JP3157175B2 - Engine block structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an engine block structure.

[0002]

2. Description of the Related Art Regarding the block structure of an engine,
Japanese Patent Application Laid-Open No. 2-108612 discloses that a scut portion of a cylinder block and a side portion of a bearing cap for supporting a crankshaft housed in the scut portion are fixed by bolts to increase the support rigidity of the crankshaft. There are disclosures of techniques that have been enhanced. Further, this publication discloses that the lower end surfaces of the bearing caps are connected by a beam made of a separate member.

[0003] On the other hand, today, attention has been paid to lightening of the engine, and the so-called short skirt is called the short skirt.
It is known to shorten the length of the girth portion and fasten a lower block made of, for example, aluminum to the lower end of the cylinder block body to form a crank chamber with the lower block. However, the lower block is conventionally
It is positioned as a member supporting the mission,
For this reason, the technology development is currently being studied from the standpoint of securing rigidity against power plant bending. To solve the problem of power plant bending, the rear end of the lower block faces the rear end. It is known that the shape gradually swells outward according to the following.

[0004]

By the way, in the case of a multi-cylinder engine, the ignition order is, for example, three after the first cylinder.
It is customary not to ignite adjacent cylinders one after another, such as the cylinder number. Therefore, a combination in which pistons of adjacent cylinders move in the same direction and a combination in which pistons of other adjacent cylinders move in the opposite direction are mixed.

On the other hand, in order to smoothly move the piston up and down, it is necessary to freely move the air corresponding to the stroke of the piston in the cylinder block. However,
As described above, the bearing cap that supports the crankshaft is disposed in the cylinder block, and this bearing cap is a factor that hinders the movement of the air. Of course, when the air does not move smoothly in the cylinder block, the piston performs a negative work, and the problem of pumping loss occurs. SUMMARY OF THE INVENTION An object of the present invention is to provide an engine block structure in which the problem of pumping loss does not occur due to the presence of a bearing cap.

[0006]

In order to achieve the above technical object, according to the present invention (claim 1), a cylinder block of a multi-cylinder engine comprises: a cylinder block main body having a cylinder bore; And a lower block fastened to the lower end of the skirt of the block body,
The skirt portion and the lower block form a crank chamber for housing a crankshaft, a part of a bearing portion of the crankshaft housed in the crank chamber is formed of a bearing cap, and a part of the crank chamber is formed. In an engine in which a partition wall is provided between adjacent cylinders in an inner space of the lower block to be formed, a crank chamber space of each adjacent cylinder is communicated between the bearing cap and the partition wall. The communication area of the communication part between the cylinders in which the pistons of the adjacent cylinders move in the same direction is greater than the communication area of the communication part between the cylinders in which the pistons of the adjacent cylinders move in the opposite direction. Is also made smaller. Specific embodiments of the first aspect are as described in the second and third aspects.

[0007]

[0008]

According to the first aspect of the invention, the communication area of the communication portion between the cylinders in which the piston moves in the same direction is made smaller than the communication area of the communication portion between the cylinders in which the piston moves in the opposite direction. Therefore, for example, the movement of the air accompanying the lowering of the piston moves smoothly to the cylinder side rising in the direction opposite to the moving direction of the piston of the cylinder. According to the second aspect of the present invention, as well as smoothing the movement of air in the cylinder block similarly to the first aspect of the present invention, the bearing cap is fixed to the lower block. The support rigidity of the bearing cap can be improved. According to the third aspect of the invention, the same operation as the second aspect can be more specifically obtained.

[0009]

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an engine body. The engine body 1 is a four-cycle reciprocating four-cylinder engine. A piston (not shown) is slidably inserted into a bore 2a of a cylinder block body 2. The reciprocating motion of the piston is transmitted to the crankshaft 4 via the connecting rod 3 and converted into a rotational motion.

The cylinder block main body 2 is made of cast iron, and the skirt portion 2b forming the crank chamber 5 is a so-called short skirt, and the height position of the lower end of the skirt portion 2b is substantially the same. The height is set at the rotation center 4a of the crankshaft 4. A lower block 6 is disposed at the lower end of the skirt portion 2b. The skirt portion 2b and the lower block 6 cooperate to form a substantial crank chamber 5, and the lower block 6 Oil pan 7 at the bottom
The lower block 6 and the oil pan 7 are fastened together by bolts 8. That is, the bolt 8 is inserted from the oil pan 7 side, and the lower block 6
And is fixed to (the lower end flange of) the cylinder block 2. The size of the oil pan 7 will be described later.

The lower block 6 will be described in detail with reference to FIGS. In this embodiment, the lower block 6 is made of aluminum (Al) to reduce its weight. The rear end 6a of the lower block 6 is gradually swelled downward and laterally toward the rear, so that a transmission (not shown) is attached to the rear end face 6b.

As shown in FIG. 2, the inner space of the lower block 6 includes four partition walls 9 spaced from the front side to the rear side (from right to left in FIG. 2).
, The space between the first partition wall 9 and the second partition wall 10 is defined as a crank space NO1 for the most cylinder,
The space between the second partition wall 10 and the third partition wall 11 is a crank space NO2 for the second cylinder, and the space between the third partition wall 11 and the fourth partition wall 12 is the crank space NO2 for the third cylinder. A space NO3 is provided, and a space between the fourth partition wall 12 and the rear end wall 6c of the lower block 6 is a crank space NO4 for the fourth cylinder (the left side in FIG. 2). The partition walls 9 to 12 are connected to each other by a partition wall plate portion 13, and a rib 1 is provided between the first partition wall 9 and the front end wall 6d of the lower block 6.
4, the space between the fourth partition wall 14 and the rear end wall 6c of the lower block 6 is connected by the bottom plate 6f of the lower block 6, and the partition walls 9 to 14 are formed by these elements 13, 14 and the like. 12 are suppressed.

The plate 13 between the partition walls is provided with an oil return hole as shown by reference numeral 13a in FIG. 2 and passes through the oil return hole 13a to be the first to third cylinder. Oil in the cylinder crank spaces NO1 to NO3 is returned to the oil pan 7. An opening 13b is formed in the plate 13, and the opening 13b communicates the crank spaces NO1 to NO3 for the first to third cylinders with the space in the oil pan 7. This opening 13b
Are provided on both sides of the lower block 6 (both sides of the plate 13), and the crank spaces NO1 to NO3 of the first to third cylinders are provided.
The mist-like oil in the NO 3 is returned to the space inside the oil pan 7 through the opening 13b.

That is, as the pistons of the first to third cylinders descend, the air in the crank spaces NO1 to NO3 is pushed out to the space in the oil pan 7, and together with the movement of the air in the crank space, ~ Crank space of the third cylinder
Mist oil in NO1 to NO3 is returned to the space in the oil pan 7. The oil stored in the oil pan 7 is pumped by an oil pump (not shown), and the pumped oil is guided to each sliding portion. In FIG. 2, reference numeral 15 denotes an oil strainer, and the oil purified by the oil strainer 15 is guided to the oil pump through an oil feed pipe 16.

The oil pan 7 has a longitudinal dimension from the front end of the lower block 6 to the third cylinder NO3 in relation to a transmission mounting portion 6b formed at the rear end of the lower block 6. Accordingly, as shown in FIG. 5, the seat 6g for mounting the oil pan of the lower block 6 has its rear end located in front of the third partition wall 11 close to the third partition wall 11. The rear end of the lower block 6 (the above-described downwardly and laterally swelling portion) is a portion where the fourth cylinder is located.

The partition walls 9 and 1 except for the third partition wall 11
As shown in FIGS. 2 to 5, a bolt insertion hole 18 extending in the vertical direction is formed at the center of the rear end wall 6c of the lower block 6 in the longitudinal direction. Two partition walls 9, 10, 12 and a rear end wall 6 c of the lower block 6 are provided at intervals in the longitudinal direction.

A bolt 19 is inserted into the bolt insertion hole 18 from below, and the tip of the bolt 19 is screwed into a screw hole (not shown) formed on the lower surface of the bearing cap 20. The lower block 6 and the bearing cap 20 are integrated by the bolt 19 on the inner side of the bolt 20b for fastening the bearing cap 20 and a bearing (not shown) of the cylinder block body 2. As is known, the bearing cap 20 constitutes a part (lower half) of the bearing portion of the crankshaft 4.
Is usually made of cast iron.

The first of the bearing caps 20
The bearing cap 20 disposed on the partition wall 9, the third partition wall 11, and the rear end wall 6 c of the lower block 6 has its side part integrated with the lower block 6.

That is, as shown in FIG. 3, the first partition wall 9, the third partition wall, and the rear end wall 6c have lateral through holes 2 opening in the side walls 6e of the lower block 6 and extending in the left-right direction.
The slide bush 22 is inserted into the horizontal through hole 21. On the other hand, the bearing cap 20 (the bearing cap provided on the first and third partition walls 9 and 11 and the rear end wall 6c of the lower block 6) is
A boss portion 20a protruding outward is provided on the side portion, and a screw hole (not shown) is formed in the boss portion 20a. The tip of the bolt 23 inserted into the slide bush 22 is screwed into a screw hole formed in the boss 20a, whereby the side wall 6e of the lower block 6 and the side of the bearing cap 20 are integrated. Has been

That is, the bearing cap 20 disposed corresponding to the first and third partition walls 9 and 11 and the rear end wall 6c has its side portion integrated with the lower block 6 (the first end). The bearing cap 20 disposed on the first partition wall 9 and the rear end wall 6c is also integrated with the lower block 6 at the lower part thereof, while the second and fourth partition walls 10, 12 are provided. As shown in FIG. 4, the bearing cap 20 </ b> A is not provided with the boss portion 20 a on its side, and only the lower portion is integrated with the lower block 6.

With the above configuration, the bearing cap 2
Since the reference numeral 0 is fixed to the lower block 6, the support rigidity of the bearing cap 20 can be improved without using a separate beam as in the prior art. In particular, in the bearing cap 20 with a boss, the side portion is fixed to the lower block 6 and is pressed from the side by the lower block 6, so that the occurrence of cracks in the bearing cap 20A can be prevented. It becomes possible. In particular, the bearing cap 20 disposed on the first partition wall 9 and the rear end wall 6c is also integrated with the lower block 6 at its lower part, and is pressed down by the lower block 6 from below. Therefore, the occurrence of cracks in the bearing cap 20 can be more effectively prevented.

Further, since the slide bush 22 is interposed for fixing the side portion of the bearing cap 20, the dimensional error of the bearing cap 20A and the like can be absorbed by the slide bush 22. There is no loss of sex.

A space 25 formed between the bossed bearing cap 20 and the partition wall 9 and the like (hereinafter referred to as a bossed space; see FIG. 3) and a space between the bossless bearing cap 20A and the partition wall 10 and the like. The space 26 formed by
(Hereinafter referred to as a boss-free space; see FIG. 4), the boss-free space 26 is at least the boss portion 2.
Since the space 0a does not exist, the space is larger than the space 25 with the boss.

The difference in size between the bossed space 25 and the bossless space 26 means the following. As described above, the second partition wall 10 on which the bossless bearing cap 20A is disposed partitions between the crank space NO1 for the first cylinder and the crank space NO2 for the second cylinder. Therefore, the boss-free space 26 constitutes a communicating portion that communicates between the crank spaces NO1 and NO2. Similarly, the bossless space 2 of the fourth partition wall 12
Numeral 6 constitutes a communicating part which communicates between the third cylinder crank space NO3 and the fourth cylinder crank space NO4. On the other hand, the space 2 with the boss of the third partition 11
Reference numeral 5 designates a communicating portion which communicates between the crank space NO2 for the second cylinder and the crank space NO3 for the third cylinder. The NO2-NO3 communicating portion 25 includes the NO1-NO2 and NO3- The passage effective area is smaller than that of the NO4 communication portion 26.

By the way, when the ignition order of the engine body 1 is indicated by the cylinder number, NO1 (first cylinder) -NO3 (third cylinder) -NO4 (fourth cylinder) -NO2 (second cylinder) Cylinder). Therefore, the piston of the first cylinder NO1 and the piston of the fourth cylinder are in the same direction (for example, ascending).
, The piston of the second cylinder NO2 and the piston of the third cylinder NO3 move in the same direction (for example, descend). In other words, the pistons of the first cylinder NO1 and the second cylinder NO2, and the third cylinder NO3 and the fourth cylinder NO4 sandwiching the bossless communication portion 26 having the large passage effective area have the pistons move in opposite directions. On the other hand, the pistons of the second cylinder NO2 and the third cylinder NO3 sandwiching the communication portion 25 with the boss having a small effective passage area move in the same direction.

Therefore, for example, the air in the second and third crank spaces NO2 and NO3 passes through the communicating portion 26 having a large effective passage area as the piston of the corresponding cylinder descends. The air in the third space NO2 (air for the stroke of the piston) smoothly moves to the first space NO1 (the piston moves up), and the air in the third space NO3 moves to the fourth space NO4 (the piston (Ascending movement). Therefore, the upward movement or the downward movement of the piston is not hindered by the air in the crank space, and the negative work (pumping loss) caused by the air in the crank space hindering the movement of the piston is reduced. can do.

In particular, the crank space NO4 for the fourth cylinder is
As described above, since the opening is defined by the bottom plate portion 6f of the lower block 6 and is not directly communicated with the space inside the oil pan 7 (like the other crank space NO3, the opening communicating with the oil pan 7). Since the portion 13b does not exist), the fourth cylinder crank space NO4 is communicated with the third cylinder crank space NO3 through the large communication portion 26, thereby forming the fourth cylinder NO4. Pumping loss can be reduced.

FIG. 6 shows the lower block 6 viewed from the side. The side wall 6e of the lower block 6
It is formed of pillars 31 and ribs 32 arranged side by side at intervals. Then, bolts 8 for fastening the lower block 6 and the cylinder block body 2 to the column 31 are provided.
Insertion holes are formed. The ribs 32 are arranged in a cross shape to increase the torsional rigidity of the lower block 6. In the thin plate portion 30, the thin plate portion 30 is not provided in the portion 33 facing the crank space NO3 of the third cylinder and the portion 34 facing the crank space NO4 of the fourth cylinder. That is, the portions 33 and 34 are open portions opened to the side of the lower block 6.

The open portions 33 and 34 correspond to these portions 3
In order not to impair the communication relationship between the lower block 3 and the lower block 6, the lower block 6 is covered by a plate member 35, for example. That is, the plate member 35 is fixed to the side wall 6e of the lower block 6 using a bolt (not shown). The bolt is screwed into a screw hole (formed on the side wall 6e of the lower block 6) indicated by reference numeral 36 in FIG.

With the above configuration, the third cylinder crank space NO3 and the fourth cylinder crank space NO4 are formed on the sides of the lower block 6 by the plate members 35 passing through the open portions 33 and 34. Are communicated with each other through the passage. Thereby, regarding the fourth cylinder NO4, it is possible to further reduce the pumping loss of the fourth cylinder together with the communication part 26.

The open portions 33 and 34 and the plate member 35 may be provided only on one side wall 6e of the lower block 6, or may be provided on both sides 6e of the lower block 6.
6e. Further, the plate member 35 also functions as a reinforcing member for the lower block 6 (improving the bending rigidity of the lower block 6). Such a reinforcing function can be easily adjusted by changing the material or plate thickness of the plate member 35, or can be adjusted by forming a bead on the plate member 35. It is.

Referring to FIGS. 5 and 7, lower block 6 will be described.
The rear end 6a will be described. As described above, the rear end 6a of the lower block 6 has a shape that bulges laterally and downward from the fourth partition wall 12 toward the rear end 6b of the lower block 6. The swelling shape at the rear end 6a of the lower block 6 ensures the rigidity of the lower block 6 (cylinder block 2) including the transmission with respect to power plant bending.

Then, the rear end 6a of the lower block 6
In each of the lower portions, a plurality of ribs 40 are formed on both sides of the lower portion to connect between the oil pan mounting seat 6g and the rear end wall 6c of the lower block 6. Further, a concave portion 41 opening downward is formed in a central portion sandwiched between the portions (the above both side portions) where the ribs 40 are formed, and the concave portion 41 and the side where the ribs 40 are formed are formed. The portion is partitioned by a second rib 42 extending between the oil pan mounting seat 6g and the rear end wall 6c of the lower block 6. The length of the bolt insertion hole 18 formed in the fourth partition wall 12 and the rear end wall 6c of the lower block 6 is reduced by the recess 41 so that the bolt insertion hole 18 formed in the other partition wall 11 or the like is inserted. The length of the hole 18 is the same as that of the hole 18.

With the above arrangement at the rear end 6a of the lower block 6, first, the ribs 40 and 41
Rear end wall 6 of lower block 6 to which the mission is attached
c is connected to the fourth partition wall 12 in a rigid relationship. Accordingly, the rigidity of the rear end wall 6c of the lower block 6, which is directly affected by the power plant, is increased, and the suppression of the power plant bending or the generation of abnormal noise due to the power plant bending is suppressed. Can be.

Further, the bolt insertion hole 1 formed in the fourth partition wall 12 and the rear end wall 6c of the lower block 6 is formed.
8 is the same as the length of the bolt insertion hole 18 formed in the other partition wall 11 and the like, the fourth partition wall 12 and the rear end wall 6c of the lower block 6 are formed.
, The support rigidity of the bearing cap 20 disposed at the bottom can be improved.

That is, when the lower portion of the bearing cap 20 is to be bolted without forming the concave portion 41, the bolt 19 having a large shaft length is reduced by the amount by which the rear end 6a of the lower block 6 bulges downward. Must be used. On the other hand, in the present embodiment, the formation of the recess 41 makes it possible to use the bolt 19 having a short shaft length, and shortening the bolt 19 increases the support rigidity of the bearing cap 20. can do.

[0038]

As is apparent from the above description, according to the first to third aspects of the present invention, the movement of air in the cylinder block is not hindered by the presence of the bearing cap, so that the problem of pumping loss is solved. be able to. Further, according to the second and third aspects of the present invention, the support rigidity of the bearing cap can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a lower half of an engine body.

FIG. 2 is a plan view of the lower block as viewed from above.

FIG. 3 is a sectional view taken along the line III-III shown in FIG. 2;

FIG. 4 is a sectional view taken along the line IV-IV shown in FIG. 2;

FIG. 5 is a bottom view of the lower block as viewed from below.

FIG. 6 is a side view of the lower block as viewed from the side.

FIG. 7 is a sectional view taken along the line VII-VII shown in FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder block main body 2a Cylinder bore 4 Crankshaft 5 Crank chamber 6 Lower block 9-12 Partition wall 18 Bolt insertion hole formed in partition wall 19 Bolt 20 Bearing cap 20a Boss part 20A Bearing cap without boss 23 Bolt 25 Boss 26 Space between bearing cap with cap and partition wall 26 Space between bearing cap without boss and partition wall

Claims (3)

(57) [Claims] 1. A cylinder block of a multi-cylinder engine,
The cylinder block body having a cylinder bore, and a lower block fastened to the lower end of the skirt portion of the cylinder block body, the skirt portion and the lower block to form a crank chamber for accommodating a crankshaft, A part of the bearing portion of the crankshaft housed in the crank chamber is constituted by a bearing cap , and
Internal space of the lower block forming a part of the rank chamber
In an engine provided with a partition wall between adjacent cylinders, an adjacent engine is provided between the bearing cap and the partition wall.
The communication part that communicates the crankcase space of each cylinder
Between the cylinders in which the pistons of adjacent cylinders move in the same direction.
The communication area of the communication portion is such that the piston of the adjacent cylinder is reversed.
Smaller than the communication area of the communication part between the cylinders moving in the direction
A block structure of an engine, characterized by being cut down . 2. The bearing cap according to claim 1, wherein, among the bearing caps, a bearing cap between cylinders in which pistons of adjacent cylinders move in the same direction is fixed to the lower block, and a piston of an adjacent cylinder is fixed to the lower block. A bearing cap between cylinders moving in opposite directions, a lower portion of which is fixed to the lower block, an engine block structure. 3. The bearing cap according to claim 2, wherein the bearing cap between the cylinders in which the pistons of the adjacent cylinders move in the same direction includes a boss protruding laterally on a side thereof. An engine block structure, wherein a side portion of the bearing cap is fixed to the lower block by connecting the lower cap to the lower block.