US3875908A

US3875908A - Valve gear and lash adjuster for same

Info

Publication number: US3875908A
Application number: US370881A
Authority: US
Inventors: Harry Vincent Ayres
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 1973-06-18
Filing date: 1973-06-18
Publication date: 1975-04-08
Anticipated expiration: 1992-04-08
Also published as: GB1476357A; CA1018032A; DE2428951A1; BR7404992D0

Abstract

An overhead valve gear of cam-over-rocker type for an internal combustion engine in which the rocker is pivoted at one end on a stationary hydraulic adjuster. An aperture is formed in the rocker arm at the pivot end, and oil discharged through radial holes in the rotating cam lobes impinges on an arcuate collector baffle to drip by gravity flow into the lash adjuster. A deflector is also mounted on the pivoted end of the rocker arm for deflecting oil discharged from the cam lobes into the aperture in the rocker arm. The lash adjuster operates from oil received only by gravity flow from the rocker aperture. The body of the adjuster is stationary with respect to the engine, and has a movable plunger with a one-way check valve for admitting and retaining oil between the adjuster body and the plunger. A portion of the plunger extends beyond the body and has a rounded end for pivotally engaging the rocker with a passage in the plunger for permitting gravity flow of oil from the rocker aperture to the check valve.

Description

United States Patent 91 Ayres 1 1 VALVE GEAR AND LASH ADJUSTER FOR SAME [75] Inventor: Harry Vincent Ayres, Saginaw,

Mich.

[731 Assignee: Eaton Corporation, Cleveland. Ohio [22] Filed: June 18, 1973 1211 Appl. No: 370,881

[52] U.S. Cl. 123/9036; 123/9027; 123/9034; 123/9037; 123/9043; 123/9044; 123/9046;

[451 Apr. 8, 1975 Primary E.\-uminer-Manuel A. Antonakas Assistant Examiner-Daniel J. OConner Attorney, Agent. or Firm-Teagno & Toddy [5 7] ABSTRACT An overhead valve gear of cam-over-rocker type for an internal combustion engine in which the rocker is pivoted at one end on a stationary hydraulic adjuster. An aperture is formed in the rocker arm at the pivot end. and oil discharged through radial holes in the rotating cam lobes impinges on an arcuate collector baffle t0 drip by gravity flow into the lash adjuster. A deflector is also mounted on the pivoted end of the rocker arm for deflecting oil discharged from the cam lobes into the aperture in the rocker arm. The lash adjuster operates from oil received only by gravity flow from the rocker aperture. The body of the adjuster is stationary with respect to the engine. and has a movable plunger with a one-way check valve for admitting and retaining oil between the adjuster body and the plunger. A portion of the plunger extends beyond the body and has a rounded end for pivotally engaging the rocker with a passage in the plunger for permitting gravity flow of oil from the rocker aperture to the check valve.

17 Claims, 2 Drawing Figures .\'AI.VE GEAR AND LASH ADJUSTER FOR SAME BACKGROUND OF THE INVENTION In relatively small displacement multicylinder internal combustion engines of the type having overhead valve gear. for example. four cylinder in-line engines. it is not uncommon for such engines to operate at high rotational speeds. for example. 4()()()6()()() r.p.m.s. during a large percentage of the normal duty cycle. In this r.p.m. regime. the inertial forces of the valve gear can become critical with respect to the valve spring closing force. In order to reduce the inertial forces of the valve gear. it is desirable to eliminate a pushrod type valve gear and utilize a direct acting or cam-overrockcr arrangement. This arrangement eliminates the tappets and pushrods between the camshaft and the valve rocker arms.

However. in designing valve gear for a cam-overrocker arrangement where the cam lobes contact the rocker arms directly. the usual technique. employed in pushrod type valve gear. of providing lash adjustment in the tappet is not available. In conventional pushrod type valve gear. the last adjustment is usually provided in the form of a combination tappethydraulic valve lifter between the pushrod and the camshaft. The location of the camshaft in the engine block for conventional pushrod valve gear provides convenient access to the oil pressure galleries. and thus hydraulic valve lifters for lash adjustment may be employed and may be easily operated from pressurized oil in the engine oil pump circuit.

Where attempts have been made to utilize hydraulic lash adjusters for cam-ovcr-rocker valvc gear. it has been found that the most compact arrangement is to provide the lash adjustment at a stationary pivot about which one end of the valve rocker is pivoted. However. where the lash adjusters operate from pressurized engine oil. the force of the oil acting on the end of the adjuster plunger was increased by mechanical advantage and applied to the cam lobe at the rocker contact surface. This additional force must be overcome during operation in order to open the valve and results in the need for greater valve spring forces at high r.p.m.

In the cam-over-rocker type overhead valve gear. it is not convenient to provide additional connections to oil galleries in the cylinder head for supplying pressurized oil to hydraulic lash adjusters. In the cam-overrocker type valve gear. the only convenient source of pressurized oil in the valve gear is that supplied to the camshaft for lubricating the camshaft bearings. The usual practice is to provide a connecting tube or conduit from the engine oil pump circuit in the engine block to the camshaft bearings for providing a flow of pressurized oil to the camshaft bearings. Therefore. it

has been desirable to find some convenient and inexpensive means of providing hydraulic lash adjustment for overhead valve gear of the cam-ovcr-rocker type without the need of providing a separate oil gallery and feed holes in the cylinder head.

SUMMARY OF THE INVENTION present lash adjusters require only gravity feed. or drip flow of oil. for proper operation. The present valve gear utilizes rocker arms each having one end contacting the stem end of an engine poppet valve. with the other end of the rocker pivoted about a stationary hydraulic lash adjuster attached to the engine head. The camshaft is mounted above the rocker arms such that the rotating cam lobes contact the rocker arms at a desired point intermediate the ends thereof. The camshaft has a central oil gallery with radical oil ports communicating therefrom to each cam lobe base circle and to each of the camshaft bearings. A stationary arcuate baffle or collector is provided adjacent each cam lobe in order that. as the cam lobc rotates. oil discharged from the radial oil port in the cam lobe impinges on the baffle and drips by gravity flow to the pivoted end of the rocker arm.

The pivoted end of the rocker arm has an aperture therein such that oil from the baffle drips by gravity flow into the aperture to supply oil to the stationary lash adjuster. A deflector is mounted on the pivot end of the rocker adjacent the aperture to further deflect oil discharged from the cam lobe ports to flow by gravity to the aperture in the rocker arm.

The hydraulic lash adjuster has a body mounted in a stationary manner to the engine head. with a movable plunger received in a cavity. thereby forming an oil chamber between the end of the plunger and the body cavity. The plunger extends outwardly from the body and has a rounded end for pivotally connecting to the end of the rocker arm. An oil passage is provided which communicates from the rounded pivot end of the plunger to the oil chamber. A one-way check valve is provided in the end ofthe plunger received in the body to permit oil to flow from the plunger into the oil chamber between the plunger and the body cavity. The oil from the baffle means and deflector flows by gravity through the aperture in the rocker arm. then through the passage in the plunger. to the check valve in the hydraulic lash adjuster.

The valve gear and hydraulic lash adjuster of the present invention thus provide a simple means of hy draulically adjusting the rocker lash of overhead valve gear of the cam-ovcr-rocker type. which lash adjust ment does not require pressurized oil from the engine oil pump circuit.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a transverse cross section through the cylinder head and camshaft of an overhead valve cam-overrocker engine employing the valve gear of the present invention; and

FIGv 2 is a section view taken along section indicating lines 2-2 of FIG. 1 and shows details of the stationary gravity-fed hydraulic lash adjuster.

DETAILED DESCRIPTION Referring now to FIG. 1, the cylinder head H of an engine is shown in cross section with the overhead valve gear 1 for a single valve for communicating with the combustion chamber. The valve gear includes a poppet valve 10 having a stem portion 11 and a head portion 12 with the stem received in a valve guide 13 provided in the engine cylinder head H. The stem of the valve has a groove 15 formed therein in which is engaged a peripherally split keeper 14 for retaining thereon a spring washer 16 which provides a register for the valve compression spring 17.

An overhead rocker arm 20 is provided with a cam follower pad 21 provided on one side intermediate the ends thereof and has a contact pad 25 provided on one end on the side opposite the cam follower, for contacting the end of the valve stem. The opposite end of the rocker arm has a pivot recess 23 formed therein on the same side of the rocker as the valve stem pad 25 with a collector means preferably in the form of an aperture 24 having chamfer 24a, or oil feed hole, provided therethrough to communicate with the recess 23 from the opposite, or cam follower side, of the rocker. An oil deflector means 26 extends from the surface of the rocker arm, preferably in a direction generally parallel to the oil feed hole 24 on the end of the rocker arm adjacent aperture 24.

The end of the rocker arm having the pivot recess 23 formed therein is pivotally connected to a stationary pivot means in the form of a stationary hydraulic lash adjuster 40. The engine camshaft 30 is disposed over the rocker and is mounted in bearings (not shown) attached to the engine cylinder head H in the usual manner. The camshaft has a plurality of lobes 32 each having a base circle portion 31 and the camshaft has a central oil gallery 33 in the form of a longitudinal bore therethrough. Each cam lobe has a radial oil port 34 communicating with the oil gallery 33 and extending radiallyoutwardly to communicate with the base circle portion 31 of the cam lobe.

In operation, as the camshaft rotates, engine oil under pressure is supplied to the gallery 33 by a suitable rotary connection (not shown) communicating with the engine oil pump circuit. The oil is discharged radially outwardly from the oil ports 34 for providing lubrication of the cam lobe as it contacts the pad 21 of the rocker arm. It will be readily apparent that, during the majority of each revolution of the camshaft, the oil discharged from the radial port 34 is discharged freely outwardly into the space surrounding the camshaft. Disposed in the path of this free discharge of oil is a baffle 3 in the form of a shield located adjacent each cam lobe, such that the oil discharged from each radial port 34 impinges on the baffle 3 during rotation of the camshaft. In the presently preferred practice of the invention, the baffle 3 has an arcuate configuration and is concentric with the camshaft. Alternatively, a plurality of baffles may be used, in which case each baffle is mounted at an axial position along the camshaft coincident with one of the cam lobes. The arcuate baffle 3 is preferably semicircular with the ends terminating at a horizontal line through the camshaft axis. The baffle has a radius such that one end is disposed vertically directly above the aperture 24 formed in the pivoted end of the rocker arm. Thus, as oil is impinged upon the baffle 3 during rotation of the camshaft, oil flows under the influence of gravity to the ends of the baffle 3 and drips vertically downwardly to the end of the rocker arm so as to provide a continuous gravity flow of oil to the aperture 24.

In the preferred practice of the invention, oil is supplied to the collector means 24 by discharge from a radial port in the camshaft impinging on baffle means 3 and flowingby gravity to the collector aperture. However, it will be apparent that other means may be utilized to supply oil forv gravity flow to the collector means as, for example, a stationary distributor tube 4 (not shown) communicating with the engine oil pump circuit. The preferred oil supply means shown in FIG. 1, however, eliminates any need for separate tubes and connections to oil galleries in the cylinder head or engine block and is thus less costly.

Referring now to FIG. 2, the stationary lash adjuster 40 is shown as having a body 41 preferably of cylindrical configuration with a bore 41a having a blind end 41b formed therein and with preferably a two-

piece plunger

42, 45 slidably received in the bore in close fitting relationship. The plunger is shown in preferred form as formed of two pieces, an upper section 42 and a lower section 45, but it will be understood that the plunger may be made of one piece, if desired..The plunger is preferably made in two sections to permit enlargement of an oil passage therethrough in the region intermediate the ends of the plunger. The upper section 42 of the plunger has an exterior portion 42a extending outwardly from the body 41 with the end of the plunger having a rounded tip 43, preferably ofspherical radius. provided thereon for pivotally engaging the recess 23 in the rocker arm. The remainder of the upper section 42 is slidably received in bore 41a in a closely fitting relationship. An oil passage 44 is provided longitudinally through the upper portion 42a of the plunger and extends the full length of the section 42. The passage 44' may, if desired, have a greater transverse dimension in the portion of section 42 received in the bore 41a, than the transverse dimension of the passage 44 in the exterior portion 42a in order to provide added capacity to the reservoir of oil in the passage.

The lower section 45 abuts the upper section 42. The lower section of the plunger 45 also has a passage 45a provided therein which extends longitudinally therethrough. The passage 45a, if desired, may be enlarged in the region of abutment to provide added oil reservoir capacity to the passage. The end of the lower section 45 of the plunger forms, in cooperation with the end 41b of the blind bore 41a, to format chamber 410 for retaining oil to maintain the plunger position for lash adjustment. A check valve 46 is provided in the end of the passage 45a of the lower section 45 of the plunger so as to permit one-way flow of oil from the passage 45a through the end of lower section 45 of the plunger to the chamber 410. The

passages

44 and 45a each preferably have a minimum transverse dimension equal to one third the transverse dimension of the plunger.

The check valve 46 preferably has a valve seat 47 formed at the juncture of the passage 45a with the end of the lower section 45 of the plunger and the valve 46 has a movable member 48, preferably a check ball, received therein. The member 48 is movable from a closed position contacting the valve seat 47 to an open position spaced from the valve seat 47. A cage 49 is received over the check ball and serves to retain the ball therein. A bias spring 50 is provided within the cage to urge the check ball 48 to a closed position in contact with the valve seat 47. A plunger bias spring 51 is provided in the chamber 41c to register against the end of the lower portion of the plunger 45 to urge the plunger in a direction away from the blind end 4112 of the bore 41a. An annular plunger retainer 53 is provided over the upper end of the body 41 with the exterior portion 42a of the upper plunger section received therethrough, and serves to retain the plunger in the body against the bias force of spring 51, when no load is presem on the plunger.

In operation. during rotation of the camshaft, oil impinges on the baffle 3 and drips through the oil feed hole 24 in the end of the rocker and through the passage 44 and a. respectively. to the check valve 46. As the base circle portion of the cam rotates to a position in contact with the pad 21 on the rocker arm. the spring 51 urges the

plunger sections

42 and 45 away from bore end 41h so the rounded tip 43 moves the rocker to contact and urge the recess 23 in the rocker arm upward until the pad 21 is forced to contact the base circle portion of the cam. As the cam lobe 32 contacts the pad 21 of the rocker arm and asserts a force on the pivoted end of the rocker arm. both of the

plunger sections

42, 45 are forced downward together as a unit in a manner tending to compress oil trapped in chamber 41c. The check valve 46 prevents unwanted flow of oil from the chamber 410 and thus prevents further downward movement of the plunger sections. shortening of the adjuster and further movement of the rocker pivot.

The collector 26 provided on the end of the rocker arm also has oil discharged from the radial ports in the cam lobe impinged thereon and collector 26 serves to deflect additional flow by gravity into the oil apertuure 24 in the pivot end of the rocker arm 20.

Since the lash adjuster of the present invention does not require oil pressurized from the engine oil pump. only a small force generated by the plunger return spring 51 is applied by the

plunger

42, 45 to the rocker arm at the recess 23, when the base circle portion of the cam is in contact with the rocker pad 21. Therefore. the gravity fed lash adjuster of the present invention reduces the loads applied to the camshaft and reduces wear of the cam lobes and rocker arm. Furthermore. as mentioned above, lighter valve spring force may be used which lowers the valve gear dynamic forces at high engine rotational speeds.

The valve gear and stationary hydraulic adjuster of the present invention thus provide a novel and eonve nient technique for providing hydraulic lash adjustment to overhead valve gear of the cam-over-rocker type. The hydraulic lash adjuster of the present invention receives oil only from gravity flow from a baffle upon which oil. discharged through radial ports in the camshaft, impinges.

What is claimed is:

1. ln internal combustion engine valve gear of the type having overhead valves actuated by pivoted rocker members which operatively contact a rotating camshaft having a plurality of axially spaced lobes each having a base circle portion. with the camshaft being disposed over the rockers, the improvement comprising:

a. said rocker members each having an elongated configuration with one end thereof contacting the end of one of said valves with each of said rockers having a portion intermediate the ends thereof contacting one of said cam lobes;

b. a plurality of stationary pivot means attached to said engine with the remaining end of each of said rocker member operatively connected to one of said pivot means. with each of said pivot means including hydraulic lash adjustment means therein, said lash adjustment means requiring engine oil supplied only by gravity flow therein;

c. means for supplying engine oil in vertical proximity to said pivot means and discharging oil in a manner such that oil flows only by gravitational force to said pivot means;

d. collector means for directing said gravity flow of oil to said lash adjustment means: and,

e. one-way valve means disposed in said lash adjustment means for permitting gravity flow of oil thereto when each of said rockers is in contact with the base circle portion of one of said cam lobes.

2. The valve gear defined in claim 1, wherein said means for supplying engine oil in proximity to said pivot means includes.

a. an axial oil gallery formed in said camshaft with a plurality of radial oil ports communicating with and extending outwardly therefrom. with each of said ports communicating with the base circle portion of one of said cam lobes; and,

b. baffle means disposed adjacent each of said cam lobes such that during rotation of said camshaft. engine oil from said pressure gallery flows through each ofsaid radial ports and impinges on said baffle means. said baffle means including means for directing oil by gravity flow to each of said collector means.

3. The improved valve gear defined in claim 1.

wherein a. said collector means includes an aperture formed in each of said rocker members in said end connected to said pivot means. such that oil drips from said supply means and flows by gravity through said aperture to said pivot means; and.

b. said lash adjustment means includes a stationary body attached to the engine. said body having a cavity formed therein and a plunger slidably mounted in said cavity such that an oil chamber is formed in said cavity by one end of said plunger. with the opposite end of said plunger pivotally contacting the end of said rocker, said plunger having a passage therein communicating said chamber with said aperture in said rocker. and one-way valve means operative only to admit oil from said passage to said chamber.

4. The improved valve gear defined in claim 2, wherein said baffle means includes a plurality of arcuate members with each of said arcuate members disposed axially coincident with one of said radial ports such that, during rotation of said camshaft, oil discharges from said radial ports and impinges on each of said arcuate members.

5. The improved valve gear defined in claim 4, wherein each of said arcuate members has a constant radius of curvature and is disposed concentrically with the axis of said camshaft.

6. The improved valve gear defined in claim 1, wherein said collector means includes deflector means attached to the pivoted end of each of said rockers and movable therewith, said deflector means being disposed adjacent said apertures such that oil discharged from one of said radial ports impinges on said deflector means during a portion of each revolution of said camshaft and flows by gravity to said aperture.

7. A hydraulic lash adjuster for internal combustion engine overhead valve gear of the type having the camshaft disposed over the valve rockers and the lash adjuster stationary with respect to the engine, said aduster comprising:

a. a body having a longitudinally disposed bore formed therein, said bore being closed at one end of said body;

b. plunger means slidably received in said bore in a closely fitting relationship, with one end of said plunger means extending from the open end of said bore and having a portion of said end defining a pivot surface for contacting one end of a valve rocker. with the opposite end of said plunger means defining. in cooperation with the closed end of said bore, an oil cavity. said plunger means having passage means formed therein which passage means is operative to communicate oil by gravity flow from said pivot surface to said cavity;

c. said passage means includes one-way valve means. which valve means permits said gravity flow of oil into said cavity when said plunger has no load applied thereon in a direction to move said plunger into said cavity; and

d. means biasing said plunger in a direction outwardly of said cavity.

8. The hydraulic lash adjuster defined in claim 7, wherein said pivotal surface has a spherical radius and said passage is a central axial bore through said plunger.

9. The hydraulic lash adjuster defined incl-aim 7, wherein said passage has a transverse dimension of at least one-third of the largest transverse dimension of said plunger.

10. The hydraulic lash adjuster defined in claim 7, wherein said one-way valve means includes a valve seat formed at the juncture of said passage and the end of said plunger means forming said chamber;

a. a movable member movable from a closed position contacting said valve seat and an open position spaced from said valve seat; and

b. means biasing said movable member to the closed position.

11. The hydraulic lash adjuster defined in claim 10, wherein said movable member is a ball check and said valve seat has a conical configuration.

12. The hydraulic lash adjuster defined in claim 9, wherein a. said valve means includes a cage received over said movable member and attached to the end of said plunger; and,

b. said means biasing said movable member is a coil spring intermediate said cage and said movable member.

13. The hydraulic lash adjuster defined in claim 7, wherein said passage has a substantially smaller transverse dimension in the region where said valve means is disposed than the transverse dimension thereof at said pivot surface.

14. The hydraulic lash adjuster defined in claim 7, wherein the portion of said plunger extending from said body has the largest transverse dimension thereof less than the largest transverse dimension of the portion of said plunger means slidably mounted in said body.

15. The hydraulic lash adjuster defined in claim 7, wherein said plunger means includes a first axial member having said valve means therein and a second axial member having said pivot surface thereon with said first section being slidably received the full length thereof in said body bore and said second axial member having only a portion thereof slidably received in said body bore.

16. A hydraulic lash adjuster for internal combustion engine overhead valve gear of the type having the camshaft disposed over the valve rockers and the lash adjuster stationary with respect tothe engine. said adjuster comprising:

a. a body having a longitudinally disposed bore formed therein. said bore being closed at one end 7 of said body:

b. plunger means slidably received in said bore in with one end of said plunger means extending from the open end of said bore and having a portion of said end defining a pivot surface for contacting a valve rocker. with the opposite end of said plunger means defining. in cooperation with the closed end of said bore, an oil cavity;

c. means communicating a gravity flow of oil only through said pivot surface with said oil cavity. said means communicating said gravity flow of oil in cluding one-way valve means; and,

d. means biasing said plunger means in a direction outwardly of said cavity.

17. A hydraulic lash adjuster for internal combustion engine overhead valve gear. said adjuster comprising:

b. plunger means slidably received in said bore with one end of said plunger means having a portion thereof defining a pivot surface for contacting associated members of the engine valve gear with the opposite end of said plunger means defining, in cooperation with the closed end of said bore. an oil cavity;

c. means communicating a gravity flow of oil only through said pivot surface with said oil cavity, said means communicating said gravity flow of oil including one-way valve means: and

d. means biasing said plunger means in a direction outwardly of said cavity.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CQREQTIQN PATENT NO. 1 3 75 90 DATED 1 April 8, 1975 INVENTOR(S) I Harry V Ayres It is certified that error appears in the above-ide rtified parent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 23: "last" should read -lash.

line 63: Before "adjustment" insert-lash--.

Column 2, line 10: "radicalfshould read radial-,

Column 5, line 61: "member" should read-members-.

Signed and Scaled this twenty-sixth D3) of August 1975 [SEAL] RUTH C. MASON C. MARSHALL DANN Arresting Officer (ommisxr'mu'r nj'PaIents and Trademarks

Claims

1. In internal combustion engine valve gear of the type having overhead valves actuated by pivoted rocker members which operatively contact a rotating camshaft having a plurality of axially spaced lobes each having a base circle portion, with the camshaft being disposed over the rockers, the improvement comprising: a. said rocker members each having an elongated configuration with one end thereof contacting the end of one of said valves with each of said rockers having a portion intermediate the ends thereof contacting one of said cam lobes; b. a plurality of stationary pivot means attached to said engine with the remaining end of each of said rocker member operatively connected to one of said pivot means, with each of said pivot means including hydraulic lash adjustment means therein, said lash adjustment means requiring engine oil supplied only by gravity flow therein; c. means for supplying engine oil in vertical proximity to said pivot means and discharging oil in a manner such that oil flows only by gravitational force to said pivot means; d. collector means for directing said gravity flow of oil to said lash adjustment means; and, e. one-way valve means disposed in said lash adjustment means for permitting gravity flow of oil thereto when each of said rockers is in contact with the base circle portion of one of said cam lobes.

2. The valve gear defined in claim 1, wherein said means for supplying engine oil in proximity to said pivot means includes, a. an axial oil gallery formed in said camshaft with a plurality of radial oil ports communicating with and extending outwardly therefrom, with each of said ports communicating with the base circle portion of one of said cam lobes; and, b. baffle means disposed adjacent each of said cam lobes such that during rotation of said camshaft, engine oil from said pressure gallery flows through each of said radial ports and impinges on said baffle means, said baffle means including means for directing oil by gravity flow to each of said collector means.

3. The improved valve gear defined in claim 1, wherein a. said collector means includes an aperture formed in each of said rocker members in said end connected to said pivot means, such that oil drips from said supply means and flows by gravity through said aperture to said pivot means; and, b. said lash adjustment means includes a stationary body attached to the engine, said body having a cavity formed therein and a plunger slidably mounted in said cavity such that an oil chamber is formed in said cavity by one end of said plunger, with the opposite end of said plunger pivotally contacting the end of said rocker, said plunger having a passage therein communicating said chamber with said aperture in said rocker, and one-way valve means operative only to admit oil from said passage to said chamber.

7. A hydraulic lash adjuster for internal combustion engine overhead valve gear of the type having the camshaft disposed over the valve rockers and the lash adjuster stationary with respect to the engine, said adjuster comprising: a. a body having a longitudinally disposed bore formed therein, said bore being closed at one end of said body; b. plunger means slidably received in said bore in a closely fitting relationship, with one end of said plunger means extending from the open end of said bore and having a portion of said end defining a pivot surface for contacting one end of a valve rocker, with the opposite end of said plunger means defining, in cooperation with the closed end of said bore, an oil cavity, said plunger means having passage means formed therein which passage means is operative to communicate oil by gravity flow from said pivot surface to said cavity; c. said passage means includes one-way valve means, which valve means permits said gravity flow of oil into said cavity when said plunger has no load applied thereon in a direction to move said plunger into said cavity; and d. means biasing said plunger in a direction outwardly of said cavity.

9. The hydraulic lash adjuster defined in claim 7, wherein said passage has a transverse dimension of at least one-third of the largest transverse dimension of said plunger.

10. The hydraulic lash adjuster defined in claim 7, wherein said one-way valve means includes a valve seat formed at the juncture of said passage and the end of said plunger means forming said chamber; a. a movable member movable from a closed position contacting said valve seat and an open position spaced from said valve seat; and b. means biasing said movable member to the closed position.

12. The hydraulic lash adjuster defined in claim 9, wherein a. said valve means includes a cage received over said movable member and attached to the end of said plunger; and, b. said means biasing said movable member is a coil spring intermediate said cage and said movable member.

16. A hydraulic lash adjuster for internal combustion engine overhead valve gear of the type having the camshaft disposed over the valve rockers and the lash adjuster stationary with respect to the engine, said adjuster comprising: a. a body having a longitudinally disposed bore formed therein, said bore being closed at one end of said body; b. plunger means slidably received in said bore in with one end of said plunger means extending from the open end of said bore and having a portion of said end defining a pivot surface for contacting a valve rocker, with the opposite end of said plunger means defining, in cooperation with the closed end of said bore, an oil cavity; c. means communicating a gravity flow of oil only through said pivot surface with said oil cavity, said means communicating said gravity flow of oil including one-way valve means; and, d. means biasing said plunger means in a direction outwardly of said cavity.

17. A hydraulic lash adjuster for internal combustion engine overhead valve gear, said adjuster comprising: a. a body having a longitudinally disposed bore formed therein, said bore being closed at one end of said body; b. plunger means slidably received in said bore with one end of said plunger means having a portion thereof defining a pivot surface for contacting associated members of the engine valve gear with the opposite end of said plunger means defining, in cooperation with the closed end of said bore, an oil cavity; c. means communicating a gravity flow of oil only through said pivot surface with said oil cavity, said means communicating said gravity flow of oil including one-way valve means; and d. means biasing said plunger means in a direction outwardly of said cavity.