Engine oil return structure

Abstract

To provide a structure suitable for returning engine oil supplied to a journal section of a crank shaft.SOLUTION: A crank shaft 3 has a first journal 10a, as a journal section 10 thereof, supported with a bearing section 33 installed on a hole section 35 penetrating an external wall section 32 of a crank case 2. The crank case 2 has a cover member 40 which is fixed to the external wall section 32 and covers the hole section 35 with a sealed space 40X communicated with the hole section 35 formed between the external wall section 32 and the cover member. The external wall section 32 of the crank case 2 has an engine oil discharge hole 61 and an air supply hole 62 which communicate the sealed space 40X formed by the cover member 40 with a storage space 3X of the crank shaft 3 formed by the crank case 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an engine oil return structure. [Background technology]

[0002] For example, as shown in Patent Document 1, the journal portion of a crankshaft housed in an engine crankcase is rotatably supported by a bearing portion having a sliding bearing configuration. Engine oil is supplied to the bearing portion to lubricate the bearing portion and the journal portion of the crankshaft. The engine oil supplied to the bearing portion is discharged from both axial sides of the journal portion to the outside of the bearing portion. This allows the engine oil supplied to the journal portion to return to an oil pan provided at the bottom of the crankcase.

[0003] In many cases, one end of the crankshaft constitutes the output shaft of the engine, and a pulley is fixed to the other end of the crankshaft, which rotates to drive the engine's auxiliaries and also functions as a damper to absorb torsional vibrations of the crankshaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-327388 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, there may be cases where it is not necessary to provide a pulley on the end of the crankshaft. In addition, in such cases, the end of the crankshaft can be supported as a journal on the outer wall of the crankcase, making it possible to reduce the size of the engine. Accordingly, an appropriate return structure is required for the engine oil supplied to the journal supported on the outer wall. [Means for solving the problem]

[0006] The engine oil return structure that solves the above problem is a return structure for engine oil supplied to a journal portion of a crankshaft accommodated in a crankcase, wherein the crankshaft has, as the journal portion, a first journal supported on a bearing portion provided in a hole portion that penetrates an outer wall portion of the crankcase, and the crankcase is provided with a cover member that covers the hole portion while being fixed to the outer wall portion to form an enclosed space communicating with the hole portion between the outer wall portion and the cover member, and the outer wall portion is provided with an engine oil discharge hole and an air supply hole that communicate with the enclosed space and the crankshaft accommodation space formed by the crankcase.

[0007] That is, by providing a journal portion supported on the outer wall portion of the crankcase without providing a pulley at the axial end of the crankshaft as described above, the engine size can be reduced in the axial direction. According to the above configuration, the engine oil supplied to the first journal of the crankshaft flows out from the hole of the crankcase in which the bearing portion is provided into the sealed space between the outer wall portion in which the hole is provided and the cover member covering the hole. Then, the engine oil flowing into this sealed space is discharged into the crankshaft accommodation space through a discharge hole provided in the outer wall portion of the crankcase. At this time, air in the crankshaft accommodation space flows into the sealed space between the cover member and the outer wall portion through a supply hole also provided in the outer wall portion of the crankcase. This allows the engine oil supplied to the first journal of the crankshaft to be smoothly returned to the oil pan located below the accommodation space.

[0008] In addition, engine oil is less likely to remain in the sealed space formed by the cover member, which suppresses an increase in internal pressure and thus prevents engine oil from leaking from the portion where the cover member is fixed to the outer wall of the crankcase. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an engine, showing a crankshaft housed in a crankcase and a circulation path of engine oil supplied to a journal portion of the crankshaft. [Diagram 2] 4 is a cross-sectional view of a first journal of a crankshaft supported in a bearing portion provided in a hole penetrating an outer wall portion of the crankcase, and the vicinity of a cover member covering the hole. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of an engine oil return structure will be described with reference to the drawings. As shown in Fig. 1, engine 1, which is configured as a piston-type internal combustion engine, has a crankshaft 3 housed in a crankcase 2. In this embodiment, crankcase 2 is formed by fixing a lower case 6 from below to an upper case 5 that is integral with a cylinder block 4. The crankshaft 3 is supported rotatably while being sandwiched between the upper case 5 and the lower case 6.

[0011] More specifically, the crankshaft 3 includes a plurality of journal portions 10 that serve as a rotation axis, and crank pins 11 that are disposed at positions radially offset from each of the journal portions 10. The crankshaft 3 has each journal portion 10 rotatably supported by a bearing portion 7 provided in the crankcase 2. Furthermore, a connecting rod (not shown) is connected to the crank pin 11. The crankshaft 3 is configured to rotate about the axis of each journal portion 10 based on the reciprocating motion of a piston (not shown) connected via the connecting rod.

[0012] Specifically, the engine 1 of this embodiment has a configuration as a V-type 6-cylinder engine, and one side of the V-type bank is diagrammatically shown in FIG. That is, when the angle of the V-shaped bank is 120°, a pair of pistons facing each other across the crankshaft 3 share one crankpin 11. When the angle of the V-shaped bank is other than 120°, the crankpin 11 is configured to have a pair of connecting rod connection parts whose phases are offset from each other according to the angle. Furthermore, the crankshaft 3 has journal parts 10, 10 that axially sandwich the crankpin 11, each of which is supported by bearing parts 7, 7 provided in the crankcase 2. Thus, in the engine 1 of this embodiment, the crankshaft 3 has three crankpins 11 and four journal parts 10, and the crankcase 2 has four bearing parts 7.

[0013] Furthermore, each of the bearings 7 provided in the crankcase 2 is configured as a sliding bearing. Furthermore, engine oil is supplied to each of the bearings 7 to lubricate each of the journals 10 and each of the bearings 7. This allows the crankshaft 3 of the engine 1 of this embodiment to rotate smoothly.

[0014] More specifically, in the engine 1 of this embodiment, engine oil is supplied to each bearing 7 of the crankcase 2 through an oil passage 15 provided in the cylinder block 4. As a result, an oil film is formed between each bearing 7 and each journal 10 of the crankshaft 3, lubricating each bearing 7 and each journal 10.

[0015] Furthermore, the engine oil supplied to each bearing 7 is discharged to the outside of each bearing 7 from both axial sides of each bearing 7 and each journal portion 10. In the engine 1 of this embodiment, the lower case 6 constituting the lower part of the crankcase 2 functions as a tray for engine oil circulated within the engine 1, that is, as an oil pan 20.

[0016] The engine 1 of this embodiment employs a dry sump lubrication system. That is, the engine 1 of this embodiment is provided with a scavenge pump 21 that sucks the engine oil that has returned to the oil pan 20 out of the crankcase 2. The engine 1 of this embodiment is further provided with a reservoir tank 22 that stores the engine oil thus recovered, and a feed pump 23 that pressure-feeds the engine oil in the reservoir tank 22 into the engine 1. In the engine 1 of this embodiment, this forms an engine oil circulation device 25.

[0017] (Engine oil return structure) Next, an engine oil return structure in the engine 1 of this embodiment will be described. 1, in the engine 1 of this embodiment, the crankshaft 3 is housed in the crankcase 2 with one axial end 3a protruding to the outside. In the engine 1 of this embodiment, the one axial end 3a protruding from the crankcase 2 serves as the output shaft 30.

[0018] In addition, the crankshaft 3 of this embodiment has an axial end 3b opposite to one axial end 3a constituting the output shaft 30 of the engine 1, which constitutes the journal portion 10. That is, in the engine 1 of this embodiment, a damper pulley is not provided for the other axial end 3b. Note that such a configuration in which the axial end 3b of the crankshaft 3 does not have a damper pulley is adopted, for example, in racing engines. In the engine 1 of this embodiment, the camshaft and auxiliary devices such as a pump are driven via a gear train (not shown) provided on the side of one axial end 3a constituting the output shaft 30.

[0019] Furthermore, in the engine 1 of this embodiment, the other axial end portion 3b is designated as the first journal 10a, and each journal portion 10 is designated by a number in the order of arrangement along the axial direction of the crankshaft 3. That is, the crankshaft 3 includes a first journal 10a, a second journal 10b, a third journal 10c, and a fourth journal 10d. The engine 1 of this embodiment is configured to reduce the size in the axial direction by supporting the first journal 10a of the crankshaft 3 by a bearing portion 33 provided on an outer wall portion 32 of the crankcase 2.

[0020] 1 and 2, in the engine 1 of this embodiment, a hole 35 is provided in an outer wall 32 of the crankcase 2 at a position where an upper case 5 and a lower case 6 that form the crankcase 2 are joined, and the hole 35 penetrates the outer wall 32. The first journal 10a of the crankshaft 3 is rotatably supported by a bearing 33 provided in the hole 35.

[0021] 2, the engine 1 of this embodiment includes a cover member 40 that is fixed to the outer wall portion 32 of the crankcase 2 to cover from the outside the hole 35 in which the bearing portion 33 is provided. Specifically, in the engine 1 of this embodiment, the cover member 40 has an outer shape of a substantially hemispherical flattened dome. Based on the dome shape, the cover member 40 of this embodiment is configured to form an enclosed space 40X that communicates with the hole 35 between the cover member 40 and the outer wall portion 32 of the crankcase 2 to which the cover member 40 is fixed.

[0022] In the engine 1 of this embodiment, the hole 35 opens into a bottom portion of a recess 45 provided in the outer wall 32 of the crankcase 2. Furthermore, the cover member 40 is fixed to this recess 45. Thus, the engine 1 of this embodiment is configured to be further miniaturized by suppressing the amount of protrusion of the cover member 40.

[0023] In addition, in the engine 1 of this embodiment, the outer wall portion 32 of the crankcase 2 is provided with a first communication hole 51 and a second communication hole 52 that communicate between the sealed space 40X formed by the cover member 40 and the accommodating space 3X of the crankshaft 3 formed by the crankcase 2.

[0024] Specifically, the first communication hole 51 is provided at a position lower than the hole 35 (lower side in FIG. 2), and the second communication hole 52 is provided at a position higher than the hole 35 (upper side in FIG. 2). The first communication hole 51 has an opening 51b for the accommodation space 3X of the crankshaft 3 lower than an opening 51a for the sealed space 40X formed by the cover member 40. The second communication hole 52 has an opening 52b for the accommodation space 3X of the crankshaft 3 higher than an opening 52a for the sealed space 40X formed by the cover member 40. In the engine 1 of this embodiment, a return structure 60 for engine oil supplied to the first journal 10a of the crankshaft 3 is thus formed.

[0025] Next, the operation of this embodiment will be described. That is, the engine oil supplied to the first journal 10a of the crankshaft 3 flows from the hole 35 in which the bearing portion 33 is provided into the sealed space 40X between the cover member 40 covering the hole 35 and the outer wall portion 32 of the crankcase 2. Furthermore, the engine oil that has flowed into the sealed space 40X is discharged into the accommodation space 3X of the crankshaft 3 formed by the crankcase 2 through the first communication hole 51 provided in the outer wall portion 32 as the discharge hole 61. At this time, the air in the accommodation space 3X flows into the sealed space 40X through the second communication hole 52 also provided in the outer wall portion 32 as the supply hole 62. In the engine 1 of this embodiment, the engine oil supplied to the first journal 10a of the crankshaft 3 is thereby smoothly returned to the lower case 6 of the crankcase 2, which functions as the oil pan 20.

[0026] Next, the effects of this embodiment will be described. (1) The crankshaft 3 has, as its journal portion 10, a first journal 10a supported by a bearing portion 33 provided in a hole 35 penetrating an outer wall portion 32 of the crankcase 2. The crankcase 2 is also provided with a cover member 40 that is fixed to the outer wall portion 32 to cover the hole 35 in a state in which an enclosed space 40X that communicates with the hole 35 is formed between the cover member 40 and the outer wall portion 32. The outer wall portion 32 of the crankcase 2 is provided with an engine oil drain hole 61 and an air supply hole 62 that communicate between the enclosed space 40X formed by the cover member 40 and an accommodation space 3X for the crankshaft 3 formed by the crankcase 2.

[0027] That is, as described above, the journal portion 10 is supported by the outer wall portion 32 of the crankcase 2 without providing a pulley at the axial end portion 3b of the crankshaft 3, so that the engine size can be reduced in the axial direction. According to the above configuration, the engine oil supplied to the first journal 10a of the crankshaft 3 flows out from the hole portion 35 of the crankcase 2 in which the bearing portion 33 is provided, into the sealed space 40X between the cover member 40 covering the hole portion 35 and the outer wall portion 32. Then, the engine oil flowing into the sealed space 40X is discharged into the accommodation space 3X of the crankshaft 3 through the discharge hole 61 provided in the outer wall portion 32 of the crankcase 2. Furthermore, at this time, the air in the accommodation space 3X of the crankshaft 3 flows into the sealed space 40X between the cover member 40 and the outer wall portion 32 through the supply hole 62 also provided in the outer wall portion 32 of the crankcase 2. This allows the engine oil supplied to the first journal 10a of the crankshaft 3 to be smoothly returned to the oil pan 20 located below the accommodation space 3X.

[0028] In addition, engine oil is less likely to remain in the sealed space 40X formed by the cover member 40, thereby suppressing an increase in the internal pressure. This makes it possible to prevent engine oil from leaking from the portion where the cover member 40 is fixed to the outer wall portion 32 of the crankcase 2.

[0029] (2) The outer wall portion 32 of the crankcase 2 is provided with a first communication hole 51 and a second communication hole 52 that communicate between the sealed space 40X defined by the cover member 40 and the accommodation space 3X for the crankshaft 3 defined by the crankcase 2. The first communication hole 51 is provided at a position below the hole portion 35. The second communication hole 52 is provided at a position above the hole portion 35. Thus, the first communication hole 51 constitutes an engine oil discharge hole 61, and the second communication hole 52 constitutes an air supply hole 62.

[0030] According to the above configuration, engine oil that has flowed into the sealed space 40X tends to flow into the first communication hole 51 and tends to flow into the second communication hole 52. This makes it possible to form the engine oil drain hole 61 and the air supply hole 62 that are independent of each other. As a result, the engine oil supplied to the first journal 10a of the crankshaft 3 can be more smoothly returned to the oil pan 20 located below the accommodation space 3X.

[0031] (3) The first communication hole 51 has an opening 51b corresponding to the accommodating space 3X of the crankshaft 3 below an opening 51a corresponding to the sealed space 40X formed by the cover member 40. The second communication hole 52 has an opening 52b corresponding to the accommodating space 3X of the crankshaft 3 above an opening 52a corresponding to the sealed space 40X formed by the cover member 40.

[0032] According to the above configuration, engine oil that has flowed into the sealed space 40X is more easily discharged through the first communication hole 51 that constitutes the discharge hole 61, and is less likely to flow into the second communication hole 52 that constitutes the air supply hole 62. This allows the engine oil supplied to the first journal 10a of the crankshaft 3 to be more smoothly returned to the oil pan 20 located below the accommodation space 3X.

[0033] (4) The hole 35 in which the bearing 33 that supports the first journal 10a of the crankshaft 3 is provided opens into the bottom portion of a recess 45 provided in the outer wall 32 of the crankcase 2. The cover member 40 is fixed to this recess 45.

[0034] According to the above-described configuration, it is possible to reduce the amount of protrusion of the cover member 40 fixed to the outer wall portion 32 of the crankcase 2. This allows for further miniaturization. The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0035] In the above embodiment, the engine 1 is configured as a V6 engine. However, the number of cylinders and the engine layout may be changed as desired, for example, to an in-line 4-cylinder engine.

[0036] In the above embodiment, a dry sump lubrication system is employed for the engine 1, but the present invention may be applied to an engine that employs a wet sump lubrication system. In the above embodiment, engine oil is supplied to each bearing portion 7 of the crankcase 2 and the journal portion 10 of the crankshaft 3 supported by each bearing portion 7 through the oil passage 15 provided in the cylinder block 4. However, the present invention is not limited to this, and the method of supplying engine oil to the journal portion 10 of the crankshaft 3 may be changed as desired. For example, engine oil may be supplied to the journal portion 10 of the crankshaft 3 from the lower case 6 side that constitutes the lower portion of the crankcase 2. And, for example, engine oil may be supplied to the journal portion 10 of the crankshaft 3 through the oil passage 15 provided inside the crankshaft 3.

[0037] In the above embodiment, the cover member 40 has a substantially hemispherical flattened dome-like outer shape, but the shape may be changed arbitrarily as long as it is fixed to the outer wall portion 32 of the crankcase 2 to form an enclosed space 40X between itself and the outer wall portion 32 and covers the hole portion 35 in which the bearing portion 33 of the first journal 10a is provided.

[0038] Also, with regard to the outer wall portion 32 of the crankcase 2, the shape of the portion to which the cover member 40 is fixed may be changed as desired. It is not necessary for the bottom surface portion to have a recess 45 into which the hole 35 opens.

[0039] In the above embodiment, the outer wall portion 32 of the crankcase 2 is provided with the first communication hole 51 and the second communication hole 52 that communicate between the sealed space 40X formed by the cover member 40 and the accommodation space 3X of the crankcase 3 formed by the crankcase 2. The first communication hole 51 forms the engine oil discharge hole 61, and the second communication hole 52 forms the air supply hole 62. However, this is not limited to the above, and the outer wall portion 32 of the crankcase 2 may have three or more communication holes. At least one of these may form the engine oil discharge hole 61, and at least one of these may form the air supply hole 62.

[0040] The arrangement and shapes of the discharge hole 61 and the supply hole 62 may be changed as desired. For example, the air supply hole 62 does not necessarily have to be provided above the hole portion 35 in which the bearing portion 33 of the first journal 10a is provided. However, from the viewpoint of ensuring smooth discharge of the engine oil that has flowed into the sealed space 40X, it is preferable to provide the discharge hole 61 below the hole portion 35. Similarly to the first communication hole 51 in the above embodiment, the shape of the discharge hole 61 is also preferably a shape that extends downward from the sealed space 40X formed by the cover member 40 and opens into the accommodation space 3X of the crankshaft 3. [Explanation of symbols]

[0041] 2. Crankcase 3…Crankshaft 3X…Containment space 10. Journal Section 10a…1st Journal 32…Outer wall part 33...Bearing part 35...hole 40…Cover member 40X…Closed space 61...Discharge hole 62…Supply hole

Claims

[Claim 1] An engine oil return structure for supplying oil to a journal portion of a crankshaft housed in a crankcase, comprising: The crankshaft includes, as the journal portion, a first journal supported by a bearing portion provided in a hole portion penetrating an outer wall portion of the crankcase, The crankcase is provided with a dome-shaped cover member that is fixed to the outer wall portion to cover the hole in a state in which an enclosed space communicating with the hole is formed between the outer wall portion and the dome-shaped cover member, The hole is open to a bottom surface of a recess provided in the outer wall, The cover member is fixed to the recessed portion so as to be convex toward an outside of the crankcase, The outer wall portion is provided with an engine oil discharge hole and an air supply hole which communicate the sealed space with a space for accommodating the crankshaft defined by the crankcase. Engine oil return structure.

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