Passage structure in an internal combustion engine

Abstract

To provide a passage structure in an internal combustion engine capable of improving the flexibility of design of a passage.SOLUTION: A passage structure of an internal combustion engine is equipped with a shaft that can rotate around a rotation axis, a rotator that is attached to the shaft, a wall portion that is provided with a hole through which the shaft passes, on which the hole opens, and that turns to the rotator, and a cover that is attached to the wall portion and covers at least a part of the side surface. One of the wall portion and the cover is provided with a groove blocked by the other of the wall portion and the cover. The groove has a first end portion communicating to an upper passage located above the shaft, and a second end portion opening outside the wall portion and the cover under the shaft. A fluid can passe through the groove between the first end portion and the second end portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a passage structure in an internal combustion engine. [Background technology]

[0002] An internal combustion engine is provided with various passages such as a passage for oil, a passage for air-fuel mixture, a passage for air, a passage for blow-by gas, etc. These passages are provided inside a member such as a cylinder block. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-55585 Summary of the Invention [Problem to be solved by the invention]

[0004] The passages are formed inside the component, for example, by a mold during casting or by a drill after casting. The portion of the component that has the strength and thickness to form the passages is limited. In other words, when the passages are formed inside the component, the degree of freedom in designing the passages is reduced.

[0005] The present invention has been made in view of the above, and has an object to provide a passage structure in an internal combustion engine that allows for an increased degree of freedom in designing the passages. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the object, the passage structure in an internal combustion engine according to the present invention comprises: Each Rotatable around the axis of rotation Two a shaft; Two attached to the shaft Two a rotating body; Two The shaft passes through Two A hole is provided, and Two The hole opens and the Two a wall portion having a side surface facing a rotating body; and a cover attached to the wall portion and covering at least a part of the side surface, wherein one of the wall portion and the cover is provided with a groove that is closed by the other of the wall portion and the cover, and the groove is Two a first end communicating with an upper passage located above the shaft; Two a second end portion that is open to the outside of the wall portion and the cover below the shaft, The upper passage is disposed between the two holes in the lateral direction, and the cross-sectional area of ​​the groove is formed to be larger than the cross-sectional area of ​​the upper passage; Fluid can pass through the groove between the first end and the second end.

[0007] According to this configuration, by closing the groove with the wall or cover, the groove forms a passage through which fluid can pass between the upper passage located above the shaft and the space located below the shaft (outside the wall and cover). This makes it easier to provide a passage in an internal combustion engine compared to when a passage is provided inside a wall. For example, by forming a passage with a closed groove, the degree of freedom in designing the passage is improved compared to when a passage is provided inside a wall.

[0008] In the passage structure for an internal combustion engine according to the present invention, the groove and the rotor are aligned in a radial direction perpendicular to the rotation axis.

[0009] According to this configuration, the groove fits into the space (dead space) created by the rotor being disposed on the outside of the side surface, and an increase in the length of the internal combustion engine in the axial direction can be suppressed.

[0010] In the passage structure for an internal combustion engine according to the present invention, the cover covers the rotating body.

[0011] According to this configuration, the cover serves both as a cover having or covering the groove and a cover covering the rotating body, which eliminates the need for the internal combustion engine to have separate covers for the groove or covering the groove and the rotating body, thereby suppressing increases in costs. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a passage structure in an internal combustion engine that allows for an increased degree of freedom in the design of passages. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a bottom view showing a part of an internal combustion engine according to a first embodiment. [Figure 2] FIG. 2 is a side view showing a part of the internal combustion engine of the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing a part of the internal combustion engine of the first embodiment taken along line F3-F3 in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a part of the internal combustion engine of the first embodiment taken along line F4-F4 in FIG. [Figure 5] FIG. 5 is a cross-sectional view that schematically shows a part of an internal combustion engine according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) The first embodiment will be described below with reference to FIGS. 1 to 4. In this specification, components according to the embodiment and descriptions of the components may be described using multiple expressions. The components and their descriptions are merely examples and are not limited by the expressions in this specification. The components may also be identified by names different from those in this specification. Furthermore, the components may also be described using expressions different from those in this specification.

[0015] FIG. 1 is a bottom view showing a portion of an internal combustion engine 10 according to a first embodiment. FIG. 2 is a side view showing a portion of the internal combustion engine 10 according to the first embodiment. The internal combustion engine 10 is, for example, a reciprocating engine mounted on a vehicle. Note that the internal combustion engine 10 may be another type of internal combustion engine, or may be mounted on another device.

[0016] As shown in the drawings, for convenience, the X-axis, Y-axis, and Z-axis are defined in this specification. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The X-axis is aligned along the width of the vehicle. The Y-axis is aligned along the length of the vehicle. The Z-axis is aligned along the height of the vehicle.

[0017] Furthermore, in this specification, the X direction, Y direction, and Z direction are defined. The X direction is a direction along the X axis, and includes the +X direction indicated by the X axis arrow and the -X direction opposite to the X axis arrow. The Y direction is a direction along the Y axis, and includes the +Y direction indicated by the Y axis arrow and the -Y direction opposite to the Y axis arrow. The Z direction is a direction along the Z axis, and includes the +Z direction indicated by the Z axis arrow and the -Z direction opposite to the Z axis arrow.

[0018] In the following description, the +Z direction is defined as the vertically upward direction, and the -Z direction is defined as the vertically downward direction. Note that the Z direction may differ from the vertical direction depending on various conditions such as the location of the vehicle and the condition of the tires.

[0019] As shown in FIG. 2, the internal combustion engine 10 has a cylinder block 11, a crankcase 12, an oil pan 13, a crankshaft 14, a crank gear 15, a balance shaft 16, and a balance gear 17. Also, as shown in FIG. 1, the internal combustion engine 10 further has a cover 18. Note that the internal combustion engine 10 is not limited to this example. Also, in FIG. 2, the cover 18 is omitted. The crankshaft 14 or the balance shaft 16 is an example of a shaft. The crank gear 15 or the balance gear 17 is an example of a rotating body.

[0020] The cylinder block 11, crankcase 12, oil pan 13, crankshaft 14, crank gear 15, balance shaft 16, and balance gear 17 are made of, for example, metal. The cover 18 may be made of metal or other materials such as synthetic resin.

[0021] The cylinder block 11 of this embodiment is a single member (monoblock) in which a general cylinder block and a cylinder head are integrated together, but the cylinder block 11 is not limited to this example.

[0022] Two cylinders 21 aligned in the Y direction are provided in the cylinder block 11. Each of the two cylinders 21 is a substantially cylindrical space extending in the Z direction. Note that the number and arrangement of the cylinders 21 are not limited to this example.

[0023] A plurality of valves, such as intake valves and exhaust valves, are attached to the cylinder block 11. In addition, other components, such as an ignition device, are also attached to the cylinder block 11.

[0024] The cylinder block 11 may be separable into a cylinder block in which the cylinders 21 are provided and a cylinder head in which valves and an ignition device are attached. The cylinder block 11 may also be integrated with the crankcase 12.

[0025] The crankcase 12 is located below the cylinder block 11 and is attached to the cylinder block 11 by, for example, bolts. The crankcase 12 has a rear wall 31. The rear wall 31 is an example of a wall portion.

[0026] The rear wall 31 is formed in a generally plate-like shape that extends approximately along the XZ plane. However, the shape of the rear wall 31 is not limited to this example. The rear wall 31 has a side surface 31a. The side surface 31a is the outer surface of the crankcase 12 that faces approximately in the -Y direction. The side surface 31a may have irregularities. The side surface 31a faces, for example, the transmission case.

[0027] A first insertion hole 35 and a second insertion hole 36 are provided in the rear wall 31. The first insertion hole 35 and the second insertion hole 36 are examples of holes. Each of the first insertion hole 35 and the second insertion hole 36 penetrates the rear wall 31 substantially in the Y direction and opens to the side surface 31 a.

[0028] The oil pan 13 is located below the crankcase 12 and is attached to the crankcase 12, for example, by bolts. The oil pan 13 can store oil. The internal space of the oil pan 13 can communicate with the internal space of the crankcase 12 and with the cylinder 21 through the gap between the piston and the inner surface of the cylinder 21. This allows blow-by gas to flow from the cylinder 21 into the internal space of the oil pan 13.

[0029] The crankshaft 14 passes through the first insertion hole 35 and extends substantially in the Y direction. The crankshaft 14 is supported by the crankcase 12 so as to be rotatable about a first rotation axis Ax1. The first rotation axis Ax1 is, for example, an imaginary axis that passes through the center of the crankshaft 14 and is an example of a rotation axis. The crankcase 12 may support the crankshaft 14 via a bearing.

[0030] The crank gear 15 is attached to the crankshaft 14. The crank gear 15 is rotatable around the first rotation axis Ax1 together with the crankshaft 14. The crank gear 15 is a disk-shaped gear that is substantially perpendicular to the first rotation axis Ax1.

[0031] Fig. 3 is a cross-sectional view showing a part of the internal combustion engine 10 of the first embodiment taken along line F3-F3 in Fig. 2. As shown in Fig. 3, the balance shaft 16 extends substantially in the Y direction through the second insertion hole 36. That is, the crankshaft 14 and the balance shaft 16 extend substantially parallel to each other. The balance shaft 16 is supported by the crankcase 12 via a bearing 37, for example.

[0032] The balance shaft 16 is rotatable around a second rotation axis Ax2. The second rotation axis Ax2 is, for example, an imaginary axis that passes through the center of the balance shaft 16 and is an example of a rotation axis. The crankcase 12 may directly support the balance shaft 16.

[0033] The balance gear 17 is attached to the balance shaft 16. The balance gear 17 is rotatable around the second rotation axis Ax2 together with the balance shaft 16. The balance gear 17 is a disk-shaped gear that is substantially perpendicular to the second rotation axis Ax2.

[0034] 2, the crank gear 15 and the balance gear 17 mesh with each other. Therefore, the crankshaft 14 can transmit rotation to the balance shaft 16 via the crank gear 15 and the balance gear 17. The balance shaft 16 rotates together with the crankshaft 14, thereby reducing vibrations generated by the crankshaft 14.

[0035] The crank gear 15 and the balance gear 17 are located outside the crankcase 12. A side surface 31a of the rear wall 31 faces the crank gear 15 and the balance gear 17 via a gap. Note that other parts or members may be disposed between the side surface 31a and the crank gear 15, and between the side surface 31a and the balance gear 17.

[0036] The rear wall 31 further has a protruding wall 41. The protruding wall 41 protrudes from the side surface 31a in approximately the −Y direction. The protruding wall 41 extends around the crank gear 15 and the balance gear 17 along the side surface 31a.

[0037] The protruding wall 41 surrounds the crank gear 15 and the balance gear 17. In other words, at least a portion of the crank gear 15 and the balance gear 17 is disposed in a space S inside the protruding wall 41. The space S is in communication with the space inside the oil pan 13, for example.

[0038] The protruding wall 41 has a first end face 41a, a second end face 41b, a top face 41c, and an inner circumferential face 41d. The first end face 41a and the second end face 41b are located at opposite ends of the protruding wall 41 in the direction in which the protruding wall 41 extends.

[0039] The first end face 41a is adjacent to the crank gear 15. The second end face 41b is adjacent to the balance gear 17. In the Z direction, the first end face 41a and the second end face 41b are located at approximately the same position as the end 12a of the crankcase 12 in the -Z direction (downward).

[0040] The top surface 41c is provided at the end of the protruding wall 41 in the -Y direction. The top surface 41c is formed to be approximately flat and faces the -Y direction. The top surface 41c may have an uneven surface or face in another direction. The inner peripheral surface 41d faces the inside of the space S. Therefore, the inner peripheral surface 41d faces the crank gear 15 and the balance gear 17 via a gap.

[0041] An upper passage 45, a groove 46, and a plurality of screw holes 47 are provided in the rear wall 31. The upper passage 45 is provided inside the rear wall 31. The upper passage 45 extends approximately in the Z direction and communicates with an internal passage 48 provided inside the cylinder block 11.

[0042] The upper passage 45 is located above the crankshaft 14 and the balance shaft 16. In other words, in the Z direction, the upper passage 45 is spaced apart in the +Z direction (upward) from the crankshaft 14 and the balance shaft 16. The upper passage 45 is located above the crank gear 15, for example. Note that the crankshaft 14 or the balance shaft 16 may be located above a portion of the upper passage 45.

[0043] The groove 46 and the screw hole 47 open to the top surface 41c. The groove 46 further opens to the first end surface 41a. The groove 46 has an arc-shaped portion 46a. The arc-shaped portion 46a extends in a substantially arc shape along the outer periphery of the crank gear 15. In other words, the arc-shaped portion 46a extends in the circumferential direction around the first rotation axis Ax1. Note that the groove 46 is not limited to this example.

[0044] At least a portion of the groove 46 is aligned with the crank gear 15 and the balance gear 17 in a radial direction perpendicular to the first rotation axis Ax1 or the second rotation axis Ax2. In other words, in the Y direction, the crank gear 15 and the balance gear 17 and at least a portion of the groove 46 are disposed at approximately the same position.

[0045] 1, the cover 18 is attached to the protruding wall 41 of the rear wall 31. The cover 18 may also be attached to another portion of the rear wall 31. The cover 18 has an outer periphery 51 and a gear cover 52.

[0046] The outer peripheral portion 51 extends along the protruding wall 41 and covers substantially the entire top surface 41c of the protruding wall 41. Therefore, the outer peripheral portion 51 closes the groove 46. Another component such as a gasket may be interposed between the outer peripheral portion 51 and the top surface 41c.

[0047] The outer peripheral portion 51 is attached to the protruding wall 41 by, for example, bolts 55, which are shown imaginarily by two-dot chain lines in Fig. 1. The bolts 55 pass through holes provided in the outer peripheral portion 51 and are fitted into the screw holes 47. The bolts 55 attach the outer peripheral portion 51 to the protruding wall 41 at a position farther away from the space S than the grooves 46.

[0048] The gear cover 52 is connected to the outer periphery 51 and covers the side surface 31a of the rear wall 31 and the balance gear 17. Therefore, in the Y direction, the balance gear 17 is located between at least a portion of the gear cover 52 and the side surface 31a. The gear cover 52 leaves at least a portion of the crank gear 15 exposed without covering it. Note that the gear cover 52 may cover a portion of the crank gear 15. The gear cover 52 may also hold, for example, an oil seal for the crank gear 15.

[0049] 4 is a cross-sectional view showing a part of the internal combustion engine 10 of the first embodiment taken along line F4-F4 in FIG. 3. The groove 46 can be used as a passage by being covered with the outer peripheral portion 51. In other words, a space serving as a passage is formed between the cover 18 and the inner surface of the groove 46. As shown in FIG. 4, the groove 46 covered with the outer peripheral portion 51 has a first end 46b and a second end 46c.

[0050] The first end 46b communicates with the upper passage 45 above the crank gear 15. The second end 46c opens to the first end face 41a of the protruding wall 41. Therefore, the second end 46c opens to the outside of the rear wall 31 and the cover 18 below the crankshaft 14 and the balance shaft 16. In this embodiment, the second end 46c communicates with the space inside the oil pan 13. The groove 46 extends between the upper passage 45 located above the crankshaft 14 and the space inside the oil pan 13 located below the crankshaft 14.

[0051] The cross-sectional area of ​​the groove 46 covered by the outer circumferential portion 51 is larger than the cross-sectional area of ​​the upper passage 45. The cross-sectional area of ​​the groove 46 is the area of ​​a cross section perpendicular to the direction in which the groove 46 extends. The cross-sectional area of ​​the upper passage 45 is the area of ​​a cross section perpendicular to the direction in which the upper passage 45 extends. The cross-sectional area of ​​the groove 46 does not have to be constant. For example, the groove 46 may taper from the second end 46c toward the first end 46b.

[0052] The upper passage 45 and groove 46 of the crankcase 12 and the internal passage 48 of the cylinder block 11 form a blow-by gas discharge passage C. In other words, the blow-by gas discharge passage C has the upper passage 45, the groove 46, and the internal passage 48. Note that the blow-by gas discharge passage C may have other passages.

[0053] The blow-by gas discharge passage C connects the internal space of the oil pan 13 with the intake manifold. In this embodiment, the groove 46 connects the internal passage of the oil pan 13 with the upper passage 45. The upper passage 45 connects a first end 46b of the groove 46 with an internal passage 48 of the cylinder block 11.

[0054] The internal passage 48 extends substantially in the Z direction. The internal passage 48 connects the upper passage 45 with a passage provided in a head cover attached to the cylinder block 11. Note that the internal passage 48 may be connected to another passage.

[0055] The blow-by gas flows from the cylinder 21 into the space inside the oil pan 13. The blow-by gas is sucked from the second end 46c of the groove 46 into the groove 46 (blow-by gas discharge passage C).

[0056] The cross-sectional area of ​​the groove 46 is set to be relatively large. Therefore, the flow speed of the blow-by gas in the groove 46 is relatively slow. Therefore, oil mixed in the blow-by gas is likely to adhere to the inner surface of the groove 46 and is separated from the blow-by gas. Note that oil may be mixed in the blow-by gas that has passed through the groove 46.

[0057] The blow-by gas flows from the second end 46c to the first end 46b in the groove 46. In other words, the blow-by gas can pass through the groove 46 between the first end 46b and the second end 46c.

[0058] The blow-by gas flows from the first end 46b of the groove 46 through the upper passage 45 into the internal passage 48 of the cylinder block 11. The blow-by gas then flows through the internal passage 48 into the passage in the head cover. In the passage in the head cover, oil is separated from the blow-by gas. The blow-by gas from the head cover is mixed with a new air-fuel mixture in the intake manifold and supplied to the cylinder 21.

[0059] In the internal combustion engine 10 according to the first embodiment described above, the rear wall 31 is provided with a second insertion hole 36 through which the balance shaft 16 passes, and has a side surface 31a in which the second insertion hole 36 opens and which faces the balance gear 17. The cover 18 is attached to the rear wall 31 and covers at least a portion of the side surface 31a. One of the rear wall 31 and the cover 18 is provided with a groove 46 that is closed by the other of the rear wall 31 and the cover 18. The groove 46 has a first end 46b that communicates with an upper passage 45 located above the balance shaft 16, and a second end 46c that is below the balance shaft 16 and opens to the outside of the rear wall 31 and the cover 18. Fluid can pass through the groove 46 between the first end 46b and the second end 46c. That is, by the rear wall 31 or the cover 18 closing the groove 46, the groove 46 forms a passage through which a fluid can pass between the upper passage 45 located above the balance shaft 16 and a space (outside the rear wall 31 and the cover 18) located below the balance shaft 16. This allows the passage structure of the internal combustion engine 10 to be more easily provided than when a passage is provided inside the rear wall 31. For example, by forming a passage using the closed groove 46, the degree of freedom in designing the passage is increased compared to when a passage is provided inside the rear wall 31. Furthermore, compared to when a passage is provided inside the rear wall 31 using, for example, a drill, the passage is more easily formed and the processing cost is reduced. Furthermore, because the passage is formed by the cover 18 covering the side surface 31a and the rear wall 31, both the balance gear 17 and the passage (groove 46) are provided outside the side surface 31a. That is, the groove 46 can be provided in a space (dead space) created by arranging the balance gear 17 outside the side surface 31a. Therefore, the passage structure in the internal combustion engine 10 can reduce the need for complex design changes to form the passage (groove 46) compared to when the passage is provided inside the rear wall 31, and can reduce increases in design costs and material costs.

[0060] The groove 46 and the balance gear 17 are aligned in a radial direction perpendicular to the second rotation axis Ax2. In other words, the groove 46 and the balance gear 17 are arranged at approximately the same position (coordinate) in the axial direction along the second rotation axis Ax2. As a result, the groove 46 fits into a space (dead space) created by arranging the balance gear 17 outside the side surface 31a, and an increase in the length of the internal combustion engine 10 in the axial direction can be suppressed.

[0061] The cover 18 covers the balance gear 17. That is, the cover 18 serves both as a cover in which the groove 46 is provided or that covers the groove 46, and as a cover that covers the balance gear 17. This eliminates the need for the internal combustion engine 10 to have separate covers in which the groove 46 is provided or that cover the groove 46, and a cover that covers the balance gear 17, thereby preventing an increase in costs.

[0062] The internal combustion engine 10 has a single cylinder block 11. The cylinder block 11 is provided with cylinders 21 and valves attached. In other words, the cylinder block 11 is an integrated component that combines a typical cylinder block 11 in which the cylinders 21 are provided and a cylinder head in which the valves are attached. It is more difficult to form passages in the integrated cylinder block 11 than in a separable component. However, with the passage structure of the internal combustion engine 10 of this embodiment, as described above, it is easier to form passages.

[0063] The internal combustion engine 10 has two cylinders 21. Compared to an internal combustion engine 10 with three or more cylinders 21, a two-cylinder internal combustion engine 10 has fewer areas where a passage can be formed, making it more difficult to form a passage. For example, a blow-by gas discharge passage is generally provided in a thick portion provided between adjacent cylinders. However, when there are two cylinders 21, the number of such thick portions is reduced. In contrast, with the passage structure of the internal combustion engine 10 of this embodiment, as described above, it is easier to provide a passage.

[0064] (Second embodiment) The second embodiment will be described below with reference to Fig. 5. In the following description of the embodiment, components having the same functions as components already described are given the same reference numerals as the components already described, and further description may be omitted. Furthermore, multiple components given the same reference numerals do not necessarily have all the same functions and properties, and may have different functions and properties according to each embodiment.

[0065] Fig. 5 is a cross-sectional view schematically showing a portion of an internal combustion engine 10 according to a second embodiment. As shown in Fig. 5, in the second embodiment, a second end 46c of the groove 46 is spaced apart from the crank gear 15. Specifically, the distance between the second end 46c and the crank gear 15 in a radial direction perpendicular to the first rotation axis Ax1 or the second rotation axis Ax2 is longer than the width of the groove 46.

[0066] Furthermore, the distance between the second end 46c and the crank gear 15 is longer than the distance between other parts of the groove 46 and the crank gear 15. For example, the distance between the second end 46c and the crank gear 15 is longer than the distance between the groove 46 and the crank gear 15 in the vicinity of the first end 46b.

[0067] In the internal combustion engine 10 of the second embodiment described above, the second end 46c is spaced apart from the crank gear 15. This allows the internal combustion engine 10 to prevent oil adhering to the crank gear 15 and oil scattered from the rotating crank gear 15 from being sucked into the groove 46 through the second end 46c.

[0068] In the above-described embodiments, the protruding wall 41 and the groove 46 are provided on the rear wall 31. However, the protruding wall and the groove may be provided on the cover 18, and the rear wall 31 may close the groove. That is, the groove is provided on one of the rear wall 31 and the cover 18, and is closed by the other of the rear wall 31 and the cover 18.

[0069] In the above-described embodiments, blow-by gas passes through the groove 46. However, the fluid passing through the groove 46 is not limited to this example. For example, an air-fuel mixture, air, other gases, oil, or other liquids may pass through the groove 46.

[0070] In the above description, suppression is defined as, for example, preventing an event, action, or influence from occurring, or reducing the degree of an event, action, or influence. Also, in the above description, restriction is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range.

[0071] The above-described embodiments of the present invention do not limit the scope of the invention, but are merely examples within the scope of the invention. Some embodiments of the present invention may be modified, omitted, or added to the above-described embodiments, for example, with respect to at least part of the specific applications, structures, shapes, actions, and effects, without departing from the spirit of the invention. [Explanation of symbols]

[0072] 10...internal combustion engine, 11...cylinder block, 14...crankshaft (shaft), 15...crank gear (rotating body), 16...balance shaft (shaft), 17...balance gear (rotating body), 18...cover, 21...cylinder, 31...rear wall (wall portion), 31a...side surface, 35...first insertion hole (hole), 36...second insertion hole (hole), 45...upper passage, 46...groove, 46b...first end, 46c...second end, Ax1...first rotating shaft (rotating shaft), Ax2...second rotating shaft (rotating shaft).

Claims

1. Two shafts rotatable around their respective rotation axes; Two rotating bodies attached to the two shafts; a wall portion provided with two holes through which the two shafts pass, the wall portion having a side surface into which the two holes open and facing the two rotating bodies; a cover attached to the wall portion and covering at least a portion of the side surface; Equipped with a groove is provided in one of the wall portion and the cover and is closed by the other of the wall portion and the cover; The groove has a first end communicating with an upper passage located above the two shafts, and a second end below the two shafts and open to the outside of the wall portion and the cover, the upper passage being disposed between the two holes in the lateral direction, the groove being formed so that the cross-sectional area is larger than the cross-sectional area of ​​the upper passage, and fluid can pass through the groove between the first end and the second end. Passage structure in an internal combustion engine.

2. The groove and the two rotating bodies are aligned in a radial direction perpendicular to the rotation axis. A passage structure for an internal combustion engine according to claim 1.

3. The cover covers the two rotating bodies.

3. A passage structure for an internal combustion engine according to claim 1 or 2.

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