JP3458633B2 - Oil pan vibration control structure of internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping structure for an oil pan attached to the 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 automobile internal combustion engines, an oil pan having a shallow bottom portion and a deep bottom portion is attached to the lower surface of a cylinder block. It is structured so that it is sucked up by and pumped to each part. Here, the oil pan generally has a thin structure in which a metal plate is press-molded, and therefore, there is a problem in that the vibration of the film causes the vibration of the engine to generate a relatively large radiated sound. In particular, a large radiant sound is likely to be generated in the shallow bottom portion as compared with the deep bottom portion where a large amount of lubricating oil is always present.

Therefore, from the past, there has been a conventional practice of Shokai 62-6794.
As disclosed in Japanese Patent No. 5 and Japanese Utility Model Laid-Open No. 1-61443, at least the shallow bottom portion of the oil pan is made of, for example, aluminum die-cast, and the bottom wall of the shallow bottom portion is sufficiently thick. As the above, one that reduces the radiation sound from the shallow bottom is known. In addition, such an oil pan improves the rigidity of the entire oil pan,
It becomes a kind of structural member and can increase the rigidity of the entire engine. For example, the rigidity of the power plant such as the rigidity of coupling between the oil pan and the transmission is improved, which effectively reduces vibration for relatively low frequencies centered at 200 to 500 Hz.

Also, as in Japanese Utility Model Laid-Open No. 7-14106, there is proposed a device in which a straightening vane is formed on the bottom surface of the shallow bottom portion to improve the rigidity of the bottom wall of the shallow bottom portion.

[0005]

[SUMMARY OF THE INVENTION However, the above conventional oil pan, it will occur membrane resonance of the bottom wall of the shallow bottom portion at a high frequency region, as shown in FIG. 1 0,
In the shallow bottom portion 52 of the oil pan 51, 1 to 1.2 kH
A basic film mode 53 of z is generated. As a result, for example, when a high frequency input is remarkable as in a diesel engine, in particular, a direct injection diesel engine, resonance occurs in a high frequency region and the engine downward noise increases.

As disclosed in Japanese Utility Model Laid-Open No. 7-14106, if the rigidity of the bottom wall of the shallow bottom is simply increased by using a rectifying plate, human hearing characteristics are sensitive to frequencies of about 1 to 3 kHz. The occurrence cannot be suppressed. For example, the engine speed corresponding to the vibration order of the injection pump or the like is slightly deviated to the high speed side, and annoying noise is not reduced.

The main object of the present invention is to reduce the rigidity of the bottom wall of the shallow bottom to shift the membrane resonance generation frequency to a region where the radiation efficiency is low and to increase the vibration level for this low frequency region. This is to suppress the viscous damping force due to the squeeze effect by adopting a double structure oil pan structure to efficiently draw out the viscous damping force.

[0008]

An oil pan damping structure for an internal combustion engine according to the present invention is mounted on the lower surface of a cylinder block of the internal combustion engine and has a deep bottom portion for storing lubricating oil at one end side in the longitudinal direction of the engine. together with, have a shallow portion on the other end side, and part or whole contains at least shallow bottom
In an oil pan made of light alloy die-cast , in a part including the oil pan substantially central part of the bottom wall of the shallow bottom part ,
Thinned relatively to the thickness of the side edge of the bottom wall
An inner pan having a bottom wall having a shape along the bottom wall surface of the shallow bottom so as to form a meat portion and cover the thin wall portion is housed in the shallow bottom portion without being fixed to the oil pan, and the inner pan and the shallow portion It is characterized in that a thin oil layer is formed between the bottom wall surface and the bottom .

By making the wall thickness of the bottom wall of the shallow bottom part thin in a range including at least the substantially central portion of the oil pan, the rigidity of the bottom wall becomes low, and the membrane resonance generation frequency from the high frequency side. Move to the low frequency region. Further, the inner pan arranged so as to face the thin bottom wall is not fixed and settles in the oil, and the oil pan bottom surface and the inner pan bottom wall come close to each other. Lubricating oil is interposed between the oil pan and the inner pan, whereby a thin oil layer is formed between them. When the shallow bottom of the oil pan vibrates in this state, the oil layer expands and contracts due to a minute change in the distance between the two. That is, the lubricating oil tries to flow in the thin oil layer along the surfaces of the oil pan and the inner pan, and the energy damping action is obtained by the viscosity of the lubricating oil. This makes it possible to efficiently reduce the vibration level of the film resonance frequency of the thin portion that has moved to the low frequency side.

According to a second aspect of the present invention, a straightening vane is formed on the upper surface of the bottom wall of the inner pan along the longitudinal direction of the engine.

In this structure, the lubricating oil flows quickly from the shallow bottom portion to the deep bottom portion, and the straightening vane functions as a kind of reinforcing member to increase the rigidity of the entire inner pan. Thereby, elastic deformation of the inner pan is suppressed, and the squeeze action generated between the oil pan and the inner pan becomes stable.

According to a third aspect of the present invention, a baffle plate is attached to the opening side of the upper surface of the oil pan, and the movable range of the inner pan in the vertical direction is restricted by the baffle plate. Claims
No. 4 is characterized in that the convex portion formed on the inner surface of the side wall of the oil pan along the longitudinal direction of the engine restricts the movement of the inner pan in the longitudinal direction of the engine.

In these constructions, the relative positions of the oil pan and the inner pan are regulated, the inner pan is prevented from falling off, and excessive collision with the oil pan is suppressed. As a result, the secondary vibration input is reduced. Further, as in the invention of claim 5, the convex portion may be configured by utilizing a boss portion having a screw portion for fixing the baffle plate by bolts.

According to a sixth aspect of the present invention, a step is formed between the side edge portion of the shallow bottom portion along the longitudinal direction of the engine and the thin portion, and the step portion is covered by a part of the inner pan. The size of the inner pan is set, and a gap serving as an oil layer is formed between the bottom wall of the inner pan and the bottom wall surface of the shallow bottom by the step.

The smaller the thickness of the oil layer, that is, the smaller the gap between the bottom wall of the inner pan and the bottom wall of the shallow bottom, the greater the energy damping effect associated with the flow of lubricating oil.
Since the oil pan made of the light alloy die-casting has a sufficiently high manufacturing accuracy, the height of the step can be manufactured sufficiently low. Therefore, the gap between the bottom wall of the inner pan and the bottom wall surface of the shallow bottom can be set to be narrow.

[0016] In the seventh aspect, a plurality of projections on the bottom wall surface of the thin portion of the shallow bottom portion is formed, between the bottom wall and the bottom wall of the shallow bottom part of the In'napan by the protrusion A gap that forms an oil layer is formed in the.

In this structure, as in claim 7,
The gap between the bottom wall of the inner pan and the bottom wall surface of the shallow bottom can be set small, and the protrusion reliably ensures a gap to be an oil layer even in the central portion of the bottom wall of the inner pan.

[0018]

According to the oil pan damping structure for an internal combustion engine according to the present invention, the wall thickness of the bottom wall of the shallow bottom portion is partially thinned at least in the range including the substantially central portion of the oil pan. The resonance generation frequency shifts from the high frequency side to the low frequency side, and for example, resonance in the high frequency region can be avoided in a direct injection diesel engine or the like in which the high frequency input is remarkable. At the same time, the vibration level at the membrane resonance frequency of the thin portion that has moved to the low frequency side can be reduced by the squeeze action generated between the oil pan and the inner pan. As a result, the vibration level is reduced in a wide range from the low frequency side to the high frequency side. Therefore, the sound radiated from the oil pan is suppressed, and the noise below the engine is reduced.

According to the structure of claim 2, the surface rigidity of the inner pan is improved. As a result, the squeeze action generated between the oil pan and the inner pan becomes stable, and a further effect of suppressing radiated sound is obtained.

According to the third and fourth aspects of the invention, since the relative position between the oil pan and the inner pan is restricted, the secondary vibration input due to the collision between the two is reduced, so that the oil pan from the oil pan is reduced. The generation of abnormal noise is suppressed. In particular, since the boss portion restricts the movement of the inner pan in the front-rear direction of the engine, it is not necessary to provide a separate restriction member on the oil pan, and the movement can be restricted at low cost.

According to the sixth and seventh aspects, since the oil layer between the bottom wall of the inner pan and the bottom wall of the shallow bottom can be formed extremely thin, the squeeze effect can effectively reduce the radiation noise. To be

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

1 to 7 show an embodiment of the present invention. An oil pan 1 attached to the lower surface of a cylinder block (not shown), more specifically to the lower edge of the skirt, is composed of an oil pan body 2 made of aluminum die cast and a tank portion 3 made by press-molding a metal plate. The oil pan body 2 constitutes a flat shallow bottom portion 4, and the tank portion 3 constitutes a deep bottom portion 5 in which lubricating oil is stored.

The tank portion 3 is located on the lower surface of the front end portion of the internal combustion engine, and is fixed to a flange portion 7 formed on the lower surface of the opening portion 6 of the oil pan main body 2 through a bolt (not shown), so that the oil It is integrated with the bread body 2.

The front portion of the shallow bottom portion 4, that is, the bottom wall 12 at the substantially central portion of the oil pan body 2 is a thin thin portion 4a in a substantially rectangular range, and the rear end portion of the remaining portion and the longitudinal direction of the engine. Both side edge portions along the side wall are thick-walled portions 4b that are relatively thick. The thick rear end portion is provided with a bulging portion 8 bulging upward for mounting a transmission (not shown). Further, four boss portions 10 are formed on the inner surface of the side wall 9 of the oil pan body 2 along the longitudinal direction of the engine. More specifically, as shown in FIG. 4, bosses 10 are formed at positions near the vertices of the thin portion 4a having a substantially rectangular shape, and a screw hole 11 is provided at the upper end of each boss 10. The thickness of the thin portion 4a is slightly smaller than that of the thick portion 4b. As a result, step portions 14 corresponding to the difference in wall thickness between the thin portion 4a having a substantially rectangular shape are formed on both sides and on the rear three sides.

At the front end of the shallow bottom portion 4, that is, at the opening edge of the opening portion 6, there is formed a projection portion 15 having a substantially columnar shape and protruding from the bottom surface of the thin portion 4a. The oil pan body 2
A flange portion 16 joined to a cylinder block side flange surface (not shown) is formed on the outer peripheral portion of the upper surface of the.

Inside the oil pan body 2, a substantially rectangular inner pan 17 is housed in a non-fixed state so as to cover the thin portion 4a. The inner pan 17 is made of a press-formed product of a steel plate or a cast product of a light alloy such as aluminum, and has a bottom wall having a flat surface.
It is formed to be slightly larger than the thin portion 4a so as to cover the step portion 14. Further, side walls having a low height are provided on both side edges of the inner pan 17, and the side walls are bent along the side walls 9 of the oil pan body 2 surrounding the shallow bottom portion 4. Further, each corner portion of the substantially rectangular inner pan 17 is an R-shaped cutout portion 18 corresponding to the boss portion 10. The engagement of the cutout portion 18 and the boss portion 10 causes the inner pan 17 to move in the front-rear direction of the engine. Is restricted (see FIG. 7). On the bottom surface of this inner pan 17, as shown in FIG.
The straightening vanes 19 and 20 are arranged over substantially the entire length of the inner pan 17. These straightening vanes 19 and 20 have an L-shaped cross section, are joined to the bottom wall of the inner pan 17 by welding, etc., and divide the bottom surface of the inner pan 17 into three passage portions. Further, the rear ends of the straightening vanes 19 and 20 are curved so as to face each other in the rotation direction of the crankshaft (not shown) (direction of arrow ω in FIGS. 2 and 3).

The inner pan 17 is not fixed to the oil pan 1, but the peripheral edge of the bottom wall of the inner pan 17 is supported so as to ride on the step 14 (see FIG. 2). As a result, the bottom wall of the inner pan 17 and the thin portion 4a
A minute gap is formed between the bottom surface and.

The baffle plate 2 is formed so as to cover the bottom surface of the oil pan body 2, that is, almost the entire bottom surface 4.
1 is provided, and the inner pan 17 is housed below the baffle plate 21, that is, between the baffle plate 21 and the shallow bottom portion 4. As a result, excessive movement of the inner pan 17 upward is restricted, and there is no risk of interfering with, for example, a connecting rod or a crankshaft (not shown). The baffle plate 21 is formed by press-molding a relatively thin metal plate, and has a through hole 22 formed at a position corresponding to the boss portion 10 of the oil pan body 2, and the mounting bolt 23 is attached to the through hole 22. It is fixed by passing it through and screwing it into the screw hole 11 of each boss portion 10 (see FIG. 3).

Further, as shown in FIG. 6, the baffle plate 21 is provided with recesses 24, 2 at three positions in the longitudinal direction of the engine.
5, 26 are provided. These recesses 24-26
Corresponds to each cylinder of the internal combustion engine, and is formed along the motion trajectory 27 of a rotating object such as a connecting rod,
The widthwise center is the lowest (Figs. 2 and 3).
reference). Each of the recesses 24 to 26 is provided with an elongated slit-shaped oil recovery hole 28 along the longitudinal direction of the engine. In addition, the baffle plate 2 in which the third recess 26 is located
A substantially rectangular notch 29 is formed at the rear end of the first portion, corresponding to the bulging portion 8. The baffle plate 21 is attached so that a slight gap is formed between the cutout portion 29 and the bulging portion 8.

Next, the operation of the configuration of the above embodiment will be described.

As described above, in the oil pan body 2 made of aluminum die cast, which has a high rigidity as a whole, the basic film mode of about 1 to 1.2 kHz is likely to occur in the central portion of the bottom wall thereof. When the thickness of the bottom wall 12 in the central portion, which is a mode generating portion, is reduced by 20 to 30% with respect to the thickness of the surrounding thick portion 4b as the thin portion 4a, the membrane resonance frequency is proportional to this. Transition from high frequency side to low frequency side. For example, the falling resonance frequency of the bearing cap is usually around 1 kHz, but the membrane resonance frequency is 700H by reducing the thickness of the bottom wall 12 of the thin portion 4a.
It can be reduced to about z.

On the other hand, the lubricating oil stored in the deep bottom portion 5 is sucked up by an oil pump (not shown) and pressure-fed to each portion of the engine. The lubricating oil used in each portion is
The oil is discharged from the oil return hole on the upper surface of the crankcase, flows along the inner wall surface of the crankcase, and flows down to the oil pan 1. Then, a part thereof flows into the shallow bottom portion 4 through the oil recovery hole 28 of the baffle plate 21. Oil droplets scattered in the crankcase also enter the shallow bottom portion 4. Further, the lubricating oil also flows into the shallow bottom portion 4 through the gap between the cutout portion 29 of the baffle plate 21 and the bulging portion 8 of the oil pan body 2. Then, during engine operation, the lubricating oil actively flows from the shallow bottom portion 4 toward the deep bottom portion 5. As a result, the lubricating oil flows between the bottom wall of the inner pan 17 and the bottom surface of the thin portion 4a, and an oil layer is always formed between them.

Here, when the bottom wall 12 of the shallow bottom portion 4, particularly the bottom wall 12 of the thin portion 4a, undergoes film vibration due to vibration input from the cylinder block side with the oil layer formed, a slight change in the distance from the inner pan 17 occurs. When this occurs, the lubricating oil in the oil layer tends to flow along the two surfaces. As a result, the vibration energy is converted into the kinetic energy of the lubricating oil,
Moreover, it is attenuated by friction with each wall surface and friction between oils. That is, a so-called squeeze action occurs between the inner pan 17 and the bottom wall 12.

In this way, the bottom wall 1 serves as the thin portion 4a.
By reducing the wall thickness of 2, the membrane resonance generation frequency of the oil pan body 2 shifts from the high frequency side to the low frequency side.
Therefore, for example, resonance due to high frequency input in a direct injection diesel engine can be avoided. The vibration level of the membrane resonance at the low frequency shifted from the high frequency side can be effectively attenuated by the squeeze action generated between the bottom wall 12 and the inner pan 17. Therefore, the vibration actually generated is greatly suppressed, and the radiated sound emitted downward from the oil pan 1 is reduced. In particular, it is possible to efficiently reduce the vibration level of 1 to 3 kHz, which has a high sound generation efficiency.

In the above embodiment, the surface rigidity of the inner pan 17 is improved by the straightening vanes 19 and 20 of the inner pan 17. Thereby, elastic deformation of the inner pan 17 is suppressed, so that the squeeze action generated between the bottom wall 12 and the inner pan 17 described above is improved. In addition, the boss portion 10 of the oil pan body 2 and the baffle plate 21
Regulates the relative position between the oil pan body 2 and the inner pan 17, and the secondary vibration input due to the collision between the two is reduced, so that the generation of abnormal noise from the oil pan 1 is suppressed. Moreover, by restricting the position of the inner pan 17,
The oil layer clearance ΔH (see FIG. 2) can be kept constant. Since the movement of the inner pan 17 in the front-rear direction of the engine is restricted by the boss portion 10, it is not necessary to provide a separate restriction member.

In the squeeze action, when the bottom wall 12 of the thin portion 4a vibrates at the velocity V, the damping force is proportional to the oil viscosity μ and also to the inverse of the cube of the oil layer clearance ΔH. That is, the smaller the oil layer clearance ΔH, the greater the damping effect. Here, since the manufacturing tolerance of the thickness of the aluminum die cast is about ± 0.4 mm, the stepped portion 14 of the thin portion 4a can be manufactured with sufficiently high accuracy. As a result, the oil layer clearance ΔH can be set extremely small, and a high damping effect can be obtained.

FIG. 8 is a characteristic diagram showing the radiated sound of the oil pan 1, more specifically, the vibration level of the shallow bottom portion 4. The solid line is
The vibration level in the configuration of the above embodiment is shown, and the broken line shows the conventional characteristic. The alternate long and short dash line represents the characteristic of the reference example in which the inner pan 17 is not provided and the shallow bottom portion 4 is simply made thin. As is clear from these comparisons, simply thinning the inside of the shallow bottom portion 4 can suppress resonance in the high-frequency region, but on the contrary, increases vibration in the low-frequency region. In the present invention, the resonance frequency is shifted to the low frequency side, and at the same time, the vibration on the low frequency side is effectively damped, so that the vibration level can be suppressed over a wide frequency range.

Next, FIG. 9 shows a different embodiment of the present invention.

In this embodiment, a plurality of minute projections 30 are formed on the bottom surface of the bottom wall 12 instead of the step 14 of the above-described embodiments, and the projections 30 form the inner pan 17. The bottom wall is supported. This protrusion 3
0, in Figure Shimesuru so, and has a frustoconical outer peripheral surface is inclined loosely.

In the above embodiment, since the inner pan 17 is evenly supported by the protrusions 30 even in the central portion, an appropriate oil layer clearance can be secured without being affected by manufacturing errors of the inner pan 17, and its reliability is improved. improves.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an entire oil pan showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a plan view showing only an oil pan body.

FIG. 5 is a plan view showing only the inner pan.

FIG. 6 is a plan view showing only the baffle plate.

FIG. 7 is a plan view showing a state where the inner pan is housed in the oil pan body.

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 essential part of an oil pan showing a different embodiment of the present invention.
Cross-sectional view of.

FIG. 10 is an explanatory diagram showing a basic film mode on the bottom surface of a conventional oil pan.

[Explanation of symbols]

1 ... Oil pan 2 ... Oil pan body 3 ... Tank 4a ... Thin portion 10 ... Boss part 14 ... Step 17 ... Inna bread 19, 20 ... Current plate 21 ... Baffle plate 30 ... Projection

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Claims (7)

(57) [Claims] 1. A is attached to the cylinder block lower surface of the internal combustion engine, which has a deep bottom portion for storing lubricating oil to one side of the engine longitudinal direction, have a shallow portion on the other end, and
At least part of the light alloy, including the shallow bottom,
A part of the oil pan made of ecast, including the oil pan approximately center part of the bottom wall of the shallow bottom part
In addition, the thickness becomes relatively thin with respect to the thickness of the side edge portion of the bottom wall.
To form a thin wall portion, and to cover the thin wall portion , an inner pan having a bottom wall having a shape along the bottom wall surface of the shallow bottom portion is housed in the shallow bottom portion without being fixed to an oil pan, and An oil pan damping structure for an internal combustion engine, characterized in that a thin oil layer is formed between the shallow bottom surface and the bottom wall surface. 2. A method according to claim 1, characterized in that the formation of the rectifying plate along the engine longitudinal direction in the bottom wall upper surface of the In'napan
Oil pan damping structure of the serial loading of the internal combustion engine. 3. fitted with a baffle plate to the upper opening side of the oil pan, according to claim 1 or 2, characterized in that so as to regulate the vertical movable range of the In'napan by the baffle plate Oil pan damping structure for internal combustion engine. 4. A according to claim 1 to 3, characterized in that so as to restrict the movement of the front and rear engine of the In'napan direction by the oil engine longitudinally convex portion formed on the inner surface of the side wall along the pan The oil pan damping structure for an internal combustion engine according to any one of claims. 5. The oil pan damping structure for an internal combustion engine according to claim 4 , wherein the convex portion is formed of a boss portion having a screw portion for fixing the baffle plate by bolts. With step between the wherein the shallow engine longitudinal side edges along the bottom and the thin portion is formed, the size of the In'napan to the step portion is part of In'napan cover is is set, according to claim 1, characterized in that gap becomes oil layer is formed between the bottom wall and the shallow bottom part the bottom wall surface of the In'napan by the step
5. An oil pan damping structure for an internal combustion engine according to any one of items 1 to 5 . A plurality of protrusions are formed to 7. bottom wall surface of the thin portion of the shallow bottom part, a gap by the projections become oil layer between the bottom wall and the shallow bottom part the bottom wall surface of the In'napan Claim is formed, It is characterized by the above-mentioned.
An oil pan damping structure for an internal combustion engine according to any one of 1 to 5 .