Indirect separation method for connecting rod journal profile error

Abstract

The application discloses a connecting rod neck contour error direct separation method and relates to the field of connecting rod neck contour error analysis.The application comprises the following steps: grinding the crankshaft connecting rod neck and the adjacent spindle neck to obtain the basic machining parameters of the connecting rod neck radius, the connecting rod neck eccentric distance and the grinding wheel radius; the connecting rod neck contour error and the spindle neck contour error after grinding are measured, wherein the connecting rod neck contour error is the separation object, namely the total error; the equivalent X-axis position control error is obtained by using the spindle neck contour error; the contour error caused by the equivalent X-axis position control error is calculated, namely the non-following error is obtained; the following error is solved by using the total error and the non-following error, and the error separation is completed.In the case that the C-axis and X-axis position control errors cannot be directly obtained or it is inconvenient to directly obtain the C-axis and X-axis position control errors, the indirect separation method disclosed by the application is very effective, and the indirect separation method has important significance for the debugging error identification and the guiding redesign in the development process of the high-end numerical control following crankshaft grinding machine.

Description

Technical Field

[0001] This invention relates to the field of connecting rod neck profile error analysis, and more specifically to an indirect method for separating connecting rod neck profile errors. Background Technology

[0002] To facilitate the qualitative description of error sources, factors influencing workpiece surface contour errors caused by traditional cylindrical grinding machines, such as the rotational accuracy of the grinding wheel spindle, the runout of the headstock spindle, the magnitude and stability of the tailstock clamping force, and the wear degree of the tailstock center, are defined as non-following error sources. The C-axis position control error and X-axis position control error, which result from the use of follower grinding, causing connecting rod journal contour errors, are defined as following error sources. The crankshaft connecting rod journal contour error is affected by both following and non-following error sources.

[0003] The crankshaft connecting rod journal profile error caused by both the follower error source and the non-follower error source are defined as the follower error and the non-follower error, respectively. Effectively separating the follower error and the non-follower error from the total crankshaft profile error after grinding allows for the identification of the main error source types affecting the profile error. This is of great significance for guiding the debugging and redesign during the development of high-end CNC follower crankshaft grinding machines.

[0004] There are two methods for separating the connecting rod journal profile error into follower error and non-follower error. One is a direct separation method, which calculates the follower error using the position control errors of the C-axis and X-axis, and then separates the non-follower error from the total error. Because the position control errors of the C-axis and X-axis are collected simultaneously during the follower grinding of the connecting rod journal, the data is accurate, and the calculated follower error is accurate. The other is an indirect method, which calculates the non-follower error using the profile error of the main journal in adjacent gears, and then separates the follower error from the total error. This method is very effective when the C-axis and X-axis position control errors cannot be directly obtained or are inconvenient to acquire. Summary of the Invention

[0005] In view of this, the present invention provides an indirect method for separating the profile error of a connecting rod neck.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for indirect separation of connecting rod neck profile error includes the following steps:

[0008] Grind the crankshaft connecting rod journal and the main journal of the adjacent gear to obtain the basic machining parameters: connecting rod journal radius, connecting rod journal eccentricity, and grinding wheel radius.

[0009] The measured connecting rod neck profile error after grinding is the separated object, i.e., the total error.

[0010] The profile error of the spindle journal after grinding is measured, and this profile error serves as the basis for indirectly evaluating the non-follower error.

[0011] The equivalent X-axis position control error is obtained by utilizing the main journal profile error;

[0012] The contour error caused by the equivalent X-axis position control error is the non-follow-up error.

[0013] The following error is obtained by using the total error and the non-following error, that is, by subtracting the non-following error from the total error, thus completing the error separation.

[0014] Optionally, it also includes the process of obtaining the equivalent X-axis position control error using the main journal profile error:

[0015] Input the main journal profile error (α, Δr) Mα The contour error is actually caused by the machine tool's non-follow-up error factor, which can be equivalently caused by the machine tool's X-axis position control error. Therefore, the equivalent X-axis position control error is (α, -Δr). Mα ), denoted as (α, Δd).

[0016] Optionally, the solution process for the non-follower error is as follows:

[0017] Input basic machining parameters, including connecting rod journal radius r0, connecting rod journal eccentricity R, and grinding wheel radius R. gw ;

[0018] Input the equivalent X-axis position control error (α, Δd);

[0019] Calculate the contour control equation based on the basic machining parameters;

[0020] Grinding motion control equations calculated using contour control equations theory

[0021] A contour model is established based on the theoretical grinding motion control equations;

[0022] The input of the contour model is calculated based on the input basic machining parameters and the equivalent X-axis position control error, namely the theoretical control value of the C-axis and the equivalent actual control value of the X-axis. Then, the contour model data is calculated based on the contour model.

[0023] The reference circle is obtained by fitting the contour model data using the least squares method.

[0024] Based on the basic machining parameters and the calculated contour model data and reference circle information, the connecting rod neck contour error is calculated based on the geometric relationship, which is the non-follow-up error.

[0025] Optionally, it also includes preprocessing of non-following errors: linear interpolation data alignment is performed on the non-following errors, followed by filtering to align the non-following errors with the total error data and subject them to the same filtering conditions.

[0026] Optional, in xO p In the y-coordinate system, the polar coordinate point corresponding to the center of the grinding wheel is (ρ, θ), and the rectangular coordinate is (dcosα-R, dsinα). ρ(θ) is the trajectory function obtained by fitting a spline curve to the discrete point (ρ, θ) collected on the trajectory of the grinding wheel center. The formula for the contour model is as follows:

[0027]

[0028]

[0029] In the formula, d is the distance from the center of the grinding wheel to the center of the crankshaft rotation, and α is the angle through which the connecting rod journal rotates relative to the initial phase.

[0030] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an indirect separation method for connecting rod journal contour error. The non-following error is calculated by the contour error of the main journal of adjacent gears, and then the following error is separated from the total error. When it is not possible or inconvenient to directly obtain the C-axis and X-axis position control errors, the separation method is very effective. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the process of the present invention;

[0033] Figure 2 The results show the measurement of the connecting rod neck profile error and total error after grinding;

[0034] Figure 3 The results of the profile error measurement of the spindle journal after grinding;

[0035] Figure 4 The non-following error results are calculated for three grinding operations;

[0036] Figure 5 The result is the follow-up error obtained from the separation corresponding to three grinding operations. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention discloses an indirect method for separating the profile error of a connecting rod neck, such as... Figure 1 As shown, it includes the following steps:

[0039] Grind the crankshaft connecting rod journal and the main journal of the adjacent gear to obtain the basic machining parameters: connecting rod journal radius, connecting rod journal eccentricity, and grinding wheel radius.

[0040] The measured connecting rod neck profile error after grinding is the separated object, i.e., the total error.

[0041] The profile error of the spindle journal after grinding is measured, and this profile error serves as the basis for indirectly evaluating the non-follower error.

[0042] The equivalent X-axis position control error is obtained by utilizing the main journal profile error;

[0043] The contour error caused by the equivalent X-axis position control error is used to obtain the non-following error;

[0044] The following error is obtained by using the total error and the non-following error. The following error is obtained by subtracting the non-following error from the total error, thus completing the error separation.

[0045] On a CNC follow-up crankshaft grinding machine, the same connecting rod journal and adjacent main journals of the same gear on three crankshafts were ground. The serial numbers were recorded as 4#, 5#, and 6#. The basic machining parameters were: connecting rod journal radius r0 = 49.12 mm, connecting rod journal eccentricity R = 43 mm, and grinding wheel radius R = 43 mm. gw The value is 299.97 mm. The total error, calculated after grinding, is the connecting rod journal profile error. Figure 2 As shown, the measurement of the main journal profile error is as follows: Figure 3 As shown, a low-pass Gaussian filter with a cutoff frequency of 50 UPR was set during the measurement.

[0046] Calculate the contour control equation based on the basic machining parameters;

[0047] The grinding motion control equations in theory are calculated using the contour control equations.

[0048] A contour model is established based on the theoretical grinding motion control equations, in xO pIn the y-coordinate system, the polar coordinate point corresponding to the center of the grinding wheel is (ρ, θ), and the rectangular coordinate is (dcosα-R, dsinα). ρ(θ) is the trajectory function obtained by fitting a spline curve to the discrete point (ρ, θ) collected on the trajectory of the grinding wheel center. The formula for the contour model is as follows:

[0049]

[0050]

[0051] In the formula, d is the distance from the center of the grinding wheel to the center of the crankshaft rotation, and α is the angle through which the connecting rod journal rotates relative to the initial phase.

[0052] Main journal profile error (α, Δr) Mα The contour error is actually caused by the machine tool's non-follow-up error factor, which can be equivalently caused by the machine tool's X-axis position control error. Therefore, the equivalent X-axis position control error is (α, -Δr). Mα ), denoted as (α, Δd).

[0053] The input of the contour model is calculated based on the input basic machining parameters and the equivalent X-axis position control error, namely the theoretical control value of the C-axis and the equivalent actual control value of the X-axis. Then, the contour model data is calculated based on the contour model.

[0054] The reference circle is obtained by fitting the contour model data using the least squares method.

[0055] Based on the basic machining parameters and the calculated contour model data and reference circle information, the connecting rod neck contour error is calculated based on the geometric relationship, which is the non-follow-up error.

[0056] Linear interpolation is performed on the non-following error to align it with the total error data, followed by 50UPR low-pass Gaussian filtering. The result after processing the non-following error is as follows. Figure 4 As shown.

[0057] The following error is obtained by using the total error and the non-following error, i.e., subtracting the non-following error from the total error. Figure 5 As shown, error separation is completed.

[0058] During the commissioning phase, this CNC follower crankshaft grinding machine grinded three crankshafts at the same gear connecting rod journal and adjacent gear main journals. Using the indirect separation method disclosed in this invention, the connecting rod journal contour errors were separated. The non-follower error amplitude and waveform fluctuations in the connecting rod journal contour errors calculated using the main journal contour errors were significant. The separated follower error had a relatively larger amplitude than the non-follower error, but the follower error waveform consistency was good. The total contour error of these three crankshaft connecting rod journals was mainly composed of the follower error, and the fluctuation of the total error was caused by the fluctuation of the non-follower error. Because the relatively consistent follower error can be controlled through compensation, in the current state, the main error source of the crankshaft connecting rod journal contour error of this CNC follower crankshaft grinding machine is the non-follower error source.

[0059] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0060] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for indirect separation of connecting rod neck profile error, characterized in that, Includes the following steps: Grind the crankshaft connecting rod journal and the main journal of the adjacent gear to obtain the basic machining parameters: connecting rod journal radius, connecting rod journal eccentricity, and grinding wheel radius. The connecting rod neck profile error after grinding is measured. The measured connecting rod neck profile error is the separated object, i.e., the total error. The profile error of the spindle journal after grinding is measured, and the profile error is used as the basis for indirectly evaluating the non-following error. The equivalent X-axis position control error is obtained by utilizing the main journal profile error; The contour error caused by the equivalent X-axis position control error is used to obtain the non-following error; The following error is obtained by using the total error and the non-following error. The following error is obtained by subtracting the non-following error from the total error, thus completing the error separation.

2. The method for indirect separation of connecting rod neck profile error according to claim 1, characterized in that, The process of obtaining the equivalent X-axis position control error using the main journal profile error is as follows: Input the main journal profile error (α, Δr) Mα ), contour error (α, Δr) Mα The error is caused by non-follow-up error of the machine tool, which is equivalent to the X-axis position control error of the machine tool. Therefore, the equivalent X-axis position control error is (α, -Δr). Mα ), denoted as (α, Δd).

3. The method for indirect separation of connecting rod neck profile error according to claim 1, characterized in that, The process for solving the non-follower error is as follows: Input basic machining parameters, including connecting rod journal radius r0, connecting rod journal eccentricity R, and grinding wheel radius R. gw ; Input the equivalent X-axis position control error (α, Δd); Calculate the contour control equation based on the basic machining parameters; Grinding motion control equations calculated using contour control equations theory A contour model is established based on the theoretical grinding motion control equations; The input of the contour model is calculated based on the input basic machining parameters and the equivalent X-axis position control error, and then the contour model data is calculated based on the contour model. The reference circle is obtained by fitting the contour model data using the least squares method. Based on the basic machining parameters and the calculated contour model data and reference circle information, the connecting rod neck contour error is calculated based on the geometric relationship, which is the non-follow-up error.

4. The method for indirect separation of connecting rod neck profile error according to claim 1, characterized in that, It also includes preprocessing of non-following errors: linear interpolation data alignment is performed on the non-following errors, followed by filtering to align the non-following errors with the total error data and subject them to the same filtering conditions.

5. The method for indirect separation of connecting rod neck profile error according to claim 3, characterized in that, In xO p In the y-coordinate system, the polar coordinate point corresponding to the center of the grinding wheel is (ρ, θ), and the rectangular coordinate is (dcosα-R, dsinα). ρ(θ) is the trajectory function obtained by fitting a spline curve to the discrete point (ρ, θ) collected on the trajectory of the grinding wheel center. The formula for the contour model is as follows: In the formula, d is the distance from the center of the grinding wheel to the center of the crankshaft rotation, and α is the angle through which the connecting rod journal rotates relative to the initial phase.

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