Abstract:
An oil pan is disposed in a lower part of an internal combustion engine and has an oil pan body divided, with respect to a vertical direction, into oil pan elements having bottom walls respectively of different depths. A baffle plate divides the interior of the oil pan body into a plurality of spaces at the boundary of adjacent ones of the bottom walls to regulate the flow of oil between the adjacent ones of spaces. The baffle plate is divided with respect to a vertical direction into a plurality of baffle plate elements. The baffle plate elements are formed integrally with the oil pan elements, respectively. The oil pan for an internal combustion engine can be manufactured by reduced time and reduced labor at a low manufacturing cost.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an oil pan which acts as an oil reservoir disposed in a lower part of an internal combustion engine. 
         [0003]    2. Description of the Related Art 
         [0004]    Various oil pans like such an oil pan are proposed in, for example, JP-U 57-66211 A. The interior of the previously proposed oil pan is divided into a deep bottom space, namely, a lowermost space, and a shallow bottom space, by a baffle plate disposed near the boundary between a deep-bottom section and a shallow-bottom section. The baffle plate regulates the flow of the oil between the deep bottom space and the shallow bottom space, particularly, the flow of the oil from the deep bottom space into the shallow bottom space such that an amount of the oil not smaller than a predetermined amount is reserved always in the deep bottom space so that the oil can be surely pumped up from the bottom of the deep bottom space. 
         [0005]    The previously proposed oil pan is provided with a separate baffle plate attached to a part of an oil pan body near the boundary between the deep-bottom section and the shallow-bottom section. 
         [0006]    Openings are provided in a base part of the baffle plate joined to the oil pan body. The oil pan body and the baffle plate need to be manufactured individually, the oil pan is built by joining the baffle plate to the oil pan body, and the openings need to be formed in the baffle plate. Thus the oil pan has many component members, and requires many man-hours and much cost to manufacture the same. 
         [0007]    The shape of oil pans has become complicated in recent years. Consequently, the number of the component parts of oil pans, and man-hours needed to manufacture oil pans have been progressively increased, and there is a tendency that time and labor necessary for manufacturing oil pans increase. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide an oil pan, for an internal combustion engine, capable of being manufactured by reduced time and labor at a reduced cost. 
         [0009]    To attain the above object, the present invention provides an oil pan, for an internal combustion engine, disposed in a lower part of the internal combustion engine, said oil pan comprising; an oil pan body having a plurality of bottom sections respectively of different depths, and a baffle plate disposed between adjacent ones of the bottom sections to regulate flow of oil between adjacent ones of spaces defined by the bottom sections; wherein the oil pan body having the bottom sections of different depths is divided into oil pan elements with respect to a vertical direction; the baffle plate is divided together with the oil pan body into half baffle plates; and the half baffle plates are formed integrally with the oil pan elements, respectively. 
         [0010]    In the oil pan of the present invention for an internal combustion engine, the baffle plate is divided into the half baffle plates together with the oil pan elements, and the half baffle plates are formed integrally with the oil pan elements, respectively. Therefore, the baffle plate elements can be formed integrally with the oil pan elements, respectively, and the oil pan can be produced by simply joining the oil pan elements. Thus the oil pan of the present invention needs a reduced number of component members and reduced man-hours. Thus the oil pan requires reduced time and labor for manufacturing the same. 
         [0011]    Preferably, the oil pan body has a shallow-bottom section having a smaller depth, and a deep-bottom section having a greater depth, the oil pan body is divided into an upper oil pan element having the shallow-bottom section, and a lower oil pan element having the deep-bottom section; the baffle plate is divided into an upper half baffle plate and a lower half baffle plate respectively for the upper oil pan element and the lower half oil pan element; the upper half baffle plate is formed integrally with the upper oil pan element; and the lower half baffle plate is formed integrally with the lower oil pan element. 
         [0012]    The upper and the lower half baffle plate can be formed integrally with the upper and the lower half oil pan, respectively, and the oil pan provided with the baffle plate can be completed simply by joining together the upper and the lower half oil pan. Thus the oil pan has a reduced number of component members, requires reduced man-hours, and can be manufactured by reduced time and labor. 
         [0013]    Preferably, the baffle plate divides the interior space of the oil pan into a deep space and a shallow space, the baffle plate is provided with an opening by means of which the deep and the shallow space communicate with each other, and the opening is formed by cutting the lower half baffle plate downward from an upper edge of the lower half baffle plate. The opening can be easily formed in the lower half baffle plate. 
         [0014]    Desirably, the opening is formed in each of opposite side parts of the lower half baffle plate. The oil flows along the opposite side walls of the lower half oil pan and hence the oil in a central part of the deep space can be stabilized. 
         [0015]    An oil strainer may be extended through a concavity formed in the baffle plate to be held on the baffle plate so as to extend in both the shallow and the deep space. 
         [0016]    Typically, the oil strainer has a suction opening disposed adjacent to a central part of the deep space, trough-shaped oil passages are formed along inside surfaces of the opposite side walls of the upper oil pan element near the opposite side parts of the upper half baffle plate of the upper oil pan element, and return openings are formed in the bottoms of the oil passages to cause the oil to drop into the lower oil pan element. 
         [0017]    The collected oil flows in the opposite oil passages, and can drop into regions spaced a long distance apart from the central region in the lower oil pan element through the return openings formed in the opposite oil passages. Thus the oil in the central region in which the suction opening of the oil strainer is located can be stabilized to prevent the oil strainer from sucking air. 
         [0018]    The return openings may be formed in the bottoms of the oil passages so as to open into the shallow space. When the return openings are thus formed, the oil drops through the return openings into a space separated by the baffle plate from the deep space, in which the suction opening of the oil strainer is located. Thus the baffle plate prevents the disturbance of the oil in the deep space by the oil that would otherwise drops into the deep space to stabilize the oil in the deep space. Consequently, suction of air by the oil strainer can be reduced to the least possible extent. 
         [0019]    Desirably, the concavity through which the oil strainer is extended is formed in the upper baffle plate so as to open upward. Thus the concavity, namely, the recess opening upward, for the oil strainer can be easily formed. The oil strainer extended through the concavity does not protrude upward from the oil pan. Therefore, the oil strainer does not place any restrictions on the arrangement of parts above the oil pan and the internal combustion engine can formed in a low height. 
         [0020]    Preferably, the oil strainer is provided with a flange-like member greater in area than the concavity for the oil strainer. The flange-like member is disposed contiguously with the concavity when the oil strainer is extended through the concavity. Thus the flow of the oil between the deep and the shallow space through the concavity can be suppressed. 
         [0021]    The oil pan is mounted on a vehicle, and a middle part of the baffle plate may be bulged in a running direction in which the vehicle runs for forward travel. When the baffle plate is thus formed, a large amount of the oil that moves forward when the vehicle decelerates is held in the bulged middle part of the baffle plate and hence the amount of the oil that flows forward beyond the baffle plate can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a side elevation of an oil pan in a preferred embodiment of the present invention, in which two-dot chain lines indicate an internal combustion engine; 
           [0023]      FIG. 2  is a top view of the oil pan shown in  FIG. 1 , combined with an oil strainer; 
           [0024]      FIG. 3  is a sectional view taken on the line III-III in  FIG. 2 ; 
           [0025]      FIG. 4  is a sectional view taken on the line IV-IV in  FIG. 3 ; 
           [0026]      FIG. 5  is a top view of an upper half oil pan element; 
           [0027]      FIG. 6  is a top view of the lower half oil pan element; 
           [0028]      FIG. 7  is a sectional view of the upper and the lower oil pan element taken on the line VII-VII in  FIGS. 5 and 6 ; and 
           [0029]      FIG. 8  is a sectional view of the upper and the lower half oil pan element taken on the line VIII-VIII in  FIGS. 5 and 6 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    An oil pan  10  in a preferred embodiment of the present invention will be described with reference to  FIGS. 1 to 8 . 
         [0031]    The oil pan  10  is used in combination with an in-line five-cylinder four-cycle stroke internal combustion engine  1 . The oil pan  10  forms a bottom part of the engine  1 .  FIG. 1  shows the oil pan  10  in a side elevation, in which the outline of the engine  1  is indicated by two-dot chain lines. 
         [0032]    Hereinafter, terms, such as front, rear, right, left, longitudinal, lateral and such, are used to indicate positions, directions and such with respect to the direction of forward travel of the vehicle provided with the engine  1 . 
         [0033]    The engine  1  is a longitudinal engine mounted on the vehicle with its crankshaft longitudinally extended and the five cylinders arranged in a longitudinal straight row.  FIG. 1  is a side elevation taken from the left side of the oil pan  10 . In the engine  1 , a cylinder head  3  is joined and fastened to the upper end of a cylinder block  2 , the cylinder head  3  is covered with a cylinder head cover  4 , and the oil pan  10  is joined to the lower end of the cylinder block  2 . 
         [0034]    The oil pan  10  is a longitudinally long, rectangular vessel. The oil pan  10  has a bottom wall having a front half part forming a shallow-bottom section  10 S, and a part of a rear half part, excluding a rear end part, forming a deep-bottom section  10 D deeper than the shallow-bottom section  10 S. 
         [0035]    When the vehicle is in a horizontal position and not tilted in any directions, the bottom wall of the shallow-bottom section  10 S of the oil pan  10  slightly slopes down toward the rear. As shown in  FIGS. 7 and 8 , the oil pan  10  is divided into an upper half oil pan element  21  having the shallow-bottom section  10 S, and a lower half oil pan element  11  having the deep-bottom section  10 D. 
         [0036]    Referring to  FIGS. 6 to 8 , the lower half oil pan element  11  is a somewhat laterally long, rectangular vessel having a rectangular bottom wall  12 , and front, rear, right and left side walls  13  respectively rising from the front, the rear, the right and the left side of the bottom wall  12 . Upper edge parts of the side walls  13  are extended outward to form a flange having an upper joining surface  13   a  to be joined to the upper half oil pan element  21 . As shown in  FIG. 6 , bolt holes  13   b  are formed in the flange having the upper joining surface  13   a . The bottom wall  12  of the lower half oil pan element  11  forms the deep-bottom section  10 D. 
         [0037]    A lower half baffle plate  18  is formed integrally with the bottom wall  12  so as to rise from the bottom wall  12  parallel to the front side wall  13 . The lower half baffle plate  18  is at a short distance rearward from the front side wall  13 . The upper end surface  18   a  of the lower half baffle plate  18  is at a level slightly below the level of the joining surface  13   a  of the side wall  13 . 
         [0038]    The right and the left end of the lower half baffle plate  18  are spaced a short distance apart from the right and the left side wall  13  to form gaps  19  between the right end of the lower half baffle plate  18  and the right side wall  13  and between the left end of the lower half baffle plate  18  and the left side wall  13 , respectively. A middle part, with respect to a lateral direction, of the lower half baffle plate  18  is slightly bulged forward as shown. 
         [0039]    Referring to  FIGS. 5 ,  7  and  8 , the upper half oil pan  21  is a longitudinally long rectangular frame having front, rear, right and left side walls  23 , and a bottom wall  22  forming the shallow-bottom section  10 S. The bottom wall  22  is in a front half part of the upper half oil pan element  21 . A rectangular connecting opening  25  is formed in a rear part of the upper half oil pan element  21 . The opening  25  opens into the lower half oil pan element  11 . A shallow rear end bottom wall  24  having a relatively small longitudinal width is formed in a rear end part of the upper half oil pan element  21 . 
         [0040]    Lower portions of rear half parts of the right and the left side wall  23  are bulged laterally outward and extend downward to form right and left side walls defining the connecting opening  25 . A rear part of the bottom wall  22  slopes down rearward gradually to form an inclined part  22   s  serving as a front end wall of the connecting opening  25 . A front part of the rear end bottom wall  24  extends down forward to form a vertical wall  24   v . The vertical wall  24   v  is the rear side wall of the connecting opening  25 . The front, the rear, the right and the left side wall connect to the front, the rear, the right and the left side wall  13  of the lower half oil pan element  11 , respectively. 
         [0041]    Right and left trough-like, longitudinal oil passages  26  are formed along the right and the left side walls  23  of the rear half part of the upper half oil pan element  21 . Each of the oil passages  26  is formed by longitudinally extending a bottom wall  26   a  and an inner side wall  26   b  along an upper inside surface of each of the right and the left side walls  23 . The right and the left oil passages  26  are substantially symmetrical with respect to the longitudinal center axis of the upper half oil pan element  21 . 
         [0042]    Formed in a front half part of the upper half oil pan element  21  are trough-like oil passages  27  defined respectively between the right side wall  23  and a right inner wall  27   b  formed integrally with and rising from the bottom wall  22 , and between the left side wall  23  and a left inner wall  27   b  formed integrally with and rising from the bottom wall  22 . As shown in  FIG. 7 , the upper edges of the inner wall  27   b  forming the oil passages  27  are horizontal and substantially level with the bottom walls  26   a  of the oil passages  26 . As shown in  FIG. 5 , front end parts of the inner walls  27   b  are bent outward and connected to the side walls  23  to close the front ends of the oil passages  27 . 
         [0043]    As mentioned above, the bottom wall  22  has the inclined part  22   s  sloping down rearward. The oil passages  27  are formed by using parts of the bottom wall  22 . Therefore, the depth of the oil passages  27  increases from the closed front ends toward the connecting opening  25 . 
         [0044]    The bottom walls  26   a  of the oil passages  26  formed in the rear part of the upper half oil pan element  21  are substantially level with the upper edges of the inner walls  27   b  of the oil passages  27 . Front end parts of the bottom walls  26   a  are bent slightly so as to slope downward and have cutouts, respectively. As shown in  FIG. 5 , a vertically elongated oil return port  31  is formed between the front end edge, at a high level, of each of the bottom walls  26   a  of the oil passages  26 , and the rear end edge, at a low level, of each of the bottom walls  22  of the oil passages  27 . Other oil return ports  32  are formed in rear end parts of the bottom walls  26   a  of the oil passages  26 , respectively. 
         [0045]    An upper half baffle plate  28  is formed integrally with the upper half oil pan element  21  at a position above the front part of the connecting opening  25  and in a rear part of the upper half oil pan element  21  so as to extend vertically between the right and the left side wall  23 . 
         [0046]    The upper half baffle plate  28  has an upper part extended between the right and the left inner wall  26   b  of the right and the left oil passage  26 , and a lower part extending to the joining surface  23   a  joined to the lower half oil pan element  11 . The lower end edge of the lower part of the upper half baffle plate  28  is flush with the joining surface  28   a.    
         [0047]    As shown in  FIG. 8 , the lateral width of the upper part of the upper half baffle plate  28  extending between the inner walls  27   b  is narrow, and the lateral width of the lower part of the upper half baffle plate  28  extending between the laterally bulged right and the left side wall  23  widens toward the lower end of the upper half baffle plate  28 . A middle part of the upper half baffle plate  28 , similarly to the middle part of the lower half baffle plate  18 , is bulged forward slightly. 
         [0048]    When the upper half oil pan element  21  and the lower half oil pan element  11  are joined together with the upper opening of the lower half oil pan element  11  aligned with the connecting opening  25  of the upper half oil pan element  21 , the upper half baffle plate  28  and the lower half baffle plate  18  form a single vertical wall. A gap on the order of 0.5 mm is formed between the lower end surface  28   a  of the upper half baffle plate  28  and the upper end surface  18   a  of the lower half baffle plate  18  because the upper end surface  18   a  of the lower half baffle plate  18  is recessed below the joining surface  23   b  of the joining surfaces  13   a  of the side walls  13  as shown in  FIG. 4 . 
         [0049]    The upper ends of the opposite inner side walls  26   b  forming the oil passages  26  are at a level below the joining surface  23   b  to be joined to the cylinder bock  2 . Opposite side parts of the upper end surface  28   b  of the upper half baffle plate  28  decline gradually toward the middle of the upper half baffle plate  28 . Parts of each of the opposite side parts of the upper end surface  28   b  are inclined at different inclinations. A deep concavity  29  for receiving the oil strainer is formed in a part of the upper half baffle plate  28  at a short distance to the right from the middle of the upper half baffle plate  28 . 
         [0050]    When the upper half oil pan element  21  and the lower half oil pan element  11  are joined together with the upper opening of the lower half oil pan element  11  aligned with the connecting opening  25  of the upper half oil pan element  21  by bringing the joining surfaces  23   a  and  13   a  together and fastening the upper half oil pan element  21  and the lower half oil pan element  11  together with bolts  33 , the upper half baffle plate  28  and the lower half baffle plate  18  are aligned to form a substantially single vertical wall. A small gap is formed between the lower end surface  28   a  of the upper half baffle plate  28  and the upper end surface  18   a  of the lower half baffle plate  18 . 
         [0051]    Referring to  FIG. 3 , the internal space of the oil pan  10  is divided by the upper half baffle plate  28  and the lower half baffle plate  18  into a shallow space Sf in the front shallow-bottom section  10 S, and a deep space Sr occupying most part of the rear deep-bottom section  10 D. A front deep part, on the front side of the lower half baffle plate  18 , in the deep-bottom section  10 D formed by the bottom wall  12  of the lower half oil pan element  11  is separated from the rear deep space Sr by the lower half baffle plate  18  and is continuous with the shallow space Sf. 
         [0052]    The oil return ports  31  formed on the front side of the front ends of the bottom walls  26   a  of the right and the left oil passages  26  open into the shallow space Sf on the front side of the upper half baffle plate  28  and the lower half baffle plate  18 . 
         [0053]    An oil pump is disposed at a position slightly to the right on the bottom wall  22  of the shallow space Sf of the oil pan  10 . A front end of a tubular oil strainer  41  is connected to the oil pump. The oil strainer  41  is extended obliquely rearward along the bottom surface of the shallow-bottom section  10 S, is extended through the concavity  29  formed in the upper half baffle plate  28  into the deep space Sr. The oil strainer  41  is bent downward in the deep space SR such that a suction opening  41 a formed at the rear end thereof is located adjacent to a central part of the bottom surface of the deep space SR. 
         [0054]    As shown in  FIGS. 2 ,  3  and  4 , a flange-like member  42  provided with a cylindrical central boss is put on the strainer  41 . The flange-like member  42  is disposed close to the rear surface of the upper half baffle plate  28  parallel to the same  28 . The central cylindrical boss of the flange-like member  42  is put on the strainer  41 . The flange-like member  42  has rectangular right and left parts greater in area than the concavity  29  of the upper half baffle plate  28 . The flange-like member  42  covers the concavity  29  in the deep place Sr. 
         [0055]    A middle part of a support member  43  is attached to a part of the oil strainer  41  on the rear side of the flange-like member  42 . The support member  43  has support arms  43   r  and  43   l  extending obliquely rightward and obliquely leftward, respectively. The upper ends of the support arms  43   r  and  43   l  are fastened with bolts to bosses protruding into the oil passages  26 . Thus the rear part of the oil strainer  41  is supported by the support member  43  and the front end of the oil strainer  41  is connected to the oil pump to suspend the oil strainer  41 . 
         [0056]    The oil strainer  41  is completely sunk in the concavity  29  formed in the upper end surface  28   a  of the upper half baffle plate  28  and any part of the oil strainer  41  does not protrude from the upper end of the concavity  29 . Therefore, the cylinder block  2  does not need to provide any space for the oil strainer  41  and the internal combustion engine can be built in a low height. 
         [0057]    The open upper end of the oil pan  10  is covered with a horizontal baffle plate  50  to separate the interior of the oil pan  10  from a space in which the crankshaft is extended. As indicated by two-dot chain lines in  FIGS. 2 and 4 , the horizontal baffle plate  50  is a longitudinally elongated, rectangular plate extending horizontally between the right and the left oil passages  26  and  27 . The horizontal baffle plate  50  is curved in a downward convex shape to prevent interference between the horizontal baffle plate  50 , and the webs of the rotating crankshaft disposed above the horizontal baffle plate  50 . The horizontal baffle plate  50  is provided with openings arranged in right and left longitudinal rows. 
         [0058]    The upper end surface  28   a  of the upper half baffle plate  28  is adjacent to the horizontal baffle plate  50 . The horizontal baffle plate  50  suppresses the waving of the oil contained in the oil pan  10  caused by the jolting of the vehicle to reduce the absorption of air by the oil to the least possible extent. 
         [0059]    In the oil pan thus constructed, the oil collected on the bottom wall  22  in the shallow-bottom section  10 S flows rearward along the bottom surface sloping down toward the rear and the inclined part  22   s  into the deep-bottom section  10 D. The oil is reserved mainly in the deep-bottom section  10 D (bottom wall  12 ). 
         [0060]    The interior of the deep-bottom section  10 D is divided into a front space and a rear space by the upper half baffle plate  18  and the lower half baffle plate  18 . The front and the rear space respectively on the front and the rear side of the lower half baffle plate  18  communicate with each other by way of the gaps  19  at the right and the left end of the lower half baffle plate  18 . The oil flows through the gaps  19  from the front space into the rear space in the deep space Sr. An amount of the oil not smaller than a predetermined amount is reserved always in the deep space Sr so that the suction opening  41 a of the oil strainer  41  disposed in the deep space Sr may be always sunk in the oil reserved in the deep space Sr to avoid sucking air into the oil strainer  41 . 
         [0061]    The oil flows into the deep space Sr through the right and the left gap  19  at the right and the left end of the lower half baffle plate  18  apart from the suction opening  41   a  of the oil strainer  41  disposed in the central part of the deep space Sr. Therefore, suction of the oil containing air absorbed while the oil flows through the gaps  19  can be prevented in an utmost possible degree. 
         [0062]    The forward flow of the oil from the deep space Sr into the shallow space Sf when the traveling vehicle decelerates is dammed back by the upper half baffle plate  28  and the lower half baffle plate  18  so that the suction opening  41   a  of the oil strainer  41  may not appear outside the oil reserved in the deep space Sr due to the reduction of the amount of the oil contained in the deep space Sr. Thus suction of air by the oil strainer  41  is prevented. 
         [0063]    The respective middle parts of the upper half baffle plate  28  and the lower half baffle plate  18  are bulged forward to form the deep space Sr in the largest possible volume and to hold the oil caused to move forward by the deceleration of the vehicle by the bulged middle parts to suppress the amount of the oil that flows through the gaps  19  into the shallow space Sf. 
         [0064]    The concavity  29  through which the strainer  41  is extended is formed in the upper half baffle plate  28 . The flange-like member  42  has rectangular right and left flange parts greater than the concavity  29  of the upper half baffle plate  28 . Since the concavity  29  is covered with the flange-like member  42  put on the oil strainer  41  so as to be located close to the concavity  29  from the side of the deep space Sr, the oil tending to flow from the deep space Sr through the concavity  29  into the shallow space Sf is stopped by the flange-like member  42 , so that the flow of the oil into the shallow space Sf can be suppressed. 
         [0065]    The trough-shaped oil passages  26  and  27  are formed in the right and the left side part of the upper half oil pan  21 . Drip of the oil from the oil passages  26  into the deep-bottom section  10 D is regulated to suppress the suction of the oil containing absorbed air into the oil strainer  41 . 
         [0066]    The oil that has flowed into the oil passages  27  on the front side flows rearward along the inclined part  22   s  of the bottom wall  22  and drops through the oil return ports  31  into the deep-bottom section  10 D. If the oil collected in the rear oil passages  26  flows forward, the oil drops through the oil return ports  31  into the deep-bottom section  10 D. 
         [0067]    The oil return ports  31  are located in the part of the deep-bottom section  10 D but on the front side of the half baffle plates  18  and  28  connecting to the shallow space Sf. Further, the oil return ports  31  are separated by the half baffle plates  18  and  28  from the deep space Sr in which the suction opening  41   a  of the oil strainer  41  is located. Thus the half baffle plates  18  and  20  prevents disturbance of the oil reserved in the deep space Sr by the oil that flows and drops through the oil return ports  31 . Consequently, the oil reserved in the deep space Sr is stabilized and suction of air into the oil strainer  41  can be prevented to an utmost possible degree. 
         [0068]    The oil return ports  32  are formed in the rear end parts of the bottom walls  26   a  of the oil passages  26 , respectively. The oil collected in the oil passages  26  is caused to flow rearward and drops through the oil return ports  32  into the deep-bottom section  10 D. The oil return ports  32  are disposed in the right and the left side parts of the rear part of the deep space Sr and are spaced a long distance apart from the suction opening  41  of the oil strainer  41  disposed in the central region of the deep space Sr. Therefore, the oil that has dropped through the oil return ports  32  will not disturb the suction of the oil by the oil strainer  41 . The distance between the suction opening  41   a  of the oil strainer  41  and each of the rear oil return ports  32  is longer than that between the suction opening  41   a  of the oil strainer  41  and each of the front oil return ports  31 . 
         [0069]    The oil pan  10  is divided into the upper half oil pan element  21  having the shallow-bottom section  10 S, and the lower half oil pan element  11  having the deep-bottom section  10 D. The substantially vertical upper half baffle plate  28  is formed integrally with the upper half oil pan element  21 , and the substantially vertical lower half baffle plate  18  is formed integrally with the lower half oil pan element  11 . Therefore, the upper half oil pan element  21  integrally provided with the upper half baffle plate  28 , and the lower half oil pan element  11  integrally provided with the lower half baffle plate  18  can be formed by casting. The oil pan  10  provided with the baffle plate can be built simply by joining together the upper half oil pan element  21  and the lower half oil pan element  11 . Thus the oil pan  10  has a small number of component parts, can be made by small man-hours, and can be manufactured by reduced time and labor. 
         [0070]    The respective half baffle plates  18  and  28  of the lower half oil pan element  11  and the upper half oil pan element  21  serve as ribs to enhance the rigidity of the lower and upper half oil pan elements  11  and  21 . 
         [0071]    Since the half oil pan elements individually provided with the half baffle plates have increased rigidity, the half oil pan elements can be securely joined together. 
         [0072]    Since the half baffle plates are formed integrally with the half oil pan elements, gaps are hardly formed between the half oil pan elements and the corresponding half baffle plates. 
         [0073]    The connecting openings formed in the right and the left end part of the lower half baffle plate  18  are the gaps  19  extending downward from the upper end surface  18   a  of the lower half baffle plate  18 . Therefore, the lower half baffle plate  18  can be easily formed integrally with the lower half oil pan element  11  by casting without requiring machining work. 
         [0074]    Since the gaps  19  and the concavity  29  for the strainer  41  are formed in the lower half baffle plate  18  and the upper half baffle plate  28 , respectively, reduction of the rigidity of the lower half baffle plate  18  and that of the upper half baffle plate  28  can be limited to a minimum. 
         [0075]    Ribs or protrusions may be formed on the surfaces of the lower half baffle plate  18  and the upper half baffle plate  18  to enhance the rigidity of the lower and upper half baffle plate  18  and  28 . The waving of the oil can be suppressed by forming the ribs or protrusions in a shape effective in breaking waves, such as the shape of a grid. 
         [0076]    Although the present invention has been described in terms of the oil pan  10  to be attached to the lower end of the cylinder block  2 , the present invention is applicable to the lower block of an internal combustion engine using a bottom part thereof as an oil reservoir. 
         [0077]    The oil pan  10  in this embodiment is divided into two parts, namely, the upper and the lower half oil pan elements, together with the baffle plate. The present invention is applicable to an oil pan divided into three or more parts with respect to a vertical direction. 
         [0078]    In the oil pan  10  in this embodiment, the half baffle plates  18  and  28  divide the interior of the oil pan into the front and the rear section. The present invention is applicable to an oil pan having an interior space divided into right and left sections by a baffle plate. 
         [0079]    Although the invention has been applied to the oil pan for the longitudinal internal combustion engine  1  mounted on the vehicle with its crankshaft extended longitudinally, the present invention is applicable also to an oil pan for a transverse internal combustion engine mounted on a vehicle with its crankshaft laterally extended.