ES2932877T3 - Device and method for separating lubricating oil mist from an interior - Google Patents

Abstract

An oil mist separation device (D) from an internal combustion engine, the device comprises a filtration assembly consisting of a labyrinth filter (L), a cyclone filter (C) and an impact separator (W ) arranged in sequence to be traversed by a gas in which the oil mist is dispersed. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Device and method for separating lubricating oil mist from an interior

Cross reference to related requests

This patent application claims the priority of Italian patent application No. 102018000010913 filed on 10/12/2018.

Technical field of the invention

The invention relates to a device and method for separating oil mist from an internal combustion engine, according to the preamble of claim 1, which corresponds to document DE10127817A1.

Background of the invention

As is known, endothermic engines are equipped with a crankcase ventilation circuit, which is designed to release the so-called "exhaust" gases to the outside of the crankcase itself, that is, those gases that escape from the cylinders into the engine. crankcase past the piston sealing rings. Ventilation is necessary both to prevent pressure build-up inside the crankcase and to compensate for volume changes due to piston movement. The exhaust gases contain droplets of atomized/sprayed oil as well as other impurities, such as unburned particles of carbonic nature (particulate matter). The ventilation circuit can be of the open type, that is, it releases exhaust gases into the atmosphere, or it can be of the closed type, that is, it is connected to the intake duct of the internal combustion engine to ensure complete combustion of particulate matter. . In this case, there is a "recirculation" of exhaust gas.

While in the first case the oil and the particulate matter must be separated from the gases for obvious reasons of environmental and health protection (particulate matter has carcinogenic effects), in the second case the oil and the particulate matter must be disposed of so as not to damage the engine components that come into contact with the recirculated flow to the combustion chamber. In fact, oil residues and particulate matter tend to form residual sediments. These residues are deposited on the intake valves and, in the case of supercharged engines, also on the compressor and intercooler, thus compromising their efficiency due to an aerodynamic disturbance in the first case and a greater thermal resistance in the latter. the second case. In addition, in catalytic vehicles, the combustion of lubricating oil possibly recirculated in the intake has deleterious effects on the exhaust gas aftertreatment device. In fact, some oils generate residues that cannot be burned and therefore cannot be removed by the particulate filter, even through active regenerations.

The oil dragged in the exhaust gases, both recirculated and non-recirculated, represents a consumption that, given the same volume of deposits used to contain it, typically oil pans, reduces the replacement interval. To obtain the separation of the lubricating oil from the exhaust gases, it is known to use separation or purification systems of different types, for example, impact separators, in which the gas flow is directed, through one or more nozzles, against a wall, which causes sudden changes in the direction of the wall; separators of this type have a very high filtering power and/or efficiency compared to other filtering devices, so that they manage to purify almost all of the oil mist dispersed in the exhaust gases; however, they suffer from the drawback of generally having a relatively short life, since they are subjected to conditions where they quickly become dirty. Impact separators can also be relatively large in size and have high pressure losses when the gases to be filtered pass through them.

The use of a traditional filter element, usually a labyrinth filter, combined with an impact separator has proven unsatisfactory. Indeed, when the filter, as a whole, needs to achieve a filtration power of more than 80%, the impact separator must separate more than 80% of the total oil dispersed in the form of mist in the exhaust gases. Therefore, even in this case, significant pressure drops occur and the impacted separator becomes dirty quickly.

The cyclonic filter, on the other hand, does not even exceed 50% in terms of filtering power and, therefore, its use has been abandoned for a long time.

If not specifically excluded by the detailed description below, the information contained in this part should be considered an integral part of the detailed description itself.

Summary of the invention

The object of the invention is to offer a lubricating oil mist separator device for the separation of drops of lubricant from crankcase exhaust gases, said separator device allowing manufacturers to overcome, in one way in a simple and inexpensive way, the drawbacks arising from the known purification devices mentioned above.

The idea on which the invention is based is that of implementing a succession of a labyrinth filter, a cyclone filter and an impact separator, which leads to a corresponding filtering sequence.

The cyclone filter and the impact separator are dimensioned to obtain a moderate separation of the oil mist. This implies that a simple cyclonic filter is implemented, which is large. In other words, it is not necessary to obtain high tangential velocities, since it is only necessary to recover medium-sized drops. Therefore, a simple cyclone filter with low tangential velocities makes it possible to limit the pressure drop offered by the separation device as a whole. Consequently, as regards the impact separator that follows the cyclone filter, it is not necessary for it to have a filtering power greater than 70%, so that low pressure losses of the filtering assembly as a whole are ensured.

Therefore, the filter set only includes the three mentioned filters, strictly in this sequence.

The separation device preferably comprises a single casing, in which three different housings are obtained, which house, respectively, the mentioned filters; in particular, said housings can be accessed through a simple common cover.

The casing comprises at least one inlet and at least one outlet and comprises a pneumatic path, which establishes a communication between said at least one inlet and said at least one outlet and crosses the mentioned three housings, so that the gases flow through them. the aforementioned filters according to the sequence described above.

Preferably, the pneumatic path is such that it leads the flow of gas along an oscillating movement towards and away from a bottom wall of the casing.

According to another preferred aspect of the invention, which can be combined with the previous ones, the gas covers, in the separation device, a U-shaped path: a first part of the path consists of going through the aforementioned three filters, while the rest of the path is roughly straight.

According to another preferred aspect of the invention, which can be combined with the previous ones, the gas covers, in the separation device, a U-shaped path with inversion of movement, which is carried out inside a valve body used to adjust the pressure. established inside the crankcase of the internal combustion engine.

The aforementioned objective is achieved by the invention according to the features set forth in claim 1.

The dependent claims describe preferred embodiments of the invention, thus forming an integral part of the description.

Brief description of the figures.

Other objects and advantages of the invention will be better understood by reading the following detailed description of an embodiment thereof (and relative variants) and the attached figures that are offered as a mere non-limiting example, in which:

Figure 1 shows an example of a device for the separation of lubricating oil mist in an internal combustion engine, shown in an exploded view, according to the invention;

Figure 2 is a top view of the example of Figure 1, with the cover removed;

Figure 3 is a longitudinal section according to a section plane identified by the line MI-IM of Figure 2, perpendicular to said cover;

Figure 4 is a top view, with a transparent cover, of the example of Figure 1;

Figure 5 shows, on a larger scale, a detail of figure 3.

In the figures, the same numbers and the same reference letters indicate the same elements or components.

For the purposes of the invention, the term "second" component does not imply the presence of a "first" component. In fact, these terms are only used as labels for clarity and should not be construed in a limiting manner.

The elements and characteristics contained in the different preferred embodiments, figures included, can be combined with each other, without leaving the scope of protection of this patent application, as described below.

Detailed description of embodiments

Figure 1 shows an exploded view of an example of a separation device D according to the invention, according to a perspective view with parts exploded.

The separating device D comprises a casing H with side walls LW projecting perpendicular to a substantially flat bottom wall F, whereby the casing H is substantially a straight and hollow prism. The casing H further comprises a cover LD, which is distinct from the other parts and is designed to operatively contact the side walls to close the casing H, thus preventing the gas to be filtered from leaking into the atmosphere before that the dispersed oil mist is recovered through the filter assembly contained in the H housing.

The shell H has a substantially oblong shape along an axis Z; the filter assembly consists of a labyrinth filter L, a cyclone filter C, and an impingement separator W, in the same order as listed, arranged along the Z axis. Therefore, the gas flowing through the Separation device D is firstly purified from large oil droplets by means of the labyrinth filter, and then further purified by means of the cyclone filter C, which, as is known, uses an acceleration centrifuge to force the remaining oil droplets towards and along the walls of the filter. Finally, the gas is led through the impingement separator W.

The Z axis of the separating device D is parallel to the bottom wall F.

Advantageously, the coexistence of the cyclone filter C and the impact separator W, downstream of the labyrinth filter L, allows low pressure losses of the filter assembly as a whole.

Preferably, the L-labyrinth filter is designed to remove only macrodroplets and offer, for example, a filtering power of up to 5%. However, in general, labyrinth filters can offer up to 40% filtering power or efficiency.

Preferably, the cyclone filter C is designed to have a filtering power of up to 30%. However, in general, C cyclonic filters can offer up to 60% filtering power or efficiency.

Finally, the W impact separator is designed to have a filtering power of 70% to 75%. However, generally speaking, impingement separators can achieve up to 90% filtration power or efficiency. Therefore, the total filtering power exceeds 80%; in fact, in the example given above: 1 x 0.95 x 0.7 x 0.25 = 0.166, where 0.166 represents the fraction of flowing oil mist.

Therefore, the solution suggested here consists of three stages of filtration in series, the first stage being defined to which the flow is subjected by the labyrinth filter L, the second stage by the cyclonic filter C and the third stage by the separator. of impact W. This arrangement allows a progressive reduction of the oil drops, that is to say, a reduction of the number and/or of the dimensions of the drops, stage after stage. In effect, the filtering power increases from the first to the second stage, and then from the second to the third stage.

Therefore, the amount of oil reaching the third filtering stage, which is defined by the impact separator, is progressively reduced by the previous two filtering stages, so that the degree of fouling of the impact separator W is significantly more limited compared to known solutions, in which this last type of filter is used alone, without previous filtering stages.

Thanks to this relatively low degree of soiling, the solution proposed here has a relatively long lifetime, for example a lifetime corresponding to approximately 300,000 km traveled by the vehicle, so that it basically requires no maintenance or replacement.

At the same time, the overall efficiency of the filter assembly is extremely high, especially thanks to the third stage defined by the W impact separator.

Furthermore, the solution suggested here is relatively compact, despite the presence of three filter stages in series. The impact separator W comprises a chamber, preferably in the shape of a parallelepiped flattened along the axis Z, having an inlet I and an outlet U arranged at opposite points of the chamber so that the gas flowing through it is undergoes two deflections of approximately 90°.

According to figure 5, the inlet I is defined by at least one nozzle arranged in such a position that it directs a corresponding flow along an axis A towards an impact wall P, which is arranged orthogonally to the axis A. The axis A is preferably parallel to axis Z. In particular, the outlet U is obtained at wall P and has an axis B, which is parallel and spaced from the A axis. In other words, input I and output U are spaced from each other along the A axis and along a Y axis, which is orthogonal to the A and B axes. Specifically, the Y axis is orthogonal to the lower wall F.

In particular, according to figure 1, the inlet I is defined by two nozzles separated from each other along a direction, which is orthogonal to the axis A and to the direction Y.

The nozzles defining the inlet I preferably have a shape that accelerates the flow, that is, they converge towards the wall P.

Inside the chamber and axially opposite the inlet I there is preferably a mat of coalescing material M. The mat M is supported in a fixed position by the wall P, so that it is axially spaced from the nozzles. Therefore, the flow is directed by the nozzles towards the mat M, so that the oil droplets hit the mat M (or the wall P, if there is no mat M) and coalesce, while the gases they are deflected by approximately 90° along the Y axis to arrive at output U, which is also indicated by the flow line shown in Figure 3.

In the specific example, the outlet U is obtained from the outside of the perimeter of the mat M. According to a variant that is not shown here, the outlet U is obtained from the inside of the perimeter of the mat M.

The oil recovered by the three filters slides down, specifically towards the bottom F, due to the force of the weight and is collected in a recovery pipe (not shown), which leads the oil back to the engine oil sump. internal combustion through a return tube (not shown).

If necessary, a check valve is arranged along the return pipe.

The separation device D preferably also includes a regulating valve V. It is arranged downstream of the filter assembly to allow the gas to drain to the outside in the event of overpressure or to obstruct the recirculation of exhaust gases in order to maintain a pressure, in the crankcase of the internal combustion engine, within a predetermined pressure range. It is evident that the possibly released gas is purified from the oil mist.

The housings, which respectively house the three filters of the filtering assembly, and the regulating valve V are aligned along the Z axis of the housing H.

In the valve body of the regulating valve V, the gas reverses its movement, thus receding in the opposite direction to that used to flow through the filter assembly.

Therefore, the gas follows a U-shaped path that has a first portion, upstream of said inversion, and a second portion downstream of said inversion of movement; the first portion involves the crossing of the filter assembly, while the second portion is approximately straight.

This U-shaped path is particularly clear with reference to figure 2, which shows the pneumatic path of the gas to be filtered by means of thick arrows, where the pneumatic path preferably starts from a first inlet IN1, which is obtained on a side wall of said casing H, and from a second input IN2, which is obtained on said bottom wall F, to a single output OUT, which is arranged on the other side wall of casing H, opposite the side wall where input IN1 is obtained.

Figure 3 shows, in longitudinal section, the separation device D, perpendicular to the bottom wall F and to the cover LD. The lid LD is parallel to the bottom wall F at least in a relative portion. Figure 3 shows the first portion of the U-shaped route, which involves the crossing of the filtering assembly.

Referring to Figure 3, the first portion of the U-shaped path is oscillating toward and away from a bottom wall F of the casing.

With reference to figure 5, the heights Q1 and Q2, according to a direction perpendicular to the lower wall F, that is to say parallel to the axis Y, of the cyclone filter C and of the impact separator W, respectively, are different from each other and, in In particular, Q1 is greater than Q2.

This fact forces the gas to carry out the mentioned movement towards the lower wall F, in an area between the filters C and W.

The separation device D described here is designed to be associated with a one or two bank internal combustion engine. Therefore, the input IN2 obtained on the bottom wall F of the casing H may be absent.

The lower wall F will be operatively horizontal, that is, parallel to the ground, to operatively transport the oil collected in a return pipe (not shown), which is connected to the oil sump of the internal combustion engine. The regulating valve V comprises a movable fan Vs, which is held in position by a helical retaining spring S, which is arranged perpendicular to the bottom wall F, as shown in Figure 3. In case of exhaust gas overpressure, the movable fan Vs moves against the effect of the retaining spring S and thus allows gas to flow through an outlet Vout of the valve (figure 1), which is obtained in the cover LD. Vice versa, in case of depression, the movable spring VS moves in the opposite direction to regulate the flow of exhaust gas, thus regulating the pressure inside the crankcase of the internal combustion engine.

Therefore, the cover LD forms a portion of the valve body V. Figure 4 shows a view from the top of the separating device D, that is, a view that is perpendicular to the bottom wall F, where, without However, the lid is transparent.

Another aspect of the invention that plays an important role is the modular character of the separation device D. In fact, the three filters define respective modules that are coupled to the respective housings in the housing H and are different from each other, so that they can be be mounted independently of each other. Preferably, all three filters can be removed from their housings and therefore replaced independently of one another. Furthermore, the U-shaped pneumatic path is achieved regardless of the presence, in the relative housings, of the three filters. The non-limiting example described above may be subject to variations, without thereby departing from the scope of protection of the invention, comprising all the embodiments that, for an expert in the field, are defined by the claims.

On reading the above description, a person skilled in the art can carry out the object of the invention without introducing further manufacturing details.

Claims (10)

1. An oil mist separator device (D) of an internal combustion engine, said device comprising a filter assembly consisting of a preliminary filter, a cyclone filter (C) and an additional filter to be passed through by a gas in which said oil mist is dispersed; said cyclone filter (C) being arranged in sequence after said preliminary filter; said additional filter being arranged in sequence after said cyclone filter; characterized in that said preliminary filter is a labyrinth filter (L) and said additional filter is an impact separator. Device according to claim 1, comprising a simple casing (H), wherein three casings are provided, the casings being respectively coupled to said filters, and where the casing presents at least one input (IN; IN1, IN2 ) and a simple output (OUT) and a pneumatic path, which interconnects said at least one input with said simple output through said three housings. The device according to claim 2, wherein said casing has the shape of a right prism with respect to a bottom wall (F), and wherein said pneumatic path is such that it induces gas flow along an oscillatory motion. towards and from said bottom wall. The device according to any of the preceding claims, comprising a regulating valve (V) suitable for maintaining a pressure in the crankcase of the internal combustion engine within a predefined pressure range; wherein said valve is arranged downstream of said filter assembly. The device according to claim 4, wherein said pneumatic path, according to a projection on said lower wall (F), is U-shaped, and wherein a direction reversal is performed within a valve body of said regulating valve ( V). The device according to claim 5, wherein said U-shaped path comprises a first portion, upstream of said inversion, and a second portion, downstream of said inversion, and wherein said first portion of the path involves the crossing of said filtering assembly, while the second portion is approximately rectilinear. The device according to any of the claims 3 to 6, wherein a first inlet (IN1) is provided in a side wall of said casing and a second inlet (IN2) in said bottom wall. Internal combustion engine comprising an oil mist separator device (D) according to any of the preceding claims 1 to 7. 9. A method for the separation of oil mist from an internal combustion engine, which comprises a filtering procedure consisting of a sequence of a first filtering by means of a labyrinth filter (L), a second filtering by means of a cyclonic filter (C) and a third filtering through an impact separator (W). A land vehicle comprising an internal combustion engine according to claim 8.