Patent Publication Number: US-10774704-B2

Title: Engine head cover

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. § 119(b) to Japanese Application No. 2016-244000, filed Dec. 16, 2016, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an engine head cover. 
     (2) Description of Related Art 
     Conventionally, in a blowby gas recirculation structure of an engine, oil separated from a blowby gas by a filter or a maze (labyrinth) is returned to an inside of an engine through a return hole on a shielding plate that forms a blowby gas passage in a head cover. 
     SUMMARY OF THE INVENTION 
     In the above-described conventional art, oil or an oil mist reversely flowing from a return port of trapped oil flows directly from a blowby gas outlet to the intake system. Thus, there are concerns that not only an oil trapping rate (oil throw performance) deteriorates but also the oil consumption amount is increased. 
     An object of the present invention is to improve an engine head cover which includes a blowby gas passage having a PCV valve and a filter inside a head cover, by further devising a structure, to enable a flowdown of trapped oil to a valve chamber without deteriorating oil throw performance and increasing an oil consumption amount. 
     The present invention is an engine head cover which includes a blowby gas passage for guiding a blowby gas in a crankcase to an intake path through an inside of a head cover attached to a cylinder head, the engine head cover including: a pressure regulating valve disposed on an outlet side of the blowby gas passage; a filter disposed on an inlet side of the blowby gas passage; a labyrinth disposed between the pressure regulating valve and the filter in the blowby gas passage; and a recovery hole which causes a flowdown of oil trapped in the blowby gas passage, in which the recovery hole is formed at a portion on a downstream side of the filter and on a lower side of the labyrinth and the pressure regulating valve. 
     According to the present invention, the recovery hole is disposed at a portion below and away from the labyrinth or the pressure regulating valve at a terminal end portion of the flow of the blowby gas in the head cover. Therefore, even if oil or an oil mist reversely flows from the recovery hole, there is a level difference between the outlet of the blowby gas and the recovery hole and influence by the flow of the blowby gas is hardly received. Therefore, a flow of the reversely flowing oil from the outlet to the intake system is restricted as much as possible. 
     As a result, it is possible to provide an engine head cover which is improved to improve an oil trapping rate (oil throw performance) and reduce the oil consumption amount. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view illustrating an internal structure of a head cover; 
         FIG. 2  is a bottom view of the head cover in  FIG. 1 ; 
         FIG. 3  is a plan view of the head cover in  FIG. 1 ; 
         FIG. 4  is an enlarged cross-sectional view of a main portion illustrating a structure of a terminal end portion of a blowby gas passage; 
         FIG. 5  is an enlarged cross-sectional view of a main portion illustrating a head cover having a specification with an on-off valve; 
         FIGS. 6A and 6B  illustrate an on-off valve portion, where  FIG. 6A  is a cross-sectional view taken along line A-A in  FIG. 5 , and  FIG. 6B  is a bottom view; and 
         FIGS. 7A and 7B  illustrate a valve body, where  FIG. 7A  is a plan view, and  FIG. 7B  is a cross-sectional view taken along line A-A in  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of an engine head cover according to the present invention will be described with reference to the drawings in the case of a vertical multi-cylinder engine. Front, rear, left, and right sides of the engine in the case where a side of engine cooling fan (not illustrated) is the front side are illustrated in each figure for reference. 
     First Embodiment 
     As illustrated in  FIG. 1 , in a vertical multi-cylinder engine E, a cylinder head  2  is assembled to an upper portion of a cylinder block  1 . A cylinder head cover (hereinafter simply referred to as a head cover)  3  is assembled to an upper portion of the cylinder head  2 . A valve device (not illustrated) is formed in the cylinder head  2  in such a manner as to protrude upward from the cylinder head  2 . The head cover  3  is a component which covers the valve device (not illustrated) and serves as a lid for the cylinder head  2 . 
     As illustrated in  FIGS. 1 to 3 , the head cover  3  is provided with a partition plate (an example of a partition structure)  5  made of a steel plate which partitions an internal space into upper and lower portions. An upper space portion which is the upper portion of the partition plate  5  is formed in a blowby gas passage W having an inlet  6  which communicates with the interior of a crankcase  1 B and an outlet  7  which communicates with an intake path  9 . A portion inside the head cover  3  below the partition plate  5  is a housing space portion (valve chamber)  4  which covers the valve device (not illustrated). That is, the engine head cover includes a partition structure  5  which partitions an inside of the head cover  3  into upper and lower portions, and in which the upper portion forms the blowby gas passage W. 
     The head cover  3  having a rectangular shape which is long in a longitudinal direction in a plan view has a cross-sectional shape having a downward open U-shape. As illustrated in  FIG. 3 , an upper cover portion  3 A having a planar upper surface and which forms the blowby gas passage W is formed in a shape protruding upward from a lower cover portion  3 B. On a front side of the upper cover portion  3 A, an oil supply port  8  is formed so as to protrude upward from the lower cover portion  3 B. 
     As illustrated in  FIGS. 1 and 2 , the head cover  3  includes therein a plurality of reinforcing ribs extending downward. The plurality of reinforcing ribs include a left vertical rib  10  and a right vertical rib  11  extending in the longitudinal direction, and a coupling horizontal rib  12  which connect front end portions of the left vertical rib  10  and the right vertical rib  11 . The partition plate  5  is screwed in a state where the lid is placed over distal end surfaces (lower end surfaces) of the left and right vertical ribs  10  and  11  and the coupling horizontal rib  12 . The partition plate  5  includes a partition main body  5 A and an inlet plate  5   a  fixed to the partition main body  5 A. The inlet  6  of the blowby gas passage W is formed by a gap between the inlet plate  5   a  and a cover sidewall  3   s , i.e., a gap having a substantially C shape in a plan view. The inlet plate  5   a  may be made of a plate material having multiple holes such as a punching metal. 
     A filter  13  is disposed on the inlet side of the blowby gas passage W surrounded by the upper cover portion  3 A and the partition plate  5 , and traps oil contained as an oil mist in a blowby gas. The outlet  7  of the blowby gas passage W is a longitudinally and laterally extending opening formed at a front end portion of the upper cover portion  3 A. A PCV valve (an example of a pressure regulating valve)  14  is screwed to a taper thread formed at the outlet  7 . In addition, a labyrinth  15  is formed between the PCV valve  14  and the filter  13  in the blowby gas passage W and close to the PCV valve  14 , and causes the blowby gas to make a detour by a bent path. 
     The filter  13  is configured by a filter case  13 A and a pair of filter media  13   a  and  13   a  installed in the filter case  13 A, and is sandwiched between the upper cover portion  3 A and the partition plate  5  at the inlet side of the blowby gas passage W. Therefore, the blowby gas entering from the inlet  6  to the blowby gas passage W passes through the filter  13 , then flows toward the outlet  7  after the oil component is removed as much as possible. As the filter medium  13   a , various materials such as a metal mesh and a glass fiber can be used. 
     As illustrated in  FIGS. 1, 2, and 4 , the labyrinth  15  is formed by providing a partition member  18  made of the steel plate disposed immediately before the PCV valve  14 . The partition member  18  is bolted to a bolt seat  19  in a state where the partition member  18  is in contact with distal end surfaces (lower end surfaces) of a first horizontal rib  16  and the bolt seat  19  formed inside the upper cover portion  3 A. The first horizontal rib  16  is a rib wall which is formed over a short sidewall  21  on the front side of the upper cover portion  3 A, and the left vertical rib  10 , and is short in left and right directions. 
     The bolt seat  19  is formed at a bent middle portion of an L-shaped rib  17  formed over an oblique sidewall  20  having the outlet  7  and the left vertical rib  10 . A protrusion amount of the L-shaped rib  17  including a horizontal rib portion  17   a  and a vertical rib portion  17   b  is slightly smaller than that of the seat surface  19   a  of the bolt seat  19 . A gap between the horizontal and vertical rib portions  17   a ,  17   b  and the partition member  18  is configured as a bent maze, and a labyrinth  15  which guides the blowby gas to the PCV valve  14  by causing the blowby gas to make a detour. 
     As illustrated in  FIGS. 1 to 4 , the PCV valve  14  is screwed to the outlet  7  formed by the taper thread formed in the above-described oblique sidewall  20  of the upper cover portion  3 A, and also substantially serves as the outlet of blowby gas passage W. As illustrated in  FIG. 1 , the blowby gas having passed through the PCV valve  14  is recirculated to the intake path  9  through a blowby path  22  such as a tube. 
     As illustrated in  FIG. 1 , the blowby gas from the crankcase  1 B enters from the housing space portion  4  in the blowby gas passage W through the inlet  6 . The blowby gas having passed through the filter  13  disposed near the inlet  6  passes through the labyrinth  15 , passes through the PCV valve  14  which is the outlet  7 , and then recirculates to the intake path  9 . The blowby gas passage W includes a passage main portion  34  which extends between the filter  13  and the labyrinth  15  and below the labyrinth  15 , and a PCV front chamber (an inlet portion of the PCV valve  14 )  35  which includes the outlet  7  surrounded by the partition member  18  and the labyrinth  15 . 
     As illustrated in  FIGS. 1, 2 and 4B , a recovery hole  23  which causes a flowdown of oil trapped in the blowby gas passage W is formed at a portion on a downstream side of the filter  13  in a flow direction of the blowby gas in the blowby gas passage W and on a lower side of the labyrinth  15  and the PCV valve  14 . More specifically, at a portion at a side next to the upper cover portion  3 A and immediately below the PCV valve  14 , the recovery hole  23  is formed in a hanging portion  24  having a vertically elongated columnar shape and formed protruding downward while penetrating a circular hole  5   b  of the partition plate  5  from a ceiling wall  4   a  of the housing space portion  4  of the head cover  3 . A reinforcing wall  36  is formed at a portion of the ceiling wall  4   a  corresponding to the hanging portion  24 , and bulges slightly upward. 
     A vertically elongated hole  25  is formed upward from a bottom surface  24   a  in the hanging portion  24 . A horizontal hole  26 , which communicates with an upper end portion of the vertically elongated hole  25  and is open in the blowby gas passage W, is formed. That is, the recovery hole  23  is formed by the vertically elongated hole  25  and the horizontal hole  26 . Further, the lowest point (hole bottom) of the horizontal hole  26  is set slightly higher than the upper surface of the partition plate  5  by a height h. 
     Due to a continuous operation of the engine E, scattered oil trapped mainly by the filter  13  accumulates on the partition plate  5  in the blowby gas passage W. As illustrated in  FIG. 1 , when the oil accumulates at the height h or more on the partition plate  5 , the oil passes from the horizontal hole  26  through the recovery hole  23  and flows down (drops) to the housing space portion  4 . In addition, while the engine E is stopped, it is possible to cause oil which accumulates in a short time to flow down from the recovery hole  23 . 
     A differential pressure between the blowby gas passage W and the housing space portion  4  during the operation of the engine E is approximately 10 mmAq. A long-term continuous operation stabilizes an oil surface at a head (vertical difference) corresponding to 10 mmAq from the horizontal hole  26  (from the height h) (see  FIG. 1 ). The vertically elongated hole  25  is opened at a position of the housing space portion  4  where a component (a rocker arm or a retainer) which scatters the oil is not present, to reduce the flow of the oil mist from the recovery hole  23  into the blowby gas passage W without passing through the filter  13 . 
     In addition, the presence of the recovery hole  23  which short-circuits the blowby gas passage W and the housing space portion  4  is likely to cause air bubbles to escape from the horizontal hole  26  to the blowby gas passage W, and scatter the oil. However, the labyrinth  15  is located with respect to the recovery hole  23  in the flow direction of the blowby gas and on the upstream side, so that the following operation and effect are obtained. 
     That is, the partition member  18  which partitions the labyrinth  15  and the PCV valve  14 , and the recovery hole  23  into the upper and lower sides serves as a partition wall. The horizontal hole  26  communicates with (or is directly connected to) the blowby gas passage W at a portion between the filter  13  and the labyrinth  15 . That is, the horizontal hole  26 , and the PCV front chamber  35  which is an inlet portion of the PCV valve  14  communicate via the labyrinth  15  in a detour. Reverse flow air bubbles from the recovery hole  23  join as a flow in a direction opposite to the flow of the blowby gas. Therefore, the presence of the labyrinth  15  whose flow direction is different in a detour and which exhibits the function of shaking off the oil mist by the maze provides an effect of minimizing a negative influence that the scattered oil from the recovery hole  23  which does not pass through the filter  13  reaches the outlet  7 . 
     In addition, the partition member  18  which serves as a partition wall against the reverse flow oil mist from the recovery hole  23  is formed as a structure which forms the labyrinth  15 . Consequently, it is possible to provide an advantage of realizing rationalization such as cost reduction and efficient utilization of space as a result of use of members in combination. That is, the engine head cover includes a partition member  18  which partitions the labyrinth  15  and the pressure regulating valve  14 , and the recovery hole  23  into upper and lower sides to communicate a portion between the filter  13  and the labyrinth  15  in the blowby gas passage W, and the recovery hole  23 . 
     In addition, air bubbles may escape from the horizontal hole  26  to the blowby gas passage W, scatter the oil and increase the carryover. That is, the height of the oil accumulated on the partition plate  5  may rise to approximately the height H position indicated by a virtual line in  FIG. 1 . 
     However, the scattered oil is likely to flow together with the air bubbles from the recovery hole  23  into the blowby gas passage W. However, the labyrinth  15  is disposed on the upstream side in the flow direction of the blowby gas and is located above with respect to the horizontal hole  26 . Consequently, the partition member  18  serves as the partition wall to minimize the influence of the scattering oil. 
     Second Embodiment 
     As illustrated in  FIGS. 5, 6A, and 6B , the head cover  3  may include an on-off valve  27  provided at a lower portion of a recovery hole  23 . The head cover  3  according to the second embodiment is the same as the head cover of the first embodiment illustrated in  FIG. 1  except that the on-off valve  27  is added. The on-off valve  27  provided at the lower portion of the recovery hole  23 , more specifically, at a lower end portion of a vertically elongated hole  25  is formed by a lower end portion  24 A of the hanging portion  24  and a valve body  28 . 
     As illustrated in  FIG. 5 , the valve body  28  having an axial center P includes a valve main body portion  28 A which is slidably fitted to the vertically elongated hole  25 , a valve flange portion  28 B which is slidably fitted in a large diameter hole portion  25 A at a lower end of the elongated hole  25 , and a hole portion  29  which is recessed upward. In an outer peripheral portion of the valve main body portion  28 A, vertical slits  30  which open upward and terminate in the valve flange portion  28 B are formed, and laterally extending communication holes  31  which opens in a hole portion  29  and penetrates in a radial direction is formed. The large diameter hole portion  25 A is provided with a circlip  32  which prevents the valve body  28  from falling down. 
     The structure of the valve body  28  will be described in detail. As illustrated in  FIGS. 7A and 7B , the four vertical slits  30  in total are formed per equal angle (90 degrees) in a circumferential direction with respect to the axial center P, and outer circumferential surfaces  28   a  which are fitted with the vertically elongated hole  25  are formed at four portions between the neighboring vertical slits  30 . The above-described communication holes  31  are formed at two portions penetrating the two of the four outer circumferential surfaces  28   a , two outer circumferential surfaces  28   a  and  28   a  having circumference lengths slightly long and being opposed to each other. 
     An upper end corner peripheral portion of the valve main body portion  28 A and an upper end corner peripheral portion of the valve flange portion  28 B are chamfered. The circumferential upper surface  25   a  of the large diameter hole portion  25 A and the chamfered portion  37  of the valve flange portion  28 B are chamfered at the same angle to enable surface contact. When the valve body  28  is raised to a highest position (a position indicated by a virtual line in  FIG. 5 ), the circumferential upper surface  25   a  and the chamfered portion  37  come into surface contact with each other to form a seal portion. The hole portion  29  has a large diameter opening hole portion  29   a  and a tapered hole portion  29   b  whose diameter is reduced from the large diameter opening hole portion  29   a  in the valve flange portion  28 B. 
     As shown in  FIGS. 5 and 6A , the on-off valve  27  is located at a lowermost position at which the valve body  28  is supported by the circlip  32  in a free state. An upper portion of the valve body  28  in the vertically elongated hole  25  and the hole portion  29  communicate with each other via the vertical slits  30 , a circumferential space portion  33  formed at an upper side of the valve flange portion  28 B in the large diameter hole portion  25 A, and a communication hole  31 . Therefore, oil recovered on the partition plate  5  can flow down through the recovery hole  23  and the on-off valve  27 , and can be recovered. 
     During operation of an engine E, a differential pressure between the blowby gas passage W and the housing space portion  4  moves the valve body  28  upward, the circumferential upper surface  25   a  and the chamfered portion  37  come into contact with each other, and the on-off valve  27  is placed in a closed state (a state where the valve body  28  is raised to the position of the virtual line illustrated in  FIG. 5 ). This closed valve state prevents a reverse flow from the recovery hole  23  to the blowby gas passage W. 
     Then, when the recovered oil accumulated on the partition plate  5  is a prescribed amount (e.g., a head difference of approximately 25 mm Aq of a ventilation resistance of a filter  13 ) or more, the above differential pressure disappears, the valve body  28  is lowered until the valve body  28  comes into contact with the circlip  32 , and the on-off valve  27  is placed in an open state. In this open state, the oil flows down to the housing space portion  4 . Even while the engine E is stopped, the on-off valve  27  is in the open state. 
     An on-off valve  27  which is opened when a differential pressure between a pressure of the blowby gas passage W and a pressure of the housing space portion  4  becomes smaller than a predetermined value, and is closed when the differential pressure becomes larger than a predetermined value is provided at a lower end portion of the recovery hole  23 . Consequently, during the operation of the engine E, a reverse flow from the recovery hole  23  is prevented. In addition, when the recovered oil accumulates in the blowby gas passage W to some extent, it is possible to cause the oil to flow down from the blowby gas passage W to the housing space portion  4  through the recovery hole  23 . 
     Therefore, oil or an oil mist reversely flowing from the recovery hole  23  are restricted from flowing directly from the outlet  7  into the intake path  9 . As a result, an oil trapping rate (oil throw performance) is further improved, and the oil consumption amount is drastically reduced, so that it is possible to provide a further improved engine head cover.