JPH0634152U - Piston structure of internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the lubrication performance and reduce the sliding frictional resistance of the piston against the cylinder wall to improve the engine output and reduce fuel consumption. [Structure] The outer peripheral edge of the upper end of the skirt portion 20 is approximately 0.1 °.
The inclined surface 22 having an inclination angle θ of ˜3 ° is formed, and the angle θ1 of the inclined surface 22a on the anti-thrust side is set to be larger than the angle θ2 of the inclined surface 22b on the thrust side. Then, at the lower outer peripheral edge 24 of the inclined surface 22, the cylinder 1
The lubricating oil adhering to the one side surface 10a of No. 0 was scraped so as to have an appropriate oil film thickness.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of a piston structure of an internal combustion engine.

[0002]

[Prior art]

 As is well known, for example, a piston of an internal combustion engine for an automobile is exposed to high heat due to the combustion gas pressure during the expansion stroke and undergoes thermal expansion change, and at the same time, it is caused by the reaction force that presses the stove by the explosive force. As a result, a side force that is pressed against the wall surface of the cylinder, that is, a thrust force acts. For this reason, between the piston and the cylinder wall surface, it is easy for the tapping sound of the piston slap and the abrasion due to the sliding resistance to occur.

Therefore, for example, as shown in FIG. 4, the outer peripheral surface of the crown portion 2 of the piston 1 having the largest amount of change in thermal expansion from the outer peripheral surface of the ring groove land portion 3 and the upper end portion 4a of the skirt portion 4 is formed into a ball shape. In addition, there is also provided a technique for making the amount of change in thermal expansion uniform and preventing the occurrence of wear or the like due to local sliding frictional resistance (see Japanese Utility Model Laid-Open No. 61-3948).

[0004]

[Problems to be solved by the device]

 However, in the conventional piston structure described above, since the entire outer peripheral surface 4b of the upper end portion 4a of the skirt portion 4 is a circular arc surface, the piston 1 tilts, for example, during the exhaust stroke so that the crown portion 2 side becomes the cylinder wall 5. Of the non-thrust side outer peripheral surface 4b of the abutting skirt portion 4 at the non-contact portion 4d above the contact portion 4c abutting on the cylinder wall 5, the lubricating oil adhering to the cylinder wall 5 is scraped off or an appropriate oil film thickness is obtained. It is impossible to level it. Therefore, the lubrication performance between the contact portion 4c of the outer peripheral surface 4b and the cylinder wall 5 may be deteriorated, and the sliding friction resistance may be increased.

[0005]

[Means for Solving the Problems]

 The present invention has been devised in view of the above-mentioned conventional circumstances, and an internal combustion engine including a piston ring groove provided at a lower end portion of a crown portion and a skirt portion provided at a lower portion of the piston ring groove at the lowermost end side. In the above piston structure, an inclined surface is formed on the outer peripheral edge of the upper end portion of the skirt that constitutes the piston ring groove on the lowermost end side, and the inclined surface angle on the anti-thrust side is larger than the inclined surface angle on the thrust side. The feature is that it is set.

[0006]

[Action]

 According to the present invention having the above-described structure, for example, during an exhaust stroke, the lower end outer peripheral edge of the inclined surface formed at the upper end of the skirt part scrapes the entire lubricating oil adhering to the cylinder wall to obtain an appropriate oil film thickness. Can be done. For this reason, the lubrication performance between the cylinder wall and the contact portion with the cylinder wall under the inclined surface is improved.

Moreover, by setting the inclined surface angle on the anti-thrust side larger than the thrust side inclined surface angle with respect to the contact portion of the skirt portion, when the piston is tilted, that is, when the crown portion is tilted to the cylinder wall side. The contact area of the anti-thrust side inclined surface with the cylinder wall is reduced. Therefore, the sliding friction resistance is reduced in combination with the formation and uniformization of the oil film.

[0008]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For convenience of explanation, the gap between the cylinder and the piston is exaggerated.

FIG. 3 shows an embodiment of a piston structure of an internal combustion engine according to the present invention. That is, the piston 11 that reciprocates in the cylinder 10 formed in the cylinder block includes a crown portion 13 that receives an explosive force in the combustion chamber 12, and a top ring 14 that is formed on the outer periphery of the lower portion of the crown portion 13. The piston ring grooves 17, 18 and 19 in which the second ring 15 and the oil ring 16 are fitted and held respectively, the skirt portion 20 at the lower end of each piston ring groove 17, 18 and 19, and the small end portion of the connecting rod are connected. And a piston pin 21.

The skirt portion 20 has a substantially circular cross section, and a flat inclined surface 22 is formed on the entire outer peripheral edge of an upper end portion 20 a which constitutes a part of the oil ring groove 19 at the lowermost end portion. There is. The inclination angle θ of the inclined surface 22 is set to 0.1 ° to 3 ° with reference to the linear contact portion 23 that comes into contact with the wall surface of the cylinder 10 below the inclined surface 22, and the height L1 is set. It is set from 3 mm to about 1/4 mm of the height L of the skirt portion 20. The lower peripheral edge 24 of the inclined surface 22 is formed in an arc shape and is continuously connected to the contact portion 23 with a smooth curve.

Further, as shown in FIGS. 1 and 2, when the piston 11 moves upward during an exhaust stroke of the engine, the inclined surface 22 tilts so that the crown portion 13 becomes a cylinder. The inclination angle θ1 of the so-called anti-thrust side inclined surface 22a that hits the one side wall 10a of 10 is set to be larger than the inclination angle θ2 of the opposite thrust side inclined surface 22b. That is, for example, if the inclination angle θ2 of the thrust side inclined surface 22b is 1 °, the inclination angle θ1 of the anti-thrust side inclined surface 22a is set to 3 °.

Therefore, according to this embodiment, when the piston 11 moves upward while tilting toward the cylinder one side surface 10a during the exhaust stroke or the compression stroke, the lower outer peripheral edge 24 of the inclined surface 22a moves toward the cylinder one side surface 10a. While slidably contacting, the lubricating oil adhering to the one side surface 10a is scraped and evened to a certain suitable oil film thickness. Therefore, the lubrication performance between the contact portion 23 of the skirt portion 20 and the cylinder one side surface 10a is improved. As a result, the sliding frictional resistance of the piston 11 with respect to the cylinder 10 is reduced.

Moreover, since the inclination angle θ1 of the anti-thrust side inclined surface 22a is set to be larger than the inclination angle θ2 of the thrust side inclined surface 22b, when the piston 11 tilts, the anti-thrust side inclined surface 22a is inclined. The contact area of the lower outer peripheral edge 24 with the one side surface 10a of the cylinder is smaller than that of the lower outer peripheral edge on the thrust side. Therefore, the sliding frictional resistance between the contact portion 23 and the one side surface 10a of the cylinder is further reduced in combination with the scraping of the lubricating oil and the uniformization of the oil film thickness. As a result, the output of the engine can be improved and the fuel consumption can be reduced.

Further, since the inclined surface 22 and the contact portion 23 are continuously connected by a smooth curve, the lubricating oil scraped up by the outer peripheral edge 24 can be smoothly delivered toward the contact portion 23, and the lubricating action Will be even better.

As a result of experiments conducted by the inventor, the inclination angle and the height L1 of the inclined surface 22 are the most appropriate and assured, as described above, for the collecting action of the lubricating oil and the leveling action of the oil film thickness. It was selected by what was done.

Further, the inclined surface 22 can be formed in a gentle curved surface shape in addition to the flat shape.

[0017]

[Effect of device]

 As is clear from the above description, according to the piston structure of the internal combustion engine according to the present invention, when the piston moves upward, it is attached to the cylinder wall by the lower peripheral edge of the inclined surface formed at the upper end of the skirt. Since the lubricating oil that is present can be collected and leveled to an appropriate oil film thickness, the lubricating performance between the skirt portion and the cylinder wall is improved, and sliding friction resistance is sufficiently reduced.

Moreover, since the inclined surface angle on the anti-thrust side is set to be larger than the inclined surface angle on the thrust side, the contact area with the cylinder wall becomes small. Therefore, the sliding frictional resistance of the piston is further reduced in combination with the scraping action of the lubricating oil and the uniform action of the oil film thickness. As a result, the output of the engine can be improved and the fuel consumption can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged view of part A of FIG. 3 showing an embodiment of the present invention.

FIG. 2 is an enlarged view of part B in FIG.

FIG. 3 is a front view showing the piston structure of the present embodiment.

FIG. 4 is a front view showing a conventional piston structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cylinder 10a ... One side surface 11 ... Piston 13 ... Crown part 17, 18, 19 ... Piston ring groove 20 ... Skirt part 20a ... Upper end part 22 ... Inclined surface 22a ... Anti thrust side inclined surface 22b ... Thrust side inclined surface

Claims (1)

[Scope of utility model registration request] 1. A piston structure for an internal combustion engine, comprising: a piston ring groove at a lower end of a crown portion; and a skirt portion at a lower part of the piston ring groove at a lowermost end side, wherein the piston ring groove at the lowermost end side is formed. The piston structure of the internal combustion engine, wherein an inclined surface is formed on an outer peripheral edge of an upper end portion of the skirt portion, and the inclined surface angle on the anti-thrust side is set to be larger than the inclined surface angle on the thrust side.