US2252974A - Crankcase ventilating system - Google Patents

Description

A w.w LQwTHER a v2,252,974

' CRANKCASE VENTILATING SYSTEM 'V Aug. r9', 1941*.

original Filed., lay v', 193e Patented Aug; 19, 1941 CRANKCASE vENTmATING' SYSTEM Wilfred W. Lowther, St. Paul, Minn., assignor to n Donaldson Company, Inc., St. Paul, Minn., a f corporation of Delaware original application May 21, 1938, serial No.

.$210,409.` Divided and this application Februj ary 10, 1940, Serial No. 318,337

- Claims. '(Cl. 123-1) This invention relates to internal combustion engines and more particularly to a novel system of obtainair1g-a uni-directional ow of air, under pressure above that of atmosphere, outwardly `from the intake manifolds of internal combustion engines, wherein the predominate pressure is above' that of atmosphere. While the general principles involved in the system broadly referred to above are adapted for a wide variety of applications, they most readily adapt themselves for use in the ventilation of crank cases of internal combustion engines and, insofar as` the present application is concerned, the description thereof will be limited to two such adaptations.

`The "Crank-case Ventilating system of my prior Patent No, 2,060,883 of November 1'7, 1936, /has Worked out in practice with a very high degree. of success in connection with gasoline engines, but that system, being dependent for its operation upon a pressure differential in the engine air intake duct established by a restrictionproducing device such as a carburetor or throttle valve, does notreadily lend itself to use in connection with the Diesel type of engine, sincev in this latter type there is usually no carburetor orthrottle valve in the engine intake to produce a'pressure differential at diierent points therein. The present crank-case Ventilating system makes use of the intermittent pressure surges produced in the engines intake valveor valves to produce or aid in producing a forced circulation of air from the intake conduit through the engines .l crank-case and, hence, is not restricted to use therejis produced for each valve closure, a pres-V sure surge which is momentarilymuch greater than the predominating or mean .average pres-1 yconduit to the crank case.

In accordance with the instant invention this intermittent air-ram effect in the intake conduit is harnessed to create or aid in creating a forced movement of air from the engines air intake Preferably this is accomplished'by extending a suitable conduit between'the engines intake conduit, at a point on the atmosphere side of the intake Valve, and the crank-case and interposing in that connection or conduit a one-way check valve permitting free ilow of air from the engines4 intake conduit to the crank-case under intermittent air-ram efsure in-,the intake conduit and which usually exl ceeds atmospheric pressure. The intermittent pressure surges produced by intermittent closing of the intake valve and resultant rapid stopping of the fast moving air column through the intake conduit may properly beA` referred to as the airram 'effects in the intake conduit and may hereinafter be referred to as such.

fects or pressure surgesy but which prevents return' ow of air from the crank-case underal` ternate lower pressure or partial .vacuum conditions of the engines intake. If air is to be circulated through the crank-case as a result of these pressure surges there must,'of course, be provided an air outlet from the crank-case and although this may be direct to atmosphere, such crank-case outlet is preferably connected back to the engines intake where it will be subject to a predominating' vacuum condition ofthe engines intake which willfurther aid in the circulation of" air through the crank-case. Further, since it is desired to keep thecrank-c'ase as free aspossible from dust and other foreign substance and since engines of the present day are almost universally equipped with air cleaners in their air intakes, the air supplied -to the crank-case in the manner above described can easily bekept free from air by making the said connection or connections from' the crank-case to the intake conduit at a point or points after the-intake air cleaner.

. This application is in the nature of a division of my co-pending application S. N."'2l0,409 filed May 27, 1938, and entitled Crank-case ventilating system.

Whereas the claims in this application are confined to the method phase of the invention, the claims of my above identied copending application are directed to the broad coverage of the apparatusphase of the invention.

In the accompanying drawings like characters indicate like parts throughout the several views.

Referring to the drawings:

Fig. 1 is a transverse sectional view through an internal combustion engine incorporating one embodiment of the invention;

Fig. 2 is an enlarged detail view in the side elevation with some parts broken away and some parts shown in section .of the check valve of Fig. 1;

Fig. 3 is a transverse sectional view taken on 2 Laaxsacvfi theline 3-#3 of Fig. 2 and looking upwardly, in respect to Fig. 2;

Fig. 4 is a detail sectional view illustrating a valvedisc of different material than that illus--l trated in Figs. land 2 but which may be substituted for the valve disc ofqFigs. 1, 2 and 3;

Fig. 1 is a transverse sectional view similar'to Fig. 1 but illustrating'another embodiment of the Figs. 1 lto 4 inclusive, will first be described. The

engine illustrated in Fig. l is of the conventional character and, as previously stated, may be considered to be of the Diesel or oil burning type, since the intake conduitthereof incorporates no throttle valve or-carburetor.` Obviously, the en- 20 of Figs. 1 and 2, is made of thin sheet metal such,

gine illustrated may incorporatel any number of cylinders,`.but, for the purpose of kthis case, it may just as well be considered as a one-cylinder engine.

,Of the conventional partsy of the engine the cylinder block thereof is indicated as an entirety by 5, the cylinder'bore thereof by 6, .the piston by l 1, the crank shaft by 8, the connecting rod :by 9, the crank-case by I0, the cam shaft by Ill, the

intake valve operating cam by I2, the cylinder head by I3, the combustion chamber formed in the cylinder head above the cylinder borel 6 by I4, the spring-closed intake valve by I5, the roller tappet assembly by I6, the push rod byc rI1 and the intermediately pivoted rocker arm by I8.

In accordance with general practicefthe bottom of the crank-case I is closed by a removable oil pan I9,-'containing a suitable body of lubrieating oil y, and the valve actuating connections I1 and I8 are enclosed by a removable inspecttion plate and a removable hood I2l. Also in accordance with conventional practice, inoverhead engines free communication is established between the valve mechanism chamber within the hood l2| and the' crank-case I0. In accordance with the ypresent'. illustration, such communication is established through passages 22, 23 and 24. The cylinder head I3 is provided with an intake 'port l25 that is controlledl by the intake valve I5, and this intake port 25 is connected to atmosphere throughv a 'combustion chamber air intake duct 26 having, applied therein a suitable air cleaner 21.

y In accordance with the present illustration the ventilationinlet to' ther crank-case is made to one side thereof at 28 and the ventilation outlet from the crank-case is made from the ,valve mechanism 'chamberwithin4 thevhood 2I at 29. The ventilation inlet 29 to the crank-case is rconnected to the combustion chamber -air'intake duct 26 at a point intermediate the air cleaner 21 and intakevalve I5 by a relatively large area check-valve-equipped crank-case air intake duct 3,0, and the 'ventilation outlet in the crankcase is also connected [to the combustion chamber air intake duct .26 at a point intermediate 65 the air. cleaner 21 and intake valve I5. Ihislatter connection between the crank-case and intake duct, however, is preferably'made through arelatively small area duct or conduit 3l.

The check valve in thel crank-case air inlet duct 30 is 'indicated asan entirety by 32, and in acordance with the present illustration, includes a two-part'valve body 33, which parts are de- .tachably'secured tgethe'r by screws or the like j 34. The upperA portion of the valve body is 75 pressureperiods,that the average condition withformed with an externally threaded tapered neck 35 that is screw threaded into combustion cha-mber intake duct 26, and the lower half of the I valve body 33 is internally threaded at 36 to facil# 5 itate coupling to the conduit 30. The bore cf the upper portion of the'valve body 33 \is coaxial with but of smaller diameter than that of the lower valve body so as to form, at the point of 'I joindure of the upper and lower portions of the l0 valve body, a shoulder 31 that aiords a valve seat. In axially spaced relation to the shoulder 31 the lower portion of the valve body 33 is provided with arseries of circumferentially spaced inwardly projecting supporting lugs 38, on which l5 lugs 38 is seated awire screen supporting disc 39 Loosely applied in the space between the valve seat shoulder 31 andthe wire screen support 39 is an air pressure actuated valve disc 40, which valve .disc according to the illustration 25 is illustrated -in Fig. 4;, wherein lit is indicated The valve disc 40 obviously must be.

by 40a. of smaller diameter than that of the bore inthe lower portion of the valve body 33, so that when it is seated upon .the supporting' screen 39, air

will be permitted to passv therebetween and the.

walls of the bore 36 at points intermediate-the supporting lugs 38; but it is-equally important that the valve disc 40 beof greater diameter than that of the bore 'in the upperportion of the valve body 33, so that when it is in its elevated position against the valve surface 31 it will completely out oi and close the bore through the up.

per portion ofthe valve body.

Under operation of the'engine the intake valve 40 I5 will, of course, be opened during the downward intake strokes of the piston l1A so as to permit air to be drawn from the atmosphere through the intake conduit 2l and interposed air cleanerV i 21 to the combustion chamber vI4throi1gh the in take port 25, andsaid valve will be closed at, the

termination of the intake stroke of the piston compression, explosion and exhaust strokes of the piston. This rapidly occurring series of air intake cycles will produce a low pressure or relatively high vacuum condition in the intake con- ',duit as a result of the-'restriction to air flow afforded by the conduit 26 and interposed air 'cleaner. yIn. other words, underoperating conditions 5'5 of the engine the mean average pressure condition in the intake conduit, as measured,.for example, bythe conventional U-tube manometer,

will be a sub-atmospheric pressure orso-called ypartial vacuum.- However, asv previously indi- 60, cated, the pressure in the intake conduit is not constant even under constant throttle and constant load but does, in fact, reach its lowest pressure or greatest condition of depression during the intakev stroke of the piston, at which time the valve I5 is open; and then, upon closing of the intake v alve I5, the abrupt stopping of the rapid' ly moving column of air through the intake conduit 26 results in momentary rise in. pressure within the in take conduit, which oftentimes, quite pressure.

considerably' exceeds atmospheric These pressure surges, while quite great in ex-u tent, are, nevertheless, of such short duration as compared to the duration of the extreme low and will remain closed during the succeeding y in the-intake conduit isy still considerably below atmospheric pressure.

Operation of Fics. Ito 4, inclusive Under the above described conditions existing in the air intake conduit 26, under operation of the engine, the valve disc .40 will vbe elevatedto its upper valve closed position, shown by dotted 1 lines in Fig. 2', during all times that the pressure within the intake conduit 26 at the point of connection of the conduit 3,0 thereto is below that existing in the crank-case I0, during pressuresurge intervals caused by rapid closing of the valve l5 and resulting in pressure surgesin the intake conduit 26 which exceed the pressure existing in the crank-case I0. Hence, each time the valve I5 is closed the pressure surge within the conduit 26 will momentarily be sufilcient to open' the valve 32 and cause injection of air from the intake conduit 26 through the valve 32 and conduit 30 to the crank-case, and this intermittently valve seats 31. These valve ap elements are' formed oi resilient sheet material and are rig'idly anchored each at one point by anchoring screws or the like 41.

intake conduit 26', the flap valve elements 40' seat tightly against their respective seats 31 and prevent movements of air in a direction from the `crank-case to the intake conduit, but under pressure surge conditions within the intake conduit when the pressure therein becomes above that within the crank case, the nap valve elei ments 40' readily yield and permit free passage of air from thetintake conduit to the crank-case. In this preferred adaptation of the invention to engines having throttle valve equipped carburetors in the intakes, the operation of a ventilating system is substantially the same as deinjected clean fresh air will be returned to the vrially aids in the circulation of air through the crank-case. It has been found desirable to maintain a pressure condition in the crank-case slightly above that of atmosphere, so that the tendencyawill be to blow air out through any such small leaks as may occur in even a well sealed crank-case rather than draw air in through such possible leaks; and this condition can quite readily be brought about with the system described by merely so proportioning the air-handling ability oi the crank-case inlet and crank-case outlet 3l as to obtain the desired pressure balance. In arriving ata proper balance to obtain this slight positive. pressure condition in the crank-case, piston blow-by must, of course, be taken into consideration. Usually,v the cross-sectional'area of the conduit' 3l will be much less than that of the conduit til.

Figs. 1 and 2' In Fig. 1' the conventional parts oi the en gine illustrated are substantially like, those indicated in Fig. l and are indicated by like charu acters plus the prime mark. In Fig. 1, however, the engine may, as previously indicated, be assumed to.be-of gasoline burning type since a carburetor 45, having a conventional butterliy throttle valve 46, is illustrated as being interposed in the intake conduit 26.

The Ventilating system of Figs. 1 and 2 is similar to that of Figs 1 to 4 inclusive, 'and includes a crank-case air inlet conduit 3Q' from the engines intake to the crank-case having interposed therein a one way check valve 32 that is similar to that of Figs. l to 4, anda crankcase air outlet conduit. 29 that connects the crank-case to the engines intake conduit 26', in a manner similar to that' of conduit 29 of' check valve 32' could be exactly the same as the check valve 320i Figs.'1 to 4 but 'a slight somewhat different form is illustrated for the -purpose of example, and is,-in fact, equally adapted to either of the forms herein illustrated. The valve 32 isprovided with a pair of :dap

i then present in the intake conduit at the point of connection of the conduit 29'. Otherwise scribed in connection with Figs. 1 to 4, inclusive -when the throttle valve is open andthe engine operating under comparatively high speed or load conditions, but when the throttle valve 46 is closed down to slow speed, low load or idling gpositiona ventilation of the crank case will be 25v maintainedA largely by virtue of the extremely high vacuum or low sub-atmospheric pressure stated, the velocity through the intake conduit 26' will decrease as the throttle valve 46 is moved from open toward closed position and I will be vso low when'the valve 46 reaches its idling Aposition shown in the drawings that the tendij encyfor air to move into the crank case through the conduit 36 as a result of air ram effects in the conduit 26 will be -very low. However,' in about the same degree as the positive pressure air ram effects decrease under closing oi the throttle valve, the degree of vacuum within the .conduit 26 at the engine side of the throttle valve will be built up and will become increasingly more eiective so that the velocity of air movement through the crank case will be maintained quite uniform under widely varyingdevgrees of engine speed or load. When the throttle valvefis fully closed to its low speed idling posia tion illustrated, circulation will be maintained through thecrank case largely by virtueof the average pressure differential within the intake conduit 2B- at opposite sides of the throttle valve,

las in the crank case Ventilating system of myprior patent before herein identified, although even under these conditions there will be a lower pressuremaintained within the crank case of the present system by virtue oi the slight positive pressure pulsations or air ram effects within the conduit 26.' at the point of connection oi conduit 30', Of course, when the throttle valve is open the restriction produced thereby will be so low that the system will function a1- most identically to that of Figs. 1 to 4,

I claim:

1. The method of obtaining an intermitten but unidlrectionalilow oi air outwardly from an engines air intake duct to a chamber wherein the predominant pressure is above the mean average pressure in the intake duct, but is below the pressure in the intake duct during intermitvalve elements 40' that co-operate withopposite 15' during intermittent tent pressure surges therein produced by air- Yrain actionvresulting from intermittent rapid- Under conditions of. 'vacuum or sub-atmospheric pressure within the 'duct' when pressure rises above' that in said chamber, and automatically cutting oi such Icommunication during intervals when the pressure in the engines ,intake duct is below that in said intake chamber.

2. The' method of obtaining an intermittent but unidirectional iiow of air outwardly from an engines air intake duct to the crank chamber of the engine wherein the` predominant'pressure is above-the mean average pressure in the air intake duct but is' below the pressure in the air intake d uct during intermittent pressure surges in the intake duct produced by air-ram action resulting from intermittent rapid closing of the engines intake valve, which consists in automatically establishing communication between the intake duct and crank chamber during intermittent pressure' surges in the intake duct when pressure rises above that in the crank chamber, and'automatically cutting oil such communication during intervals when the pressure in the intake duct is below that in the crank chamber,

3. The method of Ventilating crank chambers of internal combustion engines which consists in providing two passages between the engines air intake duct and its crank chamber, subjecting the crank chamber to the mean average pressure in theintake duct'through one of said passages, and subjecting the crank chamber to only the high pressure surges produced in the engines intake duct,l as a result ofrapid closing of the intake valve,- through the other of said passages..

4. 'I'he method of obtaininga uni-directional Cil ow of air outwardly from an engine's intake conduit to the engines crankchamber through one passage and outwardly from the engines crank chamber to the engines intake duct through another passage, Which consists inpermitting conv stant uninterrupted flow through one of said@ .passages and automatically cutting oi communication between the intake duct and crank chamber through the other of said passages during inltervals when the pressure in the intake duct is below that in the crank chamber,4 and automatically reestablishing communication through said last named passage during intervals when the pressure in the intake duct rises above the pressure existing in the crank chamber.

5. The method of flowing air outwardly from an engines air intake conduit to a zone of application whereat the mean average pressure is above the mean average pressure condition inthe intake duct, which consists in automatically establishing communication between the engines ,intake duct and said zone of application during intervals when the pressure in the intake duct exceeds that at said zone of application as a result of -air-ram action produced by abrupt closing of the engines intake valve, and automatically closing off communication between the intake duct and said zone of application during 'intervals when the pressure inthe engines intake duct is below that existing at -said zone of application.

, WILFRED W. LOWTHER.

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