Frustoconical valve stem sealing element

Abstract: A valve stem seal assembly 10 includes a rigid cylindrical shell 12 and an annular resilient seal body 14 contained entirely within the shell 12. Integral to the seal body 14 is a frustoconical sealing element 18 adapted to engage a valve guide 50 of an internal combustion engine (not shown). The sealing element 18 converges radially inwardly, and upon installation of the assembly on a valve guide 50 the outer surface of the sealing element 18 bends further radially inwardly to effectively seal the top surface of the guide 50. The seal body 14 includes a stem sealing aperture, which in one preferred embodiment is designed to engage the valve stem 40 without a spring. In the same or a similar embodiment, the shell 12 contains a circumferential array of tangs 38 for retention of the assembly on the guide 50.

Description: Background of the Invention This invention relates to valve stem seals utilized in intake and exhaust manifolds of internal combustion engines. More particularly, this invention relates to sealing elements in valve stem seals which assure against oil leakage at the tops of valve guides. Internal combustion engines contain intake and exhaust valves, each valve including a head and a stem integrally fixed to the head, and reciprocally mounted in a guide. As the valve stem ordinarily operates in a substantial volume of oil, much effort is directed to limiting the amount of oil consumed by the engine. In order to control oil consumption, valve seals are mounted on valve guides to meter oil flow between the stems and guides. A significant number of valve stem seal assemblies include a metallic casing or shell adapted to retain a resilient seal member, typically made of an elastomer or a polytetrafluoroethylene base material. Much effort has been directed to the shape of the resilient portion of the seal, particularly to the extent that the seal must not only engage the stem, but must also directly engage a portion of the valve guide itself. A major problem in designing seals relates to tolerance variations encountered in the manufacture of seal assembly parts. Tolerance variations in the valve assembly casings designed for securement to valve guides affect those portions of the seal which engage the valve guide and valve stem. Thus, inadequate sealing caused by tolerance variations may result in excessive oil consumption, notwithstanding the purpose of the seal. Several designs have been offered to compensate for tolerance variations, but none have been found to be fully satisfactory. DE-C-1196035 discloses a valve stem seal for sealing between a value guide and a valve stem of an internal combustion engine, the seal comprising a rigid cylindrical shell defining a longitudinal axis and having an end wall containing an aperture, and an annular resilient seal body disposed within the shell, the body comprising: a first annular portion, the interior annular surface of which provides a first sealing surface; and a second annular portion integrally formed with the first annular portion. EP-0392893 (which was published after the priority date of the present application but has an earlier priority date) discloses a valve stem seal assembly for sealing between an valve guide and a valve stem of an internal combustion engine, the seal comprising a rigid cylindrical shell defining a longitudinal axis and having an end wall containing an aperture and an annular resilient seal body disposed within the shell the body comprising: a first annular portion, the interior annular surface of which provides a first sealing surface; and a second annular portion in the form of frustoconical sealing element integrally formed with the first annular portion and which, in its free and unrestrained state, converges radially inwardly with respect to said axis the sealing element comprising an inboard sealing surface facing said axis and an outboard surface facing away from said axis. According to the present invention,the outboard surface is a sealing surface, and the inboard and outboard sealing surfaces converge to form an annular arcuate apex. The arcuate apex is disposed for sealing contact with a surface of the valve guide which lies in a plane perpendicular to the axis of the shell. Generally, the seal body may further comprise at least one annular rib extending circumferentially about the body, the rib being adapted to frictionally engage interior wall of the shell. Preferably, the seal body, including the frustoconical sealing element, are entirely contained within the interior of the shell. The shell may further comprise means for securing the shell to a valve guide, which means may comprises a circumferential array of tangs formed in the interior wall of the shell. The first sealing surface may be defined by a plurality of radially disposed serrations. The resilient body may further contain a spring extending circumferentially about the first sealing surface and which engages the exterior of the seal body. The sealing element preferably converges radially inwardly within a range of 30 to 60°C in its free and unrestrained state. Moreover, upon installation, the frustoconical element bends radially inwardly as the arcuate apex engages the annular top surface of the valve guide. The valve stem seal assembly of the a present invention includes a valve stem sealing element designed to accommodate commutative tolerance variations between the valve guide and the seal assembly. Brief Description of the Drawings Figure 1 is a cross-sectional side view of one preferred embodiment of a valve stem seal assembly constructed in accordance with the present invention, shown in its free and unrestrained state. Figure 2 is a cross-sectional side view of the preferred embodiment of Figure 1, after the assembly has been installed over a valve stem and valve guide. Figure 3 is a cross-sectional side view of a second preferred embodiment of the valve stem seal of the present invention, shown in a free and unrestrained state. Figure 4 is a cross-sectional side view the preferred embodiment of Figure 3, shown installed over a valve stem and valve guide. Detailed Description of Preferred Embodiments Referring initially to Figures 1 and 2, a first preferred embodiment of a valve stem seal assembly 10 is shown having a two-piece construction consisting of a rigid cylindrical casing or shell 12 and a resilient seal body 14. The seal body 14 is formed of an elastomer, and is frictionally retained within the preferably metallic shell 12. The body 14 contains a circumferential sealing surface 16 defined by an aperture as shown. The sealing surface 16 is adapted to sealingly engage a valve stem 40 in order to control oil consumption associated with the reciprocal movement of the stem 40 in a valve guide 50, as will be appreciated by those skilled in the art. In the preferred form, the surface 16 is formed of a plurality of annular lips. Extending radially inwardly toward a longitudinal axis "a-a" of the shell 12 is a frustoconical sealing element 18. In the preferred form, the sealing element 18 is integral with the seal body 14, and tends to collapse into an annular ring upon installation as shown in Figure 2, although the latter degree of bending is unnecessary to achieve an effective seal. Figures 1 and 2 show the relative positions of the sealing element prior to and after installation of the seal assembly 10 on the cylindrical valve guide 50 of an internal combustion engine (not shown). The element 18 comprises an elongate inboard surface 20 and an opposed elongate outboard surface 22. The outboard surface 22 is adapted to make sealing contact with a radially extending annular top surface 52 of the valve guide 50. The inboard and outboard surfaces 20, 22 converge to form an arcuate apex 24 which facilitates radially inward bending of the sealing element 18 upon installation (Figure 2). The rigid cylindrical shell 12 has an endwall 26 adapted for axial retention of the resilient seal body 14 within the shell 12. The endwall 26 has an aperture 28 which accommodates a valve stem passage through and into the interior of the seal assembly 10. The circumferential exterior 30 of the seal body 14 has at least one annular rib 32, sized for interference fit with the cylindrical interior wall 34 of the shell 12. The latter is for retention of the seal body in the shell during shipment. As earlier noted, the frustoconical sealing element 18 extends radially inwardly, preferably within a range of 30 to 60 degrees, relative to the axis "a-a" of the shell 12 in its free and uncompressed state. When installed, the element 18 collapses radially inwardly at an elbow 36 located at the interface of the element and the seal body 14. The outboard surface 22 of the sealing element 18 provides a sealing contact with the top 52 of the valve guide over a range of angles. In the practice of this invention, it is not necessary that the frustoconical element 18 be bent entirely perpendicularly to the axis "a-a" as shown. The seal is designed to be effective at any angle between the free and uncompressed state of the element up to the practical limit of the bend as shown in Figure 2. In the embodiment of Figures 1 and 2, the retention of the shell 12 on the valve guide 50 may be effected by a variety of methods, two of which are shown for convenience in Figure 2. At the left hand portion of Figure 2 retention is by means of a friction fit between the interior cylindrical wall 34 of the shell 12 and the cylindrical exterior 56 of the valve guide. Under the latter arrangement, the lower extremity 42 of the shell 12 bottoms against an annular step 58 on the valve guide 50. Referring to the right hand portion of Figure 2, retention is by means of a circumferential array of tangs 38 in the interior cylindrical wall 34 of the shell 12. The tangs engage a groove 54 in the guide 50. Referring now to Figures 3 and 4, a second preferred embodiment 10′ of a valve stem seal assembly is shown. The embodiment of Figures 3 and 4 is similar to that of Figures 1 and 2 except for the several features now described. First, a single annular rib 32′ is sized for interference fit with the interior wall 34′ of the shell 12′, and provides substantially the only frictional retaining force for holding the seal body 14′ in the shell 12′ prior to assembly. Secondly, a garter spring 60, supported in an exterior groove 62 of the resilient seal body 14′, is used to provide a compressive force between the seal body and stem. Thirdly, a more bulbous sealing element 18′ is utilized, although by reference to Figure 4, it will be appreciated that the element 18′ functions substantially in the same way as the element 18 of Figures 1 and 2. Finally, the left-hand portions of Figures 3 and 4 show an alternate single lip 16′, which may be utilized in lieu of the multiple lip surfaces 16 and 16'' otherwise shown.

Claims: A valve stem seal for sealing between a valve guide (50) and a valve stem (40) of an internal combustion engine, the seal comprising a rigid cylindrical shell (12) defining a longitudinal axis (a-a) and having an end wall (26) containing an aperture (28), and an annular resilient seal body (14) disposed within the shell (12), the body comprising: a first annular portion, the interior annular surface of which provides a first sealing surface (16); and a second annular portion in the form of frustoconical sealing element (18) integrally formed with the first annular portion and which, in its free and unrestrained state, converges radially inwardly with respect to said axis (a-a), the sealing element (18) comprising an inboard sealing surface (20) facing said axis (a-a) and an outboard surface (22) facing away from said axis (a-a), characterised in that the outboard surface (22) is a sealing surface, and in that the inboard and outboard sealing surfaces (20,22) converge to form an annular arcuate apex (24). A valve stem seal as claimed in claim 1 characterised in that the seal body further comprises at least one annular rib which extends circumferentially about the body and frictionally engage an internal wall of the shell. A valve stem seal as claimed in claim 1 or 2 characterised in that the seal body is entirely contained within the interior of the shell. A valve stem seal as claimed in any of claims 1 to 3 characterised in that the shell further comprises means for securing the shell to a valve guide. A valve stem seal as claimed in claim 4 characterised in that the means for securing the shell comprises a circumferential array of tangs formed in an interior wall of the shell. A valve stem seal as claimed in any preceding claim characterised in that the first sealing surface comprises a plurality of radially disposed serrations. A valve stem seal as claimed in any preceding claim characterised in that the seal body further comprises a spring which extends circumferentially about the first sealing surface, the spring engaging an exterior of the seal body.

Inventors: BINFORD J DUDLEY, BOND PHILIP L, BRUNS IVAN J, FIEDLER DAVID F, BINFORD, J. DUDLEY, BOND, PHILIP L., BRUNS, IVAN J., FIEDLER, DAVID F.
Applicants: DANA CORP, DANA CORPORATION
Application year: 1990
Main classification: F01L3
IPC codes: F01L3