A method for estimating the pass rate of the coaxiality of a marine multi-cylinder diesel engine hole system with a small sample

Abstract

The application discloses a kind of marine multi-cylinder diesel engine hole system coaxiality qualified rate small sample estimation method, comprising the following steps: to the same type diesel engine that processing is completed is numbered, determine the number of hole system hole that need to be processed, the spatial coordinates of each hole center are measured, based on measured data establish hole system spatial coordinates sample space, from sample space with return extraction data, repeat M-1 times, reconstruct a diesel engine hole system coordinate data, based on coordinate data calculate reconstructed diesel engine hole system coaxiality, repeat reconstruction E diesel engine, calculate the qualified rate of E diesel engine hole system coaxiality.The present application is based on random sampling method, based on the actual hole system processing data of diesel engine, can realize the reasonable estimation of diesel engine hole system coaxiality processing level under the condition of small sample.

Description

Technical Field

[0001] This invention relates to a method for evaluating the quality of hole system machining processes, and more particularly to a small sample estimation method for the coaxiality pass rate of hole systems in marine multi-cylinder diesel engines. Background Technology

[0002] The machining quality of marine diesel engines plays a crucial role in the development of the shipbuilding industry. Hole machining constitutes a significant proportion of diesel engine production, and its quality directly impacts engine performance. The level of hole machining quality is also an important indicator of a diesel engine manufacturer's machining capabilities. Coaxiality (◎), a key performance indicator for diesel engine body machining quality, is primarily used to control the degree of misalignment between the measured axis (which should theoretically be coaxial) and the reference axis. It is vital for the smooth operation of the diesel engine and provides a fundamental guarantee for proper assembly. For mass production, the coaxiality pass rate can be directly used to evaluate machining quality. However, for large diesel engines, the sample size is extremely small, sometimes only a few units per year. If even one unit fails the coaxiality test, it will significantly impact the overall machining pass rate. Conversely, if all samples pass, the results are from a small sample size and do not necessarily indicate a 100% coaxiality pass rate.

[0003] Therefore, the above problems urgently need to be solved. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a small sample estimation method for the coaxiality qualification rate of the bore system of marine multi-cylinder diesel engines. This method is based on random sampling and uses actual bore system machining data of diesel engines as a basis to more accurately and reasonably estimate the coaxiality machining level of the bore system of diesel engines.

[0005] Technical Solution: To achieve the above objectives, this invention discloses a small-sample estimation method for the coaxiality qualification rate of the bore system in marine multi-cylinder diesel engines, comprising the following steps:

[0006] (1) Number the diesel engines of the same model that have been processed. Assuming that the total number is N, each diesel engine is recorded as diesel engine 1, diesel engine 2, ..., diesel engine N.

[0007] (2) Assume that the number of cylinders of this type of diesel engine is M, and the number of holes to be machined corresponding to the hole system is M+1. From the input end to the output end, each hole is called the first gear, the second gear, ..., the M+1th gear;

[0008] (3) For the i-th (i = 1, ..., N) diesel engine, measure the spatial coordinates of the centers of each gear hole. Take the spatial coordinate of the center of the first gear hole as the origin, i.e., (0, 0, 0), and mark the spatial coordinates of the center of the (M+1)-th gear hole as (Ma, 0, 0), where a is the horizontal axial distance between two adjacent gear holes. Then the spatial coordinates of the center of the j-th (j = 1, ..., M+1)-th gear hole are ((j-1)a, x ij y ij , where x ij y ij These are the horizontal and vertical coordinates of the j-th gear hole of the i-th diesel engine, respectively.

[0009] (4) Based on the measured coordinate axes, the coaxiality of the entire length of the i-th (i = 1, ..., N) diesel engine bore is calculated as follows:

[0010] p=1,…,M+1,q=1,…,M+1,p≠q

[0011] Based on the coaxiality of the holes in the j-th gear and the adjacent (j+1)-th gear,

[0012]

[0013] (5) Since the spatial coordinates of the center of the first gear hole and the (M+1)th gear hole are fixed values, the xy plane coordinates of the measured coordinate values ​​of the N diesel engines from the second gear to the Mth gear are used as the sample space Ω:

[0014] Ω={x ij y ij |i=1,…,N; j=2,…,M}

[0015] (6) The data sample was expanded by random sampling to reconstruct a diesel engine;

[0016] (7) Repeat step (6) E times to obtain the spatial coordinate data of the hole center of diesel engines E. Based on step (4), the coaxiality of the total length of the hole of the e-th (e = 1, ..., E) diesel engine can be obtained as follows:

[0017] p=1,…,M+1,q=1,…,M+1,p≠q

[0018] Based on the coaxiality of adjacent gears in gear j and the (j+1)th gear,

[0019]

[0020] (8) When the calculated results of the overall coaxiality of the diesel engine and the coaxiality of two adjacent gears meet the requirements, the diesel engine is deemed qualified, i.e., it satisfies the following formula:

[0021]

[0022] Wherein, Φ0 is the overall coaxiality tolerance of the diesel engine, and Φ1 is the coaxiality tolerance between two adjacent gears of the diesel engine;

[0023] (9) The coaxiality pass rate of the bore system of this type of marine diesel engine can be expressed as:

[0024]

[0025] Among them, the hole system is the crankshaft hole system.

[0026] Preferably, the hole system is a cylinder hole system.

[0027] Furthermore, the hole system is a camshaft hole system.

[0028] Furthermore, in step (3), a coordinate measuring machine is used to measure the spatial coordinates of the center of each hole.

[0029] Furthermore, the specific method for reconstructing a diesel engine in step (6) is as follows: keep the spatial index of the first gear hole center and the spatial coordinate of the second gear hole center unchanged, and extract M-1 data from the sample space Ω with replacement. These M-1 data constitute the reconstruction data of a diesel engine.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention is based on a random sampling method, which can estimate the coaxiality machining level of the diesel engine hole system under small sample conditions; and the whole process is based on the actual machining data of the diesel engine hole system, so the reliability is high; in addition, the convergence of this method is good as the amount of reconstructed sample increases. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the spatial coordinates of the center of the diesel engine at each gear in this invention;

[0032] Figure 2 This is a schematic diagram of the spatial coordinates of the center of the diesel engine at each gear in this invention;

[0033] Figure 3 This is a graph showing the change in the pass rate of diesel engine body processing under different sampling quantities in this invention. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, taking the crankshaft bore of a diesel engine as an example, this invention discloses a small-sample estimation method for the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine, including the following steps:

[0036] (1) Number the diesel engines of the same model that have been processed. Assuming that the total number is N, each diesel engine is recorded as diesel engine 1, diesel engine 2, ..., diesel engine N.

[0037] (2) Assuming that the number of cylinders of this type of diesel engine is M, taking the crankshaft hole of the diesel engine body as an example, the number of crankshaft holes that need to be machined is M+1. From the input end to the output end, each hole is called the 1st gear, the 2nd gear, ..., the M+1st gear.

[0038] (3) For the i-th (i = 1, ..., N) diesel engine, use a coordinate measuring machine or other testing equipment to measure the spatial coordinates of the crankshaft hole centers of each gear. Take the spatial coordinate index of the crankshaft hole center of the first gear as the origin, i.e., (0, 0, 0), and mark the spatial coordinates of the crankshaft hole center of the (M+1)-th gear as (Ma, 0, 0), where a is the horizontal axial distance between two adjacent crankshaft holes. Then the spatial coordinates of the crankshaft hole center of the j-th (j = 1, ..., M+1)-th gear are ((j-1)a, x ij y ij ), where x ij y ij The horizontal and vertical coordinates of the crankshaft bore in the j-th gear of the i-th diesel engine are shown below. A schematic diagram of the spatial coordinates of the center of each gear of the diesel engine is also provided. Figure 2 As shown;

[0039] (4) Based on the measured coordinate axes, the coaxiality of the entire crankshaft bore of the i-th (i = 1, ..., N) diesel engine is calculated as follows:

[0040] p=1,…,M+1,q=1,…,M+1,p≠q

[0041] Based on the coaxiality of adjacent gears in gear j and the (j+1)th gear,

[0042]

[0043] (5) Since the spatial coordinates of the center of the crankshaft bore in the first gear and the crankshaft bore in the (M+1)th gear are fixed values, the xy plane coordinates of the measured coordinate values ​​from the second gear to the Mth gear of N diesel engines are used as the sample space Ω:

[0044] Ω={x ij y ij |i=1,…,W; j=2,…,M}

[0045] (6) The data sample is expanded by random sampling. The specific method is as follows: Keep the first crankshaft hole center space index and the M+1 crankshaft hole center space coordinate unchanged, and extract M-1 data from the sample space Ω with replacement. The M-1 data constitute the reconstructed data of a diesel engine. Calculate the coaxiality of the diesel engine based on the reconstructed data.

[0046] (7) Repeat step (6) E times to obtain the spatial coordinate data of the crankshaft bore center of diesel engine E. Based on step (4), the coaxiality of the entire length of the crankshaft bore of the e-th (e = 1, ..., E) diesel engine can be obtained as follows:

[0047] p=1,…M+1,q=1,…,M+1,p≠q

[0048] Based on the coaxiality of adjacent gears in gear j and the (j+1)th gear,

[0049]

[0050] (8) When the calculated results of the coaxiality of the entire length of the diesel engine and the coaxiality of two adjacent gears meet the requirements, the diesel engine is deemed qualified, i.e., it satisfies the following formula.

[0051]

[0052] Wherein, Φ0 is the overall coaxiality tolerance of the diesel engine, and Φ1 is the coaxiality tolerance between two adjacent gears of the diesel engine;

[0053] (9) The coaxiality pass rate of the crankshaft bore system of this type of marine diesel engine can be approximately expressed as:

[0054]

[0055] The method for estimating the coaxiality qualification rate is similar for other bore systems of marine diesel engines, such as cylinder bore systems and camshaft bore systems.

[0056] Example 1

[0057] Based on the actual machining of a certain model of diesel engine body from a certain diesel engine factory, there are two diesel engine bodies that have been machined. The coordinates of their vertical and horizontal values ​​at each stage are shown in Table 1.

[0058] Table 1. Inspection Data of Processed Diesel Engines / mm

[0059]

[0060] According to the machining drawings for this type of diesel engine, its overall coaxiality tolerance is 0.2, and the coaxiality tolerance between two adjacent gears is 0.06. Calculations show that the overall coaxiality of the two engine blocks is 0.052 and 0.044, respectively, both less than 0.2; the maximum coaxiality values ​​between two adjacent gears are 0.029 and 0.044, both less than 0.06. Therefore, both diesel engines meet the design requirements.

[0061] Due to the extremely small sample size, random sampling was used to expand the data sample. The specific method is as follows: keeping the measured values ​​at distances of 0mm and 3450mm constant at (0, 0), nine sets of data were extracted with replacement from the detection data at other distances. These eleven sets of data constituted the reconstructed data for one diesel engine, and the coaxiality of the diesel engine was calculated based on the reconstructed data. Based on this method, the detection data of 30 diesel engines were reconstructed. Taking the results of a random sampling as an example, the coaxiality data of the crankshaft bores of the 30 diesel engines obtained based on random sampling are shown in Table 2.

[0062] Table 2 shows the calculation results of the coaxiality of the crankshaft bore in the engine block of 30 diesel engines based on the reconstructed data.

[0063]

[0064]

[0065] Based on the sampling results, an analysis of the coaxiality of the 30 diesel engines revealed that the coaxiality of adjacent gears in engines 5, 7, 10, and 21 was partially out of tolerance, failing to meet design requirements. The estimated pass rate for these engines was [value missing].

[0066] Both diesel engine blocks that were actually machined met the machining requirements. However, after random sampling based on measured data, four blocks did not meet the requirements. Analysis revealed that for the fifth randomly sampled diesel engine, the machining coordinates for the 3rd and 4th crankshaft holes (at 690mm and 1035mm) were (-0.008, 0.010) and (0.018, -0.006), respectively, indicating relatively large machining errors. By adjusting the process parameters and correcting the machining holes, the machining stability of the diesel engine block improved while still meeting the machining requirements. The seventh, tenth, and twenty-first randomly sampled diesel engine blocks exhibited similar patterns. Therefore, improving the machining process and enhancing the machining accuracy of the hole system are crucial for improving the precision and stability of diesel engine machining.

[0067] Following the above sampling method, the sample size was varied, and the pass rate of diesel engine block machining was calculated for different sample sizes. The results are as follows: Figure 3 As shown, observations revealed that as the number of samples increased, the pass rate for diesel engine block machining gradually converged to around 87%.

[0068] If the traditional pass rate calculation method is used to evaluate the machining process level of the diesel engine body, both machined bodies meet the drawing requirements, meaning the pass rate is 100%. However, in actual machining, a 100% pass rate is impossible. Due to the limited sample size, it is difficult to reasonably evaluate the machining process level. However, the proposed random sampling method yields a pass rate of approximately 87% for the diesel engine body machining. This result better reflects the actual machining process level and has better applicability.

Claims

1. A method for estimating the coaxiality pass rate of the bore system in a marine multi-cylinder diesel engine using a small sample, characterized in that, Includes the following steps: (1) Number the diesel engines of the same model that have been processed. Assuming that the total number is N, each diesel engine is recorded as diesel engine 1, diesel engine 2, ..., diesel engine N. (2) Assume that the number of cylinders of this type of diesel engine is M, and the number of holes to be machined corresponding to the hole system is M+1. From the input end to the output end, each hole is called the first gear, the second gear, ..., the M+1th gear; (3) For the i-th (i = 1, ..., N) diesel engine, measure the spatial coordinates of the centers of each gear hole. Take the spatial coordinate of the center of the first gear hole as the origin, i.e., (0, 0, 0), and mark the spatial coordinates of the center of the (M+1)-th gear hole as (Ma, 0, 0), where a is the horizontal axial distance between two adjacent gear holes. Then the spatial coordinates of the center of the j-th (j = 1, ..., M+1)-th gear hole are ((j-1)a, x ij y ij ), where x ij y ij These are the horizontal and vertical coordinates of the j-th gear hole of the i-th diesel engine, respectively. (4) Based on the measured coordinate axes, the coaxiality of the entire length of the i-th (i = 1, ..., N) diesel engine bore is calculated as follows: Based on the coaxiality of the holes in the j-th gear and the adjacent (j+1)-th gear, (5) Since the spatial coordinates of the center of the first gear hole and the (M+1)th gear hole are fixed values, the xy plane coordinates of the measured coordinate values ​​of the N diesel engines from the second gear to the Mth gear are used as the sample space Ω: Ω={x ij ,y ij |i=1,…,N;j=2,…,M} (6) The data sample was expanded by random sampling to reconstruct a diesel engine; (7) Repeat step (6) E times to obtain the spatial coordinate data of the hole center of diesel engines E. Based on step (4), the coaxiality of the total length of the hole of the e-th (e = 1, ..., E) diesel engine can be obtained as follows: Based on the coaxiality of adjacent gears in gear j and the (j+1)th gear, (8) When the calculated results of the overall coaxiality of the diesel engine and the coaxiality of two adjacent gears meet the requirements, the diesel engine is deemed qualified, i.e., it satisfies the following formula: Wherein, Φ0 is the overall coaxiality tolerance of the diesel engine, and Φ1 is the coaxiality tolerance between two adjacent gears of the diesel engine; (9) The coaxiality pass rate of the bore system of this type of marine diesel engine can be expressed as:

2. The method for estimating the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine according to claim 1, characterized in that: The hole system is a crankshaft hole system.

3. The method for estimating the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine according to claim 1, characterized in that: The hole system is a cylinder hole system.

4. The method for estimating the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine according to claim 1, characterized in that: The hole system is a camshaft hole system.

5. The method for estimating the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine according to claim 1, characterized in that: In step (3), a coordinate measuring machine is used to measure the spatial coordinates of the center of each hole.

6. The method for estimating the coaxiality pass rate of the bore system of a marine multi-cylinder diesel engine according to claim 1, characterized in that: The specific method for reconstructing a diesel engine in step (6) is as follows: keep the center space index of the first gear hole and the center space coordinate of the M+1 gear hole unchanged, and extract M-1 data from the sample space Ω with replacement. These M-1 data constitute the reconstruction data of a diesel engine.

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