US 2984410 A
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May 16, 1961 D. GIACOSA 2,984,410 CENTRIFUGAL FILTER, MORE PARTICULARLY FOR THE LUBRICATING OIL OF INTERNAL COMBUSTION ENGINES Filed May 19, 1958 Fig. 7
United States Patent CENTRIFUGAL FILTER, MORE PARTICULARLY FOR THE LUBRICATING OIL OF INTERNAL 5 COMBUSTION ENGINES Dante Giacosa, Turin, Italy, assignor to Fiat Societa per Azioni, Turin, Italy This invention relates to a centnfugal filter, more particularly for cleaning lubricating oil of internal combustion engines, of the type comprising a hollow rotor ribbed inside and provided with an inner dish-shaped partition for subdividing the rotor hollow into a chamber for centrifugal oil flow and a chamber for centripetal oil flow interconnected at their peripheries, the oil filter moreover comprising supply conduits for the oil to be cleaned to the centrifugal flow chamber and outlet conduits for the oil from the centripetal flow chamber.
In oil filters of this type the blading adapted to impart a rotational movement to the oil supplied to the filter mostly fills the portion adjacent the outer periphery of one or both chambers only.
Applicants ascertained that oil flowing through a filter of the above construction undergoes a substantial drop in pressure which research work made explains for the following reason. The oil flowing centripetally in a radial direction into the centripetal flow chamber takes, as it leaves the bladed region an angular velocity exceeding the angular velocity of the filter through the well known principle of the preservation of momentum (referred to in the present application as rotary motion).
While the centrifugal pressures in the bladed outer annular regions of the centrifugal and centripetal chambers are mutually balanced, the centrifugal pressure set up by the higher peripheral velocity at the middle nonbladed region of the centripetal chamber is not balanced and gives therefore rise to the abovementioned pressure drop.
This invention provides a centrifugal cleaner of the type referred to above which substantially avoids the abovementioned drawback.
The improved centrifugal filter distinguishes by the fact that the blades of the centripetal chamber substantially extend to a region axially facing the opening of the outlet conduits.
Further characteristic features of this invention will be understood from the appended detailed description referring to the accompanying drawings, given by way of example only, wherein:
Figure l is an axial sectional view of the improved filter, and
Figure 2 is a part view of the forward filter portion looking from the inside.
The centrifugal filter shown in the drawings has the form of a flat drum fastened on the extension 3a of a hollow shaft 3 such as the crank-shaft of an internal combusition engine. The drum comprises two components one of which is a cup-shaped element 2 having a tubular sleeve 6 fitting over the end of the shaft 3 and prevented from rotating with respect to said extension and shaft by means of a key 30. The other component of the drum is a dish-shaped cover 1 secured to said cup-shaped element 2 by means of screws 4, and defining together with the element 2 a substantially cylindrical space. The end of the tubular sleeve 6 bears on the adjacent side of a sprocket chain wheel 31, keyed to the extension 3a of the shaft 3 and the other side of the wheel 31 bears through the interposition of a washer 32 rotatable with the shaft 3 and of a pair of rings 33 and 34, which are stationary and L shaped in cross-section, on the annular front face 3b of the first journal 3c of the crank-shaft. This journal is rotatably mounted in a bearing 35 mounted in turn in a flanged support 29 which is fixed to the crank case 36 by means of screws 37.
Inside of the filter is arranged a dished baffle or annular partition 5, the inner periphery of which is pressed between the hub 2b of the cup shaped element 2 and a flange 9a of an axially bored plug 9 screwed within the inner hole of the extension 3a of the hollow shaft 3. The outer periphery of the extension 312 has provided therein axial ducts or grooves 38 which communicate at one end with the inside of the filter through openings 2c provided in the hub 2b and at the other end with an annular chamber 39 formed between the stationary rings 33 and 34. The chamber 39 communicates in turn through a bore 40 provided in the flanged support 29 and a bore 41 provided in the crank-case 36 with a duct 42 leading to a pump (not shown) feeding oil under pressure. The bored plug 9 projects inside the filter but its free end is spaced from the central portion of the bottom of the dish-shaped cover I, whereby the inner bore 7 of the plug 9 communicates with the inside of the filter and connects it with the hole 3d of the shaft 3.
The bafile 5 subdivides the inside of the filter into two chambers, one of which, denoted by 43, is comprised between the bafile 5 and the bottom of the element 2 and communicates with the axial ducts 38 provided on the extension 3a of the shaft 3 and therefore with the pump feeding oil under pressure, and the other denoted by 44 communicates with the bore 7 and therefore with the hole 3d in the shaft 3. Said chambers communicate further with each other through the annular clearance left between the outer edge of the baffle 5 and the inner peripheral wall of the filter.
The chamber 43 and the outer peripheral portion of the chamber 44 are subdivided into radially extending sectors by means of radial blades 1a and 2a carried by the cover 1 and the element 2, respectively.
The structure heretofore described and its operation are the same as just disclosed in our co-pending U.S.P. application Ser. No. 663,632 filed June 5, 1957, now Patent No. 2,908,352.
The central portion of the bottom of the cover 1 has a diametrically extending blading 8. In the example shown said blading has the form of a ridge provided at the bottom of the cover 1 and axially projecting towards the free end of the plug 9, so as to subdivide the central part of the chamber 44 into two equal parts and to leave but a small clearance between its edge and the plug itself.
Where the bore in the plug is not coaxial with the axis of the extension 3a of the shaft carrying the filter, but is replaced by a number of eccentrically arranged bores, the blade or ridge 8 need not reach the axis of the filter and may be interrupted immediately after having faced said eccentric bores.
In operation the crankshaft 3 of the engine rotates the filter 1, 2 and simultaneously the sprocket 31 and the washer 32. Inasmuch as the oil feeding pump is actuated, oil under pressure flows through the duct 42, the bores 41 and 40, the annular chamber 39 formed between the rings 33 and 34, the ducts 38 at the outer periphery of the extension 3a of the shaft 3 and the openings 2c, and reaches the chamber 43. Here it enters the spaces between the blades 2a and is rotated at the same rotational speed as the filter and is subjected to the action of a centrifugal force which causes it to flow towards the outer periphery of the filter. Therefore, chamber 43 is called centrifugal oil flow chamber or simply centrifugal chamber.
During the flow through the centrifugal chamber separation of the impurities suspended in the oil occurs and the separated particles are deposited on the inner peripheral wall of the filter. Then the oil overflows the outer edge of the baffie 5 and reaches the chamber 44 entering the spaces between the blades 1a and rotates still at an angular speed substantially equal to that of the filter and of the shaft 3. However, the flow of the oil is now directed towards the axis of the shaft 3 and the chamber is therefore called centripetal oil fiow chamber or simply centripetal chamber. In this chamber the separation of impurities still occurs and the oil leaving the spaces between the blades 1a reaches the zone of said chamber arranged near the axis of the shaft 3, where it enters the bore 7 in the plug 9, then the inner hole 3d of the shaft 3 for flowing to the main bearings of the shaft and for lubricating other engine parts subjected to wear.
The provision of the blade 8 arranged at the zone of the centripetal chamber at which the oil leaves the filter avoids any drop in pressure of the oil, inasmuch as oil is prevented at this zone from acquiring an angular speed exceeding that at which the filter and shaft 3 rotate. This results in a more efficient lubrication of the engine parts which require oil under pressure lubrication, without unduly enlarging the cross section of the ducts through which the oil flows or raising the delivery pressure of the pump feeding the oil to the filtering system.
Of course, it will be understood that within the principle of the invention embodiments and constructional details can be widely varied from the example described and shown without departing from the scope of this in vention.
What I claim is:
1. An improved centrifugal oil filter for cleaning the lubricating oil used in internal combustion engines, said filter comprising a hollow rotor having an axis of rotation, means for attaching said rotor to a drive shaft for rotation about its axis of rotation, a dish-shaped partition axially mounted in said rotor for dividing the rotor interior into a centrifugal flow chamber and a centripetal fiow chamber, said chambers interconnecting at their outer peripheries, means defining conduits near the axis of rotation for supplying oil under pressure to be cleaned to the centrifugal flow chamber, means defining an outlet conduit coincident with the axis of rotation for the exit of cleaned oil from said centripetal chamber, said centripetal flow chamber having a central wall portion spaced axially from said outlet conduit, blades radially mounted in said centrifugal flow chamber for directing the flow of incoming oil toward the periphery of the rotor and toward the centripetal flow chamber, and blades radially mounted in said centripetal flow chamber, a plurality of said centripetal blades extending from the periphery of said centripetal flow chamber for approximately half the distance to said axis of rotation for guiding the oil inward toward the oil outlet, and one said centripetal blade being disposed on said central wall portion and extending interjacently of two oppositely disposed peripheral blades of said plurality of said centripetalblades and across said axis of rotation to bisect said centripetal chamber in a region axially facing the opening of said outlet conduit, for maintaining the angular velocity of said oil flow equal to that of said filter at said oil outlet conduit, thereby supplying said clean oil at a pressure substantially the same as the entrance pressure of said incoming oil.
2. A centrifugal oil filter according to claim 1, in which said centripetal chamber further comprises an annular partition projecting toward said dish-shaped partition and dividing said centripetal chamber into a central portion in which said one centripetal blade is disposed and an outer annular portion in which said plurality of centripetal blades are disposed.
References Cited in the file of this patent UNITED STATES PATENTS 1,678,272 Rushmore July 24, 1928 1,95 6,496 Degerth Apr. 24, 1956 2,750,107 More June 12, 1956 FOREIGN PATENTS 113,848 Sweden Apr. 17, 1945 224,711 Switzerland Mar. 16, 1943 607,994 France Apr. 10, 1926