Patent Publication Number: US-10774706-B2

Title: Internal combustion engine

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to an internal combustion engine provided with a blow-by gas treating device. 
     2. Description of Related Art 
     Japanese Laid-Open Patent Publication No. 10-184336 discloses an internal combustion engine provided with a blow-by gas treating device. The blow-by gas treating device includes a blow-by gas passage and a communicating passage. The blow-by gas passage connects a section of the intake passage on the downstream side of the throttle valve to the head cover. The communicating passage connects a section of the intake passage on the upstream side of the throttle valve to the head cover. The internal combustion engine has a pressure sensor that detects an anomaly in the blow-by gas treating device such as line disconnection. Specifically, the pressure sensor provided in the blow-by gas passage detects the pressure in the blow-by gas passage. An anomaly is detected based on a change in the detected pressure. 
     In a configuration that detects line disconnection based on a change in the pressure detected by a pressure sensor, line disconnection cannot be detected if a change in the pressure before and after the line disconnection is small enough to be within the range in which it is determined that anomaly is not occurring. 
     For example, assume that a section of the intake passage on the downstream side of the throttle valve is at a negative pressure during operation of the internal combustion engine. If the blow-by gas passage is disconnected at the joint with the intake passage, the blow-by gas passage is opened. If a pressure sensor is provided in the blow-by gas passage as in the case of the internal combustion engine described in the above publication, line disconnection can be detected since the detection value of the pressure sensor is changed to approach the atmospheric pressure. In contrast, if the blow-by gas passage is disconnected at the joint with the head cover, the blow-by gas passage, to which the pressure sensor is connected, is maintained to be connected to the section of the intake passage on the downstream side of the throttle valve. If the pressure sensor is maintained to be connected to the section of the intake passage on the downstream side of the throttle valve, there is only a small change in the pressure before and after line disconnection occurs. Line disconnection thus may be undetectable. 
     Also, in a case in which a pressure sensor is provided in a passage connected to a section of the intake passage on the upstream side of the throttle valve as in the case of the communicating passage of the internal combustion engine described in the above publication, line disconnection may be undetectable. For example, assume that the interior of the head cover is at a negative pressure during operation of the internal combustion engine. When the communicating passage is disconnected at the joint with the intake passage while the communicating passage and the head cover are maintained to communicate with each other, there is only a small change in the pressure before and after the occurrence of line disconnection. Line disconnection thus may be undetectable. 
     As described above, depending on the location where line disconnection occurs, a change in the detection value of the pressure sensor is small, and the line disconnection may be undetectable. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In a general aspect, an internal combustion engine including a blow-by gas treating device is provided. The blow-by gas treating device includes a blow-by gas passage, a separator, an intake connection line, and a pressure sensor. The blow-by gas passage is configured to release blow-by gas that has leaked to a crankcase from a combustion chamber of the internal combustion engine to a section of an intake passage that is on a downstream side of a throttle valve. The separator is configured to separate oil from the blow-by gas. The intake connection line connects the intake passage to the separator. The pressure sensor is configured to detect pressure in the intake connection line. The separator includes a line connection portion. The line connection portion includes an intake connection union, a sensor connection union, a partition plate, and a constriction. The intake connection union is attached to the intake connection line. The pressure sensor is connected to the sensor connection union. The partition plate divides a space in the separator into a first space and a second space. The constriction is provided in the partition plate and allows the first space and the second space to communicate with each other. The line connection portion is constituted by combining a first unit, which includes the partition plate and defines the first space, and a second unit, which defines the second space with the partition plate of the first unit. The intake connection union and the sensor connection union are provided in the second unit. 
     With the above-described line connection portion, the sensor connection union, to which the pressure sensor is connected, is provided at a position closer to the intake connection union than the constriction. Thus, in both of a case in which the intake connection line is disconnected at the joint with the intake passage and a case in which the intake connection line is disconnected at the joint with the line connection portion, the part in which the sensor connection union is provided is exposed to the atmosphere after the intake connection line is disconnected. The detection value of the pressure sensor thus readily approaches the atmospheric pressure. That is, when the intake connection line is disconnected, the line disconnection is detected through a change in the detection value of the pressure sensor. 
     In one example of the above-described internal combustion engine, when the internal combustion engine is in a position of being mounted, the sensor connection union is located vertically above the constriction. 
     In the internal combustion engine of the above-described configuration, oil can enter the line connection portion when the blow-by gas that has leaked to the crankcase from the combustion chamber flows toward the intake connection line. This may cause the oil to collect on the pressure sensor, reducing the detection sensitivity of the pressure sensor. 
     With the above-described configuration, the sensor connection union is located vertically above the constriction even if oil enters the second space after passing through the constriction together with blow-by gas. This prevents the oil that has entered the second space from reaching the pressure sensor after passing through the sensor connection union. Accordingly, oil is prevented from collecting on the pressure sensor. That is, the above-described configuration limits reduction in the detection sensitivity of the pressure sensor and thus limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor. 
     In one example of the above-described internal combustion engine, a central axis of an opening of the constriction is defined as a first central axis, and a central axis of the sensor connection union is defined as a second central axis. The constriction and the sensor connection union are arranged at positions where the first central axis and the second central axis are displaced from each other. 
     The above-described configuration prevents blow-by gas from directly flowing into the sensor connection line after flowing into the second space through the constriction. In other words, the blow-by gas that flows into the second space after passing through the constriction readily strikes the inner wall of the second unit. This allows oil to be separated from the blow-by gas, thereby limiting reduction in the detection sensitivity of the pressure sensor due to the flow of blow-by gas containing oil toward the pressure sensor. That is, the above-described configuration limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor. 
     In one example of the above-described internal combustion engine, a central axis of the intake connection union is defined as a third central axis. The constriction, the sensor connection union, and the intake connection union are arranged at positions where any two of the first central axis, the second central axis, and the third central axis do not intersect with each other. 
     The above-described configuration prevents blow-by gas from directly flowing into the sensor connection line after flowing into the second space through the constriction. Also, the above-described configuration prevents blow-by gas from directly flowing into the intake connection line after flowing into the second space through the constriction. That is, the blow-by gas that flows into the second space after passing through the constriction readily strikes the inner wall of the second unit. Accordingly, oil is separated from the blow-by gas. This restricts the flow of blow-by gas containing oil toward the pressure sensor, thereby limiting reduction in the detection sensitivity of the pressure sensor. Further, the above-described configuration prevents the blow-by gas containing oil from being released into the intake passage. 
     In one example of the above-described internal combustion engine, when the internal combustion engine is in the position of being mounted, the second unit is located vertically above the first unit, and the partition plate constitutes a floor surface of the second space. The partition plate is inclined such that a section in which the constriction is provided is located at a lowest position. 
     The oil contained in the blow-by gas that has flowed into the second space strikes the wall surface of the second unit to be separated, and dribbles down to the partition plate, which constitutes the floor surface of the second space. The above-described configuration allows the oil that has dribbled down to the partition plate to flow down to the constriction under its own weight. Thus, when the operation of the internal combustion engine is stopped and inflow of blow-by gas to the second space through the constriction is stopped, the oil stored in the second space is returned to the first space, which is adjacent to the separator, through the constriction. This prevents the oil from flowing into the sensor connection line and the intake connection line. That is, the above-described configuration limits reduction in the detection sensitivity of the pressure sensor and thus limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor. 
     In one example of the above-described internal combustion engine, the intake connection line connects the separator to a section of the intake passage that is on an upstream side of the throttle valve. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an internal combustion engine according to an embodiment. 
         FIG. 2  is a front view showing the head cover of the internal combustion engine of the embodiment. 
         FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of a line connection portion in an internal combustion engine of a comparative example. 
         FIG. 6  is a schematic diagram showing a line connection portion of an internal combustion engine of a modification. 
         FIG. 7  is a schematic diagram showing a line connection portion of an internal combustion engine of another modification. 
     
    
    
     Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. 
     DETAILED DESCRIPTION 
     This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations are exemplary, and may be changed as apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted. 
     Exemplary embodiments may have different forms, and are not limited to the examples described. However, the examples described are thorough and complete, and convey the full scope of the disclosure to one of ordinary skill in the art. 
     An internal combustion engine  90  according to an embodiment will now be described with reference to  FIGS. 1 to 4 . 
       FIG. 1  shows the internal combustion engine  90 , which is provided with a blow-by gas treating device  30 . 
     The internal combustion engine  90  includes a cylinder block  91 , a cylinder head  97 , a head cover  98 , a crankcase  95 , and an oil pan  96 . 
     The cylinder block  91  includes cylinders  92 . Each cylinder  92  accommodates a piston  94 . Each piston  94  reciprocates in conjunction with rotation of the crankshaft accommodated in the crankcase  95 . The internal combustion engine  90  is a multi-cylinder engine. 
     The cylinder head  97  has intake valves and exhaust valves of the internal combustion engine  90 . The head cover  98  is attached to the cylinder head  97  to cover the camshaft, which actuates the intake valves and the exhaust valves. The head cover  98  is made of plastic. A baffle plate (not shown) is attached to a part of the head cover  98  that is adjacent to the cylinder head  97 . 
     The oil pan  96  stores oil used to lubricate components of the internal combustion engine  90  and to operate hydraulic mechanisms. 
     The internal combustion engine  90  includes combustion chambers  93 , which are defined by the cylinders  92 , the pistons  94  and the cylinder head  97 . The internal combustion engine  90  includes an intake passage  71  configured to introduce air to the combustion chambers  93 . The internal combustion engine  90  includes an exhaust passage  78  configured to discharge air-fuel mixture that has been burned in the combustion chambers  93 . 
     The internal combustion engine  90  includes a forced-induction device  80  of an exhaust gas turbine type. The forced-induction device  80  includes a turbine  82  arranged in the exhaust passage  78 . The forced-induction device  80  includes a compressor  81  arranged in the intake passage  71 . The compressor  81  is integrally rotational with the turbine  82 . 
     The internal combustion engine  90  includes an air cleaner  72  in a section of the intake passage  71  on the upstream side of the compressor  81 . The internal combustion engine  90  further includes an intercooler  73  on the downstream side of the compressor  81 . A throttle valve  74  is arranged on the downstream side of the intercooler  73 . An intake manifold  75  is arranged on the downstream side of the throttle valve  74 . The intake manifold  75  is connected to the cylinder head  97 . 
     Intake air that has passed through the intake manifold  75  is introduced into the combustion chambers  93  through intake ports  76  provided in the cylinder head  97 . The cylinder head  97  includes exhaust ports  77  configured to discharge exhaust gas from the combustion chambers  93 . The exhaust gas discharged from the combustion chambers  93  is discharged to the exhaust passage  78 . 
     The blow-by gas treating device  30  includes a blow-by gas passage  49 , which connects the crankcase  95  and the intake passage  71  to each other. The blow-by gas treating device  30  delivers, to the intake passage  71 , blow-by gas that has leaked from the combustion chambers  93  to the crankcase  95 . 
     The blow-by gas treating device  30  includes a first separator  43 , which is an oil separator arranged in the blow-by gas passage  49 . The first separator  43  separates oil from blow-by gas. The first separator  43  is provided in the head cover  98 . The first separator  43  is connected to the intake manifold  75  via a blow-by gas release line  47 . A hose or a plastic pipe may be used as the blow-by gas release line  47 . A PCV valve  48  is provided in the blow-by gas release line  47 . The PCV valve  48  selectively connects and disconnects the first separator  43  to and from the intake manifold  75 . The PCV valve  48  opens to connect the first separator  43  to the intake manifold  75  when the pressure in the intake manifold  75  is lower than the pressure in the first separator  43 . 
     The blow-by gas treating device  30  includes a suction passage  41  configured to introduce the blow-by gas in the crankcase  95  to the first separator  43 . The suction passage  41  is provided in the cylinder block  91  and the cylinder head  97 . The suction passage  41  includes a pre-separator  42 , which separates oil from the blow-by gas that passes through the suction passage  41 . 
     The blow-by gas treating device  30  includes a fresh air introducing line  31  configured to introduce fresh air from the intake passage  71  to the crankcase  95 . A hose or a plastic pipe may be used as the fresh air introducing line  31 . One end of the fresh air introducing line  31  is connected to a section of the intake passage  71  between the air cleaner  72  and the compressor  81 . The other end of the fresh air introducing line  31  is connected to a second separator  32 , which is an oil separator provided in the head cover  98 . The second separator  32  is defined by the head cover  98  and the baffle plate. The second separator  32  includes a line connection portion  10  to which the fresh air introducing line  31  is attached. A pressure sensor  54  is connected to the line connection portion  10  via a sensor connection line  55 . The pressure sensor  54  detects the pressure in the fresh air introducing line  31 . The detection signal of the pressure sensor  54  is delivered to the control unit (not shown) of the internal combustion engine  90 . The control unit includes a detection section that detects the pressure in the fresh air introducing line  31  based on the detection signal of the pressure sensor  54 . The detection section detects that the fresh air introducing line  31  is disconnected when a change in the detected pressure is increased to exceed a specified range. 
     The cylinder block  91  includes a communicating passage  99 , which communicates with the crankcase  95 . The intake passage  71  is connected to the crankcase  95  via the fresh air introducing line  31  and the second separator  32 . Hereinafter, the passage that includes the fresh air introducing line  31  and connects the intake passage  71  to the crankcase  95  will be referred to as a fresh air introducing passage in some cases. 
     The blow-by gas treating device  30  includes an ejector  50 , which generates negative pressure in conjunction with the operation of the forced-induction device  80 . The ejector  50  includes an ejector main body  51  connected to the first separator  43 . The ejector main body  51  is connected to a first intake air circulation line  52  and a second intake air circulation line  53 . The first intake air circulation line  52  is connected to a section of the intake passage  71  between the compressor  81  and the intercooler  73 . The second intake air circulation line  53  is connected to a section of the intake passage  71  between the air cleaner  72  and the compressor  81 . The joint between the second intake air circulation line  53  and the intake passage  71  is located on the downstream side of the joint between the fresh air introducing line  31  and the intake passage  71 . The ejector main body  51  includes a nozzle  51 A, which ejects intake air supplied via the first intake air circulation line  52  toward the second intake air circulation line  53 . The ejector main body  51  includes a diffuser  51 B, which is located closer to the second intake air circulation line  53  than the nozzle  51 A. The diffuser  51 B has a gas flow path that is gradually enlarged. The ejector  50  is constituted by the ejector main body  51 , the first intake air circulation line  52 , and the second intake air circulation line  53 . 
     When the internal combustion engine  90  is not operating in the forced-induction region and the pressure in the intake manifold  75  is lower than the pressure in the first separator  43 , the PCV valve  48  opens to deliver the blow-by gas in the first separator  43  to the intake passage  71 . At this time, the blow-by gas in the crankcase  95  is drawn into the first separator  43  via the suction passage  41 . Also, intake air is drawn into the crankcase  95  from the intake passage  71  via the fresh air introducing passage. 
     In contrast, when the internal combustion engine  90  is operating in the forced-induction region, the difference between the intake pressure on the upstream side of the compressor  81  and the intake pressure on the downstream side of the compressor  81  causes the intake air that has been flowed into the first intake air circulation line  52  from the section of the intake passage  71  on the downstream side of the compressor  81  to return to the section on the upstream side of the compressor  81  via the ejector main body  51  and the second intake air circulation line  53 . When the intake air passes through the nozzle  51 A of the ejector main body  51 , negative pressure is generated inside the ejector main body  51 . At this time, the ejector  50  draws in the blow-by gas in the crankcase  95  via the first separator  43  and releases the blow-by gas that has passed through the diffuser  51 B to the intake passage  71  via the second intake air circulation line  53 . 
     When the internal combustion engine  90  is operating in the forced-induction region, the pressure of the blow-by gas leaking from the combustion chambers  93  to the crankcase  95  is relatively high. When the pressure in the crankcase  95  is higher than the internal pressure of the section of the intake passage  71  to which the fresh air introducing line  31  is connected, the blow-by gas in the crankcase  95  flows into the intake passage  71  via the fresh air introducing passage. Even when the internal combustion engine  90  is not operating in the forced-induction region, if the throttle valve  74  is fully open, for example, the blow-by gas leaking from the combustion chambers  93  to the crankcase  95  may flow into the intake passage  71  via the fresh air introducing passage. 
     The line connection portion  10  will be described with reference to  FIGS. 2 to 4 .  FIG. 3  shows arrows indicating the vertical direction and the horizontal direction of the internal combustion engine  90  in the position of being mounted on the vehicle. 
       FIG. 2  illustrates the head cover  98 . The line connection portion  10  of the second separator  32  includes an intake connection union  25 , to which the fresh air introducing line  31  is connected. The intake connection union  25  is inserted into the fresh air introducing line  31  so that the fresh air introducing line  31  and the line connection portion  10  are connected to each other. The line connection portion  10  includes a sensor connection union  23 , to which the sensor connection line  55  is connected. The sensor connection union  23  is inserted into the sensor connection line  55  so that the sensor connection line  55  and the line connection portion  10  are connected to each other. 
     As shown in  FIG. 3 , the line connection portion  10  includes a partition plate  12 , which divides the space inside the second separator  32  into a first space  19  and a second space  29 . The first space  19  and the second space  29  are arranged in the vertical direction. In the fresh air introducing passage, the second space  29  is located at a position closer to the intake passage  71  than the first space  19 . The partition plate  12  has a constriction  13 , through which the first space  19  and the second space  29  communicate with each other.  FIG. 3  shows a first axis C 1 , which is defined as the central axis of an opening  13 A of the constriction  13 . The partition plate  12  is inclined such that the section in which the constriction  13  is provided is located at the lowest position. 
     The line connection portion  10  is constituted by combining a first unit  11 , which defines the first space  19 , and a second unit  21 , which defines the second space  29 . 
     The first unit  11 , which constitutes the line connection portion  10 , is provided integrally with the head cover  98 . The partition plate  12  is the top plate of the first unit  11 . The first space  19  is defined by a first side wall  14  and the partition plate  12  of the first unit  11 . 
     The second unit  21 , which constitutes the line connection portion  10 , is located vertically above the first unit  11  and is shaped as a box with the side adjacent to the first unit  11  open. Like the first unit  11  (the head cover  98 ), the second unit  21  is made of plastic. The second unit  21  includes a flange  26 , to which the first unit  11  is welded. The second space  29  is surrounded by a second side wall  24  of the second unit  21 , which extends vertically upward from the flange  26 . A top plate  22  is provided at the upper end of the second side wall  24  in the vertical direction. The second space  29  is defined by the partition plate  12  of the first unit  11  and the top plate  22  and the second side wall  24  of the second unit  21 . That is, the partition plate  12  constitutes the floor surface of the second space  29 . 
     As shown in  FIGS. 2 and 3 , the sensor connection union  23  is provided on the top plate  22  of the second unit  21 . The sensor connection union  23  extends in the vertical direction.  FIG. 3  shows a second axis C 2 , which is defined as the central axis of the passage in the sensor connection union  23 . The top plate  22  is inclined relative to the horizontal direction, and the sensor connection union  23  is provided in a section of the top plate  22  closer to the top. 
     As shown in  FIGS. 2 and 4 , the intake connection union  25  is provided in the second side wall  24  of the second unit  21 .  FIGS. 3 and 4  illustrate an open end  25 A of the intake connection union  25 , which opens in the second side wall  24 .  FIG. 4  shows a third axis C 3 , which is defined as the central axis of the passage in the intake connection union  25 . 
     As shown in  FIGS. 3 and 4 , the constriction  13  and the sensor connection union  23  are arranged at positions in the line connection portion  10  where the first axis C 1  and the second axis C 2  are displaced from each other. In other words, the constriction  13  and the sensor connection union  23  are arranged at positions where the first axis C 1  and the second axis C 2  are non-coaxial. The constriction  13  and the sensor connection union  23  are arranged such that the first axis C 1  and the second axis C 2  are not arranged on the same straight line. In the present embodiment, the first axis C 1  and the second axis C 2  are parallel with each other and do not intersect with each other as shown in  FIG. 3 . That is, the first axis C 1  and the second axis C 2  are non-crossing. As shown in  FIG. 4 , in the second unit  21 , the sensor connection union  23  and the intake connection union  25  are arranged at positions where the second axis C 2  and the third axis C 3  do not intersect with each other. In other words, the sensor connection union  23  and the intake connection union  25  are arranged at positions where the second axis C 2  and the third axis C 3  are non-crossing. Further, the intake connection union  25  is arranged at a position where the first axis C 1  and the third axis C 3  do not intersect with each other. In other words, the intake connection union  25  is arranged at a position where the first axis C 1  and the third axis C 3  are non-crossing. That is, in the line connection portion  10 , the second axis C 2  and the third axis C 3  are at positions of skew lines, and the first axis C 1  and the third axis C 3  are at positions of skew lines. As described above, in the line connection portion  10 , the constriction  13 , the sensor connection union  23 , and the intake connection union  25  are arranged at positions where any two of the first axis C 1 , the second axis C 2 , and the third axis C 3  do not intersect with each other, that is, are non-crossing. 
     Operation and advantages of the present embodiment will now be described. 
     The internal combustion engine  90  includes the line connection portion  10 . The line connection portion  10  includes the intake connection union  25  between the constriction  13  and the sensor connection union  23 , to which the pressure sensor  54  is connected. Thus, in both of a case in which the fresh air introducing line  31  is disconnected at the joint with the intake passage  71  and a case in which the fresh air introducing line  31  is disconnected at the joint with the line connection portion  10 , the part in which the sensor connection union  23  is provided is exposed to the atmosphere after the fresh air introducing line  31  is disconnected. The detection value of the pressure sensor  54  thus readily approaches the atmospheric pressure. That is, when the fresh air introducing line  31  is disconnected, the line disconnection is detected through a change in the detection value of the pressure sensor  54 . 
     The blow-by gas that has leaked from the combustion chambers  93  contains oil and passes through the communicating passage  99 . Although the second separator  32  traps some of the oil in the blow-by gas, oil that has not been separated may enter the line connection portion  10 . If oil enters the line connection portion  10  and collects on the pressure sensor  54 , which is connected to the line connection portion  10 , the detection sensitivity of the pressure sensor  54  may be reduced. However, with the line connection portion  10  of the internal combustion engine  90 , the sensor connection union  23  is located vertically above the constriction  13  even if oil enters the second space  29  after passing through the constriction  13  together with blow-by gas. This prevents the oil that has entered the second space  29  from reaching the pressure sensor  54  through the sensor connection union  23 . Accordingly, oil is prevented from collecting on the pressure sensor  54 . That is, the present embodiment limits reduction in the detection sensitivity of the pressure sensor  54  and thus limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor  54 . 
     The blow-by gas also contains water. Since the sensor connection union  23  is located vertically above the constriction  13 , the water contained in the blow-by gas is prevented from reaching the pressure sensor  54 . 
     Further, in the line connection portion  10  of the internal combustion engine  90 , the constriction  13  and the sensor connection union  23  are arranged at positions where the first axis C 1  and the second axis C 2  are displaced from each other. The constriction  13 , the sensor connection union  23 , and the intake connection union  25  are arranged at positions where any two of the first axis C 1 , the second axis C 2 , and the third axis C 3  do not intersect with each other. Thus, the blow-by gas that flows into the second space  29  through the constriction  13  flows toward the top plate  22  of the second unit  21 . That is, the present embodiment prevents the blow-by gas flowing into the second space  29  from directly flowing into the sensor connection line  55 . Further, the present embodiment prevents the blow-by gas that flows into the second space  29  from directly flowing into the fresh air introducing line  31 . Also, when blow-by gas passes through the constriction  13 , which has a small cross-sectional flow area, its flow velocity is increased. Thus, in the line connection portion  10 , blow-by gas readily strikes the top plate  22  of the second unit  21 . As described above, blow-by gas readily strikes the inner wall of the second unit  21 . This allows oil to be separated from the blow-by gas, thereby limiting reduction in the detection sensitivity of the pressure sensor  54  due to the flow of blow-by gas containing oil toward the pressure sensor  54 . That is, the present embodiment limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor  54 . 
     Since the blow-by gas flowing into the second space  29  is prevented from directly flowing into the fresh air introducing line  31 , the blow-by gas containing oil is prevented from being released to the intake passage  71 . 
     Further, any two of the first axis C 1 , the second axis C 2 , and the third axis C 3  do not intersect with each other. This reduces the influence of pulsation of the blow-by gas passing through the line connection portion  10  on the detection value of the pressure sensor  54 . That is, the present embodiment limits reduction in the detection sensitivity of the pressure sensor  54  and thus limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor  54 . 
     In the line connection portion  10  of the internal combustion engine  90 , oil contained in the blow-by gas that has flowed into the second space  29  strikes the wall surface of the second unit  21  to be separated and dribbles down to the partition plate  12 , which constitutes the floor surface of the second space  29 . The partition plate  12  is inclined such that the section in which the constriction  13  is provided is located at the lowest position. This allows the oil that has dribbled down to the partition plate  12  to flow down to the constriction  13  under its own weight. Thus, when the operation of the internal combustion engine  90  is stopped and inflow of blow-by gas to the second space  29  through the constriction  13  is stopped, the oil stored in the second space  29  is returned to the first space  19 , which is adjacent to the second separator  32 , through the constriction  13 . This prevents oil from flowing into the sensor connection line  55  and the fresh air introducing line  31 . That is, the present embodiment limits reduction in the detection sensitivity of the pressure sensor  54  and thus limits reduction in the detection sensitivity to line disconnection due to reduction in the detection sensitivity of the pressure sensor  54 . 
     The line connection portion  10  of the present embodiment includes the second unit  21 , which includes the sensor connection union  23  and the intake connection union  25 , is welded to the first unit  11 , which includes the constriction  13 . Since the line connection portion  10  is divided into two units, the line connection portion  10  is relatively easily formed using plastic. In this regard, a line connection portion  110  shown in  FIG. 5  will now be described as a comparative example. 
       FIG. 5  shows, as a comparative example, the line connection portion  110 , which is provided in a separator  132 . The line connection portion  110  and the separator  132  are made of plastic. The line connection portion  110  is integrally molded with the separator  132 . The line connection portion  110  includes an intake connection union  125  and a sensor connection union  123 . The intake connection union  125  is connected to an intake connection line  131 , which is connected to the intake passage. The sensor connection union  123  is connected to a sensor connection line  155 , to which a pressure sensor is connected. As illustrated in the drawing, the line connection portion  110  is branched into two sections between a constriction  113  and the intake connection line  131 . The intake connection union  125  and the sensor connection union  123  are arranged at the two branched sections, respectively. 
     When performing plastic molding through injection molding using molds, the movable mold plate is moved to approach the fixed mold plate. Then, the cavity between the fixed mold plate and the movable mold plate is filled with plastic. After the plastic solidifies, the movable mold plate is moved away from the fixed mold plate, and the molded product is removed. Further, when forming a union in the separator  132  (head cover) as in the case of the line connection portion  110  shown in  FIG. 5 , a slide core is additionally used to form a passage in the union. In this case, a columnar slide core is moved in the direction in which the passage in the union extends when the fixed mold plate and the movable mold plate approach or move away from each other. However, in a case in which the sensor connection union  123  is branched off the intake connection union  125  as in the case of the line connection portion  110 , slide cores of different moving directions interfere with each other at the branching portion. This may complicate the molding process or require a secondary working after removing the product from the mold. 
     In contrast, the second unit  21  of the line connection portion  10  of the present embodiment has an open side adjacent to the first unit  11 . That is, the inner wall of the second unit  21  can be molded by the movable mold plate. During molding, the movable mold plate is located at the part corresponding to the second space  29 . Thus, the slide core for molding the intake connection union  25  and the slide core for molding the sensor connection union  23 , which are slide cores of different moving directions, do not interfere with each other. In this manner, the line connection portion  10  of the present embodiment can be formed through injection molding without any constraints on the molds and is thus easier to manufacture than the line connection portion  110  shown in  FIG. 5 . 
     The correspondence between the items in the above-described embodiment and the items described in the above BACKGROUND is as follows. 
     The second separator  32  corresponds to “the separator that separates oil from blow-by gas.” The fresh air introducing line  31  corresponds to “the intake connection line that connects the intake passage and the separator to each other.” 
     The above-described embodiment may be modified as follows. The above-described embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other. 
     The configuration of the line connection portion  10  of the above-described embodiment may be applied to the ejector  50 .  FIG. 6  illustrates an example in which a line connection portion  210  is provided between the ejector main body  51  and the second intake air circulation line  53 . 
     As shown in  FIG. 6 , the line connection portion  210  is provided in the ejector main body  51  such that a first space  219  is located at a position that is closer to the second intake air circulation line  53  than the diffuser  51 B of the ejector main body  51 . A second space  229 , which is separated from the first space  219  by a partition plate  212 , is located vertically above the first space  219 . The partition plate  212  has a constriction  213 . The sensor connection line  55 , to which the pressure sensor  54  is connected, is attached to the sensor connection union of the line connection portion  210 . A pipe constituting the second intake air circulation line  53  is attached to an intake connection union  225  of the line connection portion  210 . The constriction  213  may be used as the diffuser  51 B of the ejector  50 . This configuration allows the pressure sensor  54  to detect line disconnection of the second intake air circulation line  53  as in the case of the above-described embodiment. Further, as in the case of the above-described embodiment, oil is trapped from the blow-by gas discharged from the intake passage  71 , which prevents oil from entering the intake passage  71 . 
     The correspondence between the items in the above-described embodiment and the items described in the above BACKGROUND is as follows. The first separator  43 , to which the ejector main body  51  is attached, corresponds to “the separator that separates oil from blow-by gas.” The second intake air circulation line  53  corresponds to “the intake connection line that connects the intake passage and the separator to each other.” 
     The configuration of the line connection portion  10  of the above-described embodiment may be applied to the blow-by gas passage  49 .  FIG. 7  illustrates an example in which a line connection portion  310  is provided between the first separator  43  and the blow-by gas release line  47 . 
     As shown in  FIG. 7 , the line connection portion  310  connects the blow-by gas release line  47  to the first separator  43  and includes an intake connection union  325 , to which the blow-by gas release line  47  is attached. A PCV valve  48  is provided in the blow-by gas release line  47 . The PCV valve  48  selectively connects and disconnects the line connection portion  310  to and from the intake manifold  75 . Also, the sensor connection line  55 , to which the pressure sensor  54  is connected, is attached to the sensor connection union of the line connection portion  310 . The line connection portion  310  includes a partition plate  312 , which divides the space inside the first separator  43  into a first space  319  and a second space  329 . The partition plate  312  has a constriction  313 . 
     In the configuration shown in  FIG. 7 , when the blow-by gas release line  47  is disconnected at the joint with the intake connection union  325 , the detection value of the pressure sensor  54  approaches the atmospheric pressure. This allows the line disconnection to be detected. In this manner, when the line disconnection occurs at a position closer to the line connection portion  310  than the PCV valve  48 , the pressure sensor  54  can detect the line disconnection. In contrast, when the blow-by gas release line  47  is disconnected at the joint with the intake manifold  75 , the PCV valve  48  is connected to the line connection portion  310  and the first separator  43 . The detection value of the pressure sensor  54  is unlikely to change, so that the pressure sensor  54  is unable to detect the line disconnection. In this case, however, the blow-by gas release line  47  is disconnected from the intake manifold  75 , so that the intake manifold  75  is opened. Accordingly, the operating state of the internal combustion engine  90  is likely to change. Line disconnection is detected based on such a change in the operating state of the internal combustion engine  90 . 
     This configuration allows the pressure sensor  54  to detect line disconnection of the blow-by gas release line  47  as in the case of the above-described embodiment. Further, as in the case of the above-described embodiment, oil can be trapped from the blow-by gas discharged to the intake manifold  75  of the intake passage  71 , which prevents oil from entering the intake passage  71 . 
     The correspondence between the items in the above-described embodiment and the items described in the above BACKGROUND is as follows. The first separator  43  corresponds to “the separator that separates oil from blow-by gas.” The blow-by gas release line  47  corresponds to “the intake connection line that connects the intake passage and the separator to each other.” 
     In the above-described embodiment, the partition plate  12  is inclined. However, the partition plate  12  may be arranged to be horizontal. Also, a partition plate with a center portion recessed vertically downward may be used so that the floor surface of the second space  29  has a bowl shape. In this case, the opening  13 A of the constriction  13  may be provided in the portion that is recessed vertically downward. 
     The above-described embodiment is configured such that any two of the first axis C 1 , the second axis C 2 , and the third axis C 3  do not intersect with each other. However, the intake connection union  25  may be provided such that the third axis C 3  and the first axis C 1  intersect with each other, or the third axis C 3  and the second axis C 2  intersect with each other. If the constriction  13  and the sensor connection union  23  are arranged at positions where the first axis C 1  and the second axis C 2  are displaced from each other, the blow-by gas that flows into the second space  29  after passing through the constriction  13  readily strikes the top plate  22  of the second unit  21 . That is, the above-described embodiment prevents the blow-by gas flowing into the second space  29  from directly flowing into the sensor connection line  55 . 
     In the above-described embodiment, the intake connection union  25  is provided in the second side wall  24  of the second unit  21 . The intake connection union  25  may be provided in the top plate  22  of the second unit  21 . 
     The above-described embodiment describes the line connection portion  10 , in which the first space  19  and the second space  29  are arranged in the vertical direction. However, the line connection portion is not limited to this. For example, the first space  19  and the second space  29  may be arranged in the horizontal direction. 
     Even in a line connection portion in which the first space  19  and the second space  29  are not arranged vertically, line disconnection can be detected by the pressure sensor  54  if the first unit  11  includes the constriction  13 , and the second unit  21  includes the intake connection union  25  and the sensor connection union  23 . 
     Further, if the sensor connection union  23  is located vertically above the constriction  13 , it is possible to prevent oil from collecting on the pressure sensor  54 . 
     Also, if the constriction  13  and the sensor connection union  23  are arranged at positions where the first axis C 1  and the second axis C 2  are displaced from each other, it is possible to cause blow-by gas to strike the inner wall of the second unit  21  to trap oil in the second space  29 . 
     In the above-described embodiment, the pressure sensor  54  is connected to the line connection portion  10  via the sensor connection line  55 . However, the sensor connection line  55  may be omitted and the pressure sensor  54  may be directly connected to the sensor connection union  23  of the line connection portion  10 . That is, the shape of the sensor connection union  23 , which is an example of the shape into which the sensor connection line  55  is inserted, may be changed to a shape to which the pressure sensor  54  can be connected. This allows the sensor connection line  55  to be omitted and the pressure sensor  54  to be directly connected to the sensor connection union  23  of the line connection portion  10 . 
     In the above-described embodiment, the first unit  11  of the line connection portion  10  and the head cover  98  are molded integrally. The first unit  11  and the head cover  98  may be molded separately and combined together. 
     Although the internal combustion engine  90  of the above-described embodiment is provided with the forced-induction device  80 , a forced-induction device is not necessarily required. Even in an internal combustion engine without a forced-induction device, the line connection portion  10  is able to detect line disconnection of the fresh air introducing line  31  by using the pressure sensor  54  as in the case of the above-described embodiment. Also, even in an internal combustion engine without a forced-induction device, if the throttle valve  74  is fully open, blow-by gas leaking from the combustion chambers  93  to the crankcase  95  may flow into the intake passage  71  via the fresh air introducing passage. Accordingly, when blow-by gas passes through the fresh air introducing passage, oil is prevented from collecting on the pressure sensor  54  as in the case of the above-described embodiment. 
     When the internal combustion engine  90  of the above-described embodiment is operating in the forced-induction region, the ejector  50  generates negative pressure to discharge blow-by gas to the intake passage  71 . However, the ejector  50  may be omitted. In this case, when the internal combustion engine  90  is operating in the forced-induction region, blow-by gas can be discharged to the intake passage via the fresh air introducing passage. 
     Various changes in form and details may be made to the examples above without departing from the spirit and scope of the claims and their equivalents. The examples are for the sake of description only, and not for purposes of limitation. Descriptions of features in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined differently, and/or replaced or supplemented by other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the disclosure.