JP3487198B2 - Oil return structure for crankcase - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil return structure for a crankcase in which oil is returned into the crankcase from an oil return hole of a cylinder block in an engine.

[0002]

2. Description of the Related Art As a conventional oil return structure for a crankcase of this type, for example, a structure shown in FIG. 4 is known. That is, in this conventional configuration,
The crankcase 21 is formed by aluminum casting or the like into a substantially bottomed box shape having an open upper surface, and a flange portion 23 is formed on the outer peripheral edge of the opening portion 22. On the inner surface of the side wall of the crankcase 21, a plurality of boss portions 24 are formed to extend vertically in a state of bulging inward.

The flange portion 23 is joined to a flange portion of a cylinder block (not shown), and bolts are screwed onto the boss portions 24 from above the cylinder block, whereby the crankcase 21 is attached to the lower surface of the cylinder block. It is designed to be used. In this state, a plurality of oil return holes formed in the cylinder block are arranged above and in the vicinity of the peripheral edge of the opening 22 of the crankcase 21, and the oil falling from these oil return holes is returned to the inside of the crankcase 21. It is like this.

[0004]

However, in this conventional crankcase oil return structure, since the boss portion 24 is bulged on the inner surface of the side wall of the crankcase 21, as shown by the chain line in FIG. The boss 24
When oil falls from the oil return hole of the cylinder block to the upper surface of the bottom wall of the crankcase 21 in the vicinity of
The oil has its flow changed by the boss portion 24 and is guided to the center side of the crankcase 21. As a result, there is a problem in that the oil is agitated by the crankshaft when the engine rotates and the oil temperature rises and friction of the lubrication part increases.

[0005] Conventionally, for example, the actual development Sho 58-13211
As is seen in Japanese Patent Publication No. 3, a structure is known in which an oil return passage for directly connecting the oil return hole and the oil pan is provided between the oil return hole of the cylinder block and the oil pan under the crankcase. However, the structure is complicated and the manufacturing cost is inevitable.

The present invention has been made by paying attention to the problems existing in such conventional techniques. The purpose is that even if a bulging portion such as a boss is formed on the inner surface of the side wall of the crankcase, it is easier to guide the oil falling near the bulging portion to the center side of the crankcase. (EN) Provided is an oil return structure for a crankcase, which can be prevented by a structure, and can prevent the temperature of the oil from being stirred by the crankshaft and the friction of the lubrication portion from increasing.

[0007]

In order to achieve the above-mentioned object, according to the invention described in claim 1, oil is returned into the crankcase from an oil return hole formed in the cylinder block. In the oil return structure, on the inner surface of the side wall of the crankcase, so as to be adjacent to the bulging portion formed on the inner surface of the side wall of the crankcase,
A straightening wall corresponding to the oil return hole is formed to project.

Therefore, even if a bulging portion such as a boss portion is formed on the inner surface of the side wall of the crankcase, the oil that falls near the bulging portion is rectified by the flow straightening wall and the crank portion is not touched. It flows along the side edges of the top surface of the bottom wall of the case. Therefore, the oil is not guided to the center side of the crankcase by the bulging portion and is not stirred by the crankshaft, and it is possible to prevent the temperature of the oil from increasing and the friction of the lubricating portion to increase.

According to a second aspect of the present invention, in the crankcase oil return structure according to the first aspect, the straightening wall is formed so as to extend along a corner portion between an inner surface of a side wall and an inner surface of a bottom wall of the crankcase. It was done.

Therefore, the oil falling near the bulging portion is
The flow straightening wall extending along the corner portion smoothly smoothes the flow to a position where it does not touch the bulging portion, and flows along the side edge of the upper surface of the bottom wall of the crankcase. Therefore, it is possible to more reliably prevent the oil from being guided to the center of the crankcase.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to FIGS. As shown in FIG. 1 and FIG. 2, the crankcase 11 is formed into a box-like shape with an open top by aluminum casting or the like.
A flange portion 13 is formed on the outer peripheral edge of the opening 12. On the inner surface of the side wall of the crankcase 11, a plurality of bosses 14 as bulges are bulged inward and extend vertically. The bottom wall of the crankcase 11 is formed so as to gradually descend toward the left side of FIGS. 1 and 2, and a deep-bottomed oil pan (not shown) is formed at the left end thereof.

On the other hand, as shown in FIG. 3, the cylinder block 15 is formed into a substantially box shape by opening the lower surface by aluminum casting or the like, and a flange portion 16 is formed on the outer peripheral edge of the opening portion. A plurality of oil return holes 17 are formed on the inner surface of the side wall of the cylinder block 15, and their lower ends are opened in the vicinity of the lower surface opening of the cylinder block 15.

The flange portion 13 of the crankcase 11 is joined to the flange portion 16 of the cylinder block 15, and bolts (not shown) are screwed onto the boss portions 14 of the crankcase 11 from above the cylinder block 15. As a result, the crankcase 11 is attached to the lower surface of the cylinder block 15. In this state,
The oil return holes 17 of the cylinder block 15 are arranged facing each other in the vicinity of the peripheral edge of the opening 12 of the crankcase 11 so that the oil falling from the oil return holes 17 is returned to the inside of the crankcase 11. .

Here, in this embodiment, FIG.
As shown in FIG. 3, a rectifying wall 18 is formed on the inner surface of the side wall of the crankcase 11 so as to be adjacent to the boss portion 14 at a position corresponding to the oil return hole 17 near the boss portion 14. The straightening wall 18 is formed in a circular arc shape by substantially the same amount as the boss portion 14 and extends along the corner portion between the inner surface of the side wall and the inner surface of the bottom wall of the crankcase 11.

Next, the operation of the oil return structure for the crankcase constructed as described above will be described. When the engine is rotating, each oil return hole 17 of the cylinder block 15
Then, the oil is returned to the inside of the crankcase 11 through the vicinity of the periphery of the opening 12 of the crankcase 11. At this time, in the vicinity of the boss portion 14 that is formed to bulge on the inner surface of the side wall of the crankcase 11, the oil that drops from the oil return hole 17 is bossed by the rectifying wall 18 as shown by the chain line in FIGS. It is rectified to a position where it does not touch the portion 14 and guided to the inner surface of the bottom wall of the crankcase 11. Then, this oil flows along the inclined surface of the bottom wall of the crankcase 11 to the left side in FIGS. 1 and 2 without touching the boss portion 14. Therefore, the oil that drops from the oil return hole 17 in the vicinity of the boss portion 14 is not changed in flow path to the center side of the crankcase 11 due to the contact with the boss portion 14.

The effects expected from such an embodiment will be described below. (1) In the crankcase oil return structure of this embodiment, oil is returned to the inside of the crankcase 11 from the oil return hole 17 formed in the cylinder block 15. A straightening wall 18 corresponding to the oil return hole 17 is formed on the inner surface of the side wall of the crankcase 11 so as to be adjacent to the boss 14 as a bulge formed on the inner surface of the side wall of the crankcase 11. There is.

Therefore, even if the boss portion 14 is bulged on the inner surface of the side wall of the crankcase 11, the boss portion 14 is formed.
The oil that falls near is rectified by the rectification wall 18,
The fluid flows along the side edges of the upper surface of the bottom wall of the crankcase 11 without touching the boss portion 14. Therefore, the oil is guided to the center side of the crankcase 11 by the boss portion 14,
It is not agitated by the crankshaft, and it is possible to prevent the temperature of the oil from increasing and the friction of the lubricating portion from increasing.

Since the straightening wall 18 is formed so as to project from the inner surface of the side wall of the crankcase 11, the crankcase 1
The surface rigidity of the side wall of No. 1 is improved. Therefore, the resonance noise generated from the crankcase 11 due to the rotation of the engine can be reduced.

(2) In the crankcase oil return structure of this embodiment, the straightening wall 18 is formed so as to extend along the corner portion between the inner surface of the side wall and the inner surface of the bottom wall of the crankcase 11. Therefore, the oil that falls near the boss portion 14 is smoothly rectified by the rectifying wall 18 to a position where it does not touch the boss portion 14, and flows along the side edge of the upper surface of the bottom wall of the crankcase 11. Therefore, it is possible to more reliably prevent the oil from being guided to the center side of the crankcase 11.

Note that this embodiment can be modified and embodied as follows. -The shape, the protrusion amount, and the protrusion length of the flow regulating wall 18 may be appropriately changed and configured as necessary.

A rectifying wall 18 is formed so as to project from the inner surface of the side wall of the crankcase 11 corresponding to a bulging portion different from the boss portion 14.

[0022]

Since the present invention is constructed as described above, it has the following effects. According to the invention described in claim 1, even if a bulging portion such as a boss portion is formed on the inner surface of the side wall of the crankcase, the oil falling near the bulging portion is rectified to a position where it does not touch the bulging portion. You can
It is possible to prevent the oil from being guided to the center side of the crankcase. Therefore, it is possible to prevent the risk that the oil is agitated as the crankshaft rotates and that the temperature of the oil rises and the friction of the lubricating portion increases.

Further, according to the present invention, the surface rigidity of the side wall of the crankcase can be enhanced by forming the protruding rectifying wall, and the resonance noise generated from the crankcase can be reduced.

According to the second aspect of the invention, the oil falling near the bulging portion can be smoothly rectified to a position where it does not touch the bulging portion, and the oil is guided to the center side of the crankcase. It is possible to more surely prevent it from being struck.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a crankcase showing an embodiment of the present invention.

FIG. 2 is a partial plan view of the crankcase.

FIG. 3 is a partial cross-sectional view of the crankcase.

FIG. 4 is a partial perspective view showing a conventional crankcase.

[Explanation of symbols]

11 ... Crank case, 14 ... Boss portion as bulging portion,
15 ... Cylinder block, 17 ... Oil return hole, 18 ...
Straightening wall.

Claims (2)

(57) [Claims] 1. An oil return structure for a crankcase, wherein oil is returned to the inside of the crankcase through an oil return hole formed in a cylinder block, so as to be adjacent to a bulging portion formed on an inner surface of a side wall of the crankcase. The crankcase oil return structure is characterized in that a straightening wall corresponding to the oil return hole is formed on the inner surface of the side wall of the crankcase. 2. The oil return structure for a crankcase according to claim 1, wherein the straightening wall is formed so as to extend along a corner portion between an inner surface of a side wall and an inner surface of a bottom wall of the crankcase.