Mechanical lash ring for a switchable valve train member

A switchable valve train member, such as a deactivating valve lash adjuster or a deactivating hydraulic valve lifter, including a pin housing slidably disposed within an axial bore in a body. A transverse bore in the pin housing contains a retractable locking pin that engages a feature in the body including a locking surface whereby the body and the pin housing are locked together for mutual actuation by rotation of a cam lobe. A lash ring at the outer end of the body includes a portion extending into the axial bore that limits the travel of the pin housing within the body and thereby sets the internal mechanical lash in the switchable member. The axial thickness of the lash ring may be varied between assemblies to compensate for manufacturing variation in the components and is secured to the body in any of various configurations.

TECHNICAL FIELD

The present invention relates to switchable valve train members such as deactivating hydraulic lash adjusters (DHLAs) and deactivating hydraulic valve lifters (DHVLs) in internal combustion engines; and more particularly, to an apparatus for setting internal mechanical lash in switchable valve train members.

BACKGROUND OF THE INVENTION

It is well known that overall fuel efficiency in a multiple-cylinder internal combustion engine can be increased by selective deactivation of one or more of the engine valves, especially the intake valves, under certain engine load conditions. For cam-in-block engines, a known approach to providing selective deactivation is to equip the hydraulic valve lifters for those valve trains with means whereby the lifters may be rendered incapable of transferring the cyclic motion of the engine cam into reciprocal motion of the associated valves. For an overhead-cam engine, a known approach is to equip the hydraulic lash adjusters for those valve trains with means whereby the rocker arm may be rendered incapable of transferring the motion of engine the cams into reciprocal motion of the associated valves.

Typically, a DHLA includes, in addition to the conventional hydraulic lash elimination means, a concentric inner pin housing and outer HLA body which are mechanically responsive to the force of the rocker arm as exerted by the cam lobe, and which may be selectively latched and unlatched hydromechanically to each other, typically by the selective engagement of pressurized engine oil on locking pins.

An important consideration in a DHLA is the amount of internal mechanical lash deliberately incorporated into the DHLA. In prior art DHLAs, a transverse bore in the pin housing contains the two opposed locking pins which are urged outwards of the pin housing by a pin-locking spring disposed in compression therebetween to engage a circumferential groove including a locking surface in the inner wall of the HLA body whereby the HLA body and the pin housing are locked together to produce reciprocal motion of a rocker arm disposed on the DHLA. When valve deactivation is desired, the pins are withdrawn from the DHLA body by application of hydraulic fluid such as engine oil to the outer ends of the pins at pressure sufficient to overcome the force of the pin-locking spring.

Prior art DHVLs, such as shown in U.S. Pat. No. 6,578,535, typically are assembled from a top end of the DHVL body (which is closed at its bottom end) by insertion of components through the open top end and securing the components with one or more retaining rings and the like, fitting into an annular groove formed in the inner wall of the DHVL body below the open end thereof. The rings also serve to set internal mechanical lash in the DHVL by the selection of rings of appropriate thickness during assembly of the DHVL. The rings act as a mechanical stop to limit the outward motion of the pin housing prior to engagement and disengagement of the locking pins. Preferably, the lash rings permit the pin housing to travel to a position wherein the locking pins can clear the bottom surface, or ledge, of the locking feature in the DHVL body by a small amount, typically about 0.005 inches or less. Excess internal mechanical lash results in clatter and wear of the DHVL during engine operation, and can have an adverse effect on the lift characteristics of the associated valve. Thus, controlling the axial position of the underside of the retaining rings with respect to the ledge of the locking feature is of critical importance.

Typically, because of variation in manufacturing tolerances of the body, pin housing, and pins, the correct lash is obtained only by iterative trial and measurement using rings of differing thickness. However, setting the lash in this fashion is difficult, requiring repeated assembly and disassembly of the pin housing from the DHVL body because accessing the lash-setting retaining snap rings to remove the pin housing once installed is difficult and complicated.

Further, in cases where the wall of the DHVL body is thin because of packaging constraints, the presence of an inner-wall annular groove for the retaining rings near the open end of the DHVL body structurally weakens the wall of the body.

Referring to U.S. Pat. No. 6,513,470, a spring seat is shown for an external lost motion (LM) spring in a DHVL, wherein the spring seat also functions as a variable-thickness shim for setting the internal mechanical lash in each valve deactivation assembly. The spring seat is held in place by the LM spring that is captured by a spring tower. The spring seat rests on the outer end of the lifter body and also includes a cylindrical portion that extends into the lifter bore to engage the pin housing therein, the cylindrical portion being selectively varied to control mechanical lash. Thus, the seat serves to control mechanical lash without a requirement for a retaining groove in the inner wall of the lifter bore.

This latter approach for setting lash is not adaptable to current DHLAs since, in prior art DHLAs, the LM spring is internal to the assembly, and thus there is no spring seat requirement at the outer end of the body.

What is needed in the art is an improved DHLA wherein components are easily assembled, wherein mechanical lash is easily set, and wherein an annular groove for locking a retaining ring is obviated.

It is a principal object of the present invention to reduce the cost and complexity of an improved DHLA, to improve the ease and reliability of assembly thereof, and to increase the operating reliability thereof.

SUMMARY OF THE INVENTION

Briefly described, a DHLA in accordance with the present invention includes a conventional hydraulic lash adjustment mechanism disposed within a plunger slidably disposed within a pin housing that is slidably disposed within an axial bore in a lifter body. A transverse bore in the pin housing contains two opposed, selectively-retractable locking pins that engage a circumferential groove including a locking surface in the lifter body whereby the lash adjuster body and the pin housing are locked together for mutual actuation by rotary motion of the cam lobe to produce reciprocal motion of an engine RFF pivotably disposed on a domed head of the plunger.

A lash ring disposed at the outer end of the DHLA body and surrounding the pin housing includes a portion extending into the bore in the DHLA body to engage the pin housing. The lash ring thus functions to limit the travel of the pin housing within the DHLA body and thereby sets the internal mechanical lash in the deactivation mechanism. The lash ring may be provided as an inexpensive two-part ring, the first part being a standard-thickness ring and the second part being a shim having a thickness selected to provided a predetermined amount of mechanical lash in the assembled lifter. Preferably, the lash ring is provided as a single ring of desired thickness, which thickness varies from assembly to assembly to compensate for manufacturing variation in the components. The lash ring may be secured to the body in any of various configurations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, a prior art DHVL10is shown, substantially as disclosed in U.S. Pat. No. 6,578,535, the relevant disclosure of which is incorporated herein by reference. DHVL10has a generally cylindrical body12. A pin housing14is slidably disposed within a first axial bore16in body12. Pin housing14itself has a second axial bore18for slidably receiving a plunger20having a pushrod seat22for receiving an end28of a valve actuator such as pushrod30in cam-in-block engine valve train (not shown). Pin housing14has a transverse bore24slidably receivable of two opposed locking pins26separated by a pin-locking spring28disposed in compression therebetween. First axial bore16in body12is provide with an engagement feature such as circumferential groove31for receiving the outer ends of locking pins26, thrust outwards by spring28when pins26are axially aligned with groove31. In such configuration, DHVL10is in valve-activation mode. (FIG. 1is a split view of DHVL10. The left side shows DHVL10in a valve activation mode; the right side shows DHVL10in a valve deactivation mode). An LM spring34is disposed within a chamber35below pin housing for absorbing lost motion of pin housing14within bore16when DHVL10is in deactivation mode.

Groove31further defines a reservoir for providing high pressure oil against the outer ends36of locking pins26to overcome spring28and retract the locking pins into bore24, thereby unlocking the pin housing from the adjuster body to deactivate the DHLA. In use, groove31is in communication via at least one port38with an oil gallery (not shown) in an engine40, which in turn is supplied with high pressure oil by an engine control module (not shown) under predetermined engine parameters in which deactivation of valves is desired.

Plunger20includes a hydraulic lash adjuster (HLA) mechanism42lodged at an inner end thereof. The arrangement of components and operation of HLA mechanism42has been well known in the prior art for many years. HLA mechanism42comprises a spring loaded check ball44lodged against a seat46formed in plunger20separating a low-pressure oil reservoir48from a high-pressure chamber50formed between HLA mechanism42and pin housing14. Oil may be supplied to low pressure reservoir48annular chamber51from an engine oil gallery (not shown) via hollow passage29in pushrod29.

In operation, prior art DHVL10is disposed in a bore in engine40such that housing12is free to move up and down in the bore. When the associated cam17exert force on roller19, in lost motion (valve-deactivation) mode, plunger20and pin housing14are forced into body12in a lost-motion stroke, compressing LM spring34.

Of particular interest to the present invention is the means by which the outward stroke of pin housing14is limited in prior art body12. An annular groove64formed in bore16near the outer end thereof receives a retaining clip66that extends into bore16to engage the upper end68of pin housing14. The axial thickness70of clip66is selected from a family of such clips having differing thicknesses to set the amount of axial mechanical lash72in DHVL10. As described above, the amount of lash72is an important manufacturing parameter which must be calibrated for each DHVL assembly because of manufacturing variability in the length74, from lower end69of groove64to the lower edge76of pins26, and length78, from the upper edge80of groove64to the lower edge82of groove31. The trial-and-error method of assembly, measurement, disassembly, reassembly, and remeasurement is time-consuming, costly, and difficult when using prior art groove64and clip66. Further, the presence of groove64in the inner wall of bore16at this location is undesirable as the groove weakens the wall and, if the wall is already thin, can result in failure by rupture of the small flange remaining between the upper end of the groove and the end of body12.

Referring now toFIG. 2, a prior art DHVL84is shown substantially as disclosed in U.S. Pat. No. 7,296,548 B1, the relevant disclosure of which is incorporated herein by reference. DHVL84comprises all of the elements shown in DHVL10inFIG. 1, except that the lost motion spring34′ is disposed externally of body12′ on a spring seat86retained by spring34′ and spring tower88.

Spring seat86comprises a flange portion90that rests on the upper end92of body12′ and a cylindrical portion94that extends axially into bore16′ in body12′ to engage pin housing14′. Thus, the axial length96of cylindrical portion94defines a gauge that sets the internal mechanical lash (not visible inFIG. 2) for DHVL84.

It is an object of the present invention to adapt to a switchable valve train member DHLA the principles for setting internal mechanical lash as disclosed by DHVLs10and84, with important improvements thereto, thereby simplifying the setting of lash, and strengthening the wall of the switchable valve train member as seen as a shortfall in the groove design disclosed in DHVL10.

For simplicity of presentation, the improved mechanical lash setting mechanism is shown adapted to a DHLA. However, it is understood that the improvements can be applied to other switchable valve train members, such as DHVLs, with equal resulting benefits.

Referring now toFIGS. 3 through 9, a first embodiment110of an improved DHLA in accordance with the invention comprises many components identical or analogous to those described hereinabove for prior art DHVL10, which components bear the same identification numbers plus 100. Components which are different or significantly modified bear new numbers in the 100 and 200 series. For clarity of presentation, only a central portion of a complete DHLA in accordance with the invention is shown; however, a complete DHLA having other portions generally comporting with the locking feature disclosed above in DHVLs10and84.

DHLA110has a generally cylindrical lash adjuster body112. The lash adjuster body is case hardened. A pin housing114is slidably disposed within a first axial bore116in lash adjuster body112. Pin housing114itself has a second axial bore118which in turn slidably receives a plunger120. In the case of a DHLA, the top of the plunger is domed to provide a pivot point to a socket end of the valve actuator such as a valve train rocker arm, as known in the art. Body112is provided with a stepped counterbore121defining an axial surface123for receiving a flange portion190of a lash-setting retaining ring186(also referred to herein as a “lash ring”). A hard turning process may be used to remove the hardened case to expose the softer inner core for subsequent processing. A cylindrical portion194extends axially into bore116in body112to engage pin housing114. Thus, the axial length196of cylindrical portion194defines a gauge that sets the internal mechanical lash (not visible inFIG. 3) for DHLA110. As in the prior art, axial length196is selected to provide a specified amount of lash by compensating for manufacturing variation in various components as described above.

The remainder of the present disclosure deals with various means for securing a lash ring to the lash adjuster body after the appropriate-thickness lash ring has been selected and installed.

Lash ring186may be secured to lash adjuster body112, for example, by a weld171, after first removing the body's hardened case in the area of the weld by the hard turning process mentioned above. (FIG. 3); by staking or crimping over a thinned extension173of lash adjuster body112, after the hardened case in the area of the thinned extension is first removed by the hard turning process (FIG. 4); by providing a snap ring175engaged into an annular groove177formed in the outer surface of lash adjuster body112(FIG. 5); by providing a radially crushable ring179similar to a beverage crown cap engaged into annular groove177(FIG. 6); or by providing a threaded ring181engaged into a threaded portion183of lash adjuster body112(FIG. 7). InFIGS. 5,6and7, note that the feature (annular groove177or threaded portion183) formed on the outer surface of the body need not be precisely positioned or formed since the position of the lash-setting retaining ring186will be controlled by its mating with the axial surface of the body (123inFIG. 4), which is readily accessible for precision machining. Further, in these embodiments, snap ring175, crushable ring179and threaded ring181can be manufactured inexpensively as well.

A lash ring may also be provided integrally with a retaining means. For example, an integral lash retaining ring286may also comprise a snap ring279for engaging into annular groove177(FIG. 8), wherein offset299sets the internal mechanical lash; or an integral lash retaining ring386may also comprise a radially crushable ring379for engaging into annular groove177(FIG. 9).