HYDRAULIC LASH ADJUSTER EQUIPPED WITH AUXILIARY CHECK VALVE

Abstract

An auxiliary check valve is provided in a hydraulic lash adjuster of the type wherein the plunger-to-body clearance is sealed. The auxiliary check valve is derived so that it remains open until the plunger has been moved to the limit of its travel by rotation of the engine camshaft during engine assembly. The auxiliary check valve permits fluid within the hydraulic lash adjuster high pressure chamber to be displaced to the reservoir chamber allowing the hydraulic lash adjuster to shorten from its free length to the proper installed length.

Description

FIELD OF THE INVENTION

The present invention relates to valve trains for internal combustion engines. More particularly, the present invention relates to an improved hydraulic lash adjustment device for use in a valve train for internal combustion engines.

BACKGROUND OF THE INVENTION

This invention relates to hydraulic lash adjusters for internal combustion engines and to a system comprising a hydraulic lash adjuster in combination with an auxiliary check valve therefore. Those skilled in the art of engine valve train design recognize that hydraulic lash adjusters are variable length devices capable of automatically varying their length to eliminate any gaps or “lash” within a valve train system.

Upon installation into an engine valve train, hydraulic lash adjusters shorten from their free, extended length to an installed length consistent with positive closure of their associated engine valves. The installed length varies by engine valve location due to valve train system manufacturing variations, temperature, and wear. As disclosed in U.S. Pat. Nos. 2,956,557 and 6,598,572, hydraulic lash adjusters incorporate a combination seal-check valve which closes the high pressure chamber within the hydraulic lash adjuster as necessary to transmit cam motion to an engine valve. The disclosure of U.S. Pat. No. 6,598,572 differs from that of U.S. Pat. No. 2,956,557 in that the former adds a spring which biases the combination seal-check valve normally open.

As a practical matter, these prior art hydraulic lash adjusters are difficult, if not impossible, to install in an engine valve train during automated assembly and also during manual assembly under ordinary environmental conditions. During installation of these prior art hydraulic lash adjusters, an internal plunger displaces fluid from the high pressure chamber to the reservoir past a combination seal-check valve. However, viscous drag forces coincident to fluid flow cause the combination seal-check valve to close, halting both fluid flow and plunger motion, and thereby preventing the hydraulic lash adjuster from assuming the proper installed length. With respect to the hydraulic lash adjuster disclosed in U.S. Pat. No. 6,598,572, the viscosity and velocity of the fluid displaced around the combination seal-check valve tends to produce viscous drag forces which exceed the leaf spring load, prematurely, thereby closing the check valve and preventing the hydraulic lash adjuster from assuming the proper and desired installed length. The occurrence of installation difficulties of this kind is a principal reason why prior art hydraulic lash adjusters that incorporate a combination seal-check valve are not commonly in commercial use.

SUMMARY OF THE INVENTION

The invention comprises an improvement in hydraulic lash adjusters of the type described in U.S. Pat. No. 2,956,557 which incorporate a combination seal-check valve. The improvement comprises an auxiliary check valve system, the purpose of which is to facilitate installation of this particular type of hydraulic lash adjuster into an engine valve train. An overview of an engine valve train is described in U.S. Pat. No. 2,956,557 and that description is incorporated herein by reference. In accordance with the invention, the novel auxiliary check valve provided by the invention is devised to be maintained in the open state until installed in an engine valve train and the camshaft is rotated through one full revolution. In the installation the first actuation of the valve train bottoms the plunger, thereby semi-permanently closing the auxiliary check valve of the invention which is devised to be maintained closed by means such that the bottoming action of the plunger assembly, fits into or over a feature on the bottom of the plunger assembly so as to permanently or semi-permanently close off the high pressure chamber until such time as the valve train requires service and the check valve is manually reset to the open state.

To ensure proper valve train operation, hydraulic lash adjusters must, during each valve event, shorten from their operating length by an amount slightly greater than that required to ensure positive closure of the associated engine valves. This is especially true when starting an engine at extreme cold environmental conditions, e.g., at temperatures of the order at about 40° C. A “valve event” herein is defined as the period during which cam lift is non-zero. At the end of the valve event, the hydraulic lash adjuster must automatically extend to an operating length consistent

The invention differs from known prior art hydraulic lash adjusters which comprise an external, cylindrical body within which is slideably fitted a cylindrical plunger equipped with a check valve that limits the flow of fluid, usually engine oil, out of a “high pressure” chamber enclosed by the body and the plunger. The plunger is select fitted to the body with a typical plunger-to-body diametrical clearance of approximately 5.1-5.8 μm (0.000200-0.000230 in.) to provide an annular passageway through which a small amount of fluid may be displaced from the high pressure chamber during the valve event, thereby allowing the hydraulic lash adjuster to shorten from its operating length in anticipation of dimensional changes in the associated valve train components due to thermal effects and wear. At the end of the valve event, a plunger return spring concurrently extends the plunger to eliminate lash and the check valve opens to permit the passage of fluid from the internal reservoir to the high pressure chamber.

As noted hereinabove, the hydraulic lash adjuster of this invention pertains to the kind described in U.S. Pat. No. 2,956,557 which differs from those commonly in production today in that it incorporates a combination seal-check valve in lieu of the select fit plunger-to-body clearance and separate check valve. In the type of hydraulic lash adjuster described in U.S. Pat. No. 2,956,557, since the plunger-to-body clearance is essentially sealed, instead of shortening from its operating length over the entire duration of the valve event, it shortens from its operating length only at the beginning of the valve event. It does so when the plunger is moved through the distance necessary to abut the seal against the seal gland, e.g., 0.13 mm (0.005 in.). A hydraulic lash adjuster of that kind is difficult, if not impossible, to install in an engine valve train because the plunger must typically be depressed up to 2 mm (0.080 in.) to attain the appropriate installed length.

This invention accordingly has the objective of providing an improvement over prior art hydraulic lash adjusters of the type described in U.S. Pat. No. 2,956,557 and U.S. Pat. No. 6,598,572 by the addition of an auxiliary check valve which permits the plunger to be freely depressed to the limit of its travel and by this action, to be semi-permanently closed until resetting is necessary to facilitate reinstallation such as during engine service. Other objects and advantages of the invention will be apparent from the following description when considered in connection with the accompanying drawings.

The invention in essence provides a hydraulic lash adjuster assembly for an internal combustion engine having a lash adjuster body with a bore formed therein, a plunger assembly, a fluid chamber containing said plunger assembly; the chamber being equipped to contain therein a supply of hydraulic fluid. The pressure chamber is formed between the bottom of said first bore and said plunger assembly. The plunger assembly has a valve opening to permit the fluid communication between the fluid chamber and said pressure chamber. A check valve is provided for selectively opening and closing said plunger assembly valve opening. The check valve is arranged such that the check valve opening remains open until closed by concurrent engagement of the check valve element and the plunger assembly with the bottom of the bore body in response to movement of the plunger assembly in an inward direction with respect to the bore body, and such that the check valve opening then remains closed until opened by outside intervention. A biasing means urges the plunger assembly in an outward direction with respect to the bore, thus enlarging the pressure chamber to take up slack in the valve drive train. A sealing means engaged with the bore body is activated to move in sealing engagement with the plunger assembly in response to movement of the plunger assembly in an inward direction with respect to the bore for restricting fluid flow from the pressure chamber and to inhibit further movement of the plunger assembly in an inward direction. The lash adjuster being arranged such that the plunger assembly is disengaged from said sealing means and pressure in said pressure chamber is relieved upon movement of the plunger assembly in an outward direction, so that a limit of inward movement can take place each time a load is applied to the plunger assembly before the pressure chamber is again closed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a prior art hydraulic lash adjuster.

FIG. 2 is an elevational view of the hydraulic lash adjuster of the present invention.

FIG. 3A is a cross-sectional view taken along line 3-3 of FIG. 2 showing the auxiliary check valve in the closed position ready for engine operation.

FIG. 3B is a cross-sectional view taken along line 3-3 of FIG. 2 showing the auxiliary check valve in the open position, ready for installation into an engine valve train.

FIG. 3C is a cross-sectional view taken along line 3-3 of FIG. 2 showing an alternative construction of the auxiliary check valve in the closed position ready for engine operation.

FIG. 3D is a cross-sectional view taken along line 3-3 of FIG. 2 showing the alternative construction of the auxiliary check valve illustrated in FIG. 3C, in the open position ready for installation into an engine valve train.

FIG. 4 is a detail, fragmented, enlarged sectional view of the lower encircled portion of FIG. 3A to better illustrate the combination seal-check valve and auxilary check valve.

FIG. 5 is a detail, fragmented, enlarged sectional view of the lower encircled portion of FIG. 3B to better illustrate the combination seal-check valve and auxiliary check valve.

FIG. 6 is a perspective view of the auxiliary check valve pin.

FIG. 7 is a perspective view of an alternative construction auxiliary check valve pin.

DETAILED DESCRIPTION OF THE INVENTION

This present invention provides the means to facilitate hydraulic lash adjuster installation by providing an auxiliary check valve which remains open until the lash adjuster plunger has been moved to the limit of its travel. By this means the hydraulic lash adjuster relatively easily assumes its proper installed length. A final step in hydraulic lash adjuster installation is the rotation of the camshaft through one full revolution. During the rotation the valve closing force of each engine valve spring is in turn transmitted to each hydraulic lash adjuster. This force is sufficient to overcome the opposing force of the plunger return spring and allow the hydraulic lash adjuster to shorten to the limit of its available travel.

As the hydraulic lash adjuster is shortened in length, the plunger assembly displaces fluid through the auxiliary check valve from the high pressure chamber to the reservoir chamber. Viscous drag forces acting on the check valve pin element of the auxiliary check valve are insufficient to move it since it is held in place within the check valve body, for example, by means of an interference fit or a spring. As the hydraulic lash adjuster continues to shorten in length, the end of the check valve pin extending from the check valve body contacts the lash adjuster body and stops such that the check valve body element of the plunger assembly continues to move until the tapered surfaces of the check valve pin and check valve body are mated, halting the flow of fluid through the auxiliary check valve and halting as well the movement of the plunger assembly. As the camshaft continues to rotate, the plunger return spring extends the plunger assembly, and as it does so, the combination seal-check valve opens and fluid is drawn from the reservoir chamber to the high pressure chamber until the hydraulic lash adjuster installed length is achieved.

Throughout this and subsequent valve events, the auxiliary check valve remains closed due to the action of a self-locking taper between the check valve pin and the check valve body and/or the hydraulic pressure sustained in the high pressure chamber. The auxiliary check valve is able to be reset to the open position, for example during engine valve train service, by depressing the check valve pin through the rocker arm lubrication port of the ball plunger while holding the ball plunger fixed.

As shown in FIG. 1, a prior art hydraulic lash adjuster 1 is illustrated comprising a body 3, a plunger assembly 5 defined by a ball plunger element 7 and a leakdown plunger element 9 which are received within the body 3 in close fitting relationship and which define a reservoir chamber 11 between them. The bottom of the leakdown plunger element 9 forms, in cooperation with the end of a reduced diameter portion 13 of the body bore, a high pressure chamber 15. A separate check valve 17 is provided in the end of a passage 19 which connects the reservoir chamber 11 and the high pressure chamber 15. The check valve 17, which is shown as a ball, but which can be a flat disk or the like, is retained by a check valve retainer 19 which is in interference fit with a counter bore 21 formed in the leakdown plunger element and which provides a seat for the plunger return spring 23.

In general in most prevalent prior art designs a compression spring 25 acting between the bottom of the check valve retainer 19 and the check valve 17 biases the check valve 17 into a normally closed position. An oil feed hole 27 opens into the body bore and intersects an oil feed groove 29 which in turn intersects an oil feed hole 31 in the ball plunger element 7 to supply hydraulic fluid to the reservoir chamber 11. An axial port 33 at the top supplies lubricant to a rocker arm (not shown) which engages the semi-spherical end 35 formed at the upper end of the ball plunger element 7. The plunger assembly 5 is retained within the body 3 by means of a cap retainer 37.

In the prior art embodiments of the kind illustrated in FIG. 1, the amount of plunger deflection or “leak down” which occurs during an engine valve event is controlled by the fit between the body bore and the outside diameter of the leakdown plunger element 9, requiring the clearance between these members to be held very precisely, e.g., to the range of about 5.1-5.8 μm (0.000200-0.000230 in.), which can only be achieved by machining the individual parts to extremely close tolerances and selectively pairing the leakdown plunger elements and the bodies to obtain the desired clearance. This is an extremely demanding requirement; a requirement alleviated by the present invention.

Referring to FIG. 3A, a cross-sectional view of the hydraulic lash adjuster 41 configured in accordance with a preferred embodiment of the invention is shown, comprising a body 43 and a plunger assembly 45 slideably fitted within the bore of body 43. The plunger assembly 45 is provided with a cap element 47 and a valve seat element 49 which is received within the base of the body 43 with the cap 47 and top of the valve seal 49 defining a reservoir chamber 51 between the interior of cap 47 and the top of the valve seat 49. The bottom of the valve seat element 49 forms, in cooperation with the bottom portion 53 of the interior of body 43, a high pressure chamber 55.

It is seen in accordance with the invention that a combination seal-check valve 57 is provided between passageways and component clearances which connect the reservoir chamber 51 and the high pressure chamber 55. The combination seal-check valve 57 shown comprises a ring with a locational transition or locational interference fit with the interior bore of the body 43. The combination seal-check valve 57 is free to move within the axial space created between the valve seat 49 and a ring seal retainer 59 which is in interference fit on the end portion of valve seat 49. The bottom face of the valve seat 49 provides a seat for the plunger return spring 61.

An oil feed hole 63 opens into the body 43 and intersects an oil feed groove 65 in the cap element 47 which intersects an oil feed hole 67 in the cap element 47 to supply hydraulic fluid to the reservoir chamber 51. An axial port 69 in the top of the semi-spherical top end 71 supplies lubricant to a rocker arm (not shown) which engages the semi-spherical end 71 formed at the top of the cap 47. The plunger assembly 45 is retained within the body 43 by means of a retainer 73.

With reference to FIG. 3A and, in particular, to the enlarged fragmentary depiction of FIG. 4, it is seen that the auxiliary check valve is comprised of a valve pin element 75 which is slideably fitted through the bore 77 in valve seat 49.

The amount of plunger deflection which occurs during an engine valve event is controlled not by “leak down” as in prior art hydraulic lash adjusters of the kind illustrated, for example, by FIG. 1, but by the axial clearance 79 (FIG. 4) between the combination seal-check valve 57 and the valve seat 49 as shown in FIGS. 3A and 4. Because the combination seal-check valve 57 of the invention is interference fitted to the bore of the body 43, when the plunger assembly 45 shown in FIG. 3A is depressed relative to the body 43 during the initial portion of the engine valve event, the combination seal-check valve 57 remains stationary until the plunger assembly has moved through a distance equal to the axial clearance 79.

It is to be noted that, as the plunger assembly 45 is depressed, fluid within the high pressure chamber 55 is displaced to the reservoir chamber 51 by first flowing through a multiplicity of openings 81 provided in the ring seal retainer 59, through the radial clearance 83 and axial clearance 79, then through the radial clearance 85, and finally, respectively through the multiplicity of connecting valve seat radial and axial passages 87 as shown more clearly in FIG. 4. When fluid passage through the axial clearance 79 is interrupted by the abutment of the combination seal-check valve 57 against the bottom surface 89 (FIG. 4) of the valve seat 49, the pathway for fluid flow between the high pressure chamber 55 and the reservoir chamber 51 is closed as shown in FIG. 5 and further plunger deflection is resisted by the resulting hydraulic pressure forces within the high pressure chamber 55.

The hydraulic pressure forces act on the combination seal-check valve 57 to enforce respectively axial and radial seals where its surfaces abut the valve seat 49 and the bore of the body 43 as shown in FIG. 5. At the conclusion of the valve event, the plunger return spring 61 extends the plunger assembly 45 relative to the body 43 to compensate for any lash in the engine valve train (not shown) and as it does so, the axial clearance 79 is restored as shown in FIG. 4 and fluid is transferred from the reservoir chamber 51 to the high pressure chamber 55 in the manner previously described.

Those skilled in the art of hydraulic lash adjuster design recognize that prior art hydraulic lash adjusters incorporating a combination seal-check valve present difficulties when the adjuster is being installed in an engine valve train because the installed length of the hydraulic lash adjuster within the valve train requires that the plunger assembly 45 be depressed into the body 43 through a distance greater than the axial clearance 79. However, as seen by reference to FIG. 3B and FIG. 5, and for the reasons which follow the auxiliary check valve of the present invention resolves this prior art difficulty by the novel arrangement provided.

Referring in particular to FIG. 3B and FIG. 5 it is seen that the hydraulic lash adjuster of the invention comprises a valve pin 75 that is positioned relative to the valve seat 49 by utilizing an interference fit between the mating cylindrical surfaces of valve pin 75 and the bore 77 (FIG. 5) of valve seat 49. It will be apparent that an alternative embodiment (not shown) may utilize alternatives, such as a conventional spring or a frangible element to position the valve pin 75 relative to the valve seat 49. With the valve pin 75 positioned as shown in FIG. 5, there exists a radial clearance 91 (FIG. 5) between mating tapered surfaces 93 and 95 respectively of the valve seat 49 and valve pin 75.

As the engine valve train (not shown) is initially rotated to install the hydraulic lash adjuster 41, depressing the plunger assembly 45 into the body 43, after the combination seal-check valve has been closed as shown in FIG. 5 by the mechanism previously described, fluid continues to be displaced from the high pressure chamber 55 to the reservoir chamber 51 through the clearance 91 and through one or more passageways 97 formed in the valve pin 75 shown in FIG. 6 or alternatively through a helical passageway arrangement 103 formed in the valve pin 75 shown in FIG. 7. As the plunger assembly 45 is further deflected, the end bottom portion 99 of the valve pin 75 contacts the interior bottom 101 of the body 43 and ceases movement. In this position, the valve seat 49 then slides down over the end portion 95 of valve pin 75, and as it does so diminishes the clearance 91 to zero, thereby closing the valve to fluid flow and halting further deflection of the plunger assembly.

At the conclusion of the valve event, the plunger return spring 61 extends the plunger assembly 45 relative to the body 43 to compensate for any lash in the engine valve train (not shown) and as it does so, the axial clearance 79 is restored and fluid is transferred from the reservoir chamber 51 to the high pressure chamber 55 in the manner previously described and is position ready as shown in FIG. 3B for engine operation. In a preferred embodiment the mating lower portion 95 of valve pin 75 (FIG. 6) and valve seat 49 surfaces comprise a self-locking taper which semi-permanently maintains the valve in the closed position as shown in FIG. 4. The bottom end portion 99 of the valve pin 75 which extends below the plunger assembly 45 limits plunger travel in the bore at the bottom 101 (FIG. 5) of the body 43 of the hydraulic lash adjuster assembly. The valve pin 75 may be reset as shown in FIG. 5, for example during engine valve train service, by depressing the pin 75 relative to the plunger assembly 45 through the port 69.

FIGS. 3C and 3D illustrate an alternate auxiliary check valve wherein the auxiliary check valve mechanism comprises a spherical configuration 105 positioned on the bottom of the body 43 and a suitably configured opening 77 in the bottom of the

Various alterations and modifications will become apparent to those skilled in the art from a reading of the detailed disclosure presented herein and it is intended that such apparent alterations and modifications from the disclosure herein provided are encompassed within the contemplations of the invention to the extent that such are within the scope of the appended claims.

Claims

1. A hydraulic lash adjuster assembly for an internal combustion engine, the lash adjuster comprising:

a) a lash adjuster body having a body bore formed therein;

b) a plunger assembly that includes a reservoir chamber equipped to contain therein a supply of hydraulic fluid positioned within said body bore;

c) a fluid pressure chamber formed between the bottom of said bore and the bottom of said plunger assembly;

d) a valve opening in said plunger assembly to permit fluid communication between said reservoir chamber and said pressure chamber;

e) a plunger check valve for selectively opening and closing said check valve arranged such that the check valve opening remains open until closed by concurrent engagement of the check valve element and the plunger assembly with the bottom of the body bore in response to a linear movement of the plunger assembly thereby retaining the check valve opening in a closed position until opened by outside intervention;

f) a biasing means for urging the plunger assembly in a direction that increases the volume of the pressure chamber to take up slack of a valve drive train;

g) a sealing means engaging the plunger assembly in response to movement of the plunger for restricting fluid flow from the pressure chamber and to inhibit further movement of the plunger assembly; and

h) said lash adjuster being arranged such that the plunger assembly is disengaged from said sealing means and pressure in said pressure chamber is relieved upon movement of the plunger assembly as the volume of the pressure chamber increases so as to limit inward movement of the plunger assembly when a load is applied to the plunger assembly and before the pressure chamber is again closed.

2. The lash adjuster of claim 1 wherein the fluid chamber contains a supply of hydraulic fluid.

3. The hydraulic lash adjuster of claim 1 where said valve opening in said plunger assembly comprises a cylindrical coaxial portion and where said plunger check valve comprises a complementary cylindrical coaxial portion.

4. The hydraulic lash adjuster of claim 1 wherein said valve opening in said plunger assembly comprises a cylindrical coaxial tapered portion and where said check valve element comprises a spherical configuration coupled with a mating sealable complemental opening.

5. The hydraulic lash adjuster of claim 3 wherein the check valve element is provided with at least one groove providing fluid communication between said fluid chamber and said pressure chamber such that when said check valve is open, said groove communicates with fluid between said reservoir chamber and said pressure chamber.

6. The hydraulic lash adjuster of claim 3 where said groove is longitudinal.

7. The hydraulic lash adjuster of claim 3 where said groove is helical.

8. In a hydraulic lash adjuster system for an internal combustion engine, comprising an outer cylindrical body, a plunger assembly slideably positioned within said body and a valve pin movably positioned within said plunger assembly, the improvement comprising:

a) a moveable plunger equipped with an auxiliary check valve in combination with said lash adjuster;

b) said check valve devised to be maintained in an open position until the plunger has been moved to a level of its movement range;

c) said combination upon installation in association with an engine valve with valve spring and with rotatable camshaft enables the check valve to be maintained in a closed position by means of a locking contacting engagement by a self-locking auxiliary check valve.