Patent Publication Number: US-2021172353-A1

Title: Blowby-gas reflux system, blowby-gas reflux-system control device, and recording medium

Description:
TECHNICAL FIELD 
     The present disclosure relates to a blow-by gas reflux system, a blow-by gas reflux system control device and a storage medium. 
     BACKGROUND ART 
     In the related art, known is a blow-by gas reflux system including a blow-by gas reflux path for refluxing a blow-by gas discharged from an internal combustion engine to an intake passage on a further upstream-side than a compressor of a supercharger after causing the blow-by gas to pass through an oil separator configured to remove oil from the blow-by gas (for example, refer to PTL 1). According to the blow-by gas reflux system, it is possible to suppress oil contained in the blow-by gas discharged from the internal combustion engine from being released into the atmosphere in a large amount. 
     In the meantime, PTL 2 can be exemplified as another patent literature. PTL 2 discloses a phenomenon where oil contained in the blow-by gas caulks (carbonization) (referred to as “oil caulking”). 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-2011-33032 
     PTL 2: JP-A-2005-264759 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the blow-by gas reflux system, the oil contained in the blow-by gas discharged from the internal combustion engine is removed via the oil separator. However, the oil may not be completely removed by the oil separator, so that a small amount of oil may be contained in the blow-by gas after passing through the oil separator. In a case where an operating state of the compressor is a high supercharging operating state (a case where an intake air temperature after supercharging is high, a case where an intake air pressure after supercharging is high, and the like), when the blow-by gas after passing through the oil separator is refluxed to the intake passage and is introduced into the compressor, oil caulking due to the oil contained in the blow-by gas may occur in the compressor. 
     The present disclosure has been made in view of the above situations, and an object thereof is to provide a blow-by gas reflux system, a blow-by gas reflux system control device and a storage medium capable of suppressing occurrence of oil caulking. 
     Solution to Problem 
     In order to achieve the above object, a blow-by gas reflux system according to an illustrative aspect of the present disclosure includes: a blow-by gas reflux path causing a blow-by gas discharged from an internal combustion engine to pass through an oil separator, which is configured to remove oil from the blow-by gas, and then refluxing the blow-by gas to an intake passage of the internal combustion engine positioned on a further upstream-side than a compressor of a supercharger disposed on the intake passage; an atmospheric release mechanism disposed at a position further downstream side of the blow-by gas reflux path than the oil separator, the atmospheric release mechanism being configured to release the blow-by gas after passing through the oil separator into an atmosphere; and a control device, wherein the control device includes: a determination unit configured to determine whether oil caulking occurs in the compressor, based on an operating state of the compressor, the oil caulking being caused due to oil contained in the blow-by gas after passing through the oil separator; and a control unit configured to: in a case the determination unit determines that the oil caulking does not occur, stop the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism; and in a case the determination unit determines that the oil caulking occurs, control the atmospheric release mechanism to release the blow-by gas into the atmosphere. 
     Further, in order to achieve the above object, a control device of a blow-by gas reflux system of an illustrative aspect of the present disclosure is a control device applied to a blow-by gas reflux system, the blow-by gas reflux system including: a blow-by gas reflux path for causing a blow-by gas discharged from an internal combustion engine to pass through an oil separator, which is configured to remove oil from the blow-by gas, and then refluxing the blow-by gas to an intake passage of the internal combustion engine positioned on a further upstream-side than a compressor of a supercharger disposed on the intake passage; and an atmospheric release mechanism disposed at a further downstream-side part of the blow-by gas reflux path than the oil separator and configured to release the blow-by gas after passing through the oil separator into an atmosphere, the control device includes: a determination unit configured to determine whether oil caulking occurs in the compressor, based on an operating state of the compressor, the oil caulking being caused due to oil contained in the blow-by gas after passing through the oil separator; and a control unit configured to: in a case the determination unit determines that the oil caulking does not occur, stop the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism; and in a case the determination unit determines that the oil caulking occurs, control the atmospheric release mechanism to release the blow-by gas into the atmosphere. 
     Further, a computer-readable storage medium of an illustrative aspect of the present disclosure is a computer-readable medium storing a computer program readable by a computer of a vehicle, the vehicle including a blow-by gas reflux system including a blow-by gas reflux path for causing a blow-by gas discharged from an internal combustion engine to pass through an oil separator configured to remove oil from the blow-by gas and then refluxing the blow-by gas to an intake passage of the internal combustion engine positioned on a further upstream-side than a compressor of a supercharger disposed on the intake passage; and an atmospheric release mechanism disposed at a further downstream-side part of the blow-by gas reflux path than the oil separator and configured to release the blow-by gas after passing through the oil separator into an atmosphere, and wherein the computer program, when executed by the computer, causes the vehicle to perform: determining whether oil caulking occurs in the compressor, based on an operating state of the compressor, the oil caulking being caused due to oil contained in the blow-by gas after passing through the oil separator; stopping the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism, when it is determined that the oil caulking does not occur; and causing the atmospheric release mechanism to release the blow-by gas into the atmosphere, when it is determined that the oil caulking occurs. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to suppress occurrence of oil caulking. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a pictorial configuration view of an internal combustion engine system to which a blow-by gas reflux system in accordance with a first embodiment and a second embodiment is applied, depicting a state where a blow-by gas is refluxed to an intake passage. 
         FIG. 2  is a pictorial configuration view of the internal combustion engine system to which the blow-by gas reflux system in accordance with the first embodiment and the second embodiment is applied, depicting a state where the blow-by gas is released into an atmosphere. 
         FIG. 3  is a flowchart depicting an example of control processing of an atmospheric release mechanism that is performed by a control device in accordance with the first embodiment. 
         FIG. 4  is a flowchart depicting an example of control processing of the atmospheric release mechanism that is performed by the control device in accordance with the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Hereinbelow, a blow-by gas reflux system  60  and a control device  50  of the blow-by gas reflux system  60  in accordance with a first embodiment will be described with reference to the drawings. Specifically, a schematic configuration of an internal combustion engine system  1  to which the blow-by gas reflux system  60  in accordance with the present embodiment is applied is first described, and the blow-by gas reflux system  60  and the control device  50  thereof are then described. 
     The internal combustion engine system  1  exemplified in  FIG. 1  includes an internal combustion engine  10 , an intake passage  20 , an air cleaner  30 , a supercharger  40 , a control device  50 , and a blow-by gas reflux system  60 . In the meantime, the internal combustion engine system  1  in accordance with the present embodiment is mounted on a vehicle. A specific type of the vehicle is not particularly limited, and a variety of vehicles such as a passenger car, a commercial vehicle can be used. 
     The internal combustion engine  10  has an internal combustion engine main body  11 . The internal combustion engine main body  11  has a cylinder block in which cylinders are formed, a cylinder head disposed on an upper part of the cylinder block, a piston disposed in the cylinder, and a crankshaft connected to the piston via a connecting rod. Also, the internal combustion engine  10  has a crankcase  12 . The crankcase  12  is connected to a lower part of the cylinder block. The crankshaft is accommodated in the crankcase  12 . Also, the internal combustion engine  10  has a cylinder head cover  13 . The cylinder head cover  13  is disposed on an upper part of the cylinder head. In the cylinder head cover  13 , a valve mechanism such as a cam is accommodated. 
     A specific type of the internal combustion engine  10  is not particularly limited, and a variety of internal combustion engines such as a Diesel engine, a gasoline engine and the like can be used. In the present embodiment, a Diesel engine is used as an example of the internal combustion engine  10 . 
     The intake passage  20  is a passage through which an intake air (A) sucked in the internal combustion engine  10  passes. A downstream-side end portion of the intake passage  20  connects to an intake port of the internal combustion engine  10 . In the meantime, although not shown, the internal combustion engine  10  has also an exhaust passage through which an exhaust air discharged from the internal combustion engine  10  passes. An upstream-side end portion of the exhaust passage connects to an exhaust port of the internal combustion engine  10 . The air cleaner  30  is disposed at a further upstream part of the intake passage  20  than the supercharger  40 . In the meantime, the intake air that flows into the intake passage  20  from an upstream-side end portion of the intake passage  20  is fresh air. The air cleaner  30  is a member having a function of removing foreign materials such as dirt and dust contained in the fresh air. 
     The supercharger  40  is a device configured to supercharge the intake air sucked in the internal combustion engine  10  by a compressor  41 . A specific configuration of the supercharger  40  is not particularly limited inasmuch as it has such function. For example, a variety of superchargers such as a turbo supercharger where the compressor  41  is driven using energy of the exhaust air, a mechanical supercharger where the compressor  41  is driven by power of the internal combustion engine  10 , an electric supercharger where the compressor  41  is driven by power of an electric motor, and the like can be used. In the present embodiment, a turbo supercharger is used as an example of the supercharger  40 . Specifically, the supercharger  40  in accordance with the present embodiment includes a turbine (not shown) disposed on the exhaust passage, the compressor  41  disposed on the intake passage  20 , and a rotary shaft (not shown) coupling the turbine and the compressor  41 . The turbine is driven by receiving the energy of the exhaust air, so that the compressor  41  connected to the turbine via the rotary shaft is driven to supercharge the intake air. 
     The control device  50  is configured by an electronic control device. Specifically, the control device  50  in accordance with the present embodiment includes a microcomputer having a CPU (Central Processing Unit)  51  configured to execute a variety of control processing and a storage unit  52  configured to store a program, data and the like that are used for operations of the CPU  51 . In the meantime, the storage unit  52  includes a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. 
     The control device  50  in accordance with the present embodiment is configured to control operations of the internal combustion engine  10  by controlling a fuel injection timing, a fuel injection amount and the like of the internal combustion engine  10 . Also, the control device  50  in accordance with the present embodiment functions as a control device of the blow-by gas reflux system  60 . In the meantime, the control device of the blow-by gas reflux system  60  may also be a control device that is provided separately from the control device configured to control the internal combustion engine  10 . 
     The blow-by gas reflux system  60  in accordance with the present embodiment is applied to the internal combustion engine system  1  as described above. Subsequently, a configuration of the blow-by gas reflux system  60  is described. The blow-by gas reflux system  60  includes a blow-by gas reflux path  70 , an oil separator  80 , an atmospheric release mechanism  90  (an atmospheric release passage  91  and a three-way valve  92 ), a sensor  100   a,  a sensor  100   b  and the control device  50  as a part of the constitutional elements. 
     The blow-by gas reflux path  70  is a flow path for refluxing a blow-by gas (Gb) discharged from the internal combustion engine  10  to a further upstream-side part (in the present embodiment, a further downstream-side part than the air cleaner  30 ) of the intake passage  20  than the compressor  41  after causing the blow-by gas to pass through the oil separator  80 . Specifically, the blow-by gas reflux path  70  in accordance with the present embodiment has an upstream-side end portion connected to a blow-by gas exhaust port provided on an outer wall of a side surface of the cylinder head cover  13  of the internal combustion engine  10 , and a downstream-side end portion connected to a part of the intake passage  20  on a further upstream-side than the compressor  41  and on a further downstream-side than the air cleaner  30 . The oil separator  80  is disposed on the way of the blow-by gas reflux path  70 . 
     The oil separator  80  has a function of removing oil contained in the blow-by gas introduced into the oil separator  80 . A specific configuration of the oil separator  80  is not particularly limited inasmuch as it has such function, and a well-known oil separator (which may also be referred to as an oil mist separator) can be used. For this reason, the descriptions of the detailed structure of the oil separator  80  are omitted. 
     The blow-by gas generated in the internal combustion engine  10  is leaked from a gap between each cylinder and the piston therein to the crankcase  12 , passes through the inside of the cylinder head cover  13 , and is then introduced into the blow-by gas reflux path  70 . Then, the blow-by gas passes through the oil separator  80  and is then refluxed to a further upstream-side part of the intake passage  20  than the compressor  41 . In the meantime, the oil contained in the blow-by gas discharged from the internal combustion engine  10  is removed as it passes through the oil separator  80 . However, the oil may not be completely removed by the oil separator  80 . In this case, a small amount of oil may be contained in the blow-by gas after passing through the oil separator  80 . 
     The atmospheric release mechanism  90  is disposed at a further downstream-side part of the blow-by gas reflux path  70  than the oil separator  80 . The atmospheric release mechanism  90  is configured to release the blow-by gas after passing through the oil separator  80  into the atmosphere, in response to an instruction of the control device  50 . A specific configuration of the atmospheric release mechanism  90  is not particularly limited inasmuch as it has such function. However, the atmospheric release mechanism  90  in accordance with the present embodiment has an atmospheric release passage  91  and a three-way valve  92 , as an example. 
     The atmospheric release passage  91  has a downstream-side end portion opening to the atmosphere and an upstream-side end portion connected to a further downstream-side passage part of the blow-by gas reflux path  70  than the oil separator  80 . The three-way valve  92  is disposed at the connection place of the atmospheric release passage  91  to the blow-by gas reflux path  70 . That is, the atmospheric release passage  91  in accordance with the present embodiment is connected to the blow-by gas reflux path  70  via the three-way valve  92 . 
     The three-way valve  92  has a gas inlet  93 , a gas outlet  94   a  and a gas outlet  94   b,  and the gas inlet  93  and the gas outlet  94   a  are provided at a further downstream-side passage part of the blow-by gas reflux path  70  than the oil separator  80 . The upstream-side end portion of the atmospheric release passage  91  is connected to the gas outlet  94   b  of the three-way valve  92 . The gas inlet  93  of the three-way valve  92  is always in an opened state. In the meantime, the three-way valve  92  has such a structure that it is controlled by the control device  50 , thereby opening and closing independently each of the gas outlet  94   a  and the gas outlet  94   b.    
     As exemplified in  FIG. 1 , when the three-way valve  92  opens the gas outlet  94   a  and closes the gas outlet  94   b,  the blow-by gas after passing through the oil separator  80  is not released into the atmosphere and passes through the blow-by gas reflux path  70  and is then refluxed to the intake passage  20 . 
     In the meantime, as exemplified in  FIG. 2 , when the three-way valve  92  closes the gas outlet  94   a  and opens the gas outlet  94   b,  the blow-by gas after passing through the oil separator  80  is released into the atmosphere through the atmospheric release passage  91  (in this case, the blow-by gas is not refluxed to the intake passage  20 ). In this way, the atmospheric release mechanism  90  in accordance with the present embodiment releases the blow-by gas after passing through the oil separator  80  into the atmosphere. 
     The three-way valve  92  is an example of a member having a function as a flow path switching mechanism configured to switch a flow destination of the blow-by gas after passing through the oil separator  80  between the atmospheric release passage  91  and the intake passage  20 . 
     The configuration of the flow path switching mechanism is not limited to the three-way valve  92  as described above. As another example of the flow path switching mechanism, the flow path switching mechanism may include a first opening/closing valve disposed on the atmospheric release passage  91  and configured to open/close the atmospheric release passage  91  and a second opening/closing valve disposed on a further downstream-side passage part of the blow-by gas reflux path  70  than the connection place of the atmospheric release passage  91  and configured to open/close the connection place. In this case, the control device  50  can release the blow-by gas after passing through the oil separator  80  into the atmosphere through the atmospheric release passage  91  by controlling the first opening/closing valve to an opened state and the second opening/closing valve to a closed state. On the other hand, the control device  50  can reflux the blow-by gas after passing through the oil separator  80  to the intake passage  20  by controlling the first opening/closing valve to a closed state and the second opening/closing valve to an opened state. 
     Also, the place of the blow-by gas reflux path  70  on which the three-way valve  92  is disposed may be a further downstream-side part than the oil separator  80  and is not limited to the place exemplified in  FIGS. 1 and 2 . In the meantime, as the place of the blow-by gas reflux path  70  on which the three-way valve  92  is disposed is closer to the oil separator  80 , it is possible to more effectively suppress the blow-by gas from being cooled by the atmosphere until the blow-by gas after passing through the oil separator  80  flows into the three-way valve  92 . Therefore, it is preferably to set the disposal place of the three-way valve  92 , taking into account this point. 
     Referring to  FIG. 1 , the sensor  100   a  is configured to detect a temperature (referred to as “intake air temperature T after supercharging”) of the intake air supercharged by the compressor  41  and to transmit a detection result to the control device  50 . That is, the sensor  100   a  in accordance with the present embodiment is a temperature sensor configured to detect the intake air temperature T after supercharging. Specifically, the sensor  100   a  in accordance with the present embodiment is disposed near an intake air outlet of the compressor  41 , and is configured to detect a temperature of the intake air immediately after discharged from the compressor  41 . 
     The sensor  100   b  is configured to detect a temperature of the atmosphere (referred to as “atmospheric temperature Ta”) and to transmit a detection result to the control device  50 . That is, the sensor  100   b  in accordance with the present embodiment is a temperature sensor configured to detect the atmospheric temperature Ta. In the meantime, the detection result of the sensor  100   b  is not used in control processing (control processing shown in  FIG. 3 , which will be described later) in accordance with the present embodiment, and the detection result of the sensor  100   b  is used in control processing of  FIG. 4  (control processing of a second embodiment). For this reason, the blow-by gas reflux system  60  in accordance with the present embodiment may also be configured not to include the sensor  100   b.    
     Subsequently, control of the atmospheric release mechanism  90  that is performed by the control device  50  is described with reference to a flowchart shown in  FIG. 3 . In the meantime, each step in  FIG. 3  is executed by the CPU  51  of the control device  50 , based on a program stored in the storage unit  52 . The control device  50  first starts the flowchart of  FIG. 3  at the same time when the internal combustion engine  10  starts (i.e., the flowchart of  FIG. 3  is periodically executed during the operation of the internal combustion engine  10 ). Also, it is assumed that upon first start of  FIG. 3 , the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism  90  is stopped. 
     In step S 10  of  FIG. 3 , the control device  50  determines whether oil caulking due to the oil contained in the blow-by gas (Gb) after passing through the oil separator  80  occurs in the compressor  41 , based on the operating state of the compressor  41 . The specific execution content of step S 10  is described as follows. 
     First, the control device  50  in accordance with the present embodiment uses the temperature (i.e., the intake air temperature T after supercharging) of the intake air supercharged by the compressor  41 , as a parameter relating to the operating state of the compressor  41 . As an operating load of the compressor  41  increases, the intake air temperature T after supercharging intends to increase. That is, the intake air temperature T after supercharging is a parameter having correlation with the operating load of the compressor  41 . The control device  50  obtains the detection result of the sensor  100   a  to obtain the intake air temperature T after supercharging. The control device  50  determines whether the obtained intake air temperature T after supercharging is equal to or higher than a predetermined threshold value T1, and determines that oil caulking occurs (YES) when it is determined that the intake air temperature T after supercharging is equal to or higher than the threshold value T1. 
     The threshold value T1 may be any value by which it is possible to determine that oil caulking occurs when the intake air temperature T after supercharging is equal to or higher than the corresponding value. As the threshold value T1, an appropriate value may be obtained in advance by performing a test, a simulation and the like, and may be stored in the storage unit  52  of the control device  50 . In this way, step S 10  in accordance with the present embodiment is executed. 
     The execution content of step S 10  is not limited to the above. As another example, in step S 10 , the control device  50  may estimate the intake air temperature T after supercharging, based on a parameter (for example, the operating state of the internal combustion engine  10 ) having correlation with the intake air temperature T after supercharging, instead of using the detection result of the sensor  100   a.  Specifically, in this case, a control map in which the intake air temperature T after supercharging is associated with the number of rotations of the internal combustion engine  10  and the load of the internal combustion engine  10  (for example, a fuel injection amount) is stored in advance in the storage unit  52 . The control device  50  may obtain the number of rotations and the load of the internal combustion engine  10 , extract the intake air temperature T after supercharging corresponding to the obtained number of rotations and load from the control map, and use the extracted intake air temperature T after supercharging in step S 10 . 
     Alternatively, in step S 10 , the control device  50  may use a pressure (referred to as “supercharging pressure P”) of the intake air supercharged by the compressor  41 , as a parameter relating to the operating state of the compressor  41 . The supercharging pressure P is also a parameter whose value tends to increase as the operating load of the compressor  41  increases. In the meantime, when the supercharging pressure P is used as a parameter relating to the operating state of the compressor  41 , a pressure sensor configured to detect the supercharging pressure P is used as the sensor  100   a.  In step S 10 , the control device  50  determines whether the supercharging pressure P detected by the sensor  100   a  as the pressure sensor is equal to or higher than a predetermined threshold value P1, and determines that oil caulking occurs (YES) when it is determined that the supercharging pressure P is equal to or higher than the threshold value P1. Similarly to the threshold value T1, the threshold value P1 may also be any value by which it is possible to determine that oil caulking occurs when the supercharging pressure P is equal to or higher than the corresponding value. As the threshold value P1, an appropriate value may be obtained in advance by performing a test, a simulation and the like, and may be stored in the storage unit  52  of the control device  50 . 
     Also, when obtaining the supercharging pressure P, the control device  50  may estimate the same, based on a parameter (for example, the operating state of the internal combustion engine  10 ) having correlation with the supercharging pressure P. Specifically, in this case, a control map in which the supercharging pressure P is associated with the number of rotations of the internal combustion engine  10  and the load of the internal combustion engine  10  is stored in advance in the storage unit  52 . The control device  50  may obtain the number of rotations and the load of the internal combustion engine  10 , extract the supercharging pressure P corresponding to the obtained number of rotations and load from the control map, and use the extracted supercharging pressure P in step S 10 . 
     By the diverse methods, step S 10  can be executed. When a determination result in step S 10  is NO (when it is determined that oil caulking does not occur), the control device  50  executes step S 20 . In step S 20 , the control device  50  stops the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism  90  (when the release of the blow-by gas into the atmosphere has been already stopped before execution of step S 20 , this state is maintained in step S 20 ). Specifically, as described above, the control device  50  controls the gas outlet  94   a  of the three-way valve  92  of the atmospheric release mechanism  90  to the opened state and the gas outlet  94   b  to the closed state. Thereby, the blow-by gas after passing through the oil separator  80  passes through the blow-by gas reflux path  70  and is then refluxed to the intake passage  20 . After executing step S 20 , the control device  50  again executes the flowchart from the start (return). 
     On the other hand, when a determination result in step S 10  is YES (when it is determined that oil caulking occurs), the control device  50  executes step S 30 . In step S 30 , the control device  50  causes the atmospheric release mechanism  90  to release the blow-by gas into the atmosphere. Specifically, as described above, the control device  50  controls the gas outlet  94   a  of the three-way valve  92  of the atmospheric release mechanism  90  to the closed state and the gas outlet  94   b  to the opened state. Thereby, the blow-by gas after passing through the oil separator  80  passes through the atmospheric release passage  91  and is then released to the atmosphere. 
     After executing step S 30 , the control device  50  again executes the flowchart from the start (return). In the meantime, the release of the blow-by gas into the atmosphere in step S 30  is continuously executed until when a determination result in step S 10  becomes NO during the re-execution of the flowchart. That is, according to the present embodiment, the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism  90  is continuously executed until it is determined that oil caulking does not occur in the compressor  41 . 
     In the present embodiment, the CPU  51  of the control device  50  that executes step S 10  is an example of a member having a function as “determination unit”. Also, the CPU  51  of the control device  50  that executes step S 20  and step S 30  is an example of a member having a function as “control unit”. 
     According to the present embodiment as described above, when it is determined based on the operating state of the compressor  41  that oil caulking occurs (YES in step S 10 ), the control processing relating to step S 30  is executed, so that the blow-by gas after passing through the oil separator  80  can be released into the atmosphere. Thereby, since the blow-by gas containing oil is not introduced into the compressor  41 , it is possible to suppress oil caulking from occurring in the compressor  41 . Also, according to the present embodiment, since the blow-by gas after passing through the oil separator  80  is released into the atmosphere, the amount of oil in the blow-by gas that is released into the atmosphere is smaller, as compared to a case where the blow-by gas before passing through the oil separator  80  is released into the atmosphere. That is, according to the present embodiment, while suppressing the oil contained in the blow-by gas discharged from the internal combustion engine  10  from being released into the atmosphere in a large amount, it is possible to suppress oil caulking from occurring in the compressor  41 . 
     As a result, according to the present embodiment, while suppressing atmospheric pollution due to the oil released into the atmosphere as much as possible, it is possible to suppress oil caulking from occurring in the compressor  41 , thereby suppressing lowering in supercharging efficiency of the compressor  41  due to oil caulking. 
     Second Embodiment 
     Subsequently, a blow-by gas reflux system  60  and a control device  50  in accordance with a second embodiment are described. In the meantime, the hardware configuration of the blow-by gas reflux system  60  in accordance with the present embodiment is the same as that of the blow-by gas reflux system  60  in accordance with the first embodiment. The processing that is executed by the control device  50  of the blow-by gas reflux system  60  in accordance with the present embodiment is different from the first embodiment. Specifically, the control device  50  in accordance with the present embodiment is different from the control device  50  in accordance with the first embodiment, in that a flowchart of  FIG. 4  is executed instead of the flowchart of  FIG. 3 . 
     The flowchart of  FIG. 4  is different from the flowchart of  FIG. 3 , in that it further includes step S 15 . The control device  50  in accordance with the present embodiment executes step S 15  when a determination result in step S 10  of  FIG. 4  is YES. In step S 15 , the control device  50  determines whether the atmospheric temperature Ta is equal to or lower than a predetermined threshold value Ta1 (i.e., low temperature). The technical background of executing step S 15  and detailed contents of step S 15  are described as follows. 
     First, when step S 30  is executed and the blow-by gas after passing through the oil separator  80  is thus released into the atmosphere, the blow-by gas does not pass through the connection place (specifically, the place in which the three-way valve  92  is disposed) of the atmospheric release mechanism  90  on the blow-by gas reflux path  70 . As a result, a further downstream-side part of the blow-by gas reflux path  70  than the atmospheric release mechanism  90  is cooled by the atmosphere, so that the temperature thereof is lowered. 
     Herein, when the atmospheric temperature is low, as the moisture attached to the further downstream-side part of the blow-by gas reflux path  70  than the atmospheric release mechanism  90  is frozen, the blow-by gas reflux path  70  is further cooled. In the cooled state, when the reflux of the blow-by gas to the intake passage  20  is resumed, the moisture contained in the blow-by gas is frozen at the time when the moisture is attached to a pipe wall part of the blow-by gas reflux path  70 . As a result, a frozen material (for example, chips of ice) due to the freezing is generated in the blow-by gas reflux path  70 . When the frozen material flows downstream together with the blow-by gas and is introduced into the compressor  41 , the compressor  41  may malfunction. 
     Therefore, in the present embodiment, in order to solve the above problem, step S 15  is executed. Specifically, the threshold value Ta1 that is used for the determination processing in step S 15  is stored in advance (i.e., predetermined) in the storage unit  52  of the control device  50  in accordance with the present embodiment. In the present embodiment, as the threshold value Ta1, an atmospheric temperature at which the freezing occurs in the further downstream-side part of the blow-by gas reflux path  70  than the atmospheric release mechanism  90  is used. That is, in the present embodiment, when the atmospheric temperature Ta is equal to or lower than the threshold value Ta1, as the freezing occurs in the further downstream-side part of the blow-by gas reflux path  70  than the atmospheric release mechanism  90 , the atmospheric temperature Ta is lowered. As the threshold value Ta1, an appropriate value may be obtained in advance by performing a test, a simulation and the like, and may be stored in the storage unit  52  of the control device  50 . 
     Then, in step S 15 , the control device  50  obtains the atmospheric temperature Ta, based on the detection result of the sensor  100   b,  and determines whether the obtained atmospheric temperature Ta is equal to or lower than the threshold value Ta1 stored in the storage unit  52 . When it is determined that the atmospheric temperature Ta is equal to or lower than the threshold value Ta1, the control device  50  determines YES and executes step S 20 . When it is determined that the atmospheric temperature Ta is not equal to or lower than the threshold value Ta1, the control device  50  determines NO and executes step S 30 . 
     That is, when it is determined that oil caulking occurs (YES in step S 10 ) and it is also determined that the atmospheric temperature Ta is equal to or lower than the threshold value Ta1 (YES in step S 15 ), the control device  50  in accordance with the present embodiment stops the release of the blow-by gas into the atmosphere performed by the atmospheric release mechanism  90  and refluxes the blow-by gas to the intake passage  20  (step S 20 ), and when it is determined that oil caulking occurs (YES in step S 10 ) and it is also determined that the atmospheric temperature Ta is not equal to or lower than the threshold value Ta1 (NO in step S 15 ), the control device  50  causes the atmospheric release mechanism  90  to release the blow-by gas into the atmosphere (step S 30 ). 
     In the present embodiment, the execution sequence of step S 10  and step S 15  is not limited to the sequence shown in  FIG. 4 . As another example, the control device  50  may execute step S 15  before step S 10 . In this case, when a determination result in step S 15  is NO, step S 10  is executed, and when a determination result in step S 15  is YES, step S 20  is executed. 
     In the present embodiment, the CPU  51  of the control device  50  that executes step S 10  and step S 15  is an example of a member having a function as “determination unit”. Also, the CPU  51  of the control device  50  that executes step S 20  and step S 30  is an example of a member having a function as “control unit”. 
     According to the present embodiment as described above, it is possible to achieve following effects, in addition to the operational effects of the first embodiment. Specifically, according to the present embodiment, it is possible to suppress the frozen material generated in the further downstream-side part of the blow-by gas reflux path  70  than the atmospheric release mechanism  90  from being introduced into the compressor  41 . Thereby, it is possible to suppress the malfunction of the compressor  41 , which is caused when the frozen material is introduced. Specifically, it is possible to suppress the malfunction such as a damage of the compressor  41 , which is caused when the frozen material is introduced into the compressor  41 . 
     Although the embodiments of the present disclosure have been described, the present disclosure is not limited to the specific embodiments and can be diversely modified/changed within the scope of the present invention. 
     The subject application is based on Japanese Patent Application No. 2018-078205 filed on Apr. 16, 2018, the contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The present invention has the effect of suppressing occurrence of oil caulking, and is useful for the blow-by gas reflux system, the blow-by gas reflux system control device, the storage medium, and the like. 
     REFERENCE SIGNS LIST 
     
         
           1 : internal combustion engine system 
           10 : internal combustion engine 
           20 : intake passage 
           30 : air cleaner 
           40 : supercharger 
           41 : compressor 
           50 : control device 
           51 : CPU (determination unit, control unit) 
           52 : storage unit 
           60 : blow-by gas reflux system 
           70 : blow-by gas reflux path 
           80 : oil separator 
           90 : atmospheric release mechanism 
           91 : atmospheric release passage 
           92 : three-way valve 
           100   a,    100   b:  sensor