High-speed deep hole drilling method for diesel engine crankshaft

Abstract

This invention provides a high-speed deep-hole drilling method for diesel engine crankshafts. The clamping apparatus includes three V-shaped modules and two tool guide sleeves. Each V-shaped module has a V-shaped positioning groove on its upper part, and each tool guide sleeve has a guide hole. The V-shaped positioning groove on the upper part of the V-shaped module supports the corresponding journal of the crankshaft, and the guide hole of the tool guide sleeve provides a through-hole guide for a high-precision jet-suction drilling device. The high-precision jet-suction drilling device consists of a jet-suction drill bit and an extended tool shank connected by threads. The extended tool shank consists of an inner tube and an outer tube sleeved together, with an oil supply gap formed between the inner and outer tubes. This invention improves the machining efficiency of deep holes in the main oil passages of high-power diesel engine crankshafts with large length-to-diameter ratios, ensures dimensional and positional accuracy, reduces the overall machining progress of parts, lowers manufacturing costs, and meets production requirements. It is applicable to the machining of deep holes in the main oil passages of various crankshaft models with different length-to-diameter ratios, and has wide application and strong versatility.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, and in particular relates to a method for machining diesel engine crankshafts by high-speed deep hole drilling. Background Technology

[0002] As the primary power source for equipment, the machining precision, assembly accuracy, and performance indicators of the major components of the diesel engine's internal transmission, fuel supply, and valve train systems directly affect the engine's service life and performance stability under harsh operating environments such as high and low temperatures, high altitudes, and high salt spray. The crankshaft is one of the typical core components within the diesel engine's transmission system, requiring continuous power output under high torque and high load conditions. The crankshaft main oil passage is a crucial hole system that runs through the main journal of the crankshaft. Its function is to transmit lubricating oil under pressure to the bearing surface, forming a lubricating film. This ensures that the connecting rod small end and the crankshaft connecting rod journal's moving pair surface are adequately lubricated, allowing for high-speed centrifugal rotation and providing high power output to the diesel engine. The machining precision and surface quality of the crankshaft main oil passage wall directly affect the lubrication effect on the crankshaft and connecting rod. Because the main oil passage is a deep hole with a large length-to-diameter ratio (up to 63 times the diameter), this particular hole is particularly important. When machining deep holes with a large length-to-diameter ratio, the traditional drilling method uses an extended twist drill and an extended reamer in combination. However, when the machine tool spindle rotates, the extended twist drill or reamer is subject to centrifugal force, which causes the drill and reamer to be unable to keep the center of the cutting edge at the center of the cutting surface. Although the drill can be guided to drill to a certain depth first, the accuracy and geometric tolerance of the hole system are ultimately unable to meet the design requirements due to the large length-to-diameter ratio of the hole system. This directly leads to a low product qualification rate and seriously affects the overall production progress. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides the following technical solution:

[0004] A method for machining diesel engine crankshafts using high-speed deep hole drilling is characterized in that the clamping process device used in this method includes three V-shaped modules and two tool guide sleeves. Each V-shaped module has a V-shaped positioning groove formed on its upper part, and each tool guide sleeve has a guide hole. The V-shaped positioning groove formed on the upper part of the V-shaped module supports the journal corresponding to the crankshaft, and the guide hole of the tool guide sleeve provides a through-path guide for the high-precision jet-suction drilling device.

[0005] Furthermore, the high-precision jet-suction drilling device used in this method consists of a jet-suction drill bit and an extended tool bar connected by threads. The extended tool bar is composed of an inner tube and an outer tube sleeved together, and an oil supply gap is formed between the inner and outer tubes.

[0006] First, place and fix the three V-shaped modules supporting the crankshaft and the two tool guide sleeves on the working platform of the horizontal machining center according to the rules. Then, align the tool guide sleeves and V-shaped modules in sequence, that is, the X and Y coordinate axes of each tool guide sleeve and V-shaped module are on the same horizontal line as the spindle center line of the machine tool.

[0007] The arrangement of the three V-shaped modules is as follows: the two V-shaped modules at the beginning and end are located at the corresponding positions of the second and second-to-last main journals of the crankshaft being machined, respectively, and the V-shaped module in the middle is located at the corresponding position of the middle main journal of the crankshaft being machined.

[0008] The placement rules for the two tool guide sleeves are as follows: one tool guide sleeve is located at the corresponding position of the connecting rod journal between the first and second main journals of the crankshaft being machined, and the other tool guide sleeve is located between the V-type module at the tail end and the V-type module in the middle, and is located near the V-type module at the tail end.

[0009] Furthermore, the high-precision jet-suction drilling device is clamped onto the machine tool spindle;

[0010] Then, place the corresponding main journal of the crankshaft on the V-groove of the corresponding V-module, and use a clamping device to fasten the crankshaft to prevent loosening.

[0011] The cutting tip of the jet-suction drill bit is moved to the surface of the hole to be machined through the machine tool control system, and the zero point of the cutting Z value is found through trial cutting;

[0012] Finally, locate the X and Y zero points on the outer circle of the crankshaft and input the zero point coordinate values ​​into the machine tool program coordinate system;

[0013] The machining process for deep holes with a large length-to-diameter ratio of the crankshaft begins.

[0014] Furthermore, fastening bolts are used to connect and fix each V-shaped module and tool guide sleeve to the machine tool platform.

[0015] Furthermore, the tool guide sleeve and V-shaped module are aligned sequentially using a dial indicator.

[0016] Furthermore, another tool guide sleeve is located at the corresponding position of the connecting rod journal of the second-to-last main journal of the crankshaft being machined.

[0017] Furthermore, the X and Y zero points of the crankshaft outer circle are located using a dial indicator.

[0018] Furthermore, the deep hole is a 63-times diameter deep hole, the crankshaft is made of 34CrNimo6 special steel, the main cutting edge is a 45° carbide coated insert, the cutting edge for finishing the hole surface is a 90° carbide coated insert, the rotation speed is 900 rpm, and the feed rate is G95F50mm.

[0019] This invention improves the machining efficiency of deep holes in the main oil passages of high-power diesel engine crankshafts with large length-to-diameter ratios, ensures dimensional and positional accuracy, reduces the overall machining progress of parts, lowers manufacturing costs, and meets production requirements. It is applicable to the machining of deep holes in the main oil passages of various crankshaft models with different length-to-diameter ratios, and has wide application and strong versatility. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram showing the arrangement of the clamping process device and the high-precision jet-suction drilling device used in this invention.

[0022] Figure 2 This is a schematic diagram of the crankshaft being placed on the clamping process device. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] This invention is based on a high-precision jet-suction drilling device. By developing a self-made clamping process device, analyzing the material properties of the parts, and matching reasonable process parameters, stable processing quality and production efficiency can be achieved. This method can adapt to the drilling needs of crankshaft deep holes with different length-to-diameter ratios simply by adjusting the distance of the clamping process device. At the same time, it can also meet the accuracy and geometric tolerance technical requirements proposed by the designer, and further master the core technology of drilling deep holes with large length-to-diameter ratios.

[0026] The clamping apparatus used in this method includes three V-shaped modules 1 and two tool guide sleeves 2. Each V-shaped module 1 has a V-shaped positioning groove 11 formed on its upper part, and each tool guide sleeve 2 has a guide hole 21 through which a high-precision jet-suction drilling device passes.

[0027] The high-precision jet-suction drilling device used in this method consists of a jet-suction drill bit 31 and an extended cutter bar 32 connected by threads. The extended cutter bar 32 is composed of an inner tube 322 and an outer tube 321 sleeved together, and an oil supply gap is formed between the inner and outer tubes.

[0028] Specific methods

[0029] First, place the three V-shaped modules 1 supporting the crankshaft and the two tool guide sleeves 2 on the working platform of the horizontal machining center. After connecting each V-shaped module 1 and tool guide sleeve 2 to the machine tool platform with fastening bolts, use a dial indicator to align the tool guide sleeve 2 and V-shaped module 1 in turn, that is, ensure that the X and Y coordinate axes of each tool guide sleeve 2 and V-shaped module 1 are on the same horizontal line as the spindle centerline of the machine tool.

[0030] The arrangement of the three V-shaped modules 1 is as follows: the two V-shaped modules 1 located at the beginning and end are respectively located at the corresponding positions of the second main journal and the second to last main journal of the crankshaft being machined, and the V-shaped module 1 located in the middle is located at the corresponding position of the middle main journal of the crankshaft being machined.

[0031] The placement rules for the two tool guide sleeves 2 are as follows: one tool guide sleeve 2 is located at the corresponding position of the connecting rod journal between the first and second main journals of the crankshaft being machined, and the other tool guide sleeve 2 is located between the V-shaped module at the tail end and the V-shaped module in the middle, and is located near the V-shaped module at the tail end; preferably, the other tool guide sleeve 2 is located at the corresponding position of the connecting rod journal near the penultimate main journal of the crankshaft being machined.

[0032] Secondly, the jet-suction drill bit and the extended tool holder are assembled using a threaded connection and then clamped onto the machine tool spindle.

[0033] Then, as Figure 2 The crankshaft shown has 9 main shafts from 1 to 9 and 8 connecting rod journals from I to VIII. The 2nd, 5th, and 8th main shaft journals of the crankshaft are placed on the V-shaped positioning grooves of the corresponding V-shaped modules, and the crankshaft is fastened to prevent loosening using a clamping process device. The two tool guide sleeves 2 are placed at the corresponding positions of the I connecting rod journal and the VII connecting rod journal, respectively, to provide through-path guidance for the high-precision jet-suction drilling device.

[0034] The cutting tip of the jet-suction drill bit is moved to the surface of the hole to be machined through the machine tool control system, and the zero point of the cutting Z value is found through trial cutting.

[0035] Finally, using a dial indicator, locate the X and Y zero points of the crankshaft's φ95 outer diameter and input the zero-point coordinates into the machine tool program coordinate system. After the above operations, the machining of the crankshaft's large length-to-diameter ratio deep hole process can begin.

[0036] This invention utilizes existing horizontal machining center equipment. An external oil pump draws approximately 5MPa pressure cutting oil from the pump's tank. The other end of the pump connects to an oil delivery channel on one side of the machine tool spindle. The cutting oil, under pressure, flows rapidly through a 1mm gap between the inner and outer tubes of the extended tool holder held by the spindle towards the suction drill bit. Because the inner thread of the tool holder's outer tube connects to the outer thread of the suction drill bit, and the end face of the inner tube is tightly sealed to the end face of the inner hole of the suction drill bit, the high-pressure cutting oil is ejected through the φ3 hole at the front end of the suction drill bit, forming high-pressure cutting oil. This cutting oil effectively reduces the cutting heat generated by the tool, extending its service life, and also lubricates the hole machining process, improving the surface finish. During part machining, the chips generated by rapid drilling are carried by high-pressure cutting oil into the chip removal groove at the front end of the jet-suction drill and flow into the inner tube of the tool holder. The chips and cutting oil create a backflow effect, flowing back to the chip removal pipeline on the other side of the machine tool spindle. The cutting oil and chips flow into the chip recovery vehicle through the chip removal pipeline. The vehicle has a filter device, and the cutting oil is filtered and then flows back into the oil pump for reuse.

[0037] Regarding technical parameters

[0038] Since machining a crankshaft with a 63-fold diameter deep hole is a difficult process, the appropriate selection of cutting tools and process parameters are key factors in ensuring product yield. This machining technique uses a jet-suction drill bit with an extended tool holder to drill directly from one end of the crankshaft to the other in a single machining step. During drilling, the characteristics of the material were considered firstly. The crankshaft is made of 34CrNiMo6 special steel, which has high strength and toughness, with a yield strength of 1000MPa~1300MPa and a tensile strength of 1200MPa~1600MPa. After heat treatment and tempering, the material's hardness is between 36HRC and 42HRC. Secondly, to ensure the drilling accuracy and surface quality of the deep hole system, 45° carbide-coated inserts were selected for the main cutting edge, and 90° carbide-coated inserts were used for finishing the hole surface. Furthermore, after multiple tests, the optimal machining parameters were determined to be a rotation speed of 900rpm and a feed rate of G95. F50mm, this parameter can produce chips with optimal ribbon-like chip shape while controlling hole system accuracy of 0.02mm~0.05mm, hole system straightness ≤0.02mm, and inner hole surface roughness ≤Ra1.6, which can be quickly discharged from the cutting area and cutting groove.

[0039] The processing parameters of this invention are the optimal processing parameters selected after multiple rounds of verification. The rationality of the processing parameters affects the shape of the chips formed during the processing and whether the chips are discharged smoothly, as well as the processing accuracy and surface quality of the hole system.

[0040] This method can cover the efficient machining of deep holes with different length-to-diameter ratios for all crankshafts made of this material, effectively improving machining efficiency, reducing the overall machining progress of parts, lowering manufacturing costs, and meeting production requirements.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for machining diesel engine crankshafts using high-speed deep hole drilling, characterized in that, The clamping device used in this method includes three V-shaped modules and two tool guide sleeves. Each V-shaped module has a V-shaped positioning groove on its upper part, and each tool guide sleeve has a guide hole. The V-shaped positioning groove formed on the upper part of the V-shaped module supports the journal corresponding to the crankshaft, and the guide hole of the tool guide sleeve provides a through-path guide for the high-precision jet-suction drilling device. The high-precision jet-suction drilling device used in this method consists of a jet-suction drill bit and an extended tool bar connected by threads. The extended tool bar is composed of an inner tube and an outer tube sleeved together, and an oil supply gap is formed between the inner and outer tubes. First, place and fix the three V-shaped modules supporting the crankshaft and the two tool guide sleeves on the working platform of the horizontal machining center according to the rules. Then, align the tool guide sleeves and V-shaped modules in sequence, that is, the X and Y coordinate axes of each tool guide sleeve and V-shaped module are on the same horizontal line as the spindle center line of the machine tool. The arrangement of the three V-shaped modules is as follows: the two V-shaped modules at the beginning and end are located at the corresponding positions of the second and second-to-last main journals of the crankshaft being machined, respectively, and the V-shaped module in the middle is located at the corresponding position of the middle main journal of the crankshaft being machined. The placement rules for the two tool guide sleeves are as follows: one tool guide sleeve is located at the corresponding position of the connecting rod journal between the first and second main journals of the crankshaft being machined, and the other tool guide sleeve is located between the V-shaped module at the tail end and the V-shaped module in the middle, and is adjacent to the V-shaped module at the tail end. Secondly, the high-precision jet-suction drilling device is clamped on the machine tool spindle; Then, place the corresponding main journal of the crankshaft on the V-groove of the corresponding V-module, and use a clamping device to fasten the crankshaft to prevent loosening. The cutting tip of the jet-suction drill bit is moved to the surface of the hole to be machined through the machine tool control system, and the zero point of the cutting Z value is found through trial cutting; Finally, locate the X and Y zero points on the outer circle of the crankshaft and input the zero point coordinate values ​​into the machine tool program coordinate system; Begin machining the crankshaft's large length-to-diameter ratio deep hole process; Each V-shaped module and tool guide sleeve is connected and fixed to the machine tool platform using fastening bolts; Use a dial indicator to align the tool guide sleeve with the V-shaped module in sequence; Another tool guide sleeve is located at the corresponding position of the connecting rod journal of the second to last main journal of the crankshaft being machined; Use a dial indicator to find the X and Y zero points on the outer circle of the crankshaft; The deep hole is 63 times the diameter, and the crankshaft is made of 34CrNiMo6 special steel material with a rotation speed of 900 rpm.

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