Patent Publication Number: US-2017370329-A1

Title: Vehicular egr cooler

Description:
TECHNICAL FIELD 
     The present invention relates to an EGR cooler, and more specifically, to an EGR cooler having improved cooling performance by allowing a gas tube disposed inside a housing to have a long flat portion in a longitudinal direction to increase an area in which exhaust gas exchanges heat with a cooling fluid. 
     BACKGROUND ART 
     Generally, a large amount of harmful substances such as carbon monoxide, nitrogen oxide, and hydrocarbons are included in exhaust gas of a vehicle. In particular, an emission of the harmful substances like the nitrogen oxide increase as a temperature of an engine rises. 
     Today, exhaust gas regulations are being tightened in each country. In order to satisfy the tightened exhaust gas regulations for each country, various devices are installed in a vehicle to reduce the harmful substances like the nitrogen oxide among the exhaust gases. 
     In particular, since a vehicle equipped with a diesel engine has components of combusted fuel different from those of a vehicle equipped with a gasoline engine, the vehicle equipped with the diesel engine is equipped with devices such as a diesel particulate filter (DPF) and an exhaust gas recirculation (EGR) to satisfy the exhaust gas regulations by reducing the harmful exhaust gases like the nitrogen oxide. 
     In general, the DPF collects a particulate matter (PM) included in the exhaust gas into a filter and then injects fuel into an exhaust pipe at a front end of the filter to forcibly burn the particulate matter, thereby reducing the exhaust gas and regenerating the filter. 
     The exhaust gas recirculation (EGR) sucks some of the exhaust gases of the vehicle together with a mixer to lower a temperature of a combustion chamber, thereby reducing the emission of harmful substances such as nitrogen oxide and sulfur oxide. 
     Today, in addition, to cope with tightening of regulation on air pollution worldwide, an EGR cooler are applied together to lower a temperature of EGR gas. The exhaust gas introduced into the EGR cooler is cooled by coolant (cooling fluid) discharged through the engine. 
     As the related technology, there is Korean Patent No. 0748756 (Title: EGR cooler of EGR device for vehicle, Registration Date: Aug. 6, 2007). 
     The existing EGR cooler includes a cooler main body having both ends provided with a coolant inlet pipe and a coolant outlet pipe and a plurality of gas tubes arranged inside the cooler main body in parallel in a longitudinal direction, in which one side of the cooler main body is provided with a lead valve. 
     Accordingly, the coolant supplied through the coolant inlet pipe exchanges heat with the exhaust gas flowing through the gas tube in the cooler main body, and the coolant that has undergone the heat exchange is discharged through the coolant outlet pipe, thereby cooling the high-temperature exhaust gas. 
     By the way, in the EGR cooler in which the gas tube is formed of a U-bent type or an S-bent type among the existing EGR coolers, an exhaust gas inlet and an exhaust gas outlet are generally formed in one direction, and a length of the tube exchanging heat with the coolant in the housing is relatively short, and thus there is a problem in that the cooling performance deteriorates. 
     Further, in the case of the existing EGR cooler, as a pressure difference between the exhaust gas inlet and the exhaust gas outlet is large, the exhaust gas is not sufficiently cooled and thus there is a problem in that the engine performance deteriorates. 
     Further, in the case of the existing EGR cooler, as the length of the tube exchanging heat with the coolant is long, the EGR cooler may not be miniaturized, and there is a problem that a space for the EGR cooler is restrictive. 
     In addition, the existing I-flow tube type or U-bent type and S-bent type EGR cooler can not be applied when the exhaust gas inlet and the exhaust gas outlet are formed to be spaced apart from each other on the same plane, and thus have a limit in an applicable model. 
     DISCLOSURE 
     Technical Problem 
     An object of the present invention is to provide an EGR cooler for a vehicle capable of increasing space utilization with a compact configuration, increasing an area in which exhaust gas exchanges heat with a cooling fluid, and reducing a pressure difference in exhaust gas at an exhaust gas inlet and an exhaust gas outlet since a plurality of gas tubes installed in a housing, respectively, are configured of a flat portion, a first bent portion, and a second bent portion and a length of the flat portion is longer than a height of the first bent portion and the second bent portion. 
     Another object of the present invention is to provide an EGR cooler capable of improving fluidity of a cooling fluid introduced into a housing by adjusting a height of an end of a tube plate. 
     Still another object of the present invention is to provide an EGR cooler for a vehicle capable of being applied to a vehicle layout in which a housing is formed to correspond to an outer wall surface of a cylinder block positioned at an outer side of a water jacket of an internal combustion engine equipped in the vehicle to be disposed on the outer wall surface of the cylinder block and an exhaust gas inlet and an exhaust gas outlet are spaced apart from each other by a predetermined distance. 
     Technical Solution 
     In one general aspect, an EGR cooler for a vehicle includes: a housing  100  provided with a cooling fluid inlet  110  and a cooling fluid outlet  120 ; a plurality of gas tubes  200  disposed in the housing  100  to form an exhaust gas channel and including a flat portion  210  extending along a longitudinal direction of the housing  100 , a first bent portion  220  bent at one end of the flat portion  210 , a second bent portion  230  bent at the other end of the flat portion  210  to face the first bent portion  220 , a length L of the flat portion  210  being longer than a height H of the first bent portion  220  and the second bent portion  230 ; a tube plate  300  fixing the plurality of gas tubes  200 ; and a cover  400  coupled with the housing  100  at an outer side of the tube plate  300  and provided with an exhaust gas inlet  410  and an exhaust gas outlet  420 . 
     The gas tube  200  may be formed so that the length L of the flat portion  210  is greater than 1 time and less than 20 times the height H of the first bent portion  220  and the second bent portion  230 . 
     In the gas tube  200 , the first bent portion  220  and the second bent portion  230  may be vertically bent at both ends of the flat portion  210  to be parallel with each other. 
     In the gas tube  200 , the first bent portion  220  and the second bent portion  230  may be bent to form an obtuse angle α with respect to the flat portion  210  at both ends of the flat portion  210 . 
     In the gas tube  200 , a part of the first bent portion  220  may be bent so that the first bent portion  220  forms an obtuse angle β, and a part of the second bent portion  230  may be bent so that the second bent portion  230  forms the obtuse angle β while facing the first bent portion  220 . 
     In the gas tube  200 , the first bent portion  220  and the second bent portion  230  may be bent round to have a predetermined curvature R at both ends of the flat portion  210 . 
     The cooling fluid inlet  110  may be formed at a position corresponding to a rounded region of the first bent portion  220  and the cooling fluid outlet  120  may be formed at a position corresponding to a rounded region of the second bent portion  230 . 
     In the gas tube  200 , the flat portion  210 , the first bent portion  220 , and the second bent portion  230  may be integrally formed. 
     The gas tubes  200  may be installed in a multi-stage manner so as to be spaced apart from each other by a predetermined distance along a height direction of the housing  100  within the housing  100  and may be installed in a multi-row manner so as to be spaced apart from each other by a predetermined distance along a width direction of the housing  100  within the same stage. 
     In the gas tube  200 , a concave portion  211  may be formed on an outer side surface or an inner side surface of the flat portion  210 , the first bent portion  220 , and the second bent portion  230 . 
     In the gas tube  200 , a radiating fin  240  may be inserted into the flat portion  210  or into the first bent portion  220  and the second bent portion  230 . 
     The gas tubes  200  may be installed in a multi-stage manner so as to be spaced apart from each other by a predetermined distance along the height direction of the housing  100  within the housing  100  and may be formed as a single tube  300  extending along a width direction of the housing  100  within the same stage. 
     The tube plate  300  may include a tube insertion hole  310  having both ends of the gas tube  200  inserted thereinto and a cooling fluid guide part  320  whose inner side surface of a position corresponding to the flat portion  210  of the gas tube  200  protrudes toward the flat portion  210 . 
     A height D 1  of the cooling fluid guide part  320  may be formed to be equal to or less than 0.85 times a distance D 2  between a tube positioned at the outermost side of the tube plate  300  among the gas tubes  200  and the tube plate  300 . 
     The tube plate  300  may have a turbulent flow forming part  330  formed on a side surface facing the gas tube  200  of the cooling fluid guide part  320 . 
     The turbulent flow forming part  330  may be depressed in a dimple or a wave shape. 
     The housing may be formed to correspond to an outer wall surface of a cylinder block  10  positioned at an outer side of a water jacket  11  of an internal combustion engine equipped in the vehicle and thus may be disposed on the outer wall surface of the cylinder block  10 . 
     The gas cover  400  may have the exhaust gas inlet  410  formed at one side thereof and the exhaust gas outlet  420  formed at the other side thereof, in a longitudinal direction, and the exhaust gas inlet  410  and the exhaust gas outlet  420  may be spaced apart from each other by a diameter R of at least one engine cylinder. 
     In the gas cover  400 , a spaced distance S between the exhaust gas inlet  410  and the exhaust gas outlet  420  may be 1 to 3 times as large as the diameter R of the engine cylinder. 
     A spaced distance S between the exhaust gas inlet  410  and the exhaust gas outlet  420  may be formed to be 0.8 to 1.2 times as large as the length L of the flat portion  210  of the gas tube. 
     The cooling fluid inlet  110  of the housing  100  and the exhaust gas inlet  410  of the gas cover  400  may be formed to be opposite to each other in a longitudinal direction. 
     The EGR cooler for a vehicle may further include: a gasket  500  installed between the housing  100  and the tube plate  300 . 
     The EGR cooler for a vehicle may further include: a sealing member  600  installed between the tube plate  300  and the gas cover  400 . 
     The housing  100 , the gasket  500 , the tube plate  300 , the sealing member  600 , and the gas cover  400  may be coupled at an edge by a bolt. 
     The tube plate  300  and the gas cover  400  may be coupled by brazing. 
     Advantageous Effects 
     Accordingly, the EGR cooler for a vehicle according to the exemplary embodiment of the present invention may improve the cooling performance of the EGR cooler as the gas tube disposed in the housing is formed to have the long flat portion in the longitudinal direction and thus the area in which the exhaust gas exchanges heat with the cooling fluid is increased and increases the space utilization with the compact configuration. 
     In addition, the EGR cooler for a vehicle according to the exemplary embodiment of the present invention may save the manufacturing costs and the manufacturing time of the EGR cooler as the plurality of tubes are easily mounted on the plate. 
     In particular, according to the EGR cooler for a vehicle according to the exemplary embodiment of the present invention, the tube plate protrudes toward the gas tube so that the space between the tube plate and the gas tube is filled to improve the fluidity so that the cooling fluid introduced into the housing is mostly guided toward the gas tube, thereby improving the cooling efficiency. 
     In addition, according to the EGR cooler for a vehicle according to an exemplary embodiment of the present invention, the turbulent flow forming part is formed on the tube plate in the dimple or the wave shape, thereby improving the cooling efficiency due to the turbulence of the coolant flow. 
     Further, according to the EGR cooler for a vehicle according to the exemplary embodiment of the present invention, the cooling fluid inlet and the cooling fluid outlet are disposed in the region in which the curved surface of the gas tube is formed to prevent the cooling fluid introduced into the housing from flowing into the bottom surface of the tube plate, thereby improving the fluidity. 
     Further, the EGR cooler for a vehicle according to the exemplary embodiment of the present invention may reduce the pressure difference in the exhaust gas at the exhaust gas inlet and the exhaust gas outlet to shorten the heat exchange time of the EGR cooler, thereby minimizing the degradation in the engine performance depending on the back pressure. 
     Further, the EGR cooler for a vehicle according to an exemplary embodiment of the present invention may be applied to the vehicle layout in which the exhaust gas inlet and the exhaust gas outlet are spaced apart from each other by the predetermined distance, thereby diversifying the applicable models. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of an EGR cooler according to an exemplary embodiment of the present invention. 
         FIG. 2  is a front view of the EGR cooler for a vehicle according to the exemplary embodiment of the present invention. 
         FIG. 3  is a front view illustrating a state in which the EGR cooler according to the exemplary embodiment of the present invention is mounted at an outer side of an engine cylinder. 
         FIG. 4  is a perspective view illustrating a state where a gas tube is coupled with a tube plate according to an exemplary embodiment of the present invention. 
         FIG. 5  is a side perspective view of a partially cut state in a state in which the gas tube is coupled with the tube plate according to the exemplary embodiment of the present invention. 
         FIG. 6  is a side perspective view of a partially cut state in the state in which the gas tube is coupled with the tube plate according to the exemplary embodiment of the present invention. 
         FIGS. 7 to 10  are cross-sectional views of the gas tube according to various exemplary embodiments of the present invention. 
         FIG. 11  is a front view illustrating a state in which a housing is removed from the EGR cooler for a vehicle according to the exemplary embodiment of the present invention. 
         FIG. 12  is a diagram illustrating a result of analyzing a flow of a cooling fluid in the EGR cooler for a vehicle according to the exemplary embodiment of the present invention. 
         FIG. 13  is a front view of the existing EGR cooler for a vehicle. 
         FIG. 14  is a diagram illustrating the result of analyzing the flow of the cooling fluid in the EGR cooler for a vehicle according to the exemplary embodiment of the present invention of  FIG. 13 . 
         FIGS. 15 and 16  are plan views of the tube plate according to various exemplary embodiments of the present invention. 
         FIG. 17  is a perspective view illustrating a gas cover of an EGR cooler according to the exemplary embodiment of the present invention. 
         FIG. 18  is an exploded perspective view of the EGR cooler according to the exemplary embodiment of the present invention. 
     
    
    
     BEST MODE 
     Hereinafter, an EGR cooler for a vehicle according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     As illustrated in  FIGS. 1 and 2 , an EGR cooler  1  for a vehicle according to an exemplary embodiment of the present invention is configured to include a housing  100 , a gas tube  200 , a tube plate  300 , and a gas cover  400 . 
     The housing  100  is configured to include a cooling fluid inlet  110  and a cooling fluid outlet  120  and the inside of the housing  100  is formed with a space in which a cooling fluid introduced through the cooling fluid inlet  110  may be accommodated is formed in the housing  100 . Here, as the cooling fluid, coolant is generally used, but other cooling fluids may be used. 
     The cooling fluid inlet  110  is formed in a part of a main body part  101 . The coolant is introduced into the main body part  101  through the cooling fluid inlet  110 . 
     The cooling fluid outlet  120  is formed in a part of the main body part  101 . The coolant is discharged to the outside of the main body part  101  through the cooling fluid outlet  120 . 
       FIGS. 1 and 2  illustrate that the cooling fluid inlet  110  and the cooling fluid outlet  120  are formed on different surfaces of the main body part  101 , but the present invention is not limited thereto. That is, if necessary, the cooling fluid inlet  110  and the cooling fluid outlet  120  may be formed on the same surface of the main body part  101 . 
     In the housing  100 , a coupling hole  130  is formed at an edge of the main body part  101 , and a gasket, a plate, a sealing member, and a cover which will be described below are fastened to the housing by a bolt. Although not necessarily limited thereto, it is preferable that at least two or more coupling holes  130  are formed at the edges of the main body part  110  in order to firmly fasten the gasket, the plate, the sealing member, and the cover, which will be described below, to the housing. 
     As illustrated in  FIGS. 1 and 2 , the housing  100  may have a rectangular parallelepiped shape whose one side is open or may also be formed in shapes corresponding to shapes of peripheral parts in consideration of the shapes of the peripheral parts. The housing  100  may be formed separately from an engine block and installed between an intake manifold and an exhaust manifold of an engine. 
     In this case, as illustrated in  FIG. 3 , the housing  100  is formed to correspond to an outer wall surface of a cylinder block  10  positioned at an outer side of a water jacket  11  of an internal combustion engine equipped in the vehicle, and is disposed to contact the outer wall surface of the cylinder block  10 . 
     The housing  100  may be integrally formed with the engine block. In this case, as the cooling fluid inlet  110  and the cooling fluid outlet  120  do not have to be formed separately, it is possible to save manufacturing time and manufacturing costs of the housing  100  of the EGR cooler  1  by reducing the number of assembling processes and minimize a space in which the EGR cooler  1  is installed in an engine room of the vehicle. 
     Gas tubes  200  are arranged in a multi-stage and multi-row manner so as to be spaced apart from each other in a height direction within the housing  100 , thereby forming an exhaust gas channel. That is, the exhaust gas flows through the plurality of gas tubes  200 . In this case, the exhaust gas flowing in the housing  100  is cooled by exchanging heat with a cooling fluid in the housing  100 . 
     As illustrated in  FIG. 4 , the gas tube  200  of the EGR cooler  1  for a vehicle according to an exemplary embodiment of the present invention is configured to include a first bent portion  220 , a second bent portion  230 , and a flat portion  210 . 
     The flat portion  210  extends horizontally along a longitudinal direction of the housing  100 , the first bent portion  220  is bent at one end of the flat portion  210  and the second bent portion  230  is bent at the other end of the flat portion  210 . 
     At this point, the second bent portion  230  is formed to have the same length as the first bent portion  220  while facing the first bent portion  220 . 
     That is, the gas tube  200  is generally formed in a ‘C’-letter form. In particular, when a length L of the flat portion  210  is formed to be longer than a height H of the first bent portion  220  and the second bent portion  230 . 
     Therefore, in the gas tube  200 , the length L of the flat portion  210  is longer than the height H of the first bent portion  220  and the second bent portion  230 , such that an area in which the exhaust gas exchanges heat with the cooling fluid increases, thereby improving the cooling performance of the EGR cooler  1  and reducing the pressure difference in exhaust gas at the exhaust gas inlet  410  and the exhaust gas outlet  420 . 
     In this case, the gas tube  200  is formed so that the length L of the flat portion  210  is formed to be greater than 1 time and less than 20 times the height H of the first bent portion and the second bent portion. That is, a ratio of the length L of the flat portion  210  to the height H of the first bent portion  220  and the second bent portion  230  is formed to be 20:1 
     In the gas tube  200 , when the length L of the flat portion  210  is less than or equal to 1 time the height H of the first bent portion  220  and the second bent portion  230 , the difference between the pressure of the exhaust gas introduced into the first bent portion  220  and the pressure of the exhaust gas discharged to the second bent portion  230  increases, which causes a problem in that the cooling efficiency deteriorates. 
     Further, when the length L of the flat portion  210  exceeds 20 times the height H of the first bent portion  220  and the second bent portion  230 , the size of the EGR cooler  1  including the housing  100  is too large, and thus the housing  100  may not be integrally formed in the engine block. Even when the housing  100  is separately formed, there is a restriction on the space provided in the engine room, such that the problem in that the miniaturization of the EGR cooler  1  may not be achieved is caused. 
     The first bent portion  220  and the second bent portion  230  of the gas tube  200  may be bent round so as to have a predetermined curvature R at both ends of the flat portion  210 . 
     Since the first bent portion  220  and the second bent portion  230  of the gas tube  200  are bent round to have a predetermined curvature R at one end and the other end of the flat portion  210 , the exhaust gas introduced into the first bent portion moves to the flat portion  210  along the rounded surface and then is discharged to the outside along the rounded surface of the second bent portion so as to smoothly induce the flow of the exhaust gas as far as possible, thereby increasing a circulation speed of the exhaust gas to increase the cooling efficiency of the EGR cooler  1 . 
     Although not necessarily limited thereto, the flat portion  210 , the first bent portion  220 , and the second bent portion  230  of each of the gas tubes  200  may be integrally formed of a metal material. 
     In this case, it is preferable that the curvature R of the first bent portion and the second bent portion formed at one end and the other end of the flat portion  210  is greater than 6 mm but less than 30 mm. (6 mm&lt;R&lt;30 mm). When the curvature R is equal to or less than 6 mm, there arises a problem that it is difficult to ensure the preparation of the tube. Further, when the curvature R is greater than 30 mm, the overall size of the tube  300  becomes larger and thus the overall size of the EGR cooler  1  including the housing  100  becomes larger, and thus there is a problem that it is difficult to ensure the installation position of the EGR cooler  1  separately installed in the engine block or the engine room. 
     Further, in the EGR cooler  1  for a vehicle according to the exemplary embodiment of the present invention, a radiating fin  240  may be inserted into the flat portion  210  of each tube or into the first bent portion and the second bent portion. Therefore, the EGR cooler  1  for a vehicle according to the exemplary embodiment of the present invention may increase the contact area of the exhaust gas passing through the inside of the housing  100  with the cooling fluid, thereby increasing a heat exchange amount. 
     Further, as illustrated in  FIG. 2 , the EGR cooler  1  for a vehicle according to the exemplary embodiment of the present invention is configured so that the cooling fluid inlet  110  of the housing  100  may be formed at a position corresponding to the rounded region of the first bent portion  220  and the cooling fluid outlet  120  may be formed at a position corresponding to the rounded region of the second bent portion  230 . 
     As a result, the EGR cooler  1  for a vehicle according to the exemplary embodiment of the present invention may prevent the cooling fluid introduced into the housing  100  from moving to a bottom surface of the tube plate  300 , thereby improving fluidity. 
     As illustrated in  FIG. 8 , according to another exemplary embodiment of the present invention, the first bent portion  220  and the second bent portion  230  of the gas tube  200  may be vertically bent at both ends of the flat portion  210  to be parallel to each other. 
     Therefore, as the first bent portion  220  and the second bent portion  230  of the gas tube  200  are vertically bent to form 90° with respect to the flat portion  210  at one end and the other end of the flat portion  210 , the pressure difference between the exhaust gas inlet and the exhaust gas outlet is reduced, such that the cooling performance and the engine efficiency of the EGR cooler may be achieved and the first bent portion  220  and the second bent portion  230  may easily be coupled with a tube insertion hole  310  of the tube plate  300  to be described below. 
     As illustrated in  FIG. 9 , according to another exemplary embodiment of the present invention, the first bent portion  220  and the second bent portion  230  of the gas tube  200  may be bent at both ends of the flat portion  210  to form an obtuse angle α with respect to the flat portion  210 . 
     That is, as the first bent portion  220  and the second bent portion  230  of the gas tube  200  are formed to have an obtuse angle α that is larger than 90° and smaller than 180° with respect to the flat portion  210 , the flow of the exhaust gas flowing inside the gas tube  200  is smooth to increase the circulation of the exhaust gas, thereby improving the cooling efficiency of the EGR cooler. 
     As illustrated in  FIG. 10 , according to another exemplary embodiment of the present invention, a part of the first bent portion  220  may be bent so that the first bent portion  220  of the gas tube  200  forms an obtuse angle β and a part of the second bent portion  230  may be bent so that the second bent portion  230  forms the obtuse angle β while facing the first bent portion  220 . 
     In the gas tube  200 , a part of the first bent portion  220  and a part of the second bent portion  330  are bent, and thus the flow of the exhaust gas flowing in the gas tube  200  is smooth, such that the cooling efficiency of the EGR cooler may be improved and the first bent portion  220  and the second bent portion  230  may be easily coupled with the tube insertion hole  310  of the tube plate  300 . 
     Further, the gas tubes  200  may be installed in a multi-stage manner so as to be spaced apart from each other by a predetermined distance along the height direction of the housing  100  within the housing  100  and may be installed in a multi-row manner so as to be spaced apart from each other by a predetermined distance along a width direction of the housing  100  within the same stage. 
     As the gas tubes  200  are arranged in the housing  100  in a multi-stage and multi-row manner along the height direction of the housing  100  and the width direction of the housing  100 , the contact area of the exhaust gas passing through the inside of the main body part  101  of the housing  100  with the cooling fluid may be increased to increase the heat exchange amount. 
     As illustrated in  FIGS. 4 and 5 , in the gas tube  200 , a concave portion  211  may be formed on an outer side surface or an inner side surface of the flat portion  210 , the first bent portion  220 , and the second bent portion  230 . 
       FIGS. 4 and 5  illustrate that a plurality of concave portions  211  are formed in a diagonal direction with respect to the width direction. However, the present invention is not necessarily limited thereto, and the shape and the direction of the concave portion  211  may be variously formed as needed. 
     As illustrated in  FIG. 6 , the gas tubes  200  may be installed in a multi-stage manner so as to be spaced apart from each other by a predetermined distance along the height direction of the housing  100  within the housing  100  and may be formed as a single tube  300  formed to extend along the width direction of the housing  100  within the same stage. 
     As the gas tubes  200  are arranged in a multi-stage manner along the height direction of the housing  100  within the housing  100  and the single tube  300  extends along the width direction of the housing  100  within the same stage, the contact area of the exhaust gas passing through the inside of the main body part  101  of the housing  100  with the cooling fluid may be increased. 
     Meanwhile, the tube plate  300  has both ends of the gas tube  200  inserted thereinto and is formed to include tube insertion holes  310  corresponding to the number of gas tubes  200 . 
     In particular, the tube plate  300  includes a cooling fluid guide part  320  whose inner side surface protrudes toward the flat portion  210  at a position corresponding to the flat portion  210  of the gas tube  200 , thereby improving the fluidity of the cooling fluid flowing into the housing  100 . 
     In other words, when there is no the cooling fluid guide part  320 , some of the cooling fluid in the housing  100  may flow into a space between the tube positioned at an outermost side of the tube plate  300  among the gas tubes  200  and an inner surface of the tube plate  300  and then immediately be discharged to the cooling fluid outlet  120 , such that some of the cooling fluid may be discharged without exchanging heat with the gas tube  200 . 
     In order to prevent this, the EGR cooler  1  for a vehicle of the exemplary embodiment of the present invention has a cooling fluid guide part  320  formed between the gas tube  200  and the tube plate  300  so that most of the cooling fluid introduced through the cooling fluid inlet  110  may move along a path where the gas tube  200  is positioned and then may be discharged to the cooling fluid outlet  120 , thereby improving the fluidity of the cooling fluid. 
     In this case, it is preferable that a height D 1  of the cooling fluid guide part  320  is formed to be equal to or less than 0.85 times a distance D 2  between the tube positioned at the outermost side of the tube plate  300  in the gas tube  200  and the tube plate  300 . 
     When the cooling fluid guide part  320  is formed too high, the cooling fluid flowing in the housing  100  may hit the tube plate  300  and the gas tube  200  to generate noise, and therefore it is recommended to be formed at the same height as described above. 
     Further, as illustrated in  FIGS. 15 and 16 , the tube plate  300  may include a turbulent flow forming part  330  that is depressed on a side surface facing the gas tube  200  of the cooling fluid guide part  320  in a dimple or a wave shape. 
     Accordingly, the EGR cooler  1  according to the exemplary embodiment of the present invention uses the flow turbulence of the cooling fluid flowing in the housing by the turbulent flow forming part  330 , thereby improving the cooling efficiency and reinforcing the rigidity of the tube plate  300 . 
     The EGR cooler  1  for a vehicle according to the exemplary embodiment of the present invention is coupled to the housing  100  at the outer side of the tube plate  300  and further includes a gas cover  400  that has an exhaust gas inlet  410  formed on one side in a longitudinal direction thereof and an exhaust gas outlet  420  formed on the other side thereof. 
     The gas cover  400  is formed so that a spaced distance S between the exhaust gas inlet  410  and the exhaust gas outlet  420  is 1 to 3 times as larger as a diameter R of an engine cylinder, and as a result the EGR cooler  1  may be applied to the vehicle layout in which the exhaust gas inlet  410  and the exhaust gas outlet  420  are spaced apart from each other by a predetermined distance on the same plane, thereby diversifying the applicable model. 
     In this case, the exhaust gas inlet  410  and the exhaust gas outlet  420  may have an angle variously changed depending on the applicable model and the exhaust gas inlet  410  may be disposed on the same side as the cooling fluid inlet  110  of the housing  100  in the longitudinal direction and may also be disposed on an opposite side to the cooling fluid inlet  110  of the housing  100  in the longitudinal direction. 
     Further, in the EGR cooler  1  for a vehicle, the spaced distance S between the exhaust gas inlet and the exhaust gas outlet may be 0.8 to 1.2 times as larger as the length L of the flat portion  210  of the gas tube  200 , such that the heat exchange area between the cooling fluid and the gas tube  200  may be secured above a certain area within the housing  100 , thereby improving the cooling performance of the EGR cooler  1 . 
     In addition, as illustrated in  FIG. 18 , the EGR cooler  1  for a vehicle according to another exemplary embodiment of the present invention may further include a gasket  500  or a sealing member  600 . 
     The gasket  500  is installed between the housing  100  and the tube plate  300  to primarily prevent the cooling fluid from being leaked to the outside of the housing  100 . 
     The gasket  500  may have a substantially rectangular plate shape and may be formed to correspond to a shape of an outer circumferential surface of the housing  100  and may be coupled to the housing  100  by a bolt. 
     The sealing member  600  is additionally installed between the tube plate  300  and the gas cover  400  to prevent exhaust gas introduced through the exhaust gas inlet  410  from being leaked. The sealing member  600  may be formed to correspond to the shape of the outer circumferential surface of the gas cover  400  and may be coupled between the tube plate  300  and the gas cover  400  by a bolt in the same manner as the gasket. 
     At this point, in the EGR cooler for a vehicle of the exemplary embodiment of the present invention, the tube plate  300  and the gas cover  400  may be coupled by brazing without the sealing member  600 . 
     The present invention is not limited to the above-mentioned embodiments but may be variously applied, and may be variously modified by those skilled in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. 
     
       
         
           
               
             
               
                   
               
               
                 [Detailed Description of Main Elements] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1: 
                 EGR cooler 
               
               
                 100: 
                 Housing 
               
               
                 101: 
                 Main body part 
               
               
                 110: 
                 Cooling fluid inlet 
               
               
                 120: 
                 Cooling fluid outlet 
               
               
                 130: 
                 Coupling hole 
               
               
                 200: 
                 Gas tube 
               
               
                 210: 
                 Flat portion, 
               
               
                 211: 
                 Concave portion 
               
               
                 220: 
                 First bent portion, 
               
               
                 230: 
                 Second bent portion 
               
               
                 240: 
                 Radiating fin 
               
               
                 300: 
                 Tube plate 
               
               
                 310: 
                 Tube insertion hole 
               
               
                 400: 
                 Gas cover 
               
               
                 410: 
                 Exhaust gas inlet, 
               
               
                 420: 
                 Exhaust gas outlet 
               
               
                 500: 
                 Gasket 
               
               
                 600: 
                 Sealing member