Abstract:
A positive crankcase ventilation (PCV) valve installation structure for installing a PCV valve of an engine on an engine body includes: a blow-by gas recirculation system that includes a ventilation hose that connects the engine body to an intake device introducing outside air into the engine body and that has a recirculation passage recirculating blow-by gas arising in the engine body to the intake device and an oil cooler device that exchanges heat between lubricating oil and a medium solution that is lower in temperature than the lubricating oil; and a cover that transfers heat of the oil cooler device to the PCV valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase application of International Application No. PCT/IB2011/002478, filed Oct. 19, 2011, and claims the priority of Japanese Application No. 2010-236710, filed Oct. 21, 2010, the content of both of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a positive crankcase ventilation (PCV) valve installation structure of a blow-by gas recirculation system provided for an internal combustion engine and, more particularly, to a PCV valve installation structure in an internal combustion engine equipped with an oil cooler device that cools lubricating oil. 
     2. Description of Related Art 
     In general, a blow-by gas recirculation system for returning blow-by gas to an intake system is provided for an internal combustion engine (hereinafter, simply referred to as engine) mounted on an automobile, or the like. In addition, there is a V-engine in which cylinder banks are arranged in a V shape centering on a crankshaft as one type of the engine of an automobile. Then, a blow-by gas recirculation system is also provided for the V-engine as well. 
     In a related art, there is known a blow-by gas recirculation system that is provided for such a V-engine and in which, as shown in  FIG. 7 , PCV valves  100  and  101  are attached to corresponding cylinder head covers  102  and  103  (for example, see Japanese Patent Application Publication No. 2007-224736 (JP-2007-224736)). For example, in a left bank  105  of such a V-engine  104 , an existing blow-by gas recirculation system  106  includes a separator case  107  that is provided for the cylinder head cover  102  and that separates blow-by gas and oil mist from each other, the left PCV valve  100  that emits the blow-by gas separated by the separator case  107  and a left blow-by gas supply tube  108  that couples the left PCV valve  100  to an intake pipe at a portion downstream of a throttle valve. In addition, in a right bank  109  of the V-engine  104 , an existing blow-by gas recirculation system  110  includes a separator case  111  that is provided for the cylinder head cover  103 , the right PCV valve  101  that emits blow-by gas separated by the separator case  111  and a right blow-by gas supply tube  112  that couples the right PCV valve  101  to the intake pipe at a portion downstream of the throttle valve. These two PCV valves  100  and  101  are exposed to an engine room. 
     With such a configuration, in the blow-by gas recirculation systems  106  and  110 , for example, when the left PCV valve  100  of the left bank  105  is open and the right PCV valve  101  of the right bank  109  is closed, blow-by gas blown through a gap between a cylinder  113  and a piston  114  into a crank chamber  115  in a compression cycle or expansion cycle of the V-engine  104  is introduced into the separator case  107  via a blow-by gas passage  116  and cam chamber  117  of the left bank  105 . Blow-by gas from which oil mist is separated and removed by the separator case  107  flows out to the left blow-by gas supply tube  108  via the left PCV valve  100 , and is introduced into the intake pipe at a portion downstream of the throttle valve. 
     On the other hand, there is suggested a blow-by gas recirculation system that is provided for a V-engine and that has a breather between left and right banks (for example, see Japanese Patent Application Publication No. 2006-70833 (JP-A-2006-70833)). In this blow-by gas recirculation system, blow-by gas that has reached a breather chamber from a crank chamber is separated into gas and liquid in the breather chamber. Then, blow-by gas from which oil mist is separated is emitted through a blow-by gas introducing hole formed above the breather chamber. 
     However, in the existing blow-by gas recirculation systems  106  and  110  in which the PCV valves  100  and  101  are respectively provided for the cylinder head covers  102  and  103  as described above, the PCV valves  100  and  101  are exposed to the engine room, and the PCV valves  100  and  101  do not have a heating mechanism, such as a heater, so there is a problem that the PCV valves  100  and  101  may freeze because of running wind while the automobile equipped with the blow-by gas recirculation systems  106  and  110  is running in an environment below freezing. When the PCV valves  100  and  101  freeze, blow-by gas is not emitted from the crank chamber  115 , so degradation of lubricating oil may be facilitated. 
     In addition, in the existing blow-by gas recirculation system having the breather chamber between the left and right banks as described above, the PCV valve is assumed to be installed at a blow-by gas introducing hole above the breather chamber, so, as in the case where the PCV valves  100  and  101  are respectively provided for the cylinder head covers  102  and  103  as described above, the PCV valve may freeze because of running wind while an automobile equipped with the blow-by gas recirculation system is running in an environment below freezing. 
     On the other hand, in order to prevent freeze of the PCV valve, it is conceivable to provide a heating mechanism, such as a heater, around the PCV valve; however, in this case, the number of components increases to lead to a complex configuration and increased component cost. 
     SUMMARY OF THE INVENTION 
     The invention provides a PCV valve installation structure that is able to efficiently suppress freeze of the PCV valve due to running wind while an automobile is running in an environment below freezing without an increase in the number of components. 
     An aspect of the invention relates to a positive crankcase ventilation (PCV) valve installation structure for installing a PCV valve of an internal combustion engine on an engine body. The PCV valve installation structure includes: a blow-by gas recirculation system that includes: a ventilation hose that connects the engine body to an intake device introducing outside air into the engine body and that has a recirculation passage recirculating blow-by gas arising in the engine body to the intake device; and the PCV valve that is installed on the engine body and that opens or closes the recirculation passage of the blow-by gas; a heat exchanger that exchanges heat between lubricating oil and a medium solution that is lower in temperature than the lubricating oil; and a heat transfer portion that transfers heat of the heat exchanger to the PCV valve. 
     With the above configuration, while an automobile equipped with the internal combustion engine is running, heat of the heat exchanger is transferred to the PCV valve by the heat transfer portion, so, even when outside air enters an engine room while the automobile is running in an environment below freezing, the possibility that the PCV valve freezes is considerably reduced. By so doing, the PCV valve is hard to freeze in comparison with the structure that the PCV valve is simply installed at an existing cylinder head or between the left and right banks, it is possible to suppress degradation of the lubricating oil when blow-by gas is not emitted because of a clogging due to freeze of the PCV valve. In addition, the heat exchanger of lubricating oil, equipped for the automobile, is used as a heat source, so it is possible to suppress an increase in component cost in comparison with the case where a heater is installed as a new heat source. 
     In the PCV valve installation structure according to the above aspect, the heat transfer portion may be a cover of the heat exchanger, and the PCV valve may be installed on the cover. With the above configuration, an additional component other than the existing components does not need to be provided as the heat transfer portion, so it is possible to suppress an increase in the number of components. 
     In the PCV valve installation structure according to the above aspect, the PCV valve may be arranged adjacent to the heat exchanger. With the above configuration, in comparison with the case where the PCV valve is located remote from the heat exchanger, it is possible to reduce a heat loss in the heat transfer portion. Thus, it is possible to efficiently suppress freeze of the PCV valve. 
     The PCV valve installation structure according to the above aspect may further include an inlet pipe that is arranged near the PCV valve and that flows the lubricating oil into the heat exchanger. With the above configuration, heat of lubricating oil flowing through the inlet pipe is transferred to the PCV valve, so it is possible to suppress freeze of the PCV valve. 
     In the PCV valve installation structure according to the above aspect, the heat exchanger may be an oil cooler device, the oil cooler device may include: an oil cooler body that has a wall partitioning an inner side from an outer side and that flows the lubricating oil through the inner side surrounded by the wall; and a water jacket that surrounds the oil cooler body and that flows the medium solution so as to be in contact with the wall of the oil cooler body from the outer side, and heat of the lubricating oil may be transferred to the medium solution via the wall. With the above configuration, the oil cooler device is utilized to make it possible to prevent freeze of the PCV valve. 
     In the PCV valve installation structure according to the above aspect, the engine body may be a V-engine having left and right banks, and the heat exchanger and the PCV valve may be arranged between the left and right banks. With the above configuration, the dead space between the left and right banks of the V-engine may be effectively utilized. 
     In the PCV valve installation structure according to the above aspect, the PCV valve may be arranged at a rear side of the engine body. With the above configuration, when freezing outside air enters from the front of the engine room, the outside air passes around the engine body and various pipes until the outside air reaches the PCV valve located at the rear side of the engine, so the outside air is heated and exceeds 0° C. when it reaches the PCV valve, so it is possible not to freeze the PCV valve. 
     The PCV valve installation structure according to the above aspect may further include: a blow-by gas pressure measuring device that measures an atmospheric pressure of the blow-by gas introduced into the PCV valve; and a determining unit that determines that the PCV valve is clogged when the atmospheric pressure measured by the blow-by gas pressure measuring device is higher than a reference value. 
     Another aspect of the invention relates to a positive crankcase ventilation (PCV) valve installation structure for installing a PCV valve of an internal combustion engine on an engine body. The PCV valve installation structure includes: a blow-by gas recirculation system that includes: a ventilation hose that connects the engine body to an intake device introducing outside air into the engine body and that has a recirculation passage recirculating blow-by gas arising in the engine body to the intake device; and the PCV valve that is installed on the engine body and that opens or closes the recirculation passage of the blow-by gas; and a heat exchanger that exchanges heat between lubricating oil and a medium solution that is lower in temperature than the lubricating oil, wherein the PCV valve is arranged adjacent to the heat exchanger. 
     Here, in an existing art, work for checking whether the PCV valve remains closed because of freeze or a clogging with sludge, or the like, is, for example, conducted in such a manner that, in the case of the PCV valve formed of a one-way valve, a hose for supplying blow-by gas, which is connected to the PCV valve, is pinched and released during idling of the engine to make determination on the basis of whether the PCV valve gives operating sound like chattering or the PCV valve is removed and then air is blown into or drawn into the PCV valve to determine whether air conducts only in one direction. However, with the above described configuration according to the aspect of the invention, for example, the blow-by gas pressure at which the PCV valve should originally open is set as a reference value. By so doing, when the blow-by gas pressure measuring device detects a blow-by gas pressure that exceeds the reference value, it is possible to detect that there is an abnormal clogging in the PCV valve. Thus, it is possible to easily conduct work for checking for a clogging of the PCV valve. 
     According to the aspects of the invention, the heat transfer portion that transfers heat of the heat exchanger to the PCV valve is provided to transfer heat of the heat exchanger to the PCV valve, so it is possible to provide a PCV valve installation structure that is able to efficiently suppress freeze of the PCV valve due to running wind while an automobile is running in an environment below freezing without an increase in the number of components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a schematic view of an engine having a PCV valve installation structure according to a first embodiment of the invention; 
         FIG. 2  is a schematic plan view of an engine body having the PCV valve installation structure according to the first embodiment of the invention; 
         FIG. 3  is an exploded view that shows a blow-by gas recirculation system and oil cooler device that have the PCV valve installation structure according to the first embodiment of the invention; 
         FIG. 4  is a cross-sectional view of a cylinder block, taken along the line IV-IV in  FIG. 3 ; 
         FIG. 5  is a central longitudinal cross-sectional view of a separator case having the PCV valve installation structure according to the first embodiment of the invention; 
         FIG. 6  is a schematic view of an engine having a PCV valve installation structure according to a second embodiment of the invention; and 
         FIG. 7  is a cross-sectional view of an engine having an existing PCV valve installation structure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, first and second embodiments of the invention will be described with reference to the accompanying drawings. In the first and second embodiments, a PCV valve installation structure according to the aspect of the invention is applied to an engine of an automobile. 
     First Embodiment 
     First, the configuration of the first embodiment will be described. As shown in  FIG. 1  and  FIG. 2 , an engine  1  is a V-ten gasoline engine that includes a left bank  2  and a right bank  3 . The left bank  2  and the right bank are respectively provided at the left and right sides in a V shape. The engine  1  includes an engine body  4 , an intake device  5 , an exhaust device (not shown), a lubricating device  6 , a cooling device  7 , a blow-by gas recirculation system  8  and an oil cooler device  9 .  FIG. 1  is a schematic longitudinal cross-sectional view of the engine body  4  when viewed from its side.  FIG. 1  shows five cylinders  11  inside the engine body  4 , and illustrates one of the cylinders  11  at the rear portion of the engine body  4 . However, actually, the cylinders  11  are not installed at the rear portion of the engine body  4 , but, as shown in  FIG. 2 , five cylinders  11  are arranged in each of the left and right banks  2  and  3  in the longitudinal direction, and the engine body  4  includes ten cylinders  11 . Each of the cylinders  11  is coupled to the intake device  5  and the exhaust device. 
     The engine body  4  includes a cylinder head  14 , a cylinder block  15 , a crankcase  16 , pistons, a crankshaft, connecting rods, an oil pan  17  and a pressure gauge  10 . The pistons are accommodated in the cylinder block  15 . The connecting rods respectively couple the pistons to the crankshaft. The oil pan  17  is provided at the lower portion of the crankcase  16 . The pressure gauge  10  serves as a blow-by gas pressure measuring device and measures the atmospheric pressure inside the crankcase  16 . 
     The engine body  4  is mounted on a vehicle body via an engine mount (not shown). In addition, the cylinder head  14  has intake ports  18 , exhaust ports  19  and combustion chambers  20 . The intake ports  18  and the exhaust ports  19  are in communication with the corresponding cylinders  11 . The intake device  5  is connected to the cylinder head  14 , and intake air is supplied to each combustion chamber  20  via the corresponding intake port  18 . In addition, the exhaust device is connected to the cylinder head  14 , and exhaust gas in each combustion chamber  20  is emitted via the corresponding exhaust port  19 . 
     The intake device  5  includes an air cleaner  21 , an intake pipe  22 , a throttle valve  23  and intake manifolds  24 . The air cleaner  21  purifies intake air. Intake air from the air cleaner  21  flows through the intake pipe  22 . The throttle valve  23  is provided at a downstream portion of the intake pipe  22 , and adjusts the flow rate of intake air supplied into each combustion chamber  20 . The intake manifolds  24  are connected to the intake pipe  22  to flow intake air into each intake port  18 . In addition, the intake device  5  includes a head intake pipe  25  and a communication passage  26 . The head intake pipe  25  couples the air cleaner  21  to the cylinder head  14 . The communication passage  16  extends from the cylinder head  14  and communicates with the crankcase  16  through the inside of the cylinder block  15 . 
     The lubricating device  6  includes a strainer  28 , an oil pump  29 , an oil filter  30  and a flow passage  31 . The strainer  28  is used to draw lubricating oil  27  stored in the oil pan  17 . The oil pump  29  discharges the lubricating oil  27  drawn from the strainer  28  to supply the lubricating oil  27  to the oil cooler device  9 . The oil filter  30  filters the lubricating oil  27  drained from the oil cooler device  9 . The flow passage  31  supplies the filtered lubricating oil  27  to various portions of the engine body  4 . The lubricating path of the lubricating oil  27  starts from the oil pan  17 , passes through the strainer  28 , the oil pump  29 , the oil cooler device  9 , the oil filter  30  and the flow passage  31 , and returns to the oil pan  17 . 
     The cooling device  7  includes a coolant pump  32 , cooling passages  33 , a radiator  34 , a thermostat  35  and a heater core  36 . The cooling passages  33  are used to cool various portions of the engine body  4 . The radiator  34  air-cools coolant. When the temperature of the coolant is higher than or equal to a predetermined temperature, the thermostat  35  conducts to flow coolant. The heater core  36  uses coolant heated by the oil cooler device  9  as a heat source. The cooling path of part of coolant starts from the coolant pump  32 , passes through the cooling passages  33 , the radiator  34  and the thermostat  35 , and returns to the coolant pump  32 . In addition, the cooling path of the other part of coolant starts from the coolant pump  32 , passes through the cooling passages  33 , the oil cooler device  9 , the heater core  36  and the thermostat  35 , and returns to the coolant pump  32 . 
     Here, in the thermostat  35 , the path from the heater core  36  to the coolant pump  32  is normally open, and the path from the radiator  34  to the coolant pump  32  is opened or closed depending on the temperature of coolant flowing therethrough. That is, when the temperature of coolant is lower than a predetermined value (when the engine is just started), the path from the radiator  34  to the coolant pump  32  is closed to prevent overcooling of coolant. In addition, when the temperature of coolant is higher than the predetermined value (when the engine is sufficiently warmed up), the path from the radiator  34  to the coolant pump  32  is opened to cool coolant by the radiator  34 . 
     As shown in  FIG. 2 , the blow-by gas recirculation system  8  and the oil cooler device  9  are installed adjacent to each other between the left and right banks  2  and  3 . 
     As shown in  FIG. 1  and  FIG. 2 , the blow-by gas recirculation system  8  includes a PCV chamber  37 , a cover  38  of the PCV chamber  37 , a separator case  39 , PCV valves  41 , ventilation hoses  42  and an oil reservoir  43 . The PCV chamber  37  is formed between the left and right banks  2  and  3 . The separator case  39  is integrated with the cover  38 , and separates blow-by gas and the lubricating oil  27  into gas and liquid. The PCV valves  41  are respectively provided at gas emission ports  40  of the separator case  39 . The ventilation hoses  42  each have a recirculation passage  42   a  that couples each PCV valve  41  to the corresponding intake manifold  24  and that recirculates blow-by gas to the corresponding intake manifold  24 . The oil reservoir  43  stores the lubricating oil  27  drained to the PCV chamber  37  and returns the lubricating oil  27  to the oil pan  17 . 
     The PCV chamber  37  is a top-open box formed just above the crankcase  16 , and is formed over substantially all the range in the longitudinal direction of the engine body  4 . The cover  38  closes the PCV chamber  37  from the upper side. The separator case  39  is integrally attached to the rear portion on the back side of the cover  38 . As shown in  FIG. 5 , a gasket  44  is interposed between the cover  38  and the separator case  39 . An oil recovery hole  45  is provided at the bottom portion of the PCV chamber  37 . The lubricating oil  27  drained from the separator case  39  flows down through the oil recovery hole  45 . The oil reservoir  43  has an upper introducing port  46  and a lower drain port  47 . The oil recovery hole  45  is connected to the introducing port  46  of the oil reservoir  43 . The drain port  47  of the oil reservoir  43  is connected to the crankcase  16 . 
     The separator case  39  is surrounded by a front wall  39   a , a bottom wall  39   b , a rear wall  39   c  and left and right walls (not shown), and the top of the separator case  39  is hermetically sealed by the cover  38  attached via the gasket  44 . In addition, the separator case  39  has a separator introducing port  48 , a flow passage  49 , the gas emission ports  40  and an oil drain port  50 . The separator introducing port  48  is used to introduce blow-by gas and fresh air. The flow passage  49  flows these gases to separate the gases into gas and liquid. The gas emission ports  40  emit separated blow-by gas and fresh air. The oil drain port  50  drains separated oil. The separator introducing port  48  extends upward as a vertical linear passage configuration so as to penetrate through the cover  38 . The oil drain port  50  is provided at the bottom wall  39   b  of the separator case  39 , and extends substantially vertically downward so as to penetrate through the bottom wall  39   b . The gas emission ports  40  extend upward as a vertical linear passage configuration so as to penetrate through the cover  38 . 
     The flow passage  49  is defined by a longitudinal plate  51 , a first lateral plate  52  and a second lateral plate  53 . The longitudinal plate  51  faces the front wall  39   a  of the separator case  39  and extends downward from the separator introducing port  48 . The first lateral plate  52  faces the bottom wall  39   b  of the separator case  39 , and extends rearward from the lower end portion of the longitudinal plate  51 . The second lateral plate  53  faces the upper side of the first lateral plate  52 , and extends forward from the rear wall  39   c  of the separator case  39 . 
     The flow passage  49  includes a downward passage  54 , a first rearward passage  55 , a forward passage  56  and a second rearward passage  57 . The downward passage  54  extends downward from the separator introducing port  48  between the front wall  39   a  of the separator case  39  and the longitudinal plate  51  to the bottom wall  39   b  of the separator case  39 . The first rearward passage  55  extends rearward from the lower end portion of the downward passage  54  between the bottom wall  39   b  of the case and the first lateral plate  52  to the rear wall  39   c . The forward passage  56  extends upward from the rear end portion of the first rearward passage  55 , turns the direction, and extends forward between the first lateral plate  52  and the second lateral plate  53  to the longitudinal plate  51 . The second rearward passage  57  extends upward from the front end portion of the forward passage  56 , turns the direction, and extends rearward between the cover  39  and the second lateral plate  53  to the two gas emission ports  40 . In this way, the flow passage  49  is narrow and has many short turns, so the misty lubricating oil  47  frequently collides with the longitudinal plate  51 , the first lateral plate  52 , the second lateral plate  53  and the walls  39   a ,  39   b  and  39   c  to thereby efficiently separate and remove oil mist. 
     The PCV valves  41  each are formed as a one-way valve that allows blow-by gas and fresh air having a pressure higher than or equal to a predetermined value to flow only in a direction in which gas is emitted through the gas emission ports  40 . In the present embodiment, the two PCV valves  41  are provided on the upper surface of the cover  38 . Then, one of the PCV valves  41  is connected to the intake manifold  24  of the left bank  2  by the ventilation hose  42 , and the other one of the PCV valves  41  is connected to the intake manifold  24  of the right bank  3  by the ventilation hose  42 . In addition, each PCV valve  41  is connected to the corresponding gas emission port  40  having a vertical linear passage configuration from the upper side. Therefore, the PCV valves  41  may be replaced from the upper side of the cover  38 . 
     In addition, as shown in  FIG. 1 , the separator case  39  and the crankcase  16  are connected by a blow-by gas introducing pipe  58 . By so doing, the separator introducing port  48  is in communication with the inside of the crankcase  16 . Furthermore, the communication passage  26  from the cylinder head  14  to the crankcase  16  is in communication with the separator introducing port  48  by a fresh air introducing pipe  59 . By so doing, fresh air from the communication passage  26  passes through the fresh air introducing pipe  59  and is introduced from the separator introducing port  48  into the separator case  39  to thereby make it possible to push out blow-by gas. 
     The recovery path of blow-by gas leaked through a gap between the pistons and the cylinders into the crankcase  16  starts from the cylinder block  15 , passes through the crankcase  16 , the blow-by gas introducing pipe  58 , the separator case  39 , the PCV valves  41 , the intake manifolds  24  and the intake ports  18 , and reaches the combustion chambers  20 . 
     As shown in  FIG. 3 , the oil cooler device  9  includes an oil cooler body  60  and a water jacket  61 . The oil cooler body  60  has a wall  60   a  that partitions an inner side from an outer side. The lubricating oil  27  flows through the inner side surrounded by the wall  60   a . The water jacket  61  surrounds the oil cooler body  60 , and flows coolant so as to be in contact with the wall  60   a  of the oil cooler body  60  from the outer side. Then, heat of the lubricating oil  27  is transferred to coolant via the wall  60   a.    
     The oil cooler body  60  closely adheres to the back side of the cover  38  via a gasket (not shown). The oil cooler body  60  has an oil introducing port  62  and an oil drain port  63 . The oil introducing port  62  penetrates through the cover  38  and is provided at the rear top portion. The oil drain port  63  penetrates through the cover  38  and is provided at the front top portion. The oil introducing port  62  is connected to the oil pump  29  of the lubricating device  6  by an introducing port-side pipe  64  that serves as an inlet pipe. As shown in  FIG. 2 , the introducing port-side pipe  64  is provided so as to pass near the PCV valves  41  above the cover  38 . In addition, the oil drain port  63  is connected to the oil filter  30  of the lubricating device  6  by a drain port-side pipe  65 . These introducing port-side pipe  64  and drain port-side pipe  65  are connected to each other by a by-pass pipe  66  above the cover  38 . A large number of horizontal fin-shaped radiator plates  60   b  are formed on the outer side portion of the wall  60   b  of the oil cooler body  60  to increase contact area with coolant to thereby enhance the efficiency of heat transfer. 
     The water jacket  61  is integrally formed with the PCV chamber  37 , and is formed in a top-open box shape. The water jacket  61  is installed so that the upper end portion closely adheres to the back side of the cover  38  via a gasket  71 . The water jacket  61  has coolant introducing ports  67  and a coolant drain port  68 . The coolant introducing ports  67  are formed at both side portions at the front side of the water jacket  61 . The coolant drain port  68  is provided at the rear side of the water jacket  61 . The coolant introducing ports  67  formed at both side portions are respectively connected to parts of the cooling passages  33  formed in the left and right banks  2  and  3 . In addition, the coolant drain port  68  extends upward through the cover  38 , and is connected to the heater core  36  by a coolant drain pipe  69 . In addition, a spacer  70  is provided between the oil cooler body  60  and the water jacket  61 . The spacer  70  is used to ensure a gap between the outer surface of the oil cooler body  60  and the inner surface of the water jacket  61 . 
     Here, a structure for installing the PCV valves  41  in the present embodiment is formed of the blow-by gas recirculation system  8 , the oil cooler device  9  and the cover  38 . These respectively correspond to the blow-by gas recirculation system, the heat exchanger and the heat transfer portion in the PCV valve installation structure according to the aspect of the invention. 
     Furthermore, in the present embodiment, the operation of the engine  1  is controlled by an electronic control unit (ECU) (not shown) that serves as a determining unit. In the ECU, a pressure at which the PCV valves  41  open is set to a reference value, the pressure gauge  10  is used to measure the blow-by gas pressure in the crankcase  16  during operation of the engine  1 , and, when it is detected that the internal pressure of the crankcase  16 , that is, the internal pressure of the separator case  39 , is higher than the reference value, it is determined that at least any one of the PCV valves  41  is clogged and is hard to open. 
     Subsequently, the procedure of installing the blow-by gas recirculation system  8  and the oil cooler device  9  between the left and right banks  2  and  3  will be described. As shown in  FIG. 3 , the separator case  39  and the oil cooler body  60  are assembled to the cover  38  in advance. Then, the cover  38  is attached so that the oil cooler body  60  is placed inside the water jacket  61  in the PCV chamber  37 . By so doing, an assembly of the cover  38  is just installed between the left and right banks  2  and  3  to thereby make it possible to position and install the separator case  39  and the oil cooler body  60  at an appropriate position. Then, the blow-by gas recirculation system  8  and the oil cooler device  9  are piped to other devices. 
     Next, the operation of the engine  1  will be described. Dust is removed from intake air by the air cleaner  21 , and the intake air flows from the intake pipe  22  to the intake ports  18  via the throttle valve  23  and the intake manifolds  24 . On the other hand, blow-by gas and fresh air are supplied to the intake manifolds  24  from the blow-by gas recirculation system  8  via the respective ventilation hoses  42 . Therefore, fresh air and blow-by gas are mixedly supplied to the intake ports  18 . The mixed gas is burned in the combustion chambers  20 . In addition, part of unburned gas in the combustion chambers  20  passes around the pistons and flows from the cylinder block  15  into the crankcase  16 . 
     On the other hand, part of intake air from the air cleaner  21  passes through the head intake pipe  25  and is supplied to the cylinder head  14 . Intake air is supplied from the cylinder head  14  to the cylinder block  15  and the crankcase  16  via the communication passage  26 . The intake air pushes out blow-by gas inside the cylinder block  15  and the crankcase  16 , and causes the blow-by gas to be introduced into the separator case  39  via the blow-by gas introducing pipe  58 . At this time, part of fresh air taken in through the air cleaner  21  is introduced into the separator case  39  through the path from the cylinder head  14  via the communication passage  26  to the fresh air introducing pipe  59 , and is mixed with blow-by gas. 
     Blow-by gas introduced into the separator case  39  contains misty lubricating oil  27 . Therefore, the misty lubricating oil  27  collides with the longitudinal plate  51 , the first lateral plate  52 , the second lateral plate  53  and the walls  39   a ,  39   b  and  39   c  to liquefy inside the separator case  39 , and is drained through the oil drain port  50  provided at the lower portion. The drained lubricating oil  27  is drained through the oil recovery hole  45  at the lower portion of the PCV chamber  37 , and is stored in the oil reservoir  43 . In addition, blow-by gas and fresh air separated by the separator case  39  are released by opening the PCV valves  41 . The released blow-by gas is supplied to the left and right intake manifolds  24  via the corresponding ventilation hoses  42 . 
     On the other hand, the lubricating oil  27  stored in the oil pan  17  is drawn and discharged by the oil pump  29  via the strainer  28 . Part of the discharged lubricating oil  27  flows in from the introducing port-side pipe  64  of the oil cooler device  9 , passes through the inside of the oil cooler body  60  and is cooled by coolant, and then flows out from the drain port-side pipe  65 . In addition, the other part of the lubricating oil  27  discharged by the oil pump  29  flows from the introducing port-side pipe  64  to the drain port-side pipe  65  via the by-pass pipe  66 . Here, the introducing port-side pipe  64  passes near the PCV valves  41 , so heat of the lubricating oil  27  is transferred to the PCV valves  41 , and the PCV valves  41  are heated. The lubricating oil  27  drained to the drain port-side pipe  65  is filtered by the oil filter  30  and is supplied to the cylinder block  15 . Then, the lubricating oil  27  of the cylinder block  15  passes through the crankcase  16  and is stored in the oil pan  17 . 
     In addition, coolant is discharged from the coolant pump  32 , passes through the cylinder block  15  to cool the cylinder block  15 , and part of the coolant is supplied from the coolant introducing ports  67  of the water jacket  61  of the oil cooler device  9  to the water jacket  61 . By so doing, the lubricating oil  27  that flows through the oil cooler body  60  is water-cooled. Coolant is drained through the coolant drain port  68  of the water jacket  61 , and is supplied to the heater core  36 . Coolant flows through the heater core  36 , passes through the thermostat  35 , and returns to the coolant pump  32 . Here, when the temperature of coolant is lower than a predetermined temperature as in the case of the start of operation of the engine  1 , the path from the radiator  34  to the coolant pump  32  in the thermostat  35  is closed. In addition, when the engine  1  is sufficiently heated and the temperature of coolant is higher than or equal to the predetermined value, the path from the radiator  34  to the coolant pump  32  is opened. 
     On the other hand, the other part of coolant that has passed through the cylinder block  15  flows into the radiator  34 . Here, the thermostat  35  is provided downstream of the radiator  34  and coolant flows through the thermostat  35  only when the temperature of coolant is higher than or equal to the predetermined temperature, so coolant flows through the radiator  34  only when the thermostat  35  allows flow of coolant. Coolant that has been cooled by the radiator  34  and that has passed through the thermostat  35  returns to the coolant pump  32 . 
     Here, the oil cooler device  9  is operating during operation of the engine  1 , so the heat of the oil cooler device  9  conducts through the cover  38  and reaches the PCV valves  41 . That is, the heat of the oil cooler device  9  is transferred to the portion of the cover  38  at which the oil cooler device  9  is installed, and the heat is transferred therefrom along the cover  38 . Then, the oil cooler device  9  and the separator case  39  are arranged adjacent and close to each other, so the heat of a portion of the cover  38  near the oil cooler device  9  is transferred to the PCV valves  41  with a minimum heat loss to make it possible to heat the PCV valves  41 . Therefore, even when outside air enters an engine room while the automobile is running in an environment below freezing, the possibility that at least any one of the PCV valves  41  freezes may be considerably reduced. 
     Here, the pressure at which the PCV valves  41  open is set to a reference value. In this case, when the PCV valves  41  normally operate, the PCV valves  41  open to release blow-by gas in the separator case  39  when the gas pressure of the blow-by gas is higher than the reference value, so the atmospheric pressure of blow-by gas will not be higher than the reference value. In contrast to this, when at least any one of the PCV valves  41  is clogged with sludge, or the like, and is hard to open, the at least any one of the PCV valves  41  does not open even when the atmospheric pressure is higher than the reference value. Therefore, the atmospheric pressure of blow-by gas in the separator case  39  may be considerably higher than the reference value. In addition, the internal pressure of the separator case  39  is equivalent to the internal pressure of the crankcase  16  that is located upstream of the separator case  39 . 
     Then, during operation of the engine  1 , the pressure gauge  10  is used to measure the atmospheric pressure of blow-by gas in the crankcase  16 , and, when it is detected that the internal pressure of the crankcase  16 , that is, the internal pressure of the separator case  39 , is higher than the reference value, it may be determined that at least any one of the PCV valves  41  is clogged and is hard to open. Note that the result of determination in the case where at least any one of the PCV valves  41  is hard to open is provided to a driver by a display unit, such as a warning lamp. 
     The structure for installing the PCV valves  41  according to the first embodiment is configured as described above, so the following advantageous effects may be obtained. 
     That is, during operation of the engine  1 , the heat of the oil cooler device  9  conducts through the cover  38  and reaches the PCV valves  41 , and the heat of the introducing port-side pipe  64  reaches the PCV valves  41  on the cover  38 , so, even when outside air enters the engine room while the automobile equipped with the engine  1  is running in an environment below freezing, the possibility that at least any one of the PCV valves  41  freezes may be considerably reduced. By so doing, the PCV valves  41  are hard to freeze in comparison with the structure that the PCV valves  41  are simply installed at an existing cylinder head or between the left and right banks  2  and  3 , it is possible to suppress degradation of the lubricating oil  27  when blow-by gas is not emitted because of a clogging of the PCV valves  41 . In addition, the oil cooler device  9  equipped for the automobile is used as a heat source, so it is possible to suppress an increase in component cost in comparison with the case where a heater is installed as a new heat source. 
     Furthermore, the PCV valves  41  are provided adjacent to the oil cooler device  9 , so it is possible to reduce a heat loss in the cover  38  in comparison with the case where the PCV valves  41  are provided remote from the oil cooler device  9 , and it is possible to further effectively suppress freeze of the PCV valves  41 . Moreover, the PCV valves  41  are arranged at the rear side of the engine body  4 , so, when freezing outside air enters from the front of the engine room, the outside air passes around the engine body  4  and various pipes until the outside air reaches the PCV valves  41  located at the rear side of the engine  1 . Therefore, outside air is heated and exceeds 0° C. when it reaches the PCV valves  41 , so it is possible not to freeze the PCV valves  41 . 
     In addition, the atmospheric pressure of blow-by gas in the crankcase  16  is measured to make it possible to detect a clogging of at least any one of the PCV valves  41 , so it is possible to considerably easily conduct checking work for the PCV valves  41 , such as not only checking for a frozen PCV valve  41  but also whether at least any one of the PCV valves  41  is clogged with sludge. 
     Moreover, the PCV valves  41  are installed on the cover  38  between the left and right banks  2  and  3  so as to be replaceable from the upper side, so it is possible to easily replace the PCV valves  41  in comparison with the case where a PCV valve is provided at a portion that is hidden by another cover, or the like, or an inaccessible portion and work for detaching another member is, for example, required in order to replace the PCV valve. Thus, it is possible to considerably easily conduct checking work for the PCV valves  41  in such a manner that the pressure gauge  10  is used to measure the atmospheric pressure of blow-by gas in the crankcase  16 , and, if it is detected that at least any one of the PCV valves  41  is clogged as a result of checking, it is possible to easily replace the at least any one of the PCV valves  41 . 
     In addition, the separator introducing port  48  is formed as a vertical linear passage configuration that penetrates through the cover  38 , so it is possible to effectively utilize dead space in comparison with the case where the separator introducing port  48  is formed as a configuration that extends in another direction. Furthermore, the blow-by gas recirculation system  8  and the oil cooler device  9  are provided between the left and right banks  2  and  3 , so it is possible to effectively utilize the dead space of the V-engine. 
     Second Embodiment 
     In an engine  1  according to a second embodiment, a dry sump is employed. Therefore, the oil pan  17  formed in the crankcase  16  according to the first embodiment differs from that of the second embodiment; however, the other components are similarly configured. Thus, the same components as those of the first embodiment shown in  FIG. 1  to  FIG. 5  will be described using like reference numerals, and the difference will be specifically described in detail. 
     As shown in  FIG. 6 , a partition plate  80  is provided at the lower portion of the crankcase  16  for each cylinder  11 . Each of the bottom portions of spaces partitioned by the partition plates  80  has a suction hole  81 . Furthermore, each suction hole  81  is connected to a scavenge pump  82 . The scavenge pump  82  is used to draw blow-by gas and fresh air in the crankcase  16  and lubricating oil stored at the bottom portion. At this time, the bottom portion of the crankcase  16  is partitioned by the partition plates  80 , so lubricating oil may be efficiently drawn even when a lateral load is applied to the engine  1 . These blow-by gas, fresh air and oil are stored in an oil tank  83  from the scavenge pump  82 . 
     The oil tank  83  has a gas emission port  84  formed at an upper portion and an oil drain port  85  formed at a lower portion. The gas emission port  84  is connected to the separator introducing port  48  of the separator case  39  by the blow-by gas introducing pipe  58 . Therefore, blow-by gas and fresh air pushed out through the gas emission port  84  are introduced into the separator case  39 . 
     Furthermore, a pressure gauge  86  is provided for the oil tank  83 . The pressure gauge  86  is used to measure the internal atmospheric pressure. The internal pressure of the separator case  39  is equivalent to the internal pressure of the oil tank  83  that is located upstream of the separator case  39 . Therefore, the pressure gauge  86  is used to measure the atmospheric pressure of blow-by gas in the oil tank  83  to thereby make it possible to measure the internal pressure of the separator case  39 . By so doing, it is possible to determine whether at least any one of the PCV valves  41  is clogged and is hard to open. 
     In the present embodiment, the lubricating device  6  includes the oil tank  83 , the oil pump  87 , the oil filter  30 , the flow passage  31  and the scavenge pump  82 . The oil tank  83  is provided outside the engine body  4 . The oil pump  86  discharges lubricating oil supplied from the oil tank  83  and supplies the lubricating oil to the oil cooler device  9 . The oil filter  30  filters the lubricating oil drained from the oil cooler device  9 . The flow passage  31  supplies the filtered lubricating oil to various portions in the engine body  4 . The scavenge pump  82  draws lubricating oil stored at the bottom portion of the crankcase  16 . The lubricating path starts from the oil tank  83 , passes through the oil pump  87 , the oil cooler device  9 , the oil filter  30 , the flow passage  31 , the crankcase  16  and the scavenge pump  82 , and returns to the oil tank  83 . 
     Blow-by gas arises in the combustion chambers  20 . The recovery path of the blow-by gas starts from the combustion chambers  20 , and passes through the cylinder block  15 , the crankcase  16 , the scavenge pump  82 , the oil tank  83 , the separator case  39 , the PCV valves  41 , the intake manifolds  24 , the intake ports  18 , and returns to the combustion chambers  20 . 
     In addition, the communication passage  26  from the cylinder head  14  to the crankcase  16  is directly connected to the scavenge pump  82 . Furthermore, separately from the communication passage  26 , a fresh air introducing passage  88  that couples the cylinder head  14  to the scavenge pump  82  is provided. By so doing, a large amount of fresh air may be introduced from the scavenge pump  82  into the oil tank  83 . 
     The structure for installing the PCV valves  41  according to the second embodiment is configured as described above, so the following advantageous effects may be obtained. 
     That is, because the dry sump is employed as described above, lubricating oil may be stably stored in the oil tank  83 , a friction loss may be reduced, for example, biasing or foaming of lubricating oil in the crankcase  16  may be prevented, and lubricating oil may be stably supplied to lubricated portions of the engine body  4 . 
     In addition, as in the case of the first embodiment, during operation of the engine  1 , the heat of the oil cooler device  9  conducts through the cover  38  and reaches the PCV valves  41 , and the heat of the introducing port-side pipe  64  reaches the PCV valves  41  on the cover  38 , so, even when outside air enters the engine room while the automobile equipped with the engine  1  is running in an environment below freezing, the possibility that at least any one of the PCV valves  41  freezes may be considerably reduced. 
     Furthermore, the PCV valves  41  are provided adjacent to the oil cooler device  9 , so it is possible to reduce a heat loss in the cover  38  in comparison with the case where the PCV valves  41  are provided remote from the oil cooler device  9 , and it is possible to further effectively suppress freeze of the PCV valves  41 . 
     In addition, the atmospheric pressure of blow-by gas in the crankcase  16  is measured to make it possible to detect a clogging of at least any one of the PCV valves  41 , so it is possible to considerably easily conduct checking work for the PCV valves  41 , such as not only checking for a frozen PCV valve  41  but also whether at least any one of the PCV valves  41  is clogged with sludge. Moreover, the PCV valves  41  are installed on the cover  38  between the left and right banks  2  and  3  so as to be replaceable from the upper side, so it is possible to easily replace the PCV valves  41 . 
     Here, in the above described structures for installing the PCV valves  41  according to the first and second embodiments, the PCV valves  41  are installed at the rear portion of the engine body  4 ; instead, in the PCV valve installation structure according to the aspect of the invention, the position at which the PCV valves  41  are installed may be another portion, and may be, for example, at the front portion or center portion of the engine body  4 . 
     In addition, in the structures for installing the PCV valves  41  according to the first and second embodiments, each PCV valve  41  is formed of a one-way valve; however, in the PCV valve installation structure according to the aspect of the invention, each of the PCV valves  41  is not limited to a mechanical one-way valve. Each of the PCV valves  41  may be an electromagnetic valve that may be electrically controlled to open or close or that is able to electrically control the flow rate. 
     In addition, in the structures for installing the PCV valves  41  according to the first and second embodiments, the pressure gauge  10  or  86  is used to detect whether at least any one of the PCV valves  41  is hard to open; instead, in the PCV valve installation structure according to the aspect of the invention, the pressure gauge  10  or  86  may be omitted. 
     Furthermore, in the structures for installing the PCV valves  41  according to the first and second embodiments, the engine  1  is of a V-ten type; instead, in the PCV valve installation structure according to the aspect of the invention, the engine  1  may be of another type, and may be, for example, of a V-six type, a V-eight type or an in-line type other than a V type. When the engine  1  is of an in-line type, there is no space between the banks  2  and  3  as described in the present embodiments, so, for example, a blow-by gas recirculation system and an oil cooler device are installed at a side portion of an engine body, or the like. 
     As described above, the PCV valve installation structure according to the aspect of the invention is able to prevent freeze of the PCV valve at low cost without providing another member, such as a heater, even when freezing outside air blows into an engine room, and is useful in all the PCV valve installation structures suitable for the case where an automobile used in cold climate areas includes a blow-by gas recirculation system.