STRUCTURE OF INTERNAL COMBUSTION ENGINE

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of foreign priority to Japanese Patent Application No. 2019-106615, filed on Jun. 7, 2019, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a structure of an internal combustion engine.

BACKGROUND

A conventionally known structure of an internal combustion engine includes an oil pan disposed on a lower side of an engine body, and a baffle plate disposed in and attached to an oil pan (see, for example, JP 2009-281177 A).

According to this structure of an internal combustion engine, engine oil dropped, for example, from an inner wall of a piston and a crank shaft is accumulated in a bottom portion of the oil pan. The baffle plate is disposed to divide the internal space of the oil pan into upper and lower spaces. The baffle plate is bolted to the oil pan.

In this conventional structure, there has been a growing demand for a more improved rigidity of the oil pan because the oil pan is joined to the lower portion of the engine body. It is therefore conceivable that the rigidity of the baffle plate bolted to the oil pan is increased to enhance the rigidity of the oil pan.

However, if the thickness of the baffle plate is increased or the baffle plate is made of a material having a higher rigidity for instance, the structure of the internal combustion engine increases in weight. Increasing the weight of the structure of the internal combustion engine will result in decreased fuel efficiency of a vehicle equipped with this structure of the internal combustion engine.

In view of the above, the present invention seeks to provide a structure of an internal combustion engine capable of reducing the weight thereof while increasing the rigidity of the oil pan.

SUMMARY

In one aspect, the present invention relates to a structure of an internal combustion engine comprising: an oil pan connected to a main body portion of the internal combustion engine; and a plurality of baffle plates disposed in and fastened to the oil pan.

In another aspect, the present invention relates to a structure of an internal combustion engine comprising: an oil pan connected to a main body portion of the internal combustion engine, the oil pan including a deep bottom portion for receiving oil and a shallow bottom portion, the deep bottom portion having a relatively deep depth and the shallow bottom portion having a relatively shallow depth; and a plurality of baffle plates disposed in and fastened to the oil pan, wherein among the plurality of baffle plates, a rigidity of a baffle plate disposed at the shallow bottom portion is higher than a rigidity of a baffle plate disposed at the deep bottom portion.

In still another aspect, the present invention relates to a structure of an internal combustion engine comprising: an oil pan connected to a main body portion of the internal combustion engine; and a plurality of baffle plates disposed in and fastened to the oil pan, wherein the oil pan comprises a bottom portion for receiving oil, and a heavy-equipment joint portion disposed on a side portion of the oil pan, and wherein among the plurality of baffle plates, a rigidity of a baffle plate disposed at the heavy-equipment joint portion is higher than a rigidity of another baffle plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present invention in any way.

FIG. 1 is a front view of a structure of an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a perspective view of an oil pan in which baffle plates are disposed.

FIG. 3 is a sectional view taken along the line of FIG. 2.

FIG. 4 is a top view of the oil pan.

FIG. 5 A is a top view of a first baffle plate.

FIG. 5B is a bottom view of the first baffle plate.

FIG. 6 is a top view of a second baffle plate.

FIG. 7A is a graph showing a relationship between a cut distance [%] of a baffle plate and a torsional rigidity [μm/Nm] of an oil pan, and a relationship between a cumulative mass [kg] of the oil pan and the cut distance [%] of the baffle plate.

FIG. 7B is a view explaining the cut distance [%] of the baffle plate as shown in FIG. 7A.

FIG. 8A is a view showing a distribution of distortion generated in the first baffle plate according to the embodiment of the present invention.

FIG. 8B is a view showing a distribution of distortion generated in the first baffle plate according to a modified embodiment.

DETAILED DESCRIPTION

A structure of an internal combustion engine according to one embodiment for implementing the present invention is described below with reference made to the accompanying drawings where appropriate. In the drawings to be referred to, directions such as upper, front and right directions shown by arrows correspond to directions such as upper, front and right directions of a vehicle on which the structure of the internal combustion engine according to this embodiment is mounted.

The structure of the internal combustion engine according to this embodiment is configured such that a plurality of baffle plates are disposed in and fastened to an oil pan that is connected to a main body portion of the internal combustion engine.

First, the overall configuration of the structure of the internal combustion engine is described below, and then the oil pan and the baffle plates are described in detail.

FIG. 1 is a front view of a structure C of an internal combustion engine (hereinafter also referred to as an “internal combustion engine structure C”) according to one embodiment of the present invention. In FIG. 1, a transmission 4 is shown by phantom line (chain double-dashed line).

As seen in FIG. 1, the internal combustion engine structure C includes a main body portion 1 of the internal combustion engine (hereinafter referred to as an “internal combustion engine main body 1”), an oil pan 2 having baffle plates 3 (see FIG. 2), and a transmission 4. In this embodiment, an inline four-cylinder gasoline engine is assumed as the internal combustion engine main body 1.

The internal combustion engine main body 1 includes a cylinder block 11 for forming cylinders. A crankcase 12 for forming a crank chamber is provided on a lower portion of the cylinder block 11. The crankcase 12 is integrated with the cylinder block 11 as a single component. A crank shaft 13 extending in a direction of a cylinder bank is provided in the crankcase 12.

A cylinder head 14 is attached to an upper portion of the cylinder block 11, and a head cover 15 is attached to an upper portion of the cylinder head 14.

A valve operation chamber is formed in the cylinder head 14 and the head cover 15.

An oil pan 2 to be described later in detail is fastened to a lower portion of the crankcase 12 by a plurality of bolts B1.

Further, a transmission 4, to which a driving force of the crank shaft 13 is transmitted, is attached to a left side portion of the cylinder block 11 by bolts B2.

The oil pan 2 according to this embodiment has joint portions 24 for the attachment of the transmission 4. The joint portion 24 is described later in detail together with the oil pan 2.

The internal combustion engine main body 1 as describe above is assumed such that components such as the cylinder block 11, the cylinder head 14 and the head cover 15 are die-cast products made of aluminum alloy.

Next, the oil pan 2 (see FIG. 1) is described below.

FIG. 2 is a perspective view of the oil pan 2 in which baffle plates 3 are disposed.

As seen in FIG. 2, the oil pan 2 according to this embodiment is formed in the shape of a box with an open top. The inner space of the oil pan 2 is vertically divided by the baffle plates 3 to be described later in detail into a space facing the crankcase 12 (see FIG. 1) and an oil chamber 26 formed on a bottom side of the oil pan 2.

Further, when viewed from above, the oil pan 2 is formed generally in the shape of a rectangle extending long in the lateral direction (right-left direction). A flange 25 is formed along an open edge of the upper opening of the oil pan 2. The flange 25 has a plurality of insertion holes 25a along the open edge, and bolts B1 (see FIG. 1) are inserted into the insertion holes 25a.

Provided at the upper opening of the oil pan 2 are joint portions 24 for the transmission 4 (see FIG. 1); the joint portions 24 are formed respectively on the front end portion and the rear end portion of the edge portion corresponding to the left side of the rectangle. It should be noted that the joint portions 24 correspond to a “heavy-equipment joint portion” defined in the claims.

Each of the joint portions 24 extends along the edge portion corresponding to the left side of the rectangle in a direction away from the upper opening.

Further, as seen in FIG. 1, the oil pan 2 is fastened to the transmission 4 through the joint portions 24 and by the bolts B2 as described above.

It should, however, be noted that the “heavy-equipment joint portion” defined in the claims is not limited to the joint portions 24 for the transmission 4 according to this embodiment, and may be any joint portion for a heavy equipment. For example, the heavy-equipment joint portion may be a joint portion through which the oil pan 2 is fastened to a driving motor of a hybrid vehicle.

FIG. 3 is a sectional view taken along the line of FIG. 2. In FIG. 3, an inner peripheral wall 22a of a deep bottom portion 22 of the oil pan 2 is shown by hidden line (dotted line).

As seen in FIG. 3, the oil pan 2 includes a deep bottom portion 22 for receiving lubricating oil (oil) and a shallow bottom portion 21. The deep bottom portion 22 has a relatively deep depth, and the shallow bottom portion 21 has a relatively shallow depth. In FIG. 3, the reference numeral 3a indicates a first baffle plate (to be described later) disposed in the shallow bottom portion 21.

To be more specific, as seen in FIG. 1, the oil pan 2 includes the deep bottom portion 22, an intermediate portion 23, and the shallow bottom portion 21 in this order from the right side to the left side in the longitudinal direction of the oil pan 2.

In other words, the shallow bottom portion 21 of the oil pan 2 is disposed between the intermediate portion 23 and the joint portions 24 for the transmission 4 (on the side of the intermediate portion 23 closer to the joint portions 24). The deep bottom portion 22 of the oil pan 2 is disposed on the opposite side of the intermediate portion 23 from the shallow bottom portion 21 (i.e., the deep bottom portion 22 and the shallow bottom portion 21 are disposed on opposite sides of the intermediate portion 23).

According to this embodiment, the intermediate portion 23 is formed of an inclined surface smoothening a height difference between the deep bottom portion 22 and the shallow bottom portion 21. However, the intermediate portion 23 in this embodiment is not an essential component for implementing the present invention. Therefore, the oil pan 2 may have a stepped structure having a step height steeply (almost perpendicularly) rising from the deep bottom portion 22 to the shallow bottom portion 21.

Next, reference is made to FIG. 4. FIG. 4 is a top view of the oil pan 2. In FIG. 4, the baffle plates 3 are shown by phantom line (chain double-dashed line).

As seen in FIG. 4, the oil pan 2 has a plurality of bolt bosses 20 in the oil chamber 26.

The bolt bosses 20 according to this embodiment include a total of nine bolt bosses, including, from the left side to the right side in the longitudinal direction of the oil pan 2, a first bolt boss 20a, a second bolt boss 20b, a third bolt boss 20c, a fourth bolt boss 20d, a fifth bolt boss 20e, a sixth bolt boss 20f, a seventh bolt boss 20g, an eighth bolt boss 20h, and a ninth bolt boss 20i. If it is not necessary to distinguish these bolt bosses, they may be collectively referred to as bolt bosses 20, and individually as a bolt boss 20.

Five of these bolt bosses 20, including the first to fifth bolt bosses 20a, 20b, 20c, 20d, 20e, are formed in the shallow bottom portion 21. Whereas, four of these bolt bosses 20, including the sixth to ninth bolt bosses 20f, 20g, 20h, 20i are formed in the deep bottom portion 22.

Further, four of the total of nine bolt bosses 20, including the second bolt boss 20b, the fifth bolt boss 20e, the seventh bolt boss 20g, and the ninth bolt boss 20i, are formed along the front open edge of the oil pan 2 to be aligned in the longitudinal direction (lateral direction or right-left direction) of the oil pan 2. Whereas, four of the total of nine bolt bosses 20, including the first bolt boss 20a, the fourth bolt boss 20d, the sixth bolt boss 20f, and the eighth bolt boss 20h, are formed along the rear open edge of the oil pan 2 to be aligned in the longitudinal direction (lateral direction or right-left direction) of the oil pan 2.

The third bolt boss 20c is formed in a position corresponding to a node Nd for torsional vibration defined in the oil pan 2 according to this embodiment.

To be more specific, the oil pan 2 according to this embodiment is fastened, as described above, to the internal combustion engine main body 1 (see FIG. 1) and the transmission 4 (see FIG. 1) by the bolts B1, B2 (see FIG. 1). Accordingly, it is assumed that a motion (torsional vibration) in which the angle of torsion periodically changes around the longitudinal axis Ax of the oil pan 2 (i.e., center axis Ax extending in the longitudinal direction (right-left direction) of the oil pan 2) as shown in FIG. 4 occurs in the oil pan 2.

It should be noted that the node Nd for torsional vibration defined in the oil pan 2 according to this embodiment is formed in the shallow bottom portion 21 based on the distribution of rigidity on the shallow bottom portion 21, the intermediate portion 23, and the deep bottom portion 22 that constitute the oil pan 2.

As described above, in the oil pan 2 according to this embodiment, the third bolt boss 20c is disposed in the position corresponding to the node Nd formed in the shallow bottom portion 21.

In this embodiment, the bolt bosses 20 are assumed to be provided at the same horizontal height. However, the bolt bosses 20 in the shallow bottom portion 21 and the bolt bosses 20 in the deep bottom portion 22 may be provided at different horizontal heights.

As described later in detail, bolts B3 (see FIG. 2) for attaching the baffle plates 3 to the oil pan 2 are inserted into and secured to these bolt bosses 20.

Although not shown in the drawings, the oil pan 2 is equipped with an oil pump configured to suck the lubricating oil (oil) in the oil chamber 26 (see FIG. 2) and to pump it to the internal combustion engine main body 1 (see FIG. 1), and an oil strainer through which the lubricating oil (oil) sucked in the oil pump from the oil chamber 26 flows.

Next, the baffle plates 3 (see FIG. 2) are described below.

As seen in FIG. 2, a plurality of baffle plates 3 are disposed in the oil pan 2. According to this embodiment, two baffle plates 3 are disposed in the oil pan 2. To be more specific, the baffle plates 3 include a first baffle plate 3a having a relatively high rigidity and a second baffle plate 3b having a relatively low rigidity.

In the following description, if it is not necessary to distinguish the first baffle plate 3a and the second baffle plate 3b, they may be collectively referred to as baffle plates 3, and individually as a baffle plate 3.

These baffle plates 3 are fastened to the corresponding bolt bosses 20 (see FIG. 4) of the oil pan 2 by the bolts B3.

FIG. 5 A is a top view of the first baffle plate 3a, and FIG. 5B is a bottom view of the first baffle plate 3a. In FIG. 5A, lightened portions 34b of ribs (see FIG. 5B) that are formed in the bottom surface of the first baffle plate 3a are shown by hidden line (dotted line). Further, in FIG. 5B, a lightened portion 34a (see FIG. 5A) of the ribs 33 (see FIG. 5A) that is formed in the upper surface of the first baffle plate 3a is shown by hidden line (dotted line).

As shown in FIGS. 5A and 5B, the first baffle plate 3a is formed in the shape of a rectangle when viewed from above.

Further, as shown in FIGS. 5A and 5B, the first baffle plate 3a has a plurality of bolt holes 30 for inserting the bolts B3 (see FIG. 2). These bolt holes 30 include five bolt holes corresponding to the first to fifth bolt bosses 20a, 20b, 20c, 20d, 20e shown in FIG. 4, including a first bolt hole 30a, a second bolt hole 30b, a third bolt hole 30c, a fourth bolt hole 30d, and a fifth bolt hole 30e.

To be more specific, the first bolt hole 30a, the second bolt hole 30b, the fourth bolt hole 30d, and the fifth bolt hole 30e are formed at four corners of the first baffle plate 3a. The third bolt hole 30c is formed in a central portion of the first baffle plate 3a in a position corresponding to the node Nd (see FIG. 4) for torsional vibration of the oil pan 2 (see FIG. 4). In the following description, if it is not necessary to distinguish the first to fifth bolt holes 30a, 30b, 30c, 30d, 30e, they may be collectively referred to as bolt holes 30, and individually as a bolt hole 30.

Further, as seen in FIG. 5A, the first baffle plate 3a has ribs 33 in the upper surface of the first baffle plate 3a. When viewed from above, the ribs 33 are arranged in an approximately X-shape layout so as to connect the five bolt holes 30.

To be more specific, the ribs 33 connect the first bolt hole 30a, the third bolt hole 30c, and the fifth bolt hole 30e along a diagonal line, and connects the second bolt hole 30b, the third bolt hole 30c, and the fourth bolt hole 30d along a diagonal line.

As described later in detail, these ribs 33 include a main body 33a (see FIG. 8A) and a main body reinforcing portion 33b (see FIG. 8A).

The ribs 33 are formed in the upper surface of the first baffle plate 3a so as to partly bulge upward.

Further, as seen in FIG. 5A, the first baffle plate 3a includes a lightened portion 34a having a reduced thickness partly formed in the upper surface of the first baffle plate 3a. Further, as seen in FIG. 5B, the first baffle plate 3a includes lightened portions 34b having a reduced thickness partly formed in the bottom surface of the first baffle plate 3a at positions corresponding to the ribs 33.

As shown in FIG. 5A, the lightened portion 34a and the lightened portions 34b are formed at positions clear of an imaginary line connecting the first bolt hole 30a, the third bolt hole 30c, and the fifth bolt hole 30e and an imaginary line connecting the second bolt hole 30b, the third bolt hole 30c, and the fourth bolt hole 30d.

Further, as seen in FIGS. 5A and 5B, the first baffle plate 3a includes a lightened portion 34c in the upper surface of the first baffle plate 3a and in the bottom surface of the first baffle plate 3a at positions clear of the ribs 33.

The first baffle plate 3a according to this embodiment is assumed to be a die-cast product made of aluminum-based material.

FIG. 6 is a top view of the second baffle plate 3b.

As seen in FIG. 6, when viewed from above, the second baffle plate 3b has a generally U-shaped configuration that opens to the right.

The second baffle plate 3b has a plurality of bolt holes 30 for inserting the bolts B3 (see FIG. 2). These bolt holes 30 include four bolt holes corresponding to the sixth to ninth bolt holes 20f, 20g, 20h, 20i shown in FIG. 4, including a sixth bolt hole 30f, a seventh bolt hole 30g, an eighth bolt hole 30h, and a ninth bolt hole 30i.

To be more specific, the seventh bolt hole 30g and the ninth bolt hole 30i are formed along the front open edge of the oil pan 2 shown in FIG. 4 to be aligned in the longitudinal direction (lateral direction or right-left direction) of the oil pan 2. Whereas, the sixth bolt hole 30f and the eighth bolt hole 30h are formed along the rear open edge of the oil pan 2 shown in FIG. 4 to be aligned in the longitudinal direction (lateral direction or right-left direction) of the oil pan 2.

In the following description, if it is not necessary to distinguish the sixth to ninth bolt holes 30f, 30g, 30h, 30i, they may be collectively referred to as bolt holes 30, and individually as a bolt hole 30.

Further, the second baffle plate 3b has a clearance 35 for a structural member within an inner side of the generally U-shaped configuration.

The clearance 35 for a structural member according to this embodiment is assumed to be an installation space for a balancer (not shown) as the structural member. Although not shown in the drawings, the balancer includes a first balancer shaft configured to rotate by a crank shaft 13 (see FIG. 1) through a chain or the like, a second balancer shaft configured to be meshed with the first balancer shaft through a helical gear or the like and to rotate in a direction reverse to the first balancer shaft, and a housing for accommodating the first balancer shaft and the second balancer shaft.

It should be noted that the structural member is not limited to the balancer and may be the oil strainer (not shown) as described above.

To be more specific, in the internal combustion engine structure C according to this embodiment, the structural member is fitted into the clearance 35, so that the second baffle plate 3b integrated with the structural member cooperates with the structural member to improve the baffle function. Therefore, as long as the structural member has a configuration to be fitted into the clearance 35, the structural member is not limited to a particular device or component.

The second baffle plate 3b according to this embodiment is made of an iron-based material, and the second baffle plate 3b is assumed to be formed of a plate member that is thinner than that of the first baffle plate 3a. Although the second baffle plate 3b is made of an iron-based material with a Young's modulus higher than that of an aluminum-based material constituting the first baffle plate 3a, the second baffle plate 3b is formed of a thin plate member, so that the second baffle plate 3b is relatively lower in rigidity than the first baffle plate 3a.

Next, the length of the first baffle plate 3a and the length of the second baffle plate 3b in the longitudinal direction (lateral direction or right-left direction) of the oil pan 2 according to this embodiment are described below.

FIG. 7A is a graph showing a relationship between a cut distance [%] of a baffle plate 3 and a torsional rigidity [μm/Nm] of an oil pan 2, and a relationship between a cumulative mass [kg] of the oil pan 2 and the cut distance [%] of the baffle plate 3. FIG. 7B is a view explaining the cut distance [%] of the baffle plate 3 as shown in FIG. 7A.

In this embodiment, the length of the first baffle plate 3a and the length of the second baffle plate 3b are set from a single baffle plate 3 that is assumed to consist of a first baffle plate 3a and a second baffle plate 3b made of the same material and integrated one from the other, and based on the torsional rigidity [μm/Nm] of the oil pan 2 in accordance with the cut distance [%] of the baffle plate 3 as shown in FIG. 7B.

The cut distance [%] is defined that the length of the baffle plate 3 (longitudinal length of the oil pan 2) in which the first baffle plate 3a and the second baffle plate 3b are integrated together is set to 100 [%]. Further, the position for determining the length of the first baffle plate 3a and the length of the second baffle plate 3b is shown by the cut distance [%] of the baffle plate 3.

In this embodiment, the torsional rigidity [μm/Nm] of the oil pan 2 in accordance with the cut distance [%] was obtained using CAE (Computer Aided Engineering). It should be noted that the torsional rigidity [μm/Nm] indicates the torsional rigidity [μm/Nm] of the oil pan 2 around the longitudinal axis thereof (torsional rigidity [μm/Nm] along the longitudinal direction of the oil pan 2 around the center axis). The result was shown in FIG. 7A. In this embodiment, the smaller the value of the torsional rigidity [μm/Nm], the better the torsional rigidity.

The torsional rigidity [μm/Nm] of the oil pan 2 defined by the left vertical axis of FIG. 7A did not change by the cut distance [%] between the third bolt hole 30c and the fourth bolt hole 30d (fifth bolt hole 30e) of the baffle plate 3.

On the contrary, the value of the torsional rigidity [μm/Nm] decreased with the increasing cut distance [%] from the fourth bolt hole 30d (fifth bolt hole 30e).

When the cut distance [%] exceeded 40%, the torsional rigidity [μm/Nm] reached saturation. In other words, when the oil pan 2 was divided into the first baffle plate 3a and the second baffle plate 3b generally at an intermediate position between the fourth bolt hole 30d (fifth bolt hold 30e) and the sixth bolt hole 30f, the torsional rigidity [μm/Nm] of the oil pan 2 became the minimum value, that is, showed the most excellent torsional rigidity.

In FIG. 7A, the right vertical axis of FIG. 7A indicates the cumulative mass [kg] of the oil pan corresponding to the cut distance [%].

Next, the relationship between distortion generated in the first baffle plate 3a (see FIG. 2) and the shape of the ribs 33 (see FIG. 5A) is described below.

FIG. 8A is a view showing a distribution of distortion generated in the first baffle plate 3a according to this embodiment, and FIG. 8B is a view showing a distribution of distortion generated in the first baffle plate 3c according to a modified embodiment.

The distribution of distortion in the first baffle plate 3a, 3c such as shown in FIG. 8A and FIG. 8B was obtained by calculating, with CAE (Computer Aided Engineering), the distortion generated in the first baffle plate 3a, 3c when the internal combustion engine main body 1 (see FIG. 1) was driven under a certain condition.

In FIGS. 8A and 8B, the distribution of distortion is shown by a blank area A1 representing an area with the smallest distortion and other shaded areas in which the depth of shades are changed in three levels, such as an area A2 with “small distortion”, an area A3 with “intermediate distortion”, and an area A4 with “large distortion”. The magnitude of distortion follows the relationship, in which the area A1<the area A2<the area <A3, the area A4.

The first baffle plate 3c (see FIG. 8B) according to a modified embodiment is described below. The first baffle plate 3c has substantially the same structure as that of the first baffle plate 3 according to the embodiment except for the shape of the ribs 33c to be described next.

As shown in FIG. 8B, the ribs 33 of the first baffle plate 3c extend respectively from the first bolt hole 30a, the second bolt hole 30b, the fourth bolt hole 30d, and the fifth bolt hole 30e that are formed in the four corners of the first baffle plate 3c, toward the third bolt hole 30c. These ribs 33c are formed to partly rise upward in the upper surface of the first baffle plate 3c.

These four ribs 33c may have a width, for example, equal to or greater than the width of the bolt boss 20 (see FIG. 4), and preferably less than 2.4 times the width of the bolt boss 20.

The distribution of distortion in the first baffle plate 3c having the ribs 33c as described above is obtained such that although the areas A4 with “large distortion” are scattered in the proximity of and on the left side of the third bolt hole 30c, that is, on the side of the transmission 4 (see FIG. 1), the distribution of distortion generally consist of the area A1 with the smallest distortion and the area A2 with “small distortion”.

In other words, the torsional rigidity of the first baffle plate 3c can be enhanced by the ribs 33c.

In contrast, as seen in FIG. 8A, in the first baffle plate 3a according to the embodiment, the ribs 33 include main bodies 33a and main body reinforcing portions 33b.

In FIG. 8A, the main bodies 33a of the ribs 33 are shown by phantom line (chain double-dashed line), and have the same structure as that of the ribs 33c in the first baffle plate 3c (see FIG. 8B) according to the modified embodiment.

The main body reinforcing portions 33b of the ribs 33 are formed by four regions each extending radially around the third bolt hole 30c and between two adjacent main bodies 33a.

As shown by hatching (oblique lines) in FIG. 8A, the four main body reinforcing portions 33b have a generally triangular shape with the third bolt hole 30c being a vertex when viewed from above. The size of each of the main body reinforcing portions 33b may be set such that, for example, the outer edge corresponding to the base of a generally triangular shape is located in a region equal to or greater than ⅓ of lengths of the radially extending main bodies 33a from the third bolt hole 30c side and less than ⅔ of the lengths thereof.

These four main body reinforcing portions 33b are integrated with the main bodies 33a to form the ribs 33. As described above, the ribs 33 are arranged in an approximately X-shape layout when viewed from above so as to connect the five bolt holes 30a, 30b, 30c, 30d, 30e.

As seen in FIG. 8A, the first baffle plate 3a according to this embodiment is configured such that the area A4 with “large distortion” is significantly reduced and the area A2 with “small distortion” is also reduced to equal to or smaller than ½ of the area A2 with “small distortion” in the first baffle plate 3c (see FIG. 8B) according to the modified embodiment.

It should be noted that the present invention does not exclude the modified embodiment in which the baffle plates 3 include the first baffle plate 3c (see FIG. 8B). According to this first baffle plate 3c, the rigidity of the oil pan 2 can be enhanced and the weight of the first baffle plate 3c can be reduced in a more reliable manner.

The first baffle plate 3a (see FIG. 2) and the first baffle plate 3c (see FIG. 8B) are relatively higher in rigidity than the second baffle plate 3b (see FIG. 2).

The first baffle plate 3a and the baffle plate 3c are assumed to be formed such that the thickness of a so-called general portion other than the portions where the ribs 33 (see FIG. 8A) and the ribs 33c (see FIG. 8B) are formed and the portions where the lightened portions 34b (see FIG. 5B) are formed is larger than the thickness of the second baffle plate 3b (see FIG. 2) made of a thin plate member.

According to this configuration, although the first baffle plate 3a and the first baffle plate 3c are made of an aluminum-based material with a Young's modulus lower than that of an iron-based material constituting the second baffle plate 3b, the first baffle plate 3a and the first baffle plate 3c are relatively higher in rigidity than the second baffle plate 3b.

Further, the first baffle plate 3a, 3c is assumed to be attached to the oil pan 2 (see FIG. 4) at five fastening points through the bolt holes 30a, 30b, 30c, 30d, 30e (see FIGS. 8A and 8B). In contrast, the second baffle plate 3b (see FIG. 2) is assumed to be attached to the oil pan 2 (see FIG. 4) at four fastening points through the bolt holes 30f, 30g, 30h, 30i (see FIG. 6).

Further, the first baffle plate 3a and the first baffle plate 3c are configured respectively such that the five fastening points to be fastened to the oil pan 2 (see FIG. 4) through the bolt holes 30a, 30b, 30c, 30d, 30e (see FIGS. 8A and 8B) are connected by the ribs 33 (see FIG. 8A) and the ribs 33c (see FIG. 8B). In contrast, the second baffle plate 3b (see FIG. 2) does not have any ribs formed to connect fastening points for the oil pan 2 (see FIG. 4).

Further, the first baffle plate 3a and the first baffle plate 3c are formed generally in the shape of a rectangle when viewed from above. In contrast, the second baffle plate 3b (see FIG. 2) has a shape with a cut-out central portion, specifically, a generally U-shaped configuration.

Unlike the first baffle plates 3a, 3c according to this embodiment, it is assumed that the first baffle plates 3a, 3c have a thickness equal to or lower than the thickness of the second baffle plate 3b (see FIG. 2). If the first baffle plates 3a, 3c based on this assumption are made of a material with a Young's modulus higher than a material constituting the second baffle plate 3b, the first baffle plate 3a and the first baffle plate 3c are relatively higher in rigidity than the second baffle plate 3b.

Although various methods for increasing the rigidity of the first baffle plates 3a, 3c than that of the second baffle plate 3b have been specifically exemplified, the method for increasing the rigidity of the first baffle plates 3a, 3c is not limited to these specific methods. Therefore, the rigidity of the first baffle plates 3a, 3c can be made higher than that of the second baffle plate 3b by appropriately selecting and/or combining mechanical structures, materials and the like of the first baffle plates 3a, 3c and the second baffle plate 3b, respectively.

In this embodiment, the first baffle plat 3a is prepared by the cut distance [%] of 40% (see FIG. 7B) and fastened, as seen in FIG. 4, to the five bolt bosses 20 of the shallow bottom portion 21, including the first to fifth bolt bosses 20a, 20b, 20c, 20d, 20e, using the bolts B3 (see FIG. 2).

In this embodiment, as seen in FIG. 4, the second baffle plate 3b is disposed to spaced apart from the first baffle plate 3a with a certain gap G formed therebetween. Further, the second baffle plate 3b is fastened to the four bolt bosses 20 of the deep bottom portion 22, including the sixth to ninth bolt bosses 20f, 20g, 20h, 20i, using the bolts B3 (see FIG. 2).

The gap G may be set to have an appropriate distance, without limitation, such that vibration is not transmitted between the first baffle plate 3a and the second baffle plate 3b and that the second baffle plate 3b constituting a U-shaped configuration is fastened to the above-described four bolt bosses 20.

Further, the gap G according to this embodiment is assumed to have a distance in the lateral direction (right-left direction). However, the gap G may be set such that the first baffle plate 3a and the second baffle plate 3b are spaced apart from each other in the vertical direction.

The baffle plates 3 are fastened to the oil pan 2 as described above, so that the first baffle plate 3a having a higher rigidity is fastened to the oil pan 2 at the joint portions 24 (see FIG. 4) for the transmission 4 (see FIG. 1).

Further, the second baffle plate 3b having a rigidity lower than that of the first baffle plate 3a is fastened to the oil pan 2 at the opposite side from the joint portions 24 in the longitudinal direction of the oil pan 2 and adjacent to the first baffle plate 3a.

Operational advantages of the internal combustion engine structure C in this embodiment are described below. The internal combustion engine structure C in this embodiment is configured such that a baffle plate 3 is divided into a plurality of baffle plates 3.

According to the internal combustion engine structure C, since the baffle plate 3 is divided into a plurality of baffle plates 3, characteristics of each of the baffle plates 3, such as rigidity and weight (mass) can be set individually. To be more specific, among components of the oil pan 2, the first baffle plate 3a having a relatively higher rigidity is disposed in a position where a higher rigidity is required. On the contrary, among the components of the oil pan 2, the second baffle plate 3b having a relatively lower rigidity is disposed in a position where a rigidity as high as the above-described position (where a higher rigidity is required) is not required.

According to this internal combustion engine structure C, as compared with an alternative configuration in which baffle plates 3 having a higher rigidity are evenly fastened to the oil pan 2, the second baffle plate 3b having a lower rigidity is disposed partly, so that the weight of the internal combustion engine structure C can be reduced while increasing the rigidity of the oil pan 2.

In this internal combustion engine structure C, the first baffle plate 3a having a relatively higher rigidity is disposed in the shallow bottom portion 21 where a higher rigidity is required. On the contrary, among the components of the oil pan 2, the second baffle plate 3b having a relatively lower rigidity is disposed in the deep bottom portion 22 where a rigidity as high as the above-described position (where a higher rigidity is required) is not required.

According to this internal combustion engine structure C, the weight thereof can be reduced at specific portions of the oil pan 2 while increasing the rigidity of the oil pan 2 in a more reliable manner.

Further, in this internal combustion engine structure C, among components of the oil pan 2, the first baffle plate 3a having a relatively higher rigidity is disposed in a position where a higher rigidity is required, that is, on the side of the joint portions 24 for the attachment of the transmission 4 (at a heavy-equipment joint portion). On the contrary, among the components of the oil pan 2, the second baffle plate 3b having a relatively lower rigidity is disposed in a position where a rigidity as high as the above-described position (where a higher rigidity is required) is not required (e.g., deep bottom portion 22).

In other words, according to the internal combustion engine structure C in this embodiment, the first baffle plate 3a having a higher rigidity and the second baffle plate 3b having a lower rigidity are arranged in accordance with rigidities required for the respective portions of the oil pan 2.

Further, in this internal combustion engine structure C, the second baffle plate 3b has the clearance 35 for the structural member.

According to this internal combustion engine structure C, the weight of the second baffle plate 3b can be reduced further.

Further, in this internal combustion engine structure C, the gap G is formed between the first baffle plate 3a and the second baffle plate 3b.

According to this internal combustion engine structure C, the first baffle plate 3a and the second baffle plate 3b do not contact with each other when the internal combustion engine main body 1 vibrates. This can prevent the internal combustion engine structure C from generating strange noise. Further, according to this internal combustion engine structure C, wear and damage of the first baffle plate 3a and the second baffle plate 3b due to contact thereof can be prevented.

Further, in this internal combustion engine structure C, the first baffle plate 3a has the ribs 33 formed to connect the bolt holes 30 serving as fastening points for the oil pan 2.

According to this internal combustion engine structure C, the rigidity of the first baffle plate 3a can be increased efficiently.

Further, in this internal combustion engine structure C, the lightened portions 34a, 34b are formed in the first baffle plate 3a at portions corresponding to the ribs 33.

According to this internal combustion engine structure C, the weight of the first baffle plate 3a can be reduced.

Although the present invention has been described with reference to the above-described embodiment and modification, the present invention is not limited to these specific embodiments. It is to be understood that various changes and modifications may be made without departing from the scope of the present invention.

For example, in the above-described embodiment, two baffle plates 3 including the first baffle plate 3a and the second baffle plate 3b are employed. However, three or more baffle plates 3 may be employed.

Further, in the above-described embodiment, the first baffle plate 3a is fastened to the bolt bosses 20 formed in the shallow bottom portion 21, and the second baffle plate 3b is fastened to the bolt bosses 20 formed in the deep bottom portion 22.

However, a part of the fastening points for the first baffle plate 3a and the second baffle plate 3b may be set to bolt bosses (not shown) formed in the intermediate portion 23.

Further, in the above-described embodiment, the first baffle plate 3a made of an aluminum-based material and the second baffle plate 3b made of an iron-based material have been described. However, in the internal combustion engine structure C, the first baffle plate 3a may be made of an iron-based material, and the second baffle plate 3b may be made of an aluminum-based material.

According to this internal combustion engine structure C, as compared with an alternative configuration in which baffle plates 3 made of an iron-based material and having a higher rigidity are evenly fastened to the oil pan 2, the second baffle plate 3b made of an aluminum-based material having a specific gravity lower than that of the iron-based material is disposed partly, so that the weight of the internal combustion engine structure C can be reduced while increasing the rigidity of the oil pan 2.

Further, because the aluminum-based material is more ductile than the iron-based material, the second baffle plate 3b having a lower rigidity can be advantageously made thinner.

Further, the rigidity of the first baffle plate 3a and the rigidity of the second baffle plate 3b may be adjusted in such a manner that the overall thickness of the first baffle plate 3a is increased or the thickness of the first baffle plate 3a is partly increased like the ribs, or that the thickness of the second baffle plate 3b is partly reduced to form a lightened portion. Accordingly, irrespective of the difference of the materials from which the first baffle plate 3a and the second baffle plate 3b are made, the rigidity of the first baffle plate 3a and the rigidity of the second baffle plate 3b can be adjusted only based on the difference in mechanical structures thereof.

Further, in the above-described embodiment, the iron-based material and the aluminum-based material are exemplified as materials for the baffle plates 3. However, the materials for the baffle plates 3 are not limited to these specific materials, and various other heat-resistant materials, such as a carbon fiber composite material including polyimide resin as a base material, may be used.

Further, in the above-described embodiment, the oil pan 2 is assumed to have the shallow bottom portion 21 and the deep bottom portion 22, between which a stepped portion having a relative height difference. However, the oil pan 2 may have an inclined bottom in which a height difference is continuously formed in the longitudinal direction.

According to the oil pan 2 including such an inclined bottom, the divided baffle plates 3 are arranged in the longitudinal direction of the oil pan 2. In this embodiment, if one of the divided baffle plates 3 is disposed, for example, on the lower side of the inclined bottom, the other divided baffle plate 3 is inevitably disposed on the higher side of the inclined bottom.

According to the oil pan 2 including this inclined bottom, the other baffle plate 3 is higher in rigidity (by using the first baffle plate 3a) and the one baffle plate 3 is lower in rigidity (by using the second baffle plate 3b).

STRUCTURE OF INTERNAL COMBUSTION ENGINE

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