A new method for designing piston skirt longitudinal profile

Abstract

This invention discloses a novel method for designing the longitudinal profile of a piston skirt, comprising the following steps: Step 1: Fitting the longitudinal profile using three points A, B, and C, which consists of two arc segments connected to a middle straight line segment; Point B is the piston's central convex point, located at a certain point on the middle straight line segment, with the major axis of the outer ellipse at the central convex point being D; Point A is the upper endpoint of the longitudinal profile near the piston top; Point C is the lower endpoint of the longitudinal profile near the piston bottom; Point B1 is set as the upper endpoint of the middle straight line segment, and Point B2 as the lower endpoint of the middle straight line segment; Step 2: The radius reduction of the longitudinal profile at point A is 0.04% to 0.15% of the major axis length D of the outer ellipse at the central convex point; the radius reduction of the longitudinal profile at point C is 0.01% to 0.1% of the major axis length D of the outer ellipse at the central convex point. This invention provides a parametric equation fitting approach for longitudinal profiles, offering a new feasible method for piston design and optimization, facilitating the application of parametric equations in piston profile design, and opening up new avenues of thought.

Description

Technical Field

[0001] This invention relates to the technical field of engine pistons, and in particular to a novel method for designing the longitudinal profile of the piston skirt. Background Technology

[0002] Existing piston designs have the following drawbacks:

[0003] 1. The longitudinal profile design of pistons often adopts quadratic and cubic polynomials, which is a relatively simple approach and not entirely applicable to all types of engines;

[0004] 2. Optimizing the piston longitudinal profile by modifying polynomial parameters is costly, labor-intensive, and complex to operate; the method is relatively simple and not entirely applicable to all types of engines.

[0005] The brachistochrone equation is a parametric equation. This invention uses the brachistochrone equation to fit the longitudinal profile of the piston, providing a new way to optimize the design of the piston longitudinal profile and promoting the application of parametric equations in fitting piston profiles. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above-mentioned novel methods for designing the longitudinal profile of the piston skirt, this invention is proposed.

[0008] Therefore, the purpose of this invention is to provide a new method for designing the longitudinal profile of a piston skirt, which provides a parametric equation fitting approach for the longitudinal profile to meet the working requirements of the piston skirt, thus offering a new and feasible method for piston design and optimization.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a new method for designing the longitudinal profile of a piston skirt, comprising the following steps:

[0010] Step 1: Fit a longitudinal profile using points A, B, and C, which consists of two arcs connected to the middle straight line segment; point B is the convex point in the piston, located somewhere on the middle straight line segment, and the length of the major axis of the outer ellipse at the convex point of the piston is D; point A is the upper endpoint of the longitudinal profile near the top of the piston; point C is the lower endpoint of the longitudinal profile near the bottom of the piston; set point B1 as the upper endpoint of the middle straight line segment and point B2 as the lower endpoint of the middle straight line segment;

[0011] Step 2: The radius reduction at point A of the longitudinal profile is 0.04% to 0.15% of the length D of the major axis of the outer ellipse at the mid-convex point; the radius reduction at point C of the longitudinal profile is 0.01% to 0.1% of the length D of the major axis of the outer ellipse at the mid-convex point.

[0012] Step 3: Fit the upper and lower arcs of the longitudinal profile using the brachistochrone equation. The expression for the brachistochrone equation is:

[0013]

[0014] In the formula: α is a variable parameter. Assuming that α is a constant, let θ = π × t. The value of t increases continuously from 0. The scanned curve is the steepest descent curve. This curve changes periodically as the value of t increases.

[0015] Step 4: Assuming α is a constant, adjust the t value to scan from t=1 to t=2, controlling the length of the steepest descent curve;

[0016] Step 5: Assuming the scanning range of t is fixed, let α = p / π, adjust the value of p to control the period and curvature of the brachistochrone curve;

[0017] Step Six: Fit the longitudinal profile using the brachistochrone equation. Except for adjusting the t value to scan from t=1 to t=2, when t is any odd number, the tangent line of the curve at the coordinate point (x,y) is parallel to the x-axis, and the brachistochrone curve and the perpendicular line drawn from the coordinate point (x,y) to the x-axis are symmetrically distributed. Select this point as the endpoint of the middle straight line segment of the longitudinal profile. From this point, the scanning range of t can be established in any direction to both ends of the curve. Adjust the value of parameter p to fit the longitudinal profile.

[0018] As a preferred embodiment of the novel piston skirt longitudinal profile design method of the present invention, the height h of point B from the lower part of the pin hole and from the center of the pin hole is a×D, where a = 8%-15%; the length of the middle straight segment is 0-5mm.

[0019] As a preferred embodiment of the novel piston skirt longitudinal profile design method of the present invention, in step three, when t∈[0,2], the complete curve of the first period of the brachistochrone curve is scanned. When t=1, the curve is symmetrical about the straight line x=απ. At this time, the coordinate point (x,y) of the brachistochrone curve is farthest from the t axis, and the tangent equation at this coordinate is parallel to the t axis.

[0020] As a preferred embodiment of the novel piston skirt longitudinal profile design method of the present invention, in step three, the coordinate point (x, y) at t=1 is taken as the fitting starting point at the endpoint of the middle straight line segment of the longitudinal profile, the curves on both sides of the straight line segment are fitted, and the x-axis is kept parallel to the piston axis. This can eliminate the need for calculation of using low-order spline interpolation to ensure smooth transition at the segment points of the longitudinal profile, thus simplifying the design process.

[0021] As a preferred embodiment of the novel method for designing the longitudinal profile of the piston skirt according to the present invention, the following steps are taken: A coordinate system 1 is established according to the approach described in step three, with point B1 as the origin. X1 represents the piston height, and Y1 represents the longitudinal profile gap. Let X1 = xp and Y1 = y - 2α. This allows the coordinates of the brachistochrone vertex to be transformed to the origin of the fitting coordinate system 1, keeping the relative positions of points B1 and A unchanged. The magnitude of parameter p and the scanning range of parameter t are adjusted so that B1 and A are located in the same curve segment, fitting the longitudinal profile from the middle straight line segment to the top of the piston skirt.

[0022] As a preferred embodiment of the novel method for designing the longitudinal profile of the piston skirt according to the present invention, the following steps are taken: A coordinate system 2 is established according to the approach described in step three, with point B2 as the origin. X2 represents the piston height, and Y2 represents the longitudinal profile gap. Setting X2 = xp and Y2 = y - 2α transforms the coordinates of the brachistochrone vertex to the origin of the fitting coordinate system 2. The relative positions of points B2 and C remain unchanged. The magnitude of parameter p and the scanning range of parameter t are adjusted so that B2 and C are located in the same curve segment. The longitudinal profile from the middle straight line segment to the bottom of the piston skirt is then fitted.

[0023] The beneficial effects of this invention are:

[0024] 1. To provide a feasible method for longitudinal profile design of pistons for different types of engines;

[0025] 2. Provides a new direction for piston profile optimization design;

[0026] 3. It facilitates the application of parametric equations in piston profile design, opening up new avenues of thought. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0028] Figure 1This diagram illustrates the fitting process of a single longitudinal profile in the novel piston skirt longitudinal profile design method of this invention.

[0029] Figure 2 This is a longitudinal profile diagram from the middle straight line segment to the top of the piston skirt, which is the fitting method for the novel longitudinal profile design of the piston skirt according to the present invention.

[0030] Figure 3 This is a longitudinal profile diagram from the middle straight line segment to the bottom end of the piston skirt, which is the result of fitting the novel longitudinal profile design method for the piston skirt of this invention. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0034] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0035] Reference Figure 1 A novel method for designing the longitudinal profile of a piston skirt is provided, comprising the following steps:

[0036] Step 1: Fit a longitudinal profile using points A, B, and C, which consists of two arcs connected to the middle straight line segment; point B is the convex point in the piston, located somewhere on the middle straight line segment, and the length of the major axis of the outer ellipse at the convex point of the piston is D; point A is the upper endpoint of the longitudinal profile near the top of the piston; point C is the lower endpoint of the longitudinal profile near the bottom of the piston; set point B1 as the upper endpoint of the middle straight line segment and point B2 as the lower endpoint of the middle straight line segment;

[0037] Step 2: The radius reduction at point A of the longitudinal profile is 0.04% to 0.15% of the length D of the major axis of the outer ellipse at the mid-convex point; the radius reduction at point C of the longitudinal profile is 0.01% to 0.1% of the length D of the major axis of the outer ellipse at the mid-convex point.

[0038] Step 3: Fit the upper and lower arcs of the longitudinal profile using the brachistochrone equation. The expression for the brachistochrone equation is:

[0039]

[0040] In the formula: α is a variable parameter. Assuming that α is a constant, let θ = π × t. The value of t increases continuously from 0. The scanned curve is the steepest descent curve. This curve changes periodically as the value of t increases.

[0041] Step 4: Assuming α is a constant, adjust the t value to scan from t=1 to t=2, controlling the length of the steepest descent curve;

[0042] Step 5: Assuming the scanning range of t is fixed, let α = p / π, adjust the value of p to control the period and curvature of the brachistochrone curve;

[0043] Step Six: Fit the longitudinal profile using the brachistochrone equation. Except for adjusting the t value to scan from t=1 to t=2, when t is any odd number, the tangent line of the curve at the coordinate point (x,y) is parallel to the x-axis, and the brachistochrone curve and the perpendicular line drawn from the coordinate point (x,y) to the x-axis are symmetrically distributed. Select this point as the endpoint of the middle straight line segment of the longitudinal profile. From this point, the scanning range of y can be established in any direction to both ends of the curve. Adjust the value of parameter p to fit the longitudinal profile.

[0044] Wherein, the height h of point B from the lower part of the pin hole and from the center of the pin hole is a × D, where a = 8% - 15%; the length of the middle straight segment is 0 to 5 mm.

[0045] Furthermore, in step three, when t∈[0,2], the complete curve of the first period of the brachistochrone curve is scanned. When t=1, the curve is symmetrical about the line x=απ. At this time, the coordinate point (x,y) of the brachistochrone curve is farthest from the x-axis, and the tangent equation at this coordinate is parallel to the x-axis. Specifically, in step three, the coordinate point (x,y) at t=1 is taken as the fitting starting point at the endpoint of the middle straight line segment of the longitudinal profile. The curves on both sides of the straight line segment are fitted, and the x-axis is kept parallel to the piston axis. This can eliminate the need to use low-order spline interpolation to ensure a smooth transition at the segment points of the longitudinal profile, simplifying the design process.

[0046] like Figure 2As shown: Following the approach in step three, establish coordinate system 1 required for fitting the longitudinal profile, with point B1 as the origin, where X1 is the piston height and Y1 is the longitudinal profile gap. Let X1 = xp and Y1 = y - 2α, which can transform the coordinates of the peak of the brachistochrone to the origin of the fitting coordinate system 1. Keep the relative positions between points B1 and A unchanged, adjust the value of parameter p and the scanning range of parameter t so that B1 and A are located in the same curve segment, and fit the longitudinal profile from the middle straight line segment to the top of the piston skirt.

[0047] like Figure 3 As shown: Following the approach in step three, establish coordinate system 2 required for fitting the longitudinal profile. Take point B2 as the origin, where X2 is the piston height and Y2 is the longitudinal profile gap. Let X2 = xp and Y2 = y - 2α to transform the coordinates of the peak of the brachistochrone to the origin of the fitting coordinate system 2. Keep the relative positions between points B2 and C unchanged, adjust the value of parameter p and the scanning range of parameter t so that B2 and C are located in the same curve segment, and fit the longitudinal profile from the middle straight line segment to the bottom of the piston skirt.

[0048] To address the operational requirements of the piston skirt, this invention provides a method for fitting longitudinal profiles with parametric equations, offering a new and feasible approach for piston design and optimization. This facilitates the application of parametric equations in piston profile design and opens up new avenues of thought.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A novel method for designing the longitudinal profile of a piston skirt, characterized in that, Includes the following steps: Step 1: Fit the longitudinal profile to three points A, B, and C. It is formed by two arcs connected to the middle straight line segment. Point B is the convex point in the piston, located at a certain point on the middle straight line segment. The length of the major axis of the outer ellipse at the convex point of the piston is D. Point A is the upper end point of the longitudinal profile near the top of the piston. Point C is the lower end point of the longitudinal profile near the bottom of the piston. Set point B1 as the upper endpoint of the middle straight line segment and point B2 as the lower endpoint of the middle straight line segment; Step 2: The radius reduction at point A of the longitudinal profile is 0.04% to 0.15% of the major axis length D of the outer ellipse at the midpoint of the convex point; the radius reduction at point C of the longitudinal profile is 0.01% to 0.1% of the major axis length D of the outer ellipse at the midpoint of the convex point. Step 3: Fit the upper and lower arcs of the longitudinal profile using the brachistochrone equation. The expression for the brachistochrone equation is: ； In the formula: Assuming that the parameter is variable, Let it be a constant. , The value starts from 0 and increases continuously; the scanned curve is the steepest descent curve. This curve... The value increases in a periodic manner; in step three, when At that time, the complete curve of the first cycle of the steepest descent line is scanned. When, the curve is about the straight line Symmetry, at this point, the coordinates of the brachistochrone curve. distance The furthest point on the axis, and its coordinates. Tangent equation and The axes are parallel; following the approach described in step three, establish coordinate system 1 required for longitudinal profile fitting, so that... Point is taken as the origin of the coordinate system, where Piston height For the longitudinal profile gap, let , It can transform the coordinates of the vertex of the brachistochrone to the origin of the fitted coordinate system 1, while keeping the relative positions between points B1 and A unchanged, and adjusting the parameters. Size and parameters The scanning range is adjusted so that B1 and A are located in the same curve segment, and the longitudinal profile from the middle straight line segment to the top of the piston skirt is fitted; according to the idea of ​​step three, the coordinate system 2 required for fitting the longitudinal profile is established, so as to... Point is taken as the origin of the coordinate system, where Piston height For the longitudinal profile gap, let , This allows the coordinates of the brachistochrone vertex to be transformed to the origin of the fitted coordinate system 2, while maintaining the relative positions of points B2 and C, and adjusting the parameters. Size and parameters The scanning range is such that B2 and C are located in the same curve segment, fitting the longitudinal profile from the middle straight line segment to the bottom of the piston skirt; Step 4: Assumption For a fixed value, adjust Value from Start towards Scanning to control the length of the steepest descent curve; Step 5: Assumption The scanning range is fixed, so that ,Adjustment The value controls the period and curvature of the brachistochrone curve. Step Six: Fit the longitudinal profile using the brachistochrone equation, except for adjustments. Value from Start towards In addition to scanning, when For any odd number, the coordinates of the point The tangents to the curve at each point are all... The axes are parallel, and the steepest descent curve is parallel to the coordinate point. Towards The perpendicular lines drawn from the axes are symmetrically distributed; select coordinate points. As the endpoint of the middle straight segment of the longitudinal profile, from the coordinate point It can be established in any direction at both ends of the curve The scan range was adjusted, and the parameters were modified. The value is used to fit the longitudinal profile.

2. The novel method for designing the longitudinal profile of the piston skirt according to claim 1, characterized in that: The height h of point B from the lower part of the pin hole and from the center of the pin hole is a×D, where a=8%-15%; the length of the middle straight segment is 0~5mm.

3. The novel method for designing the longitudinal profile of the piston skirt according to claim 2, characterized in that: In step three, take Coordinates of time As the starting point for fitting at the endpoint of the straight segment in the middle of the longitudinal profile, the curves on both sides of the straight segment are fitted, ensuring... The shaft is parallel to the piston axis.

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