TECHNICAL FIELD AND PRIOR ART
The present invention relates to an improved-efficiency device for recovering the oil contained in combustion gas, and to an internal combustion engine including such a device.
During the operation of an internal combustion engine, combustion gas leaks, also referred to as blow-by gas, occur in particular past the piston rings, the turbocharger shaft bearing, and the valve stem gaskets. This gas is recovered for reinjection into the admission to ensure that it is burnt.
Unfortunately, this gas is charged with oil, in particular the oil used for lubricating the air admission and exhaust mechanism made up of one or more cam shafts and valves.
In order to reduce the oil consumption of the engine and reduce exhaust gas pollution, the oil entrained by the blow-by gas, and also the oil projected by the moving parts of the engine, is for the most part recovered and returned to the sump, with the blow-by gas that has been separated by the oil being returned to the engine admission.
Oil is extracted from the blow-by gas by means of a separator device, also referred to a decanter device and generally located on the cylinder-head cover.
By way of example, the separator device is made up of one or two chambers including baffles through which the blow-by gas flows, with the drops of oil that are transported by the gas impacting against the walls making up the baffles. These drops then flow under gravity along said walls and they are collected and return to the oil circuit.
The device may comprise a first chamber in which first oil recovery is performed, followed by a second chamber of larger size in which second oil recovery is performed. Having two chambers can enable better separation efficiency to be achieved.
The oil drops are entrained in the separator and recovery device by the blow-by gases or they are projected into the device, e.g. by the cam shaft being splash-lubricated in oil.
By way of example, one such device is known from document GB 2 441 404. That document describes a device for separating and recovering oil from blow-by gas, in which the blow-by gas is conveyed into a chamber that communicates in its top portion, via baffles, firstly with a blow-by gas outlet orifice that is open in the top wall of said chamber, and secondly with a channel for recovering the oil contained in the gas and extending vertically at the center of the chamber.
Overall, known devices give satisfaction.
However, because of the reduction in the amount of space in motor vehicles that is dedicated to the engine compartment and to the engine itself, in order to increase the size of the cabin and/or in order to add new systems in the engine compartment, in particular safety systems, such devices also occupy an ever-smaller amount of space. The blow-by gas capture section formed by the intersection of the engine and the recovery device is then small compared with the flow rate.
The gas then travels at very high speed through the recovery device, in particular through the first chamber, thereby having the consequence, when the drops recovered in this first chamber fall under gravity, of said drops being re-entrained by the blow-by gas. These drops then become atomized into fine droplets when they strike the walls of the first chamber. Unfortunately, such fine droplets are difficult to separate from the blow-by gas. They are of a diameter that is small enough to ensure that they continue to be entrained by the gas without impacting against the walls of the recovery device, so the gas leaving the device and reinjected into the admission is still charged with oil, thereby leading to an increase in oil consumption by the engine.
Consequently, an object of the present invention is to provide an oil separator/recovery device of improved efficiency, while still being compact.
SUMMARY OF THE INVENTION
The above-specified object is achieved by a device for recovering the oil contained in blow-by gas, the device comprising first and second recovery chambers, the first chamber including oil recovery means that perform first separation of the oil from the blow-by gas.
The recovered oil is advantageously reinjected into the oil circuit of the engine upstream from the first chamber.
Thus, at least a majority of the recovered oil is returned to the oil circuit of the engine without being entrained by the blow-by gas.
In other words, a flow channel is provided for the oil that forms on the walls of the first chamber as a result of the blow-by gas striking said walls, which channel is physically separated from a flow channel for the blow-by gas leaving the engine directly.
In particularly advantageous manner, provision is made to cause the blow-by gas to pass through a volume of oil, this passage causing drops of oil entrained by the gas to be retained in the volume of oil. Advantageously, this volume of oil is fed with recovered oil.
The present invention thus mainly provides a device for recovering the oil contained in the combustion gas leaving an engine and traveling to the air admission of the engine including at least one collector orifice for incoming gas, a flow channel for said incoming gas, an outlet orifice for said combustion gas that has been at least partially de-oiled, a wall closing said flow channel for the incoming gas, a recovery channel for recovering the oil that becomes deposited on said wall, and a partition separating said recovery channel from the incoming gas flow channel, wherein the incoming gas flow channel is defined by a first cylinder, the oil recovery channel is defined by the first cylinder and by a second cylinder surrounding the first cylinder, the separation partition being formed by the first cylinder, the wall forming an end wall of the second cylinder, and a passage being defined between said end wall and one end of the first cylinder facing said end wall.
The wall is advantageously concave and connects continuously with at least a portion of the second cylinder, thereby ensuring a good flow for the drops of oil.
The recovery device of the invention may include a gutter surrounding the collector orifice, extending radially outwards from the first cylinder, a passage being provided relative to an end of the second cylinder that is remote from the end wall.
In a variant embodiment, the gutter may include drain holes for the collected oil, the drain holes enabling the oil to return to the engine upstream from the gas collector orifice.
Advantageously, the gutter is suitable for containing a volume of oil that is sufficient to constrain the combustion gas to pass through said volume, this passage serving to achieve additional oil recovery.
The first and second cylinders may be surrounded by a third cylinder forming an outer wall of a first chamber, said third cylinder being connected to the first cylinder to form the gutter, said device also including a second chamber connected to the incoming gas flow channel by the oil collector channel and the gutter, said main chamber including baffles for the combustion gas and being connected to an admission of the engine.
In an embodiment, the device includes three first chambers connected in parallel to a single main chamber.
Advantageously, the device comprises two parts made by molding a plastics material, the first part including the first and third cylinders, a bottom of a link duct between the first tank and the main tank, and a bottom of the main tank, and a second part comprising the second cylinder, a top of the link duct, a top and the baffles of the main tank, sealing means being interposed between the two parts.
The present invention also provides an internal combustion engine including a device of the invention for recovering the oil contained in the combustion gas leaving the engine and traveling to the air admission of the engine, which device is fastened on a cylinder-head cover in sealed manner, said device being connected to the engine in such a manner as to collect the combustion gas leaving the engine and return the oil collected from said gas, and in such a manner as to reinject said gas at the outlet from said device to the admission of said engine.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be better understood with the help of the following description and the accompanying drawings, in which:
FIGS. 1A and 1B are respectively a perspective view from above and a plan view of an embodiment of a recovery device of the present invention shown overall;
FIGS. 2A and 2B are respectively a perspective view from below and a plan view of the recovery device of FIGS. 1A and 1B;
FIG. 3 is a view from below identical to that of FIG. 2B, with the bottom portion of the second chamber removed;
FIG. 4 is a section view on plane AA showing part of the FIG. 3 device of the present invention; and
FIG. 5 is a view on a larger scale showing a portion of FIG. 4, the device being in operation.
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
In FIGS. 4 and 5, there can be seen a section view of an embodiment of a recovery device of the present invention that comprises a first oil separation/recovery chamber 2 and a second oil separation/recovery chamber 4, also referred to as a main chamber.
In the description below, the separation/recovery device is referred to merely as a recovery device.
The recovery device of the present invention is placed under a cylinder-head cover 8 and includes at least one orifice 6 for capturing blow-by gas escaping via piston rings. This orifice 6 forms the inlet to the device of the present invention.
In the example shown in FIGS. 1A to 3, the device has three gas capture orifices 6, 106, 206 disposed in parallel and serving to collect gas all along the cylinder-head cover 8.
Each orifice 6, 106, 206 is connected to a first chamber 2, 102, 202 that is distinct from the chambers of the other orifices, the three first chambers 2, 102, 202 being similar in structure so only one of them is described in detail.
The first chamber 2 includes a first duct 10 for channeling the incoming blow-by gas, a wall 12 opposite from the capture orifice 6 in the gas flow direction, against which wall the gas impacts, in particular the drops of oil that are deposited, at least in part, on said wall, and a second duct 14 for channeling the oil that deposits on the wall 12 while isolating it from the incoming gas stream.
For this purpose, the first duct is defined by an inside face of a first cylinder 16 located further inside the device, the first cylinder extending from the capture orifice 6 towards the impact wall 12. The second duct 14 is defined by an outside face of the first cylinder 16 and by an inside face of a second cylinder 18 that surrounds the first cylinder, the second cylinder extending from the impact wall 12 and co-operating therewith to form a substantially continuous surface towards the capture orifice. A third cylinder 19 is provided outside the second cylinder, surrounding it, and forming the outside wall of the first chamber 2.
Arrows 20 show the path followed by gas through the device.
The drops of oil entrained by the gas impact against the wall 12 and adhere thereto, and thereafter under the effects of gravity they run along the second cylinder in the second duct. These drops are isolated from the incoming gas by the first cylinder 16.
The gas that is at least partially de-oiled reaches the main chamber 4 via a link duct 22 after initially passing through a baffle 24 defined by the first, second, and third cylinders 16, 18, and 19.
The impact wall advantageously forms a half-vault that thus enables flow to take place by gravity towards the outside of the inside face of the second cylinder 18, and advantageously avoids drops from falling vertically into the incoming gas flow. Naturally, a horizontal wall, or a wall in the form of a complete vault, would not go beyond the ambit of the present invention, with drops of oil falling vertically directly into the incoming stream being reduced in comparison with devices in the state of the art.
In general, the impact wall is advantageously concave in shape and connects with at least a portion of the second cylinder 18 so as to form a continuous surface encouraging drops to flow along said surface.
The cylinders may present a section of arbitrary shape. In the example shown, the cylinders are substantially rectangular in section.
However, the three cylinders are advantageously selected so as to have sections that are geometrically similar in order to ensure that oil and gas are collected uniformly on the way to the main chamber 4.
In the example shown, there are physically two chambers connected in series, however it should naturally be understood that it is possible to provide only one chamber, with the means of the present invention being located at the inlet to the chamber and with the conventional partitions forming a labyrinth being located downstream from the separator means in the gas flow direction.
The first and third cylinders are joined together at their bottom ends so as to form a gutter 26 in which the collected oil is stored.
In the example shown, the gutter 26 includes holes 28 so as to allow oil to be drained towards the engine. These holes 28 are adjacent to the blow-by gas flow passage, thus preventing the collected oil from being directly re-entrained by the blow-by gas.
As a function of the size of the holes 28 and of the running speed of the engine, a volume of oil may be stored in the gutter 26, while the blow-by gas, on being exhausted towards the main chamber, passes through this volume of oil. As it passes through, oil still contained in the gas is captured.
Provision may be made not to pierce holes in the bottom of the gutter 26, thereby ensuring that a volume of oil V is present on a permanent basis.
The oil as decanted in this way in the first chamber passes into the main body of the decanting device in the form of streams or packets of oil. The oil in this form is then handled properly by a conventional baffle decanting device.
In the example shown, the right-hand side of the inner cylinder is lower than its left-hand side. The blow-by gas then tends to leave from the lower side of the cylinder since that is the side that presents the lesser head loss. Because of the slope of the vault, the recovered oil tends to flow from the side of the cylinder that is the highest. By means of this construction, the risk of putting the oil into contact with the blow-by gas is reduced, and consequently the risk of entraining oil that has already been separated is likewise reduced.
The operation of the separator device of the present invention is described below.
The blow-by gas, repented by arrows 20, that escapes from the engine via the piston rings is loaded with the oil used for lubricating the moving parts of the engine, said gas passing through the cylinder-head cover via the orifice 6 and penetrating into the first chamber 2, and more particularly into the first cylinder 16.
Thereafter, the blow-by gas strikes the half-vault 12, and oil becomes deposited on said half-vault in the form of drops.
The drops then flow by gravity along the half-vault 12 and then over the inside face of the second cylinder 18 so as to reach the gutter 26.
This oil is then returned to the engine via the drain holes 28.
The blow-by gas, partially de-oiled in this way, also passes between the first and second cylinders 16 and 18, passing via the baffle that is formed by the gutter 26.
If the gutter contains oil, then the gas passing through this volume loses more of the oil that it is conveying.
The gas then travels along the passage defined between the second and the third cylinders 18 and 19, and then along the link duct 22 so as to reach the main chamber 4. In the main chamber 4, the gas passes via a series of baffles 23 serving to enable the gas to lose even more of the remaining oil that it is transporting.
It should be observed that oil collection and gas flow take place over the entire periphery of the first chamber 2.
As can be seen in the example shown in FIGS. 1A to 3, the oil recovery device has three first chambers 2, 102, 202 in parallel that are located on the cylinder-head cover, all along its length. However this number is not limiting in any way and it may be modified as a function of the characteristics of the engine.
These three first chambers 2, 102, 202 are connected to a single main chamber 4 via respective link ducts 22, 122, 222, with the inside of the main chamber 4 being visible in FIG. 3, in particular its multiple baffles 23 for recovering the remaining oil.
The main tank 4 includes an outlet orifice 30 for the blow-by gas that has been de-oiled in full or in part, which orifice is provided in a top portion of the main tank 4, said orifice 30 including an endpiece 32 for connection to the admission of the engine, where the gas is burnt, and outlet orifices 34 for collected oil located at the ends of pipes 36 passing through the cylinder-head cover and the cylinder head, in order to return it to the engine.
By way of example, the oil recovery device is made of a plastics material, advantageously by molding. For this purpose, provision is made for the device to be made as two parts, a bottom part 38 including the first and third cylinders 16 and 19, the bottom of the link duct 22, and the bottom of the main tank 4, and a second part including the second cylinder, the top of the link duct, the top and the baffles 23 of the main tank 4.
One or more gaskets 42 are interposed between the first and second parts 38 and 40. Gaskets 44 are also provided between the recovery device and the cylinder-head cover, in particular between the bottom of the gutter 26 and the cylinder-head cover. For example, a groove 46 surrounding the blow-by gas inlet orifice into the first tank 1 is provided through the bottom of the gutter 26, at the outside thereof.
The first and second parts are secured to each other, e.g. by melting the plastics material, or by snap-fastening.
Fabrication by molding enables the production costs of the device to be reduced. By way of example, the device may be made of polyamide, of polypropylene, and with or without glass fibers.
A device for recovering the oil contained in the blow-by gas has been successively made that enables direct re-entrainment of the collected oil by the gas entering the device to be avoided, thereby avoiding the formation of fine droplets that are difficult to separate from the gas stream.