Patent Publication Number: US-2015083083-A1

Title: Engine

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an engine in which a fuel tube is arranged on a cylinder head. 
     2. Background Art 
     Conventionally known configurations of an engine mounted in an automobile, a ship, or the like, include a configuration provided with a valve cover (cylinder head cover) that covers an air intake valve or an exhaust valve. In an engine of this type, a fuel tube for fuel supply may be arranged on the valve cover. Patent Document 1 discloses this type of engine. 
     The engine disclosed in the Patent Document 1 is a diesel engine including a common-rail fuel injection mechanism. The common-rail fuel injection mechanism includes, as its main elements, a common rail, a high-pressure tube (fuel tube), and an injector. The common rail, which is arranged above the valve cover, stores under high pressure a fuel supplied from a fuel tank. The high-pressure tube, which is arranged above the valve cover, connects the common rail and the injector to each other. The injector, which is arranged corresponding to each cylinder, injects the fuel in response to an instruction given from an electronic control device. 
     In an engine mounted in a ship, a cover (top cover) may be arranged in an upper end region of the engine, because an operator works on the upper end of the engine when performing a maintenance operation. Patent Document 2 discloses an engine provided with such a top cover. In the Patent Document 2, a common rail is arranged below the top cover. 
     PRIOR-ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2005-30346 
     Patent Document 2: Japanese Patent Application Laid-Open No. 2010-59807 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the fuel injection mechanism of the diesel engine, sealing is provided in, for example, a connection portion between the common rail and the high-pressure tube, in order to prevent leakage of the fuel. Depending on the use environment or the like, however, loosening of the connection portion, damage to the fuel tube, etc., or the like, may occur, which in the worst case could cause leakage of the fuel. Occurrence of leakage of the fuel may cause the fuel to burst and splash because the fuel is stored under high pressure in the high-pressure tube. 
     Conventionally, therefore, a high-temperature part (for example, a part through which an exhaust gas passes) of the engine that might be exposed to the fuel, even a small chance, needs to be covered with a heat insulating material or the like. In some cases, in addition to or instead of the covering with the heat insulating material, the high-pressure tube may be double-structured for ensuring the prevention of leakage of the fuel. 
     Such a configuration adopting the covering with the heat insulating material or the like leads to an increased number of parts and a complicated assembling process. Particularly in an engine including a plurality of cylinders, the length of a high-pressure tube is elongated, so that the range in which where is the risk of fuel splashing is widened. Additionally, the high-pressure tube (fuel tube) is arranged for each cylinder. In an engine including a plurality of cylinders, therefore, many high-pressure tubes need to be double-structured. This increases the number of cylinders included in the engine, which leads to an increase in the cost, labor in the production, and complication of the assembling process. 
     The present invention has been made in view of the circumstances described above, and a primary object of the present invention is to provide an engine configured such that a high-temperature part is not exposed to a fuel when, for example, a high-pressure tube is damaged, at a low cost and with a simple structure. 
     Means for Solving the Problems and Effects Thereof 
     Problems to be solved by the present invention are as described above, and next, means for solving the problems and effects thereof will be described. 
     In an aspect of the present invention, an engine having the following configuration is provided. The engine includes an exhaust manifold, a valve cover, a plate-like cover, and a fuel tube. The exhaust manifold collects exhaust gases discharged from a plurality of cylinders. The valve cover is a cover that covers all of a plurality of valves for air intake or air discharge to or from the cylinders. The plate-like cover is a cover that covers the valve cover. The fuel tube is arranged in a space between the valve cover and the plate-like cover, and allows a fuel to flow therethrough. The plate-like cover is provided with a partition that is arranged so as to separate a side where the exhaust gas flows immediately after being discharged from the exhaust manifold from a side where the fuel tube is arranged. 
     Accordingly, even when the fuel leaks out of the fuel tube, a part (a high-temperature part of the engine) through which the exhaust gas passes can be prevented from being exposed to the fuel. This can eliminate the need of double-structuring the fuel tube for the purpose of preventing leakage of the fuel, and moreover can eliminate the need of covering an exhaust pipe and the like with a heat insulating material for the purpose of lowering the surface temperature. Additionally, since the partition is included in the plate-like cover, it is not necessary to provide any special member for supporting the partition. Thus, the above-described problems can be solved at a low cost and with a simple structure. 
     In the engine, it is preferable that the partition has a height that occupies half or more of the distance between the valve cover and the plate-like cover. 
     This makes it easy for the partition to catch the fuel splashing from the fuel tube, thus more surely preventing the high-temperature part of the engine from being exposed to the fuel. 
     In the engine, it is preferable that the partition is formed so as to extend from one end to the other end of the plate-like cover with respect to a crank axis direction. 
     Accordingly, the high-temperature part of the engine can be prevented from being exposed to the fuel even in a case where the fuel tube is arranged in an elongated manner in the crank axis direction. 
     In the engine, it is preferable that the partition is a plate-like portion that is formed integrally with the plate-like cover and that protrudes perpendicularly from the plate-like cover. 
     Since the partition and the plate-like cover are formed integrally with each other, reduction in the number of parts and simplification of an assembling operation are achieved. Additionally, since the partition has a plate-like shape, the space occupied by the partition can be restricted with achievement of the effects of the present invention. 
     In the engine, it is preferable that the valve cover is provided with a second partition that is arranged so as to separate the side where the exhaust gas flows immediately after being discharged from the exhaust manifold from the side where the fuel tube is arranged. 
     Accordingly, even when the fuel leaks out of the fuel tube, a part (high-temperature part of the engine) through which the exhaust gas passes can be more surely prevented from being exposed to the fuel. 
     In the engine, it is preferable that the second partition has a height that occupies half or more of the distance between the valve cover and the plate-like cover. 
     This makes it easy to catch the fuel splashing from the fuel tube, thus more surely preventing the high-temperature part of the engine from being exposed to the fuel. 
     In the engine, it is preferable that the second partition is formed so as to extend from one end to the other end of the valve cover with respect to a crank axis direction. 
     Accordingly, the high-temperature part of the engine can be prevented from being exposed to the fuel even in a case where the fuel tube is arranged in an elongated manner in the crank axis direction. 
     In the engine, it is preferable that the second partition is a plate-like portion that is formed integrally with the valve cover and that protrudes from the valve cover. 
     Since the second partition and the valve cover are formed integrally with each other, reduction in the number of parts and simplification of an assembling operation are achieved. Additionally, since the second partition has a plate-like shape, the space occupied by this partition can be restricted with achievement of the effects of the present invention. 
     In the engine, it is preferable that the partition is arranged near the second partition and on the fuel tube side relative to the second partition. 
     This enables the fuel, even splashing along the plate-like cover, to be caught without fail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A perspective view of a marine engine according to an embodiment of the present invention. 
         FIG. 2  A plan view of the marine engine. 
         FIG. 3  A front elevational view of the marine engine. 
         FIG. 4  A perspective view showing members arranged around a valve cover. 
         FIG. 5  A cross-sectional view showing a space between the valve cover and a top cover. 
         FIG. 6  Perspective views showing the shapes of the valve cover and the top cover. 
         FIG. 7  A perspective view showing the positional relationship among devices of an air supply system. 
         FIG. 8  Cross-sectional views showing another configuration of the valve cover and another configuration of the top cover. 
     
    
    
     EMBODIMENT FOR CARRYING OUT THE INVENTION 
     Next, an embodiment of the present invention will be described with reference to the drawings. Firstly, an overall configuration of a marine engine  1  will be described with reference to  FIGS. 1 to 4 .  FIG. 1  is a perspective view of the marine engine  1  according to an embodiment of the present invention.  FIG. 2  is a plan view of the marine engine  1 .  FIG. 3  is a front elevational view of the marine engine  1 .  FIG. 4  is a perspective view showing members arranged around a valve cover  41 . 
     In the following description, the vertical direction of the marine engine (engine)  1  will be referred to as height direction, the longitudinal direction of a crankshaft  61  (see  FIG. 2 ) of the marine engine  1  will be referred to as crank axis direction, and the direction perpendicular to both the height direction and the crank axis direction will be referred to as device width direction, as shown in  FIG. 1 . The top side of  FIG. 1  (the side in which a top cover  10  which will be described later is arranged) with respect to the height direction is defined as the upper side. 
     The marine engine  1  of this embodiment is a diesel engine of in-board type that is mounted in a ship such as a pleasure boat. The marine engine  1  adopts a two-stage turbocharging system. 
     As shown in  FIG. 1 , etc., the marine engine  1  includes a top cover (plate-like cover)  10 . The top cover  10  is in the shape of a flat plate, and arranged with its thickness direction parallel to the height direction. The shape of the top cover  10  is not limited to a flat plate shape, but the top cover  10  may be at least partially bent (or curved). A valve cover, a cylinder block, and the like, are arranged below the top cover  10 . 
     The marine engine  1  includes a two-stage turbocharging system implemented by a first turbocharger  22 , a first intercooler  23 , a second turbocharger  24 , a second intercooler  25 , and air supply pipes  21   a  to  21   d  that connect them. 
     The first turbocharger  22  includes a turbine and a compressor provided in a housing. The turbine is configured to rotate by using an exhaust gas. The compressor is connected to a shaft to which the turbine is also connected, and configured to rotate along with rotation of the turbine, Rotation of the compressor enables the first turbocharger  22  to compress air and forcibly supply air. This configuration is able to, by using the exhaust gas, increase the flow volume of air supplied to a cylinder, and thus achieves an increased output of the marine engine  1 . Air intake performed by the first turbocharger  22  causes rapid compression of air, which makes the temperature of the air high. This high-temperature air is sent out through the air supply pipe  21   a  to the first intercooler  23 . 
     A plurality of cooling pipes through which sea water flows are arranged within a housing of the first intercooler  23 . The air sent out from the first turbocharger  22  flows around the cooling pipes. Such a configuration enables the first intercooler  23  to cool the air sent out from the first turbocharger  22  by means of heat exchange between the air and the sea water. The air cooled by the first intercooler  23  is sent out through the air supply pipe  21   b  to the second turbocharger  24 . 
     The second turbocharger  24 , which has a configuration equivalent to the configuration of the first turbocharger  22 , is able to compress air sent out from the first intercooler  23  by using an exhaust gas. This compressed air has a high temperature in the same manner as described above. The high-temperature air is sent out through the air supply pipe  21  c to the second intercooler  25 . 
     The second intercooler  25 , which has a configuration equivalent to the configuration of the first intercooler  23 , cools the air sent out from the second turbocharger  24  by means of heat exchange between the air and the sea water. The air cooled by the second intercooler  25  is sent out through the air supply pipe  21   d  to an air supply manifold  28 . 
     A common-rail fuel injection mechanism is arranged in a cylinder head provided inside the top cover  10 . The marine engine  1  is configured such that a compressed air supplied to a cylinder is further compressed and then the fuel injection mechanism injects a fuel to thereby drive a piston up and down. This enables the marine engine  1  to generate power. Details of the fuel injection mechanism will be described later. 
     A flywheel housing  62  is arranged in an end portion on the first turbocharger  22  side with respect to the crank axis direction. A transmission  71  is coupled to a flywheel provided in the flywheel housing  62  with interposition of, for example, a clutch (not shown). A propulsion unit of a ship, or the like, is coupled to the transmission  71 . Thus, the output of the marine engine  1  can be transmitted to the propulsion unit or the like, and blocking of the transmission can be made. 
     An oil pan  63  is arranged on a surface (bottom surface) opposite to the top cover  10  with respect to the height direction. The oil pan  63  is a member for storage of an engine oil that is to be supplied to the inside of the engine (for example, to a component part included in a main drive system, such as the cylinder). The engine oil reserved in the oil pan  63  is sent out to the inside of the engine by means of an oil pump (not shown). 
     The engine oil sent out by the oil pump passes through an oil filter  26 . As a result, metal powder, foreign substances, and the like, contained in the engine oil can be removed. In this embodiment, the oil filter  26  includes two filters (a full flow filter and a bypass filter). 
     The engine oil sent out by the oil pump passes through an oil filter  26 . As a result, metal powder, foreign substances, and the like, contained in the engine oil can be removed. In this embodiment, the oil filter  26  includes two filters (a full flow filter and a bypass filter). The oil filter  26  is arranged near an end portion (an end portion on the side opposite to the side where the first turbocharger  22  is arranged) of the marine engine  1  with respect to the crank axis direction. 
     As shown in  FIG. 4 , an exhaust manifold  45  is arranged in an end portion on the second turbocharger  24  side with respect to the device width direction. In the exhaust manifold  45 , exhaust gases discharged from a plurality of (in this embodiment, six) cylinders are collected and then sent out through one or more (in this embodiment, three) air discharge ports  46 . The second turbocharger  24 , an EGR pipe, and the like, are connected to the air discharge ports  46 . 
     The exhaust gas sent out to the second turbocharger  24  is used to rotate the turbine of the second turbocharger  24 , as mentioned above. The exhaust gas, after passing through the second turbocharger  24 , is used to rotate the turbine of the first turbocharger  22 , and then discharged. 
     The exhaust gas sent out to the EGR pipe is, through the air supply pipe  21   d  and the like, supplied to the cylinder again. This configuration achieves reduction of nitrogen oxides in the exhaust gas and improvement in the fuel efficiency. 
     Next, details of the cylinder head and therearound, and particularly the fuel injection mechanism, the valve cover  41 , and the top cover  10 , will be described with reference to  FIGS. 4 to 6 .  FIG. 5  is a cross-sectional view showing a space between the valve cover  41  and the top cover  10 .  FIG. 6  is perspective views showing the shapes of the valve cover  41  and the top cover  10 . 
     As shown in  FIGS. 4 and 5 , the marine engine  1  includes a fuel injection mechanism implemented by a common rail  31 , connectors  32 , fuel supply pipes (fuel tubes)  33 , a fuel return pipe (fuel tube)  34 , and injectors  35 . In  FIG. 5 , illustration of the fuel return pipe  34  is omitted for clarity of the drawing. 
     The common rail  31 , which is a tube-shaped member made of a metal or other materials, is arranged above the valve cover  41  with its longitudinal direction parallel to the crank axis direction. A high-pressure fuel is supplied from a fuel tank to the common rail  31  by, for example, a high-pressure pump. The number of the connectors  32  included in the common rail  31  is equal to the number of cylinders (in this embodiment, six). The fuel supply pipes  33  are connected to the connectors  32 , respectively. 
     The injectors  35  are arranged corresponding to the cylinders, respectively. The injectors  35  are connected to the common rail  31  via the fuel supply pipes  33  and the connectors  32 . The injector  35 , in response to an instruction from an electronic control device (not shown), injects the fuel. This configuration enables the fuel to be injected into each of the cylinders at an appropriate timing. 
     The fuel injection mechanism also includes a single fuel return pipe  34  that connects one end portion of the common rail  31  to the other end portion thereof. The fuel return pipe  34  is arranged so as to form a loop surrounding all the injectors  35 . The injectors  35  returns a surplus of the supplied fuel through the fuel return pipe  34  to the common rail  31  or the fuel tank. 
     Next, the valve cover  41  will be described. The valve cover  41  is a cover arranged above the cylinders (above an air intake valve or an exhaust valve). The valve cover  41  has holes for mounting of the injectors  35 , holes for fixing of the valve cover  41  to the cylinder block or the like. The valve cover  41  also has a second partition  42 . 
     As shown in  FIGS. 5 and 6(   a ), the second partition  42  is a plate-like part extending upward from the valve cover  41  toward the top cover  10  side (the upper side). The second partition  42  is formed across opposite end portions of the valve cover  41  with respect to the longitudinal direction (crank axis direction). 
     The second partition  42  is located on the second turbocharger  24  side (on the exhaust manifold  45  side) relative to the center with respect to the device width direction. More specifically, the second partition  42  is arranged so as to separate the side where the second turbocharger  24  is arranged (the side where the exhaust gas flows immediately after being discharged from the exhaust manifold  45 ) from the side where the fuel supply pipes  33  are arranged. 
     As shown in  FIG. 5 , the second partition  42  has a height that occupies half or more of the distance between the valve cover  41  and the top cover  10  (cover-to-cover distance). Here, the cover-to-cover distance means a distance obtained by vertical measurement of the distance to the top cover  10  from the position at Which the second partition  42  is formed (see  FIG. 5 ). The second partition  42  is formed integrally with the valve cover  41  through, for example, a casting process it may not be indispensable that the second partition  42  is formed integrally with the valve cover  41 , For example, the second partition  42  may be attached to the valve cover  41  by welding, screwing, or the like. 
     Next, the top cover  10  will be described, As mentioned above, the top cover  10  is a plate-like cover arranged so as to cover the valve cover  41 . As shown in  FIGS. 5 and 6(   b ), the top cover  10  is provided with a partition  11  that is a plate-like portion extending toward the valve cover  41  (the lower side). 
     The partition  11  is formed across opposite end portions of the top cover  10  with respect to the longitudinal direction (crank axis direction). The partition  11  is located on the second turbocharger  24  side (on the exhaust manifold  45  side) relative to the center with respect to the device width direction. More specifically, the partition  11  is arranged so as to separate the side where the second turbocharger  24  is arranged (the side where the exhaust gas flows immediately after being discharged from the exhaust manifold  45 ) from the side where the fuel supply pipes  33  are arranged. The partition  11  is formed integrally with the top cover  10  through, for example, a casting process. It may not be indispensable that the partition  11  is formed integrally with the top cover  10 . For example, the partition  11  may be attached to the top cover  10  by welding, screwing, or the like. 
     The two partitions  11  and  42  are arranged so as to overlap each other when seen in the device width direction. The partition  11  is arranged near the second partition  42  and on the fuel supply pipe  33  side relative to the second partition  42 . 
     Next, effects of the partitions  11  and  42  will be described with reference to  FIG. 5 . 
     In the fuel injection mechanism of this embodiment, the connectors  32  are configured so as to prevent leakage of the fuel between the common rail  31  and each fuel supply pipe  33 . Depending on the use environment or the like, however, loosening of the connection, damage to the fuel supply pipes  33  or the fuel return pipe  34 , or the like, may occur, which results in leakage of the fuel. 
     The exhaust gas, immediately after being discharged from the exhaust manifold  45 , has a very high temperature. Accordingly, the surroundings of the air discharge ports  46 , the second turbocharger  24  having the exhaust gas flowing therethrough, and the like, also have a very high temperature (hereinafter, called a high-temperature part). It is therefore necessary to prevent the high-temperature part from being exposed to the fuel in a case of occurrence of leakage and splashing of the fuel. In this embodiment, the partitions  11  and  42  mentioned above serve for preventing the high-temperature part from being exposed to the fuel. 
     For example, in a case where the fuel leaks out of the connector  32 , the fuel bursts and splashes because of its high pressure. Even when part of the splashing fuel goes toward the second turbocharger  24 , the partitions  11  and  42  are able to catch the fuel. Thus, the high-temperature part is prevented from being exposed to the fuel. 
     Here, a case is assumed where the second partition  42  is located closer to the fuel supply pipe  33  than the partition  11  is. In this case, when the fuel splashes along the top cover  10 , the fuel may flow through a gap between the partition  11  and the second partition  42  and may reach the high temperature-side of the engine. In this respect, this embodiment has the partition  11  arranged closer to the fuel supply pipe  33  than the second partition  42  is, as described above. This enables the fuel, even splashing along the top cover  10 , to be caught without fail. 
     As described above, the partitions  11  and  42  are arranged with one of them located near the other of them, so as to overlap each other when seen in the device width direction. This can more surely prevent the high-temperature part from being exposed to the splashing fuel. 
     As thus far described, the marine engine  1  includes the exhaust manifold  45 , the valve cover  41 , the top cover  10 , and the fuel supply pipes  33  (or the fuel return pipe  34 ). The exhaust manifold  45  collects the exhaust gases discharged from the plurality of cylinders. The valve cover  41  is a cover that covers all of the air intake valve or the exhaust valve. The fuel supply pipe  33  is arranged outside the valve cover  41 , and allows the fuel to flow therethrough. The top cover  10  is provided with the partition  11  that is arranged so as to separate the side where the exhaust gas flows immediately after being discharged from the exhaust manifold  45  from the side where the fuel supply pipe  33  is arranged. 
     Accordingly, even when the fuel leaks out of the fuel supply pipe  33 , the part (the high-temperature part of the engine such as the second turbocharger  24 ) through which the exhaust gas passes can be prevented from being exposed to the fuel. This can eliminate the need of double-structuring the fuel supply pipe  33  for the purpose of preventing leakage of the fuel, and moreover can eliminate the need of covering an exhaust pipe and the like, with a heat insulating material for the purpose of lowering the surface temperature. Thus, reduction in the number of parts and simplification of an assembling operation are achieved. 
     In the marine engine  1  of this embodiment, the partition  11  has a height that occupies half or more of the cover-to-cover distance. 
     This makes it easy for the second partition  42  to catch the fuel splashing from the fuel supply pipe  33 , thus more surely preventing the part through which the exhaust gas passes from being exposed to the fuel. 
     In the marine engine  1  of this embodiment, the partition  11  is formed so as to extend from one end to the other end of the top cover  10  with respect to the crank axis direction. 
     Accordingly, the second turbocharger  24  and the like can be prevented from being exposed to the fuel even in a case where the common rail  31  and the fuel supply pipes  33  are arranged in an elongated manner in the crank axis direction as illustrated in this embodiment. 
     In the marine engine  1  of this embodiment, the partition  11  is a plate-like portion that is formed integrally with the top cover  10  and that protrudes from the top cover  10 . 
     Since the partition  11  and the top cover  10  are formed integrally with each other, reduction in the number of parts and simplification of the assembling operation are achieved. Additionally, since the partition  11  has a plate-like shape, the space occupied by the partition  11  can be restricted while the second turbocharger  24  and the like are prevented from being exposed to the fuel. 
     Next, arrangement of the oil filter  26  and the devices included in the two-stage turbocharging system of this embodiment will be described from various aspects in the following description, the devices (the first turbocharger  22 , the first intercooler  23 , the second turbocharger  24 , and the second intercooler  25 ) included in the two-stage turbocharging system as well as the oil filter  26  may be collectively called “the turbochargers and the like”. 
     Firstly, referring to a plan view ( FIG. 2 ), arrangement of the turbochargers and the like in a plan view will be described. Since the thickness direction of the top cover  10  is parallel to the height direction as mentioned above, a plan view in this embodiment can be also regarded as “a view as seen in the thickness direction of the top cover  10 ”. 
     The first turbocharger  22  is arranged in one end portion of the marine engine  1  with respect to the crank axis direction. All of the first intercooler  23 , the second turbocharger  24 , and the second intercooler  25  are arranged in one end portion of the marine engine  1  with respect to the device width direction. These three devices are arranged side by side with the first intercooler  23  located closer to the first turbocharger  22 . The oil filter  26  is arranged in the other end portion (the end portion opposite to the transmission  71  side) of the marine engine  1  with respect to the crank axis direction. 
     In this embodiment, the turbochargers and the like are arranged so as not to overlap one another. This enables an operator who is working on the top cover  10  when performing a maintenance operation to perform the maintenance operation without the need to remove other devices, thus achieving a layout that facilitates the operation. 
     Next, referring to a front elevational view ( FIG. 3 ), the positions of the turbochargers and the like with respect to the height direction will be described. In this embodiment, an upper surface of the top cover  10  constitutes a part of an upper surface of the marine engine  1 . A lower surface of the oil pan  63  constitutes a part of a lower surface of the marine engine  1 . Accordingly, the distance from the lower surface of the oil pan  63  to the upper surface of the top cover  10  can be considered as the height of the marine engine  1 . In the following, half the height of the marine engine  1  will be defined as “reference height”, as shown in  FIG. 3 . 
     All of the turbochargers and the like are arranged higher (closer to the top cover  10 ) than the reference height. To be more specific, not only the upper ends of the turbochargers and the like but also middle portions and the lower ends thereof are located higher than the reference height. The first turbocharger  22 , the first intercooler  23 , and the second intercooler  25  are arranged with their upper surfaces being substantially identical to the upper surface of the marine engine  1 . 
     Such a configuration in which the turbochargers and the like are arranged in an upper region of the marine engine  1  achieves a layout that allows an operator who is working on the top cover  10  in performing a maintenance operation to easily access the turbochargers and the like (the operation is facilitated). 
     Next, comparison among the lengths of the air supply pipes  21   a  to  21   d  will be given with reference to a perspective view showing the positional relationship among the devices of the air supply system ( FIG. 7 ). 
     Here, the length of the air supply pipe  21   a  means the length of a path of air extending from the first turbocharger  22  to the first intercooler  23 . The same applies to the other air supply pipes. Therefore, this embodiment can provide comparison among the lengths of paths of air supplied to the cylinder based on comparison among the lengths of the air supply pipes. 
     In this embodiment, the condition that “the length of the air supply pipe  21   a &lt;the length of the air supply pipe  21   b ” is established, and the condition that “the length of the air supply pipe  21   c &lt;the length of the air supply pipe  21   d ” is established. 
     This configuration enables the air supply pipe  21   a  and the air supply pipe  21   c , through which high-temperature air passes, to be relatively short. Accordingly, parts of all the air supply pipes that need to be covered with a heat insulating material or the like can be shortened, which leads to cost reduction. 
     Although a preferred embodiment of the present invention has been described above, the above-described configuration can be modified, for example, as follows. 
     While the above-described embodiment adopts combined use of the partition  11  and the second partition  42 , the effects of the present invention can be exerted also by a configuration including the partition  11  alone (see  FIG. 8(   a )) or a configuration including the second partition  42  alone (see  FIG. 8(   b )). Since the above-described embodiment adopts combined use of two partitions, the partition  11  has a short length. In a case where the second partition  42  is not provided, however, it is preferable that the partition  11  has a large length. In  FIG. 8(   a ), the length of the partition  11  is half or more of the cover-to-cover distance. 
     The shapes of the parts included in the marine engine  1  and the layout thereof are merely illustrative, and can be modified as appropriate. For example, the number of cylinders, the arrangement of the turbochargers and the intercoolers, and the like, may be changed in accordance with, for example, a required size or specifications. 
     The fuel injection mechanism need not always be of electronic control type, but may be of mechanical type that drives arranged injection pumps by means of a cam, for example. Moreover, the fuel injection mechanism need not always be of common rail type. 
     In the configuration illustrated above, the partitions  11  and  42  have plate-like shapes, but any appropriate shape is adoptable as long as it is able to catch a splashing fuel. The positions where the partitions  11  and  42  are provided can be changed as long as the partitions  11  and  42  are arranged so as to separate the high-temperature part of the engine from the fuel supply pipe  33  and the fuel return pipe  34 . 
     The present invention is applicable to either main equipment or auxiliary equipment for use in a ship. Furthermore, the present invention is applicable not only to ships but also to engines of automobiles or work vehicles. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           1  marine engine (engine) 
           10  top cover (plate-like cover) 
           11  partition 
           21   a  to  21   d  air supply pipe 
           22  first turbocharger 
           23  first intercooler 
           24  second turbocharger 
           25  second intercooler 
           31  common rail 
           32  connector 
           33  fuel supply pipe (fuel tube) 
           34  fuel return pipe (fuel tube) 
           35  injector 
           41  valve cover 
           42  second partition