Patent Description:
Crankcase gas is ventilated from a crankcase of an internal combustion engine, ICE. The crankcase gas is the result of the high pressure within the cylinders of the ICE forcing some of the combustion gas and liquid and solid residues past the piston rings down into the crankcase of the ICE. If not ventilated, an increased pressure within the crankcase may impede ICE operation, may cause engine oil to leak out of the ICE, and/or may cause the liquid and solid residues to contaminate and/or dilute the engine lubricating oil.

Ventilated crankcase gas may be disposed of in an environmentally friendly manner instead of being ventilated in untreated form to the atmosphere. For certain types of combustion engines, legislation requires crankcase gas to be disposed of in an environmentally friendly manner.

Crankcase gas comprises combustion gas, oil, other liquid hydrocarbons, soot, and other solid combustion residues. In order to dispose of crankcase gas suitably, the gas is separated from oil, soot, and other residues. The separated gas may be led to an air intake of the combustion engine or vented to the atmosphere, and the oil may be led back to an oil sump of the combustion engine optionally, via an oil filter for removing soot and other solid residues from the oil.

A separator may be utilised for disposing of crankcase gas. In the separator, the crankcase gas is separated into heavy constituents of the crankcase gas, such as oil and soot, and into a cleaned gaseous phase. Depending on the type of separator used, the heavy constituents are collected in the separator or led out of the separator via an outlet. The gaseous phase is lead out of the separator via a gas outlet and may be directed to an air intake of the ICE.

A pressure at the air intake of the ICE is commonly sub-atmospheric e.g., due to a turbocharger of the ICE rotating at high speed to compress air that has been drawn into the ICE. This sub-atmospheric pressure thus, also prevails at the gas outlet of the crankcase gas separator connected to the air intake. A gas pressure regulating valve may be arranged at the gas outlet in order to prevent too large a sub-atmospheric pressure from propagating through the crankcase gas separator to the crankcase of the relevant ICE, which is not desirable.

On the other hand, when the turbocharger is not rotating or only rotating at low speed, it does not build up any sub-atmospheric pressure that could propagate through crankcase gas separator.

There are different kinds of crankcase gas separators. One way of classifying crankcase gas separators may be as a passive kind and an active kind.

In the passive kind of crankcase gas separator, the overpressure of the crankcase i.e., an above atmospheric pressure at the inlet of the crankcase gas separator, and the sub-atmospheric pressure at the gas outlet of the crankcase gas separator transport the gas through the separator. Put differently, in the crankcase gas separator itself there is not supplied any energy to the crankcase gas flowing through the separator.

The passive kind of crankcase gas separator may rely on a filter element, such as a mesh filter and/or on directional changes of the gas flow through the crankcase gas separator for separating the heavy constituents from the crankcase gas.

Under ICE operating conditions when the turbocharger does not build up any sub-atmospheric pressure, the crankcase gas separator of the passive kind does not contribute to drawing crankcase gas from the relevant ICE. Instead, the overpressure produced in the crankcase of the ICE forms the only means of directing the crankcase gas through the separator. This may not always be sufficient to relieve the crankcase gas from its heavy constituents.

In the active kind of crankcase gas separator, energy is supplied in the separator to the crankcase gas flowing therethrough. Thus, also under ICE operating conditions when the turbocharger does not build up any sub-atmospheric pressure, crankcase gas is drawn from the relevant ICE by the crankcase gas separator and relieved of its heavy constituents therein.

One type of active crankcase gas separator comprises a rotor that is actively driven to rotate. The rotation creates a centrifugal force acting on the heavy constituents of the crankcase gas thus, facilitating and/or improving separation thereof. Moreover, the rotor has a pumping effect i.e., a pressure increasing effect, on the crankcase gas and cleaned gas passing through crankcase gas separator.

Accordingly, since the crankcase gas separator of the passive type relies on gas pressure external of the separator and the pressure drop over the separator for separation of the heavy constituents, and since the crankcase gas separator of the active type is driven to separate the heavy constituents - the pressure distribution within the respective separator type, the pressure drop over the respective separator type, and the gas flow conditions within the respective separator type are distinctly different in the passive type of crankcase gas separator and the active type of the crankcase gas separator.

Therefore, any valve operating to control a gas flow through a separator of the passive type has distinctly different operating conditions than a valve of a separator of the active type. Inter alia, the valve of a separator of the passive type must ensure a sufficient passage of gas to enable separation of the heavy constituents, whereas a valve of a separator of the active type must be adapted to operate with the pressure increase caused by the rotor.

For instance, <CIT>, <CIT> and <CIT> show crankcase gas separators of the active type, wherein the gas outlet is provided with a gas pressure regulating valve adapted to operate under pressure increasing conditions caused by a rotor of the relevant separator.

Increased efficiency in internal combustion engines is an aim in the development of such engines. Put differently, a reduction in energy consumption of the engine including its auxiliary components such as an active crankcase gas separator, is desirable.

Accordingly, it would be desirable to provide a crankcase gas separator comprising a rotor, which crankcase gas separator has a lower energy consumption than any of the crankcase gas separators disclosed in <CIT> or <CIT>. To better address one or more of these concerns, a crankcase gas separator having the features defined in the independent claim is provided.

According to an aspect of the invention, there is provided a crankcase gas separator comprising a separator housing delimiting at least part of a separation space, a rotor arranged in the separation space, a gas outlet passage from the separation space, and a gas pressure regulating valve arranged in fluid communication with the gas outlet passage, wherein the gas pressure regulating valve comprises a valve seat and a membrane configured to seal against the valve seat and provides a flow direction for gas from the gas outlet passage through the gas pressure regulating valve, and wherein in relation to the flow direction, the membrane is arranged downstream of the valve seat.

Since in relation to the flow direction, the membrane is arranged downstream of the valve seat, a lower pressure drop prevails over the gas pressure regulating valve when the valve is open than in a regulating valve of the kind shown in <CIT> and <CIT>, each of which has the membrane arranged upstream of the valve seat.

Since the pumping of the crankcase gas and the cleaned gas, actuated by the rotating rotor, is operating against this lower pressure drop over the regulating valve, less energy is required for pumping the gas out of the crankcase gas separator than in a crankcase gas separator having a valve with its membrane arranged upstream of the valve seat. Thus, less energy is consumed by the present crankcase gas separator and accordingly, also by the internal combustion engine comprising the crankcase gas separator.

Moreover, in a regulating valve of the kind shown in <CIT> and <CIT>, with the membrane arranged upstream of the valve seat, a small valve seat is required in order to provide a desirable even valve characteristic. A small valve seat produces higher pressure drop than a larger valve seat.

It has been realised by the inventor that, in the present gas pressure regulating valve, with the membrane arranged downstream of the valve seat, the situation is the opposite, a large valve seat is required in order to provide the desirable even valve characteristic. Thus, the even valve characteristic is provided in a valve with a low pressure drop, in comparison with the small valve seat in a regulating valve of the kind shown in <CIT> and <CIT>.

In this context a large valve seat may be defined as a valve seat having a through flow area within a range of <NUM> x Amin to <NUM> x Aclose. The through flow area of the valve seat may be seen perpendicularly to the valve seat. Amin is the smallest cross-sectional area for the gas to pass in the separator. Depending on the separator, Amin may be at a crankcase gas inlet of the separator, the total area of the interspaces between the separation aids at the centre of the rotor, the gas outlet passage upstream of the gas pressure regulating valve, etc. Aclose is the closing area of the membrane i.e., the area of the membrane outside the valve seat, see further below.

The crankcase gas separator is arranged for cleaning crankcase gas from an internal combustion engine, ICE. Such an ICE may be configured for propelling a vehicle, a vessel, or may be a stationary combustion engine, for instance for driving a generator for generating an electrical current.

The crankcase gas separator is configured to separate heavy constituents of the crankcase gas as a liquid phase from a gaseous phase. Accordingly, the liquid phase may comprise one or more of oil, other liquid hydrocarbons, soot, and other solid combustion residues.

The crankcase gas, also referred to as blow-by gas, may be ventilated from the crankcase of the ICE via a crankcase ventilation system. The centrifugal separator may form part of the crankcase ventilation system.

In the separation space and the rotor of the crankcase gas separator, the crankcase gas is separated into the liquid phase and the gaseous phase.

The crankcase gas separator is a centrifugal separator since it comprises the rotor arranged in the separation space. The rotor may be connected to a rotor shaft, which is journalled in the separator housing and arranged to be rotated about a rotational axis.

If not otherwise stated, axial and radial references and directions used herein are defined in relation to the rotational axis of the rotor.

Herein, the crankcase gas separator may alternatively be referred to simply as separator, or as centrifugal separator. The gas pressure regulating valve may alternatively be referred to as, the pressure regulating valve, the regulating valve, or as the valve.

The separator comprises an inlet for the crankcase gas. The inlet is arranged in fluid communication with the separation space. Also the gas outlet passage is arranged in fluid communication with the separation space. The gas outlet passage forms part of a gas outlet for the gaseous phase separated in the separator. The crankcase gas separator comprises a liquid outlet for the liquid phase separated in the separator. Also the liquid outlet is arranged in fluid communication with the separation space.

In operation of the centrifugal separator, crankcase gas is led into the separation space and the rotor via the inlet for the crankcase gas. The crankcase gas enters the rotor from a central portion thereof. As the rotor rotates, the heavy constituents are separated therein and are propelled from an outer periphery of the rotor as droplets against a circumferential inner wall surface of the separator housing. The droplets form the separated liquid phase which is led out of the centrifugal separator via the liquid outlet. The gaseous phase i.e., the crankcase gas relieved of its heavy constituents, is led out of the centrifugal separator via the gas outlet passage and the gas pressure regulating valve.

The rotation of the rotor has a pumping effect on the crankcase gas and the gaseous phase, which increases a gas pressure between the inlet for crankcase gas and the gas outlet passage.

The centrifugal separator may be configured for concurrent separation. That is, the two separated phases travel in the same direction through the rotor of the centrifugal separator. More specifically, as discussed above, the liquid phase travels from within the rotor towards its periphery. Similarly, the gaseous phase is formed as the crankcase gas is separated from the heavy constituents while traveling from the central portion of the rotor towards its periphery. Thus, both the liquid phase and the gaseous phase exit the rotor at its periphery.

The rotor may comprise a separation aid e.g., a number of separating members, which improve the separation of the heavy constituents from the crankcase gas. The separation aid may comprise separating members in the form of e.g., axially extending vanes which are directed radially from the rotor shaft or axially stacked frustoconical separation discs. As the rotor rotates, the heavy constituents are forced against radially inwardly facing surfaces of the separating members, forming thereon droplets of the liquid phase and flowing towards the periphery of the rotor.

The separator housing is stationary in relation to the ICE. The rotor shaft and the rotor are arranged to rotate in relation to the separator housing. The rotor shaft may be rotated by a driving member, such as a turbine wheel, an electric, pneumatic, or hydraulic motor, etc..

The gas pressure regulating valve is configured to regulate a gas pressure within the separation space. For instance, the pressure regulating valve may ensure that a minimum pressure level within the separation space does not drop below a minimum pressure level. That is, below the minimum pressure level, the pressure regulating valve may close the gas outlet passage and above the minimum pressure level, the pressure regulating valve may open the gas outlet passage.

The gas outlet passage may extend at least upstream of the valve seat i.e., forming at least a portion of a flow path between the separation space and the valve seat.

The membrane being configured to abut and/or seal against the valve seat herein, does not necessarily mean a gas tight seal but refers to at least a portion of the membrane abutting against a portion of the valve seat. Accordingly, the abutment and/or seal achieved may reduce the gas passage to a lesser or larger extent.

For instance, the membrane generally, may extend substantially perpendicularly to a plane including the valve seat e.g., a plane of an abutment area of the membrane may extend within a range of <NUM> - <NUM> degrees to the plane including the valve seat. For instance, if there is an angle between the two planes, the membrane will abut gradually against the valve seat as a pressure difference over the valve seat increases, with the lower pressure being on the downstream side of the regulating valve.

The terms upstream and downstream refer to a direction or position seen along a flow direction i.e., upstream is closer to a source of the flow and downstream is farther from the source of the flow. In the present case, according to the invention the membrane being arranged downstream of the valve seat means that a component of the gas flowing through the pressure regulating valve will reach the valve seat before reaching the membrane.

The expression "a flow direction for gas from the gas outlet passage through the gas pressure regulating valve" refers generally to the flow direction through the regulating valve, from its inlet to its outlet. Accordingly, along this flow direction, the physical path of the gas flowing through the regulating valve may change direction one or more times.

A spring or other resilient member may be arranged to interact with the membrane in order to provide desired opening and/or closing characteristics of the valve
According to embodiments, seen perpendicularly to a plane including the valve seat, a gas throughflow area within the valve seat, and an area of the membrane outside the valve seat may have a ratio within a range of <NUM> : <NUM> to <NUM> : <NUM>. In this manner, a smooth valve characteristic may be provided.

Also, within this range a characteristic of the regulating valve may be achieved that closes the present valve with the membrane arranged downstream of the valve seat to prevent too low a pressure downstream of the valve from propagating through the valve and the separator.

The gas throughflow area within the valve seat or more specifically, its projected area on the membrane, acts as a valve/membrane opening area. The area of the membrane outside the valve seat i.e., an area having a ring-shape in the case of a substantially circular membrane, acts as a valve/membrane closing area.

According to embodiments, seen perpendicularly to a general plane of the membrane, a centre of the membrane may be offset from a centre of the valve seat. In this manner, pressure drop characteristics of the regulating valve may be adaptable in response to physical positioning of components of the regulating valve. For instance, in relation to as gas outlet conduit for the gaseous phase of the regulating valve, which conduit is arranged downstream of the membrane.

The general plane of the membrane is a flat plane extending in parallel with a widest portion of the membrane.

According to embodiments, the centre of the membrane may be offset from the centre of the valve seat towards the gas outlet conduit. In this manner, low pressure drop, in comparison with a membrane that is centred in relation to the valve seat, may be provided.

According to embodiments, a plane including the valve seat and a plane of an abutment area of the membrane configured to abut against the valve seat, may be arranged at an angle to each other. In this manner, oscillating vibrations in the membrane and/or oscillating closing and opening movements of the membrane against the valve seat may be avoided since the membrane may gradually come into contact with the entire valve seat.

Further features of, and advantages with, the invention will become apparent when studying the appended claims and the following detailed description.

Various aspects and/or embodiments of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:.

Aspects and/or embodiments of the invention will now be described more fully.

<FIG> schematically illustrates a cross section through a crankcase gas separator <NUM> according to embodiments.

The separator <NUM> is a centrifugal separator. The separator <NUM> is configured for separating a liquid phase and a gaseous phase from a crankcase gas coming from an internal combustion engine, ICE.

The separator <NUM> comprises a separator housing <NUM> delimiting at least part of a separation space <NUM> and a rotor <NUM> arranged in the separation space <NUM>. During use of the separator <NUM>, the crankcase gas is separated into the liquid phase and the gaseous phase in the rotor <NUM>.

The separator <NUM> further comprises a gas outlet passage <NUM> from the separation space <NUM> and a gas pressure regulating valve <NUM> arranged in fluid communication with the gas outlet passage <NUM>.

The gas outlet passage <NUM> is configured for leading a separated gaseous phase out of the separation space <NUM> and towards the valve <NUM>. Accordingly, the separation space <NUM> is arranged in fluid communication with the regulating valve <NUM> via the gas outlet passage <NUM>.

Downstream of the regulating valve <NUM>, there is provided a gas outlet <NUM> for the gaseous phase from the separator <NUM>. The gas outlet <NUM> may be connected to an air intake of the relevant ICE, upstream of its turbocharger.

The gas pressure regulating valve <NUM> is schematically indicated in <FIG>. The valve <NUM> may be a biased valve configured to open when a predetermined minimum gas pressure level prevails in the separation space <NUM>. Thus, the valve <NUM> ensures that the gas pressure within the separation space <NUM> is above the predetermined minimum gas pressure level. The valve <NUM> prevents too low a pressure, connected to the gas outlet <NUM> of the valve <NUM> from drawing excessive amounts of crankcase gas from a relevant ICE through the separator <NUM>.

A rotor shaft <NUM> extends through the separation space <NUM> in an axial direction. The rotor <NUM> is connected to the rotor shaft <NUM>. The rotor <NUM> and the rotor shaft <NUM> are arranged to rotate about a rotational axis <NUM>.

The rotor shaft <NUM> is brought to rotate about the rotational axis <NUM> by a driving member <NUM>. In the embodiments illustrated in <FIG>, the driving member <NUM> is a turbine wheel connected to the rotor shaft <NUM>. The turbine wheel is driven by a stream of oil, such as engine lubricating oil, directed against the turbine wheel.

The rotor shaft <NUM> is journalled in the separator housing <NUM>. The rotor shaft <NUM> may be journaled e.g., in ball bearings, roller bearings, or plain bearings.

In the illustrated embodiments, an operating position of the separator <NUM> is shown with a vertical orientation of the rotational axis <NUM>. In alternative embodiments, the operating position may be with a horizontal orientation of the rotational axis or with an orientation in between a vertical and horizontal orientation.

Suitably, the separator <NUM> further comprises an inlet <NUM> into the separation space <NUM> for the crankcase gas and a liquid outlet <NUM> for the separated liquid phase.

In <FIG>, the separated liquid phase flows from the separation space <NUM> through the lower bearing to the liquid outlet <NUM>. Additionally or alternatively, other flow paths for the liquid phase from the separation space <NUM> to the liquid outlet <NUM> may be provided.

The rotor <NUM> comprises a separation aid in the form of a stack <NUM> of separation discs <NUM>, each separation disc <NUM> having a frustoconical, shape. Between the separation discs <NUM> in the stack <NUM>, interspaces are formed through which the crankcase gas travels from an inner periphery towards an outer periphery while being separated into the liquid phase and the gaseous phases as the rotor <NUM> rotates. In <FIG> only some of the separation discs <NUM> are indicated.

In these embodiments the frustoconical separation discs <NUM> are stacked with their wide ends facing downwardly. In alternative embodiments, the frustoconical separation discs may be stacked with their wide ends facing upwardly.

In alternative embodiments, other types of separation aids may be utilised, such as e.g. axially extending vanes projecting radially outwardly from the rotor shaft.

The centrifugal separator <NUM> is configured for concurrent separation. During use of the separator <NUM>, the crankcase gas enters the rotor <NUM> from a central portion thereof. As the rotor <NUM> rotates, the heavy constituents are separated therein and are propelled from an outer periphery of the rotor <NUM> as droplets against a circumferential inner wall surface <NUM>, which extends circumferentially around the rotor <NUM> and may form part of the housing <NUM>.

When, as illustrated, the separator <NUM> is configured to be positioned with the rotational axis <NUM> extending substantially vertically during use of the separator <NUM>, the liquid outlet <NUM> is arranged at a lower end of the housing <NUM>. The separated liquid phase may thus, be transported by gravity towards the liquid outlet <NUM>.

If the separator, during use, is configured for a different orientation suitably, the liquid outlet is arranged at a lower end of the housing in the relevant orientation.

The flow of crankcase gas, gaseous phase, and liquid phase through the separator <NUM> is indicated with small arrows in <FIG>.

<FIG> schematically illustrates a cross section through a portion of the crankcase gas separator <NUM> shown in <FIG>. In <FIG> the gas pressure regulating valve <NUM> is shown in more detail. In the following reference is also made to <FIG>.

The gas pressure regulating valve <NUM> comprises a valve seat <NUM> and a membrane <NUM> configured to seal against the valve seat <NUM>. The regulating valve <NUM> provides a flow direction for gas from the gas outlet passage <NUM> through the gas pressure regulating valve <NUM>. The flow direction for gas from the gas outlet passage <NUM> through the regulating valve <NUM> and to the gas outlet <NUM> of the separator <NUM> is indicated with arrows in <FIG>. Accordingly, the gas outlet <NUM> of the separator <NUM> is arranged downstream of the membrane <NUM>.

In relation to the flow direction for gas from the gas outlet passage <NUM>, the membrane <NUM> is arranged downstream of the valve seat <NUM>.

The regulating valve <NUM> is arranged to regulate a pressure within the separation space <NUM> of the separator <NUM>. A relative high pressure within the separation space <NUM> acts via the gas outlet passage <NUM> on a central portion of the membrane <NUM> to separate the membrane <NUM> from the valve seat <NUM> in order to open the valve <NUM>. A relative low pressure connected to the gas outlet <NUM> of the separator <NUM> acts on a peripheral portion of the membrane <NUM> to seal the membrane <NUM> against the valve seat <NUM> in order to close the valve <NUM>.

Mentioned purely as an example, at least a portion of the membrane <NUM> may be made from an elastomer, such a thermoplastic elastomer, natural rubber, or synthetic rubber.

Seen perpendicularly to a plane <NUM> including the valve seat <NUM>, a gas throughflow area within the valve seat <NUM> and an area of the membrane <NUM> outside the valve seat <NUM> may have a ratio within a range of <NUM> : <NUM> to <NUM> : <NUM>. The plane <NUM> including the valve seat <NUM> is indicated with a broken line <NUM> in <FIG>.

Mentioned as an example, in case of a circular valve seat <NUM> with a throughflow area having a diameter, d, and a circular membrane <NUM> having a diameter, D, the above mentioned ratio may be expressed as: <NUM> : (D x D /<NUM> - d x d /<NUM>) / (d x d / <NUM>).

The membrane <NUM> generally, may extend substantially in parallel with the plane <NUM> including the valve seat <NUM>. For instance, an abutment plane <NUM> of the membrane <NUM> configured to abut against the valve seat <NUM> may extend within a range of <NUM> - <NUM> degrees to the plane <NUM> including the valve seat <NUM>.

The abutment plane <NUM> of the membrane <NUM> is a plane of an abutment area of the membrane <NUM> configured to abut against the valve seat <NUM>. The abutment plane <NUM> of the membrane <NUM> is indicated with a broken line <NUM> in <FIG>.

The gas pressure regulating valve <NUM> further comprises a biasing member <NUM> arranged to bias the membrane <NUM> in a direction away from the valve seat <NUM>. In this manner, temperature dependency of the membrane characteristics may be evened out or at least reduced. Namely, in this manner, the physical properties of the membrane <NUM> and the biasing member <NUM>, together, determine the characteristics of the valve <NUM>.

In the illustrated embodiments, the biasing member <NUM> is schematically illustrated as a compression spring. That is, when the membrane <NUM> moves towards the valve seat <NUM> the compression spring is compressed by the membrane <NUM>. The spring force urging the compression spring to return to its initial length biases the membrane <NUM> in the direction away from the valve seat <NUM>.

Any alternative other suitable element may be utilised as biasing member <NUM>.

The biasing member <NUM> biases the membrane <NUM> into an open position permitting the gaseous phase to flow through the valve <NUM>, as shown in <FIG>. If however, a pressure downstream of the membrane <NUM> i.e., at the gas outlet <NUM>, is at such a low level that its resulting force affecting the membrane <NUM> exceeds a total force of the biasing member <NUM>, the force of the inherent resilience of the membrane <NUM>, and the force caused by the pressure affecting the membrane <NUM> upstream of the valve seat <NUM>, the valve <NUM> will close. The valve <NUM> will open again once the pressure difference between upstream and downstream the valve seat <NUM> is such that the total force of the biasing member <NUM>, the force of the inherent resilience of the membrane <NUM>, and the force caused by the pressure affecting the membrane <NUM> upstream of the valve seat <NUM> causes the membrane <NUM> to move away from the valve seat <NUM>.

According to some embodiments such as the illustrated embodiments, the gas outlet passage <NUM> from the separation space <NUM> may be connected to an inlet passage <NUM> of the gas pressure regulating valve <NUM>, wherein the inlet passage <NUM> leads to the valve seat <NUM>. In this manner, the gas outlet passage <NUM> from the separation space <NUM> may transition into the inlet passage <NUM> of the gas pressure regulating valve <NUM>.

According to embodiments such as the illustrated embodiments, the inlet passage <NUM> of the gas pressure regulating valve <NUM> may extend substantially perpendicularly to the plane <NUM> including the valve seat <NUM>. In this manner, the regulating valve <NUM> may be adapted to being positioned with the plane <NUM> of the valve seat <NUM> extending substantially tangentially with the separation space <NUM>. This in turn, provides for a compact separator <NUM> since also the membrane <NUM> thus, may be positioned to extend substantially tangentially with the separation space <NUM>. Accordingly, in this manner, the valve <NUM> may be designed for being arranged close to the housing <NUM> of the separator <NUM>.

According to embodiments such as the illustrated embodiments, a valve closing motion of the membrane <NUM> may be in a direction opposite to a direction of gas flowing into the gas pressure regulating valve <NUM>. This arrangement is a consequence of the membrane <NUM> being arranged downstream of the valve seat <NUM>.

The direction of gas flowing into the gas pressure regulating valve <NUM> is provided by the inlet passage <NUM> of the regulating valve <NUM> being directed towards the membrane <NUM>.

The direction of gas flowing into the regulating valve <NUM> has one physical direction as it flows through the inlet passage <NUM> of the regulating valve <NUM> to its valve seat <NUM>.

According to embodiments such as the illustrated embodiments, the gas pressure regulating valve <NUM> may comprise a gas outlet conduit <NUM> downstream of the membrane <NUM>, wherein the gas outlet conduit <NUM> may extend substantially in parallel with the membrane <NUM>. In this manner, a compact separator <NUM> may be provided since the gas outlet conduit <NUM> may be arranged to be directed in parallel with a tangent of the separation space <NUM> and the housing <NUM> of the separator <NUM>.

Depending on the relevant ICE, in relation to which the separator <NUM> is to be mounted, the gas outlet conduit <NUM> may be arranged to point in a suitable direction while extending substantially in parallel with the membrane <NUM>.

Further conduits (not shown) leading from the gas outlet conduit <NUM> to e.g., a turbocharger of the relevant ICE may have to be directed away from separator <NUM> in order to reach the turbocharger. However, the gas outlet conduit <NUM> extending substantially in parallel with the membrane <NUM> provides for the separator <NUM> to be easily positioned in relation to the ICE.

The expression "substantially in parallel with the membrane <NUM>" may in this context be e.g., within a range of -<NUM> to <NUM> degrees of a plane of the membrane <NUM>, such as the indicated abutment plane <NUM> or a general plane of the membrane <NUM>. As mentioned above, a general plane of the membrane <NUM> is a flat plane extending in parallel with a widest portion of the membrane <NUM>.

<FIG> schematically illustrate a gas pressure regulating valve <NUM> according to embodiments. The regulating valve <NUM> is a valve of a crankcase gas separator comprising a rotor, such as the separator <NUM> discussed above with reference to <FIG> and <FIG> shows a cross section through the valve <NUM> and <FIG> shows a top view of selected elements of the valve <NUM>.

The regulating valve <NUM> of <FIG> resembles in much the regulating valve <NUM> of <FIG>. Accordingly, in the following mainly the differences will be discussed.

Again, the valve <NUM> comprises a valve seat <NUM> and a membrane <NUM> configured to seal against the valve seat <NUM>. A gas outlet <NUM> for the gaseous phase of the relevant crankcase gas separator is arranged downstream of the membrane <NUM>.

Again, the regulating valve <NUM> provides a flow direction for gas from the gas outlet passage <NUM> through the gas pressure regulating valve <NUM>. In relation to the flow direction for gas from the gas outlet passage <NUM>, the membrane <NUM> is arranged downstream of the valve seat <NUM>.

Again, seen perpendicularly to a plane <NUM> including the valve seat <NUM>, a gas throughflow area within the valve seat <NUM>, and an area of the membrane <NUM> outside the valve seat <NUM> has a ratio within a range of <NUM> : <NUM> to <NUM> : <NUM>. The plane <NUM> including the valve seat <NUM> is indicated with a dash-dotted line <NUM> in <FIG>.

In <FIG>, the valve <NUM> is shown in an open state and the flow of the separated gaseous phase past the valve seat <NUM>, past the membrane <NUM>, and through the gas outlet <NUM> for the gaseous phase is indicated with arrows in <FIG>.

Again, the valve <NUM> comprises a biasing member <NUM> arranged to bias the membrane <NUM> in a direction away from the valve seat <NUM>.

In these embodiments, the biasing member <NUM> is schematically illustrated as a tension spring connected to the membrane <NUM> and a housing member of the valve <NUM>. Accordingly, when the membrane <NUM> moves towards the valve seat <NUM> the tension spring is extended by the membrane <NUM>. The spring force urging the tension spring to return to its initial length biases the membrane <NUM> in the direction away from the valve seat <NUM>.

Again, the gas outlet passage <NUM> from the separation space <NUM> may be connected to an inlet passage <NUM> of the gas pressure regulating valve <NUM>, the inlet passage <NUM> leading to the valve seat <NUM>.

Again, the inlet passage <NUM> of the gas pressure regulating valve <NUM> may extend substantially perpendicularly to the plane <NUM> including the valve seat <NUM>.

In this context, the expression "substantially perpendicularly to the plane <NUM> including the valve seat <NUM>" e.g., may relate to a minimum angle β between the plane <NUM> and a centre line <NUM> extending along the inlet passage <NUM> within a range of <NUM> to <NUM> degrees.

Again, the gas pressure regulating valve <NUM> may comprise a gas outlet conduit <NUM> downstream of the membrane <NUM>, the gas outlet conduit <NUM> extending substantially in parallel with the membrane <NUM>.

According to the embodiments of <FIG>, seen perpendicularly to a general plane <NUM> of the membrane <NUM>, a centre <NUM> of the membrane <NUM> is offset from a centre <NUM> of the valve seat <NUM>. In these embodiments, the centre <NUM> of the membrane <NUM> is offset from the centre <NUM> of the valve seat <NUM> towards the gas outlet conduit <NUM> and the gas outlet <NUM>.

A pressure drop in the valve <NUM> may thus be reduced in comparison with a membrane that is centred in relation to the valve seat.

The centre <NUM> of the membrane <NUM> and the centre <NUM> of the valve seat <NUM> are indicated with lines in <FIG>. The centre <NUM> of the valve seat <NUM> may coincide with the centre line <NUM> of the inlet passage <NUM>, as shown in <FIG>.

In <FIG>, the general plane <NUM> of the membrane is indicated to coincide with an abutment plane <NUM> of the membrane <NUM>. Again, the abutment plane <NUM> of the membrane <NUM> is a plane <NUM> of an abutment area <NUM> of the membrane <NUM> configured to abut against the valve seat <NUM>.

If the valve seat <NUM> has a generally circular shape, then also the abutment area <NUM> has a generally circular shape.

According to the embodiments of <FIG>, the plane <NUM> including the valve seat <NUM> and the plane <NUM> of the abutment area <NUM> of the membrane <NUM> are arranged at an angle α to each other.

For instance, the plane <NUM> of the abutment area <NUM> i.e., the abutment plane <NUM>, may extend within a range of <NUM> - <NUM> degrees to the plane <NUM> including the valve seat <NUM>.

The arrangement of the two planes <NUM>, <NUM> at the angle α may prevent vibrations in the membrane <NUM> and/or oscillating closing and opening movements of the membrane <NUM> against the valve seat <NUM>. Namely, as the membrane <NUM> moves into abutment with the valve seat <NUM>, the abutment area <NUM> of the membrane <NUM> will gradually come into contact with the valve seat <NUM>. That is, at first a contact area between abutment area <NUM> of the membrane <NUM> and the valve seat <NUM> will be small but if the pressure difference over the valve <NUM> increases, so will the contact area, until the abutment area <NUM> of the membrane <NUM> contacts the entire valve seat <NUM>.

Claim 1:
A crankcase gas separator (<NUM>) comprising a separator housing (<NUM>) delimiting at least part of a separation space (<NUM>),
a rotor (<NUM>) arranged in the separation space (<NUM>), wherein the rotor (<NUM>) comprises a separation aid in the form of a stack (<NUM>) of separation discs (<NUM>),
a gas outlet passage (<NUM>) from the separation space (<NUM>), and
a gas pressure regulating valve (<NUM>) arranged in fluid communication with the gas outlet passage (<NUM>), wherein
the gas pressure regulating valve (<NUM>) comprises a valve seat (<NUM>) and a membrane (<NUM>) configured to seal against the valve seat (<NUM>) and provides a flow direction for gas from the gas outlet passage (<NUM>) through the gas pressure regulating valve (<NUM>), and
characterized in that,
in relation to the flow direction, the membrane (<NUM>) is arranged downstream of the valve seat (<NUM>).