Optimization method for centering operation of piston of marine low-speed two-stroke diesel engine

Abstract

An optimization method for centering operation of a piston of a low-speed two-stroke diesel engine for a ship optimizes matching values of adjusting shims and structures of small side plates, and comprises the following steps: firstly, checking related sizes, adjusting the thicknesses of the adjusting shims, adjusting the using models of the shims and the number of the shims of different models according to data matching, and then adjusting the matching values of the adjusting shims and the small side plates; and determining the value of the small side plate recessed in advance according to the result. The utilization rate of the adjusting shim is effectively increased, the repair probability of the small side plate on site is reduced, the efficiency of piston centering operation is improved, and the piston centering device can be suitable for piston centering operation of most marine low-speed two-stroke diesel engines.

Description

Technical Field

[0001] The invention relates to a production process of a ship main engine, in particular to an optimization method for centering a piston of a low-speed two-stroke marine diesel engine, and belongs to the technical field of marine diesel engine manufacturing. Background Art

[0002] The engine base, frame and cylinder block are the three main components of a low-speed two-stroke marine diesel engine. There will be cumulative errors in their dimensions during assembly and fitting, which will cause the piston and cylinder liner to wear on one side easily as the crankshaft reciprocates after the piston is installed on the crosshead. Figure 1 , the piston must be in the center position during the movement. Due to the processing errors of the large guide plate 1 of the frame and the crosshead 2, when the small side plate 3 installed on the crosshead 2 moves up and down along the large guide plate 1 of the frame, the piston may be in a tilted state during the movement, resulting in eccentric wear of the piston during the up and down movement, causing abnormal damage to the cylinder liner and other parts that cooperate with it. Therefore, after the base, frame and cylinder body of the main engine are closed, the piston needs to be centered so that the piston can be located in the center position to avoid unilateral wear between the piston and the cylinder liner. In the process of piston centering, it is impossible to achieve the purpose of centering the piston by simply adjusting the small side plate 3. Therefore, it is necessary to use an aluminum adjustment gasket 4 installed between the crosshead 2 and the small side plate 3 to adjust the relative position of the piston.

[0003] Usually the piston centering operation is mainly divided into two steps:

[0004] The first step is to measure the gap and measure the main parameters.

[0005] The clearance measurement must be carried out after the base, frame and cylinder block have been tightened through the connecting bolts, and the entire measurement process must be carried out at room temperature. Before measurement, the measuring tools need to be installed. The digital micrometer is installed at a convenient position between the piston rod and the piston skirt to measure the clearance between the piston and the cylinder liner; the micrometer with a magnetic bracket is installed below the stuffing box at the top of the frame to measure the inclination of the piston rod.

[0006] The specific measurement process is as follows: according to the specifications, reverse the car to the two positions of 45° after the bottom dead center and 35° before the top dead center of the piston, read the actual measurement values ​​of the two micrometers and micrometers in turn, and record them in the corresponding table; then reverse the car to the position 45° after the bottom dead center or a position close to and convenient for operation, read the values ​​of the two micrometers and micrometers, and then use the feeler gauge to measure the gap between the front and rear ends of the piston and the cylinder liner, the gap between the slider and the crosshead, the corresponding actual gap of the 3:7 gap of the big end of the connecting rod, and the actual gap between the small side plate and the frame guide rail; after the corresponding gap value measurement is completed, continue to reverse the car to the position 30° before the top dead center or a position close to and convenient for operation, repeat the same operation at the position 45° after the bottom dead center in turn and record the corresponding actual values.

[0007] The second step is gap adjustment.

[0008] According to the actual measured values ​​of the above-mentioned related gaps, use the adjusting shim 4 to adjust the total gap between the small side plate 3 and the frame guide rail. If the adjusting shim 4 cannot meet the gap adjustment requirements, the thickness of the small side plate 3 is repaired on the machine tool.

[0009] The adjusting gasket 4 used in the above process is selected from a ready-made set of adjusting gaskets of various customized specifications, such as thicknesses of 1.0, 0.5, 0.25, and 0.1 mm, and its specifications and quantity are also limited.

[0010] The above piston centering method has certain defects, that is, the specifications and quantity of the existing conventional adjustment gaskets are difficult to meet the requirements of piston centering operations for various types of ship main engines. Since the structural types of each main engine are different, the sizes of adjustment gaskets required for different types of main engines are also different. This will lead to the following difficulties:

[0011] 1. The inherent specifications and quantity of the adjusting shims are difficult to meet the needs of piston centering for all types of marine low-speed diesel engines. Often, a small number of ship main engines cannot complete the piston centering operation under the conditions of the existing specifications and quantity of adjusting shims;

[0012] 2. After completing the piston centering operation of the previous ship main engine, the set of adjustment shims will have incomplete specifications and quantities left, which makes it difficult to ensure the needs of the next ship main engine piston centering operation. Usually, the necessary specifications and quantities of adjustment shims must be supplemented at this time. After completing the piston centering operation of the next ship main engine, more specifications and incomplete quantities of adjustment shims will remain. Over time, the number of remaining adjustment shims increases, far exceeding the number required. At the same time, the commonly used specifications are becoming increasingly scarce, making it impossible to reasonably utilize the remaining adjustment shims accumulated on site. This has led to an unreasonable phenomenon that on the one hand, the new main engine lacks suitable adjustment shims, while on the other hand, the remaining adjustment shims are accumulated in large quantities;

[0013] 3. The unreasonable configuration of the specifications and quantity of the adjustment gaskets leads to the cumbersome and difficult selection of the adjustment gaskets on site during the piston centering process, which seriously affects the efficiency of the piston centering operation, and also increases the probability of rework of the small side plate, increases the processing cost, and prolongs the production cycle. Summary of the invention

[0014] The problem to be solved by the present invention is to overcome the defects of the prior art and provide an optimization method for the piston centering operation of a marine low-speed two-stroke diesel engine, optimize the ratio, model and quantity of adjusting gaskets, the total thickness of the adjusting gaskets and the size of the small side plates, so as to improve the efficiency of the on-site piston centering operation, increase the utilization rate of the adjusting gaskets, and reduce the probability of on-site rework of the small side plates.

[0015] The technical solution of the present invention for solving the technical problem is as follows:

[0016] An optimization method for centering the piston of a low-speed two-stroke marine diesel engine is characterized in that: first, the thickness of the gasket is adjusted by checking the relevant dimensions, the gasket model and the number of gaskets of different models are adjusted by data matching, and then the value of the early concave of the small side plate is inferred based on the above results.

[0017] Furthermore, the matching value of the adjustment gasket and the structure of the small side plate are optimized.

[0018] Furthermore, under the premise of meeting the requirements of on-site adjustment, the on-site repair rate of the small side panels is reduced as much as possible.

[0019] Furthermore, the optimization method comprises the following steps:

[0020] 1) By checking the frame opening size, confirming the CNC machine tool processing accuracy, checking the opening value and tolerance requirements of the outer side of the small side plate, checking the total thickness of the adjustment gasket and the model of the adjustment gasket, and analyzing the structure of the small side plate;

[0021] 2) According to the verification results of step 1), simulate the use of the adjustment gasket under different conditions;

[0022] 3) According to the simulation results of step 2), the structure of the small side plate is optimized, and the value of the concave of the small side plate is tested through comprehensive judgment;

[0023] 4) Conduct experiments on the host and ultimately evaluate the feasibility of the optimization solution and the necessity of extending it to other hosts.

[0024] Furthermore, the adjustment gasket has model thicknesses of 1.0 mm, 0.5 mm, 0.25 mm, 0.15 mm and 0.10 mm.

[0025] Furthermore, the value of the concave portion of the small side panel is 1 mm.

[0026] Compared with the prior art, the present invention achieves the following beneficial effects:

[0027] The optimization method considers in advance the problems that may be encountered in the centering process of the adjustment gasket and the small side plate, and considers in advance the adjustment margin in the form of the concave structure of the small side plate, optimizes the proportion model and quantity of the adjustment gasket, the total thickness of the adjustment gasket and the size of the small side plate, thereby effectively improving the utilization rate of the adjustment gasket, reducing the probability of rework of the small side plate on site, and improving the efficiency of the piston centering operation. The present invention basically covers the needs of the piston centering operation of most marine low-speed two-stroke diesel engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the principle of the present invention.

[0029] Figure 2 It is a schematic diagram of the optimized structure of the small side panel.

[0030] Figure 3 It is a data simulation schematic diagram of the present invention.

[0031] In the figure:

[0032] 1—large guide plate of the frame, 2—crosshead, 3—small side plate, 4—adjusting gasket. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention shall not be limited thereby.

[0034] The present invention is used for positioning and recording specific tooling at a production site, and mainly includes adjusting the number of gaskets and the optimization of the model configuration and the optimization of the small side plate structure.

[0035] In order to solve the problems existing in the prior art, the applicant and inventor of the present invention specifically tracked the process of main engine piston centering, communicated with on-site operators on the usage rules of adjusting gaskets, listened to the suggestions of on-site operators on piston centering operations, and communicated and discussed together to determine the types of adjusting gaskets to be used and the quantity of gaskets of each specification. After confirming the optimal configuration plan for the specifications and quantity of the adjusting gaskets, the errors that occurred in the machine tool during the processing of the large guide plate were considered, and measures were taken to optimize the small side plate structure in advance to avoid delays in the progress of the piston centering operation due to part processing errors.

[0036] Example

[0037] like Figure 1As shown, the outer dimensions of the adjusting gasket 4 are the same as those of the small side plate 3. In order to meet the mutual movement of the small side plate 3 and the large guide plate 1 of the frame during the movement of the crosshead, and to avoid damage to the mounting surfaces of the small side plate 3 and the crosshead 2 during the force process, the material of the adjusting gasket 4 is selected as Cu. At the same time, the specifications of the adjusting gasket 4 are increased from the original 4 to 5, avoiding the situation that the adjusting gasket 4 cannot meet the actual needs during the piston centering process.

[0038] Table 1 Adjustment gasket model and quantity statistics

[0039] Specifications(mm) 1.0 0.5 0.25 0.15 0.1 quantity 1 1.5 1 1 1

[0040] Since the small side plate 3 and the large guide plate 1 of the frame move relative to each other, in order to enhance the surface hardness, the surface of the small side plate 3 is coated with a suitable coating. Based on the processing error of the large guide plate 1 of the frame and the cumulative error in the closing process of the three major parts, it is very common to re-process the non-alloy surface of the small side plate 3. In order to solve the problem of re-processing the small side plate 3, an adjustment gap is reserved in advance for the installation surface of the small side plate 3, and the non-alloy surface is concave by 1.0 mm (such as Figure 2 shown).

[0041] Among them, the adjusting gasket 4 is installed between the small side plate 3 and the crosshead slider. By adjusting the number of adjusting gaskets 4, the gap between the small side plate 3 and the large guide plate 1 of the frame meets the required gap in the drawing, so that the piston is in the center position during the up and down movement process, avoiding the occurrence of unilateral wear.

[0042] Inspection method——

[0043] ⒈Data simulation:

[0044] By checking the relevant dimensions and calculating the possible use probability of adjusting gaskets of different thicknesses, the limit situation can be judged.

[0045] The probability of using each specification adjustment gasket: Pn=Zn÷Z

[0046] n=1.0(0.5, 0.25, 0.15, 0.10),

[0047] Zn = the number of Z1.0 (0.5, 0.25, 0.15, 0.10); the total number of Z P0.5 = n÷z;

[0048] ① Minimum value (such as Figure 3 )

[0049] TMin1=0.5~Total clearance=J1+X1+P1+M1+TMin1-(1.5~2.0)

[0050] ② Maximum value (such as Figure 3 )

[0051] TMax=3.6~Total clearance=J2+X2+P2+M2+TMax-1.0

[0052] Table 2 Simulation analysis of extreme cases

[0053]

[0054] 2. When installing the adjustment gaskets in advance, plan the thickness and corresponding quantity of the adjustment gaskets to be installed.

[0055] 3. Track the process of piston centering on site, and count the gaps between the small side plates of all cylinders and the large guide plates of the frame, as well as the use of adjustment gaskets. The specific situation is shown in Table 3.

[0056] Table 3 Clearance between small side plate and large guide plate of the rack

[0057]

[0058] Based on the calculation and verification of the above three aspects, the total thickness of the adjustment gasket is determined to be 2.25mm, the ratio of specifications is 1.0, 0.5, 0.25, 0.15, 0.10mm, and the contact surface between the small side plate and the large guide plate is concave by 1.0mm. This meets the requirements of on-site piston centering and solves the problem of large waste of on-site adjustment gaskets and reprocessing of the small side plate.

[0059] The protection scope claimed by the present invention is not limited to the above-mentioned embodiments, but should also include other obvious changes and alternatives to the present invention.

Claims

1. An optimization method for piston centering of a low-speed two-stroke marine diesel engine, characterized in that: First, check the relevant dimensions and adjust the thickness of the gasket. Adjust the gasket model and the number of gaskets of different models through data matching. Then, infer the value of the early concave of the small side panel based on the above results.

2. The optimization method for piston centering of a low-speed two-stroke marine diesel engine according to claim 1, characterized in that: The matching value of the adjustment gasket and the structure of the small side plate are optimized.

3. The optimization method for piston centering of a low-speed two-stroke marine diesel engine according to claim 1, characterized in that: Under the premise of meeting on-site adjustments, reduce the on-site repair rate of small side panels as much as possible.

4. The optimization method for piston centering of a low-speed two-stroke marine diesel engine according to claim 1, characterized in that: The optimization method comprises the following steps: 1) By checking the frame opening size, confirming the CNC machine tool processing accuracy, checking the opening value and tolerance requirements of the outer side of the small side plate, checking the total thickness of the adjustment gasket and the model of the adjustment gasket, and analyzing the structure of the small side plate; 2) According to the verification results of step 1), simulate the use of the adjustment gasket under different conditions; 3) According to the simulation results of step 2), the structure of the small side plate is optimized, and the value of the concave of the small side plate is tested through comprehensive judgment; 4) Conduct experiments on the host and ultimately evaluate the feasibility of the optimization solution and the necessity of extending it to other hosts.

5. The optimization method for piston centering of a low-speed two-stroke marine diesel engine according to claim 1, characterized in that: The thicknesses of the adjusting gaskets are 1.0mm, 0.5mm, 0.25mm, 0.15mm and 0.10mm.

6. The optimization method for piston centering of a low-speed two-stroke marine diesel engine according to claim 1, characterized in that: The value of the concave portion of the small side plate is 1 mm.

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