Internal combustion engine

Abstract

Provided is an internal combustion engine. The internal combustion engine is provided with a first blow-by gas mixture passage sectioned in a second wall. The internal combustion engine is provided with a second blow-by gas mixture passage sectioned in a third wall. The internal combustion engine is provided with a third blow-by gas mixture passage sectioned in a fourth wall. The first to third blow-by gas mixture passages connect an oil chamber and an oil separator. The second wall is provided with a first communication passage. The fourth wall is provided with a second communication passage. The first communication passage connects a first crank chamber and a second crank chamber. The second communication passage connects a third crank chamber and a fourth crank chamber. The third wall does not have a passage connecting the second crank chamber and the third crank chamber.

Description

Technical Field

[0001] This disclosure relates to internal combustion engines. Background Technology

[0002] The internal combustion engine disclosed in Japanese Patent Application Publication No. 2020-067005 includes a crankshaft and four pistons. Furthermore, the internal combustion engine has four cylinders, four crankshaft chambers, and an oil chamber. Each cylinder houses a piston. The four cylinders are arranged along the axis of the crankshaft. The crankshaft chamber is the space for crankshaft rotation. Each of the four crankshaft chambers is connected to its corresponding cylinder. The oil chamber is the space for storing oil. The oil chamber is connected to the four crankshaft chambers on the side opposite to the cylinders. The internal combustion engine is divided into three connecting passages. Each connecting passage connects adjacent crankshaft chambers.

[0003] The internal combustion engine described in Japanese Patent Application Publication No. 2020-067005 has multiple blow-by mixture passages. These passages guide gas from the oil chamber to the oil separator. In such an engine, airflow is generated in the crankshaft chamber and oil chamber as the pistons reciprocate. When unexpected turbulence occurs in these chambers, excess oil may flow into the oil separator, or the oil may not be properly separated within the separator. Summary of the Invention

[0004] To address the aforementioned problems, according to a first aspect of this disclosure, an internal combustion engine is provided, comprising: a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder, arranged sequentially in a first direction along the axis of a crankshaft; a first crankshaft chamber, a second crankshaft chamber, a third crankshaft chamber, and a fourth crankshaft chamber, wherein the first crankshaft chamber is connected to the first cylinder, the second crankshaft chamber is connected to the second cylinder, the third crankshaft chamber is connected to the third cylinder, and the fourth crankshaft chamber is connected to the fourth cylinder; and an oil chamber, located on the side opposite to the cylinders, connected to the first crankshaft chamber, the second crankshaft chamber, the third crankshaft chamber, and the fourth crankshaft chamber. The second, third, and fourth crankshaft chambers are connected and store oil; a first piston, a second piston, a third piston, and a fourth piston, wherein the first piston reciprocates within the first cylinder, the second piston reciprocates within the second cylinder at a phase opposite to that of the first piston, the third piston reciprocates within the third cylinder at a phase opposite to that of the first piston, and the fourth piston reciprocates within the fourth cylinder at the same phase as that of the first piston; a first wall, a second wall, a third wall, a fourth wall, and a fifth wall, wherein the first wall divides the first crankshaft chamber from a second direction opposite to the first direction, the second wall separates the first crankshaft chamber from the second crankshaft chamber, the third wall separates the second crankshaft chamber from the third crankshaft chamber, the fourth wall separates the third crankshaft chamber from the fourth crankshaft chamber, and the fifth wall divides the fourth crankshaft chamber from the first direction; a first, second, and third cross-flow mixing passage, wherein the first cross-flow mixing passage is located within the second wall and connects the oil chamber to the oil separator. The second crankshaft mixing passage is partitioned within the third wall and connects the oil chamber to the oil separator; the third crankshaft mixing passage is partitioned within the fourth wall and connects the oil chamber to the oil separator; and a first connecting passage and a second connecting passage, the first connecting passage being partitioned within the second wall and connecting the first crankshaft chamber to the second crankshaft chamber; the second connecting passage being partitioned within the fourth wall and connecting the third crankshaft chamber to the fourth crankshaft chamber; the third wall does not have a passage connecting the second crankshaft chamber to the third crankshaft chamber. Attached Figure Description

[0005] Figure 1 It is a cross-sectional view of an internal combustion engine.

[0006] Figure 2 yes Figure 1 The sectional view at line 2-2 in the diagram.

[0007] Figure 3 yes Figure 1 The sectional view at line 3-3 in the diagram. Detailed Implementation

[0008] <Brief Structure of an Internal Combustion Engine>

[0009] The following is based on Figures 1-3 Here is an explanation of one embodiment of this disclosure. First, the general structure of the internal combustion engine 100 will be described. In addition, when referring to the front-back, left-right, and up-down directions in the following description, it refers to the direction observed from the driver sitting in the driver's seat of the vehicle when the internal combustion engine 100 is mounted on the vehicle.

[0010] like Figure 1 As shown, the internal combustion engine 100 includes an internal combustion engine body 10, multiple pistons 81, multiple connecting rods 82, a crankshaft 83, an intake manifold 91, and an exhaust manifold 92. The internal combustion engine body 10 includes a cylinder head cover 20, a cylinder head 30, a cylinder block 40, a crankcase 50, and an oil pan 60.

[0011] The cylinder block 40 is generally prism-shaped. It contains four cylinders 41. Each cylinder 41 is roughly cylindrical. The cylinders 41 extend from the top of the cylinder block 40 to near the center of the upper and lower parts of the cylinder block 40. The cylinders 41 are the spaces used for combustion of the fuel-air mixture. Figure 2 As shown, four cylinders 41 are arranged in a row along the axis of crankshaft 83. In this embodiment, the internal combustion engine 100 is a so-called inline four-cylinder engine. Furthermore, the crankshaft 83 extends to the left and right of the vehicle. In this embodiment, the internal combustion engine 100 is a so-called transversely mounted engine. Hereinafter, when referring to the four cylinders 41 collectively, they will simply be called cylinders 41. When referring to the four cylinders 41 separately, they will be called first cylinder 41A, second cylinder 41B, third cylinder 41C, and fourth cylinder 41D in order from right to left.

[0012] like Figure 1 As shown, piston 81 is located inside cylinder 41. Piston 81 is connected to crankshaft 83 via connecting rod 82. As the fuel-air mixture burns in cylinder 41, piston 81 reciprocates inside cylinder 41. Furthermore, the reciprocating motion of piston 81 rotates crankshaft 83. Corresponding to the four cylinders 41, internal combustion engine 100 includes four pistons 81 and four connecting rods 82. Hereinafter, when referring to the four pistons 81 collectively, they will simply be called piston 81. However, when distinguishing the four pistons 81, they will be referred to as first piston 81A, second piston 81B, third piston 81C, and fourth piston 81D in order from right to left.

[0013] In this embodiment, the internal combustion engine 100 performs its combustion stroke in the order of first cylinder 41A, third cylinder 41C, fourth cylinder 41D, and second cylinder 41B. Furthermore, each cylinder 41 repeatedly performs the intake stroke, compression stroke, combustion stroke, and exhaust stroke every two revolutions of the crankshaft 83. Therefore, when the first cylinder 41A is in its combustion stroke, the third cylinder 41C is in its compression stroke, the fourth cylinder 41D is in its intake stroke, and the second cylinder 41B is in its exhaust stroke. In other words, the second piston 81B and the third piston 81C reciprocate in the opposite phase to the first piston 81A. Conversely, the fourth piston 81D reciprocates in the same phase as the first piston 81A.

[0014] The cylinder block 40 has four upper spaces 42 as internal spaces. The upper spaces 42 are connected to the lower ends of the cylinders 41. The upper spaces 42 extend from the lower ends of the cylinders 41 to the lower ends of the cylinder block 40. The longitudinal dimension of the upper spaces 42 along the vehicle is larger than the longitudinal dimension of the cylinders 41 along the vehicle. The lateral dimension of the upper spaces 42 along the vehicle is smaller than the lateral dimension of the cylinders 41 along the vehicle. Hereinafter, when referring to the four upper spaces 42 collectively, they will only be called upper spaces 42. Furthermore, when describing the four upper spaces 42 separately, they will be referred to as first upper space 42A, second upper space 42B, third upper space 42C, and fourth upper space 42D in order from right to left.

[0015] like Figure 2 As shown, the cylinder body 40 includes a first upper wall 45A, a second upper wall 45B, a third upper wall 45C, a fourth upper wall 45D, and a fifth upper wall 45E as walls dividing the upper space 42. The first upper wall 45A divides the first upper space 42A from the right side. The second upper wall 45B separates the first upper space 42A from the second upper space 42B. The third upper wall 45C separates the second upper space 42B from the third upper space 42C. The fourth upper wall 45D separates the third upper space 42C from the fourth upper space 42D. The fifth upper wall 45E divides the fourth upper space 42D from the left side.

[0016] The cylinder block 40 has five upper recesses 49. Each upper recess 49 is recessed upwards from the lower surface of the cylinder block 40. The upper recesses 49 are located one by one within the first upper wall 45A to the fifth upper wall 45E. When the internal combustion engine 100 is viewed to the left, the five upper recesses 49 are located in the same position. When the internal combustion engine 100 is viewed to the left, the space defined by the upper recesses 49 is approximately semi-circular. The inner wall surface of the upper recesses 49 supports the crankshaft 83 from the upper side via a bearing (not shown). Furthermore, in... Figure 2 The simplified diagram of crankshaft 83 is shown in the figure.

[0017] like Figure 1As shown, the crankcase 50 is connected to the lower end of the cylinder block 40. The crankcase 50 has a so-called trapezoidal frame structure. Therefore, the crankcase 50 has four lower spaces 51 as internal spaces. The lower spaces 51 extend from the upper end to the lower end of the crankcase 50. The front-to-back dimensions of the lower spaces 51 are approximately the same as the front-to-back dimensions of the upper spaces 42. The left-to-right dimensions of the lower spaces 51 are approximately the same as the left-to-right dimensions of the upper spaces 42. The lower spaces 51 are connected to the lower ends of the upper spaces 42. Hereinafter, when referring to the four lower spaces 51 collectively, they will only be called lower spaces 51. Furthermore, when describing the four lower spaces 51 separately, as... Figure 2 As shown, in order from right to left, they are called the first lower space 51A, the second lower space 51B, the third lower space 51C, and the fourth lower space 51D.

[0018] like Figure 1 As shown, in this embodiment, the upper space 42 and the lower space 51 constitute the crankshaft chamber 12. Therefore, as Figure 2 As shown, the first upper space 42A and the first lower space 51A are the first crankshaft chamber 12A. The second upper space 42B and the second lower space 51B are the second crankshaft chamber 12B. The third upper space 42C and the third lower space 51C are the third crankshaft chamber 12C. The fourth upper space 42D and the fourth lower space 51D are the fourth crankshaft chamber 12D.

[0019] The crankcase 50 includes a first lower wall 55A, a second lower wall 55B, a third lower wall 55C, a fourth lower wall 55D, and a fifth lower wall 55E as walls dividing the lower space 51. The first lower wall 55A divides the first lower space 51A from the right side. The second lower wall 55B separates the first lower space 51A from the second lower space 51B. The third lower wall 55C separates the second lower space 51B from the third lower space 51C. The fourth lower wall 55D separates the third lower space 51C from the fourth lower space 51D. The fifth lower wall 55E divides the fourth lower space 51D from the left side.

[0020] In this embodiment, the first upper wall 45A and the first lower wall 55A are first walls 71 that divide the first crankshaft chamber 12A from the right side. The second upper wall 45B and the second lower wall 55B are second walls 72 that separate the first crankshaft chamber 12A from the second crankshaft chamber 12B. The third upper wall 45C and the third lower wall 55C are third walls 73 that separate the second crankshaft chamber 12B from the third crankshaft chamber 12C. The fourth upper wall 45D and the fourth lower wall 55D are fourth walls 74 that separate the third crankshaft chamber 12C from the fourth crankshaft chamber 12D. The fifth upper wall 45E and the fifth lower wall 55E are fifth walls 75 that divide the fourth crankshaft chamber 12D from the left side.

[0021] The crankcase 50 has five recesses 59 as internal spaces. Each recess 59 is recessed downwards from the upper surface of the crankcase 50. The recesses 59 are located one by one within the first lower wall 55A to the fifth lower wall 55E. When the internal combustion engine 100 is viewed to the left, the five recesses 59 are located in the same position. Furthermore, each recess 59 is vertically opposite to the upper recess 49 of the cylinder block 40. When the internal combustion engine 100 is viewed to the left, the space defined by the recesses 59 is approximately semi-circular in shape. The inner wall of the recesses 59 supports the crankshaft 83 from below via bearings (not shown).

[0022] like Figure 1 As shown, the oil pan 60 is connected to the lower end of the crankcase 50. The oil pan 60 is shaped like a roughly quadrangular box with a bottom. Therefore, the oil pan 60 has an oil chamber 61 as its internal space. The dimensions of the oil chamber 61 along the front and rear of the vehicle are approximately the same as the dimensions of the lower space 51 along the front and rear of the vehicle. The dimensions of the oil chamber 61 along the left and right of the vehicle are larger than the dimensions from the left end of the lower space 51 located at the left end of the vehicle to the right end of the lower space 51 located at the right end of the vehicle. The oil chamber 61 is connected to the lower ends of the four lower spaces 51. Therefore, when viewed from the crankcase 12, the oil chamber 61 is connected to the side opposite to the cylinder 41. The oil chamber 61 is capable of storing oil.

[0023] The cylinder head 30 is connected to the upper end of the cylinder block 40. The cylinder head 30 is generally prism-shaped. The cylinder head 30 has four intake ports 31, four exhaust ports 32, and four combustion recesses 33 as internal spaces. The combustion recesses 33 are recessed upwards from the lower surface of the cylinder head 30. The combustion recesses 33 are connected to the upper end of the cylinder 41. In addition, the combustion recesses 33, the cylinder 41, and the piston 81 divide the combustion chamber.

[0024] The first end of the air intake port 31 is connected to the combustion recess 33. The second end of the air intake port 31 opens on the front surface of the cylinder head 30. The intake pipe 91 is connected to the front surface of the cylinder head 30. The air intake port 31 introduces intake air from outside the internal combustion engine 100 into the cylinder 41 via the intake pipe 91. Additionally, in Figure 3 The diagram of air intake 31 is omitted in the image.

[0025] like Figure 1 As shown, the first end of the exhaust port 32 is connected to the combustion recess 33. The second end of the exhaust port 32 opens on the rear surface of the cylinder head 30. The exhaust pipe 92 is connected to the rear surface of the cylinder head 30. The exhaust port 32 discharges exhaust gas from the cylinder 41 to the outside of the internal combustion engine 100 via the exhaust pipe 92.

[0026] The cylinder head cover 20 is connected to the upper end of the cylinder head 30. The cylinder head cover 20 is roughly box-shaped with a top plate. Therefore, the cylinder head cover 20 has an internal space 21. The internal space 21 accommodates valve mechanisms (not shown).

[0027] <Structure of the mixture passage for cylinder blockage>

[0028] like Figure 1 and Figure 3 As shown, the crankcase 50 has three upstream passages 52 as its internal space. The upstream passages 52 extend from the upper end to the lower end of the crankcase 50. When viewed from the recess 59, the upstream passages 52 are located on the forward side. One of the upstream passages 52 is located within the second lower wall 55B. One of the upstream passages 52 is located within the third lower wall 55C. One of the upstream passages 52 is located within the fourth lower wall 55D. When viewing the internal combustion engine 100 to the left, the three upstream passages 52 are located in the same position. Hereinafter, when collectively referring to the three upstream passages 52, they will only be called upstream passages 52. Furthermore, when distinguishing the three upstream passages 52, they will be referred to as the first upstream passage 52A, the second upstream passage 52B, and the third upstream passage 52C in order from right to left.

[0029] The cylinder block 40 has three mid-stream passages 43 and three downstream passages 44 as its internal space. The mid-stream passages 43 extend from the lower end of the cylinder block 40 to near the upper and lower center of the cylinder block 40. The lower end of the mid-stream passage 43 connects to the upper end of the upstream passage 52. One of the mid-stream passages 43 is located within the second upper wall 45B. One of the mid-stream passages 43 is located within the third upper wall 45C. One of the mid-stream passages 43 is located within the fourth upper wall 45D. When viewing the internal combustion engine 100 to the left, the three mid-stream passages 43 are located in the same position. The downstream passages 44 extend from the upper end of the mid-stream passages 43 to the front surface of the cylinder block 40. Hereinafter, when collectively referring to the three mid-stream passages 43, they will only be called mid-stream passages 43. Furthermore, when distinguishing the three mid-stream passages 43, they will be referred to as the first mid-stream passage 43A, the second mid-stream passage 43B, and the third mid-stream passage 43C in order from right to left. Similarly, when collectively referring to the three downstream pathways 44, they are simply called downstream pathways 44. Furthermore, when distinguishing the three downstream pathways 44, they are referred to as the first downstream pathway 44A, the second downstream pathway 44B, and the third downstream pathway 44C, in order from right to left.

[0030] In this embodiment, the upstream passage 52, the midstream passage 43, and the downstream passage 44 constitute the cross-flow mixture passage 13. Therefore, the first upstream passage 52A, the first midstream passage 43A, and the first downstream passage 44A are the first cross-flow mixture passage 13A. The second upstream passage 52B, the second midstream passage 43B, and the second downstream passage 44B are the second cross-flow mixture passage 13B. The third upstream passage 52C, the third midstream passage 43C, and the third downstream passage 44C are the third cross-flow mixture passage 13C.

[0031] The internal combustion engine 100 includes an oil separator 95. The oil separator 95 is fixed to the front surface of the cylinder block 40. The oil separator 95 can separate the oil contained in the gas introduced into its interior. The oil separator 95 is connected to the downstream passage 44 of the cylinder block 40. Therefore, the oil separator 95 can introduce gas into the oil chamber 61 via the blow-by mixture passage 13. Furthermore, the gas after oil separation in the oil separator 95 flows into the internal space 21 of the cylinder head cover 20 via a connection passage (not shown). Figure 1 The simplified diagram in the image shows the oil separator 95.

[0032] like Figure 3 As shown, the crankcase 50 has a first recess 56 and a second recess 57 as internal spaces. The first recess 56 is recessed downward from the upper surface of the crankcase 50. When viewed from the lower recess 59, the first recess 56 is located on the front side. The first recess 56 is located within the second lower wall 55B of the second wall 72. The first recess 56 extends from the first crankshaft chamber 12A to the second crankshaft chamber 12B. Therefore, the space defined by the first recess 56 is the first connecting passage 56Z connecting the first crankshaft chamber 12A and the second crankshaft chamber 12B. The first connecting passage 56Z is also connected to the first blow-by mixture passage 13A. In this embodiment, the upper surface of the crankcase 50 is the connection surface between the cylinder block 40 and the crankcase 50.

[0033] The second recess 57 is recessed downwards from the upper surface of the crankcase 50. When viewed from the lower recess 59, the second recess 57 is located on the front side. The second recess 57 is located within the fourth lower wall 55D of the fourth wall 74. The second recess 57 extends from the third crankcase 12C to the fourth crankcase 12D. Therefore, the space defined by the second recess 57 is the second connecting passage 57Z that connects the third crankcase 12C and the fourth crankcase 12D. The second connecting passage 57Z is also connected to the third blow-by mixture passage 13C.

[0034] In this embodiment, when the internal combustion engine 100 is viewed to the left, the first connecting passage 56Z and the second connecting passage 57Z are located in the same position. Furthermore, the third wall 73 does not have a passage connecting the second crankshaft chamber 12B to the third crankshaft chamber 12C.

[0035] <The function of this implementation method>

[0036] Assume that during the driving process of the internal combustion engine 100, the second cylinder 41B enters its combustion stroke. At this time, the second piston 81B and the third piston 81C move downwards to approach the oil chamber 61. Under this movement, the pressure of the gas near the third wall 73 in the oil chamber 61 rises. Therefore, as... Figure 3 As indicated by the solid arrow, the gas near the third wall 73 in oil chamber 61 flows into the interior of oil separator 95 via the second cross-flow mixing passage 13B. As a result, the pressure inside oil separator 95 increases. Consequently, the gas inside oil separator 95 flows into the first crankshaft chamber 12A and into the vicinity of the second wall 72 in oil chamber 61 via the first cross-flow mixing passage 13A. Similarly, the gas inside oil separator 95 flows into the fourth crankshaft chamber 12D and into the vicinity of the fourth wall 74 in oil chamber 61 via the third cross-flow mixing passage 13C.

[0037] Furthermore, it is assumed that during the driving process of the internal combustion engine 100, the second cylinder 41B enters its exhaust stroke. At this time, the second piston 81B and the third piston 81C move upward to leave the oil chamber 61. During this movement, the pressure of the gas near the third wall 73 in the oil chamber 61 decreases. Therefore, as... Figure 3 As indicated by the double-dotted arrow, the gas inside the oil separator 95 flows through the second cross-flow mixing passage 13B to the vicinity of the third wall 73 in the oil chamber 61. As a result, the pressure inside the oil separator 95 decreases. Consequently, the gas in the first crankshaft chamber 12A and the gas near the second wall 72 in the oil chamber 61 flow into the oil separator 95 through the first cross-flow mixing passage 13A. Similarly, the gas in the fourth crankshaft chamber 12D and the gas near the fourth wall 74 in the oil chamber 61 flow into the oil separator 95 through the third cross-flow mixing passage 13C.

[0038] Thus, in the internal combustion engine 100, the assembly of the first piston 81A and the second piston 81B, and the assembly of the third piston 81C and the fourth piston 81D, reciprocate symmetrically with the third wall 73 as the boundary. Consequently, symmetrical airflow is generated in the space on the left side when viewed from the third wall 73 and the space on the right side when viewed from the third wall 73.

[0039] <Effects of this implementation method>

[0040] (1) Assume that the third wall 73 has a passage connecting the second crankshaft chamber 12B and the third crankshaft chamber 12C. In this case, gas can move between the second crankshaft chamber 12B and the third crankshaft chamber 12C via this passage. On the other hand, the second piston 81B and the third piston 81C reciprocate in the same phase. Therefore, ideally, the gas flow in the second crankshaft chamber 12B is the same as the gas flow in the third crankshaft chamber 12C. As a result, even though the third wall 73 has a passage connecting the second crankshaft chamber 12B and the third crankshaft chamber 12C, not a large amount of gas will flow through this passage. However, in reality, due to the slight difference between the gas flow in the second crankshaft chamber 12B and the gas flow in the third crankshaft chamber 12C, gas may sometimes flow through the passage of the third wall 73. Thus, due to the movement of gas through the passage of the third wall 73, the symmetrical airflow between the space on the left side when viewed from the third wall 73 and the space on the right side when viewed from the third wall 73 may not be generated. Furthermore, when the symmetry of gas flow is disordered as described above, it cannot be guaranteed that the gas will flow in the mixing passage 13 of each cylinder as designed.

[0041] In this embodiment, the third wall 73 does not have a passage connecting the second crankshaft chamber 12B and the third crankshaft chamber 12C. Therefore, gas will not move between the second crankshaft chamber 12B and the third crankshaft chamber 12C via the passage of the third wall 73. As a result, the symmetrical airflow between the space on the left side when viewed from the third wall 73 and the space on the right side when viewed from the third wall 73 is generated more reliably. As a result, turbulence generated in the space inside the internal combustion engine body 10 can be suppressed. In addition, if turbulence can be suppressed in this way, the excessive oil flowing into the oil separator 95 due to the increased oil content in the gas can be prevented. Furthermore, the oil contained in the gas can be properly separated in the oil separator 95.

[0042] (2) In this embodiment, the first connecting passage 56Z is also connected to the first cylinder block mixture passage 13A. Here, in the internal combustion engine 100, the first piston 81A and the second piston 81B reciprocate in opposite phases. Therefore, for example, when the second cylinder 41B reaches its combustion stroke, such as Figure 3 As indicated by the solid arrow, gas flows from the second crankshaft chamber 12B to the first crankshaft chamber 12A via the first connecting passage 56Z. On the other hand, for example, when the second cylinder 41B experiences its exhaust stroke, as... Figure 3As indicated by the double-dotted arrow, gas flows from the first crankshaft chamber 12A to the second crankshaft chamber 12B via the first connecting passage 56Z. This creates a regular gas flow within the first connecting passage 56Z, following the cycle of the reciprocating motion of the first piston 81A and the second piston 81B. That is, unintended turbulence is less likely to occur within the first connecting passage 56Z. Therefore, even if the first connecting passage 56Z is connected to the first cylinder head gas mixture passage 13A, turbulence generated within the first connecting passage 56Z can be suppressed from occurring in the first cylinder head gas mixture passage 13A. Of course, the gas flow within the first crankshaft chamber 12A and the second crankshaft chamber 12B actively promotes gas flow within the first cylinder head gas mixture passage 13A. Furthermore, although detailed explanation is omitted, the same applies to the second connecting passage 57Z.

[0043] (3) In this embodiment, when the internal combustion engine 100 is viewed from the left, the first connecting passage 56Z and the second connecting passage 57Z are located at the same position. Therefore, the gas flow in the space on the left side when viewed from the third wall 73 and the space on the right side when viewed from the third wall 73 is more likely to become more symmetrical. In this way, the more symmetrical the gas flow in the two spaces, the better it is possible to prevent the generation of unintended turbulence inside the internal combustion engine body 10.

[0044] (4) In this embodiment, the space defined by the first recess 56 functions as the first connecting path 56Z, and the space defined by the second recess 57 functions as the second connecting path 57Z. Therefore, compared to the case where the space defined by both the recesses of the cylinder block 40 and the crankcase 50 functions as the first connecting path 56Z, the first connecting path 56Z can be implemented with a simpler structure. The same applies to the second connecting path 57Z.

[0045] (5) Generally speaking, the structure of the cylinder block 40 tends to become more complex compared to the structure of the crankcase 50. In this respect, in this embodiment, the crankcase 50 has a first recess 56 and a second recess 57. Therefore, the relatively complex structure of the cylinder block 40 does not require a structure for implementing the first connecting passage 56Z and the second connecting passage 57Z. Thus, it is possible to prevent the structure of the cylinder block 40 from becoming further complex due to the first recess 56 and the second recess 57.

[0046] <Example of Change>

[0047] This embodiment can be implemented by modification as follows. This embodiment and the following modifications can be combined with each other within the scope of technical non-inconsistency.

[0048] In the above embodiment, the order in which the four cylinders 41 engage in the combustion stroke can be changed. For example, the internal combustion engine 100 can also be structured such that when the first cylinder 41A engages in the combustion stroke, the second cylinder 41B engages in the compression stroke, the fourth cylinder 41D engages in the intake stroke, and the third cylinder 41C engages in the exhaust stroke. That is, as long as the second piston 81B and the third piston 81C reciprocate with a phase opposite to that of the first piston 81A, and the fourth piston 81D reciprocates with a phase in the same direction as that of the first piston 81A, the order in which the four cylinders 41 engage in the combustion stroke can be changed.

[0049] In the above embodiments, the shapes of the first connecting path 56Z and the second connecting path 57Z can also be changed. For example, the first connecting path 56Z can also bypass the first crankshaft mixing passage 13A and connect the first crankshaft chamber 12A to the second crankshaft chamber 12B. Similarly, the second connecting path 57Z can also bypass the third crankshaft mixing passage 13C and connect the third crankshaft chamber 12C to the fourth crankshaft chamber 12D.

[0050] In the above embodiments, the positions of the first connecting passage 56Z and the second connecting passage 57Z can also be changed. For example, the first connecting passage 56Z may be located in front of or behind the second connecting passage 57Z. Additionally, for example, the first connecting passage 56Z may be located above or below the second connecting passage 57Z. That is, when viewing the internal combustion engine 100 to the left, the first connecting passage 56Z and the second connecting passage 57Z may not be located in the same position. Furthermore, the first connecting passage 56Z and the second connecting passage 57Z may not open on the upper surface of the crankcase 50, but may be located inside the crankcase 50. That is, the first connecting passage 56Z may also be a through hole penetrating the second lower wall 55B of the crankcase 50. Similarly, the second connecting passage 57Z may be a through hole penetrating the fourth lower wall 55D of the crankcase 50.

[0051] In the above embodiments, the components constituting the first connecting passage 56Z and the second connecting passage 57Z can also be modified. For example, the first connecting passage 56Z may be a space defined by the first recess 56 of the crankcase 50 and the recess of the cylinder block 40. Alternatively, for example, the first connecting passage 56Z may be a space defined only by the recess of the cylinder block 40. Moreover, for example, when the first connecting passage 56Z is defined only by the cylinder block 40, the first connecting passage 56Z may not open on the lower surface of the cylinder block 40, but may be located inside the cylinder block 40. That is, the first connecting passage 56Z may also be a through hole penetrating the second upper wall 45B of the cylinder block 40. Similarly, the components constituting the second connecting passage 57Z can also be modified.

[0052] In the above embodiment, a crankshaft cover may be used instead of a crankcase 50. In this case, the crankshaft cover functions as the first lower wall 55A to the fifth lower wall 55E.

[0053] In the above embodiments, the internal combustion engine 100 is not limited to an inline four-cylinder engine; for example, it can also be a V8 engine. That is, as long as the internal combustion engine 100 has four cylinders 41 arranged along the axis of the crankshaft 83, the technology of the present invention can be applied.

Claims

1. An internal combustion engine, comprising: The first cylinder, the second cylinder, the third cylinder, and the fourth cylinder are cylinders arranged sequentially in a first direction along the axis of the crankshaft; The system comprises a first crankshaft chamber, a second crankshaft chamber, a third crankshaft chamber, and a fourth crankshaft chamber, wherein the first crankshaft chamber is connected to the first cylinder, the second crankshaft chamber is connected to the second cylinder, the third crankshaft chamber is connected to the third cylinder, and the fourth crankshaft chamber is connected to the fourth cylinder. An oil chamber, which stores oil, is connected to the first crankshaft chamber, the second crankshaft chamber, the third crankshaft chamber, and the fourth crankshaft chamber on the side opposite to the cylinder. The system comprises a first piston, a second piston, a third piston, and a fourth piston. The first piston reciprocates within the first cylinder. The second piston reciprocates within the second cylinder at a phase opposite to that of the first piston. The third piston reciprocates within the third cylinder at a phase opposite to that of the first piston. The fourth piston reciprocates within the fourth cylinder at the same phase as that of the first piston. A first wall, a second wall, a third wall, a fourth wall, and a fifth wall, wherein the first wall divides the first crankshaft chamber from a second direction side opposite to the first direction, the second wall separates the first crankshaft chamber from the second crankshaft chamber, the third wall separates the second crankshaft chamber from the third crankshaft chamber, the fourth wall separates the third crankshaft chamber from the fourth crankshaft chamber, and the fifth wall divides the fourth crankshaft chamber from the first direction side; The system comprises a first cylinder-to-cylinder mixing passage, a second cylinder-to-cylinder mixing passage, and a third cylinder-to-cylinder mixing passage. The first cylinder-to-cylinder mixing passage is enclosed within the second wall and connects the oil chamber to the oil separator. The second cylinder-to-cylinder mixing passage is enclosed within the third wall and connects the oil chamber to the oil separator. The third cylinder-to-cylinder mixing passage is enclosed within the fourth wall and connects the oil chamber to the oil separator. A first connecting path and a second connecting path, the first connecting path being partitioned within the second wall and connecting the first crankshaft chamber and the second crankshaft chamber, the second connecting path being partitioned within the fourth wall and connecting the third crankshaft chamber and the fourth crankshaft chamber. The third wall does not have a passage connecting the second crankshaft chamber to the third crankshaft chamber. The internal combustion engine also features: The cylinder block is divided into the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder; A crankcase, connected to the cylinder block, and dividing the cylinder into a first crankshaft chamber, a second crankshaft chamber, a third crankshaft chamber, and a fourth crankshaft chamber; and An oil pan, connected to the crankcase, divides the oil chambers. One of the cylinder block and the crankcase includes: a first recess in the connecting surface between the cylinder block and the crankcase; and a second recess in the connecting surface. The space defined by the first recess is the first connecting path. The space defined by the second recess is the second connecting path. The first connecting passage is connected to the first cylinder mixing passage. The second connecting path is connected to the third cylinder mixing passage. When viewed in the first direction, the first connecting path and the second connecting path are located at the same position. The first piston and the second piston group and the third piston and the fourth piston group reciprocate symmetrically with the third wall as the boundary.

2. The internal combustion engine according to claim 1, wherein, The crankcase has a first recess and a second recess.

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