OIL PAN

Abstract

 An oil pan 10 includes an oil pan main body 11 whose bottom wall 14 includes a deep bottom portion 14A and a shallow bottom portion 14B. The shallow bottom portion 14B is arranged adjacent the deep bottom portion 14A in a crankshaft axial direction 4a and located at a higher position than deep bottom portion 14A. The shallow bottom portion 14B connects with the deep bottom portion 14A through a stepped portion 14C. When a specified amount of oil is stored in the oil pan main body 11, the level of the oil lies above the shallow bottom portion 14B. The shallow bottom portion 14B includes a middle bottom section 14D, a front raised bottom section 14E, and a rear raised bottom section 14F. The middle bottom section 14B occupies a central portion of the shallow bottom portion 14B in a direction crossing the crankshaft 4. The front raised bottom section 14E and the rear raised bottom section 14F are arranged on opposite sides of the middle bottom section 14B in the direction crossing the crankshaft 4 and located at a higher position than the middle bottom section. This structure serves to optimize the volume and level of oil stored in the oil pan main body 11 and reduce mechanical vibration of the oil pan main body 11.

Description

Technical Field

[0001] The present invention generally relates to an oil pan.

Background Art

[0002] Usually, internal combustion engines have an oil pan in which oil is stored to lubricate moving parts of the internal combustion engine and which is disposed below a main body of the internal combustion engine.

[0003] There is known a typical oil pan which is of a box-shape designed to have an upper opening and has a bottom wall, a peripheral wall extending upward from a circumferential edge of the bottom wall with round corners, and a flange extending outward horizontally from an upper edge of the peripheral wall (see Japanese Patent First Publication No. 1996-161069).

[0004] The peripheral wall is waved in a planar view thereof along the circumferential edge of the bottom wall to have convex portions bulging inwardly and concave portions bulging outwardly which alternate with each other. The peripheral wall is capable of storing a given volume of lubricating oil equivalent to a total volume of the concave portions of the peripheral wall which bulge outwardly. The waved shape of the peripheral wall also serves to enhance the rigidity of the oil pan.

[0005] Too high the level of oil accumulated in the oil pan may result in a risk that the oil may be agitated by a counterweight of a crankshaft of the internal combustion engine. Conversely, too low the level of oil in the oil pan may cause air to be sucked into an oil pump.

[0006] It is, therefore, necessary to keep the level of oil stored in the oil pan at a required level. The level of oil stored in the oil pan, however, depends upon a stored amount of the oil. Increasing the stored amount of oil to increase the level of the oil in the oil pan will result in an increase in weight of the oil or may lead to a risk that the amount of oil which needs to be discarded upon oil change may be undesirably increased.

SUMMARY OF THE INVENTION

[0007] The present invention was made in view of the above problem. It is an object of the invention to provide an oil pan which is capable of optimizing the volume or level of oil stored in a main body of the oil pan and minimizing the mechanical vibration of the oil pan.

[0008] According to one aspect of the invention, there is provided an oil pan for an internal combustion engine which comprises: an oil pan main body which includes a flange, a peripheral wall, and a bottom wall. The flange has a rectangular opening and is joined to a lower portion of a body of an internal combustion engine equipped with a crankshaft. The peripheral wall extends downward from an inner edge of the flange. The bottom wall is joined to a lower end of the peripheral wall. The bottom wall includes a deep bottom portion and a shallow bottom portion. The shallow bottom portion is arranged adjacent the deep bottom portion in a direction in which the crankshaft extends and located at a higher position than the deep bottom portion. The shallow bottom portion is joined to the shallow bottom portion through a stepped portion. The oil pan main body is configured to have the shallow bottom portion above which a level of a specified amount of oil stored in the oil pan main body lies. The shallow bottom portion includes a middle bottom section, a first raised bottom section, and a second raised bottom section. The middle bottom section occupies a central portion of the shallow bottom portion in a direction crossing the crankshaft. The first raised bottom section and the second raised bottom section are arranged on opposite sides of the middle bottom section in the direction crossing the crankshaft and located at a higher position than the middle bottom section.

BENEFICIAL ADVANTAGES OF THE INVENTION

[0009] The above structure in the invention serves to optimize the volume and level of oil stored in oil pan main body and reduce mechanical vibration of the oil pan main body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 

Fig. 1 is a schematic view which illustrates an internal combustion engine equipped with an oil pan in an embodiment of the invention, as viewed from a right side thereof.

Fig. 2 is a perspective view of an oil pan according to an embodiment of the invention.

Fig. 3 is a front view of an oil pan according to an embodiment of the invention.

Fig. 4 is a plan view of an oil pan according to an embodiment of the invention.

Fig. 5 is a rear view of an oil pan according to an embodiment of the invention.

Fig. 6 is a perspective sectional view taken along the line VI-VI in Fig. 4.

Fig. 7 is a perspective sectional view taken along the line VII-VII in Fig. 4.

MODE FOR CARRYING OUT THE INVENTION

[0011] An oil pan for an internal combustion engine according to an embodiment of the invention comprises an oil pan main body which includes a flange, a peripheral wall, and a bottom wall. The flange has a rectangular opening and is joined to a lower portion of a body of an internal combustion engine equipped with a crankshaft. The peripheral wall extends downward from an inner edge of the flange. The bottom wall is joined to a lower end of the peripheral wall. The bottom wall includes a deep bottom portion and a shallow bottom portion. The shallow bottom portion is arranged adjacent the deep bottom portion in a direction in which the crankshaft extends and located at a higher position than the deep bottom portion. The shallow bottom portion is joined to the shallow bottom portion through a stepped portion. The oil pan main body is configured to have the shallow bottom portion above which a level of a specified amount of oil stored in the oil pan main body lies. The shallow bottom portion includes a middle bottom section, a first raised bottom section, and a second raised bottom section. The middle bottom section occupies a central portion of the shallow bottom portion in a direction crossing the crankshaft. The first raised bottom section and the second raised bottom section are arranged on opposite sides of the middle bottom section in the direction crossing the crankshaft and located at a higher position than the middle bottom section.

[0012] The above structure in the embodiment of the invention is capable of optimizing the volume and level of oil stored in oil pan main body and reducing mechanical vibration of the oil pan main body.

EMBODIMENT

[0013] An oil pan according to an embodiment of the invention will be described below with reference to the drawings.

[0014] Figs. 1 to 7 are views which illustrates the oil pan in the embodiment of the invention. In Figs. 1 to 7, a vertical, longitudinal, and lateral directions will also be defined in the following way.

[0015] A direction which a crankshaft of an internal combustion engine extends will be defined as a lateral direction of the internal combustion engine. A region in which a left side wall of an oil pan exists along the crankshaft will be defined as a left side. A region in which a right side wall of the oil pan exist will be defined as a right side. A direction which horizontally extends perpendicular to the crankshaft will be referred to as a longitudinal direction of the internal combustion engine. A direction vertically extending perpendicular to the crankshaft will be referred to as a vertical direction.

[0016] The structure will be first described below.

[0017] Referring to Fig. 1, the engine 1 which is mounted in a vehicle includes the engine body 2 and the oil pan 10. The engine body 2 is equipped with the cylinder block 2A which retains the crankshaft 4 to be rotatable. The crankshaft 4 extends in a width-wise direction (i.e., the lateral direction) of the vehicle.

[0018] The cylinder block 2A has formed therein a plurality of cylinders, not shown, which are arrayed in the width-wise direction of the vehicle. Each of the cylinders has a piston, not shown, disposed therein. The pistons are connected to the crankshaft 4 through a connecting rod, not shown.

[0019] The pistons reciprocate in the cylinders to rotate the crankshaft 4 through the connecting rod. The engine body 2 includes a cylinder head, not shown, which is arranged on an upper portion of the cylinder block 2A and a cylinder head cover, not shown, which is disposed on an upper portion of the cylinder head. The engine 1 in this embodiment is implemented by an internal combustion engine. The engine body 2 constitutes a body of the internal combustion engine.

[0020] The oil pan 10, as clearly illustrated in Figs. 2 and 3, includes the oil pan main body 11. The oil pan main body 11 is equipped with the flange 12, the peripheral wall 13, and the bottom wall 14.

[0021] The flange 12, as clearly illustrated in Figs. 2 and 4, has the rectangular opening 12a. The flange 12 is fixed on the flange 2a (see Figs. 6 and 7) disposed on a lower portion of the cylinder block 2A using bolts, not shown.

[0022]  The peripheral wall 13, as clearly illustrated in Fig. 2, extends downward from the inner edge 12b of the flange 12 and is of a box-shape. The bottom wall 14 is joined to a lower end of the peripheral wall 13. The peripheral wall 13 has an opened upper end and a lower end closed by the bottom wall 14.

[0023] The bottom wall 14, as can be seen in Figs. 2 and 3, includes the deep bottom portion 14A and the shallow bottom portion 14B. The deep bottom portion 14A is located on the right side of the crankshaft 4, as viewed in the direction in which the crankshaft 4 extends (which will also be referred to below as a crankshaft axial direction 4a). The shallow bottom portion 14B is arranged on the left side of the deep bottom portion 14A, that is, located adjacent the deep bottom portion 14A in the crankshaft axial direction 4a and at a higher position than the deep bottom portion 14A in the vertical direction. The shallow bottom portion 14B is joined to the deep bottom portion 14A through the stepped portion 14C. The stepped portion 14C, as referred to herein, is defined as a riser of a step. Specifically, the stepped portion 14C is formed by a portion of the bottom wall 14 which extends vertically between the deep bottom portion 14A and the shallow bottom portion 14B.

[0024] In brief, the bottom wall 14 in this embodiment is shaped stepwisely to have the deep bottom portion 14A and the shallow bottom portion 14B which are arranged adjacent each other in the width-wise direction of the vehicle and different in height in the vertical direction.

[0025] The stepped portion 14C is, as clearly illustrated in Figs. 2 and 3, arranged on a middle portion of the bottom wall 13 in the crankshaft axial direction 4a. The deep bottom portion 14A occupies substantially a right half of the oil pan main body 11, while the shallow bottom portion 14B occupies substantially a left half of the oil pan main body 11.

[0026]  The peripheral wall 13, as can be seen in Fig.2, includes the front wall 15, the rear wall 16, the left side wall 17, and the right side wall 18.

[0027] The front wall 15 is, as shown in Fig. 4, joined to a front edge (also called first edge) 14a of the deep bottom portion 14A which extends perpendicular to the crankshaft 4 and a rear edge (also called first edge) 14b of the shallow bottom portion 14B. The front wall 15 extends along the front edge 14a of the deep bottom portion 14A and the front edge 14b of the shallow bottom portion 14B in the crankshaft axial direction 4a. The front wall 15 has the flange 12 joined to an upper end thereof.

[0028] The crankshaft 4 is of a crank-shape. The direction perpendicular to or crossing the crankshaft 4, as referred to herein, is defined as a direction which horizontally crosses the center axis of rotation of each straight section of the crankshaft 4. The crankshaft axial direction 4a, as referred to herein, is defined to coincide with the center axis of rotation of the crankshaft 4.

[0029] The rear wall 16 is joined to a rear edge (also called second edge) 14c of the deep bottom portion 14A (see Fig. 6) which faces to cross the crankshaft 4 and a rear edge (also called second edge) 14d of the shallow bottom portion 14B which faces to cross the crankshaft 4.

[0030] The rear wall 16 extends along the rear edge 14c of the deep bottom portion 14A and the rear edge 14d of the shallow bottom portion 14B in the crankshaft axial direction 4a and has the flange 12 joined to an upper end thereof. The front wall 15 and the rear wall 16 are oriented to face each other in a direction (i.e., the longitudinal direction) perpendicular to the length of the crankshaft 4.

[0031] The left side wall 17 is located at the left end (also referred to as a first end) of the peripheral wall 13 and faces the right end of the peripheral wall 13 in the crankshaft axial direction 4a. The left side wall 17 connects the left end of the front wall 15, the left end of the rear wall 16, and the left end of the shallow bottom portion 14B together.

[0032] The right side wall 18 is located on the right end (also referred to as a second end) of the peripheral wall 13 and faces the right end (i.e., the left side wall 17) in the crankshaft axial direction 4a. The right side wall 18 connects the right end of the front wall 15, the right end of the rear wall 16, and the right end of the deep bottom portion 14A together. The left side wall 17 faces the right side wall 18 in the crankshaft axial direction 4a.

[0033] In this embodiment, the left side wall 17 constitutes a first side wall. The right side wall 18 constitutes a second side wall. The front wall 15 constitutes a third side wall. The rear wall 16 constitutes a fourth side wall.

[0034] The shallow bottom portion 14B, as can be seen in Figs. 2 and 4, includes the middle bottom section 14D, the front raised bottom section 14E (which will also be referred to below as a first raised bottom section), and the rear raised bottom section 14F (which will also be referred to below as a second raised bottom section).

[0035] The middle bottom section 14D occupies a central area of the shallow bottom portion 14B in the longitudinal direction (i.e., horizontal direction) crossing the crankshaft 4.

[0036] The front raised bottom section 14E is arranged in front of the middle bottom section 14D in the longitudinal direction perpendicular to the crankshaft 4 and, as clearly illustrated in Fig. 7, located at a higher position than the middle bottom section 14D.

[0037] The front raised bottom section 14E is joined at a front end thereof to the front wall 15 (see Fig. 7). The front end of the front raised bottom section 14E coincides with the front edge 14b of the shallow bottom portion 14B.

[0038] The rear raised bottom section 14F is arranged in back of the middle bottom section 14D in the longitudinal direction crossing the crankshaft 4 and located at a higher position than the middle bottom section 14D (see Fig. 7). The rear raised bottom section 14F is joined at a rear end thereof to the rear wall 16 (see Fig. 7). The rear end of the rear raised bottom section 14F coincides with the rear edge 14d of the shallow bottom portion 14B.

[0039] The front raised bottom section 14E is, as can be seen in Fig. 7, located at a higher position than the rear raised bottom section 14F. The middle bottom section 14D protrudes downward from the front raised bottom section 14E and the rear raised bottom section 14F.

[0040] The shallow bottom portion 14B, as apparent from the above discussion, includes the front raised bottom section 14E and the rear raised bottom section 14F which are arranged on opposite sides of the middle bottom section 14D and face each other in the longitudinal direction crossing the crankshaft 4. The front raised bottom section 14E and the rear raised bottom section 14F are located at a higher position than the middle bottom section 14D in the vertical direction. Each of the front raised bottom section 14E and the rear raised bottom section 14F will also be referred to as a raised bottom section.

[0041] The front raised bottom section 14E and the rear raised bottom section 14F are, as can be seen in Fig. 4, formed to occupy an entire area between the stepped portion 14C and the left side wall 17 which face each other in the crankshaft axial direction 4a. The left ends of the front raised bottom section 14E and the rear raised bottom section 14F are joined to the left side wall 17.

[0042] The deep bottom portion 14A, as clearly illustrated in Figs. 1 and 4, includes the central deepest bottom section 14G, the front raised bottom section 14H, and the rear raised bottom section 141.

[0043] The central deepest bottom section 14G occupies a central area of the deep bottom portion 14A between the ends of the deep bottom portion 14A which face each other in the longitudinal direction crossing the crankshaft 4. The central deepest bottom section 14G is the deepest in the bottom wall 14.

[0044] The front raised bottom section 14H is, as can be seen in Figs. 6 and 7, arranged in front of the central deepest bottom section 14G in the longitudinal direction crossing the length of the crankshaft 4 and located at a higher position than the central deepest bottom section 14G in the vertical direction (see Figs. 6 and 7).

[0045] The front raised bottom section 14H has a front end joined to the front wall 15. The front end of the front raised bottom section 14H coincides with the front edge 14a of the deep bottom portion 14A.

[0046] The rear raised bottom section 141 is arranged in back of the central deepest bottom section 14G in the longitudinal direction crossing the length of the crankshaft 4 and located at a higher position than the central deepest bottom section 14G in the vertical direction.

[0047] The rear raised bottom section 141 has a rear end joined to the rear wall 16. The rear end of the rear raised bottom section 141 coincides with the rear edge 14c of the deep bottom portion 14A. The rear raised bottom section 141 is located at a higher position than the front raised bottom section 14H in the vertical direction.

[0048] As apparent from the above discussion, the deep bottom portion 14A includes the front raised bottom section 14H and the rear raised bottom section 14I which are arranged on opposite sides of the central deepest bottom section 14G in the longitudinal direction crossing the length of the crankshaft 4 and located at higher positions than the central deepest bottom section 14G in the vertical direction.

[0049] Each of the front raised bottom section 14H and the rear raised bottom section 141, as can be seen in Fig. 4, has a right end joined to the right side wall 18 and extends from the right side wall 18 toward the stepped portion 14C.

[0050] The front raised bottom section 14E and the rear raised bottom section 14F in this embodiment, as can be seen in Fig. 7, have the upper surfaces 14e and 14f which are located below the lower level L that is a lower limit of the level of stored oil. The upper surfaces 14e and 14f are arranged in the vicinity of the lower level L.

[0051] The oil pan main body 11 in this embodiment is configured to store a specified amount of oil therein. The level of the stored oil lies above the shallow bottom portion 14B (i.e., the middle bottom section 14D, the front raised bottom section 14E, and the rear raised bottom section 14F).

[0052] The specified amount of oil, as referred to herein, is defined to have the level of oil which is stored in the oil pan main body 11 and located between the upper level H (i.e., an upper limit level) and the lower level L (i.e., a lower limit level).

[0053] The level of oil stored in the oil pan main body 11 can be measured by an oil level gauge, not shown, and is regulated to lie between marks of the oil level gauge indicating the lower level L and the upper level H.

[0054] The front wall 15, as illustrated in Figs. 2 and 4, has the filter mounting wall 14J and the bulging wall 14K.

[0055] The filter mounting wall 14J protrudes from an upper portion of the front wall 15 which is located near the flange 12 toward the rear wall 16 and is of a semicircular shape. The filter mounting wall 14J has a lower surface serving as the filter mounting surface 14g (see Fig. 7) to which the oil filter 21 is secured.

[0056] The oil filter 21 is secured to the filter mounting surface 14g so that it hangs from the filter mounting wall 14J.

[0057] As viewed from above the oil pan 10 in Fig. 4, the bulging wall 14K bulges from the front wall 15 toward the rear wall 16 in a semicircular shape to surround the oil filter 21 indicated by an imaginary line. The bulging wall 14K has an upper end joined to the top 14j of the filter mounting wall 14J, as viewed in a direction in which the filter mounting wall 14J protrudes.

[0058] The oil filter 21 in this embodiment is of a cylindrical shape. The semicircular bulging wall 14K is arranged to face the oil filter 21 through a given gap between itself and the oil filter 21 which is constant in a circumferential direction thereof.

[0059] As viewed from above the oil pan 10 in Fig. 4, the oil filter 21 is arranged partially inside the oil pan main body 11 to have the rear end 21a which faces the rear wall 16 away from the front wall 15 and also have the front end 21b exposed frontward outside the front wall 15

[0060] With the above arrangements, the oil filter 21 does not protrude greatly outside the oil pan main body 11, thereby reducing the volume of space occupied by installation of the oil filter 21 outside the oil pan main body 11.

[0061] The right end of the front raised bottom section 14E and the left end of the front raised bottom section 14H are, as illustrated in Figs. 2 and 4, joined to the bulging wall 14K. The oil is stored in a space above the front raised bottom section 14E surrounded by the bulging wall 14K, the front wall 15, and the left side wall 17.

[0062] The oil pan main body 11, as illustrated in Fig. 4, has the oil strainer 22 disposed thereon. The oil strainer 22 is arranged above the deep bottom portion 14A and has an oil inlet, not shown, formed in a lower surface thereof.

[0063] The oil strainer 22 has the oil outlet 22a which is connected to an oil pump, not shown, through an oil pathe formed in the cylinder block 2A.

[0064] When the oil pump is activated, the oil strainer 22 sucks oil and filters it. The oil is then sucked into the oil pump through an oil pipe, not shown.

[0065] The filter mounting wall 14J has the oil inlet hole 14h and the oil outlet hole 14i formed therein (see Fig. 4). The oil inlet hole 14h and the oil outlet hole 14i communicate with the oil filter 21.

[0066] The oil sucked from the oil pan main body 11 into the oil pump is discharged from the oil pump into the oil path, not shown, formed in the cylinder block 2A and then delivered into the oil filter 21 through the oil inlet hole 14h.

[0067] Afterward, the oil is filtered by the oil filter 21 and then discharged from the oil outlet hole 14i and supplied through a main gallery in the cylinder block 2A to parts of the engine 1 required to be lubricated.

[0068] The front raised bottom section 14E is, as illustrated in Fig. 4, equipped with the rib 15A. The rib 15A protrudes upwardly from the front raised bottom section 14E and extends from the left side wall 17 toward the oil strainer 22.

[0069] The above structure of the rib 15A serves to mechanically reinforce the front raised bottom section 14E, thereby enhancing the stiffness of the front raised bottom section 14E.

[0070] The rear raised bottom section 14F is equipped with the rib 15B. The rib 15B protrudes upward from the rear raised bottom section 14F and extends from the rear wall 16 toward the front wall 15.

[0071] The above structure of the rib 15B serves to mechanically reinforce the rear raised bottom section 14F, thereby enhancing the stiffness of the rear raised bottom section 14F.

[0072] The central deepest bottom section 14G are equipped with the ribs 15C and 15D. The ribs 15C and 15D protrude upward from the central deepest bottom section 14G and extend from the right side wall 18 toward the stepped portion 14C.

[0073] The above structures of the ribs 15C and 15D serve to mechanically reinforce the central deepest bottom section 14G, thereby enhancing the stiffness of the central deepest bottom section 14G.

[0074] The deep bottom portion 14A, as illustrated in Figs. 4 and 5, has the drain hole 14m formed therein. The drain hole 14m is closed by the plug 50 (see Fig. 1). When it is required to exchange the oil stored in the oil pan 10, it is discharged from the drain hole 14m.

[0075] The oil pan 10 in this embodiment, as apparent from the above discussion, includes the oil pan main body 11 and the plug 50.

[0076]  The operation of and beneficial advantages offered by the oil pan 10 in this embodiment will be described below.

[0077] The oil pan 10 includes the flange 12 and the oil pan main body 11. The flange 12 has the rectangular opening 12a formed therein and is joined to the lower portion of the cylinder block 2A equipped with the crankshaft 4. The oil pan main body 11 includes the peripheral wall 13 extending downward from the inner edge 12b of the flange 12 and the bottom wall 14 joined to the lower end of the peripheral wall 13.

[0078] The bottom wall 14 includes the deep bottom portion 14A and the shallow bottom portion 14B. The shallow bottom portion 14B is located on an opposite side (i.e., the left side) of the crankshaft axial direction 4a to the deep bottom portion 14A and at a higher position than the deep bottom portion 14A. The shallow bottom portion 14B is also connected to the deep bottom portion 14A through the stepped portion 14C. The oil pan main body 11 is configured so that the level of stored oil is located above the shallow bottom portion 14B.

[0079] The shallow bottom portion 14B includes the middle bottom section 14D, the front raised bottom section 14E, and the rear raised bottom section 14F. The middle bottom section 14D occupies a central portion of the shallow bottom portion 14B in a direction crossing the crankshaft 4. The front raised bottom section 14E and the rear raised bottom section 14F are located on opposite sides of the middle bottom section 14D and face each other in the direction crossing the crankshaft 4 and at higher positions than the middle bottom section 14D.

[0080] The front raised bottom section 14E and the rear raised bottom section 14F, therefore, serve to decrease the volume of oil stored on the shallow bottom portion 14B and also raise the level of oil totally stored in the oil pan main body 11.

[0081] When the level of oil stored in the oil pan main body 11 is excessively high, it leads to a risk that the oil may be agitated by a counterweight, not shown, of the crankshaft 4. Conversely, when the level of oil stored in the oil pan main body 11 is excessively low, it may result in a risk that an oil inlet of the oil strainer 22 may suck air which then enters the oil pump.

[0082] The oil pan 10 in this embodiment is capable of raising the level of oil stored in the oil pan main body 11 using the front raised bottom section 14E and the rear raised bottom section 14F, thereby keeping the level of oil stored in the oil pan main body 11 at a desired level even when the volume of coil stored in the shallow bottom portion 14B is decreased.

[0083] Since the oil strainer 22 is designed to suck the oil to be stored in the deep bottom portion 14A through the oil inlet, it is arranged on the deep bottom portion 14A. In contrast, there is no interferer, such as the oil strainer 22, on the shallow bottom portion 14B, thereby facilitating increasing the size of the front raised bottom section 14E and the rear raised bottom section 14F.

[0084] It is, therefore, possible to eliminate the need for delivering the volume of oil into the oil pan main body 11 which is greater than that required to lubricate the engine 1 in order to raise the level of oil totally stored in the oil pan main body 11. This alleviates a risk that the oil in the oil pan main body 11 may be agitated by the counterweight.

[0085] It is also possible to alleviate a risk that the level of oil stored in the oil pan main body 11 may be undesirably decreased due to a decrease in volume of oil needed to be delivered into the oil pan main body 11, thereby avoiding suction of air into the oil pump.

[0086] The oil pan 10 in this embodiment is configured to have the middle bottom section 14D which protrudes downward in a convex shape relative to the front raised bottom section 14E and the rear raised bottom section 14F and is formed in the shallow bottom portion 14B. This enables the middle bottom section 14D which is of a curved convex shape in cross section to function as a rib joining the shallow bottom portion 14B to the stepped portion 14C, thereby enhancing the stiffness of the oil pan main body 11 to minimize mechanical vibration of the oil pan main body 11.

[0087] The oil pan 10 in this embodiment is, as apparent from the above discussion, capable of optimizing the volume and the level of oil stored in the oil pan main body 11 and also minimizing the mechanical vibration of the oil pan main body 11.

[0088] The oil pan 10 is also capable of reinforcing the mechanical strength of the front raised bottom section 14E, the rear raised bottom section 14F, and the central deepest bottom section 14G using the ribs 15A, 15B, 15C, and 15D to increase the stiffness of the front raised bottom section 14E, the rear raised bottom section 14F, and the central deepest bottom section 14G. This enhances the entire rigidity of the oil pan main body 11, thereby greatly reducing the mechanical vibration of the oil pan main body 11.

[0089] The oil pan 10 is, as described above, designed to include the front raised bottom section 14E and the rear raised bottom section 14F which have the upper surfaces 14e and 14f located below the lower level L defining a lower limit(s) of the level (i.e., surface) of oil stored in the oil pan 10. The upper surfaces 14e and 14f are also located near the lower level L of oil.

[0090] The above structure serves to prevent the level of oil from being lowered suddenly below the upper surfaces 14e and 14f of the front raised bottom section 14E and the rear raised bottom section 14F when the oil is consumed by operation of the engine 1, so that the level of the oil decreases from the upper level H to the lower level L. This minimizes a risk that air may be sucked into the oil pump.

[0091] The oil pan 10 is also equipped with the peripheral wall 13 which includes the left side wall 17 and the right side wall 18. The left side wall 17 is located at the right side of the oil pan 10. The right side wall 18 is located at the left side of the oil pan 10 which faces the left side (i.e., the left side wall 17) thereof in the crankshaft axial direction 4a.

[0092] The front raised bottom section 14E and the rear raised bottom section 14F occupy an entire area between the stepped portion 14C and the left side wall 17 in the crankshaft axial direction 4a.

[0093] The above structure enables an area occupied by the front raised bottom section 14E and the rear raised bottom section 14F to be increased in the crankshaft axial direction 4a, thereby facilitating adjustment of the volume and level of oil stored in the oil pan main body 11. This achieves effective optimization of the volume and level of oil stored in the oil pan main body 11.

[0094] The oil pan 10 has the peripheral wall 13 which includes the front wall 15 and the rear wall 16. The front wall 15 extends in the crankshaft axial direction 4a along the front edge 14a of the deep bottom portion 14A and the front edge 14b of the shallow bottom portion 14B which face in a direction crossing the crankshaft axial direction 4a. The rear wall 16 extends in the crankshaft axial direction 4a along the rear edge 14c of the deep bottom portion 14A and the rear edge 14d of the shallow bottom portion 14B which face in a direction crossing the crankshaft axial direction 4a. The front wall 15 and the rear wall 16 have upper ends joined to the flange 12.

[0095] The front wall 15 is equipped with the filter mounting wall 14J which protrudes from the upper portion of the front wall 15 toward the rear wall 16 and has a lower surface serving as the
filter mounting surface 14g to which the oil filter 21 is secured.

[0096] The front wall 15 also includes the bulging wall 14K. The bulging wall 14K is shaped to bulge from the front wall 15 toward the rear wall 16 and surround the oil filter 21. The bulging wall 14K has the upper end connecting with the top 14j of the filter mounting wall 14J which faces in a direction in which the bulging wall 14K bulges. The bulging wall 14K also connects with the front raised bottom section 14E and the front raised bottom section 14H.

[0097] The above structure of the bulging wall 14K is capable of regulating the volume of the oil pan main body 11, thereby achieving the optimization of the volume and level of oil stored in the oil pan main body 11.

[0098] The bulging wall 14K also serves to mechanically reinforce the front raised bottom section 14E and the front raised bottom section 14H to increase the rigidity of the front raised bottom sections 14E and 14H. The bulging wall 14K also enhances the rigidity of the front wall 15. This minimizes the mechanical vibration of the oil pan main body 11.

[0099] While the present invention has been disclosed in terms of the preferred embodiment in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible equivalents or modifications to the shown embodiment which can be embodied without departing from the principle of the invention as set forth in the appended claims.

Claims

1. An oil pan for an internal combustion engine, comprising:

an oil pan main body (11) which includes a flange (12), a peripheral wall (13), and a bottom wall (14), the flange having a rectangular opening (12a) and being joined to a lower portion of a body of an internal combustion engine (1) equipped with a crankshaft (4), the peripheral wall extending downward from an inner edge (12b) of the flange, the bottom wall being joined to a lower end of the peripheral wall, characterized in that

the bottom wall includes a deep bottom portion (14A) and a shallow bottom portion (14B), the shallow bottom portion being arranged adjacent the deep bottom portion in a direction in which the crankshaft extends and located at a higher position than the deep bottom portion, the shallow bottom portion being joined to the deep bottom portion through a stepped portion (14C),

the oil pan main body is configured to have the shallow bottom portion above which a level of a specified amount of oil stored in the oil pan main body lies, and

the shallow bottom portion includes a middle bottom section (14D), a first raised bottom section (14E), and a second raised bottom section (14F), the middle bottom section occupying a central portion of the shallow bottom portion in a direction crossing the crankshaft, the first raised bottom section and the second raised bottom section being arranged on opposite sides of the middle bottom section in the direction crossing the crankshaft and located at a higher position than the middle bottom section.

2. The oil pan as claimed in 1, wherein the first raised bottom section and the second raised bottom section have upper surfaces which are located below a lower level which defines a lower limit of the level of oil stored in the oil pan main body and near the lower level.

3. The oil pan as claimed in claim 1 or 2, wherein the peripheral wall includes a firs side wall (17) located at a first end of the peripheral wall and a second side wall (18) located at a second end of the peripheral wall which is opposed to the first end in the direction in which the crankshaft extends, and wherein the first and second raised bottom sections occupy an entire area between the stepped portion and the first side wall in the direction in which the crankshaft extends.

4. The oil pan as claimed in any one of claims 1 to 3, wherein the peripheral wall includes a third side wall (15) and a fourth side wall (16), the third side wall extending in the direction in which the crankshaft extends along a first edge (14a) of the deep bottom portion and a first edge (14b) of the shallow bottom portion which face in a direction crossing the crankshaft, the third side wall having an upper end joined to the flange, the fourth side wall extending in the direction in which the crankshaft extends along a second edge (14c) of the deep bottom portion and a second edge (14d) of the shallow bottom portion which face in the direction crossing the crankshaft, the fourth side wall having an upper end joined to the flange, wherein the third side wall has a filter mounting wall (14J) and a bulging wall (14K), the filter mounting wall protruding from an upper portion of the third side wall toward the fourth side wall and having a lower surface serving as a filter mounting surface (14g) to which an oil filter (21) is secured, wherein the bulging wall bulges from the third side wall toward the fourth side wall and surrounds the oil filter and connects with a top (14j) of the filter mounting wall which faces in a direction in which the bulging wall bulges, and wherein the first raised sections connect with the bulging portion.

Drawing