SEPARATION UNIT FOR CRANKCASE EMISSIONS OF AN IC ENGINE

Abstract

 Separation unit (11) for leakage emissions of an IC engine, comprising a housing (13) having a squashed elongated shape, in which a separation chamber (15) provided with an inlet opening (17) and an outlet opening (19) is provided, a separation device (21) of the inertial type and a coalescence filter (25) arranged downstream of the separation device (21), said device and filter being housed in said chamber (15) for being passed through by the flow of leakage emissions, drain valves (31) for evacuating oil from the chamber (15) towards the crankcase of the IC engine, a non-return valve (35) arranged at the outlet opening (19) and adapted to allow evacuation of the oil-poor or oil-free leakage emissions from the separation chamber (15) towards the suction circuit of the engine when a predetermined threshold pressure is exceeded.

Description

Technical Field

[0001] The invention relates to a separation unit for leakage emissions of an IC engine, especially, though not exclusively, of a motor vehicle.

Prior Art

[0002] IC engines with which motor vehicles are equipped generally comprise a crankcase housing the crankshaft and containing lubricating oil. During operation of the engine, part of the exhaust gases leaks from the combustion chamber through the compression rings between pistons and cylinders and penetrates into the crankcase. In order to prevent excessive increase of the pressure inside the crankcase, the leakage emissions, commonly known within the field as blow-by gases or emissions, are returned to the combustion chamber through a duct connecting the crankcase of the engine to the manifold of the suction circuit. The connection is usually effected downstream of the air filter and upstream of the turbine if existing. However, the leakage emissions returned to the combustion chamber have become enriched with the oil droplets sprayed inside the crankcase and it is necessary to use a separation filter for preventing heavy hydrocarbons from being burnt off and consequently generating pollutant emissions. For the application mentioned above, separation devices of the inertial type are used. A cartridge filter arranged in series may be further associated to the inertial separator. An example of a separator of the known type is disclosed in WO2007129137 (A1). Known separators and filters intended for the aforesaid purpose, however, have a number of drawbacks. A first drawback lies in the insufficient separation efficiency. A second drawback consists in the manufacturing complexity. A third drawback is the excessive size, which is often incompatible with the limited space available in the engine compartment. A fourth drawback lies in the limited duration of the separation efficiency and in the consequent need for frequent replacement.

[0003] It is a main object of the present invention to provide a separation unit for leakage emissions of an IC engine that does not have the drawbacks of the prior art. Another object of the invention is to provide a separation unit that can be manufactured industrially in a cost-effective manner.

Disclosure of the Invention

[0004] The aforementioned and other objects are attained with the separation unit as claimed in the appended claims.

[0005] The separation unit for leakage emissions of an IC engine according to the invention comprises a housing inside which a separation chamber is defined. According to the invention, the housing preferably has a body with a squashed elongated or flat shape. This configuration advantageously allows to obtain a separation unit that is compact and easy to install in most IC engines, especially, though not exclusively, of motor vehicles. The housing is provided with at least one inlet opening for allowing the entrance of oil-rich leakage emissions into the separation chamber, and at least one outlet opening for allowing the exit of purified, and therefore oil-poor or oil-free leakage emissions from the separation chamber. The inlet opening is adapted to be communicated with the crankcase of an IC engine. The outlet opening is adapted to be communicated with the suction circuit of the IC engine. A first advantage of the invention derives from the high separation efficiency. This result is achieved especially by virtue of the fact that the separation chamber houses a separation device of the inertial type and a coalescence filter, said device and filter being arranged in series. According to the invention, the coalescence filter may comprise a single-layer or multi-layer filtering mass of a suitable material. The separation device is adapted to subject the flow of leakage emissions to accelerations due to direction changes and to separate by inertia the oil contained in the emissions passing through the separation chamber. The coalescence filter is adapted to separate by coalescence the oil contained in the emissions passing through the separation chamber. According to the invention, the separation device and the coalescence filter are arranged in the separation chamber so that the entire flow of leakage emissions passes at first through the separation device and then through the coalescence filter. In addition, the separation device and the coalescence filter are preferably arranged in the chamber so as to define an inlet volume into which the at least one inlet opening opens and which is arranged upstream of the separation device, and an evacuation volume into which the outlet opening opens and which is arranged downstream of the filter. Still according to a preferred embodiment of the invention, the separation device and the filter are arranged in the separation chamber so as to be separated from each other along the longitudinal axis of the chamber housing them, and between the separation device and the coalescence filter there is provided a settling volume arranged downstream of the inertial separation device and upstream of the coalescence filter. Advantageously, the settling volume is adapted to delay entrance of the flow of leakage emissions into the coalescence filter. Advantageously, the settling volume is adapted to delay entrance of the flow of leakage emissions into the coalescence filter. This delay has the advantage of allowing the flow of emissions exiting the separation device to distribute homogeneously before entering the coalescence filter, thus improving the performance of the coalescence filter. The separation device and the coalescence filter are associated to at least one corresponding drain valve for evacuating oil form the housing. Further drain valves may be provided in the separation chamber for instance at the settling volume or at the evacuation volume. The outlet opening is provided with a non-return valve adapted to allow evacuation of the oil-poor or oil-free leakage emissions from the separation chamber, when a predetermined threshold pressure is exceeded.

[0006] The housing of the separation unit according to the invention can be easily made of plastics by using the molding technique. Said housing may further be provided with holes and protrusions for fixing by means of nuts or bolts. This circumstance brings about the advantage of allowing to manufacture the separation unit in a cost-effective manner and in large numbers.

Brief Description of the Drawings

[0007] Some preferred embodiments of the invention will be described by way of nonlimiting example with reference to the annexed drawings, in which:

• Fig.1 is a plan view in longitudinal section of the separation unit of a first embodiment of the invention;
• Fig.2 is a perspective view in longitudinal section of the separation unit of a second embodiment of the invention;
• Fig.3 is an overall view of the unit of Fig.2.

[0008] In all the figures, the same reference numerals have been used for identifying same or functionally equivalent parts.

Description of a Preferred Embodiment

[0009] Referring to Fig.1, the separation unit for leakage emissions of an IC engine according to the invention has been identified as a whole with reference numeral 11. The unit 11 comprises a housing 13 defining at its inside a separation chamber 15. The unit 11 comprises at least one inlet opening 17 for allowing the entrance of oil-rich leakage emissions into the separation chamber 15. Each inlet opening 17 is adapted to be communicated with the crankcase of an IC engine. The unit 11 further comprises at least one outlet opening 19 for allowing the exit of oil-poor or oil-free leakage emissions from the separation chamber 15. The outlet opening 19 is adapted to be communicated with the suction circuit of the IC engine. A separation device 21 of the inertial type is housed in the separation chamber 15. The device 21 is housed in the separation chamber 15 so as to define an inlet volume 23 of the separation chamber 15 arranged upstream of the device 21. The device 21 is adapted to subject the flow of leakage emissions to accelerations due to direction changes and to separate by inertia the oil contained in the emissions passing through the separation chamber 15.

[0010] A coalescence filter 25 is further housed in the separation chamber. The filter 25 is housed in the separation chamber 15 upstream of the separation device 21. In addition, the filter 25 is arranged in the chamber 15 so as to define an evacuation volume 27 of the separation chamber 15 arranged downstream of the filter. The filter 25 is adapted to separate by coalescence the oil contained in the emissions passing through the separation chamber 15. According to this embodiment of the invention, a settling volume 29 is further defined downstream of the inertial separation device 21 and upstream of the coalescence filter 25. The settling volume 29 is adapted to delay entrance of the flow of leakage emissions into the coalescence filter 25. The unit 11 comprises at least one first drain valve 31 associated to the inertial separation device 21 for evacuating from the chamber 15 the oil removed by the separation device 21. The unit 11 further comprises at least one second drain valve 33 associated to the coalescence filter, in order to evacuate from the chamber 15 the oil removed by the filter. In the shown example, said valve 33 is arranged in the evacuation volume 27. A non-return valve 35 is arranged at the outlet opening 19. The valve 35 is adapted to allow evacuation of the oil-poor or oil-free leakage emissions from the separation chamber 15, when a predetermined threshold pressure is exceeded.

[0011] According to this preferred embodiment of the invention, the housing 13 comprises an elongated body made of plastic material and having a substantially rectangular cross-section, in which the short side is at least half the length of the long side. Advantageously, said elongated body is therefore squashed or flat and has remarkably reduced overall dimensions especially in its height.

[0012] The separation chamber 15 further develops longitudinally inside the housing 13 and preferably occupies substantially the whole available space. The chamber 15 preferably further comprises an oval or elliptical cross-section with the major axis parallel to the long side of the substantially rectangular cross-section of the housing 13.

[0013] The housing 13 preferably comprises a pair of mutually perpendicular inlet openings 17 communicating with the inlet volume 23. Said opening are provided with a cylindrical extension 17a of the housing 13 defining a corresponding sleeve adapted to be associated to a corresponding opening, for instance one for each bank of valves, in the engine from which leakage emissions leak.

[0014] Still referring to Fig.1, the drain valves 31 are membrane-like unidirectional check valves. In other embodiments, the valves 31 may be unidirectional umbrella-like check valves. In the illustrated example, the drain valve 33 comprises a frusto-conical seat 33a provided with an inlet opening 33b and an outlet opening 33c and a ball 33d housed within the seat 33a and adapted to freely move between a closing position, proximal with respect to the inlet opening 33b, for closing the outlet opening 33c, and an opening position, distal with respect to the inlet opening 33b, for opening the outlet opening 33c. According to the invention, the valves 31 and 33 can be all of the same kind or of different kinds.

[0015] Still referring to Fig.1, the non-return valve 35 comprises a frusto-conical element 35a coaxially arranged inside the separation chamber 15 and with its perimetral edge 35b fixed to the inner wall of the chamber 15 and centrally open, and a second closing element 35c having the shape of a cylindrical or frusto-conical cup. The cup 35c is pressed against the opening 35d of the frusto-conical element 35a by a coil spring 35e arranged between the perimetral edge 35f of the closing element 35c and an abutment seat 35g provided in the wall of the separation chamber 15.

[0016] In this first embodiment of the invention, the coalescence filter 25 comprises a toroidal cartridge having a coaxial support 25a and being held against the walls of the chamber 15 between a sleeve 25b housed in the settling volume 29 and the frusto-conical element 35a of the valve 35.

[0017] The separation device 21 comprises a first plurality 41a of opposite coaxial frusto-conical elements 43 partially inserted into one another which define a labyrinth path 45 for the emissions passing through the separation device 21, and a second plurality 41b of frusto-conical elements 43 arranged in a mirror-like manner adjacent and coaxial to those of the first plurality 41 a. More particularly, each plurality of frusto-conical elements 41a,41b comprises a first frusto-conical element 43 defining a corresponding trumpet 47 which is centrally open and has its perimetral edge 47a fixed to the inner wall of the separation chamber 15. The trumpet 47 is arranged with its conicity tapering in the advancing direction of the flow of the leakage emissions. Each plurality 41a,41b further comprises a second frusto-conical element 43 defining a trumpet 49 which is centrally open and has its perimetral edge 49a fixed to the inner wall of the separation chamber 15. The trumpet 49 is arranged with its conicity tapering in the advancing direction of the flow of the leakage emissions. Furthermore, the second trumpet is arranged around the first trumpet 47. Each plurality 41a,41b further comprises a third frusto-conical element 43 defining a cup 51 with its conicity tapering in the direction opposite to the advancing direction of the flow of the leakage emissions, said cup being partially inserted between the first two trumpets 47,49. A fourth frusto-conical element 43, defining a cup 53 with its conicity tapering in the direction opposite to the advancing direction of the flow of the leakage emissions, is partially inserted between the second trumpet 49 and the wall of the separation chamber 15. The base of the cup 51 is fixed to the base of the cup 53 and located inside the latter. The cup 53 is provided with circumferential openings 55 for the passage of the leakage emissions.

[0018] Referring to Fig.2, there is illustrated a second embodiment in which the coalescence filter 25 is a prismatic mass having a substantially parallelepipedal shape and housed in the chamber 15.

[0019] Referring also to Fig.3, the housing 13 comprises a longitudinal duct 37 communicating with the outlet opening 19 and ending with a transverse extension 39 defining a corresponding radial outlet sleeve. The outlet sleeve 39 is adapted to be associated to a connecting duct for conveying the leakage emissions towards the suction circuit of the engine, preferably downstream of the filter and upstream of the turbine if existing. This arrangement advantageously allows to arrange the outlet sleeve 39 near the inlet extensions 17a, thus making the unit 11 compact and facilitating mounting of the unit 11 for instance on an engine cylinder head.

[0020] The housing 13 is further preferably provided with a perimetral fixing frame equipped with holes 61 for the passage of bolts 63 for fixing the unit 11 for instance to the cylinder head of an IC engine.

[0021] The separation unit as described and illustrated may undergo several variants especially in its height and modifications falling within the same inventive principle.

Claims

1. Separation unit (11) for leakage emissions of an IC engine, comprising:

- a housing (13) defining at its inside a separation chamber (15);

- at least one inlet opening (17) for allowing the entrance of oil-rich leakage emissions into the separation chamber (15), said inlet opening (17) being adapted to be communicated with the crankcase of an IC engine;

- at least one outlet opening (19) for allowing the exit of oil-poor or oil-free leakage emissions from the separation chamber (15), said outlet opening (19) being adapted to be communicated with the suction circuit of the IC engine;

- a separation device (21) of the inertial type housed in the separation chamber (15) so as to define an inlet volume (23) of the separation chamber (15) arranged upstream of the separation device (21), said separation device (21) being adapted to subject the flow of leakage emissions to accelerations due to direction changes and to separate by inertia the oil contained in the emissions passing through it;

- a coalescence filter (25) housed in the separation chamber (15) and arranged downstream of the separation device (21) so as to define an evacuation volume (27) of the separation chamber (15) arranged downstream of the coalescence filter (25) and adapted to separate by coalescence the oil contained in the emissions passing through the separation chamber (15);

- at least one first drain valve (31) associated to the inertial separation device (21), for evacuating oil from the chamber (15) towards the crankcase of the IC engine;

- at least one second drain valve (33) associated to the coalescence filter (25), for evacuating oil from the chamber (15) towards the crankcase of the IC engine;

- a non-return valve (35) arranged at the outlet opening (19) and adapted to allow evacuation of the oil-poor or oil-free leakage emissions from the separation chamber (15) towards the suction circuit of the engine, when a predetermined threshold pressure is exceeded.

2. Unit according to claim 1, wherein a settling volume (29) is defined in said chamber (15), said settling volume being arranged downstream of the inertial separation device (21) and upstream of the coalescence filter (25) and being adapted to delay entrance of the flow of leakage emissions into the coalescence filter (25).

3. Unit according to claim 1 or 2, wherein the housing (13) comprises an elongated body made of plastic material and having a substantially rectangular cross-section, the length of the short side being at least half the length of the long side, said elongated body having therefore a squashed elongated shape.

4. Unit according to claim 1 or 2 or 3, wherein the separation chamber (15) develops longitudinally inside the housing (13) and substantially occupies the whole available space and comprises an oval or elliptical cross-section with the major axis parallel to the long side of the substantially rectangular cross-section of the housing (13).

5. Unit according to any of the claims 1 to 4, wherein the housing (13) comprises a longitudinal duct (37) communicating with the outlet opening (19) and ending with a transverse extension (39) defining a corresponding sleeve adapted to be associated to a connecting duct for conveying the leakage emissions towards the suction circuit of the engine, preferably downstream of the filter and upstream of the turbine if existing.

6. Unit according to any of the preceding claims, wherein the separation device (21) comprises a first plurality (41a) of coaxial frusto-conical elements (43) that are mutually alternate and opposite and partially inserted into one another and define a labyrinth path (45) for the emissions passing through the separation device (21) and a second plurality (41b) of frusto-conical elements (43) arranged in a mirror-like manner adjacent and coaxial to those of the first plurality (41 a).

7. Unit according to claim 6, wherein each of said first and second pluralities of frusto-conical elements (41a,41b) comprises:

- a first frusto-conical element (43) defining a corresponding trumpet (47) which is centrally open and has its perimetral edge (47a) fixed to the inner wall of the separation chamber (15), said trumpet (47) being arranged with its conicity tapering in the advancing direction of the flow of the leakage emissions;

- a second frusto-conical element (43) defining a trumpet (49) which is centrally open and has its perimetral edge (49a) fixed to the inner wall of the separation chamber (15), said trumpet (49) being arranged with its conicity tapering in the advancing direction of the flow of the leakage emissions and being arranged around the first trumpet (47);

- a third frusto-conical element (43) defining a first cup (51) with its conicity tapering in the direction opposite to the advancing direction of the flow of the leakage emissions, said cup being partially inserted between the first two trumpets (47,49);

- a fourth frusto-conical element (43) defining a second cup (53) with its conicity tapering in the direction opposite to the advancing direction of the flow of the leakage emissions, said cup being partially inserted between the second trumpet (49) and the wall of the separation chamber (15), the base of the first cup (51) being fixed to the base of the second cup (53) and located inside the latter, said second cup being provided with circumferential openings (55) for the passage of the leakage emissions.

8. Unit according to any of the preceding claims, wherein at least one of the drain valves (31,33) comprises a frusto-conical seat (33a) provided with an inlet opening (33b) and an outlet opening (33c) and a ball (33d) housed within the seat (33a) and adapted to freely move between a closing position, proximal with respect to the inlet opening (33b), for closing the outlet opening (33c), and an opening position, distal with respect to the inlet opening (33b), for opening the outlet opening (33c).

9. Unit according to any of the claims 1 to 8, wherein at least one of the drain valves (31,33) comprises an umbrella-like or membrane-like unidirectional check valve.

10. Unit according to any of the preceding claims, wherein the non-return valve (35) comprises a frusto-conical element (35a) coaxially arranged inside the separation chamber (15) and with its perimetral edge (35b) fixed to the inner wall of the separation chamber (15) and centrally open, and a second closing element having the shape of a cylindrical or frusto-conical cup (35c) and being pressed against the opening (35d) of the frusto-conical element (35a) by a coil spring (35e) arranged between the perimetral edge (35f) of the closing element and an abutment seat (35g) provided in the wall of the separation chamber (15).

Drawing