Abstract:
An air/oil separator includes a housing having an inlet for aerated oil or hydraulic fluid and outlets for the separated air and oil or fluid. The housing is generally cylindrical and defines an upper, inlet portion, a center, separator portion and a lower collector portion. The upper, inlet portion of the housing includes a first, tangential inlet passageway which merges with a second, spiral or circular passageway. The spiral or circular passageway communicates with the cyclonic separator portion which may be either cylindrical or frusto-conical. A coaxial outlet in the upper, inlet portion allows separated air to return to the engine or transmission housing while an outlet in the lower, collector portion returns oil or hydraulic fluid to the device.

Description:
FIELD 
     The present disclosure relates to an air/oil separator and more particularly to an air/oil separator for use with automatic transmissions and transaxles. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     Dry sump lubrication systems are increasingly popular in both engines and transmissions. In dry sump systems, oil is stored in a sump that, unlike wet sump systems, is separate from the crankshaft and main bearings in an engine and from the gear sets and clutches in a transmission. After use in the engine or transmission, oil is pumped out by scavenger pumps acting through oil pick-ups appropriately placed in the device&#39;s underside and is returned to the main sump for recirculation. Unfortunately, not only is the typical lubrication system not sealed off from the environment but also oil and hydraulic fluids have a marked affinity for air. Consequently, air becomes entrained in the oil or hydraulic fluid. It has also been found that the more effective the scavenger pumps and oil pumps are, the greater the quantity of air entrained in the oil. 
     Since air does not lubricate engine or transmission components, nor does it provide cooling to such components, as effectively as oil, unless the air is removed, even though the requisite volume of oil is seemingly being provided to an engine or transmission to lubricate and cool the components, in fact, the lubrication and cooling will be insufficient. As a consequence, the expected service life of engine and transmission components may not be realized. 
     Clearly there are issues associated with dry sump lubrication systems and the present invention is directed to ameliorating one issue. 
     SUMMARY 
     The present invention provides an air/oil separator for use with engines, transmissions and transaxles. The separator includes a housing having an inlet for aerated oil or hydraulic fluid and outlets for the separated air and oil or fluid. The housing is generally cylindrical and defines an upper, inlet portion, a center, separator portion and a lower collector portion. The upper, inlet portion of the housing includes a first, tangential inlet passageway which merges with a second spiral or circular passageway. The spiral or circular passageway communicates with the cyclonic separator portion which may be either cylindrical or frusto-conical. A coaxial outlet in the upper, inlet portion allows separated air to return to the engine or transmission housing while an outlet in the lower, collector portion returns oil or hydraulic fluid to the device. Such tangential and spiral feed of the aerated oil into the separator portion forms a vortex creating centrifugal forces which cause oil droplets to impact and agglomerate on the walls of the separator. This same process causes the lighter, liberated air to collect in the center of the separator. As the oil is drawn down the walls of the separator by gravity, the air flows out the outlet in the top of the separator. 
     Thus it is an object of the present invention to provide an air/oil separator for an engine, transmission or transaxle. 
     It is a further object of the present invention to provide an air/oil separator for an engine, transmission or transaxle having a dry sump lubrication system. 
     It is a still further object of the present invention to provide an air/oil separator for an engine, transmission or transaxle having a housing defining upper, center and lower portions. 
     It is a still further object of the present invention to provide an air/oil separator for an engine, transmission or transaxle having a housing defining upper inlet, center separator and lower collector portions. 
     It is a still further object of the present invention to provide an air/oil separator for an engine, transmission or transaxle having a housing defining an inlet passageway having tangential and spiral or concentric portions. 
     Further objects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic diagram of an exemplary dry sump transmission incorporating an air/oil separator according to the present invention; 
         FIG. 2  is a perspective view of an air/oil separator according to the present invention; 
         FIG. 3  is a full sectional view of an air/oil separator according to the present invention taken along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a front elevational view of an air/oil separator according to the present invention with portions broken away; and 
         FIG. 5  is a full sectional view of an alternate embodiment of an air/oil separator according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     With reference now to  FIG. 1 , a portion of an exemplary automatic transmission is illustrated and generally designated by the reference number  10 . The automatic transmission  10  includes a housing  12 , an input shaft or member  14 , a dual clutch assembly  16 , a plurality of gear sets or assemblies  18 , a hydraulic system  20  and an output shaft or member  22 . The input shaft  14  is driven either directly by the output of a prime mover such as an internal combustion gas, Diesel engine or a hybrid power plant or through a torque converter (all not illustrated) and drives the dual clutch assembly  16 . The dual clutch assembly  16 , in turn, selectively drives the plurality of gear sets  18 . The dual clutch assembly  16  and the plurality of gear sets  18  cooperate to provide a plurality of forward and reverse speed or gear ratios to the output shaft  22 . The output shaft  22  is coupled to and drives and final drive unit or transfer case (both not illustrated). It should be appreciated that the exemplary automatic transmission  10  may include more or fewer components and may be a different design such as a multiple planetary gear set type and still fall within the broad purview of the present invention. 
     The hydraulic system  20  is operable to collect, de-aerate, pressurize and distribute hydraulic fluid, such as an oil, throughout the automatic transmission  10  in order to provide cooling, lubrication and control to the dual clutch assembly  16  and the plurality of gear sets  18 . The hydraulic system  20  includes a first reservoir  30 , a second reservoir  32 , a third reservoir  34 , a first pump  36 , a second pump  38 , an air/oil separator  40  and a control valve assembly  44 . 
     The first reservoir  30  is a sump or tank for storing at least partially de-aerated hydraulic fluid. The partially de-aerated hydraulic fluid is hydraulic fluid that has been de-aerated to an extent compatible with the hydraulic requirements of the automatic transmission  10 . The first reservoir  30  is located between the second reservoir  32  and the third reservoir  34 . The second reservoir  32  is a sump or tank for collecting at least partially aerated fluid from the plurality of gear sets  18 . Aerated hydraulic fluid is hydraulic fluid having air or other gasses entrained within it to an extent that it is incompatible or undesirable with the hydraulic requirements of the automatic transmission  10 . The second reservoir  32  is separate from the first reservoir  30  and is located near the rear of the automatic transmission  10  proximate the output shaft  22 . The third reservoir  34  is also separate from the first reservoir  30  and the second reservoir  32  and is located near the front of the automatic transmission  10  proximate the dual clutch assembly  16 . 
     The first or main pump  36  may be one of many types such as, for example, a crescent pump, an impeller pump, a gear pump, a gerotor pump or a vane pump, without departing from the scope of the present invention. The inlet of the first or main pump  36  communicates with a first filter  46  disposed within the first reservoir  30  which removes particulates from hydraulic fluid drawn from the first reservoir  30 . The first or main pump  36  provides pressurized hydraulic fluid to the control valve assembly  44 . 
     The second or scavenger pump  38  may also be one of the many types listed above. The inlet of the second or scavenger pump  38  communicates with a second filter  48  disposed within the second reservoir  32  and a third filter  52  disposed within the third reservoir  34  and the outlet of the second or scavenger pump  38  communicates with the air/oil separator  40 . The second filter  48  removes particulates from hydraulic fluid drawn from the second reservoir  32  by the second or scavenger and the third filter  52  removes particulates from hydraulic fluid drawn from the third reservoir  33  by the second or scavenger pump  38 . The second or scavenger pump  38  provides pressurized hydraulic fluid to the air/oil separator  40 . Preferably, the air/oil separator  40  is located in an upper region  54  of the first reservoir  30 . 
     Referring now to  FIGS. 2 and 3 , the air/oil separator  40  includes a complexly configured, multiple piece housing  60 . The housing  60  preferably includes a top or cap portion  62 , an upper body portion  64  and a lower body portion  66  which may be individually molded or formed of a plastic such as ABS or similar material and secured together by adhesives, autogenous bonding or other means such as mechanical fasteners. It will be appreciated, however, that other, comparable physical configurations and assembly techniques are within the purview of this invention. 
     The lower body portion  66  of the housing  60  includes a segmented inlet duct assembly  70  having a first, vertical passageway or portion  72  which receives aerated oil, i.e., an air/oil mix from the second or scavenger pump  38 . The first, vertical portion  72  of the inlet duct assembly  70  communicates with a second, horizontal passageway or portion  74  which, in turn, communicates with a third, vertical passageway or portion  76 . Preferably, the first, second and third portions  72 ,  74  and  76  of the inlet duct assembly  70  define passageways of equal diameter or area. An additional fourth, vertical passageway or portion  78  of the inlet duct assembly  70  is included in the upper body portion  64  of the housing  60 . Preferably, the fourth, vertical passageway or portion  78  defines a slight taper or narrowing in the direction of flow which increases the velocity of flow of the aerated oil through the fourth, vertical portion  78  while lowering its pressure. 
     The fourth, vertical passageway or portion  78  of the inlet duct assembly  70  communicates, at a right angle, with a fifth, tangential passageway or portion  82 . The fifth, tangential passageway or portion  82  extends into the upper body portion  64  of the housing  60  and merges with a sixth, circular or spiral passageway or portion  84 . The sixth, circular or spiral passageway or portion  84  is preferably concentric with the axis of the housing  60  and extends at least about 270° around this axis to impart a swirling or circular motion to the aerated oil. The sixth, circular or spiral passageway or portion  84  terminates in a streamlined outlet  86 . The top or cap portion  62  of the housing  60  closes off the fifth, tangential passageway or portion  82  and the sixth, circular or spiral passageway or portion  84  and includes a preferably circular passageway and opening  88  defined by a cylindrical wall  90  which is concentric with the axis of the housing  60  and communicates with the interior  92  of the housing  60  but not the sixth, circular passageway or portion  84 . 
     Referring now to  FIGS. 3 and 4 , The interior  92  of the housing  60  is defined by an upper cylindrical wall  94  which is formed by the upper body portion  64  and a lower cylindrical wall  96  which is formed by the lower body portion  66 . At the lower region of the interior  92 , the lower cylindrical wall  96  of the housing  60  tapers inwardly and merges with a generally rectangular horizontal outlet duct or passageway  100 . The outlet duct or passageway  100  terminates in an oblique mouth  102 . The lower body portion  66  also preferably includes a pair of opposed, outwardly extending mounting ears or lugs  104  reinforced by pairs of webs or gussets  106 . Each of the mounting ears or lugs  104  includes a through opening  108  which is adapted to receive a fastener (not illustrated) for securing the air/oil separator  40  within the housing  12  of the transmission  10 . 
     Referring now to  FIG. 5 , an alternate embodiment of an air/oil separator is illustrated and generally designated by the reference number  120 . The alternate embodiment air/oil separator  120  is the same in many respects as the air/oil separator  40  and includes the top or cap portion  62  defining the opening  88 , the upper body portion  64  including the fifth, tangential passageway or portion  82 , the sixth, circular or spiral passageway or portion  84  and the cylindrical wall  90  as well as the inlet duct assembly  70 . The air/oil separator  120  includes a different lower body portion  126 . Here, the lower body portion  126  has a significant downward and inward taper such that a lower wall  128  defines a frustum of a cone, i.e., is frusto-conical. The frusto-conical lower wall  128  terminates in a depending lip  130  which is received within and spaced from a cylindrical outer wall  132  which defines an anti-swirl chamber  134 . The anti-swirl chamber  134  has a diameter significantly larger than the smallest diameter of the frusto-conical lower wall  128  (which is defined by the depending lip  130 ) such that a relatively quiescent zone is created which further assists separation and agglomeration of the oil. The oil moves out of the separator  120  through a generally rectangular horizontal outlet duct or passageway  100 ′. 
     In operation, the air/oil separators  40  and  120  according to the present invention provide improved lubrication and cooling performance of oil and hydraulic fluid in engines, transmissions and transaxles by removing entrained air from the oil or fluid, especially in dry sump systems. Aerated oil is supplied to the inlet duct  70  by, for example, the second or scavenger pump  38  of, for example, the automatic transmission  10 . The aerated oil is accelerated through the fourth, vertical passageway or portion  78 , through the fifth, tangential passageway or portion  82  and around the sixth, circular or spiral passageway or portion  84  which imparts a swirling, circular motion to the aerated oil. The swirling, aerated oil passes through the outlet  86  and enters the interior  92  of the separator  40  or  120  where a fluid vortex is formed. The centrifugal force exerted on the swirling, aerated oil drives the oil into contact with the inner walls  94  and  96  while the less dense air collects in the center of the separators  40  and  120 . The air/oil separators  40  and  120  are capable of accelerating the oil laterally to 8750 meters per second for 75 milliseconds. 
     The substantially air-free oil then collects in the bottom of the separator  40  and flows out the horizontal outlet duct or passageway  100  while the air moves upward through the passageway and outlet  88 . The anti-swirl chamber  134  of the alternate embodiment air/oil separator  120 , as noted, has a diameter larger than the smallest diameter of the frusto-conical lower wall  128  of the separator  120  thereby causing the exiting fluid to decelerate and further assist air/oil separation. 
     It should be understood that although the air/oil separators  40  and  120  have been described above in conjunction with a dry sump automatic transmission, they are equally suited for and provide the same benefits in dry sump engines, manual transmissions and transaxles. 
     The foregoing description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention and the following claims.