US2146550A

US2146550A - Hydraulic valve tappet

Info

Publication number: US2146550A
Application number: US169380A
Authority: US
Inventors: Pierce Erold Francis
Original assignee: Wright Aeronautical Corp
Current assignee: Wright Aeronautical Corp
Priority date: 1937-10-16
Filing date: 1937-10-16
Publication date: 1939-02-07
Anticipated expiration: 1956-02-07

Description

Feb. 7, 1939.

E. F. PIERCE HYDRAULIC VALVE TAPPET I Filed Oct. 16, 1937 R ww J w R R2 Y mP m N5 R 1 0 wm W mm A a Q Q Q w m E A ww 3 MN v Y Q mm Y m 2 w m w MN W mm &\ Q m Patented Feb, 7, 1939 2,146,556 v RA i Y IWLE- 1mm i' i El-oldlFrancis PiercasPines toflWright Aeronautical Corporation, a corpo- I Application October 1 6,; 1937, Serial No. v 110 Claims; l (Cl. 123 90, I I r I cumferential conduit,fl interrupted byithe sev- .,;'This invention, relates to internal 'cornbustion j engines, and has particular reference to improved means'for automaticallymaintainingzero clear o ame between theengine: valve and the operating 1 5; cam therefor. In the prior art, it is known that Y bothhydraulic' and mechanical systems have.

been-suggestedjfor'maintaining zero valve clear- I ance throughout the entire range of engine operpresent invention I 110 contemplates the provision of a hydraulic sys-f tern which is'positivelyop'erated and is not sub;

ating temperatures, and the ..ject to inertia effects under highspeed operat fl .ying conditions, which effects have'been found detrimental in the operation 5r systems 01 the prior art.

, tively operatedhydraulic valve clearance adj stn 'system 1 I .o

" urtner' objecv is f w-tween'a valve tappet anda 'camffollower and",

*subsequently,' to provide ir n'eans" responsive. to

, I mnfollo'wer movement foropening the cell to externally imposed hydraulic I pressure,

5 w I Stillanother object" is to coordinate a hy-" ,draulic'-v'alve tappetadjusting systemwith an} automatic valve lubricating system', to 'theend that the number of extraneouspa'rts incident'to .4 '-both systems will-b minimized; 30 Further-objects will be apparent froma liar parts, and in which:

-.Flg. 1 is an axial section through part of a radial cylinder internal combustion engine;

I13. 2 is an enlarged section on the line 2-2:-

" ori-"i 1; and

Fig. 3 is an enlarged section i m nner-3 of i 4o Fig- 1.

The drawing shows an engine cylinder Hi i ,bolted to a crankcase I2 including a rearhalf i II and a front half 14, which crankcase supports .aire'arward portion 28 'thereoLWhich "oil passes through conduit 30 to the' crankpin l8, and

50 thence through a conduit u to a car'riv bearing 34 on which is mounted 'a cam 36 of the concentric multi-lobe type driven from "the engine fcrankshaft byv suitable gearing m eans (not shown).

Oneor more cam follower and tappet assemblies 55 38 areproyided for each cylinder |0,'thevalve gear of the cylinder, since it is not a specific part i of this inventiomhnot being shown. The assemblyuybetter shown in'Flg. 2, comprises a cam follower guide mounted in a portion of the 60 front crankcase half l4, the latter having'a cirof the hydraulic 1 A n objectof the invention is to provide a; posi-.-

g to provid ejcam operated 20 valve means for controlling ajhydraulic cell be- 4 H h or backlash existing ther'ebetweem- Asysoon as a fcam lobe starts 'to raise the follower, thepresreadij i ingof'the subjoined specification and claims, to

'gether with an examination of the'accompan'ying j drawing, in which similarnumbers-indicate-simh line 46' fed with oilvu'nder pressurefrom-the coneraiguides 411. r Between'each adjacent pair of guides an axial bore 44 is'formed inthe crankcasesectionyall communicating with an oil feed I .duit 32. The, guide f40embraces a ca m ifollwer 48 and a tappet 50, these two' elements, being fitted as a" plunger cylinder assembly which defines a cavity. '52f'therebetween, said cavitybeing fo'pen, througha port 54, to a port in the guide '4 ll'lir'ii constant registryi'with *the duct 42. The t tappet 50' drives a; push 'rod which serves to operate .the conv ntional cylinder head rocker arm and valve W With oil under pressure fedfto-theduct 42, it

will beJapparent that when the follower 48 is in its lowermostigpositiongbetween cam lobes, the. "cavity o cent-52' wili b'e open to fluidpressure, and this ,fluid pressure will separate .the ,follower I 48 from'the tappetiflft'o takeup any-Qclearance sure between the follower and ,the 'tappet exceeds the normal oil pressure, and the-follower 48 'wouldtend to raisea s'light-amount prior to lift-' V ing'thetappetgfll. Accordingly, Iprovide ashutoff valve 60 in the bore 42 ata point closeto the port56, this valve having' a (rain -contacting ele- 't ment 6 2 rotationallyin advance of the cam fol- "lower 48, the valve being held in a normally ,open

positionby means of a- 'spri'ng 64.v Now, as the c'arn 'rotates, the valve will be closed before the v 1 cam lob'ejraises the cami follower" 48, thus trap-v pingfiuid within the' cavi'ty.v 52 so-that raising of.

the cam follower will raise the--'tappet 50 without lossof oil from'the "cavity 52 The valve 60 willfof course, open-before the-cam follower 48 .leaves the cam lob, but the operating pressure 'of the follower upon the tappet will not :result in loss of fluid from the cell 52, since'theports and 56 will not be in 'registry until the'ca'm follower leaves the cam lobe. Whe'nthese two parts Hand 56 come into'registrv'any slight excess pressure, over the normal :oil pressure, will be 'relieved,}but the normal oilpressu're will simuitaneousiy'be im'posedljupon the cell; to replenish any leakage arid to take upnt he coacting camv follower and tapper 'el ementsto provide ..jzero' valve'clearan'ce. Y

.In certain"hydraulic valve tal p t arrange ments of the-prior art; a, spring loaded relief "valve was incorporatedginl the cam'followenand tappet system, permittingal ,the admission 01 oil under pumppressure to Separate the follower andtappet whenthe-fol1ower was not being acted upon by a cam lobe. Then,; the"check valve would prevem'ioss 'of fluid when thefifollolwer was raised. 'Slight leakage between the several elements would compensate for the changes in adjustment v necessary between the elements under varying engine temperature conditions. This type of arrangement is generally satisfactory at low engine operating speeds, but under high speed conditions the check valve would not seat promptly when the cam follower was raised, resulting in a loss of fluid between the cam follower and tappet with consequent maladjustment in valve timing and degree of valve opening. The subject invention overcomes these inertia effects by providing the positively operated shut-off valveBll whereby no fluid may be lost when the cam follower is raised.

It has been conventional practice for some time to provide for automatic valve gear lubrication through the medium of a hollow tappet and pushrod arrangement. This is included in the present disclosure in coordination with the tappet adthrough the passage 42 to the right and to the, left of the passage 44, respectively, for valve gear lubrication and valve gear adjustment, all of the several cam follower and tappet assemblies being thus taken care of on a radially arranged engine such as that illustrated.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modiflcations and changes.

I claim as my invention:

'1. In a hydraulic valve tappet mechanism, a

support having a bore, a cam follower, reciprocable therein, a valve tappet reciprocable in said .bore due to cam follower operation and forming with said cam follower a cavity, a cam for raising said cam follower, a pressure oil conduit opening to said cavity, and valve means'operated oil pressure conduit in said support communicat-' ing with said cavity, and cam-operated means rotationally in advance of the cam follower for opening and closing said conduit.

3. A valve operating mechanism comprising a cam, a cam follower bearing thereon, a guide for said follower, a valve tappet aligned with said follower, a source of fluid under pressure, said guide having a fluid duct opening between said tappet and follower, and a shut-off valve in said duct having a cam engaging operating element rotationally in advance of said cam follower.

4. In a valve operating mechanism, a cam, a follower therefor, a tappet connected with said follower, a plunger-cylinder mechanism forming the connection between said follower and tappet,

a fluid pressure conduit opening to said cylinder,

and cam-operated valve means for positively closing said conduit in time relation prior to raising of said follower by said cam.

5. In a valve operating mechanism, a cam, a follower therefor, a tappet connected with said follower, a plunger-cylinder mechanism forming the connection between said follower and tappet, a fluid pressure conduit opening to said cylinder, a valve in said conduit, and a valve operating element independent of the cam follower operated directly by said cam prior to contact of said cam with said cam follower.

6. In a cam-operated cam follower-tappet as sembly, a hydraulic cell between the follower and tappet, a conduit for pressure fluid leading to said cell, valve means in said conduit responsive to cam follower raisingmovement for closing and opening said conduit, and a second valve means independent of the cam follower in said conduit operated by said cam for positively closing said conduit in timed relation prior to raising movement of said cam follower due to said cam.

7. In a cam-operated cam follower-tappet assembly, a hydraulic cell between the follower and tappet, a conduit for pressure fluid leading to said cell, and valve means operated by said cam to close off said cell from said conduit prior to follower raising by said cam and to open said cell to said conduit upon cessation of follower raising by said cam.

8. In a cam-operated cam follower-tappet assembly, a follower-tappet guide having a port, said port registering w th the zone of contact of said follower and tappet when at rest, said follower, during follower raising by said cam, closing said port; a pressure fluid conduit communicating with said port, and a valve for closing said conduit including an operating element contacting said cam rotationally in advance of said cam follower.

9. In a valve operating mechanism for an engine, a housing having a fluid passage, a cam, a cam follower slidable in the housing, a hollow valve tappet slidable in the housing, concentric with and axially spaced from the follower and movable with and with respect thereto, a hollow pushrod bearing on and operated by the tappet, the hollows of the pushrod and tappet being in communication with one another, and connections from said fluid passage respectively to the hollow of said tappet and to the space between the cam follower and tappet.

10. In a valve operating mechanism for an engine, a housing having a fluid passage, a cam, a cam follower slidable inthe housing, a hollow valve tappet slidable in the housing, concentric with and axially spaced from the follower and movable with and with respect thereto, a hollow pushrod bearing on and operated by the tappet, the hollows of the pushrod and tappet being in communication with one another, connections from said fluid passage respectively to the hollow of said tappet and to the space between the cam follower and tappet, a valve in the connection from said passage to said space, and mean-s to move the valve to a connection closing position comprising a. cam-engaging element rotationally in advance of said cam follower.

EROLD FRANCIS PIERCE.