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 inter

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

Examples

Experimental program
Comparison scheme
Effect test

Example Embodiment

[0061] Example 1:

[0062] A design method for the outer circle profile curve of a large ellipse piston adopts a combined ellipse and cycloid curve. The cycloid is also called a sinusoidal acceleration curve. The acceleration characteristic of this curve is a sinusoidal curve. The ellipse and cycloid combined curve can avoid the instantaneous sudden change of acceleration at the intersection θ, and reduce the impact of the processing process. It includes the following steps:

[0063] Step 1 Take the center of the piston skirt section as the center of the ellipse, and take the diameter D of the major axis of the piston skirt as the major axis of the ellipse, and determine the minor axis of the ellipse 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 of the ellipse and the eccentric circle is θ, the offset of the eccentric circle relative to the short semi-axis of the ellipse ...

Example Embodiment

[0077] Example 2:

[0078] The expression of elliptical linear acceleration is:

[0079] 0-θ elliptical acceleration expression: 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 formula (5). Therefore, the eccentric circular shape is replaced by a gradual ellipse line that changes with the quadratic sine law to smoothly transition the displacement, velocity and acceleration at the tip of the combined curve.

[0083] A method for designing the outer circular surface curve of a large elliptic piston, which adopts the ellipse superimposed gradient ellipse combined curve, and includes the following steps:

[0084] Step 1 Take the center of the piston skirt section as the center of the ellipse, and take the diameter D of the major axis of the piston skirt as the major axis of the ellipse, and determine the minor axis of the ellipse by the ellipticity G of the piston skirt;

[0085]...

Example Embodiment

[0097] Example 3:

[0098] Taking the angle of intersection θ=54°, the eccentricity e=2.44, the offset of the eccentric circle relative to the short semi-axis of the ellipse is h=0.4, and the 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 "ellipse + ellipse" combination are as follows Figure 6(a)-Figure 6(d) As shown, the curve characteristics of the “ellipse + cycloid” combination 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 spindle speed of the comparison experiment is 800 rpm.

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

[0101]

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

[0103] (1) The displacement, velocity, acce...

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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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