CA2214740C - Crankcase breather valve for engines with synchronous piston movement - Google Patents

Abstract

A crankcase breather valve for ventilation and pressure control within the crankcase of an internal combustion engine in which pistons stroke upwardly and downwardly in a synchronous movement. The valve is inserted into a breather hose which conducts gases into and out of the crankcase. The valve comprises a resilient valve member preferably an elastomeric umbrella-type seal spaced above a seal seat and forming a gap therebetween through which gases may flow either direction during portions of the pistons stroke cycle. The valve construction permits three operating modes: firstly to permit the egress of positive pressure gas out of the crankcase and through the gap while the pistons stroke downwardly; secondly, to permit the ingress of a small amount of gas back through the gap into the crankcase when the crankcase pressure changes from positive to negative; and thirdly to check further ingress of gas into the crankcase at greater crankcase suctions developed when the pistons are moving upwardly.

Description

CA 022l4740 l997-09-0~

FIELD OF THE INVENTION

2 The invention relates to the ventilation of a crankcase of an internal

3 combustion engine and more particularly to the use of a valve to re9~l''te the pressure

4 therein.

7 I"~e",al combustion engines col~lprise pistons which rec;procate within 8 cylinders. Up and down movement of the pistons is converted to a circular output g motion through a crankshaft. The pistons are co""e~ed to the crankshaft with 10 cor",e~ling rods. The crankshaft and connecting rods are housed in a crankcase. In 11 operalion cor"pressed combustion gases can leak past the pistons and enter the 12 crankcase. These gases are normally rerer, ed to as "blow-by" gases. The crankcase is 13 enclosed and thus accumulating blowby gases and the e~Jansion of gases through 14 heating can cause pressure to build up in the crankcase. Further the gas-space in the 15 crankcase is contiguous with the bore of the cylinders which is below the pistons. Up 16 and down movement of the pistons within the cylinders varies the volume between 17 pistons and the crankcase which can affect the pressure in the crankcase.
18 Conventional multi-cylinder engines use altemating piston movement one 19 piston rising while another descends thus balancing the displaced volume and 20 minimizing the variation in crankcase pressure.

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Harley Davidson ( Harley) ",otor~;ycle engines have two cylinders and 2 differ from conventional multi-cylinder internal combustion engines in that the two 3 connecting rods run on a single crank. In other words both of the pistons stroke 4 upwardly together and stroke downwardly together sy"~1ronously. The piston movement is cou,Iterl ald"ced with two large crankshaft-mounted flywheels.
6 Accordingly on the downstroke both pistons simultaneously move downward and 7 diminish the volume available for the contained gases. The pistons co" ,press the gases 8 in the crankcase pressurizing the crankcase gases to above dl",ospheric pressure g ( positive pressure). On the upstroke both pistons simultaneously decor"press 10 crankcase gases reducing the crankcase pressure to below aL"~ospheric pressure l ( "egdli~e pressure). Accordingly Harley engines produce large alter"dling positive 12 and negative crankcase pressures.
13 Most visibly high crankcase pressure is ~ssoçi~led with leakage from 14 crankcase seals.
On Harley engines prodl~ced earlier than 1993 the ",a"age",enl of 16 crankcase pressure is pe,rur",ed with a breather gear driven and timed by the 17 crankshaft. The gear is typically set to open and vent crankcase gases be~oon 10 o lô before top dead center (before TDC) through 75 o after bottom dead center (after BDC).

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The bredtl ,er gear vents crankcase gas to a separale calllshdrl chamber where the bulk 2 of the oil mist is knocked out. The de-misted gas is then di,e~led through a breather 3 hose to the air cleaner. Due to the inherent physical lil "italions the gear timing venting 4 iS not optimal at all engine speeds and throttle conditions. High uankcase pressures

5 still result.

6 In a,,ull,er aspect the oil system of Harley engines is also rather unique

7 being of the dry sump variety and having a separale oil tank. A scavenging pump

8 collects oil from the bottom of the crankcase routes it through an oil filter and on to an g oil reservoir or tank. Oil flows under gravity feed from the oil tank to a feed pump which 10 delivers oil to the engine cor"ponenls. Baffles in the calllshcrl ~1a",ber separale retuming oil mist from crankcase gases before the oil collects at the scavenging pump.
12 There are two aspects of this system which are sensitive to crankcase pressure. Firstly 13 eAcessive suction in the oil tank the head space of which is in commu".-~ion with the 14 crankcase adversely affects the supply of oil to the feed pump. Secondly lack of a 15 head of oil at the inlet of the scavenging pump and excessive suction in the crankcase 16 can starve the scavenging pump of oil. In short the excessive suction can result in oil-17 related engine failure.
18 In post-1993 Harley engines the breather hose has been relocated from 19 the crankcase to each of the two rocker housings. Crankcase gases and pressure 20 communicate with the rocker housings through the push rod tubes. A one-way check CA 022l4740 l997-09-0~

valve mounted within each rocker housing rcloaccs excessive uankcase pressure into 2 the housing. The check valve is an "umbrella-type" valve having a port or ports blocked 3 with an elaslon,eric umbrella valve head. The umbrella is normally closed over the port 4 to prevent inflow of gases into the crankcase. Pressure flexes the umbrella off of the port so as to release gases from the engine. A small bleed hole is provided which 6 permits collected oil to drain back to the crankcase. It is apparenl that the bleed hole 7 can also permit some gases to return to the aankcase. In the stock a" d,lgeme"l a port 8 directs the gases directly into the air c,ea,ler. As an ~Gcessory after-market uoss-over g tubing can be installed between the two rocker housings. A "tee" in the tubing directs 10 the crankcase gases to a discharge tube and filter which removes oil mist.
1 Others have utilized crankcase bredLI ,er valves in the conlext of 12 conve"lional 4-stroke engines. The valves are known for reducing oil seal leakage by 13 releasi,lg excess pressure and forming a predon,inately negative pressure in the 14 uankcase. Several breall,er valves use the "umbrella-typeU valve heads ("umbrella").
For i"-~lance in US Patent 5 067 449 to Bonde and US Patent 5 205 243 to Buchholz 16 disclose crankcase b,~dll,er asser,lblies. An assembly is inserted into a port formed in 17 the crankcase. The asse",bly ir,cor~orales an outer groove which retainably engages a 18 lip formed in the port. The asse",bly further incor~,ordLes an umbrella which covers and 19 seats over a circular array of ports. The umbrella is normally-closed so as to ensure only one-way flow through the ports. In US Patent 5 027 784 Osawa et al. improved CA 022l4740 l997-09-0~

the operability of an umbrella-type valve by inler~Josing a washer between the umbrella 2 and the ports. The washer reduces over-flexing and premdlure failure of the umbrella.
3 Despite the presence of the washer, Osawa's umbrella still rests in the normally-closed 4 position.
Thus check valves of the umbrella-type are known and they are all of the 6 normally-closed, one-way variety. Accordingly, while these valves permit flow out of the 7 crankcase on over-pressure, they do not permit any gas flow back into the crankcase, 8 except for a small amount of sealing hysterisis.
g While the sy"chr~nous piston movement in a Harley Davidson engine can 10 benefit from a redl ~ction of maximum crankcase pressure, it must do so while avoiding 1l the crealiG,l of excessive crankcase suction which can be ~.ssoci 'ed with loss of oil 12 pump operation. Further, a device which meets the above objectives must do so without 13 modification to the uankcase.

SUMMARY OF THE INVENTION
16 It has been determined that the pressure-related problems of the 17 simultaneous upward and downward action of the pistons includes not only affects seal-18 leakage but also i",pa~;ts on engine power. Further, direct application of conventional 19 one-way flow check valves for releasing uankcase pressure results in undesirable side-20 effects, namely a loss of power at higher engine speeds and the formation of 21 excessively high crankcase suction. Further, an external in-line device is preferred to 22 avoid modifications to the engine crankcase.

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More particularly a device is provided which is inse,led into the e,~i~ling 2 external breather hose. The device permits a small amount of gas flow back into the 3 crankcase as the pressure in the crankcase begins to be drawn negative thereby 4 ultimately avoiding excessively high crankcase suction at the top of the pistons stroke.
Thus in a broad aspect of the invention a novel valve is provided for 6 installation on an engine such as a Harley Davidson ",otorcycle engine which has two 7 or more pistons which move simultaneously upwardly and simultaneously downwardly.
8 The valve is installed on a brecll,er hose extending from a port on the crankcase for g discha,ye outside the crankcase. The valve is constructed such that it operates to control the flow of crankcase gases in three modes. Firstly to permit the egress of 11 positive pressure gas from the crankcase while the pistons are moving downwardly;
12 secondly to permit the irlyless of a small amount of gas back into the crankcase when 13 the crankcase pressure cha"yes from positive to negative; and finally to check the 14 further ingress of gas into the crankcase at y,ealer crankcase suctions when the 15 piston s are moving upwardly.
16 rleferably the valve coi"l rises the following construction for 17 i",p!e "e"li"g the three operating modes. Firstly the valve comprises an inlet and 18 outlet and a valve chamber i"ler",ediale the inlet and outlet. Within the valve chamber 19 a valve seat is formed at the discharge of the inlet to the Chall ,ber. A resilient " ,e" ,ber is 20 spaced above the seal seat so as to form a gap through which gases may flow either CA 022l4740 l997-09-0~

direction. Accordingly, gas is able to flow from the inlet, past the member and on out of 2 the valve's outlet. Under low pressure dirrer~"lials across the member, gas will also 3 flow back from the outlet, past the member, through the gap and out of the inlet so as to 4 return to the crankcase. Under higher pressure differentials, the ",e",ber flexes and 5 blocks the seal seat, preventing further back flow from the outlet to the inlet and allowing 6 the crankcase pressure to becor"e negative.
7 More prererably, the resilient member is an elastomeric umbrella-type 8 valve head, or a flexible reed.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a simplified cross section of a pre-1993 Harley Davidson 12 engine having a breather hose which is conne~ted from the crankcase to the air-13 cleaner. The figure further illustrates both pistons being simultaneously positioned at 14 top dead center of their stroke;
Figure 2 is a flow d;ag,d", of the oil flow, the oil pumps and the crankcase 16 venting system of the engine of Fig. 1;
17 Figure 3 is a cross section of the prerer,~d valve of the present invention;

18 Figure 4 is a chart illustrating the horsepower and torque output versus 19 engine rpm for a pre-1993 Harley engine, with and without the apparalus of Fig. 3 installed; and 21 Figure 5 is a chart illustrating the horsepower and torque output versus 22 engine rpm for a post-1993 Harley engine, with and without the apparatus of Fig. 3 23 installed.

CA 022l4740 l997-09-0~

DESCRIPTION OF THE PREFERRED EMBODIMENT

3 Having rererence to Fig. 1, a Harley Davidson ("Harley") engine 1 has two 4 cylinders 2. Pistons 3 are connected to a crankshaft 4 with connecting rods 5. Both pistons 3 stroke upwardly together and stroke downwardly together within the cylinders 6 2. The movement of the pistons 3 is counterbalanced with two large crankshaft-7 mounted flywheels 6.
8 The crankshaft 4, flywheel 6 and conne~;ting rods 5 are housed in ag uankcase 7. The uankcase 7 forms a chal"ber 8 which is contiguous with bores 9 of 10 cylinders 2. On the downstroke, both pistons 3 simultaneously move downward in cylinders 2, reducing the volume of the crankcase chahlber 8 and raising its pressure to 12 above al",ospheric ("positive pressure"). On the upstroke, an incraasing amount of the 13 cylinder's bore 9 is exposed. This action increases the volume of the crankcase 14 char,lber 8, dec~mpressing uankcase gases and reducing the uankcase pressure to 15 below dl"lospl,eric pressure (I'negali~/e'' pressure).
16 Port 10 is formed (via an oil pump housing ~li~clQsed below) in the17 crankcase 7. In conventional use, port 10 has a brealller hose 11 connected for 18 directing positive crankcase gases to an air cleaner 12 (Fig. 2).
19 Having rerere,lce to Fig. 2, the oil system is illusllaled fancifully in a flow 20 diagram format. An oil pump housing 13 is shown in a detached view from its normal 21 atlachment to the crankcase 7. A pair of gear pumps reside within the oil pump housing 22 13; a scavenger pump and a feed pump (not shown). The two pumps have oil flow23 systems which are maintained sepal dle from each other. The scavenger pump receives CA 022l4740 l997-09-0~

oil directly from the bottom of the crankcase 7 routes it via hose 14 to an oil filter (not 2 shown) and delivers it via hose 15 into an oil tank 16. Oil in tank 16 gravity flows 3 through hose 17 as feed to the feed pump. The feed pump delivers oil through the 4 crankcase to the engine components. Baffles within the crankcase separale returning oil mist from crankcase gases and the oil drains to the scavenging pump for completion 6 of the oil system cycle.
7 As stated above port 10 is conne~Led to the air cleaner 12 via breather 8 hose 11. The crankcase 7 is also vented through the oil pump housing 13 to the chain g oiler 19 and to the oil tank 16 via hose 18. Thus as the pressure changes in the 10 crankcase 7 so does the pressure in the oil tank 16.
11 For implementing the present invention a novel valve 22 (Fig. 2) is12 inserted into breather hose 11.
13 Having reference to Fig. 3 valve 22 is depicted in cross section. The 14 valve comprises an inlet housing 23 and an outlet housing 24. The inlet and outlet 15 housings 23 24 have co",~ cme,llaly mating ends 25 and 26 respe~Li~ely. Mating end 16 25 has an exter"al circu"~erer,lial seal recess 27 bearing an O-ring 18. Outlet mating 17 end 26 has an internal recess 28. When mated exter"al O-ring 28 engages internal 18 recess 29 holding the two housings 23 24 together. Outlet housing 24 is cylindrical in 19 form having a cavity at its mating end 26 which forms chamber 30 when mated with the 20 inlet housing 23. O-ring 28 seals chamber 30 from the aL" ~osphere.

CA 022l4740 l997-09-0~

Inlet housing 23 has an inlet nozle 31 opposite the mating end 25. A
2 first p~ss~geway 32 is formed which extends through the inlet housing 23 from the inlet 3 nozle 31 to the mating end 25. At mating end 25 the first p~.ssage,~vay 32 divides into 4 a plurality of ports 33 distributed circu",rer~i,lially about a central boss 34. The central boss 34 has a central opening 35. Within char"ber 30 an elasloi"eric valve head 36 is 6 located comprising an umbrella-shaped seal or "umbrella" 37 with a central and integral 7 tang 38. The tang 38 fits into the boss's central opening 35 for securing the valve head 8 thereto. A seal seat 39 extends circu",rerer,lially about the p~ssageway ports 33. The g height of boss 34 and the construction of valve head tang 38 cooperale to space the 10 sealing periphery of umbrella 37 from seal seat 39 forming a gap G.
1 The outlet housing 24 has an outlet nozle 40 opposile its mating end 26.
12 A second p~ss~geway 41 is formed which exte"ds through the outlet housing 34 from 13 the nozle 40 to ~a",ber 30.
14 In operation valve 22 permits three gas flow modes through port 10: gas flowing vigorously out of the crankcase 7; a small flow of gas into the crankcase; and no 16 gas flow into or out of the crankcase.
17 In greater detail in the first mode upon the downstroke of the pistons 3 18 positive pressure is formed and forces crankcase gas out of crankcase port 10 and 19 along the breather hose 11. The gases enter the inlet nozle 31 of the valve 22 and are routed through the first p~ss~geway 32 to ports 33. The gases flow through the gap 21 G. At high pressures and flows the elastomeric umbrella 37 flexes even further away 22 from the seal seat 39 permitting increased flow therelhruugh.

CA 022l4740 l997-09-0~

In the second mode, while the pistons 3 stroke upwardly, the pressure in 2 the crankcase 7 diminishes from its previous positive pressure. Upon the crankcase 3 pressure becoming negative, the flow of crankcase gases through the breather hose 11 4 reverses and begin to flow into the crankcase 7. Gas flows into the outlet nozle 40 of the valve 22, is routed through the second p~ssage,lvay 41 and flows on into clla"lber 6 30. At low flows, the gases flow around umbrella 37 and through gap G.
7 In the third mode, as the pistons 3 continue to stroke upwardly, the 8 differential pressure between allnosphere and the negative pressure in the crankcase 7 g becor,les so great that the umbrella 37 flexes to seal against the seal seat 39, blocking further flow Ll ,er~ll ,rough.
11 Tests of the novel valve 22 were pe,ror"led on a Harley Davidson 12 "lolor~;ycle engine as illusl,aled in the following exa,n~'Es.
13 In each case, an engine was setup on a dy~a~lor"eter ("dyno"). The dyno 14 was equipped to measure horsepower (HP) and torque (ft-lbs). Pressure 9~l Iges were 15 fitted to the crankcase and oil tank to measure peak positive and negative pressures. In 16 Example 1, convel,Lional engine a"dngel,lenLs and conventional one-way valves were 17 tested as a baseline. In Example 2, testing was pelrorl,led on a pre-1993 crankcase-18 breathing engine, and in Example 3 testing was performed on a post-1993, rocker 19 housing breathing engine.

CA 022l4740 l997-09-0~

E)~AMPLE 1 2 Early testing involved use of a conventional, one-way umbrella valve of 3 the prior art. The prior art valve was inserted into the breather hose 11 of a pre-1993 4 Harley engine. This prior art valve did not permit any flow back into the crankcase 7 under negative pressure conditions. The results indicated little change in the engine 6 pe,roi"~a"ce through to 4000 rpm but at higher speeds there was a decrease in7 pelrUIII ,ance.
8 Further, at engines speeds of 1000 - 1500 rpm, pressure in the oil tank

9 16, normally being positive at about 0 to 2 in. Hg (all pressures are gauge pressure) dropped to a negative pressure of 1 to 4 in. Hg (vacuum), risking loss of oil pump prime and resultant engine failure. It becar"e clear that application of the conventional one-12 way valve technology was not apprupriate when applied to the peculiar chara~leristics 13 of Harley engines.
14 Prior to conducting Exalllp!es 2 and 3 which follow, the sig,1iricance of the 15 spacing of the umbrella 37 from the seal seat 39 was investigated. Valve 22 was 16 manufactured in accordal1ce with the pr~fe"ed embodiment. Inlet and outlet housings 17 23,24 were manufactured having an assembled cylindrical diameter of about 1.5 inches 18 and a length of 1.5 inches. Inlet and outlet nozles 31,40, each a further % inches long, 19 had inlet and outlet p~ss~ges 32,41 having an inside diameter of 5/16 inches. A one 20 inch diametervalve head 37, formed of nitrile, and having a 1/32 inch thick umbrella 37 21 was installed. The umbrella 37 is available from James Gaskets of Medesto, CA, Part 22 No. 26856-89.

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Six 3/16 inch cliar"eter holes were drilled at about 45 o angle to the inlet 2 p~ss~geway 31, forming an array of ports 33 on the inlet housing's mating end 25. All 3 ports 33 lay within the circ~""rerence of the umbrella 37 so that they could be sealed by 4 the umbrella.
To properly set the gap G between the umbrella 37 and the seal seat 39, 6 shims were successively applied between the umbrella tang 38 and the center boss 34 7 and the pe~rur",a"ce of the engine was re-tested.
8 Given the flexibility and the particular thickness of the given nitrile g umbrella from James Gaskets, an optimal gap was G determined to be 0.030 inches

10 with a maximum of about 0.045 inches. Beyond the ",~imal gap spac;ng, valve 22

11 permitted too much flow into the crankcase 7 to permit formation of a negative pressure.

12 Accordingly, for Examples 2 and 3 below, a valve 22 was provided in13 accorda"ce with the prere"ed embodiment, particularly using the above-desc,ibed 14 nitrile umbrella 37 having a 0.030 inch spac;ng, as desc, il.ed above.

16 E)(AMPLE 2 17 A pre-1993 Harley engine was tested on the dyno. Two a"d,lge",enls 18 were run: firstly using the conventional Harley or stock arrangement using a breather 19 hose connected directly to the air cleaner; and secondly, using the novel valve 22 of the 20 present invention, installed within the breather hose 11.

CA 022l4740 l997-09-0~

Rerer,i"g to Fig. 4, lines A and B illustrate the horsepower and torque 2 pe, rurll ,ance, respectively, of the first, conventional engine ar,angement. Lines C and D
3 represent the respective horsepower and torque for the second arrangement 4 imple",enli"g the prese"l invention.
Reflecting on the horsepower results at 4000 rpm, line C represents a 9 %
6 increase in HP due to the addition of the novel valve. Further, increased power was 7 obta;ned throughout the entire engine speed range up to 5000 rpm, the maximum safe 8 operali,lg speed for the engine. Cor~espol ,d;ng increases were achieved in the torque.
g Through observations made through clear tubing, and using the novel10 valve, oil pump prime was not corllprc""ised, despite oil tank pressures which measured from 0.5 to 2 in. Hg vacuum.
12 Using the conventional breathing a"angel"ent, without a valve, pressures

13 measured in the crankcase ranged from 5 to 6 in. Hg positive pressure (piston14 downstroke) and 5 to 6 in. Hg negative pressure (piston upstroke). Upon installing the 15 novel valve, the pressures ranged from 2.5 to 3 in. Hg positive pressure and 7.5 to 8 in.
16 Hg negative pressure.
17 Further, crankcase oil seal leakage was virtually eliminated.

A post-1993 engine was tested on the dyno. Again, two arrangements 21 were run: firstly using the conventional arrangement using solely a breather hose; and 22 secondly, using the novel valve of the present invention.

CA 022l4740 l997-09-0~

Referring to Fig. 5 lines E and F illustrate the horsepower and torque 2 pe, rur" ,ance respectively of the first convel ,lional engine arrangement. Lines G and H
3 represent the respective horsepower and torque for the second anc"gel"ent 4 implementing the presel ll invention.
Rerlec~ing on the hGr.~epower results smaller yet measurable gains were 6 oblained in horsepu~lver (about 5 %) at the lower end. Pel ror" ,ance beca" ,e 7 substantially the same at engines speeds approaci,ing 4000 rpm. Torque was also 8 improved at the 3000 to 4000 rpm range; in the order of 5 %. It is hypothesized that the g lesser improvement is due in part to the pre-e,~islence of a conventional one-way valve and bypass bleed hole. The slight improvement in pelror",ance using the novel valve 11 can be attributed to better pressure managen,e"l than could be achieved with the one-12 way valve and bleed hole.
13 ' Various modifications are apparel,L to those skilled in the art. For

14 inslance variances in the materials of manufacture of the valve head will clearly affect

15 the gap used. Further use of a reed-type valve spaced above a seal seat and being

16 e"closed within a housing can be seen to provide an equivalent valve in these

17 ill~lanCeS.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A crankcase ventilation system for an internal combustion engine having a crankcase defining a volume containing gases and having two or more cylinders extending from the crankcase, the bores of the cylinders being contiguous with the crankcase, the cylinders having two or more pistons movable therein, the system comprising:
pistons which move simultaneously inwardly and simultaneously outwardly from the crankcase during one piston cycle of normal engine operation, so that when moving inwardly, the volume of crankcase is caused to decrease with a resulting increase in pressure, and when moving outwardly, the volume of the crankcase is increased with a resulting decrease in pressure;
a breather hose having one end connected to the crankcase for flowing gases between the crankcase and atmosphere; and valve means located within the breather hose, said valve means being operative between three modes during one piston cycle, firstly to release buildup of pressure in the crankcase which becomes positive, being pressure greater than atmospheric, by flowing gas out of the crankcase, through the breather hose and through the valve means, secondly to permit a small amount of gas to flow into the crankcase through the breather hose and valve means as the pressure in the crankcase changes from positive to negative and thirdly to block further ingress of gas into the crankcase as the pressure continues to become more negative so that pressure in the crankcase becomes negative.

2. The crankcase ventilation system as recited in claim 1 wherein the valve means comprise:
a housing having a passageway formed therethrough, said passageway having a inlet end and an outlet end;
a valve chamber formed in the passageway intermediate the inlet and outlet ends said valve chamber having a inlet port which communicates with the inlet end and a outlet port communicating with the outlet end;
a valve seat formed at the inlet port; and a resilient member which is spaced above the valve seat to form a gap and being operable between the three modes as follows, in the first mode, gas flows from the inlet end and past the resilient member to the outlet end, in the second mode, a small amount of gas flows from the outlet end, through the gap and to the inlet end, and in the third mode, the flow of gas from the second mode causing the resilient member to flex and seal against the valve seat, preventing any further flow of gas from the outlet end to the inlet end.

3. The crankcase ventilation system as recited in claim 2, wherein the member is a resilient umbrella-shaped disk.

4. The crankcase ventilation system as recited in claim 3, wherein the member is manufactured of nitrile.

5. The crankcase ventilation system as recited in claim 4, wherein the gap between the nitrile member and the valve seat is in the range of 0.030 and 0.045 inches.

6. The crankcase ventilation system as recited in claim 2, wherein the valve seat comprises a center boss having a central bore with an array of holes distributed therearound, the holes communicating with the inlet end of the passageway and forming the inlet port, the resilient member comprising a mushroom-shaped disk having a center stem, the center stem being fitted into the bore of the center boss so that the disk covers the array of holes, and the boss and stem cooperating to suspend the disk above the holes so as to form a gap between the valve seat and the disk through which gas can flow.

7. The crankcase ventilation system as recited in claim 2, wherein the member is a resilient reed-like strip.

8. The crankcase ventilation system as recited in claim 4 or 7 wherein the valve seat comprises a circular array of holes communicating with the inlet end of the passageway and forming the inlet port, the area circumscribed by the ports being smaller than the resilient member.

9. The crankcase ventilation system as recited in claims 3, 6 or 7 wherein the engine is a Harley Davidson motorcycle engine.

10. A crankcase breather valve for an internal combustion engine having a crankcase defining a volume containing gases and having two or more cylinders extending from the crankcase, the bores of the cylinders being contiguous with the crankcase, the cylinders having two or more pistons movable therein, the pistons moving simultaneously inwardly and simultaneously outwardly from the crankcase during one piston cycle of normal engine operation, so that when moving inwardly, the volume of crankcase is caused to decrease with a resulting increase in pressure, and when moving outwardly, the volume of the crankcase is increased with a resulting decrease in pressure, and a breather hose having one end connected to the crankcase for flowing gases between the crankcase and atmosphere, the breather valve being inserted into the breather hose, comprising:
a housing having a passageway formed therethrough, said passageway having a inlet end connected to the breather hose leading from the crankcase and having an outlet end;
a valve chamber formed in the passageway intermediate the inlet and outlet ends, said valve chamber having a inlet port which communicates with the inlet end and a outlet port communicating with the outlet end;
a valve seat formed at the inlet port; and a resilient member which is spaced above the valve seat to form a gap and being operable between the three modes as follows, in the first mode, gas flows from the inlet end and past the resilient member to the outlet end, in the second mode, a small amount of gas flows from the outlet end, through the gap and to the inlet end, and in the third mode, the flow of gas from the second mode causing the resilient member to flex and seal against the valve seat, preventing any further flow of gas from the outlet end to the inlet end.

11. The crankcase ventilation system as recited in claim 10 wherein the member is a resilient umbrella-shaped disk.

12. The crankcase ventilation system as recited in claim 11, wherein the member is manufactured of nitrile.

13. The crankcase ventilation system as recited in claim 12 wherein the gap between the nitrile member and the valve seat is in the range of 0.030 and 0.045 inches.

14. The crankcase ventilation system as recited in claim 13 wherein the engine is a Harley Davidson motorcycle engine.