Over-boundary lubrication piston pin hole structure and manufacturing method

Abstract

The invention relates to the technical field of piston manufacturing, in particular to an over-boundary lubrication piston pin hole structure, micro oil grooves are formed in the inner surface of a piston pin hole, the micro oil grooves are of a continuous or discontinuous spiral structure and extend in the axial direction of the piston pin hole, and micro cutter line areas are arranged on the inner surface of the piston pin hole and located between every two adjacent micro oil grooves. A plurality of ring grooves are formed in the micro-cutter line area at intervals in the axial direction of the piston pin hole. The high-pressure-bearing and boundary lubricating miniature oil groove is formed in the surface of the piston pin hole, the lubricating performance between the piston pin and the piston pin hole is improved, abrasion is reduced, the bearing capacity of the piston pin hole and the piston pin is further enhanced, and the reliability and durability of an engine are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piston manufacturing, in particular to a super-boundary lubrication piston pin hole structure and a manufacturing method thereof. BACKGROUND

[0002] In modern internal combustion engines, the piston as a key component, its cooperation with the piston pin has an important influence on the performance, reliability and durability of the engine. The traditional piston pin hole is usually a smooth cylindrical surface, and during the operation of the engine, the piston pin and the piston pin hole mainly rely on the oil film formed by the lubricating oil to realize lubrication and reduce wear. However, as the engine develops towards high power and high speed, higher requirements are put forward for the lubrication and wear resistance between the piston and the piston pin. The smooth surface of the piston pin hole is difficult to ensure the continuous and stable thickness of the oil film under certain working conditions, which leads to local dry friction or semi-dry friction between the piston pin and the piston pin hole, and further causes problems such as increased wear, increased noise and piston pin loosening, which affects the normal operation and service life of the engine. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a super-boundary lubrication piston pin hole structure and a manufacturing method thereof, which improves the lubrication performance between the piston pin and the piston pin hole by setting high-pressure boundary lubrication micro oil grooves on the surface of the piston pin hole, reduces wear, further strengthens the load-carrying capacity of the piston pin hole and the piston pin, and improves the reliability and durability of the engine.

[0004] The present application is realized by the following technical solutions: A super-boundary lubrication piston pin hole structure is provided, the inner surface of the piston pin hole is formed with a micro oil groove, the micro oil groove is in a continuous or intermittent spiral structure, and extends along the axial direction of the piston pin hole, the inner surface of the piston pin hole is provided with a micro knife line area between adjacent two micro oil grooves, and a plurality of annular grooves are formed in the micro knife line area along the axial direction of the piston pin hole.

[0005] Further, the distance between the adjacent two micro oil grooves is t, and 10mm≤t≤15mm.

[0006] In the oil groove distance t range, the effective storage and transportation of the lubricating oil in the high-pressure boundary lubrication micro oil groove can be ensured, and the bearing area of the piston pin hole will not be excessively reduced due to too large distance, or the machining precision of the high-pressure boundary lubrication micro oil groove and the flow performance of the lubricating oil will be affected due to too small pitch.

[0007] Further, the height of the micro oil groove is h, and 0.01mm≤h≤0.05mm.

[0008] Further, 0.02mm≤h≤0.04mm.

[0009] The oil groove height h can form an oil groove with a suitable depth on the surface of the piston pin hole to effectively store lubricating oil.

[0010] Further, the micro oil groove is formed by the intersection of two symmetrical inclined surfaces, the included angle between the two inclined surfaces is α, and 60°≤α≤120°.

[0011] Further, 80°≤α≤100°.

[0012] The intersection of the two inclined surfaces of the micro oil groove forms a tooth angle, which can ensure sufficient lubricating oil storage space in the high-pressure boundary lubrication micro oil groove while making the flow of lubricating oil in the high-pressure boundary lubrication micro oil groove smoother, which is conducive to forming a good lubrication effect between the piston pin and the piston pin hole.

[0013] Further, the cross section of the ring groove is an inverted isosceles trapezoid.

[0014] Further, the depth of the ring groove is d, and 0.3≤d≤0.5μm, the distance between adjacent two ring grooves is w, and 0.2≤w≤0.6μm.

[0015] By designing the micro knife groove and limiting the distance and depth, the contact between the piston pin and the mating part can be more uniform during relative motion of the piston pin and the piston pin hole, which can accelerate the running-in process, guide the lubricating oil to form a continuous and stable oil film between the two, make the mating surfaces better fit, improve the mating precision and stability, and better withstand the load on the piston pin, reduce wear and fatigue damage.

[0016] A manufacturing method of an ultra-boundary lubrication piston pin hole structure, comprising the following steps: S1, pretreatment: cleaning and degreasing the piston to be processed, and then heat treating; S2, rough machining: boring the pretreated piston, the size precision of the pin hole is controlled within ±6.3μm, and 3.2μm of machining allowance is reserved for subsequent machining; S3, semi-finishing: electrolytic machining the rough machined piston, measuring the size precision and surface roughness of the pin hole, the size precision reaches ±2.0μm, and the surface roughness is reduced to Ra1.6μm; S4, micro oil groove machining: using high-frequency energy percussion to machine the micro oil groove on the pin hole of the semi-finished piston, the width of the micro oil groove is controlled within ±50μm, the depth is controlled within ±0.5μm, and the position accuracy is controlled within ±0.8μm; S5, finishing: the processed micro oil groove of the piston is polished and polished to reduce the surface roughness to Ra0.4nm below, the size accuracy reaches ±60nm, the shape accuracy reaches ±90nm, and the sub-micron level accuracy requirement is met.

[0017] The beneficial effects of the present application are: The present application provides a new structure of high-pressure boundary lubrication micro oil groove shape, which can make the piston suitable for super high power, super high load, ultra low friction and wear, and very strict structure strength requirement and pin hole surface lubrication of diesel engine. The engine piston pin hole and piston pin have high bearing capacity, sufficient lubrication, very small friction and wear, and softer operation process.

[0018] The present application can improve the lubrication performance: by setting high-pressure boundary lubrication micro oil groove on the inner surface of the piston pin hole, the lubricating oil can be effectively guided to form a continuous and stable oil film between the piston pin and the piston pin hole, which can significantly improve the lubrication effect, reduce the occurrence of dry friction and semi-dry friction phenomenon, reduce wear and prolong the service life of the piston and the piston pin.

[0019] The present application can improve the reliability of the engine: good lubrication performance can reduce the problems of piston pin loosening and noise increase caused by wear between the piston pin and the piston pin hole, improve the stability and reliability of the engine operation, reduce the probability of engine failure, and reduce the maintenance cost.

[0020] The present application can adapt to different working conditions: the groove distance, oil groove height, oil groove angle and rotation direction of high-pressure boundary lubrication micro oil groove can be optimized according to different working requirements and working conditions of the engine, so that the structure of the piston pin hole with high-pressure boundary lubrication micro oil groove shape can better adapt to various complex working conditions and improve the performance of the engine under different working conditions.

[0021] The processing technology of the present application has high feasibility: the processing of high-pressure boundary lubrication micro oil groove can adopt existing precision machining technology such as numerical control machining and electric spark machining, which has high process feasibility and machining precision and can meet the requirements of mass production. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The structure of the piston pin hole in the present application is shown in the figure.

[0023] Figure 2 The enlarged schematic view of the micro oil groove in the present application is shown in the figure.

[0024] Figure 3 The Figure 2 The enlarged schematic view of A in the present application is shown in the figure.

[0025] Figure 4A schematic view of the cooperation between the piston pin hole and the piston pin in the present application.

[0026] Figure 5 A perspective view of the piston head in the present application.

[0027] The figure shows: 1, piston body, 2, micro oil groove, 3, pin hole, 4, micro knife mark area, 5, piston pin, 6, ring groove. DETAILED DESCRIPTION

[0028] In order to clearly illustrate the technical features of the present application, the present application will be described below through specific embodiments.

[0029] A super-boundary lubrication piston pin hole structure is suitable for a four-stroke diesel engine, and the piston material is one of aluminum alloy, titanium alloy, hard alloy and steel alloy. In the present embodiment, the piston material uses steel alloy, the inner surface of the piston pin hole is formed with a micro oil groove 2, the micro oil groove 2 is in a continuous or intermittent spiral structure, and extends along the axial direction of the piston pin hole 3, the rotation direction of the micro oil groove 2 can be selected according to the working requirements of the engine and the movement direction of the piston, which can be left-handed or right-handed. For example, for a certain rotating direction of the engine crankshaft, the rotation direction of the high-pressure boundary lubrication micro oil groove 2 is reasonably selected, which can better bring the lubricating oil into the gap between the piston pin and the piston pin hole 3 by using the inertia of the piston in the movement process and the relative movement between the piston pin and the piston pin hole 3, and improve the lubrication efficiency.

[0030] Among them, the distance between the two adjacent micro oil grooves 2 is t, which is set to 12mm.

[0031] The height of the micro oil groove 2 is h, and 0.01mm≤h≤0.05mm, as an embodiment in the present embodiment, the height of the micro oil groove is 0.03mm.

[0032] The micro oil groove 2 is formed by the intersection of two symmetrical inclined surfaces, the included angle between the two inclined surfaces is α, and 60°≤α≤120°. As an embodiment of the present embodiment, the included angle is set to 90°.

[0033] The inner surface of the piston pin hole 3 is provided with a micro knife mark area 4 between the two adjacent micro oil grooves 2, a plurality of ring grooves 6 are formed in the micro knife mark area 4 along the axial direction of the piston pin hole 3, the cross section of the ring groove 6 is an inverted isosceles trapezoid, the depth of the ring groove 6 is d, which is set to 0.4μm, and the distance between the two adjacent ring grooves 6 is w, which is set to 0.5μm.

[0034] The working principle of the present application is as follows: when the engine is working, the piston body 1 reciprocates in the cylinder, and the relative motion exists between the piston pin 5 and the piston pin hole 3. At this time, the lubricating oil adhering to the surfaces of the piston pin 5 and the piston pin hole 3 will be guided by the high-pressure boundary lubrication micro-groove 2. Due to the spiral structure of the high-pressure boundary lubrication micro-groove 2, the lubricating oil will form a continuous oil film between the piston pin 5 and the piston pin hole 3 along the high-pressure boundary lubrication micro-groove, and under the action of the pressure generated by the relative motion of the piston pin 5 and the piston pin hole 3, the lubricating oil can be continuously supplemented to the friction surface, thereby effectively reducing the direct contact and wear between the piston pin 5 and the piston pin hole 3. At the same time, the high-pressure boundary lubrication micro-groove 2 can also store a certain amount of lubricating oil, which can play a buffering role when the engine operating condition changes and the lubricating oil supply is temporarily insufficient, maintain the lubricating effect, and ensure the stable operation of the engine.

[0035] A manufacturing method of an ultra-boundary lubrication piston pin hole structure, comprising the following steps: S1, pretreatment: according to the material, size and design requirements of the piston, select appropriate machining equipment, tools, electrolyte, abrasive materials and polishing materials, etc. Carry out comprehensive inspection and debugging of the machining equipment to ensure that the performance indicators of the equipment meet the requirements. The piston to be machined is cleaned and degreased to remove surface dirt and impurities, and then heat treated to improve the hardness and strength of the piston material.

[0036] S2, rough machining: install the pretreated piston body 1 on a high-precision numerical control boring machine, and use a hard alloy tool for rough machining. According to the preset cutting parameters such as cutting speed, feed rate and cutting depth, boring machining is carried out, and after machining, the size accuracy of the pin hole is controlled within ±6.3μm, and 3.2μm machining allowance is reserved for subsequent machining.

[0037] S3, semi-finishing: transfer the rough machined piston to the electrolytic machining equipment, and configure the electrolyte such as specific electrolyte composition and concentration. Set the electrolytic machining parameters, such as machining voltage, current density and machining time, and carry out electrolytic machining. After machining, measure the size accuracy and surface roughness of the pin hole, the size accuracy reaches ±2.0μm, and the surface roughness is reduced to Ra1.6μm.

[0038] S4, micro oil groove 2 processing: the semi-finished piston is fixed on the workbench of high-frequency energy knocking device, the parameters of high-frequency energy knocking forming are adjusted, pulse energy, pulse width, repetition frequency, and high-frequency energy knocking is focused on the wall of piston pin hole 3. According to the preset scanning path and scanning speed, micro oil groove 2 processing is carried out. During the processing, the processing situation is observed through the real-time monitoring system to ensure the processing quality of the groove. After the processing is completed, the size and position accuracy of the micro oil groove 2 are detected, the width is controlled within ± 50 μm, the depth is controlled within ± 0.5 μm, and the position accuracy is controlled within ± 0.8 μm.

[0039] S5, finishing: the piston with micro oil groove 2 is installed on the precise grinding and polishing equipment, and appropriate grinding and polishing materials are selected. The grinding and polishing parameters, grinding pressure, polishing speed and processing time are set, and grinding and polishing treatment is carried out. After the processing is completed, the various parameters of the piston pin hole are detected again, the surface roughness is reduced to below Ra0.4nm, the size accuracy reaches ± 60nm, and the shape accuracy reaches ± 90nm, meeting the sub-micron level precision requirement.

[0040] S6, detection and quality control: after each processing step is completed, the piston pin hole 3 is detected. The three-coordinate measuring instrument is used to detect the size accuracy and shape accuracy of the pin hole, the surface roughness measuring instrument is used to detect the surface roughness, and the microscope is used to observe the quality of the micro oil groove 2. The detection data is recorded and compared with the design requirements for analysis. If the processing quality is found to be not in line with the requirements, the processing parameters are adjusted in time or appropriate improvement measures are taken, such as re-adjusting the tool path, optimizing the electrolyte formula, adjusting the laser processing parameters, etc., to ensure that the final processing quality meets the design standard.

[0041] Of course, the above description is not limited to the above examples, and the technical features not described in the application can be realized by or using the prior art, which will not be described here; the above examples and drawings are only used to illustrate the technical solutions of the application and are not a limitation of the application, the preferred embodiments of the application are described in detail, and those skilled in the art should understand that the changes, modifications, additions or replacements made by those skilled in the art within the essential scope of the application do not deviate from the purpose of the application, and should also belong to the protection scope of the claims of the application.

Claims

1. A super-baffled lubricated piston pin bore structure characterized by: The inner surface of the piston pin hole is formed with micro oil grooves in continuous or discontinuous spiral structure and extending along the axial direction of the piston pin hole.

2. The super-toleranced lubricated piston pin bore structure of claim 1, wherein: The distance between the two adjacent micro oil grooves is t, and 10mm≤t≤15mm.

3. The super-toleranced lubricated piston pin bore structure of claim 1, wherein: The height of the micro oil groove is h, and 0.01mm≤h≤0.05mm.

4. The super-tolerance lubricated piston pin bore structure of claim 3, wherein: 0.02mm≤h≤0.04mm.

5. The super-toleranced lubricated piston pin bore structure of claim 1 wherein: The micro oil groove is formed by the intersection of two symmetrical inclined surfaces, and the included angle between the two inclined surfaces is α, and 60°≤α≤120°.

6. The super-tolerance lubricated piston pin bore structure of claim 5, wherein: 80°≤α≤ 100°。 7. The super-tolerance lubricated piston pin bore structure of claim 1, wherein: The cross section of the ring groove is an inverted isosceles trapezoid.

8. The super- boundary lubrication piston pin bore structure according to claim 1 or 7, characterized by: The depth of the ring groove is d, and 0.3≤d≤0.5μm, and the distance between the two adjacent ring grooves is w, and 0.2≤w≤0.6μm.

9. A method of manufacturing the super-bush-lubricated piston pin bore structure of claim 1, characterized by: The method comprises the following steps: S1, pretreatment: after cleaning and degreasing of the piston to be machined, heat treatment is carried out; S2, rough machining: boring machining is carried out on the pretreated piston, and the size accuracy of the pin hole is controlled within ±6.3μm, and 3.2μm machining allowance is reserved for subsequent machining; S3, semi-finish machining: electrolytic machining is carried out on the rough machined piston, the size accuracy and surface roughness of the pin hole are measured, the size accuracy reaches ±2.0μm, and the surface roughness is reduced to Ra1.6μm; S4, micro oil groove machining: high frequency energy knocking is used for micro oil groove machining on the pin hole of the semi-finished piston, the width of the micro oil groove is controlled within ±50μm, the depth is controlled within ±0.5μm, and the position accuracy is controlled within ±0.8μm; S5, finish machining: grinding and polishing treatment is carried out on the piston with micro oil groove, so that the surface roughness is reduced to below Ra0.4nm, the size accuracy reaches ±60nm, and the shape accuracy reaches ±90nm, which meets the sub-micron level precision requirement.

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