JP2009191779A - Piston of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance cooling efficiency by inhibiting oil from flowing in an unnecessary direction. <P>SOLUTION: A piston includes a pair of pin boss sections 26, 27 for holding a piston pin, which is formed on a pair of sidewall sections 24, 25 provided in a manner of connecting a pair of skirt sections 22, 23 suspended from a crown section 21. In this piston, an oil guide path 31 is formed in a back surface of the crown section to extend between the pair of skirt sections so that the oil injected from an oil jet device toward a one side of the oil guide path is guided toward the other side of the oil guide path, and stepped portions 45, 46 for regulating a flow of the oil moving toward a sidewall section side are formed along the opposite sides of the oil guide path in a manner of connecting the pair of skirt sections. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piston for an internal combustion engine that is cooled by injecting cooling oil from an oil jet device toward the back of the top.

  In internal combustion engines for automobiles, a technology for injecting cooling oil toward the back of the top of the piston to cool the piston has been widely adopted, but in recent years, the heat load of the piston has increased with higher output As a result, the temperature of the piston tends to rise, and further improvement in the cooling performance of the piston is required.

With regard to such piston cooling, conventionally, there has been a technique in which oil is sprayed toward a position near the skirt portion on the thrust side, and the oil flows along the back surface of the top portion from the thrust side to the anti-thrust side. It is known (see Patent Document 1).
Japanese Patent No. 2669126

  However, in the prior art, oil flows from the thrust side to the anti-thrust side through a pair of pin bosses that hold the piston pin. There is a problem that the cooling efficiency is lowered because a part of the oil flows in an unnecessary direction, that is, in the axial direction of the piston pin, and the oil toward the anti-thrust side decreases.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to prevent the oil from flowing in an unnecessary direction so as to increase the cooling efficiency. It is in providing the piston comprised in.

  In order to solve such a problem, in the present invention, as shown in claim 1, a top portion (21), a pair of skirt portions (22, 23) suspended from the top portion, and the pair of skirt portions are provided. An oil jet device having a pair of side wall portions (24, 25) connected to each other and a pair of pin boss portions (26, 27) provided on the pair of side wall portions and holding a piston pin (4) In the piston (3) which is cooled by spraying cooling oil from the top toward the back of the top, an oil guide path (31) extending between the pair of skirts on the back of the top And the oil jetted from the oil jet device toward the one end side of the oil guide path is guided toward the other end side of the oil guide path, and the oil guide In the form of connecting the pair of skirt portions to each other along both sides, a built-up portion (step portions 45 and 46) for restricting the flow of oil toward the sidewall portion side is formed. .

  According to this, since the flow of oil toward the side wall portion side (the axial direction of the piston pin) is restricted by the build-up portion, it is possible to avoid a decrease in the oil flowing to the other end side along the oil guide path. In this way, the entire top portion is appropriately cooled, and the cooling efficiency can be increased.

  In the piston, as described in claim 2, the build-up portion can be a step portion formed so as to fill a corner portion between the back surface of the top portion and the inner surface of the sidewall portion. .

  According to this, since a top part and a side wall part are connected via a step part, the rigidity of a piston can be improved. In this case, the flow of oil is restricted by the step surface of the step portion that is one step higher than the bottom surface of the oil guide path.

  In addition to the stepped portion, the build-up portion can be configured to protrude in a rib shape from the back surface of the top portion.

  In the piston, as shown in claim 3, the build-up portion may be formed in such a manner that the pin boss portion and the skirt portion are connected to each other.

  According to this, since the pin boss portion is connected to the skirt portion via the stepped portion, the support rigidity of the pin boss portion can be improved.

  In addition to the form which mutually connects a pin boss | hub part and a skirt part, the form which connects a pair of skirt part mutually without connecting with a pin boss | hub part is also possible for a build-up part.

  In the piston, as shown in claim 4, the lower surface of the built-up portion is formed in a concave surface shape having a substantially arc-shaped cross section that is continuously curved from the outer peripheral surface of the pin boss portion. it can.

  According to this, the weight of the piston can be reduced by reducing the useless meat.

  In the piston, as described in claim 5, the build-up portion is formed on both sides of the pin boss portion, and the curvatures of the lower surfaces of the build-up portions on both sides can be different from each other.

  According to this, the volume of the built-up portion changes according to the curvature of the lower surface of the built-up portion, and the piston changes by changing the curvature of the lower surface of the built-up portion between the built-up portions on both sides according to the degree of unbalance of the piston. It is possible to optimize the weight balance.

  In the piston, as shown in claim 6, the curvature of the lower surface of the build-up portion located on the offset side of the piston pin is larger than the curvature of the lower surface of the build-up portion located on the anti-offset side, can do.

  According to this, since the build-up part on the offset side is larger than the build-up part on the anti-offset side, the mass on the offset side can be relatively increased, and thereby the center of gravity biased to the anti-offset side due to the piston pin offset. Can be corrected.

  Thus, according to the present invention, since the flow of oil toward the sidewall portion side is regulated by the build-up portion, it can be avoided that the amount of oil flowing to the other end side along the oil guide path decreases. Thereby, the whole top part is cooled appropriately and cooling efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a main part of an internal combustion engine to which a piston according to the present invention is applied. In this internal combustion engine, a cylindrical cylinder bore 2 is formed in a cylinder block 1, and a piston 3 is slidably accommodated in the cylinder bore 2. An upper end of a connecting rod 5 is connected to the piston 3 via a piston pin 4, and a lower end of the connecting rod 5 is connected to a crankshaft 7 via a crank pin 6.

  A crankcase 8 is coupled to the lower side of the cylinder block 1, and a crank chamber 9 for accommodating the crankshaft 7 is defined by the crankcase 8 and the lower portion of the cylinder block 1. An oil pan (not shown) that receives the oil that has descended from above is provided on the lower side of the crankcase 8. A cylinder head (not shown) provided with an intake port and an exhaust port that are opened and closed by an intake valve and an exhaust valve, respectively, is coupled to the upper side of the cylinder block 1. A combustion chamber is defined by the inner peripheral surface of the cylinder bore 2.

  An oil jet device 11 that injects oil for cooling the piston 3 is disposed near the lower end of the cylinder bore 2 in the cylinder block 1. The oil jet device 11 includes a nozzle 12 having a tip directed upward, and oil is jetted from below toward the piston 3, in particular, the exhaust side where the temperature is high in this case.

  FIG. 2 is a perspective view of the piston shown in FIG. FIG. 3 is a cross-sectional view of the piston shown in FIG. 2 cut along a plane along the axis. FIG. 4 is a bottom view of the piston shown in FIG.

  As shown in FIG. 2, the piston 3 includes a top portion 21 where the pressure of the combustion gas acts, a pair of skirt portions 22, 23 provided in a manner suspended from the top portion 21, and the pair of skirt portions 22, 23. Are connected to each other, and a pair of side wall portions 24 and 25 and a pair of pin boss portions 26 and 27 provided on the pair of side wall portions 24 and 25 are provided.

  A ring groove 29 to which a top ring, a second ring, and an oil ring (not shown) are respectively attached is formed on the outer periphery of the top portion 21. A pin insertion hole 30 through which the piston pin 4 is inserted is formed in the pin boss portions 26 and 27, and both ends of the piston pin 4 are held by the pair of pin boss portions 26 and 27.

  The pair of skirt portions 22, 23 are formed in an arcuate cross section along the inner peripheral surface of the cylinder bore 2, and are disposed on the anti-thrust side (intake side) and the thrust side (exhaust side), respectively, The wall portions 24 and 25 extend in a direction perpendicular to the axis of the piston pin 4 and have a closed cross-sectional structure in which the pair of skirt portions 22 and 23 and the pair of sidewall portions 24 and 25 form a substantially oval cross section as a whole. Is formed.

  An oil guide passage 31 extending between the pair of skirt portions 22 and 23 is formed on the back surface of the top portion 21, and is directed from the oil jet device 11 to one end side (exhaust side) of the oil guide passage 31. The injected oil is guided toward the other end side (intake side) of the oil guide path 31.

  The pair of pin bosses 26 and 27 includes an inner projecting portion 32 projecting to the inner surface side of the sidewall portions 24 and 25 and an outer projecting portion 33 projecting to the outer surface side of the sidewall portions 24 and 25. The inner projecting portions 32 project greatly from the inner surfaces of the sidewall portions 24, 25, and on both sides of the pin boss portions 26, 27, the projecting portions 32 of the pin boss portions 26, 27, the sidewall portions 24, 25, and the skirt portion 22. -The recesses 35 and 36 of the aspect enclosed by 3 sides with 23 are defined.

  The sidewall portions 24 and 25 are formed with thick portions 38 along the lower ends, and the skirt portions 22 and 23 are also formed with thick portions 39 in the circumferential direction in the vicinity of the lower ends. The thick portions 38 of the portions 24 and 25 are provided so as to connect the thick portions 39 of the skirt portions 22 and 23 and the lower end portions of the projecting portions 32 inside the pin boss portions 26 and 27 to each other.

  As shown in FIG. 3, the bottom surface of the oil guide path 31 is formed in a concavo-convex cross section, and oil is injected toward a bulging portion 41 formed in the vicinity of the exhaust-side skirt portion 23. Further, the oil is guided by the bulging portion 42 formed in the vicinity of the skirt portion 22 on the intake side so that the flow direction changes downward.

  Recesses 43 and 44 on the intake side and the exhaust side are recessed on the surface of the top portion 21 corresponding to an intake valve and an exhaust valve (not shown), respectively. In the recess 43 on the intake side, the recesses corresponding to the two intake valves communicate with each other (see FIG. 4), and the center portion corresponding to the oil guide path 31 on the back side is also recessed, and this surface shape Correspondingly, on the back side of the top portion 21, the middle portion of the oil guide path 31 is the lowest, the intake side of the oil guide path 31 is formed higher than the exhaust side, and the bulging portion 42 on the intake side is exhausted. The bulge is larger than the bulge portion 41 on the side.

  On the exhaust side of the pin boss portions 26 and 27, as shown in FIG. 2, the oil injected toward the bulging portion 41 in the vicinity of the exhaust-side skirt portion 23 is directed toward the side wall portions 24 and 25. A stepped portion (filled portion) 45 that regulates the above is formed. Further, on the intake side of the pin boss portions 26 and 27, a step portion (filling portion) 46 is formed that restricts the oil flowing along the oil guide path 31 from moving toward the side wall portions 24 and 25. These step portions 45 and 46 are provided symmetrically along both sides of the oil guide path 31.

  The step portions 45 and 46 are formed so as to fill the corners of the top portion 21 and the side wall portions 24 and 25 in a manner that is one step higher than the bottom surface of the oil guide path 31, and the step surface 45a of the step portions 45 and 46 is formed. -Oil flow is restricted at 46a. Further, the step surfaces 45a and 46a are formed substantially flush with the inner end surface of the projecting portion 32 inside the pin boss portion so that the oil flows smoothly along the oil guide path 31 (see FIG. 4). ).

  Further, since the skirt portions 22 and 23 and the pin boss portions 26 and 27 are connected to each other via the step portions 45 and 46, the support rigidity of the pin boss portions 26 and 27 can be improved. Furthermore, since the top portion 21 and the side wall portions 24 and 25 are connected to each other via the step portions 45 and 46, the rigidity of the entire piston 3 can be improved.

  The lower surfaces 45b and 46b of the stepped portions 45 and 46 are concave surfaces having a substantially arc-shaped cross section that is continuously curved from the outer peripheral surface of the semicircular arc-shaped portion 32a centering on the pin insertion hole 30 in the pin boss portions 26 and 27. Formed, and the gradient gradually decreases from the pin boss portions 26 and 27 toward the skirt portions 22 and 23, and is formed on the inner surface of the skirt portions 22 and 23 corresponding to the portion where the ring groove 29 of the top portion 21 is formed. Connected to the stepped portion 48. Thus, by forming the lower surfaces 45b and 46b of the stepped portions 45 and 46 in a concave shape, it is possible to reduce wasteful meat and reduce the weight of the piston 3.

  FIG. 5 is a cross-sectional view schematically showing a form of a step portion in the piston shown in FIG. The piston 3 is a so-called offset piston in which the piston pin 4 is offset, and is formed in a state where the center axis of the piston pin 4 is offset laterally from the center line of the piston 3. In particular, here, the piston pin 4 is offset to the exhaust side.

  When the piston pin 4 is offset in this way, the anti-offset side becomes heavy with the piston pin 4 as the center. Therefore, it is necessary to relatively increase the mass on the offset side to optimize the weight balance of the piston 3, Here, the volume of the step portions 45 and 46 provided on both sides of the pin boss portions 26 and 27 is changed, that is, the volume of the step portion 45 located on the offset side (exhaust side) is located on the non-offset side (intake side). By making it larger than the stepped portion 46, it is possible to relatively increase the mass on the offset side and correct the center of gravity that is biased toward the non-offset side.

  The volume of the step portions 45 and 46 can be adjusted by the curvature of the concave lower surfaces 45b and 46b, and the curvature r1 of the lower surface 45b of the step portion 45 located on the offset side (exhaust side) is set to the anti-offset side ( By setting the curvature larger than the curvature r2 of the lower surface 46b of the step 46 located on the intake side), the volume of the offset step 45 can be made larger than that of the counter-offset step 46.

  Specifically, a conventional pin boss in which a flat surface extending from the outer surface of the semicircular arc portion 32a of the pin boss portions 26 and 27 in a direction parallel or slightly inclined with respect to the center line of the piston 3 does not have a stepped portion. It becomes the outer surface 51 of the parts 26 and 27, and the part outside the conventional outer surface 51 becomes a part whose volume is increased by the step portions 45 and 46. Here, the lower surfaces 45b and 46b have a substantially ¼ arc-shaped cross-sectional shape, a plane passing through the upper ends of the lower surfaces 45b and 46b and orthogonal to the center line of the piston 3, the conventional outer surface 51, the lower surface 45b, The volume of the portions 53a and 54a sandwiched between 46b increases as the curvature of the lower surfaces 45b and 46b increases, and the volume of the portion 53a with the large curvature r1 becomes larger than the portion 54a with the small curvature r2.

  Note that the volume of the entire stepped portions 45 and 46 also changes depending on the volume of the portions 53b and 54b above the lower surfaces 45b and 46b, and the volume of the offset-side portion 53b is larger than the counter-offset-side portion 54b or offset. If the volume of the portion 53b on the side is not smaller than the volume difference between the portions 53a and 54a compared to the portion 54b on the anti-offset side, the volume of the step 45 on the offset side should be larger than the step 46 on the anti-offset side. Can do.

  FIG. 6 is a perspective view showing a state in which oil flows in the piston shown in FIG. The oil jetted from the oil jet device 11 toward the exhaust-side bulging portion 41 flows along the oil guide path 31 from the exhaust side toward the intake side, and flows downward by the intake-side bulging portion 42. It is changed and returned from the piston 3 to the oil pan.

  At this time, the oil flow toward the side wall portions 24 and 25 (in the axial direction of the piston pin 4) is regulated by the step surfaces 45a and 46a of the step portions 45 and 46, and the pin boss portions 26 and 27 and the side wall portion 24 are controlled. Oil that is prevented from entering oil in the recesses 35 and 36 (see FIGS. 2 and 4) surrounded by the 25 and the skirts 22 and 23 and flows to the intake side along the oil guide path 31 Can be avoided, whereby the entire top portion 21 is appropriately cooled, and the cooling efficiency can be increased.

  In particular, here, the oil jet device 11 is disposed at a position shifted in the axial direction of the piston pin 4 with respect to the center line of the cylinder bore 2, and the oil is in a slightly inclined direction with respect to the center line of the cylinder bore 2. A nozzle 12 is provided so as to be jetted. For this reason, between the top dead center shown in FIG. 6 (A) and the bottom dead center shown in FIG. 6 (B), the part where oil is sprayed according to the position of the piston 3 extends in the width direction of the oil guide path 31. Although slightly deviated, the flow of oil is appropriately regulated by the step surfaces 45a and 46a of the step portions 45 and 46 on both sides, so that the oil can flow smoothly along the oil guide path 31.

  In the above example, the oil is injected toward the exhaust side (thrust side) that is hotter than the intake side, but when the cooling on the intake side by the low-temperature mixture is insufficient, From the viewpoint of improving knocking toughness, a configuration in which oil is injected toward the intake side (anti-thrust side) is also possible.

It is sectional drawing which shows the principal part of the internal combustion engine to which the piston by this invention is applied. It is a perspective view of the piston shown in FIG. It is sectional drawing which cut | disconnected the piston shown in FIG. 2 by the plane along an axis line. FIG. 3 is a bottom view of the piston shown in FIG. 2. It is sectional drawing which shows typically the form of the step part in the piston shown in FIG. It is a perspective view which shows the condition where the oil in the piston shown in FIG. 2 flows.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder bore 3 Piston 4 Piston pin 11 Oil jet apparatus 12 Nozzle 21 Top part 22/23 Skirt part 24/25 Side wall part 26/27 Pin boss part 31 Oil guide path 35/36 Recess 41/42 Swell part 45・ 46 stepped parts (filled parts), 45a ・ 46a stepped surface, 45b ・ 46b bottom surface

Claims (6)

A top, a pair of skirts depending from the top, a pair of sidewalls connecting the pair of skirts to each other, and a pair of pin bosses provided on the pair of sidewalls to hold a piston pin A piston that is cooled by injecting cooling oil from the oil jet device toward the back surface of the top,
An oil guide path extending between the pair of skirt portions is formed on the back surface of the top, and the oil injected from the oil jet device toward one end side of the oil guide path is the other end of the oil guide path. Be guided to the side,
A piston characterized in that a build-up portion for restricting the flow of oil toward the sidewall portion side is formed in a mode in which the pair of skirt portions are connected to each other along both sides of the oil guide path. .   2. The piston according to claim 1, wherein the build-up portion is a step portion formed so as to fill a corner portion between a back surface of the top portion and an inner surface of the sidewall portion.   3. The piston according to claim 1, wherein the build-up portion is formed in such a manner that the pin boss portion and the skirt portion are connected to each other.   4. The piston according to claim 3, wherein a lower surface of the build-up portion is formed in a concave shape having a substantially arc-shaped cross section continuously curved from an outer peripheral surface of the pin boss portion.   The piston according to claim 4, wherein the build-up portions are formed on both sides of the pin boss portion, and curvatures of lower surfaces of the build-up portions on both sides are different from each other.   The piston according to claim 5, wherein a curvature of a lower surface of the build-up portion located on the offset side of the piston pin is larger than a curvature of a lower surface of the build-up portion located on the anti-offset side.

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