Patent Publication Number: US-7712456-B2

Title: Blow-by gas processing apparatus

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a blow-by gas processing apparatus provided in an internal combustion engine provided with a supercharger. 
   A vehicle internal combustion engine can be provided with, for example, a blow-by gas processing apparatus. The blow-by gas processing apparatus recirculates a combustion gas leaking to a crank chamber from a gap between a cylinder and a piston of the engine, that is, a blow-by gas to an intake passage. Specifically, an intake negative pressure generated in a portion of the intake passage in a downstream side of a throttle valve draws the blow-by gas in an interior of the engine so as to flow into a breather passage. The blow-by gas is returned to the intake passage from the breather passage, is again fed to the combustion chamber, and is burned. Accordingly, it is possible to reduce a discharge amount of hydrocarbon (HC) to the atmosphere. Further, it is possible to inhibit the blow-by gas from deteriorating oil in the interior of the engine. As mentioned above, the blow-by gas processing apparatus ventilates the interior of the engine. 
   However, in the case that the supercharger is provided in the engine, if the supercharger is operated, the intake negative pressure is lost. Japanese Laid-Open Patent Publication No. 2001-164918 discloses a gas pump provided in a breather passage, however, no supercharger is provided in the engine in the publication. 
   An objective of the present invention is to provide a blow-by gas processing apparatus which efficiently ventilates the interior of an engine. 
   In accordance with one aspect of the present invention, a blow-by gas processing apparatus applicable to an internal combustion engine is provided. An intake passage extends from the engine. Intake air flows from an upstream side to a downstream side in the intake passage, whereby the intake air flows toward the engine. A supercharger and a throttle valve are arranged in the intake passage. A throttle valve is positioned downstream of the supercharger. The supercharger pressure feeds the intake air flowing through the intake passage toward the engine, thereby supercharging the intake air to the engine. The throttle valve variably sets a passage cross-sectional area of the intake passage. The intake passage has an upstream portion, an intermediate portion, and a downstream portion. The upstream portion is positioned upstream of the supercharger. The intermediate portion is positioned between the supercharger and the throttle valve. The downstream portion is positioned in a downstream side of the throttle valve. The processing apparatus has a first breather passage, a second breather passage, and an introduction passage. The first breather passage connects the interior of the engine with the downstream portion. The first breather passage has a one-way valve allowing only a gas discharge from the interior of the engine to the intake passage. The second breather passage connects the interior of the engine with the intake passage. The second breather passage has a pump pressure feeding the gas to the intake passage from the interior of the engine. The introduction passage connects at least one of the upstream portion and the intermediate portion with the interior of the engine. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a schematic view of a blow-by gas processing apparatus in accordance with a first embodiment of the present invention; 
       FIG. 2  is a graph showing a relationship between a gas flow rate of the first breather passage shown in  FIG. 1 , and a pressure in a downstream side of a throttle valve; 
       FIG. 3  is a graph showing a relationship between a gas flow rate of the second breather passage shown in  FIG. 1 , and the pressure in the downstream side of the throttle valve; 
       FIG. 4  is a graph showing a relationship between a gas discharge amount from the interior of the engine shown in  FIG. 1  to an intake passage, and a pressure in a downstream side of the throttle valve; 
       FIG. 5  shows a second embodiment according to the present invention, and shows a relationship between a gas discharge amount from the interior of an engine, and a pressure in a downstream side of a throttle valve, in the case that a coolant temperature is a predetermined value; 
       FIG. 6  is a schematic view of a blow-by gas processing apparatus in accordance with a modified embodiment of the present invention; 
       FIG. 7  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment; 
       FIG. 8  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment; 
       FIG. 9  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment; 
       FIG. 10  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment; 
       FIG. 11  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment; and 
       FIG. 12  is a schematic view of a blow-by gas processing apparatus in accordance with another modified embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 4  show a first embodiment according to the present invention.  FIG. 1  shows an engine  10  to which a blow-by gas processing apparatus in accordance with a first embodiment is applied. 
   As shown in  FIG. 1 , the engine  10  is an internal combustion engine provided with a cylinder block  11 . A cylinder head  12  is provided on an upper portion of the cylinder block  11 . A head cover  13  is installed to an upper portion of the cylinder head  12 . A crankcase  14  is formed in a lower portion of the cylinder block  11 . An oil pan  15  is attached to a lower portion of the crankcase  14 . Oil for lubricating the engine  10  is stored in the oil pan  15 . Hereinafter, the interior of the engine  10  represents interior of the head cover  13  and a crank chamber  14   a.    
   A cylinder  16  is formed in the cylinder block  11 . A piston  17  is arranged in the cylinder  16  so as to reciprocate. The engine  10  has a combustion chamber  18 . An inner peripheral wall of the cylinder  16 , a top surface of the piston  17 , and a lower surface of the cylinder head  12  define the combustion chamber  18 . An intake passage  20  is connected to the combustion chamber  18  via an intake valve  19 , and an exhaust passage  22  is connected thereto via an exhaust valve  21 . In other words, each of the intake passage  20  and the exhaust passage  22  extends from the engine  10 . A communicating passage  23  is formed in the engine  10 . The communicating passage  23  extends in such a manner as to connect the interior of the head cover  13  with the crank chamber  14   a.    
   One exhaust-driven supercharger  24  is provided in the intake passage  20  and the exhaust passage  22 . The supercharger  24  is provided with a turbine wheel  25  provided in the exhaust passage  22 , and a compressor impeller  26  provided in the intake passage  20 . The shaft  27  couples the turbine wheel  25  to the compressor impeller  26  in such a manner as to be integrally rotatable. 
   If the amount of the exhaust gas flowing through the exhaust passage  22  becomes large so as to be sprayed to the turbine wheel  25 , the turbine wheel  25  and the compressor impeller  26  are integrally rotated. Accordingly, the intake air flowing through the intake passage  20  is forcibly pressure-fed to the combustion chamber  18 . In other words, the supercharger  24  supercharges the intake air to the combustion chamber  18 . The supercharger  24  is not operated in the case that a load of the engine  10  is close to zero (work load≈“0”), and is operated in the case that the load of the engine  10  is large (work load&gt;&gt;“0”). In other words, the supercharger  24  is not operated in the case that the amount of the exhaust gas flowing through the exhaust passage  22  is small, and is operated in the case that the amount of the exhaust gas is large. 
   The intake air flows to a downstream side from an upstream side in the intake passage  20 , whereby the intake air flows toward the engine  10 . In other words, the intake air in the intake passage  20  flows from an upstream side in an intake air flowing direction toward a downstream side, thereby moving toward the engine  10 . An air cleaner  28 , the compressor impeller  26 , an intercooler  29  and a throttle valve  30  are arranged in the intake passage  20  in this order from the upstream side toward the downstream side. The air cleaner  28  filtrates the intake air. The intercooler  29  lowers a temperature of the intake air by executing a heat exchange between the intake air and the external ambient atmosphere. The throttle valve  30  is a throttle valve variably setting a passage cross-sectional area of the intake passage  20 . The turbine wheel  25  is arranged in the exhaust passage  22 . The engine  10  is provided with a fuel injection valve (not shown) injecting (supplying) the fuel to the combustion chamber  18 . The engine  10  need not be a direct fuel-injection engine having the fuel injection valve, but may be a port-injection engine or a diesel engine. 
   The intake passage  20  has an upstream portion  20   a , an intermediate portion  20   b , and a downstream portion  20   c . The upstream portion  20   a  corresponds to a portion of the intake passage  20  between the air cleaner  28  and the supercharger  24 . In other words, the upstream portion  20   a  corresponds to a portion of the intake passage  20  in an upstream side of the supercharger  24 . The intermediate portion  20   b  corresponds to a portion of the intake passage  20  between the supercharger  24  and the throttle valve  30 . In other words, the upstream portion  20   a  and the intermediate portion  20   b  correspond to a portion of the intake passage  20  in an upstream side of the throttle valve  30 . The downstream portion  20   c  corresponds to a portion of the intake passage  20  in a downstream side of the throttle valve  30 . 
   The pressure of the downstream portion  20   c  is referred to as a downstream pressure P 1 . In other words, the downstream pressure P 1  indicates a pressure in an interior of the passage in the portion of the intake passage  20  in the downstream side of the throttle valve  30 . A pressure of the upstream portion  20   a  is referred to as an upstream pressure P 2 . A pressure of the crank chamber  14   a  is referred to as an engine internal pressure P 3 . A pressure of the intermediate portion  20   b  is referred to as an intermediate pressure P 4 . The state in which the downstream pressure P 1  is made higher than the atmospheric pressure by the operation of the supercharger  24  is referred to as “supercharging time”, and the state in which the downstream pressure P 1  is lower than the atmospheric pressure is referred to as “non-supercharging time.” 
   Combustion gas in the combustion chamber  18  passes through a gap of sliding surfaces between the cylinder  16  and the piston  17 , and leaks to the crank chamber  14   a . The combustion gas leaking as mentioned above corresponds to a blow-by gas. Hereinafter, the blow-by gas leaking to the crank chamber  14   a  from the combustion chamber  18  may be referred to as a leaked blow-by gas. The engine  10  is provided with a blow-by gas processing apparatus recirculating the blow-by gas to the intake passage  20 . 
   The blow-by gas processing apparatus is provided with a first breather passage  41 , a second breather passage  42 , and an introduction passage  43 . Each of the first breather passage  41  and the second breather passage  42  discharges the blow-by gas in the crank chamber  14   a  to the intake passage  20 . In other words, the blow-by gas in of the engine  10  passes through the first breather passage  41  or the second breather passage  42 , and is recirculated to the intake passage  20 . The introduction passage  43  introduces a part of the intake air of the intake passage  20  into the interior of the head cover  13 . In other words, a part of the intake air in the intake passage  20  passes through the introduction passage  43 , and can flow into the interior of the engine  10 . 
   The first breather passage  41  connects the crank chamber  14   a  with the downstream portion  20   c . In other words, an inlet of the first breather passage  41  is connected to the crank chamber  14   a  via a positive crankcase ventilation (PCV) valve  44 . The inlet of the breather passage  41  corresponds to an end portion of the side of the crankcase  14  of the first breather passage  41 . An outlet of the first breather passage  41  is connected to the downstream portion  20   c.    
   The PCV valve  44  corresponds to a one-way valve, and a differential pressure valve. In the case that the engine internal pressure P 3  is higher than the downstream pressure P 1 , an opening degree of the PCV valve  44  is reduced as the pressure difference between both the pressures is increased. In other words, the PCV valve  44  autonomously regulates a flow rate of the blow-by gas passing through the first breather passage  41  on the basis of the pressure difference between the downstream pressure P 1  and the engine internal pressure P 3 . In the case that the engine internal pressure P 3  is equal to or less than the downstream pressure P 1 , the PCV valve  44  is closed. The PCV valve  44  corresponding to the one-way discharge valve allows the blow-by gas in the crank chamber  14   a  to recirculate to the intake passage  20 , however, inhibits the intake air in the intake passage  20  from flowing into the crank chamber  14   a.    
   A first oil separator  45  is arranged in the crankcase  14 . The first oil separator  45  separates oil mist from the blow-by gas. The PCV valve  44  is connected to the first oil separator  45 . In other words, an inlet of the first breather passage  41  is connected to the crank chamber  14   a  via the PCV valve  44  and the first oil separator  45 . 
   The second breather passage  42  connects the crank chamber  14   a  with the upstream portion  20   a . An electrically driven pump  46  is provided in the middle of the second breather passage  42 . The pump  46  is a scavenging pump that pressure feeds the gas in the crank chamber  14   a  to the intake passage  20 . In other words, the pump  46  forcibly discharges the blow-by gas in the crank chamber  14   a  to the intake passage  20 . 
   An inlet of the second breather passage  42  is connected to the first oil separator  45 . In other words, both of the inlet of the first breather passage  41  and the inlet of the second breather passage  42  communicate with the first oil separator  45 . In other words, the first oil separator  45  is the same portion (common portion) to which both of the inlet of the first breather passage  41  and the inlet of the second breather passage  42  are connected. 
   The introduction passage  43  connects the upstream portion  20   a  with the interior of the head cover  13 . An inlet of the introduction passage  43  is connected to the upstream portion  20   a  in an upstream side of an outlet of the second breather passage  42 . In other words, the inlet of the introduction passage  43  corresponds to an end portion of the side of the intake passage  20  of the introduction passage  43 . A second oil separator  47  separating an oil mist from the blow-by gas is arranged in the head cover  13 . An outlet of the introduction passage  43  is connected to the second oil separator  47 . 
   The engine control unit controlling the engine  10  has various sensors detecting the operating states of the engine  10 . The various sensors include an accelerator pedal sensor  51 , a speed sensor  52 , a pressure sensor  53 , and a temperature sensor  54 . The accelerator pedal sensor  51  detects a pedaling amount of the accelerator pedal (not shown), that is, an accelerator pedal operating amount AC. The speed sensor  52  detects a rotating speed of an engine output shaft (not shown), that is, an engine speed NE. The pressure sensor  53  detects a downstream pressure P 1 . The temperature sensor  54  detects a temperature of an engine coolant, that is, a coolant temperature THW. The coolant temperature THW corresponds to an index value of the temperature of the engine  10 . 
   The engine control unit is provided with an electronic control unit  50  including a microcomputer. The electronic control unit  50  loads the output signals of the sensors  51  to  54 , carries out various computations on the basis of these signals, and carries out various controls in connection with the operation of the engine  10  on the basis of the results of computations. In other words, the electronic control unit  50  carries out a fuel injection control for controlling a fuel injection valve (not shown) and a pump control for controlling a pump  46 . 
   The electronic control unit  50  calculates a target fuel injection amount Qm corresponding to a control target value of a fuel injection amount on the basis of an accelerator pedal operation amount AC and an engine speed NE indicating an operating state of the engine  10 , at a time of executing a fuel injection control. The electronic control unit  50  opens and closes the fuel injection valve in correspondence to the target fuel injection amount Qm. As a result, the fuel injection valve injects a fuel amount matching to the operating state of the engine  10 . 
   The electronic control unit  50  increases the target fuel injection amount Qm in the case that the coolant temperature THW is low. In other words, the electronic control unit  50  executes a process to increase the target fuel injection amount Qm in the case that the coolant temperature THW is low. 
   In the case that the temperature of the engine  10  is low, a part of the fuel injected to the combustion chamber  18  collects on a wall surface of the combustion chamber  18 . Accordingly, the part of the fuel does not burn in the combustion chamber  18 . An unburned phenomenon of the fuel in the combustion chamber  18  causes a torque shortage of the engine  10 , thereby generating an unstableness of the operating state of the engine  10 . Accordingly, the unburned phenomenon is not preferable. In order to avoid disadvantages mentioned above, the electronic control unit  50  executes an amount increasing process of the amount Qm. As the temperature of the engine  10  becomes lower, the amount of the unburned fuel in the combustion chamber  18  is increased. Accordingly, in the amount increase compensating process, the electronic control unit  50  increases the fuel injection amount as the coolant temperature THW is lowered. 
   Further, the electronic control unit  50  controls the pump  46  on the basis of the downstream pressure P 1  (a pump control). In other words, the blow-by gas processing apparatus is provided with the electronic control unit  50 . At the non-supercharging time, the downstream pressure P 1  is low. In this case, the electronic control unit  50  stops the pump  46 . In other words, in the case that the intake negative pressure exists and a relative value of the downstream pressure P 1  to the atmospheric pressure is large in a negative direction, the pump  46  is maintained in a stop state. An intake negative pressure refers to an intake pressure that has a negative value when the atmospheric pressure is defined as zero. If the downstream pressure P 1  ascends such as the supercharging time, the electronic control unit  50  drives the pump  46 . In other words, if the downstream pressure P 1  becomes higher than a predetermined value, the electronic control unit  50  drives the pump  46 . 
   Next, a description will be given of an operation of the blow-by gas processing apparatus. 
   At a non-supercharging time, the intake negative pressure is generated. In other words, the downstream pressure P 1  at the non-supercharging time is lower than an upstream pressure P 2 . Accordingly, a gas flow shown by filled-in arrows in  FIG. 1  is generated on the basis of a pressure difference between the downstream pressure P 1  and the upstream pressure P 2 . In other words, the intake air flowing through the upstream portion  20   a , that is, the intake air passes through the introduction passage  43  and is introduced into the interior of the engine  10 . As shown by the filled-in arrows in  FIG. 1 , the blow-by gas in the engine  10  passes through the first breather passage  41  and is drawn (recirculated) into the intake passage  20 . 
     FIG. 2  shows a first breather line BR 1  indicating a relationship between a gas flow rate of the first breather passage  41  and the downstream pressure P 1  by a solid line. A chain line in  FIG. 2  indicates a leaking flow rate BL of the blow-by gas from the combustion chamber  18  to the crank chamber  14   a . In other words, the leaking flow rate BL corresponds to the amount of the leaking blow-by gas per unit of time. If the downstream pressure P 1  is increased, the leaking flow rate BL increased monotonically. In other words, if the downstream pressure P 1  is increased over both of a case that the downstream pressure P 1  is less than the atmospheric pressure and a case that it is equal to or more than the atmospheric pressure, the leaking flow rate BL increases monotonically. 
   As shown in  FIG. 2 , if the downstream pressure P 1  is changed, the first breather line BR 1  is changed. In other words, in the case that the downstream pressure P 1  is lower than the atmospheric pressure, if the downstream pressure P 1  is increased, the first breather line BR 1  is increased, and rapidly decreases below a maximum value. In the case that the downstream pressure P 1  is equal to or more than the atmospheric pressure, the first breather line BR 1  is zero. A value of the downstream pressure P 1  in the case that the first breather line BR 1  is close to the maximum value is referred to as a drive starting pressure α. The drive starting pressure α is a predetermined value which is lower than the atmospheric pressure. 
   As shown in  FIG. 2 , in the case that the downstream pressure P 1  is lower than the atmospheric pressure, that is, the intake negative pressure exists, the first breather line BR 1  is larger than the leaking flow rate BL of the blow-by gas. Accordingly, at the non-supercharging time, the downstream pressure P 1  (the intake negative pressure) draws the gas in the engine  10  into the first breather passage  41  at a flow rate which is larger than the leaking flow rate BL of the blow-by gas, and recirculates the gas to the intake passage  20 . 
     FIG. 3  shows a second breather line BR 2  indicating a relationship between a gas flow rate of the second breather passage  42 , and the downstream pressure P 1 . A chain line corresponds to the leaking flow rate BL of the blow-by gas. 
   As shown in  FIG. 3 , in the case that the downstream pressure P 1  is lower than the drive starting pressure α, the electronic control unit  50  stops the pump  46 . Accordingly, as shown by the first breather line BR 1  in  FIG. 2 , only a ventilation of the interior of the engine  10  caused by the intake negative pressure is executed. In other words, the drive starting pressure a corresponds to a threshold value for determining whether or not starting the drive of the pump  46 . 
   In other words, the blow-by gas processing apparatus ventilates the interior of the engine  10  on the basis of the intake negative pressure at the non-supercharging time. In other words, the pump  46  is not always driven at an operating time of the engine  10 , but the pump  46  is stopped in the case that the downstream pressure P 1  is lower than the drive starting pressure α. In other words, in the case that the intake negative pressure can ventilate the interior of the engine  10 , the electronic control unit  50  stops the pump  46 . Accordingly, the pump  46  is efficiently driven. 
   On the other hand, at the supercharging time, the downstream pressure P 1  is increased, and the intake negative pressure is lost. In this case, as shown in  FIG. 2 , the first breather line BR 1  comes to zero. In other words, the blow-by gas discharge generated by the first breather passage  41  is stopped. However, in the case that the downstream pressure P 1  is equal to or more than the drive starting pressure α as shown in  FIG. 3 , the electronic control unit  50  drives the pump  46 . Accordingly, the pump  46  forcibly draws the gas in the engine  10  to the second breather passage  42 , and recirculates the gas to the intake passage  20 . Therefore, as shown by open arrows in  FIG. 1 , the blow-by gas in the engine  10  passes through the second breather passage  42  and is returned to the intake passage  20 . As a result, since the gas in the engine  10  is reduced, the intake air in the intake passage  20 , that is, the intake air flows through the introduction passage  43  so as to be drawn (introduced) to the interior of the engine  10 . 
   As shown in  FIG. 2 , the electronic control unit  50  controls the gas pressure feeding amount of the pump  46  on the basis of the downstream pressure P 1 . Specifically, since the first breather line BR 1  suddenly decreases in the case that the downstream pressure P 1  exists between the drive starting pressure α and the atmospheric pressure, the electronic control unit  50  suddenly increases the second breather line BR 2 . In the case that the downstream pressure P 1  is equal to or more than the atmospheric pressure, the second breather line BR 2  is always positioned above the leaking flow rate BL of the blow-by gas. In the case that the downstream pressure P 1  is equal to or more than the atmospheric pressure, the electronic control unit  50  raises the second breather line BR 2  in accordance with a steeper slope than the leaking flow rate BL of the blow-by gas little by little. 
     FIG. 4  shows a relationship between a total breather line L 1  and the downstream pressure P 1 . The total breather line L 1  corresponds to a sum of the first breather line BR 1  and the second breather line BR 2 . In other words, the total breather line L 1  indicates a total of the gas discharge amount from the interior of the engine  10  to the intake passage  20  by the first breather passage  41 , and the gas discharge amount from the interior of the engine  10  to the intake passage  20  by the second breather passage  42 . 
   As shown in  FIG. 4 , the electronic control unit  50  drives the pump  46  in such a manner that the total breather line L 1  is positioned above the leaking flow rate BL of the blow-by gas at any downstream pressure P 1 . In other words, if the downstream pressure P 1  is increased in both of the case that the downstream pressure P 1  is less than the atmospheric pressure and the case that it is equal to or more than the atmospheric pressure, the total breather line L 1  is increased monotonically. In other words, in order to compensate the lack of the gas discharge capacity on the basis of the reduction of the intake negative pressure, the electronic control unit  50  regulates the gas discharge amount from the interior of the engine  10  to the second breather passage  42  by controlling the pump  46 . Accordingly, the blow-by gas in the engine  10  is sufficiently recirculated to the intake passage  20 . In other words, the interior of the engine  10  is sufficiently ventilated. As mentioned above, the first embodiment ensures the ventilation function of the blow-by gas by driving the pump  46  at the supercharging time. In other words, even if the supercharger  24  increases the downstream pressure P 1 , that is, the intake negative pressure comes to zero, the pump  46  ensures the ventilation function of the blow-by gas. 
   An inlet of the introduction passage  43  is connected to the upstream portion  20   a . Accordingly, even if the supercharger  24  increases the intermediate pressure P 4  and the downstream pressure P 1 , the intermediate pressure P 4  and the downstream pressure P 1  are not directly introduced to the interior of the engine  10 . Therefore, it is possible to prevent the pressure in the engine  10  from becoming excessively high. 
   Since the intermediate portion  20   b  and the downstream portion  20   c  exist in a downstream side of the supercharger  24 , the downstream pressure P 1  and the intermediate pressure P 4  can become larger than the upstream pressure P 2  at the supercharging time. In accordance with the present embodiment, an outlet of the second breather passage  42  is connected to the upstream portion  20   a . Accordingly, it is possible to reduce the load of the pump  46 , for example, in comparison with the case that the outlet of the second breather passage  42  is connected to the intermediate portion  20   b  or the downstream portion  20   c.    
   In the case that some kind or another trouble is generated in the engine  10 , and the leaking flow rate BL of the blow-by gas suddenly ascends, the blow-by gas in the engine  10  passes through the introduction passage  43  so as to flow into the intake passage  20 . Accordingly, it is possible to prevent the pressure in the engine  10  from excessively ascending. Therefore, it is possible to inhibit the reliability of a seal member sealing between the interior of the engine  10  and the outer portion from being lowered. In other words, it is possible to maintain the prevention of the gas flow from the interior of the engine  10  to the outer portion, and the prevention of the gas intrusion from the outer portion of the engine  10  to the interior, at a high reliability. As a result, it is possible to inhibit the reliability of the engine  10  from being lowered. 
   In the case that the flow direction of the blow-by gas and the intake air in the engine  10  is different between the supercharging time and the non-supercharging time, the blow-by gas flow and the intake air flow in the engine  10  become disturbed each time there is a switch between the operating state and the non-operating state of the supercharger  24 , and can stagnate temporarily. In the case that the flow direction of the blow-by gas in the passage connecting the interior of the engine  10  with the intake passage  20 , and the flow direction of the intake air are counterchanged at the non-supercharging time and the supercharging time, the blow-by gas discharged from the interior of the engine can be again returned to the interior of the engine  10 . In the case mentioned above, it is impossible to efficiently ventilate the interior of the engine  10 . In other words, it is impossible to efficiently replace the blow-by gas in the engine  10  into the intake air. 
   However, in the present embodiment, the flow directions of the blow-by gas in the first breather passage  41  and the second breather passage  42  are always constant in both of the supercharging time and the non-supercharging time. Further, the flow direction of the intake air in the introduction passage  43  is always constant in both of the supercharging time and the non-supercharging time. Accordingly, even if the supercharging time and the non-supercharging time are switched, a back flow of the blow-by gas in the first breather passage  41  and the second breather passage  42  is not generated. In the same manner, a back flow of the intake air in the introduction passage  43  is not generated. 
   The inlet of the first breather passage  41  and the inlet of the second breather passage  42  are connected to the first oil separator  45  corresponding to a common portion (the same portion) in the engine  10 . In other words, the blow-by gas in the engine  10  is always discharged to the outer portion from the first oil separator  45  with or without the operation of the supercharger  24 . In other words, the blow-by gas in the engine  10  is discharged from the connecting portion of the first oil separator  45  in the crankcase  14 . Further, the outlet of the introduction passage  43  is connected to the second oil separator  47 . In other words, the intake air is always introduced to the interior of the engine  10  from the second oil separator  47  with or without the operation of the supercharger  24 . In other words, the intake air is introduced to the interior of the engine  10  from the connecting portion of the second oil separator  47  in the head cover  13 . Accordingly, it is possible to respectively fix the flow direction of the blow-by gas in the engine  10 , and the flow direction of the intake air in the engine  10  with or without the operation of the supercharger  24 . Accordingly, even if the supercharging time and the non-supercharging time are switched, the blow-by gas flow and the intake air flow in the engine  10  are not largely disturbed. Accordingly, it is possible to efficiently ventilate the interior of the engine  10 . 
   The first embodiment has the following advantages. 
   (1) The blow-by gas processing apparatus is provided with the first breather passage  41 , the second breather passage  42 , and the introduction passage  43 . The pump  46  is arranged in the second breather passage  42 . 
   Since the intake negative pressure is generated in the downstream portion  20   c  at the non-supercharging time, the downstream pressure P 1  is lower than the upstream pressure P 2  and the intermediate pressure P 4 . Accordingly, the intake air in the upstream portion  20   a  passes through the introduction passage  43  so as to be introduced to the interior of the engine  10  on the basis of the pressure difference between the downstream pressure P 1  and the upstream pressure P 2 . The blow-by gas in the engine  10  passes through the first breather passage  41  so as to be recirculated to the intake passage  20 . 
   At the supercharging time, the electronic control unit  50  drives the pump  46 , whereby the blow-by gas in the engine  10  passes through the second breather passage  42  so as to be recirculated to the intake passage  20 . As a result, since the blow-by gas in the engine  10  is reduced, the intake air in the intake passage  20  passes through the introduction passage  43  so as to be introduced to the interior of the engine  10 . 
   In other words, the blow-by gas processing apparatus ventilates the interior of the engine  10  by utilizing the intake negative pressure at the non-supercharging time, and ventilates the interior of the engine  10  by driving the pump  46  at the supercharging time. Accordingly, it is possible to always efficiently ventilate the blow-by gas in the engine  10 . 
   (2) The electronic control unit  50  changes the gas pressure feeding amount of the pump  46  on the basis of the downstream pressure P 1 . Accordingly, it is possible to regulate the gas pressure feeding amount of the pump  46  in correspondence to the leaking flow rate BL of the blow-by gas changing in accordance with the downstream pressure P 1 . As a result, it is possible to compensate the lack of the gas discharging capacity in the case that the intake negative pressure comes to zero. 
   (3) The electronic control unit  50  stops the pump  46  in the case that the downstream pressure P 1  is lower than the drive starting pressure α. Accordingly, the interior of the engine  10  is ventilated on the basis of the blow-by gas discharge by the first breather passage  41 , and the intake air introduction by the introduction passage  43 , at the non-supercharging time. Further, in the case that the downstream pressure P 1  is higher than the drive starting pressure α, the electronic control unit  50  drives the pump  46 . Accordingly, the interior of the engine  10  is ventilated on the basis of the blow-by gas discharge by the second breather passage  42 , and the intake air introduction by the introduction passage  43 , at the supercharging time. In other words, in the case that the intake negative pressure can sufficiently ventilate the interior of the engine  10 , the electronic control unit  50  stops the pump  46 . As mentioned above, the electronic control unit  50  does not always drive the pump  46 . Therefore, it is possible to efficiently drive the pump  46 . 
   (4) The inlet of the introduction passage  43  is connected to the upstream portion  20   a  corresponding to the upstream of the supercharger  24 . Accordingly, it is possible to prevent the pressure in the engine  10  from becoming excessively high at the supercharging time. 
   (5) The outlet of the second breather passage  42  is connected to the upstream portion  20   a  corresponding to the upstream of the supercharger  24 . Accordingly, it is possible to reduce the load of the pump  46 , for example, in comparison with the case that the pump  46  pressure feeds the gas to the intermediate portion  20   b  or the downstream portion  20   c.    
   (6) The inlet of the first breather passage  41  and the inlet of the second breather passage  42  communicate with the first oil separator  45  corresponding to the same portion in the engine  10 . Accordingly, even if the supercharging time and the non-supercharging time are switched, the blow-by gas flow in the engine  10  and the great disturbance of the intake air flow are hardly generated. Therefore, it is possible to efficiently ventilate the interior of the engine  10 . 
   (7) The outlet of the introduction passage  43  is connected to the head cover  13 . Generally, if the blow-by gas deteriorates the oil, oil sludge is generated. The oil sludge can be generated in the crank chamber  14   a  and/or the interior of the head cover  13 , and the oil sludge can be more easily generated in the interior of the head cover  13 . Since the introduction passage  43  in accordance with the present embodiment can directly feed the intake air to the interior of the head cover  13 , the introduction passage  43  suppresses the generation of the oil sludge more efficiently. 
   (8) The inlet of the first breather passage  41 , and the inlet of the second breather passage  42  are connected to the crank chamber  14   a . The outlet of the introduction passage  43  is connected to the head cover  13 . Accordingly, the intake air introduced to the interior of the head cover  13  from the introduction passage  43  efficiently pushes out the blow-by gas in the order of the interior of the head cover  13 , the crank chamber  14   a  and the intake passage  20 . In other words, a whole of the interior of the engine  10  is efficiently ventilated. 
   A description will be given below of a second embodiment according to the present invention. The description will be mainly given of a different point between the second embodiment and the first embodiment. 
   The electronic control unit  50  in accordance with the first embodiment uses only the downstream pressure P 1  as a setting parameter for setting the gas pressure feeding amount of the pump  46 . However, an electronic control unit  50  in accordance with the second embodiment employs both of the downstream pressure P 1  and the coolant temperature THW, as setting parameters. 
   If the temperature (the coolant temperature THW) of the engine  10  is lowered, the electronic control unit  50  increases an increasing degree of the fuel injection amount in accordance with the amount increasing process. In other words, if the temperature of the engine  10  is lowered, a contaminated material such as an unburned fuel or the like contained in the leaked blow-by gas from the combustion chamber  18  to the crank chamber  14   a  is increased. If the temperature of the engine  10  is lowered, the gas temperature and the oil temperature in the engine  10  are lowered. Therefore, the contaminated material in the blow-by gas tends to be mixed more into the oil. 
   Accordingly, if the temperature of the engine  10  is lowered, the electronic control unit  50  in accordance with the second embodiment increases the gas pressure feeding amount of the pump  46 . In other words, if the coolant temperature THW is lowered, the electronic control unit  50  increases the gas discharge amount from the interior of the engine  10 , and increases the intake air introduction amount to the interior of the engine  10 . As a result, it is possible to improve the ventilating performance of the interior of the engine  10 . In other words, it is possible to suppress the deterioration of the oil by the blow-by gas. 
     FIG. 5  shows a relationship between a gas discharge amount from the interior of the engine  10 , and the downstream pressure P 1 , in the case that the coolant temperature THW is a predetermined value. In other words,  FIG. 5  shows a first total breather line L 1  and a second total breather line L 2 . The first total breather line L 1  is the same as the total breather line L 1  in  FIG. 4  in the first embodiment. 
   In the case that the temperature of the engine  10  is high such as a warm-up finishing time of the engine  10 , for example, in the case that the coolant temperature THW ≧80° C., the electronic control unit  50  drives the pump  46  in such a manner as to achieve the gas discharge amount shown in the first total breather line L 1 . In other words, the electronic control unit  50  sets the gas pressure feeding amount on the basis of only the downstream pressure P 1 . In this case, the control of the pump  46  is the same as the first embodiment. 
   On the other hand, in the case that the coolant temperature THW is low, for example, in the case of the coolant temperature THW &lt;80° C., the electronic control unit  50  drives the pump  46  in such a manner as to come to the gas pressure feeding amount indicating the second total breather line L 2 . The second total breather line L 2  is always positioned above the first breather line BR 1  in both of the case that the downstream pressure P 1  is less than the atmospheric pressure, and the case that it is equal to or more than the atmospheric pressure. In other words, the electronic control unit  50  drives the pump  46  even in the case that the downstream pressure P 1  is equal to or less than the drive starting pressure α. A hatched region SR shown in  FIG. 5  indicates the difference between the second total breather line L 2  and the first breather line BR. In other words, the hatched region SR indicates the increased amount of the gas pressure feeding amount of the pump  46 . If the downstream pressure P 1  is lowered, the hatched region SR is increased. It is set such that if the coolant temperature THW is lowered, the hatched region SR is increased. In other words, the second total breather line L 2  indicates a gas discharge amount obtained by increasing the first total breather line L 1  corresponding to the gas discharge amount corresponding only to the downstream pressure P 1  so as to also correspond to the coolant temperature THW. 
   As mentioned above, the electronic control unit  50  in accordance with the second embodiment increases the gas pressure feeding amount of the pump  46  in correspondence to the temperature of the engine  10 , in the case that the temperature of the engine  10  is low so as to tend to cause the oil deterioration by the blow-by gas. Accordingly, it is possible to improve the ventilating performance of the interior of the engine  10 . As a result, it is possible to inhibit the contaminated material from being mixed into the oil. In other words, it is possible to preferably suppress the oil deterioration by the blow-by gas. 
   The second embodiment has the advantages (1) to (6) and further has the following advantage (7). 
   (7) If the coolant temperature THW is lowered, the electronic control unit  50  increases the drive current of the pump  46 . Accordingly, it is possible to preferably suppress the oil deterioration by the blow-by gas. 
   Each of the embodiments may be modified as follows. 
   In the first embodiment, the pump  46  may be driven in the case that the downstream pressure P 1  is lower than the drive starting pressure α. In this case, it is possible to rapidly discharge the blow-by gas in the case of P 1 &lt;α. 
   In the second embodiment, the pump  46  may be controlled in such a manner as to increase the gas pressure feeding amount of the pump  46  by a previously set amount in the case that the coolant temperature THW is lower than a predetermined temperature, and equalize the gas pressure feeding amount of the pump  46  with the first total breather line L 1  in the case that the coolant temperature THW is equal to or more than the predetermined temperature. 
   In the second embodiment, an index value of the temperature of the engine  10  is not limited to the coolant temperature THW, but may be constituted, for example, by a detected value of an oil temperature. Further, the temperature of the engine  10  may be directly detected. 
   The drive system of the pump  46  is not limited to the electric drive system, but may employ an engine drive system utilizing a rotation of the engine output shaft, or an oil drive system utilizing the oil pressure. 
   As shown in  FIG. 6 , a third oil separator  60  and a return passage  61  may be provided. The third oil separator  60  is arranged in a portion of the second breather passage  42  between the pump  46  and the intake passage  20 . The return passage  61  connects the third oil separator  60  with the crank chamber  14   a.    
   An oil separating capacity of the third oil separator  60  can be set in such a manner as to match to the gas flow rate of the second breather passage  42 . Accordingly, the third oil separator  60  can reliably separate the oil from the gas flowing through the second breather passage  42 . The return passage  61  returns the oil in the third oil separator  60  to the crank chamber  14   a.    
   At a time of driving the pump  46 , the pressure in the portion of the second breather passage  42  between the pump  46  and the engine  10  becomes lower than the pressure in the portion of the second breather passage  42  between the pump  46  and the intake passage  20 . In other words, the intake pressure of the pump  46  becomes lower than the discharge pressure of the pump  46 . Since the third oil separator  60  is arranged between the pump  46  and the intake passage  20 , the engine internal pressure P 3  becomes lower than an internal pressure of the third oil separator  60 . Accordingly, it is possible to efficiently return the oil in the third oil separator  60  to the interior of the engine  10 . 
   The third oil separator  60  in  FIG. 6  is not limited to be arranged between the pump  46  and the intake passage  20 , but may be arranged between the pump  46  and the engine  10 . 
   The blow-by gas processing apparatus may also be applied to the engine  10  which does not execute the amount increasing process of the target fuel injection amount Qm. 
   The outlet of the second breather passage  42  may be connected to the intermediate portion  20   b  or the downstream portion  20   c.    
   The inlet of the introduction passage  43  may be connected to the intermediate portion  20   b  as long as it is possible to prevent the pressure in the engine  10  from becoming excessively high at the supercharging time. 
   As shown in  FIG. 7 , the first oil separator  45  may be arranged in the head cover  13 , and the second oil separator  47  may be arranged in the crankcase  14 . In other words, the inlet of the first breather passage  41 , and the inlet of the second breather passage  42  are connected to the head cover  13 . The outlet of the introduction passage  43  is connected to the crank chamber  14   a.    
   As shown in  FIG. 8 , both of the first oil separator  45  and the second oil separator  47  may be arranged in the head cover  13 . In other words, all of the inlet of the first oil separator  45 , the inlet of the second oil separator  47 , and the outlet of the introduction passage  43  are connected to the head cover  13 . In this case, it is desirable to devise the shape of the communicating passage  23  in such a manner that the intake air is smoothly introduced from the interior of the head cover  13  to the crank chamber  14   a , and that the blow-by gas is conducted out from the crank chamber  14   a  to the interior of the head cover  13 . For example, two communicating passages  23  are arranged on a diagonal line of the cylinder block  11 . 
   As shown in  FIG. 9 , both of the first oil separator  45  and the second oil separator  47  may be arranged in the crankcase  14 . In other words, all of the inlet of the first breather passage  41 , the inlet of the second breather passage  42 , and the outlet of the introduction passage  43  are connected to the crank chamber  14   a.    
   In the case that it is possible to avoid the oil intrusion from the interior of the engine  10  to the first breather passage  41  and the second breather passage  42 , the first oil separator  45  may be omitted. Further, in the case that the oil intrusion from the interior of the engine  10  to the introduction passage  43 , the second oil separator  47  may be omitted. 
   As shown in  FIG. 10 , the blow-by gas processing apparatus may be applied to a V-engine  90  having cylinders arranged to form the letter V. The outlet of the introduction passage  43  is connected to each of a left head cover  13   a  provided in a left bank Va and a right head cover  13   b  provided in a right bank Vb. The inlet of the first breather passage  41 , and the inlet of the second breather passage  42  are connected to the common crankcase  14 . 
   As shown in  FIG. 11 , the inlet of the first breather passage  41 , and the inlet of the second breather passage  42  may be connected to the right head cover  13   b . The outlet of the introduction passage  43  is connected only to the left head cover  13   a.    
   As shown in  FIG. 12 , the inlet of the first breather passage  41  and the inlet of the second breather passage  42  may be connected to the left head cover  13   a , and the outlet of the introduction passage  43  may be connected to the crankcase  14 . The inlet of the first breather passage  41  and the inlet of the second breather passage  42  are also connected to the right head cover  13   b.    
   The inlet of the first breather passage  41  and the inlet of the second breather passage  42  may be respectively connected to different portions in the engine  10 . 
   The supercharger  24  provided in the engine  10  is not limited to the exhaust gas drive system, but may be constituted by an engine drive system. Further, the intake passage  20  to the intercooler  29  may be omitted. The blow-by gas processing apparatus in accordance with the present invention may be applied to the engine  10  in these cases.