Piston and internal combustion engine

Abstract

To effectively utilize lubricating oil discharged from a cooling cavity.SOLUTION: The piston 30 includes a cooler 40 which is formed in an annular cavity inside the head 32 and through which the lubricant flows, a discharge port 44 which communicates with the cooler 40 and discharges the lubricant from the cooler 40 to the lower side of the head 32, and a skirt 36A extending downward from the lower end of the outer periphery of the head 32. The skirt part 36A has a groove part 50 which is formed on the inner peripheral surface 37 and in which the lubricant discharged from the discharge port 44 flows along the inner peripheral surface 37.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A piston in an internal combustion engine is provided with a cooling cavity through which lubricating oil flows inside the head in order to cool the head, which can become hot (see Patent Document 1 below). The lubricating oil flowing through the cooling cavity is discharged from an outlet connected to the cooling cavity and falls into an oil pan located at the bottom of the internal combustion engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-39340 Summary of the Invention [Problem to be solved by the invention]

[0004] To reduce friction caused by the sliding of the piston relative to the cylinder, a film of lubricating oil is formed on the inner wall surface of the cylinder. To maintain the oil film, it has been proposed to supply the lubricating oil discharged from an outlet to the cylinder, but because the outlet is located away from the inner wall surface of the cylinder, it has been difficult to direct the lubricating oil discharged from the outlet toward the inner wall surface of the cylinder.

[0005] The present invention has been made in consideration of these points, and aims to make effective use of the lubricating oil discharged from the cooling cavity. [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 head having a combustion chamber formed on its top surface; a cooling section formed in an annular cavity inside the head and through which lubricating oil flows; an outlet communicating with the cooling section and discharging the lubricating oil from the cooling section below the head; and a skirt section extending downward from the lower end of the outer periphery of the head, wherein the skirt section is formed on the inner periphery opposite to the outer periphery facing the cylinder, and has a flow path section through which the lubricating oil discharged from the outlet flows along the inner periphery.

[0007] The flow path may be formed on the inner circumferential surface up to a lower end of the skirt portion.

[0008] The flow path may be a groove formed by recessing the inner circumferential surface of the skirt portion along the axial direction of the piston.

[0009] The distance between the bottom surface of the groove and the outer circumferential surface of the skirt may decrease toward the lower end of the skirt.

[0010] The width of the groove in a direction perpendicular to the up-down direction may be greater than the diameter of the discharge port.

[0011] The width of the groove in a direction perpendicular to the up-down direction may increase toward the lower end of the skirt portion.

[0012] The flow path may be formed on the inner circumferential surface from the upper end to the lower end of the skirt portion.

[0013] The flow path portion may be connected to a discharge path having the discharge outlet formed at a tip thereof.

[0014] 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 comprising: a head having a combustion chamber formed on its top surface; a cooling section formed in an annular cavity inside the head and through which lubricating oil flows; an outlet communicating with the cooling section and discharging the lubricating oil from the cooling section below the head; and a skirt section extending downward from a lower end of the outer periphery of the head, the skirt section being formed on the inner periphery opposite to the outer periphery facing the cylinder and having a flow path section through which the lubricating oil discharged from the outlet flows along the inner periphery. [Effects of the Invention]

[0015] According to the present invention, it is possible to effectively utilize the lubricating oil discharged from the cooling cavity of the piston. [Brief explanation of the drawings]

[0016] [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] FIG. 2 is a cross-sectional view of FIG. [Figure 4] FIG. 2 is a view of the piston 30 as seen from below. DETAILED DESCRIPTION OF THE INVENTION

[0017] <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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] <Internal structure of the piston> The internal structure of the piston 30 will be described with reference to FIGS.

[0025] Fig. 2 is a schematic diagram showing the internal configuration of the piston 30. Fig. 3 is a cross-sectional view taken along line II in Fig. 2. Fig. 4 is a view of the piston 30 as seen from below. As shown in FIG. 2, the piston 30 has a head 32, a connecting portion 35, a skirt portion 36, a cooling portion 40, an inlet 42, an outlet 44, and a groove portion 50.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 piston 30 is the thrust region, and the portion on the right side of the piston 30 is the anti-thrust region.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The discharge port 44 is connected to 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 connected to the cooling section 40 via a discharge path 45. The discharge port 44 is formed along the vertical direction of the head 32. The discharge port 44 is located at the lower end, which is the tip of the discharge path 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.

[0035] 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.

[0036] In this embodiment, to effectively utilize the lubricating oil discharged from the discharge port 44, the skirt portion 36 (here, the skirt portion 36A on the thrust region side of the inner wall surface 13) has a flow path that directs the lubricating oil discharged from the discharge port 44 from the back surface (inner circumferential surface 37) of the skirt portion 36A toward the inner wall surface 13 of the cylinder 12. Specifically, the flow path supplies the lubricating oil discharged from the discharge port 44 between the thrust region of the inner wall surface 13 of the cylinder 12 and the skirt portion 36A when the piston 30 descends. This allows a large amount of lubricating oil to be supplied between the thrust region of the inner wall surface 13 and the skirt portion 36A, forming a thick oil film in the thrust region. As a result, friction can be reduced when the skirt portion 36A slides against the thrust region of the inner wall surface 13 when the piston 30 descends.

[0037] In this embodiment, the flow path is a groove 50 formed on the inner circumferential surface 37 of the skirt portion 36A on the side opposite to the outer circumferential surface 38 that faces the cylinder 12. The groove 50 allows the lubricating oil discharged from the discharge port 44 to flow along the inner circumferential surface 37. Specifically, the lubricating oil discharged from the discharge port 44 flows along the groove 50 due to intermolecular forces and inertial forces. As the lubricating oil flows along the groove 50 (the lubricating oil flows as indicated by arrow D in FIG. 2), the lubricating oil is more likely to adhere to the inner wall surface 13 of the cylinder 12. As a result, it is possible to prevent the lubricating oil discharged from the discharge port 44 from being wasted and falling into the oil pan 18 (FIG. 1).

[0038] Groove 50 is formed on inner circumferential surface 37 up to lower end 39 of skirt portion 36A. This allows lubricating oil to easily flow down groove 50 to lower end 39 of skirt portion 36A due to intermolecular forces and inertial forces, making it easier for lubricating oil to move from lower end 39 to inner wall surface 13 of cylinder 12, and as a result, lubricating oil is more likely to adhere to inner wall surface 13.

[0039] In this embodiment, because the thickness of the skirt portion 36A is small, a groove portion 50 serving as a flow path is formed on the inner circumferential surface 37 of the skirt portion 36A. In particular, by providing the groove portion 50 also on the lower end 39 of the skirt portion 36A, the lubricating oil can more easily move from the lower end 39 to the inner wall surface 13 of the cylinder 12.

[0040] The groove 50 is formed on the inner circumferential surface 37 from the upper end to the lower end of the skirt portion 36A. This increases the amount of lubricating oil that flows along the groove 50. As a result, a large amount of lubricating oil adheres from the lower end of the skirt portion 36A to the inner wall surface 13 of the cylinder 12, increasing the thickness of the oil film.

[0041] The thickness of the skirt portion 36A decreases toward the lower end 39 of the piston 30. Therefore, the distance between the bottom surface of the groove portion 50 and the outer peripheral surface 38 of the skirt portion 36A decreases toward the lower end 39 of the skirt portion 36A. As a result, the radial distance of the cylinder 12 between the lower end 39 of the skirt portion 36A and the inner wall surface 13 is short, so that the lubricating oil flowing along the bottom surface of the groove portion 50 can easily move from the lower end of the skirt portion 36A to the inner wall surface 13 of the cylinder 12.

[0042] The groove 50 is a groove formed by recessing the inner circumferential surface 37 of the skirt portion 36A along the axial direction of the piston 30. The depth of the groove 50 is constant here, and is, for example, approximately the same size as the diameter of the discharge port 44. On the other hand, the width of the groove 50 in a direction perpendicular to the up-down direction (width L shown in FIG. 3) increases toward the lower end of the skirt portion 36A. Therefore, the shape of the groove 50 is trapezoidal as shown in FIG. 3. Note that, although the depth of the groove 50 is constant in the above description, this is not limiting and the depth of the groove 50 does not have to be constant.

[0043] The width of the lower end of groove portion 50 in the orthogonal direction is set, for example, to be the same as the circumferential width of the thrust region of inner wall surface 13. This makes it easier for the lubricating oil discharged from outlet 44 to adhere to the entire thrust region of inner wall surface 13. As a result, the thickness of the oil film in the thrust region of inner wall surface 13 increases, reducing the frictional force that occurs when skirt portion 36A slides over the thrust region of inner wall surface 13 as piston 30 moves from top dead center to bottom dead center.

[0044] The groove portion 50 is connected to the discharge path 45. This allows the lubricating oil flowing through the discharge path 45 to easily flow along the groove portion 50. In addition, the width of the groove portion 50 in the orthogonal direction perpendicular to the up-down direction is larger than the diameter of the discharge port 44. This increases the area through which the lubricating oil flows in the groove portion 50, making it easier for most of the lubricating oil flowing through the discharge path 45 to flow along the groove portion 50.

[0045] In the above description, the groove 50 is a flow path through which the lubricating oil discharged from the discharge port 44 flows along the inner circumferential surface 37 of the skirt portion 36A. However, this is not limited to the above, and for example, a hole provided so as to penetrate the skirt portion 36A along the inner circumferential surface 37 may also be the flow path. In such a case, the lubricating oil discharged from the discharge port 44 can be directed toward the inner wall surface 13 of the cylinder 12.

[0046] <Effects of this embodiment> The piston 30 according to this embodiment has an outlet 44 that discharges the lubricating oil from the communicating cooling section 40 downwardly to the head 32, and a skirt section 36A that extends downward from the lower end of the outer periphery of the head 32. The skirt section 36A is formed on the inner circumferential surface 37 on the side opposite to the outer circumferential surface 38 that faces the cylinder 12, and has a groove section 50 that is a flow path through which the lubricating oil discharged from the outlet 44 flows along the inner circumferential surface 37. As a result, the lubricating oil discharged from the discharge port 44 flows along the grooves 50 formed in the inner circumferential surface 37 of the skirt portion 36A, moving from the skirt portion 36A to the inner wall surface 13 of the cylinder 12, and forming an oil film of the lubricating oil on the inner wall surface 13. As a result, the lubricating oil discharged from the discharge port 44 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 36A Skirt part 37 Inner circumferential surface 38 Outer Peripheral Surface 40 Cooling section 44 Discharge outlets 45 Drainage path 50 ditch part

Claims

1. A piston that reciprocates within a cylinder, a head having a combustion chamber formed on a top surface thereof; 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; a skirt portion extending downward from a lower end of the outer periphery of the head; Equipped with The skirt portion is formed on an inner peripheral surface opposite to an outer peripheral surface facing the cylinder, and has a flow path portion through which the lubricating oil discharged from the discharge port flows along the inner peripheral surface. piston.

2. The flow path portion is formed on the inner circumferential surface up to the lower end of the skirt portion. The piston of claim 1.

3. The flow path portion is a groove portion formed by recessing the inner circumferential surface of the skirt portion along the axial direction of the piston. The piston of claim 1.

4. The distance between the bottom surface of the groove and the outer circumferential surface of the skirt portion becomes smaller toward the lower end of the skirt portion.

4. The piston of claim 3.

5. The width of the groove in a direction perpendicular to the vertical direction is greater than the diameter of the discharge port.

4. The piston of claim 3.

6. The width of the groove in a direction perpendicular to the up-down direction increases toward the lower end of the skirt portion.

4. The piston of claim 3.

7. The flow path portion is formed on the inner circumferential surface from the upper end to the lower end of the skirt portion. The piston of claim 1.

8. The flow path portion is connected to a discharge path having the discharge outlet formed at a tip thereof. The piston of claim 1.

9. A cylinder and a piston that reciprocates within the cylinder, The piston is a head having a combustion chamber formed on a top surface thereof; 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; a skirt portion extending downward from a lower end of the outer periphery of the head, The skirt portion is formed on an inner peripheral surface opposite to an outer peripheral surface facing the cylinder, and has a flow path portion through which the lubricating oil discharged from the discharge port flows along the inner peripheral surface. Internal combustion engine.

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