JP4427506B2 - Piston for internal combustion engine - Google Patents

Description

  The present invention relates to a piston for an internal combustion engine having a wear-resistant ring and an annular oil passage.

  In recent years, diesel engines tend to be operated at high speed and high load, so that the heat load on the piston has become severe. For this reason, the vicinity of the TOP ring groove of the piston not only becomes high temperature due to thermal energy due to compression and explosion, but also generates and adheres soot due to carbonization and combustion of engine lubricating oil, and friction with the piston ring causes friction of the piston ring. Function tends to decrease and oil consumption tends to increase.

  In order to improve this, there has been proposed a piston in which a wear resistant ring made of Nires cast iron having excellent wear resistance at high temperatures is cast in the vicinity of the TOP ring groove, and an oil passage is formed inside the wear resistant ring. (See Patent Document 1). A piston in which a U-shaped sheet metal member is joined to a wear-resistant ring and cast is also proposed (see Patent Document 2).

  However, in both cases, the height of the oil passage and the wear-resistant ring are almost the same, so if you want to obtain sufficient cooling performance by increasing the cross-sectional area of the oil passage, the distance from the combustion chamber wall surface to the oil passage Becomes smaller and it becomes difficult to obtain the strength required for the piston.

  In recent years, diesel engines have a tendency to increase the diameter of the combustion chamber due to the demand for low exhaust gas, making it more difficult to provide an oil passage inside the wear-resistant ring. Note that the position of the TOP ring groove tends to rise to the top surface side, but in this case as well, it is difficult to ensure a sufficient distance from the combustion chamber wall surface to the oil passage.

  Furthermore, in the latter piston, a belt-shaped steel plate is welded into a ring shape and then formed into a cross-sectional U-shape by drawing, so there is a problem that it is expensive or requires processing equipment, which causes a cost increase. .

In view of this, the applicant of the present invention, in the latter piston, comprises a sheet metal member composed of two upper and lower members, and the upper surface of the oil passage is inclined so as to approach the lower side, and the oil passage is moved toward the internal space of the piston body. The piston which proposed the piston which expanded the cross-sectional area of the oil path and improved the cooling performance by ensuring arrangement | positioning was ensured (refer patent document 3).
Japanese Utility Model Publication No. 58-52346 JP-A-5-231539 JP 2005-36771 A

  However, in this piston, the oil inlet / outlet is opened in the sheet metal member by drilling. However, since it is necessary to use a sheet metal member having excellent pressability, burrs due to drilling are likely to occur. Since this burr has a crown shape protruding into the oil passage, the oil passage is narrowed by the height of the burr, the amount of oil flowing into the oil passage is reduced, and the cooling performance is deteriorated.

  In view of such circumstances, an object of the present invention is to provide a piston for an internal combustion engine in which the cooling performance does not deteriorate even if burrs are generated by drilling.

  In order to solve the above-mentioned problems, the present invention has a structure in which a sheet metal member is joined to a wear-resistant ring to form an annular oil passage, the wear-resistant ring and the sheet metal member are embedded in the piston body, and the oil passage in the sheet metal member is connected to the piston body. In an internal combustion engine piston having an oil inlet / outlet opening on the inner surface of the cylinder, the oil inlet forming portion of the sheet metal member is bulged toward the internal space of the piston body.

  According to such a configuration, even if a burr occurs at the oil inlet of the sheet metal member, a sufficient clearance is formed between the tip and the upper surface of the oil passage, and the oil passage is not narrowed. It is possible to suppress an increase in resistance, secure a sufficient oil flow rate in the oil passage, and prevent a decrease in cooling performance.

  It is preferable that the oil outlet forming portion of the sheet metal member bulges toward the internal space side of the piston body.

  According to this configuration, even if burrs occur at the oil outlet of the sheet metal member, a sufficient clearance is formed between the tip and the upper surface of the oil passage, and the oil passage is not narrowed. The increase in resistance is suppressed, the oil is smoothly discharged from the oil passage, and the effect of preventing the cooling performance from being deteriorated is further improved.

  It is preferable that the sheet metal member is composed of two upper and lower members, and a recess is formed by recessing the oil inlet / outlet forming portion of the lower member.

  According to such a configuration, the convex portion can be formed on the lower member prior to the coupling of the upper member and the lower member, and the processing becomes easy.

  According to the present invention, even if burrs occur at the oil inlet of the sheet metal member, the oil passage is not narrowed, so the increase in oil flow resistance is suppressed, and the oil flow rate in the oil passage is sufficiently secured, Decrease in cooling performance can be prevented.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a piston of a diesel engine.

  This piston 1 has a wear-resistant ring 3 made of Ni-resist cast iron cast into a piston body 2 made of an aluminum alloy. A top ring groove 4 is formed in the wear ring 3. An oil passage 6 is formed in the piston body 2 by casting a sheet metal member 5 made of austenitic stainless steel. An oil inlet 7 and an outlet 8 are formed at the bottom of the sheet metal member 5. Further, oil passages 9 and 10 are formed in the piston body 2 so that the oil passage 6 in the sheet metal member 5 is communicated with the internal space 11 of the piston body 2.

  A second ring groove 12 and an oil ring groove 13 are formed below the wear-resistant ring 3 on the peripheral surface of the piston body 2. Further, a combustion chamber 14 is formed on the top surface of the piston body 2. In addition, a hole 15 into which a connecting rod connecting piston pin is inserted is formed in the peripheral wall of the piston body 2.

  2 to 4 show a structure in which the metal plate member 5 is assembled to the wear-resistant ring 3.

  The sheet metal member 5 includes two ring-shaped upper and lower members 20 and 21. The upper member 20 has bent pieces 20b extending from both ends of a ring-shaped main body 20a. The lower member 21 is formed in a substantially L-shaped cross section, and bent pieces 21b are extended at both ends of the main body portion 21a. The bent pieces 20b and 21b of both the upper and lower members 20 and 21 are joined by brazing, and the wear-resistant ring 3 is sandwiched by brazing with the opposite bent pieces 20b and 21b.

  The wear-resistant ring 3 and the sheet metal member 5 assembled in this way are cast into the molten metal, and the piston body 2 is formed. Next, a drill blade is inserted into the internal space 11 of the piston body 2 to open oil passages 9 and 10 in the piston body 2, and an oil inlet 7 and outlet 8 are opened in the sheet metal member 5.

  The lower member 21 has a recess 22 formed by recessing the periphery of the location where the oil inlet 7 and outlet 8 are to be formed. On both sides of the recess 22, inclined portions 23 connected to the bottom wall general portion are provided. The inlet 7 and the outlet 8 are arranged substantially symmetrically with respect to the center 0 of the lower member 21.

  Since the sheet metal member 5 is configured as described above, when this is combined with the wear-resistant ring 3 and cast into the piston main body 2, the upper surface of the oil passage 6 (formed by the main body portion 20 a of the upper member 20). ) Is inclined so as to be closer to the lower side, and the oil passage 6 is disposed closer to the inner space 11 side of the piston body 2. For this reason, the cross-sectional area of the oil passage 6 can be increased to improve the cooling performance, and a sufficient distance A from the combustion chamber wall surface to the oil passage 6 can be secured to obtain the necessary strength as a piston.

  By the way, since the austenitic stainless steel excellent in pressability is used as the material of the sheet metal member 5, burrs due to drilling are likely to occur at the peripheral edges of the oil inlet 7 and outlet 8. This burr has a crown shape protruding into the oil passage 6. In the conventional sheet metal member, as shown in FIG. 5, the height of the oil passage 6 is constant, so that the oil passage 6 becomes narrower by the height of the burr B, and the flow resistance of the oil O increases. For this reason, a part of the oil O injected from the oil jet OJ cannot flow into the oil passage 6, the oil flow rate in the oil passage 6 is reduced, and the cooling performance is lowered.

  On the other hand, in this embodiment, as shown in FIG. 6, since the oil inlet 7 and outlet 8 are opened in the recess 22 of the sheet metal member 5, even if a burr B is generated, the tip and the oil passage A sufficient clearance is formed between the upper surface of 6 and the oil passage 6 is not narrowed. For this reason, an increase in the flow resistance of the oil O can be suppressed, a sufficient oil flow rate in the oil passage 6 can be secured, and a decrease in cooling performance can be prevented.

  In order to suppress an increase in the flow resistance of the oil O and increase the amount of the oil O flowing in the oil passage 6, it is preferable to provide the concave portions 22 of the sheet metal member 5 at both the inlet 7 and the outlet 8. However, the increase in the flow resistance of the oil O is more influenced by the burr B on the inlet 7 side than the burr B on the outlet 8 side. May be omitted.

  Further, since the sheet metal member 5 is composed of the upper and lower two members 20 and 21, the convex portion 22 can be formed on the lower member 21 prior to the coupling of these members 20 and 21, and processing is easy. become.

Sectional drawing which shows the piston for internal combustion engines of this invention. The front view which shows what assembled the wear ring and the sheet metal member. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. The bottom view of FIG. The figure explaining the flow of the conventional oil. The figure explaining the flow of the conventional oil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston 2 Piston main body 3 Wear-resistant ring 5 Sheet metal member 6 Oil passage 7 Inlet 8 Outlet 11 Internal space 20 Upper member 21 Lower member 22 Recessed part 23 Inclined part

Claims (3)

  A sheet metal member is joined to the wear ring to form an annular oil passage, and the wear ring and sheet metal member are embedded in the piston body, and the oil passage in the sheet metal member is opened on the inner surface of the piston body to form an oil inlet / outlet port. A piston for an internal combustion engine, wherein an oil inlet forming portion of a sheet metal member is bulged toward the internal space side of the piston body.   2. The piston for an internal combustion engine according to claim 1, wherein an oil outlet forming portion of the sheet metal member is bulged toward the internal space side of the piston body. The piston for an internal combustion engine according to claim 1 or 2, wherein the sheet metal member is composed of two upper and lower members, and a recess is formed by recessing an oil inlet / outlet forming portion of the lower member.

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