US3542001A

US3542001A - Hydraulic lifter with lash compensator

Info

Publication number: US3542001A
Application number: US770482A
Authority: US
Inventors: Gerald D Line
Original assignee: Eaton Yale and Towne Inc
Current assignee: Eaton Corp
Priority date: 1968-10-25
Filing date: 1968-10-25
Publication date: 1970-11-24
Anticipated expiration: 1987-11-24

Description

United States Patent l1n3,542,001

[72] Inventor Gerald D. Line 2,874,684 2/1959 Thompson 123/90 S i Michigan 3,1 24,1 15 3/1964 Vo'orhies 123/90 [211 App]. No. 770,482 3,142,290 7/1964 Lesher..;. 123/90 [22] Filed Oct. 25, 1968 3,304,925 2/1967 Rhoads 123/90 [45 Patented 1970 Primary ExaminerAl Lawrence Smith [73 Assgnee gfgz zz fg r Anorney Yount, Flynn 8; Tarolli a corporation of Ohio [54] HYDRAULIC LIFTER WITH LASH ABSTRACT: An improved hydraulic lifter or lash ad uster has COMPENSATOR l7 Claims8Dmwing Figs. a compensator assembly for providing a predetermmed amount of lash in a valve train. The compensator assembly in- U-S- N clude's a member which is biased outwardly a Spllllg (0 pro.

l23/9055 vide a clearance, corresponding to the predetermined lash, [51] Int. Cl... F01ll/l8, between th compensator membe and a stop surface on a 1/24 plunger. The compensator member is brought into engage- [50] Field of Search 123/90al1 mem with the Stop surface by operation f a cam iated References Cited with the valve train to thereby eliminate the clearance and take up the lash. A stop means is provided to limit outward UNITED STATES PATENTS movement ofthe compensator member under the influence of 2,812,750 11/1957 Lesher 123/90 the spring.

Paten ted Nov. 24, 1910 3,542,001

Sheet 1 M2 FIG.2-

FIG .4

' INVENTOR. GHQ/1L0 Q L/IVE Patented Nov. 24, 1970 3,542,001 I 90b FIG 8 FIG. 6

INVENTOR. GERALD 0. LINE BY ,y AZOR/VEYS HYDRAULIC LIFTER WITH LASI-I COMPENSATOR This invention relates to a hydraulic lifter or lash adjuster having a compensator assembly for providing a predetermined amount of lash in a valve train.

During operation of an engine, a hydraulic lifter often tends to obtain too large an axial extent due to pumping up" of the lifter. This pumping up" of the hydraulic lifter results from the lifter responding to temporary or momentary slack in the valvetrain which may be caused by resilient deflection and separation of various parts of the valve train and the action of the valve spring. Upon a pumping up of the hydraulic lifter, the associated valve cannot close and the efficiency of operation of the engine is decreased=ln addition, the valve may be held open due to eccentricity of the cam base circle or deflection of the camshaft.

Accordingly, it is an object of this invention to provide a new and improved hydraulic lifter having a compensator assembly for establishing valve train lash to take up temporary shock in a valve train to thereby prevent pumping up of the lifter.

Another object of this invention is to provide a new and improved hydraulic lifter having a compensator assembly which provides a clearance between a stop surface on a plunger member and a compensator member to thereby provide a corresponding lash in the valve train.

Another object of this invention is to provide a new and improved hydraulic lifter having a compensator assembly including a spring biased compensator member for providing lash in a valve train by establishing a clearance between the compensator member and a stop surface on a plunger member, the

compensator member being moved into engagement with the stop surface in response to operation of a cam to eliminate the clearance and take up the lash in the valve train.

These and other objects and features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein: FIG. 1 is an illustration of a hydraulic lifter or lash adjuster, constructed in accordance with the present invention, in a valve train for operating a valve of an overhead cam engine;

FIG. 2 is a sectional view, taken along line 2-2 of FIG. 1, illustrating the internal structure of the hydraulic lifter;

FIG. 3 is an enlarged sectional view illustrating the structure of a compensator assembly which is included in the hydraulic lifter of FIG. 2 and provides a predetermined clearance and corresponding lash in the valve train of FIG. 1;

FIG. 4 is an enlarged sectional view, similar to FIG. 3, illustrating the compensator assembly in an operated position in which the clearance is eliminated to take up the corresponding lash in the valve train;

' cordance with the present invention and adapted to be used in an engine having a camshaft mounted in the engine block.

The present invention provides a hydraulic lifter or lash adjuster having an improved compensator assembly in association with a pair of plunger members for preventing pumping up or undesirable lengthening of the lifter by providing for the establishing of a predetermined amount of lash in a valve train. In addition, the compensator assembly also prevents an associated valve from being held open due to eccentricity of the cam base circle or deflection of the camshaft by taking up or absorbing the dimensional increase or negative clearance in the valve train caused by the eccentricity of the cam or deflection of the camshaft. The compensator assembly includes a spring which presses a-compensator member toward one of This lash is taken up by elimination of the clearance as a result of movement of the compensator member into engagement with the stop surface upon operation of a cam associated with the valve train. The compensator assembly prevents pumping up of the hydraulic lifter by reestablishing the clearance. Reestablishing of the clearance prevents "pumping up" of the lifter by absorbing any temporary or momentary slack in the valve train due to the action of a spring for closing the valve, deflection of parts of the valve train, and/or instantaneous separation of the parts of the valve train. The compensator absorbs a dimensional increase or negative clearance in the valve train by enabling the compensator member and one plunger member to move toward the other plunger member. I Although a hydraulic lifter or lash adjuster l0 constructe in accordance with the present invention can be used in many different types oflengines, the hydraulic lifter is illustrated in FIG. 1 in a valve train 12 of an engine 14 having an over head cam 16. The valve train 12 is actuated by the cam l6 to operate a valve 20 (shown in FIG. 1 in a closed position) to control the flow of gases from a combustion chamber 22 in a known manner. To operate the valve 20, the valve train 12 includes a rocker arm 26' which has an end or nose portion 28 for engaging the stem30 of the valve. The opposite end 31' of the rocker arm 26 is connected by a clip 32 to the hydraulic lifter l0. 7

Upon rotation of the cam 16ina clockwise direction, a leading ramp 36 of an actuating or nose portion 38 of the cam engages a follower surface 40 on the rocker arm 26 to open the valve 20 by pivoting the rocker arm about the hydraulic lifter l0. Continued rotation of the cam 16 brings the trailing ramp 42 of the cam into engagement with the follower surface 40. The valve 20 then moves toward the illustrated closed position under the influence of valve spring 44. After a base circle portion 48 of the cam 16 engages the follower surface. 40, the valve 20 is held closed by the valve spring 44 until the leading ramp 36 of the cam is again brought into engagement with the follower surface 40.

The hydraulic lifter l0 adjusts the valve train 12 to maintain a predetermined relationship between the rocker arm 26 and cam 16 even though the dimensions ofthe valve 20 and rocker arm 26 may vary due to wear, thermal effects and other reasons. To this end, the hydraulic lifter 10 includes a generally cylindrical, stationary outer housing or casing 52 having a central chamber or cavity 54 (See FIG. 2) in which a first or inner plunger member 56 and a second or outer plunger 58 are slidably mounted in a coaxial relationship. The

plunger members

56 and 58 define

central cavities

62 and 64 which cooperate to form a fluid reservoir 66 for holding oil or other lubricant. The reservoir 66 isconnected in fluid communication with an oil pump or other source of lubricant under pressure (not shown) by holes or

apertures

70 and 72 in the body and

plunger member

52 and 58 and by passages 74 in the engine block.

A check valve assembly 78 cooperates with the

plunger members

56 and 58 to. compensate for dimensional changes in the valve train 12 by varying the axial extent of the hydraulic lifter 10 to thereby maintain a predetermined relationship between the cam 16, rocker arm 26 and valve 20 (See FIG. 1). This is accomplished by providing a pressure chamber 80 in which fluid is subjected to pressure by the downward force of the rocker arm 26 on the

plunger members

56 and 58 when? the operating portion or nose 38 of the cam 16 engages the follower surface 40 to open the valve 20 (FIG. 1). Some of the fluid in the pressure chamber 80 (FIG, 2) is forced out of the chamber along a relatively small clearance 82 between the cylindrical peripheral surfaces of the

plunger members

56 and 58 and the cylindrical inner surface of the body 52. This leakage of fluid is commonly referred to as leakdown and results in a slight inward movement of the

plunger members

56 and 58 and a corresponding contraction of the pressure chamber 80.

When the force against the outer plunger 58 is reduced by engagement of the base circle 48 of the cam 16 with the follower surface 40 of the. rocker arm 26, a plunger spring 84 in the pressure chamber 80 presses the

plungers

56 and 58 outwardly to press the rocker arm 26 against the base circle 48 of the cam 16. This outward movement of the

plunger members

56 and 58 causes the pressure chamber 80 to expand slightly and reduces the fluid pressure within the chamber. Fluid pressure in the reservoir 66 is then greater than the fluid pressure in the chamber 80 and a valve member 86 of the check valve assembly 78 (FIG. 2) is moved out of engagement with a valve seat 88 against the influence of a valve spring. 90 to enable fluid to flow from the reservoir 66 through a passage 94 to the pressure chamber 80 to replace the fluid which previously leaked out of the pressure chamber. If the effective length of the valve train 12 should increase from one revolution of the cam 16 to the next, the distance which the plunger spring 84 moves the plungers S6 and 58 and the amount of replacement fluid which flows into the pressure chamber 80 is decreased to thereby decrease the effective axial extent of the hydraulic lifter 10. Conversely, if the effective length of the valve train 12 should decrease from one revolution of the camshaft 16 to the next, the plunger spring 84 moves the

plunger members

56 and 58 outwardly to expand the pressure chamber 80 and enable a relatively large amount of replacement fluid to flow into the pressure chamber to thereby effect an increase in the axial length of the hydraulic lifter 10. In this manner the check valve assembly 78 and plunger

members

56 and 58 cooperate to maintain a predetermined relationship between the cam'16, rocker arm 26 and valve 20 even though the effective dimensions of the valve train 12 change during operation of the engine 14. Of course, a ball-type check valve member could be used instead of the member 86.

If temporary or momentary slack should occur in the valve train 12 due to the action of the valve spring 44, deflection of the parts of the valve train, or instantaneous separation of the parts of the valve train, the check valve assembly 78 responds to this temporary or momentary slack to increase the size of the pressure chamber 80 and the effective axial length of the hydraulic lifter 10 more than is necessary to maintain the desired predetermined relationship between the cam 16, rocker arm 26 and valve 20. This undesired increase in the effective axial length or extent of the hydraulic lifter 10 due to temporary or momentary slack in the valve train 12 is commonly called pumping up of the hydraulic lifter l and results in the valve 20 being held in an open condition due to a raising or outward movement of the plunger member 58 and a corresponding lowering or inward movement of the nose portion 28 of the rocker arm 26. Of course, when the valve member 20 is held in a partially opened condition due to a pumping up of the hydraulic lifter 10, the flow of gases from the combustion chamber 22 is improperly controlled and there is a decrease in operating efficiency of the engine 14. In addition to being susceptible to being held open due to a pumping up of the hydraulic lifter 10, the valve 20 will be held open due to eccentricity of the cam 16 or deflection of the camshaft.

In accordance with the present invention, a compensator assembly 100 is provided in association with the plunger memlifter and for taking up or absorbing negative clearance in the valve train. The compensator assembly 100 prevents pumping up of the hydraulic lifter 10 by providing a clearance or space 104 (FIGS. 2 and 3) which is taken up-or absorbed upon downward or inward movement of the rocker arm 26 under the influence of the cam 16. Upon the subsequent occurrence of temporary or momentary slack in the valve train, the clearance 104 is at least partially reestablished to prevent the check valve assembly 78 from responding to the momentary slack and pumping up the lifter 10. The clearance 104 is formed between an annular stop surface 108

bers

56 and 58 for preventing pumping up of the hydraulic on an outer end portion of the inner plunger member 56 and a parallel annular stop surface 110 on an annular head portion 114 of a compensator member 116. When the actuating portion 38 of the cam 16 moves the rocker arm 26 downwardly (See FIG. 1), an annular end surface 118 of the outer-plunger member 58 is pressed downwardly against an annular outer surface 122 of the head portion 114 (FIG. 3) to force the compensator member 116 axially inwardly or downwardly against the influence of a compensator spring 120 which is located between a base portion 123 of the compensator member 116 and an end wall 124 of the inner plunger member 56 (FIG. 2). The stop surface 110 on the head portion 114 of the compensator member 116 is then pressed against the stop surface 108 on the inner plunger member 56, in the manner illustrated in FIG. 4, to enable force to be transmitted from the outer plunger member 58 through the compensator member 116 to the inner plunger member 56 to apply pressure to the fluid in the pressure chamber (FIG. 2).

Pumping up of a hydraulic lifter may result from the occurrence of temporary or momentary slack in the valve train 12 when the crest or nose of the actuating portion 38 of the cam 16 (FIG. 1) is moving onto or off of the follower surface 40. During this period of operation, the compensator assembly expands axially from the operated condition, shown in FIG. 4, to the normal or expanded condition, shown in FIG. 3. Any temporary or momentary slack in the valve train is absorbed or taken up by a reestablishment of the clearance 104 under the influence of the compensator spring 120. Accordingly, the compensator spring moves the compensator member axially outwardly from the position shown in FIG. 4 toward the position show in FIG. 3 to maintain the plunger member 58 in engagement with the rocker arm 26 and absorb momentary slack caused by a temporary decrease in the effective length in the valve train 12. When the effective length of the valve train is increased, that is when the momentary slack is removed from the valve train, the actuator member 116 is moved inwardly toward stop surface 108. The compensator spring exerts a force, tending to separate the

plunger members

56 and 58, which is greater than the force exerted by the plunger spring 84. In the illustrated embodiment, the compensator spring 120 has a higher spring, rate than does the plunger spring 84.

From the foregoing description it can be seen that the compensator assembly 100 prevents a pumping up" of the hydraulic lifter 10 by absorbing temporary or momentary slack in the valve train 12 by moving the compensator member 116 under the influence of the compensator spring 120. Movement of the compensator member 110 temporarily reestablishes the clearance 104 to enable the outer plunger member 58 to move outwardly without a corresponding outward movement of the inner plungermember 56 under the influence of the plunger spring 84. This operation of the compensator assembly 100 prevents unwanted operation of the valve assembly 78, in response to movement of the inner plunger member 56, by absorbing the temporary slack and effectively insulating the inner plunger member and the valve assembly from the effects of the occurrence of the temporary slack.

The compensator assembly 100 is effective to absorb or take up negative clearance in the valve train resulting from eccentricity of the cam 16 or deflection of the associated camshaft. This negative clearance is taken up by inward movement of the outer plunger member 58 and compensator member against the influence of the compensator spring 120. This inward movement decreases the extent of the clearance 104 and enables the valve 20 to close.

A stop ring or member is provided for limiting outward rocker arm 26, the compensator assembly 100 moves from the operated condition of FIG 4 to the normal condition of FIG. 3. As this is occurring the spring 120 moves the base portion 122 of the compensator member 116 through a distance 138 (FIG. 4) which is equal to the clearance 104 to bring an outer or upper limit or stop surface 140 of the compensator member 116 into engagement with the stop ring 130 (FIG. 3) to thereby reestablish the clearance 104. Continued movement of the trailing ramp 42 relative to the follower surface 40 then enables the

plunger members

56 and 58 to be moved axially outwardly by the plunger spring 84 to thereby expand the pressure chamber 80 .(See FIG. 2) and open the valve as sembly 78 to enable replacement fluid to flow through the passage 94 into the pressure chamber in the manner previously explained. It should be noted that the valve spring44 (See FIG. I) has a higher load or spring rate than both the compensator spring 120 and plunger spring 84 so that the valve 20 is not forced open by the combined action of these two springs.

For purposes of affording a more complete understanding of the invention, several modified forms of the invention are shown in FIGS. 5-8. In these modified forms or embodiments of the invention numerals like those used in connection with the embodiment of FIGS. 1-4. have been used to designate like parts with the suffix letters a, b and being employed to distinguish the elements associated with FIGS. 5, 6 and 7, and 8, respectively. It should be understood that the invention is not to be limited to the particular embodiments described herein since many other embodiments come within the true spirit and scope of the invention.

The hydraulic lifter 10a of FIG. includes a body or casing 52am which a first or inner plunger member 560 and a second or outer plunger member 580 are slidably positioned. A check valve assembly (not shown), similar to the check valve assembly 78 of FIG. 2, is associated with the inner plunger member 56a to control the flow of fluid or lubricant from a reservoir 66a to a pressure chamber (not shown). A compensator assembly 100a is provided in association with the

plunger members

56a and 58a to prevent a pumping up" of the hydraulic lifter a by resiliently absorbing or taking up temporarv slack in a valve train in much the same manner as in which the compensator assembly 100 of FIGS. 24 prevents the hydraulic valve lifter 10 from being pumped up The compensator assembly 100a includes a compensator member 1160 having a flat, annular disklike configuration similar to that of a washer. The compensator member 1160 is normally pressed against a stop ring or member 1300 by a compensator spring 120a to provide a clearance 104a between an annular stop surface 1080 on the inner plunger member 56a and a parallel annular stop surface 110a formed on an inner side of the compensator member 116a.

Operation of a cam. similar to the cam '16 of FIG. 1, results in the plunger member 58a of the hydraulic lifter 100 being pressed inwardly against the influence of the compensator spring 120a to take up or eliminate the clearance 104a bypressing the surface 1100 of the compensator member 116a into abutting engagement with the stop surface 108a on the inner plunger member 56a. If temporary or momentary slack should occur in the valve train upon further rotation of the cam. this temporary or momentary slack is absorbed or taken up by reestablishing the clearance 104a in the manner previously explained in connection with the embodiment of FIGS. 24 to thereby prevent a pumping up of the hydraulic lifter 1011. It should be noted that the compensator member 116a is chamber 80b in association with the inner plunger member 56b to control a flow fluid or lubricant from a reservoir 66b through a passage 94b into the pressure chamber 80b and thereby adjusts the extent of the hydraulic lifter 10b in the manner previously explained in connection with the hydraulic valve lifter 10 of FIGS. 24. A compensator assembly 10% is provided in association with the

plunger members

56b and 58b to prevent pumping up of the hydraulic lifter 10b by resiliently absorbing or taking up temporary slack in an associated valve train resulting from a deflection or separation of parts of the valve train and/or the action of a valve spring (similar to the valve spring 44 of FIG. 1). To this end the compensator assembly 10% includes a compensator member 116b having a cylindrical pin like configuration with

opposite end portions

150 and 152 located in openings or

apertures

154 and 156 in the inner plunger member 56b. The compensator member or pin ll6b has a diameter which is smaller than the a diameter of the

circulator openings

154 and 156 to provide a clearance 104b between a stop surface portion 108b of the

openings

154 and 156 and lower or inner stop surface portions ll0b of the ends l50.and 152 of the compensator member 116b.

Upon rotation of the cam (not shown), the hydraulic lifter 10b is actuated to move the compensator member l16b inwardly or downwardly against the influence of a compensator spring 120b This movement takes up or eliminates the clearance l04b by moving an outer or upper stop surface portion 162 of the compensator member l16b away from outer or upper stop surface positions 166 (FIG. 7) of the

openings

154 and 156 and through a distance corresponding to the clearance 104b. It should be noted that the stop surface portions 166 function in the same manner as do the stop rings 130.

and 130a of the embodiments of FIGS. 25 to limit the outward motion of the compensator member 1l6b under the influence of the spring 12%.

The compensator assembly 100b resiliently absorbs or takes up temporary or momentary slack in the valve train to prevent a pumping up" of the hydraulic valve lifter 10b in the manner previously explained in connection with the valve lifter 10 of FIGS. 24. Thus, once the compensator assembly l00b has been actuated to the operated condition of FIG. 7, the com-' pensator spring 120b moves the compensator member 1l6b away from the stop surface l08b to at least partially reestablish the clearance l04b and thereby absorb or take up any temporary or momentary slack in the valve train. While the compensatormember l16b has been illustrated in FIGS. 6 and 7 as having a generally pin like configuration, it is contemplated that compensator members having different configurations could be loosely mounted in openings ofa configuration other than that of the

openings

154 and 156 to provide a suitable clearance between an inner or lower portion of the compensator member and a stop surface.

Although the hydraulic lifter 10 has been previously depicted herein in association with a valve train 12 (-See FIG. 1) of an over head cam engine 14, it is contemplated that hydraulic lifters constructed in accordance with the present invention and having compensator assemblies similar to the

compensator assemblies

100, 100a and 10% will be used in association with other known types of engines wherein the cam shaft is mounted in the block of the engine and the valve train includes a rocker arm which is operated in a known manner by a push rod. This adaptation of the hydraulic lifter is clearly illustrated inthe embodiment of FIG. 8 wherein the hydraulic lifter 100 is shown in association with a cam 16c and a push rod 200.

The hydraulic lifter 10c includes a casing or body 520 in which a first or inner plunger member 560 and a second or outer plunger member 580 are slidably mounted. A check yalve assembly, similar to the check valve assembly 78 of FIG. 2, is associated with the inner plunger member 56c for controlling the flow of fluid or lubricant from a reservoir 66c to a pressure chamber, similar to the pressure chamber of FIG. 2. A compensator assembly 1000 is combined with the outer plunger member 580 and functions in a manner similar to the compensator member 116 of FIG. 2 to establish a clearance 1040 between an annular stop surface 1080 and a stop surface 1100 formed on an inner or lower portion of the plunger member 58c. The plunger member 580 is pressed outwardly or upwardly by a combined plunger and compensator spring 204 which is positioned in a fluid or lubricant reservoir 66c formed in the inner plunger member 56c. A stop ring or member 130s is mounted in a groove 1320 formed in the inner plunger member 560 to engage an outer stop surface 1220 on the plunger member 580 to limit outward movement of the plunger member 580 under the influence of the spring 204.

Upon operation of the cam 160, the body 52c and push rod 200 are raised to open a valve, similar to the valve 20. Upon this movement of the body 52c, the spring 204 is compressed by relative movement between the inner and outer plunger members 560 and 580 so that the plunger member 580 is brought into engagement with the stop surface l08c. The compensator assembly 1000 prevents pumping up of the hydraulic lifter 100 by resiliently absorbing or taking up temporary or momentary slack in the valve train, the spring 204 presses the plunger member 580 outwardly to at least partially reestablish the clearance 104C. Since the temporary slack is taken up by the operation of the compensator assembly 1000. A check valve assembly, similar to the check valve assembly 78, associated with the inner plunger member 56c is not operated in response to the occurrence of the temporary slack to provide a pumping up" or undesired extension of the effective length of the hydraulic lifter 10c.

In view of the foregoing description, it is apparent that each of the hydraulic lifters 10. 10a, 10b and 10c have a

compensator assembly

100, 100a, 1001: or lc for providing for the establishing of a predetermined clearance and a corresponding lash in a valve train to thereby prevent pumping up of the hydraulic lifter and for taking up negative clearance in the valve train This predetermined clearance is established between a stop surface formed on the inner plunger member and a similar stop surface on a compensator member. Upon operation of a cam associated with the hydraulic lifter, the stop surface on the inner plunger member and the opposing stop surface on the compensator member are brought into engagement to thereby enable forces to be transmitted from the outer plunger member through the compensator member to the inner plunger member. Upon the occurrence of a temporary or momentary slack in the valve train, a compensator spring presses the compensator member outwardly to at least partially reestablish the clearance between the stop surfaces on the inner plunger member and the compensator member to thereby absorb or take up the temporary slack. This taking up of the temporary slack by the compensator assembly prevents a pumping up" of the hydraulic lifter by preventing the check valve assembly associated with the inner plunger member from adjusting the position of the inner plunger in response to the occurrence of the temporary slack. The negative clearance is taken up by inward movement of the outer plunger member against the influence of the compensator spring I claim 1 A hydraulic lifter for use in a valve train, said hydraulic lifter comprising a body. first and second plunger members located at least partially within said body, a compensator member mounted in said body in association with said plunger members, and spring means for biasing said compensator member in a first direction away from said, first plunger member to provide a clearance between a stop surface on said first plunger member and said compensator member and a corresponding lash in the valve train, said spring means acting between said compensator member and said first plunger and having a first end portion disposed in engagement with said first plunger member and a second end portion disposed in engagement with said compensator member, said compensator member being movable in said first direction under the influence of said spring means to move said second plunger member away from said first plunger member and being movable in a second direction into engagement with the stop surface on said first plunger member upon relative movement between said plunger members against the bias of said spring means in response to operation of a cam to thereby take up the valve train lash corresponding to the aforesaid clearance.

2. A hydraulic lifter as set forth in claim 1 further including stop means associated with said first plunger member for limiting outward movement of said compensator member under the influence of said spring means.

3. A hydraulic lifter as set forth in claim 1 wherein said compensator member has one surface portion which abuttingly engages a surface of said second plunger member and an opposite surface portion which abuttingly engages the stop surface on said first plunger member upon the aforesaid relative movement between said plunger members.

4. A hydraulic lifter for use in a valve train, said hydraulic lifter comprising a body, first and second plunger members located at least partially within said body, a compensator member mounted in said body in association with said plunger members, spring means for biasing said compensator member and said second plunger member away from said first plunger member to provide a clearance between a stop surface on said first plunger member and said compensator member and a corresponding lash in the valve train, said compensator member being movable into engagement with the stop surface on said first plunger member upon relative movement between said plunger members against the bias of said spring means in response to operation of a cam to thereby take up the valve train lash corresponding to the aforesaid clearance, stop means associated with said first plunger member for limiting outward movement of said compensator member under the influence of said spring means, and second spring means for urging said plunger members outwardly of said body, said second spring means having a lower spring load than said spring means for biasing said compensator member and said second plunger member outwardly.

5. A hydraulic lifter for use in a valve train, said hydraulic lifter comprising a body, first and second plunger members located at least partially within said body, a compensator member mounted in said body in association with said plunger members, said compensator member having at least a portion thereof disposed between said first and second plunger members, and spring means for biasing said compensator member and said second plunger member away from said first plunger member to provide a clearance between a stop surface on said first plunger member and said compensator member and a corresponding lash in the valve train, said compensator member being movable into engagement with the stop surface on said first plunger member upon relative movement between said plunger members against the bias of said spring means in response to operation of a cam to thereby take up the valve train lash corresponding to the aforesaid clearance.

6. A hydraulic lifter for use in a valve train, said hydraulic lifter comprising a body, first and second plunger members located at least partially within said body, a compensator member mounted in said body in association with said plunger member, spring means for biasing said compensator member and said second plunger member away from said first plunger member to provide a clearance between a stop surface on said first plunger member and said compensator member and a corresponding lash in the valve train, said compensator member being movable into engagement with the stop surface on said first plunger member upon relative movement between said plunger members against the bias of said spring means in response to operation of a cam to thereby take up the valve train lash corresponding to the aforesaid clearance and having one annular surface which abuttingly engages an annular surface of said second plunger member and another annular surface which abuttingly engages the stop surface on said first plunger member upon the aforesaid movement between said plunger members, and an annular stop means mounted on said first plunger member for engagement with said compensator member to limit outward movement of said compensator member relative to said first plunger member under the influence of said spring means.

7. A hydraulic lifter as set forth in claim 6 wherein said compensator member is a washer and said one annular surface is substantially flat and adapted to engage said annular stop means, said spring means being located in said first plunger member in engagement with said other annular surface.

8. A hydraulic lifter as set forth in claim 6 wherein said compensator member includes an annular head portion, an annular base portion and a cylindrical body portion interconnecting said base and head portions, said annular surfaces being on opposite sides of said head portion, said base portion being adapted to engage said annular stop means, said spring means being located in said first plunger member in engagement with said base portion.

9. A hydraulic lifter for use in a valve train, said hydraulic lifter comprising a body, first and second plunger members located at least partially within said body, a compensator member mounted in said body in association with said plunger members, spring means for biasing said compensator member and said second plunger member away from said first plunger member to provide a clearance between a stop surface on said first plunger member and said compensator member and a corresponding lash in the valve train, said compensator member being movable into engagement with the stop surface on said first plunger member upon relative movement between said plunger members against the bias of said spring means in response to operation of a cam to thereby take up the valve train lash corresponding to the aforesaid clearance and stop means on said first plunger member for limiting outward movement of said compensator member under the influence of said spring means, said compensator member being mounted on said first plunger member for movement between a first position and a second position, said compensator member in said first position having one surface portion in engagement with said stop means and another surface portion spaced from said stop surface by a distance corresponding to the aforesaid clearance, said compensator member when in said second position having said one surface portion spaced from said stop means by a distance corresponding to the aforesaid clearance and said other surface portion in engagement with said stop surface.

10. A hydraulic lifter as set forth in claim 9 wherein said stop means includes a ring mounted on said first plunger member and said spring. means is mounted in a cavity in said first plunger member and presses said compensator member toward said first position.

l]. A hydraulic lifter as set forth in claim 9 wherein said stop surface is formed by one portion of the surface means defining an opening in said first plunger member and said stop means includes another portion of said surface means defining an opening in said first plunger member, said compensator member being at least partially positioned within said opening and being movable relative to said surface portions.

12. A hydraulic lifter as set forth in claim 11 wherein a second opening is formed in said first plunger member and said spring means is located in a cavity formed in said first plunger member between said openings, said compensator member being a pin having opposite end portions located in said openings and extending across said cavity.

plunger member and said body member, a passageway disposed in said first plunger member to provide for fluid flow from said second cavity to said first cavity, valve means associated with said first plunger member and said passageway for controlling said fluid flow from said second cavityto said first cavity, a spring means mounted in said second cavity for urging said second plunger member outwardly relative to said first plunger member, stop means mounted on said first plunger member for limiting outward movement of said second plunger member relative to said first plunger member under the influence of said spring means, a first stop surface formed on said first plunger member, a second stop surface formed on said second plunger member, said spring means urging said second stop surface away from said first surface to establish a predetermined clearance therebetween when said second plunger member is in engagement with said stop means, said second plunger member being movable relative to said first plunger member against the influence of said spring means in response to the operation of the cam in the valve train to bring said first stop surface into engagement with said second stop surface to thereby take up valve train lash corresponding to the aforesaid clearance.

14. A hydraulic lifter as set forth in claim 13 wherein said stop means includes ring mounted in a groove formed on said first plunger member.

15. A hydraulic lifter as set forth in claim 14 wherein said first stop surface has a generally annular configuration, and

said spring means is located in the cavity in said first plunger member axially inwardly of said second plunger member and is circumscribed by said first stop surface when said first and second stop surfaces are spaced apart.

16. A hydraulic lifter for use in a valve train, said lifter comprising a body defining a cavity, first and second plunger members located at least partially within the cavity in said body,

said first and second plunger members defining a first chamber which receives fluid from a source of fluid, said first plunger member and said body defining a second chamber which receives fluid from said first chamber, valve means as sociated with said first plunger member and operable to provide for fluid flow from said first chamber to said second chamber, and compensating means .for preventing an operation of said valve means in which pumping up of said hydraulic lifter occurs, said compensating means including a compensator member operatively associated with said second plunger member and means for moving said compensator member so that said compensator member effects movement of said second plunger member away from said first plunger member in response to a temporary slack in the valve train.

17. A hydraulic lifter as set forth in claim 16 further including spring means for biasing said compensator member away from said first plunger member to thereby provide a clearance between a stop surface on said first plunger member and said compensator member.