Centrifugal separator for separating oil droplets from the crankcase ventilation gas of an internal combustion engine

Abstract

Centrifugal separator (1) for separating oil droplets from the crankcase ventilation gas of an internal combustion engine, comprising a rotor (2) with a central shaft (27) with plates (23) arranged one above the other at a distance from each other and forming a plate stack (20), wherein adjacent plates (23) each define a flow gap (24), comprising a housing (3) rotatably receiving the rotor (2) and comprising a raw gas inlet (32), a clean gas outlet (33) and an oil outlet (34) and a rotary drive for the rotor (2), wherein - the stack of plates (20) is divided in its axial direction into two stack of plates parts (21, 22) which are separated from each other in terms of flow within the rotor (2) by a separating element (26), - the raw gas inlet (32) opens into a radially inner region (21') of a first plate stack part (21) and the first plate stack part (21) can be permeated by the crankcase ventilation gas in a direction from radially inside to radially outside during operation of the centrifugal separator (1), - a second plate stack part (22) in the operation of the centrifugal separator (1) is permeable to the crankcase ventilation gas in a direction from radially outside to radially inside and the clean gas outlet (33) originates from a radially inner area (22') of the second plate stack part (22), characterized in that , - that the axial distance between adjacent plates (23) in the first plate stack part (21) of the plate stack (20) is smaller than in the second plate stack part (22) of the plate stack (20), - that all plates (23) in the plate stack (20) are identical, that each plate (23) can be brought into rotationally fixed engagement with the central shaft (27) in at least two different relative rotational positions, and that each plate (23) is provided with two such different spacers (25.1, 25.2) that, depending on a rotational position of two adjacent plates (23), two different axial distances of the adjacent plates (23) in the plate stack (20) can be set relative to each other.

Description

[0001] The present invention relates to a centrifugal separator for separating oil droplets from the crankcase ventilation gas of an internal combustion engine, comprising the features of the preamble of claim 1.

[0002] Rotors of centrifugal separators with a stack of discs for cleaning crankcase ventilation gas of an internal combustion engine are preferably designed for radial flow from the inside out, due to the requirement of low pressure in the crankcase of the internal combustion engine. This design utilizes the pumping effect of the rotor on the gas flow. This pumping effect also supports the recirculation of the oil separated in the centrifugal separator, since, viewed in the direction of gas flow, the pressure is higher behind the rotor than in front of it. On the other hand, it is known that rotors with a stack of discs, flowing radially from the outside in, exhibit better oil separation under the same boundary conditions. However, in this case, the pumping effect of the rotor opposes the flow direction, necessitating the use of additional pumping devices, such as compressors, for the gas flow.

[0003] Document DE 100 44 615 A1 discloses a venting device for the crankcase of an internal combustion engine, comprising a centrifugal oil separator with a mixture inlet for an air-oil mixture, an air outlet for clean air, and an oil outlet for oil. The centrifugal oil separator is designed as a disc separator. Preferably, the disc separator has a stator designed as a housing, in which a rotor is accommodated. The rotor has several discs arranged parallel to each other and coaxially to the rotor axis. A gap is formed between each pair of adjacent discs, connecting an annular space inside the rotor with a space surrounding the rotor inside the housing.Furthermore, the venting device can include a compressor located upstream or downstream of the disc separator, the compressor being essentially dimensioned to at least compensate for any pressure loss that occurs during the flow through the disc separator. In a first embodiment, during operation of the oil separator, the airflow to be de-oiled flows radially from the outside to the inside through the rotor's slots, i.e., against the centrifugal force generated by the rotor's rotation, which necessitates the use of the aforementioned compressor. The compressor serves, on the one hand, to essentially compensate for the pressure loss that inevitably occurs during the flow through the disc separator. On the other hand, the compressor can also be dimensioned to generate a pressure increase across the separator-compressor unit.In another embodiment, the flow direction of the airflow to be de-oiled in the disc separator is reversed, i.e., it runs radially from the inside to the outside through the gaps of the rotor, in which case no separate compressor is required.

[0004] Another separator of the type mentioned above is known from document DE 10 2007 054 922 A1. This document discloses a separator for separating oil mist from the crankcase ventilation gas of an internal combustion engine, in particular of a motor vehicle, with a gas cleaning chamber in which a rotatably mounted centrifugal rotor is arranged. The gas cleaning chamber has a raw gas inlet, a clean gas outlet, and an oil outlet. The crankcase ventilation gas can be introduced into a radially inner region of the centrifugal rotor through the raw gas inlet, clean gas freed from oil mist can be discharged from the gas cleaning chamber through the clean gas outlet, and oil separated from the gas can be discharged from the gas cleaning chamber through the oil outlet.A rotary drive for the rotor is located in a drive chamber of the separator, separate from the gas cleaning chamber. It is operated with pressurized lubricating oil from the internal combustion engine and is connected to the centrifugal rotor via a shaft extending from the drive chamber into the gas cleaning chamber. The centrifugal rotor is preferably formed by a stacked-plate separator consisting of a number of plates stacked one above the other, which are positively and / or non-positively engaged with each other and / or with the shaft. This separator is designed for radial flow through the rotor from the inside to the outside, thus utilizing the rotor's conveying effect on the gas flow. However, this does not achieve optimal oil separation from the crankcase ventilation gas.

[0005] Document DE 10 2004 057 411 A1 describes a disc separator used for removing impurities from a fluid. The disc separator comprises a rotor that supports several axially stacked and axially spaced discs in a rotationally fixed manner, and a stator containing a dirt collection chamber in which the rotor is arranged. A fluid path is formed within the disc separator, leading from an inlet into the dirt collection chamber, from the dirt collection chamber radially inward between the discs into a central discharge channel, and from the discharge channel out of the disc separator through an outlet. The dirt collection chamber is axially divided into at least two sub-chambers by means of at least one throttling point, from which the fluid can flow parallel between the discs to the discharge channel. The throttling point is formed by an annular gap located in a parting plane extending perpendicular to the axis of rotation.During operation of the disc separator, a fluid to be cleaned flows through it via the aforementioned fluid path, while the rotor simultaneously rotates. Due to friction and inertial effects, contaminants carried by the fluid are displaced radially outwards and thus remain in the dirt collection chamber, while the fluid flows inwards. The application for such disc separators is in the lubrication oil circuit of an internal combustion engine, where they are used to clean the lubricating oil of contaminants. This disc separator is neither designed nor suitable for separating oil droplets from the crankcase ventilation gas of an internal combustion engine.

[0006] Document DE 689 28 908 T2 discloses a device for separating a liquid from a substance dispersed in it with a higher density than that of the liquid. The device comprises a separation centrifuge with a rotor rotatable about an axis of rotation and forming a separation chamber, with a stack of conical separating plates arranged coaxially with the rotor in the separation chamber, and with spacers. The spacers are designed and arranged between the separating plates in such a way that, together with the latter, they form several different flow paths between each pair of adjacent separating plates, each having an inlet and an outlet area located at different distances from the axis of rotation of the rotor.Furthermore, the device includes a means for supplying liquid to the inlet area of ​​each flow path and a means for discharging liquid free of dispersed substance from the outlet area of ​​each flow path. The inlet and outlet areas of each flow path are located at such radial positions that the majority of the liquid in the flow path must cross the greater part of the radial extent of the two separating plates between which the flow path is formed. The rotor is rotatable in a predetermined direction, and each pair of successive spacers between two successive separating plates is shaped such that they extend from the inlet to the outlet area of ​​the flow path formed between them in a direction that has a radial component and a component in the circumferential direction of the rotor.In a preferred embodiment, the centrifuge rotor has an upper and a lower part, which are held together axially by a locking ring. The centrifuge rotor is supported by a drive shaft connected to the rotor lower part. The rotor parts form a separation chamber in which two stacks of semi-conical separating discs are arranged coaxially with the rotor, with the separation chamber rotating together with the rotor during operation. A semi-conical partition is inserted between the stacks of separating discs. The separating discs and the partition are fixed radially and circumferentially relative to each other. This disc separator is neither designed nor suitable for separating oil droplets from the crankcase ventilation gas of an internal combustion engine.

[0007] Document AT 290 477 B discloses a centrifugal separator for separating the gas and liquid components of a foam, without reference to the separation of oil droplets from a crankcase ventilation gas, and it is not disclosed that the axial distance of adjacent plates in a first group is smaller than in a second group of plates.

[0008] Document US 2 179 941 A shows a centrifugal separator with two plate stack sections, wherein the axial distance between adjacent plates in the first plate stack section is smaller than in the second plate stack section.

[0009] Other such centrifugal separators with two stacked plate sections, each with differently spaced plates, are known from documents JP S50 - 38 858 A and US 5 921 909 A.

[0010] The present invention therefore aims to create a centrifugal separator of the type mentioned above which, on the one hand, provides good separation of oil droplets from the crankcase ventilation gas of an internal combustion engine and, on the other hand, offers a usable pumping effect for the crankcase ventilation gas without requiring an additional pumping device, such as a compressor.

[0011] The problem is solved according to the invention with a centrifugal separator according to the features of claim 1.

[0012] Here, the axial distance between adjacent plates in the first part of the plate stack is smaller than in the second part of the plate stack, and all plates in the plate stack are identical, and each plate can be brought into rotationally fixed engagement with the central shaft in at least two different relative rotational positions, and each plate is equipped with two such different spacers that, depending on a rotational position of two adjacent plates relative to each other, two different axial distances of the adjacent plates in the plate stack can be set.

[0013] In this design of the centrifugal separator, only a single type of plate is required, which is equipped with spacers that allow two different plate spacings to be set depending on the angle of rotation.

[0014] The two-stage oil separation process, with the crankcase ventilation gas flowing through the two disc stack sections in succession, achieves particularly effective separation of oil droplets from the crankcase ventilation gas. The second disc stack section, through which the gas flows from the outside to the inside, contributes significantly to this efficiency. Simultaneously, the centrifugal separator exhibits a pumping effect on the crankcase ventilation gas flow, generated by the first disc stack section. This effect can be used to prevent undesirable differential pressure across the centrifugal separator or even to create a desired low pressure or vacuum in the crankcase. Furthermore, this pumping effect allows for active oil return through the oil outlet, preferably back into the crankcase of the associated internal combustion engine.A further advantage is that the oil droplets separated from the crankcase ventilation gas in the centrifugal separator are kept away from the clean gas outlet, thus avoiding the risk of previously separated oil being carried along with the clean gas into the clean gas outlet.

[0015] The separation mechanism in centrifugal separators with a rotor with a stack of discs for separating oil droplets from the crankcase ventilation gas of an internal combustion engine is in itself well known and therefore does not need to be described separately here.

[0016] Furthermore, for the centrifugal separator according to the invention, it is preferably provided that the first plate stack section, into whose radially inner region the raw gas inlet opens, forms a lower plate stack section during operation of the centrifugal separator, and that the second plate stack section, from whose radially inner region the clean gas outlet originates, forms an upper plate stack section during operation of the centrifugal separator. Since a larger proportion of the oil droplets are separated in the first plate stack section, this embodiment allows for an advantageously short path for oil discharge from the housing of the centrifugal separator.Alternatively, the first plate stack section, into whose radially inner area the raw gas inlet opens, can form the upper plate stack section during operation of the centrifugal separator, and the second plate stack section, from whose radially inner area the clean gas outlet originates, can form the lower plate stack section during operation of the centrifugal separator. Effective oil separation is also achieved with this configuration of the centrifugal separator.

[0017] Another embodiment provides that the number of plates in the first part of the plate stack is greater than in the second part. This ensures uniform oil separation in both parts of the plate stack and a sufficiently high conveying effect. A favorable and therefore preferred ratio of the number of plates in the first part of the plate stack to the number of plates in the second part is, for example, in the range of 1.5 to 1 to 3 to 1.

[0018] Preferably, the plates each have a frustoconical contour with a radially inner, flat plate portion featuring at least one flow perforation and a radially outer, conical plate portion without perforations. The plates thus have a simple yet effective shape for oil separation and can be manufactured cost-effectively, for example, as injection-molded plastic parts or stamped sheet metal parts. Furthermore, the supply and distribution of the flow of crankcase ventilation gas to be cleaned in the first plate stack portion and the collection and discharge of the cleaned crankcase ventilation gas in the second plate stack portion can be achieved through the flow perforations in the plates of the plate stack, thus eliminating the need for a central shaft for gas flow.

[0019] In order to keep the separating element, which fluidly separates the two plate stack parts within the rotor, simple, it is preferably formed by a flow-interruption-free separating disc arranged between the two plate stack parts.

[0020] It is further preferably provided that the separating disc forming the separating element has a shape corresponding to or approximating the shape of the plates and, like the plates, is arranged on the central shaft in a rotationally fixed manner. The separating disc can thus be easily manufactured as a variant of the plates; for example, in the case of a plastic plate, by means of an interchangeable injection mold insert, or in the case of a sheet metal plate, by omitting a punch for the central flow opening.

[0021] Another embodiment provides that the plates each have a frustoconical contour with a radially inner, unperforated flat plate portion and a radially outer, unperforated conical plate portion; that the central shaft is a hollow shaft in flow communication with the raw gas inlet, with radial flow perforations opening into the flow gaps between the plates; and that the separating element is formed by a barrier arranged in the hollow central shaft. In this embodiment, the central shaft is used for supplying and distributing the flow of the crankcase ventilation gas to be cleaned in the first plate stack portion and for collecting and discharging the flow of the cleaned crankcase ventilation gas in the second plate stack portion, so that the plates are available with their full surface area for oil separation.

[0022] An embodiment of the centrifugal separator, which is not part of the invention, provides that all plates in the plate stack are identical and that separate first spacers, shorter in the axial direction of the plate stack, are arranged between each pair of plates in the first plate stack section, and separate second spacers, taller in the axial direction of the plate stack, are arranged between each pair of plates in the second plate stack section. In this embodiment, a single plate design is sufficient, and only two different spacers, which are simpler than the plates themselves, are required.

[0023] An embodiment of the centrifugal separator, which is not part of the invention, provides that two different types of discs are arranged in the disc stack. The first section of the disc stack contains discs with lower spacers in the axial direction, while the second section contains discs with higher spacers in the axial direction. Although this requires two different types of discs, it simplifies the assembly of the rotor because it is not necessary to ensure a specific rotational orientation of the discs relative to each other when attaching them to the shaft.

[0024] Finally, the centrifugal separator according to the invention is provided in that the housing of the centrifugal separator has a circumferential wall, the inner surface of which surrounds the rotor at a distance and to whose lower end, during operation of the centrifugal separator, the oil outlet is connected. Gravity is used to remove the separated oil, which is deposited on the circumferential wall. This, in conjunction with the pumping effect of the rotor, ensures a reliable and rapid discharge and return of the oil.

[0025] Exemplary embodiments of the centrifugal separator according to the invention are explained below with reference to a drawing. The figures in the drawing show: Fig. 1 a centrifugal separator with rotor, in a schematic longitudinal section, Fig. 2 one opposite Fig. 1 differently designed rotor of the centrifugal separator, in top view, Fig. 3 the rotor off Fig. 2 in longitudinal section according to section line III - III in Fig. 2, and Fig. 4. Turn the rotor off Fig. 2 and Fig. 3 in a view taken at an angle from above.

[0026] In the following figure description, identical parts in the different drawing figures are always provided with the same reference symbols, so that it is not necessary to explain all reference symbols again for each drawing figure.

[0027] Fig. Figure 1 of the drawing shows a centrifugal separator 1 in a schematic longitudinal section. The centrifugal separator 1 has a rotor 2 and a housing 3 that receives and surrounds the rotor 2. The rotor has a stack of discs 20 consisting of a plurality of discs 23 with a frustoconical contour, which are arranged one above the other at a distance and which form flow gaps 24 between each other. The stack of discs 20 is bounded and held together on the underside by a stack base 28 and on the upper side by a stack top 28'. The rotor 2 is rotatably mounted in the housing 3 by means of two bearings 29, 29' and is connected via a Fig. 1 rotary drive not shown, which is known per se, can be set in rotation about the axis of rotation 27'.

[0028] The stack of plates 20 is composed of a first, lower stack of plates 21 and a second, upper stack of plates 22, each consisting of several plates 23 arranged in a rotationally fixed manner on a central shaft 27 (only indicated here). A separating element 26, designed as a separating disc adapted in shape to the shape of the plates 23, is arranged between the two stack of plates 21 and 22 to separate them fluidically.

[0029] In the first, lower stack of plates 21, the axial distance between the individual plates 23 is smaller than the distance between the individual plates 23 in the second, upper stack of plates 22. Furthermore, the number of plates 23 in the first, lower stack of plates 21 is greater than the number of plates 23 in the upper, second stack of plates 22.

[0030] The housing 3 has an interior 30 in which the rotor 2 is arranged. A circumferential wall 31 of the housing 3 surrounds the rotor 2 at a radial distance. A raw gas inlet 32 ​​is arranged centrally on the underside of the housing 3, a clean gas outlet 33 is arranged centrally on the top side of the housing 3, and an oil outlet 34 is arranged radially outwards on the underside of the housing 3.

[0031] The central shaft 27 is a hollow shaft in flow communication with the raw gas inlet 32, with radial flow openings opening into the flow gap 24 between the plates 23. The separating element 26 can also be a barrier that only blocks the free cross-section of the hollow central shaft 27.

[0032] During operation of the centrifugal separator 1, the rotor 2 is set into rapid rotation by the rotary drive (not shown here). Crankcase ventilation gas, which is to be cleaned of oil droplets, flows from the crankcase of an associated internal combustion engine through the central raw gas inlet 32 ​​and a lower part of the hollow central shaft 27 into the radially inner region 21' of the first, lower plate stack section 21. From there, the crankcase ventilation gas flows radially outwards through the flow gaps 24 between the plates 23 of the first, lower plate stack section 21.

[0033] The separating element 26 prevents the direct axial flow of crankcase ventilation gas from the radially inner area 21' of the first, lower plate stack part 21 into the radially inner area 22' of the second, upper plate stack part 22.

[0034] The oil droplets carried in the gas stream initially settle on the underside of the plates 23 and are then conveyed radially outwards by centrifugal force and finally flung radially outwards, after which the oil droplets 4 settle on the inner surface of the circumferential wall 31.

[0035] The crankcase ventilation gas exits radially outwards from the flow gaps 24 between the plates 23 of the first, lower plate stack section 21, then flows radially upwards outside the plate stack 20 and enters the flow gap 24 between the plates 23 of the second, upper plate stack section 22. In these flow gaps 24, the crankcase ventilation gas flows radially from the outside to the inside, whereby any remaining oil droplets contained in the gas stream are separated and transported radially outwards by centrifugal force and then also flung onto the circumferential wall 31 of the housing 3.

[0036] The purified crankcase ventilation gas then enters the radially inner region 22' of the second, upper plate stack part 22 and from there through the upper part of the hollow central shaft 27 into the subsequent, central clean gas outlet 33. The clean gas outlet 33 can, for example, be connected to an air intake tract of the associated internal combustion engine.

[0037] The flow path of the crankcase ventilation gas through the centrifugal separator 1 is shown in Fig. 1 illustrated by flow arrows.

[0038] The oil droplets 4 deposited on the inner surface of the circumferential wall 31 form an oil film which, under the influence of gravity, flows downwards into the oil outlet 34 and is discharged through it, in particular back into the crankcase of the associated internal combustion engine. The oil outlet 34 is thus advantageously located in a region of the housing 3 through which the crankcase ventilation gas flows, having already passed through the first, lower plate stack section 21, but not yet through the second, upper plate stack section 22.

[0039] Since the clean gas outlet 33 is located far away from the circumferential wall 31 of the housing 3 which collects and drains the separated oil, there is no risk of unwanted carryover of already separated oil into the clean gas outlet 33.

[0040] Fig. Figure 2 shows a top view of the rotor 2 of the centrifugal separator 1. A central shaft 27 is visible in the center of the rotor 2. The discs of the disc stack 20, which are not visible here and are covered by the stack extension 28', are mounted onto this shaft in a rotationally fixed manner, for example by means of mutual interlocking. The rotor 2 is rotatable about the axis of rotation 27', which corresponds to the longitudinal center axis of the shaft 27. Radially inside are Fig. 2 several flow openings 23' are discernible, which are arranged here in the radially inner area of ​​the stack attachment 28' and also of the plate covered by the latter.

[0041] Fig. Figure 3 shows rotor 2. Fig. 2 in longitudinal section according to section line III - III in Fig. 2. Centrally located in Fig. Figure 3 shows the essentially vertically running shaft 27 during operation of the centrifugal separator. Below in Fig. The stacking base 28, which is formed in one piece with the shaft 27, lies at position 3. A first, lowest plate 23 rests on the stacking base 28.

[0042] The central shaft 27 has a metallic core, e.g., made of steel, shown in view, and a surrounding sheath, in particular an injection-molded plastic sheath, shown in section. The central shaft 27 is, unlike in Fig. 1. Not hollow, and therefore the flow openings 23' are provided radially inside the plates 23 as well as in the stack base 28' and stack top 28. The central shaft 27 has an unclad end section at the top and bottom, which serve for the rotatable bearing of the rotor 2 and for the connection of its rotary drive.

[0043] Further up in Fig. Figure 3 shows two further plates 23 and a separating element 26 arranged between them. Further plates 23, provided between the lowest plate 23 and the plate 23 arranged below the separating element 26, are not shown here for clarity, but are present in practice.

[0044] At the very top in Fig. Figure 3 shows the stacking attachment 28' with a top plate 23 arranged directly below it. Further plates 23, provided between the top plate 23 and the plate 23 arranged above the separating element 26, are not shown here for clarity, but are present in practice.

[0045] All the discs 23 of the rotor 2 together form the disc stack 20. The discs 23 that are arranged below the separating element 26 form a first, lower disc stack part 21 of the disc stack 20, and the discs 23 that are arranged above the separating element 26 form a second, upper disc stack part 22 of the disc stack 20. The individual discs 23 and the central shaft 27 are in rotationally fixed engagement with each other by means of mutual toothing.

[0046] On the underside of each of the plates 23, a number of spacers 25.1, 25.2 are integrally formed, which have the form of ribs extending radially along the plates 23 and spaced apart from each other circumferentially. The flow gaps 24 extend between the plates 23, which are axially spaced apart from each other by the spacers 25.1, 25.2.

[0047] To produce the based on the Fig. As already explained, the different plate spacings in the two plate stack parts 21, 22 are as follows: the spacers 25.1 on the plates 23 in the first, lower plate stack part 21 are designed with a smaller axial height, and the spacers 25.2 on the plates 23 in the second, upper plate stack part 21 are designed with a larger axial height in comparison.

[0048] In practice, the axial height of the flow gaps is usually only a few tenths of millimeters and the difference in the plate spacing in the first and second plate stack part is only a few tenths of millimeters, so that the differences in distance are practically not visible to the naked eye.

[0049] Instead of integrally formed spacers 25.1, 25.2, separate spacers with two different axial heights can also be arranged between the identical plates 23. It is also possible that all plates 23 in the plate stack 20 are identical, that each plate 23 can be brought into rotationally fixed engagement with the central shaft 27 in at least two different relative rotational positions, and that each plate 23 is provided with two such different spacers 25.1, 25.2 that, depending on a rotational position of two adjacent plates 23 relative to each other, two different axial distances between the adjacent plates 23 in the plate stack 20 can be set.

[0050] To the right of wave 27, one of the flow penetrations 23' in each of the plates 23 is cut and thus visible.

[0051] The plates 23 each have a frustoconical contour with a radially inner, flat plate part 23.1 formed with flow openings 23' and a radially outer, open-hole, conical-shell-shaped plate part 23.2.

[0052] It becomes clear in Fig. 3 furthermore, that the separating element 26, which resembles the plates 23 in its shape, has no flow openings and that thus a direct flow of crankcase ventilation gas from the radially inner region 21' of the first, lower plate stack part 21 into the radially inner region of the second, upper plate stack part 22 is blocked. This ensures that, during operation, the first, lower plate stack part 21 is permeated by the crankcase ventilation gas in a radial direction from the inside to the outside, and subsequently the second, upper plate stack part 22 is permeated by the crankcase ventilation gas in a radial direction from the outside to the inside.

[0053] Fig. 4 finally shows rotor 2. Fig. 3 in a view obliquely from above. The central shaft 27 projects upwards from the rest of the rotor 2 with an unclad end section, for example to accommodate a rotary bearing and / or to connect a rotary drive (not shown here).

[0054] At the very bottom in Fig. 4 the stacking base 28 is located and above in Fig. The stack attachment 28' is located at position 4, and the stack of plates 20 is positioned between them. The flow openings 23' are visible radially inwards on the upper side of the rotor 2.

[0055] In this embodiment, the separating element 26 is located approximately halfway up the stack of plates 20, fluidly separating the first, lower part of the plate stack 21 from the second, upper part of the plate stack 22 within the stack of plates 20. This separation is achieved by means of the... Fig.The flow arrows drawn to the left and right of rotor 2 illustrate that the flow of crankcase ventilation gas, after exiting radially outwards from the first, lower plate stack part 21 through which the gas flows, flows radially outwards around the separating element 26 and then flows with a radially inwards direction into the second, upper plate stack part 22 through which the gas flows subsequently.

[0056] The separation efficiency of the centrifugal separator 1 and its conveying effect on the crankcase ventilation gas, as well as the setting of a defined pressure difference across the centrifugal separator 1 during its operation, can be specifically influenced as required, e.g., by changing the number and / or size of the plates 23 in the plate stack 20, by changing the ratio of the number of plates in the two plate stack parts 21, 22, and / or by changing the distance between the plates 23 in the plate stack parts 21, 22 in the plate stack 20, and thus adapted and optimized for the respective application of the centrifugal separator 1. Reference symbol list: 1 centrifugal separator 2 Rotor 20 stacks of plates 21 First stack of plates (bottom) 21' radial inner area of ​​21 22 second stack of plates (top) 22' radial inner area of ​​22 23 plates 23' Flow breakthroughs in 23 23.1 radial inner plate part 23.2 radial outer plate part 24 flow gaps 25.1, 25.2 first, second spacers 26 separating element 27 central wave 27' pivot axis 28 stacking bases 28' Stackable Top 29, 29' Lager 3 cases 30 Interior 31 Perimeter wall 32 Raw gas inlet 33 Clean gas outlet 34 Oil outlet 4 drops of oil

Claims

[1] Centrifugal separator (1) for separating oil droplets from the crankcase ventilation gas of an internal combustion engine, comprising a rotor (2) with a central shaft (27) with plates (23) arranged one above the other at a distance from each other in a rotationally fixed manner, forming a plate stack (20), wherein adjacent plates (23) each define a flow gap (24), comprising a housing (3) rotatably receiving the rotor (2) and comprising a raw gas inlet (32), a clean gas outlet (33) and an oil outlet (34) and a rotary drive for the rotor (2), wherein - the stack of plates (20) is divided in its axial direction into two stack of plates parts (21, 22) which are separated from each other in terms of flow within the rotor (2) by a separating element (26), - the raw gas inlet (32) opens into a radially inner region (21') of a first plate stack part (21) and the first plate stack part (21) can be permeated by the crankcase ventilation gas in a direction from radially inside to radially outside during operation of the centrifugal separator (1), - a second plate stack part (22) in the operation of the centrifugal separator (1) is permeable to the crankcase ventilation gas in a direction from radially outside to radially inside and the clean gas outlet (33) originates from a radially inner area (22') of the second plate stack part (22), characterized by , - that the axial distance between adjacent plates (23) in the first plate stack part (21) of the plate stack (20) is smaller than in the second plate stack part (22) of the plate stack (20), - that all plates (23) in the plate stack (20) are identical, that each plate (23) can be brought into rotationally fixed engagement with the central shaft (27) in at least two different relative rotational positions, and that each plate (23) is provided with two such different spacers (25.1, 25.2) that, depending on a rotational position of two adjacent plates (23), two different axial distances of the adjacent plates (23) in the plate stack (20) can be set relative to each other. [2] Centrifugal separator according to claim 1, characterized by, that the first plate stack part (21), into whose radially inner region (21') the raw gas inlet (32) opens, forms a lower plate stack part of the plate stack (20) during operation of the centrifugal separator (1), and the second plate stack part (22), from whose radially inner region (22') the clean gas outlet (33) originates, forms an upper plate stack part of the plate stack (20) during operation of the centrifugal separator (1), or that the first plate stack part (21), into whose radially inner region (21') the raw gas inlet (32) opens, forms an upper plate stack part of the plate stack (20) during operation of the centrifugal separator (1), and the second plate stack part (22), from whose radially inner region (22') the clean gas outlet (33) originates, forms a lower plate stack part of the plate stack (20) during operation of the centrifugal separator (1). [3] Centrifugal separator according to claim 1 or 2, characterized by, that the number of plates (23) in the first plate stack part (21) of the plate stack (20) is greater than in the second plate stack part (22) of the plate stack (20). [4] Centrifugal separator according to any one of claims 1 to 3, characterized by , that the plates (23) each have a frustoconical contour with a radially inner, flat plate part (23.1) formed with at least one flow perforation (23') and a radially outer, perforation-free, conical plate part (23.2). [5] Centrifugal separator according to any one of claims 1 to 4, characterized by , that the separating element (26) arranged between the two plate stack parts (21, 22) is formed by a flow-interruption-free separating disc. [6] Centrifugal separator according to claims 4 and 5, characterized by, that the separating disc forming the separating element (26) has a shape corresponding to or approximating the shape of the plates (23) and is arranged on the central shaft (27) in a rotationally fixed manner like the plates (23). [7] Centrifugal separator according to any one of claims 1 to 3, characterized by , that the plates (23) each have a frustoconical contour with a radially inner, perforation-free flat plate part (23.1) and a radially outer, perforation-free conical plate part (23.2), that the central shaft (27) is a hollow shaft in flow communication with the raw gas inlet (32) with radial flow perforations opening into the flow gap (24) between the plates (23), and that the separating element (26) is formed by a barrier arranged in the hollow central shaft (27). [8] Centrifugal separator according to any one of claims 1 to 7, characterized by, that the housing (3) of the centrifugal separator (1) has a circumferential wall (31) whose inner surface surrounds the rotor (2) at a distance and that the oil outlet (34) is connected to the lower end of the inner surface of the circumferential wall (31) during operation of the centrifugal separator (1).

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