Patent Publication Number: US-11028742-B2

Title: Crankcase ventilation system for an internal combustion engine

Description:
BACKGROUND AND SUMMARY 
     The present invention relates to a crankcase ventilation system for an internal combustion engine comprising a crankcase. The invention also relates to an internal combustion engine comprising such a device. 
     When operating an internal combustion engine, it is necessary to handle the small amount of gases leaking past the piston rings of the cylinder and into a crankcase of the engine. The crankcase gas may in some applications be vented to the atmosphere, or as an alternative the crankcase gas may be fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. 
     However, before re-entering the combustion chamber or entering the atmosphere, the crankcase gas is typically cleaned, allowing for removal of small particles, solid and/or liquid, suspended in the crankcase gas. Different types of crankcase ventilation systems have been proposed, including passive type crankcase ventilation systems comprising some form of filter member or active type crankcase ventilation system including for example a centrifugal separator. 
     An exemplary passive type crankcase ventilation system is disclosed in U.S. Pat. No. 7,562,652. In U.S. Pat. No. 7,562,652, a hydrophobic, oleophobic membrane is used as the filter member for separating oil droplets from the crankcase gas before the crankcase gas exit the crankcase. The membrane allows air and other vapors to pass but separates the oil droplets out for return to the crankcase thus reducing oil loss through the crankcase emission control system. 
     An exemplary active type crankcase ventilation system is disclosed in EPI532353B1. In EP 1532353B1, solid and/or liquid particles are separated out from the crankcase gas. The separator has a conical rotor that is formed to a plate stack and is situated in a thereto provided housing, where the conical rotor is set into rotation by an electric motor. The crankcase gas that is to be cleaned enters the housing axially and flows through the rotor in the direction from radially inner to radially outer. The separated-out particles contact the inner surface of a circumferential wall of the housing of the centrifugal separator, and from there they are led downward by the action of gravity, to a separate outlet. The cleaned gas flows upward in the axial direction, to a cleaned gas outlet provided there. 
     The passive type crankcase ventilation systems will typically comprise less moving parts as compared to the active type crankcase ventilation systems, thus making the active type crankcase ventilation systems more prone to failure. On the other hand, the passive type crankcase ventilation systems may in some situations introduce an undesirable pressure drop of the crankcase gas, e.g. due to accumulation of contaminants at a surface of the filter member. In view of the above, there seems to be room for further improvements of crankcase ventilation systems provided for crankcase gas cleaning. 
     According to an aspect of the invention, the above is at least partly alleviated by a crankcase ventilation system for an internal combustion engine comprising a crankcase, the system comprising a first filter arrangement arranged for cleaning a crankcase gas generated during operation of the engine, wherein the system comprises a device for altering a temperature of the crankcase gas towards a desired temperature, at which the first filter arrangement is adapted for an efficient cleaning. 
     By means of the inclusion of a temperature altering device with the crankcase ventilation system, it is possible to adapt a temperature of the crankcase gas such that the first filter arrangement is allowed to operate where an effective level of cleaning of the crankcase gas is made possible, where the temperature may be targeted to the specific type of first filter arrangement. 
     Preferably, the first filter arrangement comprises a filter element for cleaning the contaminated crankcase gas. When a filter element is comprised with the first filter arrangement and adapted for cleaning of the crankcase gas, the temperature of the crankcase gas may for example be adapted such that the above mentioned undesirable pressure drop is achieved. 
     In an embodiment, the filter element is of an oleophobic type, preferably of a hydrophobic type, arranged to inhibit the passage of liquid contaminants comprised with the crankcase gas. An advantage of using such a filter element is that this type of filter element is less affected by liquid contaminants as compared to e.g. filter element comprising woven filter media, when it comes to accumulation of the contaminants at the surface of the filter element. 
     In a preferred embodiment the filter element is of an expanded oleophobic type. An advantage of using a filter element of the expanded oleophobic type as compared to the “non-expanded” oleophobic type of filter element as exemplified in above mentioned U.S. Pat. No. 7,562,652 is that an expanded oleophobic type filter element may be specifically arranged to have a customized expansion ratio that will help to balance the back pressure and venting requirements of the crankcase ventilation system. This is made possible since the expanded oleophobic type filter element may be provided with more even micro pore sizes as compared to the non-expanded oleophobic type of filter element. 
     In an embodiment the expanded oleophobic type filter element may be arranged as a membrane, for example manufactured from a modified acrylic copolymer cast on a thin, non-woven polyester support that is treated with an oleophobic/hydrophobic substance or a modified polyethersulfone polymer cast on a non-woven polyester support treated with an oleophobic/hydrophobic substance. Examples of such oleophobic/hydrophobic substances include fluoropolymers such as a fluorosulfone (e.g., polyfluorosulfone acrylate), a polyvinylidene fluoride, a polytetrafluoroethylene (PTFE), and most preferably an Expanded Polytetrafluoroethylene (ePTFE). In a specific embodiment a porosity of the membrane is at least 80%. 
     In an embodiment, the temperature altering device is adapted for controlling the temperature of the crankcase gas towards the desired temperature, preferably for cooling the crankcase gas. Cooling of the crankcase gas to a desired temperature, selected based on the type of filer element has shown to be advantageous, specifically where the filter element is of the expanded oleophobic type. 
     The temperature control may be provided using at least one or a combination of active and passive means. In an embodiment the temperature altering device comprises a first conduit arranged for connection to the crankcase at a first end and to the first filter arrangement at a second end, where for example the first conduit may be configured for active cooling of the crankcase gas flowing through the first conduit, for example using a fan. Alternative or also, the first conduit is configured for passive cooling of the contaminated crankcase gas flowing through the first conduit, for example by arranging the first conduit on a cool side of the engine. 
     In an embodiment, the temperature altering device further comprises a control unit and a temperature sensor, where the temperature sensor is electrically connected to the control unit and configured to measure a temperature of the crankcase gas. The control unit is further configured for comparing the sensed temperature with a predetermined threshold and to generate a control signal if the sensed temperature is above the predetermined threshold. Advantages with this embodiment includes the possibility of only cooling the crankcase gas once the temperature of the crankcase gas has reached a predefined temperature level (the predetermined threshold), thereby also ensuring that the temperature of the crankcase gas is kept high enough such that operation of the engine in e.g. winter conditions does not introduce possible icing problems due to water vapor comprised with the crankcase gas. This may for example be achieved by arranging the temperature altering device to further comprise a heat exchanger, preferably operatively connected with a cooling system of the engine. The heat exchanger may for example be operated/activated based on the mentioned control signal. 
     In an embodiment the filter element is arranged to have at least one of a spherical or a cylindrical form, preferably with a surface area of the filter element being at least 0.01 m2, preferably at least 0.015 m2. With the suggested form and surface area, in combination with the temperature altering device, an improved cleaning of the crankcase gas may be achieved while at the same time keeping the pressure drop below a desired pressure drop threshold. As mentioned above, when the filter element is of the expanded oleophobic type it is preferably arranged as a membrane. The membrane, when arranged in the spherical or the cylindrical form, is preferably arranged within a housing comprised with the first filter arrangement. 
     In a possible embodiment, the crankcase ventilation system further comprises a second filter arrangement corresponding to the first filter arrangement, wherein the second filter arrangement is arranged in series with the first filter arrangement, downstream of the first filter arrangement. Advantages with such an implementation is the possibility of further improving the cleaning of the crankcase gas, or for allowing the filter element provided with each of the first and the second filter arrangement to be selected to give an in comparison lower pressure drop as the cleaning may be split between the two filter arrangements. It may of course be possible to include more than a second filter arrangement with the disclosed crankcase ventilation system. 
     The first filter arrangement may be provided with a crankcase gas outlet, where the crankcase gas outlet of the first filter arrangement is connected to a crankcase gas inlet comprised with the second filter arrangement. Correspondingly, the first filter arrangement may be configured to comprise a crankcase gas inlet, typically connected to the first conduit as discussed above. A crankcase gas outlet may also be comprised with the second filter arrangement. As mentioned above, the first and the second filter arrangement may each comprise a housing, each housing comprising the mentioned gas inlet and gas outlet. 
     In an embodiment, the first (and also the second) filter arrangement further comprises a contaminant outlet provided at the housing and configured to release contaminants to an oil sump comprised with the engine. The contaminant outlet is preferably arranged at the mentioned housing. Accordingly, as the contaminants typically include oil droplets from the engine, they are thus allowed to be re-entered to the engine. 
     In a possible embodiment, the crankcase ventilation system is configured to recirculate the crankcase gas through the first filter arrangement. For example, if it is determined (e.g. by means of a thereto included sensor connected to the above mentioned control unit) that the crankcase gas has not been sufficiently cleaned; the crankcase gas may once again be allowed to pass through the first filter arrangement. This may for example be achieved using a controllable valve mechanism configured to adjust a level of crankcase gas recirculation based on a crankcase gas pressure. Possibly, the valve mechanism may be configured to be controlled based on a crankcase gas pressure in the crankcase. 
     In a possible embodiment, the crankcase ventilation system further comprises a fan configured to control a flow of the crankcase gas flowing through the first filter arrangement. Accordingly, such an implementation may further allow for the pressure drop of the crankcase gas to be minimized, or at least controlled to be within a desired range. 
     The crankcase ventilation system preferably forms part of an internal combustion engine. The internal combustion engine may in turn form part of a power train. The powertrain is preferably arranged in a vehicle, such as a heavy-duty vehicle, specifically in relation to a truck, a bus or any form of construction equipment. 
     Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled addressee realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which: 
         FIG. 1  illustrates a vehicle equipped with an internal combustion engine according to the invention; 
         FIG. 2  conceptually illustrates an internal combustion engine equipped with a crankcase ventilation system; 
         FIGS. 3 a  and 3 b    conceptually illustrates a first and a second embodiment of the crankcase disclosed ventilation system, and 
         FIGS. 4 a  and 4 b    conceptually illustrates a first and a second currently preferred embodiment of a filter element comprised with the crankcase ventilation system. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled addressee. Like reference characters refer to like elements throughout. 
     Referring now to the drawings and to  FIG. 1  in particular, there is depicted an exemplary vehicle, here illustrated as a truck  100 . The truck  100  is provided with a source of motive power  102  for propelling the truck via a driveline connecting the power source to the wheels. The power source  102  is constituted by an internal combustion engine (ICE) in the form of a diesel engine. It will in the following for ease of presentation be referred to as an internal combustion engine  102 . 
       FIG. 2  shows the internal combustion engine  102  equipped with a crankcase ventilation system  200  according to the invention. 
     During use of the ICE  102 , ambient air will be drawn though an air filter  202 , pass a turbo  204  and into an upper part of a cylinder  206 , above a piston  208 , where it will be mixed with a fuel, such as for example diesel or petrol. As the air/fuel mixture in the cylinder  206  is ignited, portions of the combustion gases will leak past the sides of the piston  208  (past piston ring(s) of the piston) and into a crankcase  210  comprised with the ICE  102 . 
     The combustion gases entering the crankcase  210  comprise contaminants, such as for example soot particles. The combustion gases will further come in contact with and be partly mixed with further contaminants comprised in the crankcase  210 , such as oil, forming a contaminated crankcase gas. A pressure formed by the combustion gases entering the crankcase  210  needs to be vented in a controlled manner, in accordance to the present disclosure through the crankcase ventilation system  200 . The crankcase gas is allowed to exit the crankcase  210  through an outlet  212 , for example arranged at an upper portion of the ICE  102 , other placements of such an outlet is of course possible and within the scope of the invention. 
     A first conduit  214  is provided for transporting the crankcase gas from the outlet  212  of the ICE  102  to an inlet  216  of the crankcase ventilation system  200 . The crankcase gas is cleaned inside of the crankcase ventilation system  200 , as will be further discussed below, and a cleaned crankcase gas will be released through a first outlet  218  of the crankcase ventilation system  200 . A fan function may be provided inside of and/or outside of the crankcase ventilation system  200  for assisting the transportation of the crankcase gas through the crankcase ventilation system  200 . The cleaned crankcase gas may for example, as illustrated in  FIG. 2 , be mixed with ambient air before entering the turbo  204 . A second conduit  220  may be provided for connecting the first outlet  218  of the crankcase ventilation system  200  to the turbo  204 . Alternatively, the cleaned crankcase gas may be allowed to enter the atmosphere, possibly passing through further filters members before doing so. 
     The contaminants/particles having been removed from the contaminated crankcase gas are preferably passed back to an oil sump comprised with the ICE  102  through a second outlet  222  of the crankcase ventilation system  200  and by a third conduit  224 . Furthermore, it should be noted that it is desirable to arrange some form of check valve (one-way valve) functionality between the second outlet  222  of the crankcase ventilation system  200  and the crankcase  210 , thereby only allowing contaminants to be passed back to the crankcase  210  and not allowing contaminated crankcase gases to be sucked “backwards” into the crankcase ventilation system  200 . 
     Turning now to  FIG. 3 a   , which illustrates an exemplary embodiment of a single stage crankcase ventilation system  200  that may be used together with the ICE  102 . In the illustrated embodiment, the crankcase ventilation system  200  comprises a first filter arrangement  300 . The first filter arrangement  300  in turn comprises a housing  302  having a gas inlet  304  and a gas outlet  306 . The first conduit  214  is arranged to be connected to the gas inlet  304  and the second conduit  220  is arranged to be connected to the gas outlet  306 . The housing  302  further comprises a contaminant outlet  308  arranged to be connected to the third conduit  224 . 
     The first filter arrangement  300  further comprises a filter element in the form of an expanded oleophobic membrane  310  formed as a cylinder, further discussed below in relation to  FIGS. 4 a    and  4   b.    
     In addition, the crankcase ventilation system  200  further comprises a passive temperature altering device, in the illustrated embodiment implemented by means of heat flanges  312  arranged together with the first conduit  214 . 
     During operation of the crankcase ventilation system  200 , the crankcase gas will be sucked from the crankcase, by the outlet  212  and through the first conduit  214 . When passing the first conduit  214 , ambient air for example by the first conduit  214  being arranged on a cold side of the ICE  102  (completely passive cooling) or in the vicinity of a fan (not shown, providing semi-passive cooling) comprised with the ICE  102  will alter the temperature of the crankcase gas, before the crankcase gas reaches the first filter arrangement  300 . The design of the heat flanges  312  may for example be selected such that the crankcase gas once reaching the first filter arrangement  300  has a desired temperature essentially matches a filtration temperature of the expanded oleophobic membrane  310  where the cleaning of the crankcase gas reaches is performed as is desired for the specific implementation. The temperature of the crankcase gas may for example be altered such that the amount of contaminants adhering to an inside surface of the expanded oleophobic membrane  310  is reduced, and/or such that a gas flow through the expanded oleophobic membrane  310  is kept above a predetermined threshold. In an embodiment, the heat flanges  312  are implemented such that the temperature of the crankcase gas is between 250-320 degrees C. once the crankcase gas reaches the first filter arrangement  300 . 
     Once the crankcase gas reaches the first filter arrangement  300 , the expanded oleophobic membrane  310  will inhibit the passage of e.g. liquid contaminants comprised with the crankcase gas. The liquid contaminants will accordingly “stay on the inside” of the cylindrically formed expanded oleophobic membrane  310 . The non-sticky properties of the expanded oleophobic membrane  310  will together with gravitation then force the liquid contaminants towards a downward pointing conical bottom section  316  of the housing  302  of the first filter arrangement  300 , eventually reaching the contaminant outlet  308 , to subsequently reach the oil sump  314  of the ICE  102 , for further use during operation of the ICE  102 . 
     In the illustrated embodiment the gas inlet  304  of the first filter arrangement  300  is further provided with a passage  318 , allowing the liquid contaminants to pass downward to the bottom section  316  of the housing  302 . The passage  318  is arranged to at least partly encircle the gas inlet  304  of the housing  302 . 
     In the illustrated embodiment the housing  302  comprises the mentioned bottom section  316  and a top section  320 . In a possible embodiment of the invention the bottom section  316  and the top section  320  may be separated (i.e. detachably connected), allowing the expanded oleophobic membrane  310  to be exchanged once its lifetime has passed, e.g. when performing service of the ICE  102 . Alternatively, all of the first filter arrangement is exchanges once the crankcase ventilation system  200  is serviced. 
     Turning now to  FIG. 3 b   , which illustrates an alternative exemplary embodiment of the crankcase ventilation system  200 , here presented in the form of a multi-stage crankcase ventilation system  200 ′. In addition to the first filter arrangement  300  comprised with the single stage crankcase ventilation system  200  shown in  FIG. 3 a   , the multi-stage crankcase ventilation system  200 ′ further comprises a second filter arrangement  322  corresponding to the first filter arrangement  300 , wherein the second filter arrangement  322  is arranged in series with the first filter arrangement  300 , downstream of the first filter arrangement  300 . 
     Preferably, the second filter arrangement  322  is arranged such that the gas outlet  306  of the first filter arrangement  300  is connected to a gas inlet  324  of the second filter arrangement  322 , comprised with a housing  326  of the second filter arrangement  322 . The second filter arrangement  322  further comprises a gas outlet  328  connected to the second conduit  220 . The second filter arrangement  322  further comprises a corresponding expanded oleophobic membrane  310  as comprised with the first filter arrangement  300 . 
     As mentioned, the crankcase ventilation system  200  shown in  FIG. 3 a    comprises a passive temperature altering device. In comparison, the crankcase ventilation system  200 ′ shown in  FIG. 3 b    is provided with an active temperature altering device, implemented by means of a heat exchanger  330 . In the illustrated embodiment, the heat exchanger  330  is arranged with the first conduit  214 , such that the crankcase gas is allowed to flow through the heat exchanger  330 . The heat exchanger  330  is in turn connected to e.g. a cooling circuit (not shown) of the ICE  102 . The flow of a coolant flowing through the heat exchanger  330  may be controlled by e.g. a valve  334  provided with the heat exchanger  330 . 
     During operation of the crankcase ventilation system  200 ′ shown in  FIG. 3 b   , a temperature of the crankcase gas may be monitored, for example using a temperature sensor  336  arranged at a vicinity to the gas inlet  324 . A control unit  338  may for example be arranged to sample a signal from the temperature sensor  336 , determine a temperature of the crankcase gas and comparing the determined temperature with a predetermined threshold. In case the temperature is outside of a predetermined threshold/temperature range (e.g. the above mentioned 250-320 degrees C.), the valve  334  may be controlled for increasing or decreasing the flow of the coolant flowing through the heat exchanger  330 , thereby altering the temperature of the crankcase gas towards the desired temperature/temperature range. It could also be possible to allow a heated fluid to be circulated through the heat exchanger  330 , thereby allowing the crankcase gas to be heated towards the desired temperature. 
     As mentioned above, by means of introducing the second filter arrangement  322 , it may be possible to adapt e.g. parameters of the expanded oleophobic membrane  310 , for example allowing a higher pass-through, providing less reduction of a pressure drop of the crankcase gas with e.g. the same level of cleaning of the crankcase gas. Alternatively, an increased cleaning of the crankcase gas may be implemented as the crankcase gas has to pass through two separate and essentially identical filter arrangements. 
     It should be understood that it also may be possible to alternatively arrange the first filter arrangement  300  in parallel with the second filter arrangement  322 . Such an implementation could allow for improved redundancy. In addition, liquid contaminants from both the first  300  and the second  322  filter arrangements may both be collected within the oil sump  314 . 
     Turning finally to  FIGS. 4 a  and 4 b   , conceptually illustrates a first and a second currently preferred embodiment of a filter element comprised with the crankcase ventilation system. 
     In the first embodiment of the filter element as shown in  FIG. 4 a   , the filter element is arranged as the cylindrically formed expanded oleophobic membrane  310 , for example shown in  FIGS. 3 a    and  3   b.    
     In the second embodiment of the filter arrangement as shown in  FIG. 4 b   , the filter element is arranged as a spherical formed expanded oleophobic membrane  402 . The form of the filter element is typically depending on the implementation at hand, and possible real-estate constraints posed when implementing the ICE  102  with the truck  100 . In any case and as mentioned above, it is desirable to select the form such that a surface area is large enough for only imposing a smaller pressure drop to the crankcase gas. In a specific embodiment the surface area of the filter element is at least 0.01 m2, preferably at least 0.015 m2. 
     In summary, the present invention relates to a crankcase ventilation system for an internal combustion engine comprising a crankcase, the system comprising a first filter arrangement arranged for cleaning a crankcase gas generated during operation of the engine, wherein the system comprises a device for altering a temperature of the crankcase gas towards a desired temperature, at which the first filter arrangement is adapted for an efficient cleaning. 
     By means of the inclusion of a temperature altering device with the crankcase ventilation system, it is possible to adapt a temperature of the crankcase gas such that the first filter arrangement is allowed to operate where an effective level of cleaning of the crankcase gas is made possible, where the temperature may be targeted to the specific type of first filter arrangement. 
     Even though the present disclosure has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art from a study of the drawings, the disclosure, and the appended claims. In addition, in the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.