JPH09280109A - Oil pan vibration damping structure for internal internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively apply a viscosity attenuating force based on an oil layer squeezing effect by forming a thin oil layer between an oil pan inner wall surface and an inner pan outer wall surface and specifying a gap between the wall surfaces of this oil layer. SOLUTION: An oil pan 1 is composed of an oil pan main body 2 and a sub-tank 3, and an inner pan 8 formed by press-molding a steel plate is housed inside the oil pan main body 2. A slight gap 9 is formed between wall surfaces of the inner pan 8 and the oil pan main body 2, and lubricating oil is supplied into this gap. This gap 9 is set lower than the gap dimension of a curving point in which the change rate of the attenuating force of a squeezing action determined by the following expression becomes small with respect to the gap 9. F=1.5μVa<4> /h<3> , F is an attenuating force (N), μ a viscosity factor (N/mm<2> .S), V an oil pan vibration speed (mm/S), a target film mode radius (mm) and h an oil layer gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping structure for an oil pan mounted on a lower surface of a cylinder block of an internal combustion engine.

[0002]

2. Description of the Related Art In many internal combustion engines typified by internal combustion engines for automobiles, an oil pan having a shallow portion and a deep portion is attached to the lower surface of a cylinder block, in which lubricating oil is stored and an oil pump is provided. It sucks up and feeds it to each part. Here, the oil pan generally has a thin-walled structure formed by press-molding a metal plate. Therefore, there is a problem in that the film vibrates due to the vibration input of the engine, and a relatively large radiation sound is generated. In particular, a large radiated sound is more likely to be generated at a shallow bottom than at a deep bottom where a large amount of lubricating oil is always present. For example, FIG. 9 is an explanatory view showing a first-order membrane mode (membrane vibration mode) in a general oil pan 51, and this oil pan 51 is
It is roughly divided into a deep bottom portion 52 provided in a tank shape at the front end portion and a shallow bottom portion 53 that is substantially flat, and large film vibration occurs in the shallow bottom portion 53. Further, FIG. 10 is an explanatory view showing a primary film mode in the case where the shallow bottom portion 53 is divided into two flat surface portions 53a and 53b by the step portion 54, and in this case, the respective flat surface portions are formed. Membrane vibration is generated individually at 53a and 53b.

Therefore, in the past, Japanese Patent Laid-Open No. 3-2946
As disclosed in Japanese Patent Publication No. 11 etc., the oil pan has a double structure of an outer oil pan and an inner oil pan, and a gap between the oil pan and the oil pan is filled with lubricating oil to vibrate due to energy damping action due to deformation of the oil layer. A low noise oil pan that suppresses the noise has been proposed. In this case, when the outer oil pan vibrates, the oil layer formed between the outer oil pan and the inner oil pan expands and contracts, and the vibration energy is attenuated by the viscous action of the lubricating oil.

[0004]

However, in the above-mentioned conventional structure, even if the thickness of the oil layer formed by the outer oil pan and the inner oil pan, that is, the gap between the two, is kept uniform, in practice. In some cases, due to manufacturing tolerances, the gap may become large at the antinode position of the membrane mode, so a good vibration damping effect cannot always be obtained.

Therefore, an object of the present invention is to provide an oil pan damping structure capable of effectively exhibiting a viscous damping force due to the squeeze effect of an oil layer.

[0006]

According to an oil pan damping structure for an internal combustion engine according to the present invention, an oil pan inner wall surface is formed so as to form a slight gap between the oil pan inner wall surface including at least a part of a bottom surface. Inner bread with outer wall along
It is arranged inside the oil pan to form a thin oil layer between the inner pan outer wall surface and the oil pan inner wall surface, and the gap between the wall surfaces forming the oil layer is defined by the squeeze action damping force F determined by the following equation. It was set below the gap size at the inflection point where the rate of change with respect to the gap becomes small.

F = 1.5 μVa ⁴ / h ³ where F is the damping force (N) and μ is the viscosity coefficient (N / mm ² ·
s), V is the oil pan vibration speed (mm / s), a is the radius (mm) of the target membrane mode, and h is the oil layer gap.

That is, as shown by modeling in FIG. 1, when the oil pan is vibrated by the vibration of the engine, for example, the central portion of the bottom plane portion tends to vibrate vertically. The radius a of the above film mode is equal to the radius of the circle of this vibrating portion. The lowest-order membrane mode has the highest sounding efficiency, and the diameter of the lowest-order membrane mode is approximately equal to the width of the oil pan. With the vertical movement of the oil pan, the oil in the gap tries to move along the plane of the inner pan at the velocity U, and at that time, the damping force F is generated. Here, the damping force F generated is proportional to the viscosity μ of the oil and the velocity V of the vibration, and is also proportional to the reciprocal of the cube of the gap h. Further, it is proportional to the radius of the oscillating circle, that is, the fourth power of the radius a of the target film mode.

The damping force F thus generated has a larger value as the gap h is narrower. In reality, however, the damping force F should be made uniform and sufficiently narrow due to manufacturing tolerances and manufacturing costs. It is difficult.

With respect to the damping force F, focusing on the relationship between the damping force F and the gap h, there is an inflection point P where the rate of change with respect to the gap h becomes small, as illustrated in FIG. . In other words, in a region where the gap h is larger than the inflection point P, the rate of change is substantially constant, and in a region where the gap h is smaller than the inflection point P, the damping force F decreases as the gap h decreases. It has a characteristic of rapidly increasing.

Therefore, if the upper limit design value of the gap h is set to this inflection point P, even if the gap h becomes large due to manufacturing tolerances, the decrease in the damping force F due to this is minimized. That is, the damping force F can be most efficiently exerted with the minimum size control.

When the gap h is made uniform over the entire surface of the inner pan, the size of the gap h may be set equal to the value of the inflection point P.

According to a second aspect of the present invention, when the upper limit Hmax of the gap h (mm) is a radius of the target membrane mode is a (mm), Hmax = 2.4-0.014a + 0.00
It was set to 013a ² . In consideration of the fact that the inflection point P is affected by the size of the film mode, the relationship between the radius a of the film mode and the gap h that becomes the inflection point P is calculated,
It is shown as an approximate expression. Note that the number of significant digits is 2 in consideration of general tolerance.

In FIG. 2, the radius a of the film mode is 5 cm,
Although the relationship between the damping force F and the gap h in the case of 8 cm and 10 cm is shown, the straight lines L corresponding to the respective inclinations are drawn respectively in the regions where the gap h in which the rate of change is substantially constant is relatively large. Then, the point that deviates sharply from the straight line L becomes the inflection point P described above. When the radius is 5 cm, the inflection point P is about 2 mm, and when the radius is 8 cm, about 2.1 mm, the radius 10
Although it is approximately 2.2 mm in cm, it is shown by an approximate expression by obtaining a curve S connecting these points.

A third aspect of the present invention relates to a vibration damping structure for an oil pan of an internal combustion engine for an automobile, wherein the diameter of the lowest-order membrane mode is 15 to 20 cm, and the gap h is approximately 2.3.
It was set to mm or less. In addition, as described above, the diameter of the lowest-order membrane mode is determined by the width dimension of the oil pan.

In order to obtain the gap h as described above, in the present invention, the oil pan is made of aluminum alloy die cast, and the gap is provided at a plurality of positions on the lower surface of the inner pan facing the bottom surface of the oil pan. A protrusion having a height corresponding to

That is, the projection on the lower surface of the inner pan comes into contact with the bottom surface of the oil pan, so that a predetermined gap is secured in the portion other than the projection.

Further, in the present invention, a baffle plate is disposed above the inner pan, the inner pan is pressed against the oil pan by the baffle plate, and at least a part of the outer peripheral portion of the baffle plate has an error. A fragile part is provided for absorption.

Therefore, the inner pan provided with the projection is surely pressed against the bottom surface of the oil pan, and the gap between the inner pan and the inner pan is secured within a predetermined range without expanding. When there is a dimensional error, the fragile portion of the baffle plate is deformed and absorbed.

[0020]

According to the present invention, the squeeze effect of the oil layer can be always exerted favorably against the vibration of the oil pan, a large damping force is surely generated, and the membrane vibration on the bottom surface of the oil pan is effective. Can be reduced to That is, the damping force can be most efficiently exhibited with the minimum dimensional control, and the oil pan noise can be reduced.

Further, according to the fourth and fifth aspects, the gap between the inner pan and the oil pan can be easily obtained to a predetermined value, and the noise suppressing action becomes more stable.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

3 and 4 show a first embodiment of the present invention. The oil pan 1 is composed of an oil pan body 2 formed by press-molding a steel plate, and a sub-tank 3 that is a separate member fixed to the front end portion of the oil pan body 2. The oil pan body 2 has a substantially rectangular deep bottom portion near the front end of the engine, and the remaining portion is a shallow bottom portion. An opening (not shown) is provided on the bottom surface of the deep bottom, and the sub-tank 3 is provided on the periphery of the opening.
Are fixed by welding. In this sub tank 3,
A suction pipe of an oil pump (not shown) is provided to suck up the lubricating oil stored therein. The sub-tank 3 has a width larger than the width of the oil pan body 2, as shown in FIG. Here, the bottom wall 5 of the shallow bottom portion is divided into two plane portions 5a and 5b by a step portion 6 at the center. Therefore, as shown in FIG. 3, the film vibration occurs in each of the flat surface portions 5a and 5b. Further, a flange portion 7 is formed on the outer peripheral edge portion of the oil pan 1, specifically, the oil pan main body 2, and the flange portion 7 is bolted to the lower edge of the cylinder block (not shown). ing.

An inner pan 8 formed by press forming a steel plate is housed inside the oil pan body 2. The inner pan 8 has a shape along the inner wall surface of the oil pan body 2 as a whole. That is, the bottom wall and the side wall having a shape along the bottom wall surface and the side wall surface of the oil pan main body 2 are formed, and a slight gap 9 may be generated between the respective wall surfaces when the oil pan main body 2 is stacked and arranged. In addition, the overall shape of the oil pan body 2 is slightly smaller than that of the inner wall surface of the oil pan body 2. The above inner bread 8
The side wall of is formed lower than the side wall of the oil pan body 2, and the lubricating oil flows into the gap 9 from here.

The inner pan 8 is not fixed to the oil pan 1 and is settled by its own weight. The gap 9 generated between the oil pan 1 and the oil pan 1 when settled in the oil pan 1 is set so as to satisfy the above-described relationship with the radius a of the membrane mode (see FIG. 3).

In each figure, the bottoms of the oil pan 1 and the inner pan 8 are shown as if they were completely flat, but this is sufficient if it is substantially flat, and there are no irregularities such as ribs. It does not mean that it does not exist at all. At least, in order to increase the rigidity of the oil pan 1, generally, a relatively shallow rib (not shown) is appropriately formed so as to project downward, and in this rib portion, the gap 9 is partially enlarged. It will be what you did. And even in the enlarged portion as described above, within the above-mentioned upper limit value, for example, 2.3.
The gap 9 is mm. If a rib similar to the oil pan 1 is formed on the inner pan 8 side as well, the gap 9 can be kept constant even at the rib portion, which is more preferable in terms of damping force.

5 to 6 show a second embodiment of the present invention, in which the oil pan 11 is formed by die casting of an aluminum alloy so as to have a wall thickness of about 3 mm, and the lower surface of the front end portion of the oil pan 11 is formed. The tank portion 12 made of a steel plate is fixed. The bottom of the oil pan 11 is substantially flat, and as shown in FIG. 7, the center is formed slightly higher.
A partition wall-shaped guide wall 13 is formed at the center of the oil pan 11 so as to extend in the axial direction of the crankshaft. A baffle plate 14 is fixed in such a manner that the inside of the oil pan 11 is divided into upper and lower stages. Both sides of the baffle plate 14 are fixed to the boss portion on the side of the oil pan 11 with bolts (not shown), and as shown in FIG. 7, avoid interference with the rotation locus 15 of the connecting rod. The central part is slightly depressed downward. Further, the baffle plate 14 is provided with a large number of openings 16 for allowing the lubricating oil to flow downward. Reference numeral 17 denotes a flange portion around the oil pan 11.

An inner pan 18 made of a steel plate is sandwiched between the bottom of the oil pan 11 and the baffle plate 14. As shown in FIG. 5, the inner pan 18 is a relatively small one that covers only the central portion of the bottom of the oil pan 11, and has a substantially flat rectangular shape as a whole.
In addition, it has side wall portions 19 bent upward at right angles on both side portions. In addition, having a slit-shaped opening 20 in the central portion,
The opening 20 is loosely fitted in the guide wall 13.
Protrusions 21 having a height corresponding to a desired gap size are formed at a plurality of locations on the bottom surface of the inner pan 18. The upper end of the side wall portion 19 is in pressure contact with the baffle plate 14.

That is, the inner pan 18 is forcibly pressed against the bottom surface of the oil pan 11 by the baffle plate 14, and the projection 22 secures a gap 22 therebetween. As shown in FIG. 7, the gap 22 is narrow in the central portion in the width direction and wide on both side portions where the protrusions 21 are located. It is smaller than the upper limit.

A fragile portion 2 formed by bending the baffle plate 14 in a V-groove shape or a U-groove shape along both sides.
3 is formed, and the inner portion of the fragile portion 23 is in contact with the inner pan 18. Therefore, even if there is a dimensional error in the height of the side wall portion 19 of the inner pan 18 or the height of the boss portion that supports the baffle plate 14, the fragile portion 23 is easily deformed and the error can be absorbed. . Therefore, the size of the gap 22 can be reliably ensured to be a predetermined value.

FIG. 8 shows a concrete oil pan radiation noise in comparison with the present invention and a conventional example not having an inner pan, and the oil pan itself has the same structure.

As is clear from this characteristic diagram, according to the present invention, as compared with the structure without inner bread,
A large radiation sound reduction effect can be obtained in the 3 kHz region.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating the principle of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a damping force and a gap.

FIG. 3 is a bottom view of the entire oil pan showing the first embodiment of the present invention.

FIG. 4 is a sectional view taken along the line AA of FIG.

FIG. 5 is a plan view of the entire oil pan showing the second embodiment of the present invention.

FIG. 6 is a vertical sectional view of the second embodiment.

FIG. 7 is a sectional view taken along the line BB of FIG. 5;

FIG. 8 is a characteristic diagram showing a radiated sound characteristic of the present invention in comparison with a conventional one.

FIG. 9 is an explanatory view showing a primary film mode on the surface of a conventional oil pan.

FIG. 10 is an explanatory view showing a primary film mode on the surface of a different conventional oil pan.

[Explanation of symbols]

 1 ... Oil pan 5 ... Bottom wall 8 ... Inner pan 9 ... Gap 11 ... Oil pan 14 ... Baffle plate 18 ... Inner pan 21 ... Projection 22 ... Gap 23 ... Fragile part

Claims (5)

[Claims] 1. An inner pan having an outer wall surface along the inner wall surface of the oil pan so as to form a slight gap with the inner wall surface of the oil pan including at least a part of the bottom surface is arranged inside the oil pan, A thin oil layer is formed between the inner wall surface of the inner pan and the inner wall surface of the oil pan, and the gap between the wall surfaces that form the oil layer is an inflection that reduces the rate of change of the damping force F of the squeeze action determined by the following equation with respect to the gap. An oil pan damping structure for an internal combustion engine, characterized in that it is set to be equal to or less than a point gap size. F = 1.5 μVa ⁴ / h ³ However, F: damping force (N) μ: viscosity coefficient (N / mm ² · s) V: oil pan vibration speed (mm / s) a: radius of target membrane mode (Mm) h: Oil layer gap 2. An inner pan having an outer wall surface along the inner wall surface of the oil pan so as to form a slight gap with the inner wall surface of the oil pan including at least a part of the bottom surface is arranged inside the oil pan, A thin oil layer is formed between the outer wall surface of the inner pan and the inner wall surface of the oil pan, and the upper limit Hmax of the gap h (mm) between the wall surfaces to be the oil layer is set to the radius of the target membrane mode is a (mm). And when Hma
oil pan damping structure for an internal combustion engine, characterized in that set to x = 2.4-0.014a + 0.00013a ^2. 3. The diameter of the lowest order membrane mode is 15 to 20c.
In the structure for damping the oil pan of the internal combustion engine for automobiles, the outer wall surface along the oil pan inner wall surface is formed so as to form a slight gap between the oil pan inner wall surface including at least a part of the bottom surface. The inner pan that is provided is disposed inside the oil pan, a thin oil layer is formed between the outer wall surface of the inner pan and the inner wall surface of the oil pan, and the gap between the wall surfaces serving as the oil layer is set to approximately 2.3 mm or less. An oil pan damping structure for an internal combustion engine, which is characterized in that 4. The oil pan is made of aluminum alloy die-cast, and projections having a height corresponding to the gap are formed at a plurality of locations on the lower surface of the inner pan facing the bottom surface of the oil pan. Claim 1 characterized by
4. An oil pan damping structure for an internal combustion engine according to any one of 3 to 3. 5. A baffle plate is disposed above the inner pan, the inner pan is pressed against the oil pan by the baffle plate, and at least a part of the outer peripheral portion of the baffle plate is fragile for absorbing an error. The oil pan damping structure for an internal combustion engine according to claim 4, wherein a portion is provided.