JP2008075631A - Multi-cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-cylinder engine capable of improving durability of a crankshaft bearing hole. <P>SOLUTION: When providing a side oil pathway 8 extending in a fore and aft direction in a lateral one side of a cylinder block 1, providing a first feed oil pathway 9 branched off from the side oil pathway 8 in a bearing wall 3, communicating a tip of the first feed oil pathway 9 with a bearing hole oil groove 10 formed on an inner circumference face of the crankshaft bearing hole 4, communicating an oil inlet of a bearing metal 5 with the bearing hole oil groove 10, communicating a metal oil groove formed on an inner circumference face of the bearing metal 5 with the oil inlet, providing a second feed oil pathway 13 led out from the bearing hole oil groove 10 in the bearing wall 3, and communicating a lead-out end of the second feed oil pathway 13 with an interlock shaft bearing hole 14 of a rotary interlock shaft provided in a lateral other side of the cylinder block 1, the bearing hole oil groove 10 is formed only on an inner circumference face of an upper half part of the crankshaft bearing hole 4, and an inner circumference face of a lower half part of the crankshaft bearing hole 4 is shaped into an arced curved face without an uneven part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-cylinder engine, and more particularly to a multi-cylinder engine that can increase the durability of a crankshaft bearing hole.

  As a conventional multi-cylinder engine, as in the present invention, a bearing wall is provided in the crankcase of the cylinder block, a crankshaft bearing hole is formed in the bearing wall, and a bearing metal is fitted in the crankshaft bearing hole. There is a metal bearing for the journal of the crankshaft (see, for example, Patent Document 1).

  However, the conventional multi-cylinder engine has a problem because the bearing hole oil groove is formed on the inner peripheral surface of the lower half of the crankshaft bearing hole.

Japanese Patent Laid-Open No. 6-74230 (see FIGS. 1 and 4)

The above prior art has the following problems.
<Problem> The crankshaft bearing hole has low durability.
Since the bearing hole oil groove is formed in the inner peripheral surface of the lower half of the crankshaft bearing hole, the contact area between the inner peripheral surface and the bearing metal is reduced, the surface pressure of the inner peripheral surface is increased, and the explosion occurs. This inner peripheral surface is easily damaged by pressure, and the durability of the crankshaft bearing hole is low.

  An object of the present invention is to provide a multi-cylinder engine that can solve the above-described problems, that is, a multi-cylinder engine that can improve the durability of a crankshaft bearing hole.

Invention specific matters of the invention according to claim 1 are as follows.
As illustrated in FIGS. 1 and 2, a bearing wall (3) is provided in the crankcase (2) of the cylinder block (1), and a crankshaft bearing hole (4) is formed in the bearing wall (3). In a multi-cylinder engine in which a bearing metal (5) is fitted into a crankshaft bearing hole (4) and the journal portion (7) of the crankshaft (6) is supported by the bearing metal (5),
The longitudinal direction of the crankshaft (6) is the longitudinal direction, the width direction of the cylinder block (1) is the lateral direction, and the axial direction of the cylinder (34) is the vertical direction. A side oil passage (8) extending to the side oil passage (8) is provided, a first oil supply passage (9) branched from the side oil passage (8) is provided in the bearing wall (3), and the tip of the first oil supply passage (9) is provided. Communicating with a bearing hole oil groove (10) formed in the inner peripheral surface of the crankshaft bearing hole (4);
The oil inlet (11) of the bearing metal (5) is communicated with the bearing hole oil groove (10), and the metal oil groove (12) formed on the inner peripheral surface of the bearing metal (5) is connected to the oil inlet (11). While communicating,
A second oil supply passage (13) led out from the bearing hole oil groove (10) is provided in the bearing wall (3), and a lead-out end portion (26) of the second oil supply passage (13) is connected to the cylinder block (1). When communicating with the interlocking shaft bearing hole (14) of the rotation interlocking shaft provided on the other side,
The bearing hole oil groove (10) is formed only on the inner peripheral surface of the upper half portion of the crankshaft bearing hole (4), and the inner peripheral surface of the lower half portion of the crankshaft bearing hole (4) is arcuate without any irregularities. A multi-cylinder engine characterized by a curved surface.

(Invention according to Claim 1)
<Effect> The durability of the crankshaft bearing hole can be enhanced.
As illustrated in FIG. 1, the bearing hole oil groove (10) is formed only on the inner peripheral surface of the upper half of the upper half and the lower half of the crankshaft bearing hole (4), and the crankshaft bearing Since the inner peripheral surface of the lower half of the hole (4) is an arcuate curved surface with no irregularities, the contact area between the inner peripheral surface of the lower half and the bearing metal (5) increases, and this lower half The surface pressure of the inner peripheral surface of the shaft is reduced, damage to the inner peripheral surface of the lower half due to explosion pressure is suppressed, and the durability of the crankshaft bearing hole (4) can be enhanced.

<Effect> Oil can be supplied to a plurality of bearing portions by a simple passage structure.
As illustrated in FIGS. 1 and 2, a side oil passage (8) extending in the front-rear direction is provided on one side of the cylinder block (1), and a first oil supply passage branched from the side oil passage (8) ( 9) is provided in the bearing wall (3), and the tip of the first oil supply passage (9) is communicated with a bearing hole oil groove (10) formed in the inner peripheral surface of the crankshaft bearing hole (4). The oil inlet (11) of the bearing metal (5) is communicated with the hole oil groove (10), and the metal oil groove (12) formed on the inner peripheral surface of the bearing metal (5) is communicated with the oil inlet (11). In addition, a second oil supply passage (13) led out from the bearing hole oil groove (10) is provided in the bearing wall (3), and the lead-out end of the second oil supply passage (13) is connected to the other side of the cylinder block (1). Since oil is communicated with the interlocking shaft bearing hole (14) of the rotation interlocking shaft provided on the side, oil can be supplied to the plurality of bearing holes (4) and (14) with a simple passage structure.

(Invention according to Claim 2)
In addition to the effect of the invention according to claim 1, the following effect is achieved.
<Effect> Oil leakage from the cylinder block is suppressed.
As illustrated in FIG. 1, the cylinder block (1) has a vertically divided structure including a block upper part (15) and a block lower part (16), and the upper part of the crankshaft bearing hole (4) is formed in the block upper part (15). The lower part of the block (16) is provided with the lower half of the crankshaft bearing hole (4), and the oil hole (10) in the bearing hole of the crankshaft bearing hole (4) is connected to the upper and lower parts of the block (15) (16). Since the length does not reach each mating surface (17), the oil in the bearing hole oil groove (10) does not easily enter between the mating surfaces (17) and (17) of the block upper and lower portions (15) and (16). Oil leakage from the cylinder block (1) is suppressed.

(Invention according to claim 3)
In addition to the effect of the invention according to claim 2, the following effect is achieved.
<Effect> Oil leakage from the cylinder block is suppressed.
As illustrated in FIG. 1, vertical bolt insertion holes (18) penetrating the mating surfaces (17) of the block upper and lower portions (15) and (16) of the cylinder block (1) are formed in the bearing wall (3). When connecting the block upper and lower portions (15) and (16) with the block fastening bolt (19) inserted through the bolt insertion hole (18), the lower opening (18a) of the bolt insertion hole (18) is connected to the crankcase ( 2) Since the oil is positioned in the bearing hole oil groove (10), the oil enters the bolt insertion hole (18) from between the mating surfaces (17) and (17) of the block upper and lower parts (15) and (16). However, this oil can only escape into the crankcase (2), and oil leakage from the cylinder block (1) is suppressed.

(Invention of Claim 4)
In addition to the effect of the invention according to claim 3, the following effect is achieved. << Effect >> The engine can be downsized.
As illustrated in FIG. 1, a bearing hole oil groove (10) is formed only in the upper half of the upper half and the lower half in the upper half of the crankshaft bearing hole (4), and the lower half Since the inner peripheral surface of the shaft is an arc-shaped curved surface without unevenness, the bolt insertion hole (18) can be brought close to the crankshaft bearing hole (4) without contacting the bearing hole oil groove (10), and the lateral width of the engine The engine can be downsized.

(Invention according to claim 5)
In addition to the effects of the invention according to any one of claims 1 to 4, the following effects are provided.
<Effect> The durability of the bearing metal can be increased.
As illustrated in FIG. 2, the bearing metal (5) has a vertically divided structure composed of a metal upper portion (30) and a metal lower portion (31), and the metal upper portion (31) of the metal upper portion (30) and the metal lower portion (31). The metal oil groove (12) is formed only on the inner peripheral surface of 30), and the inner peripheral surface of the metal lower portion (31) is an arcuate curved surface without irregularities. And the contact area between the crankshaft (6) and the journal part (7) is increased, the surface pressure of the inner peripheral surface of the lower metal part (31) is reduced, and damage to the lower metal part (31) due to explosion pressure is suppressed. Thus, the durability of the bearing metal (5) can be improved.

(Invention of Claim 6)
In addition to the effect of the invention according to claim 5, the following effect is achieved.
<Effect> The longitudinal dimension of the engine can be shortened.
As illustrated in FIG. 8, a part of the wall of each mating surface (32) of the metal upper part (30) and the metal lower part (31) is bent outward to form a detent locking part (20). When engaging the locking portion (20) with the engaging portion of the crankshaft bearing hole (4), the metal oil groove (12) is not long enough to reach the locking portion (20) of the upper metal portion (30). Therefore, even if the anti-rotation locking portion (20) and the metal oil groove (12) are close to each other in the front-rear width direction, they do not contact each other, which hinders the production of the bearing metal (5). Does not occur. For this reason, the front-rear width of the bearing metal (5) can be shortened, and the dimension in the front-rear direction of the engine can be shortened.

(Invention of Claim 7)
In addition to the effects of the invention according to any one of claims 1 to 6, the following effects are provided.
<Effect> Lubricating performance of each interlocking shaft bearing hole of the vertical rotation interlocking shaft housing chamber is enhanced.
As illustrated in FIG. 1, the branch oil passage (27) is branched from the middle of the second oil supply passage (13), and the tip end portion (26) of the second oil passage (13) is located above the side water passage (23). Is connected to the interlocking shaft bearing hole (14) of the upper rotation interlocking shaft accommodating chamber (21) disposed in the lower rotation interlocking shaft accommodating chamber (27) disposed below the side water channel (23). 22) is connected to the interlocking shaft bearing hole (28), and the leading end portion (26) of the second oil passage (13) is sandwiched between the side water passage (23) and the cylinder jacket (25) ( 1) is formed in the first wall (29), and the branch oil passage (27) is formed between the first wall (29) and the interlocking shaft bearing hole (28) of the lower rotation interlocking shaft accommodating chamber (22). Since it is formed in the second wall (33) of the cylinder block (1) sandwiched between them, it is supplied to the continuous coaxial bearing holes (14), (28) of the vertical rotation interlocking shaft accommodating chambers (21), (22). The oil to be used is the side water channel (8) and the cylinder jacket. The coolant is cooled by cooling water passing through the shaft (25), and the decrease in the viscosity of the oil is suppressed, and the lubrication performance of each interlocking shaft bearing hole (14) (28) of the vertical rotation interlocking shaft accommodating chamber (21) (22) is improved. Rise.

  Embodiments of the present invention will be described with reference to the drawings. 1 to 8 are diagrams for explaining a multi-cylinder engine according to an embodiment of the present invention. In this embodiment, a water-cooled vertical in-line four-cylinder diesel engine will be described.

The outline of the embodiment of the present invention is as follows.
As shown in FIG. 3, a cylinder head (35) is assembled to the upper part of the cylinder block (1), a head cover (36) is assembled to the upper part of the cylinder head (35), and an oil pan (37) is installed to the lower part of the cylinder block (1). ). As shown in FIG. 5, a front case (38) is attached to the front part of the cylinder block (1), and a timing gear train (39) and a flywheel (40) are arranged at the rear part of the cylinder block (1). . As shown in FIG. 7, the front case (38) includes a water pump (24) and an oil pump (41). As shown in FIG. 3, the rotation interlocking shaft and the fuel injection pump (42) are driven by the crankshaft (6) through the timing gear train (39). The rotation interlocking shafts are one valve camshaft (43) and three secondary rotation balancer shafts (44) (45) (46).

The outline of the crankshaft bearing structure is as follows.
As shown in FIG. 1, a bearing wall (3) is provided in the crankcase (2) of the cylinder block (1), a crankshaft bearing hole (4) is formed in the bearing wall (3), and the crankshaft bearing hole is formed. The bearing metal (5) is fitted into (4), and the journal portion (7) of the crankshaft (6) is supported by the bearing metal (5). The bearing wall (3) partitions the crankcase (2) for each cylinder (34).

The device for the crankshaft bearing structure is as follows.
As shown in FIG. 1, the cylinder block (1) has a crankshaft (6) erected in the front-rear direction, the cylinder block (1) in the width direction in the lateral direction, and the cylinder (34) in the axial direction. A side oil passage (8) extending in the front-rear direction is provided on the left side of the first oil passage, and a first oil passage (9) branched from the side oil passage (8) is provided in the bearing wall (3). The tip of 9) is communicated with a bearing hole oil groove (10) formed on the inner peripheral surface of the crankshaft bearing hole (4). The oil inlet (11) of the bearing metal (5) is communicated with the bearing hole oil groove (10), and the metal oil groove (12) formed on the inner peripheral surface of the bearing metal (5) is connected to the oil inlet (11). The second oil supply passage (13) led out from the bearing hole oil groove (10) is provided in the bearing wall (3), and the lead-out end portion (26) of the second oil supply passage (13) is a cylinder block. It communicates with the interlocking shaft bearing hole (14) of the rotation interlocking shaft provided on the right side of (1). In doing so, the bearing hole oil groove (10) is formed only on the inner peripheral surface of the upper half of the upper half and the lower half of the crankshaft bearing hole (4), and the crankshaft bearing hole ( 4) The inner peripheral surface of the lower half is an arcuate curved surface with no irregularities.

  As shown in FIGS. 2 (A) and 2 (B), there are two oil inlets (11) of the bearing metal (5) at the end of the first oil supply passage (9) and the start of the second oil supply passage (13), respectively. They are facing each other. As shown in FIG. 7, the oil pumped from the oil pump (41) is supplied to the side oil passage (8) through the oil cooler (47) and the oil filter (48).

The structure of the bearing hole oil groove is as follows.
As shown in FIG. 1, the cylinder block (1) has a vertically divided structure composed of a block upper part (15) and a block lower part (16), and the upper half part of the crankshaft bearing hole (4) is formed in the block upper part (15). The lower half of the block (16) is provided with the lower half of the crankshaft bearing hole (4), and the bearing hole oil groove (10) of the crankshaft bearing hole (4) is connected to each of the block upper and lower parts (15) and (16). The length does not reach the mating surface (17).

The cylinder block connection structure is as follows.
A vertical bolt insertion hole (18) penetrating each mating surface (17) of the block upper and lower portions (15), (16) of the cylinder block (1) is formed in the bearing wall (3), and this bolt insertion hole (18 In order to connect the block upper and lower portions (15) and (16) with the block fastening bolt (19) inserted through the bolt, the lower opening (18a) of the bolt insertion hole (18) is positioned in the crankcase (2). . When the bolt insertion holes (18) are arranged on the left and right sides of the crankshaft bearing hole (4), only the upper half of the upper half and the lower half of the upper half of the crankshaft bearing hole (4) are arranged. A bearing hole oil groove (10) is formed, and the inner peripheral surface of the lower half is an arcuate curved surface with no irregularities.

The structure of the bearing metal is as follows.
As shown in FIG. 2, the bearing metal (5) has a vertically divided structure composed of a metal upper part (30) and a metal lower part (31), and the metal upper part (30) of the metal upper part (30) and the metal lower part (31). The metal oil groove (12) is formed only on the inner peripheral surface of the metal lower part (31), and the inner peripheral surface of the metal lower part (31) is an arcuate curved surface having no irregularities. A portion of the wall near the mating surface (32) of the metal upper part (30) and the metal lower part (31) is bent outward to form a detent locking part (20), and this detent locking part (20) Is engaged with the engaging portion (not shown) of the crankshaft bearing hole (4). The metal oil groove (12) is formed over the entire length of the inner peripheral surface of the metal upper part (30). FIG. 8 shows a modified example of the bearing metal, in which the metal oil groove (12) is formed to a length that does not reach the wall near the mating surface (32) of the metal upper part (30), and the front and rear width of the bearing metal is shortened. Yes.

The lubrication structure of the rotation interlocking shaft bearing is as follows.
As shown in FIG. 1, a pair of rotation interlocking shaft accommodating chambers (21) and (22) are provided on the right side of the cylinder block (1), and the side interlocking channel extending in the front-rear direction through the rotation interlocking shaft accommodating chambers (21) and (22). The cooling water is disposed above and below (23), and the cooling water discharged from the water pump (24) is introduced into the cylinder jacket (25) of the cylinder block (1) through the side water channel (23). In doing so, the first branch oil passage (27) is branched from the middle of the second oil supply passage (13), and the outlet end portion (26) of the second oil passage (13) is connected to the side water passage (23). A lower rotation interlocking shaft that is communicated with the interlocking shaft bearing hole (14) of the upper rotation interlocking shaft accommodating chamber (21) disposed above and the first branch oil passage (27) is disposed below the side water passage (23). The lead-out end (26) of the second oil passage (13) was sandwiched between the side water passage (23) and the cylinder jacket (25) in communication with the interlocking shaft bearing hole (28) of the storage chamber (22). Formed in the first wall (29) of the cylinder block (1), the first branch oil passage (27) is connected to the first wall (29) and the interlocking shaft bearing hole of the lower rotation interlocking shaft housing chamber (22). (28) is formed in the second wall (33) of the cylinder block (1).

  As shown in FIG. 3, the first secondary rotation balancer shaft (44) is accommodated in the upper rotation interlocking shaft accommodation chamber (21). The valve drive camshaft (43) is housed in the lower rotation interlocking shaft housing chamber (22). A lowermost rotation interlocking shaft accommodating chamber (49) is disposed obliquely below the lower rotation interlocking shaft accommodating chamber (22), and the second secondary rotation balancer shaft (45) is accommodated therein. A side oil passage side rotation interlocking shaft accommodation chamber (50) is arranged on the left side of the cylinder block (1), and the third secondary rotation balancer shaft (46) is accommodated therein. As shown in FIG. 1, a second branch oil passage (51) is branched from the second oil supply passage (13), and the second branch oil passage (51) is then bearing hole of the lowest rotation interlocking shaft housing chamber (49). (52). A branch path (53) is branched from the first oil supply path (9), and the branch path (53) is communicated with the bearing hole (54) of the side oil path side rotation interlocking shaft accommodating chamber (50). As shown in FIGS. 5 and 6, the vertical rotation interlocking shaft accommodation chambers (21) and (22), the lowermost rotation interlocking shaft accommodation chamber (49), and the side oil passage side rotation interlocking shaft accommodation chamber (50) have both front and rear ends. Bearing holes are provided at three locations, i.e., the front and rear intermediate portions. As shown in FIG. 7, cooling water cooled by a radiator (not shown) is pumped and supplied to the side water channel (23) by a water pump (24). As shown in FIG. 4, the side water channel (23) passes by the side of each cylinder (34), and has a plurality of water channel outlets (55) at both ends and an intermediate part, and each water channel outlet (55) The cylinder jacket (25) is communicated with the laterally projecting end portion (56) of the cylinder wall of the cylinder (34). A tappet guide hole (57) is formed between adjacent water channel outlets (55) and (55). A transverse water channel (58) is formed between adjacent cylinders (34) and (34).

1 is a longitudinal front view of a cylinder block of a multi-cylinder engine according to an embodiment of the present invention. FIG. 2A is a front view of the upper part of the metal, FIG. 2B is a bottom view of the upper part of the metal, and FIG. 2C is a plan view of the lower part of the metal. FIG. 2 (D) is a front view of the lower part of the metal. 1 is a longitudinal front view of a multi-cylinder engine according to an embodiment of the present invention. It is a cross-sectional plan view of the cylinder block of FIG. FIG. 4 is a cross-sectional plan view of the engine of FIG. 3 including a side oil passage, a valve camshaft, and a lower right secondary rotation balancer shaft. FIG. 4 is a cross-sectional plan view of the engine of FIG. 3 including a left secondary rotation balancer shaft, a valve operating cam shaft, and an upper right secondary rotation balancer shaft. It is a schematic diagram of the engine of FIG. 3 which shows the flow of cooling water and oil. FIG. 8A is a front view of the upper part of the metal, FIG. 8B is a bottom view of the upper part of the metal, FIG. 8C is a plan view of the lower part of the metal, and FIG. D) is a front view of the lower part of the metal.

Explanation of symbols

(1) Cylinder block
(2) Crankcase
(3) Bearing wall
(4) Crankshaft bearing hole
(5) Bearing metal
(6) Crankshaft
(7) Journal Department
(8) Side oilway
(9) 1st oiling passage
(10) Bearing hole oil groove
(11) Oil inlet
(12) Metal oil groove
(13) Second oilway
(14) Interlocking shaft bearing hole
(15) Upper part of block
(16) Lower block
(17) Mating surface
(18) Bolt insertion hole
(18a) Lower opening
(19) Block fastening bolt
(20) Anti-rotation locking part
(21) Upper rotation interlocking shaft accommodation chamber
(22) Lower rotation interlocking shaft storage chamber
(23) Side waterway
(24) Water pump
(25) Cylinder jacket
(26) First branch oilway
(27) Second branch oilway
(28) Interlocking shaft bearing hole
(29) 1st wall
(30) Metal upper part
(31) Lower metal
(32) Mating surface

Claims (7)

A bearing wall (3) is provided in the crankcase (2) of the cylinder block (1), a crankshaft bearing hole (4) is formed in the bearing wall (3), and a bearing metal ( 5) In a multi-cylinder engine in which the journal (7) of the crankshaft (6) is bearing with the bearing metal (5),
The longitudinal direction of the crankshaft (6) is the longitudinal direction, the width direction of the cylinder block (1) is the lateral direction, and the axial direction of the cylinder (34) is the vertical direction. A side oil passage (8) extending to the side oil passage (8) is provided, a first oil supply passage (9) branched from the side oil passage (8) is provided in the bearing wall (3), and the tip of the first oil supply passage (9) is provided. Communicating with a bearing hole oil groove (10) formed in the inner peripheral surface of the crankshaft bearing hole (4);
The oil inlet (11) of the bearing metal (5) is communicated with the bearing hole oil groove (10), and the metal oil groove (12) formed on the inner peripheral surface of the bearing metal (5) is connected to the oil inlet (11). While communicating,
A second oil supply passage (13) led out from the bearing hole oil groove (10) is provided in the bearing wall (3), and a lead-out end portion (26) of the second oil supply passage (13) is connected to the cylinder block (1). When communicating with the interlocking shaft bearing hole (14) of the rotation interlocking shaft provided on the other side,
Of the upper half and lower half of the crankshaft bearing hole (4), the bearing hole oil groove (10) is formed only on the inner peripheral surface of the upper half, and the lower half of the crankshaft bearing hole (4). The multi-cylinder engine is characterized in that the inner peripheral surface of the is an arc-shaped curved surface without irregularities. The multi-cylinder engine according to claim 1,
The cylinder block (1) has an upper and lower divided structure composed of a block upper part (15) and a block lower part (16), and an upper half part of the crankshaft bearing hole (4) is provided in the block upper part (15). Is provided with a lower half portion of the crankshaft bearing hole (4), and the bearing hole oil groove (10) of the crankshaft bearing hole (4) extends to the mating surfaces (17) of the upper and lower blocks (15) and (16). A multi-cylinder engine characterized by having no length. The multi-cylinder engine according to claim 2,
A vertical bolt insertion hole (18) penetrating each mating surface (17) of the block upper and lower portions (15), (16) of the cylinder block (1) is formed in the bearing wall (3), and this bolt insertion hole (18 In order to connect the block upper and lower portions (15) and (16) with the block fastening bolt (19) inserted through the lower end (18a) of the bolt insertion hole (18), the lower opening (18a) is positioned in the crankcase (2). This is a multi-cylinder engine. The multi-cylinder engine according to claim 3,
When the bolt insertion holes (18) are arranged on the left and right sides of the crankshaft bearing hole (4), only the upper half of the upper half and the lower half of the upper half of the crankshaft bearing hole (4) are arranged. A multi-cylinder engine characterized in that a bearing hole oil groove (10) is formed and an inner peripheral surface of a lower half portion is an arcuate curved surface having no irregularities. The multi-cylinder engine according to any one of claims 1 to 4,
The bearing metal (5) has a vertically divided structure composed of a metal upper part (30) and a metal lower part (31), and only the inner peripheral surface of the metal upper part (30) of the metal upper part (30) and the metal lower part (31). A multi-cylinder engine characterized in that the metal oil groove (12) is formed, and the inner peripheral surface of the metal lower part (31) is an arcuate curved surface having no irregularities. The multi-cylinder engine according to claim 5,
A portion of the wall near the mating surface (32) of the metal upper part (30) and the metal lower part (31) is bent outward to form a detent locking part (20), and this detent locking part (20) Is engaged with the engaging portion of the crankshaft bearing hole (4),
A multi-cylinder engine characterized in that the metal oil groove (12) is formed to a length that does not reach the wall near the mating surface (32) of the metal upper part (30). The multi-cylinder engine according to any one of claims 1 to 6,
A plurality of rotation interlocking shaft accommodating chambers (21) and (22) are provided on the other side of the cylinder block (1), and the upper and lower sides of the side water channel (23) extending in the front-rear direction through the rotation interlocking shaft accommodating chambers (21) and (22). The cooling water discharged from the water pump (24) is introduced into the cylinder jacket (25) of the cylinder block (1) through the side water channel (23).
The branch oil passage (27) is branched from the middle of the second oil supply passage (13), and the lead-out end portion (26) of the second oil passage (13) is arranged above the side water passage (23). The interlocking shaft bearing hole of the lower rotation interlocking shaft accommodating chamber (22) is connected to the interlocking shaft bearing hole (14) of the shaft accommodating chamber (21), and the branch oil passage (27) is disposed below the side water passage (23). The first wall of the cylinder block (1) which is communicated with (28) and the leading end portion (26) of the second oil passage (13) is sandwiched between the side water passage (23) and the cylinder jacket (25). A cylinder block formed in (29) and having a branch oil passage (27) sandwiched between the first wall (29) and the interlocking shaft bearing hole (28) of the lower rotation interlocking shaft accommodating chamber (22). A multi-cylinder engine formed in the second wall (33) of (1).

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