Internal combustion engine

Abstract

To reduce friction loss in an internal combustion engine.SOLUTION: An internal combustion engine 1 includes a crank shaft 20 which rotates in combination with reciprocating-motion of pistons 14a-14d within cylinders 12a-12d, bearings 40 supporting the crank shaft 20 with inner peripheral surfaces thereof, and intersection surfaces 50 formed in axial opposite ends of inner peripheral surfaces of the bearings 40 and intersecting with the inner peripheral surface and a side surface of the bearing 40. A length of the intersection surface 50 in an axial direction is larger than a thickness of the bearing 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] In an internal combustion engine, a crankshaft is provided as a rotating member that rotates in conjunction with the reciprocating motion of the pistons and converts the reciprocating motion of the pistons into rotational motion. The crankshaft rotates with its shaft portion, the crank journal, supported by bearings. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-207167 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when an external force is applied to the crankshaft, which is a rotating member, causing the crankshaft to rotate at an angle, the crankshaft will come into contact with the end of the inner circumferential surface of the bearing, increasing the sliding contact resistance and therefore the friction loss.

[0005] The present invention has been made in consideration of these points, and has an object to reduce friction loss in an internal combustion engine. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided an internal combustion engine comprising: a rotating member that rotates in conjunction with the reciprocating motion of a piston in a cylinder; a bearing that supports the rotating member on its inner circumferential surface; and an intersecting surface that is formed on both axial ends of the inner circumferential surface of the bearing and intersects with the inner circumferential surface and a side surface of the bearing, wherein the axial length of the intersecting surface is greater than a thickness of the bearing.

[0007] The intersecting surface may be a curved surface that is curved at a predetermined curvature. The intersecting surface may be an inclined surface inclined at a predetermined angle.

[0008] The axial length of the intersecting surface may be less than twice the thickness of the bearing.

[0009] The intersecting surface may be formed over one circumference in the circumferential direction of the bearing.

[0010] The rotating member may be a crankshaft connected to the piston via a connecting rod, and the bearing may support a shaft portion of the crankshaft.

[0011] The rotating member may be a connecting rod having both ends connected to the piston and the crankshaft, and the bearing may support one end of the connecting rod.

[0012] In a second aspect of the present invention, there is provided an internal combustion engine comprising a rotating member that rotates in conjunction with the reciprocating motion of a piston in a cylinder, and a bearing that supports the rotating member on its inner circumferential surface, wherein a diameter of both axial ends of the inner periphery of the bearing is larger than a diameter of a central part of the inner periphery in the axial direction, and the axial length of both ends is larger than a thickness of the bearing. Effect of the Invention

[0013] According to the present invention, an effect of reducing friction loss in an internal combustion engine is achieved. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a schematic configuration of an internal combustion engine according to one embodiment; [Diagram 2] 2 is a schematic diagram for explaining the configuration of a bearing 40. FIG. [Diagram 3] 3 is a cross-sectional view of FIG. 2 taken along line B-B. [Figure 4] FIG. 4 is an enlarged view of a portion C in FIG. [Diagram 5] 4 is a schematic diagram showing a state in which a bearing 40 supports a journal portion 22 of a tilted crankshaft 20. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Configuration of an internal combustion engine> FIG. 1 is a schematic diagram showing a schematic configuration of an internal combustion engine according to one embodiment. As an example, the internal combustion engine 1 is an engine mounted on a vehicle. The internal combustion engine 1 burns and expands a mixture of intake air (air) and fuel to generate power for running the vehicle. The internal combustion engine 1 is a diesel engine here, but is not limited thereto and may be a gasoline engine. As shown in FIG. 1, the internal combustion engine 1 has a cylinder block 10, pistons 14a to 14d, connecting rods 16a to 16d, a crankshaft 20, a support block 30, a bearing 40, and an oil pan 60.

[0016] Here, the cylinder block 10 has four cylinders 12a to 12d. However, the number of cylinders 12 in the internal combustion engine 1 is not limited to four. An intake passage for drawing in intake air and an exhaust passage for discharging exhaust gas after combustion are connected to each of the cylinders 12a to 12d.

[0017] The pistons 14a to 14d perform up and down reciprocating motion within the cylinders 12a to 12d. Specifically, the pistons 14a to 14d repeat reciprocating motion between top dead center and bottom dead center within the cylinders 12a to 12d through four strokes of intake, compression, combustion, and exhaust.

[0018] The connecting rods 16a to 16d connect the pistons 14a to 14d to the crankshaft 20. Both ends of the connecting rods 16a to 16d connect the pistons 14a to 14d to the crankshaft 20. The connecting rods 16a to 16d transmit the reciprocating motion of the pistons 14a to 14d to the crankshaft 20. Each of the connecting rods 16a to 16d has a small end connected to the piston 14a to 14d and a big end connected to the crankshaft 20.

[0019] The crankshaft 20 is a rotating member that rotates in conjunction with the reciprocating motion of the pistons 14a to 14d. The crankshaft 20 is connected to the pistons 14a to 14d via the connecting rods 16a to 16d. The crankshaft 20 converts the reciprocating motion transmitted from the pistons 14a to 14d via the connecting rods 16a to 16d into rotational motion. As shown in FIG. 1, the crankshaft 20 has a journal portion 22, an arm portion 23, and a crank pin 24.

[0020] The journal portions 22 are shaft portions of the crankshaft 20. The journal portions 22 are provided at predetermined intervals in the axial direction of the crankshaft 20. Here, five journal portions 22 are provided.

[0021] A plurality of arm portions 23 are provided at predetermined intervals in the axial direction of the crankshaft 20. The arm portions 23 are fixed to the axial end portions of the journal portions 22, and extend radially outward from the journal portions 22.

[0022] The crank pin 24 is fixed between adjacent arm portions 23 and positioned parallel to the journal portion 22. The crank pin 24 is connected to the big ends of the connecting rods 16a to 16d.

[0023] The support block 30 is a block that supports the crankshaft 20. The support block 30 is fixed to the cylinder block 10 via a fastening member. The support block 30 has a lower support portion 32 (see FIG. 2 ) that supports the journal portion 22 of the crankshaft 20. The lower support portion 32 supports the lower half of the journal portion 22 via a bearing 40. The upper half of the journal portion 22 is supported by the cylinder block 10 via the bearing 40. In this way, the journal portion 22 is surrounded by the support block 30 and the cylinder block 10.

[0024] The bearing 40 supports the crankshaft 20 on its inner circumferential surface 41. Specifically, the bearing 40 supports the journal portion 22, which is the main shaft portion of the crankshaft 20. The bearing 40 is a sliding bearing. An oil film is formed between the bearing 40 and the journal portion 22 by lubricating oil. In this embodiment, as will be described in detail later, a configuration is provided in which both ends of the inner circumference of the bearing 40 are unlikely to come into contact with the journal portion 22 of the crankshaft 20 in order to suppress an increase in friction loss when the crankshaft 20 rotates.

[0025] The oil pan 60 is located below the support block 30 and stores engine oil, which is a lubricating oil. The engine oil stored in the oil pan 60 is sucked up by a pump and can circulate throughout the internal combustion engine 1. The engine oil forms an oil film, for example, between the pistons 14a-14d and the cylinders 12a-12d, and between the journal portion 22 and the bearing 40.

[0026] <Bearing details> Fig. 2 is a schematic diagram for explaining the configuration of bearing 40, and is a cross-sectional view taken along line AA in Fig. 1. Fig. 3 is a cross-sectional view taken along line BB in Fig. 2. Fig. 4 is an enlarged view of portion C in Fig. 3. For ease of explanation, Figs. 2 to 4 show the thin-walled bearing 40 to be thicker than it actually is.

[0027] Since the five bearings 40 have the same configuration, one bearing 40 will be described as an example. The bearing 40 supports the journal portion 22 of the crankshaft 20. As shown in Fig. 2, the inner peripheral surface 41 of the bearing 40 faces the outer peripheral surface of the journal portion 22 of the crankshaft 20 with a small gap therebetween. An oil film of lubricating oil is formed in the gap.

[0028] 2, the outer peripheral surface 42 of the bearing 40 contacts the cylinder block 10 and the support block 30. Specifically, the outer peripheral surface 42 of the upper half of the bearing 40 contacts the upper support portion 18 of the cylinder block 10, and the outer peripheral surface 42 of the lower half of the bearing 40 contacts the lower support portion 32 of the support block 30. The bearing 40 can be divided into an upper half and a lower half.

[0029] As shown in FIG. 2, the inner circumference of the bearing 40 is formed in a circular shape when viewed from the axial direction. In this embodiment, the diameter of the inner circumference of the bearing 40 at both axial ends is larger than the diameter at the axial center. In addition, the length L1 from the side surface 45 of the bearing 40 to both axial ends (parts where the inner circumference of the bearing 40 has a larger diameter) is longer than the thickness L2 of the bearing 40. The inner circumference of the bearing 40 is not necessarily limited to a circular (perfect circle) shape, but may include distortions or shapes that can be considered to be substantially circular. The specific structure of the bearing 40 will be described below.

[0030] 3, the bearing 40 has intersecting surfaces 50 formed at both axial ends of the inner periphery of the bearing 40. The intersecting surfaces 50 are formed by cutting both axial ends of the inner periphery of the bearing 40.

[0031] The intersecting surface 50 intersects with the inner circumferential surface 41 and the side surface 45 of the bearing 40. As shown in Fig. 4, the intersecting surface 50 is a surface that connects one axial end 41a of the inner circumferential surface 41 and an upper end 45a of the side surface 45. Specifically, the intersecting surface 50 connects one end 41a of the inner circumferential surface 41 and an upper end 45a that is located radially outward of the one end 41a.

[0032] As described above, by forming the crossing surfaces 50 at both ends of the bearing 40 in the axial direction, the diameter of the inner circumference of the bearing 40 defined by the crossing surfaces 50 at the axial end sides of the bearing 40 becomes larger than the diameter of the inner circumference of the bearing 40 defined by the inner circumferential surface 41 at the axial center side of the bearing 40. By making the diameter of the inner circumference in the axial direction different in this way, even if the crankshaft 20 is tilted, the journal portion 22 is less likely to come into contact with the crossing surfaces 50. Even if the journal portion 22 comes into contact with the crossing surfaces 50, the journal portion 22 will be in surface contact with the crossing surfaces 50, and the pressure (hereinafter also referred to as surface pressure) that the crossing surfaces 50 receive from the journal portion 22 can be reduced. The portion where the diameter of the inner circumference becomes larger is a portion of the bearing 40 from the axial end portion to a length L1. Here, it is desirable that the length L1 is larger than the thickness L2 of the axial center portion of the bearing 40.

[0033] The intersecting surface 50 is formed around the entire circumference of the bearing 40. Therefore, the thickness of the bearing 40 at the axial end portions is smaller than the thickness of the bearing 40 at the axial center portion.

[0034] As shown in Fig. 4, the axial length L1 of the intersecting surface 50 is greater than the thickness L2 of the bearing 40. Here, the thickness L2 of the bearing 40 is the thickness between the inner peripheral surface 41 and the outer peripheral surface 42 at the axial center of the bearing 40. By providing such an intersecting surface 50 in the bearing 40, even if the crankshaft 20 is tilted, the journal portion 22 is less likely to come into contact with the intersecting surface 50. Even if the journal portion 22 comes into contact with the intersecting surface 50, the journal portion 22 will be in surface contact with the intersecting surface 50, and the pressure (hereinafter also referred to as surface pressure) that the intersecting surface 50 receives from the journal portion 22 can be reduced.

[0035] Here, the cause of the tilt of the crankshaft 20 will be explained. When the pistons 14a to 14d reciprocating up and down reach bottom dead center, a downward force acts on the crankshaft 20 from the pistons 14a to 14d via the crankpin 24. This force causes the crankshaft 20 to tilt. When the crankshaft 20 tilts, the journal portion 22, which is originally parallel to the bearing 40, also tilts.

[0036] Unlike this embodiment, if the intersecting surface 50 is not formed at the axial end of the inner circumference of the bearing 40 (also simply referred to as the inner circumference end), the inclined journal portion 22 will thin the oil film between the journal portion 22 and the bearing 40, or will come into point contact with the inner circumference end of the bearing 40, increasing the pressure. If the crankshaft 20 continues to rotate in this state, the sliding resistance between the journal portion 22 and the bearing 40 will increase, resulting in increased friction loss.

[0037] Fig. 5 is a schematic diagram showing a state in which the bearing 40 supports the journal portion 22 of the tilted crankshaft 20. When the intersecting surface 50 having the axial length L1 greater than the thickness L2 is provided as in this embodiment, even if the journal portion 22 is tilted as shown in Fig. 5, it is difficult to thin the oil film and the journal portion 22 is unlikely to come into contact with the bearing 40. Even if the journal portion 22 comes into contact with the bearing 40, the surface contact of the journal portion 22 with the intersecting surface 50 reduces the surface pressure, and therefore the sliding resistance also reduces. As a result, the friction loss can also be reduced.

[0038] It is desirable that the axial length L1 of the intersecting surface 50 is smaller than twice the thickness L2 of the bearing 40. As an example, the axial length L1 of the intersecting surface 50 is 3 mm, and the thickness L2 of the bearing 40 is 2 mm. If the length L1 of the intersecting surface 50 is too long, the function of the bearing 40 to support the journal portion 22 may be reduced. In response to this, by making the length L1 of the intersecting surface 50 smaller than twice the thickness L2, it is possible to prevent the function of the bearing 40 from being reduced and to suppress a reduction in friction loss.

[0039] The intersecting surface 50 is a curved surface curved at a predetermined curvature. Specifically, as shown in FIG. 4, the intersecting surface 50 is a surface curved at a predetermined curvature between one end 41a of the inner circumferential surface 41 and an upper end 45a of the side surface 45. The predetermined curvature is, for example, about 66.5 mm (diameter 133 mm). By the intersecting surface 50 being a curved surface, the intersecting surface 50 and the inner circumferential surface 41 are smoothly connected, and the intersecting surface 50 can be made wide. By the intersecting surface 50 being a curved surface, the outer circumferential surface of the journal portion 22 is easily brought into surface contact with the curved surface when the journal portion 22 is tilted, and it is possible to suppress an increase in surface pressure due to edge contact.

[0040] In the above description, the intersecting surface 50 is a curved surface, but is not limited thereto. For example, the intersecting surface 50 may be an inclined surface inclined at a predetermined angle. For example, the intersecting surface 50 is an inclined surface inclined at a certain angle with respect to the inner circumferential surface 41 from one end 41a of the inner circumferential surface 41 to the upper end 45a of the side surface 45. Even when the intersecting surface 50 is an inclined surface, the journal portion 22 is less likely to come into contact with the intersecting surface 50 even if the crankshaft 20 is inclined. Furthermore, even if the journal portion 22 comes into contact with the intersecting surface 50, the journal portion 22 is more likely to come into surface contact with the intersecting surface 50.

[0041] In the above description, the bearing 40 supports the journal portion 22 of the crankshaft 20, which is a rotating member, but this is not limiting. For example, the bearing 40 may be provided in the large diameter portion of the connecting rod 16a-16d that is connected to the crank pin 24 of the crankshaft 20. In this case, by providing the bearing 40 on which the intersecting surface 50 is formed, friction loss due to contact between the connecting rod 16a-16d and the crankshaft 20 can be suppressed. The bearings 40 may be provided in small diameter portions of the connecting rods 16a to 16d that are connected to the pistons 14a to 14d. That is, the bearings 40 support the ends of the connecting rods 16a to 16d, which are rotating members.

[0042] <Effects of this embodiment> The internal combustion engine 1 of the embodiment described above has a bearing 40 that supports, on an inner circumferential surface 41, a rotating member (for example, the crankshaft 20) that rotates in conjunction with the reciprocating motion of the pistons 14a to 14d. Intersecting surfaces 50 that intersect with the inner circumferential surface 41 and the side surface 45 are formed on both axial ends of the inner circumferential surface 41 of the bearing 40. The axial length L1 of the intersecting surfaces 50 is greater than the thickness L2 of the bearing 40. With the above-mentioned configuration, even if the crankshaft 20 is tilted due to an external force, the journal portion 22 is unlikely to come into contact with the intersecting surface 50. Even if the journal portion 22 comes into contact with the intersecting surface 50, the journal portion 22 will be in surface contact with the intersecting surface 50, and the surface pressure acting on the intersecting surface 50 can be reduced. This makes it possible to reduce the sliding resistance between the journal portion 22 and the bearing 40, thereby reducing the friction loss of the internal combustion engine 1.

[0043] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0044] 1. Internal combustion engine 12a~12d Cylinder 14a~14d Piston 16a~16d Connecting rod 20 Crankshaft 22 Journal Section 40 Bearings 41 Inner surface 45 Side 50 Intersection

Claims

1. a rotating member that rotates in conjunction with the reciprocating motion of a piston in a cylinder; A bearing that supports the rotating member on an inner circumferential surface thereof; an intersecting surface formed at both axial ends of the inner circumferential surface of the bearing and intersecting the inner circumferential surface and a side surface of the bearing; Equipped with The axial length of the intersecting surface is greater than a thickness of the bearing.

2. The intersecting surface is a curved surface curved with a predetermined curvature.

2. The internal combustion engine of claim 1.

3. The intersecting surface is an inclined surface inclined at a predetermined angle.

2. The internal combustion engine of claim 1.

4. the axial length of the intersecting surface is less than twice the thickness of the bearing; 2. The internal combustion engine of claim 1.

5. The intersecting surface is formed around one circumference in the circumferential direction of the bearing.

2. The internal combustion engine of claim 1.

6. the rotating member is a crankshaft connected to the piston via a connecting rod, The bearing supports a shaft portion of the crankshaft.

2. The internal combustion engine of claim 1.

7. the rotating member is a connecting rod having both ends connected to the piston and the crankshaft, The bearing supports an end of the connecting rod.

2. The internal combustion engine of claim 1.

8. a rotating member that rotates in conjunction with the reciprocating motion of a piston in a cylinder; A bearing that supports the rotating member on an inner circumferential surface thereof; Equipped with a diameter of each end portion of the inner periphery of the bearing in the axial direction is larger than a diameter of a central portion of the inner periphery in the axial direction; The axial length of each of the two ends is greater than a thickness of the bearing.

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