US3163158A

US3163158A - Hydraulic lash adjusting device

Info

Publication number: US3163158A
Application number: US356757A
Authority: US
Inventors: Derek B Green
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1964-04-02
Filing date: 1964-04-02
Publication date: 1964-12-29
Anticipated expiration: 1981-12-29

Description

Dec. 29, 1964 D. B. GREEN 3,163,158

HYDRAULIC LASH ADJUSTING DEVICE Filed April 2, 1964 2 Sheets-Sheet l fig. 1.

DEREK B. GREEN Inventor Home ys Dec. 29, 1964 D. B. GREEN 3,163,153

HYDRAULIC LASH ADJUSTING DEVICE Filed April 2, 1964 2 Sheets-Sheet 2 r I I DEREK BGREEN venlor ttorneys United States Patent C) 3,163,153 HYDRAULEE LASH ADEUSTING DEVMJE Derek B. Green, Four Oaks, England, assignor to Ford Motor Company, Dearhorn, Mich, a corporation of Delaware Filed Apr. 2, 1964, Ser. No. 356,757 7 Claims. (Cl. 1239tl) This invention relates to lash adjusting devices for the valve train of an internal combustion engine and more particularly to sealed hydraulic lash adjusting devices.

The use of hydraulic tappets to eliminate lash in the valve train of an internal combustion engine is well known. Although the hydraulic tappets found in conventional engines differ in structural details, they all rely upon the engine lubricating system for a source of actuating hydraulic fluid. Because the conventional hydraulic tappet uses engine lubricating oil as an operating medium, tappet failures may be caused by contaminates contained by the lubricating oil or by chemical action of the lubrieating oil upon the tappet.

It has been proposed to provide a sealed hydraulic lash adjusting device that has a self-contained operating liquid. The most desirable liquid may then be chosen, and foreign matter will not become entrapped within the tappet.

It is the principal object of this invention to provide an improved, self-contained hydraulic lash adjusting device for the valve gear of an internal combustion engine.

An internal combustion engine embodying this invention comprises a camshaft and a valve train for transmitting motion from the camshaft to an engine poppet valve. The valve train includes a sealed hydraulic lash adjusting device comprising a body member and a plunger supported for reciprocation by the body member. First and second cup-shaped members are positioned within the body member and divided by a disc to provide first and second fluid chambers. Means are provided to permit fluid communication between the fluid chambers. The cup-shaped members have longitudinally spaced, transversely extending flexible walls. One of the flexible walls engages the plunger. The other flexible wall is engaged by a spring-biased member that tends to deform the flexible wall and decrease the volume in the associated fluid chamber to drive fluid into the other fluid chamber and deform its flexible wall. The deformation of the flexible wall causes axial movement of the plunger in a first direction relative to the body member. Check valve means are provided for precluding the flow of fluid between the fluid chambers upon movement of the plunger in a second axial direction relative to the body member.

Further objects and advantages of this invention will become more apparent when considered in conjunction with the accompanying drawings, wherein:

FIGURES 1-3 are cross-sectional views through 'a sealed hydraulic lash adjusting device, showing a first embodiment of the invention. The views illustrate the position of the parts of the lash adjusting device during different stages of operation.

FIGURE 4 is a cross-sectional view of the upper portion of a hydraulic lash adjusting device, showing a second embodiment of the invention.

FIGURE 5 is a cross-sectional view, in part similar to FIGURES 1-3, showing another embodiment of the invention.

Referring now to FIGURES 1 to 3, the illustrated tappet comprises a casing 1 formed of two

parts

3 and 5. An internal bore of the upper part 3 has a pair of shoulders 7 and 9 and an internally threaded lower sec tion. The lower part 5 screws into the lower section and has a flange 11 which is slightly spaced from the lower ice end of the threaded section. The upper end of the lower part 5 is spaced from the shoulder 9 so as to form a recess 13. The casing 1 is slidable in a bore (not shown) in an engine cylinder block, and its base is engaged by a conventional cam 15 on a camshaft (not shown).

A sealed liquid chamber is formed by two

cups

17 and 19 each having out turned rims 21 which project into the recess 13 and which are spaced from each other by a resilient diaphragm 23 and a rigid plate 25. The diaphragm 23, which in its unstressed condition is planar, has a central aperture 27. The plate 25, which has a concave upper surface, has two apertures 29. The upper cup 17 forms a valve train compartment 31, and the lower cup 19 forms a reservoir compartment 33.

A piston 34 having a convex upper surface is slidable in the lower part 5 of the casing and is forced upwardly into engagement with a flexible lower Wall of the lower cup 19 by a clearance coil spring 35 compressed between the piston and base of the casing. The spring 35, acting on piston 34 exerts a less effective force on the associated engine poppet valve than the valve spring (not shown) exerts on the associated engine poppet valve when the latter is in its closed position. A channel 37 connects the part of the casing 1 beneath the piston 34 with atmosphere.

A plunger 39 which engages a conventional push rod (not shown) is slidable in the upper part 3 of the casing and has a shoulder 41 and a convex lower end which is engaged by a flexible upper wall of the cup 17. The shoulder 41 radially overlaps but is axially spaced from the shoulder 7 of the casing upper part 3.

The tappet functions as follows. When the component parts of the valve train contract when the engine is stopped (FIG. 3), the spring 35 forces the piston 34 upwardly to contract the reservoir compartment 33 and so force liquid from the latter compartment through the apertures 2? and 27 in the plate 25 and diaphragm 23 respectively to expand the valve train compartment 31. This forces the plunger 41 upwardly into contact with the push rod to take up any clearances. The coil spring 35 also acts upon the piston 34 to decrease the volume in the reservoir compartment 33 when the engine is running and the engine poppet valve is closed. Liquid will be driven from the reservoir compartment 33 through the

apertures

29 and 27 into the vale train compartment 31 to cause the flexible Wall of the cup 17 to deform upwardly and move the plunger 39 a suflicient amount to eliminate clearance in the system.

When the component parts of the valve train expand (FIG. 1), the valve train compartment 31 is contracted by the push rod and liquid is forced out of the latter compartment through the

apertures

27 and 29 into the reservoir compartment 33 which is therefore expanded. The expansion of the latter compartment forces the piston 34 downwardly against the action of the clearance spring 35.

When the engine is operating through the normal speed range and the tappet is being moved to open the valve (FIG. 2), the valve spring tries to contract the valve train compartment 31 and does in fact increase the pressure in the latter compartment. This increase in pressure causes some liquid to try to flow from the valve train compartment 31 through the

apertures

27 and 29 into the reservoir compartment 33. Due to the restriction by the aperture 27 to this high rate displacement and before any appreciable amount of liquid can pass, the diaphragm 23 flexes into contact with the concave surface of plate 25 to block communication between the two compartments. Except at low speeds communication between the two compartments is virtually blocked and the system will act as a solid tappet.

When the engine isoperating at low speeds and the tappet is being moved to open the valve, the valve spring is desirable.

tries to contract the valve train compartment 31 and does in fact increase the pressure in the latter compartment. This fairly slow increase in pressure first causes the liquid to fioW from the valve train compartment 31 into the reservoir compartment 33. The restriction caused by the aperture 27, however, causes the diaphragm 23 to flex into contact with the convex surface of the plate 25 to block communication between the two compartments. The time effect of the low pressure loss through the aperture 27 results in a small amount of lost motion in the valve train, so that the valves open slightly late at low speeds, which At high operating speeds the pressure difference across aperture 27 is such that very little liquid is able to flow through the aperture 27 during opening of the valve. Consequently there is very little lost motion in the valve train. By selecting proper sizes of the apertu-re 27 in the diaphragm 23, the degree of late opening of the valves at varying speeds may be adjusted.

In the tappet shown in FIGURE 4, the plunger 39 is replaced by a ball 42, and the push rod 43 has a part spherical surface which engages the ball 42. In all other respects the tappet is identical to that shown in FIGURES 1 to 3.

In the tappet shown in FIGURE 5 there are two difierences from the tappets shown in FlGURES l to 4. Firstly the rims-21 of the cups are bent around the plate 25; and secondly the plunger 39 has a second shoulder e5 which radially overlaps the upper part 3 of the casing. The shoulder 45 ensures that the valve is opened if the liquid in the valve trains compartment 31 should escap The tappet then functions as a normal, solid tappet with cold clearance.

The tappets shown and described are exemplary only of preferred forms the invention may take. The tappets also may be positioned at any convenient location within the valve tnain and may be used in conjunction with an overhead camshaft valve gear. Other changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.

-I claim:

1. An internal combustion engine comprising a camshaft and a valve train for transmitting motion from said can shaft to an engine poppet valve, said valve train including a sealed hydraulic lash adjusting device comprising a body member, a plunger supported for reciprocation by said body member, a disc contained Within said body member, a first cup-shaped member supported within said body member on one side of said disc to define a first fluid chamber therewith, a second cup-shaped member contained within said body member on the other side of said disc to define a second fluid chamber therewith, each of said cupshaped members having axially spaced ilexible Walls extending transversely to the longitudinal axis of said body member, means providing fluid communication between said fluid chambers, said plunger being in engagement With the flexible Wall of said first cup-shaped member, a spring-biased member in engagement with the flexible wall of said second cup-shaped member for deforming said flexible wall to decrease the volume in said second fluid chamber and urge liquid into said first fluid chamber for deforming the flexible wall of said first cupshaped member to urge said plunger in a first axial direction relative to said body member, and check valve means for resisting liquid flow from said first fluid chamber to said second fluid chamber upon deformation of the flexible Wall of said first cup-shaped member by movement of said plunger in a second axial direction relative to said body member.

2. An internal combustion engine as defined by claim 1 wherein means are provided to positively limit the movement of the plunger in the second axial direction relative to the body member.

3. An internal combustion engine comprising a cam shaft anda valve train for transmitting motion from sai tin camshaft to an engine poppet valve, said valve train including a sealed hydraulic lash adjusting device comprising a body member, a plunger supported for reciproccp tion by said body member, a disc contained Within said body member, a first resilient member supported Within said body member on one side of said disc to a first expansiblc fluid chamber therewith, a second resilient member supported Within said body member on the other side of said disc to define a second cxpansible fluid chamber therewith, said disc having a concave surface facing said first fluid chamber, a fluid passage extending from said concave surface through said disc to said second expansible fluid chamber for fluid flow between said chambers, a plunger in engagement W'"h first resilient member, means biasing said second remlient member in a direction to decrease the volume in said sec- 0nd expansible fiuid chamber and urge fiuid therefrom into said first expansible chamber for urging said plunger in a first axial direction relative to said body member, a flexible diaphragm positioned across said disc adjacent said concave surface, said diaphragm being deformable into engagement with said concave surface upon an increase in pressure in said first expansible fluid chamber to close the fluid passage in said disc and prevent fluid flow into said second expansible fiuid chamber, and a restricted fiuid passage in said diaphragn 4. An internal combustion engine conrising a camshaft and a valve train for transmitting motion from said camshait to an e C no poppet valve, said valve train including a sealed hydraulic lash adjusting device comprising a body member having a longitudinally extending bore therein, a plunger supported for reciprocation in an open end of said bore, a disc extending transverse across said bore, a first cup-shaped member having a cylindrical section engaging said bore and terminating at one end adjacent one side of said disc, said cylindrical section terminating at its other end in a resilient Wall extending transversely across said bore and defining a first fiuid chamber with said disc, a second cup-shaped member having a cylindrical section engaging s id bore and terminating at one end adjacent the other side of said disc, the other end of tr e cylindrical section of said second cup-shaped member terminating in a resilient wall extending transversely across said bore and defining a second fiuid chamber with said disc, fiuid passage means extending through said disc for fluid flow between said fiuid chambers. said plunger having a convex surface in engagement with the resilient Wall of said first cup-shaped member for deforming said resilient Wall and decreasing the volume in said ii at fluid chamber upon movement of said plunger in a first axial direction within said bore, a spring-biased member having a convex surface in engagement with the resilient Wall of said second cup-shaped member for deforming said wall and decreasing the volume in said second fluid chamber to induce fiow into said first fluid chamber and move said plunger in a second axial direction Within said bore, and check valve. means in said fiuid passage means for restricting fluid flow from said first fluid chamber into said second fiuid chamber upon movement or said plunger in said first axial direction.

5. An internal combustion engine as defined by claim 4 wherein means are provided on the plunger to coact with means on the body member to positively limit movement of said plunger relative to said body member in the first axial direction.

6. An internal combustion engine comprising a cam shaft and a valve train for transmitting motion from said camshaft to an engine poppet valve, said valve train including a sealed hydraulic lash adjusting device comprising a body member having a longitudinally extending bore therein, a plunger supported for reciprocation in an open end of said bore, a disc extending transversely across said bore, a first cup-shaped member having a cylindrical section engaging said bore and terminating at one end adjacent one side of said disc, said cylindrical section terminating at its other end in a resilient wall extending transversely across said bore and defining a first fluid chamber With said disc, a second cup-shaped member having a cylindrical section engaging said bore and terminating at one end adjacent the other side of said disc, the other end of the cylindrical section of said second cup-shaped member erminating in a resilient Wall extending transversely across said bore and defining a second fluid chamber with said disc, said disc having a concave surface facing said first fluid chamber, a fluid passage extending from said concave surface through said disc to said second fluid chamber of fluid flow between said chambers, said plunger having a convex surface in engagement with the resilient Wall of said first cup-shaped member for deforming said esilient Wall and decreasing the volume in said first fluid chamber upon movement of said plunger in a first axial direction Within said bore, a spring-biased member having a convex surface in engagement with the resilient wall of said second cup-shaped member for deforming said Wall and decreasing the volume in said second fluid chamber to induce flow into said first fluid chamber and move said plunger in a second axial direction Within said bore, a flexible diaphragm positioned across said disc adjacent said concave surface, said diaphragm being deformable into engagement with said concave surface upon an increase in pressure in said first fluid chamber to close the fluid passage in said disc and prevent fluid flow into said second fluid chamber, and a restricted fluid passage in said diaphragm.

7. An internal combustion engine comprising a camshaft and a valve train for transmitting motion from said camshaft to an engine poppet valve, said valve train including a sealed hydraulic lash adjusting device comprising a first body member having a first bore extending longitudinally from one end thereof, a second bore extending longitudinally from the other end of said first body member and terminating adjacent said first bore at a shoulder, a second body member having an outer surface in engagement with said second bore and terminating at a shoulder that is axially spaced from the shoulder of said first body member, a third bore in said second body member, a first cup-shaped member having a cylindrical section engaging said first bore and terminating at one end in a flange portion in engagement with the shoulder of said first body member, said first cup-shaped member terminating at its other end in a resilient Wall extending transversely across said first bore, a resilient diaphragm extending transversely across said one end of said first cup-shaped member and being in engagement around its outer periphery With said flange portion, a substantially rigid disc positioned adjacent said resilient diaphragm and having a convex surface facing said diaphragm, a second cup-shaped member having a cylindrical section engaging said third bore and terminating at one end in a flange portion, said flange portion being in engagement at one side with said disc and at the other side with the shoulder of said second body member, the other end of said cylindrical section of said second cup-shaped member terminating in a resilient Wall extending transversely across said third bore, said first cup-shaped member and said resilient diaphragm forming a first fluid chamber, said second cup-shaped member and said disc forming a second fluid chamber, fluid passage means extending through said disc, said resilient diaphragm being deformable upon an increase in fluid pressure in said first chamber to engage said concave surface of said disc and close said fluid passage means, an orifice in said resilient diaphragm for limited fluid flow therethrough, a plunger supported for reciprocation in the open end of said first bore, said plunger having a convex inner surface in engagement with the resilient Wall of said first cup-shaped member for deforming said resilient wall and decreasing the volume of said first fluid chamber upon movement of said plunger in a first axial direction in said first bore, and a spring-biased member positioned in said third bore, said spring-biased member having a convex surface in engagement with the resilient Wall of said second cup-shaped member for deforming said Wall and decreasing the volume in said second fluid chamber.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. AN INTERNAL COMBUSTION ENGINE COMPRISING A CAMSHAFT AND A VALVE TRAIN FOR TRANSMITTING MOTION FROM SAID CAMSHAFT TO AN ENGINE POPPET VALVE, SAID VALVE TRAIN INCLUDING A SEALED HYDRAULIC LASH ADJUSTING DEVICE COMPRISING A BODY MEMBER, A PLUNGER SUPPORTED FOR RECIPROCATION BY SAID BODY MEMBER, A DISC CONTAINED WITHIN SAID BODY MEMBER, A FIRST CUP-SHAPED MEMBER SUPPORTED WITHIN SAID BODY MEMBER ON ONE SIDE OF SAID DISC TO DEFINE A FIRST FLUID CHAMBER THEREWITH, A SECOND CUP-SHAPED MEMBER CONTAINED WITHIN SAID BODY MEMBER ON THE OTHER SIDE OF SAID DISC TO DEFINE A SECOND FLUID CHAMBER THEREWITH, EACH OF SAID CUP-SHAPED MEMBERS HAVING AXIALLY SPACED FLEXIBLE WALLS EXTENDING TRANSVERSELY TO THE LONGITUDINAL AXIS OF SAID BODY MEMBER, MEANS PROVIDING FLUID COMMUNICATION BETWEEN SAID FLUID CHAMBERS, SAID PLUNGER BEING IN ENGAGEMENT WITH THE FLEXIBLE WALL OF SAID FIRST CUP-SHAPED MEMBER, A SPRING-BIASED MEMBER IN ENGAGEMENT WITH THE FLEXIBLE WALL OF SAID SECOND CUP-SHAPED MEMBER FOR DEFORMING SAID FLEXIBLE WALL TO DECREASE THE VOLUME IN SAID SECOND FLUID CHAMBER AND URGE LIQUID INTO SAID FIRST FLUID CHAMBER FOR DEFORMING THE FLEXIBLE WALL OF SAID FIRST CUP SHAPED MEMBER TO URGE SAID PLUNGER IN A FIRST AXIAL DIRECTION RELATIVE TO SAID BODY MEMBER, AND CHECK VALVE MEANS FOR RESISTING LIQUID FLOW FROM SAID FIRST FLUID CHAMBER TO SAID SECOND FLUID CHAMBER UPON DEFORMATION OF THE FLEXIBLE WALL OF SAID FIRST CUP-SHAPED MEMBER BY MOVEMENT OF SAID PLUNGER IN A SECOND AXIAL DIRECTION RELATIVE TO SAID BODY MEMBER.