Curve design method for large-ellipticity piston excircle profile

A kind of curve design, large ellipse technology, applied in the direction of piston, mechanical equipment, machine/engine, etc., can solve the problems such as the adverse effect of the shape accuracy of the processed curve, discontinuous acceleration, etc., to avoid sudden acceleration of acceleration, continuous displacement curve, and improve processing. The effect of precision

Active Publication Date: 2018-07-03
BINZHOU BOHAI PISTON CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] The "ellipse + ellipse" combination curve realizes the continuity of the speed in the cutting process of the piston cross-section curve; but the acceleration is discontinuous at the intersection of the ellipse and the eccentric circle, and there is a finite value mutation, which causes a flexible impact and still has a negative impact on the shape accuracy of the processed curve.

Method used

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  • Curve design method for large-ellipticity piston excircle profile
  • Curve design method for large-ellipticity piston excircle profile
  • Curve design method for large-ellipticity piston excircle profile

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Experimental program
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Effect test

Embodiment 1

[0062]The invention discloses a method for designing the outer circle profile curve of a piston with large ellipticity, which adopts an ellipse superimposed cycloid composite curve, and the cycloid is also called a sinusoidal acceleration curve, and the acceleration characteristic of the curve is a sinusoidal curve. The combination curve of ellipse superimposed cycloid can avoid the sudden sudden change of acceleration at the intersection point θ, and reduce the impact of the processing process. Include the following steps:

[0063] In step 1, the center of the cross-section of the piston skirt is used as the center of the ellipse, the diameter D of the major axis of the piston skirt is used as the major axis of the ellipse, and the minor axis of the ellipse is determined by the ellipticity G of the piston skirt;

[0064] Step 2: Make an eccentric circle on the short axis of the piston skirt, the angle formed by the intersection point of the ellipse and the eccentric circle is...

Embodiment 2

[0078] The expression of elliptical linear acceleration is:

[0079] 0-θ elliptical acceleration expression: such as formula (4)

[0080] θ-90° elliptical acceleration expression:

[0081]

[0082] The sudden change of acceleration is due to the instantaneous increase of H in the formula (5), so the gradient elliptical line with quadratic sinusoidal change is used instead of the eccentric circular line, and the displacement, velocity and acceleration at the cusp of the combined curve are smoothly transitioned.

[0083] A method for designing the outer circle profile curve of a piston with large ellipticity, using ellipse superimposed gradient ellipse combined curve, comprising the following steps:

[0084] In step 1, the center of the cross-section of the piston skirt is used as the center of the ellipse, the diameter D of the major axis of the piston skirt is used as the major axis of the ellipse, and the minor axis of the ellipse is determined by the ellipticity G of the...

Embodiment 3

[0098] Taking intersection angle θ=54°, eccentric distance e=2.44, offset of eccentric circle relative to the semi-minor axis of ellipse h=0.4, and ellipticity G=0.3 as the simulation experiment conditions, the combination of "ellipse + eccentric circle" is obtained Curve characteristics such as Figure 5(a)-Figure 5(d) As shown, the curve characteristics of the combination of "ellipse + ellipse" are as follows Figure 6(a)-Figure 6(d) As shown, the curve characteristics of the combination of "ellipse + cycloid" are as follows Figure 7(a)-Figure 7(d) As shown, the curve characteristics of the combination of "ellipse + gradient ellipse" are as follows Figure 8(a)-Figure 8(d) shown.

[0099] The comparative experiment spindle speed was 800 rpm.

[0100] Table 1 Comparison of motion law characteristics of four methods

[0101]

[0102] Through comparison, the following conclusions are drawn:

[0103] (1) The time-varying curves of displacement, velocity, acceleration an...

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Abstract

The invention discloses a curve design method for a large-ellipticity piston excircle profile. According to the curve design method, an 'ellipse + cycloid' combined curve and an 'ellipse + gradually-varied ellipse' combined curve are designed; the curve design method disclosed by the invention can make curve displacement be smoother, realizes continuous speed and acceleration and prevents saltation; an eccentric circle part is redesigned as a gradually-varied ellipse of which the ellipticity increment changes according to a quadratic sine law; therefore the problem about discontinuous cuspidalpoint and acceleration of displacement at an ellipse and eccentric circle combined type line intersection point is solved; smooth transition of the acceleration at an intersection point of an ellipseand an eccentric circle is realized; acceleration saltation in a machining process can be effectively prevented; impact of a cutter is reduced; and the machining precision is improved.

Description

technical field [0001] The invention relates to the field of heavy-duty engines, in particular to a method for designing a large ellipticity piston outer circle profile curve. Background technique [0002] For heavy-duty engines, in order to prevent the piston from "cracking" under high-speed and heavy-load operation, it is necessary to increase the ellipticity of the cross-section of the outer circle of the skirt. The common method is to superimpose an eccentric circle on the ellipse basis. In order to avoid the non-smooth connection of radial shrinkage at the intersection of ellipse + eccentric circle, cosine curves are also used for smooth transition. [0003] The eccentric circle is superimposed on the basis of the ellipse, and the short axis shrinkage is increased through the eccentric circle. Radial shrinkage Δ is the radius difference between the ellipse and the perfect circle whose diameter is the major axis of the ellipse at a certain angle. The radial shrinkage o...

Claims

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Application Information

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IPC IPC(8): F02F3/00
CPCF02F3/00
Inventor 翟鹏林风华王春阳马学军刘淼秦磊龙强韩宇珍尚自河杨润青张国华
Owner BINZHOU BOHAI PISTON CO LTD
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