engine

Abstract

To facilitate discharge of excessive engine oil from a cylinder.SOLUTION: An engine 100 includes a cylinder 1 which has a center axis along a horizontal direction H1 and a piston 2 which is reciprocated along the horizontal direction H1. The piston 2 has a piston head 21 which contains a first end part 2A of the piston 2 and demarcates a part of a combustion chamber 11 and a skirt 22 which contains a second end part 2B of the piston 2 on the opposite side of the piston head 21. The skirt 22 has a coating 23 on an area containing a lowermost part L1 of the skirt 22. The coating 23 contains a cavity 23a on an edge part of the second end part 2B side. The second end part 2B, when being located on a bottom dead center Dc2, is protruded to the outer side of an inner wall 12 of the cylinder 1 in the horizontal direction H1, and at least a part of the cavity 23a, when being located on the bottom dead center Dc2, is located on the outer side of the inner wall 12 of the cylinder 1 in the horizontal direction H1.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In engines, engine oil is used to reduce wear between the piston and the cylinder, and a coating may be provided on the skirt of the piston. For example, Patent Document 1 discloses a piston with a resin coating on the skirt. A groove is provided at the lower end of this resin coating to hold engine oil. In Patent Document 1, the engine oil held in the groove reduces impact noise caused by contact between the skirt and the cylinder.

[0003] Some engines use pistons that reciprocate horizontally. In this case, engine oil tends to accumulate at the bottom of the cylinder due to gravity. Therefore, excess engine oil may accumulate at the bottom of the cylinder. In this case, the excess engine oil causes oil rise and causes deterioration of oil consumption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-182612 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an engine that can promote the discharge of excess engine oil from the cylinders. [Means for solving the problem]

[0006] An engine according to one aspect of the present invention includes a cylinder having a central axis along a horizontal direction, and a piston reciprocating along the horizontal direction inside the cylinder. The piston has a piston head including a first end of the piston in the horizontal direction and defining a part of a combustion chamber, and a skirt including a second end of the piston opposite the piston head in the horizontal direction. The skirt has a coating in an area including a bottom part of the skirt, and the coating is applied to an edge on the second end side. Has a smaller thickness than other parts of the coating The second end protrudes outwardly from the inner wall of the cylinder in the horizontal direction when the piston is located at the bottom dead center, and at least a portion of the recess is located outwardly from the inner wall of the cylinder in the horizontal direction when the piston is located at the bottom dead center. Effect of the Invention

[0007] According to the present invention, it is possible to promote the discharge of excess engine oil from the cylinder. [Brief description of the drawings]

[0008] [Figure 1] 1 is a side cross-sectional view showing an engine according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a partial bottom cross-sectional view showing an engine according to a first embodiment of the present invention. [Diagram 3] FIG. 6 is a bottom view showing a piston of the engine according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, values, etc. shown in the embodiment are merely examples for easy understanding, and do not limit the present invention unless otherwise specified. In the specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanation. In addition, elements not directly related to the present invention are not shown.

[0010] [First embodiment] 1 is a side cross-sectional view showing an engine 100 according to a first embodiment of the present invention. For better understanding, some components (e.g., a right piston 2, a connecting rod 4, and a crankshaft 5, etc.) are shown in a side view rather than a cross-sectional view. The engine 100 is, for example, a gasoline engine or a diesel engine, and can be mounted on a vehicle such as a HEV (Hybrid Electric Vehicle), a gasoline automobile, or a diesel automobile.

[0011] The engine 100 includes a cylinder 1 and a piston 2. The cylinder 1 has a central axis along a horizontal direction (first horizontal direction) H1. The piston 2 reciprocates inside the cylinder 1 along the horizontal direction H1. In this embodiment, the engine 100 is a horizontally opposed engine and includes multiple sets (two sets in FIG. 1) of cylinders 1 and pistons 2. The multiple pistons 2 reciprocate in the horizontal direction H1 so as to face each other. In other embodiments, the engine 100 may be another type of engine as long as it includes pistons 2 that reciprocate in the horizontal direction. An end of the cylinder 1 that faces the piston head 21 of the piston 2 is closed by a cylinder head 10. A combustion chamber 11 is defined by the cylinder 1, the piston 2, and the cylinder head 10.

[0012] The engine 100 includes a piston pin 3, a connecting rod 4, and a crankshaft 5. The piston pin 3 is inserted into the piston 2 along a horizontal direction (second horizontal direction) H2. The horizontal direction H2 is perpendicular to the horizontal direction H1.

[0013] A first end 41 of the connecting rod 4 is pivotally connected to the piston 2 via the piston pin 3. A second end 42 of the connecting rod is pivotally connected to a crank arm 52 of the crankshaft 5 via a crank pin 51. The crank pin 51 is offset from the central axis A1 of the crankshaft 5. The crankshaft 5 is housed in a crankcase 6.

[0014] In the engine 100 as described above, a mixture of fuel and air is burned in the combustion chamber 11. The combustion causes the piston 2 to reciprocate between a top dead center Dc1 and a bottom dead center Dc2 along the horizontal direction H1. In FIG. 1 and FIG. 2, the piston 2 is located at the bottom dead center Dc2. The reciprocating motion of the piston 2 moves the second end 42 of the connecting rod 4 in both the horizontal direction H1 and the vertical direction, thereby rotating the crank arm 52 around the central axis A1. Thus, the reciprocating motion of the piston 2 is converted into the rotational motion of the crankshaft 5. In this disclosure, the "top dead center" means the position where the piston 2 is disposed farthest from the crankshaft 5, and the "bottom dead center" means the position where the piston 2 is disposed closest to the crankshaft 5. In this disclosure, the "top dead center" does not mean an upper position in the vertical direction, and the "bottom dead center" does not mean a lower position in the vertical direction.

[0015] Next, the piston 2 will be described in detail.

[0016] The piston 2 has a piston head 21 and a skirt 22. The piston head 21 includes a first end 2A of the piston 2 in the horizontal direction H1. The piston head 21 defines a portion of the combustion chamber 11 in the horizontal direction H1.

[0017] The skirt 22 includes a second end 2B of the piston 2 in the horizontal direction H1. The second end 2B is located on the opposite side to the piston head 21 (or the first end 2A) in the horizontal direction H1. The second end 2B faces the inside of the crankcase 6. The skirt 22 has a generally cylindrical shape. The skirt 22 has a central axis along the horizontal direction H1.

[0018] The skirt 22 has arc-shaped surfaces 22a above and below the piston pin 3. The surface 22a has an outer diameter approximately the same as the inner diameter of the cylinder 1. The surface 22a slides on the inner wall 12 of the cylinder 1. Of the upper and lower contact portions between the surface 22a and the cylinder 1, one is the thrust side and the other is the anti-thrust side. The thrust side means the side where the piston 2 is pressed against the inner wall 12 of the cylinder 1 immediately after the top dead center Dc1, and the anti-thrust side means the side opposite to the thrust side. The surface 22a prevents the piston 2 from tilting inside the cylinder 1 around the piston pin 3.

[0019] Fig. 2 is a partial bottom cross-sectional view showing the engine 100 according to the first embodiment of the present invention. For better understanding, Fig. 2 shows only one set of the cylinder 1 and the piston 2 in Fig. 1 (the set of the cylinder 1 and the piston 2 on the left side in Fig. 1), and the piston 2 is shown in a bottom view rather than a cross-sectional view. A line L1 indicates the bottom of the cylinder 1 and the piston 2. On the surface 22a, a central portion in the horizontal direction H2 of the second end 2B protrudes toward the crankshaft 5 (not shown in Fig. 2) along the horizontal direction H1.

[0020] The skirt 22 has a surface 22b perpendicular to the piston pin 3 (not shown in FIG. 2). In the horizontal direction H2, the length between the surfaces 22b is smaller than the inner diameter of the cylinder 1. Therefore, the surface 22b does not contact the inner wall 12 of the cylinder 1.

[0021] 1, the second end 2B of the piston 2 (i.e., the end 2B of the skirt 22) is located outside the inner wall 12 of the cylinder 1 in the horizontal direction H1 when the piston 2 is located at the bottom dead center Dc2. That is, the end 2B of the skirt 22 protrudes from the end 12a of the inner wall 12 of the cylinder 1 along the horizontal direction H1 when the piston 2 is located at the bottom dead center Dc2.

[0022] Referring to FIG. 2, the skirt 22 has a coating 23 on the surface 22a. The coating 23 is formed on both the upper surface 22a (not shown in FIG. 2) and the lower surface 22a. The contact pressure between the skirt 22 and the inner wall 12 of the cylinder 1 is higher in the portion that receives pressure vertically from the piston pin 3 (i.e., the top and bottom of the skirt 22). Therefore, the coating 23 is provided at least in a region including the top of the skirt 22 (not shown in FIG. 2) and a region including the bottom L1 of the skirt 22. For example, the coating 23 is formed on the surface 22a in a region excluding the vicinity of the edge. The coating 23 is formed, for example, by a resin-based coating.

[0023] The coating 23 has a recess 23a on the edge portion on the end 2B side of the skirt 22 (or along the end 2B). In this embodiment, the recess 23a is provided in a region including the lowest portion L1 of the skirt 22. In this embodiment, the recess 23a has a generally trapezoidal shape. However, the shape of the recess 23a is not limited to this, and in other embodiments, the recess 23a may have other shapes (e.g., semicircular). The width (length in the horizontal direction H2) of the recess 23a ensures, for example, a convex width of 2 mm or more at both ends. The depth (length in the horizontal direction H1) of the recess 23a is, for example, about 1 mm or more and 3 mm or less. The size of the recess 23a is not limited to this, and in other embodiments, the recess 23a may have other sizes.

[0024] In this embodiment, the surface 22a is exposed in the depression 23a. In other embodiments, the surface 22a may not be exposed in the depression 23a, in which case the depression 23a may have a smaller thickness than the thickness of other portions of the coating 23.

[0025] 2, the end 12a of the inner wall 12 of the cylinder 1 that contacts the surface 22a is indicated by a dashed line. The recess 23a is located outside the inner wall 12 of the cylinder 1 in the horizontal direction H1 when the piston 2 is located at the bottom dead center Dc2. In this embodiment, the entire recess 23a is located outside the inner wall 12 of the cylinder 1 at the bottom dead center Dc2. In other embodiments, at least a part of the recess 23a may be located outside the inner wall 12 of the cylinder 1 at the bottom dead center Dc2.

[0026] Next, the function of the recess 23a will be described.

[0027] When the piston 2 moves from the top dead center Dc1 toward the bottom dead center Dc2, the engine oil is captured by the recess 23a. When the piston 2 reaches the bottom dead center Dc2, the recess 23a is located outside the inner wall 12 of the cylinder 1 and is released from contact with the inner wall 12, as shown in Fig. 2. Referring to Fig. 1, since the recess 23a (not shown in Fig. 1) is formed in the lower surface 22a of the skirt 22, the engine oil captured in the recess 23a falls into the crankcase 6 by gravity at the bottom dead center Dc2.

[0028] In engine 100, because cylinder 1 has a central axis along horizontal direction H1, engine oil tends to accumulate in the lower part of cylinder 1 due to gravity. Therefore, excess engine oil may accumulate in the lower part of cylinder 1. However, because depression 23a is formed in lower surface 22a of skirt 22, the excess engine oil that accumulates in the lower part of cylinder 1 is captured in depression 23a and discharged into crankcase 6 at bottom dead center Dc2.

[0029] The engine 100 as described above includes a cylinder 1 having a central axis along a horizontal direction H1, and a piston 2 reciprocating along the horizontal direction H1 inside the cylinder 1. The piston 2 includes a piston head 21 including a first end 2A of the piston 2 in the horizontal direction H1 and defining a part of the combustion chamber 11, and a skirt 22 including a second end 2B of the piston 2 on the opposite side of the piston head 21 in the horizontal direction H1. The skirt 22 includes a coating 23 in a region (surface 22a) including the lowest part L1 of the skirt 22. The coating 23 includes a recess 23a on an edge portion on the second end 2B side. The second end 2B protrudes outside the inner wall 12 of the cylinder 1 in the horizontal direction H1 when the piston 2 is located at the bottom dead center Dc2, and at least a part of the recess 23a of the coating 23 is located outside the inner wall 12 of the cylinder 1 in the horizontal direction H1 when the piston 2 is located at the bottom dead center Dc2. Therefore, excess engine oil accumulated in the lower part of the cylinder 1 can be captured by the recess 23a and can be discharged to the outside of the inner wall 12 of the cylinder 1 at the bottom dead center Dc2. This facilitates the discharge of excess engine oil from the cylinder 1.

[0030] Furthermore, in the engine 100, the recess 23a is formed in a region of the coating 23 that includes the lowest part L1 of the skirt 22. Engine oil accumulates most at the lowest part L1 in the cylinder 1. In the above embodiment, the recess 23a is formed in a region that includes the lowest part L1 of the skirt 22, so that excess engine oil can be efficiently captured. Therefore, the discharge of excess engine oil from the cylinder 1 can be further promoted.

[0031] [Second embodiment] 3 is a bottom view showing piston 20 of an engine according to a second embodiment of the present invention. Piston 20 according to the second embodiment differs from piston 2 according to the first embodiment in that the shape of recess 23b is different from the shape of recess 23a according to the first embodiment. In other respects, piston 20 may be similar to piston 2. Therefore, a description of the other points will be omitted.

[0032] In the piston 20, the recesses 23b are provided in an area of ​​the lower surface 22a excluding the lowest part L1. Specifically, two recesses 23b are formed in the edge of the coating 23 along the end 2B. The two recesses 23b are arranged along the horizontal direction H2, sandwiching the lowest part L1. The two recesses 23b are arranged symmetrically with respect to the central axis of the piston 20 in a bottom view.

[0033] In an engine equipped with the piston 20 as described above, like the engine 100 according to the first embodiment, excess engine oil accumulated in the lower part of the cylinder 1 can be captured by the recess 23b and can be discharged to the outside of the inner wall 12 of the cylinder 1 at the bottom dead center Dc2. This facilitates the discharge of excess engine oil from the cylinder 1.

[0034] In addition, in the piston 20, the recess 23b is formed in the coating 23 in an area excluding the bottom L1 of the skirt 22. As described above, the contact pressure between the skirt 22 and the inner wall 12 of the cylinder 1 is high in the portion that receives pressure vertically from the piston pin 3 (i.e., the top and bottom L1 of the skirt 22). By forming the recess 23b in the area excluding the bottom L1 of the skirt 22, the coating 23 can be left in the bottom L1 that receives high pressure. Therefore, wear between the skirt 22 and the inner wall 12 of the cylinder 1 can be reduced.

[0035] Although the embodiments have been described above with reference to the accompanying drawings, the present invention is not limited to such embodiments. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that such examples also naturally belong to the technical scope of the present invention.

[0036] For example, in the above embodiment, the depressions 23a, 23b are formed only in the coating 23 on the lower surface 22a. However, in other embodiments, the depressions 23a, 23b may also be formed in the coating 23 on the upper surface 22a. [Explanation of symbols]

[0037] 1 cylinder 2,20 Piston 2A First end of piston 2B Second end of piston 3 Piston pin 12 Inner wall of cylinder 21 Piston head 22 Skirt 22a Upper and lower surfaces of the skirt 23 Coating 23a Depression 23b Depression 100 Engine Dc2 Bottom dead center H1 horizontal direction L1 Bottom of cylinder and piston

Claims

1. A cylinder having a central axis along a horizontal direction; a piston that reciprocates along the horizontal direction inside the cylinder; Equipped with The piston is a piston head including a first end of the piston in the horizontal direction and defining a portion of a combustion chamber; a skirt including a second end of the piston opposite the piston head in the horizontal direction; having the skirt having a coating in an area including a bottom portion of the skirt; the coating includes a recess at an edge portion on the second end side, the recess having a thickness smaller than other portions of the coating; the second end protrudes outward from an inner wall of the cylinder in the horizontal direction when the piston is located at the bottom dead center, At least a portion of the recess is located outside an inner wall of the cylinder in the horizontal direction when the piston is located at a bottom dead center. engine.

2. The engine of claim 1 , wherein the recess is formed in the coating in an area that includes a lowermost portion of the skirt.

3. The engine of claim 1 , wherein the recesses are formed in the coating in an area other than a lowermost portion of the skirt.

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