Piston and internal combustion engine

Abstract

To effectively utilize lubricating oil adhering to an inner peripheral surface of a skirt part.SOLUTION: The piston 30 is provided with a skirt part 36A extending downward from a lower end part of an outer periphery of the head 32, and a connecting part 35 connected to a crankshaft for converting reciprocating motion into rotary motion via a connecting rod. The skirt part side 36A has a projection part 50 projecting toward the connecting part 35 from a lower part of an inner peripheral surface 37 on the opposite side of an outer peripheral surface 38 opposed to the cylinder 12 and capable of holding the lubricant.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Lubricating oil is supplied to internal combustion engines to reduce friction caused by sliding between parts, but the lubricating oil can adhere to the inner circumferential surface of the piston. For example, in Patent Document 1 listed below, lubricating oil splashed from the crankshaft adheres to the inner circumferential surface of the piston skirt and flows down the inner circumferential surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-25424 Summary of the Invention [Problem to be solved by the invention]

[0004] It has been proposed to supply lubricating oil adhering to the inner peripheral surface of the skirt to the cylinder in order to maintain a film of lubricating oil on the inner wall surface of the cylinder. However, with this technique, the lubricating oil runs down the inner peripheral surface of the skirt, making it difficult to maintain an oil film on the inner wall surface of the cylinder.

[0005] The present invention has been made in consideration of these points, and has as its object to effectively utilize the lubricating oil adhering to the inner peripheral surface of the skirt portion. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided a piston that reciprocates within a cylinder, comprising: a skirt portion extending downward from a lower end of an outer periphery of a head; and a connecting portion that is connected via a connecting rod to a crankshaft that converts the reciprocating motion into rotational motion, wherein the skirt portion protrudes from a lower portion of an inner periphery opposite to an outer periphery facing the cylinder toward the connecting portion and has a protrusion that can retain lubricating oil.

[0007] The protrusion may protrude from a lower end of the skirt portion toward the connecting portion.

[0008] The protrusion may protrude horizontally from the inner circumferential surface. The protrusion may be formed along the circumferential direction at a lower portion of the inner circumferential surface.

[0009] The head may further include a cooling section formed in a ring-shaped cavity inside the head through which lubricating oil flows, and an outlet connected to the cooling section and discharging the lubricating oil from the cooling section downwardly of the head, and the convex section may be located vertically below the outlet.

[0010] The height of the protrusion in the protruding direction may be smaller than the thickness of the skirt portion.

[0011] The protrusion may also retain lubricating oil adhering to the inner circumferential surface of the skirt portion from the crankshaft during rotation.

[0012] In a second aspect of the present invention, there is provided an internal combustion engine comprising: a cylinder; and a piston that reciprocates within the cylinder, the piston having a skirt portion extending downward from a lower end of an outer periphery of a head; and a connecting portion that is connected via a connecting rod to a crankshaft that converts the reciprocating motion into rotational motion, the skirt portion protruding from a lower portion of an inner periphery opposite to the outer periphery facing the cylinder toward the connecting portion and having a protrusion that can retain lubricating oil.

[0013] The cylinder may also include a thrust region on its inner wall surface against which the skirt portion is pressed when the piston descends, and the convex portion may be located in a portion of the inner surface of the skirt portion that corresponds to the thrust region. [Effects of the Invention]

[0014] According to the present invention, it is possible to effectively utilize the lubricating oil adhering to the inner peripheral surface of the skirt portion of the piston. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing the configuration of an internal combustion engine 1 according to one embodiment. [Figure 2] 2 is a schematic diagram showing the internal configuration of a piston 30. FIG. [Figure 3] 10 is a schematic diagram showing how the lubricating oil is held in the protrusion 50 when the piston 30 is at the bottom dead center. FIG. [Figure 4] 10 is a schematic diagram showing how the lubricating oil is retained in the protrusion 50 when the piston 30 moves from the bottom dead center to the top dead center. FIG. [Figure 5] 10 is a schematic diagram showing how the lubricating oil is held in the protrusion 50 when the piston 30 is at the top dead center. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Configuration of an internal combustion engine> 1 is a schematic diagram showing the configuration of an internal combustion engine 1 according to one embodiment. Here, the internal combustion engine 1 is mounted on a vehicle such as a truck, but is not limited to this and may also be mounted on a ship, for example.

[0017] The internal combustion engine 1 is, for example, a diesel engine. The internal combustion engine 1 is a power source that generates power to run a vehicle by burning and expanding an intake fuel mixture in a combustion chamber 2. The internal combustion engine 1 has a cylinder block 10, a cylinder head 20, a piston 30, a crankshaft 60, and an injection unit 70.

[0018] The cylinder block 10 has a cylinder 12 that houses a piston 30 so that the piston 30 can reciprocate, and a crankcase 16 that houses a crankshaft 60. An oil pan 18 that stores lubricating oil is attached to the crankcase 16.

[0019] The cylinder head 20 is provided on top of the cylinder block 10. The cylinder head 20 has an injector 22, an intake valve 25, and an exhaust valve 26. The injector 22 injects fuel into a combustion chamber 2 defined by the top surface of the piston 30, the inner wall surface 13 of the cylinder 12, and the cylinder head 20. The intake valve 25 opens and closes to introduce fresh air into the combustion chamber 2 from an intake port 23. The exhaust valve 26 opens and closes to guide exhaust gas from the combustion chamber 2 to an exhaust port 24.

[0020] The piston 30 reciprocates within the cylinder 12. When the piston 30 reciprocates between top dead center and bottom dead center, it slides on the inner wall surface 13 of the cylinder 12. Lubricating oil is supplied to the inner wall surface 13, and an oil film is formed on the inner wall surface 13. The formation of the oil film on the inner wall surface 13 reduces the frictional force when the piston 30 slides on the inner wall surface 13. The detailed configuration of the piston 30 will be described later.

[0021] The crankshaft 60 is connected to the piston 30 via a connecting rod (hereinafter referred to as connecting rod) 62. The crankshaft 60 converts the reciprocating motion of the piston 30 into rotational motion.

[0022] The injector 70 injects lubricating oil toward the piston 30. For example, the injector 70 injects lubricating oil toward the piston 30 when the piston 30 is located at bottom dead center. Specifically, the injector 70 injects the lubricating oil toward the inlet 42 (FIG. 2) of the piston 30 so that the lubricating oil is supplied to the cooling portion 40 (FIG. 2) of the piston 30.

[0023] <Internal structure of the piston> The internal structure of the piston 30 will be described with reference to FIGS.

[0024] Fig. 2 is a schematic diagram showing the internal configuration of piston 30. Note that piston 30 shown in Fig. 2 is located at bottom dead center. Piston 30 has head 32, connecting portion 35, skirt portion 36, cooling portion 40, inlet port 42, outlet port 44, and protrusion 50.

[0025] The head 32 is a cylindrical portion formed on the top of the piston 30. A cavity 33 is formed in the center of the top surface of the head 32, recessed from the top surface. The cavity 33, together with the cylinder 12 and the cylinder head 20, forms the combustion chamber 2 (FIG. 1) in which fuel and air are combusted. Fuel is injected into the cavity 33 from the injector 22 (FIG. 1). In addition, a groove 34 in which a piston ring is fitted is formed on the outer circumferential surface of the head 32. The piston ring functions to seal combustion gases and maintain a predetermined thickness of oil film on the inner wall surface 13 of the cylinder 12.

[0026] The connecting portion 35 is a piston pin in this case, and connects the piston 30 and the connecting rod 62. The connecting portion 35 is formed in a cylindrical shape and fits into a pin hole in the piston 30. The connecting portion 35 is arranged from the front to the back of the paper in FIG.

[0027] The skirt portion 36 is the bottom portion of the piston 30. The skirt portion 36 extends downward from the lower end of the outer periphery of the head 32. The skirt portion 36 is formed in a cylindrical shape. The skirt portion 36 is provided to prevent the piston 30 from tilting inside the cylinder 12. The skirt portion 36 is formed so that its thickness decreases toward the lower end 39.

[0028] The skirt portion 36 is provided not around the entire circumference of the piston 30, but in a portion of the inner wall surface 13 of the cylinder 12 that faces the thrust region and the anti-thrust region. The thrust region of the inner wall surface 13 is the region against which the skirt portion 36 slides when the piston 30 moves from top dead center to bottom dead center. The anti-thrust region of the inner wall surface 13 is the region against which the skirt portion 36 slides when the piston 30 moves from bottom dead center to top dead center. In FIG. 2, the portion on the left side of the connecting portion 35 (piston pin) is the thrust region, and the portion on the right side of the connecting portion 35 is the anti-thrust region.

[0029] Skirt portion 36 includes skirt portion 36A located on the left side as viewed from connecting portion 35, and skirt portion 36B located on the right side as viewed from connecting portion 35. Skirt portion 36A faces the thrust region, and skirt portion 36B faces the anti-thrust region. Skirt portions 36A and 36B are located symmetrically with respect to connecting portion 35.

[0030] The cooling section 40 is a lubrication path through which the lubricating oil cools the head 32, which becomes hot. The cooling section 40 is formed as an annular cavity inside the head 32. The cavity is a cooling cavity through which the lubricating oil flows. The cooling section 40 is formed to surround the periphery of the cavity 33.

[0031] The inlet 42 is connected to the cooling section 40 and is an opening for introducing lubricating oil into the cooling section 40. The inlet 42 is provided in the lower part of the head 32 and is connected to the cooling section 40 via an inlet passage 43. The inlet passage 43 is formed along the vertical direction within the head 32. The inlet 42 is located at the lower end, which is the tip of the inlet passage 43. The inlet 42 is formed in a portion of the head 32 facing the anti-thrust region of the inner wall surface 13 of the cylinder 12.

[0032] The inlet 42 guides the lubricating oil sprayed by the spray unit 70 (FIG. 1) to the cooling unit 40 when the piston 30 is at bottom dead center. The inlet 42 is formed at a position directly below the spray unit 70 when the piston 30 is at bottom dead center. The lubricating oil introduced into the cooling unit 40 from the inlet 42 circulates through the cavity of the cooling unit 40.

[0033] The discharge port 44 is in communication with the cooling section 40 and is an opening for discharging the lubricating oil flowing through the cooling section 40. The discharge port 44 is provided in the lower part of the head 32 and is in communication with the cooling section 40 via a discharge passage 45. The discharge port 44 is located at the lower end, which is the tip of the discharge passage 45. The discharge port 44 is formed in a portion of the head 32 facing the thrust region of the inner wall surface 13 of the cylinder 12.

[0034] The discharge port 44 discharges the lubricating oil that has flowed from the cooling unit 40 through the discharge path 45 below the head 32. The lubricating oil flowing through the cooling unit 40 flows into the discharge path 45, for example, when the piston 30 moves from the bottom dead center to the top dead center.

[0035] Incidentally, lubricating oil is supplied to the crankshaft 60 to ensure smooth rotation of the crankshaft 60, and the lubricating oil adheres to the crankshaft 60. Specifically, the lubricating oil adheres to the outer peripheral surface of the balance weight 61 of the crankshaft 60. In this case, when the crankshaft 60 rotates in conjunction with the reciprocating motion of the piston 30, the lubricating oil adhering to the outer peripheral surface of the balance weight 61 splashes onto the inner peripheral surface 37 of the skirt portion 36 (for example, the lubricating oil splashes in the direction D1 indicated by the wavy line in FIG. 2 ), and adheres to the inner peripheral surface 37. In particular, when the piston 30 is positioned near the bottom dead center, the lubricating oil adhering to the outer peripheral surface of the balance weight 61 is likely to adhere to the inner peripheral surface 37 located near the balance weight 61.

[0036] In this embodiment, in order to effectively utilize the lubricating oil adhering to the inner circumferential surface 37 of the skirt portion 36 (here, the skirt portion 36A on the thrust region side of the inner wall surface 13), a protrusion 50 is provided on the inner circumferential surface 37 of the skirt portion 36A to retain the lubricating oil flowing along the inner circumferential surface 37. The protrusion 50 is provided so as to protrude in the normal direction of the inner circumferential surface 37. Specifically, the protrusion 50 is provided so as to face the central axis C ( FIG. 2 ) of the piston 30. The protrusion 50 also protrudes from a lower portion of the inner circumferential surface 37 of the skirt portion 36A toward the connecting portion 35.

[0037] Fig. 3 is a schematic diagram showing how the lubricating oil is held in the protrusions 50 when the piston 30 is at bottom dead center. Fig. 4 is a schematic diagram showing how the lubricating oil is held in the protrusions 50 when the piston 30 moves from bottom dead center to top dead center. Fig. 5 is a schematic diagram showing how the lubricating oil is held in the protrusions 50 when the piston 30 is at top dead center. The protrusions 50 protruding from the inner circumferential surface 37 retain lubricating oil flowing down the inner circumferential surface 37 when the piston 30 reciprocates (for example, lubricating oil that has splashed from the crankshaft 60 and adhered to the inner circumferential surface 37). For example, as the piston 30 moves from bottom dead center to top dead center, the protrusions 50 retain the lubricating oil flowing down the inner circumferential surface 37 as shown in FIG. 3. When the piston 30 is at bottom dead center, the downward inertial force is large, making it easier for the lubricating oil to flow down the inner circumferential surface 37. However, because the protrusions 50 protrude from the inner circumferential surface 37, the protrusions 50 can retain the lubricating oil as shown in FIG. 3. Furthermore, when the piston 30 moves from bottom dead center to top dead center, the downward inertial force is smaller than when the piston 30 is at bottom dead center, so the protrusions 50 can retain the lubricating oil as shown in FIG. 4.

[0038] The lubricating oil held in the protrusions 50 when the piston 30 moves to the top dead center moves from the protrusions 50 to the inner wall surface 13 of the cylinder 12 as the piston 30 moves from the top dead center to the bottom dead center, and adheres to the inner wall surface 13. In particular, since the upward inertial force is large when the piston 30 is located at the top dead center, the lubricating oil held in the protrusions 50 moves from the protrusions 50 to the thrust region of the inner wall surface 13 and adheres to it, as shown in FIG. 5. The lubricating oil adhering to the thrust region forms an oil film, which reduces friction when the piston 30 slides against the thrust region of the skirt portion 36A as it moves to the bottom dead center.

[0039] The protrusions 50 protrude horizontally from the inner circumferential surface 37. Because the protrusions 50 protrude horizontally, the protrusions 50 are more likely to retain the lubricating oil that flows vertically downward along the inner circumferential surface 37 of the skirt portion 36A. In particular, the protrusions 50 are more likely to retain the lubricating oil even when the piston 30 is located at the bottom dead center.

[0040] The protrusion 50 protrudes from the lower end of the skirt portion 36A toward the connecting portion 35. When the protrusion 50 is provided at the lower end of the skirt portion 36A, the lubricating oil held by the protrusion 50 is more likely to move to the inner wall surface 13 of the cylinder 12 that is adjacent in the radial direction of the piston 30. This allows the lubricating oil flowing along the inner circumferential surface 37 of the skirt portion 36A to adhere to the inner wall surface 13 and form an oil film. However, the present invention is not limited to the above, and the protrusion 50 may be formed at a position spaced upward from the lower end of the skirt portion 36A.

[0041] The height of the protrusions 50 in the protruding direction (hereinafter also referred to as the protruding height) is set to be smaller than the thickness of the skirt portion 36A. For example, the protruding height of the protrusions 50 is 5 mm. This makes it easier for the lubricating oil held by the protrusions 50 to move to the inner wall surface 13 of the cylinder 12 compared to when the protruding height of the protrusions 50 is greater than that of the skirt portion 36A, so that more lubricating oil can adhere to the inner wall surface 13.

[0042] The protrusions 50 are formed along the circumferential direction on the lower part of the inner circumferential surface 37 of the skirt portion 36A. For example, the protrusions 50 are formed from one end to the other end of the circumferential direction on the lower part of the inner circumferential surface 37 of the skirt portion 36A. As one example, the protrusions 50 are formed so that the angle formed by a first line connecting one end of the inner circumferential surface 37 to the center of the piston 30 and a second line connecting the other end of the inner circumferential surface 37 to the center of the piston 30 is 60 degrees. In this case, the protrusions 50 can retain the lubricating oil flowing along the inner circumferential surface 37 of the skirt portion 36A over a wide area.

[0043] Furthermore, the protrusions 50 are located on the inner circumferential surface 37 of the skirt portion 36A in a portion corresponding to the thrust region of the inner wall surface 13 of the cylinder 12. For example, the circumferential length of the protrusions 50 is the same as the circumferential length of the thrust region of the inner wall surface 13. In this case, the lubricating oil moving from the protrusions 50 to the inner wall surface 13 adheres to a wide area in the circumferential direction of the thrust region, thereby forming an oil film over a wide area of ​​the thrust region. However, this is not limited to the above, and the circumferential length of the protrusions 50 may be greater than the circumferential length of the thrust region of the inner wall surface 13.

[0044] The protrusion 50 is located vertically below the discharge port 44. In this case, the protrusion 50 can hold the lubricating oil discharged from the discharge port 44. In particular, the protrusion 50 can hold the lubricating oil that is discharged from the discharge port 44 and falls along the inner circumferential surface 37. This allows the lubricating oil discharged from the discharge port 44 to be effectively utilized without falling into the oil pan 18.

[0045] In the above description, the cooling portion 40 is provided on the head 32 of the piston 30, but this is not limiting, and the cooling portion 40 may not be provided on the head 32. Even in this case, the provision of the protrusions 50 on the inner peripheral surface 37 of the skirt portion 36A is significant in that the protrusions 50 can retain lubricating oil that has adhered from the outer peripheral surface of the crankshaft 60 to the inner peripheral surface 37 of the skirt portion 36A.

[0046] <Effects of this embodiment> The piston 30 according to this embodiment has a skirt portion 36A extending downward from the lower end of the outer periphery of the head 32, and a connecting portion 35 that is connected via a connecting rod to a crankshaft that converts reciprocating motion into rotational motion. The skirt portion 36A has a protrusion 50 that protrudes from the lower portion of the inner circumferential surface 37 toward the connecting portion 35 and is capable of retaining lubricating oil. As a result, when the piston 30 reciprocates, the lubricating oil flowing along the inner circumferential surface 37 is held by the convex portions 50 protruding from the lower part of the inner circumferential surface 37. The lubricating oil held by the convex portions 50 then moves from the convex portions 50 to the inner wall surface 13 of the cylinder 12 (specifically, the thrust region), where it is possible to form a film of lubricating oil on the inner wall surface 13. As a result, the lubricating oil adhering to the inner circumferential surface 37 of the skirt portion 36A can be effectively utilized.

[0047] The present invention has been described above using embodiments, but 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 functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0048] 1. Internal combustion engine 12 cylinders 30 pistons 32 heads 35 Connecting part 36A Skirt part 37 Inner peripheral surface 38 Outer surface 40 Cooling section 44 Outlet 50 convex part

Claims

1. A piston that reciprocates within a cylinder, a skirt portion extending downward from a lower end portion of the outer periphery of the head; a connecting portion connected via a connecting rod to a crankshaft that converts the reciprocating motion into rotational motion; Equipped with The skirt portion protrudes from a lower portion of an inner circumferential surface opposite to an outer circumferential surface facing the cylinder toward the connecting portion and has a protrusion capable of retaining lubricating oil. piston.

2. The protrusion protrudes from a lower end of the skirt portion toward the connecting portion. The piston of claim 1.

3. The protrusion protrudes horizontally from the inner circumferential surface. The piston of claim 1.

4. The protrusion is formed along the circumferential direction at a lower portion of the inner circumferential surface. The piston of claim 1.

5. a cooling portion formed in an annular cavity inside the head and through which lubricating oil flows; a discharge port communicating with the cooling portion and discharging the lubricating oil from the cooling portion to below the head, The convex portion is located vertically below the outlet. The piston of claim 1.

6. The height of the protrusion in the protruding direction is smaller than the thickness of the skirt portion. The piston of claim 1.

7. The protrusion retains lubricating oil adhering to the inner circumferential surface of the skirt portion from the crankshaft during rotation. The piston of claim 1.

8. A cylinder and a piston that reciprocates within the cylinder, The piston is a skirt portion extending downward from a lower end portion of the outer periphery of the head; a connecting portion connected via a connecting rod to a crankshaft that converts the reciprocating motion into rotational motion, The skirt portion protrudes from a lower portion of an inner circumferential surface opposite to an outer circumferential surface facing the cylinder toward the connecting portion and has a protrusion capable of retaining lubricating oil. Internal combustion engine.

9. the cylinder includes an inner wall surface including a thrust region against which the skirt portion is pressed when the piston descends, the protrusion is located at a portion of the inner circumferential surface of the skirt portion that corresponds to the thrust region, 9. The internal combustion engine according to claim 8.

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