or the opposed outer cylindrical surfaces of the chamber and the inertial mass, and the centering element configured and arranged to bias the axis of rotation of the inertial mass towards alignment with the central axis of said chamber.
The damper may further comprise a second centering element (36) between the opposed inner cylindrical surfaces of the chamber and the inertial mass or the opposed outer cylindrical surfaces of the chamber and the inertial mass, the second centering element configured and arranged with the centering element to bias the axis of rotation of the inertial mass towards alignment with the central axis of the chamber. The centering element may be between the opposed inner cylindrical surfaces of the chamber and the inertial mass and the second centering element may be between the opposed outer cylindrical surfaces of the chamber and the inertial mass. The centering element may be an O-ring. The inner cylindrical surface of the inertial mass may comprise a groove and the O-ring may be seated in the groove and extend in an uncompressed state at least beyond the edge of the groove and the inner cylindrical surface of the inertial mass. The inner cylindrical surface of the inertial mass may comprise a first groove (33) and a second groove (34), the centering element may comprise an O-ring (35) seated in the first groove, and the second centering element may comprise an O-ring (36) seated in the second groove. The outer cylindrical surface of the inertial mass may comprise a first groove and a second groove, the centering element may comprise an O-ring seated in the first groove, and the second centering element may comprise an O-ring seated in the second groove. The inner cylindrical surface of the chamber may comprise a first groove and a second groove, the centering element may comprise an O-ring seated in the first groove, and the second centering element may comprise an O-ring seated in the second groove. The outer cylindrical surface of the chamber may comprise a first groove and a second groove, the centering element may comprise an O-ring seated in the first groove, and the second centering element may comprise an O-ring seated in the second groove. The damper may further comprise a bypass channel (38) extending through the inertial mass. At least one of the chamber and the inertial mass may comprise a recess (25) configured to provide a reservoir for the fluid and the channel may communicate with the reservoir.
In another aspect, the viscous torsional vibration damper may comprise a housing adapted to be connected to a rotary member to be damped, the housing comprising an annular chamber having an inner cylindrical surface and an outer cylindrical surface elongated about a central axis, an inertial mass within the chamber and having an inner cylindrical surface and an outer cylindrical surface elongated about an axis of rotation, the inertial mass and the chamber configured such that the inertial mass is rotatable in the chamber relative to the housing, a first annular centering element and a second annular centering element between the opposed inner cylindrical surfaces of the chamber and the inertial mass or the opposed outer cylindrical surfaces of the chamber and the inertial mass, the annular centering elements configured and arranged to bias the axis of rotation of the inertial mass towards alignment with the central axis of the chamber, a clearance gap between the housing and the inertial mass, the clearance gap having a first portion and a second portion separated by at least one of the centering elements, a bypass channel extending through the inertial mass or at least one of the centering elements from the first portion of the clearance gap to the second portion of the clearance gap, and a viscous fluid within the clearance gap.
The first centering element may be between the opposed inner cylindrical surfaces of the chamber and the inertial mass and the second centering element may be between the opposed outer cylindrical surfaces of the chamber and the inertial mass. The inner cylindrical surface of the inertial mass may comprise a groove and the first centering element may comprise an O-ring seated in the groove. The inner cylindrical surface of the inertial mass may comprise a second groove and the second centering element may comprise a second O-ring seated in the second groove. The outer cylindrical surface of the inertial mass may comprise a groove and the first centering element may comprise an O-ring seated in the groove. The outer cylindrical surface of said inertial mass may comprise a second groove and the second centering element may comprise a second O-ring seated in the second groove. The inner cylindrical surface of the chamber may comprise a groove and the first centering element may comprise an O-ring seated in the groove. The inner cylindrical surface of the chamber may comprise a second groove and the second centering element may comprise a second O-ring seated in the second groove. The outer cylindrical surface of the chamber may comprise a groove and the first centering element may comprise an O-ring seated in the groove. The outer cylindrical surface of the chamber may comprise a second groove and the second centering element may comprise a second O-ring seated in the second groove. The chamber or the inertial mass may comprise a recess configured to provide a reservoir for the fluid and the channel may communicate with the reservoir. The channel may extend through both the inertial mass and at least one of the centering elements.
Accordingly, the general object of the invention is to provide a viscous damper having efficient damping at low operating speeds.
Another object is to provide a viscous damper with efficient fluid dispersion.
These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the claims.
At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces, consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.
Referring now to the drawings, and more particularly to
An internal flywheel 28 is contained within chamber 19 of housing 16. Flywheel 28 is adapted to rotate within chamber 19 relative to housing 16 and is oriented about an axis of rotation r-r and has an outer cylindrical surface 29, an annular left side surface 30, an annular right side surface 31, and an inner cylindrical surface 32. Flywheel 28 is proportioned so as to provide small gaps, spaces or clearances 44a-d between surfaces 21, 22, 23 and 24 of chamber 19 and opposed surfaces 29, 30, 31 and 32 of flywheel 28, respectively. Clearances 44a-d between such surfaces contain a viscous fluid or medium, such as silicon. Inner cylindrical surface 24 includes a recessed area 25 for holding a limited supply of such viscous fluid and thereby acts as a fluid reservoir. A tapped fill port 26 is provided through housing 16 in order to allow for chamber 19 to be filled with the viscous fluid.
Flywheel 28 is generally free floating within chamber 19 within the relatively close limits permitted by O-rings 35, 36 and bearings 42, 43 described below and the narrow side and outer peripheral clearances 44a-d containing viscous fluid. As clearances 44a-d are generally filled with a viscous fluid having a high shear and compression resistance, at high speeds the viscous fluid becomes more and more resistant to relevant movement of flywheel 28 and housing 16. With the various surfaces of flywheel 28 closely spaced with respect to the opposing surfaces of chamber 19, maximum shear resistance efficiency is obtained in the operation of damper 15. Damper 15 thereby operates to damp vibration in the shaft or other rotational mass or member to which damper 15 is operatively connected.
As shown on
It is contemplated that the centering elements may be located between opposed surfaces of flywheel 28 and chamber 19 at other locations or in other relative orientations. For example, rather than in the inner cylindrical surface 32 of flywheel 28, the grooves and corresponding O-rings could be provided in the inner cylindrical surface 24 of housing 16, in the outer cylindrical surface 29 of flywheel 28, in the outer cylindrical surface 21 of housing 16, or in a combination of the forgoing. While centering elements 35 and 36 are O-rings in the preferred embodiment, it is contemplated that they can be made of other elastomeric or springlike materials and may have other cross-sections. Similarly, grooves 34 and 35 may have other non-rectangular cross-sections. As a further alternative, other compressible mechanical spring-like elements may be used to create a radial centering bias to flywheel 28, with the preload of the compressible elements radially centering or aligning flywheel 28 in housing 16.
If self-centering rings 35 and 36 are made of a compressible material, the amount of hardness, compress and torsional elasticity designed into the centering rings allows for further adjustment of the damping rate of damper assembly 15. By controlling the compression and the amount of torsional elasticity developed by centering rings 35 and 36 between flywheel 28 and housing 16, it is possible to develop a controlled amount of damping. This is in addition to the viscous damping due to shear of the viscous medium in gap 44 between flywheel 28 and housing 16. Additional damping is adjustable by manipulation of the centering rings, which allows damper 15 to be tuned to better damp the torsional vibrations occurring at the specific operational ranges being damped. Also, additional damping by manipulation of the properties of the self-centering rings may allow the damping rate of the damper to be increased to a level that is not otherwise achievable through other means, such as adjustment of the clearance gaps 44 between flywheel 28 and housing 16 or adjustment of the viscosity of the viscous medium in clearance gaps 44.
As shown in
The present invention contemplates that many changes and modifications may be made. Therefore, while the presently-preferred forms of the damper has been shown and described, and a number of alternatives discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.
