Patent Publication Number: US-7900612-B2

Title: Valve and cylinder head cover for crankcase ventilation of an internal combustion engine

Description:
The invention relates to a valve for crankcase ventilation of an internal combustion engine, and a cylinder head cover with such valve integrated. 
     Valves for crankcase ventilation are known for instance from DE 101 53 120 A1 and JP 2003 090207 A. The respective valve is made as a check valve. It is therefore not possible to provide deventilation of the crankcase, which can be desirable particularly for full-load operation, via the ventilation line. 
     U.S. Pat. No. 5,499,604 discloses a PCV-valve in a deventilation line connected upstream of the throttle valve. Known PCV-valves (see for instance U.S. Pat. No. 2,407,178, U.S. Pat. No. 3,766,898, U.S. Pat. No. 4,686,952, US 2003-0213479 A1), however, are disadvantageous in that, due to the comparatively large mass of the valve cone to be moved and the necessity of a thrust spring, they work relatively inert and do not therefore satisfy the requirements of modern engine control. In addition, the opening cross-section depends on the respectively prevailing excess pressure. 
     An air valve to be installed between the crankcase and the intake section is known from DE 10 2005 043 735 A1, which comprises a valve disc that is pre-loaded by means of a spring. When crankcase deventilation is functioning properly, the valve disc keeps the valve closed under the thrust of the pre-loaded spring. When crankcase deventilation does not function properly, the valve element will be lifted by the excess pressure inside the crankcase against the force exerted by the spring so that the valve acts in the deventilation direction as an excess-pressure limiting valve. 
     Umbrella-shaped ventilation/deventilation valves with an umbrella part made of flexible material are known from GB 1 514 237, U.S. Pat. No. 3,159,176, WO 2005 116497 A1, WO 98 20236 A1, JP 61 016218 A. When excess pressure prevails under the umbrella part then the umbrella part will be lifted up under flexible deformation in order to open passage orifices. Such umbrella-type valves also react relatively inertly owing to the restoring force of the umbrella-type part which has to be overcome, and the open cross-section of the orifice depends on the prevailing excess pressure. Furthermore, such umbrella-type valves are prone to wear because of permanent deformation. 
     Laid-open document DE 1 916 788 discloses a ventilation system for crankcase with an ventilation check valve and a separate deventilation check valve. The check valves are formed in an embodiment with a plate made of flexible material; in case excess pressure prevails under the plate, said plate will be lifted by means of flexible deformation in order to open the passage orifices. In a further deventilation line connected underneath the throttle valve a device for regulating the flow rate can be provided, which is formed in an embodiment of a sphere and a pipe piece with sections that protrude inwards. Sludge that would otherwise collect inside the pipe piece is expelled or removed through the reciprocating movement of the sphere. 
     Laid-open document DE 1 149 957 discloses a safety valve, in particular, for a low-pressure steam generator that works in an open position as a ventilation/deventilation valve. The valve body is displaced in a sealing position when a certain excess pressure value is reached, however, as soon as permissible maximum pressure is reached; it is displaced into a safety deventilation position against the restoring force of an elastic collar. 
     DE 27 02 621 A1 discloses a lid for the oil filling nozzle with an air valve pre-loaded by means of a spring and a separate deventilation valve formed as a flexible umbrella valve. 
     The object of the invention is to provide a quick and cost-effective valve for efficient ventilation/deventilation of the crankcase. 
     The invention solves this object. Owing to the omission of a thrust spring for the valve body, the valve body can be displaced rapidly from one limit stop position to the other. Even when only slight pressure differences prevail, the valve body will be displaced into the respective limit stop position and it will open a defined flow cross-section, wherein the opened flow cross-section does not depend on the magnitude of the pressure difference between the fresh-air side and the engine side, so that adequate deventilation/ventilation is provided for small pressure differences as well. 
     The change of flow cross-section is achieved only through the displacement of the valve insert as a whole. “As a whole” means that all parts that are firmly connected with the valve insert will be displaced together with it. In particular, the change of the flow cross-section can be attained without deformation of the valve insert, for instance, as it is the case with conventional umbrella-type valves. Due to the displacement of the valve insert without deformation is the opened flow cross-section independent of the then acting pressure. In addition, wear due to deformation is avoided. 
     It is essential for the invention to be able to set the flow cross-section in the deventilation direction differently from the flow cross-section in the ventilation direction. In the ventilation direction, particularly in near-idling operation, the fresh air quantity by-passed at the throttle valve can make the engine control more difficult, whilst in the deventilation direction, particularly at near-full throttle operation, a flow cross-section that is as large as possible is desired in order to avoid impermissible high excess pressure inside the crankcase. It is therefore advantageous if the valve insert at the limit stop in the deventilation direction opens a larger flow cross-section than at the limit stop in the ventilation direction. Larger cross-section preferably implies at least 25%, further preferably at least 50% greater size. Under certain conditions, it can be appropriate, however, also if the flow cross-section in the ventilation direction is greater than the flow cross-section in deventilation direction. 
     In view of a reduced weight and thus smaller inertia, the valve insert preferably consists of plastic, a thermoplastic elastomer and/or an elastomer. The valve insert can also be made of a combination of suitable materials, for instance, a shaft made of plastic and a disc made of thermoplastic elastomer or elastomer. The valve insert is not restricted to the above-mentioned materials, for instance, also a light metal comes in question. 
    
    
     
       The invention is explained as follows, based on advantageous embodiments with reference to the attached figures which show: 
         FIG. 1 : an internal combustion engine with an intake section and an essentially closed throttle valve; 
         FIG. 2 : an internal combustion engine with an intake section and an opened throttle valve; 
         FIG. 3 : a throttle valve in the ventilation limit-stop position; and 
         FIG. 4 : a throttle valve in the deventilation limit-stop position. 
     
    
    
     The internal combustion engine  10  depicted in  FIGS. 1 and 2  comprises oil sump  11 , crankcase  12 , cylinder  13 , cylinder head  14  and cylinder head cover  15  with oil separator  16  and pressure control valve  17 . Blow-by gases are passed via channels  18  inside the engine block to a gas inlet  19  into the cylinder head cover  15  and pass through the oil separator  16  where separated oil flows back through the oil return line  20  into the engine oil circuit and the cleaned gas is passed via the pressure control valve  17  and a deventilation line  22  back into the intake section  21 . 
     In addition to the above-described deventilation of the crankcase  12 , ventilation of the crankcase  12  is provided via line  23  connecting the intake section  21  with the crankcase  12 . This is particularly appropriate for Otto engines in which the water and/or the fuel content in the blow-by gas is comparatively high. 
     Should the ventilation occur through line  23  without external power, then pressure gradient is required from the point of fresh air supply from the intake section  21  up to the introduction of air enriched with water and fuel vapours together with the blow-by gas in the intake section  21  via line  22 . In general, the line  23  for fresh air supply therefore branches from the intake section  21  after the air filter  24  and before the throttle valve element  25  with the throttle valve  26 , whilst the line  22  for discharge leads into the intake section  21  after the throttle valve element  25 . “Before” and “after” thereby refer to the flow direction of combustion air. 
     The precondition for ventilation is furthermore a sufficient pressure gradient between the tapping point before and the discharge point after the throttle valve element  25  that is at least present for a partially closed throttle valve  26 . Ventilation is therefore only possible in the idling state with a closed throttle valve  26  or in a partial-load operation state with a partially closed throttle valve  26 , as shown in  FIG. 1 . 
     In particular, in near-idling operation, the fresh air volume bypassing the throttle valve  26  via the lines or channels  23 ,  18 ,  22  can make engine control to become more difficult. To counteract this effect, a valve  27  for metering the fresh air volume for ventilating the crankcase  12  is located in line  23 . 
     By further opening the throttle valve  26 , i.e., by increasing the load up to full engine load, the pressure rises inside the crankcase  12  above the pressure upstream of the throttle valve  26  due to the increase of blow-by gases. Valve  27  is realised as a two-way element so that the flow direction in line  23  for deventilating the crankcase can reverse. Line  23  therefore serves as a ventilation and deventilation line depending on the pressure relations. 
     A preferred embodiment of valve  27  is shown in the  FIGS. 3 and 4 . The valve  27  comprises a pipe-shaped housing part  28  and particularly a housing wall part  38  that separates a fresh-air side  39  of the valve  27  from an engine side  40 . The housing wall part  38  is appropriately essentially perpendicular to the flow direction through valve  27 . 
     On a fresh-air-side end  39 , the tubular housing part  28  for instance can feature a hose connection nipple  36  for connecting a hose  37  for connection with the intake section  21 . 
     The engine side  40  of valve  27  is in connection with the engine crankcase  12 . When valve  27  is a separate component, this can be a hose connection  42  for instance (see  FIGS. 1 and 2 ). When, as shown in the preferred embodiment according to  FIGS. 3 and 4 , valve  27  is integrated in the cylinder head cover  15 , in which the engine side  40  of valve  27  is particularly located in the gas inlet  19  section of the cylinder head cover, then the engine side  40  is connected via channel  18  for the blow-by gas with the crankcase  12  and an additional, external hose or line connection is dispensable. 
     A valve insert  31  is movably mounted in valve  27 . To be precise, the valve insert  31  comprises a shaft  32  that is mounted in a movable manner in a bore  30  of housing wall part  38 . 
     Valve insert  31  further comprises a first limit stop, here in the form of disc  34  on the fresh-air-side end of shaft  32  and a further limit stop  35  on the opposite engine-side end of shaft  32 . The other limit stop  35  in the present example is formed by hook-shaped tongues on the engine-side end of the valve insert  31 . Using the hook-shaped tongues  35  the valve insert  31  can be latched from the fresh-air side  39  into the bore  30  and is then held inside via a corresponding clip-type connector such that it cannot get lost. 
     Inside the housing wall part  38  there are other passage openings  41  provided radially outside the bore  33 , however within the surface covered by the disc  34 . 
     When the pressure on the fresh-air side  39  of the valve  27  is higher than the pressure on the engine side  40 , the valve insert will be shifted automatically into the limit-stop position depicted in  FIG. 3 , in which the disc  34  comes in contact with the housing wall part  38  and thereby covers the passage openings  41 . In this limit-stop position, fresh air can be supplied to crankcase  12  through a passage bore  33  of the shaft with a defined cross-section. “Automatically” means without additional control means and without external power, solely based on pressure difference. 
     When, on the other hand, the pressure on the fresh-air side  39  of valve  27  is lower than the pressure on the engine side  40 , then the valve insert will be lifted automatically in the opposite limit-stop position, as depicted in  FIG. 4 , in which the hook-shaped tongues  35  come in contact with the housing wall part  38 . In this limit-stop position, the flow direction is reversed and blow-by gas can be discharged, on the one hand, through the passage bore  33  of the shaft out of crankcase  12 . Simultaneously, the disc  34  opens the passage openings  41  so that blow-by gas can be additionally discharged through the passage openings  41  from the crankcase  12 . The flow cross-section is therefore larger in the deventilation direction than the flow cross-section in ventilation direction, by a magnitude equal to the flow cross-section of passage openings  41 . By means of this, efficient deventilation and throttled ventilation of the crankcase can be achieved with regard to stable engine control. 
     As described earlier, there are only two stable positions for the valve insert  31  based on the two limit-stop positions, namely deventilation and ventilation position. Between these two stable positions, the valve insert  31  is freely movable without, for instance, having to overcome a pre-load force exerted by a spring. Just a small pressure difference between the fresh air and the engine side of valve  27  is enough for the valve insert  31  to be shifted into the corresponding limit-stop position and to open the cross-section for maximum deventilation or ventilation. In this regard, the valve  27  differs from the ventilation valve according to DE 10 2005 043 735 A1, in which the valve body must be moved against the force of a thrust spring in the ventilation direction and the maximum ventilation cross-section only opens under substantial excess pressure inside the crankcase. 
     In a not shown embodiment passage openings can be provided between the fresh-air side  39  and the engine side  40 , instead of or in addition to the passage bore  33  of the valve insert  31 , which are opened independently of the position of the valve insert  31 . The shaft  32  therefore must not necessarily be a hollow shaft; it can also be solid. 
     In the embodiments shown in the Figures, the valve is integrated in the cylinder head cover  15 . However, the valve may also be contained in a separate unit. 
     All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification. 
     It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.