Novel method for designing longitudinal molded line of piston skirt

Abstract

The invention discloses a novel method for designing a longitudinal molded line of a piston skirt, which comprises the following steps of: 1, fitting the longitudinal molded line by a point A, a point B and a point C, and connecting two sections of arc lines with a middle straight line section; the point B is a middle convex point of the piston and is located at a certain position of the middle straight line section, and the length of an outer ellipse long axis at the middle convex point of the piston is D; the A point is the upper end point of the longitudinal molded line close to the piston top; the C point is a lower end point of the longitudinal molded line close to the bottom of the piston; setting a point B1 as an upper end point of the middle straight line section and a point B2 as a lower end point of the middle straight line section; secondly, the radius reduction amount of the point A of the longitudinal molded line is 0.04%-0.15% of the length D of the long axis of the outer ellipse at the position of the middle protruding point; and the radius reduction amount of the C point of the longitudinal molded line is 0.01-0.1% of the length D of the long axis of the outer ellipse at the middle convex point. According to the method, the idea of fitting the longitudinal molded line through the parameter equation is provided, a new feasible mode is provided for piston design and optimization, application of the parameter equation in the aspect of piston molded line design is facilitated, and a new idea is opened.

Description

Technical Field

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

[0002] The existing piston design has the following defects:

[0003] 1. The longitudinal profile design of the piston mostly adopts quadratic or cubic polynomials, which is a relatively simple method and is not completely applicable to all types of engines;

[0004] 2. Modifying polynomial parameters to optimize the longitudinal profile of the piston has high trial and error costs, large workload, and complex operation; the method is relatively simple and not completely applicable to all types of engines;

[0005] The brachistocentre equation is a parametric equation. The present invention uses the brachistocentre equation to fit the longitudinal profile of the piston, provides a new method for optimizing the design of the longitudinal profile of the piston, and promotes the application of parametric equations in fitting the piston profile. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

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

[0008] Therefore, the purpose of the present invention is to provide a new method for designing the longitudinal profile of a piston skirt, which provides a method for fitting the longitudinal profile with a parametric equation based on the working requirements of the piston skirt, thereby providing a new feasible way for piston design and optimization.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions: a new method for designing the longitudinal profile of a piston skirt, comprising the following steps:

[0010] Step 1: Fit the longitudinal profile with three points A, B and C, which is connected by two arc segments and the middle straight line segment; point B is the convex point in the piston, located somewhere in the middle straight line segment, and the length of the major axis of the outer ellipse at the convex point in the piston is D; point A is the upper end point of the longitudinal profile close to the top of the piston; point C is the lower end point of the longitudinal profile close to the bottom of the piston; set point B1 as the upper end point of the middle straight line segment, and point B2 as the lower end point of the middle straight line segment;

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

[0012] Step 3: Use the brachistocentre equation to fit the upper and lower arcs of the longitudinal profile. The brachistocentre equation is expressed as:

[0013]

[0014] Where: α is a variable parameter. Assume that α is a constant value, let θ = π × t, and the t value increases continuously from 0. The scanned curve is the brachistocentric curve, which changes periodically as the t value increases.

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

[0016] Step 5: Assuming that 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 6: Use the brachistocentre equation to fit the longitudinal profile. In addition to adjusting the t value to scan from t=1 to t=2, when t is any odd number, the tangent of the curve at the coordinate point (x, y) is parallel to the x-axis, and the brachistocentre curve and the perpendicular line 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 to any direction at both ends of the curve, the scanning range of t can be established, and the parameter p value is adjusted to fit the longitudinal profile.

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

[0019] As a preferred solution of the new method for designing the longitudinal profile of the piston skirt described in the present invention, wherein: in the step three, when t∈[0,2], the first period complete curve of the brachistoline is scanned out, and when t=1, the curve is symmetric about the straight line x=απ, at which time the coordinate point (x, y) of the brachistoline curve is farthest from the t-axis, and the tangent equation at this coordinate is parallel to the t-axis.

[0020] As a preferred solution of the new method for designing the longitudinal profile of a piston skirt described in the present invention, the coordinate point (x, y) at t=1 in step three is taken as the fitting starting point at the end point 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 ensured to be parallel to the piston axis. This can omit the calculation of using low-order spline interpolation to ensure smooth transition at the segmentation points of the longitudinal profile, thereby simplifying the design process.

[0021] As a preferred solution of the new method for designing the longitudinal profile of the piston skirt of the present invention, the coordinate system 1 required for longitudinal profile fitting is established according to the idea of ​​step 3, with point B1 as the coordinate origin, where X 1 is the piston height, Y 1 is the longitudinal profile clearance, let X 1 =xp,Y 1 =y-2α, the coordinates of the vertex of the brachistodes curve can be transformed to the origin of the fitting coordinate system 1, the relative position between points B1 and A is kept unchanged, the size of parameter p and the scanning range of parameter t are adjusted, so that B1 and A are located in the same curve, and the longitudinal profile from the middle straight line segment to the top of the piston skirt is fitted.

[0022] As a preferred solution of the new method for designing the longitudinal profile of the piston skirt of the present invention, the coordinate system 2 required for longitudinal profile fitting is established according to the idea of ​​step 3, with point B2 as the coordinate origin, where X 2 is the piston height, Y 2 is the longitudinal profile clearance, let X 2 =xp,Y 2 =y-2α can transform the coordinates of the vertex of the brachistodes curve to the origin of the fitting coordinate system 2, keep the relative position between points B2 and C unchanged, adjust the size of parameter p and the scanning range of parameter t, so that B2 and C are located in the same curve, and fit the middle straight line segment to the longitudinal profile of the bottom end of the piston skirt.

[0023] Beneficial effects of the present invention:

[0024] 1. Provide a feasible method for longitudinal profile design for different types of engine pistons;

[0025] 2. Provide new directions for piston profile optimization design;

[0026] 3. It is conducive to the application of parametric equations in piston profile design and opens up new ideas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0028] Figure 1 A diagram showing the fitting process of a single longitudinal profile of the new method for designing the longitudinal profile of a piston skirt according to the present invention.

[0029] Figure 2 This is a longitudinal profile diagram from the fitted middle straight line segment to the top of the piston skirt according to the new method for designing the longitudinal profile of the piston skirt of the present invention.

[0030] Figure 3 This is a longitudinal profile diagram from the fitted middle straight line segment to the bottom end of the piston skirt according to the new method for designing the longitudinal profile of the piston skirt of the present invention. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present 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 term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0034] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

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

[0036] Step 1: Fit the longitudinal profile with three points A, B and C, which is connected by two arc segments and the middle straight line segment; point B is the convex point in the piston, located somewhere in the middle straight line segment, and the length of the major axis of the outer ellipse at the convex point in the piston is D; point A is the upper end point of the longitudinal profile close to the top of the piston; point C is the lower end point of the longitudinal profile close to the bottom of the piston; set point B1 as the upper end point of the middle straight line segment, and point B2 as the lower end point of the middle straight line segment;

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

[0038] Step 3: Use the brachistocentre equation to fit the upper and lower arcs of the longitudinal profile. The brachistocentre equation is expressed as:

[0039]

[0040] Where: α is a variable parameter. Assume that α is a constant value, let θ = π × t, and the t value increases continuously from 0. The scanned curve is the brachistocentric curve, which changes periodically as the t value increases.

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

[0042] Step 5: Assuming that 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 6: Use the brachistocentre equation to fit the longitudinal profile. In addition to adjusting the t value to scan from t=1 to t=2, when t is any odd number, the tangent of the curve at the coordinate point (x, y) is parallel to the x-axis, and the brachistocentre curve and the perpendicular line 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 to any direction at both ends of the curve, the y scanning range can be established, and the parameter p value is adjusted to fit the longitudinal profile.

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

[0045] Furthermore, in the step three, when t∈[0,2], the first cycle complete curve of the brachistodes curve is scanned out, and when t=1, the curve is symmetric about the straight line x=απ. At this time, the coordinate point (x, y) of the brachistodes curve is farthest from the x-axis, and the tangent equation at this coordinate is parallel to the x-axis. Specifically, in the step three, the coordinate point (x, y) at t=1 is taken as the fitting starting point at the end point of the middle straight line segment of the longitudinal profile, and the curves on both sides of the straight line segment are fitted, and the x-axis is ensured to be parallel to the piston axis. This can omit the calculation of using low-order spline interpolation to ensure smooth transition at the segmentation points of the longitudinal profile, thereby simplifying the design process.

[0046] like Figure 2 As shown: According to the idea of ​​step 3, the coordinate system 1 required for longitudinal profile fitting is established, with point B1 as the coordinate origin, where X 1 is the piston height, Y 1 is the longitudinal profile clearance, let X 1 =xp,Y 1 =y-2α, the coordinates of the vertex of the brachistodes curve can be transformed to the origin of the fitting coordinate system 1, the relative position between points B1 and A is kept unchanged, the size of parameter p and the scanning range of parameter t are adjusted, so that B1 and A are located in the same curve, and the longitudinal profile from the middle straight line segment to the top of the piston skirt is fitted.

[0047] like Figure 3 As shown: According to the idea of ​​step 3, the coordinate system 2 required for longitudinal profile fitting is established, with point B2 as the coordinate origin, where X 2 is the piston height, Y 2 is the longitudinal profile clearance, let X 2 =xp,Y 2 =y-2α, the coordinates of the vertex of the brachistodes curve can be transformed to the origin of the fitting coordinate system 2, the relative position between points B2 and C is kept unchanged, the size of parameter p and the scanning range of parameter t are adjusted, so that B2 and C are located in the same curve, and the longitudinal profile from the middle straight line segment to the bottom end of the piston skirt is fitted.

[0048] In view of the working requirements of the piston skirt, the present invention provides an idea of ​​fitting the longitudinal profile with a parametric equation, provides a new feasible approach for piston design and optimization, is conducive to the application of parametric equations in piston profile design, and opens up new ideas.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A new method for designing the longitudinal profile of a piston skirt, characterized in that: The following steps are involved: Step 1: Fit the longitudinal profile with three points A, B and C, which are connected by two arc segments and the middle straight line segment; Point B is the convex point in the piston, located somewhere in the middle straight line segment, and the length of the major axis of the outer ellipse at the convex point in the piston is D; Point A is the upper end point of the longitudinal profile close to the top of the piston; Point C is the lower end point of the longitudinal profile close to 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 reduction amount of the radius of point A of the longitudinal profile is 0.04% to 0.15% of the length D of the outer ellipse major axis at the middle convex point; the reduction amount of the radius of point C of the longitudinal profile is 0.01% to 0.1% of the length D of the outer ellipse major axis at the middle convex point; Step 3: Use the brachistocentre equation to fit the upper and lower arcs of the longitudinal profile. The brachistocentre equation is expressed as: Where: α is a variable parameter. Assume that α is a constant value, let θ = π × t, and the t value increases continuously from 0. The scanned curve is the brachistocentric curve, which changes periodically as the t value increases. Step 4: Assuming α is a constant, adjust the t value to scan from t = 1 to t = 2 to control the length of the brachistocentre curve; Step 5: Assuming that 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; Step 6: Use the brachistocentre equation to fit the longitudinal profile. In addition to adjusting the t value to scan from t=1 to t=2, when t is any odd number, the tangent of the curve at the coordinate point (x, y) is parallel to the x-axis, and the brachistocentre curve and the perpendicular line 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 to any direction at both ends of the curve, the scanning range of t can be established, and the parameter p value is adjusted to fit the longitudinal profile.

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

3. The novel method for designing the longitudinal profile of a piston skirt according to claim 1, characterized in that: In the step three, when t∈[0,2], the first period complete curve of the brachistocentric curve is scanned out, and when t=1, the curve is symmetric about the straight line x=απ. At this time, the coordinate point (x, y) of the brachistocentric curve is farthest from the x-axis, and the tangent equation at this coordinate is parallel to the x-axis.

4. The novel method for designing the longitudinal profile of a piston skirt according to claim 3 is characterized in that: In the step 3, the coordinate point (x, y) at t=1 is taken as the fitting starting point at the end point 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 ensured to be parallel to the piston axis. This can omit the calculation of using low-order spline interpolation to ensure smooth transition at the segmentation points of the longitudinal profile, thereby simplifying the design process.

5. The novel method for designing the longitudinal profile of a piston skirt according to claim 1, characterized in that: According to the idea of ​​step three, the coordinate system 1 required for longitudinal profile fitting is established, with point B1 as the coordinate origin, where X1 is the piston height, Y1 is the longitudinal profile gap, and X1=xp, Y1=y-2α is set. The coordinates of the vertex of the brachistocentre line can be transformed to the origin position of the fitting coordinate system 1, keeping the relative position between points B1 and A unchanged, adjusting the size of parameter p and the scanning range of parameter t, so that B1 and A are located in the same curve, and fitting the longitudinal profile from the middle straight line segment to the top of the piston skirt.

6. The novel method for designing the longitudinal profile of a piston skirt according to claim 1, characterized in that: According to the idea of ​​step three, the coordinate system 2 required for longitudinal profile fitting is established, with point B2 as the coordinate origin, where X2 is the piston height, Y2 is the longitudinal profile gap, and X2=xp, Y2=y-2α is set. The coordinates of the vertex of the brachistocentre line can be transformed to the origin position of the fitting coordinate system 2, keeping the relative position between points B2 and C unchanged, adjusting the size of parameter p and the scanning range of parameter t, so that B2 and C are located in the same curve, and fitting the longitudinal profile from the middle straight line segment to the bottom of the piston skirt.

Images