Switchable Valve Lifter Having a Mis-Assembly Indicator

Abstract

An improved SHVL for an internal combustion engine comprises an improved arrangement for locking a spring tower into a pin housing. The spring tower is provided with an annular OD groove as in the prior art. The pin housing ID groove is modified to have a two-step groove comprising two adjacent regions having different depths (different diameters) and having a distinct transition lip therebetween. A spring clip of the correct size seats properly in the spring tower groove and in the lesser-diameter pin housing groove, resulting in a correct overall length of the SHVL. Any oversize clip is caught between the lower lip of the spring tower groove and the transition lip of the two-step pin housing groove, resulting in a SHVL distinctly shorter than nominal, which is easily detected by either direct length measurement or a gauge.

Description

TECHNICAL FIELD

The present invention relates to hydraulic valve lifters for internal combustion engines; more particularly, to a switchable valve-deactivating hydraulic valve lifter having an external lost motion spring and spring tower; and most particularly, to an improved arrangement for securing the spring tower to the pin housing that indicates when mis-assembly has occurred.

BACKGROUND OF THE INVENTION

Hydraulic valve lifters that are specially equipped for selective lost motion in an engine valvetrain to switchably deactivate an intake or exhaust valve are well known in the engine arts. In one form, such a “switchable hydraulic valve lifter” (SHVL) is provided with a lost motion coil spring that is captured on an end of the SHVL body by a spring tower. The spring tower extends within the body to mate with a pin housing that is slidably disposed within the body. When transverse locking pins in the pin housing are extended into engagement with the body, the SHVL is rigid and acts to faithfully translate the rotary motion of a cam lobe into reciprocal motion of an associated valve stem. When the locking pins are withdrawn into the pin housing, the cam lobe causes the pin housing to reciprocate within the body without such translation (in “lost motion” of the cam lobe). That is, the body moves in a first direction responsive to the cam lobe, against the force of the lost motion spring while the pin housing remains stationary. Thus, the associated valve becomes “deactivated”.

During assembly of a SHVL, the spring tower enters the end of the pin housing, the lost motion spring being in compression, and is retained therein by an expandable spring clip that is engaged in both an external annular groove in the spring tower and an internal annular groove in the pin housing, the clip being captured between the two components. Assembling these components requires that the clip be expanded around the spring tower (into the pin housing groove), allowing the spring tower to pass through the spring clip. The clip then must snap into the annular groove of the spring tower and also lock into the groove of the pin housing when the compression of the spring is reduced. The annular groove in the pin housing has a sloping side to accommodate slight variations in clip diameter.

The prior art assembly just described is especially vulnerable to failure from spring clips which are oversize. If the ID of the clip is too large by as little as 0.15 mm, the clip may not fully lock into the tower groove, allowing spontaneous dis-assembly under use conditions in an engine, which is highly undesirable. Unfortunately, there is no simple means at present for determining that this unsatisfctory condition exists in any SHVL after assembly.

What is needed in the art is a means for recognizing, in a population of manufactured SHVLs, any SHVLs have been mis-assembled with an unacceptably large clip, to permit the faulty SHVLs to be segregated and reworked before being installed into engines.

It is a principal object of the present invention to permit simple recognition of a mis-assembled SHVL.

SUMMARY OF THE INVENTION

Briefly described, an improved SHVL in accordance with the present invention includes an improved arrangement for locking a spring tower into a pin housing. The spring tower is provided with an annular OD groove as in the prior art. However, the pin housing ID groove is modified to provide a two-step groove comprising two adjacent regions having different depths (different diameters) and having a distinct transition lip therebetween. An expansion clip of the correct size seats properly in the spring tower groove and in the lesser-diameter pin housing groove, resulting in a secure mating and a correct overall length of the SHVL. Any oversize expansion clip is caught between the lower lip of the spring tower groove and the transition lip of the two-step pin housing groove, resulting in a SHVL approximately 1.0 mm shorter than nominal, which is easily detected by either direct length measurement or a gauge.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an elevational cross-sectional view of a portion of a prior art SHVL, substantially as shown in U.S. Pat. No. 6,866,014 B2;

FIG. 2 is a schematic cross-sectional view of a correctly-assembled prior art pin housing, spring tower, and expansion clip;

FIG. 3 is a schematic cross-sectional view of a mis-assembled prior art pin housing resulting from an expansion clip having an excessively large ID;

FIG. 4 is a schematic cross-sectional view of a correctly-assembled pin housing, spring tower, and expansion clip in accordance with the present invention; and

FIG. 5 is a schematic cross-sectional view of a mis-assembled pin housing in accordance with the present invention resulting from an expansion clip having an excessively large ID.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a prior art SHVL 10 comprises a body 12. A pin housing 14 is slidably disposed in a first bore 15 in body 12 and retained therein by a spring seat 16 mounted on the end of body 12. A plunger 18 and pushrod seat 17 are slidably disposed within a second bore 19 in pin housing 14 for actuation by a conventional lash-adjustment mechanism (not appearing in the SHVL portion in FIG. 1). A lost-motion coil spring 20 is mounted on spring seat 16 and is captured by a spring tower 22 disposed within spring 20 and having a terminal flange 24. Spring tower 22 extends into second bore 19 and is captured therein by a tower-locking mechanism 26, the improvement of which is the object of the present invention.

Referring to FIG. 2, a correct prior art tower-locking mechanism 26 is shown. Pin housing 14 is provided with an ID annular groove 28 having a lower wall 30 orthogonal to second bore 19 and an upper wall 32 formed at an incline to second bore 19. Spring tower 22 is provided with an OD annular groove 34 configured similarly to pin housing groove 28. An expandable clip 36 is captured within both grooves 28,34, preventing spring tower 22 from being forced from second bore 19 by the expansive force of compressed lost-motion spring 20 (FIG. 1). To assemble mechanism 26, clip 36 is inserted into groove 28, then the nose 37 of spring tower 22 is forced through clip 36, which is expanded thereby into groove 28. Clip 36 slides along spring tower 22 until clip 36 reaches and snaps radially inward into groove 34. Spring tower 22 then is urged outwards of the SHVL by spring 20 until clip 36 also engages wall 32 of groove 28. The spring tower is thus correctly locked into the pin housing.

Referring to FIG. 3, it is seen that if the ID of an incorrect clip 36′ is only slightly larger than nominal, clip 36′ cannot properly snap into groove 34 and instead becomes trapped between wall 32 and the lower corner 38 of groove 34. This is a metastable position that can allow the SHVL to appear to be locked correctly, yet under a load in use conditions in an engine 35, corner 38 may be forced past clip 36′ by a slight expansion of clip 36′ along wall 32, allowing the SHVL to become catastrophically dis-assembled. Thus, it is highly desirable to be able to recognize when such mis-assembly has occurred, before installing a mis-assembled SHVL into an engine 35.

Referring to FIG. 4, an improved tower-locking mechanism 126 in accordance with the present invention is shown. Spring tower 22 is substantially as shown in the prior art in FIGS. 1-3, comprising groove 34, nose 37, and lower lip 38. However, pin housing 114 is modified such that ID annular groove 128 is a two-step groove having a first and greater ID portion 128′, a second and lesser ID portion 128″, and a transition lip 140 therebetween. The difference between the inner and outer diameters of clip 36 (thickness of the clip itself) is approximately equal to the difference between the diameters of groove 34 and groove 128″. Thus, a correctly-sized clip 36 is trapped therebetween, as shown in FIG. 4, resulting in a correct assembly similar to the prior art assembly shown in FIG. 1.

Referring now to FIG. 5, the benefit of the invention becomes obvious. Because groove 128 is provided in two steps 128′, 128″ having transition lip 140 therebetween, oversize clip 36′ when mis-assembled into a SHVL cannot be seated in step 128″, in the correct fashion shown in FIG. 4. Rather, clip 36′ is trapped between lower lip 38 and transition lip 140, thus causing spring tower 22 to be axially displaced from its proper location by a distance 142. This distance is equal to an overall shortening of the assembled SHVL. Judicious selection of the shapes and lengths of groove steps 128′, 128″ can amplify relatively small degrees of oversize of clip 36′ into relatively large values of distance 142. The resulting deviations of overall SHVL length from nominal are easily detected by direct measurement or gauging, thus permitting sorting of mis-assembled deactivating hydraulic valve lifters from a population of deactivating hydraulic valve lifters.

While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

1. A switchable hydraulic valve lifter for an internal combustion engine, comprising: a) a spring tower having an annular groove formed in an outer surface thereof;b) a pin housing having a bore for receiving said spring tower and having a two-step annular groove formed in an inner surface thereof; andc) an expansion clip disposed in said spring tower annular groove and said pin housing two-step annular groove for locking said spring tower into said pin housing bore,wherein said two-step annular groove is defined by a first groove having a first diameter, a second groove adjacent said first groove and having a second and larger diameter,wherein a correctly-sized expansion clip is accepted into said spring tower annular groove and into said pin housing first groove, resulting in said switchable hydraulic valve lifter having a first overall length, andwherein an oversized expansion clip is prevented from entering said pin housing first groove, resulting in said switchable hydraulic valve lifter having a second overall length.

2. A switchable hydraulic valve lifter, in accordance with claim 1, wherein said two-step annular groove includes a transition lip formed between said first and second grooves.

3. A switchable hydraulic valve lifter, in accordance with claim 1, wherein said first overall length is greater than said second overall length.

4. An internal combustion engine, comprising a switchable hydraulic valve lifter including a spring tower having an annular groove formed in an outer surface thereof,a pin housing having a bore for receiving said spring tower and having a two-step annular groove formed in an inner surface thereof, andan expansion clip disposed in said spring tower annular groove and said pin housing two-step annular groove for locking said spring tower into said pin housing bore,wherein said two-step annular groove is defined by a first groove having a first diameter, a second groove adjacent said first groove and having a second and larger diameter,wherein a correctly-sized expansion clip is accepted into said spring tower annular groove and into said pin housing first groove, resulting in said switchable hydraulic valve lifter having a first overall length, andwherein an oversized expansion clip is prevented from entering said pin housing first groove, resulting in said switchable hydraulic valve lifter having a second overall length.

5. A method for sorting mis-assembled switchable hydraulic valve lifters from a population of switchable deactivating hydraulic valve lifters, comprising the steps of: a) establishing a predetermined correct overall length for a correctly-assembled switchable hydraulic valve lifter;b) measuring the overall length of each of said switchable hydraulic valve lifters; andc) segregating any switchable hydraulic valve lifters having an overall length other than said predetermined correct overall length.