JPH05149198A - Piston for engine - Google Patents

Abstract

PURPOSE:To provide a piston for an engine wherein, during the use of a piston, lubricating oil is difficult to escape through fine grooves and the piston is reliably levitated from the inner wall of a cylinder. CONSTITUTION:A number of fine grooves 6 for holding lubricating oil are formed in a lateral waveform, crossing an axial direction, in a wire area below piston ring grooves 2 in the outer peripheral surface of a piston 1. When the piston 1 is slid along the inner wall of a cylinder 9, the fine grooves 6 are formed in a lateral waveform and long. Besides, by causing lubricating oil to flow from the crest part of the fine groove 6 to a root part 12, the lubricating oil is difficult to escape in recessed parts 4 formed in the piston 1. A large quantity of the lubricating oil can be held between the fine grooves 6 and the inner wall of the cylinder 9, and the high pressure part of the lubricating oil is wide and the pressure thereof is also increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine piston having an outer peripheral surface formed with a thin groove for retaining lubricating oil.

[0002]

2. Description of the Related Art Conventionally, as a piston for an engine, FIG.
As shown in FIG. 1, piston pin holes 3 are provided below the piston ring groove 2 of the piston 1 so as to face each other, and a recess 4 is formed on the outer peripheral surface so as to surround these pin holes 3 and a notch is formed below the recess 4. What formed the part 5 is generally used.

Further, the piston 1 is turned into a circular cross-sectional area by a cutting tool (not shown). The fine grooves 6 for retaining the lubricating oil are formed in a spiral shape by the substantially linear cutting traces 6a. In FIG. 9, 7 is a crown portion of the piston 1, 8 is a piston ring fitted and held in the piston ring groove 2, and 9 is a cylinder.

As shown in FIG. 10, the engine piston having the above-described structure is formed in the lower portion of the piston ring groove 2 on the outer peripheral surface when the piston 1 slides in the cylinder 9 in the axial direction during use. The thin groove 6 holds the lubricating oil 10, and at the same time, due to the viscous resistance of the lubricating oil to the cylinder wall surface, the lubricating oil 10 flows relatively rearward with respect to the piston as shown by an arrow b in FIG. The dynamic pressure indicated by the arrow c acting on the piston contributes to the floating of the piston 1 from the inner wall 9a of the cylinder 9.

[0005]

However, in the above-mentioned conventional engine piston, since the fine groove 6 formed by the cutting trace 6a is formed in the outer peripheral surface in a straight line shape substantially orthogonal to the axial direction, it becomes a high pressure portion. From the central portion d between the concave portions 4 on the outer peripheral surface of the piston 1 toward the portion e near the concave portion 4 which is the low pressure portion,
There is a problem that the lubricating oil 10 retained in the narrow groove 6 easily escapes along the narrow groove 6, and the lubricating oil 10 does not sufficiently contribute to the floating from the cylinder inner wall of the piston.

The present invention solves the above-mentioned problems,
To provide a piston for an engine in which lubricating oil does not easily escape from a small groove for retaining lubricating oil, and the dynamic pressure allows the piston to be reliably levitated from the inner wall of the cylinder, enabling smoother reciprocating movement of the piston. The purpose is that.

[0007]

In the engine piston of the present invention, a narrow groove for retaining lubricating oil is formed in a wide corrugated shape on the outer peripheral surface below the piston ring groove in a lateral corrugation intersecting the axial direction. ..

[0008]

In the engine piston according to the present invention, when the piston axially slides along the inner wall of the cylinder during use, the narrow groove formed on the outer peripheral surface has a lateral corrugation. The length is longer than that of the straight linear grooves that intersect at right angles, and moreover, the lubricating oil flows into the troughs of the horizontal corrugated grooves from the peaks on both sides of these, and it is difficult for the lubricating oil to escape to the recesses of the piston. The lubricating oil can be retained between the narrow groove and the inner wall of the cylinder.

The high-pressure portion of the dynamic pressure of the lubricating oil generated during the compression stroke of the piston becomes wider than that of the conventional one,
Since the pressure in the high-pressure portion also becomes high, the piston floats sufficiently from the inner wall of the cylinder, and a smoother axial reciprocating motion of the piston becomes possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1, 2, and 3 are a front view, a side view, and a plan explanatory view of an engine piston according to an embodiment of the present invention. The basic structure of the engine piston of this embodiment is the same as that of the conventional one shown in FIG. 9 and described above. In FIGS. 1, 2 and 3, the same reference numerals as those in FIG. 9 correspond to the corresponding parts.

In this embodiment, a large number of independent fine grooves 6 formed by cutting scratches 6a form a lateral corrugation on the entire outer surface of the cylinder 1 other than the recess 4 below the piston ring groove 2 so as to intersect the axial direction. Has been formed. Horizontal corrugated narrow groove 6
Is a shape in which the narrow grooves 6 are formed in parallel with each other in the axial direction of the piston 1, that is, in the vertical direction, and each groove 6 has six valleys 12 formed by a sine curve at equal intervals in the circumferential direction of the piston 1. In addition, it was cut with a cutting tool.

Further, as shown in FIG. 3, the piston 1 is machined into a plane elliptical shape. Although the difference in length between the actual major axis r ₁ and the minor axis r ₂ is slight, the major axis r ₁ is shown in FIG.
The difference between ₁ and the minor axis r ₂ is drawn larger than it actually is. In order to form a large number of narrow grooves 6 on the piston 1 in a horizontal corrugation,
As shown in FIG. 3, the piston 1 which is not processed with the fine groove by the chuck 15 is detachably attached to the tip of the spindle 14 mounted on the headstock 13.

In this state, the numerical controller 16 drives the memory 1
In accordance with a command based on the machining program of No. 7, the headstock advancing / retreating motor 19 is driven through the drive means 18 to drive the headstock 1
While advancing and retracting 3 in the x-axis direction, the spindle driving motor 21 is driven via the drive means 20 to rotate the spindle 14, thereby rotating the piston 1 integrally with the chuck 15.

At the same time, according to the command, the tool rest driving motor 23 is driven through the drive means 22 to move the tool rest 24 back and forth in the y-axis direction, while the tool rest 24 is detachably held on the tip end thereof. Piston 1 with the tip of bit 25
Then, a cutting process is performed by applying it to the outer peripheral surface to form lateral corrugated narrow grooves in which the above-mentioned six valleys formed by the sine curve are provided at equal intervals. In addition, 26 in FIG. 4 shows an input device.

Based on the θy table of the memory 17, the cutting tool 25 is moved forward and backward in the y direction corresponding to the angle θ of the piston 1. As a result, the piston 1 is turned into an elliptical cross section. At the time of this turning, x
= Sin6θ + θ / 360 ° × a + n × a by the amount of movement in the x direction, the lateral corrugated narrow groove 6 is formed in a spiral shape. Where θ is the rotation angle of the piston 1, n is the rotation speed of the piston 1,
a represents the pitch of the fine grooves 6 in the x direction. After the formation of the narrow groove is completed, the motors 19, 21 and 23 are all stopped and the piston 1 is removed from the chuck 15.

In the engine piston of the embodiment constructed as described above, when the piston 1 slides in the cylinder in the axial direction during use, the narrow groove 6 formed on the outer peripheral surface of the piston 1
Is a lateral corrugation, the thin grooves are curved and their length becomes long when the area of the portion where the narrow grooves are formed and the width of the narrow grooves are equal to those of the above-mentioned conventional ones. As shown by the arrow f, the lubricating oil flows into the troughs 12 of the narrow groove 6 from the ridges on both sides thereof, and it is difficult for the lubricating oil to escape to the recess side, so that a large amount of lubricating oil flows between the narrow groove 6 and the inner wall of the cylinder. Can be held between.

During the compression stroke in which the piston 1 moves upward, a dynamic pressure is generated in the lubricating oil as in the case of the conventional one shown in FIG. 10, but the high pressure part d of the dynamic pressure is wider than that of the conventional one. As a result, the pressure in the high pressure portion d also increases, so that the piston floats above the inner wall of the cylinder more than before. In the above-described embodiment, the shape of the transverse wave of the narrow groove and the number of troughs can be changed as appropriate, the intervals between the troughs need not be equal, and the positions of the troughs can be changed as appropriate.

Further, the present invention is not limited to the narrow groove formed by the cutting striations, but the thin groove 6 may be formed in a lateral corrugation having a valley 12 by laser processing or etching processing as shown in FIG. Of course, the narrow groove 6 formed by laser processing has a substantially semi-circular cross section as shown in FIG. 7, and the narrow groove 6 formed by etching has a substantially rectangular cross section as shown in FIG.

Further, the basic shape of the engine piston of the present invention is not necessarily limited to that of the embodiment, but can be changed appropriately.

[0020]

As described above, in the engine piston of the present invention, the lubricating oil holding fine groove is formed in a wide corrugated shape on the outer peripheral surface below the piston ring groove in a lateral corrugation crossing the axial direction. The following effects are obtained. That is, when the piston for an engine according to the present invention is used, when the piston slides along the inner wall of the cylinder in the axial direction, the narrow groove formed on the outer peripheral surface has a lateral corrugation. The length is longer than that of the straight linear groove, and moreover, the lubricating oil flows into the troughs of the horizontal corrugated groove from the peaks on both sides of these, and it is difficult for the lubricating oil to escape to the recess of the piston. The lubricating oil can be retained between the narrow groove and the inner wall of the cylinder.

Further, the high pressure portion of the dynamic pressure of the lubricating oil generated during the compression stroke of the piston becomes wider than that of the conventional one,
Since the pressure in the high-pressure portion also becomes high, the piston floats sufficiently from the inner wall of the cylinder, and a smoother axial reciprocating motion of the piston becomes possible.

[Brief description of drawings]

FIG. 1 is a front view showing an engine piston according to an embodiment of the present invention.

2 is a side view of the engine piston of FIG. 1. FIG.

FIG. 3 is a plan view of the engine piston of FIG.

FIG. 4 is a schematic plan view of a cutting machine for cutting fine grooves of an engine piston according to the present invention.

5 is a partially enlarged front view showing the flow of lubricating oil of the engine piston of FIG.

FIG. 6 is a schematic plan view showing an engine piston according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a narrow groove formed by laser processing.

FIG. 8 is a sectional view of a narrow groove formed by etching.

FIG. 9 is a front view showing a conventional engine piston.

10 is a partial vertical cross-sectional view showing the flow of lubricating oil when the engine piston of FIG. 9 is used.

[Explanation of symbols]

 1 Piston 2 Piston Ring Groove 3 Piston Pin Hole 4 Recess 6 Fine Groove 6a Cutting Slit 10 Lubricant 12 Valley of Fine Groove

Front page continuation (72) Inventor Hiromitsu Ota 1-1-1, Asahi-cho, Kariya city, Aichi prefecture Toyota Koki Co., Ltd.

Claims (1)

[Claims] 1. A piston for an engine, characterized in that a narrow groove for retaining a lubricating oil is formed in a wide corrugated shape in a wide area below the piston ring groove on the outer peripheral surface in a lateral corrugation crossing the axial direction.