Patent Publication Number: US-11396834-B2

Title: Blow-by gas discharging device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage entry of PCT Application No: PCT/JP2019/037261 filed Sep. 24, 2019, which claims priority to Japanese Patent Application No. 2018-182123 filed Sep. 27, 2018, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a blow-by gas discharge device, and more particularly, to a device for discharging blow-by gas into the atmosphere through a blow-by gas pipe exposed to the outside air. 
     BACKGROUND ART 
     In general, blow-by gas generated in the crankcase of an internal combustion engine is circulated into an air intake system, is sent into a combustion chamber, and is burned together with air-fuel mixture in the combustion chamber. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP H01-95513 U 
     SUMMARY OF INVENTION 
     Technical Problem 
     Meanwhile, a device that discharges blow-by gas into the atmosphere instead of circulating it into an air intake system is also known (see Patent Literature 1 for instance). In this case, it can be considered to provide a blow-by gas pipe that is exposed to the outside air and that extends from a height position of an upper end part of the internal combustion engine to a height position of a lower end part of the internal combustion engine, and to discharge the blow-by gas into the atmosphere through the blow-by gas pipe. 
     However, in such a case, since the blow-by gas pipe is cooled by the outside air, the blow-by gas passing through the pipe is also cooled, so condensed water attributable to the blow-by gas is generated in the pipe. If the temperature of the outside air is equal to or lower than the freezing point, the condensed water may freeze and block the inside of the pipe. 
     The present disclosure provides a blow-by gas discharge device capable of preventing freezing of condensed water in a blow-by gas pipe. 
     Solution to Problem 
     According to an aspect of the present disclosure, a blow-by gas discharge device includes: a blow-by gas pipe that extends from a height position of an upper end part of an internal combustion engine to a height position of a lower end part of the internal combustion engine, the blow-by gas pipe being exposed to an outside air and having an outlet part released to an atmosphere; a heat chamber provided in a middle of the blow-by gas pipe and in a flywheel housing of the internal combustion engine, the heat chamber being configured to heat blow-by gas; and a drain mechanism provided in the heat chamber and configured to discharge oil accumulated in the heat chamber. 
     The drain mechanism may include a drain valve configured to prevent the oil from being discharged when the drain valve is closed, and to allow the oil to be discharged when the drain valve is opened. 
     The drain valve may be a check valve, and the check valve may include a valve body, and a biasing member configured to bias the valve body toward a valve closing side. 
     The drain valve may be a drain bolt. 
     The drain valve may be configured to be accessible through a hole provided in the flywheel housing. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to prevent freezing of condensed water in a blow-by gas pipe. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional side view illustrating a structure of an end part of an internal combustion engine. 
         FIG. 2  is a schematic cross-sectional rear view illustrating a heat chamber. 
         FIG. 3  is a schematic cross-sectional rear view illustrating a drain mechanism. 
         FIG. 4  is a schematic cross-sectional rear view for explaining a working method for discharging oil. 
         FIG. 5  is a schematic cross-sectional rear view illustrating a drain mechanism according to a first modification. 
         FIG. 6  is a schematic cross-sectional rear view illustrating a drain mechanism according to a second modification. 
         FIG. 7  Parts (A) and (B) of  FIG. 7  show a drain mechanism according to a third modification, part (A) of  FIG. 7  is a left side view of a drain bolt, and part (B) of  FIG. 7  is a schematic cross-sectional rear view. 
         FIG. 8  Parts (A) and (B) of  FIG. 8  show a drain mechanism according to a fourth modification, and part (A) of  FIG. 8  is a left side view of a drain bolt, and part (B) of  FIG. 8  is a schematic cross-sectional rear view. 
         FIG. 9  is a schematic cross-sectional rear view illustrating a drain mechanism according to a fifth modification. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. However, it is to be noted that the present disclosure is not limited to the following embodiment. 
       FIG. 1  is a cross-sectional side view illustrating a structure of an end part of an internal combustion engine according to the present embodiment. An internal combustion engine (engine)  1  is a diesel engine mounted on a vehicle (not shown in the drawing), and the vehicle is a large vehicle such as a truck. However, the types, uses, and so on of the vehicle and the engine are not particularly limited, and the vehicle may be a small vehicle such as a car, and the engine may be a gasoline engine. The engine is mounted vertically on the vehicle. The front, rear, left, right, upper, and lower sides of the vehicle and the engine are as shown in the drawing. 
     The engine  1  includes a cylinder block  2  integrally including a crankcase (not shown in the drawing), a cylinder head  3  fastened to an upper end part of the cylinder block  2 , a head cover  4  fastened to an upper end part of the cylinder head  3 , and an oil pan  5  fastened to a lower end part of the crankcase. A crankshaft  6  is rotatably supported by the crankcase, and a camshaft  7  is rotatably supported by the cylinder head  3 . 
     A flywheel  8  is attached to a rear end surface part of the crankshaft  6  by a plurality of bolts  9 . A flywheel housing  10  that accommodates the flywheel  8  is attached to the cylinder block  2  by bolts or the like (not shown in the drawing). However, the flywheel housing  10  may be integrally formed in the cylinder block  2 . In the flywheel housing  10 , a cylindrical flywheel chamber  11  is provided, which accommodates the flywheel  8  such that the flywheel is substantially rotatable. A clutch device (not shown in the drawing) is connected to a rear end part of the flywheel housing  10 , and a clutch input shaft of the clutch device is coaxially connected to the crankshaft  6 . A part of the oil pan  5  is attached to the flywheel housing  10  by a bolt  12 . 
     A mechanism chamber is provided between a rear end surface part of the cylinder block  2  and the flywheel housing  10 . Inside the mechanism chamber, a power transmission mechanism that transmits power from the crankshaft  6  to the camshaft  7  is accommodated. In the present embodiment, the power transmission mechanism includes a gear mechanism  13  including a plurality of gears meshing with each other, and the mechanism chamber includes a gear chamber  14 . However, the type of the power transmission mechanism is arbitrary, and for example, the power transmission mechanism may include a chain mechanism. The gear mechanism  13  includes a crank gear  15  fixed to the crankshaft  6 , a cam gear  16  fixed to the camshaft  7 , and a plurality of (in the present embodiment, two) intermediate gears  17 A and  17 B interposed between the crank gear  15  and the cam gear  16 . The gear chamber  14  communicates with a crank chamber  18  in the crankcase, a valve chamber  3 A of the cylinder head  3 , and a cover chamber  19  of the head cover  4 . 
     C 1  and C 2  represent a central axis of the crankshaft  6  and a central axis of the camshaft  7 , respectively. 
     A rear end part of the cylinder head  3  is provided integrally with a gear chamber partition wall  20  having a half-rectangular frame shape (a shape like U letter) as seen in a plan view and protruding from the rear end part of the cylinder head  3 . An inner space of the gear chamber partition wall  20  is a part of the gear chamber  14 . An upper end surface of the flywheel housing  10  is brought into close contact with a lower end surface of the gear chamber partition wall  20 , and a lower end surface of the head cover  4  is brought into close contact with an upper end surface of the gear chamber partition wall  20 . 
     A rear end part of the crankshaft  6  protrudes into the flywheel chamber  11  located rearwardly through an insertion hole  21  of the flywheel housing  10 . On a peripheral part of the insertion hole  21 , a sealing member (not shown in the drawing) is provided, which prevents oil and gas from leaking from the gear chamber  14 . 
     As is known, blow-by gas leaks from a combustion chamber of a cylinder into the crank chamber  18  though a gap between a piston ring and a cylinder bore. The blow-by gas is introduced into the cover chamber  19  through the gear chamber  14  and another gas passing hole. 
     In the cover chamber  19 , an oil separator  22  is provided, which separates oil from blow-by gas. Although not shown in the drawing, the oil separator  22  has a meandering passage that allows blow-by gas to flow therethrough. In the present embodiment, blow-by gas from which oil has been separated by the oil separator  22  is discharged into the atmosphere through a gas pipe  23  serving as a blow-by gas pipe. 
     The gas pipe  23  is exposed to the outside air, and is cooled directly by the outside air. Especially, the gas pipe  23  of the present disclosure is formed of a metal such as stainless steel, and the entire gas pipe  23  is exposed to the outside air, so it is easily cooled by the outside air. As a result, blow-by gas passing through the gas pipe  23  is also cooled, and condensed water attributable to the blow-by gas is generated in the gas pipe  23 . Therefore, for example, in a cold region or the like, when the temperature of the outside air is equal to or lower than the freezing point, the condensed water may freeze and block the inside of the gas pipe  23 . If the inside of the gas pipe  23  is blocked, it may disrupt discharge of blow-by gas. 
     For this reason, in the present embodiment, a heat chamber  24  that heats blow-by gas is provided in the middle of the gas pipe  23 . Blow-by gas is heated in the heat chamber  24 , whereby generation of condensed water attributable to blow-by gas and freezing thereof are prevented. Especially, the heat chamber  24  is provided inside the flywheel housing  10 , is adjacent to the gear chamber  14  with a partition (in the present embodiment, a lid  41  to be described below) interposed therebetween, and heats blow-by gas by heat received from oil in the gear chamber  14 . Therefore, it is possible to efficiently heat blow-by gas without providing a dedicated heat source. Hereinafter, the configuration of the blow-by gas discharge device will be described in detail. 
     The whole of the gas pipe  23  extends from a height position of an upper end part of the engine  1  to a height position of a lower end part of the engine  1 . However, the gas pipe  23  is divided into two parts at a position in the middle of the height direction, i.e. an upstream side gas pipe  25  and a downstream side gas pipe  26  (shown by an imaginary line in  FIG. 1 ). The heat chamber  24  is connected between the upstream side gas pipe  25  and the downstream side gas pipe  26 . Both of the upstream side gas pipe  25  and the downstream side gas pipe  26  are formed of a metal such as stainless steel, and are exposed to the outside air outside the engine. 
     An inlet part  27  of the upstream side gas pipe  25  is connected to the oil separator  22 . In the head cover  4 , an outlet port  28  is provided, which allows blow-by gas from which oil has been separated to outflow from the oil separator  22 . The inlet part  27  of the upstream side gas pipe  25  is connected to the outlet port  28 . The inlet part  27  of the upstream side gas pipe  25  is an inlet part of the gas pipe  23 . Since the head cover  4  and the oil separator  22  are provided at the height position of the upper end part of the engine  1 , and the inlet part  27  of the upstream side gas pipe  25  is connected to the oil separator  22 , the gas pipe  23  extends downstream from the height position of the upper end part of the engine  1 . 
     The oil separator  22  may not be provided inside the head cover  4 , but may be provided outside the head cover  4 . The reference symbol “ 22 A” in the drawing represents a partition wall that defines the oil separator  22 . 
     On the other hand, as also shown in  FIG. 2 , an outlet part  29  of the upstream side gas pipe  25  is connected to the heat chamber  24 . In a right and upper end part of the heat chamber  24 , an introduction port  30  that introduces blow-by gas into the heat chamber  24  is provided, and the outlet part  29  of the upstream side gas pipe  25  is connected to the introduction port  30 . 
     Also, an inlet part  31  of the downstream side gas pipe  26  is connected to the heat chamber  24 . In a left and upper end part of the heat chamber  24 , a discharge port  32  that discharges blow-by gas from the heat chamber  24  is provided, and the inlet part  31  of the downstream side gas pipe  26  is connected to the discharge port  32 . 
     On the other hand, as shown in  FIG. 1 , the downstream side gas pipe  26  passes through the left side of the flywheel housing  10  and extends downward as it goes downstream. Further, an outlet part  33  of the downstream side gas pipe  26  is disposed at the height position of the lower end part of the engine  1 , and is released to the atmosphere in a state where the outlet part  33  faces downward. As a result, it is possible to prevent the engine from being contaminated by blow-by gas discharged from the outlet part  33 . The outlet part  33  of the downstream side gas pipe  26  is the outlet part of the gas pipe  23 . Therefore, the gas pipe  23  is extended to the height position of the lower end part of the engine  1 . 
     The heat chamber  24  is provided inside the flywheel housing  10  and in an upper end part of the flywheel housing  10 . The heat chamber  24  is mainly defined by a hollow space  40  provided in the flywheel housing  10  and opened toward the front side, and the lid  41  closing a front end opening of the hollow space  40 . The flywheel housing  10  is cast in aluminum or iron, and the lid  41  is formed of an arbitrary metal plate. However, it is preferable that the material of the lid  41  should be a material excellent at heat resistance and corrosion resistance and having relatively high thermal conductivity, for example, aluminum or stainless. The lid  41  is superimposed on a lid mounting surface  42  of the flywheel housing  10  positioned around the front end opening of the hollow space  40 , and is fixed detachably and airtightly by a plurality of bolts  43 . 
     As shown in  FIG. 2 , the heat chamber  24  of the present embodiment has a fan shape or a substantial fan shape extending around the central axis C 1  of the crankshaft in a rear view as seen from the rear side (i.e. one end side in the direction of the central axis C 1  of the crankshaft). The shape of the lid  41  as seen in a rear view is the same. The introduction port  30  is provided on the right side of the upper end part of the heat chamber  24 , and the discharge port  32  is provided on the left side of the upper end part of the heat chamber  24 . The central axes of the introduction port  30  and the discharge port  32  extend substantially along the radial direction from the central axis C 1  of the crankshaft. 
     Inside the heat chamber  24 , a partition wall  44  that forms a meandering passage in the heat chamber  24  is provided. The partition wall  44  is integrally provided in the flywheel housing  10 . As shown in  FIG. 1 , the partition wall  44  protrudes from a rear inner wall surface  45  of the heat chamber  24 , which is the bottom of the hollow space  40 , toward the front side integrally and straightly, and is airtightly in contact with the lid  41 , thereby vertically partitioning the space in the heat chamber  24 . Further, as shown in  FIG. 2 , the partition wall  44  extends integrally and in an arc shape rightward from the left inner wall surface  46  of the heat chamber  24 , which is one side surface of the hollow space  40 , to a position where a predetermined gap  48  is formed between the partition wall  44  and a right inner wall surface  47  of the heat chamber  24 , which is the other side surface of the hollow space  40 . 
     An outlet of the introduction port  30  faces the gap  48  and a lower inner wall surface  49  of the heat chamber  24 . Therefore, the introduction port  30  is configured to allow blow-by gas discharged from the introduction port  30  to linearly flow into a space  50  below the partition wall  44  through the gap  48  as shown by arrows. 
     As shown in  FIG. 1 , the heat chamber  24  and the flywheel chamber  11  are overlapped in the vertical direction, and a lower end part of the heat chamber  24  is disposed on a front side of the upper end part of the flywheel chamber  11 . In the lower space  50  of the heat chamber  24 , a step  51  protruding toward the front side is provided on the rear inner wall surface  45  of the heat chamber  24 . Since the step  51  is provided, it is possible to provide the flywheel chamber  11  having a sufficient size on the rear side behind the rear inner wall surface  45  while making room for the flywheel  8 . 
     The shape of the heat chamber  24  is not limited to the above-mentioned shape, and can be changed to an arbitrary shape. Unlike the present embodiment, the number of partition walls  44  may not be one, and a plurality of partition walls may be provided. If possible, the step  51  may not be provided. 
     By the way, since blow-by gas flows in the heat chamber  24 , oil contained in the blow-by gas may gradually accumulate in the heat chamber  24  by long-term use. Further, the accumulated oil may disrupt the flow of blow-by gas in the heat chamber  24  originally scheduled. 
     In the present embodiment, blow-by gas from which oil has been separated by the oil separator  22  flows into the heat chamber  24 . Therefore, the oil content of blow-by gas in the heat chamber  24  is relatively small. Nevertheless, an unacceptable amount of oil may accumulate in the heat chamber  24  over a long period of time. 
     For this reason, in the present embodiment, a drain mechanism  60  that discharges oil accumulated in the heat chamber  24  is provided in the heat chamber  24 . As a result, it is possible to discharge oil accumulated in the heat chamber  24 , and it is possible to solve problems attributable to accumulated oil (for example, the problem that accumulated oil disrupts a desired flow of blow-by gas in the heat chamber  24 ). 
     As shown in  FIG. 2  and  FIG. 3 , the drain mechanism  60  is provided at the lowest position of the heat chamber  24 , specifically, at the lower left corner, and is capable of discharging oil accumulated in the heat chamber  24  as much as possible. The drain mechanism  60  includes a drain valve which can be opened and closed, and the drain valve prevents oil from being discharged when the drain valve is closed, and allows oil to be discharged when the drain valve is opened. In the present embodiment, the drain valve is a check valve  61 . 
     At the lowest position of a left wall part  62  which forms a left inner wall surface  46  of the heat chamber  24 , a horizontal drain hole  63  is formed through the left wall part  62 . The check valve  61  is attached to an outer surface of the left wall part  62  by appropriate means such as welding, bolting, or the like so as to communicate with the drain hole  63 . 
     The check valve  61  includes a main valve body  64  attached to the left wall part  62 , a valve hole  65  formed through the main valve body  64 , a valve body chamber  66  provided in the middle of the valve hole  65  such that the diameter of the valve hole  65  expands, a valve body  67  disposed in the valve body chamber  66 , and a spring  68  serving as a biasing member that biases the valve body  67  toward a valve closing side. 
     The valve hole  65  coaxially communicates with the drain hole  63 , and extends in the left-right direction and the horizontal direction. The valve body  67  is a metal ball such as an iron ball. The spring  68  biases the valve body  67  toward the left side which is the opposite side to the heat chamber  24 , thereby closing the check valve  61 . Therefore, in the example shown in the drawing, the left side which is the opposite side to the heat chamber  24  is the valve closing side, and the right side which is close to the heat chamber  24  side is the valve opening side. The spring  68  is a coil spring. 
     Meanwhile, as shown in  FIG. 2 , the check valve  61  is accessible through a hole provided in the flywheel housing  10 , i.e. a housing hole  70 . The housing hole  70  is specifically a service hole for performing visual checking of the inside of the flywheel housing  10  and so on after assembly, and is usually blocked with a detachable plug  71  such as a screw-in plug. If the plug  71  is removed, it becomes possible to access the check valve  61  from the outside of the flywheel housing  10 . The valve hole  65  faces the housing hole  70  positioned on its left side. 
     The flow of blow-by gas in the configuration of the present embodiment is as shown by the arrows in  FIG. 1  and  FIG. 2 . Blow-by gas from which oil has been separated by the oil separator  22  flows into the heat chamber  24  through the upstream side gas pipe  25  and the introduction port  30 . In the heat chamber  24 , as shown in  FIG. 2 , the blow-by gas discharged from the introduction port  30  enters the lower space  50  linearly and smoothly through the gap  48 . The blow-by gas first advances to the left side in the lower space  50 , and makes a U-turn to the right side, and rises in the gap  48 , and enters an upper space  52  partitioned by the partition wall  44 . Then, the blow-by gas advances to the left side in the upper space  52 , and is discharged from the discharge port  32  into the downstream side gas pipe  26 . Thereafter, the blow-by gas flows through the downstream side gas pipe  26 , and is discharged into the outside air (i.e. released into the atmosphere) through the outlet part  33 . 
     As described above, it is possible to make the blow-by gas meander in the heat chamber  24 , thereby making the blow-by gas temporally stay. 
     Relatively high temperature oil in the gear chamber  14  lubricating the gear mechanism  13  is attached to the flywheel housing  10  and the lid  41 , so the flywheel housing  10  and the lid  41  are heated by the oil. Therefore, due to this heat, it is possible to heat the blow-by gas in the heat chamber  24  to keep it warm, or at least, it is possible to prevent its temperature from dropping. Therefore, it is possible to prevent generation of condensed water attributable to condensation of moisture contained in the blow-by gas, freezing of condensed water in the gas pipe  23 , and blocking of the inside of the gas pipe  23  by freezing. Since the blow-by gas is made meander and stay in the heat chamber  24 , a long heating time is secured, and this is advantageous to prevent generation of condensed water and so on. 
     Especially, as blow-by gas flows to the downstream side in the gas pipe  23  exposed to the outside air, it is likely cooled by the outside air and its temperature decreases. The most remarkable part is the outlet part  33  of the downstream side gas pipe  26  where the temperature of blow-by gas decreases the most. Meanwhile, the outside air including a traveling wind entering the outlet part  33 , and in a cold region, for example, the outside air entering the outlet part  33  is also very cold. Under such circumstances, condensed water and freezing are likely to occur in the outlet part  33 . 
     However, according to the configuration of the present embodiment, since blow-by gas can be heated by the heat chamber  24  provided in the middle of the gas pipe  23 , the temperature of the blow-by gas that reaches the outlet part  33  is raised, so it is possible to effectively prevent generation and freezing of condensed water in the outlet part  33 . 
     Also, according to the configuration of the present embodiment, since the heat chamber  24  is formed by the hollow space  40  provided integrally with the flywheel housing  10  and the lid  41  closing the hollow space  40 , it is possible to easily form the heat chamber as compared to a case where a heat chamber which is a completely closed space is formed in the flywheel housing. Also, since the lid  41  is detachable, it is possible to remove the lid  41  to inspect and maintain the inside of the heat chamber  24  if necessary. Also, the lid  41  can be regarded as a part of the separated flywheel housing  10 . 
     However, the heat chamber which is the completely closed space may be formed in the flywheel housing. 
     By the way, in the present embodiment, if oil accumulates in the heat chamber  24  over a long-term use, it is possible to discharge the accumulated oil through the drain mechanism  60 . 
     As shown in  FIG. 4 , when discharging oil O accumulated in the heat chamber  24 , a maintenance mechanic removes the plug  71  and inserts a jig or a tool  72  into the flywheel housing  10  through the housing hole  70 . Then, the maintenance mechanic inserts a tip of the tool  72  into the valve hole  65  and pushes the tool  72  to the valve opening side (the right side) such that the valve body  67  is pushed out against the biasing force of the spring  68  by the tip of the tool  72 , thereby opening the check valve  61 . 
     As a result, the oil O is discharged from the heat chamber  24  through the drain hole  63  and the valve hole  65  in order. The discharged oil O may drop in the flywheel housing  10  However, even though the discharged oil drops, since the inside of the flywheel housing  10  also is oily and the amount of oil is very small, there is no problem. 
     According to the configuration of the present embodiment, even though oil accumulates in the heat chamber  24 , it is possible to discharge the oil regularly at a timing of the maintenance, thereby solving problems attributable to accumulation of oil while preventing accumulation of oil. Also, since it is possible to discharge oil only by inserting the tool  72  through the housing hole  70  and pushing the valve body  67  by the tip of the tool  72 , it is possible to easily perform the oil discharge work. 
     Now, modifications will be described. By the way, parts identical to those of the above-described basic example are denoted by the same reference numbers, and a description thereof will be omitted, and hereinafter, differences from the basic example will be mainly described. 
     In a first modification shown in  FIG. 5 , the valve body  67  of the check valve  61  is a bottomed cylindrical hollow piston. The left end of the valve body  67  is closed, and is pressed against a valve seat  69  by the spring  68 . The right end of the valve body  67  is opened, and the spring  68  is inserted into the valve body  67  therefrom. 
     In a second modification shown in  FIG. 6 , the drain valve is a drain bolt  75 . The drain bolt  75  is tightened to an internal screw  76  provided on an inner surface of an outlet part of the valve hole  65 , and blocks the valve hole  65 . As a result, the drain valve becomes the closed state. The drain bolt  75  is a general hexagon bolt having a hexagonal head  77 , and is tightened to the internal screw  76  with a washer  78  interposed therebetween. When the drain bolt  75  is loosened, oil leaks out from the gap between the drain bolt  75  and the internal screw  76  and is discharged. Therefore, the valve hole  65  becomes substantially the open state, and the drain valve becomes the open state. As described above, the drain bolt  75  is switched between the closed state and the open state by tightening and loosening, so it can be regarded as a drain valve. 
     When discharging oil from the heat chamber  24 , a socket wrench (not shown in the drawing) is inserted into the flywheel housing  10  through the housing hole  70 , and a socket part of the socket wrench is fit on the head  77 . Then, the socket wrench is turned to loosen the drain bolt  75 , whereby the drain valve becomes the open state, and oil is discharged. 
     In a third modification shown in parts (A) and (B) of  FIG. 7 , the drain bolt  75  is a general hexagon socket head cap screw having a hexagon hole  79 . When discharging oil from the heat chamber  24 , a hexagon wrench is inserted through the housing hole  70 , and the drain bolt  75  is loosened by the hexagon wrench. 
     In a fourth modification shown in parts (A) and (B) of  FIG. 8 , the drain bolt  75  is also a hexagon socket head cap screw. However, in an external screw part  80  of the drain bolt  75 , a groove  81  is provided and extends in the axial direction. According to this configuration, when the drain bolt  75  is loosened, it is possible to allow oil to flow through the groove  81  more aggressively, so it is possible to more quickly discharge oil. Since the groove  81  is longer than the internal screw  76 , when the drain bolt  75  is loosened such that the groove  81  extends from a position that is beyond the internal screw  76  on the heat chamber  24  side to a position that is beyond the internal screw  76  on the opposite side to the heat chamber  24 , it is possible to quickly discharge oil using the internal screw  76  as a shortcut. The groove  81  can be applied to arbitrary drain bolts including the drain bolt  75  of the second modification ( FIG. 6 ). 
     In a fifth modification shown in  FIG. 9 , the drain mechanism  60  is a check valve  82  However, this check valve  82  is a gravity type, not a spring type, unlike the basic example ( FIG. 3 ). 
     That is, a valve body  83  of the check valve  82  seats on a valve seat  84  due to its own weight when the engine stops, whereby the check valve  82  is closed. On the other hand, when the engine operates, due to the pressure in the flywheel chamber  11  that is increased by rotation of the flywheel  8 , the valve body  83  rises as shown by an imaginary line, whereby the valve body is separated from the valve seat  84  and the check valve  84  is opened. Therefore, it is possible to discharge oil when the engine operates. 
     In the present modification, at the lowest position of a lower wall part  85  which forms a lower inner wall surface  49  of the heat chamber  24 , a vertical drain hole  86  is formed through the lower wall part  85 . The check valve  82  is attached to an outer surface of the lower wall part  85  by appropriate means such as welding, bolting, or the like so as to communicate with the drain hole  86 . 
     The check valve  82  includes a main valve body  87  attached to the lower wall part  85 , a valve hole  88  formed through the main valve body  87 , a valve body chamber  89  provided in the middle of the valve hole  88  such that the diameter of the valve hole  88  expands, and a valve body  83  disposed so as to be movable vertically in the valve body chamber  89 . The valve hole  88  coaxially communicates with the drain hole  86 , and extends in the vertical direction. The valve body  83  has a disk shape. The valve seat  84  and the peripheral edge of the lower end of the valve body  83  which seats on the valve seat have a tapered shape. 
     The embodiments of the present disclosure have been described above in detail. However, other embodiments of the present disclosure also are possible. 
     (1) For example, the oil separator  22  may be omitted. In this case, oil accumulates in the heat chamber  24  for a shorter time, but it is possible to discharge the accumulated oil by the drain mechanism. 
     (2) The installation position of the drain mechanism can be changed to a position other than the above-mentioned position. 
     The configurations of the embodiments and the modifications described above can be combined partially or totally unless there is any particular contradiction. Embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents encompassed within the idea of the present disclosure defined by claims are also included in the present disclosure. Therefore, the present disclosure should not be interpreted in a limited manner, and can also be applied to other arbitrary technologies belonging to the range of the idea of the present disclosure. 
     This application is based on Japanese Patent Application (Japanese Patent Application No. 2018-182123) filed on Sep. 27, 2018, the contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     According to the present disclosure, it is possible to prevent freezing of condensed water in a blow-by gas pipe. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  Internal Combustion Engine (Engine) 
               10  Flywheel Housing 
               23  Gas Pipe 
               24  Heat Chamber 
               33  Outlet Part 
               60  Drain Mechanism 
               61  Check Valve 
               67  Valve Body 
               68  Spring 
               70  Housing Hole 
               75  Drain Bolt