JP5656499B2 - Piston of internal combustion engine - Google Patents

Description

  The present invention relates to a piston for an internal combustion engine.

  Patent Document 1 discloses a piston for an internal combustion engine. This piston has a cylindrical main body portion (hereinafter, this portion is referred to as a “piston main body portion”). An annular passage for flowing oil (hereinafter referred to as “oil passage”) is formed in the piston main body. When the fuel burns in the combustion chamber in the expansion stroke, the temperature of the piston main body increases. The oil flowing in the oil passage serves to cool the piston main body portion that has become hot. In this piston, in particular, in order to increase the cooling effect of the central portion of the piston main body portion by the oil flowing in the oil passage, a part of the oil passage is formed in a region closer to the central portion of the piston main body portion. Yes.

  That is, in the piston disclosed in Patent Document 1, when the fuel burns in the combustion chamber in the expansion stroke, the temperature of the piston main body increases, and in particular, the temperature of the central portion of the piston main body increases. The oil passage is formed inside the piston main body so that the passage passes through a region close to the central portion of the piston main body. Thus, in the field of pistons, there is a demand for efficiently cooling particularly high temperature portions of the piston.

JP 2009-185746 A JP 2009-228483 A

  By the way, a pair of skirt portions extending downward from the piston main body portion (that is, a direction away from the combustion chamber), and a pair of sidewall portions connecting the skirt portions to each other and extending downward from the piston main body portion. There is known a piston having a portion and a pin hole portion provided in each sidewall portion. In this piston, since the temperature of the upper part of the pin hole is particularly high, it is preferable to cool the upper part of the pin hole.

  Accordingly, an object of the present invention is to efficiently cool an upper portion of a pin hole portion in a piston having the pin hole portion.

In order to achieve the above object, the present invention provides a cylindrical piston main body and a pin hole portion disposed below the piston main body, the center being perpendicular to the central axis of the piston main body. The present invention relates to a piston of an internal combustion engine having a pin hole portion having an axis and a connecting portion that connects the pin hole portion and the piston main body portion to each other. In the piston of the internal combustion engine of the present invention, the outer wall surface of the connecting portion adjacent to the pin hole portion is formed as a substantially upward wall surface extending inward substantially above the pin hole portion. A protruding portion extending in an obliquely upward direction in a direction away from the pin hole portion from the region of the connection portion in the vicinity of the wall surface facing substantially upward and in the vicinity of the pin hole portion. It is provided on the outer wall surface.

In this case , since the outer wall surface of the connecting portion adjacent to the pin hole portion is formed as a substantially upward wall surface substantially above the pin hole portion, cooling oil is supplied to the periphery of the pin hole portion. At this time, the cooling oil accumulates on the wall surface facing substantially upward of the connecting portion. Here, since the wall surface facing substantially upward of the connecting portion is located at a position close to the upper portion of the pin hole portion, the cooling oil staying on the wall surface facing substantially upward of the connecting portion is above the pin hole portion. The part is cooled. Furthermore, the raised portion is provided in the consolidated portion. And this protruding part is extended in the diagonally upward direction from the area | region of the connection part of the wall surface vicinity which faced the upper direction and the pin hole part vicinity. Therefore, at least the raised portion has a wall surface facing substantially upward. Therefore, when the cooling oil is supplied to the periphery of the raised portion, the cooling oil stays on the wall surface facing substantially upward of the raised portion. In addition, even if the cooling oil that has once remained on the wall surface facing substantially upward of the connecting portion flows out of the wall surface facing substantially upward of the connecting portion, the flowing cooling oil also faces substantially upward of the raised portion. You will stay on the wall. That is, not only the cooling oil supplied to the periphery of the raised portion but also the cooling oil that has flowed out from the substantially upwardly directed wall surface of the connecting portion remains on the wall surface facing the upward portion of the raised portion. . Therefore, the amount of cooling oil that remains on the wall surface facing substantially upward of the raised portion is large. Here, since the wall surface facing substantially upward of the raised portion is generally located at a position close to the upper portion of the pin hole portion, a large amount of cooling oil stays on the wall surface facing substantially upward of the raised portion. The upper part of the part is cooled. Thus, by the large amount of cooling oil to remain on the wall surface facing substantially above the cooling oil and the raised portion to remain on the wall surface facing substantially upwards of consolidated portion, the upper portion of the pin hole portion is cooled Therefore, the upper part of the pin hole is efficiently cooled.

Furthermore , the wall surface facing substantially upward of the connecting portion is inward and extends obliquely upward.

  According to this invention, at least a part of the cooling oil supplied to the wall surface facing substantially upward of the connecting portion is rebounded upward by the wall surface facing substantially upward of the connecting portion. For this reason, since the cooling oil is supplied further upward, the portion of the piston above the wall surface facing substantially upward of the connecting portion is efficiently cooled.

Alternatively , the piston is inclined in the direction away from the pin hole portion from the region of the connection portion in the vicinity of the wall surface in which the raised portion faces substantially upward of the connection portion and in the vicinity of the pin hole portion. It extends to the region of the connecting part adjacent to the main body part.

  According to this invention, the piston which can make the diameter of a pin hole small is provided, suppressing fatigue deterioration of the upper part of a pin hole part. That is, when the piston is disposed in the cylinder bore and the internal combustion engine is operated, when the fuel burns in the combustion chamber in the expansion stroke, a large combustion pressure load (that is, a large pressure due to the combustion pressure) is applied to the top wall surface of the piston body. Load). Then, due to this large combustion pressure load, the inner peripheral wall surface of the upper portion of the pin hole (that is, the upper portion of the pin hole portion) is the outer peripheral wall surface of the upper portion of the piston pin (that is, the upper portion of the piston pin inserted into the pin hole). So that the radius of curvature of the inner peripheral wall surface of the upper pin hole portion and the outer peripheral wall surface of the upper piston pin portion is larger than the original radius of the pin hole and the original radius of the piston pin, respectively. Both the upper part and the piston pin are deformed. As a result, tensile stress is generated in the inner wall surface side portion of the pin hole upper portion. On the other hand, in the exhaust stroke and the intake stroke following the expansion stroke, the pressure in the combustion chamber becomes low, so the tensile stress generated in the inner peripheral wall surface portion of the upper portion of the pin hole disappears. During the engine operation, the expansion stroke, the exhaust stroke, and the intake stroke are repeatedly performed, so that the portion above the pin hole is likely to be fatigued. Here, in the present invention, a raised portion is provided in the sidewall portion. And this bulging part is a side wall in the direction from the area of the outer wall surface of the sidewall part adjacent to the piston body part and the skirt part to the area of the outer wall surface of the sidewall part adjacent to the side part of the pin hole part. It extends in the department. Therefore, this protruding portion transmits the bending force of the piston main body due to the combustion pressure load to the side portion of the pin hole portion. Then, due to the force transmitted to the side portion of the pin hole portion, a force is applied to the pin hole portion in the direction of suppressing the bending of the upper portion of the pin hole due to the combustion pressure load in the expansion stroke. Thereby, the bending of the upper portion of the pin hole is suppressed, and as a result, the occurrence of tensile stress in the upper portion of the pin hole portion is suppressed. For this reason, even if the diameter of the pin hole is reduced, fatigue deterioration of the upper portion of the pin hole portion is suppressed. Therefore, according to this invention, the piston which can make the diameter of a pin hole small is provided, suppressing the fatigue deterioration of the upper part of a pin hole part.

Alternatively , a first oil passage for flowing cooling oil is formed inside the piston, and an inner wall surface of the connecting portion corresponding to the raised portion defines a groove extending along the raised portion. A second oil passage for flowing cooling oil is formed by closing the groove with a wall, and the second oil passage is connected to the first oil passage.

  According to the present invention, the second oil passage eventually passes in the vicinity of the upper portion of the pin hole. Therefore, the upper part of the pin hole is also cooled by the cooling oil flowing in the second oil passage. In addition, since the second oil passage is formed using a groove formed on the inner wall surface of the connecting portion corresponding to the raised portion, the weight of the piston is reduced.

(A) is a side view of the piston of the first embodiment, and (B) is a bottom view of the piston. (A) is a side view of the piston of the first embodiment similar to FIG. 1 (A), and (B) is a bottom view of the same piston as FIG. 1 (B). It is sectional drawing of the protruding part of the piston of 1st Embodiment along line XX of FIG. It is the same figure as FIG. 1 (A), However, It is the side view which showed the piston provided with the protruding part different from the protruding part of 1st Embodiment. FIG. 2 is a view similar to FIG. 1A and showing a plurality of surfaces taking cross sections of a sidewall portion and a skirt portion of the piston of the first embodiment. FIG. 6 is a view similar to FIG. 5 for explaining the surface shown in FIG. 5. (A) is the figure which showed the cross section of the side wall part and skirt part of the piston of 1st Embodiment which followed the surface A of FIG. 5, Similarly, (B)-(G) is respectively It is the figure which showed the cross section of the side wall part and skirt part of the piston of 1st Embodiment which followed the surface BG of FIG. 5, (H) is the side wall part and skirt of the piston of 1st Embodiment. It is the figure which showed the bottom end surface with a part. FIG. 2 is a view similar to FIG. 1A and showing a plurality of surfaces taking cross sections of a sidewall portion and a skirt portion of the piston of the first embodiment. FIG. 9 is a view similar to FIG. 8 for explaining the surface shown in FIG. 8. FIG. 2 is a view similar to FIG. 1A and showing a plurality of surfaces taking cross sections of a sidewall portion and a skirt portion of the piston of the first embodiment. FIG. 11 is a view similar to FIG. 10 for explaining the surface shown in FIG. 10. FIG. 2 is a view similar to FIG. 1A and showing a plurality of surfaces taking cross sections of a sidewall portion and a skirt portion of the piston of the first embodiment. FIG. 13 is a view similar to FIG. 12 for explaining the surface shown in FIG. 12. (A) is a longitudinal sectional view around the skirt portion of the piston of the first embodiment, (B) is a longitudinal sectional view around the skirt portion of the piston different from the piston of the embodiment of the present invention, ( C) is a longitudinal sectional view around the skirt portion of the modified example of the piston of the first embodiment. (A) is a view similar to FIG. 1 (A), and is a side view of the piston of the second embodiment, and (B) is a side wall of the piston along line YY of (A). It is a longitudinal cross-sectional view of a part. FIG. 15A is a view similar to FIG. 15B, showing a state in which oil is retained in a recess of the piston when the piston of the second embodiment is disposed in the cylinder bore. (B) is the same figure as Drawing 15 (B), and is a figure showing signs that oil diffuses in the hollow of the piston when the piston is arranged in a cylinder bore. It is a figure similar to FIG.1 (B), Comprising: It is a bottom view of the piston of 3rd Embodiment. It is a figure similar to FIG.1 (B), Comprising: It is a bottom view of the piston of 4th Embodiment. (A) is a view similar to FIG. 3, and is a cross-sectional view of a raised portion provided on the first sidewall portion of the piston of the fifth embodiment, and (B) is a view similar to FIG. 3. It is sectional drawing of the protruding part provided in the 2nd side wall part of the same piston.

  Hereinafter, embodiments of the piston of the present invention will be described with reference to the drawings. FIG. 1 shows the piston of the first embodiment. FIG. 1 (A) is a side view of the piston of the first embodiment, and FIG. 1 (B) is a bottom view of the piston. As shown in FIG. 1, the piston 10 includes one main body portion (hereinafter referred to as “piston main body portion”) 11, a pair of skirt portions 12 </ b> A and 12 </ b> B, a pair of sidewall portions 13 </ b> A and 13 </ b> B, Pin hole portions 14A and 14B.

  In the following description, the term “upward” refers to “upward” in the drawing of FIG. 1A (for example, when the piston body 11 is disposed when the pin hole portions 14A and 14B are used as a reference). The term “downward” represents “downward” (that is, the direction opposite to “upward”) on the drawing of FIG. 1A, and the term “side” The term “outward” represents the direction from the inside of the piston 10 toward the outside of the piston, and the term “inward” represents the direction of the piston 10. The direction from the outside toward the inside of the piston (that is, the direction opposite to “outward”). The “bottom end surface” is an end surface facing downward.

  The piston main body 11 is a cylindrical portion centered on the piston center axis C1. The piston main body 11 has a wall surface 111 (hereinafter referred to as “piston main body top wall surface”) 111 and a piston central axis C1 that forms a circular surface centered on the piston central axis C1 and faces upward. One wall surface (hereinafter referred to as the “piston body bottom wall surface”) 112 that forms a circular surface at the center and faces downward, and a cylindrical surface centered on the piston center axis C1 are arranged outward. 1 facing outer peripheral wall surface (hereinafter, this wall surface is referred to as “piston body outer peripheral wall surface”) 113.

  The piston body outer peripheral wall surface 113 connects the outer peripheral end of the piston main body top wall surface 111 and the outer peripheral end of the piston main body bottom wall surface 112 to each other. The piston body outer peripheral wall surface 113 is formed with a plurality of annular grooves 114 centered on the piston center axis C1. Each of these grooves 114 accommodates an annular oil ring (not shown). A cavity 115 is formed in the piston main body top wall surface 111.

  Each skirt portion 12A, 12B is a substantially partial annular portion centered on the piston center axis C1. Each of the skirt portions 12A and 12B has one outer peripheral wall surface (hereinafter referred to as “skirt outer peripheral wall surface”) 121 that forms a substantially partial cylindrical surface centered on the piston center axis C1 and faces outward. And an inner peripheral wall surface 122 (hereinafter also referred to as a wall surface “skirt inner peripheral wall surface”) 122 facing inward and forming a substantially partial cylindrical surface centered on the piston center axis C1. Further, the skirt portions 12A and 12B are disposed on opposite sides symmetrically with respect to the piston center axis C1. In other words, the skirt portions 12A and 12B extend downward in parallel to the piston center axis C1 from the partial annular outer peripheral region of the piston body bottom wall surface 112 located on the opposite side to the piston center axis C1. Exist. Each skirt outer peripheral wall surface 121 is substantially flush with the piston main body outer peripheral wall surface 113.

  Each of the sidewall portions 13A and 13B is a flat portion. Each of the sidewall portions 13A and 13B has a flat outer surface (hereinafter referred to as a “side wall outer wall surface”) 131 and a flat inner surface. One inner wall surface (hereinafter, this wall surface is also referred to as “side wall inner wall surface”) 132. Further, the sidewall portions 13A and 13B are disposed on opposite sides symmetrically with respect to the piston center axis C1. In other words, the sidewall portions 13A and 13B extend downward in parallel to the piston center axis C1 from the rectangular region of the piston main body bottom wall surface 112 located on the opposite side to the piston center axis C1. ing. Further, the side ends of the sidewall portions 13A and 13B are connected to the corresponding side ends of the skirt portion 12. Therefore, each side wall part 13A, 13B is arrange | positioned between the two skirt parts 12A, 12B, and has connected these two skirt parts 12A, 12B mutually.

  Each pin hole part 14A, 14B is an annular part. Therefore, through holes (hereinafter referred to as “pin holes”) 141 are formed in the pin hole portions 14A and 14B. In these pin holes 141, one common piston pin (not shown) for connecting the piston 10 to a connecting rod (not shown) is inserted. Each pin hole portion 14A, 14B has a central axis line (that is, a central axis line of the pin hole 141, hereinafter referred to as "pin hole central axis line") C2 extending from the sidewall portions 13A, 13B. It is provided so as to be perpendicular to the plane and penetrate substantially the middle part of the sidewall portions 13A and 13B. Accordingly, one end of each of the pin hole portions 14A and 14B in a direction parallel to the pin hole center axis C2 protrudes outward from the sidewall outer wall surface 131 and is parallel to the pin hole center axis C2. The other end of each of the pin hole portions 14A and 14B in the right direction protrudes inward from the sidewall inner wall surface 132.

  In addition, each pin hole part 14A, 14B is arrange | positioned so that the center axis C2 of one pin hole 141 may correspond with the center axis C2 of the other pin hole 141. FIG. Further, since the respective pin hole portions 14A and 14B are provided in the sidewall portions 13A and 13B, and the respective sidewall portions 13A and 13B are connected to the piston main body bottom wall surface 112, the respective sidewall portions 13A and 13B. Can be said to be a connecting portion that connects the piston body 11 and the pin hole portions 14A and 14B to each other.

  Further, in the following description, the upper portions of the pin hole portions 14A and 14B indicated by the reference numeral 143 in FIG. 1A are referred to as “pin hole upper portions”, and the reference numeral 142 in FIG. The side portions of the pin hole portions 14A and 14B shown are referred to as “pin hole side portions”.

  Ribs 30 are provided on the sidewall outer wall surfaces 131 between the pin hole portions 14 </ b> A and 14 </ b> B and the piston main body portion 11. The rib 30 extends in parallel to the piston center axis C <b> 1 and connects the pin hole upper portion 143 and the piston body bottom wall surface 112.

  A cavity (hereinafter referred to as “piston cavity”) 101 is formed inside the piston 10. The piston cavity 101 is generally defined by a piston main body bottom wall surface 112, a skirt inner peripheral wall surface 122, and a sidewall inner wall surface 132.

  An oil passage (not shown) is formed inside the piston main body 11 for passing oil for cooling the piston main body 11.

  As shown in FIG. 1B, one pin hole portion (hereinafter, this pin hole portion is referred to as “first pin hole portion”) 14A and one skirt portion (hereinafter, this skirt portion is referred to as “first pin portion”). An oil introduction passage defining wall 103 is provided on the inner wall surface 132 of one side wall portion (hereinafter referred to as “first side wall portion”) 13 </ b> A between the two side walls 12 </ b> A ”(referred to as“ one skirt portion ”). ing. The oil introduction passage defining wall 103 extends from the region near the bottom end face of the first sidewall portion 13A substantially upward to the piston main body bottom wall surface 113 through the region near the first pin hole portion 14A. The oil introduction passage defining wall 103 defines an oil introduction passage 102 for introducing oil into the oil passage formed inside the piston main body 11. The oil introduction passage 102 is connected to the oil passage at the piston main body bottom wall surface 113.

  In addition, the other pin hole portion (hereinafter, this pin hole portion is referred to as “second pin hole portion”) 14B and the other skirt portion (hereinafter, this skirt portion is referred to as “second skirt portion”) 12B. An oil discharge passage defining wall 105 is provided on an inner wall surface 132 of a sidewall portion (hereinafter, this sidewall portion is referred to as a “second sidewall portion”) 13B. The oil discharge passage defining wall 105 extends from the region near the bottom end surface of the second sidewall portion 13B to the piston body bottom wall surface 113 through the region near the second pin hole portion 14B substantially upward. The oil discharge passage defining wall 105 defines an oil discharge passage 104 for discharging the oil in the oil passage formed inside the piston main body 11. The oil discharge passage 104 is connected to the oil passage at the piston main body bottom wall surface 113.

  Accordingly, the defining walls 103 and 105 are provided on the sidewall inner wall surfaces 132 corresponding to each other symmetrically with respect to the piston center axis C1.

  In the following description, the side end of the first sidewall portion 13A closer to the oil introduction passage defining wall 103 is referred to as “first side end”, and the side farther from the oil introduction passage defining wall 103 is referred to as “first side end”. The side end of the first sidewall portion 13A is referred to as “second side end”, and the side end of the second sidewall portion 13B closer to the oil discharge passage defining wall 105 is referred to as “first side end”. The side end of the second sidewall portion 13B far from the oil discharge passage defining wall 105 is referred to as a “second side end”. In the following description, the side end of the first skirt portion 12A connected to the first side end of the first sidewall portion 13A is referred to as a “first side end”, and the second sidewall portion 13B. The side end of the first skirt portion 12A connected to the second side end of the first side is referred to as a “second side end”, and the second side end connected to the first side end of the second sidewall portion 13B. The side end of the skirt portion 12B is referred to as “first side end”, and the side end of the second skirt portion 12B connected to the second side end of the first sidewall portion 13A is referred to as “second side end”. Called “end”.

  Two raised portions 20 are provided on the first sidewall portion 13A, and two raised portions 20 are also provided on the second sidewall portion 13B. These raised portions 20 are portions of the sidewall portions 13A and 13B, and are portions that protrude outward from the other portions of the sidewall portions 13A and 13B. Therefore, the sidewall outer wall surface 131 in the region corresponding to the raised portion 20 protrudes outward as compared to the sidewall outer wall surface 131 in the region other than the region.

  Next, the raised portions 20 will be described in detail.

  In the following description, the region indicated by the reference symbol AR1 in FIG. 2 is referred to as an “upper corner region”. This region is a region of the sidewall outer wall surface 131 in the vicinity of the upper end of the connection portion between the sidewall portions 13A and 13B and the skirt portions 12A and 12B (that is, in the vicinity of the connection portion between the skirt portions 12A and 12B and the piston main body portion 11). Of the outer wall surface 131 of the sidewall. Further, the region indicated by the reference symbol AR2 in FIG. 2 is referred to as a “lower corner region”. This region is a region of the sidewall outer wall surface 131 in the vicinity of the lower end of the connection portion between the sidewall portions 13A and 13B and the skirt portions 12A and 12B. Further, the region indicated by the reference symbol AR3 in FIG. 2 is referred to as “pin hole side region”. This region is a region of the sidewall outer wall surface 131 in the vicinity of the pin hole side portion 142.

  Each sidewall outer wall surface 131 has two upper corner regions AR1, two lower corner regions AR2, and two pin hole side regions AR3. Each raised portion 20 is provided on each of the sidewall portions 13A and 13B so as to extend from the upper corner area AR1 to the pin hole side area AR3 closer to the upper corner area AR1. More specifically, each raised portion 20 has a left and right pin hole portion with respect to the pin hole center axis as viewed in FIG. 2 as well as the pin hole portion 14B above the pin hole center axis as viewed in FIG. 14B extends substantially straight from the upper corner area AR1 to the pin hole side area AR3 toward a substantially central part (hereinafter referred to as “an obliquely upper part of the pin hole”). In other words, a plane including the pin hole center axis and the piston center axis is referred to as a pin hole vertical plane, and a plane including the pin hole center axis and perpendicular to the piston center axis is referred to as a pin hole lateral plane. When the portion of the pin hole portion 14B in the vicinity of the pin hole lateral plane is referred to as a pin hole lateral portion, the pin hole upper portion 143 is a portion of the pin hole portion in the vicinity of the pin hole longitudinal plane and is a piston with respect to the pin hole central axis. It is a part on the main body part 11 side, the pin hole obliquely upper part is a part of the pin hole part 14B located substantially in the middle of the pin hole upper part 143 and the pin hole lateral part, and the raised part 20 is from the upper corner area AR1. It extends substantially straight to the pin hole side area AR3 adjacent to the pin hole diagonally upper part. Further, as shown in FIG. 3, the outer wall surface of each raised portion 20 protrudes so as to form a substantially partial cylindrical surface having a line along the extending direction of the raised portion 20 as a generating line.

  Further, as shown in FIG. 3, the inner wall surface of each raised portion 20 (that is, the sidewall inner wall surface 132 corresponding to the raised portion 20) has a line along the extending direction of the raised portion 20 as a bus. It is recessed so as to form a substantially partial cylindrical surface. That is, the sidewall inner wall surface 132 is recessed along the raised portion 20 in a region corresponding to the raised portion 20. Therefore, the sidewall inner wall surface 132 is formed with a groove 21 extending from the upper corner area AR1 to the pin hole side area AR3 closer to the upper corner area AR1.

  By providing the raised portions 20 on the sidewall portions 13A and 13B, the following effects can be obtained.

  That is, when the piston 10 is disposed in the cylinder bore of the internal combustion engine, the combustion chamber (not shown) is formed by the piston body top wall surface 111, the cylinder bore inner wall surface (not shown), and the cylinder head bottom wall surface (not shown). Is formed. A piston pin (not shown) is inserted into the pin hole 141, and the piston 10 is connected to a connecting rod (not shown) via the piston pin.

  Here, when the internal combustion engine is operated and a mixture of fuel and air is combusted in the combustion chamber in the expansion stroke, a large combustion pressure load (that is, a load due to the combustion pressure) is applied to the piston main body top wall surface 111. Then, due to this large combustion pressure load, the inner peripheral wall surface of the pin hole upper portion 143 is pressed against the outer peripheral wall surface of the piston pin upper portion (that is, the upper portion of the piston pin), and as a result, the inner peripheral wall surface of the pin hole upper portion 143 And the pin hole upper part 143 and the piston pin are both deformed so that the curvature radius of the outer peripheral wall surface of the piston pin upper part is larger than the original radius of the pin hole 141 and the original radius of the piston pin, respectively. As a result, tensile stress is generated in the inner peripheral wall surface portion of the pin hole upper portion 143. On the other hand, in the exhaust stroke and the intake stroke following the expansion stroke, the pressure in the combustion chamber decreases, so the tensile stress generated in the inner peripheral wall surface portion of the pin hole upper portion 143 disappears.

  Since the expansion stroke, the exhaust stroke, and the intake stroke are repeatedly performed during engine operation (that is, during operation of the internal combustion engine), the pin hole upper portion 143 is likely to be deteriorated due to fatigue (hereinafter referred to as deterioration due to this fatigue). Is called "fatigue degradation").

  Here, in the piston of the first embodiment, the raised portions 20 are provided on the sidewall portions 13A and 13B. These raised portions 20 extend substantially straight from the upper corner region AR1 to the pin hole side region AR3 toward the diagonally upper portion of the pin hole in the sidewall portions 13A and 13B. Therefore, these raised portions 20 transmit the bending force of the piston main body 11 due to the combustion pressure load to the pin hole side portion 142. Then, due to the force transmitted to the pin hole side portion 142, a force is applied to the pin hole portion 14B in a direction to suppress the bending of the pin hole upper portion 143 due to the combustion pressure load in the expansion stroke. Thereby, the bending of the pin hole upper portion 143 is suppressed, and as a result, the occurrence of tensile stress in the pin hole upper portion 143 is suppressed. For this reason, even if the diameter of the pin hole is reduced, fatigue deterioration of the pin hole upper portion 143 is suppressed. Therefore, according to the first embodiment, the diameter of the pin hole can be reduced while suppressing fatigue deterioration of the pin hole upper portion 143.

  By the way, the raised part 20 of 1st Embodiment is an example of the raised part of this invention. That is, the raised portion of the present invention includes any raised portion extending in the direction from the upper corner area AR1 toward the pin hole side area AR3. In other words, in the raised portion of the present invention, the compressive force applied to the sidewall portions 13A and 13B by the displacement of the piston body outer peripheral portion 116 due to the deflection of the piston body portion 11 is applied to the sidewall portion 13A. , 13B along any path extending from the upper corner area AR1 to the pin hole side area AR3. In other words, the protruding portion of the present invention has a protruding portion on the pin hole side from the upper corner region AR1 so as to suppress the deflection of the piston body 11 when the piston body top wall surface 111 receives a combustion pressure load. Any raised portion extending in the direction toward the region AR3 is included.

  Accordingly, the raised portion of the present invention also includes a raised portion 20 of the shape shown in FIG. That is, each raised portion 20 shown in FIG. 4 extends in a substantially arc shape with a central portion protruding toward the lower corner area AR2 in the extending direction. In other words, each raised portion 20 extends from the upper corner area AR1 substantially downward to the central portion thereof, and the extending direction of the raised portion 20 is pin hole side portion 142 in the central portion. The direction gradually changes in the direction toward, and extends toward the pin hole side portion 142 when the center portion is exceeded.

  Moreover, in 1st Embodiment, it replaces with providing the protruding part 20 extended from upper corner area | region AR1 to pin hole side area | region AR3 in side wall part 13A, 13B, and replaces from upper corner area | region AR1 to pin hole side area | region. You may make it provide the protruding part extended in a part of area | region to AR3 in side wall part 13A, 13B.

  Moreover, in 1st Embodiment, it replaces with providing the protruding part 20 extended continuously in sidewall part 13A, 13B, and the protruding part divided | segmented into several parts and extended is sidewall part 13A, 13B. You may make it provide in.

  Further, in the first embodiment, instead of providing the protruding portion 20 protruding outward in the sidewall portions 13A and 13B, the protruding portion protruding inward may be provided in the sidewall portions 13A and 13B. Good. In this case, in the first embodiment, instead of forming the groove 21 extending along the raised portion 20 on the sidewall inner wall surface 132, the groove extending along the raised portion is formed on the sidewall outer wall surface 131. It is formed.

  By the way, as described above, the groove 21 is formed along the raised portion 20 in the sidewall inner wall surface 132 corresponding to the raised portion 20. When the groove 21 is formed in this way, the effect that the piston 10 is reduced in weight can be obtained. Of course, when this effect is not required or when it is preferable that the groove 21 is not provided on the sidewall inner wall surface 132, the groove 21 may not be formed on the sidewall inner wall surface 132.

  Next, a connection form between the sidewall portions 13A and 13B and the skirt portions 12A and 12B will be described.

  In the following description, the side wall portions 13A, 13B and the skirt portions 12A, 12B are collectively referred to as “piston lower wall”, and the cross section of the piston lower wall cut by a specific surface is referred to as “piston lower wall cross section”. The bottom end surface of the piston lower wall is referred to as the “piston lower wall bottom end surface”, and the connecting portion between the side wall portion and the skirt portion of the piston lower wall cross section or the piston lower wall bottom end surface is referred to as the “piston lower wall connecting portion”. The side wall portion in the vicinity of the piston lower wall connection portion is referred to as “side wall connection portion”, the skirt portion in the vicinity of the piston lower wall connection portion is referred to as “skirt connection portion”, and the piston lower wall cross section Or, the direction in which the side wall connecting portion extends toward the piston lower wall connecting portion on the bottom end surface of the piston lower wall is The direction in which the skirt connecting portion extends toward the piston lower wall connecting portion on the piston lower wall cross section or the bottom surface of the piston lower wall is called the “skirt extending direction”. The angle at which the direction and the skirt extending direction intersect is referred to as “piston lower wall intersection angle”.

  As shown in FIG. 5, a plurality of surfaces A to G for taking a piston lower wall cross section are set. Here, as shown in FIG. 6, a plane P1 perpendicular to the piston center axis C1 is referred to as a “horizontal plane”, and a distance D1 between the horizontal plane P1 and the pin hole center axis C2 is defined as a “horizontal plane distance”. The planes A to G shown in FIG. 5 are horizontal planes P1 having different horizontal plane distances D1.

  In the example shown in FIG. 5, the horizontal plane distance D1 of the surface D is zero. With respect to the surface D, the surface A and the surface G are symmetric, the surface B and the surface F are symmetric, and the surface C and the surface E are symmetric. Further, the horizontal plane distance D1 between the surfaces A and G is the largest, the horizontal plane distance D1 between the surfaces B and F is the next largest, and the horizontal plane distance D1 between the surfaces C and E is set the next largest.

  7A to 7G show cross sections of the piston lower wall when viewed from below by cutting the piston lower wall along these surfaces A to G, respectively, and the piston lower wall bottom end surface is shown in FIG. 7 (H).

  As can be seen from FIG. 7, in the piston 10, the piston lower wall crossing angle (the angle indicated by the reference sign AN in FIG. 7) gradually increases from the lower side to the upper side in the piston lower wall. .

  Therefore, the piston lower wall crossing angle in the upper part of the skirt portions 12A and 12B is relatively large. According to this, the following effects can be obtained.

  That is, when the piston 10 is disposed in the cylinder bore and the internal combustion engine is operated, the skirt portions 12A and 12B receive a so-called thrust force from the inner peripheral wall surface of the cylinder bore. During engine operation, the temperature of the upper part of the skirt parts 12A and 12B (hereinafter, this part is also referred to as “skirt upper part”) is the center part of the skirt part (hereinafter referred to as “skirt central part”) and the skirt part. It becomes higher than the temperature of the lower part (hereinafter, this part is referred to as “skirt lower part”). For this reason, the degree of thermal expansion of the upper part of the skirt is greater than the degree of thermal expansion of the central part of the skirt and the lower part of the skirt. Therefore, when the thrust resistance of the upper part of the skirt (that is, resistance to deformation due to the thrust force) is high, there is a high possibility that a so-called interference fit is generated in which the upper part of the skirt is relatively strongly pressed against the inner peripheral wall surface of the cylinder bore. On the other hand, when the thrust resistance of the upper part of the skirt is low, when the upper part of the skirt is thermally expanded, the upper part of the skirt can be deformed inward in the radial direction with respect to the piston center axis C1. Low. Therefore, in order to suppress the interference fit, it is preferable to reduce the thrust resistance of the upper part of the skirt.

  Here, the greater the piston lower wall crossing angle, the lower the thrust resistance of the skirt portions 12A, 12B. In the piston 10, since the piston lower wall crossing angle gradually increases from the lower side to the upper side in the piston lower wall, the piston lower wall crossing angle of the upper part of the skirt is relatively large. Accordingly, since the thrust resistance of the upper part of the skirt is low, the interference fit of the upper part of the skirt is suppressed.

  Moreover, in the piston 10, the piston lower wall crossing angle of the lower part of the skirt is relatively small. According to this, the following effects can be obtained.

  That is, when the piston 10 is disposed in the cylinder bore and the internal combustion engine is operated, a force is applied to the piston 10 to displace the piston 10 so that the piston center axis C1 is inclined with respect to the cylinder bore center axis. The lower part of the skirt is pressed against the inner peripheral wall surface of the cylinder bore. At this time, if the rigidity of the lower part of the skirt is low, the lower part of the skirt can be easily deformed inward. Therefore, when the lower part of the skirt is pressed against the inner peripheral wall surface of the cylinder bore, the lower part of the skirt is deformed inward. On the other hand, if the rigidity of the lower part of the skirt is high, even if the lower part of the skirt is pressed against the inner peripheral wall surface of the cylinder bore, the lower part of the skirt does not deform inward. Therefore, in order to prevent the skirt lower part from being deformed inward, it is preferable to increase the rigidity of the skirt lower part.

  Here, the smaller the piston lower wall crossing angle, the higher the rigidity of the skirt portions 12A and 12B. In the piston 10, since the piston lower wall crossing angle gradually increases from the lower side to the upper side in the piston lower wall, the piston lower wall crossing angle of the lower part of the skirt is relatively small. Therefore, since the rigidity of the lower part of the skirt is high, the inward deformation of the lower part of the skirt is suppressed.

  Thus, in the piston 10, the piston lower wall crossing angle gradually increases from the lower side to the upper side in the piston lower wall, thereby suppressing the interference fit of the upper part of the skirt and inward of the lower part of the skirt. Suppression of deformation is achieved at the same time.

  By the way, in the piston 10, a plurality of piston lower wall cross sections are obtained as follows, and when the piston lower wall cross section and the piston lower wall cross angle at the piston lower wall bottom end face are compared with each other, the piston lower wall cross angle is also compared. Is gradually increased from below to above in the piston lower wall.

  That is, as shown in FIG. 8, a plurality of surfaces A to G for taking a piston lower wall cross section are set. Here, as shown in FIG. 9, a plane P2 including the pin hole center axis C2 and the piston center axis C1 is referred to as a “reference plane”, and a plane P3 extending to one side of the reference plane P2. And the plane P4 extending to the other side of the reference plane P2 is a pair of planes P3 and P4 that are symmetrical with respect to the reference plane P2 and intersect with each other. When a pair of planes coinciding with the axis C2 are referred to as “pair planes” and an angle AN1 between the pair planes P3 and P4 is referred to as “interplane angle”, planes A to G shown in FIG. The plane-to-plane angles AN1 are different planes P3 and P4, respectively.

  In the example shown in FIG. 8, the inter-plane angle AN1 is set to be larger in the order of the opposite planes A to G.

  When the piston lower wall crossing angle in the piston lower wall cross section when the piston lower wall is cut along these opposite planes A to G and the piston lower wall crossing angle in the piston lower wall bottom end surface are compared with each other, the piston lower wall The crossing angle gradually increases from the bottom to the top in the piston lower wall.

  Further, in the piston 10, a plurality of piston lower wall cross sections are obtained as follows, and the piston lower wall cross angle is also compared when the piston lower wall cross section and the piston lower wall cross angle at the piston lower wall bottom end surface are compared with each other. Is gradually increased from below to above in the piston lower wall.

  That is, as shown in FIG. 10, a plurality of surfaces A to G for taking a piston lower wall cross section are set. Here, as shown in FIG. 11, a plane P2 including the pin hole center axis C2 and the piston center axis C1 is referred to as a “reference plane”, and a plane P5 extending to one side of the reference plane P2. A pair of planes P5 and P6 constituted by a plane P6 extending to the other side of the reference plane P2 and symmetric with respect to the reference plane P2 are referred to as “pair planes”. When the angle AN2 between the planes P5 and P6 is referred to as an “interplanar angle”, and the distance D2 between the line intersecting the planes P5 and P6 and the pin hole central axis C2 is referred to as a “plane distance”, FIG. The planes A to G shown in FIG. 2 are opposite planes P5 and P6 with different plane-to-plane angles AN2 and cross-sectional plane distances D2.

  In the example shown in FIG. 10, the angle between the planes of the plane D is 180 °. And with respect to the opposing plane D, the opposing planes A to C are arranged on the upper side, and the opposing planes E to G are arranged on the lower side. Further, with respect to the pair plane D, the pair plane A and the pair plane G are symmetric, the pair plane B and the pair plane F are symmetric, and the pair plane C and the pair plane E are symmetric. The plane distance D2 between the planes A and G is the largest, the plane distance D2 between the planes B and F is the next largest, and the plane distance D2 between the planes C and E is the next largest. Further, the inter-plane angle AN2 is set to be larger in the order of the planes A to C and E to G.

  When the piston lower wall crossing angle in the piston lower wall cross section when the piston lower wall is cut along these opposite planes A to G and the piston lower wall crossing angle in the piston lower wall bottom end surface are compared with each other, the piston lower wall The crossing angle gradually increases from the bottom to the top in the piston lower wall.

  Further, in the piston 10, a plurality of piston lower wall cross sections are obtained as follows, and the piston lower wall cross angle is also compared when the piston lower wall cross section and the piston lower wall cross angle at the piston lower wall bottom end surface are compared with each other. Is gradually increased from below to above in the piston lower wall.

  That is, as shown in FIG. 12, a plurality of surfaces A to G for taking a piston lower wall cross section are set. Here, as shown in FIG. 13, a plane P2 including the pin hole center axis C2 and the piston center axis C1 is referred to as a “reference plane”, and a cylindrical surface having the center axis on the reference plane P2 as the center. When P7 is simply referred to as “cylindrical surface” and the distance D3 between the line intersecting the cylindrical surface P7 and the reference plane P2 and the pin hole central axis C2 is referred to as “cylindrical surface distance”, it is shown in FIG. The surfaces A to C and E to G are cylindrical surfaces P7 having different radii of curvature and cross-sectional plane distances D3, and the surface D shown in FIG. 12 is perpendicular to the reference plane P2. It is a surface including the pin hole central axis C2.

  In the example shown in FIG. 12, with respect to the surface D, the cylindrical surfaces A to C are arranged on the upper side, and the cylindrical surfaces E to G are arranged on the lower side. Regarding the surface D, the cylindrical surface A and the cylindrical surface G are symmetric, the cylindrical surface B and the cylindrical surface F are symmetric, and the cylindrical surface C and the cylindrical surface E are symmetric. The sectional plane distance D3 between the cylindrical surfaces A and G is the largest, the sectional plane distance D3 between the cylindrical surfaces B and F is the next largest, and the sectional plane distance D3 between the cylindrical surfaces C and E is set the next largest. Yes. Further, the radius of curvature of the cylindrical surfaces A and G is the smallest, the radius of curvature of the cylindrical surfaces B and F is set to the next smallest, and the radius of curvature of the cylindrical surfaces C and E is set to the next smallest.

  And when the piston lower wall is cut along these cylindrical surfaces A to C and E to G and the surface DD, the piston lower wall crossing angle in the piston lower wall cross section and the piston lower wall crossing angle in the piston lower wall bottom end surface Are compared with each other, the piston lower wall crossing angle gradually increases from the lower side to the upper side on the piston lower wall.

  As described above, if the characteristics related to the piston lower wall crossing angle described with reference to FIGS. 5 to 13 are comprehensively expressed, in the piston 10, at least the piston lower wall crossing angles (at the two piston lower wall cross sections that do not cross each other) Or, the piston lower wall crossing angle in the piston lower wall cross-section located higher is lower than the piston lower wall crossing angle in one piston lower wall cross-section and the piston lower wall bottom end face). It can be said that it is larger than the piston lower wall crossing angle in the piston lower wall cross section (or the piston lower wall bottom end face).

  Incidentally, as can be seen from FIG. 7, in the piston 10, the side wall connecting portion (that is, the portion of the side wall portions 13 </ b> A and 13 </ b> B near the piston lower wall connecting portion) is at least curved. The curvature radius of the side wall connecting portion (hereinafter, this curvature radius is referred to as “side wall curvature radius”) gradually decreases from the lower side to the upper side in the side wall portion.

  In the piston 10, the side wall connecting portion at the bottom end surface of the piston lower wall may extend linearly, or the lower side section of the lower piston wall and the side wall connecting portion at the bottom end surface of the piston lower wall are linear. It may extend to.

  As described above, in the piston 10, the side wall curvature radius gradually decreases from the lower side to the upper side in the side wall portions 13A and 13B. Therefore, the sidewall curvature radius in the upper portion of the sidewall is relatively small. According to this, the following effects can be obtained.

  That is, as described above, in order to suppress the interference fit, it is preferable to reduce the thrust resistance of the upper part of the skirt. Here, the smaller the sidewall curvature radius, the lower the thrust resistance of the skirt. Therefore, in the piston 10, the sidewall curvature radius gradually decreases from the lower side to the upper side in the side wall portions 13A and 13B, so that the thrust resistance of the upper part of the skirt is low, and the interference fit of the upper part of the skirt is suppressed. Is done.

  Further, as described above, in the piston 10, the sidewall curvature radius gradually decreases from the lower side to the upper side in the side wall portions 13A and 13B. Therefore, the sidewall curvature radius in the lower portion of the sidewall is relatively large. According to this, the following effects can be obtained.

  That is, as described above, in order to suppress the inward deformation of the skirt lower part, it is preferable to increase the rigidity of the skirt lower part. Here, the larger the sidewall curvature radius, the higher the rigidity of the skirt portion. Therefore, in the piston 10, the sidewall curvature radius gradually decreases from the lower side to the upper side in the side wall portions 13A and 13B. Therefore, the rigidity of the lower part of the skirt is high, and the deformation of the lower part of the skirt is inward. Is suppressed.

  As described above, in the piston 10, the side wall curvature radius gradually decreases from the lower side to the upper side in the side wall portions 13A and 13B, thereby suppressing the interference fit of the upper part of the skirt and the inner side of the lower part of the skirt. Suppression of deformation to the same is achieved at the same time.

  Next, the thickness of the skirt portions 12A and 12B when measured in a direction perpendicular to the piston center axis C1 will be described.

  In the piston 10, the skirt portions 12A and 12B have a thickness that gradually increases from the top to the bottom in the skirt portion as shown in FIG. The thickness is also called “skirt thickness”). According to this, the following effects can be obtained.

  That is, the skirt portions 12A and 12B are connected to the piston main body 11 having high rigidity at their upper ends (hereinafter, the upper ends are referred to as “skirt upper ends”). Accordingly, if the skirt portions 12A and 12B have a constant thickness throughout, the thrust resistance of the skirt portion (that is, the ability to withstand deformation due to the thrust force) is the lower end of the skirt portion (hereinafter referred to as this lower portion). The end tends to become higher from the “skirt lower end” toward the upper end of the skirt.

  Therefore, for example, as shown in FIG. 14B, when the skirt portions 12A and 12B have a thickness that gradually decreases from the upper end of the skirt toward the lower end of the skirt, the central region of the skirt portion The thickness of this part (hereinafter this part is also referred to as “skirt central part”) and the part of the lower region of the skirt part (hereinafter this part is also referred to as “skirt lower part”) are relatively thin. The thrust resistance of these parts is significantly reduced. In this case, when the thrust force is applied to the skirt portions 12A and 12B, at least the central portion of the skirt is recessed. In this case, an acute corner portion is formed at the boundary portion between the concave portion of the skirt central portion and the non-dented portion of the skirt portion. When such a corner portion is formed in the skirt portions 12A and 12B, friction between the skirt portion and the inner peripheral wall surface of the cylinder bore increases at the corner portion.

  However, when the skirt portions 12A and 12B have a thickness that gradually increases from the upper end of the skirt toward the lower end of the skirt as in the piston 10, the thickness of the skirt central portion and the thickness of the skirt lower portion are relatively Since it is thick, the thrust resistance of these parts is relatively high. Of course, the thickness of the upper region of the skirt portions 12A and 12B (hereinafter, this portion is referred to as the “skirt upper portion”) is relatively thin, but since this portion is a portion close to the piston body 11, The thrust resistance of this part is relatively high.

  Thus, in the piston 10, since the thrust resistance of the skirt portions 12A and 12B as a whole is high, the central portion of the skirt is not recessed by the thrust force (or even if the skirt central portion is deformed so as to be recessed). The deformation amount is very small and the area of the recessed portion is very small). Therefore, an increase in friction between the skirt portions 12A and 12B and the cylinder bore inner peripheral wall surface is suppressed.

  By the way, as described above, when the thrust resistance of the upper part of the skirt is high, there is a high possibility that the interference of the upper part of the skirt will occur. It is preferable to reduce the resistance.

  Here, in the piston 10, as described above, the skirt portions 12A and 12B have a thickness that gradually increases from the lower end of the skirt toward the upper end of the skirt, and the thickness of the upper portion of the skirt becomes relatively thin. Yes. Accordingly, since the thrust resistance of the upper part of the skirt is low, the interference fit of the upper part of the skirt is suppressed.

  By the way, as shown in FIG. 14A, the skirt outer peripheral wall surface 121 is a partial cylindrical surface with the piston center axis C1 as the center, but a portion having a large diameter with respect to the piston center axis C1 (hereinafter, this portion is referred to as “ When the large-diameter portion is on the skirt outer peripheral wall surface 121, a large thrust force is applied to the large-diameter portion. Therefore, it can be said that this large diameter portion is easily dented by the thrust force. And as above-mentioned, in order to suppress that the friction between skirt part 12A, 12B and a cylinder bore inner peripheral wall surface becomes large, it is preferable to suppress that the skirt outer peripheral wall surface 121 dents. Therefore, when the diameter of each part of the skirt outer peripheral wall surface 121 with respect to the piston center axis C1 is different, the thickness of each part may be increased in proportion to the diameter of the part. According to this, even when the skirt outer peripheral wall surface 121 has a large-diameter portion, the friction between the skirt portions 12A, 12B and the cylinder bore inner peripheral wall surface is suppressed.

  As described above, when the thickness of each part of the skirt parts 12A and 12B is increased in proportion to the diameter of the part, when the large diameter part is in the central region of the skirt outer peripheral wall surface 121, as a result, The thickness of the upper part of the skirt is thin. For this reason, since the thrust resistance of the upper part of the skirt is low, the interference fit of the upper part of the skirt is suppressed.

  By the way, when the large diameter portion is in the central region of the skirt outer peripheral wall surface 121, the skirt outer peripheral wall surface 121 is prevented from being recessed radially inward with respect to the piston center axis C1, and the interference fit of the upper portion of the skirt is suppressed. For this, at least the thickness of the central part of the skirt should be relatively thick and the thickness of the upper part of the skirt should be relatively thin. Therefore, in this case, the thickness of the lower part of the skirt may be relatively thin. Therefore, when the large-diameter portion is in the central region of the skirt outer peripheral wall surface 121, as shown in FIG. 14C, the thickness of the skirt central portion is made relatively thick, and the skirt upper portion and the skirt lower portion The thickness may be made relatively thin.

  In this case, since the thickness of the lower part of the skirt is relatively thin, an effect of reducing the weight of the piston 10 can be obtained.

  By the way, as mentioned above, when the piston main body part 11 bends, the side wall parts 13A and 13B are also bent using the pin hole upper part 143 as a fulcrum. Thus, the pin hole upper portion 143 serves as a fulcrum for bending the sidewall portions 13A and 13B. For this reason, the temperature of the pin hole upper portion 143 and the vicinity thereof tends to be higher than the temperatures of the other portions. Therefore, in order to suppress fatigue deterioration of the pin hole upper portion 143 and the vicinity thereof, it is desired to cool these portions efficiently.

  Therefore, in the piston 10, the pin hole upper portion 143 and the vicinity thereof may be configured as shown in FIG. That is, in the embodiment shown in FIG. 15 (hereinafter, this embodiment is referred to as “second embodiment”), the ribs 30 are recessed in the sidewall outer wall surface 131 near the pin hole upper portion 143 on both sides of the rib 30 (FIG. 15). (A), a shaded portion denoted by reference numeral 31 is provided. The wall surface that defines each recess 31 is at least approximately inwardly extending from the region adjacent to the pin hole upper portion 143 toward the inside of the sidewall portions 13A and 13B and obliquely upward. And a wall surface 33 extending substantially perpendicularly to the piston center axis C1 from the inner end of the recess slope 32 to the outside.

  The following effects are acquired by providing the depression 31 in the sidewall outer wall surface 131 in the vicinity of the pin hole upper portion 143 as in the second embodiment.

  That is, when the piston 10 of the second embodiment is disposed in the cylinder bore and the internal combustion engine is operated, oil for cooling / lubricating is provided from below into the space between the sidewall outer wall surface 131 and the cylinder bore inner wall surface. Blown up. The blown oil arrives at the pin hole upper portion 143 and the vicinity thereof through a space between the sidewall outer wall surface 131 and the cylinder bore inner wall surface.

  Here, when the depression slope 32 is not provided in the vicinity of the pin hole upper portion 143, the oil that has arrived at this portion flows out from this portion relatively early. That is, the time for the oil to stay around the portion near the pin hole upper portion 143 is short.

  On the other hand, when the depression slope 32 is provided in the vicinity of the pin hole upper portion 143 as in the second embodiment, the time that the oil stays in the vicinity of the portion near the pin hole upper portion is increased for the following reason. . That is, as shown in FIG. 16A, when the piston 10 is disposed in the cylinder bore 50, the piston center axis C1 is substantially parallel to the vertical direction. Therefore, when the piston is disposed in the cylinder bore, the concave slope 32 is disposed obliquely with respect to the vertical direction. For this reason, the oil that has arrived in the vicinity of the upper portion of the pin hole stays on the concave slope 32 as shown in FIG. For this reason, when the concave slope 32 is provided in the vicinity of the pin hole upper portion, the time for the oil to stay around the portion near the pin hole upper portion becomes longer.

  According to the second embodiment, the oil stays in the vicinity of the portion near the pin hole upper portion 143, so that the portion of the piston around the portion near the pin hole upper portion (that is, the pin hole upper portion 143 and The portion in the vicinity thereof is efficiently cooled.

  Furthermore, when the concave slope 32 is provided in the vicinity of the pin hole upper portion 143 as in the second embodiment, the time that the oil stays in the vicinity of the portion near the pin hole upper portion is further increased for the following reason. become longer. That is, as shown in FIG. 16B, when the piston 10 is disposed in the cylinder bore 50, the recessed inclined surface 32 is disposed obliquely with respect to the vertical direction. For this reason, the hollow slope 32 is inclined with respect to the diffusion direction of the oil arriving there. Therefore, as indicated by an arrow A in FIG. 16B, the depression slope 32 can rebound the oil that has arrived there upward. For this reason, the oil arriving at the depression slope 32 is scattered in the depression 31. That is, the oil that has arrived in the vicinity of the pin hole upper portion 143 stays around the portion in the vicinity of the pin hole upper portion. For this reason, when the concave slope 32 is provided in the vicinity of the pin hole upper portion 143 as in the second embodiment, the time for the oil to stay around the portion in the vicinity of the pin hole upper portion is further increased.

  According to the second embodiment, the oil stays in the vicinity of the portion near the pin hole upper portion 143, so that the portion of the piston around the portion near the pin hole upper portion (that is, the pin hole upper portion 143). And the vicinity thereof) are further efficiently cooled.

  By the way, the hollow 31 of 2nd Embodiment is an example of the hollow of this invention. That is, the depression of the present invention includes any depression that can retain oil in a portion near the upper portion of the pin hole.

  Therefore, in the piston of the second embodiment, instead of providing the depressions 31 on the sidewall outer wall surfaces 131 on both sides of the rib 30, the depressions are provided only on the sidewall outer wall surface 131 on one side of the rib 30. Also good.

  Further, the rib 30 has an effect of increasing the rigidity of the sidewall portions 13A and 13B between the pin hole upper portion 143 and the piston main body portion 11. However, if priority is given to the effect of retaining a larger amount of oil in the region in the vicinity of the pin hole upper portion 143 than such an effect, the sidewall outer wall surfaces on both sides of the rib 30 in the piston of the second embodiment. In addition to providing the recess 31 in 131, a recess similar to the recess 31 of the piston 10 of the second embodiment may be provided on the outer wall surface of the rib 30 near the pin hole upper portion 143.

  Of course, in the piston of the second embodiment, instead of providing the depression 31 on the sidewall outer wall surface 131 on both sides of the rib 30, the piston of the second embodiment is formed on the outer wall surface of the rib 30 near the pin hole upper portion 143. You may make it provide the hollow similar to the hollow 31 of ten.

  Moreover, the hollow slope 32 of 2nd Embodiment is an example of the hollow slope of this invention. That is, the concave slope of the present invention includes any wall surface that can retain oil arriving at a portion near the upper portion of the pin hole when the piston is disposed in the cylinder bore. In addition, the hollow surface of the present invention includes any wall surface that can rebound upwardly the oil arriving at a portion near the pin hole upper portion when the piston is disposed in the cylinder bore.

  Therefore, as in the second embodiment, instead of providing the depression slope 31 extending obliquely upward from the sidewall outer wall surface 131 in the vertical direction on the sidewall outer wall surface 131 in the vicinity of the pin hole upper portion 143, A wall surface extending obliquely downward from the region near the pin hole upper portion 143 toward the inside of the sidewall portions 13A and 13B with respect to the piston center axis C1 is provided on the sidewall outer wall surface 131 near the pin hole upper portion 143. Alternatively, the wall surface extending in the direction perpendicular to the piston center axis C1 from the region near the pin hole upper portion 143 toward the inside of the side wall portions 13A and 13B is the side near the pin hole upper portion 143. You may make it provide in the wall outer wall surface 131. FIG.

  Incidentally, as shown in FIG. 15A, in the second embodiment, the sidewall outer wall surface 131 is provided with a raised portion 20 similar to the raised portion 20 of the first embodiment. For this reason, the portion near the pin hole upper portion 143 is more efficiently cooled by the oil for the following reason.

  That is, the raised portion 20 of the second embodiment is provided on the sidewall portions 13A and 13B so as to extend from the pin hole side region AR3 to the upper corner region A1 in the same manner as the raised portion 20 of the first embodiment. ing. In other words, the raised portion 20 is in the direction away from the pin hole from the region of the sidewall outer wall surface 131 in the vicinity of the depression 31 (that is, in the vicinity of the depression slope 32) and in the vicinity of the pin holes 14A and 14B. In this case, the sidewall outer wall surface 131 extends obliquely upward. In other words, the raised portion 20 is in the vicinity of the depression 31 (that is, in the vicinity of the depression slope 32) and away from the pin hole portion from the region of the sidewall outer wall surface 131 in the vicinity of the pin hole portions 14A and 14B. It extends in the direction and obliquely upward to the region of the sidewall outer wall surface 131 adjacent to the piston body 11.

  Therefore, when the piston 10 is disposed in the cylinder bore so that the piston center axis C1 is parallel to the vertical direction, the upper region of the raised portion 20 (that is, the outer wall surface of the raised portion 20 extends along the extending direction thereof. The outer wall surface of a region located on the upper side when divided into two regions by a surface perpendicular to the sidewall outer wall surface 131 is inclined at least with respect to the vertical direction. For this reason, this outer wall surface can capture and retain the oil flowing out from the recess 31, and can also capture and retain the oil arriving at the sidewall outer wall surface 131 above the raised portion 20. Can do. In other words, the raised portion 20 can keep the oil in the vicinity of the pin hole upper portion 143 and the vicinity thereof. Then, the pinned oil cools the portion near the pin hole upper portion 143 and the surrounding portion. For this reason, in the second embodiment, the portion in the vicinity of the pin hole upper portion 143 and the surrounding portion are further efficiently cooled by the oil.

  In addition, the recess 31 of the above-described embodiment can retain oil not a little regardless of the viscosity of the oil. However, the higher the viscosity of the oil, the more the recess 31 can hold the oil more reliably. In addition, the raised portion 20 of the above-described embodiment can retain oil not a little regardless of the viscosity of the oil. However, the higher the oil viscosity, the more reliably the raised portion 20 can retain the oil.

  As shown in FIG. 1B, in the above-described embodiment, the oil introduction passage defining wall 103 is provided on the inner wall surface of the first sidewall portion 13A, and the inner wall of the second sidewall portion 13B is provided. An oil discharge passage defining wall 105 is provided on the wall surface. Next, the defining walls 103 and 105 will be described in detail.

  When the oil introduction passage defining wall 103 is provided as shown in FIG. 1B, the oil introduction passage defining wall 103 is a portion near the first side end of the first sidewall portion 13A. As a result, the rigidity of the portion in the vicinity of the first side end of the first skirt portion 12A connected to the first side end of the first sidewall portion 13A is also increased. However, the second side wall portion 13B is not provided with a wall such as the oil introduction passage defining wall 103 that increases the rigidity of the second side wall portion 13B in the vicinity of the second side end. The rigidity of the portion in the vicinity of the second side end of the first skirt portion 12A connected to the second side end of 13B is not increased. Therefore, the rigidity of the portion near the first side end of the first skirt portion 12A is higher than the rigidity of the portion near the second side end of the first skirt portion 12A.

  By the way, when the piston is disposed in the cylinder bore and the internal combustion engine is operated, the skirt portions 12A and 12B receive a thrust force from the inner peripheral wall surface of the cylinder bore. This thrust force increases or decreases. Here, when the thrust force increases, at least a part of the skirt portions 12A and 12B is deformed by the thrust force. After that, when the thrust force is reduced, the shape of the deformed skirt portions 12A and 12B returns to the original shape.

  Here, the rigidity of the portion in the vicinity of the first side end of the first skirt portion 12A is higher than the rigidity of the portion in the vicinity of the second side end of the first skirt portion 12A by the oil introduction passage defining wall 103. In this case, the degree of deformation of the first side end portion of the first skirt portion 12A due to the thrust force is smaller than the degree of deformation of the second side end portion of the first skirt portion 12A due to the thrust force. That is, in the first skirt portion 12A, the degree of deformation of the first side end portion due to the thrust force is different from the degree of deformation of the second side end portion due to the thrust force. When the deformation degrees are different from each other as described above, a large stress is generated in a part of the first skirt portion 12A when the first skirt portion 12A is deformed by receiving a thrust force. After that, when the thrust force received by the first skirt portion 12A is reduced, the shape of the deformed portion of the first skirt portion 12A returns to the original shape, and the large amount generated in a part of the first skirt portion 12A. The stress disappears. As described above, when a large stress is generated in the first skirt portion 12A or the large stress disappears, the first skirt portion 12A is deteriorated due to fatigue.

  Therefore, in order to suppress such fatigue deterioration of the first skirt portion 12A, as shown in FIG. 17, the first side end of the first skirt portion 12A is not provided without providing the oil introduction passage defining wall 103. An oil introduction port 104 for introducing oil into the oil passage inside the piston main body 11 is formed in a portion of the piston main body bottom wall surface 112 near the upper end of the connection portion between the first side wall 13A and the first side wall 13A. You may make it provide.

  In the embodiment shown in FIG. 17 (hereinafter, this embodiment is referred to as “third embodiment”), the rigidity of the first skirt portion 12A is uniform over the entire area. Generation of a large stress in a part is suppressed. For this reason, fatigue deterioration of the first skirt portion 12A is suppressed.

  Similarly, the rigidity of the portion near the first side end of the second skirt portion 12B is higher than the rigidity of the portion near the second side end of the second skirt portion 12B by the oil discharge passage defining wall 105. In this case, the degree of deformation of the portion on the first side end side of the second skirt portion 12B due to the thrust force is smaller than the degree of deformation of the portion on the second side end side of the second skirt portion 12B due to the thrust force. That is, in the second skirt portion 12B, the degree of deformation of the first side end portion due to the thrust force and the degree of deformation of the second side end portion due to the thrust force are different from each other. When the deformation degrees are different from each other as described above, a large stress is generated in a part of the second skirt portion 12B when the second skirt portion 12B is deformed by receiving a thrust force. Then, when the thrust force received by the second skirt portion 12B is reduced, the shape of the deformed portion of the second skirt portion 12B returns to the original shape, and the large amount generated in a part of the second skirt portion 12B. The stress disappears. As described above, when a large stress is generated in the second skirt portion 12B or the large stress disappears, the second skirt portion 12B is deteriorated due to fatigue.

  Therefore, in order to suppress the fatigue deterioration of the second skirt portion 12B, as shown in FIG. 17, the first side end of the second skirt portion 12B is not provided without providing the oil discharge passage defining wall 105. An oil discharge port 105 for discharging oil from the oil passage inside the piston body 11 to the piston body bottom wall surface 112 in the vicinity of the upper end of the connection portion between the first sidewall and the first side wall 13B. May be provided.

  In the third embodiment shown in FIG. 17, since the rigidity of the second skirt portion 12B is uniform throughout, it is possible to suppress a large stress from being generated in a part of the second skirt portion 12B. . For this reason, fatigue deterioration of the 2nd skirt part 12B is suppressed.

  By the way, in the above-described embodiment, when the piston is disposed in the cylinder bore, oil is blown to the oil inlet 104 from below the bottom end surface of the sidewall, and this blown oil is applied to the oil inlet 104. Inflow. Therefore, when the oil introduction port 104 is provided in the piston main body bottom wall surface 112 like 3rd Embodiment, oil will not flow into the oil introduction port 104 efficiently.

  Therefore, the second skirt portion 12B is provided on the thrust side in order to efficiently flow oil into the oil inlet 104 while suppressing fatigue deterioration of the skirt portions due to the uneven rigidity of the skirt portions 12A and 12B. 18, the inner wall surface of the first sidewall portion 13A between the first pin hole portion 14A and the first lateral end of the first skirt portion 12A as shown in FIG. An oil introduction passage defining wall 103 extending from the bottom end surface of the first side wall portion 13A to the piston body bottom wall surface 112 is provided at 132, and the oil introduction passage defined by the oil introduction passage defining wall 103 is defined as a piston. 10 is connected to the oil passage in the interior of the piston 10 in the vicinity of the upper end of the connecting portion between the first side end of the second skirt portion 12B and the first side end of the second sidewall portion 13B. The oil discharge port 105 may be provided in the bottom wall surface 112 (that is, the second sidewall portion 13B between the second pin hole portion 14B and the first side end of the second skirt portion 12B). The oil discharge passage defining wall 105 is not provided on the inner wall surface).

  In the embodiment shown in FIG. 18 (hereinafter, this embodiment is referred to as “fourth embodiment”), since the second skirt portion 12B is disposed on the thrust side, the first skirt portion is operated during engine operation. The thrust force received by 12A is smaller than the thrust force received by second skirt portion 12B. Accordingly, the oil introduction passage defining wall 103 is provided on the inner wall surface 132 of the first sidewall portion 13A between the first pin hole portion 14A and the first lateral end of the first skirt portion 12A. Even if the rigidity of the first side end portion of the first skirt portion 12A and the rigidity of the second side end portion of the first skirt portion 12A are different from each other, the thrust force received by the first skirt portion 12A Is relatively small, a large stress is not generated in a part of the first skirt portion 12A. Therefore, fatigue deterioration of the first skirt portion 12A is suppressed.

  In the fourth embodiment, the oil introduction passage defining wall 103 extends from the bottom end surface of the first sidewall portion 13A to the piston main body bottom wall surface 112, so that the oil introduction port 104 is connected to the first sidewall portion 13A. It is formed near the bottom end face. Therefore, the oil efficiently flows into the oil inlet 104.

  On the other hand, in the fourth embodiment, the oil discharge passage defining wall 105 is provided on the inner wall surface 132 of the second sidewall portion 13B between the second pin hole portion 14B and the first lateral end of the second skirt portion 12B. Since this is not done, the rigidity of the second skirt portion 12B is uniform throughout. Therefore, even if the second skirt portion 12B is disposed on the thrust side and the thrust force received by the second skirt portion 12B is relatively large, a large stress is not generated in a part of the second skirt portion 12B. Therefore, fatigue deterioration of the second skirt portion 12B is suppressed.

  By the way, in the above-described embodiment, the combustion chamber formed by the piston top wall surface 111 and the cylinder bore inner peripheral wall surface generally discharges exhaust gas from the intake port and the combustion chamber for introducing air into the combustion chamber. The exhaust port is connected. Here, the temperature of the exhaust gas discharged from the combustion chamber is higher than the temperature of the air introduced into the combustion chamber. Therefore, the temperature in the region in the combustion chamber near the exhaust port is higher than the temperature in the region in the combustion chamber near the intake port. Therefore, the temperature of the cylinder bore inner peripheral wall surface close to the exhaust port is higher than the temperature of the cylinder bore inner peripheral wall surface close to the intake port. Therefore, when the piston of the above-described embodiment is disposed in the cylinder bore and the internal combustion engine is operated, the temperature of the piston portion close to the exhaust port becomes higher than the temperature of the piston portion close to the intake port.

  On the other hand, in the above-described embodiment, the cooling effect by the oil in the piston portion near the oil introduction port 104 is higher than the cooling effect by the oil in the piston portion far from the oil introduction port 104.

  Therefore, from the viewpoint of efficiently cooling the entire piston with oil, the skirt portion closer to the oil inlet 104 (that is, the first skirt portion 12A in the above-described embodiment) is disposed near the exhaust port and The piston of the above-described embodiment is disposed in the cylinder bore so that the skirt portion far from the oil inlet 104 (that is, the second skirt portion 12B in the above-described embodiment) is disposed near the intake port. Is preferred.

  Incidentally, in the first embodiment, the oil introduction passage defining wall 103 and the oil discharge passage defining wall 105 are provided on the sidewall inner wall surface 132 in order to form the oil introduction passage 102 and the oil discharge passage 104. When the defining walls 103 and 105 are provided on the sidewall inner wall surface 132 as described above, the weight of the piston is larger than when the defining walls 103 and 103 are not provided on the sidewall inner wall surface 132. Becomes heavier. On the other hand, in the field of pistons, there is a demand for weight reduction of pistons. Therefore, even when the oil introduction passage 102 and the oil discharge passage 104 are formed, it may be desired to reduce the weight of the piston as much as possible.

  Therefore, in the first embodiment, even if the oil introduction passage 102 and the oil discharge passage 104 are formed, these passages 102 and 104 are formed as shown in FIG. 19 in order to reduce the weight of the piston as much as possible. May be.

  That is, in the embodiment shown in FIG. 19 (hereinafter, this embodiment is referred to as “fifth embodiment”), as shown in FIG. 19A, the first pin hole portion 14A and the first skirt Oil is obtained by closing the groove 21 formed along the raised portion 20 on the inner wall surface of the raised portion 20 provided in the first sidewall portion 13A between the first side end of the portion 12A with the wall 22. An introduction passage 102 is formed. That is, the raised portion 20 is used as a part of the oil introduction passage defining wall 103.

  As described above, when the raised portion 20 is used as a part of the oil introduction passage defining wall 103, the weight of the piston is reduced as compared with the case where the raised portion 20 is not used as a part of the oil introduction passage defining wall 103. The

  In the fifth embodiment, as shown in FIG. 19B, the second sidewall portion 13B between the second pin hole portion 14B and the first lateral end of the second skirt portion 12B is provided. An oil discharge passage is formed by closing a groove 21 formed along the raised portion 20 on the inner wall surface of the provided raised portion 20 with a wall 23. That is, the raised portion 20 is used as a part of the oil discharge passage defining wall 105.

  Thus, when the raised portion 20 is used as a part of the oil discharge passage defining wall 105, the weight of the piston is reduced compared to the case where the raised portion 20 is not used as a part of the oil discharge passage defining wall 105. The

  The concept of the fifth embodiment in which the raised portion 20 is used as a part of the oil introduction passage defining wall 103 is that the oil discharge passage defining wall 105 is not provided and only the oil introduction passage defining wall 103 is provided. It is also applicable to the fourth embodiment.

  By the way, the piston of embodiment mentioned above has a pair of pin hole part. However, the piston of the above-described embodiment may have one substantially annular pin hole. In this case, the pin hole portion is provided so as to penetrate both the sidewall portions 13A and 13B. Of course, the central axis of this pin hole is perpendicular to the extending plane of both sidewalls 13A, 13B.

  DESCRIPTION OF SYMBOLS 10 ... Piston, 11 ... Piston main-body part, 12A, 12B ... Skirt part, 13A, 13B ... Side wall part, 14A, 14B ... Pin hole part, 20 ... Raised part, 21 ... Groove, 31 ... Depression, 32 ... Depression slope 101 ... Piston cavity, 112 ... Bottom wall surface of piston body part, 121 ... Outer wall surface of skirt part, 122 ... Inner wall surface of skirt part, 131 ... Outer wall surface of side wall part, 132 ... Inner wall surface of side wall part , 142 ... side part of the pin hole part, 143 ... upper part of the pin hole part, AR1 ... upper corner area, AR2 ... lower corner area, AR3 ... pin hole side area, C1 ... piston central axis

Claims (5)

A cylindrical piston main body, a pin hole disposed below the piston main body, the pin hole having a central axis perpendicular to the central axis of the piston main body, and the pin hole In the piston of the internal combustion engine having a connecting portion that connects the piston portion and the piston body portion, an outer wall surface of the connecting portion adjacent to the pin hole portion extends inward substantially above the pin hole portion. Is formed as a substantially upward-facing wall surface, in the vicinity of the substantially upward-facing wall surface and in a direction away from the pin hole portion and obliquely upward from the region of the connecting portion in the vicinity of the pin hole portion. A raised portion extending to the outer wall surface of the connecting portion ,
A piston of an internal combustion engine, wherein a wall surface facing substantially upward of the connecting portion is inward and extends obliquely upward . The piston main body portion is in the vicinity of the wall surface in which the raised portion faces substantially upward of the connecting portion and in the direction away from the pin hole portion and obliquely upward from the region of the connecting portion in the vicinity of the pin hole portion. The piston of the internal combustion engine according to claim 1, which extends to a region of the connecting portion adjacent to the internal combustion engine. A cylindrical piston main body, a pin hole disposed below the piston main body, the pin hole having a central axis perpendicular to the central axis of the piston main body, and the pin hole In the piston of the internal combustion engine having a connecting portion that connects the piston portion and the piston body portion, an outer wall surface of the connecting portion adjacent to the pin hole portion extends inward substantially above the pin hole portion. Is formed as a substantially upward-facing wall surface, in the vicinity of the substantially upward-facing wall surface and in a direction away from the pin hole portion and obliquely upward from the region of the connecting portion in the vicinity of the pin hole portion. A raised portion extending to the outer wall surface of the connecting portion,
The piston main body portion is in the vicinity of the wall surface in which the raised portion faces substantially upward of the connecting portion and in the direction away from the pin hole portion and obliquely upward from the region of the connecting portion in the vicinity of the pin hole portion. until said region of the connecting portion that has extended, the inner combustion engine piston adjacent.   A first oil passage for flowing cooling oil is formed inside the piston, and an inner wall surface of the connecting portion corresponding to the raised portion defines a groove extending along the raised portion. A second oil passage for flowing cooling oil is formed by closing the groove with a wall, and the second oil passage is connected to the first oil passage. The piston of the internal combustion engine as described in any one of these. A cylindrical piston main body, a pin hole disposed below the piston main body, the pin hole having a central axis perpendicular to the central axis of the piston main body, and the pin hole In the piston of the internal combustion engine having a connecting portion that connects the piston portion and the piston body portion, an outer wall surface of the connecting portion adjacent to the pin hole portion extends inward substantially above the pin hole portion. Is formed as a substantially upward-facing wall surface, in the vicinity of the substantially upward-facing wall surface and in a direction away from the pin hole portion and obliquely upward from the region of the connecting portion in the vicinity of the pin hole portion. A raised portion extending to the outer wall surface of the connecting portion,
A first oil passage for flowing cooling oil is formed inside the piston, and an inner wall surface of the connecting portion corresponding to the raised portion defines a groove extending along the raised portion. A piston for an internal combustion engine in which a second oil passage for flowing cooling oil is formed by closing the groove with a wall, and the second oil passage is connected to the first oil passage. .

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