Oil Separator for Crankcase Fumes

With the growing concern over air pollution, it has become imperative that crankcase fumes, generated during the normal operation of an internal combustion engine, not be vented into the atmosphere. Numerous crankcase ventilation systems have been developed which recirculate such fumes into the fuel-air intake of an engine. However, with the the high efficiency engines of today a serious problem is created when the recirculated fumes contain an excessive quantity of oil vapors or mist. The delicate fuel-air balance can be upset and improper combustion can occur with all of its attendent problems. Prior art oil separators for crankcase fumes have been used with only limited success. The problem appears to reside in achieving an acceptable balance between a separator's capability of separating oil vapors and mist from the crankcase fumes and its capability to return the separated oil to the engine from the separator. Accordingly, it is a general object of this invention to produce an oil separator which effectively separates an acceptable amount of oil from the crankcase fumes and has an enhanced capability of effectively making the collected oil available to the engine crankcase.

Generally speaking, this invention relates to an oil separator device for removing a substantial portion of the oil contained in the crankcase fumes of an internal combustion engine while the engine is in operation. The device is designed to be incorporated into the crankcase ventilation system as a component thereof. Preferably, it is mounted on the inside of a rocker arm cover of the engine. A plurality of superposed spaced apart internal baffle plate members direct a laminar flow of crankcase fumes through the separator canister along a continuous-fold type path from an inlet in the bottom of the canister to an outlet in the top. Partially isolated channels extend along opposite edges of the flow path. Oil in the fumes attaches itself to the internal surfaces of the separator and flows down these surfaces, which in their normal attitude are inclined towards a single drain corner, to a sump in the bottom of the separator. A tubular assembly connected to the bottom of the separator provides a fume inlet passageway and a parallel oil return passageway. The distal end of this tubular assembly is cut off at an acute angle which gives it a configuration that restricts the entry and upward flow of crankcase fumes into or through the oil return passageway, and enhances the collection and downward return flow of separated oil therein. This angular configuration provides a larger entrance opening than that provided by a square cut end. As a result of this increased peripheral length, the incoming fume flow velocity over the peripheral edge of the inlet is reduced. The reduced velocity enables return oil droplets, which form on the end of the assembly, to drop away without being reintroduced into the fume stream inlet particularly when the oil return passageway is located on the side of the tubular assembly which coincides with the tip of the cutoff end.

The advantages and features of the oil separator of this invention will be understood best if the detailed description is read with reference to the accompanying drawings.

FIG. 1 is a sectional side view of a preferred embodiment of the oil separator of this invention,

FIG. 2 is a sectional view taken along lines 2--2 of FIG. 3,

FIG. 3 is a sectional view taken along lines 3--3 of FIG. 1,

FIG. 4 is a sectional view of the tube assembly taken along lines 4--4 of FIG. 1,

FIG. 5 is a bottom view of the oil separator,

FIG. 6 is an enlarged fragmented view taken from an end of the oil separator showing cross sectional details of the foot sections,

FIGS. 7 A,B,C and D are plan views of the respective baffle plate members from top to bottom,

FIG. 8 is an exploded fragmented view in perspective of the interior elements of the drain corner of the oil separator, and

FIG. 9 is a perspective view of the bulkhead partition.

Referring to the drawings it will be noted that the above mentioned oil separator device 20 is comprised basically of a canister 22, a plurality of superposed equally spaced baffle plate members 24a, 24b, 24c, 24d positioned inside the canister and a tubular assembly 30 affixed centrally in the bottom of the canister. The tubular assembly defines a fume inlet passageway 32 and a separated oil return passageway 34.

Canister 22 has a generally rectangular boxlike shape formed by a pan member 36 and a top or cover member 38. Pan member 36 has upright side walls 40, 42, upright end walls 44, 46 and a boat shaped bottom 48. It may also have mounting or stabilizing flanges 50, 52 extending laterally outward from the top edges of the end walls. The aft portion of the bottom, that is the portion on the left of FIG. 5 which extends slightly to the right of center, is comprised of three rectangular panels 54, 56, 58 arranged side-by-side with the panels 54, 58 on opposite sides of the central panel 56 being angled upwardly therefrom. The forward portion of the bottom has an upwardly inclined truncated triangular central panel 60 with a pair of generally triangular side panels 62, 64 continuing respectively in the same planes as those of the aft side panels 54, 58. The primary objective of this bottom configuration is to provide surfaces which are sloped towards the inlet of the oil return passageway 34 when the canister is mounted in its normally tilted attitude inside a rocker arm cover of an automotive engine.

Canister cover member 38 has a generally flat top panel with side 66, 68 and end 70, 72 walls depending from its periphery. It also has an annular dome 74 surrounding a fume outlet means or collared aperture 75 in its center. The cover 38 is flush mounted on the inside of the top portion of the pan and sealed in place. Side walls 66, 68 extend deeper into the pan than the cover end walls and engage the edge of the top baffle 24a to forcibly hold the stack of baffle plate members together.

The baffle members 24a, 24b, 24c, 24d, corresponding respectively to the baffles shown in FIGS. 7a, 7b, 7c, 7d, are essentially alike in many respects so similar numbers are used to desiginate similar parts. They all have matching generally rectangular peripheral shapes and are preferably made from flat sheet material of uniform thickness. Each baffle plate member is comprised of three narrow rectangular flat panel sections 76, 78, 80 arranged side-by-side with the two side or wing panels 76, 80 being inclined upwardly relative to the central panel 78. Each baffle plate member also has "L" shaped step sections 82, 84 extending respectively along the outer longitudinal edge or side of each wing panel 76, 80 and depending therefrom. The riser 86 and tread 88 portions of the "L" shaped step sections in combination with the adjoining sidewall surfaces of the pan member define side channels 90, 92. The ends of the step sections are offset downwardly and inwardly to provide a foot 94, 96, 98, 100 adjacent to each of the four corners, respectively, of each baffle plate member for supporting the baffle plate members in a stacked relationship as illustrated in the drawings. The inward displacement is sufficient to allow the inside corner edge of each foot to rest on the top corner of the step below it (see FIG. 6). The downward displacement of each foot raises the intermediate portions of the steps and produces a narrow gap or slot aperture between these portions of the superposed steps, i.e. the bottom corner of this portion of each step is about 0.030 of an inch above the top corner of the step below it and the slot length is about 4 inches. Preferably the length-to-width ratio of the slot aperture is between 100:1 and 200:1. The narrowness of the slot aperture serves to partially isolate the side channels 90, 92 from the main stream of fluids flowing through the central portion of the oil separating baffle means and thus these side channels are denoted quiescent zone channels. Each of the three separating baffle plate members 24a, 24b, 24c has a mainstream fume flow path orifice 102 extending crosswise at one end thereof. However, the orifices 102 are on alternate ends of succeeding baffle plate members in the series. This produces the continuous-fold type flow pattern through the separating means.

The lower baffle member 24d in the superposed stack of baffle members cooperates with the bottom portion of the pan member to define the oil separator sump 104. The only access to the sump from above is through an opening formed by a single cutaway corner 106 of the lower baffle. A vertically disposed passageway, denoted the drainback passageway 108, is produced by this opening and the corresponding cutaway corners 106 of the other three baffles. It is located at the lowest corner of the separator when the separator is oriented in its normally inclined attitude in the engine. A drain dam 110 blocks the flow of fluid between the drain passageway and the flow path passegeways, defined by the baffle plate members, except for the flow of fluid between the drain passageway and some of the quiescent channels, specifically the uppermost three quiescent channels (as shown in FIGS. 2 and 8). This dam comprises a flat main section 112 which extends laterally inward from the quiescent channel risers 86 along the facing edges of the cutaway corners 106 of the baffles in tight contact therewith to a laterally disposed flat wing section 114 extending directly to the adjacent end wall 46 of the pan member at right angles thereto. Wing section 114 is located in a position which is equivalent to the adjoining end of a flow path orifice 102. Hanger flaps 116, 118 at the top of each dam section extend over the corner of baffle plate member 24a and are affixed thereto to support the dam member in position. A tab section 120 at a lower corner of the main section 112 covers the end of the bottom quiescent channel. A "D" shaped inlet aperture 122, which in turn has an extruded collar 124 of corresponding shape depending from its periphery, is located in the center of lower baffle member 24d.

In addition to the flow path orifices 102 and the drain passageway corner cutaways 106, the separating baffle plate members 24a, 24b, 24c have shunt apertures of relatively smaller size which allow portions of the crankcase fumes to bypass the mainstream flow path through the separator (see FIG. 7). For example, each of these baffle plate members has a small semicircular cutout 126 in the edge of its foot section 94 adjacent to the corner diametrically opposite from the drain passageway corner. They also have a pair of cutaway corner shunt apertures 128, 130 at opposite corners in the same end. At the other end in the corner opposite from the drain passageway, the upper two baffle plate members 24a, 24b also have an additional cutaway corner shunt aperture 131.

The aforementioned tubular assembly 30 is comprised of an inner tube member 132, defining the crankcase fumes inlet passageway 32, fitted inside of and projecting beyond both ends of a cylindrical outer tube member 136. The ends of the tube members adjacent to the pan member, referred to herein as the upper ends, are square cut whereas their opposite or lower ends are cut on an angle, preferably less than 45 degrees, for example, at an angle of thirty degrees from their tubular axes. Inner tube member 132 has two offset parallel flat side sections 138, 140 disposed end to end and extending along a common side over the full length of the tube member. The internal cross sectional size and shape of the upper end of this inner tube member matches the external size and shape of the "D" shaped collar 124 around which it is fitted and sealed. The flat side of this "D" shaped collar faces the end of the separator which contains the drainback passageway 108. This arrangement serves to orient the tube assembly rotationally so that the oil return passageway of the tubular assembly also faces that end.

The outer surfaces of flat side sections 138, 140 cooperate with the confronting arcuate inside surface of the outer tube member to define corresponding first and second portions of the oil return passageway 34. Because flat section 140, defining the second or lower portion of the passageway, is offset laterally outward from flat section 138, towards the surrounding cylindrical outer tube member, the axial length and cross sectional area of the second portion of the oil return passageway is less than that of the first portion. It is to be noted also that the lower tip of flat section 140 projects below the adjoining tip of the outer member.

The illustrated geometric shape of the oil return passageway, particularly the cross sectional shape of both the upper and lower passageway portions as well as that of the restricted oil return outlet orifice 142 at the bottom end of the second portion, is believed to impede the flow of crankcase fumes upwardly into and through the oil return passageway and also promote the downward return flow of the separated oil out of the device. The upper end of the outer tube member is fitted inside of and sealed to an extruded annular collar protruding from the bottom of the pan member 36.

The angular cut on the lower end of the inlet tube member provides an oblong or elliptical opening. This angular cut is significant in two respects. First of all, it provides a point on the periphery of the opening that is lower than any other point thereof and secondly, it increases the length of the periphery over that of a square cut tube thus reducing the flow velocity of the fume at the edge of the opening particularly at the outermost or lower point of the opening. It should be noted that this lowest end of the inlet tube corresponds to the lowest point on the similarly but slightly greater angled outer tube.

A bulkhead partition 144 is erected adjacent to the midsection of the separator, in the space between the bottom baffle 24d and the next baffle 24c above it in the stack, to block the flow of incoming crankcase fumes from flowing into the primary drainback end of the separator and to direct them towards the opposite end of the separator, i.e., towards the end of baffle 24c having the fume flow path notch 102 (on the left end of FIGS. 1 and 2). It also acts as a curb to direct any separated oil that accumulates on the surface of that end of baffle 24d into the flat or lower velocity side of the fume inlet tube. The bulkhead partition 144 (see FIG. 9) has an angular mounting flange 146 for attaching it to the bottom baffle 24d, such as by brazing, an angular upright blocking flange 148 shaped so as to close the primary space between the the aforementioned two baffles and a pair of depending tabs 150 to close off the side channels.

While the improved oil separator of this invention has been described with respect to a single illustrated embodiment, it is to be understood that various modifications may be made without departing from the scope of the invention which is defined primarily by the appended claims.