JP2010065647A - Piston structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston structure which can retain a cooling effect of an outer edge of a piston as before and which can improve the cooling effect of the midsection of the piston without having any influence on fuel efficiency. <P>SOLUTION: A cooling channel (an oil passage for cooling the piston) of the piston structure 10 is provided with an annular circulating passage 11 and a center passage 12. The annular circulating passage 11 is provided to the back of the top surface of the piston along the outer edge of the piston, and the oil injected from an oil jet flows in the annular circulating passage 11. The center passage 12 temporarily branches off from the circulating passage 11 and passes through the back of the midsection of the top surface of the piston. After that, the center passage 12 merges with the circulating passage 11 again. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston structure.

The piston top land and top ring groove may be damaged or seized if the piston temperature rises at high rotation and high load. It is necessary to cool the piston to prevent the above problems. Conventionally, there is known a piston structure in which a piston cooling oil passage called a cooling channel for flowing oil jetted from an oil jet is provided on the back side of the piston crown, and the engine oil is circulated in the passage to cool the piston. Yes. For example, Patent Document 1 describes a piston structure of a cooling channel provided in an annular shape along an outer edge of the piston.
JP 2002-480001 A

  When the piston crown surface is flat like a gasoline engine piston, the temperature at the center of the crown surface where combustion starts is considered to be the highest. However, the conventional cooling channel has an annular shape along the outer periphery of the piston, and the central portion of the piston crown surface is not directly cooled, so that the cooling efficiency of the entire piston is low. In addition, in order to improve the cooling performance, the oil circulation flow rate flowing in the cooling channel is increased, or the combustion temperature is reduced by adjusting the ignition timing or the air-fuel ratio.

  The present invention has been made paying attention to such a conventional problem, and maintains the piston outer edge cooling effect as before, and at the same time, the piston structure that improves the cooling effect of the central portion of the piston without affecting the fuel efficiency. The purpose is to provide.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  According to the present invention, in a cooling channel having a piston structure, an annular circulation passage (11) provided along the outer edge of the piston on the back surface of the piston (10) and through which oil injected from an oil jet flows, and once branched from the circulation passage And a central passage (12) that passes through the back of the central portion of the piston crown surface and merges with the circulation passage again.

  According to the present invention, since the cooling channel is provided not only on the outer edge of the piston but also on the back of the central portion of the piston crown surface in the piston structure, the central portion of the piston crown surface can be directly cooled. Thereby, the effect of reducing the average temperature of the piston can be obtained without affecting the fuel consumption.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a view showing a first embodiment of a piston structure according to the present invention. FIG. 1A is a perspective view. The piston 10 includes a circulation passage 11 and a central passage 12. The cooling channel includes a circulation passage 11 and a central passage 12, and is provided behind the crown surface of the piston 10. FIG. 1B is a longitudinal sectional view of a piston showing an oil flow path flowing through the cooling channel. Oil injected from the oil jet 20 flows into the circulation passage 11 from an oil inlet 13 disposed in the circulation passage 11. Then, the oil that has flowed through the circulation passage 11 and the central passage 12 flows out from the oil outlet 14 disposed in the circulation passage 11. Arrows A, B, and C in FIG. 1B indicate the direction of oil flow.

  2 is also a view showing a first embodiment of a piston structure according to the present invention, as in FIG. FIG. 2A is a front view of the piston. FIG. 2B is a cross-sectional view taken along the line AA in FIG. The piston 10 includes a circulation passage 11, a central passage 12, an oil inlet 13, and an oil outlet 14.

  The circulation passage 11 is provided in an annular shape along the outer periphery of the piston behind the piston crown. The central passage 12 once branches from the circulation passage 11 at a branch portion 12a. The central passage 12 passes through the central part of the piston crown. The central passage 12 joins the circulation passage 11 again at the joining portion 12b. Further, the central passage 12 is provided in a direction orthogonal to the crankshaft direction in FIG. Further, the central passage 12 is arranged to have the diameter of the circulation passage 11.

  The oil inflow port 13 does not overlap the branch portion 12a between the circulation passage 11 and the central passage 12, and is disposed not near the branch portion 12a and the junction portion 12b but near the branch portion 12a. The oil inlet 13 is located on the intake side. Here, the intake side means the intake side of the combustion chamber, and is the left half region in FIG. The oil jetted from the oil jet 20 flows into the oil inlet 13. The oil outlet 14 does not overlap with the joining portion 12b between the circulation passage 11 and the central passage 12, and is disposed near the joining portion 12b, not in the middle between the branching portion 12a and the joining portion 12b. The oil outlet 14 is located on the exhaust side of the circulation passage 11. Here, the exhaust side means the exhaust side of the combustion chamber, and is the right half region in FIG. Then, the oil that has flowed through the circulation passage 11 flows out from the oil outlet 14. Here, the oil inlet 13 and the oil outlet 14 are disposed at both ends of the diameter of the circulation passage 11.

  In the present embodiment, a central passage 12 is added to the circulation passage 11. For this reason, it becomes possible to directly cool the central portion of the crown surface, which is the highest temperature in the piston crown surface, by the central passage 12, and the effect of reducing the average temperature of the piston can be obtained.

  In general, the temperature of the piston crown surface is higher on the exhaust side where hot exhaust gas flows than on the intake side. And when the temperature is low, the viscosity of the oil increases, and when the temperature is high, the viscosity decreases. The viscosity and flow of the oil are closely related to each other. When the viscosity increases, the oil hardly flows and when the viscosity decreases, the oil tends to flow. In this embodiment, the oil outlet 14 is provided on the exhaust side where the temperature is high by utilizing such properties of the oil, so that the oil flows more easily on the downstream side. As a result, the flow of the whole oil becomes smooth.

  In addition, the oil injected from the oil jet 20 flows into the oil inlet 13 so that the pressure is highest on the circulation passage 11. This also allows oil to flow smoothly from the oil inlet 13 (high pressure side) to the oil outlet 14 (low pressure side).

  When the oil inlet 13 and the branching portion 12a from the circulation passage 11 to the central passage 12 are in the same position, the distribution of the oil flow rate flowing to the circulation passage 11 and the central passage 12 is biased, and the central passage 12 A lot of oil flows in. This is because the flow passage resistance of the central passage 12 is smaller than the flow passage resistance of the circulation passage 11. Here, the flow path resistance refers to a resistance acting on oil flowing between the branch portion 12a and the merge portion 12b. Generally, if the other conditions are the same, the longer the channel, the greater the channel resistance. And the smaller the channel resistance, the smoother the flow. The circulation passage 11 has a longer distance to the oil outlet 14 than the central passage 12, and the shape of the circulation passage 11 is curved while the central passage 12 is a straight line. It is considered to be larger than the passage 12.

  Accordingly, by shifting the arrangement of the branch portion 12a between the circulation passage 11 and the central passage 12 and the oil inlet 13, all the oil flowing from the oil inlet 13 once flows into the circulation passage 11 and then the circulation passage. 11 and the central passage 12 flow in a balanced manner. Further, when the oil inlet 13 and the oil outlet 14 are arranged at both ends of the diameter of the circulation passage 11, the circulation passage 11 is symmetrical with respect to the diameter, so that the balance is good.

  In the vicinity of the outer edge of the piston, the temperature of the thrust direction parts 10a and 10b may become high due to the head swing of the piston, and there is a risk of seizing. Therefore, it is desired to secure an appropriate amount of oil flow through the part. Therefore, the central passage 12 is arranged so as to have the diameter of the circulation passage 11 in the thrust direction.

  Since it comprised in this way, the oil which flowed into the circulation channel | path 11 from the oil inflow port 13 flows into two hands, the circulation channel | path 11 and the center channel | path 12, after passing the high temperature part 10a of the piston outer periphery periphery. After that, the oil flows into the high temperature portion 10b around the outer periphery of the piston after the circulation passage 11 and the central passage 12 merge to become one. Thereby, the cooling effect of the high temperature part around the outer periphery of the piston can be maintained without being affected by the decrease in the oil flow rate due to the addition of the central passage 12. Further, since the shape is symmetrical with respect to the crankshaft, the weight balance of the piston can be maintained.

(Second embodiment)
FIG. 3 is a plan sectional view showing a second embodiment of the piston structure according to the present invention. In the following description, the same functions as those described above are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

  Since the connecting rod is inserted into the central portion of the piston, the piston crown surface has a reverse concave shape. When the central passage is provided so as to pass above the connecting rod insertion portion 15, the thickness of the connecting rod insertion portion on the piston crown surface is reduced, and the rigidity is lowered.

  In contrast, in the present embodiment, two central passages 12 (121, 122) are provided in parallel so as to sandwich the connecting rod insertion portion. The two central passages 121 and 122 are oriented perpendicular to the crankshaft direction in FIG. Further, the flow passage cross-sectional area S1 of the central passage 121 close to the oil inlet 13 is smaller than the flow passage cross-sectional area S2 of the other central passage 122.

  Since it comprised in this way, it can prevent that the rigidity of a piston crown surface falls. Since two central passages 12 are provided and the surface area is increased, the cooling effect of the central portion of the piston crown surface is increased. Further, since the channel cross-sectional area S1 of the central passage 121 near the oil inlet 13 is smaller than the channel cross-sectional area S2 of the other central passage 122, a large amount of oil flows through the central passage 121 near the oil inlet 13. This prevents the oil from flowing throughout the balance.

(Third embodiment)
FIG. 4 is a plan sectional view showing a third embodiment of the piston structure according to the present invention.

  The central passage 12 of the present embodiment is Y-shaped as shown in FIG. 4 and includes two branch passages 123 and 124 and a collecting passage 125. The branch passage 123 is provided in the thrust direction on the intake side, and the branch passage 124 is provided in a direction (crankshaft direction) obtained by rotating the branch passage 123 90 degrees counterclockwise. The channel cross-sectional area S4 of the branch passage 124 is smaller than the channel cross-sectional area S3 of the branch passage 123. The branch passages 123 and 124 merge at the central portion of the piston crown surface and continue to the collecting passage 125. The collecting passage 125 is provided on the exhaust side, and the flow passage sectional area S5 of the collecting passage 125 is larger than the flow passage sectional areas S3 and S4 of the branch passages. Further, the oil inlet 13 is disposed between the branch passages 123 and 124, and the oil outlet 14 is disposed in the vicinity of the joining portion 12 b between the collecting passage 125 and the circulation passage 11.

  Since it comprised in this way, the oil which flows into the both sides of the circulation channel | path 11 from the oil inflow port 13 can be flowed through the two branch channel | paths 123 and 124 to a piston crown surface center part, Since the oil flow volume which flows through the center channel | path 12 increases. The cooling efficiency of the center part of the piston crown surface is increased. The flow passage cross-sectional area S3 of the branch passage 123 is larger than the flow passage cross-sectional area S4 of the branch passage 124. Therefore, the oil flow rate flowing into each branch passage inlet that is equidistant from the oil inlet 13 is surely greater in the branch passage 123 than in the branch passage 124. Thereby, the oil flow rate that passes through the high temperature portion in the thrust direction around the outer periphery of the piston can be secured, and the cooling effect can be maintained. Since the flow passage cross-sectional area S5 of the collecting passage 125 is larger than the flow passage cross-sectional areas S3 and S4 of the branch passages, the oil flowing into the collecting passage 125 from the two branch passages 123 and 124 is allowed to flow without stagnation. Can do it. Furthermore, since the joining portion 12b of the collecting passage 125 and the circulation passage 11 is disposed in the vicinity of the low-pressure oil outlet 14, the oil flow becomes smooth due to the pressure difference from the inlet side.

(Fourth embodiment)
FIG. 5 is a plan sectional view showing a fourth embodiment of the piston structure according to the present invention.

  The central passage 12 of this embodiment is S-shaped as shown in FIG. 5, and includes an inlet-side passage 126, an enlarged passage 127, and an outlet-side passage 128. The inlet-side passage 126 branches from the vicinity of the oil inlet 13 of the circulation passage 11. The enlarged passage 127 is continuous with the inlet side passage 126. The outlet side passage 128 continues to the enlarged passage 127 and joins in the vicinity of the oil outlet 14 of the circulation passage 11. Further, the flow passage sectional area S7 of the enlarged passage 127 is larger than the flow passage sectional area S6 of the inlet side passage 126 and the flow passage sectional area S8 of the outlet side passage. The flow passage cross-sectional area S6 of the inlet-side passage 126 and the flow passage cross-sectional area S8 of the outlet-side passage 128 are smaller than the flow passage cross-sectional area S0 of the circulation passage 11.

  Since it comprised in this way, the surface area of the center channel | path 12 is large, and the cooling effect of a piston crown surface center part goes up. Further, since the inlet-side passage 126 and the outlet-side passage 128 are respectively provided in the oil inlet 13 and the oil outlet 14 having the largest pressure difference, the oil flowing through the central passage 12 flows smoothly. In order to allow an appropriate amount of oil to flow into the circulation passage 11, the flow path cross-sectional area S 6 of the inlet side passage 126 and the flow path cross-sectional area S 8 of the outlet side passage 128 are determined from the flow path cross-sectional area S 0 of the circulation passage 11. Is also small. However, since the flow passage cross-sectional area S7 of the enlarged passage 127 is larger than the flow passage cross-sectional area S6 of the inlet-side passage 126 and the flow passage cross-sectional area S8 of the outlet-side passage 128, the cooling effect at the central portion of the piston crown surface can be sufficiently obtained. It is.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention. For example, in the second and third embodiments, the number of central passages is not limited to two, and a plurality of central passages may be provided. Further, in the fourth embodiment, the shape of the central passage is not limited to the S shape, and the same effect can be obtained as long as the central passage is formed by a straight portion and a curved portion and passes through the back of the central portion of the piston crown surface. .

It is a perspective view which shows 1st Embodiment of the piston structure by this invention. It is the front view and plane sectional view which show 1st Embodiment of the piston structure by this invention. It is a plane sectional view showing a 2nd embodiment of the piston structure by the present invention. It is a plane sectional view showing a 3rd embodiment of the piston structure by the present invention. It is a plane sectional view showing a 4th embodiment of the piston structure by the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piston 11 Circulation passage 12 Central passage 12a Branch part of a circulation passage and a central passage 12b Merge part of a circulation passage and a central passage 13 Oil inlet 14 Oil outlet 15 Connecting rod insertion part

Claims (8)

An annular circuit passage provided along the outer periphery of the piston on the crown surface of the piston, through which oil injected from the oil jet flows,
A central passage that once branches from the circulation passage, passes through the center portion of the piston crown, and then joins the circulation passage again;
Piston structure with An oil inlet provided on the intake side of the circulation passage, into which oil injected from an oil jet flows;
An oil outlet that is provided on the exhaust side of the circulation path and from which oil that flows through the circulation path flows out;
The piston structure according to claim 1, comprising: The oil inlet and the oil outlet are arranged at both ends of the diameter of the circulation passage,
The piston structure according to claim 1 or 2, characterized by the above. The oil inlet is arranged shifted from a portion where the central passage branches off from the circulation passage,
The oil outlet is arranged so as to be shifted from a portion where the central passage merges with the circulation passage.
The piston structure according to any one of claims 1 to 3, wherein: The central passage is provided in a direction orthogonal to the crankshaft direction when seen through from the piston crown side.
The piston structure according to any one of claims 1 to 4, wherein: A plurality of the central passages are provided across the connecting rod insertion part of the central part of the piston.
The piston structure according to any one of claims 1 to 5, wherein: The central passage is
A plurality of branch passages provided on the intake side and branching from the circulation passage;
A collecting passage that is provided on the exhaust side and collects the plurality of branch passages and joins the circulation passage;
Including
The oil inflow port is disposed between branch portions of the plurality of branch passages,
The oil outlet is disposed in the vicinity of the merged portion of the collecting passage.
The piston structure according to any one of claims 1 to 3, wherein: The central passage is
An inlet-side passage that branches off from the vicinity of the oil inlet of the circulation passage and passes through the back of the periphery of the piston crown surface;
An enlarged passage that is continuous with the inlet-side passage, passes through the back of the central portion of the piston crown surface, and has a passage cross-sectional area larger than that of the inlet-side passage;
An outlet-side passage that is continuous with the enlarged passage, passes through the peripheral back of the piston crown surface, and merges in the vicinity of the oil outlet of the circulation passage;
The piston structure according to any one of claims 1 to 3, wherein the piston structure is included.

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