GB2180894A - Improved seal for a reciprocating valve - Google Patents

Abstract

An improved seal (44) for a reciprocating valve journalled in a valve guide is formed of a resilient elastomeric material and includes a valve stem sealing section (50) and a valve guide sealing section (52). A helical spring (48) is co-axially embedded in the seal. The spring (48) is preferably formed from a single piece of round wire extending throughout both of the sealing sections (50, 52). Alternatively, the spring can be formed in two pieces (62, 66, Figure 3), one for each of the sealing sections, or can be formed from flat wire (84, Figure 4). The seal can be quickly and easily installed about a reciprocable valve (28) in an internal combustion engine. <IMAGE>

Description

SPECIFICATION Improved seal for a reciprocating valve Background of the invention This invention relates generally to a means for effecting a seal around reciprocating members. More specifically, the invention concerns a means for effecting a seal around a reciprocating valve stem journalled in a valve stem guide in an internal combustion engine.

Internal combustion engines have a plurality of intake and exhaustvalves contained therein. Each of these valves includes a valve head connected to a valve stem. The valve stem is reciprocally mounted within a valve guide. The valve guide may be an integral part ofthe cylinder head or block, or it may be formed as a separate bushing fitted in a bore formed through the cylinder head or block. The end of the valve stem opposite the valve head is typically engaged buy a cam on a rocker arm in an overhead valve engine or bya plunger in an L-head engine. In either case, there must be provided a valve seal, which includes both a valve guide sealing section and a valve stem sealing section.The valve guide sealing section is operable to engage the exterior surface of the valve guide, while the valve stem sealing section is operably to engage the exterior surface of the valve stem.

In prior art seals, various means have been employed to effect a tight seal between the valve guide sealing section and the valve guide, as well as between the valve stem sealing section and the valve stem. Certain prior art structures utilize a seal including first and second annularspring steel members.

The first spring member is positioned around the ex- terior of the valve guide sealing section of the seal.

The second spring member is positioned around the exterior of the valve stem sealing section of the seal.

This configuration suffers from two major drawbacks. First, installation of the seal is a multiple step process, requiring the steps of initially assembling valve guide and valve stem spring members about the seal priorto installation on an engine, then installing the seal carrying the spring memberaboutthe valve in the engine. Second,when the seal is positioned on a valve stem carried in a bore which is formed not exactly concentric with the exterior surface of the valve guide (which is engaged by the valve guide sealing section of the seal), the seal will be constantlyflexed to accommodate the eccentricity of the bore relative to the exterior surface of the valve guide. This flexs rue is concentrated at the points where the spring members contact the exterior surface of the seal.As a consequence, the seal is subject to degradation, particularlyadjacentthespring members.

Other priorartstructures utilize a seal wherein a resilient sleeve and a reinforcing metal sleeve surround the portion of the resilient seal adjacent to the valve stem guide. The end of the reinforcing metal sleeve closest to the valve head is provided with a plurality of sealing flanges which, priorto installation, extend radially outwardly. When the seal is positioned around the guide, the sealing flanges are def ormed radially inwardlyto securethe seal tothe valve stem guide. The other end ofthe reinforcing metal sleeve projects radially inwardly at a point below the top of the valve stem guide. Installation of such a seal is a two-step process, requiring the steps of positioning the seal around the valve guide and deforming the sealing flanges radially inwardly.In addition, this seal is subject to degradation in a mannersimilartothe seal described above, part icularly at points adjacent to the portion of the metal sleeve which projects radially inwardly.

Summary of the invention The present invention relates to an improved seal for a reciprocating valve journalled in a valve guide.

The seal is formed of a resilient elastomeric material and includes a valve stem sealing section and avalve guide sealing section. A helical spring is co-axially embedded in the seal. The spring is preferably formed from a single piece of round wire extending throughout both of the sealing sections. Alternatively, the spring can be formed in two pieces, onefor each of the sealing sections, or can be formed from flatwire. The seal can be quickly and easily installed about a reciprocable valve in an internal combustion engine.

Accordingly, it is an object of the present invention to provide an improved seal for a reciprocating valve stem journalled in a valve stem guide.

It is another object of the present invention to provide an improved valve seal which requires no external retaining means and can be installed quickly and easily.

It is further object of the present invention to provide an improved valve seal which readily accom modates flexu re stress caused by an eccentric valve stem bore.

Briefdescription ofthe drawings Figure lisa fragmentary side elevational view, partially in section, of a cylinder head of an overhead valve engine provided with an improved valve seal in accordance with the present invention.

Figure2 is an enlarged view, partially broken away, of the valve seal illustrated in Figure 1.

Figure3 is an enlarged sectional elevational view of a second embodiment of an improved valve seal in accordance with the present invention.

Figure 4 is an enlarged sectional elevational view, partially broken away, of a third embodiment of an improved valve seal in accordance with the present invention.

Detailed description of the preferred embodiments Referring now to Figure 1, a portion of a cylinder head of an internal combustion engine is shown generally at 10 as having a passageway 12, which passageway 12 may either be part of the fuel intake system or the exhaust system of the engine. The passageway 12 communicates through an opening 14, bounded by a valve seat 16, with a combustion chamber 18. Secured in a bore 19formedthroughthe cylinder head 10 into the passageway 12 is a valve guide 20, which is illustrated as being formed as a separate member rigidly secured thereto. Alternati vely, the valve guide 20may be formed as an integral part ofthe cylinder head 10. The valve guide 20 is provided with a central longitudinal bore 22.Avalve, indicated generally at 24, is slidably disposed in the valve guide bore 22 for axial reciprocal movement.

The valve 24 includes a valve stem 26 received within the valve guide bore 22. The valve stem 26 is connected to a valve head 28 positioned belowtheopening 14. Thevalve head 28 is adapted to sealingly engage the valve seat 16 to alternately permit and prevent communication between the passageway 12 and the combustion chamber 18 as the valve 24 reciprocates downwardly and upwardly.

The valve stem 26 projects upwardly through the valve guide bore 22 beyond the top of the guide 20 and is usually provided, in the proximity of its upper end,with asnap ring 30forretainingthereon acollar 32 having an annular flange 34. Disposed between the collar flange 34 and the cylinder head loins a coil spring 36. The coil spring 36 biases the valve 24 axially upwardlytoward a position wherein the head 28 of the valve 24 engages the valve seat 16 to prevent communication between the passageway 12 and the combustion chamber 18.Atop end 38 ofthevalve stem 26 is engaged by a conventional rocker arm 40.

The rocker arm 40 is actuated, through a push rod 42, by a conventional cam shaft (not shown) within the engine. When actuated, the rocker arm 40 bears downwardly againstthe top end 38 to move the valve 24 axially downwardly against the urging ofthe coil spring 36, thereby displacing the valve head 28 from engagement with the valve seat 16 to permitcom- munication between the passageway 12 and the combustion chamber 18. Because of the friction generated by the contact between the rocker arm 40 and the top end 38 of the valve stem 26, oil must be supplied to such point of contact to prevent excess wear.

This oil is supplied conventionally from an opening (not shown) formed in the rocker arm 40. A portion of the oil travels down the stem 26 to further lubricate the valve stem 26 as it reciprocates within the valve guide bore 22.

Fastened aboutthe uppermost portion ofthevalve guide 20 is an improved valve seal, indicated generally at 44, in accordance with the present invention.

The seal 44 is provided to preventoilfrom running down the valve stem 26 toward the valve head 28 and into the combustion chamber 18. As illustrated in more detail in Figure 2, the seal 44 includes a resilient body 46 having a helical spring 48 co-axially embed- ded therein throughout its length. The resilient body 46 is preferablycomposed of a polymerizedfluoroelastomer, such as the one commercially available underthe trade designation "Viton".Other suitable materials ofwhich the resilient body 46 may be com- posed include Buna-N rubber, poly tetrafluoroethylene, and nylon, as well as a host of other elastomericmaterials.The composition ofthe resilient body 46 is not critical, so long as it is composed of a material which is resilient and resistantto degradation in the temperature ranges encountered in a particular application.

The resilient body 46 is molded or otherwise formed about the helical spring 48so that the latter becomes an integral portion of the former. The seal 44 is shaped to form a valve stem sealing section 50 and a valve guide sealing section 52. In the valve guide sealing section 52, there is a cylindrical valve guide sealing surface 54which defines a valve guide cavity 55. The diameter of the valve guide sealing surface 54 is slightly smaller in diameter that the diameter of the exterior surface of the associated valve guide 20 such thatthevalveguidesealing surface 54 sealingly engages the exterior surface of the associated valve guide 20, as illustrated in Figure 1. The helical spring 48 also maintains the valve guide sealing surface 54 in sealing engagement with the exterior surface ofthevalve guide 20.Similarly, the valve stem sealing section 50 is provided with a cylindrical valve stem sealing surface 56 which defines a valve stem cavity 57. The valve stem sealing surface 56 may be formed with a helical groove, as illustrated in Figure 1,to provide a meansforcontrollingtheflow of lubricating oil downwardly along the valve stem 26 in accordance with the invention disclosed in U.S.

Patent No. 3,498,621 and, therefore, does not constitute a feature of the instant invention. Alternatively, the valve stem sealing surface 56 may be formed with a plurality ofannulargroovestherein or may simply be formed with a smooth interior cyiindrical surface. The valve stem sealing surface 56 in also formed with a diameter which is slightly less than the diameter ofthe exterior surface of the associated valve stem 26, as illustrated in Figure 1.

When the seal 44 is installed in the engine, the exterior surface of the valve stem 26 will compress the portion of the resilient body 46 between the valve stem sealing surface 56 and the helical spring 48.

This occurs because the co-axiallywrapped spring 48 is relatively inexpandable, as compared with the resilient body 46. Consequently, the valve stem sealingsurface56will bearsnuglyagainsttheenclosed valve stem 26. Similarly, the portion of the resilient body 46 between the valve guide sealing surface 54 and the helical spring 48 will also be compressed. As a result, the valve guide sealing section 52 will tightly engage the exterior surface ofthevalve guide 20 and maintain the seal 44 in a fixed position relative thereto. It will thus be appreciated that the seal 44 can be quicklyand easily installed aboutthevalve 24 withoutthe use of externai bands or rings.Further- more, it can be seen thatthe seal 44 will conform to out-of-round valve guides 20 and off-centervalve guide bores 22 without significant additional degradation during use.

Asecondembodimentofan improved valve seal in accordance with the present invention is indicated generally at 60 in Figure 3. In this embodiment, are silient body 61 has a first helical spring 62 embedded therein within a valve stem sealing section 64. A second helical spring 66 is embedded within a valve guide sealing section 68. The valve stem sealing section 64 may be formed with an outer diameter which is less than the outer diameter of the valve guide sealing section 68. A valve guide cavity 70 is defined by a cylindrical valve guide sealing surface 72 formed in the valve guide sealing section 68.The valve guide cavity 70 is sized in accordance with the valve guide cavity 55 described above such thatthe valve guide sealing section 68 will be compressed between the helical spring 66 and the valve guide sealing surface 72 when inserted about the valve guide 20. Similarly, a valve stem cavity 74 is defined by a valve stem seal ing surface 76 provided on the interior of the valve stem sealing section 64. The valve stem opening 74is sized in accordance with the valve stem 57 described above such thatthevalve stem sealing section 64will be compressed between the helical spring 62 and the valve stem sealing surface 76 when inserted about the valve stem 26.The valve stem sealing surface 76 shown in Figure 3 includes a plurality of annular grooves designed to control the flow of lubricating oil through the valve stem sealing section 64, as mentioned above.

Athird embodiment of an improved valve seal in accordance with the present invention is indicated generally at 80 in Figure 4. The seal 80 includes are silient body 82 having a helical spring 84 embedded therein. The helical spring 84 is composed of a flat wire, as distinguished from the round wires forming the helical spring 36 (illustrated in Figure 2), and the first and second helical springs 62 and 66 (illustrated in Figure 3). The seal 80further includes a valve stem sealing section 86 and a valve guide sealing section 88. Avalve stem cavity 90 is defined by a cylindrical valve stem sealing surface 92 formed in the valve stem sealing section 86. Avalve guide cavity 94 is defined by a cylindrical valve guide sealing surface 96 formed in the valve guide sealing section 88.The valve stem cavity 90 and the valve guide cavity 94 are sized as described above in connection with the cor responding cavities 55 and 57, respectively.

All of the above-described seals obviate the ex ternal retainer means associated with prior art valve seals. Furthermore, such seals can be installed in a single step, i.e. simply by positioning the seal around the valve stem and guide of an internal combustion engine. Flexure stresses caused by eccentric valve guide bores will be evenly distributed throughout seals produced in accordance with the presentinven tion, thereby improving the useful life thereof. It will be appreciated bythose skilled in theartthatthe pre- sent invention is susceptible to many variations. The foregoing disclosure illustrates the best modes cur rently known to the inventor for practicing the pre sent invention. Itwill be apparent that many depar- tures from the foregoing disclosure can be made without departing from the scope of the invention as defined bythefollowing claims.

Claims (12)

1. Aseal adapted for installation about a valve stem journalled for reciprocating movement in a valve guide of an internal combustion engine com prising; a valve guide sealing section composed of an elas tomeric material and having an interior surface and an exterior surface; a valve stem sealing section composed of an elas tomeric material and having an interior surface and an exterior surface; and spring means co-axially embedded within said valve guide sealing section and said valve stem seal ing section between the interior and exterior surfaces thereof.

2. The invention defined in Claim 1,wherein said valve guide sealing section and said valve stem sealing section are formed from a unitary body and said spring means includes a helical spring co-axiallyembedded within said body.

3. The invention defined in Claim 2 wherein said helical spring is formed of round wire.

4. The invention defined in Claim 2 wherein said helical spring is formed offlatwire.

5. The invention defined in Claim 1 wherein said valve guide sealing section and said valve stem sealing section are formed from a unitary body and said spring means includes respective helical springs coaxially embedded within each of said sealing sections.

6. The invention defined in Claim Swherein said helical springs are formed of round wire.

7. The invention defined in Claim Swherein said helical springs are formed of flat wire.

8. A seal adapted for installation about a valve stem journalled for reciprocating axial movement in a valve guide of an internal combustion engine comprising: a valve guide sealing section composed of an elas tomericmaterial and having an interiorsurfaceand an exterior surface, said interior surface having a diameter which is smal ler than the diameter of the valve guide adapted to be received therein; a valve stem sealing section composed of an elastomeric material and having an interior surface and an exterior surface, said interior surface having a diameter which is smallerthan the diameter of the valve stem adapted to be received therein; and helical spring means co-axiai ly embedded within said valve guide sealing section and said valve stem sealing section between the interior and exteriorsurfaces thereof, whereby said valve guide sealing section and said valve stem sealing section are compressed between the valve guide and the valve stem, respectively, and said helical spring means when the seal is stalled thereabout.

9. The invention defined in Claim 8wherein said sealing sections are formed of a unitary body and said helical spring means is formed of round wire.

10. The invention defined in Claim 8 wherein said sealing sections are formed of a unitary body and said helical spring means is formed ofaflatwire.

11. Avalve stem seal substantially as described herein with reference to, and as shown in, the accompanying drawings.

12. An internal combustion engine including a valve stem seal in accordance with any one of the preceding claims.